无线传感器网络对称密钥建立方案

传感器网络的固有特点要求密钥建立方案既要达到一定的安全性标准又要高效。基于密钥池的密钥预分配方案虽然比较适合无线传感器网络,但节点的安全链路连通率不高。基于双变量多项式的密钥预分配方案具有高连通率的特点,但安全性存在缺陷。为此,将基于多项式的密钥建立方案与基于密钥池的密钥建立方案相结合,提出一种新的密钥建立方案。分析和实验表明,该方案在安全性、安全链路连通性、可扩展性、有效性等方面和现有一些典型方案相比有较大的提高。     

Optimal pricing and two-dimensional warranty policies for a new product

For commercial products, pricing and warranty are two crucial marketing strategies, which are used to promote the potential market share. The warranty policy adopted by most of the capital-intensive products, such as machines and automobiles, usually has two dimensions, i.e. warranty age and warranty usage. In this paper, we propose to investigate the profit-maximisation problem, in which the revenue and costs will be affected by the product price and the area of warranty region, for a new product sold under two-dimensional warranty. We assume that the product sales can be captured by a stochastic Bass model based on the nonhomogeneous Poisson process. The product follows a two-dimensional failure process and is covered by a non-renewable free minimal-repair warranty, with age and usage limits. We focus on three revenue/cost components, i.e. sales revenue, warranty cost and production cost, that will significantly affect a firm’s total profit. The profit is maximised by jointly optimising three decision variables, i.e. product price, warranty age limit and warranty usage limit. Numerical experiments are conducted to illustrate the effects of some key parameters, including product reliability, price elasticity, warranty elasticity and learning effect factor, on the optimal settings of the price and warranty region.     

条件期望在两变量洪水频率分析中的应用

针对现行单变量洪水频率分析计算方法无法考虑洪水要素之间的相关性这一不足,采用Copula函数构建洪水峰、量之间的二维联合分布,根据条件期望的原理,提出了一种推求两变量设计洪水的新方法。以清江隔河岩水库为例,计算了1 000 a一遇的两变量设计洪水,推求了对应的设计洪水过程线,并与单变量设计值进行了比较。结果表明,两变量设计值大于单变量设计值,两变量设计值对应的水库调洪最高水位略高于单变量设计值。由于两变量频率分析考虑了洪水峰、量之间的内在相关性,更符合水文现象的内在规律,所推求的两变量条件期望设计值组合相对于单变量设计值而言也是偏安全的。所提方法为洪水频率分析提供了一条新途径。     

一种无线传感器网络预分配密钥管理方案的改进

无线传感器网络在应用二元多项式密钥预分配协议时,通常容易遭受到敌方的合谋攻击。为了更好地解决这一问题,通过减少普通节点共享的密钥个数,改变簇首间建立共享密钥的方式,改进了一种无线传感器网络的密钥预分配管理方案。分析表明,改进后的方案保留了原方案的网络高安全性等优点,而且进一步节省了普通节点的内存空间,减少了节点间的通信量,延长了网络的生存周期,能够有效地抵御敌方的合谋攻击。     

基于多项式无线传感器网络密钥预分配方案*

针对无线传感器网络密钥管理中连通性、效能及安全性不足问题,基于阶层式无线传感器网络与二元对称多项式提出ESKDM （Efficient and Scalability Key Distribution Mechanism）方案。该方案通过运用多项式的特性,使传感器节点之间只需透过ID的信息交换即可建立密钥。相较于同类方案,ESKDM方案大幅度的降低传感器节点的通信成本,并完全抵抗节点捕获攻击。无论网络节点的大小,一般节点所需要储存的秘密信息都为固定的信息,能够支持大型的WSN。也提出在新增节点的同时,不需要在线的基站存在,更能适用于实际应用。     

Computation of stability radius for families of bivariate polynomials

In this paper we apply optimization techniques to the problem of robust stability of a family of bivariate polynomials under affine coefficient perturbations. The size of the perturbations is measured by a convex function. In this paper we concentrate onl ^p weighted norms, for three special casesp = 1,p = 2, andp = . Necessary and sufficient conditions for robust stability are provided. Evaluation of the stability radius is reduced to a minimization problem in two-dimensional space. The results open the door to the development and implementation of reliable and efficient algorithms for the computation of the stability radius.     

