bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of Micro-Spikes and Herringbones Structures by Femtosecond Laser Pulses on a Titanium Plate—A New Material for Water Organic Pollutants Degradation
Authors: Kisała Joanna , Gnilitskyi Iaroslav , Cieniek Bogumił , Krzemiński Piotr , Marchewka Michał , Barylyak Adriana , Bobitski Yaroslav
Published: September 2021

(1) Background: The shrinkage of water resources, as well as the deterioration of its quality as a result of industrial human activities, requires a comprehensive approach relative to its protection. Advanced oxidation processes show high potential for the degradation of organic pollutants in water and wastewater. TiO2 is the most popular photocatalyst because of its oxidizing ability, chemical stability and low cost. The major drawback of using it in powdered form is the difficulty of separation from the reaction mixture. The solution to this problem may be immobilization on a support (glass beads, molecular sieves, etc.). In order to avoid these difficulties, the authors propose to prepare a catalyst as a titanium plate covered with an oxide layer obtained with laser treatment. (2) Methods: In the present work, we generated titanium oxide structures using a cheap and fast method based on femtosecond laser pulses. The structurized plates were tested in the reaction of methylene blue (MB) degradation under UVA irradiation (365 nm). The photocatalytic activity and kinetic properties for the degradation of MB are provided. (3) Results: Studies of X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirm a titanium oxide layer with laser-induced generated structures that are called “spikes” and “herringbones”. The structurized plates were effective photocatalysts, and their activity depends on the structure of the oxide layer (spike and herringbone). (4) Conclusions: The immobilization of the catalyst on a solid support can be performed in a fast and reproducible manner by using the technique of laser ablation. The layers obtained with this method have been shown to have catalytic properties.
Effect of Particle Size Distributions and Shapes on the Failure Behavior of Dry Coke Aggregates
Authors: Sadeghi-Chahardeh Alireza , Mollaabbasi Roozbeh , Picard Donald , Taghavi Seyed Mohammad , Alamdari Houshang
Published: September 2021

Carbon anodes participate in chemical reactions to reduce alumina in the Hall–Héroult process, of which coke aggregates make up a major part. The failure analysis of coke aggregates not only leads to a better understanding of the deformation mechanisms of anode paste under compressive loading but also can identify potential causes of structural defects in carbon anodes, such as horizontal cracks. The coke aggregates are composed of particles with different size distributions and shapes, which may strongly affect the failure behavior of the anode during compaction. In this paper, the effects of particle size distributions and shapes on the mechanical behavior and the failure of coke aggregates are investigated using the discrete element method modeling technique. The numerical results reveal that, although the mechanical behavior of coke mixtures is generally dependent on larger particles, the presence of fine particles in the coke aggregates reduces fluctuations in the stress–strain diagram. In addition, the rolling resistance model is employed as a parameter representing the effect of particle shape. It is shown that the rolling resistance model can be an alternative to the overlapped spheres model, which has a higher computational cost than the rolling resistance model. The second-order work criterion is used to evaluate the stability of the coke aggregates, the results of which indicate that the addition of fine particles as well as increasing the rolling resistance between the particles increases the stability range of the coke aggregates. Moreover, by using the analysis of micro-strain contour evaluations during the compaction process, it is shown that, both by adding fine particles to the coke mixture and by increasing the rolling resistance between the particles, the possibility of creating a compression band in the coke aggregates is reduced. Since the presence of the compaction bands in the anode paste creates an area prone to horizontal crack generations, the results of this study could lead to the production of carbon anodes with fewer structural defects.
Experimental Investigation to Study the Feasibility of Fabricating Ultra-Conductive Copper Using a Hybrid Method
Authors: Pallikonda Mahesh K. , Nayfeh Taysir H.
Published: September 2021

Ultra-conductive copper (UCC) has an enormous potential to disrupt the existing electrical and electronic systems. Recent studies on carbon nanotubes (CNTs), a new class of materials, showed the ballistic conductance of electricity. Researchers around the world are able to demonstrate ultra-conductivity in micro- and millimeter-length sections using various processing techniques by embedding CNTs in the copper matrix. Although multiple methods promise the possibility of producing copper-based nanocomposites with gains in electrical conductivity, thus far, scaling up these results has been quite a challenge. We investigated a hybrid method of both hot-pressing followed by rolling in order to produce UCC wire. Cu/CNT billets of 1/10%, 1/15%, and 1/20% were hot-pressed and the conductivity results were compared to a hot-pressed pure copper billet. Our results indicated that this method is not a viable approach, as the gains in electrical conductivity are neutralized, followed by attenuation of the wire cross-section.
Microstructure Evolution Mechanism of Wf/Cu82Al10Fe4Ni4 Composites under Dynamic Compression at Different Temperatures and Strain Rates
Authors: Wu Zhe , Zhang Yang , Jiang Haifeng , Zhao Shuai , Wang Qingnan
Published: September 2021

