• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.815-820
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• 2010

Fuel spray characteristics of the gasoline engine injector has been studied experimentally. Wall wetting fuel stream of the 4-hole and 12-hole injectors has been tested and measured with various installation angle and port masking shapes. Spray visualization has been performed to analyze spray formation, spray angle, and penetration length. Test result shows that wall wetting is greatly influenced by the induction air flow and injector installation angle. Wall wetting amount decreased as injector installation angle decreased. Masking decreased wall wetting amount by increasing local intake-air flow velocity due to the decreased section area. Spray visualization showed that the 12-hole injector has robust performance characteristics compared with the 4-hole injector.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.115-121
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• 2008

A core engine for pre-cooled turbojet engines is designed and its component performances are examined both by CFD analyses and experiments. The engine is designed for a flight demonstration of precooled turbojet engine cycle. The engine uses gas hydrogen as fuel. The external boundary including measurement devices is set within $23cm{\times}23cm$ of rectangular cross section, in order to install the engine downstream of the air intake. The rotation speed is 80000 rpm at design point. Mixed flow compressor is selected to attain high pressure ratio and small diameter by single stage. Reverse type main combustor is selected to reduce the engine diameter and the rotating shaft length. The temperature at main combustor is determined by the temperature limit of non-cooled turbine. High loading turbine is designed to attain high pressure ratio by single stage. The firing test of the core engine is conducted using components of small pre-cooled turbojet engine. Gas hydrogen is injected into the main burner and hot gas is generated to drive the turbine. Air flow rate of the compressor can be modulated by a variable geometry exhaust nozzle, which is connected downstream of the core engine. As a result, 75% rotation speed is attained without hazardous vibration and heat damage. Aerodynamic performances of both compressor and turbine are obtained and evaluated independently.

• Journal of Animal Science and Technology
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• v.45 no.6
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• pp.1061-1066
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• 2003

The present study was performed to investigate the effect of ozonation of the swine nursery building on indoor air quality and growth efficiency of the weanling piglets. Forty 21-day-old, cross-bred weanling piglets were housed in two ozonated or unozonated pens(10 males and 10 females per pen) for 3 wk alternately in a swine nursery building and this procedure was repeated three times. Ozone was generated using a commercial apparatus outside the nursery building and infused into the nursery building through a duct at a level of 0.03 ppm. Indoor concentrations of harmful gases were measured at 2-h intervals for a 24-h period per each 3-wk feeding trial. Indoor ammonia and carbon dioxide gas concentrations were reduced by the ozonation(P〈0.01) by 21% and 7%, respectively, compared with those of the control(unozonation), although hydrogen sulfide concentration was not affected by the treatment. However, the weight gain, feed intake and feed/gain of the piglets did not change due to the ozonation. Results suggest that ozonation of the swine nursery building is effective for improving the indoor air quality without affecting the production efficiency of weanling piglets.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2003.05a
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• pp.148-148
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• 2003

