• Proceedings of the KSRS Conference
• /
• 2005.10a
• /
• pp.564-566
• /
• 2005

The relation between HPA (High Power Amplifier) and COMS (Communication Ocean Meteorological Satellite) multi-carrier is analyzed in this paper. MODAC (Meteorological and Ocean Data Application Center) has a primary mission to transmit processed data, HRIT (High Rate Information Transmission) and LRIT (Low Rate Information Transmission), which is normalized and calibrated by pre-processing. It is also replaced with the SOC (Satellite Operation Center) in emergency case and can transmit the command and ranging tones for operation of COMS. From the result of simulation with modelled HPA, it is found that the multi-carrier in one HPA can give rise to an inter-modulation which makes harmonic and spurious elements increase in-band. Under the environment of these increased parasitic elements, the degradation of multi-carrier's quality is estimated from the ratio of the amount of noise to total output power of HPA.

• Proceedings of the KSRS Conference
• /
• 2005.10a
• /
• pp.116-119
• /
• 2005

As to the synthetical estimation of land covering parameters or the compounded land covering classification for multi-resolution satellite data, former researches mainly adopted linear or nonlinear regression models to describe the regression relationship of land covering parameters caused by the degradation of spatial resolution, in order to improve the retrieval accuracy of global land covering parameters based on 1;he lower resolution satellite data. However, these methods can't authentically represent the complementary characteristics of spatial resolutions among different satellite data at arithmetic level. To resolve the problem above, a new compounded land covering classification method at arithmetic level for multi-resolution satellite data is proposed in this .paper. Firstly, on the basis of unsupervised clustering analysis of the higher resolution satellite data, the likelihood distribution scatterplot of each cover type is obtained according to multiple-to-single spatial correspondence between the higher and lower resolution satellite data in some local test regions, then Parzen window approach is adopted to derive the real likelihood functions from the scatterplots, and finally the likelihood functions are extended from the local test regions to the full covering area of the lower resolution satellite data and the global covering area of the lower resolution satellite is classified under the maximum likelihood rule. Some experimental results indicate that this proposed compounded method can improve the classification accuracy of large-scale lower resolution satellite data with the support of some local-area higher resolution satellite data.

• Journal of KIISE:Computing Practices and Letters
• /
• v.9 no.3
• /
• pp.311-321
• /
• 2003

A current firewall or IDS (intrusion detection system) of the network level suffers from many vulnerabilities in internal computing servers. For a secure Linux implementation using system call hooking, this paper defines two requirements such as the multi-level security function of TCSEC B1 and a prevention of hacking attacks. This paper evaluates the secure Linux implemented in terms of the mandatory access control, anti-hacking and performance overhead, and thus shows the security, stability and availability of the multi-level secure Linux. At the kernel level this system protects various hacking attacks such as using Setuid programs, inserting back-door and via-attacks. The performance degradation is an average 1.18% less than other secure OS product.

• The Journal of the Acoustical Society of Korea
• /
• v.21 no.3
• /
• pp.230-236
• /
• 2002

A study on architecture of new parallel interference canceller which can be applied for reverse link of next generation mobile communication system supporting multi-rate is performed on this paper. The proposed method adopts new algorithm which can be applied for multi-rate system to reduce multiple access interference (MAI) which cause performance degradation of CDMA system and limit of channel capacity. The proposed system is evaluated by simulation results under various conditions. As a result, performance enhancement is achieved compared to existing conventional interference cancellers. Although the amount of calculation is increased, we can find that the performance is improved generally.

• Journal of Korea Multimedia Society
• /
• v.6 no.5
• /
• pp.753-768
• /
• 2003

In this paper, we propose a multi-dimensional index structure, tailed a VA(Vector Approximate)-tree that is constructed with vector approximates of multi-dimensional feature vectors. To save storage space for index structures, the VA-tree employs vector approximation concepts of VA-file that presents feature vectors with much smaller number of bits than original value. Since the VA-tree is a tree structure, it does not suffer from performance degradation owing to the increase of data. Also, even though the VA-tree is MBR(Minimum Bounding Region) based tree structure like a R-tree, its split algorithm never allows overlap between MBRs. We show through various experiments that our proposed VA-tree is a suitable index structure for large amount of multi-dimensional data.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2017.05a
• /
• pp.142-143
• /
• 2017

