期刊文献+
共找到6,519篇文章
< 1 2 250 >
每页显示 20 50 100
Estimation of the anisotropy of hydraulic conductivity through 3D fracture networks using the directional geological entropy 被引量:1
1
作者 Chuangbing Zhou Zuyang Ye +2 位作者 Chi Yao Xincheng Fan Feng Xiong 《International Journal of Mining Science and Technology》 SCIE EI CAS CSCD 2024年第2期137-148,共12页
With an extension of the geological entropy concept in porous media,the approach called directional entrogram is applied to link hydraulic behavior to the anisotropy of the 3D fracture networks.A metric called directi... With an extension of the geological entropy concept in porous media,the approach called directional entrogram is applied to link hydraulic behavior to the anisotropy of the 3D fracture networks.A metric called directional entropic scale is used to measure the anisotropy of spatial order in different directions.Compared with the traditional connectivity indexes based on the statistics of fracture geometry,the directional entropic scale is capable to quantify the anisotropy of connectivity and hydraulic conductivity in heterogeneous 3D fracture networks.According to the numerical analysis of directional entrogram and fluid flow in a number of the 3D fracture networks,the hydraulic conductivities and entropic scales in different directions both increase with spatial order(i.e.,trace length decreasing and spacing increasing)and are independent of the dip angle.As a result,the nonlinear correlation between the hydraulic conductivities and entropic scales from different directions can be unified as quadratic polynomial function,which can shed light on the anisotropic effect of spatial order and global entropy on the heterogeneous hydraulic behaviors. 展开更多
关键词 3D fracture network Geological entropy directional entropic scale ANISOTROPY Hydraulic conductivity
下载PDF
MSD-Net: Pneumonia Classification Model Based on Multi-Scale Directional Feature Enhancement
2
作者 Tao Zhou Yujie Guo +3 位作者 Caiyue Peng Yuxia Niu Yunfeng Pan Huiling Lu 《Computers, Materials & Continua》 SCIE EI 2024年第6期4863-4882,共20页
Computer-aided diagnosis of pneumonia based on deep learning is a research hotspot.However,there are some problems that the features of different sizes and different directions are not sufficient when extracting the f... Computer-aided diagnosis of pneumonia based on deep learning is a research hotspot.However,there are some problems that the features of different sizes and different directions are not sufficient when extracting the features in lung X-ray images.A pneumonia classification model based on multi-scale directional feature enhancement MSD-Net is proposed in this paper.The main innovations are as follows:Firstly,the Multi-scale Residual Feature Extraction Module(MRFEM)is designed to effectively extract multi-scale features.The MRFEM uses dilated convolutions with different expansion rates to increase the receptive field and extract multi-scale features effectively.Secondly,the Multi-scale Directional Feature Perception Module(MDFPM)is designed,which uses a three-branch structure of different sizes convolution to transmit direction feature layer by layer,and focuses on the target region to enhance the feature information.Thirdly,the Axial Compression Former Module(ACFM)is designed to perform global calculations to enhance the perception ability of global features in different directions.To verify the effectiveness of the MSD-Net,comparative experiments and ablation experiments are carried out.In the COVID-19 RADIOGRAPHY DATABASE,the Accuracy,Recall,Precision,F1 Score,and Specificity of MSD-Net are 97.76%,95.57%,95.52%,95.52%,and 98.51%,respectively.In the chest X-ray dataset,the Accuracy,Recall,Precision,F1 Score and Specificity of MSD-Net are 97.78%,95.22%,96.49%,95.58%,and 98.11%,respectively.This model improves the accuracy of lung image recognition effectively and provides an important clinical reference to pneumonia Computer-Aided Diagnosis. 展开更多
关键词 PNEUMONIA X-ray image Resnet multi-scale feature direction feature TRANSFORMER
下载PDF
Spontaneous Recovery in Directed Dynamical Networks
3
作者 Xueming Liu Xian Yan H.Eugene Stanley 《Engineering》 SCIE EI CAS CSCD 2024年第6期208-214,共7页
