Axial Ends Research Articles

Pulse Shortening in Recirculating Planar Magnetrons

Recirculating planarmagnetron (RPM) experiments at the University of Michigan have utilized a 12-frame ultrafast intensified CCD camera to analyze the effect of plasma formation on microwave pulse duration. The RPM was driven by a −300-kV voltage pulse for 0.3–1.0 $\mu $ s, with a 0.08–0.27-T axial magnetic field. The RPM has previously demonstrated peakmicrowave powers of over 150 MW, with typical microwave pulse durations of 50–150 ns, far shorter than the available voltage pulse. To investigate possible causes of pulse shortening, the RPM was imaged with both S-band (2 GHz) and L-band (1 GHz) anodes, as well as two different cathodes with substantially different anode–cathode (AK) gap widths and end caps. It was found that a smaller AK gap produced brighter plasma and allowed for improvements in temporal resolution of the imaging configuration at the expense of larger end-loss current. Many shotsdemonstrated a direct correlationbetween intervane anode plasma formation and a sharp reduction in RF power. Anode vane plasma is formed at the axial ends of the anode, indicating field enhancement effects. Contact resistance plasma was also observed at the back of anode vane cavities. Details of plasma formation are illustrated and methods for remediating these plasmas are proposed.

Thermoelastic damping in microstretch thermoelastic rectangular plate

The present paper deals with the deflection and thermoelastic damping analysis of micro-scale microstretch, micropolar, generalized thermoelastic thin plate. The analytical expressions for the transverse vibrations of a homogeneous, isotropic, microstretch, micropolar, generalized thermoelastic thin plate, based on Kirchhoff theory have been derived. The axial ends of the plate are assumed to be at either clamped or simply supported conditions. Analytical results for deflection, microstretch functions, temperature distribution, thermoelastic damping and frequency shift have been obtained. The numerical simulation has been carried out with the help of MATLAB software for magnesium like material. The graphical representations and interpretations have been discussed for thermoelastic damping of plate under various boundary conditions and for distinct considered values of thickness and length as well.

Deflection analysis of micro-scale microstretch thermoelastic beam resonators under harmonic loading

In this paper, the flexural vibrations of homogeneous, isotropic, generalized micropolar microstretch thermoelastic thin Euler–Bernoulli beam resonators, due to time harmonic load have been investigated. The axial ends of the beam are assumed to be at either clamped-clamped, simply supported-simply supported or clamped-free conditions. The governing equations have been solved analytically by using Laplace transforms technique twice with respect to time and space variables respectively. The inversion of Laplace transform in time domain has been performed by using the calculus of residues to obtain deflection. The numerical simulation has been carried out with the help of MATLAB software for magnesium like material. The graphical representations and observations have been discussed for deflection of beam under various boundary conditions and for distinct considered values of time and space as well.

Dynamic microfluidic control of supramolecular peptide self-assembly.

The dynamic nature of supramolecular polymers has a key role in their organization. Yet, the manipulation of their dimensions and polarity remains a challenge. Here, the minimalistic diphenylalanine building block was applied to demonstrate control of nano-assemblies growth and shrinkage using microfluidics. To fine-tune differential local environments, peptide nanotubes were confined by micron-scale pillars and subjected to monomer flows of various saturation levels to control assembly and disassembly. The small-volume device allows the rapid adjustment of conditions within the system. A simplified kinetic model was applied to calculate parameters of the growth mechanism. Direct real-time microscopy analysis revealed that different peptide derivatives show unidirectional or bidirectional axial dimension variation. Atomistic simulations show that unidirectional growth is dictated by the differences in the axial ends, as observed in the crystalline order of symmetry. This work lays foundations for the rational control of nano-materials dimensions for applications in biomedicine and material science.

