• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 춘계학술대회 논문집
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• pp.67-70
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• 1994

On this study, we fabricated humudity sensor with polyimide thin film from the nonaqueous emulsion by the electrophoretic deposition as a function of film thickness. then evaluated performance of the sensor with increasing relative humidity if constant temperature constant humidity chamber, which is electronically controlled. we designed upper electrode of the sensor to brush type to make moisture particles permeate into the polymer bulk. sensing properties of the sensor on % RH shows proportion on the low %RH. Fer the 30V-30S- 200$^{\circ}C$ sample, percentage changing of capacitance on from 30 %RH to 90 %RH is 45.8 %, and increasing rate per 1 % RH of capacitance is 11.25 pF

• 산업식품공학
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• 제15권2호
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• pp.155-161
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• 2011

본 실험은 압출성형을 통한 저DE덱스트린 제조공정을 확립하기 위해서 수분함량 25, 35% 배럴온도 100, $120^{\circ}C$, 스크루 회전속도 150, 250 rpm에서 압출성형한 전분을 알 파아밀라아제로 당화시켰을 때 당화특성을 연구하였다. 수 분용해지수는 원료전분 수분함량이 25%로 감소할 경우 증 가되었으며, 수분흡착지수도 수분의 감소와 함께 전체적으 로 증가하였다. 환원당함량의 경우 수분함량이 낮고 배럴온 도 높을수록 증가되었다. 120 분간 당화 후 DE 63.8로 높 게 나타났다. 비기계적 에너지 투입량(SME)의 증가와 함께 수분용해도는 증가하는 경향이었다. 또한 수분함량의 감소 와 함께 비기계적 에너지 투입량과 수분용해도는 증가하였 다. 페이스트점도는 원료전분의 수분이 낮고, 스크루 회전 속도가 증가할수록 전분사슬의 절단에 따라 저온최고점도 가 감소하는 경향을 보였다. 초기반응속도는 수분함량이 25%로 낮고 배럴온도 $120^{\circ}C$, 스크루 회전수 250 rpm에서 $2.26{\times}10^{-3}mmol/mL{\cdot}min$로 가장 높았다. 시중 호화전분 $1.83{\times}10^{-3}mmol/mL{\cdot}min$에 비해서도 높은 결과를 보였다. 당화속도상수는 히구치모델을 응용하였으며, 수분함량이 낮 고 배럴온도가 $120^{\circ}C$일 때 전체적으로 높게 나타났다. 본 실험에서 초기반응속도, 당화속도상수, 당화수율 등을 고려 할 때, 최적조건은 수분함량 25%, 배럴온도 $120^{\circ}C$, 스크루 회전속도 250 rpm이었다.

• Agricultural and Biosystems Engineering
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• 제1권1호
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• pp.30-37
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• 2000

Wet porous media representing agronomic soil that contains variable water content with variable electrolyte concentration was measured to study the shape of the curves of the electric double layer capacitance versus frequency (from 10 KHz to 10 MHz. This was done in an attempt to find the lowest practical operating frequency for developing low cost dielectric constant soil moisture probes. Cellulose sponge was used as the porous media. A high frequency electronic bridge circuit was developed for measuring the equivalent network parallel resistance and capacitance of porous media. It appears that the effects of the electric double layer component of the total parallel network capacitance essentially disappear at operating frequencies greater than approximately 25 MHz at low electrolyte concentrations but are still important at 50 MHz at higher concentrations. At these frequencies, the double layer capacitance masks the diffusion region capacitance where true water content capacitance values reside. The general shape of the curve of volumetric water content versus porous media dielectric constant is presented, with an empirical equation representing data for this type of curve. It was concluded that the lowest frequency where dielectric constant values which represent true water content information will most likely be found is between 30 and 50 MHz at low electrolyte concentrations but may be above 50 MHz when the total electrolyte concentration is near the upper level required for most mesophyte plant nutrition.

• 한국방재안전학회논문집
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• 제10권1호
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• pp.61-66
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• 2017

지표투과레이다 탐사에 있어서 지하매질의 전기적 특성 파악은 매우 중요하다. 지하매질의 전기적 특성에 따라 전자기파의 에너지가 상대적으로 작아져 경계면으로부터 반사가 어려워 질수 있다. 이 연구에서는 다양한(느슨하고 조립한) 조건의 모래지반에 대한 전기적 특성을 분석 한 결과, 마른모래에서는 상대밀도가 증가할수록 유전상수는 증가하였으며, 모래의 함수율이 증가할수록 유전상수와 전기전도도의 값은 증가 하였다.

