1,189 research outputs found
Formal Verification of Safety Properties for Ownership Authentication Transfer Protocol
In ubiquitous computing devices, users tend to store some valuable
information in their device. Even though the device can be borrowed by the
other user temporarily, it is not safe for any user to borrow or lend the
device as it may cause private data of the user to be public. To safeguard the
user data and also to preserve user privacy we propose and model the technique
of ownership authentication transfer. The user who is willing to sell the
device has to transfer the ownership of the device under sale. Once the device
is sold and the ownership has been transferred, the old owner will not be able
to use that device at any cost. Either of the users will not be able to use the
device if the process of ownership has not been carried out properly. This also
takes care of the scenario when the device has been stolen or lost, avoiding
the impersonation attack. The aim of this paper is to model basic process of
proposed ownership authentication transfer protocol and check its safety
properties by representing it using CSP and model checking approach. For model
checking we have used a symbolic model checker tool called NuSMV. The safety
properties of ownership transfer protocol has been modeled in terms of CTL
specification and it is observed that the system satisfies all the protocol
constraint and is safe to be deployed.Comment: 16 pages, 7 figures,Submitted to ADCOM 201
A sensitivity study on the role of the swamps of southern Sudan in the summer climate of North Africa using a regional climate model
We used the regional climate model RegCM3 to investigate the role of the swamps of southern Sudan in affecting the climate of the surrounding region. Towards this end, we first assessed the performance of a high resolution version of the model over northern Africa. RegCM3 shows a good skill in simulating the climatology of rainfall and temperature patterns as well as the related circulation features during the summer season, outperforming previous coarser resolution applications of the model over this region. Sensitivity experiments reveal that, relative to bare soil conditions, the swamps act to locally modify the surface energy budget primarily through an increase of surface latent heat flux. Existence of the swamps leads to lower ground temperature (up to 2 °C), a larger northâsouth temperature gradient, and increased local rainfall (up to 40 %). Of particular importance is the impact on rainfall in the surrounding regions. The swamps have almost no impact on the rainfall over the source region of the Nile in Ethiopia or in the Sahel region; however, they favor wetter conditions over central Sudan (up to 15 %) in comparison to the bare desert soil conditions.Abdus Salam International Centre for Theoretical Physics (Earth System Physics)International Atomic Energy AgencySTEP progra
Effect of water-wall interaction potential on the properties of nanoconfined water
Much of the understanding of bulk liquids has progressed through study of the
limiting case in which molecules interact via purely repulsive forces, such as
a hard-core potential. In the same spirit, we report progress on the
understanding of confined water by examining the behavior of water-like
molecules interacting with planar walls via purely repulsive forces and compare
our results with those obtained for Lennard-Jones (LJ) interactions between the
molecules and the walls. Specifically, we perform molecular dynamics
simulations of 512 water-like molecules which are confined between two smooth
planar walls that are separated by 1.1 nm. At this separation, there are either
two or three molecular layers of water, depending on density. We study two
different forms of repulsive confinements, when the interaction potential
between water-wall is (i) and (ii) WCA-like repulsive potential. We
find that the thermodynamic, dynamic and structural properties of the liquid in
purely repulsive confinements qualitatively match those for a system with a
pure LJ attraction to the wall. In previous studies that include attractions,
freezing into monolayer or trilayer ice was seen for this wall separation.
Using the same separation as these previous studies, we find that the crystal
state is not stable with repulsive walls but is stable with WCA-like
repulsive confinement. However, by carefully adjusting the separation of the
plates with repulsive interactions so that the effective space
available to the molecules is the same as that for LJ confinement, we find that
the same crystal phases are stable. This result emphasizes the importance of
comparing systems only using the same effective confinement, which may differ
from the geometric separation of the confining surfaces.Comment: 20 pages, 10 figure
A physics-aware deep learning model for energy localization in multiscale shock-to-detonation simulations of heterogeneous energetic materials
Predictive simulations of the shock-to-detonation transition (SDT) in
heterogeneous energetic materials (EM) are vital to the design and control of
their energy release and sensitivity. Due to the complexity of the
thermo-mechanics of EM during the SDT, both macro-scale response and sub-grid
mesoscale energy localization must be captured accurately. This work proposes
an efficient and accurate multiscale framework for SDT simulations of EM. We
employ deep learning to model the mesoscale energy localization of
shock-initiated EM microstructures upon which prediction results are used to
supply reaction progress rate information to the macroscale SDT simulation. The
proposed multiscale modeling framework is divided into two stages. First, a
physics-aware recurrent convolutional neural network (PARC) is used to model
the mesoscale energy localization of shock-initiated heterogeneous EM
microstructures. PARC is trained using direct numerical simulations (DNS) of
hotspot ignition and growth within microstructures of pressed HMX material
subjected to different input shock strengths. After training, PARC is employed
to supply hotspot ignition and growth rates for macroscale SDT simulations. We
show that PARC can play the role of a surrogate model in a multiscale
simulation framework, while drastically reducing the computation cost and
providing improved representations of the sub-grid physics. The proposed
multiscale modeling approach will provide a new tool for material scientists in
designing high-performance and safer energetic materials
From Cellular Characteristics to Disease Diagnosis: Uncovering Phenotypes with Supercells
