The Arun mega\|antiform, a large N—S structure transversal to the tectonic trend of the E Nepal Himalaya, is a tectonic window offering a complete section of the Himalayan nappe pile, from the Lesser Himalayan zone t...The Arun mega\|antiform, a large N—S structure transversal to the tectonic trend of the E Nepal Himalaya, is a tectonic window offering a complete section of the Himalayan nappe pile, from the Lesser Himalayan zone to the Tethyan Himalaya. At the northern end of the Arun tectonic window (ATW), the Ama Drime—Nyonno Ri range of south Tibet exposes a section of that portion of the Main Central Thrust (MCT) zone and Lesser Himalayan Crystallines (LHC) which elsewhere in Nepal is concealed below the overlying Higher Himalayan Crystalline (HHC) nappe (Fig. 1). As throughout the Himalaya at the structural level of the MCT, the ATW is characterized by an inverted metamorphic field gradient characterized by a progression from chlorite to sillimanite grade from low to high structural levels of the nappe pile. Metamorphic peak temperatures rise from circa 400℃ in the pelitic and psammitic Precambrian metasediments of the Lesser Himalayan Tumlingtar Unit, to 550～620℃ in the overlying LHC, to over 700℃ in the muscovite\|free Barun Gneiss, the lowermost HHC unit in the Arun valley.展开更多
Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest ...Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest Pacific Acoustic Experiment was conducted in 2015. A low-frequency horizontal line array towed at the depth of around 150 m on a receiving ship was used to receive the noise radiated by the source ship. During this experiment, a beating-splitting phenomenon in the direct zone was observed through conventional beamforming of the horizontal line array within the frequency band 160 Hz- 360 Hz. In this paper, this phenomenon is explained based on ray theory. In principle, the received signal in the direct zone of deep water arrives from two general paths including a direct one and bottom bounced one, which vary considerably in arrival angles. The split bearings correspond to the contributions of these two paths. The beating-splitting phenomenon is demonstrated by numerical simulations of the bearing-time records and experimental results, and they are well consistent with each other. Then a near-surface source ranging approach based on the arrival angles of direct path and bottom bounced path in the direct zone is presented as an application of bearing splitting and is verified by experimental results. Finally, the applicability of the proposed ranging approach for an underwater source within several hundred meters in depth in the direct zone is also analyzed and demonstrated by simulations.展开更多
Continent-continent collision is the most important driving mechanism for the occurrence of various geological processes in the continental lithosphere. How to recognize and determine continent-continent collision, es...Continent-continent collision is the most important driving mechanism for the occurrence of various geological processes in the continental lithosphere. How to recognize and determine continent-continent collision, especially its four-dimensional temporal-spatial evolution, is a subject that geological communities have long been concerned about and studied. Continent-continent collision is mainly manifested by strong underthrusting (subduction) of the underlying block along an intracontinental subduction zone and continuous obduction (thrusting propagation) of the overlying block along the intracontinental subduction zone, the occurrence of a basin-range tectonic framework in a direction perpendicular to the subduction zone and the flexure and disruption of the Moho. On the basis of numerical modeling, the authors discuss in detail the couplings between various amounts and rates of displacement caused by basin subsidence, mountain uplift and Moho updoming and downflexure during obduction (thrusting propagation) and subduction and the migration pattern of basin centers. They are probably indications or criteria for judgment or determination of continent-continent collision.展开更多
Based on the theories of shock wave and energy,this paper inquires into the effect range of shock wave in rock blasting with cylindrical coupling charges, and a new method for calculating the effect range is developed...Based on the theories of shock wave and energy,this paper inquires into the effect range of shock wave in rock blasting with cylindrical coupling charges, and a new method for calculating the effect range is developed. A calculation example sbows that the new method is reasonable.展开更多
The high frequency hybrid technique based on an iterative Physical Optics(PC)) and the method of equivalent current (MEC) approach is developed for predicting rangeresolution of the Radar Cross Section (RCS) in the sp...The high frequency hybrid technique based on an iterative Physical Optics(PC)) and the method of equivalent current (MEC) approach is developed for predicting rangeresolution of the Radar Cross Section (RCS) in the spatial domain. We introduce the hybrid highfrequency method to simulate range resolution of the extremely large target in the near zone. Thispaper applies this method to simulate the range resolution of the two 1 m X 1 m plates and the ship.The study improves the speed of simulatingthe range resolution of the extremely large target and isprepared for the application of the extrapolation and interpolation in the spatial domain.展开更多
