• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.693-697
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• 2007

The SSB modem performs the modulation process which converts the digital voltage level to the audible frequency band signal and the demodulation process which converts reversely the audible frequency signal to the digital voltage level. The modulator and the demodulator are implemented with a single DSP chip. Because of the SSB specific character, the distortion occurs when the frequency is changed. This distortion has no effect on voice communication, but it has an significant effect on data communication. In other words, it is impossible to send data stream with adjacent 2 periods. Therefore, in case of using 2-tone FSK, it is needed to send at least 3 periods to transmit 1 bit. Therefore we implemented the modem using modified phase-delay shift keying to transmit 1 tone signal for high speed transmission. In the 1200[bps] mode, it generates 0, $187{\mu}s$ delay time at 1.3kHz symbol frequency, and in the 2400[bps] mode, 0, $70{\mu}s$, $130{\mu}s$, $200{\mu}s$ delay time at 1.5kHz symbol frequency. Finally, in the maximum 3600[bps] mode, it generates 0, $100{\mu}s$, $160{\mu}s$, $250{\mu}s$ delay time at 2.0kHz symbol frequency. The measured results of the implemented SSB modem shows a good transfer functional characteristic by spectrum analyzer, almost same bandwidth in pass band and 20dB higher SNR comparing the German PACTOR and American CLOVER and in the experimental transmitting test, we verified the transmitted data is received correctly in platform.

• Journal of the Korean Society for Railway
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• v.8 no.2
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• pp.145-154
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• 2005

Traffic accidents at highway-rail crossing result in larger social and economic damages than the accidents at the typical highway intersections. The traditional control and warning systems of the highway-rail crossing have limitations in that 1) they do not recognize the differences of the trains' arrival times because they rely on the distance-based control system, rather than the time-based one, and 2) thereby they usually cause longer delays of vehicles and pedestrians at the highway-rail crossings. The objective of this study is to develop a time-based railroad crossing control system which takes into account the speed and expected arrival time of trains. using the spot speeds and acceleration rates of trains measured at three points, the developed system was found to be able to accurately estimate the arrival time of train. VISSIM simulation package was utilized to compare system effect of the developed time-based railroad crossing control system with that of the conventional distance-based one. It was found that the developed time-based railroad crossing control system reduced the average travel time, maximum delay length, average delay time, and average number of stop-experienced vehicles as much as 7.0$\%$, 75.6$\%$, 12.7$\%$, and 60.0$\%$, respectively, compared with those from the conventional distance-based one.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.3
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• pp.8-14
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• 2019

Most of the data envelopment analysis (DEA) models evaluate the relative efficiency of a decision making unit (DMU) based on the assumption that inputs in a specific period are consumed to produce the output in the same period of time. However, there may be some time lag between the consumption of input resources and the production of outputs. A few models to handle the concept of the time lag effect have been proposed. This paper suggests a new multi-period input DEA model considering the consistent time lag effects. Consistency of time lag effect means that the time delay for the same input factor or output factor are consistent throughout the periods. It is more realistic than the time lag effect for the same output or input factor can vary over the periods. The suggested model is an output-oriented model in order to adopt the consistent time lag effect. We analyze the results of the suggested model and the existing multi period input model with a sample data set from a long-term national research and development program in Korea. We show that the suggested model may have the better discrimination power than existing model while the ranking of DMUs is not different by two nonparametric tests.

• Korea Journal of Hospital Management
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• v.15 no.3
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• pp.47-68
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• 2010

One of the important complaint factors by the patients using medical institutions is various kinds of waiting time. This research is about the causal relationships among waiting time(application of waiting time, perceived of waiting time, fairness of waiting, explanation of the delay, acceptance possibility), service values, and customer satisfaction. The subjects for this study were 256 out-patients currently using seven general hospitals in the Busan area. The findings of the empirical analysis are as follows: First, the good application of waiting time or fair waiting time procedure didn't actually affect perceived waiting time. Second, though the application of waiting time didn't affect acceptance possibility, the fair procedure of waiting time had an affirmative effect on acceptance possibility. Third, even when there was enough explanation about the need to wait, it could shorten perceived waiting time but failed to get sufficient sympathy or agreement from the patients. Fourth, the possibility of acceptance following the sufficient sympathy of patients had an effect on shortening perceived waiting time. Fifth, perceived waiting time lowered customer satisfaction, but had no negative effect on service values. Finally, the ranges of acceptance possibility by the patients were found to increase customer satisfaction and maximize service values. In conclusion, every medical institution needs to focus on, first of all, shortening waiting time for more customer satisfaction and improved service values.

