期刊文献+
共找到67,722篇文章
< 1 2 250 >
每页显示 20 50 100
User Assisted Cooperative Relaying in Beamspace Massive MIMO NOMA Based Systems for Millimeter Wave Communications 预览
1
作者 Jaipreet Kaur Maninder Lal Singh 《中国通信:英文版》 SCIE CSCD 2019年第6期103-113,共11页
A novel scheme‘user assisted cooperative relaying in beamspace massive multiple input multiple output(M-MIMO)non-orthogonal multiple access(NOMA)system’has been proposed to improve coverage area,spectrum and energy ... A novel scheme‘user assisted cooperative relaying in beamspace massive multiple input multiple output(M-MIMO)non-orthogonal multiple access(NOMA)system’has been proposed to improve coverage area,spectrum and energy efficiency for millimeter wave(mmWave)communications.A downlink system for M users,where base station(BS)is equipped with beamforming lens antenna structure having NRF radio frequency(RF)chains,has been considered.A dynamic cluster of users is formed within a beam and the intermediate users(in that cluster)between beam source and destination(user)act as relaying stations.By the use of successive interference cancellation(SIC)technique of NOMA within a cluster,the relaying stations relay the symbols with improved power to the destination.For maximizing achievable sum rate,transmit precoding and dynamic power allocation for both intra and inter beam power optimization are implemented.Simulations for performance evaluation are carried out to validate that the proposed system outperforms the conventional beamspace M-MIMO NOMA system for mmWave communications in terms of spectrum and energy efficiency. 展开更多
关键词 cooperative RELAYING system(CRS) millimeter wave(mmWave) MASSIVE MULTIPLE input MULTIPLE output(M-MIMO) non-orthogonal MULTIPLE access(NOMA) power allocation sum rate
在线阅读 下载PDF
Frameworks of Non-Orthogonal Multiple Access Techniques in Cognitive Radio Communication Systems 预览
2
作者 Prabhat Thakur Alok Kumar +2 位作者 S Pandit G Singh S N Satashia 《中国通信:英文版》 SCIE CSCD 2019年第6期129-149,共21页
Recently,the increasing demand of radio spectrum for the next generation communication systems due to the explosive growth of applications appetite for bandwidths has led to the problem of spectrum scarcity.The potent... Recently,the increasing demand of radio spectrum for the next generation communication systems due to the explosive growth of applications appetite for bandwidths has led to the problem of spectrum scarcity.The potential approaches among the proposed solutions to resolve this issue are well explored cognitive radio(CR)technology and recently introduced non-orthogonal multiple access(NOMA)techniques.Both the techniques are employed for efficient spectrum utilization and assure the significant improvement in the spectral efficiency.Further,the significant improvement in spectral efficiency can be achieved by combining both the techniques.Since the CR is well-explored technique as compared to that of the NOMA in the field of communication,therefore it is worth and wise to implement this technique over the CR.In this article,we have presented the frameworks of NOMA implementation over CR as well as the feasibility of proposed frameworks.Further,the differences between proposed CR-NOMA and conventional CR frameworks are discussed.Finally,the potential issues regarding the implementation of CR-NOMA are explored. 展开更多
关键词 cognitive radio channel state information non-orthogonal MULTIPLE ACCESS power DIVISION MULTIPLE ACCESS superposition-coding successive-interference-cancellation
在线阅读 下载PDF
MIMO-WiMAX system incorporated with diverse transformation for 5G applications
3
作者 Lavish KANSAL Vishal SHARMA Jagjit Singh MALHOTRA 《中国光电子学前沿:英文版》 EI CSCD 2019年第3期296-310,共15页
Wireless systems and standards are now progressing toward the implementation of fifth generation (5G) to combat with an expected and explosive growth of demands of wireless services in future. Consequently, wireless i... Wireless systems and standards are now progressing toward the implementation of fifth generation (5G) to combat with an expected and explosive growth of demands of wireless services in future. Consequently, wireless interoperability for microwave access (WiMAX) with orthogonal frequency division multiplexing (OFDM) technology at its physical layer is being utilized for the uplink and downlink transmission to afford the high spectral