Discrete element modeling of dry granular material using a massively parallel supercomputer

It is the state-of -the-art within Geotechnical Engineering to model soils as systems of particles rather than using the traditional continuum approach. Simulating these systems of particles for geotechnical boundary value problems results in systems which are of necessity large, motivating the application of massively parallel supercomputers. This thesis pursues such an approach. The following work describes numerical experiments using a Discrete Element Method (DEM) paradigm for soils (Trubal) together with massively parallel computers with Single Instruction Multiple Data (SIMD) architecture. The discrete element method describes the behavior of granular assemblies using the classical mechanics of discrete bodies. The computational requirements of DEM algorithms introduce time complexities, which mandate a compatible topology for massively parallel machines in order to achieve optimal performance. This thesis demonstrates the compatibility of a Single Instruction Multiple Data (SIMD) topology in performing discrete element simulations for 3-d spherical dry granular media. The serial algorithm, Trubal, was first modified to run with a parallel data structure on a SIMD architecture. The modified version, known as Trubal for Parallel Machines (TPM), is the data parallel version that was tested on the connection machines (CM-2) and (CM-5), consisting of 32,768 processors and 512 nodes, respectively. The first version of TPM was tested on the CM-2 machine before its use was discontinued. Because the architecture is synchronized at each instruction, elemental data movements reduce the performance of the machine\u27s overall resources and increase the latency of the communication between processors. This issue is addressed within the design of the algorithm so that the SIMD vector processing capability can adapt to a dynamic memory data structure. A second version of TPM was subsequently designed for the CM-5 machine using a more efficient parallel data structure to improve the performance of the simulations. TPM version 2.0 was able to obtain a speedup in performance by handling all possible contacts within each processor, thereby creating a homogeneous data structure. The overall efficiency is governed by the global communication which is a function of the speed of the interconnection network within the architecture. TPM\u27s improved performance is demonstrated using two different triaxial simulations. One of them involved a physical triaxial experiment with steel spheres performed by Rowe (1962) and later simulated by Cundall (1979). The remodeling of this numerical simulation validated TPM version 2.0 overall performance where a nine-fold speedup was obtained. TPM\u27s reproduction of these results and its improved speedup encourage further investigations using discrete models on parallel platforms. This thesis substantiates the use of parallel computing as a technique for geotechnical applications. It is further anticipated that developing and adapting heterogeneous platforms to DEM models will make the application of parallel computing more attractive in geotechnical engineering

PRACTICES USED BY DAIRY FARMERS TO REDUCE SEASONAL PRODUCTION VARIABILITY

Results of this study further support the effectiveness of the seasonal pricing plan in reducing seasonal production variability. Florida Dairy farmers were able to change factors that affect production in order to take advantage of the seasonal pricing plan and that farmers that chose not to participate were able to affect factors to increase production seasonality.seasonality, Demand and Price Analysis, Livestock Production/Industries,

Family Strengths Among Black Families In Alaska: A Case Study

The idea of a strong family is a very subjective concept. A strength, according to one set of criteria, could easily be interpreted as a weakness according to another set of criteria--and vice-versa. Most scholars of the family would agree that a strong bond of affection between family members is usually an asset. But if this affection is manifested in extremely dependent and stifling relationships among family members, such a bond would generally be characterized as a pathological liability. The family has traditionally provided the foundation for society, and, though in contemporary America some of its functions have been absorbed by other social systems, it is still responsible for the primary socialization and care of people. Moreover, most adults report that achieving satisfying relationships within the family is very important (Stinnett and Walters, 1977). The concept of family strengths implies that the stronger family is more desirable for the stability of society (Grams, 1967), and it has been noted that societies with strong family systems tend to recuperate rapidly from conditions of adversity whereas the opposite types recover only with great difficulty (Zimmerman, 1972). Because of these factors, healthy families are both functional for society and the individual. The fact that American Black families have survived under such political, social and economic adversity can be seen as a monument to their strength. This case study was designed to analyze what were perceived as family strengths among Black families in Alaska. The results of this research will be used to educate the Department of Family and Youth Services\u27 workers and Juvenile Probation Officers through in-service seminars to the fact that all families have strength and that Black families should not continually be defined as a pathological unit. A series of workshops will be designed and implemented to train probation officers and social workers assigned to the Department of Family and Youth Services (DFYS) in the concept of building family strengths. The training will consist of ten sessions called the Building Family Strength program. The program will include six basic areas of strengths identified through past research and any new strengths that were identified as a result of this study of Black families. The six basic strengths on which the workshops will be based are commitment, wellness orientation, effective communication, frequent appreciation, positive time together, and constructive strategies for dealing with conflict, stress and family crises. These workshops will be conducted ln a relaxed, peer-group environment utilizing the basic assumption of the Building Family Strength (BFS) model that all families have strengths. The implications of these workshops will be that a more professional and understanding attitude will be assumed by caseworkers and probation officers within DFYS when dealing with families, especially minority families. The BFS model is preventive and promotive of change within the family. Most existing educational models are reactive: they focus on what to do after a problem already exists. A preventive and promotive educational model is proactive in the sense that its focus is to anticipate changes that take place over the no=mal course of family development. The need for family educational intervention through the family strengths model is significant. Families are often left on their own to cope with the extreme pressures brought on by conflict, stress and crisis. The implications to society are far-reaching if families do not have the tools with which to survive and grow. Families need help in learning to more effective utilize available resources, generate new ones, and build family strengths. In that sense, the family is a natural resource