缅甸作为全球受地震灾害影响甚为严重的国家之一,因缺乏区域地震观测资料,对其孕震构造环境的详细分析研究十分不足.本文利用中缅联合地球物理探测(CMGSMO)项目在缅甸布设的密集宽频带地震台阵观测数据,对印缅山脉至中央盆地的地震活动...缅甸作为全球受地震灾害影响甚为严重的国家之一,因缺乏区域地震观测资料,对其孕震构造环境的详细分析研究十分不足.本文利用中缅联合地球物理探测(CMGSMO)项目在缅甸布设的密集宽频带地震台阵观测数据,对印缅山脉至中央盆地的地震活动特征进行了分析.基于改进的剪切-粘贴法(generalized Cut And Paste,gCAP)新获得了28个ML3.0~5.0地震事件的震源机制解等震源参数信息,并结合全球矩心矩张量(Global Centroid Moment Tensor,GCMT)目录及其他已发表的震源机制解资料,应用区域阻尼应力场反演算法得到了研究区的应力分布状态,综合探讨了研究区域深浅部构造关系及孕震机制.研究表明印度板块持续的斜向俯冲控制着印缅山脉和中央盆地的地震活动,但其影响向东逐渐减弱,浅部最大主应力方向的变化可能反映的是局部应力集中或者是相对短时间内的应力调整,不同区域的地震活动差异主要受区域构造及其浅部断层的影响,中央盆地下方的两个邻区之间的最大主应力轴的偏转可能与深部活动相关.展开更多
With the loss of substantial natural wetlands in coastal zones,artificial wetlands provide alternative habitats for many shorebirds.Scientific management of artificial wetlands used by shorebirds plays an important ro...With the loss of substantial natural wetlands in coastal zones,artificial wetlands provide alternative habitats for many shorebirds.Scientific management of artificial wetlands used by shorebirds plays an important role in maintaining the stability of shorebird population.Satellite tracking technique can obtain high-precision location information of individuals day and night,providing a good technical support for the study of quantitative relationship between waterfowls and their habitats.In this study,satellite tracking method,Remote Sensing(RS)and Geographic Information System(GIS)technology were used to analyze the activity pattern and habitat utilization characteristics of Pied Avocet during breeding period in an artificial wetland complex in the Yellow River Delta(YRD),China.The results showed that the breeding Pied Avocets had a small range of activity,with a total core and main home range of 33.10 km^(2) and 216.30 km^(2),respectively.This species tended to forage in the pond and salt pan during the day and night,respectively,with an unfixed staying time in the breeding ground.The distance between breeding ground and feeding ground was less than 6 km.It is emphasized that in addition to improving the conditions of the remaining natural habitats,effective managing artificial habitats is a priority for shorebird conservation.This research could provide reference for the management of artificial wetlands in coastal zones and supply technique support for the protection of shorebirds and their habitats,and alleviate human-bird conflicts and sustainable development of coastal zones.展开更多
文摘The Arun mega\|antiform, a large N—S structure transversal to the tectonic trend of the E Nepal Himalaya, is a tectonic window offering a complete section of the Himalayan nappe pile, from the Lesser Himalayan zone to the Tethyan Himalaya. At the northern end of the Arun tectonic window (ATW), the Ama Drime—Nyonno Ri range of south Tibet exposes a section of that portion of the Main Central Thrust (MCT) zone and Lesser Himalayan Crystallines (LHC) which elsewhere in Nepal is concealed below the overlying Higher Himalayan Crystalline (HHC) nappe (Fig. 1). As throughout the Himalaya at the structural level of the MCT, the ATW is characterized by an inverted metamorphic field gradient characterized by a progression from chlorite to sillimanite grade from low to high structural levels of the nappe pile. Metamorphic peak temperatures rise from circa 400℃ in the pelitic and psammitic Precambrian metasediments of the Lesser Himalayan Tumlingtar Unit, to 550～620℃ in the overlying LHC, to over 700℃ in the muscovite\|free Barun Gneiss, the lowermost HHC unit in the Arun valley.
基金Project supported by the Program of One Hundred Talented People of the Chinese Academy of SciencesNational Natural Science Foundation of China(Grant Nos.11434012 and 41561144006)
文摘Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest Pacific Acoustic Experiment was conducted in 2015. A low-frequency horizontal line array towed at the depth of around 150 m on a receiving ship was used to receive the noise radiated by the source ship. During this experiment, a beating-splitting phenomenon in the direct zone was observed through conventional beamforming of the horizontal line array within the frequency band 160 Hz- 360 Hz. In this paper, this phenomenon is explained based on ray theory. In principle, the received signal in the direct zone of deep water arrives from two general paths including a direct one and bottom bounced one, which vary considerably in arrival angles. The split bearings correspond to the contributions of these two paths. The beating-splitting phenomenon is demonstrated by numerical simulations of the bearing-time records and experimental results, and they are well consistent with each other. Then a near-surface source ranging approach based on the arrival angles of direct path and bottom bounced path in the direct zone is presented as an application of bearing splitting and is verified by experimental results. Finally, the applicability of the proposed ranging approach for an underwater source within several hundred meters in depth in the direct zone is also analyzed and demonstrated by simulations.
