36,613 research outputs found
Robust H∞ feedback control for uncertain stochastic delayed genetic regulatory networks with additive and multiplicative noise
The official published version can found at the link below.Noises are ubiquitous in genetic regulatory networks (GRNs). Gene regulation is inherently a stochastic process because of intrinsic and extrinsic noises that cause kinetic parameter variations and basal rate disturbance. Time delays are usually inevitable due to different biochemical reactions in such GRNs. In this paper, a delayed stochastic model with additive and multiplicative noises is utilized to describe stochastic GRNs. A feedback gene controller design scheme is proposed to guarantee that the GRN is mean-square asymptotically stable with noise attenuation, where the structure of the controllers can be specified according to engineering requirements. By applying control theory and mathematical tools, the analytical solution to the control design problem is given, which helps to provide some insight into synthetic biology and systems biology. The control scheme is employed in a three-gene network to illustrate the applicability and usefulness of the design.This work was funded by Royal Society of the U.K.; Foundation for the Author of National Excellent Doctoral Dissertation of China. Grant Number: 2007E4; Heilongjiang Outstanding Youth Science Fund of China. Grant Number: JC200809; Fok Ying Tung Education Foundation. Grant Number: 111064; International Science and Technology Cooperation Project of China. Grant Number: 2009DFA32050; University of Science and Technology of China Graduate Innovative Foundation
Carrier Sense Random Packet CDMA Protocol in Dual-Channel Networks
Code resource wastage is caused by the reason that many hopping frequency (FH) sequences are unused, which occurs under the condition that the number of the actual subnets needed for the tactical network is far smaller than the networking capacity of code division net¬working. Dual-channel network (DCN), consisting of one single control channel and multiple data channels, can solve the code resource wastage effectively. To improve the anti-jamming capability of the control channel of DCN, code division multiple access (CDMA) technology was introduced, and a carrier sense random packet (CSRP) CDMA protocol based on random packet CDMA (RP-CDMA) was proposed. In CSRP-CDMA, we provide a carrier sensing random packet mechanism and a packet-segment acknowledgement policy. Furthermore, an analytical model was developed to evaluate the performance of CSRP-CDMA networks. In this model, the impacts of multi-access interference from both inter-clusters and intra-clusters were analyzed, and the mathematical expressions of packet transmission success probability, normalized network throughput and signal interference to noise ratio, were also derived. Analytical and simulation results demonstrate that the normalized network throughput of CSRP-CDMA outperforms traditional RP-CDMA by 10%, which can guarantee the resource utilization efficiency of the control channel in DCNs
Effective Mass of the Four Flux Composite Fermion at
We have measured the effective mass () of the four flux composite
fermion at Landau level filling factor (CF), using the
activation energy gaps at the fractional quantum Hall effect (FQHE) states
= 2/7, 3/11, and 4/15 and the temperature dependence of the Shubnikov-de
Haas (SdH) oscillations around . We find that the energy gaps show a
linear dependence on the effective magnetic field (), and from this linear dependence we obtain and
a disorder broadening 1 K for a sample of density /cm. The deduced from the temperature dependence of
the SdH effect shows large differences for and . For
, . It scales as with the mass
derived from the data around and shows an increase in as , resembling the findings around . For ,
increases rapidly with increasing and can be described by . This anomalous dependence on is
precursory to the formation of the insulating phase at still lower filling.Comment: 5 pages, 3 figure
Spatial oscillations in the spontaneous emission rate of an atom inside a metallic wedge
A method of images is applied to study the spontaneous emission of an atom
inside a metallic wedge with an opening angle of , where N is an
arbitrary positive integer. We show the method of images gives a rate formula
consistent with that from Quantum Electrodynamics. Using the method of images,
we show the correspondence between the oscillations in the spontaneous emission
rate and the closed-orbits of emitted photon going away and returning to the
atom inside the wedge. The closed-orbits can be readily constructed using the
method of images and they are also extracted from the spontaneous emission
rate.Comment: 8 figure
General covariant geometric momentum, gauge potential and a Dirac fermion on a two-dimensional sphere
For a particle that is constrained on an ()-dimensional ()
curved surface, the Cartesian components of its momentum in -dimensional
flat space is believed to offer a proper form of momentum for the particle on
