• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.2134-2143
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• 2018

This work introduces a fault diagnosis method for transformer based on self-powered radio frequency identification (RFID) sensor tag and improved Hilbert-Huang transform (HHT). Consisted by RFID tag chip, power management circuit, MCU and accelerometer, the developed RFID sensor tag is used to acquire and wirelessly transmit the vibration signal. A customized power management including solar panel, low dropout (LDO) voltage regulator, supercapacitor and corresponding charging circuit is presented to guarantee constant DC power for the sensor tag. An improved band restricted empirical mode decomposition (BREMD) which is optimized by quantum-behaved particle swarm optimization (QPSO) algorithm is proposed to deal with the raw vibration signal. Compared with traditional methods, this improved BREMD method shows great superiority in reducing mode aliasing. Then, a promising fault diagnosis approach on the basis of Hilbert marginal spectrum variations is brought up. The measured results show that the presented power management circuit can generate 2.5V DC voltage for the rest of the sensor tag. The developed sensor tag can achieve a reliable communication distance of 17.8m in the test environment. Furthermore, the measurement results indicate the promising performance of fault diagnosis for transformer.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권7호
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• pp.3447-3469
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• 2019

It is well-known that the cooperative communication and error control technology can improve the network performance, but most existing cooperative MAC protocols have not focused on how to cope with the contention process caused by cooperation and how to reduce the bad influence of channel packet error rate on the system performance. Inspired by this, this paper first modifies and improves the basic rules of the IEEE 802.11 Medium Access Control (MAC) protocol to optimize the contention among the multi-relay in a cooperative ARQ scheme. Secondly, a hybrid ARQ protocol with soft combining is adopted to make full use of the effective information in the error data packet and hence improve the ability of the receiver to decode the data packet correctly. The closed expressions of network performance including throughput and average packet transmission delay in a saturated network are then analyzed and derived by establishing a dedicated two-dimensional Markov model and solving its steady-state distribution. Finally, the performance evaluation and superiority of the proposed protocol are validated in different representative study cases through MATLAB simulations.

• Current Optics and Photonics
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• 제5권3호
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• pp.220-228
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• 2021

To improve the measurement accuracy of a solar-radiation observer instrument, aiming at the problem of multiorder-stray-light interference caused by the diffraction of the flat-field concave grating in the spectroscopic system, straylight suppression methods for different forms of optical traps are studied. According to the grating surface-scattering distribution-function model, the bidirectional scattering distribution function (BSDF) of a dust-polluted surface and the flat-field concave grating's transition area of the spectroscopic system is calculated, and a Lyot stop with blade baffle is designed to suppress this kind of stray light. For diffraction multiorder stray light, based on the theory of light-energy transmission, a design for precise positioning of the trench optical trap is proposed. The superiority of the method is verified through simulation and actual measurement. The simulation results show that in a spectroscopic system approximately 160 mm × 140 mm × 80 mm in size, the energy of the stray light is reduced by one order of magnitude by means of the trench optical trap and Lyot stop, and the number of beams is reduced from 5664 to 1040. The actual measurements show that the stray-light-suppression efficiency is about 69.4%, which is effective reduction of the amount of stray light.

• 한국항행학회논문지
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• 제25권6호
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• pp.551-556
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• 2021

본 논문에서는 시변 지연 시간이 있는 선형 구간 이산 시스템에 비구조화된 불확실성이 존재하는 경우에 대하여 안정조건을 다룬다. 이산 시스템의 시스템 행렬들이 구간행렬의 형태로 주어지는 구간시스템에 대하여, 지연 시간이 일정 구간 범위 안에서 시변으로 변동되고, 비선형성을 포함한 불확실성이 그 크기만이 주어지는 비구조화된 불확실성의 형태로 존재하는 시스템의 안정성 조건을 제안한다. 안정조건의 유도는 기존의 리아프노프 방정식의 상한 해를 이용한 방법과는 다르게 리아프노프 안정 조건을 기반으로 이루어지며, 간단한 부등식의 형태로 표현되어 안정성 판단에 편리하게 적용될 수 있는 장점을 갖는다. 또한, 제안된 안정조건은 기존에 발표된 다양한 선형 이산 시스템의 안정조건들을 포함하는 매우 포괄적이고 강력한 것으로, 시변 지연시간 변동 크기, 불확실성의 크기와 구간행렬의 범위를 모두 조건식에 포함하게 된다. 새로운 조건의 우수함은 유도과정에서 증명되어지며 수치예제를 통하여 제안된 조건의 효용성과 우수성을 검증한다.

• 대한산업공학회지
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• 제31권1호
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• pp.79-86
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• 2005

The transportation problem (TP) is one of the traditional optimization problems. Unlike the TP, the fixed charge transportation problem (FCTP) cannot be solved using polynomial time algorithms. So, finding solutions for the FCTP is a well-known NP-complete problem involving an importance in a transportation network design. So, it seems to be natural to use evolutionary algorithms for solving FCTP. And many evolutionary algorithms have tackled this problem and shown good performance. This paper introduces an efficient evolutionary algorithm for the FCTP. The proposed algorithm can always generate feasible solutions without any repair process using the random key representation. Especially, it can guide the search toward the basic solution. Finally, we performed comparisons with the previous results known on the benchmark instances and could confirm the superiority of the proposed algorithm.

