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A pneumatic microvalve which can be used in pneumatic pressure control for lab-on-a-chip applications is presented in this paper. In order to realize a feedback control and miniaturization, a micro stepper-motor is selected to control the opening of the microvalve. After introducing the structure and working principle of the pneumatic microvalve driven by a stepper-motor, the static flow rate simulation of pneumatic stepper-motor microvalve is processed in the condition of different opening sizes of the microvalve and pressure difference over the valve. The stepper-motor microvalve is fabricated and corresponding control circuit is designed. Experiments on static and dynamic characteristics of the microvalve are carried out. Good agreement has been shown between the simulation and experimental results.

Using basic physical arguments, we present a design and method for the fabrication of a pneumatic micro PDMS actuator using multilayer soft lithography based on dry-film photoresist. Its novel structure consists of a three-way electromagnetic microvalve for gas flow control which is connected with gas inlet microchannel for the actuator. Then the whole system is considered as a throttle blind capacitor (TBC) model and it is used to predict the response time of the pneumatic actuator by correlating its characteristics such as gas pressurizing, air resistance and membrane deformation. For this micro actuator, upward deformation motions of actuated area are observed of actuated area under 100KPa (N2) pressure and the fast open response (~ 15 ms) was achieved at 50KPa pressure. Our method provides a simple, cheap and save-time pneumatic micro actuator which can be used in active functions, such as valves, pumps and mixers integrated on pneumatic microfluidic chips for downsizing the driving pressure and improving the whole efficiency of microchips.

The mathematic model of flapper/nozzle electrohydraulic servovalves is rearranged, many factors are reconsidered which have been omitted in the past analysis which are for the purposes of convenience or on the assumption that they are of no particular significance. According to the rearranged mathematic model, the simulation model of the servovalve is established using the Matlab/simulink software, dynamic response characteristics of the servovalve is simulated when the parameters of the discharge coefficient of nozzles and the viscous damping constant of torque motor and flapper are changed. Simulation results show that the change of the parameters influence the dynamic response of the spool displacement.

Based on the original image of plants leaves, the edge detection method will be used to extract the geometrical morphology of leaves. The characteristic points of the contour can be calculated by Harris method. The contours of plant leaves is constructed by the quadratic B-spline interpolating curve, the leaf vein is generated by L system. The simulation of plant leaves is realized in OpenGL.

China is launching the Chang'e project to send automated machine for acquiring the lunar soil and returning to the earth. Thus, we are trying to develop a kind of effective mechanism for the exploration mission of lunar soil coring. This paper presents a rotary-percussive coring drill which is a novel scheme for the deep surface soil acquirement. Two degrees of freedom are included in the proposed drill mechanism. Specifically-designed drill unit including auger and drill bit is employed to finish the coring of the simulant of lunar regolith. We have proposed a novel coring concept named soft-bag coring. Since there is no relative motion between the soft-bag and the cut soil core, the soft-bag method may keep the original stratification of lunar soil. A test-bed has been developed to conduct experimental tests under different drilling parameters and circumstances. The related drilling parameters such as rotary speed, penetration ratio, and percussive frequency are adjusted to adapt to different situations in the experiments. The experimental results indicate that the specifically considered drill mechanism with soft-bag inside can get high coring ratio and excellent stratification of the soil.

The hydropower, as the renewable energy, the development strategy of which is the important part of China’s whole energy development strategy in the 12th Five-Year Plan. The insufficient capital injection of government is the main restriction factor of the hydropower development. The paper introduces the Public-Private-Partnerships (PPP) theories and practices, combining with the situations of China’s tight financing policies, sufficient private capital stock and so on, analyses the main problems on China’s hydropower financing and then builds the PPP structure to solve the problems, expounds the advantages, supports and safeguard measures of PPP structure. The paper puts forward the ideas that considering the hydropower project is quasi commonweal infrastructure, it is necessary for the governments to give rational compensation or Taxes and dues preferential policies to the SPC in order to guarantee stable cash flow and reasonable return on investment.

