• Korean Journal of Food Science and Technology
• /
• v.32 no.5
• /
• pp.1093-1101
• /
• 2000

The effects of concentration and pH on the emulsifying and rheological properties of the pine nut's protein extract(PNPE) and carbohydrate extract(PNCE) were investigated. Emulsifying activity index(EAI) of sample containing PNPE was minimal at pH 4.0 and the alteration of pH from 4 to 3 or 8 increased EAI regardless of concentration. The most EAI(about 6.44 $m^2/g$ solid) significantly(p<0.05) observed in solution containing 1% PNPE at pH 8.0, but that of 3% PNPE(0.10 $m^2/g$ solid) was minimal at pH 4.0. The emulsion stability exhibited maximum value(about 20) in 3% PNPE emulsion at pH 8.0. However, EAI of samples containing PNCE increased gradually with the increase of pH, but it had lower value than that of samples containing PNPE. At pH 7.0 and 8.0, the rheological behavior of emulsion solutions showed Newtonian fluid(n=1, $r^2>0.99$) regardless of concentration in all samples containing PNPE, but the samples containing PNCE showed pseudoplastic behavior(n<1) in all conditions. The sample with the better emulsion stability index(ESI) significantly(p<0.05) exhibited the higher L, b, and ${\delta}E$, however, lower a value.

• Korean Chemical Engineering Research
• /
• v.57 no.5
• /
• pp.706-713
• /
• 2019

In this study, basic research was conducted to provide guidelines for selecting printers and materials suitable for each application case by analyzing 3D printing method and surface characteristics of materials suitable for microfluidic system. We have studied the surface characteristics according to the materials for the two typical printing methods: The most commonly used method of Fused Deposition Modeling (FDM) printing and the relatively high resolution method of Stereolithography (SLA) printing. The FDM prints exhibited hydrophilic properties before post - treatment, regardless of the material, but showed hydrophobic properties after post - treatment with acetone vapor. It was confirmed by the observation of surface roughness using SEM that the change of the contact angle was due to the removal of the surface structure by post-treatment. SLA prints exhibited hydrophilic properties compared to FDM prints, but they were experimentally confirmed to be capable of surface modification using hydrophobic coatings. It was confirmed that it is impossible to make a transparent specimen in the FDM method. However, sufficient transparency is secured in the case of the SLA method. It is also confirmed that the electroporation chip of the digital electroporation system based on the droplet contact charging phenomenon was fabricated by the SLA method and the direct application to the microfluidic system by demonstrating the electroporation successfully.

• Journal of the Korean Institute of Gas
• /
• v.27 no.2
• /
• pp.7-15
• /
• 2023

The electric submersible pump (ESP) has been operating in production wells around the world because of its high applicability and operational efficiency among artificial lift techniques. When operating an ESP in a reservoir, variables such as temperature, pressure, gas/oil ratio, and flow rate are factors that affect ESP performance. In particular, free gas in the production fluid is a major factor that reduces the life and operational efficiency of ESP. This study presents the flow loop system which can implement the performance and damage tests of ESP considering field operating conditions to quantitatively analyze the variables that affect ESP performance. The developed apparatus in an integrated system that can diagnose the failure and causes of ESP, and detect leak of tubing by linking ESP and tubing as one system. In this study, the flow conditions for stable operation of ESP were identified through single phase and two phase flow experiments related to evaluation for the performance of ESP. The results provide the basic data to develop the failure prediction and diagnosis program of ESP, and are expected to be used for real-time monitoring for optimal operating conditions and failure diagnosis for ESP operation.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.5 no.5
• /
• pp.1-11
• /
• 2001

The purpose of this study is to develop the main program and pre/post processor for the geometric and plastic non-linear analysis of steel jacket structures subjected to wave and earthquake loadings. In this paper, steel jackets are modelled using geometric non-linear space frames and wave loadings re evaluated based on Morrison equation using the linear Airy theory and the fifth Stokes theory. Random wave is generated using JONSWAP spectrum. For earthquake analysis, dynamic analysis is performed using artificial earthquake time history. Also the plastic hinge method is presented for limit analysis of steel jacket. In the companion paper, the pre/post processor is developed and the numerical examples are presented for linear and non-linear dynamic analysis of steel jackets.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.4
• /
• pp.79-84
• /
• 2005

