• Journal of Sensor Science and Technology
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• v.23 no.1
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• pp.24-28
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• 2014

A lock-in amplifier was proposed for capacitive sensor applications. This amplifier was based on a general-purpose microcontroller and had only a charge amplifier as analog circuits. All the other functions of lock-in amplifier except for the charge amplifier were implemented with firmware and the internal resources of the microcontroller. A rectangular signal, generated by the microcontroller, was used in a sensor-driving signal instead of a conventional sinusoidal signal. This makes it possible that the phase comparison circuit in the lockin amplifier is made with analog-to-digital converter, a timer and an interrupt controller. Using the oversampling method and the rectangular driving signal, we can make it easy to implement the peak detection function with software and sample the peak-to-peak signal at charge amplifier output. A charge amplifier was proposed to cancel out the base capacitance existing in capacitive sensors structurally. The experimental results show that the lock-in amplifier operating in the supply voltage of 3.0 V cancels out the base capacitance and has good linearity.

• Journal of Industrial Technology
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• v.18
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• pp.355-362
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• 1998

The deadlock detector is a DBMS sub-component that examines periodically whether system is in a deadlock state based on lock waiting information of transactions. The deadlock detector and transactions execute concurrently in a DBMS and read and/or write the lock waiting information simultaneously. Since the lock waiting information is a shared one, we need an efficient method guaranteeing its physical consistency by using mutual exclusion. In this paper, we propose a new method that effectively guarantees physical consistency of lock waiting information. Two primary goals of our method is to minimize the processing overhead and to maximize system concurrency.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.11
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• pp.995-999
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• 2007

We investigated the characteristics of a flux-lock type superconducting fault current limiter(SFCL) considering magnetization characteristic of iron core. The flux-lock type SFCL, like other types of SFCLs using the iron core, undergoes the saturation of the iron core during the initial fault time. Therefore, if the design to prevent the saturation of the iron core is considered, the effective fault current limiting operation can be achieved. Through the analysis for its equivalent circuit including the magnetization characteristic of the iron core, the limiting impedance of the flux-lock type SFCL was drawn. The magnetization currents and the limited currents of SFCL, which were dependent on the winding direction and the turns' ratio between two coils, were investigated from the short circuit experiment. It was confirmed that their experimental results agreed with the analysis ones.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.165-166
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• 2005

In this paper, we investigated the quench generation of HTSC elements in fault types according to inductance variation in the integrated three-phase flux-lock type SFCL. The integrated three-phase flux-lock type SFCL was the upgrade version of the single-phase flux-lock type SFCL. The structure of the integrated three-phase flux-lock type SFCL consisted of three-phase flux-lock reactor wound on an iron core with the ratio of the same turn between coil 1 and coil 2 in each phase. When the SFCL is operated under the normal condition, the flux generated in the iron core is zero because the flux generated between two coils of each single phase is canceled out. Therefore, the SFCL's impedance is zero, and the SFCL has negligible influence on the power system. However, if a fault occurs in any single-phase among three phases, the flux generated in the iron core is not zero any more. The flux makes HTSC elements of all phases quench irrespective of the fault type, which reduces the current of fault phase as well as the current of sound phase. It was observed that the fault current limiting characteristics of the suggested SFCL were dependent on the quench characteristics of HTSC elements in all three phases.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.54-56
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• 2005

In this paper, we investigated the quench characteristics of HTSC elements in the integrated three-phase flux-lock type SFCL according to fault types such as the single-line-to-ground fault, the double-line-to-ground fault, the line-to-line fault and the three-line-to-ground fault. The integrated three-phase flux-lock type SFCL was the upgrade version of the single-phase flux-lock type SFCL. The structure of the integrated three-phase flux-lock type SFCL consisted of three-phase flux-lock reactor wound on an iron core with the ratio of the same turn between coil 1 and coil 2 in each phase. When the SFCL is operated under the normal condition, the flux generated in the iron core is zero because the flux generated between two coils of each single phase is canceled out. Therefore, the SFCL's impedance is zero, and the SFCL has negligible influence on the power system. However, if a fault occurs in any single-phase among three phases, the flux generated in the iron core is not zero any more. The flux makes HTSC elements of all phases quench irrespective of the fault type, which reduces the current of fault phase as well as the current of sound phase. It was observed that the fault current limiting characteristics of the suggested SFCL were dependent on the quench characteristics of HTSC elements in all three phases.

