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    31 January 2017, Volume 51 Issue 1 Previous Issue    Next Issue
    Numerical Method of Detection Efficiency for adioactive Waste Drum Detections Detections
    2017, 51 (1):  1. 
    Abstract ( 971 )   Save

    bstract: In order to calibrate detection efficiency fast and accurately, a realtime numerical method was proposed for measuring radiation of low and medium radioactive waste based on the spatial distribution of detect objects, collimator, and taking the HPGe detector as an example. This method can calculate detection efficiency of point source with different locations and energies, and the relative deviations are less than 5% by comparing with the results of Monte Carlo calculation. The γray detection system was used to measure waste drum samples of wood and polyurethane with 137Cs and 60Co nuclides, and the relative errors between numerical calculation and experimental measurement were within 12%, and most of them were less than 5%. Thus, this numerical calculation method can be used as an accurate and quick calibration of detection efficiency for radioactive waste drum detection.

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    Regeneration Period Control in NOx Storage/Reduction Reaction
    ZOU Shan,LIN Da,WEN Yalin,ZHANG Wugao
    2017, 51 (1):  6. 
    Abstract ( 942 )   Save

    Abstract: Comprehensive NOx storage/reduction (NSR) experiments were conducted in a quartz flow reactor to investigate the influence of regeneration period, temperature and volume fraction of reductant on NSR performance of Pt/Ba/Ce/γAl2O3 when H2 was used as a reducing agent. It is found that the highest conversion ratio in the optimum regeneration time can be obtained, and it is dependent on the temperature and the volume fraction of the reducing agent. As the temperature increases,  the optimum regeneration time increases. As the volume fraction of the reducing agent increases, the optimum regeneration time decreases.

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    ThreeDimensional Numerical Study of Natural Convection of Supercritical Binary Fluid
    LI Tian1,ZHANG Peng1,LONG Zhiqiang1,SHEN Biao1,2
    2017, 51 (1):  12. 
    Abstract ( 701 )   Save

    Abstract: This paper numerically investigated the natural convection of supercritical nitrogen/argon (n(N2)∶n(Ar)=0.9∶0.1,  n is amount of substance) binary fluid in a 3dimensional rectangular cavity. The results showed that a stable thermal boundary layer forms at the bottom of the cavity during the initial heating phase, and the Piston effect plays a dominant role to accelerate the energy transport in this period. After the thermal plume breaks the boundary layer and moves upward, the natural convection occurs with the appearance of a cold boundary layer near the top. The Soret effect caused by the temperature gradient drives the component migration, and results in the Dufour effect which promotes the energy transport. This results indicate that the Soret effect and Dufour effect can promote the heat and mass transfer in the natural convection of supercritical binary fluids.

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    A Numerical Study of Turbulent Flow and Heat Transfer of Dimples at Different Depths
    YANG Yun,RAO Yu
    2017, 51 (1):  18. 
    Abstract ( 808 )   Save

    Abstract: Based on numerical simulations, the friction factors and heat transfer coefficients of four dimples with different depths were obtained by using the standard kω turbulence model, and the relations for the heat transfer and friction factors were also presented when the Reynolds number (Re) varies from 8 500 to 60 000. The results showed that the average heat transfer coefficient and the friction factor gradually increase with the increasing of the depth. They also increase as the Reynolds number increases. In the case of Re=8 500 and  σ=0.1 or 0.3 (σ: the ratio of depth to face diameter), the average heat transfer coefficient and the friction factor are almost invariant, the average heat transfer coefficient increases 40% to flat plate channel. Compared with the depth of σ=0.1, a dimple depth of σ=0.3 achieves a heat transfer enhancement of more than 11% at the Reynolds number of 50 500. Compared to the flat plate channel, the average heat transfer performances of the dimpled channels increase by about 42.1% and 51.6%, friction factors increase 30% and 120%, respectively; and also the overall heat transfer coefficients increase by 10% to 35%; the heat transfer coefficient decreases as the increase of the depth. The distribution of local Nusselt number in the flow direction of shallow dimpled channel at a dimple depth of σ=0.1 and σ=0.2 is symmetric. However, it becomes asymmetric in deep dimpled channel at a dimple depth of σ=0.26 and σ=0.3. The reason may be the different vortex structures in shallow dimples and deep dimples.