Complex networked systems,which range from biological systems in the natural world to infrastructure systems in the human-made world,can exhibit spontaneous recovery after a failure;for example,a brain may spontaneous... Complex networked systems,which range from biological systems in the natural world to infrastructure systems in the human-made world,can exhibit spontaneous recovery after a failure;for example,a brain may spontaneously return to normal after a seizure,and traffic flow can become smooth again after a jam.Previous studies on the spontaneous recovery of dynamical networks have been limited to undirected networks.However,most real-world networks are directed.To fill this gap,we build a model in which nodes may alternately fail and recover,and we develop a theoretical tool to analyze the recovery properties of directed dynamical networks.We find that the tool can accurately predict the final fraction of active nodes,and the prediction accuracy decreases as the fraction of bidirectional links in the network increases,which emphasizes the importance of directionality in network dynamics.Due to different initial states,directed dynamical networks may show alternative stable states under the same control parameter,exhibiting hysteresis behavior.In addition,for networks with finite sizes,the fraction of active nodes may jump back and forth between high and low states,mimicking repetitive failure-recovery processes.These findings could help clarify the system recovery mechanism and enable better design of networked systems with high resilience. 展开更多
关键词 network resilience directed dynamical networks Spontaneous recovery
下载PDF
Direct Photolithography of WO_(x) Nanoparticles for High‑Resolution Non‑Emissive Displays
4
作者 Chang Gu Guojian Yang +7 位作者 Wenxuan Wang Aiyan Shi Wenjuan Fang Lei Qian Xiaofei Hu Ting Zhang Chaoyu Xiang Yu‑Mo Zhang 《Nano-Micro Letters》 SCIE EI CAS 2025年第3期297-309,共13页
High-resolution non-emissive displays based on electrochromic tungsten oxides(WOx)are crucial for future near-eye virtual/augmented reality interactions,given their impressive attributes such as high environmental sta... High-resolution non-emissive displays based on electrochromic tungsten oxides(WOx)are crucial for future near-eye virtual/augmented reality interactions,given their impressive attributes such as high environmental stability,ideal outdoor readability,and low energy consumption.However,the limited intrinsic structure of inorganic materials has presented a significant challenge in achieving precise patterning/pixelation at the micron scale.Here,we successfully developed the direct photolithography for WOx nanoparticles based on in situ photo-induced ligand exchange.This strategy enabled us to achieve ultra-high resolution efficiently(line width<4μm,the best resolution for reported inorganic electrochromic materials).Additionally,the resulting device exhibited impressive electrochromic performance,such as fast response(<1 s at 0 V),high coloration efficiency(119.5 cm^(2) C^(−1)),good optical modulation(55.9%),and durability(>3600 cycles),as well as promising applications in electronic logos,pixelated displays,flexible electronics,etc.The success and advancements presented here are expected to inspire and accelerate research and development(R&D)in high-resolution non-emissive displays and other ultra-fine micro-electronics. 展开更多
关键词 Electrochromic direct photolithography WOx nanoparticles In situ photo-induced ligand exchange High-resolution displays
下载PDF
Immune indicators and depression in adolescents:Associations with monocytes,lymphocytes,and direct bilirubin
5
作者 Jian Dai Xiao-Tong Lin +5 位作者 Lu-Lu Shen Xi-Wen Zhang Zi-Wen Ding Jing Wang Xi-Wang Fan Wei-Dong Ning 《World Journal of Psychiatry》 2025年第2期23-32,共10页
BACKGROUND Depression is a significant psychiatric disorder with particularly high prevalence among adolescents.This mental health condition can have severe consequences,including academic failure,social withdrawal,an... BACKGROUND Depression is a significant psychiatric disorder with particularly high prevalence among adolescents.This mental health condition can have severe consequences,including academic failure,social withdrawal,and suicidal behavior.Given the increasing rate of depression in this age group,understanding the underlying biological mechanisms is essential for early detection and intervention.Recent studies have suggested that immune markers play a role in the pathophysiology of depression,prompting further investigation of their potential association with depressive symptoms in adolescents.AIM To investigate the relationship between immune markers(monocytes,lymphocytes,and direct bilirubin)and the incidence and severity of depression among adolescents.METHODS This cross-sectional study recruited 145 adolescent patients with depression[male(M)/female(F)=38/107]from Jiangbin Hospital in Guangxi,Zhuang and 163 healthy controls(M/F=77/86)from routine health check-ups.Blood samples were collected after an overnight fast.Depression severity was measured using the Zung Self-Rating Depression Scale.The inclusion criteria were age 12-24 years,diagnosis of depressive disorder(ICD-10),and no recent antidepressant use.The exclusion criteria