• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.614-621
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• 2004

At present, the electronic document is being processed in WYSWYG mode. For this, a document is structured by the logical structure and the physical structure, and is presented by the markup language. After XML is announced, an application scope of the electronic document is extended from interchanging to searching. However, in point of output quality, a XML document image on a browser has lower quality than a general document image on desktop publishing. The reason is which output function of a browser has not capability for high quality printing. The W3C developed XSL-FO(XSL-formatting Object) for style sheet formatting and PDL(Page Description Language) as like Postscript is already developed and used widely. In this paper, we designed the Postscript-Converter to get a high quality document image by converting XSL-FO into Postscript format.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.69-69
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• 2011

태양열 발전 플랜트에 사용되는 중고온 범위의 축열조에 고체-액체간 상변화를 수행하는 용융염을 축열물질로 사용하면 액체상 또는 고체상만으로 된 열저장 매체에 비해 축열조의 규모를 축소함과 동시에 축열온도의 균일성 향상에 기여할 수 있다. 중온인 $250{\sim}400^{\circ}C$ 범위에서 이용 가능한 용융염으로는 질산칼륨($KNO_3$), 질산리튬($LiNO_3$)등이 있다. 그러나 이러한 용융염의 가장 큰 단점은 열전도율이 매우 낮다는 것이며, 이로 인해 요구되는 열전달률을 성취하기 위해서는 많은 열접촉면적이 필요하다는 것이다. 이러한 단점을 극복하는 방법을 도입하지 않고서는 축열시스템의 소규화를 성취하는데 큰 효과를 가져올 수 없다. 한편 열수송 성능이 탁월한 히트파이프를 사용하면 열원 및 열침과 축열물질 사이의 열전달 효율을 증가시켜 시스템의 성능 향상과 동시에 소규모화에 기여할 수 있다. 중온 범위 히트파이프의 작동유체로서 다우섬-A(Dowtherm-A)는 $150^{\circ}C$이상 $400^{\circ}C$까지의 범위에서 소수에 불과한 선택적 대안 중 하나이다. 따라서 본 연구에서는 용융염을 사용하는 중온 태양열축열조에 적용 가능한 다우섬-A 히트파이프의 성능을 파악하여 기술적 자료를 제시하고자 하였다. 열원으로는 고온 고압의 과열증기, 그리고 열침으로는 중온의 포화증기를 고려하였다. 용융염 축열조를 수직으로 관통하는 히트파이프는 하단부에서 열원 증기와 열교환 가능하며, 중앙부에서 축열물질과 열교환하고, 상단부에서는 중온 증기와 접촉할 수 있도록 배치하였다. 축열모드에서는 히트파이프의 하단부가 증발부로 작동하고, 중앙부가 응축부로 작동하여 용융염으로 열을 방출하면 용융염의 온도가 상승하고 용융점에 도달하면 액상으로의 상변화가 진행되면서 축열이 활성화된다. 축열모드에서 히트파이프의 상단부는 단열부로 작동한다. 방열과정에서는 히트파이프의 하단부가 단열된 상태이고, 중앙부는 용융염으로부터 열을 받아 증발부로 작동하며, 상단부는 중온 증기로 열을 방출하므로 응축부로 작동한다. 즉, 축열시스템의 작동모드에 따라 하나의 히트파이프에서 증발부, 응축부, 단열부의 위치가 변하게 된다. 특히, 히트파이프의 중앙 부분이 응축부에서 증발부로 전환될 때에도 작동이 보장되려면 내부 작동유체의 연속적인 재순환이 가능해야 하므로, 일반 히트파이프에서와는 달리 초기 작동액체의 충전량을 증발부 전체의 체적보다 더 많이 과충전해야 한다. 이러한 히트파이프의 성능 파악을 위한 실험에서 고려한 변수들은 열부하, 작동액체의 충전률, 작동온도 등이며, 열수송 성능의 지표로서는 유효열전도율과 열저항을 이용하였다. 중온범위에서 적정한 작동온도를 성취하기 위해 실험에서는 전압 조절기로 열부하를 조절하는 동시에 항온조로 응축부의 냉각수 입구 온도를 제어하였다. 하나의 히트파이프에 대해서 최대 1 kW까지의 열부하에서 냉각수 입구 온도를 $40^{\circ}C$에서 $80^{\circ}C$ 범위로 변화시키면 히트파이프 작동온도를 약 $250^{\circ}C$ 내외로 조절 가능하였다. 히트파이프 작동액체 충전률은 윅구조물의 공극 체적을 기준으로 372%에서 420%까지 변화 시켰다. 실험 결과를 토대로 열저항과 유효 열전도율을 각각 입력 열유속, 작동온도, 작동액체 충전률 등의 함수로 제시했다. 동일한 냉각수 온도에서는 충전률이 높을수록 히트파이프의 작동온도가 감소하였다. 열저항 값의 범위는 최소 $0.12^{\circ}C/W$에서 최대 $0.15^{\circ}C/W$까지로 나타났으며 유효 열전도율의 값은 최소 $7,703W/m{\cdot}K$에서 최대 $8,890W/m{\cdot}K$까지 변화했다. 최소 열저항은 충전률 420%인 경우에 나타났는데 이때의 작동온도는 약 $262^{\circ}C$이었다. 히트파이프의 작동한계로서 드라이아웃(dry-out)은 충전률 372%의 경우에 열부하 950 W에서 발생하였으나, 그 이상의 충전률에서는 열부하 1060 W까지 작동한계 발생이 관찰되지 않았다. 실험 결과 본 연구에서의 히트파이프는 중온 태양열 축열조에 적용되어 개당 약 1 kW의 열부하를 이송하면서 축열물질 및 축방열 대상 유동매체와 열교환을 하는데 사용하는데 충분할 것이라 판단된다.

