Uniform Cross-sectional Area Research Articles

Suppression of the sausaging effect in (Ba,Na)Fe2As2 round wires by using Ag1−zSnz/Cu double sheath

We report the fabrication of (Ba,Na)Fe2As2 round wires that are processed using the hot isostatic pressing (HIP) technique. We employed double sheaths composed of Cu and Ag1−zSnz alloy because they offer superior mechanical strength compared to pure Ag. The cross-sectional area of the wire core was measured using X-ray computed tomography. The findings of this study demonstrate that utilizing Ag1−zSnz alloy as the inner sheath material helps reduce the degree of the sausaging effect in the wire, resulting in a more uniform cross-sectional area of the wire core. However, transport critical current density (Jc) of the wires with the Ag1−zSnz alloy decreased gradually as the Sn content, z, increased, which may be attributed to the nonoptimized sintering temperatures during the HIP process. These results suggest that when heat-treated at an appropriate temperature during the HIP process, the use of Ag1−zSnz alloy holds great potential for use in high-performance applications.

Graph features based classification of bronchial and pleural rub sound signals: the potential of complex network unwrapped.

The study presents a novel technique for lung auscultation based on graph theory, emphasizing the potential of graph parameters in distinguishing lung sounds and supporting earlier detection of various respiratory pathologies. The frequency spread and the component magnitudes are revealed from the analysis of eighty-five bronchial (BS) and pleural rub (PS) lung sounds employing the power spectral density (PSD) plot and wavelet scalogram. The low-frequency spread, and persistence of the high-intensity frequency components are visible in BS sounds emanating from the uniform cross-sectional area of the trachea. The frictional rub between the pleurae causes a higher frequency spread of low-intensity intermittent frequency components in PS signals. From the complex networks of BS and PS, the extracted graph features are - graph density ([Formula: see text], transitivity ([Formula: see text], degree centrality ([Formula: see text]), betweenness centrality ([Formula: see text], eigenvector centrality ([Formula: see text]), and graph entropy (En). The high values of [Formula: see text] and [Formula: see text] show a strong correlation between distinct segments of the BS signal originating from a consistent cross-sectional tracheal diameter and, hence, the generation of high-intense low-spread frequency components. An intermittent low-intense and a relatively greater frequency spread in PS signal appear as high [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] values. With these complex network parameters as input attributes, the supervised machine learning techniques- discriminant analyses, support vector machines, k-nearest neighbors, and neural network pattern recognition (PRNN)- classify the signals with more than 90% accuracy, with PRNN having 25 neurons in the hidden layer achieving the highest (98.82%).

Geometric Assumptions in Hydrodynamic Modeling of Coronal and Flaring Loops

In coronal loop modeling, it is commonly assumed that the loops are semicircular with a uniform cross-sectional area. However, observed loops are rarely semicircular, and extrapolations of the magnetic field show that the field strength decreases with height, implying that the cross-sectional area expands with height. We examine these two assumptions directly, to understand how they affect the hydrodynamic and radiative response of short, hot loops to strong, impulsive electron beam heating events. Both the magnitude and rate of area expansion impact the dynamics directly, and an expanding cross section significantly lengthens the time for a loop to cool and drain, increases upflow durations, and suppresses sound waves. The standard T ∼ n 2 relation for radiative cooling does not hold with expanding loops, which cool with relatively little draining. An increase in the eccentricity of loops, on the other hand, only increases the draining timescale, and is a minor effect in general. Spectral line intensities are also strongly impacted by the variation in the cross-sectional area because they depend on both the volume of the emitting region as well as the density and ionization state. With a larger expansion, the density is reduced, so the lines at all heights are relatively reduced in intensity, and because of the increase of cooling times, the hottest lines remain bright for significantly longer. Area expansion is critical to accurate modeling of the hydrodynamics and radiation, and observations are needed to constrain the magnitude, rate, and location of the expansion—or lack thereof.

