• 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.

• Advances in materials Research
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• v.13 no.4
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• pp.299-319
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• 2024

Due to higher strength-to-weight ratio of composite laminates, they find uses in many weight-sensitive applications like aerospace, automobile and marine structures. From a reliability point of view, accurate prediction of failure of these structures is important. Due to the complexities in the manufacturing processes of composite laminates, there is a variation in the material properties and geometric parameters. Hence stochastic aspects are important while designing the composite laminates. Many existing works of composite laminate failure analysis are based on the deterministic approach but it is important to consider the randomness in the material properties, geometry and loading to predict accurate failure loads. In this paper the statistics of the ultimate failure load of the [0/θ]_s laminated composite plate (LCP) containing the edge crack and voids subjected to the tensile loading are presented in terms of the mean and coefficient of variance (COV). The objective is to better the efficacy of laminate failure by predicting the statistics of the ultimate failure load of LCP with random material, geometric and loading parameters. The stochastic analysis is done by using the extended finite element method (XFEM) combined with the second-order perturbation technique (SOPT). The ultimate failure load of the LCP is obtained by ply-by-ply failure analysis using the ply discount method combined with the Tsai-Wu failure criterion. The aim is to know the effect of the stacking sequence, crack length, crack angle, location of voids and number of voids on the mean and corresponding COV of the ultimate failure load of LCP is investigated. The results of the ultimate failure load obtained by the present method are in good agreement with the existing experimental and numerical results. It is observed that [0/θ]_s LCPs are very sensitive to the randomness in the crack length, applied load, transverse tensile strength of the laminate and modulus of elasticity of the material, so precise control of these parameters is important. The novelty of the present study is, the stochastic implementation in XFEM for the failure prediction of LCPs containing crack and voids.

• 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.