• 한국대기환경학회지
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• 제19권5호
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• pp.529-540
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• 2003

A closed chamber system was used for measuring $N_2$0 fluxes from an agriculturally managed upland soil in Kunsan during the growing season from May to July 2002. It is known that soil is one dominant source of atmospheric $N_2$O, contributing to about 57% (9 Tg y $^{-1}$ ) of the total annual global emission. Hence, its increasing emissions and concentrations are largely associated with agricultural activities. In order to elucidate characteristics of soil nitrogen emissions from intensively managed agricultural soils and to understand the roles of soil parameters (soil moisture, soil pH, soil temperature, and soil nitrogen) in the gas emission, $N_2$O soil emissions were measured at every hour during the experimental period (21 days). Soil $N_2$O fluxes were calculated based on changes of $N_2$O concentrations measured inside a closed chamber at every hour. The analysis of $N_2$O was made by using a Gas Chromatography (equipped with Electron Capture Detector). Soil parameters at sampling plots were also analyzed. Monthly averaged $N_2$O fluxes during May, June, and July were 0.14, 0.05, and 0.13 mg-$N_2$O m$^{-2}$ h$^{-1}$ , respectively. Soil temperature and soil pH did not significantly vary over the experimental period; soil temperatures ranged from 12∼$25^{\circ}C$, and soil pH ranged 4.56∼4.75. However, soil moisture varied significantly from 32% to 56% in WFPS. Relationships between soil parameters and $N_2$O fluxes exhibited positive linear relationships. Strong positive correlation ($R^2$ = 0.57, P< 0.0001) was found between $N_2$O flux and sil moisture. It suggests that soil moisture has affected strongly soil $N_2$O emissions during the experimental periods, while other parameters have remained relatively at constant levels. $N_2$O flux from agricultural soils was significant and should be taken account for the national emission inventory.

• 한국농공학회지
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• 제33권2호
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• pp.112-119
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• 1991

Some experiments were carried out to investigate the effects of freezing and thawing on the strength and strain characteristics of alluvial silty clay under the different temperatures, loading and moisture conditions. The results were as follows; 1. The soil used was proved to be consisted of silty clay with honey-combed structure, and showed higher dilatancy, frost activity and lower stability in natural state. 2. Soil treated with freezing and thawing cycles showed lower compressive strength compared with the non treated, The strength decreased with incement of freezing and thawing cycles. It's shapes of stress-strain curves were flat and did not formulate a peak while the peak strength of higher moisture content soil decreased with the increment of moisture content. It's decrement ratio was most distinctly shown at the first one cycle of freezing and thawing. 3. The cohesion decreased due to freezing and thawing cycles but internal frcition angle was not changed. 4. The liquid limit decreased with increment of freezing and thawing cycles, and became almost constant after three cycles of freezing and thawing. 5. The strength under simple loading at failure mode was appeared to be higher compared with the cyclic loading after freezing and thawing but initial moisture content effect was not observed. 6. Ice lense was not observed within 50% of ice content ratio but observed over 100%. The higher the ice content ratio, the higher the peak strength. As a matter of fact, it seems that an optimum ice content ratio exists for plastic mode and the least compressive strength.

• 환경생물
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• 제27권1호
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• pp.82-87
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• 2009

우리나라의 주요 우점종인 상수리나무, 굴참나무, 신갈나무의 생태적 특성을 밝히기 위하여 식물생장에서 가장 중요하다고 판단되는 광, 토양수분, 영양소를 이들 3종의 참나무 유식물에 각각 실내에서 처리하여 그 생육반응을 관찰하고, 분석하고자 시도하였다. 상수리나무와 굴참나무는 광이 높을수록 잘 자라는 경향이 있었고, 신갈나무만이 뚜렷한 경향이 없었다. 신갈나무는 낮은 광도에서도 생육이 크게 감소하지 않았다 굴참나무와 신갈나무는 수분구배에 따라 생육의 차이가 없었고, 상수리나무만이 약간 높은 구배에서 잘 자랐을 뿐이었다. 상수리나무, 굴참나무와 신갈나무 모두는 영양소가 적을 때 잘 자랐고, 높을수록 못 자랐다. 영양소 구배에 따른 감소정도는 굴참나무, 신갈나무, 상수리나무 순으로 낮았다. 이상으로 볼 때, 신갈나무는 피음조건에, 상수리나무는 토양이 다습한 조건에 그리고 굴 참나무는 유기물이 적은 조건에서 각각 적응한 종이라고 판단된다.

• Journal of the Korean Wood Science and Technology
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• 제26권4호
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• pp.43-49
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• 1998

The availability of large quantities of waste woods provides an impetus for investigating woody biomass potential uses. Polyurethane (PU) foams are prepared with reacting isocyanates and polyols, and are used. in various industry fields. Thus, lignocellulosic waste raw-materials are proposed as replacement for synthetic polyol to PU foam formulation. In this study PU foams were manufactured from liquefied woods, methanediisocyanate(MDI), catalyst, foaming stabilizer, and viscosity aids. The polyol content, isocyanate.hydroxyl group (NCO/OH) ratio, and water content were varied to evaluate their effects on the foaming and water absorption of the PU foams. Less than 400 Molecular weight. of polyethylene glycol(PEG) and 1 to 3 solvent to woody raw-material ratio were desirable for liquefying woody materials. Liquefying rate was increased with more than 3 % addition of inorganic and organic catalysts and raising reaction temperature more than $150^{\circ}C$. Addition of starch enhanced liquefying of woody materials. Fourty percents of starch resulted in about 90% liquefying rates. Foaming rates were increased with increasing moisture contents of liquefied wood. Moisture contents of 0.6% resulted in 5 time-foaming rates, and seven percents of moisture contents more than 30 time-foaming rates. But, an increase in water content may result in a decrease in cross-links between wood polyol and isocyanate, because the NCO/OH ratio is constant. Increasing moisture contents have significantly decreased density of PU foams. The optimum water content should be about 2.5% or less in this adopted condition.

