3,585 research outputs found
Weiss oscillations in the electronic structure of modulated graphene
We present a theoretical study of the electronic structure of modulated
graphene in the presence of a perpendicular magnetic field. The density of
states and the bandwidth for the Dirac electrons in this system are determined.
The appearance of unusual Weiss oscillations in the bandwidth and density of
states is the main focus of this work.Comment: 8 pages, 2 figures, accepted in J. Phys.: Conden. mat
Icmapen: an icmetric based security framework for sleep apnea monitoring
Smart devices are becoming increasingly powerful which is why they are being used for point of care health services. Wearable devices can be purchased which allow continuous monitoring of a wearers vital signs. The data is generated, processed and stored remotely where it can be readily accessible to health professionals. Recent attacks on healthcare systems and health data shows that the systems are insecure and that security is a major hurdle in their wide adoption. Conventional cryptographic systems rely on stored keys for the provision of security. The stored keys can be captured in many ways which leads to the system being exposed. The ICMetric technology remedies this by eliminating the need for stored keys. Thus, the ICMetric technology functions as a key theft deterrent and as a basis for cryptographic services. This paper studies the design and implementation of an ICMetric based health monitoring system for people diagnosed with sleep apnea. The proposed system provides key generation, authentication and confidentiality by using the novel ICMetric technology. The proposed scheme is constituent of a cloud computing component which enables remote monitoring and data storage for access by health professionals. This paper studies the performance of the proposed schemes by studying the running time. The security of the scheme has also been studied to show that the system provides high levels of security without resource compromise.Keywords: ICMetric; Sleep apnea; Cloud computing; Authentication; Confidentialit
A secure cloud framework for ICMetric based IoT health devices.
Wearable devices are an important part of internet of things (IoT)with many applications in healthcare. Prevalent security concerns create a compelling case for a renewed approach by incorporating the ICMetric technology in IoT healthcare. The ICMetric technology is a novel security approach and uses the features of a device to form the basis of cryptographic services like key generation, authentication and admission control. Cryptographic systems designed using ICMetric technology use unique measurable device features to form a root of trust. This paper uses the MEMS bias in a body wearable Shimmer sensor to create a device ICMetric. The ICMetric identity is used to generate cryptographic key to perform encryption and decryption of patients data which is being communicated to health professionals. The cloud based component of the proposed framework provides much needed distributed data processing and availability. The proposed schemes have been simulated and tested for conformance to high levels of security and performance
Multi-parameter approach to R-parity violating SUSY couplings
We introduce and implement a new, extended approach to placing bounds on
trilinear R-parity violating couplings. We focus on a limited set of leptonic
and semi-leptonic processes involving neutrinos, combining multidimensional
plotting and cross-checking constraints from different experiments. This allows
us to explore new regions of parameter space and to relax a number of bounds
given in the literature. We look for qualitatively different results compared
to those obtained previously using the assumption that a single coupling
dominates the R-parity violating contributions to a process (SCD). By combining
results from several experiments, we identify regions in parameter space where
two or more parameters approach their maximally allowed values. In the same
vein, we show a circumstance where consistency between independent bounds on
the same combinations of trilinear coupling parameters implies mass constraints
among slepton or squark masses. Though our new bounds are in most cases weaker
than the SCD bounds, the largest deviations we find on individual parameters
are factors of two, thus indicating that a conservative, order of magnitude
bound on an individual coupling is reliably estimated by making the SCD
assumption.Comment: 30 pages, 8 figures, 2 tables. Typos fixed, two references added and
references updated. Eq. (41) removed, Eq. (40) and text modified. Published
versio
Ab Initio Evidence for the Formation of Impurity d(3z^2-r^2) Holes in Doped La_{2-x}Sr_xCuO_4
Using the spin unrestricted Becke-3-Lee-Yang-Parr density functional, we
computed the electronic structure of explicitly doped La_{2-x}Sr_xCuO_4 (x =
0.125, 0.25, and 0.5). At each doping level, an impurity hole band is formed
within the undoped insulating gap. This band is well-localized to CuO_6
octahedra adjacent to the Sr impurities. The nature of the impurity hole is
A_{1g} in symmetry, formed primarily from the z^2 orbital on the Cu and p_z
orbitals on the apical O's. There is a strong triplet coupling of this hole
with the intrinsic B_{1g} Cu x^2-y^2/O1 p_{sigma} hole on the same site.
Optimization of the c coordinate of the apical O's in the doped CuO_6
octahedron lead to an asymmetric anti-Jahn-Teller distortion of the O2 atoms
toward the central Cu. In particular, the O2 atom between the Cu and Sr is
displaced 0.26 A while the O2 atom between the Cu and La is displaced 0.10 A.
