Cylinder Method Research Articles

A clearer vision: unveiling the importance of cycloplegic refraction and the pseudomyopia prevalence in Chinese preschoolers

BackgroundThis study aimed to investigate the difference between cycloplegic and noncycloplegic refraction and evaluate the pseudomyopia prevalence in Chinese preschool children during the outbreak of COVID-19.MethodsA cross-sectional study was conducted in the Tongzhou District of Beijing, China. Refractive error was measured under both noncycloplegic and cycloplegic conditions with autorefraction. The difference between noncycloplegic and cycloplegic spherical equivalent refraction (SER) and pseudomyopia prevalence were analyzed. Pseudomyopia was defined as SER ≤-0.50D in precycloplegic assessments and >-0.50D in post-cycloplegic assessments.ResultsOut of the 1487 participants who were enrolled in the study, 1471 individuals (98.92%) between the ages of 3–6 years completed all required procedures. A statistically significant difference in refraction was observed between noncycloplegic and cycloplegic measurements, the median of difference in spherical equivalent refraction (SER) of 0.88D (dioptre)(0.50,1.38). There was a high intraclass correlation (ICC) between these two methods for cylinders (ICC = 0.864; 95% CI, 0.850–0.877). The median DSE for myopia, emmetropia and hyperopia were 0.25D (0.00, 0.38),0.25D (0.06, 0.50) and 1.00D (0.62, 1.38), an hypermetropes showed considerably greater differences than myopes and emmetropes (Kruskal-Wallis test, H = 231.023, P = 0.000). Additionally, girls displayed a greater DSE than boys. Furthermore, when comparing against-the-rule (ATR) and oblique astigmatism, it was found that with-the-rule (WTR) astigmatism had the largest DSE. The study found varying prevalence rates of myopia, emmetropia, and hyperopia with and without cycloplegia, which were 1.90% vs. 10.06%, 11.49% vs. 50.31%, and 86.61% vs. 39.63%, respectively. Additionally, the overall prevalence of pseudomyopia was determined to be 8.29%. Participants with pseudomyopia had a significantly higher mean difference in SER (DSE) compared to non-pseudomyopic participants.ConclusionsCycloplegic refraction is more sensitive than a noncycloplegic one for measuring refractive error in preschool children. Pseudomyopia is prevalent in preschool children during the COVID-19 outbreak period. Our study indicates the possibility that cycloplegic refraction should be performed in preschool children routinely.

The Risk of Alkali–Carbonate Reaction and the Freeze–Thaw Resistance of Waste Dolomite Slag-Based Concrete

The alkali–carbonate reaction (ACR) is a type of alkali–aggregate reaction (AAR) that may lead to serious damage in concrete construction. There is sufficient research on the effect of the ACR on dolomite limestone; however, research on the effect of the ACR on pure dolomite is absent, and there are a large number of dolomite resources that cannot be effectively utilized in civil engineering. This study aims to investigate whether the ACR occurs in pure dolomite spoil and to determine the freeze–thaw resistance of pure waste dolomite slag-based concrete (PWDSC). In this study, X-ray diffraction (XRD) and the lithofacies method (LM) confirmed that the tested samples were pure dolomite. The rock cylinder method (RCM) and rapid preliminary screening testing for carbonate aggregates (AAR-5) were employed to determine the alkali activity of pure dolomite: the RCM indicated a variation of −0.09% in length during the 84-day test period, the AAR-5 exhibited a length expansion rate of 0.03% within 28 days, and the expansion rates were less than 0.1%. These findings suggest that pure waste dolomite slag (PWDS) does not possess alkali activity. The freeze–thaw cycle test showed no significant spalling on the concrete surface, the inside of the cement produced few micro-cracks according to scanning electron microscopy (SEM), and the uniaxial compressive strength (UCS) test showed a decrease of approximately 20% after 200 freeze–thaw cycles. The results verified that ACR does not occur in PWDS and that it can withstand freeze–thaw damage, to a certain extent, when used as concrete coarse aggregate.

