• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 전자세라믹스 센서 및 박막재료 반도체재료 일렉트렛트 및 응용기술
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• pp.104-107
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• 2000

It is well known that the state of existence of molecules on the surface of water changes during compression of the molecules. Electric methods, such as the measurement of the surface potential or displacement current, are also useful for investigating dynamic changes of the molecular state on the water surface during compression. Maxwell-Displacement-Current(MDC) measuring technique has been applied to the study of monolayers of Arachidic acid and L-$\alpha$-Dimyristoyl Phosphatidylcholine(L-$\alpha$-DMPC). The displacement current was generated from monolayers on a water surface by monolayer compression. Displacement current was generated in the gas state, gas/liquid state, and liquid state in the course of monolayer compression. The researchers examined diplacement current of electric conduction organic monolayer generated due to orient change of monolayers alkylchain.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.1
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• pp.43-49
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• 2006

The surface and pore structure of cellulose fibers have a significant impact on the properties and performance in applications. Cellulase enzymatic hydrolysis of cellulose fibers can result in changes to the surface and pore structure thus providing a useful tool for fiber modification. This research characterizes these changes using various test methods such as fiber dimension, water retention value, hard-to-remove water content, freezing and non-freezing bound water content, polymer adsorption, and crystallinity index. For a high-dosage enzyme treatment (0.10 g/g), the fiber length was significantly decreased and the fibers were 'cut' in the cross direction, not in the axial direction. The swelling capacities as measured by the WRV and HR water content increased for the high-dosage treatment. Three independent measurements (non-freezing bound water, polymer adsorption, and crystallinity index) are in good agreement with the statement that the amorphous regions of cellulose fibers are a more readily available substrate relative to crystalline regions. Based on the experimental results obtained herein, a model was proposed to explain surface and pore structure modification of cellulose fibers via enzymatic treatment.

• Structural Engineering and Mechanics
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• 제69권1호
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• pp.33-42
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• 2019

Thermal cracks are cracks that commonly form at early ages in mass concrete. During the concrete pouring process, the elastic modulus changes continuously. This requires the time domain to be divided into several steps in order to solve for the temperature, stress, and displacement of the concrete. Numerical simulations of thermal crack propagation in concrete are more difficult at early ages. To solve this problem, this study divides crack propagation in concrete at early ages into two cases: the case in which cracks do not propagate but the elastic modulus of the concrete changes and the case in which cracks propagate at a certain time. This paper provides computational models for these two cases by integrating the characteristics of the extended finite element algorithm, compiles the corresponding computational programs, and verifies the accuracy of the proposed model using numerical comparisons. The model presented in this paper has the advantages of high computational accuracy and stable results in resolving thermal cracking and its propagation in concrete at early ages.

• 대한화학회지
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• 제62권1호
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• pp.43-51
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• 2018

이 연구에서는 시각장애를 가진 중고등학생의 물의 상태변화 개념을 조사하였다. 연구대상은 국립과천과학관에서 열린 시각장애학생 대상의 과학탐구 활동에 참여한 중학생 16명과 고등학생 15명으로, 이 중 14명은 전맹, 13명은 저시력이었으며 나머지는 파악되지 않았다. 탐구활동은 이 연구를 위해 제작한 물과 얼음의 분자모형을 참여 학생들에게 개별적으로 탐색하면서 연구자와 대화하는 방식으로 진행하였다. 학생들이 모형에 대한 탐색을 마친 후 물의 상태변화 개념과 관련지어 설명하도록 하였으며, 모형의 활용 가능성에 대해서도 면담을 실시하였다. 모든 대화는 녹음되었고 그 자료를 전사한 뒤 분석하였다. 연구 결과, 시각장애학생들은 활동에 사용된 모형의 재료와 개수에 대해서는 정확히 대답하였지만 무엇을 표현한 모형인지 설명하기 어려워하였다. 물의 분자와 상태변화에 대해 배운 경험이 있다고 대답하였으나 그 개념에 대해 제대로 설명하지 못하거나 현상적인 경험에 기초한 수준에 불과했다. 활동을 통해 시각장애학생들은 물과 얼음의 분자구조와 상태변화에 대해 이해하게 되었고, 연구에서 사용된 모형이 필요하며 유용하다고 긍정적으로 인식하였다. 이러한 결과에 기초하여 교육학적 함의를 논의하였다.

