介电电泳细胞分析芯片结构设计及富集效率优化

为了研制高富集效率的介电电泳细胞分析芯片,首先从介电电泳力出发,推导了悬浮细胞所受的介电电泳力公式。通过对比常规微电极的电场强度分布,选择叉指式阵列微电极构建介电电泳芯片;通过模拟不同结构参数下微通道中的电场分布对芯片结构参数进行优化设计。针对Hep G2肝癌细胞,分别分析了细胞受介电电泳力、流体力以及重力作用下的运动情况,获得了Hep G2肝癌细胞富集的初步优化条件。为了对模拟结果进行验证,采用微加工技术制作了介电电泳细胞分析芯片。以Hep G2肝癌细胞为待测样品,当芯片所施加正弦交流电压为5 V,频率为4 MHz时,获得了88.89%的富集效率。     

Finite element modeling of micro-milling: Numerical simulation and experimental validation

In this study, micro-milling of Inconel 718 was investigated. For this purpose, cutting tests were conducted by using uncoated tools and taking four different feed rates (1.25, 2.5, 3.75, and 5 µm/flute) and a constant cutting velocity (48 m/min) into account. In numerical modeling, thermomechanical behavior was modeled using the modified Johnson–Cook material model. Analyses were also conducted for different cutting tool edge angles (+8°, 0, and ?8°). In the numerical analyses, cutting force, tool stress, and cutting temperature values were estimated depending on tool rotation and cutting tool edge type and compared with experimental results. When the results obtained from the study are considered, it is seen that the experimental cutting force and temperature values are in harmony with the numerical results. Moreover, it is seen that there is an increase in cutting force, cutting temperature, and stress values depending on the feed rate. In addition, in the numerical analyses for different cutting tool edge geometries it was observed that cutting force temperature and tool stress values varied depending on the edge geometries.     

Numerical simulation and experimental validation of a ductile damage model for DIN 1623 St14 steel

St14 steel (DIN 1623) is widely used in sheet metal forming industries because of its remarkable formability and also its low price. In this paper, damage behaviour of St14 steel is studied in order to be used in complex forming conditions with the goal of reducing the number of costly trials. Damage parameters of St14 steel have been determined by using standard tensile and Vickers micro-hardness tests. A fully coupled elastic-plastic-damage model has been developed and implemented into an explicit code. With this model, damage propagation and crack initiation, and ductile fracture behaviour of drilled and notched specimens are predicted. The model can quickly predict both deformation and damage behaviour of the part because of using plane stress algorithm, which is valid for thin sheet metals. Experiments are also carried out to validate the results. It is concluded that finite element analysis (FEA) in conjunction with continuum damage mechanics (CDM) can be used as a reliable tool to predict ductile damage and fracture of St14 steel.     

一种新型石油射孔弹的数值模拟分析

为了提高油气井的产量及保护油气层,需要对射孔弹的设计理论及射孔机理进行大量的研究与分析,从而设计出一系列针对不同岩层,能够达到不同射孔要求的射孔弹.根据已有的射孔弹壳体要求,设计了一种由两层药型罩组合而成的新型双层复合罩.这种新型药型罩是由一个主装药和两个药型罩组成,应用Truegrid建立有限元模型,对不同药型罩模型进行数值分析,比较两种不同模型金属射流参数,为新型石油射孔弹的设计提供有力依据.     

一种新型热翅板式电子散热器的模拟研究

由于现代电子设备及元器件不断向高集成度、高紧凑性发展,其散热量也不断增大,威胁到其正常工作的安全性和可靠性.为此,一种新型的热翅板式散热器结构被提出,并针对高散热量的电子元件(CPU芯片)进行了散热能力的研究.通过数值模拟分析了该新型散热器的散热性能,得到不同热功率下芯片的温度分布,分析了冷却温度、冷却风量等对散热性能的影响,最终得到了正常工况下的最佳风量.     

Numerical simulation and experimental research on passive hydrodynamic bearing in a blood pump

The current research of hydrodynamic bearing in blood pump mainly focuses on the bearing structure design.Compared with the typical plane slider bearing and Rayleigh step bearing,spiral groove bearing has excellent performance in load-carrying capacity.However,the load-carrying capacity would decrease significantly with increasing flow rate in conventional designs.In this paper,the special treatment is made to the upper spiral groove bearing to make sure that both the circulatory flowing and load-carrying capacity are high.Three-dimensional computational fluid dynamics(CFD) models in the space between rotor and shaft are developed by using FLUENT software.Effects of groove number,film height and groove depth on load-carrying capacity of the spiral groove bearings are investigated by orthogonal experiment design.The experimental results show that film height is the most remarkable factor to the load-carrying capacity.The variation tendency of load-carrying capacity reveals that the best combination of geometry is the one with groove number of 8,film height 0.03 mm and groove depth 0.08 mm.The velocity and pressure distributions in spiral groove bearings are also analyzed,and the analysis result shows that the distributions are in conformity with the design of the blood pump based on the principle of hydrodynamic bearing.The displacement of the rotor with the best combination parameters is tested by using laser displacement sensors,the testing result shows that the suspending performance is satisfactory both in axial and radial directions.This research proposes a bearing design method which has sufficient load-carrying capacity to support rotor as an effective passive hydrodynamic bearing.     

