18 October 2012, Volume 30 Issue 30

  • Select all
  • SUN Min;XIAO Kui;DONG Chaofang;LI Xiaogang;ZHONG Ping
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    The Stress Corrosion Cracking (SCC) behavior of a new ultrahigh strength stainless steel Cr12 was studies by Slow Strain Rate Tensile (SSRT) test and microstructure observation of fracture surface. The results indicate that the neck surrounding area of Cr12 steel tested in air is the crack origin and fast-propagating region, mainly with a quasi-cleavage fracture. In the weak acid solution, the SCC susceptibility of Cr12 steel increases and the fracture surface remains quasi-cleavage fracture, and slippage steps appear in some local areas. In the weak acid spray test, the oxygen is able to fast diffuse through the thin film to the reaction interface, therefore the cathodic reaction is enhanced by the sufficient amount of oxygen and the passive films are destroyed. The Cl-significantly increases the SCC susceptibility of Cr12 steel by reducing the strength and plasticity of the steel. The pitting is the origin of stress corrosion crack and the SCC mechanism of Cr12 steel is able to be explained by using the slip and cracking of passive film theory.
  • LI Rui;LIU Xiangyu;GUO Yuhua;JI Yongqiang
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    Density functional theory is used to study the CH3+H2 reaction mechanism, based on the group level of the B3LYP/6-31G*, 6-311G**, 6-311++G**, and cc-pvtz, the CH3+H2→CH4+H reaction, including reaction intermediates, transition states, and product geometries, are optimized in order to calculate the energy, at the same time the vibration analysis is carried out. The results show that the selection of the basis set does not affect stationary points geometries; the barrier 39.61kJ/mol calculated at the 6-31G* level is consistent with the 39.41kJ/mol of experimental value; there is a j vibration mode guiding reaction process on the reaction pathway, the vibration interval is in the range of -0.57 to 0.60 amu1/2Bohr.
  • ZHU Zengqing;LIU Guoliang
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    To overcome the limitation of random method that is not suitable for the case of small sample, the objective unascertained information is fully used, and the dynamic characteristics analysis model of space beam-plate composite structures is built, in which structural elastic module and mass density are all considered as unascertained variables. And a structure analysis method based on the unascertained factor method is given. Firstly, the structural element stiffness and mass matrices are built based on the mathematics expression of unascertained factor. Then by using the arithmetic operation rules of unascertained rational numbers, the computational expressions of dynamic eigenvalue for the beam-plate structures are derived from the Rayleigh's quotient. It is concluded that the confidence level of structural responses are in direct proportion to the confidence level of each parameter. Comparing with the mature random method, the proposed method is able to obtain reliability result of safer and higher faith degree in the case of inadequate data or insufficient information; moreover, it is simple and easy to apply. At last, an example is given, in which the possible values and confidence levels of natural frequencies for the unascertained beam-plate composite structures are obtained. The rationality and validity of presented method are demonstrated.
  • WANG Meizhu;YU Rongze;CUI Maolei;YANG Zhengming;WANG Xuewu
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    The reservoir in the Daqing Peripheral Oilfield is characterized not only by thin thickness, small sand scale, and ultralow permeability, but also by strong vertical heterogeneity. Interlayer interference is a serous problem in waterflooding exploitation. It is absolutely necessary to recognize the effect of vertical heterogeneity on reservoir development before interlayer interference being solved. Based on the geological characteristics of actual data, a five-point well geological model which is vertical heterogeneity and positive rhythm for the numerical simulation is established. Considering the non-linear seepage law and pressure sensitivity features in special-low permeability reservoir, the seepage law of different cycle water injection is studied. The results show that with the same water ratio, the recovery degree of augmented-abated injection mode is higher than that of augmented-suspended mode. The injection profile of augmented-abated mode is more uniform than that of augmented-suspended mode, the water absorption ability of relatively low permeability reservoir is strengthened, and the water absorption capability of relatively high permeability reservoir is weakened. The pressure gradient of injection well near bottom is generally higher than 0.2MPa/m in the increasing part of augmented-suspended water injection mode; water injection energy is expended in an establishing water flow path. The distributions could provide the intuitive judgment on the affect of cycle water injection on the vertical heterogeneity development.