Wf/Cu82Al10Fe4Ni4 composites were fabricated by the pressure infiltration method. The composites were compressed by means of a split Hopkinson pressure bar (SHPB) with strain rates of 800 and 1600 s−1 at different temperatures. The microstructure of the composites after dynamic compressing was analyzed by transmission electron microscopy (TEM). Observation revealed that there were high-density dislocations, stacking faults, twins, and recrystallization existing in the copper alloy matrix of the composites. High-density dislocations, stacking faults, and twins were generated due to the significant plastic deformation of the copper alloy matrix under dynamic load impact. We also found that the precipitated phase of the matrix played a role in the second phase strengthening; recrystallized microstructures of copper alloy were generated due to dynamic recrystallization of the copper alloy matrix under dynamic compression at high temperatures.
Influence of the Gap between Substrates in the Laser-Induced Transference of High-Viscosity Pastes
Authors: Moreno-Labella Juan José , Munoz-Martin David , Vallejo Guillermo , Molpeceres Carlos , Morales Miguel
Published: September 2021

Laser-induced forward transfer for high-viscosity—of Pa·s—pastes differ from standard LIFT processes in its dynamics. In most techniques, the transference after setting a great gap does not modify the shape acquired by the fluid, so it stretches until it breaks into droplets. In contrast, there is no transferred material when the gap is bigger than three times the paste thickness in LIFT for high-viscosity pastes, and only a spray is observed on the acceptor using this configuration. In this work, the dynamics of the paste have been studied using a finite-element model in COMSOL Multiphysics, and the behavior of the paste varying the gap between the donor and the acceptor substrates has also been modeled. The paste bursts for great gaps, but it is confined when the acceptor is placed close enough. The obtained simulations have been compared with a previous work, in which the paste structures were photographed. The analysis of the simulations in terms of speed allows for predicting the burst of the paste—spray regime—and the construction of a printability map regarding the gap between the substrates.
Spiky Durian-Shaped Au@Ag Nanoparticles in PEDOT:PSS for Improved Efficiency of Organic Solar Cells
Authors: Alkhalayfeh Muheeb Ahmad , Abdul Aziz Azlan , Pakhuruddin Mohd Zamir , M. Katubi Khadijah Mohammedsaleh
Published: September 2021

The localized surface plasmon resonance (LSPR) effects of nanoparticles (NPs) are effective for enhancing the power conversion efficiency (PCE) of organic solar cells (OSCs). In this study, spiky durian-shaped Au@Ag core-shell NPs were synthesized and embedded in the hole transport layer (HTL) (poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)) of PTB7:PC71BM bulk-heterojunction OSCs. Different volume ratios of PEDOT:PSS-to-Au@Ag NPs (8%, 10%, 12%, 14%, and 16%) were prepared to optimize synthesis conditions for increased efficiency. The size properties and surface morphology of the NPs and HTL were analyzed using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). UV–Vis spectroscopy and current density–voltage (J-V) analysis were used to investigate the electrical performance of the fabricated OSCs. From the results, we observed that the OSC with a volume ratio of 14% (PEDOT:PSS–to–Au@Ag NPs) performed better than others, where the PCE was improved from 2.50% to 4.15%, which is a 66% increase compared to the device without NPs.
Laboratory Evaluation of Mechanical Properties of Modified Asphalt and Mixture Using Graphene Platelets (GnPs)
Authors: Eisa Mohamed Samir , Mohamady Ahmed , Basiouny Mohamed E. , Abdulhamid Ayman , Kim Jong R.
Published: September 2021

Recently, nanomaterials have attracted attention in the field of pavement construction as modifiers to endure heavy loads and climate changes. In this study, conventional asphalt (bitumen) of penetration grade AC (60/70) was modified with graphene platelets (GnPs) at three different contents: 0.5%, 1.0%, and 1.5% by weight of asphalt content. Kinematic viscosity, softening point, penetration, and dynamic shear rheology tests were performed to evaluate the mechanical properties of modified binder. The results showed that adding GnPs improves the mechanical properties of asphalt binder; the kinematic viscosities, softening points, and rutting parameters increased but penetrations decreased with the contents of GnPs. Hot mix asphalt specimens with GnPs-modified asphalt were prepared and characterized with Marshall tests, thermal stress restrained specimen tests (TSRST), wheel tracking tests, and indirect tensile tests. Similar to the results of asphalt binder, the mechanical properties of asphalt mixture were improved by GnPs. Marshall stability increased by 21% and flow decreased by 24% with accepted value of 2.8 mm in penetration when the mixture was modified with 1.0 wt% of GnPs. At the same GnPs content, modified asphalt mixture led to lower failure temperature by 2 °C in comparison with unmodified asphalt mixture and the cryogenic failure stress was improved by 12%. The wheel tracking tests showed that GnPs-modified asphalt mixture has outstanding deformation resistance in comparison with unmodified asphalt mixtures: after 5000 cycles, 1.0 wt% of GnPs reduced the rut depth of asphalt mixture by 60%—the rut depth of unmodified asphalt mixture was 6.9 mm compared to 2.75 mm for modified asphalt mixture. After 10,000 cycles, the modified asphalt mixture showed rut depth of 3.24 mm in comparison with 8.12 mm in case of unmodified asphalt mixture. Addition of GnPs into asphalt mixture significantly improved the indirect tensile strength: 1.0 wt% of GnPs increased the indirect tensile strength of unmodified asphalt mixture from 0.79 to 1.1 MPa recording ~40% increment. The results of this study can confirm that graphene platelets enhance the mechanical properties of asphalt mixture and its performance.
Strength and Durability Properties of Antimony Tailing Coarse Aggregate (ATCA) Concrete
Authors: Li Long , Wang Jianqun , Zhang Longwei , Deng Renjian , Zhou Saijun , Wang Gongxun
Published: September 2021