efficiency in fading environments. However, the 5G implementation requires additional improvements to meet the futuristic stress. This work proposes an innovative solution that combines WiMAX system with multiple input multiple output (MIMO) technology to meet the required elevated data rates as desired by the growing application needs of 5G. MIMO is capable to fulfil the vision of 5G to realize a huge number of base stations equipped with a large number of terminals to be served in the same time-frequency resource without severe inter-user interference. Furthermore, the proposed system is demon- strated incorporation with discrete wavelet transform (DWT), and fractional Fourier transforms (FrFTs) in the physical layer of the WiMAX system. The evaluated outcomes exemplify a considerable improvement in bit error rate (BER) performance in contrast with the earlier reported work. 展开更多
关键词 wireless interoperability for microwave access (WiMAX) ORTHOGONAL frequency division MULTIPLEXING (OFDM) MULTIPLE input MULTIPLE output (MIMO) fast FOURIER TRANSFORM (FFT) discrete wavelet TRANSFORM (DWT) fractional FOURIER TRANSFORM (FrFT)
Is China’s Economy Overestimated?*——Counter-Evidence from the Underground Economy 预览
4
作者 王永兴 《中国经济学人:英文版》 2019年第3期30-43,共14页
Over the past four decades of reform and opening up since 1978, China’s GDP has been growing at 9.5% on an annual average basis. While some scholars believe that China’s economic growth is systematically overestimat... Over the past four decades of reform and opening up since 1978, China’s GDP has been growing at 9.5% on an annual average basis. While some scholars believe that China’s economic growth is systematically overestimated, this paper carries out an estimation of China’s underground economy and finds that due to the existence of the underground economy, China’s real GDP is systematically underestimated. China’s official GDP statistics generally reflect a real picture of its economic growth. The size of China’s underground economy is significantly influenced by total electricity consumption, the selfemployed ratio, labor participation rate and money supply. These findings are of great significance for policy-making. 展开更多
关键词 underground economy LATENT variable CASH ratio MODEL MULTIPLE indicators MULTIPLE causes (MIMIC) MODEL
在线阅读 下载PDF
Temporal variability of visibility and its parameterizations in Ningbo,China
5
作者 Jingjing Zhang Lei Tong +4 位作者 Chenghui Peng Huiling Zhang Zhongwen Huang Jun He Hang Xiao 《环境科学学报:英文版》 SCIE EI CAS CSCD 2019年第3期372-382,共11页
Simultaneous and continuous measurements of visibility, meteorological parameters and air pollutants were carried out at a suburban site in Ningbo from June 1, 2013 to May 31,2015. The characteristics of visibility an... Simultaneous and continuous measurements of visibility, meteorological parameters and air pollutants were carried out at a suburban site in Ningbo from June 1, 2013 to May 31,2015. The characteristics of visibility and their relationships with air pollutants and meteorological factors were investigated using multiple statistical methods. Daily visibility ranged from 0.6 to 34.1 km, with a mean value of 11.8 km. During the 2-year experiment,43.4% of daily visibility was found to be less than 10.0 km and only 9.2% was greater than 20.0 km. Visibility was lower in winter with a frequency of 53.4% in the range of 0.0–5.0 km.Annual visibility had an obvious diurnal variation, with the lowest and highest visibility being 7.5 km at approximately 06:00 local time and 15.6 km at approximately 14:00 local time, respectively. Multiple correspondence analysis(MCA) indicated that the different ranges of visibility were significantly affected by different levels of pollutants and meteorological conditions. Based on the analyses, visibility was found to be an exponential function of PM2.5 concentrations within a certain range of relative humidity. Thus, nonlinear models combining multiple linear regressions with exponential regression were subsequently developed using the data collected from June 2014 to May 2015, and the data from June 2013 to May 2014 was used to evaluate the performance of the model. It was demonstrated that the derived models can quantitatively describe the relationships between visibility, air quality and meteorological parameters in Ningbo. 展开更多
