18 August 2014, Volume 32 Issue 23

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  • SHI Fang, GAO Feng, GAO Yanan
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    A numerical method is presented for obtaining the stress intensity factors of cracks terminating at a bimaterial interface based on extended finite element method (XFEM). A new 6-term crack tip displacement enrichment function is derived. Based on the analytical solution of the stress and displacement fields around the crack tip, the expression of the path independent integral J and the stress intensity factors K and K, is established. The XFEM numerical solution is used to calculate the integral J, and the stress intensity factors are obtained by using the above expression. Finally, the maximum circumferential stress criterion is used to request the crack propagation angle θp. Results of the numerical simulations show that propagation problems of vertical crack at the bimaterial interface can be solved efficiently by the combination of the integral J method and the XFEM. The crack propagation angle θp is smaller when the crack propagates from a softer material into a harder material, but θp is larger when the crack propagates from a harder material into a softer material. In the case of the four-point bending test, the crack propagation angle θp is independent of the ratio of the Poisson's ratios (v1/v2) of materials on both sides of the interface, but θp and the logarithm of the ratio of elasticity modulus lg(E1/E2) meet an exponential relation.
  • LI Junjun, WANG Zhizhang, WANG Zheng, JIANG Dan
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    This paper applies cluster analysis method to primary classification of the samples and group them into Ⅰ, Ⅱ and Ⅲ flow units. By using the correspondence analysis method, the paper studies the spatial distribution pattern and genetic relationship of the samples on the plane graph in order to make geological interpretation and inference. The research suggests that the factor f1 which is related to sedimentation is the primary control factor of the flow unit classification, while the factor f2 which is related to diagenesis is the secondary control factor. Finally, the paper establishes the discriminant formulas to make judgment on the samples. The result shows that the discrimination function is effective and can be used in other wells. The research idea and method in the paper provide a theoretic basis and technical support for reservoir flow unit study in other similar oilfields.
  • LI Zhiping, GUO Zhenzhen, LIN Na
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    Through study of gas-liquid interfacial tension of condensate gas reservoir and conventional gas well continuousremoval liquid model, this paper proposes a calculation method of critical flow rate in condensate gas wells with real interfacial tension to improve the accuracy of judgment of gas well liquid loading status used by conventional models. Analysis of the changing characteristics of interfacial tension shows that condensate oil has low interfacial tension. When condensate gas well liquid loading is analyzed, wells are suggested to be divided into two types: oil-gas wells and oil-water wells. Oil-gas interfacial tension was used in calculation for oil-gas wells, while gas-water interface tension was used in calculation for oil-water wells. According to the well production state, the actual temperature and pressure were used to calculate the interfacial tension. Three general models were modified by considering the variable interfacial tension, and the critical flow rates were calculated for 20 gas wells of a condensate gas field in Xinjiang. The results show that the accuracy rate of critical flow rate calculated by the modified Turner's model reached 90%, which can be used as the judging standard of prediction of liquid loading in this region.
  • LIU Yuying
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    Image reconstruction using classic multiple signal classification (MUSIC) algorithms contains little target information. To solve this problem, time reversal matrix theory was adopted to obtain the image of scattering objects. The positioning accuracy of the modified MUSIC algorithm and its relationship with array element space, signal-to-noise ratio, and difference of signal incident angle were analyzed. Ipswich experimental datasets indicate that the improved image reconstruction algorithm realized better image reconstruction, providing evidence for advantages of the algorithm and other algorithms in determination of the morphology of obstacles. Comparative experiment on non-symmetric double-circle metal cylinder shows that the algorithm achieved better image reconstruction in high frequency conditions, and the higher the frequency, the smaller the eigenvalue of image reconstruction, and the higher the resolution.
  • ZHAO Su, LIU Dawei, ZHAO Yue, LÜ Jian, TIAN Zhongxin
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    Acid leaching is used to extract alumina from fly ash with generally concentrated sulfuric acid as solvent and fluoride as co-solvent. This method has some problems such as low leaching rate, fluoride environmental pollution, etc. The factors influencing the leaching rate with orthogonal test method are studied in this paper. By optimizing the experimental conditions, not only is the leaching rate of aluminum improved but also the environmental pollution is reduced. The results show that when the temperature reaches the boiling temperature of the dissolution, the concentration of sulfuric acid is 12 mol/L, the solid-to-liquid ratio is 1:3, the elution time is 120 min, and m(KF):m(fly ash)=0.04, the leaching rate of aluminum can be up to 91.2%, and the toxic fluoride dosage is reduced by half in the same leaching rate.
  • ZHOU Zilong, WU Zhibo, ZHAO Yunlong, GUO Min, SUN Jingjing
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    The application of point load is involved in many fields of practical engineerings such as the rock-breaking of boom-type roadheader, high-frequency hammer, etc. As the contact area between the machine and rock mass is very small and can be seen as a point contact, the rock-breaking type is equivalent to cyclic point loading. In order to understand the effect of upper limit stress on fatigue life (the time required for destruction) of red sandstone under the cyclic loading of point load, the MTS Landmark test system is adopted for the fatigue test with different upper limit stress ratios including 0.70, 0.80, 0.85, and 0.90. The experimental result shows that the fatigue lifetime of red sandstone decreases with the increase of upper limit stress when the loading waveform is a gradient sine wave and the lower limit stress ratio and the loading frequency are 0.3 and 1 Hz, respectively. It is also shown that the terminal strain corresponding to fatigue failure is equal to the one corresponding to the point where the post-peak stress-strain curve and the line of the maximum cyclic load intersect, which is called the deformation control law.