Multi-fidelity, steady-state aeroelastic modelling of a 22-megawatt wind turbine

In this work we present multi-fidelity steady-state aeroelastic framework that leverages the state-of-the-art simulation tool HAWC2 for the structural model, and a variety of aerodynamic models, comprising of the low fidelity blade element momentum (BEM) method, the medium fidelity blade element vortex cylinder (BEVC) method and the coupled near wake and vortex cylinder method, and finally the high-fidelity CFD solver EllipSys3D. The aeroelastic framework is part of AESOpt, an aerostructural framework for design of wind turbine blades. The different aerodynamic models are applied to compute the aeroelastic steady state of the newly designed IEA 22 MW Reference Wind Turbine. The results show a very good agreement between the medium- and high-fidelity aerodynamic models with a maximum of 2.7% difference between the high-fidelity aeroelastic response and that of the lower fidelities.

A correction model for the effect of spanwise flow on the viscous force contribution in BEM and Lifting Line methods

Design optimization and aeroelastic load evaluation for wind turbines are still infeasible for CFD due to computational cost. These tasks are carried out using 3D engineering aerodynamic methods, where the local aerodynamic loads are obtained from tabulated 2D aerodynamic polars, which makes the models fast. With recent developments such as highly flexible blades, coned/prebent/swept blades, the relative inflow direction to the “inner” 2D airfoil section systems can have a significant component in the spanwise direction. The Crossflow Principle (CP) is used to treat the effects of this in a physically consistent manner. Cases dominated by pressure forces are described well with the CP method, but it is shown in the paper that CP fails to describe the part of the forces stemming from the friction forces correctly. It is shown in the paper that the power loss due to friction forces will be underestimated with the crossflow principle for rotors with significantly swept blades or other designs with a significant amount of local crossflow on the blades. The present work presents a simple model to correct the baseline crossflow principle method to take into account also the friction force part in a consistent manner. The model is validated with 3D CFD results on a 2D airfoil section. It is shown that the new model successfully corrects for the addition of the viscous forces due to spanwise flow component. The paper includes examples of the effect of using the model on rotor designs with different amounts of blade sweep simulated using a blade element momentum (BEM) and blade element vortex cylinder (BEVC) methods.

Structural Interaction between BaO and Al2O3 in Aluminosilicate Slags

The effect of BaO and Al2O3 on the viscosity of SiO2–CaO–MgO–Al2O3–BaO slag from 1673 to 1873 K is studied by the rotating cylinder method. The structure of slag is examined by Raman spectroscopy and molecular dynamics simulation. In this study of viscosity, Al2O3 shows amphoteric oxide characteristics and BaO shows characteristics different from the basic oxide. The viscosity increases as the BaO increases from 2 to 4 wt% in the slag with CaO/SiO2 = 1.07. However, the viscosity decreases when the BaO content increases from 6 to 8 wt%. From molecular dynamics simulations and Raman analysis, the increase in BaO content leads to a greater aggregation of Al around Ba atoms and increases the number of Al–O bonds. This indicates that higher BaO content promotes the polymerization of the [AlO4] tetrahedral structure. Furthermore, a good quantitative relationship between viscosity and the ratio of Q3/Q2 of the Raman spectrum of the slag is observed.

Preoperative assessment of bone density for dental implantation: a comparative study of three different ROI methods

BackgroundDental cone beam computed tomography (CBCT) is commonly used to evaluate cancellous bone density before dental implant surgery. However, to our knowledge, no measurement approach has been standardized yet. This study aimed to evaluate the relationship between three different regions of interest (ROI) methods on cancellous bone density at the dental implant site using dental CBCT images.MethodsPatients’ dental CBCT images (n = 300) obtained before dental implant surgery were processed using Mimics (Materialise, Leuven, Belgium). At the potential implant sites, the rectangle, cylinder, and surrounding cylinder ROI methods were used to measure bone density. Repeated measures one-way analysis of variance was performed to compare the three ROI methods in terms of measurement results. Pearson correlation analysis was performed to identify the likely pair-wise correlations between the three ROI methods.ResultsThe density value obtained using the surrounding cylinder approach (grayscale value [GV],523.56 ± 228.03) was significantly higher than the values obtained using the rectangle (GV, 497.04 ± 236.69) and cylinder (GV,493 ± 231.19) ROI methods in terms of results. Furthermore, significant correlations were noted between the ROI methods (r > 0.965; p < 0.001).ConclusionsThe density measured using the surrounding cylinder method was the highest. The choice of method may not influence the trends of measurement results.Trial registrationThis study was approved by the Institutional Review Board of China Medical University Hospital, No. CMUH111-REC3-205. Informed consent was waived by the Institutional Review Board of China Medical University Hospital, CMUH111-REC3-205, owing to the retrospective nature of the study.

