• Journal of Welding and Joining
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• v.20 no.1
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• pp.55-61
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• 2002

The automobile is made up of about twenty thousand parts. Some parts are formed by pressing and combined by spot welding. Among them, steel palate of fuel tank is formed in the metal mold and bending parts are jointed by spot and seam welding. To find weldability conditions of spot welding, clearance between two welding steel plates was made and after spot welding, weldability is evaluated by means of tensile shear load, nugget size and shape. Specimen used in this study was a mild steel of 1.2mm thickness and electrode was Cu-Cr alloy of 6mm diameter. When spot welding started, the clearance of two steel plates was changed 0mm, 3mm and 5mm step by step. The fractured surface of specimen after this test was observed by Optical Microscope to measure microstructure and nugget shape. When clearance of two specimen was 3mm and 5mm, strength and nugget size was decreased and nugget shape was not clear.

• Proceedings of the KWS Conference
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• 2003.05a
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• pp.269-271
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• 2003

A simplified analysis method is proposed in this paper, through which the deformation due to spot welding is obtained. In order to analyze the spot welding process, the finite elements are axisymmetrically modeled, and the results from them are used for analyzing the deformation of spot welded structure. It takes more little time in this simplified analysis than the analysis by 3-D continuum elements, and this analysis produces the results that nearly agree with the measured data.

• Journal of the Korean Society of Industry Convergence
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• v.14 no.3
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• pp.105-111
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• 2011

Landmark Spots in 2D gel electrophoresis are used in many methods of 2DEG spot matching. Landmark Spots are obtained manually and it is a bottle neck in the entire protein analysis process. Automated landmark spots detection is a very crucial topic in processing a massive amount of 2DGE data. In this paper, Automated landmark spot detection is proposed using point pattern matching and graph theory. Neighbor spots are defined by a graph theory to use and only a centered spot and its neighbor spots are considered for spot matching. Normalized Hausdorff distance is introduced as a criterion for measuring degree of similarity. In the conclusion, the method proposed in this paper can get about 50% of the total spot pairs and the accuracy rate is almost 100%, which the requirements of landmark spots are fully satisfied.

• Korean Journal Plant Pathology
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• v.11 no.3
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• pp.217-223
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• 1995

Nature of graft transmissibility of pear abnormal leaf spot disease was examined by various grafting methods in the greenhouse and field. When the diseased and symptomless twigs were collected in winter and grafted in the next spring to the seed-originated healthy root stock, the abnormal leaf spot was developed only in the case of the diseased twigs. Double grafting on a seed-originated healthy root stock, where the diseased and the symptomless twigs were used as 1st and 2nd scions, respectively, developed abnormal leaf spot lesions without exception on the 2nd scions. Tongue-graft with the diseased and the symptomless trees also incited abnormal leaf spots on the both trees. Abnormal leaf spots of were also developed on HN-39, an indicator pear tree, used as a 2nd scion in a double graft test, where the diseased twig and a seed-originated healthy tree were used as the 1st scion and the root stock, respectively. When the diseased twig was top-grafted to the healthy root stock, lesion development of abnormal spot was limited to the grafted twig itself in the 1st year, but expanded to the main branches in the 2nd year, and spread over the whole tree in the 3rd year. This result indicates that the causal agent of abnormal leaf spot disease is transmitted by graft.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.3
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• pp.41-49
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• 1997

Laser spot welding offers a unique combination of high speed. precision and low heat distortion, compared with conventional resistance spot welding. This combinatin of advantages is especially attractive for the automotive industry. Until now automobile fabrication is widely used resistance spot welding, however, because of geometric and structural problem, spot welding is required many welding machine in that reason by substituting spot welding with laser welding, it save the equipment cost. In the present study we measured ultimate strength and observed bead cross section of laser welded specimen and compared with that of the resistance spot welding results in order to adapt laser welding in automobile industry. Also for strength esti- mation we calculated the residual stress of laser welded zone. All calculations are performed with the ABAQUS code on a workstation.

