bluuebunny/crossref_metadata_2025 huggingface dataset:
The Mediating Effects of Implied Volatility and Exchange Rate on the U.S. Tourism-Growth Nexus
Authors: Obi Pat , Ogbeide Godwin-Charles
Published: March 2022

In this paper, we examine the impact of destination risk and currency valuation on the U.S. tourism-growth nexus using the recently developed nonlinear autoregressive distributed lag cointegration technique. Tourism development is proxied by tourist arrivals, while growth is measured by real GDP. Empirical results show evidence of long-run asymmetric bidirectional causality. Positive shocks in tourism development directly impact growth, while negative shocks in GDP have a negative causal effect on tourism. This latter finding, which supports the growth-led tourism hypothesis, suggests that in the long run, tourism tends to improve following periods of economic weakness, perhaps due to the dollar’s weakness at such times. However, we have evidence only of unidirectional causality running from GDP to tourism in the short run. An important implication of these findings is the need to promote inbound tourism, especially when weakness in the U.S. economy is accompanied by a decline in the value of the dollar.
Urban Expansion in China: Spatiotemporal Dynamics and Determinants
Authors: Jing Shengqiang , Yan Yueguan , Niu Fangqu , Song Wenhui
Published: March 2022

China’s urbanization has attracted many scholars’ attention due to its significant impact on socioeconomic sustainability. Many studies have explored the spatial pattern and effects of the factors influencing urban expansion. However, the spatiotemporal dynamics integrating spatial and temporal dimensions and the spatial scales of the influencing factors are always ignored. This study applied the framework of exploratory space–time data analysis (ESTDA) to investigate the spatiotemporal dynamics of urban expansion across 342 cities in China from 1990 to 2017 and, further, used multiscale geographically weighted regression (MGWR) to estimate the effects of influencing factors on urban expansion. We found that urban expansion had an obvious south–north division, and yet the effects of influencing factors usually showed an east–west division. We also found that the dynamic local spatial dependency of urban expansion was accompanied by a volatile coevolution process and inclined to transfer from heterogeneity to homogeneity, and homogeneity tended to be stable. The coevolution of urban expansion between cities and other neighboring ones became stronger with increases in time and regional integration. These findings support the use of customized urban planning for specific regions in different spatial dependence to improve land-use efficiency and coordinate regional development.
Understanding the Intensity of Land-Use and Land-Cover Changes in the Context of Postcolonial and Socialist Transformation in Kaesong, North Korea
Authors: Kim Oh Seok , Václavík Tomáš , Park Mi Sun , Neubert Marco
Published: March 2022

This study examines the land-use and land-cover changes (LUCCs) in Kaesong, a North Korean city, and the area adjacent to the Korean Demilitarized Zone (DMZ). An intensity analysis—a framework decomposing LUCCs into interval, category, and transition levels—is applied to the land-cover maps of 1916, 1951, and 2015 to understand the importance of the historical period and associated land regimes (imperialism and socialism) in shaping LUCCs. The five land-cover classes—Built, Agriculture, Forest, Water, and Others—were analyzed among the two historical periods from Imperial Japan’s colonization (1910–1945) and the South–North division since the Korean War (1953–present). The results show that, at the interval level, the colonial period LUCCs were more intensive than the division period. However, >50% of the study area underwent changes during each period. At the category level, river channel modifications were the most intensive, followed by deforestation. In terms of transition, consistent intensity trends from Others to Built and Agriculture were observed across both land regimes. In conclusion, the LUCCs were more intensive under Japanese imperialism than the North Korean socialist regime, but the economic and geographic factors were not substantially affected by such land regimes. These underlying forces may be more significant fundamental drivers of LUCCs than land regimes themselves.
Spanish in Albuquerque, New Mexico: Spanish-English Bilingual Adults’ and Children’s Vocalic Realizations
Authors: Lease Sarah
Published: March 2022

This study explores vocalic production and variation in 29 Spanish-English bilingual children and adults from Albuquerque, New Mexico. Linear mixed-effects models analyzed the effects of lexical stress, word position, phonetic context, Spanish use, and lexical frequency on the F1 (height) and F2 (frontedness) values of 2041 /i e a o u/ vowels. Importantly, results show that /u/ fronting is pervasive in both children and adults’ speech, but in contrast to adults’ more general /u/ fronting, children’s Spanish use also predicted atonic /u/ fronting. Expanding the range of data to include children also showed that children’s realizations displayed a generalized stress effect, whereby the atonic space was condensed compared to the tonic space. The generalized stress effect was absent among the adults. Changes in the degree of phonetic convergence between the adults and children are attributed to acquisitional paths and demographic changes in their community.
Predominance of Antioxidants in Some Edible Plant Oils in Ameliorating Oxidative Stress and Testicular Toxicity Induced by Malathion
Authors: Abu Zeid Isam , Al-Asmari Khalid , Altayb Hisham , Al-Attar Atef , Qahl Safa , Alomar Mohammed
Published: March 2022

