• Journal of IKEEE
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• v.25 no.4
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• pp.689-696
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• 2021

In this paper, in order to apply Prognostics and Health Management(PHM) to an electronic system or circuit, a circuit capable of detecting and predicting defect characteristics inside the system or circuit is implemented, and the results are described. In the previous study, we demonstrated that the frequency of the amplitude of S-parameter changed as the circuit defect progressed. These characteristics were measured by network analyser. but in this study, even if the same defect detection method is used, a circuit is proposed to check the progress of the defect, the remaining time, and the occurrence of the defect without large measurement devices. The circuit is designed to detect the change in impedance that generates changes of S-parameter, and it is verified through simulation using the measurement results of Bond-wires.

• Journal of IKEEE
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• v.26 no.3
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• pp.488-493
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• 2022

In manufacturing sites, bearing fault in eletrically driven motors cause the entire system to shut down. Stopping the operation of this environment causes huge losses in time and money. The reason of this bearing defects can be various factors such as wear due to continuous contact of rotating elements, excessive load addition, and operating environment. In this paper, a motor driving environment is created which is similar to the domestic manufacturing sites. In addition, based on the established environment, we propose a dataset for bearing fault detection by collecting changes in vibration characteristics that vary depending on normal and defective conditions. The sensor used to collect the vibration characteristics is Microphone G.R.A.S. 40PH-10. We used various machine learning models to build a prototype bearing fault detection system trained on the proposed dataset. As the result, based on the deep neural network model, it shows high accuracy performance of 92.3% in the time domain and 98.3% in the frequency domain.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.40 no.2
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• pp.109-118
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• 2022

GPR (Ground Penetrating Radar), developed as a technology for geotechnical investigations such as sinkhole exploration, was used limitedly as a method to resolve undetectable lines in underground facility exploration. To improve the accuracy of underground facility data, the government made it possible to explore underground facilities using a non-metallic pipeline probe from July 2022. However, GPR has a problem in that the exploration rate is lowered in the soil with high moisture content, such as soft soil, such as clay layer, and there is a lot of variation in long-term accuracy. In this study, as a way to improve the accuracy of exploration considering the characteristics of GPR and the environment of underground facilities, we propose a GPR exploration method for underground facilities using permittivity constant correction and pattern analysis of GPR image data. Through this study, the accuracy of underground facility exploration and high reproducibility were derived as a result of field verification applying GPR frequency band and heterogeneous GPR.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.11
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• pp.1635-1641
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• 2021

Portable systems with built-in active noise control is required low power operation. Excessive anti noise search operation can lead to rapid battery consumption. A method that can adaptively cancel noise according to the operating conditions of the system is required and the methods of reducing power are becoming very important key feature in today's portable systems. In this paper, we propose the method of active noise control(ANC) using binary search algorithm in noisy systems. The implemented architecture detects a frequency component considered as noise from the input signal and by using the binary search algorithm, the system find out an appropriate amplitude value for anti-noise in a much faster time than the general linear search algorithm. Through the experimental results, it was confirmed that the proposed algorithm performs a successful functional operation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.7
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• pp.1040-1046
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• 2022

In this paper, we consider a system with massive user equipments (UEs) in a cell and assume path loss and Rayleigh fading channels between the base station (BS) and UEs. In addition, it is assumed that the system bandwidth consists of multiple identical frequency subchannels. Under such assumptions, we propose a channel state information (CSI) feedback scheme and a resource allocation scheme for non-orthogonal multiple access (NOMA) transmission in order to reduce the feedback overhead of CSI generated by massive UEs and to reduce the complexity of resource allocation. In particular, for the proposed schemes, we analyze the sum data rate achievable by massive UEs in a cell and the outage probability with which the UEs in a cell do not meet the target data rate. Through the simulation results, we show that the proposed schemes can provide the superior outage probability, although it degrades the average sum data rate.

