• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.70-81
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• 2024

In this study, Tridimensional Hybrid Isolation System(THIS) was proposed as a vibration isolator for traffic loads, combining vertical and horizontal isolation systems. Its efficacy in improving serviceability for vertical vibration was analytically evaluated. Firstly, for the analysis, the major vibration modes of the existing apartment were identified through eigenvalue analysis for the system and pulse response analysis for the bedroom slab using commercial structural analysis software. Subsequently, a 16-story model with horizontal, vertical and rotational degrees of freedom for each slab was numerically organized to represent the achieved modes. The dynamic analysis for the measured acceleration from an adjacent ground to high-speed railway was performed by state-space equations with the stiffness and damping ratio of THIS as variables. The result indicated that as the vertical period ratio increased, the threshold period ratio where the slab response started to be suppressed varied. Specifically, when the period ratio is greater than or equal to 5, the acceleration levels of all slabs decreased to approximately 70% or less compared to the non-isolated condition. On the other hand, it was ascertained that the influence of damping ratios on the response control of THIS is inconsequential in the analysis. Finally, the improvement in vertical vibration performance of THIS was evaluated according to design guidelines for floor vibration of AIJ, SCI and AISC. It was confirmed that, after the application of THIS, the residential performance criteria were met, whereas the non-isolated structure failed to satisfy them.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.74-74
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• 2011

본 연구에서는 중앙경간 54m, 교폭 4m의 사장교형식의 보도교로 측경간은 계단으로 이루어진 1경간 케이블교량을 대상으로 보행하중에 의한 수직진동을 제어하기 위해 제진장치(TMD)를 적용하기로 하고 실물 TMD의 설계 및 제작 그리고 설치 및 제어성능실험을 수행하였다. 우선 사장교형식의 교량. 그리고 1경간 교량이라는 점에서 상대적으로 감쇠율이 낮을 것으로 예측되었고 또한 54m의 경간장이 보행자가 가진 주파수에 근접한 고유진동수를 나타낼 것으로 사료되어 Eurocode 2 part 2(EC5-2)의 규준에 따라 1인 및 다수 보행하중에 의한 보도교의 발생가속도를 산출하였다. 이 경우 최대가속도는 다수의 보행자가 연속적으로 진행할 때 발생하였으며, 수직방향의 가속도가 사용성기준을 초과하는 것으로 나타났다. 또한 구조해석프로그램에 의한 고유치 해석결과, 보행하중의 주파수대역내에 진동모드가 존재하는 것으로 나타났다. 따라서 본 교량의 설계단계에 있어서 보행진동을 제어하기 위하여 유지관리가 용이한 수동형의 동조질량감쇠장치(Tuned Mass Damper)를 적용하기로 하였으며 TMD의 설계에서는 TMD의 제어목표를 만족시킬 수 있는 TMD의 가동질량(moving mass)을 우선적으로 결정하였고, 이로부터 Den Hartog의 제안식에 따라 TMD의 고유진동수비, 유효감쇠비를 산정하였다. 산정된 변수들을 이용하여 설계된 TMD는 현장설치 및 튜닝의 편의성을 고려하여 수평 외팔보형식으로 설계, 제작되었으며 제작된 TMD의 경우 회전축에 대해 질량, 스프링, 댐퍼의 중심거리를 조정함으로써 TMD의 진동수, 강성, 감쇠력을 상대적으로 매우 용이하게 조절할 수 있으며, 조정범위 또한 광범위하여 일반 TMD에 비해 현장설치시 대상구조물에 동조시키기가 용이하며, 작동시 마찰감쇠가 거의 없다는 장점이 있다. 현장설치전에 제작된 TMD를 대상으로 자유진동 시험을 통하여 질량의 중심거리, 스프링 크기 그리고 댐퍼의 설치유무를 각각 변화시키며 TMD의 자유진동 데이터를 취득하였다. 각각의 시험에서 얻어진 데이터로부터 스펙트럼해석을 통하여 고유진동수를 구하였고, 자유진동 파형으로 부터 감쇠비를 구하였다. TMD는 일반적으로 제어모드의 변형형상이 가장 큰 곳에 설치되었을 때 최대의 제진효과를 발휘할 수 있다. 그러나 현장여건상 설치가 불가능하거나 미관을 해치는 경우에는 가능한 범위 내에서 TMD 제어효율이 가장 크게 발휘할 수 있는 곳을 선택하여야 한다. 본 보도교의 경우, 중앙경간 중심부에서 가장 큰 모드변형형상을 나타내지만, 보도교의 상판 연결부 등에 따른 TMD 시공문제로 인하여 TMD 설치위치는 교량 중앙에서 양 방향으로 1.25m 떨어진 곳에 대칭으로 총 2기를 설치하기로 하였다. 일반적으로 TMD의 모든 설계변수는 구조물의 설계단계에서 수행된 구조해석결과에 근거하여 설정하므로 완공된 구조물, 즉 실제보도교의 동적특성을 계측하여 정확하게 진동수를 튜닝하여야 한다. 구조해석에 의한 보도교의 수직방향(TMD 작동방향) 고유진동수는 1.5225 Hz이며, 감쇠비는 규준에 의하여 0.6 %로 가정하였다. 그러나 이 값들은 구조해석모델 및 재료적 특성과 시공상의 오차에 의하여 실제와 다를 수 있으므로 현장계측에 의한 확인이 요구된다. 또한 TMD의 제진효율이 설계시의 목표대로 확보되었는지도 확인해야 하므로 현장튜닝 및 성능시험을 실시하였다. 보도교의 가진은 사전에 실시한 상시 미진동계측결과를 토대로 2Hz를 목표로 하여 인력가진실험을 수행하였고, 탁월진동 주파수는 1.9896Hz로 나타나 구조해석결과와 오차가 있음을 알 수 있다. 가진실험결과를 토대로 TMD의 진동수를 최적진동수비로 튜닝하고 인력가진 실험을 다시 실시하여 TMD의 진동제어성능을 검토하였다. TMD 튜닝 전, 후의 보도교 감쇠비를 비교한 결과, TMD를 설치함으로써 약 4.218%의 감쇠비 증가가 있음을 알 수 있다.

