2,790 research outputs found
Reduced O diffusion through Be doped Pt electrodes
Using first principles electronic structure calculations we screen nine
elements for their potential to retard oxygen diffusion through
poly-crystalline Pt (p-Pt) films. We determine that O diffuses preferentially
as interstitial along Pt grain boundaries (GBs). The calculated barriers are
compatible with experimental estimates. We find that Be controls O diffusion
through p-Pt. Beryllium segregates to Pt GBs at interstitial (i) and
substitutional (s) sites. i-Be is slightly less mobile than O and it repels O,
thus stuffing the GB. s-Be has a high diffusion barrier and it forms strong
bonds to O, trapping O in the GB. Experiments confirm our theoretical
predictions.Comment: 3 pages, 2 figure
Reflectance measurement of two-dimensional photonic crystal nanocavities with embedded quantum dots
The spectra of two-dimensional photonic crystal slab nanocavities with
embedded InAs quantum dots are measured by photoluminescence and reflectance.
In comparing the spectra taken by these two different methods, consistency with
the nanocavities' resonant wavelengths is found. Furthermore, it is shown that
the reflectance method can measure both active and passive cavities. Q-factors
of nanocavities, whose resonant wavelengths range from 1280 to 1620 nm, are
measured by the reflectance method in cross polarization. Experimentally,
Q-factors decrease for longer wavelengths and the intensity, reflected by the
nanocavities on resonance, becomes minimal around 1370 nm. The trend of the
Q-factors is explained by the change of the slab thickness relative to the
resonant wavelength, showing a good agreement between theory and experiment.
The trend of reflected intensity by the nanocavities on resonance can be
understood as effects that originate from the PC slab and the underlying air
cladding thickness. In addition to three dimensional finite-difference
time-domain calculations, an analytical model is introduced that is able to
reproduce the wavelength dependence of the reflected intensity observed in the
experiment.Comment: 24 pages, 7 figures, corrected+full versio
Taxonomic status of Bambusaspis miliaris : B. robusta, and B. pseudomiliaris (Hemiptera: Coccoidea: Asterolecaniidae)
Based on an assessment of 50 morphological characters from 110 specimens of Bambusaspis miliaris (BoisduvalI869), B. robusta (Green 1908), andB. pseudomiliaris (Green 1922) from different geographic regions around the world, we conclude that these specimens represent the same species. Therefore, the taxa B. robusta and B. pseudomiliaris are considered junior subjective synonyms of B. miliaris
On optimality of kernels for approximate Bayesian computation using sequential Monte Carlo
Approximate Bayesian computation (ABC) has gained popularity over the past few years for the analysis of complex models arising in population genetics, epidemiology and system biology. Sequential Monte Carlo (SMC) approaches have become work-horses in ABC. Here we discuss how to construct the perturbation kernels that are required in ABC SMC approaches, in order to construct a sequence of distributions that start out from a suitably defined prior and converge towards the unknown posterior. We derive optimality criteria for different kernels, which are based on the Kullback-Leibler divergence between a distribution and the distribution of the perturbed particles. We will show that for many complicated posterior distributions, locally adapted kernels tend to show the best performance. We find that the added moderate cost of adapting kernel functions is easily regained in terms of the higher acceptance rate. We demonstrate the computational efficiency gains in a range of toy examples which illustrate some of the challenges faced in real-world applications of ABC, before turning to two demanding parameter inference problems in molecular biology, which highlight the huge increases in efficiency that can be gained from choice of optimal kernels. We conclude with a general discussion of the rational choice of perturbation kernels in ABC SMC settings
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Investigating the Intelligibility of a Computer Vision System for Blind Users
Computer vision systems to help blind usersare becoming increasingly common yet often these systems are not intelligible. Our work investigates the intelligibility of a wearable computer vision system to help blind users locate and identify people in their vicinity. Providing a continuous stream of information, this system allows us to explore intelligibility through interaction and instructions, going beyond studies of intelligibility that focus on explaining a decision a computer vision system might make. In a study with 13 blind users, we explored whether varying instructions (either basic or enhanced) about how the system worked would change blind usersâ experience of the system. We found offering a more detailed set of instructions did not affect how successful users were using the system nor their perceived workload. We did, however, find evidence of significant differences in what they knew about the system, and they employed different, and potentially more effective, use strategies. Our findings have important implications for researchers and designers of computer vision systemsfor blind users, as well more general implications for understanding what it means to make interactive computer vision systems intelligible