the surface, which is called the geometric momentum as it depends on the mean
curvature. Once the momentum is made general covariance, the spin connection
part can be interpreted as a gauge potential. The present study consists in two
parts, the first is a discussion of the general framework for the general
covariant geometric momentum. The second is devoted to a study of a Dirac
fermion on a two-dimensional sphere and we show that there is the generalized
total angular momentum whose three cartesian components form the
algebra, obtained before by consideration of dynamics of the particle, and we
demonstrate that there is no curvature-induced geometric potential for the
fermion.Comment: 8 pages, no figure. Presentation improve
Semi-active control of an integrated full-car suspension with seat suspension and driver body model using ER dampers
In this paper, an integrated vehicle semi-active suspension control system that includes a full-car suspension model (7 Degree-Of-Freedom (DOF)), a seat suspension model (2 DOF) and a driver body model (4 DOF) is developed. A H∞ static output feedback controller which only uses measurable variables as feedback signals is designed to improve vehicle ride comfort performance in terms of driver head acceleration under constraints of actuator saturation, suspension deflection limitation and road holding capability. The controller design conditions, which are expressed as Linear Matrix Inequalities (LMIs) are derived by dealing with each control input separately under a common Lyapunov function, so that a feasible solution can be found for the integrated high order system that has five control inputs and ten control outputs; each control input may require different feedback signals and have different saturation limitations. Furthermore, a semiactive control strategy is applied to implement the proposed control system using electrorheological (ER) dampers. Numerical simulations are used to evaluate theimprovement of ride comfort performance in terms of driver head acceleration responses under typical road disturbances
Detection of OD towards the low-mass protostar IRAS16293-2422
Although water is an essential and widespread molecule in star-forming
regions, its chemical formation pathways are still not very well constrained.
Observing the level of deuterium fractionation of OH, a radical involved in the
water chemical network, is a promising way to infer its chemical origin. We aim
at understanding the formation mechanisms of water by investigating the origin
of its deuterium fractionation. This can be achieved by observing the abundance
of OD towards the low-mass protostar IRAS16293-2422, where the HDO distribution
is already known. Using the GREAT receiver on board SOFIA, we observed the
ground-state OD transition at 1391.5 GHz towards the low-mass protostar
IRAS16293-2422. We also present the detection of the HDO 111-000 line using the
APEX telescope. We compare the OD/HDO abundance ratio inferred from these
observations with the predictions of chemical models. The OD line is detected
in absorption towards the source continuum. This is the first detection of OD
outside the solar system. The SOFIA observation, coupled to the observation of
the HDO 111-000 line, provides an estimate of the abundance ratio OD/HDO ~
17-90 in the gas where the absorption takes place. This value is fairly high
compared with model predictions. This may be reconciled if reprocessing in the
gas by means of the dissociative recombination of H2DO+ further fractionates OH
with respect to water. The present observation demonstrates the capability of
the SOFIA/GREAT instrument to detect the ground transition of OD towards
star-forming regions in a frequency range that was not accessible before.
Dissociative recombination of H2DO+ may play an important role in setting a
high OD abundance. Measuring the branching ratios of this reaction in the
laboratory will be of great value for chemical models.Comment: 6 pages, 6 figures, 3 tables, accepted for publication in A&A
SOFIA/GREAT special issu
A half-car model for dynamic analysis of vehicles with random parameters
A half-car model is used to investigate the dynamic response of cars with uncertainty under random road input excitations in this paper. The mass of the vehicle body, mass moment of inertia of the vehicle body, masses of the front/rear wheels, damping coefficients and spring stiffness of front/rear suspensions, distances of the front/rear suspension locations to the centre of gravity of the vehicle body and the stiffness of front/rear tires are considered as random variables. The road irregularity is considered a Gaussian random process and modeled by means of a simple exponential power spectral density. The mean value and standard deviation of the vehicle’s natural frequencies and mean square value of vehicle’s random response are obtained by using the Monte-Carlo simulation method. The influences of the randomness of the vehicle’s parameters on the vehicle’s dynamic characteristic and response are investigated in detail using a practical example
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