• 한국도로학회논문집
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• 제15권1호
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• pp.11-21
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• 2013

PURPOSES: As pavement generally provides service shorter than an expected life cycle, maintenance cost increases gradually. In order to help extending the service life and reduce maintenance cost, a new multi-functional composite pavement system is being developed in Korea. METHODS: This study is a part to develop the multi-functional composite pavement and is to investigate the mechanical performances of fiber-reinforced lean concrete for pavement subbase. The inherent problem of fiber reinforced concrete is dispersion of fibers in concrete mix. This study additionally evaluated fiber dispersion characteristics with respect to different fiber types. RESULTS: From the test results, the compressive strengths of the concretes satisfied the required limit of 5MPa at 7days. The standard deviation of the measured number of fibers were lower in the order of nylon, steel fiber and polypropylene. CONCLUSIONS: Reject ash was shown to be satisfactory as a replacement material to Portland cement in lean concrete base. The fiber volume fraction is suggested to be 0.4% even though the fracture toughness did not vary significantly with respect to fiber types. However, fracture energy absorbed up to complete failure increased with the increased fiber volume fraction increment.

• International Journal of Contents
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• 제14권4호
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• pp.70-75
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• 2018

The purpose of this corpus-based study was to find 4-word lexical bundles in computer science research articles. As the demand for research articles (RAs) for international publication increases, the need for acquiring field-specific writing conventions for this academic genre has become a burning issue. Particularly, one area of burgeoning interest in the examination of rhetorical structures and linguistic features of RAs is the use of lexical bundles, the indispensable building blocks that make up an academic discourse. To illustrate, different academic discourses rely on distinctive repertoires of lexical bundles. Because lexical bundles are often acquired as a whole, the recurring multi-word sequences can be retrieved automatically to make written discourse more fluent and natural. Therefore, the proper use of rhetorical devices specific to a particular discipline can be a vital indicator of success within the discourse communities. Hence, to identify linguistic features that make up specific registers, this corpus-based study examines the types and usage frequency of lexical bundles in the discipline of CS, one of the most in-demand fields world over. Given that lexical bundles are empirically-derived formulaic multi-word units, identifying core lexical bundles used in RAs, they may provide insights into the specificity of particular CS text types. This will in turn provide empirical evidence of register specificity and technicality within the academic discourse of computer science. As in the results, pedagogical implications and suggestions for future research are discussed.

• 정보보호학회논문지
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• 제15권2호
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• pp.113-122
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• 2005

본 논문에서는 악의적인 공격에는 워터마크가 쉽게 깨어지고 비악의적인 공격에는 워터마크가 쉽게 깨어지지 않도록 하는 투 가지 목적을 동시에 만족시키기 위한 다중 워터마킹 알고리즘을 제안한다. Discrete Wavelet Transform(DWT)의 계수를 이용해 이미지를 인증하는 기법으로, 워터마크로 사용될 이진 이미지와 LL3 영역에서 추출된 특징을 조합하여 이미지에 삽입될 정보를 생성한다 이미지의 공간영역과 주파수영역에 정보를 다중으로 삽입하여 공간영역에서 일어날 수 있는 악의적인 공격에 대응할 뿐만 아니라 주파수영역에서의 blurring, sharpening 및 JPEG 압축과 간은 비 악의적인 공격을 허용하는 기법이다. 공간영역에서는 이미지 블록의 모든 픽셀의 Least Significant Bit(LSB)에 정보를 삽입하고, 주파수영역에서는 삽입할 정보에 따라 LH2와 HL2의 계수를 조절하므로 정보를 삽입하게 된다.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.936-942
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• 2018

The diagnostic multi-leaf collimator preventing unnecessary dose from entering into patients during the diagnostic examination was made in this study. The movement of the entire 50 leaves was embodied with the group of 25 ones thereof configured in a pair facing each other on the left and right of the median line. Dimensions of the length, width, and height of each shielding leaf were $5{\times}0.5{\times}0.5cm^3$ resulting in the maximum boost field of $10{\times}10cm^2$. The material of multi-leaf collimator had the excellence on the machinability with the use of the SKD-11 alloy tool steel having the high wear resistance against frequent movement, and it was devised to control both-side's shielding leaves by moving 2 motors unlike existing remedial multi-leaf collimator that use as many motors as the number of 50 shielding leaves. Thereafter, the transmission dose of leaves, cross-leaf leakage dose, and inter-leaf leakage dose were measured by the developed multi-leaf collimator attached to X-ray equipment. An ionization chamber was used to detect doses there from, and the comparative analysis was carried out by means of the radiographic film that was easy to detect the dose leakage in between each leaf. Results obtained from the test conducted in comparative analysis yielded approximately 98%, 96%, and 94% of shielding efficiency realized at each level of energy of 80kV, 100kV, and 120kV it was confirmed there was no dose leakage resulted from the varied level of irradiation energy. Thus the multi-leaf collimator to be developed based on this study is thought that it could fully reduce the unnecessary dose to patients in the diagnostic test and the shielding efficiency thereof is expected to be increasing if it is made in a miniaturized form with a way of increasing the thickness of each leaf later for an extended application to general diagnostic purposes.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.88.1-88.1
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• 2010

