• Steel and Composite Structures
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• 제39권4호
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• pp.401-417
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• 2021

This study experimentally reveals the influence of welding on grade S690Q high strength steel (HSS) butt joints from both micro and macro levels. Total eight butt joints, taking plate thickness and welding heat input as principal factors, were welded by shielded metal arc welding. In micro level, the microstructure transformations of the coarse grain heat affected zone (CGHAZ), the fine grain heat affected zone (FGHAZ) and the tempering zone occurred during welding were observed under light optical microscopy, and the corresponding mechanical performance of those areas were explored by micro-hardness tests. In macro level, standard tensile tests were conducted to investigate the impacts of welding on tensile behaviour of S690Q HSS butt joints. The test results showed that the main microstructure of S690Q HSS before welding was tempered martensite. After welding, the original microstructure was transformed to granular bainite in the CGHAZ, and to ferrite and cementite in the FGHAZ. For the tempering zone, some temper martensite decomposed to ferrite. The performed micro-hardness tests revealed that an obvious "soft layer" occurred in HAZ, and the HAZ size increased as the heat input increased. However, under the same level of heat input, the HAZ size decreased as the plate thickness increased. Subsequent coupon tensile tests found that all joints eventually failed within the HAZ with reduced tensile strength when compared with the base material. Similar to the size of the HAZ, the reduction of tensile strength increased as the welding heat input increased but decreased as the thickness of the plate increased.

• Computers and Concrete
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• 제33권1호
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• pp.77-90
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• 2024

Waste foundry sand (WFS) is the waste product that cause environmental hazards. WFS can be used as a partial replacement of cement or fine aggregates in concrete. A database comprising 234 compressive strength tests of concrete fabricated with WFS is used. To construct the machine learning-based prediction models, the water-to-cement ratio, WFS replacement percentage, WFS-to-cement content ratio, and fineness modulus of WFS were considered as the model's inputs, and the compressive strength of concrete is set as the model's output. A base extreme gradient boosting (XGBoost) model together with two hybrid XGBoost models mixed with the tunicate swarm algorithm (TSA) and the salp swarm algorithm (SSA) were applied. The role of TSA and SSA is to identify the optimum values of XGBoost hyperparameters to obtain the higher performance. The results of these hybrid techniques were compared with the results of the base XGBoost model in order to investigate and justify the implementation of optimisation algorithms. The results showed that the hybrid XGBoost models are faster and more accurate compared to the base XGBoost technique. The XGBoost-SSA model shows superior performance compared to previously published works in the literature, offering a reduced system error rate. Although the WFS-to-cement ratio is significant, the WFS replacement percentage has a smaller influence on the compressive strength of concrete. To improve the compressive strength of concrete fabricated with WFS, the simultaneous consideration of the water-to-cement ratio and fineness modulus of WFS is recommended.

• 경영과학
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• 제23권3호
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• pp.77-93
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• 2006

In the highly competitive world, there has been a concomitant increase in the need for the research and planning methodology, which can perform an advanced assessment of technological opportunities and an early Perception of threats and possibilities of the emerging technology according to the nation's economic and social status. This research is aiming to provide indicators and visualization methods to measure the latest research trend and aspect underlying scientific and technological documents to researchers and policy planners using 'Co-word Analysis' Organic light emitting diodes(OLED) is an emerging technology in various fields of display and which has a highly prospective market value. In this paper, we presented an analysis on OLED. Co-word analysis was employed to reveal patterns and trends in the OLED fields by measuring the association strength of terms representatives of relevant publications or other texts produced in the OLED field. Data were collected from SCI and the critical keywords could De extracted from the author keywords. These extracted keywords were further standardized. In order to trace the dynamic changes in the OLED field, we presented a variety of technology mapping. The results showed that the OLED field has some established research theme and also rapidly transforms to embrace new themes.

