合龙方案对大跨度连续梁桥线形控制的影响研究

合龙方案是大跨度连续梁桥悬臂施工的关键步骤,工程后期合龙方案的变更将会对桥梁线形产生不良影响,借助有限元分析软件MIDAS分析方案变更对桥梁线形及合龙口高差的影响。     

Endeavouring to be in the good books. Awarding DTN network use for acknowledging the reception of bundles

This paper describes an incentive scheme for promoting the cooperation, and, therefore, avoiding selfish behaviours, in Delay Tolerant Networks (DTN) by rewarding participant nodes with cryptographic keys that will be required for sending bundles. DTN are normally sparse, and there are few opportunistic contacts, so forwarding of other’s bundles can be left out. Moreover, it is difficult to determine the responsible nodes in case of bundle loss. The mechanism proposed in this paper contributes to both problems at the same time. On one hand, cryptographic receipts are generated using time-limited Identity Based Cryptography (IBC) keys to keep track of bundle transmissions. On the other hand, these receipts are used to reward altruistic behaviour by providing newer IBC keys. Finally, these nodes need these IBC keys to send their own bundles. When all nodes behave in a cooperative way, this incentive scheme works as a virtuous circle and achieves a Nash equilibrium, improving very much the network performance in terms of latency. The scheme is not difficult to implement, and it can use an already existing IBC infrastructure used for other purposes in a DTN.     

Backstepping-based robust-adaptive control of a nonlinear 2-DOF piezoactuator

This paper deals with the control of a two degrees of freedom (2-DOF) piezoelectric actuator for precise positioning and which exhibits strong hysteresis nonlinearity and strong cross-couplings. To tackle the nonlinearity and the cross-couplings, we propose two decoupled models in which they are considered as (fictive) external disturbances which require proper characterization. Then, a backstepping technique is proposed to construct a robust controller that merges sliding-mode and adaptive schemes. Extensive experimental tests are finally carried out to prove the efficiency of the modeling and control technique proposed.     

A Secure Key Predistribution Scheme for WSN Using Elliptic Curve Cryptography

Security in wireless sensor networks (WSNs) is an upcoming research field which is quite different from traditional network security mechanisms. Many applications are dependent on the secure operation of a WSN, and have serious effects if the network is disrupted. Therefore, it is necessary to protect communication between sensor nodes. Key management plays an essential role in achieving security in WSNs. To achieve security, various key predistribution schemes have been proposed in the literature. A secure key management technique in WSN is a real challenging task. In this paper, a novel approach to the above problem by making use of elliptic curve cryptography (ECC) is presented. In the proposed scheme, a seed key, which is a distinct point in an elliptic curve, is assigned to each sensor node prior to its deployment. The private key ring for each sensor node is generated using the point doubling mathematical operation over the seed key. When two nodes share a common private key, then a link is established between these two nodes. By suitably choosing the value of the prime field and key ring size, the probability of two nodes sharing the same private key could be increased. The performance is evaluated in terms of connectivity and resilience against node capture. The results show that the performance is better for the proposed scheme with ECC compared to the other basic schemes.     

On the Performance of Linear Profile Methodologies Under Runs Rules Schemes

There are many practical situations where product quality is function of two or more related quality characteristics that may establish a linear relationship in the form of a linear profile. In this study, we have investigated different methodologies based on simple and general linear profile datasets for paired observations using efficient runs rules schemes. We have covered different methodologies such as T‐square, coding method approach, global F‐test under simple, and multiple linear models. We have performed comparisons among their performance using power under different runs rules schemes. The comparisons revealed that different methodologies for simple and multiple profile charts with a variety of runs rules schemes have attractive abilities to detect shifts in different parameters including intercept, slope, and process variance under special process scenarios. An application example is also provided in support of the study. Copyright © 2014 John Wiley & Sons, Ltd.     

面向新工科的电工学系列课程教学体系改革与探索

电工学系列课程是非电类理工科专业的重要工程基础课程,其教学方案和效果与新工科卓越工程人才的培养质量直接相关。本文在新工科建设的指导思想下,对国内外电工学系列课程现状进行调研,在分析学生实际需求的基础上,构建与研究非电类理工科专业电工学系列课程建设方案和教学基本要求,以促进新型工程技术人才的培养,为新工科的建设奠定坚实的实践基础。     

有限域上两类新的2-重量码的构造

有限域上二重量码的构造是图论、编码与密码中的重要研究课题.本文得到了有限域上两类新的2-重量码并且它们都是最优的,达到了Griesmer界.这些码由有限域的扩域上迹码的p元像定义,有阿贝尔码的代数结构,利用特征和和高斯和来计算了它们的重量分布.我们也计算了这些像码的对偶码的极小距离.最后对扩域上迹码的像在秘钥共享方案中的应用进行了刻画.     

考虑负荷差异化需求响应的配电网多目标扩展规划

为应对不断增长的能源需求和环境污染,发展分布式电源(distributed generation,?DG)、需求侧响应(demand response,?DR)成为促进全球能源体系发展的重要举措。基于此,提出基于改进k-means聚类和最优特征集提取的用电行为画像方法,以实现针对用户差异化用电特征的需求响应方案界定。然后,构建考虑差异化需求响应方案的配电网扩展规划模型,在决策目标中添加年综合成本、DG利用率等优化目标,采用规格化法平面约束法(normalized normal constraint,?NNC)求解帕累托最优解集。最后,在IEEE33节点系统上验证了该需求响应方案界定方法和扩展规划模型的有效性。     

Assessing sustainability of rural gravity-fed water schemes on Idjwi Island,D.R. Congo

ABSTRACT

To assess the sustainability of rural gravity-fed water schemes on Idjwi Island, the association between four hypothesized drivers of sustainability – perceived sense of ownership, willingness to pay for maintenance, trust in the water committee, and household involvement in the project – and service reliability, the main outcome variable, was analyzed. Primary data were gathered through in-person surveys of 1253 user households. The results provide two significant insights. First, during the 5–10 years after implementation, in the presence of an external intervention, a lower perceived sense of ownership for the water system was associated with higher service reliability. This stands in contrast with much of the existing literature, which outlines a consistent positive association between sense of ownership and sustainability of rural water systems. Second, despite 77% of beneficiaries stating that they were willing to pay for maintenance service, such contributions were not forthcoming, due to lack of trust in the water committee. In this scenario, almost 42% of the water points are reported as non-functional, 5–10 years after completion.