• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.107-117
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• 2016

We develop a new method to globally calibrate the feature points that are derived from the binocular systems at different positions. A three-DOF (degree of freedom) global calibration system is established to move and rotate the 3D calibration board to an arbitrary position. A three-DOF global calibration model is constructed for the binocular systems at different positions. The three-DOF calibration model unifies the 3D coordinates of the feature points from different binocular systems into a unique world coordinate system that is determined by the initial position of the calibration board. Experiments are conducted on the binocular systems at the coaxial and diagonal positions. The experimental root-mean-square errors between the true and reconstructed 3D coordinates of the feature points are 0.573 mm, 0.520 mm and 0.528 mm at the coaxial positions. The experimental root-mean-square errors between the true and reconstructed 3D coordinates of the feature points are 0.495 mm, 0.556 mm and 0.627 mm at the diagonal positions. This method provides a global and accurate calibration to unity the measurement points of different binocular vision systems into the same world coordinate system.

• Journal of Welding and Joining
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• v.13 no.3
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• pp.106-115
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• 1995

To know the bonding phenomena of Ti/Cu brazed joint, a characteristic of microstructures in bonding interlayer of vacuum brazed pure Ti to Cu has been studied in the temperature range from 1088 to 1133K for various bonding times using Ag-28wt%Cu filler metal. Also intermediate phases formed in bonded interlayer and behavior of layer growth have been investigated. The obtained results in this study are as follows: 1) Liquid insert metal width at the each brazing temperature was proportional to the square root of brazing time, and it was considered that the liquid insert metal width was controlled by the diffusion rate process of primary .alpha.-Cu formed at the Ti side. 2) Intermediate phases formed near the Ti interface were .betha.-Ti and intermetallic compounds TiCu, Ti$_{2}$Cu, Ti$_{3}$Cu, and TiCu. 3) .betha.-Ti formed in Ti base metal durig brazing transformed to lamellar structure, .alpha.-Ti + Ti$_{2}$Cu. The structure came from the eutectoil decomposition reaction in cooling. And the width of .betha.-Ti layer was proportional to the square root of brazing time, and it was considered that the growth of .betha.-Ti layer was controlled by interdiffusion rate process in .betha.-Ti. 4) The layer growth of TiCu, Ti$_{3}$Cu$_{4}$ and TiCu, phases formed near the Ti interface was linerface was linearly proportional to the brazing time, and it was considered that the layer growth of these phases was controlled by the chemical reaction rate at the interface.

• The Korean Journal of Applied Statistics
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• v.23 no.5
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• pp.955-966
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• 2010

Canonical correlation biplot is a useful biplot for giving a graphical description of the data matrix which consists of the association between two sets of variables, for detecting patterns and displaying results found by more formal methods of analysis. Nevertheless, when some values are missing in data, most biplots are not directly applicable. To solve this problem, we estimate the missing data using the median, mean, EM algorithm and MCMC imputation methods according to missing rates. Even though we estimate the missing values of biplot of incomplete data, we have different shapes of biplots according to the imputation methods and missing rates. Therefore we use a RMS(root mean square) which was proposed by Shin et al. (2007) and PS(procrustes statistic) for measuring and comparing the shape variability between the original biplots and the estimated biplots.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.7
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• pp.782-790
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• 2014

In this paper, we apply the 2-D Matrix Pencil Method(MPM) to the estimation of the direction of arrival(DOA) of multiple signals of interest(SOIs) in bistatic MIMO radar. The 2-D MPM shows remarkable performance under a low SNR environment and low computational complexity to estimate the DOA of multiple SOIs. Also, it is possible to estimate the direction of departure(DOD) which is an angle from transmitter to target. To verify the proposed algorithm, we applied the proposed algorithm to a uniformly spaced linear array(ULA) and compared the RMSE(Root Mean Square Error) of DOA and DOD under the various SNR with those of the 2-D Capon algorithm.

• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.341-346
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• 2014

This paper has presented the design and fabrication of phase correlator for wideband digital frequency discriminator (DFD) operating over the 6.0 to 18.0 GHz frequency range. Fabricated DFD phase correlator has been measured I or Q output signal, and analyzed frequency discrimination error. The operation of the proposed mixer type correlator has been analyzed by deriving some analytic equations. To design the phase correlator, this paper has modeled and simulated IQ mixer and 8-way power divider by using RF simulation tool. Designed phase correlator has fabricated and measured. The phase error and frequency discrimination error have been presented using by measured I and Q output signal. Over the 6.0~18.0 GHz range, the root mean square(RMS) phase error is $4.81^{\circ}$, RMS and frequency discrimination error is 1.49 MHz, RMS.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.627-632
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• 2005

