• Journal of Welding and Joining
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• v.28 no.2
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• pp.91-95
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• 2010

Stress distribution and deformation on the CT-type(Cross Tension type) spot welded lap joint subjected to out of plane tensile load were investigated by finite element method. Using the maximum principal stresses at the nugget edge obtained by FEM analysis, evaluated the fatigue strength of the CT-type spot welded lap joints having various dimensions and materials. and also, the influence of the geometrical parameters of CT-type spot welded lap joints on stress distribution and fatigue strength must be evaluated. thus, in this paper, ${\Delta}P-N_f$ curve were obtained by fatigue tests. Using these results, ${\Delta}P-N_f$ curve were systematically rearranged in the $\Delta\sigma-N_f$ relation with the hot spot stresses at the CT-type spot welded lab joints. It was found that the proposed $\Delta\sigma-N_f$ relation could provide a more reasonable fatigue design criterion for the CT-type spot welded lap joints.

• Journal of Welding and Joining
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• v.17 no.6
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• pp.25-31
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• 1999

Stainless steel sheets are commonly used for vehicles such as the bus and the train. These are mainly fabricated by spot-welding. By the way, its fatigue strength is lower than base metal due to high stress concentration at the nugget. edge of the spot-welding. By the way, its fatigue strength is lower than base metal due to high stress concentration at the nugget edge of the spot-welding point. Especially, it is influenced by welding conditions as well as geometrical factors of spot welded joint. Therefore, it is not too much to say that structural rigidity and strength of spot-welded structures is decided by fatigue strength of spot welded lap joint. Thus, it is necessary to establish a reasonable and systematic long life design criterion for the spot-welded structure. In this study, numerical stress analysis was performed by using 3-dimensional finite element model on IB-type spot-welded lap joint of 304 stainless steel sheet under tension-shear load. Fatigue tests were also conducted on them having various thickness, joint angle, lapped length, and width of the plate. From the results, it was found that fatigue strength of IB-type spot-welded lap joints was influenced by its geometrical factors, however, could be systematically rearranged by maximum principal stress ({TEX}$σ_{1max}${/TEX}) at the nugget edge of the spot-welding point.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1383-1388
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• 2007

Accuracy and processing time are very important factors when the desired shape is fabricated with Selective Laser Sintering (SLS), one of Solid Freeform Fabrication (SFF) systems. In a conventional SLS process, laser spot size is fixed during laser exposing on the sliced figure. Therefore, it is difficult to accurately and rapidly fabricate the desired shape. In this paper, to deal with those problems an SFF system having ability of changing spot size is developed. The system provides high accuracy and optimal processing time. Specifically, a variable beam expander is employed to adjust spot size for different figures on a sliced shape. Finally, Design and performance estimation of the SFF system employing a variable beam expander are achieved and the mechanism will be addressed to measure the real spot size generated from the variable beam expander.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.121-128
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• 1992

This study aims to define the algorithm for self-calibration bundle adjustment with additional parameters, which is fit for the correction systematic errors in the SPOT satellite imagery, and to present a suitable term of additional parameters for the data form of SPOT satellite imagrery. As a result, an algorithm of self-calibration bundle adjustment for SPOT satellite imagery was settles, and the computer program was developed. Also, the suitable term of additional parameters to correct the systematic errors for each data form was defined through examination for determination effect of additional parameters and significance test. The algorithm of self-calibration bundle adjustment for SPOT satellite imagery according to this study could improve the accuracy of positioning.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.5
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• pp.42-50
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• 1991

According as the members and inner and outer plates of the automobile body structure have been thinned their thickness and have become high strength, each part of the body structure has been put more severe stress condition. Therefore, it has been increasingly required to improve the fatigue strength of the spot welded structures. As one of the improving methods for such problem, the author had previously proposed the method of alleviating stress concentration at nugget edge of the spot weld part and improving its fatigue strength [1]. But, because fatigue strength of the spot welded lap joint is influenced by its geometrical and mechanical factors, welding condition and etc., there needs a quantitative and systematic estimation method of them. In this report, by considering nugget edge of the spot weld part of the spot welded lap joint subjected to tensile load to the ligament crack, fatigue strength of various spot welded lap joints was estimated with the stress intensity factor (S.I.F.) K which is fracture mechanical parameter. It is known that evaluation of fatigue strength of the spot welded lap joint by the stress intensity factor (S.I.F.) K is more effective than the maximum stress $(\sigma_{ymax}$) at edge of the spot weld part on the center line of width of the plate.

