Better materials can reduce the threat from terrorism

... you will never have a perfect defense, not against the bullet, not against the tank and not against nuclear weapons. What you can do is vastly complicate an attacker’s calculations, blunt his force and save millions of lives. For more information, contact Toni Maréchaux at National Research Council, 2101 Constitution Ave. NW, National Materials Advisory Board, Washington, D.C., 20418; e-mail tmarecha@nas.edu.; www.national academies.org/nmab.     

The Reliability of Microalloyed Sn-Ag-Cu Solder Interconnections Under Cyclic Thermal and Mechanical Shock Loading

In this study, the performance of three microalloyed Sn-Ag-Cu solder interconnection compositions (Sn-3.1Ag-0.52Cu, Sn-3.0Ag-0.52Cu-0.24Bi, and Sn-1.1Ag-0.52Cu-0.1Ni) was compared under mechanical shock loading (JESD22-B111 standard) and cyclic thermal loading (40 ± 125°C, 42 min cycle) conditions. In the drop tests, the component boards with the low-silver nickel-containing composition (Sn-Ag-Cu-Ni) showed the highest average number of drops-to-failure, while those with the bismuth-containing alloy (Sn-Ag-Cu-Bi) showed the lowest. Results of the thermal cycling tests showed that boards with Sn-Ag-Cu-Bi interconnections performed the best, while those with Sn-Ag-Cu-Ni performed the worst. Sn-Ag-Cu was placed in the middle in both tests. In this paper, we demonstrate that solder strength is an essential reliability factor and that higher strength can be beneficial for thermal cycling reliability but detrimental to drop reliability. We discuss these findings from the perspective of the microstructures and mechanical properties of the three solder interconnection compositions and, based on a comprehensive literature review, investigate how the differences in the solder compositions influence the mechanical properties of the interconnections and discuss how the differences are reflected in the failure mechanisms under both loading conditions.     

Characterization of UHF RFID tags fabricated directly on convex surfaces by pad printing

The possibility of pad printing in RFID tag antenna manufacturing is investigated. Passive UHF RFID tags were printed on flat and on convex surfaces with two different polymer thick-film silver inks. The effect of the ink and substrate material properties on tag antenna performance was examined. The goal was to provide information which is needed in adapting the pad-printing technique in RFID tag manufacture. The results show that pad printing is suitable for tag manufacturing on flat and on convex surfaces. The curvature of the substrate did not significantly affect the tag performance. It was more important to take into consideration other substrate properties, ink characteristics, morphology, and printing parameters. The best practice is to take these matters into consideration in the initial tag design process to ensure proper tag performance at the desired frequency.     

Heat and mass transfer during adsorption of ammonia in a cylindrical adsorbent bed: thermal performance study of a combined parabolic solar collector, water heat pipe and adsorber generator assembly

In this paper we present the study of adsorption refrigerator which use an activated carbon-pair ammonia. The ability of activated carbons to adsorb large mass of ammonia makes them ideal for use in adsorption refrigeration and pump systems. These systems have not reasonable efficiency. In order to make these systems economically viable, their size must be reduced. This implies a need for a rapid heating and cooling the adsorbent/refrigerant pair. However, the main problems to be overcome is related to the poor heat transfer in the adsorbent bed. So, it is necessary to study and understand the heat and mass transfer within the bed and to improve it. A detailed model of heat and mass transfer into the generator has been developed. For a given heat flux, temperature and adsorbed mass have been computed in every point at each step time along the adsorbed bed (generator). Experimental installation simulating an adsorption machine working within a temperature ranging from 20 to 250 °C and pressure ranging from 0 to 2.5 × 10⁶ Pa, allows for identification of the generator's equivalent thermal conductivity and internal heat transfer coefficient. These two parameters are then used to simulate thermal performance of a design whose features include the insertion of stainless steel water heat pipe (HP's) condensers into the generator. The HP's evaporator heat input is of solar origin using a compound parabolic collector (CPC). Nominal Solar coefficient of performance, COPs =14.37% obtained through both Adimensional Exergy Loss (AEL), and COP study, shows the competitiveness of the proposed design.     

