支撑柱型电容式超声传感器有限元分析

利用COMSOL软件建立简化的分析模型,对支撑柱型电容式超声传感器(CMUT)模型进行有限元分析,并将其与圆形空腔CMUT模型进行对比。结果表明,支撑柱型CMUT模型的共振频率为10 kHz,塌陷电压为52 V,有利于进行低频化设计。与圆形空腔CMUT模型相比,支撑柱型CMUT模型的有效面积较大,寄生电容较少,器件的灵敏度较高,塌陷电压较低,振膜的振幅较大,工作时发出的声信号较弱。     

固定化假丝酵母脂肪酶催化合成辛酸甘油酯

以自制固定化假丝酵母脂肪酶作为催化剂,研究了无溶剂体系中辛酸和甘油直接酯化合成辛酸甘油酯的反应条件。考察了酶的种类、底物的物质的量之比、温度、酶量、甘油的初始含水量和反应时间等因素对辛酸转化率和产物组成的影响。结果证明,以纺织物作为载体制备的固定化假丝酵母脂肪酶适宜催化辛酸甘油酯的合成。最优反应条件为：辛酸与甘油的物质的量之比为2∶1,固定化假丝酵母脂肪酶加量为0.5g/0.69g甘油,温度为40 ℃,振荡培养箱转速为190 r/min。最优反应条件下辛酸转化率可以达到94%以上,经过简单处理的固定化酶可以重复使用4批。     

MASS TRANSFER IN AC ELECTROLYSIS: EXTENSION OF A FILM MODEL TO TURBULENT FLOW ON A ROTATING HEMISPHERE

Turbulent mass transfer to a rotating hemisphere during AC electrolysis was examined with a film model. The analytical results for the limiting AC current density were compared to the experimental data obtained with sinusoidal, square and triangular wave AC. The limiting AC current density in turbulent flow was found to depend on both the Reynolds number as a dimensionless AC frequency K = (ω/Ω)Sc^1/3 The prediction by the film model agreed with the experimental data to within ±15%. For a given root-mean-square of applied AC, the periodic concentration overpotential decreased in the order of quare, sinusoidal, and triangular AC. The phase shift between the applied AC and the concentration overpotential wave decreased with increasing Reynolds number in turbulent flow.     

A unified approximate reasoning theory suitable for both propositional calculus system L and predicate calculus system K

The concepts of metric R0-algebra and Hilbert cube of type RO are introduced. A unified approximate reasoning theory in propositional caculus system ? and predicate calculus system (?) is established semantically as well as syntactically, and a unified complete theorem is obtained.     

Scalar-Lyapunov-function method for single- and multimachine problems in power systems

A systematic method is proposed to derive appropriate Lyapunov functions for single- and multimachine problems in power systems that will enable suitable stability-region estimates to be determined. Initially, the Lyapunov function for a simplified second-order system is derived. This function is then modified to form a suitable Lyapunov function for the actual non-linear system under study. Six examples for single- and multimachine problems are considered.     

基于QFD和前景理论的产品规划方案选择方法

为了以有效的方式反映决策者的心理和行为特征,提出基于不确定语言信息熵和前景理论的产品规划方案选择方法.客户代表使用不确定语言变量表征本企业及竞争对手产品的竞争性,利用信息熵的方法确定各项客户需求项目的竞争优先次序,据此得出产品规划的备选方案;引入前景理论的思想,依据备选方案的投入成本,计算各个方案的成本感知价值;再次,计算不同风险场景和盈利场景的价值和权重,确定各个方案的风险感知价值和盈利感知价值;依据成本感知价值、风险感知价值和盈利感知价值,确定各个备选方案的综合感知价值,并据此得到产品规划的最优方案.以PE破碎机的改进为例,说明了所提方法的实用性和可靠性.     

Solid Phase Microextraction for Cheese Volatile Compound Analysis

Cheese headspace volatile compounds were extracted with solid-phase microextraction (SPME) fibers, coated with either polydimethylsiloxane or polyacrylate, and thermally desorbed in the injector port for gas chromatographic (GC) analysis. Results with polyacrylate-coated fibers were better than those with a polydimethylsiloxane fiber. Major cheese volatile components such as volatile fatty acids and 5-lactones were readily extracted by both SPME fibers, but minor components such as volatile sulfur compounds were not observed. SPME-GC patterns were distinctly different among cheese varieties, and characteristic volatile compounds could be identified using multivariate techniques.     

超深井高速率连续波MWD信道传输系统(英文)

At present,the MWD systems continuous wave mud pulse telemetry transmit is not faster than 1or 2bits/s from deep wells containing highly attenuative mud,because positive pulsers create strong signals but large axial flow forces impede fast reciprocation while mud sirens provide high data rates without higher signal strength.A high-data-rate system providing 10bits/s and operable up to30 000 ft is described,which creates strong source signals by using downhole constructive wave interference in two novel ways.Telemetry schemes,frequencies and pulser locations in the MWD drill collar are selected for positive wave phasing,and sirens-in-series are used to create additive signals——both without incurring power and erosion penalties.The positions normally occupied by pulsers and turbines are reversed to minimize times required for constructive interference and modulation.A system design approach is undertaken,e.g.,strong source signals are augmented with new multiple-transducer surface signal processing methods to remove mudpump noise and signal reflections at both pump and desurger,and mud,bottomhole assembly and drill pipe properties,to the extent possible in practice,are controlled to reduce signal attenuation.The results of detailed acoustic modeling in realistic drilling telemetry channels are described,and short and long wind tunnels for signal strength,torque,erosion and jamming testing,and telemetry and signal processing evaluation,respectively,are introduced.Special scaling methods are developed to extrapolate cost-effective wind tunnel test results to real muds flowing at any downhole speed.New siren concept prototype hardware and also typical acoustic test results are also given.