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Increasing college degree attainment for students from disadvantaged backgrounds is a prominent component of numerous state and federal legislation focused on higher education. In 1999, the National Science Foundation (NSF) instituted the "Computer Science, Engineering, and Mathematics Scholarships" (CSEMS) program; this initiative was designed to provide greater access and support to academically talented students from economically disadvantaged backgrounds. Originally intended to provide financial support to lower income students, this NSF program also advocated that additional professional development and advising would be strategies to increase undergraduate persistence to graduation. This innovative program for economically disadvantaged students was extended in 2004 to include students from other disciplines including the physical and life sciences as well as the technology fields, and the new name of the program was Scholarships for Science, Technology, Engineering and Mathematics (S-STEM). The implementation of these two programs in Louisiana State University (LSU) has shown significant and measurable success since 2000, making LSU a Model University in providing support to economically disadvantaged students within the STEM disciplines. The achievement of these programs is evidenced by the graduation rates of its participants. This report provides details on the educational model employed through the CSEMS/S-STEM projects at LSU and provides a path to success for increasing student retention rates in STEM disciplines. While the LSU's experience is presented as a case study, the potential relevance of this innovative mentoring program in conjunction with the financial support system is discussed in detail. (Contains 5 figures.)

In the United States, less than half of the students who enter into science, technology, engineering, and mathematics (STEM) undergraduate curricula as freshmen will actually graduate with a STEM degree. There is even greater disparity in the national STEM graduation rates of students from underrepresented groups with approximately three-fourths of minority students leaving STEM disciplines at the undergraduate level. A host of programs have been designed and implemented to model best practices in retaining students in STEM disciplines. The Howard Hughes Medical Institute (HHMI) Professors Program at Louisiana State University, under leadership of HHMI Professor Isiah M. Warner, represents one of these programs and reports on a mentoring model that addresses the key factors that impact STEM student attrition at the undergraduate level. By integrating mentoring and strategic academic interventions into a structured research program, an innovative model has been developed to guide STEM undergraduate majors in adopting the metacognitive strategies that allow them to excel in their programs of study, as they learn to appreciate and understand science more completely. Comparisons of the persistence of participants and nonparticipants in STEM curricular, at the host university and with other national universities and colleges, show the impact of the model's salient features on improving STEM retention through graduation for all students, particularly those from underrepresented groups.

Two methods for calculating the derivatives of a repeated eigenvalue of viscously damped vibrating systems with respect to a parameter are given. The first method implements the subspace spanned by the eigenvectors corresponding to the repeated eigenvalue. The second method is based on an explicit formula that uses the characteristic equation directly, without explicitly employing the eigenvector data. Examples demonstrate the various results.

Over the years, there has been mounting interest in the use of recycled tire rubbers in highway construction. Tire rubber-filled concrete, a rubberized Portland cement concrete with a portion of aggregates replaced by tire rubber particles, represents an alternative of using recycled tire rubbers. It is found that rubberized concrete has very high toughness. However, its strength decreases significantly as the rubber content increases. This limits its application to secondary structural components only. Very little progress has been made in increasing the strength of rubberized concrete due to the lack of understanding of the toughing mechanism. In this study, rubberized concrete was treated as a multiphase particulate-filled composite material. A modified three-layer built-in composite model was proposed based on a previous study on ordinary concrete. Finite element analysis was conducted on the developed composite model. Cylindrical rubberized concrete samples and ordinary concrete samples were prepared and tested to provide basic physical/mechanical properties in the analysis. The effect of various design parameters on the composite strength was evaluated. The finite element analysis validated the test results. CE Database subject headings: Composite materials; Portland cements; Concrete; Recycling; Rubber; Tires.

The distresses of asphalt pavement, which include fatigue, rutting, and low temperature cracking, are related to the elastic modulus of asphalt concrete (AC). In addition, the elastic modulus of AC is a design variable for asphalt pavement structural design when elastic-layer system theory is employed. However, in the most commonly used AC design methods (the Marshall, Hveem, and Superpave methods), the elastic modulus is not used as a control variable. Therefore, these design methods do not ensure that the desired elastic modulus of AC will be obtained. In this paper, AC is treated as a two-phase composite with aggregates dispersed in the asphalt matrix. based on this treatment, a two-layer built-in micromechanical model of AC is developed by embedding an asphalt-coated circular aggregate into an equivalent AC medium. Using this model, an equation predicting the elastic modulus of AC is derived. The elastic modulus of AC predicted by the present model is compared with the Hashin and Shtrikman theoretical bounds and the Heukelom and Klomp equation. Using these comparisons, the proposed model is shown to be reasonable and applicable for predicting the elastic modulus of AC. Thus, the existing mix design approaches can be improved by using the modulus prediction model presented in this paper.

First-order laminated plate theory was used to derive a model of a taper-taper adhesive-bonded joint under cylindrical bending. Transverse shear deformation was accounted for by the use of shear correction factors. The COSMOS/M commercial finite element package was used to develop a finite element model to verify the analytical model for a cross-ply laminate. The analytical model results agreed well with the finite element models.

Owing to the lack of reliable and cost-effective joining methods, composite materials have not yet achieved their full market potential. The use of heat-activated thermal couplings offers a quick and cost-effective method for joining composite-to-composite pipe. In this study, a prepreg laminate containing thermoset resins and fiberglass reinforcements is wrapped around the ends of the components to be joined. A shrink tape, constructed of an oriented polyester film, is placed over the prepreg laminate. When heat is applied to the thermal coupling for curing, the shrink tape shrinks and compresses the prepreg to improve adhesion. Tests of the heat-activated thermal coupling in bending shows an increase of 29% over the currently used butt-weld method. A finite element model has been developed to assist in determining the most appropriate cure cycle required for different joint configurations. This reduces the need for experimentation when a variable has been changed. based on the tested prepreg material properties and model, the FEA temperature distribution differs less than 10% from that of experimental results., INTRODUCTION Composite materials have gained wide acceptance in various industries, such as aerospace, automotive, and marine, because of their light weight and corrosion resistance. As a result of properly developed [...]

A model for analyzing the strain-stress distributions in an adhesive-bonded taper-taper joint between two composite flat plates under tension loading was developed using first-order laminated plate theory with a correction for traverse shear deformation effects. The model consists of 18 linear, coupled first-order differential equations with variable coefficients. A linear Shooting Method was used to numerically test the model. Results have shown that the analytical model can calculate the peak peel and shear stresses within five to eight percent.

A correlation of strengths of orthotropic plates having a circular hole under tension and bending is suggested. This is based on Lekhnitskii's solutions for infinite wide plates. Finite element analysis (FEA) is used to ascertain theoretical correlation. Uniaxial tension and four-point bending tests are also performed on Scotchply samples with circular holes of different sizes. A good agreement is found between the theoretical, FEA and experimental findings.

A novel analytical model determines stress and strain distributions in adhesive-bonded composite single-lap joints under tension. The model is based on the laminated anisotropic plate theory and can give closed-form solutions for stress distributions of the laminates and the adhesive. The governing equations of the two bonded laminates can be derived using the anisotropic plate theory. These solutions correlate with the solutions obtained from finite element model.