Interlaminar Stress Behaviour of the Flywheel Rotor

Interlaminar Stress Behaviour of the Flywheel Rotor 1.1 History of the Flywheel For over thousands of years, flywheels have been used in potter wheels and spindle wheel whorls Gowayed et al., 2002 The concept of storing energy in a rotating disk dates as far back as 2400 BC when rotating wheels were used by Egyptians to handcraft pottery. In fact, flywheel systems were widely used in everyday life (Genta, 1985): in warring chariots, water pumps and even power generations. However, these conventional flywheels are not as efficient as energy storage devices due to the large amount of mass required for the relatively meagre amount of energy stored not to mention the capability of delivering power for only a relatively short period. The advent of the industrial revolution brought about the significant advances of the flywheels. In the 18th century, Man witnessed the widespread use of metal in the construction of machines and soon, flywheel had found its way into steam engines. This development of the flywheel had been attributed to the works of James Watt. With flywheels made of cast iron, a higher mass moment of inertia could be achieve and thus a significant weight saving as well. During the industrial revolution, James Pickard developed a solution for transforming reciprocating to rotary motion with the combination of a crank and flywheel. And it was not till the last thirty years that we witness high performance flywheels being significantly developed with marked improvement and demonstrate the potential as energy storage systems in a wide range of applications. The energy crisis of then 1970s marked the beginning of another significant era for the development of flywheels as the need to search for an alternative energy storage implement. Large amount of money were invested by the governments of many nations into the development of flywheel energy storage technology with subsequent establishment of research programs in the development of flywheel devices as alternative energy storage systems (Genta, 1985). However, development pace since to slow down as fuel prices begin to stabilized in the early 1980s. That particular time period was nevertheless a crucial development era for the flywheel; during which the use of flywheels are explored and developed for electrical vehicles. In addition it was also explored as a device to help utilities manage peak power demand. With the incorporation of high specific strength advanced composite materials into flywheel designs, weight reductions and strength increment can be achieved; and this cannot be achieved with the use of metallic alloy. However, the use of flywheels can yet be commercialized even with the significant improvements in the design concept of flywheel as it remains a challenge still to design flywheel systems that are cost competitive to other energy storage devices. In addition, composites, though stronger than metal, would require the use of advanced bearings due to the inability to withstand certain forces exposed in high performance application (Kim, T.H. 2003). The 1990s witnessed developments in stronger, lightweight composite materials, magnetic bearings and other electronic devices, and all of which contribute to the exciting development of the flywheel. Excessively high rotational speed could now be reached, with a subsequent increment in energy stored, making them a possible candidate again for energy storage system of superior performance. As a summary, the improvement in the flywheel quick energy recovery, high efficiency, low maintenance and long service life, high amount of stored energy per unit volume and mass, high output power levels, as well as lower product and operational cost (Horner, 1996) as well as environmental friendly components are all that have made the flywheel energy storage system a feasible option. 1.1.2 Flywheel as an Energy Storage Device Flywheel energy storage (FES) has, in various past researches, proven its superiority over conventional battery technology based energy storage system in terms of its higher energy density, durability, rapid charge and discharge capability, as well as its tolerance over a wide range of temperature with very minute environmental concerns; and with the progress in power electronics, loss reductions techniques and advanced materials, the then seemingly inconceivable idea of economical flywheel energy storage (FES) devices are no longer chimerical (Hebner et al, 2002). In fact, all of the prepossessing characteristics mentioned briefly above (in comparison with those that of conventional battery system) are what that result in the advanced flywheel systemsà ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬Ãƒ ¢Ã¢â‚¬Å¾Ã‚ ¢ appeal as one of the fast- gaining attention alternative for energy storage devices. (Arvin Bakis, 2006) A flywheel is an inertial energy storage system where the rotating mass functions as the energy storage retainer. While connected to the motor (possibly electrical motor), a flywheel can be accelerated to a specific angular velocity. In this process, electrical energy was converted into kinetic energy and the rotating inertia of the composite rotor acts to store this form of mechanical energy. When the need arises, the mechanical energy can be transformed back to electrical power by the motor. Thus, the motor in the flywheel system acts not merely as a motor to accelerate the energy storing process but also as a generator in recovering the transformed electrical energy. A typical flywheel energy storage system consists of five primary components (Lazarewicz et al., 2006), namely the rotor, the bearings, the motor/generator unit, the vacuum enclosure and the power electronics. A rotor consists of a hub and rim. As the rim is the main rotating mass of the rotor, it is quite easy to comprehend the fact that the rim acts to store most of the energy whereas the hub functions to connect to the rim to a shaft. The rotating flywheel shaft on the other hand is supported by bearings which could either be of the mechanical or magnetic variety. These bearings allow for low resistance to rotor rotation. However, magnetic bearings are preferred over mechanical ones due to the energy loss associated with energy loss. The motor, as the third major component introduced, acts to accelerate the rotor when electrical energy us supplied to it; whereas the generator acts to extract electrical energy from the rotating rotor by decelerating the rotor. This is in accordance with the principle of conservation of energy. As a result of the rotor deceleration, torque is inevitably produced and is typically transferred between the rotor rim and the motor unit via the hub and the shaft. In addition, as the occurrence of input and output events are not concurrent, the combination of the motor and generator into a single functional unit is typically done to the advantages of weight and cost reduction (Hebner et al. 2002). In addition, a low pressure, vacuum environment is maintained via the use of a pressure vessel enclosure, which serves also to support the structural assemblage of the flywheel and bearing system. This vacuum compartment also serves to house all of the rotating components of the flywheel to reduce aerodynamic drag. Other than that, such a compartment is also crucial in protecting the system from catastrophic failure as a consequence of high energy debris. The power electronics on the other hand act as the interface between the motor/ generator unit and that of the electrical power system by converting the input power into a suitable electrical signal for the operations of the motor/ generator unit. Flywheel energy storage devices have the potential to store a higher amount of energy per unit mass than typical chemical batteries. Where design weight is of major concern, and where maximum energy storage is a fundamental necessity, flywheel energy storage systems seem to offer the most appealing capabilities. This is particularly so in space applications where the crucial design weight necessitates the need for a high energy storage capacity in the smallest available size and mass (and thus weight). Other than its high specific energy density, flywheel also possesses superior specific power and when used with magnetic bearings and advanced motor/ generator system, more than 90% of the storage energy can be retrieved, an efficiency far more superior than that if conventional chemical batteries are used where the reclaimed energy constitutes less than 80% of the energy input. In addition, the increment of the amount of energy stored in flywheels can be achieved via the increase of s peed of the rotating rotor while chemical batteries would possibly need some reassembling of the connections from parallel to serial. Flywheels are very effective devices in avoiding unbalanced or oversized design of power systems due to the way they store energy and this is especially crucial in the deliverance of peak power on demand. For instant access to the desired efficiency of energy storage as well as energy required, flywheels repeat the charging and discharging cycle. This process of charging and discharging occurs at a rapid speed as both processes occur in the very same motor/generator. In