• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.185-190
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• 2005

This work presents a numerical procedure to optimize the elliptic-shaped pin fin arrays to enhance turbulent heat transfer. The response surface method is used as an optimization technique with Reynolds-averaged Navier Stokes analysis of flow and heat transfer. Shear stress transport (SST) turbulence model is used as a turbulence closure. Computational results for average heat transfer rate show a reasonable agreement with the experimental data. Four variables including major axis length, minor axis length, pitch and the pin fin length nondimensionalized by duct height are chosen as design variables. The objective function is defined as a linear combination of heat transfer and friction-loss related terms with weighting factor. D-optimal design is used to reduce the data points, and, with only 28 points, reliable response surface is obtained. Optimum shapes of the pin-fin arrays have been obtained in the range from 0.0 to 0.1 of weighting factor.

• Journal of information and communication convergence engineering
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• v.15 no.2
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• pp.91-96
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• 2017

PIN-entry interfaces have high risks to leak secret values if the malicious attackers perform shoulder-surfing attacks with advanced monitoring and observation devices. To make the PIN-entry secure, many studies have considered invisible radio channels as a secure medium to deliver private information. However, the methods are also vulnerable if the malicious adversaries find a hint of secret values from user's $na{\ddot{i}}ve$ gestures. In this paper, we revisit the state-of-art radio channel based bimodal PIN-entry method and analyze the information leakage from the previous method by exploiting the sight tracking attacks. The proposed sight tracking attack technique significantly reduces the original password complexities by 93.8% after post-processing. To keep the security level strong, we introduce the advanced bimodal PIN-entry technique. The new technique delivers the secret indicator information through a secure radio channel and the smartphone screen only displays the multiple indicator options without corresponding numbers. Afterwards, the users select the target value by following the circular layout. The method completely hides the password and is secure against the advanced shoulder-surfing attacks.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.9-17
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• 2010

In this study, von Mises stress and total strain energy density characteristics of lead pin in PGA (Pin Grid Array) packages have been calculated by using the FEM (Finite Element Method). FEM computation is carried out with various heat treatment conditions of lead pin material under $20^{\circ}$ bending and 50 mm tension condition. Results show that von Mises stress locally concentrated on lead pin corners and interface between lead pin head and solder. von Mises stress and total strain energy density decrease as heat treatment temperature of lead pin increases. Also, round shaped corner of lead pin decreases both von Mises stress and total strain energy density on interface between lead pin head and solder. This means that PGA package reliability can be improved by changing the mechanical property of lead pin through heat treatment. This has been known that solder fatigue life decreases as total strain energy density of solder increases. Therefore, it is recommended that both optimized lead pin shape and optimized material property with high lead pin heat treatment temperature determine better PGA package reliability.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.481-485
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• 2000

A new type of compliant press-fit pin has been developed and evaluated for use packaging of electronic telecommunications equipments. Main requirements for design are defined the upper limit of pin insertion force and the lower limit of pin retention force. Upper limit of pin insertion force is set to protect the copper plate of the inner PTH wall. Lower limit of pin retention force is set to satisfy a wire-wrapping specification. Results are represented by insertion force and retention force variations according to the front angle, rear angle and material, etc.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.4
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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.

• Journal of Ocean Engineering and Technology
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• v.14 no.4
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• pp.79-85
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• 2000

Press-fit pin connection is the solderless interference-fit between pins and plated through holes(PTH) in the printed curcuit board(PCB). Because of not only its simple assembly and absence of problems associated with soldering, but also its good mechanical and electrical characteristics, the press-fit pin connection technology has quickly gained wide acceptance in the telecommunications and computer industries. In this paper, the contact stress characteristics of the domestic CPF pin when inserted into the friction coefficients were compared and the stress variations of the compliant part of the pin, which have an influence on the performance, were displayed with the time and arc length after complete connected. It is supposed that the results will provide useful data to improve the performance of the pin-PCB interconnection mechanism.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.1
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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.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.6
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• pp.131-138
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• 2004

The objective of this paper is to decide optimal location of a pin-hole to minimize stress concentration around the hole in a rotating disc. The focus of this investigation is to evaluate the effect of pin-hole on stress distribution around the hole using optimum design technique and finite element analysis. Design variables are the radial and the angular location of pin-hole from center of the hole and objective function is the maximum stress around hole in a rotating disc. Using first order method of optimization technique, we found that the maximum equivalent stress around the hole with optimized pin-hole could be reduced by 15.1% compared to that without pin-hole.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1138-1141
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• 2010

모바일 기기나 ATM에서의 사용자 인증에는 PIN(Personal Identification Number)이 주로 사용된다. 그 이유는, PIN은 사용자가 외우기 쉽고 단순한 UI(User Interface)로 구현이 가능하다는 장점이 있기 때문이다. 하지만 PIN은 어깨너머 공격에 취약하다는 단점이 있다. 기존의 연구들은 이미지 기반, 인식 기반, PIN과 이미지의 혼합방식을 이용한 다양한 사용자 인증 방법들을 제안하였다. 하지만 이들 연구는 모바일의 작은 화면을 고려하지 않아 구현이 어렵거나, 어깨너머 공격에 취약하거나, 사용자에게 기억에 대한 부담을 증가시키는 등의 문제점이 있다. 본 논문에서는 PIN과 패턴 이미지를 결합하여 모바일 기기에 적합하면서, 어깨너머 공격에 대해 기존의 방법들에 비해 안전하고 사용자가 외워야 하는 기호(숫자, 이미지 등)가 적은 사용자 인증 방법을 제안한다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.74-78
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• 2003

Stress analysis was conducted with finite element method to study the stress distributions in both single-pin and multi-pin loaded composite laminates. The various parameters involved in the design of the joint method were considered. The stress distributions in the vicinity of the holes were predicted considering the effects of various parameters such as the lay-ups, number of pins, number of rows, row spacing, and hole patterns. The results show that the performance of joint is greatly affected by these parameters.