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Effective control measures to minimize cost overrun during construction phase of high-rise residential building projects in Chongqing, China

Wang Yue, Ghazali Farid Ezanee Mohamed

Archives of Civil Engineering

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2023

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Vol. 69, nr 3

79--94

EN

Cost overrun during construction is one of the most common problems occur in construction projects around the world, which also includes the area of Chongqing in China. At present, there are few studies related to cost overruns at the construction stage of high-rise residential building projects (HRBPs) in Chongqing. The purpose of this study is to develop effective control measures from the contractor’s perspective to help projects to minimize cost overruns during the construction phase of HRBPs in Chongqing. Firstly, through the literature review and semi-structured interviews, 65 cost overrun-related risk factors in construction projects were identified. All the risk factors have been prioritized through the analytic hierarchy process (AHP) based on their importance to project success. Out of the 65 factors identified, 12 were classified as the critical ones that have a great potential to instigate a cost overrun during construction to take place in the real project. There were four risk factors that have the greatest impact on cost overruns, and their weights were 0.04 or above, including low bid, force majeure, undetailed/inaccurate geological survey data, and increased loan interest rates. Finally, control measures were developed for these four critical cost overrun risk factors (CCORFs). The measures developed provided a guideline to control the risk of cost overruns and clear control key points to help contractors minimize cost overruns on construction projects.

2

Study on glass-forming ability and corrosion performance of Ca-based biomedical materials

Feng Jing, Wang Yue, Liu Dehua, Yhang Yong, Geng Guihong

Acta of Bioengineering and Biomechanics

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2023

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Vol. 25, no. 4

93--101

EN

Stress shielding and the need for secondary surgery are the two major challenges faced by permanent metallic implants, and the emerging Ca-Mg-Zn calcium-based bulk amorphous alloys, with Young’s modulus comparable to that of human bone, good biocompatibility, and in vivo degradation, are highly promising materials for bioimplants. Few studies have been reported on the glass formation ability (GFA) and corrosion degradation behavior of Ca-Mg-Zn amorphous alloys in the human body. In this work, we discuss a study on Ca53+xMg20Zn27–x (x = 0, 2, 4, 6, 8, 10) alloys, focusing on changes in Zn content near eutectic points and their impact on microstructure and biological corrosion behavior. A copper mold spray casting method has been developed to prepare amorphous bar alloys and amorphous crystalline composite bar alloys with a diameter of 3 mm, which has been verified by X-ray diffraction, electrochemical treatment, and immersion tests. The experimental results demonstrated that the Ca3Zn and CaZn2 phases were precipitated in the 3 mm bar material Ca53+xMg20Zn27–x (x = 0, 2, 4), and Ca53+xMg20Zn27–x (x = 6, 8, 10) was completely amorphous. The Ca63Mg20Zn17 alloy showed the best glass-forming ability, while the Ca59Mg20Zn21 alloy exhibited superior corrosion resistance. Cytotoxicity experiments showed that Ca-Mg-Zn alloys have good biocompatibility and can be used as biomedical materials.

3

Significance of reagents addition sequence on iron anionic reverse flotation and their adsorption characteristics using QCM-D

Hou Ying, Sobhy Ahmed, Wang Yue

Physicochemical Problems of Mineral Processing

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2021

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Vol. 57, iss. 1

284--293

EN

To explore the influence of reagents addition sequence of the pH regulator and the starch depressant on the anionic reverse flotation of iron oxide, flotation conditional experiments were performed on mixed low-intensity and high-gradient magnetic concentrates which is the flotation feed acquired from the iron processing plant. Besides, quartz crystal micro-balance with dissipative (QCM-D) was conducted to detect the adsorption phenomena of the flotation reagent on iron oxide sensors at different addition orders. The outcomes showed that the flotation performance using the pH regulator prior to the depressant was the best. For example, at 1.6 kg/Mg starch dosage, the recovery and separation efficiencies were improved by 18.3% and 21.2%, respectively, with keeping the concentrate Fe grade as high as 69.5%. Also, QCM-D frequency shifted by -41 Hz from 17 Hz to -24 Hz with increased dissipation from -2.6 x 10-6 to 8.2 x 10-6, indicating an increase in the mass of slightly-rigid starch adsorption layer on the surface of iron oxide under a strong alkaline condition with adsorption density of about 0.46 mg/cm2. On the other hand, under weak alkaline conditions, starch was adsorbed, and then the starch was desorbed upon the addition of the strong alkaline solution. Whereas, adding the pH modifier to create a strong alkaline condition enhanced the starch adsorption significantly with coordination and hydrogen bonds, and prevented the following adsorption of the anionic collector for more efficient reverse flotation of iron oxide minerals.

