bluuebunny/crossref_metadata_2025 huggingface dataset:
In-Process Monitoring of Changing Dynamics of a Thin-Walled Component During Milling Operation by Ball Shooter Excitation
Authors: Bachrathy Daniel , Kiss Adam K. , Kossa Attila , Berezvai Szabolcs , Hajdu David , Stepan Gabor
Published: August 2020

During the milling of thin-walled workpieces, the natural frequencies might change radically due to the material removal. To avoid resonant spindle speeds and chatter vibration, a precise knowledge of the instantaneous modal parameters is necessary. Many different numerical methods exist to predict the changes; however, small unmodelled effects can lead to unreliable results. The natural frequencies could be measured by human experts based on modal analysis for an often interrupted process; however, this method is not acceptable during production. We propose an online measurement method with an automatic ball shooter device which can excite a wide frequency range of the flexible workpiece. The method is presented for the case of blade profile machining. The change of the natural frequencies is predicted based on analytical models and finite element simulations. The measurement response for the impulse excitation of the ball shooter device is compared to the results of impulse modal tests performed with a micro hammer. It is shown that the ball shooter is capable of determining even the slight variation of the natural frequencies during the machining process and of distinguishing the slight change caused by different clamping methods. An improved FE model is proposed to include the contact stiffness of the fixture.
Intercomparison of Assimilated Coastal Wave Data in the Northwestern Pacific Area
Authors: Hisaki Yukiharu
Published: August 2020

The assimilated coastal wave data are useful for wave climate study, coastal engineering, and design for marine disaster protection. However, the assimilated coastal wave data are few. Here, wave analysis data produced by the JMA (Japan Meteorological Agency) and ERA5 wave data were compared with GPS (Global Positioning System) buoy-measured wave data. In addition, the accuracy of ERA5 wave data for various conditions was investigated. The accuracy of JMA analysis wave height was better than that of ERA5 wave height. The ERA5 wave height was underestimated as the wave height increased. The accuracy of the ERA5 wave height was significantly different in fetch-unlimited and fetch-limited conditions. The difference of the skill metrics between fetch-unlimited and fetch-limited conditions was due to the overestimation of the fetch in the ERA5 grid. This result also applied to the wave period.
Zinc Binding by Histatin 5 Promotes Fungicidal Membrane Disruption in C. albicans and C. glabrata
Authors: Norris Hannah L. , Kumar Rohitashw , Ong Chih Yean , Xu Ding , Edgerton Mira
Published: August 2020

Histatin 5 (Hst 5) is an antimicrobial peptide produced in human saliva with antifungal activity for opportunistic pathogen Candida albicans. Hst 5 binds to multiple cations including dimerization-inducing zinc (Zn2+), although the function of this capability is incompletely understood. Hst 5 is taken up by C. albicans and acts on intracellular targets under metal-free conditions; however, Zn2+ is abundant in saliva and may functionally affect Hst 5. We hypothesized that Zn2+ binding would induce membrane-disrupting pores through dimerization. Through the use of Hst 5 and two derivatives, P113 (AA 4-15 of Hst 5) and Hst 5ΔMB (AA 1-3 and 15-19 mutated to Glu), we determined that Zn2+ significantly increases killing activity of Hst 5 and P113 for both C. albicans and Candida glabrata. Cell association assays determined that Zn2+ did not impact initial surface binding by the peptides, but Zn2+ did decrease cell association due to active peptide uptake. ATP efflux assays with Zn2+ suggested rapid membrane permeabilization by Hst 5 and P113 and that Zn2+ affinity correlates to higher membrane disruption ability. High-performance liquid chromatography (HPLC) showed that the higher relative Zn2+ affinity of Hst 5 likely promotes dimerization. Together, these results suggest peptide assembly into fungicidal pore structures in the presence of Zn2+, representing a novel mechanism of action that has exciting potential to expand the list of Hst 5-susceptible pathogens.
Community Participation for the Use of Renewable Energies in Ciudad Ixtepec, Oaxaca (2008–2015)
Authors: Sánchez-Casanova Wendy , Desilus Bendreff
Published: August 2020

This paper aims to examine the redefinition of rural actors and practices in the context of the Wind Farm Corridor of the Isthmus of Tehuantepec. That redefinition addresses issues such as the benefits of wind farms, the role of the land in the use of wind energy, requirements for the use of wind, arguments of disagreement with wind farms, manifestations of that disagreement, and the feasibility of community wind farms. Adopting a case study methodology from a qualitative perspective, and “worded” data collected through semi-structured interviews, it was detected that, despite the disapproval of residents of the Oaxacan Isthmus due to a dispossession claimed to the Federal Electricity Commission (Comisión Federal de Electricidad, CFE) and private companies, many of the landowners in Ciudad Ixtepec have decided to become wind entrepreneurs by a community wind farm, facing opposition and mistrust regarding their capacities.
Capital Structure and Bank Profitability in Vietnam: A Quantile Regression Approach
Authors: Le Tu D. Q. , Nguyen Dat T.
Published: August 2020

