• Mineral and Industry
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• v.26
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• pp.13-21
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• 2013

This study is carried out experiments on various factors for improving the grade of low grade scheelite by Knelson concentrator prior to the main beneficiation process. Even though there are several gravity separators such as Jig, Spirals and etc. for rougher concentrate, the KC3 Knelson Concentrator was adopted to get better separation efficiency and beneficiating effects for pre-concentration of the low grade scheelite ore. The feed samples was prepared to minus 1mm in size by crushing and grinding. The important factors in the KC3 Knelson Concentrator test were examined in terms of the variations such as number of treatment, feed rate, rotation speed of bowl(G force), water flow rate, pre-removal of magnetic minerals, feed size and feed grade. According to the result of experiment, it shows that the important technical variations are limited in terms of number of treatment, feed rate, feed size and feed grade. The final result shows that the KC3 Knelson Concentrator obtains the scheelite pre-concentrate of about $3%WO_3$ grade and 90% recovery, respectively, from the feed containing about $0.8-1.0%WO_3$ grade.

• Journal of Korean Orthopaedic Sports Medicine
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• v.8 no.1
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• pp.39-45
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• 2009

Purpose: We intended to classify the pattern and to seek the cause of fractures and/or dislocations related to middle and high school Taekwondo athletes in competition and try to get the ways for preventing them. Materials and Methods: We studied 50 fractures and dislocations of the athletes in competition, which were surveyed in 2005-2007 national middle and high school Taekwondo tournament annually. We analyzed the type and the cause of the injury, performed survey at postinjury l year in 32 cases, sought proper treatments and methods for prevention. Results: The 26 cases (52%) of foot fracture, 15 cases (30%) of hand fracture and 9 cases (18%) of forearm fracture are occurred in this study. The 9 cases (28%) of satisfaction in treatment, 15 cases (47%) of average and 8 cases (25%) of dissatisfaction are surveyed in the 32 cases. The causes of dissatisfaction are lack of rest (7 cases), excessive training (5 cases), immoderate participation of match (6 cases) and the others. The athletes were returned to the match before complete recovery in 21 cases (67%). Conclusion: The causes of fractures and dislocations in middle and high school Taekwondo athletes were stroke on upper and lower extremities and high-speed hyperflexion injury that was occurred during spraining of great toe on the floor. We consider that the athletes need the development of effective protector, improvement of equipment in stadium and enough rest and education.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.41-47
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• 2007

The first geostationary satellite made by Korea, COMS, has the three different payload ; Meteorological sensor, Oceanographic sensor and Ka-band communication payload. There are Meteorological & Ocean Data Communication Subsystem(MODCS) and Telemetry, Command and Ranging Subsystem(TC&R) as other RF radiation sources. MODCS transmits and receives Meteo and Ocean measurement data from/to earth using L-band and TC&R using S-band. The Ka-band communication payload will provide high-speed multimedia services and communication services for natural disaster such as prediction, prevention, and recovery services in the government communications network.Ka-band beacon is for the earth antenna pointing and the experiment of rain fading. This paper gives the analysis results about the mutual radiation effect on Ka-band communication payload, Ka-band beacon, MODCS and TC&R. Up/Down link power and coupling factor including the geometrical position and distance of antenna, filter rejection and degradation factor due to the different polarization are considered. The results show MODCS and TC&R are compatible for Ka-band communication payload and Ka-band beacon does not interfere with MODCS and TC&R normal operation.

• Journal of the Korean Chemical Society
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• v.58 no.6
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• pp.535-542
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• 2014

A simple and efficient preconcentration method was developed using three-phase liquid phase microextraction prior to HPLC-UV for simultaneous extraction and determination of tetracycline antibiotics (tetracycline, oxytetracycline, and chlortetracycline). The tetracycline antibiotics were separated simultaneously on a column ($C_8$, $3.0{\times}150mm$, $3{\mu}m$) with high selectivity and sensitivity using gradient elution. Under optimized conditions (extraction solvent, heptanal; pH of donor, 9.0; pH of acceptor, 1.0; stirring speed, 700 rpm; NaCl salt, 0%; and extraction time, 60 min), enrichment factors (EF) were between 5.6 and 22.3. The limit of detection (LOD) and limit of quantitation (LOQ) in the spiked urine matrix were in the concentration range of $0.08{\sim}0.8{\mu}g/mL$ and $0.4{\sim}1.6{\mu}g/mL$, respectively. The calibration curves were linear within the range of $0.1{\sim}32{\mu}g/mL$ with the square of the correlation coefficient being more than 0.995. The precision (as a relative standard deviation, RSD) and accuracy (as a relative recovery) within working range were 1.3~9.1% and 84~118%, respectively.