Organic dyes, because of their many advantages, such as high molar extinction coefficients, convenience of customized molecular design for desired photophysical and photochemical properties, inexpensiveness with no transition metals contained, and environment-friendliness, are suitable as photosensitizers for the Dye-sensitized Solar Cell (DSSC). The efficiency of DSSC based on metal-free organic dyes is known to be much lower than that of Ru dyes generally, but a high solar energy-to-electricity conversion efficiency of up to 8% in full sunlight has been achieved by Ito et al. using an indoline dye. This result suggests that smartly designed and synthesized metal-free organic dyes are also highly competitive candidates for photosensitizers of DSSCs with their advantages mentioned above. Recently, the performance of DSSC based on metal-free organic dyes has been remarkably improved by several groups. We had reported the novel organic dye with double electron acceptor chromophore, which was a new strategy to design an efficient photosensitizer for DSSC. To verify the strategy, we synthesized organic dyes whose geometries, electronic structures and optical properties were derived from preceding density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. In this paper, we successfully synthesized the chromophore containing multi-acceptor push-pull system from triphenylamine with thiophene moieties as a bridge unit. Organic dyes with a single electron acceptor and double acceptor system were also synthesized for comparison purposes. The photovoltaic performances of these dyes were compared, and the recombination dark current curves and the incident photon-to-current (IPCE) efficiencies were also measured in order to characterize the effects of the multi-anchoring groups on the open-circuit voltage and the short-circuit current. In order to match specifications required for practical applications to be implemented outdoors, light soaking and thermal stability tests of these DSSCs, performed under $100mWcm^{-2}$ and $60^{\circ}C$ for 1000h.

• 한국생활과학회지
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• 제20권5호
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• pp.1075-1091
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• 2011

The purposes of this study were to investigate the actual state of indoor air quality in semi-underground multi-family housing units in early summer, to analyze the influencing factors, and to make suggestions for improvement. A series of field investigations were conducted in four target units between June 22, 2010, and June 28, 2010. The field investigations included measurements of indoor air quality as well as the observation of architectural characteristics and living conditions. In addition to the field investigation, on-site questionnaire surveys were administrated to residents in 90 units. The findings are summarized as follows: (1) The average $CO_2$ levels in each of the four units ranged from 759ppm to 1885ppm. $CO_2$ levels in three units exceeded the evaluation standard (1000ppm), and one unit was lower than the standard. This unit had smaller number of staying person and a large amount of ventilation than others; (2) the average CO levels in each unit were almost 0ppm, but 0.1~1.1 levels of CO were revealed at several times; (3) the average PM-10 levels ranged from $8{\mu}g/m^3$ to $40{\mu}g/m^3$, which distributes within the standard ($150{\mu}g/m^3$). The influencing factors of PM-10 levels were analyzed as inflow from outside, the use of a gas range, and the residents' activities; (4) therefore, it was evaluated to be necessary to improve ventilation for the indoor air quality of semi-underground housing in aspect of $CO_2$ levels.

• Structural Monitoring and Maintenance
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• 제2권3호
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• pp.269-282
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• 2015

Civil structures should be designed with the lowest cost and longest lifetime possible and without service failure. The efficient and sustainable use of materials in building design and construction has always been at the forefront for civil engineers and environmentalists. Timber is one of the best contenders for these purposes particularly in terms of aesthetics; fire protection; strength-to-weight ratio; acoustic properties and seismic resistance. In recent years, timber has been used in commercial and taller buildings due to these significant advantages. It should be noted that, since the launch of the modern building standards and codes, a number of different structural systems have been developed to stabilise steel or concrete multistorey buildings, however, structural analysis of high-rise and multi-storey timber frame buildings subjected to lateral loads has not yet been fully understood. Additionally, timber degradation can occur as a result of biological decay of the elements and overloading that can result in structural damage. In such structures, the deficient members and joints require strengthening in order to satisfy new code requirements; determine acceptable level of safety; and avoid brittle failure following earthquake actions. This paper investigates performance assessment and damage assessment of older multi-storey timber buildings. One approach is to retrofit the beams in order to increase the ductility of the frame. Experimental studies indicate that Sprayed Fibre Reinforced Polymer (SFRP) repairing/retrofitting not only updates the integrity of the joint, but also increases its strength; stiffness; and ductility in such a way that the joint remains elastic. Non-linear finite element analysis ('pushover') is carried out to study the behaviour of the structure subjected to simulated gravity and lateral loads. A new global index is re-assessed for damage assessment of the plain and SFRP-retrofitted frames using capacity curves obtained from pushover analysis. This study shows that the proposed method is suitable for structural damage assessment of aged timber buildings. Also SFRP retrofitting can potentially improve the performance and load carrying capacity of the structure.

