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41.
We give a simple O(nlogn) algorithm to compute the convex hull of the (possibly Θ(n2)) intersection points in an arrangement of n line segments in the plane. We also show an arrangement of dn hyperplanes in d-dimensions whose arrangement has Θ(nd−1) intersection points on the convex hull. 相似文献
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Many existing systems are written in C and are not re‐entrant or thread safe. Sometimes these systems are required in a context for which they were not first designed, possibly meaning they now need to be re‐entrant. This article introduces a program that filters C source code, modifying shared resources (the global variables) to make the code re‐entrant: ‘virtualizing’ the code. The code is then compiled as normal. This approach allows programmatic virtualization with little cost at runtime. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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We advocate the use of quickly‐adjustable, computer‐controlled color spectra in photography, lighting and displays. We present an optical relay system that allows mechanical or electronic color spectrum control and use it to modify a conventional camera and projector. We use a diffraction grating to disperse the rays into different colors, and introduce a mask (or LCD/DMD) in the optical path to modulate the spectrum. We analyze the trade‐offs and limitations of this design, and demonstrate its use in a camera, projector and light source. We propose applications such as adaptive color primaries, metamer detection, scene contrast enhancement, photographing fluorescent objects, and high dynamic range photography using spectrum modulation. 相似文献
46.
In this paper we describe a general grouping technique to devise faster and simpler approximation schemes for several scheduling
problems. We illustrate the technique on two different scheduling problems: scheduling on unrelated parallel machines with
costs and the job shop scheduling problem. The time complexity of the resulting approximation schemes is always linear in
the number n of jobs, and the multiplicative constant hidden in the O(n) running time is reasonably small and independent of the error ε.
Supported by Swiss National Science Foundation project 200020-109854, “Approximation Algorithms for Machine scheduling Through
Theory and Experiments II”.
A preliminary version of this paper appeared in the Proceedings of ESA’01. 相似文献
47.
Iris Reinbacher Marc Benkert Marc van Kreveld Joseph S. B. Mitchell Jack Snoeyink Alexander Wolff 《Algorithmica》2008,50(3):386-414
In geographic information retrieval, queries often name geographic regions that do not have a well-defined boundary, such
as “Southern France.” We provide two algorithmic approaches to the problem of computing reasonable boundaries of such regions
based on data points that have evidence indicating that they lie either inside or outside the region. Our problem formulation
leads to a number of subproblems related to red-blue point separation and minimum-perimeter polygons, many of which we solve
algorithmically. We give experimental results from our implementation and a comparison of the two approaches.
This research is supported by the EU-IST Project No. IST-2001-35047 (SPIRIT) and by grant WO 758/4-2 of the German Research
Foundation (DFG). 相似文献
48.
Observed finger behaviour during computer mouse use 总被引:1,自引:0,他引:1
Two-button computer mouse users may exhibit sustained, static finger lifting behaviours to prevent inadvertent activations by avoiding finger pressure on the buttons, which leads to prolonged, static finger extensor muscle loading. One hundred graduate students were observed during normal computer work in a university computer facility to qualify and quantify the prevalence of lifted finger behaviours and extended finger postures, as well as wrist/forearm and grip behaviour, during specific mouse activities. The highest prevalences observed were 48% of the students lifted their middle finger during mouse drag activities, and 23% extended their middle finger while moving the mouse. In addition, 98% of the students rested their wrist and forearm (77%) or wrist only (21%) on the workstation surface, and 97% had an extended wrist posture (15 degrees -30 degrees ) when using the mouse. Potential applications of these findings include future computer input device designs to reduce finger lifting behaviour and exposures to risk factors of hand/forearm musculoskeletal pain. 相似文献
49.
每年1月,汽车音响行业都会翘首以盼阿尔派音响改装样板车问世。一般,在拉斯维加斯的国际消费类电子产品展览会(CES)上,阿尔派设计人员都会向人们展示其样板车。在过 相似文献
50.