• The Mathematical Education
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• v.17 no.2
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• pp.33-35
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• 1979

• The Korean Journal of Pain
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• v.9 no.2
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• pp.349-353
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• 1996

Background: Although the paramedian approach for epidural blockade is useful in some clinical situation, the parameters which are correlated with the distance from skin to the epidural space has not been established. Methods: We studied in 143 patients having elective continuous epidural blocks for relief of postoperative pain. All blocks were performed using paramedian approach with Tuohy needle in the lumbar (group 1, n=100) and thoracic (group 2, n=45) area. We measured the distance from skin to the epidural space, body weight, height, and the angle between the shaft of the needle and the skin. Data were analyzed by linear regression. The relationships between parameters identified by the F-test with a P value of less than 0.05 were considered statistically significant. Results: The mean distance from skin to the lumbar epidural space was $4.4{\pm}0.7$ cm. significant correlation between the body weight and the depth of lumbar epidural space ($\gamma$ value : 0.492) was noted with regression equation of depth(cm)=2.293+0.034${\times}$body weight (kg). Also the significant correlation between the ponderal index (PI) and the depth of lumbar epidural space ($\gamma$ value : 0.539) was noted with regression equation of depth(cm)=1.703+0.07${\times}$PI, The mean distance from skin to the thoracic epidural space was $5.2{\pm}0.7cm$ which did not correlated with other anatomic measurements. Conclusion: We found that PI and body weight are the suitable predictors of the depth of the lumbar epidural space, but not the thoracic epidural space.

• Nuclear Engineering and Technology
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• v.31 no.2
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• pp.202-213
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• 1999

Effects of the rotary inertia of concentrated masses on the natural vibrations of fluid conveying pipes have been studied by theoretical modeling and computer simulation. For analysis, two boundary conditions for pipe ends, simply supported and clamped-clamped, are assumed and Galerkin's method is used for transformation of the governing equation to the eigenvalues problem and the natural frequencies and mode shapes for the system have been calculated by using the newly developed computer code. Moreover, the critical velocities related to a system instability have been investigated. The main conclusions for the present study are (1) Rotary inertia gives much change on the higher natural frequencies and mode shapes and its effect is visible when it has small value, (2) The number and location of nodes can be changed by rotary inertia, (3) By introducing rotary inertia, the second natural frequency approaches to the first as the location of the concentrated mass approaches to the midspan of the pipe, and (4) The critical fluid velocities to initiate the system unstable are unchanged by introduction of rotary inertia and the first three velocities are $\pi$, 2$\pi$, and 3$\pi$ for the simply supported pipe and 2$\pi$, 8.99, and 12.57 for the clamped-clamped pipe.

• Korean Journal of Mathematics
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• v.19 no.3
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• pp.331-342
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• 2011

We consider the multiplicity of the solutions for a class of a system of critical growth beam equations with periodic condition on t and Dirichlet boundary condition $$\{u_{tt}+u_{xxxx}=av+\frac{2{\alpha}}{{\alpha}+{\beta}}u_{+}^{{\alpha}-1}v_{+}^{\beta}+s{\phi}_{00}\;\;in\;(-\frac{\pi}{2},\;\frac{\pi}{2}){\times}R,\\u_{tt}+v_{xxxx}=bu+\frac{2{\alpha}}{{\alpha}+{\beta}}u_{+}^{\alpha}v_{+}^{{\beta}-1}+t{\phi}_{00}\;\;in\;(-\frac{\pi}{2},\;\frac{\pi}{2}){\times}R,$$ where ${\alpha}$, ${\beta}$ > 1 are real constants, $u_+=max\{u,0\}$, ${\phi}_{00}$ is the eigenfunction corresponding to the positive eigenvalue ${\lambda}_00=1$ of the eigenvalue problem $u_{tt}+u_{xxxx}={\lambda}_{mn}u$. We show that the system has a positive solution under suitable conditions on the matrix $A=\(\array{0&a\\b&0}\)$, s > 0, t > 0, and next show that the system has another solution for the same conditions on A by the linking arguments.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.799-802
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• 2004

There are many methods in controlling inverter's voltage and currents. most of all, PI control method is a general method. PI control has some merits. But, PI control has zero effect. So, steady-state response errors always exist by the zero effect. For removing the steady-state error, This paper presents the modeling, design and analysis of the double loop feedback control scheme. and computing the value of parameters and applying In the single-phase full bridge inverter for comparison and analysis between the PI control and PDFF control. The system model is employed to examine the dynamics of power circuit and select appropriate feedback variables for stable operation of the closed-loop UPS inverter system. It analyzes and proves the output characteristic of inverter system with the PDFF control.

