• Journal of the Korean Society of Industry Convergence
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• v.26 no.2_2
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• pp.285-291
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• 2023

In this paper, in order to secure the safety and productivity of pine cone harvest, modeling and structural analysis of the hammering system for pine cone harvest drone that can easily access pine cone of Pinus koraiensis and collide with them to harvest them was performed. It calculate the equivalent stress for the structure of the hammering system and the yield strength of the applied material by applying the shear force of the stalk at which the pine cone is separated from the branch, and it is to verify the safety of the structure and propose an optimal design through appropriate factor of safety and design change. The shear force of the stalk at which the pine cone was separated from the branch was 468 N, and was applied to both ends of the hammering system. The yield strength of SS400 steel used in the hammering system is 245 ㎫, and the design change and structural analysis were performed so that the Von Mises stress could be less than 122.5 ㎫ by applying the factor of safety of 2.0 or more. As a result of the structural analysis of the frist modeling, the Von Mises stress was 220.3 ㎫, the factor of safety was 1.12, and the stress was concentrated in the screw fastening holes. As a result of the design change of the screw fastening holes, the Von Mises stress was 169.4 ㎫, the factor of safety was 1.45, and the stress was concentrated on the side part. As a result of the design change by changing screw fastening holes and adding ribs, the Von Mises stress was 121.6 ㎫, and the factor of safety was 2.02. The safety of the hammering system was secured with an optimal design with little change in mass. There was no deformation or damage as a result of experimenting on pine cone harvest by manufacturing the hammering system with an optimal design.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.422-422
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• 2009

This paper describes the structural design of small wind turbine blade by using design of experiments. Blade structure consists of skin, spar and foam. The materials for skin and spar are a kind of Glass/Epoxy and form is polyurethane. It has 7 lay-ups with different ply angle. A factorial design is applied to design the ply angles considering manufacturing constraints and to investigate the safety factor which is calculated by structural analysis. In order to perform the structural analysis, the commercial software ABAQUS is used. Tsai-Wu failure criterion is chosen to compute safety factor. The determination of the significance of effects in the experiments is made through the analysis of variance. The results show that ply angle at skin affects the safety factor of wind turbine blade. And from this result, optimal ply angles of composite blade are achieved.

• Structural Engineering and Mechanics
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• v.54 no.5
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• pp.973-986
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• 2015

Ethylene tetrafluoroethylene (ETFE) foil is a novel structural material which has being used in shell and spatial structures. This paper studies biaxial creep property of ETFE foil by creep tests and numerical simulation. Biaxial creep tests of cruciform specimens were performed using three stress ratios, 1:1, 2:1 and 1:2, which showed that creep coefficients in biaxial tension were much smaller than those in uniaxial one. Then, a reduction factor was introduced to take account of this biaxial effect, and relation between the reduction factor and stress ratio was established. Circular bubble creep test and triangle cushion creep test of ETFE foil were performed to verify the relation. Interpolation was adopted to consider creep stress and reduction factor was involved to take account of biaxial effect in numerical simulation. Simulation results of the bubble creep test embraced a good agreement with those measuring ones. In triangle cushion creep test, creep displacements from numerical simulation showed a good agreement with those from creep test at the center and lower foil measuring points.

• Journal of Internet Computing and Services
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• v.15 no.6
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• pp.77-84
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• 2014

The purpose of this study is to explore factors affecting the effect of e-learning, and to find out the casual relationship among these factors. Subjects are 2,091 students who have participated in e-learning based class during the period of second semester in 2013. Those of them, 1,732 students response to the survey questions. After gathering data, they are analyzed by using Confirmative Factor Analysis and Structural Equation Modeling. From the result of Confirmative Factor analysis, data have reduced four factors, and are named as four latent variables likes e-learning effect, contents satisfaction, managing assistant factor, and system functional factor. From the result of Structural Equation Modeling, it is known as the relation and impact among factors: (a) "managing assistant factor" affects to "contents satisfaction" directly. (b) "contents satisfaction" affects to "e-learning effect" directly. (c) "system function factor" affects directly to "contents satisfaction", but does not affect directly to "e-learning effect". (d) both "managing assistant factor" and "system function factor" have an indirect effect on "e-learning effect" via "contents satisfaction".

