Matching ultrasonic transducer using two matching layers where one of them is glue

The aim of this work is to propose an original solution to the acoustic impedance mismatch between a PZT transducer and a water load. The characteristic acoustic impedance of the PZT is around 33 MRayl. Theoretically, a quarter-wave layer with characteristic acoustic impedance equal to 7 MRayl is necessary to match the transducer to water. In practice, it is difficult to find a material with this particular impedance. Two or more quarter-wave layers may also be used. The following proposed solution consists in using two matching layers where one of them is the glue. Moreover, their thicknesses are not equal to a quarter of their individual wavelength. Once the glue is taken as the first matching layer, the specific material of the second layer can easily be found. In this work, the second layer, which is also the front layer, is made of glass. The thickness of each matching layer is then calculated as a function of the characteristic acoustic impedance of the two layers. The influence of the thickness of these layers is discussed. The proposed matching configuration is analyzed and theoretical results have been carefully and successfully compared with measurements.     

Do organisational and environmental factors moderate the effects of Internet-based interorganisational systems on firm performance?

We developed a model of the relationships among several organisational, interorganisational and technological factors, the adoption of Internet-based interorganisational systems (IBIS) and various measures of firm performance. We used structural equation modelling to empirically test these relationships. The findings showed that adopting IBIS indirectly improves the operational performance of firms through business process performance. The positive effect on financial performance of adopting IBIS is not direct, but through the mediating effects of operational performance and business process performance. We also utilised multiple group analysis to test some of the model relationships across firms using several organisational and environmental factors as moderators. The organisational factors tested are firm type, age and ownership type. The environmental factors consisted of dynamism, complexity and hostility. We found that the organisational factors are significant moderators and that complexity and hostility are not significant moderators. However, the effects of dynamism as a moderator are less clear.     

Effect of circuit switched services on the capacity of HSDPA

This paper focuses on the effect of circuit switched (CS) services on high speed downlink packet access (HSDPA) packet services in the context of the UMTS FDD system. An objective of the analysis is to provide guidelines for the UMTS planning process to prioritize services when resources are dynamically shared between circuit and packet services. An analytical model, taking into account some of the features introduced in HSDPA (namely adaptive modulation and coding (AMC), hybrid automatic repeat request (HARQ) and fast cell selection) and the interaction between CS services and HSDPA, is proposed to approximate the HSDPA cell capacity. Simulation results to assess the efficiency of the analytical model are also reported.     

Effect of section width and casting rate on variations of formwork pressure of self-consolidating concrete

The influence of formwork dimensions and rate of casting of self-consolidating concrete (SCC) on the development and variations of lateral pressure were evaluated using two types of experimental columns; the first measuring 2100 mm in height and 200 mm in diameter, and the second 3600 mm in height and 920 mm in diameter. Variations of heat of hydration and setting time were correlated to the rate of decrease in formwork pressure.Test results show that the scale effect has an influence on the rate of drop in lateral pressure with time. Two distinctive rates of pressure drop were obtained during the plastic and setting stages of hydration. A rate of pressure decrease of 5.3 kPa/hr was obtained during the first 6 hours of time and is mostly associated with the increase in the restructuring process due to the reversible effect of thixotropy. A second distinctive slope of 2 kPa/hr was noted beyond 6 hours until the canceling of pressure, and is related to setting. The increase in the casting rate from 10 to 25 m/hr in the 200-mm diameter column resulted in slightly higher lateral pressure.     

A wide-range programmable frequency synthesizer based on a finite state machine filter

In this article, an FPGA-based design and implementation of a fully digital wide-range programmable frequency synthesizer based on a finite state machine filter is presented. The advantages of the proposed architecture are that, it simultaneously generates a high frequency signal from a low frequency reference signal (i.e. synthesising), and synchronising the two signals (signals have the same phase, or a constant difference) without jitter accumulation issue. The architecture is portable and can be easily implemented for various platforms, such as FPGAs and integrated circuits. The frequency synthesizer circuit can be used as a part of SERDES devices in intra/inter chip communication in system-on-chip (SoC). The proposed circuit is designed using Verilog language and synthesized for the Altera DE2-70 development board, with the Cyclone II (EP2C35F672C6) device on board. Simulation and experimental results are included; they prove the synthesizing and tracking features of the proposed architecture. The generated clock signal frequency of a range from 19.8?MHz to 440?MHz is synchronized to the input reference clock with a frequency step of 0.12?MHz.     

