• Journal of the Korean Vacuum Society
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• v.2 no.2
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• pp.131-138
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• 1993

The Project of a superconducting asymmetric multipole wiggler in the 1.5GeV electron storage ring DELTA is in progress. In this work, the influences of nonlinear effects due to the this insertion device are investigated. The standard lattice is tolerable on the beam dynamics problems for all errors which are considered in our work.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.95-98
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• 2005

Shafts having asymmetry or odd number of symmetry in the cross-section can not be simply manufactured by conventional incremental radial forging. In order to manufacture such shafts, the new concept of incremental forging with one punch and a flexible fixture is developed by suggesting a flexible fixture, instead of two opposed punches used in radial forging, so that the flexible fixture only supports the workpiece while the punch is moving during forming. A new flexible fixture is designed using the steel shots and vacuum technology. An equilateral triangular cross-section is selected as the sample shape to be manufactured by the proposed manufacturing method. The desired triangular cross-sectional shaft is manufactured with the errors of $3.0\%$.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.73.2-74
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• 2015

The gas cloud G2 falling toward Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, is supposed to provide valuable information on the physics of accretion flows and the environment of the black hole. We observed Sgr A* with four European stations of the Global Millimeter Very Long Baseline Interferometry Array (GMVA) at 86 GHz on 1 October 2013 when parts of G2 had already passed the pericenter. We searched for possible transient asymmetric structure - such as jets or winds from hot accretion flows - around Sgr A* caused by accretion of material from G2. The interferometric closure phases (which are zero if the spatial brightness distribution of the target is symmetric, and deviate from zero otherwise) remained zero within errors during the observation time. We thus conclude that Sgr A* did not show significant asymmetric (in the observer frame) outflows in late 2013. Using simulations, we constrain the size of the outflows that we could have missed to ${\approx}2.5$ mas along the major axis, ${\approx}0.4$ mas along the minor axis of the beam, corresponding to approximately 232 and 35 Schwarzschild radii, respectively; we thus probe spatial scales on which the jets of radio galaxies are suspected to convert magnetic into kinetic energy. As probably less than 0.2 Jy of the flux from Sgr A* can be attributed to accretion from G2, one finds an effective accretion rate ${\eta}M{\leq}1.5{\times}10^9kg/s{\approx}7.7{\times}10^{-9}M_{earth}/yr$ for material from G2. Exploiting the kinetic jet power-accretion power relation of radio galaxies, one finds that the rate of accretion of matter that ends up in jets is limited to $M{\leq}10^{17}kg/s{\approx}0.5M_{Earth}/yr$ less than about 20% of the mass of G2. Accordingly, G2 appears to be largely stable against loss of angular momentum and subsequent (partial) accretion at least on time scales ${\leq}1$ year.

• Journal of the Korean Association of Geographic Information Studies
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• v.20 no.1
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• pp.71-84
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• 2017

Radon, which enters the interior environment from soil, rocks, and groundwater, is a radioactive gas that poses a serious risk to humans. Indoor radon concentrations are measured to investigate the risk of radon gas exposure and reliable radon concentration mapping is then performed for further analysis. In this study, we compared the predictive performance of various univariate kriging algorithms, including ordinary kriging and three nonlinear transform-based kriging algorithms (log-normal, multi-Gaussian, and indicator kriging), for mapping radon concentrations with an asymmetric distribution. To compare and analyze the predictive performance, we carried out jackknife-based validation and analyzed the errors according to the differences in the data intervals and sampling densities. From a case study in South Korea, the overall nonlinear transform-based kriging algorithms showed better predictive performance than ordinary kriging. Among the nonlinear transform-based kriging algorithms, log-normal kriging had the best performance, followed by multi-Gaussian kriging. Ordinary kriging was the best for predicting high values within the spatial pattern. The results from this study are expected to be useful in the selection of kriging algorithms for the spatial prediction of data with an asymmetric distribution.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.3
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• pp.75-89
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• 1993

The present paper describes an application of UA(Uncertainty Analysis) to seakeeping model test, basically according to the Performance Test Code of ASME(American Society of Mechanical Engineers), in which all the possible error sources involved in the preparation of test, calibration of instruments, data acquisition and analysis are quantified, and summed up with error propagation coefficients to the final uncertainties. The differences between the static test such as resistance and propulsion test and the dynamic test like seakeeping test are clearly identified during all the procedures of UA and asymmetric bias errors are considered. The DRE(data reduction equation) subject to present UA are the heave and pitch response amplitude operator and nondimensionalized absolute frequency. The usefulness of UA in seakeeping test were confirmed not only for quantifying errors and improving measurement accuracy but also for the validation of various seakeeping analysis tools.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.1
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• pp.66-73
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• 2017

