• Korean Journal of Optics and Photonics
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• v.23 no.1
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• pp.42-51
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• 2012

In this paper, injection-locking characteristics versus active layer structures in Fabry-Perot laser diodes (FP-LD) are compared. TE and TM gain spectra and peak gains versus carrier density in polarized and unpolarized multiple quantum well structures and in an unpolarized bulk structure are calculated. The calculated gain parameters are applied to a time-domain large-signal model to simulate the injection-locking characteristics. The results show that RIN in unpolarized FD-LDs is about 3 dB lower than that in a polarized FP-LD and that the eye characteristics of the unpolarized FP-LD are much better than those of the polarized FP-LD.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.11
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• pp.1471-1477
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• 2019

Currently, there are various security methods in smart phone. Among them, pin number and pattern lock were used long as they were used from early smart phone. However, security is weak that much. The security of pin number is slightly high, but the security of conventional pattern lock remains moderate. However, the conventional pattern lock is still used by several people because of convenience. This is because some users' smart phones don't support biometric security. The most convenient security method for devices that don't support biometric security is pattern lock. However, this method is vulnerable to shoulder surfing attack and smudge attack. Therefore, we introduce random pattern lock that solves the vulnerability of the conventional pattern lock while maintaining the convenience of the pattern lock. This is a lock method that places each point placed on the screen in a circular shape and assigns a random number to it. Therefore, If this is introduced, It's expected to solve vulnerability.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.2
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• pp.227-242
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• 2022

This paper presents a Cache-Coherency Interconnect(CCI)-based Android pattern screen lock(PSL) attack on modern ARM processors. CCI has been introduced to maintain the cache coherency between the big core cluster and the little core cluster. That is, CCI is the central interconnect inside SoC that maintains cache coherency and shares data. In this paper, we reveal that CCI can be a side channel in security, that an adversary can observe security-sensitive operations. We design and implement a technique to compromise Android PSL within only a few attempts using the information of CCI in user-level applications on Android Nougat. Further, we analyzed the relationship between the pattern complexity and security. Our evaluation results show that complex and simple patterns would have similar security strengths against the proposed technique.

• Journal of Digital Contents Society
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• v.18 no.1
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• pp.101-108
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• 2017

In existing public parcel locker, if there is not an empty storage box, it is not used. In existing private parcel locker, because it is a lock-based locker, there is strong weak point in security. To prevent these drawbacks, the proposed private parcel locker has a menu-driven remote control application which is operated on smartphone. The lock release and the security number change by the security number which is stored in the Electrically erasable read-only memory, are possible. As a result, the proposed method has better advantages than the existing methods in terms of unnecessariness of empty storage box check and security by the security number accumulation function and the automatic SMS transmission representing parcel locker operation result.

• Journal of Korea Game Society
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• v.20 no.5
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• pp.53-64
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• 2020

Supporting NNS method in KD-Tree algorithm is essential in multidimensional data applications. In this paper, we propose HD-Tree, a high-performance Lock-Free KD-Tree that supports NNS in situations where reads and writes occurs concurrently. HD-Tree reduced the number of synchronization nodes used in NNS and requires less atomic operations during Lock-Free method execution. Comparing with existing algorithms, in a multi-core system with 8 core 16 thread, HD-Tree's performance has improved up to 95% on NNS and 15% on modifying in oversubscription situation.

• Journal of Korea Game Society
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• v.21 no.1
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• pp.55-66
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• 2021

Multi-thread programming is essential in high performance game programming. But, the widely used C++11 shared_ptr and weak_ptr have malfunction and performance problems in multi-thread environments. In this paper, we propose Lock-Free shared_ptr and weak_ptr, which have higher performance than current error preventing methods. These use a non-blocking algorithm to prevent data race in multi-thread environments. As a result of experimenting in an 8 thread environment, performance has improved up to 7424% in a situation where competition between threads is low, and 3767% in high competition.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.3
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• pp.32-41
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• 1995

In the analysis of metal forming processes by the finite element method, there are many numerical instabilities such as element locking, hourglass mode and shear locking. These instabilities may have a bad effect upon accuracy and convergence. The present work is concerned with improvement of stability and efficiency in two-dimensional rigid-plastic finite element method using various type of elemenmts and numerical intergration schemes. As metal forming examples, upsetting and backward extrusion are taken for comparison among the methods: various element types and numerical integration schemes. Comparison is made in terms of stability and efficiency in element behavior and computational efficiency and a new scheme of adaptive directional reduced integration is introduced. As a result, the finite element computation has been stabilized from the viewpoint of computational time, convergency, and numerical instability.

• Journal of Navigation and Port Research
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• v.28 no.3
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• pp.227-232
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• 2004

Vehicle dynamics control systems are complex and non-linear, so they have difficulties in developing a controller for the anti-lock braking systems and the auto-traction systems. Currently the fuzzy-logic technique to estimate the absolute vehicle speed supplies good results in normal conditions. But the estimation error in severe braking is discontented In this paper, we estimate the absolute vehicle speed of UCT(Unmanned Container Transporter) by using the wheel speed data from standard anti-lock braking system wheel speed sensors. Radial symmetric basis function of the neural network model is proposed to implement and estimate the absolute vehicle speed, and principal component analysis on input data is used 10 algorithms are verified experimentally to estimate the absolute vehicle speed and one of them is perfectly shown to estimate the vehicle speed within 4％ error during a braking maneuver.