• Structural Engineering and Mechanics
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• v.63 no.6
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• pp.743-750
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• 2017

Modal parameter identification plays a key role in the structural health monitoring (SHM) for civil engineering. Eigensystem realization algorithm (ERA) is one of the most popular identification methods. However, the complex environment around civil structures can introduce the noises into the measurement from SHM system. The spurious modes would be generated due to the noises during ERA process, which are usually ignored and be recognized as physical modes. This paper proposes an improved stabilization diagram method in ERA to distinguish the spurious modes. First, it is proved that the ERA can be performed by any two Hankel matrices with one time step shift. The effect of noises on the eigenvalues of structure is illustrated when the choice of two Hankel matrices with one time step shift is different. Then, a moving data diagram is proposed to combine the traditional stabilization diagram to form the improved stabilization diagram method. The moving data diagram shows the mode variation along the different choice of Hankel matrices, which indicates whether the mode is spurious or not. The traditional stabilization diagram helps to determine the concerned truncated order before moving data diagram is implemented. Finally, the proposed method is proved through a numerical example. The results show that the proposed method can distinguish the spurious modes.

• Korean Institute of Interior Design Journal
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• v.17 no.1
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• pp.77-83
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• 2008

MVRDV is most important architect as created interesting architectural space in contemporary architecture, and so they applies to the unique theory in their architecture. They used to architectural diagram, program, datascape, density as a design tool. Especially, they have create new architectural space and form in using architectural diagram, program, datascape, density, and void. So, this study is purposed to explain how they use as architectural tool to make composition of it's architectural space and is purpose to explain what is their main concept in architectural space. MVRDV's architectural space has fundamental methodology. That is Datascape on uncertainty and continuity between urban space and architectural space. The former consist in using diagram and architectural program and the latter consist in operating architectural void and inner continuity surface. The conclusion is follows 1. The mode of spacial composition by architectural void is correspond density of city as MVRDV's architectural thinking. 2. The mode of spacial composition by architectural program is ambiguous to the boundary between inner and exterior space by transparency. 3. The mode of spacial composition by architectural diagram make to generate the architectural form and space, through the reinterpretation and relocation of architectural program. 4. The mode of spacial composition inner continuity plane is make relative between site and inner space.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.366-371
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• 2001

Dynamic stability of an oscillating cantilever plate is investigated in this paper. The equations of motion include harmonically oscillating parameters which originate from the motion-induced stiffness variation. Using the multiple scale perturbation method is employed to obtain a stability diagram. The tability diagram shows that relatively large unstable regions exist when the frequency of oscillation is near twice the frequencies of the 1st torsion natural mode and the 1st chordwide bending mode.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.5
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• pp.329-336
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• 2015

This paper presents a sorting method of mode vectors and natural frequencies about a rotor-journal bearing system. The rotor is solved by the finite element method, the bearing stiffness and damping coefficient are solved by the finite difference method. At any rotation speed section through the eigenvalue analysis of the system, mode vectors and natural frequencies not sorted are confirmed via the Campbell diagram and the MAC(modal assurance criterion). To sort mode vectors and natural frequencies of the section, a mode sorting method is presented through a method of rearranging the MAC of the mode vectors. Finally, the mode vectors and the natural frequencies are sorted by using the presented method, these are verified through the MAC.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.2
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• pp.51-60
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• 2012

An improved method for detecting fault distance in overhead transmission lines is described in this paper. Based on single-ended measurement, propagation theory of traveling waves together with the wavelet transform technique is used. In estimating fault location, a simple, but fundamental method using the time difference between the two consecutive peaks of transient signals is considered; however, a new method to enhance measurement sensitivity and its accuracy is sought. The algorithm is developed based on the lattice diagram for traveling waves. Representing both the ground mode and alpha mode of traveling waves, in a lattice diagram, several relationships to enhance recognition rate or estimation accuracy for fault location can be found. For various cases with fault types, fault locations, and fault inception angles, fault resistances are examined using the proposed algorithm on a typical transmission line configuration. As a result, it is shown that the proposed system can be used effectively to detect fault distance.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.246-251
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• 1998

