No description available.

This dissertation considers sheltering network planning and operations for natural disaster preparedness and responses with a two-stage stochastic program. The first phase of the network design decides the locations, capacities and held resources of new permanent shelters. Both fixed costs for building a new permanent shelter and variable costs based on capacity are considered. Under each disaster scenario featured by the evacuee demand and transportation network condition, the flows of evacuees and resources to shelters, including permanent and temporary ones, are determined in the second stage to minimize the transportation and shortage/surplus costs. Typically, a large number of scenarios are involved in the problem and cause a huge computational burden. The L-shaped algorithm is applied to decompose the problem into the scenario level with each sub-problem as a linear program. The Sheltering Network Planning and Operation Problem considered in this dissertation also has a special structure in the second-stage sub-problem that is a minimum cost network flow problem with equal flow side constraints. Therefore, the dissertation also takes advantages of the network simplex method to solve the response part of the problem in order to solve the problem more efficiently. This dissertation investigates the extending application of special minimum cost equal flow problem. A case study for preparedness and response to hurricanes in the Gulf Coast region of the United States is conducted to demonstrate the usage of the model including how to define scenarios and cost structures. The numerical experiment results also verify the fast convergence of the L-shaped algorithm for the model.

In this thesis we study two reaction-diffusion models that have been used to analyze the existence of alternate stable states in ecosystems. The first model describes the steady states of a logistic growth model with grazing in a spatially homogeneous ecosystem. It also describes the dynamics of the fish population with natural predation. The second model describes phosphorus cycling in stratified lakes. The same equation has also been used to describe the colonization of barren soils in drylands by vegetation. In this study we discuss the existence of multiple positive solutions, leading to the occurrence of S-shaped bifurcation curves. We were able to show that both the models have alternate stable states for certain ranges of parameter values. We also introduce a constant yield harvesting term to the first model and discuss the existence of positive solutions including the occurrence of a Sigma-shaped bifurcation curve in the case of a one-dimensional model. Again we were able to establish that for certain ranges of parameter values the model has alternate stable states. Thus we establish analytically that the above models are capable of describing the phenomena of alternate stable states in ecological systems. We prove our results by the method of sub-super solutions and quadrature method.

縄文時代早期末に出現した玦状耳飾をはじめとする「縄文玉製品」の諸様相を分析することによって、日本列島固有の文化であると強調されがちな縄文文化に、中国大陸の新石器時代の文化に起源がある要素の存在を明らかにした。それと同時に、縄文玉製品が他の文化要素と融合し、汎列島的に展開していることから、縄文文化の枠組みを示すような重要な要素であることも示した。 / 博士(文化史学) / Doctor of Philosophy in History / 同志社大学 / Doshisha University

