• 농업과학연구
• /
• 제45권4호
• /
• pp.811-821
• /
• 2018

This study focused on the improvement of blueberry delivery service using pre-cooled ice and $SO_2$ pads to prevent an increase in the fruit temperature as well as decay. To maintain the fruit quality during low temperature storage, the effect of a $SO_2$ pad and modified atmosphere packaging was also examined. Harvested blueberries were precooled at $15^{\circ}C$, sorted, and packaged. And the fruits were placed in a similar environment as that for the parcel service. Part of the fruits were stored at $0^{\circ}C$ for long term storage. The air temperature in the delivery box increased along with an increase in the simulated delivery time regardless of the treatment. However, the rate of temperature increase was lower in the ice pad treatment. No significant difference was not found after 48 h. The oxygen concentration in the box ranged between 10.5 - 14.5% in the ice pad treatment, which was higher than that of the untreated control (7.5 - 11.9%) whereas the $CO_2$ concentration was lower in the ice pad treatment. No differences were found in the occurrence of off-flavor, decay, and sensory quality loss during the 48 hours of the parcel service simulation. The combined treatment of the $SO_2$ pad and modified atmosphere packaging (MAP) using a perforated film increased the shelf-life of the blueberry fruits, the overall quality such as firmness, and the soluble solid content was not different between the treatments except for the decay incidence. No decayed fruit was found in the combined treatment. However, the percentage of decayed fruit in the control was 25% on day 15 of storage and 75% on day 33 of storage, respectively.

• 한국환경과학회:학술대회논문집
• /
• 한국환경과학회 2003년도 봄 학술발표회 발표논문집
• /
• pp.155-160
• /
• 2003

Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Although technologies exist to measure these factors, direct measurements are often difficult. The purpose of this study was to develop an alternative method to characterize indoor environmental factors by multiple indoor and outdoor measurements. Daily indoor and outdoor $NO_2$ concentrations were measured for 30 consecutive days in 28 houses in Brisbane, Australia, and for 21 consecutive days in 37 houses in Seoul, Korea. Using a mass balance model and regression analysis, penetration factor (ventilation rate divided by the sum of ventilation rate and deposition constant) and source strength factor (source strength divided by the sum of ventilation rate and deposition constant) were calculated using multiple indoor and outdoor measurements. Subsequently, the ventilation rate and $NO_2$ source strength were estimated. Geometric means of ventilation rate were 1.44 ACH in Brisbane, assuming a residential $NO_2$ deposition constant of 1.05 $hr^{-1}$, and 1.36 ACH in Seoul, with the measured residential $NO_2$ deposition constant of 0.94 $hr^{-1}$. Source strengths of $NO_2$ were 15.8 $\pm$ 18.2 ${\mu}g$/$m^3$.hr and 44.7 $\pm$ 38.1${\mu}g$/$m^3$.hr in Brisbane and Seoul, respectively. In conclusion, indoor environmental factors were effectively characterized by this method using multiple indoor and outdoor measurements.

• 대한치과교정학회지
• /
• 제27권6호
• /
• pp.943-954
• /
• 1997

교정적인 치아이동에 필요한 힘들은 orthodontic wire나 여러 가지 elastic rubber등으로 얻을 수 있다. 이중 교정용 elastic rubber는 환경 변화, 시간 경과, 신장(stretch) 정도에 따라 영구 변형과 힘의 소실(force decay)이 다양하게 나타나므로 적용된 힘을 예측하기 힘든 단점이 있다. 본 연구에서는 임상에서 널리 사용되는 3가지 종류 (Ormco : Generation II Power Chains ; brand A, RMO : Energy-Chain ; brand B, Unitek : AlastiK ; brand C)의 교정용 합성고무탄성재를 실험 환경, 초기 힘의 크기, 고무탄성재의 형태 그리고 신장속도를 달리한 뒤 시간에 따른 잔존 힘의 변화를 비교하였으며, 종류에 따른 특징적인 물리적 성질에 대하여 다음과 같은 결론을 얻었다. 1. 세 종류 모두에서 상온의 공기에 보관된 경우 잔존 힘의 비율이 가장 컸으며 물과 타액 간에는 차이가 없었다. 2. 세 종류 모두에서 24시간 이후로는 초기 힘의 크기에 따른 잔존 힘의 비율에 차이가 없었다. 3. A, B는 filament 유무에 따른 잔존 힘의 비율에 차이가 없었으나 C에서는 filament가 있는 경우 힘의 소실이 더 많았다. 4. 신장속도를 달리하여도 잔존 힘의 비율에는 큰 차이가 없었다. 5. B는 각각의 실험조건에서 A, C보다 상대적으로 잔존 힘의 비율이 높았다.

