Erasure code is widely used as the redundancy scheme in distributed storage system. When a storage node fails, the repair process often requires to transfer a large amount of data. Regenerating code and hierarchical c...Erasure code is widely used as the redundancy scheme in distributed storage system. When a storage node fails, the repair process often requires to transfer a large amount of data. Regenerating code and hierarchical code are two classes of codes proposed to reduce the repair bandwidth cost. Regenerating codes reduce the amount of data transferred by each helping node, while hierarchical codes reduce the number of nodes participating in the repair process. In this paper, we propose a "sub-code nesting framework" to combine them together. The resulting regenerating hierarchical code has low repair degree as hierarchical code and lower repair cost than hierarchical code. Our code can achieve exact regeneration of the failed node, and has the additional property of low updating complexity.展开更多
To maximize the aggregate throughput achieved in heterogeneous networks, this paper investigates inter-session network coding for the distribution of layered source data. We define inter-layer hierarchical random line...To maximize the aggregate throughput achieved in heterogeneous networks, this paper investigates inter-session network coding for the distribution of layered source data. We define inter-layer hierarchical random linear network codes （IHRLNC）, which not only take the flexibility of intersession network coding for layer mixing but also consider the strict priority inherent in the layered source data. Furthermore, we propose the inter-layer hierarchical multicast （IHM）, which performs IHRLNC in the network such that each sink can recover some source layers according to its individu- al capacity. To determine the optimal type of IHRLNC that should be performed on each edge in IHM, we formulate an optimization problem based on 0-1 integer linear programming, and propose a heuristic approach to approximate the optimal solution in polynomial time. Simulation results show that the proposed IHM can achieve throughput gains over the layered muhicast schemes.展开更多
For rate control (RC) of hierarchical structure coding, an independent rate-quantization (R-Q) model was proposed based on mean absolute differences (MADs) in different temporal levels (TLs). In the proposed R-Q model...For rate control (RC) of hierarchical structure coding, an independent rate-quantization (R-Q) model was proposed based on mean absolute differences (MADs) in different temporal levels (TLs). In the proposed R-Q model, a novel MAD model was developed according to the hierarchical structure. The experimental results demonstrate that the proposed algorithm provides better performance, in terms of average peak signal-to-noise ratio (PSNR) and quality smoothness, than the H.264 reference model, JM14.2, under various sequences.展开更多
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
To decrease the computational complexity of adaptive inter-layer prediction and improve the encoding efficiency in sealable video coding, a mode decision algorithm is proposed by exploiting the part of used candidate ...To decrease the computational complexity of adaptive inter-layer prediction and improve the encoding efficiency in sealable video coding, a mode decision algorithm is proposed by exploiting the part of used candidate modes of the co-located reference macrobloeks for Hierarchical-B pictures. This scheme reduces the amount of the candidate modes to generate a dynamic list for the current encoding macroblock according to the statistical information derived from the co-located reference macroblocks in different temporal levels. The experimental results show that this fast algorithm reduces approximately 31% encoding time on average with the negligible loss of encoding performance.展开更多
In this paper, an investigation is made on compatibility of the video formats TV (625/50/2:1/4:3), EDTV (625/50/1:1/16:9), HDTVint (1250/50/2:1/16:9) and HDTVpro(1250/50/2:1/16:9) in three-dimensional subband coding. ...In this paper, an investigation is made on compatibility of the video formats TV (625/50/2:1/4:3), EDTV (625/50/1:1/16:9), HDTVint (1250/50/2:1/16:9) and HDTVpro(1250/50/2:1/16:9) in three-dimensional subband coding. A hierarchical method is proposed leading to a more reasonable joint solution for the issues of digital transmission evolution and interlace-to-progressive scanning conversion ill the frame work of bit rate compression. Conventional HDTVint with the diamond shaped spectrum is proposed to be replaced by a kind of 'switching'HDTVin signal which consists of three components and motion detection bits (MDB). The first component and the MDB represent TV. The first plus the second component and the MDB represent EDTV.HDTVpro is splitted into switching HDTVint and extra component. The switching threshold and the length of temporal filter banks are discussed. Rearranging the pixels in subbands is recommended. Based on the proposed method, the transmission system can evolve through four steps: TV, EDTV, HDTVint and HDTVpro Results of bit rate compression are also presented. TV, EDTV, HDTVint and HDTVpro are compressed to approximately 40, 80, 128 and 256 Mbit/s respectively. Interlace scanning has drawbacks such as line flicker and line crawling as the eye follows the line structure in the picture. Progressive version switching TV and HDTVint can be reconstructed using one frame memory without the problems of handling temporal-vertical diamond shaped spectra of conventional TV and HDTVint based on a one-frame memory algorithm in the receiver.展开更多