Multizone model of a refused derived fuel gasification: A thermodynamic Semi-empirical approach

Substitution of fossil fuels by sustainable energy sources has raised attention worldwide. Refuse derived fuel (RDF), which is the combustible fraction of Municipal solid waste (MSW), is used as an alternative fuel through combustion route. The gasification of RDF is gaining importance due to the operational issues of RDF combustion. The multizone RDF gasification model is developed to predict syngas composition in the present study. A stoichiometric approach is followed for modelling the pyrolysis and combustion zone. The reduction zone is modelled as a cylindrical fixed bed reactor with a uniform cross-sectional area. The developed set of differential equations is solved using MATLAB to predict the syngas properties. The novelty lies in the fact that the model can predict the output of each zone satisfactorily since the model assumptions are more realistic and cater to the heterogeneous nature of RDF. The impact of Equivalence ratio (ER), moisture content and reduction zone length on the performance of the gasifier are evaluated. The optimum values of lower heating value (LHV), gas yield, cold gas efficiency (CGE) and carbon conversion efficiency (CCE) for three different RDF at optimum ER is determined. Notably, 90% of the conversion is achieved within 60% length of reduction zone for all three types of RDF at all ERs. Predicting syngas properties can pave the way for the process integration of RDF gasification-based syngas in various industrial applications.

Theoretical analysis on the dynamic compressive behavior of cellular solids with non-linear variation in cross-sectional area

The dynamic compressive behavior of foams with a non-linear variation in the cross-sectional area profiles is studied. A theoretical model has been developed based on the one-dimensional shock theory and the rigid, perfectly-plastic, and locking (RPPL) material model, to establish the governing equations of motion of an initially stationary foam struck by a rigid projectile. Both decreasing and increasing cross-sectional area profiles with various power-law exponents are considered. The numerical simulations suggest that the decreasing area profiles, referred to as the convergent foams, exhibit a double-shock mode. In contrast, the foams with an increasing area-profile, referred to as the divergent foams, exhibit a single-shock mode. The theoretical predictions of both the double-shock and the single-shock cases are validated against the finite element simulations. Compared to the foam with a uniform cross-sectional area, the convergent foams transmit lower mean forces at the distal end, and the divergent foams transmit higher forces at higher impact velocities. An interesting phenomenon observed is that the mean force at the distal end decreases with an increase in the impact velocity beyond the densification velocity, for the convergent foams. An expression for the plastic energy dissipated by convergent foams has been derived, and we observe that the convergent foams dissipate less energy than the divergent foams. The performance of the foams has been compared through the dissipation performance parameter, defined as the ratio of non-dimensional plastic energy dissipated at the end of the crushing process to the mean non-dimensional force at the distal end. Convergent foams with low gradients and high power-law exponents have the highest dissipation performance. A special case of a decreasing density-gradient combined with an increasing area-gradient is shown (through finite element simulations) to be beneficial for structural protection.

Analytical solutions of acoustic field in annular combustion chambers with non-uniform cross-sectional surface area and mean flow

Low-order acoustic network models, treating the complex combustor geometry as a network of simple geometry elements, are typically used to analyse circumferential combustion instabilities in annular combustion chambers. These elements are typically assumed to have uniform cross-sectional surface area and average radius so that the analytical solutions of the acoustic field within them can be directly obtained. However, this may lead to errors in the combustion instability analyses. The present work derives the analytical solutions of the acoustic field in annular combustion chambers with both varying cross-sectional surface area and average radius sustaining a mean flow. A wave equation for the pressure perturbation is firstly derived based on very few assumptions. Analytical solutions of the acoustic field are then derived based on a modified WKB approximation. These solutions are then validated by comparing them to results by numerically resolving the linearised Euler equations. Results show that accurate predictions can always be obtained for a smooth change of the cross-sectional surface area and small-to-moderate subsonic axial Mach numbers as long as the frequency is larger than a certain value.

ASILI KÜTLE-YAY SİSTEMLERİNE SAHİP KOMPOZİT EĞRİ KİRİŞİN DİNAMİK KARARLILIK ANALİZİ

In this study, the dynamic stability of a laminated composite curved beam with a suspended mass-spring system is investigated. The composite curved beam is considered as a uniform cross-sectional area Euler-Bernoulli beam and effective flexibility module is utilized. The curved beam model is obtained by using the Bolotin approach and the finite element model based on energy equations. The natural frequencies of the composite curved beam obtained with a finite element code developed in MATLAB are compared with the results of ANSYS model. It is found that the results are very good agreement. The effects of the number and position of the suspended mass-spring system on the instability regions of the beam are surveyed considered that also dynamic load parameter and static load parameter for different fiber orientation angles of the layered composite curved beam. The dynamic stability regions of both types of the curved beam with and without suspended spring-mass system are presented in figures.