included psychiatric comorbidities and serious somatic diseases.Key statistical methods included group comparisons and correlation analyses.RESULTS There was a higher prevalence of females in the depression group(P<0.001).Significant age differences were observed between the groups(Z=9.43,P<0.001).The depression group had higher monocyte(Z=3.43,P<0.001)and lymphocyte(t=2.29,P<0.05)counts,and higher serum direct bilirubin levels(Z=4.72,P<0.001).Monocyte count varied significantly according to depression severity,with lower counts in the mild group(Z=-2.90,P<0.05).A negative correlation between age and lymphocyte counts was observed(ρ=-0.22,P<0.01).Logistic regression analysis showed that serum direct bilirubin levels significantly predicted depression.CONCLUSION The potential role of elevated levels of immune markers in the early detection of depression in adolescents has been highlighted.Therefore,it is necessary to explore further the relationships between these immune markers and depression. 展开更多
关键词 DEPRESSION Adolescents Immune markers MONOCYTE LYMPHOCYTE direct bilirubin
下载PDF
Behaviors of vanadium and chromium in coal-based direct reduction of high-chromium vanadium-bearing titanomagnetite concentrates followed by magnetic separation 被引量:6
6
作者 赵龙胜 王丽娜 +3 位作者 陈德胜 赵宏欣 刘亚辉 齐涛 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2015年第4期1325-1333,共9页
The reduction behaviors of FeO·V2O3 and FeO·Cr2O3 during coal-based direct reduction have a decisive impact on the efficient utilization of high-chromium vanadium-bearing titanomagnetite concentrates. The ef... The reduction behaviors of FeO·V2O3 and FeO·Cr2O3 during coal-based direct reduction have a decisive impact on the efficient utilization of high-chromium vanadium-bearing titanomagnetite concentrates. The effects of molar ratio of C to Fe n(C)/n(Fe) and temperature on the behaviors of vanadium and chromium during direct reduction and magnetic separation were investigated. The reduced samples were characterized by X-ray diffraction(XRD), scanning election microscopy(SEM) and energy dispersive spectrometry(EDS) techniques. Experimental results indicate that the recoveries of vanadium and chromium rapidly increase from 10.0% and 9.6% to 45.3% and 74.3%, respectively, as the n(C)/n(Fe) increases from 0.8 to 1.4. At n(C)/n(Fe) of 0.8, the recoveries of vanadium and chromium are always lower than 10.0% in the whole temperature range of 1100-1250 °C. However, at n(C)/n(Fe) of 1.2, the recoveries of vanadium and chromium considerably increase from 17.8% and 33.8% to 42.4% and 76.0%, respectively, as the temperature increases from 1100 °C to 1250 °C. At n(C)/n(Fe) lower than 0.8, most of the FeO·V2O3 and FeO·Cr2O3 are not reduced to carbides because of the lack of carbonaceous reductants, and the temperature has little effect on the reduction behaviors of FeO·V2O3 and FeO·Cr2O3, resulting in very low recoveries of vanadium and chromium during magnetic separation. However, at higher n(C)/n(Fe), the reduction rates of FeO·V2O3 and FeO·Cr2O3 increase significatly because of the excess amount of carbonaceous reductants. Moreover, higher temperatures largely induce the reduction of FeO·V2O3 and FeO·Cr2O3 to carbides. The newly formed carbides are then dissolved in the γ(FCC) phase, and recovered accompanied with the metallic iron during magnetic separation. 展开更多
关键词 high-chromium vanadium-bearing titanomagnetite concentrates coal-based direct reduction magnetic separation reduction behavior VANADIUM CHROMIUM
下载PDF
Grain refinement of pure aluminum by direct current pulsed magnetic field and inoculation 被引量:6
7
作者 陈航 接金川 +2 位作者 付莹 马红军 李廷举 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2014年第5期1295-1300,共6页
The combined effects of direct current pulsed magnetic field (DC-PMF) and inoculation on pure aluminum were investigated, the grain refinement behavior of DC-PMF and inoculation was discussed. The experimental resul... The combined effects of direct current pulsed magnetic field (DC-PMF) and inoculation on pure aluminum were investigated, the grain refinement behavior of DC-PMF and inoculation was discussed. The experimental results indicate that the solidification micro structure of pure aluminum can be greatly refined under DC-PMF. Refinement of pure aluminum is attributed to electromagnetic undercooling and forced convection caused by DC-PMF. With single DC-PMF, the grain size in the equiaxed zone is uneven. However, under DC-PMF, by adding 0.05% (mass fraction) Al5Ti-B, the grain size of the sample is smaller, and the size distribution is more uniform than that of single DC-PMF. Furthermore, under the combination of DC-PMF and inoculation, with the increase of output current, the grain size is further reduced. When the output current increases to 100 A, the average grain size can decrease to 113 μn. 展开更多
