• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.201-210
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• 2018

This paper proposes a new start-up method for a load commutated inverter (LCI) in a large synchronous gas-turbine generator. The initial rotor position for start-up torque is detected by the proposed initial angle detector, which consists of an integrator and a phase-locked loop. The initial rotor position is accurately detected within 150ms, and the angle difference between the real position and the detected position is less than 1%. The LCI system operates in two modes (forced commutation mode and natural commutation mode) according to operating speed range. The proposed controllers include a forced commutation controller for the low-speed range, a PI speed controller and a PI current controller, where the forced commutation controller is connected to the current controller in parallel. The current controller is modeled by Matlab/Simulink, where a six-pulse delay of the thyristor and a processing delay are considered by using a zero-order hold. The performance of the proposed start-up method is evaluated in Matlab/Psim at standstill and at low speed. To verify the feasibility of the method, a 5kVA LCI system prototype is implemented, and the proposed initial angle detector and the system performance are confirmed by experimental results from standstill to 900rpm.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.2
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• pp.87-96
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• 1993

Because of the complexity, nonlinearity and long-time delay of power plant, the star-up operation of a fossil power plant is very difficult to automate. So the start-up operation is always carried out by the skilled human operators, who utilize their knowledges and experiences for the predesigned start-up schedules and procedures. In this paper, a fuzzy logic controller is designed for the start-up operation of the power plant. And the operators experiences are modeled in terms of fuzzy sets and variables. To validate the controller, a drum-type boiler of the Seoul Power Plant is constructed via the signal flow diagram. Using the model, the suggested automatic start-up operation is verified, and the results are also presented.

• The KIPS Transactions:PartA
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• v.16A no.5
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• pp.347-356
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• 2009

Precise branch prediction is a critical factor in the IPC Improvement of modern microprocessor architectures. In addition to the branch prediction accuracy, branch prediction delay have a profound impact on overall system performance as well. However, it tends to be overlooked when the architects design the branch predictor. To tolerate branch prediction delay, this paper proposes Early Start Prediction (ESP) technique. The proposed solution dynamically identifies the start instruction of basic block, called as Basic Block Start Address (BB_SA), and the solution uses BB_SA when predicting the branch direction, instead of branch instruction address itself. The performance of the proposed scheme can be further improved by combining short interval hiding technique between BB_SA and branch instruction. The simulation result shows that the proposed solution hides prediction latency, with providing same level of prediction accuracy compared to the conventional predictors. Furthermore, the combination with short interval hiding technique provides a substantial IPC improvement of up to 10.1%, and the IPC is actually same with ideal branch predictor, regardless of branch predictor configurations, such as clock frequency, delay model, and PHT size.

• Journal of Korean Society of Transportation
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• v.6 no.1
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• pp.55-64
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• 1988

Prior to using any computer model, the program-embedded palameters showing significant differences from real world should be calibrated. This is especially true when the model is expected to be used fro various roadway and traffic condition. The calibration of TRANSYT model was conducted for the parameters of start-up delay, and lag, stop penalty(K), platoon dispersion factor, and saturation flow rate. The values of the parameters were obtained by theoretical methods from actual field measurements for discharging and arrival pattern. The sites elected for the study was an intersection of Dongil-Ro and Hwarang-Ro, and a 334 meter downstrean section from the intersection stop line on westbound Hwarang-Ro. The study results showed that the start-up delay was 2.6 sec, end lag was 1.0 sec, saturation flow rate was 2287 pcphgpl, platoon dispersion factor was 0.2-03, and stop penalty(K) was 32. However, since these parameters re apt to depend on traffic and roadway condition, it is doubtful whether the obtained values will be applicable to the area-wide situation other than this particular site.

• Journal of Communications and Networks
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• v.8 no.3
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• pp.351-359
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• 2006

In this article, we present a new slow-start variant, which improves the throughput of transmission control protocol (TCP) Vegas. We call this new mechanism Gallop-Vegas because it quickly ramps up to the available bandwidth and reduces the burstiness during the slow-start phase. TCP is known to send bursts of packets during its slow-start phase due to the fast window increase and the ACK-clock based transmission. This phenomenon causes TCP Vegas to change from slow-start phase to congestion-avoidance phase too early in the large bandwidth-delay product (BDP) links. Therefore, in Gallop-Vegas, we increase the congestion window size with a rate between exponential growth and linear growth during slow-start phase. Our analysis, simulation results, and measurements on the Internet show that Gallop-Vegas significantly improves the performance of a connection, especially during the slow-start phase. Furthermore, it is implementation feasible because only sending part needs to be modified.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.5
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• pp.427-434
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• 2000

The paper proposes a zero speed start-up scheme of direct rector controlled induction motor drive without any torque jerk. At standstill condition, a method is derived to calculate a stator flux with only stator current. The programmable 3-stage low pass filters with programmable time constants is used in order to solute the problem of integration for stator flux estimation in the direct vector control mode. Due to the time delay of 3-stage low pass filter, the status flux decreases rapidly and also the torque jerk occurs during the transition from standstill mode to the direct rector control mode. A feedforward control strategy of the stator flux is suggested to prevent the torque jerk at start-up. Through results of simulation and experiment with 32 bit DSP, the performance of the start-up scheme is verified.

