Sinterability and Decomposition of Pb0.9175La0.055Zr0.975Ti0.025O3: Influence of Calcination and Sintering Temperature

The sinterability and decomposition of PLZT, (Pb,La)(Zr,Ti)O₃, depend on the temperature and soaking time of both the calcination and sintering temperature. They were determined from the density, linear shrinkage, weight loss, and appearance of extra phases. At moderate calcination temperatures and times, there is no escape of PbO from the PLZT. At calcination temperatures higher than 1050°C and soaking times above 3 h, PbO escapes, and ZrO₂ and La₂Zr₂O₇ can be detected. Even when sintered in a PbO-rich atmosphere, some PbO evaporates during sintering either from free PbO or from the PbO bound in the PLZT in regions in the outer surfaces of the sintered body. An aggressive depletion of PbO during sintering can result in a complete disappearance of the grain boundary phase, giving an intragranular fracture.     

A quantitative assessment of structural errors in grid maps

Various common error sources affect the quality of a map, e.g., salt and pepper noise and other forms of noise that are more or less uniformly distributed over the map. But there also exist errors that only occur very rarely in the mapping process but that have severe effects on the final result. They influence not only the local accuracy but also the whole spatial layout of the map. Examples of related error sources include bump noise in the robot’s pose or residual errors in Simultaneous Localization and Mapping (SLAM). The concept of brokenness is introduced in this article to capture the notion of structural errors in grid maps. The map is partitioned into regions that are locally consistent with ground truth but “off” relative to each other. Brokenness measures the number of these regions and their spatial relations. A theoretical basis is introduced to derive the concept of brokenness in a formal way. Furthermore, it is shown how brokenness can be computed in an algorithmic way. Experiments with maps from simulated as well as real world data are presented. They show that the metric can indeed be used to automatically determine the structural quality of a map in a quantitative way.     

Transmission of 32-Tb/s Capacity Over 580 km Using RZ-Shaped PDM-8QAM Modulation Format and Cascaded Multimodulus Blind Equalization Algorithm

In this paper, we propose a novel synthesizing method for high-speed 8-ary quadratic-amplitude modulation (QAM) optical signal generation using commercial optical modulators with binary electrical driving signals. Using this method, we successfully generated 114-Gb/s pulse-duration modulation (PDM)-8QAM optical signals. Intradyne detection of PDM-8QAM optical signals with robust blind polarization demultiplexing has been demonstrated by using a new cascaded multimodulus equalization algorithm. With return-to-zero-shaped PDM-8QAM modulation and the proposed blind polarization demultiplexing algorithm, we demonstrate transmission of a record 32-Tb/s fiber capacity (320$,times,$114 Gb/s) over 580 km of ultralow-loss single-mode fiber-28 fiber by utilizing ${rm C}+{rm L}$-band erbium-doped fiber-amplifier-only optical amplification and single-ended coherent detection technique at an information spectral efficiency of 4.0 bit/s$cdot$Hz.      

CFD modeling of LPG vessels under fire exposure conditions

Fire exposure of tanks used for the storage and transportation of liquefied gases under pressure may cause complex heat‐ and mass‐transfer phenomena that may contribute to compromise the integrity of the vessels in accident scenarios. Heat transfer through vessel lading results in the heat‐up of the internal fluid and the increase of vessel internal pressure. However, local temperature gradients in the liquid phase cause liquid stratification phenomena that result in a more rapid vaporization and pressure build‐up in the liquid phase. These fundamental phenomena were analyzed by a computational fluid dynamic model. The model was specifically focused on the early steps of vessel heat‐up, when liquid stratification plays a relevant role in determining the vessel internal pressure. A two‐dimensional transient simulation was set up using ANSYS FLUENT in order to predict the evolution of the liquid and vapor phases during the tank heat up. The model was validated against large scale experimental data available for liquefied petroleum gas vessels exposed to hydrocarbon fires, and was applied to case studies derived from recent accidental events in order to assess the expected time of pressure build‐up in different fire scenarios. © 2014 American Institute of Chemical Engineers AIChE J 60: 4292–4305, 2014     

A modified scaled boundary finite element method for three‐dimensional dynamic soil‐structure interaction in layered soil

This paper is devoted to the analysis of elastodynamic problems in 3D‐layered systems which are unbounded in the horizontal direction. For this purpose, a finite element model of the near field is coupled to a scaled boundary finite element model (SBFEM) of the far field. The SBFEM is originally based on describing the geometry of a half‐space or full‐space domain by scaling the geometry of the near field / far field interface using a radial coordinate. A modified form of the SBFEM for waves in a 2D layer is also available. None of these existing formulations can be used to describe a 3D‐layered medium. In this paper, a modified SBFEM for the analysis of 3D‐layered continua is derived. Based on the use of a scaling line instead of a scaling centre, a suitable scaled boundary transformation is proposed. The derivation of the corresponding scaled boundary finite element (SBFE) equations in displacement and stiffness is presented in detail. The latter is a nonlinear differential equation with respect to the radial coordinate, which has to be solved numerically for each excitation frequency considered in the analysis. Various numerical examples demonstrate the accuracy of the new method and its correct implementation. These include rigid circular and square foundations embedded in or resting on the surface of layered homogeneous or inhomogeneous 3D soil deposits over rigid bedrock. Hysteretic damping is assumed in some cases. The dynamic stiffness coefficients calculated using the proposed method are compared with analytical solutions or existing highly accurate numerical results. Copyright © 2011 John Wiley & Sons, Ltd.     

Deep surface transformation and cladding of net shape commercial steel parts by simultaneous multiple pulsed laser radiation

 A key innovation in materials processing of pre-formed metal parts is reported herein. The ”QQC Process” involves the judicious selection of exposure parameters to three pulsed lasers (excimer, Nd-YAG and CO₂) simultaneously for treatment of the work piece. Pre-formed commercial steel parts are hardened and/or toughened, and/or clad with TiC improving performance by at least one order of magnitude. Two examples are detailed: a punch for aluminum can production and a fuel injector nozzle. In the latter case it has been shown that some tens of microns of the metal are transformed to a noncrystalline phase, in the middle of the workpiece. Received: 10 December 1998 / Reviewed and accepted: 18 December 1998     

Symmetric matrix-valued frequency to time transformation for unbounded domains applied to infinite beams

In structural dynamics coupled systems with unbounded deformable members are characterized by radiation damping. Typically, the unbounded subsystem is described in the frequency domain; either numerically or analytically by means of dynamical stiffness matrices. Recent papers describe a matrix-valued rational interpolation of the dynamical stiffness and straightforward transformation into the time-domain. In addition, the asymptotic behaviour has been considered, too, by adding fractional derivatives. However, the matrices involved in this process are unsymmetric even if the original dynamical stiffnesses are symmetric. The approach presented in this paper maintains the symmetry a priori without any numerical operations by simply using a rational approximation with a matrix-valued numerator but a scalar-valued denominator and contains some further numerical advantages. The method is demonstrated by treating an infinite beam on an elastic foundation.     

An empirical analysis of the IEEE-1394 serial bus protocol

The statistics collector and analyzer records, displays, and analyzes performance measurements from an active IEEE-1394 bus in real time. An empirical analysis using SCA exposes the unique, complex arbitration mechanisms used by IEEE-1394 nodes and their effect on the performance of higher level protocols