• Journal of the Korean Society for Precision Engineering
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• v.7 no.2
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• pp.39-46
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• 1990

In this study, the mechanical behavious of a center crack which propagates between two holes in a panel are investigated. It is confirmed experimentally and analytically that a center crack stops and a small crack initiates from holes and propagates to fracture because of the compressive stress arising along the path of the fatigue crack propagation. Futhermore, it is noted that regardless of the configuration of the crack and the structure, Paris' law can be applied to the fatigue crack propagation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.1
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• pp.127-138
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• 1994

The application of fault tree technique to the analysis of compressor failure is considered. The techniques involve the decomposition of the system into a form of fault tree where certain basic events lead to a specified top event which signifies the total failure of the system. In this paper, fault trees are made by using fault train of screw type air compressor failure. The fault trees are used to obtain minimal cut sets from the modes of system failure and, hence the system failure rate for the top event can be calculated. The method of constructing fault trees and the subsequent estimation of reliability of the system is illustrated through compressor failure. It is proved that FTA is efficient to investigate the compressor failure modes and diagnose system.

• Review of KIISC
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• v.32 no.3
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• pp.57-64
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• 2022

우리 사회에서 AI 활용이 더욱 보편화 되어가고 있는 가운데 AI 신뢰에 대한 사회적 요구도 증가했다. 특히 최근 대화형 인공지능'이루다'사건으로 AI 윤리에 대한 논의가 뜨거워졌다. 금융 분야에서도 로보어드바이저, 보험 심사 등 AI가 다양하게 활용되고 있지만, AI 윤리 문제가 AI 활성화에 큰 걸림돌이 되고 있다. 본 논문에서는 인공지능으로 발생할 수 있는 윤리적 문제를 활용 도메인과 데이터 분석 파이프라인에 따라 나눈다. 금융 AI 기술 분야에 따른 윤리 문제를 분류했으며 각 분야별 윤리사례를 제시했고 윤리 문제 분류에 따른 대응 방안과 해외에서의 대응방식과 우리나라의 대응방식을 소개하며 해결방안을 제시했다. 본 연구를 통해 금융 AI 기술 발전에 더불어 윤리 문제에 대한 경각심을 고취시킬 수 있을 것으로 기대한다. 금융 AI 기술 발전이 AI 윤리와 조화를 이루며 성장하길 바라며, 금융 AI 정책 수립 시에도 AI 윤리적 문제를 염두해 두어 차별, 개인정보유출 등과 같은 AI 윤리 규범 미준수로 파생되는 문제점을 줄이며 금융분야 AI 활용이 더욱 활성화되길 기대한다.

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.4
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• pp.297-305
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• 2018

Purpose: This study aimed to analyze stress distribution and maximum von Mises stress generated in intracoronal restorations and in tooth structures of mandibular molars with various types of cavity designs and materials. Materials and Methods: Three-dimensional solid models of mandible molar such as O inlay cavity with composite and gold (OR-C, OG-C), MO inlay cavity with composite and gold (MR-C, MG-C), and minimal invasive cavity on occlusal and proximal surfaces (OR-M, MR-M) were designed. To simulate masticatory force, static axial load with total force of 200 N was applied on the tooth at 10 occlusal contact points. A finite element analysis was performed to predict stress distribution generated by occlusal loading. Results: Restorations with minimal cavity design generated significantly lower values of von Mises stress (OR-M model: 26.8 MPa; MR-M model: 72.7 MPa) compared to those with conventional cavity design (341.9 MPa to 397.2 MPa). In tooth structure, magnitudes of maximum von Mises stresses were similar among models with conventional design (372.8 - 412.9 MPa) and models with minimal cavity design (361.1 - 384.4 MPa). Conclusion: Minimal invasive models generated smaller maximum von Mises stresses within restorations. Within the enamel, similar maximum von Mises stresses were observed for models with minimal cavity design and those with conventional design.

