Miracle-dz/UniFAR-FTUs huggingface dataset:
Photothermovoltaic effect in carbon nanotubes: En route toward junctionless infrared photocells and light sensors

Optically induced voltage was studied in carbon nanotube films configured as two-terminal resistive elements and operating as junctionless photocells in the infrared. The photovoltage is found to appear only for asymmetric/off-contact illuminations and the effect is explained based on photogenerated heat flow model. The engineered cell prototypes were found to yield electrical powers of ∼30 pW while demonstrating improved conversion efficiency under high-flux illumination. The cell is also shown to act as uncooled infrared sensor with its dark-to-photocurrent ratio improving as temperature increases. The concept might enable nanotube’s use in applications ranging from heat recycling to self-powered infrared sensors.
Evidence for environmental effects on early-type galaxy X-ray halos

Possible causes for the large dispersion in the X-ray luminosities (Lx) of early-type galaxies are discussed. It is shown that early-type galaxies with relatively low values of Lx for a given optical luminosity L(B) have about 50 percent more neighbors than galaxies with relatively high Lx, suggesting that low-Lx galaxies tend to be in denser environments. It is concluded that the large dispersion in X-ray luminosity, for a given L(B) might be caused either by ram-pressure stripping of the gaseous halos or by mergers. 53 refs.
A capillary-based probe for in situ detection of enhanced fluorescence signals

A simple, compact, and high sensitivity capillary-based probe for the in situ detection of fluorescence signals with high sensitivity is demonstrated. A home-made single–multi-mode fiber coupler that is coaxially aligned with the capillary-based probe provides for the transmission of excitation light and the collection and transmission of fluorescence. We propose a conceptually straightforward theoretical model to optimize the factors affecting the fluorescence-capture capability of the capillary-based probe. The fluorescence signal detected by fiber-optic spectroscopy non-linearly increases with the length of the capillary-based probe. In addition, the thicker the capillary tube wall is, the less the fluorescence signals determined are. The performance of the proposed probe is evaluated experimentally by measuring the fluorescence spectra of Cy5.5 dye and blue-green algae. The experimental results show that the proposed probe provides more than a ten-fold increase in fluorescence signal compared with direct measurements by a flat-tipped multi-mode fiber probe. The advantages of the capillary-based probe, which include its simple and compact structure, excellent light collection efficiency, requirement of small sample volume, and recoverability of samples, allow its wide application to in situ detection in the medical, forensic, biological, geological, and environmental fields with high sensitivity.
An Inferential Conception of Scientific Representation

This paper defends an inferential conception of scientific representation. It approaches the notion of representation in a deflationary spirit, and minimally characterizes the concept as it appears in science by means of two necessary conditions: its essential directionality and its capacity to allow surrogate reasoning and inference. The conception is defended by showing that it successfully meets the objections that make its competitors, such as isomorphism and similarity, untenable. In addition the inferential conception captures the objectivity of the cognitive representations used by science, it sheds light on their truth and completeness, and it explains the source of the analogy between scientific and artistic modes of representation.
A sustainable running criterion for biped balance control

This paper aims at exploring a novel criterion for sustainable running of biped robots subject to external perturbations. A new notion of running-feasible state is introduced to ensure that a biped can sustain a running motion starting from this state by an allowable control. Then a running-feasible set is estimated by using the orbit energy and the symmetric property of the inverted pendulum model. Based on the developed sustainable running criterion, a non-periodic reference trajectory is generated within a running-feasible set for disturbance rejection in real time and a control law is then designed to track the reference trajectory. In simulation, a five-link, four-actuator biped transits its speed between 2.8 m/s and 4.8 m/s in responding to external disturbances of pushing forward and backward. The simulation results confirm the effectiveness of balance recovery in a running biped, resembling the reaction pattern of a human being.
New permanental upper bounds for nonnegative matrices

