复合弯扭作用下预应力单箱组合梁的扭转承载能力分析

组合梁结构在实际工程中常处于弯扭复合受力状态,为探讨预应力单箱组合梁在复合弯扭作用下的扭转承载性能,引入了弯矩影响系数和预应力影响系数,提出了预应力单箱组合梁在弯扭作用下的开裂扭矩计算公式.并在大扭弯比条件下,基于空间桁架理论,推导了预应力单箱组合梁在弯扭作用下的极限扭矩计算公式.为了验证该理论的正确性,设计了4根模型梁试件进行弯扭加载试验.理论计算值与试验值的对比结果表明,由理论计算公式得出的结果与实际吻合良好,可为研究组合梁结构的复合弯扭问题提供一定的理论参考.     

Extended trajectory shaping guidance law considering a first-order autopilot lag

To satisfy the terminal position and impact angel constraints, an optimal guidance problem was discussed for homing missiles. For a stationary or a slowly moving target on the ground, an extended trajectory shaping guidance law considering a first-order autopilot lag (ETSGL-CFAL) was proposed. To derive the ETSGL-CFAL, a time-to-go-nth power weighted objection function was adopted and three different derivation methods were demonstrated while the Schwartz inequality method was mainly demonstrated. The performance of the ETSGL-CFAL and the ETSGL guidance laws was compared through simulation. Simulation results show that although a first-order autopilot is introduced into the ETSGL-CFAL guidance system, the position miss distance and terminal impact angle error induced by the impact angle is zero for different guidance time.     

Effect of tin addition on the microstructure and properties of ferritic stainless steel

This article reports the effects of Sn on the inclusions as well as the mechanical properties and hot workability of ferritic stainless steel. Precipitation phases and inclusions in Sn-bearing ferritic...     

Risk evaluation of rock burst through theory of static and dynamic stresses superposition

Rock burst is one of the most catastrophic dynamic hazards in coal mining. A static and dynamic stresses superposition-based(SDSS-based) risk evaluation method of rock burst was proposed to pre-evaluate rock burst risk. Theoretical basis of this method is the stress criterion incurring rock burst and rock burst risk is evaluated according to the closeness degree of the total stress(due to the superposition of static stress in the coal and dynamic stress induced by tremors) with the critical stress. In addition, risk evaluation criterion of rock burst was established by defining the "Satisfaction Degree" of static stress. Furthermore,the method was used to pre-evaluate rock burst risk degree and prejudge endangered area of an insular longwall face in Nanshan Coal Mine in China. Results show that rock burst risk is moderate at advance extent of 97 m, strong at advance extent of 97-131 m,and extremely strong(i.e. inevitable to occur) when advance extent exceeds 131 m(mining is prohibited in this case). The section of two gateways whose floor abuts 15-3 coal seam is a susceptible area prone to rock burst. Evaluation results were further compared with rock bursts and tremors detected by microseismic monitoring. Comparison results indicate that evaluation results are consistent with microseismic monitoring, which proves the method’s feasibility.     

Effects of COD to Phosphorus Ratios on the Metabolism of PAOs in Enhanced Biological Phosphorus Removal with Different Carbon Sources

To elucidate the phosphorus removal and metabolism under various COD / P ratio,a sludge highly enriched in PAOs was used to investigate the impacts of COD / P in batch tests under different carbon supply conditions. Acetate,propionate and a mixture of acetate and propionate at a ratio of 3 ∶ 1( COD basis) was used as carbon sources with the COD / P of 20,15,10 and 5. 0 g COD /gP,respectively. The minimum COD / P ratios for complete P removal were found to be 8. 24 g COD /gP for acetate,11. 40 g COD /gP for propionate and9. 10 g COD /gP for the 3 ∶ 1 mixture of acetate and propionate. Converted to a mass basis,all three cases had a very similar ratio of 7. 7 g VFA /gP,which represented a useful guide for operation of EBPR plants to identify possible shortages in VFAs. The trend in PHV accumulation during the anaerobic period along with the decrease of COD / P ratios suggested that,PAOs may use the TCA pathway for anaerobic VFA uptake to maintain the required NADH production with reduced glycogen degradation. During the aerobic phase,the glycogen pool was reduced but remained enough compared to the requirement for anaerobic VFA uptake,and the synthesis and degradation of glycogen was not the inhibition factor of PAOs.     

