An exotensioned composite structure is developed as a light-weight and low-cost load carrying members for structural applications. The beam body, consisting of carbon-fiber composite skeletons with insertions of high-tension fiber strands, is externally weaved to provide extra structural integrity. Monotonic and cyclic flexural loading experiments are performed in this study to quantify the basic mechanical response of the structure. The bending strength, ductility, and fatigue resistance are specifically assessed.

In this paper, a resonator is modeled as a microbeam under the effect of thermoelastic damping and actuated electrically. Two models, small and large deformation models, are represented by considering linear and nonlinear Euler-Bernoulli beam theory. These models are compared against voltage, and the difference between these models is shown and discussed. In the large deformation model, the microbeam deflected due to applied DC voltage, and vibration of microbeam occurs around this static deflection. The vibration equation is linearized around static deflection and by applying harmonic vibration, equation for mode shape and frequency is obtained. The complex frequency is calculated by numerical method and then used for obtaining the Q-factor of thermoelastic damping. The stretching effect and thermoelastic damping is validated with the literature. The result shows that for the high values of voltage, the large deformation model is more accurate. The behavior of thermoelastic damping is also investigated against the geometrical and material properties.

This paper shows that the mobilized shear strength of a two-dimensional (2-D) spatially variable saturated undrained clay is closely related to the extreme value of a one-dimensional (1-D) continuous stationary stochastic process. This 1-D stochastic process is the integration of the 2-D spatially variable shear strength along potential slip curves. Based on this finding, a probability distribution model for the mobilized shear strength of the 2-D clay is developed based on a probability distribution model for the extreme value of the 1-D stochastic process. The latter (the model for the 1-D extreme value) has analytical expressions. With the proposed probability distribution model, the mobilized shear strength of a 2-D clay can be simulated without the costly random field finite element analyses.

First-principles calculations were employed to investigate the adsorption-induced surface stress of self-assembled alkanethiolate monolayers on a Au(111) surface as a function of the alkyl chain length. A recently developed fully nonlocal van der Waals density functional was used to accurately account for the chain-chain interactions. We found that surface charge redistribution produces compressive surface stress, while chain-chain interactions produce tensile surface stress. The stress induced by surface charge redistribution is about one order of magnitude greater than that of chain-chain interactions. We observed that the chain-chain interactions play an important role in determining the molecular configuration during adsorptions, and also contribute significantly to the induced anisotropic tensile (positive) surface stress. As the chain length increases the tensile stress increases at a rate of ∼ 0.32 (∼ 0.18) N/m for the direction perpendicular (parallel) to the chain tilt direction.

This research experimentally investigated effects of injection pressure, formation chamber and bypass flow on spray performances and cryogenic characteristics of CO2 snow under cryosurgery guided by endoscopic. Results show that CO2 snow has a superior freezing capability in the application of cryosurgery. The length of formation chamber is an effective design parameter to control spray performances and cryogenic characteristics. Increase in the length of formation chamber can increase snow size and conversion ratio, as well as the cooling rate and impact area of the tissue. Thus, it is suitable for the application on wider range nidus. Moreover, the bypass flow can efficiently modulate the cooling effect of the main flow with CO2 snow particles, and extend the operation time of cryosurgery. The experimental results also show that decrease the cylinder pressure, decrease the length of formation chamber, and increase the diameter of bypass apertures can slow down the flying velocity of CO2 snow which are effective methods to control the jet velocity and prevent the risk of penetration.

To improve the urine distributing mechanism of bladder power pump, a novel urethra valve was proposed in this study. The urine-flow-rate performance equation of the valve was derived on the basis of hydromechanics and electromagnetic theories, and the effect of different parameters on the urine-flow-rate performance was analyzed. The reliability simulation model of the valve was established according to the working principle and fault tree of the valve, a reliability simulation algorithm was proposed based on the basic idea of Monte Carlo method, and some reliability indexes were gained. The results show that increasing electromagnet current and decreasing air gap can increase the maximal urine-flow-rate, the reliability of the valve reaches 0.73 when the average life of the valve is 50000 times, and the shedding and aging of elastic bands are the weak links of the valve. The conclusions can provide the basis for the structural optimization and reliability improvement of bladder power pump, as well as the guidance for the design of implantable biomedicine electromechanical device.