Antimony (Sb) is a trace element applied widely in modern industry. A large number of tailing solid wastes are left and accumulated in the mining area after purifying the precious antimony from the antimony ores, causing serious pollution to the environment. The major aim of this study is to investigate the feasibility of utilizing antimony tailing coarse aggregate (ATCA) as a complete substitute for natural coarse aggregate (NCA) in high-strength concrete. Concrete specimens with 25%, 50%, 75%, and 100% ATCA replacing the NCA in conventional concrete were prepared for evaluating the performance of ATCA concrete. The investigators find that ATCA concrete has good workability, and the mechanical properties and long-term behavior (shrinkage and creep) of ATCA concrete with all replacement levels are superior to those of NCA concrete. The durability indices of ATCA concrete, such as the frost-resistant, chloride permeability, and resistance to carbonation, are better than those of NCA concrete. While the alkali activity and cracking sensitivity behavior of ATCA concrete seem to be decreased, nevertheless, the difference is not significant and can be neglected. The researchers demonstrate that all of the control indices of ATCA concrete meet the requirements of the current industry standards of China. Overall, ATCA can be used in concrete to minimize environmental problems and natural resources depletion.
Tensile and Impact Toughness Properties of a Zr-Based Bulk Metallic Glass Fabricated via Laser Powder-Bed Fusion
Authors: Sohrabi Navid , Parrilli Annapaola , Jhabvala Jamasp , Neels Antonia , Logé Roland E.
Published: September 2021

In the past few years, laser powder-bed fusion (LPBF) of bulk metallic glasses (BMGs) has gained significant interest because of the high heating and cooling rates inherent to the process, providing the means to bypass the crystallization threshold. In this study, (for the first time) the tensile and Charpy impact toughness properties of a Zr-based BMG fabricated via LPBF were investigated. The presence of defects and lack of fusion (LoF) in the near-surface region of the samples resulted in low properties. Increasing the laser power at the borders mitigated LoF formation in the near-surface region, leading to an almost 27% increase in tensile yield strength and impact toughness. Comparatively, increasing the core laser power did not have a significant influence. It was therefore confirmed that, for BMGs like for crystalline alloys, near-surface LoFs are more detrimental than core LoFs. Although increasing the border and core laser power resulted in a higher crystallized fraction, detrimental to the mechanical properties, reducing the formation of LoF defects (confirmed using micro-computed tomography, Micro-CT) was comparatively more important.
A Data-Driven Framework for Early-Stage Fatigue Damage Detection in Aluminum Alloys Using Ultrasonic Sensors
Authors: Dharmadhikari Susheel , Bhattacharya Chandrachur , Ray Asok , Basak Amrita
Published: September 2021

The paper presents a coupled machine learning and pattern recognition algorithm to enable early-stage fatigue damage detection in aerospace-grade aluminum alloys. U- and V-notched Al7075-T6 specimens are instrumented with a pair of ultrasonic sensors and, thereafter, tested on an MTS apparatus integrated with a confocal microscope and a digital microscope. The confocal microscope is focused on the notch root of the specimens, whereas the digital microscope is focused on the side of the notch. Two features, viz., the crack opening displacement (COD) and the crack length, are extracted during the tests in addition to the ultrasonic signal data. These signal data are analyzed using a machine learning framework that is built upon a symbolic time-series algorithm. This framework is interrogated for crack detection in the crack coalescence (CC) regime defined by COD of ~3 μm and detected through the confocal microscope. Additionally, the framework is probed in the crack propagation (CP) regime characterized by a crack length of ~0.2 mm and detected via the digital microscope. For the CC regime, training accuracies of 79.82% and 81.94% are achieved, whereas testing accuracies of 68.18% and 74.12% are observed for the U- and V-notched specimens, respectively. For the CP regime, overall training accuracies of 88.3% and 91.85% are observed, and accordingly, testing accuracies of 81.94% and 85.62% are obtained for the U- and V-notched specimens, respectively. The results show that a combined machine learning and pattern recognition algorithm enables robust and reliable fatigue damage detection in aerospace structural components.
Continuous Control of an Underground Loader Using Deep Reinforcement Learning
Authors: Backman Sofi , Lindmark Daniel , Bodin Kenneth , Servin Martin , Mörk Joakim , Löfgren Håkan
Published: September 2021

The reinforcement learning control of an underground loader was investigated in a simulated environment by using a multi-agent deep neural network approach. At the start of each loading cycle, one agent selects the dig position from a depth camera image of a pile of fragmented rock. A second agent is responsible for continuous control of the vehicle, with the goal of filling the bucket at the selected loading point while avoiding collisions, getting stuck, or losing ground traction. This relies on motion and force sensors, as well as on a camera and lidar. Using a soft actor–critic algorithm, the agents learn policies for efficient bucket filling over many subsequent loading cycles, with a clear ability to adapt to the changing environment. The best results—on average, 75% of the max capacity—were obtained when including a penalty for energy usage in the reward.
G3 Shape Adjustable GHT-Bézier Developable Surfaces and Their Applications
Authors: BiBi Samia , Misro Md Yushalify , Abbas Muhammad , Majeed Abdul , Nazir Tahir
Published: September 2021