• Smart Structures and Systems
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• 제8권1호
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• pp.69-92
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• 2011

This paper presents an emergent pattern recognition approach based on the immune network theory and hierarchical clustering algorithms. The immune network allows its components to change and learn patterns by changing the strength of connections between individual components. The presented immune-network-based approach achieves emergent pattern recognition by dynamically generating an internal image for the input data patterns. The members (feature vectors for each data pattern) of the internal image are produced by an immune network model to form a network of antibody memory cells. To classify antibody memory cells to different data patterns, hierarchical clustering algorithms are used to create an antibody memory cell clustering. In addition, evaluation graphs and L method are used to determine the best number of clusters for the antibody memory cell clustering. The presented immune-network-based emergent pattern recognition (INEPR) algorithm can automatically generate an internal image mapping to the input data patterns without the need of specifying the number of patterns in advance. The INEPR algorithm has been tested using a benchmark civil structure. The test results show that the INEPR algorithm is able to recognize new structural damage patterns.

• Coupled systems mechanics
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• 제5권4호
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• pp.315-327
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• 2016

Undergoing large volumetric changes upon incremental environmental stimulation, hydrogels are interesting materials which hold immense potentials for utilization in a wide array of applications in diverse industries. Owing to the large magnitudes of deformation it undergoes, swelling induced instability is a commonly observed sight in all types of gels. In this work, we investigate the instability of photo-thermal sensitive hydrogels, produced by impregnating light absorbing nano-particles into the polymer network of a temperature sensitive hydrogel, such as PNIPAM. Earlier works have shown that by using lights of different intensities, these hydrogels follow different swelling trends. We investigate the possibility of utilizing this fact for remote switching applications. The analysis is built on a thermodynamic framework of inhomogeneous large deformation of hydrogels and implemented via commercial finite element software, ABAQUS. Various examples of swelling induced instabilities, and its corresponding dependence on light intensity, will be investigated. We show that the instabilities that arise have their morphologies dependent on the light intensity.

• Structural Engineering and Mechanics
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• 제39권4호
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• pp.499-520
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• 2011

The effectiveness of a technique for the repair of reinforced concrete members in combination with a technique for the repair of masonry walls of infilled frames, damaged due to cyclic loading, is experimentally investigated. Three single - story, one - bay, 1/3 - scale frame specimens are tested under cyclic horizontal loading, up to a drift level of 4%. One bare frame and two infilled frames with weak and strong infills, respectively, have been tasted. Specimens have spirals as shear reinforcement. The applied repair technique is mainly based on the use of thin epoxy resin infused under pressure into the crack system of the damaged RC joint bodies, the use of a polymer modified cement mortar with or without a fiberglass reinforcing mesh for the damaged infill masonry walls and the use of CFRP plates to the surfaces of the damaged structural RC members, as external reinforcement. Specimens after repair, were retested in the same way. Conclusions concerning the effectiveness of the applied repair technique, based on maximum cycles load, loading stiffness, and hysteretic energy absorption capabilities of the tested specimens, are drawn and commented upon.

• 한국약용작물학회지
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• 제27권2호
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• pp.75-85
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• 2019

Background: Medicinal plants are widely used in Asia. They have proven to be an invaluable asset in modern drug discovery and their demand has been steadily increasing across various industries. Methods and Results: Using 4,867 valid patents related to 12 oriental medicinal plants of 10 country groups, the growth and development potential of patents was evaluated. The cites per patent (CPP) and patent family size (PFS) indices were used to evaluate the market capability and technological level of the collected patents. Meanwhile, the patent impact index (PII) and technology strength (TS) were used to compare the technological competitiveness of patents among various technology types and markets. Both CPP and PFS indices showed that magnolia-vine and balloon flower have numerous core or original patents. Furthermore, an increase in both PII and TS indices was observed. A newly designed intellectual property multi-layer (IPM) model predicted that the medicine, genome and cosmetic categories have a high possibility of patent application growth. Conclusions: The IPM model can be used to provide the scope of particular technology fields for patent development. In addition, this study can assist patents to advance in the international market and guide the development of a national industrial strategy.

