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Promoting life-long learning skills in CAD using the peergenerated screencast tutorials
No full textTo promote life-long learning skills in Computer-Aided Design (CAD) education, authors designed and implemented a student-centered instruction in the CAD courses. A quasiexperimental pre-and-post test research design was implemented. Experimental group students were asked to design screencast tutorials with their verbal explanations recorded. Students shared their screencast tutorials with their peers and provided feedback to each other\u27s video tutorials. Control group students were asked to review the instructor made screencast tutorials. A life-long learning survey, an engineering attitude survey, an exit project survey, and a CAD modeling exam were used as the study instruments. A total of 147 students participated in this study over three years. Findings indicated that female and first generation college students in the experimental group performed better than their peers in the control group in the CAD modeling exam. Our student-centered instruction was more affective on female students\u27 and first generation college students\u27 skills and knowledge than male students\u27 and not-first generation college students\u27 skills and knowledge
Application of Taylor-Pade technique for obtaining approximate solution for system of linear Fredholm integro-dierential equations
Get PDFIn this article, we introduce a modification of the Taylor matrix method using Pad´e approximation to obtain an accurate solution of linear system of Fredholm integro-differential equations (FIDEs). This modification is based on, first, taking truncated Taylor series of the functions and then substituting their matrix forms into the given equations. Thereby the equation reduces to a matrix equation, which corresponds to a system of linear algebraic equations with unknown Taylor coefficients. Finally, we use Pad´e approximation to obtain an accurate numerical solution of the proposed problem. To demonstrate the validity and the applicability of the proposed method, we present some numerical examples. A comparison with the standard Taylor matrix method is given
Transient Solution of M[X1],M[X2]/G1,G2/1 with Priority Services, Modified Bernoulli Vacation, Bernoulli Feedback, Breakdown, Delaying Repair and Reneging
Get PDFThis paper considers a queuing system which facilitates a single server that serves two classes of units: high priority and low priority units. These two classes of units arrive at the system in two independent compound Poisson processes. It aims to decipher average queue size and average waiting time of the units. Under the pre-emptive priority rule, the server provides a general service to these arriving units. It is further assumed the server may take a vacation after serving the last high priority unit present in the system or at the service completion of each low priority unit present in the system. Otherwise, he may remain in the system. Also, if a high priority unit is not satisfied with the service given it may join the tail of the queue as a feedback unit or leave the system. The server may break down exponentially while serving the units. The repair process of the broken server is not immediate. There is a delay time to start the repair. The delay time to repair and repair time follow general distributions. We consider reneging to occur for the low priority units when the server is unavailable due to breakdown or vacation. We concentrate on deriving the transient solutions by using supplementary variable technique. Further, some special cases are also discussed and numerical examples are presented
Analytical solution for determination the control parameter in the inverse parabolic equation using HAM
Get PDFIn this article, the homotopy analysis method (HAM) for obtaining the analytical solution of the inverse parabolic problem and computing the unknown time-dependent parameter is introduced. The series solution is developed and the recurrence relations are given explicitly. Special attention is given to satisfy the convergence of the proposed method. A comparison of HAM with the variational iteration method is made. In the HAM, we use the auxiliary parameter ~ to control with a simple way in the convergence region of the solution series. Applying this method with severa
Sulfuric acid and Amberlyst-H\u3csup\u3e+\u3c/sup\u3e catalyzed condensation reactions of renewable keto acids with paraformaldehyde: Synthesis of a new dispiro bis-lactone ring system 2,9,13-trioxadispiro[4.1.4.3]tetradecane-3,6,10-trione
No full textThe sulfuric acid and Amberlyst-H+ catalyzed condensation reactions of renewable feedstock levulinic acid with paraformaldehyde under neat conditions at 80 °C gives 2,9,11,14-tetraoxadispiro[4.1.5.3]pentadecane-3,6-dione in 91-93% yield, in which the structure was confirmed by single crystal X-ray crystallography. A similar condensation reaction between 4-ketopimelic acid and paraformaldehyde at 80 °C gives 2,9,13-trioxadispiro[4.1.4.3]tetradecane-3,6,10-trione. This new dispiro bis-lactone was found to composed of a 1.6 : 1 mixture of isomers with planes of symmetry bisecting the tetrahydro-2H-pyran-4-one rings through the carbonyl groups
