bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical study of the effects of pulsed plasma actuator on physical behavior of the fluid flow around a ducted wind turbine
Authors: Mofateh Mohsen , Ghafouri Ashkan , Kosarineia Abbas , Changizian Maziar
Published: May 2022

As with other types of wind turbines, the ducted wind turbine has a bright future. On the other hand, flow separation has a consistent effect on this type of turbine, resulting in aerodynamic losses and load fluctuations. As a result, flow control systems for ducted wind turbines are critical for improving aerodynamic performance. Additionally, in this technological age, noise pollution has developed into a serious problem that must be minimized and controlled to the greatest extent feasible. This research investigates the impact of a plasma actuator as an active control approach on the flow dynamics on the blades using a finite volume code. To decrease computing costs, the URANS model and mesh adaptive methods are applied. The numerical results are confirmed by comparing them to a previously collected experimental dataset. The flow dynamics and noise emission of a micro dielectric-barrier-discharge plasma actuator were examined under the impact of discontinuous pulsing. This actuator was fitted in three distinct places at the beginning point of separation in the blade without using the ducted wind turbine’s control approach. The results indicated that positioning the actuator near the blades’ tip improves aerodynamic performance. Additionally, when the plasma actuator’s power is raised, the vortex cancellation is maximized. The results indicated that the DBD actuator generated a considerable portion of reverse flow, in this case in the opposite direction to the tip flow. The reverse flow was used to alter the pressure gradient in the tip gap area, thereby eliminating the vortex. Also, using the plasma actuator reduces the ducted wind turbine’s noise output by cutting down on the wake zone and vortices, which are the main sources of noise.
*-Graded Capelli polynomials and their asymptotics
Authors: Benanti F. S. , Valenti A.
Published: May 2022

Let [Formula: see text] be the free *-superalgebra over a field [Formula: see text] of characteristic zero and let [Formula: see text] be the [Formula: see text]-ideal generated by the set of the *-graded Capelli polynomials [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] alternating on [Formula: see text] symmetric variables of homogeneous degree zero, on [Formula: see text] skew variables of homogeneous degree zero, on [Formula: see text] symmetric variables of homogeneous degree one and on [Formula: see text] skew variables of homogeneous degree one, respectively. We study the asymptotic behavior of the sequence of *-graded codimensions of [Formula: see text] In particular, we prove that the *-graded codimensions of the finite dimensional simple *-superalgebras are asymptotically equal to the *-graded codimensions of [Formula: see text], for some fixed natural numbers [Formula: see text] and [Formula: see text].
Ordering braids: In memory of Patrick Dehornoy
Authors: Rolfsen Dale
Published: May 2022

With the untimely passing of Patrick Dehornoy in September 2019, the world of mathematics lost a brilliant scholar who made profound contributions to set theory, algebra, topology, and even computer science and cryptography. And I lost a dear friend and a strong influence in the direction of my own research in mathematics. In this paper, I will concentrate on his remarkable discovery that the braid groups are left-orderable, and its consequences, and its strong influence on my own research. I’ll begin by describing how I learned of his work.
Birth of Garside groups in memory of Patrick Dehornoy
Authors: Paris Luis
Published: May 2022

This paper, in homage to Patrick Dehornoy, tells the birth of Garside groups.
A meeting with Patrick DeHornoy
Authors: Kauffman Louis H.
Published: May 2022

This paper recalls my first meeting with Patrick DeHornoy and its consequences.
Meshfree Collocation Framework for Multi-Phase Coupling Nonlinear Dynamic System in a Porous Enclosure
Authors: Yang Judy P. , Chang Heng-Chun
Published: May 2022

This study is aimed at establishing an effective incremental-iterative framework, for the first time, using reproducing kernel collocation method for solving multi-phase dynamic coupling problems in a porous enclosure. The central difference method is utilized in the temporal discretization while direct collocation with reproducing kernel approximation is adopted in the spatial discretization, in particular, with Newton–Raphson method for nonlinear iteration. Under the proposed numerical framework, a determined and well-conditioned nonlinear system is ensured during nonlinear iteration. In addition to the traditional mesh-based weak-form methods, it is shown that the present study provides an alternative effective approach to solve unsteady-state double-diffusive convection problems.
Large deviations for Hamiltonian systems on intermediate time scales
Authors: Yan Shuo
Published: May 2022

We consider a two-dimensional Hamiltonian system perturbed by a small diffusion term, whose coefficient is state-dependent and nondegenerate. As a result, the process consists of the fast motion along the level curves and slow motion across them. On finite time intervals, the large deviation principle applies, while on time scales that are inversely proportional to the size of the perturbation, the averaging principle holds, i.e. the projection of the process onto the Reeb graph converges to a Markov process. In our paper, we consider the intermediate time scales and prove the large deviation principle, with the action functional determined in terms of the averaged process on the graph.
INVESTIGATION OF DISCRETE WAVELET TRANSFORM DOMAIN OPTIMAL PARAMETRIC APPROACH FOR DENOISING OF PHONOCARDIOGRAM SIGNAL
Authors: GHOSH SAMIT KUMAR , PONNALAGU R. N.
Published: May 2022

