Determining the stress required for deformation twinning in nanocrystalline and ultrafine-grained copper

Deformation twinning in nanocrystalline and ultrafine-grained materials has attracted much attention in recent years due to the ability of a high density of twin boundaries to dramatically improve mechanical properties such as yield strength and ductility. Various processing conditions such as ball milling, cryomilling, electrodeposition, and equi-channel angular extrusion have been used to form deformation twins in metals. Most techniques for estimating the shear stress needed to form deformation twins are based indirectly on the processing conditions. Here, a new method to directly measure the shear stress needed to form twin boundaries through in-situ transmission electron microscopy nanocompression testing will be described.     

Influence of Zn2+ Doping on CaFe2O4 Spinel Ferrites: An Analysis of Experimental Charge Density and Magnetism

Journal of Superconductivity and Novel Magnetism - Single-phase, nanocrystalline Zn2+ substituted cubic spinel CaFe2O4 with the composition ZnxCa1-x Fe2O4 (x?=?0.0, 0.05, 0.1, 0.15) was...     

Mechanical and Thermal Properties Modeling,Sorption Characteristics of Multiscale (Multiwalled Carbon Nanotubes/Glass Fiber) Filler Reinforced Polypropylene Composites

The present work was aimed to investigate the individual and hybrid reinforcement effect of multiscale fillers [glass fibers (GF)/multiwalled carbon nanotubes (MWCNTs)] in polypropylene (PP) matrix. The MWCNT content in the hybrid composites was varied from 0.5 to 5 wt%, and glass fiber fraction was fixed as 20 wt%. The morphology of nano and hybrid composite revealed reasonable dispersion of MWCNTs and glass fibers in the matrix. At a MWCNT content of 3 wt%, the optimum tensile properties for the hybrid composites were achieved and beyond which it declined due to agglomeration effects as revealed by transmission electron microscopy. A comparative study of the experimental and predicted values of moduli of nano, micro, and hybrid composites using various micromechanical models was conducted. The simultaneous incorporation of MWCNTs and glass fibers in PP restricted the mobility of polymer chains as indicated by the increase in storage modulus and rise in glass transition temperature obtained by dynamic mechanical analysis. The differential scanning calorimetry studies indicated that the inclusion of 2 wt% of MWCNTs increased the crystallinity of PP from 58.2 to 69.1% in hybrid composites. The Avrami and Mo models were used to explore nonisothermal crystallization kinetics, and Mo model was in close agreement with the experimental results. The sorption behavior of the composites revealed that the formation of immobilized regions developed by the simultaneous inclusion of micro and nano fillers delayed the transport of the solvent. J. VINYL ADDIT. TECHNOL., 25:E94–E107, 2019. © 2019 Society of Plastics Engineers     

Anomalies due to delay and loss in AAL2 packet voice systems:performance models and methods of mitigation

This paper investigates the packet delay variation and packet loss probabilities to be expected in typical applications of voice trunking using ATM adaptation layer type 2 (AAL2) and the consequences these may have, such as the need for sequence numbers in voice packet headers. Simulations have been run for the case of 32-kb/s ADPCM encoded voice across a physical link whose bandwidth is 1/4, 1/2, or 1 times DS1 (1.536 Mb/s). The results show the number of calls that can be admitted while meeting the ninety-ninth percentile queuing delay objective of 20 ms or less. The delay budget that can be allocated to packet queuing delay at access is about 20 ms, given a one-way end-to-end delay budget of 100 to 150 ms for conversational voice. The number of calls is also limited so that the ratio of late or lost packets does not exceed 10^-3. Voice quality is known to be tolerant to packet losses of up to one in 100. When the packet delay variation is significant, as it threatens to be in this situation, sequence numbers can help a receiver to detect and to recover from anomalies-lost, early, or late packets-and make fewer reconstruction errors than if sequence numbers were absent or ignored. Three circumstances are identified where packet slips can occur with ripple effects. An analysis of these cases leads to lower bounds on the sequence number modulus. The appropriate value of the sequence number modulus depends on the desired call load and performance objectives, and can be deduced from the results presented     

