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Study of Ga+ implantation in Si diodes: effect on optoelectronic properties using micro-spectroscopy
No full textIon implantation has been widely used in various device fabrication applications, including that of optoelectronic components. Focused Ion Beam (FIB) is an especially versatile implantation method, since it can be used for well controlled doping with sub-micron spatial precision. Here, we report FIB induced gallium doping in micrometer-sized regions on shallow Silicon p-n junction devices and its effect on the device optoelectronic properties investigated through micro-spectroscopic measurements. The effect of varying dose levels has been quantified in terms of photo voltage, Raman spectroscopy, XPS and reflectance measurements to investigate the effect of radiation damage and surface amorphization. Based on these observations we report simultaneous occurrence of two scenarios, channeling of high-energy gallium ions beyond the junction depth, as well as formation of an amorphous silicon layer, which cumulatively degrade the optoelectronic properties of the diodes
DISTINGUISHING HERMITIAN CUSP FORMS OF DEGREE 2 BY A CERTAIN SUBSET OF ALL FOURIER COEFFICIENTS
No full textWe prove that Hermitian cusp forms of weight k for the Hermitian modular group of degree 2 are determined by their Fourier coefficients indexed by matrices whose determinants are essentially square-free. Moreover, we give a quantitative version of the above result. This is a consequence of the corresponding results for integral weight elliptic cusp forms, which are also treated in this paper
On reducing submodules of Hilbert modules with G(n)-invariant kernels
No full textFix a bounded domain Omega subset of C-n and a positive definite kernel K on Omega, both invariant under G(n), the permutation group on n symbols. Let H subset of Hol(Omega) be the Hilbert module determined by K. We show that H splits into orthogonal direct sum of subspaces PpH indexed by the partitions p of n. We prove that each submodule PpH is a locally free Hilbert module of rank equal to square of the dimension chi(p) (1) of the irreducible representation corresponding to p. Given two partitions p and q, we show that if chi(p)(1) not equal chi(q)(1), then the sub-modules PpH and PqH are not unitarily equivalent. We prove that if H is a contractive analytic Hilbert module on Omega, then the `Taylor joint spectrum of the n-tuple of multiplication operators by elementary symmetric polynomials on PpH is clos (s(Omega)), where s : C-n -> C-n is the symmetrization map. It is then shown that this commuting tuple of operators defines a contractive homomorphism of the ring of symmetric polynomials Cz](Gn) in n variables, equipped with the sup norm on clos (s(Omega)). (C) 2018 Elsevier Inc. All rights reserved
Determination of yielding point by means a probabilistic method on acoustic emission signals for application to health monitoring of reinforced concrete structures
No full textReinforced concrete (RC) flanged beam specimens were tested under incremental cyclic load till failure in flexure, and simultaneously, the acoustic emission (AE) signals released by the specimens were recorded. To assess damage in RC structures, a previously published index of damage (ID) based on AE signals was used. This index, however, needs to know the yielding point of the specimen. In the present study, yielding point was identified with a probabilistic method known as Gaussian mixture modeling (GMM) applied to the AE signals, as compared with that obtained by means of the plastic strain energy. It was observed that yielding load obtained with both methodologies was almost same, thus validating the GMM method. This result permits to use the ID index for damage monitoring of RC structure in practical scenarios, by using only information hidden in the AE signals. The influence of loading rate, failure type (tensile and shear), RC beam depth, concrete compressive strength, and percentage of tensile steel reinforcement on ID were studied in this work
Connecting CuA with metal centers of heme a, heme a(3), CuB and Zn by pathways with hydrogen bond as the bridging element in cytochrome c oxidase
No full textPathways formed of delocalized pi-electron systems and polar groups of polypeptide chains bridged by hydrogen bonds are referred as pi-H pathways. Suitable for electron transfer, these pathways in cytochrome c oxidase connect CuA, the source of electrons distributed in cytochrome c oxidase, with the metal centers, heme a, heme a(3), CuB, the constituents of the catalytic binuclear center. The unusually rapid electron transfer between heme a and heme a(3) would have been facilitated by the link pathway of a long sequence of alternate peptide unit and hydrogen bond spanning Pro336-Val374, referred as suprahelix, between these hemes. Two pathways between CuA center and zinc center, share some portions with purported proton-translocating channels, designated ``K'' and ``D''. (C) 2019 Elsevier Inc. All rights reserved
Machine vision quality assessment for robust face detection
No full textMachine vision quality (MVQ) assessment for face detection refers to image quality as judged by face detection algorithms. While perceptual image quality usually depends on human observers, MVQ depends on factors such as the face detection algorithm and performance measures such as recall and precision. We define the MVQ index as a weighted combination of the predicted precision and recall of the face detection algorithm and predict it using image features based on natural scene statistics. A filter bank framework is developed to achieve image enhancement of distorted images for face detection, where the enhancement operations can be optimized for either perceptual quality or MVQ. It is shown that MVQ can be effectively used to control the relative performance of recall and precision that can be achieved on enhanced images. For certain face detection algorithms, optimizing for MVQ instead of perceptual quality can lead to improved face detection performance. The MVQ is developed for three different face detection algorithms and the image enhancement framework is tested on a dataset based on the IDEAL-LIVE Distorted Face Database. A computationally efficient method to optimize for MVQ is designed by predicting the MVQ of enhanced images directly from features extracted from distorted images and filter parameters. The optimization framework is further enhanced by allowing for filter bank independent optimization of MVQ
