• 한국세라믹학회지
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• 제54권5호
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• pp.349-365
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• 2017

Graphene has attracted a lot of attentions due to the unique electrical and optical properties. Compared with the noble metal plasmons in the visible and near-infrared frequencies, graphene can support surface plasmons in the lower frequencies of terahertz and mid-infrared and it demonstrates an extremely large confinement at the surface because of the particular electronic band structures. Especially, the surface conductivity of graphene can be tuned by either chemical doping or electrostatic gating. These features make graphene a promising candidate for plasmonics, biosensing and transformation optics. Furthermore, the combination of graphene and metasurfaces presents a powerful tunability for exotic electromagnetic properties, where the metasurfaces with the highly-localized fields offer a platform to enhance the interaction between the incident light and graphene and facilitate a deep modulation. In this paper, we provide an overview of the key properties of graphene, such as the surface conductivity, the propagating surface plasmon polaritons, and the localized surface plasmons, and the hybrid graphene/metasurfaces, either metallic and dielectric metasurfaces, from terahertz to near-infrared frequencies. Finally, there is a discussion for the current challenges and future goals.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 추계종합학술대회
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• pp.658-661
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• 2005

클라이언트/서버 기반 방식의 컨텐츠 전송 시스템은 서버로 작업요청이 많아질 경우에는 서버에 처리부하가 집중되는 병목현상으로 인하여 시스템이 마비 되는 취약점을 가지고 있다. 그러나 인터넷 사용자의 폭발적인 증가와 컨텐츠 품질 향상 요구로 인하여 서버의 증설만으로는 한계에 이르렀다. 그러므로 이러한 문제점들을 개선하기 위해 P2P 기반 컴퓨팅방식을 사용한다. 본 논문에서는 컴퓨팅 자원의 공유를 목적으로 하는 P2P 컴퓨팅 환경에서 유휴 컴퓨팅 자원을 이용하여 교육 콘텐츠 전송 시스템을 설계하고 구현한다. 제안된 시스템은 인터넷 전송뿐만 아니라 위성 채널을 통해 콘텐츠를 전송할 수 있도록 시스템을 구현하고, 실시간 강의와 비실시간 강의의 콘텐츠를 모두 전송하도록 설계한다.

• 한국표면공학회지
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• 제52권3호
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• pp.123-129
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• 2019

With recent demand for the renewable energy resources, we conducted a research on the energy conversion and storage device of supercapacitor. The hybrid graphene-zinc oxide(GZO) electrodes for the supercapacitors (SCs) were fabricated and investigated. To increase the electrical conductivity of the GZO electrode, the rapid thermal annealing(RTA) in $Ar/H_2$(10%) atmosphere was applied and the effect was examined by comparing it with RTA at Ar atmosphere. In Raman spectroscopy, the electrodes annealed at 400? in $Ar/H_2$ atmosphere showed a lower ratio of D/G peak than that of annealed at Ar atmosphere, and had a larger specific capacitance(Sc) in the cyclic voltammetry(CV), and a lower the equivalent series resistance(ESR) in the electrochemical impedance spectroscopy(EIS). The reason seems to come from the better mixing of the graphene and zinc oxide by the RTA in $Ar/H_2$(10%).

• 국제강구조저널
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• 제18권5호
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• pp.1784-1800
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• 2018

Tension-shear loading is a common loading condition in steel structures during the earthquake shaking. To study ductile fracture in structural steel under multiple stress states, experimental investigations on the different fracture mechanisms in Chinese Q235 steel were conducted. Different tension-shear loading conditions achieved by using six groups of inclined notch butterfly configurations covering pure shear, tension-shear and pure tension cases. Numerical simulations were carried out for all the specimens to determine the stress and strain fields within the critical sections. Two tension-shear fracture models were calibrated based on the hybrid experimental-numerical procedure. The equivalent fracture strain obtained from the round bar under tensile loading was used for evaluating these two models. The results indicated that the tension-shear criterion as a function of the shear fracture parameter had better performance in predicting the fracture initiation of structural steel under different loading conditions.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1706-1713
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• 2020

Functionally gradient material (FGM) is promisingly effective in mitigating the thermal stress between plasma facing materials (PFM) and structural materials. However, the corresponding research with respect to W/V FGM has not been reported yet. In this work, we firstly report the successful fabrication of W/V FGM by a combined technology of mechanical alloying (MA) and spark plasma sintering (SPS). The microhardness and microstructure of the consolidated sample were both investigated. W/V stacks show significantly enhanced microhardness (>100%) compared with pure W plate, which is beneficial to the integral strength of the hybrid structure. Furthermore, we clarify that the different ductility of W and V should be carefully considered, otherwise W/V powder might aggregate and lead to the formation of compositional segregation, and simultaneously unmask the impact of V proportion on the distribution of second phase in W-V binary alloy system. This work provides an innovative approach for obtaining W-V connections with much better performance.

• Smart Structures and Systems
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• 제32권2호
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• pp.101-109
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• 2023

In order to improve the measurement accuracy of the 6-dimensional accelerometer, the cross coupling compensation method of the accelerometer needs to be studied. In this paper, the non-linear error caused by cross coupling of piezoelectric six-dimensional accelerometer is compensated online. The cross coupling filter is obtained by analyzing the cross coupling principle of a piezoelectric six-dimensional accelerometer. Linear and non-linear fitting methods are designed. A two-level calibration hybrid compensation algorithm is proposed. An experimental prototype of a piezoelectric six-dimensional accelerometer is fabricated. Calibration and test experiments of accelerometer were carried out. The measured results show that the average non-linearity of the proposed algorithm is 2.2628% lower than that of the least square method, the solution time is 0.019382 seconds, and the proposed algorithm can realize the real-time measurement in six dimensions while improving the measurement accuracy. The proposed algorithm combines real-time and high precision. The research results provide theoretical and technical support for the calibration method and online compensation technology of the 6-dimensional accelerometer.