  • YANG Guochen;;JIAO Daqing;XIAO Bin;LIU Jianjun;CHEN Yuling
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    Chagan Sag has experienced the extremely-complex tectonic activity processes and formed several unconformity types. Based on the systematical subdivision of different-order sequences from Cretaceous through Cenozoic in the Sag, the unconformity types of different-order sequence boundaries are identified, and a new classification scheme for unconformity types is put forward. Mainly according to the geometrical relationship between the two sides of unconformity plane, the seismic reflection termination style, and the unconformity formation mechanism (tectonism and deposition), the unconformities in Chagan Sag are divided into two categories, including angle unconformity and parallel-or-slight-angled unconformity, and further divided into seven basic types, including three kinds of tectonic unconformities, such as fold unconformity, fault-fold unconformity, and truncation unconformity, and four kinds of depositional unconformities, such as overlap unconformity, offlap unconformity, toplap unconformity, and concordance unconformity. Based on the seven basic types of unconformities, and according to the new method that divides unconformity types based on A/B-C·D code system, the unconformities in Chagan Sag are subdivided into nine sub-types, including six angle unconformity types, such as onlap/concordance-overlap type, onlap/toplap-overlap type, onlap/truncation-overlap truncation type, onlap/truncation-fault-fold offlap type, concordance/truncation-truncation type, and concordance/truncation-fold type, and three parallel-or-slight-angled unconformity types, such as concordance/toplap-toplap type, concordance/concordance-concordance α type, and concordance/concordance-concordance β type. The basic distribution law for the unconformity types of different-order sequence boundaries is that parallel-or-slight-angled unconformity types are mainly formed in sub-sag center and angle unconformity types at outskirts, and the boundaries of high-order sequence units, such as first-order sequence, tectonic sequence, and super sequence, usually have a variety of angle unconformity types as their main body, and the boundaries of low-order sequence units, such as third-order sequence, usually have a variety of parallel-or-slight-angled unconformity types as their main body.
  • MAO Wei;BAO Zhijing;DU Pengju
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    The maximum starting pressure gradient and the nonlinear percolation area distribution are studied based on the low rate non-Darcy flow. From the minimum starting pressure gradient obtained from experiments and the relationship between the starting pressure gradient and the throat radius, the limit shear stress and the maximum starting pressure gradient are obtained. The range of the nonlinear percolation area pressure gradient is determined by using a regression analysis. When the pressure gradient range is related with the pressure gradient distribution, the nonlinear percolation area distribution range can be obtained. Two well group examples show that the nonlinear percolation area distribution range thus obtained is consistent with the oil well dynamics. The method is shown to be practicable. A new method to calculate the limit injection production well spacing is proposed according to the injection production pressure gradient distribution and can be used for calculation of the injection production well spacing in an oilfield development plan.
  • ZHOU Chenyu;ZHANG Yaqi;LI Jian
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    Vehicle identification is a very difficult problem and the accuracy of identification results is very low, a method to identify vehicle is proposed based on statistical pattern recognition, adopting nonlinear Support Vector Machine(SVM) to identify the target vehicle. First, the image information of vehicles in the front and the back of the vehicle is collected by using the vehicle-mounted CCD camera. The collected images are filtered by wavelet denoising and processed with image binaryzation in order to eliminate the noise interference. Through the coordinate transformation, one-to-one correspondence relationship between the vehicles in image and the real ones is established. Then, the target vehicle is correctly positioned. Secondly, the processed images are partitioned into 8×8 grids. The ratio of the number of pixels meeting the requirements to the total pixels in each grid is served as the only decision condition for the output (0 or 1) of each grid. The total output for each row could be taken as the characteristic vector's element. The best parameter combination is determined by using the cross validation and genetic algorithm. The vehicles located at10-20m before and after the subject vehicle are taken as the training sample to train the model. The model is verified. Test results show that the algorithm is able to accurately distinguish the types of the vehicles.
  • KONG Wei;CHENG Yinjian;HU Kunqi;ZHAO Jia;CHENG Zhi
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    A new anti-vibration hardware, that is, the damping spring spacer of vibration and dance reduction has improved the method of traditional hardware fittings in vibration reduction, adopting the joint vibration reduction of damping spring and heavy ball to keep down breeze vibration in the transmission lines. The quite big innovation has achieved on the components and structure form of new anti-vibration hardware by forming spacer framework, damping spring, and heavy ball as a whole. For obtaining the effect of vibration reduction, the vibration energy is dissipated through the constant movement of damping spring and heavy ball. The finite element software of ANSYS is used to build conductors on a quad bundled model equipped with spacer to simulate breeze vibration. By comparing the curves of displacement process in the cases of no conductor spacer, ordinary conductor spacer, and damping spring spacer of vibration and dance reduction, respectively, it is known that the strengths of the new anti-vibration hardware in vibration reduction, i.e. damping spring spacer of vibration and dance reduction is able to decrease the maximum amplitude of the conductor to the minimum at the same time. Conductor spacer parameter with optimal vibration reduction performance is obtained by nonlinear fitting and parameter optimization. ANSYS is used to verify optimal data, and finally found that when the quality of heavy ball is 1.8kg and the stiffness of spring is 0.7kN/m, damping spring spacer of vibration and dance reduction is able to achieve the optimal effect of vibration reduction.
