169,887 research outputs found
On the Competitive Ratio of Evaluating Priced Functions
No full textLet f be a function on a set of variables V. For each x ∈ V, let c(x) be the cost of reading the value of x. An algorithm for evaluating f is a strategy for adaptively identifying and reading a set of variables U ⊆ V whose values uniquely determine the value of f. We are interested in finding algorithms which minimize the cost incurred to evaluate f in the above sense. Competitive analysis is employed to measure the performance of the algorithms. We address two variants of the above problem. We consider the basic model in which the evaluation algorithm knows the cost c(x), for each x ∈ V. We also study a novel model where the costs of the variables are not known in advance and some preemption is allowed in the reading operations. This model has applications, for example, when reading a variable coincides with obtaining the output of a job on a CPU and the cost is the CPU time.
For the model where the costs of the variables are known, we present a polynomial time algorithm with the best possible competitive ratio γcf for each function f that is representable by a threshold tree and for each fixed cost function c(·). Remarkably, the best-known result for the same class of functions is a pseudo-polynomial algorithm with competitiveness 2γcf . Still in the same model, we introduce the Linear Programming Approach (LPA), a framework that allows the design of efficient algorithms for evaluating functions. We show that different implementations of this approach lead in general to the best algorithms known so far—and in many cases to optimal algorithms—for different classes of functions considered before in the literature.
Via the LPA, we are able to determine exactly the optimal extremal competitiveness of monotone Boolean functions. Remarkably, the upper bound which leads to this result, holds for a much broader class of functions, which also includes the whole set of Boolean functions.
We also show how to extend the LPA (together with these results) to the model where the costs of the variables are not known beforehand. In particular, we show how to employ the extended LPA to design a polynomial-time optimal (with respect to competitiveness) algorithm for the class of monotone Boolean functions representable by threshold trees
On the star decomposition of a graph: Hardness results and approximation for the max{\textendash}min optimization problem
No full textWe study the problem of decomposing a graph into stars so that the minimum size star in the decomposition is as large as possible. Problems of graph decomposition have been actively investigated since the 70's. The question we consider here also combines the structure of a facility location problem (choosing the centres of the stars) with a max-min fairness optimization criterion that has recently received attention in resource allocation problems, e.g., the Santa Claus problem.We focus on computational and algorithmic questions: We show that the problem is hard even in the case of planar graphs of maximum degree not larger than four, and already for decompositions into stars of size at least three. We are able to tightly characterize the boundaries between efficiently solvable instances and hard ones: we show that relaxing any of the conditions in our hardness result (minimum size of the stars or degree of the input graph) makes the problem polynomially solvable.Our complexity result implies also the APX hardness of the problem ruling out any approximation guarantee better than 2/3. We complement this inapproximability result with a 1/2-approximation algorithm. Finally, we give a polynomial time algorithm for trees. A nice property of our algorithms is that they can all be implemented to run in time linear in the size of the input graph. (C) 2020 Published by Elsevier B.V
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
State\u27s Motion to Exclude Rebuttal Testimony of Laber
No full textThe State contends that admitting Plaintiff’s expert testimony would violate of the rules of evidence and the court’s case management order, Local Rule 21.1. Terry Laber performed experiments with blood spatter and stains on a wrist watch and was to testify that the stains on Dr. Sheppard’s watch were not consistent with impact spatter. The State argued that this testimony would be a violation of 702(c) of the Rules of Evidence because it was going to be used to bolster the Plaintiff’s case in chief and was not rebuttal testimony. The State argued that it did not introduce any new evidence that would permit Laber’s testimony about the blood spatter on the watch. The State also argued that Laber’s testimony should not be considered as expert testimony because it was novel; had no controls; had no peer review, and had no documentation. The State’s second reason for excluding the testimony was that it violated Local Rule 21.1. The court’s case management order indicated that all supplemental reports were due by January 31, 2000, however Plaintiff’s expert witness report was dated February 14, 2000 and was served upon defendant on February 17. The state argues that Local Rule 21.1\u27s “all supplemental reports” includes expert reports used for rebuttal
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
A 0.12mm<sup>2</sup> Wien-Bridge Temperature Sensor with 0.1°C (3σ) Inaccuracy from -40°C to 180°C
No full text Resistor-based temperature sensors can achieve much higher resolution and energy efficiency than conventional BJT-based sensors [1], but they typically occupy more area (> 0.25 mm 2 ) and have lower operating temperatures (le 125 {circ} {C}) [2]-[4]. This work describes a 0.12mm 2 resistor-based sensor that uses a Wien-bridge (WB) filter to achieve 0.1 {circ} {C} (3 sigma) inaccuracy from - 40 {circ} {C} to 180 {circ} {C}. Compared to a state-of-the-art WB sensor [4], it occupies 6 × less area and achieves comparable relative accuracy over a 76% wider operating range. Session 10.3 Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic InstrumentationMicroelectronic
A ±25A Versatile Shunt-Based Current Sensor with 10kHz Bandwidth and ±0.25% Gain Error from -40°C to 85°C Using 2-Current Calibration
No full textAccurate current sensing is critical in many industrial applications, such as battery management and motor control. Precise shunt-based current sensors have been reported with gain errors of less than 1% over the industrial temperature range (-40°C to 85°C) [1]–[4]. However, since they are intended for coulomb counting, their bandwidth is limited to a few tens of Hz, making them unsuitable for battery impedance or motor-current sensing. This paper presents a current sensor with a wide (10kHz) bandwidth and a tunable temperature compensation scheme (TCS), which allows it to be flexibly used with different types of shunts while maintaining high accuracy. A low-cost room-temperature calibration scheme is proposed to optimize gain flatness over temperature by exploiting the shunt's self-heating at large currents. Over the industrial temperature range and a ±25A current range, it achieves state-of-the-art gain error (±0.25%) with both low-cost PCB and stable metal-alloy shunts.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic InstrumentationMicroelectronic
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C-Graded Vertex Algebras and their Representations
No full textIn this thesis we consider two related classes of vertex algebras. The first class we consider consists of objects called C-graded vertex algebras. These are vertex algebras with additional structure that allows for the construction of a Zhu algebra with a sufficiently well-behaved representation theory. This additional structure is minimal in the sense that it is necessary for the construction of the Zhu algebra. Given a C-graded vertex algebra, we provide a construction of the Zhu algebra and a pair of functors which are inverse bijections between the appropriate module categories.The second class we consider arises from considering conformal deformations of vertex operator algebras. These structures are called pseudo vertex operator algebras, and their main distinguishing feature is that the operator L(0) is not assumed to be semi-simple and is permitted to have complex eigenvalues. Similar theories have been studied: In the context of logarithmic conformal field theory, for example, L(0) is not required to be semi-simple on modules. Here, we extend that notion to allow L(0) to be non semi-simple on V itself. We show how to construct a family of pseudo vertex operator algebras from a given vertex operator algebra, and we prove that all such pseudo vertex operator algebras are C-graded vertex algebras. We then prove that every pseudo vertex operator algebra obtained via conformal deformation of a lattice vertex operator algebra is regular, which means that the category of admissible modules is semi-simple
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