期刊文献+
共找到409篇文章
< 1 2 21 >
每页显示 20 50 100
Secure Transmission of Compressed Medical Image Sequences on Communication Networks Using Motion Vector Watermarking
1
作者 Rafi Ullah Mohd Hilmi bin Hasan +1 位作者 Sultan Daud Khan Mussadiq Abdul Rahim 《Computers, Materials & Continua》 SCIE EI 2024年第3期3283-3301,共19页
Medical imaging plays a key role within modern hospital management systems for diagnostic purposes.Compression methodologies are extensively employed to mitigate storage demands and enhance transmission speed,all whil... Medical imaging plays a key role within modern hospital management systems for diagnostic purposes.Compression methodologies are extensively employed to mitigate storage demands and enhance transmission speed,all while upholding image quality.Moreover,an increasing number of hospitals are embracing cloud computing for patient data storage,necessitating meticulous scrutiny of server security and privacy protocols.Nevertheless,considering the widespread availability of multimedia tools,the preservation of digital data integrity surpasses the significance of compression alone.In response to this concern,we propose a secure storage and transmission solution for compressed medical image sequences,such as ultrasound images,utilizing a motion vector watermarking scheme.The watermark is generated employing an error-correcting code known as Bose-Chaudhuri-Hocquenghem(BCH)and is subsequently embedded into the compressed sequence via block-based motion vectors.In the process of watermark embedding,motion vectors are selected based on their magnitude and phase angle.When embedding watermarks,no specific spatial area,such as a region of interest(ROI),is used in the images.The embedding of watermark bits is dependent on motion vectors.Although reversible watermarking allows the restoration of the original image sequences,we use the irreversible watermarking method.The reason for this is that the use of reversible watermarks may impede the claims of ownership and legal rights.The restoration of original data or images may call into question ownership or other legal claims.The peak signal-to-noise ratio(PSNR)and structural similarity index(SSIM)serve as metrics for evaluating the watermarked image quality.Across all images,the PSNR value exceeds 46 dB,and the SSIM value exceeds 0.92.Experimental results substantiate the efficacy of the proposed technique in preserving data integrity. 展开更多
关键词 block matching algorithm(BMA) compression full-search algorithm motion vectors ultrasound image sequence WATERMARKING
下载PDF
Integration of Sequence Stratigraphic Analysis and 3D Geostatistical Modeling of Pliocene–Pleistocene Delta,F3 Block,Netherlands 被引量:1
2
作者 Haris Ahmed KHAN Ali Asghar SHAHID +3 位作者 Muhammad Jahangir KHAN Taher ZOUAGHI Maria Dolores ALVAREZ Syed Danial Mehdi NAQVI 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2023年第1期256-268,共13页
This research is focused on the analysis of the sequence stratigraphic units of F3 Block,within a wave-dominated delta of Plio–Pleistocene age.Three wells of F3 block and a 3D seismic data,are utilized in this resear... This research is focused on the analysis of the sequence stratigraphic units of F3 Block,within a wave-dominated delta of Plio–Pleistocene age.Three wells of F3 block and a 3D seismic data,are utilized in this research.The conventional techniques of 3D seismic interpretation were utilized to mark the 11 surfaces on the seismic section.Integration of seismic sequence stratigraphic interpretation,using well logs,and subsequent 3D geostatistical modeling,using seismic data,aided to evaluate the shallow hydrocarbon traps.The resulting models were obtained using System Tract and Facies models,which were generated by using sequential stimulation method and their variograms made by spherical method,moreover,these models are validated via histograms.The CDF curve generated from upscaling of well logs using geometric method,shows a good relation with less percentage of errors(1 to 2 for Facies and 3 to 4 for System Tract models)between upscaled and raw data that complements the resulted models.These approaches help us to delineate the best possible reservoir,lateral extent of system tracts(LST and/or HST)in the respective surface,and distribution of sand and shale in the delta.The clinoform break points alteration observed on seismic sections,also validates the sequence stratigraphic interpretation.The GR log-based Facies model and sequence stratigraphy-based System Tract model of SU-04-2 showed the reservoir characteristics,presence of sand bodies and majorly LST,respectively,mainly adjacent to the main fault of the studied area.Moreover,on the seismic section,SU-04-2 exhibits the presence of gas pockets at the same location that also complements the generated Facies and System Tract models.The generated models can be utilized for any similar kind of study and for the further research in the F3 block reservoir characterization. 展开更多