• The KIPS Transactions:PartC
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• v.16C no.2
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• pp.151-164
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• 2009

The importance of sensor networks as a base of ubiquitous computing realization is being highlighted, and espicially the security is recognized as an important research isuue, because of their characteristics.Several efforts are underway to provide security services in sensor networks, but most of them are preventive approaches based on cryptography. However, sensor nodes are extremely vulnerable to capture or key compromise. To ensure the security of the network, it is critical to develop security Intrusion Detection System (IDS) that can survive malicious attacks from "insiders" who have access to keying materials or the full control of some nodes, taking their charateristics into consideration. In this perper, we design a distributed and adaptive IDS architecture on sensor networks, respecting both of energy efficiency and IDS efficiency. Utilizing a modified HEED algorithm, a clustering algorithm, distributed IDS nodes (dIDS) are selected according to node's residual energy and degree. Then the monitoring results of dIDSswith detection codes are transferred to dIDSs in next round, in order to perform consecutive and integrated IDS process and urgent report are sent through high priority messages. With the simulation we show that the superiorities of our architecture in the the efficiency, overhead, and detection capability view, in comparison with a recent existent research, adaptive IDS.

• Journal of the Korean Society for Railway
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• v.16 no.3
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• pp.207-216
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• 2013

The components of concrete track (rail and rail fastening system) in railway bridge deck ends are damaged and deteriorated by track-bridge interaction forces such as uplift forces and compression forces owing to their structural flexural characteristics (bridge end rotation). This had led to demand for alternatives to improve structural safety and serviceability. In this study, the authors aim to develop a transition track to enhance the long term workability and durability of concrete track components in railway bridge deck ends and thereby improve the performance of concrete track. A time-history analysis and a three-dimensional finite element method analysis were performed to consider the train speed and the effect of multiple train loads and the results were compared with the performance requirements and German standard for transition track. Furthermore, two specimens, a normal concrete track and a transition track, were fabricated to evaluate the effects of application of the developed transition track, and static tests were conducted. From the results, the track-bridge interaction force acting on the track components (rail displacement, rail stress, and clip stress) of the railway bridge deck end were significantly reduced with use of the developed transition track compared with the non-transition track specimen.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.182-192
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• 2023

In this study, the efficacy of Engineered Cementitious Composite(ECC) jacket for masonry fences subjected to lateral dynamic load was experimentally verified through a shaking table test, comparing it with the performance of an unreinforced masonry(URM) fence. Firstly, dominant frequencies, modal damping ratios and deformed shapes were identified through an impact hammer test. URM and ECC-strengthened fences with heights of 940mm and 970mm had natural frequencies of 6.4 and 35.3Hz, and first modal damping ratios of 7.0 and 5.3%, respectively. Secondly, a shaking table test was conducted in the out-of-plane direction, applying a historical earthquake, El Centro(1940) scaled from 25 to 300%. For the URM fence, flexural cracking occurred at the interface of brick and mortar joint(i.e., bed joint) at the ground motion scaled to 50%, and out-of-plane overturning failure followed during the subsequent test conducted at the ground motion scaled to 30%. On the other hand, the ECC-jacketed fence showed a robust performance without any crack or damage until the ground motion scaled to 300%. Finally, the base shear forces exerted upon the URM and ECC-jacketed fences by the ground motions scaled to 25~300% were evaluated and compared with the ones calculated according to the design code. In contrast to the collapse risk of the URM fence at the ground motion of 1,000-year return period, the ECC-jacketed fence was estimated to remain safe up to the 4,800-year return period ground motion.

