• 한국자동차공학회논문집
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• 제13권5호
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• pp.127-133
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• 2005

Rotary swaging is one of the incremental forming process which is a chipless process using the reduction of cross-sections of bars, tubes and wires. The TDS(Tube Drive Shaft) of monobloc used in automotive has been developed by the rotary swaging process. The mechanical characteristics of swaged parts such as the hardness, thickness and roughness are also estimated to conduct experimental analyses of rotary swaging process with the materials of 34Mn5 Furthermore the change in the vibration mode of TDS due to design parameters, which are the tube length, diameter and thickness, has been investigated and analysed. The weight of the TDS product is smaller by about $12.8\%$ than that of SDS with the same performance. It could be evidently found that the TDS is designed to be much lighter than SDS (Solid Drive Shaft). This advantage might give some possibility to improve the NVH (Noise-Vibration-Harshness) characteristics. A maximum torque and a total number of torsional repetitions for the TDS is checked and measured to know the torsional intensity and fatigue strength through the static torsion test and torsional durability test, respectively. A total number of the torsional repetitions up to the fracture for the TDS is greater than 250,000 times.

• 항공우주기술
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• 제10권1호
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• pp.183-192
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• 2011

최근 항공기의 성능향상 및 경량화 등의 필요에 의해 많은 항공기 특히 소형항공기 구조물에 있어 복합재료의 사용이 증가되고 있다. 그러나 복합재료의 복잡한 기계적 거동 특성 및 파손양상 등으로 인하여 그 사용에는 많은 제한이 따르고 있는 실정이다. 복합재에 발생하는 저속충격은 외관상 드러나지는 않기 때문에 복합재 구조물을 설계하는 데 있어 매우 중요하며, 특히 충격 후 충격손상으로 야기되는 층간 분리등은 구조물의 압축강도를 현저하게 저하시킬 수 있다. 본 연구에서는 적층복합재 구조물의 저속충격에 의한 손상거동 및 충격 후 잔류압축강도를 수치적으로 예측하였다. 예측 된 충격하중 이력곡선과 충격후의 압축 강도를 시험결과와 비교하였고 잘 일치함을 확인 할 수 있었다.

• 한국식품영양과학회지
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• 제28권2호
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• pp.429-437
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• 1999

A mathematical model was established for estimating changes in pressure and volume of permeable kimchi packages. The model comprises the CO2 gas production from kimchi and permeation of O2, CO2 and N2 through the permeable film or sheet. Using the developed model, the effects of various packaging variables on the pressure and volume changes were analyzed for rigid and flexible packag es of kimchi(3% salt content) at 15oC, and then effect of storage temperature was also looked into. In case of rigid pack of 400g, using the plastic sheet of high CO2 permeability and initial vacuumizing can help to relieve the problem of pressure build up. The lower fill weight can further reduce the pressure, but will result in higher packaging cost. For the flexible package of 3 kg, highly permeable films such as low density polyethylene(LDPE) and polypropylene can reduce the volume expansion. Higher ratio of CO2 permeability to O2 and N2 permeabilities are effective in reducing the volume expansion. Increased surface area cannot contribute to reduction of volume expansion for highly permeable flexible packages of kimchi. For the impermeable packages, pressure and volume at over ripening stage (acidity 1.0%) increase with decreased temperature, while those at optimum ripening stage(acidity 0.6%) change little with temperature. Pressure of permeable rigid LDPE package increases with tem perature at any ripening stage, and temperature affects the volume of flexible LDPE package very slightly. Experimental verification of the present results and package design with economical consid eration are needed as a next step for practical application.

• 한국터널지하공간학회 논문집
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• 제15권2호
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• pp.123-134
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• 2013

도시지역에 주로 건설되는 지하차도는 기존의 터널과 달리 지표면에 근접한 지반에 시공되어 지하수의 양압력에 의한 구조물 부상 및 손상이 발생할 수 있다. 도심지 지하차도의 기존 설계방법(사하중 증가 또는 영구앵커 등의 부력 대처공법)은 지나치게 안전측인 보수적 설계를 수행하고 있어 시공기간 및 경제적 비용 증가를 초래한다. 최근 이를 보완하는 공법으로 영구배수공법 사용이 증가하고 있으나 대상 토질과 지하수 등을 고려한 적절한 분석과정 없이 선정되는 실정이다. 따라서 본 연구에서는 최근 Y지역에 설치되는 영구배수공법의 일종인 유도배수공법을 대상으로 지반공학적 관점에서 합리적인 설계체계를 수립하기 위해 지하수위 변화, 지하차도 옹벽 높이, 기초지반 조건 등 다양한 매개변수에 대한 수치해석을 수행하였다. 본 연구 결과로부터 유도배수공법은 지하수에 의해 발생하는 양압력을 효과적으로 저감시킬 수 있음을 확인하였다.

