• Tribology and Lubricants
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• v.12 no.4
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• pp.52-59
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• 1996

The results of the electrical contact conductivity of multi-contact spots accounting the surface roughness and the non-conductive films of different origins such as air, water, cutting oil, and machining oil are presented. The array of metal spheres compressed between two flat plates has been used for simulation of the contact behavior of multiple contact of solids, under normal loading. Measurement of electrical contact resistance has been made using the equipment providing the adequate accuracy in the range of micro Ohms. The data on electrical contact resistance have been compared with theoretical predictions using the multiple contact model of constriction resistance. The effect of single spot number and array on conductivity of contact has been evaluated. The results of the experiments show that the contact resistance are closely related to the number of loading cycles, form of surface roughness, and presence of non-conductive films that reduce the size of the real electrical contact spots.

• Steel and Composite Structures
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• v.19 no.4
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• pp.995-1009
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• 2015

This study presents design optimization of spot welded structures to attain maximum strength by using the Nelder-Mead (Simplex) method. It is the main idea of the algorithm that the simulation run is executed several times to satisfy predefined convergence criteria and every run uses the starting points of the previous configurations. The material and size of the sheet plates are the pre-assigned parameters which do not change in the optimization cycle. Locations of the spot welds, on the other hand, are chosen to be design variables. In order to calculate the objective function, which is the maximum equivalent stress, ANSYS, general purpose finite element analysis software, is used. To obtain global optimum locations of spot welds a methodology is proposed by modifying the Nelder-Mead (Simplex) method. The procedure is applied to a number of representative problems to demonstrate the validity and effectiveness of the proposed method. It is shown that it is possible to obtain the global optimum values without stacking local minimum ones by using proposed methodology.

• The Plant Pathology Journal
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• v.21 no.2
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• pp.164-166
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• 2005

Corynespora leaf spot occurred severely on balsam pear (Momordica charantia) at Changwon, Gyeongnam province in Korea in November and December 2003. The causal fungus isolated from infected leaves of the plants grew well on potato dextrose agar showing gray to brown color. Solitary or catenary conidia of the fungus were obclavate to cylindrical in shape, and pale olivaceous brown or brown in color. The number of isthmus pseudosepta ranged from 4 to 20 and measured 36~186${\times}$8~19 ${\mu}m$ in size. Conidiophores were pale to light brown in color and measured 94~648${\times}$3~8 ${\mu}m$ in size. Optimal temperature for mycelial growth was $30{\circ}C$. On the basis of mycological characteristics and pathogenicity, the fungus was identified as Corynespora cassiicola (Berk. & Curt.) Wei. This is the first report on the corynespora leaf spot of M. charantia caused by C. cassiicola in Korea.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.29B no.10
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• pp.69-77
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• 1992

Pattern Recognition is one of the fundamental areas of computer vision. The recognition of patterns with varying size and severe defects is especially important. However, it is known that the conventional algorithms such as GHT or structural approaches have limitations in speed and accuracy. In this paper, in order to avoid above-mentioned problems, we propose a new recognition algorithm which exploits the histogram of contour directions and the sampled spot matching method. While the former provides little influence against size variation, the latter has strong immunity to noise and defects. We applied those proposed algorithms for the recognition of numbers extracted from the car number plates and shapes of aircraft. Experimental result shows that it is possible to solve above-mentioned problems by complementary uses of those two suggested algorithms. The contour directional histogram method resulted in high-speed of average 0.013 sec/char and 0.1 sec/aircraft-image on IBM-386. The accuracy of recognition is as high as 99%. Sampled spot matching method has less speed than the former one, however, it showed fairly strong immunity to noise and defects.

• Journal of Soil and Groundwater Environment
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• v.19 no.1
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• pp.26-33
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• 2014

Uncertainty associated with a sampling method is very high in evaluating the degree of site contamination; therefore, such uncertainty affects the reliability of precise investigation and remediation verification. In particular, in evaluating a site for a small-sized filling station, underground utilities, such as connection pipes and oil storage tanks, make grid-unit sampling impossible and the resulting increase in uncertainty is inevitable. Accordingly, this study quantified the uncertainty related to the evaluation of the degree of contamination by total petroleum hydrocarbon and by benzene, toluene, ethylene, and xylene. When planning a grid aimed at detecting a hot spot, major factors that influence the increase in uncertainty include grid interval and the size and shape of the hot spot. The current guideline for soil sampling prescribes that the grid interval increase in proportion to the area of the evaluated site, but this heightens the possibility that a hot spot will not be detected. In evaluating a site, therefore, it is crucial to estimate the size and shape of the hot spot in advance and to establish a sampling plan considering a diversity of scenarios.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.3
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• pp.296-302
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• 2008

