1,577 research outputs found
Ballistic transport and electrostatics in metallic carbon nanotubes
We calculate the current and electrostatic potential drop in metallic carbon
nanotube wires self-consistently, by solving the Green's function and
electrostatics equations in the ballistic case. About one tenth of the applied
voltage drops across the bulk of a nanowire, independent of the lengths
considered here. The remaining nine tenths of the bias drops near the contacts,
thereby creating a non linear potential drop. The scaling of the electric field
at the center of the nanotube with length (L) is faster than 1/L (roughly
). At room temperature, the low bias conductance of large
diameter nanotubes is larger than due to occupation of non crossing
subbands. The physics of conductance evolution with bias due to the
transmission Zener tunneling in non crossing subbands is discussed
A three-dimensional viscous flow analysis for the helicopter tip vortex generation problem
The tip vortex flow field occurring in the vicinity of the tip region of a a helicopter rotor blade is a very complicated three-dimensional, viscous flow phenomenon. The details of the flow in the tip region can have a major effect in determining the generated rotor noise and can significantly affect the performance and dynamic loading of the rotor blade. The three-dimensional viscous subsonic tip vortex generation processes is investigated by a numerical procedure which allows spatial forward-marching integration, utilizing flow approximations from the velocity-decomposition approach of Briley and McDonald. The approach has been applied to compute the laminar and turbulent tip vortex flows for a constant thickness slab airfoil with a square tip, a constant thickness slab airfoil with a half round tip and a NACA 0012 airfoil with a half round tip. The basic mechanism of the tip vortex generation process as well as the prediction of vortex appearance, strength and secondary flow shown by the calculations are in qualitative agreement with experimental results
End wall flows in rotors and stators of a single stage compressor
A computer code for solving the parabolized Navier-Stokes equations for internal flows was developed. Oscillations that develop in the calculation procedure are discussed. The measurements made in the hub and annulus wall boundary layers are summarized. The flow in the hub wall boundary layer, starting ahead of the inlet guide vanes to the inlet of the rotor is traced
Estimation of time delay by coherence analysis
Using coherence analysis (which is an extensively used method to study the
correlations in frequency domain, between two simultaneously measured signals)
we estimate the time delay between two signals. This method is suitable for
time delay estimation of narrow band coherence signals for which the
conventional methods cannot be reliably applied. We show by analysing coupled
R\"ossler attractors with a known delay, that the method yields satisfactory
results. Then, we apply this method to human pathologic tremor. The delay
between simultaneously measured traces of Electroencephalogram (EEG) and
Electromyogram (EMG) data of subjects with essential hand tremor is calculated.
We find that there is a delay of 11-27 milli-seconds () between the tremor
correlated parts (cortex) of the brain (EEG) and the trembling hand (EMG) which
is in agreement with the experimentally observed delay value of 15 for the
cortico-muscular conduction time. By surrogate analysis we calculate error-bars
of the estimated delay.Comment: 21 pages, 8 figures, elstart.cls file included. Accepted for
publication in Physica
Biomass and composition of zooplankton in and around Gulf of Kutch
The faunal composition, distribution and abundance of zooplankton from 28 stations in and around the Gulf of Kutch, were studied during INS Darshak cruise in January, 1975. Zooplankton biomass was about 4.5 times more in the outside Gulf region (mean: 50.3 ml/100 m super(3)) than in the inside Gulf (mean: 11.1 ml/100 m super(3)). The mean zooplankton biomass of Dwarka (66.3 ml/100 m super(3)) was about 2.5 times more than that off Okha (26.8 ml/100 m super(3)). A rich zooplankton production in the Saurashtra waters corresponded to a rich fishery prevailing in this region
Utilization of the potential Marine Fishery Resources of India
India's potential marine fishery resources, which have been projected at 4.5 million tonnes per annum, is thrice the current
average production. The most important methods of utilization of fish in the country at present are in fresh condition and
By salt-curing and drying, which together use up 87% of the catches. Of the remaining, 5% each is utilized frozen for export
And for reduction into fishmeal. The rest is utilized for canning and for miscellaneous purposes like extraction of oil, manure
Etc. With the introduction of more efficient craft and gear and Modern methods of harvesting worked out by our Research
Institutions, a major portion of our potential resources, if not all, is likely to be netted in the near future. It then becomes
binding on our part to make the best use of this natural bounty without any wastage whatsoever. This latter aspect has been
Fully tackled and solved by recent researches carried out on post harvest Technology, the more salient points of which are discussed
in this paper
Utility of Different Electrocardiographical Leads during Diagnostic Ajmaline Test for Suspected Brugada Syndrome
In order to compare the value of different leads and lead combinations to detect the signature Brugada type ECG pattern, we analysed digital 10-second, 15-lead ECGs (12 standard leads + leads V1 to V3 from 3rd intercostal (i.c.) space, V1h to V3h) acquired during diagnostic Ajmaline testing in 128 patients (80 men, age 37±15 years) with suspected Brugada syndrome (BS) (patient group), 15-lead resting ECGs of 108 healthy subjects (53 men, age 31.9±10.5 years) (control group A) and standard 12-lead resting ECGs of 229 healthy subjects (111 men, age 33±4 years) (control group B). Bipolar leads between V2 (positive pole) and V4 or V5 (leads V2-4V2-5) were derived by subtracting leads V4 and V5 from V2 (custom-made program). The 6 peripheral, 6 right precordial leads (V1 to V3, V1h to V3h) and leads V2-4 and V2-5 of the patients group, leads V1h to V3h of control group A, and leads V2-4 and V2-5 of control group B were analysed for the presence of type 1 Brugada pattern. There were 21 (16.4%) positive and 107 (83.6%) negative Ajmaline tests. In 7 positive tests (33%), type 1 pattern appeared only in leads V1h to V3h, whereas in 14 tests 67%) it appeared in both V1 to V3 and V1h to V3h. Lead V2 displayed type 1 pattern during 10 positive tests; in all of them, plus 10 other positive tests type 1 was also noted in lead V2h (n=20, 95.2%). In all 10 cases, in which lead V2 exhibited type 1 pattern (n=10), lead V2-4 and/or V2-5 also exhibited type 1-like pattern. During 7 positive tests, in which lead V2h but not V2 exhibited type 1 pattern, lead V2-4 and/or V2-5 also demonstrated type 1 pattern. Type 1 pattern was observed in leads V3 and V3h during 1 (5%) and 5 (24%) positive tests, in 0 ECGs (0%) in control group A and in 1 ECG (0.4%) in control group B. In conclusion, the "high" V1 and V2 leads (3rd i.c. space) detect more sensitively Brugada type 1 pattern than the standard V1 and V2 leads (4th i.c. space); leads V3 and V3h are not essential for the diagnosis of BS; bipolar leads V2-4 and V2-5 are superior to lead V2 for the ECG diagnosis of BS
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