• Geomechanics and Engineering
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• v.19 no.6
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• pp.485-498
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• 2019

Pre-tensioned rock bolts can be classified into fully anchored, lengthening anchored and point anchored bolts based on the bond length of the resin or cement mortar inside the borehole. Bolts in varying anchoring methods may significantly affect the supporting effect of surrounding rock around a tunnel. However, thus far, the theoretical basis of selecting a proper anchoring method has not been thoroughly investigated. Based on this problem, 16 schemes were designed while incorporating the effects of anchoring length, pretension, bolt length, and spacing, and a systematic numerical experiment was performed in this paper. The distribution characteristics of the stress field in the surrounding rock, which corresponded to various anchoring scenarios, were obtained. Furthermore, an analytical approach for computing the active and passive strengthening index of the anchored surrounding rock is presented. A new fully anchoring method with pretension and matching technology are also provided. Then, an isolated loading model of the anchored surrounding rock was constructed. The physical simulation test for the bearing capacity of the model was performed with three schemes. Finally, the strengthening mechanism of varying anchoring methods was validated. The research findings in this paper may provide theoretical guidelines for the design and construction of bolting support in tunnels.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.151-159
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• 2006

This paper describes a design process of end-milling cutters: solid model of the designed cutter is constructed along with computation of cutter geometry, and the wheel geometry as well as wheel positioning data f3r fabricating end-mills with required cutter geometry is calculated. In the process, the main idea is to use the cutting simulation method by which the machined shape of an end-milling cutter is obtained via Boolean operation between a given grinding wheel and a cylindrical workpiece (raw stock). Major design parameters of a cutter such as rake angle, inner radius can be verified by interrogating the section profile of its solid model. We studied relations between various dimensional parameters and proposed an iterative approach to obtain the required geometry of a grinding wheel and the CL data for machining an end-milling cutter satisfying the design parameters. This research has been implemented on a commercial CAD system by use of the API function programming, and is currently used by a tool maker in Korea. It can eliminate producing a physical prototype during the design stage, and it can be used for virtual cutting test and analysis as well.

• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.1-6
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• 2005

Analogue physical modelling using granular materials (i.e., sandbox experiments) has been applied with great success to a number of geological problems at various scales. Such physical experiments can also be simulated numerically with the Discrete Element Method (DEM). In this study, we apply the DEM simulation to the collision between the Indian subcontinent and the Eurasian Plate, one of the most significant current tectonic processes in the Earth. DEM simulation has been applied to various kinds of dynamic modelling, not only in structural geology but also in soil mechanics, rock mechanics, and the like. As the target of the investigation is assumed to be an assembly of many tiny particles, DEM simulation makes it possible to treat an object with large and discontinuous deformations. However, in DEM simulations, we often encounter difficulties when we examine the validity of the input parameters, since little is known about the relationship between the input parameters for each particle and the properties of the whole assembly. Therefore, in our previous studies (Yamada et al.,2002a,2002b,2002c), we were obliged to tune the input parameters by trial and error. To overcome these difficulties, we introduce a numerical biaxial test with the DEM simulation. Using the results of this numerical test, we examine the validity of the input parameters used in the collision model. The resulting collision model is quite similar to the real deformation observed in eastern Asia, and compares well with GPS data and in-situ stress data in eastern Asia.

• Journal of dental hygiene science
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• v.12 no.6
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• pp.652-659
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• 2012

The purpose of this study was to examine whether senior simulation would bring any positive change to the attitude of dental hygiene students toward the elderly. The experimental group consisted of 58 dental hygiene students at a college. The experimental procedure was to do activities for 40 minutes wearing aging simulation suit. Self administered questionnaires were used to ask the attitude toward the elderly after senior simulation. The data were analyzed with SPSS program. General and aging related characteristics of subjects were analyzed through descriptive statistics. To testify the differences of the attitude after senior simulation, paired t-test was used. An experiment was conducted from May 27 to June 14, 2012, and the findings of the study were as follows: 1. There wasn't any perfect positive change in the overall attitude of the students toward elderly people after senior simulation, but their attitude got a little more positive whereas they took a neutral attitude in the past; 2. The students who had ever lived with elderly people under the same roof and who had ever received education related to the elderly underwent a more positive change in their attitude toward the elderly; 3. To what extent senior simulation was helpful for the understanding of the elderly was checked, and the majority replied that it was very useful or useful for the understanding of their physical aspects. The findings of the study confirmed that senior simulation didn't change the overall attitude of the students toward the elderly in a positive way yet brought about some positive changes in part. Therefore senior simulation is expected to be one of significant educational programs that could encourage students to have a better physical understanding of the elderly, to take a more positive attitude to them and to provide them with quality dental service.

