• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.289-295
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• 1995

구조물의 동적부하에 대한 동적변형 응답을 정확히 예측하고, Over Design이나 Under Design이 아닌 합리적인 설계방안의 개발은 중요한 과제이다. 동적강도해석이나 소음 승차감과 같은 진동 및 충격에 기인하는 제반 문제를 복잡한 구조물을 대상으로 합리적으로 처리하기 위한 Dynamic Design Analysis는 높은 신뢰성의 추구와 더불어 필요불가결한 기술이 되고 있다. 동적해석 방법으로는 현재 유한요소법이 널리 사용되고 있으며 여러 종류의 범용 프로그램들이 보급되어 있는 실정이다. 그러나 특히 동적문제에 있어서는 형상이나 거동이 복잡한 구조물의 경우, 또는 차량의 차체와 같이 많은 장착물이 부착된 경우에는 유한요소법의 적용이 곤란하여, 지금까지 대처할 수 있는 유용한 방법이 없었다. 따라서 비교적 용이하고 간단하게 적용가능한 진동실험을 기초로 한 구조물의 동적 응답해석 및 설계 방안의 개발이 필요하다. 본 연구에서는 진동시험으로 얻어진 부분구조물의 응답특성과 결합특성으로부터 결합 후의 응답특성을 예측할 수 있는 방법을 전달함수합성이론을 기초로하여 프로그래밍 package화 한다. 그리고 평판구조물에 대하여 진동시험과 컴퓨터 시뮬레이션을 통하여 개발된 방법의 타당성을 검증한다. 또한 실제 차량에서 차체만의 진동시험과 엔진의 자유진동시험에 의한 시험데이터로부터 차체와 엔진이 마운트 결합된 후의 진동특성을 예측한다. 진동시험시에 입력과 출력에 노이즈가 필연적으로 혼입되어 주파수응답함수의 크기(magnitude)와 위상(phase)을 왜곡시킨다. 특히 위상의 왜곡은 복소수연산을 하는 전달함수합성법의 결과에 중요한 영향을 미치게 된다. 본 연구에서는 데이타 획득시 입력과 출력의 시간지연으로 생기는 위상왜곡을 보정하는 방법을 제시하고, 그 개선 정도를 조사한다.는 소견의 확실도로서 가능성을 표현한 것이다. 예를 들면, 진동진폭 스펙트럼상에 2X 성분이 상당히 크게 나타나 정렬불량의 가능성이 0.7 정도라고 판정하는 것 등은 이러한 수치적진리치를 이용하는 방법이다. 그러나 상기의 수치적 표현만으로는 확실도를 한개의 수치로서 대표하게 하는 것은 진단의 정밀도에 문제가 있을 것으로 생각된다. 따라서 언어적진리치가 도입되어 [상당히 확실], [확실], [약간 확실] 등의 언어적인 표현을 이용하여 애매성을 표현하게 되었다. 본 논문에서는 간이진단 결과로부터 추출된 애매한 진단결과중에서 가장 가능성이 높은 이상원인을 복수로 선정하고, 여러 종류의 수치화할 수 없는 언어적(linguistic)인 정보ㄷㄹ을 if-then 형식의 퍼지추론으로 종합하는 회전기계의 이상진단을 위한 정밀진단 알고리즘을 제안하고 그 유용성을 검토한다. 존재하여도 모우드 변수들을 항상 정확하게 구할 수 있으며, 또한 알고리즘의 안정성이 보장된 것이다.. 여기서는 실험실 수준의 평 판모델을 제작하고 실제 현장에서 이루어질 수 있는 진동제어 구조물에 대 한 동적실험 및 FRS를 수행하는 과정과 동일하게 따름으로써 실제 발생할 수 있는 오차나 error를 실험실내의 차원에서 파악하여 진동원을 있는 구조 물에 대한 진동제어기술을 보유하고자 한다. 이용한 해마의 부피측정은 해마경화증 환자의 진단에 있어 육안적인 MR 진단이 어려운 제한된 경우에만 실제적 도움을 줄 수 있는 보조적인 방법으로 생각된다.ofile whereas relaxivity at high field is not affected by τS. On the other hand, the change in τV does not affect low field profile but strongly in fluences on bot

• Journal of Korean Society of Steel Construction
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• v.27 no.2
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• pp.143-153
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• 2015

