• 한국도로학회논문집
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• 제16권1호
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• pp.11-19
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• 2014

PURPOSES : The purpose of this article is to investigate the predicted life of jointed concrete pavement (JCP) with two variables effecting on axle load spectra (ALS). The first variable is different data acquisition methods whether using high-speed weigh-in-motion (HS-WIM) or not and the other one is spectra distribution due to overweight enforcement on main-lane of expressway using HS-WIM. METHODS : Three sets of ALS had been collected i) ALS provided by Korea Pavement Research Program (KPRP), which had been obtained without using HS-WIM ii) ALS collected by HS-WIM before the enforcement at Kimcheon and Seonsan site iii) ALS collected after the enforcement at the same sites. And all ALS had been classified into twelve vehicle classes and four axle types to compare each other. Among the vehicle classes, class 6, 7, 10 and 12 were selected as the major target for comparing each ALS because these were considered as the primary trucks with a high rate of overweight loading. In order to analyze the performance of JCP based on pavement life, fatigue crack and International Roughness Index (IRI) were predicted using road pavement design program developed by KPRP and each ALS with same annual average daily traffic (AADT) was applied to design slab thickness. RESULTS : Comparison ALS of KPRP with those of HS-WIM shows that the ALS of KPRP has a low percentage of heavy spectra such as 6~9 tonnes for single axle, 18~21 tonnes for tandem axle and 27~30 tonnes for tridem axle than other two ALS of HS-WIM in most vehicle classes and axle types. It means that ALS of KPRP was underestimated. And after the enforcement, percentage of heavy spectra close to 10 tonnes per an axle are lowered than before the enforcement by the effect of overweight enforcement because the spectra are related to overweight regulation. Prediction results of pavement life for each ALS present that the ALS of HS-WIM collected before the enforcement makes the pavement life short more than others. On the other hand, the ALS of KPRP causes the longest life under same thickness of slab. Thus, it is possible that actual performance life of JCP under the traffic like ALS of HS-WIM could be short than predicted life if the pavement was designed based on ALS provided by KPRP. CONCLUSIONS : It is necessary to choose more reliable and practical ALS when designing JCP because ALS can be fairly affected by acquisition methods. In addition, it is important to extend performance life of the pavement in service by controlling traffic load such as overweight enforcement.

• 한국강구조학회 논문집
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• 제16권1호통권68호
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• pp.43-49
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• 2004

건축물이 초고층화 및 장스팬화 됨에 따라 일반 구조용 강재에 비해서 강도도 높고, 판의 두께도 두꺼워지고, 성능도 우수한 신강종이 요구된다. TMC 강재는 내진성능이 우수하며, 용접성이 뛰어나고, 판두께가 뚜꺼워도 설계기준강도를 저감할 필요가 없기 때문에 건축구조물에 널리 사용된다. 그러나 대구경 후육강관에 TMC 강재를 사용하기 위해서는 2차 가공으로 인한 물성 변화가 건축구조물 안정성에 영향을 미치는가를 검토해야 한다. 본 연구에서는 SAW로 용접한 SM520TMC 강관의 물성 열화도를 평가하였다. 이때 실험변수로는 강관 제조 프로세스와 강종으로 하였다. 실험결과 강관을 롤 벤딩이나 프레스 성형으로 제관하든지 또는 강종이 국산 SM620TMC이냐 일본산 SM520TMC 이든지에 상관없이 항복강도와 인장강도는 증가하였고, 연신율은 저하하였다.

• 패션비즈니스
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• 제11권5호
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• pp.15-34
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• 2007

This study held a questionnaire for men in their 60s or above to analyze the market research of slacks, understand the characteristics of their lower body types, and provide the basic data for the slacks pattern-making fitting the body types of senior citizens. The findings are as follows. According to the results of a questionnaire, elderly men preferred order-made slacks for better fitness, but they favored ready-made owing to the matter of prices. In particular, the girth of waist was the most considered when purchasing. However, as most customers tended to repair slacks length and the waist part, their unsatisfaction with sizes was rather high. In body measurements, elderly men had higher variable coefficients or more individual differences in the items of thickness and angles than in those of height, length, and girth. Factor analysis revealed 5 front and 6 side factors. According to the results of front-side somatotype analysis, pimento-flat, trapezoid-flat, and bent-flat types require narrower pattern designs in down-upper width than the middle-aged class. In addition, pimento-protruded hip and straight-jar types need to be designed in the same amount as in the middle-aged class. Based on the questionnaire results, down-upper length as 1cm above real dimensions was analyzed to have superior sense of wearing.

