bluuebunny/crossref_metadata_2025 huggingface dataset:
Facile fabrication of sodium carboxymethyl cellulose/reduced graphene oxide composite hydrogel and its application for Pb(II) removal
Authors: Zhang Yakun , Huang Runmin , Yu Jingang , Jiang Xinyu
Published: December 2020

The sodium carboxymethyl cellulose/reduced graphene oxide (rGO‐CMC) composite hydrogel was fabricated via environmental friendly one‐step hydrothermal reduction method. The morphology, pore structure and surface properties of the as‐prepared sample were characterized by scanning electron microscopy, Brunauer–Emmett–Teller surface area measurement and zeta potential analyser, respectively. To investigate the adsorption behaviour of rGO‐CMC for Pb(II), effects of contact time, temperature, initial concentration and pH were studied in detail. The rGO‐CMC composite before and after adsorption of Pb(II) was analysed by Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy to further explore adsorption mechanism. Compared with rGO, the adsorption capacities of rGO‐CMC‐3 composite for heavy metals including Pb(II), Cu(II), Ni(II), Mn(II), Co(II) were increased to 156.85, 35.70, 21.40, 20.85 and 15.80 mg g−1, respectively. In addition, the rGO‐CMC composite formed a complete aerogel after freeze‐drying, which confirms its great potential as an easily separable adsorbent to remove heavy metals in aqueous solutions.
A membrane raindrop generator and its application as a self‐powered pH sensor
Authors: Chen Chunxu , Xie Guangzhong , Yao Mingliang , Pan Hong , Su Yuanjie
Published: December 2020

Raindrop contains a large amount of renewable mechanical energy. Acid rain has adverse impact on the plants, aquatic animals and infrastructure. In this work, a triboelectric raindrop generator (TRG) was developed to harvest raindrop energy on a large scale. The TRG consists of electrification layer, electrodes and substrate. At the rainfall rate of 53 mL/s, the open‐circuit voltage and short‐circuit currents of the device reaches 27 V and 4.6 μA, respectively, which can simultaneously drive 60 LED light‐emitting diodes or charge a 5 μF capacitor. In addition, relied on the electrostatic shielding effect of the solid–liquid interface, the pH value of ambient solution drops can be spontaneously detected to reveal the potential in real‐time monitoring of environmental quality. By integrating with a signal processing circuit, a self‐powered acid rain alert system was formed for real‐time monitoring the acidity of the falling raindrops. This work proposes a feasible and innovative approach for active environmental monitoring.
Preparation of (CaY)F2:Tm3+,Yb3+ deposited porous TiO2 matrix with highly near‐infrared light photocatalytic activity
Authors: Zhao Xiaoyan , Kang An , Zhou Linxi , Zhou Huan , Qi Qianyu , Wang Hongshui , Xu Defeng , Liang Chunyong
Published: December 2020

Porous titanium dioxide (TiO2) matrix deposited with upconversion luminescence agent (CaY)F2:Tm3+,Yb3+ was sol–gel prepared using polymethyl methacrylate (PMMA) microspheres as sacrificing template and tetrabutyl titanate as TiO2 precursors. The resulted photocatalysts were subsequently characterized by X‐ray diffraction, scanning microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy, photoluminescence spectra (PL) etc. The photocatalytic activity and biocompatibility of TiO2/(CaY)F2:Tm3+,Yb3+ were evaluated by photocatalytic degradation of methyl orange (MO) and fibroblast cytotoxicity analysis, respectively. The results revealed that (CaY)F2:Tm3+,Yb3+ nanoparticles were well dispersed onto the pore walls of porous TiO2 matrix to generate a biocompatible composite. In addition, TiO2/(CaY)F2:Tm3+,Yb3+ was found to show excellent photocatalytic activity in both UV and infrared spectra, highlighted with the fact that (CaY)F2:Tm3+,Yb3+ nanocrystals can be excited to release UV light under near infrared light source, which can in consequence active TiO2. When the mass ratio of TiO2 to (CaY)F2:Tm3+,Yb3+ nanocrystals is 2:1, the best photocatalytic efficiency can be achieved with most of UV light released by (CaY)F2:Tm3+,Yb3+ absorbed by TiO2 to induce photo‐oxidation. The outstanding photocatalytic performance along with its biocompatibility, makes TiO2/(CaY)F2:Tm3+,Yb3+ a promising candidate in environmental and biomedical applications.
Nano‐MgO prepared via templating on biodegradable filter paper
Authors: Chen Hukui , Mu Xiaxia , Jiang Yu , Huang Jie , Jiang Hongli , He Zhijun
Published: December 2020

Nano‐MgO was successfully fabricated by a facile, inexpensive, and environment‐friendly synthetic method using filter paper as a bio‐template. The influence of the concentration of raw material Mg(CH3COO)2·4H2O on the textural properties of nano‐MgO was investigated, and the as‐prepared nano‐MgO was characterized by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X‐ray analysis, thermo gravimetric analysis, Fourier transform infrared spectroscopy. The results of the experiment show the synthetic MgO fibres are composed of 20 nm tiny particles with a surface area of 68.28 m2/g and a pore width of 13 nm. When the concentration of Mg(CH3COO)2·4H2O solution was 0.03 mol/L, the product MgO copied the micro‐morphology of the filter paper. In addition, the photocatalytic activity of the prepared sample was investigated, and the results showed that the nano‐MgO prepared by this method has a higher catalytic activity than that prepared without a template.
Fabrication of durable superamphiphobic PA‐66 fabrics with wear‐resistance performance
Authors: Wang Xuman , Zhang Caining
Published: December 2020

