• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.12
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• pp.2662-2670
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• 2009

The effect of the reflector type for the SAW filter on the characteristics of the slanted finger IDT filter have been studied by computer simulation. The IDT was evaporated by Aluminum-Copper alloy. The design condition was optimized by the phase shift of the SAWfilter for WCDMA. We have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness are $5,000{\AA}$, and the width and the space of reflector are $3.6{\mu}m$ and $2.0{\mu}m$, respectively. Frequency response of the fabricated SFIT filter has the property that the center frequency is about 190MHz and bandwidth at the 3dB is probably 8.2MHz. And we could obtain that the return loss is less then 16dB, the ripple characteristics is probably 4dB and the triple transit echo is less then 18dB after when we have matched impedance.

• The KIPS Transactions:PartD
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• v.13D no.3 s.106
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• pp.347-356
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• 2006

A video stream can be represented by a sequence of data points in a multidimensional space. In this paper, we introduce a trend vector that approximates values of data points in a sequence and represents the moving trend of points in the sequence, and present a pattern similarity matching method for data sequences using the trend vector. A sequence is partitioned into multiple segments, each of which is represented by a trend vector. The query processing is based on the comparison of these vectors instead of scanning data elements of entire sequences. Using the trend vector, our method is designed to filter out irrelevant sequences from a database and to find similar sequences with respect to a query. We have performed an extensive experiment on synthetic sequences as well as video streams. Experimental results show that the precision of our method is up to 2.1 times higher and the processing time is up to 45% reduced, compared with an existing method.

• Proceedings of the KAIS Fall Conference
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• 2003.11a
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• pp.223-230
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• 2003

Feature-based similarity retrieval has become an important research issue in multimedia database systems. The features of multimedia data are useful for discriminating between multimedia objects (e 'g', documents, images, video, music score, etc.). For example, images are represented by their color histograms, texture vectors, and shape descriptors, and are usually high-dimensional data. The performance of conventional multidimensional data structures(e'g', R- Tree family, K-D-B tree, grid file, TV-tree) tends to deteriorate as the number of dimensions of feature vectors increases. The R＊-tree is the most successful variant of the R-tree. In this paper, we propose a SOM-based R＊-tree as a new indexing method for high-dimensional feature vectors.The SOM-based R＊-tree combines SOM and R＊-tree to achieve search performance more scalable to high dimensionalities. Self-Organizing Maps (SOMs) provide mapping from high-dimensional feature vectors onto a two dimensional space. The mapping preserves the topology of the feature vectors. The map is called a topological of the feature map, and preserves the mutual relationship (similarity) in the feature spaces of input data, clustering mutually similar feature vectors in neighboring nodes. Each node of the topological feature map holds a codebook vector. A best-matching-image-list. (BMIL) holds similar images that are closest to each codebook vector. In a topological feature map, there are empty nodes in which no image is classified. When we build an R＊-tree, we use codebook vectors of topological feature map which eliminates the empty nodes that cause unnecessary disk access and degrade retrieval performance. We experimentally compare the retrieval time cost of a SOM-based R＊-tree with that of an SOM and an R＊-tree using color feature vectors extracted from 40, 000 images. The result show that the SOM-based R＊-tree outperforms both the SOM and R＊-tree due to the reduction of the number of nodes required to build R＊-tree and retrieval time cost.

• Journal of Internet Computing and Services
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• v.16 no.5
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• pp.1-9
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• 2015

As attacks in cyber space become advanced and complex, monotonous defense approach of one-one matching manner between attack and defense may be limited to defend them. More efficient defense method is required. This paper proposes multi layers security scheme that can support to defend assets against diverse cyber attacks in systematical and adaptive. We model multi layers security scheme based on Defense Zone including several defense layers and also discuss essential technical elements necessary to realize multi layers security scheme such as cyber threats analysis and automated assignment of defense techniques. Also effects of multi layers security scheme and its applicability are explained. In future, for embodiment of multi layers security scheme, researches about detailed architecture design for Defense Zone, automated method to select the best defense technique against attack and modeling normal state of asset for attack detection are needed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.12
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• pp.2374-2381
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• 2007

.We have studied to obtain the properly conditions about impedance matching of the SAW filter for the SPUDT type and the bidirectional transducer type later. And we have studied to obtain the SAW filter for the Slanted Finger Interdigital Transducer(SFIT), was formed on the Langasite substrate and was evaporated by Aluminum-Copper alloy and then we performed computer-simulated by simulator In case the SPUDT, we have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness and the width of reflector are $5000{\AA}$ and $3.6{\mu}m$, respectively. And the of the bidirectional transducer, the width of IDT' fingers and the space between IDT' finger and reflector is $1.8{\mu}m$, respectively. Also, we have performed to series connected the SPUDT type with the bidirectional transducer type filter. The frequency response of the fabricated SAW filter has the property that the center frequency is about 190MHz and bahdwidth at the 3dB is probably 5.3MHz after when we have matched impedance. Also, we could obtain that ripple characteristics is less than 0.3dB and insert loss is probably -20dB after when we have matched impedance.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.152-152
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• 2019

