• Transactions of the Society of Information Storage Systems
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• v.1 no.1
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• pp.58-66
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• 2005

Pseudo-Near Field Recording (Pseudo-NFR) system is proposed to prevent contamination and oxidation of media surface occurred in conventional NFR systems. To solve these critical problems of the NFR systems, we investigate the optimal thickness of cover layer for Pseudo NFR. This paper presents the theoretical analysis for cover layer thickness based on the measured length of dust particle and numerical simulation for the temperature distribution using Finite Difference Time Domain (FDTD) method and heat conduction equation. To verify the simulation results, we conduct and compare simulation results in case of far field MO recording and near field MO recording. A measured dust particle length in general environment was mostly less than $20{\mu}m$, and the optimal thickness of cover layer is $30{\mu}m$ in this case. Based on the designed optimal cover layer thickness, temperature distribution is simulated to have $800{\~}850^{\circ}C$.

• The Korean Journal of Community Living Science
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• v.21 no.4
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• pp.517-528
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• 2010

The number of young children who attend daycare center, preschool or kindergarten and are taken care of by teachers during a day has skyrocketed in Korea. The purpose of this study was to analyze the contents of the research on infant/child-teacher attachment in Korea. Thirty five studies (5 doctoral dissertations, 24 masters' theses, and 6 academic journal articles) published from 1993 to 2010 were analyzed in the matter of the publication period, the related variables, and methodology for analyzing the data. The findings are as follows: 1) More than two-thirds of the research were from masters' theses. The number of studies conducted in the late 2000s doubled compared to that in the 1990s. 2) Each study on infant/child-teacher attachment had at least one related variable regarding social, emotional, cognitive or physical development, but not language. The studies on infant/child-teacher attachment related to social development have rapidly increased in the late 2000s. 3) The majority of studies were conducted using quantitative analyses and Attachment Q-set version 3.0. Difference analysis and relational analysis were most frequently used in many studies. There was only one study which was analysed with the advanced statistical methodology. The implication for a future study was also discussed.

• The Journal of Korean Physical Therapy
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• v.32 no.4
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• pp.245-249
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• 2020

Purpose: This study examined the effects of local vibration using a massage gun on the triceps surae flexibility by measuring the ankle dorsiflexion range of motion (ROM) compared to static stretching in healthy adults. Methods: Twenty healthy subjects were instructed in this study. They were allocated randomly to two groups: local vibration (LV) and static stretching (SS). The ankle dorsiflexion ROM was measured before and after the intervention in supine (open kinetic chain, OKC) and standing (closed kinetic chain, CKC). The LV group received local vibration using a massage gun for five minutes on their triceps surae, and the SS group stood on the Q board with a dorsiflexed ankle for five minutes. The ROM between pre- and post-intervention and the change in ROM between two groups were analyzed. A paired t-test was used to compare the ROM between pre- and post-intervention, while an independent t-test was used to compare the change in ROM between the two groups. Results: Both groups showed a significant difference between pre- and post-intervention in the position of both the OKC and CKC. The change in ROM, however, was not significantly different between the two groups. Conclusion: The application of local vibration using a massage gun for five minutes on the triceps surae could improve its flexibility as much as the application of static stretching. A massage gun for the application of a local vibration stimulus may be effective, simple, portable, and comfortable.

• Journal of the Korean Chemical Society
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• v.11 no.4
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• pp.159-164
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• 1967

An exact expression of the titration fraction as a function of the potential is derived for the cases where the coefficients of the both half reactions involved in the titration are homogeneous. It shows that the potential is independent of the concentration of the reagents not only at the equivalence point but also at all titration fractions. The sharpness of the end point detection by potentiometric method is shown to depend not only on the difference of the normal potentials involved but also strongly on the number of electrons transferred in each half reaction. The inflexion point of the potentiometric titration curve is shown to be slightly off from the equivalence point, including the cases where the number of electrons involved are equal. Completeness of the reaction in the course of titration is analyzed, too, mostly in terms of equilibrium constant, thus most of the results are applicable to any type of equilibrium in a single phase with particular relationship of coefficients of chemical equation.

• Transactions of Materials Processing
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• v.3 no.4
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• pp.427-439
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• 1994

The high temperature deformation behavior of $SiC_p/Al-Si$ composites and Al-Si matrix was studied by hot torsion test in a range of temperature from $270^{\circ}C$ to $520^{\circ}C$ and at strain rate range of $1.2{\times}10_{-3}~2.16{\times}10_{-1}/sec$. The hot restoration mechanisms for both matrix and composites were found to be dynamic recrystallization(DRX) from the investigation of flow curves and microstructural evolutions. The Si precipitates and SiC particles promoted DRX, and the peak strain$({\varepsilon}_p)$ of the composites was smaller than that of the matrix. Flow stresses of $SiC_p/Al-Si$ composites were found to be generally higher than the matrix, but the difference was quite small at higher temperature due to the decrease of capability of load transfer by SiC particles. With increasing temperature, failure strain of matrix and composites are inclined to increase, the increasing value of failure strain for the $SiC_p/Al-Si$ composites was small compared to that of matrix. The stress dependence of both materials on strain rate() and temperature(T) was examined by hyperbolic sine law, $\.{\varepsilon}=A_1[sinh({\alpha}{\cdot}{\sigma})]_n$exp(-Q/RT)

