18 November 2013, Volume 31 Issue 32

    

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  A Prediction Method for Low-speed Turbulent Flow Noise

  NI Daming;ZHANG Wenping;MING Pingjian

  . 2013, 31(32): 15-19. https://doi.org/10.3981/j.issn.1000-7857.2013.32.001

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  In order to study acoustic noise generation and propagation while considering that internal viscosity of the propagation medium affects the results of aeroacoustics numerical simulation, a decomposition technique and a turbulent model were introduced in time-domain. Based on an unstructured collocated grid and finite volume method, the compressible N-S equation was divided into a viscous incompressible N-S equation and the viscous perturbation equation, and a SimpleC algorithm was used to solve the problem of velocity-pressure decoupling. Appropriate non-reflecting boundary conditions were adopted at the inflow and outflow boundaries. The governing acoustic equations of boundaries are discretized over finite volume method and the transient term is discretized by the second-order Euler implicit scheme. Numerical simulation of noise induced by flow around a circular cylinder at small and big Reynolds number has been conducted and compared with the aeroacoustic theory in time domain, in order to study the effect of viscosity on aeroacoustic numerical simulation. Comparing the two results, good results and more details about flow and sound could be obtained by splitting method, which could be used to provide some information for reducing the noise in actual engineering. The work demonstrated that the numerical algorithm can be used for the simulation and analysis of flow-induced noise at a flow with low speed.
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  Characteristics of Flexural Vibration Band Gaps of Periodic Euler Beam on the Winkler Foundation

  ZHANG Ziming;HE Jing;ZHANG Yan;JIANG Linhua

  . 2013, 31(32): 20-24. https://doi.org/10.3981/j.issn.1000-7857.2013.32.002

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  Periodic Euler beam has flexural vibration band gap characteristics. In order to study the flexural vibration band gap features of the periodic Euler beam on the Winkler foundation, the transfer matrix method and Bloch theorem are used to calculate the vibration band structure and analyze the impact of the parameters of foundation and structure on the band gaps. The results show that the existence of Winkler foundation makes vibration band gaps trend to higher frequency, and a new band gap that starts at 0 Hz appears in the case of having a foundation. Additional results demonstrate that with increasing the foundation reaction modulus, the range of the 1st band gap becomes wider and the range of the 2nd band gap becomes narrower. Along with the increase of the length ratio, the range of the 1st band gap and the 2nd band gap both become narrower. Compared with the homogeneous Euler beam, periodic Euler beam has better vibration isolation characteristics at low frequency.
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  Mechanical Response of Asphalt Mixture Overlay Based on Viscoelastic Theory

  CAO Yi;WEI Lianyu;MA Shibin;YU Huan

  . 2013, 31(32): 25-28. https://doi.org/10.3981/j.issn.1000-7857.2013.32.003

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  A three-dimensional viscoelastic finite element model of asphalt overlay was constructed based on the viscoelastic characteristics of asphalt mixture, and dynamic loading tests were performed by using the finite element software ABAQUS. The results show that, a different and more complex mechanical response than that of elastic material is generated because of the viscoelastic characteristic of asphalt mixture overlay itself. The stress state changes with the loading and unloading process-a compressive stress is generated on the surface, and a tensile stress is on the bottom surface when loading. The unloading process is on the contrary. A residual stress will be generated on the surface and the bottom surface under the alternately repeated compressive stress and tensile stress. Furthermore, the residual stress decreases with increasing the temperature, while the relaxation capacity increases and the viscoelasticity decreases. This method gives a more accurate and scientific description on the mechanical behavior feature of asphalt overlay than treating the asphalt mixture overlay as an elastic material.
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  Research and Analysis on Wavelet of Mine Microseismic Signals

