期刊文献+
共找到6,562篇文章
< 1 2 250 >
每页显示 20 50 100
Multilevel analysis of the central-peripheral-target organ pathway:contributing to recovery after peripheral nerve injury
1
作者 Xizi Song Ruixin Li +6 位作者 Xiaolei Chu Qi Li Ruihua Li Qingwen Li Kai-Yu Tong Xiaosong Gu Dong Ming 《Neural Regeneration Research》 SCIE CAS 2025年第10期2807-2822,共16页
Peripheral nerve injury is a common neurological condition that often leads to severe functional limitations and disabilities.Research on the pathogenesis of peripheral nerve injury has focused on pathological changes... Peripheral nerve injury is a common neurological condition that often leads to severe functional limitations and disabilities.Research on the pathogenesis of peripheral nerve injury has focused on pathological changes at individual injury sites,neglecting multilevel pathological analysis of the overall nervous system and target organs.This has led to restrictions on current therapeutic approaches.In this paper,we first summarize the potential mechanisms of peripheral nerve injury from a holistic perspective,covering the central nervous system,peripheral nervous system,and target organs.After peripheral nerve injury,the cortical plasticity of the brain is altered due to damage to and regeneration of peripheral nerves;changes such as neuronal apoptosis and axonal demyelination occur in the spinal cord.The nerve will undergo axonal regeneration,activation of Schwann cells,inflammatory response,and vascular system regeneration at the injury site.Corresponding damage to target organs can occur,including skeletal muscle atrophy and sensory receptor disruption.We then provide a brief review of the research advances in therapeutic approaches to peripheral nerve injury.The main current treatments are conducted passively and include physical factor rehabilitation,pharmacological treatments,cell-based therapies,and physical exercise.However,most treatments only partially address the problem and cannot complete the systematic recovery of the entire central nervous system-peripheral nervous system-target organ pathway.Therefore,we should further explore multilevel treatment options that produce effective,long-lasting results,perhaps requiring a combination of passive(traditional)and active(novel)treatment methods to stimulate rehabilitation at the central-peripheral-target organ levels to achieve better functional recovery. 展开更多
关键词 central nervous system central peripheral target organ multilevel pathological analysis nerve regeneration peripheral nerve injury peripheral nervous system target organs therapeutic approach
下载PDF
Multilevel carbon architecture of subnanoscopic silicon for fast‐charging high‐energy‐density lithium‐ion batteries 被引量:1
2
作者 Meisheng Han Yongbiao Mu +2 位作者 Lei Wei Lin Zeng Tianshou Zhao 《Carbon Energy》 SCIE EI CAS CSCD 2024年第4期256-268,共13页
Silicon(Si)is widely used as a lithium‐ion‐battery anode owing to its high capacity and abundant crustal reserves.However,large volume change upon cycling and poor conductivity of Si cause rapid capacity decay and p... Silicon(Si)is widely used as a lithium‐ion‐battery anode owing to its high capacity and abundant crustal reserves.However,large volume change upon cycling and poor conductivity of Si cause rapid capacity decay and poor fast‐charging capability limiting its commercial applications.Here,we propose a multilevel carbon architecture with vertical graphene sheets(VGSs)grown on surfaces of subnanoscopically and homogeneously dispersed Si–C composite nanospheres,which are subsequently embedded into a carbon matrix(C/VGSs@Si–C).Subnanoscopic C in the Si–C nanospheres,VGSs,and carbon matrix form a three‐dimensional conductive and robust network,which significantly improves the conductivity and suppresses the volume expansion of Si,thereby boosting charge transport and improving electrode stability.The VGSs with vast exposed edges considerably increase the contact area with the carbon matrix and supply directional transport channels through the entire material,which boosts charge transport.The carbon matrix encapsulates VGSs@Si–C to decrease the specific surface area and increase tap density,thus yielding high first Coulombic efficiency and electrode compaction density.Consequently,C/VGSs@Si–C delivers excellent Li‐ion storage performances under industrial electrode conditions.In particular,the full cells show high energy densities of 603.5 Wh kg^(−1)and 1685.5 Wh L^(−1)at 0.1 C and maintain 80.7%of the energy density at 3 C. 展开更多
关键词 fast charging high energy densities lithium‐ion batteries multilevel carbon architecture subnanoscopic silicon anode
下载PDF
