• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.12
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• pp.2765-2772
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• 2015

In Korea MVNO was introduced in 2011 when twenty seven years had passed since Korea Mobile Telecom(now SK Telecom) started mobile phone service. MVNO can make competition more effective to lower communication costs through the alternatives. In the early 2000s, the need for the introduction of the MVNO has been raised already by scholars in Korea. But it wasn't until the late 2000s when rate cuts appeared to be a major policy issue, and Korean government introduced MVNO. In April 2015, MVNO's market share reached 8.8%, but Korea does not have a firm system yet. This rapid growth of MVNO market in Korea was made possible by consumers' demand for cheaper services and late introduction of MVNO. And telecom companies(MNO) abuse their supreme power against small and medium firm MVNOs and reserved market share using their subsidiary companies. Thus proper regulation is necessary. However, the government authorities should have recognized global MVNO flow quickly and have to make a sufficient effort to establish proper competition condition of the mobile telecom market.

• The KIPS Transactions:PartC
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• v.11C no.2
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• pp.245-252
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• 2004

Stream Control Transmission Protocol(SCTP) is a new connection-oriented, reliable delivery transport protocol operating on top of an unreliable connectionless packet service such as IP. It inherits many of the functions developed for TCP, including flow control and packet loss recovery functions. In addition, it also supports transport layer multihoming and multistreaming In this paper, we study the impact of multi-homing on the performance of SCTP. We first compare performance of single-homed SCTP. multi-homed SCTP, TCP Reno and TCP SACK. We, then describe potential flaw in the current SCTP retransmission policy, when SCTP host is multihomed. Our Results show that SCTP performs better than TCP Reno and TCP SACK due to several changes from TCP in its congestion control mechanism. In particular. multi-homed SCTP shows the best result among the compared schemes. Through experimentation for multi-homed SCTP, we found that the current SCTP retransmission policy nay deteriorate the perfomance when the retransmission path it worse than the original path. Therefore, the condition of retransmission path is a very important factor In SCTP performance and a proper mechanism would be required to measure the condition of the retransmission path.

• The Journal of Information Technology
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• v.7 no.2
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• pp.69-76
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• 2004

This paper presents the results of spectral analysis about waveforms and leakage current waveforms on contaminated silicon insulators under various environment conditions.(salt fog, clean fog, rain). The larger the leakage current during 200ms, the higher the power spectrum at 60Hz. If contaminated insulators suffers from high salt density fog, the leakage current occurs with high crest value intermittently, results in the low spectrum. Analysis of leakage current data showed that this electrical activity was characterized by transient arcing behavior contaminants are deposited on the insulator surface during salt fog tests. This provides a path for the leakage current to flow along the surface of the insulator. It is important to have an indication of the pollution accumulation in order to evaluate the test performance of a particular insulator. If the drop in surface resistivity is severe enough, then the leakage current may escalate into service interrupting flashover that degrade power quality.

• Journal of Preventive Medicine and Public Health
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• v.46 no.3
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• pp.118-126
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• 2013

We investigated the major trends in health aid financing in the Democratic People's Republic of Korea (DPRK) by identifying the primary donor organizations and examining several data sources to track overall health aid trends. We collected gross disbursements from bilateral donor countries and international organizations toward the DPRK according to specific health sectors by using the Organization for Economic Cooperation and Development creditor reporting system database and the United Nations Office for the Coordination of Humanitarian Affairs financial tracking service database. We analyzed sources of health aid to the DPRK from the Republic of Korea (ROK) using the official records from the ROK's Ministry of Unification. We identified the ROK, United Nations Children's Fund (UNICEF), World Health Organization (WHO), United Nations Population Fund (UNFPA), and The Global Fund to Fight AIDS, Tuberculosis and Malaria (GFATM) as the major donor entities not only according to their level of health aid expenditures but also their growing roles within the health sector of the DPRK. We found that health aid from the ROK is comprised of funding from the Inter-Korean Cooperation Fund, private organizations, local governments, and South Korean branches of international organizations such as WHO and UNICEF. We also distinguished medical equipment aid from developmental aid to show that the majority of health aid from the ROK was developmental aid. This study highlights the valuable role of the ROK in the flow of health aid to the DPRK, especially in light of the DPRK's precarious international status. Although global health aid from many international organizations has decreased, organizations such as GFATM and UNFPA continue to maintain their focus on reproductive health and infectious diseases.