• 한국산학기술학회논문지
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• 제16권11호
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• pp.7385-7393
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• 2015

본 연구는 청소년 대상으로 현미와 채식 급식을 제공하여 주관적 건강상태, BMI, 혈액학적 지표들의 변화를 알아보기 위한 단일군 실험설계 연구이다. 연구대상자는 현재 고등학교에 재학 중인 17명의 남학생과 18명의 여학생이었다. 12주간 학교 급식으로 대상자들에게 현미와 채식 식단을 점심과 저녁에 제공하였으며, 프로그램 적용 전후 설문조사와 혈액검사를 통해 자료를 수집하였고, 수집된 자료는 paired t-test로 차이검증 하였다. 12주후에 대상자들은 주관적 건강상태가 좋아졌으며, BMI는 감소하였고, 혈액 소견 중에 Hct, Hb, Hct, total protein과 albumin은 감소하였으며, 여학생 군에서는 Ca과 triglyceride level도 유의하게 감소하였다. 하지만 감소된 모든 수치는 정상범위 내였다. 이러한 결과는 청소년기 때 현미와 채식 식단은 건강한 식습관 형성을 통해 체중을 감소시키고, 성인기의 뇌심혈관계 질병들을 예방하는데 도움이 될 것이다.

• 기술사
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• 제1권1호
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• pp.18-25
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• 1968

Higher yield in rice paddies is greatly dependent on adequately balanced and timely supply of water. A majority of rice paddy in Korea is generally irrigated by rainfall, but in many cases it has to be supplemented by artificial irrigation for optimum rice culture. Although the water requirement of rice plant is for higher Than that of athec crops, submerged condition of rice paddy is not Necessarily required. The moisture requirement of rice plant varies with its growing stages, and it is possible to increase the irrigation efficiency through reduction of water loss due to percolation in rice paddies. An experimental plots were set up by means of sandomized block design with three duplication; (a) All time submerged, (b) Economically controlled, and (c) Extremely controlled. Three different irrigation periods Were (a) Initial sage, (b) Inter-stage, and (c) Yast stage. The topsoil of the three plots were excavated to the depth of 30 cm and then compacted with clay of 6 cm thickness. There after, they were piled up with the excavated top soils, leveled and cored with clay of 6 cm thickness around footpath in order to prevent leakage. The results obtained from the experiments are as follows, 1. There is no difference among the three experiments plots in terms of physical and chemical conditions, soil properties, and other characteristics. 2. Culm length and ear length are not affected by different irrigation methods. 3. There is no difference in the mature rate and 1, 000 grain weight of rice for the three plots. 4. The control plot which was irrigated every three days shows an increased yield over the all the time submerged plot by 17.8 percent. 5. The clay lined plot whose water holding capacity was held 5 days long, needs only to be irrigated every 7 days. 6. The clay lined plot shows an increased yield over the untreated plot ; over all-the-time submerged plot by 18 percent ; extremely controlled plot by 18 percent, and economically controlled plot by 33 percent. 7. It may be saved in water requirement about one Thirds.

• 한국수소및신에너지학회논문집
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• 제29권6호
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• pp.570-577
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• 2018

Composite pressure vessels made through filament winding are widely used in various fields. Numerous studies regarding composite pressure vessels have been conducted in the automotive industry to improve the space efficiency of trunks as well as the fuel efficiency. Compared with steel liquefied petroleum gas (LPG) vessels used in the conventional LPG vehicles, the use of type 4 composite pressure vessels has advantages in terms of reduction of the weight of vehicles. This study focused on development of type 4 composite pressure vessels that can be installed in the spare tire well. Those type 4 composite pressure vessels are designed with torispherical dome shapes instead of geodecis dome shapes because of the space limitation. To reduce deformation due to the stresses in the axial direction of the vessels, thereby securing the safety of the container, the reinforcing bar concept was applied. A structural analysis software, ABAQUS, confirmed the effect of the reinforcing bar on the axial deformation through the type 4 composite pressure vessel. As a result, the final winding angle of the composite layer was analyzed by applying $26^{\circ}/28^{\circ}/26^{\circ}/28^{\circ}/26^{\circ}/88^{\circ}$ The tensile stress was 939.2 MPa and the compressive stress was 249.3 MPa.