• Korean Journal of Plant Resources
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• v.9 no.3
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• pp.224-229
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• 1996

Floral flavonoids of Hibiscus syriacus L. six complex with 68 formac all in all were examined. Thirteen flavonoids appeared on the two dimensional chromatogtams. Spot 5, however, occupied more than 50% in total flavonoid contents, and other spots were invariably minor pigments in all samples examined. Ten spots among 13 spots showed the characteristics of flavones, having color of purple to dark purple under UV light and yellow under ammonia gas, while spots reagents suggests that 10 purple spots are 4', 5-OH aglycone type. Four spots out of 10 purple spots were possible to be identified: spot 5, saponarin, spot 7, vitexin, spot 9, xylovitexin, and spot 11, rhamnosylvitexin, respectively. It was suggested that spot 13 might be apigenin-7-O-diglycoside.

• 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.

• Journal of Korean Neurosurgical Society
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• v.56 no.2
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• pp.86-90
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• 2014

Objective : The spot sign is related with the risk of hematoma expansion in spontaneous intracerebral hemorrhage (ICH). However, not all spot sign positive patients undergo hematoma expansion. Thus, the present study investigates the specific factors enhancing the spot sign positivity in predicting hematoma expansion. Methods : We retrospectively studied 316 consecutive patients who presented between March 2009 to March 2011 with primary ICH and whose initial computed tomography brain angiography (CTA) was performed at our Emergency Department. Of these patients, 47 primary ICH patients presented spot signs in their CTA. We classified these 47 patients into two groups based on the presence of hematoma expansion then analyzed them with the following factors : gender, age, initial systolic blood pressure, history of anti-platelet therapy, volume and location of hematoma, time interval from symptom onset to initial CTA, spot sign number, axial dimension, and Hounsfield Unit (HU) of spot signs. Results : Of the 47 spot sign positive patients, hematoma expansion occurred in 26 patients (55.3%) while the remaining 21 (44.7%) showed no expansion. The time intervals from symptom onset to initial CTA were $2.42{\pm}1.24$ hours and $3.69{\pm}2.57$ hours for expansion and no expansion, respectively (p=0.031). The HU of spot signs were $192.12{\pm}45.97$ and $151.10{\pm}25.14$ for expansion and no expansion, respectively (p=0.001). Conclusions : The conditions of shorter time from symptom onset to initial CTA and higher HU of spot signs are the emphasizing factors for predicting hematoma expansion in spot sign positive patients.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.701-709
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• 2000

As the welding spot forms a singular geometry of an external crack type, fatigue failure of spot-welded specimens can be evaluated by means of a fracture parameter. Recasting the load vs. fatigue life relationships experimentally obtained, we predicted the fatigue life of spot-weld specimens with a single parameter denoted the equivalent stress intensity factor. This crack driving parameter is demonstrated to successfully describe the effects of specimen geometry and loading type in a comprehensive manner. The suggested fatigue life formula for a single spot weld can play a key role in the design and assessment of spot-welded panel structures, in that the fatigue strength of multi-spots is eventually determined by the fatigue strength of each single spot. We therefore attempt to evaluate the effectiveness and validity of $K_e$ in predicting the fatigue life of auto seat belt anchor panel. We first establish finite element models reflecting the actual mechanical behavior of 3 types of seat belt anchor specimens. Using finite element models elaborately established, we then obtain the effective crack driving parameter $K_e$ composed of its ductility -dependent modal components. It is confirmed that the $K_e$ concept successfully predicts the fatigue life of multi-spot welded panel structures represented by auto seat belt anchors here.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.3
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• pp.224-231
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• 1984

Having found by means of a tension-shear test an optimal spot welding condition under which the maximum weld strength is to be brought forth, this study made an examination of behavior of fracture concerned with behavior of stress distribution, observed around the nugget periphery of the specimens prepared under the optimal conditions, with one point spot welded mild steel sheets. The resultant findings are as follows: (1)There remarkably exists an optimal spot welding condition to indicate the maximum weld strength, and fracture of the specimens spot welded under that condition occurs outside the nugget boundary. (2)An experiment on the basis of a photoelastic model reveals that the maximum stress is distributed along the center line of the steel plate width but occurs on the region corresponding to heat affected zone of spot welds. (3)Heat affected zone of spot welds consists of coarse grains with considerably low micro Vickers hardness value and of fine grains of high micro Vickers hardness value, and in this unbalanced structure weak region are represented in coarse grain region, where fracture is initiated and continues its propagation.