关键词 VISIBILITY MULTIPLE CORRESPONDENCE analysis(MCA) MULTIPLE NON-LINEAR regression
Establishment and verification of a surgical prognostic model for cervical spinal cord injury without radiological abnormality 预览
6
作者 Jie Wang Shuai Guo +2 位作者 Xuan Cai Jia-Wei Xu Hao-Peng Li 《中国神经再生研究:英文版》 SCIE CAS CSCD 2019年第4期713-720,共8页
Some studies have suggested that early surgical treatment can effectively improve the prognosis of cervical spinal cord injury without radiological abnormality,but no research has focused on the development of a progn... Some studies have suggested that early surgical treatment can effectively improve the prognosis of cervical spinal cord injury without radiological abnormality,but no research has focused on the development of a prognostic model of cervical spinal cord injury without radiological abnormality.This retrospective analysis included 43 patients with cervical spinal cord injury without radiological abnormality.Seven potential factors were assessed:age,sex,external force strength causing damage,duration of disease,degree of cervical spinal stenosis,Japanese Orthopaedic Association score,and physiological cervical curvature.A model was established using multiple binary logistic regression analysis.The model was evaluated by concordant profiling and the area under the receiver operating characteristic curve.Bootstrapping was used for internal validation.The prognostic model was as follows:logit(P)=-25.4545+21.2576VALUE+1.2160SCORE-3.4224TIME,where VALUE refers to the Pavlov ratio indicating the extent of cervical spinal stenosis,SCORE refers to the Japanese Orthopaedic Association score(0–17)after the operation,and TIME refers to the disease duration(from injury to operation).The area under the receiver operating characteristic curve for all patients was 0.8941(95%confidence interval,0.7930–0.9952).Three factors assessed in the predictive model were associated with patient outcomes:a great extent of cervical stenosis,a poor preoperative neurological status,and a long disease duration.These three factors could worsen patient outcomes.Moreover,the disease prognosis was considered good when logit(P)≥-2.5105.Overall,the model displayed a certain clinical value.This study was approved by the Biomedical Ethics Committee of the Second Affiliated Hospital of Xi’an Jiaotong University,China(approval number:2018063)on May 8,2018. 展开更多
关键词 nerve REGENERATION SURGICAL prognostic model CERVICAL SPINAL cord injury retrospective study MULTIPLE binary logistic regression analysis BOOTSTRAPPING internal validation MULTIPLE imputations CERVICAL SPINAL stenosis duration of disease Pavlov ratio neural REGENERATION
在线阅读 下载PDF
Wideband MIMO Radar Waveform Optimization Based on Range Profile 预览
7
作者 Qun Zhang Yishuai Gong Yijun Chen 《北京理工大学学报:英文版》 EI CAS 2019年第1期137-145,共9页
Aiming at the signal bandwidth design problem for multi-target imaging task,a kind of multiple input multiple output(MIMO)radar waveform design method is proposed.At first,the closed-loop feedback between the range pr... Aiming at the signal bandwidth design problem for multi-target imaging task,a kind of multiple input multiple output(MIMO)radar waveform design method is proposed.At first,the closed-loop feedback between the range profile and the signal bandwidth,which can design the minimum bandwidth of a transmitting signal that can distinguish each scatterer of the target in range direction,is established.Then,considering the request of beam pattern and the bandwidth limitation,a waveform optimization model is established and solved.Therefore,the multi-target observation and the dynamic adjustment of the signal bandwidth are accomplished.In the end,the simulation results prove the performance of the algorithm in a low SNR circumstance. 展开更多
关键词 MULTIPLE input MULTIPLE output(MIMO)radar COGNITION WAVEFORM design RANGE profile RANGE RESOLUTION
在线阅读 免费下载
Design of Power Amplifier for mm Wave 5G and Beyond 预览
8
作者 LI Lianming SI Jiachen CHEN Linhui 《南京航空航天大学学报:英文版》 EI CSCD 2019年第4期579-588,共10页