关键词 direct current pulsed magnetic field pure aluminum inoculation grain refinement solidification micro structure
下载PDF
Effect of configuration on magnetic field in cold crucible using for continuous melting and directional solidification 被引量:4
8
作者 陈瑞润 杨劼人 +4 位作者 丁宏升 黄锋 苏彦庆 郭景杰 傅恒志 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2012年第2期404-410,共7页
To improve the power efficiency and optimize the configuration of cold crucible using for continuous melting and directional solidification (DS), based on experimental verification, 3D finite element (FE) models w... To improve the power efficiency and optimize the configuration of cold crucible using for continuous melting and directional solidification (DS), based on experimental verification, 3D finite element (FE) models with various configuration-elements were developed to investigate the magnetic field in cold crucible. Magnetic flux density (B) was measured and calculated under different configuration parameters. These parameters include the inner diameter (D2), the slit width (d), the thickness of crucible wall, the section shape of the slit and the shield ring. The results show that the magnetic flux density in z direction (Bz) both at the slit and at the midpoint of segment will increase with the decrease of D2 or with the increase of the width of the slit and the section area of wedge slit or removing the shield ring. In addition, there is a worst wall thickness that can induce the minimum Bz for a cold crucible with a certain outer diameter. 展开更多
关键词 cold crucible magnetic flux density configuration design directional solidification
下载PDF
Effect of traveling magnetic field on dendrite growth of Pb-Sn alloy during directional solidification 被引量:4
9
作者 闵志先 沈军 +1 位作者 王灵水 刘林 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2011年第9期1976-1980,共5页
The influence of melt convection on dendrite growth during the upward-directional solidification of Pb-33%Sn binary alloys was investigated.The melt convection was modulated by traveling magnetic field.When the direct... The influence of melt convection on dendrite growth during the upward-directional solidification of Pb-33%Sn binary alloys was investigated.The melt convection was modulated by traveling magnetic field.When the direction of traveling magnetic field was changed from upward to downward,the primary dendrite spacing gradually increased,and the distribution peak of the primary dendrite spacing shifted to the field of narrower spacing.These result from the different intensities of melt convection,which are controlled by the traveling magnetic field.The effects of the traveling magnetic field on melt convection are similar to those of adjustment in the gravity level,thus,the primary dendrite spacing varies.When the intensity of the traveling magnetic field was 1 mT,and the drawing speed was 50 μm/s,the gravity acceleration reached 0.22g for the downward-traveling magnetic field and 3.07g for the upward-traveling magnetic field. 展开更多
关键词 directional solidification MICROSTRUCTURE Pb-Sn alloy traveling magnetic field
下载PDF
Effect of travelling magnetic field on interface morphology in directionally solidified Sn-Cd alloy 被引量:2
10
作者 王雷 沈军 +2 位作者 王灵水 冯周荣 傅恒志 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2013年第8期2454-2459,共6页
The diversity of interface morphologies is observed for directionally solidified Sn-0.65%Cd alloy under a travelling magnetic field (TMF) in the 4 mm-diameter sample. Under an upward TMF, planar and cellular interfa... The diversity of interface morphologies is observed for directionally solidified Sn-0.65%Cd alloy under a travelling magnetic field (TMF) in the 4 mm-diameter sample. Under an upward TMF, planar and cellular interface morphologies transform alternately with increasing magnetic flux density (B≤10.3 mT). The interface morphology transforms from shallow cellular to deep cellular morphology under a weak downward TMF (B=3.2 mT). When the magnetic flux density increases further, both sides of the interface morphology appear to be slightly inconsistent, but they roughly tend to be planar under a strong downward TMF (BS10.3 mT). The interface instability may be attributed to the flow driven by the TMF. Moreover, the shape of interface appears to be almost flat under an upward TMF, but deflective under a downward TMF. 展开更多
关键词 directional solidification travelling magnetic field interface morphology Sn-Cd alloy
下载PDF
Directional growth behavior of a(Al) dendrites during concentration-gradientcontrolled solidification process in static magnetic field 被引量:2
11
