汽车安全气囊传感器市场发展趋势

自20世纪70年代出现以来至今,安全气囊系统有了很大的发展,目前乘客/前排安全气囊已经在全球范围内成为新生产汽车的标准配置。根据市场报告,在一些新产品特性的推动下,如保护头部、胸部及膝盖的侧面气囊以及智能乘客检测系统等,到2010年,全球总的安全气囊应用数量将达到1.8亿个。为了达到政府或碰撞试验机构(如EuroNCAP)的最高安全性要求,当前高端汽车上用于探测碰撞的加速度传感器的数量已经达到6个,并且仍有增加趋势。而加速度传感器的设计者们也正在采用新材料及新技术来保持整个安全气囊系统的市场竞争力。基于MEMS(微机电系统)的…     

Thermal stability of the 248-nm-induced presensitization process in standard H2-loaded germanosilicate fibers

Grating growths through exposure of presensitized standard fibers to KrF light were recorded in various experimental condition. It is shown that there exists an optimum sensitization fluence at which the efficiency of the sensitization process is higher. Isochronal thermal annealing of pre-exposed fibers led to a decrease in the sensitization-induced enhancement of photosensitivity. IR-absorption spectroscopy was carried out in fibers or preform plates to monitor the attenuation ascribed to H-bearing species in the same samples. The annealing-induced decay in photosensitivity cannot be correlated with those of the H-bearing species in the whole temperature range (110 degrees C-800 degrees C). This indicates that the enhancement of photosensitivity comes from the transformation of more than one species.     

Thermal and Photo-Degradation Study of α-FAPbI3-Based Perovskite Using In Situ X-Ray Diffraction

Hybrid halide perovskite has established its credibility as high performance thin film photovoltaic technology. Perovskite based on formamidinium cation is at the core composition to top performances and stability. Herein, a depth study based on temperature-controlled in situ X-ray diffraction focusing on the photo-active formamidinium lead iodide (α-FAPbI₃) is reported. In particular, the thermal stability of the latter and the degradation pathways under different experimental conditions are clarified. Based on this in situ technique, the lattice thermal expansion coefficient is reported that provides relevant information on possible mechanical stress created upon temperature cycling or damp heat test. The results support that α-FAPbI₃ degradation is substantially accelerated when temperature is combined to illumination and when it is interfaced with the extraction layers. In addition, by contrast to in darkness for which α-FAPbI₃ degrades directly into PbI₂, the existence of a temperature gap under illumination involving an intermediate step with a non-crystalline phase resulting from the perovskite degradation and contributing to the formation of PbI₂ by-product is revealed.     

On the availability of a k-out-of-N system given limited spares and repair capacity under a condition based maintenance strategy

This paper considers a k-out-of-N system with identical, repairable components. Maintenance is initiated when the number of failed components exceeds some critical level. After a possible set-up time, all failed components are replaced by spares. A multi-server repair shop repairs the failed components. The system availability depends on the spare part stock level, the maintenance policy and the repair capacity. We present a mathematical model supporting the trade-off between these three parameters. We present both an exact and an approximate approach to analyse our model. In some numerical experiments, we provide insight on the impact of repair capacity, number of spares and preventive maintenance policy on the availability.     

Comments on “Design and performance evaluation of load distribution strategies for multiple loads on heterogeneous linear daisy chain networks”

Min, Veeravalli, and Barlas have proposed strategies to minimize the overall execution time of one or several divisible loads on a heterogeneous linear network, using one or more installments [Han Min Wong, Bharadwaj Veeravalli, Scheduling divisible loads on heterogeneous linear daisy chain networks with arbitrary processor release times, IEEE Trans. Parallel Distrib. Syst. 15 (3) (2004) 273–288; Han Min Wong, Bharadwaj Veeravalli, Gerassimos Barlas, Design and performance evaluation of load distribution strategies for multiple divisible loads on heterogeneous linear daisy chain networks, J. Parallel Distrib. Comput. 65 (12) (2005) 1558–1577]. We show using a very simple example that their approach does not always produce a solution and that, when it does, the solution is often suboptimal. We also show how to find an optimal scheduling for any instance, once the number of installments per load is given. Finally, we formally prove that under a linear cost model, as in both the above-mentioned references, an optimal schedule has an infinite number of installments. Therefore such a cost model should not be used to design practical multi-installment algorithms.     