• 한국환경과학회지
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• 제30권2호
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• pp.135-143
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• 2021

This study executed evaluation of drying characteristics based on the polymer injection rate (8%, 10% and 12%) and the drying method[NIF(near-infrared ray). According to this study analyzed VS, VS/TS, and calorific value compared with 'the auxiliary fuel standard of the thermoelectric power plant and the combined heat & power plant'. The results are as follows. In the case of NIR, the VS was slightly changed at the early stage of the material preheating period and the constant drying rate period with low moisture evaporation. But VS reduction was shown higher as moisture was dried. In the case of non-digested sludge with high VS content, the VS reduction rate by drying was shown lower than that of digested sludge. As the flocculant injection rate increased, the VS loss due th drying was found to be small. Also, the higher the flocculant injection rate was the longer the drying time. Especially, in the case of the NIR drying equipment, as the moisture content of sewage sludge decreased(moisture content 20~40%), the loss of net VS also showed a tendency to increase sharply. It is shown that the high calorific value according to the drying time of the non-digested sludge was changed from 590 kcaℓ/kg to 3,005 kcaℓ/kg and from 539 kcaℓ/kg to 2,796 kcaℓ/kg.

• 한국식품과학회지
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• 제27권3호
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• pp.428-438
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• 1995

Corn starch와 waxy corn starch를 사용하여 중간수분계의 수분함량으로 반죽을 제조하고 수분함량과 가열온도, 가열시간에 따른 전분 반죽의 호화양상을 밝혀 보고자 하였다. Corn starch와 waxy corn starch의 amylograph 호화 특성은 1% CMC를 첨가하여 측정한 호화개시 온도가 모두 약 $64^{\circ}C$로 나타났다. DSC특성은 corn starch호화 개시 온도가 $68.15^{\circ}C$, 최대호화온도가 $74.01^{\circ}C$, 호화종결 온도가 $85.65^{\circ}C$, 호화엔탈피는 3.2 cal/gram이었으며, waxy corn starch의 호화개시온도는 $68.24^{\circ}C$, 최대호화온도 $75.43^{\circ}C$, 호화종결온도 $93^{\circ}C$, 호화엔탈피는 4.2 cal/gram으로 나타났다. 수분함량$(X_1)\;36{\sim}52%)$, 가열온도$(X_2)\;60{\sim}100^{\circ}C$, 가열시간$(X_3)$ $0{\sim}2.0$분으로 가열시 corn starch와 waxy corn starch 반죽의 호화도(Y) 변화를 실험계획법으로 조사한 반응표면 회귀 방정식은 corn starch 반죽의 경우 $Y=28.659＋8.638\;X_1+15.675\;X_2+7.770\;X_3-1.620\;{X_1}^2+10.790\;X_1X_2-4.220\;{X_2}^2+0.510\;X_1X_3+1.980\;X_2X_3-6.850\;{X_3}^2$ $(R^2=0.9714)$ 이었고 waxy corn starch 반죽의 경우는 $Y=32.617+12.535\;X_1+20.470\;X_2+8.608\;X_3+4.093\;{X_1}^2+13.550\;X_1X_2-4.467\;{X_2}^2+1.560\;X_1X_3+2.160\;X_2X_3-9.527\;{X_3}^2$ $(R^2=0.9621)$이었다. 즉 수분함량과 가열온도, 가열시간이 증가할수록 반죽의 호화도는 모두 증가하는 경향을 나타내었고 같은 조건에서는 waxy corn starch가 corn starch 반죽보다 $10{\sim}20%$ 정도 더 호화되는 것을 알 수 있었다. Corn starch 와 waxy corn starch 반죽의 호화 속도를 보면 가열온도 $70^{\circ}C$와 $80^{\circ}C$에서는 가열시간 0.5분 이내에서 비교적 빠른 속도로 반죽이 호화되고 가열시간이 그 이상으로 증가할 때도 반죽의 호화가 약간은 진행되지만 $90^{\circ}C$ 이상의 가열온도에서는 가열시간 0.5분 이내에 반죽의 호화가 급속히 일어나고 가열 시간을 증가시켜도 더이상의 호화는 일어나지 않았다. 같은 조건에서는 waxy corn starch 반죽의 호화 속도가 corn starch보다 더 빠른 것으로 나타났다. 대표적으로 52% 수분함량에서 반응속도상수(k)와 가열온도(T)사이의 관계식은 corn starch의 경우 $logk=11.1140-4.1226{\times}10^3(1/T)$, waxy corn starch의 경우 $logk=10.1195-3.7090{\times}10^3(1/T)$이었다.