期刊文献+
共找到1,471篇文章
< 1 2 74 >
每页显示 20 50 100
In-situ calibration of acoustic measurements of suspended sediment
1
作者 Guo Jijie Ren inifa and Li Yunwu( Institute of Ocean Technology, State Oceanic Administratiod, Tianjin 300ill, China) (Shangha caustics Labortory, Chinese Academy of thences, Shangha 200032, China) 《Acta Oceanologica Sinica》 SCIE CAS CSCD 1999年第4期535-542,共8页
The key to the Problems of probing the concentration of suspended sediment in water and its variationwith acoustic equiprnent is for to calibrate the Obboned data. Carbining the acoustic bebotter intensity data witht... The key to the Problems of probing the concentration of suspended sediment in water and its variationwith acoustic equiprnent is for to calibrate the Obboned data. Carbining the acoustic bebotter intensity data withthe real concentration of suspended sediment from water Samples collected for the Changjiang Estuary, three in-situcalibration metyods for transfrming transforming measured sediment are induced. Results show that the discrepancies for cali- brated values given by characteristic the calibration and real ones are less than the values given by single shot method,and the statistted are is 20% approximately. The calibration on charactedstic times is praCtical and sabler than simultaneous calibration. 展开更多
关键词 Suswted sedirnent acoustic probing in-situ calibration
下载PDF
Development of in-situ Marine Sediment Geo-Acoustic Measurement System with Real-Time and Multi Frequencies (the Second Generation) 被引量:7
2
作者 陶春辉 邓显明 +6 位作者 李红星 周建平 金肖兵 傅顺声 Wlkens R. H 顾春华 何拥华 《China Ocean Engineering》 SCIE EI 2009年第4期769-778,共10页
Compared with the laboratory acoustic measurement of sediment samples, the in-situ acoustic measurement in marine sediment is considered more accurate and rehable, because it covers all of the surrounding environment ... Compared with the laboratory acoustic measurement of sediment samples, the in-situ acoustic measurement in marine sediment is considered more accurate and rehable, because it covers all of the surrounding environment factors and avoids the disturbance during the course of sampling and transporting of sediment samples. A new multi-frequency in-situ geoacoustic measurement system (MFIS^AMS) has been developed. The system can provide acoustic vdocity (compressional wave) and attenuation profiles of the uppermost 4 - 8 m sediment in the seafloor. It consists of 8 channels with 12 frequencies (multi-frequencies) and 0.5 - 2 MHz sampling rates. The data collected can be transmiuted in real-time. Associated with inclinometer and altimeter, it can provide the data for depth emendation. Acoustic velocity and attenuation data have been obtained from two in-situ experiments conducted in the Hangzhou Bay. 展开更多
关键词 marine sediment in-situ acoustic measurement acoustic velocity and attenuation
下载PDF
Tests of new in-situ seabed acoustic measurement system in Qingdao 被引量:1
3
作者 侯正瑜 郭常升 +2 位作者 王景强 李会银 李铁刚 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2014年第5期1172-1178,共7页
A new in-situ seabed acoustic measurement system is developed for direct in-situ measurement of sediment geoacoustic properties (compressional wave velocity and attenuation). The new in-situ system consists of two p... A new in-situ seabed acoustic measurement system is developed for direct in-situ measurement of sediment geoacoustic properties (compressional wave velocity and attenuation). The new in-situ system consists of two parts: the deck control unit and the underwater measurement unit. The underwater measurement unit emits sonic waves that propagate through the seafloor sediment, receives the returning signals, and transmits them to the deck control unit for waveform display and analysis. The entire operation is controlled and monitored in real time by the deck control unit on the research vessel and can provide recording of full waveforms to determine the sound velocity and attenuation. This paper outlines the design of the system, the measurement process, and demonstrates its application in tests carded out on seabed sediment off the Qingdao coast, China. The test results show that the system performed well and rapidly provided accurate in-situ acoustic velocity and attenuation estimates of the seafloor sediment. 展开更多
关键词 seafloor sediment in-situ measurement sound velocity and attenuation.
