• Earthquakes and Structures
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• 제11권3호
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• pp.387-406
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• 2016

The main purpose of this paper is to determine the dynamic characteristics and the structural stability of the two approach viaducts of the Bosphorus Suspension Bridge under the expected stresses that would be caused during earthquake conditions. The Ortakoy and the Beylerbeyi approach viaducts constitute the side spans of the bridge at two locations. The bridge's main span over the Bosphorus is suspended, whereas they are supported at the base at either end. For the numerical investigation of the viaducts, 3-D computational structural finite element-FE models were developed. Their natural frequencies and the corresponding mode shapes were obtained, analyzed, presented and compared. The performances of the viaducts, under earthquake conditions, were studied considering the P-Delta effects implementing the push-over (POA) and the non-linear time-history analyses (NTHA). For the NTHA, three earthquake ground motions were generated depending on the location of the bridge. Seismic performances of the viaducts were determined in accordance with the requirements of the Turkish Seismic Code for the Earthquake Design of Railways Bridges (TSC-R/2008) and those of Caltrans (CALTRANS-2001) given for Seismic Design of Steel Bridges, separately. Furthermore, the investigation was extended for evaluating the possible need for retrofitting in the future. After the analysis of the resultant data, a retrofit recommendation for the viaducts was presented.

• 한국위성정보통신학회논문지
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• 제10권3호
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• pp.32-37
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• 2015

무인항공기는 조종사 없이 지상에서의 원격조종에 의해 스스로 비행하는 비행체이다. 하지만 무인항공기는 제어가 쉽다는 장점이 있지만, 어떤 한 지점 위를 정지하여 비행하는 호버링 기능을 할 수 없다는 단점이 있다. 그에 비해 무인항공기 중 하나인 쿼드콥터는 동작원리가 간단하고 호버링이 가능하고, 비행의 안정성이 높다는 장점이 있다. 본 논문에서는 쿼드콥터의 안정화 비행을 위한 PID 제어 방식과 Fuzzy 제어 방식을 이용하는 비행 안정화 알고리즘을 제안한다. 본 시스템은 자이로 센서와 가속도 센서의 결합을 통해 드론의 현재 자세 값을 알아낸 후 자세 제어 알고리즘을 통해 안정화 비행을 실시한다. 또 GPS 센서를 이용하여 현재의 위치를 외부조작 없이 유지하는 위치고정 모드를 제안한다.

• Journal of Astronomy and Space Sciences
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• 제18권2호
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• pp.137-144
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• 2001

1995년에 발사된 무궁화위성 1, 2호기 REA 추력기에 대한 성능을 지상국에서 측정된 추적데이터를 이용하여 추정하였다 추정에 사용된 추적데이터는 1999년 말에서 2000년 초에 측정된 값들을 사용하였다. 추정을 위해 사용된 기법은 일반적으로 널리 알려진 최소자승추정 법(Least Square Estimation)방법이며 궤도추정과 병행해서 추력기의 작동에 의해 발생하는 기동속도변화를 추정하도록 구성하였다 추력기 성능 추정 결과 무궁화위성 1호기 REA의 경우에 계획치 대 획득속도변화의 비율이 온펄스 모드의 경우 64%로서 상당히 많은 성능감소가 있었음을 알 수 있었으며 무궁화위성 2호의 경우는 5년 이상의 임무를 수행했음에도 불구하고 100%에 이르는 상당히 양호한 성능을 유지하고 있음을 밝힐 수 있었다

• 한국환경과학회지
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• 제23권6호
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• pp.1165-1173
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• 2014

For the field application of dielectric barrier discharge plasma reactor in nutrient solution culture, a filtration-DBD (dielectric barrier discharge) plasma reactor was investigated for the Ralstonia solanacearum which causes bacterial wilt in aquiculture. The filtration-DBD plasma reactor system of this study was consisted of filter, plasma reactor, reservoir. The DBD plasma reactor consisted of a quartz dielectric tube, discharge electrode (inner) and ground electrode (outer). The experimental results showed that the inactivation of R. solanacearum with filter media type in filter reactor ranked in the following order: anthracite > fiber ball > sand > ceramic ball > quartz ceramic. In filtration + plasma process, disinfection effect with the voltage was found to small. In disinfection time of 120 minutes, residual R. solanacearum concentration was 1.17 log (15 CFU/mL). When the continuous disinfection time was 120 minute, disinfection effect was thought to keep the four days. In sporadic operation mode of 30 minutes disinfection - 24 hours break, residual R. solanacearum concentration after five days was 0.3 log (2 CFU/mL). It is considered that most of R. solanacearum has been inactivated substantially.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1340-1347
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• 2006

Dynamic response of buried pipelines both in the axial and the transverse directions on concrete pipe and steel pipe, FRP pipe were investigated through a free vibration analysis. End boundary conditions considered herein consist of free ends, fixed ends, and fixed-free ends in the axial and the transverse direction. Guided ends, simply supported ends, and supported-guided ends were added to the transverse direction. The buried pipeline was regarded as a beam on an elastic foundation and the ground displacement of sinusoidal wave was applied to it. Natural frequencies and mode shapes were determined according to end boundary conditions. In addition, the effects of parameters on the natural frequency were evaluated. The natural frequency is affected most significantly by the soil stiffness and the length of the buried pipelines. The natural frequency increases as the soil stiffness increases while it decreases as the length of the buried pipeline increases. Such behavior appears to be dominant in the axial direction rather than in the transverse direction of the buried pipelines.

