• Journal of Astronomy and Space Sciences
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• v.26 no.1
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• pp.31-46
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• 2009

An Unscented Kalman Filter (UKF) for estimation of the attitude and rate of a spacecraft using only magnetometer vector measurement is developed. The attitude dynamics used in the estimation is the nonlinear Euler's rotational equation which is augmented with the quaternion kinematics to construct a process model. The filter is designed for small satellite in low Earth orbit, so the disturbance torques include gravity-gradient torque, magnetic disturbance torque, and aerodynamic drag torque. The magnetometer measurements are simulated based on time-varying position of the spacecraft. The filter has been tested not only in the standby mode but also in the detumbling mode. Two types of actuators have been modeled and applied in the simulation. The PD controller is used for the two types of actuators (reaction wheels and thrusters) to detumble the spacecraft. The estimation error converged to within 5 deg for attitude and 0.1 deg/s for rate respectively when the two types of actuators were used. A joint state parameter estimation has been tested and the effect of the process noise covariance on the parameter estimation has been indicated. Also, Monte-Carlo simulations have been performed to test the capability of the filter to converge with the initial conditions sampled from a uniform distribution. Finally, the UKF performance has been compared to that of the EKF and it demonstrates that UKF slightly outperforms EKF. The developed algorithm can be applied to any type of small satellites that are actuated by magnetic torquers, reaction wheels or thrusters with a capability of magnetometer vector measurements for attitude and rate estimation.

• Journal of Information Technology Services
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• v.15 no.4
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• pp.25-39
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• 2016

The drone is an unmanned aerial vehicle which has no human pilot. Drones can be classified into military drones, commercial drones, and personal drones by usage. Also, drones can be classified from large-sized to nano-sized drone by size and autonomous, remote controlled drone by control type. Especially, military drones can be classified into low-altitude drones, medium-altitude, and high-altitude drones by altitude. Recently, the drone industry is one of the fast growing industries in the world. As drone technologies have become more advanced and cost-effective, Korean government has set its goal to become a top-level country in drone business. However, the government's strict regulation for drone operations is one of the biggest hurdles for the development of the related technologies in Korea and other countries. For example, critical problems for drone delivery can be classified into technical issues and institutional issues. Technical issues include durability, conditional awareness, grasp and release mechanisms, collision avoidance systems, drone operating system. Institutional issues include pilot and operator licensing, privacy rules, noise guidelines, security rules, education for drone police. This study analyzes the trends of the drone industry from the viewpoint of technology and regulation. Also, we define the business areas of drone utilization. Especially, the drone business types or models for public sector are proposed. Drone services or functions promoting public interests need to be aligned with the business reference model of Korean government. To define ten types of drone uses for public sector, we combine the business types of government with the future uses of drones that are proposed by futurists and business analysts. Future uses of drones can be divided into three sectors or services. First, drone services for public or military sectors include early warning systems, emergency services, news reporting, police drones, library drones, healthcare drones, travel drones. Second, drone services for commercial or industrial services include parcel delivery drones, gaming drones, sporting drones, farming and agriculture drones, ranching drones, robotic arm drones. Third, drone services for household sector include smart home drones.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2367-2374
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• 2014

This paper proposes a speech enhancement method which can be independently applied to different types of speech recognition systems. Feature compensation methods are well known to be effective as a front-end algorithm for robust speech recognition in noisy environments. The feature types and speech model employed by the feature compensation methods should be matched with ones of the speech recognition system for their effectiveness. However, they cannot be successfully employed by the speech recognition with "unknown" specification, such as a commercialized speech recognition engine. In this paper, a speech enhancement method is proposed, which is based on the PCGMM-based feature compensation method. The experimental results show that the proposed method significantly outperforms the conventional front-end algorithms for unknown speech recognition over various background noise conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.1
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• pp.454-463
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• 2013

Upon changing architectural education system into 5-year program, the design studio in university should meet the requirement in order to acquire the accredition. This study investigates on student' perceptions and responses, according to the configuration(open, mixed, closed), to their studio environment. Results and suggestions are as follows for all types: First, there should be space for individual activities for the student: Second, excluding space for excluding space for the individual work, seperated area must be provided for co-operative work, such as making models; Third, a clear territorial distintion between the individual and the co-work space should be able to set by the students, using. for instance, movable partition or corridor; Fourth, however, in line with the types, a seperated lecture or seminar room in the open type, a device to prevent distraction such as noise in the mixed type, and more space for co-work in the closed type are also suggested.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.1
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• pp.13-20
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• 2021