Malathion (MAL) is an insecticide that has been linked to reproductive system damage in both humans and animals. In the present investigation, the antitoxic effects of coffee and olive oils on MAL-induced testicular dysfunctions were evaluated. MAL-intoxicated rats were supplemented with coffee and olive oils (400 mg/kg) for 7 weeks. Exposure to MAL resulted in statistically altered antioxidant enzymes and histopathological findings of necrotic seminiferous tubules and spermatogenetic arrest in rats after seven weeks of treatment. The effects of MAL intoxication on physiological and histopathological changes were improved by the use of these oils. Murine double minute 2 (MDM2) was found to interact well with chlorogenic acid and oleuropein, two compounds from coffee and olive oils, respectively. Coffee oil and olive oil were found to be promising therapeutic agents for MAL-induced testicular toxicity and oxidative damage.
Renal Apoptosis in the Mycotoxicology of Penicillium polonicum and Ochratoxin A in Rats
Authors: Miljkovic Ana , Mantle Peter
Published: March 2022

Penicillium polonicum K. M. Zaleski, which is common on foodstuffs in Balkan regions that are notable for their history of endemic nephropathy, has been shown experimentally to cause a striking histopathological renal change in rats that are given feed contaminated by this fungus. The nephrotoxic agent(s) are only partially characterized. The principal change seen in the cortico-medullary region is karyocytomegaly, but apoptosis, identified with the ApopTag® methodology, is the first response to a dietary extract of P. polonicum-molded wheat after a few days of exposure. Chromatin debris migrates along the nephrons into the medulla, but whether the damaged epithelial fate is via autophagy is unclear. In intermittent exposure experiments, renal apoptosis was resolved with the cessation of exposure and was restored with renewed exposure. Apoptosis became less evident after 3 months of chronic exposure. In contrast, a relatively high dose of dietary ochratoxin A, a potent nephrocarcinogen in male rats after many months of dietary exposure, gave no evidence of apoptosis in asymptomatic weanlings over a few days of dietary exposure. This was attributed to a masking effect by concomitant marked histological disruption in renal tissue. However, in young adults, renal apoptosis was a primary outcome of dietary exposure to either the P. polonicum extract or to ochratoxin A, but the histopathological response to the former was less distorted. The apparent conflicted use in the literature of P. polonicum as a descriptor is highlighted.
Pulmonary Complications after COVID-19
Authors: Jakubec Petr , Fišerová Kateřina , Genzor Samuel , Kolář Milan
Published: March 2022

Coronavirus disease 2019 (COVID-19) is a threat to patients not only because of its acute course, but also because of various complications occurring in the following period, that is, more than 28 days after the onset of acute infection. The present study identified a total of 121 patients hospitalized 29 or more days after the first positive result of a PCR test for SARS-CoV-2, of whom 98 patients were included in the study. Patients were divided into two groups by the time interval between the positive COVID-19 test result and hospitalization date. The time intervals were week 5–11 in an ongoing-COVID group (57.1% of patients) and 12 or more weeks in a post-COVID-group (42.9%). The most frequent reason for hospitalization was respiratory tract infection (58.2%). Pneumonia accounted for 77.2% of these cases. Other reasons for hospitalization were interstitial lung disease (22.4%), pulmonary embolism (8.2%), and sarcoidosis (6.1%). The study group was further divided according to the causes of hospitalization into subgroups with infections and other causes. In the group with infectious diseases, there was a shorter time period between PCR positivity and hospitalization and there were significantly more frequent non-respiratory complications. In the entire sample, the in-hospital mortality was 5.1%.
Numerical and Experimental Study on the Direct Chill Casting of Large-Scale AA2219 Billets via Annular Coupled Electromagnetic Field
Authors: Zhao Haodong , Zhang Zhifeng , Bai Yuelong , Li Bao , Gao Mingwei
Published: March 2022

The internal coupled electromagnetic melt treatment (ICEMT) method is firstly proposed to produce high-quality and large-sized aluminum alloy billets. A three-dimensional model was established to describe the ICEMT process of direct chill casting (DC casting). The effect of ICEMT on the fluid flow patterns and temperature field in the DC casting of ϕ880 mm AA2219 billets is numerically analyzed. Moreover, the mechanisms of the ICEMT process on grain refinement and macrosegregation were discussed. The calculated results indicate that the electromagnetic field appears to be coupled circinate at the cross section of the melt, the fluid flow becomes unstable accompanied by the bias flow, and the temperature profiles are significantly more uniform. An experimental verification was conducted and the results prove that compared with traditional direct chill casting, the microstructures of the AA2219 large-scale billet under the ICEMT process are uniform and fine.
Secondary Creep Analysis of FG Rotating Cylinder with Exponential, Linear and Quadratic Volume Reinforcement
Authors: Sahni Manoj , Mehta Parth Dinesh , Sahni Ritu , León-Castro Ernesto , Espinoza-Audelo Luis F.
Published: March 2022