Design of an axially concave pad profile for a large turbine tilting-pad bearing

To improve operational safety and/or achieve a higher load capacity of turbine tilting-pad bearings, an axially concave pad profile is presented. The thermal and mechanical stress of the loaded pads of a test bearing in load between pivot configuration has been analysed. Both film thickness and pressure distribution have been measured at a very high resolution. A fluid film calculation program in combination with a finite-volume-based structural mechanics program is used to simulate the deformation of a single pad under high circumferential speeds. In this context, the axial and tangential heat transfer coefficients of the pad surface, which act as boundary conditions for the calculation of the 3D temperature distribution, are determined using an optimization process. Herein, the match of predicted and measured pad temperatures is the goal. It can be shown that there must be a huge difference in heat transfer in axial and tangential direction in order to match the large measured temperature gradient in circumferential direction. Based on the measured deformed profile the program code is used to derive a concave pad profile, which will result in an axially non-arched sliding surface under the expected thermal load. Therefore, an iterative simulation procedure is used. By decreasing the axial arching of the pad and thus the large film thickness at the axial ends using an improved profile designed for a specific operation point, the minimum film thickness and maximum pad temperature can be influenced beneficially. The comparison of measurement data and calculation results shows very good agreement regarding the pad deformations. The results indicate that by axially concave profiling of the loaded pads of a large tilting-pad bearing for a specific operation point, the static characteristics in the form of temperature, film thickness and load capacity can be improved.

Pulse-Shortening in a Relativistic Magnetron: The Role of Anode Block Axial Endcaps

A six-vane relativistic magnetron with a single radial output slot is studied by 3-D particle in cell simulations without the presence of plasma. We find that when the six radial slots in the anode block are closed at their axial ends by conducting endcaps, the power flow behaves in a way different from that when they are not. When there are no endcaps, microwave power pulse-shortening is the result of the magnetron impedance being undermatched to the pulsed-power generator, and it cancels when the magnetron impedance is increased sufficiently. The axial electron current flowing in the downstream cavity reduces to negligible values and plays no part in the power flow. When anode block endcaps are added, this axial leakage current is significant and the downstream cavity acts as a second load attached in parallel to the magnetron. For pulse-shortening to cancel, the magnetron impedance needs to increase, which can be achieved by reducing the downstream axial section impedance. We demonstrate this by increasing the axial current. Between the parameter regions where pulse-shortening exists and where it does not, there is a metastable transition region where there is mode competition resulting in a beating pattern separating two regions each characterized by a single mode.

Response of anisotropic thermoelastic micro-beam resonators under dynamic loads

In this paper, the dynamic response of homogeneous, transversely isotropic, thermoelastic micro-beam resonators subjected to time-varying transverse loads has been investigated in the context of generalised theory of thermoelasticity. The micro-beam is modeled based on Euler–Bernoulli beam theory. The beam is assumed to be at clamped–clamped conditions at its axial ends. The analytical solution has been obtained by using the Laplace transform technique in the time domain. The inversion of the transformed solution has been carried out by using calculus of residues. The analytical expressions for deflection obtained in the physical domain have been computed numerically for a silicon micro-beam with the help of MATLAB software. The numerically analysed results for deflection of clamped–clamped thermoelastic silicon (Si) micro-beam with length, time and frequency ratio due to acting dynamic loads have been presented graphically. The present model may be used in microelectromechanical applications such as relay switches, frequency filters, mass flow sensors, accelerometers and resonators.

Modeling and analysis of forced vibrations in transversely isotropic thermoelastic thin beams

In this paper, the transverse vibrations in a homogenous, transversely isotropic, thermoelastic thin beams due to time varying patch loads have been investigated. The governing equations of motion for classical elasticity and heat conduction for non-Fourier (non-classical) process have been integrated to model the transverse vibrations in a homogenous, transversely isotropic thin beam in closed form by employing Euler–Bernoulli beam theory. The axial ends of the beam are assumed to be at either clamped–clamped or clamped-free/cantilever conditions. The model equation governing transverse vibrations in a thermoelastic thin beam has been solved analytically by employing Laplace transform technique with respect to space and time variables. In order to obtain deflection and other quantities in the physical domain, the inversion of Laplace transform in the time domain has been performed by using the calculus of residues. The variational iteration method along with Durbin technique has also been employed to solve the model equation for comparison and validation purpose. The expressions for deflection and response ratio in the physical domain have been computed numerically with the help of MATLAB software for a silicon carbide micro-beam. The computed results have been presented graphically. The obtained analytic results are envisioned to be easy to implement for engineering analysis and designs of resonators (sensors), modulators, actuators and radio frequency filters.

