• Geomechanics and Engineering
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• v.18 no.5
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• pp.535-543
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• 2019

Building on/with expansive soils with no treatment brings complications. Compacted expansive soils specifically fall short in satisfying the minimum requirements for transport embankment infrastructures, requiring the adoption of hauled virgin mineral aggregates or a sustainable alternative. Use of hauled aggregates comes at a high carbon and economical cost. On average, every 9m high embankment built with quarried/hauled soils cost $12600MJ.m^{-2}$ Embodied Energy (EE). A prospect of using mixed cutting-arising expansive soils with industrial/domestic wastes can reduce the carbon cost and ease the pressure on landfills. The widespread use of recycled materials has been extensively limited due to concerns over their long-term performance, generally low shear strength and stiffness. In this contribution, hydromechanical properties of a waste tyre sand-sized rubber (a mixture of polybutadiene, polyisoprene, elastomers, and styrene-butadiene) and expansive silt is studied, allowing the short- and long-term behaviour of optimum compacted composites to be better established. The inclusion of tyre shred substantially decreased the swelling potential/pressure and modestly lowered the compression index. Silt-Tyre powder replacement lowered the bulk density, allowing construction of lighter reinforced earth structures. The shear strength and stiffness decreased on addition of tyre powder, yet the contribution of matric suction to the shear strength remained constant for tyre shred contents up to 20%. Reinforced soils adopted a ductile post-peak plastic behaviour with enhanced failure strain, offering the opportunity to build more flexible subgrades as recommended for expansive soils. Residual water content and tyre shred content are directly correlated; tyre-reinforced silt showed a greater capacity of water storage (than natural silts) and hence a sustainable solution to waterlogging and surficial flooding particularly in urban settings. Crushed fine tyre shred mixed with expansive silts/sands at 15 to 20 wt% appear to offer the maximum reduction in swelling-shrinking properties at minimum cracking, strength loss and enhanced compressibility expenses.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.5
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• pp.104-110
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• 2019

Shrinkage is one of typical characteristics of concrete with cement paste and aggregates. A lot of studies on this has been conducted with an assumption that the concrete is a homogeneous material. However, as shrinkage acts on only one of the components that consist of concrete, it is hard to be characterized only by the average effective properties. Therefore, in this paper, the concrete shrinkage, which is one of the typical characteristics and still has a lot of uncertainty, is simulated considering its heterogeneous properties. Using a meso model, concrete is modeled with the combination of mortar and aggregates, and the shrinkage is simulated by applying the shrinkage strain on the mortar only. According to the results, it is shown that the cracking of shrinking concrete is largely influenced by the types of aggregates and the degree of restraint. Also, the shrinkage cracking cannot be represented only by the single values such as tensile strength since the stiffness of aggregates and the degree of restraint influence the cracking.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.4
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• pp.492-500
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• 2019

Equal channel angular pressing(ECAP) is a severe plastic deformation technique capable of introducing large shear strain in bulk metal materials. However, if an ECAPed material has an inhomogeneous microstructure and anisotropic mechanical properties, this material is difficult to apply as structural components subjected to multi-axial stress during use. In this study, extruded oxygen-free copper(OFC) rods with a large diameter of 42 mm are extruded through ECAP by route Bc up to 12 passes. The variations in the microstructure, hardness, tensile properties, and microstructural and mechanical homogeneity of the ECAPed samples are systematically analyzed. High-strength OFC rods with a homogeneous and equiaxed-ultrafine grain structure are obtained by the repeated application of ECAP up to 8 and 12 passes. ECAPed samples with 4 and 8 passes exhibit much smaller differences in terms of the average grain sizes on the cross-sectional area and the tensile strengths along the axial and circumferential directions, as compared to the samples with 1 and 2 passes. Therefore, it is considered that the OFC materials, which are fabricated via the ECAP process with pass numbers of a multiple of 4, are suitable to be applied as high-strength structural parts used under multi-axial stress conditions.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.2
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• pp.143-149
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• 2019

Floating holograms are technologies that provide rich 3D stereoscopic images in a wide space such as advertisement, concert. In addition, It is possible to reduce the 3D glasses inconvenience, eye strain, and space distortion, and to enjoy 3D images with excellent realism and existence. Therefore, this paper implements a user gesture recognition system for manipulating a floating hologram characters that can be used in a small space devices. The proposed method detects face region using haar feature-based cascade classifier, and recognizes the user gestures using a user gesture-occurred position information that is acquired from the gesture difference image in real time. And Each classified gesture information is mapped to the character motion in floating hologram for manipulating a character action. In order to evaluate the performance of the proposed user gesture recognition system for manipulating a floating hologram character, we make the floating hologram display devise, and measures the recognition rate of each gesture repeatedly that includes body shaking, walking, hand shaking, and jumping. As a results, the average recognition rate was 88%.

