Non-integrability of density perturbations in the FRW universe

We investigate the evolution equation of linear density perturbations in the Friedmann-Robertson-Walker universe with matter, radiation and the cosmological constant. The concept of solvability by quadratures is defined and used to prove that there are no "closed form" solutions except for the known Chernin, Heath, Meszaros and simple degenerate ones. The analysis is performed applying Kovacic's algorithm. The possibility of the existence of other, more general solutions involving special functions is also investigated.Comment: 13 pages. The latest version with added references, and a relevant new paragraph in section I

Student-computer interface on an intelligent tutoring system for Japanese language instruction, The

Includes bibliographical references.This work describes the human-computer interaction of an intelligent tutoring system designed to mediate some of the difficulties of acquiring proficiency in reading technical Japanese material.This material is based upon work supported by the National Science Foundation under Grant No. INT8818039

Kinetic limitations on the use of redundancy in robotic manipulators

Includes bibliographical references (page 210).The kinematic specification of motion for redundant manipulators has relied primarily on a formulation that decomposes joint velocity solutions into a pseudoinverse component and a homogeneous solution component. While such a formulation is conceptually appealing, since it treats the redundant degrees of freedom as independent from those required to maintain a desired end effector trajectory, it has been shown to be physically inaccurate when applied to the kinetic behavior of redundant manipulators. In this work, the kinetic behavior of the homogeneous solution component is analyzed in order to specify realistic limitations on the use of redundancy. It is shown that the equations that govern these limitations are related to the conditions for guaranteeing stability of the local torque minimization formulation

The Effectiveness of Mainstreaming Special Needs Students with Regular Students in a High School Classroom Setting

The goals of this study were to answer the following questions: 1. Are special needs students as successful in a regular classroom setting as other students are? 2. Do special needs students work and learn as well as other students in a regular classroom setting? 3. Do special needs students respond to the various teaching methods as well as other students? 4. Do special needs students respond to media and training aids as well as other students? 5. Is mainstreaming special needs students in a regular classroom setting successful overall or should other improvements be made

Computationally efficient ray tracing of parametric surfaces

Includes bibliographical references (page 9).Abstract also in Japanese.Algorithms for ray tracing parametric surfaces are in general too computationally expensive to be widely applicable. The algorithm presented here combines well-known graphics procedures with a modified Newton iteration to provide a computationally efficient means of including parametric surfaces in a ray traced image. By allowing only planar surfaces to be reflective and/or refractive the resulting high degree of ray coherence is utilized to make the algorithm incremental and results in an order of magnitude improvement in computation speed over existing algorithms

CCD BV survey of 42 open clusters

We present results of a photometric survey whose aim was to derive structural and astrophysical parameters for 42 open clusters. While our sample is definitively not representative of the total open cluster sample in the Galaxy, it does cover a wide range of cluster parameters and is uniform enough to allow for simple statistical considerations. BV wide-field CCD photometry was obtained for open clusters for which photometric, structural, and dynamical evolution parameters were determined. The limiting and core radii were determined by analyzing radial density profiles. The ages, reddenings, and distances were obtained from the solar metallicity isochrone fitting. The mass function was used to study the dynamical state of the systems, mass segregation effect and to estimate the total mass and number of cluster members. This study reports on the first determination of basic parameters for 11 out of 42 observed open clusters. The angular sizes for the majority of the observed clusters appear to be several times larger than the catalogue data indicate. The core and limiting cluster radii are correlated and the latter parameter is 3.2 times larger on average. The limiting radius increases with the cluster's mass, and both the limiting and core radii decrease in the course of dynamical evolution. For dynamically not advanced clusters, the mass function slope is similar to the universal IMF slope. For more evolved systems, the effect of evaporation of low-mass members is clearly visible. The initial mass segregation is present in all the observed young clusters, whereas the dynamical mass segregation appears in clusters older than about log(age)=8. Low-mass stars are deficient in the cores of clusters older than log(age)=8.5 and not younger than one relaxation time.Comment: 13 pages, 8 figure