• Structural Engineering and Mechanics
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• 제44권5호
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• pp.663-680
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• 2012

Previous major earthquakes revealed that most damage of the buried segmented pipelines occurs at the joints of the pipelines. It has been proven that the differential motions between the pipe segments are one of the primary reasons that results in the damage (Zerva et al. 1986, O'Roueke and Liu 1999). This paper studies the combined influences of ground motion spatial variations and local soil conditions on the seismic responses of buried segmented pipelines. The heterogeneous soil deposits surrounding the pipelines are assumed resting on an elastic half-space (base rock). The spatially varying base rock motions are modelled by the filtered Tajimi-Kanai power spectral density function and an empirical coherency loss function. Local site amplification effect is derived based on the one-dimensional wave propagation theory by assuming the base rock motions consist of out-of-plane SH wave or combined in-plane P and SV waves propagating into the site with an assumed incident angle. The differential axial and lateral displacements between the pipeline segments are stochastically formulated in the frequency domain. The influences of ground motion spatial variations, local soil conditions, wave incident angle and stiffness of the joint are investigated in detail. Numerical results show that ground motion spatial variations and local soil conditions can significantly influence the differential displacements between the pipeline segments.

• 한국산학기술학회논문지
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• 제13권4호
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• pp.1503-1510
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• 2012

본 연구는 HVAC 시스템의 성능 개선을 위해 원심 임펠러의 블레이드의 중심각, 토출구의 길이와 같은 형상을 변화시켜 수치적으로 해석하였다. 임펠러 내의 속도장, 압력장, 난류 강도, 온도장을 계산하기 위하여 상용 CFD 코드인 FLUENT를 사용하였다. 시스템의 워밍업에 상관없이 히터 파워 레벨이 증가하면 임펠러 내 주위의 온도는 외기 투입시 온도가 증가하였지만 내기 순환 시에는 온도가 오히려 감소하였다. 결과적으로 성능 개선을 통한 $CO_2$ 감소는 블레이드 중심각 및 토출구 길이의 변화를 통한 유속 및 유량의 변화를 통해 이룰 수 있었다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.241-246
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• 2004

본 연구는 강우에 기인한 연안역의 토사 및 영양염류 유출에 관한 현지관측과 대안[( 沖蠅石垣島 ) 오끼나와 이시가키섬]이며, 이를 통한 유출지형분석, 강우강도ㆍ조석과의 영향, 유출입자의 특성(탁도, 임도, 영양염류) 등을 확인하였다. 연안부의 토사 유출과 영양염류의 농도는 강우강도와 조수간만의 시간적 변화에 따라 지역적 차이를 보였으며, 하천유역 주변 토지 이용형태와 주변 식생의 분포비율에 따라 변화되어지고 있음을 확인할 수 있었다.

• 터널과지하공간
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• 제2권2호
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• pp.224-236
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• 1992

It is very important to determine the thermo-mechanical characteristics of the rock mass surrounding the repository of radioctive waste and the LPG storage cavern. In this study, Hwasoon-Shist. Dado-Tuff adn Chunan-Tonalite were the selected rock types. Temperature dependence of the mechanical properteis such as uniaxial compressive strength, tensile strength, Young's modulus was investigated by measuring the behaviour of these properties due to the variation of temperature. Also, the characteristics of strength and deformation of these rocks were examined through high-temperature triaxial compression tests with varing temperatures and confining pressures. Important results obtained are as follows: In high temperature tests, the uniaxial compressive strength and Yong's modulus of Tonalite showed a sligth increase at a temperature up to 300$^{\circ}C$ and a sharp decrease beyond 300$^{\circ}C$, and the tensile strength showed a linear decrease with increasing heating-temperature. In high-temperature triaxial compression test, both the failure stress and Young's modulus of Tonalite increased with the increase of confining pressure at constant heating-temperature, and the failure stress decreased at 100$^{\circ}C$ but increased at 200$^{\circ}C$ under a constant confining pressure. In low temperature tests, the uniaxial compressive and tensile strengths and Young's modulus of these rocks increased as the cooling-temperature is reduced. Also, the uniaxial compressive and tensile strengths of wet rock specimens are less than those of dry rock specimens.

• 한국수산과학회지
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• 제49권2호
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• pp.198-207
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• 2016

Tanaka’s snailfish, Liparis tanakae (Gilbert and Burke, 1912), is distributed throughout the coasts of Korea. To clarify the population structure of L. tanakae, we analyzed the morphological and genetic variation among individuals sampled from three localities surrounding the Korean peninsula: Boryeong in the Yellow Sea, Jinhae in the Korea Strait and Pohang in the East Sea. Principal component analysis based on 20 morphometric characteristics revealed two slightly distinct groups (Boryeong vs. Jinhae and Pohang). However, canonical discriminant analysis clearly revealed three groups, separated according to locality. Pairwise differentiation index (F_ST) comparisons based on 762-base pairs mitochondrial cytochrome b gene sequences showed that Boryeong significantly differed from Jinhae and Pohang, but Jinhae and Pohang did not significantly differ from each other. Our findings suggest that Korean L. tanakae comprise at least two groups. Further studies using more sensitive DNA markers, such as microsatellite DNA, are required.