• Economic and Environmental Geology
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• v.34 no.3
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• pp.271-281
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• 2001

The characteristics of the heavy metal contamination in the soils affected by the tailings of the Palbong mine have been studied. The soils in the studied area consist mostly of loam by the particle size analysis, but a little of it, located near the stream, consist of loamy sand to sandy loam, finally to loam downward. The organic contents of soils are significantly low aoom 2 percent and the pH is in acidic ranging 6.0 $\pm$ 0.1. The samples of the parent rocks, the normal soils, the tailings and the channel deposits from the studied area were chemically analysed. From the result, the heavy metal concenlration of the soils is a little Jow compared with that of the parent rocks, shows the hydrologic process of the surface and the groundwater. The contamination of the tailings from the ore mining are high in lead, copper and arsenic. In the channel deposits the concenlrations of lead and copper are abnormally high but that of arsenic is uniquely low. And most of heavy metal contamination are decreased with the distance from the mine. It is caused by the properties of the surface and the ground water during the process of the heavy metal migration. The correlation-coefficient between sand and silt contents and the concentrations of Cd, Cu and Pb are significant but the amounts of As and Hg are increased with the clay contents. The dispersion of the heavy metals with the distance shows that the concentrations of them in the soils sampled at distance of 100 m to 200 m along the stream started near the Palbong mine are extremely high compared with those from other distances. These discrepancies are significant in Cd, Cu, Pb and Hg, but low in As. All the samples contain below detection limit of Cr+6 In the present stream water the concentrations of the heavy metals are not detected. So, it is interpreted that the concentrations in the soils are caused by the activities of the mining during the operation and have been continued by the dispersion from the tailings since after the closure of the mining, especially by the surface and ground water. The concentrations are diminished with the distance from the mining site, but in the interval of 800-2000 m increases abruptly. In the soil samples counted on the dispersion direction by wind, the lowering of the concentration is relatively uniform with the distance from the mining site. So, the rapid increase of the heavy metal concentrations is presumed to have been caused by the ground-water movement. In the migration of the heavy metals, the groundwater conditions, such as pH, Eh, the contents of colloidal particles, and Mn and Fe oxides are closely involveo. Integrating with these factors, it is interpreted that the groundwater conditions which have caused the heavy metal contamination of the studied area are those that the pH is about 3 in oxidized conditions, the contents of the colloidal particles are low, and Mn and Fe oxides are not involved in the migration of the heavy metals. Meanwhile, the vegetables growing on the soils in the studied area are not affected by the contamination of the heavy metals.

