• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.86-86
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• 2018

볼트, 너트 등의 파스너는 건축 재료나 기계부품을 고정하는 데 사용하는 기계요소로, 건축, 철도, 조선 등 전 산업분야에 걸쳐 사용되고 있다. 그 중 스테인리스 소재의 볼트, 너트는 뛰어난 내식성과 저렴한 가격으로 널리 사용되고 있는데, 소재의 특성 및 작업현장의 상황, 온도의 변화 등의 원인에 의해 고착현상(galling)이 발생한다. 고착현상이란 성분 혹은 표면경도가 비슷한 금속의 나사산을 조이는 과정에서 발생하는 압력의 증가 및 마찰력에 의해 냉간 용접(cold welding)이 일어나는 것으로 나사산의 표면이 눌어붙게 된다. 이러한 고착현상은 스테인리스 소재에서 많이 발생하는데, 한번 발생한 후에는 비파괴 해소가 불가능한 상태가 되어 경제적 손실을 야기한다. 이러한 고착현상의 해소를 위해 본 연구에서는 주석과 알루미늄을 사용한 새로운 열 확산 코팅 기술을 개발하고 이를 304 스테인리스강에 적용하여 열처리 온도에 따른 특성변화를 확인하였다. 열 확산 코팅을 위해 팩 세멘테이션 방법을 이용하여 아르곤 분위기 하에서 열처리 하였고, 온도는 $200{\sim}250^{\circ}C$에서 코팅을 수행하였다. 이에 따른 코팅 전과 후의 표면 및 단면 분석을 통해 성공적으로 코팅층이 형성됨을 확인하였고, 온도가 증가함에 따라 코팅성분의 양이 증가하는 현상을 보임을 알 수 있었다. 또한, 고착방지성능을 확인하기 위하여 ASTM G196-08 시험을 통해 코팅조건에 따른 고착현상을 분석하였으며, 그 결과 기존에 코팅되지 않은 304 스테인리스강보다 고착현상이 개선됨을 확인하였다. 따라서 304 스테인리스강 소재의 볼트, 너트 제품에 주석-알루미늄 코팅층을 적용시키면 기존의 고착현상을 개선하고 서비스 품질을 향상시킬 수 있을 것으로 판단된다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.11
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• pp.2411-2417
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• 2012

Globally, the emergence of smart phones vitalized the ecosystem of mobile data service industry. Consequentially, mobile data traffic has been explosively growing and the speed of growth will be more steep. New spectrum will be required in order to properly accommodate the explosively growing mobile data traffic. However, it will be difficult to acquire a sufficient guard band between different frequency bands because the range of frequency which is suitable for wireless communications is limited. Thus, the performance degradation caused by inter-band interference will be one of challenging problems in the next generation mobile communication systems. In this paper, we analyze the performance degradation caused by inter-band interference by computer simulations in various environments. Our results show that the impact of the inter-band interference is more critical when own signal is poor or its own interference from neighboring cells is low.

• The Journal of the Korea Contents Association
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• v.13 no.10
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• pp.533-546
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• 2013

This study analyzed the contents of online hotel reviews of Benikea hotels. The results were as follows: First, the outstanding customer value were functional value, emotional value, price/value for money and epistemic value, conditional value are next. Social value was not found. Functional value was provoked by the functions of hotel room, room amenities, room view, room cleaness, restaurant service, and hotel staff friendliness as human services. Emotional value was the emotional response to the qualities of hotel's functions. Price/value for money was a perceived value of hotel user by the comparison of what to invest with what to receive. From the results, it can be proposed that hotel should maintain the basic qualities of core functions of hotel.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.1
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• pp.72-78
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• 2015

Recently, the usage of the satellite is increased more and more in the areas that are communication, weather, marine, optical, radar etc. The functions of the Satellite are evolving from passive transponder to active transponder by the developing of a technology. Advanced countries in satellites install the DCAMP for increase of bandwidth efficiency, improvement of QoS by interference rejection. DCAMP includes many digital components in order to implement functions. Thus, these kinds of active transponders consume much more power compared to passive transponder and then increase the heat. In this paper, we discuss the TVAC test result of DCAMP in EQM(Engineering Qualification Model) level. The paper shows the test results of digital gain control in order to verify DCAMP status under the TVAC test. In addition, the temperature and heat condition of main components from viewpoint of derating will be treated through the official environment test for qualification.

• Journal of Broadcast Engineering
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• v.20 no.4
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• pp.497-508
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• 2015

Current communication networks consist of channels with various throughputs, protocols, and packet loss rates. Moreover, there are also diverse user multimedia consumption devices having different capabilities and screen sizes. Thus, a practical necessity of scalability on video coding have been gradually increasing. Recently, The Scalable High Efficiency Video Coding(SHVC) standard is developed by Joint Collaborative Team on Video Coding(JCT-VC) organized in cooperation with MPEG of ISO/IEC and VCEG of ITU-T. This paper introduces coding tools of SHVC including adopted and unadopted tools discussed in the process of the SHVC standardization. Furthermore, the individual tool and combined tool set are evaluated in terms of coding efficiency relative to a single layer coding structure. This analysis would be useful for developing a fast SHVC encoder as well as researching on a new scalable coding tool.

