Understanding the temperature and the chemical potential using computer simulations

Several Monte Carlo algorithms and applications that are useful for understanding the concepts of temperature and chemical potential are discussed. We then introduce a generalization of the demon algorithm that measures the chemical potential and is suitable for simulating systems with variable particle number.Comment: 23 pages including 6 figure

Weak Microlensing

A nearby star having a near-transit of a galaxy will cause a time-dependent weak lensing of the galaxy. Because the effect is small, we refer to this as weak microlensing. This could provide a useful method to weigh low-mass stars and brown dwarfs. We examine the feasibility of measuring masses in this way and we find that a star causes measurable weak microlensing in a galaxy even at 10 Einstein radii away. Of order one magnitude I < 25 galaxy comes close enough to one or other of the ~100 nearest stars per year.Comment: Accepted for publication in MNRAS (4 pages, 5 figures, 1 table

The Unsubstantiated Claims of Turkat’s Harmful Effects of Child-Custody Evaluations on Children

We welcome the opportunity to respond to Dr. Turkat’s article, Harmful Effects of Child-Custody Evaluations on Children. We believe that there are many flaws and unsubstantiated claims made by Dr. Turkat, and we challenge his primary thesis that child-custody evaluations are, by definition, harmful. Dr. Turkat sets the tone in his first paragraph with his sweeping statements that “child-custody evaluations [have] no scientific validity” and “there is still no scientific evidence whatsoever that a child-custody evaluation results in beneficial outcomes for the children involved.” His article includes too many generalized, unsupported charges to allow it to pass without challenge. We hope that our comments will contribute to more informed discussion clarifying misunderstandings about the role and value of custody evaluations and how they should properly be introduced into court proceedings

The Unsubstantiated Claims of Turkat’s Harmful Effects of Child-Custody Evaluations on Children

We welcome the opportunity to respond to Dr. Turkat’s article, Harmful Effects of Child-Custody Evaluations on Children. We believe that there are many flaws and unsubstantiated claims made by Dr. Turkat, and we challenge his primary thesis that child-custody evaluations are, by definition, harmful. Dr. Turkat sets the tone in his first paragraph with his sweeping statements that “child-custody evaluations [have] no scientific validity” and “there is still no scientific evidence whatsoever that a child-custody evaluation results in beneficial outcomes for the children involved.” His article includes too many generalized, unsupported charges to allow it to pass without challenge. We hope that our comments will contribute to more informed discussion clarifying misunderstandings about the role and value of custody evaluations and how they should properly be introduced into court proceedings

The Politics of Deference

Like so much else in our politics, the administrative state is fiercely contested. Conservatives decry its legitimacy and seek to limit its power; liberals defend its necessity and legality. Debates have increasingly centered on the doctrine of Chevron deference, under which courts defer to agencies’ reasonable interpretations of ambiguous statutory language. Given both sides’ increasingly entrenched positions, it is easy to think that conservatives have always warned of the dangers of deference, while liberals have always defended its virtues. Not so. This Article tells the political history of deference for the first time, using previously untapped primary sources including presidential and congressional archives, statements by interest groups, and partisan media sources. It recounts how the politics of deference have varied over time, even though the issue is often framed in terms that resist evolutionary analysis. As the administrative state grew in the 1970s, conservatives in Congress sought to rein in deference, while liberals defended it. These positions reversed in the 1980s, as the Reagan Administration relied on flexible readings of statutes in service of its deregulatory efforts, including in the Chevron case itself. After a period of political détente, the 2010s witnessed a resurgence of conservative opposition to and liberal support for Chevron, driven largely by the ascendance of libertarian interests in the Republican Party and the increasingly central role of administrative policymaking to the Democratic Party’s agenda. The Article then develops a framework for understanding the shifting politics of deference. It argues that the politics of deference are the politics of regulation: for nearly a half century, partisans and interest groups have viewed doctrinal debates as inexorably tied to interests in policy outcomes. Positions about Chevron have varied based on which party controls the presidency and the ideological makeup of the federal courts. But the parties are also asymmetrically reliant on the administrative state, and thus on judicial deference. Liberals depend on deference to advance their regulatory goals in the face of an often-gridlocked Congress, while conservatives have many paths to accomplishing their deregulatory ends. The conservative turn against the so- called “deep state” and Chevron’s nonapplication in areas where conservatives most favor deference (such as national security) further exacerbate the partisan split on the doctrine. And, apart from its real-world impacts, Chevron has become a rhetorical cudgel in broader debates about the legality and legitimacy of the administrative state as a whole. Unless these dynamics change, Chevron deference will continue to have a political valence. And so long as the doctrine is understood to create winners and losers, partisans and interest groups will fight to ensure its survival or hasten its demise

