• Proceedings of the KSR Conference
• /
• 2007.05a
• /
• pp.1408-1415
• /
• 2007

To operate Platform Screen Door (PSD) automatically, the operational data of PSD and the train must be interfaced properly. PSD and train are operated together by the signaling system in Automatic Train Operation (ATO) signaling system zone where interfaces are provided between PSD and train. However, the additional PSD interface system with train is required in train operating zone without the interface between PSD and train. For the PSD interface, the wireless communication system or the train status (train correct stop status / train door status) detection system has been used. Seoul Metro line No.2. has the PSD wireless communication system using 447MHz band RF. For the safety of PSD operation, it is required to prevent RF interference in the subway environment where many frequencies exist. In this paper, the PSD wireless communication system is developed using 2.4GHz band RF to prevent the interference of the wireless communication and increase the traffic of the PSD interface. Furthermore, the improved system can store, manage and display the PSD and train operational data using Human Machine Interface (HMI) in the train's driver cab.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.16 no.3
• /
• pp.565-570
• /
• 2012

This paper has proposed a multi-channel low pass filter (LPF) for LTE-Advanced systems. The proposed LPF is an active-RC 5th chebyshev topology with three cut-off frequencies of 5 MHz, 10 MHz, and 40 MHz. A 3-bit tuning circuit has been adopted to prevent variations of each cut-off frequency from process, voltage, and temperature (PVT). To achieve a high cut-off frequency of 40 MHz, an operational amplifier used in the proposed filter has employed a PMOS cross-connection load with a negative impedance. A proposed filter has been implemented in a 0.13-${\mu}m$ CMOS technology and consumes 20.2 mW with a 1.2 V supply voltage.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.6 no.4
• /
• pp.983-999
• /
• 2014

The structural design of the ships includes two main issues which should be checked carefully, namely the extreme structural response (yielding & buckling) and the fatigue structural response. Even if the corresponding failure modes are fundamentally different, the overall methodologies for their evaluation have many common points. Both issues require application of two main steps: deterministic calculations of hydro-structure interactions for given operating conditions on one side and the statistical post-processing in order to take into account the lifetime operational profile, on the other side. In the case of ultra large ships such as the container ships and in addition to the classical quasi-static type of structural responses the hydroelastic structural response becomes important. This is due to several reasons among which the following are the most important: the increase of the flexibility due to their large dimensions (Lpp close to 400 m) which leads to the lower structural natural frequencies, very large operational speed (> 20 knots) and large bow flare (increased slamming loads). The correct modeling of the hydroelastic ship structural response, and its inclusion into the overall design procedure, is significantly more complex than the evaluation of the quasi static structural response. The present paper gives an overview of the different tools and methods which are used in nowadays practice.

• Smart Structures and Systems
• /
• v.17 no.6
• /
• pp.1017-1030
• /
• 2016

This study focuses on the system identification of reinforced concrete bridges using vector autoregressive model (VAR). First, the time series output response from a bridge establishes the autoregressive (AR) models. AR models are one of the most accurate methods for stationary time series. Burg's algorithm estimates the autoregressive coefficients (ARCs) at p-lag by reducing the sum of the forward and the backward errors. The computed ARCs are assembled in the state system matrix and the eigen-system realization algorithm (ERA) computes: the eigenvector matrix that contains the vectors of the mode shapes, and the eigenvalue matrix that contains the associated natural frequencies. By taking advantage of the characteristic of the AR model with ERA (ARMERA), civil engineering can address problems related to damage detection. Operational modal analysis using ARMERA is applied to three experiments. One experiment is coupled with an artificial neural network algorithm and it can detect damage locations and extension. The neural network uses a specific number of ARCs as input and multiple submatrix scaling factors of the structural stiffness matrix as output to represent the damage.

• Aerospace Engineering and Technology
• /
• v.1 no.1
• /
• pp.1-7
• /
• 2002

This paper describes the analysis method about the dynamic characteristics and vibratory load through HDS(Helicopter Design Study). To analyze the dynamic characteristics of helicopter rotor blade, the natural frequencies and modes are calculated according to rotor operational speed(Ω). Generally the proximity of rotor natural frequency and N times of rotor operational speed is a dominant component to determine the helicopter vibration. Also we can predict the airframe vibration by calculating the airload of rotating blade exactly. We expect to establish the design procedure of rotor dynamics by describing the two major analysis methods necessary to rotor design.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.6
• /
• pp.93-100
• /
• 2020

The turbopump of the liquid rocket engine adapts an inducer to minimize the cavitation due to the variations of the propellants supply condition. However, the inducer introduces cavitation instabilities which are well-known problems in the engine development. In this paper, operational characteristics by the cavitation instabilities are analyzed and the reliability of the engine is checked when the first stage engine of the KSLV-II is tested at the low inlet pressure conditions. The characteristic frequencies representing the cavitation instabilities of the LOx pump are clearly found in various high frequency sensor signals around the entire engine in addition to the LOx and fuel pump.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.4
• /
• pp.20-29
• /
• 2022

