Current Issue : April - June Volume : 2019 Issue Number : 2 Articles : 5 Articles
In this paper, we present a power adjustment scheme to dynamically enlarge\nand shrink power coverage to speed up tag identification in a RFID system.\nBy dividing a TDMA frame into time slots, the proposed power adjustment\nscheme can adaptively increase or decrease the transmission power of a reader.\nSpecifically, due to the contention for a TDMA slot from numerous tags,\nthree states of a slot could exist; they are respectively referred to as successful,\ncollided, and idle states. An adjustment factor based on the three states is designed\nto dynamically adjust the transmission power of a reader. The design\nof the adjustment factor considers two different aspects. When the number of\nidle state far exceeds the number of collided state, the first aspect will enlarge\nthe power such that more tags within the coverage can be concurrently identified.\nOn the other hand, when the number of idle state is much smaller than\nthe number of collided state, the second aspect will shrink the power such\nthat the number of tags within the coverage is significantly reduced. The\nproposed power adjustment scheme is simulated using NS-3. In the simulation,\nwe design three different topologies which place tags in three distributions,\nuniform, random, and hotspot. From the simulation results, we demonstrate\nthat the proposed power adjustment scheme can speed up the tag\nidentification and save energy consumption, particularly when a large number\nof tags are placed in hotspot distribution....
Coal-fired plants are under pressure to reduce their carbon-intensity. Available\noptions include co-firing CO2-neutral biomass, oxy-fuel-combustion as\npart of a carbon capture process or a combination of both to give a\nâ??CO2-negativeâ? power plant. BioCCS, the combination of CO2 Capture and\nStorage (CCS) with sustainable biomass conversion, is the only large-scale\ntechnology that can achieve net negative emissions. Combining, developing\nand demonstrating the oxy-combustion of high ratios of sustainable biomass\nwith coal in flexible circulating fluidized bed (CFB) boiler will bring significant\nadvances in the reduction of greenhouse gases (GHG) emissions. Areas\naddressed include possibilities for: biomass characterization; handling and\nfeeding; co-firing ratios definition; CFB oxy-co-combustion studies; combustion\nperformance; boiler flexibility in fuel and load; main emissions analysis;\nslaging, fouling and agglomeration; corrosion and erosion; and implications\non plant operation and associated costs. The article will detail a comprehensive\nunderstanding on sustainable biomass supply, co-firing ratios and\nhow direct biomass co-combustion under oxy-fuel conditions can be implemented.\nIt seeks to push biomass co-combustion in future large-scale oxy-fuel\nCFB power stations to high thermal shares while enhancing the power plantsâ??\noperational flexibility, economic competitiveness and give operational procedures.\nThere will be a need to consider the public acceptance of power\nproduction from coal and coal sustainability, by its combination with renewable\nsources of energy (biomass)....
Hydrogen production through dimethyl ether steam reforming is an attractive\noption for mobile applications of hydrogen fuel cells. Hydrogen is a major\ntrend in the future of energy development. It is not only pollution-free,\nbut also has a high energy density. Therefore, research on hydrogen fuel cells\nis particularly important. In this paper, a numerical research on dimethyl\nether steam reforming reaction in a reactor has been presented using a computational\nfluid dynamics. A three-dimensional reactor model developed by\nthe commercial software COMSOL (version 5.2a) was used to simulate the\nreaction characteristics by modifying reforming conditions. The simulation\nresults indicate the temperature distribution, mass distribution, and reveal\nthe dependency of dimethyl ether reforming reaction rate on temperature,\npressure, the length of the reactor. The yield of H2 and conversion of dimethyl\nether with different mass ratios and inlet temperature were examined. The governing equations in the model include conservations of mass, momentum, energy and chemical species....
Distributed generation is a good option for future energy systems with respect to\nsustainable development. In this context, the small-scale combined heat and power (CHP) plants\nare seen as an efficient way to reduce greenhouse gas emissions due to lower fuel consumption\ncompared to the separate generation of the heat and electricity. The objective of this paper is to\nestablish operating strategies of the small-scale CHP plants to reduce operational cost and increase\nrevenue in liberalized electricity markets. It analyzes a cogeneration plant with organic Rankine\ncycle and biomass fuel under the conditions of the Romanian electricity market and the green\ncertificates support scheme for electricity generated in high efficiency cogeneration and from\nrenewable sources. The main finding is that choosing an appropriate mode of operation and using\ncorrelated prices of heat and electricity can increase the trading profitability of a CHP plant in\nliberalized power markets. This can be done by an analysis of the particularities and the specific\noperating conditions of the CHP plant. The results show that the operating strategies of the CHP\nplant can yield substantial net revenues from electricity and heat sales. The CHP plant can be\neconomically operated to a useful heat load of more than 40% when operating strategies are applied....
Numan is an urban center in Adamawa State North-Eastern Nigeria. Its waste\ncharacteristics are similar to other places in sub-Saharan Africa. In this paper,\nthe physico-chemical characterization of municipal solid waste generated in\nNuman Town was carried out to estimate the electrical power to be generated\nfrom it. The solid waste types were observed to comprise of polythene (27%),\norganic waste (24.1%), plastic (10.2%), textile (13.2%), paper (9.8%), glass\n(9.3%) and metals (6.4%). The moisture content as discarded and daily average\nsolid waste generation rate are 16.49% and 0.583 kg/sec respectively. The chemical\nformula with and without water was determined as C923.28H1632.60O258.28N12.89S\nand C923.28H2099.70O494.16N12.89S respectively. The suitability of the municipal\nsolid waste as a possible source of electrical power was also considered. The\nenergy content of the solid waste on ash free dry-basis was determined as\n20861.48 kJ/kg. The estimated power generation per day using incinerating\nplant at an assumed efficiency of 25% was 3031.5 kW....
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