• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.991-997
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• 2003

A flow field around a disc in an optical disc drive is invested using numerical methods. The high-speed rotating disc induces a strong flow field around the disc, which causes the pressure distribution on the surfaces of the disc. The pressure difference between the upper and the lower surfaces causes the deformation of the disc. In the first part of this study, flow fields around a rotating disc and a stationary wall are investigated using a similarity solution method, in order to identify the effect of the distance between the disc and the wall on the pressure distribution on the surfaces of the disc. In the second part, flow field in a slim-type optical disc drive is studied using a commercial code in order to consider the effect of the vortices generated by the local geometry of the drive.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2003.06a
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• pp.153-156
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• 2003

This short paper suggests a control strategy using a stepwise fuzzy moving sliding surface. The moving surface is a Sugeno-type fuzzy system that has the angle of state error vector and the distance from the origin in the phase plane as inputs and a first-order linear differential equation as an output. The surface initially passes arbitrary initial states and subsequently moves towards a predetermined surface via rotating or shifting. the proposed method reduces the reaching and tracking time and improves robustness. The asymptotic stability of the fuzzy sliding surface is proved. The validity of the proposed control scheme is shown in computer simulation for a second-order nonlinear system.

• Journal of Mechanical Science and Technology
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• v.17 no.8
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• pp.1219-1225
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• 2003

Acoustic sounds generated by uniform flow around a two-dimensional circular cylinder at Re=150 are simulated by applying the finite difference lattice Boltzmann method. A third-order-accurate up-wind scheme is used for the spatial derivatives. A second-order-accurate Runge-Kutta scheme is also used for time marching. Very small acoustic pressure fluctuation, with same frequency as that of Karman vortex street, is compared with pressure fluctuation around a circular cylinder. The propagation velocity of acoustic sound shows that acoustic approaching the upstream, due to the Doppler effect in uniform flow, slowly propagates. For the downstream, on the other hand, it quickly propagates. It is also apparent that the size of sound pressure is proportional to the central distance ${\gamma}$$\^$-1/2/ of the circular cylinder.

• The Journal of the Convergence on Culture Technology
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• v.8 no.5
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• pp.713-721
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• 2022

In order to use the LED video wall in the broadcasting studio, there are a few things to be aware of. First, since the pixels are closely arranged, a moire phenomenon may occur due to a short arrangement period, and second, the distance between pixels (pixel pitch) may be recorded on the image sensor of the broadcasting camera. When moire occurs or pixel pitch is observed, viewers feel uncomfortable. Moire effect can be reduced by adjusting the shooting distance or angle of the camera, but in order to prevent the pixel pitch from being recorded on the image sensor, secure a sufficient distance between the LED video wall and camera. even when the distance secured, the zoom lens used in the broadcasting studio must be operated by appropriately changing the magnification. If the focal length is changed by changing the magnification to obtain a desired angle of view, the pixel pitch may be unintentionally recorded. In this study we propose the range that the pixel pitch is not observed while changing the magnification ratio of the zoom lens when the distance from the video wall is sufficiently secured. The content was played back on the LED video wall and the LED video wall was recorded on the server using an HD camera equipped with a B4 mount zoom lens

• Journal of architectural history
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• v.14 no.1 s.41
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• pp.71-87
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• 2005

