• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.2
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• pp.106-113
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• 2000

This study describes how a properly calibrated simulation method could be used to investigate the latchup immunity characteristics among the various high energy ion implanted CMOS twin well (retro-grade/BILLI/BL) structures. To obtain the accurate quantitative simulation analysis of retrograde well, a global tuning procedure and a set of grid specifications for simulation accuracy and computational efficiency are carried out. The latchup characteristics of BILLI and BL structures are well predicted by applying a calibrated simulation method for retrograde well. By exploring the potential contour, current flow lines, and electron/hole current densities at the holding condition, we have observed that the holding voltage of BL structure is more sensitive to the well design rule (p+to well edge space /n +to well edge space) than to the retrograde well itself.

• Earthquakes and Structures
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• v.3 no.3_4
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• pp.435-455
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• 2012

An impact on the ground surface may represent several phenomena, such as a crash of an airplane or an explosion or the passage of a train. In order to analyze and design structures and equipment to resist such a type of shocks, the response spectra for an impact on the ground must be given. We investigated the half-space motions due to impact using the finite element method. We performed extensive parametric analyses to define a suitable finite element model and arrive at displacement time histories and response spectra at varying distances from the impact point. The principal scope of our study has been to derive response spectra which: (a) provide insight and illustrate in detail the half-space response to an impact load, (b) can be readily used for the analysis of structures resting on a ground subjected to an impact and (c) are a new family of results for the impact problem and can serve as reference for future research.

• Structural Engineering and Mechanics
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• v.60 no.6
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• pp.1093-1117
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• 2016

Global sensitivity analysis (GSA) has been widely used to investigate the sensitivity of the model output with respect to its input parameters. In this paper a new single-solution search optimization algorithm is developed based on the GSA, and applied to the size optimization of truss structures. In this method the search space of the optimization is determined using the sensitivity indicator of variables. Unlike the common meta-heuristic algorithms, where all the variables are simultaneously changed in the optimization process, in this approach the sensitive variables of solution are iteratively changed more rapidly than the less sensitive ones in the search space. Comparisons of the present results with those of some previous population-based meta-heuristic algorithms demonstrate its capability, especially for decreasing the number of fitness functions evaluations, in solving the presented benchmark problems.

• International Journal of High-Rise Buildings
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• v.13 no.2
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• pp.113-145
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• 2024

Bamboo is seen as a low cost, lightweight, widely available and environmental-friendly material. In Vietnam, it also connects deeply to our culture. However, it wasn't seen as a viable material for large structures before VTN Architects. Furthermore, Vietnamese cities are facing the same environmental problems as many developing metropolises in the world. Globally, climate change is a serious issue. The need for sustainable construction material is clear. The increasing development of eco-tourism in Vietnam and Asia is also a background. These become the background to the foundation and the development of bamboo architecture by VTN Architects. The journal analyses our development of bamboo construction, joints, structures, and how to use them to realise space and to create eco-friendly architecture. We will talk about our process of bamboo procurement, our construction methods, our unique joint system, how we make a frame unit and how we construct VTN bamboo structures from units.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.71-77
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• 2002

We consider the simultaneous slewing and vibration suppression control problem of an idealized structural model which has a rigid hub with two cantilevered flexible appendages and finite tip masses. The finite clement method(FEM) is used to obtain linear finite dimensional equations of motion for the model. In the linear quadratic regulator(LQR) problem, a simple method is introduced to provide a physically meaningful performance index for space structure models. This method gives us a mathematically minor but physically important modification of the usual energy type performance index. A numerical procedure to solve a time-variant LQR problem with inequality control constraints is presented using the method of particular solutions.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.38.3-39
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• 2017

The N159 and N160 ionized regions in the Large Magellanic Cloud are an important extragalactic star-forming complex. The physical environments and the star formation stages are different in N159 and N160. We performed near-infrared polarimetry to those star forming regions with IRSF/SIRPOL 1.4-m telescope. Near-infrared polarization enabled us to trace the detailed structure of magnetic fields in star-forming regions. Through the polarimetric data of J, H, and Ks bands, we examined the magnetic field structures in the N159/N160 complex. In this presentation, we show complex distribution of the magnetic fields associated with dust and gas structures. We verify the local magnetic fields in each star-forming region, which appear to be related with local environments, such as interior and boundary of shell structure, star-forming HII regions, and boundaries between HII regions and dense dark clouds. We discuss the formation scenario of the N159/N160 complex suggested from the magnetic field structure.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.100-104
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• 2009

