• 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 Information Processing Systems
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• v.5 no.4
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• pp.207-220
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• 2009

A large number of phone calls and data services will take place in indoor environments. In Long Term Evolution (LTE), femtocell, as a home base station for indoor coverage extension and wideband data service, has recently gained significant interests from operators and consumers. Since femtocell is frequently turned on and off by a personal owner, not by a network operator, one of the key issues is that femtocell should be identified autonomously without system information to support handover from macrocell to femtocell. In this paper, we propose a dynamic reservation scheme of Physical Cell Identities (PCI) for 3GPP LTE femtocell systems. There are several reserving types, and each type reserves a different number of PCIs for femtocell. The transition among the types depends on the deployed number of femtocells, or the number of PCI confusion events. Accordingly, flexible use of PCIs can decrease PCI confusion. This reduces searching time for femtocell, and it is helpful for the quick handover from macrocell to femtocell. Simulation results show that our proposed scheme reduces average delay for identifying detected cells, and increases network capacity within equal delay constraints.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11B
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• pp.991-1000
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• 2004

This paper presents an application layer multicast tree constructing algorithm to minimize the average time delay from the sender to end-systems for the effective real-time media delivery. Simultaneously, the proposed algorithm takes into account the computing power and the network condition of each end-system as a control variable and thus avoids the undesirable case that loads are concentrated to only several end-systems. The multicast tree is constructed by clustering technique and modified Dijkstra's algorithm in two steps, i.e. tree among proxy-senders and tree in each cluster. By the experimental results, we show that the proposed algorithm can provide an effective solution.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.2
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• pp.27-35
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• 2009

The roundabout was developed in the United Kingdom to rectify problems associated with these traffic circles. In 1966, the United Kingdom adopted a mandatory "give-way" rule at alt circular intersections, which required entering traffic to give way, or yield, to circulating traffic. However, the roundabout used in United States or Europe do not common use in Korea. The purposes of the study is to comparatively analyze the effectiveness of roundabout. In pursuing the above, this study designs the scenarios which can reflect the directional traffic volumes, and analyzes the average control delay of roundabout and 4-leg signalized intersection by SIDRA. The main study results are as follows. First, when the entering traffic volume are less than 2,000pcph, the single-lane roundabout is analyzed to be more effective than 4-leg signalized intersection. Second, when the entering traffic volume are less than 3,200pcph, the double-lane roundabout is evaluated to be more effective than 4-leg signalized intersection. Third, which is installed left and right turn lane at intersection, area for the roundabout is analyzed to be less than that for general intersection area.

• Journal of the Korean Operations Research and Management Science Society
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• v.23 no.3
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• pp.135-151
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• 1998

The demand of large capacity in coming cellular systems makes inevitable the deployment of small cells, rendering more frequent handoff occurrences of calls than in the conventional system. The key issue is then how effectively to reduce the chance of unsuccessful handoffs, since the handoff failure is less desirable than that of a new call attempt. In this study, we consider the control policies which give priority to handoff calls by limiting channel assignment for the originating new calls, and allow queueing the new calls which are rejected at their first attempts. On this system. we propose the problem of finding an optimal call control strategy which optimizes the objective function value, while satisfying the requirements on the handoff/new call blocking probabilities and the new call delay. The objective function takes the most general form to include such well-known performance measures as the weighted average carried traffic and the handoff call blocking probability. The problem is formulated into two different linear programming (LP) models. One is based on the direct employment of steady state equations, and the other uses the theory of semi-Markov decision process. Two LP formulations are competitive each other, having its own strength in the numbers of variables and constraints. Extensive experiments are also conducted to show which call control strategy is optimal under various system environments having different objective functions and traffic patterns.

