Mathematics - Science - Experience

Mathematics definition and relation to scienc

Efficiency of the Wang-Landau algorithm: a simple test case

We analyze the efficiency of the Wang-Landau algorithm to sample a multimodal distribution on a prototypical simple test case. We show that the exit time from a metastable state is much smaller for the Wang Landau dynamics than for the original standard Metropolis-Hastings algorithm, in some asymptotic regime. Our results are confirmed by numerical experiments on a more realistic test case

Teams or Tournaments? A Field Experiment on Cooperation and Competition in Academic Achievement

This paper assesses the effect of two stylized and antithetic non-monetary incentive schemes on students’ effort. We collect data from a field experiment where incentives are exogenously imposed, performance is monitored and individual characteristics are observed. Students are randomly assigned to a tournament scheme that fosters competition between coupled students, a cooperative scheme that promotes information sharing and collaboration between students and a control treatment in which students can neither compete, nor cooperate. In line with theoretical predictions, we find that competition induces higher effort with respect to cooperation and cooperation does not increase effort with respect to the baseline. However, this is true only for men, while women do not seem to react to non-monetary incentives.

Thermal Expansion and Magnetostriction Studies of a Kondo Lattice Compound: Ceagsb2

We have investigated a single crystal of CeAgSb2 using low field ac-susceptibility, thermal expansion and magnetostriction measurements in the temperature range 1.5K to 90K. The ac-susceptibility exhibits a sharp peak at 9.7K for both B//c and B perp c due to the magnetic ordering of the Ce moment. The thermal expansion coefficient alpha, exhibits highly anisotropic behaviour between 3K and 80K : alpha is positive for dL/L perp c, but negative for dL/L // c. Furthermore, alpha (for dL/L) perp c (i.e. in ab-plane) exhibits a sharp peak at TN followed by a broad maximum at 20K, while a sharp negative peak at TN followed by a minimum at 20K has been observed for (dL/L //) the c direction. The observed maximum and minimum in alpha(T) at 20K have been attributed to the crystalline field effect on the J=5/2 state of the Ce3+ ion. The magnetostriction also exhibits anisotropic behaviour with a large magnetostriction along the c-axis. The ab-plane magnetostriction exhibits a peak at B=3.3T at 3K, which is consistent with the observed peak in the magnetoresistance measurements.Comment: 4 Pages (B5), 3 figures, submitted to SCES200

Methods for heat transfer and temperature field analysis of the insulated diesel phase 2 progress report

This report describes work done during Phase 2 of a 3 year program aimed at developing a comprehensive heat transfer and thermal analysis methodology for design analysis of insulated diesel engines. The overall program addresses all the key heat transfer issues: (1) spatially and time-resolved convective and radiative in-cylinder heat transfer, (2) steady-state conduction in the overall structure, and (3) cyclical and load/speed temperature transients in the engine structure. During Phase 2, radiation heat transfer model was developed, which accounts for soot formation and burn up. A methodology was developed for carrying out the multi-dimensional finite-element heat conduction calculations within the framework of thermodynamic cycle codes. Studies were carried out using the integrated methodology to address key issues in low heat rejection engines. A wide ranging design analysis matrix was covered, including a variety of insulation strategies, recovery devices and base engine configurations. A single cylinder Cummins engine was installed at Purdue University, and it was brought to a full operational status. The development of instrumentation was continued, concentrating on radiation heat flux detector, total heat flux probe, and accurate pressure-crank angle data acquisition

General and almost general periodic functions

Difference equations and Fourier constants for solving general periodic functions problem

Methods for heat transfer and temperature field analysis of the insulated diesel

Work done during phase 1 of a three-year program aimed at developing a comprehensive heat transfer and thermal analysis methodology oriented specifically to the design requirements of insulated diesel engines is reported. The technology developed in this program makes possible a quantitative analysis of the low heat rejection concept. The program is comprehensive in that it addresses all the heat transfer issues that are critical to the successful development of the low heat rejection diesel engine: (1) in-cylinder convective and radiative heat transfer; (2) cyclic transient heat transfer in thin solid layers at component surfaces adjacent to the combustion chamber; and (3) steady-state heat conduction in the overall engine structure. The Integral Technologies, Inc. (ITI) program is comprised of a set of integrated analytical and experimental tasks. A detailed review of the ITI program approach is provided, including the technical issues which underlie it and a summay of the methods that were developed

Momentum-resolved study of an array of 1D strongly phase-fluctuating Bose gases

We investigate the coherence properties of an array of one-dimensional Bose gases with short-scale phase fluctuations. The momentum distribution is measured using Bragg spectroscopy and an effective coherence length of the whole ensemble is defined. In addition, we propose and demonstrate that time-of-flight absorption imaging can be used as a simple probe to directly measure the coherence-length of 1D gases in the regime where phase-fluctuations are strong. This method is suitable for future studies such as investigating the effect of disorder on the phase coherence.Comment: 4 pages, 4 figure

INDIAN CHILD WELFARE ACT ANNUAL CASE LAW UPDATE AND COMMENTARY

Annually there is an average of 200 appellate cases dealing with the Indian Child Welfare Act (ICWA) —though this includes published and unpublished opinions.[1] Since our first annual review of the case law in 2017, the numbers remain stable. There are approximately thirty reported state appellate court cases involving ICWA each year. This annual review is the only systematic look at the ICWA cases on appeal, including an analysis of who is appealing, what the primary issues are on appeal, and what topical trends are. This article provides a comprehensive catalogue of published ICWA cases from across all fifty states in 2019. Designed as a quick reference for the ICWA practitioner, this article summarizes key case decisions that have interpreted the law in meaningful, significant, or surprising ways and tracks current attempts by ICWA’s opponents to overturn the law piece-by-piece and in its entirety. By providing an overview of last year’s ICWA cases this article is meant to keep practitioners up-to-date so that they can be effective in the juvenile courtroom without sorting through and reading the dozens of cases published across all fifty jurisdictions. [1] Data on file with the authors and journal. Data is collected from both Westlaw and Lexis over the course of the year via case alerts that collect cases from all fifty states and using the search terms “Indian Tribe”, “American Indian”, “Native American.” The cases are sorted into an Excel spreadsheet with case name, date, court, state, whether the case is reported or not, the top two issues, up to three named tribes, the outcome of the case, and who appealed the case. Because the data is over 200 cases, the document is on file with the authors and the journal. All reported cases from the data set are listed at the end of the article