In this article, we proposed a novel method for the construction of generalized hybrid trigonometric (GHT-Bézier) developable surfaces to tackle the issue of modeling and shape designing in engineering. The GHT-Bézier developable surface is obtained by using the duality principle between the points and planes with GHT-Bézier curve. With different shape control parameters in their domain, a class of GHT-Bézier developable surfaces can be established (such as enveloping developable GHT-Bézier surfaces, spine curve developable GHT-Bézier surfaces, geodesic interpolating surfaces for GHT-Bézier surface and developable GHT-Bézier canal surfaces), which possess many properties of GHT-Bézier surfaces. By changing the values of shape parameters the effect on the developable surface is obvious. In addition, some useful geometric properties of GHT-Bézier developable surface and the G1, G2 (Farin-Boehm and Beta) and G3 continuity conditions between any two GHT-Bézier developable surfaces are derived. Furthermore, various useful and representative numerical examples demonstrate the convenience and efficiency of the proposed method.
Adaptive Robust Motion Control of Quadrotor Systems Using Artificial Neural Networks and Particle Swarm Optimization
Authors: Yañez-Badillo Hugo , Beltran-Carbajal Francisco , Tapia-Olvera Ruben , Favela-Contreras Antonio , Sotelo Carlos , Sotelo David
Published: September 2021

Most of the mechanical dynamic systems are subjected to parametric uncertainty, unmodeled dynamics, and undesired external vibrating disturbances while are motion controlled. In this regard, new adaptive and robust, advanced control theories have been developed to efficiently regulate the motion trajectories of these dynamic systems while dealing with several kinds of variable disturbances. In this work, a novel adaptive robust neural control design approach for efficient motion trajectory tracking control tasks for a considerably disturbed non-linear under-actuated quadrotor system is introduced. Self-adaptive disturbance signal modeling based on Taylor-series expansions to handle dynamic uncertainty is adopted. Dynamic compensators of planned motion tracking errors are then used for designing a baseline controller with adaptive capabilities provided by three layers B-spline artificial neural networks (Bs-ANN). In the presented adaptive robust control scheme, measurements of position signals are only required. Moreover, real-time accurate estimation of time-varying disturbances and time derivatives of error signals are unnecessary. Integral reconstructors of velocity error signals are properly integrated in the output error signal feedback control scheme. In addition, the appropriate combination of several mathematical tools, such as particle swarm optimization (PSO), Bézier polynomials, artificial neural networks, and Taylor-series expansions, are advantageously exploited in the proposed control design perspective. In this fashion, the present contribution introduces a new adaptive desired motion tracking control solution based on B-spline neural networks, along with dynamic tracking error compensators for quadrotor non-linear systems. Several numeric experiments were performed to assess and highlight the effectiveness of the adaptive robust motion tracking control for a quadrotor unmanned aerial vehicle while subjected to undesired vibrating disturbances. Experiments include important scenarios that commonly face the quadrotors as path and trajectory tracking, take-off and landing, variations of the quadrotor nominal mass and basic navigation. Obtained results evidence a satisfactory quadrotor motion control while acceptable attenuation levels of vibrating disturbances are exhibited.
An Investigation of an Integral Equation Involving Convex–Concave Nonlinearities
Authors: Agarwal Ravi P. , Jleli Mohamed , Samet Bessem
Published: September 2021

We investigate the existence and uniqueness of positive solutions to an integral equation involving convex or concave nonlinearities. A numerical algorithm based on Picard iterations is provided to obtain an approximation of the unique solution. The main tools used in this work are based on partial-ordering methods and fixed-point theory. Our results are supported by examples.
Imperceptible–Visible Watermarking to Information Security Tasks in Color Imaging
Authors: Juarez-Sandoval Oswaldo Ulises , Garcia-Ugalde Francisco Javier , Cedillo-Hernandez Manuel , Ramirez-Hernandez Jazmin , Hernandez-Gonzalez Leobardo
Published: September 2021

Digital image watermarking algorithms have been designed for intellectual property, copyright protection, medical data management, and other related fields; furthermore, in real-world applications such as official documents, banknotes, etc., they are used to deliver additional information about the documents’ authenticity. In this context, the imperceptible–visible watermarking (IVW) algorithm has been designed as a digital reproduction of the real-world watermarks. This paper presents a new improved IVW algorithm for copyright protection that can deliver additional information to the image content. The proposed algorithm is divided into two stages: in the embedding stage, a human visual system-based strategy is used to embed an owner logotype or a 2D quick response (QR) code as a watermark into a color image, maintaining a high watermark imperceptibility and low image-quality degradation. In the exhibition, a new histogram binarization function approach is introduced to exhibit any watermark with enough quality to be recognized or decoded by any application, which is focused on reading QR codes. The experimental results show that the proposed algorithm can embed one or more watermark patterns, maintaining the high imperceptibility and visual quality of the embedded and the exhibited watermark. The performance evaluation shows that the method overcomes several drawbacks reported in previous algorithms, including geometric and image processing attacks such as JPEG and JPEG2000.
A Metaheuristic Algorithm for Flexible Energy Storage Management in Residential Electricity Distribution Grids
Authors: Ivanov Ovidiu , Neagu Bogdan-Constantin , Grigoras Gheorghe , Scarlatache Florina , Gavrilas Mihai
Published: September 2021

