• Journal of Aerospace System Engineering
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• v.17 no.1
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• pp.10-15
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• 2023

Wet multi-disk clutch, a power switching device of the ducted fan, was optimized and results were analyzed. The clutch was divided into two types depending on whether a mechanical lock-up was applied or not. It was optimized under each design condition. Transfer torque capacity, friction material surface pressure, friction surface temperature, and drag torque were calculated as factors to optimize the clutch. The volume of separator plate and drag torque were used as the objective function for optimization. In the case of Type 1, which did not include a mechanical lock-up, the clutch could be operated regardless of the pitch angle of the ducted fan. However, the outer diameter of the friction surface was doubled, the volume was increased by 5~7 times, and the drag torque was increased by 7~12 times compared to those of Type 2, which included a mechanical lock-up.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.34 no.4
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• pp.651-666
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• 2024

Android devices employ lock screens with various authentication methods to protect user data. However, even with the lock screen active, the device can be accessed via the Android Debug Bridge(ADB), a powerful development tool that controls devices connected through USB. In this paper, we explore methods to bypass the lock screen security mechanism by leveraging the characteristics of ADB. To achieve this, we analyze ADB commands to categorize those that can severely impact the Android system and propose LockPickFuzzer, a fuzzing test tool that automatically explores ways to combine these commands to disable lock screen security. To demonstrate LockPickFuzzer's ability to detect security vulnerabilities using ADB, we conducted experiments on the Galaxy S23 and Pixel 8, both running Android 14. The results revealed two ADB command combinations that could either steal authentication information or bypass the lock screen. We submitted a report on these discovered vulnerabilities to the Samsung security team and received official acknowledgment (SVE-2023-1344) from Samsung Electronics for one ADB command combination that can be reproduced on user devices. LockPickFuzzer is a practical tool that operates automatically without user intervention and is expected to contribute to the effective detection of security vulnerabilities caused by ADB command combinations on Android devices.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.1
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• pp.74-84
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• 2007

This paper presents a new dual-loop Delay Locked Loop(DLL) to expand the delay lock range of a conventional DLL. The proposed dual-loop DLL contains a Coarse_loop and a Fine_loop, and its operation utilizes one of the loops selected by comparing the initial time-difference among the reference clock and 2 internal clocks. The 2 internal clock signals are taken, respectively, at the midpoint and endpoint of a VCDL and thus are $180^{\circ}$ separated in phase. When the proposed DLL is out of the conventional lock range, the Coarse_loop is selected to push the DLL in the conventional lock range and then the Fine_loop is used to complete the locking process. Therefore, the proposed DLL is always stably locked in unless it is harmonically false-locked. Since the VCDL employed in the proposed DLL needs two control voltages to adjust the delay time, it uses TG-based inverters, instead of conventional, multi-stacked, current-starved inverters, to compose the delay line. The new VCDL provides a wider delay range than a conventional VCDL In overall, the proposed DLL demonstrates a more than 2 times wider lock range than a conventional DLL. The proposed DLL circuits have been designed, simulated and proved using 0.18um, 1.8V TSMC CMOS library and its operation frequency range is 100MHz${\sim}$1GHz. Finally, the maximum phase error of the DLL locked in at 1GHz is less than 11.2ps showing a high resolution and the simulated power consumption is 11.5mW.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1618-1621
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• 2003

Wire rope is widely used to handle heavy materials. The material used to build the wire rope lock is mostly aluminum which is expensive. In this study, wire rope lock made of cheeper material with better performance is developed.

• Science of Emotion and Sensibility
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• v.17 no.4
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• pp.79-88
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• 2014

Smart-phones have become a vital part of our lives, paying a bill online, shopping using applications, using email and office applications. Therefore, the risk of the leakage of personal informations and the misuse of them becomes high, for the cost of loosing smart-phone. Many types of smart-phone security features such as password, slide-lock, and pattern lock have been introduced. However, those security locks make users not to easily access and use a smart-phone. There is tradeoff between security on one hand, and usability and cost on the other. This paper propose Self-Concealment to solve the tradeoff problem and demonstrate the effect through the experiment. In sum, Self-Concealment lowers smart-phone experience; however increases smart-phone use intension. This paper has implication for proposing new User Experience (UX) construct to resolve the trade-off between security and usability.