Creep is an irreversible time-dependent deformation in which a material under constant mechanical stress and elevated temperature for a considerably prolonged period of time, starts to undergo permanent deformation. Creep deformation occurs in three stages namely, primary, secondary and tertiary. Out of these three stages, secondary or steady state creep is particularly an area of engineering interest as it has almost a constant creep rate. Creep deformation plays a significant role in understanding effective service life of an engineering component working under high temperature conditions as such components such as super-heater and re-heater tubes and headers in a boiler, jet engines operating at temperature as high as 1200 ∘C, usually experience a failure or rupture due to creep phenomenon. Design engineers keep a close attention on working stress conditions and elevated temperature under which an engineering component is expected to work as these conditions determine the onset of creep behavior in an engineering component. By recognizing the parameters of material response to creep behavior, engineers can analyse the useful service life and hazardous working conditions for an engineering components. Recognizing the creep phenomenon as high temperature design limitation, ASME Boiler and Pressure Vessel Code have provided guidelines on maximum allowable stresses for materials to be used in creep range. One of the criteria for determination of allowable stresses is 1% creep deformation of material in 100,000 h of service. Thus, the study of creep behavior in engineering components pertaining to high stress and temperature working conditions is very important as it affects the reliability and performance of the engineering components. The aim of our study is to understand the behavior of secondary creep deformation so that an advanced reinforced functionally graded material with better creep resistance, can be designed. In this paper, a secondary creep analysis of functionally graded (FG) thick-walled rotating cylinder under internal and external pressure is conducted. The novelty of the model intends to specify secondary creep stresses and strains by employing exponential, linear and quadratic volume reinforcement for SiCp ceramic in Al metal matrix in radial direction. This will help us to understand the effect of volume reinforcement in FG cylinder under internal/external pressure and rotating centrifugal body force by obtaining secondary creep stresses and strains. The response of the FG cylinder with isotropic material is analyzed and the solution for stress–strain rates in radial and tangential directions are obtained in closed form. Comparison of steady state creep stresses and strains under exponential, linear and quadratic volume reinforcement profiles are discussed and presented graphically.
Study on the Structure and Skin Moisturizing Properties of Hyaluronic Acid Viscose Fiber Seamless Knitted Fabric for Autumn and Winter
Authors: Wang Qiuyu , Lu Jialiang , Jin Zimin , Chen Kun , Zhao Mingtao , Sun Yuqiang
Published: March 2022

In autumn and winter, the climate is dry and human skin tends to become dry as a result. The application of hyaluronic acid to a fabric has a certain moisturizing effect, which can further improve the wearing comfort of the fabric. In this study, three knitted fabric structures including weft plain stitch, 1 + 1 mock rib, and 1 + 3 mock rib were designed. The face yarn adopted hyaluronic acid viscose fiber, graphene viscose fiber, nylon, and viscose with different interweaving ratios, and the inner yarn adopted nylon/spandex-coated wire. A total of 18 sample knitted fabrics were woven according to the experimental method of the full test. The effects of the fabric structure and fabric raw materials on skin moisturizing properties were studied and analyzed by testing the skin water content and trans-epidermal water loss before and after coating the fabric on the human skin. The results show that the most significant factor affecting the skin moisture content is the raw material used in the fabric. When the interweaving ratio of hyaluronic acid viscose fiber in the fabric decreases, the moisturizing performance of the fabric on human skin is weakened. The second is the fabric structure. In terms of structure, 1 + 1 mock rib fabric has better moisturizing performance for human skin. When the material adopts hyaluronic acid viscose fiber/graphene viscose fiber (100:0) and the structure adopts 1 + 1 mock rib, the moisturizing effect on human skin is better.
Mechanical Properties of Reactive Powder Concrete with Coal Gangue as Sand Replacement
Authors: Luo Wen , Wang Haijun , Li Xiongwei , Wang Xiaolong , Wu Zhang , Zhang Yuan , Lian Xiaoqing , Li Xiaojun
Published: March 2022

Coal gangue (CG) represents a huge amount of industrial solid waste in China, and usually is used as a coarse aggregate to produce low-strength coal-gangue-based concrete. In this paper, in order to prove the possibility to obtain a higher-strength concrete with a higher CG utilization rate, reactive powder concrete (RPC) with coal gangue as a sand replacement at different replacement ratios was studied. RPC samples were prepared by replacing natural river sand (RS) with CG sand at different CG/RS weight ratios from 0–100% at intervals of 25%. Mechanical tests were carried out, and the microstructure features of RPC samples at 28 days were characterized. The test results showed that strong back shrinkage of strength existed. On days 7 and 14, the flexural strengths of samples with CG/RS replacement ratios of 0–75% fluctuated around the mean value. Strengths of samples with a CG/RS replacement ratio of 100% dropped off. However, on day 28, the flexural strengths of samples with CG were all lower than the strengths of samples on days 7 and 14. The flexural strengths and compressive strengths of the RPC with a CG/RS replacement ratio of 100% on day 14 were 14.09 MPa and 37.03 MPa, respectively, which decreased to 6.42 MPa and 28.44 MPa, respectively, on day 28. Compared with natural river sand, CG sand reduced the working performance, compressive strength, and flexural strength of RPC. Microscopic analysis showed that on day 28, increasing the CG replacement ratio could inhibit cement hydration, weaken the interface transition zone, and lead to the degradation of the RPC’s performance. Modification of CG sand would be helpful to obtain higher-strength concrete.
Microstructure and Texture Evolution during Superplastic Deformation of SP700 Titanium Alloy
Authors: Tian Ning , Ye Wenjun , Song Xiaoyun , Hui Songxiao
Published: March 2022

