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排序方式: 共有264条查询结果,搜索用时 12 毫秒
1.
A Synthetic Transcriptional Activator of Genes Associated with the Retina in Human Dermal Fibroblasts
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2.
The study focused on the in-situ synthesis of titanium (Ti)-titanium boride (TiB) composites with β phase in the matrix by reaction sintering of TiB2 with Ti and alloying element powders. The goal was to examine the nature of TiB whisker formation in three different kinds
of powder mixtures: (1) β-Ti alloy powders and TiB2; (2) α-Ti powder, a master alloy (Fe-Mo) powder containing the β-stabilizing elements, and TiB2; and (3) α-Ti powder, a β-stabilizing elemental powder (Mo or Nb), and TiB2. The effects of powder packing and the relative locations of powder particles on the morphological changes in TiB whisker
formation and their growth were studied at processing temperatures ranging from 1100°C to 1300°C. The morphology, size, and
distribution of whiskers were found to be influenced by the powder-packing conditions. A large particle-size ratio in bimodally
packed mixtures led to the formation of a TiB monolithic layer around β grains. With a relatively finer starting powder, smaller size ratio, and trimodal packing arrangement, the TiB whiskers were
found to be distributed more homogeneously in the matrix. The study also used the X-ray direct comparison method and the structure
factor for the β phase to determine the volume fraction of TiB phase from X-ray data. Tensile tests and fractographic investigations were
carried out on selected composites. The evolution of the composite microstructure, the influence of powder-packing variables,
and the morphology and growth of TiB whiskers and their effect on mechanical properties are discussed. 相似文献
3.
M. Sharan Chandran K. Padmanabhan D. K. Dipin Raj Yashasvi Chebiyyam 《Journal of Adhesion Science and Technology》2020,34(5):511-530
AbstractInterfacial adhesion of composite materials plays an important role in their mechanical properties and performance. In the present investigation, analysis of the interfacial properties of self-reinforced polyamide composites by using microbond multiple fibre pull-out test is emphasised. Microbond specimens prepared through thermal processing are tested for their interfacial properties by multiple fibre bundle pull-out tests and compared with that of traditional single fibre pull-out test specimens. Multiple fibre pull-out addresses the volume fraction as well as eliminates the possibility of fibre breakage before matrix shear. Higher scatter in the data in the samples is addressed in the present studies. FTIR and Fractographic studies are carried out for deep understanding of the post pull-out interfacial adhesion. 相似文献
4.
In this paper, the problem of delay-dependent exponential stability for fuzzy recurrent neural networks with interval time-varying delay is investigated. The delay interval has been decomposed into multiple non equidistant subintervals, on these interval Lyapunov-Krasovskii functionals (LKFs) are constructed to study stability analysis. Employing these LKFs, an exponential stability criterion is proposed in terms of Linear Matrix Inequalities (LMIs) which can be easily solved by MATLAB LMI toolbox. Numerical example is given to illustrate the effectiveness of the proposed method. 相似文献
5.
Multi-spectral fusion for surveillance systems 总被引:1,自引:0,他引:1
Simon Denman Author Vitae Todd Lamb Author Vitae Author Vitae Vinod Chandran Author Vitae Author Vitae 《Computers & Electrical Engineering》2010,36(4):643-663
Surveillance systems such as object tracking and abandoned object detection systems typically rely on a single modality of colour video for their input. These systems work well in controlled conditions but often fail when low lighting, shadowing, smoke, dust or unstable backgrounds are present, or when the objects of interest are a similar colour to the background. Thermal images are not affected by lighting changes or shadowing, and are not overtly affected by smoke, dust or unstable backgrounds. However, thermal images lack colour information which makes distinguishing between different people or objects of interest within the same scene difficult.By using modalities from both the visible and thermal infrared spectra, we are able to obtain more information from a scene and overcome the problems associated with using either modality individually. We evaluate four approaches for fusing visual and thermal images for use in a person tracking system (two early fusion methods, one mid fusion and one late fusion method), in order to determine the most appropriate method for fusing multiple modalities. We also evaluate two of these approaches for use in abandoned object detection, and propose an abandoned object detection routine that utilises multiple modalities. To aid in the tracking and fusion of the modalities we propose a modified condensation filter that can dynamically change the particle count and features used according to the needs of the system.We compare tracking and abandoned object detection performance for the proposed fusion schemes and the visual and thermal domains on their own. Testing is conducted using the OTCBVS database to evaluate object tracking, and data captured in-house to evaluate the abandoned object detection. Our results show that significant improvement can be achieved, and that a middle fusion scheme is most effective. 相似文献
6.