Cosmic Redshift in the Nonexpanding Cellular Universe: Velocity-Differential Theory of Cosmic Redshift

A review of the traditional possible causes of cosmic redshift —namely Doppler, expanding vacuum, gravitational, and tired light— is presented along with a discussion of why they failed. A new cosmic redshift mechanism is constructed based on a non-mass, non-energy, space medium (which serves as the luminiferous substrate) and the DSSU cellular cosmology (a remarkably natural problem-free cosmology). The cosmic redshift is shown to be a velocity-differential effect caused by a flow differential of the space medium. Furthermore, the velocity-differential redshift/effect is shown to be part of a much broader unification, since the very mechanism that causes the gravitation effect and sustains the Universe’s gravity-cell structure is also the mechanism that causes the λ elongation manifesting as the cosmic redshift. Agreement with the verifiable portion of the redshift-distance graph (z ≤ 5) is outstanding. The main point is that intrinsic spectral shift occurs with a transit across/through any gravity well (sink). It is caused by the difference in propagation velocity between the axial ends of the photon or wave packet. Which, in turn, is caused by the difference in velocity of the aether flow, the flow differential of the aether, that occurs throughout a gravity well. And here the causal chain is linked to gravity: the change in velocity of the aether flow is what produces the effect of gravitation. The acceleration of the aether flow is the manifestation of gravity.

Analysis of perfectly matched layer operators for acoustic scattering on manifolds with quasicylindrical ends

In this paper we prove stability and exponential convergence of the Perfectly Matched Layer (PML) method for acoustic scattering on manifolds with axial analytic quasicylindrical ends. These manifolds model long-range geometric perturbations (e.g. bending or stretching) of tubular waveguides filled with homogeneous or inhomogeneous media.We construct non-reflective infinite PMLs replacing the metric on a part of the manifold by a non-degenerate complex symmetric tensor field. We prove that the problem with PMLs of finite length is uniquely solvable and solutions to this problem locally approximate scattered solutions with an error that exponentially tends to zero as the length of PMLs tends to infinity.

Dirhodium Paddlewheel with Functionalized Carboxylate Bridges: New Building Block for Self-Assembly and Immobilization on Solid Support

A new dirhodium(II,II) paddlewheel complex, [Rh(2)(O(2)CC(6)H(4)COOC(2)H(5))(4)] (1), has been synthesized using a predesigned functionalized carboxylate, namely, 4-(ethoxycarbonyl)benzoate. The target product has been crystallized from the acetone solution and structurally characterized as a bis-acetone adduct, [Rh(2)(O(2)CC(6)H(4)COOC(2)H(5))(4)(OCMe(2))(2)]·C(6)H(14) (2). By utilizing the ability of dangling ester groups to coordinate to open axial ends of neighboring dirhodium units, 1 can self-assemble to form 2D networks upon crystallization from solutions of noncoordinating solvents such as chlorobenzene and chloroform. The resulting [Rh(2)(O(2)CC(6)H(4)COOC(2)H(5))(4)]·2C(6)H(5)Cl (3) and [Rh(2)(O(2)CC(6)H(4)COOC(2)H(5))(4)]·2CHCl(3) (4) products have microporous solid state structures with the pores filled with the corresponding disordered solvent molecules. Notably, 3 and 4 represent unique examples of 2D extended frameworks based on dirhodium tetracarboxylate paddlewheel units devoid of any exogenous ligands. In solution, the dangling ends of carboxylate bridges of 1 have been successfully utilized for condensation reaction with the selected solid support, benzylamine-functionalized polystyrene, allowing successful heterogenization of dirhodium units through the equatorial covalent attachment to the substrate. The resulting solid product was tested as a catalyst in the cyclopropanation reaction of styrene with methyl phenyldiazoacetate to show good yields and diastereoselectivity.

Self-sensing tunable vibration absorber incorporating piezoelectric ceramic–magnetostrictivecomposite sensoriactuator

A novel self-sensing tunable vibration absorber (SSTVA) is developed for activeabsorption of vibrations in vibrating structures. The SSTVA consists of a piezoelectricceramic–magnetostrictive composite sensoriactuator suspended in a mounting frame by twoflexible beams connected to the axial ends of the sensoriactuator. The sensoriactuatorserves to produce an axial force for tuning of the natural frequency of the SSTVA, togather the signals associated with structural vibrations and to provide a lumped dampedmass for the SSTVA. By monitoring the sensoriactuator output voltage whileadjusting its input magnetic field (or electric current), the natural frequencyof the SSTVA is tuned to the targeted resonance frequency of a structure. Inthis paper, the working principle, design prototype and operating performanceof a 62.5 Hz SSTVA are reported. A high tunability of the natural frequency of20% and a good sensing capability of vibrations comparable to a commercialaccelerometer are obtained, together with a high absorbability of vibrations of ∼ 4 dB in a steel-plate–neoprene resilient mount structure.