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    Aerodynamic Performance Analysis of Organic Working Fluid Turbine for Recycling of Waste Heat Produced by Chemical Distillation Process
    BO Zemin,ZHANG Qianqian,SANG Zhenkun,WENG Yiwu
    2017, 51 (1):  26. 
    Abstract ( 714 )   Save

    Abstract: For recycling the waste heat (121—146 ℃) produced by the chemical distillation process, a 150 kW organic working fluid radial turbine was designed by using R600a. Based on the preliminary structural parameters and performance parameters of the organic working fluid radial turbine by 1dimensional aerodynamic calculation, a computational fluid dynamics (CFD) numerical simulation of the organic working fluid radial turbine was conducted to investigate the overall performance and the flow field characteristics at design condition. The results indicated that under the conditions of a turbine inlet temperature of 110 ℃ and a turbine inlet pressure of 1.6 MPa, the organic working fluid radial turbine can produce an output power of 150.5 kW with a mass flow rate of 4.17 kg/s, a pressure ratio of 3.2 and an efficiency of 82.7%. The working fluid flows smoothly with a high efficiency at the design condition to meet the requirements of the organic working fluid expander of the power system.This paper can provide basic data for the organic working fluid radial turbine design by utilizing the waste heat from the chemical distillation process.

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    Effect of PODE on Combustion and Emission Characteristics of a TurboCharged Intercooled Diesel Engine
    ZHU Yijia,LIN Da,WEI Xiaodong,ZHANG Wugao
    2017, 51 (1):  33. 
    Abstract ( 783 )   Save

    Abstract: The effect of polyoxymethylene dimethyl ethers (PODE) on the combustion, emission performance and fuel economy of a turbocharged intercooled commonrail diesel engine was investigated, in the cases of pure diesel and diesel blended with 10%, 20%, 30% PODE respectively. The results showed that the added PODE affects the engine combustion characteristic significantly.  Except for the lowspeed and lightduty engine mode, the blend of PODE decreases the heat release rate of the preinjection fuel, improves the atomozation performance of the main injection fuel, increases the active ingredients in combustion chamber before the main fuel injection, increases the pressure rising rate and heat release rate as well as the incylinder mean temperature in the main fuel injection period, and shortens the combustion duration. Under test conditions, with the increasing of blended PODE ratio, the incylinder maxium temperature and the fuel combustion speed of the main injection fuel increases while the combustion duration decreases. The emission investigation showed that with the mixtured PODE, the NOx emission increases, the HC emission decreases slightly but the CO emission remains unchanged. The fuel economy is improved by adding PODE.

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    An Experimental Study of Turbulent Flow and Heat Transfer in a Cooling Channel with Small V RibDimple Compound Structure
    XING Jianfeng1,RAO Yu1,LI Bo2,RAO Kun3
    2017, 51 (1):  40. 
    Abstract ( 600 )   Save

    Abstract: A structured surface with smallsized V ribs and dimples is a potentially highperformance cooling structure used for gas turbine blades. A comparative transient liquid crystal (TLC) transient experimental study was conducted to obtain the highresolution heat transfer characteristics and pressure loss in the cooling channels with different heights of Vshaped ribdimple in the Reynolds number range of 10 000 to 60 000. The results indicated that, under the condition of fully developed turbulent flow, the Nusselt number of the Vshaped ribdimple is 1.98 to 2.46 times of that  of the smooth flat, with a friction factor of 2.24 to 4.36 times of that of the smooth flat. The Nusselt number of the Vshaped ribdimple is 1.21 to 1.76 times of that of circular dimples, with a friction factor of 1.96 to 3.89 times of that of circular dimples. Both the depth and Reynolds number of Vshaped rib can influence the flow field structure. The overall thermal performance factor of the Vshaped ribdimple with a depth of 0.6 and 1.0 mm is 4.7% to 12.8% higher than with a depth of 1.5 mm at a low Reynolds number (Re<20 000). With a continuous increase of  the Reynolds number, the overall thermal performance of Vshaped ribdimple with a depth of 0.6 and 1.0 mm depth gradually decreases, but the overall thermal performance of Vshaped ribdimple with a depth of 1.5 mm gradually increases, and is 4.7% to 8.3% higher than that with the depths  of 0.6 and 1.0 mm.

