55,805 research outputs found
Equation of motion approach to non-adiabatic quantum charge pumping
We use the equations of motion of non-interacting electrons in a
one-dimensional system to numerically study different aspects of charge
pumping. We study the effects of the pumping frequency, amplitude, band filling
and finite bias on the charge pumped per cycle, and the Fourier transforms of
the charge and energy currents in the leads. Our method works for all values of
parameters, and gives the complete time-dependences of the current and charge
at any site of the system. Our results agree with Floquet and adiabatic
scattering theory where these are applicable, and provides support for a
mechanism proposed elsewhere for charge pumping by a traveling potential wave.
For non-adiabatic and strong pumping, the charge and energy currents are found
to have a marked asymmetry between the two leads, and pumping can work even
against a substantial bias.Comment: 11 pages including 9 figures; expanded the paper to discuss
left-right asymmetry of charge and energy currents, and effect of finite bia
Applications of fuzzy theories to multi-objective system optimization
Most of the computer aided design techniques developed so far deal with the optimization of a single objective function over the feasible design space. However, there often exist several engineering design problems which require a simultaneous consideration of several objective functions. This work presents several techniques of multiobjective optimization. In addition, a new formulation, based on fuzzy theories, is also introduced for the solution of multiobjective system optimization problems. The fuzzy formulation is useful in dealing with systems which are described imprecisely using fuzzy terms such as, 'sufficiently large', 'very strong', or 'satisfactory'. The proposed theory translates the imprecise linguistic statements and multiple objectives into equivalent crisp mathematical statements using fuzzy logic. The effectiveness of all the methodologies and theories presented is illustrated by formulating and solving two different engineering design problems. The first one involves the flight trajectory optimization and the main rotor design of helicopters. The second one is concerned with the integrated kinematic-dynamic synthesis of planar mechanisms. The use and effectiveness of nonlinear membership functions in fuzzy formulation is also demonstrated. The numerical results indicate that the fuzzy formulation could yield results which are qualitatively different from those provided by the crisp formulation. It is felt that the fuzzy formulation will handle real life design problems on a more rational basis
THE-FAME: THreshold based Energy-efficient FAtigue MEasurment for Wireless Body Area Sensor Networks using Multiple Sinks
Wireless Body Area Sensor Network (WBASN) is a technology employed mainly for
patient health monitoring. New research is being done to take the technology to
the next level i.e. player's fatigue monitoring in sports. Muscle fatigue is
the main cause of player's performance degradation. This type of fatigue can be
measured by sensing the accumulation of lactic acid in muscles. Excess of
lactic acid makes muscles feel lethargic. Keeping this in mind we propose a
protocol \underline{TH}reshold based \underline{E}nergy-efficient
\underline{FA}tigue \underline{ME}asurement (THE-FAME) for soccer players using
WBASN. In THE-FAME protocol, a composite parameter has been used that consists
of a threshold parameter for lactic acid accumulation and a parameter for
measuring distance covered by a particular player. When any parameters's value
in this composite parameter shows an increase beyond threshold, the players is
declared to be in a fatigue state. The size of battery and sensor should be
very small for the sake of players' best performance. These sensor nodes,
implanted inside player's body, are made energy efficient by using multiple
sinks instead of a single sink. Matlab simulation results show the
effectiveness of THE-FAME.Comment: IEEE 8th International Conference on Broadband and Wireless
Computing, Communication and Applications (BWCCA'13), Compiegne, Franc
Tunneling through two resonant levels: fixed points and conductances
We study point contact tunneling between two leads of a Tomonaga-Luttinger
liquid through two degenerate resonant levels in parallel. This is one of the
simplest cases of a quantum junction problem where the Fermi statistics of the
electrons plays a non-trivial role through the Klein factors appearing in
bosonization. Using a mapping to a `generalized Coulomb model' studied in the
context of the dissipative Hofstadter model, we find that any asymmetry in the
tunneling amplitudes from the two leads grows at low temperatures, so that
ultimately there is no conductance across the system. For the symmetric case,
we identify a non-trivial fixed point of this model; the conductance at that
point is generally different from the conductance through a single resonant
level.Comment: 6 pages, 3 figure
Distance Aware Relaying Energy-efficient: DARE to Monitor Patients in Multi-hop Body Area Sensor Networks
In recent years, interests in the applications of Wireless Body Area Sensor
Network (WBASN) is noticeably developed. WBASN is playing a significant role to
get the real time and precise data with reduced level of energy consumption. It
comprises of tiny, lightweight and energy restricted sensors, placed in/on the
human body, to monitor any ambiguity in body organs and measure various
biomedical parameters. In this study, a protocol named Distance Aware Relaying
Energy-efficient (DARE) to monitor patients in multi-hop Body Area Sensor
Networks (BASNs) is proposed. The protocol operates by investigating the ward
of a hospital comprising of eight patients, under different topologies by
positioning the sink at different locations or making it static or mobile.