  TANG Lizhong;CHEN Zinan;ZHANG Jun;GAO Longhua

  . 2013, 31(32): 29-33. https://doi.org/10.3981/j.issn.1000-7857.2013.32.004

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  Due to the limitations of the present artificial signal recognition technology and Fourier transform in analyzing the mine microseismic signal, the Matlab wavelet toolbox analysis method was presented. Through the transformation of the microseismic signals monitored in mine, prior to the spectral analysis of transformation signals, the discontinuity of the signals were accurately observed and the first arrival time of P wave was determined. As a result, the accurate location and energy of mining shocks were concluded. Further, through the wavelet de-noising of signals and comparing the four kinds of de-noising methods, the unbiased estimate threshold method worked best and this showed the powerful function of the wavelet analysis in de-noising. Therefore, it is revealed that the wavelet analysis is an effective method of seismic signal processing and analysis as it is capable of seismic signal recognition and noise elimination.
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  CFD Simulation of Atmospheric Dispersion Influenced by Cooling Towers in Inland Nuclear Power Plant

  WANG Bo;GUO Ruiping;ZHANG Qiong;WANG Erqi;YANG Yang;LIU Fudong;WANG Xuan;GENG Nan

  . 2013, 31(32): 34-41. https://doi.org/10.3981/j.issn.1000-7857.2013.32.005

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  The spatial and temporal variations of wind field and the atmospheric turbulence characteristics are important factors that affect the migration and dispersion of local atmospheric pollutants. Considering the complexity of meteorological and landform conditions around the inland nuclear power plant, the 3-Dimensional wind field and concentration field distribution of airborne radionuclide particle ¹³⁷Cs, aerosol ¹³¹I and conventional gas pollutant CO dispersion in the atmosphere were carried out by a 3-Dimensional CFD (computational fluid dynamics) model Fluidyn-PANACHE. This method can be used to reasonably simulate the turbulent and circumferential flow around large cooling towers in the inland nuclear power plant, compensating the shortage in subtleness of the standard Gaussian model, as well as shortage in realizing multi-wind direction simulation in the calculation by the traditional CFD model. The calculation results of annual average atmospheric dispersion factor under normal operation indicated the seasonal differences, with maximum average dispersion factor in autumn, which were consistent with those suggested by Gaussian mixture model. Consequently, it's reasonable to arrange refueling overhauling in autumn to diminish pollution. The numerical simulation results from four typical fixed wind directions were compared and they are consistent with the observed values of wind tunnel experiments, providing new references for atmospheric dispersion research and evaluation on inland nuclear power plants in China.
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  Application of Test and Evaluation Technology of Pitting Corrosion in Tahe Oilfield

  TANG Shichun;ZHANG Zhihong;ZHANG Jiangjiang

  . 2013, 31(32): 42-48. https://doi.org/10.3981/j.issn.1000-7857.2013.32.006

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  The features and existing problems of Tahe Oilfield pitting corrosion testing and evaluation technology were systematically analyzed. Through 3D pitting depth sounder device and improved pitting evaluation methods, the pitting conditions of different blocks of Tahe Oilfield were rated. The corrosion behavior was analyzed and the protective effect of inhibitor and anti-corrosion effect of the new material of production system pipes on the ground were evaluated. The relationship of the mixed CO₂/H₂S environment and the pitting corrosion rate of single-well pipes and oil and gas mixed pipelines of the main block in Tahe Oilfield were obtained. At the fluid temperature of 50~70℃, corrosion pitting rate is a polynomial function of P_CO2/P_H2S, fluctuating regularly distributed. The protective effect of inhibitor craft of single-well pipes and gathering pipelines was evaluated. The results show that: for long-distance gathering pipeline or pipelines having more stations, the inhibition rate is higher in the middle of the pipeline, and the filling way of inhibitors should be segmented; for shorter-distance pipeline or pipelines having the fewer stations, the inhibition rate increased from the beginning to the end of the pipeline and inhibitors should be used at endpoint filling mode. Through the application of "pigging+inhibitor" pre-film protection technology for TH10244 single well pipe, the inhibition rate increased by 70%. The results have shown that pitting corrosion rate of new material (BX245-1Cr) coupon of gathering system of pipelines on the ground decreased by 43.7% compared with 20^# steel coupon.
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  A Calculation Method on Kill Rate of Killing Well in Empty Hole Filled with Nature Gas