Crash protectiveness to occupant injury and vehicle damage: An investigation on major car brands

This study sets out to investigate vehicles’ crash protectiveness on occupant injury and vehicle damage, which can be deemed as an extension of the traditional crash worthiness. A Bayesian bivariate hierarchical ordered logistic (BVHOL) model is developed to estimate the occupant protectiveness (OP) and vehicle protectiveness (VP) of 23 major car brands in Florida, with considering vehicles’ crash aggressivity and controlling external factors. The proposed model not only takes over the strength of the existing hierarchical ordered logistic (HOL) model, i.e. specifying the order characteristics of crash outcomes and cross-crash heterogeneities, but also accounts for the correlation between the two crash responses, driver injury and vehicle damage. A total of 7335 two-vehicle-crash records with 14,670 cars involved in Florida are used for the investigation. From the estimation results, it's found that most of the luxury cars such as Cadillac, Volvo and Lexus possess excellent OP and VP while some brands such as KIA and Saturn perform very badly in both aspects. The ranks of the estimated safety performance indices are even compared to the counterparts in Huang et al. study [Huang, H., Hu, S., Abdel-Aty, M., 2014. Indexing crash worthiness and crash aggressivity by major car brands. Safety Science 62, 339–347]. The results show that the rank of occupant protectiveness index (OPI) is relatively coherent with that of crash worthiness index, but the ranks of crash aggressivity index in both studies is more different from each other. Meanwhile, a great discrepancy between the OPI rank and that of vehicle protectiveness index is found. What's more, the results of control variables and hyper-parameters estimation as well as comparison to HOL models with separate or identical threshold errors, demonstrate the validity and advancement of the proposed model and the robustness of the estimated OP and VP.     

Modeling and Optimization of Two Stage AC Electrostatic Desalter

Electrostatic desalters are commonly used to separate water from crude oil emulsions. In this study, a novel mathematical model based on a bivariate population balance equation has been proposed to model the steady state distribution of water droplet sizes and salt concentration along an Alternative Current (AC) electrostatic desalter. Pilot plant data for two heavy crude oils are used to validate the model. Effect of different operational parameters on the outlet dehydration efficiency and salt content of crude oil have been studied. Furthermore, the effect of two-stage desalting on the outlet Basic Sediment and Water (BS&W) and salt content of oil have been studied and the optimized parameters of such configuration have been found by differential evolution method to get the best performance of the electrostatic desalters.     

Delamination identification and response prediction in composites using bivariate Gamma function-based microgenetic algorithms

This study deals with an identification of stiffness reduction and response predictions occurred by the delamination damage in laminated composite plates under impact loads. Combined bivariate Gamma function and microgenetic algorithms are developed to determine the crack region due to the delamination and predict future responses. The validity of the proposed method was verified using impact-induced data obtained from a two-dimensional delamination finite element model. Examples indicated that the proposed approach is a feasible and advantageous method through which future dynamic responses can be predicted and the distribution of the degraded stiffness of laminated composite structures can be inspected for different measuring locations and fibre angles.     

荧光粉粉浆配制中PEO胶加入量的计算

通过荧光粉粉浆续加PEO胶液的实验,对实验中的加胶重量比、婆美度变化率及粘度变化率数据,运用二元回归计算法得到三者之间的经验公式。对需要加PEO胶的粉浆,测量其重量、婆美度、粘度,运用实验所得公式,即可算出应加胶液的重量,使得荧光粉粉浆符合预期要求。