• Journal of Oriental Neuropsychiatry
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• v.17 no.2
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• pp.133-145
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• 2006

Objective : The purpose of this experimental-controlled study was to investigate the characteristics of the autonomic nervous system in students with Keongke by using HRV(Heart rate variability) and PSV(Pupil size variability). Method : The study group was consisted of 11 students with self recognition as the experimental group, and 25 normal students as the control group. Informations on gender and age were obtained by medical charts and personal interviews. By using heart rate variability and pupil size variability, we measured the value of HRT(Heart rate), SDNN(Standard deviation of NN intervals), LFnorm(Low frequency normalization), HFnorm(High frequency normalization), LF/HF ratio, Pupil area, B.S.(Basic size), C.R.(Max Constriction Rate) and 1s.d.(1sec Dilation Rate). I compared the degrees of the sympathetic and parasympathetic activity. Result : 1. In the result of heart rate variability between experimental and control group, none of the parameters of experimental group were significantly different from control group. And even though there were no statistical significance, there were some numerical differences in SDNN, LF norm, HF norm. 2. In pupil size variability, C.R. and 1s.d. of the experimental group were increased compared to control group. Conclusion : The study results suggest that the group with Keongke has differences of autonomic nervous system as compared to those in normal state. Measurement value of PSV is a new technical approach to estimate the autonomic nervous system.

• Journal of the Korea Concrete Institute
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• v.16 no.3 s.81
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• pp.425-431
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• 2004

This paper describes an experimental investigation of how time-dependent deformations of high strength concretes are affected by maximum size of coarse aggregate, curing time, and relatively low sustained stress level. A set of high strength concrete mixes, mainly containing two different maximum sizes of coarse aggregate, have been used to investigate drying shrinkage and creep strain of high strength concrete for 7 and 28-day moist cured cylinder specimens. Based upon one-year experimental results, drying shrinkage of high strength concrete was significantly affected by the maximum size of coarse aggregate at early age, and become gradually decreased at late age. The larger the maximum size of coarse aggregate in high strength concrete shows the lower the creep strain. The prediction equations for drying shrinkage and creep coefficient were developed on the basis of the experimental results, and compared with existing prediction models.

• Journal of Mechanical Science and Technology
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• v.18 no.11
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• pp.1989-1995
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• 2004

Finite element analysis(FEA) is the most popular numerical method to simulate plasticity-induced fatigue crack closure and can predict fatigue crack closure behavior. Finite element analysis under plane stress state using 4-node isoparametric elements is performed to investigate the detailed closure behavior of fatigue cracks and the numerical results are compared with experimental results. The mesh of constant size elements on the crack surface can not correctly predict the opening level for fatigue crack as shown in the previous works. The crack opening behavior for the size mesh with a linear change shows almost flat stress level after a crack tip has passed by the monotonic plastic zone. The prediction of crack opening level presents a good agreement with published experimental data regardless of stress ratios, which are using the mesh of the elements that are in proportion to the reversed plastic zone size considering the opening stress intensity factors. Numerical interpolation results of finite element analysis can precisely predict the crack opening level. This method shows a good agreement with the experimental data regardless of the stress ratios and kinds of materials.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.4
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• pp.141-145
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• 2009

Recently, inkjet technology has emerged as one of the most powerful tools for patterning electronics devices, such as large area display applications, RFID, PCB patterning, etc. By using the Inkjet technology, the droplet speed as well as the size can be controlled precisely. In this paper, the relationship between waveform and droplet size will be investigated by means of experiment. Also the relationship between inkjet speed and droplet size will be discussed. It was shown from experimental results that ink droplet size from the nozzle diameter of $50{\mu}m$ can be varied from 37 to $58{\mu}m$ by modifying the inkjet waveform when the speed of the droplet is 1m/sec. Finally, experimental results indicate that small drops are more difficult to generate than large drops since the jetting conditions for making small drops are sensitively affected by the dwell time variation.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.574-580
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• 2009

This study is investigate the bending behavior of real size RC beams strengthened with carbon fiber sheets. For experimental study, 1 control beam and 8 strengthened beams of real size(4 NU-beams and 4 U-beams) are tested and compared. NU-beam has not a V-shaped band and V-beam has a V-shaped band. The variables of experiment are composed of the number of carbon fiber sheets, the existence of U-shaped band, and four point loading, etc. The experimental results showed that the strengthening system with U-shaped band controls the premature debonding and provides a more ductile failure mode than the strengthening system without V-shaped band. It can be found from the load-deflection curves that as the number of fiber sheets is increased, the maximum strength and the flexural rigidity is increased. For the strengthening method with carbon fiber sheets of the real size RC beams, it is required the finding a solution to the bonding problem.