• Steel and Composite Structures
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• v.38 no.2
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• pp.223-239
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• 2021

This paper presents the analytical modeling and finite element (FE) analysis, using ABAQUS software, of the new types of steel reinforced lightweight aggregate concrete (SRLAC) columns with cross-shaped (+shaped and X-shaped) steel section, using proposed three analytical and two FE models in total. The stress-strain material models for different components in the columns, including the confined zones of the lightweight aggregate concrete (LWAC) using three and four concrete zones divisions approaches and with and without taking into account the stirrups reaction effect, are established first. The analytical models for determining the axial load-deformation behavior of the SRLAC columns are drawn based on the materials models. The analytical and FE models' results are compared with previously reported test results of the axially loaded SRLAC columns. The proposed analytical and FE models accurately predict the axial behavior and capacities of the new types of SRLAC columns with acceptable agreements for the load-displacement curves. The LWAC strength, steel section ratio, and steel section configuration affect the contact stress between the concrete and steel sections. The average ratios of the ultimate test load to the three analytical models and FEA model loads, Put /Pa1, Put /Pa2, Put /Pa3, and Put /PFE1, for the tested specimens are 0.96, 1.004, 1.016, and 1.019, respectively. Finally, the analytical parametric studies are also studied, in terms of the effects of confinement, LWAC strength, steel section ratio, and the reinforcement ratio on the axial capacity of the SRLAC column. When concrete strength, confinements, area of steel sections, or reinforcement bars ratio increased, the axial capacities increased.

• Membrane and Water Treatment
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• v.14 no.1
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• pp.35-45
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• 2023

Biofilms significantly affect the performance of wastewater treatment processes in which biodegradability of numerous microorganisms are actively involved, and various technologies have been applied to secure microbial biofilms. Understanding changes in biofilm characteristics by regulating expression of signaling molecules is important to control and regulate biofilms in membrane bioreactor, i.e., biofouling. This study investigated effects of addition of acyl-homoserine lactones (AHL) as a controllable factor for the microbial signaling system on biofilm formation of Pseudomonas aeruginosa PAO1 and multiple strains in membrane bioreactor. The addition of three AHL, i.e., C4-, C6-, and C8-HSL, at a concentration of 200 ㎍/L, enhanced the formation of the PAO1 biofilm and the degree of increases in the biofilm formation of PAO1 were 70.2%, 76.6%, and 72.9%, respectively. The improvement of biofilm formation of individual strains by C4-HSL was an average of 68%, and the microbial consortia increased by approximately 52.1% in the presence of 200 ㎍/L C4-HSL. CLSM images showed that more bacterial cells were present on the membrane surface after the AHL application. In the COMSTAT results, biomass and thickness were increased up to 2.2 times (PAO1) and 1.6 times (multi-strains) by C4-HSL. This study clearly showed that biofilm formation was increased by the application of AHL to individual strain groups, including PAO1 and microbial consortia, and significant increases were observed when 50 or 100 ㎍/L AHL was administered. This suggests that AHL application can improve the biofilm formation of microorganisms, which could yield an enhancement in efficiency of biofilm control, such as in various biofilm reactors including membrane bioreactor and bioflocculent systems in water/wastewater treatment processes.

• Research in Plant Disease
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• v.28 no.2
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• pp.98-107
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• 2022

The incidence of Tomato brown rugose fruit virus (ToBRFV) and biological and molecular characterization of the Palestinian isolates of ToBRFV are described in this study. Symptomatic leaf samples obtained from Solanum lycopersicum L. (tomatoes) and Nicotiana tabacum L. (cultivated tobacco) plants were tested for tobamoviruses infection by reverse transcription polymerase chain reaction. Tomato leaf samples collected from Tulkarm and Qalqilia are infected with ToBRFV-PAL with an infection rate of 76% and 72.5%, respectively. Leaf samples collected from Jenin and Nablus were found to be mixed infected with ToBRFV-PAL and Tobacco mosaic virus (TMV) (100%). Sequence analysis of the ToBRFV-PAL genome showed that the net average nucleotide divergence between ToBRFV/F48-PAL strain and the Israeli and Turkish strains was 0.0026398±0.0006638 (±standard error of mean), while it was 0.0033066±0.0007433 between ToBRFV/F42-PAL and these two isolates. In the phylogenetic tree constructed with the complete genomic sequence, all the ToBRFV isolates were clustered together and formed a sister branch with the TMV. The sequenced Palestinian isolates of ToBRFV-PAL shared the highest nucleotide identity with the Israeli ToBRFV isolate suggesting that the virus was introduced to Palestine from Israel. The findings of this study enhance our understanding of the biological and molecular characteristics of ToBRFV which would help in the management of the disease.