Superior potassium-ion hybrid capacitor based on novel P3-type layered K 0.45 Mn 0.5 Co 0.5 O 2 as high capacity cathode
No full textHerein, we demonstrate a new non-aqueous potassium-ion hybrid capacitor (KIC) using novel P3-K 0.45 Mn 0.5 Co 0.5 O 2 and commercial activated carbon (CAC) as the cathode and anode, respectively. A simple sol�gel method is used to synthesize the P3-K 0.45 Mn 0.5 Co 0.5 O 2 cathode nanoplatelets. The structural and morphological studies are performed using various characterization techniques, and their electrochemical performances are studied in half-cell configurations against metallic K. The P3-K 0.45 Mn 0.5 Co 0.5 O 2 nanoplatelets can reversibly host K + ions delivering a high capacity of 140 mAh g �1 in the wide voltage window of 1.2�3.9 V. Exhibiting smooth voltage profiles, it offers reasonable rate capability and cyclability, retaining over 80 capacity after 50 cycles. Involving a two-phase (P3�O3) redox mechanism, P3-K 0.45 Mn 0.5 Co 0.5 O 2 forms robust cathode material for potassium-ion batteries. With Activated Carbon, the capacitor could provide very high energy and power densities of 43 Wh kg �1 and 30 kW kg �1 , respectively, in the voltage range of 0�3.0 V. Even at a 3-s charge�discharge rate (10 A g �1 ), an energy density of 14.5 Wh kg �1 could be retained (corresponding to a power of 15 kW kg �1 ). Also it could retain 88 of its energy density with a substantially high stability up to 30,000 cycles at 10 A g �1 . © 2019 Elsevier B.V
Correlation between anodization variables and surface properties of titania nanotube arrays for dye-sensitized solar cells
No full textThe effect of anodization variables on the morphology and surface properties of oriented titania nanotube arrays (TNAs) was investigated. The arrays were synthesized using hydrofluoric acid based ethylene glycolelectrolyte. The results show that the anodization time plays a significant role in the surface properties as well as length of the nanotubes. However, the contribution of anodization potential to debris formation was found to be negligible within the investigated range of the potential. The F�ion concentration and aging of electrolyte were found to play crucial roles in the formation of ordered clean nanotubes. The studies conducted by employing these TNAs as photo-anodes for dye-sensitized solar cells (DSCs) show that the morphology variations alone alter the photovoltaic properties of DSCs to a great extent. © Carl Hanser Verlag GmbH & Co. KG
Search for anomalous alignments of structures in Planck data using Minkowski Tensors
No full textMinkowski Tensors are tensorial generalizations of the scalar Minkowski Functionals. Due to their tensorial nature they contain additional morphological information of structures, in particular about shape and alignment, in comparison to the scalar Minkowski functionals. They have recently been used 1 to study the statistical isotropy of temperature and E mode data from the Planck satellite. The calculation in 2 relied on stereographic projection of the fields to extract the shape and alignment information. In this work, we calculate Minkowski Tensors directly on the sphere and compute the net alignment in the data, based on a recent work that extends the definition of Minkowski Tensors to random fields on curved spaces. This method circumvents numerical errors that can be introduced by the stereographic projection. We compare the resulting net alignment parameter values obtained from the frequency coadded CMB temperature data cleaned by the SMICA pipeline, to those obtained from simulations that include instrumental beam effects and residual foreground and noise. We find very good agreement between the two within 1�. We further compare the alignments obtained from the beam-convolved CMB maps at individual Planck frequencies to those in the corresponding simulations. We find no significant difference between observed data and simulations across all {\rm Planck} frequencies, except for the 30 GHz channel. For the 30 GHz channel we find 2 � difference between the data and the simulations. This mild disagreement could originate from an inaccurate estimation of the instrumental beam at 30 GHz. © 2019 IOP Publishing Ltd and Sissa Medialab
Bounds on slow roll at the boundary of the landscape
No full textWe present strong evidence that the tree level slow roll bounds of arXiv:1807.05193 and arXiv:1810.05506 are valid, even when the tachyon has overlap with the volume of the cycle wrapped by the orientifold. This extends our previous results in the volume-dilaton subspace to a semi-universal modulus. Emboldened by this and other observations, we investigate what it means to have a bound on (generalized) slow roll in a multi-field landscape. We argue that for any point � 0 in an N-dimensional field space with V (�0) > 0, there exists a path of monotonically decreasing potential energy to a point � 1 within a path length � O(1), such that NlnV(�1)V(�0)��O(1). The previous de Sitter swampland bounds are specific ways to realize this stringent non-local constraint on field space, but we show that it also incorporates (for example) the scenario where both slow roll parameters are intermediate-valued and the Universe undergoes a small number of e-folds, as in the Type IIA set up of arXiv:1310.8300. Our observations are in the context of tree level constructions, so we take the conservative viewpoint that it is a characterization of the classical �boundary� of the string landscape. To emphasize this, we argue that these bounds can be viewed as a type of Dine-Seiberg statement. © 2019, The Author(s)