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   Science & Technology Review
2013, Vol.31, No. 24
28 August 2013

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Science & Technology Review. 2013, 31 (24): 3-3. ;  doi:
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Thermodynamic Analysis of the Efficiency Improvement of a Photovoltaic-thermoelectric Hybrid System

ZHANG Yufeng;LIN Weiqing;PAN Huaqing;SUN Zhenning;LIU Xiangxin;SHI Tianmo;ZHENG Jincheng
Science & Technology Review. 2013, 31 (24): 15-20. ;  doi: 10.3981/j.issn.1000-7857.2013.24.001
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A hybrid system formed by a photovoltaic module and a thermoelectric module has a great potential to enhance the solar-to-electricity efficiency. A mathematical model based on the first law of thermodynamics and the heat transfer analyses of the hybrid system is built, where the overall efficiency of the system is enhanced by optimizing the system as a whole. The model is used to study hybrid systems formed by commercially available photovoltaic modules and thermoelectric modules. It is found that, due to a limited incoming heat flux for the thermoelectric module, the overall performance of the hybrid system depends not only on the intrinsic properties of the materials forming such a hybrid system, but also on their working conditions, such as incoming solar radiation, geometry of each module, and interfacial properties. The results indicate that only photovoltaic modules with low temperature coefficient and low efficiency can truly benefit from forming such hybrid system, and the optimization of a hybrid system must be done as a whole.

Corrosion Behavior of a New Low Alloy Steel Q415NH

CHENG Xuequn;TIAN Yuwan;YIN Yuqun;WANG Jun;ZHOU Cheng;LI Xiaogang
Science & Technology Review. 2013, 31 (24): 21-25. ;  doi: 10.3981/j.issn.1000-7857.2013.24.002
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The corrosion behavior of a new low alloy steel Q415NH is investigated by its exposure to alternate conditions of 12min immersion in a mixed NaCl and NaHSO3 solution and 48min drying at 45℃ to provide a basis for developing new weathering steels and studying the effects of alloy elements on the corrosion resistance under high Cl- atmospheric conditions. The results suggest that the corrosion resistance of Q415NH is much better than Q420, and the anticorrosion mechanism can be summarized into the following three aspects: (1) Due to the addition of 3%Ni, Q415NH have a microstructure of large number of fine bainites dispersed on ferrite; (2) The addition of Ni can increase the potential of the steel and the resistance of rusts to improve the anodic passivation; (3) The rusts of Q415NH are much more protective by the formation of a compact and fine structure with the anodic ion-selection.

Main Influencing Factors for the Accuracy of Microseismic Source Location

DONG Longjun;LI Xibing;TANG Lizhong
Science & Technology Review. 2013, 31 (24): 26-32. ;  doi: 10.3981/j.issn.1000-7857.2013.24.003
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Abstract ( 265 )
The microseismic source location is one of the most important and foundational parameters in seismic analysis. The positioning accuracy directly affects the results of the microseismic results. The influencing factors for the accuracy of the microseismic source location, including the station error, the velocity error and the error caused by the optimization algorithm, are analyzed and discussed. The source location and the number of source events are determined by an optimization algorithm, and the source coordinates vary greatly with the use of different algorithms. It is important to select a reasonable optimization algorithm with a high accuracy. The famous optimization algorithms, such as the Levenberg-Marquardt Method (LM), the Simplex Method (SM), the Quasi-Newton Method (QN), the Max Inherit Optimization (MIO), the Self-Organizing Migrating Algorithms (SOMA), as well as the Global Optimization (GO) coupled with MIO, QN, MIO and LM, were used to locate and compare the seismic source coordinates. Results show that it is easy to be trapped into a local optimum value using MIO, QN and LM alone. Therefore, the selection of MIO, QN and LM should be careful. The joint use of the global optimal algorithm combined with MIO, QN and LM can significantly improve the positioning accuracy. The SOMA, SM coupled with GO, the MIO coupled with GO and the LM coupled with GO, which are more stable with a high positioning accuracy, should be the recommended methods to locate the seismic or acoustic emission source coordinates.