• Journal of Korean Society of Transportation
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• v.22 no.4 s.75
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• pp.43-56
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• 2004

The KHCM procedure is a micro level analysis at signalized intersections requiring a lot of input variables and complex computations. The research was to investigate the possibility of simplifying the analysis procedures by using the generalized or the combined variables that less influence on the adjusted traffic volume and through-car equivalents of left or right turns. It was also tried to make lane grouping into directional flow ratio(v/s) based on a field surveys. The maximum and minimum values of each variables were compared with each other through the KHCM analysis procedures in terms of control delay. The lane grouping and the synthetical influence of a simplified method was evaluated with the scenario built in prevailing maximum and minimum conditions. The study showed that the control delay was not significantly sensitive to the selected variables and the lane grouping and their synthetical influence as well.

• Information Systems Review
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• v.10 no.2
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• pp.21-48
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• 2008

The Korean on-line game industry is going through a rapid change. The future business environments for potential on-line game companies are very uncertain due to the new service and the different market trends. In this paper, I propose the use of morphological analysis approach for scenario generation about the future of the On-line game industry. The stages of research process were as follows; Firstly, digital contents analysis and key issues were drawn on IPTV in the on-line game industry. Secondly, each key issue was analyzed and the influence factors and directivity flow were found. Thirdly, highly probable future on-line game industry scenarios were derived. In this case, morphological analysis. On the basis of the developed scenarios, I formulated some implications for business strategy of a potential on-line game companies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.336-342
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• 2017

Traffic can be localized by reducing the traffic load on the physical network by causing traffic to be generated at the end of the packet network. By localizing traffic, the IoT-based sensitive data-related security issues can be supported effectively. In addition, it can be applied effectively to the next-generation smart network environment without changing the existing network infrastructure. In this paper, a content priority scheme was applied to smart network-based IoT data. The IoT contents were localized to efficiently pinpoint the flow of traffic on the network to enable smart forwarding. In addition, research was conducted to determine the effective network traffic routes through content localization. Through this study, the network load was reduced. In addition, it is a network structure that can guarantee user quality. In addition, it proved that the IoT service can be accommodated effectively in a smart network-based environment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.598-602
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• 2018

This study examined the characteristics of the waste catalyst used in the petroleum refinery operations. The total pore volume, specific surface area, and average pore size of the spent catalyst used in the petroleum refinery operations were 3.96cc/g, 13.81m2/g, and 1.15A, respectively. The weight loss observed in the range from $25^{\circ}C-700^{\circ}C$ for the spent catalysts using TG and DTA was approximately 23 wt. %. EDS analysis of the waste catalyst sample showed that the five major components were vanadium, nickel, manganese, iron, and copper. The extraction system is attractive for liquid-liquid extraction. In this study, Cynex 272 was used to extract vanadium from waste catalyst. The electrochemical characteristics of the extracted vanadium solution were measured by cyclic voltammetry (CV). As a result, an oxidation / reduction peak appeared, indicating the potential of an electrolytic solution.

• Structural Engineering and Mechanics
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• v.75 no.4
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• pp.497-506
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• 2020

CA mortar layer disengagement will give rise to the overall structural changes of the track and variation in the vibration form of the ballastless track. By establishing a vehicle-track-viaduct coupling analysis and calculation model, it is possible to analyze the CRTS-I type track structure vibration response while the track slab is disengaging with the power flow evaluation method, to compare the two disengaging types, namely partial contact loss at one edge beneath track slab and partial contact loss at midpoint beneath track slab. It can also study how the length of disengaging influences the track structures vibration power. It is showed that when the partial contact loss beneath track slab, and the relative vibration energy level between the rail and the track slab increases significantly within [10, 200]Hz with the same disengaging length, the partial contact loss at one edge beneath track slab has more prominent influence on the vibration power than the partial contact loss at midpoint beneath track slab. With the increase of disengaging length, the relative vibration energy level of the track slab grows sharply, but it will change significantly when it reaches 1.56 m. Little effect will be caused by the relative vibration energy level of the viaduct. The partial contact loss beneath the track slab will cause more power distribution and transmission between the trail and track slab, and will then affect the service life of the rail and track slab.

• KIISE Transactions on Computing Practices
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• v.21 no.6
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• pp.403-411
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• 2015

Nowadays, in the so-called 'smart era', people are likely to feel more comfortable in on-line meetings than in off-line meetings. However, on-line meetings are often considered unimportant and it is difficult for participants to share their feelings. This paper suggests a mobile application that can revitalize off-line meetings to address these problems. Wecok Application, which suggests the best meeting place by applying users' preferences and their locations, provides a function-oriented user interface and simple touch flow. Wecok consists of a client/server software, and currently supports only three users simultaneously. It enables exchange of off-line and on-line communication by expanding meetings from on-line to off-line. By using Wecok, users can easily decide on an off-line meeting place.