Voice over ATM using AAL2 and bit dropping: performance and calladmission control

Asynchronous transfer mode (ATM) adaptation layer 2 (AAL2) has been designed for efficient transport of voice, fax, and voiceband data (VBD) traffic over an ATM virtual circuit. The protocol helps achieve low latency and high bandwidth efficiency while applying suitable compression methods on voice/VBD/fax calls and silence elimination on voice calls. We analyze the performance and capacity of an ATM multiplexer based on AAL2 adaptation. We assume that embedded adaptive differential pulse code modulation (ADPCM) is used to compress voice, and silence elimination is used to achieve statistical multiplexing gain. The embedded ADPCM coding scheme allows selective dropping of less significant bits of voice during congestion in the ATM/AAL2 multiplexer. We compare the call capacities of voice multiplexers with and without bit dropping (BD). The performance models and results presented are based on fairly general assumptions and can be used for traffic engineering and call admission control in land-line or wireless ATM systems for a variety of voice/voiceband compression algorithms. A generalized algorithm for call admission control is also described     

Effect of polymer properties on bubble growth in polymer–paperboard composites

Foamed paperboard is a composite material used in thermally insulated food packaging and beverage containers. The paperboard is sandwiched between a layer of low‐density polyethylene and a barrier layer, and the low‐density film is foamed through heating. The moisture inside the paperboard vaporizes and serves as the driving force for creating the foam. The bubble growth on the paper surface has been tracked with high‐speed photography. The number of generated bubbles has been found to depend on the number of pores on the surface of the paperboard; there is little or no dependence on the properties of the polymer, at least across the range of properties studied. In contrast, the thickness of the foam is relatively insensitive to the paperboard properties but has a strong dependence on the thickness of the initial polymer film, the nature of the polymer, and the speed at which it is extruded onto the paperboard. It is believed that some of these variations arise from differences in the degree of adhesion between the polymer and the paperboard. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Editor's Special Invited Paper: Sequential Estimation for Time Series Models

Abstract

This article revisits sequential estimation of the autoregressive parameter β in a first-order autoregressive (AR(1)) model and construction of a sequential confidence region for a parameter vector θ in a first-order threshold autoregressive (TAR(1)) model. To resolve a theoretical conjecture raised in Sriram (1986 Sriram , T. N. ( 1986 ). Sequential Estimation of Parameters in a First Order Autoregressive Model, Ph.D. diss., Michigan State University, East Lansing.  [Google Scholar]), we provide a comprehensive numerical study that strongly suggests that the regret in using a sequential estimator of β can be significantly negative for many heavy-tailed error distributions and even for normal errors. Secondly, to investigate yet another conjecture about the limiting distribution of a sequential pivotal quantity for θ in a TAR(1) model, we conduct an extensive numerical study that strongly suggests that the sequential confidence region has much better coverage probability than that of a fixed sample counterpart, regardless of whether the θ values are inside or on or near the boundary of the ergodic region of the series. These highlight the usefulness of sequential sampling methods in fitting linear and nonlinear time series models.     

Comparative Physico-chemical and Functional Properties of Cassava Starches Obtained by Conventional and Enzyme-Integrated Conventional Techniques

Comparative studies on the physico-chemical and functional properties of the cassava starches, obtained by conventional and enzyme-integrated conventional techniques, indicated no adverse chemical modifications and nearly equal X-ray diffraction patterns as well as granular structure. The starch obtained by enzyme-integrated technique has 50% lower ash content and nearly double water solubility at room temperature. The swelling power, the swelling volume and the viscosity indices were slightly lower. Better cooking properties of the starch isolated by enzyme-integrated technique is indicated by its lower set-back viscosity. The data thus indicate a number of improved properties of cassava starch manufactured by enzyme-integrated conventional technique.     

Tracing specular light paths in point-based scenes

Massive point data sets representing meticulous details of various heritage sites and statues are now becoming available due to recent advances in multi-view stereo techniques. Photorealistic rendering of such point sets has not yet, however, matched their polygonal counterparts with respect to the interactivity of applications as well as the quality of light simulations.