Simulation and fabrication of piezoresistive membrane type MEMS strain sensors

Two piezoresistive (n-polysilicon) strain sensors on a thin Si₃N₄/SiO₂ membrane with improved sensitivity were successfully fabricated by using MEMS technology. The primary difference between the two designs was the number of strips of the polysilicon patterns. For each design, a doped n-polysilicon sensing element was patterned over a thin 3 μm Si₃N₄/SiO₂ membrane. A 1000×1000 μm² window in the silicon wafer was etched to free the thin membrane from the silicon wafer. The intent of this design was to fabricate a flexible MEMS strain sensor similar in function to a commercial metal foil strain gage. A finite element model of this geometry indicates that strains in the membrane will be higher than strains in the surrounding silicon. The values of nominal resistance of the single strip sensor and the multi-strip sensor were 4.6 and 8.6 kΩ, respectively. To evaluate thermal stability and sensing characteristics, the temperature coefficient of resistance [TCR=(ΔR/R₀)/ΔT] and the gage factor [GF=(ΔR/R₀)/] for each design were evaluated. The sensors were heated on a hot plate to measure the TCR. The sensors were embedded in a vinyl ester epoxy plate to determine the sensor sensitivity. The TCR was 7.5×10⁻⁴ and 9.5×10⁻⁴/°C for the single strip and the multi-strip pattern sensors. The gage factor was as high as 15 (bending) and 13 (tension) for the single strip sensor, and 4 (bending) and 21 (tension) for the multi-strip sensor. The sensitivity of these MEMS sensors is much higher than the sensitivity of commercial metal foil strain gages and strain gage alloys.     

氰戊菊酯剂型加工研究进展

综述了近年来氰戊菊酯剂型加工研究进展，重点介绍了其混合制剂的发展情况。     

A Piecewise Grey System Model for Study the Effects of Anthropogenic Activities on Karst Hydrological Processes

Sustainable groundwater development must rely on a good understanding of hydrological processes, especially under effects of anthropogenic activities. This paper develops a piecewise analysis based on grey system model for study effects of anthropogenic activities on hydrological processes. The time series of precipitation and spring discharge were segmented into three time periods depending on whether variations are due to climate variation: the predevelopment stage, the transition stage, and the new equilibrium stage. Then we modeled hydrological process of the predevelopment stage and new equilibrium stage by the grey system model. By comparing the model results, we can quantify the effects of human activities on hydrological processes. We applied the model to Liulin Springs China. The results indicated that the hydraulic response time of the spring discharge to precipitation from the predevelopment stage to the new equilibrium stage, ranges from less than 1 year to up to 4 years. The results revealed that human activities slow the groundwater flow. GM (1,N) models of Liulin Springs discharge showed that the driving coefficients of precipitation to the spring discharge decreased from 0.012272 in the predevelopment stage to 0.007753 in the new equilibrium stage, which means that groundwater recharge ability has reduced about 36.82 %. Human activities in Liulin Springs have drastically changed the groundwater system. Piecewise grey system model is a robust method for hydrological process simulation.     

Preface

Recently, there has been a dramatic increase in research on data mining on social networks and social media. Theubiquitous nature of Web-enabled devices, including desktops,     

复合催化法合成对硫磷

研究了以三甲胺作亲核催化剂、季铵盐A作相转移催化剂、水和极性有机溶剂B作双溶剂、亲核—相转移复合催化法合成对硫磷的方法,收率可达99％。     

石墨化炉的供电特点及发展趋势

通过对石墨化炉的特点及其供电方面的有关问题的分析，论述了石墨化炉供电的特点及其发展的趋势，并对石墨化炉在交、直流电源供电方面提出了看法，以不断提高石墨化炉供电的设计水平．     

配合煤选择性粉碎工艺的应用

介绍了配和煤选择性粉碎工艺的原理、特点及应用情况。结果表明该工艺投用后，配合煤质量明显改善。     

利用透射对应原理画透视图的探讨

用二平面及不属于这二平面的点S或根据空间笛沙格定理建立平面场的透视对应，由此建立平面上的透射对应，用透射对应原理建立透视图与平面图的对应关系，证明用透射对应画透视图的原理，探讨用此原理画透视图的方法，并将用此方法所画透视图与用视线法所画透视图进行比较。