• Journal of Sensor Science and Technology
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• v.29 no.1
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• pp.14-18
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• 2020

This study investigates the nitrogen dioxide (NO₂) sensing characteristics of an Si MOSFET gas sensor with a tungsten trioxide (WO₃) sensing layer deposited using the sputtering method. The Si MOSFET gas sensor consists of a horizontal floating gate (FG) interdigitated with a control gate (CG). The WO₃ sensing layer is deposited on the interdigitated CG-FG of a field effect transistor(FET)-type gas sensor platform. The sensing layer is deposited with different thicknesses of the film ranging from 100 nm to 1 ㎛ by changing the deposition times during the sputtering process. The sensing characteristics of the fabricated gas sensor are measured at different NO₂ concentrations and operating temperatures. The response of the gas sensor increases as the NO₂ concentration and operating temperature increase. However, the gas sensor has an optimal performance at 180℃ considering both response and recovery speed. The response of the gas sensor increases significantly from 24% to 138% as the thickness of the sensing layer increases from 100 nm to 1 ㎛. The sputtered WO₃ film consists of a dense part and a porous part. As reported in previous work, the area of the porous part of the film increases as the thickness of the film increases. This increased porous part promotes the reaction of the sensing layer with the NO₂ gas. Consequently, the response of the gas sensor increases as the thickness of the sputtered WO₃ film increases.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.1
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• pp.85-93
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• 2007

This paper presents new LVDS I/O circuits with a high noise margin for use in highly parallel I/O environments. The proposed LVDS I/O includes transmitter and receiver parts. The transmitter circuits consist of a differential phase splitter and a output stage with common mode feedback(CMFB). The differential phase splitter generates a pair of differential signals which have a balanced duty cycle and $180^{\circ}$ phase difference over a wide supply voltage variation due to SSO(simultaneous switching output) noises. The CMFB output stage produces the required constant output current and maintains the required VCM(common mode voltage) within ${\pm}$0.1V tolerance without external circuits in a SSO environment. The proposed receiver circuits in this paper utilizes a three-stage structure(single-ended differential amp., common source amp., output stage) to accurately receive high-speed signals. The receiver part employs a very wide common mode input range differential amplifier(VCDA). As a result, the receiver improves the immunities for the common mode noise and for the supply voltage difference, represented by Vgdp, between the transmitter and receiver sides. Also, the receiver produces a rail-to-rail, full swing output voltage with a balanced duty cycle(50% ${\pm}$ 3%) without external circuits in a SSO environment, which enables correct data recovery. The proposed LVDS I/O circuits have been designed and simulated with 0.18um TSMC library using H-SPICE.

• Journal of the Korean Society of Clothing and Textiles
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• v.29 no.8 s.145
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• pp.1176-1187
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• 2005

The purpose of this study was to evaluate the efficiency of cooling vests developed for farm workers harvesting red pepper in summer. The study was performed using the following two steps: 1) Climatic chamber test, 2) Field test. For the chamber test, a work environment was simulated as $33^{\circ}C$ and $65\%$RH, and the thermo-physiological and subjective responses were measured with and without cooling vests. Twelve young males participated as subjects. For the field test, three farmers participated while harvesting red pepper on the form, in summer. The measurements used were same as in the chamber test. Subjects were tested without any cooling vests, as a control. They were tested wearing vests with 2 frozen gel packs (CV2: Cooling area, $308cm^2$), and vests with 4 frozen gel packs (CV4: Sooting area, $616cm^2$). As a result of the chamber test, rectal temperature($T_{re}$) and mean skin temperature( $T_{sk}$) were lower in both CVs than in Control, and this tendency was statistically significant in CV4 (p<.05). Clothing microclimate temperature ($T_{clo}$) and total sweat rate (TSR) were significantly lower when wearing cooling vests (p<.05) Heart rate (HR) was also lower in wearing cooling vests than in Control, and the speed of recovery to the comfort level was faster when the subjects wore cooling vests. In addition, subjects felt 'less hot, less humid, and less uncomfortable' in both CVs than in Control. Field tests showed a similar tendency with the chamber tests. In particular, wearing the cooling vest was effective in restraining the raise of $T_{clo}$ on the back. It can be concluded that the cooling vest was effective in alleviating heat strain and discomfort in both the chamber test and the field test, despite the cooling area of the cooling vest being just $3.4\%$ of the body surface area ($616cm^2$).