On the Use of Monotonicity-Preserving Interpolatory Techniques in Multilevel Schemes for Balance Laws
3
作者 Antonio Baeza Rosa Donat Anna Martinez-Gavara 《Communications on Applied Mathematics and Computation》 EI 2024年第2期1319-1341,共23页
Cost-effective multilevel techniques for homogeneous hyperbolic conservation laws are very successful in reducing the computational cost associated to high resolution shock capturing numerical schemes.Because they do ... Cost-effective multilevel techniques for homogeneous hyperbolic conservation laws are very successful in reducing the computational cost associated to high resolution shock capturing numerical schemes.Because they do not involve any special data structure,and do not induce savings in memory requirements,they are easily implemented on existing codes and are recommended for 1D and 2D simulations when intensive testing is required.The multilevel technique can also be applied to balance laws,but in this case,numerical errors may be induced by the technique.We present a series of numerical tests that point out that the use of monotonicity-preserving interpolatory techniques eliminates the numerical errors observed when using the usual 4-point centered Lagrange interpolation,and leads to a more robust multilevel code for balance laws,while maintaining the efficiency rates observed forhyperbolic conservation laws. 展开更多
关键词 Hyperbolic balance laws Well-balanced schemes multilevel schemes Harten's multiresolution
下载PDF
基于Multilevel CodingTree模型的公路数字化档案标识编码研究 被引量:8
4
作者 罗竟 唐修益 +4 位作者 黄汝维 陈宁江 闫承鑫 刘晓东 高爱乐 《档案与建设》 北大核心 2015年第8期13-19,31,共8页
针对高速公路信息化建设中的编码问题,文章提出了基于Multilevel Coding Tree模型的"项目代号+属性+类别+流水号"四段位编码方案。根据该编码的结构,采用概率分析、实验测试和命题证明等手段,验证了编码的唯一性。该编码方案... 针对高速公路信息化建设中的编码问题,文章提出了基于Multilevel Coding Tree模型的"项目代号+属性+类别+流水号"四段位编码方案。根据该编码的结构,采用概率分析、实验测试和命题证明等手段,验证了编码的唯一性。该编码方案为公路信息化建设中各类文件提供了唯一的编码,达到一页(件)一码,是一种行之有效的编码方案。 展开更多
关键词 高速公路 工程档案 标识编码 multilevel CodingTree
下载PDF
Defect image segmentation using multilevel thresholding based on firefly algorithm with opposition-learning 被引量:3
5
作者 陈恺 戴敏 +2 位作者 张志胜 陈平 史金飞 《Journal of Southeast University(English Edition)》 EI CAS 2014年第4期434-438,共5页
To segment defects from the quad flat non-lead QFN package surface a multilevel Otsu thresholding method based on the firefly algorithm with opposition-learning is proposed. First the Otsu thresholding algorithm is ex... To segment defects from the quad flat non-lead QFN package surface a multilevel Otsu thresholding method based on the firefly algorithm with opposition-learning is proposed. First the Otsu thresholding algorithm is expanded to a multilevel Otsu thresholding algorithm. Secondly a firefly algorithm with opposition-learning OFA is proposed.In the OFA opposite fireflies are generated to increase the diversity of the fireflies and improve the global search ability. Thirdly the OFA is applied to searching multilevel thresholds for image segmentation. Finally the proposed method is implemented to segment the QFN images with defects and the results are compared with three methods i.e. the exhaustive search method the multilevel Otsu thresholding method based on particle swarm optimization and the multilevel Otsu thresholding method based on the firefly algorithm. Experimental results show that the proposed method can segment QFN surface defects images more efficiently and at a greater speed than that of the other three methods. 展开更多
关键词 quad flat non-lead QFN surface defects opposition-learning firefly algorithm multilevel Otsu thresholding algorithm
下载PDF
AUTOMATIC MULTILEVEL THRESHOLDING METHOD BASED ON MAXIMUM ENTROPY 被引量:2
6
作者 曹力 史忠科 郑家伟 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2005年第4期335-338,共4页
In the multilevel thresholding segmentation of the image, the classification number is always given by the supervisor. To solve this problem, a fast multilevel thresholding algorithm considering both the threshold val... In the multilevel thresholding segmentation of the image, the classification number is always given by the supervisor. To solve this problem, a fast multilevel thresholding algorithm considering both the threshold value and the classification number is proposed based on the maximum entropy, and the self-adaptive criterion of the classification number is given. The algorithm can obtain thresholds and automatically decide the classification number. Experimental results show that the algorithm is effective. 展开更多
关键词 multilevel thresholding maximum entropy classification number nonparametric method
下载PDF
Risk Assessment of Diary Cattle Brucellosis Based on Systematic Multilevel Grey Relation Entropy Method
7
作者 孙向东 江慎铭 刘拥军 《Agricultural Science & Technology》 CAS 2012年第10期2169-2174,2225,共7页
