• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.3
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• pp.222-230
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• 1998

This paper proposes a new gate drive circuit for high power IGBTs which can reduce the harmful effect of reverse recovery current at turn-on and actively suppress the overvoltage across the driven IGBT at turn-off without a snubber circuit. The turn-on scheme decreases the rising rate of the collector current by inereasing the input capacitance at turn-on transient when the gate-emitter voltage goes above threshold voltage. It results in soft transient of the reverse recovery current with no variation in turn-on delay time. The turn-off driving scheme has adaptive feature to the amplitude of collector current, so that the overvoltage can be limited much effectively at the fault collector current. Experimental results under various normal and fault conditions prove the effectiveness of the proposed circuit.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.3
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• pp.50-58
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• 2017

TPCLT(Twice Per Cycle Left-turn) operation reduces this left-turn 'spill-over' problem on an as needed basis by servicing the protected left-turn movement as a leading and a lagging left-turn. In this study, to evaluate the effectiveness of TPCLT applied to three-legged signalized intersection in Korea, the analysis was carried out using VISSIM and SSAM model analysis. The study was implemented by three cases which are TPCLT operation, non-TPCLT operation and half-cycle operation using VISSIM program. According to the 9-left-turn volume scenario, total delay and travel times of each case was analyzed by VISSIM program. The study result shows more effective applying TPCLT operaion in the present ~ +50% scenario area at the intersection in terms of total delay.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.10
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• pp.713-718
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• 1987

A new method for the modeling of non-ideal dc-dc converters whose switching times are finite is proposed. The effects of finite turn-on, turn-off times, delay time, storage time, reverse recovery process on the system stability, dc transfer function and efficiency are investigated. It is verified how system poles are changed and how dc transfer function and efficiency are decreased by non-ideal switching.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.104-108
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• 2015

Delay on State-Funded Construction Projects (SFCPs) in Dong Thap - a province in Mekong Delta of Vietnam, as many provinces of Vietnam, have caused budget overrun through many recent years. The budget-overrun situations, in turn, have deepened the delay. Identifying critical factors affecting delay SFCPs plays a key role to mitigate negative impact of delay. 134/160 questionnaires were collected from personals working for project owners, consultants, supervisors and contractors in Dong Thap Province. Convenient sampling method was used. EFA was resulted in critical 04 factors with 20 variables caused delay in SFCPs, including: "Project technic, contractor's financial capacity and adjustment role of the government", "Regulation and Policy", "Mutual benefit support and concern between the government and residents", and "Disadvantage of construction site and weather season". Reliable measures to reduce delay on SFCPs are discussed to establish legal corridors to strictly controlling the process, consider mutual benefit between the government and its residents, and evaluating construction conditions. Those measures are considered could be applied in not only Dong Thap province, but most provinces of Vietnam as well.

• Journal of Korean Society of Transportation
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• v.29 no.5
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• pp.157-167
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• 2011

Many problems, such as unexpected delay and collision with pedestrians or vehicles, occur generally at signalized intersections where bicycle users are frequently involved. These problems have hindered bicycle users from riding bicycles on urban highways. The aim of this study is to suggest proper traffic signal operation methods for safe and convenient highway crossing of bicycles. Three types of crossing methods at signalized intersections are proposed and analyzed: (1) indirect left turn, (2) direct left turn on an exclusive bicycle lane, and (3) direct left turn on a bicycle box. The VISSIM simulation tests were conducted based on fifty-four operation scenarios prepared by varying vehicle and bicycle traffic volumes. Both delay and the number of stops are used as the measures of effectiveness in the analysis. The results from the three-legged signalized intersections suggested that (1) the indirect left turn is appropriate when vehicle demand is high while bicycle demand is not, (2) direct left turn on an exclusive bicycle lane is appropriate when both vehicle and bicycle demands are high, and (3) direct left turn on a bicycle box is appropriate when both vehicle and bicycle demands are light.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.2
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• pp.156-161
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• 1997

