• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.7
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• pp.409-416
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• 2004

This paper presents the selection method o( the input current wave forms for the thrust force ripple of linear pulse motor (LPM). We have developed and tested a prototype 2-phase 4-poles LPM with the permanent magnet and its control driver. To obtain the thrust performance curve of LPM, the performance curve at the air gap and the thrust are calculated and estimated by the analytical method on the base of the magnetic equivalent circuit and the finite element method. And, the thrust characteristics at the static operation state are analyzed and experimented with the respect to the input wave forms such as the rectangular, the triangular micro-step and the sine micro-step wave forms to investigate the thrust ripple and the vibration effects of LPM.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.128-129
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• 2007

We fabricated seeded $SrBi_2Ta_2O_9$(SBT) thin films using seeding technique on the $LaZrO_x$ (LZO)/Si structure. To evaluate the ferroelectric properties of seeded SBT thin films, we investigated the crystalline phase, the surface morphology, the capacitance-voltage (C-V) curve and the current density-voltage (J-V) curve of seeded films and then compared with the physical and electrical properties of unseeded films. As the result of that, the characteristics of seeded and unseeded films have a slight difference. Therefore, the ferroelectric properties of seeded SBT thin films are not necessarily superior than unseeded films.

• Journal of Magnetics
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• v.6 no.2
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• pp.61-65
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• 2001

The Hopkinson effect in the HDDR-treated $Nd_{15}Fe_{77}B_8$ allay was examined in detail by means of a thermo-magnetic analysis with low magnetic field (600 Oe). The emergence and magnitude of maximum in magnetisation in the thermomagnetic curve due to the Hopkinson effect was correlated with the grain structure and coercivity of the HDDR-treated material. The HDDR-treated materials showed a clear Hopkinson effect (maximum in magnetisation just below the Curie temperature of the $Nd_2Fe_{14}B\;$ phase) on heating. The magnitude of the magnetisation rise due to the Hopkinson effect became smaller as the recombination time increased. The magnetisation recovery at room temperature on cooling from above the Curie temperature became smaller as the recombination time increased. The HDDR-treated materials with shorter recombination time, finer grain size and higher coercivity showed larger magnetisation maximum due to the Hopkinson effect in the thermo-magnetic curve.

• Journal of Biosystems Engineering
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• v.37 no.1
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• pp.28-35
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• 2012

Purpose: This study performed the oscillatory test using the texture analyzer to characterize the viscoelastic behavior of apples such as the storage modulus (E'), the loss modulus (E"), the complex modulus (${\mid}E^*{\mid}$) and the energy dissipated per cycle ($W_{diss}$). Methods: The sinusoidal deformation with the frequency of 1-10 Hz and the maximum displacement of 0.1 mm were applied to the flesh tissues of Fuji, Golden Delicious and Red Delicious apples. The Lissajous figure was used to measure the phase angle(${\delta}$) between stress and strain curve. Results: Trigger force was critical to the measurement of the phase angle. E', E", ${\mid}E^*{\mid}$ and Wdiss were measured using the Lissajous figure and the phase angle. The complex modulus of Golden Delicious apple was significantly lower than those of Fuji apple and Red Delicious apple. Conclusions: Apple flesh was exhibiting more elasticity at low frequency, and more viscosity at high frequency. Dynamic compressive properties of Fuji apple were similar to those of Red Delicious apple but significantly different from those of Golden Delicious apple.

• BMB Reports
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• v.34 no.3
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• pp.278-283
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• 2001

Antioxidant and redox enzyme activities are known to be involved in the cellular responses to various stresses. Their variations were observed according to the growth cycle of the fission yeast Schizosaccharomyces pombe. Peroxidase activity appeared to be notably higher in the early exponential phase than in the mid-exponential and stationary phases. However, catalase activity showed a variation pattern resembling the growth curve. Glutathione S-transferase activity was higher in the early exponential and late stationary phases. Activities of the two redox enzymes, thioredoxin and thioltransferase (glutaredoxin), were high in the stationary phase. However, their activities appeared to increase from the early exponential to mid-exponential phase. Total glutathione content had a varying pattern similar to that of thioredoxin and thioltransferase. However, its content in the early exponential phase was high. These results propose that antioxidant and redox enzymes tested are also involved in the mechanism of cell growth.