[Objective] The study was to explore the major factors affecting diary cattle brucellosis risk assessment,as well as their strong-to-weak sequence,so as to provide theoretical basis for assessing diary cattle brucello... [Objective] The study was to explore the major factors affecting diary cattle brucellosis risk assessment,as well as their strong-to-weak sequence,so as to provide theoretical basis for assessing diary cattle brucellosis risk level in different regions.[Method] From 4 dimensions of feeding and importing,breeding,housing and polyculture situation,an evaluation index system was set up,and diary cattle brucellosis risk survey was conducted in 3 typical regions.Finally,systematic multilevel grey relation entropy method was applied to perform data analysis.[Result] The strong-to-weak sequence of Level 1 impact factor of diary cattle brucellosis was as follows:feeding and importinghousingpolyculture situationbreeding;the sequence of Level 2 impact factor was U32〉U12〉U11〉U31〉U21〉U42〉U43〉U23〉U22〉U41;the risk level sequence of 3 typical regions was Province A(County A1,A2,A3)Province B(County B1,B2,B3)Province C(County C1,C2,C3).[Conclusion] According to the weight of Level 1 index strata,administrative departments at all levels and dairy cattle farmers should lay emphasis on the aspects of feeding,importing and housing;viewed from the perspective of Level 2 index strata,dairy cattle farmers should value the siting of cattle field,the brucellosis surveillance before importing and milking modes most.According to the diary cattle brucellosis risk level of 3 typical regions,if administrative departments at all levels strengthen peoples' awareness of their personal health and increase investment in this area,with new healthy cultured atmosphere built,the risk level of diary cattle brucellosis will surly decline. 展开更多
关键词 Systematic multilevel grey relation entropy method Diary cattle brucellosis Risk assessment
下载PDF
Human induced dryland degradation in Ordos Plateau,China,revealed by multilevel statistical modeling of normalized difference vegetation index and rainfall time-series 被引量:16
8
作者 Jing ZHANG JianMing NIU +4 位作者 Tongliga BAO Alexander BUYANTUYEV Qing ZHANG JianJun DONG XueFeng ZHANG 《Journal of Arid Land》 SCIE CSCD 2014年第2期219-229,共11页
Land degradation causes serious environmental problems in many regions of the world, and although it can be effectively assessed and monitored using a time series of rainfall and a normalized difference vegetation ind... Land degradation causes serious environmental problems in many regions of the world, and although it can be effectively assessed and monitored using a time series of rainfall and a normalized difference vegetation index (NDVI) from remotely-sensed imagery, dividing human-induced land degradation from vegetation dynamics due to climate change is not a trivial task. This paper presented a multilevel statistical modeling of the NDVI-rainfall relationship to detect human-induced land degradation at local and landscape scales in the Ordos Plateau of Inner Mongolia, China, and recognized that anthropogenic activities result in either positive (land restoration and re-vegetation) or negative (degradation) trends. Linear regressions were used to assess the accuracy of the multi- level statistical model. The results show that: (1) land restoration was the dominant process in the Ordos Plateau between 1998 and 2012; (2) the effect of the statistical removal of precipitation revealed areas of human-induced land degradation and improvement, the latter reflecting successful restoration projects and changes in land man- agement in many parts of the Ordos; (3) compared to a simple linear regression, multilevel statistical modeling could be used to analyze the relationship between the NDVI and rainfall and improve the accuracy of detecting the effect of human activities. Additional factors should be included when analyzing the NDVI-rainfall relationship and detecting human-induced loss of vegetation cover in drylands to improve the accuracy of the approach and elimi- nate some observed non-significant residual trends. 展开更多
关键词 NDVl-rainfall relationship anthropogenic activities multilevel statistical modeling land degradation DRYLAND Ordos Plateau
下载PDF
Improvement and performance of parallel multilevel fast multipole algorithm 被引量:16
9
作者 Zhanhe Liu Peilin Huang +1 位作者 Zhe Wu Xu Gao 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2011年第1期164-169,共6页
