• 대한기계학회논문집
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• 제17권2호
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• pp.331-341
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• 1993

The propagating crack problems under dynamic antiplane mode in orthotropic material is studied in this paper. To analyze the dynamic fracture problems by theoretical method or experimental method in orthotropic material, it is important to know the dynamic stress intensity factor in the vicinity of crack tip. Therefore the dynamic stress field and dynamic displacement field with dynamic stress intensity factor of orthotropic material in mode III were derived. When the crack propagation speed approachs to zero, the dynamic stress components and dynamic displacement components derived in this paper are identical to the those of static state. In addition, the relationships between dynamic stress intensity factor and dynamic energy release rate are determined by using the concept of crack closure energy with the dynamic stresses and dynamic displacements derived in this paper. Finally, the characteristics of crack propagation are studied with the properties of orthotropic material and crack speed. The variation of angle .alpha. between fiber direction and crack propagating direction and crack propagation speed fairly effect on stress component and displacement component in crack tip. The influence of crack propagation speed on the speed on the stress and displacement is greater in the case of .alpha.=90.deg. than in the case of .alpha.=0.deg. and the faster the crack propagation speed, the greater the stress value and displacement value.

• 한국지반신소재학회논문집
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• 제6권4호
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• pp.29-37
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• 2007

시공손상계수는 보강토 옹벽에 사용하는 지오그리드 보강재의 설계 강도 산정에 필요한 중요한 계수로서 실제 조건을 모사한 현장시험을 통해 구하고 있다. 하지만 지오그리드의 시공 중 발생하는 손상은 지오그리드의 재질, 단위면적당 중량, 뒤채움의 시공방법, 뒤채움의 입도에 따라 달라지며 현장시험을 통해 다양한 영향인자를 고려한 시공손상계수값을 도출하는데는 많은 시간과 비용이 소요된다. 본 연구에서는 시공손상에 영향을 미치는 인자들을 분석하고 뒤채움에 포함된 최대입경만을 이용하여 지오그리드 보강재의 시공손상계수를 산정하는 경험적 방법을 제시하였다.

• Journal of the Korean Wood Science and Technology
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• 제46권4호
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• pp.380-392
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• 2018

The importance of polysaccharides is increasing globally due to their role as a significant source of dietary prebiotics in the human diet. In the present study, in order to maximize the yield of crude polysaccharides from Pinus densiflora, response surface methodology (RSM) was used to optimize a two-stage extraction process consisting of steam explosion and water extraction. Three independent main variables, namely, the severity factor (Ro) for the steam explosion process, the water extraction temperature ($^{\circ}C$), and the ratio of water to raw material (v/w), were studied with respect to prebiotic sugar content. A Box-Behnken design was created on the basis of the results of these single-factor tests. The experimental data were fitted to a second-order polynomial equation for multiple regression analysis and examined using the appropriate statistical methods. The data showed that both the severity factor (Ro) and the ratio of water to material (v/w) had significant effects on the prebiotic sugar content. The optimal conditions for the two-stage process were as follows: a severity factor (Ro) of 3.86, a water extraction temperature of $89.66^{\circ}C$, and a ratio of water to material (v/w) of 39.20. Under these conditions, the prebiotic sugar content in the extract was 332.45 mg/g.

• 한국조리학회지
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• 제14권1호
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• pp.73-83
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• 2008

The purpose of this study was to investigate purchasing variables in the organic food consumption level in Busan. To achieve this purpose, 240 residential women who are organic food consumers were chosen. Among them, 149 women took part in the study. The questionnaire was composed of three parts: 8 demographic characteristics, 9 organic food purchasing conditions, and 22 purchasing variables. The research was continued from August 20th until September 10th, 2007. To derive the results, descriptive analysis, factor analysis, and ANOVA were used by spss 14.0. To sum up the results, three organic food consumption groups were classified into high, middle, and low consumption levels depending on buying condition for organic material. For the factor analysis, 5 factors were named as confidence, quality, safety, appearance, and economy. On the high consumption level, economy factor was highly important than other groups. In general, price would be a more sensitive factor, so they answered the adjusted price range; 52 participants said under 10%, 22 between 11% and 20%, and 17 over 40%.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.53-53
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• 2008

Piezoelectric transformers have been widely used such as DC-DC convertor, invertor, Ballast, etc. Because, the y have some merits compared with electro-magnetic transformers such as step-up ratio, high efficiency, small size and lg hit weight, etc. Piezoelectric transformer require high electromechanical coupling factor kp in order to induce a large out put power in proportional to applied electric field. And also, high mechanical quality factor Qm is required to prevent mechanical loss and heat generation. In general, PZT system ceramics should be sintered at high temperatures between 1200 and $1300^{\circ}C$ in order to obtain complete densification. Accordingly, environmental pollution due to its PbO evaporation. Hence, to reduce its sintering temperature, various kinds of material processing methods such as hot pressing, high energy mill, liquid phase sintering, and using ultra fine powder have been performed. Among these methods, liquid phase sintering is basically an effective method for aiding densification at low temperature. In this study, In order to comparis on low temperature sintering and solid state sintering piezoelectric transformers, rosen type transformers were fabricated u sing two PZT ceramics compositions and their electrical properties were investigated.

