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排序方式: 共有311条查询结果,搜索用时 15 毫秒
81.
Ohheum Bak Theodor S. Holstad Yueze Tan Haidong Lu Donald M. Evans Kasper A. Hunnestad Bo Wang James P. V. McConville Petra Becker Ladislav Bohatý Igor Lukyanchuk Valerii M. Vinokur Antonius T. J. van Helvoort J. Marty Gregg Long‐Qing Chen Dennis Meier Alexei Gruverman 《Advanced functional materials》2020,30(21)
Application of scanning probe microscopy techniques such as piezoresponse force microscopy (PFM) opens the possibility to re‐visit the ferroelectrics previously studied by the macroscopic electrical testing methods and establish a link between their local nanoscale characteristics and integral response. The nanoscale PFM studies and phase field modeling of the static and dynamic behavior of the domain structure in the well‐known ferroelectric material lead germanate, Pb5Ge3O11, are reported. Several unusual phenomena are revealed: 1) domain formation during the paraelectric‐to‐ferroelectric phase transition, which exhibits an atypical cooling rate dependence; 2) unexpected electrically induced formation of the oblate domains due to the preferential domain walls motion in the directions perpendicular to the polar axis, contrary to the typical domain growth behavior observed so far; 3) absence of the bound charges at the 180° head‐to‐head (H–H) and tail‐totail (T–T) domain walls, which typically exhibit a significant charge density in other ferroelectrics due to the polarization discontinuity. This strikingly different behavior is rationalized by the phase field modeling of the dynamics of uncharged H–H and T–T domain walls. The results provide a new insight into the emergent physics of the ferroelectric domain boundaries, revealing unusual properties not exhibited by conventional Ising‐type walls. 相似文献
82.
Bak Jeong-Hyeon Hwang Sung Wook Yoon Jonghyun Park Jong Hyeon Park Jong-Oh 《Intelligent Service Robotics》2019,12(3):243-253
Intelligent Service Robotics - Path planning of cable-driven parallel robots (CDPRs) is a challenging task due to cables which may cause various collisions. In this paper, three steps are suggested... 相似文献
83.
G. W. Bak 《Journal of Materials Science》1986,21(12):4327-4330
Dielectric properties ofp-terphenyl crystals (large- and small-grained polycrystalline layers and compressed pellets) have been measured. An anisotropy of the dielectric properties of the crystals has been found. The dielectric losses in disorderedp-terphenyl structures proved to be of injected carrier origin: a discontinuous change of dielectric losses in the disordered structures being found near 285 K. 相似文献
84.
Hee-Chang Youn Seong-Min Bak Sang-Hoon Park Seung-Beom Yoon Kwang Chul Roh Kwang-Bum Kim 《Metals and Materials International》2014,20(5):975-981
In this paper, we describe a binder-free reduced graphene oxide/carbon nanotube hybrid thin film electrode prepared using a one-step electrostatic spray deposition method. Though we introduce a novel method, we suspect that the greater potential impact is more related to the fact that this technique is able to accomplish producing an electrode with a single process and allows a degree of control over the film properties not yet found in other fabrication methods that require multiple steps (that include post processing). In order to investigate the effect of carbon nanotube as a nano-spacer on the electrochemical properties of the reduced graphene oxide/carbon nanotube hybrid thin film electrodes, the various content of carbon nanotube was incorporated between the 2 dimensional layered reduced graphene oxide sheets to prevent restacking among reduced graphene oxide sheets and their electrochemical properties were systemically investigated using cyclic voltammetry, galvanostatic charge/discharge test and electrochemical impedance spectroscopy. The hybrid thin film electrode delivered a higher reversible specific capacitance of 187 F·g?1 at 0.5 A·g?1 and showed a better rate capability by maintaining 73% of the specific capacitance at 16 A·g?1 (vs. 0.5 A·g?1), which exhibit remarkable electrochemical performances than a RGO thin film electrodes for supercapacitor applications. 相似文献
85.
Tadeusz Bak Janusz Nowotny Kathryn Prince Mieczyslaw Rekas Charles C. Sorrell 《Journal of the American Ceramic Society》2002,85(9):2244-2250
This paper reports the transport kinetics of Mg in cubic yttria-stabilized zirconia (containing 10% mol of Y2 O3 (10YSZ)) involving the bulk and the grain boundary diffusion coefficients. The diffusion-controlled concentration profiles of Mg were determined using secondary ion mass spectrometry (SIMS) in the range 1073–1273 K. The determined bulk diffusion coefficient and the grain boundary diffusion product may be expressed as the following functions of temperature, respectively: D = 5.7 exp[(−390 kJ/mol)/ RT ] cm2 ·s−1 and D 'αδ= 3.2 × 10−15 exp[(−121 kJ/mol)/ RT ] cm3 ·s−1 , where α is the segregation enrichment factor and δ is the boundary layer thickness. The grain boundary enhancement factor decreases with temperature from 105 at 1073 K to 103 at 1273 K. 相似文献
86.