下载PDF
Influence of Gas Hydrate on the Acoustic Properties of Sediment: A Comprehensive Review with a Focus on Experimental Measurements 被引量:1
4
作者 ZHANG Qi LIU Xin +1 位作者 HE Tao LU Hailong 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2022年第2期713-726,共14页
In recent years, natural gas hydrate has attracted increasing attention worldwide as a potential alternative energy source due to its attributes of wide distribution, large reserves, and low carbon. Since the acoustic... In recent years, natural gas hydrate has attracted increasing attention worldwide as a potential alternative energy source due to its attributes of wide distribution, large reserves, and low carbon. Since the acoustic characteristics of hydratebearing reservoirs clearly differ from those of adjacent formations, an acoustic approach, using seismic and acoustic logging, is one of the most direct, effective and widely used methods among the identification and characterization techniques for hydrate reservoir exploration. This review of research on the influence of hydrate(content and distribution) on the acoustic properties(velocity and attenuation) of sediments in the past two decades includes experimental studies based on different hydrate formation methods and measurements, as well as rock physics models. The main problems in current research are also pointed out and future prospects discussed. 展开更多
关键词 gas hydrate acoustic properties rock physics model experimental measurements
下载PDF
Simultaneous measurements of aeroacoustic sounds and wall vibration for exploring the contribution of tooth vibration in the production of sibilant sounds/s/
5
作者 Masanori Nakamura Kazunori Nozaki +3 位作者 Haruka Takimoto Kazuya Nagamune Motoharu Fujigaki Shigeo Wada 《Journal of Biomedical Science and Engineering》 2011年第2期83-89,共7页
In order to understand the contribution of teeth vibration to the production of sibilant/s/, the pre-sent study was designed to develop a method of simultaneously measuring aeroacoustic sounds and the vibration of an ... In order to understand the contribution of teeth vibration to the production of sibilant/s/, the pre-sent study was designed to develop a method of simultaneously measuring aeroacoustic sounds and the vibration of an obstacle. To measure the vibration without disturbing flow, the Michelson interferometer was employed. The flow channel, which had an obstacle wall inside of it, was fabricated such that it morphologically mimicked the simplified geometry of the oral cavity. Given airflows at a flow rate of 7.5 × 10–4 m3/s from the inlet, aeroacoustic sounds were generated. A spectrum analy-sis of the data demonstrated two prominent peaks in the sound at 1,300 and 3,500 Hz and one peak in the wall vibration at 3,500 Hz. The correlation in peak frequencies between the sound and wall vibration suggests that the sound at 3,500 Hz was induced by the wall vibration. In fact, the sound amplitude at 3,500 Hz decreased when the obstacle wall was thickened, which increased its rigidity (p < 0.05, t-test). The experimental results demonstrate that the developed techniques are capable of measuring aeroacoustic sound and obstacle wall vibration simultaneously, and suggest the potential to pave the way for detailed analysis of the production of sibilant sounds /s/. 展开更多
关键词 acoustic measurEMENT VIBRATION measurEMENT Michelson INTERFEROMETER Aeroacoustics Sibilant/s/
下载PDF
Preliminary Results of In-situ Stress Measurements along the Longmenshan Fault Zone after the Wenchuan M_s 8.0 Earthquake 被引量:32
6
作者 WU Manlu ZHANG Yueqiao +5 位作者 LIAO Chunting CHEN Qunce MA Yinsheng WU Jinsheng YAN Junfeng OU Mingyi 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2009年第4期746-753,共8页
Four months after the Wenchuan Ms 8 earthquake in western Sichuan, China, in situ stress measurements were carried out along the Longmenshan fault zone with the purpose of obtaining stress parameters for earthquake ha... Four months after the Wenchuan Ms 8 earthquake in western Sichuan, China, in situ stress measurements were carried out along the Longmenshan fault zone with the purpose of obtaining stress parameters for earthquake hazard assessment. In-situ stresses were measured in three new boreholes by using overcoring with the piezomagnetic stress gauges for shallow depths and hydraulic fracturing for lower depths. The maximum horizontal stress in shallow depths (-20 m) is about 4.3 MPa, oriented N19°E, in the epicenter area at Yingxiu Town, about 9.7 MPa, oriented N51°W, at Baoxing County in the southwestern Longmenshan range, and about 2.6 MPa, oriented N39°E, near Kangding in the southernmost zone of the Longmenshan range. Hydraulic fracturing at borehole depths from 100 to 400 m shows a tendency towards increasing stress with depth. A comparison with the results measured before the Wenchuan earthquake along the Longmenshan zone and in the Tibetan Plateau demonstrates that the stress level remains relatively high in the southwestern segment of the Longmenshan range, and is still moderate in the epicenter zone. These results provide a key appraisal for future assessment of earthquake hazards of the Longmenshan fault zone and the aftershock occurrences of the Wenchuan earthquake. 展开更多
