• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.3
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• pp.81-89
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• 2002

The sensorless AC motor drive is a popular topic of study due to the cost and reliability of speed and position sensors. Most sensorless algorithms are based on the mathematical modeling of motors including electrical variables such as phase current and voltage. Therefore, the accuracy of such variables largely affects the performance of the sensorless AC motor drive. However, the output voltage of the SVPWM-VSI, which is widely used in sensorless AC motor drives, has considerable errors. In particular, the SVPWM-VSI is error-prone in the low speed range because the constant DC link voltage causes poor resolution in a low output voltage command and the output voltage is distorted due to dead time and voltage drop. This paper investigates a novel high-performance strategy for overcoming these problems in a sensorless ac motor drive. In this paper, a variation of the DC link voltage and a direct compensation for dead time and voltage drop are proposed. The variable DC link voltage leads to an improved resolution of the inverter output voltage, especially in the motor's low speed range. The direct compensation for dead time and voltage drop directly calculates the duration of the switching voltage vector without the modification of the reference voltage and needs no additional circuits. In addition, the proposed strategy reduces a current ripple, which deteriorates the accuracy of a monitored current and causes torque ripple and additional loss. Simulation and experimentation have been performed to verify the proposed strategy.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.189-192
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• 2001

In this paper, we desire to design real time image processing system to change a various chromaticity in HDTV that has 1344*806 resolution and requires a high-speed 65MHz operation. In order to change the image chromaticity, it is necessary to calculate the color temperature of the image. Conventional way of calculating the temperature uses 2-D algorithm [1] that requires bulky hardware. This paper propose a one-dimensional color-temperature conversion that reduces the hardware complexity while keeping the performance of the 2-D algorithm. The proposed method is realized by using the Xilinx Virtex FPGA XCV 2000E-6BG560.

• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.482-486
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• 2000

The purpose of the present study was first, to evaluate the relationship between composite surface conversion and surface discoloration, second, to know if there was difference in surface discoloration between celluloid-strip-finished composite surface and polished surface. In addition, the discoloration of composite surface was also evaluated with visual inspection or digital camera with high resolution monitor, Z100, Tetric Ceram, Spectrum, and Aelitfil were used. The composite surfaces were celluloid-strip finished (group 1), polished (group 2), celluloid-strip finished under nitrogen gas purging (group 3) or only light cured without finishing or polishing under nitrogen gas purging (group 4). The microhardness of each samples were also measured in each group. The samples of each group were also divided into 4 subgroup whether they were immediately placed in disclosing solution (0.2% Elythrosin, pH 7.0) (subgroup1), 1 day after light curing(subgroup 2), 3day after light curing(subgroup 3) or 7 day after light curing(subgroup 4). The computer controlled spectrophotometer was used to determine CIELAB coordinates ($L^*$, $a^*$, $b^*$). The amounts of color difference were compared. The results were as follows; 1. There was no difference in discoloration between celluloid strip finished composite surface and polished surface. 2. The samples discolored more when they were placed in disclosing solution immediately after polymerization than other groups. 3. When the samples were light cured under nitrogen gas purging and without polishing process, they discolored more than other groups even though they showed higher micro hardness. 4. With visual inspection or digital camera, only a limited information was available in detecting composite surface discoloration.

• Journal of KIISE:Databases
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• v.31 no.3
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• pp.232-242
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• 2004

Metadata is a general notion of data about data to improve data sharing and exchanging by definitely describing meaning and representation of data. However, metadata has been created in various ways and It caused another kind of heterogeneity problem named metadata heterogeneity problem. Recently, the research on metadata gateway approach that allows metadata heterogeneity is being more actively progressed. However, the existing commercialized systems that have been implemented with the metadata gateway approach are dependent on a metadata schema. In this paper, we propose a message conversion system which separates the mapping information from the mapping rules between heterogeneous metadata schemas. The proposed system dynamically manages standardized data elements by applying ISO/IEC l1179. Therefore, the proposed system provides the set of standard data elements to create consistently metadata of new databases and provides a fundamental resolution to the metadata heterogeneity problem.

• Korean Journal of Remote Sensing
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• v.3 no.1
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• pp.41-54
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• 1987

Accurate determination of Sea Surface Temperature (SST) is essential for ocean and climate studies. This paper estimated SST in the sea region around the Korea from the Advenced Very High Resolution Radiometer(AVHRR) channel 4 data on board NOAA-9 satellite. The processing procedure used to derive SSTs utilized: 1) Ascending node prediction of satellite orbit 2) Geometric correction 3) Radiometric calibration and radiance to temperature conversion look up table 4) Removing cloudy area. SST product results are displayed as colored video and hardcopy. In this processing, geometric correction is derived from equator crossing time, ascending time and subpoint coordinate information. Also, normalized response function of infrared 10.5-11.5$\mu\textrm{m}$ wavelength is used for temperature conversion. The SST derived from this processing is relatively similar to the measurements made by ship data, but because of water vapor attenuation SST from satellite are in general 2$^{\circ}$- $^{\circ}C$ lower than the ship data.

