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Characteristics of the Seismic Waves from a New Active Source Based on Methane Gaseous Detonation 预览
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作者 WANG Weitao WANG Xiang +7 位作者 MENG Chuanmin DONG Shi WANG Zhigang XIE Junju WANG Baoshan YANG Wei XU Shanhui WANG Tao 《中国地震研究:英文版》 CSCD 2019年第2期354-366,共13页
Active seismic sources are critical for obtaining high resolution images of the subsurface.For active imaging in urban areas,environment friendly and green seismic sources are required.In present work,we introduce a n... Active seismic sources are critical for obtaining high resolution images of the subsurface.For active imaging in urban areas,environment friendly and green seismic sources are required.In present work,we introduce a new type of green active source based on the gaseous detonation of methane and oxygen.When fired in a closed container,the chemical reaction,i.e.gaseous detonation,will produce high pressure air over 150 MPa.Seismic waves are produced when high pressure air is quickly released to impact the surroundings.The first field experiment of this active source was carried out in December,2017 in Jingdezhen,Jiangxi Province,where a series of active sources were excited to explore their potential in mine exploration.In current work,we analyzed the seismic waves recorded by near-field accelerators and a dense short-period seismic array and compared them with those from a mobile airgun source,another kind of active source by releasing high pressure air into water.The results demonstrate that it can be used for high resolution near surface imaging.Firstly,the gaseous detonation productions are harmless CO2 and water,making it a green explosive source.Secondly,the dominant seismic frequencies are 10-80 Hz and a single shot can be recorded up to 15 km,making it suitable for local structure investigations.Thirdly,it can be excited in vertical wells,similar to traditional powder explosive sources.It can also act as an additional on-land active source to airgun sources,which requires a suitable water body as intermediate media to generate repeating signals.Moreover,the short duration and high frequency signature of the source signals make it safe with no damage to nearby buildings.These make it convenient to excite in urban areas.As a new explosive source,the excitation equipment and conditions,such as gas ratio,sink depth and air-releasing directions,need further investigation to improve seismic wave generation efficiency. 展开更多
关键词 ACTIVE SOURCE SEISMIC WAVES METHANE DETONATION SOURCE Green SEISMIC SOURCE
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An Experimental Study on Modulating the Large Volume Airgun Array Signals through Asynchronous Excitation 预览
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作者 YANG Wei WANG Baoshan +2 位作者 LUO Mingzhang LI Xiaobin CHEN Yong 《中国地震研究:英文版》 CSCD 2019年第2期195-207,共13页
Large volume airgun arrays have been widely used in exploring and monitoring underground structures for nearly a decade.Nowadays,large volume airgun arrays adopt the synchronous excitation mode,and source characterist... Large volume airgun arrays have been widely used in exploring and monitoring underground structures for nearly a decade.Nowadays,large volume airgun arrays adopt the synchronous excitation mode,and source characteristics are controlled by the source signal of a single airgun,which to some extent limits its application.In order to realize the asynchronous excitation of the airgun array,we developed a new firing system for the airgun array,and carried out a field experiment in the Binchuan Fixed Airgun Signal Transmission station to study the influences of the asynchronous excitation on the source signal.The experimental results show that:the newly developed airgun array firing system can ignite the airguns according to the setting time series with high precision.By designing the excitation time series,the asynchronous excitation can enhance the energy of airgun source signal at 3-5 Hz,and reduce the energy of pressure pulse wave at 6-18 Hz.The signal detection capability of the asynchronous excitation with time series mode is equivalent to the synchronous excitation. 展开更多
关键词 ACTIVE SOURCE Large VOLUME airgun ASYNCHRONOUS EXCITATION SOURCE characteristics High PRECISION
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地层因素对D-D次生γ源空间分布的影响研究
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作者 张丽 于华伟 +1 位作者 贾文宝 王印慧 《核技术》 CAS CSCD 北大核心 2019年第1期43-48,共6页