In this thesis, based on Genetic Algorithm, a new route search algorithm is presented to search an optimal route between the origin and the destination in intelligent route guidance systems in order to minimize the route traveling time. The proposed algorithm is effectively employed to complex road networks which have diverse turn constrains, time-delay constraints due to cross signals, and stochastic traffic volume. The algorithm is also shown to significantly promote search efficiency by changing the population size of path individuals that exist in each generation through the concept of age and lifetime to each path individual. A virtual road-traffic network with various turn constraints and traffic volume is simulated, where the suggested algorithm promptly produces not only an optimal route to minimize the route cost but also the estimated travel time for any pair of the origin and the destination, while effectively avoiding turn constraints and traffic jam.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.5
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• pp.37-42
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• 2012

In this paper, a new charge pump is proposed to reduce the timing mismatch in the conventional current-steering charge pumps. Conventional current-steering charge pumps used NMOS input stages both for UP and DOWN signals, which resulted in different numbers of stage for UP and DOWN delay paths. The proposed charge pump has equalized the numbers of stages for UP and DOWN signals by using a PMOS stage for the DOWN signal. The simulation results show that the conventional current-steering charge pump has 14ns and 6ns for optimized timing mismatches between UP and DOWN signals for turn-on and turn-off, respectively. On the other hand, the proposed charge pump has improved timing mismatches of 6ns and 5ns for turn-on and turn-off, respectively. As a result, the reference spurs are reduced from -26dBc to -39dBc for the proposed charge pump. The proposed charge pump was designed by using $0.18{\mu}m$ CMOS technology. The measurement results show that the maximum variation of the charging and discharging current over the charge pump output voltage range of 0.3~1.5V is approximately 1.5%.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.323-326
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• 2007

When traveling on real road network, it generally takes less travel time in a near straight path than a zig-zaged path with same source and destination. In order to making a left(right/u) turn, the delay should be required to decrease the speed. The traffic signal waiting time of left(right/u) turn is probably longer than straight driving. In this paper, we revise the previous hierarchical path finding algorithm to reduce the number of turns. The algorithm proposed in this paper complied with a hierarchical $A^*$ algorithm, but has a distinct strategy for edge weight. We define an edge that makes a turn as a turn-edge and give the turn-edge lower weight to maintain the straightness of the whole path.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.26-30
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• 2018

The turn-to-turn contact resistance of 2G high temperature superconducting (HTS) coils with metal insulation (MI) is closely related to the stability of the coils, current charging rate and delay time [1]. MI coils were fabricated using five kinds of metal tapes such as aluminum (Al) tape, brass tape, stainless steel (SS) tape, copper (Cu)-plated tape and one-sided Cu-plated SS tape. The turn-to-turn contact surface resistances of co-winding model coils using Al tape, brass tape, and SS tape were 342.6, 343.6 and $724.8{\mu}{\Omega}{\cdot}cm^2$, respectively. The turn-to-turn contact resistance of the model coil using the one-sided Cu-plated SS tape was $ 248.8{\mu}{\Omega}{\cdot}cm^2$, which was lower than that of Al and brass tape. Al or brass tape can be used to reduce contact resistance and improve the stability of the coil. Considering strength, SS tape is recommended. For strength and low contact resistance, SS tape with copper plating on one side can be used.

• Journal of Korean Society of Transportation
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• v.25 no.6
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• pp.65-77
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• 2007

A two-way left-turn lane is a continuous center left-turn lane that could be used as a deceleration and refuge area for both directions of left-turning vehicles. TWLTL's have been used effectively for access management treatment when applied to a highway that has wide-spread left turning traffic demand and a high-density of side streets. In this study, an effective analysis was carried out using a computer-based simulation tool, VISSIM, in order to evaluate performance and safety effects of TWLTLs and develop a warrant. In conclusion, the results indicated that there was a remarkable decrease of through and left-turning vehicle travel time delay on the main road and improvement of traffic safety.