The superplastic tensile test was carried out on SP700 (Ti-4.5Al-3V-2Mo-2Fe) titanium alloy sheet at 760 °C by the method of maximum m value, and the microstructure characteristics were investigated to understand the deformation mechanism. The results indicated that the examined alloy showed an extremely fine grain size of ~1.3 μm and an excellent superplasticity with fracture elongation of up to 3000%. The grain size and the volume fraction of the β phase increased as the strain increased, accompanied by the elements’ diffusion. The β-stabilizing elements (Mo, Fe, and V) were mainly dissolved within the β phase and diffused from α to β phase furthermore during deformation. The increase in strain leads to the accumulation of dislocations, which results in the increase in the proportion of low angle grain boundaries by 15%. As the deformation process, the crystal of α grains rotated, and the texture changed, accompanied by the accumulation of dislocations. The phase boundary (α/β) sliding accommodated by dislocation slip was the predominant mechanism for SP700 alloy during superplastic deformation.
Recycling of Waste Facial Masks as a Construction Material, a Step towards Sustainability
Authors: Idrees Maria , Akbar Arslan , Mohamed Abdeliazim Mustafa , Fathi Dina , Saeed Farhan
Published: March 2022

Amid the COVID-19 pandemic, a sudden surge in the production and utilization of disposable, single-use facial masks has been observed. Delinquency in proper disposal of used facial masks endangers the environment with a new form of non-biodegradable plastic waste that will take hundreds of years to break down. Therefore, there is an urgent need for the resourceful recycling of such waste in an environmentally friendly way. This study presents an efficient solution by using waste masks in fibered or crushed form to produce environmentally friendly and affordable green concrete. This investigation assessed the mechanical and durability properties of waste masks-incorporated concrete. A total of six mixes were prepared for standardized tests to determine compressive strength, split cylinder tensile strength and rapid chloride penetration test (RCPT), and freeze-thaw resistance. The percentage of mask fibers used were 0.5, 1, 1.5, and 2% of concrete by volume, while crushed masks were used at 0.5% only. The mask waste in both forms was found suitable to be used in concrete. One percent of waste mask fibers was found as an optimum value to increase compressive and tensile strength, reduce chloride permeability, and increase freeze-thaw resistance. Besides this, 0.5% crushed mask fiber also performed well, especially for producing less permeable and highly durable concrete. It is thus corroborated that waste masks that increase pollution worldwide can be utilized sustainably to help build green buildings. By reutilizing waste masks to produce improved concrete with better strengths and higher durability, circular economy and sustainability are achieved, along with efficient waste management.
Correlation Analyses on Physical and Mechanical Parameters of Concrete in Marine Environments
Authors: Yao Jinwei , Song Hui , Yang Yizhan
Published: March 2022

This work explored the correlation among the physical and mechanical parameters of concrete in marine environments during corrosion. Concrete materials with varied water–cement ratios (w/c) were soaked in four kinds of simulated seawater, including a compound solution of sodium chloride (NaCl) and magnesium sulfate (MgSO4), a solution of MgSO4, a solution of sodium sulfate (Na2SO4), and clear water. The macroscopic physical and mechanical parameters, such as compressive strength, tensile strength, mass change and ultrasonic wave velocity, were measured. The damage mechanism of corrosion products and microstructures was analyzed using microscopic approaches including scanning electron microscopy (SEM), X-ray diffraction (XRD), etc. Linear correlation was carried out on the abovementioned physical parameters, and the results revealed that, during corrosion, the correlation between compressive and tensile strength and mass (excluding Na2SO4 solution) is positive (mostly highly correlated), while that with wave velocity is poor (mostly moderately correlated).
Pin-on-Disc Modelling with Mesh Deformation Using Discrete Element Method
Authors: Yan Yunpeng , Helmons Rudy , Schott Dingena
Published: March 2022

The pin-on-disc test is a standard sliding wear test used to analyse sliding properties, including wear contour and wear volume. In this study, long-term laboratory test performance is compared with a short-term numerical model. A discrete element method (DEM) approach combined with an Archard wear model and a deformable geometry technique is used. The effect of mesh size on wear results is evaluated, and a scaling factor is defined to relate the number of revolutions between the experiment and the numerical model. The simulation results indicate that the mesh size of the disc has a significant effect on the wear contour. The wear depth and wear width follow a normal distribution after experiencing a run-in phase, while the wear volume has a quadratic relation with the number of revolutions. For the studied material combination, the calibration of the wear coefficient shows that the wear volume of the pin-on-disc test accurately matches the simulation results for a minimum of eight revolutions with a wear coefficient lower than 2 × 10−11 Pa−1.
Atypical Properties of a Thin Silver Layer Deposited on a Composite Textile Substrate
Authors: Lebioda Marcin , Korzeniewska Ewa
Published: March 2022

