• Journal of Computational Design and Engineering
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• v.3 no.3
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• pp.179-190
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• 2016

A kind of modified epoxy resin sheet molding compounds of the impeller has been designed. Through the test, the non-metal impeller has a better environmental aging performance, but must do the waterproof processing design. In order to improve the stability of the impeller vibration design, the influence of uncertainty factors is considered, and a multi-objective robust optimization method is proposed to reduce the weight of the impeller. Firstly, based on the fluid-structure interaction, the analysis model of the impeller vibration is constructed. Secondly, the optimal approximate model of the impeller is constructed by using the Latin hypercube and radial basis function, and the fitting and optimization accuracy of the approximate model is improved by increasing the sample points. Finally, the micro multi-objective genetic algorithm is applied to the robust optimization of approximate model, and the Monte Carlo simulation and Sobol sampling techniques are used for reliability analysis. By comparing the results of the deterministic, different sigma levels and different materials, the multi-objective optimization of the SMC molding impeller can meet the requirements of engineering stability and lightweight. And the effectiveness of the proposed multi-objective robust optimization method is verified by the error analysis. After the SMC molding and the robust optimization of the impeller, the optimized rate reached 42.5%, which greatly improved the economic benefit, and greatly reduce the vibration of the ventilation system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.6
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• pp.2889-2909
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• 2017

Wireless sensor networks (WSNs) have attracted lots of attention in recent years due to their potential for various applications. In this paper, we seek how to efficiently deploy relay nodes into traditional static WSNs with constrained locations, aiming to satisfy specific requirements of the industry, such as average energy consumption and average network reliability. This constrained relay node deployment problem (CRNDP) is known as NP-hard optimization problem in the literature. We consider addressing this multi-objective (MO) optimization problem with an improved Artificial Bee Colony (ABC) algorithm with a linear local search (MOABCLLS), which is an extension of an improved ABC and applies two strategies of MO optimization. In order to verify the effectiveness of the MOABCLLS, two versions of MO ABC, two additional standard genetic algorithms, NSGA-II and SPEA2, and two different MO trajectory algorithms are included for comparison. We employ these metaheuristics on a test data set obtained from the literature. For an in-depth analysis of the behavior of the MOABCLLS compared to traditional methodologies, a statistical procedure is utilized to analyze the results. After studying the results, it is concluded that constrained relay node deployment using the MOABCLLS outperforms the performance of the other algorithms, based on two MO quality metrics: hypervolume and coverage of two sets.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1349-1355
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• 2016

It should guarantee high reliability and ultra low latency communication. Additionally, it should support connection between massive devices. As one of estimated scenarios for 5G mobile communication, mobile devices and sensors using low data rate wireless communication will increase. For communication of these devices, single-carrier system can be considered. In order to satisfy these requirements, in this paper, we propose CDMA (Code Division Multiple Access) system using complex spreading and Multi-level BPSK(Binary Phase Shift Keying). The proposed system spread transmit symbol by using chip code consisted of real and imaginary number. As simulation results, we can confirm that although the proposed system has 3dB lower BER (Bit Error Rate) performance than conventional CDMA system, the proposed system can support 2 times more users in comparison with conventional CDMA system.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.950-958
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• 2017

Viaduct increases the height of subway catenary, namely magnifies lightning attraction scope that lead to higher possibility of suffering lightning stroke. Therefore, it is necessary to analyze performance of lightning striking to catenary of subway in viaduct section and propose an improving lightning protection scheme. In this paper, using ATP-EMTP simulation software to establish an associated model to evaluate lightning withstand level of catenary with existing lightning protection schemes including arrester and grounding point, an improving lightning protection scheme is proposed - every pillar ground earth and arresters are installed with some installing spacing between 200m to 400m based on lightning damage degree and reliability requirements - according to analyzing results: while lightning withstand level is lowest for lightning striking to the neutral pillar, lightning withstand level is greatest for lightning striking to the both-ends pillar that arrester and grounding point are both installed; grounding point could obviously improve lightning withstand level for lightning striking to ground wire while arrester could obviously improve the lightning withstand level for lightning striking to catenary; every pillar ground earth could enhance the lowest lightning withstanding level up to 2.5 times than of that pillar ground earth across every 200m.