This master thesis treats the numerical simulation of shaped charge jets and its fragmentation process. Shaped charges is a method to concentrate the effect of an explosive charge and penetrate deeply into a target due to a the formation of a jet with great penetration capabilities. The jet's penetration capability is limited by the eventual axial breakup and an understanding of the fragmentation process is great importance.  A literature review on the existing methods for studying the fragmentation process is presented. A physical model and its governing equations are thereafter derived based on the review. A Lagrangian approach is used to model the jet and equations based on conservation laws coupled with a constitutive relationship yielding a system of nonlinear partial differential equations.  Moreover, an analysis of the well-posedness of a simplified problem is investigated and its derived conditions are consistent with the physically expected. The flight and initial breakup of the jet is then studied numerically by employing a method of lines. The implemented numerical model's stability is investigated empirically and the theoretically expected rate of convergence is confirmed. The theoretical conditions for well-posedness are also confirmed numerically.  The derived model and its implementation is tested for a real charge and its results are compared with and found consistent with more advanced simulations. Furthermore, the jets physical properties are also investigated and the existence of a critical wavelength is shown.  The resulting model and its implementation is capable of calculating position, velocity and geometry at fragmentation. It can also be used to investigate the calculated fragmentation's dependency on different parameters and constitutive equation. The numerical simulation can therefore be used to increase the understanding under which conditions the jet breakup and which material- and geometry properties that dominates the rate in the fragmentation process. Possible future use is also as the foundation of a tool that can be used to evaluate analytical models. / Detta masterexamensarbete behandlar numerisk simulering av riktad sprängverkans fragmenteringsprocess. Riktad sprängverkan är en metod för att koncentrera verkan från en sprängladdning och tränga in ett mål genom att en stråle med hög penetrationsförmåga bildas. Strålens penetrationsförmåga är begränsad av en förekommande axiell uppdelning, således är fragmentationsförloppet av stor betydelse.  En litteraturstudie om de existerande metoderna för att studera fragmenteringsförloppet presenteras. Utifrån studien erhålls en fysikalisk modell med korresponderande styrande ekvationer. En Lagrange formulering används för att modellera strålen och konserveringsekvationer i kombination med en konstitutiv ekvation leder till ett högre ordningens system av partiella differentialekvationer.  Vidare utförs en rättställdhetsanalys för ett förenklat problem och de härledda villkoren överensstämmer med det fysikaliskt väntade beteendet.  Strålens utsträckning och fragmentering simuleras sedan numeriskt genom att använda en semidiskretisering och lösa de uppkomna ordinära differentialekvationerna. Den numeriska lösningens stabilitet testas empiriskt och den teoretiska förväntade konvergensordningen bekräftas. De teoretiska rättställdhetsvillkoren testas även i den numeriska simuleringen och bekräftas.  Den härledda modellen och dess implementering testas även för en riktig laddning och resultaten jämförs och bedöms tillfredsställande med en mer avancerad simulering. Därtill undersöks hur stålens konstitutiva relation påverkar fragmenteringsprocessen och det påvisas även en kritisk våglängds existens. Den resulterande modellen och dess implementation kan beräkna strålens position, hastighet och geometri vid fragmentering. Vidare kan den användas för att för att undersöka hur olika parametrar samt konstitutiva ekvationers form påverkar den beräknade fragmenteringen. Eventuell framtida användning kan även vara grunden för ett verktyg som används för att undersöka analytiska metoder.  Ytterligare arbete inom fortsatt fragmentering skulle vara nödvändigt för en komplett formulering av fortsatt simulering och penetrationen av fragment.

[pt] Foram determinados experimentalmente fatores de concentração de tensões teóricos para placas e eixos com entalhes simétricos e circunferenciais em U sujeitos à combinação de esforços de flexão e tração, para as placas e, flexão e torção para os eixos. Os fatores obtidos foram plotados em gráficos para comparação com fatores determinados aplicando-se o princípio da superposição. Foram utilizadas as relações geométricas D / d = 1,5; 1,25; 1,10 e r/d = 0,30; 0,25; 0,20 para as placas. Para os eixos utilizaram-se apenas as relações 0/d = 1,3 e r/d = 0,25. Também foram obtidos fatores de concentração de tensões para os esforços puros e seus valores comparados com resultados já publicados. Os resultados para as placas foram obtidos a partir da fotoelasticidade bidimensional. Foi empregado o método fotoelástico tridimensional de congelamento de tensões para os eixos. Neste caso, os modelos foram cortados em finas fatias para separação das tensões. Para o estudo tridimensional foi utilizado um material desenvolvido no laboratório de Fotomecanica da PUC-RJ. / [en] Theoretical stress concentration factors were determined experimentally for bars and shafts with symmetrical and circunferential U – shaped grooves subjected to combinations of bending – tension loads for the bars and bending – torsion loads for the shafts. The stress concentration factors obtained were plotted to compare with the factors determined by application of the superposition effects. The geometric relations used for the bars were Dd = 1,5; 1,25; 1,10 and rd = 0,30; 0,25; 0,20. The geometric relations used for the shafts were Dd = 1,3 e rd = 0,25. The stress concentration factors were also determined for single loaded specimens and they were compared wuth data already published. The stress concentration factors for the bars were determined by the two – Dimensional photoelastic method. In the case of the shafts they were determined by the three – Dimensional photoelastic Method of stress Freezing. In this method, the models developed in the laboratory of Photomechanics of the Universidade Católica.

No description available.

