• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1518-1520
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• 2008

Recent clinical studies have shown that computer navigation for total knee arthroplasty (TKA) provides improved component alignment accuracy. However, femoral stress fracture after computernavigated TKA have been reported due to the pin hole and we hypothesized that osteoporosis would be one of the key factors in pin hole fracture after computer-navigated TKA. We investigated the von-Mises stress around the femoral pin-hole for different elastic modulli and ultimate stresses and four different pin penetration modes to understand the aging effect on femoral stress fracture risk after computer-navigated TKA by finite element analysis. In this study, aging effect was shown to increase the femoral stress fracture risk for all pin penetration modes. Especially, aging effect was shown dramatically in the transcortical pin penetration mode.

• JSTS:Journal of Semiconductor Technology and Science
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• 제10권1호
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• pp.45-48
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• 2010

An inter-pin skew compensation scheme is proposed, which minimizes the inter-pin skew of parallel interface induced by unequal trace length and loading of printed circuit board (PCB). The proposed scheme measures the inter-pin skew and compensates during power-up with simple hardware. The proposed scheme is applied to 3.2-Gb/s/pin DDR4 SDRAM and implemented in a 0.18 m CMOS process. The inter-pin skew is compensated in 324-cycles of 400-MHz clock and the skew is compensated to be less than 24-ps.

• International Journal of Aeronautical and Space Sciences
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• 제16권4호
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• pp.537-547
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• 2015

A Monte Carlo (MC) simulation was conducted to predict the reliability of a newly developed pyrotechnic pin puller. The reliability model is based on the stress-strength interference model that states that failure occurs if the stress exceeds the strength. In this study, the stress is considered to be the energy consumed by movement of a pin shaft, and the strength is considered to be the energy generated by pyrotechnic combustion for driving the pin shaft. Failure of the pin puller can thus be defined as the consumed energy being greater than the generated energy. These energies were calculated using a performance model formulated in the previous study of the present authors. The MC method was used to synthesize the probability densities of the two energies and evaluate the reliability of the pin puller. From a probabilistic perspective, the calculated reliability was compared to a deterministic safety factor. A sensitivity analysis was also conducted to determine which design parameters most affect the reliability.

• 오토저널
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• 제15권1호
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• pp.89-99
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• 1993

In this research, important mechanical characteristics of Compliant Press-Fit Pin and PHT are studied through the analysis of deformation mechanisms of Press-Fit Pin and by elastic-plastic finite element method. The direct data for the optimal design of pin was obtained without interfere with the criterion on insertion force and retention force. Also, the insertion force and retention force of new type pin were measured by precision type tensile testing machine and it revealed good agreement with analytical results. In conclusion, it is believed that above results will contribute satisfactorily to the practical design of Press-Fit Pin.

• Tribology and Lubricants
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• 제24권6호
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• pp.315-319
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• 2008

This paper presents the interface bonding characteristics between a phosphor bronze and a steel plate for pin-bush bearings. The pin-bush bearing is an important component in which is used to reduce a friction loss and a wear against the piston pin. The pin-bush bearing is manufactured by hot-pressing a phosphor bronze and a back metal of a steel plate. This paper investigated the bonding interface characteristics in which is manufactured by melting a copper based bronze and a steel plate. The hardness from the inner surface of a bronze to the outer one of steel has been measured using a Vickers hardness tester. The experimental results show that the hardness of a bronze is superior to that of the conventional bronze and the transient hardness of pin-bush bearings is gradually increasing to the hardness of the steel back metal. This means that the bonding interface zone of pin-bush bearings may be fabricated by defusing a bronze to the steel plate due to a density difference between two materials.

• Tribology and Lubricants
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• 제36권3호
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• pp.168-192
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• 2020

In recently designed diesel engines, the running conditions for piston-pin bearings have become severe because of the higher combustion pressure and increased temperature. Moreover, the metal removal from the bushing material has strongly reduced the ability of the antifriction material to accept asperity contacts. Therefore, it is necessary to find ways of reducing wear scar on the connecting-rod small-end bushing and piston-pin boss bearing related to the higher combustion pressure on the power cell of an engine. In this work, the position and level of material removal from the surfaces of the bushing and bearing under such severe operating conditions - for example, maximum power and torque conditions of a passenger car diesel engine - are estimated for several combinations of surface roughness. First, piston-pin rotating motion is investigated by calculating the friction coefficient at piston-pin bearings, the oil film thickness, and the frictional torques induced by hydrodynamic shear stress. Subsequently, the wear scarring on the surfaces of a connecting-rod small-end bushing and two piston-pin boss bearings related to piston-pin rotational motion is numerically calculated under the maximum power and torque operating conditions. This work is helpful to determine the reasonable surface roughness of the bushing and bearing for reducing wear volume occurring at the interface between a bearing and a shaft.

