• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.4
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• pp.727-736
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• 2009

In this paper, the $arccos(cos^{-1})$ arithmetic unit for mobile graphics accelerator is designed. The mobile vector graphics applications need tight area, execution time, power dissipation, and accuracy constraints compared to desktop PC applications. The designed processor adopts 2nd-order polynomial approximation scheme based on IEEE floating point data format to satisfy speed and accuracy conditions and reduces area via hardware sharing structure. The arccosine processor consists of 15,280 gates and its estimated operating frequency is about 125Mhz at operating condition of $0.35{\mu}m$ CMOS technology. Because the processor can execute arccosine function within 7 clock cycles, it has about 17 MOPS(million arccos operations per second) execution rate and can be applicable to mobile OpenVG processor. And because of its flexible architecture, it can be applicable to the various transcendental functions such as exponential, trigonometric and logarithmic functions via replacement of ROM and minor hardware modification.

• Journal of IKEEE
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• v.2 no.1 s.2
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• pp.53-60
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• 1998

We develope a high repetition rate, short distance, optical range finder for surface roughness measurements of large structures, such as a highway road, etc. For range measurement based on a triangulation principle, we use a light emitting diode and an one dimensional Position sensitive photodetector for a light source and an angle detector of the reflected light at the object, respectively. The range finder has automatic power control and electrical background noise rejection capabilities which enable it to overcome variations of an object reflectance and to eliminate time-varying, as well as constant, background light noises. Our experimental results show less than ${\pm}1.5mm$ of measurement errors regardless of an object reflectance, for $22{\sim}38cm$ object ranges which are determined by considering the installation of the range finder and the depth of surface roughness.

• The Journal of the Acoustical Society of Korea
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• v.20 no.6
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• pp.75-81
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• 2001

In this paper we analyzed the localization error of near-field detection algorithm in the sea. The near-field detection algorithms using triangulation and wavefront curvature basically assume a signal in two dimension of bearing and range. But the assumption causes localization error because there is three dimension of bearing, range, and depth in the sea. Even through three dimensional effect is considered, the localization error is occurred if multipath propagation in the sea is ignored. To analyze the localization error in the sea, we simulate the near-field localization using acoustic propagation model and focused beamforming considering wavefront curvature. The simulation results indicate that localization error always occurs in the sea and the error varied with sound velocity profile, water depth, bottom slope, source range, etc.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.4
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• pp.333-342
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• 2009

Three-level Diode Clamped Multilevel Inverter, generally known as Neutral-Point-Clamped (NPC) Inverter, has an inherent problem causing Neutral Point (NP) potential variation. Until now, in many literatures NP potential problem has been investigated and lots of solutions have also been proposed. However, under fault and fault tolerant control, distinctive feature for NP potential variation problem was rarely published from the standpoint of reliability. In this paper, NP potential is analytically investigated both normal and faulty conditions under carrier based PWM. Subsequently, relation between fault detection time and size of capacitor is analyzed. This information is explored by simulation and experiment results, which contribute to enhance the reliability of inverter system.

• Journal of the Korean Society for information Management
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• v.25 no.4
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• pp.327-345
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• 2008

The main purposes of this study are to construct a Korean science network from journal contributions data of Korean researchers, and to analyze the structure and characteristics of the network. First of all, the association matrix of 140 scholarly domains are calculated based on the number of contributions in common journals, and then the Pathfinder network algorithm is applied to those matrix. The resulting network has several hubs such as 'Biology', 'Korean Language & Linguistics', 'Physics', etc. The entropy formula and several centrality measures for the weighted networks are adopted to identify the centralities and interdisciplinarity of each scholarly domain. In particular, the date hubs, which have several weak links, are successively distinguished by local and global triangle betweenness centrality measures.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.6
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• pp.50-56
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• 2015

