How do Wireless Chains Behave? The Impact of MAC Interactions

In a Multi-hop Wireless Networks (MHWN), packets are routed between source and destination using a chain of intermediate nodes; chains are a fundamental communication structure in MHWNs whose behavior must be understood to enable building effective protocols. The behavior of chains is determined by a number of complex and interdependent processes that arise as the sources of different chain hops compete to transmit their packets on the shared medium. In this paper, we show that MAC level interactions play the primary role in determining the behavior of chains. We evaluate the types of chains that occur based on the MAC interactions between different links using realistic propagation and packet forwarding models. We discover that the presence of destructive interactions, due to different forms of hidden terminals, does not impact the throughput of an isolated chain significantly. However, due to the increased number of retransmissions required, the amount of bandwidth consumed is significantly higher in chains exhibiting destructive interactions, substantially influencing the overall network performance. These results are validated by testbed experiments. We finally study how different types of chains interfere with each other and discover that well behaved chains in terms of self-interference are more resilient to interference from other chains

Reactive power minimization of dual active bridge DC/DC converter with triple phase shift control using neural network

Reactive power flow increases dual active bridge (DAB) converter RMS current leading to an increase in conduction losses especially in high power applications. This paper proposes a new optimized triple phase shift (TPS) switching algorithm that minimizes the total reactive power of the converter. The algorithm iteratively searches for TPS control variables that satisfy the desired active power flow while selecting the operating mode with minimum reactive power consumption. This is valid for the whole range of converter operation. The iterative algorithm is run offline for the entire active power range (-1pu to 1pu) and the resulting data is used to train an open loop artificial neural network controller to reduce computational time and memory allocation necessary to store the data generated. To validate the accuracy of the proposed controller, a 500-MW 300kV/100kV DAB model is simulated in Matlab/Simulink, as a potential application for DAB in DC grids

Mixed Marginal Copula Modeling

This article extends the literature on copulas with discrete or continuous marginals to the case where some of the marginals are a mixture of discrete and continuous components. We do so by carefully defining the likelihood as the density of the observations with respect to a mixed measure. The treatment is quite general, although we focus focus on mixtures of Gaussian and Archimedean copulas. The inference is Bayesian with the estimation carried out by Markov chain Monte Carlo. We illustrate the methodology and algorithms by applying them to estimate a multivariate income dynamics model.Comment: 46 pages, 8 tables and 4 figure

Feasibility of Starting a Waterjet Fabrication Plant in Amman, Jordan

This project is an attempt to investigate the feasibility of starting a waterjet fabrication plant in Amman, Jordan to precisely cut marble, granite, and ceramics. The frame work of the feasibility study included analyzing the proposed product/service, market size, price and profitability, government regulations, culture and religion, and business infrastructure in Jordan. Based on the findings detailed in this field project, it is feasible to start a waterjet plant operating at full capacity of the waterjet machine to produce and sell tiles that compete in quality and price with the local products. The table below shows the three-year operating statement for this new venture. (OMITTED HERE) Expense growth is based on the 2009 inflation rate (1.7%) for Jordan which is reported by the World Fact Book - managed by the United States Central Intelligence Agency. In addition, business growth rate is based on the 2009 GDP growth rate of 3.1% which is reported by the same agency. Rent and operating expenses are based on responses obtained from questionnaires and interviews with local tile experts with a minimum of 25 years of experience and exposure to the customer demands for marble, granite, and ceramics. Sales estimate are done based on the machine capacity of operating at 22 hours a day with two hours used for maintenance. It was not feasible to conduct a sales forecast using standard methods due to lack of historical data. However, during the business planning, a professional sales forecast should be conducted at full range. The size of the market in Jordan and the Middle East at large can support this new venture. According to Jordan Investment Board, there are new projects in the construction field planned for the next five years totaling $1.3 trillion dollars. In addition, Jordan has introduced many laws that protect foreign investments and investors. As a result, many construction projects such as the$6 billion dollar renovation project in Abdali are taking off thereby boosting demands for marble, granite, and ceramics. Moreover, Jordan has signed free trade agreements with the Arab states, the European Union, and the United States of America thereby opening exports to these countries. Local and imported marble, granite, and ceramics tiles are commonly used in the constructions and decorations of buildings in Jordan. Waterjet cutting technology can be used to capitalize on cutting irregular shapes from locally produced marble and granite slabs as well as imported ones. The technology is very precise that it could compete with Spanish and Italian imported tiles especially that the labor rates in Jordan are five to six times less than those in Spain and Italy

Development of an Efficient Ti:Sapphire Laser Transmitter for Atmospheric Ozone Lidar Measurements

The impetus of this work was to develop an all solid-state Ti:sapphire laser transmitter to replace the current dye lasers that could provide a potentially compact, robust, and highly reliable laser transmitter for differential absorption lidar measurements of atmospheric ozone. Two compact, high-energy pulsed, and injection-seeded Ti:sapphire lasers operating at a pulse repetition frequency of 30 Hz and wavelengths of 867 nm and 900 nm, with M2 of 1.3, have been experimentally demonstrated and compared to model results. The Ti:sapphire lasers have shown the required output beam quality at maximum output pulse energy, 115 mJ at 867 nm and 105 mJ at 900 nm, with a slope efficiency of 40% and 32%, respectively, to achieve 30 mJ of ultraviolet laser output at 289 run and 300 nm with two LBO nonlinear crystals