Irregular Cross Research Articles

Evaluating possible glacial modification in the Martian tropics near Gale crater using a new U-shaped valley metric

Growing evidence supports the case for glacial processes within the equatorial regions of Mars. However, few examples of modeling or numerical analysis exist to support this hypothesis. Here we apply an automated method on valleys near Gale crater to extract morphometric data and analyze formative processes responsible for their current expression. The V-index utilized is a new robust method that is an alternative to traditional valley parabolic curve fits. This approach more easily characterizes irregular valley cross sections and thus aids in distinguishing between glacial and nonglacial forms. We applied this method along with standard power law and quadratic curve fits on valley cross sections along a 2300 km extent of the Martian tropics near Gale crater. Both V-index and power law b fit values suggest that the majority of the valleys are U-shaped and possibly created through glacial erosive processes. Further, V-index and power law b values plotted against elevation show a positive trend with higher V-index (glaciated) values associated with higher elevation. This suggests that an equilibrium-line altitude (ELA) may have existed at the time of valley formation. The timing of the formation of these U-shaped valleys is poorly defined. However, our initial crater statistics conducted within the study area suggest a young ∼1.05 (±0.25) Ga relative ages of the valley floors. Equatorial glaciers that produced these and other related glacial forms may be as old as the Hesperian to Amazonian transition (∼3 Ga) but more intriguingly may be associated with Amazonian equatorward migration of the Martian cryosphere during more recent periods of high obliquity oscillations.

Numerical study on ultrasonic detection of cracks in metallic structures with variable cross-sectional thickness

The metal structures are widely used in aerospace engineering, especially in joints and spars. The safety of these parts is important to ensure the safe service of the whole structures. The ultrasonic wave is a traditional technique to detect cracks in metals. However, it is usually difficult to find all the cracks because of its difficulty in variable directions of the crack and the irregular shapes of the metals. This paper aims to address the challenge of detecting cracks in metallic structures with varying cross-sectional thicknesses using ultrasonic methods. The research investigates the behavior of ultrasonic longitudinal and transverse waves as they propagate through aluminum plates with variable cross sections. Additionally, it examines how cracks in different orientations influence these wave types. The theoretical analyses are performed which explore the reflection of oblique incidence waves and the diffraction of ultrasonic waves when they encounter semi-infinite cracks. Subsequently, numerical simulations are performed to validate the theoretical findings and to detect both horizontal and vertical cracks within metal plates of varying cross-sectional thicknesses. The findings indicate that both longitudinal and transverse waves are effective in identifying the location of damage caused by horizontal cracks. However, when it comes to vertical cracks, only transverse waves are successful in detecting their precise location. From the research of this paper, transverse ultrasonic wave is suggested to detect cracks in metal structures with irregular cross sections.

Structural parameters of Wrench – C shape building using CFD

Wind flow pattern and generation of strong and large eddies is mainly responsible to the wind pressure and suction intensity in and around the tall building. If the shape of the structure is not vary common then the wind generated effects need to evaluate for the high rise structure this is because of the reason that the data for the regular plan cross sectional shape is available in the various international standards. This study investigating the wind effects on irregular cross sectional shape tall building using CFD tool ANSYS CFX. The current study evaluates the wind impacts for a boundary layer atmospheric wind flow from 0° to 180° at a 15° interval. The power law described in IS: 875 (Part 3): 2015 for terrain category II follows the wind profile. For a rectangular model, the values of the pressure coefficients are compared using the numerical simulation and the information supplied in IS 875. Results are given at numerous locations, including pressure coefficients around the building model’s periphery and force and moment coefficients for wind incidence angles ranging from 0° to 180° at 15° intervals.

Study on the mechanism of local compression bruising in kiwifruit based on FEM

AbstractThis study focuses on the relationship between local compression and local bruise volume of kiwifruits by means of finite element method (FEM). The effects of four indenter shapes and three compression directions on the local kiwifruit bruise were considered. The local bruise volume and the irregular cross section area of kiwifruit were calculated. Multi‐scale kiwifruit 3D modelling based on irregular cross‐sectional area computed by slice‐integration method. Local compression bruise was simulated by FEM. The results of the local bruise test show that the contact force and the bruise volume of kiwifruit are positive linear correlation. Comparing the simulation with the experimental, the mean absolute percentage error (MAPE) of the reconstructed model is 0.0394, and the R2 of contact force–bruise volume curve is 0.8203. The maximum equivalent forces and abrasions occur in the 0° and 90° loading directions with the square indenter has been showed by FEM results.Practical applicationsSe‐enriched kiwifruit has high nutrition and economic value. Kiwifruits are often influenced by a variety of factors and processes from harvest to consumption time. Cleaning, transport, and various processing operations including peeling and slicing in the kiwifruit industry are responsible for local bruise to kiwifruit. Therefore, understanding the mechanism of local bruise caused by local contact force of kiwifruit plays an important role in reducing kiwifruit waste in the postharvest stage. Local bruise mechanisms can be used in harvesting and post‐harvest mechanical design and product transportation and positioning equipment.

