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It has been proved that the mold filling under low pressure casting can be described by the second order nonlinear differential equations characterized by damping oscillations. To obtain higher accuracy of the velocity field, the mold filling process with damping oscillations should be considered. A computational model taking the liquid level droping in the crucible into account based on two phase flow for filling process of damping oscillations is presented in this paper. Hydraulic simulation with the particle image velocimetry was adopted to verify the numerical simulation result. It is proved that the nemuerical simulation results used the presented model perfecly match with the particle image velocimetry results. Liquid level droping in crucible is the main reason for damping oscillations in mold filling. Velocity oscilations can be eliminated when the melt flow across a sudden expansion section. The detailed flow field based on the presented model can provide guidance to optimize the process parameters.

For the aim of analyzing focusing field characteristics of radially polarized beams, a conjoint analyzing method is presented based on LabVIEW and MATLAB. The main program is programmed in the LabVIEW environment, connecting with MATLAB program through ActiveX control. Experimental results show that the strength of the radial component in the center is zero and the strength of the axial component in the center is the largest. The conjoint analysis method realized characteristic analysis of focusing field for radially polarized beams, laying the groundwork for beam transmission of the late application.

With the aim to determine parameter influences of a measurement system based on optical feedback interference in a laser diode, a mathematic model of optical feedback interference effect is built. LabVIEW which is a kind of graphical programming language is used to realize parameter setting and graphic display by front panel and program chart. Experimental results show that the stripes of optical feedback interference effect are saw-tooth-like waveform when feedback level factor is less than and close to 1, which can be used to determine moving direction of external reflecting object. Feedback interferences generate when vibration amplitude of reflecting surfaces is greater than λ/4. The stripe number is 4N when vibration amplitude dL equals Nλ. Vibrational frequency of external reflecting surface equals the frequency of feedback interference signal and has no influence on stripe number in a period. Measurement of external reflecting object based on optical feedback interference effect has measurement precision less than laser wavelength and real time direction recognition ability.

The three-dimensional (3-D) flow structures in the Taiziji Waterway of the Lower Yangtze River were simulated by a 3-D numerical model, where the river plan form is a sharp bend and island-braided. The verification results of the 3-D model indicated that the simulated results agree with the measured data. The patterns of 3-D flow structures in this sharp bend with different discharge were analyzed based on the calculated results.The simulated results demostrated that strong 3-D features of flow structures can be found in the sharp bend of Taiziji Waterway, the bottom velocity vectors point to the convex bank while the surface vectors point to the concave bank. The velocity distribution alone the lateral direction in the sharp bend depends mostly on the flow discharge. The discharge ratio of the left branch increases as flow discharge increases.

The velocity distribution and bed deformation patterns in a meandering channel with consecutive bends were investigated by using both an experimental study and a 3-D flow and sediment transport model. The simulated results from the 3-D model agree well with the experimental data. The flow structure and bed deformation patterns in channel bends with different flow conditions were analyzed. Modeled results demonstrated that the velocity distribution and bed deformation in the meandering channel depend mostly on the flow regimes. For the case of small flow discharge, the maximum velocity occurs in the vicinity of concave bank. For the case of large discharge, the maximum velocity occurs near the center part of the channel. Consequently, bed deformation patterns in meandering channels will be influenced by the flow conditions.

This paper explores a few issues in residential planning and design, probes into the scientificalness and accuracy of the design under the theoretic of sustainable development. A real example is also used to demonstrate the idea discussed in this paper.

In reality, wireless communication channels are designed to serve for multiple users while multipath propagation interference (MPI) and other problems are deteriorating the quality of service, especially when modern wireless communication demands higher data rate giving that less and less radio spectrum resources are available. Compared to conventional techniques trying to solve the related problems, smart antenna (SA) may have shed new light on the solutions of these issues. The forming of broadcast beam of SA is studied in this paper. Firstly, the mathematical formulas for the forming of directional broadcast beam by the method of baseband-amplitude-weighting are derived, according to which the corresponding circuit diagram is given. Then the forming method for broadcast beam for SA by combining several directional radio beams is presented. Moreover, the computer simulation results of SA with 6 array elements are provided to demonstrate the accuracy and achievability of this beam-forming method.

The discharge process influences the morphological evolutions of alluvial rivers, even the channel pattern evolutions. The impacts of discharge processes on morphological evolutions in an experimental channel were investigated by a 3-D mathematical model, in which turbulence flow and sediment transport as well as bank erosion were modeling. The simulated results demonstrated that the discharge process had significant effects on morphological changes. Planfrom evolution in the period with large discharge was much more notable than that with small discharge. Different discharge processes may lead to different channel patterns. A single meandering channel was formed under steady flow condition. A braided channel was observed with unsteady flow condition.

This work focuses on the investigation of the second-order statistical descriptions for full mobile wireless networks over non-isotropic Nakagami-mfading environment. The system consists of a source, a relay, and K destination users, all of which are mobile. For the full mobile system model, we first extend the Akki and Habers mobile-to-mobile (M2M) model to non-isotropic scattering fading channels by adopting the von Mises PDF for both the angle of arrival (AnOA) and the angle of departure (AnOD). With appropriate mathematical proof, we obtain the approximate solution to the correlation function of M2M Nakagami-mfading channel envelop, and the variance of the first derivative. Secondly, using the obtained correlation, we study the average outage rate (AOR) and the average outage duration (AOD) of the multi-user single relay cooperation system in detail, and obtain the closed-form analytical expressions to AOR and AOD.

