微通道周期流动电位势及电粘性效应

求解了双电层的Poisson-Boltzmann方程和流体运动的Navier-Stokes方程,得到在周期压差作用下,二维微通道的周期流动电位势,流动诱导电场和液体流动速度的解析解.量纲分析表明,流体电粘性力与以下3个参数有关:1)电粘性数,它表示定常流动时,通道最大电粘性力与压力梯度的比;2)形状函数,它表示电粘性力在通道横截面的分布形态;3)耦合系数,它表示电粘性力的振幅衰减特征和相位差.分析结果表明,微通道周期流动诱导电场、流动速度与频率Reynolds数有关.在频率Reynolds数小于1时,流动诱导电场随频率Reynolds数变化很慢.在频率Reynolds数大于1时,流动诱导电场随频率Reynolds数的增加快速衰减.在通道宽度与双电层厚度比值较小情况下,电粘性效应对周期流动速度和流动诱导电场有重要影响.

微扩散通道中的流动电位势和电黏性效应分析

采用电解质溶液离子输运的Nernst-Planck方程、液体运动的Navier-Stokes方程和电场的Poisson方程研究了微扩散管的双电层、电解质流动电位势和电黏性效应。采用有限体积法分析了微扩散管流动电位势、流动电阻力、流量损失和流动速度形态变化。结果表明,与均匀截面微通道不同的是,流动电位势在微扩散管内呈非线性增长,流动电阻力沿微通道截面扩张方向下降。在微扩散管的横截面上也会产生流动电位势和电阻力。在微收缩管流动的电黏性效应和流量损失率比微扩散管流动略大。论文数值解给出流动电位势从瞬态到稳态发展过程的时间尺度特征,并分析了微通道扩散角对电黏性效应产生的微通道流量损失率。

基于流动电位势的自动化微小液体流量计量系统设计

微流控系统液体流量一般为每分钟几微升甚至几纳升,计量非常困难。微通道液体流量与电动流密切相关,流场、电场、离子场相互耦合作用使得流动时形成流动电位势,其与流量具有定量对应关系,本研究介绍了基于流动电位势来建立自动化微小液体流量计量系统的原理,并详细介绍了系统设计及自动化控制实现方法。

用于电离层离子探测的多路微弱电流检测电路设计

针对电离层离子探测传感器对电流检测电路的需求,设计了一种适用于阻滞势电位分析仪和离子漂移计复用传感器的多路微弱电流检测电路。在放大模块设计中,分析并仿真对比了T型电阻网络和跨阻式电阻网络的噪声及直流偏置水平,研究了不同反馈电容下的噪声、带宽和时延等特性。为降低电路噪声水平,提高电路整体性能,设计了滤波模块、采集模块和高精密电源模块。实验结果证明:该电路系统具有良好的准确性、一致性、稳定性和实际应用性,可推广应用于电离层微弱信号检测领域。

次氯酸钠在蔬菜加工中循环利用的杀菌效果评价

为保证次氯酸钠(NaClO)溶液循环使用后的杀菌效力,研究黄瓜切片、油菜连续加样对次氯酸钠(NaClO)溶液杀菌效果的影响,同时探讨油菜和黄瓜汁液对NaClO溶液的氧化还原电位势(ORP)值影响。结果表明:切片黄瓜汁液渗出较多,多于1kg的样品量即会导致NaClO溶液的ORP值和有效氯含量骤降,失去杀菌能力;而未切分的油菜对NaClO溶液的ORP值影响较弱,质量达9kg时,NaClO溶液的ORP值仍有约600mV;蔬菜汁液对NaClO溶液的ORP影响呈反"S"曲线,依据Boltzman拟合方程以及拐点理论,NaClO溶液ORP值降到600mV时,溶液已基本失去杀菌能力,需补充新鲜杀菌剂。

微纳米通道电场调控电渗流研究及控制

在通道壁面垂直施加一个调控电场可以改变双电层电荷密度和Zeta电位势,实现对电渗流的调控。采用离子输运Nernst-Planck方程、液体流动Navier-Stokes方程、以及介电层-电解液耦合双电层Poisson方程,数值求解外加均匀调控电压下微纳米通道的电渗流动,得到表面Zeta电位势、电渗流速度与外加调控电压的关系特性。数值解与基于Poisson-Boltzmann方程双电层弱重叠近似和双电容串联模型的解析解相对比,进一步研究了控制外加调控电压以及控制电渗流的方法。

三层椭球脑模型和球脑模型EEG正问题的数值解比较

EEG是研究脑神经生理活动的重要医学影像技术.在三层椭球脑模型和三层球脑模型下,运用加权残值边界元法,对不同方向和不同位置的偶极子计算了脑皮电位势及其相对偶极子位置变化时的相对差.同时比较了在不同脑模型和偶极子参数下,脑皮上电位势图像的形态和变化规律.结果表明:脑模型和偶极子参数对EEG正问题求解均有影响.在两种脑模型下,脑皮上电位势图像的形态基本相似,但是电位势峰值的大小有了明显的差异.