The global climate change mitigation efforts have increased the efforts of national governments to incentivize local households in adopting PV panels for local electricity generation. Since PV generation is available during the daytime, at off-peak hours, the optimal management of such installations often considers local storage that can defer the use of local generation to a later time. The energy stored in batteries located in optimal places in the network can be used by the utility to improve the operation conditions in the network. This paper proposes a metaheuristic approach based on a genetic algorithm that considers three different scenarios of using energy storage for reducing the energy losses in the network. Two cases considers the battery placement and operation under the direct control of the network operator, with single and multiple bus and phase placement locations. Here, the aim was to maximize the benefit for the whole network. The third case considers selfish prosumer battery management, where the storage owner uses the batteries only for their own benefit. The optimal design of the genetic algorithm and of the solution encoding allows for a comparative study of the results, highlighting the important strengths and weaknesses of each scenario. A case study is performed in a real distribution system.
On the Complex-Valued Distribution Function of Charged Particles in Magnetic Fields
Authors: Saveliev Andrey
Published: September 2021

In this work, we revisit Boltzmann’s distribution function, which, together with the Boltzmann equation, forms the basis for the kinetic theory of gases and solutions to problems in hydrodynamics. We show that magnetic fields may be included as an intrinsic constituent of the distribution function by theoretically motivating, deriving and analyzing its complex-valued version in its most general form. We then validate these considerations by using it to derive the equations of ideal magnetohydrodynamics, thus showing that our method, based on Boltzmann’s formalism, is suitable to describe the dynamics of charged particles in magnetic fields.
Optimal Stochastic Control in the Interception Problem of a Randomly Tacking Vehicle
Authors: Galyaev Andrey A. , Lysenko Pavel V. , Rubinovich Evgeny Y.
Published: September 2021

This article considers the mathematical aspects of the problem of the optimal interception of a mobile search vehicle moving along random tacks on a given route and searching for a target, which travels parallel to this route. Interception begins when the probability of the target being detected by the search vehicle exceeds a certain threshold value. Interception was carried out by a controlled vehicle (defender) protecting the target. An analytical estimation of this detection probability is proposed. The interception problem was formulated as an optimal stochastic control problem, which was transformed to a deterministic optimization problem. As a result, the optimal control law of the defender was found, and the optimal interception time was estimated. The deterministic problem is a simplified version of the problem whose optimal solution provides a suboptimal solution to the stochastic problem. The obtained control law was compared with classic guidance methods. All the results were obtained analytically and validated with a computer simulation.
Analysis of MAP/PH/1 Queueing System with Degrading Service Rate and Phase Type Vacation
Authors: Choudhary Alka , Chakravarthy Srinivas R. , Sharma Dinesh C.
Published: September 2021

Degradation of services arises in practice due to a variety of reasons including wear-and-tear of machinery and fatigue. In this paper, we look at MAP/PH/1-type queueing models in which degradation is introduced. There are several ways to incorporate degradation into a service system. Here, we model the degradation in the form of the service rate declining (i.e., the service rate decreases with the number of services offered) until the degradation is addressed. The service rate is reset to the original rate either after a fixed number of services is offered or when the server becomes idle. We look at two models. In the first, we assume that the degradation is instantaneously fixed, and in the second model, there is a random time that is needed to address the degradation issue. These models are analyzed in steady state using the classical matrix-analytic methods. Illustrative numerical examples are provided. Comparisons of both the models are drawn.
Improved Constrained k-Means Algorithm for Clustering with Domain Knowledge
Authors: Huang Peihuang , Yao Pei , Hao Zhendong , Peng Huihong , Guo Longkun
Published: September 2021

Witnessing the tremendous development of machine learning technology, emerging machine learning applications impose challenges of using domain knowledge to improve the accuracy of clustering provided that clustering suffers a compromising accuracy rate despite its advantage of fast procession. In this paper, we model domain knowledge (i.e., background knowledge or side information), respecting some applications as must-link and cannot-link sets, for the sake of collaborating with k-means for better accuracy. We first propose an algorithm for constrained k-means, considering only must-links. The key idea is to consider a set of data points constrained by the must-links as a single data point with a weight equal to the weight sum of the constrained points. Then, for clustering the data points set with cannot-link, we employ minimum-weight matching to assign the data points to the existing clusters. At last, we carried out a numerical simulation to evaluate the proposed algorithms against the UCI datasets, demonstrating that our method outperforms the previous algorithms for constrained k-means as well as the traditional k-means regarding the clustering accuracy rate although with a slightly compromised practical runtime.
Fuzzy Bit-Plane-Dependence Region Competition
Authors: Choy Siukai , Ng Tszching , Yu Carisa , Lam Benson
Published: September 2021