在D-D可控源密度测量中,为研究不同地层条件对次生γ源空间分布的影响,首先分析D-D可控源密度测量原理,在此基础上,采用蒙特卡罗方法模拟研究不同含氢指数、岩性和矿化度地层条件下的次生γ源空间分布特征,最后对其影响因素进行归纳总... 在D-D可控源密度测量中,为研究不同地层条件对次生γ源空间分布的影响,首先分析D-D可控源密度测量原理,在此基础上,采用蒙特卡罗方法模拟研究不同含氢指数、岩性和矿化度地层条件下的次生γ源空间分布特征,最后对其影响因素进行归纳总结。结果表明:次生γ源的空间位置和强度易受各种地层因素的影响,其中地层含氢指数、岩性和矿化度对次生γ源的空间分布都有影响,但影响程度不同。其中地层含氢指数的影响最大,主要影响空间位置,特别是当含氢指数在0~0.1变化时,俘获γ的空间位置变化最大。并且随着地层含氢指数增高,地层含氢量增高,对快中子的减速能力增强,更多的γ射线向中子源靠近,同时γ射线强度也逐渐增强。相比较而言,岩性和矿化度对次生γ源的强度影响较大,空间位置影响相对较小,岩性不同,地层中主要元素的种类和含量不同,热中子俘获截面不同,俘获γ强度也不相同;矿化度高的地层,氯元素含量相对较高,更多的热中子被俘获,γ射线强度增强。本研究对于D-D次生γ源的影响校正提供了基础数据,也为建立精度较高的D-D可控源密度测量方法提供依据。 展开更多
关键词 D-D中子源 密度测量 次生γ源 空间分布
Quasi-Z-Source Based Bidirectional DC-DC Converter and Its Control Strategy
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作者 Yuba Raj Kafle Saad Ul Hasan Graham E.Town 《中国电气工程学报(英文)》 2019年第1期1-9,共9页
This paper presents a quasi-Z-source based isolated bidirectional DC-DC converter(qZIBDC)for renewable energy applications.The converter utilizes a dual active bridge circuit with a quasi-Z-source network on both side... This paper presents a quasi-Z-source based isolated bidirectional DC-DC converter(qZIBDC)for renewable energy applications.The converter utilizes a dual active bridge circuit with a quasi-Z-source network on both sides,so the converter works as buck/boost converter from either side.It has a wider input/output voltage operating range,soft-switching capabilities without additional devices,and higher boost capability than a traditional dual active bridge circuit.Apart from that,shoot-through states are incorporated in its operating cycle to boost the input voltage resulting in high reliability of the proposed converter.Due to the symmetrical structure of the circuit,there is no defined high voltage or low voltage side as in traditional isolated bidirectional DC-DC converter.The operating principle and control strategy of the proposed converter are presented.Simulation and experimental results are provided to verify the effectiveness of the proposed converter topology and its control strategy. 展开更多
关键词 BIDIRECTIONAL DC-DC CONVERTER dual active bridge IMPEDANCE source quasi-Z-source DC-DC CONVERTER
“Exploring petroleum inside source kitchen”: Connotation and prospects of source rock oil and gas 预览
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作者 YANG Zhi ZOU Caineng 《石油勘探与开发:英文版》 2019年第1期181-193,共13页
Based on the transitional background of the global energy structure, exploration and development of unconventional oil and gas, and investigation of key basins, the unconventional oil and gas resources are divided int... Based on the transitional background of the global energy structure, exploration and development of unconventional oil and gas, and investigation of key basins, the unconventional oil and gas resources are divided into three types: source rock oil and gas, tight oil and gas, and retention and accumulated oil and gas. Source rock oil and gas resources are the global strategic supplies of oil and gas, the key resource components in the second 150-year life cycle of the future petroleum industry, and the primary targets for “exploring petroleum inside source kitchen”. The geological connotation of source rock oil and gas was proposed, and the models of source rock oil and gas generation, expulsion and accumulation were built, and five source rock oil and gas generation sections were identified, which may determine the actual resource potential under available technical conditions. The formation mechanism of the “sweet sections” was investigated, that is, shale oil is mainly accumulated in the shale section that is close to the oil generation section and has higher porosity and permeability, while the “sweet sections” of coal-bed methane(CBM) and shale gas have self-contained source and reservoir and they are absorbed in coal seams or retained in the organic-rich black shale section, so evaluation and selection of good 'sweet areas(sections)' is the key to “exploring petroleum inside source kitchen”. Source rock oil and gas resources have a great potential and will experience a substantial growth for over ten world-class large “coexistence basins” of conventional-unconventional oil and gas in the future following North America, and also will be the primary contributor to oil stable development and the growth point of natural gas production in China, with expected contribution of 15% and 30% to oil and gas, respectively, in 2030. Challenges in source rock oil and gas development should be paid more attention to, theoretical innovation is strongly recommended, and a development pilot zone can be est 展开更多