We study the Nth best relay selection schemes over independent and non-identically distributed (i.ni.d) Nakagami-m fading channels. For such opportunistic relaying schemes, we first obtain the closed-form expressions to the probability density function (PDF) and cumulative distribution function (CDF) of the instantaneous end-to-end signal-to-noise ratio (SNR). Then, with the obtained CDF and PDF, three main measurements are investigated, i.e., outage probability, average symbol error ratio (SER), and ergodic capacity. The numerical results show that the simulations match derivations exactly.

The work interests in the two-way opportunistic relaying (TWOR) system in which the analog network coding (ANC) employed. For the TWOR-ANC, we first present the traditional max-min best relay selection scheme as well as the corresponding closed-form analytical expressions for the cumulative distribution function (CDF) and the probability density function (PDF) of the end-to-end SNR. Then, to simplify the analysis of system performance, by using the approximation of the modified Bessel function of the second kind, , we obtain the performance bounds of the TWOR-ANC system. The analytical results show that e-z/z determines the lower bound of system performance, and the exact solution of system performance is very close to the lower bound in low SNRs. At the same time, 1/z does the upper bound, and the exact solution is very close to the upper bound in high SNRs. Thus, in high SNRs or lower SNRs, the system performance can be measured approximately by the upper bound or lower bound.

In this article, 133 massive colliery blasting accidents were statistically analyzed in China after 2000, mainly from two aspects of the accident number and death number, three aspects such as the type of accidents, the time rule of accidents, and provincial were analyzed statistically; 72 massive colliery blasting accidents caused by blasters were analyzed statistically with regard to the unsafe act of blasters. The statistical results show that the accident and death number presents a downward opening parabolic trajectory by year; The time of the accident is more concentrated, and the fate casualties happened frequently around March, July, November and December, February is the least; Coal mine gas accident is the main type of blasting accidents, and the coal dust explosion accident causes most deaths averagely; The past statistical method seriously neglected the seriousness of blasting accidents; The coal mine underwent massive colliery blasting accidents distribute widely, but six provinces (Guizhou, Shanxi, Heilongjiang, Sichuan, Henan, Hunan, Liaoning) are the key places of blasting accidents; There are 22 species of unsafe act to blasters, the most common unsafe act is no working face environmental inspection, material and tools be used unsafely and improperly. Coal enterprises, government, and regulators should strengthen the prevention of the key time, accident style, region, and the common unsafe blasting act to the regularity of coal mine blasting accidents.

A steel-prestressed concrete composite continuous beam bridge is one of new type navigational bridge structures with economic and clear mechanic behaviors. The junction of steel and concrete beam is the critical part, which makes the two different materials to be continuous structural system and transfer different kinds of loads reasonably. This article takes the Chang Bridge which locates on G318 state road in Changxing County, Zhejiang Province as the background to analyze the characteristics of transferring bending moment in the junction by the finite element method. The results show that the junction of steel and concrete designed can transfer loads smoothly. Therefore, the junction can be further researched for extensive application.

The velocity and diameter distribution of the air-assist boom spraying is studied by a laser Phase Doppler Partic1e Analyzer when the operational parameters is changed, which including airflow velocity of air curtain and vertical relative position between the air curtain and the nozzle. From the experimental results, we find the as the air curtain velocity increases , the size distribution of the droplet is conducive to uniform . At the same air curtain velocity, droplet size decreases with increasing of nozzle pressure. On the right side of each measuring point, the number of droplets is gradual decreasing with the wind velocity increasing.When the working pressure is 0.5Mpa, the droplet size does not change with the change of the horizontal distance.

Four types of bank collapses in the middle-lower Yangtze River, that is erosion type, crash type, slippage type and flow-slide type, are pointed out, and characteristics and formation conditions of each one are analyzed. In order to provide a reference for decision-making of calamity reduction and improvement project, some preventive measures on them, including monitoring of river hydrology, morphology near bank, and hydrologicalgeology, and inspection and investigation of outward indication of bank and human activity, are presented by means of analysis on above-mentioned aspects.

The paper builds up the model for exergy analysis of vapor compression refrigeration. According to the exergy analysis, it appears exergy loss degree of the main units in the system, and points out the way of reducing exergy loss and the approach utilizing energy rationally, and proceeds with exergy loss compare with aiming at that if condenser in surplus heat recycling. Conclusion is that adopting surplus heat recycling can reduce exergy loss. Furthermore, it analyzes exergy loss to a actual refrigeration aiming at temperature regulation, and provides the theory reference for improvement and optimization of the system.

Stress corrosion test of pressure vessels and piping in H2S environment has been explored extensively, but experimental research closed to the actual stress state of pipelines and the actual operating conditions, especially considered the combined effect of various factors is not common. Stress corrosion test simulated the actual operating conditions is taken in this paper. Four in-service pipes are researched as specimens and complex stress field is built by a specially designed loading device. Specimens are immersed in three different H2S concentration environments. The appearance and expansion of crack is observed regularly and the sensitivity of pipeline on stress corrosion is evaluated by metallographic examination. The result shows that: Intergranular corrosion, transgranular corrosion or micro-crack is not found in H2S corrosive solution (500×10-6, 800×10-6mg/L) after 2160 hours or in saturated H2S corrosive solution (greater than 2000×10-6mg/L) after 360 hours. A surface crack is found in H2S corrosive solution (500×10-6mg/L) after 720 hours and the expression for expansion rate of the crack during 2160 hours is a=16.835e0.0002h.