With targets of cost reduction per bit and high energy efficiency,5G and beyond call for innovation in the mmWave transmitter architecture and the power amplifier(PA)circuit.To illustrate these points,this paper first... With targets of cost reduction per bit and high energy efficiency,5G and beyond call for innovation in the mmWave transmitter architecture and the power amplifier(PA)circuit.To illustrate these points,this paper firstly explains the benefits and design implications of the hybrid beamforming structure in terms of the mmWave spectrum characteristics,energy efficiency,data rate,communication capacity,coverage and implementation technology choices.Then after reviewing the techniques to improve the power amplifier(PA)output power and efficiency,the design considerations and test results of 60 GHz and 90 GHz mmWave PAs in bulk complementary metal oxide semiconductor(CMOS)process are shown. 展开更多
关键词 5G and beyond 6G BEAMFORMING complementary metal oxide semiconductor(CMOS) mmWave multiple input multiple output(MIMO) power amplifier TRANSMITTER
在线阅读 下载PDF
Evaluating Suitability of Multiple Precipitation Products for the Lancang River Basin 预览
9
作者 TANG Xiongpeng ZHANG Jianyun +7 位作者 WANG Guoqing YANG Qinli YANG Yanqing GUAN Tiesheng LIU Cuishan JIN Junliang LIU Yanli BAO Zhenxin 《中国地理科学:英文版》 SCIE CSCD 2019年第1期37-57,共21页
Global reanalysis precipitation products could provide valuable meteorological information for flow forecasting in poorly gauged areas, helping to overcome a long-standing challenge in the field. But not all data sour... Global reanalysis precipitation products could provide valuable meteorological information for flow forecasting in poorly gauged areas, helping to overcome a long-standing challenge in the field. But not all data sources are suitable for all regions or perform the same way in hydrological modeling, so it is essential to test the suitability of precipitation products before applying them. In this study, five widely used global high-resolution precipitation products-Asian Precipitation Highly Resolved Observational Data Integration Towards Evaluation of Water Resources(APHRODITE), National Centers for Environmental Prediction Climate Forecast System Reanalysis(NCEP-CFSR), Climate Hazards Group InfraRed Precipitation with Station Data(CHIRPS), China Gauge-based Daily Precipitation Analysis developed by China Meteorological Administration(CMA) and Agricultural Model Intercomparison and Improvement Project based on the NASA Modern-Era Retrospective Analysis for Research and Applications(AgMERRA)-were evaluated using statistical methods and a hydrological approach for their suitability for the Lancang River Basin. The results indicated that APHRODITE, CMA, AgMERRA and CHIRPS were more accurate precipitation indicators than NCEP-CFSR in terms of the multiyear average and seasonal spatial distribution pattern, all of the CHIRPS, Ag MERRA and APHRODITE perform better than CMA and NCEP-CFSR at the small, medium and high precipitation intensities ranges in subbasin11 and sunbabsin46. All five products performed better in subbasin46(a low-altitude region) than in subbasin11(a high-altitude region) on the daily and monthly scales. In addition to NCEP-CFSR, the other four products all presented encouraging potential for streamflow simulation at daily(Yunjinghong) and monthly(Yunjinghong, Jiuzhou and Gajiu) scale. Hydrological simulations forced with APHRODITE were the best of the five for the Yunjinghong station in capturing daily and monthly measured streamflow. Except for NCEP-CFSR, all products were very good for hydrologic 展开更多
关键词 MULTIPLE PRECIPITATION PRODUCTS SUITABILITY evaluation the Lancang River BASIN
在线阅读 下载PDF
Weather induced subtidal flows through multiple inlets of an arctic microtidal lagoon 预览
10
作者 Chunyan Li Kevin M.Boswell +2 位作者 Nazanin Chaichitehrani Wei Huang Renhao Wu 《海洋学报:英文版》 SCIE CAS CSCD 2019年第3期1-16,共16页
Estuarine processes in the arctic lagoons are among the least studied but important subjects, especially considering the rapid warming of arctic water which may change the length of ice-free period in the summer. In t... Estuarine processes in the arctic lagoons are among the least studied but important subjects, especially considering the rapid warming of arctic water which may change the length of ice-free period in the summer. In this paper, wind-driven exchange flows in the micro-tidal Elson Lagoon of northern Alaska with multiple inlets of contrasting widths and depths are studied with in situ observations, statistical analysis, numerical experiments, a regression model on the basis of dynamics, and