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排序方式: 共有1327条查询结果,搜索用时 15 毫秒
61.
Giovanni Crupi Dominique M. M.‐P. Schreurs Alina Caddemi Antonio Raffo Giorgio Vannini 《国际射频与微波计算机辅助工程杂志》2010,20(1):87-93
The present article analyzes in detail different intrinsic small‐signal models for transistors. Particular attention is devoted to the non‐quasi‐static effects, which play a crucial role at microwave and millimeter‐wave frequencies. The advantages and disadvantages of these different equivalent circuit topologies are analyzed from both theoretical and experimental standpoints. This study clearly proves that best choice among these model representations depends on the specific device technology besides the investigated frequency range. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. 相似文献
62.
Giorgio Brajnik Yeliz Yesilada Simon Harper 《Universal Access in the Information Society》2011,10(4):403-423
Web site-evaluation methodologies and validation engines take the view that all accessibility guidelines must be met to gain
compliance. Problems exist in this regard, as contradictions within the rule set may arise, and the type of impairment or
its severity is not isolated. The Barrier Walkthrough (BW) method goes someway to addressing these issues, by enabling barrier
types derived from guidelines to be applied to different user categories such as motor or visual impairment, etc. However,
the problem remains of combinatorial explosion of possibilities when one has to consider users with multiple disabilities.
In this paper, a simple set theory operation is used to create a validation scheme for older users by aggregating barrier
types specific to motor impaired and low-vision users, thereby creating a new “older users” category from the results of this
set union. To evaluate the feasibility and validity of this aggregation approach, two BW experiments were conducted. The first
experiment evaluated the aggregated results by focusing on quality attributes and showed that aggregation generates data whose
quality is comparable to the original one. However, this first experiment could not test for validity, as the older users
category was not included. To remedy this deficiency, another BW experiment was conducted with expert judges who evaluated
a web page in the context of older users. In this second experiment, it was found that there is no significant difference
between the aggregated and the manually evaluated (by experts) barrier scores, and that the same barriers are identified using
experts and aggregation, even though there are differences in how severity scores are distributed. From these results, it
is concluded that the aggregation of barriers is a viable alternative to expert evaluation, when the target of that aggregation
could not be evaluated manually or it would not be feasible to do so. It is also argued that aggregation is a technique that
can be used in combination with other evaluation methods, like user testing or subjective assessments. 相似文献
63.
Cognitive therapy and experiential dynamic therapy show quite many similarities but they diverge in their initial approach to the patient (aiming respectively at cognitions and at emotions) and in their assumptions about core pathogenetic processes. According to cognitive therapy patients suffer because of a negative unrealistic inner representation of self and world, whereas for experiential dynamic therapy problems arise from conflictual experience and expression of healthy feelings and needs. A synthetic model of the pathogenetic core process, embracing both a conflict about healthy needs and emotions, and a negative self-image, is outlined and discussed. In particular, the model's congruence with new knowledge emerging from infant and attachment research, emotion theory, and cognitive neurosciences is illustrated. Assuming an identity of their basic pathogenetic theory, the two therapies can be thought of as two initially different approaches, the one focusing more on cognitions, the other on emotions, but converging toward the change of a common pathogenetic core. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
64.
65.
Marco Carminati Giorgio Ferrari Aleksandar P. Ivanov Tim Albrecht Marco Sampietro 《Analog Integrated Circuits and Signal Processing》2013,77(3):333-343
Solid-state nanopores have been gaining popularity in nano-biotechnology for single molecule detection, in particular for label-free high-throughput DNA sequencing. In order to address the improvement of the resolution/speed trade-off critical in this application, here we present a new two-channel current amplifier tailored for solid-state nanopore devices with integrated tunneling electrodes. The simultaneous detection of ion and tunneling currents provides enhanced molecule tracking capability. We describe the system design starting from a detailed noise analysis and device modeling, highlighting the detrimental role of the conductive silicon substrate and of all the stray capacitive couplings between the electrodes. Given the high input capacitance (0.1–1 nF), the input voltage noise has been carefully minimized choosing a discrete couple of matched low-noise JFETs as input stage, thus achieving an equivalent input noise of 1.5 nV/√Hz (corresponding to a current noise floor of 15 fA/√Hz at 10 kHz). Low-noise performance (11 pA rms noise integrated over a 75 kHz bandwidth) is preserved at a wide bandwidth (300 kHz) and high gain (100 MΩ) thanks to the adoption of an improved integrator/differentiator cascade topology. Furthermore, along with biasing networks and selectable low-pass filters, an AC-coupled channel providing additional gain has been introduced in order to “zoom” in the current signature during pore blockade events. Together with an experimental characterization of the system (and comparison with the noise performance of other instruments), the platform is validated by demonstrating the detection of λ-DNA with 20 nm pores. 相似文献
66.