• Ocean Systems Engineering
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• v.6 no.3
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• pp.217-231
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• 2016

This paper presents a new approach for underwater image analysis using the bi-dimensional empirical mode decomposition (BEMD) technique and the phase congruency information. The BEMD algorithm, fully unsupervised, it is mainly applied to texture extraction and image filtering, which are widely recognized as a difficult and challenging machine vision problem. The phase information is the very stability feature of image. Recent developments in analysis methods on the phase congruency information have received large attention by the image researchers. In this paper, the proposed method is called the EP model that inherits the advantages of the first two algorithms, so this model is suitable for processing underwater image. Moreover, the receiver operating characteristic (ROC) curve is presented in this paper to solve the problem that the threshold is greatly affected by personal experience when underwater image edge detection is performed using the EP model. The EP images are computed using combinations of the Canny detector parameters, and the binaryzation image results are generated accordingly. The ideal EP edge feature extractive maps are estimated using correspondence threshold which is optimized by ROC analysis. The experimental results show that the proposed algorithm is able to avoid the operation error caused by manual setting of the detection threshold, and to adaptively set the image feature detection threshold. The proposed method has been proved to be accuracy and effectiveness by the underwater image processing examples.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.79-84
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• 1996

Small punch test was performed on CF8 duplex stainless steel aged at 370 and 400$^{\circ}C$ up to 5,000 h to evaluate the degree of the thermal aging embrittlement. At room temperature, the SP load-displacement curve was in a similar shape to those of ferritic steels and had a good reproducibility in spite of two-phase structure. The aging heat treatment resulted in a slight increase of the yield strength. As test temperature was lowered, the SP load showed a sudden drop followed by serrations before the SP specimen was fractured, resulting from the cracking of ferrite phase. The extent of thermal embrittlement was assessed in terms of the SP energy. Aging treatment at higher temperature led to a larger shift in the transition temperature and the corresponding change in the fracture mode. The main cause of the degradation was the embrittlement of ferrite phase. Additionally the phase boundary separation profoundly contributed to the degradation of the specimen aged at 400$^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.1
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• pp.47-53
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• 2001

As the technology has developed and new materials have been produced, it is important to measure the thermal diffusivity of material and to predict the heat transfer in the solid subject to thermal processes. This measurement can be done in a non-contact way using photothermal displacenent spectroscopy. In this study, photothermal displacement method was used to measure the thermal diffusivity quantitatively. The specimens used in this study were the pure materials. The Ar-ion laser was used as an energy source and the periodical deformation induced by this pump laser was detected by the He-Ne laser. The magnitude and the phase angle of deformation gradient were measured. The thermal diffusivity was obtained by analyzing the phase angle of deformation gradient. As the result, comparing with the literature value, the thermal diffusivities of materials measured were showed about 2% error.

• Polymer(Korea)
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• v.26 no.6
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• pp.821-828
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• 2002

Regular and highly interconnected macroporous poly(L-lactic acid) (PLLA) scaffolds with pore size of 10∼300 ㎛ were fabricated through thermally induced phase separation of a PLLA-dioxane-water ternary system in the presence of a small amount of Pluronics. Addition of Pluronics to the ternary system raised the cloud-point temperature curve in the order of P-123< F-68< F-127. The Pluronics act as nuclei for the phase separation. This assistance is enhanced with increasing length of the hydrophilic PEO blocks in the Pluronics molecules. Liquid-liquid spinodal phase separation was induced at higher temperatures in the systems containing Pluronics because the spinodal region is raised to higher temperature. The absorption of Pluronics onto the interface stabilizes a macro scale structure and increases the interconnection of pores.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.7
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• pp.507-514
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• 2003

Inspection and shape measurement of three-dimensional objects are widely needed in industries for quality monitoring and control. Recently the shape measurement using interferometric principle is found to be a successful methodology among other visual or optical technologies. Especially, the measuring method using wavelength scanning interferometer(WSI) has a great advantage in comparison with other conventional jnterferometric methods in that the absolute distance from the reference surface can be directly obtained from the amount of jnterferometric phase change. However, the measurement methods using WSI proposed by other researchers have low measurement resolution so far because they can't measure fractional phase change. To avoid this shortcoming we propose a new algorithm in this paper, which can obtain a small amount of even fractional phase change by sinusoidal function fitting. To evaluate the effectiveness of the proposed sinusoidal function fitting algorithm, a series of measuring experiments are conducted for discontinuously shaped specimens which have various height. The proposed algorithm shows much more enhanced measurement resolution than other existing conventional algorithms such as zero crossing algorithm and Fourier transform algorithm.