Using a simple concavity argument together with the scale-symmetries of the permanent function, we derive a handful of upper bounds for the permanent of a nonnegative matrix. Each is better than our previously best upper bound, and agrees with the Minc-Brègman bound when applied to a (0,1)-matrix. We show how sharpening, a different application of scale-symmetries, can be used to improve upon virtually any extant permanental upper or lower bound for nonnegative matrices. Indeed, when applied to a (0,1)-matrix, the sharpened versions of the new upper bounds typically improve, sometimes considerably, upon the Minc-Brègman bound itself. We also indicate how our methods apply to lower bounds.
JD 7: The Sun and the Heliosphere as an Integrated System

As knowledge of the Sun and the heliosphere grows, it is becoming not only possible but preferable to view the global structure, the interaction with the local interstellar medium, and changes over a solar cycle as the behavior of an integrated system. This consideration motivated Joint Discussion 7, which was meant both to summarize the state of art at the time of IAU XXVand to solicit interest in this kind of approach. The Joint Discussion was arranged in four sections, two on processes that, beginning from the Sun s interior, model and shape the heliosphere (From the Transition Region to the Corona and beyond and From the Sun to the interstellar Medium), one on elemental abundances and particles in the corona and the heliosphere (Energetic Particles, Energetic Neutral Atoms and Composition) and one on forthcoming solar and heliospheric space missions. In the following we give a brief summary of the contributions presented at the JD in each section. An ext.cnded discussion of the topics cov- ered by JD is expected to appear in a comprehensive book on the Sun and the Heliosphere which will be edited by us and printed by Kluwer in year 2004. Posters which were exhibited as part of the Joint Discussion are listed at the end of this summary.
On model diagnostics using varying coefficient models

SUMMARY The paper motivates the use of varying coefficient models for diagnostics in regression models with continuous and factorial covariates. The varying coefficient model, which is restricted only by assumptions concerning the smoothness of the effects, is considered as the alternative to a parametric generalised linear model. Estimation is based on local likelihood smoothing and asymptotic properties of the estimators are derived. For the investigation of the discrepancy between the parametric model and the smooth alternative a simple graphical procedure is proposed. Moreover, tests are derived which allow for overall and componentwise investigation. The componentwise tests may be used to examine interaction effects of continuous and factorial regressors.
Chirality assignment of individual single-walled carbon nanotubes in carbon nanotube field-effect transistors by micro-photocurrent spectroscopy

We have proposed a possibility of chirality assignment of individual single-walled carbon nanotubes in nanotube field-effect transistors (FETs) by micro-photocurrent spectroscopy. The nanotube FETs were fabricated by utilizing position-controlled nanotube growth technique using alcohol chemical vapor deposition. Photocurrent signal that originated from a single single-walled carbon nanotube was obtained by using microscopic optical measurement system. A peak was observed at 1.73 eV in the photocurrent excitation spectrum. This corresponds to optical absorption by van Hove singularity of the nanotube with a diameter of ∼2 nm. Chirality of the nanotube in the nanotube FET was assigned to be (18, 10) by comparing the experimental results with theoretical calculation.
Unified treatment of electronic attraction, electric field, and electric-field gradient multicenter integrals of reened and nonscreened Coulomb potentials using overlap integrals for Slater orbitals

A unified treatment of multicenter electronic attraction (EA), electric field (EF), and electric-field gradient (EFG) integrals of Yukawa-like screened and nonscreened Coulomb potentials with Slater-type orbitals (STOs) is described. Using different sets of series expansion formulas of two-center distributions for STOs in terms of STOs at a displaced center the EA, EF, and EFG integrals over STOs are expressed through the overlap integrals between potentials or their derivatives and STOs. These two-center overlap integrals are evaluated by the use of rotational transformation for overlap integrals established by the author. The final results expressed through the overlap integrals of STOs with the same screening constants are valid for the arbitrary parameters of STOs and potentials. PACS No.: 31.15. p
Application of image visual characterization and soft feature selection in content-based image retrieval