• 대한기계학회논문집A
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• 제24권3호
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• pp.567-580
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• 2000

This paper proposes an integrated approach, which is independent of specimen geometry and loading type, for predicting the fatigue life of spot welded specimens. We first establish finite element models reflecting the actual specimen behaviors observed on the experimental load-deflection curves of 4 types of single spot welded specimens. Using finite element models elaborately established, we then evaluate fracture parameter J-integral to describe the effects of specimen geometry and loading type on the fatigue life in a comprehensive manner. It is confirmed, however, that J-integral concept alone is insufficient to clearly explain the generalized relationship between load and fatigue life of spot welded specimens. On this ground, we introduce another effective parameter $J_e$ composed of $J_I$, $J_{II}$, $J_{III}$, which has been demonstrated here to more sharply define the relationship between load and fatigue life of 4 types of spot welded specimens. The crack surface displacement method is adopted for decomposition of J, and the mechanism of the mixed mode fracture is also discussed in detail as a motivation of using $J_e$.

• Coupled systems mechanics
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• 제2권1호
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• pp.23-51
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• 2013

An analytical algorithm for the estimation of the resistance forces exerted on the dipper of a cable shovel and the specific energy consumed in the cutting-loading process is presented. Forces due to payload and to cutting of geomaterials under given initial conditions, cutting trajectory of the bucket, bucket's design, and geomaterial properties are analytically computed. The excavation process has been modeled by means of a kinematical shovel model, as well as of dynamic payload and cutting resistance models. For the calculation of the cutting forces, a logsandwich passive failure mechanism of the geomaterial is considered, as has been found by considering that a slip surface propagates like a mixed mode crack. Subsequently, the Upper-Bound theorem of Limit Analysis Theory is applied for the approximate calculation of the maximum reacting forces exerted on the dipper of the cable shovel. This algorithm has been implemented into an Excel$^{TM}$ spreadsheet to facilitate user-friendly, "transparent" calculations and built-in data analysis techniques. Its use is demonstrated with a realistic application of a medium-sized shovel. It was found, among others, that the specific energy of cutting exhibits a size effect, such that it decreases as the (-1)-power of the cutting depth for the considered example application.

• 대한전자공학회논문지TE
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• 제37권5호
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• pp.93-102
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• 2000

본 논문은 DAMA-SCPC 위성통신 시스템의 디지털 모뎀의 기능 및 성능 규격들을 제시하고, 제시한 규격을 만족하는 위성모뎀의 구조 설계 및 구현에 대하여 기술한다. 다양하면서 융통성이 요구되는 위성모뎀의 규격들을 만족시키기 위하여 디지털 신호 처리기(DSP)와 프로그래머블 게이트 어레이(FPGA)를 기반으로 하여 설계 및 구현되었다. 구현된 위성모뎀은 DAMA-SCPC 위성통신 시스템에 통합하여 수행한 시험에서 안정된 동작과 제시된 기능 및 성능 규격을 모두 만족함을 검증하였다. 연속모드(at Eb/No=4.7, FEC=3/4) 에서 측정된 BER은 약 1×10E-4의 성능을 보여 주었다.

• 국제초고층학회논문집
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• 제1권3호
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• pp.203-209
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• 2012

The purpose of this paper is to present the state of practice being used in the Philippines for the performance-based seismic design of reinforced concrete tall buildings. Initially, the overall methodology follows "An Alternative Procedure for Seismic Analysis and Design of Tall Buildings Located in the Los Angeles Region, 2008", which was developed by Los Angeles Tall Buildings Structural Design Council. After 2010, the design procedure follows "Tall Buildings Initiative, Guidelines for Performance-Based Seismic Design of Tall Buildings, 2010" developed by Pacific Earthquake Engineering Research Center (PEER). After the completion of preliminary design in accordance with code-based design procedures, the performance of the building is checked for serviceable behaviour for frequent earthquakes (50% probability of exceedance in 30 years, i.e,, with 43-year return period) and very low probability of collapse under extremely rare earthquakes (2% of probability of exceedance in 50 years, i.e., 2475-year return period). In the analysis, finite element models with various complexity and refinements are used in different types of analyses using, linear-static, multi-mode pushover, and nonlinear-dynamic analyses, as appropriate. Site-specific seismic input ground motions are used to check the level of performance under the potential hazard, which is likely to be experienced. Sample project conducted using performance-based seismic design procedures is also briefly presented.

• 국제초고층학회논문집
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• 제7권3호
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• pp.255-264
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• 2018

This paper introduces three distinctive means for the use of a 189-meter high damped structure ensuring safety against earthquake: 1. Realization of L-shaped elevational structural planning: The bottom and top of the tower have belt trusses and hat trusses respectively to restrain the bending deformation. Furthermore, large-capacity oil dampers (damping force 6,000 kN) are installed in the middle part of the tower to restrain the higher-mode deformation. 2. Realization of L-shaped planar structural planning: We devised a means of matching the centers of gravity and rigidity by adjusting planar rigidity. Moreover, viscous damping devices are located at the edges of the L-shaped plan, where torsional deformation tends to be amplified. We call this the "Damping Tail" system. 3. Composite foundation to equalize deformations under different loading conditions: We studied the vertical and horizontal deformations using sway-rocking and 3D FEM models including the ground, and applied multi-stage diameter-enlarged piles to the tower and a mat foundation to the podium to keep the foundations from torsional deformations and ensure structural safety.