• The Transactions of the Korea Information Processing Society
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• v.3 no.4
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• pp.803-816
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• 1996

It is possible to prevent deadlock if the priority which is conventionally given to transactions is endowed to data items and the transactions with the highest priority among transactions accessing the data item is allowed to proceed. Based on this observation, we proposed a Data-Priority Based Locking Protocol(DPLP) and evaluated its performance against known locking protocols in Real Time Database Management System(RTDBMS). Transaction inter-arrival time(IAT) was varied to determine success ratio, average-lateness, confict ratio and restart ratio, In these simulations we verified that the proposed DPLP performs better than the other protocols.

• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.1
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• pp.246-254
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• 2001

The breech system can be considered as a pressure vessel with an internal plug under high explosive pressure. The system consists of a breech block(internal plug) whose front surface subjects to pressure, and a breech ring(pressure vessel). There is the geometric discontinuity around roots of connection parts and then stress concentration is introduced due to pressure, where contact effect may be ignored because contact plane between two equipments is parallel ideally, Generally high stress concentration phenomena shorten the life cycle of the mechanical system. It is well known that shock load is much more harmful on safety of the system than static load. In this present paper, several geometric design variables which may affect stress condition on the system are chosen and the parametric study on the design variables is carried using commercial FEM codes. Finally, the obtained results in the single lug breech system are applied to design the 3 lugs breech system. The 3 lugs breech system can reduce the maximum stress level.

• Proceedings of the Korean Society of Computer Information Conference
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• 2010.07a
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• pp.421-423
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• 2010

본 논문에서는 ART2 알고리즘을 이용하여 잠금 상태에서 스마트폰의 어플리케이션을 쉽고 빠르게 구동하기 위한 방법을 제안한다. 자신이 원하는 그림과 설치되어 있는 어플리케이션과의 대응 테이블을 만들기 위하여 학습 어플리케이션을 실행한다. 학습 어플리케이션의 동작 순서는 어플리케이션 실행 후 화면 하단에서 빠른 실행을 하고자 하는 어플리케이션을 선택하고 좌측상단에 위치하고 있는 입력 부분에 그림을 그린 후, 학습 버튼을 클릭한다. 그려진 그림의 배경은 0으로 그림은 1로 변환하고 ART2의 입력으로 사용할 수 있도록 일정한 크기로 정규화한다. 정규화 된 데이터를 팽창 연산을 통하여 학습에 용이하도록 최외각 픽셀을 확장하여 ART2의 입력 데이터로 적용한다. 학습이 끝난 후, 잠금 상태에서 액정 윗부분에 학습된 것과 같은 모양의 그림을 그리면 해당 어플리케이션이 실행된다. 제안된 방법은 기존의 방식인 잠금 해제 후, 어플리케이션을 탐색하고, 해당 어플리케이션을 실행하는 3 단계로 된 방식을 1 단계로 줄이기 때문에 원하는 어플리케이션을 실행하는데 시간이 적게 소요되는 장점이 있다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.331-332
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• 2022

The previously used locking device is a PIN method and has a problem in that the password is exposed by malicious users. In other words, if attackers looks at lock passwords from the side, correct passwords are known. In this paper, we aim to solve these security problems in lock devices resistant to shoulder surfing attacks. The proposed encryption approach is designed so that attackers cannot know lock passwords. To this end, we use a hidden password method instead of directly entering a PIN-type password to prevent the correct password from being exposed to an attacker even if someone steals the lock password.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.2
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• pp.157-164
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• 2011

This work is devoted to the technique application of lock-in infrared Thermography in the shipbuilding and ocean engineering industry. For this purpose, an exploratory study to find the optimized test conditions is carried out by the design of experiments. It has been confirmed to be useful method that the phase contrast images were quantified by a reference image and weighted by defect hole size. Illuminated optical intensity of lower or medium strength give a good result for getting a phase contrast image. In order to get a good phase contrast image, lock-in frequency factors should be high in proportion to the illuminated optical intensity. The integration time of infrared camera should have been inversely proportional to the optical intensity. The other hand, the difference of specimen materials gave a slightly biased results not being discriminative reasoning.