• Journal of Navigation and Port Research
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• v.39 no.3
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• pp.253-260
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• 2015

There are many efforts to mechanize the process for underwater port construction due to the severe and adverse working environment. This paper presents an underwater construction robot to level rubbles on the seabed for port construction. The robot is composed of a blade and a multi-functional arm to flatten the rubble mound with respect to the reference level at uneven terrain and to dig and dump the rubbles. This research analyzes the kinematics of the blade and the multi-functional arm including track and swing motions with respect to a world coordinate assigned to a reference depth sensor. This analysis is conducted interfacing with the position and orientation sensors installed at the robot. A hydraulic control system is developed to control a track, a blade and a multi-functional arm for rubble leveling work. The experimental results of rubble leveling work conducted by the robot are presented in land and subsea. The working speed of the robot is eight times faster than that of a human diver, and the working quality is acceptable. The robot is expected to have much higher efficiency in deep water where a human diver is unable to work.

• The KIPS Transactions:PartC
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• v.9C no.4
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• pp.513-522
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• 2002

Current end-to-end congestion control depends only on the information of end points (using three duplicate ACK packets) and generally responds slowly to the network congestion. This mechanism can't avoid TCP global synchronization which TCP congestion window size is fluctuated during congestion occurred and if RTT (Round Trip Time) is increased, three duplicate ACK packets is not a correct congestion signal because congestion maybe already disappeared and the host may send more packets until receive the three duplicate ACK packets. Recently there is increasing interest in solving end-to-end congestion control using active network frameworks to improve the performance of TCP protocols. ACC (Active congestion control) is a variation of TCP-based congestion control with queue management In addition traffic modifications nay begin at the congested router (active router) so that ACC will respond more quickly to congestion than TCP variants. The advantage of this method is that the host uses the information provided by the active routers as well as the end points in order to relieve congestion and improve throughput. In this paper, we model enhanced ACC, provide its algorithm which control the congestion by using information in core networks and communications between active routers, and finally demonstrate enhanced performance by simulation.

• Journal of the Korea Computer Graphics Society
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• v.28 no.3
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• pp.91-100
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• 2022

This study proposes the metaverse content production pipeline using ZEPETO World, one of the representative metaverse platforms in Korea. Based on the Unity 3D engine, the ZEPETO world is configured using the ZEPETO template, and the core functions of the metaverse content that enable multi-user participation such as logic, interaction, and property control are implemented through the ZEPETO script. This study utilizes the basic functions such as properties, events, and components of the ZEPETO script as well as the ZEPETO player which includes avatar loading, character movement, and camera control functions. In addition, based on ZEPETO's properties such as World Multiplayer and Client Starter, it summarizes the core synchronization process required for multiplay metaverse content production, such as object transformation, dynamic object creation, property addition, and real-time property control. Based on this, we check the proposed production pipeline by directly producing multiplay metaverse content using ZEPETO World.

• The KIPS Transactions:PartC
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• v.18C no.1
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• pp.51-60
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• 2011

In this paper, we propose a P4P based P2P system for live multimedia streaming services. In order to satisfy the strict requirement of delay in live multimedia streaming, in the proposed scheme, the P4P server of network provider provides the network status information related to delay and congestion links to P2P system in addition to the information to optimize the network resource utilization. The P2P system server, then, makes the peering suggestion based on the information from the network server. Also, we propose a playback synchronization mechanism that enable each peer to start the playback within the limited variation from the playback positions of source peer. Through the simulation results, it is shown that the proposed scheme not only deals with the original objective of the P4P framework, i.e., effective network utilization, but also the live multimedia streaming requirements. It enhances the playback continuity, and reduces the playback start-up latency and the control overhead. In addition, the proposed scheme reduces the variation in playback positions of the peers.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.6
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• pp.644-661
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• 1999

