• Korean Journal of Biological Psychiatry
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• v.16 no.4
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• pp.238-245
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• 2009

Objectives : Mild Alzheimer's disease(AD) is uncertain to be related to visuospatial working memory subsystem dysfunction. We used the self ordered pointing test(SOPT) to find the characteristics of visuospatial working memory in mild AD. Methods : We compared the visuospatial working memory abilities of 20 patients with mild AD and 20 normal elderly controls(NC) using SOPT, of which stimuli consisted of two stimuli types(A : abstract, C : concrete) and two stimuli numbers(8 and 12). Therefore, working memory was tested using C8, C12, A8, and A12 stimuli conditions in SOPT. Mixed-model ANOVA was conducted with the AD and NC groups as between-subjects factor, with stimuli types and stimuli numbers as the within-subjects factors and with SOPT error rates as the dependent variable. Results : The AD group showed higher error rates in SOPT than the NC group. The NC group showed low error rates in concrete stimuli than in abstract stimuli and in small stimuli numbers than in large stimuli numbers. And the AD group showed no differences between stimuli types or stimuli numbers. Conclusion : AD patients showed a poor performance in visuospatial working memory using concrete stimuli. The result suggests that there is a non-transformation from visual input to phonological working memory in AD. Patients with AD showed a poor performance although in small stimuli number condition of SOPT. It suggests that in AD, visuospatial working memory is not working well although in low central executive loads.

• Journal of radiological science and technology
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• v.26 no.1
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• pp.31-37
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• 2003

The conclusions after appraisal usefulness of korean 30 kHz inverter type X-ray equipments which are currently used in the clinics are like those followings. 1. The specific characters of mA, kVp, msec in the radiography keep very good accuracy and showed good waveform also under KS regulations. 2. The output of the X-ray equipment is showed 1.7 times higher than single-phase. 3. mA, kVp of the fluoroscopy and Sopt film exposure mA, kVp showed appropriated results under the regulations. 4. As we consider the conversion factor of image intensifier tube used for two years, it showed pretty high results, 310 at 75 kV, and knew that the conversion factor which followed by increasing kVp increased its computations like Kim's experimentation. Those X-ray equipment showed excellent results in the appraisal while those were operating so we think that those X-ray equipments will be substitute for expensive foreign equipment in korean domestic medical equipment in the future.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.135-141
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• 2013

Subway in Korea, most of a metropolitan public transport use only worth ten million people a day floating population of wireless communication can be considered HOT SOPT. These three operators' 2G/3G/4G / Wi-Fi / T-DMB frequency and the number of services to co-exist, and the subway train passengers and subway party for operation and management of the communication network is also the co-subway passenger safety and for this service for the effects of mutual interference of whether the verification was necessary. This research and testing different frequency / communication interference between services and testing to determine whether, through the subway authorities and mobile operators in each frequency-specific interaction check and there is no interference to the safety and quality of subway passengers communication services that can be verified as the data was found. The verification methods in the metro area, not just from one region to determine whether the interference with a common verification methods can be applied.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.6
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• pp.37-43
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• 1997

The technology of Laser lamination joining of silicon steel sheets has been studied in this paper. Conventional sheets lamination process does not meet the requirments for the improvement electric parts performance. In response to this, a new Laser spot joining method has been developed. This study performs the Laser spot lamination joining while synchronizing the sillicon steel sheets in the dies with the press movement. Several conclusions have been drawn in this paper. Effects of beam focus, power, atmosphere gas and press oil etc.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.6
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• pp.113-118
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• 1999

In order to evaluate strength of spot welded joint, at first it is importent that we should know strain distribution near nugget zone. During loading, in HAZ, compressive strain increase with Increase of load, but in nugget zone tensile strain increase. During unloading, on the other hand, even through the decreases, the strain variation is not almost appeared in nugget zone and HAZ. In nugget boundary zone, the strain range increases continuously along with load increase on outer surface, but the strain increases continunously and decreases rapidly beyond yield strength on inner surface. In this paper, strain distribution are measured in inner and outer surface with variation of thickness and load under tensile-shear load. Tensile-shear strength increased as with increase of specimen thickness. As for thickness increase rates are 25%, 50%, 100%, and 150%, tensile-shear strength in crease rates are 40%, 81%, 130% and 228%.

• Steel and Composite Structures
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• v.26 no.1
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• pp.1-15
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• 2018

This study reported, the effect of random variation in system properties on bending response of single wall carbon nanotube reinforced composite (SWCNTRC) plates subjected to transverse uniform loading is examined. System parameters such as the SWCNT armchair, material properties, plate thickness and volume fraction of SWCNT are modelled as basic random variables. The basic formulation is based on higher order shear deformation theory to model the system behaviour of the SWCNTRC composite plate. A C0 finite element method in conjunction with the first order perturbation technique procedure developed earlier by the authors for the plate subjected to lateral loading is employed to obtain the mean and variance of the transverse deflection of the plate. The performance of the stochastic SWCNTRC composite model is demonstrated through a comparison of mean transverse central deflection with those results available in the literature and standard deviation of the deflection with an independent First Order perturbation Technique (FOPT), Second Order perturbation Technique (SOPT) and Monte Carlo simulation.

