一种基于m序列的关系数据库鲁棒水印算法

提出一种关系数据库水印算法,适用于数值型数据的版权保护.以连接多项式数组为密钥生成m序列,分别作为水印信号和水印嵌入策略控制信号;根据密钥和元组主键连接值的散列运算确定水印嵌入位置;通过修改数值属性低位数值的奇偶性嵌入水印,克服了常用的最低有效位重置算法易产生病态结果的缺点.水印的嵌入满足数据库动态更新的同步要求,水印的检测无需原始数据库参与.理论分析和实验表明,该算法运算开销合理,具有良好的隐蔽性和安全性,对常见的水印攻击具有良好的鲁棒性.     

基于XACML的DR-RBAC模型的研究与应用

分析了OASIS定义的基于XACML的核心和层次RBAC框架,指出了其中的不足.在对文档进行分类的基础上,定义了一种双角色的基于角色的访问控制模型,并给出了此模型的数据流图及部分以XACML形式表示的控制策略.     

个性化学习资源推荐系统研究

通过分析远程网络学习系统中学习者对学习资源的访问历史,以及与学习者有类似访问兴趣的同组学习者的学习偏好,为学习者提供个性化的资源推荐服务,能够有效提高各种学习资源的利用效率,从而提高教学质量.     

支持关键词搜索的空间连接查询研究

近年来,许多实际应用不仅需要支持空间连接查询而且需要具备关键词搜索功能,以帮助用户查找那些既满足空间连接条件又包含指定关键词的空间对象组合.正是在这种需求的驱动之下,定义了一种具备关键词搜索功能的空间连接查询(Spatial Join with Keyword Search,缩写SJKS),并提出了一种基于IR2-Tree的SJKS查询处理算法(IR2-TreeSJKS算法),旨在实现关键词搜索与空间连接查询的高效结合.实验表明,本算法可有效支持具有关键词搜索功能的空间连接查询处理.     

基于数字水印的外包数据库查询验证

外包数据库的查询验证,是指客户端对外包数据库的数据来源真实性、查询运算正确性及查询结果完整性的验证。提出一种基于脆弱型数字水印对外包数据库查询的真实性进行验证的解决方案。在密钥的控制下,以混沌方程产生随机二值序偶作为水印信号并确定其嵌入方式,通过修改数值型属性低位数字的奇偶性嵌入水印,通过对数据库查询结果运行水印检测算法进行查询验证。该方法具有冗余存储量与网络附加负载小、隐蔽性好、能同时实现篡改定位等优点。     

考虑循环寿命折损的主动配电网仿射可调鲁棒优化方法

针对主动配电网在源荷储协同下的不确定性优化问题,提出了基于仿射可调鲁棒优化的主动配电网运行策略。首先,考虑分布式光伏的可控模型、循环寿命折损的电池储能模型和ZIP负荷模型,构建了主动配电网优化运行模型。然后,采用椭球集合来描述分布式光伏出力的不确定性,并结合仿射策略形成优化模型中决策变量与分布式光伏出力不确定性变量之间的线性决策机制。最后,通过对偶变换将主动配电网鲁棒优化模型转化为一个确定性的混合整数二阶锥规划模型进行求解。在改进的IEEE33节点算例系统中对比验证了所提出的仿射可调鲁棒优化方法的有效性和优点。     

考虑电池储能老化和需求侧响应的交直流混合配电网动态重构方法

现有的电池储能模型一方面认为电池的充放电功率和效率为固定不变的,另一方面有关电池储能的充放电过程对循环老化的影响缺少考虑,这与电池单元本体的非线性等效电路模型相违背。因此,考虑电池储能的循环老化成本、需求侧响应,提出了交直流混合配电网动态重构方法。通过对实际电池储能的充放电功率的运行区域进行采样,在凸包络的采样点集合中将非理想状态下的电池储能模型重构为线性模型。在此基础上,分别建立了基于累积吞吐电量和放电深度的循环老化成本模型,构建了综合成本最小化的交直流混合配电网动态重构模型。并采用混合整数二阶锥规划方法求解。在改进的33节点算例上仿真验证了所提基于放电深度的循环老化成本模型的经济性,分析了交直流混合配电网重构方法经济性的影响因素。     