Recently, a mesh-size insensitive structural stress definition (structural stress method) is proposed that gives a stress state at weld toe with a relatively large mesh size. The structural stress definition is based on the elementary structural mechanics theory and provides an effective measure of a stress state in front of weld toe. In this study, a fatigue strength assessment for a side shell connection of a container vessel using both the hot spot stress and the Battelle structural stress method was carried out. A consistent approach to compute the extrapolated hot spot stress for design purpose is described and current fatigue guidance is evaluated. Fatigue strength predicted by the two methodologies, e.g. hot spot stress and structural stress approaches, at hot spot locations of a typical ship structure are compared and discussed.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.8
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• pp.51-59
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• 2020

The objective of this study is to enrich the literature by investigating the impact of introduction of index future trading on spot market returns and trading volume in Vietnam. Data used in this study mainly consist of daily VN30-Index and market trading volume series during the period from February 6^th, 2012 to December 31^st, 2019. Using OLS, GARCH(1,1) and EGARCH(1,1) models, the empirical findings consistently confirm that the introduction of index future trading has no impact on the spot market returns. In addition, the results of the EGARCH(1,1) model indicate that the leverage effect on the spot market volatility is existence in HOSE. Specifically, bad news has a greater effect on the market volatility than good news of the same size. Moreover, our empirical findings reveal that the introduction of index future contracts has the positive impact on the underlying market trading volume. Specifically, the trading volume of the post-index futures introduction increases by 7.5 percent compared with the pre-index futures introduction. Finally, the results obtained from the Granger causality test for the relationship between the spot market returns and the future trading activity confirm that only uni-directional causality running from the market returns to the future trading activity exists in HOSE.

• Korean Journal of Optics and Photonics
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• v.11 no.6
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• pp.411-417
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• 2000

The waveguide structure effects of a spot-size converter (SSe) of a $1.3\mu{m}$ FP(Fabry-Perot)-LD(Laser Diode) were investigated. Its coupling efficiency and alignment tolerance with a single-mode fiber (SMF) were carefully examined by using a 3dimensional BPM (Beam Propagation Method). It was shown that the fOlmation of enough length of straightened waveguide around the end of the sse region can substantially improve the optical coupling efficiency for a vertically tapered sse. In contrast, a down-taper structure for a laterally tapered sse has superior characteristics to an up-tapered one. We suggested good sse structures which can provide a high coupling efficiency as well as a large alignment tolerance with an .SMF. .SMF.

• ETRI Journal
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• v.27 no.1
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• pp.89-94
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• 2005

This paper describes a low-loss, compact, 40-channel arrayed waveguide grating (AWG) which utilizes a monolithically integrated spot-size converter (SSC) for lowering the coupling loss between silica waveguides and standard single-mode fibers. The SSC is a simple waveguide structure that is tapered in both the vertical and horizontal directions. The vertically tapered structure was realized using a shadow-mask etching technique. By employing this technique, the fabricated, 40-channel, 100 GHz-spaced AWG with silica waveguides of 1.5% relative index-contrast showed an insertion-loss figure of 2.8 dB without degrading other optical performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.748-753
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• 2000

Nowadays, many studies and researches in data storage have been carried out and storage capacity is increased. But the limitation of storage capacity is happened for several problems. One of them is spot & pit size in optical and magnetic data storage and another is the resolution of actuators. The problems in spot & pit size is covered by new data storage methods- for example, NFR{Near-Field Recoding) system. But the resolution limit of an actuator doesn't follow up the development of spot & pit size. Because of them, we should improve a resolution of an actuator. Especially, in this paper an actuator is studied and designed for NFR(in using SIL(Solid Immersion Lens) system. It is a dual stage actuator, which consists of a Fine actuator and a Coarse actuator, and should desire 100nm accuracy. But, our actuator system only includes tracking mechanism execpt focusing mechanism which is controlled by slider mechanism used in HDD. Its actuating force generation method is VCM(Voice Coil Motor). The Fine actuator is composed of 4-leaf springs and a bobbin wrapped by coil. The Coarse actuator has Coils and 3-Roller bearings.