This study demonstrates a novel approach of remotely sensed estimates of stream flow at fifteen hydrological station in the Han River Basin, Korea. Multi-temporal data of the European Space Agency's Sentinel-1 SAR satellite from 19 January, 2015 to 25 August, 2018 is used to develop and validate the flow estimation model for each station. The flow estimation model is based on a power law relationship established between the remotely sensed surface area of water at a selected reach of the stream and the observed discharge. The satellite images were pre-processed for thermal noise, radiometric, speckle and terrain correction. The difference in SAR image brightness caused by the differences in SAR satellite look angle and atmospheric condition are corrected using the histogram matching technique. Selective area filtering is applied to identify the extent of the selected stream reach where the change in water surface area is highly sensitive to the change in stream discharge. Following this, an iterative procedure called the Optimum Threshold Classification Algorithm (OTC) is applied to the multi-temporal selective areas to extract a series of water surface areas. It is observed that the extracted water surface area and the stream discharge are related by the power law equation. A strong correlation coefficient ranging from 0.68 to 0.98 (mean=0.89) was observed for thirteen hydrological stations, while at two stations the relationship was highly affected by the hydraulic structures such as dam. It is further identified that the availability of remotely sensed data for a range of discharge conditions and the geometric properties of the selected stream reach such as the stream width and side slope influence the accuracy of the flow estimation model.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.109-114
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• 2008

This paper presents the development status of a subscale precooled turbojet engine "S-engine" for the hypersonic cruiser and space place. S-engine employs the precooled-cycle using liquid hydrogen as fuel and coolant. It has $23cm{\times}23cm$ of rectangular cross section, 2.6 m of the overall length and about 100 kg of the target weight employing composite materials for a variable-geometry rectangular air-intake and nozzle. The design thrust and specific impulse at sea-level-static(SLS) are 1.2 kN and 2,000 sec respectively. After the system design and component tests, a prototype engine made of metal was manufactured and provided for the system firing test using gaseous hydrogen in March 2007. The core engine performance could be verified in this test. The second firing test using liquid hydrogen was conducted in October 2007. The engine, fuel supplying system and control system for the next flight test were used in this test. We verified the engine start-up sequence, compressor-turbine matching and performance of system and components. A flight test of S-engine is to be conducted by the Balloon-based Operation Vehicle(BOV) at Taiki town in Hokkaido in October 2008. The vehicle is about 5 m in length, 0.55 m in diameter and 500 kg in weight. The vehicle is dropped from an altitude of 40 km by a high-altitude observation balloon. After 40 second free-fall, the vehicle pulls up and S-engine operates for 60 seconds up to Mach 2. High altitude tests of the engine components corresponding to the BOV flight condition are also conducted.

• Nano
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• v.13 no.11
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• pp.1850125.1-1850125.12
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• 2018

To reduce the imbalance of impedance matching between the magnetic metal nanowires and free space, $Fe/TiO_2$ core/shell nanowire arrays with different diameters were fabricated in the templates of anodic aluminum oxide membranes by electrodeposition. The influences of the microstructure on the microwave absorption properties of the $Fe/TiO_2/Al_2O_3$ composites were studied by the transmission/reflection waveguide method. It was demonstrated experimentally that both the interfacial polarization and the diameter of the $Fe/TiO_2$ core/shell nanowires have critical effects on the microwave absorption properties. We also investigated the angle dependence of the microwave absorption properties. Due to the interfacial polarization and associated relaxation, the $Fe/TiO_2/Al_2O_3$ composites exhibited optimal microwave absorption properties when microwave propagation direction was accordant with the axis of the nanowires. Finally, we managed to obtain an optimal reflection loss of below -10 dB (90% absorption) over 10.2-14.8 GHz, with a thickness of 3.0 mm and the minimum value of -39.4 dB at 11.7 GHz.

• Journal of Convergence for Information Technology
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• v.9 no.4
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• pp.14-20
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• 2019

The purpose of this paper is to present a smart QR code recording system and a method of non­storage data delivery that transforms the original data into a form of URL information by encrypting it and encoding the URL information into a QR code so that the QR code can be written and decrypted in a medium without storing the original data. The method of the study was presented by the prior art study and the literature research. Analysis results show that the system is built on the online administration server. The data input signal matching secret code is stored in DB, the QR code generation command converts input data from the password DB to the password information combined into the subordinate locator of the admin server's domain name, URL code. Therefore, the smart QR method of data management (recording and providing) indicates that there are no limitations in the ease and space of use or obstacles to capacity use.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.6
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• pp.171-181
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• 2011

Proposed in this paper is the intelligent video surveillance system to effectively detect multiple loitering objects even that disappear from the out of camera's field of view and later return to a target zone. After the background and foreground are segmented using Gaussian mixture model and shadows are removed, the objects returning to the target zone is recognized using the chromaticity histogram and the duration of loitering is preserved. For more accurate measurement of the loitering behavior, the camera calibration is also applied to map the image plane to the real-world ground. Hence, the loitering behavior can be detected by considering the time duration of the object's existence in the real-world space. The experiment was performed using loitering video and all of the loitering behaviors are accurately detected.