关键词 SOURCE rock OIL and GAS SHALE GAS SHALE OIL coal-bed methane SWEET section SWEET area SOURCE control theory man-made OIL and GAS reservoir UNCONVENTIONAL OIL and GAS revolution large“coexistence basins”of conventional-unconventional OIL and GAS
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Assessing effects of “source-sink” landscape on non-point source pollution based on cell units of a small agricultural catchment
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作者 WANG Jin-liang CHEN Cheng-long +4 位作者 NI Jiu-pai XIE De-ti GUO Xi LUO Zhi-jun ZHAO Yue 《山地科学学报:英文版》 SCIE CSCD 2019年第9期2048-2062,共15页
Ascertaining the relationship between "source-sink" landscape and non-point source(NPS) pollution is crucial for reducing NPS pollution, however, it is not easy to realize this target on cell unit scale. To ... Ascertaining the relationship between "source-sink" landscape and non-point source(NPS) pollution is crucial for reducing NPS pollution, however, it is not easy to realize this target on cell unit scale. To reveal the relationships between "sourcesink" landscape and NPS pollution based on cell units of a small catchment in the Three Gorges Reservoir Region(TGRR), the runoff and nutrient yields were simulated first by rainfall events on a cell unit scale based on the Annualized AGricultural Non-Point Source Pollution Model(AnnAGNPS). Landscape structure and pattern were quantified with "sourcesink" landscape indicators based on cell units including landscape area indices and locationweighted landscape indices. The results showed that:the study case of small Wangjiagou catchment highlighted a good prediction capability of runoff and nutrient export by the AnnAGNPS model. Throughout the catchment, the spatial distribution trends of four location-weighted landscape indices were similar to the trends of simulated total nitrogen(TN) and total phosphorus(TP), which highlighted the importance of spatial arrangement of "source" and "sink" landscape types in a catchment when estimating pollutant loads. Results by Pearson correlation analysis indicated that the location-weighted landscape index provided a more comprehensive account of multiple factors, and can better reflect NPS-related nutrient loss than other landscape indices applied in single-factor analysis. This study provides new findings for applying the "source-sink" landscape indices based on cell units in small catchments to explain the effect of "source-sink" landscape on nutrient export based on cell unit, and helps improve the understanding of the correlation between "source-sink" landscape and NPS pollution. 展开更多
关键词 Nutrient load Non-point SOURCE pollution SOURCE sink LANDSCAPE index SMALL CATCHMENT
一起工业探伤作业引起的辐射事件的处理及经验反馈 预览
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作者 唐桢 张倩 +7 位作者 叶海峰 沈松 胡财平 徐政强 伍建华 应红梅 林绮纯 王渊高 《辐射防护通讯》 2019年第1期14-17,共4页
介绍了2017年浙江省宁波地区一起工业探伤作业(^75Se放射源)射线误照射事件和该事件处理情况。根据调查及保守剂量估算结果,本次事件中现场非探伤作业人员所受误照射剂量估计值约为29.54μSv,该估算剂量小于1mSv的公众年有效剂量当量限... 介绍了2017年浙江省宁波地区一起工业探伤作业(^75Se放射源)射线误照射事件和该事件处理情况。根据调查及保守剂量估算结果,本次事件中现场非探伤作业人员所受误照射剂量估计值约为29.54μSv,该估算剂量小于1mSv的公众年有效剂量当量限值,也小于0.25mSv每年的管理限值,管理部门根据调查和计算结果将本次误照射定性为辐射事件并通过该事件经验反馈提出监管建议。 展开更多
关键词 工业探伤 ^75Se 放射源 剂量估算 辐射事件
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Late onsets of tropical cyclones in the decaying years of super El Nino events 预览
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作者 Zhiqiang Li Runyu Zhang +2 位作者 Kai Liu Changling Zheng Zhikun Chen 《海洋学报:英文版》 SCIE CAS CSCD 2019年第7期67-73,共7页
The 2015/2016 El Nino event reached the threshold of super El Nino event,and was comparable to the super events in 1982/1983 and 1997/1998.Interestingly,the tropical cyclones(TCs)were found to have very late onsets in... The 2015/2016 El Nino event reached the threshold of super El Nino event,and was comparable to the super events in 1982/1983 and 1997/1998.Interestingly,the tropical cyclones(TCs)were found to have very late onsets in the decaying years of the super El Nino events.This study discusses the causes of late TC onsets related with atmospheric circulation,disturbance sources and trigger mechanisms.The analysis shows that the western North Pacific subtropical high(WNPSH)from January–June during the decaying years of the super El Nino events were stronger than the climatic mean,which resulted in a relatively stable atmospheric state by inhibiting deep convection.As a disturbance source,the April–June intertropical convergence zone(ITCZ)during the decaying years of the super El Nino events were significantly weaker than its climatic mean.The cross-equatorial flow and monsoon trough,as important TC generation triggers,were weaker from April–June during the decaying years of the super El Nino events,which further reduced the probability of TC generation.As for the late TC onsets,the role of atmospheric circulation anomalies(i.e.,subtropical-high,the ITCZ,cross-equatorial flow,and monsoon trough)were more important.The cross-equatorial flow may take as predictor of TC onsets in the decaying years of the super El Nino events. 展开更多
