• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.23 no.1
• /
• pp.32-37
• /
• 2014

Open-cell silicon foam is difficult to cut using conventional machining processes because of its low stiffness. That is, open-cell silicon foam is easily pressed down when the tool is engaged, which makes it difficult to remove the material in the form of chip. This study proposes an advanced method of machining open-cell silicon foam by freezing the material using liquid nitrogen. Furthermore, the machining conditions are optimized to maximize the efficiency of material removal and minimize the usage of liquid nitrogen by conducting experiments under various machining conditions. The results show that open-cell silicone foam products with free surface can be successfully machined by employing the proposed method.

• Journal of Hydrogen and New Energy
• /
• v.29 no.5
• /
• pp.466-472
• /
• 2018

The investigation of cryogenic liquid pool spreading is an essential procedure to assess the hazard of cryogenic liquid usage. In this experimental study, to measure the evaporation velocity when the pool is spreading, liquid nitrogen was continuously released onto unconfined concrete ground. Almost all of the reported results are based on a non-spreading pool in which cryogenic liquid is instantaneously poured onto bounded ground for a very short period of time. A simultaneous measurement of the pool location using thermocouples and of the pool mass using a digital balance was carried out to measure the evaporation velocity and the pool radius. A greater release flow rate was found to result in a greater average evaporation velocity, and the evaporation velocity decreased with the spreading time and the pool radius.

• Korean Journal of Soil Science and Fertilizer
• /
• v.36 no.5
• /
• pp.344-355
• /
• 2003

Korea is one of those countries that have very high usage rates of chemical fertilizers per unit area of cropland. To reduce the fertilizer application rate, a variety of agricultural polices has been introduced since the 1990s. In this study, fertilizer usage was surveyed on the farm base throughout the country in 1999, and the data were compared with those of 1992. Organic fertilizer application rates were decreased in most cereal crops with time pass, but maintained similar levels in vegetables grown in plastic-film houses and in upland soils. Chemical fertilizer application rates were decreased in most of the cereal crops and vegetables surveyed; however, this reduction was concentrated in phosphate and potassium usage, but not in nitrogen. In spite of this decrease, the fertilizer application levels to most crops were maintained at levels much higher than recommended. In the nutrient balance, which was calculated from the difference between input (chemical and organic fertilizers) and output (agricultural products), the nitrogen nutrient surplus did not decrease; however, phosphate and potassium decreased by 21% and 13%, respectively, in 1999 compared with 1992. To reduce fertilizer utilization and to conserve environment, further reduction of fertilizer application is essential.

• Journal of IKEEE
• /
• v.24 no.3
• /
• pp.913-916
• /
• 2020

In this paper, we propose the development of nitrogen cooling equipment for personalized local area. The proposed equipment consists of a cold air supply module, a body, and nitrogen injection with the following characteristics. First, it automatically controls the amount and time of cold air supply by utilizing information measuring skin temperature with volumetric temperature sensors, so it can have a competitive edge in function by ensuring complete safety. Second, if the distance measuring sensor is applied to the skin for more than a certain distance, it can block the cold air or control the discharge of nitrogen in conjunction with the control GUI to improve the efficiency of higher cooling therapy while providing safe management. Third, by installing a control module that can control the supply of nitrogen, the cost of maintenance can be minimized by minimizing the loss of nitrogen. Experiments at an external testing agency to evaluate the performance of the proposed equipment showed that the accuracy of the temperature sensor was measured in the range of ±3.8%, which is lower than the world's highest level(±5%), with a range of 110℃ to -160℃ similar to the world's highest level. Distance accuracy was measured in the range of ±3.0%, lower than the world's highest level(±5%), and weight accuracy in the range of ±0.1%, lower than the world's highest level(±5%). In addition, emission control was measured in four stages, higher than the world's highest level(stage 1) and nitrogen use was measured at 0.8L/min below the world's highest(6L/min). Therefore, the effectiveness of the methods proposed in this paper was demonstrated because they produced the same results as the world's highest levels.

• Korean Journal of Pharmacognosy
• /
• v.23 no.2
• /
• pp.89-95
• /
• 1992

The water extract of Gamidaebo-Tang depressed the lethal toxicity of cis-platin$(45{\mu}M/kg,\;s.c.)$, and mitomycin C (6mg/kg, s.c.). Significant depression of renal toxicity(indicated by an increased blood urea nitrogen value and creatinine value) of cis-platin $(35{\mu}M/kg)\;s.c.)$, was observed in mice treated with Gamidaebo-Tang. In rats treated with mitomycin C and Gamidaebo-Tang, the increased LDH activity and reduced total protein and albumin contents by mitomycin C were significantly depressed. The number of WBC was significantly increased in rats treated with mitomycin C but in the rats treated with mitomycin C and Gamidaebo-Tang, the number of WBC was increased and the hematocrit value and the number of RBC and Hgb were significantly increased in the dose-dependent manner. Therefore, bone marrow toxicity of mitomycin C in the rats treated with Gamidaebo-Tang was depressed. In the end, alleviative effects of the side actions of cis-platin and mitomycin C were acknowledged by combined usage of Gamidaebo-Tang and these anti-neoplastic drugs.