This paper presents a novel variational model based on fuzzy region competition and statistical image variation modeling for image segmentation. In the energy functional of the proposed model, each region is characterized by the pixel-level color feature and region-level spatial/frequency information extracted from various image domains, which are modeled by the windowed bit-plane-dependence probability models. To efficiently minimize the energy functional, we apply an alternating minimization procedure with the use of Chambolle’s fast duality projection algorithm, where the closed-form solutions of the energy functional are obtained. Our method gives soft segmentation result via the fuzzy membership function, and moreover, the use of multi-domain statistical region characterization provides additional information that can enhance the segmentation accuracy. Experimental results indicate that the proposed method has a superior performance and outperforms the current state-of-the-art superpixel-based and deep-learning-based approaches.
Geopolitical Uncertainties and Malaysian Stock Market Returns: Do Market Conditions Matter?
Authors: Hoque Mohammad Enamul , Zaidi Mohd Azlan Shah , Hassan M. Kabir
Published: September 2021

Geopolitical uncertainties have been a concern for global economies and financial markets’ participants. By employing Markov switching regression and quantile regression, we investigated the effect of global and country-specific geopolitical uncertainties on Malaysian Conventional and Islamic stock returns in different market conditions. The estimated results of the Markov switching regression show that Malaysian conventional and Islamic stocks react differently to global and country-specific geopolitical uncertainties under different market volatility conditions, implying volatility dependent exposures and reactions to global and country-specific geopolitical uncertainties. The quantile regression results also reveal that Malaysian conventional and Islamic stocks respond differently to global and country-specific geopolitical uncertainties at different market stages. The empirical findings, therefore, indicate a heterogeneous and non-linear stock reaction to geopolitical uncertainties, providing new insights into geopolitical uncertainties and stock return relationships. Hence, the results will be valuable for asset pricing and investments in an emerging market such as the Malaysian market.
A Comparative Analysis of Some Methods for Wind Turbine Maximum Power Point Tracking
Authors: Voloşencu Constantin
Published: September 2021

The study in the paper is placed in the broad context of research for increasing the efficiency of capturing and converting wind energy. The purpose of the study is to analyze some mathematical methods for maximum power point tracking in wind turbines. The mathematical methods studied are on–off control, fuzzy control, and neural predictive control. The rules developed for maximum power point tracking are presented. The related control structures and their design methods are presented. The behaviors of the control systems and their energy efficiency are analyzed. Maximum power point tracking ensures a significant increase in the energy generated compared to the unfavorable case of operation at a small and constant load torque. The differences in energy efficiency between the methods of maximum power point tracking studied are small.
Runge–Kutta Pairs of Orders 5(4) Trained to Best Address Keplerian Type Orbits
Authors: Kovalnogov Vladislav N. , Fedorov Ruslan V. , Karpukhina Tamara V. , Simos Theodore E. , Tsitouras Charalampos
Published: September 2021

The derivation of Runge–Kutta pairs of orders five and four that effectively uses six stages per step is considered. The coefficients provided by such a method are 27 and have to satisfy a system of 25 nonlinear equations. Traditionally, various solutions have been tried. Each of these solutions makes use of some simplified assumptions and offers different families of methods. Here, we make use of the most celebrated family to appear in the literature, where we may use as the last stage the first function evaluation from the next step (FSAL property). The family under consideration has the advantage of being solved explicitly. Actually, we arrive at a subsystem where all the coefficients are found with respect to five free parameters. These free parameters are adjusted (trained) in order to deliver a pair that outperforms other similar pairs of orders 5(4) in Keplerian type orbits, e.g., Kepler, perturbed Kepler, Arenstorf orbit or Pleiades. The training uses differential evolution technique. The finally proposed pair has a remarkable performance and offers on average more than a digit of accuracy in a variety of orbits.
A Square-Root Factor-Based Multi-Population Extension of the Mortality Laws
Authors: Jevtić Petar , Regis Luca
Published: September 2021

In this paper, we present and calibrate a multi-population stochastic mortality model based on latent square-root affine factors of the Cox-Ingersoll and Ross type. The model considers a generalization of the traditional actuarial mortality laws to a stochastic, multi-population and time-varying setting. We calibrate the model to fit the mortality dynamics of UK males and females over the last 50 years. We estimate the optimal states and model parameters using quasi-maximum likelihood techniques.
Dufour and Soret Effect on Viscous Fluid Flow between Squeezing Plates under the Influence of Variable Magnetic Field
Authors: Alam Muhammad Kamran , Bibi Khadija , Khan Aamir , Noeiaghdam Samad
Published: September 2021

The aim of this article is to investigate the effect of mass and heat transfer on unsteady squeeze flow of viscous fluid under the influence of variable magnetic field. The flow is observed in a rotating channel. The unsteady equations of mass and momentum conservation are coupled with the variable magnetic field and energy equations. By using some appropriate similarity transformations, the partial differential equations obtained are then converted into a system of ordinary differential equations and are solved by Homotopy Analysis Method (HAM). The influence of the natural parameters are investigated for the velocity field components, magnetic field components, heat and mass transfer. A direct effect of the squeeze Reynold number is observed on both concentration and temperature. Moreover, increasing the magnetic Reynold number shows an increase in the fluid temperature, but in the case of concentration, an inverse relation is observed. Furthermore, a decreasing effect of the Dufour number is observed on both concentration and temperature distribution. Besides, in case of the Soret number, a direct effect is observed on concentration, but an inverse effect can be seen on temperature distribution. Different effects are shown through graphs in this study and an error analysis is also presented through tables and graphs.
Generalizations of the Jensen–Mercer Inequality via Fink’s Identity
Authors: Matković Anita
Published: September 2021