Combinatorial electrochemical cell array for high throughput screening of micro-fuel-cells and metal/air batteries

An electrochemical cell array was designed that contains a common air electrode and 16 microanodes for high throughput screening of both fuel cells (based on polymer electrolyte membrane) and metal/air batteries (based on liquid electrolyte). Electrode materials can easily be coated on the anodes of the electrochemical cell array and screened by switching a graphite probe from one cell to the others. The electrochemical cell array was used to study direct methanol fuel cells (DMFCs), including high throughput screening of electrode catalysts and determination of optimum operating conditions. For screening of DMFCs, there is about 6% relative standard deviation (percentage of standard deviation versus mean value) for discharge current from 10 to 20 mAcm(2). The electrochemical cell array was also used to study tin/air batteries. The effect of Cu content in the anode electrode on the discharge performance of the tin/air battery was investigated. The relative standard deviations for screening of metal/air battery (based on zinc/air) are 2.4%, 3.6%, and 5.1% for discharge current at 50, 100, and 150 mAcm(2), respectively.     

Fault induction dynamic model,suitable for computer simulation: Simulation results and experimental validation

The study of induction motor behavior under not normal conditions and the ability to detect and predict these conditions has been an area of increasing interest. Early detection and diagnosis of incipient faults are desirable for interactive evaluation over the running condition, product quality guarantee, and improved operational efficiency of induction motors. The main difficulty in this task is the lack of accurate analytical models to describe a faulty motor. This paper proposes a dynamic model to analyze electrical and mechanical faults in induction machines and includes net asymmetries and load conditions. The model permits to analyze the interactions between different faults in order to detect possible false alarms. Simulations and experimental results were performed to confirm the validity of the model.     

Ultrasonic method for determination of elastic moduli—Numerical simulation and experimental results

In this work, a numerical simulation and experimental results using a modified prism technique are presented. It is based on pulse-echo technique and involves the measurement of both longitudinal and transversal waves velocities in trapezoidal-prism shaped specimens with only one transducer. Both longitudinal and transversal waves are generated through mode conversion at the interface between water and the specimen under test. Based on numerical simulation with the 2-D Elastodynamic Finite Integration Technique (EFIT), several snapshots are generated to illustrate the functionality of this new technique, and the experiment was performed on cement paste with various water/cement ratios.     

The delay & sum algorithm applied to microphone array measurements: Numerical analysis and experimental validation

The experimental validation of the beamforming technique applied to microphone array measurements is investigated in this paper. At first the method theoretical background is presented, highlighting the main parameters affecting its performances and studying their influence with the aim of producing an instrument useful in designing an efficient experimental set-up. Then, in order to prove the theory assessment and to give a first estimation of the method uncertainty, an experimental campaign is carried out to validate the exposed theory under controlled and repeatable conditions.The obtained results highlight a very good correspondence between the theoretical model and the “in field” tests, giving the possibility to correctly design microphones array for future experimental campaigns.     

Numerical simulation of the failure process for an experimental sample with a concentrator under plane bending conditions

The results of the numerical simulation of elastic-plastic deformation, crack nucleation, and propagation in a sample are presented. The simulation is performed using the laws of mechanics of a damaged medium by considering different variants of the accumulation of faults. The obtained results are in good agreement with the experimental data for the case when during the simulation both plastic and brittle failures are taken into account.     

Rotordynamic analysis and experimental validation of a high speed induction motor made by copper die casting process

A copper die casting induction motor can obtain an energy saving effect of about 2–3% compared to previous aluminum die casing induction motors. In addition, copper die casting motors can reduce the size of motors and reduce material costs. The critical speed and unbalance response of high speed machines need to be verified by rotordynamic analysis for dynamic stability of the rotors. The critical speed analysis, harmonic analysis and transient analysis by unbalance are performed for dynamic stability. The unbalance analysis results are compared with the experiment considering allowable vibration displacement (API 611) and balancing grade (ISO 1940-1). This paper dealt with the design, analysis and experimental validation of a high speed induction motor. The dynamic stability of the prototype is verified successfully, and two experimental methods by ISO 10816-3 are suitable and reliable for the allowable vibration evaluation of rotating machine.     

