Mechanical properties of a reinforced composite polymer electrolyte membrane and its simulated performance in PEM fuel cells

The hygro-thermo-mechanical properties and response of a class of reinforced perfluorosulfonic acid membranes (PFSA), that has potential application as an electrolyte in polymer fuel cells, are investigated through both experimental and numerical modeling means. A critical set of material properties, including Young's modulus, proportional limit stress, break stress and break strain, is determined for a range of temperature and humidity levels in a custom-built environmental test apparatus. The swelling strains are also determined as functions of temperature and humidity level. To elucidate the mechanical response and the potential effect these properties have on the mechanical durability, mechanics-based simulations are performed using the finite element method (ABAQUS). The results indicate that the relatively high strength of the experimental membrane, in combination with its relatively low in-plane swelling due to water absorption, should have a positive influence on membrane durability, potentially leading to longer life times for polymer electrolyte membrane fuel cells (PEMFC).     

Predictive and Adaptive Resource Reservation (PARR) for Cellular Networks

In cellular networks, a higher priority can, out of Quality of Service reasons, be given to ongoing connections than new call attempts. This can be achieved by having capacity in each cell (guard channels) exclusively reserved for arriving handover calls. In this paper, an advanced guard channel scheme, called Predictive and Adaptive Resource Reservation (PARR), will be introduced. The PARR scheme determines the amount of guard channels to allocate in a cell through subscriber movement predictions. The novelty of PARR is that both positioning and history-based measurements are used as input for the predictions. To improve the prediction accuracy, different data sets are applied for calls with different mobility and latest visited cells. Simulations will be used to show that significant performance improvements are obtainable with PARR.     

A comparison between different PMD compensation techniques

We quantify the benefits of using different techniques for compensation of polarization mode dispersion (PMD) in fiber-optic communication systems by means of numerical simulations. This is done both with respect to PMD-induced pulse broadening and in terms of system outage probability for different data formats [nonreturn-to-zero (NRZ) and return-to-zero (RZ)]. Attention is focused on simple and relevant single- and double-stage post-transmission compensators with a few degrees of freedom (DOF). It is generally believed that a PMD compensator with a polarization controller and a variable delay line can only compensate the PMD to the first order. We show, from analytical results, the counterintuitive fact that this scheme can also partially compensate for higher order PMD. We also investigate the benefit of using a polarizer as compensation element where the optical average power can be used as a feedback signal     

A comparison between NRZ and RZ data formats with respect toPMD-induced system degradation

We quantify the polarization-mode dispersion (PMD)-induced system outage probability by means of numerical simulations for nonreturn-to-zero (NRZ) and return-to-zero (RZ) data formats with proper comparative conditions and find that RZ performs better than NRZ. We also study the impact of the RZ duty-factor and the tradeoff between power margin and acceptable PMD     

A single-photon counter for long-haul telecom

Quite a few groups have turned their attention to using commercially available InGaAs/InP APDs, originally developed for optical communication applications, as SPADs for photon counting at 1300 nm and 1550 nm. This research has turned out to be quite fruitful, and there are many applications emerging in optical metrology (optical time-domain reflectometry) in eye-safe range finding and in future quantum technologies, where databits are encoded on individual photons. This article describes the status of these commercially available InGaAs/InP APDs used as single-photon counters in the telecom wavelength region of 1550 nm     

On the effects of the packet size distribution on the packet loss process

Real-time multimedia applications have to use forward error correction (FEC) anderror concealment techniques to cope with losses in today’s best-effort Internet. The efficiency of these solutions is known however to depend on the correlation between losses in the media stream. In this paper we investigate how the packet size distribution affects the packet loss process, that is, the distribution of the number of lost packets in a block, the related FEC performance and the average loss run length. We present mathematical models for the loss process of the MMPP+M/D/1/K and the MMPP+M/M/1/K queues; we validate the models via simulations, and compare the results to simulation results with an MPEG-4 coded video trace. We conclude that the deterministic packet size distribution (PSD) not only results in lower stationary loss probability than the exponential one, but also gives a less correlated loss process, both at a particular average link load and at a particular stationary loss probability as seen by the media stream.Our results show that for applications that can only measure the packet loss probability, the effects of the PSD on FEC performance are higher in access networks, where a single multimedia stream might affect the multiplexing behavior. Our results show that the effects of the PSD on FEC performance are higher in access networks, where a single multimedia stream might affect the multiplexing behavior and thus can improve the queuing performance by decreasing the variance of its PSD.     

Anatomical, histological, and physiological factors in experienced downhill skiers

1. (Methyl-3H)decamethonium dichloride was injected intravenously into the tail vein of dystrophic and normal mice of the Bar Harbour strain 129 ReJ/dy in paralysing doses. 2. Scintillation counts were made of 1 mm sections of diaphragm and tibialis anterior which showed a normal distribution of tritiated decamethonium in the dystrophic animals. 3. Intraperitoneal injections of L-(gamma-3H)leucine were made into dystrophic and normal mice. Examination of diaphragm and tibialis anterior by scintillation counting showed the abnormal uptake typical of dystrophic involvement of murine muscle. 4. The normal distribution of (methyl-3H)decamethonium dichloride uptake by the dystrophic muscle does not support the concept of active denervation in this disease.     

UPM芬欧汇川开发生物燃料转型趋向低碳经济

欧洲是全球提出低碳理念发展最早的地区,其在低碳经济的理论研究、取得成果以及研发投入等方面,也一直处于世界的前端.为迎接全球低碳时代的来临,欧盟按照欧盟委员会2007年确立的能源和碳减排目标:到2020年欧盟的温室气体排放应减少20%(如果条件合适将提高到30%),可再生能源比例达到20%,同时将能源利用效率提高20%,交通运输业生物燃料的使用达到10%.     

Internal doses of acrylamide and glycidamide in mice fed diets with low acrylamide contents

The formation of acrylamide during heating of certain foodstuffs constitutes a potential health hazard. The health risk assessment should be based on knowledge about the relation between dietary exposure to acrylamide and internal doses of acrylamide and its genotoxic metabolite glycidamide. The primary aim of this study in mice was to measure these relationships at low levels of acrylamide intake through the diet. A secondary aim was to clarify which extraction method should be used when analyzing acrylamide in food in order to obtain a correct measure of the acrylamide that is available for absorption. In the analysis procedure, alkaline extraction has earlier shown much higher measured acrylamide levels in certain foods compared to water extraction. In this subcronic study the administered diets were composed to give five levels of acrylamide intakes between 3 and 50 mug/kg body weight per day (calculated on figures obtained after water extraction). Internal doses of acrylamide and glycidamide were measured through hemoglobin (Hb)-adducts. The results showed linear relationships between the exposure of acrylamide and Hb-adduct levels from both acrylamide and glycidamide at these low exposure levels. The study also showed that the "extra" acrylamide measured with alkaline extraction does not correspond to bioavailable acrylamide.