• Journal of Korea Soil Environment Society
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• v.4 no.2
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• pp.137-147
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• 1999

Fluidized-bed thermal desorber coupled with a heat pipe was investigated for the remediation of soil contaminated with diesel oils. Thermal gravimetric analysis by Cahn-balance indicated that the desorption of diesel oils from the soil particles was mainly governed by the internal diffusion at low concentration of less than 0.5 wt. % of oils in the soil particles. In fluidized-bed experiments. increase of fluidizing gas velocity reduced the residual oils of the contaminated soils, the increase of soil feed rate decreased efficiency of fluidized-bed desorber. A mathematical model was developed by incorporating Fickian diffusion kinetics into the Kunii-Levenspiel model Simulation results showed reasonable agreement for the performance of fluidized-bed thermal desorber.

• Journal of Mechanical Science and Technology
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• v.18 no.8
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• pp.1435-1450
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• 2004

Experimental data are presented which describe the effects of a combustor-level high free-stream turbulence on the near-wall flow structure and heat/mass transfer on the endwall of a linear high-turning turbine rotor cascade. The end wall flow structure is visualized by employing the partial- and total-coverage oil-film technique, and heat/mass transfer rate is measured by the naphthalene sublimation method. A turbulence generator is designed to provide a highly-turbulent flow which has free-stream turbulence intensity and integral length scale of 14.7% and 80mm, respectively, at the cascade entrance. The surface flow visualizations show that the high free-stream turbulence has little effect on the attachment line, but alters the separation line noticeably. Under high free-stream turbulence, the incoming near-wall flow upstream of the adjacent separation lines collides more obliquely with the suction surface. A weaker lift-up force arising from this more oblique collision results in the narrower suction-side corner vortex area in the high turbulence case. The high free-stream turbulence enhances the heat/mass transfer in the central area of the turbine passage, but only a slight augmentation is found in the end wall regions adjacent to the leading and trailing edges. Therefore, the high free-stream turbulence makes the end wall heat load more uniform. It is also observed that the heat/mass transfers along the locus of the pressure-side leg of the leading-edge horseshoe vortex and along the suction-side corner are influenced most strongly by the high free-stream turbulence. In this study, the end wall surface is classified into seven different regions based on the local heat/mass transfer distribution, and the effects of the high free-stream turbulence on the local heat/mass transfer in each region are discussed in detail.

• Structural Engineering and Mechanics
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• v.49 no.4
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• pp.427-448
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• 2014

At present, the time of easy oil and gas is over. Now, the largest part of fossil fuels is concentrated in the deepest levels of tectonic structures and in the sea shelves. One of the most cumbersome operations of their extraction is the bore-hole drilling. In connection with austere tectonic and climate conditions, their drivage every so often is associated with great and diversified technological difficulties causing emergencies on frequent occasions. As a rule, they are linked with drill string accidents. A key role in prediction of these situations should play methods of theoretical modelling. For this reason, there is a growing need for development and implementation of new numerical methods for computer simulation of critical and post-critical behavior of drill strings (DSs). In this paper, the processes of non-linear deforming of a DS in cylindrical cavity of a deep bore-hole are considered. On the basis of the theory of curvilinear flexible rods, non-linear constitutive differential equations are deduced. The effects of the longitudinal non-uniform preloading, action of torque and interaction between the DS and the bore-hole surface are taken into account. Owing to the use of curvilinear coordinates in the constraining cylindrical surface and a specially chosen concomitant reference frame, it became possible to separate the desired variables and to reduce the total order of the equation system. To solve it, the method of continuation the solution by parameter and the transfer matrix technique are applied. As a result of the completed numerical analysis, the critical states of the DS loading in the cylindrical channels of inclined bore-holes are found. It is shown that the modes of the post-critical deforming of the DS are associated with its irregular spiral curving prevailing in the zone of bottom-hole-assembly. The possibility of invariant state generation during post-critical deforming is established, condition of its bifurcation is formulated. It is shown that infinite variety of loads can correspond to one geometrical configuration of the DS. They differ each from other by contact force functions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.4
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• pp.50-56
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• 2010

Supervisory Control and Data Acquisition Systems (SCADAs) is real-time monitor and control systems. SCADA systems are used to monitor or control chemical and transportation processes, in municipal water supply systems, electric power generation, transmission and distribution, gas and oil pipelines, and other distributed processes. SCADA refers to a large-scale distributed system. The supervisory control system is placed on top of a real time control system to control external processes. Emerging security technologies and security devices are decreasing the vulnerability of the power system against cyber threats. Dealing with these threats and analyzing vulnerabilities is an important task for equipment such as RTU, IED and FEP. To reduce such risks, we develop such a SCADA testbed. This paper presents the development of a testbed designed to assess the vulnerabilities SCADA networks(including serial communication).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.9
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• pp.832-838
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• 2011

The shock absorber with magnetic effect is suggested for a lunar lander. The shock absorber consists of a metal tube, a piston rod, and several permanent magnets moved by a piston rod in the tube, and the shock energy can be dispersed and dissipated by magnetic effects such as the magnetic force existed between a metal and magnets and the eddy current effect generated by a relative motion with a conductor and magnets. Besides, the shock-absorbing effect similar to that of a coil spring can be obtained by arranging the magnets in line, which are facing the same polar each other. The device has a very simple structure and is usable in space due to the unnecessariness of any oil or gas. The shock absorber was designed and manufactured for experiments and its spring and damping characteristics were studied by the theoretical, analytical and experimental methods.