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.8
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• pp.1045-1050
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• 2006

Optimum operation condition for pilot scale of alkaline processing for fish muscle was investigated by measuring protein solubility, yield, texture, and water-holding capacity. Recovered protein yield was 33.2% for whole fish and 61.8% for minced muscle. Optimum homogenized speed and time, using industrial scale homogenizer, were 3,000 rpm and 5 min, respectively. Limited centrifugal force of continuous cylinder type was 4,000 rpm for recovering soluble protein, and 2,000 rpm for recovering precipitated proteins. The pH control agents such as citric acid, sodium phosphate and calcium oxide decreased the breaking force and deformation of recovered protein gel. The breaking force and deformation of the recovered proteins were high compared to conventional surimi. The breaking force and deformation were decreased by addition of salt, starch and bovine plasma proteins. Whiteness of recovered protein gel was lower than that of conventional surimi. Alkaline processing greatly decreased nitrogen content and chemical oxygen demand in waste water. The results suggest that alkaline processing has a potential as industrial production for recovering the proteins from fish muscle.

• Clean Technology
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• v.22 no.4
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• pp.274-280
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• 2016

In this study, it was to develop a chemical method that can recycle the cutting oil which accounts for about 25% of the cost of the process among containing materials of silicon waste sludge generated in the process for producing a solar cell wafer. The 7 types of reagents have been used, including acetone, HCl, NaOH, KOH, $Na_2CO_3$, HF, $CH_2Cl_2$, etc. for this experiment. And It was carried out at a speed of 3000 rpm for 60 minutes centrifugation after performing a reaction with a waste sludge at various concentrations. As a result, the best reagents and conditions for separating the solid such as a silicon powder and a metal powder and liquid cutting oil were identified as 0.3 N NaOH. It is found to be pH 6.05 in a post-processing recycled cutting oil with 0.3 N NaOH after reaction of waste sludge and 0.1 N HCl which is effective to remove metal powder in order to adjust the pH to suit the properties of the weak acid is a commercially available cutting oil and it showed excellent turbidity than when applied to sludge with 0.3 N NaOH alone. The results of FT-IR analysis which can compare the properties of the commercially available cutting oil shows it has a possibility of recycling oil. The cutting oil recovery rate obtained through the experiment was found to be 86.9%.

• Hwankyungkyoyuk
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• v.5 no.1
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• pp.112-137
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• 1993

As the concern with the creation of environmental problems and regulations about them becomes internationally growing, environmental cooperations with countries concerned are emerging as the first item on the political agenda. In case of South Korea, cooperations with countries in the Asian region is needed urgently. In particular, cooperations with North Korea will be an important factor to reunify the Korean peninsula as well as to solve environmental problems in South Korea. Accordingly, it is necessary to seek feasible alternatives and possibilities of coping with international environment in South and North Korea. This study is limited to literature study based on collecting materials and the testimony of former residents in North Korea. The period of study ranges from May to December in 1992. The research findings show the following environmental problems and alternatives : It is recognized in South Korea that the creation of environmental problems is product of economic development. Currently, the Korean government makes an effort to revise environmental administration and law, to encourage environmental education, and to proceed with environmental technology policies by establishing environmental policies together with economic development plans. North Korea ascribes the cause of environmental problems to colonial exploitation by Japan and the U.S. Environmental pollutants in North Korea is relatively less than South Korea, provisions such as environmental conservation movement, environmental education, and environmental administration and law are not well organized in the country. However, North korea will speed up its economic development to solve economic crises. Therefore, it is expected that industrial wastes, corrosion of nature, and water pollution will result in serious environmental problems. The fields expected to cooperate with South and North Korea are in the following : South Korea may adopt the model of the former East and West Germany and proceed to cooperate with North Korea in public sector as well as private sector. The possible programs are such as academic exchange to conserve environment, joint research in the area of the Demilitarized Zone, conservation of ecosystems around Imjin and Pukhan Rivers, South Korea's support of advanced environmental technology and industrial and financial aid to North Korea. Conflicts between countries concerned in the North East Asian region will be caused by the responsibilities of pollutions because of the seashore development of the Yellow Sea by South Korea and increasing seashore industrial complexes around the Yellow Sea in China, Therefore, it is desirable that the two countries will participate in organizations related to environment. Joint projects between South and North Korea will be as follows : 1. Construction of long-range monitoring system : 2. Investigation of the state of pollutions around the Yellow Sea and alternatives : 3. Construction of joint monitoring system to regulate the movement of pollutants : 4. Cooperation of environmental technology and exchange of information ; and 5. Support of Cooperation of environment in private sector. Efforts to cooperate with North korea is expected to overcome differences between the two countries as well as to encourage unification of the korean peninsula, which will lead to reducing the cost of environmental recovery. These efforts will also contribute to the maintenance for peace and stability on the korean peninsula as well as in the North East Asian region.