• Korean Chemical Engineering Research
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• 제48권3호
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• pp.409-412
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• 2010

본 연구는 질소 분위기의 등온 열중량 분석기를 사용하여 도시 폐기물 폐목재 시료 wood, particle board, MDF의 건조특성을 측정 및 고찰하였다. 폐목재의 건조속도는 잔류 수분 분율에 대한 1차 반응속도로 잘 표현되었다. 건조 활성화 에너지는 12.72~18.31 kJ/g mol, 빈도인자는 0.2155~1.249 1/s이었다.

• Computers and Concrete
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• 제21권1호
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• pp.1-9
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• 2018

Electrical resistivity is a property associated with both the physical and chemical characteristics of concrete. It allows the evaluation of the greater or lesser difficulty with which aggressive substances penetrate the concrete's core before the dissolution of the passive film process and the consequent reinforcement's corrosion begin. This work addresses the steel fiber addition to concrete with two types and various contents from 0% to 1.3%, correlating it with its electrical resistivity. To that effect, 9 different mixes of steel fiber reinforced concrete (SFRC) were produced. The electrical resistivity was evaluated on the on six years aged SFRC by direct measurement at different frequency from 0.1 kHz to 100 kHz. The results indicate that steel fiber content is strongly conditioned by the type and quantity of the additions used. It was also found that long type of fibers has more effect on decreasing the electrical resistivity of concrete than short fibers. Therefore, they increase the corrosion risk of concrete depending on fiber volume fraction and moisture percentage.

• Preventive Nutrition and Food Science
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• 제11권4호
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• pp.339-343
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• 2006

Physicochemical properties of bread as influenced by the addition of sweet pumpkin powder (SPP) were investigated. Freeze-dried sweet pumpkin was ground, sieved through a laboratory sieve and a fraction with particles less than $250\;{\mu}m$ was used. Amount of SPP added to the bread was found to affect the bread quality significantly (p<0.05). Loaf volume and weight of the control were significantly higher than others (p<0.05) and decreased significantly (p<0.05) with the addition of SPP. In other words, the enrichment of product with SPP decreased bread volume and weight without significant changes in the moisture content. There were distinctive color changes with the addition of the powder: L- and a-values were reduced but b-value was significantly increased (p<0.05). The hardness, springiness, and gumminess of bread were found to increase with the addition of the powder. Consumer test indicated that bread contained with 3% SPP had the highest overall acceptability score while 1 or 5% addition produced an acceptable quality for the bread.

• 설비공학논문집
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• 제10권5호
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• pp.535-549
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• 1998

A numerical study for performance analysis of a counterflow type forced draft tower and natural draft cooling tower has been performed based on the method using the finite volume method with non-orthogonal body fitted and non-staggered grid system. For solving the coupling problem between water and air, air enthalpy balance, moisture fraction balance, water enthalpy balance, and water mass balance equations are solved with Navier-Stoke’s equations simultaneously. For the effect of turbulence, the standard k-$\varepsilon$ turbulent model is implied in this analysis. The predicted result of the present analysis is compared with the experimental data and the commercial software result to validate the present study, The predicted results show good agreement with the experimental data and the commercial software result. To investigate the influence of the cooling tower design parameters such as approach, range and wet bulb temperature, parametric studies are also peformed.

• International Journal of Air-Conditioning and Refrigeration
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• 제8권1호
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• pp.1-13
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• 2000

A numerical study for performance analysis of a crossflow-type forced draft cooling tower has been performed based on the finite volume method with non-orthogonal body fitted, and non-staggered grid system. For solving the coupling problem between water and air, air enthalpy, moisture fraction, water enthalpy, and water mass balance equations are solved with Navier-Stoke's equations simultaneously. For the effect of turbulence, the standard k-$\varepsilon$ turbulent model is implied in this analysis. The predicted result of the present analysis is compared with the experimental data and the commercial software result to validate the present study. The predicted results show good agreement with the experimental data and the commercial software result. To investigate the influence of the cooling tower design parameters such as approach, range and wet bulb temperature, parametric studies are also performed.