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.797-801
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• 2003

The Statistical Energy Analysis is based on the power flow and the energy conservation between sub-systems, which enable the prediction of acoustic and structural vibration behavior in mid-high frequency ranges. This paper discusses the identification of SEA coupling loss factor parameters from experimental measurements of small reverberation chamber sound pressure levels and structural accelerations. As structural subsystems, steel plates with and without damping treatment are considered. Calculated CLFs were verified by both transmission loss values for air-borne CLF case and running SEA commercial software As a result, CLFs have shown a good agreement with those computed by software. Acoustical behavior of air-borne noise and structure-borne noise has been examined. which shows reasonable results, too.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.2
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• pp.151-164
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• 2007

Criteria for rehabilitation priority are discussed to evaluate structural stability of deteriorated water transport and transmission pipes, in this study. For the purposes, safety factor is introduced and estimated by measuring tensile strength and by analyzing stress caused by the internal-external loads working on buried pipe body. Related informations are surveyed and collected under various conditions in the fields by digging out and the structural stability is assessed. In the evaluation results of structural safety, it is shown that steel pipe is more affected by external load than internal load. The average external load is estimated as $53.7kg/cm^2$ and total hoop stress is estimated by $2676.5kg/cm^2$. Also, Poisson effect into longitudinal direction due to internal and external loads is most influential on hoop stress. The calculated safety factors of hoop stress are ranged from 0.7 to 5.2 with average value of 2.1, considering a bending stress to longitudinal direction. The decision of rehabilitation priority by safety factors show that structural safety of CIP sample 1(S1) was assessed at the lowest order with safety factor value, 0.7 and that of DI sample 15(S15) was evaluated as the most stable in structural aspect.

• Journal of the Korean Society of Clothing and Textiles
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• v.35 no.11
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• pp.1362-1376
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• 2011

This study examines the effect of the structural properties of F/W wool knit fabrics for woman's knitwear on the perceptions of textures and sensible images of consumers and present basic data for textile designing by analyzing the relationship among the structural properties, mechanical properties, objective hand measurements and preferences. A total of 12 kinds of knit fabrics were prepared and investigated in terms of the differences in the subjective, mechanical properties and objective hand measurements according to the structural properties of knit fabrics. The data were analyzed by t-test. The subjective hand attributes of wool knits through factor analysis are categorized into 6 factors. In particular, the 'active/comfort' factor is a meaningful result that reflects the unique characteristics of knit fabrics compared to woven fabrics. Mechanical properties and objective hand measurements have a greater effect on textures than on sensible images; in addition, the structural properties, 'gauge' was the most important factor to influence the subjective evaluation.

• Journal of the Korea Concrete Institute
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• v.13 no.6
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• pp.544-552
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• 2001

Korea is classified into low and moderate seismic zone from the view-point of seismic hazard level. Korean seismic provisions has been developed based on UBC and ATC 3-06. Thus, in calculation of design base shear according to Korean provisions response modification factor (R) is included in the formula of design base shear. The major role of this factor is to reduce the elastic design base shear whereby structures can behave in inelastic range during design level earthquake ground motions(mean return period of 475 yrs.). R factor is assigned according to material and structural systems. In this study, R factor for bearing wall system is considered. Most of the walls of apartment buildings in Korea resist gravity and seismic loads simultaneously so that this wall system can be classified into bearing wall system. Structural details of these walls are different from those used in Japan and U.S.. They are all rectangular in sectional shape rather than barbell in shape, and also have special lateral reinforcement details at the boundaries of a wall. In Korean seismic design provisions(1988), two different values(3.0 and 3.5) of R factor are assigned to the bearing wall systems according to the wall details. However, in updated seismic provisions(2000), only one value is assigned to R factor(3.0) irrespective of wall details. In this study, the design base shear values in Korean seismic design provisions(1988, 2000), ATC 3-06, UBC are compared. Also experimental study was carried out to evaluate the seismic performance of structural walls. For this purpose, five test specimens were made which have special details used in apartment bearing wall systems in Korea. Based on the results of this study, response modification factor for bearing wall system is discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.258-264
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• 2012

The overall aim of this paper is to determine coupling loss factor of welding point between shell and cylinder using loss factor and structural loss factor. For this purpose, two kinds of loss factor were adopted. One is loss factor of each sub structure, another is structural loss factor based on the complex welded or assembled structure. Using these two parameters, it is possible to derive the coupling loss factor which represents characteristic condition of SEA theory. Coupling loss factor of conjunction in complex structure was expressed as power balance equation. The derived equation for a coupling loss factor has been simplified on the assumption of one way (uni-directional) power flow between multi-sub structures. Using these conditions, it is possible to find the equation of coupling loss factor expressed as above two loss factors. To check the effectiveness of above equation, this paper used two-stage application. The first approach was application between simple cylinder and shell. The next was adopted rotary compressor. Rotary compressor has three main conjunctions between shell and internal vibration part. This equation was applied to find out the optimum welding point with respect to reduce the noise propagation. It shows the effective tool to evaluate the coupling loss factor in complex structure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.461-468
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• 2004

Modal participation factor(MPF) is essential to analyze structural response under earthquake load. MPF of real structure differs from that of analytic mathematical model due to the error induced from analytical assumption and construction. In this study, a identification method is proposed to calculate the MPF of real structure based on H∞ optimal model reduction. The MPF is obtained from the relationship between observability, controllability matrix of realized from S.I. and typical 2-degree state space model. The proposed method is verified thorough examples.