The effects of variable viscosity and thermal conductivity on the natural convection heat transfer over a vertical plate embedded in a porous medium saturated by a nanofluid are investigated. In the nanofluid model, a gradient of nanoparticles concentration because of Brownian motion and thermophoresis forces is taken into account. The nanofluid viscosity and the thermal conductivity are assumed as a function of local nanoparticles volume fraction. The appropriate similarity variables are used to convert the governing partial differential equations into a set of highly coupled nonlinear ordinary differential equations, and then, they numerically solved using the Runge-Kutta-Fehlberg method. The practical range of non- dimensional parameters is discussed. The results show that the range of Lewis number as well as Brownian motion and thermophoresis parameters which were used in previous studies should be reconsidered. The effect of non-dimensional parameters on the boundary layer is examined. The results show that the reduced Nusselt number would increase with increase of viscosity parameter and would decrease with increase of thermal conductivity parameter.

The unsteady MHD free convection and mass transfer boundary layer flow of an incompressible electrically conducting fluid past an accelerated infinite vertical flat plate embedded in porous medium with ramped wall temperature is considered here. It is assumed that the plate accelerates in its own plane in the presence of thermal radiation incorporating first order chemical reaction. The governing equations are solved analytically using the Laplace transformation technique. The flow phenomenon has been characterized with the help of flow parameters such as permeability parameter, Hartmann number, phenomenon has been characterized with the help of flow parameters such as permeability parameter, Hartmann number, thermal radiation parameter etc. The influences of these parameters on the velocity, temperature field and concentration distribution have been studied and the results are presented graphically and discussed quantitatively. Also, the effects of the various parameters on the skin friction coefficient, the rate of heat and mass transfer at the surface are discussed.

In this paper, mixed convection stagnation point flow of nanofluids over a stretching/shrinking surface is studied numerically in the presence of thermal radiation and viscous dissipation. The governing boundary layer equations are transformed into a system of nonlinear ordinary differential equations, by using a similarity transformation, which are then solved numerically using a fifth-order Runge-Kutta-Fehlberg method with shooting technique. The effects of various physical parameters are analyzed and discussed. Computed results are presented in graphical and tabular forms. It is found that the Richardson number, thermal radiation and internal heat generation/absorption have interesting and significant effects on skin-friction and local Nusselt number for all the three types of nanofluids.

In the present study, the instability of laminar flow of two immiscible fluids is investigated. The theory of energy gradient is employed for the analysis. The distributions of energy gradient for various viscosity ratios, i.e., ratios of lower viscosity to higher one, are obtained and the results for the onset of instability are compared with the available experimental data. The comparison of the results shows excellent agreement with the existing experimental data. It will be also demonstrated that as the viscosity ratio decreases the flow becomes more stable even at high Reynolds numbers.

This paper deals with tip leakage flow structure in subsonic axial compressor rotor blades row under different operating conditions. Analyses are based on flow simulation utilizing computational fluid dynamic technique. Three different circumstances at near stall condition are considered in this respect. Tip leakage flow frequency spectrum was studied through surveying instantaneous static pressure signals imposed on blades surfaces. Results at the highest flow rate, close to the stall condition, showed that the tip vortex flow fluctuates with a frequency close to the blade passing frequency. In addition, pressure signals remained unchanged with time. Moreover, equal pressure fluctuations at different passages guaranteed no peripheral disturbances. Tip leakage flow frequency decreased with reduction of the mass flow rate and its structure was changing with time. Spillage of the tip leakage flow from the blade leading edge occurred without any backflow in the trailing edge region. Consequently, various flow structures were observed within every passage between two adjacent blades. Further decrease in the mass flow rate provided conditions where the spilled flow ahead of the blade leading edge together with trailing edge backflow caused spike stall to occur. This latter phenomenon was accompanied by lower frequencies and higher amplitudes of the pressure signals. Further revolution of the rotor blade row caused the spike stall to eventuate to larger stall cells, which may be led to fully developed rotating stall.

Even though the universal gravity force has been formulated and used for more than three hundred years, the cause of the universal gravity force has not been fully understood. This paper proposes a substantial aether model to derive universal gravity force based on Newton's laws of motion and Bernoulli's equation. The authors suggest that every aether particle has a mass and occupies a volume in space. Every aether particle has translational movement and particle spin movement. The particle spin movement does not produce the universal gravity force. The translational movement is similar to the gas particle moving in the air and produces aether pressure. The difference of aether pressure generates an aether flow velocity. The difference of aether flow velocities creates a pressure difference according to Bernoulli's equation. The summation of aether pressure difference around an object is shown to be the universal gravity force. A detailed derivation of universal gravity force from the proposed substantial aether model is presented in this paper to show the validation of this model.