• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.277-279
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• 2008

현재 많은 전력계통용 보호제어 벤더들은 변전소 자동화 국제표준 프로토콜인 IEC 61850을 적용한 전력 장비들을 개발하여 변전소에 적용하고 있다. 이러한 많은 장비들은 표준화된 IEC 61850 프로토콜을 적용하여 상호 호환성을 유지하였으며, 기존에 적용되고 있는 표준화된 기술들을 채택하고 있다. 변전소 장비들은 정밀한 시간 동기를 위해서 표준화된 시각 동기 프로토콜인 SNTP(Simple Network Time Protocol)나 NTP(Network Time Protocol)를 사용하고 있다. 본 연구에서는 IEC 61850 프로토콜을 적용한 IED가 시각 동기 장치로부터 시간 동기화되는 방안에 대해 연구하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11c
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• pp.1997-2000
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• 2003

오늘날 무선 LAN이 집안 또는 사무실, 산업현장, 공항 등과 같이 어디서나 무선으로 인터넷을 이용할 수 있게 설치되어 있다. 이런 무선 LAN 사용이 늘어나는 반면 보안상 결함을 해결할 보안 기능이 절실히 요구되는 실정이다. 본 논문에서는 무선 LAN환경에서 데이터를 안전하게 인증할 수 있는 효율적인 인증 Protocol을 제안한다. 여기서는 단일 Bit를 패킷에 추가하여 AP에서 확인 인증하는 방식을 채택하는데, 기존 방식과는 달리 AP에서 인증 스트림 동기화를 위한 작업을 수행한다. 컴퓨터 시뮬레이션이 최대 50%까지 기존 방식 보다 인증 스트림을 더 사용할 수 있게 하는 것을 보여주고 모바일 호스트의 전력 소모도 최소화한다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.4
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• pp.745-759
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• 2012

It is shown in this paper that Yuksel-Nielson's key distribution scheme is not secure against key de-synchronization attack even though their scheme supplement ZigBee-2007 specification's security problems. Furthermore, a new key distribution scheme is proposed, which is the one to fix the security weakness of Yuksel-Nielson's scheme, as well as its security and performance analysis to verify its effectiveness.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07b
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• pp.103-105
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• 2005

공공 부문이나 대기업에서 운영하는 웹 사이트의 규모가 커지면서 분야별로 사이트가 나누어지게 되는데, 사이트를 이동할 때 마다 로그인을 다시 해야 하는 불편이 있다. 따라서 최근 이용자들의 불편을 줄이기 위하여 SSO (Single Sing-On) 통합인증 체제를 도입하는 사례가 늘고 있다. 통합 인증 시스템을 구축하면서 다수 웹 사이트의 회원을 통합하고 이에 대한 회원 정보 DB를 구축하여야 하는데, 빠른 인증서비스를 위해서 LDAP(Lightweight Directory Access Protocol)를 사용하는 것이 일반적이다. 이때 회원정보 DB와 LDAP의 정보에 대한 동기화 문제와 웹 사이트를 통한 회원가입과 동시에 적용되어야 하는 요구사항을 만족시키기 위해 본 논문에서는 회원 정보 DB와 LDAP의 정보 사이의 동기화 방법을 제안하고 구현하여 그 성능을 분석하였다.

• Journal of Information Processing Systems
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• v.7 no.1
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• pp.53-62
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• 2011

With the steady growth of mobile technology and applications, demand for more storage in mobile devices has also increased. A lightweight block-level protocol, Internet Advanced Technology Attachment (iATA), has been developed to deliver a cost-effective storage network solution for mobile devices to obtain more storage. This paper seeks to contribute to designing and implementing Load Balancing (LB), Network Monitoring (NM) and Write Replication (WR) modules to improve the protocol's scalability and data availability. LB and NM modules are invoked to collect system resources states and current network status at each associate node (server machine). A dynamic weight factor is calculated based on the collected information and sent to a referral server. The referral server is responsible to analyze and allocate the most ideal node with the least weight to serve the client. With this approach, the client can avoid connecting to a heavily loaded node that may cause delays in subsequent in-band I/O operations. Write replication is applied to the remaining nodes through a WR module by utilizing the Unison file synchronization program. A client initially connected to node IP A for write operations will have no hindrances in executing the relevant read operations at node IP B in new connections. In the worst case scenario of a node crashing, data remain recoverable from other functioning nodes. We have conducted several benchmark tests and our results are evaluated and verified in a later section.