• The korean journal of orthodontics
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• v.32 no.2 s.91
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• pp.143-153
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• 2002

The bonded orthodontic retainer constructed from composite and multistrand orthodontic wire provides an esthetic and efficient system for maintained retention. This study was designed to measure shear bond strength of bonded retainers and to suggest a optimal combination of a multistrand wire and bonding method used when bonded retainer was fabricated. 160 sound maxillary and mandibular premolars were used for 80 test samples. After Uniformizing bonding area, length of wire, and thickness of composite, multistrand wire was bonded to fabricated a bonded retainer by direct or indirect bonding method. Shear bond strength and extension length of each sample were measured by a universal testing machine. The results of this study were as follows : 1. In vitro shear bond testing found 6-stranded, 0.0155 inch wires to have the largest shear bond strength and 3-stranded, 0.0195 inch wires to have the least shear bond strength. But, These difference was not statistically significant(p<0.05). 2. In vitro extension testing found 3-stranded, 0.0155 inch wires to have the largest extension length and 3-stranded, 0.0195 inch wires to have the least extension length(p<0.05). The larger diameter wire was used, the larger extension length was shown. But, the strand of wire is not related to the extension length of wire. 3. In comparison with direct bonding method, larger shear bond strength and extension length was shown in indirect bonding method(p<0.05).

• Journal of Energy Engineering
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• v.22 no.4
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• pp.394-398
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• 2013

At present, using of electromagnetic control valve (ECV) in external variable displacement swash plate type compressor is a common issue. Solenoid operated ECV controls vehicle air conditioning system through a pulse width modulation (PWM) input signal that supplied from an external source. Different port pressure controls the swash plate movement inside the compressor at certain angles that finally determines the refrigerant flow rate to the vehicle compartment for passengers comfort. In this paper, crankcase pressure flow (Pc flow) is calculated with some ECV samples with corresponding to amount of variable supply of current ranges from 0.20Amp to 0.95Amp.

• 월간낙농육우
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• v.34 no.8
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• pp.162-165
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• 2014

국내 낙농경영이 복합경영에서 규모화된 전업농 또는 기업농 형태의 단일경영으로 빠르게 변하고 있다는 것은 모두가 알고 있는 사실이다. 이에 따라 착유시설 또한 많은 변화가 있었으며, 사육규모 및 두당 유생산랑과 정(正)의 상관관계를 갖고 있다. 국내 낙농산업의 초창기 또는 본격적인 도입기였던 1970년대와 1980년대 초반은 가구당 착유우 두수가 10두 미만이었으며 주로 손으로 착유를 하였다. 1980년대 중반 이후, 콤프레셔와 버킷설비가 목장에 도입되었으며, 냉각기 보조금 지급 및 보냉 집유차량이 목장별로 운행하기 시작하였다. 1990년대에는 버킷식 착유기가 파이프라인식 착유기로 전환되면서 착유시스템이 일부 자동화됨에 따라 노동력을 낮추고 원유의 위생안전성을 향상시킬 수 있었다. 2000년대에는 많은 목장에서 탠덤 또는 헤링본식 착유시스템을 도입하였으며, 이후 일부 착유두수가 60두 이상인 대규모 농가에서는 자동착유시스템을 도입하여 현재에 이르고 있다. 사실 전업농, 기업농으로 전환된 단일경영에서 지동착유시스템의 도입에 많은 관심을 보이고 있으나, 고가의 자동칙유시스템에 대한 한정된 정보에서 기인하는 리스크(위험요소) 등으로 인하여 섣불리 결정을 내리지 못하고 있는 실정이다. 이에 자동착유시스템의 구성 국내 외 도입 현황 및 장 단점 사례조사 결과와 함께 현재 농가의 자동착유시스템 도입 결정에 도움을 주기 위해 진행하고 있는 연구 과제를 소개하고자 한다.