Numerical Simulation of 3D Unsteady Flow in Centrifugal Pump by Dynamic Mesh Technique

HUANG Si;YANG Fuxiang;GUO Jing;OU Guowei
Science & Technology Review. 2013, 31 (24): 33-36. ;  doi: 10.3981/j.issn.1000-7857.2013.24.004
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The 3-D dynamic meshing technique is applied for the numerical simulation of unsteady flow fields in a centrifugal pump using the Fluent software. The surface motion of the impeller in the computational domain is defined by the profile file in the Fluent software, in which the rotational direction and the speed of the impeller are specified. The simulation results are compared with those obtained by the widely used sliding mesh technique to illustrate the superior computational efficiency of the dynamic mesh method. In the dynamic mesh technique, all computational domains, considered as stationary, are defined in an inertial reference frame, while the topological relationships between the previous and the current mesh nodes are retained to ensure a good precision and time coherency. Three methods, namely the spring-based smoothing, the dynamic layering and the local re-meshing are used to cope with mesh deformations. Comparisons of solutions with those obtained by using the sliding mesh technique with an identical computational model, the same meshes, and initial and boundary conditions show that the results of both methods converge to comparable solutions within five revolutions of the impeller. The iterative speed of the dynamic mesh method, however, is almost three times of that of the Sliding Mesh method. The results thus suggest that the dynamic mesh technique for the flow simulation in centrifugal pumps, defined in an inertial reference frame, yields a substantially better computing efficiency than the sliding mesh method involving a comprehensive data transfer among multiple reference frames. This work shows that dynamic mesh technique can be used for numerical simulations of a three-dimensional unsteady flow field in pumps and has a strong versatility and broad application prospects.

Thermal Protection of Permanent Magnet DC Motor for Car Lifting Window Based on Software

SHI Dafa;HUANG Qing;PAN Xiaoqing;HUANG Shoudao;LIU Zhu;ZHANG Jinping
Science & Technology Review. 2013, 31 (24): 37-41. ;  doi: 10.3981/j.issn.1000-7857.2013.24.005
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In view of the working car's lifting window produces heat can destroy the motor of lifting window, a software thermal protection method of motor for car lifting window is proposed. Firstly,through analyzing the theory of permanent magnet DC motor's temperature variation under three working states, the mathematic models of thermal protection algorithm are built, and the real-time monitor software of motor's temperature is designed. Secondly, the experimental verification of software monitoring method is carried on under voltage of 12.5V and 14.5V. At last, the result shows the error between monitor temperature and actual temperature is less than 5℃, which means this method has high accuracy in monitoring of motor's temperature variation, and can realize thermal protection for the motor of car's lifting window. It will be applied in the field of motor thermal protection without temperature sensor.

New Technology of Two Step Modeling Controlled by Karst Facies of Multiscale Fractured-cavity Carbonate Reservoir

HU Xiangyang;QUAN Lianshun;HOU Jiagen
Science & Technology Review. 2013, 31 (24): 42-46. ;  doi: 10.3981/j.issn.1000-7857.2013.24.006
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Abstract ( 569 )
Taking Tahe fractured-cavity carbonate reservoirs as the prototype,a new technology of the two step modeling controlled by karst facies of multi-scale fractured-cavity reservoir is developed. It is a two step modeling method under the control of the ancient karst development mode: the first step is the establishment of four discrete distribution models of a single type of reservoir, namely, using the seismic identification and description of the results, to establish a large cave discrete distribution model and a large-scale fracture discrete distribution model. With the karst facies constraints, based on the probability of caves and fractures to be developed between the body and the wells, and the multi-attribute co-simulation, the dissolved pores stochastic model and the small scale fractures discrete model are built. In the second step the parity condition assignment algorithm is used, to integrate the four single types of models into a multi-scale discrete fractured-cavity reservoir 3D distribution model. The quantitative model in 3D space to characterize the distribution feature of the fractured-cavity reservoir may serve as a solid geological foundation for the oilfield development.