Phonocardiogram (PCG) signals are contaminated with various noise signals, which hinders the accurate diagnostic interpretation of the signal. Discrete wavelet transform (DWT) is a well-known technique used to remove noise from PCG signals and improve signal quality. The performance of DWT-based denoising depends upon several parameters involved in the process, such as mother wavelets used for decomposition, the number of decomposition levels (DLs), thresholding technique used and the threshold estimation rule followed. In this work, an investigative study is carried out to select the optimal parameter values which give the best denoising performance. The metrics such as mean-square error (MSE), normalized-mean-square error (NMSE), root-mean-square error (RMSE), percentage root-mean-square difference (PRD) and signal-to-noise ratio (SNR) are used to evaluate the performance of the denoising in this study. The results obtained show that the fifth-order Coiflet wavelet is best suited for denoising PCG signals when applied with the soft thresholding (ST) function and rigrsure threshold selection rule. Also, the optimum number of DLs resulting in better performance is level 6. SNR value obtained from the studies shows the efficacy of the parameters selected for denoising. The denoised PCG signals provide accurate information to determine various kinds of heart valve-related disorders (HVDs).
COUNTERCYCLICAL CAPITAL BUFFERS, BANK CONCENTRATION AND MACROFINANCIAL STABILITY IN AN AGENT-BASED MACRO-FINANCIAL FRAMEWORK
Authors: NEUNER MICHAEL , PROAÑO CHRISTIAN R. , RUSSO ALBERTO
Published: May 2022

This paper examines the impact of countercyclical capital buffers (CCyBs) on financial stability and contributes to the discussion of CCyBs in an agent-based framework. The main focus of this work lies upon the question whether the implementation of CCyBs according to the Basel III framework improves financial stability unconditionally, or at the expense of unintended side effects. For this purpose, we extend the agent-based model of [Riccetti, L., Russo, A. and Gallegati, M., Firm–bank credit network, business cycle and macroprudential policy, J. Econ. Interact. Coord. (2021)] to investigate the effect of credit-to-GDP gap-based CCyBs in general as well as the effects of varying the smoothing parameter lambda [Formula: see text] of the Hodrick–Prescott (HP) filter within the method of calculating CCyBs. To the best of our knowledge, this study is the first one that investigates systematically how the method of calculating credit-to-GDP gap-based CCyBs may affect macrofinancial dynamics and stability in such an agent-based framework.
DETECTING AND MEASURING FINANCIAL CYCLES IN HETEROGENEOUS AGENTS MODELS: AN EMPIRICAL ANALYSIS
Authors: GUSELLA FILIPPO
Published: May 2022

This paper proposes a macroeconometric analysis to depict and measure possible financial cycles that emerge due to the dynamic interaction between heterogeneous market participants. We consider two-type heterogeneous speculative agents: Trend followers tend to follow the price trend while contrarians go against the wind. As agents’ beliefs are unobserved variables, we construct a state-space model where heuristics are considered as unobserved state components and from which the conditions for endogenous cycles can be mathematically derived and empirically tested. Further, we specifically measure the length of endogenous financial cycles. The model is estimated using the equity price index for the 1960–2020 period for the UK, France, Germany, Italy, Ireland, and the USA. We find empirical evidence of endogenous financial cycles for all countries, with the highest frequencies in the USA and the UK.
Performance Comparison for FinFET Nanoscale Static and Domino Logic Circuits
Authors: Riaz Anjum , Sharma Vijay Kumar
Published: May 2022

The future prospects of complementary metal oxide semiconductor (CMOS) technology are estimated to be replaced by fin-shaped field effect transistor (FinFET) owing to its strong channel control, high driving capability and ease of fabrication. This paper envisages the effects of voltage, temperature and fin variation on power dissipation and delay for static and domino logic circuits. Circuit behavior becomes unpredictable due to process, voltage and temperature (PVT) variations such as irregular power consumption and performance deviation. It also accelerates circuit deterioration and makes them ineffective. The important circuit level leakage power reduction techniques like LCNT, LECTOR and INDEP have been applied to basic gates, 3-bit carry look ahead adder (CLA) and domino logic circuits at 16 nm FinFET technology. It is found that power delay product (PDP) in CLA using INDEP technique exhibits 61.48% less than conventional CLA. Leakage power reduction techniques have also been verified for the footer domino logic (FDL) circuit and performed Monte Carlo simulations for 10000 samples for reliability analysis. INDEP circuits are robust to PVT variations. The simulations have been completed using Cadence Virtuoso tool.
Chiral solitons of (2+1)-dimensional stochastic chiral nonlinear Schrödinger equation
Authors: Arshed Saima , Raza Nauman , Javid Ahmad , Baskonus Haci Mehmet
Published: May 2022

This paper studies [Formula: see text]-dimensional stochastic chiral nonlinear Schrödinger equation dynamically. A number of novel solutions such as periodic, singular, dark and bright solitons solutions are retrieved. The extraction of these solutions is helped by three efficient and robust integration tools such as the Kudryashov’s R function method, Jacobi elliptic function method (JEFM) and the modified auxiliary equations (MAE) method. The parametric constraints for the existence of such solutions are also listed. Moreover, 3D plots of few obtained solutions are presented in this paper.
Global attractivity of Nicholson’s blowflies system with patch structure and multiple pairs of distinct time-varying delays
Authors: Ding Xiaodan
Published: May 2022