• 한국초등수학교육학회지
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• 제22권4호
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• pp.517-538
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• 2018

본 연구의 목적은 다문화 학생들의 수학적 문화 배경에 대한 이해를 높여 그들의 수학 학습을 지원하기 위한 토대를 마련하는 것이다. 이를 위해 한국과 베트남의 초등 교과서에서 다루고 있는 평면도형과 넓이 측정의 지도 내용, 전개 순서, 교수-학습 방안을 비교 분석하였다. 분석 결과 베트남 교과서는 한국 교과서에 비해 수학적 엄밀성과 논리를 강조하며, 수학적 관련성에 따라 여러 영역의 학습 내용을 통합적으로 다루지만 도형의 합동, 대칭, 포함 관계 등 수학적 연결성에 관한 내용은 다루지 않는다. 한국 교과서는 학생이 도형의 개념을 스스로 찾고 정의하는 활동을 바탕으로 하며, 이를 통해 다양한 수학적 생각을 경험도록 하는 반면 베트남 교과서는 도형에 관한 개념을 직접적으로 제시하고 이를 학생이 익히도록 한다. 이러한 분석 결과를 바탕으로 베트남 다문화 학생의 수학 학습에 관한 시사점을 제시하였다.

• 경영정보학연구
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• 제22권3호
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• pp.81-97
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• 2020

최근의 감성분류 연구는 출력변수가 하나인 단일레이블 분류방법을 사용한 연구가 많다. 특히, 이러한 연구는 하나의 극성 값(긍정, 부정)만을 찾는 연구가 많다. 그러나 한 문장 안에는 다중적인 의미가 내포되어 있다. 그 중에서도 감정과 오피니언이 이러한 특징을 갖는다. 본 논문은 두 가지 연구목적을 제시한다. 첫째, 한 문장 안에 다양한 토픽(주제 또는 애스팩트)이 있다는 사실을 기반으로, 해당 문장을 각 애스팩트 별로 감성을 분류하는 애스팩트 마이닝을 수행한다. 둘째, 두개 이상의 종속변수(출력 값)를 한 번에 분석하는 다중레이블 분류방법을 적용한다. 이에 본 연구는 감성분류의 연구가 단일분류기에 의해서만 이루어진 연구를 개선하고자 다중레이블 분류방법에 의한 애스팩트 마이닝을 수행하고자 한다. 이와 같은 연구목적을 달성하기 위해 국내 뮤지컬 데이터를 수집하였다. 분석결과 문장 안에 있는 다양한 애스팩트별 감성을 추출하였고, 유의한 결과를 얻었다.

• 전기전자학회논문지
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• 제28권1호
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• pp.53-64
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• 2024

자연어 처리 모델이 발전함에 따라 챗 GPT와 같은 대화형 언어 생성 AI 모델이 널리 사용되고 있다. 따라서 자연어 처리 최신 모델의 기반이 되는 트랜스포머 알고리즘을 하드웨어로 구현하여 연산 속도와 전력 소비량을 개선하는 것은 중요하다고 할 수 있다. 특히, 행렬 곱셈을 통해 문장에서 서로 다른 단어 간의 관계를 분석하는 멀티 헤드 어텐션과 피드 포워드 네트워크는 트랜스포머에서 연산량이 가장 큰 핵심적인 알고리즘이다. 본 논문에서는 기존의 시스톨릭 어레이를 변형하여 행렬 곱 연산 속도를 개선하고, 입력 단어 개수 변동에 따라 지연시간도 변동되는 유동적인 구조를 제안한다. 또한, 트랜스포머 알고리즘의 정확도를 유지하는 형태로 양자화를 하여 메모리 효율성과 연산 속도를 높였다. 본 논문은 평가를 위해 멀티헤드어텐션과 피드포워드 네트워크에서 소요되는 클럭사이클을 검증하고 다른 곱셈기와 성능을 비교하였다.