关键词 super El Nino EVENT TC generation DISTURBANCE source TRIGGER mechanism
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Review on the quantum emitters in two-dimensional materials 预览
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作者 Shuliang Ren Qinghai Tan Jun Zhang 《半导体学报:英文版》 EI CAS CSCD 2019年第7期38-45,共8页
The solid state single photon source is fundamental key device for application of quantum communication, quantum computing, quantum information and quantum precious metrology. After years of searching, researchers hav... The solid state single photon source is fundamental key device for application of quantum communication, quantum computing, quantum information and quantum precious metrology. After years of searching, researchers have found the single photon emitters in zero-dimensional quantum dots (QDs), one-dimensional nanowires, three-dimensional wide bandgap materials, as well as two-dimensional (2D) materials developed recently. Here we will give a brief review on the single photon emitters in 2D van der Waals materials. We will firstly introduce the quantum emitters from various 2D materials and their characteristics. Then we will introduce the electrically driven quantum light in the transition metal dichalcogenides (TMDs)-based light emitting diode (LED). In addition, we will introduce how to tailor the quantum emitters by nanopillars and strain engineering, the entanglement between chiral phonons (CPs) and single photon in monolayer TMDs. Finally, we will give a perspective on the opportunities and challenges of 2D materials-based quantum light sources. 展开更多
关键词 TWO-DIMENSIONAL MATERIALS single PHOTON source QUANTUM ENTANGLEMENT
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当代研究生心理压力来源与疏导 预览
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作者 张清扬 《科技视界》 2019年第11期245-246,共2页
研究生教育作为国民教育体系的顶端,是培养高层次专门人才的主要途径。但现行的大学管理体制,高校的心理教育对于研究生群体的覆盖率远不及本科生。随着研究生群体的扩大,研究生心理健康问题日益突出。文章分析了新形势下研究生群里心... 研究生教育作为国民教育体系的顶端,是培养高层次专门人才的主要途径。但现行的大学管理体制,高校的心理教育对于研究生群体的覆盖率远不及本科生。随着研究生群体的扩大,研究生心理健康问题日益突出。文章分析了新形势下研究生群里心理压力的来源与表现,并提成了对应的疏导方式,以加强研究生心理健康教育引导,切实提高研究生心理健康水平。 展开更多
关键词 研究生 心理压力 来源 疏导
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Photo-transmutation based on resonance γ-ray source
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作者 付光永 党永乐 +3 位作者 刘伏龙 吴笛 贺创业 王乃彦 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第6期135-139,共5页
High intensity γ-ray source can be obtained through resonance reaction induced by protons. In this work, the possibility of using such high intensity MeV-range γ-ray source to transmute nuclear waste is investigated... High intensity γ-ray source can be obtained through resonance reaction induced by protons. In this work, the possibility of using such high intensity MeV-range γ-ray source to transmute nuclear waste is investigated through Mont Carlo simulation.197 Au(γ, n)196Au experiment is performed to obtain the transmutation rate and compared with the simulation result. If the current of the proton beam is 10 mA at the resonance energy of 441 keV, with the γ photons emitted from7 Li(p, γ)8 Be, then the corresponding transmutation yield for129I in 2π direction can reach 9.4 × 109 per hour. The result is compared with that of LCS γ-ray source. 展开更多
关键词 high INTENSITY Γ-RAY source photo-transmutation PHOTONUCLEAR PHYSICS
Plasma density measurement and downstream etching of silicon and silicon oxide in Ar/NF3 mixture remote plasma source
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作者 H J YEOM D H CHOI +4 位作者 Y S LEE J H KIM D J SEONG S J YOU H C LEE 《等离子体科学与技术:英文版》 SCIE EI CAS CSCD 2019年第6期52-57,共6页
