A survey of energy-efficient context recognition systems using wearable sensors for healthcare applications

Human context recognition (HCR) from on-body sensor networks is an important and challenging task for many healthcare applications because it offers continuous monitoring capability of both personal and environmental parameters. However, these systems still face a major energy issue that prevent their wide adoption. Indeed, in healthcare applications, sensors are used to capture data during daily life or extended stays in hospital. Thus, continuous sampling and communication tasks quickly deplete sensors’ battery reserves, and frequent battery replacement is not convenient. Therefore, there is a need to develop energy-efficient solutions for long-term monitoring applications in order to foster the acceptance of these technologies by the patients. In this paper, we survey existing energy-efficient approaches designed for HCR based on wearable sensor networks. We propose a new classification of the energy-efficient mechanisms for health-related human context recognition applications and we review the related works in detail. Moreover, we provide a qualitative comparison of these solutions in terms of energy-consumption, recognition accuracy and latency. Finally, we discuss open research issue and give directions for future works.     

无线传感器网络能量高效策略研究与分析

实现无线传感器网络能量高效,是无线传感器网络研究的热点问题和基本问题。该文先对无线传感器网络进行了能耗分析,然后分别从单个节点、整个网络的角度出发总结了目前已有的能量高效策略,提出了能量高效的传感器节点设计、能量高效的传感器网络设计。     

一类广义univex条件下的多目标规划

引入了一种新的广义不变凸函数,即d-ρηθ-univex函数,讨论了这一概念与d-不变凸函数、d-univex函数、d-ρηθ-不变凸函数之间的关系,并在d-ρηθ-univex条件下考察一类多目标规划问题(P).首先给出问题(P)的弱Pareto有效解存在的充分条件;进而得到问题(P)的Mond-Weir型对偶的弱对偶、强对偶和逆对偶结论以及问题(P)的广义Mond-Weir型对偶的弱对偶和强对偶论断.     

Alternative mixed integer linear programming models for identifying the most efficient decision making unit in data envelopment analysis

A mixed integer linear model for selecting the best decision making unit (DMU) in data envelopment analysis (DEA) has recently been proposed by Foroughi [Foroughi, A. A. (2011a). A new mixed integer linear model for selecting the best decision making units in data envelopment analysis. Computers and Industrial Engineering, 60(4), 550–554], which involves many unnecessary constraints and requires specifying an assurance region (AR) for input weights and output weights, respectively. Its selection of the best DMU is easy to be affected by outliers and may sometimes be incorrect. To avoid these drawbacks, this paper proposes three alternative mixed integer linear programming (MILP) models for identifying the most efficient DMU under different returns to scales, which contain only essential constraints and decision variables and are much simpler and more succinct than Foroughi’s. The proposed alternative MILP models can make full use of input and output information without the need of specifying any assurance regions for input and output weights to avoid zero weights, can make correct selections without being affected by outliers, and are of significant importance to the decision makers whose concerns are not DMU ranking, but the correct selection of the most efficient DMU. The potential applications of the proposed alternative MILP models and their effectiveness are illustrated with four numerical examples.     

Link weight assignment and loop-free routing table update for link state routing protocols in energy-aware internet

In order to lessen the greenhouse effects and diminish environmental pollution, reducing energy usage is important in designing next generation networks. Shutting down the network devices that carry light load and redirecting their traffic flows to other routes is the most common way to reduce network energy consumption. Since traffic demands among node pairs vary in different time periods, an energy efficient network has to dynamically determine the optimal active links to adapt itself to network traffic changes. However, in current IP networks, shutting down and/or turning on links would trigger link state routing protocols to reconverge to a new topology. Since the convergence time would take tens of seconds, routing table inconsistencies among routers would result in network disconnection and even worse, generating traffic loops during the convergence interval. Removing routing images inconsistent among routers to prevent loops is a critical issue in energy efficient network and this issue is still not considered in the green network design yet. The contribution of the paper is presented in two parts. First, we propose a comprehensive approach to determine a network topology and a link metric for each time period. Traffic engineering is considered in our design such that flows going on the energy-aware network are within a predetermined percentage of the link capacity such that no congestion occurs in a statistical manner. Second, to avoid transient loops during time period changes, we propose a Distributed Loop-free Routing Update (DLRU) scheme to determine the correct sequence for updating the routing table. A scrupulous proof was also presented to ensure the loop-free property of the DLRU. In this paper, we formulate an integer linear programming to determine this multi-topology and link weight assignment problem. Due to its NP-hard property, we propose an efficient algorithm, termed Lagrangian Relaxation and Harmonic Series (LR&HS) heuristic. Numerical results demonstrate that the proposed LRHS approach outperforms the other approaches on several benchmark networks and random networks by providing up to 35%-50% additional energy saving in our experimental cases.     

实现物探测线高效布设的一种方法

物探测线布设是一项重要的基础性工作,其施工效率直接影响物探勘查工作的开展。利用GPS相关软件完成测点数据的批量输入可以在很大程度上提高工作效率,但随着USB接口的支持及普及,其效果便不再那么明显和突出,相比之下兼容格式的研究与应用更能有效地提高测线布设的效率,也更为简便和有效。为了进一步提高工作效率,利用Visual C＋＋编程简化了测线布设中涉及的测线计算和数据输入等操作流程,避免了手工计算和数据格式转换的麻烦,达到了测线高效布设的目的。文中详细介绍了物探弯曲测线的计算方法和常用GPS兼容格式的转换方法与软件应用。实例表明该方法方便、有效,能节省大量的室内和野外工作量。     

石羊河流域井灌区管道灌溉系统优化模式研究

为了探求石羊河流域井灌区管道灌溉系统优化模式,对喷灌、滴灌、管灌等高效节水技术与变频调速技术进行配套,采用"恒压变量"研究方案对各灌溉技术间流量与压力协调进行了试验。结果表明:水泵的转速大于最低合理转速1 710 r/min时,在喷灌、滴灌、管灌3种工作条件下,水泵效率均较高,基本在高效区运行,同时也说明"恒压变量"一整套水泵调速工况点参数计算公式和计算方法正确可靠。     

一种快捷的LDPC码编码方法

LDPC码作为一种性能优异的纠错码，已经越来越引起通信领域的研究兴趣。而LDPC码性能的优劣，与其二分图中是否存在短长度的圈有关，也即与其奇偶校验矩阵的构造有关。本文在扩展比特填充算法的基础上，设计出一种能够直接编码的奇偶校验矩阵，并在不同码长的情况下进行了仿真，结果表明采用这种设计方法构造的LDPC码随机分布性好，不需要复杂的矩阵求逆，从而对LDPC码的实际应用具有重要参考价值。     

一种高效的数据插入方法——H221协议的组帧和解帧

根据H221协议的组帧、解帧特点,运用不同的算法进行数据插入,根据循环以及运算中的数据相关性对系统性能的影响,提出一种高效的数据插入算法并用于实际系统中,获得很好的效果.     

集值优化问题严有效意义下的鞍点与对偶

本文研究集值优化问题在严有效意义下的鞍点理论及对偶理论。首先,给出集值优化问题在严有效意义下鞍点的一个等价命题和鞍点定理。其次,在某种凸性假设下,研究严有效意义下鞍点最优性条件、弱对偶性、强对偶性、逆对偶性。