• Preventive Nutrition and Food Science
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• 제18권4호
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• pp.287-291
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• 2013

Physicochemical properties and consumer perception of white pan bread as influenced by the addition of Ecklonia cava powder (ECP) were investigated. Freeze-dried Ecklonia cava were ground, sieved through a laboratory sieve and a fraction with particles less than $250{\mu}m$ was used. Amount of ECP added (0~3%) to the bread was found to affect the bread quality significantly (P<0.05). pH, bread height, and volume of the control was significantly higher than others (P<0.05) and decreased significantly (P<0.05) with the addition of ECP. Moisture content showed no significant differences (P>0.05). There were distinctive color changes with the addition of the powder: $L^*$- and $a^*$-values decreased but $b^*$-value increased significantly (P<0.05). The hardness of bread was found to increase but both cohesiveness and springiness showed a reverse trend with the addition of the powder. Consumer acceptance test indicated that ECP content 1% on wheat flour could be the recommended supplementation level for the consumers without sacrificing sensory quality.

• Steel and Composite Structures
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• 제33권1호
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• pp.93-109
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• 2019

In the present study, vibration analysis of double bonded micro sandwich cylindrical shells with saturated porous core and carbon/boron nitride nanotubes (CNT/BNNT) reinforced composite face sheets under multi-physical loadings based on Cooper-Naghdi theory is investigated. The material properties of the micro structure are assumed to be temperature dependent, and each of the micro-tubes is placed on the Pasternak elastic foundations, and mechanical, moisture, thermal, electrical, and magnetic forces are effective on the structural behavior. The distributions of porous materials in three distributions such as non-linear non-symmetric, nonlinear-symmetric, and uniform are considered. The relationship including electro-magneto-hydro-thermo-mechanical loadings based on modified couple stress theory is obtained and moreover the governing equations of motion using the energy method and the Hamilton's principle are derived. Also, Navier's type solution is also used to solve the governing equations of motion. The effects of various parameters such as material length scale parameter, temperature change, various distributions of nanotube, volume fraction of nanotubes, porosity and Skempton coefficients, and geometric parameters on the natural frequency of double bonded micro sandwich cylindrical shells are investigated. Increasing the porosity and the Skempton coefficients of the core in micro sandwich cylindrical shell lead to increase the natural frequency of the structure. Cylindrical shells and porous materials in the industry of filters and separators, heat exchangers and coolers are widely used and are generally accepted today.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2022년도 학술발표회
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• pp.446-446
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• 2022

본 연구에서는 MODIS(MODerate resolution Imaging Spectroradiometer) 다중 위성영상을 기반으로 전국 시공간 토양수분 및 토양수분 기반의 가뭄지수 SWDI(Soil Water Deficit Index)를 산정하였다. 시공간 토양수분의 산정을 위해 입력자료로 MODIS 위성의 지표면온도(Land Surface Temperature, LST), 증발산 및 식생(Enhanced Vegetation Index, EVI; Fraction of Photosynthetically Active Radiation, FPAR; Leaf Area Index, LAI; Normalized Difference Vegetation Index, NDVI) 관련 산출물 자료와 지상 관측자료인 일 단위 강수량 자료를 구축하였다. MODIS 위성영상은 산출물별로 제공되는 QC(Quality Control) 영상을 활용해 보정을 수행하였고, 공간 강수량 자료는 기상청에서 제공하는 전국 92개 지점의 종관기상관측자료를 구축하여 공간보간기법인 역거리가중법을 적용해 생성하였다. 실측 토양수분은 농촌진흥청에서 제공하는 76개 지점의 토양 깊이 10 cm에 설치된 TDR(Time Domain Reflectomerty) 센서에서 측정된 토양수분 자료를 활용하였으며, 토양수분 모의 시 토양 속성을 고려하기 위해 국립농업과학원에서 제공하는 토양도를 구축하여 활용하였다. 토양수분 산정 모형은 다중선형회귀모형(Multiple Linear Regression Model, MLRM)을 활용하였으며, 계절 및 토성에 따른 회귀식을 산정하였다. 회귀식 기반의 토양수분과 토성별 포장용수량 및 영구위조점 값을 이용하여 SWDI를 산정하고, 실제 가뭄 발생 시기 및 지역과의 비교하고자 한다.

