Priority inheritance in soft real-time databases

Due to resource sharing among tasks, priority inversion can occur during priority-driven preemptive scheduling. In this work, we investigate solutions to the priority inversion problem in a soft real-time database environment where two-phhse locking is employed for concurrency control. We examine two basic schemes for addressing the priority inversion problem, one based on priority inheritance and the other based on priority abort. We also study a new scheme, called conditional priority inheritance, which attempts to capitalize on the advantages of each of the two basic schemes. In contrast with previous results obtained in real-time operating systems, our performance studies, conducted on an actual real-time database testbed, indicate that the basic priority inheritance protocol is inappropriate for solving the priority inversion problem in real-time database systems. We identify the reasons for this performance. We also show that the conditional priority inheritance scheme and the priority abort scheme perform well for a wide range of system workloads.This work was supported by the National Science Foundation under Grant IRI-8908693 and by the U.S. Office of Naval Research under Grant N00014-85-K0398.A previous version of this paper appeared in Real-Time Systems Symposium, Dec. 1991.     

Fluorous Iminoalditols: A New Family of Glycosidase Inhibitors and Pharmacological Chaperones

A collection of new reversible glycosidase inhibitors of the iminoalditol type featuring N‐substituents containing perfluorinated regions has been prepared for evaluation of physicochemical, biochemical and diagnostic properties. The vast variety of feasible oligofluoro moieties allows for modular approaches to customised structures according to the intended applications, which are influenced by the fluorine content as well as the distance of the fluorous moiety from the ring nitrogen. The first examples, in particular in the D ‐galacto series, exhibited excellent inhibitory activities. A preliminary screen with two human cell lines showed that, at subinhibitory concentrations, they are powerful pharmacological chaperones enhancing the activities of the catalytically handicapped lysosomal D ‐galactosidase mutants associated with GM1 gangliosidosis and Morquio B disease.     

不含BPA的塑料更安全吗？

这篇短文是对另一篇文章的评论,关注的是化学材料安全性问题。发难者认为监管机构对新材料的审批过于简单,无法足以让公众感到这些材料更为安全。作者对此表明了自己的观点：鉴于围绕化学安全性的争论经过多年仍未有定论,我不认为业界及评论人士会就怎样的测试程度才算足够、以及如何为＂安全＂一词赋予确切的定义上达成一致。     

Isolation of Ambient Particles of Known Critical Supersaturation: The Differential Activation Separator (DAS)

A field-deployable instrument has been developed that isolates from an ambient aerosol those particles that have critical supersaturations, S_c, within a narrow, user-specified, range. This Differential Activation Separator (DAS) consists of two continuous flow diffusion chambers housed within a single enclosure. Particles are introduced into the upstream chamber referred to as the CCN remover (CCNR) near the centerline between a warm, water-soaked, plate and a cool, continuously circulated, water bath. Those particles that activate at the resulting peak supersaturation, S_p, grow quickly and fall into the water bath. The remaining aerosol enters the second chamber referred to as the CCN separator (CCNS), which differs from the CCNR primarily in the use of a salt solution in the lower bath. The imposed temperature differential establishes an S_p slightly higher than that maintained in the upstream chamber, while the presence of a salt solution at the lower boundary results in a subsaturated region in roughly the lower half of the chamber. Those particles having (S_p)_CCNR < S _c < (S_p)_CCNS activate in this chamber and begin to fall due to gravitational settling. Before reaching the lower bath, the droplets evaporate in the subsaturated environment and continue to travel towards the chamber exit. The previously activated particles in the lower half of the chamber and the unactivated particles in the upper half are extracted in separate flows that are subsequently dried. Calibration of the DAS was achieved by measuring the size distribution of separated particles when a polydisperse ammonium sulfate aerosol was introduced.     

Aeroelastic stability predictions for a MW‐sized blade

Classical aeroelastic flutter instability historically has not been a driving issue in wind turbine design. In fact, rarely has this issue even been addressed in the past. Commensurately, among the wind turbines that have been built, rarely has classical flutter ever been observed. However, with the advent of larger turbines fitted with relatively softer blades, classical flutter may become a more important design consideration. In addition, innovative blade designs involving the use of aeroelastic tailoring, wherein the blade twists as it bends under the action of aerodynamic loads to shed load resulting from wind turbulence, may increase the blade's proclivity for flutter. With these considerations in mind it is prudent to revisit aeroelastic stability issues for a MW‐sized blade with and without aeroelastic tailoring. Focusing on aeroelastic stability associated with the shed wake from an individual blade turning in still air, the frequency domain technique developed by Theodorsen for predicting classical flutter in fixed wing aircraft has been adapted for use with a rotor blade. Results indicate that the predicted flutter speed of a MW‐sized blade is slightly greater than twice the operational speed of the rotor. When a moderate amount of aeroelastic tailoring is added to the blade, a modest decrease (12%) in the flutter speed is predicted. By comparison, for a smaller rotor with relatively stiff blades the predicted flutter speed is approximately six times the operating speed. When frequently used approximations to Theodorsen's method are implemented, drastic underpredictions result, which, while conservative, may adversely impact blade design. These underpredictions are also evident when this MW‐sized blade is analysed using time domain methods. Published in 2004 by John Wiley & Sons, Ltd.     

