• Journal of Astronomy and Space Sciences
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• v.28 no.4
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• pp.299-304
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• 2011

As more satellites are designed to downlink their observed image data through the X-band frequency band, it is inevitable that the occupied bandwidth of a target satellite will overlap with that of other X-band downlink satellites. For sun-synchronized low earth orbit satellites, in particular, it can be expected that two or more satellites be placed within the looking angle of a ground station antenna at the same time. Due to the overlapping in the frequency band, signals transmitted from the adjacent satellites act as interferers, leading to degraded link performance between target satellite and ground station. In this paper, link analysis was initiated by modeling the radiation pattern of ground station antenna through a validated Jet Propulsion Laboratory peak envelope model. From the relative antenna gain depending on the offset angle from center axis of maximum antenna directivity, the ratio of received interference signal level to the target signal level was calculated. As a result, it was found that the degradation increased when the offset angle was within the first point of radiation pattern. For a 7.3 m antenna, serious link degradation began at an offset angle of 0.4 degrees. From this analysis, the link performance of the coming satellite passes can be recognized, which is helpful to establish an operating procedure that will prevent the ground station from receiving corrupted image data in the event of a degraded link.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.1
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• pp.25-31
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• 1999

A real-time holography system using LCD with CCD camera is proposed. In this system, the rainbow hologram is used since it can be reconstructed by white light source. And to record on CCD camera, a kind of in-line holography method is used to widen the width of the fringe pattern. The interference fringe pattern by proposed system is detected with CCD camera and transferred to the LCD. A 3-dimensional image is reconstructed when the white light source illuminates the LCD. If the position of the input image is changed, that of the reconstructed image is also changed. So it can represent 3-dimensional moving images at real-time. In this paper, to confirm the usefulness of the proposed method, the reconstructed image by holographic film is compared to the same reconstructed image by LCD. In the recording process, the optimal ratio of the reference and object beam intensity is also investigated.

• Journal of Korea Society of Industrial Information Systems
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• v.12 no.1
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• pp.101-107
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• 2007

In this paper, we proposed an stable optical security system using interferometer and cascaded phase keys. For the encryption process, a BPCGH(binary phase computer generated hologram) that reconstructs the origial image is designed, using an iterative algorithm and the resulting hologram is regarded as the image to be encrypted. The BPCGH is encrypted through the exclusive-OR operation with the random generated phase key image. For the decryption process, we cascade the encrypted image and phase key image and interfere with reference wave. Then decrypted hologram image is transformed into phase information. Finally, the origianl image is recovered by an inverse Fourier transformation of the phase information. During this process, interference intensity is very sensitive to external vibrations. a stable interference pattern is obtained using self-pumped phase-conjugate minor made of the photorefractive material. In the proposed security system, without a random generated key image, the original image can not be recovered. And we recover another hologram pattern according to the key images, so can be used an authorized system.

• Journal of Advanced Navigation Technology
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• v.24 no.5
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• pp.393-407
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• 2020

In order to reduce the threat by illegal unmanned aerial vehicles, a tracking system based on sound was implemented. There are three main points to the drone acoustic tracking method. First, it scans the space through variable beam formation to find a sound source and records the sound using a microphone array. Second, it classifies it into a hidden Markov model (HMM) to find out whether the sound source exists or not, and finally, the sound source is In the case of a drone, a sound source recorded and stored as a tracking reference signal based on an adaptive beam pattern is used. The simulation was performed in both the ideal condition without background noise and interference sound and the non-ideal condition with background noise and interference sound, and evaluated the tracking performance of illegal drones. The drone tracking system designed the criteria for determining the presence or absence of a drone according to the improvement of the search distance performance according to the microphone array performance and the degree of sound pattern matching, and reflected in the design of the speech reading circuit.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.7 no.1
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• pp.15-22
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• 2007

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference(ISI) or Multiple Access Interference(MAI) to degrade the performance of CDMA(Code Division Multiple Access) system. Constant Modulus Algorithm which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye- pattern obtained from algorithm are compared.

• Korean Journal of Agricultural Science
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• v.22 no.1
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• pp.11-23
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• 1995

The CAD/CAM system for the manufacturing automation is the newest technology in mechanical engineering area and becomes the important research subject nowadays. Most of all hardwares and softwares for the CAD/CAM system used in the our manufacturing companies such as automobile company are developed by the foreign country and the purchasing price of them is very expensive but their applicability to a certain area is very limited. This study was conducted to develope a CAD/CAM system for the design and the automatic manufacturing of the iron pattern shaped with 3 - dimensional free curved surface, and to test its applicability to the design and the manufacturing of the rotary blade. The results obtained from the study are as follow; 1. The CAD system which can process graphic procedures from the free curved surface shaped data was developed with personal computer. 2. The CAM main program was developed. This main program could produce CL data from CAD data file by checking the tool interference according to the cutting mode. 3. The sub. program which can simulate the tool trace from the CL data was developed. 4. The post processor for the Deckel FP2NC NC milling machine from CL data file was developed and the sub program could transmit NC program through modem to NC milling machine was developed. 5. The developed CAM system seemed to be applicable to any other system. Because the measuring results of the cross sectional thickness of the plastic model from the manufacturing iron pattern by the system showed that this system could properly check the tool interference. 6. In took 75~90 hours to manufacture two iron patterns of rotary blade. For the sake of convenience in applying to the other systems, this system was developed in BASIC and FORTRAN computer language and minimum portion of machine language as possible.

