On the uniqueness of solutions for the Dirichlet boundary value problem of linear elastostatics in the circular domain

Summary The uniqueness and mathematical stability of the Dirichlet boundary value problem of linear elastostatics is studied. The problem is posed as a set of partial differential equations in terms of displacements and Dirichlet-type of boundary conditions (displacements) for arbitrary bounded domains. Then for the circular interior domain the closed form analytical solution is obtained, using an extended version of the method of separation of variables. This method with corresponding complete solution allows for the derivation of a necessary and sufficient condition for uniqueness. The results are compared with existing energy and uniqueness criteria. A parametric study of the elastic characteristics is performed to investigate the behaviour of the displacement field and the strain energy distribution, and to examine the mathematical stability of the solution. It is found that the solution for the circular element with hourglass-like boundary conditions will be unique for all v ≠ 0.5, 0.75, 1.0 and will be mathematically stable for all v ≠ 0.75. Locking of the circular element occurs for v = 0.75 as the energy tends to infinity.     

Hypoplastic model for crushable sand

A constitutive model for granular materials which considers grain crushing effects is developed in the framework of hypoplasticity. As grain crushing occurs the behaviour of granular material can usually be significantly affected. Several empirical relations between peak strength, uniformity coefficient and stiffness of sand depending on stress level or amount of grain crushing have been derived in the past. In this paper, such relations are employed to improve a basic hypoplastic constitutive model based on the changes of stress level or grain size distribution. In the proposed modified hypoplastic model only two additional physical parameters, namely uniformity coefficient and mean grain size are incorporated. The validation of the modified model for three different sands under triaxial test response with cell pressures up to 30?MPa is presented and shows a significantly better correspondence with regard to the original basic hypoplastic model.     

Stability of yellow-orange cactus pear (<Emphasis Type="Italic">Opuntia ficus-indica</Emphasis> [L.] Mill. cv. ‘Gialla’) betalains as affected by the juice matrix and selected food additives

The impact of added ascorbic, isoascorbic, and citric acid on heat stability of cactus pear betalains was investigated at pH 4 and 6, respectively. To assess the influence of cactus pear juice matrix compounds such as sugars, organic acids, amino acids, and pectic substances on pigment stability, juice and purified pigment preparations derived therefrom were assayed separately. Immediately after heating at 85 °C for 1 h and a 24 h cool storage period, betalain retention, betanin and proline-betaxanthin isomerisation as well as overall colour changes were determined. Pigment stability and colour characteristics depended on type and concentration of the respective additive as well as on pH conditions. Interestingly, the stabilising effects of the additives under investigation were less pronounced in matrix-free pigment preparations compared to juice samples. Maximum pigment retention amounting to 79% was obtained when 0.1% citric acid was added to the juice at pH 6. For the first time, formation of 2-decarboxy-betanin upon thermal treatment of yellow-orange cactus pear juice being more distinct at pH 4 as compared to pH 6 is reported.     

Expanding Urban Homesteading Lessons from the Local Property Demonstration

Responding to grass-roots pressure, Congress in 1983 expanded federal involvement in homesteading abandoned housing units through the Local Property Urban Homesteading Demonstration. The demonstration assessed the feasibility of federal assistance to state and local governments for the purchase of vacant, tax-delinquent real property for homesteading. This article evaluates whether the eleven participating cities were able to develop effective programs for purchasing tax-delinquent properties, the implications of requiring all homesteaders to have low incomes, and the prevalence of sweat equity to reduce the monetary equity or qualifying incomes of homesteaders. The findings have implications for the design of both federal and local homesteading programs.     

Using Public Housing to Achieve Self-Sufficiency: Can We Predict Success?

In the United States since the mid-1980s, self-sufficiency programs have sought to transform public housing developments from permanent housing into way stations for low-income people. This article presents exploratory research on the predictors of success in these programs. Statistical analysis of longitudinal survey data from participants in an early public housing self-sufficiency program points to lack of previous welfare experience and the presence of prior vocational training as being predictors of program success. In-depth interviews suggest that having a high-school education is important for success, and any additional education prior to participating in a self-sufficiency program is helpful. Interviews also indicate that successful program graduates alienate themselves from social groups that discourage self-sufficiency.     

PARTICIPATION IN COMMUNITY WATCH PROGRAMS

Community watch programs are spreading rapidly across the country. Based on a sample of residents in five SMSAs, this study addresses the questions: Who is aware of these programs in their local area? Who is participating in these programs? Why are they participating? The results indicate that those with higher incomes and those who are integrated into their community are more likely to be aware of community watch programs. Participation in these programs, similar to participation in general purpose community organizations, is related to income, race and the perceived effectiveness of the courts. The results provide evidence for two models of why people participate in community watch: the community responsibility model and the property protection model. Two other models, the lack of confidence in the criminal justice system model and the fear model were not supported by the data.     

Home Ownership and Access to Opportunity

Home ownership and access to opportunity are foundations of the American ethos. While little research has explicitly examined a relationship between home ownership and opportunity, considerable empirical work has examined how home ownership impacts important elements of local opportunity structures as well as individual subjective perceptions of those structures. Available evidence suggests that home ownership may affect the opportunity structure by enhancing neighbourhood stability and civic involvement in local voluntary and political affairs. Home ownership may also impact perceptions of opportunity by increasing financial resources, enhancing psychological and physical health, and influencing the behaviour of youth. There is a great need for additional research that directly assesses the impacts of home ownership on local objective opportunity structures and the perception of those structures.     

Traumatic spinal cord injury, alcohol, and the Minnesota Multiphasic Personality Inventory.

Investigated whether use of selected Minnesota Multiphasic Personality Inventory (MMPI) scales can identify personality characteristics in male patients with traumatic spinal cord injury and a positive blood alcohol concentration (BAC) at the time of injury. 20 males (aged 16–53 yrs) with a positive and 9 age-matched males with a negative BAC and 101 normal control males (aged 20–29 yrs) were contrasted on the MMPI Hysteria, Psychopathic Deviate, and Mania clinical scales and derived subscales reflecting traits such as rebelliousness and impulsivity. Results indicate that the average BAC when Ss arrived at the emergency room was 1,507 μg/ml. 75% of the positive BAC group had BAC concentrations above the legally defined limit of 1,000 μg/ml. Except for the MacAndrews Alcoholism Scale, none of the MMPI clinical scales or their corresponding derived subscales were significantly different between groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)