关键词 sequence stratigraphy facies modeling system tract modeling F3 block North Sea
下载PDF
Sedimentary microtopography in sequence stratigraphic framework of Upper Ordovician and its control over penecontemporaneous karstification,No.I slope break,Tazhong,Tarim block 被引量:5
3
作者 张云峰 王振宇 +2 位作者 屈海洲 罗春树 李越 《Journal of Central South University》 SCIE EI CAS 2014年第2期735-744,共10页
In order to reveal the relationship between the penecontemporaneous karstification and sedimentary microtopography in sequence stratigraphy,the sequence stratigraphic framework of Lianglitage formation in Upper Ordovi... In order to reveal the relationship between the penecontemporaneous karstification and sedimentary microtopography in sequence stratigraphy,the sequence stratigraphic framework of Lianglitage formation in Upper Ordovician is studied according to the well drilling,logging,geophysical data,detailed observations of core and the paleontology.The Lianglitage formation belongs to the sequence Ⅳ of Ordovician.The second member of Lianglitage formation is prograde sedimentation in highstand systems tract,and is favorable for developing reef flat.The development scale and thickness of reef flat are controlled by the variation of secondary sea level.The types and characteristics of karst in the highstand systems tract show that the late highstand systems tract is dissolved and cemented by the meteoric fresh water and mixed water.Penecontemporaneous karstification is developed at the top of parasequence and high place of geomorphology.Atmospheric diagenetic lens is formed.The developing regulations and controlling factors of penecontemporaneous karstification can provide new clues to the prediction and exploration of favorable reservoir in this area. 展开更多
关键词 sequence stratigraphy sedimentary microtopography penecontemporaneous karstification Upper Ordovician Tazhong I slope break Tarim block
下载PDF
Cyclic Characteristics of the Physical Properties of Key Strata in CBM Systems Controlled by Sequence Stratigraphy—An Example from the Gujiao Block 被引量:1
4
作者 WANG Gang QIN Yong +4 位作者 XIE Yiwei WANG Ziwei WANG Boyang WANG Qi ZHANG Xiaoyang 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2020年第2期444-455,共12页
Multiple coal seams and interbedded rock assemblages formed in vertical progression due to the influence of multiple stages of sea level transgressions.Based on mercury injection experiment,low temperature liquid nitr... Multiple coal seams and interbedded rock assemblages formed in vertical progression due to the influence of multiple stages of sea level transgressions.Based on mercury injection experiment,low temperature liquid nitrogen experiment,porosity and permeability experiment and breakthrough pressure experiment,the vertical variation characteristics of coal-bearing strata in Gujiao block are explained in detail.The results of the mercury injection and low temperature liquid nitrogen experiments show that the pore structure characteristics fluctuate with increasing depth in the strata,with fewer micropores followed by transition pores.The BET specific surface area and average pore diameter of the Shanxi Formation are generally larger than those of the Taiyuan Formation.Due to the continuous cyclic sequence stratigraphy changes,the porosity,permeability,breakthrough pressure and breakthrough time of the samples show a certain cyclicity.Within the same sequence,the porosity is larger,and the permeability is smaller near the maximum flooding surface.Although the permeability of the sandstone samples is higher,the porosity is lower,and the breakthrough pressure and breakthrough times are greater.The strata in the study area formed in an oxidized environment that was affected by freshwater,and the pore structure of different lithologies is quite different.After the formation of sandstone,the intergranular pores generally underwent filling with secondary quartz,clay minerals and organic matter,resulting in low porosity and permeability. 展开更多
