1,479 research outputs found
MPPT for Photovoltaic Systems with SEPIC Converter Counting Steady-State and Drift Analysis
A versatile voltage-sensor-based most extreme control point following calculation utilizing a variable scaling calculate for a solitary finished essential inductance converter is exhibited. In this strategy, just a voltage divider circuit is utilized to detect the photovoltaic (PV) board voltage. This technique can adequately enhance both transient and steady state execution by shifting the scaling variable as looked at with the settled stride estimate and versatile stride measure with settled scaling component. For sudden change in sunlight based insolation or, on the other hand in start-up, this technique prompts quicker following, though in enduring state, it prompts bring down motions around most extreme control point. The unfaltering state conduct and float marvels are additionally tended to in this paper to decide the following productivity. The obligation cycle is created specifically without utilizing any proportional–integral control circle to improve the control circuit. MATLAB/Simulink is utilized for reproduction thinks about, and a microcontroller is utilized as a computerized stage to actualize the proposed calculation for trial approval. The proposed framework is actualized what's more, tried effectively on a PV board in the research center
Implementation of Secure Log Management Over Cloud
A Log records are very important information which is related to activities of systems, applications or networks and these log records having various fields and their syntax. Actually logs are automatically generated on activities that are done and doing by user on system, or on any Applications such as Google Chrome or in networks. These logs are costly and need to any organization for future references such as to identify or finding any problems, to record all events, to find performance, and to investigate malicious activities in systems or networks or in application. So, protection of logs from attackers is required. Hence organization should maintain integrity, confidentiality, and security of logs. The cost to maintain logs for organizations for longer period is very less. Hence, we developed secure log management over cloud to decrease cost as well as provide security of log from attackers. To achieve this, we have done this with the help of Blowfish algorithm to Encrypt log records then SHA-1 is used to provide confidentiality while transmitting and at end point security purpose we used Shamir’s Secret sharing algorithm.
DOI: 10.17762/ijritcc2321-8169.150511
Vortex detection and quantum transport in mesoscopic graphene Josephson-junction arrays
We investigate mesoscopic Josephson junction arrays created by patterning
superconducting disks on monolayer graphene, concentrating on the high-
regime of these devices and the phenomena which contribute to the
superconducting glass state in diffusive arrays. We observe features in the
magnetoconductance at rational fractions of flux quanta per array unit cell,
which we attribute to the formation of flux-quantized vortices. The applied
fields at which the features occur are well described by Ginzburg-Landau
simulations that take into account the number of unit cells in the array. We
find that the mean conductance and universal conductance fluctuations are both
enhanced below the critical temperature and field of the superconductor, with
greater enhancement away from the graphene Dirac point.This work was financially supported by the Engineering
and Physical Sciences Research Council,
and an NPL/EPSRC Joint Postdoctoral Partnership
(RG61493).This is the accepted manuscript. The final version is available at http://journals.aps.org/prb/abstract/10.1103/PhysRevB.91.245418
Marfan syndrome and pregnancy: maternal and neonatal outcomes
Objective
To report outcomes in a recent series of pregnancies in women with Marfan syndrome (MFS).
Design
Retrospective case note review.
Setting
Tertiary referral unit (Chelsea and Westminster and Royal Brompton Hospitals).
Sample
Twenty-nine pregnancies in 21 women with MFS between 1995 and 2010.
Methods
Multidisciplinary review of case records.
Main outcome measures
Maternal and neonatal mortality and morbidity of patients with MFS and healthy controls.
Results
There were no maternal deaths. Significant cardiac complications occurred in five pregnancies (17%): one woman experienced a type–A aortic dissection; two women required cardiac surgery within 6 months of delivery; and a further two women developed impaired left ventricular function during the pregnancy. Women with MFS were also more likely to have obstetric complications (OR 3.29, 95% CI 1.30–8.34), the most frequent of which was postpartum haemorrhage (OR 8.46, 95% CI 2.52–28.38). There were no perinatal deaths, although babies born to mothers with MFS were delivered significantly earlier than those born to the control group (median 39 versus 40 weeks of gestation, Mann–Whitney U–test, P = 0.04). These babies were also significantly more likely to be small for gestational age (24% in the MFS group versus 6% in the controls; OR 4.95, 95% CI 1.58–15.55).