关键词 Wenchuan Ms 8.0 earthquake in-situ stress measurement overcoring hydraulic fracturing Longmenshan fault belt
下载PDF
Experiments on acoustic measurement of fractured rocks and application of acoustic logging data to evaluation of fractures 被引量:4
7
作者 Bao-Zhi Pan Ming-Xin Yuan +3 位作者 Chun-Hui Fang Wen-Bin Liu Yu-Hang Guo Li-Hua Zhang 《Petroleum Science》 SCIE CAS CSCD 2017年第3期520-528,共9页
Fractures in oil and gas reservoirs have been the topic of many studies and have attracted reservoir research all over the world. Because of the complexities of the fractures, it is difficult to use fractured reservoi... Fractures in oil and gas reservoirs have been the topic of many studies and have attracted reservoir research all over the world. Because of the complexities of the fractures, it is difficult to use fractured reservoir core samples to investigate true underground conditions. Due to the diversity of the fracture parameters, the simulation and evaluation of fractured rock in the laboratory setting is also difficult. Previous researchers have typically used a single material, such as resin, to simulate fractures. There has been a great deal of simplifying of the materials and conditions, which has led to disappointing results in application. In the present study, sandstone core samples were selected and sectioned to simulate fractures, and the changes of the compressional and shear waves were measured with the gradual increasing of the fracture width. The effects of the simulated fracture width on the acoustic wave velocity and amplitude were analyzed. Two variables were defined: H represents the amplitude attenuation ratio of the compressional and shear wave, and x represents the transit time difference value of the shear wave and compressional wave divided by the transit time of the compressional wave. The effect of fracture width on these two physical quantities was then analyzed. Finally, the methods of quantitative evaluation for fracture width with H and x were obtained. The experimental results showed that the rock fractures linearly reduced the velocity of the shear and compressional waves. The effect of twin fractures on thecompressional velocity was almost equal to that of a single fracture which had the same fracture width as the sum of the twin fractures. At the same time, the existence of fractures led to acoustic wave amplitude attenuations, and the compressional wave attenuation was two times greater than that of the shear wave. In this paper, a method was proposed to calculate the fracture width with x and H, then this was applied to the array acoustic imaging logging data.The application examples showed that the calculated fracture width could be compared with fractures on the electric imaging logs. These rules were applied in the well logs to effectively evaluate the fractures, under the case of no image logs, which had significance to prospecting and development of oil and gas in fractured reservoirs. 展开更多
关键词 Fractured rockacoustic wave amplitude Fracture width acoustic wave velocity Experimental measurement
下载PDF
Self-contained in situ sediment acoustic measurement system based on hydraulic driving penetration 被引量:9
8
作者 Kan Guangming Liu Baohua +2 位作者 Zhao Yuexia Li Guanbao Pei Yanliang 《High Technology Letters》 EI CAS 2011年第3期311-316,共6页