关键词 coal-bearing STRATA sequenceS physical properties cycle Gujiao block
下载PDF
Screen image sequence compression method utilizing adaptive block size coding and hierarchical GOP structure
5
作者 武星 梅亮 +2 位作者 袭奇 张申生 陈延伟 《Journal of Central South University》 SCIE EI CAS 2010年第4期786-794,共9页
To compress screen image sequence in real-time remote and interactive applications,a novel compression method is proposed.The proposed method is named as CABHG.CABHG employs hybrid coding schemes that consist of intra... To compress screen image sequence in real-time remote and interactive applications,a novel compression method is proposed.The proposed method is named as CABHG.CABHG employs hybrid coding schemes that consist of intra-frame and inter-frame coding modes.The intra-frame coding is a rate-distortion optimized adaptive block size that can be also used for the compression of a single screen image.The inter-frame coding utilizes hierarchical group of pictures(GOP) structure to improve system performance during random accesses and fast-backward scans.Experimental results demonstrate that the proposed CABHG method has approximately 47%-48% higher compression ratio and 46%-53% lower CPU utilization than professional screen image sequence codecs such as TechSmith Ensharpen codec and Sorenson 3 codec.Compared with general video codecs such as H.264 codec,XviD MPEG-4 codec and Apple's Animation codec,CABHG also shows 87%-88% higher compression ratio and 64%-81% lower CPU utilization than these general video codecs. 展开更多
关键词 screen image sequence compression adaptive block size hierarchical GOP structure intra-frame coding inter-frame coding
下载PDF
Facies Interpretation, Depositional Environment and Sequence Stratigraphy of the Sartakht Formation in the Bakhshi Section, Located in Kalmard Block, East-Central Iran
6
作者 Bibi Haniyeh Emraninasab Mohammad Hossein Adabi +1 位作者 Mahmoodreza Majidifard Nader Kohansal Ghadimvand 《Open Journal of Geology》 2016年第5期314-329,共16页
Permian rocks in Kalmard block are recognized with Khan Group, enjoying various characteristics in different outcrops. This group is made up of three informal formations, namely Chili, Sartakht and Hermez. Middle Perm... Permian rocks in Kalmard block are recognized with Khan Group, enjoying various characteristics in different outcrops. This group is made up of three informal formations, namely Chili, Sartakht and Hermez. Middle Permian deposits (Sartakht formation) are composed chiefly of sandstone and carbonate rocks. This formation is composed of 58.6 m sandstone and dolomitic limestone in the Bakhshi section. Lower Permian carbonate deposits (Chili formation) unconformably underlie this formation while lateritic paleosols of upper Permian (Hermez formation) are depicted overlying an erosional unconformity above this formation. According to lithologic and microscopic investigations, the deposits of Sartakht formation can be divided into 2 siliciclastic petrofacies and 12 carbonate microfacies. Field observations, along with microscopic examinations, have resulted in identifying tidal flat, lagoon, shoal and open marine environments in the rocks of the studied formation. Vertical changes of microfacies and depth variation curve point to the high thickness of the microfacies of lagoon and shoal environments and low thickness of the microfacies of tidal flat and open marine environments. The carbonate-siliciclastic sequence of Sartakht formation is made up of a third-order depositional sequence, separated from carbonate depositions of lower Permian (Chili formation) and lateritic paleosols of upper Permian by type 1 sequence boundary (SB1). Siliciclastic deposits include LST system tract, and carbonate microfacies involve TST and HST system tracts, separated from each other by MFS. Sartakht formation rocks in Bakhshi section are deposited in a low-angle homoclinal ramp, mostly in the inner ramp, located in the south of Paleotethys Ocean. The depositional sequence identified in Sartakht formation points to the age of middle Permian, conforming to middle Absaroka II supersequence. The upper erosional boundary between Sartakht and Hermez formations conforms to the global-scale sea level fall. 展开更多
关键词 Middle Permian Kalmard block Sartakht Formation Depositional Environment sequence Stratigraphy
下载PDF
Facies Interpretation, Depositional Environment and Sequence Stratigraphy of the Gachal Formation in the Madbeiki Section, Kalmard Block, East Central Iran
7