This paper is intended to investigate a class of Nicholson’s blowflies system with patch structure and multiple pairs of distinct time-varying delays, we are interested in finding the influence of the distinct time-varying delays in the same reproductive function on its asymptotic behavior. By using the theory of functional differential equations, the fluctuation lemma, and the technique of differential inequalities, some new delay-dependent criteria on the global attractivity of the positive equilibrium point are established. In addition, the effectiveness and feasibility of the theoretical achievements are illustrated by some numerical simulations.
Optimal harvesting of a fuzzy water hyacinth-fish model with Kuznets curve effect
Authors: Xu Jing , Yuan Sanling , Zhang Tonghua
Published: May 2022

In this paper, we consider the effects of environmental perturbations such as the variations of temperature and climate on the growth of water hyacinth and fish species, as well as the economic and application values of these two species. We first present a triangular fuzzy water hyacinth-fish ecological model with Kuznets curve effect and linear harvesting. Then, we discuss the existence of the equilibria and their stability. It is then followed by analyzing the existence of bionomic equilibrium and determining the optimal harvesting policy via Pontryagin’s Maximum Principle. Finally, numerical simulations are performed to validate the theoretical results. Our research indicates that fuzzy parameters may affect the optimal harvesting strategy.
A multidisciplinary design method and application for complex systems
Authors: Yi Guodong , Yi Lifan , Zhang Shaoju
Published: May 2022

A reasonable electrochemical mechanism model is the basis for accurately describing the actual operation of hydrogen fuel cell (HFC). In this paper, a multidisciplinary modeling and simulation method is proposed. Based on the internal electrochemical reaction kinetics and electrochemical thermodynamics mechanism of the HFC, a voltage output model and a back pressure regulation model are constructed. By analyzing the relationship between the back pressure of the anode and cathode of the HFC and the effective partial pressure of the reactant gas, a voltage output model and back pressure adjustment model are integrated to form an HFC electrochemical mechanism model, which realizes the dynamic and accurate description of the HFC output performance. The final experimental results show that the electrochemical mechanism model of the HFC can achieve good results.
Responsible data management
Authors: Stoyanovich Julia , Abiteboul Serge , Howe Bill , Jagadish H. V. , Schelter Sebastian
Published: May 2022

Perspectives on the role and responsibility of the data-management research community in designing, developing, using, and overseeing automated decision systems.
Automated, Cost-effective, and Update-driven App Testing
Authors: Ngo Chanh Duc , Pastore Fabrizio , Briand Lionel
Published: May 2022

Apps’ pervasive role in our society led to the definition of test automation approaches to ensure their dependability. However, state-of-the-art approaches tend to generate large numbers of test inputs and are unlikely to achieve more than 50% method coverage.

In this article, we propose a strategy to achieve significantly higher coverage of the code affected by updates with a much smaller number of test inputs, thus alleviating the test oracle problem.

More specifically, we present ATUA, a model-based approach that synthesizes App models with static analysis, integrates a dynamically refined state abstraction function and combines complementary testing strategies, including (1) coverage of the model structure, (2) coverage of the App code, (3) random exploration, and (4) coverage of dependencies identified through information retrieval. Its model-based strategy enables ATUA to generate a small set of inputs that exercise only the code affected by the updates. In turn, this makes common test oracle solutions more cost-effective, as they tend to involve human effort.

A large empirical evaluation, conducted with 72 App versions belonging to nine popular Android Apps, has shown that ATUA is more effective and less effort-intensive than state-of-the-art approaches when testing App updates.
SigGAN: Adversarial Model for Learning Signed Relationships in Networks
Authors: Chakraborty Roshni , Das Ritwika , Chandra Joydeep
Published: May 2022

Signed link prediction in graphs is an important problem that has applications in diverse domains. It is a binary classification problem that predicts whether an edge between a pair of nodes is positive or negative. Existing approaches for link prediction in unsigned networks cannot be directly applied for signed link prediction due to their inherent differences. Furthermore, signed link prediction must consider the inherent characteristics of signed networks, such as structural balance theory. Recent signed link prediction approaches generate node representations using either generative models or discriminative models. Inspired by the recent success of Generative Adversarial Network (GAN) based models in several applications, we propose a GAN based model for signed networks, SigGAN. It considers the inherent characteristics of signed networks, such as integration of information from negative edges, high imbalance in number of positive and negative edges, and structural balance theory. Comparing the performance with state-of-the-art techniques on five real-world datasets validates the effectiveness of SigGAN.
(Digital Presentation) Silver Nanoparticles Coated Membrane Scaffolds and Fabric Materials as a New Generation of Antiviral Surface Protection Against COVID-19
Authors: Youssef Mohamed F. , Kalil Haitham , Samir Omar , Maher Shaimaa , El-falouji Abdullah I. , Gad Emad
Published: May 2022

The current COVID-19 outbreak continues to pique the curiosity of researchers from all disciplines. Personal Protective Equipment (PPE) in terms of masks and gloves are essential for moving the battle out. Developing a highly efficient PPE is crucial, not only to reduce the spread of virus, but also to protect people who work at the frontline. Here, we tested the potential effect of silver nanoparticles as antiviral agents based on their unique properties. When compared to imitative antivirals, elemental silver nanoparticles could attack many virus sites, reducing the likelihood of the virus developing resistance. Silver nanoparticles were synthesized and loaded on cellulose membrane scaffolds, polyvinyl alcohol polymer dressings, and mask fabrics. The new generation of fiber mats have been thoroughly described and tested against SARS-CoV-2 virus using Docking molecular modeling. SEM, FT-IR, UV-Vis, and DLS were used to identify the shape and estimate the particle size of the embedded nanoparticles.
(Invited, Digital Presentation) High-κ Gate Oxide Integration and Ohmic Contact Development for AlGaN/GaN MISHEMTs
Authors: Seidel Sarah , Garbe Valentin , Schmid Alexander , Heitmann Johannes
Published: May 2022

