Exact controllability of rational expectations model with multiplicative noise and input delay

This paper considers the rational expectations model with multiplicative noise and input delay,where the system dynamics rely on the conditional expectations of future states.The main contribution is to obtain a sufficient condition for the exact controllability of the rational expectations model.In particular,we derive a sufficient Gramian matrix condition and a rank condition for the delay-free case.The key is the solvability of the backward stochastic difference equations with input delay which is derived from the forward and backward stochastic system.

Active Cancelation of Acoustic Noise in Waveguides by Standard Control Task Decision Usage

Cybernetic decision variants were analyzed in order to use for physical task of active noise cancelation. 10 dB mean active noise cancellation is demonstrated in two decades frequency band by usage of cybernetic decision for acoustical duct physical scale model. The used decision was found on minimization of acoustical field power transfer function from the beginning of waveguide to their end.

Simultaneously Suppressing Low-Frequency and Relaxation Oscillation Intensity Noise in a DBR Single-Frequency Phosphate Fiber Laser

Effective multiple optoelectronic feedback circuits for simultaneously suppressing low-frequency and relaxation oscillation intensity noise in a single-frequency phosphate fiber laser are demonstrated. The forward transfer function, which relates the laser output intensity to the pump modulations, is measured and analyzed. A custom two-path feedback system operating at different frequency bands is designed to adjust the pump current directly. The relative intensity noise is decreased by 20dB from 0.2 to 5kHz and over lOdB from 5 to lOkHz. The relaxation oscillation peak is suppressed by 22dB. In addition, a long term （24h） laser instability of less than 0.05% is achieved.

Behavioral and Physiological Responses of Sea Slug (Onchidium reevesii) to Low-Frequency Noise

A large amount of marine noise pollution from coastal industrial construction and the water transportation industry affects the growth and development of marine life,which is a big issue threatening marine organisms.However,most studies have focused on vertebrates,such as marine mammals and fishes,and little is known about the effects of noise on invertebrates.Therefore,the impacts of low-frequency noise(100,300,and 500 Hz)on behavioral and physiological responsesof the sea slug(Onchidium reevesii)were investigated.Under laboratory conditions,sea slugs were stimulated with low-frequency noise at 100,300,and 500 Hz for 1 h.Then,hemolymph enzyme activities(glucose,albumin,triglycerides,superoxide dismutase,catalase,and malondialdehyde)were measured,and mRNA expression of the hsp70 gene was detected in hemolymph and the nervous system by quantitative realtime polymerase chain reaction(qRT-PCR)analysis,while expression of the hsp70 protein was analyzed by immunohistochemistry.The results demonstrated that sea slugs were away from the stimulus source under the influence of low-frequency noise compared to the control group.Enzyme activities,as well as hsp70 gene mRNA and protein expression levels,were significantly higher in the noiseexposed groups than those in the control group.Overall,these changes indicate that low-frequency noise caused oxidative stress in sea slugs in vivo,and the oxidative damage gradually increased when the noise frequency was increased from 100 to 500 Hz.

Low-Frequency Noise in Gate Tunable Topological Insulator Nanowire Field Emission Transistor near the Dirac Point

Low-frequency flicker noise is usually associated with material defects or imperfection of fabrication procedure. Up to now, there is only very limited knowledge about flicker noise of the topological insulator, whose topologically protected conducting surface is theoretically immune to back scattering. To suppress the bulk conductivity we synthesize antimony doped Bi2Se3 nanowires and conduct transport measurements at cryogenic temperatures. The low-frequency current noise measurement shows that the noise amplitude at the high-drain current regime can be described by Hooge＇s empirical relationship, while the noise level is significantly lower than that predicted by Hooge＇s model near the Dirac point. Furthermore, different frequency responses of noise power spectrum density for specific drain currents at the low drain current regime indicate the complex origin of noise sources of topological insulator.