addition, the flywheel life will not be affected with the large amount of charging and recharging cycles whereas chemical batteries undergoing a similar process will need a replacement after every few years. In addition, flywheel, as a mechanical type of battery, is also tolerant of the extremity of temperatures and as flywheels do not contain acidic and other hazardous material, flywheels are easily handled during manufacturing process, and disposed of at the end of the flywheelsà ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬Ãƒ ¢Ã¢â‚¬Å¾Ã‚ ¢ lif e cycles. Flywheel energy storage systems had since found its way into various applications such as transportation and space satellites, to name a few. In transportation, flywheel systemsà ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬Ãƒ ¢Ã¢â‚¬Å¾Ã‚ ¢ deep recharge and rapid charging capability, the ability to provide high pulses of power as well as the tolerance to a wide operating temperature range as well as the longer operating life on top of weight reduction make flywheel systems an obvious choice in replacing chemical batteries in mobile applications such as electric vehicles. (Hebner et al 2002). A reliable, steady state power quality is of vital importance for critical manufacturing, hospitals, and internet servers. In this context, the flywheel energy storage systems have also found its way into electrical load levelling application such as in ensuring an uninterruptible power supply by providing a smooth and effective transition between a main power source when necessary (Hebner et al 2002) This is one of the current capability of the flywheel and it seems promising that as the technology improves in the near future, flywheel could possibly be applied to peak power managing, where excess energy produced us stored and later released at the peak time in energy consumption. The concept of flywheel is also not novel in the hybrid electric vehicles (HEVs) industry, where small combustion engine is operated while the vehicle is moving at a constant speed. The acceleration process is executed with the extra power provided by the additional battery power supplier. This additional power, on the other hand is generated and stored in the battery when the vehicle brakes such that no additional power is wasted in the form of heat dissipation generated by the friction during brakes. At the present moment, flywheel seems promising in being use for hybrid buses as chemical battery is expensive. In space applications, light weight, compact with high energy density storage capability devices are highly sought after. With increase performance demands on space systems, space programs had had to make consistently huge effort in reducing rim mass to increase payload capacity as well as reduce launch/ fabrication costs. Although chemical batteries had long been a trusted source of energy but flywheel offers much better weight and life benefits as well as the potential to store a larger amount of energy at a lower weight, not to mention the capability to be used as attitude control actuators in replacing reaction flywheel assemblies and control moment gyros. In 2000, Truong et al introduced the Flywheel Energy Storage Demonstration Project, initiated at the NASA Glenn Reasearch Center as a possible replacement for the Battery Energy Storage System on the International Space Station; whereas Fausz et al. had, in the very same year reported that the Flywheel Attitude Control, Energy Transmission and Storage (FACETS) system could combine all or parts of the energy storage, attitude control, and power management and distribution (PMAD) subsystems into a single system, this significantly decreasing flywheel mass (and volume). Thus, in space applications, crucial weight reductions for satellites could, and have hitherto, been achieved with the use of the multi-function high speed flywheel system which not only functions as energy storage but also in providing a gyroscopic effect for attitude control. (Bitterly, 1998, Hebner et al., 2002) But even until recently, the historical development of flywheels and their uses has largely been dependent on advances in both materials and machine technology, coupled with opportunity and necessity (Horner, et al,.1996) However with technological advancements in such a rapid pace, it is not hard to envisage the status of flywheels in the near and distant future. 1.1.3 The Use of Composite and Fiber- Reinforced Materials in Flywheel Design The kinetic energy stored in a flywheel rotor increases linearly with mass but quadratically with rotational speed. . With the increasing demand for high energy storage, flywheels in present applications are often designed for high angular velocities; and these correspond to large centrifugal loads and consequently a higher circumferential and radial stresses, i.e. the dominant stress distribution are hoop stresses (concentric). In this context, the use composite materials with fibers of high unidirectional strength would be desirable. (Shah, 2008) For a fixed axis rotation, the energy stored in a thin rotating ring rotor is [1.3.1] Where I = the rotor moment of inertia ÃÆ' °Ãƒâ€šÃ‚ Ãƒ ¢Ã¢â€š ¬Ã‚ ºÃƒâ€¦Ã‚ ¡ = is the rotor angular velocity. It seems feasible that to increase the stored energy, the mass of the flywheel must be increased and thus its moment of inertia. However, it must be noted that the energy is only linearly proportional to the mass of the flywheel whereas the energy is proportional to the square of the rotational speed. These relations indicate that the rotational speed for a given radius will have a higher influence to the energy density than that of the mass of the flywheel; and to achieve a high rotation speed, a high strength per weight material must be used. Further derivations of the equations below will explain this condition. Resultant force along the hoop and circumferential directions [1.3.2] [1.3.3] Where = force summations in the radial direction = force summations in the circumferential direction dm = mass of the mass element located at radius r rdÃÆ' °Ãƒâ€šÃ‚ Ãƒâ€¦Ã¢â‚¬Å"Æ’ = arc length of the mass element located at radius r ar = radial acceleration of the mass element located at radius r From equation [1.3.3], [1.3.4] With [1.3.5] Where ÃÆ' Ãƒâ€šÃ‚ = mass element density V=mass element velocity B=mass element width Substitute equation [1.3.5] into [1.3.4] and knowing that V=rÃÆ' °Ãƒâ€šÃ‚ Ãƒ ¢Ã¢â€š ¬Ã‚ ºÃƒâ€¦Ã‚ ¡ and for ÃÆ' °Ãƒâ€šÃ‚ Ãƒâ€¦Ã¢â‚¬Å"Æ’ [1.3.6] The tensile stress in the circumferential direction [1.3.7] The stress in a thin- ring rotor is: [1.3.8] It is observed that the maximum speed achievable by a flywheel rotor is limited by the strength of the material from which it is made. The critical speed of the thin ring rotor can be approximated as [1.3.9] Where is the material ultimate strength. From the substitution of equation [1.3.9] into [1.3.1], the specific energy stored in the rim is obtained [1.3.10] K= Flywheel shape factor (Typically 1 for uniform stress disc and 0.5 for thin ring) The dependency of the maximum specific energy stored in the flywheel on the specific strength of the material is thus observed. With the demand for high specific energy in flywheel rotor design, the use of suitable material is thus of paramount importance. Due to their high stiffness to strength, composite materials have successfully been established in flywheel rotor design. Fiber reinforced composites are particularly attractive for use as flywheel materials due to their high strength and low density (Takahashi et al., 2002) The use of composite materials in flywheel designs offer numerous advantages over metallic alloys, including weight and increased strength. This is due to the high tensile strength of the fiber reinforcement phase. In 1986, a composite flywheel rotor was developed by Potter and Medicott for used in vehicle applications. In 1995, the study by Curtiss, et al. shown that the composite Carbon fiber epoxy disc rotor is capable of a 38% higher rim speed or 91% greater rotor energy density than a rotor built of an isotropic high strength to weight ratio Titanium or steel alloys. The carbon fiber reinforced plastic (CFRP) flywheel proposed by Kojima, et al. (1997) shown that high-modulus graphite/epoxy filament wound composite flywheel is able to rotate at a higher speed. The polar woven flywheel by Huang (1999) was shown to possess weight savings features as well as the improvement in life and reliability of the total spacecraft system, and in 2002, the Multi-Direction Composite (MDC) flywheel systems was reported by Gowayed and Flowers. The MDC flywheel system studied employed a new approach to strengthen flywheels with additional reinforcement in the radial direction along with the typical hoop direction reinforcement. In fact, analytical and numerical approaches had over the years been presented to determine the stress, and displacement distribution of the rotor. With the increasing demand for high energy storage, flywheels in present applications are often designed for high angular velocities; and these correspond to large centrifugal loads and consequently a higher circumferential and radial stresses. And the determination of these stresses as well as the ply orientation became especially crucial. As