中心球模型下EEG正问题的数值模拟

目前EEG已经成为脑功能研究和临床诊断的重要技术手段.在研究EEG反问题时,大量的EEG正问题的计算是必不可少的.一方面,基于加权残值边界元法建立EEG正问题的计算公式,针对中心球模型,对不同偶极子的位置和方向分别计算了脑皮电位势.另一方面,针对EEG正问题的数值模拟,比较脑皮电位势的数值解与解析解的差异.结果表明加权残值法较以往的有限元法、差分法计算效率和精度都明显提高.因此广泛应用在计算力学的研究中.

THREE-PHASE BRIDGE INVERTER FOR 9kW DOUBLY SALIENT PERMANENT MAGNET MOTOR

The three-phase bridge inverter is used as the converter topology in the power controller for a 9 kW doubly salient permanent magnet （DSPM） motor. Compared with common three-phase bridge inverters, the proposed inverter works under more complicated conditions with different principles for special winding back EMFs, position signals of hall sensors, and the given mode of switches. The ideal steady driving principles of the inverter for the motor are given. The working state with asymmetric winding back EMFs, inaccurate position signals of hall sensors, and the changing input voltage is analyzed. Finally, experimental results vertify that the given anal ysis is correct.

Evaluation of Four Measurement Operation Modes of Streaming Potential for Microfiltration and Ultrafiltration Membranes

Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were investigated in this study, and among the four modes, the steady mode with pressure stepped downward was considered the best one. Experimental results showed that the effects of compaction on the streaming potential measurement for a microfiltration membrane was more obvious than that for a ultrafiltration membrane. Both feed pH and presoaking could affect the measurement of streaming potential.

Chemical composition and surface charge properties of montmorillonite

The effects of the cell parameter and chemical composition on the surface charge properties of five kinds of different colour montmorillonites were studied. The results indicate that the surface isoelectric point（IEP） of the montmorillonite shows positive correlation with the mass fractions of Fe203 and K20, but it has little relation to the mass fractions of other chemical compositions. At around pH=6.8, the surface zeta potential of the montmorillonite shows the negative relationship with the mass fractions of Fe203 and MgO, but it does not linearly correlate to the mass fractions of other chemical compositions. Cell parameter（bo） of the montmorillonite expresses negative linear relationship with mass fractions of K2O and Na2O, so does cosinβ with mass fractions of SlOE and Fe2O3. And there is no specific relationship between bo and IEP of different montmorillonites, but there is positive correlation between cosinβ and IEP of different montmorillonite samples.

An Investigation of the Potential Malignant Characteristics of Endometriosis

OBJECTIVE To investigate the potential malignant characteristics and pathogenesis of endometriosis as well as the role of human growth hormone and epidermal growth factor receptor in the pathogenesis of malignant transformation of endometriosis. METHODS The immunohistochemical S-P method was used to examine the expression of human growth hormone and epidermal growth factor receptor in the eutopic and ectopic endometrium of 84 cases of endometriosis. RESULTS The percentage of positive cases of human growth hormone in eutopic and ectopic endometrium was 90.77% （59/65） and 85.71% （72/ 84） respectively. The percentage of positive cases of epidermal growth factor receptor in eutopic and ectopic endometrium was 81.54% （53/65） and 89.29% （75/84） respectively. The positive rate of epidermal growth factor receptor in ectopic endometrium was higher than that in the eutopic endometrium but without a statistically significant difference （P〉 0.05）. CONCLUSION Endometriosis is caused by multiple factors, which possesses some biologic features of neoplastic tissue such as invasion and metastasis. Both human growth hormone and epidermal growth factor receptor are highly expressed in eutopic and ectopic endometrium, which lead directly or indirectly to the pathogenesis of endometriosis and promote the initiation and malignant transformation of endometriosis.

Surface-borehole electric potential survey in layered media and its applications

The method in which a source is set on the surface and electric potential is received in the borehole is called surface-borehole electric potential technique. Technique of surface-borehole electric potential was employed to study electric response of layered formation. The electric potential was obtained by solving Poisson equation with finite difference method. In the course of calculation, forward modeling wilth finite difference method was realized by adopting bandwidth non-zero storage technique and the incomplete Cholesky conjugate gradient method. The results show that method of surface-borehole can acquire anomalous electric potential corresponding tc geo-electric layers. In addition, application of appropriate mathematical operator can improve the resolution. Moreover, overburden low resistivity layers have severe influence on measuring results of surface-borehole electric potential. However, bottom low resistivity layers play a positive role in the measurement.

Relativistic Treatment of Massive Klein-Gordon Particle by Modified Generalized Hulthen Potential

Approximate bound state solutions of spinless particles with a special case of equal scalar and vector modified generalized Hulthen potential has been obtained under the massive Klein-Gordon equation. The energy eigenvalues and the corresponding wave functions expressed in terms of a Jacobi polynomial are also obtained using the parametric generalization of the Nikiforov-Uvarov （NU） method. Under limiting cases our result are in agreement with the existing literature. Our results could be used to study the interactions and binding energies of the central potential for diatomic molecules in the relativistic framework which have many applications in physics and some others related disciplines.