A novel self-contained in situ sediment acoustic measurement system based on hydraulic driving penetration is proposed to solve the problem of large disturbances to sediments of the in situ equipments already in exist... A novel self-contained in situ sediment acoustic measurement system based on hydraulic driving penetration is proposed to solve the problem of large disturbances to sediments of the in situ equipments already in existence. By using a hydraulic driving device, the system drives four acoustic probes into sediments at an even speed, and this decreases disturbances to sediments introduced by the penetration of acoustic probes. By means of the special design of the central control unit, the system can work full-automatically and the data are stored self-containedly, and this avoids the requirement of real-time remote controlling from the ship. Its operating water depth, measuring depth and measuring frequency is 500m, 1.0m and 30kHz respectively. A set of in situ sound speeds and attenuation coefficients of sediments are obtained at 40 stations using the system. The results confirm that the data obtained by the in situ sediment acoustic system are accurate and credible. 展开更多
关键词 acoustic properties sound speed sound attenuation in situ measurement system
下载PDF
In-situ 3D contour measurement for laser powder bed fusion based on phase guidance
9
作者 Yuze Zhang Pan Zhang +3 位作者 Xin Jiang Siyuan Zhang Kai Zhong Zhongwei Li 《Theoretical & Applied Mechanics Letters》 CAS CSCD 2023年第2期113-119,共7页
In-situ layerwise imaging measurement of laser powder bed fusion(LPBF)provides a wealth of forming and defect data which enables monitoring of components quality and powder bed homogeneity.Using high-resolution camera... In-situ layerwise imaging measurement of laser powder bed fusion(LPBF)provides a wealth of forming and defect data which enables monitoring of components quality and powder bed homogeneity.Using high-resolution camera layerwise imaging and image processing algorithms to monitor fusion area and powder bed geometric defects has been studied by many researchers,which successfully monitored the contours of components and evaluated their accuracy.However,research for the methods of in-situ 3D contour measurement or component edge warping identification is rare.In this study,a 3D contour mea-surement method combining gray intensity and phase difference is proposed,and its accuracy is verified by designed experiments.The results show that the high-precision of the 3D contours can be achieved by the constructed energy minimization function.This method can detect the deviations of common ge-ometric features as well as warpage at LPBF component edges,and provides fundamental data for in-situ quality monitoring tools. 展开更多
关键词 Laser powder bed fusion in-situ measurement Active contours 3D contour measurement accuracy
下载PDF
A New Method for In-Situ Measurement of Internal Solitary Waves Based on the Stimulated Raman Scattering in Optical Fibers
10
作者 WANG Jing ZHANG Meng +4 位作者 MIAO Xiangying YANG Zhonghao LI Zhixin HUO Dianheng MIAO Hongli 《Journal of Ocean University of China》 SCIE CAS CSCD 2023年第3期658-664,共7页
In-situ measurement of internal solitary waves(ISWs)is complicated in the ocean due to their randomness.At present,the ISWs are mainly detected by the chain structure of conductivity-temperature-depth systems(CTDs)or ... In-situ measurement of internal solitary waves(ISWs)is complicated in the ocean due to their randomness.At present,the ISWs are mainly detected by the chain structure of conductivity-temperature-depth systems(CTDs)or temperature sensors.The high cost limits the spatial resolution,which ultimately affects the measuring accuracy of the ISW amplitude.In this paper,we developed an experimental measurement system for detecting ISWs based on the stimulated Raman scattering in distributed optical fibers.This system has the advantages of high precision,low cost,and easy operation.The experimental results show that the system is consistent with CTDs in the measurement of vertical ocean temperature variation.The spatial resolution of the system can reach 1.0 m and the measuring accuracy of temperature is 0.2℃.We successfully detected 3 ISWs by the system in the South China Sea and two optical remote sensing images collected on May 18,2021,the same day of two detected ISWs,verify the occurrence of the measured ISWs.We used the image pairs method to calculate the phase velocity of ISW and the result is 1.71 ms^(-1).By extracting the distances between wave packets,it can be found that the semi-diurnal tide generates the detected ISWs.The impact of the tidal current velocity on the ISW in amplitude is undeniable.Undoubtedly,the system has a great application prospect for detecting ISWs and other dynamic phenomena in the ocean. 展开更多
关键词 internal solitary wave optical fiber stimulated Raman scattering in-situ measurement
下载PDF
Analysis and measurement of acoustic power in plastics ultrasonic welding process 被引量:1
11
作者 闫久春 李冬青 +1 位作者 董震 杨士勤 《China Welding》 EI CAS 1998年第2期29-34,共6页