early as 1977, Danfelt et al. published an analytical method for a hybrid multi-rim flywheel with ply-by-ply variation of material properties and based on the assumption of axisymmetry. The method by Danfelt was later extended by Tzeng (1997,2003) which accounts for viscoelasticity effects. In addition, the original method by Danfelt had also been supplemented by a series of researches by Ha with additional consideration of the interference between adjacent rims and varying fiber angles (Ha et al., 1998), the rim radii of numerous material lay- ups for a constant angular velocity (Ha et al. 1999b), residual stresses due to the curing process (Ha et al., 2001) and the subsequent research on a split- type hub (Ha et al., 2006). The effect of rim thicknesses and angular velocity was studied by Arvin and Bakis (2006) while Fabien (2007) studied the optimal continuous variation of fiber angle in a single-material rotor. Other than that, finite element approaches have also been used for stresses and displacement computations which, though computationally more demanding, have gained importance for the analysis and design optimization of flywheel rotors because of the greater modeling depth offer by such methods. It is also possible to assemble the flywheels as a hybrid with rims of different materials in a sequence of increasing ratio of stiffness per density value E/ÃÆ' Ãƒâ€šÃ‚  for increasing radius, r (Arvin Bakis, 2006) using a method called ballasting. From their studies, with circumferential fiber reinforcement, the radial stress distribution is purely tensile with a maximum located approximately in the midplane between the inner and outer radii. But with two-material rotor, the radial stresses turn compressive in the region near the material interface due to the lower stiffness of the inner material which would result in greater expansion. A compressive stress minimum thus exists at the material interface, with two tensile stress maxima found close to the innermost and outermost radius. Despite the increase in circumferential stress level for the outer composite carbon/epoxy rim, such a condition still arises due to the lower radial stresses as a consequent of rotor strength inc rement. After all, composite materials are generally weaker in the transverse direction than in the longitudinal direction. As fiber reinforcement is typically aligned in the circumferential direction, radial tensile stress is often more crucial in comparison with the other mode of stresses due to the weaker strength in this direction. Thus, the dominating stresses are typically those of the circumferential and radial stresses. In this context, much effort had been invested to enhance the efficiency of the composite flywheel rotors by applying stress reduction methods. In view of this method, Danfelt et al. (1997) suggested a sandwich-like rim lay-up with a compliant material between the composite rims of one material to decrease interlaminar stress transmission. 1.2 Literature Review 1.2.1 Interlaminar stresses of Composite Laminates Interlaminar stresses arise when there are discontinuities in the load path, such as free edges and notches. (Wilkins, 1983). In particular, models with a significant amount of curvature. This is because the presence of high interlaminar stresses due to the effect of shell curvature could result in delamination and possibly failure of the laminate at a lower load than that predicted by in-plane failure criteria had they not been properly accounted for. (Edward, K.T., Wilson, R.S. and McLean, S.K. ,1989; Lagace, P.A., 1983) The accurate determination of interlaminar stresses are thus crucial in the design of laminated composite models as the interfacial surfaces of a laminate represent planes of minimum strength (Pagano, N.J. Pipes, R. B., 1973). Classical laminated plate theory (CLPT) was formed in conjunction with the kinetical assumptions of Kirchhoff classical plate theory by assuming a layerwise plane state of stress. However, 2-D CLPT theory alone is not sufficient to explain stress concentration phenomena in various lightweight constructions in aviation vehicle, such as the free-edge effect where full-scale 3-D and singular stress fields occur in the interfaces between two dissimilar layers along the free edges of thermally and/ or mechanically loaded laminates (Mittelstedt Becker, 2003) which decay rapidly with increasing distance from the laminate edge. Such stress localization problems is caused by the discontinuous change of the elastic material properties of the laminate plies at the interfaces and might result in premature failure of the laminate. This is thus an area of concern by designers and much researched has been done since the early 1970s, with the studies initiated by of Pipes and Pagano on the free edg e effects in laminated structures. Early analytic studies were conducted by Hayashi (1967) on edge stress effects consisting of anisotropic plies and adhesive layers transferring interlaminar shear stresses. In early 1970s, Pagano and Pipes also introduced approximation equations for interlaminar normal stresses in the interfaces and was expanded by Conti/ De Paulis in 1985 for the stress- approximation in angle-ply laminates and the calculation of interlaminar stress distribution through the laminate thickness. Whitney simple stress approximations in 1973 did not fulfill the continuity conditions in the interfaces, although Whitney assumption of products of exponential and trigonometric functions did fulfilled the equilibrium conditions and the given traction-free boundary conditions. Researches in the area of free edge effects were also done using various approaches by Tang and Levy (1975) with layerwise series expansion, Hsu and Herakovich (1977) with edge displacement fields in the form of trigonometric and exponential terms, Wang Dickson (1978) with the expansion of the displacement fields into series of Legendre polynomials. However, much discrepancy has been reported. In 1981, series expansions for the stresses in the inner laminate regions and in the vicinity of the free laminate edges by Bar-Yoseph/Pian.CLPT was recovered in the inner laminates with this zero-order approach and unknown parameters obtained by minimizing the laminate complementary potential. The subsequent work by Bar-Joseph used the principle of minimum complementary potential, leading to an eigenvalue problem. The approach used by Bar-Yoseph allowed the continuity of interlaminar stresses in the interfaces as well as the fulfilment of the conditions of traction free surfaces of the laminate. The force balance method by Kassapoglou/Lagace in 1986 and 1987 was developed. Stresses were assumed to consist of layerwise products of in-plane exponential terms and polynomials through the thickness with adjustments done on the thickness terms to satisfy the continuity of all interlaminar stresses in the laminate interfaces and such that they blend into CLPT in the inner laminate regions. Despite its simplicity, the force balance method exhibited good performance even for thick laminates and was thus further explored and refined by other authors. The effects of transverse shear and continuity requirements for both displacements and interlaminar stresses on the composite interface was accounted for by Lu and Liu in developing an Interlaminar Shear Stress Continuity Theory (ISSCT) capable of being used for finite element formulation (Lu, X., Liu, D., 1990). Through that particular theory, interlaminar shear stress could be obtained directly from the constitutive equations. But as the deformation in the thickness direction was neglected during the formulation of the theory, the interlaminar normal stress could not be calculated directly from the constitutive equations. Other than that, a small discrepancy between the results of theirs and that of Pagano elasticity solution in the interlaminar shear stresses small aspect ratios composite laminates was observed (Pagano, N.J. 1969). Although, rigidly bonded laminated composite materials models are always assumed in conventional analysis; but it must be noted that poor bonding and low shear modulus could result in a non-rigid composite interface. As a continuation of the ISSCT, Lu and Liu (1992) later developed the Interlayer Shear Slip Theory (ISST) based on a multilayer approach in investigating the effect of interfacial bonding on the behavior of composite laminates. The Hermite cubic shape functions was used as the interpolation function for composite layer assembly in the thickness direction, and the closed-form solution is obtained for the cases of cylindrical bending of cross-ply laminates with non-rigid interfaces. However, results shown that at some special locations, namely singular points, the transverse shear stress or in-plane normal stress remains insensitive to the condition of interfacial bonding. A closed- form solution was later derived by Lee and Liu (1992) for the complete analysis of interlaminar stresses for both thin and thick composite laminates subjected to sinusoidal distributed loading. The theory was proven to satisfy the continuity of both interlaminar shear stress and interlaminar normal stress at the composite interface and also the interlaminar stresses could be determined directly from the