We applied the locally self-consistent multiple scattering (LSMS) method to the study Fe-based bulk amorphous metals. The LSMS method is an order-N approach to the electronic structure calculation for solid state mate...
详细信息
We applied the locally self-consistent multiple scattering (LSMS) method to the study Fe-based bulk amorphous metals. The LSMS method is an order-N approach to the electronic structure calculation for solid state materials based on density functional theory and local density approximation. Using LSMS method, we performed electronic structure calculations for the supercell samples generated by ab-initio molecular dynamics simulation. The equilibrium atomic volume and the bulk modulus are calculated based on the energy versus volume curve. The magnetic moment distribution in the samples is determined for both collinear and noncollinear cases. A comparison with the experimental results is also made.
A strategy for maintaining separation distances between several satellites in a coplanar elliptical orbiting constellation is developed. A possible scientific application of such a system would be in measuring the cur...
详细信息
A strategy for maintaining separation distances between several satellites in a coplanar elliptical orbiting constellation is developed. A possible scientific application of such a system would be in measuring the curl of the Earth's magnetic field by taking simultaneous measurements along the elliptical orbit. The strategy involves maneuvers which would cause small shifts in the direction of the four semimajor axes. With this approach for Keplerian type orbits, the separation distance between adjacent satellites remains within a few percent of the nominal separation distance. This paper emphasizes problems of implementation: 1. Initial deployment. It is assumed that the satellites are launched by a single vehicle. The method to distribute the satellites into their positions using the least maneuver energy is studied. 2. Maintenance of the separation distance. Since the math.matical model is nonlinear and time-variant, a nonlinear control law based on a Lyapunov function is applied to the osculating orbital elements of the daughter satellites. The simulation results with this control show that with perturbations (mainly caused by J2), the response to initial errors converges smoothly and the control energy spent is at a very low level.
We revisit the two standard dense methods for matrix Sylvester and Lyapunov equations: The Bartels-Stewart method for A1X+XA2+D=0 and Hammarling's method for AX+XAT+BBT=0 with A stable. We construct three schemes ...
This project used Eberhardt's team functions as an observational protocol to examine the team process as it occurred in the Engineering Practices Introductory Course Sequence (EPICS) at the Colorado School of Mine...
详细信息
This project used Eberhardt's team functions as an observational protocol to examine the team process as it occurred in the Engineering Practices Introductory Course Sequence (EPICS) at the Colorado School of Mines. A design report scoring rubric was used to evaluate the quality of the team-produced final report. The results of this study suggest that the gender composition of the teams impacted both the interactions that took place during the team process and the quality of the team's final report. Members of majority male teams were more likely to be witnessed clarifying and standard setting during team interactions than were members of majority female teams. During the first course, the final reports that were produced by majority male teams on average were judged to be of higher quality than were those that were produced by majority female teams. The reverse was found to be true in the second course.
For a class of continuous - time nonlinear system, a novel robust adaptive fuzzy controller is proposed by using of Lyapunov method. It is proven that the control algorithm is globally stable, the output tracking - er...
详细信息
ISBN:
(纸本)0780372689
For a class of continuous - time nonlinear system, a novel robust adaptive fuzzy controller is proposed by using of Lyapunov method. It is proven that the control algorithm is globally stable, the output tracking - error of the system can convergence to a domain of zero under the assumptions. As a result, the system controled has stronger robustness for disturbance and modeling error.
A common problem that faces many high-tech electronic product companies is how to effectively provide systems support for their products/machines/systems installed at various customer sites using different levels of t...
详细信息
A common problem that faces many high-tech electronic product companies is how to effectively provide systems support for their products/machines/systems installed at various customer sites using different levels of technical personnel. The problem can be viewed as a model with multiple level servers and multiple volume demands. In this paper, a semi-Markov decision process with average criterion has been employed to formulate the dynamics of the system. Optimal policies for human resource allocation decision with minimum costs have been derived and the loss rate for customer requests has been considered. We prove that the embedding Markov chain is ergodic, induced by any stationary deterministic policy. We obtain some related parameters which can answer questions from managers. We also provide some numerical examples.
The boom of electronic commerce requires existence and use of reliable means of authentication of communicating parties. We need an analogy of hand-written signature that can be applied to electronic documents. We sha...
详细信息
The boom of electronic commerce requires existence and use of reliable means of authentication of communicating parties. We need an analogy of hand-written signature that can be applied to electronic documents. We shall call such a concept an electronic signature. There is a current trend to make electronic signatures meeting some requirements equal to hand-written signatures. This makes it a very powerful tool but, on the other hand, there are some sensitive security issues that have to be discussed and that the potential users should be aware of. In this article we would like to point out some of these issues and especially those that all electronic signature users are affected by. We have to say, it is very unwise to use a software only implementation on a non-dedicated hardware to create electronic signatures if the responsibility for such signature is not limited. Using a hardware cryptographic module that is incapable of displaying the data to be signed may still be unsatisfactory. Using a module without an independent input for authorization data does not help much, a module with an independent input is significantly better but the danger is still far from negligible. Using a dedicated system to create electronic signatures can solve many of the problems. On the other hand, it is the most expensive solution considered. We will describe a solution that is both relatively cheap and reasonably secure. We also suggest some affordable key management solutions.
We present a new scheduling algorithm Odd-Even4, which not only guarantees the hard deadlines of all periodic tasks with fewer context switches but also minimizes the average response time of bounded predictable tasks...
详细信息
In this paper we propose the Sisyphus database retrieval software performance antipattern. The antipattern occurs in application designs that process large, frequently accessed lists stored in a relational database, b...
详细信息
ISBN:
(纸本)1581135637
In this paper we propose the Sisyphus database retrieval software performance antipattern. The antipattern occurs in application designs that process large, frequently accessed lists stored in a relational database, but display only a small subset to the user. Software Performance Engineering (SPE) techniques are used to analyze the antipattern. Four solutions are evaluated: rownum and index, upper/lower bound, sequence numbering, and caching. We discuss the real world challenges of correcting this antipattern early in the application life cycle.
暂无评论