• Journal of the Korean Mathematical Society
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• v.46 no.1
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• pp.41-49
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• 2009

Let $\zeta$ be a fixed complex number. In this paper, we study the quantity $S(\zeta,\;n):=mas_{f{\in}{\Lambda}_n}\;|f(\zeta)|$, where ${\Lambda}_n$ is the set of all real polynomials of degree at most n-1 with coefficients in the interval [0, 1]. We first show how, in principle, for any given ${\zeta}\;{\in}\;{\mathbb{C}}$ and $n\;{\in}\;{\mathbb{N}}$, the quantity S($\zeta$, n) can be calculated. Then we compute the limit $lim_{n{\rightarrow}{\infty}}\;S(\zeta,\;n)/n$ for every ${\zeta}\;{\in}\;{\mathbb{C}}$ of modulus 1. It is equal to 1/$\pi$ if $\zeta$ is not a root of unity. If $\zeta\;=\;\exp(2{\pi}ik/d)$, where $d\;{\in}\;{\mathbb{N}}$ and k $\in$ [1, d-1] is an integer satisfying gcd(k, d) = 1, then the answer depends on the parity of d. More precisely, the limit is 1, 1/(d sin($\pi$/d)) and 1/(2d sin($\pi$/2d)) for d = 1, d even and d > 1 odd, respectively.

• Proceedings of the KIEE Conference
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• 2005.10a
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• pp.136-138
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• 2005

The conventional self-tuning methods have the speed control problem of nonlinear BLDC motor which can't adapt against any kinds of noise or operation circumstances. In this paper, supposed to solve these problem to PI parameters controller algorithm using ANN. In the proposed algorithm, the parameters of the controller were adjusted to reduce by on-line system the error of the speed of BLDC motor. In this process, EBPA NN was constituted to an output error value of a BLDC motor and conspired an input and output. The performance of the self-tuning controller is compared with that of the PI controller tuned by conventional method(Z&N). The effectiveness of the proposed control method IS verified thought the Matlab Simulink.

• Journal of Korea Trade
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• v.23 no.5
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• pp.102-117
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• 2019

Purpose - This paper tried to identify the impact of electronic word of mouth (eWOM) on purchase intention (PI) of Korean-brand cars in the context of Russian consumers, taking into consideration the credibility, quality, and quantity of eWOM while also considering the mediation effects of brand image (BI) and perceived quality (PQ). Although there is a considerable number of studies discussing the impact of eWOM determinants on PI, not many studies were conducted focusing on the Russian market. Design/methodology - This paper is considered to fill this gap between eWOM and (PI) and, in order to do so, 211 Russian respondents were randomly selected. Descriptive analysis, factor, and reliability analysis were conducted using SPSS version 22.0. While structural equation modeling was conducted using AMOS version 24.0. Findings - The results display that, in terms of Russian consumers' perception, eWOM credibility, quality, and quantity for Korean-brand cars show a substantial impact on PI. The mediation effects of brand image, as well as perceived quality, were also supported by analysis. In the final part of the paper, theoretical and managerial implications alongside limitations with further research suggestions are presented. Originality/value - This study endeavored to explore the degree of impact of eWOM and mediating roles of BI and PQ on Russian customer intentions to buy Korean-brand cars.

• Macromolecular Research
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• v.17 no.9
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• pp.672-681
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• 2009

A series of inert and photo-stable Er(III)-encapsulated complexes based on ${\pi}$-extended dendritic anthracene ligands bearing G3-aryl-ether dendron ([G3-AnX]-$CO_2H$), which retain different ${\pi}$-bridging systems, such as single (X= S), double (X= D) and triple (X= T) bonds was designed and synthesized to establish the structure-property relationship. The near infrared emission intensities of Er(III)-encapsulated complexes were enhanced dramatically by increasing the ${\pi}$-conjugated extension of anthracene ligands. The time-resolved luminescence spectra show monoexponential decays with a lifetime of $2.0{\sim}2.4ms$ for $Er^{3+}$ ions in thin films, and calculated intrinsic quantum yields of $Er^{3+}$ ions are in the range of $0.025{\sim}0.03%$. As a result, all Er(III)-encapsulated dendrimer complexes exhibit the near IR emission with the following order: $Er^{3+}-[G3-AnD]_3$(terpy) > $Er^{3+}-[G3-AnS]_3$(terpy) ${\approx}$ $Er^{3+}-[G3-AnT]_3$(terpy), because $Er^{3+}-[G3-AnD]_3$(terpy) has a higher relatively spectral overlap J value and energy transfer efficiency. In addition, the lack of detectable phosphorescence and no significant spectral dependence of the ${\pi}$-extended anthracene moieties on the solvent polarity support energy transfer from their singlet state to the central $Er^{3+}$ ion taking place in $Er^{3+}-[G3-AnX]_3$(terpy).

• Journal of Digital Contents Society
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• v.19 no.2
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• pp.393-399
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• 2018

As the existing face recognition CCTV and home IOT have each individual hardware component, they have a disadvantage that the measured results of their sensors and the CCTV can not be viewed on one screen at a time. In order to overcome the above disadvantages of existing CCTV and home IOT, this paper proposes an integrated platform which constitutes the CCTV and home IOT as one hardware component using Raspberry Pi and shows each result on one screen through Smartphone application. The proposed integrated platform CCTV and home IOT system is a system which can run the application as a Smartphone and check the sensor value measured by Raspberry Pi and the picture taken through the Pi camera. The implemented system measures temperature, humidity, gas, and dust, and implements face recognition technology on a screen shot through a Pi camera, allowing it to be seen at a glance with a Smartphone.