• 대한산업공학회지
• /
• 제20권3호
• /
• pp.117-124
• /
• 1994

In this paper an inventory model is presented for determining the ordering schedule in which the demand rate is changing linearly with time and the decay is assumed to be a constant rate of the on-hand inventory. An easy to use heuristic is developed to find the times and sizes of replenishments so as to keep the total of ordering, inventory carrying and deteriorating costs as low as possible. Solutions of the model to test problems show that our heuristic model outperforms other existing models in the literature without sacrificing the computational complexity. When there is no deterioration, the model developed is related to the corresponding model of nondeteriorating items.

• 한국환경보건학회:학술대회논문집
• /
• 한국환경보건학회 2004년도 International Conference Current Challenges and Advances in Environmental Health
• /
• pp.45-50
• /
• 2004

Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Alt hough technologies exist to measure these factors, direct measurements are often difficult. The purpose of this study was to develop an alternative method to characterize indoor environmental factors by multiple indoor and outdoor measurements. Daily indoor and outdoor NO2 concentrations were measured for 30 consecutive days in 28 houses in Brisbane, Australia, and for 21 consecutive days in 37 houses in Seoul, Korea. Using a mass balance model and regression analysis, penetration factor (ventilation rate divided by the sum of ventilation rate and deposition constant) and source strength factor (source strength divided by the sum of ventilation rate and deposition constant) were calculated using multiple indoor and outdoor measurements. Subsequently, the ventilation rate and NO2 source strength were estimated. Geometric means of ventilation rate were 1.44 ACH in Brisbane, assuming a residential NO2 deposition constant of 1.05 hr-1, and 1.36 ACH in Seoul, with the measured residential NO2 deposition constant of 0.94 hr-1. Source strengths of N02 were 15.8 ${\pm}$ 18.2 ${\mu}$g/m3${\cdot}$hr and 44.7 ${\pm}$ 38.1 ${\mu}$g/m3${\cdot}$hr in Brisbane and Seoul, respectively. In conclusion, indoor environmental factors were effectively characterized by this method using multiple indoor and outdoor measurements.

• 한국환경과학회지
• /
• 제17권10호
• /
• pp.1069-1073
• /
• 2008

Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Although technologies exist to measure these factors, direct measurements are often difficult. The purpose of this study was to develop an alternative method to characterize indoor environmental factors by multiple indoor and outdoor measurements. Using a mass balance model and regression analysis, penetration factor (ventilation rate divided by the sum of ventilation rate and deposition constant) and source strength factor (source strength divided by the sum of ventilation rate and deposition constant) were calculated using multiple indoor and outdoor measurements. Subsequently, the ventilation rate and $NO_2$ generation rate were estimated. Mean of ventilation rate was 1.41 ACH in houses, assuming a residential N02 deposition constant of 0.94 $hr^{-1}$. Mean generation rate of $NO_2$ was 16.5 ppbv/hr. According to house characterization, inside smoking and family number were higher $NO_2$ generation rates, and apartment was higher than single-family house. In conclusion, indoor environmental factors were effectively characterized by this method using multiple indoor and outdoor measurements.