We generalize an integral Jensen–Mercer inequality to the class of n-convex functions using Fink’s identity and Green’s functions. We study the monotonicity of some linear functionals constructed from the obtained inequalities using the definition of n-convex functions at a point.
Protective Effects of Ulva lactuca Polysaccharide Extract on Oxidative Stress and Kidney Injury Induced by D-Galactose in Mice
Authors: Yang Qian , Jiang Yanhui , Fu Shan , Shen Zhaopeng , Zong Wenwen , Xia Zhongning , Zhan Zhaoya , Jiang Xiaolu
Published: September 2021

Reactive oxygen species (ROS) are the key factors that cause many diseases in the human body. Polysaccharides from seaweed have been shown to have significant antioxidant activity both in vivo and in vitro. The ameliorative effect of Ulva lactuca polysaccharide extract (UPE) on renal injury induced by oxidative stress was analyzed. As shown by hematoxylin–eosin staining results, UPE can significantly improve the kidney injury induced by D-galactose (D-gal). Additionally, the protective mechanism of UPE on the kidney was explored. The results showed that UPE could decrease the levels of serum creatinine (Scr), blood urea nitrogen (BUN), serum cystatin C (Cys-C), lipid peroxidation, protein carbonylation, and DNA oxidative damage (8-OHdG) and improve kidney glutathione content. Moreover, UPE significantly increased the activities of superoxide dismutase and glutathione peroxidase and total antioxidant activity in mice. UPE also decreased the levels of inflammatory cytokines TNF-α and IL-6. Further investigation into the expression of apoptotic protein caspase-3 showed that UPE decreased the expression of apoptotic protein caspase-3. These results indicate that UPE has a potential therapeutic effect on renal injury caused by oxidative stress, providing a new theoretical basis for the treatment of oxidative damage diseases in the future.
Cartilage Acidic Protein a Novel Therapeutic Factor to Improve Skin Damage Repair?
Authors: Félix Rute Castelo , Anjos Liliana , Costa Rita Alves , Letsiou Sophia , Power Deborah Mary
Published: September 2021

Fish skin has been gaining attention due to its efficacy as a human-wound-treatment product and to identify factors promoting its enhanced action. Skin fibroblasts have a central role in maintaining skin integrity and secrete extra cellular matrix (ECM) proteins, growth factors and cytokines to rapidly repair lesions and prevent further damage or infection. The effects on scratch repair of the ubiquitous but poorly characterized ECM protein, cartilage acidic protein 1 (CRTAC1), from piscine and human sources were compared using a zebrafish SJD.1 primary fibroblast cell line. A classic in vitro cell scratch assay, immunofluorescence, biosensor and gene expression analysis were used. Our results demonstrated that the duplicate sea bass Crtac1a and Crtac1b proteins and human CRTAC-1A all promoted SJD.1 primary fibroblast migration in a classic scratch assay and in an electric cell impedance sensing assay. The immunofluorescence analysis revealed that CRTAC1 enhanced cell migration was most likely caused by actin-driven cytoskeletal changes and the cellular transcriptional response was most affected in the early stage (6 h) of scratch repair. In summary, our results suggest that CRTAC1 may be an important factor in fish skin promoting damage repair.
Structurally Diverse Polycyclic Salicylaldehyde Derivative Enantiomers from a Marine-Derived Fungus Eurotium sp. SCSIO F452
Authors: Zhong Wei-Mao , Wei Xiao-Yi , Chen Yu-Chan , Zeng Qi , Wang Jun-Feng , Shi Xue-Feng , Tian Xin-Peng , Zhang Wei-Min , Wang Fa-Zuo , Zhang Si
Published: September 2021

To enlarge the chemical diversity of Eurotium sp. SCSIO F452, a talented marine-derived fungus, we further investigated its chemical constituents from a large-scale fermentation with modified culture. Four pairs of new salicylaldehyde derivative enantiomers, euroticins F-I (1–4), as well as a known one eurotirumin (5) were isolated and characterized. Compound 1 features an unprecedented constructed 6/6/6/5 tetracyclic structures, while 2 and 3 represent two new types of 6/6/5 scaffolds. Their structures were established by comprehensive spectroscopic analyses, X-ray diffraction, 13C NMR, and electronic circular dichroism calculations. Selected compounds showed significant inhibitory activity against α-glucosidase and moderate cytotoxic activities against SF-268, MCF-7, HepG2, and A549 cell lines.
SpCrus2 Glycine-Rich Region Contributes Largely to the Antiviral Activity of the Whole-Protein Molecule by Interacting with VP26, a WSSV Structural Protein
Authors: Wang Yue , Zhang Chao , Fang Wen-Hong , Ma Hong-Yu , Li Xin-Cang
Published: September 2021