In this work we review our latest results concerning the integration of different high-κ dielectrics e.g. Al2O3, GdScO3 and TiO2 for gate passivation and the related development of ohmic contacts in metal insulator semiconductor high electron mobility transistor. Depending on deposition and crystallization temperature of the dielectric, a high-κ first and high-κ last process was used. For both concepts, the development of suitable ohmic contacts with low formation temperature were carried out. Vanadium based contacts for high-κ first and Au-free contacts for the high-κ last approach was shown. The influence of the ohmic contact formation temperature on the performance of the MISHEMT devices were studied for all high-κ gate passivation layer.
(Digital Presentation) Optimization of MIM Rectifiers for Terahertz Rectennas
Authors: Tekin Serdar B. , Almalki Saeed , Vezzoli Andrea , O’Brien Liam , Hall Steve , Chalker Paul R. , Mitrovic Ivona Z.
Published: May 2022

Metal-Insulator-Metal (MIM) rectifiers comprising thin films of Al2O3, ZnO, NiO and Nb2O5 and metal configurations of Au/Au, Au/Zn and AuCr/AuCr, have been fabricated using atomic layer deposition and radio-frequency sputtering. The effect of device area scaling from 104 µm2 to 1 µm2 on rectification properties, in particular zero-bias dynamic resistance (R0) and zero-bias responsivity (β0) has been studied and found to be of critical importance in improving diode coupling efficiency. A significant increase of current has been found for Au/3.3 nm ZnO/Au diode when compared to the reference Au/3 nm Al2O3/Au diode, that resulted in obtaining the lowest R0 of 540 W for a device area of 104 µm2. The best performing device is found to be 1 µm2 AuCr/6.77 nm NiO/AuCr featuring (R0, b0) = (461 kW, 0.76 A/W) and a coupling efficiency of 1.5 ´ 10-5 %.
(Invited, Digital Presentation) Quantum Dots Based Transparent Light Emitting Diodes
Authors: Chrzanowski Maciej , Witczak Łukasz , Podhorodecki Artur
Published: May 2022

Open-air fabrication of printable transparent and flexible devices is of great importance for the development of the optoelectronic industry. Colloidal quantum-dot light-emitting diodes (QLEDs) have recently emerged as promising candidates for displays and lightning technology due to their remarkable performance including high efficiency, brightness, and stability. However, the fabrication of flexible and transparent QLEDs using solution-based techniques is still poorly explored. In this paper, we describe high-quality thin-film transparent conductive electrodes (TCEs) based on dielectric/metal/dielectric (DMD) multilayer fabricated using spin-coating/sputtering method and Ag-mesh electrodes fabricated by Ultra Precise Deposition (UPD). We present flexible and transparent QLEDs based on green-emitting Cd-based quantum dots using previously optimized TCEs. We also compare both deposition techniques, discuss their advantages, and predict their potential impact on the development of the optoelectronic industry.
Wet Cleaning of Molybdenum for Nano Interconnects
Authors: Le Quoc-Toan , Guevenc Haci , Ibrahim Ansar , Klipp Andreas , Decoster Stefan , Murdoch Gayle , Sanchez Efrain Altamirano
Published: May 2022

The effect of various chemical solutions on the etch characteristics of molybdenum and on the removal of post-etch residues formed between Mo lines was investigated. In contrast to diluted SC1 mixtures, it was found that diluted HF solution (0.05%) and formulated semi-aqueous alkaline mixtures are highly compatible with Mo. The high etching rate measured for SC1 is attributed to the presence of the oxidizer in the mixture. Post-etch residue removal assessment performed on a semi-damascene structure with metal pitch of 32 nm showed that cleaning using diluted HF did not completely removal the residues. On the contrary, a clean using FOTOPUR R-2403, a semi-aqueous formulated mixture, resulted in efficient removal of the residues. The effect of oxygen in the plasma gas mixture and subsequent wet cleaning on the thickness of Mooxides was also performed on blanket Mo
Effect of pH and Ion Concentration on Wetting of Nanoholes and Water Structuring
Authors: Cho Hwiwon , Vereecke Guy , Kenis Karine , Kim Tae-Gon , Park Jin-Goo , Wostyn Kurt , Sanchez Efrain Altamirano
Published: May 2022

In advanced semiconductor manufacturing, with deep contact holes with an aspect ratio higher than sixty in 3D-NAND memory, higher aspect ratio patterning is one of the important issues in advanced semiconductor manufacturing. In this work, we used an in-situ ATR-FTIR spectroscopy technique to characterize the wetting of nanostructures embedded in a silica matrix by UPW and electrolyte solutions as a function of pH. There was little influence of pH on the wetting of nanoholes in the studied range of 1 to 4, but wetting seemed to be less close to the isoelectric point. Also, HCl seemed to lend a better wetting compared to HI, in opposition to their structure breaking effect according to Marcus. A correlation was observed between these observations and the CO2 solubility, indicative of the influence of water structuring.
Wet Chemical Recess Etching of Ge2Sb2Te5 for 3D PCRAM Memory Applications
Authors: Pacco Antoine , Lai Ju-Geng , Puttarame Gowda Pallavi , De Coster Hanne , Rip Jens , Wostyn Kurt , Sanchez Efrain Altamirano
Published: May 2022

