• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.7-14
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• 1998

Noncircular gears have been used for obtaining the modified anglualr velocity ratio between parallel axes. The elliptical gear, which is a kind of noncircular gears, makes use of ellipse as a pitch curve, and is applied for the measurement of the discharge of liquid. The applications of an elliptical gear are more advantageous than any other mechanism as like a crank-slider linkage or a cam mechanism in view of the accuracy and the reliability to transmit the prescribed motion. In this paper, acceding to the theoretical involute tooth profile, two pairs of the elliptical gears were manufactured by using CNC wire electronic discharge machine. The proper ranges of the operating pressure angle and of module not to generate under cutting are studied on the change of the eccentricity, because it is the eccentricity of the pitch curve that determines most of the characteristics of the elliptical gear and then the vibration analysis is executed for the verification of harmonious rotating.

• Environmental Mutagens and Carcinogens
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• v.23 no.4
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• pp.115-130
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• 2003

Idiopathic Parkinson's disease (IPD) represents a common neurodegenerative disorder. While epidemiological studies have suggested a number of risk factors including age, gender, race, and inherited disorder, the cumulative evidence supports the view that environmental or occupational exposure to certain chemicals may contribute to the initiation and progress of Parkinsonism. More recently, clinical and laboratory investigations have led to the theory that dysregulation of iron, an essential metal to body function, may underlie IPD by initiating free radical reaction, diminishing the mitochondrial energy production, and provoking the oxidative cytotoxicity. The participation of iron in neuronal cell death is especially intriguing in that iron acquisition and regulation in brain are highly conservative and thus vulnerable to interference from other metals that bear the similar chemical reactivity. Manganese neurotoxicity, induced possibly by altering iron homeostasis, is such an example. In fact, the current interest in manganese neurotoxicology stems from two primary concerns: its clinical symptoms that resemble Parkinson's disease and its increased use as an antiknock agent to replace lead in gasoline. This article will commence with addressing the current understanding of iron-associated neurodegenerative damage. The major focus will then be devoted to the mechanism whereby manganese alters iron homeostasis in brain.

• BMB Reports
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• v.51 no.5
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• pp.211-218
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• 2018

Chromatin is an intelligent building block that can express either external or internal needs through structural changes. To date, three methods to change chromatin structure and regulate gene expression have been well-documented: histone modification, histone exchange, and ATP-dependent chromatin remodeling. Recently, a growing body of literature has suggested that histone tail cleavage is related to various cellular processes including stem cell differentiation, osteoclast differentiation, granulocyte differentiation, mammary gland differentiation, viral infection, aging, and yeast sporulation. Although the underlying mechanisms suggesting how histone cleavage affects gene expression in view of chromatin structure are only beginning to be understood, it is clear that this process is a novel transcriptional epigenetic mechanism involving chromatin dynamics. In this review, we describe the functional properties of the known histone tail cleavage with its proteolytic enzymes, discuss how histone cleavage impacts gene expression, and present future directions for this area of study.

• Computers and Concrete
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• v.1 no.3
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• pp.249-260
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• 2004

The stress transmission mechanism in pretensioned concrete beams, though very interesting from an economical point of view, is very complex, integrating various phenomenons such as sliding, bond, bursting. For long the complexity of this mechanism has led engineers to provide a massive rectangular anchorage zone at each end of the beam. The necessity of using such a concrete reinforcement is certainly unquestionable in post-tensioned beams. However in pretensioned elements the stresses induced in concrete in the anchorage zone are smaller than in post-tensioned elements. In this article the stress field in the end zone is calculated numerically and from this analysis the possible reduction of the cross-section of the anchorage block is examined.

• Journal of TMJ Balancing Medicine
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• v.7 no.1
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• pp.17-23
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• 2017

Functional neurology is a function-oriented clinical neurology with a focus on the viability, functionality, and balance of the neurologic system, which may be considered as a form of yin-yang balance medicine like Korean medicine. While it incorporates knowledge systems such as developmental neurology, neuropsychology, comparative neuroanatomy, and others, it views the neurologic system and the body as an individually different, self-regulating mechanism with the help of the active balancing mechanism within the nervous system and between the individual and the environment, which view is at the core of its effort to improve and serve the human dignity based on the best possible functioning nervous system. This article reviews core concepts of the functional neurology, discusses yin-yang balance medicine perspectives and clinical applications of it.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.15-19
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• 2002

To provide a specified power quality under electric market system is becoming an important issue for customers and utility company. However, there is no realistic infra-structure to design a power system for the specified power quality. Present electric market is operating under the economic point of view. The low price could be attractive. but the effect of low price and low power quality for the long time should be considered for the system safety. This paper presents a model which conceptualize the dynamic power quality control mechanism to minimize total cost of a society which is affected electric power quality. This model aims to produce a basic infra-structure to balance cost and quality under the electric market system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.04a
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• pp.158-165
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• 1991

DC servo motors have small torques compared to their weight. In order to reduce the speed and increase the output torque of the DC motor, a gear box is commonly used. The use of a gearbox, however, imposes limitations onmany applications because of the backlash and the reduction in transmission efficiency. Furthemore, the elastic deformation or the compliance of the gearbox decreases the accuracy of the servo mechanism and the stability of the system. In view of the many disadvantages in using the gearbox, a more effective solution has to be found. The solution is the direct drive mechanism. There are many kinds of direct drive motors. I will consider the ultrasonic motor in particular.

• Korean System Dynamics Review
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• v.11 no.1
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• pp.5-26
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• 2010

To revitalize the trucking market, many studies are being done but it still has a lot of problems such as imbalance between supply and demand, poor profit structure of truck owners, ect. Therefore, it aims to study what kinds of prerequisite are needed to solve these problems through analyzing system structure and mechanism of the market. To achieve it, System Dynamics methodology, appropriate to make a simulation model and analyze dynamics of the system, is utilized. To obtain an empirical research point of view, time series data related on trucking market-provided by The Korea Transport Institute-are used. In addition, interview with a local representative logistics company and a ICD(Inland Container Depot) operation company is performed to find out technical and functional supporting factors to solve the existing problems in the market.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2646-2648
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• 2002

This paper deals with a comparative evaluation of the reliability of control rod drive mechanisms including their driving methods for nuclear power plants. Basically there exist two types of electromagnetic-jack-type drive mechanisms in commercial use that are called as Control Rod Drive Mechanism and Control Element Drive Mechanism. Each type has corresponding drive sequence to make the movements of insertion and withdrawal. A state-space model is derived for each model graphically. Then the evaluation of the reliability is carried out on the programming tool called SHARPE. The evaluation does not give any meaningful numerical values for the reliability but just shows a relative degree to each other in view of reliability.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.2
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• pp.104-108
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• 2015

Al thin films were deposited on TiN/Si(100) via metal-organic chemical vapor deposition using N-methylpyrrolidine alane as a precursor. Characterization of the deposited films were investigated with SEM, XRD, ${\alpha}$-step, AFM, 4-point probe. The early stage of Al thin film deposition was analyzed by in-situ surface reflectance measurement with laser and photometer apparatus. The surface reflectance were changed greatly during the initial 30~40 seconds. There were two increases and two decreases in the surface reflectance, thus the sequence of Al films were deposited at 8 significant points of the surface reflectance change. Surface topograph and cross-sectional view of each film were analyzed with SEM. Al films were grown in the complex mechanism of Volmer-Weber and Stranski-Krastanov process.