Crustins are cysteine-rich cationic antimicrobial peptides with diverse biological functions including antimicrobial and proteinase inhibitory activities in crustaceans. Although a few crustins reportedly respond to white spot syndrome virus (WSSV) infection, the detailed antiviral mechanisms of crustins remain largely unknown. Our previous research has shown that SpCrus2, from mud crab Scylla paramamosain, is a type II crustin containing a glycine-rich region (GRR) and a cysteine-rich region (CRR). In the present study, we found that SpCrus2 was upregulated in gills after WSSV challenge. Knockdown of SpCrus2 by injecting double-stranded RNA (dsSpCrus2) resulted in remarkably increased virus copies in mud crabs after infection with WSSV. These results suggested that SpCrus2 played a critical role in the antiviral immunity of mud crab. A GST pull-down assay showed that recombinant SpCrus2 interacted specifically with WSSV structural protein VP26, and this result was further confirmed by a co-immunoprecipitation assay with Drosophila S2 cells. As the signature sequence of type II crustin, SpCrus2 GRR is a glycine-rich cationic polypeptide with amphipathic properties. Our study demonstrated that the GRR and CRR of SpCrus2 exhibited binding activities to VP26, with the former displaying more potent binding ability than the latter. Interestingly, pre-incubating WSSV particles with recombinant SpCrus2 (rSpCrus2), rGRR, or rCRR inhibited virus proliferation in vivo; moreover, rSpCrus2 and rGRR possessed similar antiviral abilities, which were much stronger than those of rCRR. These findings indicated that SpCrus2 GRR contributed largely to the antiviral ability of SpCrus2, and that the stronger antiviral ability of GRR might result from its stronger binding activity to the viral structural protein. Overall, this study provided new insights into the antiviral mechanism of SpCrus2 and the development of new antiviral drugs.
Sudden Fall in the Lipid-Lowering Effect of Evolocumab: The Butler Is Not Always Guilty
Authors: Fogacci Federica , Borghi Claudio , Di Micoli Antonio , Cicero Arrigo
Published: September 2021

A 78-year-old man came to our attention after undergoing coronary computed tomography angiography documenting multivessel coronary artery disease. He was started on treatment with the proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor evolocumab 140 mg subcutaneously every 2 weeks. Treatment-emergent changes in lipids and lipoproteins were long-lasting, and the medication was well tolerated by the patient in the long-term. Unexpectedly, after 2 years of continuous treatment with evolocumab, serum lipids increased, apparently without any reasonable explanation. During the follow-up visit, the patient was found to have habitually injected evolocumab into his right thumb instead of into the appropriate injection sites (i.e., abdomen, thighs or upper arms) after turning the injector upside down.
Acute Heart Failure in a Patient with Occult Barlow’s Disease Receiving Bevacizumab
Authors: Izumida Toshihide , Imamura Teruhiko , Ueno Yohei , Fukahara Kazuaki , Kinugawa Koichiro
Published: September 2021

Bevacizumab is a recombinant humanized monoclonal antibody and a key drug for treatment of various types of cancer. Bevacizumab is associated with the occurrence of heart failure, but its risk factors remain unknown. A 55-year-old woman was diagnosed with cervical cancer, which was completely treated by bevacizumab-incorporated chemotherapy. During the 9-month bevacizumab therapy, she suffered from hypertension requiring multiple antihypertensive agents. She was admitted to our hospital due to acute heart failure with afterload mismatch and severe mitral regurgitation. A transesophageal echocardiography showed Barlow’s disease with a degenerated and widely prolapsed mitral valve. She received a scheduled surgical mitral valve repair. Post-operative cause was uneventful, but metastatic dissemination developed later. The existence of mitral valve regurgitation, even when sub-clinical, might be a risk of worsening heart failure during bevacizumab therapy. Careful follow-up at an onco-cardiology clinic is highly encouraged particularly for such a cohort during bevacizumab therapy.
Diagnosing a Patient with Erdheim-Chester Disease during the COVID-19 Pandemic
Authors: Kaiafa Georgia , Pilalas Dimitrios , Koletsa Triantafyllia , Daios Stylianos , Arsos Georgios , Hatzidakis Adam , Protopapas Adonis , Stamatopoulos Kostas , Savopoulos Christos
Published: September 2021

Background: Erdheim-Chester disease (ECD) is a rare hematopoietic neoplasm of histiocytic origin characterized by an insidious course. The coronavirus disease 2019 (COVID-19) pandemic has put an enormous strain on healthcare systems worldwide both directly and indirectly, resulting in the disruption of healthcare services to prevent, diagnose and manage non-COVID-19 disease. Case Presentation: We describe the case of a 58-year-old male patient with sporadic episodes of self-resolving mild fever and anemia of chronic disease with onset two years before the current presentation. Positron emission/computed tomography scan revealed the presence of moderately hypermetabolic perirenal tissue masses. In order to achieve diagnosis, repeated perirenal tissue biopsies were performed, and the diagnostic evaluation was complicated by the strain put on the healthcare system by the COVID-19 pandemic. The patient contracted SARS-CoV-2 and required hospitalization, but recovered fully. No further ECD target organ involvement was documented. Treatment options were presented, but the patient chose to defer treatment for ECD. Conclusion: A high index of suspicion and multidisciplinary team collaboration is paramount to achieve diagnosis in rare conditions such as ECD. Disruptions in healthcare services in the pandemic milieu may disproportionately affect people with rare diseases and further study and effort is required to better meet their needs in the pandemic setting.