"Cognitive-neuropsychological function in chronic physical aggression and hyperactivity": Correction to Séguin et al. (2004).

Reports an error in "Cognitive-Neuropsychological Function in Chronic Physical Aggression and Hyperactivity" by Jean R. Séguin, Daniel Nagin, Jean-Marc Assaad and Richard E. Tremblay (Journal of Abnormal Psychology, 2004[Nov], Vol 113[4], 603-613). The use of a weighted procedure within SAS PROC GLM inflated F statistics and underestimated standard errors that affected only conclusions from secondary analyses that were drawn about the specificity of working memory effects to physical aggression and hyperactivity. The corrected conclusions are presented in the erratum. The last two sentences of the abstract also needed to be corrected in order to reflect the new conclusions. The corrected sentences appear in the erratum as well. (The following abstract of the original article appeared in record 2004-20178-011.) Histories of violence and of hyperactivity are both characterized by poor cognitive-neuropsychological function. However, researchers do not know whether these histories combine in additive or interactive ways. The authors tested 303 male young adults from a community sample whose trajectories of teacher-rated physical aggression and motoric hyperactivity from kindergarten to age 15 were well defined. No significant interaction was found. In a 1st model, both histories of problem behavior were independently associated with cognitive-neuropsychological function in most domains. In a 2nd model controlling for IQ, general memory, and test motivation, the 3 working-memory tests (relevant to executive function) remained associated with physical aggression, and 1 remained associated with hyperactivity. These results support an additive model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of high-pressure/high-temperature processing on chemical pectin conversions in relation to fruit and vegetable texture

Heat sterilization of plant derived food products entails considerable organoleptic and nutritional quality losses. For instance, texture loss of fruits and vegetables occurs, next to turgor pressure losses, mainly due to chemical changes in the cell-wall pectic polysaccharides. High-pressure sterilization, i.e. the combination of high temperature (?90 °C) with high pressure (?500 MPa), could present a positive alternative assuring safety while minimizing quality losses. In this study, the potential of high-pressure sterilization in preserving fruit and vegetable texture was evaluated by investigating the effect of combined high-pressure/high-temperature (HP/HT) treatments on two texture related chemical pectin conversions in model sytems. First, a protocol was developed to perform reproducible kinetic studies at HP/HT under constant processing conditions. Subsequently, apple pectin solutions at pH 6.5 were subjected to different HP/HT combinations (500, 600 and 700 MPa/90, 110 and 115 °C) and the extent of chemical demethoxylation and β-eliminative depolymerization was determined. At atmospheric pressure, both zero-order reaction rate constants increased with increasing temperature. At all temperatures, demethoxylation showed a higher rate constant than β-elimination. However, a temperature rise resulted in a stronger acceleration of β-elimination than of demethoxylation. When combining high temperature with high pressure, β-elimination was retarded or even stopped, whereas demethoxylation was stimulated. These results are very promising in the context of the texture preservation of high-pressure sterilized fruits and vegetables, as β-elimination is accepted to be one of the main causes of thermal softening and low methoxylated pectin can enhance tissue strength by forming cross-links with calcium ions present.     

Intoxicated behavioral disinhibition and the heart rate response to alcohol.

This study examined the association between the heart rate (HR) response to alcohol intoxication, which is thought to reflect sensitivity to alcohol-induced reward and alcohol-induced behavioral disinhibition. High- and low-HR responders to alcohol participated in a go/no-go task, under sober and intoxicated conditions. Errors of commission on this task have previously been related to behavioral disinhibition. High-HR responders made more intoxicated commission errors as compared with low-HR responders. High-HR responders also reported increased alcohol consumption, and controlling for the latter did not alter the significant association between high-HR responders and increased intoxicated errors of commission. These results are consistent with previous findings of an increased risk for addictive and disinhibited behavioral propensities in individuals with a high-HR response to alcohol intoxication. (PsycINFO Database Record (c) 2010 APA, all rights reserved)