• Journal of KIISE:Information Networking
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• v.28 no.3
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• pp.435-446
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• 2001

In this paper, a new fairness control method is proposed to distribute DQDB-SR (Distributed-Queue Dual-Bus with Slot Reuse) network bandwidth fairly to all stations on client-server environments. By using an access limit that follows a characteristic of client-sever load patterns and a bandwidth borrowing and returning mechanism, the proposed mechanism imparts fairness bandwidth control capability to DQDB-SR. To implement the proposed mechanism, we find the optimal placement of erasure nodes that maximizes network capacity for DQDB-SR, and calculate the access limit. At overload conditions, simulation results show that the proposed mechanism does not deteriorate network throughput, and outperforms other fairness control mechanisms in a success rate and an average packet transfer delay.

• Journal of the Korea Society of Computer and Information
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• v.17 no.6
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• pp.67-73
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• 2012

A distributed conference architecture with a new load control method has been suggested in this paper. A new event package in this paper enables to control conference load. Some additional elements for exchanging SIP messages between server and participants, and for distributing the load, have been added to new conference information data format. Furthermore to lessen the load, all conference servers share the processing of conference information data which should be transferred periodically to all participants. The suggested load control event package makes each server can get current load status of the overall servers. When load increases in one server SIP client requests are distributed by selecting a server which has the lowest load value, or new server is created to share the load. The performance of the proposed system has been evaluated by experiments. They shows 21.6% increase in average delay time, and 29.2% increase in average SIP message processing time.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.6
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• pp.127-136
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• 2013

In order to improve the safety and efficiency of traffic signal operation, several core projects of advanced transportation operating systems were implemented in Changwon City. This project included 10 units such as the expansion of roundabout, the permitted left-turn signal operation and the effectiveness of the projects was assessed using before and after studies. This paper presented the quantitative and qualitative evaluation results for three projects: roundabout, permitted left-turn signal operation, and left-turn actuated signal operation. From the analysis results, average travel speed was improved by 16.8% from the installation of roundabouts and average travel time and control delay were reduced by 12.4% and 41.6% respectively, from permitted left-turn operation. It was found that average control delay was reduced about 26.7% from left-turn actuated signal operation. In addition, more than 57.7% of the surveyed people was satisfied with the operational performance of the roundabout implemented. It is expected that the operational performance of traffic signal can be greatly improved by incorporating the proper projects of advanced transportation operating systems in other cities.

• Journal of the Korea Convergence Society
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• v.8 no.11
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• pp.7-13
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• 2017

In recent years, cloud computing technology has been socially emerged that provides services remotely as various devices are used. However, there are increasing attempts by some users to provide cloud computing services with malicious intent. In this paper, we propose a property - based multi - level hierarchical approach to facilitate authentication access for users accessing servers in cloud environment. The proposed method improves the security efficiency as well as the server efficiency by hierarchically distributing a set of attribute values by replacing the order of the user 's attribute values in the form of bits according to a certain rule. In the performance evaluation, the proposed method shows that the accuracy of authentication according to the number of attributes is higher than that of the existing method by an average of 15.8% or more, and the authentication delay time of the server is decreased by 10.7% on average. As the number of attributes increases, the average overhead change is 8.5% lower than that of the conventional method.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.1
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• pp.131-144
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• 2015

An extensive investigation of the influence of gate engineering on the CNTFET switching, high frequency and circuit level performance has been carried out. At device level, the effects of gate engineering on the switching and high frequency characteristics for CNTFET have been theoretically investigated by using a quantum kinetic model. It is revealed that hetero - material - gate CNTFET(HMG - CNTFET) structure can significantly reduce leakage current, enhance control ability of the gate on channel, and is more suitable for use in low power and high frequency circuits. At circuit level, using the HSPICE with look - up table(LUT) based Verilog - A models, the performance parameters of circuits have been calculated and the optimum combinations of ${\Phi}_{M1}/{\Phi}_{M2}/{\Phi}_{M3}$ have been concluded in terms of power consumption, average delay, stability, energy consumption and power - delay product(PDP). We show that, compared to a traditional CNTFET - based circuit, the one based on HMG - CNTFET has a significantly better performance (SNM, energy, PDP). In addition, results also illustrate that HMG - CNTFET circuits have a consistent trend in delay, power, and PDP with respect to the transistor size, indicating that gate engineering of CNTFETs is a promising technology. Our results may be useful for designing and optimizing CNTFET devices and circuits.