This study attempted to design lights with Type II distribution suitable for LED street lights based on the regulations of street light distribution developed by the Illuminating Engineering Society of North America (IESNA). The shape of an asymmetric lens, different from that of a rotationally symmetric lens, cannot be generated using a simple mathematical formula. In the first trial, the outline of the lens was fixed and simulated to confirm the distribution type. Following ISENA regulations, some problems that occurred during simulations and repeating was be modified that process is how we detected errors. Through optical research and simulations, a lens conforming to the regulations of Type II very short, Type II short, and Type II medium distributions was developed. A prototype was developed using simulation data and it was subjected to distribution tests. The results show that it can compare with property of Type II distribution.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.12-16
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• 2002

The clear sky radiative forcings of aerosols were evaluated over East Asia. We first investigated optical characteristics of aerosol using sky radiation measurements. An algorithm of Nakajima et al. (1996) is used for retrieving aerosol parameters such as optical thickness, ${\AA}$ngstr$\"{O}$m exponent, single scattering albedo, and size distribution from sky-radiation measurements, which then can be used for examining spatial and temporal variations of aerosol. Obtaining aerosol radiative forcing at TOA and surface, a radiative transfer model is used with inputs of obtained aerosol parameters and GMS-5 satellite-based cloud optical properties. Results show that there is a good agreement of simulated downwelling radiative flux at the surface with observation within 10 W m$^{-2}$ rms errors under the clear sky condition. However, a relatively large difference up to 40 W m$^{-2}$ rms error is found under the cloudy sky condition. The computed aerosol radiative forcing at the surface shows downward flux changes ranging from -100 to -170 W m$^{-2}$ per unit aerosol optical thickness at 0.7 $\mu$m. The different values of aerosol radiative forcing among the stations is mainly due to the differences in single scattering albedo ($\omega$$_{0.7}$) and asymmetric parameter (g$_1$) related to the geographical and seasonal variations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.630-633
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• 2007

In this paper, a blind watermarking method using binary images as watermarks is proposed. In order to enhance the detection capability against various attacks that transform watermarked image, the method uses asymmetric thresholds for inserting and detecting. Also, in order to reduce errors in the detected value of watermarks according to small changes in the coefficient values when detecting watermarks, it set the range for movement variation of the coefficients and lowered the sensitivity of variation by ignoring the variations that fall into this range. The experimental results show that the proposed method has good quality and is robust to various attacks such as the JPEG lossy compression, noise addition, cropping, blurring etc.

• The Journal of Asian Finance, Economics and Business
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• v.3 no.3
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• pp.79-91
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• 2016

This paper is the first of its kind using a non-linear approach based on cross-correlation function (CCF) to investigate the information arrival hypothesis in crude palm oil (CPO) futures market. Based on daily data from 1986 to 2010, our empirical results reveal that: First, the volume of volatility is not a proxy of information flow. Second, dependence causality running from current return to future volume in conditional variance exhibit an asymmetric pattern of time span with different signs of correlation between price and volume series. This finding indicates the presence of noise traders' hypothesis of price-volume interaction in CPO futures market. Both findings suggest that this futures market is weak-form inefficiency. In terms of investors' behavior, they tend to change their expectations on current return based on errors made in previous trade in generating abnormal volume in the subsequent period. As implied, it is advisable for the investors devise their future trading strategies according to time span and changes of return.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.124.1-124.1
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• 2012

We have made a comparison of the WSA-ENLIL CME propagation model with three cone types and an empirical model using 29 halo CMEs from 2001 to 2002. These halo CMEs have cone model parameters from Michalek et al. (2007) as well as their associated interplanetary (IP) shocks. For this study we consider three different cone models (an asymmetric cone model, an ice-cream cone model and an elliptical cone model) to determine CME cone parameters (radial velocity, angular width and source location), which are used for input parameters of the WSA-ENLIL CME propagation model. The mean absolute error (MAE) of the arrival times at the Earth for the elliptical cone model is 10 hours, which is about 2 hours smaller than those of the other models. However, this value is still larger than that (8.7 hours) of an empirical model by Kim et al. (2007). We are investigating several possibilities on relatively large errors of the WSA-ENLIL cone model, which may be caused by CME-CME interaction, background solar wind speed, and/or CME density enhancement.