Film cooling is a technique whereby air from the compressor stage of a gas turbine engine is diverted for cooling purposes to parts, such as the turbine stage, that operate at very high temperatures. Cooling arrangements include impingement jets, finned, ribbed and turbulated channels, and rows of film cooling holes, all of which over the years have become progressively more complex. This costly, but necessary complexity is a result of the industry's push to run engines at increasingly higher turbine inlet temperatures. Higher temperatures mean higher efficiency, but they also mean that the turbine first stage operates hundreds of degrees Kelvin above the melting point of the metal core of the vanes and blades. Existing cooling technology and materials make it possible to protect these parts and allow them to function for extended periods of time--but this comes at a price: the compressed air that is used for cooling represents a considerable penalty in overall turbine efficiency. The aim of current cooling research is threefold: to improve the protection of components from extreme fluxes in order to extend the life of the parts; to increase the inlet turbine operating temperature; and to reduce the amount of air that is diverted from the compressor for cooling. Current film cooling schemes consist of forcing air through carefully machined holes on a part and ejecting it at an angle with the intent of cooling that part by blanketing the surface downstream of the point of ejection. The last major development in the field has been the use of expanded hole exits, which reduce coolant momentum and allow for greater surface coverage. Researchers and designers are continuously looking for novel geometries and arrangements that would increase the level of protection or maintain it while using less coolant. It was found that the performance of fan-shaped holes inside trenches is actually diminished by the presence of the trench. It is obvious, since the fan diffuses the flow, reducing the momentum of the coolant; the addition of the trench further slows the flow down. This, in turn, leads to the quicker ingestion of the main flow by the jets resulting in lower effectiveness. The next part of the study consisted of systematically increasing the depth of the trench for the fan-shaped holes. The purpose of this was to quantify the effect of the trench on the film cooling effectiveness. It was found that the presence of the trench significantly reduces the film effectiveness, especially for the deeper cases. At the higher blowing ratios, the overall performance of the fans collapses to the same value signifying insensitivity to the blowing ratio. A recent study suggests that having a compound angle could reduce the protective effect of the film due to the elevated interaction between the non-co-flowing coolant jet and the mainstream. Although it has been suggested that a non-symmetric lateral diffusion could mitigate the ill effects of having a compound angle, little has been understood on the effect this non-symmetry has on film cooling effectiveness. The last part of this study investigates the effect of non-symmetric lateral diffusion on film cooling effectiveness by systematically varying one side of a fan-shaped hole. For this part of the study, one of the lateral angles of diffusion of a fan-shaped hole was changed from 5° to 13°, while the other side was kept at 7°. It was found that a lower angle of diffusion hurts performance, while a larger diffusion angle improves it. However, the more significant result was that the jet seemed to be slightly turning. This dissertation investigates such novel methods which one day may include combinations of cylindrical and fan-shaped holes embedded inside trenches, conical holes, or even rows of asymmetric fan-shaped holes. The review of current literature reveals that very few investigations have been done on film cooling effectiveness for uniformly diffusing conical holes. They have been treated as a sort of side novelty since industrial partners often say they are hard to manufacture. To extend our understanding of effectiveness of conical holes, the present study investigates the effect of increasing diffusion angle, as well as the effect of adding a cylindrical entrance length to a conical hole. The measurements were made in the form of film cooling effectiveness and the technique used was temperature sensitive paint. Eight different conical geometries were tested in the form of coupons with rows of holes. The geometry of the holes changed from pure cylindrical holes, a 0° cylindrical baseline, to an 8° pure cone. The coupons were tested in a closed loop wind tunnel at blowing ratios varying from 0.5 to 1.5, and the coolant employed was nitrogen gas. Results indicate that the larger conical holes do, in fact offer appropriate protection and that the holes with the higher expansion angles perform similar to fan-shaped baseline holes, even at the higher blower ratios. The study was also extended to two other plates in which the conical hole was preceded by a cylindrical entry length. The performance of the conical holes improves as a result of the entry length and this is seen at the higher blowing ratios in the form of a delay in the onset of jet detachment. The results of this study show that conical expanding holes are a viable geometry and that their manufacturing can be made easier with a cylindrical entry length, at the same time improving the performance of these holes. This suggests that the jets actually have two regions: one region with reduced momentum, ideal for protecting a large area downstream of the point of injection; and another region with more integrity which could withstand more aggressive main flow conditions. A further study should be conducted for this geometry at compound angles with the main flow to test this theory. The studies conducted show that the temperature sensitive paint technique can be used to study the performance of film cooling holes for various geometries. The studies also show the film cooling performance of novel geometries and explain why, in some cases, such new arrangements are desirable, and in others, how they can hurt performance. The studies also point in the direction of further investigations in order to advance cooling technology to more effective applications and reduced coolant consumption, the main goal of applied turbine cooling research. Trench cooling consists of having film cooling holes embedded inside a gap, commonly called a trench. The walls of this gap are commonly vertical with respect to the direction of the main flow and are directly in the path of the coolant. The coolant hits the downstream trench wall which forces it to spread laterally, resulting in more even film coverage downstream than that of regular holes flush with the surface. Recent literature has focused on the effect that trenching has on cylindrical cooling holes only. While the results indicate that trenches are an exciting, promising new geometry derived from the refurbishing process of thermal barrier ceramic coatings, not all the parameters affecting film cooling have been investigated relating to trenched holes. For example, nothing has been said about how far apart holes inside the trench will need to be placed for them to stop interacting. Nothing has been said about shaped holes inside a trench, either. This dissertation explores the extent to which trenching is useful by expanding the PI/D from 4 to 12 for rows of round and fan holes. In addition the effect that trenching has on fan-shaped holes is studied by systematically increasing the trench depth. Values of local, laterally-averaged and spatially-averaged film cooling effectiveness are reported. It is found that placing the cylinders inside the trench and doubling the distance between the holes provides better performance than the cylindrical, non-trenched baseline, especially at the higher blowing ratios, M > 1.0. At these higher coolant flow rates, the regular cylindrical jets show detachment, while those in the trench do not. They, in fact perform very well. The importance of this finding implies that the number of holes, and coolant, can be cut in half while still improving performance over regular holes. The trenched cylindrical holes did not, however, perform like the fan shaped holes.

