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CONTENTS
Volume 11, Number 5, November 2021
 


Abstract
To develop a reliable fibrous device, a strong bond between conducting materials and fibers must be ensured. While the external surface of the film is relatively flat, making it easy to deposit the electrode materials uniformly, the walls of the polymer fibers inside the porous film pose a greater challenge for ensuring a uniform coating and robust bonding with electrode material. Herein, a microfibril-based porous film was prepared by electrospinning polybutadiene-based urethane (PBU), a newly synthesized self-healing polymer, and Ti3C2-based MXene nanosheets were coated thereon to fabricate a pressure sensor whose resistance decreases with pressure. The PBU microfibrils were crosslinked under mild conditions via Diels-Alder (DA) reaction by exploiting low activation energy of the PBU. An exceptionally robust bonding between the PBU and MXene was enabled by subjecting the PBU to a retro-DA and subsequent DA reactions. The temporary increase in surface fluidity of the PBU leaded to a conformal contact between the MXene and fibers without collapse of fibrous structure, resulting in an ultra-robust bond between them. A stretchable and self-healable pressure sensor was implemented by removing unnecessary MXenes by applying ultrasonic energy to the thus-fabricated sample. The fabricated sensor showed a pressure sensitivity of around 27.9 /kPa for a wide range of pressure which is the highest level among the reported stretchable self-healing pressure sensors, while maintaining its performance even after 1000 cycles of stretching and pressing. Further, sensors attached around the carotid artery could be used to precisely detect P-, T-, and D-waves arising from blood pressure.

Key Words
MXene; polybutadiene; pressure sensor; Ti3C2Tx; urethane

Address
Yoo Bin Shin, Jung-Min Oh and Jong-Woong Kim: School of Advanced Materials Engineering, Jeonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju 54896, Republic of Korea

Youngmin Kim: Display Research Center, Korea Electronics Technology Institute, 68 Yatap-dong, Bundang-gu, Seongnam 13509, Republic of Korea

Chang Goo Kang: Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, 29 Geumgu-gil, Jeongeup-Si, Jeollabuk-Do 56212, Republic of Korea


Abstract
This research is devoted to explore the nonlinear vibration characteristics of smart nanoshells under multi-phyisical magneto-electric fields. The nano-scale shell has been treated as a thin shell with prescribed curvature which is modeled by nonlocal elasticity theory. The material composition of the smart nanoshell has been considered as a two phase composite for which the effective properties depend on the percentage of each phase. The discretization of governing equations has been carried out based on differential quadrature method (DQM). It has been exhibited that nonlinear vibration properties of curved nanoshells rely on nonlocality coefficient, piezoelectric phase percentage, radius of curvature, and electrical/magnetic potential.

Key Words
DQM; Magneto-electro-elastic material; nanoshell; nonlinear vibrations; nonlocal theory

Address
Jing He: Institute for Advanced Studies in Humanities and Social Sciences, Beihang University, Beijing 100000, Beijing, China

Yu Sun: CIGIS (China) Limited, Beijing 100007, Beijing, China

Abstract
The proper management of reservoir sedimentation is of critical importance for the sustainable development of surface water resources. Dams' reservoirs are losing their ability storage due to sedimentation processes worldwide. These losses vary from one reservoir to another depending on the characteristics of the watershed and water streams. Therefore, the performance of reservoirs is incredibly vulnerable. The area surrounding Red Sea State is under arid and semi-arid condition, and immensely suffering from a shortage of safe and reliable drinking water supplies. Wadi Arbaat is the primary source of water supply in Port Sudan city. Valleys mostly surround the Red Sea State and Wadi Arbaat suffer from a severe decline with the steep slope of 6-10 m/km. Therefore, the Wadi carries large quantities of sediments, which deposit in dams' reservoirs during the flood periods. The siltation strongly influences these dams and their reservoirs suffer from serious problems represented by increasing silting level and shortage in storage capacities. Consequently, this study aims to investigate the current situation and problems of the three existing dams and make a proper decision with a comprehensive and specific vision in the future. The main problems caused by reservoir sedimentation in the Red Sea Mountains are described as a reduction in the storage capacities, and entry of sediments into control structures such as sluice gates. The problems are further exacerbated as there is no guidance on the decision supports tool that is needed to underpin silting in the flood period and water resources management in these steep slope areas. The sedimentation processes, problems and changes of dam operation are discussed in this paper.

