Low Mass X-ray Binary As the Progenitor of PSR J1713+0747

We have calculated the evolution of low-mass X-ray binaries that leads to the formation of the binary radio pulsars like PSR J1713+0747. We show that the mass transfer is most likely to be nonconservative, due to unstable disk accretion, to account for the mass of PSR J1713+0747, which is close to its initial value. We assume that part of the lost material from the binary may form a circumbinary disk, and find that it can significantly influence the mass transfer processes. We briefly discuss the implications of the circumbinary disks on the evolution of low-mass X-ray binaries and the formation of low-mass binary pulsars.Comment: 8 pages, 4 figures, accepted for publication in PAS

The Trouble with Racial Quotas in Disparate Impact Remedial Orders

Justice Scalia’s concurring opinion in Ricci v. DeStefano highlighted severe conceptual tensions between the Equal Protection Clause of the Fourteenth Amendment, which protects individuals from racial discrimination, and disparate impact liability, which protects racial groups from adverse effects. Last year’s Supreme Court decision in Texas Department of Housing & Community Affairs v. Inclusive Communities Project, Inc. suggested that disparate impact liability under the Fair Housing Act was constitutionally unproblematic because successful fair housing lawsuits over the past four decades have led to only race-neutral remedial orders enjoining the practice causing the disparate impact. This Article analyzes the constitutionality of another disparate impact remedy: the imposition of racial quotas. Employment lawsuits brought under Title VII of the Civil Rights Act of 1964 have resulted in such remedies, potentially opening the door to an as-applied constitutional challenge arguing that the remedies violate the Equal Protection Clause. The outcome will likely hinge upon the standard of review. Many have argued that a deferential standard is appropriate in light of federal court decisions approving the use of race in census questionnaires, suspect descriptions, and school zoning. This Article challenges that notion and argues that the proper standard is strict scrutiny

Discontinuous Galerkin Method for 1D Shallow Water Flow with Water Surface Slope Limiter

A water surface slope limiting scheme is applied to numerically solve the one dimensional shallow water equations with bottom slope source term. The total variation diminishing Runge-Kutta discontinuous Galerkin finite element method with slope limiter schemes based on water surface and water depth are investigated for solving one-dimensional shallow water equations. For each slope limiter, three different Riemann solvers based on HLL, LF, and Roe flux functions are used. The three different solvers with slope limiters based on water surface and water depth are applied to simulate idealized dambreak problem, hydraulic jump, quiescent flow, subcritical flow, supercritical flow, and transcritical flow. The proposed water surface based slope limiter scheme is easy to implement and shows better conservation property compared to the slope limiter based on water depth for the tests. Of the three flux functions, the Roe approximation provides the best results while the LF function proves to be least suitable when used with either slope limiter scheme

The impact of policy reform on productivity and efficiency in Chinese agriculture: A distance function approach

The study is devoted to the measurement of productivity and efficiency change in Chinese farming sector over the reform process in the 1980s and 1990s. Within an output distance function framework, an index of total factor productivity is decomposed into technical and allocative efficiency, technical change, and scale effects. We estimate a parametric output distance function using individual farm household data from the province Zhejiang over the period 1986-2000. Results indicate that during the more market-oriented reform period in the mid 1980s productivity and technical efficiency increased while allocative efficiency remain constant. However, productivity growth and technical efficiency slow in the mid 1990s when market orientation of the reforms was reduced and self-sufficiency as a major goal reappeared on the political agenda. --productivity growth,efficiency change,China,stochastic distance frontier

