• Advances in Computational Design
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• v.2 no.3
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• pp.165-194
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• 2017

The present work proposes the thermo mechanically induced statistics of nonlinear transverse central deflection of elastically supported functionally graded (FG) plate subjected to static loadings with random system properties. The FG plate is supported on two parameters Pasternak foundation with Winkler cubic nonlinearity. The random system properties such as material properties of FG material, external loading and foundation parameters are assumed as uncorrelated random variables. The material properties are assumed as non-uniform temperature distribution with temperature dependent (TD) material properties. The basic formulation for static is based on higher order shear deformation theory (HSDT) with von-Karman nonlinear strain kinematics through Newton-Raphson method. A second order perturbation technique (SOPT) and direct Monte Carlo simulation (MCS) are used to compute the nonlinear governing equation. The effects of load parameters, plate thickness ratios, aspect ratios, volume fraction, exponent, foundation parameters, and boundary conditions with random system properties are examined through parametric studies. The results of present approaches are compared with those results available in the literature and by employing direct Monte Carlo simulation (MCS).

• Journal of the Korean Society for Library and Information Science
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• v.43 no.2
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• pp.193-213
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• 2009

During the 21st century, the rapid changes in libraries and the information environment require the reassessment of the education and certification of library and information professionals in order to enhance their competencies. The purpose of this study is to elicit and propose preliminary models in order to improve the librarian certification system in Korea. In doing so, the perceptions among librarians and users were surveyed through an online questionnaire methodology. Based on the results of the survey and analyses, a mid- and a long-term plans for improving the overall library certification system have been proposed.

• Journal of the Korea Society of Computer and Information
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• v.21 no.2
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• pp.43-49
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• 2016

In this paper, we propose the controllability function and service design to efficiently implement the control of the disaster communication network, using Internet of Things(IoT) Technology. In accordance with the spread of Information Communication Technology(ICT), the era for building a disaster communications system without exclusion over the entire areas has emerged. National wireless mesh networks for public safety and disaster relief have been evolving to strengthen the pre-disaster response system using the latest technologies through the convergence of various technologies and services from the viewpoint of the command and control between disaster response agencies. In line with such a technological paradigm shift, the controllability of the objects in the IoT has been emerging as a key quality requirement of a disaster communications system. In this study, the objects are classified by the subject of control according to the IoT component, such as data, network resources and services in order to effectively implement their controllability. In addition, based on the destination of this controllability, technologies and services have been designed that can reduce the damage caused by disasters. Technologies and services that were derived from this study must be implemented in the current disaster safety network systems together with the establishment of an infrastructure for the networks in order that all persons are able to effectively utilize the disaster communications system for their safety.

• Journal of the Korean Solar Energy Society
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• v.39 no.2
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• pp.1-9
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• 2019

In order to increase the power generation efficiency of the photovoltaic system, a new algorithm that can follow the maximum power point of the photovoltaic power generation system having nonlinear output characteristics is proposed. Conventional maximum power point tracking (MPPT) algorithms such as Perturbation and Observation (P&O) and InCond (Increment and Conductance) schemes can not find the global maximum power point at a plurality of pole points in the unmatched state of unbalanced PV modules. However, even if the global maximum power point is found at a plurality of pole points, the global maximum power that can not be the real maximum power by the photovoltaic generation system. In order to solve this problem, a few PV companies propose installing several small PV inverters instead of if big one. However, since this will require additional costs, we herein propose a Multi-MPPT system using individual 3-point MPPT to track true MPPT at a plurality of pole points in the unmatched state of unbalanced PV modules.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.2
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• pp.175-184
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• 2022

This study analyzed the allocation of the skipper's attention during fishing operation in the wheelhouse of a Korean coastal composite fishing vessel by using video observation. To summarize the results, the ratio of lookout, radar and GPS monitoring, which is essential for prevention of collision at sea, was significantly lower than that of other fishing operation due to the attention concentration on the work place during hauling line. In order to reduce exposure to risk of collisions due to concentration of attention to certain tasks such as line hauling, it is necessary to develop an alert system that can notify the approach of other ships or obstruction throughout the ship using information from radar or the automatic identification system. In addition, the order of attention allocation to devices and facilities obtained in this study is expected to be used as basic data for device or facility layout based on the principle of usage frequency in designing wheelhouse for coastal composite fishing vessels in the future.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.2
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• pp.168-175
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• 2023

