• Journal of Biomedical Engineering Research
• /
• v.30 no.6
• /
• pp.521-528
• /
• 2009

This study is about to evaluation of postural stability according to characteristics of electrical stimulation on the ankle muscles. We measured body sway(center of pressure, COP) when various parameters of electrical stimulation was applied to ankle muscles in stable and unstable posture. Subjects consisted of 10 young adults, and electrical stimulation was delivered on right and left of tibialis anterior and Achilles tendon. The body sway was measured during electrical stimulation of three duty cycle and frequencies in stable posture and three amplitudes of sensory threshold in unstable posture. Consequently, the COP Shift is higher during electrical stimulation of 1/30(duty ratio) and 100Hz(frequency) in stable posture. In unstable posture, 100% amplitude of sensory threshold induced postural stability. These findings are important for the rehabilitation system of postural stability and the use of electrical stimulation as somatosensory information.

• Journal of Chest Surgery
• /
• v.27 no.3
• /
• pp.191-195
• /
• 1994

Twenty-four patients with left main coronary artery stenosis exceeding 50% underwent coronary artery bypass grafting from January 1991 through June 1993. Four patients [17%] had stenosis only in left main coronary artery and 20 patients [83%] had associate lesion[s] in left anterior descending , circumflex, or right coronary artery. Sixteen patients [67%] had higher degrees of stenosis [>70%] in left main coronary artery. Preoperatively 18 patients [75%] had unstable angina pectoris even during aggressive medical treatment. Preoperatively aggressive medical treatment was performed to relieve the symptom in patients with unstable angina. All patients were perioperatively treated with continuous infusion of isosorbide dinitrate to stabilize symptomatic and hemodynamic states. Twenty patients underwent elective coronary bypass surgery and 4 patients urgent operations due to severe unstable angina. There was no thirty-day mortality or late death. Angina recurred in 1 patient, but coronary angiographic study showed good patency of grafts and the symptom was relieved with medical treatment. We concluded that coronary artery bypass grafting can be safely performed by perioperative efforts, including continuous infusion of isosorbide dinitrate, for hemodynamic stabilization in patients with left main coronary artery stenosis.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.3 no.1
• /
• pp.53-64
• /
• 2011

The present study considers multi-level approach for the analysis of parametric roll phenomena. Three kinds of computation method, GM variation, impulse response function (IRF), and Rankine panel method, are applied for the multi-level approach. IRF and Rankine panel method are based on the weakly nonlinear formulation which includes nonlinear Froude-Krylov and restoring forces. In the computation result of parametric roll occurrence test in regular waves, IRF and Rankine panel method show similar tendency. Although the GM variation approach predicts the occurrence of parametric roll at twice roll natural frequency, its frequency criteria shows a little difference. Nonlinear roll motion in bichromatic wave is also considered in this study. To prove the unstable roll motion in bichromatic waves, theoretical and numerical approaches are applied. The occurrence of parametric roll is theoretically examined by introducing the quasi-periodic Mathieu equation. Instability criteria are well predicted from stability analysis in theoretical approach. From the Fourier analysis, it has been verified that difference-frequency effects create the unstable roll motion. The occurrence of unstable roll motion in bichromatic wave is also observed in the experiment.

• Journal of the Korean Chemical Society
• /
• v.6 no.1
• /
• pp.77-83
• /
• 1962

The solubilities of hydrogen bromide and methyl bromide in nitrobenzene and in 1,2,4-trichlorobenzene have been measured in the presence and absence of gallium bromide. When gallium bromide does not exist in the system, the solubilities of HBr and MeBr in nitrobenzene are greater than in 1,2,4-trichlorobenzene, indicating the greater basicity of nitrobenzene than 1,2,4-trichlorobenzene. When there exists gallium bromide in the system, the addition compounds, GaBr3·HBr and GaBr3·CH3Br, have been found to exist in solution. The addition compound of GaBr3·HBr is stable in nitrobenzene but unstable in 1,2,4-trichlorobenzene. On the other hand the addition compound of $GaBr_3{\cdot}CH_3Br$ is unstable in both solvents. All of these unstable addition compounds dissociate into components to large extents according to one of the following equilibria or both: $$GaBr_3{\cdot}RBr{\leftrightarrows}GaBr_3+RBr\;GaBr_3{\cdot}RBr{\leftrightarrows}1}2\;Ga_2Br_6+RBr$.$ where R denotes either hydrogen atom or methyl group.