Stress Analysis of Fixed Tubesheet Heat Exchanger

CHU Qibao;YAO Lin;WANG Qing;FANG Yonggang
Science & Technology Review. 2013, 31 (24): 47-50. ;  doi: 10.3981/j.issn.1000-7857.2013.24.007
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Abstract ( 221 )
Shell and tube exchanger is widely used in many industrial fields because of its high reliability and wide applicability. In a conventional design based on the code of GB 151—1999 "shell and tube heat exchanger", a method of equivalent approximation is used. There is a great difference between the equivalent mechanical model and the actual structure, especially for large or high parameter heat exchanger. If the conventional design method fails, we must find a new method of design. The finite element analysis is the most common method. In this paper, a finite element model is built for the heat exchanger test-bed by ANSYS. The stress analysis for the fixedly connected structure of shell, tube plate and tube is carried out. In the model, the solid element and the beam-shell element are used respectively. Both models are under a same temperature load and a same pressure load. Under the same conditions, the diffrent experiments are carried out. The experimental results are compared with the results of the finite element analysis. It is shown that with both the beam-shell element and the solid element, accurate results can be obtained. Considering the difficulty of modeling, engineering accuracy and calculation time, for the large or high parameter heat exchanger, the use of the beam-shell element can ensure the calculation accuracy and reduce the difficulty of modeling. It is a practical and feasible method.

Production Decline Mode for Fractured Shale Gas Reservoirs with Stress Sensitivity

CAI Hua;FU Suiyi;CHENG Shiqing
Science & Technology Review. 2013, 31 (24): 51-54. ;  doi: 10.3981/j.issn.1000-7857.2013.24.008
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Abstract ( 280 )
The production decline model for conventional gas reservoirs is widely used for dynamic analysis of shale gas reservoirs at home and abroad, but due to some special features of the occurrence of the shale gas involving mainly adsorption state and free state, the regressive analysis methods of conventional gas reservoirs are no longer valid. Based on the traditional dual-porosity model, a mathematical model with consideration of the stress sensitivity and the sorption effects is established by introducing the non-dimensional stress sensitive coefficient and defining two non-dimensional adsorption parameters--dimensionless Langmuir volume and dimensionless Langmuir pressure. The numerical solution of the production is obtained together with the production decline Blasingame type curves through the numerical difference and Newton iterative methods. It is shown that the higher the stress sensitivity, the smaller the non-dimensional production, the production integral and the production decline integral derivative will be. The larger the adsorption of the shale gas matrix, the more delayed the point will be where the non-dimensional production decline integral derivative curve becomes concave down. At the same time, with the help of the shale gas well production data, the shale gas reservoir adsorption constants, other formation parameters, and the stress sensitive effect caused by the decline in the production can be obtained by typical curves.

Common Characteristics of COPD of Traditional Chinese Medicine Kidney Depletion-phlegm-stasis Syndrome and Uygur Medicine Abnormal Savda Syndrome Based on Metabonomics

XU Weifang;UPUR Halmurat;LI Fengsen;MAMTIMIN Batur;YANG Jian;AIZEZI Renaguli;WU Xiaohua;GA Lijuan
Science & Technology Review. 2013, 31 (24): 55-61. ;  doi: 10.3981/j.issn.1000-7857.2013.24.009
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Abstract ( 251 )
This paper studies the metabonomics change of COPD of the TCM types and the TUM types,through identifying the metabolic biological markers of the TCM kidney empty-phlegm-stasis syndrome and the Uygur medical abnormal savda syndrome, to guide the clinical diagnosis of COPD, and to provide some new ideas and methods. (1) A total of 105 cases of patients with COPD, diagnosed according to western medicine diagnosis classification, were chosen and divided two groups according to the TCM and the Uygur medicine on syndrome differentiation and classification. Meanwhile, a total of 52 healthy volunteers were chosen as the normal control group, from the medical center of the affiliated hospital of Chinese medicine, Xinjiang Medical University. (2) All blood samples of the subjects were tested through utilizing the NMR metabonomics; (3) The plasma 1H NMR spectra were analyzed using the orthogonal projection to the latent structure and the discriminant analysis (OPLS-DA) method with unit variance scaling. The discriminative significance of the metabolites was determined using the Pearson's product-moment correlation coefficient. 1H-NMR spectrum and 2D pattern recognition in the analysis show that for the COPD patients of the Kidney empty-phlegm-stasis syndrome group, and the abnormal savda syndrome in the normal control group, respectively, their distribution areas are separated completely, the metabolic components of plasma of the two group have a significant difference; but the metabolic components of the kidney empty-phlegm-stasis syndrome group and the abnormal black savda patients are not statistically different (P>0.05). The metabolism including the isoleucine, the leucine, the valine, the alanine, the tyrosine, the glutamine, the pheny-lalanine, is significantly reduced in level, and the lactic acid, the glycoprotein VLDL and the unsaturated fat are also significantly reduced. The carnitine is relatively higher, with a difference not statistically significant (P>0.05). Extremely low density lipoprotein plasma VLDL, the unsaturated lipid and acetone of the COPD kidney-empty-phlegm-stasis syndrome patients and the abnormal black savda patients are lower, but with a difference not statistically significant (P>0.05). So there are 14 kinds of the metabolites, which would expect to be serum specific biomarkers of the COPD kidney-empty-phlegm-stasis syndrome patients and abnormal savda patients. The results indicate that (1) the metabonomics change and the metabolic phenotype of the COPD with the kidney empty-phlegm-stasis syndrome and the abnormal savda syndrome are outstanding but similar, and also with common biomarkers, the material metabolic disorder, the low body's immune function, the endocrine disorders and the energy metabolism disorder are evident; (2) the metabonomics common features of the COPD with the TCM and the Uygur syndrome further reflect the interoperability of the two kinds of medical models of Chinese medicine, Uygur medicine and modern medicine about COPD; the COPD of syndrome differentiation would be more objective and more standard.

