Adiabatic shear localization of viscoplastic materials has been an area of great interest in the past few decades. Many numerical and theoretical investigations have been performed, yet few have ...taken into account the influence of microstructure (e.g., texture, grain size) of the material. For instance, experimental evidence has suggested enhanced shear instability for some nanostructured metals compared to their coarse-grained counterparts. Recently, Joshi and Ramesh proposed a rotational diffusion mechanism for the quasi-static shear localization behavior of nanostructured materials. Since shear band formation is generally enhanced under dynamic loading where diffusive processes are no longer essential, the adiabatic shear localization behavior at high strain rates can be different. In this work, a geometry softening mechanism is presented to study the adiabatic shear instability of viscoplastic materials. We further use the analysis to study the adiabatic shear instability in nanostructured metals under dynamic loading. This mechanism is based on grain rotation and is directly related to the grain size of the material. The mechanism was implemented into the governing equations of adiabatic shear localization and a one-dimensional numerical model was employed by using the characteristic line method. The effects of strain rate hardening, strain hardening and initial microstructure condition have been studied numerically. Examples are given for some specific metals and the results are compared with those of experiments.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Noradrenaline and α-adrenoceptors have been implicated in the modulation of pain in various behavioral conditions. Noradrenergic neurons and synaptic inputs are present in neuronal circuits critical ...for pain modulation, but their actions on neurons in those circuits and consequently the mechanisms underlying noradrenergic modulation of pain remain unclear. In this study, both recordings
in vitro
and behavioral analyses
in vivo
were used to examine cellular and behavioral actions mediated by α
1
- and α
2
-adrenoceptors on neurons in the nucleus raphe magnus. We found that α
1
- and α
2
-receptors were colocalized in the majority of a class of neurons (primary cells) that inhibit spinal pain transmission and are excited during opioid analgesia. Activation of the α
1
-receptor depolarized whereas α
2
-receptor activation hyperpolarized these neurons through a decrease and an increase, respectively, in potassium conductance. Blockade of the excitatory α
1
-receptor or activation of the inhibitory α
2
-receptor significantly attenuated the analgesia induced by local opioid application, suggesting that α
1
-receptor-mediated synaptic inputs in these primary cells contribute to their excitation during opioid analgesia. In the other cell class (secondary cells) that is thought to facilitate spinal nociception and is inhibited by analgesic opioids, only α
1
-receptors were present. Blocking the α
1
-receptor in these cells significantly reduced the hyperalgesia (increased pain) induced by opioid abstinence. Thus, state-dependent activation of α
1
-mediated synaptic inputs onto functionally distinct populations of medullary pain-modulating neurons contributes to opioid-induced analgesia and opioid withdrawal-induced hyperalgesia.
The rewarding effect of opioids, the driving force for compulsive behaviors of opioid abuse and addiction, is primarily mediated by the mu-opioid receptor. However, the role of the delta-opioid ...receptor (DOR) in opioid reward and addiction is still poorly understood. The recently discovered adaptive DOR property of exocytotic translocation in sensory neurons after chronic opioid exposure provides a new avenue of conceptual thoughts to exploring the DOR function in this psychoneurological disease. In this study, we investigated potential adaptive function of DOR in neurons of the central nucleus of the amygdala (CeA), a forebrain structure increasingly recognized for mediating stimulus reward learning in drug addiction. Using whole-cell recordings in CeA slices, we found that in rats displaying morphine-induced behavior of conditioned place preference, a behavioral measure of drug reward, the overall synaptic strength of glutamate synapses in CeA neurons was significantly enhanced. The selective DOR agonist D-Pen(2),D-Pen(5)-enkephalin, having no apparent effect on glutamatergic excitatory postsynaptic current (EPSC) in neurons from control rats, produced a significant, dose-dependent inhibition of the synaptic current in neurons from those morphine-treated rats. Detailed analyses of EPSC properties revealed that DOR activation inhibited the EPSC by reducing presynaptic release of glutamate, indicating functional DOR emerging on presynaptic glutamate terminals. The morphine treatment also significantly increased DOR proteins in CeA preparations of synaptosomes. These findings provide functional evidence for an adaptive modulation by presynaptic DOR of a key synaptic activity altered by morphine, thus implying likely important involvement of DOR in opioid reward and addiction.
Uniform FePt nanoparticles were synthesized through nanostructuring of pulsed laser deposited FePt thin films by single shot H+ ion irradiation using a plasma focus device. The annealing temperature ...required for phase transition from low Ku face-centred cubic to high Ku face-centred tetragonal, for ion irradiated samples, is simultaneously lowered down to 400 deg C. The energetic H+ ion irradiation significantly reduces the activation energy for atomic ordering by increasing the number of vacancies. The advantage of using a plasma focus device is that it can achieve nanostructuring in much shorter time, in single shot ion exposure with pulse duration of typically about a few hundreds of nanoseconds, as compared with much longer duration required by continuous ion sources.