  • YANG Xiuli, CUI Chong, CUI Xiaoyu, JIA Jianping, ZHU Zhiping
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    High-performance man-made silicate aggregate was prepared with hydrothermal method by using industrial solid wastes, which can be used to replace natural aggregate. The obtained silicate aggregate was spherical with the bulk density of 859 kg/m3 and the maximum cylinder compressive strength of 20.65 MPa. The concrete was prepared using the silicate aggregate, accounting for 50% of the total amount in volume. The compressive strength of the concrete reached 52.26-68.71 MPa, and the apparent density was 1881-1949 kg/m3. Comparison of the concrete with silicate aggregate and common concrete with the same volume of aggregate and cement mortar shows that the compressive strengths of the two kinds of concrete were close, but the density of the former was 20% lower than that of the latter. The fracture morphology of the concrete shows that the interface structure of the silicate aggregate concrete is better than that of common concrete.
  • DONG Xue, YU Yi, GAO Yong, YANG Yonghua, CHAO Gejile, GAO Jianbin
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    Natural Ammopiptanthus mongolicus in the desert region plays an important role in maintaining natural ecological balance, thus having high research value. Because of multiple factors, however, it has become endangered plant. For protecting and optimizing the population structure of this plant, it is important to explore the rejuvenation techniques. The stumping experiment was carried out on A. mongolicus in the western Ordos National Nature Reserve under different stumping heights, ground diameters, and treatments. The results show that the growth increment of new branches had apparent negative correlation with stumping heights, but had apparent positive correlation with stubble diameters. The appropriate stubble height for natural A. mongolicus was 3 cm. After the second growing season, the plant height was 44.5 cm, and the average quantity of new germinated branches was 37.4, 5.9 times of the control. After two years' growth, the length of new germinated branches reached 45.9 cm, an increase of 33.2 cm compared with that of the control, and the base diameter reached 9.98 mm. Treatment of different A. mongolicus brush had better effects than that of the same brush. The appropriate stubble diameter was 15.09-19.95 mm, and painting the stubble side helps to rejuvenate the plant.
  • MAIMAITIAILI Abudunaibi, ABUDUREHEMAN Mulati, SHABITI Aisikaer, AIBIBULA Aili, UPUR Halmurat
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    This paper aims to investigate the effects of different doses of abnormal Savda Munziq on myocardial ischemia-reperfusion injury (MI/RI) in rats with the abnormal Savda syndrome. Seventy-two rats with abnormal Savda syndrome and 24 healthy ones were selected and divided into eight groups: ischemia-reperfusion model group, high dose maturation agent group, middle dose group mature agent, small doses of maturation agent group, normal ischemia-reperfusion group, model sham group and atorvastatin intervention group (positive control group). Each group contained 12 rats. The enzyme-linked immunosorbent assay (ELISA) was used to detect the serum myocardial enzyme and troponin levels, and hematoxylin and eosin (HE) staining was used to observe changes of the myocardial tissues in the different groups. The results showed that in the Munziq intervention groups, the serum creatine kinase and troponin levels were significantly lower than those in the model group, and the middle-dose group showed the lowest levels. The HE staining of myocardial tissue showed that the myocardial edema and muscle fiber proliferation levels were significantly higher in the Munziq intervention groups than in the model ischemia-reperfusion injury group, and the middle-dose group showed the least cardiac tissue damage. Moderate to high doses of abnormal Savda Munziq may be more effective on abnormal Savda ischemia-reperfusion injury in rats than atorvastatin, but further studies are still needed to confirm the conclusion.
  • Reviews
  • WANG Weiguo, CHEN Chuang, CHENG Shasha, PENG Liying, ZHOU Qinghua, LI Haiyang
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    Ion mobility spectrometry is widely used for field detection of explosives and illegal drugs due to its satisfactory features. Ionization source is the key part of ion mobility spectrometry, which is directly related to the sensitivity and selectivity. Recently, nonirradioactive ionization sources,represented by photon ionization source,have become a hot field. This paper introduces various ionization sources based on VUV lamp,especially dopant-assisted positive and negative ionization sources developed in our labrotory and their applications in detection of envoromental pollution and typical explosives.
  • MENG Chao, WU Jiuling, SONG Bo, DI Jiangli
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    This paper reviews the correlation studies of female reproductive health and infertilityin recent years in China and abroad from two major perspectives, the current status and the influencing factors. Among them, biological factors, environmental factors and social factors are discussed.
  • Focus
  • LI Zhigang, LUO Guoliang
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    The key point of China's energy conservation is power. With continuous expansion of the power industry in China, power consumption receives increasing attention from the government. This paper introduces the changes of energy consumption of China's power industry and analyzes the energy saving effect. Electric energy can be saved mainly by the generation side and the supply side through the following ways: Shutting down small thermal power units, reducing energy loss in power supply and line loss rate, and developing renewable energy, which have contributed to energy saving and pollution reduction in China.