• Management & Information Systems Review
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• v.3
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• pp.201-214
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• 1999

Adaptive correlator receiver with neural network based on complex multilayer perceptron is persented for suppressing interference of narrow-band of direct spread spectrum communication systems. Recursive least square algorithm with backpropagation error is used for fast convergence and better performance in adaptive correlator scheme. According to signal noise and transmission power, computer simulation results show that bit error ratio of adaptive correlator using neural network improved that of adative transversal filter of direct sequence spread spectrum considering of jamming and narrow-band interference. Bit error ratio of adaptive correlator with neural network is reduced about 10-1 than that of adaptive transversal filter where interference versus signal ratio is 5dB.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1175-1182
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• 2021

The receiver of each radio telescope of KVN, has a sampler that converts astronomical radio signal to digital data. The ability of this sampler (the bandwidth, sampling frequency, and sampling bits) is improved by sqrt(n), if the bandwidth is increased by n times, and the number of observable objects increases exponentially in the case of continum spectrum radio sources. As the bandwidth increases, there are the more spectrum lines that can be simultaneously monitored in the radio source. This will greatly expand the research area in astronomical radio observation. For this reason, we are trying to independently develop the technology of the fast digital sampler. Therefore, based on the research experience and technology accumulated so far, An ability of sampling up to 3.5 GHz, that can vary the sampling frequency and can observe in a wider band, was designed and made for proto-type. In this study, we introduce the development details and test results for new sampling system.

• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.1024-1031
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• 2019

The Molten Salt Fast Reactor (MSFR) with its liquid circulating fuel and its fast neutron spectrum calls for a new safety approach including technological neutral methodologies and analysis tools adapted to early design phases. In the frame of the Horizon2020 program SAMOFAR (Safety Assessment of the Molten Salt Fast Reactor) a safety approach suitable for Molten Salt Reactors is being developed and applied to the MSFR. After a description of the MSFR reference design, this paper focuses on the identification of the Postulated Initiating Events (PIEs), which is a core part of the global assessment methodology. To fulfil this task, the Functional Failure Mode and Effect Analysis (FFMEA) and the Master Logic Diagram (MLD) are selected and employed separately in order to be as exhaustive as possible in the identification of the initiating events of the system. Finally, an extract of the list of PIEs, selected as the most representative events resulting from the implementation of both methods, is presented to illustrate the methodology and some of the outcomes of the methods are compared in order to highlight symbioses and differences between the MLD and the FFMEA.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.8
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• pp.11-18
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• 1993

In a spread spectrum system, the bandwidth and period of spreading code is wide and long, respectively. So it is necessary to make the code acquisition time as short as possible. In particular, serial search code acquisition system requires optimum dwell time for fast acquisition. In this paper, code acquisition time is calculated by varying dwell time. Among them, minimum code acquisition time is chosen and then optimum dwell time can be obtained. Detection probability (P$_{D}$) and false alarm probability (P$_{FA}$) can be obtained by integrating chi-square pdf by numerical analysis. The results are compared with that of gaussian approximation method and then it is concluded gaussian approximation method is not suitable for obtaining optimum dwell time. Computer simulation supports theoretical results.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.5
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• pp.24-30
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• 1996

In this paper, we propose a fast code acquisition method that can reduce drastically the mean acquisition time of the direct sequence spread spectrum (DS-SS) system by using and integrated search and verification (ISV) scheme. The proposed method performs simultaneously the search and verification processes at every search cell, through storing sufficiently long signal samples enough to perform the verification process form the previously received samples. We analyze and acquisition performance in the case of Gaussian channel to evaluate theacquisition perfomrance of the proposed method. From the simple numericl analysis result, we have shown that the acquisition performance of the proposed method is better than that of the conventional serial search method, and the performance improvement becomes more prominent as the channel environment becomes degraded.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.457-462
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• 2007

This paper reports on the research which investigates acoustic signals acquired in turning with rough and finish simultaneously. The material is aluminum thin pipe. Two acoustic sensors were set on CNC machine. One was set on the finish bite and the other the rough. Two signals were first analyzed in order to consider how much the acoustic signal from the finish bite was coupled by that from the rough. A simple data collecting system to acquire signals from the finish was then determined because two acoustic signals were little coupled. Second the fundamental experiments were accomplished to study the effects of machine vibration and material state. The signal characteristics due to surface defects were studied from the collected acoustic signal data. The signal analysis was based on real time data, root mean squared average and frequency spectrum by fast fourier transform. As a result, the acoustic signals were made effects by machine condition, material structure. The acoustic signal from the finish bite was closely correlated with surface quality. Two types surface micro defects were then evaluated by the signal characteristics.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.140-142
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• 2013