• Archives of design research
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• v.16 no.3
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• pp.183-190
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• 2003

It is a fundamental pre-requisite to thoroughly analyse and understand the things which are being designed in the process of industrial design. However, it is not always easy to acquire appropriate data to meet all the requirements to finally design a functionally superior products. This paper proposes an industrial design model with heightened reliability using the orthogonal array tables, which are fairly handy to apply when there are many design criteria to be considered at the onset stage Especially, in this research, the basic purpose of the orthogonal arrays that they try to compact the range of experiments and to improve the effectiveness of the experiment results is answered under average industrial design processes. At the same time, non-quantitative data of design factors are quantitative by the concurrency in design and their mutual actions are examined. This method can help industrial designers in narrowing their design possiblities by depicting more valid data, thus producing quality product designs by deriving optimal control factors.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.489-493
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• 2005

TFT-LCD(Thin Film Transistor Liquid Crystal Display) module is representative commercial product of FPD(Flat Panel Display). Thickness of TFT-LCD module is very thin. It is adopted for major display unit for IT devices such as Cellular Phone, Camcorder, Digital camera and etc. Due to the harsh user environment of mobile IT devices, it requires complicated structure and tight assembly. And user requirements for the mechanical functionalities of TFT-LCD module become more strict. However, TFT-LCD module is normally weak to high level transient mechanical shock. Since it uses thin crystallized panel. Therefore, anti-shock performance is classified as one of the most important design specifications. Traditionally, the product reliability against mechanical shock is confirmed by empirical method in the design-prototype-drop/impact testredesign paradigm. The method is time-consuming and expensive process. It lacks scientific insight and quantitative evaluation. In this article, a systematic design evaluation of TFT-LCD module for mobile IT devices is presented with combinations of FEA and testing to support the optimal shock proof display design procedure.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.840-843
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• 2002

The dry pulverizing/Mixing device is used to deal with the spent fuels for the safe disposal. The separated pellets from hulls by a slitting device are put and oxidized from UO$_2$ solid pellet to U$_3$O$\_$8/ powder in the device. The device have been developed based on a voloxidation method which is one of several dry de-cladding methods. We have benchmarked dry de-cladding methods, analyzed applicability to the advanced spent fuel management process, integrated and compared several configuration, and finally derived detailed specifications proper to requirements for the device. Also, thermal characteristics of the device such as thermal stress and strain have been analyzed by the commercial software, 1-DEAS, and the reliability of the results have been verified by the KOLAS(Korea Laboratory Accreditation Scheme). The UO$_2$ solid pellets are put in the device which has a capacity of 20 kgHM per a batch, heated up about 600$^{\circ}C$ in the air environment. Then, the UO$_2$ solid pellets are oxidized into the U$_3$O$\_$8/ powder, and the powder is collected in a special vessel. The device has been designed and developed as fellows: the multi-staged fine hole meshes are used to reduce the size of the powder gradually, heat and air(oxygen) are supplied continuously to reduce the reaction time, and slight vibration effect are applied to collect powder cling to the device.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.2
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• pp.267-271
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• 2014

Nuclear power plant data networks and their associated safety systems are being modernized to include many information technology (IT) networks and applications. Along with the advancement of plant data networks (PDN), instrumentation and control systems are being upgraded with modern digital, microprocessor-based systems. However, nuclear PDN is confronted significant side-effects, which PDN is exposed to prevalent cyber threats typically found in IT environments. Therefore, cyber security vulnerabilities and possibilities of cyber incidents are dramatically increased in nuclear PDN. Consequently, it should be designed fully ensuring the PDN meet all reliability, performance and security requirements in order to overcome the disadvantages raised from adaption of IT technology. In this paper, we provide technical security criteria should be used in design and evaluation of secure PDN. It is believed PDN, which is designed and operated along with these technical security critera, effectively protect against possible outside cyber threats.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.764-773
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• 2011

IEEE 802.15.4 is a standard for LWPAN based on TDMA. IEEE 802.15.4 has not been used widely because of restrictions on the QoS, scalability, and reliability. IEEE 802.15.4 utilizes GTS for one-hop QoS transmission. However GTS is not an effective method to satisfy QoS in multi-hop environments. Currently IEEE 802.15.4e, an extended version of IEEE 802.15.4 MAC sub-layer, is being developed to satisfy more diverse performance requirements than IEEE 802.15.4. IEEE 802.15.4e provides muti-hop QoS transmission functionality and uses multiple frequency channels. In this paper, a multi-channel TDMA scheduling scheme is proposed to satisfy end-to-end transmission delay in IEEE 802.15.4e. The performance of the proposed scheme is evaluated using simulation.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.6
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• pp.639-649
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• 2020

Air data systems measure airspeed, pressure altitude, angle of attack and angle of sideslip. These measurements are essential for operating flight control laws to ensure safe flights. Since the loss or corruption of air data measurements is considered as catastrophic, a high level of operational reliability needs to be achieved for air data systems. In the case of unmanned air vehicles, failure of any of air data sensors is more critical due to the absence of onboard pilot decision aid. This paper presents design of a dual redundancy air data system and the integration process for an unmanned air vehicle. The proposed dual-redundant architecture is based on two independent air data probes and redundancy management by central processing in two independent flight control computers. Starting from unit testing of single air data sensor, details are provided of system level tests used to meet overall requirements. Test results from system integration demonstrate the efficiency of the proposed process.