• Structural Engineering and Mechanics
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• v.75 no.6
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• pp.747-769
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• 2020

This paper provides a semi-analytical approach to investigate the variations of 3D displacement components, electric potential, stresses, electric displacements and transverse vibration frequencies in laminated piezoelectric composite plates based on the scaled boundary finite element method (SBFEM) and the precise integration algorithm (PIA). The proposed approach can analyze the static and dynamic responses of multilayered piezoelectric plates with any number of laminae, various geometrical shapes, boundary conditions, thickness-to-length ratios and stacking sequences. Only a longitudinal surface of the plate is discretized into 2D elements, which helps to improve the computational efficiency. Comparing with plate theories and other numerical methods, only three displacement components and the electric potential are set as the basic unknown variables and can be represented analytically through the transverse direction. The whole derivation is built upon the three dimensional key equations of elasticity for the piezoelectric materials and no assumptions on the plate kinematics have been taken. By virtue of the equilibrium equations, the constitutive relations and the introduced set of scaled boundary coordinates, three-dimensional governing partial differential equations are converted into the second order ordinary differential matrix equation. Furthermore, aided by the introduced internal nodal force, a first order ordinary differential equation is obtained with its general solution in the form of a matrix exponent. To further improve the accuracy of the matrix exponent in the SBFEM, the PIA is employed to make sure any desired accuracy of the mechanical and electric variables. By virtue of the kinetic energy technique, the global mass matrix of the composite plates constituted by piezoelectric laminae is constructed for the first time based on the SBFEM. Finally, comparisons with the exact solutions and available results are made to confirm the accuracy and effectiveness of the developed methodology. What's more, the effect of boundary conditions, thickness-to-length ratios and stacking sequences of laminae on the distributions of natural frequencies, mechanical and electric fields in laminated piezoelectric composite plates is evaluated.

• Investigative Magnetic Resonance Imaging
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• v.14 no.2
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• pp.87-94
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• 2010

Purpose : To calculate the appearance of the image distortion from metallic artifacts and to determine the location of a metallic needle from a distorted MR image. Materials and Methods : To examine metal artifacts, an infinite metal cylinder in a strong magnetic field are assumed. The cylinder’s axis leaned toward the magnetic field along some arbitrary angle. The Laplace equation for this situation was solved to investigate the magnetic field distortion, and the simulation was performed to evaluation the image artifact caused by both readout and slice-selection gradient field. Using the result of the calculation, the exact locations of the metal cylinder were calculated from acquired images. Results : The distances between the center and the folded point are measured from images and calculated. Percentage errors between the measured and calculated distance were less than 5%, except for one case. Conclusion : The simulation was successfully performed when the metal cylinder was skewed at an arbitrary tilted angle relative to the main magnetic field. This method will make it possible to monitor and guide both biopsy and surgery with real time MRI.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.187-194
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• 1991

Vibration analysis methods of a beam-column with elastically restrained ends and various intermediate constraints such as rectilinear springs, rotational springs and concentrated masses are presented. Firstly, an exact method of solutions based on Hamilton's principle and Laplace transform method is shown. This method of solutions is very complicate in cases of having Intermediate constraints more than two. Therefore, Rayleigh-Ritz method using the eigenfunctions of the base system, the system without intermediate constraints, are also investigated. Extensive numerical examples carried out for comparisons with known published works show that the latter method has easy adaptability for wide varieties of boundary conditions and intermediate constraints, and gloves good accuracy for various intermediate constraints with reasonable number of terms in construction of a trial function.

• Journal of Acupuncture Research
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• v.30 no.3
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• pp.135-140
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• 2013

Objectives : The purpose of this study is to investigate the repeatability and reproducibility of the Ryodoraku acupuncture device. For such device to be accepted as a good apparatus for clinical diagnosis, the score it provides should be stable no matter who measure it or when it is measured, assuming all other conditions equal. Materials and Methods : Three oriental medical doctors who were well trained and fully aware of the usage of the Ryodoraku acupuncture device examined ten randomly selected patients three times. Each doctor measured the Ryodoraku scores three times from each of the 10 selected patients. Three doctors were involved in this experiment to investigate the reproducibility and each of them measured the Ryodoraku scores three times from each patient to investigate the repeatability. Data was analyzed with Friedman test, Spearman correlation test, and intra-class correlation coefficient(ICC) in SPSS ver. 18. Results : 1. The Friedman test showed that there is no statistically significant difference between the 1st, 2nd and 3rd Ryodoraku scores measured by the same examiner. It indicates that the Ryodoraku acupuncture device provides the repeatability. 2. Spearman correlation test confirmed the results obtained by the Fiedman test by showing that there exists a strong positive correlation between the three Ryodoraku scores measured by the same examiner. 3. A very high ICC among the three examiner assured that the Ryodoraku acupuncture device achieves the reproducibility. Conclusions : The Ryodoraku acupuncture device achieves the repeatability and reproducibility. However, we still recommend that a doctor trained to a certain level use the Device to carry out the diagnosis. Also, to improve the device in terms of Reproducibility even more, it should be considered to provide a manual for the exact usage.