An analysis of the current water leak status of understand structure (underground parking lots, staircases, plumbing systems, water reservoirs, etc.) of multi-family housing in South Korea shows that water leaks are found from cracks in all areas of the underground structure caused by the degradation environment (water pressure by underground water, humidity, temperature, earth pressure, soil behaviour and vibration, etc.), which result in various problems, including mold, malodour, debonding of finishing materials, exfoliation, breakout, water leaks in electrical boxes, efflorescence, sedimentation of calcium hydroxide, decoloration, rusting, damages and pollution among others. Therefore, this study aims to analyse the current status of water leaks in underground structure and use the results as the basic data for developing a standard guideline for water leaks and maintenance by parts of the underground structure of multi-family housing.

• Microbiology and Biotechnology Letters
• /
• v.29 no.2
• /
• pp.110-114
• /
• 2001

Isolation of BacilLus sp. producing multi-enzyme and optimization of medium conditions for its production using feedstuffs for probiotics were carried out in this study. A bacterium isolated from natural resources, namely Bacillus subtilis 4-3, has multi-enzyme activity (phytase. cellulase, xylanasc, protease, and amylase. In the culture of B. subtilis 4-3 using soybean meal and rice bran. relatively low phytate degradation was noted using whereas high phytate degradability was observed with wheat bran (80.63%). The optimal composition of medium using feedstuffs was 1.0% (w/v) soybean meal and 2% (w/v) molasses to yield high cell growth.

• Smart Structures and Systems
• /
• v.30 no.3
• /
• pp.303-315
• /
• 2022

The degradation of wheel tread may result in serious hazards in the railway operation system. Therefore, timely wheel defect diagnosis of in-service trains to avoid tragic events is of particular importance. The focus of this study is to develop a novel wheel defect detection approach based on the relevance vector machine (RVM) which enables online detection of potentially defective wheels with trackside monitoring data acquired under different running-speed conditions. With the dynamic strain responses collected by a trackside monitoring system, the cumulative Fourier amplitudes (CFA) characterizing the effect of individual wheels are extracted to formulate multiple probabilistic regression models (MPRMs) in terms of multi-kernel RVM, which accommodate both variables of vibration frequency and running speed. Compared with the general single-kernel RVM-based model, the proposed multi-kernel MPRM approach bears better local and global representation ability and generalization performance, which are prerequisite for reliable wheel defect detection by means of data acquired under different running-speed conditions. After formulating the MPRMs, we adopt a Bayesian null hypothesis indicator for wheel defect identification and quantification, and the proposed method is demonstrated by utilizing real-world monitoring data acquired by an FBG-based trackside monitoring system deployed on a high-speed trial railway. The results testify the validity of the proposed method for wheel defect detection under different running-speed conditions.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.16 no.2
• /
• pp.61-68
• /
• 2023

Multi-band method which allocate the same data to different frequency bands, improves performance by compensating Doppler spreading and selective fading in underwater communications. The drawback of multi-band configuration may have worse performance because performance degradation in a particular band affects the output from the entire bands. It is very important to find which band is superior or inferior band in order to improve performance. Therefore this paper analyzes performance prediction algorithms of each band. This paper proposes three kinds of prediction methods. Through the ocean tests, this paper confirms utilizing the preamble error rates is most efficient algorithm among of them.

• Transactions of Materials Processing
• /
• v.32 no.4
• /
• pp.208-214
• /
• 2023

This paper discusses the deformation characteristics of a scaled-down automotive outer door panel with vacuum-assisted incremental sheet forming. The vacuum condition between the die and Al6052-H32 sheet with a thickness of 1.0 mm is reviewed with the goal of improving the geometrical accuracy of the target product. The material flow according to the forming tool path, including the multi-tool path and conventional contour tool path, is investigated considering the degradation of the pillow effect. To reduce friction between the tool and the sheet during incremental forming, automotive engine oil (5W-30) is used as a lubricant, and the strain field on the surface of the formed product is analyzed using ARGUS. By comparing the geometry and material flow characteristics of products under different test conditions, it is confirmed that the product surface quality can be significantly improved when the vacuum condition is employed in conjunction with a multi-tool path strategy.