作者 李磊 徐博 +6 位作者 佟伟平 何立子 班春燕 张辉 左玉波 朱庆丰 崔建忠 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2015年第7期2438-2445,共8页
The large and small sized Cu(solid)/Al(liquid) couples were prepared to investigate the directional growth behavior of primary a(Al) phase during a concentration-gradient-controlled solidification process under ... The large and small sized Cu(solid)/Al(liquid) couples were prepared to investigate the directional growth behavior of primary a(Al) phase during a concentration-gradient-controlled solidification process under various static magnetic fields(SMFs).The results show that in the large couples,the α(Al) dendrites reveal a directional growth character whether without or with the SMF.However,the 12 T magnetic field induces regular growth,consistent deflection and the decrease of secondary arm spacing of the dendrites.In the small couples,the α(Al) dendrites still reveal a directional growth character to some extent with a SMF of ≤5 T.However,an 8.8 T SMF destroys the directional growth and induces severe random deflections of the dendrites.When the SMF increases to 12 T,the a(Al) dendrites become quite regular despite of the consistent deflection.The directional growth arises from the continuous long-range concentration gradient field built in the melt.The morphological modification is mainly related to the suppression of natural convections and the induction of thermoelectric magnetic convection by the SMF. 展开更多
关键词 α(Al) dendrite diffusion couple concentration gradient field static magnetic field directional growth thermoelectric magnetic convection
下载PDF
.NET框架下Direct3D程序的快速开发 被引量:6
12
作者 刘维华 张尤赛 王敏 《电脑开发与应用》 2004年第12期34-36,共3页
为了实现利用.NET编程语言开发Direct3D程序的目的,通过.NET框架及DirectX的相关特点介 绍分析,阐述了基于托管Direct3D样例框架进行三维图形快速开发的方法步骤。
关键词 direct3D .net框架 快速开发 编程语言 三维图形 程序 托管 目的
下载PDF
Direct Ink Writing of Highly Conductive MXene Frames for Tunable Electromagnetic Interference Shielding and Electromagnetic Wave-Induced Thermochromism 被引量:14
13
作者 Xinyu Wu Tingxiang Tu +6 位作者 Yang Dai Pingping Tang Yu Zhang Zhiming Deng Lulu Li Hao-Bin Zhang Zhong-Zhen Yu 《Nano-Micro Letters》 SCIE EI CAS CSCD 2021年第10期14-28,共15页
The highly integrated and miniaturized next-generation electronic products call for high-performance electromagnetic interference(EMI)shielding materials to assure the normal operation of their closely assembled compo... The highly integrated and miniaturized next-generation electronic products call for high-performance electromagnetic interference(EMI)shielding materials to assure the normal operation of their closely assembled components.However,the most current techniques are not adequate for the fabrication of shielding materials with programmable structure and controllable shielding efficiency.Herein,we demonstrate the direct ink writing of robust and highly conductive Ti3C2Tx MXene frames with customizable structures by using MXene/AlOOH inks for tunable EMI shielding and electromagnetic wave-induced thermochromism applications.The as-printed frames are reinforced by immersing in AlCl_(3)/HCl solution to remove the electrically insulating AlOOH nanoparticles,as well as cross-link the MXene sheets and fuse the filament interfaces with aluminum ions.After freeze-drying,the resultant robust and porous MXene frames exhibit tunable EMI shielding efficiencies in the range of 25-80 dB with the highest electrical conductivity of 5323 S m−1.Furthermore,an electromagnetic wave-induced thermochromic MXene pattern is assembled by coating and curing with thermochromic polydimethylsiloxane on a printed MXene pattern,and its color can be changed from blue to red under the high-intensity electromagnetic irradiation.This work demonstrates a direct ink printing of customizable EMI frames and patterns for tuning EMI shielding efficiency and visualizing electromagnetic waves. 展开更多
关键词 MXene Electromagnetic interference shielding direct ink writing Electrical conductivity THERMOCHROMISM
下载PDF
Research into magnetic guidance technology for directional drilling in SAGD horizontal wells 被引量:10
14
作者 Gao Deli Diao Binbin +1 位作者 Wu Zhiyong Zhu Yu 《Petroleum Science》 SCIE CAS CSCD 2013年第4期500-506,共7页