The Effect of Surface Roughness on Contact Fatigue Behavior Using Mesoscopic Approach

The effect of surface roughness on the contact fatigue was investigated in this study. To accomplish this goal, contact analysis based on the influence functions and the rectangular patch solutions was performed to obtain the subsurface stress. Mesoscopic multiaxial fatigue criterion is then applied to predict fatigue damage. Rainbow counting method and damage rule were used to evaluate the fatigue life under random loadings caused by the rough surface contact. As a result of the fatigue analysis, the relationship among the fatigue life, the crack initiation depth, and the surface roughness were revealed. It is observed that the fatigue life has hardly changed and a crack is initiated at subsurface for the surface with the surface roughness below a critical value. However, if the surface roughness exceeds the critical value, fatigue life is remarkably reduced and the site of crack initiation moves to the near surface.     

<Emphasis Type="Italic">In-Situ</Emphasis> Neutron Scattering Measurement of Stress-Strain Behavior of a Bulk Metallic Glass

Bulk metallic glasses (BMGs) are an emerging class of materials whose unique properties make them excellent choices for many applications. As with crystalline metals, the processing and forming techniques used to produce BMG components necessarily result in residual stresses. However, traditional diffraction stress analysis is difficult to apply to BMG components, because they lack the long-range order necessary to produce sharp diffraction patterns, and thus, the internal strains for BMG have not been examined until recently. In this work, in-situ neutron scattering was used to measure the local elastic internal strain distribution in a Zr₅₇Nb₅Cu_15.4Ni_12.6Al₁₀ BMG as a function of applied stress. Various techniques were used to evaluate the internal strain. The strain was determined in real space, by measuring changes in the atomic pair distribution function (PDF). These results can be used to help understand the elastic deformation of BMGs as well be to evaluate current models of BMG deformation. This article is based on a presentation given in the symposium entitled “Bulk Metallic Glasses IV,” which occurred February 25–March 1, 2007 during the TMS Annual Meeting in Orlando, Florida under the auspices of the TMS/ASM Mechanical Behavior of Materials Committee.     

Improving the quality of operations in truckload trucking

In this paper, the authors discuss the quality of operations in the truckioad trucking industry. After introducing the concept of quality in the industry from the perspective of the customer, the carrier, and the driver, the authors introduce a new operational paradigm based on zone dispatching that leads to improved quality from all three perspectives. A review of the current literature indicates that the approach is unique. A comprehensive experimental design supports simulation experiments to examine operational design parameters and to determine solution robustness for zone dispatching alternatives. Results indicate that zone dispatching alternatives compare favorably with baseline point-to-point dispatching methods. Case studies supported by data provided by J.B. Hunt Transport, Inc. further demonstrate the efficacy of the approach as a means of improving the quality of operations in truckioad trucking. Additionally, a research framework is provided to guide future efforts in this area.     

Small signal modeling of GaAs PIN diodes aided by electromagnetic analysis

A systematic procedure is described for determination of GaAs PIN diode equivalent circuit models from measured S‐parameter data combined with an electromagnetic analysis of the feed structure. A new parasitic and intrinsic model topology is proposed, and found to be better suited than prior models for the particular GaAs PIN structures considered in this work. Models were developed for forward bias currents ranging from 0.01 to 100 mA, and example measured and modeled results are included to validate the approach. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 61–68, 2001.     

Risk taking by adolescents with maladaptive behavior histories.

"High-risk" adolescents with maladaptive behavior histories and control adolescents (15–17 years of age) participated in a laboratory experiment that measured aspects of risk-taking behavior. High-risk adolescents had behavioral profiles entailing combinations of past substance use disorder, early onset substance use, conduct disorder, criminal history, and dropping out of school. A risk-taking task presented participants with "risky" and nonrisky response options. The risky response option offered a low probability of a large monetary reward or a high probability of a smaller monetary loss and resulted in a net loss of monetary earnings. The nonrisky option protected current earnings. High-risk adolescents chose the risky option more often, had lower overall earnings, and were more likely to persist in making (losing) risky responses following a single gain on the risky option. The data replicate previous findings with high-risk adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)