Influence of Total Ionizing Dose Irradiation on Low-Frequency Noise Responses in Partially Depleted SOI nMOSFETs

Total ionizing dose effect induced low frequency degradations in 130nm partially depleted silicon-on-insulator （SOI） technology are studied by ^60Co γ -ray irradiation. The experimental results show that the flicker noise at the front gate is not affected by the radiation since the radiation induced trapped charge in the thin gate oxide can be ignored. However, both the Lorenz spectrum noise, which is related to the linear kink effect （LKE） at the front gate, and the flicker noise at the back gate are sensitive to radiation. The radiation induced trapped charge in shallow trench isolation and the buried oxide can deplete the nearby body region and can activate the traps which reside in the depletion region. These traps act as a GR center and accelerate the consumption of the accumulated holes in the floating body. It results in the attenuation of the LKE and the increase of the Lorenz spectrum noise. Simultaneously, the radiation induced trapped charge in the buried oxide can directly lead to an enhanced flicker noise at the back gate. The trapped charge density in the buried oxide is extracted to increase from 2.21×10^18 eV^-1 cm^-3 to 3.59×10^18？eV^-1 cm^-3 after irradiation.

Low-Frequency Noise in Amorphous Indium Zinc Oxide Thin Film Transistors with Aluminum Oxide Gate Insulator

Low-frequency noise（LFN） in all operation regions of amorphous indium zinc oxide（a-IZO） thin film transistors（TFTs） with an aluminum oxide gate insulator is investigated. Based on the LFN measured results, we extract the distribution of localized states in the band gap and the spatial distribution of border traps in the gate dielectric,and study the dependence of measured noise on the characteristic temperature of localized states for a-IZO TFTs with Al2 O3 gate dielectric. Further study on the LFN measured results shows that the gate voltage dependent noise data closely obey the mobility fluctuation model, and the average Hooge＇s parameter is about 1.18×10^-3.Considering the relationship between the free carrier number and the field effect mobility, we simulate the LFN using the △N-△μ model, and the total trap density near the IZO/oxide interface is about 1.23×10^18 cm^-3eV^-1.

Noise Control of a Two Stroke Engine Car

Aim To control the noise of two stroke engine Methods On the basis of noise identification,a new muffler and acoustic shield were designed,Results the car's pass-by noise below the national limit Conclusion through proper noise controlling measures,the pass-by noise of two stroke engines could be reduced under national permitting limit.

The Algorithms of Adaptive Active Noise Control Systems in a Duct

On the basis of the theory of adaptive active noise control(AANC) in a duct, this article discusses the algorithms of the adaptive control, compares the algorithm characteristics using LMS, RLS and LSL algorithms in the adaptive filter in the AANC system, derives the recursive formulas of LMS algorithm. and obtains the LMS algorithm in computer simulation using FIR and IIR filters in AANC system. By means of simulation, we compare the attenuation levels with various input signals in AANC system and discuss the effects of step factor, order of filters and sound delay on the algorithm's convergence rate and attenuation level.We also discuss the attenuation levels with sound feedback using are and IIR filters in AANC system.

Adaptive Active Control of Low Frequency Noise in a Duct

Aim To study a method realizing noise control for a physical model of progressive wave in a duct. Methods A mathematical model was constructed and a transfer function of the adaptive system for noise control was also worked out; moreover, the effects of some algorithms such as RLS,LMS and LSL on noise control were analyzed and compared. Results Without the feedback of sound, the mean noise reduce value(MNRV) of 27 5 dB for broadband noise from 0 to 500?Hz in frequency were achieved. When acoustic feedback took place and an air stream loudspeaker was used, the MNRV was only about 4 9?dB. But if the loudspeaker had a plain frequency feature, MNRV was improved by 10 2?dB. Conclusion The technique is applied to ruducing the noise from engines' exhausted gas pipes. It is, in principle, used for noise cancelling in a closed three dimensional space.

Simulation on a Car Interior Aerodynamic Noise Control Based on Statistical Energy Analysis

How to simulate interior aerodynamic noise accurately is an important question of a car interior noise reduction. The unsteady aerodynamic pressure on body surfaces is proved to be the key effect factor of car interior aerodynamic noise control in high frequency on high speed. In this paper, a detail statistical energy analysis （SEA） model is built. And the vibra-acoustic power inputs are loaded on the model for the valid result of car interior noise analysis. The model is the solid foundation for further optimization on car interior noise control. After the most sensitive subsystems for the power contribution to car interior noise are pointed by SEA comprehensive analysis, the sound pressure level of car interior aerodynamic noise can be reduced by improving their sound and damping characteristics. The further vehicle testing results show that it is available to improve the interior acoustic performance by using detailed SEA model, which comprised by more than 80 subsystems, with the unsteady aerodynamic pressure calculation on body surfaces and the materials improvement of sound/damping properties. It is able to acquire more than 2 dB reduction on the central frequency in the spectrum over 800 Hz. The proposed optimization method can be looked as a reference of car interior aerodynamic noise control by the detail SEA model integrated unsteady computational fluid dynamics （CFD） and sensitivity analysis of acoustic contribution.