• Journal of the Korea Convergence Society
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• v.10 no.2
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• pp.7-11
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• 2019

Due to diversification and popularization of devices that use rapid transmission, there are many security issues related to radio waves. As the disturbance and interference of the radio wave can cause a direct inconvenience to a life, it is a very important issue. In this paper, as a means to prevent radio disturbance and interference, the projected image of the reference grid and the deformed grid is obtained by measuring the projected $moir{\acute{e}}$ using the white light source, projecting grid and the light source, and a $moir{\acute{e}}$ pattern is generated with an image processing algorithm by applying a phase diagram algorithm, and generated $moir{\acute{e}}$ pattern phase diagram creates a three-dimensional shape. By making an encrypted token using this measured face shape, the transmission of the information through token ring is determined in order to transmit the horizontal transmission having the dynamic security characteristics which includes authentication strength and caller information, etc. And by confirming the uniqueness of the token and by sending and receiving the horizontal transmission using java serialization and deserialization function, a problem solving method is suggested.

• ETRI Journal
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• v.26 no.6
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• pp.520-534
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• 2004

As the density of memories increases, unwanted interference between cells and the coupling noise between bit-lines become significant, requiring parallel testing. Testing high-density memories for a high degree of fault coverage requires either a relatively large number of test vectors or a significant amount of additional test circuitry. This paper proposes a new tiling method and an efficient built-in self-test (BIST) algorithm for neighborhood pattern-sensitive faults (NPSFs) and new neighborhood bit-line sensitive faults (NBLSFs). Instead of the conventional five-cell and nine-cell physical neighborhood layouts to test memory cells, a four-cell layout is utilized. This four-cell layout needs smaller test vectors, provides easier hardware implementation, and is more appropriate for both NPSFs and NBLSFs detection. A CMOS column decoder and the parallel comparator proposed by P. Mazumder are modified to implement the test procedure. Consequently, these reduce the number of transistors used for a BIST circuit. Also, we present algorithm properties such as the capability to detect stuck-at faults, transition faults, conventional pattern-sensitive faults, and neighborhood bit-line sensitive faults.

• Phonetics and Speech Sciences
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• v.3 no.2
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• pp.11-22
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• 2011

The purpose of this study is to find the influence of Chinese falling-rising tone on the pitch pattern of corresponding Sino-Korean words delivered by Chinese learners of Korean and to examine how the falling-rising tone of corresponding Chinese words affect the pitch patterns of Sino-Korean words. The scope of this research is limited to Chinese learners of Korean, especially when they pronounce same-form-same-meaning Sino-Korean words. In this study, Chinese learners pronounced both Chinese words and corresponding Sino-Korean words. Learners' pitch patterns were recorded and analyzed using software and compared with the tone of corresponding Chinese words. Experimental results showed that Sino-Korean words were affected by Chinese 'falling-rising tone - high and level tone' when they started with lenis sounds. On the other hand, when Sino-Korean words started with aspirated sounds they were affected by Chinese 'falling-rising tone - high and level tone', 'falling-rising tone - falling-rising tone', and 'falling-rising tone - falling tone'. In conclusion, the Chinese learners' pitch patterns of Sino-Korean words are affected by Chinese falling-rising tone, especially when Sino-Korean words start with aspirated sounds.

• Design & Manufacturing
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• v.7 no.1
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• pp.11-18
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• 2013

This paper presents the plastic inhomogeneous deformation behavior of bimetal composite rods during the axisymmetric and steady-state extrusion process through a conical die. The rigid-plastic FE model considering frictional contact problem was used to analyze the co-extrusion process with material combinations of Cu/Al. Different cases of initial geometry shape for composite material were simulated under different conditions of co-extrusion process, which includes the interference and frictional conditions. The main design parameters influencing on deformation pattern are diameter ratio of the composite components and semi-die angle. Efforts are focused on the deformation patterns, velocity gradient, predicted forming load and the end distance through the various simulations. Simulation results indicate that there is an obvious difference of forming pattern with various diameter ratio and semi-die angle. The analysis in this paper is concentrated on the evaluation of the design parameters on the deformation pattern of composite rod.