• Clean Technology
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• v.17 no.1
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• pp.69-77
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• 2011

The intrinsic $CO_2$ separation and hydrogen production system is a novel concept using oxidation and reduction reactions of oxygen carrier for both $CO_2$ capture and high purity hydrogen production. The process consists of a fuel reactor (FR), a steam reactor (SR) and an air reactor (AR). The natural gas ($CH_4$) is oxidized to $CO_2$ and steam by the oxygen carrier in FR, whereas the steam is reduced to hydrogen by oxidation of the reduced oxygen carrier in SR. The oxygen carrier is fully oxidized by air in AR. In the present study, the chemical looping moving bed reactor having 200 L/h hydrogen production capacity is designed and the hydrodynamic properties were determined. Compared with other reactors, two moving bed reactors (FR, SR) were used to obtain high conversion and selectivity of the oxygen carrier. The desirable solid circulation rates are calculated to be in the range of $20{\sim}100kg/m^2s$ from the conceptual design. The solid circulation rate can be controlled by aeration in a loop-seal. To maintain the gas velocity in the moving beds (FR, SR) at the minimum fluidization velocity is found to be suitable for the stable operation. The solid holdup in moving beds decrease with increasing gas velocity and solid circulation rate.

• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.783-791
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• 2015

A fluidized-bed reactor with an inside diameter of 0.1 m and a height of 1.2 m was used to study the effect of steam and catalyst additions to air-blown biomass gasification on the production of producer gas. The equipment consisted of a fluidized bed reactor, a fuel supply system, a cyclone, a condenser, two receivers, steam generator and gas analyzer. Silica sand with a mean particle diameter of $380{\mu}m$ was used as a bed material and calcined dolomite ($356{\mu}m$), which is effective in tar reduction and producer gas purification, was used as the catalyst. Both of Korea wood pellet (KWP) and a pellet form of EFB (empty fruit bunch) which is the byproduct of Southeast Asia palm oil extraction were examined as biomass feeds. In all the experiments, the feeding rates were 50 g/min for EFB and 38 g/min for KWP, respectively at the reaction temperature of $800^{\circ}C$ and an ER (equivalence ratio) of 0.25. The mixing ratio (0~100 wt%) of catalyst was applied to the bed material. Air or an air-steam mixture was used as the injection gas. The SBR (steam to biomass ratio) was 0.3. The composition, tar content, and lower heating value of the generated producer gas were measured. The addition of calcined dolomite decreased tar content in the producer gas with maximum reduction of 67.3 wt%. The addition of calcined dolomite in the air gasification reduced lower heating value of the producer gas. However The addition of calcined dolomite in the air-steam gasification slightly increased its lower heating value.

• Journal of Soil and Groundwater Environment
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• v.13 no.4
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• pp.8-21
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• 2008

A series of three-dimensional numerical simulations using a hydrodynamic dispersion numerical model is performed to analyze quantitatively impacts of layered heterogeneity of geologic media and groundwater pumping schemes on groundwater flow and salt transport in coastal aquifer systems. A two-layer heterogeneous coastal aquifer system composed of a lower sand layer (aquifer) and an upper clay layer (aquitard) and a corresponding single-layer homogeneous coastal aquifer system composed of an equivalent lumped material are simulated to evaluate impacts of layered heterogeneity on seawater intrusion. In addition, a continuous groundwater pumping scheme and two different periodical groundwater pumping schemes, which withdraw the same amount of groundwater during the total simulation time, are applied to the above two coastal aquifer systems to evaluate impacts of groundwater pumping schemes on seawater intrusion. The results of the numerical simulations show that the periodical groundwater pumping schemes have more significant adverse influences on groundwater flow and salt transport not only in the lower sand layer but also in the upper clay layer, and groundwater salinization becomes more intensified spatially and temporally as the pumping intensity is higher under the periodical groundwater pumping schemes. These imply that the continuous groundwater pumping scheme may be more suitable to minimize groundwater salinization due to seawater intrusion. The results of the numerical simulations also show that groundwater salinization in the upper clay layer occurs significantly different from that in the lower sand layer under the periodical groundwater pumping schemes. Such differences in groundwater salinization between the two adjacent layers may result from layered heterogeneity of the layered coastal aquifer system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1092-1099
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• 2022

Research on exhaust aftertreatment devices to reduce air pollutants and greenhouse gas emissions is being actively conducted. However, in the case of the particulate matters/nitrogen oxides (PM/NOx) simultaneous reduction device for ships, the problem of back pressure on the diesel engine and replacement of the filter carrier is occurring. In this study, for the optimal design of the integrated device that can simultaneously reduce PM/NOx, an appropriate standard was presented by studying the flow inside the device and change in back pressure through the inlet/outlet pressure. Ansys Fluent was used to apply porous media conditions to a diesel particulate filter (DPF) and selective catalytic reduction (SCR) by setting porosity to 30%, 40%, 50%, 60%, and 70%. In addition, the ef ect on back pressure was analyzed by applying the inlet velocity according to the engine load to 7.4 m/s, 10.3 m/s, 13.1 m/s, and 26.2 m/s as boundary conditions. As a result of a computational fluid dynamics analysis, the rate of change for back pressure by changing the inlet velocity was greater than when inlet temperature was changed, and the maximum rate of change was 27.4 mbar. This was evaluated as a suitable device for ships of 1800kW because the back pressure in all boundary conditions did not exceed the classification standard of 68mbar.