• 한국기계가공학회지
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• 제18권6호
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• pp.98-105
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• 2019

In order to improve the fuel economy and dynamic behavior of automobiles, the weight reduction tendency of automobile parts is obvious. Also, in order to maximize assembly and maintenance convenience, various parts are integrated and modularized. Multi-piece methods require many manufacturing processes and become a factor of lowering the strength of parts. It is advantageous to overcome the disadvantages by integrally manufacturing to reduce the processing steps and ensure the strength of the parts. However, when it is necessary to process in a narrow space inside the part, it is impossible to process with the existing spindle. The angle head spindle is only a component of a machine tool, but it is a core part that requires high technology and is highly utilizable in products requiring high precision machining. Therefore, various and continuous studies needs for angle head spindles in areas such as vibration absorption, operational safety, excellent dimensional stability, and strength. In this paper, we propose an optimal design for angle head spindle by performing structural analysis and shape optimization for angle head spindle gear and case.

• Asian-Australasian Journal of Animal Sciences
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• 제32권4호
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• pp.548-555
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• 2019

Objective: The main objective of this study was to evaluate the effect of different feeding levels of a total mixed ration silage-based diet on feed intake, total tract digestion, enteric methane emissions, and energy partitioning in two beef cattle genotypes. Methods: Six mature bulls (three Thai natives, and three Thai natives - Charolais crossbreeds) were assigned in a replicated $3{\times}3$ Latin square design, with cattle breed genotype in separate squares, three periods of 21 days, and three energy feeding above maintenance levels (1.1, 1.5, and 2.0 MEm, where MEm is metabolizable energy requirement for maintenance). Bulls were placed in a metabolic cage equipped with a ventilated head box respiration system to evaluate digestibility, record respiration gases, and determine energy balance. Results: Increasing the feeding level had no significant effect on digestibility but drastically reduced the enteric methane emission rate (p<0.05). Increasing the feeding level also significantly increased the energy retention and utilization efficiency (p<0.01). The Thai native cattle had greater enteric methane emission rate, digestibility, and energy utilization efficiency than the Charolais crossbred cattle (p<0.05). The daily metabolizable energy requirement for maintenance in Thai native cattle ($388kJ/kg\;BW^{0.75}$, where $BW^{0.75}$ is metabolic body weight) was 15% less than that in Charolais crossbred cattle ($444kJ/kg\;BW^{0.75}$). Conclusion: Our results suggested that the greater feeding level in zebu beef cattle fed above maintenance levels resulted in improved energy retention and utilization efficiency because of the reduction in enteric methane energy loss. The results also indicated higher efficiency of metabolisable energy utilization for growth and a lower energy requirement for maintenance in Bos indicus than in Bos taurus.

• 한국기계가공학회지
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• 제18권1호
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• pp.24-30
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• 2019

The deck floor of a the cargo truck becomesis damaged and aged due to the continuous loading of the loading cargo and external environmental factors. Floor boards made of wood and metal are often used. In the case of wood, the cost is high due to the use of imported wood, and the strength is easily deterioratesd due to environmental factors. In the case of metal materials, the durability is higher than that of wood, but problems are raised due to the effect of major factors that hinder the weight reduction, and the effects of corrosion. In order to replace this stucturestructural design, this study proposed a wood fiber composite using natural raw materials. Woody composites are being used as environmentally and friendly exterior materials with the combined advantages of plastic, and wood,; low cost and low density. However, due to the nature of the woody composites, the properties are differentdiffer depending on the contents of the matrix, reinforcing agent, additives, compatibilizer, etc. In this study, we investigate these problems through analysis of the microstructure and mechanical properties according to proper content and injection molding conditions. As a result, it is considered that the wood deck composite can replaced the current Deck Floor Boardreplace current deck floor boards through continuous continued research and results of this study.