With recent advances in reverse engineering, attackers can reconstruct a netlist to counterfeit chips by opening the die and scanning all layers of authentic chips. This relatively easy ...counterfeiting is made possible by the use of the standard simple clocking scheme, where all combinational blocks function within one clock period, so that a netlist of combinational logic gates and flip-flops is sufficient to duplicate a design. In this article, we propose to invalidate the assumption that a netlist completely represents the function of a circuit with unconventional timing. With the introduced wave-pipelining (WP) paths, attackers have to capture gate and interconnect delays during reverse engineering, or to test a huge number of combinational paths to identify the WP paths. To hinder the test-based attack, we construct false paths with WP to increase the counterfeiting challenge. The experimental results confirm that WP true paths and false paths can be constructed in benchmark circuits successfully with only a negligible cost, thus thwarting the potential attack techniques.
The advancing of reverse engineering techniques has complicated the efforts in intellectual property protection. Proactive methods have been developed recently, among which layout-level IC ...camouflaging is the leading example. However, existing camouflaging methods are rarely supported by provably secure criteria, which further leads to over-estimation of the security level when countering the latest de-camouflaging attacks, e.g., the SAT-based attack. In this paper, a quantitative security criterion is proposed for de-camouflaging complexity measurements and formally analyzed through the demonstration of the equivalence between the existing de-camouflaging strategy and the active learning scheme. Supported by the new security criterion, two novel camouflaging techniques are proposed, the low-overhead camouflaging cell library and the AND-tree structure, to help achieve exponentially increasing security levels at the cost of linearly increasing performance overhead on the circuit under protection. A provably secure camouflaging framework is then developed by combining these two techniques. Experimental results using the security criterion show that the camouflaged circuits with the proposed framework are of high resilience against the SAT-based attack with negligible performance overhead.
The non-polarity and poor hygroscopicity of polypropylene (PP) impede its wide application. The polar monomers, glycidyl methacrylate (GMA), hydroxyethyl methacrylate (HEMA) and methacrylamido propyl ...trimethyl ammonium chloride (MAPTAC) were grafted onto the spun-blown polypropylene nonwoven fabric (SMS) under ultraviolet irradiation, and the subsequent functionalization of the grafted fabrics was implemented as well. The results show that both the monomer and the polymer of HEMA are hydrophilic and are grafted uniformly onto the fabric surface as well as into the melt-blown layer with the hydrophilicity being enhanced slightly, whereas the hydrophilic monomer yet the hydrophobic polymer of MAPTAC prefer to be grafted onto the melt-blown fibre with the wicking effect. Both the monomer and the polymer of GMA are hydrophobic and are favourably grafted into the meltblown layer with no hydrophilicity being improved. The grafting diminishes the fibre crystallinity and melting temperature, especially significant for the graftings of hydrophobic polymers, PGMA and PMAPTAC. All the grafting reduces the water flux of the grafted fabrics no matter what the grafting polymers are hydrophilicity or hydrophobicity not.
Thermomechanical stress is one of the most important issues in performance and reliability analysis of through silicon via-based 3-D integrated circuits (3-D ICs), where an accurate numerical ...approach is generally needed to produce stress models and identify weak points in the structure. In this paper, we propose a knowledge-oriented nonuniform (KONU) refinement strategy for 3-D IC stress simulation under the framework of a parallel adaptive finite element method (FEM), and apply it in 3-D IC stress and reliability analysis. Parallel adaptive FEM is promising for solving large-scale problems due to its high accuracy and parallel efficiency. It produces refined meshes based on the a posteriori error analysis, which has the quasi-optimal convergence rate for solving the problem. It has high parallel efficiency, which makes it suitable for handling large and complex structures in 3-D ICs. The KONU refinement strategy developed in this paper can efficiently reduce the number of refinement iterations in parallel adaptive FEM for 3-D IC thermomechanical stress simulation and improves the computational efficiency. It is demonstrated in this paper through several examples that parallel adaptive FEM for thermomechanical stress evaluation can be widely applied in 3-D IC reliability analysis, where accurate stress simulation and modeling is exceptionally important to produce accurate results.
An electron beam’s quality is fundamentally limited by its attributes at the cathode. The emission from photocathodes can be bright, but not necessarily uniform. Quantum efficiency (QE) maps ...generated by selectively illuminating the cathode surface reveal this nonuniformity. In this paper a proof-of-principle experiment is described in which a high resolution map of the QE is generated using a digital micromirror device. We show a substantial improvement over the best results reported for laser raster scanning.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM, UPUK
This paper reports studies into the effect of submicron and nano SiC particles on microstructure, phase composition, hardness, erosion wear, and scratch behavior of Al
2
O
3
-20wt.%8YSZ (ZrO
2
... + 8 wt.% Y
2
O
3
) coatings fabricated by atmospheric plasma spraying. The failure mode of erosion wear and scratch for coatings was established and analyzed. The hardness, density, erosion wear, and anti-scratch resistance of coatings fabricated from plasma treating feedstocks were higher than that of coatings made from sintering feedstocks. The erosion wear rate of coatings with SiC was evidently decreased, and there was some small debris on worn surface with characteristic of translamellar fracture. The spallation, fracture, plough, and cracking were main failure mechanism for coatings. In the scratch process, the critical load of coating with SiC was increased. The crack growth resistance of coatings was analyzed from crack length at end of scratch test.
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