CD57+/CD28- T cells in untreated hemato-oncological patients are expanded and display a Th1-type cytokine secretion profile, ex vivo cytolytic activity and enhanced tendency to apoptosis

Protopolystoma (Monogenea, Polystomatidae) is strictly specific to the anuran amphibian genus Xenopus. The host group is characterised by a polyploid series in which chromosome numbers reflect diploid, tetraploid, octoploid and dodecaploid constitutions; the series is considered to have evolved through interspecies hybridisation and genome duplication. This study correlates information on host evolutionary relationships with patterns of parasite speciation and host specificity. Protopolystoma is restricted to one subgenus (Xenopus) with multiples of 36 chromosomes, and is absent from the subgenus Silurana (with multiples of 20 chromosomes). Molecular, biochemical and karyotype evidence distinguishes three subgroups within Xenopus. Representative species from each subgroup, Xenopus muelleri, Xenopus fraseri and Xenopus laevis, have been examined for polystomatid infection. Two species of Protopolystoma occur in each of these host species. In X. muelleri, the two Protopolystoma species reflect parasite co-speciation corresponding with the divergence of two sibling host species. Xenopus fraseri and X. laevis (both with 2n = 36 chromosomes) are implicated in the hybrid origin of two octoploid species, Xenopus wittei and Xenopus vestitus (both 2n = 72). The relationships of the Protopolystoma species in these Xenopus taxa reflect this presumed ancestry. Xenopus wittei carries two species of Protopolystoma, one shared with X. fraseri and the other shared with X. laevis. Xenopus vestitus carries a single species of Protopolystoma which is shared with X. laevis but there is no "heirloom" which reflects its hybrid origin involving X. fraseri. In addition to these shared parasite species which may reflect shared host genes, X. fraseri and X. laevis each carry separate species-specific Protopolystoma which do not occur in other Xenopus species even where there is evidence of common genetic information (as in the allopolyploid wittei and vestitus). This case study may be interpreted as indicating a powerful influence of host genetic factors on susceptibility to infection, host-specificity, and parasite speciation.     

Surgical anatomy for endoscopic subfascial division of perforating veins

PURPOSE: This study was undertaken to define the surgical anatomy of the medial perforating veins (PVs) of the leg and to provide information on how to gain access to all medial PVs from the superficial posterior compartment during a subfascial endoscopic procedure. METHODS: The venous anatomy of 40 limbs (from 23 cadavers) were studied. Medial PVs located between the ankle and the tibial tuberosity were dissected. None of the subjects had pathologic evidence of venous disease. Each PV's type (direct or indirect), size (< 1 mm, 1 to 2 mm, > 2 mm), location (distances from ankle [D1], and tibia [D2]), and accessibility from the superficial posterior compartment were recorded. RESULTS: Five hundred fifty-two PVs were identified (mean, 13.8; range, 7 to 22). Two hundred eighty-seven PVs (52%) directly connected the superficial with the deep systems, 228 (41%) were indirect muscle perforators, and 37 PVs (7%) were undetermined. One hundred thirty-seven PVs (25%) were > 2 mm. Sixty-three percent of PVs were accessible from the superficial posterior compartment. In the distal half of the leg, two groups of direct PVs could be identified (Cockett II: D1, 7 to 9 cm; Cockett III: D1, 10 to 12 cm). In the proximal half of the leg, paratibial direct PVs (D2 < or = 1 cm) were found clustered in three groups (D1, 18 to 22 cm; D1, 23 to 27 cm; D1, 28 to 32 cm). CONCLUSIONS: Our study confirmed the presence of the Cockett II and III PVs and three groups of proximal paratibial PVs, including the "24-cm" perforators. Two thirds of the medial direct PVs are accessible for endoscopic division from the superficial posterior compartment. To divide paratibial PVs, however, incision of the paratibial deep fascia is frequently required.