• Microbiology and Biotechnology Letters
• /
• v.40 no.4
• /
• pp.424-429
• /
• 2012

The intention of this research was to investigate the solubilization of primary sewage sludge using lactic acid bacteria cultured in a glucose and yeast extract medium. Glucose as the carbon source and yeast extract as the source of nitrogen were chosen as an economic medium with the potential for the mass production of lactic acid bacteria. The optimal concentrations of the medium were 3% (w/v) glucose and 2% (w/v) yeast extract. In this study, in order to improve field applications for the solubilization of sludge at sewage treatment plants, a powdered form of lactic acid bacteria was produced. The optimal inoculum of the powder for the maximum efficiency of solubilization was 1% (w/v). In that condition, the SCOD value increased from 8600 (mg/L) at the beginning of experiment to 10290 (mg/L) at 96 h, with the highest solubilization rate (20.6% DDCOD) and 11.2% (SCOD). Also, the TVFAs of the lactic acid bacteria inoculation group were produced more than that of the control group. In particular, acetic acid was produced 5 times more in the experimental group than in the control group. In this research, the potential of lactic acid bacteria in the pretreatment of primary sewage sludge as a solubilizer, and as an energy source producer for microbial fuel cells was revealed.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.7
• /
• pp.71-81
• /
• 2014

In this paper, the performance variations of tri-gate FinFET are analyzed for different fin shapes and source/drain epitaxy types using a 3D device simulator(Sentaurus). If the fin shape changes from a rectangular shape to a triangular shape, the threshold voltage increases due to a non-uniform potential distribution, the off-current decreases by 72.23%, and the gate capacitance decreases by 16.01%. In order to analyze the device performance change from the structural change of the source/drain epitaxy, we compared the grown on the fin (grown-on-fin) structure and grown after the fin etch (etched-fin) structure. 3-stage ring oscillator was simulated using Sentaurus mixed-mode, and the energy-delay products are derived for the different fin and source/drain shapes. The FinFET device with triangular-shaped fin with etched-fin source/drain type shows the minimum the ring oscillator delay and energy-delay product.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.25 no.6
• /
• pp.433-438
• /
• 2013

With the prospect of an increasing shortage of energy resources, there has been a growing interest in renewable alternative sources of energy. An increasing effort is being directed towards resolving the problems of extracting energy from the world's oceans, as they represent a vast potential source of renewable energy. This paper summarizes the extraction and conversion techniques of the ocean's energy resources, namely, energy derived from the ocean waves, tides, thermal gradients, and currents. For each energy extraction and conversion technique, case studies are discussed.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.11a
• /
• pp.515-518
• /
• 2007

Because of their low operating and maintaining costs, ground-source heat pump(GSHP) systems are an increasingly popular choice for providing heating, cooling and water heating to public and commercial buildings. Despite these ad- vantages and the growing awareness, GSHP systems to residential sectors have not been adopted in Korea until recently. A feasibility study of a residential GSHP system was therefore conducted using the traditional life cycle cost(LCC) analysis within the current electricity price framework and potential scenarios of that framework. As a result, when the current residential electricity costs for running the GSHP system are applied, the GSHP system has weak competitiveness to conven- tional HVAC systems considered. However, when the operating costs are calculated in the modified price frameworks of electricity, the residential GSHP system has the lower LCC than the existing cooling and heating equipments. The calculation results also show that the residential GSHP system has lower annual prime energy consumption and total pollutant emissions than the alternative HVAC systems considered in this work.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.8
• /
• pp.668-674
• /
• 2004

The possibility of global noise reduction by the sound power control through selection of distribution and impedance of absorptive materials is discussed. It is necessary to investigate the relation between the global sound energy in the field and the total sound power radiated by sources. In the previous work,$^{(1.2)}$ the authors presented a useful design method to change boundary condition that can be useful to reduce noise in acoustically small enclosures. Changing boundary condition Is related to not only enclosure’s geometrical shape but also acoustical treatment on walls for example, attaching of impedance patches (ex: absorptive material). In many practical situations, we often meet situation to change acoustical treatment on walls. The possibility of total acoustic potential energy(globa1 noise) reduction by acoustic source power control is examined in an acoustically small cavity Using acoustic energy balance equation, the relation between global noise control performance and absorptive material’s arrangement/impedance is deduced. Numerical simulation is performed to interpret its physical meaning in terms of absorbent’s distribution and impedance.

