Three-dimensional Transmission Research Articles

Advanced recording schemes for electron tomography

Abstract

Prediction of model scale turbofan exhaust tone noise

This paper describes in detail the process for predicting, from first principles, the rotor–stator interaction tone levels for two realistic model-scale fans that are representative of high bypass ratio and ultrahigh bypass ratio turbofans. The prediction scheme relies on a suite of three-dimensional computational tools that include Reynolds Averaged Navier–Stokes aerodynamic models and linearized inviscid aeroacoustic models. The goal of the study was to assess the accuracy of tone-level predictions for realistic fans operating under realistic conditions. The predictions were carried out over a wide range of operating conditions that include, but were not limited to the approach, cutback, and sideline conditions for each of the two fans. The in-duct and external tonal sound fields were computed at a representative blade passing frequency harmonic tone. The predicted tone sound pressure level and sound power level have been compared with the measurements acquired at a NASA anechoic wind tunnel. The data–theory comparisons are primarily focused on the exhaust tone levels due to lack of validated models for predicting the three-dimensional tone acoustic transmission through a rotor. The data–theory comparisons show that it is possible to make accurate predictions of the exhaust rotor–stator interaction tone power levels starting with the geometry of the fan stage. Specifically, the results demonstrate that the exhaust rotor–stator interaction tone power levels can be predicted to within [Formula: see text] dB on a consistent basis for rotor at subsonic tip relative speeds by including the three-dimensional geometry of the fan stage and its flowfield. Furthermore, using the predicted in-duct sound pressure levels, the basic trends in the directivity of the exhaust tone sound pressure level can also be predicted despite the complex nature of tone directivity for realistic fans and the complicated physics of sound refraction through the exhaust shear layer.

Simulation of the Vortex Dynamics in a Real Pinning Landscape ofYBa2Cu3O7−δCoated Conductors

The ability of high-temperature superconductors (HTSs) to carry very large currents with almost no dissipation makes them irreplaceable for high-power applications. The development and further improvement of HTS-based cables requires an in-depth understanding of the superconducting vortex dynamics in presence of complex pinning landscapes. We present a critical current analysis of a real HTS sample in a magnetic field by combining state-of-the-art large-scale Ginzburg-Landau simulations with reconstructive three-dimensional scanning transmission electron microscopy tomography of the pinning landscape in Dy-doped YBa$_2$Cu$_3$O$_{7-\delta}$. This methodology provides a unique look at the vortex dynamics in the presence of a complex pinning landscape, responsible for the high current-carrying capacity characteristic of commercial HTS wires. Our method demonstrates very good functional and quantitative agreement of the critical current between simulation and experiment, providing a new predictive tool for HTS wires design.

ステンレス鋼の高出力レーザ溶接における3次元X線透視その場観察による湯流れと入射角および焦点はずし距離によるスパッタ抑制との関係

ステンレス鋼の高出力レーザ溶接における3次元X線透視その場観察による湯流れと入射角および焦点はずし距離によるスパッタ抑制との関係

Robust lateral double‐diffused MOS with interleaved bulk and source for high‐voltage electrostatic discharge protection

A device with bulk and source interleaved dotting is fabricated in a 0.5-µm 24 V CDMOS process, and the root cause of why it improves the multi-finger high-voltage lateral double-diffused MOS (LDMOS)’s electrostatic discharge (ESD) robustness is detected by Atlas three-dimensional device simulation and transmission line pulse system. Such device structure obtains strong ESD robustness by enlarging the intrinsic base resistance without increasing device area and sacrificing any ESD performance of nLDMOS. The measurement results demonstrated that, compared with traditional gate-grounded nLDMOS (GG-nLDMOS) with a total length of 400 μm, the proposed device can effectively raise the secondary breakdown current (I t2) from 2.43 A up to 5.55 A, and enhance the ESD current discharge efficiency from 0.29 to 0.70 mA/μm2.

