• Journal of the Korea Organic Resources Recycling Association
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• v.2 no.1
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• pp.87-98
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• 1994

Sludge minimization in an water treatment plant can be achieved by optimizing a main water treatment process as well as by enhancing a thickening and a dewatering facilities. In this study, dewatering and drying techniques for reducing the quantity of the water sludge generated from the conventional water treatment plant in the local states were investigated by reducing its water content. Not only the types and dosages of polymers but also the mixing intensity of the mixtures of a concentrated sludge and polymers on the different pH were evaluated for the optimum dewatering conditions of the water sludge. Weight reduction of the water sludge was also tested at a given temperature range. The dewatering efficiency of the water sludge was not affected by the types of polymer but by mixing intensity(GT value) in this study. pH effect on dewaterbility of the water sludge took a major role at the neutral pH range. The optimal polymer dose was 1.5 mg-polymer/g-TSS(about 40mg/L as polymer). Dewaterability was enhanced at a lower mixing intensity(GTbelow 10,000 sec-1). Free water in the void of sludge cake was dried around $100^{\circ}C$, chemical bound water was evaporated around $320^{\circ}C$, and organic material was burned out at the range of 300 to $600^{\circ}C$. Ignition losses of the water sludge were varied 15 to 40 % as the raw water quality. The ignition loss due to the chemical bound water was 10-20% and the loss due to the organic material was 4-20% of the total ignition loss.

• Solar Energy
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• v.17 no.4
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• pp.3-11
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• 1997

Because grain boundaries in polycrystalline silicon act as potential barriers and recombination centers for the photo-generated charge carriers, these defects degrade conversion effiency of solar cell. To reduce these effects of grain boundaries, we investigated various influencing factors such as thermal treatment, various grid pattern, selective wet etching for grain boundaries, buried contact metallization along grain boundaries, grid on metallic thin film. Pretreatment above $900^{\circ}C$ in $N_2$ atmosphere, gettering by $POCl_3$ and Al treatment for back surface field contributed to obtain a high quality poly-Si. To prevent carrier losses at the grain boundaries, we carried out surface treatment using Schimmel etchant. This etchant delineated grain boundaries of $10{\mu}m$ depth as well as surface texturing effect. A metal AI diffusion into grain boundaries on rear side reduced back surface recombination effects at grain boundaries. A combination of fine grid with finger spacing of 0.4mm and buried electrode along grain boundaries improved short circuit current density of solar cell. A ultra-thin Chromium layer of 20nm with transmittance of 80% reduced series resistance. This paper focused on the grain boundary effect for terrestrial applications of solar cells with low cost, large area, and high efficiency.

• Korean Journal of Food Science and Technology
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• v.50 no.3
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• pp.339-343
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• 2018

Effects of different drying processes, such as hot air drying (HA), superheated steam with hot air drying (SHS/HA), and superheated steam with far infrared radiation (SHS/FIR), on the properties of cherry tomatoes (Solanum lycopersicum var. cerasiforme) were studied. Characteristics of dried cherry tomatoes were determined by examining the water content, internal microstructure, and rehydration capacity under different drying processes. Moreover, ascorbic acid (AA) and lycopene levels were also measured to evaluate thermal damage caused by drying. Cherry tomatoes dried using both SHS/HA and SHS/FIR had water content and water activity similar to those of intermediate moisture food, indicating partial dehydration after combined drying processes. Although AA and lycopene levels decreased drastically after drying, tomatoes dried using SHS/FIR showed the lowest losses of AA and lycopene among samples. Cherry tomatoes dried using SHS/FIR showed a less compact internal cell structure than that of cherry tomatoes dried using HA and SHS/HA, resulting in the highest rehydration capacity. These results suggest that a combined drying process such as SHS/FIR is more effective than conventional hot air drying for the production of partially dried cherry tomatoes with improved quality attributes.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.4
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• pp.366-372
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• 1985