constitutive equations An accurate theory for interlaminar stress analysis should consider the transverse shear effect and continuity requirements for both displacements and interlaminar stresses on the composite interface. It is also advantageous if the formulation is variationally consistent so that it can also be used for finite element formulation. (Kant, T., Swaminathan, 2000) Using the first order shear deformation theory, the interlaminar stresses in laminated composite cylindrical stripes under dynamic loading are studied. Dynamic equations of equilibrium are solved by a combination of Navier approach and a Laplace transform technique. Dynamic magnification factor is calculated for the stresses and deflections for various types of loading and for different values of the geometric parameters. (Bhaskar, K. Varadan, T.K., 1993). Higher order layerwise theorectical framework has been used by Plagianakos and Saravanos (2008) in predicting the static response of thick composite and sandwich composite plates. The displacement field in each discrete layer through the thickness of the laminate include quadratic and cubic polynomial distributions of the in- plane displacements, as well as the linear approximations assumed by linear layerwise theories in addition to the Ritz- type exact solution used to yield the structural response of the thick structure. The formulation has been found to be especially robust in comparison to linear layerwise theory due to the number of discrete layers used to model the thick laminate through thickness and in the prediction of interlmainar shear stresses at the interface. In addition, the theory used also offers a better range of applicability due to the better accuracy offered. Over the years, many papers investigating the effects of interlaminar stresses had been published. The finite difference method with classical elasticity theory was used by Pipes and Pagani for determining the behaviour of finite width laminate in uniform axial strain and where interlaminar stress at the free edge is found to be of a significantly huge amount. Other studies soon ensued such as the perturbation solution techniques by Hsu and Herakovich, the finite difference method using large elements with complex stress field by Rybicki; and Wang and Crossman finite difference method, as well as the approximate analytical solution by Pagano and Wang and Choi. However, all of these studies involve the interlaminar stresses at the free edges of finite composite laminates. It is however, well acknowledged that interlaminar stresses arise such as to satisfy equilibrium at locations with in-plane stress gradients (Saeger, Lagace Dong ,2002), and material discontinuity within a structure is another source of arising in plane stress gradients, and therefore, interlaminar stress appear near the material discontinuities. (Tahani, 2005) Rose/ Herakovich, in 1993, further explore the force balance method of Kassapoglou/Lagace with the introduction of additional terms for the consideration of the discontinuous change of the elastic material properties in the interfaces and which accounted for the local mismatches in Poisson ratio and coefficient of mutual influence between adjacent layers. There are reported improvements in the resultant stress field. However, such improvements are also accompanied with a more demanding computational effort for the minimization of the complementary potential. In a similar study done by Kim/Atluri in 1995, thermal and mechanical loads were analyzed by assumed stress shapes which also accounted for both the local mismatches in Poisson ratio (similar to that of Rose/ Herakvich) and coefficient of mutual influence by applying respective mismatch terms in the stress representations. An approach that agreed to equilibrium demands and the given boundary conditions, the unknown stress functio ns were determined by application of the principle of minimum complementary energy of the laminate. The principle of minimum complementary theory was used by Bhat and Lagace (1994) to evaluate the interlaminar stresses at material discontinuities. In their analytical model, the laminate is formed by the merging of two area

Literature Review Format Essay

Literature Review This packet details the steps necessary to produce a literature review that may be required for work in various disciplines, including English, history and psychology. This packet is not intended to replace instructor guidelines and should not be used in that manner. The packet’s intended use is as a supplement to classroom instruction on assembling a literature review. Therefore, it contains only general information that must be tailored to fit specific guidelines as required by your discipline and by your instructor. This packet is subdivided into six sections: I. General Information States what a literature review is and what purpose it serves. II. Process Gives step-by-step instructions on how to get started on your literature review. III. Organization Explains the two most common ways of arranging information in a literature review. IV. Format Provides descriptions for two of the most common formats used in a literature review, the item to item comparison and contrast (Format A) and the criteria to criteria comparison and contrast (Format B). V. Checklist Allows appraisal of your completed literature review to assure that it follows all necessary guidelines. VI. Resources Lists helpful resources used to compile this packet so that you may obtain further information. General Information Definition Literature reviews can have two roles: In their first role, they function as a stand-alone paper. At other times they will actually be part of a larger research thesis. In this handout, literature reviews will be referred to in the stand-alone sense. As a stand-alone paper, literature reviews are multi-layered and are more formal and detailed than book reviews. As the author of a literature review, you must become familiar with a large amount of research on a specific topic. You will then develop your own thesis about the topic related to this research. After this, you will classify and critically analyze research on the topic by making a comparison between several different studies and by emphasizing how these studies and their comparison relate to your own thesis. In effect, a literature review is a paper that compiles, outlines and evaluates previously established research and relates it to your own thesis. It provides a context for readers as if they  Email at tutor@uhv. edu University West, room 129 (361) 570-4288 were researching the topic on their own. Just from reading your paper, readers should be able to gain insight into the amount and quality of research on the topic. Your thesis and the literature reviewed serve several important functions within the paper: †¢ Your thesis creates a foundation for the literature review because it helps narrow the topic by providing a sense of direction; however, you will have to conduct some initial research and reading before deciding on an appropriate thesis. Your personal thesis may be a statement addressing some of the following situations: â€Å"why your research needs to be carried out, how you came to choose certain methodologies or theories to work with, how your work adds to the research already carried out† (Brightwell, G. and Shaw, J. , 1997-98), or it may present some other logical perspective. †¢ Reviewed literature is organized in a logical manner that best suits the topic of the review and the hypothesis of the literature (see Organization and Format). The selected method of organization and style of format should draw attention to similarities and differences among the reviewed literature; these similarities and differences are based on specific criteria you revealed in the literature review’s introduction. According to Brightwell and Shaw (1997-98), your goal in the body of the review â€Å". . . should be to evaluate and show relationships between the work already done (Is Researcher Y’s theory more convincing than Researcher X’s? Did Researcher X build on the work of Researcher Y?) and between this work and your own [thesis]. † Additional information on these topics can be found in the Organization and Format sections of this packet. Therefore, carefully planned organization is an essential part of any literature review. Purpose Although literature reviews may vary according to discipline, their overall goal is similar. A literature review serves as a compilation of the most significant sources on a subject and relates the findings of each of these sources in a rational manner while supporting the literature review author’s own thesis. A literature review establishes which sources are most relevant to its author’s point and which sources are most credible to the discipline at hand. In a literature review, the results of previous research are summarized, organized and evaluated. Discipline-Specificity A literature review’s organization, format, level of detail and citation style may vary according to discipline because different disciplines have different audiences. Examples here pertain to the natural sciences, social sciences and humanities. †¢ Natural and social sciences The author of a literature review in the natural or social sciences must pay close attention to measurements, study populations and technical aspects of experimental findings. Typically, a portion of the natural or social sciences literature review is set aside for reviewing sources on the primary topic. Then, a comparative analysis or discussion section is used to analyze the similarities and differences among the sources, tying them in with the literature review author’s original thesis. †¢ Humanities The author of a literature review in the humanities usually does not set aside a special section for reviewing the sources; instead, citations may be found randomly throughout the paper. The literature being reviewed is arranged according to paragraphs based on the author’s points, which in turn, support the author’s thesis. The paper itself may not be called a literature review at all. It is more likely to be called a critical analysis. Remember that the best bet for determining what type of literature review is appropriate for your course is checking with the instructor prior to beginning research. Email at tutor@uhv. edu University West, room 129 (361) 570-4288 REVIEW 1. What is the purpose of a literature review? What is the connection between the author’s thesis and the literature being reviewed? 