• Human Ecology Research
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• v.54 no.3
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• pp.279-292
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• 2016

This research predicted the fit of the basic bodice patterns worn on adolescent girls' 3-dimensional scanned bodies. Six 3-dimensional scanned bodies were selected from the sixth Size Korea data. Each of them had good body posture and represented one of the three garment sizes: 79-160, 82-160, and 85-160. Experimental basic bodice patterns were drafted by three basic bodice pattern making methods. The fit of the basic bodice pattern was analyzed by the CLO 3D virtual clothing system. The results showed that the experimental basic bodice patterns did not fit well at the neck, shoulder, and back for adolescent girls. The fit of the basic bodice patterns varied by pattern making method or size. The basic bodice pattern A with the waist darts ending above the breast line showed the best fit among the three different types of experimental pattern. Among the three sizes 79-160, 82-160, and 85-120, size 79-160 basic bodice pattern showed the worst fit for adolescent girls. The results show that the placement and size of the bodice darts affect the basic bodice pattern fit. The basic bodice pattern making method of size 79-160 for adolescent girls should be studied in a future study.

• Journal of the Ergonomics Society of Korea
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• v.16 no.2
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• pp.29-38
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• 1997

The research on the factors which effect on legibility is mainly utilized as the basic data of selecting the standard guideline of VDT screen. But the research on Korean is scarcer than that of English. Furthermore, it is unreasonable to apply the results of the foreign language to Korean, beause of the difference between the typography of English and that of Korean. Therefore, more systematic and ergonomic research of the Korean typography on VDT screen is needed. In this paper, an experimental study on search speed and error rate is designed and performed according to different Korean letter size and font on search task with VDT. The experimental screen based on popular Ming and Gothic style is made up of total 12 artificial screens, each 6 different font size. As the criteria of the performance, searching speed(s.s.) and error rate (e) are selected, and CFF value is measured to evaluate user's visual fatigue. The results of experiment in font show that the Korean Gothic style is superior to the Korean Ming style in user's visual performance. The letter size that gives user the optimal performance ranges from the visual angle 39.8' to 55.5' in Ming style, from the visual angle 39.8' to 52.6' in Gothic systle. In visual fatigue experiment, the better performance of letter size is, the less tired user feels. And the smaller letter size is, the more tired user feels. There is no relationship between font and user's visual fatigue.

• Advances in nano research
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• v.14 no.2
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• pp.155-164
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• 2023

Grain size in sheet metals in one of the main parameters in determining formability. Grain size control in industry requires delicate process control and equipment. In the present study, effects of grain size on the formability of steel sheets is investigated. Experimental investigation of effect of grain size is a cumbersome method which due to existence of many other effective parameters are not conclusive in some cases. On the other hand, since the average grain size of a crystalline material is a statistical parameter, using traditional methods are not sufficient for find the optimum grain size to maximize formability. Therefore, design of experiment (DoE) and artificial intelligence (AI) methods are coupled together in this study to find the optimum conditions for formability in terms of grain size and to predict forming limits of sheet metals under bi-stretch loading conditions. In this regard, a set of experiment is conducted to provide initial data for training and testing DoE and AI. Afterwards, the using response surface method (RSM) optimum grain size is calculated. Moreover, trained neural network is used to predict formability in the calculated optimum condition and the results compared to the experimental results. The findings of the present study show that DoE and AI could be a great aid in the design, determination and prediction of optimum grain size for maximizing sheet formability.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.45
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• pp.357-364
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• 1998

This study deals with the performance evaluation of writing for designing handwriting instruments ergonomically. Experimental tests were executed on ballpoint pen., felt-tip pen, pencil, sharp-pencil, and fountain pen for ease of use and reduction of the muscles fatigue. The writing time and the degree of comfort of writing by subjects were measured on the diameters of five writing instruments. The results indicated that the ballpoint pen was rated significantly superior to the others in writing speed attribute and the instrument with the least fatigue was the fountain pen. There was a significant interaction effect between the types of instruments and their size in diameters. The diameter of instruments for considering time and comfort together was verified that the size of 9.5mm was efficient for ballpoint pen, the size of 8.1mm for felt-tip pen, the size of 7.5mm for pencil, the size of 8.2mm for sharp-pencil, and the size of 9.1mm for fountain pen.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.1
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• pp.1-10
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• 2000

The behavior of aerosos due to gravitational coagulation was studied experimentally and numerically. In experimental study, the geometric mean particel size increased as time elapsed in a vertical tube column, while the size decreased when the tube was set horizontally. The particle size distribution was observed to maintain the lognormal form during the coagulation process. Separately, numerical calculations were performed for studying the aerosol behavior under gravitational and Brownian coagulation using the moment method. By comparing the expeimented results with the numerical predictions, the governing mechanism of the aerosol behavior proved to be gravitational coagulation.