Leveraging legacy codes to distributed problem solving environments: A web service approach

This paper describes techniques used to leverage high performance legacy codes as CORBA components to a distributed problem solving environment. It first briefly introduces the software architecture adopted by the environment. Then it presents a CORBA oriented wrapper generator (COWG) which can be used to automatically wrap high performance legacy codes as CORBA components. Two legacy codes have been wrapped with COWG. One is an MPI-based molecular dynamic simulation (MDS) code, the other is a finite element based computational fluid dynamics (CFD) code for simulating incompressible Navier-Stokes flows. Performance comparisons between runs of the MDS CORBA component and the original MDS legacy code on a cluster of workstations and on a parallel computer are also presented. Wrapped as CORBA components, these legacy codes can be reused in a distributed computing environment. The first case shows that high performance can be maintained with the wrapped MDS component. The second case shows that a Web user can submit a task to the wrapped CFD component through a Web page without knowing the exact implementation of the component. In this way, a user’s desktop computing environment can be extended to a high performance computing environment using a cluster of workstations or a parallel computer

Grandparents Raising Grandchildren: Implications for School Systems and School Personnel

ABSTRACT A crucial issue facing our educational system is the changing family structure, particularly the increase in the number of children being raised by their grandparents. Many of these children live in a situation that places them at risk academically. Thus, it is vital that the educational system consider identifying the special needs of these children to provide supports. This study aimed to identify support services that middle school and high school grandparents perceived they needed from school systems and school personnel to ensure the educational success of their grandchildren. I developed a survey based on concerns and issues that were cited in the literature to determine grandparent\u27s awareness of the services provided by the public schools, the extent to which their student utilized them, and other services that the grandparents themselves needed. Participants were a convenience sample of 56 mostly African American grandparents from four high schools and five middle schools in a southern urban school district who were primarily responsible for raising their grandchildren. These grandparents contacted me to participate after receiving a recruitment flier that was sent home with each student at the participating schools. Over half of the grandchildren had received a failing grade on their report card in at least one of the core subjects the previous year. About one fourth of these children also had an Individualized Education Plan (IEP). The study found statistically significant differences in the awareness of middle school and high grandparents regarding whether their grandchild utilized the academic services of tutoring, pull-out classes, and study skills classes. According to the grandparents, high school students used the services less than middle school students. In addition, of the 29 students with discipline issues, more middle school than high school grandparents indicated that their grandchild “received help for behavior problems.” Both groups of grandparents requested support groups for their grandchildren to address behavior and provide assistance with school work. Middle school grandparents also requested support groups for teasing/ bullying. Both groups of grandparents requested that a Grandparent Education Council be formed, information on community resources, and training for teachers regarding the issues of both grandparents and grandchildren

Kink dynamics in a novel discrete sine-Gordon system

A spatially-discrete sine-Gordon system with some novel features is described. There is a topological or Bogomol'nyi lower bound on the energy of a kink, and an explicit static kink which saturates this bound. There is no Peierls potential barrier, and consequently the motion of a kink is simpler, especially at low speeds. At higher speeds, it radiates and slows down.Comment: 10 pages, 7 figures, archivin

Markov partitions reflecting the geometry of x2,x3

We give an explicit geometric description of the $\times2,\times3$ system, and use his to study a uniform family of Markov partitions related to those of Wilson and Abramov. The behaviour of these partitions is stable across expansive cones and transitions in this behaviour detects the non-expansive lines

Arithmetic and growth of periodic orbits

We give necessary and sufficient conditions for a sequence to be exactly realizable as the sequence of numbers of periodic points in a dynamical system. Using these conditions, we show that no non-constant polynomial is realizable, and give some conditions on realizable binary recurrence sequences. Realization in rate is always possible for sufficiently rapidly-growing sequences, and is never possible for slowly-growing sequences. Finally, we discuss the relationship between the growth rate of periodic points and the growth rate of points with specified least period.Comment: Revised version with new content; to appear in J.Integer Sequence

Including nonlocality in exchange-correlation kernel from time-dependent current density functional theory: Application to the stopping power of electron liquids

We develop a scheme for building the scalar exchange-correlation (xc) kernel of time-dependent density functional theory (TDDFT) from the tensorial kernel of time-dependent {\em current} density functional theory (TDCDFT) and the Kohn-Sham current density response function. Resorting to the local approximation to the kernel of TDCDFT results in a nonlocal approximation to the kernel of TDDFT, which is free of the contradictions that plague the standard local density approximation (LDA) to TDDFT. As an application of this general scheme, we calculate the dynamical xc contribution to the stopping power of electron liquids for slow ions to find that our results are in considerably better agreement with experiment than those obtained using TDDFT in the conventional LDA.Comment: 6 pages, 3 figures, accepted to Phys. Rev.

Strain driven anisotropic magnetoresistance in antiferromagnetic La0.4_{0.4}Sr0.6_{0.6}MnO3_{3}

We investigate the effects of strain on antiferromagntic (AFM) single crystal thin films of La$_{1-x}$Sr$_{x}$MnO$_{3}$ (x = 0.6). Nominally unstrained samples have strong magnetoresistance with anisotropic magnetoresistances (AMR) of up to 8%. Compressive strain suppresses magnetoresistance but generates AMR values of up to 63%. Tensile strain presents the only case of a metal-insulator transition and demonstrates a previously unreported AMR behavior. In all three cases, we find evidence of magnetic ordering and no indication of a global ferromagnetic phase transition. These behaviors are attributed to epitaxy induced changes in orbital occupation driving different magnetic ordering types. Our findings suggest that different AFM ordering types have a profound impact on the AMR magnitude and character.Comment: http://dx.doi.org/10.1063/1.489242