차세대원전을 위한 새로운 운전여유도 평가체제를 정립하였다. 본 연구에서 개발된 운전여유도 평가체제는 노심감시 및 보호체제는 그대로 유지하되 부하추종운전시 운전여유도를 만족하는 운전허용범위를 P-ASI Diagram으로 나타내는 것이다. 새로운 운전여유도 평가 방법을 사용하여 Mode K 기법에 의한 차세대원전의 일일 부하추종운전에 대한 운전여유도 평가를 수행하였으며, 운전여유도를 만족하는 범위를 P-ASI Diagram으로 나타내었다. 본 연구에서 도출한 운전여유도와 ASI의 관계를 쉽게 파악할 수 있는 P-ASI Diagram이 COLSS와 병행된다면 운전유연성 증진 뿐만아니라 운전원의 입장에서도 더욱 용이한 부하추종운전을 수행할 수 있을 것으로 판단된다.

• Transactions of Materials Processing
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• v.17 no.7
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• pp.473-480
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• 2008

Sheet metal forming of Mg alloy is usually performed at elevated temperature because of the low formability at room temperature. Therefore, strain rates affected with the forming temperature and speed must be considered as important factor about formability. Effects of process parameters such as various temperatures and forming speeds were investigated in circular cup deep drawing. From the experimental results, it is known that LDR (Limit Drawing Ratio) increase as the strain rate increase. On the contrary, the FLD (Forming Limit Diagram) shows lower value as faster strain rate. Therefore, anisotropy values are investigated according to the temperature and strain rates at each forming temperature. R-values also represent higher value as faster strain rate. It is known that the formability can be different with the deformation mode on warm forming of AZ31 alloy sheet.

• International journal of advanced smart convergence
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• v.1 no.2
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• pp.43-46
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• 2012

We analyzed a periodic thick mushroom structure for use as an artificial magnetic conductor using mode-matching method. The fields in each region were represented by either Floquet modes or waveguide modes. By applying tangential electric and magnetic field continuity conditions and using matrix equations, unknown coefficients and dispersion diagram were calculated. The proposed model can account for the effects of oblique incidence. Simulation time using the method was much faster than the commercial tools. We found that the current method produces accurate results of reflection phase and dispersion diagram.

• Journal of KSNVE
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• v.8 no.3
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• pp.504-512
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• 1998

For analyzing the torsional vibration of a multiple stepped gear system containing a pair of triple gears, a transfer matrix model based on Hibner's branch method is developed and the natural properties of the branched rotor system are calculated with using the $\lambda$-matrix formulation. A Campbell diagram, in which the excitation sources caused by the mass unbalances of the rotors and the transmitted errors of thegearings are considered, shows that, at the neighborhood of the operating speed, there are the four critical speeds amplifying the first mode and the fifth mode. For the surpression of the gear box vibration, two ways are suggested by referring the mode shapes.

• Smart Structures and Systems
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• v.17 no.3
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• pp.363-389
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• 2016

Deficient modes that cannot be always identified from different sets of measurement data may exist in the application of operational modal analysis such as the stochastic subspace identification techniques in large-scale civil structures. Based on a recent work using the long-term ambient vibration measurements from an instrumented cable-stayed bridge under different wind excitation conditions, a benchmark problem is launched by taking the same bridge as a test bed to further intensify the exploration of mode identifiability. For systematically assessing this benchmark problem, a recently developed SSI algorithm based on an alternative stabilization diagram and a hierarchical sifting process is extended and applied in this research to investigate several sets of known and blind monitoring data. The evaluation of delicately selected cases clearly distinguishes the effect of traffic excitation on the identifiability of the targeted deficient mode from the effect of wind excitation. An additional upper limit for the vertical acceleration amplitude at deck, mainly induced by the passing traffic, is subsequently suggested to supplement the previously determined lower limit for the wind speed. Careful inspection on the shape vector of the deficient mode under different excitation conditions leads to the postulation that this mode is actually induced by the motion of the central tower. The analysis incorporating the tower measurements solidly verifies this postulation by yielding the prevailing components at the tower locations in the extended mode shape vector. Moreover, it is also confirmed that this mode can be stably identified under all the circumstances with the addition of tower measurements. An important lesson learned from this discovery is that the problem of mode identifiability usually comes from the lack of proper measurements at the right locations.