• Advances in nano research
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• 제15권5호
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• pp.423-439
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• 2023

The aim of this paper is to investigate the free vibration behavior of the micro sandwich beam composing of five layers such as functionally graded (FG) porous core, nanocomposite reinforced by carbon nanotubes (CNTs) and piezomagnetic/piezoelectric layers subjected to magneto electrical potential resting on silica aerogel foundation. The effect of foundation has been taken into account using Vlasov model in addition to rigid base assumption. For this purpose, an iterative technique is applied. The material properties of the FG porous core and FG nanocomposite layers are considered to vary throughout the thickness direction of the beams. Based on the Timoshenko beam theory and Hamilton's principle, the governing equations of motion for the micro sandwich beam are obtained. The Navier's type solution is utilized to obtain analytical solutions to simply supported micro sandwich beam. Results are verified with corresponding literatures. In the following, a study is carried out to find the effects of the porosity coefficient, porous distribution, volume fraction of CNT, the thickness of silica aerogel foundation, temperature and moisture, geometric parameters, electric and magnetic potentials on the vibration of the micro sandwich beam. The results are helpful for the design and applications of micro magneto electro mechanical systems.

• Journal of Nutrition and Health
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• 제43권2호
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• pp.105-113
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• 2010

천연 생리활성 물질로서의 흰씀바귀 뿌리의 특성을 검색하고자 성분분석, 세포 생존율, DPPH 라디칼 소거능을 검색하였다. 흰씀바귀 뿌리의 수분은 79.14%이었고 냉동건조시료 100g 당 조회분 2.49 g, 조지방 2.56 g, 조단백 8.28 g, 칼륨 216.95 mg, 인 89.15 mg이었고, 유리당은 glucose, sucrose 및 fructose으로 확인되었으며, 총 페놀 함량은 59.82 mg/100 g이었다. 지방산은 linoleic acid가 41.24%로 가장 많았고, 흰씀바귀 뿌리에서 확인된 아미노산은 총 17종으로 28.12 mg/g을 함유하였으며, 주요 아미노산 함량은 glutamic acid, arginine, aspartic acid 순으로 각각 5.54 mg/g, 5.03 mg/g, 2.96 mg/g이었다. 신장세포주인 Vero cell에서 메탄올 추출물과 각 분획별로 세포 생존율을 측정한 결과, 흰씀바귀 뿌리 메탄올 추출물과 부탄올 분획물, 물 추출물에서는 높은 세포 생존율로 독성이 거의 없었고 헥산, 클로로포름, 에틸아세테이트 분획물은 $100\;{\mu}g/mL$ 이상의 농도에서 낮은 세포 생존율을 보여 신장 세포의 독성이 관찰되었다. 특히 부탄올 분획물에서는 높은 세포 생존율을 나타내 신장 세포의 성장과 증식의 속도를 증가시키는 데 도움이 될 것으로 생각된다. 간 세포주인 chang cell에서도 같은 경향을 보였다. 흰씀바귀 뿌리 메탄올 추출물과 극성이 다른 5가지 용매, 헥산, 클로로포름, 에틸아세테이트, 부탄올, 물로 계통분획하여 DPPH 라디칼 소거능을 측정한 결과, 흰씀바귀 뿌리 메탄올 추출물 및 5가지 분획물의 DPPH 라디칼 소거능은 $4,000{\sim}0.12\;{\mu}g/mL$에서 농도 의존적으로 감소하였고, 50% 소거능 (${\mu}g/mL$)에 대해 에틸아세테이트 < 부탄올 < 클로로포름 < 헥산 분획물 < 메탄올 < 물 추출물의 순으로 나타났으며, 에틸아세테이트 분획물의 DPPH 라디칼 소거 효과가 가장 좋은 것으로 확인되었다. 본 연구에서 흰씀바귀 뿌리의 성분과 추출물 및 분획물의 세포 생존율과 DPPH 라디칼 소거능이 검토하였고 흰씀바귀에 대한 여러 다른 연구물들을 바탕으로 흰씀바귀가 건강기능성 식품의 신소재로 활용 할 수 있는 가능성을 확인하였다.