• Computational Structural Engineering
• /
• v.4 no.1
• /
• pp.32-35
• /
• 1991

본 고에서는 막구조 해석.설계시의 주요 내용을 각 해석단계별로 간략히 소개하였다. 막구조는 막이론 자신이 가진 근사성, 요소의 탄성 특성의 근사, 막면 요소로 곡면을 나타내는 기하학적 근사 등으로 구조물의 형태, 막재료의 동특성에 따라 해석시 오차가 발생하게 되며, 또한 구조설계 단계에서 막 판넬 제작 및 시공에 대한 고려가 되지 않으면 그 오차는 더욱 크게 된다. 따라서 향후, 보다 정확한 막구조의 설계를 위해서는 섬유직포에 코팅한 막재의 역학적 특성을 보다 잘 표현할 수 있는 막재모델의 정식화, 막재단도 해석시 무장력 상태의 설계곡면을 구하는 방법, 막판넬을 접합하고, 장력을 도입하는 시공과정을 고려한 실초기 평형상태 및 시공과정 해석법에 대한 연구가 계속 되어야 한다. 또한 초기형상 해석에서 시공과정 해석까지 전 설계과정을 공통 Data Base에서 일관 작업이 가능하도록 막구조통합 설계 System의 개발이 필요하다.

• Proceedings of the Korean Fiber Society Conference
• /
• 1996.10a
• /
• pp.364-369
• /
• 1996

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.3
• /
• pp.218-224
• /
• 2011

A modal method is presented for the investigation of the effects of measurement errors in damage detection for dynamic structural systems. The structural modifications to the baseline system result in the response changes of the perturbed structure, which are measured to determine a unique system in the inverse problem of damage detection. If the numerical modal data are exact, mathematical programming techniques can be applied to obtain the accurate structural changes. In practice, however, the associated measurement errors are unavoidable, to some extent, and cause significant deviations from the correct perturbed system because of the intrinsic instability of eigenvalue problem. Hence, a self-equilibrating inverse system is allowed to drift in the close neighborhood of the measured data. A numerical example shows that iterative procedures can be used to search for the damaged structural elements. A small set of selected degrees of freedom is employed for practical applicability and computational efficiency.

• Journal of Welding and Joining
• /
• v.15 no.3
• /
• pp.29-35
• /
• 1997

실제로 용접구조물의 재료에는 항상 내부 잔류응력이 존재하며 그 크기는 재료내의 내부 잔류응력간의 평형의 원리(Self-equilibrating system)에 의해 결정 된다. 일반적인 구조 강도설계에서 행해지는 탄성해석에서는 재료 내부에 존재하는 잔류응력을 고려하지 않기 때문에 설계시에 계산된 응력이 심하중하의 구조물에서 발생하는 응력과 같다고 볼 수는 없다. 철강재료를 사용한 구조물의 경우 구조물 제작 공정 전반에 걸친 성형가공 및 조립과정에 수반되어 재료 내에는 잔류응력이 발생되며 특히 용접조립에 의해 용접부 근방에서는 재료의 항복강도 수준의 상당히 큰 용접응력 이 발생하게 된다. 일반적으로 용접잔류응력의 완화법으로 가장 확실한 방법은 후열 처리법(Post weld heat treatment, PWHT)이지만 이 방법의 적용은 구조물의 크기에 제한을 받게 된다. 따라서 PWHT를 적용하기 어려운 구조물에 대해서는 다른 방법에 의해 용접잔류 응력을 완화시켜야 하며 이 경우에 일반적인 방법으로 기계적 응력완화 법(Mechanical stress relief method, MSR)이 있다. 본고에서는 MSR의 기본원리에 대하여 간단하게 정리하고 실 구조물에 대한 MSR 적용시 고려해야 할 제반사항을 위하여 단순 용접부에 대한 MSR 적용 실험결과와 실제 압력용기를 대상으로 MSR을 자체 제작된 기술절차서에 따라서 시행하고 MSR의 적용성에 대해서 검토하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2012.05a
• /
• pp.265-265
• /
• 2012