A measuring principle for acoustic power in plastics ultrasonic welding process is introduced in this paper. Signal detection circuits of current, voltage, frequency, power for ultrasonic transducer of plastic ultraso... A measuring principle for acoustic power in plastics ultrasonic welding process is introduced in this paper. Signal detection circuits of current, voltage, frequency, power for ultrasonic transducer of plastic ultrasonic welder are developed. A computer controlled measuring system is designed to sample the signals of welding process parameters. By using the designed system, the acoustic power curve during welding is calculated, saved, and displayed. And the relation between fusion state of plastics workpieces and input energy of joint is analyzed. 展开更多
关键词 ultrasonic welding acoustic power power measurement
下载PDF
基于CATT-Acoustic及Cadna/A声学模拟仿真模型的城区典型变电站噪声预测及综合治理研究 被引量:1
12
作者 雷强 邵心元 +1 位作者 徐娟 郑庆梦 《电工技术》 2023年第13期54-57,62,共5页
分析了变电站主变压器、电抗器及散热风机等主要噪声源的发声特性及其传播属性,通过CATT-Acoustic及Cadna/A进行变电站声学模拟仿真噪声预测,综合考虑降噪效果与经济指标,提出针对规范中2类声环境区和1类声环境区噪声排放限制的达标设... 分析了变电站主变压器、电抗器及散热风机等主要噪声源的发声特性及其传播属性,通过CATT-Acoustic及Cadna/A进行变电站声学模拟仿真噪声预测,综合考虑降噪效果与经济指标,提出针对规范中2类声环境区和1类声环境区噪声排放限制的达标设计方案,并提出在设计阶段优先考虑合理的平面布局、在设备购置时充分考虑低噪声的性能、设备室的吸声处理与隔声处理、通风散热通道的消声处理、门窗的隔声处理等综合治理措施。 展开更多
关键词 变电站 噪声污染 降噪措施 CATT-acoustic Cadna/A
下载PDF
Influences of clean fracturing fluid viscosity and horizontal in-situ stress difference on hydraulic fracture propagation and morphology in coal seam
13
作者 Gang Wang Shuxin Wang +5 位作者 Yixin Liu Qiming Huang Shengpeng Li Shuliang Xie Jinye Zheng Jiuyuan Fan 《International Journal of Coal Science & Technology》 EI CAS CSCD 2024年第3期159-175,共17页
The viscosity of fracturing fluid and in-situ stress difference are the two important factors that affect the hydraulic fracturing pressure and propagation morphology. In this study, raw coal was used to prepare coal ... The viscosity of fracturing fluid and in-situ stress difference are the two important factors that affect the hydraulic fracturing pressure and propagation morphology. In this study, raw coal was used to prepare coal samples for experiments, and clean fracturing fluid samples were prepared using CTAB surfactant. A series of hydraulic fracturing tests were conducted with an in-house developed triaxial hydraulic fracturing simulator and the fracturing process was monitored with an acoustic emission instrument to analyze the influences of fracturing fluid viscosity and horizontal in-situ stress difference on coal fracture propagation. The results show that the number of branched fractures decreased, the fracture pattern became simpler, the fractures width increased obviously, and the distribution of AE event points was concentrated with the increase of the fracturing fluid viscosity or the horizontal in-situ stress difference. The acoustic emission energy decreases with the increase of fracturing fluid viscosity and increases with the increase of horizontal in situ stress difference. The low viscosity clean fracturing fluid has strong elasticity and is easy to be compressed into the tip of fractures, resulting in complex fractures. The high viscosity clean fracturing fluids are the opposite. Our experimental results provide a reference and scientific basis for the design and optimization of field hydraulic fracturing parameters. 展开更多
关键词 Clean fracturing fluid Hydraulic fracturing VISCOSITY Horizontal in-situ stress difference Hydraulic fracture morphology acoustic emission
下载PDF
Development of Instrumentation for the Measurement of the Performance of Acoustic Absorbers
14
作者 James Christopher Johnston Maria A. Kuczmarski Garth Olszko 《Open Journal of Acoustics》 2015年第4期172-192,共21页
In both fixed and rotary wing aircraft, the move toward lighter structures has resulted in an increase in structural vibration and interior noise. Porous materials have been proposed as acoustic absorbers to reduce th... In both fixed and rotary wing aircraft, the move toward lighter structures has resulted in an increase in structural vibration and interior noise. Porous materials have been proposed as acoustic absorbers to reduce this noise. This paper discusses the development of equipment at the NASA Glenn Research Center for characterizing the acoustic performance of porous materials: a flow resistance apparatus to measure the pressure drop across a specimen of porous material, and a standing wave tube that uses a pair of stationary microphones to measure the normal incidence acoustic impedance of a porous material specimen. Specific attention is paid to making this equipment as flexible as possible in terms of specimen sizes need for testing to accommodate the small or irregular sizes often produced during the development phase of a new material. In addition, due to the unknown performance of newly developed material, safety features are included on the flow resistance apparatus to contain test specimens that shed particles or catastrophically fail during testing. Results of measurements on aircraft fiberglass are presented to verify the correct performance of the equipment. 展开更多