Seven sensors are attached to each patient, measuring different parameters of
Electrocardiogram (ECG), pulse rate, heart rate, temperature level, glucose
level, toxins level and motion. To reduce the energy consumption, these sensors
communicate with the sink via an on-body relay, affixed on the chest of each
patient. The body relay possesses higher energy resources as compared to the
body sensors as, they perform aggregation and relaying of data to the sink
node. A comparison is also conducted conducted with another protocol of BAN
named, Mobility-supporting Adaptive Threshold-based Thermal-aware
Energy-efficient Multi-hop ProTocol (M-ATTEMPT). The simulation results show
that, the proposed protocol achieves increased network lifetime and efficiently
reduces the energy consumption, in relative to M-ATTEMPT protocol.Comment: IEEE 8th International Conference on Broadband and Wireless
Computing, Communication and Applications (BWCCA'13), Compiegne, Franc
Observational evidence for mass ejection during soft X-ray dips in GRS1915+105
We investigate the connection between the X-ray and radio properties of the
Galactic microquasar GRS1915+105, by analyzing the X-ray data observed with
RXTE, during the presence of a huge radio flare (~450 mJy). The X-ray
lightcurve shows two dips of ~100 second duration. Detailed time resolved
spectral analysis shows the existence of three spectral components: a
multicolor disk-blackbody, a Comptonized component due to hot plasma and a
power-law. We find that the Comptonized component is very weak during the dip.
This is further confirmed by the PHA ratio of the raw data and ratio of the
lightcurves in different energy bands. These results, combined with the fact
that the 0.5 -- 10 Hz QPO disappears during the dip and that the Comptonized
component is responsible for the QPO lead to the conclusion that during the
dips the matter emitting Comptonized spectrum is ejected away. This establishes
a direct connection between the X-ray and radio properties of the source.Comment: Replaced with some minor changes, corrected typos. Added Journal Re
Subsonic balance and pressure investigation of a 60 deg delta wing with leading edge devices
Low supersonic wave drag makes the thin highly swept delta wing the logical choice for use on aircraft designed for supersonic cruise. However, the high-lift maneuver capability of the aircraft is limited by severe induced-drag penalties attributed to loss of potential flow leading-edge suction. This drag increase may be alleviated through leading-edge flow control to recover lost aerodynamic thrust through either retention of attached leading-edge flow to higher angles of attack or exploitation of the increased suction potential of separation-induced vortex flow. A low-speed wind-tunnel investigation was undertaken to examine the high-lift devices such as fences, chordwise slots, pylon vortex generators, leading-edge vortex flaps, and sharp leading-edge extensions. The devices were tested individually and in combinations in an attempt to improve high-alpha drag performance with a minimum of low-alpha drag penalty. This report presents an analysis of the force, moment, and static pressure data obtained in angles of attack up to 23 deg, at Mach and Reynolds numbers of 0.16 and 3.85 x 10 to the 6th power per meter, respectively. The results indicate that all the devices produced drag and longitudinal/lateral stability improvements at high lift with, in most cases, minor drag penalties at low angles of attack
Anti-correlated time lags in the Z source GX 5-1: Possible evidence for a truncated accretion disk
We investigate the nature of the inner accretion disk in the neutron star
source GX 5-1 by making a detailed study of time lags between X-rays of
different energies. Using the cross-correlation analysis, we found
anti-correlated hard and soft time lags of the order of a few tens to a few
hundred seconds and the corresponding intensity states were mostly the
horizontal branch (HB) and upper normal branch (NB). The model independent and
dependent spectral analysis showed that during these time lags the structure of
accretion disk significantly varied. Both eastern and western approaches were
used to unfold the X-ray continuum and systematic changes were observed in soft
and hard spectral components. These changes along with a systematic shift in
the frequency of quasi-periodic oscillations (QPOs) made it substantially
evident that the geometry of the accretion disk is truncated. Simultaneous
energy spectral and power density spectral study shows that the production of
the horizontal branch oscillations (HBOs) are closely related to the
Comptonizing region rather than the disk component in the accretion disk. We
found that as the HBO frequency decreases from the hard apex to upper HB, the
disk temperature increases along with an increase in the coronal temperature
which is in sharp contrast with the changes found in black hole binaries where
the decrease in QPO frequency is accompanied by a decrease in the disk
temperature and a simultaneous increase in the coronal temperature. We discuss
the results in the context of re-condensation of coronal material in the inner
region of the disk.Comment: 40 pages, 7 figures, accepted for publication in The Astrophysical
Journal Supplement (ApJS
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