• ETRI Journal
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• v.45 no.2
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• pp.193-202
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• 2023

We demonstrate the transmission of uncompressed 4K videos over the photonics-based terahertz (THz) wireless link using a directly modulated distributed feedback laser diode (DFB-LD). For optical heterodyne mixing and data modulation, a DFB-LD was employed and directly modulated with a 5.94-Gb/s non-return-to-zero signal, which is related to a 6G-serial digital interface standard to support ultra-high-definition video resolution. We derived the optimal frequency of the THz carrier by varying the wavelength difference between DFB-LD output and Tunable LD output in the THz signal transmitter to obtain the best transmission performances of the uncompressed 4K video signals. Furthermore, we exploited the negative laser-to-filter detuning for the adiabatic chirp management of the DFB-LD by the intentional discrepancy between the center wavelength of the optical band-pass filter and the output wavelength of the DFB-LD. With the help of the abovementioned methods, we successfully transmitted uncompressed 4K video signals over the 2.3-m wireless transmission distance without black frames induced by time synchronization error.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.5
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• pp.233-241
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• 2020

This paper is to investigate the retrofitting effect for a non-seismic reinforced concrete frame strengthened by perimeter steel moment frames with indirect integrity, which ameliorates the problems of the direct integrity method. To achieve this, first, full-scale tests were conducted to address the structural behavior of a two-story non-seismic reinforced concrete frame and a strengthened frame. The non-seismic frame showed a maximum strength of 185 kN because the flexural-shear failure at the bottom end of columns on the first floor was governed, and shear cracks were concentrated at the beam-column joints on the second floor. The strengthened frame possessed a maximum strength of 338 kN, which is more than 1.8 times that of the non-seismic specimen. A considerable decrease in the quantity of cracks for the strengthened frame was observed compared with the non-seismic frame, while there was the obvious appearance of the failure pattern due to the shear crack. The lateral-resisting capacity for the non-seismic bare frame and the strengthened frame may be determined per the specified shear strength of the reinforced columns in accordance with the distance to a critical section. The effective depth of the column may be referred to as the longitudinal length from the border between the column and the foundation. The lateral-resisting capacity for the non-seismic bare frame and the strengthened frame may be reasonably determined per the specified shear strength of the reinforced columns in accordance with the distance to a critical section. The effective depth of the column may be referred to as the longitudinal length from the border between the column and the foundation. The proposed method had an error of about 2.2% for the non-seismic details and about 4.4% for the strengthened frame based on the closed results versus the experimental results.

• Steel and Composite Structures
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• v.5 no.2_3
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• pp.181-192
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• 2005

The effective length method for flexural (column) buckling has been used for many decades but its use is somewhat limited in various contemporary design codes to moderately slender structures with elastic critical load factor (${\lambda}_{cr}$) less than 3 to 5. In pace with the use of higher grade steel in recent years, the influence of buckling in axial buckling resistance of a column becomes more important and the over-simplified assumption of effective length factor can lead to an unsafe, an uneconomical or a both unsafe and uneconomical solution when some members are over-designed while key elements are under-designed. Effective length should not normally be taken as the distance between nodes multiplied by an arbitrary factor like 0.85, 1.0, 2.0 etc. Further, the classification of non-sway and sway-sensitive frames makes the conventional design procedure tedious to use and, more importantly, limited to simple regular frames. This paper describes the practical use of second-order analysis with section capacity check allowing for $P-{\delta}$ and $P-{\Delta}$ effects together with member and system imperfections. Most commercial software considers only the $P-{\Delta}$ effect, but not member and frame imperfections nor $P-{\delta}$ effect, and engineers must be very careful in their uses. A verification problem is also given for validation of software for this type of powerful second-order analysis and design. It is a trend for popular and advanced national design codes in using the second-order analysis as a norm for analysis and design of steel structures while linear analysis may only be used in very simple structures.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.3
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• pp.171-176
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• 2019