• Journal of Korean Academy of Nursing
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• v.39 no.1
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• pp.145-156
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• 2009

Purpose: This study was done to develop a school-based anger management program (SAMP) of 4 sessions and examine its effects on the anger, anger expression, psychosomatic responses, psychosocial responses, and immunologic responses in adolescents. Methods: A quasi-experimental study using a nonequivalent control group, pre-post design with repeated measures was used. Chi-square test, t-test, paired t-test, and Fisher's exact test were used to analyze the data. Results: There were no differences between the experimental and control groups in outcome variables except for lymphocytes. However, following additional analyses, statistically significant differences by time point were observed for pain sensitivity, T cell, Helper T (Th) cell, Suppressor (Ts) cell and Natural Killer (NK) cell post-treatment, entrapment and psychosomatic symptoms at the 4-week follow-up, and resilience at the 10-week follow-up for the experimental group. Conclusion: Although some modifications in contents and administration will be required to increase the effectiveness of the program for anger management, SAMP can be used to promote anger management ability in adolescents.

• Journal of Korean Academy of Nursing
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• v.48 no.2
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• pp.182-194
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• 2018

Purpose: This study aimed to estimate the effects of a health mentoring program on fasting blood sugar, total cholesterol, triglyceride, physical activity, self care behavior and social support changes among community-dwelling vulnerable elderly individuals with diabetes. Methods: A non-equivalent control group pre-post-test design was used. Participants were 70 community-dwelling vulnerable elderly individuals with diabetes. They were assigned to the experimental (n=30) or comparative (n=30) or control group (n=28). The experimental group participated in the health mentoring program, while the comparative group participated in health education program, the control group did not participate in any program. Data analyses involved a chi-square test, Fisher's exact test, a generalized linear model, and the Bonferroni correction, using SPSS 23.0. Results: Compared to the control group, the experimental and comparative groups showed a significant decrease in fasting blood sugar, total cholesterol, and triglyceride. Compared to the comparative and control groups, the experimental group showed significant improvement in self care behavior. However, there were no statistical differences in physical activity or social support among the three groups. Conclusion: These findings indicate that the health mentoring program is an effective intervention for community-dwelling vulnerable elderly individuals with diabetes. This program can be used as an efficient strategy for diabetes self-management within this population.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.33 no.5
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• pp.530-534
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• 2007

Nasal fractures are the most common type of facial fractures. Nowdays computed tomography is found to be very helpful in diagnosing nasal fracture, especially in findings the nasal septal fractures. From August 2004 to July 2005, 36 cases of nasal fracture were admited and reviewed to oral and maxillofacial surgery of Ulsan University Hospital, not including other facial bone fracture. Out of 223 cases of facial bone fractures, we treated 47 cases of nasal fractures. We reviewed and examined the 36 patients of nasal fractures 2months postoperative. The results were 28cases of male and 8cases of female. The highest age frequency was in the fourth decades group. The most frequent causes of injury were falling down and fist trauma. The 25(69%) patients were found to have septal fractures, after computed tomography findings. The treatment methods of nasal fracture were closed reduction(13cases), open reduction(20cases), ORIF(1case), non operation(2cases). Complications of nasal deformity were found in 2patients. Septoplasty was performed on 21 patients. Septal fractures in combination with nasal fracture are usually unrecognized and untreated at the time of injury, usually ended in nasal deformities. It is important to find out the exact type of nasal fractures. We will report the results of treatment of nasal fractures with a literature review.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.4
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• pp.86-93
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• 2011

The ship movement implies current position, wave, wind, and its other factors. We need to know exactly the location and the shape of the ship and control its motion because of these effects. In order to control the small ship according to the movement of the large ship, the position and shape of the ship should be given first. In this paper we propose the method with which we know the current status of the ship without dynamic equations of the ship. There are several methods to track the system such as optical, radio frequency, radar, camera, and infrared light. We propose the movement of the ship using the GPS absolute axis. But, the genuine error by the GPS itself and the movement of the ship cause the result of the GPS of not being accurate. This paper reduces the error of the location and the shape of the ship and gives the exact values of the ship movements even if the GPS implies some error itself.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.3
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• pp.11-19
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• 2008

Background subtraction, which separates moving objects in video sequences, is an essential technology for object recognition and tracking. However, background subtraction methods are often confused by shadow regions and this misclassification of shadow regions disturbs further processes to perceive the shapes or exact positions of moving objects. This paper proposes a method for shadow elimination which is based on shadow modeling by color information and Bayesian classification framework. Also, because of dynamic update of modeling parametres, the proposed method is able to correspond adaptively to illumination changes. Experimental results proved that the proposed method can eliminate shadow regions effectively even for circumstances with varying lighting condition.

• Nuclear Engineering and Technology
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• v.49 no.4
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• pp.710-720
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• 2017

In Korea, many nuclear power plants operate at a single site based on geographical characteristics, but the population density near the sites is higher than that in other countries. Thus, multiunit accidents are a more important consideration than in other countries and should be addressed appropriately. Currently, there are many issues related to a multiunit probabilistic safety assessment (PSA). One of them is the quantification of a multiunit PSA model. A traditional PSA uses a Boolean manipulation of the fault tree in terms of the minimal cut set. However, such methods have some limitations when rare event approximations cannot be used effectively or a very small truncation limit should be applied to identify accident sequence combinations for a multiunit site. In particular, it is well known that seismic risk in terms of core damage frequency can be overestimated because there are many events that have a high failure probability. In this study, we propose a quantification method based on a Monte Carlo approach for a multiunit PSA model. This method can consider all possible accident sequence combinations in a multiunit site and calculate a more exact value for events that have a high failure probability. An example model for six identical units at a site was also developed and quantified to confirm the applicability of the proposed method.