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31.
Uniaxial time-dependent creep and cycled stress behavior of a standard and toughened film adhesive were studied experimentally. Both adhesives exhibited progressive accumulation of strain from an applied cycled stress. Creep tests were fit to a viscoelastic power law model at three different applied stresses which showed nonlinear response in both adhesives. A third order nonlinear power law model with a permanent strain component was used to describe the creep behavior of both adhesives and to predict creep recovery and the accumulation of strain due to cycled stress. Permanent strain was observed at high stress but only up to 3% of the maximum strain. Creep recovery was under predicted by the nonlinear model, while cycled stress showed less than 3% difference for the first cycle but then over predicted the response above 1000 cycles by 4–14% at high stress. The results demonstrate the complex response observed with structural adhesives, and the need for further analytical advancements to describe their behavior. 相似文献
32.
Sub‐Micron Anisotropic InP‐based III–V Semiconductor Material Deep Etching for On‐Chip Laser Photonics Devices
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Doris Keh‐Ting Ng Chee Wei Lee Vivek Krishnamurthy Qian Wang 《Advanced Engineering Materials》2018,20(2)
33.
M. A. Wells I. V. Samarasekera J. K. Brimacombe E. B. Hawbolt D. J. Lloyd 《Metallurgical and Materials Transactions B》1998,29(3):611-620
A comprehensive mathematical model of the hot tandem rolling process for aluminum alloys has been developed. Reflecting the
complex thermomechanical and microstructural changes effected in the alloys during rolling, the model incorporated heat flow,
plastic deformation, kinetics of static recrystallization, final recrystallized grain size, and texture evolution. The results
of this microstructural engineering study, combining computer modeling, laboratory tests, and industrial measurements, are
presented in three parts. In this Part I, laboratory measurements of static recrystallization kinetics and final recrystallized
grain size are described for AA5182 and AA5052 aluminum alloys and expressed quantitatively by semiempirical equations. In
Part II, laboratory measurements of the texture evolution during static recrystallization are described for each of the alloys
and expressed mathematically using a modified form of the Avrami equation. Finally, Part III of this article describes the
development of an overall mathematical model for an industrial aluminum hot tandem rolling process which incorporates the
microstructure and texture equations developed and the model validation using industrial data. The laboratory measurements
for the microstructural evolution were carried out using industrially rolled material and a state-of-the-art plane strain
compression tester at Alcan International. Each sample was given a single deformation and heat treated in a salt bath at 400
°C for various lengths of time to effect different levels of recrystallization in the samples. The range of hot-working conditions
used for the laboratory study was chosen to represent conditions typically seen in industrial aluminum hot tandem rolling
processes, i.e., deformation temperatures of 350 °C to 500 °C, strain rates of 0.5 to 100 seconds and total strains of 0.5 to 2.0. The semiempirical
equations developed indicated that both the recrystallization kinetics and the final recrystallized grain size were dependent
on the deformation history of the material i.e., total strain and Zener-Hollomon parameter (Z), where
and time at the recrystallization temperature. 相似文献
34.
R. PearceAuthor Vitae T. IakimovM. AnderssonAuthor Vitae L. HultmanAuthor VitaeA. Lloyd SpetzAuthor Vitae R. YakimovaAuthor Vitae 《Sensors and actuators. B, Chemical》2011,155(2):451-455
Epitaxially grown single layer and multi layer graphene on SiC devices were fabricated and compared for response towards NO2. Due to electron donation from SiC, single layer graphene is n-type with a very low carrier concentration. The choice of substrate is demonstrated to enable tailoring of the electronic properties of graphene, with a SiC substrate realising simple resistive devices tuned for extremely sensitive NO2 detection. The gas exposed uppermost layer of the multi layer device is screened from the SiC by the intermediate layers leading to a p-type nature with a higher concentration of charge carriers and therefore, a lower gas response. The single layer graphene device is thought to undergo an n-p transition upon exposure to increasing concentrations of NO2 indicated by a change in response direction. This transition is likely to be due to the transfer of electrons to NO2 making holes the majority carriers. 相似文献
35.
Tim Van Gestel Feng Han Doris Sebold Hans Peter Buchkremer Detlev St?ver 《Microsystem Technologies》2011,17(2):233-242
A solid oxide fuel cell (SOFC) with a thin-film yttria-stabilized zirconia (YSZ) electrolyte was developed and tested. This
novel SOFC shows a similar multilayer set-up as other current anode-supported SOFCs and is composed of a Ni/8YSZ anode, a
gas-tight 8YSZ electrolyte layer, a dense Sr-diffusion barrier layer and a LSCF cathode. To increase the power density and
lower the SOFC operating temperature, the thickness of the electrolyte layer was reduced from around 10 μm in current cells
to 1 μm, using a nanoparticle deposition method. By using the novel 1 μm electrolyte layer, the current density of our SOFC
progressed to 2.7, 2.1 and 1.6 A/cm2 at operation temperatures of 800, 700 and 650°C, respectively, and out-performs all similar cells reported to date in the
literature. An important consideration is also that cost-effective dip-coating and spin-coating methods are applied for the
fabrication of the thin-film electrolyte. Processing of 1 μm layers on the very porous anode substrate material was initially
experienced as very difficult and therefore 8YSZ nanoparticle coatings were developed and optimized on porous 8YSZ model substrates
and transferred afterwards to regular anode substrates. In this paper, the preparation of the novel SOFC is shown and its
morphology is illustrated with high resolution SEM pictures. Further, the performance in a standard SOFC test is demonstrated. 相似文献
36.