Three-Pin Cluster CABRI Tests Simulating the Unprotected Loss-of-Flow Accident in Sodium-Cooled Fast Reactors

Two three-pin cluster tests simulating the Unprotected Loss-of-Flow (ULOF) accident of Sodiumcooled Fast Reactors (SFRs) were conducted focusing on postfailure fuel relocation and freezing behavior. These tests supplied complementary information to the existing CABRI tests with a single-pin geometry. Based on detailed data evaluation and theoretical interpretation for the three-pin cluster tests, it is concluded that axial fuel relocation and freezing are dominated by local fuel enthalpy, and the relation between penetration length and local fuel enthalpy observed in these CABRI tests is basically applicable to the large-bundle condition. It is also clarified that a fuel/steel mixture tends to create tight blockages near the axial ends of the relocating fuel. Part of the fission gas released from the heating-up and melting fuel is expected to be trapped within the bottled-up region between the upper and lower blockages and will keep this region pressurized for a relatively long period.

Three-Pin Cluster CABRI Tests Simulating the Unprotected Loss-of-Flow Accident in Sodium-Cooled Fast Reactors

Two three-pin cluster tests simulating the Unprotected Loss-of-Flow (ULOF) accident of Sodiumcooled Fast Reactors (SFRs) were conducted focusing on postfailure fuel relocation and freezing behavior. These tests supplied complementary information to the existing CABRI tests with a single-pin geometry. Based on detailed data evaluation and theoretical interpretation for the three-pin cluster tests, it is concluded that axial fuel relocation and freezing are dominated by local fuel enthalpy, and the relation between penetration length and local fuel enthalpy observed in these CABRI tests is basically applicable to the large-bundle condition. It is also clarified that a fuel/steel mixture tends to create tight blockages near the axial ends of the relocating fuel. Part of the fission gas released from the heating-up and melting fuel is expected to be trapped within the bottled-up region between the upper and lower blockages and will keep this region pressurized for a relatively long period.

Skeletal repair of extreme damage in rugose corals, Pella Formation (Mississippian, Iowa, USA)

Little is known about predation on rugose corals or the repair of damage to rugose coral skeletons. Here we describe a population of the solitary rugose coral Amplexizaphrentis spinulosa ( Milne-Edwards and Haime, 1851) from the Late Mississippian Pella Formation in Keokuk County, Iowa, USA wherein ∼30% of 135 specimens experienced sublethal damage resulting from compression apparently inflicted by fish or other large predators. Many corals were able to repair severe damage and re-establish a relatively normal morphology despite the loss of parts of the wall. Healed damage includes: (1) chips to the edge of the calice, (2) punctures in the wall, (3) lost sections of wall, (4) re-cemented sections of wall, some at odd angles, (5) changes in growth direction, and (6) rejuvenescence. Multiple episodes of damage and repair occurred in 5% of samples. More severe damage on the cardinal side in almost one-half of damaged samples may reflect structural weakness at the cardinal fossula relative to the counter side, but septa were broken in all positions in many samples. The pattern of alignment and preservation of broken plates in the calice suggests that soft tissues were better attached to the skeleton in a band relatively far above the calice floor. Better musculature also may have occurred in the same band. Where parts of the wall were broken free from septa that remained fixed at their axial ends, new wall was deposited as stereoplasm against and enveloping the adaxial ends of the original septa. Lost lengths of septa were replaced by adaxial growth. New septa were commonly contorted, presumably owing to deformation of surviving soft tissues that had lost structural support. Broken septa were generally healed, commonly with poor alignment. The high survival rate, even following multiple attacks, suggests that the soft tissues of the coral polyps were robust. The rarity of changes in growth direction following attacks suggests that the corals may have been more capable of righting themselves and re-establishing an optimum growth orientation than has commonly been suggested for solitary Rugosa.