SAGD horizontal wells are used to enhance oil recovery from heavy oil reservoirs.This technology requires precise separation between the production well and the injection well to ensure the efficient drainage of the r... SAGD horizontal wells are used to enhance oil recovery from heavy oil reservoirs.This technology requires precise separation between the production well and the injection well to ensure the efficient drainage of the reservoir.By studying the attitude of the downhole probe tube and the production well trajectory,an algorithm is proposed for eliminating ferromagnetic interference while drilling injection wells.A high accuracy filter circuit has been designed to correct the detected magnetic signals,which are ultra-weak,frequency-instable,and narrow-band.The directional drilling magnetic guidance system(DD-MGS) has been developed by integrating these advanced techniques.It contains a sub-system for the ranging calculation software,a magnetic source,a downhole probe tube and a sub-system for collecting & processing the detected signals.The DD-MGS has succeeded in oilfield applications.It can guide the directional drilling trajectory not only in the horizontal section but also in the build section of horizontal injection wells.This new technology has broad potential applications. 展开更多
关键词 Heavy oil SAGD horizontal wells directional drilling magnetic guidance system
下载PDF
Effect of reductant type on the embedding direct reduction of beach titanomagnetite concentrate 被引量:7
15
作者 Yong-qiang Zhao Ti-chang Sun +2 位作者 Hong-yu Zhao Chao Chen Xiao-ping Wang 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2019年第2期152-159,共8页
Iron and titanium were recovered from beach titanomagnetite(TTM) concentrate by embedding direct reduction and magnetic separation. The reduction products and the effects of the reductant type and reduction temperatur... Iron and titanium were recovered from beach titanomagnetite(TTM) concentrate by embedding direct reduction and magnetic separation. The reduction products and the effects of the reductant type and reduction temperature on the reduction behavior were investigated. The results showed that the reduction of TTM concentrate was strongly related to the gasification reactivity of the reductant. Bitumite presented a better product index than wheat-straw biochar and coke, mainly because the gasification reactivity of bitumite was better than that of the other reductants. In addition, high temperatures were not beneficial to embedding direct reduction because of the emergence of a molten phase and iron-joined crystals, which in turn reduced the diffusion rate of the reducing gas and impeded the reduction reaction in the central area of the roasted briquette. The use of bitumite as the reductant at a C/Fe molar ratio of 1.4 and a reduction temperature of 1200°C for 120 min resulted in direct-reduction iron powder assaying 90.28 wt% TFe and 0.91 wt% TiO_2 with an iron recovery of 91.83% and titanium concentrate assaying 46.01 wt% TiO_2 with a TiO_2 recovery of 91.19%. Titanium existed mainly in the form of anosovite and ilmenite in the titanium concentrate. 展开更多
关键词 BEACH TITANOMAGnetITE CONCENTRATE EMBEDDING direct REDUCTION magnetic SEPARATION reductant REDUCTION temperature
下载PDF
Direct Torque Control System and Sensorless Technique of Permanent Magnet Synchronous Motor 被引量:10
16
作者 胡育文 田淳 +2 位作者 游志青 汤立新 M.F.Rahman 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2003年第2期97-102,共6页
The direct torque control theory has achieved great success in the control ofinduction motors. However, in the DTC drive system of Permanent Magnet Synchronous Machine (PMSM)proposed a few years ago, there are many ba... The direct torque control theory has achieved great success in the control ofinduction motors. However, in the DTC drive system of Permanent Magnet Synchronous Machine (PMSM)proposed a few years ago, there are many basic theoretical problems that must be clarified. Thispaper describes an investigation about the effect of the zero voltage space vectors in the DTCsystem of PMSM and points out that if using the zero voltage space vectors rationally, not only canthe DTC system be driven successfully but also the torque ripple is reduced and the performance ofthe system is improved. This paper also studies the sensorless technique in the DTC system of PMSMand configures the DTC system of PMSM with sensorless technique including zero voltage spacevectors. Numerical simulations and experimental tests have proved the theory correct. In thecondition of sensor-less, the DTC system of PMSM is wide-rangely speed adjusting, and the ratio ofspeed adjustment is 1: 100. 展开更多
关键词 power electronics direct torque control permanent magnet motors SENSORLESS stator flux linkage
下载PDF
Economical quantum secure direct communication network with single photons 被引量:10
17
作者 邓富国 李熙涵 +2 位作者 李春燕 周萍 周宏余 《Chinese Physics B》 SCIE EI CAS CSCD 2007年第12期3553-3559,共7页