Superamphiphobic surfaces have broad application prospects. In order to obtain superamphiphobic surfaces with better wear‐resistance, a fluorine‐containing acrylate copolymer coating and montmorillonite (MMT) particles were coated on polyamide 66 (PA‐66) fabrics. Scanning electron microscopy and X‐ray photoelectron spectroscope were applied to investigate the morphology and chemical composition of PA‐66 fabrics. The prepared fabrics showed superhydrophobicity and superoleophobicity. Meanwhile, the fabrics possessed excellent mechanical durability and self‐cleaning performance. The as‐prepared fabrics could be applied in the super‐antiwetting and other areas.
A new trench gate field stop insulated gate bipolar transistor (IGBT) with a significant reduction in Miller capacitance
Authors: Liu Yan‐juan , Zhao Liang , Wang Lening , Wang Yupeng
Published: December 2020

In this paper, a new trench‐gate field‐stop insulated gate bipolar transistor (IGBT) structure having improved performances is proposed, investigated and compared with the properties of the conventional trench‐gate field‐stop IGBT. An npn structure is introduced to the gate trench in order to reduce the Miller capacitance and gate‐collector charge through the introduction of the two diode capacitances in series. The simulation results demonstrate that the proposed structure exhibits a significant improvement in the following two aspects, without degrading the other performances. The first is the reduction of the Miller capacitance by 92.0% and 48.3% at Vce = 0 V and Vce = 20 V, respectively and the second is the reduction in gate‐collector charge by 66.7%.
Facile synthesis of multifunctional m‐SiO2@ZnO nanocomposite employing biocompatible polymers for potential theranostic applications
Authors: Hassan Syed Mujtaba ul , Anis Tanzeela , Khurshid Ahmat , Shahzad Faisal , Iqbal Zafar , Ali Zhaid , Shah Attaullah , Ahmad Jamil , Mehmood Mazhar
Published: December 2020

A multifunctional nanocomposite based on ZnO and mesoporous SiO2 is presented for potential biomedical applications. A simple modified hydrothermal method is used to synthesize PEG‐coated ZnO whereas mesoporous SiO2 was obtained through sol–gel method. Nanocomposite is obtained by stirring the two products in deionized water under slightly acidic conditions. Biocompatibility is introduced through surface coating of ZnO with polyethylene glycol and of SiO2 with chitosan. ZnO nanoparticles with particle size of 50–80 nm and mesoporous SiO2 with particle size of 600 nm are obtained in the final composite. The nanocomposite has island‐type coat of ZnO nanoparticles on submicron mesoporous SiO2 with photoluminescent properties and drug‐carrying ability.
Morphological investigation of carbon nanotube reinforced polyurethane foam to analyse its acoustical and non‐acoustical properties
Authors: Basirjafari Sedigheh
Published: December 2020

Acoustic damping analysis for open‐cell polyurethane/carbon nanotube nanocomposite foam is presented. Carboxylic functionalized CNT is used as an energy decaying filler in the PU matrix. The acoustical behaviour and non‐acoustical properties of polyurethane/carbon nanotube nanocomposite foam are explained through its cell morphological properties. For this aim, cellular morphologies such as strut length, strut thickness, cell size, pore diameter, and reticulation rate of the samples are determined from field emission scanning electron microscopy images by using 'Image J' software. Therefore, the effects of adding the carboxylated CNTs with different loading fractions to the PU matrix on its morphological properties and thus on its sound absorption and non‐acoustical physical parameters such as thermal characteristic length and viscous characteristic length are determined and discussed from field emission scanning electron microscopy images. Thermal characteristic length and viscous characteristic lengths are calculated through Johnson–Champoux–Allard porous model from the morphological properties, which has been directly measured on the field emission scanning electron microscopy images. Large differences were observed in the cellular morphologies of the polyurethane/carbon nanotube nanocomposite foams compared with that of the pure PU foam. Results show that the prediction of the acoustical behaviour of the polyurethane/carbon nanotube nanocomposite foams based on their cellular morphologies is in good agreement with the direct measurement of their acoustical properties.
A novel single‐phase five‐level hybrid rectifier using two active switches
Authors: Ma Hui , Han Xiao , Wu Peng , Yin Hongpeng
Published: December 2020

