• Computers and Concrete
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• 제27권4호
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• pp.333-341
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• 2021

Steel slag, an industrial reject from the steel rolling process, has been identified as one of the suitable, environmentally friendly materials for concrete production. Given that the coarse aggregate portion represents about 70% of concrete constituents, other economic approaches have been found in the use of alternative materials such as steel slag in concrete. Unfortunately, a standard framework for its application is still lacking. Therefore, this study proposed functional model equations for the determination of strength properties (compression and splitting tensile) of steel slag aggregate concrete (SSAC), using gene expression programming (GEP). The study, in the experimental phase, utilized steel slag as a partial replacement of crushed rock, in steps 20%, 40%, 60%, 80%, and 100%, respectively. The predictor variables included in the analysis were cement, sand, granite, steel slag, water/cement ratio, and curing regime (age). For the model development, 60-75% of the dataset was used as the training set, while the remaining data was used for testing the model. Empirical results illustrate that steel aggregate could be used up to 100% replacement of conventional aggregate, while also yielding comparable results as the latter. The GEP-based functional relations were tested statistically. The minimum absolute percentage error (MAPE), and root mean square error (RMSE) for compressive strength are 6.9 and 1.4, and 12.52 and 0.91 for the train and test datasets, respectively. With the consistency of both the training and testing datasets, the model has shown a strong capacity to predict the strength properties of SSAC. The results showed that the proposed model equations are reliably suitable for estimating SSAC strength properties. The GEP-based formula is relatively simple and useful for pre-design applications.

• 한국분말재료학회지
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• 제28권2호
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• pp.110-119
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• 2021

In this study, the high-temperature oxidation properties of austenitic 316L stainless steel manufactured by laser powder bed fusion (LPBF) is investigated and compared with conventional 316L manufactured by hot rolling (HR). The initial microstructure of LPBF-SS316L exhibits a molten pool ~100 ㎛ in size and grains grown along the building direction. Isotropic grains (~35 ㎛) are detected in the HR-SS316L. In high-temperature oxidation tests performed at 700℃ and 900℃, LPBF-SS316L demonstrates slightly superior high-temperature oxidation resistance compared to HR-SS316L. After the initial oxidation at 700℃, shown as an increase in weight, almost no further oxidation is observed for both materials. At 900℃, the oxidation weight displays a parabolic trend and both materials exhibit similar behavior. However, at 1100℃, LPBF-SS316L oxidizes in a parabolic manner, but HR-SS316L shows a breakaway oxidation behavior. The oxide layers of LPBF-SS316L and HR-SS316L are mainly composed of Cr₂O₃, Fe-based oxides, and spinel phases. In LPBF-SS316L, a uniform Cr depletion region is observed, whereas a Cr depletion region appears at the grain boundary in HR-SS316L. It is evident from the results that the microstructure and the high-temperature oxidation characteristics and behavior are related.

• 인간식물환경학회지
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• 제24권1호
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• pp.39-51
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• 2021

Background and objective: Urban topology can be characterized as impervious, which changes the hydrologic features of an area, increasing surface water flow during local heavy rain events. The pluvial flooding is also influenced by the vertical structures of the urban area. This study suggested a modified digital elevation model (DEM) to identify changes in urban hydrological conditions and segmentalized urban micro catchment areas using a geographical information system (GIS). Methods: This study suggests using a modified DEM creation process based on Rolling Ball Method concepts along with a GIS program. This method proposes adding realized urban vertical data to normal DEM data and simulating hydrological analyses based on RBM concepts. The most important aspect is the combination of the DEM with polygon data, which includes urban vertical data in three datasets: the contour polyline, the locations of buildings and roads, and the elevation point data from the DEM. DEM without vertical data (DCA) were compared with the DEM including vertical data (VCA) to analyze catchment areas in Shin-wol district, Seoul, Korea. Results: The DCA had 136 catchments, and the area of each catchment ranged from 3,406 m² to 423,449 m². The VCA had 2,963 catchments, with the area of each ranging from 50 m² to 16,209 m². The most important finding is that in the overlapped VCA; the boundary of areas directly affected by flooding and the direction of surface water flow could be identified. Flooding data from September 21, 2010 and July 27, 2011 in the Shin-wol district were applied as ground reference data. The finding is that in the overlapped VCA; the boundary of areas directly affected by flooding and the direction of surface water flow could be identified. Conclusion: The analysis of the area vulnerable to surface water flooding (SWF) was more accurately determined using the VCA than using the DCA.