We empirically investigate the impact of capital structure on bank profitability using a quantile regression method in the Vietnamese banking system during 2007–2019. Our results suggest that the nonlinear relationship between capitalization and bank profitability is only significant at the 90th quantile. This is the first study to conclude that the turning point of capital ratio increases throughout the profitability distribution. Our findings thus suggest that a continuous increase in bank capital requirements does not necessarily result in higher bank profitability.
Transition to the Revised OHADA Law on Accounting and Financial Reporting: Corporate Perceptions of Costs and Benefits
Authors: Fossung Micheal Forzeh , Ntoung Lious Agbor Tabot , Santos de Oliveira Helena Maria , Pereira Cláudia Maria Ferreira , Bastos Susana Adelina Moreira Carvalho , Pimentel Liliana Marques
Published: August 2020

This paper examines the ongoing transition to the revised Organisation for the Harmonisation of Business Law in Africa Act on Accounting and Financial Reporting for companies in general and to the International Financial Reporting Standards for listed and group companies with a particular focus on recent institutional developments and corporate concerns. The study used 80 professional accountants, most of whom were members of the Institute of Chartered Accountants of Cameroon and academics. Using the descriptive statistics, the study shows that the transition to the revised OHADA brings about a high level of comparability and transparency of the financial statements, that the International Financial Reporting Standards can be implemented in Cameroon (but not fully), and that the benefit of the transition exceeds the cost.
When Peace and Quiet Is Not Enough: Place-Shaping and the Role of Leaders in Sustainability and Quality of Life in Rural Estonia and Latvia
Authors: Storie Joanna , Chenault Edith , Külvik Mart , Bell Simon
Published: August 2020

Estonian and Latvian rural inhabitants enjoy many factors enhancing the quality of life, such as the peace and quiet of the countryside, fresh food and rural activities. However, these benefits are insufficient to overcome poor employment prospects in rural areas. Place-shaping practices have transformative powers that are instrumental in achieving sustainable change in communities. The process of reappreciating local landscapes creates memories of positive associations with symbolic meaning; it helps inhabitants to strengthen their sense of place identity and re-grounds their appreciation into a specific local context. Sustainable rural futures require conditions where inhabitants feel listened to and that are responsive to their needs. They also require inspirational leaders to facilitate change and create networks of opportunities, linking inhabitants to the outside world and resources. Leaders may play an important role of re-positioning local communities for the future, creating new experiences or new opportunities, which further feeds re-appreciation of place and enhances quality of life. In order to understand the main issues of the rural areas, two villages with active rural projects in Estonia and Latvia were selected to analyse the role that leaders play in the development of the area and the barriers to a more sustainable approach.
The Responses of the Black Fungus Cryomyces Antarcticus to High Doses of Accelerated Helium Ions Radiation within Martian Regolith Simulants and Their Relevance for Mars
Authors: Pacelli Claudia , Cassaro Alessia , Aureli Lorenzo , Moeller Ralf , Fujimori Akira , Onofri Silvano
Published: August 2020

One of the primary current astrobiological goals is to understand the limits of microbial resistance to extraterrestrial conditions. Much attention is paid to ionizing radiation, since it can prevent the preservation and spread of life outside the Earth. The aim of this research was to study the impact of accelerated He ions (150 MeV/n, up to 1 kGy) as a component of the galactic cosmic rays on the black fungus C. antarcticus when mixed with Antarctic sandstones—the substratum of its natural habitat—and two Martian regolith simulants, which mimics two different evolutionary stages of Mars. The high dose of 1 kGy was used to assess the effect of dose accumulation in dormant cells within minerals, under long-term irradiation estimated on a geological time scale. The data obtained suggests that viable Earth-like microorganisms can be preserved in the dormant state in the near-surface scenario for approximately 322.000 and 110.000 Earth years within Martian regolith that mimic early and present Mars environmental conditions, respectively. In addition, the results of the study indicate the possibility of maintaining traces within regolith, as demonstrated by the identification of melanin pigments through UltraViolet-visible (UV-vis) spectrophotometric approach.
Rethinking Tribology–Tracking Trends, Their Presence at the ECOTRIB 2019 Conference, and Their Impact on Tribology Research in Austria
Authors: Franek Friedrich , Dörr Nicole , Badisch Ewald , Pauschitz Andreas
Published: August 2020

Economic and societal changes and technological development guide the focus of tribology research. “Classical” tasks, such as the improvement of materials or the tuning of a lubricant, have long been replaced by a function-oriented aggregate design, including specifications defined by needs arising from production and the environment. Tribology faces, among other remarkable changes, a paradigm shift according to the tendency to replace classic internal combustion engine (ICE) drivetrains with electric drives. How tribology will develop, and which research topics will prevail in the future, are being explored by several studies based on the experience of experts. The variety of contributions to journals and conferences provide an indicator of the importance of such tasks or topics. Here, a report on the ECOTRIB 2019—7th European Conference on Tribology held in Vienna, Austria, is presented. From the available information, an even stronger integration of other disciplines into tribology is noticeable, with certain hype in the fields of advanced material technology, sensor integration and the implementation of data science. Measures to rethink tribology from both an organizational and scientific point of view to cope with future tasks are being targeted and comprehensively implemented in the current research program “InTribology”, operated by the Austrian Center of Competence for Tribology (AC²T) in Wiener Neustadt, Austria.
Secondary Resonance Energy Harvesting with Quadratic Nonlinearity
Authors: Zhang Guoce , Zhang Bo
Published: August 2020