• Bulletin of the Korean Chemical Society
• /
• 제12권5호
• /
• pp.569-574
• /
• 1991

Methyl red diffusion in polymer solutions was studied by a transient holographic method, forced Rayleigh scattering. In semi-dilute solutions of a polystyrene, where no specific interaction with the probe exists, we found within experimental uncertainty that the retardation of diffusion rate of methyl red is independent of the solvents used. This indicates that the hydrodynamic interaction in polymer coils is not affected by the nature of solvents enough to exhibit a detectable change in the diffusion rate of the probe. On the other hand, a substantial reduction of diffusion rate was observed in poly(methyl methacrylate) solutions in toluene. Together with the similar observation reported with poly(vinyl acetate), it is confirmed that hydrogen bond between the probe and the polymer is responsible for the retarded diffusion. The decay-growth-decay profile found in this system reveals a finite difference in diffusion coefficients of cis and trans isomer of methyl red. We estimate the difference and suggest that the cis isomer interacts with the polymer more strongly than the trans isomer.

• The Korean Journal of Ecology
• /
• 제27권2호
• /
• pp.115-120
• /
• 2004

Coarse woody debris (CWD, $\ge$ 5 cm in maximum diameter) is an important functional component, especially to nutrient cycling in forest ecosystems. To compare mass and nutrient dynamics of CWD in natural oak forests, a two-year study was conducted at Quercus serrata and Q. variabilis stands in Yangpyeong, Kyonggi Province. Total CWD (snag, stump, log and large branch) and annual decomposition mass (Mg/ha) were 1.9 and 0.4 for the Q. serrata stand and 7.5 and 0.5 for the Q. variabilis stand, respectively. Snags covered 72% of total CWD mass for the Q. variabilis stand and 42% for the Q. serrata stand. Most of CWD was classified into decay class 1 for both stands. CWD N and P concentrations for the Q. variabilis stand significantly increased along decay class and sampling time, except for P concentration in 2002. There were no differences in CWD N concentration for the Q. serrata stand along decay class and sampling time. However, CWD P concentration decreased along sampling time. CWD N and P contents (kg/ha) ranged from 3.5∼4.7 and 0.8∼1.3 for the Q. serrata stand to 22.8∼23.6 and 3.7∼4.7 for the Q. variabilis stand. Nitrogen and P inputs (kg/ha/yr) into mineral soil through the CWD decomposition were 0.7 and 0.3 for the Q. serrata stand and 1.6 and 0.3 for the Q. variabilis stand, respectively. The number of CWD and decay rate were main factors influencing the difference in CWD mass and nutrient dynamics between both stands.

• 한국표면공학회지
• /
• 제51권1호
• /
• pp.79-85
• /
• 2018

We systematically investigated the optical properties of sub-micron sized methylammonium lead tribromide ($CH_3NH_3PbBr_3$) cubes in the range of 100 to 700 nm, which were prepared by a surfactant-free precipitation method. We found that despite the strong absorbance, their photoluminescence quantum yield (PLQY) is very low as 0.009~0.011 % for whole range of sizes. Surfactant-free synthesis approach results in nanocubes that has no surface passivating reagents (e.g. surfactants) on their surface. As-prepared particles contain a large number of surface defects that may cause the low PLQY. The role of the surface defects were investigated in their photoluminescence decay process, which can be correlated with the particle size. Larger particles are characterized by a slower decay rate compared to smaller particles due to a large number of surface defects in the smaller particles that trap more excitons in the fluorescence decay process. These experimental results provide new insights into the fundamental relationship between surface state and optical properties.

• 대한의용생체공학회:의공학회지
• /
• 제13권3호
• /
• pp.245-252
• /
• 1992

Air pressure decay (APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those reused in patients several times. C-DAK 4000 (Cordis Dow) and CF 15-11 (Baxter Travenol) reused dialyzers obtained (rom the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAK dialyzers had a larger APD($11.70{\pm}1.32$mmHg/min) compared to CF dialyzers($4.32{\pm}0.55$mmHg/min) (p<0.05). However, there was no observable difference in the UFR between the two dialyzers. Neither APD nor UFR showed any significant increase with an increasing number of reuses for up to more than 20reuses. A substantial number of failures observed in APD(larger than 20mmHg/min)on the reused dialyzers(2 out of 40 CF and 5 out 26 C DAK) were attributed to the possible damage on the fibers. The CF 15-11 HFDs which failed APD test did not show changes in the UFR compared to normal dialyzers indicating that APD Is a more son sitive test than UFR test to evaluate the integrity of the fibers.