Conclusions
Pregnancy in women with MFS continues to be associated with significant rates of maternal, fetal, and neonatal complications. Effective pre-pregnancy counselling and meticulous surveillance during pregnancy, delivery, and the puerperium by an experienced multidisciplinary team are warranted for women with MFS
On nonsupersymmetric \BC^4/\BZ_N, tachyons, terminal singularities and flips
We investigate nonsupersymmetric \BC^4/\BZ_N orbifold singularities using
their description in terms of the string worldsheet conformal field theory and
its close relation with the toric geometry description of these singularities
and their possible resolutions. Analytic and numerical study strongly suggest
the absence of nonsupersymmetric Type II terminal singularities (i.e. with no
marginal or relevant blowup modes) so that there are always moduli or closed
string tachyons that give rise to resolutions of these singularities, although
supersymmetric and Type 0 terminal singularities do exist. Using gauged linear
sigma models, we analyze the phase structure of these singularities, which
often involves 4-dimensional flip transitions, occurring between resolution
endpoints of distinct topology. We then discuss 4-dim analogs of unstable
conifold-like singularities that exhibit flips, in particular their Type II GSO
projection and the phase structure. We also briefly discuss aspects of
M2-branes stacked at such singularities and nonsupersymmetric AdS_4\times
S^7/\BZ_N backgrounds.Comment: Latex, 43pgs incl. appendices, 2 eps figs, v2. minor clarifications
added, to appear in JHE
Stability Constraints on Classical de Sitter Vacua
We present further no-go theorems for classical de Sitter vacua in Type II
string theory, i.e., de Sitter constructions that do not invoke
non-perturbative effects or explicit supersymmetry breaking localized sources.
By analyzing the stability of the 4D potential arising from compactification on
manfiolds with curvature, fluxes, and orientifold planes, we found that
additional ingredients, beyond the minimal ones presented so far, are necessary
to avoid the presence of unstable modes. We enumerate the minimal setups for
(meta)stable de Sitter vacua to arise in this context.Comment: 18 pages; v2: argument improved, references adde
On The Stability Of Non-Supersymmetric AdS Vacua
We consider two infinite families of Non-Supersymmetric vacua, called
Type 2) and Type 3) vacua, that arise in massive IIA supergravity with flux. We
show that both families are perturbatively stable. We then examine
non-perturbative decays of these vacua to other supersymmetric and
non-supersymmetric vacua mediated by instantons in the thin wall
approximation. We find that many decays are ruled out since the tension of the
interpolating domain wall is too big compared to the energy difference in AdS
units. In fact, within our approximations no decays of Type 2) vacua are
allowed, although some decays are only marginally forbidden. This can be
understood in terms of a "pairing symmetry" in the landscape which relate Type
2) vacua with supersymmetric ones of the same energy.Comment: 50 pages, Minor changes in section 2.2.
Accretion Disks Around Black Holes: Twenty Five Years Later
We study the progress of the theory of accretion disks around black holes in
last twenty five years and explain why advective disks are the best bet in
explaining varied stationary and non-stationary observations from black hole
candidates. We show also that the recently proposed advection dominated flows
are incorrect.Comment: 30 Latex pages including figures. Kluwer Style files included.
Appearing in `Observational Evidence for Black Holes in the Universe', ed.
Sandip K. Chakrabarti, Kluwer Academic Publishers (DORDRECHT: Holland
Foundations of Black Hole Accretion Disk Theory
This review covers the main aspects of black hole accretion disk theory. We
begin with the view that one of the main goals of the theory is to better
understand the nature of black holes themselves. In this light we discuss how
accretion disks might reveal some of the unique signatures of strong gravity:
the event horizon, the innermost stable circular orbit, and the ergosphere. We
then review, from a first-principles perspective, the physical processes at
play in accretion disks. This leads us to the four primary accretion disk
models that we review: Polish doughnuts (thick disks), Shakura-Sunyaev (thin)
disks, slim disks, and advection-dominated accretion flows (ADAFs). After
presenting the models we discuss issues of stability, oscillations, and jets.
Following our review of the analytic work, we take a parallel approach in
reviewing numerical studies of black hole accretion disks. We finish with a few
select applications that highlight particular astrophysical applications:
measurements of black hole mass and spin, black hole vs. neutron star accretion
disks, black hole accretion disk spectral states, and quasi-periodic
oscillations (QPOs).Comment: 91 pages, 23 figures, final published version available at
http://www.livingreviews.org/lrr-2013-
- …