Overcoming Psychologism. Twardowski on Actions and Products
This paper is about the topic of psychologism in the work of Kazimierz Twardowski and my aim is to revisit this important issue in light of recent publications from, and on Twardowskiâs works. I will first examine the genesis of psychologism in the young Twardowskiâs work; secondly, I will examine Twardowskiâs picture theory of meaning and Husserlâs criticism in Logical Investigations; the third part is about Twardowskiâs recognition and criticism of his psychologism in his lectures on the psychology of thinking; the fourth and fifth parts provide an overview of Twardowskiâs paper âActions and Productsâ while the sixth part addresses the psychologism issue in the last part of this paper through the delineation of psychology and the humanities. I shall conclude this study with a brief assessment of Twardowskiâs solution to psychologism
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Explaining how to play real-time strategy games
Real-time strategy games share many aspects with real situations in domains such as battle planning, air traffic control, and emergency response team management which makes them appealing test-beds for Artificial Intelligence (AI) and machine learning. End-user annotations could help to provide supplemental information for learning algorithms, especially when training data is sparse. This paper presents a formative study to uncover how experienced users explain game play in real-time strategy games. We report the results of our analysis of explanations and discuss their characteristics that could support the design of systems for use by experienced real-time strategy game users in specifying or annotating strategy-oriented behavior
A NEW APPROACH TO ANALYSING CERVICAL SPINAL MOTION
INTRODUCTION Several investigations on the problem of cervical spine motion describe the difficulties of measuring the movement exactly. Those models have to deal with the difficulties to fixate something at the human head and to track the range of motion in degrees concerning the three directions of movement, flexiodextension, lateral bending and rotation. The only objective method of measuring cervical spine movement and CO/C 1 or C 1lC2 displacements is the functional computer tomogram as described by Dvorak et. al. (1989). The aim of our survey has been to differ between the "normal" and pathologic cervical spine (after whip leash injuries, disc diseases or spondylarthrosis in sport) concerning with the range of movement and angular velocity. l b o Groups of 15 probants have been tested by a new computer-controlled setup. By using a three-dimensional motion-analysis-system special rigid-body software has been developed to calculate the cervical spine motion in all three coordinate directions (Truesdell & Noll, 1965). The first time it is possible to get results about the movement and their time-derivations. These angles and the angular velocities were traced for 15 normal individuals and 15 persons suffering with cervical spine problems. The setup for the tested patients was not more then a small frame like sunglasses which gives us an exact information about the movement in space. This information gives accurate data to calculate the amount of motion concerning the patients personal orientation in space and can be additionally used to compute the coupled motions to the probants reference coordinate system. We found significant differences in the range of motion between normal individuals as reference group and patients with cervical spine problems in all defined directions. CONCLUSIONS One conclusion, was that there were possibilities to measure those differences in cervical spine motion by the presented biomechanical measurement-setup very easily. The setup furthermore is capable of getting exact results about rang of motion, coupled motion end their time-derivations very fast and without any x-ray exposition for the patient. This possibilities and the good results are very important to judge problems after "whip lash injuries" and other cervical spine diseases in sport. REFERENCES Dvorak, A. et. al. (1989): Functional evaluation of the spinal cord by magnetic imaging in patients with rheumatoid arthritis and instability of upper cervical spine, Spine 14 (10); 1057- 1064. Truesdell, C.; W. No11 (1965): The nonlinear field theories of mechanics - Kinematics, in: Handbuch der Physik, von: S. Fliigge, Springer, New York
Taxonomic Status of \u3ci\u3eBambusaspis miliaris\u3c/i\u3e, \u3ci\u3eB. robusta\u3c/i\u3e, and \u3ci\u3eB. pseudomiliaris\u3c/i\u3e (Hemiptera: Coccoidea: Asterolecaniidae)
Based on an assessment of 50 morphological characters from 110 specimens of Bambusaspis miliaris (Boisduval 1869), B. robusta (Green 1908), and B. pseudomiliaris (Green 1922) from different geographic regions around the world, we conclude that these specimens represent the same species. Therefore, the taxa B. robusta and B. pseudomiliaris are considered junior subjective synonyms of B. miliaris
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