Piezoelectric energy harvesters can transform the mechanical strain into electrical energy. The microelectromechanical transformation device is often composed of piezoelectric cantilevers and has been largely experimented. Most resonances have been developed to harvest nonlinear vibratory energy except for combination resonances. This paper is to analyze several secondary resonances of a cantilever-type piezoelectric energy harvester with a tip magnet. The conventional Galerkin method is improved to truncate the continuous model, an integro-partial differential equation with time-dependent boundary conditions. Then, more resonances on higher-order vibration modes can be obtained. The stable steady-state response is formulated approximately but analytically for the first two subharmonic and combination resonances. The instability boundaries are discussed for these secondary resonances from quadratic nonlinearity. A small damping and a large excitation readily result in an unstable response, including the period-doubling and quasiperiodic motions that can be employed to enhance the voltage output around a wider band of working frequency. Runge–Kutta method is employed to numerically compute the time history for stable and unstable motions. The stable steady-state responses from two different methods agree well with each other. The outcome enriches structural dynamic theory on nonlinear vibration.
Properties of Styrene-Maleic Anhydride Copolymer Compatibilized Polyamide 66/Poly (Phenylene Ether) Blends: Effect of Blend Ratio and Compatibilizer Content
Authors: Aksit Alper , Geis Nico , Aksit Merve , Altstädt Volker
Published: August 2020

Two different blend ratios of polyamide 66 (PA66) and poly (2,6-dimethyl-1,4-phenylene ether) (PPE) (60/40 and 40/60 w/w) were produced via melt mixing. A styrene–maleic anhydride copolymer (SMA) was utilized at various contents from 2.5–15 wt% to compatibilize the immiscible blend system. The influence of SMA content and blend ratio was investigated based on (thermo-) mechanical and morphological properties of the PA66/PPE blends. Correlations between the interaction of SMA with the blend partners were established. For 60/40 blends, a droplet-sea morphology was visualized by transmission electron microscopy, wherein no major changes were seen upon SMA addition. In the case of 40/60 blends, strong coalescence was found in the binary blend. Up to 5 wt% SMA, the coalescence was inhibited by the interfacial activity of SMA, whereas 10 wt% SMA initiated a disperse-to-co-continuous transition, which was completed at 15 wt% SMA. An enhancement of tensile properties was achieved for all blends possessing SMA, where the maximum concentration of 15 wt% resulted in the highest elongation at break and tensile strength values. The relative improvement of the tensile properties was higher with the PPE-rich blend (40/60) which was attributed to a partial emulsification of the PPE phases forming a bimodal PPE domain size distribution with nano-droplets in the range of 60–160 nm.
Special Issue: Advanced Coatings for Corrosion Protection
Authors: Fürbeth Wolfram
Published: August 2020

Corrosion is an important issue in many industrial fields. Among others, coatings are by far the most important technology for corrosion protection of metallic surfaces. The special issue “Advanced Coatings for Corrosion Protection” has been launched as a means to present recent developments on any type of advanced coatings for corrosion protection. Fifteen contributions have been collected on metallic, inorganic, polymeric and nanoparticle enhanced coatings providing corrosion protection as well as partly other functionalities.
Fracture Load of CAD/CAM Feldspathic Crowns Influenced by Abutment Material
Authors: Bencun Mladen , Ender Andreas , Wiedemeier Daniel B. , Mehl Albert
Published: August 2020

In vitro studies investigating the mechanical properties of dental reconstructions use various materials to replicate prepared teeth. However, no uniform recommendation exists as to which material is most suitable for standardized testing. The purpose of this study was to identify a material that resembles human dentin in fracture load tests. Sixteen human teeth were scanned with an intraoral scanner to obtain copies of the original crown morphology and were then prepared for crowns. Replica dies of the prepared teeth including the root morphology were fabricated with a Computer-aided design and computer-aided manufacturing (CAD/CAM) system and divided into four groups: (A) reinforced composite (RC); (B) human dentin (HD); (C) polymethyl methacrylate (PM); and (D) hybrid ceramic (HC). Sixty-four feldspar ceramic crowns were designed with the biocopy mode, fabricated with a CAD/CAM system, luted on the dies, and then with the roots embedded in polymethyl methacrylate. Care was taken to position all specimens of the same morphology identically. Thermo-mechanical load cycling was performed in a chewing simulator followed by fractural loading of the crowns. A mixed effect linear model was fitted to the data, and pairwise contrasts were estimated on the marginal means and corrected for multiple testing according to Tukey (α = 0.05). The means for fracture load (N) were 2435 N (95% CI (2162, 2709)) for hybrid ceramic, 1838 N (95% CI (1565, 2112)) for reinforced composite, 1670 N (95% CI (1396, 1943)) for human tooth and 1142 N (95% CI (868, 1415)) for polymethyl methacrylate abutment materials. Post-hoc pairwise contrasts revealed a statistically significant (p < 0.05) difference among all groups except for reinforced composite and human dentin (p = 0.76). The results indicate that the mechanical properties of abutment dies play a significant role for a possible substitution of natural teeth in in vitro studies.
Experimental Investigation and Micromechanical Modeling of Elastoplastic Damage Behavior of Sandstone
Authors: Jia Chaojun , Zhang Qiang , Wang Susheng
Published: August 2020