• Journal of Internet of Things and Convergence
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• v.4 no.2
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• pp.1-6
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• 2018

Techniques for generating new sample data from higher dimensional data such as images have been utilized variously for speech synthesis, image conversion and image restoration. This paper adopts Progressive Growing of Generative Adversarial Networks(PG-GANs) as an implementation model to generate high-resolution images and to enhance variation of the generated images, and applied it to fashion image data. PG-GANs allows the generator and discriminator to progressively learn at the same time, continuously adding new layers from low-resolution images to result high-resolution images. We also proposed a Mini-batch Discrimination method to increase the diversity of generated data, and proposed a Sliced Wasserstein Distance(SWD) evaluation method instead of the existing MS-SSIM to evaluate the GAN model.

• Journal of Environmental Impact Assessment
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• v.18 no.5
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• pp.281-291
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• 2009

In Total Water Pollutant Load Management System of Korea, unit load approach based on land register data is currently used for the estimation of non-point pollutant load. However, a problem raised that land register data could not always reflect the actual land surface coverages which determine runoff characteristics of non-point pollution sources. As a way to overcome this, we tried to establish quantitative relationships between the aerial images (0.4m resolution) which reflect actual land surface coverages and the land registration maps according to the 19 major designated land-use categories in Kyeongan watershed. Analyses showed different relationships according to the land-use categories. Only a few land-use categories including forestry, road and river showed essentially identical and some categories such as orchard, parking lot and sport utility site showed no relationships at all between image data and land register data. Except for the two cases, all the other categories showed statistically significant linear relationships between image data and land register data. The analyses indicate that using high resolution aerial maps is a better way to estimate non-point pollutant load. If the aerial maps are not available, application of the linear relationships as conversion factors of land register data to image data could be an possible option to estimate non-point pollutant loads for the specific land-use categories in Kyeongan watershed.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.3
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• pp.3-10
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• 2014

Digital maps are made by experts who digitize the data from aerial image and field survey. And the digital maps are updated every 2 years in National Geographic Information Institute. Conventional Digitizing methods take a lot of time and cost. And geographic information needs to be modified and updated appropriately as geographical features are changing rapidly. Therefore in this paper, we modify the digital map updates the road information for rapid high-resolution aerial orthophoto taken at different times were performed HSI color conversion. Road area of the cassification was performed the region growing methods. In addition, changes in the target area for analysis by applying the CVA technique to compare the changed road area by analyzing the accuracy of the proposed extraction.

• Nuclear Engineering and Technology
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• v.53 no.6
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• pp.1964-1969
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• 2021

We developed a Dual-PPACs detector for fast neutron measurements that consists of two sets of PPAC: conventional PPAC and fission PPAC. A²³⁸U(U₃O₈) coating is placed in the fission PPAC's anode, which is used as the neutrons conversion layer. An experiment was performed to measure neutron time-of-flight (TOF) in which ²⁵²Cf spontaneous fission source was used. An excellent time resolution of 164ps has been observed at 6 mbar in isobutene gas. With the excellent time resolution of Dual-PPACs detector, exact neutron energy can be extracted from the timing measurement. The experimental detection efficiency was 1.9 × 10^-7, consistent with the efficiency of 2.5 × 10^-7 given by a Geant4 simulation. Ultimately, the results show that the Dual-PPACs detector is a suitable candidate for measuring fast neutrons in the future CiADS system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.1
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• pp.125-132
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• 2024

Optical satellite images are being used for national security and collection of information, and their utilization is increasing. However, it acquires low-quality images that are not suitable for the user's requirement due to weather conditions and time constraints. In this paper, a deep learning-based conversion of image and colorization model referring to high-resolution SAR images was created to simulate the occluded area with clouds of optical satellite images. The model was experimented according to the type of algorithm applied and input data, and each simulated images was compared and analyzed. In particular, the amount of pixel value information between the input black-and-white image and the SAR image was similarly constructed to overcome the problem caused by the relatively lack of color information. As a result of the experiment, the histogram distribution of the simulated image learned with the Gray-scale image and the high-resolution SAR image was relatively similar to the original image. In addition, the RMSE value was about 6.9827 and the PSNR value was about 31.3960 calculated for quantitative analysis.