This study is to investigate the environmental levels and trend of dioxins, which was the 3$\^$rd/ year of environmental monitoring research for endocrine disrupting chemicals since 1999. Total 282 samples were analyzed from 115 sites including 26 sites of airs, 43 sites of waters, 11 sites of sediments and 35 sites of soil, which were the same as those of investigated sites in 2000. Sampling period was from June 2001 to June 2002. Target chemicals were seventeen species of 2,3,7,8-chlorine-substituted PCDD and PCDF congeners and were analyzed by the standard methods, established by National Institute Environmental Research (NIER). The average concentration of dioxins in air decreased from 0.324 pg-TEQ/N㎥ in 2000 to 0.287 pg-TEQ/N㎥ in 2001, and those in water and soil were 0.073pg-TEQ/L and 1.703pg-TEQ/dry g, respectively, which was the less values detected in 2000. In sediment, however, the value was 0.086pg-TEQ/dry g, which was the increase from the value of the year 2000. The concentration range of dioxins in air for 26 sites in 17 regions detected were 0.013∼l.664pg-TEQ/N㎥, 4 sites from those were exceeded the Air Quality Standards of Dioxin in Japan (0.6 pg-TEQ/N㎥). The tolerable daily intake of dioxins was calculated at the highest level (1.664) in air, with referring the soil and food data from Japan, was calculated to be 2.85pg-TEQ/kg/day, which was below the level of 4 pg-TEQ/kg/day suggested in KFDA(Korea). While the average concentration of dioxins in 15 big cities was 0.190 pg-TEQ/N㎥, that in 8 medium/small cities constituting an industrial complex was 0.558 pg-TEQ/N㎥. In water, the concentration range detected were 0∼0.946pg-TEQ/L and the trend of the average concentrations shows an increase from those of 1999 but decreased from those of 2000, any sites however were not exceeded the Water Quality Standards of Dioxin in Japan (1 pg- TEQ/L). In soil. the detected range were 0∼43.333 pg-TEQ/dry g and the average concentration decreased, compared with the results of 2000. According to the monitoring results by land utilization, the detected range were 0∼43.333pg-TEQ/dry g in farmland, 0.017∼0.601 pg-TEQ/dry g in the industrial area, 0.005∼0.049pg-TEQ/dry g in the park and 0.008∼1.825 pg-TEQ/dry g in the rest. In sediment, the detected range increased from 0∼0.244 pg-TEQ/dry g to 0∼0.537 pg-TEQ/dry g, based on the results of 2000. For the proper control of dioxins, continuous monitoring needs to be performed and in addition, the dioxin inventory should be prepared for major sources through the dioxin emission survey. These results would provide sound and solid basis for proper decision making of dioxins management like establishment of environmental quality standards in Korea.

• Speech Sciences
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• v.10 no.3
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• pp.7-27
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• 2003

Esophageal Speech uses the esophageal air during phonation. Fluent esophageal speakers frequently intake air in oral communication, but unskilled esophageal speakers are difficult with swallowing lots of air. The purpose of this study was to investigate the difference of acoustic characteristics of vowel and consonants production according to the speech proficiency level in esophageal speech. 13 normal male speakers and 13 male esophageal speakers (5 unskilled esophageal speakers, 8 skilled esophageal speakers) with age ranging from 50 to 70 years old. The stimuli were sustained /a/ vowel and 36 meaningless two syllable words. Used vowel is /a/ and consonants were 18 : /k, n, t, m, p, s, c, $C^{h},\;k^{h},\;t^{h},\;p^{h}$, h, I, k', t', p', s', c'/. Fundermental frequency (Fx), Jitter, shimmer, HNR, MPT were measured with by electroglottography using Lx speech studio (Laryngograph Ltd, London, UK). 36 meaningless words produced by esophageal speakers were presented to 3 speech-language pathologists who phonetically transcribed their responses. Fx, Jitter, HNR parameters is significant different between skilled esophageal speakers and unskilled esophageal speakers (P<.05). Considering manner of articulation, ANOVA showed that differences in two esophageal speech groups on speech proficiency were significant; Glide had the highest number of confusion with the other phoneme class, affricates are the most intelligible in the unskilled esophageal speech group, whereas in the skilled esophageal speech group fricatives resulted highest number of confusions, nasals are the most intelligible. In the place of articulation, glottal /h/ is the highest confusion consonant in both groups. Bilabials are the most intelligible in the skilled esophageal speech, velars are the most intelligible in the unskilled esophageal speech. In the structure of syllable, 'CV+V' is more confusion in the skilled esophageal group, unskilled esophageal speech group has similar confusion in both structures. In unskilled esophageal speech, significantly different Fx, Jitter, HNR acoustic parameters of vowel and the highest confusions of Liquid, Nasals consonants could be attributed to unstable, improper contact of neoglottis as vibratory source and insufficiency in the phonatory air supply, and higher motoric demand of remaining articulation due to morphological characteristics of vocal tract after laryngectomy.