• Journal of Environmental Health Sciences
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• v.28 no.5
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• pp.35-41
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• 2002

This study was conducted to evaluate the effect of initial concentration on pilot-scale composting of diesel-con-laminated soil. Sandy soi] was used in this study. Target contaminant, diesel oil, was spiked. at about 10,000, 25,000, and 50,000 mg TPH/kg of dry roil. Mit ratio of soil to sludge was 1:0.5 as wet weight basis. Removal efficiencies for initial concentrations of 12,966,23,894 and 51,042 mg TPH/kg were 90, 93 and 54％, respectively, during 33 days of composting. Normal alkanes in TPH ranged from 15 to 22％ in initial soils. Volatilization of individual normal alkane in 1,999 mg n-alkanes/kgwas completed within 4 days, while n-alkane compounds of Cl1-Cl4 in 5,270 and 9,836 mg n-alkanes/kg were volatilized continuously during 33 days of composing operation. The first order degradation rate con-stants for 12,966, 23,894, and 51,042 mg TPH/kg were 0.058, 0.076, and 0.022/day, and those for 1,997 5,270, and 9,836 mg n-alkanes/kg were 0.093, 0.100, and 0.019/day, respectively. Considering TPH removal rate, $CO_2$porduction rate, and dehydrogenase activity, the concentration of 51,042 mg TPH/kg inhibited biodegradation of diesel-composting.

• Tribology and Lubricants
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• v.13 no.1
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• pp.62-69
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• 1997

Rapid increase of refrigeration and air-conditioning systems 9r & a systems) in modern industries brings attention to the urgency of research & development as a core technology in the area. And it is required to the compatibility problem of r & a systems to alternative refrigerant for the protection of environment. The, it is requested to study the lubrication characteristics of refrigerant compressor which is the core technology in the r & a systems. The study of lubrication characteristics in the critical sliding component is essential for the design of refrigerant compressor. Therefore, theoretical investigation of the lubrication characteristics of rotary compressor for r & a systems is studied. The newton-Raphson method is used for the EHL analysis between vane and rolling piston in the rotary compressor. The results show that the rotational speed of a shaft and the discharge pressure influence significantly the friction force between vane and rolling piston. This results give important basic data for the further lubrication analysis and design of a rotary compressor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05e
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• pp.44-48
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• 2003

할로겐 난연재료 및 고분자의 연소시 Dioxine의 문제점이 대두되고 있어 유럽국가를 중심으로 할로겐 난연제 사용을 규제하고 있다. 환경과 인체에 대한 안정성을 고려해서 저 유해 가스화, 저 발연화, 저 부식성, 리사이클링 등을 겸비한 제품의 개발로 관심이 모아지고 있는 실정이다. 본 연구에서는 환경친화적인 금속화합(수산화 알루미늄)을 사용하여 연소시 발생할 수 있는 난연성, 무독성, 소연성 등을 함량별로 확인하고 난연재가 증가할수록 취약한 기계적 물성 보완을 위해 moisture cure crosslikable 기술로 케이블절연 및 자켓 피복층 특성을 증가 시켰다. 그러나 수산화알루미늄 함량이 증가할수록 기계적 물성과 기타 특성도 감소하는 경향을 보이고 있어 최적의 난연제 조성함량이 약 130~150 phr정도에서 우수한 결과를 확인하였다. 또한 moisture cure agent는 전선압출 시 표면에 scorch 및 장기 압출에 영향을 주므로 약 1.5~2phr 범위에서 처방하는 것이 우수하다. 원료투입 후 mixing 공정 중에서는 온도관리가 매우 중요하므로 되도록 믹싱 온도를 $130^{\circ}C$ 이하를 유지해야한다. 온도는 수산화알루미늄의 분산성과 케이블 피복압출 시 표면에도 영향을 주기 때문이다 본 연구는 이런 작업방법을 통해 친환경 가교 난연콤파운드가 비(比) 가교된 제품에 비해 특성이 증가되는 것을 입증할 수 있었다.