Cognitive radio (CR) has been recently proposed to dynamically access unused-spectrum. Since the spectrum availability for opportunistic access is determined by spectrum sensing, sensing control is identified as one of the most crucial issues of cognitive radio networks. Out-of-band sensing to find an available channels to sense. Sensing is also required in case of spectrum hand-off. Sensing process needs to be done very fast in order to enhance the quality of service (QoS) of the CR nodes, and transmission not to be cut for longer time. During the sensing, the PU(primary user) detection probability condition should be satisfied. We adopt a channel prediction method to find target channels. Proposed prediction method combines chaotic global method and chaotic local method for channel idle probability prediction. Global method focus on channel history information length and order number of prediction model. Local method focus on local prediction trend. Through making simulation, Proposed method can find an available channel with very high probability, total sensing time is minimized, detection probability of PU's are satisfied.

• Journal of the Korean Chemical Society
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• v.15 no.1
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• pp.37-44
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• 1971

The reaction of amino acids and the reactive hydroxyl radical generated by $Ti^{3+}-H_2O_2$ system was studied using fast flow techniques coupled with ESR. Upon adding methionine to the 0.2M $H_2O_2$ solution (0.05M methionine after addition) and mixing with 0.01M $TiCl_3$, the low field component of the two incompletely resolved peaks, in the spectrum of $Ti^{3+}-H_2O_2$ system alone, vanished completely whereas the high field component remained almost constant and superimposed on the secondary spectrum of the methionine free radical. Similar results were obtained for other amino acids and proteins. The results strongly demonstrate that the $T^{3+}-H_2O_2$ flow system generates two different radical species, only one of which, giving rise to the low field component, is alone responsible for abstracting hydrogen atoms from substrate molecules. The effects of HCl, $H_2SO_4$ and NaOH on the system were also studied with widely varying results.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1789-1803
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• 2022

RAST-F is a new full-core analysis code based on the two-step approach that couples a multi-group cross-section generation Monte-Carlo code MCS and a multi-group nodal diffusion solver. To demonstrate the feasibility of using MCS/RAST-F for fast reactor analysis, this paper presents the coupled nodal code verification results for the MET-1000 and CAR-3600 benchmark cores. Three different multi-group cross-section calculation schemes are employed to improve the agreement between the nodal and reference solutions. The reference solution is obtained by the MCS code using continuous-energy nuclear data. Additionally, the MCS/RAST-F nodal solution is verified with results based on cross-section generated by collision probability code TULIP. A good agreement between MCS/RAST-F and reference solution is observed with less than 120 pcm discrepancy in k_eff and less than 1.2% root-mean-square error in power distribution. This study confirms the two-step approach MCS/RAST-F as a reliable tool for the three-dimensional simulation of reactor cores with fast spectrum.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.719-722
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• 2019

Gamma-ray images generally suffer from a lot of noise because of low photon detection in the gamma camera system. The purpose of this study is to improve the image quality in gamma-ray images using a gamma camera system with a fast nonlocal means (FNLM) noise reduction algorithm with an acceleration function. The designed FNLM algorithm is based on local region considerations, including the Euclidean distance in the gamma-ray image and use of the encoded information. To evaluate the noise characteristics, the normalized noise power spectrum (NNPS), contrast-to-noise ratio (CNR), and coefficient of variation (COV) were used. According to the NNPS result, the lowest values can be obtained using the FNLM noise reduction algorithm. In addition, when the conventional methods and the FNLM noise reduction algorithm were compared, the average CNR and COV using the proposed algorithm were approximately 2.23 and 7.95 times better than those of the noisy image, respectively. In particular, the image-processing time of the FNLM noise reduction algorithm can achieve the fastest time compared with conventional noise reduction methods. The results of the image qualities related to noise characteristics demonstrated the superiority of the proposed FNLM noise reduction algorithm in a gamma camera system.