bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytotoxicity and Efficacy in Debris and Smear Layer Removal of HOCl-Based Irrigating Solution: An In Vitro Study
Authors: Bilvinaite Goda , Zongolaviciute Ruta , Drukteinis Saulius , Bukelskiene Virginija , Cotti Elisabetta
Published: July 2022

In the present study we evaluated the cytotoxicity of super-oxidized water on human gingival fibroblasts and its efficacy in debris and smear layer removal from root canal walls. Cultured gingival fibroblasts were exposed to super-oxidized water (Sterilox), which was diluted in Iscove’s modified Dulbecco’s medium (IMDM) at 30%, 40%, 50%, 60% and 70% concentrations. The control group was maintained in IMDM. The cell viability was evaluated by means of an MTT assay after incubation periods of 1 h, 2 h, 24 h and 48 h. Pathological cellular changes were also observed under fluorescence and phase contrast microscopes. The efficacy in debris and smear layer removal was evaluated in comparison to the conventional application of sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA). Forty maxillary premolars were randomly divided into two equal groups (n = 20) and shaped with ProTaper NEXT rotary instruments using Sterilox or NaOCl/EDTA for irrigation. Afterwards, roots were split longitudinally and examined under a scanning electron microscope. The results revealed that super-oxidized water and sterile distilled water have acceptable biological properties for endodontic applications at concentrations up to 50% (p > 0.05). Moreover, super-oxidized water is equally effective in debris and smear layer removal as compared to NaOCl/EDTA (p > 0.05).
Modification of Collagen Film via Surface Grafting of Taurine Molecular to Promote Corneal Nerve Repair and Epithelization Process
Authors: Liu Yang , Zhang Chuanlei , Kong Yanhui , Liu Huiyu , Guo Jia , Yang Hui , Deng Linhong
Published: July 2022

Corneal defects can seriously affect human vision, and keratoplasty is the most widely accepted therapy method for visual rehabilitation. Currently, effective treatment for clinical patients has been restricted due to a serious shortage of donated cornea tissue and high-quality artificial repair materials. As the predominant component of cornea tissue, collagen-based materials have promising applications for corneal repair. However, the corneal nerve repair and epithelization process after corneal transplantation must be improved. This research proposes a new collagen-based scaffold with good biocompatibility and biological functionality enhanced by surface chemical grafting of natural taurine molecular. The chemical composition of collagen-taurine (Col-Tau) material is evaluated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, and its hydrophilic properties, light transmittance, swelling performance and mechanical tensile properties have been measured. The research results indicate that the Col-Tau sample has high transmittance and good mechanical properties, and exhibits excellent capacity to promote corneal nerve cell growth and the epithelization process of corneal epithelial cells. This novel Col-Tau material, which can be easily prepared at a low cost, should have significant application potential for the treating corneal disease in the future.
Comparison between the RANS Simulations of Double-Body Flow and Water–Air Flow around a Ship in Static Drift and Circle Motions
Authors: Jiang Long , Yao Jianxi , Liu Zuyuan
Published: July 2022

Manoeuvrability is one of the important ship hydrodynamic performances. That is closely related to the safety and economy of navigation. The development of a high-accuracy and high-efficiency numerical method to compute the forces and moments on manoeuvring ships has been the main task for ship manoeuvring predictions. The numerical method by solving RANS (Reynolds-Averaged Navier–Stokes) equations may be the most used one nowadays for the computations of ship manoeuvring forces and moments. However, applying a RANS tool for ship manoeuvring prediction remains very low efficiency, especially considering the six-degrees-of-freedom ship motions on the water surface. Thus, it is very necessary to introduce a few assumptions to reduce the computational time when applying a RANS tool, e.g., the assumptions of double-body flow and body force propeller, and consequently improve the application efficiency. Generally speaking, the assumption of double-body flow, in which the free-surface effects are neglected, is more suitable for low-speed ships. Nevertheless, rare publications have been reported relating to how this assumption affects the accuracy of the computed manoeuvring forces and moments. To this end, this article presents a comparative study between the RANS simulations of double-body flow and water–air flow around a container ship performing static drift and static circle motions. Three ship speeds, corresponding to the Froude numbers 0.156, 0.201, and 0.260, respectively, are considered during the simulations. The computed side forces and yaw moments obtained by the water–air flow simulations are closer to the available experimental data than that obtained by the double-body flow simulations for all ship speeds. The computed surge forces obtained by water–air flow simulations also agree well with the experimental data, whereas the computed surge forces obtained by the double-body flow simulations are wrong. The reasons are analyzed by comparing the pressure distributions on the ship surface and the flow separations around the ship.
Multiscale Energy Transfers and Conversions of Kuroshio in Luzon Strait and Its Adjacent Regions
Authors: He Zhongjie , Fu Xiachuan , Zhao Yueqi , Jiang Xuyu
Published: July 2022