In the era of the 4th Industrial Revolution, Logistic 4.0 using data-based technologies such as IoT, Bigdata, and AI is a keystone to logistics intelligence. In particular, the AI technology such as prognostics and health management for the maintenance of logistics facilities is being in the spotlight. In order to ensure the reliability of the facilities, Time-Based Maintenance (TBM) can be performed in every certain period of time, but this causes excessive maintenance costs and has limitations in preventing sudden failures and accidents. On the other hand, the predictive maintenance using AI fault diagnosis model can do not only overcome the limitation of TBM by automatically detecting abnormalities in logistics facilities, but also offer more advantages by predicting future failures and allowing proactive measures to ensure stable and reliable system management. In order to train and predict with AI machine learning model, data needs to be collected, processed, and analyzed. In this study, we have develop a system that utilizes an AI detection model that can detect abnormalities of logistics rotational equipment and diagnose their fault types. In the discussion, we will explain the entire experimental processes : experimental design, data collection procedure, signal processing methods, feature analysis methods, and the model development.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.2
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• pp.71-81
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• 2022

In order for electro-optical tracking system (EOTS) to have accurate target coordinate, accurate navigation results are required. If an integrated navigation system is configured using an inertial measurement unit (IMU) of EOTS and the vehicle's navigation results, navigation results with high rate can be obtained. Due to the time-delay of the navigation results of the vehicle in the EOTS and scale factor errors of the EOTS IMU in high-speed and high dynamic operation of the vehicle, it is much more difficult to have accurate navigation results. In this paper, an integrated navigation system of EOTS which compensates time-delay and scale factor error is proposed. The proposed integrated navigation system consists of vehicle's navigation system which provides time-delayed navigation results, an EOTS IMU, an inertial navigation system (INS), an augmented Kalman filter and integration Kalman filter. The augmented Kalman filter outputs navigation results, in which the time-delay of the vehicle's navigation results is compensated. The integration Kalman filter estimates position, velocity, attitude error of the EOTS INS and accelerometer bias, accelerometer scale factor error, gyro bias and gyro scale factor error from the difference between the output of the augmented Kalman filter and the navigation result of the EOTS INS. In order to check performance of the proposed integrated navigation system, simulations for output data of a measurement generator and land vehicle experiments were performed. The performance evaluation results show that the proposed integrated navigation system provides more accurate navigation results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1565-1576
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• 2002

By way of driving a 2-way on/off solenoid hydraulic valve with a pulse width modulation (PWM) signal, control of the pressure in a certain volume is frequently used in various applications. However, the pressure built-up according to the duty ratio and carrier frequency of the PWM signal is not so well understood. In order to clarify the characteristics of 2-way valve hydraulic pressure control systems, in this paper two formula fur the mean and ripple of the load pressure were derived through theoretical analysis. And the accuracy of the derived formula were verified by comparison with the experimental test result. Generally 2-way valve systems are constructed as a bleed-off circuit, while 3-way valves are used as a control element in a meter-in circuit pressure control system. In a bleed-off circuit, the system supply pressure from a hydraulic power pack does not remain constant, but changes according to their external load. In turn, the relief valve in the hydraulic power pack reacts accordingly showing complicated dynamic behavior, which makes an analytical study difficult. In order to resolve the problem, simple but accurate empirical dynamic models fer a bleed-off system were used in the course of formula derivation. As the result, selection criteria for two major control parameters of the driving signal is established and the basic strategy to suppress the unnecessary pressure fluctuation can be provided for a hydraulic pressure control system using a 2-way on/off solenoid valve.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.3
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• pp.319-332
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• 2010

In general, wastewater treatment systems consume high-energy consumption depending on operation characteristics of the facilities. Therefore, greenhouse gas(GHG) reduction activities that are application of digestion gas, induction of renewable energy etc. are conducted to reduce energy consumption and to increase energy independence ratio. In this study, GHG reduction in wastewater treatment system identified, searched application of Clean Development mechanism(CDM) approved methodology. If the methodologies apply to GHG reduction activities such as application of digestion gas, heat pump system using the wastewater as heat source, hydropower using the methodology determined CDM applicability, otherwise through several assumptions calculated expectable GHG reduction emissions and determined CDM applicability. As a result, the order of calculated GHG reduction emission showed that collected and energy generation of digestion gas is 66,775 $tCO_2$/yr, gas engine cogeneration system is 8,182 $tCO_2$/yr, heat pump system using the wastewater as a heat source is 72,715 $tCO_2$/yr, and hydropower is 561 $tCO_2$/yr. Consequently, the order of calculated Certified Emission Reductions(CERs) benefit showed that heat pump system using the wastewater, as a heat source is 1,381 million won/yr was estimated as the highest, followed by a collected and energy generation of digestion gas is 1,268 million won/yr.

• Journal of Digital Convergence
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• v.15 no.7
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• pp.213-222
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• 2017

This paper proposes a new service design which is deep learning-based image retrieval system for product search on O2O shopping mall platform. We have implemented deep learning technology that provides more convenient retrieval service for diverse images of many products that are sold in the internet shopping malls. In order to implement this retrieval system, real data used by shopping mall companies were used as experimental data. However, result from several experiments have confirmed deterioration of retrieval performance due to data components. In order to improve the performance, the learning data that interferes with the retrieval is revised several times, and then the values of experimental result are quantified with the verification data. Using the numerical values of these experiments, we have applied them to the new service design in this system.