期刊文献+
共找到15,777篇文章
< 1 2 250 >
每页显示 20 50 100
Engineering Thermoelectric Performance of α-GeTe by Ferroelectric Distortion 被引量:1
1
作者 Yuting Fan Chenghao Xie +5 位作者 Jun Li Xiangyu Meng Jinchang Sun Jinsong Wu Xinfeng Tang Gangjian Tan 《Energy & Environmental Materials》 SCIE EI CAS CSCD 2024年第2期171-179,共9页
The rhombohedralα-GeTe can be approximated as a slightly distorted rock-salt structure along its[111]direction and possesses superb thermoelectric performance.However,the role of such a ferroelectric-like structural ... The rhombohedralα-GeTe can be approximated as a slightly distorted rock-salt structure along its[111]direction and possesses superb thermoelectric performance.However,the role of such a ferroelectric-like structural distortion on its transport properties remains unclear.Herein,we performed a systematic study on the crystal structure and electronic band structure evolutions of Ge_(1-x)Sn_(x)Te alloys where the degree of ferroelectric distortion is continuously tuned.It is revealed that the band gap is maximized while multiple valence bands are converged at x=0.6,where the ferroelectric distortion is the least but still works.Once undistorted,the band gap is considerably reduced,and the valence bands are largely separated again.Moreover,near the ferro-to-paraelectric phase transition Curie temperature,the lattice thermal conductivity reaches its minima because of significant lattice softening enabled by ferroelectric instability.We predict a peak ZT value of 2.6 at 673 K inα-GeTe by use of proper dopants which are powerful in suppressing the excess hole concentrations but meanwhile exert little influence on the ferroelectric distortion. 展开更多
关键词 electronic band structures ferroelectric distortion lattice softening THERMOELECTRIC α-GeTe
下载PDF
Local tetragonal distortion of Pt alloy catalysts for enhanced oxygen reduction reaction efficiency
2
作者 Xiaoke Li Xiao Duan +8 位作者 Kang Hua Yongkang Wu Zhiyan Rui Rui Ding Aidong Li Chen Ouyang Jia Li Ting Li Jianguo Liu 《Carbon Energy》 SCIE EI CAS CSCD 2024年第7期41-52,共12页
Platinum-based alloy nanoparticles are the most attractive catalysts for the oxygen reduction reaction at present,but an in-depth understanding of the relationship between their short-range structural information and ... Platinum-based alloy nanoparticles are the most attractive catalysts for the oxygen reduction reaction at present,but an in-depth understanding of the relationship between their short-range structural information and catalytic performance is still lacking.Herein,we present a synthetic strategy that uses transition-metal oxide-assisted thermal diffusion.PtCo/C catalysts with localized tetragonal distortion were obtained by controlling the thermal diffusion process of transition-metal elements.This localized structural distortion induced a significant strain effect on the nanoparticle surface,which further shortened the length of the Pt-Pt bond,improved the electronic state of the Pt surface,and enhanced the performance of the catalyst.PtCo/C catalysts with special short-range structures achieved excellent mass activity(2.27 Amg_(Pt)^(-1))and specific activity(3.34 A cm^(-2)).In addition,the localized tetragonal distortion-induced surface compression of the Pt skin improved the stability of the catalyst.The mass activity decreased by only 13% after 30,000 cycles.Enhanced catalyst activity and excellent durability have also been demonstrated in the proton exchange membrane fuel cell configuration.This study provides valuable insights into the development of advanced Pt-based nanocatalysts and paves the way for reducing noble-metal loading and increasing the catalytic activity and catalyst stability. 展开更多
关键词 ELECTROCATALYSTS fuel cells local tetragonal distortion oxygen reduction
下载PDF
Linear magnetoresistance and structural distortion in layered SrCu_(4-x)P_(2) single crystals
3
作者 聂勇 陈正 +10 位作者 韦文森 李慧杰 张勇 梅明 王园园 宋文海 宋东升 王钊胜 朱相德 宁伟 田明亮 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第1期591-594,共4页
