• Journal of the Korean GEO-environmental Society
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• v.2 no.1
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• pp.31-35
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• 2001

The effects of the ratio of effective size of filter media and diatom size on filter run time were evaluated by using both reported data and experimental results from several water treatment plants. For single media at several WTPs, the range of probability of the filter run time less than 15hr was 10~60%, and for dual media, that of the filter run time less than 30hr was 10~20%. The major filter clogging algae was Synedra acus of which dominant ratio was in the range of 64~92%. The effective size(ES) of filter medium for dual media filter was 0.71~1.40mm and uniformity coefficient of the filter was 1.25~1.67. The effective size(ES) of filter medium for single medium filter was 0.52~0.65mm and uniformity coefficient of the filter was 0.25~1.40. The range of calculated penetration depth was 2.58~15.4cm for dual media and 1.29~2.17cm for single media, and average filter run time was 40.1~83.3hr and 13.9~34.9hr, respectively. When Synedra counts were over 400cells/ml for single media, filter run time was below 5hr, while filter run time for dual media filter, remained as high as 70hr.

• Journal of the Korean GEO-environmental Society
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• v.10 no.1
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• pp.5-14
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• 2009

This study is to analyze numerically the spatial behaviors of the solute transport in a spatially correlated variable-aperture fracture under the effective normal stress conditions. Numerical results show that the solute transport in a fracture is strongly affected by the spatial correlation length of apertures and applied effective normal stress. According to increasing spatial correlation length, the mean residence time of solute is decreased and the tortuosity and Peclet number (is a dimensionless number relating the rate of advection of a flow to its rate of diffusion) is also decreased. These results mean that the geometry of the aperture distribution is favorable to the solute transport as the spatial correlation length is increased. However, according to the applied effective normal stress is increased, the mean residence time and tortuosity have a tendency to increase but the Peclet number is decreased. The main reason that the Peclet number is decreased, is that the solute is displaced by one or two channels with relatively higher local flow rate due to the increment of contact areas by increasing effective normal stress. Moreover, based on numerical results of the solute transport in this study, the exponential-type correlation formulae between the mean residence time and the effective normal stress are proposed.

• Journal of Korea Water Resources Association
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• v.43 no.6
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• pp.533-541
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• 2010

It is basic for a flood prediction to calculate direct runoff from rainfall in a basin by the rainfall-runoff model. The direct runoff is calculated from rainfall excess or effective rainfall based on a rainfall-runoff model. The total rainfall minus rainfall loss equals rainfall excess with time. This loss can be treated equal to an infiltration loss under the assumption that the infiltration is a major one among the losses in the rainfall-runoff model. Practically obtaining the infiltration loss $\Phi$ index method, W index method or modified ones of these have been used. In this study it is assumed the loss of rainfall in a basin be a well-known Horton infiltration mechanism. And in case that the parameter set is given in the Horton infiltration model a procedure and assumption for calculating hourly infiltration loss and rainfall excess are offered and the results of its application are compared with those of $\Phi$ index method. By this study it is well shown the value of Horton infiltration function is exponentially decay with time as the Horton infiltration mechanism.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.5
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• pp.835-840
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• 2020

In this paper, we described the verification results on method by using the computer simulation and practical experiment for reduction of total radiated power (TRP) measurement time consuming tens of hours. TRP measurements are used in the 5G band in order to exactly evaluate the wireless communication equipment, but it takes a long measurement time because of dense sampling interval. Moreover, if there are various beam forming scenarios, the total measurement time increases exponentially. Therefore, the world-wide research on reduction method of the TRP measurement time is intensively on going. The verified method in this paper is to calculate the TRP through effective isotropical radiated power (EIRP). At first, the relation of TRP and EIRP was investigated, and an antenna for testing was designed and constructed. And, the amount of error was analyzed through simulation and measurement. The analysed results showed that the derived TRP through EIRP has very small error. This method could be applied for TRP measurements of 5G wireless communication equipments.

• Journal of the Korean Wood Science and Technology
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• v.31 no.4
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• pp.50-56
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• 2003

This research was performed to select an appropriate agent to extract preservative components from CCA-treated wood, and then to evaluate the effect of reagent concentration, extracting temperature, and extracting time on the removal of chrome, copper, and arsenic from treated wood. Hydrogen peroxide was selected as the best extracting agent when considered extraction yield as well as use and environmental safety. Its extraction yield was dependent on extracting variables (temperature, concentration, and time), and a highly significant interaction existed among variables. It should be possible to optimize extraction by manipulating these extracting variables. The results may suggest that the required temperature conditions for the reasonable removal of CCA components are at least above 40℃ because extracting time is too long at low temperature (20℃). Reagent concentrations for extracting at above 40℃ should be decided by considering the extracting time.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.148-150
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• 2004