• Health Policy and Management
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• v.16 no.1
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• pp.117-139
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• 2006

The role of medical service quality to provide patients enhances influence on the hospital performance under being severe competition among the large size hospitals and increasing the right of patients. When a large hospital perceived factors of quality that a customer expects and feels value of care and it invests its resources to improve the factors of quality, it can get successful performances. Therefore, the purpose of the study explores the factors of quality affecting the trust of care and the patient satisfaction, and tests relationship among the trust of care, patient satisfaction and revisit intention. When considering the factors, a large size hospital can increase the trust of care and the patient satisfaction, through this process the hospital can assure patients' revisit and increase its revenue. This study uses interview data on outpatients visiting clinics in about 1000 beds sized training hospital located in Seoul. This study uses casual relationship model for the analysis. This study finds that 1) the trust of care and the procedure of care significantly influence the value of care felt by patients, 2) the trust of care, quality of doctors' care, procedure of care significantly influence the patient satisfaction, 3) the trust of care increases the patient satisfaction, and 4) the value of care and the patient satisfaction increase revisit intention.

• Journal of Internet Computing and Services
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• v.6 no.2
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• pp.127-139
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• 2005

This research is in the same line of the research that was carried out in 1999 and 2001, Studies in 1999 and 2001 showed that there are significant differences in the usage levels of Internet in business between countries with longer history of using internet and those with shorter history. The 1999 and 2001 studies also suggested the model on development stages of Internet usage in business, This study is the continuation of the 1999 and 2001 research and used the previous data to compare and analyze the trend of the Internet development stages in leading 100 corporations in Korea, U,S.A., China and Japan in 2002. This study found that there have been significant developments in the ability to use Internet in business in three countries. The differences in Internet usage level in each stage among different countries are compared and analyzed in this study.

• Journal of Internet Computing and Services
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• v.12 no.2
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• pp.75-83
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• 2011

Wireless services and devices that use frequency increase more and more because of advancement of the industry. Therefore, the available spectrum band becomes increasingly insufficient. Cognitive Radio, which adaptively utilizes the vacant licensed spectrum band, is considered as an effective way to utilize the spectrum resource shortage. CR user should move from current allocated channel to vacant channel to avoid the interference to the primary user when the primary user appears in the current channel. In this case, CR system undergoes the break off time until handshake is completed. So, in order to guarantee the Quality of Service(QoS) of CR system, fast handshake method is required. In this paper, we propose the embedded control signal transmission technique to reduce the break off time. This method can transmit the control signals in data transmission period as well as the broadcasting period. Proposed method can improve the data throughput and decrease the break off time. Computer based simulation proves that our proposed scheme outperforms conventional one.

• Smart Media Journal
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• v.9 no.2
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• pp.99-109
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• 2020

This paper proposes a platform construction plan for the use of spectrum big data, collects and analyzes the big data in the radio wave field, establishes a linkage plan, and presents a support system scheme for linking and using the spectrum and public sector big data. It presented a plan to build a big data platform in connection with the spectrum public sector. In a situation where there is a lack of a support system for systematic analysis and utilization of big data in the field of radio waves, by establishing a platform construction plan for the use of big data by radio-related industries, the preemptive response to realize the 4th Industrial Revolution and the status and state of the domestic radio field. The company intends to contribute to enhancing the convenience of users of the big data platform in the public sector by securing the innovation growth engine of the company and contributing to the fair competition of the radio wave industry and the improvement of service quality. In addition, it intends to contribute to raising the social awareness of the value of spectrum management data utilization and establishing a collaboration system that uses spectrum big data through joint use of the platform.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.4
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• pp.266-271
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• 2007

In mobile channel environments, the effect of the multi-path fading reduces the performance of the mobile communication severely. Previous studies on the effect of the multi-path fading show that, only the channel between fixed base stations and mobile terminals are considered. However, the future mobile communication service such as telematics may use the communication between moving mobile terminals, so called mobile ad-hoc communication, the studies on the channel is required for such situations. In this paper we have measured the mobile channel and analyzed the fading characteristics when using the linear array antennas. In the data measurements, we sent the QPSK modulated signal with carrier frequency of 2GHz band and received the signal using the array antennas equipped on moving vehicles. We have analyzed the fading characteristics and the effects of the fading reduction using the CDF of fading depth using data collected from two moving vehicles. The simulation results show that the beamforming technique adds 6 or 7dB to the fading margin than that of the selection diversity depending on channel environments.