• Journal of Energy Engineering
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• v.28 no.4
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• pp.35-41
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• 2019

In order to overcome these disadvantages, the halogen light source, which was previously used as a vehicle fog light, has increased power consumption and a short lifetime, and thus, an automobile light source is gradually being replaced with an LED. However, when the vehicle LED fog light is turned on, there is a disadvantage in reducing the life of the fog lamp due to the high heat generated from the LED. The heat generated by the LED inside the fog lamp is mainly emitted by the heatsink, but most of the remaining heat is released to the outside through convection. When cooling efficiency decreases due to convection, thermal energy generates heat to lenses, reflectors, and bezels, which are the main parts of lamps, or generates high temperatures in LED, thereby shortening the life of LED fog lights. In this study, we tried to improve the heat dissipation performance by convection in addition to the heat dissipation method by heat sink, and to determine the installation location of vents that can discharge the internal air or intake the external air of LED fog lamp for vehicle. Thermal fluid analysis was performed to ensure that the optimal data were reflected in the design. The average velocity of air increased in the order of Case3 and Case2 compared to Case1, which is the existing prototype, and the increase rate of Case3 was relatively higher than that of other cases. This is because the vents installed above and below the fog lamps induce the convective phenomena generated according to the temperature difference, and the heat is efficiently discharged with the increase of the air speed.

• Journal of Animal Environmental Science
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• v.9 no.1
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• pp.27-34
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• 2003

This experiment was carried out to investigate the effect of dietary supplementation of fermented microbial complex(Eco-Farm$^{(R)}$) on performance of finishing pigs and indoor air quality in finishing building. A total 135 crossbred [(Landrace ${\times}$ Yorkshire) ${\times}$ Duroc] pigs were randomly arranged into nine groups and assigned to three treatments. Pigs were fed a basal diet supplemented with 0, 0.5 and 1% level of fermented microbial complex(Eco-Farm$^{(R)}$) until the market weight for 40 days of the experimental period. Average daily feed intake and feed conversion ratio were significantly improved (p<0.05) with dietary supplementation of 0.5% fermented microbial complex (Eco-Farm$^{(R)}$): however, average daily gain was not affected by dietary supplementation of fermented microbial complex(Eco-Farm$^{(R)}$). Indoor ammonia and hydrogen sulfide concentrations in the finishing building were significantly(p<0.05) decreased by dietary supplementation of fermented microbial complex(Eco-Farm$^{(R)}$) compared with those of control, however, indoor carbon dioxide concentration was not affected by dietary supplementation of fermented microbial complex(Eco-Farm$^{(R)}$). In conclusion, the results obtained from this experiment suggest that the dietary supplementation of fermented microbial complex(Eco-Farm$^{(R)}$) for finishing pigs improved performance and indoor air quality in the finishing building.hing building.

• Journal of Environmental Health Sciences
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• v.48 no.2
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• pp.75-85
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• 2022

Background: Various types of semi-volatile organic compounds (SVOCs) exist in the public's living environment. They occur in different forms in terms of their physical and chemical properties and partition coefficients. As a consequence, indoor exposure to SVOCs occurs via various routes, including inhalation of air and airborne particles, skin contact, and dust intake. Objectives: To propose a method for assessing human exposure to the SVOCs occurring in the air of an indoor environment, the concentrations of SVOCs in house dust and organic films measured in a real residential environment were estimated in terms of gas-phase concentration using the partition coefficient. Assessment of inhalation exposure to SVOCs was performed using this method. Methods: Phthalates were collected from samples of house dust and organic films from 110 households in a real residential environment. To perform an exposures assessment of the phthalates present in organic films, gas-phase concentration was calculated using the partition coefficient. The airborne gas-phase concentrations of phthalates from the house dust and organic films were estimated and exposure assessment was performed based on the assumption of inhalation exposure from air. Results: As a result of the exposure assessment for gas-phase phthalates from house dust and organic films, preschool children showed the highest level of inhalation of phthalates, followed by school children, adults, and adolescents. Conclusions: This study includes the limitation of not considering different SVOCs exposure pathways in the health impact assessment, including those of phthalates in the indoor living environment. However, this study has the significance of performing exposure assessment based on exposure to SVOCs present in indoor air that originated from organic films in the indoor residential environment. Therefore, the results of this study should be useful as basic data for exposure and health risk assessments of SVOCs associated with organic films in the indoor environment.

