Papers by Keyword: Negative Pressure

Abstract: This paper introduces a small negative pressure wall-climbing robot with the ARM system. It can complete the task on the surface of vertical, steep. First of all, describes the basic system structure of robot and mechanical configuration. Secondly, the mechanic analyses of robot dynamics modeling to explain the principle of its operation. Finally, an experiment tests the all common functions of the robot.

Abstract: The stability of the carbon nanotubes suspension is poor, resulting from the characteristic of insoluble in aqueous solution. Nevertheless, optical limiting devices need long-term stability. In the interest of finding effective and stable materials for optical limiting, we had tried to combine the multi-walled carbon nanotubes (CNTs) and ionic liquids surfactant (hydroxypropyl sulfo imidazoline) to obtain a new dispersion. Ultimately, we achieved non-covalent modification to carbon nanotubes. The electronic structure of the carbon nanotubes’ surface was protected integrality and the dispersion was stable and effective. It was verified by experimental observation through a field scanning electron microscopy (SEM). Finally we did a series of experiments to studied the optical limiting characteristics of the new dispersion. The results manifested that the dispersion system owned well optical limiting properties and better stability, at the same time, we also proved that the negative pressure environment could also do well to optical limiting effect.

Abstract: Since twentieth Century 40's, some foreign enterprises in developed countries began to study and produce sweeper [1-2]. Research on China's sweeping car began in twentieth Century 60 years, but until the 80 time end when china had been reforming and opening that it began to rapidly develope [3-4].But the study of mouth has the same general trend at home and abroad. Due to the different design of suction mouth, circulation type pneumatic conveying systems in general can be divided into open pneumatic conveying system using pure suction type suction mouth [5] and the use of reverse blowing type suction mouth delivery system [6]. Now most of the sweeper adopts the latter, but if the back blowing type suction mouth design improperly ,it can not achieve the ideal effect of absorbing dust, and may lead to strong fugitive dust [7-9].Today although road sweeper have been studied for decades at home and aboard, but these studies mainly is through the enterprise using engineering practice means to complete ,there are two situations occurring as follows: a number of technical on research and development need to rely on our own to explore; The engineering practice have greater demand for human, material and financial resources, and it is difficult to achieve better expected. In order to solve the problems of the above two points, according to the fluid mechanics analysis, this paper mainly research and analyze the sweeper suction mouth's flow field pickup role of entrainment process for particulate contamination by negative pressure suction, which can provide a foundation for the research and optimization of sweeper pneumatic conveying system.

Abstract: In order to meet the mass storage system’s need for higher density and integration, a novel structural design for micro flying head is conceived and an air bearing surface is designed based on micro fluid theory of hydrodynamics. Both positive and negative pressures can be generated by the air bearing surface, with the stiffness and motion stability enhanced by negative pressure. A lubrication model has been investigated with 1.5 order slip model of the generalized Reynolds equation, and the finite volume method is used for the simulation of the flying characteristics. The theoretical analysis and experimental results show that the proposed micro flying head exhibits satisfying flying stability, with head-disk spacing less than 75nm, and carrying capacity exceeding 93mN.

Abstract: Based on hydraulic model test, overflowing capacity, water flow state, flow speed distribution, pressure, fluctuating pressure, downstream erosion of flood discharging tunnel and other parameters while total opening and part opening of No. 1 flood discharging tunnel of Hekoucun Reservoir have been observed. It is indicated in experimental study, water at the contraction section at the end of the sluice chamber gets fierce fluctuation, with spray reaching the tunnel top, and results in great negative pressure on the lateral walls on both ends of the contraction section in the original design scheme. After changing the shape of the transition, flow state has been improved, negative pressure reduced, so the design is adaptable; It is recommended in the test guiding plate can be added on the both sides of the cleaning door so as to reduce water-wing height; Three medium-size piers have been compared with the better pier recommended in the test.

Abstract: Numerical simulation technology has been widely used to study the energy dissipation problem of hydroelectric engineering construction which combined flaring gate pier with stepped spillway. The main parameter of flaring gate pier is contraction ratio. This paper numerically simulated the length of aerated cavity and negative pressure of steps for stepped spillway combined with symmetrical Y-shape flaring gate pier which with the contraction ratio respectively of 0.4, 0.7 and 0.445. The RNG turbulence model ,VOF model of water vapor two-phase and iterative solution of geometry reconstruction format for unsteady flow has been applied to generate free surface. Velocity and pressure coupling method using PISO algorithm, with unsteady flow algorithm approaches stable solution of steady flow. And range from the upstream reservoir to downstream stilling basin. Comparatively analyze the experimental and simulation results of aeration cavity length, the two are basically in good agreement, and the maximum error is 10%. Therefore, the numerical simulation has a certain rationality and reliability. Simulation results show that aeration cavity length increased with the contraction ratio decreases, while the maximum negative pressure decreased, and more extensive distribution of negative pressure in stepped spillway.

Abstract: In order to study the aerated cavity length and negative pressure on stepped spillway which combined with Y-shape asymmetric flaring gate pier body type, this paper applied RNG turbulence model,VOF model of water vapor two-phase, iterative solution of geometry reconstruction format of unsteady flow to generate free surface. Numerically simulated the length of aerated cavity and negative pressure of stepped spillway which combined with asymmetrical Y-shape flaring gate pier that with the contraction ratio respectively of 598, 0.497 and 0.445, the range from the upstream reservoir to downstream stilling basin. And compared the simulation results with experimental results, found that the aerated cavity length on steps basically consistent with the measured cavity length, the maximum error is 9.7%. The simulation results shows that the aeration cavity length on steps increases with asymmetric flaring gate pier contraction ratio decreases, and the aerated cavity length of lateral side with smaller contraction angle is larger 4 to 5 times than lateral side with larger contraction angle.

Abstract: The article deals with the peculiarities of creation of effective negative pressure and the increase in the forbidden gap width in PbSe nanolayers. The dielectric state that maybe realized under these conditions and their appropriate doping can be considered as a new resource in lead selenide nanolayers. The increasing of the tangential lattice constant with higher growth temperature and layer growth rate confirms this consideration. When determining the forbidden gap width, the optical transmission spectra were processed by a model of the Fabry-Perot interferometer, and, at high concentration of free current carriers, the absorption on them and their degeneracy were taken into consideration.

Abstract: The impeller is key element that brings about negative pressure adsorption. The efficiency of the impeller will determine the adsorption capacity of robot. In this paper, physical model is built based on the theory of fluid dynamics by taking a common high speed rotation of impeller as a research object. The basic parameters and boundary conditions are set and a 3D fluid dynamic simulation is done based on FloEFD. The factors such as blade curve, rotational speed and air inlet velocity which have effect on surface flow field impeller are investigated. Then the results are shown by figures and the study analysis is carried on.

Abstract: Based on the existing triaxial seepage equipment, this paper choose the type of 2XZ-4 vacuum pump to provide negative pressure, type of CHF100A-1R5G-4 of Wei teng Ying transducer to control and make a constant negative pressure, and choose glass flowmeter to measure the flow of coal bed gas to explore the gas migration in coal reservoir during gas drainage. The triaxial seepage equipment after transformation can provide steady negative pressures on the range of-0.075MPa to-0.085MPa.The laboratory tests showed that the equipment can be used to conduct triaxial seepage experiments at different effective stress, different temperature and other conditions for negative pressure at exit.