  LIU Xinyun;TONG Zhen;MENG Qingkun;XU Peng;SHI Libao;LI Wei;TONG Fei

  . 2013, 31(32): 49-51. https://doi.org/10.3981/j.issn.1000-7857.2013.32.007

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  According to the fluid dynamics theory, the kill rate has an important effect on the fluid friction. So in order to calculate the kill rate of empty well control, the kill rate's effect based on previous models is considered, the quasi-transient model of rescue well killing in empty wells is improved, and a mathematical computing software is used to calculate the kill rate. The numerical calculation results show that: the kill rate has a negative relation with the density of kill fluidand the depth of the well, but has a positive relation with the size of boreholes. The validation's error is controled with in 1%, indicating that the calculation method can achieve the field accuracy requirements, so subsequent similar wells killing can get certain guidance from this study.
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  Closed-loop Reservoir Management with Multi-geological Models

  CAO Lin;KANG Zhijiang;ZHAO Hui;ZHANG Tong;LUO Xingwang

  . 2013, 31(32): 52-57. https://doi.org/10.3981/j.issn.1000-7857.2013.32.008

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  In view of the limitations of performing closed-loop reservoir management with single model, a novel approach for closed-loop management based on multi-geological realizations is proposed with the combination of reservoir numerical simulation technique. A set of realizations are sequentially updated by the ensemble kalman filter (EnKF) method to honor the measurement data. Then taking the expected NPV of the updated realizations as the objective function, the production optimization process is implemented by the simultaneous perturbation stochastic approximation (SPSA) algorithm. The example application indicates that the proposed method for closed-loop reservoir management can decrease the actual geological uncertainty and provide a reasonable estimate reservoir model, and the calculated optimal controls significantly improve the effect of waterflooding with a higher economic benefits and lower developing risks than normal operation strategies.
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  Characteristics of Effect of Low Visibility Weather Phenomena on the Highway

  YANG Xiaodan;DI Jingyue

  . 2013, 31(32): 58-63. https://doi.org/10.3981/j.issn.1000-7857.2013.32.009

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  Studying and mastering the meteorological factors influencing highway visibility and its correlation are the basis of highway visibility forecast. The weather phenomena influencing highway visibility mainly include rain, snow, fog, haze, dust etc. In this study, daily surface meteorological observation data from the meteorological stations at a distance of 5 kilometers a (from September in 2002 to March in 2010), and hourly visibility and surface meteorological observation data from the 2413 automatic meteorological stations (from January 1 to December 31 in 2008)are utilized. the characteristics of the temporal and spatial distribution of rain, snow, fog on the national highway and the relationship between the 1 hour rainfall and visibility are studied and analyzed be means of statistical methods. (1) Compared with other weather phenomena, the effects of fog on the visibility is the largest, and the low visibility range resulted from fog effect is mostly below 200 m, the frequency distribution of rain, snow and dust in time is uniform, and the influence of low visibility ranges in 500~1000m. (2) In each area of China, the main weather phenomenon that affects low visibility of highway are different. Basin in the south of Xinjiang and Inner Mongolia and other places are more influenced by dust; Northeast, North China, Tibet and other places are affected by rain and snow; South and southeast of Tibet are mostly influenced by rain. (3) The higher frequency regions with low visibility caused by precipitation are mainly the Yangtze River Basin, south of the Yangtze River, Southern China and other places. At the same time, there is negative correlation between rainfall intensity and visibility, but not to lump together. (4) The probability of low visibility in the snow weather is higher than that in rainfall weather. For snow weather, low visibility of 200~500m occours commonly, and in the rain, the probability of the low visibility of <200m appears higher than the low visibility of 200~500m.
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  Influence of LIPUS on Proliferation, Differentiation and Mineralization of MC3T3-E1 Cells

  WANG Ran;MA Jun;ZHAN Xin;XIN Min;WANG Jie;WANG Xiaowen;TANG Jintian;YUE Bingfei;