• 한국의류학회지
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• 제39권2호
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• pp.247-256
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• 2015

This study prepared fabric-heating elements of carbon nanofiber composite to characterize morphologies and electrical properties. Carbon nanofiber composite was prepared with 15wt% PVDF-HFP/acetone solution, and 0, 1, 2, 4, 8, and 16wt% carbon nanofiber. Dispersion of solution was conducted with stirring for a week, sonification for 24 hours, and storage for a month, until coating. Carbon nanofiber composite coated fabrics were prepared by knife-edge coating on nylon fabrics with a thickness of 0.1mm. The morphologies of carbon nanofiber composite coated fabrics were measured by FE-SEM. Surface resistance was determined by KS K0555 and worksurface tester. A heating-pad clamping device connected to a variable AC/DC power supply was used for the electric heating characteristics of the samples and multi-layer fabrics. An infrared camera applied voltages to samples while maintaining a certain distance from fabric surfaces. The results of morphologies indicated that the CNF content increased specifically to the visibility and presence of carbon nanofiber. The surface resistance test results revealed that an increased CNF content improved the performance of coated fabrics. The results of electric heating properties, surface temperatures and current of 16wt% carbon nanofiber composite coated fabrics were $80^{\circ}C$ and 0.35A in the application of a 20V current. Carbon nanofiber composite coated fabrics have excellent electrical characteristics as fabric-heating elements.

• Selected Papers of The Society of Naval Architects of Korea
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• 제1권1호
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• pp.76-90
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• 1993

A new propeller series is developed using the newly developed blade section (KH 18 section) which has better cavitation characteristics and higher lift-drag ratio at wade angle-of-attack range than a conventional section. The radial patch distribution of the new series propellers is variable stance they were designed adaptively to a typical wake distribution. Basic geometric particulars of the series propellers. such as chord length, thickness, skew and rake distributions, are determined on the basis of recent full scale propeller geometric data. The series is developed for propellers having 4 blades, and blade area ratios of 0.3, 0.45, 0.6 and 0.75. Mean pitch ratios are varied as 0.5, 0.6, 0.7, 0.95 and 1.1 for each blade area ratio. The new propeller series consists of 20 propellers and is named as the KD(KRISO-DAEWOO)-propeller series. Propeller open-water tests are performed at the towing tank, and cavitation observation tests and fluctuating pressure tests are carried out at the cavitation tunnel of KRISO. $B_{p}-\delta$ curves, which can be used to select the optimum propeller diameter at the preliminary design stage, are derived from a regression analysis of the propeller open-water test results. The KD-cavitation chart is derived from the cavitation observation test results by choosing the local maximum lift coefficient and the local cavitation number as parameters. The cavity extent predicted by the KD-cavitation chart would be more accurate compared to that by an existing cavitation charts, such as the Burrll's cavitation chart, since the former is derived from the cavitation observation test results in a typical ship's wake, while the lather is derived from the test results in a uniform flow.

• 대한치과보철학회지
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• 제18권1호
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• pp.37-47
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• 1980

The purpose of this study was to investigate the stresses in different proximal margins and to measure, quantitatively, the effect of different modifications in the design of preparations on the stresses using two-dimensional photoelasticity. Photoelastic stress analysis is based on the phenomenon, exhibited by most transparent solids, of becoming birefringent, or doubly refracting, when strained. Two birefringent materials were used in this study, PSM-1 and PSM-5 in .standard sheet ($10'{\times}10'{\times}\frac{1}{4}'$ thickness), PSM-1(polyester) was used for constructing the substructure, and PSM-5(epoxy resin) was used in making the restorations to be investigated. Two birefringent materials were used in the construction of composite photoelastic model. Seven variable models were constructed. The peripheral dimensions of all model were constant and the models represent an occlusomesial section of a lower posterior molar. Model 1 represents the knife edge margin (shoulderless), Model 2 represents the chamfer, Model 3 represents a rounded shoulder(no sharp angle between the axial wall and gingival floor), Model 4 represents a flat shoulder (axial wall is a $90^{\circ}$ angle to the gingival wall), Model 5 represents $+15^{\circ}$ angulation, Model 6 has a $-15^{\circ}$ angulation, and Model 7 is the same as Model 4 except that it has a $45^{\circ}$ bevel. Improved artificial stone was used to represent dental cement in luting the composite photoelastic model. Static loading procedures(100 pounds) were used at preplanned sites. The results were as follows; 1. The stresses in the proximal portion of all tested models were compressive in nature when the proximal shoulders were loaded vertically on the same proximal marginal ridge. 2. The round and chamfered preparations were the optimum designs in proximoocclusal restorations. They showed the lowest stress concentration factor, i.e. 2.16 and 2.23, respectively. The knife edged shoulder had the highest value, K=5.39. Round type shoulder geometry experiments reduced the stress concentration factor (S.C.F.) 3. The gingival portion of proximal shoulder geometry was a critical location for stress concentration.