Thin layers are widely used in electronics and protective coatings. They are also increasingly used in wearable electronics. A major challenge affecting the use of thin layers is their connection to flexible substrates, particularly textile products. This article describes the stability of the resistance of a silver layer with a thickness of 250 nm in a wide temperature range of 15–295 K. The aim was to determine the temperature dependence of the resistance of layers formed on a composite textile substrate compared with that of layers produced on an Al2O3 substrate. The results showed that the electrical parameters of the layer formed on the composite textile substrate changed in a manner atypical for metallic layers. This may have been due to the polyurethane base layer. The roughness and ability to deform under the influence of heat of the substrate can significantly affect the electrical parameters of a thin metal layer produced by the PVD coating process, which is important for the design of textronic applications.
Thermo-Mechanical Analysis of Mass Concrete Foundation Slabs at Early Age—Essential Aspects and Experiences from the FE Modelling
Authors: Smolana Aneta , Klemczak Barbara , Azenha Miguel , Schlicke Dirk
Published: March 2022

In this paper, the focus is placed on essential aspects of finite element modelling of thermo-mechanical behaviour of massive foundation slabs at early ages. Basic decision-making issues are discussed in this work: the potential need to explicitly consider the casting process in the modelling, the necessary size of the underlying soil to be modelled and the size of the FE mesh, and the need of considering daily changes of the environmental temperature and the temperature distribution over the depth of the soil. Next, the contribution of shrinkage to early age stresses, the role of the reinforcement, and the type of mechanical model are investigated. Comparative analyses aiming to investigate the most important aspects of the FE model and some possible simplifications with negligible effect on the results are made on the example of a massive foundation slab. Finally, the results are summarized with recommendations for creating the FE models of massive slabs at early ages.
Microstructural Variation of Clay during Land Subsidence and the Correlation between Macroscopic and Microscopic Parameters
Authors: Di Shengtong , Jia Chao , Ding Pengpeng , Zhu Xiao
Published: March 2022

The nonlinear deformation, visco-elasto-plasticity and other macroscopic properties of soil are the concentrated manifestations of its microstructural state. In order to study the microstructural characteristics and variations of the clay under the action of additional stress caused by groundwater exploitation, borehole sampling was carried out on the clay layers at different depths in a typical land subsidence area. Consolidation tests, freeze-drying, ion sputtering, and scanning electron microscope (SEM) were conducted in order to scan and analyze the microstructure of the test samples at different scales. The Particles and Cracks Analysis System (PCAS) was used to quantify the microscopic parameters, the variations of the microstructural parameters with consolidation loads at different sizes were revealed, and the correlation between the macroscopic and microscopic parameters were discussed. The results show that: (1) the microstructural characteristics of soils with different buried depths have directivity, to a certain extent; (2) as the consolidation load increases, the average unit area and average form factor of the soil microstructure generally decrease, the structural arrangement of the unit gradually tends to be orderly, and the average pore area, apparent void ratio and the number of pores generally show a decreasing trend; (3) under the action of a consolidation load, when the microstructure at a relatively large scale is basically stable, the microstructure at a smaller scale will continue to adjust; (4) the apparent void ratio has a good linear regression relationship with the conventional void ratio, and the apparent void ratio has a good exponential growth relationship with the compressibility.
Positron Annihilation Spectroscopy Complex for Structural Defect Analysis in Metal–Hydrogen Systems
Authors: Bordulev Iurii , Laptev Roman , Kudiiarov Viktor , Elman Roman , Popov Alexander , Kabanov Denis , Ushakov Ivan , Lider Andrey
Published: March 2022

The current work is devoted to developing a system for the complex research of metal–hydrogen systems, including in an in situ mode. The system consists of a controlled gas reactor with a unique reaction chamber, a radioisotope positron source, and a positron annihilation spectroscopy complex. The use of the system enables in situ investigation of the defect structure of solids in hydrogen sorption–desorption processes at temperatures up to 900 °C and pressures up to 50 bar. Experimental investigations of magnesium and magnesium hydride during thermal annealing were carried out to approve the possibilities of the developed complex. It was shown that one cycle of magnesium hydrogenation–dehydrogenation resulted in the accumulation of irreversible hydrogen-induced defects. The defect structure investigation of the magnesium–hydrogen system by positron annihilation techniques was supplemented with a comprehensive study by scanning electron microscopy, X-ray diffraction analysis, and hydrogen sorption–desorption studies.
The Effect of Heat Treatment on Damping Capacity and Mechanical Properties of CuAlNi Shape Memory Alloy
Authors: Ivanić Ivana , Kožuh Stjepan , Grgurić Tamara Holjevac , Vrsalović Ladislav , Gojić Mirko
Published: March 2022

This paper discusses the effect of different heat treatment procedures on the microstructural characteristics, damping capacities, and mechanical properties of CuAlNi shape memory alloys (SMA). The investigation was performed on samples in the as-cast state and heat treated states (solution annealing at 885 °C/60′/H2O and after tempering at 300 °C/60′/H2O). The microstructure of the samples was examined by light microscopy (LM) and scanning electron microscopy (SEM) equipped with a device for energy dispersive spectrometry (EDS) analysis. Light and scanning electron microscopy showed martensitic microstructure in all investigated samples. However, the changes in microstructure due to heat treatment by the presence of two types of martensite phases (β1′ and γ1′) influenced alloy damping and mechanical properties by enhancing alloy damping characteristics. Heat treatment procedure reduced the alloys’ mechanical properties and increased hardness of the alloy. Fractographic analysis of the alloy showed a transgranular type of fracture in samples after casting. After solution annealing, two types of fracture mechanisms can be noticed, transgranular and intergranular, while in tempered samples, mostly an intergranular type of fracture exists.
Shell-to-Beam Numerical Homogenization of 3D Thin-Walled Perforated Beams
Authors: Staszak Natalia , Gajewski Tomasz , Garbowski Tomasz
Published: March 2022