关键词 acoustic IMPEDANCE acoustic measurement acoustic ATTENUATION
下载PDF
PROGRESS OF ACOUSTIC WAVE TECHNIQUE ANDITS APPLICATION IN UNDERGROUND PRESSURE MEASUREMENT
15
作者 周楚良 李新元 张晓龙 《Journal of China University of Mining and Technology》 1994年第1期80-91,共12页
This paper carries out tbe experirnent study on the correlation between am stress-strain process of rock samples and the acoustie parameter change of rock by using the measurement system of KS acoustic wave data proce... This paper carries out tbe experirnent study on the correlation between am stress-strain process of rock samples and the acoustie parameter change of rock by using the measurement system of KS acoustic wave data processing device. On the spot, the stability of surrounding rock is studied by means of experiments on the relationship between the change process (from elastie to plastic failure zone) in surrounding rock of roadway and the change law of acoustic parameters of rock. These acoustie parameters inelude wave amplitude, spectral amplitude, spectrum area, spectral density,wave veloeity and attenuation coefficient etc. 展开更多
关键词 acoustic wave technique underground pressure measurement rockmass stability
下载PDF
In-situ measurement and distribution of flue gas mercury for a utility PC boiler system 被引量:3
16
作者 段钰锋 Cao Yan +3 位作者 Shawn Kellie Kunlei Liu John Riley Weiping Pan 《Journal of Southeast University(English Edition)》 EI CAS 2005年第1期53-57,共5页
The in-situ instrumentation technique for measuring mercury and itsspeciation downstream a utility 100 MW pulverized coal (PC) fired boiler system was developed andconducted by the use of the Ontario hydro method (OHM... The in-situ instrumentation technique for measuring mercury and itsspeciation downstream a utility 100 MW pulverized coal (PC) fired boiler system was developed andconducted by the use of the Ontario hydro method (OHM) consistent with American standard test methodtogether with the semi-continuous emissions monitoring (SCEM) system as well as a mobile laboratoryfor mercury monitoring. The mercury and its speciation concentrations including participate mercuryat three locations of before air preheater, before electrostatic precipitator (ESP) and after ESPwere measured using the OHM and SCEM methods under normal operation conditions of the boiler systemas a result of firing a bituminous coal. The vapor-phase total mercury Hg(VT) concentration declinedwith the decrease of flue gas temperature because of mercury species transformation from oxidizedmercury to particulate mercury as the flue gas moved downstream from the air preheater to the ESPand after the ESP. A good agreement for Hg°, Hg^(2+) and Hg( VT) was obtained between the twomethods in the ash-free area. But in the dense particle-laden flue gas area, there appeared to be abig bias for mercury speciation owing to dust cake formed in the filter of OHM sampling probe. Theparticulateaffinity to the flue gas mercury and the impacts of sampling condition to accuracy ofmeasure were discussed. 展开更多
关键词 coal fired flue gas mercury speciation in-situ measurement Ontario hydromethod (OHM) semi-continuous emissions monitoring (SCEM)
下载PDF
A distributed measurement method for in-situ soil moisture content by using carbon-fiber heated cable 被引量:14
17
作者 Dingfeng Cao Bin Shi +3 位作者 Honghu Zhu Guangqing Wei Shen-En Chen Junfan Yan 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2015年第6期700-707,共8页
Moisture content is a fundamental physical index that quantifies soil property and is closely associatedwith the hydrological, ecological and engineering behaviors of soil. To measure in-situ soil moisturecontents, a ... Moisture content is a fundamental physical index that quantifies soil property and is closely associatedwith the hydrological, ecological and engineering behaviors of soil. To measure in-situ soil moisturecontents, a distributed measurement system for in-situ soil moisture content (SM-DTS) is introduced.The system is based on carbon-fiber heated cable (CFHC) technology that has been developed to enhancethe measuring accuracy of in-situ soil moisture content. Using CFHC technique, a temperature characteristicvalue (Tt) can be defined from temperatureetime curves. A relationship among Tt, soil thermalimpedance coefficient and soil moisture content is then established in laboratory. The feasibility of theSM-DTS technology to provide distributed measurements of in-situ soil moisture content is verifiedthrough field tests. The research reported herein indicates that the proposed SM-DTS is capable ofmeasuring in-situ soil moisture content over long distances and large areas. 展开更多