In order to understand the mechanism and get rid of the high-frequency self-excited noise in a hydraulic servo-valve, in this paper, the flow field distribution in the pilot stage of a hydraulic flapper-nozzle servo-valve is investigated. An assembly is prepared representing the construction and working principle of the flow field inside the pilot stage of a hydraulic flapper-nozzle servo-valve. A method of visualization is developed by taking videos for the flow field inside the transparent assembly with a high speed video camera. In this study, at different inlet pressure the high speed video camera was utilized for flow visualization together with computer-assisted image measurement. The shape of the jet flow, the cavitations and vortex flow inside the flow field can be visualized clearly. The proposed method enables to analyze the flow-field in the pilot stage of a hydraulic flapper-nozzle servo-valve by giving useful information for better design.

Magnetic fluid (MF) shows an increased saturation magnetization when exposed to a magnetic field. In order to improve the quality of servo-valve products by depressing and overcoming the self-excited high-frequency pressure oscillations and noise appearing in pilot stage of a hydraulic servo-valve, application of magnetic fluid in a hydraulic servo-valve is developed in this paper. Large damping can be introduced by the magnetic fluids into the servo-valve if magnetic fluids are filled into the working gaps of the hydraulic servo-valve torque motor. After the construction and working principle of a hydraulic servo-valve with magnetic fluids are introduced, the high-frequency pressure oscillation signals are tested and recorded when magnetic fluids are applied or not in the servo-valve. Experimental results are compared and analyzed by using FFT analysis method. It is shown that pressure oscillations of the servo-valve are depressed when magnetic fluids are applied.

In order to predict the dynamic characteristics, the piezoelectric valve-less diffuser micropump is equivalent to the hydraulic model which consists of several hydraulic components. Using finite element analysis (FEA) method, the static analysis and the natural frequency calculation of the diaphragm are carried out. The mathematical model and the simulation method using AMESim are developed. Simulation results show the pressure and flow rate characteristics of the micropump, as well as the diaphragm stiffness influence. The agreement between the simulation results and those published previously indicates that the method combining FEA with the hydraulic analogue model provides a relatively simple and effective tool to study the dynamic characteristics of micropumps.

A spool type high temperature control valve is developed to control the flow rate of high temperature fuel supply for scramjet engines in this paper. The clearance between the friction pairs of the spool and sleeve is crucial for the proper performance of the valve working at the temperature as high as 700 K. The high temperature environment may cause problems to the valve, for instance the thermal deformation of the valve materials, the failure of the friction pairs inside the valve and even the damage of the operating proportional electromagnet. Therefore the thermodynamic analyses of the valve are carried out using 2D finite element analysis method. The heat transfer and fluid dynamic models, as well as the boundary conditions are introduced. The heat flux through the fluid/solid interface is calculated to connect the heat transfer models inside the solid domain and the fluid domain. By solving both the heat transfer and turbulent flow models in the solid and fluid domains, the flow field distribution inside the flow channel and the thermal field distribution inside all the parts of the valve are shown. Suggestions on the design of the valve are given according to the thermodynamic analysis results.

Being as a functional material, piezoelectric ceramics is applied to drive a micropump when it is composed to be a thin membrane on a brass film to form a diaphragm. According to the properties of the piezoelectric material, the stiffness of the diaphragm influences the vibration displacement and therefore the supply flow rate of the micropump. This paper focuses on the dynamic characteristic study of the micropump and the stiffness influence of the diaphragm on the characteristics. The mathematical model of the valve-less micropump considering the diaphragm stiffness is developed in order to predict the dynamic characteristics of the piezoelectric valve-less micropump. Using the 3-D finite element analysis (FEA) method, the static and vibration mode of the diaphragm are analyzed to obtain the diaphragm stiffness and natural frequency. The method using Matlab is to predict the pressure and flow rate characteristics of the micropump when the diaphragm stiffness is considered or not. Comparison of the simulation results shows the stiffness of the diaphragm influences the dynamic characteristics of micropumps. It also shows that the method combining FEA software with Matlab provides a possible and effective tool to take the diaphragm stiffness into account when the pressure and flow rate characteristics of micropumps are studied.