Determining the geometric characteristics of even complex cross-sections of steel beams is not a major challenge nowadays. The problem arises when openings of various shapes and sizes appear at more or less regular intervals along the length of the beam. Such alternations cause the beam to have different stiffnesses along its length. It has different bending and shear stiffnesses at the opening point and in the full section. In this paper, we present a very convenient and easy-to-implement method of determining the equivalent stiffness of a beam with any cross-section (open or closed) and with any system of holes along its length. The presented method uses the principles of the finite element method (FEM), but does not require any formal analysis, i.e., solving the system of equations. All that is needed is a global stiffness matrix of the representative volumetric element (RVE) of the 3D representation of a beam modeled with shell finite elements. The proposed shell-to-beam homogenization procedure is based on the strain energy equivalence, and allows for precise and quick determination of all equivalent stiffnesses of a beam (flexural and shear). The results of the numerical homogenization procedure were compared with the existing analytical solution and experimental results of various sections. It has been shown that the results obtained are comparable with the reference results.
Boundary Element and Sensitivity Analysis of Anisotropic Thermoelastic Metal and Alloy Discs with Holes
Authors: Fahmy Mohamed Abdelsabour , Alsulami Mohammed Owaidh
Published: March 2022

The main aim of this paper was to develop an advanced processing method for analyzing of anisotropic thermoelastic metal and alloy discs with holes. In the boundary element method (BEM), the heat impact is expressed as an additional volume integral in the corresponding boundary integral equation. Any attempt to integrate it directly will necessitate domain discretization, which will eliminate the BEM’s most distinguishing feature of boundary discretization. This additional volume integral can be transformed into the boundary by using branch-cut redefinitions to avoid the use of additional line integrals. The numerical results obtained are presented graphically to show the effects of the transient and steady-state heat conduction on the quasi-static thermal stresses of isotropic, orthotropic, and anisotropic metal and alloy discs with holes. The validity of the proposed technique is examined for one-dimensional sensitivity, and excellent agreement with finite element method and experimental results is obtained.
Wettability of Metal Surfaces Affected by Paint Layer Covering
Authors: Pogorzelski Stanislaw , Boniewicz-Szmyt Katarzyna , Grzegorczyk Maciej , Rochowski Pawel
Published: March 2022

The aim of the work was to quantify the surface wettability of metallic (Fe, Al, Cu, brass) surfaces covered with sprayed paints. Wettability was determined using the contact angle hysteresis approach, where dynamic contact angles (advancing ΘA and receding ΘR) were identified with the inclined plate method. The equilibrium, ΘY, contact angle hysteresis, CAH = ΘA − ΘR, film pressure, Π, surface free energy, γSV, works of adhesion, WA, and spreading, WS, were considered. Hydrophobic water/solid interactions were exhibited for the treated surfaces with the dispersive term contribution to γSV equal to (0.66–0.69). The registered 3D surface roughness profiles allowed the surface roughness and surface heterogeneity effect on wettability to be discussed. The clean metallic surfaces turned out to be of a hydrophilic nature (ΘY < 90°) with high γSV, heterogeneous, and rough with a large CAH. The surface covering demonstrated the parameters’ evolution, ΘA↑, ΘR↑, γSV↓, WA↓, and WS↓, corresponding to the surface hydrophobization and exhibiting base substratum-specific signatures. The dimensionless roughness fluctuation coefficient, η, was linearly correlated to CAH. The CAH methodology based on the three measurable quantities, ΘA, ΘR, and liquid surface tension, γLV, can be a useful tool in surface-mediated process studies, such as lubrication, liquid coating, and thermoflow.
Magnetic Properties and Biocompatibility of Different Thickness (Pd/Fe)n Coatings Deposited on Pure Ti Surface via Multi Arc Ion Plating
Authors: Yang Yang , Li Li , Li Li , Zhang Zhang , Li Li , Sheng Sheng , Ding Ding
Published: March 2022