Role of Face-to-face Talke in Raising Farmers’ Scientific Awareness

Science & Technology Review. 2013, 31 (24): 62-67. ;  doi: 10.3981/j.issn.1000-7857.2013.24.010
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This paper discusses a rural model of science popularization based on face-to-face talk pattern, which is shown to be the main channel of the rural residents' access to S & T information. Its role in raising the scientific awareness of the rural residents is analyzed based on the data of the civic scientific literacy survey in recent years. This pattern plays an important role in the rural science popularization and also in the rural model of science popularization. This paper analyzes three typical models of science popularization to improve the scientific awareness of the rural residents.

Research Progress for Cu-based Small Pore Molecular Sieves as Disel De-NOx Catalysts

WENG Duan;WANG Lei;Wu Xiaodong;RAN Rui;SI Zhichun
Science & Technology Review. 2013, 31 (24): 68-73. ;  doi: 10.3981/j.issn.1000-7857.2013.24.011
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Abstract ( 372 )
NOx is one of the main pollutants in diesel vehicle emissions. Selective catalytic reduction of NOx by ammonia (NH3-SCR) has been extensively studied for the lean NOx control due to its high performance and economic efficiency. Copper based zeolites have been widely used as the De-NOx catalysts and significant research efforts have concentrated on developing different types of zeolites to improve the activity and durability. Recently, SCR catalysts based on small-pore molecular sieves have been reported for NH3-SCR with much improved activities and high thermal durability and have received substantial attention. This review sums up the research progress related with Cu-based small pore molecular sieves, such as Cu-SSZ-13 and Cu-SAPO-34, as diesel De-NOx Catalysts with outstanding low temperature NH3-SCR activity and hydrothermal stability. The nature of the copper species and the surface acidity are the most important factors that affect the NH3-SCR performance. Important results on the active sites and catalytic mechanisms are especially discussed in details. The possible developing orientations and research interests on the novel catalysts design and mechanisms of poisoning resistance are previewed.

Progress in Freezing-thawing Rock Mechanics During the Period of 2001 to 2012

DENG Hongwei;TIAN Weigang;ZHOU Keping;LI Jielin
Science & Technology Review. 2013, 31 (24): 74-79. ;  doi: 10.3981/j.issn.1000-7857.2013.24.012
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This paper reviews the research development of freezing-thawing rock mechanics, focusing on papers related with the freezing-thawing rock mechanics in the database of Web of Science and Chinese Academic Periodical Full Text during 2001 to 2012.From the searched results,it can be seen that the number of research papers on freezing-thawing rock mechanics is in rapid growth in the last 12 years and that the research foundation in China is not good and not many papers in the field are published. Meanwhile,it is shown that the number of papers and dissertations during the period of 2007-2012 increases by 108.8% and 236.4% compared to the period of 2001-2006, which indicates that the domestic studies of the freezing-thawing rock mechanics are in a booming state in trends. Some papers related to the freezing-thawing rock mechanics published in these periodicals in recent years are specially analyzed.Studies of physical properties and damage mechanisms are briefly reviewed and some issues worth further studies are pointed out.

Science & Technology Review. 2013, 31 (24): 80-80. ;  doi:
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Science & Technology Review. 2013, 31 (24): 85-85. ;  doi:
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