GeSbTe (GST) compounds have been implemented in Phase Change Random Access Memory (PCRAM) devices. 2D scaling or stacking of PCRAM is limited by cost and therefore the development of 3D architectures is expected. A key requirement for the fabrication of this 3D architecture is the etch-back of the GST. The main objective of this study is to partially recess GST in a controllable way, leaving the surface of the GST smooth after recess. Wet isotropic recess of amorphous and crystalline blanket films as well as patterned samples was explored using commodity chemistries like APM and HPM. Due to some shortcomings of these peroxide-containing solutions, the oxidizing agent was changed from H2O2 to O3. In the ozone-containing solutions the roughness of the GST after etch-back could be controlled as well as the selectivity towards Al2O3, SiO2 and TiN ensured.
(Digital Presentation) Advanced Process Control of Dual Patterns for FinFET Mass Production
Authors: Ke Xing , Li Fengmei , Zhao Zhenyang , Ji Shiliang , Xiao Xingyu , Li Zhengning , Jiang Changcheng , Zhang Haiyang
Published: May 2022

Advanced Process Control (APC) has been widely applied in state-of-the-art semiconductor industries for the everlasting pursuit of cycle time reduction, higher yield, and zero scraps. Inline metrology is thus valuable input for the improvement of wafer-to-wafer and within-wafer CD variations originated from either abnormality or noise of different processes. Implementing a suitable APC scheme to process flow remains a challenging task for engineers. In most cases, it is enough to implement the APC to only one single pattern on Chip. However, for multi-purpose chip design, the CD control of multiple patterns is becoming important. In this paper, we presented an APC workflow to control the CD of two different patterns. It is shown that, with the same amount of APC process layers, we were able to improve from single pattern CD control to dual pattern CD control. The final process variations of two patterns can be controlled within ±0.5 nm.
(Digital Presentation) Extending the Application of Capacitively Coupled Plasma Etching Tools to the Front-End-of-Line Fin-Cut Etching Process for FinFET Mass Production
Authors: Zhao Zhenyang , Chen Zhuofan , Ke Xing , Li Fengmei , Song Jia , Ji Shiliang , Zhang Haiyang
Published: May 2022

As FinFET scales down to advanced technology nodes, Self-aligned Quadruple Patterning (SaQP) scheme is widely deployed for Fin formation, where two mandrels (MD1 and MD2) and corresponding mandrel spacers (MD1SP and MD2SP) are patterned for accurate CD transferring. The Fin-cut etching process of the MD2SP Cutting is very critical for the patterning of the Standard Cell and the SRAM patterns. This work studies the application of the Front End of Line (FEoL) MD2SP Cutting process in both inductively coupled plasma (ICP) and capacitively coupled plasma (CCP) etchers. The mismatch between the two tools is observed and discussed in detail. For CCP tools, a degradation of line width roughness (LWR) and increase of critical dimension (CD) loading between dense and isolated patterns are observed. Compared with the ICP etchers, the CCP etchers have lower plasma dissociation and stronger physical bombardment of ions. Furthermore, it is harder to control the plasma density and directionality separately. To increase CCP tool applications in FEoL processes, we introduce a Silicon coating process to modify the photoresist (PR) during the CCP etching to harden the surface of the PR and enhance the LWR performance. Furthermore, the application of atomic layer etching (ALE) technology ensures the CD loading between the dense and isolated patterns. With the application of our study, we can broaden the application of CCP tools in FEoL for FinFET mass production.
Investigation of Oxygen Reduction on Platinum Nanoparticles Deposited Onto Peat-Derived Carbon Carrier
Authors: Lobjakas Wiljar , Nerut Jaak , Kasuk Heili , Adamson Anu , Thomberg Thomas , Aruväli Jaan , Valk Peeter , Teppor Patrick , Koppel Miriam , Mikli Valdek , Volobujeva Olga , Lust Enn
Published: May 2022

Carbon supported platinum catalysts for proton exchange membrane fuel cell (PEMFC) applications have been studied intensively in the scientific community. The aim of this study was to investigate the oxygen reduction reaction (ORR) on platinum nanoparticles deposited onto peat-derived carbon. The Pt nanoparticles were deposited onto the carbon support material by three different methods – using NaBH4 (NBH), ethylene glycol (EG) or isopropyl alcohol (IA) as a reducing agent. The structure of the studied materials was characterized using N2 sorption analysis, X-ray diffraction analysis, thermogravimetric analysis and scanning electron microscopy with energy-dispersive X-ray analysis methods. For electrochemical characterization, the electrochemically active surface area (ECA) and the ORR kinetics of the materials were measured in a PEMFC. The catalytic activity of the synthesized materials depends on the Pt reduction method and increases in order: IA < NBH < EG. It was found that materials with high ECA also have high catalytic activity.
Characterisation of Novel Nitrogen Doped Reduced Graphene Oxide
Authors: Nerut Jaak , Teppor Patrick , Palm Rasmus , Jäger Rutha , Thomberg Thomas , Tuul Kenneth , Koppel Miriam , Aruväli Jaan , Kikas Arvo , Mondal Jay , Iakimov Valentino , Lust Enn
Published: May 2022

