• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.175-182
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• 1997

To design a high resolution three-mirror telescope for visible spectral region, initial design technique based on the generation of flat field anastigmatic solutions limited by mechanical structure was proposed. An initial design of the three-mirror telescope that features relatively high focal ratio(F/14.5), large aperture diameter(600 mm), and squared field of view(0.27$^{\circ}$$\times$1.3$^{\circ}$) was done using an initial design program. Code V was used to optimized the initially designed optical system. As a result, MTF value of the telescope was about 0.5 at Nyquist frequency in each field except for the edge of the CCD.

• Journal of The Korean Astronomical Society
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• v.56 no.2
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• pp.187-194
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• 2023

The remote sensing technique of measuring the magnetic field was applied first to sunspots by Hale (1908). Later Babcock (1961) showed that the solar surface magnetic field on a global scale is a dipole in first-order approximation and that this dipole field reverses once every solar cycle. The Wilcox Solar Observatory (WSO) supplies the spherical harmonics coefficients of the solar corona magnetic field of each Carrington Rotation, calculated based on the remotely-sensed photospheric magnetic field of the solar surface. To infer the internal current system producing the global solar coronal magnetic field structure and evolution of the Sun, we calculate the multipole components of the solar magnetic field using the WSO data from 1976 to 2019. The prominent cycle components over the last 4 solar activity cycles are axis-symmetric fields of the dipole and octupole. This implies that the current inversion driving the solar magnetic field reversal originates from the equatorial region and spreads to the whole globe. Thus, a more accurate solar dynamo model must include an explanation of the origin and evolution of such solar internal current dynamics.

• Bulletin of the Korean Chemical Society
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• v.29 no.1
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• pp.153-158
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• 2008

A microchip-based capillary gel electrophoresis (MCGE) technique was developed for the ultra-fast detection and differentiation of Candidatus Mycoplasma haemominutum (Candidatus M. haemominutum, California strain) and Mycoplasma haemofelis (M. haemofelis, Ohio strain) in Korean feral cats through the application of programmed field strength gradients (PFSG) in a conventional glass double-T microchip. The effects of the poly (ethyleneoxide) (PEO) concentration and electric field strength on the separation of DNA fragments were investigated. The PCR-amplified products of Candidatus M. haemominutum (202-bp) and M. haemofelis (273-bp) were analyzed by MCGE within 75 s under a constant applied electric field of 117.6 V/cm and a sieving matrix of 0.3% PEO (Mr 8 000 000). When the PFSG was applied, MCGE analysis generated results 6.8-times faster without any loss of resolution or reproducibility. The MCGE-PFSG technique was also applied to eleven samples selected randomly from 33 positive samples. The samples were detected and differentiated within 11 s. The analysis time of the MCGE-PFSG technique was approximately 980-times faster than that using conventional slab gel electrophoresis.

• Geomechanics and Engineering
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• v.30 no.3
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• pp.247-258
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• 2022

A field velocity resistivity probe (FVRP) can measure compressional waves, shear waves and electrical resistivity in boreholes. The objective of this study is to perform the soil classification through a machine learning technique through elastic wave velocity and electrical resistivity measured by FVRP. Field and laboratory tests are performed, and the measured values are used as input variables to classify silt sand, sand, silty clay, and clay-sand mixture layers. The accuracy of k-nearest neighbors (KNN), naive Bayes (NB), random forest (RF), and support vector machine (SVM), selected to perform classification and optimize the hyperparameters, is evaluated. The accuracies are calculated as 0.76, 0.91, 0.94, and 0.88 for KNN, NB, RF, and SVM algorithms, respectively. To increase the amount of data at each soil layer, the synthetic minority oversampling technique (SMOTE) and conditional tabular generative adversarial network (CTGAN) are applied to overcome imbalance in the dataset. The CTGAN provides improved accuracy in the KNN, NB, RF and SVM algorithms. The results demonstrate that the measured values by FVRP can classify soil layers through three kinds of data with machine learning algorithms.