We report a systematic study on layered metal SrCu_(4-x)P_(2) single crystals via transport, magnetization, thermodynamic measurements and structural characterization. We find that the crystals show large linear magne... We report a systematic study on layered metal SrCu_(4-x)P_(2) single crystals via transport, magnetization, thermodynamic measurements and structural characterization. We find that the crystals show large linear magnetoresistance without any sign of saturation with a magnetic field up to 30T. We also observe a phase transition with significant anomalies in resistivity and heat capacity at T_(p)~140 K. Thermal expansion measurement reveals a subtle lattice parameter variation near Tp, i.e.,?L_(c)/L_(c)~0.062%. The structural characterization confines that there is no structure transition below and above T_(p). All these results suggest that the nonmagnetic transition of SrCu_(4-x)P_(2) could be associated with structural distortion. 展开更多
关键词 linear magnetoresistance thermal expansion specific heat structural distortion
下载PDF
Bulging Distortion of Austenitic Stainless Steel Sheet on the Partially Penetrated Side of Non-Penetration Lap Laser Welding Joint
4
作者 Chengwu Yao Enze Liu +1 位作者 Jiaming Ni Binying Nie 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2024年第1期286-295,共10页
Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded aust... Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded austenitic stainless steel parts is limited owing to the micro bulging distortion that occurs on the back surface of the partial penetration side.In this paper,non-penetration lap laser welding experiments,were conducted on galvanized and SUS304 austenitic stainless steel plates using a fiber laser,to investigate the mechanism of bulging distortion.A comparative experiment of DC01 galvanized steel-Q235 carbon steel lap laser welding was carried out,and the deflection and distortion profile of partially penetrated side of the sheets were measured using a noncontact laser interferometer.In addition,the cold-rolled SUS304 was subjected to heat holding at different temperatures and water quenching after bending to characterize its microstructure under tensile and compressive stress.The results show that,during the heating stage of the thermal cycle of laser lap welding,the partial penetration side of the SUS304 steel sheet generates compressive stress,which extrudes the material in the heat-affected zone to the outside of the back of the SUS304 steel sheet,thereby forming a bulge.The findings of these experiments can be of great value for controlling the distortion of the partial penetrated side of austenitic stainless steel sheet during laser non-penetration lap welding. 展开更多
关键词 Non-penetration lap laser welding Bulging distortion Austenitic stainless steel Compressive stress Tension stress
下载PDF
Cross-section distortion and springback characteristics of double-cavity aluminum profile in force controlled stretch-bending
5
作者 Zhi-wen LIU Zi-xuan DONG +2 位作者 Cong-chang XU Jie YI Luo-xing LI 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2024年第8期2476-2490,共15页
3D elastic-plastic FE model for simulating the force controlled stretch-bending process of double-cavity aluminum profile was established using hybrid explicit−implicit solvent method.Considering the computational acc... 3D elastic-plastic FE model for simulating the force controlled stretch-bending process of double-cavity aluminum profile was established using hybrid explicit−implicit solvent method.Considering the computational accuracy and efficiency,the optimal choices of numerical parameters and algorithms in FE modelling were determined.The formation mechanisms of cross-section distortion and springback were revealed.The effects of pre-stretching,post-stretching,friction,and the addition of internal fillers on forming quality were investigated.The results show that the stress state of profile in stretch-bending is uniaxial with only a circumferential stress.The stress distribution along the length direction of profile is non-uniform and the maximum tensile stress is located at a certain distance away from the center of profile.As aluminum profile is gradually attached to bending die,the distribution