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    Revised Formula for Friction Factor Affected by Tangential Flow in an Annular Channel
    ZHANG Leihuaa,YAO Zhenqianga,b,SHEN Honga,b,CHENG Dea,XUE Yaboa
    2017, 51 (1):  46. 
    Abstract ( 845 )   Save

    Abstract: This paper aimed to find out the law of friction factor relative to the parameter of rotor rotating in the annular channel between the rotor and the stator of the canned pump. The distributions of pressure drop at different rotor speeds were measured by a scale test rig. The experimental results indicated that with the rotational speed increasing, the pressure drop between the inlet and the outlet also increases, and the original empirical formula of friction factor in an annulus channel is no longer suitable and should be revised. The function relationship between the revision factor and ratio of tangential/axial Reynold numbers was obtained by using data analysis. Thus, the revised formula of friction factor affected by tangential flow was derived. In order to verify the accuracy and universality of this formula, the flow characteristics and pressure drop of the fluid in the scale test rig and in the canned pump were studied by using the  computational fluid dynamics (CFD) method. The results showed that the bias of the friction factor calculated by simulation and the revised formula is small enough to be considered in a reasonable range.

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    Coupling Motion Hydrodynamic Analysis of Horizontal Axis Tidal Turbine
    WANG Shuqi1,MA Weijia2,XU Gang1,ZHANG Liang2
    2017, 51 (1):  51. 
    Abstract ( 766 )   Save

    Abstract: Under the condition of actual sea state, the hydrodynamic characteristic of floating horizontal axis turbine is related to wave characteristics and floating carrier wave motion response. Slipping mesh is used in this study to analyze the hydrodynamic characteristic in uniform stream when the turbine is forced to produce roll and pitch coupling movement. Results show that the turbine axial load and energy utilization ratio fluctuates, and the calculation results in coupling motion and in pitching motion only are basically identical. The fluctuation amplitude of calculated rolling torque in coupling motion is bigger than that in rolling motion only. The difference of pitching torque between coupling motion and pitching motion only is highly dependent on the rolling frequency. Results of this study can provide reference for the study of motion response of floating carrier for floating tidal current turbine system. Structural design of turbine and control of the electric output.

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    A Method for Transform of Pressure Signal from Time Domain to Angle Domain Based on Internal Clock Sampling
    JI Shaobo,ZHAO Shengjin,CHENG Yong,WANG Yang,ZHAO Xiuliang,LI Xinhai
    2017, 51 (1):  57. 
    Abstract ( 718 )   Save

    Abstract: A novel method for measurement of incylinder pressure signal is proposed in this paper. There is no  need to install angle encoder at the free end of the engine but to install pulse sensors at flywheel end to obtain wheel gear signal. The cylinder pressure and wheel gear signal are sampled using the high speed internal clock data acquisition card. The zero crossing points of wheel gear signal are calculated using the Newton interpolation algorithm. Based on the assumption that the instantaneous speed of engine is unchangeable during adjacent gears, the cylinder pressure measured in the timedomain is converted to the angledomain using the interpolation algorithm. The method is verified by an experiment, and results show that the method is reliable and able to fulfill the requirement of combustion analysis.

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    Zero Wear of Internal Combustion Engine Sliding Bearing Based on Mixed Thermo-Elastohydrodynamic Lubrication
    LIU Xiaori1,2,LI Ming1,ZHANG Tiechen1,ZHENG Qingping1,LI Su1,LI Guoxiang2
    2017, 51 (1):  62. 
    Abstract ( 700 )   Save

    Abstract: A zero wear model was established for the design of internal combustion engine sliding bearing, with the consideration of the lubrication model, the asperity contact model, the multibody dynamics model and the zero wear experiment criterion. The safety factor for zero wear was calculated to predict the reliability of wear. The zero wear model was applied to the main bearing design for a sixcylinder diesel engine. The results show that the distribution of zero wear safety factor can be predicted by using this method. This paper can provide theoretical guidance for zero wear design of bearing.