On a test bench for studying lubrication in a spherical bearing: simulations and experimental validation

In this paper a test bench dedicated to the analysis of a lubricated spherical pair is presented. The experimental set‐up has been used to validate a numerical code that has been developed by the authors in order to simulate a complex lubricated spherical pair that affects the reliability of a novel continuous variable transmission (CVT). The test bench is modular and can be adapted to other lubricated pairs, either cylindrical or spherical. The stand is equipped with an I/O control card and allows the on‐line acquisition of some important parameters. As for the numerical code, the finite‐difference method has been used to solve the indirect problem in the lubricated spherical pad, under the condition of hydrodynamic regime, with externally pressurized inlets. Two simulators are needed since the physical properties of the test bench and the real system are different. The one that simulates the behavior of the spherical pair in the test stand has been used to ascertain the numeric approach prediction capability. Indeed, the experimental tests gave results which are in very good correspondence with the numerical predictions. Hence, the second simulator, which has been tailored on the particular spherical pair the CVT is equipped with, gained reliability in predicting the behavior of the real system under different load and speed conditions. These predictions have been useful in achieving new insights into the novel CVT, which, under this new light, has been criticized by making the point that its range of application in automotive is, at the actual state of the art, rather limited, in spite of a high intrinsic complexity. Copyright © 2006 John Wiley & Sons, Ltd.     

双离合变速器敲击噪声的仿真分析与实验评价

针对某变速器在车辆一挡起步工况实验中出现敲击噪声的问题,利用LMS Virtual.Lab软件搭建了包含轴、齿轮、同步器、轴承、差速器、壳体等部件的双离合变速器刚柔耦合模型.考虑输入轴转速波动、轴承刚度非线性、齿轮啮合时变刚度和阻滞力矩,以再现敲击噪声发生时壳体的振动响应.仿真计算与实验结果的良好一致性,验证了仿真分析方法的有效性.     

Numerical and experimental study of a thermal probe for measuring groundwater velocity

A thermal method for a rapid measurement of groundwater velocity, particularly in aquifers with preferential flow where groundwater velocities over tenths of (m/d) are expected, was studied. Some instruments for measuring groundwater velocity are based on the application of heat. Those consisting of a central heater surrounded by several thermistors seem adequate for the above purpose, but their measuring range lies below 30 md (meters per day) and there are few works about their theory. Based on the diffusion-convection-dispersion equation, an electrical model is proposed for representing this type of instruments and a theoretical study is presented in an attempt to extend their measuring range. The model can be excited with any shape of power or temperature signals, allows the signals to be feedbacked for controlling the heater's excitation, and includes the thermal features of the heater and thermistors. The model was validated through laboratory tests with velocities of up to 100 md and extrapolated up to 1000 md. Numerical results suggest that exciting the heater with constant temperature allows the measuring range of these probes to be extended.     

On a new sectionalized motion control strategy for automated guided vehicles: modeling and simulation validation

As key equipment in logistics system of modern manufacturing factories, the automated guided vehicle (AGV) plays an increasingly important role. Although many strategies for AGV motion control are available, in most cases, only a single control method is utilized during the entire process, which inevitably leads to the lack of flexibility in dealing with problems encountered in various stages of the AGV motion. In this paper, a new approach called sectionalized motion control (SMC) was proposed in order to achieve superb comprehensive performance (i.e., high precision, low energy consumption, and good stability) for the entire AGV tracking process. In this method, considering AGV’s various characteristics in different motion stages (early, middle, and terminal), the neural dynamics-based tracking, energy-efficient tracking, and model predictive control technologies were adopted. Furthermore, a simulation using Matlab software was performed in order to verify the proposed approach. The simulated results showed that the SMC is capable of providing smooth, energy-efficient, robust, and globally stable control for the AGV system.     

Numerical simulation and experimental study of the accelerating structure with on-axis coupling cells for a double-sided CW racetrack microtron at an energy of 1.5 GeV

A numerical simulation of a biperiodic accelerating structure with on-axis coupling cells at a frequency of 2450 MHz for the double-sided cw race-track microtron with an energy of 1.5 GeV now being built at the Institute for Nuclear Physics, Johannes Gutenberg University (Mainz, Germany), was performed. On the basis of these calculations, test cells have been manufactured that are used to develop and refine the methods for measuring and tuning the accelerating structure. The final geometry of cells is established.Translated from Pribory i Tekhnika Eksperimenta, No. 1, 2005, pp. 24–35.Original Russian Text Copyright ¢ 2004 by Alimov, Vetrov, Ishkhanov, Kosarev, Pakhomov, Chubarov, Shvedunov, Euteneur, Jankowiak.     

Fabrication and efficiency evaluation of a hybrid NiCrAl pressure cell up to 4 GPa

A hybrid NiCrAl pressure cell was fabricated to measure magnetic quantities under high pressure above 3 GPa. A pressure of 4.0 GPa was achieved and the pressure cell was found to be reusable even after a pressurizing trial up to 4.0 GPa. Pressure was monitored using (63)Cu nuclear quadrupole resonance of Cu(2)O and ruby fluorescence. The pressure efficiency of a fresh cell was maintained at 96%, and no appreciable deformation was observed at pressures below 3 GPa; on the other hand, the efficiency after pressurizing trials decreased gradually and reached 75% at 4 GPa accompanied by a maximum expansion inside the cylinder of 2%.