• International Journal of Industrial Entomology and Biomaterials
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• v.12 no.1
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• pp.35-39
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• 2006

Fifty-six indigenous and twenty nine exotic mulberry varieties were screened against powdery mildew, Myrothecium leaf spot, Pseudocercospora leaf spot, sooty mold and bacterial leaf spot for a period of three years under field condition. The percent disease index (PDI) was recorded during peak season of the foliar diseases. Out of eighty-five varieties studied, ten varieties were highly resistant and eight were resistant to powdery mildew; six varieties were immune and seventy-eight varieties were highly resistant to Myrothecium leaf spot; sixty varieties were highly resistant and 21 were resistant to Pseudocercospora leaf spot; forty four varieties were highly resistant to sooty mold and two varieties were immune and fifty-eight were highly resistant to bacterial leaf spot. Lowest cumulatative disease index was observed in M. multicaulis (7.28) followed by Thailand lobed (7.85) and Italian mulberry (8.06).

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.9 no.1
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• pp.83-96
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• 1991

The use of SPOT Imagery is a growing trend in the field of small and middle scale mapping, as well as in establishing topographic database. This study is about 3-D positioning using the SPOT Imagery, where the accuracy and the gemetric characteristics of SPOT photos are analysed according to the preprocessing level (level 1AP,1B). As a result of this study the following could be determined, i. e 1) the geometric characteristics of SPOT Imagery according to the preprocessing level, 2) the optimal polynomial type for exterior orientations of each preprocessing level, and 3) the type of significant additional parameters. It was found that both the geometric precision and accuracy of level 1AP is higher than those of level 1B, which implies that level 1AP is more suitable for precise 3-D positioning and map production.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.221-222
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• 2023

The purpose of this study is to analyze the applicability and limitations of SPOT robots in the construction industry. The SPOT robot, which is being introduced to construction sites for smart construction with the progress of the 4th industrial revolution, is shaped like a four-legged dog and is equipped with various sensors for data collection and autonomous driving. In this study, hardware and software were analyzed, such as the size of the SPOT robot, mobility on slopes and heights, operating environment, and software functions that can collect data with a sensor weighing up to 14 kg. In addition, while the SPOT robot operates in a construction environment, performance such as stability, accuracy, signal connection distance, and obstacle avoidance are evaluated, and the applicability and limitations of the SPOT robot in the construction industry are analyzed. Based on this analysis, the purpose of this study is to evaluate when and how SPOT robots can be effectively used at construction sites, identify limitations, and derive contributions and improvements for the construction industry.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.2
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• pp.153-158
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• 2006

A new High Resolution Geometry or HRG imaging instrument is developed by CNES to be carried on-board SPOT 5. The HRG instrument offers a higher ground resolution than that of the HRV/HRVIR on SPOT 1 - 4 satellites. The field width of HRG is 60 km, same as SPOT constellation. With two HRG instruments, a maximum swath of 120 km at 5 m resolution can be achieved. The generation of Digital Elevation Models (DEMs) from satellite stereo images scores over conventional methods of DEM generation using topographic maps and aerial photographs. This global availability of satellite images allows for quicker data processing for an equivalent area. In this study, a HRG stereo images of SPOT 5 over JECHEON has been used with Leica Photogrammetry Suite OrthoBASE Pro tool for the creation of a digital elevation model (DEM). The extracted DEM was compared to the reference DEM obtained from the contours of digital topographic map.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.2
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• pp.247-254
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• 2010

In this paper, a new approach has been studied correcting the geometric distortion of SPOT 4 imagery. Two new equations were induced by the relationship between satellite and the Earth in the space. line-of-sight (LOS) vector adjustment model for SPOT 4 imagery was implemented in this study. This model is to adjust LOS vector under the assumption that the orbital information of satellite provided by receiving station is uncertain and this uncertainty makes a constant error over the image. This model is verified using SPOT 4 satellite image with high look angle and thirty five ground points, which include 10 GCPs(Ground Control Points) and 25 check points, measured by the GPS. In total thirty five points, the geometry of satellite image calculated by given satellite information(such as satellite position, velocity, attitude and look angles, etc) from SPOT 4 satellite image was distorted with a constant error. Through out the study, it was confirmed that the LOS vector adjustment model was able to be applied to SPOT4 satellite image. Using this model, RMSEs (Root Mean Square Errors) of twenty five check points taken by increasing the number of GCPs from two to ten were less than one pixel. As a result, LOS vector adjustment model could efficiently correct the geometry of SPOT4 images with only two GCPs. This method also is expected to get good results for the different satellite images that are similar to the geometry of SPOT images.