• Membrane Journal
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• v.34 no.3
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• pp.182-191
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• 2024

This review addresses the pressing need for effective wastewater treatment methodologies by exploring advanced thin-film nanocomposite (TFN) nanofiltration membranes aimed at efficient dye removal from industrial effluents. Utilizing insights from recent research, the review focuses on the fabrication of TFN membranes incorporating innovative materials such as nanocarbons, silica nanospheres, metal-organic frameworks (MOFs), and MoS₂. The primary goals are to enhance dye removal efficiency, improve antifouling properties, and maintain high selectivity for dye/salt separation. By leveraging the distinct advantages of these nanomaterials-including large surface areas, mechanical robustness, and specific pollutant interaction capabilities-this review aims to overcome the limitations of current nanofiltration technologies and provide sustainable solutions for water treatment challenges.

• Steel and Composite Structures
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• v.52 no.2
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• pp.145-163
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• 2024

This paper presents six novel hybrid machine learning (ML) models that combine support vector machines (SVM), Decision Tree (DT), Random Forest (RF), Gradient Boosting (GB), extreme gradient boosting (XGB), and categorical gradient boosting (CGB) with the Harris Hawks Optimization (HHO) algorithm. These models, namely HHO-SVM, HHO-DT, HHO-RF, HHO-GB, HHO-XGB, and HHO-CGB, are designed to predict the ultimate strength of both rectangular and circular reinforced concrete (RC) columns. The prediction models are established using a comprehensive database consisting of 325 experimental data for rectangular columns and 172 experimental data for circular columns. The ML model hyperparameters are optimized through a combination of cross-validation technique and the HHO. The performance of the hybrid ML models is evaluated and compared using various metrics, ultimately identifying the HHO-CGB model as the top-performing model for predicting the ultimate shear strength of both rectangular and circular RC columns. The mean R-value and mean a20-index are relatively high, reaching 0.991 and 0.959, respectively, while the mean absolute error and root mean square error are low (10.302 kN and 27.954 kN, respectively). Another comparison is conducted with four existing formulas to further validate the efficiency of the proposed HHO-CGB model. The Shapely Additive Explanations method is applied to analyze the contribution of each variable to the output within the HHO-CGB model, providing insights into the local and global influence of variables. The analysis reveals that the depth of the column, length of the column, and axial loading exert the most significant influence on the ultimate shear strength of RC columns. A user-friendly graphical interface tool is then developed based on the HHO-CGB to facilitate practical and cost-effective usage.

• Steel and Composite Structures
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• v.52 no.2
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• pp.165-182
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• 2024

Grouted sleeve splice (GSS) is an effective type of connection applied in the precast concrete structures as it has the advantages of rapidly assembly and reliable strength. To decrease the weight and cost of vertical rebar connection in precast shear walls, a light-weight sleeve is designed according to the thick-cylinder theory. Mechanical behaviour of the light-weighted GSS is investigated through experimental analysis. Two failure modes, such as rebar fracture failure and rebar pull-out failure, are found. The load-displacement curves exhibit four different stages: elastic stage, yield stage, strengthening stage, and necking stage. The bond strength between the rebar and the grout increases gradually from outer position to inner position of the sleeve, and it reaches the maximum value at the centre of the anchorage length. A finite element model predicting the mechanical properties of the light-weighted GSS is developed based on the Concrete Damage Plasticity (CDP) model and the Brittle Cracking (BC) model. The effect of the rebar anchorage length is significant, while the increase of the thickness of sleeve and the grout strength are not very effective. A model for estimating ultimate load, including factors of inner diameter of sleeves, anchorage length, and rebar diameter, is proposed. The proposed model shows good agreement with various test data.

• Journal of Korean Society of Transportation
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• v.32 no.2
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• pp.93-105
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• 2014

This study evaluated the relative efficiency of mobile emission reduction countermeasures through a Data Envelopment Analysis (DEA) approach and determined the priority of countermeasures based on the efficiency. Ten countermeasures currently applied for reducing greenhouse gases and air pollution materials were selected to make a scenario for evaluation. The reduction volumes of four air pollution materials(CO, HC, NOX, PM) and three greenhouse gases($CO_2$, $CH_4$, $N_2O$) for the year 2027, which is the last target year, were calculated by utilizing both a travel demand forecasting model and variable composite emission factors with respect to future travel patterns. To estimate the relative effectiveness of reduction countermeasures, this study performed a super-efficiency analysis among the Data Envelopment Analysis models. It was found that expanding the participation in self car-free day program was the most superior reduction measurement with 1.879 efficiency points, followed by expansion of exclusive bus lanes and promotion of CNG hybrid bus diffusion. The results of this study do not represent the absolute data for prioritizing reduction countermeasures for mobile greenhouse gases and air pollution materials. However, in terms of presenting the direction for establishing reduction countermeasures, this study may contribute to policy selection for mobile emission reduction measures and the establishment of systematic mid- and long-term reduction measures.