The different thickness (Fe/Pd)n coatings were prepared by vacuum ion plating technology on a pure Ti substrate. The (Fe/Pd)n coatings were magnetized using an MC-4000 high-pressure magnetizing machine. Then, the effect of the (Fe/Pd)n coating thickness on the magnetic properties was studied. The surface and section morphology, composition, phase structure, magnetic properties, and biocompatibility of the (Fe/Pd)n coatings were studied by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and CCTC-1 digital flux field measurement. The results showed that the (Fe/Pd)n coatings were granular, smooth, and compact, without cracks. In addition the (Fe/Pd)n coatings formed an L10 phase with a magnetic face-centered tetragonal-ordered structure after heat treatment. With the increase in the thickness of (FePd)n coatings, the content of L10 FePd phase increased and the remanence increased. The remanence values of the Fe/Pd, (Fe/Pd)5, (Fe/Pd)10, and (Fe/Pd)15 magnetic coatings were 0.83 Gs, 5.52 Gs, 7.14 Gs, and 7.94 Gs, respectively. Additionally, the (Fe/Pd)n magnetic coatings showed good blood compatibility and histocompatibility.
Unified Stress–Strain Model of FRP-Confined Square and Circle Rubber Concrete Columns
Authors: Cao Yugui , Zhao Guoxu , Zhang Yang , Hou Can , Mao Ling
Published: March 2022

Studying the stress–strain relationship of fiber-reinforced polymer (FRP)-confined rubber concrete (RuC) plays an important role in its application in engineering projects. Most of the existing stress–strain relationship models are established based on the test data of FRP-confined rubber concrete with circular cross-sections, and the effect of the section shape is not considered. Therefore, an analysis-oriented stress–strain model of FRP-confined circular and square rubber concrete columns was studied in this paper for the first time. A database that includes the rubber particle content and section shape on the peak stress-peak strain and axial–lateral strain relationship of FRP-confined rubber concrete was established by collecting 235 test data from the literature. By modifying the key parameters in the existing FRP-confined normal concrete stress–strain relationship model, a unified stress–strain relationship model of FRP-confined RuC with circular and square columns is established. The proposed model is verified, and a good accuracy of the model is proven.
Gas Flow Measurement Method with Temperature Compensation for a Quasi-Isothermal Cavity
Authors: Shi Yan , Chang Jiaqi , Zhang Qingzhen , Liu Lijiao , Wang Yixuan , Shi Zhaohui
Published: March 2022

Pneumatic transmission is a technology that uses compressed air as a power source to drive and control various mechanical equipment to realize the mechanization and automation of production processes. With the development of industrial mechanization and automation, pneumatic technology, represented by pneumatic muscle, is increasingly becoming more widely used in various fields. The current standards for research are more complex for the measurement of flow without a flowmeter, some of them do not consider the influence of temperature change on flow measurement, and some of them are simplified as adiabatic or isothermal models, which are inaccurate measurement methods in actual practical application. This paper describes a method to determine flow rate by measuring the pressure change in the process of gas tank inflation. This study used the method of temperature compensation to eliminate the influence of temperature in the isothermal formula. The measurement structure was simple and the calculation was accurate, which has a certain practical significance. Based on this method, charging experiments were carried out with a gas tank that had a volume of 3 L or 5 L with or without copper wire filling, and the experimental results were used in the processed research. The temperature compensation parameters were identified with or without an isothermal environment and in different sizes of tanks. This method identified the different parameters of the 5 L tank and 3 L tank. Finally, the flow compensation was completed for the gas tank filled with copper wire. After verification, the results of the quasi-isothermal calculation formula and temperature compensation formula were close to those measured by a high-precision flow sensor in the experiment. The method introduced in this study is a novel flow calculation method that is simple in structure and accurate in calculation compared with the conventional isothermal calculation method; furthermore, it can be used in real world situations without the need for a high-precision flow sensor.
Remarks on Recent Results for Generalized F-Contractions
Authors: Huang Huaping , Todorčević Vesna , Radenović Stojan
Published: March 2022

In this paper, we give some remarks on the recent papers on generalized F-contractions. Our results unify and generalize the previous results in the existing literature. Moreover, we give an example to support our results. As an application, we give the existence and uniqueness of a solution to a class of differential equations.
Cumulative Residual Tsallis Entropy-Based Test of Uniformity and Some New Findings
Authors: Mohamed Mohamed S. , Barakat Haroon M. , Alyami Salem A. , Abd Elgawad Mohamed A.
Published: March 2022

The Tsallis entropy is an extension of the Shannon entropy and is used extensively in physics. The cumulative residual Tsallis entropy, which is a generalization of the Tsallis entropy, plays an important role in the measurement uncertainty of random variables and has simple relationships with other important information and reliability measures. In this paper, some novel properties of the cumulative residual Tsallis entropy are disclosed. Moreover, this entropy measure is applied to testing the uniformity, where the limit distribution and an approximation of the distribution of the test statistic are derived. In addition, the property of stability is discussed. Furthermore, the percentage points and power against seven alternative distributions of this test statistic are presented. Finally, to compare the power of the suggested test with that of other tests of uniformity, a simulation study is conducted.
A Localized Method of Fundamental Solution for Numerical Simulation of Nonlinear Heat Conduction
Authors: Wang Feng , Liu Yan-Cheng , Zheng Hui
Published: March 2022

In this study, an efficient localized method of fundamental solution (LMFS) is applied to nonlinear heat conduction with mixed boundary conditions. Since the thermal conductivity is temperature-dependent, the Kirchhoff transformation is used to transform the nonlinear partial differential equations (PDEs) into Laplace equations with nonlinear boundary conditions. Then the LMFS is applied to the governing equation, and the nonlinear equations are treated by the fictitious time integration method (FTIM). Both 2D and 3D numerical examples are proposed to verify the effectiveness of the LMFS.
On the Global Well-Posedness and Decay of a Free Boundary Problem of the Navier–Stokes Equation in Unbounded Domains
Authors: Oishi Kenta , Shibata Yoshihiro
Published: March 2022