The Vibration of Simply Supported Non-Uniform Cross Sectional Pipe Conveying Fluid Resting on Viscoelastic Foundation

The induced flexural vibration of slender pipe systems with continuous non uniform cross sectional area containing laminar flowing fluid lying on extended Winkler viscoelastic foundation is considered. The Euler Bernoulli model of the pipe has hinged ends. The inlet flow is considered constant steady that interacts with the wall of the pipe. The mathematical model is developed and its corresponding solution is obtained. The influence of the combination of variation of cross section, foundation stiffness and damping on the critical velocities, complex natural frequencies and stabilization of the system is presented.

Carbon Nanotube (CNT) Stationary Phase for Micro Gas Chromatograph Columns

Introduction Microfabricated gas chromatography systems based upon MEMS fabrication technology are under development for portable chemical vapor analysis and chemical detection. In particular, Sandia National Laboratories has pioneered development of these miniature systems (1). Current methods for coating microfabricated gas chromatography columns are based upon deposition from a saturated mixture of siloxanes in a solvent, which are adapted from techniques developed for coating of open-tubular capillary columns (2). This static method is more successful with silica open tube columns which have a uniform cross-section area, however in a microfabricated column, a rectangular cross-section is produced in the channel. The square corners tend to have a thicker layer of material deposited using this process and hence these thicker layers provide a different retention time for the analytes which results in peak broadening and reduction in resolution and peak capacity of the column. Alternative stationary phases have been investigated (3), and using chemical vapor deposition (CVD) they can be grown with uniform thickness, for example carbon nanotubes (CNTs) (4) The CNTs have high surface area and are stable at high temperatures. Method A silicon substrate is used for the fabrication of a microfabricated spiral column, 6m in length using standard photolithography and deep reactive ion etching fabrication processes (5). An ultra-thin layer of iron catalyst is deposited by sputtering into the etched silicon channel. Using a Black Magic plasma enhanced CVD growth a layer of CNTs are formed thickness 0.5 to 1 micrometer. Figure 1 shows an SEM micrograph of the deposited CNTs layer which coats the sides of channel and base with uniform thickness. Next a layer of gold is deposited for eutectic bonding of the silicon lid in order to enclose the channel making the column. Finally high temperature annealing is carried out at 450 oC to increase bond strength. Results The column is mounted inside a commercial Agilent 6890 GC system oven with a short length of guard column, approximately 0.5m length, connect between the split injector and the flame ionization detector. A liquid injection of three compounds, hexane, octane and decane, volume of 0.02uL, was carried out with a 100:1 split and injector temperature of 275°C. The helium carrier gas flow rate was 0.1 ml/min. A typical chromatogram is shown in Figure 2. The McReynolds probes for polarity were also injected, and the Kovats indices were evaluated for comparison with OV-1 (Ohio Valley, OH) polymer stationary phase. Conclusions The use of CNT’s for a stationary phase may offer some advantages with micro-GC column fabrication because the quality of the layer can be inspected prior to bonding. We can observe the low polarity of the CNT stationary phase compared to the poly-siloxane However, it may be possible to chemically functionalize the surface for the CNTs for more polar compound separation and analysis.

Area Efficient High Through-put Dual Heavy Metal Multi-Level Cell SOT-MRAM

This paper proposes a novel multi-level cell spin-orbit torque magnetic random-access memory (MLC SOT-MRAM) cell structure and validates its functionality and performance through simulation. The proposed memory cell comprises two uniform magnetic tunnel junctions (MTJs) that can be programmed separately by the energy efficient SOT technology through two different heavy metal electrodes. This permit employing both single and dual port architectures. The uniform cross-sectional area of the in-series MTJs stack simplifies the fabrication process. In addition, the cell structure requires only four terminals to successfully read and write the two bits. This allows accessing the two bits with only three access transistors, which achieves 25% smaller 1-bit effective area compared to the conventional single level cell (SLC) SOT-MRAM that requires four transistors. Simulation results based on an approximated dynamic model shows it offers nearly similar write energy consumption compared to the conventional SOT-MRAM.