Migration Processes in Austria: Features and Trends

The article deals with the current migration situation in the European Union with an emphasis on Austria. The article analyzes the key prerequisites and factors that caused demographic and social changes in Austrian society after World War II, contribute to the preservation of the migration attractiveness of the state at the current stage. The regulatory and legal instruments for regulating migration, including the stay and employment of foreign citizens, as well as the parameters of the functioning of integration mechanisms and ensuring national security against the background of the crisis events of 2015 are summarized. In the context of increasing external pressure on the European Union, Vienna's approaches to managing migration processes are analyzed, which are traditionally characterized by a tough position and often contrast with the official course of Brussels, especially with regard to the reception of refugees. Austrians, in order to prevent irregular cross–border movements of people and secondary migration, minimize threats to national security, actively interact with neighboring states and countries – migration donors. On the domestic political track, of particular interest is the situation associated with a new phenomenon – the mass arrival of Ukrainian refugees. This flow is qualitatively and quantitatively significantly different from traditional migration (gender, educational and social level, significant number of minors). Despite the rigidity of its migration policy, Austria is forced to quickly look for solutions to a complex of problems related to the accommodation and financing of the stay of immigrants from Ukraine, as well as to explain to its electorate the reasons for negative socio-economic changes in the conditions of the chosen foreign policy course. A side effect of providing broad social and legal guarantees to Ukrainians, along with a low level of integration into society, is the growing discontent of the titular population and migrants who arrived from other countries.

Unruly Hair with Irregular Cross Sections: Answer.

*University of Arkansas for Medical Sciences, College of Medicine, Little Rock, AR; †Department of Pathology and Laboratory Medicine, Saskatchewan Health Authority, Saskatoon, Saskatchewan, Canada; and ‡Department of Dermatology, University of Arkansas for Medical Sciences, Little Rock, AR. Correspondence: Nikhil Nair, BA, University of Arkansas for Medical Sciences, College of Medicine, 4301 W. Markham Street, Little Rock, AR 72205 (e-mail: [email protected]). The authors declare no conflicts of interest. I confirm that each author acknowledges their participation in conducting the research leading to this manuscript and agrees to its submission to be considered for publication.

Unruly Hair With Irregular Cross Sections: Challenge.

*University of Arkansas for Medical Sciences, College of Medicine, Little Rock, AR; †Department of Pathology and Laboratory Medicine, Saskatchewan Health Authority, Saskatoon, Saskatchewan, Canada; and ‡Department of Dermatology, University of Arkansas for Medical Sciences, Little Rock, AR. Correspondence: Nikhil Nair, BA, 4301 W. Markham St., Little Rock, AR 72205 (e-mail: [email protected]). The authors declare no conflicts of interest. I confirm that each author acknowledges their participation in conducting the research leading to this manuscript and agrees to its submission to be considered for publication.

Analytic description of nanowires II: morphing of regular cross sections for zincblende- and diamond-structures to match arbitrary shapes.

Setting out from our recent publication [König & Smith (2021). Acta Cryst. B77, 861], we extend our analytic description of the regular cross sections of zincblende- and diamond-structure nanowires (NWires) by introducing cross section morphing to arbitrary convex shapes featuring linear interfaces as encountered in experiment. To this end, we provide add-on terms to the existing number series with their respective running indices for zinc-blende- (zb-) and diamond-structure NWire cross sections. Such add-on terms to all variables yield the required flexibility for cross section morphing, with main variables presented by the number of NWire atoms NWire(dWire[i]), bonds between NWire atoms Nbnd(dWire[i]) and interface bonds NIF(dWire[i]). Other basic geometric variables, such as the specific length of interface facets, as well as widths, heights and total area of the cross section, are given as well. The cross sections refer to the six high-symmetry zb NWires with low-index faceting frequently occurring in the bottom-up and top-down approaches of NWire processing. The fundamental insights into NWire structures revealed here offer a universal gauge and thus enable major advancements in data interpretation and the understanding of all zb- and diamond-structure-based NWires with arbitrary convex cross sections. We corroborate this statement with an exact description of irregular Si NWire cross sections and irregular InGaAs/GaAs core-shell NWire cross sections, where a radially changing unit-cell parameter can be included.

