• Smart Structures and Systems
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• 제16권4호
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• pp.593-606
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• 2015

This paper presents a novel concept of healing some of the damages in wind turbine blades (WTBs) such as cracks and delamination. This is achieved through an inherent functioning autonomous repairing system. Such wind turbine blades have the benefit of reduced maintenance cost and increased operational period. Previous techniques of developing autonomous healing systems uses hollow glass fibres (HGFs) to deliver repairing fluids to damaged sites. HGFs have been reported with some limitations like, failure to fracture, which undermines their further usage. The self-healing technique described in this paper represents an advancement in the engineering of the delivery mechanism of a self-healing system. It is analogous to the HGF system but without the HGFs, which are replaced by multiple hollow channels created within the composite, inherently in the FRP matrix at fabrication. An in-house fabricated NACA 4412 WTB incorporating this array of network hollow channels was damaged in flexure and then autonomously repaired using the vascular channels. The blade was re-tested under flexure to ascertain the efficiency of the recovered mechanical properties.

• 한국항만경제학회지
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• 제20권2호
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• pp.73-87
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• 2004

The purpose of this paper is to setup reasonable criterion for underwriters to reimburse the expenses of suing and labouring incurred by assured, using game theory. As for the upper limit for the reimbursement, MIA and ICC do not mention at all but stipulate that proper and reasonable expenses shall be reimbursed, while ITC-Hulls set the amount insured as the upper limit to compensate the sum of expenses and damage loss. And as for failed measures of averting and minimizing loss, MIA and ICC do not mention either, while ITC-Hulls stipulates underwriters shall compensate the expenses and damage loss within the amount insured. The main results of this paper are as follows: First, it is for the benefit of underwriters to reimburse the expenses incurred to take such reasonable measures to avert or minimizing a loss which would be recoverable under the insurance. Second, the expenses of single measure should not be above the amount insured. Third, even if the measures failed, the expense should be reimbursed if it is less than the expected value of the subject-matter insured that could be recovered by the measures. Last, if the measures are taken several times individually, even if the sum of expenses might be above the amount insured, it should be reimbursed.

• 한국통신학회논문지
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• 제18권5호
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• pp.611-618
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• 1993

디지털 통신 시스템에서는 미리 정해진 모양의 파형을 발생시키는 것이 필수적이다. 이를 위하여 본 논문에서는 방송계 뉴 미디어 시스템인 RDS(Radio Data System)의 부호화기에서 파형 정형의 한 방법으로 메모리의 Look-up 테이블을 이용하여 기존의 아날로그 여파기보다 효율적인 디지털 파형 여파기를 구현하는 한편, 수신단에서는 전송한 데이터가 에러없이 정확히 복원 가능함을 보인다. 디지털 파형 여파기를 구현하기 위하여 파형 여파기의 제어 알고리즘을 설계하고, IC화를 목표로 discrete 소자를 이용하여 구현하였다. 또한 RDS의 송수신단 전송 실험을 통하여 본 논문에서 제안한 디지틀 파형 여파기의 타당성을 입증하였다.

• 전자공학회논문지
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• 제53권9호
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• pp.118-125
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• 2016

방사능 누출 사고 시 대응이나 핵안보 검증을 위한 핵물질 탐지에 있어서, 방사선을 방출하는 미지의 선원에 대한 위치 정보를 파악하는 것은 중요하다. 그러한 기구 중 하나인 회전 변조 시준기는 미지 선원을 원격 감지하기 위한 장비로서 영상화를 통해 선원의 위치 탐지가 가능하다. 본 논문에서는 Kowash의 연구를 기초로 회전 변조 시준기의 시스템 모델과 그를 영상화하는 알고리즘을 소개한다. 하지만 결과 영상화 이미지는 선원의 방향은 보여줄 수 있으나 선원의 거리를 찾지 못하는 문제점이 있다. 또한 선원의 실제 방향뿐 아니라 $180^{\circ}$ 대칭방향에서도 선원을 추정하는 모호성 문제를 안고 있다. 본 논문에서 우리는 영상화 결과의 방향 대칭적 모호성을 해결하고, 두 대의 RMC를 이용해 거리를 추정하는 방법을 제안한다. 그리고 이를 RMC 시뮬레이션 데이터를 이용하여 성능을 검증한다.

• 전기학회논문지P
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• 제67권2호
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• pp.57-62
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• 2018

A brush-less type synchronous generator driven by an internal-combustion engine is used for emergency electric source. These types of generators have to maintain a certain range of output voltage even under the sudden load change conditions such as full load application and removal. This paper describes a method for suppressing the output voltage of a synchronous generator that operates excessively when the load fluctuates. The method used in this paper is a feedforward control method in which the main voltage control consists of a feedback loop using a typical PID controller and the load current is detected as a disturbance element and compensated directly. A feedforward system is constructed in which the load current is regarded as disturbance, and the appropriate feedforward controller configuration and parameters are found through simulation. Finally, it can be seen through the experiment that the feedforward control is performed properly. It can be seen that the generator terminal voltage is recovered to the steady state in a short period of time as compared with the existing PID control method even when the entire load of the generator is changed.