Adaptive ANFIS-based filter for active control of sinusoidal primary noise in nonlinear path

Linear active noise control (ANC) system is promising in suppressing broadband and narrowband noise in a linear acoustic site.However,in some situations,the acoustic systems are nonlinear which make the primary noise being nonlinear distortion at the canceling point,and the linear ANC system maybe can not work well for these cases.This paper presents an adaptive network-based fuzzy inference system (ANFIS)-based nonlinear filter for active noise control,which is expected to be successfully applied to situations with nonlinear distortion.In the proposed adaptive control algorithm,the parameters are updated by gradient descent method.In the simulations,the secondary-path FIR model coefficients are estimated in advance by off-line system identification method,and one case for sinusoidal primary noise with nonlinear distortion is presented,which verifies the effectiveness of the proposed system in suppressing sinusoidal noise generated by rotating machines,e.g.,engines in vehicles.

Fault tolerant controlled quantum dialogue against collective noise

Quantum system is inevitably affected by the external environment in the real world.Two controlled quantum dialogue protocols are put forward based on logicalχ-type states under collective noise environment.One is against collectivedephasing noise,while the other is against collective-rotation noise.Compared with existing protocols,there exist several outstanding advantages in our proposed protocols:Firstly,theχ-type state is utilized as quantum channels,it possesses better entanglement properties than GHZ state,W state as well as cluster state,which make it difficult to be destroyed by local operations.Secondly,two kinds of logicalχ-type states are constructed by us in theory,which can be perfectly immune to the effects of collective noise.Thirdly,the controller can be offline after quantum distribution and permission announcement,without waiting for all the participants to complete the information coding.Fourthly,the security analysis illuminates that our protocols can not only be free from the information leakage,but also resist against the interceptand-resend attack,the entanglement-and-measure attack,the modification attack,the conspiring attack,and especially the dishonest controller’s attacks.

Adaptive adjustment of iterative learning control gain matrix in harsh noise environment

For the robustness problem of open-loop P-type iterative learning control under the influence of measurement noise which is inevitable in actual systems, an adaptive adjustment algorithm of iterative learning nonlinear gain matrix based on error amplitude is proposed and two nonlinear gain functions are given. Then with the help of Bellman-Gronwall lemma, the robustness proof is derived. At last, an example is simulated and analyzed. The results show that when there exists measurement noise, the proposed learning law adjusts the learning gain matrix on line based on error amplitude, thus can make a compromise between learning convergence rate and convergence accuracy to some extent： the fast convergence rate is achieved with high gain in initial learning stage, the strong robustness and high convergence accuracy are achieved at the same time with small gain in the end learning stage, thus better learning results are obtained.

Feed-Forward Active Noise Control System Using Microphone Array

Feedforward active noise control(ANC)system are widely used to reduce the wide-band noise in different application.In feedforward ANC systems,when the noise source is unknown,the misplacement of the reference microphone may violate the causality constraint.We present a performance analysis of the feedforward ANC system under a noncausal condition.The ANC system performance degrades when the degree of noncausality increases.This research applies the microphone array technique to feedforward ANC systems to solve the unknown noise source problem.The generalized cross-correlation(GCC)and steering response power(SRP)methods based on microphone array are used to estimate the noise source location.Then,the ANC system selects the proper reference microphone for a noise control algorithm.The simulation and experiment results show that the SRP method can estimate the noise source direction with 84%accuracy.The proposed microphone array integrated ANC system can dramatically improve the system performance.

Subjective annoyance caused by indoor low-level and low frequency noise and control method

The influence of low_level noise has not been widely noticed. This paper discovered that low_level and low frequency noise(A_weighted equivalent level L eq <45 dB) causes higher probability of subjective annoyance. The fuzzy mathematic principle was applied to deal with the threshold level of subjective annoyance from noise in this study; there is preferable relationship between the indoor noise and noise annoyance at low frequency noise level. Study indicated at the same centered noise level, the change of annoyance probability is mainly caused by the change of the frequency spectrum characteristic of the indoor noise. Under low noise level environment, without change of the medium_low frequency noise, the slight increase of medium_high frequency noise level with the help of noise sheltering effect can significantly reduce the noise annoyance. This discovery brings a new resolution on how to improve the environmental quality of working or living places. A noise control model is given in this study according to the acoustic analysis.