• Tunnel and Underground Space
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• v.18 no.1
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• pp.44-57
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• 2008

In this study, a 2D finite-element analysis, using the SEEP/W program, was carried out to estimate the amount of groundwater flawing into a tunnel, as well as the groundwater tables around wetland areas during and after a tunnel excavation through rock mass. Four sites along the Wonhyo-tunnel in Cheonseong Mountain (Gyeongnam, Korea) were analysed, where the model damain of the tunnel included both wetland and fault zone. The anisotropy of the hydraulic conductivities of the rock mass was calculated using the DFN model, and then used as an input parameter for the cantinuum model. Parametric study on the influencing factors was perofrmed to minimize uncertainties in the hydraulic properties. Moreover, the volumetric water content and hydraulic conductivity functions were applied ta the model to reflect the ability of a medium ta store and transport water under both saturated and unsaturated conditions. The conductivity of fault zone was assumed ta be $10^{-5}m/sec\;or\;10^{-6}m/sec$ and the conductivity of grouting zone was assumed as 1/10, 1/50 or 1/100 of the conductivity of rock mass. Totally $6{\sim}8$ cases of transient flow simulation were peformed at each site. The hydraulic conductivities of fault zone showed a significant influence on groundwater inflow when the fault zone crossed the tunnel. Also, groundwater table around wetland maintained in case that the hydraulic conductivity of grouting zone was reduced ta be less than 1/50 of the hydraulic conductivity of rock mass.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.3
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• pp.97-106
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• 1989

This paper is on the modeling of two-dimensional groundwater flow, which is the first step of the development of Dynamic System Model for groundwater flow and pollutant transport in subsurface porous media. The particular features of the model are its versatility and flexibility to deal with as many real-world problems as possible. Points as well as distributed sources/sinks are included to represent recharges/pumping and rainfall infiltrations. All sources/sinks can be transient or steady state. Prescribed hydraulic head on the Dirichlet boundaries and fluxes on Neumann or Cauchy boundaries can be time-dependent or constant. Sources/sinks strength over each element and node, hydraulic head at each Dirichlet boundary node and flux at each boundary segment can vary independently of each other. Either completely confined or completely unconfined aquifers, or partially confined and partially unconfined aquifers can be dealt with effectively. Discretization of a compound region with very irregular curved boundaries is made easy by including both quadrilateral and triangular elements in the formulation. Large-field problems can be solved efficiently by including a pointwise iterative solution strategy as an optional alternative to the direct elimination solution methed for the matrix equation approximating the partial differential equation of groundwater flow. The model also includes transient flow through confining leaky aquifers lying above and/or below the aquifer of interest. The model is verified against three simple cases to which analytical solutions are available. The groundwater flow model shall be combined with the model of pollutant transport in subsurface porous media. Then the combined model, with the applications of the Eigenvalue technique and the Dynamic system theory, shall be improved to the Dynamic System Model which can simulate the real groundwater flow and the pollutant transport accurately and effectively for the analyses and predictions.

• Journal of the Korean Electrochemical Society
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• v.12 no.2
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• pp.155-161
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• 2009

Lithium secondary batteries have been widely used in the portable electric devices as power source. Recently it is expected that the realm of its applications expands to the markets such as energy storage medium of hybrid electric vehicle(HEV), electric vehicle(EV). Cathode active material is crucial in terms of performance, durability, capacity of lithium secondary batteries. It is urgent to develope the technology for mass production of cathode material to cope with the markets' demands in the near future. In this study, a calcination furnace running in real production line is modelled in 3D, and the thermal flow and gas flow after chemical reaction in the furnace is analyzed through numerical computations. Based on the results, it is shown that large volume of $CO_2$ gas is generated from chemical reaction. High concentration of $CO_2$ gas and it's stagnation is clearly found from the reactant containers in which the reaction occur to the bottom area of the furnace. It is also studied that 15% or more $CO_2$ mol fraction could affect to proper formation of $LiCoO_2$ through TGA-DSC analysis. The solutions to evacuate carbon dioxide from the furnace are suggested through the change of furnace design and operating condition as well.