作者 Soheil Erfani Mohammad Hossein Adabi +1 位作者 Mahmood Reza Majidifard Nader Kohansal Ghadimvand 《Open Journal of Geology》 2016年第6期439-458,共20页
Deposits of Lower Carboniferous rocks in Kalmard block are recognized by Gachal informal formation, showing various characteristics in different outcrops. Lower Carboniferous deposits (Gachal formation) are composed c... Deposits of Lower Carboniferous rocks in Kalmard block are recognized by Gachal informal formation, showing various characteristics in different outcrops. Lower Carboniferous deposits (Gachal formation) are composed chiefly of carbonate, evaporite and siliciclastic rocks. This formation is composed of 198 m sandstone, limestone and dolomite as well as a small amount of shale, marl and gypsum in the Madbeiki section. This formation unconformably underlies Precambrian metamorphic deposits (Kalmard formation) while lateritic soils of lower Permian (Chili formation) are depicted overlying an erosional unconformity above this formation. According to lithologic and microscopic investigations, the deposits of Gachal formation can be divided into 1 siliciclastic petrofacies, 1 evaporite microfacies and 16 carbonate microfacies. Field observations, along with microscopic examinations, have resulted in identifying tidal flat, lagoon, shoal and open marine environments in the rocks of the studied formation. Vertical changes of microfacies and depth variation curve indicate the high thickness of the microfacies of tidal flat, lagoon and shoal environments and low thickness of the microfacies of open marine environment. The carbonate-evaporite-siliciclastic sequence of Gachal formation is made up of three third-order depositional sequence, separated each other by type 1 sequence boundary (SB1). Siliciclastic and evaporite deposits include LST system tract, and carbonate microfacies involve TST and HST system tracts, separated from each other by MFS. Gachal formation rocks in Madbeiki section are deposited in a low-angle homoclinal ramp, mostly in the inner ramp, located in the southern Paleotethys Ocean. The depositional sequence identified in Gachal formation points to the age of Lower Carboniferous, conforming to upper Kaskaskia super sequence. The upper erosional boundary between Gachal and Chili formations conform to the global-scale sea level fall. 展开更多
关键词 Lower Carboniferous Kalmard block Gachal Formation Depositional Environment sequence Stratigraphy
下载PDF
PERIODIC COMPLEMENTARY BINARY SEQUENCE PAIRS 被引量:16
8
作者 XuChengqian ZhaoXiaoqun 《Journal of Electronics(China)》 2002年第2期152-159,共8页
A new set of binary sequences-Periodic Complementary Binary Sequence Pair (PCSP) is proposed. A new class of block design-Difference Family Pair (DFP) is also proposed.The relationship between PCSP and DFP, the proper... A new set of binary sequences-Periodic Complementary Binary Sequence Pair (PCSP) is proposed. A new class of block design-Difference Family Pair (DFP) is also proposed.The relationship between PCSP and DFP, the properties and existing conditions of PCSP and the recursive constructions for PCSP are given. 展开更多
关键词 Coding theory Periodic complementary binary sequence pairs Difference family pairs Autocorrelation function block design
下载PDF
STUDY ON THE SEQUENCE STRUCTURE OF BUTADIENE-STYRENE RUBBER BY ^(13)C-NMR METHOD Ⅲ. QUANTITATIVE CHARACTERIZATION OF SEQUENCE STRUCTURE
9
作者 陈晓农 胡力平 +1 位作者 严宝珍 焦书科 《Chinese Journal of Polymer Science》 SCIE CAS CSCD 1990年第3期269-278,共10页
The quantitative description of the sequence structure of emulsion-processed SBR and solution-processed SBR (by lithium catalyst)was carried out based on their spectral data Of ^(13)C-NMR.The calculating formulae whic... The quantitative description of the sequence structure of emulsion-processed SBR and solution-processed SBR (by lithium catalyst)was carried out based on their spectral data Of ^(13)C-NMR.The calculating formulae which could be used to obtain diad concentration from the peak intensifies of carbon spectra, average block length, average number of block, and the microstructure composition of the molecular chain were derived. The quantitative result showed that on the molecular chain styrene unit had the tendency to attach to trans-1,4 butadiene unit. The calculated result of the microstructure was in good agreement with that obtained through IR measurement. 展开更多
关键词 sequence structure quantitative characterization SBR diad concentration average block length average number of block.