In this paper, the standard fire resistance test under load and associated numerical study were carried out to evaluate the fire resistance of unprotected partially encased beams and slimfloor beams. The temperature evolution and the deflection increase of the composite beam specimens were investigated and the effects of the key behavioral parameters including the load ratio, the reinforcement, and the fire exposure were analyzed. The test results showed that the temperature rise of the partially encased beams and slimfloor beams is considerably slow compared to the conventional H-shape composite beams. Up to at least 90 minutes, the reinforcements in the partially encased composite beams maintained below the temperature at which the cold steel strength is sustained. Unprotected partially encased beams and slimfloor beams in the experimental program achieved the fire resistance more than 2 hours according to the limiting deflection criteria. This implies that unprotected partially encased beams and slimfloor beams can be very promising alternatives to enhancing the fire resistance of steel beams. This study also conducted the fully coupled thermal-stress analysis by using the commercial code ABAQUS to the thermal and structural behaviour of composite beams in fire. The numerical predictions provide acceptable correlations with the experimental results.

• Journal of Korean Society of Steel Construction
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• v.26 no.2
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• pp.91-103
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• 2014

High performance steel for bridges(HSB 800) with a minimum tensile stress of 800MPa was recently developed. However, the study for local buckling behavior of plate girders considering interactive effects of flanges and webs is still insufficient. In this study, the flange local buckling(FLB) strength of plate girders with HSB 800 was evaluated by nonlinear finite element analysis. The flanges and webs of plate girders having I-section were modeled as 3D shell elements in the nonlinear analysis. Initial imperfection and residual stress were imposed on the plate girder. The high performance steel was modeled as a multi-linear material. Thus, parametric study of compression flanges with a compact, noncompact and slender web was performed. The flange local buckling behavior of plate girders was analyzed, and the nonlinear analysis results were compared with the nominal flexural strength of both AASHTO LRFD(2012) and KHBDC LSD(2012) codes.

• Journal of the Korea Concrete Institute
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• v.25 no.6
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• pp.601-612
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• 2013

In the construction of nuclear power plants using massive walls, the use of high-strength re-bars for shear design is necessary to enhance the constructability and economy. In this study, low-rise walls (aspect ratio of 1.0) with grade 550 MPa bars were tested under cyclic loading to investigate the shear capacity and deformation capacity. The test parameters were the grade of horizontal re-bars (550 MPa, 420 MPa), strength of concrete compressive strength (46 MPa, 70 MPa), horizontal/vertical reinforcement ratio, use of lateral confinement hoops, shape of cross section, and failure modes (shear failure before or after flexural yielding). The test results were compared with those of walls with grade 420 MPa bars and predicted strength by current design codes. The results showed that the shear strength of the walls with 550 MPa bars was comparable to that of the walls with 420 MPa bars though the safe margin slightly decreased. ACI 349 provides underestimated shear strength for the walls with 550 MPa bars. In case of the wall with flexural yielding, a large deformation capacity was achieved. This result indicates that the ACI 349 provisions can be safely applied to seismic design of the low-rise walls (aspect ratio of 1.0) with grade 550 MPa bars.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.167-178
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• 2003

Damage and overbreak of the remaining rock induced by blasting can not be avoided during tunnel construction which may result in either short-term or long-term tunnel instability. Therefore, in this paper, a methodology to take into account the effect of blast-induced damage in tunnel stability assessment is proposed. Dynamic numerical analysis was executed to evaluate damage and overbreak of the remaining rock for the most common blasting pattern in road tunnel. Rock damage was quantified by utilizing the damage variable factor which is adopted proposed in continuum damage mechanics. The damaged rock stiffness and the damaged failure criteria are used to consider the effect of rock damage in tunnel stability analysis. The damaged geological strength index of the damaged rock was newly proposed from the relationship between deformation modulus and geological strength index. Also the Hoek-Brown failure criteria of the damaged rock was obtained using the damaged geological strength index. Analysing the tunnel stability with the consideration of the blast-induced damage of remaining rock, it was found that the extend of plastic zone and deformation increased compared to the undamaged rock. Therefore the short-term or long-term tunnel stability will be threatened when the rock damage from blasting is ignored in the tunnel stability analysis.

• 대한공업교육학회지
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• v.33 no.2
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• pp.259-272
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• 2008

In order to improve the productivity and quality of boat's mold in leisure boat industry, the development of modelling and machining technology of leisure boat's plug is strongly required. The traditional lines drawing approach by hand required the designer to both create fair curves and to make sure that the curves matched up to each other in the three main drawing views: profile, plan, and section. However, one will find when studying lines drawings in books that the curves might look smooth and fair, but the lines do not agree exactly in the three views. Therefore, the 2 dimensional drawing data of leisure boat are transformed using 3 dimensional design s/w and CAM s/w. In addition, the leisure boat is designed with a 3 dimensional s/w. The NC cutting data are generated by the CAM s/w. The surface characteristics of machined surface are investigated at various cutting conditions such as spindle speed, feed speed, and cutting material.