Elucidation of melt flows and spatter formation mechanisms during high power laser welding of pure titanium

This study was undertaken to clarify the relationship among the laser-induced plume ejected from the keyhole, the melt flows in the molten pool, and the formation mechanisms of spatters ejected from the molten pool during 10 kW laser welding of a pure titanium plate. High-speed video camera observation results showed that laser-induced plumes occurred at intervals of about 0.5 ms, and that the maximum plume ejection velocity reached 250 m/s. Three-dimensional X-ray transmission in-situ observation of the weld molten pool with tungsten carbide tracers revealed that the melt flowed mainly along the bottom of the molten pool from the keyhole tip to the rear part and then from the rear to the front near the surface of the molten pool at high speeds, while the melt in front of a keyhole flowed upward along the keyhole wall at a velocity of less than 0.6 m/s and then was accelerated to 2.1 m/s at the height of about 2 mm above the keyhole inlet. One-way upward melt flows were continuously piled up at the tip of the elongated melt, resulting in spattering as droplets from the molten pool due to the strong ejection of laser-induced plumes. Spatters were formed from part of a molten metal elongated around the keyhole inlet, and approximately 20 ms was required to form spatters. About 80% of spatters were generated from melts of the front or sides of the keyhole at the speeds of less than 50 mm/s. When the welding speed increased from 50–100 mm/s to 300 mm/s, the ratio and the size of spatters occurring from the rear part of a keyhole increased from 20% to 80% and became smaller than 1 mm.

Ultrasmall Bacteria: 150 Could Fit inside an E. coli Cell

New three-dimensional images show bacteria so tiny that 150 of them could fit into a single Escherichia coli cell. “These ultrasmall bacteria are a subset of microbial life on Earth that we know almost nothing about,” says Jill Banfield at the University of California, Berkeley. She and her colleagues used two- and three-dimensional cryogenic transmission electron microscopy to gather information about the cell walls, morphology, and volume of these ultrasmall bacteria. Details appeared 27 February 2015 in Nature Communications (doi:10.1038/ncomms7372).

An experimental and theoretical study of the dynamic behavior of double-helical gear sets

In this study, dynamic behavior of a double-helical gear pair is investigated both experimentally and theoretically. In the experimental side, a new double-helical test set-up consisting of a test machine and test specimens is developed for operating a double-helical gear pair under realistic torque and speed ranges. A test gear pair formed by novel three-piece double-helical gears is developed to allow adjustable right-to-left stagger angles. A measurement system to capture three-dimensional vibratory motions and dynamic motion transmission error under high-speed conditions is implemented. A test matrix that included various combinations of key system parameters is executed under realistic torque values within a wide speed range to establish a database. In view of this experimental data, a linear, time-invariant dynamic model of double-helical gear pair systems including shafts and bearing supports is proposed, also allowing for any stagger angle between the right and left sides of a double-helical gear pair through proper definition of phasing between the two gear mesh excitations. Direct comparisons to measurements are presented to demonstrate the accuracy of the proposed model in predicting three-dimensional gear vibrations. The right-to-left stagger angle is shown to be the most critical parameter impacting dynamic response.

Limitations of the linear and the projection approximations in three-dimensional transmission electron microscopy of fully hydrated proteins.

We establish expressions for the linear and quadratic terms in the series expansion of the phase and the phase and amplitude object description of imaging thin specimens by transmission electron microscopy. Based on these expressions we simulate the corresponding contributions to images of unstained protein complexes of varying thickness and arrive at an estimate for how much each term contributes to the contrast of the image. From this we can estimate a maximum specimen thickness for which the weak phase and the weak amplitude and phase object approximation (and therefore linear imaging) is still reasonably accurate. When discussing thick specimens it is also necessary to consider limitations due to describing the image as a filtered projection of the specimen, since the different layers of the specimen are not imaged with the same defocus value. We therefore compared simulations based on the projection approximation with the more accurate multislice model of image formation. However, we find that the errors due to nonlinear image contributions are greater than those due to the defocus gradient for the defocus values chosen for the simulations. Finally, we study how the discussed nonlinear image contributions and the defocus gradient affect the quality of three-dimensional reconstructions. We find that three-dimensional reconstructions reach high resolution when at the same time exhibiting localized systematic structural errors.