• Nuclear Engineering and Technology
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• v.52 no.9
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• pp.1926-1938
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• 2020

We validated the performance of RELAP MOD3.3 code regarding the hybrid SIT with available experimental data. The concept of the hybrid SIT is to connect the pressurizer to SIT to utilize the water inside SIT in the case of SBO or SB-LOCA combined with TLOFW. We investigated how well RELAP5 code predicts the physical phenomena in terms of the equilibrium time, stratification, condensation against Separate Effect Test (SET) data. We also conducted the validation of RELAP5 code against Integrated Effect Test (IET) experimental data produced by the ATLAS facility. We followed conventional approach for code validation of IET data, which are pre-test and post-test calculation. RELAP5 code shows substantial difference with changing number of nodes. The increase of the number of nodes tends to reduce the condensation rate at the interface between liquid and vapor inside the hybrid SIT. The environmental heat loss also contributes to the large discrepancy between the simulation results of RELAP5 and the experimental data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.355-361
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• 2000

In this study, active control magnetic actuator for reducing vibration of rotor system is performed. Identification, modeling, simulation, control system design, and evaluation of active magnetic damper system have been researched. Power amplifier modeling, connected magnetic actuator and augmented by system identification, is included to establish a magnetic damper simulation which provides close performance correspondence to the physical plant. A magnetic actuator, digital controller using DSP(Digital Signal Processor), and bipolar operational power supply/amplifiers are developed to show the effectiveness of reducing rotor vibration. Also the curve fitting procedure to obtain the transfer function of frequency dependent components is developed. Two kinds of test are executed as sliding and oil bearing. Results presented in this paper will provide a well-defined technical parameters in designing magnetic damper system for the proposed rotor.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.7
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• pp.406-412
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• 2013

A hybrid heat pump is under development with the goal of utilizing 120% of primary energy resources. A plate heat exchanger is added between the compressor and air-cooled condenser of an ordinary heat pump to heat water. For successful operation of the heat pump, it is necessary to develop a control algorithm under various operating conditions. As a virtual test bed for that purpose, a dynamic model has been developed, to simulate its dynamic behavior. It was modeled in transient one-dimensions, with varying phase lengths considered. The model was implemented in Matlab and Simulink. Simulation results were effectively applied to design a control algorithm. They also provided physical insight into how to design and operate the system.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.6
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• pp.635-641
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• 2011

In ultrasonic testing of dissimilar metal welds, application of phased array technique in terms of incident beam focusing is not easy because of complicated material structures formed during the multi-pass welding process. Time reversal(TR) techniques can overcome some limitations of phased array since they are self-focusing that does not depend on the geometrical and physical properties of testing components. In this paper, we test the possibility of TR focusing on a defect within anisotropic, heterogeneous austenitic welds. A commercial simulation software is employed for TR focusing and imaging of a side-drilled hole. The performance of time reversed adaptive focal law is compared with those of calculated focal laws for both anisotropic and isotropic welds.

• Journal of The Korean Society of Integrative Medicine
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• v.2 no.4
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• pp.91-100
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• 2014

Purpose : The purpose of this experiment is to find out the effectiveness which exert influence on cognitive skills by using the Driver Rehabilitation program for senior citizens who are over 65 years old and live in Busan. Method : From July first, 2014 to August 28th, 2014, we researched the 60 elderly people who are over 65 and go to community relief center which is in Busan. - 30 are experimental group and the other is control group. In the experimental group, we used Nintendo wii's driving simulation program and RC Car driving program in the model road. For estimation, we used MVPT-3(Motor-Free Visual Perception Test-3), Trail Making Test - 1, Trail making Test - 2 and LOTCA(Loewenstein Occupational Therapy Cognitive Assessment). Result : Nintendo wii's driving simulation program and RC Car driving program in model road results efficient visual perception ability. This programs results effectively in visual perception ability and space perception ability. This programs results effectively in motor apraxia ability. This programs results effectively in control ability for visual perception. This programs results effectively in thinking operation. Conclusion : Nintendo Wii's driving simulation program and RC Car driving program in model road positively influence improving for visual perceptual ability and cognitive function of elderly people. Also it is considered as being more efficient for improving visual perceptual ability and cognitive function to implement basic rehabilitation training with driving rehabilitation program than basic training itself.

• The Journal of the Korea Contents Association
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• v.10 no.5
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• pp.268-284
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• 2010

The purpose of this study was to evaluate the effects of horseback riding simulation training(HRST) on gross motor function of children with cerebral palsy. Twenty-four children with cerebral palsy participated were divided into two groups randomly. Control group and experimental group both received 30 minutes of regular neuro-rehab exercises for three times a week per twelve weeks, but experimental group received additional 15 minutes of the HRST. Gross Motor Function Measure(GMFM) was used to evaluate the changes before and after HRST. Normalized GMFM scores were compared using Mann-Whitney U test, statistical significance was set at a=.05. The results were as followings: First, in each compared before and after the experiment, the control group showed significantly increased GMFM score in dimensions A and B. The experimental group showed significant increasing in all dimensions of GMFM test. Second, the experimental group showed significant differences comparing to control group in dimensions C, D and E of GMFM test. Consequently, HRST should be considered as a therapeutic method for physical therapy for the children with cerebral palsy to improve the functional movements.