• International Journal of Highway Engineering
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• v.19 no.4
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• pp.69-78
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• 2017

PURPOSES : In this study, we analyzed the road crossing behavior of older pedestrians on a mid-block signalized crosswalk, and compared it to that of younger pedestrians. In addition, we analyzed the correlation between accidents involving older pedestrians while crossing roads and their behavioral characteristics. Finally, we confirmed the reasons for an increase in accidents involving older pedestrians. METHODS : First, 30 areas with the highest incidence of accidents involving older pedestrians while crossing roads were selected as target areas for analysis. Next, we measured the start-up delay (the time elapsed from the moment the signal turns green to the moment the pedestrian starts walking) and head movement (the number of head turns during crossing a road) of 900 (450 older and 450 younger) pedestrians. The next step was to conduct a survey and confirm the differences in judgment between older and younger pedestrians about approaching vehicles. Finally, we analyzed the correlation between the survey results and traffic accidents. RESULTS : The average start-up delay and head movement of the older pedestrians was 1.58 seconds and 3.15 times, respectively. A definite correlation was obtained between head movement and the frequency of pedestrian traffic accidents. The results of our survey indicate that 17.3% of the older pedestrians and 7.8% of the younger pedestrians have a high crash risk. CONCLUSIONS : Behavioral characteristics of older pedestrians were closely correlated with accidents involving older pedestrians while crossing roads in mid-block signalized crosswalks. Our study indicates that in order to reduce the number of accidents involving older pedestrians, it is necessary to develop an improvement plan including measures such as installation of safety facilities taking the behavioral characteristics of older pedestrians into consideration and their safety education.

• Journal of Korean Society of Transportation
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• v.20 no.5
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• pp.23-31
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• 2002

The headway of vehicles entering an intersection is closely related with the saturation flow rate and is a basic parameter required for determining the saturation headway and the start-up lost delay. Since such headway value reflects the drivers' behaviors and features of the intersection, all intersections don't have an equal value, but are affected by number and location of their lanes, changing types, local characteristics and time zone. Accordingly, this study attempted to suggest proper values on the basis of data by investigating headway in lanes. Number of exclusive through lanes was divided into single lane, double lanes and triple lanes, the locations of lanes were divided into inside lane, central lane and outside lane. As a result of investigating the headway, single through lane, double through lanes-inside lane, and triple through lane-outside lane showed as 1.73 sec., 1.71 sec. and 1.93sec., respectively. The result of calculating the area factor of business areas by fixing 1.00 for the residental area and applying relation between headway and saturation flow rate was 0.96. In the case of start-up lost delay lead dual left turn and directional separation were 1.41 sec. and 3.27 sec., respectively, showing the great difference. Therefore, different start-up lost delay according to changing type should be applied.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.3
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• pp.213-219
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• 2017

Recently, the Internet Protocol Television (IPTV) services have become very common, enabling various Internet-based services as well as watching TV. In the IPTV system, a Set-Top box (STB) plays a key role as a network terminal device that transmits and receives realtime multimedia contents. In addition, the IPTV networks are usually supported by broadband optical fiber-base network such as fiber-to-the-home (FTTH), However, a general IPTV STB is regarded as one of the local area network (LAN)-attached devices while sharing the bandwidth of the LAN (e.g., Ethernet). In order to overcome the limited bandwidth utilization by fully facilitating the broadband bandwidth (e.g., 1 Gbps) of the optical fiber-based network, we propose a new FC (Fiber Channel)-embedded IPTV STB which can be directly attached to the optical fiber network. Then, we verify that the impacts of the proposed FC-embedded IPTV STB by organizing the the FC-AL (Fiber Channel-Arbitration Loop) network equipped with the FC-embedded IPTV We measures the average Start-up Delay, Average Reject Ratio and the Number of Concurrent Users through extensive simulations to investigate the performances of the suggested FC-AL-based IPTV network. Surprisingly, the IPTV network architecture with the proposed FC-embedded IPTV STBs has an excellent average start-up delay of less than 10 msec, an acceptable average reject ratio of less than 3 % as well as a linear increase of the number of concurrent users when extending the architecture. This reveals that the proposed FC embedded STB has a superior impacts on the performance of the entire IPTV network by effectively utilizing the broadband bandwidth of the fiber optic-based network.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1996.10a
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• pp.198-207
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• 1996

Electro sensitive traffic system can't consider passenger car unit, so, it causes start up delay time and passenger waiting time. In this paper, it antecedently creates optimal traffic cycle of passenger car unit at the bottom traffic intersection. But, sometimes it can make mistakes due to changes in car weight, car speed, and control of feed-back data. Moreover, to prevent spillback, it can adapt control even though upper traffic intersection has a different saturation rate, road length, road slope and road width.