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1.
局部修复码(Locally Repairable Codes,简记为LRCs)是一种可以减小分布式存储系统修复带宽的新型纠删码。依据二元最优码的不同距离特性而改变校验矩阵的方法,提出了由奇距离局部修复码扩展构造偶距离局部修复码的一种方法;而且提出了通过删截的方法构造新的性能优良的局部修复码。利用这两种方法,构造出四组码长为n≤24,维数为k≥8且距离为6≤d≤8具有较小局部修复度的码,这些码都达到了C-M界。这些结果对于研究更大距离的二元最优局部修复码以及一般域上的最优局部修复码的构造,将具有借鉴意义。  相似文献   

2.
在分布式存储系统中,当节点发生故障时,局部修复码能够提高修复效率.四元距离最优码易于实现,当给定码长和维数时,四元距离最优码的纠错能力优于二元距离最优码,但目前利用四元距离最优码构造四元局部修复码的研究存在很多空白.设四元距离最优码的维数2≤k≤4,由给定维数的四元Simplex码与MacDonald码以及少量距离最优码的生成矩阵,利用扩展、删除与并置等组合方法,设法构造出任意码长n≥k+1且局部度较小的四元局部修复码.确定出达到Singleton-Like界或Cadambe-Mazumdar界的四元局部修复码.证明除55个四元局部修复码外,其余的四元局部修复码都是局部度最优的.  相似文献   

3.
局部修复码可以提高分布式存储系统中失效节点的修复效率,是分布式存储编码领域的研究热点。文章研究最优局部修复码的构造,利用二元常重量码构造了两类矩阵,并以这两类矩阵作为校验矩阵,构造了局部性为r、最小距离分别为d=5和d=6的两类最优局部修复码。  相似文献   

4.
基于最优线性码与射影几何理论,针对不同码长最优码的距离特性,研究了低维五元最优LCD码的构造。首先利用删截等方法构造了较小码长的三维和四维最优线性码以及最优LCD码;其次,借助部分已知矩阵和删截等方法构造了较大码长的三维和四维最优线性码以及最优LCD码;最后,利用已知最优LCD码和特殊码长最优自正交码构造了任意大码长的最优LCD码,完全解决了三维和四维最优LCD码的构造问题。这些LCD码的构造方法对于五元高维最优LCD码以及一般域上最优LCD码的研究具有重要的理论指导意义。  相似文献   

5.
研究具有某种最优性质的码的存在性、结构和构造是编码研究的中心问题,为构造量子纠错码开始研究具有特定对偶距离的二元自正交码。研究了码长n满足12≤n≤20的二元不可分解自对偶码B12、D14、E16、F16、H18、I18、J20、K20、L20、M20和S20的两类子码,即对偶距离最优或对偶距离拟最优的子码,以及相应的S-链的构造。依据不可分解自对偶码的生成矩阵,利用组合方法构造出对偶距离为2、3和4的对偶距离最优或拟最优的子码生成矩阵。在此基础上研究了这些子码构成的子码链,以及由它们的对偶构成的S-链。最后,利用得到的S-链构造出好的量子纠错码,这些量子码都是给定码长和维数时距离达到最大值的量子码。  相似文献   

6.
局部修复码(Locally Repairable Codes)是一种能为分布式存储系统提供信息修复能力的新型纠删码。针对目前三元域上局部修复码的研究尚不充分的情况,给出了利用循环码构造局部修复码的一般方法。首先从循环码的码长出发,计算出对应的3-分圆陪集,然后通过分圆陪集的组合确定各循环码的定义集从而确定码的距离和局部度,进而构造了码长8≤n≤50范围内达到Cadambe-Mazumdar(C-M)界的三元局部修复码。特别是通过定义集设计对偶距离,并利用BCH界筛选分圆陪集,构造了3种具有小局部度的最优局部修复码。这些研究结果进一步完善了三元局部修复码的相关构造理论。  相似文献   

7.
目的研究F4上维数为3的最优(或拟最优)自正交码的码长与极小距离之间的关系。方法组合方法。结果构造出码长n≥21的3维最优(或拟最优)自正交码的生成矩阵,确定出了其中达到Griesmer界的码。结论给出了3维的最优自正交码码长与距离的规律。  相似文献   

8.
根据四元自正交码的重量特点,研究二维最优自正交码的生成矩阵与重量分布之间的关系.通过引入二维四元码的定义向量和射影重量概念,利用Simplex码的码字构成的矩阵,建立二维最优自正交码的存在性与整数方程组的非负解之间的联系,将确定二维最优正交码的生成矩阵问题转化为求解整数方程组的非负解.对于给定码长,首先由Griesmer界确定二维最优自正交码的距离;然后,通过求解整数方程组的非负解,确定出所有二维最优自正交码的生成矩阵和重量多项式;依据二维最优自正交码的生成矩阵,利用矩阵的初等行变化、向量的坐标置换和元素的共轭变换,判断二维最优自正交码的等价性;最后,完全解决了二维最优自正交码的分类问题,给出互不等价的二维最优自正交码的生成矩阵与重量多项式.  相似文献   

9.
局部修复码(Locally Repairable Code)中每一码字的任意位发生错误可通过读取此码字的其它若干位予以修复。在应用了局部修复码的分布式存储系统中,任意节点发生损坏时均可通过读取较小数量的其它节点对其进行修复,给出了一些可以达到较小局部修复度的码的生成矩阵的构造方法。通过对相应最优码参数的分析,采用删截、扩展,并置等方法构造出了五维三元最优码的生成矩阵,分析了生成矩阵列向量之间的线性相关关系后,得到了许多具有较小局部度的五维三元最优码。  相似文献   

10.
局部修复码是一种局部纠删编码,近年来在分布式存储系统中得到了广泛的应用。码的局部修复度为r指的是,码字的任一位发生删除错误时至多需要该码字的其他r位进行恢复。研究了r≤3的二元循环局部修复码的存在性与构造。基于循环码定义集理论,采用局部修复码的对偶码描述,依据码的参数制约关系,进行局部修复码的构造及参数优化。证明了r=1的任意码长二元循环码的存在性,构造了r=1且参数达到Griesmer界的局部修复码;给出了r=2和r=3的部分码长二元循环码存在性的判据,基于7≤n≤99的二元循环码分别构造了r=2和r=3的、参数优良的短码长局部修复码。研究结果对进一步研究循环码的局部修复度与其他参数的关系、构造参数优良的一般码长局部修复码具有借鉴作用。  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

13.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

14.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

15.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

16.
Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.  相似文献   

17.
以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.  相似文献   

18.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

19.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

20.
Quality traits in wheat (Triticum aestirum L.) were studied by quantitative trait locus (QTL) analysis in a recombinant inbred line (RIL) population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross (ChSh). Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.  相似文献   

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