3D numerical model of snow deformation without failure and its application to cold room mechanical tests

A three-dimensional model developed for the slow deformation, without macroscopic failure, of a stratified snow cover has been used to simulate laboratory mechanical tests performed on sieved snow. The model is based on a non-linear visco-elastic constitutive law for snow whose parameters depend on the snow temperature and density. Snow densification is derived from the bulk viscous strain. The model has been implemented in the Flac3D finite-difference code. The experimental device is a convergent channel in which snow is forced at a constant velocity in the range 1–100 μm s^− 1. Although snow is compressed under plane strain conditions, the channel geometry allows obtaining a multi-axial stress-state. Since the testing conditions involve ranges of variation of both the snow density and the strain-rate wider than those encountered for a natural snowpack, the constitutive relations of the model had to be modified. In this paper we present the constitutive model for snow, some details about its implementation into the Flac3D code, and its application to the numerical simulation of the mechanical tests. The comparison of the model and experimental results shows a relatively good agreement, although snow microstructure is accounted for only through its density. However, the treatment of the non-linearity of the viscosity must be improved. This 3D numerical model can be regarded as an interesting tool for assessing a constitutive law for snow on the basis of cold-room experiments, as well as for studying natural snow covers.     

基于Tabu标记改进的IP追踪

概率包标记作为当前IP追踪领域的研究热点日益引起研究者的关注。然而传统方案往往存在很多不足，而且基于不现实的假设．影响了实用性。Tabu方案虽然可以改善传统方案的弱收敛性，具有抗伪造标记攻击能力，但它导致了高昂的路由器开销。基于合理的假设条件下对Tabu方案进行改进，根据TFL值计算距离和点采样等策略．改善了Tabu方案存在的问题，而且支持渐进部署，具有较好的实用性。     

折叠波导慢波电路的传输特性

研究了新型慢波结构折叠波导慢波电路的传输特性 ,利用等效电路法计算了折叠波导电路的色散特性、耦合阻抗和止带。分析和计算表明 ,该电路很适合用作短厘米波和毫米波大功率行波管的慢波结构。     

Static and low-frequency noise characterization in submicron MOSFETs for memories cells applications

In this paper, we present the extraction of oxide traps properties of n-metal-oxide-semiconductor (N-MOS) field effect transistors with W×L=0.5×0.1 μm² using low-frequency (LF and random telegraph signal) noise and static I(V) characterizations. The impact of oxide thickness, on static and noise parameters is analyzed. Static measurements on N-MOS devices with different tunnel oxide thickness show anomalies (a significant increase in V_t values for low temperature and kink effect) attributed to traps located in the oxide. From LF noise analysis we find that 1/f noise stems from carrier number fluctuations. The slow oxide trap concentration deduced from the noise data is about 10¹⁵ eV/cm³ in agreement with the state-of-the-art gate oxides. Finally, drain current RTS amplitude as large as 10% have been observed.     

Biodegradation of the cyanobacterial toxin microcystin LR in natural water and biologically active slow sand filters

A bacterium (MJ-PV) previously demonstrated to degrade the cyanobacterial toxin microcystin LR, was investigated for bioremediation applications in natural water microcosms and biologically active slow sand filters. Enhanced degradation of microcystin LR was observed with inoculated (1 x 10(6) cell/mL) treatments of river water dosed with microcystin LR (>80% degradation within 2 days) compared to uninoculated controls. Inoculation of MJ-PV at lower concentrations (1 x 10(2)-1 x 10(5) cells/mL) also demonstrated enhanced microcystin LR degradation over control treatments. Polymerase chain reactions (PCR) specifically targeting amplification of 16S rDNA of MJ-PV and the gene responsible for initial degradation of microcystin LR (mlrA) were successfully applied to monitor the presence of the bacterium in experimental trials. No amplified products indicative of an endemic MJ-PV population were observed in uninoculated treatments indicating other bacterial strains were active in degradation of microcystin LR. Pilot scale biologically active slow sand filters demonstrated degradation of microcystin LR irrespective of MJ-PV bacterial inoculation. PCR analysis detected the MJ-PV population at all locations within the sand filters where microcystin degradation was measured. Despite not observing enhanced degradation of microcystin LR in inoculated columns compared to uninoculated column, these studies demonstrate the effectiveness of a low-technology water treatment system like biologically active slow sand filters for removal of microcystins from reticulated water supplies.     