Using the local multiscale energy and vorticity analysis (MS-EVA) and based on the global high-resolution ocean reanalysis product GLORYS12V1 for 20 years, this study investigates the energy transfers and conversions of Kuroshio in the Luzon Strait and its adjacent regions through three scales, namely, the climatological scale, the seasonal scale, and the eddy scale. The results show that the inverse cascades of kinetic energy dominate the energy transfer east of Luzon (at both the eddy and seasonal scales). Kuroshio transfers the climatological kinetic energy to the eddy scale through a forward energy cascade in Luzon Strait and east of Taiwan. Because the topography of Luzon Strait and Kuroshio jointly block and limit the westward propagation of non-local eddies, the eddy energy in the South China Sea west of Luzon Strait tends to depend on local forward potential energy cascades. In these subregions, potential energy drives the accumulation of kinetic energy under the action of buoyancy conversion: interannual (seasonal) potential energy as the source of multiscale energy in the Luzon Strait (the east of Taiwan).
Research on Multi-Ship Target Detection and Tracking Method Based on Camera in Complex Scenes
Authors: Hong Xiaobin , Cui Bin , Chen Weiguo , Rao Yinhui , Chen Yuanming
Published: July 2022

Aiming at the problem that multi-ship target detection and tracking based on cameras is difficult to meet the accuracy and speed requirements at the same time in some complex scenes, an improved YOLOv4 algorithm is proposed, which simplified the network of the feature extraction layer to obtain more shallow feature information and avoid the disappearance of small ship target features, and uses the residual network to replace the continuous convolution operation to solve the problems of network degradation and gradient disappearance. In addition, a nonlinear target tracking model based on the UKF method is constructed to solve the problem of low real-time performance and low precision in multi-ship target tracking. Multi-ship target detection and tracking experiments were carried out in many scenes with large differences in ship sizes, strong background interference, tilted images, backlight, insufficient illumination, and rain. Experimental results show that the average precision of the detection algorithm of this paper is 0.945, and the processing speed is about 34.5 frame per second, where the real-time performance is much better than other algorithms while maintaining high precision. Furthermore, the multiple object tracking accuracy (MOTA) and the multiple object tracking precision (MOTP) of this paper algorithm are 76.4 and 80.6, respectively, which are both better than other algorithms. The method proposed in this paper can realize the ship target detection and tracking well, with less missing detection and false detection, and also has good accuracy and real-time performance. The experimental results provide a valuable theoretical reference for the further practical application of the method.
Bioactivity of Biomass and Crude Exopolysaccharides Obtained by Controlled Submerged Cultivation of Medicinal Mushroom Trametes versicolor
Authors: Angelova Galena , Brazkova Mariya , Mihaylova Dasha , Slavov Anton , Petkova Nadejda , Blazheva Denica , Deseva Ivelina , Gotova Irina , Dimitrov Zhechko , Krastanov Albert
Published: July 2022

The aim of this study is to characterize the bioactivity of mycelial biomass and crude exopolysaccharides (EPS) produced by Trametes versicolor NBIMCC 8939 and to reveal its nutraceutical potential. The EPS (1.58 g/L) were isolated from a culture broth. The macrofungal biomass was rich in protein, insoluble dietary fibers and glucans. The amino acid composition of the biomass was analyzed and 18 amino acids were detected. Three mycelial biomass extracts were prepared and the highest total polyphenol content (16.11 ± 0.14 mg GAE/g DW) and the total flavonoid content (5.15 ± 0.03 mg QE/g DW) were found in the water extract. The results indicated that the obtained EPS were heteropolysaccharides with glucose as the main building monosaccharide and minor amounts of mannose, xylose, galactose, fucose and glucuronic acid. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the complex structure of the crude EPS. Five probiotic lactic acid bacteria strains were used for the determination of the prebiotic effect of the crude EPS. The anti-inflammatory potential was tested in vitro using cell line HT-29. The significant decrease of IL-1 and IL-8 and increase of TGF-beta expression revealed anti-inflammatory potential of the crude exopolysaccharides from T. versicolor.
The Predictability of the Surgical Outcomes of Class III Patients in the Transverse Dimension—A Study of Three-Dimensional Assessment
Authors: Lai U-Kei , Wu Cheng-Chun , Chang Yu-Jen , Lin Shiu-Shiung , Lai Jui-Pin , Wu Te-Ju
Published: July 2022

