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41.
MEMS-based gas flow sensors 总被引:1,自引:0,他引:1
Yu-Hsiang Wang Chang-Pen Chen Chih-Ming Chang Chia-Pin Lin Che-Hsin Lin Lung-Ming Fu Chia-Yen Lee 《Microfluidics and nanofluidics》2009,6(3):333-346
Micro-electro-mechanical system (MEMS) devices integrate various mechanical elements, sensors, actuators, and electronics
on a single silicon substrate in order to accomplish a multitude of different tasks in a diverse range of fields. The potential
for device miniaturization made possible by MEMS micro-fabrication techniques has facilitated the development of many new
applications, such as highly compact, non-invasive pressure sensors, accelerometers, gas sensors, etc. Besides their small
physical footprint, such devices possess many other advantages compared to their macro-scale counterparts, including greater
precision, lower power consumption, more rapid response, and the potential for low-cost batch production. One area in which
MEMS technology has attracted particular attention is that of flow measurement. Broadly speaking, existing micro-flow sensors
can be categorized as either thermal or non-thermal, depending upon their mode of operation. This paper commences by providing
a high level overview of the MEMS field and then describes some of the fundamental thermal and non-thermal micro-flow sensors
presented in the literature over the past 30 years or so. 相似文献
42.
Solving engineering design and resources optimization via multiobjective evolutionary algorithms (MOEAs) has attracted much
attention in the last few years. In this paper, an efficient multiobjective differential evolution algorithm is presented
for engineering design. Our proposed approach adopts the orthogonal design method with quantization technique to generate
the initial archive and evolutionary population. An archive (or secondary population) is employed to keep the nondominated
solutions found and it is updated by a new relaxed form of Pareto dominance, called Pareto-adaptive ϵ-dominance (paϵ-dominance), at each generation. In addition, in order to guarantee to be the best performance produced, we propose a new
hybrid selection mechanism to allow the archive solutions to take part in the generating process. To handle the constraints,
a new constraint-handling method is employed, which does not need any parameters to be tuned for constraint handling. The
proposed approach is tested on seven benchmark constrained problems to illustrate the capabilities of the algorithm in handling
mathematically complex problems. Furthermore, four well-studied engineering design optimization problems are solved to illustrate
the efficiency and applicability of the algorithm for multiobjective design optimization. Compared with Nondominated Sorting
Genetic Algorithm II, one of the best MOEAs available at present, the results demonstrate that our approach is found to be
statistically competitive. Moreover, the proposed approach is very efficient and is capable of yielding a wide spread of solutions
with good coverage and convergence to true Pareto-optimal fronts. 相似文献
43.
Graph matching is a fundamental problem that arises frequently in the areas of distributed control, computer vision, and facility allocation. In this paper, we consider the optimal graph matching problem for weighted graphs, which is computationally challenging due the combinatorial nature of the set of permutations. Contrary to optimization-based relaxations to this problem, in this paper we develop a novel relaxation by constructing dynamical systems on the manifold of orthogonal matrices. In particular, since permutation matrices are orthogonal matrices with nonnegative elements, we define two gradient flows in the space of orthogonal matrices. The first minimizes the cost of weighted graph matching over orthogonal matrices, whereas the second minimizes the distance of an orthogonal matrix from the finite set of all permutations. The combination of the two dynamical systems converges to a permutation matrix, which provides a suboptimal solution to the weighted graph matching problem. Finally, our approach is shown to be promising by illustrating it on nontrivial problems. 相似文献
44.
Jong Sung Yoon 《Computer aided design》2008,40(9):905-915
This paper presents a simple and efficient method to approximate a developable surface to a compound design surface by a polynomial. It is required to predict a final shape of roll bending in the fabrication of a curved shell plate. The roll bending process usually makes the cylindrical or conical curvature from an initial flat plate. It means that the final shape is developable or the surface representation has zero Gaussian curvature. The fabrication shape is important in order to estimate process parameters of roller bending.An optimization problem is formulated to determine the polynomial surface which is in the closest proximity to the design surface or the given shell plate, which is subjected to developability. The results and the efficiency of this algorithm are verified and evaluated by applying it to some shell plates which are obtained from a real ship model. The predicted bending shape becomes fundamental information in determining more process parameters for the fabrication of a compound curved shell plate. 相似文献
45.
46.
As an important part of water level warning in water conservancy projects, often due to the influence of en-vironmental factors such as light and stains, the acquired water gauge images have sticky, broken and bright spot conditions, which affect the identification of water gauges. To solve this problem, a water gauge image denoising model based on improved adaptive total variation is proposed. Firstly, the regular term exponent in the adaptive total variational equation is changed to an inverse cosine function; secondly, the differential curvature is used to distinguish the image noise points and increase the smoothing strength at the noise points; finally, according to the characteristics of the gradient mode and adaptive gradient threshold after Gaussian filtering, the New model can adaptively denoise in the smooth area and protect the edge area, so as to have the characteristics of both edge-preserving denoising. The experimental results show that the new model has a great improvement in image vision, higher iteration efficiency and an average increase of 1.6 dB in peak signal-to-noise ratio, and an average increase of 9% in structural similarity, which is more beneficial to practical applications. 相似文献
47.
48.
Some control problems in practice are often formulated as a linear output regulation problem with time-varying exosystems. Although this problem has been studied recently, an explicit and constructive solution has been given only for minimum phase systems. This paper presents a solution for non-minimum phase systems whose zero dynamics is hyperbolic (or has an exponentially dichotomic split in the case of time-varying zero dynamics). The idea is inspired by the non-causal stable inversion. 相似文献
49.
Upon discerning the mere shape of an imaged object, as portrayed by projected perimeters, the full three-dimensional scattering density may not be of particular interest. In this situation considerable simplifications to the reconstruction problem are possible, allowing calculations based upon geometric principles. Here we describe and provide an algorithm which reconstructs the three-dimensional morphology of specimens from tilt series of images for application to electron tomography. Our algorithm uses a differential approach to infer the intersection of projected tangent lines with surfaces which define boundaries between regions of different scattering densities within and around the perimeters of specimens. Details of the algorithm implementation are given and explained using reconstruction calculations from simulations, which are built into the code. An experimental application of the algorithm to a nano-sized Aluminium tip is also presented to demonstrate practical analysis for a real specimen.
Program summary
Program title: STOMO version 1.0Catalogue identifier: AEFS_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEFS_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 2988No. of bytes in distributed program, including test data, etc.: 191 605Distribution format: tar.gzProgramming language: C/C++Computer: PCOperating system: Windows XPRAM: Depends upon the size of experimental data as input, ranging from 200 Mb to 1.5 GbSupplementary material: Sample output files, for the test run provided, are available.Classification: 7.4, 14External routines: Dev-C++ (http://www.bloodshed.net/devcpp.html)Nature of problem: Electron tomography of specimens for which conventional back projection may fail and/or data for which there is a limited angular range. The algorithm does not solve the tomographic back-projection problem but rather reconstructs the local 3D morphology of surfaces defined by varied scattering densities.Solution method: Reconstruction using differential geometry applied to image analysis computations.Restrictions: The code has only been tested with square images and has been developed for only single-axis tilting.Running time: For high quality reconstruction, 5-15 min 相似文献50.
The linear complete differential resultant of a finite set of linear ordinary differential polynomials is defined. We study the computation by linear complete differential resultants of the implicit equation of a system of n linear differential polynomial parametric equations in n−1 differential parameters. We give necessary conditions to ensure properness of the system of differential polynomial parametric equations. 相似文献