The Maximum Traveling Salesman Problem with Submodular Rewards

In this paper, we look at the problem of finding the tour of maximum reward on an undirected graph where the reward is a submodular function, that has a curvature of $\kappa$, of the edges in the tour. This problem is known to be NP-hard. We analyze two simple algorithms for finding an approximate solution. Both algorithms require $O(|V|^3)$ oracle calls to the submodular function. The approximation factors are shown to be $\frac{1}{2+\kappa}$ and $\max\set{\frac{2}{3(2+\kappa)},2/3(1-\kappa)}$, respectively; so the second method has better bounds for low values of $\kappa$. We also look at how these algorithms perform for a directed graph and investigate a method to consider edge costs in addition to rewards. The problem has direct applications in monitoring an environment using autonomous mobile sensors where the sensing reward depends on the path taken. We provide simulation results to empirically evaluate the performance of the algorithms.Comment: Extended version of ACC 2013 submission (including p-system greedy bound with curvature

Usage of Academic Libraries: The Role of Service Quality, Resources, and User Characteristics

published or submitted for publicatio

Analytical solutions with Generalized Impedance Boundary Conditions (GIBC)

Rigorous uniform geometrical theory of diffraction (UTD) diffraction coefficients are presented for a coated convex cylinder simulated with generalized impedance boundary conditions. In particular, ray solutions are obtained which remain valid in the transition region and reduce uniformly to those in the deep lit and shadow regions. These involve new transition functions in place of the usual Fock-type integrals, characteristics to the impedance cylinder. A uniform asymptotic solution is also presented for observations in the close vicinity of the cylinder. The diffraction coefficients for the convex cylinder are obtained via a generalization of the corresponding ones for the circular cylinder

Choice of Crops and Employment Uncertainty in the Off-farm Labor Market

Cultivator households in some developing areas use off-farm labor supply as an insurance against crop income shocks, whilst employment is uncertain in this off-farm labor market. This paper hypothesizes that, given limited opportunities for ex post consumption smoothing, employment uncertainty influences risk-averse households’ crop choice decisions-- they would opt for more conservative crop choices in case they expect unfavorable supply opportunities in the labor market. A two-period stochastic dynamic programming model is developed. A panel data set from the ICRISAT survey of the semi-arid tropics of India is examined. Estimation is based on random effects and fixed effects Tobit specifications. Estimation results indicate statistically significant impact of household expectation of harvesting period male unemployment rates on ex ante crop choices. Results also indicate strong influence of household irrigated land share on crop choices.Crop Choice; Off-farm Labor Market; Risk; Panel Data

Randomised trials relevant to mental health conducted in low and middle-income countries: protocol for a survey of studies published in 1991, 1995 and 2000 and assessment of their relevance

BACKGROUND A substantial proportion of the psychiatric burden of disease falls on the world's poorest nations. Despite this, relatively little is known about the quality and content of clinical research undertaken in these countries, or the relevance of the interventions evaluated and specifically that of randomised trials. This project aims to survey the content, quality and accessibility of a sample of trials relevant to mental health conducted within low and middle-income countries; to compare these with studies conducted in high-income countries; and to assess their relevance for the needs of low and middle-income countries. METHODS An extensive search for all trials, or possible trials, published in 1991, 1995 and 2000 with participants in low and middle-income countries has already been conducted. Studies evaluating prevention or treatment of a mental health problem within these three years will be identified and further searches conducted to assess completeness of the initial search. Data on study quality and characteristics will be extracted from each report. Accessibility will be estimated based on whether each citation is available on MEDLINE. Trials relevant to schizophrenia will be compared with a random sample of schizophrenia trials from high-income countries in the same years. Topics covered by the trials will be compared with the estimated burden of disease. CONCLUSION Trials and systematic reviews of trials are the gold standard of evaluation of care and increasingly provide the basis for recommendations to clinicians, to providers of care and to policy makers. Results from this study will present the first assessment of the scope, quality and accessibility of mental health trials in low and middle-income countries

Electron Scattering in AlGaN/GaN Structures

We present data on mobility lifetime, $\tau_t$, quantum lifetime, $\tau_q$, and cyclotron resonance lifetime, $\tau_{CR}$, of a sequence of high-mobility two-dimensional electron gases in the AlGaN/GaN system, covering a density range of $\sim1-4.5\times10^{12}$cm$^{-2}$. We observe a large discrepancy between $\tau_q$ and $\tau_{CR}$ ($\tau_q\sim\tau_{CR}$/6) and explain it as the result of density fluctuations of only a few percent. Therefore, only $\tau_{CR}$ --and not $\tau_q$ -- is a reliable measure of the time between electron scattering events in these specimens. The ratio $\tau_t / \tau_{CR}$ increases with increasing density in this series of samples, but scattering over this density range remains predominantly in the large-angle scattering regime

Disorder mediated splitting of the cyclotron resonance in two-dimensional electron systems

We perform a direct study of the magnitude of the anomalous splitting in the cyclotron resonance (CR) of a two-dimensional electron system (2DES) as a function of sample disorder. In a series of AlGaAs/GaAs quantum wells, identical except for a range of carbon doping in the well, we find the CR splitting to vanish at high sample mobilities but to increase dramatically with increasing impurity density and electron scattering rates. This observation lends strong support to the conjecture that the non-zero wavevector, roton-like minimum in the dispersion of 2D magnetoplasmons comes into resonance with the CR, with the two modes being coupled via disorder.Comment: accepted to PRB Rapid Com

Mobile Banking for Empowerment Muslim Women Entrepreneur: Evidence From Asia (Indonesia and Bangladesh)

Objective - Women entrepreneurs have positive contribution to the household economy in particular, and the sustainable economic development in general. Nevertheless, there are limitations in mobility for women entrepreneurs, especially in Muslim countries to conduct their business activities outside the home, which was due to concern, to take care of their children, and the values or customs, which is embraced by the local community, so that limited mobility of women entrepreneurs, not because of the Islamic religiosity. Therefore, is requires form of technology solutions for women entrepreneurs, which can reduce, the limitations.Methods - literature reviewResults - the role of mobile banking as well as branchless banking for women entrepreneurs has been shown to have a very important role to connect their access to financial services. The role of education for women, is also an important factor to improve the knowledge and ability to use technology, including mobile banking services. In addition to the phenomenon of the increasing number of women entrepreneurs and the growing literacy of women in developing countries such as Indonesia and Bangladesh, it will have an impact on increasing the professionalism of women entrepreneurs, and the demand for technology-based financial services such as mobile banking.Conclusions - Implementation of this program must have the support of all stakeholders, including the cooperation between the banks with microfinance institutions to expand the reach of the benefits of this technology