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    Effects of Fuel Properties and Operation Parameters on Particle Emission of Gasoline Direct Injection Engine
    ZHU Xiaohui1,CHEN Peng1,FANG Junhua2
    2017, 51 (1):  69. 
    Abstract ( 653 )   Save

    Abstract: This paper aimed to investigate the impact of fuel properties(T90 temperature and ethanol blended), engine operating parameters (load condition, spark timing etc.), and injection strategies (start of injection, split injection) on particulate size distribution and particle number. The experimental results show that T90 temperature has a significant influence on PM emission, and a low T90 temperature reduces PM emission. Particle number reaches the highest concentration at midload condition and decreases at highload because of oxidation in the high temperature exhaust and high rail pressure. E10 produces lower PM emissions. In general, advance injection timing affects fuel evaporating and mixing process and reduces PM emissions. Split injection  also reduces PM emissions and can be optimized to a lower level. As the  ignition timing is delayed, the formation of particles significantly is decelerated.

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    A Bayesian Classification Policy for Highly Reliable Products Based on Degradation Data
    CHEN Zhen,PAN Ershun
    2017, 51 (1):  76. 
    Abstract ( 613 )   Save

    Abstract: A Bayesian classification method based on degradation data of highly reliable products was proposed. The products were classified according to the maximum posterior probability. Then, the nonlinear Wiener process model was used to describe the degradation paths of the products. Next,  an algorithm which combined the expectation maximization (EM) method with Kmeans clustering was developed to estimate the unknown parameters of the model. After that, an average cost model was established to make the optimal classification policies. Finally, an example and a simulation were presented to illustrate the effectiveness of the proposed method.

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    Modeling of and Algorithm for Resource Constrained Project Scheduling Problem with Resource  Allocation Dependent Processing Time
    LIU Xinyi,LU Zhiqiang
    2017, 51 (1):  82. 
    Abstract ( 898 )   Save

    Abstract: In classical resourceconstrained project scheduling problems, the job processing times are assumed to be constant parameters. However, in many practical cases, the processing times depend on the resource allocated to the job. In this paper, the resourceconstrained project scheduling problem was introduced with resource allocation dependent processing time to minimize the duration of the project. A model was established and a genetic algorithm was proposed to solve the problem. To improve the ability of the algorithm, a 1opt based local search scheme and a 2opt based local search scheme were introduced.The related properties between different job combinations and the objective of the problem were summarized and proved. Based on these properties, the approach  for selecting effective job combinations was established, which greatly improved the efficiency of the algorithm in local search. Comparative computational results reveal that the algorithm proposed in this paper can solve the problem effectively.

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    Accurate Localization of 2D Barcode Marked in Mental Parts Under Complex Background Based on Edge and LevelSet
    GUO Gaifang,HE Weiping,LI Xiashuang,WANG Jian,WU Zhenfang
    2017, 51 (1):  90. 
    Abstract ( 917 )   Save

    Abstract: Aimed at the difficult location issue of twodimensional barcode marked in metal parts resulted from complex background and uneven illumination etc., this paper proposed an accurate localization method of 2D barcode marked in mental parts under complex background based on edge and levelset. First, the “L” edges of 2D barcode was located by line detection. Next, an improved levelset image segmentation was proposed to segment the probable barcode area, while the contour feature, gray and gradient histogram doublet features were used to judge if the probable barcode area had barcode or not. Finally, the 2D barcode area was accuratly located using Hough transform. The experimental result shows that the accuracy of the proposed method can reach up to 95%, and the processing time is less than 1 s, indicating that the proposed method is promising.

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    An Artificial Immune Network Classification Algorithm Based on VirtualForce Direction and Cell Differentiation
    YANG Bin,LU Yuliang,YANG Guozheng,ZHU Kailong
    2017, 51 (1):  98. 
    Abstract ( 830 )   Save

    Abstract: Aimed at the lack of effective methods to guide the evolution of antibodies in the traditional immune network classification algorithm, a virtual force and cell differentiation based artificial immune network classification algorithm (VCAINC) was proposed.The algorithm introduced the definition of virtual force zone to guide the  evolution of antibodies.Then, the moving convergence condition was introduced to determine the most suitable position of antibodies.For the antibodies which cannot satisfy the moving convergence condition, the strategy of cell differentiation was utilized to optimize the classifier. Finally, the performance of classification on UCI dataset was analyzed.The experimental results show that the VCAINC can effectively guide the evolution of antibodies and improve classification performance significantly.