4

Research on chaotic features of a flow field over a plunging airfoil based on dynamic mode decomposition

Qi Yuhang, Yang Wenqing, Wang Yue, Song Bifeng

Journal of Theoretical and Applied Mechanics

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2021

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Vol. 59 nr 2

293--305

EN

Periodic motion of a plunging airfoil causes continuous changes in the surrounding flow field. The time-dependent thrust coefficient depends entirely on unsteady characteristics of the flow field. On the contrary, the time-dependent thrust coefficient may also reflect the unsteady characteristics of the corresponding flow field. With the fast Fourier transform (FFT) and dynamic mode decomposition (DMD), unsteady aerodynamic forces can be correlated with the flow field characteristics in the frequency domain. In the present paper, DMD is performed to analyze the unsteady characteristics of the flow field around a plunging NACA0012 airfoil at the Reynolds number of 20 000.

5

Underground mine gas explosion accidents and prevention techniques – an overview

Song Wanting, Cheng Jianwei, Wang Wenhe, Qin Yi, Wang Zui, Borowski Marek, Wang Yue, Tukkaraja Purushotham

Archives of Mining Sciences

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2021

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Vol. 66, no. 2

297--312

EN

Mine gas explosions present a serious safety threat in the worldwide coal mining industry. It has been considered the No.1 killer for underground coal mining workers. The formation of an explosive atmosphere involves various factors. Due to complicated stratified geology and the coal production process, geological conditions and coal production process reasons and particular working sections underground present a high risk of an explosion that would most likely cause casualties and property loss. In this study, the basic conditions, propagation law and hazards analysis of gas explosions are reviewed, followed by a review of the typical locations where an explosion would occur. Finally, current technologies used in the mining industry for preventing gas explosions and suppressing the associated dangers were studied. Preventive gas explosion technologies mainly include gas drainage, gas accumulation prevention and gas and fire source monitoring technologies. The technologies often used to control or mitigate gas explosion hazards are usually divided into active and passive, and the advantages and disadvantages of each method are discussed and compared. This paper aims to summarise the latest technologies for controlling and suppressing gas explosion and guides mining engineers to design risk mitigation strategies.

6

Joint Formation and Mechanical Properties of 2060 Aluminum Alloy Refill Friction Stir Spot Welding Joint

Shang Zhen, Zuo Yingying, Ji Shude, Wang Yue, Chai Peng

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 1

153--161

EN

Refill friction stir spot welding (RFSSW) was used to weld the 2060 aluminum alloy with 2 mm thickness. Joint formation, defect characteristics and mechanical properties were investigated. Results show that stir zone (SZ) is clarified into dynamic recrystallization zone (DRZ) and heat extruded zone (HEZ) due to different microstructural features. The size of void near the hook tip decreases with the increase of the plunge depth. Different hook morphologies are obtained under different plunge depths. The tensile-shear load of joint with the void defect initially decreases and then increases with increasing plunge depth. The mean loads of joints under different plunge depths are in the range of 5.1-5.8 kN. The void separates the hook from lap interface, so the cracks initiating from the hook propagate along the sleeve retreating path. The hook has a larger influence on the tensile-shear load of joint than void. All the tensile specimens present a shear-plug fracture mode.

