8,732 research outputs found
Cracking pressure control of parylene checkvalve using slanted tensile tethers
MEMS check valves with fixed cracking pressures are important in micro-fluidic applications where the pressure, flow directions and flow rates all need to be carefully controlled. This work presents a new surface-micromachined parylene check valve that uses residual thermal stress in the parylene to control its cracking pressure. The new check valve uses slanted tethers to allow the parylene tensile stress to apply a net downward force on the valving seat against the orifice. The angle of the slanted tethers is made using a gray-scale mask to create a sloped sacrificial photoresist with the following tether parylene deposition. The resulted check valves have both the cracking pressures and flow profiles agreeable well with our theoretical analysis
Bias-free time-integrating optical correlator using a photorefractive crystal
An acoustooptic time-integrating correlator is demonstrated using a photorefractive crystal as the time-integrating detector
Diversifying Top-K Results
Top-k query processing finds a list of k results that have largest scores
w.r.t the user given query, with the assumption that all the k results are
independent to each other. In practice, some of the top-k results returned can
be very similar to each other. As a result some of the top-k results returned
are redundant. In the literature, diversified top-k search has been studied to
return k results that take both score and diversity into consideration. Most
existing solutions on diversified top-k search assume that scores of all the
search results are given, and some works solve the diversity problem on a
specific problem and can hardly be extended to general cases. In this paper, we
study the diversified top-k search problem. We define a general diversified
top-k search problem that only considers the similarity of the search results
themselves. We propose a framework, such that most existing solutions for top-k
query processing can be extended easily to handle diversified top-k search, by
simply applying three new functions, a sufficient stop condition sufficient(),
a necessary stop condition necessary(), and an algorithm for diversified top-k
search on the current set of generated results, div-search-current(). We
propose three new algorithms, namely, div-astar, div-dp, and div-cut to solve
the div-search-current() problem. div-astar is an A* based algorithm, div-dp is
an algorithm that decomposes the results into components which are searched
using div-astar independently and combined using dynamic programming. div-cut
further decomposes the current set of generated results using cut points and
combines the results using sophisticated operations. We conducted extensive
performance studies using two real datasets, enwiki and reuters. Our div-cut
algorithm finds the optimal solution for diversified top-k search problem in
seconds even for k as large as 2,000.Comment: VLDB201
Van der Waerden's Theorem and Avoidability in Words
Pirillo and Varricchio, and independently, Halbeisen and Hungerbuhler
considered the following problem, open since 1994: Does there exist an infinite
word w over a finite subset of Z such that w contains no two consecutive blocks
of the same length and sum? We consider some variations on this problem in the
light of van der Waerden's theorem on arithmetic progressions.Comment: Co-author added; new result
Parylene stiction
This paper presents a preliminary study into stiction between parylene C and substrate surfaces for biocompatible check-valve applications. During fabrication, parylene C is used as the structural material for the check-valve. The substrate surfaces studied include Au, Al, Si, parylene C, XeF_2 treated Si, and silicon dioxide. Stiction between different surfaces is created after sacrificial photoresist etching. Then, the stiction is measured using blister tests, and stiction mechanisms for different materials are investigated. The devices are released with different recipes to examine their effects. Finally, the results of the study reveal methods to control the cracking pressure of parylene check-valves
Asymmetric Monetary Policy in Australia
We find evidence for asymmetric behaviour in Australian monetary policy. During 1984-1990, the Reserve Bank of Australia acted with considerable discretion yielding poor performance of an interest rate rule. However it behaved asymmetrically to inflation and the output gap in downturns and upturns. On embracing inflation targeting from 1991, it enhanced its credibility by anchoring inflation expectations. Not only did its actions become more predictable in 1991-2002, it responded asymmetrically only to output, switching to act more acutely in downturns. While its asymmetric behaviour could result from asymmetric preferences or non-linear aggregate supply, our results support the former explanation.non-linear Phillips curve; Interest rate rules; asymmetric preferences; generalized method of moments; inflation targeting; credibility
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