Armand J. Atanacio Mohammad A. Alim Tadeusz Bak Mihail Ionescu Janusz Nowotny 《Journal of the American Ceramic Society》2017,100(1):419-428
This work reports the effect of oxygen activity on surface segregation for TiO2 co‐doped with two cations, indium and niobium (0.076 at.% In + 0.103 at.% Nb). In this work, we studied the effect of annealing at 1273 K in the gas phase of controlled oxygen activity on surface segregation of both ions. The applied oxygen activity included pure oxygen, p(O2) = 100 kPa, and argon, p(O2) = 10 Pa. The segregation‐induced concentration gradients were determined using both secondary ion mass spectrometry and X‐ray photoelectron spectroscopy. The obtained results indicate that annealing of the studied TiO2 specimens in argon results in cooperative segregation of both ions leading to the formation of a surface structure involving comparative concentrations of both cations. However, annealing in oxygen results in preferential segregation of indium leading to the formation of a In2TiO5‐type surface structure. The obtained results are considered in terms of the effect of multicomponent segregation on processing of the surface layer with controlled properties that are desired for specific applications. The present work indicates that oxygen activity may be used as the parameter in surface engineering of the solid solution. 相似文献
87.
Mohammad A. Alim Tadeusz Bak Armand Atanacio Johan Du Plessis Meifang Zhou Joel Davis Janusz Nowotny 《Journal of the American Ceramic Society》2017,100(9):4088-4100
The present work reports the electrical properties of polycrystalline Ta‐doped TiO2 (0.39 at.% Ta) determined in situ at elevated temperatures (1173‐1323 K) in the gas phase of controlled oxygen activity (10?12 Pa to 105 Pa). The effect of oxygen activity on the electrical conductivity and thermoelectric power of TiO2 is discussed in terms of defect disorder, including (1) the intrinsic electronic disorder that is governed by electronic compensation in the strongly reducing regime, (2) the extrinsic electronic disorder that is governed by electronic charge compensation in the reducing regime, and (3) the extrinsic ionic disorder that is governed by ionic compensation in the oxidizing regime. It is shown that tantalum ions are incorporated into the titanium sublattice of TiO2 leading to the formation of donor‐type energy levels. The Arrhenius‐type plot of the electrical conductivity data leads to the determination of the formation enthalpy terms. The obtained results are considered in terms of the effect of tantalum and oxygen activity on the defect disorder and the associated key performance‐related properties in the light‐induced partial water oxidation. 相似文献
88.
P92 alloy with a composition of Fe-9.1Cr-0.5Mo-1.7W (wt.%) was welded, and its oxidation behavior was studied at 600, 700
and 800 °C for up to 6 months in air. The oxidation resistance decreased in the order of the base metal, weld metal, and the
heat affected zone. The morphology and the composition of the scales formed on these samples were similar. The scales were
either uniform in thickness or nodular. The scales consisted mainly of Fe2O3. As oxidation progressed, thick, nodular oxide scales formed. The alloying elements such as Cr, W, and Mn tended to incorporate
in the lower part of the oxide scale. 相似文献
89.
Reliability-Based Analysis and Design of Strip Footings against Bearing Capacity Failure 总被引:2,自引:0,他引:2
Dalia S. Youssef Abdel Massih Abdul-Hamid Soubra Bak Kong Low 《Canadian Metallurgical Quarterly》2008,134(7):917-928
This paper presents a reliability-based approach for the analysis and design of a shallow strip footing subjected to a vertical load with or without pseudostatic seismic loading. Only the punching failure mode of the ultimate limit state is studied. The deterministic models are based on the upper-bound method of the limit analysis theory. The random variables used are the soil shear strength parameters and the horizontal seismic coefficient. The Hasofer-Lind reliability index and the failure probability are determined. A sensitivity analysis is also performed. The influence of the applied footing load on the reliability index and the corresponding design point is presented and discussed. It was shown that the negative correlation between the soil shear strength parameters highly increases the reliability of the foundation and that the failure probability is highly influenced by the coefficient of variation of the angle of internal friction of the soil and the horizontal seismic coefficient. For design, an iterative procedure is performed to determine the breadth of the footing for a target failure probability. 相似文献
90.
The liver is vulnerable to oxidative attacks from heavy metals, such as iron, as well as some drugs, including acetaminophen. It has been shown that enhanced oxidative stress in the liver leads to excessive ROS production and mitochondrial dysfunction, resulting in organ injury. The beneficial effects of Spatholobi Caulis (SC), a natural herbal medicine, include treating ischemic stroke, inhibiting tumor cell invasion, pro-angiogenic activities, and anti-inflammatory properties. Scientific studies on its effects against hepatotoxic reagents (e.g., iron and acetaminophen), as well as their underlying mechanisms, are insufficient. This study examined the antioxidant effects and mechanisms of SC in vitro and in vivo. In cells, the proinflammatory mediator, arachidonic acid (AA), plus iron, significantly induced an increase in ROS generation, the damage in mitochondrial membrane potential, and the resulting apoptosis, which were markedly blocked by SC. More importantly, SC affected the activation of AMP-activated protein kinase (AMPK)-related proteins, which were vital to regulating oxidative stress in cells. In addition, SC mediated the expression of Yes-associated protein (YAP)-related proteins. Among the active compounds in SC, the procyanidin B2, but not liquiritigenin, daidzein, and genistein, significantly inhibited the cytotoxicity induced by AA + iron, and activated the LKB1-AMPK pathway. In mice, the oral administration of SC alleviated the elevations of ALT and histological changes by the acetaminophen-induced liver injury. These results reveal the potential of SC and a key bioactive component, procyanidin B2, as antioxidant candidates for hepatoprotection. 相似文献