Calculation of the total corneal astigmatism using the virtual cross cylinder method on the secondary principal plane of the cornea

This study aimed to establish a virtual cross cylinder method to calculate the total corneal astigmatism by combining the anterior and posterior corneal astigmatism on the secondary principal plane of the cornea based on Gaussian optics. The meridian with the least refractive power, namely, the flattest meridian of the virtual cross cylinder of a ± 0.5 × C diopter, is set as the reference meridian, and the power (F) at an angle of φ between an arbitrary meridian and the reference meridian is defined as F(φ) = − 0.5 × C × cos2φ. The magnitude and axis of the total corneal astigmatism were calculated by applying trigonometric functions and the atan2 function based on the combination of the virtual cross cylinders of the anterior corneal astigmatism and the posterior corneal astigmatism. To verify the performance of the virtual cross cylinder method, a verification experiment with two Jackson cross cylinders and a lensmeter was performed, and the measured and calculated values were compared. The limit of the natural domain of the arctangent function is circumvented by using the atan2 function. The magnitude and axis of the total corneal astigmatism are determined through generalized mathematical expressions. The verification experiment results showed good agreement between the measured and calculated values. Compared to the vector analysis method, the virtual cross cylinder method is mathematically sound and straightforward. A novel technique for calculating total corneal astigmatism, the virtual cross cylinder method, was developed and verified.

Investigation on surface tension of CaF2–CaO–SiO2 (–MgO–Al2O3) melts

In this work, the surface tension of CaF2–CaO–SiO2 melt with high CaF2 contents was measured by pulling cylinder method at 1773 K. The effects of CaF2 content, basicity, and the addition of MgO and Al2O3 on the surface tension were also investigated by considering the change in the melt structure. It was observed that as the CaF2 content increased from 30 to 80 mass%, there was no further depolymerizing effect on the silicate structure of the melt, maintaining a constant basicity of 1. However, the surface tension of the melts decreased from 397 to 325 mN/m due to the surface-active effect of CaF2. With the increase of basicity from 0.5 to 3, the surface tension of the melt initially increased from 342 mN/m to a maximum value of 390 mN/m, then decreased to 368 mN/m. The maximum value occurred at a basicity of 2. Furthermore, at constant basicity, the addition of MgO from 0 to 10 mass% led to a decrease in the surface tension of the melt decreased from 358 to 326 mN/m. Similarly, with the basicity ranging from 1 to 3, the addition of 10 mass% Al2O3 resulted in a decrease in the surface tension of the melt.

Environmental assessment of the state of fallow drained meadow-soddy-gley and brown mountain-forest soils to involve them into a new agricultural turnover (on the example of the Jewish autonomous region)

Relevance. In the context of ever-increasing anthropogenic influence, the importance of agricultural land reclamation increases and becomes more complicated. Involvement of new virgin soils in agricultural circulation requires large financial investments and huge labor resources, which the local administration does not have. The secondary return to agricultural circulation of fallow reclaimed lands that are not used in agriculture may be a less costly method of increasing the area of agricultural arable land. Aim. To analyze the changes in vegetation and aggregate composition on drained fallow soils of different ages. Object. Drained fallow meadow-soddy-gley and brown mountain-forest soils of different ages. Methods. Standard geobotanical methods were used to describe the vegetation of the polygons. The granulometric analysis of soils was carried out by the method of dry sieving. Soil density was determined by the cutting cylinder method. Results. The study showed that reclaimed arable land, after being withdrawn from agricultural use, enters into a long process of self-recovery. In the course of a long-term transformation, a noticeable accumulation of humus is observed in fallow brown mountain-forest soils in comparison with adjacent arable lands. In the 20-year-old deposit, the highest content of humus is noted, while there is a decrease in saline and hydrolytic acidity. In fallows, the density of the upper soil horizon decreases, which favorably affects the structure of soils. On brown mountain-forest soils, in a 20-year-old fallow, there is a noticeable increase in the proportion of mesoaggregates (0,25–10 mm), including agronomically valuable ones. The number of micro- (&lt;0,25 mm) and macro-aggregates (&gt;10 mm) decreases, which indicates an improvement in the agronomic properties of fallow soils. The results of dry screening indicate that the fallow period of drained meadow-soddy-gley soils adversely affects their structure.