부정행위 탐지는 개별 사용자의 행동 기록과 그 사용자와 유사한 프로필을 갖고 있는 사용자들의 행동 기록을 바탕으로 행동 패턴 혹은 행동 규칙을 찾아내, 이 패턴/규칙과의 비교를 통해 현재 행위가 부정한 것인지를 결정하는 방법을 주로 사용한다. 그러나, 특정 사용자의 행위패턴이 급격하게 바뀌는 경우, 과거의 기록을 바탕으로 생성된 패턴의 유효성은 보장받을 수 없다. 더구나 기존 기록과 상이한 행위에 대한 새로운 패턴이 생성되기 위해서는 계속해서 그런 행위가 쌓여야만 하고, 그 쌓이는 양은 기존 패턴의 견고성에 비례된다. 또한 동일 사용자에게 털러 패턴을 적용시키는 방법 역시 패턴간의 충돌이 일어나는 등의 한계가 존재한다. 본 논문에서는 시간 논리(Temporal Logic)를 적용하여, 과거의 패턴의 유효성을 검증하고 신규패턴을 빠르게 찾아내는 방법을 제안하고자 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10c
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• pp.499-501
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• 2002

대리 서명이란 원 서명자가 대리 서명자에게 서명 권한을 위임하여, 대리 서명자가 원 서명자를 대신해서 서명을 생성하는 것이다. 일반적으로 대리 서명자가 위임받은 권한은 유효 기간을 갖는다. 위임 정보에 위임 기간을 포함시키는 방법으로는 대리 서명자의 서명 생성 시간을 알 수 없기 때문에 유효 기간이 만료된 대리 서명자의 서명 위조를 막을 수 없고, 위임 기간 중에 대리 서명키가 노출되었을 경우 정당한 대리 서명자가 과거에 생성한 서명의 타당성을 보호하지 못한다. 본 논문에서는 기존 대리 서명의 보안 요구사항을 만족하면서도 원 서명자가 시간 관련 파라미터를 제어함으로써 위임 기간이 만료된 대리 서명자의 서명 위조를 막고, 서명키 노출 문제를 해결하기 위한 포워드-시큐어 서명 방법을 제안하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2021.06a
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• pp.32-35
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• 2021

본 논문에서는 시간축 정보량을 감축하여 오디오 부호화 효율을 개선하기 위한 기술을 제안한다. 시간축 정보량 감축 방법은 종전의 오디오 코덱에서도 활용되었던 대표적인 기술로 TNS(temporal noise shaping) 기술이 있다. 그러나 TNS 기술은 오디오 신호의 천이구간에서 선별적으로 유효하게 동작하며 그 효율성도 간헐적으로 나타나는데 이는 MDCT(modified discrete cosine transform)에서 예측 과정을 수행하는 구조적인 문제를 갖고 있기 때문이다. 본 논문에서는 종전의 TNS 기술의 취약점을 보완한 ITES(intensive temporal envelope shaping) 기술을 제안하였다. 제안 기술은 TNS 보다 유효한 오디오 시간영역 정보량을 예측하고 감축하였으며, 개선된 음질을 나타냄을 주관적 평가를 수행하여 검증하였다.

• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.280-284
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• 2016

In this study, the extractable content of each parameters from angelica was confirmed using conventional solvent extraction and microwave extraction in order to extract the functional active ingredient. In addition, the functionality of active ingredients was evaluated by measuring the antioxidant activity and the flavonoids and total polyphenols of the active ingredient extracted from angelica, For the conventional solvent extraction at optimal conditions of the extraction time (2 h), ethanol/pure water volume ratio (60%), the extraction temperature ($60^{\circ}C$), 20.6 wt% of the active ingredient were extracted. Also, when using microwave extraction at optimal conditions of the microwave irradiation time (6 min), microwave intensity (600 W) and ethanol/pure water volume ratio (60 vol%) 22.8 wt% of the active ingredient were extracted. The microwave method required shorter time to complete extraction compared to that of using the conventional solvent extraction method. The antioxidant activity of active ingredients extracted from angelica was 31.46% of DPPH radical scavening activity. The flavonoid content was 14.20 mg QE/mg dw, and total polyphenol content was 11.70 mg GAE/g when using the microwave extraction process.

• KSBB Journal
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• v.4 no.2
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• pp.185-190
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• 1989

Semicontinuous alcohol fermentation of Jerusalem Artichoke by K. fragilis CBS 1555 was performed to investigate the effect of the effective dilution rate and influent sugar concentration to the ethanol concentration and alcohol productivity at steady state. When the time interval for the replacement of fresh influent with fermentation broth was less than or equal to 1 hr, the effective dilution rate was found out to be equal to the specific growth rate. Wash out was not occurred until the effective dilution rate, 0.425 hr-1, and the maximum alcohol productivity was around 5.5 g/1·hr. In this case, the effective dilution rate was 0.25 hr-1 and the influent sugar concentration was distributed from 85 g/l to 135 g/1.