Structure of Coatomer Cage Proteins and the Relationship among COPI, COPII, and Clathrin Vesicle Coats

COPI-coated vesicles form at the Golgi apparatus from two cytosolic components, ARF G protein and coatomer, a heptameric complex that can polymerize into a cage to deform the membrane into a bud. Although coatomer shares a common evolutionary origin with COPII and clathrin vesicle coat proteins, the architectural relationship among the three cages is unclear. Strikingly, the alphabeta'-COP core of coatomer crystallizes as a triskelion in which three copies of a beta'-COP beta-propeller domain converge through their axial ends. We infer that the trimer constitutes the vertex of the COPI cage. Our model proposes that the COPI cage is intermediate in design between COPII and clathrin: COPI shares with clathrin an arrangement of three curved alpha-solenoid legs radiating from a common center, and COPI shares with COPII highly similar vertex interactions involving the axial ends of beta-propeller domains.

Analysis of Axial Leakage in High-Speed Slotless PM Motors for Industrial Hand Tools

This paper presents an analysis of axial-leakage effects in high-speed slotless permanent-magnet (PM) motors for industrial hand-tool applications. Analytical predictions based on a 2-D model and results from a 3-D finite-element (3DFEM) simulation model are compared with experimental results from three series-produced PM motors. The reduction in flux density (resulting from 3DFEM simulations and measurements) outside the motor's axial ends is substantial; the flux density has practically vanished only a few millimeters outside the stator lamination stack. To predict the resulting flux linkage, a simple winding model is presented where the winding is made up of a discrete number of winding layers. Using this winding model, it is verified that the reduction in flux linkage, manifested as a reduction in the back electromotive force, is not only dependent on the motor's axial length but also that the effect is minor for slotless PM motors with dimensions suitable for hand-tool applications. The results are also supported by no-load line-to-line voltage measurements on the three PM motors.

M = 1 ideal kink modes in a line-tied screw pinch with finite plasma pressure

A new method for computing ideal magnetohydrodynamic linear eigenmodes in a cylindrical screw pinch with line-tying boundary conditions at the axial ends is presented. In this method, plasma volume is reflected over one of the end planes, and equations and field components are continued into the extended volume with the continuation rules prescribed by the line-tying boundary conditions. Field components in the combined volume are expanded in Fourier series in the axial coordinate. The resulting set of coupled differential equations is solved numerically in the radial coordinate by a finite difference method yielding growth rates and eigenmodes for the system. An example of an m=1 (m is the poloidal wave number) internal kink instability in a force-free plasma equilibrium with uniform pressure is considered. In contrast to a periodic screw pinch, marginally stable perturbations are essentially compressible in the line-tied geometry. Finite compressibility makes the mode more stable in addition to the usual line-tying stabilization in zero pressure plasma. The critical length corresponding to the marginal stability increases with the increase of plasma beta. A universal axial dependence for marginally stable density perturbations ρ(r,z)=ρ(r)exp[−izμ(r)] is predicted analytically and confirmed numerically, where μ(r) depends on the equilibrium magnetic field components as μ(r)=B¯θ∕rB¯z.

Heterogeneity of V2O5 Supported Cylindrical Activated Coke Used for SO2 Removal from Flue Gas

AbstractV2O5 supported activated coke (V/AC) was shown to be a good catalyst for SO2 removal from flue gas. In this work, the heterogeneities of cylindrical V/AC granules (Φ 8.5 · 12.6 mm) are investigated by peeling the granules layer by layer. The results show that the axial ends of the catalyst with a depth of ca. 2 mm contain more pores than other parts of the catalyst. This pore structure distribution results in a similar V2O5 distribution through impregnation and a similar S distribution after SO2 removal. The results show that mass transfer is the main factor affecting SO2 removal over large V/AC granules, and that SO2 removal proceeds mainly along the axial direction of the granules. The granule should be made shorter in the axial direction and longer in the radial direction to improve utilization of V/AC.

Structure and Organization of Coat Proteins in the COPII Cage

COPII-coated vesicles export newly synthesized proteins from the endoplasmic reticulum. The COPII coat consists of the Sec23/24-Sar1 complex that selects cargo and the Sec13/31 assembly unit that can polymerize into an octahedral cage and deform the membrane into a bud. Crystallographic analysis of the assembly unit reveals a 28 nm long rod comprising a central alpha-solenoid dimer capped by two beta-propeller domains at each end. We construct a molecular model of the COPII cage by fitting Sec13/31 crystal structures into a recently determined electron microscopy density map. The vertex geometry involves four copies of the Sec31 beta-propeller that converge through their axial ends; there is no interdigitation of assembly units of the kind seen in clathrin cages. We also propose that the assembly unit has a central hinge-an arrangement of interlocked alpha-solenoids-about which it can bend to adapt to cages of variable curvature.