• Proceedings of the KIPE Conference
• /
• 2015.07a
• /
• pp.103-104
• /
• 2015

Solar energy has proven to be a potential clean energy source to help offset the large consumption of fossil. Nowadays, many research projects aim to enhance photovoltaic (PV) system performance and functionality. This research focuses on integrating self-monitor capability into dc-dc converters that control PV panels to detect a fault in series-connected PV cells, called hot spotting. A detection method using ac parameter characterization is proposed and its operation is examined through simulation.

• Journal of Power Electronics
• /
• v.18 no.1
• /
• pp.70-80
• /
• 2018

A novel strategy based on a zero common mode voltage pulse-width modulation (ZCMV-PWM) technique and zero-sequence circulating current (ZSCC) feedback control is proposed in this study to eliminate ZSCCs between three-level neutral point clamped (NPC) voltage source inverters, with common AC and DC buses, that are operating in parallel. First, an equivalent model of ZSCC in a three-phase three-level NPC inverter paralleled system is developed. Second, on the basis of the analysis of the excitation source of ZSCCs, i.e., the difference in common mode voltages (CMVs) between paralleled inverters, the ZCMV-PWM method is presented to reduce CMVs, and a simple electric circuit is adopted to control ZSCCs and neutral point potential. Finally, simulation and experiment are conducted to illustrate effectiveness of the proposed strategy. Results show that ZSCCs between paralleled inverters can be eliminated effectively under steady and dynamic states. Moreover, the proposed strategy exhibits the advantage of not requiring carrier synchronization. It can be utilized in inverters with different types of filter.

• Journal of Soil and Groundwater Environment
• /
• v.23 no.4
• /
• pp.16-25
• /
• 2018

The Quaternary volcanic rocks, clastic sedimentary rocks of Kyongsang System, and carbonate rocks of Joseon and Pyongan System are known as good productive and potential aquifer systems in South Korea. National Groundwater Informaton Mangement and Service System (GIMS) indicates that the exploitable, sustainable, and current use of groundwater are about 18.8, 12.9, and $3.73billion\;m^3/a$, respectively. The rest amount ($9.1billion\;m^3/a$) can still be used for an additional water supply source. Therefore. comprehensive groundwater survey work comprising hydrogeological mapping, subsurface investigation and quantitative aquifer test etc. are highly required to establish rational groundwater management strategy.

• Journal of Institute of Convergence Technology
• /
• v.1 no.2
• /
• pp.37-42
• /
• 2011

The purpose of this research is to improve nitrogen removal efficiency in winter season through rise of water temperature of extraneous water by using solar energy which is estimated to have great potential among new regeneration energy and while operating Plug-Flow Reactor to improve nitrogen removal efficiency by selecting A/O process among sewage waste water treatment processes as the necessity of solving the problem of nitrogen removal efficiency according to reduced water temperature in winter season and strengthening of water quality criteria regarding discharged sewage waste water suggested in the research background. Summarizing the research result, supply of solar energy source improves the function outstandingly when removing nitrogen, (nitrogen removal rate before operating solar energy 55.4% ${\rightarrow}$ nitrogen removal rate after operating solar energy 84.1%).

• Proceedings of the SAREK Conference
• /
• 2008.06a
• /
• pp.30-35
• /
• 2008

This paper describes a fault detection and diagnosis (FDD) system developed for the heat source apparatus in building air-conditioning system. As HVAC&R systems in building become complex and instrumented with highly automated controllers, the processes and systems get more difficult for the operator to understand and detect the mal-functions. Poorly maintained, degraded, and improperly controlled equipment wastes an estimated 15% to 30% of energy used in commercial building. When operating a complex facility, FDD system is beneficial in equipment management to provide the operator with tools which can help in decision making for recovery from a failure of the system. Automated FDD for HVAC&R system has the potential to reduce energy and maintenance costs and improves comfort and reliability. Over the last decade there has been considerable research for developing FDD system for HVAC&R equipment. However, they are being made too much of a theoretical study, so only a small of FDD methods are deployed in the field. This study deduced an actual defect source for the heat source apparatus and suggested a low price FDD method which is ready to be deployed in the field.