The Analytic Solution of Schrdinger Equation with Potential Function Superposed by Six Terms with Positive-power and Inverse-power Potentials

The analytic solution of the radial Schrodinger equation is studied by using the tight coupling condition of several positive-power and inverse-power potential functions in this article. Furthermore, the precisely analytic solutions and the conditions that decide the existence of analytic solution have been searched when the potential of the radial Schrodinger equation is V（r） =α1r^8 ＋α2r^3 ＋ α3r^2 ＋β3r^-1 ＋β2r^-3 ＋β1r6-4. Generally speaking, there is only an approximate solution, but not analytic solution for SchrSdinger equation with several potentials＇ superposition. However, the conditions that decide the existence of analytic solution have been found and the analytic solution and its energy level structure are obtained for the Schrodinger equation with the potential which is motioned above in this paper. According to the single-value, finite and continuous standard of wave function in a quantum system, the authors firstly solve the asymptotic solution through the radial coordinate r → ∞ and r →0; secondly, they make the asymptotic solutions combining with the series solutions nearby the neighborhood of irregular singularities; and then they compare the power series coefficients, deduce a series of analytic solutions of the stationary state wave function and corresponding energy level structure by tight coupling among the coefficients of potential functions for the radial SchrSdinger equation; and lastly, they discuss the solutions and make conclusions.

Study on the large-scale assembly and fabrication method for SWCNTs nano device

The large-scale assembly and fabrication method for single-walled carbon nanotube(SWCNT) nano devices was implemented.Assembly of SWCNT field effect transistor(FET) was realized by floating potential dielectrophoresis approach.The simulation of floating potential distribution of the chip was performed by comsol multiphysics coupling software.Six hundred devices were assembled on the area of less than one square centimeter.The fabricated devices were characterized by atomic force microscopy and scanning electron microscopy.The experimental results showed that large-scale assembly had been realized,and the success rate of ideal assembly for SWCNT FET had been assessed.

Large-scale assembly of Cu/CuO nanowires for nano-electronic device fabrication

To improve the efficiency of nano-electronic device fabrication, a new method named floating electrical potential assembly is proposed to realize large-scale assembly of Cu/CuO nanowires, The simulation of floating electrical potential distribution on the micro-electrode chip is performed by COMSOL software, and the simulation result shows that the coupled electrical poten- tial on the floating drain electrodes is very close to the original electrical potential applied on the gate electrode, whicb means that the method can provide di-electrophoresis （DEP） force for all the electrode pairs at one time, thus realizing large-scale as- sembly at one time. With Cu/CuO nanowires well dispersed and micro-electrode chip fabrication, nanowires assembly experiments are performed and the experimental results show that Cu/CuO nanowires are assembled at hundreds of micro-electrodes pairs at one time, and the success rate of nanowires assembly also reaches 90%.

Interaction potential between micro/nano curved surface and a particle located inside the surface (II):Numerical experiment and equipotential surfaces

We verify the accuracy of the curvature-based potential.By means of the idealized numerical experiment,we show that the curvature-based potential is in good agreement with the numerical experiment,and the errors are within a reasonable range.Based on the curvature-based potential,the equipotential surfaces of particles are derived,and the intrinsic relations between the equipotential surfaces and Weingarten helicoids are shown.

A newly developed interatomic potential of Nb-Al-Ti ternary systems for high-temperature applications

Nb-doped TiAl alloys exhibit excellent mechanical properties at high temperatures,and the underlying mechanism and optimal doping amount remain elusive.Molecular dynamics simulation is helpful to clarify these problems,but most of the existing interatomic potentials are limited to the Ti-Al binary system and lack interatomic potentials for doped alloys.Here,an intera-tomic potential of Nb-Al-Ti ternary systems based on the modified embedded-atom method was developed.The ternary potential can accurately predict the structure and thermodynamic properties of the Nb-Al-Ti system.The potential shows that the optimal Nb content for high-temperature strength-ductility synergy of TiAl single crystals is 8%,consistent with the amount of miracle synthesis of TiAl single crystals.Tensile simulations further show that the developed potential can make an effective prediction at high temperatures,indicating the potential for the development and applications of high-temperature Nb-Al-Ti ternary systems.

Retainability of canonical distributions for a Brownian particle controlled by a time-dependent harmonic potential

The retainability of canonical distributions for a Brownian particle controlled by a time-dependent harmonic potential is investigated in the overdamped and underdamped situations, respectively. Because of different time scales, the overdamped and underdamped Langevin equations(as well as the corresponding Fokker-Planck equations) lead to distinctive restrictions on protocols maintaining canonical distributions. Two special cases are analyzed in details: First, a Brownian particle is controlled by a time-dependent harmonic potential and embedded in medium with constant temperature; Second, a Brownian particle is controlled by a timedependent harmonic potential and embedded in a medium whose temperature is tuned together with the potential stiffness to keep a constant effective temperature of the Brownian particle. We find that the canonical distributions are usually retainable for both the overdamped and underdamped situations in the former case. However, the canonical distributions are retainable merely for the overdamped situation in the latter case. We also investigate general time-dependent potentials beyond the harmonic form and find that the retainability of canonical distributions depends sensitively on the specific form of potentials.