4 royal palaces are currently remained from capital city (Seoul) of 'Cho-Sun(朝鮮)' period. In these palaces, 'Main hall of Royal Palace(正殿)' is the center of the Royal Palaces. The 'Main hall of Royal Palace' of the Royal Palace was the best building of that time. Therefore there were many studies about the 'Main hall of Royal Palace'. But these studies were individual studies of these 'Main hall of Royal Palace'. Therefore, this study is to analyze and compare 4 'Main hall of Royal Palace' of the Royal palaces. It is to study the proportion regarding the Diameter of the pillar, the Height, the pillar and pillar Interval's Distance, and the arrangement of 'Kong-Po(bracket sets)'. With these studies, it is to prove that the 'Main hall of Royal Palace' is the building which high construction technique of this time is expressed. Result of this study is as followings; First, the proportion of pillar height(H) to its diameter(D) average from H=8.0 to 8.5D. Only the Myeong-Jeong-Jeon omitted the 'Go-Ju(高柱)' in the 'Toi-Kan (退間)' to place Ea-Jwa(御座). Second, Second, the proportion of diameter of the pillar of 'Eoi-Bu-Pyeong-Ju(外部平柱)' and 'Nae-Jin-Go-Ju(內陣高柱)' average D1(Diameter of 'Eoi-Bu-Pyeong-Ju') =0.91D2 (Diameter of 'Nae-Jin-Go-Ju'). In regards to the height, the single floor 'Main hall of Royal Palace' and double floor 'Main hall of Royal Palace' seems to be different. The height proportion of the double floor 'Main hall of royal palace' is H1(Height of 'Eoi-Bu-Pyeong-Ju')=0.34H2(Height of 'Nae-Jin-Go-Ju') and single floor 'Main hall of Royal Palace' has a proportion of H1=0.62H2. Third, in Geun-Jeong-Jeon, with the proportion of height and diameter of the pillar, interval's distance between pillars and diameter, the pillar interval distance and height, of 'Ea-kan(御間)' from the 'Toi-Kan' is different from 'Main hall of Royal Palace'. This is because the structure of 'Toi-Kan' of Geun-Jeong-Jeon is not stable. In order to reinforce this, 'Gui-Go-Ju(隅高柱)' of the Geun-Jeong-Jeon jut out $4{\sim}7%$ more compared to In-Jeong-Jeon. Fourth, when comparing double floor 'Main hall of royal palace' of Geun-Jeong-Jeon and In-Jeong-Jeon, based on distance of 'Eoi-Bu-Pyeong-Ju' and 'Nae-Jin-Go-Ju' of lower level, the 'Sang-Bu-Pyeong-Ju(上部平柱)' of Geun-Jeong-Jeon jut out $4{\sim}7%$ more compared to the In-Jeong-Jeon and also It becomes thicker. Fifth, the arrangement of 'Kong-Po' on the front row of 'Gan(間)' had to do with the change of side 'Gan'. Even though the Geun-Jeong-Jeon and the In-Jeong-Jeon were double floors, the arrangement of the 'Kong-Po' is different because the number of side bay is different.

• Journal of Korean Society of Transportation
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• v.24 no.1 s.87
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• pp.121-131
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• 2006

Considering characteristics of drivers and vehicles with proper and reliable ways in highway design Procedures can ensure high level of highway safety. However, it is almost impossible to take into account all factors of drivers and vehicles influencing on the highway safety because of their uncertain and random nature. To detour the dead-end, the nature are usually assumed as simple homogeneous and deterministic one. Although the restricted assumption makes the system simple, it can produce serious problems due to lack of considering variability in the system. This paper develops a reliability-based method for determining stopping sight distance(SSD) and intersection sight distance (ISD), which are crucial elements in highway alignment design. In the study, Hasofer-Lind method is adopted. which is a well-known first-order second moment reliability method (AFOSM) The results in this study show that if mean, variance, and distribution of a particular driver-vehicle parameter are known, more reliable sight distances can be applied in highway design procedures because we can reflect uncertainties and randomness. Thus, the Probabilistic method could be adopted in designing the sight distance(s) with the desired reliability level.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.5_6
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• pp.288-296
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• 2004

This paper proposes a new mesh simplification algorithm using differential error metric. Many simplification algorithms make use of a distance error metric, but it is hard to measure an accurate geometric error for the high-curvature region even though it has a small distance error measured in distance error metric. This paper proposes a new differential error metric that results in unifying a distance metric and its first and second order differentials, which become tangent vector and curvature metric. Since discrete surfaces may be considered as piecewise linear approximation of unknown smooth surfaces, theses differentials can be estimated and we can construct new concept of differential error metric for discrete surfaces with them. For our simplification algorithm based on iterative edge collapses, this differential error metric can assign the new vertex position maintaining the geometry of an original appearance. In this paper, we clearly show that our simplified results have better quality and smaller geometry error than others.

