• Journal of Aerospace System Engineering
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• v.14 no.6
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• pp.18-25
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• 2020

This study investigated the structural behaviors and safety of an electro-mechanical linear actuator and a load simulator with a plate spring. The material and dimensions of the plate spring were determined by theoretically calculating the stress and torsional angle for the rating load of the actuator. Thereafter, a flexible multibody dynamics (FMBD) analysis was conducted on the linear actuator and load simulator to confirm the performance of the load simulator and acquire the reaction forces acting on the actuator and simulator. The structural safety of the linear actuator and load simulator was evaluated via finite element analysis using the aforementioned reaction forces. Consequently, the proposed linear actuator and load simulator were determined to be structurally safe; however, the safety factors for the actuation rod and the housing on the actuator were excessively high. Therefore, the weight and cost must be reduced to improve their design parameters in the future.

• Smart Structures and Systems
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• v.22 no.1
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• pp.13-25
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• 2018

Pedro $G{\acute{o}}mez$ Bosque footbridge is a slender and lightweight structure that creates a pedestrian link over the Pisuerga River, Valladolid, Spain. This footbridge is a singular stress ribbon structure with one span of 85 m consisting on a steel plate and precast concrete slabs laying on it. Rubber pavement and a railing made of stainless steel and glass complete the footbridge. Because of its lively dynamics, prone to oscillate, a simple and affordable structural health monitoring system was installed in order to continuously evaluate its structural serviceability and to estimate its modal parameters. Once certain problems (conditioning and 3D orientation of the triaxial accelerometers) are overcome, the monitoring system is validated by comparison with a general purpose laboratory portable analyzer. Representative data is presented, including acceleration magnitudes and modal estimates. The evolution of these parameters has been analysed over one-year time.

• Korean System Dynamics Review
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• v.16 no.4
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• pp.31-50
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• 2015

The purpose of this research is to understand a structural relationship between financial regulations and security industry based on the systems thinking perspective using causal loop analysis. As a result, the positive regulations on security technology against finance security incidents shrink the autonomy of the security industry and will deteriorate the competitiveness of the security industry through the unknown feedback loop. The conclusion provides the direction that policy makers understand causal loop diagram related current regulations and open enough to the consideration of the negative regulations.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.453-457
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• 2011

In this study, transonic aeroelastic response analyses haw been conducted for the business jet aircraft configuration considering shockwave and flow separation effects. The developed fluid-structure coupled analysis system is applied for aeroelastic computations combining computational structural dynamics(CSD), finite element method(FEM) and computational fluid dynamics(CFD) in the time domain. It can give very accurate and useful engineering data on the structural dynamic design of advanced flight vehicles. For the nonlinear unsteady aerodynamics in high transonic flow region, Navier-Stokes equations using the structured grid system have been applied to wing-body configurations. In transonic flight region, the characteristics of static and dynamic aeroelastic responses have been investigated for a typical wing-body configuration model. Also, it is typically shown that the current computation approach can yield realistic and practical results for aircraft design and test engineers.

• Korean System Dynamics Review
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• v.14 no.3
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• pp.5-23
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• 2013

This paper explores a structural mechanism underlying governmental reformulation. Studying cases of governmental reorganizations occurred during past 60 years, this paper constructs a causal map containing a principle of small government, an integrative organization of the government, and a committee organization. A positive feedback loop linking these factors produces an increase in the number of the committee organization in the government. Also, this paper points out that there might be a hidden self fullfilling prophecy that reinforces the principle of small government. Open experiment toward a big government is proposed to overcome the vicious circle of small government curse.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.11-18
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• 2004

