• Steel and Composite Structures
• /
• v.47 no.2
• /
• pp.253-267
• /
• 2023

The bearing capacities resisted by the two-bay beams of multi-story planar frames with unequal spans under column removal scenarios differ considerably owing to the asymmetric stress on the left and right beams connected to the failed column and cause the potential for beams with larger span-to-depth ratios to be unable to exert effectively, which is disadvantageous for resisting the vertical load in unequal-span frame structures. To address this problem, the structural measure of adding braces to the weak bays of multi-story unequal-span frames was proposed, with the objective of achieving a coordinated stress state in two-bay beams with unequal spans, thereby improving the collapse resistance of unequal-span frame structures. Before conducting the numerical simulation, the modeling methods were verified by previous experimental results of two multi-story planar frames with and without steel braces. Thereafter, the effects of the tensile and compressive braces on the collapse behavior of the frame structures were elucidated. Then, based on the mechanical action laws of the braces throughout the collapse process, a detailed design method for improving the collapse resistance of unequal-span frame structures was proposed. Finally, the proposed design method was verified by using sufficient example models, and the results demonstrated that the design method has good application prospects and high practical value.

• Journal of Korean Society of Water and Wastewater
• /
• v.19 no.1
• /
• pp.16-24
• /
• 2005

Mathematical model was developed to verify a sequential particle removal taking place in a granular media gravity filter. Consequential multi-layer filtration cycle model was applied to verify the fraction of filter effluent particles that are filter influent particles that were never removed as well as the fraction of filter effluent particles that were detached after deposition were performed through laboratory experiments. Three sizes of marker particles were injected ahead of the filter column as a pulse in the presence of four sizes of polystyrene particles that were used as a primary source of particles in the raw suspension to investigate particle attachment alone in contrast to net removal from attachment and detachment. Microscopic counting of filter effluent particles was assumed to reflect attachment. Experimental results indicated that particle detachment is significant beginning from the early phase of filtration. For each size of fluorescent microspheres at one filter depth, fluorescent microsphere removal increased with filter runtime to a maximum due to ripening. The detached fraction of effluent particles increased with particle size and filter depth. The presence of detached particles and the increasing fraction of detached particles in deeper bed were confirmed.

• Advances in environmental research
• /
• v.6 no.1
• /
• pp.67-81
• /
• 2017

Mining activities play a significant role in environmental pollution by producing large amounts of tailings which comprise heavy metals. The impressive increase in mining activities in recent decades, due to their high influence on the industry of developing countries, duplicates the need for a substantial effort to develop and apply efficient measures of pollution control, mitigation, and abatement. In this study, our objective was to investigate the effect of simulation of the leachate, pH and inflow intensity of transport of $Pb^{2+}$, $Zn^{2+}$, and $Cd^{2+}$ through Lakan lead and zinc plant tailings, in Iran, and to evaluate the modeling efficiency by comparing the modeling results and the results obtained from previous column studies. We used the HP1 model and the PHREEQC database to simulate metals transport through a saturated soil column during a 15 day time period. The simulations assumed local equilibrium. As expected, a lower pH and inflow intensity increased metal transport. The retardation of heavy metals followed the order $Zn^{2+}$ > $Pb^{2+}$ > $Cd^{2+}$ and the removal concentrations of Cd, Pb, and Zn at the inflow intensity critical scenario, and Cd and Pb at inflow acidity critical scenario exceeded the allowable EPA and Iranian's 1053 standard thresholds. However, although the simulation results generally agreed well with the results of the column study, improvements are expected by using multi-dimensional models and a kinetic modeling approach for the reactions involved. The results of such investigations will be highly useful for designing preventative strategies to control reactive transport of hazardous metals and minimize their environmental effects.

• International Journal of Concrete Structures and Materials
• /
• v.10 no.1
• /
• pp.1-13
• /
• 2016

The progressive collapse analysis of reinforced concrete (RC) moment-frame buildings under extreme loads is discussed from the perspective of modeling issues. A threat-independent approach or the alternate path method forms the basis of the simulations wherein the extreme event is modeled via column removal scenarios. Using a prototype RC frame building, issues and considerations in constitutive modeling of materials, options in modeling the structural elements and specification of gravity loads are discussed with the goal of achieving consistent models that can be used in collapse scenarios involving successive loss of load-bearing columns at the lowest level of the building. The role of the floor slabs in mobilizing catenary action and influencing the progressive collapse response is also highlighted. Finally, an energy-based approach for identifying the proximity to collapse of regular multi-story buildings is proposed.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.2 no.2
• /
• pp.126-131
• /
• 1997

