He Ming Cheng

Multi-Objective Optimization Design of Multi-Layer Rectangle Micro-Channel Heat Sink for Single-Phase Flow and Heat Transfer

The purpose of this paper is to optimize the structural sizes of multi-layer rectangle micro-channel heat sink, which has been widely used to cool electronic chip for its high heat transfer coefficient and compact structure. Taking the thermal resistance and the pressure drop as goal functions, a binary-objective optimization model was proposed for the multi-layer rectangle micro-channel heat sink based on Sequential Quadratic Programming (SQP) method. The number of optimized micro-channel in width n1 and that in height n2 are 21 and 7, the width of optimized micro-channel Wc and fin Wf are 340 and 130μm, the height of optimized micro-channel Hc is 415μm, and the corresponding total thermal resistance of the whole micro-channel heat sink is 1.3354 °C/W. The corresponding pressure drop is about 1.3377 Pa. When the velocity of liquid is larger than 0.3 m/s, the effect of change of velocity of liquid on the thermal resistance and pressure drop can be neglected.

Carbonation Depth of Recycled Aggregate Concrete Incorporating Fly Ash

This paper addresses the efficiency of using recycled concrete as an aggregate by systematically presenting results on the influence of fly ash on recycled aggregate concrete (RAC) properties. The percentage of recycled aggregate replacements of natural aggregate used by weight was 50%. Fly ash (FA) was used as 0, 10, 20, 30, and 40% by weight replacement of cement. The results showed that an increase in the W/B decreased the resistance to carbonation depth. Nevertheless, the use of FA as a substitute for cement decreased the carbonation depth of the recycled aggregate concrete. Being analyzed on the basis of Gray Theory, it can be seen that the biggest influence on the depth of carbonation of the recycled aggregate concrete comes from W/B, then the carbonation age and FA content affects the least.

Experiment Research on Activated Cement

Activated cement with the characters of low water demand and high activity was made with Portland cement clinker and dehydrate-gypsum and liquid superplasticizer which were used as grinding additive in the grinding process. Three states of grinding effect exist with correspondence of different dosages of super-plasticizer: the optimal grinding aid dosage, the critical dosage, and the supercritical dosage. First, under the condition of the optimal grinding effect, the activated cement had the maximum strength with little dosage of super-plasticizer and small effect on the performance of activated cement; second, within the critical dosage, the strength of activated cement was similar to the common cement, more super-plasticizer were held and the performance of cement was obviously improved; third, within the supercritical dosage, the strength of activated cement was reduced, but it can accommodate much super-plasticizer, and had a remarkable influence on the performance of cement. The experiment also shows that different properties of low water demand activated cement can be made with admixture of different concentrations of super-plasticizer. Within the allowed limit, use more admixtures was in compile with green environmental protection concept, improve the durability of concrete, and resolve the problem of compatibility between common cement and super-plasticizer, and offered technical support in the produce of commercial concrete by directly use of Portland cement clinker.

Truss Optimization Based on the Evolutionary Structural Optimization

The Evolutionary Structural Optimization (ESO) as an important structural topology optimization method has been widely used in many fields of engineering optimization. However, due to some technical constraints, the use of ESO for the truss optimization is relatively less. A method for truss optimization that combines the ESO method and the Stress Ratio method is proposed in this paper. This method solves the problems of ESO for truss optimization that the sectional area of bars cannot be changed and the speed of optimization cannot be easily controlled. It can be widely used in truss optimization and can get the same good result as other methods (such as GA and SA, etc.). Furthermore, the method proposed in this paper has the advantage that it can be easily programmed in the commercial software (such as Ansys and Abaqus, etc.) owing to its relatively simple optimization principle.