• 마이크로전자및패키징학회지
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• 제29권4호
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• pp.41-47
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• 2022

Ag sintering technologies have received great attention as it was applied to the inverter of Tesla's electric vehicle Model III. Ag sinter bonding technology has advantages in heat dissipation design as well as high-temperature stability due to the intrinsic properties of the material, so it is useful for practical use of SiC and GaN devices. This study was carried out to understand the sinter joining temperature effect on the robust Ag sintered joints in air without pressure within 10 min. Electroplated Ag finished Cu dies (3 mm × 3 mm × 2 mm) and substrates (10 mm × 10 mm × 2 mm) were introduced, respectively, and nano Ag paste was applied as a bonding material. The sinter joining process was performed without pressure in air with the bonding temperature as a variable of 175 ℃, 200 ℃, 225 ℃, and 250 ℃. As results, the bonding temperature of 175 ℃ caused 13.21 MPa of die shear strength, and when the bonding temperature was raised to 200 ℃, the bonding strength increased by 157% to 33.99 MPa. When the bonding temperature was increased to 225 ℃, the bonding strength of 46.54 MPa increased by about 37% compared to that of 200 ℃, and even at a bonding temperature of 250 ℃, the bonding strength exceeded 50 MPa. The bonding strength of Ag sinter joints was directly influenced by changes in the necking thickness and interfacial connection ratio. In addition, developments in the morphologies of the joint interface and porous structure have a significant effect on displacement. This study is systematically discussed on the relationship between processing temperatures and bonding strength of Ag sinter joints.

• 디자인학연구
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• 제19권1호
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• pp.293-302
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• 2006

빠르고 복잡 다양한 생활 속에서 사용 가능한 공예품은 현대인에게 멋과 여유를 찾아준다. 바쁜 생활문화는 식습관을 변화 시켜 커피 전문점이 골목마다 생겨나고 있다. 이러한 시기는 도자 컵의 시장을 확대할 수 있는 좋은 기회라고 할 수 있다. 바쁘게 움직이며 사용하는 컵에서 또는 뜨거운 차를 마시기 위한 컵에서는 손잡이의 역할이 매우 중요하다. 손잡이는 컵을 들기 위해 제일 처음 만져지는 부분으로 편안한 촉감적인 경험에 의해 조형성과 어울려 컵의 아름다움을 배가시킬 수 있다. 그러나 한국역사에서 손잡이가 있는 고배가 나탄 것은 신라토기부터 이다. 하지만 이는 의기나 부장품인 경우가 대부분으로 한국의 차 문화에서 실제 손잡이가 있는 컵을 사용한 역사는 그리 길지 않다. 이와 같은 이유에서 아직까지는 컵 손잡이의 기능성보다는 조형성에 치중된 디자인이 주를 이루고 있다. 그러므로 컵의 손잡이를 연구 분석하여 인체공학 적으로 기능면에서 개선된 손잡이를 제작하기 위한 이론적 근거가 필요하다. 본 연구에서는 한국과 미국의 공방에서 생산되는 손잡이가 있는 도자 컵을 연구 분석하였다. 그리고 손잡이의 크기와 위치 등의 대등한 비교를 위해 한 가지 모양으로 컵을 정하고 손잡이의 굵기, 사용하는 손가락의 수, 손잡이 형태와 부착위치와의 관계, 손잡이 지지대의 효과, 손잡이 굵기의 변형, 컵의 무게중심과 손잡이의 관계 등을 변화요인으로 하여 시험하였고 사용자들에게 선호도 조사를 하고 분석하였다. 그 결과, 손잡이가 편하게 만들어지기 위해서는 손이 쉬고 있는 형태에 근접하도록 디자인하는 것이 중요하다는 것을 알았다. 즉 손의 크기, 손가락이 구부러지는 모양 등을 고려하고 컵의 무게 중심을 컨트롤 할 수 있는 위치를 찾고 여러 손가락이 손잡이 안쪽에 들어가서 컵의 무게를 분산시켜 편안하게 컵을 들 수 있도록 디자인해야 한다. 이때 엄지의 지지대가 있다면 같은 무게의 컵이라도 더욱 가볍게 들 수 있게 된다. 디자인상에서 컵의 손잡이를 몸체 방향으로 연장시키며 타원형을 그린다. 그 타원선상에 컵의 무게중심이 위치하고 있다면 컵의 손잡이는 효율적이라 할 수 있다. 이때 손잡이가 컵 몸체의 무게 중심과 가까울수록, 컵을 드는데 힘이 덜 든다고 볼 수 있다. 이렇게 디자인상에서 또는 컵의 제작 과정에서 효율적인 손잡이의 원리를 적용시킨다면 조형적인 면 뿐 아니라 기능적으로도 훌륭한 손잡이가 있는 컵을 제작할 수 있다.