Fourier descriptors (FFT) and Hu's seven moment invariants (HSMI) are among the most popular shape-based image descriptors and have been used in various applications, such as recognition, indexing, and retrieval. In this work, we propose to use the invariance properties of Hu's seven moment invariants, as shape feature descriptors, for relevance identification in content-based image retrieval (CBIR) systems. The purpose of relevance identification is to find a collection of images that are statistically similar to, or match with, an original query image from within a large visual database. An automatic relevance identification module in the search engine is structured around an unsupervised learning algorithm, the self-organizing tree map (SOTM). In this paper we also proposed a new ranking function in the structure of the SOTM that exponentially ranks the retrieved images based on their similarities with respect to the query image. Furthermore, we propose to extend our studies to optimize the contribution of individual feature descriptors for enhancing the retrieval results. The proposed CBIR system is compatible with the different architectures of other CBIR systems in terms of its ability to adapt to different similarity matching algorithms for relevance identification purposes, whilst offering flexibility of choice for alternative optimization and weight estimation techniques. Experimental results demonstrate the satisfactory performance of the proposed CBIR system.
Diffusion of saltating particles in unidirectional water flow over a rough granular bed

We show that the motion of saltating particles on a flat rough bed in unidirectional water flow is diffusive and comprises three ranges (local, intermediate, and global) of spatial and temporal scales with different scaling behaviour and diffusion properties. Our computer simulations suggest that the ratio of the travelling particle diameter to the prevailing diameter of static bed particles (or the height of bed roughness) is one of the key parameters controlling particle diffusion.
Multifunctional composites for energy storage

Electrochemical super-capacitors have become one of the most important topics in both academia and industry as novel energy storage devices because of their high power density, long life cycles, and high charge/discharge efficiency. Recently, there has been an increasing interest in the development of multifunctional structural energy storage devices such as structural super-capacitors for applications in aerospace, automobiles and portable electronics. These multifunctional structural super-capacitors provide lighter structures combining energy storage and load bearing functionalities. Due to their superior materials properties, carbon fiber composites have been widely used in structural applications for aerospace and automotive industries. Besides, carbon fiber has good electrical conductivity which will provide lower equivalent series resistance; therefore, it can be an excellent candidate for structural energy storage applications. Hence, this paper is focused on performing a pilot study for using nanowire/carbon fiber hybrids as building materials for structural energy storage materials; aiming at enhancing the charge/discharge rate and energy density. This hybrid material combines the high specific surface area of carbon fiber and pseudo-capacitive effect of metal oxide nanowires which were grown hydrothermally in an aligned fashion on carbon fibers. The aligned nanowire array could provide a higher specific surface area that leads to high electrode-electrolyte contact area and fast ion diffusion rates. Scanning Electron Microscopy (SEM) and XRay Diffraction (XRD) measurements were used for the initial characterization of this nanowire/carbon fiber hybrid material system. Electrochemical testing has been performed using a potentio-galvanostat. The results show that gold sputtered nanowire hybrid carbon fiber provides 65.9% better performance than bare carbon fiber cloth as super-capacitor.
An EO surveillance system for harbor security

Micro USA, Inc. has designed and built an Electro-Optical (EO) system for the detection and surveillance of submerged objects in harbor and open ocean waters. The system consists of a digital camera and advanced image processing software. The camera system uses a custom designed CMOS light sensor array to facilitate the detection of low contrast underwater targets. The software system uses wavelet-based image processing to remove atmospheric and ocean reflectance as well as other noise. Target detection is achieved through a suite of optimal channel prediction algorithms. The novelties of the system are (a) camera calibration routine to remove pixel non-linearities, non-uniformities and lens effect, (b) adaptive algorithms for low-contrast detection. Our system has been tested in San Diego harbor waters and initial results indicate that we can detect small (2 feet diameter), low-reflectance (5%) targets underwater to greater than 2 diffusion depth (DD). This diffusion depth translates to about 25 feet in harbor waters.
Comparative study of phonon‐limited mobility of two‐dimensional electrons in strained and unstrained Si metal–oxide–semiconductor field‐effect transistors