  • LI Chunyan;LI Junhong;ZHANG Haiyuan;UPUR Hamurati;YANG Na;YAN Xinghai
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    In order to address the diversity and structure characteristics of gut microbiota in the patients with asthma and study the relationship between gut microbiota and asthma disease, a case-control study involving 52 asthma patients and 25 controls were conducted. Total DNA was extracted from fecal samples using PCR-DGGE, and DNA fingerprints were obtained. Based on the DGGE profile, from 7 to 31 bands, average 17 are observed in asthma patients, while the corresponding values are from 14 to 36, average 24 in controls. The Shannon-Wiener diversity index is significantly lower in asthma patients than that in controls (P<0.0001). Combining with the analysis by using multivariate statistical methods, it is indicated that two groups of samples are obviously classified by the structure of gut microbiota. However, the different between two nationalities and genders have no statistical significance. The gut microbiota of asthma patient proceeds remarkably changes at the molecular level, the diversity of gut micobiota decreases. The results suggest that there is a relationship between gut microbiota structure changes and asthma disease. Furthermore, PCR-DGGE combining with PCA and PLS-DA has the predictive and initiative advantages in the research of microbiota structure unknown samples. Therefore, the study could provide a means for the research and prevention of asthma.
  • Reviews
  • YU Shunli;FANG Weiwei
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    A brief summary on the concept of seed ecology is presented, and then its four hot research topics are introduced in detail. They are seed rain and seed dispersal ecology, seed mass ecology, soil seed bank ecology, and seed geography. On the basis of previous published theories, their research methods, research content, scientific questions, conclusions, and future research directions are addressed and summarized. Seed ecology is a developing science which studies the relationships between seed and its environment, it has lots of research contents, in which the relationships between seed germination and environment have been received more attention; however other aspects of seed ecology research are comparatively scant. Future research in seed rain are as follows: (1) to investigate seed rain characteristics of community or population types; (2) to observe seed rain for a long term; (3) to trace final destiny of dispersed seeds, and (4) to explore the geographical dispersal patterns of seed rain characteristics, such as densities of seed rain and species richness of seed rain. Future research directions related to seed mass are: (1) to explore co-evolutionary between seed mass and more micro-biological traits, such as cell biology, plant anatomy, biological chemistry; (2) to collect seeds in more regions and to found more relationships between biological macro-characteristics and seed characteristics combined with sampling materials based on more species. As for soil seed banks, future research works are: (1) to investigate species composition and seed densities of soil seed bank and its inter-annual dynamics; (2) to explore geographical variation patterns of soil seed bank traits. In seed geography, the following research regions should be paid attention to: (1) the geography of seed morphology and anatomy characteristics; (2) the geography of seed biochemical components; (3) the geography of seed physiological traits; (4) the geography of seed cell biology; (5) the geography of seed genetic traits, and (6) the geography of flowers and fruits.
  • JIN He;LIU Jing;YANG Beilei;LU Weiyuan
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    Congenital microphthalmia or anophthalmia are the rare disease. It might relate to gene and environment. At the clinical ophthalmology, due to the lack of effective eyeball stimulation, the growth of the orbit, eyelid, and maxillofacial in the sick side of children with anophthalmia or microphthalmia would lag behind the healthy side. If the effective intervention is not taken in the period of orbital-bone growth, it could cause severe facial malformations. It would have a bad impact on the beauty for sure. These children would suffer great negative effects cause by the deformity. How to dynamically take effective measures to stimulate the orbit in the sick side and let it grow along with the healthy side has long been a concerned problem in the clinic. During the fast development period of facial bone, putting inflatable tissue expander into the orbit is a good choice for the young children. It is able to reduce the number of operations. For adults and children above five years old, the size of the tissue expander could be fixed. In the process of tissue expander usage, many problems might appear, such as infection and exposure of the tissue expander. To solve these problems, many scientists are devoted to find the new material of tissue expander and operation method. The current domestic and foreign research and treatment progresses, especially during the period of children's orbital-bone growth, and the application status of orbital implant materials are summarized.