• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.4
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• pp.317-322
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• 2013

This paper presents a new laser lock-in thermography (LLT) technique for nondestructive evaluation. LLT utilizes a modulated continuous wave laser beam as a heat source to obtain high fidelity thermal wave images even at the presence of background heat disturbances. The thermal waves propagating along the surface and through-the-thickness directions of a structure are visualized using newly developed laser lock-in amplitude and phase images, enhancing the detectability of surface and subsurface defects. The LLT technique is numerically investigated and experimentally validated using thermal images obtained from a steel specimen with low emissivity.

• 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.

• 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.

• Journal of KIISE:Databases
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• v.28 no.4
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• pp.742-757
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• 2001

Since database management systems(DBMSS) have limited lock resources, transactions requesting locks beyond the limit mutt be aborted. In the worst carte, if such transactions are aborted repeatedly, the DBMS can become paralyzed, i.e., transaction execute but cannot commit. Lock escalation is considered a solution to this problem. However, existing lock escalation methods do not provide a complete solution. In this paper, we prognose a new lock escalation method, adaptive lock escalation, that selves most of the problems. First, we propose a general model for lock escalation and present the concept of the unescalatable look, which is the major cause making the transactions to abort. Second, we propose the notions of semi lock escalation, lock blocking, and selective relief as the mechanisms to control the number of unescalatable locks. We then propose the adaptive lock escalation method using these notions. Adaptive lock escalation reduces needless aborts and guarantees that the DBMS is not paralyzed under excessive lock requests. It also allows graceful degradation of performance under those circumstances. Third, through extensive simulation, we show that adaptive lock escalation outperforms existing lock escalation methods. The results show that, compared to the existing methods, adaptive lock escalation reduces the number of aborts and the average response time, and increases the throughput to a great extent. Especially, it is shown that the number of concurrent transactions can be increased more than 16 ~256 fold. The contribution of this paper is significant in that it has formally analysed the role of lock escalation in lock resource management and identified the detailed underlying mechanisms. Existing lock escalation methods rely on users or system administrator to handle the problems of excessive lock requests. In contrast, adaptive lock escalation releases the users of this responsibility by providing graceful degradation and preventing system paralysis through automatic control of unescalatable locks Thus adaptive lock escalation can contribute to developing self-tuning: DBMSS that draw a lot of attention these days.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.1
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• pp.27-33
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• 2012

The relationship between the excitation frequency and the vortex shedding frequency is analyzed during the oscillation of the circular cylinder. Two-dimension unsteady Navier-Stoke's equation is calculated by using the Optimized High Order Compact (OHOC) scheme. The flow condition is Mach number 0.3 and Reynold's number 1000. From the results acquired by calculation, it can be inferred that, when the excitation frequency is near the vortex shedding frequency at the fixed cylinder wake, the oscillation frequency of lift and drag coefficients appears to lock-on. The lock-on refers to a phenomenon in which the aerodynamic coefficient appears as one primary oscillation frequency through excitation and its amplitude is amplified. In the non-lock-on zone, the excitation frequency is not in the lock-on mode anymore and beat is formed in which two or more primary oscillation frequencies of the aerodynamic coefficient are mixed together.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.9
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• pp.44-51
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• 2019

Three types of samples with defects were measured by lock-in med-IR (infrared) thermography with various lock-in frequencies for different materials. The lock-in method can be used to detect defects when an external energy source is applied to the object, the non-uniformity of the incident thermal energy distribution is eliminated, and the camera's measurement cycle is synchronized with the load cycle of the incident energy source. For inspecting samples with defects, results of thermal images are analyzed when three types of materials, i.e., SM45C, STS316L, and AL6061 are tested and three lock-in frequencies, i.e., 0.08, 0.1, and 0.12 Hz are applied. In this study, the optimal lock-in frequencies were determined by comparing the results of each material and lock-in frequency measured using the mid-IR camera.

• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.87-89
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• 2005

In this paper, we analyzed that characteristics of flux-lock type superconducting fault current limiter (SFCL) using the third winding to fault current limiting. The flux-lock type SFCL using the third winding consists of the first and seconding windings which are wound in parallel each other a iron core. Also it connected inductively the third winding connected resistance of series. Because of the hysteresis according to the increased voltage, the distortion of current in the flux-lock type SFCL occurs. It is a disadvantage to increase the capacity of SFCL. We conformed that the third winding of the flux-lock type SFCL prevented the distortion of current. Also, the third winding did not affect the initial fault current of the flux-lock type SFCL.

• Journal of the Semiconductor & Display Technology
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• v.13 no.4
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• pp.77-81
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• 2014

There have been developed in authentication systems for information using biometric information approaches such as fingerprint, face, and iris. In general, a door-lock system is operated by touching keypads, which remains fingerprints on the keypads. Such door-lock systems do not protect personal information from others due to the exposure of fingerprints to keypads. In this paper, we propose the new door-lock system that does not leave fingerprints on the keypads. Without touching keypad the system works because the system accepts authentication information by using illuminance sensor and LED. The experiment shows that the implemented door-lock system works well under any circumstance.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.493-495
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• 2006

The hysteresis characteristics of flux-lock reactor, which is an essential component of flux-lock type superconducting fault current limiter (SFCL), was investigated. The hysteresis loss of iron core in flux-lock type SFCL does not happen due to its winding's structure especially in the normal state. From the equivalent circuit for the flux-lock type SFCL and the fault current limiting experiments, the hysteresis curves could be drawn. Through the hysteresis curves together with the fault current level due to the inductance ratio for the 1st and 2nd windings, the increase of the number of turns in the 2nd winding of the flux-lock type SFCL had a role to prevent the iron core from saturation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.601-604
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• 2003

The magnetic field generated in the iron core, which is required for the magnetic field to link each coil of the flux-lock type reactor, affects the fault current limiting characteristics of the flux-lock type high-Tc superconducting fault current limiter(SFCL). By applying numerical analysis for equivalent circuit of flux-lock type SFCL, the magnetic field induced in the iron core including currents of each coil was investigated. Through the analysis of magnetic field, we have analyzed that the magnetic field linked the 3rd coil, which is wound in the iron core, prevents the saturation of the iron core, but decreases the impedance of the flux-lock type SFCL.