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Molecular Dynamics-Based Simulation of Polyethylene Pipe Degradation in High Temperature and High Pressure Conditions

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Fluid Dynamics & Materials Processing 2024年第9期20卷 2139-2161页

作者： Guowei Feng Qing Li Yang Wang Nan Lin Sixi Zha Hang Dong Ping Chen Minjun Zheng School of Mechanical Engineering Xinjiang UniversityUrumqi830046China xinjiang Yian Special Inspection Engineering Company Limited Urumqi830063China xinjiang Uygur autonomous region Inspection Institute of Special Equipment Urumqi830000China Pressure Pipe Department China Special Equipment Inspection and Research InstituteBeijing100013China Tarim Oilfield Branch Company Korla841000China Yimai Cai Oil and Gas Management Area Tarim Oilfield Branch OfficeKorla841000China

High-density polyethylene(HDPE)pipes have gradually become the first choice for gas networks because of their excellent *** the use of pipes increases,there will unavoidably be a significant amount of waste generated when the pipes cease their operation life,which,if improperly handled,might result in major environmental contamination *** this study,the thermal degradation of polyethylene materials is simulated for different pressures(10,50,100,and 150 MPa)and temperatures(2300,2500,2700,and 2900 K)in the framework of Reactive Force Field(ReaxFF)molecular dynamics *** main gas products,density,energy,and the mean square displacement with temperature and pressure are also *** findings indicate that raising the temperature leads to an increase in the production of gas products,while changing the pressure has an impact on the direction in which the products are generated;the faster the temperature drops,the less dense the air;both temperature and pressure increase impact the system’s energy conversion or distribution mechanism,changing the system’s potential energy as well as its total energy;the rate at which molecules diffuse increases with temperature,and decreases with *** results of this investigation provide a theoretical basis for the development of the pyrolytic treatment of polyethylene waste materials.

关键词： ReaxFF MD high-density polyethylene degradation temperature pressure

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Spatial distribution features of sequence types of moderate and strong earthquake in Chinese mainland

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Acta Seismologica Sinica(English Edition) 2006年第4期19卷 417-427页

作者：蒋海昆李永莉曲延军华爱军郑建常代磊侯海峰 earthquake administration of Shandong Province earthquake administration of xinjiang autonomous region earthquake administration of Yunnan Province

Based on 294 earthquake sequences with magnitude greater than or equal to 5.0 occurred in Chinese mainland since 1970, the spatial distribution features of sequence types have been studied. In southwestern China, it takes mainshock-aftershock sequence type （MAT） as the major in Chuan-Dian rhombic block and concerned Xianshuihe-Anninghe-Xiaojiang seismic belt, as well as in Jinshajiang-Honghe seismic belt. Multiple mainshock type （MMT） mainly distributes in western Yunnan, and Longlin and Lancang areas in Tengchong-Baoshan block in west of Nujiang-Lancangjiang fault zone. A few isolated earthquake type （IET） mainly occurred in northwestern Sichuan and there is no IET occurred in Yunnan region. In northwestern China, it takes mainshock-aftershock sequence type （MAT） as the major in west segment of South Tianshan in xinjiang region. Some MMT also occurred in this area in the intersection of Kalpin block and the Puchang fault zone. It takes IET as the major in middle Tianshan in xinjiang. Along the Qilianshan seismic belt, most of sequences are MAT. In Qinghai region, it takes MAT as the major, but the regional feature of the spatial distribution of sequence types is not very clear. In North China, it takes MAT as the major in Yinshan-Yanshan-Bohai seismic belt, north edge of North China, and in Hebei plain seismic belt, as well as in sub-plate of lower river area of Yangtze River. In intersection of north segment of Shanxi seismic belt and the NW-trending Yinshan-Yanshan-Bohai seismic belt, there are several moderate or strong MMT with magnitude from 5.0 to 6.0 occurred. In south of North China around the latitude line of 35°N, it takes IET as the major. The spatial distribution of sequence types is relevant to the patterns of tectonic movements. MAT is mostly produced by the ruptures of locked units or asperities or the neonatal separating segments inside the fault zones. MMT is generally relevant to the conjugate structures or intersection of many tectonic settings.