In this study, the space gamma dose rates in the apartments structured with concrete were measured in accordance with construction year. In addition, the environmental radiation rates coming from the subway platforms and the road tunnels were analyzed in the equivalent dose by multiplying the absorbed dose with the radiation weighting factors. The space gamma dose rates measured in apartments were higher than those of outdoor which was $0.08{\sim}0.11uSv/h$ in the natural conditions. Especially, the older construction year is, the higher becomes space gamma dose rate. The average gamma dose rates in the subway platforms were measured. In the case of Busan and Daegu subway, the earlier the opening year is, the higher becomes dose rate. However, the dose rates of Seoul subway Lines were high overall, regardless of opening year. Seoul subway Line 6 showed the highest value of 0.21uSv/h. The gamma dose rate in road tunnels was higher than one of the outdoor and increased with opening year like as apartment. In dose rate comparison of the concrete structures with the outdoor, therefore, the space gamma dose rate of indoor is higher than one of the outdoor and the older structures have a higher dose rate.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.50.1-50.1
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• 2019

In coronagraph images, it is often observed that two successive CMEs merge into one another and form complex structures. This phenomenon, so called CME cannibalism caused by the differences in ejecting times and propagating velocities, can significantly degrade forecast capability of space weather, especially if it occur near the Earth. Regarding this, we attempt to analyze the cases that two CMEs are expecting to meet around 1 AU based on their arrival times. For this, we select 13 CME-CME pairs detected by ACE, Wind and/or STEREO-A/B. We find that 8 CME-CME pairs show a shock structure, which means they already met and became one structure. Meanwhile 5 pairs clearly show magnetic holes between two respective shock structures. Based on detailed investigation for each pair and statistical analysis for all events, we can get clues for following questions: 1) How does the solar wind structure change when they are merging? 2) Are there any systematic characteristics of merging process according to the CME properties? 3) Is the merging process associated with the occurrence of energetic storm particles? 4) What causes errors in calculating CME arrival times? Our results and discussions can be helpful to understand energetic phenomena not only close to the Sun but also near the Earth.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.4
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• pp.307-314
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• 2009

The present paper briefly describes the space frame element and the fundamental strategies in computational elastic bifurcation theory of geometrically nonlinear, single load parameter conservative elastic spatial structures. A method for large deformation(rotation) analysis of space frame is based on an eulerian formulation, which takes into consideration the effects of large joint translations and rotations with finite deformation(rotation). The local member force-deformation relationships are based on the beam-column approach, and the change in member chord lengths caused by axial strain and flexural bowing are taken into account. and the derived geometric stiffness matrix is unsymmetric because of the fact that finite rotations are not commutative under addition. To detect the singular point such as bifurcation point, an iterative pin-pointing algorithm is proposed. And the path switching mode for bifurcation path is based on the non-negative eigen-value and it's corresponding eigen-vector. Some numerical examples for bifurcation analysis are carried out for a plane frame, plane circular arch and space dome structures are described.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.2
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• pp.85-93
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• 2024

In this paper, we propose a method for establishing a state-space equation model for the motion analysis of floating structures subjected to wave loads, by applying system-identification techniques. Traditionally, the motion of floating structures has been analyzed in the time domain by integrating the Cummins equation over time, which utilizes a convolution integral term to account for the effects of the retardation function. State-space equation models have been studied as a way to efficiently solve floating-motion equations in the time domain. The proposed approach outlines a procedure to derive the target transfer function for the load-displacement input/output relationship in the frequency domain and subsequently determine the state-space equation that closely approximates it. To obtain the state-space equation, the method employs the N4SID system-identification method and an optimization approach that treats the coefficients of the numerator and denominator polynomials as design variables. To illustrate the effectiveness of the proposed method, we applied it to the analysis of a single-degree-of-freedom model and the motion of a six-degree-of-freedom barge. Our findings demonstrate that the presented state-space equation model aligns well with the existing analysis results in both the frequency and time domains. Notably, the method ensures computational accuracy in the time-domain analysis while significantly reducing the calculation time.