The physical and electrochemical properties of a novel nitrogen-doped reduced graphene oxide (N-rGO) material were studied. The novel material was synthesized using biological microorganisms and non-toxic chemicals. In addition, the effect of the high shear treatment on material particle size and suspension stability was investigated. The material was characterized by particle size distribution analysis, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, and gas adsorption methods. The N-rGO material has low porosity but its specific surface area and total pore volume increased fourfold and tenfold, respectively, due to the high shear treatment. Electrochemical oxygen reduction activity measurements were conducted in 0.1 M HClO₄ and 0.1 M KOH solutions using rotating disc electrode and cyclic voltammetry methods.
Optimizing The Hot-Press Procedure Of High-Temperature Proton Exchange Membrane Fuel Cells For Adhesion Strength And Conductivity
Authors: Leader Jared O , Walluk Mark R , Waller Michael G , Trabold Thomas A
Published: May 2022

High-temperature proton exchange membrane (HT-PEM) fuel cell systems are under active development for a variety of mobile and stationary power applications. Measurements of membrane-electrode assembly (MEA) thickness, impedance, and adhesion strength were obtained for samples fabricated over ranges of conditions to optimize for the most suitable processing parameters. Testing quantified the effects of hot-press time, temperature, and pressure, over ranges of 1-10 minutes, 140 – 200oC, and 7.72 – 92.67 MPa, respectively. After hot pressing, MEA samples were tested for resistance with a Solartron impedance analyzer, and for adhesion strength with a Scott internal bond tester. From these results, optimal hot-press parameters were established and four 25 cm2 MEAs were fabricated and tested. Post-pressing analysis of MEAs was conducted using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. Our results demonstrate that the optimal conditions for MEA hot-pressing for the HT-PEM system are around 170oC and 23.1 MPa for 5 minutes.
Coupling Lithium Plating with SEI Formation in a Pseudo-3D Model: A Comprehensive Approach to Describe Aging in Lithium-Ion Cells
Authors: Carelli Serena , Bessler Wolfgang G.
Published: May 2022

The lifetime of a battery is affected by various aging processes happening at the electrode scale and causing capacity and power fade over time. Two of the most critical mechanisms are the deposition of metallic lithium (plating) and the loss of lithium inventory to the solid electrolyte interphase (SEI). These side reactions compete with reversible lithium intercalation at the graphite anode. Here we present a comprehensive physicochemical pseudo-3D aging model for a lithium-ion battery cell, which includes electrochemical reactions for SEI formation on graphite anode, lithium plating, and SEI formation on plated lithium. The thermodynamics of the aging reactions are modeled depending on temperature and ion concentration, and the reactions kinetics are described with an Arrhenius-type rate law. The model includes also the positive feedback of plating on SEI growth, with the presence of plated lithium leading to a higher SEI formation rate compared to the values obtained in its absence at the same operating conditions. The model is thus able to describe cell aging over a wide range of temperatures and C-rates. In particular, it allows to quantify capacity loss due to cycling (here in % per year) as function of operating conditions. This allows the visualization of aging colormaps as function of both temperature and C-rate and the identification of critical operation conditions, a fundamental step for a comprehensive understanding of batteries performance and behavior. For example, the model predicts that at the harshest conditions (< –5 °C, > 3 C), aging is reduced compared to most critical conditions (around 0–5 °C) because the cell cannot be fully charged.
Electrodialysis of LiH2PO4 for High-Purity LiOH and Green H2 Production
Authors: Zensich M. , Rozenblit A. , Tesio A. Y. , Calvo E. J.
Published: May 2022

The current soda-lime evaporation process to recover lithium carbonate from continental brines by treatment with Solvay has a low efficiency due to the high solubility of Li2CO3, unlike precipitation of Li3PO4 after removal of alkaline earth cations, which has a very high efficiency. The main goal of this work is to provide a proof of concept for replacing the present method of LiOH.H2O production, i.e. replacing the reaction of Li
2
CO
3
with Ca(OH)2, by a single step electrodialysis of LiH2PO4 from insoluble Li3PO4 with no waste generation, recycling of phosphoric acid, better efficiency than the lithium carbonate pathway and green hydrogen generation. Experimental results have been complemented with numerical simulation of the electro-dialysis system solving the time-dependent concentration and potential profiles for two configurations: two compartments using a cation-selective membrane and a three-compartment cell with cation and anion-selective membranes operating at constant current, along with the voltage evolution and current efficiency for LiOH production.
Degradation Mechanisms in Advanced MEAs for PEM Water Electrolyzers Fabricated by Reactive Spray Deposition Technology
Authors: Zeng Zhiqiao , Ouimet Ryan , Bonville Leonard , Niedzwiecki Allison , Capuano Chris , Ayers Katherine , Soleymani Amir Peyman , Jankovic Jasna , Yu Haoran , Mirshekari Gholamreza , Maric Radenka , Bliznakov Stoyan
Published: May 2022

