28 July 2014, Volume 32 Issue 21

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  • WANG Yutao, QIU Qiu, LI Shaoshan, XIN Guorong
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    The heavy metal contaminations in agricultural soil are a great threat to human health. In this study, a greenhouse experiment was conducted to investigate the effects of arbuscular mycorrhizal fungi (AMF) inoculation on Cd and Cu accumulation in maize under Cd-Cu combined pollutions, as well as the potential toxic effects of Cd-Cu pollution on AM symbiosis. It is shown that the heavy metal contamination significantly inhibits the symbiosis between AMF and maize (P<0.05), and the inhibition effects are more significant on the vesicle and arbuscular structures than on the hyphal structure of AMF. The heavy metal contamination also significantly inhibits the growth of maize (P<0.05), but the inhibition effects are obviously alleviated by AMF colonization. Besides, AMF inoculation significantly increases the Cd and Cu accumulations in both roots and shoots of host plants (P<0.05). The results from this study indicate that mild-to middle-levels of heavy metal contaminations in the agricultural soils could threat both crops and AMF. In the heavy metal contaminated farmlands, AMF could on one hand improve the tolerance of crops to heavy metals, while on the other hand increase the risks of heavy metals entering into human food chain by improving the heavy metal absorption of crop plants.
  • DAI Qunwei, WANG Yan, ZHAO Yulian, ZHOU Shiping, YANG Xingwang, ZHANG Wei
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    In order to explore the adsorption characteristics, liquid pH, and electrical conductivity variation characteristics of bupleurum dreg to the waste water containing zinc, the bupleurum dreg was utilized as biosorbent to remove Zn2+ with batch experiments. The effect factors on biosorption were analyzed, which included pH values, initial Zn2+ concentration (C0), biosorbent concentration (ρm), and mesh size (Mz). Meanwhile, the isotherm biosorption and kinetics was analyzed. The results showed that the optimum condition for biosorption was as follows: pH was 4.5~6.0, ρm was 4.0~8.0 g/L, C0 was 0.1~2.0mmol/L, Mz was 40~100 mesh. The isotherm adsorption curve of Zn2+ on bupleurum dreg accorded well with Langmuir and Freunlich model, and the R2 value was 0.978 and 0.989 while the value of qmax was 19.96 mg/g. This shows that a bupleurum dreg has excellent adsorption capacity to zinc ions. The kinetics analysis showed that the biosorption of Zn2+ on bupleurum dreg was a rapid process, and the R2 values were all above 0.997. These indicated that its limit step was chemical adsorption process. The variation trend of pH values in liquid was increasing rapidly at initial adsorption phase and then changed slowly in the succedent phases.
  • LI Zifan, XIAO Kui, WEI Dan, DONG Chaofang, ZHANG Xin, LI Xiaogang
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    The corrosion behaviors of Fe-Cr alloy in the acidic solutions with Cl- and SO42- are investigated. The corrosion mechanisms are characterized by the linear polarization and the electrochemical impedance spectroscopy measurements, and the corrosion products are analyzed by the laser Raman spectrometry. It is shown that the Fe-Cr alloy is attributed for the passive film, which is formed more easily when the alloy contains a large quantity of Cr element. In the early immersion, the corrosion rate of Fe-Cr alloy is very small. With the immersion time increases, the passive current density firstly increases, and then decreases. The passive film can well prevent the Cl- and SO42- anion erosions. For Fe-Cr alloy, pitting occurs in an acidic solution, and it increases its extent with the increase of the immersion time. If the Fe-Cr alloy is immersed in the solutions for 150 h, the corrosion products appear in the near grain boundary, and are more likely to occur in the triangle grain boundary. The corrosion products of the Fe-Cr alloy contain CrOOH.
