Integrated SMD pressure/flow/temperature multisensor for compressed air in LTCC technology: Thermal flow and temperature sensing

In this work, we present and analyse the flow-sensing part of a recently-developed multisensor in LTCC (low-temperature co-fired ceramic) technology; this device integrates flow/pressure/temperature sensing and is designed for diagnostics monitoring of standard industrial compressed air circuits and devices such as valves and actuators. In this prototype, flow is sensed using the constant-temperature anemometric principle, with temperature-sensing active and reference thermistors placed in the fluidic channel integrated within the LTCC structure. The LTCC bridge structuration technology and electronics are analysed, and possible improvements in fabrication yield and efficiency outlined.     

Validation and automatic test generation on UML models: the AGATHA approach

The related economic goals of test generation are quite important for software industry. Manufacturers ever seeking to increase their productivity need to avoid malfunctions at the time of system specification: the later the defaults are detected, the greater the cost is. Consequently, the development of techniques and tools able to efficiently support engineers who are in charge of elaborating the specification constitutes a major challenge whose fallout concerns not only sectors of critical applications but also all those where poor conception could be extremely harmful to the brand image of a product.This article describes the design and implementation of a set of tools allowing software developers to validate UML (the Unified Modeling Language) specifications. This toolset belongs to the AGATHA environment, which is an automated test generator, developed at CEA/LIST.The AGATHA toolset is designed to validate specifications of communicating concurrent units described using an EIOLTS formalism (Extended Input Output Labeled Transition System). The goal of the work described in this paper is to provide an interface between UML and an EIOLTS formalism giving the possibility to use AGATHA on UML specifications.In this paper we describe first the translation of UML models into the EIOLTS formalism, and the translation of the results of the behavior analysis, provided by AGATHA, back into UML. Then we present the AGATHA toolset; we particularly focus on how AGATHA overcomes several problems of combinatorial explosion. We expose the concept of symbolic calculus and detection of redundant paths, which are the main principles of AGATHA's kernel. This kernel properly computes all the symbolic behaviors of a system specified in EIOLTS and automatically generates tests by way of constraint solving. Eventually we apply our method to an example and explain the different results that are computed.     

Standardized MR protocol for the evaluation of MRA sequences and/or contrast agents effects in high-degree arterial stenosis analysis

Purpose To investigate the relative role of high resolution (spatial or temporal) magnetic resonance angiography (MRA) sequence and of contrast agent properties in the evaluation of high-degree arterial stenosis. Methods We qualitatively and quantitatively studied both 50 and 95% (300 μm diameter) stenosis of a 6 mm arterial phantom with two contrast agents (CA), Gd-DOTA (r₁ =2.9 mM⁻¹ s⁻¹) versus P760 (r₁ =25 mM⁻¹ s⁻¹) at several CA concentrations, including arterial peak concentration after injection of either a single or double dose of CA, using either a high temporal (booster) or high spatial (HR) resolution 3D MRA sequences. Experimental data were then compared to theoretical data. Results With the 3D HR sequence, both visual and quantitative analysis were significantly better compared to the 3D booster sequence, at each phantom diameter. Quantitative analysis was significantly improved by injection of a double versus a single dose of each CA (Gd-DOTA or P760), primarily in high degree stenosis. Conclusion Combined MRA spatial resolution and high CA efficiency are mandatory to correctly evaluate high degree stenosis.     

Architectural lessons from environmental psychology: The case of biophilic architecture.

A review of findings from the field of environmental psychology shows that humans are aesthetically attracted to natural contents and to particular landscape configurations. These features are also found to have positive effects on human functioning and can reduce stress. However, opportunities for contact with these elements are reduced in modern urban life. It is argued how this evolution can have subtle but nontrivial adverse effects on psychological and physiological well-being. These can be countered by integrating key features of natural contents and structural landscape features in the built environment. Several practical proposals are discussed, ranging from literal imitations of natural objects (such as plants) to the use of nature's fractal geometry in an architectural context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of two models of a double inlet miniature pulse tube refrigerator: Part A thermodynamics

The cooling of electronic components is of great interest to improve their capabilities, especially for CMOS components or infrared sensors. The purpose of this paper is to present the design and the optimization of a miniature double inlet pulse tube refrigerator (DIPTR) dedicated to such applications. Special precautions have to be considered in modeling the global functioning of small scale DIPTR systems and also in estimating the net cooling power. In fact, thermal gradients are greater than those observed in normal scale systems, and moreover, because of the small dimensions of ducts (diameter), the pulse tube cannot be assumed to be adiabatic. Hence thermal heat conduction phenomena must be considered. Besides dead volumes introduced by junctions and capillaries cannot be neglected any more in front of the volume of the gas tube itself. The hydrodynamic and thermal behaviors of the cooler are predicted by means of two different approaches: a classical thermodynamic model and a model based on an electrical analogy. The results of these analysis are tested and criticized by comparing them with experimental data obtained on a small commercial pulse tube refrigerator.     

Gold nanoparticle assemblies: Thermal behaviour under optical excitation

The optical response of materials based on gold nanoparticle assemblies depends on many parameters connected to both material morphology and light excitation characteristics. The optical energy absorbed is then converted into heat through different nanoscale energy exchange mechanisms. This heating subsequently modifies itself the optical properties. We investigate the interplay between the optical and thermal responses of nanocomposite media under its theoretical aspect. In this first paper, the thermal response of gold nanoparticle assemblies under pulsed optical excitation is considered. Both conventional and original modelling approaches are presented. We first underline the role of electromagnetic interactions between particles in a dense assembly in its linear optical response. We then show how the interaction of light with matrix-embedded gold nanoparticles can result in the generation of thermal excitations through different energy exchange mechanisms. Finally, we demonstrate the possible significant influence of the heat carrier ballistic regime and phonon rarefaction in the cooling dynamics of an embedded gold nanoparticle subsequent to ultrafast pulsed laser excitation.     

Effect of gate length in InAs/AlSb HEMTs biased for low power or high gain

The effect of gate-length variation on DC and RF performance of InAs/AlSb HEMTs, biased for low DC power consumption or high gain, is reported. Simultaneously fabricated devices, with gate lengths between 225 nm and 335 nm, have been compared. DC measurements revealed higher output conductance g_ds and slightly increased impact ionization with reduced gate length. When reducing the gate length from 335 nm to 225 nm, the DC power consumption was reduced by approximately 80% at an f_T of 120 GHz. Furthermore, a 225 nm gate-length HEMT biased for high gain exhibited an extrinsic f_T of 165 GHz and an extrinsic f_max of 115 GHz, at a DC power consumption of 100 mW/mm. When biased for low DC power consumption of 20 mW/mm the same HEMT exhibited an extrinsic f_T and f_max of 120 GHz and 110 GHz, respectively.