• 한국국방경영분석학회지
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• 제33권2호
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• pp.101-113
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• 2007

국방부에서 발표한 '국방개혁에 관한 법률'에 따라 2014년까지 현역병들에 대한 복무기간이 단계적으로 단축될 예정이다. 이에 따라 육군에서는 좀 더 효율적인 직무교육 방안의 일환으로 훈련병들에게 '차등제 교육'을 시행하고 있다. 이러한 차등제 교육의 효과를 향상시키기 위해서는 훈련병들의 예상 학업 성취도를 미리 예측하여 성취집단별로 차별화 된 교육과정을 거치게 하는 것이 매우 중요하다. 따라서 본 연구에서는 입교초기에 얻을 수 있는 신병들의 제한된 자료들만을 이용하여 그들의 예상 교육 성취집단을 예측하는 모형을 개발하였다. 본 모형의 목적 변수는 '성취집단'이며 '일반관리 인원' 및 '집중관리 인원'의 두 가지 값을 갖는다. 사용된 기법은 인공신경망(Neural Network) 모형, 의사결정나무(Decision Tree) 모형, SVM 모형, 그리고 Naive Bayesian모형 등 4가지 순수 모형과, 각각의 순수 모형을 k-means군집기법과 혼합한 4가지의 혼합모형 등 총 8개의 모형의 성능을 비교 분석하였다. 실험 결과 k-means군집기법과 인공신경망 기법을 혼합한 모형이 가장 좋은 예측력을 보이는 것으로 나타났다. 이러한 교육 성취집단 예측 모형은 향후 군에서 이루어지는 다양한 교육 프로그램에 효과적으로 이용될 수 있을 것으로 기대된다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2018년도 추계학술대회
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• pp.133-136
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• 2018

제1형 당뇨 발병 시 환아들이 학습하는 당뇨 교육에 대한 환경이 매우 열악한 사실을 알 수 있었다. 따라서 환아들에게 혈당 변화에 대처하는 학습을 위한 환경을 조성하는 것이 필요하다. 그래서 본 연구에서는 제1형 당뇨 환아를 대상으로 이러한 혈당 변화 대처 요령에 대한 지식과 행동치료를 위한 디지털 콘텐츠를 제안하고자 한다. 이를 통해 아동들이 전문 지식을 학습함에 있어 효율성을 높여주는 하이브리드 방식을 사용한 교육형 게임 콘텐츠를 제안하고자 하였다. 본 연구를 위해 당뇨병 전문가를 대상으로 인터뷰를 진행한 결과를 토대로 환아에게 필요한 교육 내용으로 구성된 혈당 변화 대처 콘텐츠를 제안하였다. 본 연구 결과 어린이들에게 전문 지식인 당뇨를 게임을 통해 학습하는데 있어 하이브리드 요소가 효과적이라는 것을 알 수 있었다. 이러한 당뇨 교육형 게임 콘텐츠는 교육 환경이 열악한 지역의 당뇨 환아들이 보다 쉽게 학습을 할 수 있는 환경을 제공할 것으로 기대된다.

• BMB Reports
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• 제40권6호
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• pp.845-852
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• 2007

The highly evolved flowers of orchids have colorful sepals and fused columns that offer an opportunity to discover new genes involved in floral development in monocotyledon species. In this investigation, we cloned and characterized the homologous PISTALLATA-like (PI-like) gene PhPI15 ($\underline{Ph}alaenopsis$ $\underline{PI}$ STILLATA # $\underline{15}$), from the Phalaenopsis hybrid cultivar. The protein sequence encoded by PhPI15 contains a typical PI-motif. Its sequence also formed a subclade with other monocot PI-type genes in phylogenetic analysis. Southern analysis showed that PhPI15 was present in the Phalaenopsis orchid genome as a single copy. Furthermore, it was expressed in all the whorls of the Phalaenopsis flower, while no expression was detected in vegetative organs. The flowers of transgenic tobacco plants ectopically expressing PhPI15 showed male-sterile phenotypes. Thus, as a Class-B MADS-box gene, PhPI15 specifies floral organ identity in orchids.

• Applied Microscopy
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• 제46권1호
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• pp.37-44
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• 2016

In this study $TiO_2$/reduced graphene oxide ($TiO_2/rGO$) bipyramid with tunable nanostructure was fabricated by two-step solvothermal process and subsequent heat-treatment in air. The as-synthesized anatase $TiO_2$ nanocrystals possessed morphological bipyramid with exposed dominantly by (101) facets. Polyethylenimine was utilized during the combination of $TiO_2$ and graphene oxide (GO) to tune the surface charge, hindering the restack of graphene during solvothermal process and resulting in 1 to 5 layers of rGO wrapped on $TiO_2$ surface. After a further calcination, a portion of carbon quantum dots (CQDs) with a diameter about 2 nm were produced owing to the oxidizing and cutting of rGO on $TiO_2$. The as-prepared $TiO_2/rGO$ hybrid showed a highly photocatalytic activity, which is about 3.2 and 7.7 times enhancement for photodegradation of methyl orange with compared to pure $TiO_2$ and P25, respectively. We assume that the improvement of photocatalysis is attributed to the chemical bonding between rGO/CQDs and $TiO_2$ that accelerates photogenerated electron-hole pair separation, as well as enhances light harvest.