Spectroscopic Evidence for the Specific Na+ and K+ Interactions with the Hydrogen-bonded Water Molecules at the Electrolyte Aqueous Solution Surfaces

Sum frequency generation vibrational spectra of the water molecules at the NaF and KF aqueous solution surfaces showed significantly different spectral features and different concentration dependence. This result is the first direct observation of the cation effects of the simple alkali cations, which have been believed to be depleted from the aqueous surface, on the hydrogen bonding structure of the water molecules at the electrolyte solution surfaces. These observations may provide important clue to understand the fundamental phenomenon of ions at the air/water interface.Comment: 15 pages, 2 figure

Measuring the energy handling capability of metal oxide varistors

Metal oxide varistors are widely used in many power electronics circuits to protect against transient over voltages. Certain applications are very demanding on the energy handling capability of the varistors. This paper gives an overview of the failure modes of ZnO varistors and investigates their characteristics when subjected to repetitive current pulses. It describes the puncture failure mode caused by melting of a region in the varistor of local current concentration. Experimental tests are performed to evaluate the puncture energy using an infrared imaging camera. A relationship between the energy absorption and the varistor maximum surface temperature is obtained. It is shown that the destructive energy depends strongly on the uniformity of the varistor; the more uniform, the higher the energy handling capability. The paper also presents the results of nondestructive tests using a scanning acoustic microscope to evaluate the uniformity of the varistor

Dynamics of Heterogeneous Congestion Tolerance in the Location Choices of U.S. Gulf of Mexico Shrimp Fishermen

Location choice is one of the most important short-run decisions made by commercial fishermen. Previous studies of location choice by commercial fishermen have focused primarily on site fidelity, profit-maximization behavior, and risk attitudes as factors influencing their location choice behavior. Although the recreational literature gives extensive consideration to the influence of congestion on site selection, few studies have considered the influence of congestion tolerance on site selection in the commercial fishing sector. This study uses a mixed logit model to analyze the heterogeneous congestion tolerance in location choice among U.S. Gulf of Mexico shrimp fishermen. The dynamics of fishermen responses to economic conditions are compared and contrasted for two periods; the first period coinciding with relative economic stability in the industry and the second period coinciding with deteriorating economic conditions. Results suggest that congestion externalities have significant influence on the location choice of shrimp fishermen, but that congestion tolerance level differs among them. A better understanding of heterogeneous congestion tolerance should aid the implementation of management tools such as area closures.location choice, congestion, mixed logit, shrimp fishery, Resource /Energy Economics and Policy,

Location Choice Behavior of Gulf of Mexico Shrimpers under Dynamic Economic Conditions

This study uses a mixed logit model to analyze monetary and nonmonetary factors that influence location choice behavior of the U.S. Gulf of Mexico shrimpers. Shrimpers’ responses to economic conditions are compared and contrasted for two periods related to changing economic conditions in the industry. Results show that even though shrimpers are generally revenue driven in choosing a fishing site, their past experience also plays an important role. Further, changes in economic conditions appear to exhibit an influence on the risk attitudes of some shrimpers.location choice, loyalty, mixed Logit, risk averse, shrimp fishery, Resource /Energy Economics and Policy, Q2, L2,

Existence and comparison theorems for algebraic Riccati equations for continuous- and discrete-time systems

AbstractWe discuss two comparison theorems for algebraic Riccati equations of the form XBR-1 B∗X−X(A−BR-1C)-(A−BR-1C)∗X−(Q−C∗R-1C) = 0. Simultaneously we give sufficient conditions to obtain the existence of the maximal hermitian solution of a Riccati equation from the existence of a hermitian solution of a second Riccati equation. Further, similar results are given for discrete algebraic Riccati equations

Nodal Spin Density Wave and band topology of the FeAs based materials

The recently discovered FeAs-based materials exhibit a $(\pi,0)$ Spin Density Wave (SDW) in the undoped state, which gives way to superconductivity upon doping. Here we show that due to an interesting topological feature of the band structure, the SDW state cannot acquire a full gap. This is demonstrated within the SDW mean-field theory of both a simplified two band model and a more realistic 5-band model. The positions of the nodes are different in the two models and can be used to detected the validity of each model.Comment: rewritten for clarit