• Steel and Composite Structures
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• v.34 no.5
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• pp.681-698
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• 2020

The paper addresses contribution to the modeling and optimization of major machinability parameters (cutting force, surface roughness, and tool wear) in finish dry hard turning (FDHT) for machinability evaluation of hardened AISI grade die steel D₃ with PVD-TiN coated (Al₂O₃-TiCN) mixed ceramic tool insert. The turning trials are performed based on Taguchi's L₁₈ orthogonal array design of experiments for the development of regression model as well as adequate model prediction by considering tool approach angle, nose radius, cutting speed, feed rate, and depth of cut as major machining parameters. The models or correlations are developed by employing multiple regression analysis (MRA). In addition, statistical technique (response surface methodology) followed by computational approaches (genetic algorithm and particle swarm optimization) have been employed for multiple response optimization. Thereafter, the effectiveness of proposed three (RSM, GA, PSO) optimization techniques are evaluated by confirmation test and subsequently the best optimization results have been used for estimation of energy consumption which includes savings of carbon footprint towards green machining and for tool life estimation followed by cost analysis to justify the economic feasibility of PVD-TiN coated Al₂O₃+TiCN mixed ceramic tool in FDHT operation. Finally, estimation of energy savings, economic analysis, and sustainability assessment are performed by employing carbon footprint analysis, Gilbert approach, and Pugh matrix, respectively. Novelty aspects, the present work: (i) contributes to practical industrial application of finish hard turning for the shaft and die makers to select the optimum cutting conditions in a range of hardness of 45-60 HRC, (ii) demonstrates the replacement of expensive, time-consuming conventional cylindrical grinding process and proposes the alternative of costlier CBN tool by utilizing ceramic tool in hard turning processes considering technological, economical and ecological aspects, which are helpful and efficient from industrial point of view, (iii) provides environment friendliness, cleaner production for machining of hardened steels, (iv) helps to improve the desirable machinability characteristics, and (v) serves as a knowledge for the development of a common language for sustainable manufacturing in both research field and industrial practice.

• Journal of the Korea Institute of Building Construction
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• v.10 no.1
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• pp.57-63
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• 2010

The bearing wall apartments which occupy the majority of multi-residential apartment buildings built in Korea, are known for having limited architectural plan flexibility, posing challenges in terms of maintenance and remodeling. The economic losses and environmental issues resulting from the reconstruction of bearing wall apartments are now accumulating to the extent that they are becoming a national concern. Multi-residential apartment buildings, which are now the dominant form of residence in Korea, must accommodate diverse customer needs and changes in life style. A new concept of Rahmen structure with architectural flexibility is Green Frame. GF multi-residence housing is expected to reduce construction costs and shorten the construction schedule by overcoming the shortcomings of conventional bearing wall apartments. This goal is consistent with the national policies that target the reduction of resource and energy consumption. In addition, GF will be established as a core contributor to achieving a reduction in $CO_2$ emissions, which will enable the sustainable growth of domestic construction industry, and address the low-carbon green growth drive implemented by the government.

• The Journal of the Korea Contents Association
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• v.22 no.2
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• pp.147-161
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• 2022

This study examined changes in the ecological characteristics and design characteristics of Ban's exhibition space in three representative temporary exhibition halls and three permanent exhibition halls designed by Ban Shigeru since 2000. Through the investigation of the concepts and characteristics of ecological architecture, the design characteristics of exhibition space, the analysis framework of the design characteristics of exhibition space and the design elements of ecological architecture is obtained. The analysis results show that there are big changes between the temporary exhibition space and the permanent exhibition space in terms of building scale, space composition, function, materials and technology. On the one hand, the temporary exhibition space used recyclable materials, such as paper tubes, containers to be assembled on site into a single-layer space focused on display. The assembly method was simple and the construction period was short. After the exhibition, the exhibition space were dismantled. The materials were either transported to the next display site or recycled and reused. On the other hand, the permanent exhibition space used reinforced concrete as the main structure, and used a large amount of wood and glass materials to construct a multi-layered composite cultural space that separated the exhibition space and the leisure space. In terms of ecological characteristics, the building materials of the temporary exhibition space were recycled and no industrial wastes were generated after the demolition. The permanent exhibition hall uses eco-friendly wood for the roof and walls, so it is easy to replace and repair. Both types of exhibition halls are changing ecological architecture in a more sustainable direction by saving resources and energy through natural light and ventilation.