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排序方式: 共有101条查询结果,搜索用时 15 毫秒
41.
利用EA建模加强机构信息安全风险管理 总被引:1,自引:0,他引:1
当前很多机构信息系统都普遍存在保护措施与其保护信息价值不匹配的情况,导致过度保护或保护不足。这种情况主要是源于安全目标与机构业务目标不完全符合、安全需求获取不规范、难以判断风险管理中是否应用了合适的安全控制以及成本是否平衡。对此,该文提出了在信息系统开发生命周期(information system development life cycle,SDLC)内利用机构体系结构(enterprise architecture,EA)这一管理工具进行安全目标分析、安全需求获取、风险管理等,开发符合机构管理目标的安全信息系统,以加强机构的信息安全和风险管理。利用EA模型的方法能提供一种机构层面的整体性安全描述和分析结果,在整个SDLC内为信息系统的安全开发和管理提供指导和依据,特别是在风险管理中,为进行安全控制选择和成本平衡的决策提供了一个有效的判断机制与依据。 相似文献
42.
In this paper we show that optimal trading results can be achieved if we can forecast a key summary statistic of future prices. Consider the following optimization problem. Let the return ri (over time i=1, 2, ..., n) for the ith day be given and the investor has to make investment decision di on the ith day with di=1 representing a ‘long' position and di=0 a ‘neutral' position. The investment return is given by r=Σni=1ridi−cΣn+1i=1∣di−di−1∣, where c is the transaction cost. The mathematical programming problem of choosing d1, ..., dn to maximize r under a given transaction cost c is shown to have an analytic solution, which is a function of a key summary statistic called the largest change before reversal. The largest change before reversal is recommended to be used as an output in a neural network for the generation of trading signals. When neural network forecasting is applied to a dataset of Hang Seng Index Futures Contract traded in Hong Kong, it is shown that forecasting the largest change before reversal outperforms the k‐step‐ahead forecast in achieving higher trading profits. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
43.
This paper presents a network equilibrium formulation for modeling commuters' travel choices in a bimodal transport system with park-and-ride (P&R) trips while the total demand is elastic to the congestion level of the network. A super-network approach is adopted in the proposed model. It is assumed that commuters' trips are categorized into two types, auto mode only and a combined mode with both auto and transit modes. The former is referred to as the pure mode trip and the latter as the P&R mode trip. The proposed model simultaneously considers the commuter's choice of the pure mode versus the P&R mode, the choice of parking location for the pure mode, the choice of transfer point for the P&R mode, as well as the route choice for each mode. The demand elasticity of transport system, the capacity constraints of transport facilities, and the congestion interaction throughout the super-network are also explicitly incorporated into the proposed model. The results of the numerical experiment show the following key findings: (i) traditional parking/P&R models may overestimate or underestimate travel demand distribution over network; (ii) parking/P&R, transit scheduling, and carpooling schemes bring significant impacts on commuters' travel behavior and network performance; and (iii) different transport policies may be to some extent mutually substituted . 相似文献
44.
Mycielski图是1955年由Mycielski提出来的.任给一个图G和一个非负整数m,G的推广Mycielski图μm(G)是G的Mycielski图的一个自然的推广.推广Mycielski图的性质以及它们的点色数、圆色数和分数色数等已有许多研究.本文研究圈的推广Mycielski图的圆色数.定义Cn为n个顶点的圈.对任意非负整数m和大于2的整数n,本文确定了图μm(Cn)的圆色数,同时还得到了图μm(Cn)-v的圆色数的一些结果. 相似文献
45.
Regulation of progenitor cell proliferation and granulocyte function by microRNA-223 总被引:1,自引:0,他引:1
Johnnidis JB Harris MH Wheeler RT Stehling-Sun S Lam MH Kirak O Brummelkamp TR Fleming MD Camargo FD 《Nature》2008,451(7182):1125-1129
46.