In this paper a scheme for quantum secure direct communication (QSDC) network is proposed with a sequence of polarized single photons. The single photons are prepared originally in the same state (0) by the server... In this paper a scheme for quantum secure direct communication (QSDC) network is proposed with a sequence of polarized single photons. The single photons are prepared originally in the same state (0) by the servers on the network, which will reduce the difficulty for the legitimate users to check eavesdropping largely. The users code the information on the single photons with two unitary operations which do not change their measuring bases. Some decoy photons, which are produced by operating the sample photons with a Hadamard, are used for preventing a potentially dishonest server from eavesdropping the quantum lines freely. This scheme is an economical one as it is the easiest way for QSDC network communication securely. 展开更多
关键词 quantum secure direct communication netWORK single photons
下载PDF
The scattering fields for a spherical target irradiated by a plane electromagnetic wave in an arbitrary direction 被引量:8
18
作者 李应乐 黄际英 《Chinese Physics B》 SCIE EI CAS CSCD 2006年第2期281-285,共5页
The relation between corresponding trigonometric functions in two rotating coordinate systems is presented. The transformation formula for a vector in the two rotating spherical coordinate systems is obtained. The sca... The relation between corresponding trigonometric functions in two rotating coordinate systems is presented. The transformation formula for a vector in the two rotating spherical coordinate systems is obtained. The scattering fields for a spherical target irradiated by a plane electromagnetic wave in an arbitrary direction are derived. These fields in a particular case retrogress to those available in the literature. The obtained results have great potential in practical applications. 展开更多
关键词 scattering spherical target polarization in an arbitrary direction electromagnetic wave
下载PDF
Genetic algorithm and particle swarm optimization tuned fuzzy PID controller on direct torque control of dual star induction motor 被引量:14
19
作者 BOUKHALFA Ghoulemallah BELKACEM Sebti +1 位作者 CHIKHI Abdesselem BENAGGOUNE Said 《Journal of Central South University》 SCIE EI CAS CSCD 2019年第7期1886-1896,共11页
This study presents analysis, control and comparison of three hybrid approaches for the direct torque control (DTC) of the dual star induction motor (DSIM) drive. Its objective consists of combining three different he... This study presents analysis, control and comparison of three hybrid approaches for the direct torque control (DTC) of the dual star induction motor (DSIM) drive. Its objective consists of combining three different heuristic optimization techniques including PID-PSO, Fuzzy-PSO and GA-PSO to improve the DSIM speed controlled loop behavior. The GA and PSO algorithms are developed and implemented into MATLAB. As a result, fuzzy-PSO is the most appropriate scheme. The main performance of fuzzy-PSO is reducing high torque ripples, improving rise time and avoiding disturbances that affect the drive performance. 展开更多
关键词 dual star induction motor drive direct torque control particle swarm optimization (PSO) fuzzy logic control genetic algorithms
下载PDF
Staged reaction kinetics and characteristics of iron oxide direct reduction by carbon 被引量:4
20
作者 Ru-fei Wei Da-qiang Cang +1 位作者 Ling-ling Zhang Yuan-yuan Bai 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2015年第10期1025-1032,共8页
Staged reduction kinetics and characteristics of iron oxide direct reduction by carbon were studied in this work. The characteristics were investigated by simultaneous thermogravimetric analysis, X-ray diffraction(XR... Staged reduction kinetics and characteristics of iron oxide direct reduction by carbon were studied in this work. The characteristics were investigated by simultaneous thermogravimetric analysis, X-ray diffraction(XRD), and quadrupole mass spectrometry. The kinetics parameters of the reduction stages were obtained by isoconversional(model-free) methods. Three stages in the reduction are Fe2O3→Fe3O4, Fe3O4→Fe O, and Fe O→Fe, which start at 912 K, 1255 K, and 1397 K, respectively. The CO content in the evolved gas is lower than the CO2content in the Fe2O3→Fe3O4stage but is substantially greater than the CO2 contents in the Fe3O4→Fe O and Fe O→Fe stages, where gasification starts at approximately 1205 K. The activation energy(E) of the three stages are 126–309 k J/mol, 628 k J/mol, and 648 k J/mol, respectively. The restrictive step of the total reduction is Fe O→Fe. If the rate of the total reduction is to be improved, the rate of the Fe O→Fe reduction should be improved first. The activation energy of the first stage is much lower than those of the latter two stages because of carbon gasification. Carbon gasification and FexOy reduction by CO, which are the restrictive step in the last two stages, require further study. 展开更多
关键词 iron oxides direct reduction reduction kinetics RE
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部