characteristic of cross-section distortion along the length direction of profile changes from V-shape to W-shape.After unloading the forming tools,cross-section distortion decreases obviously due to the stress relaxation,with a maximum distortion difference of 13%before and after unloading.As pre-stretching and post-stretching forces increase,cross-section distortion increases gradually,while springback first decreases and then remains unchanged.With increasing friction between bending die and profile,cross-section distortion slightly decreases,while springback increases.Cross-section distortion decreases by 83%with adding PVC fillers into the cavities of profile,while springback increases by 192.2%. 展开更多
关键词 hollow aluminum profile force controlled stretch-bending numerical parameters springback analysis approach cross-section distortion SPRINGBACK process parameters
下载PDF
Channel estimation in integrated radar and communication systems with power amplifier distortion
6
作者 LIU Yan YI Jianxin +2 位作者 WAN Xianrong RAO Yunhua HAO Caiyong 《Journal of Systems Engineering and Electronics》 SCIE CSCD 2024年第5期1098-1108,共11页
To reduce the negative impact of the power amplifier(PA)nonlinear distortion caused by the orthogonal frequency division multiplexing(OFDM)waveform with high peak-to-average power ratio(PAPR)in integrated radar and co... To reduce the negative impact of the power amplifier(PA)nonlinear distortion caused by the orthogonal frequency division multiplexing(OFDM)waveform with high peak-to-average power ratio(PAPR)in integrated radar and communication(RadCom)systems is studied,the channel estimation in passive sensing scenarios.Adaptive channel estimation methods are proposed based on different pilot patterns,considering nonlinear distortion and channel sparsity.The proposed methods achieve sparse channel results by manipulating the least squares(LS)frequency-domain channel estimation results to preserve the most significant taps.The decision-aided method is used to optimize the sparse channel results to reduce the effect of nonlinear distortion.Numerical results show that the channel estimation performance of the proposed methods is better than that of the conventional methods under different pilot patterns.In addition,the bit error rate performance in communication and passive radar detection performance show that the proposed methods have good comprehensive performance. 展开更多
关键词 channel estimation integrated radar and communication(RadCom) passive sensing nonlinear distortion power amplifier(PA) pilot pattern
下载PDF
Computational Quantification of Map Projection Distortion by Fractal Dimension of Coastlines
7
作者 Franklin Lee 《Journal of Applied Mathematics and Physics》 2024年第5期1890-1903,共14页
Maps, essential tools for portraying the Earth’s surface, inherently introduce distortions to geographical features. While various quantification methods exist for assessing these distortions, they often fall short w... Maps, essential tools for portraying the Earth’s surface, inherently introduce distortions to geographical features. While various quantification methods exist for assessing these distortions, they often fall short when evaluating actual geographic features. In our study, we took a novel approach by analyzing map projection distortion from a geometric perspective. We computed the fractal dimensions of different stretches of coastline before and after projection using the divide-and-conquer algorithm and image processing. Our findings revealed that map projections, even when preserving basic shapes, inevitably stretch and compress coastlines in diverse directions. This analysis method provides a more realistic and practical way to measure map-induced distortions, with significant implications for cartography, geographic information systems (GIS), and geomorphology. By bridging the gap between theoretical analysis and real-world features, this method greatly enhances accuracy and practicality when evaluating map projections. 展开更多
关键词 Map Projection distortion COASTLINE Fractal Dimension CARTOGRAPHY Geographic Information Systems
下载PDF