2. What discipline will your literature review be classified in? Process 1. Find several articles that deal with your research topic. Sometimes it is helpful to review the bibliography of one of the first scholarly sources that you encounter and compare it to the bibliographies of other sources on the topic. If the same source is listed within several of these bibliographies, it is probably a fundamental, credible source that will aid you in your review. 2. Before you begin reviewing literature, realize that you are looking to accomplish two things: A. Defining your research problem/thesis (examples: finding a flaw in research, continuing previous research, etc . . . B. Reading and evaluating significant works that are relevant to your research problem. You will be conducting Steps A and B simultaneously because the two form a circular pattern. As you read related sources (Step B), you define your problem, and as you define your problem (Step A) you will more easily be able to decide what material is relevant enough to be worthy of reading (Step B). 3. Once you begin reviewing, make an entry with complete bibliographical information and comments for each work that you are going to include in the review. 4. Compare the articles by evaluating the similarities and differences among them. This will be the initial stage in the formulation of your thesis. 5. Form a thesis that is clearly written and can be logically supported by the literature you will include in your review. 6. View the articles briefly again and jot down any notes that seem to relate to your thesis. 7. Decide which organizational pattern and format are best for the topic of your review. 8. Construct an appropriate outline for the literature review. 9. Write an introduction that introduces the topic, reveals your thesis statement, and arranges key issues. 10. Organize and write the body of your paper according to the appropriate format: topical or chronological. 11. Write a conclusion that reconciles similarities and differences on the topic and reemphasizes the criteria used to arrive at this conclusion. 12. Complete the final draft of the literature review. Email at tutor@uhv. edu University West, room 129 (361) 570-4288 13. Check over the final draft for grammar and punctuation errors. 14. Use the checklist provided here to make sure that all parts of the literature review are addressed and focused. Establishing a Critical Response for a Literature Review You may find this section helpful at Steps 3, 4 and 5 of the process. When reviewing your sources, explore the following areas to help develop your critical response: What is the purpose of the research or work? What research or literary methods are used? How do the major concepts operate? In a research study, how accurate are the measurements? In a literary work, is the author’s position objective or biased? What are the different interpretations of the results of the study or of the literary work itself? REVIEW 1. What do you consider to be the most crucial step(s) in the process of your literature review? Why? Justify your response(s). Organization A literature review can be arranged either topically or chronologically. Topical organization occurs in reviews where previous research being evaluated is divided into segments with each one representing a part of some larger issue. In a topical review, the author begins by describing the characteristics of research shared by several studies and then moves on to analyze their similarities and differences. For more information, see the example below. Example The organization of a literature review begins in the introduction. For example, in the introduction of a literature review about the effect of seating arrangements on peer tutoring communication, you would first introduce the topic and what your literature review will attempt to assess: †¦Writing centers can set the table for collaborative tutoring sessions through a careful consideration of spatial arrangement . . . Then state what angle is going to be explored: †¦These studies will be used to support the author’s claims that spatial arrangement is instrumental in encouraging collaborative environments in the writing center†¦ Then, arrange key issues that will be addressed in this review by answering questions that you have personally developed and are tailored to fit your topic. In the introduction, give the audience a clear picture of how you will organize your paper: Email at tutor@uhv. edu University West, room 129 (361) 570-4288 In the following, I1 first review some relevant research concerning spatial arrangement and then discuss some recommended and alternate seating arrangements to encourage a collaborative environment in the writing center. Finally, I include some other considerations. In the body of this literature review, you would organize the information topically around each point (or question) that you asked yourself: -Research Review -Recommended Spatial Arrangement -Alternative Spatial Arrangement -Other Considerations. Then, write a conclusion that explains the significance of your findings: †¦While the seating arrangements outlined above are generally a good ‘setting’ for peer tutoring sessions, we should remember that each tutoring session is unique. Not all students will be comfortable with a side-by-side spatial arrangement at a round table. Tutors should be perceptive of and receptive to students who may have other spatial needs†¦ Chronological organization occurs when a review is organized in time order and is most often used when a historical context is needed for discussing a topic from its beginning to its current state; chronological organization is  especially helpful when discussing inactive periods and shifts in perspective on a given topic. Example The organization of a literature review begins in the introduction. For example, in the introduction of a literature review entitled Development of Social Science Research on Attitudes Towards Gender in America, you would first introduce the topic and what your review hopes to assess: †¦This literature review will assess the development of research designed to uncover gender attitudes in America during the latter part of the 20th Century†¦ Then state what angle is going to be explored: .. As research progressed throughout the 20th century, the methods that social scientists use for measuring these attitudes developed and changed as well†¦ Then, chronologically arrange issues that will be addressed in this review: Gender stereotypes still exist today, and varying attitudes can be traced over the past fifty years. Survey instruments used to gather data on these varying attitudes have also changed drastically over the course of time. In the body of this literature review, you would organize the information chronologically, adressing each point (or question) that is being asked for a particular time period: -Stereotypes and Survey Instruments of the 1950’s -Stereotypes and Survey Instruments of the 1960’s -Stereotypes and Survey Instruments of the 1970’s -Stereotypes and Survey Instruments of the 1980’s -Stereotypes and Survey Instruments of the 1990’s -Current Advancements Always clear the use of I with your instructor. An alternative to this would be the use of third person wording, such as â€Å"This paper reviews some relevant research concerning spatial arrangement and then discusses some recommended and alternate seating arrangements to encourage a collaborative environment in the writing center. † 1 Email at tutor@uhv. edu University West, room 129 (361) 570-4288 Then, write a conclusion that explains the significance of your findings: Although the survey instruments used in the 1950’s and 1960’s developed an obvious bias when surveying Americans regarding gender attitudes, the 1970’s brought about great change. Today social scientists are more careful than ever about testing the quality of a survey instrument before using it on the general public. Format There are also two suggested formats for composing your literature