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Hung T.-C.,Military Academy | Yan W.-M.,National University of Tainan | Yan W.-M.,Research Center for Energy Technology and Strategy | Wang X.-D.,North China Electrical Power University | Huang Y.-X.,National Cheng Kung University
International Journal of Heat and Mass Transfer | Year: 2012

This work uses an optimization procedure consisting of a simplified conjugate-gradient method and a three-dimensional fluid flow and heat transfer model to investigate the optimal geometric parameters of a double-layered microchannel heat sink (DL-MCHS). The overall thermal resistance R T is the objective function to be minimized, and the number of channels N, channel width ratio β, lower channel aspect ratio α l, and upper channel aspect ratio α u are the search variables. For a given bottom area (10 × 10 mm) and heat flux (100 W/cm 2), the optimal (minimum) thermal resistance of the double-layered microchannel heat sink is about R T = 0.12°C/m 2W. The corresponding optimal geometric parameters are N = 73, β = 0.50, α l = 3.52, and, α u = 7.21 under a total pumping power of 0.1 W. These parameters reduce the overall thermal resistance by 52.8% compared to that yielded by an initial guess (N = 112, β = 0.37, α l = 10.32, and α u = 10.93). Furthermore, the optimal thermal resistance decreases rapidly with the pumping power and then tends to approach an constant value. As the pumping power increases, the optimal values of N, α l, and α u increase, whereas the optimal β value decreases. However, increasing the pumping power further is not always cost-effective for practical heat sink designs. © 2012 Elsevier Ltd. All rights reserved.

Radosavljevic V.,Military Academy | Belojevic G.,University of Belgrade
Public Health | Year: 2012

Objective: To develop a model for quick and accurate evaluation of unusual epidemic events (UEE), based on the original model of bioterrorism risk assessment. Methods: A new scoring system was developed for quick differentiation between a biological attack and other epidemics, using eight qualitative and six quantitative indicators. Results: A new scoring system was applied to three UEEs: (1) a spontaneous outbreak of a new or re-emerging disease ('swine flu'); (2) a spontaneous outbreak following accidental release of a pathogen (Sverdlovsk anthrax); and (3) a spontaneous natural outbreak of a known endemic disease that may mimic bioterrorism or biowarfare (Kosovo tularaemia). The disease agent was found to be the most important and the most informative UEE component of the scoring system. Conclusions: This new scoring system may be useful for public health institutions and federal civil and military officials responsible for bio-attack investigations. © 2011 The Royal Society for Public Health.

This study utilizes two factors, EEF (exergy efficiency factor) or exergetic COP (coefficient of performance) and MTEWI (modified total equivalent warming impact), which was proposed to evaluate exergetic and environmental performance of RAC (room air conditioners) sold in the Turkish market. In the study, vapour compression cooling cycle used whole RAC units is taken as model for the analyses. The results are shown that average EEF value of units using R-22 and R-410A gas are 74.53% and 74.64% respectively. Besides, R-410A gas, which is used in many split systems and marketed as an environmental friendly gas, has an effect that is approximately 23.18% higher than the R-22 gas which is no more in use. The study finally emphasizes the reasons why EEF and MTEWI factors should be given priority in terms of efficiency and environmental effects in the RAC units. © 2012 Elsevier Ltd.

Ziya Sogut M.,Military Academy | Ziya Sogut M.,Army Academy
Energy Conversion and Management | Year: 2012

In this study, exergetic efficiency of Turkish cement production and CO 2 emissions caused by the sector due to exergetic losses and environmental effects are examined, considering the clinker production between 1999 and 2007. As a first step, exergy analyses based on dead state temperature and production data of clinker are carried out according to the second law of thermodynamics. Consequently, CO 2 emissions of the clinker production according to exergy losses, improvement and anergy potentials are determined. Exergy efficiency of the kiln and exergetic improvement potential are found as 43.04% and 123.29 × 10 6 GJ/h respectively on average. In this system, CO 2 emissions caused by exergetic losses are calculated as 75.18 × 10 6 kg/h, 25.06 × 10 6 kg/h and 81.45 × 10 6 kg/h respectively on average for the coal mixture, natural gas and fuel-oil. At the end of the study, the present technique is suggested as a useful tool to improve energy policies and provide energy conservation measures, especially in this type of industrial processes. © 2011 Elsevier Ltd. All rights reserved.

Mitrovic S.T.,Military Academy | Durovic Z.M.,University of Belgrade
Advanced Robotics | Year: 2010

This paper presents a procedure for the design of a fuzzy logic controller for the garaging of a wheeled mobile robot, with non-holonomic constraints and discrete control signal levels. The design procedure is based on the virtual fuzzy magnet principle, which implies the definition of fictive points in the garage surroundings, and which, in an appropriate manner, by robot attraction, provides an efficient garaging process. The proposed fuzzy logic controller has four input variables: two represent the robot's distancing from fictitious fuzzy magnets and two are angles that define the orientation of the vehicle. The output variables are related to voltages sent to motors in charge of propelling the left and right wheel of the robot. The efficiency and shortfalls of the proposed algorithm are analyzed by means of both detailed simulations and multiple re-runs of a real experiment. Special attention is devoted to the analysis of different initial robot configurations and the effect of an error in the estimation of the current position of the robot on garaging efficiency. © 2010 Koninklijke Brill NV, Leiden and The Robotics Society of Japan.

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