This study aimed to assess the outcomes of planned maxillary surgical movements in the transverse direction in patients possessing a Class III skeletal pattern. The available consecutive patients’ records were retrospectively reviewed. Only those possessing a Class III skeletal pattern, and for whom the same virtual planning system was used, were enrolled. The waferless technique was used to guide the jawbone repositioning. A representative triangle in the virtual maxilla of each stage was used to validate the planned surgical movements (PSMs) and the outcome discrepancy (OD). The linear and angular measurements were retrieved for the assessments of the correlation between PSM and OD. In total, 44 adult patients who met the inclusion criteria were studied. The average linear OD of the A-point in the transverse direction was 0.66 ± 0.54 mm, and the yaw correction showed 1.02 ± 0.84 degrees in difference. There was no specific correlation between the linear PSMs and ODs; however, the angular ones were positively correlated. With the help of the waferless technique to transfer the virtual planning results, the practitioners could confidently predict the postsurgical maxillary position in the transverse direction in the orthognathic surgery of Class III patients. However, the yaw correction should be carefully planned to avoid postsurgical instabilities.
Construction of a miRNA-Based Nomogram Model to Predict the Prognosis of Endometrial Cancer
Authors: Ni Leyi , Tang Chengyun , Wang Yuning , Wan Jiaming , Charles Morgan G. , Zhang Zilong , Li Chen , Zeng Ruijie , Jin Yiyao , Song Penghao , Wei Ming , Li Bocen , Zhang Jin , Wu Zhenghao
Published: July 2022

Objective: To investigate the differential expression of microRNA (miRNA) in patients with endometrial cancer and its relationship with prognosis and survival. Method: We used The Cancer Genome Atlas (TCGA) database to analyze differentially expressed miRNAs in endometrial cancer tissues and adjacent normal tissues. In addition, we successfully screened out key microRNAs to build nomogram models for predicting prognosis and we performed survival analysis on the key miRNAs as well. Result: We identified 187 differentially expressed miRNAs, which includes 134 up-regulated miRNAs and 53 down-regulated miRNAs. Further univariate Cox regression analysis screened out 47 significantly differentially expressed miRNAs and selected 12 miRNAs from which the prognostic nomogram model for ECA patients by LASSO analysis was constructed. Survival analysis showed that high expression of hsa-mir-138-2, hsa-mir-548f-1, hsa-mir-934, hsa-mir-940, and hsa-mir-4758 as well as low-expression of hsa-mir-146a, hsa-mir-3170, hsa-mir-3614, hsa-mir-3616, and hsa-mir-4687 are associated with poor prognosis in EC patients. However, significant correlations between the expressions levels of has-mir-876 and hsa-mir-1269a and patients’ prognosis are not found. Conclusion: Our study found that 12 significantly differentially expressed miRNAs might promote the proliferation, invasion, and metastasis of cancer cells by regulating the expression of upstream target genes, thereby affecting the prognosis of patients with endometrial cancer.
Allergic Asthma in the Era of Personalized Medicine
Authors: Papapostolou Niki , Makris Michael
Published: July 2022

Allergic asthma is the most common asthma phenotype and is characterized by IgE sensitization to airborne allergens and subsequent typical asthmatic symptoms after exposure. A form of type 2 (T2) airway inflammation underlies allergic asthma. It usually arises in childhood and is accompanied by multimorbidity presenting with the occurrence of other atopic diseases, such as atopic dermatitis and allergic rhinitis. Diagnosis of the allergic endotype is based on in vivo (skin prick tests) and/or in vitro (allergen-specific IgE levels, component-resolved diagnosis (CRD)) documentation of allergic sensitization. Biomarkers identifying patients with allergic asthma include total immunoglobulin E (IgE) levels, fractional exhaled nitric oxide (FeNO) and serum eosinophil counts. The treatment of allergic asthma is a complex procedure and requires a patient-tailored approach. Besides environmental control involving allergen avoidance measurements and cornerstone pharmacological interventions based on inhaled drugs, allergen-specific immunotherapy (AIT) and biologics are now at the forefront when it comes to personalized management of asthma. The current review aims to shed light on the distinct phenotype of allergic asthma, ranging over its current definition, clinical characteristics, pathophysiology and biomarkers, as well as its treatment options in the era of precision medicine.
Are Banks Still a Risk Source for Stock Market? Some Empirical Evidences
Authors: Anelli Michele , Patanè Michele , Zedda Stefano
Published: July 2022

The global financial crisis of 2008 proved that what initially appeared to be relatively small losses in the financial system can be magnified to systemic ones. The European Union debt crisis has thus revived interest in the interdependence across different markets, especially sovereign debt markets and the banking sector, and in the interlinkages among idiosyncratic and common shocks. This paper analyzes the evolution over time of the incidence of common shocks on the main Italian banking groups starting from the period of European Central Bank’s Quantitative Easing program. Results show that the banking sector is no longer perceived by the markets as a common risk source, overcoming the negative picture coming from the financial crisis of 2008–2009. The analysis also suggests that the common risk is broadly affected by the ECB monetary policy, and the idiosyncratic risk is linked to the recapitalization processes.
Financial Technology and Its Impact on Digital Literacy in India: Using Poverty as a Moderating Variable
Authors: Gautam Rahul Singh , Rastogi Shailesh , Rawal Aashi , Bhimavarapu Venkata Mrudula , Kanoujiya Jagjeevan , Rastogi Samaksh
Published: July 2022