Almost all network systems provide an authentication mechanism based on user ID and password. In such system, it is easy to obtain the user password using a sniffer program with illegal eavesdropping. The one-time password and challenge-response method are useful authentication schemes that protect the user passwords against eavesdropping. In client/ server environments, the one-time password scheme using time is especially useful because it solves the synchronization problem. It is the stability that is based on Square Root problem, and we would like to suggest OPI(One Pass Identification), enhancing the stability for all of the well-known attacks by now including Free-playing attack, off-line Literal attack, Server and so on. OPI does not need to create the special key to read the password. OPI is very excellent in identifying the approved person within a very short time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.4
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• pp.693-699
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• 2006

Digital airborne image must be precisely orthorectified to become geographical information. For orthorectification of airborne images, GPS/INS (Global Positioning System/Inertial Navigation System) and LIDAR (LIght Detection And Ranging) elevation data were employed. In this study, 635 frame airborne images were produced and LIDAR data were converted to raster image for applying to image orthorectification. To derive images with constant brightness, flat field correction was applied to images. The airborne images were geometrically corrected by calculating internal orientation and external orientation using GPS/INS data and then orthorectified using LIDAR digital elevation model image. The precision of orthorectified images was validated by collecting 50 ground control points from arbitrary five images and LIDAR intensity image. As validation result, RMSE (Root Mean Square Error) was 0.387 as almost same as only two times of pixel spatial resolution. It is possible that this automatic orthorectification method of airborne image with higher precision is applied to airborne image industry.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.4
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• pp.305-313
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• 2013

As an FMT (Filtered Multi-Tone) transmission method of Wideband VHF communication system specified by the ETS (European Telecommunications Standards) EN 300 392-2, this paper introduces three existing realization methods, i.e., the direct filtering method using different band SRRC (Square-Root Raised Cosine) filters for each subcarrier, the PPN-DFT method using the IDFT-PPN (Poly-Phase Network) and PPN-DFT at the transmitter and receiver, respectively, and the Extended DFT method. Then, it proposes the extended IDFT-SDFT (Sliding Discrete Fourier Transform) that computes the DFT values only for interested subcarriers every sample time, and shows that it has an advantage of blind symbol timing (using no training symbol) individually for each user signal (independently of other users' signals) in the multi-user environment where the subcarriers are assigned in contiguous or interleaved blocks to each user and each user signal possibly experiences different channels.

• Journal of the Korean Association of Geographic Information Studies
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• v.6 no.2
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• pp.1-9
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• 2003

Surface solar radiation over the sea is estimated using the visible and infrared spin scan radiometer (VISSR) data onboard Geostationary Meteorological Satellite(GMS)-5 from January 1997 to December 1997 in clear and cloudy conditions. The hourly insolation is estimated with a spatial resolution of $5km{\times}5km$ grid. The island pyranometer operated by the Japan Meteorological Agency(JMA) is used to validate the estimated insolation. The root mean square error of the hourly estimated insolation is $104W/m^2$ with 0.91 of the correlation coefficient. In the variability of the hourly solar radiation investigated around the Korean Peninsula, the maximum value of solar radiation is found in June at the Yellow Sea and the East Sea, while in August at the South Sea because of low pressure conditions and front in June.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.49 no.1
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• pp.18-28
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• 2013

It was compared the estimated parameters by the surplus production from three different models, i.e., three types (Schaefer, Gulland, and Schnute) of the traditional surplus production models, a stock production model incorporating covariates (ASPIC) model and a maximum entropy (ME) model. We also evaluated the performance of models in the estimation of their parameters. The maximum sustainable yield (MSY) of small yellow croaker (Pseudosciaena polyactis) in Korean waters ranged from 35,061 metric tons (mt) by Gulland model to 44,844mt by ME model, and fishing effort at MSY ($f_{MSY}$) ranged from 262,188hauls by Schnute model to 355,200hauls by ME model. The lowest root mean square error (RMSE) for small yellow croaker was obtained from the Gulland surplus production model, while the highest RMSE was from Schnute model. However, the highest coefficient of determination ($R^2$) was from the ME model, but the ASPIC model yielded the lowest coefficient. On the other hand, the MSY of Kapenta (Limnothrissa miodon) ranged from 16,880 mt by ASPIC model to 25,373mt by ME model, and $f_{MSY}$, from 94,580hauls by ASPIC model to 225,490hauls by Schnute model. In this case, both the lowest root mean square error (RMSE) and the highest coefficient of determination ($R^2$) were obtained from the ME model, which showed relatively better fits of data to the model, indicating that the ME model is statistically more stable and robust than other models. Moreover, the ME model could provide additional ecologically useful parameters such as, biomass at MSY ($B_{MSY}$), carrying capacity of the population (K), catchability coefficient (q) and the intrinsic rate of population growth (r).