An efficient fast response hysteretic buck converter suitable for mobile application is propoesed. The problems of large output ripple and difficulty in using of small power inductor that conventional hysteretic converter has are improved by adding ramp generator. and the changeable switching frequency with load current is fixed by adding a delay time control circuit composed of PLL structure resulting in decrease of EMI noise. The circuits are implemented by using BCDMOS 0.35um 2-polt 4-metal process. Measurement results show that the converter operates with a switching frequency of 1.85MHz when drives 80mA load current. As the converter drives over 170mA load current, the switching frequency is fixed on 2MHz. The converter has output ripple voltage of less 20mV and more than efficiency 85% with 50~500mA laod current condition.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.6
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• pp.828-833
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• 2009

WWW which is an applicable massive set of document on the Web is a thesaurus of various information for users. However, Search engines spend a lot of time to retrieve necessary information and to filter out unnecessary information for user. In this paper, we propose the EFAM(the Extended Fuzzy AHP Method) model to manage the Web resource efficiently, and to make a decision in the problem of specific domain definitely. The EFAM model is concerned with the emotion analysis based on the domain corpus information, and it composed with systematic common concept grids by the knowledge of multiple experts. Therefore, The proposed the EFAM model can extract the documents by considering on the emotion criteria in the semantic context that is extracted concept from the corpus of specific domain and confirms that our model provides more efficient decision-making through an experiment than the conventional methods such as AHP and Fuzzy AHP which describe as a hierarchical structure elements about decision-making based on the alternatives, evaluation criteria, subjective attribute weight and fuzzy relation between concept and object.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.1 s.116
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• pp.7-14
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• 2007

In this paper, the scan characteristics of phased array antenna consisted of rectangular open-ended waveguide with a triangular grid are investigated. An infinite array structure is analyzed by numerically solving the integral equation for the electric field over the waveguide aperture using waveguide mode function and Floquet mode function. Next, SEP(Scan Element Pattern) and SI(Scan Impedance) characteristics are simulated by CST's MWS(Microwave Studio) and Ansoft's HFSS(High Frequency Structure Simulator) for the finite and infinite array structures. Also, validity of these approaches is verified by comparing the calculated and simulated results with the measured ones for an $8{\times}8$ subarray. Within 10.5 % fractional bandwidth in the X-band, the fabricated subarray showed the flat gain characteristic in the scan range of ${\pm}45^{\circ}C$ in the E-plane(azimuth) and ${\pm}20^{\circ}C$ in the H-plane(elevation), and also showed the return loss characteristic of less than -10 dB.

• Journal of Aerospace System Engineering
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• v.13 no.5
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• pp.32-38
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• 2019

The flying wing configuration with high sweep angles and rounded leading edge represent a complex flow of structures by the leading edge vortex. For control of the tailless flying wing configuration with unstable directional stability, flaperon is used. In this study, we conducted numerical simulations for a non-slender flying wing configuration with a rounded leading edge and analyzed the effect of the sideslip angle and flaperon. Through aerodynamic coefficient analysis, it was found that the effect of AoS on lift and drag coefficient was minimal and the side force and moment coefficient were markedly influenced by AoS. As the sideslip angle increased, the pitch break, which is related to the pitching moment coefficient, was delayed. Through stability analysis, the directional and lateral static stability of the flying wing configuration were increased by flaperon. Also, the structure and behavior of the leading edge vortex were analyzed by observing the contour of the pressure coefficient and the skin friction line.

• The Journal of the Korea Contents Association
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• v.22 no.9
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• pp.497-509
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• 2022

Lines are the oldest visual elements in human history and are closely related to human life and drawings and symbols drawn with lines on cave paintings and rocks have existed as alternative images for human survival. In arts the line reveals the core of the object within a short period of time and in art therapy it becomes a medium that can diagnose the client's psychological state and intervene therapeutically. However although line drawing has therapeutic importance in the process as well as diagnosis studies on its effectiveness and therapeutic characteristic have not been actively conducted. Therefore in this study the characteristics related to line art in art therapy are first derived through 'Triangular Verification of Theory', 'Qualitative Content Analysis', and 'Finding Common Parts' in domestic and foreign literature. As a result I will examine the Movement which is a key therapeutic element of line drawing in connection with the brain structure. Through this I will examine the therapeutic mechanisms that affect the body, brain and mind of the movement of line drawing and examine and suggest how it can be used in art therapy.