• TTA Journal
• /
• s.68
• /
• pp.100-107
• /
• 2000

일상생활과 사무실에 거센 바람이 불고 있다. 그것은 근거리 무선접속규격의 신기술인 블루투스(Bluetooth)로서 우리의 모든 생활을 바꾸어 놓을 것이다. 인류의 역사를 바꾸는 신기술인 IMT-2000과 더불어 블루투스가 각광을 받고 있는 시점이다. 일상생활에서 특히 가정과 사무실에서 근거리 무선접속 구간에서의 이동성을 가진 디바이스들 간 상호통신의 새로운 표준으로 자리잡고 있다. 이와 같이, 일상생활에서의 커다란 변화와 산업 정보화시대에서 가장 큰 관건은 정보 고속화와 정보의 정확한 전달일 것이다. 이러한 것과 발맞추어 진행 중인 것이 근거리 무선구간에서의 2.4GHz대 ISM(Industrial, Scientific, Medical) 대역의 주파수를 사용하여 1Mbps 속도(실효속도 721K)로 최대 10m내에서 각종 단말기와 디바이스(예: 전화기, Fax, 데스크 탑, 노트북 컴퓨터, MP3 플레이어, 스캐너..)들을 무선 접속하는 블루투스 기술이며, 이는 기존의 유선에서의 불편함을 깔끔히 해소해 주었다. 필자는 전반적인 블루투스의 흐름을 간략하면서도 필요한 부분을 전달하는 목적으로, 또한 아직 블루투스의 위력을 인식하지 못한 기업과 독자들에게 새롭게 인식할 수 있도록 블루투스의 소개와 함께 기술적인 측면, 시스템적인 면과 회사별 제품현황에 대해 중요한 부분만을 블루투스 스팩을 기준으로 정리하였다.

• Journal of the Korean Society for Railway
• /
• v.13 no.3
• /
• pp.298-303
• /
• 2010

The transition zone of the railway is the section which roadbed stiffness is suddenly varied like as tunnel-earthwork, bridge-earthwork and concrete track-ballasted track. There are about 450 tunnel-bridge transition sections on Kyungbu high-speed railway line. It is very important to pay careful attention to construction of these transition zones, in order to secure the train running safety. So, we developed a finite element model of the moving wheel loading to simulate the behavior of bridge-earthwork transitions in this paper. The most distinctive characteristics of the model proposed is to simulate the real wheel behavior on rail. And the main analysis object is to evaluate and compare the deformation characteristics of the transition zone according to the reinforcement methods and length of transition zone which is adopted to high-speed railway. Based on the analysis results, we assessed the effect of the reinforcements on the transition zone of high-speed railway.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.1
• /
• pp.23-36
• /
• 2016

We propose a new type of OFDM-CDMA scheme which allows large inter-user timing offset using zero correlation zone(ZCZ) code in conjunction with block spreading technique. Moreover to maximize spectral efficiency, the proposed OFDMA does not have guard time(GT). This is opposite to the trends in the conventional schemes where GT are supposed to be larger to allow larger inter-user timing offset. It is remarkable that the proposed GT-free OFDM-CDMA scheme completely cancels inter-user interference in the multipath fading simply by despreading process. This inter-user interference-free feature still remains even there exist inter-user timing offsets as large as multiple OFDM symbols. Although the self-user interference exists due to no GT, it can be effectively suppressed by simple successive interference cancellation(SIC) from the first symbol in spread block as it is free from inter symbol interference(ISI).

• International Journal of Highway Engineering
• /
• v.10 no.3
• /
• pp.189-197
• /
• 2008

Using a 5 year(2003 to 2007) pavement condition survey data from the highway pavement management system(HPMS), the roughness of the bridge deck pavement was analyzed. Based on the result of this analysis, this study tried to identify the factors affecting the deterioration of the bridge deck pavement condition. The data from HPMS indicates that the roughness of the bridge deck pavement is worse than that of the general pavement on the roadbed. The worse roughness of the bridge deck pavement is caused by the settlement of approach slab as well as the surface distress on the bridge deck pavement. In order to improve effectively the roughness of the bridge deck pavement, a management system was established in which not only the regular automated pavement condition survey to check the distress of surface of the bridge deck pavement was adopted but an automated surface profiler to check the degree of settlement of approach slab was applied.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.7 no.2
• /
• pp.43-54
• /
• 1997

In this paper, we introduce a secure and minimal protocol for authenticated key distribution over the CDMA mobile communication network. The CDMA mobile communication network has been developed the security protocol that provides a means for user authentication and subsequent protection of user traffic. However, this model has no security assumptions for the intermediate, fixed networks. To avoiding these drawbacks, we introduce a minimal authenticated key distribution protocol. This protocol provides the security of the intermediate and fixed network in mobile environment, and maintains the confidentiality of user identification and the minimum size of information flow compared with the existing protocols.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.12
• /
• pp.1824-1833
• /
• 2016

In this paper, we propose networked airborne relay-based positioning scheme (N-ARPS) based on time division multiple access (TDMA) networks to improve the performance of relative navigation (RelNav). To integrate the ARPS into TDMA, there are three problems such as slot allocation, selection of airborne relays, and method for signal loss to be solved. A subframe of N-ARPS is designed to assign the slots for broadcast and relay of navigation signals consecutively to minimize the effect of mobility. The selection algorithm determines the optimum set of airborne relays by selecting evenly distributed nodes depending on their distances to the master station. Finally, we uses precise position location information (PPLI) messages, which are received in data transmission period, to estimate a user position when the navigation signals are missing. The simulation results indicate that N-ARPS significantly improves user accuracy over RelNav.