Guided Wave Excitation and Sensing in Constant Irregular Cross Section Structures with the Semianalytical Finite-Element Method

Guided Wave Excitation and Sensing in Constant Irregular Cross Section Structures with the Semianalytical Finite-Element Method

X-ray Micro CT Based Characterization of Pore-Throat Network for Marine Carbonates from South China Sea

The pore-throat network of rock exerts a vital influence on the permeability and mechanical properties of the rock. Resorting to X-ray micro-CT scanning, the present work investigates the pore-throat structure of marine biogenic carbonate samples from the South China Sea and compares them to terrigenous sedimentary sandstone. With the help of the maximum ball (MB) algorithm, the pore-throat networks inside representative elementary volumes of rock samples are revealed by stick-and-ball diagrams, which enables quantitative analyses afterwards. Higher and more deviant cross sectional porosity was observed for the carbonate samples compared to the sandstone sample, indicating relatively heterogeneous pores in the carbonate. Over 85% of pores in the carbonate samples were classified as mesopores. Irregular triangular cross sections can be inferred for the pores and throats of the carbonate. The type of rock and the porosity seem to have little effect on the shapes of the pores and throats. In the studied carbonate, the average volume of the throat was approximately one order of magnitude smaller than the average volume of a pore. The distribution of throat radius differed significantly between the studied carbonate samples. The average coordination number of the carbonate was measured to be 1.

A Stable Extended FDTD Thin-Wire Model for Lossy Wire Structures With Irregular Cross Sections

A stable extended FDTD thin-wire model for lossy wire structures with irregular cross sections is presented for lightning transient analysis. In this model, the electro-magnetic field in the vicinity of a conductor with an irregular cross section is taken into account by adopting a single constant correction factor, and the conductor loss is represented with an internal impedance. These two parameters are calculated with a charge simulation method and an equivalent circuit method, respectively. The proposed model is validated in terms of the characteristic impedance, conductor loss and time-domain waveform with analytical and numerical methods. Good agreements are observed. Considering the rigid conductor-size/cell-size requirement and eight tedious convolutional processes in the existing non-circular thin-wire model, the implementation complexity of this proposed model is significantly simplified, and the computational stability is remarkably enhanced. Without reducing the time step, the simulation can maintain its stability when the conductor size varies from 0.01 to 1 of the FDTD cell size. It is also revealed that using a single intrinsic model for conductors with different cross sections could lead to significant calculation errors. Finally, this proposed model is applied for the lightning transient analysis in an electrified railway system.

A Poisson equation method for prescribing fully developed non-Newtonian inlet conditions for computational fluid dynamics simulations in models of arbitrary cross-section

Prescribing inlet boundary conditions for computational fluid dynamics (CFD) simulations of internal flow in complex geometries such as anatomical vascular models is challenging. In the absence of patient-specific inlet velocity data, a common approach for long blood vessels is to assume that the inlet flow is fully developed. In vessels of irregular cross section, however, prescribing fully developed conditions is complicated due to the lack of a general closed-form analytical solution. In this study, we develop a simple Poisson equation method for prescribing fully developed inlet conditions for the flow of either Newtonian or non-Newtonian fluids in CFD models of arbitrary cross-section. We first derive the generalized Poisson equation for fully developed flow of a non-Newtonian fluid and we then develop and verify a methodology for numerically computing the solution on any planar boundary domain. In addition, we develop a simple extension of the method for prescribing a non-orthogonal inlet velocity that represents fully developed flow from an upstream tube that is connected to the CFD inlet at a non-orthogonal angle. This may be used to investigate a common source of uncertainty in CFD simulations of internal flow that is due to a lack of information concerning the exact streamwise flow direction at the inlets. Comparison to several Newtonian and non-Newtonian benchmark verification solutions shows the method to be extremely accurate. As a practical demonstration case, we use the method to prescribe fully developed conditions on multiple non-circular inlets for the non-Newtonian flow of blood in a patient-specific model of the inferior vena cava (IVC). Finally, we further demonstrate the utility of the method by performing a sensitivity study using the patient-specific IVC model, wherein we investigate the influence of inlet velocity flow direction on the non-Newtonian IVC hemodynamics. Given its simplicity and computational efficiency, the method is shown to be far superior to alternative approaches for prescribing fully developed inlet conditions in such complicated geometries. To facilitate the adoption of our Poisson equation method, we have distributed our OpenFOAM source code and the associated test cases from this study as open-source software.

