• 한국환경과학회지
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• 제27권3호
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• pp.167-177
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• 2018

The removal characteristics of As and Se ions from aqueous solution by hexadecyl trimethyl ammonium bromide (HTMAB) modified anthracite (HTMAB-AT) were investigated under various conditions of contact time, pH and temperature. When the pH is 6, the zeta potential value of anthracite (AT) is -24 mV and on the other hand, the zeta potential value of the HTMAB-AT is +44 mV. It can be seen that the overall increase of about 60 mV. Increasing the (+) potential value indicates that the surface of the adsorbent had a stronger positive charge, so adsorption for the anion metal was increased. The isotherm data was well described by Langmuir and Temkin isotherm model. The maximum adsorption capacity was found to be 7.81 and 6.89 mg/g for As and Se ions from the Langmuir isotherm model at 298 K, respectively. The kinetic data was tested using pseudo first and pseudo second order models. The results indicated that adsorption fitted well with the pseudo second order kinetic model. The mechanism of the adsorption process showed that adsorption was dependent on intra particle diffusion model according to two step diffusion. The thermodynamic parameters(${\Delta}G^{\circ}$, ${\Delta}H^{\circ}$, and ${\Delta}S^{\circ}$) were also determined using the equilibrium constant value obtained at different temperatures. The thermodynamic parameters indicated that the adsorption process was physisorption, and also an endothermic and spontaneous process.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.465-470
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• 2003

In this study, the state-space Newmark method based on average velocity is presented to analyse the transient dynamic response for general dynamic system. The conventional Newmark method based on average acceleration cannot he directly to the first-order state-space differential equations introducing the state-space vector. To overcome this problem, the time-step integration algorithm, based on average velocity concept, suitable for the first-order state-space differential equations is proposed In results, the proposed method has %he numerical stability and order of accuracy, which is proved analytically, equal to those of the conventional Newmark method based on average acceleration. Also, the formulation for numerical solution is very simple and the calculation time Is nearly equal to that of the conventional Newmark method based on average acceleration in spite of an increase of two times over matrix size. This method will be look forward to applying the general dynamic system to calculate the transient dynamic response.

• 공업화학
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• 제4권2호
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• pp.300-307
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• 1993

$Na_2S_2O_4$ 수용액과 $CCl_4$-toluene 용액의 2상에서 유기상에 용해하는 tricaprylmethylammonium chloride 상이동 촉매를 사용하여 methyl methacrylate의 라디칼 중합속도를 측정하여, 액-액 불균일계 접촉계면을 통한 라디칼 중합반응기구를 해석하였다. MMA의 중합속도는 수용액상에 존재하는 $Q^+$ 이온의 농도와 ${S_2O_4}^{-2}$ 이온의 농도의 제곱근에 정비례하고 $CCl_4$와 MMA의 농도에 각각 정비례하였다.

• 한국재료학회지
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• 제13권9호
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• pp.593-597
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• 2003

Anodic aluminum oxide (AAO) membrane was made of aluminum sheet (99.6%, 0.2 mm thickness). The regular array of hexagonal nano pores or channels were prepared by two step anodization process. A detail description of the AAO fabrication is presented. After the 1st anodization in oxalic acid (0.3 M) at 45 V, The formed AAO was removed by etching in a solution of 6 wt% $H_3$$PO_4$＋1.8 wt% $H_2$$CrO_4$. The regular arrangement of the pores was obtained by the 2nd anodization, which was carried out in the same condition as the 1st anodization. Subsequently, the alumina barrier layer at the bottom of the channel layer was removed in phosphoric acid (1M) after removing of aluminum. Pore diameter, density, and thickness could be controlled by the anodization process parameters such as applied voltage, anodizing time, pore widening time, etc. The pore diameter is proportional to the applied voltage and pore widening time. The pore density and thickness can be controlled by anodization temperature and voltage.

• 분석과학
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• 제8권4호
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• pp.427-434
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• 1995

Inductively coupled plasma mass spectrometry combined with the isotope dilution method is used for the determination of lithium. The isotope dilution method is based on the addition of a known amount of enriched isotope (spike) to a sample. The analyte concentration is obtained by measuring the altered isotope ratio. The spike solution is calibrated through so called reverse isotope dilution with a primary standard. The spike calibration is an important step to minimize error in the determined concentration. It has been found essential to add spike to a sample and the primary standard so that the two isotope ratios should be as dose as possible. Since lithium is neither corrosive nor toxic, lithium is used as a chemical tracer in the nuclear power plants to measure feedwater flow rate. 99.9% $^7Li$ was injected into a feedwater line of an experimental system and sample were taken downstream to be spiked with 95% $^6Li$ for the isotope dilution measurements. Effects of uncertainties in the spike enrichment and isotope ratio measurement error at various spike-to-sample ratios are presented together with the flow rate measurement results in comparison with a vortex flow meter.