• Journal of environmental and Sanitary engineering
• /
• v.17 no.2
• /
• pp.85-91
• /
• 2002

Workers who work at indoor and outdoor environment near busy road are suspected to be exposed to high-elevated air pollutant levels during working hours. This study evaluated the working-time nitrogen dioxide ($NO_2$) exposure for workers (repairmen and polishers) of shoe-stalls. Since shoe-stalls have particularly been located near busy road in Korea, workers might be high exposure to $NO_2$ from traffic exhaust as well as indoor sources of shoe-stall such as portable gas range (butane gas) during working hours. In this study, we measured the indoor and outdoor $NO_2$ concentrations of shoe-stalls. Simultaneously, outdoor $NO_2$ concentrations of building through sidewalk from shoe-stall were measured. High $NO_2$ exposure for workers of shoe-stalls was considered to be inflow of outdoor source of exhausted emission from vehicles and indoor source from usage of gas range to polish the shoe. Indoor/outdoor $NO_2$ concentration ratio ($0.94{\pm}0.22$) in Seoul was higher than that ($1.06{\pm}0.34$) in Asan, because ambient $NO_2$ level was high in Seoul and usage of gas range was prevalent in Asan. According to $NO_2$ concentrations by distance from roadside to building through sidewalk, $NO_2$ concentrations showed the decreased trend with distance. The results of this study can be utilized by municipal authorities in urban planning for evaluating effects of future traffic planning and land use.

• Journal of environmental and Sanitary engineering
• /
• v.20 no.4 s.58
• /
• pp.69-75
• /
• 2005

Professional taxi driver exposure to indoor air pollutants has been a subject of concern in recent years because of higher levels of air pollutants, comparing to the surrounding atmosphere. This study evaluated the potential exposure to respirable suspended particulate (RSP), nitrogen dioxide $(NO_2)$ and volatile organic compounds (VOCs; benzene and toluene) for professional taxi drivers inside each of 10 vehicles in Pusan, comparing weekday (Monday and Thursday) and weekend (Saturday). Indoor mean concentrations of RSP inside vehicle were $53.88\;ug/m^3\;and\;75.52\;ug/m^3$ on weekday and weekend, respectively. Measured indoor $NO_2$ concentrations were 28.32ppb and 40.69 ppb, respectively. Benzene and toluene mean concentrations inside vehicle were 5.41 ppb and 11.36 ppb, respectively. Considering no smoking of taxi drivers inside vehicle, closed window in winter, and increased usage of taxi on weekend, source of indoor air pollutants inside taxi might be mainly suggested from the number of passenger's carried, faulty exhaust systems, and engine and carburetor evaporative emissions.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.25 no.3
• /
• pp.143-150
• /
• 2005

These experiment was conducted to determine the effect of nitrogen fertilizer levels and mixture small grains on productivity and quality of spring forage rape at south region of Korea(Mokpo). The experiment was arranged in a split plot design with three replications. The main plots consisted of three different levels of nitrogen fertilizer(100, 150 and 200 kg/ha). The sub plots consisted of five kinds of mixed small grain species(Rye, Oat, Barley, Italian ryegrass, and Rape monoculture). The results obtained are summarized as follow. Dry matter(DM) content of Rye + Rape and Ba.ley + Rape mixtures were increased by $2\~3\%$ compared to Rape monoculture. The high level of nitrogen application increased the fresh matter yield, and yield of Rye + Rape and Rape monoculture were higher than that of others. Dry matter yield of Rye + Rape mixture and Rape monoculture with 200kg/ha of nitrogen application were higher by 9,449 and 9,227 kg/ha, respectively. The crude protein(CP) content of rape was high as $18.6\%$ while average CP content was $16\%$. The average total digestible nutrient(TDN) content showed high as $70\%$. It is suggested the Rye + Rape mixture or Rape monoculture would recommendable for spring usage of rape at south region of Korea.

• Journal of environmental and Sanitary engineering
• /
• v.14 no.4
• /
• pp.85-92
• /
• 1999

Indoor air quality tends to be the dominant contributor to personal exposure because most people spend over 90% of their time indoors. For some contaminants, exposure to indoor air poses a potentially greater health threat than outdoor air exposures. Indoor nitrogen dioxide ($NO_2$) levels are mainly affected gas range, flue gas spillage, kerosene heaters, wood-burning appliances and cigarette smoke. In addition, indoor $NO_2$ levels are influenced by such house characterization as surface reaction and air exchange rate. In this study, the measurements of indoor and outdoor $NO_2$ concentrations were taken using identical protocols, and information was collected on housing characteristics using identical questionnaires in 14 houses out of 15 houses for daily 30 daily 30 days in Brisbane, Australia.The usage of gas range was the most contributing factor in indoor $NO_2$ concentration in relation to house characteristics. Average indoor and outdoor ratios of NO2 concentration in electronic and gas cooking houses were $0.6{\pm}0.1$ and $0.9{\pm}0.2$, respectively. The frequency distributions of $NO_2$ concentration in each house were approximately log-normal Geometric mean of indoor $NO_2$ concentrations of electronic and gas cooking houses for daily 30 days ranged from 2.5 ppm to 11.5 ppm with a mean 6.8 and from 4.7 ppm to 28.6 ppm with a mean 15.6 ppm, respectively. The $NO_2$ concentrations between electronic and gas cooking houses were significantly different (p<0.05). Since each house has different life-style and house characteristics, sampling interval to measure the $NO_2$ levels was recommended above 7 days.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.9 no.3
• /
• pp.93-103
• /
• 2001

Once of recent issue in the leather industry is disposal of shaving scrap containing chromium. Shaving scrap is indispensible generated by control of the final thickness in the leather making process. It is the flesh layer of the skin consisting mainly of collagen. More recently, we have tried to improve the quality of the isolated gelatin. The purpose of this research was to extract gelatin for agricultural usage. As a result, it does not contain Cr and could obtained to a good gelatin that have more than 130,000Da. average molecular weight, more than 30 mps viscosity and more than 100g jelly strength. Gelatin that is extracted by alkaline condition expected to be available to high performance gelatin such as material of organic fertilizer(ex, Nitrogen-release fertilizer).