• Structural Engineering and Mechanics
• /
• 제43권2호
• /
• pp.225-237
• /
• 2012

This paper presents an experimental investigation of the flexural behavior of square hollow steel section (HSS) beams subjected to pure bending. Totally six unfilled and nine ultra high performance concrete (UHPC)-filled HSS beams were tested under four-point bending until failure. The effects of the steel tube thickness, the yield strength of the steel tube and the strength of concrete on moment capacity, curvature, and ductility of UHPC-filled HSS beams were examined. The performance indices named relative ductility index (RDI) and strength increasing factor (SIF) were investigated with regard to different height-to-thickness ratio of the specimens. The flexural strengths obtained from the tests were compared with the values predicted by Eurocode 4, AISC-LRFD and CIDECT design codes. The results showed that the increase in the moment capacity and the corresponding curvature is much greater for thinner HSS beams than thicker ones. Eurocode 4 and AISC-LRFD predict the ultimate moment capacity of the all UHPC-filled HSS beams conservatively.

• Structural Monitoring and Maintenance
• /
• 제2권4호
• /
• pp.319-338
• /
• 2015

The electro-mechanical impedance (EMI) technique makes use of surface-bonded lead zirconate titanate (PZT) patches as impedance transducers measuring impedance variations monitored on host structural components. The present experimental work further evaluate an alternative to the conventional EMI technique which performs measurements of the variations in the output voltage of PZT transducers rather than computing electromechanical impedance (or admittance) itself. This paper further evaluates a variant of the EMI approach presented in a previous work of the present authors, suitable, for low-cost concrete structures monitoring applications making use of a credit card-sized Raspberry Pi single board computer as core hardware unit. This monitoring approach is also deployed by introducing a new damage identification index based on the ratio between the area of the 2-D error ellipse of specific probability of EMI-based measurements containment over that of the 2-D error circle of equivalent probability. Experimental results of damages occurring in concrete cubic and beam specimens are investigated under increasing loading conditions. Results illustrate that the proposed technique is an efficient approach for identification and early detection of damage in concrete structures.

• 한국컴퓨터정보학회논문지
• /
• 제25권5호
• /
• pp.47-56
• /
• 2020

주가지수는 한 국가의 경제 지표뿐만 아니라 투자판단의 지표로도 활용되므로 이를 예측하는 연구가 지속해서 진행되고 있다. 주가지수 예측을 하는 작업은 기술적, 경제적 및 심리적 요인 등이 반영된 것으로 예측의 정확도를 위해서는 복합적 요인을 고려해야 한다. 따라서 지수의 변동에 영향을 미치는 요인들을 선별하여 반영한 주가지수 예측모델연구가 필요하다. 이와 관련한 기존 연구에서는 시장의 변동을 만들어 내는 뉴스 정보 또는 거시 경제 지표를 각각 이용하거나, 몇 가지의 지표 조합만을 반영한 예측 연구가 대부분이었다. 따라서 본 연구에서는 미국 다우존스지수 예측을 위해 뉴스 정보의 감성 분석과 다양한 거시경제지표를 고려하여 효과적인 지표 조합을 제시하고자 한다. 뉴스 정보의 감성 분석은 최신 자연어처리 기법인 BERT와 NLTK VADER를 사용하고, 예측모델은 주가예측모델로 적합하다고 알려진 딥러닝 예측모델 LSTM을 적용하여 가장 효과적인 지표 조합을 제시했다.

• 한국해양공학회지
• /
• 제37권6호
• /
• pp.282-282
• /
• 2023

• 산경연구논집
• /
• 제8권7호
• /
• pp.13-20
• /
• 2017

Purpose - Performance appraisal has a significant influence on the development of low-carbon tourism distribution. Research design, data, and methodology - Data of this study are collected from 27 provinces (cities) of China. SBM-Malmquist model is used to measure the TFP and its dynamic changes of low-carbon tourism distribution; TOBIT model is used to discuss the factors of TFP of low-carbon tourism distribution. Results - The results show that, there are obvious differences among regional TFP of low-carbon tourism distribution, the average change tends to grow positively in general, and the western region grows fastest on average due to the improvement of technical efficiency and technical progress, while there are technical efficiency improvement but technical regresses in eastern and central regions. The economic scale, economic strength, structure of energy consumption, location quotient and government regulation have a significant positive effect on the TFP of low-carbon tourism; energy intensity, industrial structure and opening degree have a negative effect; investments in fixed assets, intensity of R&D fund and urbanization rate have no significant influence on the TFP of low-carbon tourism. Conclusions - Improving the productivity of low-carbon tourism and reducing regional differences are effective ways to develop low-carbon tourism and enhance tourism competitiveness.

• 한국산학기술학회논문지
• /
• 제16권10호
• /
• pp.6823-6831
• /
• 2015

이 연구는 주요 시설채소 작목인 오이(반촉성) 농가의 경영현황을 진단하고 개별 오이농가의 생산효율성 증대를 위해 필요한 요인을 도출하고 있다. 주요 경영지표 검토 및 세부 경영효율성 분석 결과 오이농가에는 향후 규모화보다는 기술효율성 증대를 통한 생산효율성 증대 가능성이 더 높은 것으로 나타났다. 생산량은 순수기술효율성과 양의 상관관계를 가지지만 그 정도가 미미해, 일정한 조건 하에서는 순수기술효율성 증대를 위해 투입요소의 절감이 더 시급한 것으로 도출되었다.