关键词： spatial distribution of sequence types isolated earthquake malnshock-aftershock sequence multi-ple malnshock type patterns of tectonic movement medium environment in depth of the earth

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Anisotropic zoning in the upper crust of the Tianshan Tectonic Belt

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Science China Earth Sciences 2021年第4期64卷 651-666页

作者： Jin LI Yuan GAO Qiong WANG earthquake administration of xinjiang Uygur autonomous region Urumqi 830011China Key Laboratory of earthquake Prediction Institute of Earthquake ForecastingChina Earthquake AdministrationBeijing 100036China

The Tianshan Tectonic Belt is an intracontinental orogenic belt formed by continental convergence that has undergone long-term tectonic evolution. The reactivation that began during the Cenozoic Period has led to complex structural changes. The goals of this study are to review the seismic observational data obtained during 2009–2019 in the xinjiang regional seismic network and analyze the anisotropy of the upper crust in the Tianshan area. Therefore, a shear-wave splitting system was adopted to collect and analyze shear-wave splitting parameters of 33 stations in the study area. The anisotropy of the upper crust of the Tianshan is spatially diverse, and the dominant polarization directions of fast shear-wave reflect the spatial variations of regional tectonic stress. In addition, the time delays of slow waves are proportional to the intensities of anisotropy in the upper crustal medium. The dominant polarization direction of the fast waves in the western segment of the North Tianshan Mountain,northwestern corner of the Tarim Basin, and northeastern edge of Pamir is consistent with the tectonic stress fields in the area. In the northern part of the Keping Block, the dominant polarization directions of the fast waves are consistent with the fault trends;however, they are at a high angle to the dominant directions of the regional tectonic stress field indicating that the anisotropy is affected by the faults in the area. The anisotropy of the eastern segment of the South Tianshan Mountains and the surrounding area of Urumqi are affected by the local stress field and fault structure. The polarization directions at some of the stations are subparallel to the directions of the regional principal stress. However, for other stations, the polarization directions are aligned with the neighboring faults. The polarization directions of the fast waves in most of the study area are consistent with the local tectonic stress fields. Thus, stress compression phenomena such as the Ta

关键词： Tianshan Tectonic Belt Seismic anisotropy Shear-wave splitting Tectonic stress

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Complex complete quadratic combination method for damped system with repeated eigenvalues

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earthquake Engineering and Engineering Vibration 2016年第3期15卷 537-550页

作者： Yu Ruifang Zhou Xiyuan Abduwaris Abduwahit Institute of Geophysics China Earthquake AdministrationBeijingChina Beijing University of Technology BeijingChina earthquake administration of xinjiang Uyghur autonomous region Wulumuqi 830011China

A new response-spectrum mode superposition method, entirely in real value form, is developed to analyze the maximum structural response under earthquake ground motion for generally damped linear systems with repeated eigenvalues and defective eigenvectors. This algorithm has clear physical concepts and is similar to the complex complete quadratic combination （CCQC） method previously established. Since it can consider the effect of repeated eigenvalues, it is called the CCQC-R method, in which the correlation coefficients of high-order modal responses are enclosed in addition to the correlation coefficients in the normal CCQC method. As a result, the formulas for calculating the correlation coefficients of high-order modal responses are deduced in this study, including displacement, velocity and velocity-displacement correlation coefficients. Furthermore, the relationship between high-order displacement and velocity covariance is derived to make the CCQC-R algorithm only relevant to the high-order displacement response spectrum. Finally, a practical step-by-step integration procedure for calculating high-order displacement response spectrum is obtained by changing the earthquake ground motion input, which is evaluated by comparing it to the theory solution under the sine-wave input. The method derived here is suitable for generally linear systems with classical or non-classical damping.

