• 소음진동
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• 제11권3호
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• pp.401-409
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• 2001

Passive type mufflers installed on every car haute inherent problem of lowering engine power and fuel efficiency caused by backpressure which is byproduct of complex internal structure. Recent improvements like installing a calve to change exhaust gas path depending on power requirement and rpm have only marginally improved performance. Tremendous amount of recent research works on active exhaust noise control have failed to commercialize because of numerous physical and economical reasons. In this paper, a unique seal-active muffler using difference of transmission paths is presented. In this system exhaust pipe is divided into two and joined again downstream. Exhaust noise is reduced by destructive interference when two-divided noise join again with transmission paths'difference which is half of the wavelength of a main noise frequency. One divided path has a sliding mechanism to change length thereby transmission path length difference is adjusted to entwine rpm change. The proposed system has minimal backpressure and does not need a secondary sound source like a speaker so it can overcome many problems of failed active noise control methods. We have verified proposed system's superior performance by simulation and comparison experiment with passive mufflers.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1695-1698
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• 2005

In this paper we investigate characteristics of deflection for circular plate with the non-symmetric boundary condition that is the boundary condition partly supported along the width direction of plate according to the length change of supporting end. For two boundary conditions such as simple supported and completely clamped boundary conditions, this study derives the maximum deflection formula of the circular plate using differential equation of elastic curve, assuming that a circular plate is a beam with the change of width and thickness along the longitudinal direction. The deflection formula of circular plate is verified by carrying out finite element analysis with regard to the ratio of length of supporting end to radius of circular plate.

• 한국산업융합학회 논문집
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• 제5권3호
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• pp.225-232
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• 2002

The purpose of this study is to find the mechanical properties of lightweight concrete using expanded clay. Thus, slump, air content, compressive strength, elastic modulus, tensile strength, length change ratio, unitweight change ratio and absorption of lightweight concrete have been investigated. The conclusions of this study are as follows ; 1. The loss of slump and air content of concrete increased as the expanded clay content increased and the size of coarse aggregate decreased. 2. The compressive strength of concrete using 100% expanded clay of 13, 19mm size at 28 days were respectively 282, $252kgf/cm^2$. 3. The elastic modulus and tensile strength of concrete decreased with increase of expanded clay content. 4. The length change ratio of concrete increased with the larger coarse aggregate size, and decreased with the increase of expanded clay content. 5. The unit weight of concrete decreased with the increase of expanded clay content, and the ratio of that was larger at the early age.

• 한국환경과학회지
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• 제14권1호
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• pp.33-40
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• 2005

The size of minimum order stream has a very sensitive effect on runoff analysis model using the divergence characteristic of stream. Therefore, in this study, the threshold area of minimum order stream has been examined the change characteristic of topographical parameters. The subject basin of the research was the upper basin of the Kumho water gage station which is located in the middle of the Kumho river. The 1:25,000 numerical geography which was constructed $10{\times}10m$ mesh was used. The range of investigation of topographical parameters are number of stream order, length, area, slope, basin relief, sinuosity ratio, drainage density and total stream length etc. It was found from the result of analysis that the threshold value of minimum order stream has a very big effect on topographical parameters of basin. It was found that the threshold area of minimum ord er stream revealed under $0.10km^{2}.$ Furthermore, the parameters showed a serious change except for over $0.10km^{2}.$

• 대한치과교정학회지
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• 제13권1호
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• pp.73-82
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• 1983

The author studied on the dental arch widths and lengths and height of palates at 3 groups of dentition: mixed dentition, early permanent dentition, young adult, having normal occlusion and dentition. The models of the 336 maxillary and mandibular case, made from alginate-base hydrocolloid impressions were measured and analyzed statistically. The result as follows; 1. The upper intercanine width increased between the mixed dentition group and early permanent dentition group but there was no change in the young adult group in both sexes. The lower intercanine width increased between the mixed dentition group and early permanent dention group in the male. 2. The upper and lower 1st bimolar width increased slightly with age in the male but there was no change in the female. 3, The sex difference found in this study was one of absolute size, the female being slightly smaller than the male in the early permanent dentition group and young adult. 4. The arch length had no notable sexual differences and decreased between the mixed dentition group and early permanent dentition group. There was no change in the arch length in the young adult. 5. The height of palate increased gradually with age.