인터넷에서 통합서비스를 제공하기 위해서는 종단간 다양한 QoS를 지원해야 하는데 이를 위해서는 인터넷뿐 아니라 종단 사용자와 인터넷을 연결하는 랜에서의 QoS 지원이 필요하다. 이에, IETF는 특정 링크 계층으로 구성되는 서브넷에서 QoS 지원을 위한 기본 골격을 제안하였다. 그런데 , 매체 접근방식에 따라 서브넷이 제공할 수 있는 서비스의 정도가 크게 달라지기 때문에 실제로 IS802 모델을 특정서브넷에 구현하기 위해서는 이에 대한 고려가 필요하다. 본 논문에서는 통합서비스를 지원하기 위한 기반이 되는 서브넷 차원에서의 우선순위 지원을 목표로 IS802 모델을 전통적인 이더넷과 토큰링에 적용하여 보았다. 먼저, IS802 모델의 대역폭관리자를 적용한 이더넷 IS모델과 토큰링_IS 모델의 구현을 제안하고 특별히, 이더넷의 경우 매체 접근 방식의 특성상 IS802 모델의 적용만으로는 서브넷차원에서의 우선순위에 따른 전송을 지원할 수 없기 때문에 이를 보완하기 위한 페이즈 모델을 추가로 제안하였다. 시뮬레이션을 통해 기존의 전통적인 이더넷과 토큰링 및 새롭게 표준화된 IS802 모델을 적용한 이더넷 _IS와 토큰링 _IS, 그리고 페이즈 모델간의 성능을 비교하였다. 시뮬레이션결과 토큰링의 경우 단순한 입장 제어에 의해서도 QoS 지원 정도가 크게 향상될수 있음을 볼 수 있었다. 또한 , 페이즈 모델의 경우 이더넷의 매체 접근 방식을 상당히 보완함으로써 QoS 지원 정도가 크게 향상될 수 있음을 볼 수 있었다. 또한, 페이즈 모델의 경우 이더넷의 매체 접근 방식을 상당히 보완함으로써 QoS 지원을 요구하는 플로우에대해서는 전통적인 이더넷이나 이더넷_IS 비해 훨씬 안정적인 서브넷 차원의 우선순위지원 서비스를 제공할 수 있음을 확인할 수 있었다.제공하는 멀티미디어 동기화 편집기와 변환기 및 상영기를 ScriptX를 이용하여 Windows95 상에 구현하였다.기 위한 간단한 例를 들어 봄으로써 이 글을 쓰는 동기으 일면을 대신하고자 한다.置함으로 이것을 Multi-Drop(points) system으로 swiching System을 利用 Mini-Network을 構成할 수도 있다.크 구성 관리 서버 시스템 개발에 대한 비용을 줄일 수 있다. 기대된다.e 함량이 대체로 높게 나타났다. 점미가 수가용성분에서 goucose대비 용출함량이 고르게 나타나는 경향을 보였고 흑미는 알칼리가용분에서 glucose가 상당량(0.68%) 포함되고 있음을 보여주었고 arabinose(0.68%), xylose(0.05%)도 다른 종류에 비해서 다량 함유한 것으로 나타났다. 흑미는 총식이섬유 함량이 높고 pectic substances, hemicellulose, uronic acid 함량이 높아서 콜레스테롤 저하 등의 효과가 기대되며 고섬유식품으로서 조리 특성 연구가 필요한 것으로 사료된다.리하였다. 얻어진 소견(所見)은 다음과 같았다. 1. 모년령(母年齡), 임신회수(姙娠回數), 임신기간(姙娠其間), 출산시체중등(出産時體重等)의 제요인(諸要因)은 주산기사망(周産基死亡)에 대(對)하여 통계적(統計的)으로 유의(有意)한 영향을 미치고 있어 $25{\sim}29$세(歲)의 연령군에서, 2번째 임신과 2번째의 출산에서 그리고 만삭의 임신 기간에, 출산시체중(出産時體重) $3.50{\sim}3.99kg$사이의 아이에서 그 주산기사망률(周産基死亡率)이 각각 가장 낮았다. 2. 사산(死産)과 초생아사망(初生兒死亡)을 구분(區分)하여 고려해 볼때 사산(死産)은 모성(母性)의 임신력(姙娠歷)

• Journal of KIISE:Computing Practices and Letters
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• v.13 no.1
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• pp.59-73
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• 2007

Although there exist many middlewares such as Havi, Jini, LonWorks, UPnP, and SLP, new middlewares specialized for diverse information appliances are expected to appear continuously as home networks evolve. In this paper, we examine an integrated architecture for supporting interoperability among heterogeneous middlewares under home network, we also propose and implement a scenario-based user-oriented integrated architecture for efficient home automation which is different from existing methods. HOMI(Homenetwork Middleware for Interoperability) architecture proposed in this paper provides interfaces that assist users with designing and modifying desirable scenarios using a script interpreter language HOMIL(HOMI Language). Different from an existing integrated middleware architecture, HOMI improves efficiency and convenience of interoperation between heterogeneous appliances for home automation allowing users to design and organize scenarios through these interfaces. HOMI classifies interoperation services into time contort, synchronization context, and asynchronization context and helps to execute next services considering contexts when a specific event occurs. Applying modified scenarios immediately to home network environment, HOMI provides users with seamless services without installing new applications, updating the server, or rebooting in order to adopt new scenarios. Lastly, distribution agents into several devices, we solved the overhead problem occurred in a centralized architecture for integrated middleware.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4C
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• pp.341-348
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• 2009