• Journal of Welding and Joining
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• v.5 no.3
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• pp.11-18
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• 1987

Effects of electrode tips shapes of spot welding on the galvannealed steel have been studied, and the results obtained from this studies are as follows. 1) Expulsion had no effect on the shear strength of the specimen but been observed on the tensile strength of the specimen. 2) Effect of holding time after welding was neglegible when the spot welding supplies enough heat input. 3) Depending on the sopt welding tip shape it has different weldbility. It has better weldability in the order of pointed shape, truncated shape and dome shape. But the effect of coolind was just the opposite of the above order.

• The Journal of the Korea Contents Association
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• v.5 no.6
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• pp.129-137
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• 2005

A performance analysis of LEO Satellite Communication Service is being made in a variety of ways. In this paper we examined the variation of interference caused by the distribution of terminals within a cell and the maximum number of users according to the average distance between terminals, which had not been considered in former researches. Also we examined the interference made by sopt beam isolation value of some antennas(tapered-apertured antenna, gaussian antenna) which are used on LEO Satellite Communication Service Assigning this interference to the bandwidth of channels in LEO Satellite Communication Service, and with principal parameters(bandwidth, number of carrier) we made a performance analysis. And comparing tapered-apertured antenna with gaussian antenna we will find out which one is more effective and more suitable for interference.

• Advances in aircraft and spacecraft science
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• v.4 no.5
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• pp.585-611
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• 2017

This article covenants with the post buckling witticism of carbon nanotube reinforced composite (CNTRC) beam supported with an elastic foundation in thermal atmospheres with arbitrary assumed random system properties. The arbitrary assumed random system properties are be modeled as uncorrelated Gaussian random input variables. Unvaryingly distributed (UD) and functionally graded (FG) distributions of the carbon nanotube are deliberated. The material belongings of CNTRC beam are presumed to be graded in the beam depth way and appraised through a micromechanical exemplary. The basic equations of a CNTRC beam are imitative constructed on a higher order shear deformation beam (HSDT) theory with von-Karman type nonlinearity. The beam is supported by two parameters Pasternak elastic foundation with Winkler cubic nonlinearity. The thermal dominance is involved in the material properties of CNTRC beam is foreseen to be temperature dependent (TD). The first and second order perturbation method (SOPT) and Monte Carlo sampling (MCS) by way of CO nonlinear finite element method (FEM) through direct iterative way are offered to observe the mean, coefficient of variation (COV) and probability distribution function (PDF) of critical post buckling load. Archetypal outcomes are presented for the volume fraction of CNTRC, slenderness ratios, boundary conditions, underpinning parameters, amplitude ratios, temperature reliant and sovereign random material properties with arbitrary system properties. The present defined tactic is corroborated with the results available in the literature and by employing MCS.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.99-99
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• 2010

최근 자동차 산업은 고효율 및 친환경이라는 전세계적인 이슈에 따라 고연비의 자동차 개발에 총력을 다하고 있다. 그러므로 다양한 고강도 강 및 경량 금속이 자동차의 차체에 적용되고 있다. 특히 철강재료에 있어서 기존의 저 탄소강에서 다양한 기능을 갖은 고강도 강으로 그 종류가 다양화되고 있으며 이에 따라 저항 점용접을 이용한 차체의 접합은 점점 이종의 강판을 접합하는 비율이 점차로 늘어나고 있다. 이와 같이 강판의 종류가 다양해짐에 따라 수많은 이종 강판에 대한 조합이 생기고 있으며, 이를 모두 실험을 통해 최적 용접조건을 찾기에는 많은 시간과 노력이 투자되어야 된다. 그러나 시뮬레이션 기법으로 이종 접합의 초기 용접조건에 대한 정보를 얻는다면, 최소의 실험을 통해 좀 더 손쉽게 최적의 용접조건을 도출할 수 있다. 그러므로 본 연구에서는 실제 자동차에 많이 쓰이는 강판인 EDDQ급 도금강판 0.7t와 440R 급 1.2t 및 DP 590 1.0t의 3종류의 이종 강판에 대한 점 용접특성을 저항 점용접 전문 소프트웨어인 SORPAS를 이용하여 시뮬레이션하고 분석하였다. 시뮬레이션은 겹치기 순서에 따라 용접 전류, 가압력, 용접 시간을 변수로 하여 각각의 겹침 순서에 대한 2개의 용접 점에 대한 너겟의 크기를 분석하였으며 로브 곡선을 얻을 수 있었다. 이를 통해 3겹의 겹치기 순서에 따른 용접 특성을 비교할 수 있었으며, 이것을 실제 생산라인의 자동차 차체의 조립 순서 결정에 있어서 응용함으로써 용접 특성을 고려한 차체 조립에 적용이 가능할 것으로 사료된다.