An experimental investigation for impingement of under-expanded, axisymmetric jets on a flat plate has been conducted, and the surface pressure, the adiabatic wall temperature distributions on the plate have been measured in detail. For the explanation on the wall temperature distributions, the total temperature distributions along a free jet have also been measured with total temperature probes. In this study, the under-expansion ratio and the nozzle-to-plate distance have been considered as experimental parameters. Depending on nozzle-to-plate distances, different distributions of adiabatic wall temperature are shown by the energy separation at a jet edge and a impinged surface. Also, the recovery factor on a stagnation point decreases significantly due to the isolation of fluid particles in a central region.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.2
• /
• pp.345-353
• /
• 1987

An analysis is performed to study flow and heat transfer characteristics of mixed free and forced convection about a sphere. Nonsimilar boundary layer equations which are valid over the entire regime of mixed convection are derived in terms of the mixed convection parameter, Gr/Re$^{2}$, through a dimensional analysis. The transformed conservation equations are solved by a finite difference method for the whole range of mixed convection regime. Numerical results for fluids having the Prandtl number 0.7 and 7 are presented. As the mixed convection parameter increases, the local friction coefficient and local heat transfer coefficient increases as well. For small Prandtl number, the friction coefficient is larger, while for large Prandtl number, the heat transfer coefficient is larger. Natural convection effect on the forced flow is more sensitive for small Prandtl number fluid. Flow separation migrates rearward as an increase in the mixed convection parameter. For small Prandtl number, the buoyancy effect is relatively small so that the flow separation occurs earlier.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.376-376
• /
• 2023

전 세계적으로 중요한 담수 자원인 지하수의 미세플라스틱 오염에 대한 우려가 커지고 있다. 지하수 환경에서 미세플라스틱의 오염을 예측하고 평가하기 위해 대수층 내 현장 실태조사가 수행 중에 있으며, 실험실 규모의 컬럼 실험을 통해 지하수에서 미세플라스틱 이동 메커니즘을 조사하는 연구들이 수행되고 있다. 이러한 연구들은 많은 개수의 분석 시료를 동반하며, 환경 중 미세플라스틱 정량분석을 위해서 고가의 분석기기(라만분광기, 푸리에 변환 적외선(FTIR) 분광기, 열분해 가스크로마토그래피 질량분석기)를 사용하여 플라스틱의 종류를 판별하고 개수를 측정하고 있다. 또한, 컬럼 실험을 수행한 대부분의 선행 연구에서는 미세플라스틱 정량분석을 위해 탁도 분석, 분광광도계를 이용한 흡광도 분석, 현미경을 이용한 계수 방법 등을 이용하여 고가의 분석기기를 사용하지 않고 연구를 수행하였다. 하지만, 이러한 방법들은 유체 속 다른 물질이 포함되어있을 경우에 민감하고 농도를 비율 혹은 개수로 표현하기 때문에 질량 측면에서 미세플라스틱의 농도를 과소·과대 평가할 수 있다. 특히, 현미경을 이용한 계수 방법의 경우에는 분석에 많은 시간이 소요된다는 단점이 있다. 위에 언급한 다양한 분석법들의 단점들을 보완하기 위하여, 본 연구에서는 대수층 내 미세플라스틱 이동 특성을 규명하기 위한 실내 실험에 사용될 수 있는 형광이미지 기반의 미세플라스틱 정량분석법을 개발하였다. Nile Red 형광염료를 이용하여 미세플라스틱을 염색하고 사진을 촬영하여 미세플라스틱 시료의 질량과 미세플라스틱 형광이미지의 형광강도 간 상관관계를 분석하였다. 또한, Nile Red로 염색된 미세플라스틱 입자의 수중 노출 테스트를 진행하여, 실내 대수층 모의실험 시 미세플라스틱 질량을 정량화할 수 있는 적용 가능성을 평가하였다. 상관 분석 결과, 미세플라스틱 질량과 이미지의 형광강도는 높은 상관관계를 보였으며, 수중 노출 실험 전과 후의 미세플라스틱 입자의 형광강도 차이는 미미한 것으로 나타났다. 이러한 연구결과를 통해 본 연구에서 개발된 미세플라스틱 정량분석 방법이 포화 다공성 매체로 구성된 컬럼실험 시 유출수의 미세플라스틱 질량 추정에 유용하게 사용될 것으로 생각되며, 대수층 내 미세플라스틱의 이동 특성 규명 연구에 많은 도움이 될 것으로 기대된다.

