• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2002.11a
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• pp.139-145
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• 2002

The flow zone through propeller jets are used in evaluating the environmental and constructional effects of navigation on the waterway. It relies on the characteristics of ships and water depth. A numerical model using the momentum theory of the propeller and Shield's diagram was developed in a restricted waterway. Equations for discharge are presented based on thrust coefficients and propeller speed and are the most accurate means of defining discharge. Approximate methods for discharge are developed based on applied ship's power. Equations for discharge are as a function of applied power, propeller diameter, and ship speed. Water depth of the waterway and draft of the shop are also necessary for the calculation of the grain size of the initial motion. The velocity distribution of discharge from the propeller was simulated by the Gaussian normal distribution function. The shear velocity and shear stress were from the Sternberg's formula. Case studies to show the influence of significant factors on sediment movement induced by the ship's propeller at the channel bottom are presented.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1175-1179
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• 1999

The rheological properties of highly filled epoxy molding compound(EMC) for semi-conductor encapsulants are greatly affected by the content of filler loaded. In this study, the change of viscosity of EMC for semi-conductor encapsulants with the filler content was investigated. Also, both of Cox-Merz and modified Cox-Merz equations were applied to convert the viscosity change as a function of frequency to that of shear rate. It was ovserved that shear thinning and yield stress occured at high filler contents and that the Cox-Merz equation could not be applied at high filler contents because of the difference of viscosity according to the various strains. When the modified Cox-Merz equation was applied, the all the curves having different strain tend to be represented by one master curve, even though some deviation was obseved at high filler content and strain.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.640-640
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• 2012

낙동강 홍수예경보 시스템은 낙동강 유역의 홍수피해 방지를 위해 1986년에 구축되어 낙동강홍수통제소에서 운영되어 온 이래로 여러 차례에 거친 시스템의 개선 및 보완을 통해 현재의 시스템을 갖추게 되었다. 그러나 4대강 사업을 통해 시행된 하도 준설 및 보 설치로 인한 하도 조건의 변경과 기존의 저류함수모형 및 수위-유량 관계식을 이용한 수위예측의 한계로 인해 낙동강 하도에 대한 수리해석모형 구축의 필요성이 대두되었다. 이에 따라 낙동강 홍수통제소에서는 기존의 저류함수모형을 이용한 강우-유출 해석모형과 낙동강 본류 및 주요 지류에 대한 수리해석 모형을 구축하여 연계하는 과업을 수행 중에 있다. 본 연구에서는 하천기본계획의 설계홍수량의 산정시 적용되는 HEC-HMS 모형을 통해 강우-유출해석모형을 구축하고, 낙동강 본류 및 8개 지류에 대해 FLDWAV 모형을 이용해 수리해석 모형을 구축하여 연계하였다. 수자원단위지도의 표준유역과 수위관측소 지점을 기반으로 하여 낙동강 유역을 287개의 소유역으로 분할하였고, 271개의 분할하도 및 10개의 다목적 댐 방류량을 반영하여 강우-유출 모형을 구축하였다. 수치지형도 및 토양도, 토지이용현황도를 통해 유역유출 및 하도유출에 대한 매개변수 산정하였고, 낙동강 본류 및 지류내의 주요 수위관측소를 유량의 검보정 지점으로 설정하였다. 수리학적 모형 구축을 위해 낙동강 본류의 383개의 단면 및 8개 지류의 497개 단면을 반영하였고, 그 이외의 6개 주요 지류는 측방유입으로 처리하였으며 낙동강 본류에 신설된 8개의 다기능보의 운영을 반영하였다. 각각 구축된 강우-유출 모형과 수리학적 모형은 모듈화하여 연계하였으며, 현재 낙동강홍수통제소에서 운영되고 있는 낙동, 왜관, 현풍, 진동, 삼랑진, 구포, 동촌수위관측소를 홍수예보지점으로 선정하여 모형의 검보정을 실시하였다. 구축된 모형은 낙동강홍수통제소의 홍수예보모형의 계산결과와 비교하여 적용성 및 효율성을 입증할 수 있을 것으로 판단되며, 낙동강에서의 실시간 홍수예 경보를 위한 홍수예보모형으로 활용될 수 있을 것으로 사료된다.

• Journal of Korean Society of Transportation
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• v.29 no.4
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• pp.85-93
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• 2011

Many policies, such as transit-oriented development, encouraged use of bicycle and pedestrian, reduction of green house gas (GHG) and etc., have been deployed to support transport sustainability. Although various studies regarding GHG were presented, no one has yet adequately explained the behavior of travelers. This paper proposes a GHG emission model by highlighting its sensitivity, elasticity with regard to such travel cost as travel time, travel fare, and GHG pricing, introduced to reduce the amount of GHG in transportation system. For better estimation of GHG, the proposed model adopts (1) a production-constrained gravity model and (2) the travel distance from the origin and the destination (OD). The gravity model has a merit that it considers travel pattern between OD pairs. The model was tested with an example, and the promising results confirmed its validation and applications.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2B
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• pp.155-162
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• 2009

Univariate frequency analyses are widely used in practical hydrologic design. However, a storm event is usually characterized by amount, intensity, and duration of the storm. To fully understand these characteristics and to use them appropriately in hydrologic design, a multivariate statistical approach is necessary. This study applied a Gumbel mixed model to a bivariate storm frequency analysis using hourly rainfall data collected for 46 years at the Seoul rainfall gauge station in Korea. This study estimated bivariate return periods of a storm such as joint return periods and conditional return periods based on the estimation of joint cumulative distribution functions of storm characteristics. These information on statistical behaviors of a storm can be of great usefulness in the analysis and assessment of the risk associated with hydrologic design problems.