Financial technology is a powerful tool in financial infrastructure, used to strengthen and smooth the delivery of financial services into the broader space. Financial technology involves software, applications, and other technologies designed to improve and automate traditional forms of financial services for businesses established in different areas. The authors aimed to explore the impact of financial technology on the digital literacy rate in India, by utilizing the poverty score as a moderating variable. The panel data analysis (PDA) has been employed in the current study. Data from 29 states and two union territories (UTs) of India were considered for three financial years, i.e., 2017–2018 to 2019–2020. The study’s findings reveal that Kisan Credit Cards (KCCs), both in terms of numbers and amount, are positively associated with the literacy rate. However, ATMs are negatively significant in association with literacy rate. Furthermore, the study’s empirical results show that KCCs and ATMs positively impact literacy when interacting with poverty scores. The study’s findings bring noteworthy implications for the government and other officials to understand the situation at the ground level of Indian states and UTs while forming new rules and policies for society’s betterment, particularly in finance and digital literacy. Additionally, the findings imply that ordinary people living in urban and rural areas of India should take advantage of financial technology and get motivated towards digital literacy.
High-Mountain Landscape Classification to Analyze Patterns of Land Use and Potential Natural Vegetation
Authors: Theissen Tim , Otte Annette , Waldhardt Rainer
Published: July 2022

In Georgia’s Lesser Caucasus, extremely species rich wooded grasslands are still used as pastures or meadows. These silvopastoral systems are one of the oldest land-use types in Europe, hosting both light-demanding and shade-tolerant species. However, in Europe silvopastoral systems have decreased over the past centuries. The aim of this study is to map, quantify, and classify the local land use and forest types in comparison to the potential natural vegetation to analyze and evaluate the high-mountain landscape pattern. Therefore, we mapped a 223 km2 study area and classified this mountainous terrain by topographical variables in a cluster analysis. Our results revealed a small-scale pattern of agriculture and forest in the study area, both strongly interlinked. The forest pattern strongly depends on altitude and aspect. The mentioned wooded grassland consists of forests with varying canopy covers connecting the settlement-near pastures and meadows in the montane belt with the natural open grassland in the alpine belts. The forest is in a near-natural condition compared with the potential natural vegetation. However, the quantifications revealed shrub encroachment indicating land-use abandonment. The compiled GIS-maps and the spatial classification of the landscape can be used to support sustainable management strategies in forestry and agriculture.
Decoupling the Economic Development from Resource Consumption: Implications and Challenges in Assessing the Evolution of Forest Area in Romania
Authors: Rădulescu Carmen Valentina , Bran Florina , Ciuvăț Alexandru Liviu , Bodislav Dumitru Alexandru , Buzoianu Ovidiu Cristian , Ștefănescu Mihaela , Burlacu Sorin
Published: July 2022

The paper proposes an insight into the relation existing between economic development and resource consumption and the associated implications and challenges for forested areas in Romania. In accordance with this purpose, the methods used are both qualitative and quantitative by using a relevant literature review, including international and national reports. In the 1950s and 1960s, Simon Kuznets introduced to modern economic theory the idea that there are certain market forces directly correlated with economic development. After almost two decades of a market economy in Romania, we are witnessing a relative decoupling process between economic development and social inequality. Moreover, the country strives to make the transition to a circular economy by involving all relevant stakeholders and by attracting the necessary financial support. Sustainable development offers the perspective of reaching an equilibrium between economic, social, and environmental aspects. Finding the right tools to assess multiple impacts has always been challenging as regards decoupling the economic development from natural resource consumption. Although there are multiple interpretations of the outcomes of a decoupling process, this paper aims at assessing the evolution of forested areas through econometric research using the Environmental curve of Simon Kuznets. As our main results, we have observed a decoupling process in the GDP growth that will not lead to a decrease in wooded areas in our country, mainly due to rural–urban migration, shifts in consumption patterns (from firewood toward natural gases, etc.) and improvement in the legislative framework in the case of forestry products. Among the weaknesses of the model used are the limited data availability and the reduced number of observations with annual frequency (data were taken only for 22 years), the use of a square pattern instead of a cubic one (it is possible for the results to differ and consequently another form of this curve, either N or N-inverted) or the use of data with a low accuracy related to the total forest areas in Romania. Among the conclusions of the papers, the decoupling process is not a single action process. Our research focused on forest area and the need to connect it with other policy actions related to mainstreaming sustainability, promoting a circular economy or bioeconomy, or developing innovative public policies and instruments.
Influence of Strain Rates during Severe Plastic Strain Processes on Microstructural and Mechanical Evolution in Pure Zinc
Authors: Kulczyk Mariusz , Skiba Jacek , Skorupska Monika , Przybysz Sylwia , Smalc-Koziorowska Julita
Published: July 2022