The biosorption and desorption of Cr, Cu and Al were carried out using brown marine algae Sargassum fluitans biomass, known as the good biosorbent of heavy metals. The content of alginate bound to light metals could be changed by physical and chemical pretreatment. The maximum uptake of Cr, Cu and Al was independent of the alginate content. The maximum uptaker of Al was two times(mole basis) than those of Cu and Cr. The aluminum-alginate complex was found in the sorption solution of raw and protonated biomass. Most of Cu, Al and light metals sorbed in the biomass were eluted at pH 1.1. However, only 5 to 10% of Cr sorbed was eluted at pH 1.1. The stoiceometric ion exchange between Cu and Ca ion was observed on Cu biosorption with Ca-loaded biomass. A part of Cr ion was bound to biomass as Cr(OH)2+ or Cr(OH)2+. Al was also bound to biomass as multi-valence ion and interfered with the desorbed Ca ion. The behavior of raw S. fluitans in ten consecutive sorption-desorption cycles has been investigated in a packed bed flow-through-column during a continuous removal of copper from a 35 mg/L aqueous solution at pH 5. The eluant used was a 1%(w/v) CaCl2/HC solution at pH 3.

• Journal of Korean Society of Water and Wastewater
• /
• v.19 no.3
• /
• pp.338-347
• /
• 2005

Horizontal-Flow Roughing Filtration (HRF) is one of altemative pretreatment methods e.g. prior to Slow Sand Filtration (SSF). However, some of its limitations are that the effluent quality drops drastically at higher turbidity (>200 NTU) and at higher filtration rate (>1 m/h). To overcome these drawbacks, we suggested Direct Horizontal-Flow Roughing Filtration (DHRF), which is a modified system of Horizontal-Flow Roughing (HRF) by addition of low dose of coagulant prior to filtration. In this study to optimize the DHRF configuration, a conceptual and mathematical model for the coarse compartment has been developed in analogy with multi-plate settlers. Data from simple column settling test can be used in the model to predict the filter performance. Furthermore, the model developed herein has been validated by successive experiments carried out. The conventional column settling test has been found to be an handy and useful to predict the performance of DHRF for different raw water characteristics (e.g. coagulated or uncoagulated water, different presence of organic matter, etc.) and different inital process conditions (e.g. coagulant dose, mixing time and intensity, etc.). An optimum filter design for the coarse compartment (grain size 20mm) has been found to be of 3 m/h filtration rate with filter length of 4-4.5 m.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.5
• /
• pp.2393-2399
• /
• 2013

In this paper, we proposed a method to screening of Alzheimer's disease (AD) from Raman spectra of platelet with synthesis of basis spectra using singular value decomposition (SVD). Raman spectra of platelet from AD transgenic mice are preprocessed with denoising, removal background and normalization method. The column vectors of each data matrix consist of Raman spectrum of AD and normal (NR). The matrix is factorized using SVD algorithm and then the basis spectra of AD and NR are determined by 12 column vectors of each matrix. The classification process is completed by select the class that minimized the root-mean-square error between the validation spectrum and the linear synthesized spectrum of the basis spectra. According to the experiments involving 278 Raman spectra, the proposed method gave about 97.6% classification rate, which is better performance about 6.1% than multi-layer perceptron (MLP) with extracted features using principle components analysis (PCA). The results show that the basis spectra using SVD is well suited for the diagnosis of AD by Raman spectra from platelet.

• Korean Journal of Construction Engineering and Management
• /
• v.20 no.1
• /
• pp.52-61
• /
• 2019

On 30 June, 2017, the Ministry of Land, Infrastructure, and Transport announced the minimum size of parking section will be expanded in parking lots. The expansion of parking section could lead to increase in apartment prices because of increase in total area of the parking lots. It is necessary to adjust the column spacing and number in the parking lots and to apply the 8-Bay long-span parking module with good parking efficiency. According to the study, the construction cost of the 6-Bay module and 8-Bay module was almost the same. But The 8-Bay module was more economical than the 6-Bay module because of the reduction in total area of 8-Bay multi-moduel. The Result of construction cost of 8-Bay modules, Removal Deck-plate RC system was most economical. While the construction cost of PC system was higher due to increase in volume of the member, it would ensure sufficient economy by reducing the girder height to apply a pre-stress method. Also, the construction cost of hollow slab system was the highest. But it could be used as the underground parking lots for apartment, because it had the lowest cost per square meter. This Study has a academic significance by proving the applicability of the 8-Bay Module to underground parking lot of apartment. And it is expected that this study will be used as basic data to derive optimal construction method that applies 8-Bay Module.