A two-step efficient preparation of a renewable dicarboxylic acid monomer 5,5′-[oxybis(methylene)]bis[2-furancarboxylic acid] from D-fructose and its application in polyester synthesis
No full textD-Fructose was converted to the dialdehyde 5,5′-[oxybis(methylene)]bis[2-furaldehyde] by heating at 110°C in DMSO with the Dowex 50 W X8 solid acid catalyst in 76% yield without the isolation of the intermediate 5-hydroxymethylfurfural. This dialdehyde was then converted to the dicarboxylic acid monomer, 5,5′-[oxybis(methylene)]bis[2-furancarboxylic acid], using oxygen (1 atm.) and 5% Pt/C catalyst in 1.5 M aqueous NaOH at room temperature in 98% yield. The new dicarboxylic acid monomer can be considered as a renewable resource based alternative to terephthalic acid as demonstrated by the preparation of polyesters with 1,2-ethanediol and 1,4-butanediol in 87-92% yield
Equilibrium and uniform charge distribution of a classical two-dimensional system of point charges with hard-wall confinement
No full textWe study the minimum energy equilibrium configurations of a classical two-dimensional system of point charges confined by a triangular, square and disk region with a hard-wall boundary. It is assumed that the point charges interact via a repulsive Coulomb interaction potential. Monte Carlo simulations with the annealing algorithm suggest that the equilibrium configurations of a given system are strongly influenced by the external (isotropic/anisotropic) geometry of the hard-wall boundary. The numerically obtained energies extrapolated in the bulk limit converge to the expected continuum equilibrium values (when known). It is found that the equilibrium charge distribution is non-uniform in the continuum limit for all the hard-wall confining regions considered in this work. Since the continuum equilibrium charge distribution is not known for the case of an equilateral triangle or a square domain we choose to compare the numerically obtained bulk energy results to corresponding values for a uniformly charged system. We calculated exactly the electrostatic energy of various uniformly charged planar objects and used the results to assess the discrepancy between such results and the numerically obtained equilibrium bulk energy values for the cases of equilateral triangle and square hard-wall boundaries. These estimates help us understand how an anisotropic boundary with the shape of an equilateral triangle or square influences the energy of an equilibrium charge distribution. The results indicate that the energy discrepancy between equilibrium and uniform charge distributions in the continuum limit is not very large. It is found that the order of magnitude of the relative deviation of the energy for all three different planar domains considered here is approximately the same
Results for the energy of a finite one-dimensional ionic crystal
No full textWe consider a one-dimensional ionic crystal consisting of an arbitrary number of alternating positive and negative ions. We calculate exactly the energy per ion and uncover some interesting patterns. It is found that the energy per ion remains constant each time the size of the system increases by one ion if addition of such an ion leads to a system with a nonzero total charge. On the other hand, the energy per ion always decreases if addition of such an ion leads to a charge neutral system with a zero total charge. Explicit analytical results are provided
Race-related stress and hopelessness in community-based African American adults: Moderating role of social support
No full textObjectives: The mental health outcomes associated with racial discrimination are well documented in scientific literature. Despite strong links to mental illness, hopelessness is largely overlooked as a consequence of discrimination in empirical research. The current study examined the association of race-related stress and hopelessness in a community sample of African American adults. Utilizing a risk-resilience framework, we examined multiple dimensions of social support as plausible protective factors against the negative effects of race-related stress. Method: Self-report measures of race-related stress (Index of Race Related Stress-Brief; Utsey & Ponterotto, 1996), hopelessness (Beck Hopelessness Scale; Beck, Weissman, Lester, & Trexler, 1974), and social support (Interpersonal Support Evaluation List; Cohen & Hoberman, 1983) were completed by a sample of African American adults (N = 243; mean age = 35.89 years). Results: Multiple regression analyses were conducted to assess the main and interactive effects of race-related stress and three dimensions of social support (appraisal, belonging, and self-esteem) in relation to hopelessness ratings. All dimensions of social support were associated with self-reported hopelessness, with the self-esteem dimension emerging as the strongest predictor. Though self-esteem social support buffered the role of race-related stress on self-reported hopelessness, appraisal and belonging support did not. Conclusions: Individual and collective morale for one\u27s racial group (via self-esteem social support) may be especially valuable for African Americans who face racial discrimination. Findings highlight the importance of culturally relevant factors that may ameliorate the effects of race-related stress