Frequency selectivity emerging from spike-timing-dependent plasticity

Periodic neuronal activity has been observed in various areas of the brain, from lower sensory to higher cortical levels. Specific frequency components contained in this periodic activity can be identified by a neuronal circuit that behaves as a bandpass filter with given preferred frequency, or best modulation frequency (BMF). For BMFs typically ranging from 10 to 200?Hz, a plausible and minimal configuration consists of a single neuron with adjusted excitatory and inhibitory synaptic connections. The emergence, however, of such a neuronal circuitry is still unclear. In this letter, we demonstrate how spike-timing-dependent plasticity (STDP) can give rise to frequency-dependent learning, thus leading to an input selectivity that enables frequency identification. We use an in-depth mathematical analysis of the learning dynamics in a population of plastic inhibitory connections. These provide inhomogeneous postsynaptic responses that depend on their dendritic location. We find that synaptic delays play a crucial role in organizing the weight specialization induced by STDP. Under suitable conditions on the synaptic delays and postsynaptic potentials (PSPs), the BMF of a neuron after learning can match the training frequency. In particular, proximal (distal) synapses with shorter (longer) dendritic delay and somatically measured PSP time constants respond better to higher (lower) frequencies. As a result, the neuron will respond maximally to any stimulating frequency (in a given range) with which it has been trained in an unsupervised manner. The model predicts that synapses responding to a given BMF form clusters on dendritic branches.     

The immersive impact of meta-media in a virtual world

With the increasing importance of virtual settings, we observe a complexification of the media used by members of the virtual communities. Using as the model the Star Wars Role-Play community of the virtual environment of Second Life, and a related news-styled blog, the “Galactic News Network”, we analysed here the impact of this media complexification on immersion process. Specifically, we analysed how meta-media can act on virtual community behavior, and on the immersive potential of the virtual world. We combined “out-of-world” analysis of the blog, and “in-world” qualitative and quantitative evaluation of meta-media-related social activities. Our results demonstrate that meta-media strongly contribute to reinforce the immersive potential of the virtual setting via several mechanisms: by increasing three parameters of the virtual world (cohesion, coherence, and commitment), by increasing the social density of the virtual community, and by acting on the perceived time factor. The combined “in-world” and “out-of-world” action of the meta-media increases the possibilities of inter-individual connections. The combination of 2D asynchronous media and 3D instantaneous virtual settings in a homogeneous and coherent immersive environment reinforces the immersive potential of the virtual world. Thus, meta-media seem to be a factor of long-term stabilization of social structures in virtual environments.     

Argon Attenuates Multiorgan Failure in Relation with HMGB1 Inhibition

Argon inhalation attenuates multiorgan failure (MOF) after experimental ischemic injury. We hypothesized that this protection could involve decreased High Mobility Group Box 1 (HMGB1) systemic release. We investigated this issue in an animal model of MOF induced by aortic cross-clamping. Anesthetized rabbits were submitted to supra-coeliac aortic cross-clamping for 30 min, followed by 300 min of reperfusion. They were randomly divided into three groups (n = 7/group). The Control group inhaled nitrogen (70%) and oxygen (30%). The Argon group was exposed to a mixture of argon (70%) and oxygen (30%). The last group inhaled nitrogen/oxygen (70/30%) with an administration of the HMGB1 inhibitor glycyrrhizin (4 mg/kg i.v.) 5 min before aortic unclamping. At the end of follow-up, cardiac output was significantly higher in Argon and Glycyrrhizin vs. Control (60 ± 4 and 49 ± 4 vs. 33 ± 8 mL/kg/min, respectively). Metabolic acidosis was attenuated in Argon and Glycyrrhizin vs. Control, along with reduced amount of norepinephrine to reverse arterial hypotension. This was associated with reduced interleukin-6 and HMGB1 plasma concentration in Argon and Glycyrrhizin vs. Control. End-organ damages were also attenuated in the liver and kidney in Argon and Glycyrrhizin vs. Control, respectively. Argon inhalation reduced HMGB1 blood level after experimental aortic cross-clamping and provided similar benefits to direct HMGB1 inhibition.