• Membrane and Water Treatment
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• v.13 no.3
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• pp.111-119
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• 2022

In this research, bentonite was intercalated with CMC and then two different percentages of glutaraldehyde (5 & 10%) were added as a crosslink agent to achieve non water-soluble composites. Then the composites were coated on clay-based microfiltration membranes which were synthesized in the previous work of the authors. The XRD technique was used to track the intercalation mechanism and FTIR was used to study the crosslink procedure. SEM was used to study the microstructure and morphology of the coated samples and then the ability of non-coated and coated samples for removal of Cr³⁺ ions was studied and compared. It was seen that the samples coated with the synthesized composite including 10% of glutaraldehyde showed the best results and removed 99.7% of Cr³⁺ ions from water polluted with 5 ppm of Cr³⁺ ions.

• Ocean Systems Engineering
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• v.12 no.4
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• pp.413-437
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• 2022

An innovative concept for wet-transportation and stepwise installation of mono-bucket foundation for 15 MW offshore wind turbine is proposed. Case studies for two different mono-bucket and wrap-buoy dimensions are conducted and their hydrostatic and hydrodynamic performances are compared for both wet-towing and lowering operations. The intact stability and transient responses are analyzed in detail for various stages of lowering operation. Wave-induced motion statistics during wet tow in sea state 4 (highest operational window) are checked. The proposed concept is found to be feasible and can be an alternative cost-effective solution without using heavy-lift crane vessel in practice.

• Advances in aircraft and spacecraft science
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• v.9 no.5
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• pp.463-477
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• 2022

This study compares various ways of calculating flows for the problems with the presence of shock waves by first-order schemes and higher-order DG method on the tests from the Quirk list, namely: Quirk's problem and its modifications, shock wave diffraction at a 90 degree corner, the problem of double Mach reflection. It is shown that the use of HLLC and Godunov's numerical schemes flows in calculations can lead to instability, the Rusanov-Lax-Friedrichs scheme flow can lead to high dissipation of the solution. The most universal in heavy production calculations are hybrid schemes flows, which allow the suppression of the development of instability and conserve the accuracy of the method.

• Structural Engineering and Mechanics
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• v.88 no.3
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• pp.251-262
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• 2023

This paper presents a method for assessing the dynamic responses of gravity-based structures (GBS) under various seismic loads, with a focus on fluid-structure-ground interactions. Models of GBSs and their surrounding environments were developed, incorporating interaction effects among the structure, seawater, and seabed. Dynamic responses of the GBS subjected to three seismic loads-Chi-Chi, Northridge01, and Northridge02-were calculated, with consideration of both horizontal and vertical accelerations, as well as displacements. Parametric studies indicated that the primary factors affecting the dynamic responses of GBS were seismic loads characterized by significant input forces and accelerations. The frictional force on the ground had minimal impact on the horizontal and vertical displacements of the GBS. Weight emerged as a critical factor in anchoring the GBS to the ground and minimizing vertical accelerations and displacements.

• Advances in concrete construction
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• v.17 no.1
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• pp.27-36
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• 2024

Reinforced concrete (RC) flat slabs should be designed based on punching shear strength. As part of this study, machine learning (ML) algorithms were developed to accurately predict the punching shear strength of RC flat slabs without shear reinforcement. It is based on Bayesian optimization (BO), combined with four standard algorithms (Support vector regression, Decision trees, Random forests, Extreme gradient boosting) on 446 datasets that contain six design parameters. Furthermore, an analysis of feature importance is carried out by Shapley additive explanation (SHAP), in order to quantify the effect of design parameters on punching shear strength. According to the results, the BO method produces high prediction accuracy by selecting the optimal hyperparameters for each model. With R² = 0.985, MAE = 0.0155 MN, RMSE = 0.0244 MN, the BO-XGBoost model performed better than the original XGBoost prediction, which had R² = 0.917, MAE = 0.064 MN, RMSE = 0.121 MN in total dataset. Additionally, recommendations are provided on how to select factors that will influence punching shear resistance of RC flat slabs without shear reinforcement.

• Applied Biological Chemistry
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• v.41 no.2
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• pp.181-186
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• 1998

The effects of sewage treatment on characteristics of sludge as a composting material were investigated for a year during the initial operation at the full-scale Chunan sewage treatment plant. Due to the shortage of design capacity of belt press, a sludge dewatering unit, non-volatile solids were recirculating and concentrating in the treatment plant, resulting in an increase of MLSS and a decrease in F/M ratio at the activated sludge system. Special attention is required for long term operations since the increase of non-volatile solids in the plant would deteriorates the treatment efficiency. The sewage sludge of the Chunan sewage treatment plant showed 79.5% of water content, 11.6% of organic content, and C/N ratio of 6.1, and contained As 1.8 mg/kg, Cd 27 mg/kg, Hg <0.1 mg/kg, Pb 54 mg/kg, T-Cr 370 mg/kg, and Cu 1,100mg/kg of heavy metals. In order to be used as raw material for optimum composting, the sewage sludge requires bulking agents for moistrure/porosity control and a carbon source for adjusting C/N ratio. However, the sewage sludge is not adequate as a soil conditioner after composing due to a high content of heavy metals. If the sewage sludge has to he used as a soil conditioner after composting, it as required to identify and remove tire industrial wastewater portions in tire influent of the plant since heavy metals in the influent were mostly concentrated in dewatered sludge.