Soyuz/ACRV accommodation study

Included is a set of viewgraphs that present the results of a study conducted at the LaRC Space Station Freedom Office at the request of the Space Station Freedom Level 1 Program Office and the JSC ACRV Project Office to determine the implications of accommodating two Soyuz TM spacecraft as Assured Crew Return Vehicles (ACRV) on the Space Station Freedom (SSF) at the Permanently Crewed Capability (PCC) stage. The study examined operational as well as system issues associated with the accommodation of the Soyuz for several potential configuration options. Operational issues considered include physical hardware clearances, worst case Soyuz departure paths, and impacts to baseline operations such as Pressurized Logistics Module (PLM) exchange, Space Station Remote Manipulator System (SSRMS) attachment, Extravehicular Activity (EVA), and automatic rendezvous and docking (AR&D). Systems impact analysis included determining differences between Soyuz interface requirements and SSF capabilities for the Electrical Power System (EPS), Thermal Control System (TCS), Communications and Tracking (C&T), Audio-Video Subsystem (A/V), Data Management System (DMS), and Environmental Control and Life Support System (ECLSS). Significant findings of this study have indicated that the current AV capability of the Soyuz will need to be increased to provide adequate departure clearances for a worst case escape from an uncontrolled SSF and that an interface element will be required to mate the Soyuz vehicles to station, provide for AR&D structural loads, and to house Soyuz-to-SSF system interfaces

Overcoming the critical slowing down of flat-histogram Monte Carlo simulations: Cluster updates and optimized broad-histogram ensembles

We study the performance of Monte Carlo simulations that sample a broad histogram in energy by determining the mean first-passage time to span the entire energy space of d-dimensional ferromagnetic Ising/Potts models. We first show that flat-histogram Monte Carlo methods with single-spin flip updates such as the Wang-Landau algorithm or the multicanonical method perform sub-optimally in comparison to an unbiased Markovian random walk in energy space. For the d=1,2,3 Ising model, the mean first-passage time \tau scales with the number of spins N=L^d as \tau \propto N^2L^z. The critical exponent z is found to decrease as the dimensionality d is increased. In the mean-field limit of infinite dimensions we find that z vanishes up to logarithmic corrections. We then demonstrate how the slowdown characterized by z>0 for finite d can be overcome by two complementary approaches - cluster dynamics in connection with Wang-Landau sampling and the recently developed ensemble optimization technique. Both approaches are found to improve the random walk in energy space so that \tau \propto N^2 up to logarithmic corrections for the d=1 and d=2 Ising model

Sustainable Transportation for Maine’s Future

Maine is dependent on its transportation infrastructure for continued economic strength and growth, particularly on the 22,670 miles of public roads. Maine ranks fourteenth in the nation for the largest number of highway miles traveled annually per capita - 14,912 per year. Maine is highly reliant on its road system because large areas of the State lack transportation alternatives. This means that the current and future condition of the roadways is a major concern. How such a crucial infrastructure will continue to be supported and enhanced financially to meet the growing needs of the State must be considered carefully

Design and implementation of an execution domain for LOIS

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (leaf 82).by Adam J. Gould.M.Eng