Influence of sulfuric acid corrosion on concrete stress–strain relationship under uniaxial compression

This study aims to provide some references on understanding the uniaxial compression behaviors of concrete corroded by sulfuric acid. Six groups of concrete cylinder specimens were immersed in sulfuric acid solution with pH≈0.95 for different days. 3D laser scanning technology was applicated to obtain 3D coordinates of the points on the corroded cylindrical surface. The irregular cross sectional areas of each specimen were calculated at intervals of 1 mm along the longitudinal axis by MATLAB. The elastic modulus, peak strain, ultimate strain and peak stress were calculated through the experimental complete stress–strain curves. It showed that as the corrosion time increased, the elastic modulus, peak strain and peak stress gradually decreased. The ultimate strain decreased first and then increased over time. The parameters of the stress–strain model including the ascending and descending stages were obtained by fitting the experimental data. The relationship between the mechanical properties and mass loss was explored.

A New Method for Prediction of the Acoustic Performance and Design Parameter Sensitivity Analysis of Multi-Chamber Perforated Resonators With an Irregular Cross Section

Abstract Aiming at reducing the high-amplitude and wide-frequency noise in charged air intake system of the powertrain, this paper proposes a new method for predicting the acoustic characteristics of an irregular cross-section multi-chamber perforated resonator under flow conditions. By this method, the presence of three-dimensional sound waves and the effects of higher-order modes are considered, and the acoustic performance of the resonator can be evaluated through the computation of transmission loss. Moreover, by discretizing the cross-section of the perforated resonator and extracting node information, this method can solve the acoustic characteristics of the perforated resonator with any cross section. Based on the transfer matrix method, the quadrupole parameters of each chamber are obtained. Then, the acoustic characteristics of the multi-chamber perforated resonator could be calculated. The theoretical prediction data and the experimental data have been compared, and the results show good agreement within the entire frequency range, which verifies the accuracy of the theoretical prediction approach. Based on this prediction approach, the influence of section ratio, structure parameters, and inlet flowrate on the acoustic characteristics of the resonator is explored. The results show that when the structural parameters change, the peak resonance frequency of the resonator will have a regular shift. With the increase of the inlet flowrate, the main frequency band of sound attenuation will decrease significantly. The theoretical method developed in this work can be used for the calculation and optimization of multi-chamber resonators in various applications.

Comparative Study of Physicochemical Properties and Starch Granule Structure in Seven Ginkgo Kernel Flours.

Ginkgo biloba L. is an important economic tree species in China, and its kernels have been used as a popular food in Asian countries. Herein, the morphology, basic chemical components, starch granule structures, and physicochemical properties of kernel flours from seven ginkgo cultivars were investigated, and their relationships were analyzed. The kernels were oval or spherical in shape, with variable sizes. The starch granules exhibited both regular and irregular Maltese cross patterns. Amylose was mainly distributed in amorphous growth rings. A spatial variation in the 865/942 cm−1 ratio was observed within individual starch granules. Variations in total starch content, apparent amylose content (AAC), crude protein content (CPC), total amino acid content (TAAC), starch fine structure, and thermal and pasting properties were observed among the seven kernel flours. Pearson correlation coefficients and principle component analyses showed that the thermal properties were affected by kernel CPC, TAAC, AAC, and starch fine structure, while the pasting properties were affected by AAC and starch fine structure. Furthermore, experiments showed that the seed protein structure and α-amylase activity affected the pasting properties of ginkgo kernel flours.

Prediction of applied pressure on model lower limb exerted by an air pneumatic device

Air pneumatic compression is a concept used for management of venous disease, including oedema. A typical air pneumatic compression device (PCD) consists of an inflatable sleeve composed of either single or multiple pressure chambers that encircle a limb.The aim of this research was to develop a mathematical model to predict the pressure applied by an air pneumatic device to an irregular cross-sectional lower limb manikin.The radius of curvature at any cross-section of the lower limb (i.e. calf (gastrocnemius), tibial crest (anterior edge of the tibia bone)) is irregular, and differs amongst individuals and populations. The effectiveness of air pneumatic devices is difficult to predict with these irregular cross sections.A theoretical model was developed to calculate pressure applied by compression sleeves on a lower leg manikin and results compared against experimental pressure exerted on the manikin by a silicone-based PCD. This prediction was made at each of three positions.The theoretical model developed based on elliptical shaped forms predicted the pressure more accurately for the ankle to above ankle position, whereas the model based on circular shaped forms predicted the pressure more accurately for below the calf to below the knee position. Refinements to the theoretical model to predict the pressure applied by PCD are recommended.