• Journal of Korean Dental Science
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• 제12권1호
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• pp.13-19
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• 2019

Purpose: The aim of this study was to compare the flexural strength of provisional fixed dental prostheses which was three-dimensional (3D) printed by several build directions. Materials and Methods: A metal jig with two abutment teeth and pontic space in the middle was fabricated. This jig was scanned with a desktop scanner and provisional restoration was designed on dental computer-aided design program. On the preprocessing software, the build angles of the restorations were arranged at $0^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $90^{\circ}$ and support was added and resultant structure was sliced to a thickness of $100{\mu}m$. Processed restorations were printed with digital light processing type 3D printer using poly methyl meta acrylate-based resin. After washing and post-curing, compressive loading was applied at a speed of 1 mm/min on a metal jig fixed to a universal testing machine. The maximum pressure at which fracture occurred was measured. For the statistical analysis, build direction was set as the independent variable and fracture strength as the dependent variable. One-way analysis of variance and Tukey's post hoc analysis was conducted to compare fracture strength among groups (${\alpha}=0.05$). Result: The mean flexural strength of provisional restoration 3D printed with the build direction of $0^{\circ}$ was $1,053{\pm}168N$; it was $1,183{\pm}188N$ at $30^{\circ}$, $1,178{\pm}81N$ at $45^{\circ}$, $1,166{\pm}133N$ at $60^{\circ}$, and $949{\pm}170N$ at $90^{\circ}$. The group with a build direction of $90^{\circ}$ showed significantly lower flexural strength than other groups (P<0.05). The flexural strength was significantly higher when the build direction was $30^{\circ}$ than when it was $90^{\circ}$ (P<0.01). Conclusion: Among the build directions $0^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $90^{\circ}$ set for 3D printing of fixed dental prosthesis, an orientation of $30^{\circ}$ is recommended as an effective build direction for 3D printing.

• 한국도로학회논문집
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• 제13권2호
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• pp.103-114
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• 2011

전 세계적으로 에너지 절약과 $CO_2$ 발생량의 절감을 위해 자전거의 이용을 장려하고 있으며 국내에서도 이러한 세계적 흐름에 발맞추어 자전거 이용을 활성화하기 위해 긴 연장의 신설 자전거도로 건설 계획이 진행되고 있다. 최근 신설 자전거도로의 효과적인 건설을 위해 시멘트 수화 반응뿐만 아니라 골재 맞물림에 의해 높은 구조적 성능을 발현하고 간단한 시공절차와 적은 건설비용을 지닌 롤러 전압 콘크리트 포장을 도입하기 위해 적정 배합에 대한 강도 및 내구성 연구가 수행되었다. 하지만 실내 연구를 통해 도출된 배합은 현장다짐에 따라 발현되는 강도에 차이가 있을 수 있다. 또한 얇은 단면, 낮은 강도 등 일반 도로 포장과 요구되는 성능이 상이한 자전거도로의 적정 성능 및 공용성을 확보하기 위한 시공 방안이 정립되어 있지 않다. 따라서 본 연구에서는 실내 연구 결과를 토대로 다양한 배합 및 다짐 조건에 대한 시험시공을 실시하여 코어 물성 검토, 육안관찰, 혼합물의 함수비, 다짐률, 전압률, 미끄럼저항성 및 평탄성을 측정하였다. 이를 통하여 자전거도로 적용을 위한 롤러 전압 콘크리트 포장의 시공방안을 제시하였다.