• Journal of the Korean Applied Science and Technology
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• v.37 no.5
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• pp.1366-1377
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• 2020

The purpose of this study was to confirm the effect of the Havruta-based teaching and learning method on the academic self-efficacy, critical thinking tendency, learning satisfaction, and academic stress of nursing students. This study was conducted with 90 2nd graders of nursing department with one-group pretest-posttest design. The Havruta-based instructional design consists of five stages: the 1 stage is the pre-learning stage, the 2 stage is the introduction and development stage, the 3 stage is the organization of the class content, the 4 stage is the question and teaching stage, and the 5 stage is organized and integrated. Four weeks of Havruta-based teaching and learning method was applied. The data were analyzed by SPSS 25.0. The general characteristics of the subjects were frequency and percentage, and The dependent variable for measuring the effect of experimental treatment was analyzed by paired t-test. As a result of the study, the application of the Havruta-based teaching and learning method showed statistically significant results on academic self-efficacy(t=-3.711, p<.000), learning satisfaction(t=-2.580, p=.012), and academic stress(t=6.500, p<.000). The Havruta-based teaching and learning method has been confirmed to be an effective teaching method that increases the subject's academic self-efficacy, learning satisfaction, and lowers academic stress, so it can be applied to other major subjects in the future.

• Journal of Korean Society for Geospatial Information Science
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• v.4 no.2 s.8
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• pp.55-61
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• 1996

The objective of this paper is to show an optimal design model for branched water supply system which also can find the optimal location of pumping stations using linear programming. GIS is utilized in this model to better handle the data and the results front the optimization. The developed model considers hydraulic influences of some appurtenances such as supply tunnels and a filtration plant The model also considers tunnel construction cost which should be treated differently from pipe construction cost Different from other models presently available, the model guarantees a nonnegative pressure at every junction node in the system. The objective function includes annual operation cost (electricity rate) ill addition to initial construction cost, thus producing a more reasonable decision. The model selects the optimal diameter not in the form of continuous number but in the form of commercial discrete diameter (pipe size) using the pipe lengths as decision variables instead of pipe diameters. The model not only determines the optimal pumping head for each pumping station but also finds the optimal location and number of pumping stations. GIS is used to handle hydraulic and budgetary data automatically and to visualize the results for the of optimal design of the system. The model has been applied to an existing water supply system. 'The results show that the optimization model with the aid of GIS is helpful in the decision-nulling process for the design of more economical systems, and can be dot into practice successfully.

• Journal of the Korean Institute of Intelligent Systems
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• v.10 no.4
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• pp.343-350
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• 2000

In this paper, we propose the Multi-FPNN(Fuzzy Polynomial Neural Networks) model based on FNN and PNN(Polyomial Neural Networks) for optimal system identifacation. Here FNN structure is designed using fuzzy input space divided by each separated input variable, and urilized both in order to get better output performace. Each node of PNN structure based on GMDH(Group Method of Data handing) method uses two types of high-order polynomials such as linearane and quadratic, and the input of that node uses three kinds of multi-variable inputs such as linear and quadratic, and the input of that node and Genetic Algorithms(GAs) to identify both the structure and the prepocessing of parameters of a Multi-FPNN model. Here, HCM clustering method, which is carried out for data preproessing of process system, is utilized to determine the structure method, which is carried out for data preprocessing of process system, is utilized to determance index with a weighting factor is used to according to the divisions of input-output space. A aggregate performance inddex with a wegihting factor is used to achieve a sound balance between approximation and generalization abilities of the model. According to the selection and adjustment of a weighting factor of this aggregate abjective function which it is acailable and effective to design to design and optimal Multi-FPNN model. The study is illustrated with the aid of two representative numerical examples and the aggregate performance index related to the approximation and generalization abilities of the model is evaluated and discussed.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.675-684
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• 2010

The reinforced concrete members are designed to fail in flexural to lead ductile fracture. In the building structures, the failure is typically imposed on beams to prevent damages in columns. However, progression of plastic collapse mechanism may ultimately develop, a plastic hinge at the bottem end of the first floor column, which then can be subjected to shear or bond finally due to large axial force and small shear span-to-depth ratio. In this study, 10 RC column specimens failed in shear after flexural yielding was investigated to determine the factors affecting the plastic hinge length. The findings of this study showed that the most effective factor affecting the plastic hinge length was an axial force. As an axial force increase, an axial strain and a ductility ratio were decreased obviously. The test also shows the observed plastic hinge length was about 0.8~1.2d and the this result has difference compared with forward research.