Modeling method of irregular cross section annular axis braided preform based on finite element simulation

The irregular cross section annular axis braided preform is modeled by using finite element simulation instead of geometric modeling. The braiding process is simulated by using a finite element software to obtain the yarn path. And the braided preform is modeled by using nine virtual fibers to form irregular cross section shape of yarn. Meanwhile, a modified vertical braiding machine is used to braid the actual preform, to compare with results from the simulation model. The results show that the simulation model is consistent with the actual braided preform, braiding angle is about 36°, and yarn spacing is about 6 mm. The finite element method can predict the yarn path more accurately without the need of complex analysis and derivation, especially when the irregular mandrel is used for braiding. In addition, the cross-section shape of yarn composed of virtual fibers can be used to achieve a more realistic simulation result. FEM is an efficient simulation method, and can also provide an effective basis in studies of the actual cross-sectional shape of yarn and the properties of its composite reinforcements.

Imbibition into Capillaries with Irregular Cross Sections: A Modified Imbibition Equation for Both Liquid–Gas and Liquid–Liquid Systems

Due to discrepancies observed between many experimental results and predictions from the Bell–Cameron–Lucas–Washburn (BCLW) imbibition equation, the BCLW equation was often modified by considering the effects of pore/throat characteristics. As previous works mainly focused on liquid–gas systems, the effects of the viscosity ratios are neglected. In this study, the nonwetting-/wetting-phase-viscosity ratio ( $$ \Psi $$ ) is varied by four orders of magnitude (0.018 to 8), which covers the common fluid viscosity in waterflooded tight reservoirs. Capillaries with irregular cross sections (namely, complex capillaries), which are recognized to more representative for porous media, are used to theoretically study imbibition kinetics in both the liquid–gas and liquid–liquid system. To considering the effects of viscosity ratio, we propose a modified imbibition equation based on the Poiseuille law and a piecewise method to calculate the equivalent radius for complex capillaries. The predictivity of the new imbibition equation is mathematically validated in varying viscosity ratios and geometries characteristics (such as the radius levels and the numbers/length ratios of radius levels). The study proves that an equivalent straight capillary can globally predict imbibition behaviors in complex capillaries. Except for a few scenarios, the equivalent radius of the straight capillary is affected by capillary geometries and viscosity ratios. Only in the early stage of imbibition ( $$ l_{x} /l \le 0.12\Psi /\left( {\Psi - 1} \right) $$ ), the modified imbibition equation can be expressed as a power-law relation (i.e., $$ l_{x} /l \propto \frac{1}{\Psi }t^{\alpha } $$ ) as $$ {\Psi } $$ is higher than 1. In general, it is more suitable to express the imbibition equations in a quadratic form, especially for liquid–liquid imbibition systems.

A study of an improved RCNN network model for surface defect detection algorithm of precision workpiece and its realisation

In this paper, an improved RCNN algorithm for surface defect detection of precision workpiece is proposed. During model training, the original image is processed by data amplification, which overcomes the phenomenon of model overfitting caused by too small data set. The fuzzy image is processed by the conditional generation antagonism network, which guarantees the authenticity of the image and eliminates the fuzziness of the image. On the basis of network selection, through network training and comparative analysis, ResNet101 was selected as the basic network for feature extraction. By combining the network performance, the number of convolutional layers (model depth), system efficiency and other factors, and taking advantage of the spatial characteristics of images, the irregular cross convolution kernel idea and the differentiated convolution kernel design method are adopted to realise the feature fusion of different convolutional layers. Embedded in the target Network Squeeze and Excitation (SE) module channel features fusion module, the Feature Pyramid Network (FPN) module, ROI Network module. The experimental results show that the improved network model is used to realise the location and classification of defects on the workpiece surface. The detection accuracy was 91% and the recall rate was 93%.

Progress on rapid hot gas forming of titanium alloys: mechanism, modelling, innovations and applications

The variable cross-section thin-walled hollow components of titanium alloys are increasingly used in the power and fuel systems of aerospace vehicles, which play an important role in reducing the weight of the structure, improving the service performance and reliability, etc. However, the formability of titanium alloys is very poor at room temperature, so it is very difficult to manufacture the complex thin-walled hollow components. Hot gas forming is an efficient strategy to form integral hollow components of titanium alloys. In this paper, some progress on this forming technology from the author’s lab is presented, which includes the deformation mechanisms, constitutive equations, process simulation, technological innovations and typical applications. Based on the research about the deformation mechanisms, the unified constitutive model was developed. Then the deformation process and microstructure evolution of gas forming could be predicted numerically. According to the difficulties of different components with different materials and geometries, new forming process with non-uniform temperature field, new heating system and new tooling strategy were presented. The new technologies were applied to form the components with irregular cross sections and components with large expansion ratios, meeting the application demand of aerospace industry, etc.