The phonon‐limited mobility of strained Si metal–oxide–semiconductor field‐effect transistors (MOSFETs) fabricated on a SiGe substrate is investigated through theoretical calculations including two‐dimensional quantization, and compared with the mobility of conventional (unstrained) Si MOSFETs. In order to match both the mobility of unstrained Si MOSFETs and the mobility enhancement in strained Si MOSFETs, it is necessary to increase the coupling of electrons in the two‐dimensional gas with intervalley phonons, compared to the values used in conventional models. The mobility enhancement associated with strain in Si is attributed to the following two factors: the suppression of intervalley phonon scattering due to the strain‐induced band splitting, and the decrease in the occupancy of the fourfold valleys which exhibit a lower mobility due to the stronger interaction with intervalley phonons. While the decrease in the averaged conductivity mass, caused by the decrease in the occupancy of the fourfold valle.
Electrical resistivity and photoluminescence of zinc oxide films prepared by ultrasonic spray pyrolysis

Zinc oxide (ZnO) thin films have been prepared by ultrasonic Spray pyrolysis (USP) technique using zinc acetate dihydrate dissolved in methanol, ethanol and deionized water. A number of techniques, including X‐ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, UV–visible, electrical resistivity, and photoluminescence (PL) were used to characterize the obtained ZnO thin films. The evolution of the preferred crystalline orientations in the ZnO films was systematically investigated. The PL measurements indicated that the as‐grown ZnO thin films showed UV and green emission bands when they were excited by a Hg arc lamp using 313 nm as the excitation source. A red‐shift in the near band edge (NBE) has been observed with the increase in the substrate temperature and has been attributed to the compressive intrinsic stress present in the films. It is confirmed that oxygen vacancy (VO) is the most important factor that causes the broad visible emission. Furthermore, the visible emission and electrical resistivity of ZnO thin films are found to be a function of porosity. Also, it has been interestingly found that the intensity of green emission at ∼2.5 eV remarkably increased when the obtained ZnO films were deposited at 320 °C. The reason might be the VO, intrinsic stress, surface‐to‐volume ratio and porosity in the sample increased at low substrate temperature. The resistivity follows the same behavior as the intensity of the green emission. We propose a new luminescence mechanism based on the recombination related to oxygen vacancies in Zn‐rich or stoichiometric conditions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A general formulation of hypoplasticity

A general formulation of the theory of hypoplasticity is given, under the assumption that Cauchy stress is the only state variable. Such a formulation allows to discuss the relation between the so‐called out‐of‐axis and in‐axis moduli. It is proved that, in general, the out‐of‐axis moduli are independent from the in‐axis moduli, which allows the former to be calibrated making use of experimental shear band data, as it is done in CLoE‐hypoplasticity. The implicit assumptions made in K‐hypoplasticity are detailed for two particular models of this family. Copyright © 2004 John Wiley & Sons, Ltd.
Transient Behavior of Liquid Crystalline Solutions of Poly(benzylglutamate)

A solution of poly‐γ‐benzyl‐L‐glutamate (PBLG) in m‐cresol has been investigated. Viscoelastic properties during steady state shear flow and in oscillatory flow are presented. The existence of a stable negative first normal stress difference is confirmed. The dynamic Newtonian viscosity is considerably smaller than the corresponding steady state shear value. The transient behavior after cessation of flow is studied in detail using dynamic measurements. After cessation of flow, the dynamic moduli change over a time scale which is much larger than that for stress relaxation. Effects of frequency, temperature and previous shear rate are analyzed. The structural interpretation of the data is discussed. Available models for polymeric liquid crystals have to be developed further before a comparison with the present results becomes possible.
Beam characterization of FLASH from Hartmann data and measurement of the Wigner distribution function

