Modeling detector response function of alpha particles for neutron depth profiling

The energy spreading of recorded ions is influenced by straggling,geometrical acceptance angles and detector energy resolution effects in neutron depth profiling(NDP)and a symmetric Gaussian function model was customarily applied before.In addition,the spectra of mono-energetic alpha particles show a well known asymmetric shape as well when measured by silicon detectors.This article presents a physical model predicting the observed energy spectrum of a sample ion with target nuclides in prearranged depths.It is expressed as the convolution of a Gaussian function with a left-hand double-exponential function.Experiment showed that the predicted ions spectrum derived from the asymmetric model matches the observed energy spectrum.Therefore,the model can be applied to produce matrix for inversion of NDP spectrum.     

多线程向量处理器中向量数据存储结构的设计与实现

多线程和向量技术相结合是当前微处理器设计的一个重要趋势.提出一种多线程向量处理器中向量数据存储结构,利用多线程切换来隐藏访存延迟,并让向量数据直接访问二级cache来提高带宽.模拟实验表明在所提出的存储结构下,访存带宽随线程数线性增长,向量数据访问带宽明显高于标量数据访问带宽.     

城市生活垃圾分类计量收费设备控制装置的设计

城市生活垃圾分类计量收费是解决城市垃圾问题的有效手段。设计了一种基于单片机的垃圾分类计量控制装置,具备体积小巧、易于安装和成本低廉等优势,可推广使用。     

两电平电压源逆变器双矢量调制模型预测控制:理论分析、实验验证和推广

近年来,模型预测控制(MPC)以其良好的自适应性、鲁棒性等优越性能广泛应用于两电平电压源逆变器中.然而,常规的模型预测控制每个控制周期只使用1个电压矢量,导致电流谐波较大.为抑制电流谐波,提出一种双矢量调制模预测控制策略.首先,在每个控制周期同时使用两个电压矢量来跟踪目标矢量,且每个电压矢量的作用时间根据调制模型预测控制原理计算;其次,根据无差拍控制原理计算参考电压,并根据参考电压位置在每个控制周期仅需要选择三组电压矢量组合进行在线评估,从而得到最优电压矢量组合.最后,通过详细的理论分析,验证了所提双矢量调制模型预测控制策略的有效性.此外,该文研究还表明,所提策略还可用于控制其他类型的逆变器,如三相四开关逆变器.同时,所提方法可以获得和常规双矢量法类似的控制性能,且具有计算量小等优点.理论分析和实验结果验证了所提方法的有效性.     

Experimental investigation and numerical simulation on the hysteresis zone of a variable displacement wobble plate compressor

A test system with the variable displacement compressor (VDC) for automotive air conditioning system is built to study the changing rule of piston stroke length (PSL). It is found from our experiments that the critical suction pressure where the PSL starts to decrease is less than that where the PSL starts to increase for the same PSL; between the two critical lines, a hysteresis zone is formed, within which all the steady-state points fall and there is a multiple-valued relationship between VDC parameters; and the PSL is kept invariable when the VDC parameters change within the hysteresis zone. In order to find out the reason causing the hysteresis zone and to analyze the influence of the compressor parameters on the hysteresis zone, a steady-state mathematical model of VDC is developed and verified by our experimental data. The theoretical analysis indicates that the hysteresis zone is caused by the frictional forces among the moving components of VDC, and the greater the frictional forces, the broader the hysteresis zone and the larger the changing range of suction pressure. The influence of the discharge pressure and rotary speed on the hysteresis zone is that the hysteresis zone moves in the direction of the suction pressure decreasing along with the increase of the discharge pressure or rotary speed.     

高效稠油降粘剂的性能评价及现场应用

稠油超稠油区块进入多轮次吞吐后期普遍存在蒸汽驱替效率低、油汽比低、经济性差的问题。部分区块由于注汽压力高而导致无法正常注汽。通过室内实验研究表明，伴蒸汽注入高效稠油降粘剂CY—2可以明显提高蒸汽的驱替效率、降低注汽压力，提高注汽周期的产量及油汽比。该项技术在滨南单家寺油田大面积推广，取得了良好的经济效益，为提高稠油超稠油区块注汽开发的效果及经济性提供新的途径。     

Preparation of CuCr alloys by thermit-reduction electromagnetic stirring

The influences of the additive CaF2, different molds, mold pre-heating temperature, electromagnetic stirring, and alloying elements on CuCr have been investigated respectively during the preparation of CuCr alloys by thermit-reduction electromagnetic stirring. The results indicate that the reasonable reactant mass ratio of CuO: Cr2O3: Al is 100:140:160; CaF2 can reduce the solidifica- tion point of slags to improve the metal separating efficiency from slags; the crystal particles become thinner because of the high cooling velocity in the metal mold; while casting in the graphite mold, the casting properties of CuCr improve with the increase of pre-heating temperature; the compact alloys are prepared at 500°C; electromagnetic stirring can prevent the growth of dendrite crys- tal into refine crystal particles, as well as homogenize Cu and Cr to improve the CuCr properties; the optimal stirring time is 7 min; when the alloying elements Ni and Co are added to the reactants, elements Cu and Cr can distribute evenly but the crystal particles become thick.     

二氧化碳膨胀烟丝生产线储存皮带机的改造

通过增设导料装置、雪花喷嘴等措施对CO2膨胀烟丝生产线储存皮带机的工作状态及性能进行改造。改造后的储存皮带机性能稳定，工作状态优良，提高了成品烟丝的整丝率及填充值。     

Growth and lithium storage properties of vertically aligned carbon nanotubes

High-purity vertically aligned carbon nanotubes (CNTs) were prepared on a quartz substrate by thermal chemical vapour deposition (CVD). The as-prepared carbon nanotubes have an outer diameter of 40–60 nm and a length of 70–80 μm. HRTEM observation revealed that there were compartment structures in the carbon nanotubes. The vertically aligned CNTs exhibit a high reversible lithium storage capacity of 950 mAh/g in lithium-ion cells.     

DETERMINATION OF EQUILIBRIUM CONSTANT FOR SILICATE MELT POLYMERIZATION AND ITS APPLICATION

本文发现表征硅酸盐熔体聚合度的平衡常数与金属离子有效核电荷与原子实半径之比、形成金属离子的最后电离势及Allred-Rochow电负性之间存在良好的对应关系。由此所建立的参数方程可估计某些二元硅酸盐熔体的聚合平衡常数,与聚合理论的表达式结合,计算了金属氧化物的活度、硅酸盐阴离子分布以及平均链长等性质。由所得结果可以解释和预期熔体的某些物理性质。理论计算的结果与实验值一致。