AN EVALUATION OF THE EFFECTIVENESS OF THE FLORIDA COOPERATIVE'S SEASONAL PRICING PLAN ON SEASONAL PRODUCTION VARIABILITY

From 1993 - 1995, Florida dairy cooperatives implemented a seasonal pricing plan in an attempt to decrease the variability in seasonal production. Farmers that participated in the seasonal pricing plan were able to reduce seasonality in each year when compared to 1992 by as much as 20 percent. For farmers that did not participate, seasonality increased in each year by as much as 32 percent. Overall, the seasonal pricing plan was effective in reducing seasonality for those farmers that chose to participate in the plan and that its limited short-run success was the result of seasonality increases by non-participating farms.amplitude, seasonal pricing plan, seasonality, Livestock Production/Industries,

The Influence of Business Environmental Dynamism, Complexity and Munificence on Performance of Small and Medium Enterprises in Kenya

The main purpose of this article is to examine how business environment affects small and medium enterprises. The paper is motivated by the important contributions small and medium enterprises have in many countries, especially Kenya towards job creation, poverty reduction and economic development. Literature however argues that effectiveness of the contributions is conditioned by the state of business environmental factors such as politics, economy, socio-culture, technology, ecology and laws/regulations. Dynamism, complexity and munificence of these factors are therefore vital to achievement of organizational objectives and overall performance. Even so, a review of literature reveals contradictory views regarding the effect of these factors on performance of organizations. Furthermore, studies focusing on these factors in the Kenyan context, particularly with regard to their effect on performance of small and medium firms, are scarce. This article bridges this gap based on a study focusing on 800 manufacturing organizations in Nairobi – Kenya. A sample of 150 enterprises was selected through stratification by business sector followed by simple random sampling. The research design was cross sectional survey where data was collected using a structured questionnaire over a period of one month at the end of which 95 organizations responded giving a response rate of 64%. Reliability and validity of the instrument were determined through Cronbach’s alpha tests and expert reviews. Statistical Package for Social Sciences was used to determine normality through descriptive statistics and study hypotheses tested using inferential statistics. The study established that business environment had an overall impact on organizational performance. Specifically, dynamism, complexity and munificence each had a direct influence on the enterprises in the study. Furthermore the combined effect on performance was found to be greater than that of dynamism and complexity but less than munificence. The study also established that there is a difference in the way business environment affects performance such that it impacts on financial performance more than on non-financial performance of these enterprises. dynamism and complexity but less than munificence

Handling Qualities and Trajectory Requirements for Terminal Lunar Landing, as Determined from Analog Simulation

Trajectory requirements for terminal lunar landing from analog simulation of spacecraf

A morphometric analysis of vegetation patterns in dryland ecosystems

Vegetation in dryland ecosystems often forms remarkable spatial patterns. These range from regular bands of vegetation alternating with bare ground, to vegetated spots and labyrinths, to regular gaps of bare ground within an otherwise continuous expanse of vegetation. It has been suggested that spotted vegetation patterns could indicate that collapse into a bare ground state is imminent, and the morphology of spatial vegetation patterns, therefore, represents a potentially valuable source of information on the proximity of regime shifts in dryland ecosystems. In this paper, we have developed quantitative methods to characterize the morphology of spatial patterns in dryland vegetation. Our approach is based on algorithmic techniques that have been used to classify pollen grains on the basis of textural patterning, and involves constructing feature vectors to quantify the shapes formed by vegetation patterns. We have analysed images of patterned vegetation produced by a computational model and a small set of satellite images from South Kordofan (South Sudan), which illustrates that our methods are applicable to both simulated and real-world data. Our approach provides a means of quantifying patterns that are frequently described using qualitative terminology, and could be used to classify vegetation patterns in large-scale satellite surveys of dryland ecosystems