Hydraulic Self Servo Swing Cylinder Structure Optimization and Dynamic Characteristics Analysis Based on Genetic Algorithm

The dynamic characteristics of hydraulic self servo swing cylinder were analyzed according to the hydraulic system natural frequency formula. Based on that, a method of the hydraulic self servo swing cylinder structure optimization based on genetic algorithm was proposed in this paper. By analyzing the four parameters that affect the dynamic characteristics, we had to optimize the structure to obtain as larger the Dm(displacement) as possible under the condition with the purpose of improving the dynamic characteristics of hydraulic self servo swing cylinder. So three state equations were established in this paper. The paper analyzed the effect of the four parameters in hydraulic self servo swing cylinder natural frequency equation and used the genetic algorithm to obtain the optimal solution of structure parameters. The model was simulated by substituting the parameters and initial value to the simulink model. Simulation results show that: using self servo hydraulic swing cylinder natural frequency equation to study its dynamic response characteristics is very effective. Compared with no optimization, the overall system dynamic response speed is significantly improved.     

火驱燃烧前缘位置预测与影响因素研究

及时掌握火驱过程中火线的位置,有助于进行生产调控,通过调研现场预测火线位置的方法,得出一套针对不同特征油藏的适用方法:红外照相法适用于浅层油藏;用测温元件直接测试法适用于观察井和生产井密集的油藏;生产动态和物质平衡相结合的方法适用于均质性好且井网形式规范的油藏;示踪剂监测和生产动态相结合的方法适用于非均质性严重或井网形式不规范的油藏;压降试井法由于计算复杂,有待进一步研究。最后指出应在前期地质筛选的基础上,做到"少注气、多采油",并结合生产动态分析加强对油井的管理,引导燃烧前缘均匀稳定的推进。     

N-Fe共掺杂BiVO_4的制备及其光催化活性的研究

采用溶胶凝胶法制备了N和Fe共掺杂的Bi VO4可见光光催化剂,并用X射线衍射(XRD)、比表面积测试(BET)和紫外-可见漫反射谱(UV-Vis DRS)对其进行了表征.结果显示,N-Fe共掺杂对Bi VO4晶型没有产生影响,掺杂前后均为单斜晶系,但晶粒粒径有所减小,BET比表面积相对增大.由UV-Vis可知,N-Fe共掺杂的Bi VO4的吸光强度明显增强,禁带宽度变窄.以可见光降解甲基橙(MO)考察催化剂的光催化活性,N-Fe共掺杂的Bi VO4对MO的降解速率明显高于纯Bi VO4,证明N-Fe共掺杂产生的协同效应提高了Bi VO4在可见光照射下的光催化活性.     

孔雀绿-磷锑钼杂多酸光度法测定钢样中的磷

在OP/正戊醇/正庚烷/水微乳介质中,建立了孔雀绿-磷锑钼杂多酸缔合分光光度法测定钢样中的磷的方法,研究了显色时间、显色剂、微乳液、酸的用量对显色反应的影响.结果表明:离子缔合物的最大吸收波长为660nm,表观摩尔吸光系数为9.4×104 L·mol-1·cm-1,磷含量在0.04~0.44μg/mL内符合比尔定律.孔雀绿与磷锑钼的络合比为4∶1.该法较传统的磷的测量方法灵敏度高,14种常见离子对反应基本无干扰.用于钢样中磷的测定相对标准偏差在3%之内.     

基于多新息理论的卡尔曼滤波改进算法

系统建模是卡尔曼滤波的基础,系统模型不准确带来的验前数据误差,使滤波器精度降低,甚至可能造成发散.针对这种情况,提出一种基于多新息理论改进的卡尔曼滤波算法.多新息卡尔曼滤波算法不仅考虑了运动目标当前的运动状态,而且也充分利用目标之前运动信息,从而使得多新息卡尔曼滤波算法的滤波精度和稳定性得到改善.仿真结果表明,改进的多新息卡尔曼滤波算法较标准卡尔曼滤波算法更有效,预测精度更高.