关键词： damped system repeated eigenvalue response spectrum complex complete quadratic combination correlation coefficient high-order modal responses

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S wave inelastic attenuation and site effect in the northern Tianshan area

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Acta Seismologica Sinica(English Edition) 2007年第2期20卷 188-193页

作者：姜慧高孟潭俞言祥唐丽华 earthquake administration of Guangdong Province Institute of Geophysics China Earthquake Administration earthquake administration of xinjiang Uygur autonomous region

In this paper, according to the relationship of observation spectrum with source spectrum, travel-path attenuation factor and site effect, we use the digital seismic data of moderate-small earthquakes to invert the soft rock site effect and S wave inelastic attenuation under the constraint of site effect, and determine the parameters of path and site. The parameters obtained by this method exclude the topographic effect of seismic stations, and truly reflect the seismic effect of free soft rock sites and the S wave inelastic attenuation in the studied region. The average soft rock site effect is about 1.5 times in the frequency domain of 2-4 Hz and the S wave quality factor is obtained as Qs=278f0.346, which can be directly applied to the stochastic modeling of ground motions in the studied region.

关键词： S wave quality factor site effect inelastic attenuation northern Tianshan area

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The deformation pattern and fault rate in the Tianshan Mountains inferred from GPS observations

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Science China Earth Sciences 2008年第8期51卷 1064-1080页

作者： YANG ShaoMin1,2, LI Jie1,3 & WANG Qi2,1 1 Research Center of Space Science and Technology, China University of Geosciences, Wuhan 430074, China 2 Institute of Seismology, China earthquake administration, Wuhan 430071, China 3 earthquake administration of xinjiang Uygur autonomous region, Urumqi 830011, China Research Center of Space Science and Technology China University of Geosciences Institute of Seismology China Earthquake Administration earthquake administration of xinjiang Uygur autonomous region

Based on GPS measurements conducted from 1992 to 2006, we present the current crustal movement velocity field for approximately 400 sites in the Tianshan Mountains and their adjacent areas, and estimate slip rates on the major faults using a 2-D elastic dislocation model. Our studies show slip rates within the range of 1―4 mm/a on the NW-SE trending strike-slip faults (such as Talas-Fergana fault) in the Tianshan Mountains. We also found the slip rates on the approximately WE-SN trending gently-dipping detachment fault vary from 10―13 mm/a for the southwest Tianshan Mountains to 2―5 mm/a for the eastern Tianshan Mountains, and to 6―12 mm/a for the Kyrgrz Tianshan. The GPS velocity field reveals that the total convergence is not uniformly distributed across the Tianshan Mountains, with 80%―90% of the N-S shortening absorbed along the southern and northern edges, and relatively little deformation accommodated within the interior. This first-order feature of strain pattern is explained best by underthrusting of adjacent blocks beneath the Tianshan Mountains along a basal detachment fault. We found the occurrence of historical M7―8 earthquakes somewhere in the locked ramp that connects the creeping and locking segments of the detachment, thereby resulting in elastic strain concentration and accumulation around it. The elastic strain confined in the upper crustal layer above the detachment ultimately releases through infrequent great earthquakes in the Tianshan Mountains, resulting in considerable folding and faulting at their margins. The Tianshan Mountains propagated outward and rose progressively as a wedge-shaped block.

关键词： Tianshan Mountains GPS slip rates tectonic deformation

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Features and mechanism of neotectonic deformation of the Xishan fault system west of Urumqi

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earthquake Science 2009年第1期22卷 69-74页

作者： Chuanyong Wu Jun Shen Jun Li Zhiyong Xiang Jun Hu Yili Ya'er earthquake administration of xinjiang Uygur autonomous region Urumqi 830011 China

We have made careful field investigation and trench exploration to the Xishan fault system in west of Urumqi, and an integrated analysis in conjunction with data of deep seismic sounding. Our result suggests that under the SN-oriented compressive stress, the Xishan block moves steadily toward the Tianshan Mountains in south, resulting in southward thrust-slip and crustal shortening, particularly the southward thrust of the Xishan fault which serves as the main boundary in south. North of the Xishan fault are the Wangjiagou fault and Jiujiawan fault which are the secondary faults associated with the Xishan fault in generation. Both faults have slippage along horizons during the uplift of the Xishan block, and the Jiujiawan fault has also a component of normal faulting due to the influence of the Bogeda nappe structure. These two faults accommodate the fold deformation of the hanging wall of the Xishan fault, thus the Xishan fault-bounded swell is characterized by monocline. All secondary faults of the Xishan fault system constitute a common seismogenic structural system, so that their seismic hazards should be considered in an equal manner.