• Korean Journal of Materials Research
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• v.24 no.8
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• pp.434-442
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• 2014

Serious environmental problems have been caused by the greenhouse effect due to carbon dioxide($CO_2$) or nitrogen oxides($NO_x$) generated by the use of fossil fuels, including oil and liquefied natural gas. Many countries, including our own, the United States, those of the European Union and other developed countries around the world; have shown growing interest in clean energy, and have been concentrating on the development of new energy-saving materials and devices. Typical non-fossil-fuel sources include solar cells, wind power, tidal power, nuclear power, and fuel cells. In particular, organic solar cells(OSCs) have relatively low power-conversion efficiency(PCE) in comparison with inorganic(silicon) based solar cells, compound semiconductor solar cells and the CIGS [$Cu(In_{1-x}Ga_x)Se_2$] thin film solar cells. Recently, organic cell efficiencies greater than 10 % have been obtained by means of the development of new organic semiconducting materials, which feature improvements in crystalline properties, as well as in the quantum-dot nano-structure of the active layers. In this paper, a brief overview of solar cells in general is presented. In particular, the current development status of the next-generation OSCs including their operation principle, device-manufacturing processes, and improvements in the PCE are described.

• Journal of the Speleological Society of Korea
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• no.95
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• pp.15-21
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• 2009

Global village warming and carbon dioxide CO2 gas, and the human efforts for their healing and necessary alternative technology would be much more difficult things than that of making necessary funds and efforts to lay to sleep angry nature on the earth. The limited natural resources of fossil fuel would be dried up in several decades, and the intensity of diplomatic negotiations for natural resource guarantee among countries may be showed looking alike an war. The drain of fossil fuel called a new word of alternative policy like an environment-friendly green-growth, and the solar-cell and lighting technology for the solar energy applications were developed still more repeatedly day by day from oil lantern to LED high-tech illumination in great economy. Therefore, it was studied that the low-carbon green-growth illumination technology in cave applications with SOLAR-LED system which was produced and unified in connection with solar-cell and LED from the semiconductor production technology, and it was also clarified in necessary with useful cave lighting in heatless and with no photosynthesis of plant production in underground space.

• Journal of the Korea Society of Computer and Information
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• v.15 no.8
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• pp.157-161
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• 2010

Most of air pollution in a metropolis is the result of exhaust gas emissions from automotive vehicles, and the world-wide regulation against environmental pollution is becoming more strict. Moreover the demand on development and supply of an environment-friendly automobile is increasing and the market share about that is expected to grow rapidly in this time of high oil price. The secondary batteries the most important component to store the electrical energy in hybrid electric vehicle. It needs to the higher power characteristics to emit the energy instantaneous. In this paper, we proposed the system to monitor reliably the charge and discharge states of the secondary batteries for hybrid electric vehicle. The material is about SW and HW module the software and hardware module mounted on the charge and discharge system and the monitoring system to control the charge and discharge performance effectively.

• Journal of the Korean Wood Science and Technology
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• v.35 no.1
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• pp.1-10
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• 2007

This study was reviewed on the bioethanol production from biomass resources and feedstock supply in America. U.S. Department of Energy (USDE) and the u.s. Department of Agriculture USDA) are both strongly committed to expand the role of biomass as an energy source. They support biomass fuels and products as a way to reduce the need for oil and gas imports, to strengthen the nation's energy security and environmental quality. And it was envisioned a 20 percent replacement of the current U.S.transportation fuel consumption in 2030. Also it was reviewed policies to encourage the expanding of Bio-based fuel use to replace gasoline, such as Clean Air Act, Federal Clean Fuel Program and American Jobs Creation Act. In feedstock supply it was assumed forest biomass will be supplied in 368 million dry tons yearly and the agriculture derived biomass adopted by new technologies and land use change will be supplied in 998 million dry tons, including highly 818 million dry tons of lignocellulosic biomass such as perenial crops (hybrid trees, grasses) corn stover, other crop residues. This amount is 5 times to the amount from based current agricultural technology and crop land.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_2
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• pp.617-626
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• 2020

The drilling mud is essentially used in oil and gas development. There are several roles of using the drilling mud, such as cleaning the bottomhole, cooling and lubricating the drill bit and string, transporting the cuttings to the surface, keeping and adjusting the wellbore pressure, and preventing the collapse of the wellbore. The fragments from rocks and micro-sized bubbles generated by the high pressure are mixed in the drilling mud. The systems to separate those mixtures and to keep the uniformly maintained quality of drilling mud are required. In this study, the simulation is conducted to verify the performance of the mud tank's agitation capacity. The primary role of the mud tank is the mixing of mud at the surface with controlling the mud condition. The container type is chosen as a mud tank pursuing efficient transport and better management of equipment. The single- and two-phase simulations about the agitation in the mud tank are performed to analyze and identify the inner flow behavior. The convergence of results is obtained for the vertical- and axis-direction velocity vector fields based on the grid-dependency tests. The mixing time analysis depending on the multiphase flow conditions indicates that the utilization of a two-stepped impeller with a smaller size provides less time for mixing. This study's results are expected to be utilized as the preliminary data to develop the mixing and integrating equipment of the onshore drilling mud system.