review. Format A is used when comparing several studies that have similar hypothesis but different findings. Each piece of research is summarized individually. Format A is good for reviews with a small number of entries; however, this format may confuse the audience when used with a large number of reviews because descriptions of so many studies may get in the way of the analysis. Keep in mind that each piece of research usually will not receive equal attention in the review. Format A Outline I. Introduction consists of four parts that are usually discussed in one paragraph. a. Identify the general topic being discussed. b. Mention trends published about the topic. c. State thesis establishing the reason for writing the literature review. d. Explain criteria by giving a description of each of the criteria used in evaluating the literature review and rationalizing its organization II. Literature reviewed section is divided up according to study. a. First study is summarized and discussed. b. Second study is summarized and discussed. c. Third study is summarized and discussed. III. Comparative analysis acknowledges the similarities and differences between studies. a. Similarities (if any) among the studies are evaluated and discussed. b. Differences (if any) among the studies are evaluated and discussed. IV. Conclusion/Summary effectively wraps up the review. a. Summarize points of comparison or contrast among the works based on Section III of your review. b. Provide insight of relationship between the topic of the review and a larger area of study such as a specific discipline or profession Format B  organizes the literature review according to similarities and differences among research rather than by literature studied. In a review organized according to Format B, little background information on the literature being reviewed is given outright. Instead, it is worked into the body paragraphs of the sections on similarities and differences. The conclusion then uses these two sections (similarities and differences) to tie in points of comparison and contrast between the works. Format B better suits papers that are topically organized. Format B is outlined below. Email at tutor@uhv. edu University West, room 129 (361) 570-4288 Format B Outline I. Introduction consists of four parts usually discussed in one paragraph. a. Identify the general topic being discussed. b. Mention trends published about the topic. c. State thesis establishing the reason for writing the literature review. d. Explain criteria by giving a description of each of the criteria used in evaluating the literature review and rationalizing its organization II. Similiarities within the research are discussed. a.  First similarity among research is discussed. b. Second similarity among research is discussed. c. Third similiarity among research is discussed. III. Differences in the research are discussed. a. First difference between research is discussed b. Second difference between research is discussed c. Third difference between research is discussed IV. Conclusion/Summary a. Summarize points of comparison or contrast between the works. b. Provide insight into relationship between the topic of the literature and a larger area of study such as a specific discipline or profession. The most important thing to remember when organizing a literature review is that it is not a list summarizing one work after another. The review should be organized into sections according to theme that are set apart by subject-related headings. REVIEW 1. Which format have you chosen for your literature review? Why? A Literature Review Checklist: Did I . . . . . . ? ? Establish a valid thesis based on the examined research ? State this thesis clearly in my introduction ? Define unfamiliar terms ? Incorporate background information to define the problem ? Begin each entry in the review with a complete bibliographical reference ? List and describe the hypothesis/thesis in each work reviewed Email at tutor@uhv. edu University West, room 129 (361) 570-4288 ? Describe the outcome of the work or the research ? Develop and incorporate my own comments, including response to the research, similarities and differences among literature reviewed, and reservations regarding author’s methods or conclusions ? Avoid overquoting ? Check for grammar and punctuation errors ? Correctly cite all references in uniform documentation style Resources Brightwell, G.  and Shaw, J. (1997-98). Writing up research. Retrieved August 20, 2002 from Languages and Educational Development at the Asian Institute of Technology’s Web page at http://www. languages. ait. ac. th/EL21OPEN. HTM Central Queensland University Library. (2000). The literature review. Retrieved July 22, 2003 from http://www. library. cqu. edu. au/litreviewpages/ Cuba, L. (2002). A short guide to writing about social science. New York: Addison-Wesley Publishers. Leibensperger, S. (2003). Setting the table: Encouraging collaborative environments with spatial arrangement in the writing center. Unpublished literature review. Northern Arizona University. (1999). Electronic textbook – A blast from the past: Your literature review. Retrieved May 30, 2002 from http://jan. ucc. nau. edu/~mid/edr720/class/literature/blast/reading21-1. html Taylor, D. , & Procter, M. (2001). The literature review: A few tips on conducting it. Retrieved June 17, 2002 from http://www. utoronto. ca/writing/litrev. html Trinder, L. (2002). Appendix. The literature review. Retrieved August 27, 2003 http://www. uea. ac. uk/~w071/teaching/ppf/Appendix%20Lit%20Review. pdf The University of Wisconsin-Madison Writing Center. (2001). Academic writing: Reviews of literature. Retrieved May 30, 2002 from http://www. wisc. edu/writing/Handbook/ReviewofLiterature. html *In traditional APA style, this section would be entitled â€Å"References† and would be listed on a separate page double-spaced. Due to space constraints in this packet, it has been formatted differently. Copyright 2003 by the Academic Center and the University of Houston-Victoria. Created 2003 by Candice Chovanec-Melzow. Email at tutor@uhv. edu University West, room 129 (361) 570-4288.

The Revolution Of The United States Government - 1010 Words

Based on the information provided to me from the text, and my own personal thoughts, I am a firm believer that we are in a revolution at this day in age, and will always continue to be in a revolution so long as the human race is here. I believe that being human, means you’re always changing and society is always revolving. As there are countless revolutions occuring at this time... I will like to state a few that I have personally witnessed. These are: a political revolution, describing the never ending changes in the United States Government; and a cultural revolution, a fairly old revolution that has been gaining momentum in the past few decades. As stated in the text, a revolution is ironic! There will ALWAYS be a problem; as one is†¦show more content†¦As time continued, this battle played on every 4 years during each presidential election. Today, we see this 200 year old revolution still continue in the 2016 election and now. The Republicans (Trump), wanted a weaker government where taxes were reduced and many government programs were defunded. He wanted to emphasize greater security by bumping up our Department of Defense spending and banning refugees from Muslim dominate countries. The Democrats (Clinton) emphasized a strong central government, where taxes were raised. They leaned more towards freedoms, instead of securities. They wanted to continue to defund our military spending and fight for civil issues such as DAPL, Pro-choice on Abortions, and etc. We as a nation went from a government controlled mostly by Democrats a few years ago, to a government being controlled by Republicans. Even as the election has passed, and recorded in history, the turmoil of the recent changes have only begun. However, this is what our government was set up to be, so that no matter how much we change†¦ how much the people’s perspectives change, we will still have a foundation of human rights and ethics that is unaimiously aggreed upon to keep America going. Another revolution that has been around since the reign of King Kamehameha II (Liholiho), is a cultural revolution. A revolution, that has been both violent and peaceful, causing lots ofShow MoreRelatedWhat Factors During The Colonial Period Essay1636 Words   |  7 PagesEmpire? Be sure to discuss the economic, political, and cultural aspects of the American Revolution. PROVISIONAL HYPOTHESIS: The structure of America revolution to address a various issue, which has great impact on America It, was the procedure where the thirteen colonies of North America became independent of Great Britain also then formed a new integrated government. The major reasons of America revolution are cultural, economic and political. 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Michigan Urban Farming Initiative Is an Urban Agrihood the Answer to Food Insecurity - Free Essay Example