The method of establishing data structures plays an important role in the efficiency of parallel multilevel fast multipole algorithm(PMLFMA).Considering the main complements of multilevel fast multipole algorithm(M... The method of establishing data structures plays an important role in the efficiency of parallel multilevel fast multipole algorithm(PMLFMA).Considering the main complements of multilevel fast multipole algorithm(MLFMA) memory,a new parallelization strategy and a modified data octree construction scheme are proposed to further reduce communication in order to improve parallel efficiency.For far interaction,a new scheme called dynamic memory allocation is developed.To analyze the workload balancing performance of a parallel implementation,the original concept of workload balancing factor is introduced and verified by numerical examples.Numerical results show that the above measures improve the parallel efficiency and are suitable for the analysis of electrical large-scale scattering objects. 展开更多
关键词 multilevel fast multipole algorithm(MLFMA) electromagnetic scattering PARALLELIZATION radar cross section(RCS).
下载PDF
A Context Sensitive Multilevel Thresholding Using Swarm Based Algorithms 被引量:6
10
作者 Shreya Pare Anil Kumar +1 位作者 Varun Bajaj Girish Kumar Singh 《IEEE/CAA Journal of Automatica Sinica》 SCIE EI CSCD 2019年第6期1471-1486,共16页
In this paper, a comprehensive energy function is used to formulate the three most popular objective functions:Kapur's, Otsu and Tsalli's functions for performing effective multilevel color image thresholding.... In this paper, a comprehensive energy function is used to formulate the three most popular objective functions:Kapur's, Otsu and Tsalli's functions for performing effective multilevel color image thresholding. These new energy based objective criterions are further combined with the proficient search capability of swarm based algorithms to improve the efficiency and robustness. The proposed multilevel thresholding approach accurately determines the optimal threshold values by using generated energy curve, and acutely distinguishes different objects within the multi-channel complex images. The performance evaluation indices and experiments on different test images illustrate that Kapur's entropy aided with differential evolution and bacterial foraging optimization algorithm generates the most accurate and visually pleasing segmented images. 展开更多
关键词 COLOR image segmentation Kapur's ENTROPY multilevel THRESHOLDING OTSU method SWARM based optimization algorithms Tsalli's ENTROPY
下载PDF
A multilevel preconditioner and its shared memory implementation for a new generation reservoir simulator 被引量:2
11
作者 Wu Shuhong Xu Jinchao +6 位作者 Feng Chunsheng Zhang Chen-Song Li Qiaoyun Shu Shi Wang Baohua Li Xiaobo Li Hua 《Petroleum Science》 SCIE CAS CSCD 2014年第4期540-549,共10页
As a result of the interplay between advances in computer hardware, software, and algorithm, we are now in a new era of large-scale reservoir simulation, which focuses on accurate flow description, fine reservoir char... As a result of the interplay between advances in computer hardware, software, and algorithm, we are now in a new era of large-scale reservoir simulation, which focuses on accurate flow description, fine reservoir characterization, efficient nonlinear/linear solvers, and parallel implementation. In this paper, we discuss a multilevel preconditioner in a new-generation simulator and its implementation on multicore computers. This preconditioner relies on the method of subspace corrections to solve large-scale linear systems arising from fully implicit methods in reservoir simulations. We investigate the parallel efficiency and robustness of the proposed method by applying it to million-cell benchmark problems. 展开更多
关键词 multilevel PRECONDITIONER shared memory large-scale linear system reservoir simulation
下载PDF
A novel analytical thermal model for multilevel nano-scale interconnects considering the via effect 被引量:2
12
作者 朱樟明 李儒 +1 位作者 郝报田 杨银堂 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第11期4995-5000,共6页
Based on the heat diffusion equation of multilevel interconnects, a novel analytical thermal model for multilevel nano-scale interconnects considering the via effect is presented, which can compute quickly the tempera... Based on the heat diffusion equation of multilevel interconnects, a novel analytical thermal model for multilevel nano-scale interconnects considering the via effect is presented, which can compute quickly the temperature of multilevel interconnects, with substrate temperature given. Based on the proposed model and the 65 nm complementary metal oxide semiconductor (CMOS) process parameter, the temperature of nano-scale interconnects is computed. The computed results show that the via effect has a great effect on local interconnects, but the reduction of thermal conductivity has little effect on local interconnects. With the reduction of thermal conductivity or the increase of current density, however, the temperature of global interconnects rises greatly, which can result in a great deterioration in their performance. The proposed model can be applied to computer aided design (CAD) of very large-scale integrated circuits (VLSIs) in nano-scale technologies. 展开更多