A novel single‐phase five‐level rectifier based on two active switches is presented. The proposed novel circuit topology, with two active switches and a split dc‐link, can produce a distinct five‐level voltage with a reduced number of active switches. This circuit operates in unitary power factor mode with imposing a sinusoidal grid‐side current with low total harmonic distortion (THD) and controlled dc‐link voltage, which can be used as a low‐cost active rectifier to improve the efficiency of ac‐to‐dc rectification. This paper describes the circuit topology, the principle of operation, the feature of the circuit topology and the double‐loop control strategy in detail. The operation efficiency of the proposed topology is analysed in detail to show its benefits compared to the traditional five‐level PFC typologies. An experimental prototype with 220 V AC input, 400 V output, 500 W rated power, and 97.3% output efficiency is built to validate the proposed rectifier under real conditions of operation. The simulation and experimental results show the correctness and good performance (unitary power factor operation, sinusoidal current with low THD and dc‐link voltage regulation) of the proposed single‐phase five‐level rectifier.
First self‐resonant frequency of power inductors based on approximated corrected stray capacitances
Authors: Lope Ignacio , Carretero Claudio , Acero Jesus
Published: December 2020

Inductive devices are extensively employed in power electronic systems due to their magnetic energy storage and power transfer capabilities. The current trend is towards increasing the frequency of operation in order to reduce the size of the magnetic components, but the main drawback is that the parasitic capacitance effect can become significant, and degrade the performance of the system. This work analyses the influence of this stray capacitance, and considers how to improve the performance of the device. In general, the impact of the stray capacitance on a magnetic component can be reduced by two methods: reducing the parasitic capacitance between turns of the winding or, alternatively, modifying the arrangement of the connection between turns. To evaluate the last option, an approximated expression of the first self‐resonant frequency of the magnetic device is proposed. This gives a rapid assessment of the performance of different devices maintaining the overall equivalent inductance. The proposed expression accounts for the influence of the connection between turns in the bandwidth of the component. Finally, some numerical results are verified with planar coils manufactured on two‐layer printed circuit boards.
Single‐phase wind‐BES microgrid with seamless transition capability
Authors: Gupta Tripurari Nath , Singh Bhim
Published: December 2020

A new control strategy for a wind‐BES (battery energy storage) microgrid is presented, which controls the power transfer and the mode of operation seamlessly from an islanded mode (IM) to the grid connected mode (GCM) and vice versa. In GCM, the DC link voltage regulation, the load reactive power compensation and harmonics current mitigation are performed by the load side voltage source converter (LVSC) using a double sinusoidal signal integrator (DSSI) based control algorithm. The maximum power from the wind generation is extracted by operating the generator side voltage source converter (GSC). At the grid fault or grid disturbances, this microgrid operates in IM and LVSC is controlled in the voltage control mode. A synchronizing controller is utilized to control the operation of synchronization. The grid current and point of common coupling (PCC) voltage distortions are kept within the limit as per the IEEE‐519‐2014 and the IEEE‐1547 standards. The system operation is demonstrated through test results at several conditions such as, changing wind speeds, varying loads and seamless transition.
High performance current control of single‐phase grid‐connected converter with harmonic mitigation, power extraction and frequency adaptation capabilities
Authors: Somkun Sakda
Published: December 2020

Grid‐connected converters in distributed generation systems are required to operate under highly distorted voltage with a wide frequency range, and to provide active/reactive power information for ancillary services and power control. This paper presents multiple unbalanced synchronous reference frame control for regulating and mitigating the grid current distortion of a voltage source converter caused by grid voltage distortion and converter deadtime. The proposed control technique has intrinsic power extraction and frequency adaptation capabilities. The multiple unbalanced synchronous reference frame control is compared with the proportional multi‐resonant control. A new controller which combines the unbalanced synchronous reference frame control for regulation of the fundamental component current and the multi‐resonant control for harmonic compensation is presented. The proposed control techniques were verified with a 1.5‐kVA LCL‐filtered grid connected inverter. The multiple unbalanced synchronous reference frame control with odd harmonic orders 3rd to 13th exhibited excellent harmonic rejection with a total harmonic distortion (THD) less than 0.60% under a highly distorted voltage. The proposed combined control technique provided slightly inferior performance with the grid current THD less than 0.65%. The combined control scheme retains functionalities as the multiple unbalanced synchronous reference frame control with a significant reduction of computational effort.
Analysis and improvement of fourth‐order generalised integrator based phase‐locked loop
Authors: Li Jinbo , Wang Qin , Xiao Lan , Lu Yichen , Wu Qunfang
Published: December 2020

The fourth‐order generalised integrator is very suitable for single‐phase phase‐locked loop because it can provide orthogonal signal conveniently and block harmonic voltages effectively. In the conventional fourth‐order generalised integrator based phase‐locked loop, the resonance frequency of fourth‐order generalised integrator needs to be adjusted according to the grid frequency. To improve the phase‐locked loop performance, a non‐adaptive fourth‐order generalised integrator is suggested for single‐phase system, and this paper presents a correction method. According to the estimated grid frequency, the amplitude imbalance and phase error caused by non‐adaptive fourth‐order generalised integrator can be calculated, and two adaptive units are added to deal with the problems. Moreover, the small‐signal model of the proposed phase‐locked loop is carried out, and the control parameters are tuned. Compared to conventional fourth‐order generalised integrator based phase‐locked loop, the proposed phase‐locked loop shows a better performance, which is verified through simulation and experimental results.
Compensated active disturbance rejection control for voltage regulation of a DC–DC boost converter
Authors: Yuan Hai‐Bo , Kim Young‐Bae
Published: December 2020