Sample details Pages: 10 Words: 2946 Downloads: 9 Date added: 2019/02/15 Category Health Essay Level High school Topics: Food Insecurity Essay Did you like this example? While urban farming has a long history, both in the US and globally, there appears to have been a resurgence, as urban populations become more interested in local food production. Not limited to quaint community farms or small backyard projects, it often comes with lofty dreams of a self-reliant, fully sustainable city. Urban farms have environmental, health, and social benefits, but perhaps the most encouraging of these is the promise of increasing access to healthy food. Don’t waste time! Our writers will create an original "Michigan Urban Farming Initiative: Is an Urban Agrihood the Answer to Food Insecurity" essay for you Create order Detroit is one city in which urban agriculture has a long history. Community gardens have been operating there for a long time, even though they were legalized only recently in 2013 (21). An estimation by Keep Growing Detroit states the city is home to approximately 1,500 gardens and farms of varying scales (4). These farms often work in tandem with each other to provide their neighborhoods with access to local, healthy produce. The Michigan Urban Farming Initiative (MUFI) is one of the largest nonprofit farms in the city, promising to fix both food scarcity and blighted or vacant land. MUFI differs from other farms in the area, due to the fact that their central focus is development and neighborhood development, centered around their 3-acre farm. MUFI was founded in 2011 and is run primarily by Tyson Gersh in order to provide the neighborhood with low-cost produce, and to reduce blight by increasing green space (16). They hope, in doing this, they will be able to decrease vacant land and food insecurity (8). Gersh worked in tandem with community leader Dolores Bennett, the founder of the North End Youth Improvement Council, until her death in early 2017 (10, 20). It is readily apparent why such a project is needed in the city, as Wayne County is â€Å"the most food insecure county in Michigan† and is considered by many to be a food desert (4). Urban food deserts are defined by the American Nutrition Association as an area where â€Å"at least 33% of the census tract’s population reside[s] more than one mile from a supermarket (7).† The Detroit Food Policy Council recently found that 30,000 people in the Detroit area don’t have access to healthy food, and 48% of households are food insecure. There are â€Å"74 full-line grocery stores operating within the city limits† but there are still gaps in accessibility (5). A large part of this is probably due to the fact that approximately 25% of Detroit households are car-less, making them largely transit-dependent. This is significantly higher than the national average of 8.7% (6). In addition, urban decay is a continual problem in the city of Detroit. One report from the Detroit Blight Removal Task Force states that approximately 40,000 land parcels (of the 380,000 surveyed) meet the definition of blight, with an additional 38,429 labeled as â€Å"at risk† of becoming blighted. 98% of these properties are located in residential districts (22). The community as a whole might benefit from a large urban farm, especially a volunteer-run nonprofit that prioritizes low prices. It also has great appeal to new, young homebuyers who, along with being attracted to low housing prices, close proximity to transit, and in-town location of the North Side, are increasingly invested in locally sourced, organic food. Other community gardens in the area, howeve r, might find it difficult to keep up with the competition, especially given that MUFI is largely volunteer-driven and gives away free produce to over 2,000 households (13). It becomes clear that urban farming is a movement that has a far-reaching impact, and that MUFI does not exist in a vacuum. MUFI’s main purpose is redevelopment centered around agriculture. They address food insecurity by prioritizing a â€Å"pay-what-you-can† model, while also providing to local markets, churches, restaurants, and food pantries. Over 50,00 pounds of produce have been produced since its founding in 2011. It is almost entirely volunteer-run, and a large amount of those volunteers are from outside of the community. In addition to production farming taking up 1/3 of the campus, the 3-acre land includes a high-density fruit orchard, a children’s interactive garden, rainwater collection/irrigation system, and a public composting toilet. The rainwater retention pond, in particular, is promising, especially as farming has a heavy water requirement. A vacant building on the lot is being converted into a community resource center, for administrative purposes, production/packaging, and a marketplace space open to the public Perhaps their most ambitious project is shipping conta iner homes. Currently, only one is under construction, which is intended for an on-site, full-time intern, but Gersh aims to scale up the project, providing affordable housing ownership to low-income households within the community (8). While it is worth noting that many people within the community express enthusiastic support for the organization and its mission, there are still numerous criticisms from people within the North Side community, as well as from other farmers in the city of Detroit. Gersh’s free produce model is frequently criticized, partly because it is enabled by donations from companies like BASF and MiracleGro, which some say is counterproductive to sustainable, organic agriculture. Another source of criticism is that MUFI is able to sustain their free produce model because it is largely driven by corporate volunteers outside of the community, in lieu of creating steady jobs for those in North End. In this way, it can be argued that giving away free produce is merely a band-aid for the problem of food insecurity, while neglecting to address the root causes and support the long-term resiliency of the community. In the words of Shane Bernardo, a long-time resident, social justice activist, an d former farmer in Detroit, â€Å"food security and poverty have less to do with access and more do with structural and historical disparities around power.† Another frequent criticism is that MUFI focuses on development rather than food scarcity. North End has become one of Detroit’s â€Å"up and coming† neighborhoods, with property values rising and younger, whiter homeowners moving in. By definition, an â€Å"agrihood† is only sustainable for the immediate surrounding housing developments. An in-town neighborhood close to transit is already conducive to gentrification, and some long-time residents argue that Gersh, who arrived in North End only 7 years ago, is accelerating it. Gersh is transparent about targeting young, comparatively wealthy homebuyers from out of town in order to further develop the neighborhood, and he has reportedly tried to get long-time homeowners to sell their properties (10,13). Another controversy surrounding Gersh is his staunch disapproval of the Vanguard CDC (10), which is constructing a swath of multi-family, mixed-income housing in the North End (37). He has done so without proposing an alternative solution for affordable housing, and this has earned him further disfavor among residents who are proponents of the Vanguard project. A more practical problem is the fact that MUFI only owns about 1.5 acres from private sales or foreclosure auctions. The other 2.5 acres are government-owned, making Gersh a prime example of the homesteading that is rather common in urban farms. This could cause problems in the future, as the city desires denser construction or projects that provide more jobs to the community. If Gersh can no longer find vacant properties to steward, it might be difficult to continue the acreage-intensive project that is farming (10). In order to find solutions, it might be helpful to see how other urban farms address these problems, and Detroit has no shortage of alternative urban farming models. One of the most prominent voices in the field is Malik Yakini of D-Town. The 7-acre farm was founded in 2006 by the Detroit Black Community Food Security Network (DBCFSN), of which Yakini is a chairman. Perhaps the most notable thing about Yakini and his projects is the focus on social justice. He seeks to â€Å"identify and alleviate the impact of racism and white privilege on the food system,† and has drafted food security policy to do just that (17, 23). Another project, Oakland Avenue Urban Farm, headed by Jerry Hebron is a community-based farm is a project of the Northend Christian Community Development Corporation (CDC). Along with its food production and hoop houses, it consists of a farm-fresh convenience store and arts venue, as well as a community dining hall/hostel being converted from a vacant building (9). Oakland Avenue is just one branch of the community-focused entity that is Northend Christian CDC, which also oversees afterschool programs and skill development for youth in the area (29). Other farms put collaboration at the center, with the City Commons Community Supported Agriculture being the prime example in Detroit. The City Commons consists of seven participating farms throughout the city of Detroit. Members of the community support the farm by purchasing â€Å"shares,† giving them access to a weekly box of fresh produce throughout the growing season. They also accept EBT, a viable