An axis-parallel k-dimensional box is a Cartesian product R 1×R 2×???×R k where R i (for 1≤i≤k) is a closed interval of the form [a i ,b i ] on the real line. For a graph G, its boxicity box?(G) is the minimum dimension k, such that G is representable as the intersection graph of (axis-parallel) boxes in k-dimensional space. The concept of boxicity finds applications in various areas such as ecology, operations research etc. A number of NP-hard problems are either polynomial time solvable or have much better approximation ratio on low boxicity graphs. For example, the max-clique problem is polynomial time solvable on bounded boxicity graphs and the maximum independent set problem for boxicity d graphs, given a box representation, has a $\lfloor 1+\frac{1}{c}\log n\rfloor^{d-1}An axis-parallel k-dimensional box is a Cartesian product R
1×R
2×⋅⋅⋅×R
k
where R
i
(for 1≤i≤k) is a closed interval of the form [a
i
,b
i
] on the real line. For a graph G, its boxicity box (G) is the minimum dimension k, such that G is representable as the intersection graph of (axis-parallel) boxes in k-dimensional space. The concept of boxicity finds applications in various areas such as ecology, operations research etc.
A number of NP-hard problems are either polynomial time solvable or have much better approximation ratio on low boxicity graphs.
For example, the max-clique problem is polynomial time solvable on bounded boxicity graphs and the maximum independent set
problem for boxicity d graphs, given a box representation, has a
?1+\frac1clogn?d-1\lfloor 1+\frac{1}{c}\log n\rfloor^{d-1}
approximation ratio for any constant c≥1 when d≥2. In most cases, the first step usually is computing a low dimensional box representation of the given graph. Deciding whether
the boxicity of a graph is at most 2 itself is NP-hard. 相似文献
7.
The goal in global illumination solutions for dynamic environments is to update a scene based on past scenes. For this difficult problem, current state of the art solutions are either not applicable, or unduly complex, when there are large changes in the illumination of unbounded number of objects. Such changes may be caused by the appearance of unexpected (at modeling time), irregular light sources.
We define a subset of dynamic environments in which new light sources may be user introduced, and implement solutions that complement existing schemes. 相似文献
8.
TiB whisker coating on titanium surfaces by solid-state diffusion: Synthesis,microstructure, and mechanical properties 总被引:1,自引:0,他引:1
The study demonstrates the feasibility of synthesizing TiB whiskers on titanium (Ti) surfaces by solid-state diffusion to
form a hard and wear-resistant coating. The microstructural and mechanical properties of the TiB coating layer have also been
investigated. The TiB coating was formed by the solid-state diffusion of boron (B) from a powder mixture containing amorphous
boron, Na2CO3 powder, and charcoal (activated) powder. The diffusion process was carried out at various temperatures ranging from 800 °C
to 1000 °C for various periods of time ranging from 1 to 24 hours. The amount of Na2CO3 in the mixture was also varied. It has been found that pristine and extremely fine TiB whiskers form on the surfaces of titanium,
with the whiskers growing more or less normal to the surface. A maximum coating thickness of about 218 μm was observed for the pack diffusion conditions at 850 °C for 24 hours with 15 pct Na2CO3. The kinetics of TiB formation was found to follow the growth rates in bulk composites. The X-ray diffraction (XRD) patterns
of the coatings revealed the dominant TiB peaks with a very few TiB2 peaks, with small intensity at higher temperature and time. The surface hardness of the coated layer increased to a Vickers
hardness of about 550 kgf/mm2 due to the presence of TiB whiskers in the coating. It is shown that pack diffusion of boron in the solid state is a simple
and very effective means of generating hard and wear-resistant coatings on titanium. 相似文献
9.
Polymer Nanowires: Enhanced Photoresponse of Conductive Polymer Nanowires Embedded with Au Nanoparticles (Adv. Mater. 15/2016)
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10.
The authors propose retransmission error control schemes for broadcast channels. In their selective-repeat-ARQ (automatic repeat request) method, they incorporate some aspects of implementation that they believe were ignored by all the previous work. Based on this protocol, they also propose a type-2 hybrid ARQ scheme that uses parity retransmission. They apply the dynamic programming optimization technique of Wang and Silvester (1987), with some modification, to their schemes. Analysis shows that their schemes outperform all the existing schemes. As special cases of their proposed schemes, the authors can obtain point-to-point ARQ schemes which also outperform all the existing point-to-point schemes. Thus, their schemes extend the useful range of retransmission error control schemes for these channels 相似文献