• 한국진공학회지
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• 제4권S1호
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• pp.190-195
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• 1995

The feature scale model for selective chemical vapor deopsition process was proposed and the simulation was performed to study the selectivity and uniformity of deposited thin film using Monte Carlo method and string algorithm. The effect of model parameters such as sticking coefficient, aspect ratio, and surface diffusion coefficient on the deposited thin film pattern was improved for lower sticking coefficient and higher aspect ratio. It was revealed that the selectivity loss ascrives to the surface diffusion. Different values of sticking coefficients on Si and on SiO2 surface greatly influenced the deopsited thin film profile. In addition, as the lateral wall angle decreased, the selectively deposited film had improved uniformity except the vicinity of trench wall. The optimum eondition for the most flat selective film deposition pattern is the case with low sticking coefficient and slightly increased surface diffusion coefficient.

• 공업화학
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• 제10권2호
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• pp.206-211
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• 1999

본 연구에서는 NaCl수용액의 초저이온 농도범위 ($1.0{\times}10^{-4}M$ 이하)에서 양이온 교환수지 대 음이온 교환수지의 비, 수지량, 계의 온도를 함수로 한 혼합층 이온교환의 거동을 실험적으로 연구하였다. 실험실 크기의 연속흐름 칼럼을 통하여 양이온 교환수지와 음이온 교환수지의 교환능이 소모될 때까지의 유출농도를 처리된 유량의 함수로 측정하여 파과곡선을 구하였다. 초기누출은 수지량이 적은 경우 양이온과 음이온의 파과곡선에 나타났으나, 선택도계수가 낮은 양이온의 파과곡선에 현격하게 크게 나타났다. 선택도계수는 파과곡선의 기울기에 영향을 미쳤으며, 계수값이 큰 음이온의 파과곡선의 기울기가 급격하였다. 온도변화는 파과곡선의 기울기에 영향을 미쳤으며, 온도가 증가할수록 이온교환속도가 증가하였다. 이 온도효과는 수지비에 관계없이 수지총량이 증가할수록 또는 이온교환수지의 교환능이 감소하여 파과곡선이 평형에 가까워질수록 감소하였다.

• Fisheries and Aquatic Sciences
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• 제11권1호
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• pp.61-69
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• 2008

Using empirical data of fish performance and physiological limits as well as physical stimuli and environmental data, a cod-end selectivity model based on a chaotic behavior model using the psycho-hydraulic wheel and neural-network approach was established to predict fish escape or herding responses in trawl and cod-end designs. Fish responses in the cod-end were categorized as escape or herding reactions based on their relative positions and reactions to the net wall. Fish movements were regulated by three factors: escape time, a visual looming effect, and an index of body girth-mesh size. The model was applied to haddock in a North Sea bottom trawl including frequencies of movement components, swimming speed, angular velocity, distance to net wall, and the caught-fish ratio; simulation results were similar to field observations. The ratio of retained fish in the cod-end was limited to 37-95% by optomotor coefficient values of 0.3-1.0 and to 13-67% by looming coefficient values of 0.1-1.0. The selectivity curves generated by this model were sensitive to changes in mesh size, towing speed, mesh type, and mesh shape.

• Bulletin of the Korean Chemical Society
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• 제12권6호
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• pp.625-628
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• 1991

Using uniform flat plate-like samples of ZSM-5 zeolites, diffusion coefficients were measured volumetrically for the diffusion of xylene, ethyltoluene and diethylbenzene by direct measurement of sorption rate. Toluene disproportionation over H(100)-, K(72)-and Cs(82)-ZSM-5 at 773 K and toluene methylation, toluene ethylation and ethylbenzene ethylation over Cs(75)-ZSM-5 at 623 K were carried out. The selective formation of para xylene during the toluene disproportionation, presumably due to the increased tortuosity over Cs-ZSM-5, could be explained by smaller diffusion coefficient in Cs-ZSM-5 than in K-and H-ZSM-5. The para selectivity increased in the order; toluene methylation < toluene ethylation < ethylbenzene ethylation. As the chain length of the alkyl substituent in dialkylbenzenes is increased, the para selectivity of the products was improved. It may be attributed to the differences in the ratios of diffusion coefficient of para products to that of ortho ones. Diffusion coefficient of m-xylene was about 1 order of magnitude smaller than that of o-xylene.

• 한국환경과학회지
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• 제16권8호
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• pp.907-912
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• 2007

Ion exchange resin was used to remove silica ion at ultralow concentration. The effects of temperature, type of ion exchange resin and single/mixed-resin systems on removal efficiency were estimated. As temperature increased, the slope of concentration profile became stiff, and the equilibrium concentration was higher. In the single resin system, the removal of silica was continued up to 400 min, but the silica concentration was recovered to initial concentration after 400 min due to the effect of dissolved $CO_2$. In the mixed-resin system it took about 600 min to reach equilibrium. Because of faster cation exchange reaction than anion exchange reaction, the effect of $CO_2$ could be removed. Based on the experimental results carried out in the mixed-resin system, the selectivity coefficients of silica ion for each ion exchange resin were calculated at some specific temperatures. The temperature dependency of the selectivity coefficient was expressed by the equation of Kraus-Raridon type.

• Bulletin of the Korean Chemical Society
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• 제27권12호
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• pp.1985-1988
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• 2006

The polymeric membrane electrodes based on urea derivative as an ionophore were prepared and studied for the iodide-ion selective electrode. This membrane exhibits a linear stable response over a wide concentration range ($1.0\;{\times}\;10^{-5}\sim1.0\;{\times}\;10^{-2}$) with a slope of -57.7 mV/decade, a detection limit of log[$I^-$] = -5.63, and a selectivity coefficient for iodide against perchlorate anion (log$K^{pot}_{I^-,j}$ = -1.42). The selectivity series of the membrane gives the follow as $I^-$ > $SCN^-$, $Sal^-$ > $ClO_4^-$ > $NO_3^-$ > $Br^-$ > $NO_2^-$ > $Cl^-$ > $F^-$. The proposed electrode showed good selectivity and response for iodide anion over a wide variety of other anions in pH 5.0 buffer solutions.

