• 대한금속재료학회지
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• 제49권9호
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• pp.671-677
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• 2011

Steel columns used in steel buildings are inclined to lose their strength when exposed to severe fire conditions, so fire resistance is required in most countries to protect against loss of life and building collapses. In Korea, the fire resistance of columns can be obtained by the fire test defined in KS F 2257-1, 7. The fire resistance of a steel column should be evaluated in terms of the column's conditions, such as various section types (H-section, hollow-section), the column's length and boundary conditions, and whether it is fixed or hinged. However, fire testing of steel columns is usually conducted on one standard-sized H-section over 3,000 mm, and the result is used as the column's fire resistance. This is not a reasonable way to ensure that a building can withstand fire conditions. In this study, to evaluate the possibility of calculating the fire resistance of steel columns with material properties of high tensile strength of SS 400, both load-bearing fire tests and calculation of steel temperatures were carried out. The results of temperature calculation were very similar to those obtained by fire test.

• 한국기계가공학회지
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• 제13권5호
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• pp.57-63
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• 2014

At present, a high-speed swivel tool head of a small size is required to improve the productivity of CNC automatic lathes. Hence, there is growing interest in shorter machining times with higher cutting speeds. However, an increase in the rotation speed of a swivel tool head also has adverse effects, such as vibration and noise caused by the swivel tool head system. In this work, the fatigue life and contact pressure of a swivel tool head bearing system driven by gears were calculated. Based on the calculated results, a prototype swivel tool head was manufactured and its static and dynamic characteristics, i.e., the vibration, noise and precision, were measured using a reliability testing device which allows the application of cutting force to the end of the swivel tool head.

• Tribology and Lubricants
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• 제24권4호
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• pp.179-185
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• 2008

Microporous polymer lubricants(MPLs) are solid polymer materials containing micropores which are filled with liquid lubricants, and which are molded or formed to suit rolling bearings or other machine parts requiring lubrication. MPLs can be effectively applied to provide long-term, maintenance-free lubrication of a variety of machine elements without fully replacing of oils and greases. The application of rolling bearings packed fully with an MPL could reduce or eliminate the problems such as grease deterioration, leakage, under-lubrication caused by insertion of water or foreign matters under severe operation conditions. This paper discuss the application of MPLs for lubrication of rolling ball bearings. Two different MPLs were synthesized and the features of MPLs were tested. Characteristics of the bearings which are packed fully with synthesized MPLs were investigated using SEM, TG/DSC, extents of oil leakage, OIT, and life time test. After these preliminary tests twelve MPLs were synthesized and evaluated by measuring extents of oil leakage and OIT values. Then synthesis conditions for the optimum MPL were selected by SSRED(Six Sigma Robust Engineering Design) pro gram using extents of oil leakage and OIT values respectively. The optimum MPL by means of OIT value showed higher performance such as long life time and application at higher temperature of $140^{\circ}C$ than previous temperature of $100^{\circ}C$.

• Journal of Biosystems Engineering
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• 제43권1호
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• pp.1-13
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• 2018

Purpose: The development of compact tractors that can be used in dry fields, greenhouses, and orchards for pest control, weeding, transportation, and harvesting is necessary. The development and performance evaluation of power transmission units are very important when it comes to tractor development. This study evaluates the performance of a driving power transmission unit of a 50 kW multi-purpose narrow tractor. Methods: The performance of the transmission and forward-reverse clutch, which are the main components of the driving power transmission unit of multi-purpose narrow tractors, was evaluated herein. The transmission performance was evaluated in terms of power transmission efficiency, noise, and axle load, while the forward-reverse clutch performance was evaluated in terms of durability. The transmission's power transmission efficiency accounts for the measurement of transmission losses, which occur in the transmission's gear, bearing, and oil seal. The motor's power was input in the transmission's input shaft. The rotational speed and torque were measured in the final output shaft. The noise was measured at each speed level after installing a microphone on the left, right, and upper sides. The axle load test was performed through a continuous equilibrium load test, in which a constant load was continuously applied. The forward-reverse clutch performance was calculated using the engine torque to axle torque ratio with the assembled engine and transmission. Results: The loss of power in the transmission efficiency test of the driving power unit was 6.0-9.7 kW based on all gear steps. This loss of horsepower was equal to 11-18% of the input power (52 kW). The transmission efficiency of the driving power unit was 81.5-89.0%. The noise of the driving power unit was 50-57 dB at 800 rpm, 70-77 dB at 1600 rpm, and 76-83 dB at 2400 rpm. The axle load test verified that the input torque and axle revolutions were constant. The results of the forward-reverse clutch performance test revealed that hydraulic pressure and torque changes were stably maintained when moving forward or backward, and its operation met the hydraulic design standards. Conclusions: When comprehensively examined, these research results were similar to the main driving power transmission systems from USA and Japan in terms of performance. Based on these results, tractor prototypes are expected to be created and supplied to farmhouses after going through sufficient in-situ adaptability tests.