In this paper, an efficient model reduction scheme is presented for large scale dynamic systems. The method is founded on a modal analysis in which optimal eigenvalue is extracted from time samples of the given system response. The techniques we discuss are based on classical theory such as the Karhunen-Loeve expansion. Only recently has it been applied to structural dynamics problems. It consists in obtaining a set of orthogonal eigenfunctions where the dynamics is to be projected. Practically, one constructs a spatial autocorrelation tensor and then performs its spectral decomposition. The resulting eigenfunctions will provide the required proper orthogonal modes(POMs) or empirical eigenmodes and the correspondent empirical eigenvalues (or proper orthogonal values, POVs) represent the mean energy contained in that projection. The purpose of this paper is to compare the reduced order model using Karhunen-Loeve expansion with the full model analysis. A cantilever beam and a simply supported plate subjected to sinusoidal force demonstrated the validity and efficiency of the reduced order technique by K-L method.

• Korean System Dynamics Review
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• v.10 no.1
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• pp.97-107
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• 2009

In this paper, a structural similarity between traditional oriental philosophy and systems thinking is discussed. The polarity of causal relationship and feedback loops can be interpreted in terms of yin and yang of oriental philosophy. A positive feedback loop which is linked to the yang is a force or mechanism that accelerates changes in systems. A negative feedback loop which is linked to the yin can be interpreted as a force oppressing any changes. In this sense, systems thinking can be related to the oriental philosophy. With this linking pin between them, systems thinking can be introduced and educated more friendly in oriental society. Furthermore, systems thinking can get a set of rich insights from the oriental philosophy. This paper suggests a linking leverage between systems thinking and oriental philosophy.

• Korean System Dynamics Review
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• v.11 no.3
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• pp.87-104
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• 2010

This research aims at designing policy alternatives which would facilitate the supply of the national rental housing units, especially targeted for the low-income households who need special types of social support for their residences. In order to illuminate structural characteristics of the national rental housing policies, it heavily depends on collection of secondary survey data, in addition to existing documents. From the institutional dimension, it focuses on major issues related to the residential development, which is pivotal in supplying the required national rental housing units. Furthermore, applying causal loop diagramming techniques derived from the System Dynamics (SD), it tries to divulge dynamic relationships between key stakeholders including the government, developers and tenants. Finally, this research stresses the point that the government should fulfill its basic duty as a financial supporter and the developer should not procrastinate in providing diverse options, timely reflecting tenants' needs.

• International conference on construction engineering and project management
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• 2013.01a
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• pp.151-157
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• 2013

Since the sub-prime mortgage crisis from the US in 2008, the Korean housing market has plummeted. However, the deposit prices of the Korean local lease contract, Chonsei, had been increasing. This increase of Chonsei prices can be a threat to low-income people, most of whom prefer to live in houses with a Chonsei contract. In the housing and Chonsei market, there are many stakeholders with their own interest, hence, simple thoughts about housing and Chonsei market, such as more house supply, will decrease house price, would not work in a real complex housing market. In this research, we suggests system dynamics conceptual model which consists of causal-loop-diagrams for the Chonsei market as well as the housing market. In conclusion, the Chonsei price has its own homeostasis characteristics and different price behavior with housing price in the short and long term period. We found that unless government does not have a structural causation mind in implementing policies in the real estate market, the government may not attain their intended effectiveness on both markets.

• Structural Engineering and Mechanics
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• v.49 no.6
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• pp.687-703
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• 2014

This paper develops a new nonlinear model for active control of three-dimensional (3D) irregular building structures. Both geometrical and material nonlinearities with a neuro-controller training algorithm are applied to a multi-degree-of-freedom 3D system. Two dynamic assembling motions are considered simultaneously in the control model such as coupling between torsional and lateral responses of the structure and interaction between the structural system and the actuators. The proposed control system and training algorithm of the structural system are evaluated by simulating the responses of the structure under the El-Centro 1940 earthquake excitation. In the numerical example, the 3D three-story structure with linear and nonlinear stiffness is controlled by a trained neural network. The actuator dynamics, control time delay and incident angle of earthquake are also considered in the simulation. Results show that the proposed control algorithm for 3D buildings is effective in structural control.