In this study,plasma density measurements were performed near the plume region of the remote plasma source (RPS) in Ar/NF3 gas mixtures using a microwave cutoff probe.The measured plasma density is in the range of 101... In this study,plasma density measurements were performed near the plume region of the remote plasma source (RPS) in Ar/NF3 gas mixtures using a microwave cutoff probe.The measured plasma density is in the range of 1010-1011 cm-3 in the discharge conditions with RPS powers of 2-4 kW and gas pressures of 0.87-4 Torr.The plasma density decreased with increasing gas pressures and RPS powers under various Ar/NF3 mixing ratios.This decrease in the plasma density measured at the fixed measurement position (plume region) can be understood by the reduction of the electron energy relaxation length with increases in the gas pressures and mixing ratio of NF3/(Ar/NF3).We also performed downstream etching of silicon and silicon oxide films in this system.The etch rate of the silicon films significantly increases while the silicon oxide is slightly etched with the gas pressures and powers.It was also found that the etch rate strongly depends on the wafer position on the processing chamber electrode,and that the etch selectivity reached 96-131 in the discharge conditions of RF powers (3730-4180 W) and gas pressures (3.6-4 Torr). 展开更多
关键词 REMOTE plasma source electron density CUTOFF probe DOWNSTREAM ETCH
Fluid Inclusion and H-O Isotope Geochemistry of the Phapon Gold Deposit, NW Laos: Implications for Fluid Source and Ore Genesis
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作者 Linnan Guo Shusheng Liu +6 位作者 Lin Hou Jieting Wang Meifeng Shi Qiming Zhang Fei Nie Yongfei Yang Zhimin Peng 《地球科学学刊:英文版》 SCIE CAS CSCD 2019年第1期80-94,共15页
The Phapon gold deposit, located in northern Laos, is a unique large-scale gold deposit in Luang Prabang-Loei metallogenic belt. It is hosted in the Lower Permian limestone and controlled by a NE-trending ductile-brit... The Phapon gold deposit, located in northern Laos, is a unique large-scale gold deposit in Luang Prabang-Loei metallogenic belt. It is hosted in the Lower Permian limestone and controlled by a NE-trending ductile-brittle fault system. There are three types of primary ore including auriferous calcite vein type, disseminated type, and breccia type, and the first two are important in the Phapon gold deposit. Based on fluid inclusion petrography and microthermometry, three types of primary fluid inclusions including type 1 liquid-rich aqueous, type 2 vapor-rich aqueous and type 3 daughter mineralbearing aqueous were identified in hydrothermal calcite grains. The ore-forming fluids are normally homogeneous, as indicated by the widespread type 1 inclusions with identical composition. The coexistence of type 1 and type 2 inclusions, showing similar final homogenization temperature but different compositions, indicate that fluid immiscibility did locally take place in both two types of ores. The results of microthermometry and H-O isotopes geochemistry indicate that there are little differences on ore-fluid geochemistry between the auriferous calcite vein-type and disseminated type ores. The oreforming fluids are characterized by medium-low temperatures(157–268 oC) and low salinity(1.6 wt.%–9.9 wt.% NaCl eq.). It is likely to have a metamorphic-dominant mixed source, which could be associated with dehydration and decarbonisation of Lower Permian limestone and Middle–Upper Triassic sandstones during the dynamic metamorphism. The fluid-wallrock interaction played a major role, and the locally occurred fluid-immiscible processes played a subordinate role in gold precipitation. Combined with the regional and ore deposit geology, and ore-fluid geochemistry, we suggest that the Phapon gold deposit is best considered to be a member of the epizonal orogenic deposit class. 展开更多
关键词 FLUID inclusion H-O isotopes FLUID SOURCE ore genesis Phapon gold deposit northern Laos
Boundary Estimation in Annular Two-Phase Flow Using Electrical Impedance Tomography with Particle Swarm Optimization 预览
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作者 Rongli Wang 《现代电子技术(英文)》 2019年第1期15-19,共5页
In this study we consider the boundary estimation of annular two-phase flow in a pipe with the potential distribution on the electrodes mounted on the outer boundary of the pipe, by taking use of electrical impedance ... In this study we consider the boundary estimation of annular two-phase flow in a pipe with the potential distribution on the electrodes mounted on the outer boundary of the pipe, by taking use of electrical impedance tomography (EIT) technique with the numerical solution obtained from an improved boundary distributed source (IBDS) method. The particle swarm optimization (PSO) is used to iteratively seek the boundary configuration. The simulation results showed that PSO and EIT technique with numerical solution obtained from IBDS has been successfully applied to the monitoring of an annular two-phase flow. 展开更多