The wavefront as well as beam parameters of the free electron laser FLASH emitting in the EUV spectral range were determined from wavefront measurements using self supporting Hartmann sensors. The devices were applied for alignment of the ellipsoidal focusing mirror at Beamline 2 (BL2), reducing the rms wavefront aberrations by more than a factor of 3. Beam quality M² and other beam parameters were evaluated from wavefront and intensity data delivered by the Hartmann sensor. Furthermore, 100 two-dimensional single pulse intensity distributions were recorded at each of 32 axial positions, spaced app. ±2 Rayleigh lengths around the waist of the optimized FEL beam with a magnifying EUV sensitized CCD camera. From these beam profile data the Wigner distribution function was reconstructed on two dimensional orthogonal subspaces. For separable beams this yields the complete Wigner distribution and gives comprehensive and high-resolution information on the propagation characteristics, including wavefront, mode content and spatial coherence. The wavefront of the optimized beam evaluated at waist position was in the order of λ? 4 peak valley, whereas a significant contribution of uncorrelated higher order Hermite-Gauss modes and a global degree of coherence of 0.12 can be detected, leading to a substantial increase of the M² factor, which was determined to ~ 4.2 and ~ 3 in the horizontal and vertical direction, respectively. The obtained results are compared to the Hartmann experiments.
Tokamak plasma edge modelling including the main chamber wall

Quantifying main chamber wall recycling, erosion and resulting material migration, at least on the basis of known or empirical far scrape-off layer (SOL) processes, is still highly uncertain, despite its relevance for ITER and fusion reactor design studies. This affects, for example, the design problem of first mirror performance of many optical diagnostics in the harsh ITER environment. Poor computational access is not least due to a fundamental technical limitation in apparently all current tokamak edge plasma fluid codes, which implicates a wide computationally unresolved gap between the outermost plasma layer treated in codes and the real vessel wall. We show how the current ITER version of the B2-EIRENE code (SOLPS-4.3) can be extended to cover also this far SOL, on the same footing as the rest of the plasma transport model. We discuss consequences of this new model for estimating plasma power and particle sink terms caused by a fairly realistic wall in ITER based on the conventional Bohm criterion along all plasma–wall interfaces. Corrections were made to this article on 14 July 2011. The authors have been assigned to the correct affiliations.
Geometric super-resolution via log-polar FFT image registration and variable pixel linear reconstruction

Various image de-aliasing techniques and algorithms have been developed to improve the resolution of pixel-limited imagery acquired by an optical system having an undersampled point spread function. These techniques are sometimes referred to as multi-frame or geometric super-resolution, and are valuable tools because they maximize the imaging utility of current and legacy focal plane array (FPA) technology. This is especially true for infrared FPAs which tend to have larger pixels as compared to visible sensors. Geometric super-resolution relies on knowledge of subpixel frame-toframe motion, which is used to assemble a set of low-resolution frames into one or more high-resolution (HR) frames. Log-polar FFT image registration provides a straightforward and relatively fast approach to estimate global affine motion, including translation, rotation, and uniform scale changes. This technique is also readily extended to provide subpixel translation estimates, and is explored for its potential combination with variable pixel linear reconstruction (VPLR) to apportion a sequence of LR frames onto a HR grid. The VPLR algorithm created for this work is described, and HR image reconstruction is demonstrated using calibrated 1/4 pixel microscan data. The HR image resulting from VPLR is also enhanced using Lucy-Richardson deconvolution to mitigate blurring effects due to the pixel spread function. To address non-stationary scenes, image warping, and variable lighting conditions, optical flow is also investigated for its potential to provide subpixel motion information. Initial results demonstrate that the particular optical flow technique studied is able to estimate shifts down to nearly 1/10th of a pixel, and possibly smaller. Algorithm performance is demonstrated and explored using laboratory data from visible cameras.