The mechanical behavior of the sandstone at the dam site is important to the stability of the hydropower station to be built in Southwest China. A series of triaxial compression tests under different confining pressures were conducted in the laboratory. The critical stresses were determined and the relationship between the critical stress and confining pressure were analyzed. The Young’s modulus increases non-linearly with the confining pressure while the plastic strain increment Nϕ and the dilation angle ϕ showed a negative response. Scanning electron microscope (SEM) tests showed that the failure of the sandstone under compression is a coupled process of crack growth and frictional sliding. Based on the experimental results, a coupled elastoplastic damage model was proposed within the irreversible thermodynamic framework. The plastic deformation and damage evolution were described by using the micromechanical homogenization method. The plastic flow is inherently driven by the damage evolution. Furthermore, a numerical integration algorithm was developed to simulate the coupled elastoplastic damage behavior of sandstone. The main inelastic properties of the sandstone were well captured. The model will be implemented into the finite element method (FEM) to estimate the excavation damaged zones (EDZs) which can provide a reference for the design and construction of such a huge hydropower project.
Effect of Graphene Family Materials on Multiple Myeloma and Non-Hodgkin’s Lymphoma Cell Lines
Authors: Strojny Barbara , Jaworski Sławomir , Misiewicz-Krzemińska Irena , Isidro Isabel , Rojas Elizabeta A. , Gutiérrez Norma C. , Grodzik Marta , Koczoń Piotr , Chwalibog André , Sawosz Ewa
Published: August 2020

The interest around the graphene family of materials is constantly growing due to their potential application in biomedical fields. The effect of graphene and its derivatives on cells varies amongst studies depending on the cell and tissue type. Since the toxicity against non-adherent cell lines has barely been studied, we investigated the effect of graphene and two different graphene oxides against four multiple myeloma cell lines, namely KMS-12-BM, H929, U226, and MM.1S, as well as two non-Hodgkin lymphoma cells lines, namely KARPAS299 and DOHH-2. We performed two types of viability assays, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide conversion) and ATP (adenosine triphosphate detection), flow cytometry analysis of apoptosis induction and cell cycle, cell morphology, and direct interaction analysis using two approaches—visualization of living cells by two different systems, and visualization of fixed and dyed cells. Our results revealed that graphene and graphene oxides exhibit low to moderate cytotoxicity against cells, despite visible interaction between the cells and graphene oxide. This creates possibilities for the application of the selected graphene materials for drug delivery systems or theragnostics in hematological malignancies; however, further detailed studies are necessary to explain the nature of interactions between the cells and the materials.
The Structural and Mechanical Properties of the UHMWPE Films Mixed with the PE-Wax
Authors: Dayyoub Tarek , Olifirov Leonid K. , Chukov Dilyus I. , Kaloshkin Sergey D. , Kolesnikov Evgeniy , Nematulloev Saidkhodzha
Published: August 2020

Since obtaining a highly oriented structure based on a large-scale commercial ultra-high molecular weight polyethylene (UHMWPE) is considered very difficult due to its high molecular weight and melting index, modifying the structure of these cheap commercial UHMWPE brands into a supra-molecular structure with fiber-forming properties by adding a small amount of polyethylene wax (PE-wax) will provide the possibility to obtain highly oriented UHMWPE products with enhanced mechanical and tribological properties. In this work, highly oriented UHMWPE/PE-wax films were prepared. The PE-wax affected the UHMWPE as an intermolecular lubricant. The obtained lamellar structure of the UHMWPE/PE-wax composites had a better processability. The UHMWPE and UHMWPE/PE-wax structures for the xerogels and the films were studied by using differential scanning calorimetry and scanning electron microscopy. The PE-wax presence enhanced the mechanical properties of the UHMWPE/PE-wax films to a high degree. The highest average value of the tensile strength was 1320 MPa (an increase of 78%) obtained by adding a PE-wax content of 1.0 wt.%, and the highest average value of the Young’s modulus was 56.8 GPa (an increase of 71%) obtained by adding a PE-wax content of 2.0 wt.%. The addition of the PE-wax increased the work of fracture values of the UHMWPE/PE-wax films up to 233%. The formation of the cavities was observed in the virgin UHMWPE films more than in the UHMWPE/PE-wax films, and the whitening of the oriented films was related to the crystallization process more than to the cavitation phenomenon. The coefficient of friction of the oriented UHMWPE/PE-wax films improved by 33% in comparison with the isotropic UHMWPE, and by 7% in comparison with the oriented virgin UHMWPE films.
Advanced Strategy of Speed Predictive Control for Nonlinear Synchronous Reluctance Motors
Authors: Farhan Ahmed , Abdelrahem Mohamed , Hackl Christoph M. , Kennel Ralph , Shaltout Adel , Saleh Amr
Published: August 2020