• Analytical Science and Technology
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• v.15 no.1
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• pp.67-71
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• 2002

The residual analysis and half-life time of imidazole fungicide prochloraz in soils (silty clay) were investigated by gas chromatography equipped electron capture detector (GC-ECD). The soil samples were extracted acetone/hexane(1:1) solvent and analyzed after separated by $LC-NH_2$ Sep-Pak solid column. Linear sensitivity of standard calibration curve was Y = 268.8600X + 0.0664, $R^2=0.9998$ between 0.05~1.00 ng. The detection limit was 0.02 mg/L and the average recoveries were 94.5~97.3% from the standard additional experiments with 0.10 and 0.40 mg/L. The half-life time was 24.4 days in room laboratory and 7.6 days in the field test soil.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.3
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• pp.395-402
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• 2003

The capacity of a CDMA cellular system is determined by the amount of interference, therefore the exact estimation of interference is important to evaluate the system performance. In this paper, we propose an approximated equation which calculates reverse link other cell interference in the CDMA cellular systems. The equation using Riemann-Zeta function has a property that it is useful in case of any radio propagation loss exponents. And we compare calculation results with simulation results in other to verify it's usefulness. The upper bound of system capacity calculated with the proposed approximated equation gives almost alike result with the simulation. The proposed interference bound is useful to calculate system capacity and to evaluate some algorithm in a hierarchical cellular system which must be considered various propagation exponents.

• The Journal of the Acoustical Society of Korea
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• v.24 no.3
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• pp.133-140
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• 2005

Crosstalk canceller in stereo channel audio reproduction system has the purpose to deliver desired signals exactly at the listener's ear. Generally. it has a Poor performance in low frequency bands. Frequency-warped Otters are used to provide improved performance in crosstalk canceller for these problems. However. such filters are more complex to implement than conventional filters. This paper presents an efficient method for low-order IIR approximation of frequency warped crosstalk cancellation filters using Pole-zero dewarping. The method preserves the advantages of frequency warping, but has a computational complexity that is similar to the conventional method. This Paper also presents a series of experiments that validate the method of crosstalk canceller.

• Journal of Korean Society of Transportation
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• v.33 no.6
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• pp.575-583
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• 2015

The Korea Transport Institute (KOTI) builds the origin and destination(O-D) trip data with relatively smaller zone size such as Eup, Myeon, Dong administration unit districts in metropolitan area. Otherwise, O-D trip data was built by bigger size of traffic analysis zone(TAZ) such as Si, Gun, Gu administration unit districts for rural area. In some cases, it is needed to divide a zone into several sub-zones for rural area in order to analyze travel distribution pattern in detail for a certain highway and rail project. The study suggested a method to estimate O-D trips for sub-zones in the larger-size zones in rural area. Two different distribution models, direct demand model and gravity model, were calibrated for sub-zone's intra-zonal O-D trip pattern with metropolitan area O-D data which has smaller zone-size (sub-zone) data categorized by low, middle and high population density. The calibration results were compared between the two models. The gravity model with impedance function of power functional form was selected with better explanation for all groups in the metropolitan area. The adjusted $R^2$ was 0.7426, 0.6456 and 0.7194 for low, middle and high population density group, respectively. The suggested O-D trip estimating method is expected to produce enhanced trip patterns with sub-divided small zones.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.1
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• pp.33-40
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• 1989

In the design of reinforced concrete framed structures, which consist of various design variables, the objective and the constraint functions are formulated in complicated forms. Usually iterative methods have been used to optimize the design variables. In this paper, multilevel formulation is adopted, and design variables are selected in reduced numbers at each level, to reduce the iterative cycle and to accelerate the convergence rate. At level 1, elastic analysis is performed to get the upper and lower bounds of the redistributed design moments due to inelastic behavior of the frame. Then the design moments are taken as design variables and optimized at level 2, and the sizing variables are optimized at level 3. The optimization of redistributed moments is performed using the design sensitivity obtained at the level 2, and force approximation technique is used to reflect the variation of design variables in the lower level to the upper level. The design variables are selected in reduced numbers at each level, and the optimization formulation is simplified effectively. A cost function is taken as the objective function, and the constraints of the stress of the structures are derived from BSI CP 110 following limit state theory. Numerical examples are included to prove the effectiveness of the developed algorithm.