• 복식
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• 제58권5호
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• pp.178-197
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• 2008

Due to the inflow of the western culture since the 19th century, female skirts and jackets have been changed considerably in detail though their basic composition was maintained. The analysis on female jackets from the start of the modern period to 1960s has been undertaken with artefacts as well as reports and research dissertations related to them. For period appraisal, analysis was divided into several periods which are from 1890s to 1910s, and every 10 years afterwards. As a result, aspects for the appraisal in each period was found. Aspects for period appraisal in modern jackets can be a change in total length and side length, a change in shape of the sleeves (from straight to round), a change in width, and a difference in closed shape of the collars. Material and color can be another aspect which shows fashionable material or new materials (man-made textile or nylon) of each period, color combination of surface and lining material as well as other parts of the jacket, use of a stiffener made with net or sheer textiles. Research using books and archives is important for the appraisal of the garment artifact. However, most of all, one should have the attitude of examining the artifacts frequently in order to achieve deeper understanding and an eye for accurate appraisal.

• 한국태양에너지학회 논문집
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• 제31권5호
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• pp.85-90
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• 2011

The effects of $CO_2$ ppm in atmosphere on the values of the total emissivity are studied. The predictions by several methods are compared. The predicted value differences between modified Kondratyev model and Hottel model are the smallest with in the range of values tested. The $CO_2$ ppm is varied from 300 ppm to 600 ppm. By Wide Band model, the total emissivity increases with increasing density-path length product rather linearly up to 0.1 g/$cm^2$. For given $CO_2$ ppm, the total emissivity increases as the air thickness increases. The same is true for both temperature and pressure increase. The temperature range tested is 220 to 300 K. Around 260K, the total emissivity is less sensitive with increasing temperature than with decreasing temperature. The pressure is varied from 0.94 to 1.06 atm. The percentage change of total emissivity with pressure change from 1atm is at most the percentage change of the pressure.

• 한국의류학회지
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• 제24권2호
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• pp.226-236
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• 2000

The mutual relation dynamics between the chulik and the Po for man in the period of chosun dynasty. The objectives of this study are to find out the mutual relation between the chulik and the Po for man-symeui, danryeong, changeui, jikryeong-, te change of chulik, and the ideas that made this change. Conclusions are decribed as followes: 1. The pattern of chulik and symeui is same, and they consist of bodice and skirt's length of the chulik was 1 : 1.3∼2 and it is effected by symeui. And symeui was effected by pratical structure of the chulik. 2. The functions of the chulik were the underwear of danryeong and the upperwear as military uniform. And then the length of chulik was shorter than danryeong in the early period of shosun dynasty. The sleeves were changed as large as danryeong in the late period of chosun dynasty. It is assumed that the changes were to be a functional underwear and to appear authority as upperwear. 3. Chulik as the underwear was hardly worm in the 17th centuries, and changeui was widely enjoyed instead of it. The reason of this change is that the pragmatism was emphasied in that period. 4. Chulik was widly worm instead of court dress, until the mid of 17th century after war. It was effected by outer factor of the war. And jikryeong was widly worm instead of chulik in the late period of chosun dynasty. It shows that military officers wanted to appear authority.

• 콘크리트학회논문집
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• 제21권3호
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• pp.303-310
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• 2009

CFRP (carbon fiber reinforced polymer) 긴장재는 PC 강연선의 부식문제를 해결하기 위해 대안으로 사용될 수 있다. CFRP 긴장재를 콘크리트구조물에 적용하기 위해서는 부착강도, 전달길이, 정착길이와 같은 재료적 특성이 명확히 결정되어야 한다. 특히 프리텐션 콘크리트 부재에 CFRP 긴장재가 적용될 경우 전달길이는 긴장력 도입에 있어서 중요한 요소가 된다. 본 연구에서 개발된 CFRP 전달길이 및 정착길이를 산정하기 위해 프리텐션 보 9개를 제작하였다. 전달길이 실험결과, 긴장력 25%인 경우는 34D, 긴장력 50%인 경우는 55D로 측정되었고, 긴장력이 커지면 전달길이가 증가하는 것으로 나타났다. 시간경과에 따른 전달길이 변화를 살펴보면, 긴장력의 크기에 따라 시간경과가 전달길이에 영향을 주는 것으로 나타났다. 보강재 특성계수 산정 결과, 본 연구에서 개발된 CFRP 긴장재의 보강재-특성 계수 ${\alpha}_t$는 2.3으로 PS강연선 (${\alpha}_t=2.4$)과 비슷한 것으로 나타났다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(I)
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• pp.220-224
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• 2002

As the train run through the tunnels, especially at high speed, pressure shock developed by the running train gives the influence on the pressure fluctuation inside the tunnel and consequently, inside the car. This pressure changes and pressure gradient is closely related with the tunnel section, train speed, air tightness of the train, length of the tunnel, etc. This study includes the analysis of the pressure behavior at the varied train speed and tunnel length. The results show that train speed affects the pressure gradient inside the car almost linearly, and that there exist the critical tunnel lengths that gives the maximum value of pressure change and pressure gradient, respectively.