• 센서학회지
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• 제16권6호
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• pp.395-400
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• 2007

Ambient drying sol-gel processing was used for monolithic silica ambigels in the temperature range of $130-250^{\circ}C$. A new method of mesopore ambigels, which mean the aerogels prepared by ambient pressure drying process synthesis, is suggested at first. This method includes two important approaches. The first point is that $SiO_{2}$ surface modification of wet gel was performed by trimethylchlorosilane in n-butanol solution. This procedure is provided the silica gel mesopore structure formation. The second point is a creation of the ternary azeotropic mixture water/n-butanol/octane as porous liquid, which is effectively provided removing of water such a low temperature by 2 step drying condition under ambient pressure. The silica aerogels, which were prepared by ambient pressure drying from azeotropic mixture of water/n-butanol/octane, are transparent, crack-free and mesoporous (pore size ${\sim}$ 5.6 nm) with surface area of ${\sim}$ $923{\;}m^2/g$, bulk density of $0.4{\;}g/cm^3$ and porosity of 85 %.

• Nuclear Engineering and Technology
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• 제45권1호
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• pp.115-124
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• 2013

Among the several options to solve PWR spent fuel accumulation problem in Korea, the dry storage method could be the most realistic and applicable solution in the near future. As the basic objectives of dry storage are to prevent a gross rupture of spent fuel during operation and to keep its retrievability until transportation, at the same time the importance of a spent fuel integrity evaluation that can estimate its condition at the final stage of dry storage is very high. According to the national need and technology progress, two representative nations of spent fuel dry storage, the USA and Japan, have established different system temperature criteria, which is the only controllable factor in a dry storage system. However, there are no technical criteria for this evaluation in Korea yet, it is necessary to review the previously well-organized methodologies of advanced countries and to set up our own domestic evaluation direction due to the nation's need for dry storage. To satisfy this necessity, building a domestic spent fuel test database should be the first step. Based on those data, it is highly recommended to compare domestic data range with foreign results, to build our own criteria, and to expand on evaluation work into recently issued integrity problems by using a comprehensive integrity evaluation code.

• Nuclear Engineering and Technology
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• 제43권3호
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• pp.243-256
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• 2011

This paper considers the concept of analog computing based on a cellular neural network (CNN) paradigm to simulate nuclear reactor dynamics using a time-dependent second order form of the neutron transport equation. Instead of solving nuclear reactor dynamic equations numerically, which is time-consuming and suffers from such weaknesses as vulnerability to transient phenomena, accumulation of round-off errors and floating-point overflows, use is made of a new method based on a cellular neural network. The state-of-the-art shows the CNN as being an alternative solution to the conventional numerical computation method. Indeed CNN is an analog computing paradigm that performs ultra-fast calculations and provides accurate results. In this study use is made of the CNN model to simulate the space-time response of scalar flux distribution in steady state and transient conditions. The CNN model also is used to simulate step perturbation in the core. The accuracy and capability of the CNN model are examined in 2D Cartesian geometry for two fixed source problems, a mini-BWR assembly, and a TWIGL Seed/Blanket problem. We also use the CNN model concurrently for a typical small PWR assembly to simulate the effect of temperature feedback, poisons, and control rods on the scalar flux distribution.

• Journal of Welding and Joining
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• 제20권5호
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• pp.93-98
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• 2002

The effect of bonding misfit on single crystallization of transient liquid phase (TLP) bonded joints of single crystal superalloy CMSX-2 was investigated using MBF-80 insert metal. The bonding misfit was defined by (100) twist angle (rotating angle) at bonded interface. TLP bonding of specimens was carried out at 1523K for 1.8ks in vacuum. The post-bond heat treatment consisted of the solution and sequential two step aging treatment was conducted in the Ar atmosphere. The crystallographic orientation analysis across the TLP bonded joints was conducted three dimensionally using the electron back scattering pattern (EBSP) method. EBSP analyses f3r the bonded and post bonded heat treated specimens were conducted. All bonded joints had misorientation centering around the bonded interface for as-bonded and post-bond heat treated specimens with rotating angle. The average misorientation angle between both solid phases in bonded interlayer was almost identical to the rotating angle at bonded interface. HRTEM observation revealed that the atom arrangement of both solid phases in bonded interlayer was quite different across the bonded interface. It followed that grain boundary was formed in bonded interface. It was confirmed that epitaxial growth of the solid phase occurred from the base metal substrates during TLP bonding and single crystallization could not be achieved in joints with rotating angle.

• 대한조선학회논문집
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• 제33권1호
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• pp.9-18
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• 1996

본 논문은 불균일한 선미 유동장에서 작동하는 프로펠러의 성능 해석을 위한 포텐셜을 기저로 한 판요소법을 기술하고 있다. 본 방법은 법선 다이폴과 쏘오스를 프로펠러의 날개, 허브, 그리고 후류면에 분포하였고, 비정상 유동의 해석 방법으로는 시간 전진법에 의한 방법을 취함으로써 다이폴의 세기를 미지수로 하는 적분방정식을 얻고, 이산화하여 수치적으로 계산하였다. 2차원 날개에 대한 수치해석을 수행하여 해석해와 비교함으로써 시간간격에 대한 수렴성을 확보하였다. 또한, DTRC 4118 프로펠러에 대하여 조화반류하에서 작동하는 프로펠러의 비정상 성능을 해석하여 실험치와 비교함으로써 시간영역에서 프로펠러의 비정상 성능해석이 가능함을 보였다.