A Simulation study on Interference in CSMA/CA Ad-Hoc Networks using Point Process

Performance of wireless ad-hoc networks is essentially degraded by co-channel interference. Since the interference at a receiver crucially depends on the distribution of the interfering transmitters, mathematical technique is needed to specifically model the network geometry where a number of nodes are randomly spread. This is why stochastic geometry approach is required. In this thesis, we study about stochastic point processes such as Poisson Point Process, Matérn Point Process, and Simple Sequential Inhibition Point Process. The interference distributions resulting from the different point process are compared, and in CSMA/CA networks, point process's limitation issue such as the under-estimation of the node density is discussed. Moreover, we show that the estimated interference distribution obtained by Network Simulator 2, is different with respect to the different point process. Even if there is the existence of gap between the distributions from the point processes and the simulator due to active factors, they all offer similar shape which follows a peak and an asymmetry with a more or less heavy tail. This observation has promoted an interest in characterizing the distribution of the aggregated interference with the Log-normal, Alpha-stable, and Weibull distributions as a family of heavy tail distributions. Even though hypothesis tests have mostly led to the reject of the null assumption, that the interference distribution by the simulator, is a random sample from these heavy tailed distributions, except for the Alpha-stable distribution in high density. The hypothesis statistics systematically yield agreement on the choice of the better approximation. Moreover, the log probability process certainly makes it possible to reliably select the most similar heavy tailed distribution to the empirical data set on the variation of node density

Retraction: Cortical Margining Capabilities of Fins Associated with Ventral Cervical Spine Instrumentation

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An Essay on Sharing Express Box under Sharing Logistics

Sharing economy has emerged as a viable business model in various industries. Successful examples include Uber and Airbnb. In the logistics context, sharing trend has captivated attention from practitioners. Everything sharing is by no means a slogan, sharing the express box also successfully entered the consumer's life by the Double 11 trend (Double 11: Double Eleven Shopping Carnival refers to the online promotion day of November 11th every year, which is originated from the online promotion held by Taobao Mall). In fact, the sharing express box is not a simple derivative of the sharing economy, but a self-adjustment made by related industries under the protection of the environment. Undoubtedly, sharing express boxes provide a new idea for solving the problems of over-packaging and express garbage. It creates a new opportunity for green logistics which aims to protect environment. This paper examines the types of express package and the problems surrounding the business model of sharing express boxes. Design analysis was carried out for the emergence and the operation model of sharing express boxes. In addition, the case analysis of the rental mode of the sharing express box and the case analysis of the self-operating mode were introduced, and the comparison of the two modes and the enlightenment obtained were carried out. Finally, through the green sharing, the prospect of the sharing box is introduced

Analysis of Problems in Cut Slope Survey and Design Based on Case Studies

In construction of roads or large residential complexes, the formation of large scale cut slopes is inevitable due to the large proportion of mountains in Korea. The problems involving the slope stability has emerged as a major concern. Inaccurate subsurface exploration can result in slope failure during or after the construction, thereby increasing the construction cost and delaying the construction duration. This study reviews problems involving the cut slope survey methods, design criteria, and examining the collapse mechanisms through various case studies. This study suggests the optimum survey methods and design criteria based on the possible failure mechanisms