• 가정과삶의질연구
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• 제2권1호
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• pp.111-129
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• 1984

The purpose of this study is to make a model of Family Life Cycle in Korea now. Answers to a questionnaire were collected from 724 housewives in Seoul area, 232 housewives in big cities, 203 housewives in small cities. The questionnaire contained 10 items about family situations,. Analyzing method employed for modeling to family life cycle are frequency, percentage, X2 -test . Results and findings are as follows; 1) The mean of first marriage age is 22.4yrs old. 23.5yrs old is the result of statistical materials published by E.P.B. 1975. The age of first marriage is higher according to the age, education & residential area. 2) The mean of first baby bearing age is 24.2 yrs old (generally 1 year after marriage). This age is the same as the result of statistical materials published by E.P.B. 3) the mean of last baby berating age is 32.6 yrs old compared to the E.P.B. statistical materials 3 yrs. low. This age is very different according to the age, education & residential area. 4) The mean of first child marriage age is 46.4 yrs old compared to the E.P.B. statistical materials 2.5 yrs old low. 5) the mean of last marriage age is 52.7 yrs old. this age is also 2.3 yrs low compared to the result of E.P.B. materials. 6) The number of child & interval is quite different according to the result of family planning generation of not. 7)According to the wife's employment, it does not show and difference. 8)The result of analyzing by F.L.C.,, we don't have launching stage & middle age stage apparently. So, we can make model of F.L.C. in Korea as follows (it will be change). 1) Establishment stage; from marriage to first baby born (23yrs old -24yrs old). 2) Child bearing & rearing stage; form first baby born to first child enter primary school(24 yrs old-30 yrs old). 3) Families with children's education stage; from first child primary school to high school graduation (30 yrs old-42yrs old) 4)Families with adult children stage; form first child got army college or stay at home(42 yrs- 48 yrs old). 5)Families with children's marriage stage; from first child marriage to last child marriage (48yrs old-57yrs old). 6) Aging stage; from last child marriage to self dying.

• Journal of Nutrition and Health
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• 제36권10호
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• pp.1022-1029
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• 2003

This study was undertaken to evaluate the antitumor activities of Cordyceps militaris of silkworm pupa (CMP) and silkworm larva (CML), as compared with the effect of cordycepin, an active compound found in Cordyceps militaris. Antiproliferation effect of the test materials were evaluated in the sarcoma-180 cells using the MTT test. For the in vivo study, ICR mice were inoculated i.p. with 1.0 ${\times}$ 10$^{6}$ sarcoma-180 cells/mouse on Day 0, and were again i.p. injected with one of the following substances from Day 1 to Day 10 : saline (control group), 50 mg/kg (CMP50, CML50) ,100 ma/kg (CMP100, CML100), or 200 mg/kg (CMP200, CML200) of Cordyceps militaris water extracts, or 1 mg/kg (C1), 2 mg/kg (C2), or 4 mg/kg (C4) of cordycepin. Pretreatment of the sarcoma-180 cells with 100 mg/ml, 500 mg/ml, and 1000 mg/ml of CML (60.1$\pm$2.5％, 49.8$\pm$3.7％, and 45.4$\pm$0.1％ of the value for untreated control cells, respectively) or CMP (68.3$\pm$2.1％, 55.1$\pm$0.9％, and 51.4$\pm$3.5％ of the value for control cells, respectively) for 48 hrs significantly decreased the survival rate (proliferation) of tumor cells (p<0.05). Body weight of the control mice bearing ascites tumor and injected with saline was 1.4 times of the value for normal animals at day 18. Mice bearing ascites tumor and injected with cordycepin (1, 2, or 4 mg/kg) exhibited a significantly lighter body weight compared with the control mice, while animals injected with CMP or CML (50, 100, or 200 mg/kg) showed a significantly lighter body weight compared with the mice injected with cordycepin. Mice injected with CMP50, CMP100, or CMP200 mg/kg (or CML50, CML100, or CML200 mg/kg) showed a 133％ (or 90％), 80％ (or 62％), and 68％ (or 52％) longer mean survival time, and those treated with C1, C2, or C4 exhibited a 54％, 91％ and 80％ longer survival time compared to the value for control mice injected with saline. These results indicate that the hot-water extracts of Cordyceps militaris of both silkworm pupa and silkworm larva have an anti-proliferation effect of tumor cells as well as the life prolongation effect in mice bearing ascites tumor, which are superior to the activities of cordycepin.