In this paper, the authors propose a new approach to image compression based on the principle of Set Partitioning in Hierarchical Tree algorithm （SPIHT）. Our approach, the modified SPIHT （MSPIHT）, distributes entr...In this paper, the authors propose a new approach to image compression based on the principle of Set Partitioning in Hierarchical Tree algorithm （SPIHT）. Our approach, the modified SPIHT （MSPIHT）, distributes entropy differently than SPIHT and also optimizes the coding. This approach can produce results that are a significant improvement on the Peak Signal-to-Noise Ratio （PSNR） and compression ratio obtained by SPIHT algorithm, without affecting the computing time. These results are also comparable with those obtained using the Embedded Zerotree Wavelet （EZW） and Joint Photographic Experts Group 2000 （JPG2） algorithms.展开更多
Computer-aided design(CAD)software continues to be a crucial tool in digital twin application and manufacturing,facilitating the design of various products.We present a novel CAD generation method,an agent that constr...Computer-aided design(CAD)software continues to be a crucial tool in digital twin application and manufacturing,facilitating the design of various products.We present a novel CAD generation method,an agent that constructs the CAD sequences containing the sketch-and-extrude modelling operations efficiently and with high quality.Starting from the sketch and extrusion operation sequences,we utilise the transformer encoder to encode them into different disentangled codebooks to represent their distribution properties while considering their correlations.Then,a combination of auto-regressive and non-autoregressive samplers is trained to sample the code for CAD sequence con-struction.Extensive experiments demonstrate that our model generates diverse and high-quality CAD models.We also show some cases of real digital twin applications and indicate that our generated model can be used as the data source for the digital twin platform,exhibiting designers'potential.展开更多
当前基于深度学习的中文长文本摘要生成的研究存在以下问题:(1)生成模型缺少信息引导,缺乏对关键词汇和语句的关注,存在长文本跨度下关键信息丢失的问题;(2)现有中文长文本摘要模型的词表常以字为基础,并不包含中文常用词语与标点,不利...当前基于深度学习的中文长文本摘要生成的研究存在以下问题:(1)生成模型缺少信息引导,缺乏对关键词汇和语句的关注,存在长文本跨度下关键信息丢失的问题;(2)现有中文长文本摘要模型的词表常以字为基础,并不包含中文常用词语与标点,不利于提取多粒度的语义信息.针对上述问题,本文提出了融合引导注意力的中文长文本摘要生成(Chinese Long text Summarization with Guided Attention,CLSGA)方法.首先,针对中文长文本摘要生成任务,利用抽取模型灵活抽取长文本中的核心词汇和语句,构建引导文本,用以指导生成模型在编码过程中将注意力集中于更重要的信息.其次,设计中文长文本词表,将文本结构长度由字统计改变至词组统计,有利于提取更加丰富的多粒度特征,进一步引入层次位置分解编码,高效扩展长文本的位置编码,加速网络收敛.最后,以局部注意力机制为骨干,同时结合引导注意力机制,以此有效捕捉长文本跨度下的重要信息,提高摘要生成的精度.在四个不同长度的公共中文摘要数据集LCSTS(大规模中文短文本摘要数据集)、CNewSum(大规模中国新闻摘要数据集)、NLPCC2017和SFZY2020上的实验结果表明:本文方法对于长文本摘要生成具有显著优势,能够有效提高ROUGE-1、ROUGE-2、ROUGE-L值.展开更多
随着纠删码在分布式存储系统中的实际应用,纠删码为存储系统提供了更加优秀的存储效率,但当节点丢失时,相较于传统副本技术更多的网络传输带宽开销成为了造成系统性能瓶颈的关键因素。为了解决MDS编码高带宽开销对系统性能的影响,一类...随着纠删码在分布式存储系统中的实际应用,纠删码为存储系统提供了更加优秀的存储效率,但当节点丢失时,相较于传统副本技术更多的网络传输带宽开销成为了造成系统性能瓶颈的关键因素。为了解决MDS编码高带宽开销对系统性能的影响,一类新型编码方案——分组码被应用在分布式存储系统中,相较于传统MDS编码能够有效地降低节点修复时的数据传输量,从而减少网络带宽需求。在Pyramid分组码的基础上进行层次扩展,提出一种HLRC(hierarchical local repair codes)纠删码。HLRC相较于LRC引入了层次编码模型,将原始数据块构建为编码矩阵,根据层次进行分别编码,生成包含数据块范围不同的局部校验块;每个层次包含的数据块数量不同,可以保证修复节点时的低修复成本,同时还拥有较高的存储效率。HLRC相较于Pyramid拥有额外的校验块冗余,能够降低校验块出错和多节点出错时的恢复开销。在基于Ceph的分布式存储系统中的实验结果表明,HLRC与Pyramid等分组码相比,单节点修复开销最高可降低48.56%,多节点修复开销最高可降低25%。展开更多
基金Supported by 973 Project of China (No. 2012CB315803)Research Fund for the Doctoral Program of Higher Education of China (No. 20100002110033)Open research Fund of National Mobile Communications Research Laboratory, Southeast University (No. 2011D11)
文摘Erasure code is widely used as the redundancy scheme in distributed storage system. When a storage node fails, the repair process often requires to transfer a large amount of data. Regenerating code and hierarchical code are two classes of codes proposed to reduce the repair bandwidth cost. Regenerating codes reduce the amount of data transferred by each helping node, while hierarchical codes reduce the number of nodes participating in the repair process. In this paper, we propose a "sub-code nesting framework" to combine them together. The resulting regenerating hierarchical code has low repair degree as hierarchical code and lower repair cost than hierarchical code. Our code can achieve exact regeneration of the failed node, and has the additional property of low updating complexity.