The Young Experimentalists

Experimental architecture in Italy began to take a new form in the 1990s when young architects, who were embracing new digital technologies, also began to go abroad to study and practise in greater numbers. Anna Baldini outlines a fecund strand in Italian architecture which, while no longer wholly new or youthful, retains its vitality. She highlights, in particular, the contributions of: Avatar Architettura, Gianluca Brini, Elastico spa+3, Exposure Architects, Giuliano Fausti, Luisa Fontana, Giorgio Goffi, ian+, Iotti+Pavarani Architetti, Fabrizio Leoni, ma0/emmeazero, Antonella Mari, Metrogramma, Open Building Research (OBR), RoccAtelier, studio.eu and Vulcanica Achitettura. Copyright © 2007 John Wiley & Sons, Ltd.     

适用于制备粉体石膏建材的脱硫建筑石膏

通过对脱硫建筑石膏的三相分析,确定适用于制备粉体石膏建材的脱硫建筑石膏:二水石膏含量宜<4.00%,无水石膏(Ⅲ型)宜<5.00%.宜采用低温慢烧工艺对脱硫石膏原料进行煅烧.     

Recent advances for ion beam therapy accelerators using synchrotrons

Ion beam therapy has evolved a lot during the last years. After more than a decade of successful clinical studies and first treatment in hospital environment, the carbon beam treatment, which always relies on a synchrotron as main accelerator, has clearly shown its own potential. The clinical success of carbon beam treatment is indicated by the growing number of new fully clinical based facilities. There is a lot of improvement potential for these facilities in order to increase their treatment quality, functionality and capacity as well as the cost effectiveness of the patient treatment. This article focuses on the currently ongoing investigations to fully explore this potential. It can be concluded that synchrotron based ion beam facilities are improving into many directions. This will further improve their impact on the cancer treatment and consequently their benefit to the whole society.     

Comparison of supercritical CO2, liquid CO2, and solvent extraction of chemicals from a commercial slow pyrolysis liquid of beech wood

Innovative extraction methods with supercritical CO₂ and liquid CO₂ have been employed to obtain value-added chemicals from a slow pyrolysis liquid. Sequential solvent extraction with hexane and acetone was carried out for comparison. Pyrolysis liquid was first adsorbed on silica (SiO₂) with weight ratios SiO₂:oil of 100:40 and 100:80. Pyrolysis liquid and extracts were mainly characterized by GC–MS/FID, elemental analysis, and water content. Results show that scCO₂ extraction is mainly controlled by dissolution at the first 3 h during a 6-h extraction period and by combination of dissolution and diffusion at later extraction periods. Around 60–65% of the CO₂ and hexane extracts could be identified by GC compared to 49% of the starting pyrolysis liquid. GC data confirmed that, CO₂ extraction effectively enriched both non-aromatics and aromatic compounds. Hexane extracts contained lower contents of organic acids. Hexane enabled a complete extraction of aromatics. Chemical composition of extracts from scCO₂ and liquid CO₂ are very similar. Extraction with scCO₂ and liquid CO₂ proves to be an effective and innovative pre-treatment process for the production of chemicals from pyrolysis liquid.     

Waste to energy valorization of poultry litter by slow pyrolysis

The slow pyrolysis process of poultry litter was investigated using different experimental and analytical techniques. A fixed bed reactor was used for the simulation of the slow pyrolysis process up to a constant temperature (400–800 °C) under nitrogen flow. Yields of the different product fractions were determined. On-line FTIR techniques were used to detect the most significant compounds in the evolved gas (carbon dioxide, carbon monoxide and methane). GC–MS results allowed the identification of the more important categories of compounds in the liquid condensate (phenols, fatty acids, sterols, N-containing compounds). The fate of nitrogen and sulphur, present in relevant amounts in the original substrate, was investigated: sulphur remains mostly in char at any investigated temperature, while nitrogen is split among the different products, slightly increasing its transfer to the gas phase only at higher pyrolysis temperatures. The energy transfer from the original biomass substrate to the different product fractions was also investigated. The fraction of biomass energy transferred to non-condensable gases raises with pyrolysis temperature and was estimated to be able to thermally sustain the process at 550 °C. The results obtained shed some light on the potential use of the slow pyrolysis process for sanitation and waste-to-energy valorization of poultry litter.