水稻内稃扭曲突变体palea distortion 1(pd1)的鉴定与基因定位 被引量:1
8
作者 郭爽 李云峰 +3 位作者 任德勇 王增 杜青 何光华 《分子植物育种》 CAS CSCD 2011年第3期256-260,共5页
在对籼稻缙恢10进行EMS(ethyl methane sulfonate)处理后的群体中,发现一个花器官突变体,主要表现为内稃扭曲并呈现外稃化特征,浆片数目增加且呈现稃状特征,雄蕊数目减少至1~4个,部分雄蕊的花丝呈现浆片化特征,暂将其命名为水稻颖壳扭... 在对籼稻缙恢10进行EMS(ethyl methane sulfonate)处理后的群体中,发现一个花器官突变体,主要表现为内稃扭曲并呈现外稃化特征,浆片数目增加且呈现稃状特征,雄蕊数目减少至1~4个,部分雄蕊的花丝呈现浆片化特征,暂将其命名为水稻颖壳扭曲突变体palea distortion 1(pd1)。遗传分析表明该突变性状受一个隐形单基因控制。利用群体分离分析法(bulked segregation analysis,BSA),将PD1基因定位在第2染色体的RM13693和RM13936之间,遗传距离分别为3.25cM和3.90cM。该研究结果为PD1基因的图位克隆奠定了基础。 展开更多
关键词 水稻 palea distortion 1(pd1) 突变体 基因定位
下载PDF
Application of the Delaunay triangulation interpolation in distortion XRII image 被引量:2
9
作者 李元金 舒华忠 +3 位作者 罗立民 陈阳 王涛 岳座刚 《Journal of Southeast University(English Edition)》 EI CAS 2014年第3期306-310,共5页
To alleviate the distortion of XRII X-ray image intensifier images in the C-arm CT computer tomography imaging system an algorithm based on the Delaunay triangulation interpolation is proposed.First the causes of the ... To alleviate the distortion of XRII X-ray image intensifier images in the C-arm CT computer tomography imaging system an algorithm based on the Delaunay triangulation interpolation is proposed.First the causes of the phenomenon the classical correction algorithms and the Delaunay triangulation interpolation are analyzed.Then the algorithm procedure is explained using flow charts and illustrations. Finally experiments are described to demonstrate its effectiveness and feasibility. Experimental results demonstrate that the Delaunay triangulation interpolation can have the following effects.In the case of the same center the root mean square distances RMSD and standard deviation STD between the corrected image with Delaunay triangulation interpolation and the ideal image are 5.760 4 ×10 -14 and 5.354 2 ×10 -14 respectively.They increase to 1.790 3 2.388 8 2.338 8 and 1.262 0 1.268 1 1.202 6 after applying the quartic polynomial model L1 and model L2 to the distorted images respectively.The RMSDs and STDs between the corrected image with the Delaunay triangulation interpolation and the ideal image are 2.489 × 10 -13 and 2.449 8 ×10 -13 when their centers do not coincide. When the quartic polynomial model L1 and model L2 are applied to the distorted images they are 1.770 3 2.388 8 2.338 8 and 1.269 9 1.268 1 1.202 6 respectively. 展开更多
关键词 XRII image Delaunay triangulation interpolation distortion correction
下载PDF
A Novel Segregation Distortion in Intraspecific Population of Asian Cotton(Gossypium arboretum L.)Detected by Molecular Markers 被引量:2
10
作者 李武 林忠旭 张献龙 《Journal of Genetics and Genomics》 SCIE CAS CSCD 北大核心 2007年第7期634-640,共7页
The segregation ratio of markers in an F2 population derived from Rudongjijiaoyaguo (Rdjjyg) and Zhongmian971 (Zm971) was studied using 3 morphological markers, 20 SSR markers, and ll SRAP markers. Totally, 24 mar... The segregation ratio of markers in an F2 population derived from Rudongjijiaoyaguo (Rdjjyg) and Zhongmian971 (Zm971) was studied using 3 morphological markers, 20 SSR markers, and ll SRAP markers. Totally, 24 markers (77.42%) showed a distorted segregation and all of them skewed toward the female genotype, which was peculiar in recent cotton research. All the three types of SSR markers and SRAP marker showed distorted segregation, but the morphological markers (Purple stem, Okra leaf, and Red spot color) were normally segregated. This indicated that such a novel segregation distortion phenomenon resulted from interior genetic factors, The allele frequency and the distribution of different genotype frequencies in the F2 population were analyzed in codominant markers, to find out factors attributed to distorted segregation. Most of them implied distorted allele frequency, but it was normal genotype frequency, which showed that these markers were influenced at the gamete level. 展开更多
关键词 Gossypium arboretum L. segregation distortion SSR EST-SSR SRAP
下载PDF
The anti-correlation method for removing harmonic distortion in vibroseis slip-sweep data 被引量:1
11
作者 张红静 周辉 +1 位作者 Abd E1-Aziz Khairy Abd E1-Aal 张洁 《Applied Geophysics》 SCIE CSCD 2012年第2期159-167,234,共10页