下载PDF
Depositional environments and sequence stratigraphy of the Bahram Formation(middleelate Devonian) in north of Kerman, south-central Iran
10
作者 Afshin Hashmie Ali Rostamnejad +3 位作者 Fariba Nikbakht Mansour Ghorbanie Peyman Rezaie Hossien Gholamalian 《Geoscience Frontiers》 SCIE CAS CSCD 2016年第5期821-834,共14页
This study is focused on sedimentary environments, facies distribution, and sequence stratigraphy. The facies and sequence stratigraphic analyses of the Bahram Formation(middleelate Devonian) in southcentral Iran ar... This study is focused on sedimentary environments, facies distribution, and sequence stratigraphy. The facies and sequence stratigraphic analyses of the Bahram Formation(middleelate Devonian) in southcentral Iran are based on two measured stratigraphic sections in the southern Tabas block. The Bahram Formation overlies red sandstones Padeha Formation in sections Hutk and Sardar and is overlain by Carboniferous carbonate deposits of Hutk Formation paraconformably, with a thickness of 354 and386 m respectively. Mixed siliciclastic and carbonate sediments are present in this succession. The field observations and laboratory studies were used to identify 14 micro/petrofacies, which can be grouped into 5 depositional environments: shore, tidal flat, lagoon, shoal and shallow open marine. A mixed carbonate-detrital shallow shelf is suggested for the depositional environment of the Bahram Formation which deepens to the east(Sardar section) and thins in southern locations(Hutk section). Three 3rdorder cyclic siliciclastic and carbonate sequences in the Bahram Formation and one sequence shared with the overlying joint with Hutk Formation are identified, on the basis of shallowing upward patterns in the micro/pertofacies. 展开更多
关键词 Bahram Formation DEVONIAN Facies analysis Mixed carbonate-detrital shallow-shelf sequence stratigraphy Tabas block
下载PDF
Fuzzy Based Adaptive Deblocking Filters at Low-Bitrate HEVC Videos for Communication Networks
11
作者 Anudeep Gandam Jagroop Singh Sidhu 《Computers, Materials & Continua》 SCIE EI 2021年第3期3045-3063,共19页
In-loop filtering significantly helps detect and remove blocking artifacts across block boundaries in low bitrate coded High Efficiency Video Coding(HEVC)frames and improves its subjective visual quality in multimedia... In-loop filtering significantly helps detect and remove blocking artifacts across block boundaries in low bitrate coded High Efficiency Video Coding(HEVC)frames and improves its subjective visual quality in multimedia services over communication networks.However,on faster processing of the complex videos at a low bitrate,some visible artifacts considerably degrade the picture quality.In this paper,we proposed a four-step fuzzy based adaptive deblocking filter selection technique.The proposed method removes the quantization noise,blocking artifacts and corner outliers efficiently for HEVC coded videos even at low bit-rate.We have considered Y(luma),U(chromablue),and V(chroma-red)components parallelly.Finally,we have developed a fuzzy system to detect blocking artifacts and use adaptive filters as per requirement in all four quadrants,namely