This study analysed the output voltage control and performance of a DC–DC boost converter. The focus is on the continuous conduction mode of a DC–DC boost converter and each component is designed and selected for circuit assembly. A small‐signal AC model based on a pulse‐width modulated DC–DC boost converter is constructed, and four control algorithms, namely the ‐integral control, deadbeat control, linear quadratic regulator control, conventional active disturbance rejection control and new compensated active disturbance rejection control are put forward to regulate the converter output voltage when faced with immeasurable input and load disturbance. The paper emphasises the objective steering the output voltage to its reference with fast response, little overshoot, and ripples. The equivalent input disturbance observer is utilised to compensate for the tracking error existing in the observed system. Scenarios for validation are investigated in MATLAB/Simulink environment and LabVIEW‐based field‐programmable gate‐array experimental rig. The results indicate that the proposed method has the best rejection effect on the above‐mentioned system disturbances with stability improvement.
Generalised Tapped Inductor Switcher (GTIS) approach to modelling of high‐order converters
Authors: Yao Jia , Ping Jiang , Zheng Kaisheng , Abramovitz Alexander
Published: December 2020

A generalized modelling technique suited to integrated and high order Pulse‐Width‐Modulation (PWM) topologies is studied and proposed here. Most integrated converters have their switches shared by more than one inductive element. The proposed generalised tapped inductor switcher model takes full account of the properties of the shared switcher assembly and so extends the capabilities of the earlier tapped inductor switcher model. The proposed generalised tapped inductor switcher can accommodate both voltage and current switched inputs and thus can model a wide range of high‐order PWM topologies. The topology of the GTIS block is proposed and its static and small‐signal models are derived. The proposed approach is illustrated by analysing a tapped inductor Single Eneded Primary Inductor converter. The validity of the proposed approach is verified by comparison of the theoretical, simulated and experimental results.
Variable fractional power‐least mean square based control algorithm with optimized PI gains for the operation of dynamic voltage restorer
Authors: Naidu Talada Appala , Arya Sabha Raj , Maurya Rakesh , Sanjeevikumar P.
Published: December 2020

The operation of Dynamic Voltage Restorer has been studied for the mitigation of supply voltage disturbances like sag, swell, distortions, and unbalances. A Dynamic Voltage Restorer with three single‐phase Voltage Source Converters has been implemented for this purpose. Dynamic Voltage Restorer's compensation capability has been evaluated while introducing the above‐said voltage related disturbances in the supply by different means. A control algorithm named Variable Fractional Power‐Least Mean Square has been proposed for generating the load reference voltage for Dynamic Voltage Restorer. Variable Fractional Power‐Least Mean Square extracts the fundamental active and reactive component out of non‐ideal supply voltage and is thus, used in generating reference load voltage. This algorithm is more robust with respect to disturbance due to variable step size and is computationally less expensive. In addition, an optimization‐based approach has been proposed to estimate the approximate values of PI control gains. For this reason, a population‐based optimization method known as Sine Cosine Optimization has been used. The added feature of the optimization method is the reduction of computational time as compared to conventional PI controller tuning. A model of Dynamic Voltage Restorer using Variable Fractional Power‐Least Mean Square control algorithm with Sine Cosine Optimization tuned PI gains has been built in MATLAB Simulink as well as a reduced scale experimental prototype and their results have been presented with discussion.
Tracing molecular stratification within an edge-on protoplanetary disk
Authors: Ruíz-Rodríguez D. , Kastner J. , Hily-Blant P. , Forveille T.
Published: December 2020

High-resolution observations of edge-on protoplanetary disks in emission from molecular species that sample different critical densities and formation pathways offer the opportunity to trace the vertical chemical and physical structures of protoplanetary disks. Among the problems that can be addressed is the origin and significance of the bright CN emission that is a ubiquitous feature of disks. Based on analysis of subarcsecond-resolution Atacama Large Millimeter Array archival data for the edge-on Flying Saucer disk (2MASS J16281370-2431391), we establish the vertical and radial differentiation of the CN emitting regions of the disk with respect to those of 12CO and CS, and we model the physical disk conditions from which the CN emission arises. We demonstrate that the 12CO (2–1), CN (2–1), and CS J = 5–4 emitting regions of the disk decrease in scale height above the midplane, such that 12CO, CN, and CS trace layers of increasing density and decreasing temperature. We find that at radii >100 au from the central star, CN emission predominantly arises from intermediate layers, while in the inner region of the disk CN appears to arise from layers closer to the midplane. We investigate the physical conditions of the disk within the CN emitting regions, as well as the ranges of CN excitation temperature and column density, via RADEX non-local thermodynamic equilibrium (non-LTE) modeling of the three brightest CN hyperfine lines. Near the disk midplane, where we derive densities of nH2 ~ 107 cm−3 at relatively low Tkin (~12 K), we find that CN is thermalized, while sub-thermal, non-LTE conditions appear to obtain CN emission from higher (intermediate) disk layers. We consider whether and how the particular spatial location and excitation conditions of CN emission from the Flying Saucer can be related to CN production that is governed, radially and vertically, by the degree of irradiation of the flared disk by X-rays and UV photons from the central star.
Improvement of laser absorption and control of particle acceleration by subwavelength nanowire target
Authors: Xie R. , Cao L. H. , Chao Y. , Jiang Y. , Liu Z. J. , Zheng C. Y. , He X. T.
Published: December 2020