Axial shift mapping: a self-referencing test for measuring the axial figure of near-cylindrical surfaces

Lateral shearing self-referencing interferometry methods shift the surface under test between measurements to separate its topography from that of the reference surface. However, rigid body errors occur during shifting, creating an ambiguity in the quadratic term of the extracted surfaces. We present axial shift mapping, a lateral shearing self-referencing interferometry method for cylinders, in which the quadratic ambiguity is resolved by measuring the rigid body errors using known artifact mirrors residing in the interferometer’s field of view. First, one-dimensional lines of a flat mirror are measured with 2.8 nm RMS difference compared to a three flat test. Then, axial shift mapping is extended to cylindrical surfaces using a computer generated hologram. We find that axial shift mapping results in full surface extraction of cylindrical optics, along the axial direction, with a repeatability of 4.4 nm RMS. We also find that the reference surface extracted through axial shift mapping is within 4.5 nm RMS of the transmitted wavefront error of the computer generated hologram substrate, which was expected to be the largest contribution of reference wavefront error.

Thermal-fluid-structure coupling progressive failure analysis for the type III composite cylinder under localized fire

Predicting the failure characteristics of composite cylinders under fire is the key to improve the fire resistance and safety of cylinders. However, the current thermal-mechanical coupled failure analysis methods for composite cylinders under fire have several limitations such as oversimplification of the cylinder dome's geometric model and the fire source. To solve these problems, a comprehensive three-dimensional thermal-fluid-structure coupling progressive failure analysis method is developed. This method encompasses a fully coupled conjugate heat transfer model, a FLUENT-ABAQUS data transfer method, and a progressive failure analysis model integrates the Hashin failure criterion and nonlinear damage evolution for fiber reinforced composites. The method is adopted to analyze the fire-resistant performance of a type Ⅲ cylinder to obtain the fire-resistant time, failure pressure and burst location of the cylinder, finding that the pattern of failure pressure depreciation correlates with the burst location of cylinder under localized fire. Besides, the influence of the glass-fiber/epoxy layer on the fire-resistant performance of the cylinder is discussed, demonstrating that even a thin layer of glass-fiber epoxy can significantly increase the fire resistance time of the cylinder.

Effect of TiO2 and FeO on viscosity and structure of HIsmelt titanium-containing slag

HIsmelt is considered one of the most promising processes for future vanadium-titanium magnetite smelting. In this study, we investigated the effects of TiO2 and FeO on the viscosity and structure properties of HIsmelt titanium-containing slag using the rotating cylinder method, the Fourier Transform Infrared, and Raman. Experimental findings indicate a significant reduction in melting temperature with increasing TiO2 content, accompanied by a rapid decrease in slag viscosity followed by a gradual increase, reaching a minimum at 30 wt% TiO2. The FeO content exerts minimal influence on slag viscosity and melting temperature. FTIR spectroscopy results reveal a gradual depolymerization of the [SiO4] structure with the introduction of TiO2 and FeO while having little influence on [AlO4] and Si–O–Al structural changes. Raman spectroscopy results indicate an increase in Q0 and a decrease in Q1 and Q2 with elevated TiO2 and FeO content, leading to a reduction in the degree of polymerization (DOP) within the silicate structure and, consequently, lower slag viscosity. Maintaining FeO content within the range of 2–4% and TiO2 content at approximately 30 % will be advantageous for industrial production.

