Range-Based Sleep Scheduling (RBSS) for Wireless Sensor Networks

Sleep scheduling in a wireless sensor network is the process of deciding which nodes are eligible to sleep (enter power-saving mode) after random deployment to conserve energy while retaining network coverage. Most existing approaches toward this problem require sensor’s location information, which may be impractical considering costly locating overheads. This paper proposes range-based sleep scheduling (RBSS) protocol which needs sensor-to-sensor distance but no location information. RBSS attempts to approach an optimal sensor selection pattern that demands the fewest working (awake) sensors. Simulation results indicate that RBSS is comparable to its location-based counterpart in terms of coverage quality and the reduction of working sensors.

Clustering coefficient of wireless ad hoc networks and the quantity of hidden terminals

The clustering coefficient has been proposed to characterize complex networks. Hidden terminals may degrade the performance of the CSMA (carrier sense multiple access) protocol. This letter computes analytically the clustering coefficient and the quantity of hidden terminals for ad hoc networks. The former turns out to be a constant and the latter is proportional to n/sup 3/ p/sup 2/, where n is the number of nodes and p is the link probability. The connection between them has been established, and simulation results confirm our analytical work.     

金华火腿传统工艺过程挥发性风味物质的分析研究

通过对金华火腿传统工艺过程晒后、中温发酵、高温成熟、成熟下架样品中挥发性风味物质的分析测定,研究传统工艺过程中挥发性风味物质的发展规律,结果表明:共有78种挥发性风味物质检出,醛、羧酸、醇、酯、酮、脂肪族和芳香族碳氢化合物、含硫化合物、吡嗪是主要成分;工艺工程中醛和酮的相对含量随温度的升高而逐渐降低,羧酸、酯、吡嗪和含硫化合物的相对含量逐渐增加。金华火腿的高温成熟工艺使来自于美拉德反应的羧酸有显著增加,这是金华火腿与地中海地区干腌火腿最显著的区别,也是金华火腿具有其独特风味的主要原因。     

Expected k-coverage in wireless sensor networks

We are concerned with wireless sensor networks where n sensors are independently and uniformly distributed at random in a finite plane. Events that are within a fixed distance from some sensor are assumed to be detectable and the sensor is said to cover that point. In this paper, we have formulated an exact mathematical expression for the expected area that can be covered by at least k out of n sensors. Our results are important in predicting the degree of coverage a sensor network may provide and in determining related parameters (sensory range, number of sensors, etc.) for a desired level of coverage. We demonstrate the utility of our results by presenting a node scheduling scheme that conserves energy while retaining network coverage. Additional simulation results have confirmed the accuracy of our analysis.     

Multi-objective Dimensional Optimization of a 3-DOF Translational PKM Considering Transmission Properties

Machine Intelligence Research - Multi-objective dimensional optimization of parallel kinematic manipulators (PKMs) remains a challenging and worthwhile research endeavor. This paper presents a...     

Bounding cache-related preemption delay for real-time systems

Cache memory is used in almost all computer systems today to bridge the ever increasing speed gap between the processor and main memory. However, its use in multitasking computer systems introduces additional preemption delay due to the reloading of memory blocks that are replaced during preemption. This cache-related preemption delay poses a serious problem in realtime computing systems where predictability is of utmost importance. We propose an enhanced technique for analyzing and thus bounding the cache-related preemption delay in fixed-priority preemptive scheduling focusing on instruction caching. The proposed technique improves upon previous techniques in two important ways. First, the technique takes into account the relationship between a preempted task and the set of tasks that execute during the preemption when calculating the cache-related preemption delay. Second, the technique considers the phasing of tasks to eliminate many infeasible task interactions. These two features are expressed as constraints of a linear programming problem whose solution gives a guaranteed upper bound on the cache-related preemption delay. This paper also compares the proposed technique with previous techniques using randomly generated task sets. The results show that the improvement on the worst-case response time prediction by the proposed technique over previous techniques ranges between 5 percent and 18 percent depending on the cache refill time when the task set utilization is 0.6. The results also show that as the cache refill time increases, the improvement increases, which indicates that accurate prediction of cache-related preemption delay by the proposed technique becomes increasingly important if the current trend of widening speed gap between the processor and main memory continues     

磁选尾矿回收钼流程考查结果分析

对选厂选钼生产工艺进行全流程考查,收集、整理和分析了考查数据,表明该生产工艺粗选矿浆浓度过低,粗精矿再磨分级效率低,造成过磨等问题,并对改进后的工艺流程提出了建议。