The effects of the subwavelength nanowire target on the enhanced laser absorption, heating of electrons, and acceleration and control of energetic ions are investigated by using two-dimensional particle-in-cell simulations. Compared with the flat target, the conversion efficiency and acceleration of target normal sheath acceleration can be improved remarkably. In the condition considered in this paper, the conversion efficiency from the laser to electrons can be increased by about four times (14.74% to 65.78%), and the cutoff energy of electrons can be raised by 1.5 times. Furthermore, the cutoff energies of both protons and carbon ions are increased by almost two times. The dependence of this effect for different nanowire widths is discussed by numerical simulations. It is found that the efficiency from the laser to electrons reaches the highest value when the nanowire width is d=0.2 μm. The optimum width for C6+ ions is d=0.3 μm, while d=0.8 μm is better for proton acceleration. Thus, the laser absorption, electron heating, and ion acceleration could be controlled by selecting the width of subwavelength nanowires.
Using mathematical models to improve risk-scoring in acute myeloid leukemia
Authors: Stiehl Thomas
Published: December 2020

Acute myeloid leukemia (AML) is an aggressive cancer of the blood forming (hematopoietic) system. Due to the high patient variability of disease dynamics, risk-scoring is an important part of its clinical management. AML is characterized by impaired blood cell formation and the accumulation of so-called leukemic blasts in the bone marrow of patients. Recently, it has been proposed to use counts of blood-producing (hematopoietic) stem cells (HSCs) as a biomarker for patient prognosis. In this work, we use a non-linear mathematical model to provide mechanistic evidence for the suitability of HSC counts as a prognostic marker. Using model analysis and computer simulations, we compare different risk-scores involving HSC quantification. We propose and validate a simple approach to improve risk prediction based on HSC and blast counts measured at the time of diagnosis.
High permeability and low loss flaky carbonyl iron soft magnetic composite for 5G applications
Authors: Liu Xi , Wu Peng , Wang Guowu , Qiao Liang , Wang Tao , Li Fashen
Published: December 2020

A soft magnetic composite (SMC) material with a large aspect ratio is prepared by a ball-milling method. Such SMCs have excellent high-frequency performance such as high permeability, saturation magnetization, and resonance frequency, which makes them have great potential in the field of 5G and high-frequency power devices. The flaky particles with large aspect ratios can effectively reduce eddy current loss and obtain larger permeability. Simultaneously, we also further studied the high-frequency magnetic properties and loss of SMCs with different aspect ratios. We obtained the magnetic spectra of samples with different aspect ratios and then established a loss model for flaky samples under high frequency and performed loss separation for these samples. The relationship between the aspect ratios, permeabilities, and three types of loss after separation is analyzed and discussed. A large aspect ratio can effectively improve the permeability and reduce the eddy current loss, and a high permeability due to a large aspect ratio can also reduce the hysteresis loss. The differentiation of magnetic domain and the variation in the number of domain walls caused by the process of obtaining the large aspect ratio (ball milled), high permeability caused by this process and number of displaced domain walls also affect the excess loss. This provides the possibility for the application of soft magnetic material composites at high frequencies.
Antiferromagnetic fluctuations in the one-dimensional Hubbard model
Authors: Janiš Václav , Klíč Antonín , Yan Jiawei
Published: December 2020

We study the low-temperature critical behavior of the one-dimensional Hubbard model near half filling caused by enhanced antiferromagnetic fluctuations. We use a mean-field-type approximation with a two-particle self-consistency renormalizing the bare interaction. It allows us to control a transition from high to low temperatures as well as from weak to strong-coupling. We show that there is a crossover temperature T0 = t exp{−1/Uρ(0)} for arbitrary interaction U > 0 and the bare density of states at the Fermi energy ρ(0) > 0. The solution at lower temperatures goes over to strong coupling and approaches a quantum critical point with the diverging staggered susceptibility and a gap in the excitation spectrum at zero temperature.
Direct and continuous generation of pure acetic acid solutions via electrocatalytic carbon monoxide reduction
Authors: Zhu Peng , Xia Chuan , Liu Chun-Yen , Jiang Kun , Gao Guanhui , Zhang Xiao , Xia Yang , Lei Yongjiu , Alshareef Husam N. , Senftle Thomas P. , Wang Haotian
Published: December 2020

Significance

Using electricity to reduce CO
2
or CO back into valuable liquid fuels can revolutionize the way we produce chemicals/fuels. However, there are two types of impurity challenges involved: Different liquid products were typically cogenerated on Cu catalysts; in addition, those generated liquid fuels were inevitably mixed with ion impurities in liquid electrolytes. By integrating the rational design of Cu nanocube catalyst and porous solid electrolyte reactor, we report a direct and continuous generation of high-purity acetic acid solutions via electrochemical CO reduction.
Appraisal of sedimentary alkenones for the quantitative reconstruction of phytoplankton biomass
Authors: Raja Maria , Rosell-Melé Antoni
Published: December 2020