Drones are highly utilized because they can efficiently acquire long-distance videos. In drone operation, the speed, which is the magnitude of the velocity, can be set, but the moving direction cannot be set, so accurate information about the drone's movement should be estimated. In this paper, we estimate the velocity of the drone moving at a constant speed and direction. In order to estimate the drone's velocity, the displacement of the target frame to minimize the sum of absolute difference (SAD) of the reference frame and the target frame is obtained. The ground truth of the drone's velocity is calculated using the position of a certain matching point over all frames. In the experiments, a video was obtained from the drone moving at a constant speed at a height of 150 meters. The root mean squared error (RMSE) of the estimated velocities in x and y directions and the RMSE of the speed were obtained showing the reliability of the proposed method.

• Korean Journal of Agricultural Science
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• v.38 no.3
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• pp.505-512
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• 2011

Structural characteristics for standard models of single-span plastic greenhouse in Korea and high tunnels in North America were analyzed, and comparative analysis for greenhouse environments measuring in Korean farmhouse and Rutgers high tunnel was carried out to find structural and environmental improvements of single-span plastic greenhouses that occupy most of Korean greenhouse. Widths of high tunnels are similar to single-span plastic greenhouses but their heights are high comparatively and their side heights are fairly higher than single-span plastic greenhouses specially. Rafters, which are main frames, section sizes of high tunnels are bigger and their intervals are wider than single-span plastic greenhouses. Relative bending resistances compared with representative Korean greenhouse were analyzed by 0.92 to 1.42 in single-span plastic greenhouses, and 1.38 to 2.96 in high tunnels. Frame ratios of single-span plastic greenhouses were 6.8 to 8.6%, and those of high tunnels were 5.5 to 8.7%. We analyzed air temperatures and solar radiations measured in single-span plastic greenhouse and high tunnel on clear days in late March. There were outside temperatures in generally similar range, and judging by rise of indoor temperatures, ventilation performance of high tunnel is more excellent than single-span plastic greenhouse. Solar radiations of two areas were no big difference but light transmittance of high tunnel was a little bit higher than single-span plastic greenhouse. Single-span plastic greenhouses are disadvantageous in environmental managements such as ventilation performance and light transmittance because distance between greenhouses is too narrow and length of greenhouse is too long compared to high tunnels. To get the environmental improvement effects as well as to increase the structural resistance of single-span plastic greenhouses are achievable by widening the width of greenhouse in possible range, widening the space between rafters, and enlarging the section size of rafters. Also, we need to secure enough distance between greenhouses and to restrict the length of greenhouse by maximum 50 m in order to improve the ventilation performance and the light transmittance.

• Korean Journal of Applied Biomechanics
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• v.25 no.1
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• pp.1-10
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• 2015

Objective : The purpose of this study was to find some kinetic variable's relationships between personal records and low records in female high jump. Methods : Collected data of the subjects(N=8, ages: $25.5{\pm}1.85$, height: $173{\pm}5.83$, mass: $54.75{\pm}6.36$ personal record: $1.71{\pm}0.04$, low record: $1.62{\pm}0.03$) were used for the last three strides and take-off phase. Five video cameras set in 30frames/s were used for recording. After digitizing motion, the Direct Linear Transformation(DLT) technique was employed to obtain 3-D position coordinates. The kinematic and kinetic factors of distance, velocity, angle, impulse, jerk variables were calculated. A paired t-test was applied for the difference of variables between personal records and lower records and for correlation with performances and variables. The significance level was accepted at p<.05. Results : There was no relationship between pattern of stride and performance. However, rate of change of velocity was related with cental of mass height(CMH) at peak point(PP). Knee, hip, backward lean, foot plant, approach and take off angle showed no difference between best record and low record. Vertical impulse momentum also showed no difference between performances. Conclusion : According to a t-test result, there were significant differences in CMH at PP and jerk at touch down between best record and low record.