Proton exchange membrane water electrolyzers (PEMWEs) have demonstrated enormous potential as the next generation hydrogen production technology. The main challenges that the state-of-the-art PEMWEs are currently facing are excessive cost and poor durability. Understanding the failure modes in PEMWEs is a key factor for improving their durability, lowering the precious metal loading, and hence cost reduction. In this work, reactive spray deposition technology (RSDT) has been used to fabricate a membrane electrode assembly (MEA) with one order of magnitude lower Pt and Ir catalyst loadings (0.2–0.3 mgPGMcm−2) in comparison to the precious metal loadings in the stat-of-the-art commercial MEAs (2–3 mgPGMcm−2). As fabricated MEA with an active area of 86 cm2, has been tested for over 5000 h at steady-state conditions that are typical for an industrial hydrogen production system. Herein, we present and discuss the results from a comprehensive post-test analysis of the MEA of interest. The main degradation mechanisms, governing the performance loss in the RSDT fabricated MEA with ultra-low precious metal loadings, have been identified and discussed in detail. All failure modes are critically compared and the main degradation mechanism with the highest impact on the MEA performance loss among the others is identified.
Electrolyte Solvation and Ionic Association: VIII. Reassessing Raman Spectroscopic Studies of Ion Coordination for LiTFSI
Authors: Henderson Wesley A. , Helm Monte L. , Seo Daniel M. , Trulove Paul C. , De Long Hugh C. , Borodin Oleg
Published: May 2022

Raman spectroscopy is widely used to evaluate the ionic interactions and solvates present in electrolytes. As shown here, however, Raman spectra for crystalline solvates containing the lithium bis(trifluoromethanesulfonyl)imide (or amide) (i.e., LiN(SO2CF3)2, LiTFSI, LiTFSA, LiNTf2 or LiTf2N) salt indicate that the commonly used vibrational band analyses are likely to be inaccurate and thus result in misleading conclusions about the ion interactions in liquid electrolytes with this salt. In particular, it is found by examining the Raman spectrum of a known crystalline solvate with the CIP-I-C
2 coordination mode (i.e., a TFSI− anion with a C
2 conformation coordinated to a single Li+ cation via a single oxygen atom), that the vibrational band for this mode of coordination overlaps (or is closely positioned beside) that for the uncoordinated (i.e., SSIP) TFSI− anion. This realization further complicates the assessment of Raman data for LiTFSI-based electrolytes.
Dimethyl Sulfoxide Treated Ti3C2TX as a Catalyst for V3+/V2+ Reaction in Vanadium Redox Flow Batteries
Authors: Li Qiang , Zhang Xianduo , Sun Hong
Published: May 2022

To enable the excellent performance of vanadium redox flow batteries (VRFBs) at high current density, dimethyl sulfoxide (DMSO) treated Ti3C2TX as an electrocatalyst for V3+/V2+ reaction is proposed in this paper. Furthermore, the influence of treatment method on the property of surface terminations of Ti3C2TX and the corresponding catalytic activity toward V3+/V2+ reaction is revealed. The results demonstrate that DMSO treated Ti3C2TX exhibits better catalytic activity than sodium hydroxide (NaOH) treated Ti3C2TX. The cell equipped with DMSO treated Ti3C2TX presents an energy efficiency (EE) of 81.5% and discharge capacity of 690 mAh at the current density of 150 mA·cm−2, which is 16.2% and 30.9% higher than that with polyacrylonitrile-based graphite felt (GF). Additionally, the efficiency of the cell has no decay during 400 cycles of charge-discharge tests at 150 mA·cm−2. The improved cell performance is attributed to abundant active sites and improved reaction kinetics toward V3+/V2+ reaction due to introducing DMSO treated Ti3C2TX.
Vibrational Entropy Contribution to Mixing Free Energy of Ni-Rich LiNi1-y
Co
y
O2
Authors: Benedek Roy
Published: May 2022

First principles density-functional-theory calculations are performed of the mixing free energy of the layered oxide LiNi1−y
Co
y
O2, a model Li-ion-battery cathode material, at 1000 K. Analysis of internal energy, LN exchange, configurational entropy and vibrational entropy are combined to obtain the net mixing free energy. The vibrational entropy requires a more indirect treatment than the other terms; analysis based on heat capacity is presented to show that the vibrational entropy is of comparable magnitude to the configurational entropy, and it tends to promote solid-solution behavior in LiNi1−y
Co
y
O2.
Intelligent Physical Training Data Processing Based on Wearable Devices
Authors: Liu Xuguang
Published: May 2022

Intelligent processing of physical training data based on wearable devices is conducive to improving the efficiency and rationality of physical training. The current data processing methods cannot effectively extract the features contained in the data, resulting in low accuracy in tasks such as classification. This paper proposes an intelligent processing method for sports training data based on statistical methods and deep learning methods. First, the original data are preprocessed by some statistical methods to obtain the original feature vector. Then, the autoencoder model is used to extract the high-level hidden features in the original data. Finally, we input the extracted feature vector into a designed convolutional neural network classification model and generate the final classification result. Evaluation on the open Human Activity Recognition Using Smartphones Dataset shows that our proposed method achieves the best results compared with current methods.
Inequalities Involving A‐Numerical Radius and Operator A‐Norm for a Class of Operators Related to (α, β) − A‐Normal Operators
Authors: Ould Ahmed Mahmoud Sid Ahmed , Jah Sidi Hamidou
Published: May 2022