• Journal of Animal Science and Technology
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• v.47 no.6
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• pp.955-962
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• 2005

This study was conducted to examine the nutrient digestibility and ruminal fermentation characteristics in sheep fed diets containing four substitution levels of E. ulmoides leaves for rice straw. For the experiment, they were given a basal diet consisting of rice straw and concentrate at a 3:7 ratio (DM basis). The treatments were designed as a 4$\time$4 Latin square design with four sheep (50.2$\pm$1.6 kg body weight). Sheep were allotted in one of four treatments, which were designed to progressively substitute Eucommia ulmoides for 0, 3, 5 and 10% of rice straw in the basal diet. The digestibility of crude fat was significantly (p<0.05) improved by 12.5 to 17.5% in 3% and 5% air dried Eucommia ulmoides leaves compared with that in control. The digestibility of crude fiber in the 3, 5 and 10% treatments was significantly (p<0.05) higher than that of the control. Dry matter intake was highest (p<0.05) in sheep fed 10% air dried E. ulmoides). Retained nitrogen in the 3, 5 and 10% treatments was increased up to 97%, 173% and 192%, respectively, compared to that in control (p<0.05). Organic matter utilization was higer in 3% and 5% treatments than control (p<0.05). Purine derivatives and microbial nitrogen synthesis were significantly increased by the dietary substitution of 5 % E. ulmoides leaves (p<0.05) compared with control and the 3% treatment. Ruminal concentration of total-VFA was significantly (p<0.05) higher in sheep fed all levels of air dried Eucommia ulmoides than those of control. It is concluded that air-dried E. ulmoides leaves given to ruminants can increase nutrient digestibility and palatability and improve ruminal fermentation. Therefore, the 5 and 10% substitution of E. ulmoides for roughage are highly recommended to be used in practice.

• Journal of the Korean Institute of Gas
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• v.23 no.6
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• pp.90-96
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• 2019

Natural gas has been regarded as one of major alternative fuels, because of the increment of mining shale gas and supplying PNG(Pipeline Natural Gas) from Russia. Thus, it needs to broaden the usage of natural gas as the increasing its supplement. In this situation, application of natural gas on the transport area is a good suggestion to reduce exhaust emissions such as CO₂(carbon dioxides) and soot from vehicles. For this reason, natural gas can be applied to SI(spark ignition) engines due to its anti-knocking and low auto-ignitibility characteristics. Recently, since turbocharged SI engine has been widely used, it needs to apply natural gas on the turbocharged SI engine. However, there is a major challenge for using natural gas on turbocharged SI engine, because it is hard to make natural gas direct injection in the cylinder, while gasoline is possible. As a result, there is a loss of fresh air when natural gas is injected by MPI (multi-point injection) method under the same intake pressure with gasoline-fueled condition. It brings the power reduction. Therefore, in this research, intake pressure was increased by controling the turbocharger system under natural gas-fueled condition to improve power output. The goal of improved power is the same level with that of gasoline-fueled condition under the maximum torque condition of each engine speed. As a result, the maximum power levels, which are the same with those of gasoline-fueled conditions, with improved brake thermal efficiency could be achieved for each engine speed (from 2,000 to 6,000 rpm) by increasing intake pressure 5-27 % compared to those of gasoline-fueled conditions.