334 research outputs found
Stabilization and Performance over a Gaussian Communication Channel for a Plant with Time Delay
Two problems that have received much attention are those of finding the minimum channel signal to noise ratio compatible with closed loop stability, and of finding the optimal performance, in terms of disturbance attenuation, for a channel with specified signal to noise ratio. In this paper, we study these problems for the case in which the plant has relative degree greater than one, and thus introduces a delay greater than one time step. We show that, unlike the relative degree one case, for the problem of stabilization linear time varying control and communication strategies may have advantages over linear
time invariant strategies. We derive a lower bound on optimal disturbance response at a fixed terminal time. If the encoder has access to the state of the plant, then this bound is achievable using linear time varying communication and control
Piezoelectric power scavenging of mechanical vibration energy
The process of acquiring the energy surrounding a system and converting it into usable electrical energy is termed power harvesting. With piezoceramic materials, it is possible to harvest power from vibrating structures. It has been proven that micro-to milliwatts of power can be generated from vibrating systems. The project targets the
transformation of mechanical vibration into electrical energy using piezoelectric material. In some mining applications, eg water jet drilling; large high frequency
vibrations may be present. If successfully harvested, this energy could be used to eliminate batteries in wireless sensors. This article presents a model of a piezoelectric
transducer, a mechanical vibration spectrum, the simulation of the model, prototype of the power scavenging circuit, experimental results and its future perspectives
Piezoelectric power scavenging of mechanical vibration energy
The process of acquiring the energy surrounding a system and converting it into usable electrical energy is termed power harvesting. With piezoceramic materials, it is possible to harvest power from vibrating structures. It has been proven that micro-to milliwatts of power can be generated from vibrating systems. The project targets the
transformation of mechanical vibration into electrical energy using piezoelectric material. In some mining applications, eg water jet drilling; large high frequency
vibrations may be present. If successfully harvested, this energy could be used to eliminate batteries in wireless sensors. This article presents a model of a piezoelectric
transducer, a mechanical vibration spectrum, the simulation of the model, prototype of the power scavenging circuit, experimental results and its future perspectives
Fundamental Limitations in Control over a Communication Channel
Fundamental limitations in feedback control is a well established area of research.
In recent years it has been extended to the study of limitations imposed by the
consideration of a communication channel in the control loop. Previous results characterised these limitations in terms of a minimal data transmission rate necessary
for stabilisation. In this paper a signal-to-noise ratio (SNR) approach is used to
obtain a tight condition for the linear time invariant output feedback stabilisation
of a continuous-time, unstable, non minimum phase (NMP) plant with time-delay
over an additive Gaussian coloured noise communication channel. By working on a
linear setting the infimal SNR for stabilisability is defined as the infimal achievable
H2 norm between the channel noise input and the channel signal input. The result
gives a guideline in estimating the severity of the fundamental SNR limitation imposed by the plant unstable poles, NMP zeros, time-delay as well as the channel
NMP zeros, bandwidth, and channel noise colouring
Minimum Variance Control over a Gaussian Communication Channel
We consider the problem of minimizing the response
of a plant output to a stochastic disturbance using a
control law that relies on the output of a noisy communication
channel. We discuss a lower bound on the performance
achievable at a specified terminal time using nonlinear timevarying
communication and control strategies, and show that
this bound may be achieved using strategies that are linear
Reducing computational time via order reduction of a class of reaction–diffusion systems
In this paper, we consider a class of reaction–
diffusion PDEs. For this class, a suitable state transformation
allows conversion to a heat equation together with a lower
order PDE set. By giving an explicit solution to the heat
equation we are able to obtain a complete solution to the
original PDE. By focusing on the computational load, we
give a comparison of the pure numerical, analytical/numerical,
analytical/approximated, and approximated methods of solving
the PDE. In some examples, we note an almost order of
magnitude improvement in computational load
A first-in-human phase I study to determine the maximum tolerated dose of the oral Src/ABL inhibitor AZD0424
BACKGROUND: Src is involved in cancer invasion and metastasis. AZD0424, an oral inhibitor of Src and ABL1, has shown evidence of anti-tumour activity in pre-clinical studies. METHODS: A phase Ia, dose escalation study was performed to assess the safety of continuous oral dosing with AZD0424 in advanced solid tumours. Secondary objectives included investigation of AZD0424 pharmacokinetics, effect on Src activity using markers of bone turnover, and anti-tumour activity. RESULTS: 41 patients were treated; 34 received AZD0424 once-daily at doses ranging from 5 mg to 150 mg, and 7 received 40 mg bi-daily 41.5% of patients experienced at least one AZD0424-related adverse event that was Grade 3-5 in severity, with patients treated at doses above 60 mg per day experiencing multiple treatment-related toxicities. The most commonly observed AZD0424-related adverse events were nausea, fatigue, anorexia and alopecia. Cmaxand AUC increased linearly with dose and the mean±standard deviation t1/2was 8.4±2.8 h. Clear evidence of Src target inhibition was seen at doses ⩾20 mg per day. No responses were observed and 7 patients (17.1%) achieved stable disease lasting 6 weeks or more. CONCLUSIONS: AZD0424 displayed no evidence of efficacy as monotherapy despite a clear pharmacodynamic effect. Further evaluation of AZD0424 monotherapy in patients with solid tumours is not recommended
Scaling and self-averaging in the three-dimensional random-field Ising model
We investigate, by means of extensive Monte Carlo simulations, the magnetic
critical behavior of the three-dimensional bimodal random-field Ising model at
the strong disorder regime. We present results in favor of the two-exponent
scaling scenario, , where and are the
critical exponents describing the power-law decay of the connected and
disconnected correlation functions and we illustrate, using various finite-size
measures and properly defined noise to signal ratios, the strong violation of
self-averaging of the model in the ordered phase.Comment: 8 pages, 6 figures, to be published in Eur. Phys. J.
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS
The chi_b(nP) quarkonium states are produced in proton-proton collisions at
the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS
detector. Using a data sample corresponding to an integrated luminosity of 4.4
fb^-1, these states are reconstructed through their radiative decays to
Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks
corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new
structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is
also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes.
This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table,
corrected author list, matches final version in Physical Review Letter
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