• Proceedings of the KIEE Conference
• /
• 1990.11a
• /
• pp.287-290
• /
• 1990

The paper describes the correction of the switching dead times avoiding a bridge leg short circuit in pulse width modulated voltage sorce inverters. The co consequences on AC variable speed drives with synchronous and asynchronous motors are described by harmonic analysis and by computer simulation.

• 제어로봇시스템학회:학술대회논문집
• /
• 1987.10a
• /
• pp.847-850
• /
• 1987

In this paper a new method to correct the differential non-linearity(D NL) error for a successive approximation is proposed. The DNL of ADC is very important characteristic in the field of radiation pulse height analysis or measurement of probability density function. The results of computer simulations are shown to demonstrate the feasibility of the proposed correction method.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.5
• /
• pp.447-447
• /
• 2021

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.1
• /
• pp.132-144
• /
• 1987

This paper presents the theroetical analysis of the crack tip stress intensity factor for a center crack in a finite width plate with variable thickness. The analyses were based on Laurent's expansions of complex stress potentials where the expansion coefficients are determined from the boundary conditions. The perturbation method was employed in numerical calculations. The correction factor F(.lambda.)is given in the form of power series of .lambda. [a numerical formula] where .lambda.=a/w$^{1}$; Dimensionless crack length, .betha.=t$_{2}$/t; Thickness ratio .omega.=w$_{2}$/w$_{1}$; width ratio The correction factor values vary with the width ratio .omega. and the maximum variation occurs around .betha.=1. For the case of .betha.=1 or .betha.=0 (uniform thickness plate0, the correction factor values agree well with Feddersen's formula. In all cases, as .lambda. approaches to 1 (thickness interface), the correction factor values are decreased rapidly for .betha.>1, and increased rapidly for .betha.<1.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2006.06b
• /
• pp.77-85
• /
• 2006

The last target of this study is to develop ship's Digital Compass that can be substitute with conventional ship's Magnetic Compass. At first, new Digital Compass system was developed with three-axis high accuracy Flux-gate sensors and small sized step motor. Then after, new deviation correction theory without ship's swinging procedures was proposed to provide automatic deviation analysis, correction and renewal. Throughout the performance evaluation tests on the training ship 'SAE-NU-RI', the effectiveness of developed Digital Compass and proposed deviation correction theory are verified.

• Proceedings of the KSPS conference
• /
• 2003.10a
• /
• pp.29-32
• /
• 2003

This paper proposes an automatic pronunciation correction system which provides users with correction guidelines for each pronunciation error. For this purpose, we develop an HMM speech recognizer which automatically classifies pronunciation errors when Korean speaks foreign language. And, we collect speech database of native and nonnative speakers using phonetically balanced word lists. We perform analysis of mispronunciation types from the experiment of automatic mispronunciation detection using speech recognizer.

• Journal of Power Electronics
• /
• v.6 no.2
• /
• pp.121-130
• /
• 2006

This paper presents the performance and efficiency of a drive system incorporating a switched-reluctance motor (SRM) with input power factor correction (PFC). The proposed system consists of a PFC, bi-directional converter, an inverter, and a SRM operating as based voltage source drives (VSD). First, theoretical analysis is made for each identified mode of operation in the drive system. This is followed by comparing the performance of the SRM drive system with and without a PFC circuit. The losses are also calculated for both systems and overall efficiency. Experimental results are presented to prove the theoretical analysis.

• Journal of Korea Port Economic Association
• /
• v.39 no.2
• /
• pp.129-141
• /
• 2023

This study analyzes the dynamic characteristics of daily freight rates of dry bulk and tanker shipping markets and their forecasting accuracy by using the error correction models. In order to calculate the error terms from the co-integrated time series, this study uses the common stochastic trend model (CSTM model) and vector error correction model (VECM model). First, the error correction model using the error term from the CSTM model yields more appropriate results of adjustment speed coefficient than one using the error term from the VECM model. Furthermore, according to the adjusted determination coefficients (adjR²), the error correction model of CSTM-model error term shows more model fitness than that of VECM-model error term. Second, according to the criteria of mean absolute error (MAE) and mean absolute scaled error (MASE) which measure the forecasting accuracy, the results show that the error correction model with CSTM-model error term produces more accurate forecasts than that of VECM-model error term in the 12 cases among the total 15 cases. This study proposes the analysis and forecast tasks 1) using both of the CSTM-model and VECM-model error terms at the same time and 2) incorporating additional data of commodity and energy markets, and 3) differentiating the adjustment speed coefficients based the sign of the error term as the future research topics.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.9 no.2
• /
• pp.159-172
• /
• 2006

In this study, the series of Landsat TM/ETM+ images was acquired to extract land surface temperature for wide-area and executed geometric correction and radiometric correction. And the land surface temperature was extracted using NASA Model, and achieved the first correction by performing land coverage category for study area and applied characteristic emission rate. Land surface temperature which was acquired by the first correction was analyzed in correlation with Meteorological Administration's temperature data by regression analysis, and established correction formula. And I wished to improve accuracy of land surface temperature extraction using satellite image by second correcting deviations between two data using establishing correction formula. As a result, land surface temperature acquired by 1st and 2st correction could be corrected in mean deviation of about ${\pm}3.0^{\circ}C$ with Meteorological Administration data. Also, I could acquire land surface temperature about study area by higher accuracy by applying to other Landsat images for re-verification of study results.

• Korean Journal of Remote Sensing
• /
• v.40 no.3
• /
• pp.257-268
• /
• 2024

Drone-mounted hyperspectral sensors (DHSs) have revolutionized remote sensing in agriculture by offering a cost-effective and flexible platform for high-resolution spectral data acquisition. Their ability to capture data at low altitudes minimizes atmospheric interference, enhancing their utility in agricultural monitoring and management. This study focused on addressing the challenges of radiometric and geometric distortions in preprocessing drone-acquired hyperspectral data. Radiometric correction, using the empirical line method (ELM) and spectral reference panels, effectively removed sensor noise and variations in solar irradiance, resulting in accurate surface reflectance values. Notably, the ELM correction improved reflectance for measured reference panels by 5-55%, resulting in a more uniform spectral profile across wavelengths, further validated by high correlations (0.97-0.99), despite minor deviations observed at specific wavelengths for some reflectors. Geometric correction, utilizing a rubber sheet transformation with ground control points, successfully rectified distortions caused by sensor orientation and flight path variations, ensuring accurate spatial representation within the image. The effectiveness of geometric correction was assessed using root mean square error(RMSE) analysis, revealing minimal errors in both east-west(0.00 to 0.081 m) and north-south directions(0.00 to 0.076 m).The overall position RMSE of 0.031 meters across 100 points demonstrates high geometric accuracy, exceeding industry standards. Additionally, image mosaicking was performed to create a comprehensive representation of the study area. These results demonstrate the effectiveness of the applied preprocessing techniques and highlight the potential of DHSs for precise crop health monitoring and management in smart agriculture. However, further research is needed to address challenges related to data dimensionality, sensor calibration, and reference data availability, as well as exploring alternative correction methods and evaluating their performance in diverse environmental conditions to enhance the robustness and applicability of hyperspectral data processing in agriculture.