• Journal of Oral Medicine and Pain
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• v.38 no.3
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• pp.267-274
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• 2013

This study was performed to investigate the skeletal factors related to open lock of the temporomandibular joint(TMJ). We compared the skeletal measurements on the cephalogram and transcranial radiograph among 3 groups, open lock group consisting of consecutively filed 50 patients with at least one open lock episode within recent 1 year, temporomandibular disorder(TMD) group of 50 TMD patients without open lock diagnosed by Research Diagnostic Criteria for TMD (RDC/TMD) Axis I, and normal group of 50 patients without TMD or open lock. The patients of TMD and normal group were randomly selected in an age-and-gender-matched way with ones of open lock group. Open lock group showed smaller saddle angle than normal group on cephalograms and steeper inclination of the articular eminence than TMD and normal groups on transcranial radiographs. These results imply that the patients with the joint located more anterior and the articular eminence with steeper inclination might be riskier to TMJ open lock.

• Journal of the Korean Institute of Navigation
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• v.21 no.1
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• pp.13-31
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• 1997

Being situated at the key point of northeast asia, the port of Inchon as an entrance to the captial city, Seoul is expected to play in marine transportation in Korean Pennisular on the verge of its reunification. In this thesis, inner-lock physical disstribution system of the port was analyzed, which treats more than 82% of total incoming and outgoing cargoes. The overall findings are as follows; 1. In thet viewpoint of physical distribution system of the port, it takes disadvantages of accessing to inner lock berth due to such natural restrictions as tides, passing the lock and so on. And insufficient port facilities as a whole, causes delay in quay-handling, transfer and storage, also facing with serious congestion in inland transport on the road. 2. It was revealed that the port facilities are insufficient yet in spite of its improved productivity by means of raising the effectiveness of port operation and of installing advanced cargo handling facilities. 3. In order to enhance the effectiveness of inner port physical distribution system , the improvement of lock facilities, expansionof port facilities and more effective terminal operating system are crucial. 4. To ensure the measures to solve the above problem, existent outer-lock ports such as Inchon Sourthern-port and Northern-port are necessary to be redeveloped more positively , otherwise a new port at outskirt of the city should be developed to ensure free connection to inland transportation.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.18 no.6
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• pp.133-145
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• 2023

This paper examines whether investors have adapted to the venture capital(VC) investment style. VC firms invest in privately held companies and generate returns by selling them after the lock-up period expires. We analyze the impact on stock prices before and after the lock-up period expiration, and compare the Cumulative Abnormal Return(CAR) between the past period(2015-2017) and the recent period(2020-2022) to investigate the effect of the second venture boom. The main findings are as follows. First, unlike in the past, stock price returns around the lock-up period expiration have been lower than the KOSDAQ index in recent years. Second, the impact on stock prices is significant for both 1-month and 12-month lock-up periods. Specifically, it is confirmed that stocks held by venture capital and professional investors with a 1-month lock-up period respond in advance to their information after the second venture boom. Finally, we find that there is a difference in CAR depending on whether or not the company received VC investment after the second venture boom. Based on our findings, we suggest that VC firms need to revise their exit strategies to improve performance. This includes finding ways to reduce information asymmetry and fees, as well as developing strategies to mitigate market volatility. Additionally, the current lock-up period for VCs should be reconsidered as it may increase the risk of stock price decline. We recommend that the government revise the scope and duration of lock-up periods to protect investors after IPO.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.8
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• pp.747-753
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• 2005

We Investigated the current limiting characteristics of the flux-lock type superconducting fault current limiter(SFCL) by fault angles. The flux-lock type SFCL consists of the primary and the secondary copper coils wound in parallel through the iron core and YBCO thin film. In this paper, the current limiting characteristics of the flux-lock type SFCL by fault angles in case of the subtractive and the additive polarity windings were compared and analyzed. The flux-lock type SFCL limited fault current more quickly as the fault angles increased. On the other hand, the initial power burden of the superconducting element during the fault increased as the fault angles increased. In addition, we found that the resistance of the flux-lock type SFCL in case of the subtractive polarity winding was more increased than that of the additive polarity winding. The peak current of the fault current in case of the subtractive polarity winding was larger than that of the additive polarity winding.

• Transactions on Electrical and Electronic Materials
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• v.6 no.4
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• pp.159-163
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• 2005

We analyzed the fault current limiting characteristics of a flux-lock type $high-T_c$ super­conducting fault current limiter (HTSC-FCL) using series resonance between capacitor for series resonance and magnetic field coil which was installed in coil 3. The capacitor for the series resonance in the flux-lock type HTSC-FCL was inserted in series with the magnetic field coil to apply enough magnetic field into HTSC element, which resulted in higher resistance of HTSC element. However, the impedance of the flux lock type HTSC-FCL has started to decrease since the current of coil 3 exceeded one of coil 2 after a fault accident. The decrease in the impedance of the FCL causes the line current to increase and, if continues, the capacitor for the series resonance to be destructed. To avoid this operation, the flux-lock type HTSC-FCL requires an additional device such as fault current interrupter or control circuit for magnetic field. From the experimental results, we investigated the parameter range where the operation as mentioned above for the designed flux-lock type HTSC-FCL using series resonance occurred.