스퍼터링을 이용하여 금속을 코팅하면 대부분 주상정 형태의 미세구조로 성장한다. 금속 코팅층의 미세구조를 코팅공정으로 제어하여 치밀한 구조의 코팅층을 합성하기 위해서 평형(balanced magnetron)과 비평형(unbalanced magnetron) 스퍼터링에 의한 박막 구조 변화를 비교하고, 빗각 증착(oblique angle deposition) 효과가 코팅층의 미세구조에 미치는 영향을 확인하였다. 실험에 사용된 타겟은 6 인치 직경의 알루미늄이었으며 기판은 실리콘 웨이퍼와 냉연강판이 사용되었다. 알루미늄 코팅층은 주사전자현미경으로 미세구조를 관찰하였으며, 미세구조 변화가 내부식 특성에 미치는 영향을 평가하기 위해서 알루미늄이 코팅된 냉연강판의 염수분무 시험을 실시하였다. 빗각 증착에 의한 코팅층 미세구조 변화가 가장 두드러지게 나타났으며, 빗각 증착에 의해서 알루미늄 코팅층이 치밀해지는 현상을 관찰할 수 있었다. 알루미늄이 코팅된 냉연강판을 분석한 결과, 빗각 증착으로 코팅된 알루미늄 코팅층이 두께 약 $3{\mu}m$에서 염수분무 200 시간 후에도 적청이 발생하지 않는 우수한 내식성을 보였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.9
• /
• pp.1037-1044
• /
• 2010

In this paper, a new size-reduced, wideband ring-hybrid coupler is presented, and a design of a planar single-balanced doubler using the ring-hybrid is shown. This ring-hybrid coupler employs a pair of ultra-wideband transitions for phase inversion, which consists of in-phase and out of-phase transitions providing a good amplitude and phase balances for wide frequency ranges. The implemented ring-hybrid is 65 % smaller than conventional ring-hybrids, and provides 92.5 % and 81.3 % bandwidth at $\sum$ and $\Delta$ ports, respectively. Thanks to good amplitude and phase balances over wide bandwidth, the ring-hybrid can be applied to implement various balanced components. The implemented single-balanced doubler utilizing the ring-hybrid exhibits typical conversion loss of 10.5 dB for the output frequency range of 4~12 GHz with fundamental suppression level of 30 dB. The performance was also well-predicted with the nonlinear circuit simulation.

• Clean Technology
• /
• v.28 no.3
• /
• pp.249-257
• /
• 2022

The adsorption equilibria of nitrogen on a region of nanoporous carbonaceous adsorbent with local molecular orientation (LMO) were calculated by grand canonical Monte Carlo simulation at 77.16 K. Regions of LMO of identical size were arranged on a regular lattice with uniform spacing. Microporosity was predominately introduced to the model by removing successive out-of-plane domains from the regions of LMO and tilting pores were generated by tilting the basic structure units. This pore structure is a more realistic model than slit-shaped pores for studying adsorption in nanoporous carbon adsorbents. Their porosities, surface areas, and pore size distributions according to constrained nonlinear optimization were also reported. The adsorption in slit shaped pores was also reported for reference. In the slit shaped pores, a clear hysteresis loop was observed in pores of greater than 5 times the nitrogen molecule size, and in capillary condensation and reverse condensation, evaporation occurred immediately at one pressure. In the LMO pore model, three series of local condensations at the basal slip plane, armchair slip plane and interconnected channel were observed during adsorption at pore sizes greater than about 6 times the nitrogen molecular size. In the hysteresis loop, on the other hand, evaporation occurred at one or two pressures during desorption.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.9 no.2
• /
• pp.163-172
• /
• 2005

This study aims to evaluate the feasibility of remodeling business by predicting the future price of apartment house after remodeling using Hedonic Price Model. The data concerning such 9 independent variables as location, unit size, unit plan, landscape, parking, the number of elapsed years after completion, number of units, mechanical performance, interior from 25 regions in Seoul metropolitan city were collected and evaluated by established evaluation criteria. The coefficients affecting the price of apartment unit were made by way of linear multi-regression and put into Hedonic Price Model. The feasibility evaluation model for apartment was made and verified by data of remodelled apartment. The predicted results using suggested evaluation model coincide with actual apartment market situations.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.24 no.1
• /
• pp.87-95
• /
• 2011

A rational method for determination of initial cable forces in cable-stayed bridges without complicated nonlinear analysis is presented. Initial shape analysis for cable-stayed bridges should be able to find optimizated initial cable forces and unstrained length that minimize deflection and vending moments of the deck and pylon. A presented method utilizing the idea of force equilibrium organizes initial shape analysis for each types of cable-stayed bridges. The results of that analysis were compared to several existing methods for 2D numerical examples. And for 3D actual bridges, the improved TCUD method was performed to demonstrate the accuracy of this study.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.10 no.12
• /
• pp.3622-3625
• /
• 2009

This study develops a variable structure controller using the time-varying nonlinear sliding surface instead of the fixed sliding surface, which has been the robustness against parameter variations and extraneous disturbance during the reaching phase. By appling TS algorithm to the regulation of the rionlinear sliding surface, the reaching time of the system trajectory is faster than the fixed method. This proposed scheme has better performance than the conventional method in reaching time, parameter variation and extraneous disturbance. The effectiveness of the proposed control scheme is verified by simulation results.