Atomistic analysis of nanoextrusion process for fabrication of gold nanowires

The effects of extrusion temperature and velocity on extruded gold nanowires (NWs) are studied using molecular dynamics simulations based on the many-body embedded-atom potential. The effects are investigated in terms of atomic trajectories, common neighbor analysis, flow field, and the extruded NW length-pressing ram displacement curve. The simulation results show that NWs extruded at a temperature of 300 K are longer and have a more uniform cross-sectional area compared to those extruded at higher temperatures. Higher temperature increases the cross-sectional area of extruded NWs, whereas higher extrusion velocity decreases it. In the extrusion process, dislocations first nucleate around the mold outlet and propagate along the close-packed plane {111} toward the interior. The number of disordered structures significantly increases with increasing extrusion temperature and velocity.

Enabling a Robust Copper Seed Etch Process for Fine Line RDL by Electroplating on a Thin PVD Seed Layer

Abstract Integration of heterogeneous chips into fanout packages requires interconnection by redistribution lines (RDL). As I/O counts increase, higher density routing is required, and can be achieved by finer RDL line/space dimension, stacking multiple RDL layers, or both. Conventional WLP plating processes for pillar or RDL use a PVD deposited copper seed layer between 1000 and 4000Å thick. Removal of this copper seed layer by isotropic wet etching leads to sidewall loss that can be ignored on larger features, but can lead to significant copper cross sectional area loss on features with 2/2μm line/space and below. By enabling plating onto much thinner seed layers, next generation WLP plating chambers enable a conventional copper seed layer etch process with less sidewall loss and more uniform cross-sectional area across plated features.

Effects of the Canopy and Flux Tube Anchoring on Evaporation Flow of a Solar Flare

Abstract Spectroscopic observations of flare ribbons typically show chromospheric evaporation flows, which are subsonic for their high temperatures. This contrasts with many numerical simulations where evaporation is typically supersonic. These simulations typically assume flow along a flux tube with a uniform cross-sectional area. A simple model of the magnetic canopy, however, includes many regions of low magnetic field strength, where flux tubes achieve local maxima in their cross-sectional area. These are analgous to a chamber in a flow tube. We find that one-third of all field lines in a model have some form of chamber through which evaporation flow must pass. Using a one-dimensional isothermal hydrodynamic code, we simulated supersonic flow through an assortment of chambers and found that a subset of solutions exhibit a stationary standing shock within the chamber. These shocked solutions have slower and denser upflows than a flow through a uniform tube would. We use our solution to construct synthetic spectral lines and find that the shocked solutions show higher emission and lower Doppler shifts. When these synthetic lines are combined into an ensemble representing a single canopy cell, the composite line appears slower, even subsonic, than expected due to the outsized contribution from shocked solutions.

Grain refinement and amorphization in nanocrystalline NiTi micropillars under uniaxial compression

Microscale plastic deformation mechanisms of nanocrystalline NiTi micropillars with an average grain size (GS) of 65 nm are investigated by uniaxial compression. Cuboidal NiTi micropillars with uniform cross-sectional area along the height are manufactured by focused ion beam. It is found that the plastic deformation of the micropillars under compression is realized by localized shear band formation with large strain bursts, leading to significant amorphization and GS reduction from 65 nm to as small as 11 nm in the shear band. The experiment indicates that microfabrication by severe plastic deformation could be a promising manufacturing technology.

INVESTIGATIONS ON DAMPING CHARACTERISTICS OF LIQUID COLUMN VIBRATION ABSORBER

ABSTRACTThis work deals with the damping characteristics and optimum performance of apassive liquid column vibration absorber (LCVA) which is effective to decrease thevibration of engineering systems. A numerical technique is applied to solve thenonlinear equations of motion to study the influence of the design parameters suchas frequency tuning ratio, length ratio, area ratio, blocking ratio and mass to mitigateexcessive vibrations. A constrained multi-objective optimization problem isconstructed and solved numerically to minimize the maximum master structuredisplacement in a broad range of excitation frequency with considering a limit of themaximum liquid displacement in the vertical tube as an extra objective. It is foundthat the best vibration attenuation can be achieved by using the LCVA with a uniformcross-section area while the non-uniform LCVA offer greater flexibility to modify thenon-appropriate total length. The TCVA mass and the structural damping have aninfluence on all optimum parameters. The optimal values of the blocking ratio areproportional and depend on the intensity of the excitation. The list of necessaryoptimal parameters and the corresponding performance indices are presented indesign tables as a guidance for industrial practices.