• Journal of the Korea Society of Computer and Information
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• v.10 no.6 s.38
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• pp.209-218
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• 2005

In this paper, we present an Active Optical Network(AON) . The AON uses the Dense Wavelength Division Multiplexing(DWDM) from optical communication access network of ring type, and will be able to provide the smoothly service in the Bandwidth on Demand by using DWDM. It supports the connection of the multiple wavelength and the Sub-Carrier from the optical gigabit ethernet switch. The Wavelength Add Drop Multiplexer(WADM) extracts a specific wavelength, and composes a node of the ring network. The specific wavelength becomes demultiplexing in the Sub-Carrier and it is distributed in the user The active connection of optical gigabit ethernet switch where the distribution of access network is started and access terminal connection equipment is possible. By the BoD from the AON it compares the buffer size which changes, and it analyzes. Also the Time delay of bit compares with the throughput of server The limit of amount of time is decided. Consequently it will be able to realize the dynamic use protocol and an efficient algorithm of the network.

• Journal of the Korean Institute of Intelligent Systems
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• v.8 no.6
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• pp.37-47
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• 1998

This paper proposes a controller design method using the evolutionary computation algorithm and the fuzzy logic to control the wafer temperature in rapid thermal processing. First, we design the feedforward static controller to provide the control powers of the lamps for the given steady state temperature. Second, the feedforward dynamic controller is designed for the additional control powers to achieve a given transient response. These feedforward controllers are implemented by using the fuzzy logic to act as a global nonlinear controller over a wide range of operating points. The parameters of these controllers are optimized by using the evolutionary computation algorithm so that it can be used when the mathematical model is not available. In addition, the feedback error controller is introduced to compensate the feedforward controllers when there exist disturbances and modeling errors. The gain of feedback error controller is also obtained by the evolutionary computation algorithm. Through simulations, we verify the proposed control system can give a satisfactory performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.11
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• pp.1262-1270
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• 2007

In this paper, we propose a new distortion cancellation mechanism for a balanced power amplifier structure using the carrier cancellation loop of a feedforward and post-distortion technique. The proposed cross post-distortion balanced linear amplifier can reduce nonlinear components as much as the conventional feedforward amplifier through the output dynamic range and broad bandwidth. Also the proposed system provides higher efficiency than the feedforward. The capacities of power amplifier and error power amplifier in the proposed system are analyzed and compared with those of feedforward amplifier. Also the operation mechanisms of the three kind loops are explained. The proposed cross post-distortion balanced linear power amplifier is implemented at the IMT-2000($f_0=2.14\;GHz$) band. With the commercial high power amplifiers of total power of 240 W peak envelope power fer base-station application, the adjacent channel leakage ratio measurement with wideband code division multiple access 4FA signal shows 18.6 dB improvement at an average output power of 40 dBm. The efficiency of fabricated amplifier Improves about 2 % than the conventional feedforward amplifier.

• KIPS Transactions on Software and Data Engineering
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• v.2 no.7
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• pp.471-478
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• 2013

This paper proposes a black-box based test case generation method for Simulink/Stateflow model utilizing the RRT algorithm which is a method to efficiently solve the path planning for complicated systems. The proposed method in the paper tries to solve the reachability problem with the RRT algorithm, which has to be solved for black-box based test case generations. A major problem of the RRT based test case generation algorithms is that the cost such as running time and required memory size is too much for complicated Stateflow model. The typical RRT algorithm expands rapidly-exploring random tree (RRT) in a single state space. But the proposed method expands it in dynamic state space based on the state of Simulink model, consequently reducing the cost. In the paper, a new definition of RRT state space, a distance measure and a test case generation algorithm are proposed. The performance of proposed method is verified through the experiment against Stateflow model.

• The KIPS Transactions:PartC
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• v.9C no.3
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• pp.323-330
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• 2002

Multicast services are gradually diversified and used widely. Proportionately, they become the center of attackers' attention and there are growing possibilities of an intelligence leak. Therefore, research related to secure multicast should be required to provide multicast service efficiently. This paper presents the architecture for secure multicast which provides efficient group management mechanism in group consists using member's dynamic join and leave. This architecture can provide secure multicast services to many users with regard to security aspects in one-to-many communication. The simulation results show that the proposed architecture achieves an efficient group management and a secure data transmission with low latency compared with the other existing secure multicast architecture.