In this paper, we establish the unique existence and some decay properties of a global solution of a free boundary problem of the incompressible Navier–Stokes equations in Lp in time and Lq in space framework in a uniformly H∞2 domain Ω⊂RN for N≥4. We assume the unique solvability of the weak Dirichlet problem for the Poisson equation and the Lq-Lr estimates for the Stokes semigroup. The novelty of this paper is that we do not assume the compactness of the boundary, which is essentially used in the case of exterior domains proved by Shibata. The restriction N≥4 is required to deduce an estimate for the nonlinear term G(u) arising from divv=0. However, we establish the results in the half space R+N for N≥3 by reducing the linearized problem to the problem with G=0, where G is the right member corresponding to G(u).
3-Derivations and 3-Automorphisms on Lie Algebras
Authors: Xia Haobo
Published: March 2022

In this paper, first we establish the explicit relation between 3-derivations and 3- automorphisms of a Lie algebra using the differential and exponential map. More precisely, we show that the Lie algebra of 3-derivations is the Lie algebra of the Lie group of 3-automorphisms. Then we study the derivations and automorphisms of the standard embedding Lie algebra of a Lie triple system. We prove that derivations and automorphisms of a Lie triple system give rise to derivations and automorphisms of the corresponding standard embedding Lie algebra. Finally we compute the 3-derivations and 3-automorphisms of 3-dimensional real Lie algebras.
Effects of Chemical Cleaning on the Ageing of Polyvinylidene Fluoride Microfiltration and Ultrafiltration Membranes Fouled with Organic and Inorganic Matter
Authors: Chheang Mariny , Hongprasith Narapong , Ratanatawanate Chalita , Lohwacharin Jenyuk
Published: March 2022

Herein, the effects of cleaning with sodium hydroxide and citric acid solutions as cleaning reagents on the changes in the properties of two hollow-fiber PVDF microfiltration (MF) and ultrafiltration (UF) membranes fouled with organic and inorganic matter were investigated. Accelerated membrane ageing was induced by use of high concentrations of tannic acid and iron oxide (Fe2O3) particles in the feed water; these conditions were kept with different membrane soaking times to observe temporal effects. It was found that tannic acid molecules adsorb onto the membrane surface that results in changes in surface characteristics, particularly surface functional groups that are responsible for enhancing membrane’s hydrophilicity. Experimental results demonstrate that NaOH had a stronger effect on the tensile strength and surface chemistry of the fouled MF and UF membranes than citric acid. Prediction of lifetime by an exponential (decay) model confirmed that the UF membrane cleaned with NaOH would be aged within about 1.8 years and the MF membrane after about 5 years, at cleaning every 15 days, downtime 2 h per cleaning, when a 10% tensile strength decrease against the original membrane is allowed.
Effect of Protocatechuic Acid Ethyl Ester on Biomembrane Models: Multilamellar Vesicles and Monolayers
Authors: Torrisi Cristina , Malfa Giuseppe Antonio , Acquaviva Rosaria , Castelli Francesco , Sarpietro Maria Grazia
Published: March 2022

The interactions of drugs with cell membranes are of primary importance for several processes involved in drugs activity. However, these interactions are very difficult to study due to the complexity of biological membranes. Lipid model membranes have been developed and used to gain insight into drug–membrane interactions. In this study, the interaction of protocatechuic acid ethyl ester, showing radical-scavenging activity, antimicrobial, antitumor and anti-inflammatory effects, with model membranes constituted by multilamellar vesicles and monolayers made of DMPC and DSPC, has been studied. Differential scanning calorimetry and Langmuir–Blodgett techniques have been used. Protocatechuic acid ethyl ester interacted both with MLV and monolayers. However, a stronger interaction of the drug with DMPC-based model membranes has been obtained. The finding of this study could help to understand the protocatechuic acid ethyl ester action mechanism.
Design and Experimental Investigation of a Rotational Piezoelectric Energy Harvester with an Offset Distance from the Rotation Center
Authors: Chen Jun , Liu Xiangfu , Wang Hengyang , Wang Sheng , Guan Mingjie
Published: March 2022

Rotational energy harvesting technology has attracted more and more attention recently. This paper presents a piezoelectric rotational energy harvester that can be mounted with an offset distance from the rotation center. The piezoelectric energy harvester is designed to be dynamically excited by the force due to gravity, which causes the piezoelectric cantilever beams in the harvester to vibrate periodically as the harvester rotates. A novel design of the harvester structure with a hollow mass is proposed and analyzed in this paper. Experiments were performed to investigate the design and analysis. A power output of 106~2308 μW can be achieved at the rotating frequencies of 0.79~14 Hz with a piezoelectric cantilever beam in the prototyped energy harvester. Results showed that the prototyped harvester can be mounted on a rotating wheel hub and output sufficient power in a wide frequency range for wireless monitoring sensors.