• Korean Journal of Digital Imaging in Medicine
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• v.10 no.2
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• pp.17-22
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• 2008

It is to improve customer satisfaction measurement and CT Scan process without delay of examination time when is using Scan positioning time(Planning time) that time is happened always between research reactor CT examination to increase fear and examination satisfaction by the customer's comprehension tribe which get the latest contrast enhancement CT examination. Needs and interests that customer wants to compose visual and auditory Contents to be played to Scan positioning time did questionnaire about curiosity later before CT examination to 600 people for October - November 2 months of 2006 to customer whole that get CT examination on source. Data getting through questionnaire investigated examination comprehension and satisfaction through questionnaire after experiment Scan Positioning to 500 coming to help customers to be source CT examination for 3 months February December - 2007 year in 2006 manufacturing Voice and Visual announce media for reference. To customer who interest degree appeared, and answers preparatory audit from preparatory audit about curiosity of CT examination customer to order of examination time required(43%), contrast media side effect(26%), examination region(20%), breath(10%), etc..(1.5%) audio-visual materials in questionnaire that attain after do reclamation among examination age, sex, reception type of irrelatively in 91% of target increase of hailing degree and examination satisfaction appear. Searched that customer hailing and satisfaction are increased greatly when use of audio-visual materials in satisfaction result that use CT Positioning delay time. In experiment process, It took lacking part by method that use hearing in case of do not use sight as is unavoidable in subject position or old age. Through this, audio-visual materials could analogize that it is more useful method that use sight and hearing at the same time.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.5
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• pp.409-415
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• 2012

This paper presents a new software-based on-line dead-time compensation technique for a single-phase grid-connected photovoltaic (PV) inverter system. To prevent a short circuit in the inverter arms, a switching delay time must be inserted in the pulse width modulation (PWM) signals. This causes the dead-time effect, which degrades the system performance around zero-crossing point of the output current. To reduce the dead-time effect around the zero-crossing point of grid current, a harmonic mitigation of grid current is used as an additional part of the synchronous frame current control scheme. This additional task mitigates the harmonic components caused by the dead-time from the grid current. Simulation and experimental results are shown to verify the effectiveness of the proposed dead-time compensation method in the single-phase grid-connected inverter system.

• Journal of the Korean Society of Radiology
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• v.10 no.1
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• pp.29-37
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• 2016

This study aims to improve the satisfaction level of the patient who undergoes CT contrast examination by developing and applying pretreatment process system, which not only can reduce the side effects caused by the test but also can help carry out the test smoothly. The subjects were 214 patients who booked CT contrast examination from January 2014 to February 2014 but could not carry out their test on schedule. We analyzed the reasons for the delay and conducted follow-up survey on them. We analyzed the usefulness of pretreatment process system by contemplating and developing pretreatment process system and applying it to the patients for whom follow-up survey was conducted from January 2015 to February 2015. The number of outpatients who came to the hospital form January to February 2014 was 2,846 and the number of patients who could not undergo the test was 214, accounting for 7.52% of the total. The specific reason for the delay includes 214 cases of unknown creatinine 98 with 120 minutes of average delay time, 40 cases of creatinine over 1.3(19%) with 30minutes of average delay time, 34 cases of past contrast media side effect 6% with 40 minutes of average delay time and 25 cases of lack of pretreatment such as fasting, etc. 11% with 120minutes of average delay time. The number of CT scan has been increasing ever since the development of CT and the frequency of using the contrast media is expected to increase. If we can employ pretreatment process system in order to effectively control the side effect of contrast media and help the CT contrast examination to be smoothly conducted on schedule, I'm sure we could improve the quality of our medical service and increase our patients' satisfaction who come to our CT scan room.

• Journal of the Korea Society for Simulation
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• v.28 no.4
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• pp.45-56
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• 2019

Literatures have considered mathematical model that change the job order of shipper for improving the operation time of yard crane. However, on the real site, it is impossible to change the job order decided according to the shipper's arrival order. Therefore, operation managers have been utilized the relatively simple strategy that job control is better but the process time of yard crane is longer due to the growth of yard crane's interference time and empty drive time. This study proposed a new yard-crane scheduling approach that decided the job order before the shipper's truck arrived the yard terminal. We utilize the Container Pre-Information Notice estimating the arrival time of truck. We developed the container terminal simulation model for validation of the effect of proposed scheduling approach. The results show that the proposed scheduling reduced the interference delay time and empty moving time of yard crane and shipper's truck delay time.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.5
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• pp.426-435
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• 2002

In this paper we present an indoor propagation model for indoor wireless LAN service in the ISM band. We primarily use a 3D ray tracing as well as a patch scattering model in order to take into account the indoor fixtures. Therefore input parameters such as indoor environment parameters and antenna's types, polarizations are considered. As the results, we present fading characteristics and rms delay spread from time delay spread. In order to investigate the accuracy of the presented model, comparisons of predictions with measurement and simulations are performed in indoor wireless LAN service environments. The results show that measurements and simulations are very similar. Therefore in this paper, the effect of presented indoor propagation model is confirmed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.600-606
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• 2004

An interleaving delay diversity scheme is investigated in this paperand the applications in the multi-code WCDMA system along with antenna selection diversity is proposed. The proposed algorithm utilizes interleaving and delayed duplicated transmission mechanism to mitigate the effect of noise and fading. The interleaved signal and the original signal are both transmitted at intervals to obtain time diversity without any increase in required capacity. By adjusting the number of retransmissions of the information signal properly, the system achieve the receive diversity efficiently. For transmission power efficiency the proposed system also applies antenna selection diversity. By computer simulation, it has been shown that the proposed algorithm achieves better performance than the conventional algorithms by more than 2dB.