• Geomechanics and Engineering
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• v.15 no.5
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• pp.1029-1038
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• 2018

A superposition-iteration (S-I) model is proposed to simulate the jet grouting pre-reinforcing impact for a shallow-buried tunnel. The common model is deduced by theoretical (force equilibrium) analysis and then transformed into the numerical formulation. After applying it to an actual engineering problem, the most obvious deficiency was found to be continuous error accumulation, even when the parameters change slightly. In order to address this problem, a superposition-iteration model is developed based on the basic assumption and superposition theory. First, the additional deflection between two successive excavation steps is determined. This is caused by the disappearance of the supporting force in the excavated zone and the soil pressure in the disturbed zone. Consequently, the final deflection can be obtained by repeatedly superposing the additional deflection to the initial deflection in the previous steps. The analytical solution is then determined with the boundary conditions. The superposition-iteration model is thus established. This model was then applied and found to be suitable for real-life engineering applications. During the calculation, the error induced by the ill-conditioned problem of the matrix is easily addressed. The precision of this model is greater compared to previous models. The sensitivity factors and their impact are determined through this superposition-iteration model.

• Transactions of Materials Processing
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• v.11 no.8
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• pp.682-690
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• 2002

The formation of adiabatic shearband in tungsten heavy alloys(WHA) was studied in this investigation. Five prismatic specimens were loaded by high velocity impacts and treated as plane strain problems. To find out the effect of particle's volume ratio, specimens containing 81%, 93% and 97% volume percents of tungsten particles were used. Also the effects of particle's geometry and size on the formation of shearband were studied for 81% volume percent alloys by small size particle model, large size particle model and undulated particle models, and the results were discussed.be used to diagnose the causes of necking and fracture in industrial practice and to investigate whether these defects were caused by material property variation, changes in lubrication, or incorrect press settings. In non-axisymmetric deep drawing, three modes of forming regimes are found: draw, stretch, plane strain. The stretch mode for non-axisymmetric deep drawing could be defined when the major and minor strains are positive. The draw mode could be defined when the major strain is positive and minor strain is negative, and plane strain mode could be defined when the major strain is positive and minor strain is zero. Through experiments the draw mode was shown on the wall and flange are one of a drawn cup, while the plane strain and the stretch mode were on the punch head and the punch corner area respectively, We observed that the punch load of elliptical deep drawing was decreased according to increase of die corner radius and the thickness deformation of minor side was more large than major side.

• Earthquakes and Structures
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• v.14 no.6
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• pp.615-626
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• 2018

The seismic vulnerability of Turkey is relatively high due to its active fault systems with potential to create destructive earthquakes. Thus, reducing the loss of life and property, the number of the earthquake-prone buildings and their retrofit requirements are considerably significant key issues under the scenario earthquakes. The street survey based rapid assessment (SSRA) method can be considered as a powerful tool to determine the seismic vulnerability of building stock of an earthquake-prone city/state. In this study, the seismic vulnerability of the building stock of the Kirikkale province in Turkey is aimed to be estimated adopting the street survey based rapid assessment method (SSRA). For this purpose, central 2074 existing reinforced concrete (R/C) buildings were structurally surveyed with rapid visual site screening and disadvantages such as, the existence of short-column, soft-story, heavy overhangs, pounding effect and local soil conditions were determined for obtaining the structural performance score of each. The results obtained from the study demonstrate that 11-25% of the surveyed buildings in the study region needs to be investigated through more advanced assessment methods. Besides, higher correlation between increasing story number and unsafe/safe building ratio is obtained for the buildings with soft-story parameter than that for those with heavy overhangs and short-column parameters. The conformity of the results of the current study with the previous documented cases of rapid assessment efforts in the recent earthquakes in Turkey shows that the SSRA method for the Kirikkale province performed well, and thus this methodology can be reliably used for similar settlement areas.

• Advances in environmental research
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• v.3 no.2
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• pp.163-172
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• 2014

Magnetite was chosen as a typical adsorbent to study its phosphate adsorption capacity in water body with low concentration of phosphorus (below $2mg\;PL^{-1}$). Magnetite was collected from Luoyang City, Henan Province, China. In this research, three factors have been studied to describe the adsorption of phosphate on magnetite, which was solution concentration (concentration ranging from 0.1 to $2.5mg\;PL^{-1}$), suspension pH (1 to 13) and temperature (ranging from $10^{\circ}C$ to $40^{\circ}C$). In addition, the modified samples had been characterized with XRD and FE-SEM image. The results show that iron ions contains in magnetite were the main factors of phosphorus removal. The behavior of phosphorus adsorption to substrates could be fitted to both Langmuir and Freundlich isothermal adsorption equations in the low concentration phosphorus water. The theoretical saturated adsorption quantity of magnetite is 0.158 mg/g. pH has great influence on the phosphorus removal of magnetite ore by adsorption. And pH of 3 can receive the best results. While temperature has little effect on it. Magnetite was greatly effective for phosphorus removal in the column experiments, which is a more practical reflection of phosphorous removal combing the adsorption isotherm model and the breakthrough curves. According to the analysis of heavy metals release, the release of heavy metals was very low, they didn't produce the secondary pollution. The mechanism of uptake phosphate is in virtue of chemisorption between phosphate and ferric ion released by magnetite oxidation. The combined investigation of the magnetite showed that it was better substrate for water body with low concentration of phosphorus.