up 45◦,down 45◦,up 135◦,and down 135◦across horizontal and vertical block boundaries.In this context,experimentation is done on a wide variety of videos.An objective and subjective analysis is carried out with MATLAB software and Human Visual System(HVS).The proposed method substantially outperforms existing postprocessing deblocking techniques in terms of YPSNR and BD_rate.In the proposed method,we achieved 0.32–0.97 dB values of YPSNR.Our method achieved a BD_rate of+1.69%for the luma component,−0.18%(U)and−1.99%(V)for chroma components,respectively,with respect to the stateof-the-art methods.The proposed method proves to have low computational complexity and has better parallel processing,hence suitable for a real-time system in the near future. 展开更多
关键词 Adaptive deblocking filters high efficiency video coding blocking artifacts corner outliers bitrate YPSNR BD_rate
下载PDF
Comparative Analysis of Mitochondrial Control Region Sequence from Three Flatfish Species(Pleuronectidae)
12
作者 YUJianzhong KONGXiaoyu +1 位作者 YUZiniu ZHOULishi 《Journal of Ocean University of China》 SCIE CAS 2005年第1期80-84,共5页
The 5’-end of the mitochondrial control region sequences of three flatfishes (Pleuronectiformes: Pleuronectidae) were amplified and sequenced. These sequences were compared with those of other three Pleuronectids spe... The 5’-end of the mitochondrial control region sequences of three flatfishes (Pleuronectiformes: Pleuronectidae) were amplified and sequenced. These sequences were compared with those of other three Pleuronectids species retrieved from GenBank. A phylogenetic tree was constructed based on the partial control region sequences. The results of phyloge- netic analysis are consistent with those of conventional systematics. Compared to previous studies, the structure of the 5’-end of mitochondrial control region was analyzed. The terminal associated sequence motif and its complementary motif were i- dentified at the 5’-end of the sequences. A conserved sequence block, named as CM5’d, was identified in the 5’-end of con- trol region sequences in all Pleuronectids. Another central conserved sequence block, named as CSB-F, was detected in the central conserved blocks. 展开更多
关键词 PLEURONECTIDAE FLATFISH mitochondrial control region terminal associatedsequence conserved sequence block
下载PDF
Sequence Stratigraphy of Lower Carboniferous Rocks in Bakhshi Section, East-Central Iran
13
作者 Soheil Erfani Mohammad Hossein Adabi +2 位作者 Mahmood Reza Majidifard Nader Kohansalghadimvand Bibihaniyeh Emraninasab 《Open Journal of Geology》 2017年第2期200-211,共12页
The deposits of Lower Carboniferous rocks in Kalmard Block are characterized by Gachal informal formation, showing various properties in different outcrops. These deposits (in Gachal formation) are composed chiefly of... The deposits of Lower Carboniferous rocks in Kalmard Block are characterized by Gachal informal formation, showing various properties in different outcrops. These deposits (in Gachal formation) are composed chiefly of carbonate, evaporite and siliciclastic rocks. This formation commonly hosts 190 m sandstone, limestone, dolomitic limestone and