The slip-sweep technique is one of the high-efficiency, high-fidelity, and environmental vibroseis seismic prospecting techniques which consists of a vibrator group sweeping without waiting for the previous group's s... The slip-sweep technique is one of the high-efficiency, high-fidelity, and environmental vibroseis seismic prospecting techniques which consists of a vibrator group sweeping without waiting for the previous group's sweep to terminate. The cycle time can be reduced drastically and hence the production efficiency can be increased significantly but harmonic distortion of one sweep will leak into the record of the other sweep. In this paper, we propose an anti-correlation method for removing harmonic distortion in vibroseis data. This method is based on decomposition of the ground force signal into fundamental and harmonic components. Then the corresponding anti-correlation operator can be computed to estimate the energy of each harmonic after correlating the vibroseis data with the corresponding harmonic component. Finally, the vibroseis harmonic noise to be removed can be obtained by subtracting the extracted harmonic noise from the traces of the previous group's sweep. The advantage of the proposed method is that it can process both uncorrelated and correlated vibroseis seismic data. Moreover, the algorithm is simple, stable, and computationally fast. Especially, the significant contribution of this method is a considerable reduction in the harmonic without any alteration of the desired signals. The method was tested on both synthetic and field data sets to validate the good harmonic noise suppression results. 展开更多
关键词 VIBROSEIS slip-sweep acquisition anti-correlation method harmonic distortion removal
下载PDF
Cascade Kalman filter for gravity anomaly distortion correction based on second order potential model 被引量:1
12
作者 赵立业 李宏生 +1 位作者 周百令 李坤宇 《Journal of Southeast University(English Edition)》 EI CAS 2008年第4期482-486,共5页
Using a gravity anomaly covariance function based on the second-order Ganssian Markov gravity anomaly potential model, the state equation of a gravity anomaly signal is obtained in marine gravimetry. Combined with the... Using a gravity anomaly covariance function based on the second-order Ganssian Markov gravity anomaly potential model, the state equation of a gravity anomaly signal is obtained in marine gravimetry. Combined with the system state equation and the measurement equation, a new method of the cascade Kalman filter is proposed and applied to the correction of gravity anomaly distortion. In the signal processing procedure, an inverse Kalman filter is used to restore the gravity anomaly signal and high frequency noises first. Then an adaptive Kalman filter, which uses the gravity anomaly state equation as the system equation, is set to estimate the actual gravity anomaly data. Emulations and experiments indicate that both the cascade Kalman filter method and the single inverse Kalman filter method are effective in alleviating the distortion of the gravity anomaly signal, but the performance of the cascade Kalman filter method is better than that of the single inverse Kalman filter method. 展开更多
关键词 GRAVIMETER gravity anomaly cascade Kalman filter inverse Kalman filter distortion correction
下载PDF
RESEARCH ON NONLINEAR DISTORTION IN AMPLIFIERS 被引量:2
13
作者 王成华 包骅 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2000年第2期182-187,共6页
Transistors are nonlinear devices, which can produce nonlinear distortion in amplifier while amplifying signals. For weak nonlinear distortion, the expressions of total harmonic distortion (THD), the second order in... Transistors are nonlinear devices, which can produce nonlinear distortion in amplifier while amplifying signals. For weak nonlinear distortion, the expressions of total harmonic distortion (THD), the second order intermodulation distortion(IM2 ), the third order intermodulation distortion(IM 3) and intercept point(IP 3) are deduced. With the aid of software Multisim, we simulate transistor common emitter amplifier, transistor common emitter amplifier with resistor in emitter, differential amplifier and differential amplifier with resistor between emitters. The simulational results and theoretical analyses are almost the same. 展开更多
