ATM layouts with bounded hop count and congestion

Summary. In this paper we introduce and analyze two new cost measures related to the communication overhead and the space requirements associated with virtual path layouts in ATM networks, that is the edge congestion and the node congestion. Informally, the edge congestion of a given edge e at an incident node u is defined as the number of VPs terminating at or starting from u and using e, while the node congestion of a node v is defined as the number of VPs having v as an endpoint. We investigate the problem of constructing virtual path layouts allowing to connect a specified root node to all the others in at most h hops and with maximum edge or node congestion c, for two given integers h and c. We first give tight results concerning the time complexity of the construction of such layouts for both the two congestion measures, that is we exactly determine all the tractable and intractable cases. Then, we provide some combinatorial bounds for arbitrary networks, together with optimal layouts for specific topologies such as chains, rings and grids. Received: December 1997 / Accepted: August 2000     

Regulatory focus as a mediator of the influence of initiating structure and servant leadership on employee behavior.

In this research, the authors test a model in which the regulatory focus of employees at work mediates the influence of leadership on employee behavior. In a nationally representative sample of 250 workers who responded over 2 time periods, prevention focus mediated the relationship of initiating structure to in-role performance and deviant behavior, whereas promotion focus mediated the relationship of servant leadership to helping and creative behavior. The results indicate that even though initiating structure and servant leadership share some variance in explaining other variables, each leadership style incrementally predicts disparate outcomes after controlling for the other style and dispositional tendencies. A new regulatory focus scale, the Work Regulatory Focus (WRF) Scale, also was developed and initially validated for this study. Implications for the results and the WRF Scale are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of low molecular weight ABS species on properties of PC/ABS systems

Differential scanning calorimetry (DSC), scanning electron microscopy (SEM) rheological, mechanical and impact tests were performed on alloys consisting of polycarbonate (PC) and diverse acrylonitrile‐butadiene‐styrene copolymers (ABS), from which different amounts of low molecular (M) weight (W) species had been previously extracted in a Soxhlet apparatus by methanol. The influence on properties of the alloy composition and of the low MW species amount was investigated. The glass transition temperature (Tg) was found to be a useful probe for monitoring the migration trends of low MW ABS species towards the PC domains for the different alloys. In a morphological analysis it was found that the higher the ABS extraction extent the less the penetration of the etching agent into the surfaces of smoothed specimens. The blend rheological behavior showed that the capability of improving the PC processability, characteristic of commercial ABS's, was strongly lowered by the ABS extracted ones. The alloy modulus was higher when the ABS extraction extent was larger. The yield stress of alloys showed higher values than that of the PC one, particularly at low ABS content. The alloy composition, for which the impact resilience was at its maximum value, strongly depended on the extraction extent. All the above findings seem to suggest an increased adhesion between PC and ABS domains with enhanced extraction amounts of low MW species from the ABS component.     

Cognitive–behavioral therapy to reduce weight concerns improves smoking cessation outcome in weight-concerned women.

Women smokers concerned about weight gain (N?=?219) were randomly assigned to 1 of 3 adjunct treatments accompanying group smoking cessation counseling: (a) behavioral weight control to prevent weight gain (weight control); (b) cognitive–behavioral therapy (CBT) to directly reduce weight concern, in which dieting was discouraged; and (c) standard counseling alone (standard), in which weight gain was not explicitly addressed. Ten sessions were conducted over 7 weeks, and no medication was provided. Continuous abstinence was significantly higher at posttreatment and at 6 and 12 months of follow-up for CBT (56%, 28%, and 21%, respectively), but not for weight control (44%, 18%, and 13%, respectively), relative to standard (31%, 12%, and 9%, respectively). However, weight control, and to a lesser extent CBT, was associated with attenuation of negative mood after quitting. Prequit body mass index, but not change in weight or in weight concerns postquit, predicted cessation outcome at 1 year. In sum, CBT to reduce weight concerns, but not behavioral weight control counseling to prevent weight gain, improves smoking cessation outcome in weight-concerned women. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Use of microwave dielectric loss for characterisation of natural rubber/carbon black composites

Summary Microwave dielectric loss spectroscopy (MDS) has shown remarkable potential as a tool for the observation of changes in elastomer network structure within the interphase region of natural rubber/ carbon black composites. During crosslinking (non elemental sulphur system) the dielectric loss progressively increased. However, during ageing at high temperature the dielectric loss decreased. Parallel studies on the unfilled matrix yielded no such variation in dielectric loss. It was therefore concluded that the changes in microwave responses were related to the development of the interphase during curing and its subsequent destruction during ageing. The microwave response was related to the composite mechanical properties as a function of ageing time. The effect of stabiliser was also investigated. Received: 13 September 1999/Revised version: 7 February 2000/Accepted: 10 February 2000     

A system for in-vivo cardiac optical mapping

Optical mapping of cardiac electrical activity is a valuable technique for studying arrhythmias, particularly the effects of defibrillation shocks. This technique has been exclusively applied to in-vitro preparations of hearts or tissues removed from an animal. But verification of experimental results and hypotheses is ideally performed in vivo on the heart as it remains in place in the animal. However, in-vitro optical mapping instrumentation and techniques cannot be easily applied in vivo. This article describes a system the authors developed to address this problem     

High Loading Fe-supported Fischer–Tropsch Catalysts: Optimization of the Catalyst Performance

The iron loading of catalysts, supported on SiO₂, was investigated between 10 and 75 wt%, with and without the addition of promoters (K and Cu), in order to highlight the different catalytic performances of the samples in the Fischer–Tropsch synthesis. An optimization study of the prepared catalysts (active metal/promoters ratio, catalysts’ activation procedure before the Fischer–Tropsch runs, influence of the feeding gas composition) is reported. The mechanical resistance of the catalysts was also evaluated using a suitable method involving ultrasound.     

Thermo-Elastic Dynamic Instability (TEDI)—a review of recent results

Frictional instabilities arise in a number of engineering and scientific contexts, when the presence of friction renders unstable the uniform motion between parts under nominally uniform conditions. Various classes of friction instabilities exist, those involving friction weakening with speed, and those at constant coefficient of friction. In the latter class, in turn, there are Dynamic Instabilities (DI) and Thermo-Elastic Instabilities (TEI). Recently, by including inertia terms in the formulations of the simple models already studied, the merging of TEI and DI has shown that, although the coupling of dynamic and thermal terms is generally weak (given the significant difference in the typical time scales of the two processes), thermal effects are capable of making otherwise neutrally stable dynamic modes unstable, rendering the new form of instability TEDI (ThermoElastoDynamic Instability) potentially interesting in a number of applications. Some results involving 1D and 2D models of TEDI are reviewed.     

Sandwiched-Beam Procedure for Precracking Brittle Materials

A technique for precracking brittle materials is presented. This procedure, which is called the sandwiched-beam (SB) technique, allows the production of sharp through-thickness cracks with predetermined length in specimens with a rectangular section. A bar, in which an initial notch is produced by using a conventional saw, is inserted between two supporting beams and the sandwich assembly is loaded in three-point bending. Conditions can be defined that allow the stable propagation of a sharp flaw from the notch as the applied load is increased. Then, the cracked bar can be used to determine the fracture toughness. The SB technique is applied to different brittle materials, including soda-lime-silica glass, alumina, Si₃N₄, a SiC _w -Si₃N₄ composite, graphite, a Ti-Al intermetallic, and Carrara marble.