A series of numerical experiments with measurements observed at continuously operating reference stations (CORS) of the international GNSS services (IGS) and the national geographical information institute of Korea (NGII) have been intensively carried out to evaluate the quality of pseudo-ranges and carrier-phases of GPS L2C signal obtained by various receiver types, benign and harsh operational environment. In this analysis, some quality measures, such as signal-to-noise ratio (SNR), the magnitude of multipath, and the number of cycle slips, the pseudo-range and carrier phase obtaining rate were computed and compared. The SNR analysis revealed an impressive result that the trend in the SNR of C/A and the L2C comparably depends upon type of receivers. The result of multipath analysis also showed clearly different tendency depending on the receiver types. The reason for this inconsistent tendency was seemed to be that the different multipath mitigation algorithm built-in each receiver. The number of L2C cycle slip was less than P2(Y), and L2C measurements obtaining rate was higher than that of P2(Y) in three receiver types. In the harsh observational environment, L2C quality was not only superior to P2(Y) in all aspects such as SNR, multipath magnitude, the number of cycle slips, and measurement obtaining rate, but also it could maintain a level of quality equivalent to C/A. According to the results of this analysis, it's expected that improved positioning performance like accuracy and continuity can be got through the use of L2C instead of existing P2(Y).

• Journal of the Institute of Convergence Signal Processing
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• v.16 no.4
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• pp.149-155
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• 2015

Tooth implant is located in oral cavity and affects neck, skull base, and facail image. These magnetic inhomogeneities are usually frequency encoding direction which cause artifacts due to change of signal strength and geometric distortion. First, to evaluate signal to noise ratio (SNR) of magnetic resonance image caused by tooth implant this study uses meat phantom which is similar to human body and is consisted with fat, muscle, and water to measure signal to noise ratio. Second, signal to noise ratio by using custom-made fixed phantom is measured, and then signal to noise ratio size of different tooth implant types is compared and analyzed. The measured signal to noise ratio values of Brushite, HSA, Metal, and RBM for meat phantom were 2.76, 2.22, 1.88, and 1.57 on T1 SE, 1.88, 1.78, 1.65, and 1.79 on T2 FLAIR, 2.28, 2.25, 2.88, and 2.05 on T2 FSE, and 2.74, 1.94, 1.67, and 1.48 on T2 GRE. The measured signal to noise ratio values of Brushite, HSA, Metal, and RBM for fixed water phantom were 1.2, 1.06, 1.12, and 1.22 on DWI, 1.93, 1.87, 1.93, and 2.06 T1 SE, 1.83, 1.76, 1.82, and 1.92 on T2 FLAIR, 1.85, 1.79, 7.86, and 1.97 on T2 FSE, and 1.97, 1.93, 1.99, and 2.06 on T2 GRE. By considering through the results, patients and dentists need to consider some impacts from testing many aspects although their main purpose of having tooth implants is a dental restoration. Moreover, depending on the tooth implant characteristics of individual patients this study results can be used as baseline data when choosing test protocol.

• Journal of Information Processing Systems
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• v.2 no.1
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• pp.52-57
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• 2006

One of the important functions of an Intelligent Transportation System (ITS) is to classify vehicle types using a vision system. We propose a method using machine-learning algorithms for this classification problem with 3-D object model fitting. It is also necessary to detect road lanes from a fixed traffic surveillance camera in preparation for model fitting. We apply a background mask and line analysis algorithm based on statistical measures to Hough Transform (HT) in order to remove noise and false positive road lanes. The results show that this method is quite efficient in terms of quality.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.706-708
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• 2002

Vibration, giving rise to acoustical noise, is an important index of motor performance. The unbalance force due to rotor eccentricity caused by manufacturing imprecision or bearing defects is one possible source of excitation to vibration. With the advent of new high-energy magnetic material together with high precision motor applications, magnetic sources of vibration are becoming more serious. This paper introduces two types of high-speed slotless permanent magnet (PM) machine for electro-mechanical battery and investigates unbalance force due to static eccentricity with finite element method.

• Korean Journal of Cognitive Science
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• v.3 no.2
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• pp.249-270
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• 1992

The purpose of this paper is to classify the types of input characters,printed Hangul characters,using Maximum Run Length Projection(MRLP)that is used to extract features of input character.Because the number of Hangul characters is large and its structure is complex,there exists close similarities among characters.This paper,therefore,tried to increment the type classification rate using fuzzy resoning.The Maximum Run Length Projection is very immune to noise,and also useful to extracting the demanding information efficiently.In a test case with the most frequently use 917 printed Hangul characters,it achieved 98.58%correct classification rate.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.71.2-71.2
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• 2015

We present the high-resolution near-infrared spectra of standard stars observed with Immersion Grating Infrared Spectrograph (IGRINS). IGRINS covers the full spectral range of H and K bands simultaneously with a high spectral resolution (R=40,000), revealing many previously undetected and/or unknown lines. In this work, we present preliminary results of spectroscopic diagnostics for stellar physical parameters. Our ultimate goal is to provide a library of near-infrared spectra of standard stars, which covers all spectral types and luminosity classes, with a high-resolution and high signal to noise ratio ($SNR{\geq}200$).