7

Characteristics and Tensile-Shear Properties of Refill FSSW Joint Under Different Plunge Depths in 2060 Aluminum Alloy

Wang Yue, Chai Peng

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 2

451--460

EN

Refill friction stir spot welding (refill FSSW) was used to weld 3.2-mm-thick 2060 aluminum alloy. Joint formation, defect characteristics and tensile-shear property were analyzed. Results show that keyhole can be completely eliminated under different plunge depths. However, defects such as void, unconnected welding, hook can be observed under the plunge depths of 3.4-4 mm.The size of the overall void initially increased and then decreased with the increase of the plunge depth, while the void was the smallest under the plunge depth of 3.4 mm. The unconnected defect at the lap interface gradually shrank a welding line from obvious crack. Different hook morphologies were observed under different plunge depths. The tensile-shear load of joint increased with the increase of the plunge depth and was up to the largest under the plunge depth of 4 mm. All the tensile-shear specimens fractured along the lap interface. Compared with the void, the unconnected defect had a greater influence on the tensile-shear property.

8

Research on mine seal stability under explosion load and ground pressure in underground coal mines

Cheng Jianwei, Song Wanting, Jing Yi, Zhang Xixi, Korzec Marek, Borowski Marek, Wang Yue

Archives of Mining Sciences

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2020

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Vol. 65, no. 1

71--87

EN

The mine seals in coal mines with a good impact resistance and air tightness are mainly used to isolate abandoned mining areas from active workings. For one thing, it can prevent the leakage of harmful gases, such as toxic gas from abandoned areas. For another, once an underground mine explosion happens, it can effectively block the spread of the explosion between the abandoned mining areas and the active workings. Hence, it is of great significance to study the explosion-proof performance and mechanical properties of the mine seals. First of all, the effect of slotting on the stability of the seals in coal mines under explosion load was explored in this study. By numerical simulations, the mechanical response characteristics of the seals with or without cutting a slot under the explosion load were compared in detail. The results show that slotting improved the stress concentration at the contact surface of surrounding rock by transferring partial impact received by mine seals to the surrounding rocks, thus, to achieve the effect of buffering explosion impact. Besides, such effect will be enhanced with increasing cutting depth into rock, and will stabilize when the depth is 20 cm. On this basis, the mechanical properties and damage of the seals constructed by different materials (standard brick and #C40 concrete) under the explosion load were compared. It was found that once a slot was set, the maximum deformation of the concrete seal was reduced, while the maximum deformation of the brick seal increased. Since the non-deformability of the concrete seal is obviously stronger than that of the brick seal, with the impact resistance stronger than that of the brick seal, the concrete seal is more suitable for slotting. Moreover, the damage of the seals in underground coal mines under the strata ground pressure was studied; the results of which show that the damage state under the ground pressure can be divided into 3 levels, i.e. no damage, minor damage and rapid development of damage. Meanwhile, it was found that the prestressed structure fordem by the ground pressure at the level of no damage can enhance the protective effect of the seals in coal mines. However, when the ground pressure was further developed, the seal itself was destroyed and the protective effect was lost. In addition, the influence of roof to floor moving convergence, a deformation parameter of the roadway, on the seals was also investigated. The results show that the ground pressure and roof-to-floor convergence act on the seals in coal mines in the same way, thus roof to floor moving convergence can replace the ground pressure to analyze other related mechanical properties of the seals in coal mines in the future researches.

9

High Cycle Fatigue Performance of Hollow-Extruded 6005A-T6 Aluminum Alloy Characterized by a Layered Microstructure

Ma Zhongwei, Ma Lin, Xu Bo, Dan Chuchen, He Zhaokun, Wang Yue

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 1

285--292

EN

Sound joint of hollow-extruded 6005A-T6 aluminum alloy was achieved by friction stir welding and its high cycle fatigue performance was mainly investigated. As a result, the joint fatigue limit reaches 128.1 MPa which is 55% of the joint tensile strength. The fatigue fracture mainly occurs at the boundary between the stir zone and thermo-mechanically affected zone due to the large difference in the grain size. This difference is caused by the layered microstructure of the base material. The shell pattern with parallel arcs is the typical morphology in the fracture surface and the distance between arcs is increased with the increase of stress level. The specimen with the fracture located in the stir zone possesses a relatively low fatigue life.