• Elastomers and Composites
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• 제49권2호
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• pp.160-166
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• 2014

자동차 선도장용으로 알루미늄 페이스트를 사용하여 6가지 베이스코트용 포뮬레이션이 설계되었다. 알루미늄 페이스트는 pancake 형태의 금속 안료인 #501, #801, #601와 cornflake 형태의 금속 안료인 #750, #770, #790가 사용되었다. 베이스코트의 상대적인 경화 밀도는 #501, #801, #601, #750, #770, #790 순으로 증가하였다. T-bending, 내충격성, 테이핑 부착력은 경화 밀도의 증가에 따라 향상되었다. Cornflake 형태의 안료에 대한 외관(combined factor) 테스트에서 입자가 가장 작은 #790이 다른 두 가지(#750, #770)와 비교하였을 때 가장 좋은 combined factor를 보여 주었다.

• 대한기계학회논문집
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• 제17권2호
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• pp.313-330
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• 1993

The propagating crack problems under dynamic plane mode in orthotropic material is studied in this paper. To analyze the dynamic fracture problems in orthortropic material, it is important to know the dynamic stress components and dynamic displacement components around the crack tip. Therefore the dynamic stress components of dynamic stress field and dynamic displacement components of dynamic displacement field in the crack tip of orthotropic material under the dynamic load and the steady state in crack propagation were derived. When the crack propagation speed approachs to zero, the dynamic stress component and dynamic displacement components derived in this study are identical to the those of static state. In addition, the relationships between dynamic stress intensity factor and dynamic energy release rate are determinded by using the concept of crack closure closure energy with the dynamic stresses and represented according to physical properties of the orthotrophic material and crack speeds. The faster the crack velocity, the greater the stress value of stress components in crack tip. The stress value of the stress component of crack tip is greater when fiber direction coincides with the crack propagation than when fider direction is normal to the crack propagation.

• 한국공간구조학회:학술대회논문집
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• 한국공간구조학회 2008년도 춘계 학술발표회 논문집
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• pp.19-24
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• 2008

본 논문은 풍동실험과 정적하중 실험을 실시하여 강풍 설계시 대공간 구조물의 막구조 동적응답을 확인하여 거스트 계수(gust factor)를 산출해 보고자한다. 이를 위해 섬유재료의 변형률에 따라 하중을 구할 수 있는 막재료 성능실험과 4가지(saddle형, wave형, arch형, point형) 막구조 모형에 따른 횡방향 동적하중과 동적변형응답을 측정할 수 있는 풍동실험, 동적변형응답에 따라 정적하중을 구할 수 있는 정적하중실험을 실시함으로써 거스트 계수(gust factor)를 산출하였다.

• 한국재료학회지
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• 제31권8호
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• pp.450-457
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• 2021

From measured thermal conductivity and modeling by simulation, this study suggests that U-factors are highly related to materials used between steel and polymer. The objective and prospective point of this study are to relate the relationship between the U-factor and the thermal conductivity of the materials used. For the characterization, EDX, SEM, a thermal conductive meter, and computer simulation utility are used to analyze the elemental, surface structural properties, and U-factor with a simulation of the used material between steel and polymer. This study set out to divide the curtain wall system that makes up the envelope into an aluminum frame section and entrance frame section and interpret their thermal performance with U-factors. Based on the U-factor thermal analysis results, the target curtain wall system is divided into fix and vent types. The glass is 24 mm double glazing (6 mm common glass +12 mm Argon +6 mm Low E). The same U-factor of 1.45 W/m²·K is applied. The interpretation results show that the U-factor and total U-value of the aluminum frame section are 1.449 and 2.343 W/m²·K, respectively. Meanwhile, those of the entrance frame section are 1.449 and 2.

• 전력전자학회논문지
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• 제4권2호
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• pp.122-127
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• 1999

본 논문에서는 3마력의 컴프레샤 모터를 갖는 대용량의 인버터 에어컨의 원가절감과 성능향상을 위해서 병렬구동방식을 사용한 역률제어회로를 제안하였다. 역률개선 LC필터를 제거하고 출력캐패시터와 인버터 스위치의 정격축소를 통해서 재료비를 줄이기 위해서 적절한 설계절차를 제시하였다. 이렇게 결정된 소자를 사용하여 6[kW] 소지전력을 갖는 프로토형 회로를 구성하고 제안된 회로의 동작을 확인하기 위해서 실험을 하였다.