Energy, Delay, and Outage Analysis of a Buffer-Aided Three-Node Network Relying on Opportunistic Routing

In this contribution, we propose and study a bufferaided opportunistic routing (BOR) scheme, which combines the benefits of both opportunistic routing and multihop diversity (MHD) aided transmissions. It was conceived for a buffer-aided three-node network (B3NN) composed of a source node (SN), a buffer-aided relay node (RN) and a destination node (DN). In this network, there are three channels namely the SN-RN, RN-DN and SN-DN channels. The key motivation is that we are aiming for activating the specific channels requiring a recuded energy dissipation. In order to study this problem, a three-dimensional (3D) transmission activation probability space (TAPS) is proposed, which is divided into four regions representing each of the three channels plus an outage region. In a specific time slot (TS), the instantaneous channel fading values may be directly mapped to a specific point in this 3D channel space. The BOR scheme then relies on the position of this point to select the most appropriate channel for its transmission. Both the energy dissipation and the outage probability (OP) are investigated for transmission in this network. The results show that when the system is operated at a normalized throughput of 0.4 packet/TS, the energy dissipation was reduced by 24.8% to 77.6% compared to three different benchmark schemes. Alternatively, our technique is capable of reducing the OP by 89.6% when compared to conventional opportunistic routing. As in all buffer-aided system, the performance improved with the cost of higher packet delay, which is also studied.

ステンレス鋼の高輝度・高出力レーザ溶接時の溶融池内湯流れに及ぼす溶接速度の影響の三次元X線透視その場観察法による解明

This research was performed with the objective of clarifying the effect of welding speed on melt flows during melt-run welding of SUS304 stainless steel plates with a 6-kW power laser beam on the basis of three-dimensional X-ray transmission in-situ observation. As welding speed increased from 25 mm/s to 250 mm/s, three kinds of welds characterized by porosity formation, no defects or underfilling due to spatters were produced. The average and the maximum values of measured melt flow velocity were three and ten times higher than the welding speed, respectively. Two kinds of circulation flows at the inlet or the tip of a keyhole were confirmed to control heat transfer in a molten pool. It was found that the circulation flows were so sensitive to the welding speed that bubbles resulting in porosity or spatters were often formed. Accoriding to the X-ray observation of the spatters formation with tungsten carbide (WC) tracers, as the melt flow rose along the keyhole wall, the velocity was accelerated from 0.24 m/s to 0.54 m/s near the keyhole inlet. Consequently, the melt flows made the convex surface behind the keyhole grow higher, resulting in spattering.

A Robust Numerical Algorithm for Computing Maxwell's Transmission Eigenvalue Problems

We study a robust and efficient eigensolver for computing a few smallest positive eigenvalues of the three-dimensional Maxwell's transmission eigenvalue problem. The discretized governing equations by the Nedelec edge element result in a large-scale quadratic eigenvalue problem (QEP) for which the spectrum contains many zero eigenvalues and the coefficient matrices consist of patterns in the matrix form $XY^{-1}Z$, both of which prevent existing eigenvalue solvers from being efficient. To remedy these difficulties, we rewrite the QEP as a particular nonlinear eigenvalue problem and develop a secant-type iteration, together with an indefinite locally optimal block preconditioned conjugate gradient (LOBPCG) method, to sequentially compute the desired positive eigenvalues. Furthermore, we propose a novel method to solve the linear systems in each iteration of LOBPCG. Intensive numerical experiments show that our proposed method is robust, although the desired real eigenvalues are surrounded by complex eigenv...