To gain fast dynamic response, high performance, and good tracking capability, several control strategies have been applied to synchronous reluctance motors (SynRMs). In this paper, a nonlinear advanced strategy of speed predictive control (SPC) based on the finite control set model predictive control (FCS-MPC) is proposed and simulated for nonlinear SynRMs. The SPC overcomes the limitation of the cascaded control structure of the common vector control by employing a novel strategy that considers all the electrical and mechanical variables in one control law through a new cost function to obtain the switching signals for the power converter. The SynRM flux maps are known based on finite element method (FEM) analysis to take into consideration the effect of the nonlinearity of the machine. To clear the proposed strategy features, a functional and qualitative comparison between the proposed SPC, field-oriented control (FOC) with an anti-windup scheme, and current predictive control (CPC) with outer PI speed control loop is presented. For simplicity, particle swarm optimization (PSO) is performed to tune all the unknown parameters of the control strategies. The comparison features include controller design, dynamic and steady-state behaviors. Simulation results are presented to investigate the benefits and limitations of the three control strategies. Finally, the proposed SPC, FOC, and CPC have their own merits, and all methods encounter the requirements of advanced high-performance drives.
Some High-Order Iterative Methods for Nonlinear Models Originating from Real Life Problems
Authors: Zaka Ullah Malik , Behl Ramandeep , Argyros Ioannis K.
Published: August 2020

We develop a sixth order Steffensen-type method with one parameter in order to solve systems of equations. Our study’s novelty lies in the fact that two types of local convergence are established under weak conditions, including computable error bounds and uniqueness of the results. The performance of our methods is discussed and compared to other schemes using similar information. Finally, very large systems of equations (100×100 and 200×200) are solved in order to test the theoretical results and compare them favorably to earlier works.
Memory in a New Variant of King’s Family for Solving Nonlinear Systems
Authors: Kansal Munish , Cordero Alicia , Bhalla Sonia , Torregrosa Juan R.
Published: August 2020

In the recent literature, very few high-order Jacobian-free methods with memory for solving nonlinear systems appear. In this paper, we introduce a new variant of King’s family with order four to solve nonlinear systems along with its convergence analysis. The proposed family requires two divided difference operators and to compute only one inverse of a matrix per iteration. Furthermore, we have extended the proposed scheme up to the sixth-order of convergence with two additional functional evaluations. In addition, these schemes are further extended to methods with memory. We illustrate their applicability by performing numerical experiments on a wide variety of practical problems, even big-sized. It is observed that these methods produce approximations of greater accuracy and are more efficient in practice, compared with the existing methods.
Guaranteed Lower Bounds for the Elastic Eigenvalues by Using the Nonconforming Crouzeix–Raviart Finite Element
Authors: Zhang Xuqing , Zhang Yu , Yang Yidu
Published: August 2020

This paper uses a locking-free nonconforming Crouzeix–Raviart finite element to solve the planar linear elastic eigenvalue problem with homogeneous pure displacement boundary condition. Making full use of the Poincaré inequality, we obtain the guaranteed lower bounds for eigenvalues. Besides, we also use the nonconforming Crouzeix–Raviart finite element to the planar linear elastic eigenvalue problem with the pure traction boundary condition, and obtain the guaranteed lower eigenvalue bounds. Finally, numerical experiments with MATLAB program are reported.
Similarity Measure of Lattice Ordered Multi-Fuzzy Soft Sets Based on Set Theoretic Approach and Its Application in Decision Making
Authors: Begam S Sabeena , J Vimala , Selvachandran Ganeshsree , Ngan Tran Thi , Sharma Rohit
Published: August 2020

Many effective tools in fuzzy soft set theory have been proposed to handle various complicated problems in different fields of our real life, especially in decision making. Molodtsov’s soft set theory has been regarded as a newly emerging mathematical tool to deal with uncertainty and vagueness. Lattice ordered multi-fuzzy soft set (LMFSS) has been applied in forecasting process. However, similarity measure is not used in this application. In our research, similarity measure of LMFSS is proposed to calculate the similarity between two LMFSSs. Moreover, some of its properties are introduced and proved. Finally, an application of LMFSS in decision making using similarity measure is analysed.
Evolution Model for Epidemic Diseases Based on the Kaplan-Meier Curve Determination
Authors: Calabuig Jose M. , García-Raffi Luis M. , García-Valiente Albert , Sánchez-Pérez Enrique A.
Published: August 2020

We show a simple model of the dynamics of a viral process based, on the determination of the Kaplan-Meier curve P of the virus. Together with the function of the newly infected individuals I, this model allows us to predict the evolution of the resulting epidemic process in terms of the number E of the death patients plus individuals who have overcome the disease. Our model has as a starting point the representation of E as the convolution of I and P. It allows introducing information about latent patients—patients who have already been cured but are still potentially infectious, and re-infected individuals. We also provide three methods for the estimation of P using real data, all of them based on the minimization of the quadratic error: the exact solution using the associated Lagrangian function and Karush-Kuhn-Tucker conditions, a Monte Carlo computational scheme acting on the total set of local minima, and a genetic algorithm for the approximation of the global minima. Although the calculation of the exact solutions of all the linear systems provided by the use of the Lagrangian naturally gives the best optimization result, the huge number of such systems that appear when the time variable increases makes it necessary to use numerical methods. We have chosen the genetic algorithms. Indeed, we show that the results obtained in this way provide good solutions for the model.
The Strong Resolving Graph and the Strong Metric Dimension of Cactus Graphs
Authors: Kuziak Dorota
Published: August 2020