remote sensing data. Water velocity profiles were obtained from a bottom deployed acoustic Doppler current profiler(ADCP) in the northwestern Eluitkak Pass connecting the Beaufort Sea to the Elson Lagoon during a 4.9 day ice-free period in the summer of 2013. The subtidal flow is found correlated with wind(R~2 value ~96%). Frequently occurring east, northeast and north winds from the arctic atmospheric high-and low-pressure systems push water from the Beaufort Sea into the lagoon through the wide inlets on the eastern side of the lagoon, resulting in an outward flow against the wind at the narrow northwestern inlet. The counter-wind flow is a result of an uneven wind forcing acting through the asymmetric inlets and depth,an effect of 'torque' or vorticity. Under northwest wind, the exchange flow at the northwestern inlet reverses its direction, with inward flows through the upwind northwestern inlet and outward flows through the downwind eastern inlets. A regression model is established based on the momentum equations and Taylor series expansions. The model is used to predict flows in July and August of 2015 and July of 2017, supported by available Landsat satellite images. About 73%–80% of the time the flows at Eluitkak Pass are out of Elson Lagoon for the summer of 2015 and 2017. Numerical experiments are conducted to corroborate the findings and illustrate the effects under various wind conditions. A quasi-steady state balance between wind force and surface pressure gradient is confirmed. 展开更多
关键词 WIND-DRIVEN FLOWS MULTIPLE INLETS micro-tidal numerical model experiments counter-wind FLOWS quasi-steady state
在线阅读 下载PDF
Synchronous resection of esophageal cancer and other organ malignancies:A systematic review 预览
11
作者 Dimitrios Papaconstantinou Diamantis I Tsilimigras +7 位作者 Dimitrios Moris Adamantios Michalinos Aikaterini Mastoraki Efstratia Mpaili Natasha Hasemaki Anargyros Bakopoulos Dimitrios Filippou Dimitrios Schizas 《世界胃肠病学杂志:英文版》 SCIE CAS 2019年第26期3438-3449,共12页
BACKGROUND Neoplasms arising in the esophagus may coexist with other solid organ or gastrointestinal tract neoplasms in 6%to 15%of patients.Resection of both tumors synchronously or in a staged procedure provides the ... BACKGROUND Neoplasms arising in the esophagus may coexist with other solid organ or gastrointestinal tract neoplasms in 6%to 15%of patients.Resection of both tumors synchronously or in a staged procedure provides the best chances for long-term survival.Synchronous resection of both esophageal and second primary malignancy may be feasible in a subset of patients;however,literature on this topic remains rather scarce.AIM To analyze the operative techniques employed in esophageal resections combined with gastric,pancreatic,lung,colorectal,kidney and liver resections and define postoperative outcomes in each case.METHODS We conducted a systematic review according to PRISMA guidelines.We searched the Medline database for cases of patients with esophageal tumors coexisting with a second primary tumor located in another organ that underwent synchronous resection of both neoplasms.All English language articles deemed eligible for inclusion were accessed in full text.Exclusion criteria included:(1)Hematological malignancies;(2)Head/neck/pharyngeal neoplasms;(3)Second primary neoplasms in the esophagus or the gastroesophageal junction;(4)Second primary neoplasms not surgically excised;and(5)Preclinical studies.Data regarding the operative strategy employed,perioperative outcomes and longterm outcomes were extracted and analyzed using descriptive statistics.RESULTS The systematic literature search yielded 23 eligible studies incorporating a total of 117 patients.Of these patients,71%had a second primary neoplasm in the stomach.Those who underwent total gastrectomy had a reconstruction using either a colonic(n=23)or a jejunal(n=3)conduit while for those who underwent gastric preserving resections(i.e.,non-anatomic/wedge/distal gastrectomies)a conventional gastric pull-up was employed.Likewise,in cases of patients who underwent esophagectomy combined with pancreaticoduodenectomy(15%of the cohort),the decision to preserve part of the stomach or not dictated the reconstruction method(whether by a gastric pullup or a colonic/jej 展开更多
关键词 ESOPHAGECTOMY Esophageal neoplasm Second PRIMARY Multiple PRIMARY CONCURRENT neoplasms Management