Modelling the changes induced by chronic desipramine treatment on the factors governing the agonism at prejunctional alpha 2-adrenoceptors

1. The adaptational changes induced after chronic desipramine treatment on functional responsiveness of alpha 2-adrenoceptor activation were investigated in prostatic portions of the rat vas deferens. 2. For this purpose, clonidine and xylazine were studied for their effects on twitch contractions elicited by electrical field stimulation of prostatic portions removed 48 h after the last injection to the animals of vehicle or desipramine (10 mg kg-1, i.p.; 14 days). Operational model-fitting and the nested hyperbolic method were used to analyse the effects of irreversible receptor alkylation by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ, 300 nM) on the alpha 2-adrenoceptor-mediated effects of clonidine, either in vehicle- or in desipramine-treated animals. 3. Treatment with desipramine decreased the potency (increased the EC50) of clonidine and xylazine by about 12 and 9 fold respectively. However, the treatment did not modify the maximal effect (alpha) elicited by either agonist. The estimates of apparent affinity for clonidine did not depend on the method of calculation as the 'null' method and the 'operational' method gave similar answers. Estimates of tau values for both agonists revealed that chronic desipramine treatment resulted in significant decreases in the efficacy of agonists. However, desipramine treatment was not associated with significant changes in the affinity constant for clonidine while for xylazine, the operational model provided a higher estimate of KA (lower affinity) after desipramine treatment. 4. The results indicate a large receptor reserve at prejunctional alpha 2-adrenoceptors which is modulated by chronic desipramine treatment. 5. The comparison of results obtained after chronic desipramine exposure with those by using EEDQ suggests that chronic desipramine treatment is not a useful experimental intervention for the purpose of estimating agonist affinities and efficacies.     

System-level power-performance tradeoffs for reconfigurable computing

In this paper, we propose a configuration-aware data-partitioning approach for reconfigurable computing. We show how the reconfiguration overhead impacts the data-partitioning process. Moreover, we explore the system-level power-performance tradeoffs available when implementing streaming embedded applications on fine-grained reconfigurable architectures. For a certain group of streaming applications, we show that an efficient hardware/software partitioning algorithm is required when targeting low power. However, if the application objective is performance, then we propose the use of dynamically reconfigurable architectures. We propose a design methodology that adapts the architecture and algorithms to the application requirements. The methodology has been proven to work on a real research platform based on Xilinx devices. Finally, we have applied our methodology and algorithms to the case study of image sharpening, which is required nowadays in digital cameras and mobile phones.     

Effects of success and failure on cheating behavior.

Studied the relationship between cheating and previous success-failure experiences in 32 college students. Ss were informed that if they performed above average on a free-recall task they would receive bonus credit. Half of them were told their performance on a 1st test was poor and half were told that their initial performance was good. During a subsequent test, half of the words were left "carelessly" exposed so that Ss could copy them if they wished. Significant cheating occurred in the success but not in the failure condition, suggesting that failure following initial success may be more repugnant than failure following initial failure. Cheating elevated the number of recorded exposed words, while attention factors and/or arousal reduced recall of stored unexposed words. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Automatic acquisition of syntactic verb classes with basic resources

This paper describes a methodology aimed at grouping Catalan verbs according to their syntactic behavior. Our goal is to acquire a small number of basic classes with a high level of accuracy, using minimal resources. Information on syntactic class, expensive and slow to compile by hand, is useful for any NLP task requiring specific lexical information. We show that it is possible to acquire this kind of information using only a POS-tagged corpus. We perform two clustering experiments. The first one aims at classifying verbs into transitive, intransitive and verbs alternating with a se-construction. Our system achieves an average 0.84 F-score, for a task with a 0.33 baseline. The second experiment aims at further distinguishing among pure intransitives and verbs bearing a prepositional object. The baseline for the task is 0.51 and the upperbound 0.98. The system achieves an average 0.88 F-score.