Contracts, Quality, and Default: Endogenizing a Buyer's Rejection Rate

Replaced with revised version of paper 08/06/07.Consumer/Household Economics, Demand and Price Analysis,

Saturated Critical Heat Flux in a Multi-Microchannel Heat Sink Fed by a Split Flow System

An extensive experimental campaign has been carried out for the measurement of saturated critical heat flux in a multi-microchannel copper heat sink. The heat sink was formed by 29 parallel channels that were 199 μm wide and 756 μm deep. In order to increase the critical heat flux and reduce the two-phase pressure drop, a split flow system was implemented with one central inlet at the middle of the channels and two outlets at either end. The base critical heat flux was measured using three HFC Refrigerants (R134a, R236fa and R245fa) for mass fluxes ranging from 250 to 1500 kg/m2 s, inlet subcoolings from −25 to −5 K and saturation temperatures from 20 to 50 °C. The parametric effects of mass velocity, saturation temperature and inlet subcooling were investigated. The analysis showed that significantly higher CHF was obtainable with the split flow system (one inlet–two outlets) compared to the single inlet–single outlet system, providing also a much lower pressure drop. Notably several existing predictive methods matched the experimental data quite well and quantitatively predicted the benefit of higher CHF of the split flow

Idempotency of linear combinations of an idempotent matrix and a t-potent matrix that commute

AbstractThis paper deals with idempotent matrices (i.e., A2=A) and t-potent matrices (i.e., Bt=B). When both matrices commute, we derive a list of all complex numbers c1 and c2 such that c1A+c2B is an idempotent matrix. In addition, the real case is also analyzed

Advanced superconducting magnets investigation

Mathematical models for steady state behavior of composite superconductors and experimental verification using magnet coi

Two-Phase Cooling of Targets and Electronics for Particle Physics Experiments

An overview of the LTCM lab’s decade of experience with two-phase cooling research for computer chips and power electronics will be described with its possible beneficial application to high-energy physics experiments. Flow boiling in multi-microchannel cooling elements in silicon (or aluminium) have the potential to provide high cooling rates (up to as high as 350 W/cm2), stable and uniform temperatures of targets and electronics, and lightweight construction while also minimizing the fluid inventory. An overview of two-phase flow and boiling research in single microchannels and multi-microchannel test elements will be presented together with video images of these flows. The objective is to stimulate discussion on the use of two-phase cooling in these demanding applications, including the possible use of CO2

Design study of superconducting magnets for a combustion magnetohydrodynamic (MHD) generator

Design trade off studies for 13 different superconducting magnet systems were carried out. Based on these results, preliminary design characteristics were prepared for several superconducting magnet systems suitable for use with a combustion driven MHD generator. Each magnet generates a field level of 8 T in a volume 1.524 m (60 in.) long with a cross section 0.254 m x 0.254 m (10 in. x 10 in.) at the inlet and 0.406 m x .406 m (16 in. x 16 in.) at the outlet. The first design involves a racetrack coil geometry intended for operation at 4.2 K; the second design uses a racetrack geometry at 2.0 K; and the third design utilizes a rectangular saddle geometry at 4.2 K. Each case was oriented differently in terms of MHD channel axis and main field direction relative to gravity in order to evaluate fabrication ease. All cases were designed such that the system could be disassembled to allow for alteration of field gradient in the MHD channel by changing the angle between coils. Preliminary design characteristics and assembly drawings were generated for each case

M-222 Slope Stabilization Case History – Geotechnical Lessons Learned from Michigan Department of Transportation Design Build Project

In 2009, the Michigan Department of Transportation (MDOT) became concerned about ongoing slope movements adjacent to a segment of M-222 located on outside bend of the Kalamazoo River in the City of Allegan, Michigan. Over the next couple years, continued river erosion and seasonally wet springs caused 8- to 10-foot high scarps adjacent to M-222, condemnation of a home, and several large block slides into the river. In the early spring of 2011, MDOT secured their first Construction Manager/General Contractor (CMGC) delivery method contract to protect M-222 and repair the slope. Improvements included constructing an up to 26-foot tall retaining wall, re-grading the roughly 70-foot high slope, and armoring the toe of slope. The improvements used were selected based on assessed risks and mobility requirements. Construction of the project began in July of 2011 and was completed in spring of 2012. A history of the slope instability progression using aerial photography, selection and design of the improvements, and resulting construction challenges are discussed. The authors conclusions on geotechnical lessons learned are shared

ZNF804A genotype modulates neural activity during working memory for faces

Copyright © 2013 S. Karger AG, Basel.Peer reviewedPublisher PD

Blink rate and blink timing in children with ADHD and the influence of stimulant medication

Spontaneous eye blink rate is modulated by task demands and internal state, and is demonstrated to reflect central dopamine activity. Also, spontaneous eye blinks are strategically timed around salient stimuli. This study investigates whether children with attention deficit hyperactivity disorder (ADHD) show reduced blink rates, blink modulation and blink timing, and whether this is influenced by stimulant medication. The electrooculogram was measured in 18 typically developing children, 16 children with ADHD off methylphenidate (Mph), and 16 children with ADHD on Mph during a rest period and during performance of a 60-min visual selective attention task. Blink rate and timing was extracted from the electrooculogram. No evidence was found for aberrant blink rate or blink modulation in children with ADHD off Mph. All groups increased blink rates from rest to task, and no group differences were found in blink rate during rest and task, or in the modulation of blink rate from rest to task. Time-on task resulted in a similar increase in blink rates in all three groups. Stimulant medication appeared not to influence blink rate and blink modulation, except that in the ADHD off Mph group the blink rate was enhanced only under conditions with performance feedback. All groups inhibited blinks before stimulus presentation and strategically timed their blinks after the stimulus. Children with ADHD off Mph showed reduced blink inhibition before the stimulus; however, given the low incidence (\1 % of the trials) and long latency this is not likely to impair their visual intake