关键词 nonlinear distortion intermodulation distortion intercept point negative feedback differential amplifier
下载PDF
Application of stiffness matrix of a beam element considering section distortion effect 被引量:2
14
作者 李海锋 罗永峰 《Journal of Southeast University(English Edition)》 EI CAS 2010年第3期431-435,共5页
According to the stationary principle of potential energy and the generalized coordinate method, a stiffness matrix of a beam element considering distortion effects is derived. Using the stiffness matrix of the beam e... According to the stationary principle of potential energy and the generalized coordinate method, a stiffness matrix of a beam element considering distortion effects is derived. Using the stiffness matrix of the beam element, a finite element program for computing thin-walled box steel beams is developed. And the program can take the section distortion and warping effects into account. The influences of diaphragm spacing on the mechanical behavior of thin-walled box beams are analyzed by the program. The numerical analysis shows that setting diaphragms have the greatest influence on the distortion normal stress, while there is very little influence on the bending normal stress. Only when the distance of adjacent diaphragms decreases to a certain value, will the distortion normal stress in the thin-walled box beam obviously reduce under the distortion load. Finally, a distortion-warping coefficient γ is introduced for simplifying the calculation of the longitudinal normal stress of thin-walled box beams. When the ratio of diaphragms adjacent space L to the maximum section dimension H is less than 2, the distortion-warping coefficient γ tends to one, which means that the distortion normal stress of the thin-walled box beam tends to zero, and the effect of the section distortion can be ignored. 展开更多
关键词 thin-walled box beam stationary principle of potential energy generalized coordinate method distortion WARPING distortion-warping coefficient
下载PDF
Distortion Behavior for SOI MOSFET
15
作者 张国艳 黄如 +1 位作者 张兴 王阳元 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2003年第8期809-812,共4页
Distortion analysis of SOI MOS transistor is presented.By the power series method,the distortion behaviors of FD (fully depleted) and RC (recessed channel) SOI MOS transistor configurations are investigated.It is show... Distortion analysis of SOI MOS transistor is presented.By the power series method,the distortion behaviors of FD (fully depleted) and RC (recessed channel) SOI MOS transistor configurations are investigated.It is shown that the distortion figures deteriorate with the scaling down of channel length,and the RC SOI device shows better distortion performance than the FD SOI device.At the same time,the experimental data show that the ineffective body contact can lead to an increase of the harmonic amplitude due to the bulk resistance.The presented results give an intuitive knowledge for the design of low distortion mixed signal integrated system. 展开更多
关键词 distortion behavior power series method SOI MOSFET
下载PDF
The Third-Order Intermodulation Distortion in the AlGaAs/GaAs HBT Amplifier
16
作者 廖小平 魏同立 《Journal of Southeast University(English Edition)》 EI CAS 1999年第1期33-38,共6页
An accurate circuit model of the microwave small signal characteristics of AlGaAs/GaAs HBT (heterojunction bipolar transistor) is extremely useful for microwave linear applications of the device. This paper presents ... An accurate circuit model of the microwave small signal characteristics of AlGaAs/GaAs HBT (heterojunction bipolar transistor) is extremely useful for microwave linear applications of the device. This paper presents a small signal AlGaAs/GaAs HBT equivalent circuit, based on the DC characteristics and S parameter of the device. Using Volterra series, we have calculated the third order intermodulation distortion in a linear AlGaAs/GaAs HBT amplifier. The calculations are well concordant with the measurements from two tone signals intermodulation distortion test, and its excellent third order intermodulation performance shows that AlGaAs/GaAs HBT is a very attractive candidate for linear amplification. 展开更多
