• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1566-1570
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• 2005

The aspherical lenses are used as optical lens of HMD optical system. The optimum cutting condition of PMMA lens sample with ultra precision SPDT, the diamond tool nose radius, the cutting speed, the feed rate, the depth of cut, and cutting fluid type are found. The demanded surface roughness 10 nm Ra, aspherical form error $1.0\;\mu{m}$ P-V for aspherical lens of optical data storage device are satisfied.

• Journal of the Korean Magnetic Resonance Society
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• v.12 no.2
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• pp.96-102
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• 2008

Direct quantification of methanol in polymer electrolyte membrane (PEM) by solid-state nuclear magnetic resonance (NMR) spectroscopy was studied and the methanol concentrations in PEM produced by crossover and diffusion were compared. The error range of the quantification was not smaller than ${\pm}15%$ and the amount of the methanol crossed over in our direct methanol fuel cells (DMFCs) was less than the methanol diffused to PEM. The methanol concentration in the PEM of the DMFC operated at different current densities were equivalent.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.470-475
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• 1999

Recently as the application of gear drive increases in high-speed and high-loading, the concern of designing multi-stage gear drive is being risen. Until now however, the research of gear drive is focused on single-stage gear drive and the design depends on experiences and know-how of designer and is carried out by trial and error. This research automated the basic design and the configuration design for two and three-stage gear drives which consist of cylindrical gears. In basic design, design is executed with two design processes, which minimize the overall volume of gear, and whose results are compared each other. In configuration design, the positions of gears are determined to minimize the volume of gearbox using the result of basic design and simulated annealing algorithm.

• ETRI Journal
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• v.26 no.1
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• pp.57-60
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• 2004

We propose an inductive compensation method for a surface-mountable 10 Gbps photoreceiver module. Since many typical 10 Gbps photoreceiver modules consist of a photodetector and low-noise pre-amplifier, the impedance mismatch between the photodetector and pre-amplifier, as well as package parasitics, may reduce the frequency bandwidth. In this paper, we inserted an inductive component between the photodetector and pre-amplifier in order to create frequency bandwidth expansion. From the measurement results, we have found that the proposed technique can increase the -3 dB bandwidth about 4.2 GHz wider compared with an uncompensated module. And, from a bit-error rate (BER) test, we observed -15.7 dB sensitivity at $10^{-12}$ BER. This inductive compensation can be implemented easily and is compatible with common manufacturing processes of photoreceiver modules.

• Journal of the Korean Society of Safety
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• v.27 no.4
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• pp.90-95
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• 2012

To prevent similar accidents with the basis of industrial accidents already occurred in industrial plants, it would be possible only after true causes are grasped. Unfortunately, however, most accident investigation carried out with the basis of legal regulation failed to grasp them so that similar accidents have been repeated without cease. This research aimed to find out differences between results from conventional accident investigation and those from human error analysis, and to draw out effective and practical counter-plans against industrial accidents occurred repeatedly in an autoglass manufacturing company. As for analysis, about 110 accident cases that occurred for last 7 years were collected, and by adopting the Comprehensive Human Error Analysis Technique developed by the previous researchers, not direct causes but basic fundamental causes that might induce workers to human errors were sought. In consequence, the result showed that facility factors or environmental factors such as improper layout, mistakes in engineering design, and malfunction of interlock system were authentic major accident causes as opposed to managerial factors such as personal carelessness or failure to wearing personal protective equipments, and/or improper work methods.

• The Journal of the Korea Contents Association
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• v.9 no.7
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• pp.141-148
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• 2009

Recently there have been many research efforts focused on imbalanced data classification problems, since they are pervasive but hard to be solved. Approaches to the imbalanced data problems can be categorized into data level approach using re-sampling, algorithmic level one using cost functions, and ensembles of basic classifiers for performance improvement. As an algorithmic level approach, this paper proposes to use multilayer perceptrons with higher-order error functions. The error functions intensify the training of minority class patterns and weaken the training of majority class patterns. Mammography and thyroid data-sets are used to verify the superiority of the proposed method over the other methods such as mean-squared error, two-phase, and threshold moving methods.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1911-1916
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• 2005

In this study, the basic motor control system had been investigated. The Discrete-Time Feedback Error Learning (DTFEL) method is used to control this system. This method is anologous to the original continuous-time version Feedback Error Learning(FEL) control which is proposed as a control model of cerebellum in the field of computational neuroscience. The DTFEL controller consists of two main parts, a feedforward controller part and a feedback controller part. Each part will deals with different control problems. The feedback controller deals with robustness and stability, while the feedforward controller deals with response speed. The feedforward controller, used to solve the tracking control problem, is adaptable. To make such the tracking perfect, the adaptive law is designed so that the feedforward controller becomes an inverse system of the controlled plant. The novelty of FEL method lies in its use of feedback error as a teaching signal for learning the inverse model. The PD control theory is selected to be applied in the feedback part to guarantee the stability and solve the robust stabilization problems. The simulation of each individual part and the integrated one are taken to clarify the study.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1654-1668
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• 1992

The acoustic field resulted by the radiation of sound from vibrating structure is predicted based on the sound pressure measurements. The sound pressures are measured at discreate point on the measurement plane ; Hologram. Based on these discreate measurements, the sound field away from the acoustic source is constructed based on the discreate form of Kirchhoff-Helmohltz integral equations The velocities, intensities, and pressures of arbitrary plane of interest in space are predicted and visualized The effects on the sound field reconstruction ; finite aperture effect, effect of finite sampling interval in space studied in terms of wraparound error and spatial aliasing. Numerical simulations and experimental verifications are performed to see these effects. To reduce the wraparound error, zero padding technique in space is used and the usefulness of the method is demonstrated by various examples.

• Journal of the Ergonomics Society of Korea
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• v.30 no.1
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• pp.1-8
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• 2011

While human error has been one of the main technical issues from the early era of human factors engineering, it still remains hot and somewhat vague due to the various types of the concepts and words on human errors in practice. There may be some technical limitations hindering human error prevention activities. This paper introduces the human error activities described in the papers if this issue of ESK Journal according to a few criteria proposed for more effective technical review. And two basic technical issues are discussed on the concepts, perspectives, and classifications about human errors. Each activity shows its own artifacts associated with the safety purpose and the nature of the industry. This paper also provides a set of new technical bases proposed for a more effective management of human errors by considering the dependability, representativeness, and structuredness of human errors. Additionally, this paper includes some new challenges over the current prevention-oriented activities; positive utilizations of human errors to training/education, advertisements, fun and entertainments, and nudges.

• The Journal of the Acoustical Society of Korea
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• v.22 no.5
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• pp.345-350
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• 2003

Acoustic intensity is usually estimated by the cross-spectrum of acoustic pressure at two adjacent microphones. The cross-spectrum calculated by digital Fourier transform technique will unavoidably have leakage error since the period of signal will not be usually coincident with record length. Therefore, the acoustic intensity estimated by the conventional FFT analyzer will show distorted value. In this paper, the expression of the Fourier transformed data of a harmonic signal with a single frequency is formulated when there is leakage error. The method to eliminate the effect of leakage error from the contaminated data is also proposed. Some numerical examples show the validation of the proposed method.