The study presents an analysis of the influence of the plastic strain rate on the mechanical and structural properties of pure zinc. Thanks to the use of unconventional methods of plastic processing, the process of the equal channel angular pressing (ECAP) and the process of hydrostatic extrusion (HE), the tests were performed in a wide range of plastic strain rates, between 0.04 s−1 and 170 s−1. Plastic strain rate changes were carried out in the course of the significant plastic strain processes, and not on previously deformed samples. All tests were carried out at a constant value of plastic strain rate, ε ~ 2. A strong influence of the plastic strain rate on changes in the microstructure in zinc was observed during the tests. For the rates in the range of 0.04 s−1 to 0.53 s−1 its bimodal nature was observed, and in the range of 7 s−1 to 170 s−1 high homogeneity and evenness of grains related to the processes of continuous dynamic recrystallization was noticed. The effect of the strong homogenization of the microstructure was the increase in mechanical properties, yield point and tensile strength to the maximum values of UTS = 194 MPa, YS = 145 MPa at a strain rate of 170 s−1. Compared to the material with a bimodal microstructure, an over seven-fold increase in the elongation value was observed.
Constitutive Model and Fracture Failure of Sandstone Damage under High Temperature–Cyclic Stress
Authors: Luo Ji’an , He Jun
Published: July 2022

Deformation and damage characteristics of high-temperature rocks during underground coal gasification are the fundamental mechanical problems encountered in coal-bed gasification production. In order to study the characteristics of deformation and damage processes of rocks under the joint action of high temperature and high stress, a damage intrinsic model under the joint action of high temperature–cyclic loading is needed. In this paper, we used the damage mechanics theory to establish the damage instantiation model of rocks under the joint action of high temperature loads based on the Mohr–Coulomb strength criterion. It was found that the higher the temperature, the lower the strength of sandstone, the lower the peak stress, and the higher the peak strain, the peak stress decreased from 95.6 MPa at room temperature to 74.8 MPa at 400 °C to 49.5 MPa at 800 °C, and the peak strain increased from room temperature to 400 °C to 800 °C by 27.9% and 33.4%, respectively. With the increase in temperature, the internal microcracks of sandstone increased and expanded, which caused the degree of damage to intensify, and the macroscopic expression was the reduction in strength and stiffness of the sandstone. The rock went through four stages from loading to damage, including damage weakening, plastic deformation, strain softening, and residual deformation. The four types of fractures that led to the overall rupture of the rock were open fracture, secondary coplanar fracture, secondary inclined fracture, and oblique fracture. The damage intrinsic model constructed in this paper could better reflect the damage process of thermally damaged sandstone under the action of periodic loading, and had certain rationality. The damage intrinsic evolution curve, as well as the damage mechanism of sandstone under the action of macroscopic high temperature-loading, were discussed from the perspective of microscopic damage evolution, and the fracture extension pattern and penetration mechanism of the rock under different temperatures were analyzed. The research results provide an important reference for the design and engineering application of gasifiers in coal-bed underground gasification projects.
Broadband Sound Insulation and Dual Equivalent Negative Properties of Acoustic Metamaterial with Distributed Piezoelectric Resonators
Authors: Zhang Zhifu , Wang Jiaxuan , Li Zhuang , Zhang Xirui
Published: July 2022

Aiming at the unsatisfactory sound transmission loss (STL) of thin-plate structures in the low-mid frequency range, this paper proposes an acoustic insulation metamaterial with distributed piezoelectric resonators. A complete acoustic prediction model is established based on the effective medium method and classical plate theory, and the correctness is verified by the STL simulation results of the corresponding acoustic-structure fully coupled finite-element model. Moreover, the intrinsic relationship between the dual equivalent negative properties and STLs is investigated to reveal the insulation mechanisms of this metamaterial. Then, the influence of the geometric and material parameters on the double equivalent negative characteristics is studied to explore the broadband STL for distributed multi-modal resonant energy-dissipation modes in the frequency band of interest. The results show that the two acoustic insulation crests correspond to the dual equivalent negative performances, and the sound insulation in the low-mid frequency range is improved by more than 5 dB compared with that of the substrate, even up to 44.49 dB.
Synthesis and Processing Parameter Optimization of Nano-Belite via One-Step Combustion Method
Authors: Sun Hongfang , Lian Weixing , Zhang Xiaogang , Liu Wei , Xing Feng , Ren Jie
Published: July 2022

This paper proposes a new chemical combustion method for the synthesis of nano-low-carbon belite cement via a simple one-step process without using any oxidizers, and related mechanisms are briefly introduced. The starting materials used, including micro-silica (silica fume) as a byproduct of the metallurgic industry and CaCO3 powders, are of great abundance, and the processing parameters involved were optimized using a series of systematic experiments based on X-ray diffraction (XRD) and the Rietveld fitting method. Besides, the properties of the synthesized belite cement were characterized by the Brunauer–Emmett–Teller (BET) technique and scanning electron microscopy (SEM). Experimental results revealed that the optimized fuel agent was urea with a dosage of 4.902 times that of the starting materials by mass, and the corresponding holding temperature and time were 1150 °C and 2 h, respectively. In addition, the CaO/(SiO2 + CaO) for the starting materials should be set at 62.5% by mass ratio. BET and SEM results showed that the obtained belite cement had a specific surface area of 11.17 m2/g and a size of around 500 nm or even smaller in spherical shapes, suggesting that this method was successfully implemented. Thus, it can be a promising approach for the synthesis of nano-belite particles as a low-carbon construction material, which could be used more in the near future, such as for low-carbon concrete productions.
Influence of Creep Damage on the Fatigue Life of P91 Steel
Authors: Mroziński Stanisław , Lis Zbigniew , Egner Halina
Published: July 2022