关键词 multilevel interconnects temperature distribution SELF-HEATING via effect
下载PDF
Multilevel read-only optical recording methods 被引量:2
13
作者 宋洁 徐端颐 +3 位作者 齐国生 胡华 张启程 熊剑平 《Chinese Physics B》 SCIE EI CAS CSCD 2006年第8期1788-1792,共5页
The advantages of read-only storage is the predominance of optical recording relative to magnetic and other rewritable methods. Multilevel (ML) read-only technology has been a trend to improve the data capacity and ... The advantages of read-only storage is the predominance of optical recording relative to magnetic and other rewritable methods. Multilevel (ML) read-only technology has been a trend to improve the data capacity and transfer rate. Based on the principle and coding method of ML, this paper demonstrates some ML read-only recording methods, of which a new ML read-only recording is developed. This recording method integrates amplitude modulation achieved by the reaction mechanism of physics and chemistry of photoresist with the run-length-limited technology. The discs can be achieved using standard photoresist mastering and replication techniques with great compatibility to conventional binary read-only discs. 展开更多
关键词 multilevel optical recording read-only amplitude modulation
下载PDF
Comparison of Alternative Strategies for Multilevel Optimization of Hierarchical Systems 被引量:2
14
作者 Saber DorMohammadi Masoud Rais-Rohani 《Applied Mathematics》 2012年第10期1448-1462,共15页
The augmented Lagrangian penalty formulation and four different coordination strategies are used to examine the nu- merical behavior of Analytical Target Cascading (ATC) for multilevel optimization of hierarchical sys... The augmented Lagrangian penalty formulation and four different coordination strategies are used to examine the nu- merical behavior of Analytical Target Cascading (ATC) for multilevel optimization of hierarchical systems. The coordination strategies considered include augmented Lagrangian using the method of multipliers and alternating direction method of multipliers, diagonal quadratic approximation, and truncated diagonal quadratic approximation. Properties examined include computational cost and solution accuracy based on the selected values for the different parameters that appear in each formulation. The different strategies are implemented using two- and three-level decomposed example problems. While the results show the interaction between the selected ATC formulation and the values of associated parameters, they clearly highlight the impact they could have on both the solution accuracy and computational cost. 展开更多
关键词 ANALYTICAL Target CASCADING multilevel Design Optimization AUGMENTED LAGRANGIAN Method of MULTIPLIERS
下载PDF
Efficient analysis of dielectric radomes using multilevel fast multipole algorithm with CRWG basis 被引量:2
15
作者 Que Xiaofeng Nie Zaiping Hu Jun 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2008年第1期81-87,共7页
A full-wave analysis of the electromagnetic problem of a three-dimensional (3-D) antenna radiating through a 3-D dielectric radome is preserued. The problem is formulated using the Poggio-Miller-Chang-Harrington- Wu... A full-wave analysis of the electromagnetic problem of a three-dimensional (3-D) antenna radiating through a 3-D dielectric radome is preserued. The problem is formulated using the Poggio-Miller-Chang-Harrington- Wu(PMCHW) approach for homogeneous dielectric objects and the electric field integral equation for conducting objects. The integral equations are discretized by the method of moment (MoM), in which the conducting and dielectric surface/interfaces are represented by curvilinear triangular patches and the unknown equivalent electric and magnetic currents are expanded using curvilinear RWG basis functions. The resultant matrix equation is then solved by the multilevel fast multipole algorithm (MLFMA) and fast far-field approximation (FAFFA) is used to further accelerate the computation. The radiation patterns of dipole arrays in the presence of radomes are presented. The numerical results demonstrate the accuracy and versatility of this method. 展开更多
关键词 multilevel fast multipole algorithm antenna radome curvilinear RWG basis PMCHW formulation fast far-field approximation.