基金the National Natural Science Foundation of China(grant 19972072)Project of the Open Laboratory of Continental Geodynamics of the Ministry of Land and Resources(grant 9812) Stat Project 305 rgrant 96—915—06—04).
文摘Continent-continent collision is the most important driving mechanism for the occurrence of various geological processes in the continental lithosphere. How to recognize and determine continent-continent collision, especially its four-dimensional temporal-spatial evolution, is a subject that geological communities have long been concerned about and studied. Continent-continent collision is mainly manifested by strong underthrusting (subduction) of the underlying block along an intracontinental subduction zone and continuous obduction (thrusting propagation) of the overlying block along the intracontinental subduction zone, the occurrence of a basin-range tectonic framework in a direction perpendicular to the subduction zone and the flexure and disruption of the Moho. On the basis of numerical modeling, the authors discuss in detail the couplings between various amounts and rates of displacement caused by basin subsidence, mountain uplift and Moho updoming and downflexure during obduction (thrusting propagation) and subduction and the migration pattern of basin centers. They are probably indications or criteria for judgment or determination of continent-continent collision.
文摘Based on the theories of shock wave and energy,this paper inquires into the effect range of shock wave in rock blasting with cylindrical coupling charges, and a new method for calculating the effect range is developed. A calculation example sbows that the new method is reasonable.
基金Supported by the National Natural Science Foundation of China(60301007)
文摘The high frequency hybrid technique based on an iterative Physical Optics(PC)) and the method of equivalent current (MEC) approach is developed for predicting rangeresolution of the Radar Cross Section (RCS) in the spatial domain. We introduce the hybrid highfrequency method to simulate range resolution of the extremely large target in the near zone. Thispaper applies this method to simulate the range resolution of the two 1 m X 1 m plates and the ship.The study improves the speed of simulatingthe range resolution of the extremely large target and isprepared for the application of the extrapolation and interpolation in the spatial domain.
文摘缅甸作为全球受地震灾害影响甚为严重的国家之一,因缺乏区域地震观测资料,对其孕震构造环境的详细分析研究十分不足.本文利用中缅联合地球物理探测(CMGSMO)项目在缅甸布设的密集宽频带地震台阵观测数据,对印缅山脉至中央盆地的地震活动特征进行了分析.基于改进的剪切-粘贴法(generalized Cut And Paste,gCAP)新获得了28个ML3.0~5.0地震事件的震源机制解等震源参数信息,并结合全球矩心矩张量(Global Centroid Moment Tensor,GCMT)目录及其他已发表的震源机制解资料,应用区域阻尼应力场反演算法得到了研究区的应力分布状态,综合探讨了研究区域深浅部构造关系及孕震机制.研究表明印度板块持续的斜向俯冲控制着印缅山脉和中央盆地的地震活动,但其影响向东逐渐减弱,浅部最大主应力方向的变化可能反映的是局部应力集中或者是相对短时间内的应力调整,不同区域的地震活动差异主要受区域构造及其浅部断层的影响,中央盆地下方的两个邻区之间的最大主应力轴的偏转可能与深部活动相关.
基金Under the auscpices of Shandong Provincial Natural Science Foundation (No.ZR2020QD090)Research Funds of Beijing VMinFull Limted (No.VMF2021RS)+1 种基金National Natural Science Foundation of China (No.42176221)Seed Project of Yantai Institute of Coastal Zone Research,Chinese Academy of Sciences (No.YICE351030601)。
文摘With the loss of substantial natural wetlands in coastal zones,artificial wetlands provide alternative habitats for many shorebirds.Scientific management of artificial wetlands used by shorebirds plays an important role in maintaining the stability of shorebird population.Satellite tracking technique can obtain high-precision location information of individuals day and night,providing a good technical support for the study of quantitative relationship between waterfowls and their habitats.In this study,satellite tracking method,Remote Sensing(RS)and Geographic Information System(GIS)technology were used to analyze the activity pattern and habitat utilization characteristics of Pied Avocet during breeding period in an artificial wetland complex in the Yellow River Delta(YRD),China.The results showed that the breeding Pied Avocets had a small range of activity,with a total core and main home range of 33.10 km^(2) and 216.30 km^(2),respectively.This species tended to forage in the pond and salt pan during the day and night,respectively,with an unfixed staying time in the breeding ground.The distance between breeding ground and feeding ground was less than 6 km.It is emphasized that in addition to improving the conditions of the remaining natural habitats,effective managing artificial habitats is a priority for shorebird conservation.This research could provide reference for the management of artificial wetlands in coastal zones and supply technique support for the protection of shorebirds and their habitats,and alleviate human-bird conflicts and sustainable development of coastal zones.