• Journal of Animal Science and Technology
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• 제64권6호
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• pp.1237-1244
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• 2022

Horse breeders suffer massive economic losses due to dystocia, abortion, and stillbirths. In Thoroughbred mares, breeders often miss the foaling process because approximately 86% of the foaling events occur from 19:00 to 7:00; consequently, breeders cannot assist mares experiencing dystocia. To solve this problem, various foaling alarm systems have been developed. However, there is a need to develop a new system to overcome the shortcomings of the existing devices and improve their accuracy. To this end, the present study aimed to (1) develop a novel foaling alarm system and (2) compare its accuracy with that of the existing Foalert^TM system. Specifically, eighteen Thoroughbred mares (11.9 ± 4.0 years old) were included. An accelerometer was used to analyze specific foaling behaviors. Behavioral data were transmitted to a data server every second. Depending on the acceleration value, behaviors were automatically classified by the server as categorized behaviors 1 (behaviors without change in body rotation), 2 (behaviors with sudden change in body rotation, such as rolling over), and 3 (behaviors with long-term change in body rotation, such as lying down laterally). The system was designed to alarm when the duration of categorized behaviors 2 and 3 was 12.9% and that of categorized behavior 3 was 1% during 10 min. The system measured the duration of each categorized behavior every 10 min and transmitted an alarm to the breeders when foaling was detected. To confirm its accuracy, the foaling detection time of the novel system was compared with that of Foalert^TM. The novel foaling alarm system and Foalert^TM alarmed foaling onset respectively 32.6 ± 17.9 and 8.6 ± 1.0 min prior to foal discharge, and the foaling detection rate of both systems was 94.4%. Therefore, the novel foaling alarm system equipped with an accelerometer can precisely detect and alert foaling onset.

• 한국컴퓨터정보학회논문지
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• 제27권12호
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• pp.51-58
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• 2022

본 논문에서 우리는 기존 식품과 웹 크롤링으로 찾은 식품 데이터에 대해 기계학습으로 식품군을 분류하여 식품교환표를 갱신하기 위한 의사결정트리 기반의 기계학습 모델을 제안한다. 식품교환표는 영양 관리가 필요한 환자의 식이요법이나 다이어트 식단을 편성할 때 식품 교환 섭취에 사용된다. 식단의 기준이 되는 식품교환표는 국민건강영양조사를 통한 개정과정에서 많은 인력과 시간이 소요되어 새로운 식품이나 트렌드에 따른 식품 변화를 신속하게 반영하기 어렵다. 제안 기법은 기존의 식품군을 바탕으로 새롭게 추가되는 식품을 분류하기 때문에 식품의 트렌드를 반영한 식품교환표 구성이 가능하다. 연구에서 제안 모델로 식품을 분류한 결과, 식품교환표의 식품군에 대한 정확도가 97.45%로 나타났으며, 본 식품 분류 모델은 병원, 요양원 등에서 식단 구성에 활용도가 높을 것으로 전망된다.

• 터널과지하공간
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• 제33권4호
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• pp.244-254
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• 2023

TBM에 장착되어 암석을 절삭하는 디스크커터에는 암반을 굴착하는 과정에서 세 방향의 절삭력이 작용한다. 일반적으로 디스크커터의 절삭력은 굴착대상암반의 강도에 따라 증가하는 것으로 알려져 있고, 디스크커터가 여러 원인에 의해 정상적으로 회전이 이루어지지 않는 경우에는 회전력이 급격하게 증가할 수 있다. 따라서 굴착 도중 디스크커터에 작용하는 절삭력은 굴착의 대상이 되는 암반의 상태나 디스크커터의 절삭상태를 나타내는 중요한 정보가 될 수 있다. 이러한 이유로 해외를 중심으로 디스크커터의 작용력을 실시간으로 측정하기 위한 기술의 개발이 이루어지고 있으며, 본 연구에서는 현재까지 해외의 문헌을 통해 보고되고 있는 TBM 디스크커터의 하중계측에 관한 연구현황에 대하여 소개하고자 하였다. 향후 국내에서도 유사한 기술의 개발이 이루어지는 경우에 유용한 참고자료가 될 수 있을 것으로 판단된다.

• 디자인융복합연구
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• 제15권2호
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• pp.301-317
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• 2016

새롭게 등장하는 플렉서블 디스플레이 인터페이스에서는 곡면표현이 가능하고 구부리거나 말거나 접는 등 디스플레이의 변형이 일어나는 특성을 바탕으로 새로운 사용행태를 야기할 수 있다는 점에서, 기존의 딱딱한 평면 디스플레이가 제공하지 못했던 새로운 경험을 줄 수 있을 것으로 논의되고 있다. 그러나 현재 플렉서블 디스플레이 분야에서 사용자경험의 총체적인 속성을 밝히는 연구를 찾기 어려움에 따라, 본 연구에서는 플렉서블 디스플레이 인터페이스에서 사용자가 기대하는 경험이 무엇인지 밝히고자 하였다. 이를 위해, 먼저 기존의 디지털 미디어 인터페이스에서의 사용자경험에 대한 문헌과 플렉서블 디스플레이 인터페이스에서의 사용자경험에 대한 문헌을 조사하고, 현재 사용자의 인식을 반영하기 위한 인터뷰를 진행하여 사용자경험을 나타내는 52개 항목을 수집하였다. 이 항목들은 사용자 기대경험 차원 도출을 위한 측정 문항으로 사용되었으며, 308명을 대상으로 설문조사를 진행하였다. 조사 결과, 플렉서블 디스플레이 인터페이스에서 기대되는 사용자경험은 기능성, 이해성, 유희성, 편의성, 친숙성, 자극성, 적응성, 공동성, 실제성, 심미성의 10가지 차원으로 나타났다.