下载PDF
MULTILEVEL INDEX STRUCTURE FOR INFORMATION FILTERING BASED ON USER CHARACTERISTIC 被引量:1
16
作者 He jun Zhou Mingtian (College of Computer Sci. and Eng., UEST of China, Chengdu 610054) 《Journal of Electronics(China)》 2001年第3期267-271,共5页
Aimed at information overload and personalized characteristic of user information requirement, this letter presents a type of multilevel index structure and algorithm which is applied to large scale information filter... Aimed at information overload and personalized characteristic of user information requirement, this letter presents a type of multilevel index structure and algorithm which is applied to large scale information filtering system and has better performance and stronger scalability. 展开更多
关键词 INFORMATION FILTERING USER model multilevel INDEX
下载PDF
Multilevel cervical spondylotic myelopathy treated by anterior cervical decompression in subsection and autograft fusion 被引量:4
17
作者 赵建华 刘鹏 李起鸿 《Journal of Medical Colleges of PLA(China)》 CAS 2007年第4期209-215,共7页
Objective:To investigate a novel surgical method for multilevel cervical spondylotic myelopathy (CSM). Methods: Totally 21 patients with multilevel CSM undergoing a novel surgical procedure from April 2001 to Janu... Objective:To investigate a novel surgical method for multilevel cervical spondylotic myelopathy (CSM). Methods: Totally 21 patients with multilevel CSM undergoing a novel surgical procedure from April 2001 to January 2004 were analyzed retrospectively. All patients experienced anterior cervical decompression surgery in subsection, autograft fusion and internal fixation. Preoperative, immediate postoperative and follow-up image data, X-rays and semi-quantitative Japanese orthopaedics association (JOA) scores were used to evaluate the restoration of lordosis (Cobb's angle), intervertebral heights, the stability of the cervical spine and the improvement of neurological impairment. Results: Preoperative symptoms were markedly alleviated or disappeared in most of the patients. According to the JOA scores, the ratio of improvement in neurological function was 72. 2%, including excellent in 9 cases (42.9%), good in 7 cases (33.3%), fair in 3 cases (14.3%) and poor in 2 cases (9.5%). Immediate postoperative X-rays showed obvious improvements in lordosis and in the intervertebral height of the cervical spine (P〈0. 01). There is no evidence of instrument failure during the mean follow-up period of 14. 2 months (9-24 months, P〉0. 01). Conclusion:Anterior cervical decompression in subsection, autograft fusion and internal fixation is a rational effective method for the surgical treatment of multilevel CSM. 展开更多
关键词 cervical spondylotic myelopathy multilevel anterior decompression FUSION internal fixation
下载PDF
Mechanical response and microscopic damage mechanism of pre-flawed sandstone subjected to monotonic and multilevel cyclic loading:A laboratory-scale investigation 被引量:5
18
作者 Kesheng Li Shengqi Yang +3 位作者 Chuanxiao Liu Yun Chen Guanglei Zhang Qing Ma 《International Journal of Mining Science and Technology》 SCIE EI CAS CSCD 2023年第12期1487-1510,共24页
This study aims to investigate the mechanical response and acoustic emission(AE)characteristic of pre-flawed sandstone under both monotonic and multilevel constant-amplitude cyclic loads.Specifically,we explored how c... This study aims to investigate the mechanical response and acoustic emission(AE)characteristic of pre-flawed sandstone under both monotonic and multilevel constant-amplitude cyclic loads.Specifically,we explored how coplanar flaw angle and load type impact the strength and deformation behavior and microscopic damage mechanism.Results indicated that being fluctuated before rising with increasing fissure angle under monotonic loading,the peak strength of the specimen first increased slowly and then steeply under cyclic loading.The effect of multilevel cyclic loading on the mechanical parameters was more significant.For a single fatigue stage,the specimen underwent greater deformation in early cycles,which subsequently stabilized.Similar variation pattern was also reflected by AE count/energy/b-value.Crack behaviors were dominated by the fissure angle and load type and medium-scale crack accounted for 74.83%–86.44%of total crack.Compared with monotonic loading,crack distribution of specimen under cyclic loading was more complicated.Meanwhile,a simple model was proposed to describe the damage evolution of sandstone under cyclic loading.Finally,SEM images revealed that the microstructures at the fracture were mainly composed of intergranular fracture,and percentage of transgranular fracture jumped under cyclic loading due to the rapid release of elastic energy caused by high loading rate. 展开更多