Cell heterogeneity and the inherent complexity due to the interplay of multiple molecular processes within the cell pose difficult challenges for current single-cell biology. We introduce an approach that identifies a disease phenotype from multiparameter single-cell measurements, which is based on the concept of ââsupercell statisticsââ, a single-cell-based averaging procedure followed by a machine learning classification scheme. We are able to assess the optimal tradeoff between the number of single cells averaged and the number of measurements needed to capture phenotypic differences between healthy and diseased patients, as well as between different diseases that are difficult to diagnose otherwise. We apply our approach to two kinds of single-cell datasets, addressing the diagnosis of a premature aging disorder using images of cell nuclei, as well as the phenotypes of two non-infectious uveitides (the ocular manifestations of Behcžetâs disease and sarcoidosis) based on multicolor flow cytometry. In the former case, one nuclear shape measurement taken over a group of 30 cells is sufficient to classify samples as healthy or diseased, in agreement with usual laboratory practice. In the latter, our method is able to identify a minimal set of 5 markers that accurately predict Behcžetâs disease and sarcoidosis. This is the first time that a quantitative phenotypic distinction between these two diseases has been achieved. To obtain this clear phenotypic signature, about one hundred CD8+ T cells need to be measured. Although the molecular markers identified have been reported to be important players in autoimmune disorders, this is the first report pointing out that CD8+ T cells can be used to distinguish two systemic inflammatory diseases. Beyond these specific cases, the approach proposed here is applicable to datasets generated by other kinds of state-of-the-art and forthcoming single-cell technologies, such as multidimensional mass cytometry, single-cell gene expression, and single-cell full genome sequencing techniques.Fil: Candia, Julian Marcelo. University of Maryland; Estados Unidos. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de FĂsica de LĂquidos y Sistemas BiolĂłgicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de FĂsica de LĂquidos y Sistemas BiolĂłgicos; ArgentinaFil: Maunu, Ryan. University of Maryland; Estados UnidosFil: Driscoll, Meghan. University of Maryland; Estados UnidosFil: Biancotto, AngĂ©lique. National Institutes of Health; Estados UnidosFil: Dagur, Pradeep. National Institutes of Health; Estados UnidosFil: McCoy Jr., J Philip. National Institutes of Health; Estados UnidosFil: Nida Sen, H.. National Institutes of Health; Estados UnidosFil: Wei, Lai. National Institutes of Health; Estados UnidosFil: Maritan, Amos. UniversitĂ di Padova; ItaliaFil: Cao, Kan. University of Maryland; Estados UnidosFil: Nussenblatt, Robert B. National Institutes of Health; Estados UnidosFil: Banavar, Jayanth R.. University of Maryland; Estados UnidosFil: Losert, Wolfgang. University of Maryland; Estados Unido
Radiative Phase Transitions and Casmir Effect Instabilities
Molecular quantum electrodynamics leads to photon frequency shifts and thus
to changes in condensed matter free energies often called the Casimir effect.
Strong quantum electrodynamic coupling between radiation and molecular motions
can lead to an instability beyond which one or more photon oscillators undergo
a displacement phase transition. The phase boundary of the transition can be
located by a Casimir free energy instability.Comment: ReVTeX4 format 1 *.eps figur
Sustainability of crop production from polluted lands
Sustainable food production for a rapidly growing global population is a major challenge of this century. In order to meet the demand for food production, an additional land area of 2.7 to 4.9 Mha year -1 will be required for agriculture. However, one third of arable lands are already contaminated, therefore the use of polluted lands will have to feature highly in modern agriculture. The use of such lands comes however with additional challenges and suitable agrotechnological interventions are essential for ensuring the safety and sustainability of relevant production system. There are also other issues to consider such as, cost benefit analysis, the possible entry of pollutants into to the phytoproducts, certification and marketing of such products, in order to achieve a the large scale exploitation of polluted land
Raman Evidence for Superconducting Gap and Spin-Phonon Coupling in Superconductor Ca(Fe0.95Co0.05)2As2
Inelastic light scattering studies on single crystal of electron-doped
Ca(Fe0.95Co0.05)2As2 superconductor, covering the tetragonal to orthorhombic
structural transition as well as magnetic transition at TSM ~ 140 K and
superconducting transition temperature Tc ~ 23 K, reveal evidence for
superconductivity-induced phonon renormalization; in particular the phonon mode
near 260 cm-1 shows hardening below Tc, signaling its coupling with the
superconducting gap. All the three Raman active phonon modes show anomalous
temperature dependence between room temperature and Tc i.e phonon frequency
decreases with lowering temperature. Further, frequency of one of the modes
shows a sudden change in temperature dependence at TSM. Using first-principles
density functional theory-based calculations, we show that the low temperature
phase (Tc < T < TSM) exhibits short-ranged stripe anti-ferromagnetic ordering,
and estimate the spin-phonon couplings that are responsible for these phonon
anomalies
Research gaps and technology needs in development of PHM for passive AdvSMR components
Advanced small modular reactors (AdvSMRs), which are based on modularization of advanced reactor concepts, may provide a longer-term alternative to traditional light-water reactors and near-term small modular reactors (SMRs), which are based on integral pressurized water reactor (iPWR) concepts. SMRs are challenged economically because of losses in economy of scale; thus, there is increased motivation to reduce the controllable operations and maintenance costs through automation technologies including prognostics health management (PHM) systems. In this regard, PHM systems have the potential to play a vital role in supporting the deployment of AdvSMRs and face several unique challenges with respect to implementation for passive AdvSMR components. This paper presents a summary of a research gaps and technical needs assessment performed for implementation of PHM for passive AdvSMR components
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