The following paper presents the results of tests on samples made of P91 steel under the conditions of simultaneously occurring fatigue and creep at a temperature of 600 °C. The load program consisted of symmetrical fatigue cycles with tensile dwell times to introduce creep. Static load (creep) was carried out by stopping the alternating load at the maximum value of the alternating stress. The tests were carried out for two load dwell times, 5 s and 30 s. A comparative analysis of the test results of fatigue load with a dwell time on each cycle confirmed that creep accompanying the variable load causes a significant reduction in sample durability. It was shown in the paper that regarding the creep influence in the linear fatigue damage summation approach, it is possible to improve the compliance of the fatigue life predictions with the experimental results.
The Importance of the Geometry of the Down Sprue in the Gravity Casting Process
Authors: Dojka Rafał , Jezierski Jan , Szucki Michał
Published: July 2022

This article presents the results of experiments on the optimization of down sprue geometry in the process of pouring sand molds. Theoretical assumptions and computer simulation tests are presented. The starting point was the theory and experience of gas entrapment caused mainly by a poorly designed gating system and the down sprue. Simulations were performed using Magmasoft software. First, initial studies were carried out to determine how the geometry (mainly the channel cross-section) of the sprue affects the problem, and then a detailed experiment was carried out on the so-called ‘short sprue’ version. The air entrapment process was analyzed, as were the parameters of the liquid alloy flow that passes through the analyzed channels. Nine geometric versions of the sprue were proposed and analyzed, and the results allowed us to conclude which sprue geometry is the best from the point of view of minimization of the gas entrapment problem.
New Segmented Poly(Thiourethane-Urethane)s Based on Poly(ε-Caprolactone)Diol Soft Segment: Synthesis and Characterization
Authors: Puszka Andrzej , Sikora Janusz W.
Published: July 2022

New segmented poly(thiourethane-urethane)s (SPTURs) were synthesized by the reaction of 1,1′-methanediylbis (4-isocyanatocyclohexane) (Desmodur W®, HMDI) and poly(ε-caprolactone)diol (PCL) and (methanediyldibenzene-4,1-diyl)dimethanethiol as nonconventional polymer chain extender. FTIR spectroscopy was used for the structural analysis of obtained polymers. The molecular weight distribution was examined by GPC chromatography. Based on the measured contact angles, free surface energy parameters were calculated. Thermal properties of polymers were examined by DSC and TGA, while viscoelastic properties were measured by DMTA. The tensile, adhesive and optical properties were also investigated for the obtained polymers. It was shown that SPTURs were transparent or partially transparent solids with high molar masses up to 84,300 Da. These polymers showed a good resistance to hydrolysis during incubation in Optylite® physiological saline over 8 weeks. Obtained polymers possessed a tensile strength of up to 43.26 MPa, hardness of up to 96.25/59.00 Sh A/D and adhesion to copper of 14.66 MPa. The surface properties of the obtained polymers show that all obtained SPTURs were hydrophilic (CAs for water between 64.07° and 73.12°) with calculated SFE up to 46.69 mN/m.
pH-Dependent Photophysical Properties of Metallic Phase MoSe2 Quantum Dots
Authors: Ko Boemjin , Ahn Jaegyu , Song Sung Ho
Published: July 2022

Fluorescence properties of quantum dots (QDs) are critically affected by their redox states, which is important for practical applications. In this study, we investigated the optical properties of MoSe2-metallic phase quantum-dots (MoSe2-mQDs) depending on the pH variation, in which the MoSe2-mQDs were dispersed in water with two sizes (Φ~3 nm and 12 nm). The larger MoSe2-mQDs exhibited a large red-shift and broadening of photoluminescence (PL) peak with a constant UV absorption spectra as varying the pH, while the smaller ones showed a small red-shift and peak broadening, but discrete absorption bands in the acidic solution. The excitation wavelength-dependent photoluminescence shows that the PL properties of smaller MoSe2-mQDs are more sensitive to the pH change compared to those of larger ones. From the time-resolved PL spectroscopy, the excitons dominantly decaying with an energy of ~3 eV in pH 2 clearly show the shift of PL peak to the lower energy (~2.6 eV) as the pH increases to 7 and 11 in the smaller MoSe2-mQDs. On the other hand, in the larger MoSe2-mQDs, the exciton decay is less sensitive to the redox states compared to those of the smaller ones. This result shows that the pH variation is more critical to the change of photophysical properties than the size effect in MoSe2-mQDs.
Quantifying Alignment Deviations for the In-Plane Biaxial Test System via a Shape-Optimised Cruciform Specimen
Authors: Chen Junxian , Zhang Jianhai , Zhao Hongwei
Published: July 2022