• Journal of the Korean Chemical Society
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• v.9 no.4
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• pp.174-178
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• 1965

p-Phenylenediamine dihydrobromide and p-phenylenediamine dihydrochloride are found to be isomorphous. p-Phenylenediamine dihydrobromide is triclinic with lattice parameters, $a=4.52{\pm}0.02{\AA}\;b=6.13{\pm}0.02{\AA},c=8.88{\pm}0.03{\AA},\;{\alpha}=111{\pm}1^{\circ},\;{\beta}=97{\pm}1^{\circ},\;{\gamma}=101{\pm}1^{\circ}.$ It belongs to space group $P\bar{1}$, and there is one molecule in the unit cell. The crystal structure is determined according to the method of Fourier synthesis from the electron density projections in three principal crystallographic axes. The crystal structure, thus determined is refined by the method of two-dimensional difference Fourier synthesis.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.577-584
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• 2002

We have employed two methods to remove slime at the end of the sampler in clay layers. The first method is a sampling process that harnesses low pressure to clean up the ground around the sampler tip. The second method, in consideration of a disturbed layer, involves a technique of inserting the sampler 50 cm deep into the ground before cleaning up the verge of the sampler by using high pressure. Physical and mechanical properties of these two methods have been compared and analyzed to investigate how different sampling methods affect degree of disturbance. The first method shows little disturbance since the unconfined compression test results in quite greater E$\_$50//q$\_$u/ in the first method than in the second method. On the other hand, the consolidation test results in a slightly greater compression index in the second method than in the first method, when their indexes are compared in the same depth. This suggests that the second method demonstrates less disturbance than the first method does. It is assumed that the second method may reduce disturbance slightly, However, we suspect that choosing any of the two methods would not obtain a considerable difference in sampling.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.7
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• pp.615-620
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• 2015

DOB (Disturbance Observer) is an useful control method for estimating the disturbance applied to dynamic systems. Disturbance observer can be used to implement a robust control system to generate a control input for rejecting the disturbance, and it can be also used to estimate the disturbance to obtain information. The system that uses disturbance estimation is investigated for high performance control such as automatic door systems, walking robot and electric power steering system in vehicles. In this paper, a novel disturbance observer which is called disturbance and current observer for estimating load torque in the motor system is proposed. The difference between the DOB for disturbance rejection and DCOB is mathematically verified. Current and angular velocity are required for estimating the load torque of the motor in DOB. However, the DCOB can estimate load torque and current without current sensor. DCOB is designed based on modeling of the motor system. Appropriate Q-filter is selected and the applicability of DCOB is verified by simulation. The estimated disturbance and current of the electric motor can be verified without current sensor, as experiments of the actual motor system.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.2
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• pp.148-154
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• 2009

In this paper, an embedded Kalman filter for a time-delayed controller is designed on an FPGA to estimate accelerations of the robot arm. When the time-delayed controller is used as a controller, the inertia estimation along with accelerations is needed to form the control law. Although the time-delayed controller is known to be robust to cancel out uncertainties in the nonlinear systems, performances are very much dependent upon estimating the acceleration term ${\ddot{q}}(t-{\lambda})$ along with inertia estimation ${\hat{D}}(t-{\lambda})$. Estimating accelerations using the finite difference method is quite simple, but the accuracy of estimation is poor specially when the robot moves slowly. To estimate accelerations more accurately, various filters such as the least square fit filter and the Kalman filter are introduced and implemented on an FPGA chip. Experimental studies of following the desired trajectory are conducted to show the performance of the controller. Performances of different filters are investigated experimentally and compared.

• The Korean Journal of Emergency Medical Services
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• v.21 no.1
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• pp.17-44
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• 2017

Purpose: This study aimed to identify the effects of cardiopulmonary resuscitation (CPR) training using a meta-analysis by effect size. Methods: The effect sizes for each variable and the overall effect size for the collected data were identified. The homogeneity verification of the effect size and the difference among the average effect sizes for each mediation variable were determined. Results: The overall average effect size for CPR training was 1.747. Homogeneity verification of the overall effect size was a Q-value of 3716.962, which was statistically significant (p=.000) when${\alpha}=.05$. CPR training showed statistically significant differences depending on age (p=.002), sex (p=.006), number of trainees (p=.000), research design (p=.000), training method (p=.027), and practical training tools (p=.000). Conclusion: CPR training can effectively improve knowledge, skills, and attitudes about CPR. The results of this meta-analysis contribute to the development of more effective educational guidelines for future CPR training and the advancement of the CPR education field.