• 유공압시스템학회논문집
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• 제4권3호
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• pp.7-12
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• 2007

This paper presents an energy saving hydrostatic pressure exchanger for sea water desalination equipment. In a reverse osmosis(RO) system for desalinating sea water, more than 70 percent of the supplied sea water, brines which were impassable through RO membrane are bypassed, resulting in high energy losses. In this paper, a hydrostatic pressure exchanger consisting of an embedded water hydraulic piston motor and a water hydraulic piston pump was proposed and investigated in order to recover the energy of the bypassed brines. The pressurized brines are supplied to the embedded water hydraulic piston motor as power sources and the water hydraulic piston pump is driven by the output torque of the embedded water hydraulic piston motor as well as electric motor. Consequently, the energy of the bypassed brines can be recovered. To examine the electric energy saving characteristics of the hydrostatic pressure exchanger, a simulation model was constructed using commercial software and experiments were conducted. Through the results of simulation and experiment, the feasibility of the electric energy saving effect of the proposed hydrostatic pressure exchanger was investigated.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1047-1052
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• 2008

The aim of this paper is that studies on the characteristics of the liquid-gas ejector. Could get data about various model using numerical analysis. Compare and analyze result that get by an experiment and numerical analysis. And studied Characteristics of the ejector. In this paper, Numerical analysis model is gotten divided according to each Throat ratio as three types. Each throat ratio is 0, 4 and 7.5. According to the result that analyze basic model, pressure became lower causing the volume flow rate increase. In CFD studies, Fixed volume flow rate by these result and analyzed ejector performance. As a result, there was no change of pressure to Throat's Enterance, and pressure became low while pass the throat. Since, pressure recovered while passing diffuser. The outer flow velocity did not change greatly to change of volume flow rate. This research expects that is utilized to data for performance elevation hereafter.

• 센서학회지
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• 제22권5호
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• pp.315-320
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• 2013

In this paper, the properties of strain sensors made of spin-capable multi-walled carbon nanotubes (MWCNTs) were characterized and their sensing mechanisms analyzed. The key contribution of this paper is a new fabrication technique that introduces a simpler transfer method compared to spin-coating or dispersion CNT. Resistance of the MWCNT sheet strain sensor increased linearly with higher strain. To investigate the effect of CNT concentration on sensitivity, two strain sensors with different layer numbers of MWCNT sheets (one and three layers) were fabricated. According to the results, the sensor with a three-layer sheet showed higher sensitivity than that with one layer. In addition, experiments were conducted to examine the effects of environmental factors, temperature, and gas on sensor sensitivity. An increase in temperature resulted in a reduction in sensor sensitivity. It was also observed that ambient gas influenced the properties of the MWCNT sheet due to charge transfer. Experimental results showed that there was a linear change in resistance in response to strain, and the resistance of the sensor fully recovered to its unstressed state and exhibited stable electromechanical properties.

• 동남아시아연구
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• 제20권3호
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• pp.41-64
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• 2010

The recent global financial crisis triggered by the sub-prime mortgage debacle in the United States hit hard most ASEAN countries that have just recovered from the unprecedented economic crisis ten years ago. This paper, using individual time-series and panel data from 1990 to 2009, intends to investigate and compare the impacts of the two aforementioned economic crises on trade in the four developing ASEAN countries that encompass Indonesia, Malaysia, the Philippines and Thailand. In doing so, the paper traces the behaviors of main macroeconomic variables before and after the crises on graphs, and then estimates classical export and import demand functions that include real exchange rate, home and foreign GDPs as explanatory variables. In the estimation functions, two dummy variables are added to consider the effects of the two economic crises separately. Individual country data analyses reveal that by and large the 1997 economic crisis seems hit those ASEAN countries' exports and imports harder than the recent global financial crisis. Surprisingly the recent financial crisis turns out more or less statistically insignificant for those countries' export and import performances. The fixed effect model estimation using panel data of those four ASEAN countries also shows that the 1997 economic crisis had affected exports and imports of those countries negatively while the recent global financial crisis was not statistically significant. These results indicate that overall the effect from the 1997 crisis was more devastating than that of the recent global crisis for those ASEAN countries.

• International journal of advanced smart convergence
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• 제12권3호
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• pp.68-74
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• 2023

The food industry has been hit hard since the first outbreak of COVID-19 in 2019. However, as of April 2022, social distancing has been resolved and the restaurant industry has gradually recovered, interest in restaurant start-ups is increasing. Therefore, in this paper, 'restaurant start-up' was cited as a key keyword through social media big data analysis using TexTom, and word frequency and cone analysis were conducted for big data analysis. The keyword collection period was selected from May 1, 2022, when social distancing due to COVID-19 was lifted, to May 23, 2023, and based on this, a plan to develop chatbot services for restaurant start-ups was proposed. This paper was prepared in consideration of what to consider when starting a restaurant and a chatbot service that allows prospective restaurant founders to receive information more conveniently. Based on these analysis results, we expected to contribute to the process of developing chatbots for prospective restaurant founders in the future