alternative to MUFI’s free produce model (27). Some urban agricultural models veer even further from the traditional idea, however. For instance, Hantz Woodlands, a for-profit organization, is taking a different approach to greenspace by focusing on beautification rather than food production. Their mission is to reduce blight by planting forestry which they will eventually be able to harvest for timber. CEO John Hantz has invested over $1 million to demolish abandoned buildings, as well as provide entrepreneurship and vocational training (26). The significant thing about Hantz’ beautification plan is that it is centered around improving property values for existing residents, rather than those looking to move into the area, and thus has garnered significant community approval. It is worth noting, however, that the land grab that allowed Hantz to purchase approximately 140 acres of land is looked at rather unfavorably by black farmers in the area who have historically had a difficult time gaining ownership of the land they farm. Hantz and Gersh are sometimes put into the same category, as out-of-touch outsiders who don’t reflect the needs and desires of the city as a whole. A more high-tech approach to food production is found in Green Collar Foods (GCF). GCF operates indoor vertical farms in places such as Detroit, Florida, and Northern England (28). It might also be helpful to look at the effect other â€Å"agrihoods† have had on their respective cities. Most developments are located in rural areas, making comparison difficult, but there are a few located in cities, though certainly none are as large or as ambitious as MUFI. Gateway Heights is one such development located in the southern side of Macon, Georgia. The project’s aim is primarily to remove blighted parcels and increase greenspace, as well as provide fresh produce to locals (34). While Macon might not be the hotspot for gentrification that larger cities are, it is still apparent from walking the streets of its in-town neighborhoods that it has become one of Georgia’s trendy cities. Agritopia is an example of a more fully developed agrihood, located in Gilbert, Arizona, in the southeastern side of the Phoenix metro area. Gilbert was once primarily an agricultural town, and their agrihoods appears to hearken back to these roots. Agritopia is transpa rently marketed as an upscale living community, with fresh, local produce as the biggest drawing factor. Homes sell for upwards of $300,000, and the website boasts a â€Å"connected† community, conjuring up images of Mayberry, a small town feel amongst luxury condominiums (32). The town of Gilbert has a median income nearly double that of Phoenix (31), so it is unlikely that the food produced in the agrihood is going to address real problems of food insecurity. It seems this model of community living might be here to stay, with Forbes even suggesting that agrihoods might be the millennial equivalent of golf course communities (36). Taking these examples into account makes it easier to see what MUFI can do to better assist its community. Perhaps the first thing that needs addressing is the way Gersh presents himself to the public. Certainly, the words, â€Å"I want to be Elon Musk when I grow up† don’t exactly inspire confidence in a city with a 34.5% poverty rate, 22.2% higher than the national average (10, 30, 31). Being located in Detroit means having an in-depth knowledge of the social and racial dynamics is essential to responding to the needs of the community and being a white outsider from Ann Arbor means treading carefully. A quick Google search of farming in Detroit shows MUFI being covered as at the forefront of the city’s agricultural scene, but a look at the history of â€Å"guerilla gardening† shows a vastly different picture. Local residents have been farming on vacant city properties since before it was legal, says Jerry Hebron of the Oakland Avenue Farm (10). Even now, local black farmers have a significantly more difficult time owning land and keeping their farms afloat than newcomers like Gersh. A prime example is Marc Peeples, a local gardener who tends to vegetables such as kale and radishes in the near-abandoned Hunt Playground in Detroit. Peeples was arrested after numerous police calls were made from white neighbors, accusing him of crimes ranging from vandalism to sexual assault. While it was eventually tossed out by the judge, his case stands testament to the racial inequity that remains in urban agriculture (33). While part of the reason that MUFI has been covered as particularly groundbreaking falls on the press coverage it has received, Gersh tends to not acknowledge the great work being done by long-time residents to address the existing community’s needs. Additionally, asking residents to sell their properties gave him a less-than-favorable reputation in the North End. Citizens there might be looking for a change, but blatant displacement likely isn’t the change they’re looking for. It is also clear that simply giving away produce is not enou gh to fix the problem of food insecurity that is largely a product of intentional disinvestment in the city of Detroit. Selling their food would be a small step but might enable MUFI to hire a small group of employees. Urban agriculture is rarely a large job creator, but it is surely better to do something on a small scale than to do nothing. Even without job creation, revenue from produce could enable them to provide resources to the community such as vocational training or after school programs. Their shipping container home is promising, but without the revenue to back it up, it seems their plan for development and revitalization lacks an affordable housing solution. A public timeline might be helpful in inspiring confidence within the community. Collaboration is another area in which it would benefit MUFI to improve. Many local farms, including the Oakland Avenue Farm, are working together to achieve a final goal of growing â€Å"two percent of the produce that’s consumed in the city (10).† MUFI has a massive production farming campus with the potential to do a significant amount of good if they turned their efforts to the city as a whole, rather than to the immediate surrounding housing development. The logistical issues of not owning the land, however, might not be as easily fixed as a bad reputation. Informal homesteading has played a large role in the history of urban farming, as local gardeners have been tending to plots of vacant land since before the l egality of it became clear. However, the possibility always exists that the city of Detroit might want to use that land for different kinds of development, and this could leave the future of MUFI uncertain. As the home values in the North End rise, it is possible that the city might prefer the higher revenues and greater number of jobs brought by retail establishments. This scenario has played out with other local farms before, and the result nearly always favors the larger, more profitable development. Perhaps the most disturbing aspect of this project, however, comes to light when we compare it to other agrihoods, such as Gilbert’s Agritopia. The very model itself, of building a community around agriculture, seems like a breeding ground for gentrification. Where other farms and community gardens seek to provide food to the existing population, MUFI appears to be attracting out-of-towners to a trendy, up-and-coming neighborhood where they can get locally grown, organic produce. Such development might work for wealthier towns and suburbs, but it is unlikely to do much for the North End other than displacement. The success of the redevelopment model is dependent on its ability to bring in new people. Other areas which have seen agriculture-centered development differ greatly from North End. Often, they are more rural, or at least suburban, than North End. They also tend not to have the same existing history of community farms, nor the same racial dynamics as Detroit. Whether t he area will become one of upscale houses and condominiums is yet to be seen, but property values continue to rise. It would be unfair to blame it entirely on Gersh’s enterprise, as the natural cycle of a neighborhood often includes some level of gentrification. It is possible for MUFI to remain a net positive force in the community, in my opinion, if they can revise their mission to put existing residents at the center of their redevelopment, and if they cease being active opposition to Vanguard and other organizations who seek to secure affordable or mixed income housing in the area. To sum up, focusing on neighborhood â€Å"revitalization† is unlikely to solve the problem of food insecurity. While attracting young homebuyers to the area might bring a Whole Foods or trendy fresh-produce eateries to the area, it is unlikely to bring affordably priced fresh foods into the city on a large scale. Fresh, healthy food is a great need in the North End, and the nonprofit has great potential to do good. However, as it stands now, the food produced might not continue to benefit existing residents. In order to do this, MUFI will have to shift its focus to collaboration with established, locally-owned farms, rather than property development wrapped in a shiny agricultural package.