  . 2013, 31(32): 64-67. https://doi.org/10.3981/j.issn.1000-7857.2013.32.010

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  The aim of the present study is to investigate the effectiveness of low-intensity pulsed ultrasound(LIPUS) on cell proliferation, differentiation and mineralizationusing of MC3T3-E1 cell line. The MC3T3-E1 cells were exposed to LIPUS with different parameters(frenquency and intensity). The cell proliferations, differentiation, and mineralization were determined by CCK-8 method, alkaline phosphatase detection kit, and alizarin red staining, respectively. The ultrasound intensity of 30mW/cm² and 40mW/cm² could promote cell proliferation, while 50mW/cm² inhibit it. The lower intensity group under 1.5MHz and 1.7MHz present better alkaline phosphatase activity. The 1.5MHz and 40 mW/cm² groups showed better mineralization effect than others. LIPUS can promote MC3T3-E1 on cell proliferation, differentiation and mineralization. LIPUS may act as a new method forprevention and treatment of osteoporosis.
Reviews
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  Diagnosis of Parkinson’s Disease Using Molecular Imaging

  DU Dan;HAN Hongbin

  . 2013, 31(32): 68-73. https://doi.org/10.3981/j.issn.1000-7857.2013.32.011

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  Parkinson's Disease(PD) is a common neurodegenerative disorder which is of hidden onset and slow progress. The pathological findings are characterized by the selective loss of dopaminergic neurons in the substantia nigra pars compact, the different degrees of multiplication of gliocytes, intracellular α-syniclein deposition and the remaining Lewy bodies in the cytoplasm of gliocytes. The clinical diagnosis of PD is currently based on a combination of the main signs of parkinsonism: bradykinesia, rigidity, resting tremor and loss of postural reflexes. As the progress of illness, there is a serious limit in mobility, which has great impact on the quality of life. If the effective management cannot be performed, the life span have to be shorten sharply, even worse, the patient may be died because of complications which are derived from pneumonia and urinary system infection due to long-time bedridden. However, diagnosis of patients with PD and atypical parkinsonism is still clinically difficult, especially at the early stages of the disease. Also, it is suggested that the symptoms of PD do not appear until approximately 70% of the Nigral Dopamine (DA) neurons have been lost. Therefore, the safe, simple and effective methods should be available to offer evidences for early diagnosis, management and tracking of disease progression about PD. Therefore, combined analysis using several kinds of methods, including clinical symptoms, genetics and imaging, may allow the detection of preclinical PD, which in turn may facilitate a prevention of disease onset.
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  Advances in the Key Technologies of Drilling and Completion for Tight Sand-stone Gas Reservoirs

  CHEN Zhixue;FENG Xiaowei;CUI Longlian;DAI Wei;LIU Li;BI Wenxin

  . 2013, 31(32): 74-79. https://doi.org/10.3981/j.issn.1000-7857.2013.32.012

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  Since 1970s, the wide development of American tight sandstone gas reservoirs have reveived the widespread attention. In the way of driling and completion for the tight sandstone gas reservoirs, a series of mature advanced matching technologies have formed. Well design has witnessed a process of development from the initial single vertical wells to horizontal wells and cluster horizontal wells, and the longest horizontal segment is more than 3000m. The way of well spacing has been changed from single well drilling into the factory drilling to improve the operation efficiency. Many advanced technologies have been utilized for ROP improvement, such as unbalanced drilling, MPD and high quality drilling fluid to realize safe and fast drilling during the long lateral section. Well completion has a development from conventional acidizing technology to large-scale multi-stage fracturing, whose stimulation stage is more than 60, and the individual well production has increased by more than 45%, making low cost and high efficiency come true during the development of tight sandstone gas reservoirs. According to tight sandstone gas reservoir features in China, cluster horizontal wells factory drilling and long horizontal-section with staged fracturing transformative technology have been carried out in Changqing and Jilin Oilfield. The longest horizontal segment is 2800 m, and remoulding stage numbers are more than 25. Single well cost savings are about more than one million yuan, and the output is 3-10 times as the vertical wells. Finally remarkable application results have been achieved. The formation of these supporting technologies gradually improve drilling and completion technologies of the tight sandstone gas reservoirs in China, and it has important guiding significance to accelerating the development pace of tight sandstone gas reservoirs.