• Steel and Composite Structures
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• v.46 no.4
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• pp.451-469
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• 2023

The use of precast hollow-core slabs (PCHCS) in civil construction has been increasing due to the speed of execution and reduction in the weight of flooring systems. However, in the literature there are no studies that present a finite element model (FEM) to predict the load-slip relationship behavior of pushout tests, considering headed stud shear connector and PCHCS placed at the upper flange of the downstand steel profile. Thus, the present paper aims to develop a FEM, which is based on tests to fill this gap. For this task, geometrical non-linear analyses are carried out in the ABAQUS software. The FEM is calibrated by sensitivity analyses, considering different types of analysis, the friction coefficient at the steel-concrete interface, as well as the constitutive model of the headed stud shear connector. Subsequently, a parametric study is performed to assess the influence of the number of connector lines, type of filling and height of the PCHCS. The results are compared with analytical models that predict the headed stud resistance. In total, 158 finite element models are processed. It was concluded that the dynamic implicit analysis (quasi-static) showed better convergence of the equilibrium trajectory when compared to the static analysis, such as arc-length method. The friction coefficient value of 0.5 was indicated to predict the load-slip relationship behavior of all models investigated. The headed stud shear connector rupture was verified for the constitutive model capable of representing the fracture in the stress-strain relationship. Regarding the number of connector lines, there was an average increase of 108% in the resistance of the structure for models with two lines of connectors compared to the use of only one. The type of filling of the hollow core slab that presented the best results was the partial filling. Finally, the greater the height of the PCHCS, the greater the resistance of the headed stud.

• Journal of the Korean Geotechnical Society
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• v.24 no.8
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• pp.149-160
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• 2008

Offshore pile foundations are prone to lateral soil pressures resulting from embankment construction for the reclamation on deepwater soft clay. Since the 1990s, offshore reclamation has actively progressed in Korea, connecting with the development of Songdo newtown, Incheon newport, and Busan newport representatively. Special attention has been given to lateral soil-structure interaction problems related to passively-loaded offshore pile foundations. Based on a plane strain large deformation finite element (LDFE) approach, this paper presents the results of investigation into undrained (short-term) and drained (long-term) behavior of passively-loaded offshore pile foundations. This study examines the effects of major factors, such as soil profile, pile head boundary condition, magnitude of embankment load, and average degree of consolidation. The results allowed quantification of differences in the magnitude of lateral soil pressure acting on the piles between undrained and drained phases.

• Wind and Structures
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• v.37 no.4
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• pp.289-302
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• 2023

Insulating glass units (IGUs) have been widely used in buildings in recent years due to their superior thermal insulation performance. However, because of the panel reciprocating motion and fatigue deterioration of sealants under long-term wind loads, many IGUs have the problem of early failure of watertight properties in real usage. This study aimed to propose a statistical method for wind-induced deflection of IGU panels during the whole life service period, for further precise analysis of the accumulated fatigue damage at the sealed part of the edge bond. By the estimation of the wind occurrence regularity based on wind pressure return period, the events of each wind speed interval during the whole life were obtained for the IGUs at 50m height in Beijing, which are in good agreement with the measured data. Also, the wind-induced deflection analysis method of IGUs based on the formula of airspace coefficient was proposed and verified as an improvement of the original stiffness distribution method with the average relative error compared to the test being about 3% or less. Combining the two methods above, the deformation of the outer and inner panes under wind loads during 30 years was precisely calculated, and the deflection and stress state at selected locations were obtained finally. The results show that the compression displacement at the secondary sealant under the maximum wind pressure is close to 0.3mm (strain 2.5%), and the IGUs are in tens of thousands of times the low amplitude tensile-compression cycle and several times to dozens of times the relatively high amplitude tensile-compression cycle environment. The approach proposed in this paper provides a basis for subsequent studies on the durability of IGUs and the wind-resistant behaviors of curtain wall structures.