基金Supported by the National Natural Science Foundation of China （ No. 60832001 ）.
文摘To maximize the aggregate throughput achieved in heterogeneous networks, this paper investigates inter-session network coding for the distribution of layered source data. We define inter-layer hierarchical random linear network codes （IHRLNC）, which not only take the flexibility of intersession network coding for layer mixing but also consider the strict priority inherent in the layered source data. Furthermore, we propose the inter-layer hierarchical multicast （IHM）, which performs IHRLNC in the network such that each sink can recover some source layers according to its individu- al capacity. To determine the optimal type of IHRLNC that should be performed on each edge in IHM, we formulate an optimization problem based on 0-1 integer linear programming, and propose a heuristic approach to approximate the optimal solution in polynomial time. Simulation results show that the proposed IHM can achieve throughput gains over the layered muhicast schemes.
基金National Natural Science Foundations of China (No. 60972035,No. 61074009)Natural Science Foundation Program of Shanghai,China ( No. 10ZR1432800)
文摘For rate control (RC) of hierarchical structure coding, an independent rate-quantization (R-Q) model was proposed based on mean absolute differences (MADs) in different temporal levels (TLs). In the proposed R-Q model, a novel MAD model was developed according to the hierarchical structure. The experimental results demonstrate that the proposed algorithm provides better performance, in terms of average peak signal-to-noise ratio (PSNR) and quality smoothness, than the H.264 reference model, JM14.2, under various sequences.
基金Project(60873230) supported by the National Natural Science Foundation of China
文摘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.
基金Sponsored by the Fundamental Research Funds for the Central Universities(Grant No. HEUCF11805)
文摘To decrease the computational complexity of adaptive inter-layer prediction and improve the encoding efficiency in sealable video coding, a mode decision algorithm is proposed by exploiting the part of used candidate modes of the co-located reference macrobloeks for Hierarchical-B pictures. This scheme reduces the amount of the candidate modes to generate a dynamic list for the current encoding macroblock according to the statistical information derived from the co-located reference macroblocks in different temporal levels. The experimental results show that this fast algorithm reduces approximately 31% encoding time on average with the negligible loss of encoding performance.
文摘In this paper, an investigation is made on compatibility of the video formats TV (625/50/2:1/4:3), EDTV (625/50/1:1/16:9), HDTVint (1250/50/2:1/16:9) and HDTVpro(1250/50/2:1/16:9) in three-dimensional subband coding. A hierarchical method is proposed leading to a more reasonable joint solution for the issues of digital transmission evolution and interlace-to-progressive scanning conversion ill the frame work of bit rate compression. Conventional HDTVint with the diamond shaped spectrum is proposed to be replaced by a kind of 'switching'HDTVin signal which consists of three components and motion detection bits (MDB). The first component and the MDB represent TV. The first plus the second component and the MDB represent EDTV.HDTVpro is splitted into switching HDTVint and extra component. The switching threshold and the length of temporal filter banks are discussed. Rearranging the pixels in subbands is recommended. Based on the proposed method, the transmission system can evolve through four steps: TV, EDTV, HDTVint and HDTVpro Results of bit rate compression are also presented. TV, EDTV, HDTVint and HDTVpro are compressed to approximately 40, 80, 128 and 256 Mbit/s respectively. Interlace scanning has drawbacks such as line flicker and line crawling as the eye follows the line structure in the picture. Progressive version switching TV and HDTVint can be reconstructed using one frame memory without the problems of handling temporal-vertical diamond shaped spectra of conventional TV and HDTVint based on a one-frame memory algorithm in the receiver.