Noise reduction mechanism of high-speed railway box-girder bridges installed with MTMDs on top plate

The issue of low-frequency structural noise radiated from high-speed railway(HSR) box-girder bridges(BGBs) is a significant challenge worldwide. Although it is known that vibrations in BGBs caused by moving trains can be reduced by installing multiple tuned mass dampers(MTMDs) on the top plate, there is limited research on the noise reduction achieved by this method. This study aims to investigate the noise reduction mechanism of BGBs installed with MTMDs on the top plate. A sound radiation prediction model for the BGB installed with MTMDs is developed, based on the vehicle–track–bridge coupled dynamics and acoustics boundary element method. After being verified by field tested results, the prediction model is employed to study the reduction of vibration and noise of BGBs caused by the MTMDs. It is found that installing MTMDs on top plate can significantly affect the vibration distribution and sound radiation law of BGBs. However, its impact on the sound radiation caused by vibrations dominated by the global modes of BGBs is minimal. The noise reduction achieved by MTMDs is mainly through changing the acoustic radiation contributions of each plate of the bridge. In the lower frequency range, the noise reduction of BGB caused by MTMDs can be more effective if the installation of MTMDs can modify the vibration frequency and distribution of the BGB to avoid the influence of small vibrations and disperse the sound radiation from each plate.

Active Noise Control of the Heavy Truck Interior Cab

In order to control the noise of the heavy truck interior cab effectively, the active noise control methods are employed. First, an interior noise field test for the heavy truck is performed, and frequencies of interior noise of this vehicle are analyzed. According to the spectrum analysis of acquired noise signal, it is found out that the main frequencies of interior noise are less than 800Hz. Then the least squares lattice （LSL） algorithm is used as signal processing algorithm of the controller and a closed-loop control DSP system, based on TMS 320VC5416, is developed. The residual signal at driver＇s ear is used as feedback signal. Lastly, the developed ANC system is loaded into the heavy truck cab, and controlling the noise at driver＇ s ear for that truck at different driving speeds is attempted. The noise control test results indicate that the cab interior noise is reduced averagely by 0.9 dBA at different driving speeds.

Guaranteed control performance robust LQG regulator for discrete-time Markovian jump systems with uncertain noise

Robust LQG problems of discrete-time Markovian jump systems with uncertain noises are investigated. The problem addressed is the construction of perturbation upper bounds on the uncertain noise covariances so as to guarantee that the deviation of the control performance remains within the precision prescribed in actual problems. Furthermore, this regulator is capable of minimizing the worst performance in an uncertain case. A numerical example is exploited to show the validity of the method.

Effect of cavity flow control on high-speed train pantograph and roof aerodynamic noise

The pantograph and its recess on the train roof are major aerodynamic noise sources on high-speed trains.Reducing this noise is particularly important because conventional noise barriers usually do not shield the pantograph.However,less attention has been paid to the pantograph recess compared with the pantograph.In this paper,the flow features and noise contribution of two types of noise reduction treatments rounded and chamfered edges are studied for a simplified high-speed train pantograph recess,which is represented as a rectangular cavity and numerically investigated at 1/10 scale.Improved delayed detached-eddy simulations are performed for the near-field turbulent flow simulation,and the Ffowcs Williams and Hawkings aeroacoustic analogy is used for far-field noise prediction.The highly unsteady flow over the cavity is significantly reduced by the cavity edge modifications,and consequently,the noise radiated from the cavity is reduced.Furthermore,effects of the rounded cavity edges on the flow and noise of the pantographs(one raised and one folded)are investigated by comparing the flow features and noise contributions from the cases with and without rounding of the cavity edges.Different train running directions are also considered.Flow analysis shows that the highly unsteady flow within the cavity is reduced by rounding the cavity edges and a slightly lower flow speed occurs around the upper parts of the raised pantograph,whereas the flow velocity in the cavity is slightly increased by the rounding.Higher pressure fluctuations occur on the folded pantograph and the lower parts of the raised pantograph,whereas weaker fluctuations are found on the panhead of the raised pantograph.This study shows that by rounding the cavity edges,a reduction in radiated noise at the side and the top receiver positions can be achieved.Noise reductions in the other directions can also be found.