• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.8
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• pp.76-82
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• 2015

A hybrid fiber-optic sensor system which combines fiber Bragg grating sensors and a Michelson interferometer has been constructed and evaluated for condition monitoring of large scale wind turbines. In order to measure multiple stresses applied to wind turbines such as strain, temperature and vibration, the system uses single broadband light source. It addresses both types of sensors, which simplifies the optical setup and enhances the cost-effectiveness of condition monitoring system. An athermal-packaged FBG is used to supply quasi-coherent light, of which coherence length is about 3.28mm, for the Michelson interferometer demodulation. Experimental results demonstrated that the proposed fiber-optic sensor system was capable of measuring strain and temperature with measurement accuracy of 1pm. Also 500~2000Hz vibration signals were successfully analyzed by applying FFT signal processing to interference signals.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.6
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• pp.770-778
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• 2012

In this paper, we propose a multi-path construction scheme to improve the survivability of a multicast session in military hybrid networks. A military hybrid network consists of a static backbone network and multiple mobile stub networks where some nodes are frequently susceptible to be disconnected due to link failure and node mobility. To improve the survivability of multicast sessions, we propose a construction scheme of ${\kappa}$ redundant multi-paths to each receiver. In order to take account of different characteristics of static and mobile networks, we propose quite different multi-path setup approaches for the backbone and stub networks, respectively, and combine them at the boundary point called gateway. We prove that our proposed scheme ensures that each receiver of a multicast session has ${\kappa}$ redundant paths to the common source. Through simulations, we evaluate the performance of the proposed schemes from three aspects : network survivability, recovery cost, and end-to-end delay.

• Journal of Power Electronics
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• v.7 no.2
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• pp.109-117
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• 2007

In this paper, a novel proposal for a utility-interactive three-phase soft commutation sinewave PWM power conditioner with an auxiliary active resonant DC-link snubber is developed for fuel cell and solar power generation systems. The prototype of this power conditioner consists of a PWM boost chopper cascaded three-phase power conditioner, a single two-switch auxiliary resonant DC-link snubber with two electrolytic capacitors incorporated into one leg of a three-phase V-connection inverter and a three-phase AC power source. The proposed cost-effective utility-interactive power conditioner implements a unique design and control system with a high-frequency soft switching sinewave PWM scheme for all system switches. The operating performance of the 10 kW experimental setup including waveform quality, EMI/RFI noises and actual efficiency characteristics of the proposed power conditioner are demonstrated on the basis of the measured data.

• Journal of Welding and Joining
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• v.23 no.5
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• pp.43-48
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• 2005

Conventional non-destructive techniques for inspection of the weld in pipelines require significant test time and high cost. Ultrasonic guided waves have been widely studied and successfully applied to various non-destructive tests with advantage of the long-range inspection. In this paper, a study on the application of ultrasonic guided waves to the long-range inspection of the pipeline is presented using a long-range guided wave inspection system, Wavemaker SE16, GUL. The characteristics and setup of the long-range guided wave inspection system and experimental results in pipes of with various diameter are introduced. The experimental results in mock-up pipes with cluster type detects show that the minimum detectable wall thickness reduction with this guided wave system is $2\~3\%$ in the pipe cross section area. And the wall thickness reduction of $5\%$ in cross section area can be detected when actual detection level is used. Therefore, the applicability of the guided wave systeme to long-range inspection of wall thickness reduction in pipes is verified.

• Journal of Power Electronics
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• v.19 no.2
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• pp.529-539
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• 2019

The modular multilevel converter (MMC) has become a promising topology for high-voltage direct current (HVDC) transmission systems. To control a MMC system properly, the ac-side current, circulating current and submodule (SM) capacitor voltage are taken into consideration. This paper proposes a low-computation indirect model predictive control (IMPC) strategy that takes advantages of the conventional MPC and has no weighting factors. The cost function and duty cycle are introduced to minimize the tracking error of the ac-side current and to eliminate the circulating current. An optimized merge sort (OMS) algorithm is applied to keep the SM capacitor voltages balanced. The proposed IMPC strategy effectively reduces the controller complexity and computational burden. In this paper, a discrete-time mathematical model of a MMC system is developed and the duty ratio of switching state is designed. In addition, a simulation of an eleven-level MMC system based on MATLAB/Simulink and a five-level experimental setup are built to evaluate the feasibility and performance of the proposed low-computation IMPC strategy.