The birth rate of subluminous and overluminous type Ia supernovae

Based on the results of Chen & Li (2009) and Pakmor et al. (2010), we carried out a series of binary population synthesis calculations and considered two treatment of common envelope (CE) evolution, i.e. $\alpha$-formalism and $\gamma$-algorithm. We found that the evolution of birth rate of these peculiar SNe Ia is heavily dependent on how to treat the CE evolution. The over-luminous SNe Ia may only occur for $\alpha$-formalism with low CE ejection efficiency and the delay time of the SNe Ia is between 0.4 and 0.8 Gyr. The upper limit of the contribution rate of the supernovae to all SN Ia is less than 0.3%. The delay time of sub-luminous SNe Ia from equal-mass DD systems is between 0.1 and 0.3 Gyr for $\alpha$-formalism with $\alpha=3.0$, while longer than 9 Gyr for $\alpha=1.0$. The range of the delay time for $\gamma$-algorithm is very wide, i.e. longer than 0.22 Gyr, even as long as 15 Gyr. The sub-luminous SNe Ia from equal-mass DD systems may only account for no more than 1% of all SNe Ia observed. The super-Chandrasekhar mass model of Chen & Li (2009) may account for a part of 2003fg-like supernovae and the equal-mass DD model developed by Pakmor et al. (2010) may explain some 1991bg-like events, too. In addition, based on the comparison between theories and observations, including the birth rate and delay time of the 1991bg-like events, we found that the $\gamma$-algorithm is more likely to be an appropriate prescription of the CE evolution of DD systems than the $\alpha$-formalism if the equal-mass DD systems is the progenitor of 1991bg-like SNe Ia.Comment: 8 pages, 2 figures, accepted for publication in A&

MODELING ONE- AND TWO-DIMENSIONAL SHALLOW WATER FLOWS WITH DISCONTINUOUS GALERKIN METHOD

Numerical models for one- and two-dimensional shallow water flows are developed using discontinuous Galerkin method. Formulation and characteristics of shallow water equations are discussed. The well-balanced property and wetting/drying treatment are provided in the numerical models. The shock-capturing property is achieved by the approximate Riemann solvers in the schemes. Effects of different approximate Riemann solvers are also investigated. The Total Variation Diminishing property is achieved by adoption of slope limiters. Different slope limiters and their effects are compared through numerical tests. Numerical tests are performed to validate the models. These tests include dam-break flows, hydraulic jump and shocks in channels, and flows in natural rivers. Results show that the numerical models developed in present work are robust, accurate, and efficient for modeling shallow water flows. The one-dimensional model shows that the area based slope limiter provided the best solution in natural channels. The slope limiter based on the water depth or water surface elevation performs progressively poorer as the cross-section shape deviates from rectangular. In the approximate Riemann solver, the wave speeds are based on the original form of the equations, although the pressure force and the gravity force terms are combined for solving the shallow water equations with discontinuous Galerkin method. The combined term is discretized, in one- and two-dimensional models, such that the stationarity property is preserved. Different wetting and drying procedures are evaluated for the one- and two-dimensional models. Analytical, laboratory, and field tests are conducted to verify the accuracy of the wetting and drying procedures

Policy Reform and Productivity Change in Chinese Agriculture: A Distance Function Approach

Agricultural policy reform has been an important source of change in the Chinese agricultural sector. The reforms led to productivity growth and helped China in pursuing its self-sufficiency goal especially in the grain sector. To analyse whether observable productivity growth stems from technologically induced components, or from the market induced parts, a multi-input-multi-output model is derived using an econometric distance function framework. A decomposition allows to distinguish allocative effects, scale effects, technological change, and technical efficiency change. Data on farms in Zhejiang from 1986 to 1999 are used to analyse the impact of policy reform.Productivity growth, China, Policy reform, Distance function, Productivity Analysis,

POLICY REFORM AND PRODUCTIVITY CHANGE IN CHINESE AGRICULTURE: A DISTANCE FUNCTION APPROACH

Agricultural policy reform has been an important source of change in the Chinese agricultural sector. The reforms led to productivity growth and helped China in pursuing its self- sufficiency goal especially in the grain sector. To analyse whether observable productivity growth stems from technologically induced components, or from the market induced parts, a multi-input-multi-output model is derived using an econometric distance function framework. A decomposition allows to distinguish allocative effects, scale effects, technological change, and technical efficiency change. Data on farms in Zhejiang from 1986 to 1999 are used to analyse the impact of policy reform.Agricultural and Food Policy,