The loading coaxiality of an in-plane biaxial test system and the structure of a cruciform specimen markedly affect the test results. However, due to the lack of methods for correcting the loading coaxiality and designing the cruciform specimen, the data scatter of the test results of the in-plane biaxial test systems varies from the laboratory to different tests. To quantify the loading coaxiality of the in-plane biaxial test system, we first developed a model to calculate alignment deviations with strain distribution of the shape-optimised cruciform specimen with Automated Machine Learning (AutoML). Our results demonstrated that 99.2% (54,536 of 54,976) of the quantified errors are less than 5%. Quantifying alignment deviations for an in-plane biaxial test system has been solved. The quantified method of alignment deviations could enhance the reliability of test data, improve assembly efficiency, and aid in constructing failure criteria of materials under biaxial stress.
A Comparative Evaluation of the Strain Transmitted through Prostheses on Implants with Two Different Macro-Structures and Connection during Insertion and Loading Phase: An In Vitro Study
Authors: Kassem Riyam , Samara Amar , Biadsee Ameer , Masarwa Shchada , Mtanis Tarek , Ormianer Zeev
Published: July 2022

Background: The purpose of this study was to measure and compare the strain levels in the peri-implant bone as generated by the blade-like implant (BLI) and the screw-type implant (STI) with two different internal connections (hexagonal and conical) and with a 1:1 and 2:1 crown/implant (C/I) ratio. Methods: The implants (BLI and STI) were placed into sawbones according to the manufacturer’s protocol. Two strain gauges, horizontal and vertical to the implant axis, were placed around each implant on the bone surface 1 mm from the cervical part. Each implant was loaded by a material testing machine at a force of 100 N. Micro-strains (με) generated in the surrounding bone were measured by a strain gauge and recorded. Results: Recorded micro-strains were not significant in both the insertion and loading phases (p < 0.0625). The average recorded micro-strain values were lower in the horizontal dimension of STI with hexagonal connection when the C/I ratio was 2:1 compared with BLI, 210 με and 443 με, respectively. Conclusion: Within the limitations of this study, implant design, implant-abutment connection and C/I ratio did not influence strain values in bone and there is no statistically significant effect of these parameters on bone.
Experimental and Numerical Investigations of Cement Bonding Properties at Elevated Temperatures—The Effect of Sample Cooling
Authors: Lambrescu Ionut , Teodoriu Catalin
Published: July 2022

Well integrity is currently defined through the concept of well barriers, in which one or more barriers are used to prevent unwanted fluid flow. Many papers have highlighted that the casing–cement interfacial bonding is critical for well integrity, but many discrepancies between laboratory experiments and field data have been noticed. The use of finite element analysis is now established as an alternative to complex in situ tests, but these simulations are sensitive to the input parameters, which results in many discrepancies across published works. Currently, the cohesive zone material (CZM) method is considered to offer good results if the correct parameters are selected or experimentally determined. The novelty of this paper lies in the development of a better workflow that enables the simulation of three processes that are acting on the laboratory-scale casing–cement system: temperature changes, debonding, and post-debonding behavior. The aim of this paper is to fully understand the debonding process within laboratory-scale samples, and thus to eventually enable upscaling in the near future. The paper presents a new workflow generated using FEM that allows us to determine the contact stresses at the casing–cement interface during temperature changes at the moment of debonding and post-debonding. The results presented within this paper show that temperature samples tested according to the push-down setup will provide similar interfacial bonding shear strength values; however, post-debonding, there is a remaining frictional force slightly higher than that of the room-temperature samples. In this case, the results are within a 5% error of the average field data, which is slightly higher than in our previous experiments, where only room temperature data were considered. A major outcome of our paper is the demonstration of the existence of friction forces after debonding, which are a result of radial stresses induced during the debonding process.
Portevin-Le Chatelier Characterization of Quenched Al-Mg Alloy Sheet with Different Mg Concentrations
Authors: Tian Ni , Wang Wenze , Feng Zhen , Song Weihao , Wang Tianshi , Zeng Zijie , Zhao Gang , Qin Gaowu
Published: July 2022