• The KIPS Transactions:PartA
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• v.11A no.5
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• pp.383-390
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• 2004

This paper propose a method that controls facial expression of 3D avatar by having the user select a sequence of facial expressions in the space of facial expressions. And we setup its system. The space of expression is created from about 2400 frames consist of motion captured data of facial expressions. To represent the state of each expression, we use the distance matrix that represents the distances between pairs of feature points on the face. The set of distance matrices is used as the space of expressions. But this space is not such a space where one state can go to another state via the straight trajectory between them. We derive trajectories between two states from the captured set of expressions in an approximate manner. First, two states are regarded adjacent if the distance between their distance matrices is below a given threshold. Any two states are considered to have a trajectory between them If there is a sequence of adjacent states between them. It is assumed . that one states goes to another state via the shortest trajectory between them. The shortest trajectories are found by dynamic programming. The space of facial expressions, as the set of distance matrices, is multidimensional. Facial expression of 3D avatar Is controled in real time as the user navigates the space. To help this process, we visualized the space of expressions in 2D space by using the multidimensional scaling(MDS). To see how effective this system is, we had users control facial expressions of 3D avatar by using the system. As a result of that, users estimate that system is very useful to control facial expression of 3D avatar in real-time.

• The Journal of the Korea Contents Association
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• v.7 no.2
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• pp.117-124
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• 2007

This paper describes methodology that enables animators to create the facial expression animations and to control the facial expressions in real-time by reusing motion capture datas. In order to achieve this, we fix a facial expression state expression method to express facial states based on facial motion data. In addition, by distributing facial expressions into intuitive space using LLE algorithm, it is possible to create the animations or to control the expressions in real-time from facial expression space using user interface. In this paper, approximately 2400 facial expression frames are used to generate facial expression space. In addition, by navigating facial expression space projected on the 2-dimensional plane, it is possible to create the animations or to control the expressions of 3-dimensional avatars in real-time by selecting a series of expressions from facial expression space. In order to distribute approximately 2400 facial expression data into intuitional space, there is need to represents the state of each expressions from facial expression frames. In order to achieve this, the distance matrix that presents the distances between pairs of feature points on the faces, is used. In order to distribute this datas, LLE algorithm is used for visualization in 2-dimensional plane. Animators are told to control facial expressions or to create animations when using the user interface of this system. This paper evaluates the results of the experiment.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.607-611
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• 2008

This paper proposes new video signature using spatio-temporal information for copy detection. The proposed video copy detection method is based on concentric circle partitioning method for each key frame. Firstly, key frames are extracted from whole video using temporal bilinear interpolation periodically and each frame is partitioned as a shape of concentric circle. For the partitioned sub-regions, 4 feature distributions of average intensity, its difference, symmetric difference and circular difference distributions are obtained by using the relation between the sub-regions. Finally these feature distributions are converted into binary signature by using simple hash function and merged together. For the proposed video signature, the similarity distance is calculated by simple Hamming distance so that its matching speed is very fast. From experiment results, the proposed method shows high detection success ratio of average 97.4% for various modifications. Therefore it is expected that the proposed method can be utilized for video copy detection widely.

• Journal of the Korea Society of Computer and Information
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• v.11 no.4 s.42
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• pp.97-107
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• 2006

In this paper, we present a method for the detection and recognition of rectangular markers from a camera image. It converts the camera image to a binary image and extracts contours of objects in the binary image. After that. it approximates the contours to a list of line segments. It finds rectangular markers by using geometrical features which are extracted from the approximated line segments. It normalizes the shape of extracted markers into exact squares by using the warping technique. It extracts feature vectors from marker image by using principal component analysis. It then calculates the distance between feature vector of input marker image and those of standard markers. Finally, it recognizes the marker by using minimum distance method. Experimental results show that the Proposed method achieves 98% recognition rate at maximum for 50 markers and execution speed of 11.1 frames/sec for images which contains eleven markers.