• Progress in Superconductivity and Cryogenics
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• v.22 no.3
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• pp.13-19
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• 2020

This study presents the experiment and simulation results on the magnetic field response and electrical stability behaviors of no-insulation (NI) and metal insulation with stainless steel tape (MI-SS) which wound in form of racetrack type coils. First of all, the structural design of the racetrack type bobbin was shown along with its parameters. Then, the current-voltage tests were carried out to measure the critical current of both test coils. Also, the sudden discharging and charging tests were performed in the steady state to estimate the decay field time and magnetic field response, respectively. Finally, the overcurrent tests were conducted in the transient state to investigate the electrical stability of these test coils. Based on the experimental results, the contact surface resistances were calculated and applied to the field coils (FCs) of 10-MW-class second generation high temperature superconducting generator (2G HTSG) used in wind offshore environment. The charging delay time and electrical stability for NI and MI-SS HTS FCs of 10-MW-class 2G HTSG are analyzed by the equivalent circuit model and the key parameters which were obtained from the electromagnetic finite element analysis results.

• Radiation Oncology Journal
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• v.1 no.1
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• pp.25-28
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• 1983

Anterior and posterior parallel opposed field technique covering entire neck is desirable for elimination of junctional problems in treating upper neck with bilateral parallel opposed fields and lower neck with anterior one field. For good dose distribution in neck, dose in build-up region should be high for anterior field and should be low for posterior field. And so, with 10 MV X-ray, lead absorber was used for anterior field only. The adequate thickness of lead absorber, absorber-skin separation, width of central cord block for posterior field and anterior & posterior field weight were studied using film dosimery. The results are as follows. 1. As the thickness of the lead absorber increased the dose in build-up region increased. 2. As the absorber-skin separation decreased the dose in build-up region increased. 3. The adequate thickness of lead absorber was around 5.6mm. 4. The adequate absorber-skin separation was around 5cm. 5. The adequate posterior cord block width was 3cm. 6. 4:1 weighting for anterior and posterior field was adequate. And so with this technique, adequate dose distribution could be made as well as elimination junction problems.

• Journal of the Korean Mathematical Society
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• v.38 no.3
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• pp.523-559
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• 2001

To predict the fate of groundwater contaminants, accurate spatially continuous information is needed. Because most field sampling of groundwater contaminants are not conducted spatially continuous manner, a special estimation technique is required to interpolate/extrapolate concentration distributions at unmeasured locations. A practical three-dimensional estimations method for in situ groundwater contaminant concentrations is introduced. It consistas of two general steps: estimation of macroscopic transport process and kriging. Using field data and nonlinear optimization techniques, the macroscopic behavior of the contaminant plume is estimated. A spatial distribution of residuals is obtained by subtracting the macroscopic transport portion from field data, then kriging is applied to estimate residuals at unsampled locations. To reduce outlier effects on obtaining correlations between residual data which are needed for determining variougram models, the R(sub)p-estimator is introduced. The proposed estimation method is applied to a field data set.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.4
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• pp.31-40
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• 2013

This paper proposes a performance improvement of synchronous generator using exciter control with field coils parameter estimation technique. In general, the generator excitation system controller uses the PID controller. When the Field winding impedance changed, the PID gains must be changed. General method is difficult to apply varying capacity of the synchronous generator. The proposed control method determine automatically measure the internal impedance of the synchronous generator's exciter and configure the controller. This method can be applied regardless of the generator capacity. So it is possible to apply a variety of synchronous generator systems. The validity of the proposed algorithm is verified by simulations and experiments.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2195-2199
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• 2007

We demonstrate that high-resolution (~60 nm) near-field fluorescence images of fluorescent nanospheres can be obtained by utilizing the tip-induced fluorescence quenching process. A time-stamped photon counting (TSPC) technique employed enables us to efficiently measure the degree of fluorescence quenching caused by the dielectric or metallic atomic force microscopy tip. We find that the degree of quenching is not only determined by the tip-material but also by the local morphology of the tip. The fringe patterns around individual nanospheres observed are explained in terms of the interference between the excitation field that is directly induced by the laser source, and the scattered excitation field from the tip.

• Journal of electromagnetic engineering and science
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• v.4 no.1
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• pp.13-16
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• 2004

In this paper, FDTD analysis of the bow-tie antenna is investigated by incorporating static field solution that is suitable to the bow-tie antenna without increasing computational time. Transforming static feld solution to the rotated grid system, we can obtain the transformed static field solution which is able to represent field behavior near the oblique edge line of the bow-tie antenna. The result shows a good agreement with a MoM analysis and is compared conformal modeling technique and regular FDTD method.