Significance

Biomarker proxies, namely alkenones, are commonly used to reconstruct past primary productivity. However, their value has been questioned as they are posited to be controlled by diagenetic processes and often limited to draw qualitative inferences on the carbon cycle. In fact, most proxies have not been globally appraised with ocean biogeochemical data. Here, we use a combination of remote sensing and geochemical data to provide a spatial-based global scale calibration that shows the use of alkenones to quantify past sea surface chlorophyll-aconcentration, which ultimately can be used to infer quantitatively past primary productivity in paleorecords. This calibration paves the way to clarify the relative role of the marine carbon cycle in climate variability using field data, and tests biogeochemical models.
Superconductor–insulator transition in two-dimensional indium–indium-oxide composite
Authors: Hen Bar , Zhang Xinyang , Shelukhin Victor , Kapitulnik Aharon , Palevski Alexander
Published: December 2020

Significance

The magnetic-field–tuned superconductor-to-insulator transition (H-SIT) in disordered two-dimensional thin-film materials is paradigmatic for quantum phase transition. While in the standard approach pairing persists into the insulating phase, and the transition is driven by quantum phase fluctuations, the role of its associated inhomogeneous nature, particularly in the widely studied InOx system, remains an open question. Here we use a granular structure of pure indium islands where pairing amplitude is well defined, superimposed on a uniform thin film of barely insulating InOx, which provide the intergrain coupling, to preferentially gain insight into the role of phase fluctuations in InOx H-SIT. The robust pairing in the indium islands helps mitigate nonequilibrium effects that often disrupt the approach to H-SIT in InOx experiments.
Angelika Amon (1967–2020): Breakthrough scientist, extraordinary mentor, and loyal friend
Authors: Visintin Rosella , Marston Adele L.
Published: December 2020

Visintin and Marston discuss the life and achievements of Angelika Amon, who passed away on October 29, 2020.
A novel MEMS-RIMU self-calibration method based on gravity vector observation
Authors: Cheng Jianhua , Liu Ping , Wei Zhenyu , Luo Guangdi
Published: December 2020

The microelectromechanical system (MEMS) redundant inertial measurement unit (RIMU) is a low-cost navigation system, which can improve reliability effectively. In existing MEMS-RIMU calibration schemes, extra equipment with higher accuracy is required. However, on some occasions, a rotation platform or other reference equipment cannot be provided, and calibration of the MEMS-RIMU is limited. To solve the problem, a novel self-calibration method for the MEMS-RIMU based on gravity vector observation is proposed, which can estimate the bias, scale errors and alignment errors of accelerometers and gyroscopes without extra equipment or rotation platforms. In this paper, a novel calibration model for accelerometers and gyroscopes is built by analyzing the relationship between gravity vector observation and the measurement value of the MEMS-RIMU. There is no attitude information in the calibration model, so the RIMU can be calibrated without attitude references via extra equipment. Then, a derivative unscented Kalman filter is proposed to estimate the bias, scale errors and alignment errors of accelerometers and gyroscopes, which can reduce the computation load. Finally, the simulation and experimental results demonstrate the efficiency and accuracy of the proposed calibration scheme.
CVD growth of rhenium sulfide on carbon nanotubes as an anode for improving the performance of lithium ion batteries
Authors: Cao Kai , Hu Zhengguang , Wang Jianyu , Liu Fengliang , Wu Xiaoqin , Wang Zhendong , Wang Li
Published: December 2020

Lithium ion batteries have widely been used for electronic devices and electric vehicles. However, commercial anodes, generally graphite, have not been improved a great deal. Thus, we successfully constructed ReS2/carbon nanotube (CNT) composites by a chemical vapor deposition method, which exhibit excellent electrochemical performances when serving as anode materials for lithium ion batteries (LIBs). We confirmed that ReS2 crystals are grown on the surface of the CNTs by using scanning electron microscopy and transmission electron microscopy. As a result, the LIBs show much better long-cycle and rate performances than bare ReS2 and CNTs. The ReS2/CNTs were assembled in coin cells CR2025, presenting a stability capacity of 488 mAh g−1 at a rate of 5C. The anodes maintain a reversible capacity of 1050 mAh g−1 after nearly 60 cycles at 0.2C, which indicates that it is a promising technique to improve the performance of LIBs.
Physical aspects of convective and radiative molecular theory of liquid originated nanofluid flow in the existence of variable properties
Authors: Rehman Aysha , Hussain Azad , Nadeem Sohail
Published: December 2020

A numerical approach is adopted to explore the analysis of combined convection and thermal radiation on molecular theory of liquid originated nanofluid over an extendable surface. The temperature-dependent viscosity is considered through Vogel’s and Renold’s model. The physical problem gains more significance in the presence of temperature-dependent thermal conductivity. Nanofluid attributes are explored through thermophoresis and Brownian motion effect. Radiative heat flux is also taken into account to study the thermal radiation aspects. Characteristics of sundry physical parameters on the velocity, thermal energy and mass transfer are computed numerically and graphically. Velocity pattern expands for growing the size of thermophoresis diffusion and decline by the expanding amount of fluid parameter for Vogel’s and Renold’s model. Temperature fluctuation rises when the quantity of variable thermal conductivity parameter getting up and falls for radiation parameter. Concentration curve increases if the values of Prandtl number enlarge for Renold’s model. Concentration boundary layer thickness declines for inclining in Brownian diffusion, radiation and Prandtl number for Vogel’s model.
Local and nonlocal (2 + 1)-dimensional Maccari systems and their soliton solutions
Authors: Pekcan Aslı
Published: December 2020