• 대한의용생체공학회:의공학회지
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• 제29권6호
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• pp.451-456
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• 2008

Total knee arthroplasty(TKA) using computer-assisted navigation has been increased in order to improve the accuracy of femoral and tibial components implantation. Recently, a few clinical studies have reported on the femoral stress fracture after TKA using computer-assisted navigation. The purpose of this study is to investigate the stress concentration around the femoral pin-hole for different pin-hole diameter, the modes of pin penetration by finite element analysis to understand the effects of pin-hole parameters on femoral stress fracture risk. A three-dimensional finite element model of a male femur was reconstructed from 1 mm thick computed tomography(CT) images. The bone was rigidly fixed to a 25 mm above the distal end and 1500 N of axial compressive force and 12 Nm of axial torsion were applied at the femoral head. For all cases, transcortical pin penetration mode showed the highest stress fracture risk and unicortical pin penetration mode showed the lowest stress concentration. Pin-hole diameter increased the stress concentration, but pin number did not increase the stress dramatically. The results of this study provided a biomechanical guideline for pin-hole fracture risk of the computer navigated TKA.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제6권12호
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• pp.497-506
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• 2017

스마트폰의 가속도 센서로 사용자의 걸음이나 행동을 분석하여 사용자 인증을 하는 연구는 이전에도 있었으나, PIN 입력에 적용하기에는 사용자 편의성이 낮아서 부족한 면이 있었다. 이 논문에서는 스마트폰의 스크린을 직접 터치하는 것이 아니라, 스마트폰의 진동 센서와 가속도 센서를 이용하여 PIN을 입력하는 기법을 제안한다. 우리는 제안한 기법을 이용하여 사용성 실험을 진행하였고 사용자가 이 기법에 익숙해짐에 따라 사용성이 높아진다는 것과 그로인해 평균 12.9초, 100%의 확률로 PIN을 입력할 수 있다는 것을 확인하였다. 또한 보안성 실험을 통해 공격자가 촬영 공격을 이용하여 사용자를 공격했을 때 공격 성공률이 0%이였다는 것과 그로인해 기존에 존재하는 PIN 입력 기법보다 안전하다는 것을 확인하였다. 결과적으로 충분히 사용될 수 있는 기법이라는 것을 확인하였다.

• 대한기계학회논문집B
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• 제29권7호
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• pp.828-836
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• 2005

Impingement/effusion cooling technique is used for combustor liner or turbine parts cooling in gas turbine engine. In the impingement/effusion cooling system, the crossflow generated in the cooling channel induces an adverse effect on the cooling performance, which consequently affects the durability of the cooling system. In the present study, to reduce the adverse effect of the crossflow and improve the cooling performance, circular pin fins are installed in impingement/effusion cooling system and the heat transfer characteristics are investigated. The pin fins are installed between two perforated plates and the crossflow passes between these two plates. A blowing ratio is changed from 0.5 to 1.5 for the fixed jet Reynolds number of 10,000 and five circular pin fin arrangements are considered in this study. The local heat/mass transfer coefficients on the effusion plate are measured using a naphthalene sublimation method. The results show that local distributions of heat/mass transfer coefficient are changed due to the installation of pin fins. Due to the generation of vortex and wake by the pin fin, locally low heat/mass transfer regions are reduced. Moreover, the pin fin prevents the wall jet from being swept away, resulting in the increase of heat/mass transfer. When the pin fin is installed in front of the impinging let, the blockage effect on the crossflow enhances the heat/mass transfer. However, the pin fin installed just behind the impinging jet blocks up the wall jet, decreasing the heat/mass transfer. As the blowing ratio increases, the pin fins lead to the higher Sh value compared to the case without pin fins, inducing $16\%{\~}22\%$ enhancement of overall Sh value at high blowing ratio of M=1.5.

• 산업융합연구
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• 제20권11호
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• pp.191-196
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• 2022

핀테크 환경에서 스마트 폰을 이용한 금융거래가 활발하게 이루어지고 있다. 안전한 금융거래를 위해 사용자 인증 기술이 필수적이다. 기존 보안 키패드를 통한 PIN 인증은 입력 편리성이 좋지만, 보안성이 떨어지고 취약점이 존재한다. 생체인증 기법은 보안성이 안전하지만 오탐 및 미탐 인증 가능성이 있다. 이를 보완하기 위해 2-factor 인증을 사용한다. 본 논문에서는 생체인증 기법을 적용한 PIN 입력을 통해 편리성과 보안성을 높일 수 있는 1.5-factor 인증을 제안하고자 한다. 지문인증의 안정성과 2~4번의 PIN 입력을 통해 편리성을 제공하여 안전한 금융거래가 가능하다. 제안기법은 PIN 입력 시 생체인증을 동시에 수행하므로 PIN 입력할 때 터치하는 영역에 지문인식을 적용하는 방식이다. 보안이 요구되는 경우 높은 안전성이 요구되는 상황에서는 추가적인 PIN 입력을 통해 입력 편리성을 보장하면서 사용자 인증을 수행하여 안전한 금융거래가 가능하다.