  • WANG Zhizhong, LIU Guohou, BAO Yulan, GONG Donghui, LI Xuehai
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    This paper presents a comparative study of the characteristics of phycocyanin between Spirulina Erdosensis and the imported species to find out the characteristics of two spieces of spirulina platensis, and obtain the optimal parameters of phycocyanin in the process of extraction and preservation. The results show that the purity and the yield of the two Spirulina species of phycocyanin are the best and the phycocyanin purity of Spirulina Erdosensis is 1.67 times of the imported species and the yield of phycocyanin of two Spirulina species is basically the same with 40% (NH4)2SO4 saturation. The phycocyanin is more sensitive to temperature than the introduced species. The reduced percentage of the phycocyanin purity of Spirulina Erdosensis is larger than that of the introduced species under the conditions of 35℃, 45℃, 55℃, while it is twice as large under the conditions of 25℃. Nonetheless, the reduced purity of Spirulina Erdosensis is still higher than the highest purity of the introduced Spirulina species, showing the advantages of Erdos Spirulina platensis on phycocyanin. The phycocyanin from Spirulina Erdosensis can be extracted at 55℃ and the lowest temperature should be chosen for both extracting efficiency and purity in the permissible process and environmental conditions. The phycocyanin purity of two Spirulina species is the largest when pH value takes 5-6, while the pH stability of phycocyanin for two Spirulina species is quite consistent.
  • DENG Yu, HE Qinghua, ZHANG Yunlong, LIU Xueliang
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    Of the methods on power-matching control of hydraulic excavator now, the rotary inducing control is commonly used but has shortcoming of response lag. According to the dynamic characteristics of diesel engine and hydraulic pump in power system of hydraulic excavator, method of constant torque control combined with rotation speed feedback control is proposed, the system simulation model is established in Simulink, with the load signal in actual condition imported to the model, the two control methods are analyzed. The result indicate that the method of constant torque control combined with rotation speed feedback can stabilize the engine's speed and reduce the maximum lose of engine speed, make the hydraulic pump can make full use of the engine, so that elevate the excavator's effect.
  • LIU Yubo, LI Ziqiang, BAI Xue
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    This paper shows the importance of the performance of the hydraulic support and the characteristics of the virtual prototype technology. Using the three-dimensional modeling software Pro/E, the solid modeling of the hydraulic support is made and is imported into the multi-body dynamics software ADAMS. Dynamic simulations with the ADAMS software of the hydraulic support are carried out to obtain the dynamic characteristics of the hydraulic support. The movement of the four bar linkage and the track of the top beam end and the relationship between the top beam displacement and the roof force during the raising and falling periods of the hydraulic support are obtained and verified. The performance of the dynamic model of the hydraulic support is evaluated through the simulation of the whole motion process of the hydraulic support. The establishment of a digitized prototype for the hydraulic support may reduce the design cycle time as well as improve the design quality, which is helpful for the optimization design of the hydraulic support.
  • XIE Songfang, ZHU Shoulin, QI Chunhua, YANG Feng
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    The vision system is the main channel for the driver to obtain traffic information, and the highway roadside landscape is an important factor in the visual stimulus to the driver. With different roadside landscapes of the prairie highway straight line section, the eye movement indexes of 5 drivers are collected and analyzed by the eye tracker. The results show that the driver's pupil diameter and the saccade amplitude are larger, but the blink duration and the fixation duration are shorter in the relatively complex roadside landscape section. The effect of the different roadside landscapes on the driver's blink duration, the fixation duration and the saccade amplitude are not significant, but the effect on the driver's pupil diameter is significant. The results may provide a reference for studying the effect of the prairie highway roadside landscape on driver's fatigue.
  • HE Hanping, HUANG Jianlin, ZHAO Fenglan, LIU Huanle
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    The asphalt precipitation and deposition in the tubing inside wall have a serious impact on the well testing and the preproduction downhole operations in Yada oilfield, Iran, for example, they hinder the slickline tool running and the retrieving of downhole tools. In order to identify the asphalt precipitation and the precipitation trend and behavior in the crude oil, based on reservior characteristics in Yada oilfield, the asphalt precipitation extent is analyzed using a quantitative calculation for the colloidal system stability and the SARA data. Based on the thermodynamic equilibrium theory and the solid model, in combination with the predicted temperature and the pressure profiles inside tubing at different production rates, the initial pressure and temperature of the asphalt precipitation are analyzed and forecasted, and through laboratory testing, the asphalt scavengers are evaluated and optimized. The quantitative calculation results about the crude oil colloidal stability show that the crude oil colloidal system tends to be unstable and the asphalt separation is made easy. The predicted depth for the asphalt precipitation is in the range of 3000-3780 m, which indicates that since the beginning of the production wells the asphalt precipitation is unavoidable. Asphalt scavenger lab test results show that a single scavenger can not achieve satisfactory results, and an optimization for operation and treatment is proposed.