The operational modal analysis (OMA) technique, which extracts the modal parameters of a structural system using ambient vibrations, has been actively developed as a field of structural health monitoring of cable-supported bridges. In this paper, the short and long-term modal parameters of a cable-stayed bridge were evaluated using the acceleration data obtained from the two ambient vibration tests (AVTs) and three years of continuous measurements. A total of 27 vertical modes and 1 lateral mode in the range 0.1 ~ 2.5 Hz were extracted from the high-resolution AVTs which were conducted in the 6th and 19th years after its completion. Existing OMA methods such as Peak-Picking (PP), Eigensystem Realization Algorithm with Data Correlation (ERADC), Frequency Domain Decomposition (FDD) and Time Domain Decomposition (TDD) were applied for modal parameters extraction, and it was confirmed that there was no significant difference between the applied methods. From the correlation analysis between long-term natural frequencies and environmental factors, it was confirmed that temperature change is the dominant factor influencing natural frequency fluctuations. It was revealed that the decreased natural frequencies of the bridge were not due to changes in structural performance and integrity, but to the environmental effects caused by the temperature difference between the two AVTs. In addition, when the TDD technique is applied, the accuracy of extracted mode shapes is improved by adding a proposed algorithm that normalizes the sequence so that the autocorrelations at zero lag equal 1.

• Structural Engineering and Mechanics
• /
• v.28 no.1
• /
• pp.53-67
• /
• 2008

Anisotropic materials are increasingly required in modern technological applications. Certainly, civil, mechanical and naval engineers frequently deal with the situation of analyzing the dynamical behaviour of structural elements being composed of such materials. For example, panels of anisotropic materials must sometimes support electromechanical engines, and besides, holes are performed in them for operational reasons e.g., conduits, ducts or electrical connections. This study is concerned with the natural frequencies and normal modes of vibration of rectangular anisotropic plates supported by different combinations of the classical boundary conditions: clamped, simply - supported and free, and with additional complexities such holes of free boundaries and attached concentrated masses. A variational approach (the well known Ritz method) is used, where the displacement amplitude is approximated by a set of beam functions in each coordinate direction corresponding to the sides of the rectangular plate. Consequently each coordinate function satisfies the essential boundary conditions at the outer edge of the plate. The influence of the position and magnitude of both hole and mass, on the natural frequencies and modal shapes of vibration are studied for a generic anisotropic material. The classical Ritz method with beam functions as spatial approximation proved to be a suitable procedure to solve a problem of such analytical complexity.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.11
• /
• pp.1129-1136
• /
• 2004

The structural modification to install a heavy sensor was made at the front extremities of the foreign-produced helicopter operated in the Korea Navy Mounting the sensor directly to the nose structure is unlikely to be practical because it lowers a dynamic mode of the airframe close to rotor blade passing frequencies, leading to increased helicopter vibration. Unfortunately we have no information on dynamic characteristics of the imported helicopter. So the experimental modal model derived from shake testing on the overall airframe of a working helicopter was used to solve the sensor Installation problems. The sensitivity analysis was done to evaluate what the best of modification woo)d be. Simple ID model and experimental modal data for mount system with sensor were Incorporated into overall dynamic model to assess the effects of the sensor installation on helicopter. Modal testing for the modified helicopter shows that the airframe modes are sufficiently displaced from rotor passing frequencies. The mount system has been proven fight to be sufficiently stable to meet vibration-level requirement for all required operational profiles.

• Smart Structures and Systems
• /
• v.26 no.1
• /
• pp.1-10
• /
• 2020

Turkey is a transcontinental country located partly in Asia and partly in Europe, and hosted by diverse civilizations including Hittite, Urartu, Lydia, Phrygia, Pontius, Byzantine, Seljuk's and Ottomans. At various times, these built many historic monuments representing the most significant characteristics of their civilizations. Today, these monuments contribute enormously to the esthetic beauty of environment and important to many cities of Turkey in attracting tourism. The survival of these monuments depends on the investigation of structural behavior and implementation of needed repairing and/or strengthening applications. Hence, many countries have made deeper investigations and regulations to assess their monuments' structural behavior. This paper presents the dynamic behavior investigation of a monumental masonry mosque, the "İskenderpaşa Mosque" in Trabzon (Turkey), by performing an experimental examination with non-destructive testing. The dynamic behavior investigation was carried out by determining the dynamic characteristic called as natural frequencies, mode shapes and damping ratios. The experimental dynamic characteristics were extracted by Operational Modal Analysis (OMA). In addition, Finite Element (FE) model of masonry mosque was constructed in ANSYS software and the numerical dynamic characteristics such as natural frequencies and mode shapes were also obtained and compared to experimental ones. The paper aims at presenting the non-destructive testing procedure of a masonry mosque as well as the comparison of experimental and numerical dynamic characteristics obtained from the mosque.