• 공업화학
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• 제25권2호
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• pp.142-146
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• 2014

9성분계 모델 콜타르 유분 중에 함유된 질소고리화합물(NHC)의 분리를 분배평형에 의해 검토했다. 원료로서는 NHC group (NHCs; quinoline (Q), iso-quinoline (iQ), indole (In), quinaldine(Qu)), 2환 방향족 화합물 group (BACs; 1-methylnaphthalene (1MN), 2-methylnaphthalene (2MN), dimethylnaphthalene (DMN)), biphenyl (Bp)과 phenyl ether (Pe)로 제조한 모델 콜타르 유분을, 용매로서는 메탄올 수용액을 각각 사용했다. 액-액 접촉 장치로서는 회분 교반기를 각각 사용했다. 평형조작 온도가 상승함에 따라 NHCs의 분배계수는 증가했으나, 역으로 BACs를 기준한 NHCs의 선택도는 감소했다. 초기 물/용매의 체적비가 감소함에 따라 BACs를 기준한 NHCs의 선택도는 급격히 감소했으나, NHCs의 분배계수는 증가했다. 일정 조건하에서, 각 group별 분배계수와 BACs를 선택도의 순서는 NHCs > Bp > BACs > Pe와 NHCs > Bp > Pe를 각각 나타냈다. 또한 전체 성분에 대한 분배계수의 순서는 In > iQ = Q > Qu > Bp > 1MN = 2MN > Pe > DMN을 나타냈다. 메탄올 추출에 의해 얻어진 NHCs의 최대 수율과 BACs를 기준한 NHCs의 최대 선택도는 각각 94%, 23이었다. 본 연구를 통해 얻어진 실험적 결과를 이용하여 콜타르 중에 함유된 NHCs의 회수공정을 검토했다.

• Journal of Ecology and Environment
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• 제33권4호
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• pp.307-315
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• 2010

Males of the field cricket Teleogryllus emma produce calling songs that are attractive to receptive females. The calling songs of T. emma consist of two components, the long chirp that is composed of up to 12 single pulses, followed by a variable number of short chirps. Based on the analysis of coefficient of variation (CV), temporal characters of the long chirp were less variable than those of the short chirps in male calling songs. To test for phonotactic selectivity of females, we conducted a single-stimulus playback experiment in which five stimuli (standard, long chirp only, long chirp augmented, short chirps only, and short chirps augmented) were used. The standard stimulus included both long and short chirps whose characteristics were derived from the calling songs of field populations. Results of the playback experiment showed that female crickets oriented more frequently toward the stimuli that included the long chirp (standard, long chirp only, and long chirp augmented stimuli) than toward the stimuli lacking the long chirp (short chirps only and short chirps augmented stimuli), indicating that the long chirp in the calling songs was required to elicit positive phonotaxis in the female crickets. The result of CV analysis of the male calling songs and the findings of the female phonotaxis experiment suggested that the long chirp of calling songs may play a role in species recognition in T. emma.

• 한국환경과학회지
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• 제21권12호
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• pp.1449-1454
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• 2012

The ion selective microelectrodes (ISME) have been applied to observe the continuous profiles of NO3-N and NH4-N in bulk solutions or biofilms. In order to evaluate the performance and applicability of ion concentration measuring system, the characteristics, such as slope of calibration curve, detection limit and potentiometric selectivity coefficient were investigated. The slopes of calibration curve showed high degree of correspondence for each target ion concentrations. And the detection limits of nitrate and ammonia ion selective microelectrode were 10-4.7 M and 10-4.4 M, respectively. These ion selective microelectrodes were proved that their own performance could be maintained for 16 days after making. NO3-N and NH4-N selective microelectrodes were also adapted to detect the continuous ion profiles of cilia media packed MLE (Modified Ludzack-Ettinger) process. And the monitored nitrate and ammonia ion profiles with the ion selective microelectrode were stable and well corresponded to the results with conventional ion chromatograph. However, the electric potential was unstable until 8 hr because of the unknown noise. The tip shape and performance of the ion selective microelectrode was stably kept over 2 days continuous monitoring.

• 한국전기전자재료학회논문지
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• 제11권4호
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• pp.298-305
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• 1998

The PVC membrane electrode for measuring perchlorate ion was developed by incorporating various quaternary ammonium sallts. The effect of chemical structure, the content of active material, the kind of plasticizers, and the membrane thickness on the electrode characteristic such as the linear response range and Nernstian slope of the electrode were studied. It was obtained that the effect of the chemical structure of an active material on the electrode characteristics was improved with increasing the alkyl chain length of the quarternary ammonium salts in the ascending order of Aliquat 336P, TOAP, TDAP, and TDDAP. The optimum membrane composition was 9.09wt% of TDDAP, 30.3wt% of PVC, and 60.6wt% of plasticizer(DBP). And the optimum membrane thickness was 0.45mm at this composition. Under the above condition, the linear response range was $10^{-1}~1.2\times10^{-6}$M, and the detection limit was $5.1\times10^{-7}$M with the Nernstian slope of 57mV/decade of activity of perchlorate ion. The electrode potential was stable within the pH range from 4 to 11. The selectivity coefficient was as shown below: $SCN^->I^-NO_3^->Br^->ClO_3^->F^->Cl^->SO_4^{2-}$