• 한국습지학회지
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• 제25권4호
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• pp.291-296
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• 2023

철강산업의 산 회수설비에서 발생하는 염화수소 가스를 처리하기 위하여 마이크로버블을 발생할 수 있는 습식스크러빙 장치(DIWS)가 도입되었다. 산 회수 설비에서 발생하는 염소가스는 수소 가스와 결합하여 염화수소 가스의 농도를 50% 정도 증가시켰다. DIWS장치에 염소 제거를 위한 Na₂S₂O₃를 투입한 이후의 유입수 염화수소 가스 농도는 13.1 ~13.4 ppm, 유출수는 1.5~1.7 ppm이었고, 제거율은 87.5~88.8%로 안정되게 유지하였다. DIWS는 대기배출기준을 안정적으로 만족함에 따라 현장 적용에 적용할 수 있는 공정으로 판단된다.

• 소성∙가공
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• 제33권3호
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• pp.200-207
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• 2024

In this study, we developed a semi-analytical approach for the numerical analysis of residual stress in oxide scales formed on hot-rolled steels. The oxide scale, formed during the hot rolling process, experiences complex interactions due to thermal and mechanical influences, significantly affecting the material's integrity and performance. Our research focuses on integrating various stress components such as thermal stress, growth stress, and creep behavior to predict the residual stress within the oxide layer. The semi-analytical method combines analytical expressions for each stress component with numerical integration to account for their cumulative effects. Validation through instrumented indentation tests confirms the reliability of our model, which considers thermal expansion coefficient (CTE) differences, scale growth, and creep-induced stress relaxation. Our findings indicate that thermal stress resulting from CTE differences significantly impacts the overall residual stress, with growth stress contributing a compressive component during cooling, and creep behavior playing a minor role in stress relaxation. This comprehensive approach enhances the accuracy of residual stress prediction, facilitating the optimization of material design and processing conditions for hot-rolled steel products.

• Asia pacific journal of information systems
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• 제20권1호
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• pp.127-140
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• 2010

The benefit that a consumer derives from the use of a good often depends on the number of other consumers purchasing the same goods or other compatible items. This property, which is known as network externality, is significant in many IT related industries. Over the past few decades, network externalities have been recognized in the context of physical networks such as the telephone and railroad industries. Today, as many products are provided as a form of system that consists of compatible components, the appreciation of network externality is becoming increasingly important. Network externalities have been extensively studied among economists who have been seeking to explain new phenomena resulting from rapid advancements in ICT (Information and Communication Technology). As a result of these efforts, a new body of theories for 'New Economy' has been proposed. The theoretical bottom-line argument of such theories is that technologies subject to network effects exhibit multiple equilibriums and will finally lock into a monopoly with one standard cornering the entire market. They emphasize that such "tippiness" is a typical characteristic in such networked markets, describing that multiple incompatible technologies rarely coexist and that the switch to a single, leading standard occurs suddenly. Moreover, it is argued that this standardization process is path dependent, and the ultimate outcome is unpredictable. With incomplete information about other actors' preferences, there can be excess inertia, as consumers only moderately favor the change, and hence are themselves insufficiently motivated to start the bandwagon rolling, but would get on it once it did start to roll. This startup problem can prevent the adoption of any standard at all, even if it is preferred by everyone. Conversely, excess momentum is another possible outcome, for example, if a sponsoring firm uses low prices during early periods of diffusion. The aim of this paper is to analyze the dynamics of the adoption process in markets exhibiting network effects by focusing on two factors; switching and agent heterogeneity. Switching is an important factor that should be considered in analyzing the adoption process. An agent's switching invokes switching by other adopters, which brings about a positive feedback process that can significantly complicate the adoption process. Agent heterogeneity also plays a important role in shaping the early development of the adoption process, which has a significant impact on the later development of the process. The effects of these two factors are analyzed by developing an agent-based simulation model. ABM is a computer-based simulation methodology that can offer many advantages over traditional analytical approaches. The model is designed such that agents have diverse preferences regarding technology and are allowed to switch their previous choice. The simulation results showed that the adoption processes in a market exhibiting networks effects are significantly affected by the distribution of agents and the occurrence of switching. In particular, it is found that both weak heterogeneity and strong network effects cause agents to start to switch early and this plays a role of expediting the emergence of 'lock-in.' When network effects are strong, agents are easily affected by changes in early market shares. This causes agents to switch earlier and in turn speeds up the market's tipping. The same effect is found in the case of highly homogeneous agents. When agents are highly homogeneous, the market starts to tip toward one technology rapidly, and its choice is not always consistent with the populations' initial inclination. Increased volatility and faster lock-in increase the possibility that the market will reach an unexpected outcome. The primary contribution of this study is the elucidation of the role of parameters characterizing the market in the development of the lock-in process, and identification of conditions where such unexpected outcomes happen.