关键词 AlGaAs/GaAs HBT the third order intermodulation distortion equivalent circuit
下载PDF
X-ray image distortion correction based on SVR
17
作者 袁泽慧 李世中 《Journal of Measurement Science and Instrumentation》 CAS CSCD 2015年第3期302-306,共5页
X-ray image has been widely used in many fields such as medical diagnosis,industrial inspection,and so on.Unfortunately,due to the physical characteristics of X-ray and imaging system,distortion of the projected image... X-ray image has been widely used in many fields such as medical diagnosis,industrial inspection,and so on.Unfortunately,due to the physical characteristics of X-ray and imaging system,distortion of the projected image will happen,which restrict the application of X-ray image,especially in high accuracy fields.Distortion correction can be performed using algorithms that can be classified as global or local according to the method used,both having specific advantages and disadvantages.In this paper,a new global method based on support vector regression(SVR)machine for distortion correction is proposed.In order to test the presented method,a calibration phantom is specially designed for this purpose.A comparison of the proposed method with the traditional global distortion correction techniques is performed.The experimental results show that the proposed correction method performs better than the traditional global one. 展开更多
关键词 X-ray image distortion correction support vector regression machine
下载PDF
Rate-distortion理论在H.264编码器中的应用
18
作者 李星 王涛 +1 位作者 张志洪 李秉智 《计算机工程与设计》 CSCD 2004年第12期2360-2362,共3页
编码模式的选择是视频编码器控制的一个重要功能,它直接决定了编码器的性能和效率。新的视频压缩协议H.264协议比其它视频压缩协议提出了更多的编码模式,这就决定了H.264编码器不能像H.263编码器一样,通过比较某个门限值来简单地决定采... 编码模式的选择是视频编码器控制的一个重要功能,它直接决定了编码器的性能和效率。新的视频压缩协议H.264协议比其它视频压缩协议提出了更多的编码模式,这就决定了H.264编码器不能像H.263编码器一样,通过比较某个门限值来简单地决定采用哪种编码模式。另一方面,根据Rate-distortion理论,在失真度与比特率之间存在一个最佳折衷点。如果确定了合适的拉各朗日(Lagrangian)参数,就能利用拉各朗日公式找到这个最佳折衷点。把这一理论作为H.264编码器的模式选择算法,将会使H.264编码器根据图像内容自适应地选择最佳的编码模式,达到最佳的压缩效果。 展开更多
关键词 H.264 编码模式 视频编码器 比特率 H.263 视频压缩 失真度 图像内容 算法 自适应
下载PDF
Correction of buckling distortion by ultrasonic shot peening treatment for 5A06 aluminum alloy welded structure 被引量:7
19
作者 何亚章 王东坡 +1 位作者 王颖 张海 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2016年第6期1531-1537,共7页
Ultrasonic shot peening treatment (USPT) was proposed to correct welding buckling distortion. The residual stress distribution along the depth direction of the peened zone was measured by an X-ray diffractometer. T... Ultrasonic shot peening treatment (USPT) was proposed to correct welding buckling distortion. The residual stress distribution along the depth direction of the peened zone was measured by an X-ray diffractometer. The microstructure of the treated specimens was investigated by scanning electron microscopy (SEM). The Vickers microhardness was measured in different areas of welded joint before USPT and along the depth direction of the weld after USPT. The experimental results indicated that the welding buckling distortion of 5A06 aluminum alloy butt joint can be essentially corrected by USPT; the average correction rate reached 90.8% in this study. Furthermore, USPT enhanced specimens by work hardening. The microstructure of the peened zone was improved; moreover, the distribution of the precipitates and grains presented an apparent orientation. 展开更多
关键词 welding bulking distortion CORRECTION ultrasonic shot peening treatment residual stress
下载PDF
WTO体制中的“扭曲”(DISTORTION)概念解析
20
作者 盛杰民 云昌智 《经济法论坛》 2003年第1期181-201,共21页
在国际贸易法最近十几年的发展中,尤其是在 WTO 成立以来,国际贸易法总体上经历了一个朝着全球一体化方向迅速发展的过程。而就国际贸易法的传统部门法——国际反补贴规则体系而言,一个居于核心地位的概念始终吸引着我们的理论兴趣,这就... 在国际贸易法最近十几年的发展中,尤其是在 WTO 成立以来,国际贸易法总体上经历了一个朝着全球一体化方向迅速发展的过程。而就国际贸易法的传统部门法——国际反补贴规则体系而言,一个居于核心地位的概念始终吸引着我们的理论兴趣,这就是"扭曲"(DISTORTION)概念。虽然在"乌拉圭回合补贴与反补贴措施协定"中回避了在立法中直接加入"扭曲"概念的做法,而是采取以"负面影响"(ADVERSE EFFECTS) 展开更多
关键词 国际贸易法 概念解析 WTO体制 distortion 乌拉圭回合 规则体系 部门法 反补贴法 理论兴趣 复杂型
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部