  • TANG Lizhong, GAO Longhua, WANG Chun, JIANG Feng
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    To study the influence of weak interlayers on the stability of roadway surrounding rocks under dynamic disturbance, the finite element software Abaqus was used to numerically analyze the mechanical response of surrounding rocks of Dongguashan copper mine roadway under blasting, and an optimized support scheme was proposed. The results show that the vertical stress of roadway vault and bottom amplitude fluctuation of the roadway with weak interlayers are higher than those of the roadway without weak interlayers, and the bottom changed apparently, while the horizontal stress fluctuation amplitude of the roadway with weak interlayers is lower than that of the roadway with no weak interlayers. The deformation of the vault and two sides of the roadway is larger than that of the bottom, and roadway surrounding rocks without weak interlayers apparently have larger deformation than those with weak interlayers, and have larger deformation rate. The farther away from the explosion source, the smaller the stress and deformation of roadway surrounding rocks, but the change is not apparent, which tends to be stabilized after about 0.15 s under dynamic disturbance. Based on the investigation of Dongguashan copper mine, the destruction form of surrounding rocks is roof caving. Thus an optimized support scheme was proposed, with which the deformation of surrounding rocks is about 1/3 of that with no support, effectively reducing the deformation of roadway surrounding rocks.
  • WEI Yong, LI Meng
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    The tailing reservoir disaster not only causes a serious leakage, but also the related tailing flow can submerge the farmland, pollute the environment and endanger people's lives and property in the downstream. Therefore, the detailed study of the dam-break flow is important in the design and siting of tailing reservoirs, the disaster prevention and mitigation and the daily safe operation. In this paper, a mathematical model is proposed to describe the routing of the tailing flow in the downstream after tailing dam break based on the rheological properties of the tailing flow. The fourth order parabola is used for the discharged tailing flow process curve of the tailing reservoir dam-break, by which important parameters of the tailing dam break are determined such as the gross leakage of the tailing, the average width of the dam break, the maximum tailing flow at the tailing dam, the flow graph of tailings at the dam. Finally, with a tailing reservoir failure as an example, the mathematical model is used to study the dam-break tailing flow routing and the flow in the downstream in the context of the following three aspects: the plane area of the deposition, the longitudinal profile of the deposition and the cross section of the deposition.
  • Reviews
  • ZHANG Xiaotao, HOU Hongwei, LIU Yong, WANG An, HU Qingyuan
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    The head and neck cancers are the sixth most common cause of cancer deaths. The head and neck squamous cell carcinomas (HNSCCs) are caused by the tobacco and alcohol consumption and by the infection of high-risk types of human papillomavirus. Due to the lack of biomarkers for early detection and risk assessment, more than 50% of head and neck cancer patients are often diagnosed at a late stage, and the five-year survivor rate is lower than 50%. The high-throughput analysis method based on the metabolomics technology has the potential to come up with tumor-associated biomarkers. This paper reviews the progress and challenges of the metabolomics technology in its way into the biomarker discovery of the head and neck cancer, and the future development is also discussed.
  • MA Tao, WANG Qiang, CHEN Wenzheng, NIE Jun
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    The technologies of natural gas flooding are reviewed in this paper. The natural gas flooding is mostly applied in America, Canada and the former Soviet Union. Typical projects are described. The causes of slow development of the natural gas flooding in China are analyzed. The natural gas flooding projects in Changqing oil field and the Daqing oil field are taken as samples in China. The oil reservoir conditions, the well net, the well spacing, the injecting conditions and the injecting modes in the natural gas flooding peojects are analyzed. The problems and their solutions during the natural gas flooding operation are discussed.
  • Focus
  • LIU Tao
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    With the change of the internal and external environments and the space security concept, the US military space strategy undergoes major adjustments, from emphasis on improving the satellite system function to focus on how to improve the protective abilities of the space architectures and how to secure the functions of space architectures under the adverse conditions. This paper traces the change of the US space security concept also the purpose and the method of the strategy transformation to a disaggregated military space architecture. The strategy transformation is analyzed from various aspects such as the top level planning, the evaluation indexes of the architecture and the main difficulties. The implementation statues, the methods and the difficulties of the strategy transition in the fileds of the military communication, the missile warning, the reconnaissance, the meteorology and the navigation satellite systems are analyzed.