In this article, we introduce and study a new class of operators, larger than (α, β) − A‐normal operators and different than (α, β) − A‐normal operators, named m‐quasi‐(α, β) − A‐normal operators. Considering the semi‐inner product induced by a positive operator A, the m‐quasi‐(α, β) − A‐normal operators turn into a generalization (for this new structure) of classical m‐quasi‐(α, β)‐normal operators. Several results concerning properties of this kind of operators are presented in the paper. Several inequalities for the A‐numerical radius and A‐operator norm for members of this class are established.
Effectiveness of “Internet+” Based Cardiac Rehabilitation on Prognosis of Patients with Coronary Heart Disease: A Meta-Analysis
Authors: Ding Meng , Zhang Fan , Hu Jiashun
Published: May 2022

Objective. Meta-analysis was used to systematically evaluate the impact of Internet-based cardiac rehabilitation on the health of patients with coronary heart disease. Methods. Randomized controlled trial study (RCTs) of the effects of Internet-based cardiac rehabilitation on cardiovascular risk factors, motor function and psychological status in patients with coronary heart disease has been systematically studied. Results. A total of 13 articles were included. Meta-analysis showed that internet-based cardiac rehabilitation training could effectively reduce the total cholesterol level [MD = -0.15, 95% CI (-0.28, -0.02), P = 0.02] and triglyceride level [MD = -0.19, 95% CI (-0.32, -0.06), P = 0.01], increase the maximal oxygen uptake (VO2 max) [MD = 0.9995, CI (0.161.83) P = 0.02] and physical activity level [SMD = 0.51, 95% CI (0.07, 0.9), P = 0.02], and improve the self-efficacy [SMD = 0.50, 95% CI (0.17, 0.83), P = 0.01] and improved quality of life [SMD = 1.34, 95% CI (0.12, 2.56), P = 0.03] of patients. However, there was no significant improvement in blood pressure and body mass index, depression and anxiety. Conclusion. Internet-based cardiac rehabilitation can significantly reduce cholesterol and triglyceride levels and improve theVO2 max, physical activity, self-efficacy and quality of life, but is not effective on the level of blood pressure, BMI, anxiety and depression. Due to the limitations of methodological quality and sample size of included studies, more studies with high-quality and large sample are needed to further evaluate its effectiveness.
Influence of Drying Temperature on the Different Thermodynamic Parameters during the Indirect Convective Solar Drying of Crocus sativus L. Of Morocco Thin-Layer Solar Drying of Moroccan Saffron
Authors: Oubella Khadija , Mouhanni Hind , Bahammou Younes , Idlimam Ali , Lamharrar Abdelkader , Bendou Abdelaziz
Published: May 2022

This work deals with the study of the drying kinetics of Crocus sativus L. using convective solar drying. The main objective was to identify the influence of airflow drying temperatures for ambient air temperature ranged between 15.6 and 18.9°C, and a relative humidity between 24.4 and 46.5%. The equilibrium moisture content varies from 0.09 to 0.06 (% d.b), respectively, for drying air temperatures 35–50°C. The airflow velocity was about 0.2 m s−1, which implied establishing a phenomenological diffusion model of the water within the matrix. Empirical models were also determined as well as a polynomial equation (order 3) of the characteristic drying curve. The Midilli–Kucuk model was found to be the best to describe the experimental drying curves of Crocus sativus L. The effective moisture diffusivity ranged between 0.87 and 1.46 10−11 m2 s−1 for airflow temperature 35 and 50°C, while the average activation energy was calculated as 28.76 kJ mol−1. The increase in temperature decreases the total energy consumption which varies, respectively, from 3.211 to 2.681 kWh.
Effects of Variable Proportions of Concrete Fragments on Urban Soil Moisture Transport: An Experimental and Simulation Study
Authors: Yang Changkun , Jiang Gengmin , Wang Siyu , Han Xinyu , Xu Jun , Zhao Dongsheng
Published: May 2022

In order to investigate the effects of typical anthropogenic concrete fragments on moisture infiltration and evaporation in urban soils, the effects of typical anthropogenic concrete fragments on wetting peak transport distance, cumulative infiltration, cumulative evaporation, evaporation rate, and soil profile moisture at four levels (0, 5%, 10%, and 20%) were investigated by indoor soil column experiments. The results showed that the presence of concrete fragments promoted the wetting peak transport distance and cumulative infiltration, and the promotion effect increased gradually with the increase of the ratio, but there was a threshold value, and the promotion effect was least when the ratio was 20%. When the evaporation period was 35 d, concrete fragment treatment can increase the cumulative evaporation and promote the evaporation of urban soil moisture; the promotion effect increases with the increase of the proportion, but there is a threshold value; when the proportion is 20%, the promotion effect is the smallest. The evaporation rate was consistent with the different stages of evaporation process during evaporation. The concrete fragment treatment reduced the time required for moisture to reach the same depth during infiltration; the moisture coefficient of variation of the concrete fragment treatment during evaporation showed a trend of decreasing, then increasing, and then decreasing, which increased the uncertainty of moisture in the evaporation process. The model simulation results show that the models such as the power function, Kostiakov model, and Rose model fit well, and the coefficient of determination

R

2

is greater than 0.99, among which the Kostiakov model fits best. The research results can provide a theoretical scientific basis for building an efficient ecological city.