关键词 Electrical impedance tomography MESHLESS METHOD Improved BOUNDARY distributed source METHOD Particle SWARM optimization ANNULAR TWO-PHASE flow
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Isotope analysis of nitrate pollution sources in groundwater of Dong'e geohydrological unit 预览
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作者 LI Yang KANG Feng-Xin ZOU An-de 《地下水科学与工程:英文版》 2019年第2期145-154,共10页
As nitrate pollution in groundwater has become increasingly serious in recent years, nitrogen isotope was adopted in this paper to define its sources in a typical agricultural area of Dong5e hydrogeological unit. The ... As nitrate pollution in groundwater has become increasingly serious in recent years, nitrogen isotope was adopted in this paper to define its sources in a typical agricultural area of Dong5e hydrogeological unit. The results show that: Higher content of NO3^- detected in shallow groundwater is 27.77 mg/L on average and δ^15N content ranges from 7.8‰ to 12 ‰, indicating that shallow groundwater is mainly contaminated by sewage or feces. In contrast, less NO3^- in deep groundwater (karst water) has an average value of 12.81 mg/L and δ^15N content is between 7.2‰ and 14.3‰, which is closely related to human disturbance as mentioned above. In addition, considering relatively low groundwater quality at some monitoring sites, reasonable fertilization is a better choice in the study area to reduce nitrate source in groundwater. 展开更多
关键词 NITROGEN ISOTOPE GROUNDWATER NITROGEN POLLUTION source AGRICULTURAL area
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An improved empirical green function method to extract microseismic signals
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作者 Dayong Yu Pan Wang 《大地测量与地球动力学:英文版》 2019年第1期42-48,共7页
In mining, reservoir impoundment and hydraulic fracturing exploitation, the induced microseismic clusters may present complex waveforms at receivers since the individual events generally arrive very close. And the rou... In mining, reservoir impoundment and hydraulic fracturing exploitation, the induced microseismic clusters may present complex waveforms at receivers since the individual events generally arrive very close. And the routine methods for arrival picking are insufficiently efficient due to these strong influences. Here, we modified the empirical green function method and applied it to extract the green functions and the radiation coefficients of microseismic events with the largest energy in clusters.Multiple-channel records were used to estimate an 'average' source spectrum and then the 'average' source wavelet was removed from the records by deconvolution. We applied this method to the real data,and the result indicated clear improvement in extracting the dominant event of the clusters. 展开更多
关键词 Microseismic SIGNALS Empirical green FUNCTION SOURCE SPECTRA
Current-limiting characteristics of saturated iron-core fault current limiters in VSC-HVDC systems based on electromagnetic energy conversion mechanism 预览
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作者 Botong LI Hanqing CUI +2 位作者 Fangjie JING Bin LI Yichao LIU 《现代电力系统与清洁能源学报(英文)》 CSCD 2019年第2期412-421,共10页
A common method to examine the current-limiting performance of saturated iron-core fault current limiter(SI-FCL) in high-voltage direct-current transmission based on voltage source converter(VSC-HVDC) systems is to so... A common method to examine the current-limiting performance of saturated iron-core fault current limiter(SI-FCL) in high-voltage direct-current transmission based on voltage source converter(VSC-HVDC) systems is to solve differential equations based on the system fault transient characteristics and the equivalent inductance calculation equation. This method analyzes the fault current of the VSC-HVDC system in the time domain. However, it is computationally complex and cannot directly reflect the relationship between parameters and the currentlimiting effect of the SI-FCL.In this paper,the relationship between the magnetic flux density and magnetic field energy of the SI-FCL is analyzed. The energy exchange between the DC capacitor and the SI-FCL in the DC short circuit fault process is