An Experimental Protocol Development of Three-Dimensional Transmission Electron Microscopy Methods for Ferrous Alloys: Towards Quantitative Microstructural Characterization in Three Dimensions

The majority of engineering steels are ferromagnetic and structurally inhomogeneous on scales ranging from nanometers to micrometers, and their physical properties depend on the three-dimensional (3D) features in their microstructures. Thus, obtaining a 3D image with a large field of view is desirable for transmission electron microscopy (TEM) based microstructure characterization in order to establish the relationship between the microstructure and the physical properties with a reasonable statistical relevancy. Here, we use a conventional sample preparation process, i.e., mechanical polishing followed by electropolishing, and optimizing experimental protocols for electron tomography (ET) of ferromagnetic materials, to carry out microstructural characterization of engineering steel. We determined that the sample thickness after the mechanical polishing step is a critical experimental parameter affecting the success rate of tilt-series image acquisitions. For example, for ferritic heat-resistant 9Cr steel, mechanical thinning down to 30 μm or less was necessary to acquire an adequate tilt-series image of the carbide precipitates in the annular dark-field scanning TEM (ADF-STEM) mode. However, acquiring tilt-series images of dislocation structures remains a challenge due to an unavoidable, significant electron beam deflection during specimen tilt, even with a thinned sample. To overcome the electron beam deflection problem, we evaluated several relatively accessible approaches including the “Low-Mag STEM and Lorentz TEM” modes. Although rarely used for ET, both modes reduce or even zero the objective lens current, likely weakening the magnetic interference between the ferromagnetic specimen and the objective lens magnetic field. The advantages and disadvantages of these experimental components are discussed.

Three-dimensional image transmission and reconstruction for multisensor imaging system using interleaver division multiple access

In this paper, we present an optical image transmission and reconstruction system of 3D objects using a multisensor imaging system and interleaver division multiple access (IDMA) channel. When the 3D image data from the multisensor imaging system are transmitted over a wireless channel, loss or distortion of original data may occur by wireless channel environment, such as multiple access interference and channel noise. To solve this problem, an optical 3D image reconstruction scheme and IDMA technique can be used. Reconstructed 3D image data at the receiver is clear enough to distinguish the depth of 3D objects. To prove our proposed scheme, we carry out an optical experiment for sensing 3D information and simulation for data transmission of a multisensor imaging system via IDMA with channel noise.

Local Plasmonic Studies on Individual Core–Shell Gold–Silver and Pure Gold Nano-Bipyramids

Bimetallic systems present new opportunities to tailor the optical properties of nanoparticles. Morphology, structural, and optical properties of gold and of gold–silver nanoparticles have been studied by three-dimensional (3D) scanning transmission electron microscopy (STEM), STEM imaging, and monochromated subnanometer electron beams. The 3D morphology of these nanoparticles consists of bipyramidal prisms with well-defined facets. Furthermore, in the case of the core–shell nanoparticles, from these tomographical studies, we have determined the silver (shell) distribution and their atomic arrangement. Multipolar localized surface plasmon resonances (LSPR) have been studied, at subnanometer level and at high-energy resolution, as a function of their shape, their size (aspect ratio), and the surrounding environment. These results have been interpreted in the framework of the discrete dipole approximation (DDA) simulations. The effect of the silver outer-shell has been elucidated. We observed a significant damping of plasmon excitations due to the difference of dielectric function of these two metals. In addition, we have shown that the combination of the tomographical and plasmonic (experiments and simulations) studies with such high spatial resolution constitutes a very powerful and fundamental tool for understanding and optimizing the photonics properties of nanomaterials.

STUDIES ON BOUND RUBBER OF CB BEFORE/AFTER VULCANIZATION OF ISOPRENE RUBBER

ABSTRACT The high abrasion furnace (HAF), fast extrusion furnace (FEF), and fine thermal (FT) loadings used in this study were adjusted to keep the carbon black (CB)–specific area of cetyl trimethyl ammonium bromide adsorption to 2490 m2g−1. Their polyisoprene (IR) compounds and vulcanizates were investigated. Regarding the dependence of the CB gel fraction (FCB gel) on the IR gel/CB weight ratio (WRIR/CB), the amount of CB in the CB gel increased with a larger CB aggregate size, whereas the amount of the IR gel decreased. With regard to the dependence of the activation energy (ΔE(T2)) of the spin–spin relaxation time (T2) on the CB aggregate size, an immobilized rubber layer around CB formed more easily in the order of FT < FEF < HAF. Moreover, it became clear from the relationship between WRIR/CB and ΔE(T2) that the amount of the IR gel in the CB gel increased with decreasing ΔE(T2). The unique ratio of the surface area to the volume of CB aggregates (SCB/VCB) was obtained from results of three-dimensional transmission electron microscopy observation. The dependence of the amount of dibutyl phthalate (DBP) adsorption and compressed DBP adsorption on SCB/VCB was approximately linear, which suggested that SCB/VCB was closely related to CB aggregates and CB agglomerates. The linear relationship seen between SCB/VCB and ΔE(T2) revealed that an immobilized rubber layer was present around CB. The dependence of (qCB/qIR)(WRIR/CB) on SCB/VCB was also investigated using the densities (ρIR and ρCB) of IR and CB. The slope (tirl) of their approximately linear relationship was about 3.9 nm, which almost agreed with the bound rubber thickness reported in the literature to date. It is also inferred that because the intercept (α), which reflects the change in the IR gel weight fraction, was about 0.04 (4%), the IR gel weight fraction changed very little between before and after vulcanization.