67.
On measuring the accuracy of SLAM algorithms 总被引:1,自引:0,他引:1
Rainer Kümmerle Bastian Steder Christian Dornhege Michael Ruhnke Giorgio Grisetti Cyrill Stachniss Alexander Kleiner 《Autonomous Robots》2009,27(4):387-407
In this paper, we address the problem of creating an objective benchmark for evaluating SLAM approaches. We propose a framework
for analyzing the results of a SLAM approach based on a metric for measuring the error of the corrected trajectory. This metric
uses only relative relations between poses and does not rely on a global reference frame. This overcomes serious shortcomings
of approaches using a global reference frame to compute the error. Our method furthermore allows us to compare SLAM approaches
that use different estimation techniques or different sensor modalities since all computations are made based on the corrected
trajectory of the robot.
We provide sets of relative relations needed to compute our metric for an extensive set of datasets frequently used in the
robotics community. The relations have been obtained by manually matching laser-range observations to avoid the errors caused
by matching algorithms. Our benchmark framework allows the user to easily analyze and objectively compare different SLAM approaches. 相似文献
68.
Marano S Palmieri F Franceschetti G 《Journal of the Optical Society of America. A, Optics, image science, and vision》2002,19(7):1319-1333
A fully self-contained discrete framework with discrete equivalents of Stokes's, Gauss's, and Green's theorems is presented. The formulation is analogous to that of continuous operators, but totally discrete in nature, and the exact relationships derived are shown to hold provided that a set of predefined rules is followed in building discrete contours and domains. The method allows for an analytical rigor that is not guaranteed if one translates the classical continuous formulations onto a discretized approximated framework. We clarify several issues related to the use of discrete operators, which may play a crucial role in specific applications such as the two-dimensional phase-unwrapping problem, chosen as our main application example, and we show that reconstruction on irregular domains and/or in the presence of undersampling and noise is better formulated in the discrete framework than in the continuous domain. 相似文献
69.
Petritoli A Ravegnani F Giovanelli G Bortoli D Bonafè U Kostadinov I Oulanovsky A 《Applied optics》2002,41(27):5593-5599
An airborne UV-visible spectrometer, the Gas Analyzer Spectrometer Correlating Optical Differences, airborne version (GASCOD/A4pi) was successfully operated during the Airborne Polar Experiment, Geophysica Aircraft in Antarctica airborne campaign from Ushuaia (54 degrees 49' S, 68 degrees 18' W), Argentina in southern spring 1999. The instrument measured scattered solar radiation through three optical windows with a narrow field of view (FOV), one from the zenith, two from the horizontal, as well as actinic fluxes through 2pi FOV radiometric heads. Only a few airborne measurements of scattered solar radiation at different angles from the zenith are available in the literature. With our configuration we attempted to obtain the average line-of-sight concentrations of detectable trace gases. The retrieval method, based on differential optical absorption spectroscopy, is described and results for ozone are shown and compared with measurements from an in situ instrument as the first method of validation. 相似文献
70.
Murphy Dana R.; Schneider Bruce A.; Speranza Filippo; Moraglia Giampaolo 《Canadian Metallurgical Quarterly》2006,21(4):763
The authors conducted 3 experiments investigating the effects of aging on higher order auditory processes. They compared younger and older adults with respect to (a) their auditory channel capacity, (b) the extent of their top-down control over auditory gain, and (c) their ability to focus attention on a narrow band of frequencies. To ensure that subclinical cochlear processing deficits in older adults (e.g., higher thresholds, poorer discrimination of frequency and intensity differences) did not limit performance, the authors used only stimuli that were perfectly discriminable by all participants. No age differences were found in any of these experiments, suggesting that some higher order auditory processes (e.g., top-down control over auditory gain, auditory attention) are preserved in normal aging, despite numerous age-related declines in peripheral auditory functionality. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献