dolomite as well as a small amount of shale and marl in the Bakhshi section. It unconformably underlies Devonian deposits (Rahdar formation) while lateritic soils of lower Permian (Chili formation) are depicted overlying an erosional unconformity above this formation. The mixed carbonate-evaporite-siliciclastic sequence of Gachal formation is made up of three third-order depositional sequences, separated from each other by Type 1 sequence boundary (SB1). Siliciclastic and evaporite deposits include LST system tract, whereas carbonate microfacies involve TST and HST system tracts, separated from each other by MFS. The depositional sequences identified in Gachal formation point to the Lower Carboniferous age, conforming to upper Kaskaskia supersequence. The upper erosional boundary between Gachal and Chili formations complies with the global-scale sea level fall. 展开更多
关键词 LOWER CARBONIFEROUS Kalmard block Gachal Formation sequence STRATIGRAPHY
下载PDF
基于GPS数据分析巴颜喀拉块体边界强震活动特征
14
作者 李宁 季灵运 +2 位作者 蒋锋云 朱良玉 刘传金 《地震研究》 CSCD 北大核心 2024年第3期405-418,共14页
基于巴颜喀拉块体边界大地震序列,运用多弹簧滑块系统理论分析未来各边界断裂发生强震的可能时间;基于1991—2016年中国大陆GPS水平速度场数据,采用均匀弹性块体模型计算了巴颜喀拉块体各边界断裂带的长期活动特征,并以此作为参考背景,... 基于巴颜喀拉块体边界大地震序列,运用多弹簧滑块系统理论分析未来各边界断裂发生强震的可能时间;基于1991—2016年中国大陆GPS水平速度场数据,采用均匀弹性块体模型计算了巴颜喀拉块体各边界断裂带的长期活动特征,并以此作为参考背景,计算了1999—2007、2009—2013、2013—2015、2015—2017、2017—2020年各边界断裂带的活动性质及时空演化特征,同时结合1995年以来发生在各边界断裂带上的M≥7.0地震震源机制解综合分析强震活动与块体运动的关系。结果表明:1995年以来发生在块体各边界断裂带上的M≥7.0地震震源机制与块体边界的运动特征一致,这一系列地震可能是由巴颜喀拉块体向E—SE向运动增强所致。综合块体边界大震序列与块体相对运动结果认为,未来十年,甘孜—玉树断裂、龙门山断裂南段、东昆仑断裂带东段存在发生M≥7.0地震的可能。 展开更多
关键词 巴颜喀拉块体 大地震序列 块体运动 均匀弹性模型 强震活动
下载PDF
混沌密码理论研究与应用新进展
15
作者 赵耿 马英杰 董有恒 《信息网络安全》 CSCD 北大核心 2024年第2期203-216,共14页
混沌密码研究主要包括混沌序列密码、混沌分组密码和混沌公钥密码。混沌序列密码具有软硬件实现简单、加解密处理速度快、没有或只有有限的错误传播等特点。混沌序列密码的设计方面研究成果极为丰硕,但其安全性分析一般停留在统计性验... 混沌密码研究主要包括混沌序列密码、混沌分组密码和混沌公钥密码。混沌序列密码具有软硬件实现简单、加解密处理速度快、没有或只有有限的错误传播等特点。混沌序列密码的设计方面研究成果极为丰硕,但其安全性分析一般停留在统计性验证分析阶段,而对可证明安全性或其他有条件安全性的证明和分析很少,因此证明混沌序列密码的安全性已成为该领域亟需填补的空白。混沌分组密码的研究颇为成熟,但其整体结构一般受限于Feistel结构、SPN结构、Lai-Massey结构及其变形结构。因此,构建突破传统结构的创新性密码架构成为混沌分组密码亟待解决的关键问题之一。混沌公钥密码的研究相对薄弱,利用混沌系统特有的密码特性和公钥密码系统相结合的混沌公钥密码算法不仅具有理论研究意义,而且具有实际应用价值。混沌系统也被广泛应用于通信传输、语音加密、图像加密和扩频通信等保密通信领域。电、光混沌系统实现简便,其计算复杂性不会随着密钥空间的增大而明显增大,能够为无线通信、物理层链路安全、应用层数据安全等不同场景提供安全保护。 展开更多
关键词 保密通信 混沌系统 混沌序列密码 混沌分组密码 混沌公钥密码
下载PDF
基于帝国竞争反向传播神经网络的断块油田开发顺序优化
16
作者 徐庆岩 孙晓飞 +3 位作者 翟光华 王瑞峰 雷诚 张瑾琳 《石油地质与工程》 CAS 2024年第3期77-81,89,共6页
明确断块油田群中断块的开发顺序是进行开发方案设计的前提条件。断块油田数量较少时,可以进行技术经济的组合对比,但是断块数量较多时会形成海量的组合,耗费时间也长。断块油田开发顺序评价的现有方法有权重评价法、层次分析法、综合... 明确断块油田群中断块的开发顺序是进行开发方案设计的前提条件。断块油田数量较少时,可以进行技术经济的组合对比,但是断块数量较多时会形成海量的组合,耗费时间也长。断块油田开发顺序评价的现有方法有权重评价法、层次分析法、综合模糊评判法等,这些方法在选择评价指标和指标权重上带有较强的主观性,无法做到完全客观的评价。因此本文提出一种基于帝国竞争算法改进的反向传播神经网络模型,首先采用Spearman相关系数法确定影响断块油田开发的主控因素,其次使用分段三次Hermite插值方法实现断块油田群开发数据库的扩充,最后在扩充后的大量数据库训练样本的基础上,基于帝国竞争算法改进的反向传播神经网络模型可以确定影响开发效果参数的权重并预测断块油田群中各断块油田的净现值,根据净现值大小可以确定每个断块的开发顺序。该方法以实际断块油田群的地质油藏数据库作为评价依据,断块油田的开发顺序更加的科学合理,项目整体的净现值也明显高于依靠传统方法确定的开发顺序组合,避免了人为主观性,也节省了数值模拟和经济评价的工作量,克服了现有方法的局限性,对于提高断块油田群开发综合效益具有重要意义。 展开更多
关键词 帝国竞争算法 反向传播神经网络 开发参数权重 投产顺序优化 断块油田群 净现值
下载PDF
LMR-CBT: learning modality-fused representations with CB-Transformer for multimodal emotion recognition from unaligned multimodal sequences 被引量:1