• Journal of Microbiology
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• 제42권2호
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• pp.69-73
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• 2004

Vibrio vulnificus, a Gram-negative bacterium found in estuarine waters, is responsible for over 95％ of all seafood-related deaths in the United States. As a result of a temperature downshift to 5$^{\circ}C$, this organism enters the viable but nonculturable (VBNC) state. Changes in the membrane fatty acid (FA) composition of V. vulnificus may be a contributing factor to the ability of this organism to enter into and survive in the VBNC state. This hypothesis was tested by incubating the organism at 5$^{\circ}C$ in arti-ficial sea water and analyzing the cells' FAs during the initial hours of temperature and nutrient down-shift. Prior to downshift, the predominant FAs were 16:0, 16:1 and 18:0. During the first four hours of downshift, statistically significant changes occurred in 15:0, 16:1, 16:0, 17:0, and 18:0. These results indicate that changes in FA composition occur prior to entry of V. vulnificus into the VBNC state, suggesting that the ability to maintain membrane fluidity may be a factor in this physiological response. Cells in which fatty acid synthesis was inhibited did not survive, indicating that active fatty acid metab-olism is essential for entry of cells into the VBNC state.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2002년도 학술발표회 논문집(I)
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• pp.3-16
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• 2002

This article describes some of the recent and on-going research developments of the author at Colorado State University. Advances in the field of sedimentation and river mechanics include basic research and computer modeling on several topics. Only a few selected topics are considered here: (1) analytical determination of velocity profiles, shear stress and sediment concentration profiles in smooth open channels; (2) experiments on bedload particle velocity in smooth and rough channels; (3) field measurements of sediment transport by size fractions in curved flumes. In terms of computer modeling, significant advances have been achieved in: (1) flashflood simulation with raster-based GIOS and radar precipitation data; and (2) physically-based computer modeling of sediment transport at the watershed scale with CASC2D-SED. Field applications, measurements and analysis of hydraulic geometry and sediment transport has been applied to: (1) gravel-bed transport measurements in a cobble-bed stream at Little Granite Creek, Wyoming; (2) sand and gravel transport by size fraction in the sharp meander bends of Fall River, Colorado; (3) changes in sand dune geometry and resistance to flow during major floods of the Rhine River in the Netherlands; (4) changes in hydraulic geometry of the Rio Grande downstream of Cochiti Dam, New Mexico; and (5) analysis of the influence of water temperature and the Coriolis force on flow velocity and sediment transport of the Lower Mississippi River in Louisiana. Recent developments also include two textbooks on "Erosion and Sedimentation" and "River Mechanics" by the author and state-of-the-art papers in the ASCE Journal of Hydraulic Engineering.

• Water Engineering Research
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• 제4권1호
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• pp.31-43
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• 2003

The impacts of climate change on soil moisture in sub - Arctic watershed simulated by using the hydrologic model. A range of arbitrary changes in temperature and precipitation are applied to the runoff model to study the sensitivity of soil moisture due to potential changes in precipitation and temperature. The sensitivity analysis indicates that changes in precipitation are always amplified in soil moisture with the amplification factor for flow. The change in precipitation has effect on the soil moisture in the catchment. The percentage change in soil moisture levels can be greater than the percentage change in precipitation. Compared to precipitation, temperature increases or decreases alone have impacts on the soil moisture. These results show the potential for climate change to bring about soil moisture that may require a significant planning response. They are also indicative of the fact that hydrological impacts affecting water supply may be important in consider-ing the cost and benefits of potential climate change.

• 한국농공학회지
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• 제36권4호
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• pp.87-94
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• 1994

The aim of the work descrihed in this paper is to study a characteristics of an unsaturated soil for the different matric suctions. To this end, a series of suction controlled isotropic and triaxial compression tests is conducted on silty sands. Matric suction is controlled by the axis translation technique using high air entry ceramic disk. Total volume change, air and water volume changes are measured by the device made for the experiment. The specimens are compacted using a half of Proctor compaction energy and with the water contents of 5% drier than the optimum moisture contents. Isotropic compression and triaxial compression tests are conducted on the specimen at each equilibrium state of matric suction. From test results, volume changes and deviator stresses are analyzed at each state and their relationships are formulated.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
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• pp.103-106
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• 2003

It is well known that the state of existence of molecules on the surface of water changes during compression of the molecules. Electric methods, such as measurement of the surface potential or displacement current are also useful for investigating dynamic changes of molecular state on the water surface during compression. In this paper, We studied on the Bio thin film by Langmuir-Biodgett(LB) method. The Experiment method used displacement current, $\pi-A$ isotherm and BAM (Brewster Angle Microscopy). using the BAM, we can to the molecular orientation of monolayer on the water surface and directly see the morphology of the films on water subphase as well as that of the films.

• Environmental Engineering Research
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• 제12권5호
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• pp.197-200
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• 2007

Advanced control is getting increasingly demanded in water and wastewater treatment systems. Various case studies have shown significant savings in operating costs, including energy costs, and remarkably short payback times. It has been demonstrated that instrumentation, control and automation (ICA) may increase the capacity of biological nutrient removing wastewater treatment plants by 10-30% today. With further understanding and exploitation of the mechanisms involved in biological nutrient removal the improvements due to ICA may reach another 20-50% of the total system investments within the next 10-20 years. Disturbances are the reason for control of any system. In a wastewater treatment system they are mostly related to the load variations, but many disturbances are created also within the plant. In water supply systems some of the major disturbances are related the customer demand as well as to leakages or bursts in the pipelines or the distribution networks. Hardly any system operates in steady state but is more or less in a transient state all the time. Water and energy are closely related. The role of energy in water and wastewater operations is discussed. With increasing energy costs and the threatening climate changes this issue will grow in importance.