Contrary to expectations, investigation of a 0.1 A enhanced Jahn-Teller
distortion of this octahedron does not force formation of an x^2-y^2 hole, but
instead leads to migration of the z^2 hole to the four other CuO_6 octahedra
surrounding the Sr impurity. This latter observation offers a simple
explanation for the bifurcation of the Sr-O2 distance revealed in x-ray
absorption fine structure data.Comment: Submitted to Phys. Rev. B. See http://www.firstprinciples.com for
more informatio
Commissioning Existing Buildings: A Program Perspective
Since September 2002, the Oakland Energy
Partnership's Large Commercial Building Tune-Up
Program has recruited managers and operators of
existing large commercial buildings in the City of
Oakland for program participation. The Tune-Up
Program is an aggressive effort to obtain 16.7 GWh
in energy savings in over 10 Mft2 in office,
institutional, healthcare, hotel, educational, and
retail buildings. Sponsored under the California
Public Utility Commission's 2002 Local Program
initiative, the Tune-Up program provides retro
commissioning (r-Cx) teams to help building
owners and operators thoroughly investigate the
operations and performance of their existing
building systems, identify measures that improve
energy performance, assist with measure
installation and verification, and provide
documentation to operators on optimum system
performance.
Great importance has been placed on the initial
assessment of each building, in order to answer
important questions from the program's and
owner's perspectives. These issues include:
condition of building's systems and equipment,
amount of savings potential, skill sets of r-Cx
teams, assurance that measures will be installed,
persistence of installed measures.
This paper describes how the program recruits
buildings, assesses the potential for savings, and
assigns engineering teams. The type and size of
buildings, their HVAC and lighting configurations,
common r-Cx measures found, and their savings
are described Results for each building are
described, and the program's cost-effectiveness is
reviewed. Currently, six buildings totaling 2.8
million square feet have been recruited, for an
expected savings of approximately 2.4 GWh. This
is 14% toward our program goal
Electronic and Optical Properties of Aluminum Oxide Before and After Surface Reduction by Ar+ Bombardment
The electronic and optical properties of a-Al2O3 after induced by 3-keV Ar+ sputtering have been studied quantitatively by use of reflection electron energy loss spectroscopy (REELS) spectra. The band gap values of a-Al2O3 was determined from the onset values of the energy loss spectrum to the background level of REELS spectra as a function of time Ar+ bombardment. The bandgap changes from 8.4 eV before sputtering to 6.2 eV after 4 minutes of sputtering.The optical properties of α-Al2O3 thin films have been determined by comparing the experimental cross section obtained from reflection electron energy loss spectroscopy with the theoretical inelastic scattering cross section, deduced from the simulated energy loss function (ELF) by using QUEELS-ε(k)-REELS software. The peak assignments are based on ELF and compared with reported data on the electronic structure of α-Al2O3 obtained using different techniques. The results demonstrate that the electronic and optical properties before and after surface reduction will provide further understanding in the fundamental properties of α-Al2O3 which will be useful in the design, modeling and analysis of devices applications performance.Received: 18 November 2013; Revised:12 June 2014; Accepted: 25 June 2014
Determination of the Half-Value Layer by Using Filter Aluminum Sheets for Digital Mammography
A method of determining the half-value layers (HVL) with or without using an aluminum (Al) filter sheet for digital mammography has been developed. HVL measurements using a single exposure method are performed without the addition of an aluminium filter. This study was conducted to evaluate the accuracy of measurements of HVL values in a single exposure method using a RaySave ion space detector. a standard method with a variation in aluminium filter thickness from 0.110 to 0.980 mm. The HVL measurement values were performed with the distance between the focus of the detector 60.5 cm, and the current 80 mAs at a voltage of 23 kVp, 25 kVp, 27 kVp, 29 kVp and 32 kVp. The HVL value is determined by using the interpolation formula. The results showed that the HVL value using aluminium filter was 0.03 mm higher than the standard method by using multiple exposures for the same thickness of the aluminium filter
Electronic and Optical Properties of Aluminum Oxide Before and After Surface Reduction by Ar+ Bombardment
The electronic and optical properties of a-Al2O3 after induced by 3-keV Ar+ sputtering have been studied quantitatively by use of reflection electron energy loss spectroscopy (REELS) spectra. The band gap values of a-Al2O3 was determined from the onset values of the energy loss spectrum to the background level of REELS spectra as a function of time Ar+ bombardment. The bandgap changes from 8.4 eV before sputtering to 6.2 eV after 4 minutes of sputtering.The optical properties of α-Al2O3 thin films have been determined by comparing the experimental cross section obtained from reflection electron energy loss spectroscopy with the theoretical inelastic scattering cross section, deduced from the simulated energy loss function (ELF) by using QUEELS-ε(k)-REELS software. The peak assignments are based on ELF and compared with reported data on the electronic structure of α-Al2O3 obtained using different techniques. The results demonstrate that the electronic and optical properties before and after surface reduction will provide further understanding in the fundamental properties of α-Al2O3 which will be useful in the design, modeling and analysis of devices applications performance.Received: 18 November 2013; Revised:12 June 2014; Accepted: 25 June 201
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