Key Words
sea port corporation dam; sedimentation; siphon system; sluice gate; upper gate dam; Wadi Arbaat

Address
Abubakr Taha Bakheit Taha: Department of Civil Engineering, College of Engineering, Prince Sattam bin Abdulaziz University, Al-kharj 16273, Saudi Arabia/ Department of Civil Engineering, Faculty of Engineering, Red Sea University, Port Sudan, Sudan

Ali Aldrees: Department of Civil Engineering, College of Engineering, Prince Sattam bin Abdulaziz University, Al-kharj 16273, Saudi Arabia


Abstract
The provided paper considers the vibrations of viscoelastic sandwich disk reinforced by graphene nano-platelets (GPLs) filled viscoelastic concrete (GPLRVC) honeycomb core and face sheets via deep learning. The optimum values of the parameters involved in the fully connected neural network are determined through the momentum-based optimizer. The strength of the method applied in this study comes from the high accuracy besides lower epochs needed to train the multi-layered network. The honeycomb core would be manufactured by aluminum according to its great stiffness and lightweight. The mixture rule and modified Halpin–Tsai model have been involved in creating an efficient concrete material constant. By applying energy methods, the system's governing equations have been extracted and solved through Generalize Differential Quadrature (GDQ) technique. In the given research, Kelvin-Voigt viscoelasticity has been applied to model viscoelastic properties. The time-dependent deflection would be solved applying the fourth-order Runge-Kutta computational approach. Then, a parametric study has been conducted to analyze the influences of the external and internal radius ratio, thickness to length ratio of the concrete, hexagonal core angle, the GPLs' weight fraction, and the honeycomb core's thickness to internal radius ratio on the vibrations of the viscoelastic sandwich disk considering face sheet of FG-GPLRVC and honeycomb core.

Key Words
deep learning; GDQ; honeycomb core; vibrations; viscoelastic sandwich disk

Address
Xusheng Wang: Xi'an University of Technology, Xi'an 710048, Shaanxi, China

Liang Zhang: School of Aerospace Engineering, Tsinghua University, Beijing 100084, China

Abstract
Natural and anthropogenic activities lead to the generation of polycyclic aromatic hydrocarbons (PAHs), persistent contaminants that adversely affect the environment and public health. However, highly sensitive, fast, and portable techniques for the detection of PAHs remain a technological challenge. The rapid analysis of urinary levels of 1-hydroxypyrene (1-HP) would enable PAH carcinogens to be measured using biomonitoring techniques. Here, we demonstrate biocompatible, easy-to-use, and portable sensors based on novel π-conjugated metal-organic frameworks (MOFs) for the detection of 1-HP. These sensors were developed by incorporating nonionic conjugated polythiophenes with a PLQY as high as 65% into lanthanide-MOFs (CP1-Eu-MOF and CP2-Eu-MOF) using an in-situ synthesis strategy. The emission of the sensors can be effectively quenched by 1-HP via hydrophobic, π–π stacking, and hydrogen bonding interactions. Significantly, the unique structure of CP2-Eu-MOF sensor displays superior performance with enhanced sensitivity (LOD ~1.02 pM) that is 1.63 times higher than that of CP1-Eu-MOF (LOD ~1.66 pM). More importantly, we successfully demonstrated the possibility of employing wax-printed paper in combination with a fast and cost-effective smartphone for rapid 1-HP detection. Moreover, portable sensory films were fabricated by incorporating CP2-Eu-MOF into a poly(vinylidene difluoride) (PVDF) matrix to produce CP2-Eu-MOF/PVDF films for the visual detection of 1-HP levels as low as 25 pM. Finally, the feasibility of successfully analyzing the levels of 1-HP in urine was verified by testing real urine samples with satisfactory recoveries of 94.1-103.5%. This method provides new pathways for the biomonitoring of polyaromatic environmental pollutants.