• 대한조선학회논문집
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• 제38권1호
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• pp.27-36
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• 2001

현재, 유럽에서 중요한 역할을 담당하고 있는 수송모델로서 바다와 강을 연계한 Sea-river 수송모델은 황해권 지역에서의 국내 외 화물수송과 여객수송에 있어 장래에 매우 중요한 역할을 할 것이다. 본 연구에서는 육상수송에 따른 국내 교통 혼잡문제와 극동아시아 국가의 화물량 증대로 인한 물류 문제의 개선을 위해 경인운하의 운항조건에 적합한 sea-river 연계 바아지선단의 수송모델을 제안한다. 즉, 본 연구에서는 경인운하의 형상과 크기 등의 제한조건 등을 고려하여 바아지선단의 수송효율 측면의 경제성을 바탕으로 경인운하를 이용한 황해권의 sea-river 연계 수송모델로서 효율적인 바아지선단 구성의 표준화를 제시하고자 한다.

• 자원환경지질
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• 제21권1호
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• pp.97-106
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• 1988

The purpose of this study is to collect basic data which are prerequisite for quantitative analysis of coal logging data. The study involves laboratory measurements of physical properties such as seismic velocities (P,S-waves), resitivity and density of domestic and imported foreign coals. The relationships between these properties were analyzed by using cross-plots. Correlation between the physical properties of coal and the results of chemical analysis (calorie, fixed carbon, ash, moisture, volatile matter and sulfur contents) was also studied to obtain ideas about coal quality analysis using logging data. Summarized results are as follows: 1. $V_P$ is exponentialy related to $V_S$. And the average value of $V_P$ is about l.8 times as large as $V_S$. 2. Since coal has very low density compared with surrounding sedimentary rocks, density logging is appeared to be the best method for identifying coal seams and evaluating their qualities. 3. For the case of domestic coals, the ash contents and calorie show a perfect inverse relationship. Since the density increases as increase of ash content with a well-defined functional form, the ash content of domestic coals can be estimated by density measurements. 4. Because of low ash content, low density and high resistivity, foreign coals and domestic lignites are easily distinguished from domestic coals.

• 전기전자학회논문지
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• 제22권3호
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• pp.532-538
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• 2018

본 논문은 자성센서 기반 지뢰탐지기를 개발하는 과정에서 필요한 신호처리 알고리즘을 제안한다. 탐지신호의 세기는 탐지 코일에 수신된 자기장의 변화량을 이용하여 얻는다. 표적이 없을 때 대비 표적이 있을 때의 상대적인 신호세기를 계산하기 때문에 표적이 없는 상태에서 calibration data를 만든다. 자기장은 장비 자체의 전기적인 잡음 또는 주변 환경의 영향을 받으므로 calibration을 지속적으로 수행하고 갱신하는 것이 중요하다. 마지막으로 표적에 의해 발생하는 신호크기의 변화량, 즉 단위 시간 당 그래프의 기울기 값이 일정 수준 이상 도달하는지 감시하여 정확한 탐지지점과 신호크기를 판별한다.

• Membrane and Water Treatment
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• 제4권2호
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• pp.127-142
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• 2013

In order to investigate the significance of "salting-out" and "pore swelling" effects on the nanofiltration of neutral solutes, rejection properties of two NF ceramic and polymeric membranes were studied with single polyethyleneglycol (PEG) solution and mixed PEG/inorganic electrolyte solutions. For both membranes, the rejection rate of PEG was found to decrease significantly in the presence of ions. In the case of the ceramic membrane (rigid pores), this phenomenon was imputed to the sole partial dehydration of PEG molecules induced by the surrounding ions. This assumption was confirmed by the lowering of the PEG rejection rates which followed the Hofmeister series. Experimental data were used to compute the resulting decrease in the Stokes radius of PEG molecules in the presence of the various salts. Concerning the polymeric membrane, the decrease in the rejection rate was found to be systematically higher than for the ceramic membrane. The additional decrease was then ascribed to the swelling of the pores. The experimental data of rejection rates were then used to compute the variation in the mean pore radius in the presence of the various salts. The pore swelling phenomenon due to accumulation of counterions inside pores was supported by electrokinetic charge density measurements.

• Geomechanics and Engineering
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• 제15권1호
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• pp.621-630
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• 2018

In the note a comprehensive and optimal passive-active mode for describing the limit failure of circular shallow tunnel with settlement is put forward to predict the catastrophic stability during the geotechnical construction. Since the surrounding soil mass around tunnel roof is not homogeneous, with tools of variation calculus, several different curve functions which depict several failure shapes in different soil layers are obtained using virtual work formulae. By making reference to the simple-form of Power-law failure criteria based on numerous experiments, a numerical procedure with consideration of combination of upper bound theorem and stochastic medium theory is applied to the optimal analysis of shallow-buried tunnel failure. With help of functional catastrophe theory, this work presented a more accurate and optimal failure profile compared with previous work. Lastly the note discusses different effects of parameters in new yield rule and soil mechanical coefficients on failure mechanisms. The scope of failure block becomes smaller with increase of the parameter A and the range of failure soil mass tends to decrease with decrease of unit weight of the soil and tunnel radius, which verifies the geomechanics and practical case in engineering.