磁场对电晕放电电场及细小粉尘荷电的影响

磁增强正负电晕放电用于细小气溶胶颗粒荷电,研究结果表明,磁增强正负电晕放电预荷电器对细小粉尘的荷电是有效的;磁增强正电晕放电预荷电器的荷电效率低于磁增强负电晕放电预荷电器。与传统的电晕放电相比,磁增强正负电晕放电中电晕区附近积累更多的正离子,使得空间电荷对极间电场的影响增强;在磁增强负电晕放电中,负离子的浓度再次被提升,更有益于细小粉尘荷电;在磁增强正电晕放电中,电晕区中的电场强度被削弱,而荷电区中的电场强度被增强。分析认为,磁增强正电晕预荷电器的效率比传统正预荷电器要高。     

滚筒干燥器中杆状颗粒混合特性的三维数值模拟

为研究杆状颗粒在滚筒干燥器中的混合运动,建立了杆状颗粒运动特性的三维数值实验平台.采用离散元法直接跟踪滚筒中的每一个颗粒,对杆状颗粒在滚筒干燥器中碰撞、摩擦的混合运动过程进行数值模拟,并把杆状颗粒和球形颗粒在滚筒中的混合特性进行对比.结果表明:随着转速的增加,颗粒混合均匀的速度加快;滚筒内杆状颗粒和球形颗粒均在近壁区域混合程度好;杆状颗粒混合达到均匀的速度较球形颗粒快;杆状颗粒整体混合均匀程度优于球形颗粒.模拟结果还表明,杆状颗粒的混合特性与球状颗粒的混合特性存在很大区别,在以往数值模拟中将杆状颗粒假设成球形颗粒存在较大误差,对杆状颗粒所建立的模型能更好地符合杆状颗粒的运动规律.     

新型零电流PWM全桥DC-DC变换器

为降低IGBT在关断过程中所产生的损耗,提高电源的开关频率.通过在变压器副边增加一个由谐振电感、谐振电容、辅助箝位二极管以及辅助开关管组成的辅助电路,在主开关管关断之前短暂开通辅助开关管,通过谐振电感和谐振电容之间的谐振使原边电流迅速复位,从而实现主电路开关管的零电流开关(ZCS).实验结果表明,此变换器可在全负载范围内实现所有开关管的ZCS和输出整流管的软换流,其辅助电路的谐振电感还具有帮助主电路实现主开关管软开通的功能.这种拓扑结构简洁,可以较好地实现软开关且不会增大整流二极管的电压应力,变换器的效率也达到了90%以上且有提升空间.     

The minimization of non-equilibrium plasma source at high pressure

The density of plasma produced by atmospheric non-equilibrium plasma source is the function of energy dissipation rate in ionization electric field and gas particles momentum. The experiment shows that the plasma density highly rises with the increasing of energy dissipation rate and gas particles momentum. When the energy dissipation rate of activation field is 2.18 Wh/m^3 and the average gas particles momentum is 109×10^-22 g· m/s, the air throughput of plasma source whose volume is only 2.5 cm^3 can be up to 12 m^3/h and the density of plasma can be up to 10^10 cm^-3. The research can develop a method of producing minitype plasma source which is low energy consumption but high ion concentration used for chemical industry, environmental engineering and military.     

催化共振散射光谱法测定木瓜蛋白酶活力

木瓜蛋白酶催化水解酪蛋白生成小分子氨基酸和肽,剩余底物酪蛋白与三氯乙酸结合形成粒径约为1740nm的缔合物微粒。该微粒在360、400、420、470、520nm处产生5个共振散射峰,其中最强峰位于470nm。在选定条件下,随着木瓜蛋白酶量的增加,体系中剩余酪蛋白浓度降低,470nm处的共振散射光强度,Ⅰ470nm降低。木瓜蛋白酶的酶活力在0．024～4．8 USP／mL范围内与470nm处的共振散射光强度降低值△Ⅰ470nm呈现良好线性关系,检出限为0．0083 USP／mL。该共振散射光谱法用于嫩肉粉中木瓜蛋白酶活力测定,结果满意。     

一类二阶中立型时滞微分方程的渐近稳定性

研究了一类二阶中立型时滞微分方程零解的渐近稳定性,借助于推广的Halanay一维时滞微分不等式,利用构造函数法给出了判定其零解渐近稳定的与时滞无关的一个充分条件．     

Key roles of micro-particles in water on occurrence of cavitation-erosion of hydro-machinery

It has been believed for about one hundred years that the cavitation directly induces the cavitation erosion. It is proposed in this research that cavitation is only the necessary condition but not the sufficient condition of the cavitation erosion. The experiment performed on the rotary disk cavitation system shows that the mi- cro-particles in the fluid play indispensable roles in the cavitation erosion process, and the generation of the erosion pits on the steel surface is also affected by the particles＇ size. These cracks and deformations on the sample surface indicate that the erosion is the result of the mechanical behavior. Numerical calculations are also provided to support this mechanism.     

Poka Yoke——A Way to Achieve Zero Defect

How can all defects in a complex manufacturing, service, or software development operation be prevented if no statistical process control (SPC) is used and if the engineering staff is very small? People unfamiliar with Poka Yoke (mistake proofing devices) usually claim that this is not possible. However, Dr. Shigeo Shingo developed a system of mistake proofing that eliminates defects without the use of SPC or complex solutions. This paper explains how Poka Yoke devices work and how to apply poka yoke devices now to eliminate defects.     

纳米镓粒子的超声制备与表征

文章主要研究了纳米金属镓粒子的制备技术与稳定分散技术,以聚乙烯吡咯烷酮（PVP）为稳定剂,采用超声将碎法制备出均匀分散的纳米镓粒子,并借助于TEM、FT-IR、XPS分析手段对纳米粒子的微观结构进行表征。TEM表明超芦20min即可制得粒径约为40～50nm的纳米镓粒子;FT-IR、XPS表明在超声辐射下,PVP中的N原子和O原子实现了与纳米钧粒子表面原子的配位作用,使纳米稼粒子得到稳定。     

零函数的性质

Rudin W著的《Read and Complex Analysis》（第三版）7．18节中给出一个未加证明的命题：设f（x）是区间I上的连续非减实函数,且把零测度集映成零测度集,则x＋f（x）也把零测度集映成零测度集。本文给出了这一命题的证明,并推广到一般的零函数。