A vertex w of a connected graph G strongly resolves two distinct vertices u,v∈V(G), if there is a shortest u,w path containing v, or a shortest v,w path containing u. A set S of vertices of G is a strong resolving set for G if every two distinct vertices of G are strongly resolved by a vertex of S. The smallest cardinality of a strong resolving set for G is called the strong metric dimension of G. To study the strong metric dimension of graphs, a very important role is played by a structure of graphs called the strong resolving graph In this work, we obtain the strong metric dimension of some families of cactus graphs, and along the way, we give several structural properties of the strong resolving graphs of the studied families of cactus graphs.
Mathematical Modeling of Vortex Interaction Using a Three-Layer Quasigeostrophic Model. Part 2: Finite-Core-Vortex Approach and Oceanographic Application
Authors: Sokolovskiy Mikhail A. , Carton Xavier J. , Filyushkin Boris N.
Published: August 2020

The three-layer version of the contour dynamics/surgery method is used to study the interaction mechanisms of a large-scale surface vortex with a smaller vortex/vortices of the middle layer (prototypes of intrathermocline vortices in the ocean) belonging to the middle layer of a three-layer rotating fluid. The lower layer is assumed to be dynamically passive. The piecewise constant vertical density distribution approximates the average long-term profile for the North Atlantic, where intrathermocline eddies are observed most often at depths of 300–1600 m. Numerical experiments were carried out with different initial configurations of vortices, to evaluate several effects. Firstly, the stability of the vortex compound was evaluated. Most often, it remains compact, but when unstable, it can break as vertically coupled vortex dipoles (called hetons). Secondly, we studied the interaction between a vertically tilted cyclone and lenses. Then, the lenses first undergo anticlockwise rotation determined by the surface cyclone. The lenses can induce alignment or coupling with cyclonic vorticity above them. Only very weak lenses are destroyed by the shear stress exerted by the surface cyclone. Thirdly, under the influence of lens dipoles, the surface cyclone can be torn apart. In particular, the shedding of rapidly moving vortex pairs at the surface reflects the presence of lens dipoles below. More slowly moving small eddies can also be torn away from the main surface cyclone. In this case, they do not appear to be coupled with middle layer vortices. They are the result of large shear-induced deformation. Common and differing features of the vortex interaction, modeled in the framework of the theory of point and finite-core vortices, are noted.
Pricing of Barrier Options on Underlying Assets with Jump-Diffusion Dynamics: A Mellin Transform Approach
Authors: Rodrigo Marianito R.
Published: August 2020

A barrier option is an exotic path-dependent option contract where the right to buy or sell is activated or extinguished when the underlying asset reaches a certain barrier price during the lifetime of the contract. In this article we use a Mellin transform approach to derive exact pricing formulas for barrier options with general payoffs and exponential barriers on underlying assets that have jump-diffusion dynamics. With the same approach we also price barrier options on underlying futures contracts.
Nonlinear Position Control with Nonlinear Coordinate Transformation Using Only Position Measurement for Single-Rod Electro-Hydrostatic Actuator
Authors: Kim Wonhee , Won Daehee
Published: August 2020

In existing methods, full-state feedback is required for the position tracking of single-rod Electro Hydrostatic Actuators (EHAs). Measuring a full state is not always possible because of cost and space limitations. Furthermore, measurement noise from pressure sensors may degrade the control performance. We propose an observer-based nonlinear position control with nonlinear coordinate transformation while only using position measurement to improve the position tracking of single-rod EHAs. The proposed method comprises a position controller and an observer. We propose a nonlinear coordinate transform for the controller design. The desired force is designed for the position tracking and boundedness of the internal state. The position controller is designed to track the desired state variables for the EHAs. Meanwhile, a nonlinear observer is proposed in order to estimate a full state using only the position measurement. The stability of the closed-loop system is investigated via an input-to-state stability property. The performance of the proposed method is validated via both simulations and experiments.
Completeness in Quasi-Pseudometric Spaces—A Survey
Authors: Cobzas Ştefan
Published: August 2020

The aim of this paper is to discuss the relations between various notions of sequential completeness and the corresponding notions of completeness by nets or by filters in the setting of quasi-metric spaces. We propose a new definition of right K-Cauchy net in a quasi-metric space for which the corresponding completeness is equivalent to the sequential completeness. In this way we complete some results of R. A. Stoltenberg, Proc. London Math. Soc. 17 (1967), 226–240, and V. Gregori and J. Ferrer, Proc. Lond. Math. Soc., III Ser., 49 (1984), 36. A discussion on nets defined over ordered or pre-ordered directed sets is also included.
Exploration of the Electrophilic Reactivity of the Cytotoxic Marine Alkaloid Discorhabdin C and Subsequent Discovery of a New Dimeric C-1/N-13-Linked Discorhabdin Natural Product
Authors: Lam Cary F. C. , Cadelis Melissa M. , Copp Brent R.
Published: August 2020