Wang PY Caspi L Lam CK Chari M Li X Light PE Gutierrez-Juarez R Ang M Schwartz GJ Lam TK 《Nature》2008,452(7190):1012-1016
Energy and glucose homeostasis are regulated by food intake and liver glucose production, respectively. The upper intestine has a critical role in nutrient digestion and absorption. However, studies indicate that upper intestinal lipids inhibit food intake as well in rodents and humans by the activation of an intestine-brain axis. In parallel, a brain-liver axis has recently been proposed to detect blood lipids to inhibit glucose production in rodents. Thus, we tested the hypothesis that upper intestinal lipids activate an intestine-brain-liver neural axis to regulate glucose homeostasis. Here we demonstrate that direct administration of lipids into the upper intestine increased upper intestinal long-chain fatty acyl-coenzyme A (LCFA-CoA) levels and suppressed glucose production. Co-infusion of the acyl-CoA synthase inhibitor triacsin C or the anaesthetic tetracaine with duodenal lipids abolished the inhibition of glucose production, indicating that upper intestinal LCFA-CoAs regulate glucose production in the preabsorptive state. Subdiaphragmatic vagotomy or gut vagal deafferentation interrupts the neural connection between the gut and the brain, and blocks the ability of upper intestinal lipids to inhibit glucose production. Direct administration of the N-methyl-d-aspartate ion channel blocker MK-801 into the fourth ventricle or the nucleus of the solitary tract where gut sensory fibres terminate abolished the upper-intestinal-lipid-induced inhibition of glucose production. Finally, hepatic vagotomy negated the inhibitory effects of upper intestinal lipids on glucose production. These findings indicate that upper intestinal lipids activate an intestine-brain-liver neural axis to inhibit glucose production, and thereby reveal a previously unappreciated pathway that regulates glucose homeostasis. 相似文献
47.
Surface morphological study of ehrlich ascites tumor cells exposed to microware irradiation and heat
E. C. Chew D. J. Riches T. K. Lam H. L. Hou-Chan 《Cellular and molecular life sciences : CMLS》1984,40(8):881-884
Summary Microwave irradiation of EAT cells caused an increase in length and number of surface microvilli. The tumor cells tend to form large aggregates by means of extensive interdigitation of surface microvilli. On the other hand, heat hyperthermia caused a decrease of surface microvilli but an increase of surface blebs. Hence the surface morphology of EAT cells after in vitro exposure to microwave irradiation differs markedly from that after heat hyperthermia.Part of the results was presented a the Fifth meeting of the European Co-operative Hyperthermia Group, Essen, July 1983. 相似文献
48.
Ian Gibson Monica M Savalani Christopher XF Lam Radoslow Olkowski Andrew K Ekaputra Kim Cheng Tan Dietmar W Hutmacher 《清华大学学报》2009
This paper describes fabrication of scaffolds for load-bearing applications, with primary consideration from the manufacturing perspective. An extrusion device, inspired by the FDM process, was used to create scaffolds from a variety of different polymeric materials and mixtures. The effectiveness of these scaffolds to host cells for bone regeneration has been investigated. This ongoing work has generated significant insight into the future direction of research and the possibilities of developing scaffolds for medium/high load-bearing applications. 相似文献
49.
50.
Mills RE Walter K Stewart C Handsaker RE Chen K Alkan C Abyzov A Yoon SC Ye K Cheetham RK Chinwalla A Conrad DF Fu Y Grubert F Hajirasouliha I Hormozdiari F Iakoucheva LM Iqbal Z Kang S Kidd JM Konkel MK Korn J Khurana E Kural D Lam HY Leng J Li R Li Y Lin CY Luo R Mu XJ Nemesh J Peckham HE Rausch T Scally A Shi X Stromberg MP Stütz AM Urban AE Walker JA Wu J Zhang Y Zhang ZD Batzer MA Ding L Marth GT McVean G Sebat J Snyder M Wang J Ye K Eichler EE Gerstein MB Hurles ME Lee C McCarroll SA 《Nature》2011,470(7332):59-65
Genomic structural variants (SVs) are abundant in humans, differing from other forms of variation in extent, origin and functional impact. Despite progress in SV characterization, the nucleotide resolution architecture of most SVs remains unknown. We constructed a map of unbalanced SVs (that is, copy number variants) based on whole genome DNA sequencing data from 185 human genomes, integrating evidence from complementary SV discovery approaches with extensive experimental validations. Our map encompassed 22,025 deletions and 6,000 additional SVs, including insertions and tandem duplications. Most SVs (53%) were mapped to nucleotide resolution, which facilitated analysing their origin and functional impact. We examined numerous whole and partial gene deletions with a genotyping approach and observed a depletion of gene disruptions amongst high frequency deletions. Furthermore, we observed differences in the size spectra of SVs originating from distinct formation mechanisms, and constructed a map of SV hotspots formed by common mechanisms. Our analytical framework and SV map serves as a resource for sequencing-based association studies. 相似文献