This thesis discusses a comparison of the differences in aerodynamic performance of wings designed with elliptical and bell-shaped lift distributions. The method uses a Standard Cirrus sailplane wing with a lift distribution associated with the induced drag benefits of an elliptical distribution (span efficiency = 0.96) as the basis of comparison. The Standard Cirrus is a standard class sailplane with 15-meter wingspan that was designed by Schempp-Hirth in 1969. This sailplane wing was modeled and analyzed in XFLR5, then validated against existing wind tunnel airfoil data, and Standard Cirrus flight test data. The root bending moment of the baseline wing was determined and used as the primary constraint in the design of two wings with bell-shaped lift distribution. These wings were modeled in XFLR5 by adjusting chord length and geometric twist respectively, and then they were studied using fixed speed lifting line analysis. Steady state cruise conditions for the Standard Cirrus sailplane were taken from the flight test data and applied for the analysis. The wing designed with chord variation posed incompatibilities with the lifting line method. The resulting planform was strongly tapered in the wingtip region and the reference chord length there was such that the software could not solve for a Reynolds number the magnitude resulting from two-dimensional airfoil analysis. However, the wing geometry provided insight into the design aspect of wings with bell-shaped lift distribution. Using chord variation to shape the lift distribution, the wing featured a 12% increase in wingspan but a 6.5% decrease in total wetted area when compared to the baseline. The results of the analysis of the wing designed with geometric twist indicate that induced drag decreased by 5% when compared to the baseline wing. The constraint on root bending moment resulted in a 12% increase in wingspan. Wetted area also increased by 14.8% over the baseline yielding an estimated 15% increase in skin friction.

Thesis advisor: Christopher Maxwell / The questions that this paper intends to answer are: 1) Is there a U-shaped relationship between the female labor force participation (FLFP) rate and development in the present day? And 2) If we group countries geographically, will we see the U-shaped function outlined as development occurs over time? The U-shaped function is important because it allows us to predict the direction that the FLFP rate will move, dependent on a country's level of development. This prediction is crucial because there are endless gains of increased FLFP to both women and to society at large. Previous research has shown that in a snapshot in time (1985), there was evidence of the U-shaped function. However, there has been little research on how the function has played out throughout the past 30+ years. This paper finds that the U- shaped function remains robust to present day data. However, grouping countries geographically does not always produce results that support movement along the U-shaped function. Having a clearer understanding of the trends that FLFP follows through development will allow us to more successfully monitor and create policy to help women and society at large reap the benefits of increased women in the workforce. / Thesis (BA) — Boston College, 2019. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Departmental Honors. / Discipline: Economics.