In this paper, we propose a grouping technique for the SDD(Synchronous Digital Duplexing) based on OFDMA(Orthogonal Frequency Division Multiple Access). The SDD has advantages of increasing data efficiency and flexibility of resource since SDD can transmit uplink signals and downlink signals simultaneously by using mutual time information and mutual channel information, obtained during mutual ranging process. However, the SDD has a disadvantage of requiring additional CS to maintain orthogonality of OFDMA symbols when the sum of mutual time difference and mutual channel length between AP(access point) and SS(subscriber station) or among SSs are larger than CP length. In order to minimize the length of CS for the case of requiring additional CS in SDD, we proposes a grouping technique which controls transmit timing and receive timing of AP and SS in a cell by classifying them into groups. Performances of the proposed grouping technique are evaluated by computer simulation.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.6
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• pp.18-24
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• 2012

This paper reports the test results of a 50MHz/s 10 bits DAC developed with $0.18{\mu}m$ CMOS process for the wireless sensor network application. The 10bits DAC, not likely a typical segmented type, has been designed as a current driving type with double step thermometer decoding architecture in which 10bits are divided into 6bits of MSB and 4bits of LSB. MSB 6bits are converted into 3 bits row thermal codes and 3 bits column thermal codes to control high current cells, and LSB 4 bits are also converted into thermal codes to control the lower current cells. The high and the lower current cells use the same cell size while a bias circuit has been designed to make the amount of lower unit current become 1/16 of high unit current. All thermal codes are synchronized with output latches to prevent glitches on the output signals. The test results show that the DAC consumes 4.3mA DC current with 3.3V DC supply for 2.2Vpp output at 50MHz clock. The linearity characteristics of DAC are the maximum SFDR of 62.02dB, maximum DNL of 0.37 LSB, and maximum INL of 0.67 LSB.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.1-9
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• 2016

Railroad bridges account for 25% of the entire high-speed rail network. Railway bridges are subject to gradual structural degradation or fatigue accumulation due to consistent and repeating excitation by fast moving trains. Wireless sensing technology has opened up a new avenue for bridge health monitoring owing to its low-cost, high fidelity, and multiple sensing capability. On the other hand, measuring the transient response during train passage is quite challenging that the current wireless sensor system cannot be applied due to the intrinsic time delay of the sensor network. Therefore, this paper presents a framework for monitoring such transient responses with wireless sensing systems using 1) real-time excessive vibration monitoring through ultra-low-power MEMS accelerometers, and 2) post-event time synchronization scheme. The ultra-low power accelerometer continuously monitors the vibration and trigger network when excessive vibrations are detected. The entire network of wireless smart sensors starts sensing through triggering and the post-event time synchronization is conducted to compensate for the time error on the measured responses. The results of this study highlight the potential of detecting the impact load and triggering the entire network, as well as the effectiveness of the post-event time synchronized scheme for compensating for the time error. A numerical and experimental study was carried out to validate the proposed sensing hardware and time synchronization method.

• The KIPS Transactions:PartC
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• v.15C no.4
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• pp.281-288
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• 2008

Recently, the advance of multimedia hardware has fostered the development of wireless multimedia sensor network which is able to ubiquitously obtain multimedia content such as image or audio from the environment. The multimedia data which has several characteristics such as large size and correlation between the data requires reliability in transmission. However, the existing solution which take the focus on the efficiency of network mainly, is not appropriate to transmit the multimedia data. In the paper, we proposes a reliable asynchronous image transfer protocol, RAIT. RAIT applies double sliding window method in node-to-node image tansfer to prevent the packet loss caused by network congestion. The double sliding window consists of one sliding window for the receiving queue, which is used for prevention of packet loss caused by communication failure between nodes and the other sliding window for the sending queue which prevents the packet loss caused by network congestion. the routing node prevents the packet loss and guarantees the fairness between the nodes by scheduling the packets based on the image non-preemptively. The RAIT implements the double sliding window method by cross layer design between RAIT layer, routing layer, and queue layer. The experiment shows that RAIT guarantees the reliability of image transmission compared with the existing protocol.