• Nuclear Engineering and Technology
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• v.50 no.7
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• pp.1154-1159
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• 2018

Precise prediction of the radiation interaction position in scintillators plays an important role in medical and industrial imaging systems. In this research, the incident position of the gamma rays was predicted precisely in a plastic rod scintillator by using attenuation technique and multilayer perceptron (MLP) neural network, for the first time. Also, this procedure was performed using nonlinear regression (NLR) method. The experimental setup is comprised of a plastic rod scintillator (BC400) coupled with two PMTs at two sides, a $^{60}Co$ gamma source and two counters that record count rates. Using two proposed techniques (ANN and NLR), the radiation interaction position was predicted in a plastic rod scintillator with a mean relative error percentage less than 4.6% and 14.6%, respectively. The mean absolute error was measured less than 2.5 and 5.5. The correlation coefficient was calculated 0.998 and 0.984, respectively. Also, the ANN technique was confirmed by leave-one-out (LOO) method with 1% error. These results presented the superiority of the ANN method in comparison with NLR and the other methods. The technique and set up used are simpler and faster than other the previous position sensitive detectors. Thus, the time, cost and shielding and electronics requirements are minimized and optimized.

• International Journal of Computer Science & Network Security
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• v.21 no.8
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• pp.161-166
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• 2021

The term parking management system usually refers to the custom built hardware intensive systems installed in building and malls. However, there are many places where such expensive solutions cannot be installed due to various reasons, like cost and urgent/temporary setup requirements. This project focuses on developing a parking management system based on image processing to detect vacant parking slot in an area where automated systems are not installed. Camera images of the parking area are subjected to image processing algorithm which marks virtual slots in the area and extracts occupancy information to guide the incoming drivers about availability and position of vacant spaces. The application consists of two interfaces: one for the guidance of the incoming drivers and the other one for the administrator. The later interface also informs the administrator if a car is not parked properly in the virtual slot. This parking system would reduce the stress and time wastage associated with car parking and would make the management of such areas less costly.

• Tribology and Lubricants
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• v.36 no.6
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• pp.297-306
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• 2020

This paper reviews studies on the types and functions of oil sensors used for machine condition monitoring. Machine condition monitoring is essential for maintaining the reliability of machines and can help avoid catastrophic failures while ensuring the safety and longevity of operation. Machine condition monitoring involves several components, such as compliance monitoring, structural monitoring, thermography, non-destructive testing, and noise and vibration monitoring. Real-time monitoring with oil analysis is also utilized in various industries, such as manufacturing, aerospace, and power plants. The three main methods of oil analysis are off-line, in-line, and on-line techniques. The on-line method is the most popular among these three because it reduces human error during oil sampling, prevents incipient machine failure, reduces the total maintenance cost, and does not need complicated setup or skilled analysts. This method has two advantages over the other two monitoring methods. First, fault conditions can be noticed at the early stages via detection of wear particles using wear particle sensors; therefore, it provides early warning in the failure process. Second, it is convenient and effective for diagnosing data regardless of the measurement time. Real-time condition monitoring with oil analysis uses various oil sensors to diagnose the machine and oil statuses; further, integrated oil sensors can be used to measure several properties simultaneously.

• Asia Marketing Journal
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• v.16 no.1
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• pp.229-241
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• 2014

In 1997 the Asian Foreign Currency Crisis hit Korean shores. In its wake, Korean consumers demanded cost-saving solutions which will increase both the use-life and the fuel efficiency their vehicles. Bullsoneshot's effects include increases in gas mileage as well as cleaner cylinders, intakes and exhaust valves, the product was welcomed by an explosive demand from people driving older cars in an adverse economy. The history of Bullsone can be categorized as two major stages. The First stage is lunching era of "Bullone Shot" following competitor brand. The second stage is extension stage of brand and line based on Bullsone's positive brand equity. Mr. Hyun Woo Shin, formal CEO of OXY inc. and also formal vice president of OCI (Oriental Chemical Industries) take charge of New CEO of Bullsone. He energetically push the Bullsone's family brands and got a desirable results. He also setup ambitious goal : reach 100bn KRW in gross sales within 3 years. "Ripping itself free from 30~40 bn KRW sales range in which the company has stagnated in the last 10 years, Bullsone intends to be aggressive enough in marketing to reach 150 bn KRW in sales in 2013, and reach 700 bn KRW by 2018." This is the goal iterated by Bullsone's top executive team.

• Structural Engineering and Mechanics
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• v.89 no.5
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• pp.467-477
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• 2024

Manufacturing industries, now-a-days, focus mostly on redesigning of the products for reducing cost and lead-time via detailed analysis of its composition and constructional design regarded as the Reverse Engineering (RE) process that involves the acquisition of relevant data of the original product, analysis for its functional use and finally, reproduction of the design for improving the functionality. In the present work, a new model based on optimization at different steps of RE, is proposed to redesign a structural component, which is subjected to severe tensile stress while in service. The component under study is an accessory namely, hitch bracket, attached to the rear axle of a tractor to connect it to the plough. The methodology includes building of a 3D Computer Aided Design (CAD) model from the scanned data of the existing component with the help of 3D scanner. Computer Aided Engineering (CAE) analysis is carried out on the CAD model with existing load conditions by Finite Element Analysis (FEA). Topological optimization is carried out giving rise to a modified/optimized design of the component. It is observed that the performance of the modified component improves significantly with simultaneous weight reduction without affecting its functional use and the manufacturing process setup.