The cytotoxic marine natural product discorhabdin C contains a 2,6-dibromo-cyclohexa-2,5-diene moiety, previously proposed to be a critical feature required for biological activity. We have determined that the dienone-ring of discorhabdin C is indeed electrophilic, reacting with thiol and amine nucleophiles, affording debrominated adducts. In the case of reaction with 1-aminopentane the product contains an unusual C-2/N-18 ring closed, double-hydrate moiety. This electrophilic reactivity also extends to proteins, with lysozyme-discorhabdin C adducts being detected by ESI mass spectrometry. These results prompted further examination of an extract of discorhabdin C-producing sponge, Latrunculia (Latrunculia) trivetricillata, leading to the isolation and characterisation of a new example of a C-1/N-13 linked discorhabdin dimer that shared structural similarities with the 1-aminopentane-discorhabdin C adduct. To definitively assess the influence of the dienone moiety of discorhabdin C on cytotoxicity, a semi-synthetic hydrogenation derivative was prepared, affording a didebrominated ring-closed carbinolamine that was essentially devoid of tumour cell line cytotoxicity. Antiparasitic activity was assessed for a set of 14 discorhabdin alkaloids composed of natural products and semi-synthetic derivatives. Three compounds, (-)-discorhabdin L, a dimer of discorhabdin B and the discorhabdin C hydrogenation carbinolamine, exhibited pronounced activity towards Plasmodium falciparum K1 (IC50 30–90 nM) with acceptable to excellent selectivity (selectivity index 19–510) versus a non-malignant cell line.
Are Mutations in the DHRS9 Gene Causally Linked to Epilepsy? A Case Report
Authors: Calì Francesco , Elia Maurizio , Vinci Mirella , Vetri Luigi , Correnti Edvige , Trapolino Emanuele , Roccella Michele , Vanadia Francesca , Romano Valentino
Published: August 2020

The DHRS9 gene is involved in several pathways including the synthesis of allopregnanolone from progesterone. Allopregnanolone is a positive modulator of gamma aminobutyric acid (GABA) action and plays a role in the control of neuronal excitability and seizures. Whole-exome sequencing performed on a girl with an early onset epilepsy revealed that she was a compound heterozygote for two novel missense mutations of the DHRS9 gene likely to disrupt protein function. No previous studies have reported the implication of this gene in epilepsy. We discuss a new potential pathogenic mechanism underlying epilepsy in a child, due to a defective progesterone pathway.
Postpartum Follow-Up of Women Who Developed Subclinical Hypothyroidism during Pregnancy
Authors: Linardi Anastasia , Kakoulidis Ioannis , Ilias Ioannis , Michou Aikaterini , Pappa Athina , Venaki Evangelia , Koukkou Eftychia
Published: August 2020

There is inconsistency in the literature regarding the management of women diagnosed with subclinical hypothyroidism (SCH) during pregnancy in the postpartum period. The purpose of our study was to assess the need for continuation of levothyroxine (LT4) treatment after delivery. We conducted a retrospective cohort study of 114 women with new-onset SCH during pregnancy and at 1-year follow-up postpartum. Criteria for continuation of LT4 after delivery were breastfeeding, thyrotropin (TSH) levels at diagnosis >5 mIU/L, positive antithyroid antibodies and LT4 dose before delivery >50 μg/day. On treatment initiation, mean TSH ± SD was 5.24 ± 2.55 mIU/L. One year after delivery, most patients (86/114) were still on LT4. This was related to TSH levels at the initiation of treatment in gestation (p = 0.004) and inversely related to primiparity (p = 0.019). In the group of patients who stopped LT4 postpartum, treatment was reinstated in 11 out of 39 (28.2%) due to SCH relapse (mean TSH ± SD = 9.09 ± 5.81 mIU/L). Most women in our study continued treatment after delivery, and a considerable number of women who had discontinued LT4 restarted treatment postpartum. These results stress the need to reassess thyroid function at 6 to 12 months postpartum.
Novel Carbon Quantum Dots/Silver Blended Polysulfone Membrane with Improved Properties and Enhanced Performance in Tartrazine Dye Removal
Authors: Gan Jin Yee , Chong Woon Chan , Sim Lan Ching , Koo Chai Hoon , Pang Yean Ling , Mahmoudi Ebrahim , Mohammad Abdul Wahab
Published: August 2020

This study produced a novel polysulfone (PSF) membrane for dye removal using lemon-derived carbon quantum dots-grafted silver nanoparticles (Ag/CQDs) as membrane nanofiller. The preparation of CQDs was completed by undergoing hydrothermal treatment to carbonize the pulp-free lemon juice into CQD solution. The CQD solution was then coupled with Ag nanoparticles to form Ag/CQDs nanohybrid. The synthesized powders were characterized in terms of morphologies, functional groups and surface charges. A set of membranes was fabricated with different loadings of Ag/CQDs powder using the nonsolvent-induced phase separation (NIPS) method. The modified membranes were studied in terms of morphology, elemental composition, hydrophilicity and pore size. In addition, pure water flux, rejection test and fouling analysis of the membranes were evaluated using tartrazine dye. From the results, 0.5 wt % of Ag/CQD was identified as the optimum loading to be incorporated with the pristine PSF membrane. The modified membrane exhibited an excellent pure water permeability and dye rejection with improvements of 169% and 92%, respectively. In addition, the composite membrane also experienced lower flux decline, higher reversible fouling and lower irreversible fouling. This study has proven that the addition of CQD additives into membrane greatly improves the polymeric membrane’s properties and filtration performance.
Joining of Oxide Dispersion-Strengthened Steel Using Spark Plasma Sintering
Authors: Naimi Foad , Niepce Jean-Claude , Ariane Mostapha , Cayron Cyril , Calapez José , Gentzbittel Jean-Marie , Bernard Frédéric
Published: August 2020