• Journal of Advanced Navigation Technology
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• v.11 no.2
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• pp.163-169
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• 2007

In this paper, we propose a method of trigger pulse generation to capture the image on time by making a synchronization between the x-ray generator and digital x-ray image acquisition system. we designed a wireless trigger pulse generation circuit to make a synchronization between x-ray generator and digital image acquisition system and analysis its performance. When it starts to detect a certain level of x-ray radiation or above from the air, this method starts to generate a ACQ_START signal to indicate the timing for image acquisition starting from digital image acquisition system. Hence, when it starts to detect under certain level of x-ray signal from the air, this method starts to generate a ACC_END signal to indicate the timing for image acquisition stop from digital image acquisition system. Image acquisition is activated only this time between ACQ_START and ACQ_END signal. By doing this wireless detecting of x-ray signal from remote, we can get more accurate timing for capturing the x-ray image and any type of x-ray generator can be connected to digital image acquisition system, regards of wired protocol. This makes easy installation. We could get 3.5 line pair / mm resolution at 20 mAs of x-ray level with resolution chart. This is same or better image comparing to conventional wired result.

• Journal of Broadcast Engineering
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• v.17 no.4
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• pp.596-610
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• 2012

This paper proposes a method to provide the high quality 3D broadcasting service in a mobile broadcasting system. In this method, audio and video data are delivered through a heterogeneous network, consisting of a mobile network as well as a broadcasting network, due to the limited bandwidth of the broadcasting system. However, it is more difficult to synchronize the left and right video frames of a 3D stereoscopic service, which come through different types of networks. The proposed method suggests the use of the offset from the initial timestamp of RTP (Real Time Protocol) to determine the order of frames and to find the pair of a left and a right frame that must be played at the same time. Additionally, a new signaling method is introduced for a mobile device to request a 3D service and to get the initial RTP timestamp.

• Journal of Veterinary Clinics
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• v.34 no.2
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• pp.82-86
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• 2017

We determined the risk factors for late embryonic mortality in dairy cows. We diagnosed pregnancy at 31 days and then confirmed the diagnosis at 45 days after artificial insemination (AI) via ultrasonography. The presence of an embryo with a heartbeat was the criterion for a positive pregnancy diagnosis. A diagnosis of late embryonic mortality was made when there was no positive sign of pregnancy in cows previously diagnosed as pregnant. The overall incidence of late embryonic mortality among 3,695 pregnancies was 6.9%. Logistic regression analysis revealed that herd size, AI month, synchronization protocol, and postpartum disease were important risk factors for late embryonic mortality. Herd size > 100 (odds ratio [OR]: 0.66, p < 0.05) and 50-100 lactating cows (OR: 0.63, p < 0.01) had lower risks of late embryonic mortality than herd size < 50 lactating cows. Cows inseminated during May-July had a higher risk (OR: 1.49, p < 0.05) of late embryonic mortality than cows inseminated during February-April. Cows inseminated after estrus following $PGF_{2{\alpha}}$ treatment also had a higher risk (OR: 1.77, p < 0.001) of late embryonic mortality than cows inseminated following natural estrus. Lastly, cows with postpartum disease tended to have a higher risk (OR: 1.26, p < 0.1) of late embryonic mortality than cows without postpartum disease. In conclusion, late embryonic mortality associated with the herd size, AI month, synchronization protocol, and postpartum disease in dairy cows.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2001.10a
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• pp.19-25
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• 2001

At present the identification of vessels is still depending on the OOW (Officer Of Wateh) in VTS (Vessel Traffic Service), which is completed by radar, and also by the combination of VHF radio and VHF direction finder. However, with the development of port transportation and economic, this conventional way of identification can't satisfy more and more request for the information that the VTS needs from the vessels. In such a case, the AIS(Automatic Identification System) precept which is based on STDMA (Self-organized Time Division Multiple Access) technique is put forward by IMO (International Maritime Organization). AIS can automatically provide the information, including own ship's identification, type, position, course, speed, and other information to the appropriately equipped coast station and other ships. At the same time it can also automatically monitor and track the nearby ships similarly fitted with AIS. On the basis of describing the whole comprising and the format of transmission information of AIS, this paper mainly studies the key communication techniques in AIS, such as STDMA protocol, net synchronization and GMSK(Gaussian Minimum Shift Keying)technique, and so on. At last this paper briefly introduces the recommendation decided by IMO on forcing the sea-going ships to fixed with AIS equipments, and it continuos with the unexploited potential of AIS if it applies in VTS.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.722-728
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• 2011

Most services need to have authentication protocols to verify users' eligibility in the network environment. For this, a lot of user authentication protocols have been researched and developed. Two of them, SPMA and I-SPMA protocols, introduced the lack of mutual authentication and vulnerability to the reply attack of the prior protocols and suggested revised protocols. Nevertheless, these protocols did not mention about the critical problem caused when the server and the client lose synchronization on the secret information between them. Therefore, in this paper, we analyze the security characteristics of the existing protocols and prove the vulnerability to the synchronization of the protocols.