Laboratory equipment for practice learning in the framework of educational course “Molecular Physics and Thermodynamics”

This article presents laboratory equipment for practice learning of physics specialties students in the framework of educational course “Molecular Physics and Thermodynamics”. The presented laboratory equipment allows measuring the temperature dependence of the thermal conductivity coefficient of molecular liquids under atmospheric pressure and saturated vapors pressure in the temperature range from 150K to 400K. A general scheme of the developed experimental setup for measuring the thermal conductivity of liquids by the steady-state method under isobaric condition has been described. The created laboratory setup uses general design solutions of the coaxial cylinder method, preserving its features and measurement precision in general. The measurements are carried out on coaxial-geometry cell under atmospheric pressure. A modified heat potentiometer method with one thermometer was used, which allowed us to minimize the error in the estimation of the thermal conductivity coefficient due to the uncontrollable heat flows and different calibration of thermometers. The total systematic error in the measurement of the molecular liquids thermal conductivity does not exceed 3%. The procedures for direct measurement and calculation of the thermal conductivity coefficient of molecular liquids using the developed laboratory equipment are described.

Evaluation of the shear adhesion strength of impact ice by a new method

Aircraft icing has a detrimental effect on flight safety. The design of aircraft anti-icing/de-icing systems requires a thorough comprehension of the adhesion between the ice and the substrate. In this research, the multi-hole rotating cylinder method (MHRC) is developed in an icing wind tunnel. Simulations of interfacial stress show that ice thickness does not change the evenness of stress, whereas reducing the contact area can impair uniformity. Moreover, the ice layer would not experience any cohesive damage during the experiments. The shear ice adhesion strength is evaluated using the methodology outlined in this research. At lower temperatures, glaze ice demonstrates a rise in its shear adhesion strength, while the change trend is the opposite for rime ice. The lowest adhesion strength is observed at the medium volume diameter (MVD) of 45 µm. Furthermore, the growing liquid water content (LWC), rough surfaces, and surface painting will enhance the interface adhesion of ice to the substrate to varying degrees. Stainless steel substrate exhibits higher adhesion strength with ice as compared to aluminum and titanium. In addition, superhydrophobic surfaces have proven to possess a significant reduction in adhesion strength at higher temperature. The proposed experimental method and platform afford accurate measurements of the shear adhesion strength of impact ice in the icing wind tunnel.

Dissolution behavior of palladium and rhodium in glass melts: Implications for the viscosity and electrical conductivity of high-temperature melts

This article investigated the solubility of platinum group metals (PGMs) in sodium borosilicate glass and its effect on the viscosity and electrical conductivity of melts. The role of PGMs in the viscosity and electrical conductivity of melts was examined using the rotating cylinder method and impedance spectroscopy, respectively. Moreover, XRD, XPS, and SEM were used to measure the phase compositions, valence states, and microstructures, respectively, of the glass samples with different PGMs contents. The results showed that the solubility of Pd and Rh in sodium borosilicate glass was estimated to be less than 110 ppm by weight. The higher concentrations of Pd and Rh resulted in Pd-rich and Rh-rich inclusions in the glass matrix, which eventually agglomerated to form metallic Pd, Rh and Rh2O3. The evolution of viscosity and electrical conductivity with different temperatures followed the Arrhenius equation with a fairly good linear relationship between ln η and ln κ.

A Comparative Study: Evaluation of Wastewater Suspensions Flocculation Performance Using Laboratory Graduated Cylinder and Jar Test Methods

A Comparative Study: Evaluation of Wastewater Suspensions Flocculation Performance Using Laboratory Graduated Cylinder and Jar Test Methods