Nanostructural characterization of carbon nanotubes in laser-sintered polyamide 12 by 3D-TEM

Abstract

Evaluation of Long Term Evolution Cellular Network Performance when Transmitting Multi-view Video Content

The Long Term Evolution (LTE) cellular technology provides higher data rates than its predecessor technologies. This advancement paves the way for more data services, including improved multimedia services. Three-dimensional (3D) video transmission is one such service that can benefit from LTE deployment. For a positive uptake of 3D video transmission, the network must provide a good Quality of Service (QoS). In this paper the authors evaluate the LTE network's performance when transmitting Multi-view Video Coding (MVC) using simulcast and inter-view prediction coding. Furthermore, the authors evaluate the system using both the H.264/AVC (Advanced Video Coding) and the more recent High Efficiency Video Coding (HEVC) and their MVC extensions. Results show that, in an urban environment, LTE can accommodate a maximum of 93 users per cell, with adequate QoS, when transmitting 3D HEVC video at Common Intermediate Format (CIF) resolution. Moreover, cross-layer techniques can be used to reduce the QoS degradation as the user moves away from the eNodeB by transmitting lower resolution video.

Double Helical Synchronous Belt Transmission Design

The meshing impact noise caused by the gradually engagement between double helical synchronous belt and the pulley was reduced due to its spiral angle effect. Therefore, double helical synchronous belt transmission receives much concern with its excellent characteristics of de-noising, low transmission error and high carrying capacity. The profiles of synchronous belt and belt pulley were studied based on conjugate-curvature high degree contact meshing theory under the circumstance that the pitch of belt and belt pulley are identical. The higher contact strength of the belt teeth and a smaller clearance in the contact point adjacent area were ensured with Hertz contact theory as the synchronous belt is in contact with pulley. And then a conjugated arc tooth profile with two-step contact and three-step adjacent gap infinitesimal was proposed based on the simple easy to processing method, which was adopted as main parameters for double synchronous belt and pulley’s normal teeth profile. The three-dimensional transmission model was built and the static nonlinear contact analysis was done with finite element software ANSYS. Finally, the noise experiment was conducted on the high speed test bench to compare the noise reduction effect between double helical synchronous belt and straight tooth timing belt with the identical end face profile. The simulation and experiment result show that the double helical synchronous belt transmission can reduce noise level by 11dB approximately compared with straight tooth timing belt transmission.

How TEM Projection Artifacts Distort Microstructure Measurements: A Case Study in a 9 pct Cr-Mo-V Steel

Morphological data obtained from two-dimensional (2D) and three-dimensional (3D) transmission electron microscopy (TEM) observations were compared to assess the effects of TEM projection errors for submicron-size precipitates. The microstructure consisted of M23C6 carbides in a 9 pct Cr-Mo-V heat resistant steel before and after exposure to creep conditions. Measurements obtained from about 800 carbides demonstrate that particle size and spacing estimates made from 2D observations overestimate the more accurate values obtained from 3D reconstructions. The 3D analysis also revealed the M23C6 precipitates lengthen anisotropically along lath boundary planes, suggesting that coarsening during the early stage of creep in this alloy system is governed by grain boundary diffusion.