• Journal of the Korean Society of Radiology
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• v.16 no.4
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• pp.395-403
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• 2022

Flat-panel detector (FPD) used in digital radiographic imaging systems was used to perform a quantitative power spectrum evaluation as a result of the thickness change of polymethyl methacrylate (PMMA), a tissue equivalent. As the PMMA thickness increases with the resolution-chart phantom image, the effect of the scattering line increases, indicating that the modulation characteristics decrease, and the image is bright. The results show that the noise of the image increases, and noise-power spectral images are obtained by Fourier transform to confirm by spatial frequency. Thus, it can be verified that the PMMA thickness and noise are proportional through the result of evaluating the change of resolution characteristics and representing the 2D noise-power spectrum as one-dimensional values by evaluating the change of scattering line with MTF as the PMMA thickness increases in the image.

• Journal of Broadcast Engineering
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• v.28 no.1
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• pp.3-20
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• 2023

A computer-generated hologram (CGH) is a digitally calculated and recorded hologram in which the amplitude and phase information of an image is transmitted in free space. The CGH is in the form of a complex hologram, but it is converted into a phase-only hologram to display through a phase-only spatial light modulator (SLM). In this paper, in the process of including the amplitude information of an object in the phase information, when a technique that includes subsampling such as DPAC is used, we showed experimentally that the bandwidth of the phase-only hologram increases, and as a result, aliasing that was not present in the complex hologram can occur. In addition, it was experimentally shown that it is possible to generate a high-quality phase-only hologram by restricting the spatial frequency range even at a distance where the numerical reconstruction performance is degraded by aliasing.

• Journal of the Institute of Convergence Signal Processing
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• v.23 no.2
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• pp.84-90
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• 2022

Machine tool state monitoring is a process that automatically detects the states of machine. In the manufacturing process, the efficiency of machining and the quality of the product are affected by the condition of the tool. Wear and broken tools can cause more serious problems in process performance and lower product quality. Therefore, it is necessary to develop a system to prevent tool wear and damage during the process so that the tool can be replaced in a timely manner. This paper proposes a method for diagnosing five tool states using a deep learning-based hierarchical convolutional neural network to change tools at the right time. The one-dimensional acoustic signal generated when the machine cuts the workpiece is converted into a frequency-based power spectral density two-dimensional image and use as an input for a convolutional neural network. The learning model diagnoses five tool states through three hierarchical steps. The proposed method showed high accuracy compared to the conventional method. In addition, it will be able to be utilized in a smart factory fault diagnosis system that can monitor various machine tools through real-time connecting.

• Journal of the Korean Geotechnical Society
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• v.23 no.12
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• pp.117-124
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• 2007

This study investigates the effect of spatial averaging and compliance taken account of in the analysis of earthquake-induced permanent deformation of slopes. At present, the rigid block analysis originally proposed by Newmark is widely used in the deformation analysis, mainly because of its computational efficiency. This type of approach, however, adopts the so-called decoupled approach, in which seismic response and deformation analyses are carried out separately. Original Newmark block analysis assumes the potential sliding mass to be noncompliant, and has been criticized to be potentially unconservative. This paper reviews the impact of the noncompliance assumption of the potential sliding mass in the Newmark-type analysis. The gross effects of earthquake shaking on the potential sliding mass are estimated by spatial averaging method and analyzed in frequency domain. The results indicate that there is a simple criterion that can be used to determine the level of compliance of the potential sliding mass.

• Composites Research
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• v.19 no.3
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• pp.1-6
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• 2006

As the structures of the high performance electronic equipments and devices recently become more complex, the electromagnetic interference (EMI) and compatibility (EMC) have been very essential for commercial and military purposes. Thus, sensitive electrical devices and densely packed systems need to be protected from electromagnetic wave. In this research, glass fabric/epoxy composites containing conductive multi-walled carbon nanotube (MWNT) and carbon fiber/epoxy composites as electrical shielding materials were fabricated and electrical properties of the composites were measured. The concerning frequency band is from 300 MHz to 1 GHz. The performances of composite shielding enclosures were predicted using electromagnetic wave 3-D simulation tool, CST Microwave Studio. The shielding enclosure made of carbon fiber/epoxy composites were fabricated and the shielding effectiveness (SE) was measured in the anechoic chamber.