In this work, by using the Hirota bilinear method, we obtain one- and two-soliton solutions of integrable (2 + 1)-dimensional 3-component Maccari system which is used as a model describing isolated waves localized in a very small part of space and related to very well-known systems like nonlinear Schrödinger, Fokas, and long wave resonance systems. We represent all local and Ablowitz-Musslimani type nonlocal reductions of this system and obtain new integrable systems. By the help of reduction formulas and soliton solutions of the 3-component Maccari system, we obtain one- and two-soliton solutions of these new integrable local and nonlocal reduced 2-component Maccari systems. We also illustrate our solutions by plotting their graphs for particular values of the parameters.
Single and Multiple Imputation Method to Replace Missing Values in Air Pollution Datasets: A Review
Authors: Libasin Zuraira , Zia Ul-Saufie Ahmad , Ahmat Hasfazilah , Nur Shaziayani Wan
Published: December 2020

Imputation plays an essential role in handling the issue of missing data. The conventional techniques applied to overcome this problem are single imputation (SI) and multiple imputations (MI). These statistical strategies have their strengths and limitations in replacing missing data. This article reviews the state of the art of imputation methods employed in general publications in replacing missing values for air pollution data. A comprehensive review of the literature identifies the use of SI and MI slightly increases over the year. This paper concludes on the trend and the approaches used in the imputation methods. Subsequently, this paper put forward the gaps in imputation technique that less utilized a machine-learning approach in providing a substitute for missing values in air pollution data. The future direction of the research is to extend more machine-learning approach with higher accuracy with higher performance in imputing missing values.
Meteorological Parameters and Air Pollution in Urban Environments in the Context of Sustainable Development
Authors: Deak György , Raischi Natalia , Matei Monica , Boboc Madalina , Cornateanu Gabriel , Raischi Marius , Matei Stelian , Yasina Yusuf Sara
Published: December 2020

In big cities, certain meteorological phenomena can affect air quality even in cases where the main sources of pollution such as traffic have low intensity. The air pollution varies greatly, depending on the emission source and the type of pollutant. In addition, the dispersion of air pollutants is influenced by weather conditions, as well as other factors such as the type of pollutant and regional and local topography. The air quality is one of the targets of the 11th goal of the UN 2030 AGENDA for sustainable development, also adopted at the national level. This study aims to correlate temperature and humidity with atmospheric pollutants, like PM10. The data were obtained by continuous monitoring for a period of 9 days (5 days when precipitation was recorded and 4 days when precipitation was absent) in which the relative humidity varying between 32-104% while the concentration of PM10 between 13-118 µg/m3. The measurements on air quality parameters were performed in the central area of Bucharest city, near an important boulevard with intensive vehicle traffic and sometimes traffic jams. During daytime period, it was observed that the temperature inversion could be the cause the accumulation of high PM10 levels near the road surface for some hours of the monitoring period.
Optimization of SiO2/Al2O3 Ratio in the Preparation of Geopolymer from High Calcium Fly Ash
Authors: Faradilla F S , Nugroho D T , Hidayati R E , Nurlina  , Bayuaji R , Hartanto D , Fansuri H
Published: December 2020

High-calcium fly ash-based geopolymers have been successfully synthesized. The source of fly ash used in this study is fly ash from PT. IPMOMI, PT. Holcim and Paiton PLTU 9. The variation in the mole ratio of SiO2/Al2O3 carried out in this study was 3,0; 3,3; 3,6; 3,9 and 4,2. Compressive strength tests were carried out on geopolymers aged 7, 14, and 28 days. A geopolymer with a ratio of 3,6 has the best compressive strength. The compressive strength test results for IPMOMI, Holcim, and Paiton 9 geopolymers were 75,37; 50,95; and 39,25 MPa. The highest geopolymers with compressive strength were characterized using XRD and SEM. The results of the XRD showed that geopolymers had an amorphous phase and gibbsite mineral in the three geopolymers which indicated that there was still Al(OH)3 which had not reacted. Microstructure analysis using SEM shows the all of three solid structure of geopolymers. There is efflorescence on Holcim and Paiton 9 geopolymers which causes lower compressive strength than IPMOMI geopolymers.
New Model to Calculate Blast Loading on Above and Underground Structures
Authors: Farag Hassan M.
Published: December 2020

Blast loading is a type of extraordinary dynamic load to which structures or any object may be exposed to. The load resulted on structures or any targets from explosion is a complicated task to do. This paper presents an accurate and so simple model and program “
BLAST
” to predict the blast or shock wave resulted from the explosion that termed “Over Pressure” which comes from conventional and non-conventional weapons (such as Nuclear weapons). The pressure from the mass of air flow at and behind the shock front that termed the “Dynamic Pressure” is also predicted.

The loads on any structure or target from the explosion are combination of overpressure Ps(t) and dynamic pressure Pd(t), this dynamic load on different faces of a structure either above or under the ground is predicted and presented in this paper.