关键词 SANDSTONE Pre-existing coplanar flaws multilevel constant-amplitude cyclic loading Mechanical behavior Microscopic damage mechanism
下载PDF
Gaussian shaper for nuclear pulses based on multilevel cascade convolution 被引量:6
19
作者 Min Wang Jian‑Bin Zhou +2 位作者 Xiao‑Ping Ouyang Ying‑Jie Ma Xu Hong 《Nuclear Science and Techniques》 SCIE EI CAS CSCD 2022年第12期116-127,共12页
For nuclear measurements,it is necessary to obtain accurate information from nuclear pulses,which should be obtained by first shaping the pulses outputted by the detectors.However,commonly used pulse-shaping algorithm... For nuclear measurements,it is necessary to obtain accurate information from nuclear pulses,which should be obtained by first shaping the pulses outputted by the detectors.However,commonly used pulse-shaping algorithms have certain problems.For example,certain pulse-shaping algorithms have long dead-times in high-counting-rate environments or are difficult to achieve in digital systems.Gaussian signals are widely used in analog nuclear instruments owing to their symmetry and completeness.A Gaussian signal is usually implemented by using a multilevel S–K filter in series or in parallel.It is difficult to construct a real-time digital Gaussian filter for the complex Gaussian filtering algorithm.Based on the multilevel cascade convolution,a pulse-shaping algorithm for double exponential signals is proposed in this study,which,in addition to double exponential signals,allows more complex output signal models to be used in the new algorithm.The proposed algorithm can be used in high-counting-rate environments and has been implemented in an FPGA with fewer multipliers than those required in other traditional Gaussian pulse-shaping algorithms.The offline processing results indicated that the average peak base width of the output-shaped pulses obtained using the proposed algorithm was reduced compared with that obtained using the traditional Gaussian pulse-shaping algorithm.Experimental results also demonstrated that signal-to-noise ratios and energy resolutions were improved,particularly for pulses with a low energy.The energy resolution was improved by 0.1–0.2%while improving the counting rate. 展开更多
关键词 Impulse shaping multilevel cascade convolution S–K filter Gaussian-like distribution Double exponential signal
下载PDF
Multilevel security model for ad hoc networks 被引量:1
20
作者 Wang Changda Ju Shiguang 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2008年第2期391-397,F0003,共8页
Modern battlefield doctrine is based on mobility, flexibility, and rapid response to changing situations. As is well known, mobile ad hoc network systems are among the best utilities for battlefield activity. Although... Modern battlefield doctrine is based on mobility, flexibility, and rapid response to changing situations. As is well known, mobile ad hoc network systems are among the best utilities for battlefield activity. Although much research has been done on secure routing, security issues have largely been ignored in applying mobile ad hoc network theory to computer technology. An ad hoc network is usually assumed to be homogeneous, which is an irrational assumption for armies. It is clear that soldiers, commanders, and commanders-in-chief should have different security levels and computation powers as they have access to asymmetric resources. Imitating basic military rank levels in battlefield situations, how multilevel security can be introduced into ad hoc networks is indicated, thereby controlling restricted classified information flows among nodes that have different security levels. 展开更多
关键词 ad hoc network multilevel security model access control.
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部