• Economic and Environmental Geology
• /
• v.56 no.3
• /
• pp.311-330
• /
• 2023

Development of Carbon Capture and Storage (CCS) technique is becoming increasingly important as a method to mitigate the strengthening effects of global warming, generated from the unprecedented increase in released anthropogenic CO₂. In the recent years, the characteristics of basaltic rocks (i.e., large volume, high reactivity and surplus of cation components) have been recognized to be potentially favorable in facilitation of CCS; based on this, research on utilization of basaltic formations for underground CO₂ storage is currently ongoing in various fields. This study investigated the feasibility of underground storage of CO₂ in basalt, based on the examination of the CO₂ storage mechanisms in subsurface, assessment of basalt characteristics, and review of the global research on basaltic CO₂ storage. The global research examined were classified into experimental/modeling/field demonstration, based on the methods utilized. Experimental conditions used in research demonstrated temperatures ranging from 20 to 250 ℃, pressure ranging from 0.1 to 30 MPa, and the rock-fluid reaction time ranging from several hours to four years. Modeling research on basalt involved construction of models similar to the potential storage sites, with examination of changes in fluid dynamics and geochemical factors before and after CO₂-fluid injection. The investigation demonstrated that basalt has large potential for CO₂ storage, along with capacity for rapid mineralization reactions; these factors lessens the environmental constraints (i.e., temperature, pressure, and geological structures) generally required for CO₂ storage. The success of major field demonstration projects, the CarbFix project and the Wallula project, indicate that basalt is promising geological formation to facilitate CCS. However, usage of basalt as storage formation requires additional conditions which must be carefully considered - mineralization mechanism can vary significantly depending on factors such as the basalt composition and injection zone properties: for instance, precipitation of carbonate and silicate minerals can reduce the injectivity into the formation. In addition, there is a risk of polluting the subsurface environment due to the combination of pressure increase and induced rock-CO₂-fluid reactions upon injection. As dissolution of CO₂ into fluids is required prior to injection, monitoring techniques different from conventional methods are needed. Hence, in order to facilitate efficient and stable underground storage of CO₂ in basalt, it is necessary to select a suitable storage formation, accumulate various database of the field, and conduct systematic research utilizing experiments/modeling/field studies to develop comprehensive understanding of the potential storage site.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.06a
• /
• pp.182.1-182.1
• /
• 2010

현재 전 세계적으로 가장 널리 개발하고 보급되어지고 있는 풍력산업의 시장 규모는 매년 확대되고 있다. 특히 소형 풍력발전 시스템은 낙도 등의 전력 공급이 어려운 지역에 경제성 있는 전력 보급을 가능하게 한다. 국내의 미전화 지역과 일반 가정에서 풍력 에너지 자원을 적극 활용 개발하기 위해서 보다 우수한 성능의 풍력발전기용 블레이드를 설계하고자, 공기역학적인 최적설계에 대해 연구함으로써 추후 보급형 풍력발전 시스템의 개발에 필요한 설계 기술을 확립하고자한다. 본 연구는 설계된 블레이드의 유동해석 및 성능예측을 위하여 경제적으로 많은 지원이 필요한 대규모 풍동실험이 아닌 상용 CFD를 사용하여 보다 효율적으로 우수한 성능을 가지는 풍력 터빈을 설계함에 있다. Reynolds Averaged Navier-Stokes 방정식에 기반을 둔 CFD의 경우 이론적으로 명확한 해석이 가능하고, 실제 터빈의 운전 환경과 동일한 다양한 물리적 변수를 입력 데이터로서 활용할 수 있는 장점이 있기 때문에 풍력 터빈의 설계 과정에서 반영된 미소한 블레이드 형상변화 및 운전 조건의 변화에 따른 유동장의 변화 및 풍력터빈 성능을 정확히 예측할 수 있는 장점을 가지고 있다.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.6
• /
• pp.1799-1806
• /
• 1991

The effect of an elastic intermediate support on the vibration characteristics of a fluid conveying pipe system modeled as simply-simply supported and fixed-fixed supported pipes has been investigated. The approach is based on solving the closed form equation of the 4th order polynomials. The change of natural frequency and critical velocity are also investigated with the fluid density, the fluid velocity, the position and stiffness of the elastic intermediate support varied. The results show that the vibration characteristics of pipe system could be controled by changing the position and/or stiffness of the elastic intermediate support.