• 제어로봇시스템학회논문지
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• 제5권5호
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• pp.558-567
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• 1999

X-ray laminography and DT(digital tomosynthesis) that can form a cross-sectional image of 3-D objects promis to be good solutions for inspecting interior defects of industrial products. DT is a kind of laminography technique and the difference is in the fact that it synthesizes the several projected images by use of the digitized memory and computation. The quality of images acquired from the DT system varies according to image synthesizing methods, the number of images used in image synthesizing, and X-ray projection angles. In this paper, a new image synthesizing method named 'log-root method' is proposed to get clear and accurate cross-sectional images, which can reduce both artifact and blurring generated by materials out of focal plane. To evaluate the quality of cross-sectional images, two evaluating criteria : (1) shape accuracy and (2) clearness of the cross-sectional images are defined. Based on these criteria, a series of simulations are performed, and the results show the superiority of the new synthesizing method over the existing ones such as averaging and minimum methods.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.294-297
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• 2009

Multi-view video consists of a set of multiple video sequences from multiple viewpoints or view directions in the same scene. It contains extremely a large amount of data and some extra information to be stored or transmitted to the user. This paper presents inter-view correlations among video objects and the background to reduce the prediction complexity while achieving a high coding efficiency in multi-view video coding. Our proposed algorism is based on object-based segmentation scheme that utilizes video object information obtained from the coded base view. This set of data help us to predict disparity vectors and motion vectors in enhancement views by employing object registration, which leads to high compression and low-complexity coding scheme for enhancement views. An experimental results show that the superiority can provide an improvement of PSNR gain 2.5.3 dB compared to the simulcast.

• Journal of Astronomy and Space Sciences
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• 제29권4호
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• pp.413-422
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• 2012

In recent years, a number of missions have been planned and conducted worldwide on the planets such as Mars, which involves the unmanned robotic exploration with the use of rover. The rover is an important system for unmanned planetary exploration, performing the locomotion and sample collection and analysis at the exploration target of the planetary surface designated by the operator. This study investigates the development of mobility system for the rover ground model necessary to the planetary surface exploration for the benefit of future planetary exploration mission in Korea. First, the requirements for the rover mobility system are summarized and a new mechanism is proposed for a stable performance on rough terrain which consists of the passive suspension system with 8 wheeled double 4-bar linkage (DFBL), followed by the performance evaluation for the mechanism of the mobility system based on the shape design and simulation. The proposed mobility system DFBL was compared with the Rocker-Bogie suspension system of US space agency National Aeronautics and Space Administration and 8 wheeled mobility system CRAB8 developed in Switzerland, using the simulation to demonstrate the superiority with respect to the stability of locomotion. On the basis of the simulation results, a general system configuration was proposed and designed for the rover manufacture.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권9호
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• pp.4510-4526
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• 2017

Most available methods of facial gender recognition work well under a constrained situation, but the performances of these methods have decreased significantly when they are implemented under unconstrained environments. In this paper, a method via low-rank and collaborative representation is proposed for facial gender recognition in the wild. Firstly, the low-rank decomposition is applied to the face image to minimize the negative effect caused by various corruptions and dynamical illuminations in an unconstrained environment. And, we employ the collaborative representation to be as the classifier, which using the much weaker $l_2-norm$ sparsity constraint to achieve similar classification results but with significantly lower complexity. The proposed method combines the low-rank and collaborative representation to an organic whole to solve the task of facial gender recognition under unconstrained environments. Extensive experiments on three benchmarks including AR, CAS-PERL and YouTube are conducted to show the effectiveness of the proposed method. Compared with several state-of-the-art algorithms, our method has overwhelming superiority in the aspects of accuracy and robustness.

• 대한디지털의료영상학회논문지
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• 제6권1호
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• pp.19-23
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• 2003

In recent years, many computer systems that are used for patient diagnostic and treatment purpose s are being introduced within hospitals. Therefore, being in a position to manage the hospital entirely, efforts to integrate their own unique system into one have started. A system values humans and creates the surrounding atmosphere into one which maximizes the abilities of individuals. For this, a scientific integration management operation system is required. The type of system that is demanded due to this requirement is an ERP(Enterprise Resource Planning) system. Lately, even the hospital industry is beginning to show interest in efficient administrative methods. To deliver more predominant medical services, hospitals are trying to introduce scientific administrative methods, whose superiority were proven in enterprises, to the operation system of the hospital organization. ERP values humans over systems, and within a superior system, emphasizes the efficiency of the organization. This sort of process does not just evaluate and manage the working abilities of individuals, but provides an advanced working environment that increases the abilities of members within the organization by fold. Therefore, this research estimates through questionnaires and introductive cases how the introduction of ERP may change the work of customers within hospitals such as the radiologic technology department, and how it may also change the environment of medical services, thus striving to create a radiologic technology department that will not fall behind the times.