在线阅读 免费下载
The Modern Changes of“Gesar”Thangka Under Multiple Contexts 预览
12
作者 CHEN Meizhen 《文学与艺术研究:英文版》 2019年第7期797-802,共6页
“Gesar”Thangka is an important type of Tibetan Tangka.With the generation and spread of Gesar epic,“Gesar”Thangka is also undergoing complex historical changes in the social and historical process of Tibetan areas... “Gesar”Thangka is an important type of Tibetan Tangka.With the generation and spread of Gesar epic,“Gesar”Thangka is also undergoing complex historical changes in the social and historical process of Tibetan areas.Since the 1980s,in the context of the rescue of Gesar epic,the rise of market economy,and the protection of intangible cultural heritage,“Gesar”Thangkar has gained creative vitality and experienced modern changes,presenting the aesthetic characteristics of secularization,sanctification,and art. 展开更多
关键词 “Gesar”Thangka MULTIPLE CONTEXT MODERN ALTERATION
在线阅读 下载PDF
New ex vivo demyelination/ remyelination models to defeat multiple sclerosis and neuromyelitis optica 预览
13
作者 Yiting Liu 《中国神经再生研究:英文版》 SCIE CAS CSCD 2019年第10期1715-1716,共2页
Multiple sclerosis (MS) and neuromyelitis optica (NMO) are inflammatory diseases of the central nervous system (CNS) resulting in CNS inflammation, infiltration of peripheral immune cells, loss of myelin and oligodend... Multiple sclerosis (MS) and neuromyelitis optica (NMO) are inflammatory diseases of the central nervous system (CNS) resulting in CNS inflammation, infiltration of peripheral immune cells, loss of myelin and oligodendrocytes, interruption of axonal communication, and neurologic deficits. Following oligodendrocyte injury, newly generated myelinating oligodendrocytes derived from oligodendrocyte progenitors (OPCs) may produce new myelin sheaths around denuded axons (remyelination) restoring neuronal function (Verden and Macklin, 2016). While remyelination is apparent in MS lesions, the process is often inefficient;in NMO, remyelination is even more limited. 展开更多
关键词 Multiple sclerosis(MS) inflammatory diseases REMYELINATION is EVEN more LIMITED
在线阅读 下载PDF
宁泌泰胶囊治疗Uu和Mh多重耐药的NGU临床疗效分析
14
作者 李群生 钟林芝 +5 位作者 杨文涛 周磊 张文龙 孟农钦 韦文华 廖建 《中国男科学杂志》 CAS CSCD 2019年第3期66-69,共4页
目的探讨宁泌泰胶囊治疗解脲支原体(ureaplasma urealyticum,Uu)和人型支原体(M.hominis,Mh)多重耐药的非淋菌性尿道炎(non-gonococcal urethritis,NGU)的临床疗效。方法选取30例Uu和Mh多重耐药的NGU患者给予宁泌泰胶囊口服治疗,15 d为... 目的探讨宁泌泰胶囊治疗解脲支原体(ureaplasma urealyticum,Uu)和人型支原体(M.hominis,Mh)多重耐药的非淋菌性尿道炎(non-gonococcal urethritis,NGU)的临床疗效。方法选取30例Uu和Mh多重耐药的NGU患者给予宁泌泰胶囊口服治疗,15 d为一个疗程,每个疗程结束后3 d复查支原体,若结果未转阴,继续下一个疗程,每例患者最多进行3个疗程。观察临床疗效,主要复查支原体转阴情况。结果 30例中有18例在第一个疗程后支原体转阴,5例经2个疗程治疗后支原体转阴,2例经3个疗程治疗后支原体转阴,治疗总有效率达83.3%。结论宁泌泰胶囊治疗Uu和Mh多重耐药的NGU患者疗效良好,在抗生素耐药的情况下,宁泌泰胶囊可做为治疗Uu和Mh多重耐药NGU的参考药物,值得在临床中推广。 展开更多
关键词 宁泌泰胶囊 非淋菌性尿道炎 抗药性 多药
Microstructural Characteristics and Mechanical Properties of Low-Alloy, Medium-Carbon Steels After Multiple Tempering
15
作者 Erfan Abbasi Quanshun Luo Dave Owens 《金属学报:英文版》 SCIE EI CAS CSCD 2019年第1期74-88,共15页
The microstructure and mechanical properties of NiCrMoV-and NiCrSi-alloyed medium-carbon steels were investigated after multiple tempering. After austenitising, the steels were hardened by oil quenching and subsequent... The microstructure and mechanical properties of NiCrMoV-and NiCrSi-alloyed medium-carbon steels were investigated after multiple tempering. After austenitising, the steels were hardened by oil quenching and subsequently double or triple tempered at temperatures from 250 to 500 °C. The samples were characterised using scanning electron microscopy and X-ray diffraction, while the mechanical properties were evaluated by Vickers hardness testing, V-notched Charpy impact testing and tensile testing. The results showed that the retained austenite was stable up to 400 °C and the applied multiple tempering below this temperature did not lead to a complete decomposition of retained austenite in both steels. It was also found that the microstructure, hardness and impact toughness varied mainly as a function of tempering temperature,regardless of the number of tempering stages. Moreover, the impact toughness of NiCrMoV steel was rather similar after single/triple tempering at different temperatures, while NiCrSi steel exhibited tempered martensite embrittlement after single/double tempering at 400 °C. The observed difference was mainly attributed to the effect of precipitation behaviour due to the effect of alloying additions in the studied steels. 展开更多