• 국제학술발표논문집
• /
• The 5th International Conference on Construction Engineering and Project Management
• /
• pp.315-320
• /
• 2013

The aim of this study is to compare efficiency and Total Factor Productivity(TFP) between Korean and Japanese construction firms in Korea and Japan over the period of 2005-2011. The results of this study are as follows. Efficiency scores of Korean construction firms are 0.797, and Japanese construction firms are 0.921. Second, annual total factor productivity growth of Korean construction firms is 0.5% and technical progress do much for TFP decrease. However Japanese construction firms marked annual increasing of 2.5% of TFP. Third, technical progress contributed in TFP increase of construction firms in Korea. Korean construction firms, however, relatively lagged behind Japanese construction firms in technical progress. Therefore, Korean construction firms need strategies to achieve technical advances including adopting new technology or process innovation to maintain competitiveness, survive, and develop in the future competition with Japan.

• 국제지역연구
• /
• 제14권2호
• /
• pp.43-60
• /
• 2010

본 연구는 비모수적 추정방법인 DEA와 맴퀴스트지수를 통해 한 중 일 3국의 연구개발투자의 효율성과 생산성 변화를 측정하였다. 분석결과는 다음과 같다. 첫째, 분석기간 동안 한국과 일본의 효율성지수는 0.837과 0.834로서 OECD 평균 0.809를 상회하는 효율성을 보인 반면 중국의 경우는 0.420으로 가장 낮은 효율성을 보이고 있다. 둘째, 맴퀴스트지수에 의한 연구개발투자의 생산성 변화를 분석한 결과 일본과 중국은 각각 1.9%와 0.9%의 생산성감소를 보인 반면 한국의 경우 연평균 25%의 생산성증가를 시현하고 있다. 셋째, 생산성 변화를 기술의 변화와 효율성의 변화로 분해한 결과 분석기간 동안 연평균 1.9%의 생산성하락을 나타낸 일본의 경우는 기술진보 1.006, 기술효율성변화 0.975로서 생산성 감소는 기술효율성 하락에 의해 발생하고 있다. 한편 연평균 0.9%의 생산성하락을 보인 중국의 경우는 기술진보와 기술효율성변화가 각각 0.966과 1.026으로 나타나 기술진보보다는 기술효율성이 생산성을 견인하는 전형적인 기술추격형 개도국의 모습을 보이고 있다. 반면 한국의 경우는 효율성의 증가가 18.2% 기술진보가 5.9%로 나타나고 있어 선진국 따라잡기형 효율성증가가 생산성증가를 견인하고 기술진보가 이를 뒷받침하는 선진국형과 개도국형의 중간적인 모습을 보이고 있다.

• Geomechanics and Engineering
• /
• 제23권2호
• /
• pp.115-125
• /
• 2020

This study aims to explore practical and useful equations for rapid evaluation of uniaxial compressive strength of concrete (UCS-C) during the preliminary design stage of aggregate selection. For this purpose, aggregates which were produced from eight different intact rocks were used in the production of concretes. Laboratory experiments involved the tests for uniaxial compressive strength (UCS-R), point load index (PLI-R), P wave velocity (UPV-R), apparent porosity (n-R), unit weight (UW-R) and aggregate impact value (AIV-R) of the rock samples. UCS-C, point load index (PLI-C) and P wave velocity (UPV-C) of concrete samples were also determined. Relationships between UCS-R-rock parameters and UCS-C-concrete parameters were developed by regression analyses. In the simple regression analyses, PLI-C, UPV-C, UCS-R, PLI-R, and UPV-R were found to be statistically significant independent variables to estimate the UCS-C. However, higher coefficients of determination (R²=0.97-1.0) were obtained by multiple regression analyses. The results of simple regression analysis were also compared to the limited number of previous studies. The strength conversion factor (k) values were found to be 14.3 and 14.7 for concrete and rock samples, respectively. It is concluded that the UCS-C can roughly be estimated from derived equations only for the specified rock types.

• 펄프종이기술
• /
• 제45권3호
• /
• pp.52-58
• /
• 2013

To evaluate the anisotropic characteristics of Korean traditional paper-Hanji, the physical and mechanical characteristics of hand-made hanji, and machine-made hanji were investigated in this research. The densities of copying paper and newsprint paper appeared to be two times higher than the densities of hand-made hanji using Ssangbal sheet forming and hanji made of paper mulberry fiber. The breaking length, and tear index of both Hanji using Owangbal sheet forming, and hand-made Hanji using Ssangbal sheet forming appeared to be different according to the directions in paper. The breaking lengths of Hanji using Owangbal sheet forming showed little differences according to the directions. Breaking length of Hanji using Ssangbal sheet were slightly higher than those of Hanji using Owangbla sheet forming. The breaking lengths of machine-made hanji, copying paper, and newsprint paper were two to four times higher than those of hand-made Hanji. The breaking length showed higher differences according to the direction than the tear index. The tensile strength according to the directions in paper showed significant differences (${\alpha}$=0.05) in all papers used in this research.