• Journal of Fisheries and Marine Sciences Education
• /
• v.28 no.5
• /
• pp.1395-1406
• /
• 2016

The purpose of this study was to examine the effects of interaction based mother-child art therapy on the change of child and mother's interactions in a child who was in trouble due to attachment problems. The subject in this study was a six-year-old child who faced difficulties in peer relationship building and who were maladjusted to kindergarten because of unstable attachment and negative feedback from his parents. Also, he showed serious problem behaviors at home. The ABA design was adopted among single-subject research designs, and the Target child was observed in the sessions in terms of the subfactors of Marschak's Behavioral Rating Scale to gather data related to the changes of child and mother's interactions. As a result of analyzing the collected data, there were positive changes in all the subfactors that were the child's verbal/nonverbal interactions, the mother's verbal/nonverbal interactions and mother-child interactions. Therefore the interaction based mother-child art therapy that was designed to boost child and mother's interactions was effective at furthering the mother-child interactions of the child with attachment problems.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.33 no.1
• /
• pp.33-40
• /
• 2010

Because sampling interval for data collection tends to be short compared with the overall processing time, in chemical process, instrumental process related tanks or furnace collected data have a significant autocorrelation. Insufficient control technique and frequent control actions cause unstable condition of the process. Traditional control charts which were developed based on iid (independently and identically distributed) among data cannot be applied on the existence of autocorrelation. Also unstable process is difficult to identity or diagnose. Because large-scale process has a lot of measurable variables and multi-step-structures among data, it is difficult to find relation between measurable variables and nonconformity. In this paper, we suggested an appicable model to diagnose the process and to find relation between measurable variables (CTQ) and nonconformity in the process having autocorrelation, unstable condition frequently, a lot of measurable variables, and multi-step-structure. And we applied this model to real process, to verify that the process engineers could easily and effectively diagnose the process and control the nonconformity.

• Journal of the Korean Society for Railway
• /
• v.16 no.4
• /
• pp.253-261
• /
• 2013

According to the measured results of KTX brake squeal noise in this study, high level brake noise occurred in a wide frequency range, 100~18,000Hz. To identify the sources of the brake squeal noise, unstable vibration modes due to brake disc/pad interaction were analyzed under various conditions by the finite element method. Complex eigenvalues for a brake unit with a disc and four pads were obtained. It was found that the real parts of the complex eigenvalues, that is, unstable vibration modes, were closely related to friction coefficients, pressure on the brake cylinders, elastic moduli of the components, and other conditions.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.13 no.3
• /
• pp.373-384
• /
• 1989

The motions of a spinning rotor and a fluid enclosed in its cavity are known to have mutual interactions, which change the frequencies of forced vibrations and cause instabilities. These phenomena are of technical importance for fluid-cooled turbines as well as spin-stabilized satellites or rockets containing liquid fuels. In this paper the characteristics of unstable whirling of a rotor containing a partitioned cavity filled with two kinds of liquids are investigated experimentally. It studies the influence of rotational speed and filling ratio of two kinds of liquids on unstable whiring. As a result, it is found that the whirl velocity is approximately equal to, or slightly lower for large masses of trapped fluid than rotor critical speed. In case of a spinning rotor partially filled with two kinds of liquids the boundary surface plays a similar role to the free surface, and cases unstable forward whirl.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.2 no.2
• /
• pp.99-109
• /
• 1999

This paper is concerned with instability of flow fields which are dominated by the entropy mode with the presence of usual acoustic and vortical modes. These combined modes lead to nonlinear unstable waves which may occur in automobile, aircraft, or rocket engines. In this study instability in a side-burning rocket is investigated. It is shown that the energy growth rate parameters increase with an increase of the energy growth factor. The energy growth rate parameters for turbulent flows are larger than those for laminar flows. It is further shown that unstable wave motions for the high-temperature side-burning rocket are dictated mostly by the entropy mode, somewhat by the vortical mode, and least by the acoustic mode.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.4
• /
• pp.567-575
• /
• 2008

Transient security assessment(TSA) is becoming an essential requirement not only for security monitoring but also for stabilizing control of power systems under new electricity environments. It has already been pointed out that fast transient stability study is an important part for monitoring and controlling system security. In this paper, we discuss an energy function method for stabilizing control of transiently unstable systems by introducing generator tripping system to enhance the transient stability of power systems. The stabilization with less tripped power can be obtained by tripping the generators faster than out-of-synchronism relay. Fast transient stability assessment based on the state estimation and direct transient energy function method is an important part of the stabilizing scheme. It is possible to stabilize the transiently unstable system by tripping less generators before the action of out-of-synchronism relay, especially when a group of generator are going to be out-of-synchronism. Moreover, the amount of generator output needed for tripping can be decided by Transient Energy Function(TEF) method. The main contribution of this paper is on the stabilizing scheme which can be running in the Wide Area Control System.