In the present paper, we report results of surveys in 2003 in Japan and Denmark about patients' views about adverse events, focusing on the actions of healthcare staff involved in a medical accident. Results show that patients were more likely to indicate negative expectations to a doctor's reactions after a medical accident when asked in general terms than when asked in relation to concrete case stories. When asked in general terms, 66% (47%) of Japanese (Danish) respondents expected that doctors sometimes hold back on providing information to patients about a medical accident, while 37% (7%) did so when asked about a concrete, mild-outcome case. We examine some possible reasons for the relatively high level of distrust of Japanese patients, and we discuss whether the seemingly lower level of disclosure in Japan than in Denmark and the negative stories in the Japanese press may have an impact. We also suggest some implications for introducing a patient-centred or customer-centred approach to risk management in healthcare and other domains. 相似文献
37.
Christian Bur Peter Reimann Mike Andersson Anita Lloyd Spetz Andreas Schütze 《Microsystem Technologies》2012,18(7-8):1015-1025
A silicon carbide based enhancement type metal insulator field effect transistor with porous gate metallization has been investigated as a total NO x sensor operated in a temperature cycling mode. This operating mode is quite new for gas sensors based on the field effect but promising results have been reported earlier. Based on static investigations we have developed a suitable T-cycle optimized for NO x detection and quantification in a mixture of typical exhaust gases (CO, C2H4, and NH3). Significant features describing the shape of the sensor response have been extracted and evaluated with multivariate statistics (e.g. linear discriminant analysis) allowing quantification of NO x . Additional cleaning-cycles every 30?min improve the stability of the sensor further. With this kind of advanced signal processing the influence of sensor drift and cross sensitivity to ambient gases can be reduced effectively. Measurements have proven that different concentrations of NO x can be detected even in a changing mixture of other typical exhaust gases under dry and humid conditions. In addition to that, unknown concentrations of NO x can be detected based on a small set of training data. It can be concluded that the performance of GasFETs for NO x determination can be enhanced considerably with temperature cycling and appropriate signal processing. 相似文献
38.
Bubble formation and stability in the film blowing processing of in situ polymerized and melt-compounded polyamide 6-based layered silicate nanocomposites (LSNs) are correlated to their underlying rheology, structure, and crystallization behavior. The layered silicates enhance melt elasticity, induce γ -form crystallinity, and increase crystallization rates without having any significant effect on the extent of crystallinity. A bubble stability quantification method employed to assess the level of instability during the film blowing process finds the in situ polymerized LSNs to be more stable than PA6, while melt-compounded LSNs do not display such an improved processability. All of the LSN films produced by film blowing possess superior mechanical properties compared to neat nylon 6, despite their relatively rougher film surfaces. 相似文献
39.
Thomas Manke Lloyd Demetrius Martin Vingron 《Journal of the Royal Society Interface》2006,3(11):843-850
The structure of molecular networks is believed to determine important aspects of their cellular function, such as the organismal resilience against random perturbations. Ultimately, however, cellular behaviour is determined by the dynamical processes, which are constrained by network topology. The present work is based on a fundamental relation from dynamical systems theory, which states that the macroscopic resilience of a steady state is correlated with the uncertainty in the underlying microscopic processes, a property that can be measured by entropy. Here, we use recent network data from large-scale protein interaction screens to characterize the diversity of possible pathways in terms of network entropy. This measure has its origin in statistical mechanics and amounts to a global characterization of both structural and dynamical resilience in terms of microscopic elements. We demonstrate how this approach can be used to rank network elements according to their contribution to network entropy and also investigate how this suggested ranking reflects on the functional data provided by gene knockouts and RNAi experiments in yeast and Caenorhabditis elegans. Our analysis shows that knockouts of proteins with large contribution to network entropy are preferentially lethal. This observation is robust with respect to several possible errors and biases in the experimental data. It underscores the significance of entropy as a fundamental invariant of the dynamical system, and as a measure of structural and dynamical properties of networks. Our analytical approach goes beyond the phenomenological studies of cellular robustness based on local network observables, such as connectivity. One of its principal achievements is to provide a rationale to study proxies of cellular resilience and rank proteins according to their importance within the global network context. 相似文献
40.
This two-part paper presents modelling and scheduling approaches of flexible manufacturing systems using Petri nets (PNs) and artificial intelligence (AI)-based heuristic search methods. In Part I, PN-based modelling approaches and basic AI-based heuristic search algorithms were presented. In Part II, a new heuristic function that exploits PN information is proposed. Heuristic information obtained from the PN model is used to dramatically reduce the search space. This heuristic is derived from a new concept, the resource cost reachability matrix, which builds on the properties of B-nets proposed in Part I. Two hybrid search algorithms, (1) an approach to model dispatching rules using analysis information provided by the PN simulation and (2) an approach of the modified stage-search algorithm, are proposed to reduce the complexity of large systems. A random problem generator is developed to test the proposed methods. The experimental results show promising results. 相似文献