• Publications of The Korean Astronomical Society
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• v.38 no.2
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• pp.59-73
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• 2023

Since the farside of the moon is a place to avoid artificial radio frequency interference (RFI) created by human civilization, it is a most suitable place for searching technosignature, which are signs of technological civilization in the universe, in the radio band. The RFI is a factor that makes the study of searching technosignature quite complicated because it is difficult to distinguish between technological signals produced by human and extraterrestrial civilizations. In this paper, we review why the farside of the moon is the best place to detect technosignature and also introduce radio observatories on the farside of the moon that have been proposed in radio astronomy. The SETI (Search for Extraterrestrial Intelligence) project on the farside of the moon is expected to be one of the main candidates for international collaboration research topics on lunar surface observatory.

• Publications of The Korean Astronomical Society
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• v.38 no.2
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• pp.75-89
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• 2023

Technosignature, previously known as SETI(search for extraterrestrial intelligence), is the scientific evidence of past or present extraterrestrial civilizations. Since NRAO's Project Ozma was performed in 1960, most of the noticeable technosignature searches have been done by radio telescopes, hoping to find strong and narrow bandwidth signals that cannot be explained by known natural processes. Recently, the Breakthrough Listen project has opened a new opportunity for technosignature by utilizing both optical telescopes, radio telescopes, and next-generation radio telescope arrays. In this review, mainly based on NASA Technosignatures Workshop (2018), we review the current trends of technosignature surveys, as well as other possible methods for detecting technosignature. Also, we suggest what the Korean community could contribute the technosignature research, including the new SETI project with Korea VLBI Network (KVN).

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.2
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• pp.41-50
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• 2004

Since the MPEG-4 visual standard enables content-based functionalities, it is necessary to extract video objects from video sequences. Segmentation algorithms can largely be classified into two different categories: automatic segmentation and user-assisted segmentation. In this paper, we propose a new user-assisted image segmentation method based on the active contour. If we define a shape space as a set of all possible variations from the initial curve and we assume that the shape space is linear, it can be decomposed into the column space and the left null space of the shape matrix. In the proposed method, the shape space vector in the column space describes changes from the initial curve to the imaginary feature curve, and a dynamic graph search algorithm describes the detailed shape of the object in the left null space. Since we employ the shape matrix and the SUSAN operator to outline object boundaries, the proposed algorithm can ignore unwanted feature points generated by low-level image processing operations and is, therefore, applicable to images of complex background. We can also compensate for limitations of the shape matrix with a dynamic graph search algorithm.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.609-614
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• 1989

A collision avoidance algorithm based on a heuristic graph search and subgoals is presented. The joint angle space is quantized into cells. The evaluation function for a heuristic search is defined by the sum of the distance between the links of a manipulator and middle planes among the obstables and the distance between the end-effector and the subgoals on desired trajectory. These subgoals reduce the combinatorial explosion in the search space. This method enables us to avoid a dead-lock in searching. Its effectiveness has been verified by simulation studies.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.531-533
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• 1997

PI(proportional-integral) controller has been extensively used in the industrial field. But in practicle case, it is difficult to tune PI gains. Evolution Strategy(ES) is used as an effective search algorithm in optimization programs. In this paper we proposed a PI controller for Spot welder system using ES with varying search space. ES with varying search space which depends on fitness values at each generation is used to tune PI control parameters. Simulation results show the proposed algorithm has accurate and robust performance with effective search ability.

• Journal of Creative Information Culture
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• v.6 no.1
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• pp.41-48
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• 2020

In order to represent and process spatial data, hierarchical data structures such as a quadtree or a bintree are used. Various approaches for linearly representing the bintree have been proposed. S-Tree has the advantage of compressing the storage space by expressing binary region image data as a linear binary bit stream, but the higher the resolution of the image, the longer the length of the binary bit stream, the longer the storage space and the lower the search performance. In this paper, we construct a hierarchical structure of multiple separated bintrees with a full binary tree structure and express each bintree as two linear binary bit streams to reduce the range required for image search. It improves the overall search performance by performing a simple number conversion instead of searching directly the binary bit string path. Through the performance evaluation by the worst-case space-time complexity analysis, it was analyzed that the proposed method has better search performance and space efficiency than the previous one.

• The Bulletin of The Korean Astronomical Society
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• v.30 no.2
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• pp.72.2-72.2
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• 2005

• Journal of Power Electronics
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• v.15 no.3
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• pp.670-684
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• 2015

The hybrid cascaded multilevel inverter (HCMLI) is a popular converter topology that is being increasingly used in high power medium voltage drives. The intricacy of the control technique for a HCMLI increases with the number of levels and due to fluctuating dc voltages. This paper presents a novel offline quadrant search based space vector modulation technique to synthesize a sinusoidal output from a dispersed pattern of voltage vectors due to different voltages in the auxiliary unit. Such an investigation has never been reported in the literature and it is being attempted for the first time. The method suggested distributes the voltage vectors for a reduced total harmonic distortion at minimal computation. In addition, the proposed algorithm determines the maximum modulation index in the linear modulation range in order to synthesize a sinusoidal output for both normal and abnormal vector patterns. It is better suited for a wide range of practical applications. It is particularly well suited for renewable source fed inverters which utilize large capacitor banks to maintain the dc link, which are prone to such slow fluctuations. The proposed quadrant search space vector modulation technique is simulated using MATLAB/SIMULINK and implemented using a Nexys-2 Spartan-3E FPGA for a developed prototype.

• The Journal of the Acoustical Society of Korea
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• v.21 no.6
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• pp.543-551
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• 2002

In this paper, we present an efficient decoding method that performs in real time for 20k word continuous speech recognition task. Basic search method is a one-pass Viterbi decoder on the search space constructed from the novel language model network. With the consistent search space representation derived from various language models by the LM network, we incorporate basic pruning strategies, from which tokens alive constitute a dynamic search space. To facilitate post-processing, it produces a word graph and a N-best list subsequently. The decoder is tested on the database of 20k words and evaluated with respect to accuracy and RTF.

• Bulletin of the Korean Space Science Society
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• 2007.10a
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• pp.36-36
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• 2007