• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.9
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• pp.960-966
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• 2007

High-efficient machining, which means to machine a part in the least amount of time, is the most effective tool to improve productivity. In this study, a new feed optimization method based on virtual manufacturing was proposed to realize the high-efficient machining in turning process through the cutting power regulation. The cutting area was evaluated by using the Boolean intersection operation between the cutting tool and workpiece. And the cutting force and power were predicted from the cutting parameters such as feed, depth of cut, spindle speed, specific cutting force, and so on. Especially, the reliability of the proposed optimization method was validated by comparing the predicted and measured cutting forces. The simulation results showed that the proposed optimization method could effectively enhance the productivity in turning process.

• IEMEK Journal of Embedded Systems and Applications
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• v.3 no.3
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• pp.151-157
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• 2008

In this paper, we propose a three dimensional distance measurement method for a stereo system by using web cams. Using a parallel stereo system, a robot gets two images from each webcam and equalize brightness of both images. And we suggest an image processing method such as labeling, isolating an object from background and finding center of an object. We also propose a method of calculating the focal distance by using least square algorithm based on triangulation and we can reduce calculation error by this method. From experimental results, we show that the proposed method can be effective for 3D distance measurement.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.459-463
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• 2003

Waveform inversion requires extracting a reliable low frequency content of seismic data for estimating of the low wave number velocity model. The low frequency content of the seismic data is usually discarded or neglected because of the band-limited response of the source and the receivers. In this study, however small the spectral of the low frequency seismic data is, we assume that it is possible to extract a reliable phase information of the low frequency from the seismic data and use it in waveform inversion. To this end, we exploit the frequency domain finite element modeling and source-receiver reciprocity to calculate the $Frech\`{e}t$ derivative of the phase of the seismic data with respect to the earth model parameter such as velocity, and then apply a damped least squares method to invert the phase of the seismic data. Through numerical example, we will attempt to demonstrate the feasibility of our method in estimating the correct velocity model for prestack depth migration.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.93-96
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• 2004

A turbo-fan for the 4-way cassette indoor units of air-conditioners has been investigated. The main purpose of this investigation is the reduction of the turbo-fan noise. In order to reduce the noise level, many design parameters of turbo-fans such as blade section, blade thickness, geometry of blade leading edge, blade width, blade angle and bellmouth depth have been studied. With the experimental data of these parameters, a new turbo-fan was made for our system. The noise level of the new system was at least 3 dB(A) lower than that of the current in use.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.159-163
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• 2004

The KNR(Korean National Railroad) has a speed limit regulation(130km/h) for the train passing the turnout to guarantee a safety. Since that speed is set as below the maximum commercial speed(140km/h), it has been regarded as a major factor to obstacle the total efficiency. The crossing rail part of the turnout system is formed into a antisymmetric, furthermore, there are several discontinuous part. Thus, measuring the strain signals of this part is impossible actually and it must be in the most difficult work related the turnout research. In this research, the program that can anticipate the signals at the various conditions with considering its own shape was developed and the preciousness of its results had been examined by comparing analyzed and measured ones at the other parts. The simulation was performed with varying the factors such as train speed and contact depth. As a results, it was proved that the regulation was not useless and very important guide at least up to now.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.3 s.258
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• pp.313-321
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• 2007

In this work, the prior indentation theory for a bulk material is extended to an indentation theory for evaluation of thin-film material properties. We first select the optimal data acquisition location, where the strain gradient is the least and the effect of friction is negligible. A new numerical approach to the thin-film indentation technique is then proposed by examining the finite element solutions at the optimal point. With this new approach, from the load-depth curve, we obtain the values of Young's modulus, yield strength, strain-hardening exponent. The average errors of those values are less than 3, 5, 8% respectively.

• Journal of Korean Academy of Nursing
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• v.46 no.2
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• pp.215-225
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• 2016

Purpose: This study was performed to identify the meaning of life experience following suicide attempt among middle-aged men. Methods: A qualitative research design was adopted using van Manen's hermeneutic phenomenological approach. The participants were six middle-aged men who had attempted suicide at least one time. Data were collected in 2013 through in-depth interviews. Individual interviews were recorded; and literary, art works and phenomenological literature were searched to identify the meaning of the experience. Results: The five essential themes of the life experience of middle-aged men who attempted suicide were 'Bitter reality confronted again', 'Anger buried deep inside', 'Broken family, inescapable fetters', 'Blocked relationships, closed world' and 'A step towards a new life'. Conclusion: The meaning of lived experience found in this study provides deep insight into the experience following suicide attempt in middle-aged men and crucial information to give directions to appropriate support and nursing interventions.

• Journal of Species Research
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• v.1 no.1
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• pp.100-103
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• 2012

Nutria Myocastor coypus is one of a well known invasive riparian mammal found species around world from North America to Eurasia and Africa. In South Korea, feral nutrias inhabit areas from the Nakdonggang and Namgang (River) to their tributaries and Upo Wetland where they have had devastating effects on environment. Nevertheless, there has been little research about nutrias in Korea. This study is to analyze the genetic structure of the nutria population in the Upo Wetland and identify the origin of the source populations. Twenty individuals from the Upo Wetland were genotyped using 25 microsatellite loci. When compared with another introduced population, that of the Blackwater Nation Wildlife Refuge in U.S., the Upo population contains considerable genetic variations. Tests for Hardy-Weinberg equilibrium and Bayesian clustering analysis suggest the Upo population is genetically structured and has at least two source populations. This preliminary study presents the need for further in-depth studies about this species which should combine genetic and ecological studies.

• The Journal of Korea Robotics Society
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• v.3 no.1
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• pp.33-41
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• 2008

Based on object recognition technology, we present a new global localization method for robot navigation. For doing this, we model any indoor environment using the following visual cues with a stereo camera; view-based image features for object recognition and those 3D positions for object pose estimation. Also, we use the depth information at the horizontal centerline in image where optical axis passes through, which is similar to the data of the 2D laser range finder. Therefore, we can build a hybrid local node for a topological map that is composed of an indoor environment metric map and an object location map. Based on such modeling, we suggest a coarse-to-fine strategy for estimating the global localization of a mobile robot. The coarse pose is obtained by means of object recognition and SVD based least-squares fitting, and then its refined pose is estimated with a particle filtering algorithm. With real experiments, we show that the proposed method can be an effective vision- based global localization algorithm.

• International Journal of Precision Engineering and Manufacturing
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• v.5 no.4
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• pp.43-49
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• 2004

A spring-actuated linkage system is used to satisfy the desired opening and closing characteristics of the electric contacts of a vacuum circuit breaker. If the type of a circuit breaker and the structure of the linkage system are predetermined, then design parameters such as stiffness, free length and attachment points of the spring become the important issues. In this paper, based on the energy conservation, the total system energy is constant throughout the operating range of the mechanism; a systematic procedure to optimize the spring design parameters is developed and applied to a simplified mechanism of a circuit breaker. The developed procedure is converted to the environment of the multi-body dynamics program, ADAMS for an in-depth consideration of the complex dynamics of a circuit breaker mechanism.