analyzed. From the perspective of electromagnetic energy conversion, the criterion for determining the current-limiting ability of the SI-FCL in the transient process is given based on the parameters of the SI-FCL and VSC-HVDC system. On this basis, the characteristics of the DC side fault current and the capacitor voltage when the SI-FCL has current-limiting ability are examined.Based on the parameters of the SI-FCL and VSC-HVDC system, a method for calculating the fault current peak value and capacitor voltage drop time is given. Finally, the accuracy of the analysis of the SI-FCL in the VSC-HVDC system based on the electromagnetic energy conversion mechanism is demonstrated through a case study and simulation results of the VSC-HVDC system with different SI-FCLs. 展开更多
关键词 ELECTROMAGNETIC energy Saturated iron-core FAULT current limiter(SI-FCL) HIGH-VOLTAGE direct-current transmission based on voltage source converter(VSCHVDC) system FAULT analysis
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Design and testing of an internal hot-cathode-type PIG ion source for superconducting cyclotron 预览
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作者 Shi-Wen Xu Yun-Tao Song +6 位作者 Gen Chen Yu-Qian Chen Liu-Si Sheng Man-Man Xu Oleg Karamyshev Galina Karamysheva Grigori Shirkov 《核技术:英文版》 SCIE CAS CSCD 2019年第6期10-15,共6页
The superconducting cyclotron SC200 is intended to generate a 200 MeV, 400 nA proton beam for future particle therapy. The internal hot-cathode-type Penning ionization gauge (PIG) ion source for the SC200 is designed ... The superconducting cyclotron SC200 is intended to generate a 200 MeV, 400 nA proton beam for future particle therapy. The internal hot-cathode-type Penning ionization gauge (PIG) ion source for the SC200 is designed for the generation of hydrogen ions. A brief description of the design of ion source and test bench, which are used in SC200, is given in this paper. The ion source has been verified on the test bench, and the results indicated that the designed ion source meets the expected requirements. The lifetime of the filament exceeded 100 h in the test. In addition, the extraction voltage and the gas flow that influence the extracted ion current intensity have been tested in the experiment. 展开更多
关键词 CYCLOTRONS Ion source Test BENCH Simulation
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蔬菜重金属污染与防治研究综述 预览
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作者 刘希元 吴春燕 +1 位作者 张广臣 杨璐 《安徽农业科学》 CAS 2019年第15期10-12,17共4页
随着工业化和城市化的推进,蔬菜也受到不同程度的污染,其中包括重金属对蔬菜的污染。在前人研究的基础上,总结了重金属对蔬菜生长发育影响的4个方面及富集规律,从土壤和大气2个方面归纳重金属的来源,进而提出4种缓解蔬菜重金属污染的措... 随着工业化和城市化的推进,蔬菜也受到不同程度的污染,其中包括重金属对蔬菜的污染。在前人研究的基础上,总结了重金属对蔬菜生长发育影响的4个方面及富集规律,从土壤和大气2个方面归纳重金属的来源,进而提出4种缓解蔬菜重金属污染的措施,为更好地治理农田重金属污染、进一步研究重金属在蔬菜作物中的分子机理等提供参考。 展开更多
关键词 蔬菜 重金属 来源 生理影响 富集规律
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A Generalized Propagator Algorithm for Localization of Non-circular Sources Using Arbitrary Array Geometry 预览
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作者 CAO Renzheng ZHANG Xiaofei 《南京航空航天大学学报:英文版》 EI CSCD 2019年第2期339-351,共13页
A propagator-based algorithm for direction of arrival(DOA)estimation of noncoherent one-dimensional(1-D)non-circular sources is presented such as binary phase shift keying(BPSK)and amplitude modulation(AM).The algorit... A propagator-based algorithm for direction of arrival(DOA)estimation of noncoherent one-dimensional(1-D)non-circular sources is presented such as binary phase shift keying(BPSK)and amplitude modulation(AM).The algorithm achieves DOA estimation through searching a 1-D spectrum,which is newly formed on the basis of the rank reduction criterion,and works well without knowledge of the non-circular phases.And then,a search-free implementation of the algorithm is also developed by using the polynomial rooting technique.According to the non-circular property,the algorithm can virtually enlarge the array aperture,thus significantly improving its estimation accuracy and enabling it to handle more sources than the number of sensors.Moreover,the algorithm requires no rotational invariance,so it can be applied to arbitrary array geometry and dispense with the high-complexity procedure of the eigen-decomposition of the correlation sample matrix.Finally,numerical simulations verify the performance and effectiveness of the proposed algorithm. 展开更多
关键词 direction of arrival(DOA) SUBSPACE method RANK reduction criterion PROPAGATOR NON-CIRCULAR source
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