Probability Distribution of Flexural Fatigue Life for Glass Fiber Reinforced Concrete

Through the fatigue experiments of glass fiber reinforced concrete (GFRC) specimens with 0%0.6%0.8% and 1% glass fiber volume fraction, the fatigue-lives of GFRC at various stress levels were obtained. The results indicate that the statistical distribution of fatigue-life of GFRC is in agreement with the two-parameter Weibull distribution. According to the statistical analysis of fatigue-life,the study shows the fatigue life of GFRC follows both the two-parameter Weibull distribution and three-parameter Weibull distribution, but three-parameter Weibull distribution is more suitable for expressing the law. Besides, the S-N curves and P-S-N curves which can be used to determine the life of GFRC under constant amplitude fatigue load were obtained.The results indicate that GFRC has distinguished anti-fatigue property.

Numerical Simulation of Multi-Layer Rectangle Micro-Channel Heat Sink for Single-Phase Flow and Heat Transfer

The single-phase flow and heat transfer for multi-layer rectangle micro-channel heat sink are numerically simulated. During the simulation, Finite Volume Method (FVM) was used to solve Computational Fluid Dynamics (CFD) problem. First order upwind scheme was used to discrete control equations, and semi-implicit method for pressure-linked equations was used to solve discretization equations. The maximum temperature difference is 76.2362 °C, and the total thermal resistance is 0.4765 °C/W, which agrees well with the result of analysis result 0.5145 °C/W. The corresponding pressure drop is about 54.1360 N/m2.

The Numerical Analysis of Ultimate Efficiency for Vertically Loaded Anchors

The purpose of this article is to deepen the understanding and knowing for the limited efficiency of bearing of plate anchors by means of the calculation of the ultimate holding capacity (UPC) of plate anchors with different shapes. In the process of calculation of UPC, the commercial software MARC is employed. The soil is assumed to be elastic-perfect plastic with yield determined by the VON MISES condition. And displacement constraints are imposed and the corresponding ultimate anti-force can be determined. Then the ultimate bearing efficiency of anchor plates with different shapes can be obtained.

Optimization Design the Configuration Sizes of Multi-Layer Rectangle Micro-Channel Heat Sink

The configuration sizes of multi-layer rectangle micro-channel heat sink are optimized, which has been widely used to cool electronic chip for its high heat transfer coefficient and compact structure. Taking the thermal resistance and the pressure drop as goal functions, a binary-objective optimization model was proposed for the multi-layer rectangle micro-channel heat sink based on Sequential Quadratic Programming (SQP) method. The number of optimized micro-channel in width n1 and that in height n2 are 24 and 3, the width of optimized micro-channel Wc and fin Wf are 360 and 55μm, the height of optimized micro-channel Hc is 1000μm, and the corresponding total thermal resistance of the whole micro-channel heat sink is 1.5429 °C/W. The corresponding pressure drop is about 2.3454 Pa. When the velocity of liquid is larger than 0.3 m/s, the effect of change of velocity of liquid on the thermal resistance and pressure drop can be neglected.

Developed New Type of Pneumatic Spray Nozzle and Research of Spray Characteristic

The Pneumatic atomizing nozzle is quenching test professional nozzle which is designed for new quenching process taking high-pressure nitrogen gas water as quenching medium. It meets the requirements of high pressure nitrogen quenching process and reaches the requirements that particle size can be adjusted, flow spray field coverage angle is large, flow and pressure are adjustable and the amplitude of accommodation is big. The nozzle special for high-pressure gas quenching test is less and it can only be chose from other functional nozzles, having great limitations. The development of nozzle special for high-pressure gas quenching will have a certain role in promoting the popularization of high-pressure gas quenching technology and the development of nozzle technology.

Numerical Simulation of Pressure Difference about Curve Ball in Flight

Life lies in movement, Football is now the most popular sport in the world. Fluent12.1 software is employed in this thesis to model the numerical simulation of the pressure which the ball with different angular velocity and different velocity bears. Simulation results show that the pressure difference on the surface of the ball with a certain speed will increase if the angular velocity increases. The pressure difference on the surface of the ball with a certain angular velocity will increase if the velocity increases. The radian of ball will become more bigger.