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    Adaptive Energy Saving Mechanism with Delay Aware in Hybrid OpticalWireless Broadband Access Networks
    WANG Ruyan1, 2,ZHOU Chao3,WU Dapeng1, 2,XIE Yi4,XIANG Luoyong4
    2017, 51 (1):  105. 
    Abstract ( 764 )   Save

    Abstract: Gateway utilization is low in hybrid opticalwireless broadband access networks. Therefore, the energy efficiency can be effectively enhanced by employing the gateway sleep scheduling mechanism at the expense of increasing the system delay. In this paper, a novel adaptive energy saving mechanism with delay aware in hybrid opticalwireless broadband access networks was proposed based on the delay tolerance feature of data. In order to fully exploit the delay tolerance feature of data, and to adaptively determine the sleeping interval according to arrival rate, the queuing theory model was introduced to analyse the energy consumption and the data gateway latency. Meanwhile, to achieve the energy efficiency, the path reconstruction delay and congestion rate were dramatically reduced by the proposed multigateway loadbalance mechanism. The results show that the proposed mechanism can reduce the total energy consumption of gateways by 36%. Besides, the utilization rate of the gateway is effectively improved and the path delay is reduced.

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    Cohesive Zone Modeling for Model III Crack Based on Near Tip Stress Field
    DUAN Hongyan,WANG Zhiming,SANG Yuancheng
    2017, 51 (1):  113. 
    Abstract ( 1055 )   Save

    Abstract: A cohesive zone model for model III crack in powerlaw hardening was studied under small scale yielding conditions. The cohesive tractionseparation displacement in the cohesive zone and the stressstrain fields were obtained. The results show that the stress distribution in a large portion of the plastic zone is significantly altered with the introduction of the cohesive zone, for a modest hardening material, if the peak cohesive traction is less than 2.5 times yield stress, which implies that the disparity in terms of the fracture prediction between the classical approach of elasticplastic fracture mechanics and the cohesive traction becomes infinitely large. When the peak cohesive traction becomes infinitely large, the stress distribution with and without the cohesive zone converges.

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    Effects of Compressive Mode on Macroscopic Deformation and Microstructure Evolution of Magnesium Alloy
    JIN Zhaoyang1,LI Nannan1,LI Keyan1,YAN Kai1,CUI Zhenshan2
    2017, 51 (1):  119. 
    Abstract ( 760 )   Save

    Abstract: A microstructural evolution model was integrated with a thermalmechanical elasticplastic finite element method to quantitatively simulate the hot deformation and microstructural evolution of magnesium alloy AZ31B at two different compressive modes, constant strain rate and constant die velocity. The stressstrain curves and recrystallized grain sizes were obtained from hot compressive deformation of AZ31B on Gleeble1500 thermosimulation machine and integrated with the finite element model through the user subroutine interface. It is shown that the fields of deformation and microstructure are nonuniformly distributed as a result of the existence of friction. Compared with the sample compressed at a constant strain rate, the mean value of the grain size decreases and the mean square error increases slightly for the sample at a constant die velocity.

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    High Precision Measurement of Specific Heat Using Dual Heating and Cooling
    TAO Shengjie,YANG Zhengwei,TIAN Gan,ZHANG Wei
    2017, 51 (1):  124. 
    Abstract ( 632 )   Save

    Abstract: A dual heating and cooling method was proposed to precisely measure specific heat in this paper. The apparatus with no load and with the measured object was heated and cooled respectively. The temperature sequences during the four courses were processed to calculate the specific heat. The proposed method can eliminate the influence of heat dissipation on measurement and significantly improve the precision. A measurement experiment was conducted on a bit of water as specimen. The measurement error is less than 1% under normal heat dissipation condition, which validates the effectiveness of the method. The proposed method is suitable for measuring the specific heat of a small sample within certain error limit. It can be operated conveniently on simplified apparatus and realize the specific heat measurement with higher precision in a wider region cooperating with other methods.

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