关键词 MEDIUM-CARBON steels MULTIPLE TEMPERING Alloying addition MECHANICAL properties RETAINED AUSTENITE Precipitation behaviour
互联网语境中立体性文化记忆与多重性国家认同 预览
16
作者 黄卫星 张玉能 《青岛科技大学学报:社会科学版》 2019年第2期87-92,共6页
互联网语境使得文化记忆具有了立体性,即成了多维度的立体形象世界记忆,多种感觉融会贯通的联觉记忆,超越现实真实性的仿真、拟像的记忆。在这种语境下,立体性文化记忆也形成了知(认识)情(情感)意(意志)多种感觉融合的国家认同。在这种... 互联网语境使得文化记忆具有了立体性,即成了多维度的立体形象世界记忆,多种感觉融会贯通的联觉记忆,超越现实真实性的仿真、拟像的记忆。在这种语境下,立体性文化记忆也形成了知(认识)情(情感)意(意志)多种感觉融合的国家认同。在这种强烈的立体性文化记忆所形成的多重性国家认同主导下,国家认同的理性观念在文化记忆的立体感性形象世界中显现出来,使得国家认同转化为了理性与感性高度统一、情感与意志高度融合的信念和信仰,更加有利于促进和加强民族团结和国家统一。 展开更多
关键词 互联网 文化记忆 立体性 多重性 国家认同
在线阅读 免费下载
Performance Characterization and Receiver Design for Random Temporal Multiple Access in Non-Coordinated Networks 预览
17
作者 Yin Lu Jun Fang +1 位作者 Zhong Guo J.Andrew Zhang 《中国通信:英文版》 SCIE CSCD 2019年第6期173-184,共12页
Random access is a well-known multiple access method for uncoordinated communication nodes.Existing work mainly focuses on optimizing iterative access protocols,assuming that packets are corrupted once they are collid... Random access is a well-known multiple access method for uncoordinated communication nodes.Existing work mainly focuses on optimizing iterative access protocols,assuming that packets are corrupted once they are collided,or that feedback is available and can be exploited.In practice,a packet may still be able to be recovered successfully even when collided with other packets.System design and performance analysis under such a situation,particularly when the details of collision are taken into consideration,are less known.In this paper,we provide a framework for analytically evaluating the actual detection performance in a random temporal multiple access system where nodes can only transmit.Explicit expressions are provided for collision probability and signal to interference and noise ratio(SINR)when different numbers of packets are collided.We then discuss and compare two receiver options for the AP,and provide detailed receiver design for the premium one.In particular,we propose a synchronization scheme which can largely reduce the preamble length.We also demonstrate that system performance could be a convex function of preamble length both analytically and via simulation,as well as the forward error correction(FEC)coding rate. 展开更多
关键词 RANDOM TEMPORAL multiple access non-coordination NETWORKS packet COLLISION
在线阅读 下载PDF
Fast density peak-based clustering algorithm for multiple extended target tracking 预览
18
作者 SHEN Xinglin SONG Zhiyong +1 位作者 FAN Hongqi FU Qiang 《系统工程与电子技术:英文版》 SCIE EI CSCD 2019年第3期435-447,共13页
The key challenge of the extended target probability hypothesis density (ET-PHD) filter is to reduce the computational complexity by using a subset to approximate the full set of partitions. In this paper, the influen... The key challenge of the extended target probability hypothesis density (ET-PHD) filter is to reduce the computational complexity by using a subset to approximate the full set of partitions. In this paper, the influence for the tracking results of different partitions is analyzed, and the form of the most informative partition is obtained. Then, a fast density peak-based clustering (FDPC) partitioning algorithm is applied to the measurement set partitioning. Since only one partition of the measurement set is used, the ET-PHD filter based on FDPC partitioning has lower computational complexity than the other ET-PHD filters. As FDPC partitioning is able to remove the spatially close clutter-generated measurements, the ET-PHD filter based on FDPC partitioning has good tracking performance in the scenario with more clutter-generated measurements. The simulation results show that the proposed algorithm can get the most informative partition and obviously reduce computational burden without losing tracking performance. As the number of clutter-generated measurements increased, the ET-PHD filter based on FDPC partitioning has better tracking performance than other ET-PHD filters. The FDPC algorithm will play an important role in the engineering realization of the multiple extended target tracking filter. 展开更多
关键词 FAST DENSITY peak-based clustering (FDPC) MULTIPLE extended target partition probability hypothesis DENSITY (PHD) filter track.