The Law of Gas–Liquid Shear Mixing under the Synergistic Effect of Jet Stirring

At present, there is a common problem that the mixing mode is single and it is difficult to overcome the inherent bottleneck of multiphase mixing. A mixing device combining the advantages of jet entrainment and mixing dispersion was designed and built. In an effort to determine the mixing degree of two phases, the mixing coefficient of gas–liquid charging was measured using the cylinder method with the optimal working parameters. To explore the optimization of the mixing conditions and control mechanism of multiphase materials, the law of gas–liquid shear mixing in the process of multi-force field synergistic change was revealed. Based on the testing of the gas injection capacity under different working conditions and the calculation of the gas–liquid two-phase mixing coefficient, it was concluded that the flow rate was the direct key factor affecting the gas injection capacity. The working speed also had a certain impact on the gas injection capacity. When working at a high speed and high flow rate, the jet beam broke through the cutting barrier and presented a superposition effect. The jet impact assisted the rotation, and the suction performance of the device was significantly improved, which was conducive to the mixing of the gas and liquid phases. According to the test results of the measuring cylinder method, the calculated average inflation volume is 0.01 m3/(m2·min), the inflation uniformity coefficient is 77.51, and the mixing coefficient of the gas and liquid phases is 0.12.

Research on protection methods for 70 MPa on-board Type IV hydrogen storage cylinders under localized fire conditions

When hydrogen fuel cell vehicles (HFCVs) occur fires, the localized fire protection methods for on-board hydrogen storage cylinders can reduce the failure possibility of cylinders. This paper describes an experimental study of 70 MPa Type IV on-board hydrogen storage cylinders exposed to localized and engulfing fires. A three-dimensional (3D) computational fluid dynamics (CFD) model is developed to simulate the effects of various protection methods on the heat transfer characteristics of cylinders. The results demonstrate that both fire-protection coatings and fire-protection baffles effectively reduce the maximum temperature of cylinder surfaces and enhance the fire resistance of cylinders under localized fire conditions. Specifically, using a 2 mm thick fire-protection coating and a circular fire-protection baffle with a width equal to 100% of the cylinder diameter proves to be more suitable protection methods. These measures significantly decrease the risk of explosion and leakage in Type IV hydrogen storage cylinders during localized fire conditions.

Effect of Cr2O3 Content on the Viscosity and Crystallization Properties of Continuous Casting Mold Slag

Herein, the effect of Cr2O3 on the crystallization and flow behavior of CaO–SiO2–Al2O3–Na2O–CaF2 continuous casting mold slags is investigated. The viscosity in the slag at 1200–1500 °C is measured by the rotating cylinder method and a quantitative relationship between the viscosity and the Raman structure Q3/Q2 is constructed. The time–temperature–transformation and continuous cooling transformation diagrams for various slags are obtained using a single hot‐thermocouple technique. The results show that with the crystallization temperature decreases, it can be observed that the crystal growth mode gradually changes from 3D spherical and 2D massive to 1D needle‐like. The study finds the transition from network modifier to network forming agent in the slag for Cr2O3 content from 0 to 3 wt%. The Cr2O3 added to 1–2 wt% decreases the viscosity and promotes crystallization. The viscosity increases and the crystallization is inhibited when the content of Cr2O3 increases to 3 wt%. Meanwhile, when Cr2O3 is added to 3 wt%, the Cr2O3 crystalline phase precipitates except for the main crystalline phase 2CaO·SiO2.

Influence of Cr2O3 on the Viscous Flow Behavior and Structure of Cr‐Containing Molten Titanium Slag

Herein, the influence of Cr2O3 on the viscous flow behavior and structure of Cr‐containing molten titanium slag is investigated in this work. The melting and viscosity properties are studied by hemisphere method and rotating cylinder method, respectively. In addition, the structure of Cr‐containing molten titanium slag is investigated by Raman spectroscopy. It is shown in the results that the melting temperature and viscosity both increase with the increase of Cr2O3 content. The activation energy for viscous flow increases with increasing Cr2O3 content, which is in the same trend as viscosity. When the Cr2O3 content increases from 0% to 3%, the simpler 6‐coordinated Ti4+ and TiO44− monomer unit transformed into more complex O–Ti–O deformation and Ti2O64− chain unit. Furthermore, the fraction of relatively complex silicate structural units shows an increasing trend. Cr2O3 behaves as a network former and enhances the degree of polymerization of network structure, and the variation of Cr‐containing molten titanium slag structure is consistent with the increasing trend of viscosity.