The over pressures resulted from different charges or weapon yields that are calculated in this study are compared to those obtained from “ConWep”.

The load on structures predicted by the present study is also compared to that obtained from “AUTODYN” software. A study is performed to investigate the effect of depth of burial on the load affecting the different faces of the buried structure.
The history of monasteries in Egypt as self-sustained settlements
Authors: Romel G , Sherif L , Ashour S
Published: December 2020

Monasticism initiated in Egypt and has spread worldwide. It introduced a new self-sustained architectural innovation called “monasteries”. Monasteries can be considered as homogeneous self-sustained settlements through history. This paper aims to document the origins of monasticism, leading to the development of self-sustained monasteries: conceptually, economically, and architecturally. It relies on observations, maps, and historical references. The main challenges in collecting data for this paper were the lack of published references about origins of monasticism. Most of the resources are rare documents stored in the Coptic Clerical and Theological College of Cairo, and libraries of monasteries. Thus, the paper analysis present monasteries as self-sufficient, self-sustained settlements that survived through history since the fourth century to the current state through: (zoning, architectural elements, building materials, and buildingtechniques. The architectural analysis shows that the architectural solutions of monasteriesevolved in respect to the geographical location, and context. Monasteries architecture relies on trials and errors, until it reached an applicable architectural model.
Design out waste as an approach for achieving sustainability in Egyptian housing projects
Authors: Elsawaf Laila A. , Othman Ayman A. E.
Published: December 2020

Housing projects have been increasing rapidly during the previous years to fulfil community needs and achieve the national and international sustainable development objectives. Due to their nature, housing projects generate a significant amount of waste that accounts for approximately 40% of the solid waste that the construction industry generates annually. Many of these wastes are a result of inappropriate decisions adopted during the design process such as using non-sustainable materials and inefficient use of natural recourses. Meanwhile, research has revealed that achieving sustainability within housing projects is a crucial challenge, yet an essential one. This called to think differently and adopting creative strategies for reducing construction waste during the design process. Therefore, this research aims to develop a matrix that correlates the aspects of sustainability with design out waste strategy as an approach within RIBA design phases for achieving sustainability in Egyptian public housing projects. A research methodologyconsists of literature review and case study was designed to achieve a working matrix by accomplishing three objectives. Firstly, literature review was used to investigate the topics of sustainability, design out waste strategy and housing projects. Secondly, a case study collected by literature presentedand analysedto identify the design out waste strategy for reducing waste as an approach to achieve sustainability. Finally, developing a matrix that correlates sustainability and design out waste strategy within RIBA design phases.
Managing of city transition toward sustainable Eco urbanism (Proposed paradigm)
Authors: Fayad Mohamad F. , Elmahdy Maged , Sabri Sherif , Kasem A. Alrahim
Published: December 2020

The research clarifies transition strategy towards sustainable Eco urbanism, and what spinoff the reliable Universal Criteria, in addition to concept the managing of sustainability transition in cities.

The aim of the research is to present and elaborate a proposed model for managing the sustainable transformation of Egyptian cities, so that they are suitable to deal with and apply to most existing and new urban communities, with a view to transforming them into sustainable environmental cities and communities, by working to develop a future vision for the sustainable image that the city will reach, dependent on Scientific foundations and an understanding of the problems these regions suffer from, to explain sustainability strategies in light of the general data for these areas and the current and future needs of the population and the available capabilities.

The proposed paradigm consists of ten consecutive stages of operations and is related to each other, where the subsequent stage is based on the data of the previous stage, and the success of the previous stage has a positive impact on the success of the subsequent stage and vice versa.
Thermal Conductivity for Foamed Paste made of Cement and Cement kiln dust
Authors: Wahab Rafik K. Abdel
Published: December 2020

As with most large manufacturing industries, by-product materials are generated. Cement kiln dust is a by - product material of cement manufacturing process. The aim of this paper is to investigate the properties of foamed paste made of CKD in addition of different percentages of cement. Compressive strength and thermal conductivity were determined. Sixty three cubes in three groups with different densities, amount of cement, CKD, water and foaming agent were cast. The results were encourage to use the Foamed( Cement kiln dust – cement) Paste (FCKDC) as an insulation materials. The results indicates’ a comparable value for thermal conductivity which vary from (0.074-0.3) W/mk.
Exploratory Analyses for Missing Data in Meta-Analyses and Meta-Regression: A Tutorial
Authors: Schauer Jacob M , Diaz Karina , Pigott Therese D , Lee Jihyun
Published: December 2020

Objectives

In this tutorial, we examine methods for exploring missingness in a dataset in ways that can help to identify the sources and extent of missingness, as well as clarify gaps in evidence.

Methods

Using raw data from a meta-analysis of substance abuse interventions, we demonstrate the use of exploratory missingness analysis (EMA) including techniques for numerical summaries and visual displays of missing data.

Results

These techniques examine the patterns of missing covariates in meta-analysis data and the relationships among variables with missing data and observed variables including the effect size. The case study shows complex relationships among missingness and other potential covariates in meta-regression, highlighting gaps in the evidence base.

Conclusion

Meta-analysts could often benefit by employing some form of EMA as they encounter missing data.