关键词 in-situ soil moisture content Distributed measurement Carbon-fiber heated cable (CFHC) Fiber-optic sensing
下载PDF
Advance of in-situ stress measurement in China 被引量:10
18
作者 Meifeng Cai Hua Peng 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE 2011年第4期373-384,共12页
In-situ stress is an essential parameter for design and construction of most engineering projects that involve excavation in rocks. Progress in in-situ stress measurement from the 1950s in China is briefly introduced.... In-situ stress is an essential parameter for design and construction of most engineering projects that involve excavation in rocks. Progress in in-situ stress measurement from the 1950s in China is briefly introduced. Stress relief by overcoring technique and hydraulic fracturing: technique are the two main techniques for in-situ stress measurement in China at present. To make them suitable for application at great depth and to increase their measuring reliability and accuracy, a series of techniques have been developed. Applications and achievements of in-situ stress measurement in Chinese rock engineering, including mining, geotechnical and hydropower engineering, and earthquake prediction, are introduced. Suggestions for further development of in-situ stress measurement are also proposed. 展开更多
关键词 in-situ stress measurement new development of techniques engineering application
下载PDF
Study of A Geo-Acoustic Model of Gas-Bearing Sediment and Its Application in Sediment with Low Acoustic Veloctiy 被引量:2
19
作者 陶春辉 李红星 +5 位作者 邓显明 周建平 FU Shun-sheng R. H. Wilkens 顾春华 何拥华 《China Ocean Engineering》 SCIE EI 2010年第2期381-390,共10页
A new geo-acoustic model for gas-bearing sediment is proposed based on the work of Dvorkin and Prasad, and Biot theory. Only five geophysical parameters: sediment mineral composition, free gas saturation, tortuosity ... A new geo-acoustic model for gas-bearing sediment is proposed based on the work of Dvorkin and Prasad, and Biot theory. Only five geophysical parameters: sediment mineral composition, free gas saturation, tortuosity (also known as the structure factor), permeability, and porosity, are considered in the model. A benefit of this model is that we need only five parameters instead of ten parameters in the Blot' s formulas for acoustic velocity and attenuation calculation. Here the model is demonstrated with the in-situ experimental data collected from the Hangzhou Bay, China. The results of this study suggest that free gas content in sediment is the most critical condition resulting in a low acoustic velocity (compressional wave). The respective contributions of the other four parameters in the model are also discussed. 展开更多
关键词 geo-acoustic model sediment with low acoustic velocity gas-bearing in-shu acoustic measurement
下载PDF
Deep Sea AUV Navigation Using Multiple Acoustic Beacons 被引量:2
20
作者 冀大雄 宋伟 +1 位作者 赵宏宇 刘健 《China Ocean Engineering》 SCIE EI CSCD 2016年第2期309-318,共10页
Navigation is a critical requirement for the operation of Autonomous Underwater Vehicles(AUVs).To estimate the vehicle position,we present an algorithm using an extended Kalman filter(EKF) to integrate dead-reckon... Navigation is a critical requirement for the operation of Autonomous Underwater Vehicles(AUVs).To estimate the vehicle position,we present an algorithm using an extended Kalman filter(EKF) to integrate dead-reckoning position with acoustic ranges from multiple beacons pre-deployed in the operating environment.Owing to high latency,variable sound speed multipath transmissions and unreliability in acoustic measurements,outlier recognition techniques are proposed as well.The navigation algorithm has been tested by the recorded data of deep sea AUV during field operations in a variety of environments.Our results show the improved performance over prior techniques based on position computation. 展开更多
关键词 deep sea AUV acoustic navigation range measurements multiple beacons outlier recognition
下载PDF
上一页 1 2 74 下一页 到第
使用帮助 返回顶部