• Information and Communications Magazine
• /
• v.10 no.12
• /
• pp.77-90
• /
• 1993

1980년대 미국, 일본, 영국을 필두로 시작되었던 기본통신분야의 경쟁은 최근 호주와 뉴질랜드가 경쟁을 시작하였고 유럽 등에서도 경쟁도입을 고려하는 등 세계적인 추세이다. 국내 기본통신사장에 경쟁에 도입되면 신기술 도입에 의한 통신시설투자의 합리화로 가입자 요금이 인하되고 다양한 서비스의 창출과 서비스 품질 향상을 기대할 수 있으며, 특히 통신망의 이원화로 국가 기간통신망의 신뢰성 향상을 도모할 수 있다. 경쟁도입을 성공적으로 이끌기 위해서는 통신정책뿐만 아니라 기술적 조건이 만족되어야 하는데, 특히 통신망간의 상호접속이 가장 중요한 문제중의 하나이다. 호접속지연 등 가입자의 서비스품질향상과 사업자간 동등접속을 위해서는 초기에는 시외국계위로 접속하고 점차 단국계위에 접속하는 것이 합리적인 방안이며, 가입자의 접속편이를 위하여 다이얼링 수고를 덜 수 있는 사업자 사전지정방식이 추진되어야 한다. 최근 전화서비스의 핵심인 지능망서비스의 효과적인 제공을 위해서는 시내외 구간의 지능망서비스 제공이 가능하도록 함이 타당할 것이다.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.247-248
• /
• 2008

신도시의 건설뿐만 아니라 기존 거대 도시에서의 전력 소모량을 계속적으로 증가하고 있는 추세이다. 한전계통에 적용되는 지중 송전용 케이블 대부분의 경우 동(Cu)도체를 사용하고 있으나, 현재 LME의 급격한 상승 때문에 국외에서는 지중 송전용 케이블의 도체를 동도체에서 알루미늄(AL) 도체로 대체하고 있다. 이에 알루미늄은 자체의 독특한 특성 때문에 동도체와 같은 방법(슬리브 압착)으로 접속할 경우 접속부에서 도체 과열과 같은 예기치 못한 문제로 접속 구간뿐만 아니라 인근 계통에도 큰 문제를 발생시킬 수 있다. 그리하여 본 논문에서는 초고압 지중송전용 케이블에 동도체 대신 적용되는 알루미늄 도체의 접속기술에 관한 연구를 진행하였다.

• Journal of Wetlands Research
• /
• v.23 no.1
• /
• pp.85-93
• /
• 2021

Sewage separation which often involves installing a new pipe to separate wastewater flow from stormwater runoff flow can be costly and depends highly on its feasibility in a site. To be able to develop a potentially more economical alternative that can also lessen major road traffic disturbance during this process, a different approach where a smaller sewage separator pipe is installed inside an existing combined sewer pipe was investigated. A small-scale of a box sewer and the proposed sewage separator pipe was constructed in the laboratory to observe and compare the deposition of solids and other solid-associated major pollutants at different flow rates. In addition, three-dimensional flow simulations considering five different scenarios were conducted using Ansys Fluent to observe the effect of the proposed sewage separator pipe to the hydraulic flow if installed inside the combined sewer pipe. Results revealed that the deposition of TSS, TCOD, TN, and TP were reduced by at least 60% when the wastewater was conveyed by the sewage separator pipe instead of the combined sewer pipe. Moreover, the flow simulations conducted showed that there was little to no major disturbance in hydraulic flow and velocity distribution when the sewage separator was installed inside a straight pipe and even at pipe transitions such as intersections, turns, and drop in elevation. Considering the pipe dimensions and the results of the study, the proposed approach can be promising in terms of reduction in pollutant deposition without a major effect on the hydraulic flow. Further investigation and cost-analysis should be done in the future to support these preliminary findings and help alleviate the problems caused by combined sewer overflows by introducing an alternative approach.

• The Journal of the Convergence on Culture Technology
• /
• v.8 no.5
• /
• pp.547-552
• /
• 2022

In this study, shape-based track management by analyzing track irregularity was studied in terms of force-based track irregularity analysis by numerical analysis of wheel-rail interaction force using by the measured vertical irregularity. The effect of the vertical irregularity of the track due to the difference in track types on the wheel-rail interaction force and the track acceleration in the connecting section of the sleeper floating track and the direct fixation track on concrete bed were analyzed. As the results of this study, the measured vertical irregularity was directly affect the vertical wheel load (the wheel-rail interaction force) and the rail acceleration, and it has been demonstrated to change consistently. In this study, the adequacy and necessity of the force-based track irregularity analysis method was verified based on the wheel-rail interaction analysis using the the measured vertical irregularity.