文摘In this paper, the authors propose a new approach to image compression based on the principle of Set Partitioning in Hierarchical Tree algorithm （SPIHT）. Our approach, the modified SPIHT （MSPIHT）, distributes entropy differently than SPIHT and also optimizes the coding. This approach can produce results that are a significant improvement on the Peak Signal-to-Noise Ratio （PSNR） and compression ratio obtained by SPIHT algorithm, without affecting the computing time. These results are also comparable with those obtained using the Embedded Zerotree Wavelet （EZW） and Joint Photographic Experts Group 2000 （JPG2） algorithms.
基金National Key Research and Development Program of China,Grant/Award Number:2022YFF0904303Beijing Science and Technology Planning Project,Grant/Award Number:Z221100006322003National Natural Science Foundation of China,Grant/Award Number:61932003。
文摘Computer-aided design(CAD)software continues to be a crucial tool in digital twin application and manufacturing,facilitating the design of various products.We present a novel CAD generation method,an agent that constructs the CAD sequences containing the sketch-and-extrude modelling operations efficiently and with high quality.Starting from the sketch and extrusion operation sequences,we utilise the transformer encoder to encode them into different disentangled codebooks to represent their distribution properties while considering their correlations.Then,a combination of auto-regressive and non-autoregressive samplers is trained to sample the code for CAD sequence con-struction.Extensive experiments demonstrate that our model generates diverse and high-quality CAD models.We also show some cases of real digital twin applications and indicate that our generated model can be used as the data source for the digital twin platform,exhibiting designers'potential.
文摘针对无人机(Unmanned Aerial Vehicles,UAV)集群网络通信中存在的智能组网协议和高效通信技术问题,文中采用了一种可行的基于分层网络架构的信息交互与协同组网方法。文中从网络编码层、网络层、链路层、物理层和无线通信硬件设计等方面对系统总体设计方案进行了详细描述,提出了基于分层网络架构的网络编码通信方法。使用地面站参与初始分簇、空中节点自组织维护的方式得到面对集群节点移动表现相对稳定的分簇网络。设计基于网络编码的增强型TCP(Transmission Control Protocol)协议,能够实现无人机网络数据链中信息的高吞吐量快速传输。仿真实验结果表明,网络编码TCP方法性能优于传统TCP方法,适用于误码率较大的无人机集群通信环境,其可利用网络编码的优势实现节点之间、节点和地面站之间数据的高效快速传输。
文摘当前基于深度学习的中文长文本摘要生成的研究存在以下问题:(1)生成模型缺少信息引导,缺乏对关键词汇和语句的关注,存在长文本跨度下关键信息丢失的问题;(2)现有中文长文本摘要模型的词表常以字为基础,并不包含中文常用词语与标点,不利于提取多粒度的语义信息.针对上述问题,本文提出了融合引导注意力的中文长文本摘要生成(Chinese Long text Summarization with Guided Attention,CLSGA)方法.首先,针对中文长文本摘要生成任务,利用抽取模型灵活抽取长文本中的核心词汇和语句,构建引导文本,用以指导生成模型在编码过程中将注意力集中于更重要的信息.其次,设计中文长文本词表,将文本结构长度由字统计改变至词组统计,有利于提取更加丰富的多粒度特征,进一步引入层次位置分解编码,高效扩展长文本的位置编码,加速网络收敛.最后,以局部注意力机制为骨干,同时结合引导注意力机制,以此有效捕捉长文本跨度下的重要信息,提高摘要生成的精度.在四个不同长度的公共中文摘要数据集LCSTS(大规模中文短文本摘要数据集)、CNewSum(大规模中国新闻摘要数据集)、NLPCC2017和SFZY2020上的实验结果表明:本文方法对于长文本摘要生成具有显著优势,能够有效提高ROUGE-1、ROUGE-2、ROUGE-L值.
文摘随着纠删码在分布式存储系统中的实际应用,纠删码为存储系统提供了更加优秀的存储效率,但当节点丢失时,相较于传统副本技术更多的网络传输带宽开销成为了造成系统性能瓶颈的关键因素。为了解决MDS编码高带宽开销对系统性能的影响,一类新型编码方案——分组码被应用在分布式存储系统中,相较于传统MDS编码能够有效地降低节点修复时的数据传输量,从而减少网络带宽需求。在Pyramid分组码的基础上进行层次扩展,提出一种HLRC(hierarchical local repair codes)纠删码。HLRC相较于LRC引入了层次编码模型,将原始数据块构建为编码矩阵,根据层次进行分别编码,生成包含数据块范围不同的局部校验块;每个层次包含的数据块数量不同,可以保证修复节点时的低修复成本,同时还拥有较高的存储效率。HLRC相较于Pyramid拥有额外的校验块冗余,能够降低校验块出错和多节点出错时的恢复开销。在基于Ceph的分布式存储系统中的实验结果表明,HLRC与Pyramid等分组码相比,单节点修复开销最高可降低48.56%,多节点修复开销最高可降低25%。