• 청정기술
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• 제10권4호
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• pp.189-194
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• 2004

최근 환경부와 과학기술부에서 과학기술 분야의 효율적인 발전을 도모하고자 해당 기술분야의 기술지도를 마련하였다. 이를 위하여 산업기술동향을 분석한 후, 미래유망 기술 및 세계적 경쟁력을 확보할 수 있는 핵심기술 등이 도출되었고, 마련된 기술지도는 산 학 연 관의 전략적 연구 및 기술개발사업 추진에 방향성을 제시하고 있다. 여기에서는 최근 친환경공정기술과 관련한 분야로, 과학기술부 국가기술지도의 '환경/에너지 프론티어 진흥' 중 '환경친화적 소재/제품 및 공정기술' 부문과 환경부 차세대 핵심환경기술개발사업 10개년 종합계획의 '친환경 공정기술' 부문에서 작성된 기술지도 내용에서 무배출 기술 중심으로 살펴보았다. 그리고 해당 기술분야의 강점, 약점, 기회, 위협을 분석하고, 앞으로의 연구수행에 전략수립과 효율적인 발전에 기여하고자 하였다.

• 산업경영시스템학회지
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• 제39권2호
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• pp.11-18
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• 2016

Product liability (PL), which began enforcement in 2002, refers to the legal responsibility of the manufacturers or sellers (wholesales or retailers) for the property damage or bodily harm caused by their product. With a strong enforcement of the Product Liability (PL) Act, companies are required to structure and operate a response system to defend or prevent product accidents efficiently, but small and medium enterprises (SMEs) are unable to respond more aggressively due to limitation of management resources. In this manner, it is important to develop response strategies for SMEs to efficiently cope with the PL Act. In this paper, the PEST (Political, Economic, Social, and Technological) analysis is performed to reveal the impact of the PL Act on SMEs in macro-economic point of view. To formulate SME's PL response strategy, SWOT analysis is performed to categorize each factors from PEST analysis and AHP is applied to identify the intensities of SWOT factors. The prioritized SWOT factor, results of PEST-SWOT-AHP analysis, are used to formulate SME's PL response strategies. The study results are briefly summarized as follows. To reduce product defects, it is necessary for SMEs to formulate PL response strategies for each phase of the product life cycle by continuously collecting and analyzing PL cases in the same industry or for similar products. In addition, SMEs should invest more technological effort to ensure product safety. Further, SMEs should spread PL awareness to all staff members by training internal PL experts. Moreover, a SME should enroll in PL insurance and spread this information to its customers so that they become aware that the company is proactively conforming to the PL law.

• 콘크리트학회논문집
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• 제18권3호
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• pp.389-395
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• 2006

실존하는 콘크리트 구조체를 평가할 때, 그 콘크리트의 강도를 알아내는 것이 매우 중요하다. 콘크리트의 강도를 알아내기 위하여 재하시험이나 코어시험을 하는 것은 시험비용, 편의성, 시간, 구조체에 대한 손상, 신뢰성등 많은 문제점이 있다. 그러므로 이러한 문제점들을 극복하기 위하여 여러 가지 비파괴 시험과 통게적 해석을 통한 구조해석법이 발전해 오고 있다. 본 연구에서는 재령 3, 7, 14, 28, 90, 180, 365, 730일에 대하여 28일 표준실린더 압축강도 65.0MPa인 고강도 콘크리트 구조체의 실제강도를 알기 위한 일련의 실험을 하였고, 각 실험결과를 SPSS 프로그램으로 회귀분석 하였다. 회귀분석에 의한 강도추정식과 코어강도값을 비교하여 오차율을 계산하고, 기존식과 비교하여 추정식의 유의성을 검토한 결과 기존식들은 보통강도 콘크리트에는 적용할 수 있지만 고강도 콘크리트에는 적용에 한계가 있음이 밝혀졌다. 따라서 40MPa 이상의 고강도 콘크리트의 슈미트 해머 시험에 의한 강도 추정을 위해 다음과 같은 강도식을 제안하였다.