In the present study, the PLC characteristic parameters and DSA mechanism of Al-(2.86~9.41) Mg alloy sheets were investigated during tensile testing at room temperature with a tensile rate of 1 × 10−3 s−1. On the basis of the solution Mg concentrations in the α-Al matrix, the initial vacancy concentration, the second-phase particle configuration and the recrystallized grain configuration are almost the same by quenching treatment. The results show that the type of room-temperature tensile stress–strain curves of quenched Al-(2.86~9.41) Mg alloy sheets varied according to the Mg content. The type of stress–strain curve of the Al-2.86 Mg alloy sheet was B + C, while the type of stress–strain curve of the Al-(4.23~9.41) Mg alloy sheets was C. When the quenched Al-(2.86~9.41) Mg alloy sheets were stretched at room temperature, the strain cycle of the rectangular waves corresponding to the high stress flow ΔεTmax and stress drop amplitude Δσ on the zigzag stress–strain curve of alloy sheets increased with increasing the Mg content. Moreover, the strain cycle of ΔεTmax and Δσ on the stress–strain curve of alloy sheets increased gradually with increasing tensile deformation. The yield stress of quenched Al-(2.86~9.41) Mg alloy sheets increased gradually with increasing the Mg content. Moreover, the critical strain corresponding to yield stress εσ and the critical strain corresponding to the occurrence of the PLC shearing band εc of alloy sheets both increased with increasing the Mg content. However, the difference in flow strain value Δεc−σ between εc and εσ of alloy sheets decreased gradually with increasing the Mg content.
Constitutive Relations of Anisotropic Polycrystals: Self-Consistent Estimates
Authors: Li Aimin , Zhao Tengfei , Lan Zhiwen , Huang Mojia
Published: July 2022

In this paper, the elastic constitutive relation of polycrystals contains the effect of the mesostucture coefficients. We consider a general case and derive the average elastic constitutive relation pertaining to polycrystals of cubic crystals with any symmetry of crystalline orientation in their statistical distribution. Following Budiansky and Wu, we used self-consistent estimates of eigenstrain to obtain the effective elastic constitutive relation of polycrystals in an explicit form. For the Voigt assumption and the Reuss assumption, the effective elastic constitutive relation of polycrystals on cubic crystals contains the the mesostructure coefficients up to linear terms. In general, the linear term expression works well for materials such as aluminum, the single crystal of which has weak anisotropy. However the same expression (which allows the anisotropic part of the effective elastic constitutive relation to depend only linearly on the mesostructure coefficients) does not suffice for materials such as copper, in which the single crystal is strongly anisotropic. Per the Taylor theorem, we expand the expression based on the self-consistent estimates with respect to the mesostructure coefficients up to quadratic terms for anisotropic polycrystals of cubic crystals. While our numerical data are very close to those of Morris, our expression is much simpler.
Effects of Snake-Bioinspired Surface Texture on the Finger-Sealing Performance under Varied Working Conditions
Authors: Chen Lingping , Zhang Yanchao , Cui Yahui , Wang Jie , Wang Mingfeng
Published: July 2022

The tribological performance of the friction pair between the rotor and finger feet is a crucial index affecting the service life of finger seals. In recent years, the surface texture has attracted a considerable number of researchers owing to its extraordinary potential in improving antifriction and wear resistance. This paper, inspired by snakeskins, introduces three texture forms (e.g., diamond, ellipse, and hexagon) into the rotor. The effects on finger-sealing performance are analyzed by considering finger seals’ varied working conditions. First, a numerical model of textured finger seals under hydrodynamic lubrication is established based on the Reynolds equation. Then, the sealing performance analysis of textured finger seals is performed considering varied working conditions given rotation speed, pressure difference, seal clearance, and working temperature. The numerical results show that: (1) the textured domain produces a noticeable hydrodynamic pressure effect and cavitation, which effectively improves the bearing capacity of the fluid film; (2) the higher the rotation speed or the lower the inlet/outlet pressure difference, the stronger the dynamic pressure effect of textured finger seals and the better the antifriction and wear resistance; (3) for good antifriction and wear resistance of a textured finger seal, the seal clearance should be as shallow as possible (≤10 μm), and the working temperature should be as low as possible (≤120 °C); and (4) the ellipse texture has a higher average dimensionless pressure and a lower friction coefficient, which is superior to diamond and hexagon ones in terms of friction and wear performance.
Estimation of Positions and Poses of Autonomous Underwater Vehicle Relative to Docking Station Based on Adaptive Extraction of Visual Guidance Features
Authors: Lv Fengtian , Xu Huixi , Shi Kai , Wang Xiaohui
Published: July 2022

The underwater docking of autonomous underwater vehicles (AUVs) is conducive to energy supply and data exchange. A vision-based high-precision estimation of “the positions and poses of an AUV relative to a docking station” (PPARD) is a necessary condition for successful docking. Classical binarization methods have a low success rate in extracting guidance features from fuzzy underwater images, resulting in an insufficient stability of the PPARD estimation. Based on the fact that guidance lamps are blue strong point light sources, this study proposes an adaptive calculation method of binary threshold for the guidance image. To decrease the failure of guidance feature extraction, a guidance image enhancement method is proposed to strengthen the characteristic that the guidance lamps are strong point light sources with a certain area. The PPARD is estimated through solving the minimum value of the imaging error function for the vision-based extracted guidance features. The experimental results showed that the absolute estimation error for each degree of freedom in the PPARD was at most 10%, which was lower than that of the orthogonal iteration (OI) method. In addition, the proposed guidance feature extraction method proved to be better than the classical methods, with the extraction success rate reaching 87.99%.