Soil temperatures and soil physical properties were investigated in order to better understand the effects of mulchings in the red pepper field. The red pepper was planted in the lysimeter installed at the Yesan sandy loam with 20% slope and 10cm slope length. The results were summarized as follows: 1. Average soil temperatures at 10cm and 20cm depth in vinyl mulching plots were $1.6^{\circ}C$ and $1.1^{\circ}C$ higher than those of control, respectively. However, the average soil temperatures in rice straw mulching plots were relatively lower than those of control during the growing season. 2. The greatest diurnal fluctuation of soil temperature was found at the vinyl mulching plots and it was decreased with increasing soil depth. 3. The calculated thermal diffusivities were 0.011, 0.009 and $0.007cm^2/sec$ for the vinyl mulching, control and straw mulching, respectively. 4. Soil losses were 103kg/10a for the vinyl mulching and 36kg/10a for the straw mulching which were nearly negligible as compared to the control. 5. Soil physical properties such as bulk density, hardness and water content were significantly improved by the vinyl and straw mulchings.

• Journal of the Korean Geotechnical Society
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• v.40 no.3
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• pp.77-84
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• 2024

Aging and damaged underground utilities cause cavity and ground subsidence under roads, which can cause economic losses and risk user safety. This study used infrared cameras to assess the thermal characteristics of such cavities and evaluate their reliability using a CNN algorithm. PVC pipes were embedded at various depths in a test site measuring 400 cm × 50 cm × 40 cm. Concrete blocks were used to simulate road surfaces, and measurements were taken from 4 PM to noon the following day. The initial temperatures measured by the infrared camera were 43.7℃, 43.8℃, and 41.9℃, reflecting atmospheric temperature changes during the measurement period. The RP algorithm generates images in four resolutions, i.e., 10,000 × 10,000, 2,000 × 2,000, 1,000 × 1,000, and 100 × 100 pixels. The accuracy of the CNN model using RP images as input was 99%, 97%, 98%, and 96%, respectively. These results represent a considerable improvement over the 73% accuracy obtained using time-series images, with an improvement greater than 20% when using the RP algorithm-based inputs.

• Korean Journal of Agricultural and Forest Meteorology
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• v.8 no.1
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• pp.1-9
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• 2006

Regardless of the recent observed warmer winters in Korea, more freeze injuries and associated economic losses are reported in fruit industry than ever before. Existing freeze-frost forecasting systems employ only daily minimum temperature for judging the potential damage on dormant flowering buds but cannot accommodate potential biological responses such as short-term acclimation of plants to severe weather episodes as well as annual variation in climate. We introduce 'dormancy depth', in addition to daily minimum temperature, as a complementary criterion for judging the potential damage of freezing temperatures on dormant flowering buds of grape vines. Dormancy depth can be estimated by a phonology model driven by daily maximum and minimum temperature and is expected to make a reasonable proxy for physiological tolerance of buds to low temperature. Dormancy depth at a selected site was estimated for a climatological normal year by this model, and we found a close similarity in time course change pattern between the estimated dormancy depth and the known cold tolerance of fruit trees. Inter-annual and spatial variation in dormancy depth were identified by this method, showing the feasibility of using dormancy depth as a proxy indicator for tolerance to low temperature during the winter season. The model was applied to 10 vineyards which were recently damaged by a cold spell, and a temperature-dormancy depth-freeze injury relationship was formulated into an exponential-saturation model which can be used for judging freeze risk under a given set of temperature and dormancy depth. Based on this model and the expected lowest temperature with a 10-year recurrence interval, a freeze risk probability map was produced for Hwaseong County, Korea. The results seemed to explain why the vineyards in the warmer part of Hwaseong County have been hit by more freeBe damage than those in the cooler part of the county. A dormancy depth-minimum temperature dual engine freeze warning system was designed for vineyards in major production counties in Korea by combining the site-specific dormancy depth and minimum temperature forecasts with the freeze risk model. In this system, daily accumulation of thermal time since last fall leads to the dormancy state (depth) for today. The regional minimum temperature forecast for tomorrow by the Korea Meteorological Administration is converted to the site specific forecast at a 30m resolution. These data are input to the freeze risk model and the percent damage probability is calculated for each grid cell and mapped for the entire county. Similar approaches may be used to develop freeze warning systems for other deciduous fruit trees.