• Computers and Concrete
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• 제19권4호
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• pp.357-363
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• 2017

This paper conveys the effects of fly ash and silica fume incorporated in concrete at various replacement ratios on the durability properties of concretes. It is quite well known that concrete durability is as much important as strength and permeability is the key to durability. Permeability is closely associated with the voids system of concrete. Concrete, with less and disconnected voids, is assumed to be impermeable. The void system in concrete is straightly related to the mix proportions, placing, compaction, and curing procedures of concrete. Reinforced concrete structures, particularly those of subjected to water, are at the risk of various harmful agents such as chlorides and sulfate since the ingress of such agents through concrete becomes easy and accelerates as the permeability of concrete increases. Eventually, both strength and durability of concrete reduce as the time moves on, in turn; the service life of the concrete structures shortens. Mineral additives have been proven to be very effective in reducing permeability. The tests performed to accomplish the aim of the study are the rapid chloride permeability test, pressurized water depth test, capillarity test and compressive strength test. The results derived from these tests indicated that the durability properties of concretes incorporated fly ash and silica fume have improved substantially compared to that of without mineral additives regardless of the binder content used. Overall, the improvement becomes more evident as the replacement ratio of fly ash and silica fume have increased. With regard to permeability, silica fume is found to be superior to fly ash. Moreover, at least a 30% fly ash replacement and/or a replacement ratio of 5% to 10% silica fume have been found to be highly beneficial as far as sustainability is concerned, particularly for concretes subjected to chloride bearing environments.

• 한국지반환경공학회 논문집
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• 제10권5호
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• pp.41-47
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• 2009

본 논문에서는 폐타이어 활용 재생혼합토(Tire Shred-Sandy Soil Mixture)로 조성된 도로성토구조물의 장기성능을 평가하고자 현장계측 및 현장시험을 수행하였다. 최대 크기 76mm의 폐타이어와 사질토를 50 : 50의 체적비로 혼합한 재생혼합토 성토구조물은 도로개통 후 침하, 변형, 온도측면에서 장기적으로 안정된 모습을 보였으며, 특히 FWD 시험결과, 기존 성토재료로 조성된 성토구간의 지지성능과 동등한 수준으로 설계수명을 만족하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.178.2-178.2
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• 2010

The wind turbine gearbox is important rotating part to transmit torque from turbine blade to generator. Generally, gear shaft which rotates causes vibration by influence of stiffness and mass with gear shaft. Root cause of this vibration source is well known to gear transmission error that is decided from gear tooth property. Transmission error excites a gear, and makes excitation force that is vibrated shaft. This vibration of shaft is transmitted to gearbox housing through gearbox bearing. If the resonance about which the natural frequency of the gearbox accords with shaft exciting frequency occurs, a wind turbine can lead to failure. The gearbox for wind turbine should be considered influence of vibration as well as the fatigue life and its performance by such reason. The cause to vibration should be closely examined to reduce influence of such vibration. In this paper, the cause of the vibration which occurs by a gearbox is closely examined and the method which can reduce the vibration which occurred is shown. It is compared with vibration test outcome of a 3MW gearbox for verification of the method shown by this paper.

• 한국의상디자인학회지
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• 제14권2호
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• pp.215-227
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• 2012

This study aims to analyze the influences of LOHAS cuticle management, which based on LOHAS consciousness among customers using nail art shops and removes only Cuticle layer without Eponychium, on the preference and expected value of service quality. Further, it tackles how above related variables have important bearing on reuse intention. A survey was conducted only with customers over the age of 20 in Seoul, Daejeon and Daegu areas in terms of LOHAS consciousness. For the collected 389 data, frequency analysis, t-test, ANOVA, correlation analysis and multiple regression analysis were carried out by using SPSS 18.0 Version statistical package. The results are as follows. First, according to the results, it shows high positive correlation between LOHAS cuticle management based on the consciousness of LOHAS, and LOHAS cuticle management preference, tendency and willingness to transfer toward it. Second. it is proven that LOHAS consciousness tend to be possessed in older age groups, married and a professional employee layers and this LOHAS motivated groups showed high LOHAS cuticle management preference, inclination and intention of a change in management. Lastly, the reuse intention is mostly affected by experience and preference of LOHAS cuticle management. There is negative correlation between reuse intention and experience in blooding and pain during care service. Higher interest in preference of LOHAS cuticle management has highly influenced positive link with the repurchase intention.