17
作者 Ziwang FU Feng LIU +2 位作者 Qing XU Xiangling FU Jiayin QI 《Frontiers of Computer Science》 SCIE EI CSCD 2024年第4期39-47,共9页
Learning modality-fused representations and processing unaligned multimodal sequences are meaningful and challenging in multimodal emotion recognition.Existing approaches use directional pairwise attention or a messag... Learning modality-fused representations and processing unaligned multimodal sequences are meaningful and challenging in multimodal emotion recognition.Existing approaches use directional pairwise attention or a message hub to fuse language,visual,and audio modalities.However,these fusion methods are often quadratic in complexity with respect to the modal sequence length,bring redundant information and are not efficient.In this paper,we propose an efficient neural network to learn modality-fused representations with CB-Transformer(LMR-CBT)for multimodal emotion recognition from unaligned multi-modal sequences.Specifically,we first perform feature extraction for the three modalities respectively to obtain the local structure of the sequences.Then,we design an innovative asymmetric transformer with cross-modal blocks(CB-Transformer)that enables complementary learning of different modalities,mainly divided into local temporal learning,cross-modal feature fusion and global self-attention representations.In addition,we splice the fused features with the original features to classify the emotions of the sequences.Finally,we conduct word-aligned and unaligned experiments on three challenging datasets,IEMOCAP,CMU-MOSI,and CMU-MOSEI.The experimental results show the superiority and efficiency of our proposed method in both settings.Compared with the mainstream methods,our approach reaches the state-of-the-art with a minimum number of parameters. 展开更多
关键词 modality-fused representations cross-model blocks multimodal emotion recognition unaligned multimodal sequences computational affection
原文传递
基于负序电流幅值的含光伏配电网两相短路故障方向判据
18
作者 牟锐 何佳伟 +3 位作者 李斌 周博昊 张永伍 黄家凯 《电力系统自动化》 EI CSCD 北大核心 2024年第19期148-161,共14页
当分布式光伏接入的配电网发生故障时,传统功率方向元件在光伏低电压穿越以及负序电流抑制控制策略的影响下动作性能降低。文中首先分析了典型两馈线配电网保护正、反向区域发生两相短路故障时负序电流及负序电压的分布特性。在此基础上... 当分布式光伏接入的配电网发生故障时,传统功率方向元件在光伏低电压穿越以及负序电流抑制控制策略的影响下动作性能降低。文中首先分析了典型两馈线配电网保护正、反向区域发生两相短路故障时负序电流及负序电压的分布特性。在此基础上,提出一种适用于分布式光伏接入的配电网两相短路故障方向判别方法,利用负序电流幅值实现两相短路故障方向的可靠判别,并引入负序电压判据,实现三相短路故障下的可靠闭锁。进一步地,提出了判据动作定值的理论计算方法,并定量分析了光伏接入容量对所提方向判据灵敏性的影响及其最大耐受过渡电阻能力。最后,基于PSCAD/EMTDC平台进行了算例仿真,结果验证了所提判据的有效性。 展开更多
关键词 分布式光伏 配电网 方向判据 负序电流 负序电压闭锁
下载PDF
生物信息学Blocks和Motifs方法在病毒研究中的应用 被引量:1
19
作者 肖明 张楚瑜 《武汉大学学报(理学版)》 CAS CSCD 2000年第6期709-716,共8页
评述了生物信息学分析方法及几种主要分析软件的基本原理 ;提出了蛋白质、核酸序列分析、搜索Blocks和 Motifs的基本方法 。
关键词 blockS MOTIFS 序列分析 病毒
下载PDF
一种水性封闭型异氰酸酯的解封温度和应用研究
20
作者 崔丽荣 崔峰波 +3 位作者 冉文华 袁向静 张萍 陆沈奇 《聚氨酯工业》 CAS 2024年第5期41-43,共3页
对一种水性封闭型多异氰酸酯进行热失重和红外光谱分析,并采用丙酮萃取法对水性封闭型异氰酸酯和聚氨酯乳液的交联反应进行研究。结果表明,通过外推法推导出该水性封闭型多异氰酸酯解封起始温度和峰值温度约为108℃和164℃。当聚氨酯乳... 对一种水性封闭型多异氰酸酯进行热失重和红外光谱分析,并采用丙酮萃取法对水性封闭型异氰酸酯和聚氨酯乳液的交联反应进行研究。结果表明,通过外推法推导出该水性封闭型多异氰酸酯解封起始温度和峰值温度约为108℃和164℃。当聚氨酯乳液中加入质量分数5%~10%的水性封闭型多异氰酸酯,且固化温度为160~180℃时,其胶膜丙酮萃取率较低,交联固化程度较高。 展开更多
关键词 水性封闭型多异氰酸酯 水性聚氨酯 解封起始温度 解封峰值温度 交联
下载PDF
上一页 1 2 21 下一页 到第
使用帮助 返回顶部