Enhancement of Condensation Heat Transfer Rate of the Air-Steam Mixture on a Passive Condenser System Using Annular Fins

This paper presents an experimental investigation on the enhancement of the heat transfer rate of steam condensation on the external surfaces of a vertical tube with annular fins. A cylindrical condenser tube, which is 40 mm in outer diameter and 1000 mm in length, with annular disks of uniform cross-sectional area is fabricated in the manner of ensuring perfect contact between the base surface and fins. A total of 13 annular fins of 80 mm diameter were installed along the tube height in order to increase the effective heat transfer area by 85%. Through a series of condensation tests for the air-steam mixture under natural convection conditions, the heat transfer data was measured in the pressure range of between 2 and 5 bar, and the air mass fraction from 0.3 to 0.7. The rates of heat transfer of the finned tube are compared to those that are measured on a bare tube to demonstrate the enhanced performance by extended surfaces. In addition, based on the experimental results and the characteristics of steam condensation, the applicability of finned tubes to a large condenser system with a bundle layout is evaluated.

A comparison on the heat load of HTS current leads with respect to uniform and non-uniform cross-sectional areas

A comparison on the heat load of HTS current leads with respect to uniform and non-uniform cross-sectional areas

Study on finned pipe performance as a ground heat exchanger

The GHEs (ground heat exchangers) is an important element that determines the thermal efficiency of the entire ground-source heat-pump system. The aim of the present study is to clarify thermal performance of a new type GHE pipe, which consists straight fins of uniform cross sectional area. In this paper, GHE model is introduced and an analytical model of new type GHE pipe is developed. The heat exchange rate of BHEs utilizing finned pips is 40.42 W/m, which is 16.3% higher than normal BHEs, based on simulation analyses.

Flow design and simulation of a gas compression system for hydrogen fusion energy production

An innovative gas compression system is proposed and computationally researched to achieve a short time response as needed in engineering applications such as hydrogen fusion energy reactors and high speed hammers. The system consists of a reservoir containing high pressure gas connected to a straight tube which in turn is connected to a spherical duct, where at the sphere’s centre plasma resides in the case of a fusion reactor. Diaphragm located inside the straight tube separates the reservoir’s high pressure gas from the rest of the plenum. Once the diaphragm is breached the high pressure gas enters the plenum to drive pistons located on the inner wall of the spherical duct that will eventually end compressing the plasma. Quasi-1D and axisymmetric flow formulations are used to design and analyse the flow dynamics. A spike is designed for the interface between the straight tube and the spherical duct to provide a smooth geometry transition for the flow. Flow simulations show high supersonic flow hitting the end of the spherical duct, generating a return shock wave propagating upstream and raising the pressure above the reservoir pressure as in the hammer wave problem, potentially giving temporary pressure boost to the pistons. Good agreement is revealed between the two flow formulations pointing to the usefulness of the quasi-1D formulation as a rapid solver. Nevertheless, a mild time delay in the axisymmetric flow simulation occurred due to moderate two-dimensionality effects. The compression system is settled down in a few milliseconds for a spherical duct of 0.8 m diameter using Helium gas and a uniform duct cross-section area. Various system geometries are analysed using instantaneous and time history flow plots.

A finite element based method for estimating natural frequencies of locally damaged homogeneous beams

Vibration-based damage detection from frequency changes requires the calculation of natural frequencies from assumed damage scenarios and conduct a comparison to the actual frequency of the structure. Analytical solutions in obtaining the natural frequency of homogeneous beams are currently limited to beams with uniform cross-sectional area. Changes in cross-sectional area might occur due to damage within the length of the beam. Finite element modeling and analysis is required in these instances, but may not be efficient in terms of computational effort. For the assumed damaged scenarios, there are unlimited number of possible damage combinations for which the natural frequency will be obtained. There is a need for an analytical alternative as a substitute to the finite element method to calculate these frequencies. This study presents an analytical method to estimate the natural frequencies of locally damaged homogeneous beams based on statistical data obtained from finite element modeling and analysis. The method proposes a multiplier function in terms of the extent of area reduction, length, and location of damage in order to estimate the damaged frequency. The function was derived using curve-fitting techniques of data obtained from finite element modeling and analysis of typical beams with assumed damage cases. Examples show that the method is a good alternative to finite element analysis in estimating the natural frequencies of locally damaged homogeneous beams. The method can be used for vibration-based structural health monitoring to predict the damage state of beams given the change in frequency without the computational burden of finite element modeling and analysis.