Difficulties with joining oxide dispersion-strengthened (ODS) steels using classical welding processes have led to the development of alternative joining techniques such as spark plasma sintering (SPS). SPS, which is classically employed for performing sintering, may also be used to join relatively large components due to the simultaneous application of electrical pulsed current and uniaxial charge. SPS technology was tested by joining two ODS steel disks. The preliminary tests showed that it is necessary to control surface roughness before joining. Furthermore, the use of ground and lapped surfaces seemed to improve the quality of the interface. Tensile tests on two ODS cylinders joined using SPS were performed at 750 °C without any additives. Failure occurred away from the interface with a total elongation close to 50% and an ultimate stress of 110 MPa.
Erect Au Nanocones Drawn from Au Nano-Films by Nano-Size Au-Si Eutectic Clamping with High Adhesion to Substrates
Authors: Yu Xinxiang , Zhao Zhiguo , Shi Dandan , Dong Xiaoyan , Shi Xianli , Zhao Junfeng , Dai Han
Published: August 2020

Erect Au nanocones with high adhesion to substrates are obtained by simply drawing from Au nano-films through Au-Si eutectic welding. Nanocones with diameters ranging from about 5 to 150 nm and length ranging from about 60 to 600 nm can be observed on both Au and Si substrate surfaces. Nano-scale Au-Si eutectics formed at the rough Au–silicon film interface under annealing at 450 °C and the subsequent cooling process facilitate the formation of nano-bonding points and draw Au nanocones from Au nano-film by mechanical separation. Erect Au nanocones adhered to Au or Si substrates shows higher light enhancement than itself, observed by FDTD simulation. This method provides new strategy for the fabrication of SERS detectors, solar cells et al. with high stability.
Effects of Wire Drawing and Annealing Conditions on Torsional Ductility of Cold Drawn and Annealed Hyper-Eutectoid Steel Wires
Authors: Jung Jin Young , An Kang Suk , Park Pyeong Yeol , Nam Won Jong
Published: August 2020

The effects of microstructural features on torsional ductility of cold drawn and annealed hyper-eutectoid steel wires were investigated. The patented wire rods were successively dry drawn to ε = 0.79 (54.7%) ~ 2.38 (90.7%). To examine the effects of hot-dip galvanizing conditions on torsional ductility, steel wires with ε = 1.95 were annealed at 500 °C for 30 s for ~1 h in a salt bath. In cold drawn wires, the number of turns to failure increased steadily, showing the maximum peak, and then decreased with drawing strain. During the post-deformation annealing at 500 °C, torsional ductility of steel wires decreased with annealing time, except for the rapid drop due to the occurrence of delamination for 10 s annealing. The decrease of the number of turns to failure would be attributed to the microstructural evolutions, accompanying the spheroidization and growth of cementite particles and the recovery of ferrite in cold drawn steel wires. From the relationship between microstructural evolution and torsional ductility, it was found that among microstructural features, the shape and orientation of lamellar cementite showed the significant effect on torsional ductility of cold drawn and annealed hyper-eutectoid steel wires.
Micro-/Nano-Texturing of Aluminum by Precise Coining for Functional Surface Decoration
Authors: Aizawa Tatsuhiko , Yoshino Tomoaki , Inohara Tadahiko
Published: August 2020

The AISI316 austenitic stainless steel die was prepared and nitrided at 673 K for 14.4 ks. Through this low temperature plasma nitriding, the AISI316 die was homogeneously hardened up to 1400 HV within its surface layer of 50 μm. This nitrided AISI316 die was utilized to print the tailored micropattern with nanotextures onto its surface by the femtosecond laser processing. Each micropattern consisted of the tailored segments to have unidirectional nanotextures with different orientations. Each segment was recognized by its intrinsic surface plasmonic brilliance to tailored nanotextures. The CNC (Computer Numerical Control) stamping system was used to coin these micropatterns with nanotextures onto the AA1060 aluminum plates with the thickness of 1 mm. SEM (Scanning Electron Microscopy) and optical microscopy were employed to characterize the original micro-/nano-textures on the AISI316 die as well as the coined nanotextured patterns on the AA1060 plate surfaces.
Real-Time Temperature Measurement Using Infrared Thermography Camera and Effects on Tensile Strength and Microhardness of Hot Wire Plasma Arc Welding
Authors: Naksuk Nirut , Nakngoenthong Jiradech , Printrakoon Waravut , Yuttawiriya Rattanapon
Published: August 2020

The hot wire plasma arc welding process, a hybrid process between the plasma arc welding (PAW) process and hot wire process, is used to weld 316 stainless steel sheets, in which the temperature generated during welding is recorded in real time with a high-speed infrared thermography camera. Therefore, this research studies the factors in the hot wire process, of which there are two: (1) wire feed rate and (2) wire current; this study investigated the tensile strength, microhardness, and relationship of cooling rate per tensile strength and microhardness. The study found that the hot wire current plays an important role in cooling rates and tensile strength. The temperature results from high-speed infrared thermography camera show that the maximum welding temperature is around 1300 °C. The weld pool has a temperature between 900 and 1300 °C and the temperature profile of the weld pool will look like an “M” shaped, which is caused by the hot wire process. Finally, the appropriate hot wire parameters are 1.5 m/min for wire feed rate and 40A for wire current, which will give the workpiece cooling rate of 800–500 °C as 13.42 °C/s, tensile strength of 610.95 MPa, and the average Vickers microhardness of 195 HV.