• Progress in Superconductivity
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• v.8 no.2
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• pp.152-157
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• 2007

Uniaxial square Helmholtz coils for testing SQUID sensors were designed and their field distributions were calculated. Optimum parameters for maximizing the uniform region in the Helmholtz mode were obtained for different uniformity tolerances. The coil system consists of 2 pairs of identical square loops, a Helmholtz pair for generating uniform fields and the other for the 2nd-order gradient fields in combination with the Helmholtz pair. Full expressions of the axial component of the field were calculated by using Biot-Savart's law. To understand the behavior of the field near the coil center, analytical expressions were obtained up to the 4th-order in the midplane and along the coil axis. The Helmholtz condition for generating uniform fields was calculated to be $d/{\alpha}=0.544505643$, where 2d is the inter-coil distance and $2{\alpha}$ is the side length of the coil square. Maximized uniform range can be obtained for a given nonuniformity tolerance by choosing $d/{\alpha}$ slightly lower than the Helmholtz condition. The pure second-order gradient field can be generated by subtracting the Helmholtz field from the field of the 2nd pair with equal magnitudes of the center fields of the two pairs. The coil system is useful for testing balance and sensitivity of SQUID gradiometers.

• The Journal of Bigdata
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• v.5 no.1
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• pp.155-180
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• 2020

It takes the most important role the problem of assigining vehicles and desigining optimal routes for each vehicle in order to enhance the logistics service level. While solving the problem, various cost factors such as number of vehicles, the capacity of vehicles, total travelling distance, should be considered at the same time. Although most of logistics service providers introduced the Transportation Management System (TMS), the system has the limitation which can not consider the practical constraints. In order to make the solution of TMS applicable, it is required experts revised the solution of TMS based on their own experience and intuition. In this research, different from previous research which have focused on minimizing the total cost, it has been proposed the methodology which can enhance the efficiency and fairness of asset utilization, simultaneously. First of all, it has been adopted the Cluster-First Route-Second (CFRS) approach. Based on the location of customers, we have grouped customers as clusters by using four different clustering algorithm such as K-Means, K-Medoids, DBSCAN, Model-based clustering and a procedural approach, Fisher & Jaikumar algorithm. After getting the result of clustering, it has been developed the optiamal vehicle routes within clusters. Based on the result of numerical experiments, it can be said that the propsed approach based on CFRS may guarantee the better performance in terms of total travelling time and distance. At the same time, the variance of travelling distance and number of visiting customers among vehicles, it can be concluded that the proposed approach can guarantee the better performance of assigning tasks in terms of fairness.

• Journal of Korea Multimedia Society
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• v.19 no.2
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• pp.418-427
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• 2016

A smart parking management requires to track a vehicle in a indoor parking lot and to detect the place where the vehicle is parked. An advanced parking system watches all space of the parking lot with CCTV cameras. We can use these cameras for vehicles tracking and detection. In order to cover a wide area with a camera, a fisheye lens is used. In this case the shape and size of an moving vehicle vary much with distance and angle to the camera. This makes vehicle detection and tracking difficult. In addition to the fisheye lens, the vehicle headlights also makes vehicle detection and tracking difficult. This paper describes a method of realtime vehicle detection and tracking robust to the harsh situation described above. In each image frame, we update the region of a vehicle and estimate the vehicle movement. First we approximate the shape of a car with a quadrangle and estimate the four sides of the car using multiple histograms of oriented gradient. Second we create a template by applying a distance transform to the car region and estimate the motion of the car with a template matching method.