Key Words
conjugated polymers; fluorescent film; metal-organic framework nanostructures; PAHs sensor; Paper-smartphone devices; polycyclic aromatic hydrocarbons

Address
Salah M. Tawfik: Department of Petrochemicals, Egyptian Petroleum Research Institute (EPRI) Nasr City, Cairo 11727, Egypt

Yong-Ill Lee: Department of Materials Convergence and System Engineering, Changwon National University, Changwon 51140, Republic of Korea

Abstract
Mathematical modelling of quadrilateral concrete foundation is a novel topic in the literature. In this paper, dynamic response of quadrilateral concrete foundation resting on soil medium subjected to blast load is presented for the first time. The concrete foundation is covered by nano-fiber reinforced polymer (NFRP) layers at the top and bottom surfaces for improving the stiffness. The NFRP are containing carbon nano-fibers (CNF) and its equivalent material characteristics are calculated by Mori-Tanaka model incorporating the agglomeration effects. On the basis of Sinusoidal shear deformation theory (SSDT) and Hamilton's principle, the motion final equations are obtained assuming structural damping utilizing Kelvin-Voigt model. The dynamic deflection of the quadrilateral concrete foundation is discussed based on transformed weighing (TW) coefficients-differential quadrature method (DQM) in conjunction with Newmark method. The influences of different parameters of soil foundation, blast load, volume fraction and agglomeration of CNFs, structural damping, NFRP layer, geometrical parameters and side angles of the quadrilateral concrete foundation are shown on the dynamic displacement. The results are compared with other published works in the literature for presenting the accuracy of the applied model and method. The outcomes show that the dynamic defection will be reduced with enhancing the CNFs volume fraction. In addition, with with increasing the side angle of quadrilateral plate, the dynamic deflection is increased.

Key Words
blast load; dynamic response; NFRP layer; quadrilateral concrete foundation; TW-DQM

Address
Mahdi Mahjoobi, Mahmood Rabani Bidgoli and Hamid Mazaheri: Department of Civil Engineering, Khomein Branch, Islamic Azad University, Khomein, Iran

Abstract
In the present research, the dynamic characteristics of the nanoscale tubes and pipes with nonuniform cross-sections are examined. The aforementioned nanostructures are made by imperfect axially functionally graded materials (AFGM) that compose ceramic and metal phases along the tube length direction, involving the porous voids. To this purpose, the Hamilton principle is implemented to obtaining the governing equation and related boundary conditions using classical beam theory coupled to the nonlinear Von-Kármán theory. In order to apply the size impact, the nonlocal strain gradient theory is considered that both hardening and softening parameters are involved. Also, iteration techniques, including the generalized differential quadrature method (GDQM), are used to solve linear and nonlinear derived partial differential equations (PDE). Finally, the obtained results are explained in detail to investigate the impact of nonlinear amplitude, nonlocal and strain gradient parameter, porosity parameter, etc., for both clamped and simply-supported types of boundary conditions, which are helpful to design the nanoelectromechanical structures (NEMS).

Key Words
axially functionally graded tube; gradient strain theory; imperfect; nonlinear vibration; non-uniform; porous; tapered tube; truncated conical tube

Address
Jian Zhao: School of Information Science and Technology, Northwest University, Xian 710127, Shaanxi, China

Zhuo Yu: School of Computer Science and Engineering, North Minzu University, Yinchuan 750021, Ningxia, China

Abstract
The merits of self-consolidating concrete (SCC) such as high deformability, excellent resistance to segregation, and usability without applying vibration is highly common. To gain an environment-friendly approach or improving SCC properties, cement in SCC can be partially replaced with other materials. However, identifying the most effective parameters on the Superplasticizer demand (SP demand) of SSC would not be easy after the replacement. The main aim of this study is to identify the most influencing approaches on SP demand prediction. Hence, five different approaches in SP demand prediction, including Jring test, V funnel test, Ubox test, 3-min slump value, and 50-min slump value have been considered. Then, different models of an artificial intelligence approach are developed and the most influential one in an accurate SP demand prediction was determined. In comparison with other methods, it was indicated that in estimating the SP demand, V-funnel can be a better technique because of producing the lowest RMSE.

Key Words
ANFIS; prediction; self consolidating concrete; superplasticizer demand

Address
Arian Heirati, Shahriar Tavousi Tafreshi and Manuchehr Behruyan: Department of Civil Engineering, Faculty of Civil and Earth Resources Engineering, Central Tehran Branch,
Islamic Azad University, Tehran, Iran

Yousef Zandi: Department of Civil Engineering,Tabriz Branch, Islamic Azad University, Tabriz, Iran


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