关键词： Urumqi Xishan fault system neotectonic deformation deformation mechanism

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Statistical features of aftershock distribution size for moderate and large earthquakes in Chinese mainland

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Acta Seismologica Sinica(English Edition) 2007年第2期20卷 158-171页

作者：蒋海昆郑建常吴琼曲延军李永莉代磊 China earthquake Networks Center China Earthquake Administration earthquake administration of Shandong Province earthquake administration of xinjiang Uygur autonomous region earthquake administration of Yunnan Province

Based on data of earthquake sequences with Ms≥5.0 in Chinese mainland from 1970 to 2004, for different sequence types and different rupture modes of the main shock, the relationship between aftershock distribution size R and the magnitude of the main shock Mo has been studied statistically. Considering the rupture mode of the main shock, we give the quantitative statistical relationships between R and Mo under 95% confidence level for different sequence typos. Qualitatively, lgR, the logarithm of the aftershock distribution size, is positively correlative to the M0, but the data distribution is dispersed. Viewing from different sequence typos, the correlation between R and M0 is very weak for isolated earthquake type （lET） sequence, R distributes in the range from 5 to 60 km; For mainshock-aftershock type （MAT）, lgR is positively correlative to M0; For multiple main shock type （MMT）, the corelation between lgR and M0 is not very obvious when M0≤6.2 and R distributes in the range from 5 to 70 km, while it shows a linear correlation when M0≥6.3. The statistical results also show that the occupational ratios of different sequence types for strike-slip and oblique slip are almost the same. But for dip-slip （mostly are thrust mechanisms）, the ratio of MAT is higher than that of IET and MMT. Comparing with previous results, it indicates that, when M0 is large enough, R is mainly determined by M0 and there is almost no relationship with the rupture mode of the main shock.

关键词： Chinese mainland aftershock distribution size types of aftershock sequences rupture mode ofthe main shock

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Analysis on Characteristics of Focal Mechanisms for the M_S7.3 Yutian earthquake Sequence of February 12,2014

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earthquake Research in China 2015年第4期29卷 527-538页

作者： Li Jin Wang Qiong earthquake administration of xinjiang Uygur autonomous region

The paper inverts the focal mechanism solutions of the Yutian M_S7. 3 main shock,foreshocks and M_S≥3. 5 aftershocks by using the CAP method,based on the broadband waveforms recorded by the xinjiang and Tibet Digital Seismic Networks. The results show that the M_S7. 3 strong earthquake is of strike-slip type with a normal faulting component,and combined with the analysis of focal structure and the aftershock distribution,the nodal plane I with strike 241°,dip 90° and rake- 22° is considered to be the seismogenic fault plane of the main shock. The direction of P-axis for the main shock is 194°,close to the near NS direction of the principal stress P-axis of historical strong earthquakes in this region. The focal mechanism solution of the M_S5. 4 foreshock has a good consistency with that of the main shock. Among the 18 aftershocks,10 are of strike-slip type,6 are of normal faulting type and 2 are of thrust type. 70% of the aftershocks in the sequence have a focal mechanism with P-axis in the near-NS direction. The focal depths of this M_S7. 3 earthquake sequences are distributed in the range of 5km- 28 km,with the majority in the depth range of 15km- 20 km,slightly deeper than the depth of 10 km of the main shock as calculated.

关键词： Yutian MS7.3 earthquake Focal mechanism CAP method Aftershock

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Study on Critical Slowing Down Phenomenon before the Two Medium-strong earthquakes in xinjiang

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earthquake Research Advances 2015年第3期29卷 394-403页

作者： Gao Lijuan Yang Youling Liu Jianming Zhu Chengying earthquake administration of xinjiang Uyghur autonomous region

We study the critical slowing down phenomenon in deformation and groundwater observations before the Nilka-Gongliu MS6. 0 earthquake on November 1, 2011 and Xinyuan-Hejing M S6. 6 earthquake on June 30,2012. Firstly,we remove the annual variation and tendency change of basic data by means of wavelet transform ***,we calculate the autocorrelation coefficients and variance of the critical slowing down phenomenon. Lastly,we try to verify the critical slowing down phenomenon before an earthquake. The result indicates that there was obvious critical slowing down of the records at different stations before earthquakes.

关键词： Critical slowing down Autocorrelation coefficient Variance earthquake prediction

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