在线阅读 下载PDF
Integrating multiple images in a sampled phase-only hologram
19
作者 曾伟明 T.-C. Poon +2 位作者 王敏 朱秀玲 陈建龙 《中国光学快报:英文版》 SCIE EI CAS CSCD 2019年第5期11-14,共4页
Past research has demonstrated that a sampled phase-only hologram (SPOH) is capable of representing an image without the magnitude component of the hologram. At present, an SPOH can only record and reconstruct a singl... Past research has demonstrated that a sampled phase-only hologram (SPOH) is capable of representing an image without the magnitude component of the hologram. At present, an SPOH can only record and reconstruct a single source image. In this Letter, we propose, for the first time, to the best of our knowledge, a method for representing multiple images with a single integrated SPOH (ISPOH). Subsequently, each image can be retrieved from the ISPOH with a unique key parameter and displayed as a visible image on a phase-only spatial light modulator. 展开更多
关键词 Integrating multiple IMAGES SAMPLED PHASE-ONLY HOLOGRAM MAGNITUDE COMPONENT
MicroRNAs in blood and cerebrospinal fluid as diagnostic biomarkers of multiple sclerosis and to monitor disease progression 预览
20
作者 Bridget Martinez Philip V.Peplow 《中国神经再生研究:英文版》 SCIE CAS CSCD 2020年第4期606-619,共14页
Multiple sclerosis is a chronic autoimmune disease of the central nervous system.It is the main cause of non-traumatic neurological disability in young adults.Multiple sclerosis mostly affects people aged 20–50 years... Multiple sclerosis is a chronic autoimmune disease of the central nervous system.It is the main cause of non-traumatic neurological disability in young adults.Multiple sclerosis mostly affects people aged 20–50 years;however,it can occur in young children and much older adults.Factors identified in the distribution of MS include age,gender,genetics,environment,and ethnic background.Multiple sclerosis is usually associated with progressive degrees of disability.The disease involves demyelination of axons of the central nervous system and causes brain and spinal cord neuronal loss and atrophy.Diagnosing multiple sclerosis is based on a patient’s medical history including symptoms,physical examination,and various tests such as magnetic resonance imaging,cerebrospinal fluid and blood tests,and electrophysiology.The disease course of multiple sclerosis is not well correlated with the biomarkers presently used in clinical practice.Blood-derived biomarkers that can detect and distinguish the different phenotypes in multiple sclerosis may be advantageous in personalized treatment with disease-modifying drugs and to predict response to treatment.The studies reviewed have shown that the expression levels of a large number of miRNAs in peripheral blood,serum,exosomes isolated from serum,and cerebrospinal fluid are altered in multiple sclerosis and can distinguish the disease phenotypes from each other.Further studies are warranted to independently validate these findings so that individual or pairs of miRNAs in serum or cerebrospinal fluid can be used as potential diagnostic markers for adult and pediatric multiple sclerosis and for monitoring disease progression and response to therapy. 展开更多
关键词 clinically isolated syndrome CSF disease progression EXOSOMES humans microRNA multiple sclerosis peripheral blood PHENOTYPES serum
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