scholarly journals Reflected Wave Reduction Based on Time-Delay Separation for the Plane Array of Multilayer Acoustic Absorbers

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8432
Author(s):  
Hwijin Park ◽  
Yeong Bae Won ◽  
Sehyeong Jeong ◽  
Joo Young Pyun ◽  
Kwan Kyu Park ◽  
...  
Keyword(s):  
Time Delay ◽  
Low Frequency ◽  
Acoustic Signals ◽  
Control Technique ◽  
Experimental Comparison ◽  
Frequency Noise ◽  
Attenuation Rate ◽  
Wide Range ◽  
Sound Reduction ◽  
Active Controls

This paper presents a control technique for reducing the reflection of acoustic signals for the plane array of multilayer acoustic absorbers underwater. In order to achieve this, a plane array of multilayer acoustic absorbers is proposed to attenuate low-frequency noise, with each unit consisting of a piezoelectric transducer, two layers of polyvinylidene fluorides and three layers of the acoustic window. Time-delay separation is used to find the incident and reflected acoustic signals to achieve reflected sound reduction. Experimental comparison of the attenuation rate of the reflected acoustic signal when performing passive and active controls is considered to verify the effectiveness of the time-delay separation technique applied plane array absorbers. Experiments on the plane array of smart skin absorbers confirmed that the reduction of reflected acoustic signals makes it suitable for a wide range of underwater applications.

Low Frequency Vibration Isolation Through an Active-on-Active Approach: Coupling Effects

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Qiao Sun ◽  
Robert A. Wolkow ◽  
Mark Salomons
Keyword(s):  
Vibration Isolation ◽  
Low Frequency ◽  
Noise Cancellation ◽  
Frequency Noise ◽  
Active Stage ◽  
Coupling Effects ◽  
Active Approach ◽  
Low Frequency Vibration ◽  
Wide Range ◽  
Coupling Characteristics

The extreme sensitivity of a scanning probe microscope demands an exceptional noise cancellation device that could effectively cut off a wide range of vibration noise. Existing commercial devices, although excellent in canceling high frequency noise, commonly leave low frequency vibration unattenuated. We design an add-on active stage that can function together with a standalone existing active stage. The objective is to provide a higher level of noise cancellation by lowering the overall system cut-off frequency. This study is concerned with the theoretical aspects of the coupling characteristics involved in stacking independently designed stages together to form a two-stage isolator. Whether an add-on stage would pose a stability threat to the existing stage needs to be addressed. In addition, we explore the use of coupling effects to optimize the performance of the overall system.

Cascade controllers design based on model matching in frequency domain for stable and integrating processes with time delay

2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohd Atif Siddiqui ◽  
Md Nishat Anwar ◽  
Shahedul Haque Laskar
Keyword(s):  
Time Delay ◽  
Frequency Domain ◽  
Disturbance Rejection ◽  
Low Frequency ◽  
Cascade Control ◽  
Model Matching ◽  
Content Type ◽  
Proportional Integral ◽  
Load Disturbance ◽  
Wide Range

Purpose This paper aims to present an efficient and simplified proportional-integral/proportional-integral and derivative controller design method for the higher-order stable and integrating processes with time delay in the cascade control structure (CCS). Design/methodology/approach Two approaches based on model matching in the frequency domain have been proposed for tuning the controllers of the CCS. The first approach is based on achieving the desired load disturbance rejection performance, whereas the second approach is proposed to achieve the desired setpoint performance. In both the approaches, matching between the desired model and the closed-loop system with the controller is done at a low-frequency point. Model matching at low-frequency points yields a linear algebraic equation and the solution to these equations yields the controller parameters. Findings Simulations have been conducted on several examples covering high order stable, integrating, double integrating processes with time delay and nonlinear continuous stirred tank reactor. The performance of the proposed scheme has been compared with recently reported work having modified cascade control configurations, sliding mode control, model predictive control and fractional order control. The performance of both the proposed schemes is either better or comparable with the recently reported methods. However, the proposed method based on desired load disturbance rejection performance outperforms among all these schemes. Originality/value The main advantages of the proposed approaches are that they are directly applicable to any order processes, as they are free from time delay approximation and plant order reduction. In addition to this, the proposed schemes are capable of handling a wide range of different dynamical processes in a unified way.

scholarly journals Micromechanical Process Integration and Material Optimization for High Performance Silicon-Germanium Bolometers

2012 ◽  
Vol 1437 ◽  
Author(s):  
Gunnar B. Malm ◽  
Mohammadreza Kolahdouz ◽  
Fredrik Forsberg ◽  
Niclas Roxhed ◽  
Frank Niklaus
Keyword(s):  
Integrated Circuits ◽  
Silicon Germanium ◽  
High Performance ◽  
Large Scale ◽  
Process Integration ◽  
Low Frequency ◽  
Single Layer ◽  
Sige Layer ◽  
Frequency Noise ◽  
Wide Range

ABSTRACTSemiconductor-based thermistors are very attractive sensor materials for uncooled thermal infrared (IR) bolometers. Very large scale heterogeneous integration of MEMS is an emerging technology that allows the integration of epitaxially grown, high-performance IR bolometer thermistor materials with pre-processed CMOS-based integrated circuits for the sensor read-out. Thermistor materials based on alternating silicon (Si) and silicon-germanium (SiGe) epitaxial layers have been demonstrated and their performance is continuously increasing. Compared to a single layer of silicon or SiGe, the temperature coefficient of resistance (TCR) can be strongly enhanced to about 3 %/K, by using thin alternating layers. In this paper we report on the optimization of alternating Si/SiGe layers by advanced physically based simulations, including quantum mechanical corrections. Our simulation framework provides reliable predictions for a wide range of SiGe layer compositions, including concentration gradients. Finally, our SiGe thermistor layers have been evaluated in terms of low-frequency noise performance, in order to optimize the bolometer detectivity.

Research on High Dynamic Target Electro-Optical Tracking Based Improved Robust Disturbance Observer

2011 ◽  
Vol 328-330 ◽  
pp. 2215-2219
Author(s):  
Xiang Yu ◽  
Zheng Hua Liu ◽  
Yan Ren
Keyword(s):  
Disturbance Observer ◽  
Control Method ◽  
Tracking System ◽  
Effective Means ◽  
Low Frequency ◽  
Optical Tracking ◽  
Control Technique ◽  
Frequency Noise ◽  
Optical Tracking System ◽  
Dynamic Target

The compound axis control technique is an effective means to improve the accuracy and bandwidth of high precision electro-optical tracking systems. However, traditional methods of lead and lag correction can not achieve ideal performance. The robust control method based on the disturbance observer (DOB) is introduced in this paper, and the method is applied to the electro-optical tracking system together with the Kalman Filter. Compared to the traditional method of lead and lag correction, the method based on DOB can inhibit high-frequency noise and compensate for low-frequency interference better, such as frictions, and achieve better precision finally.

Optimal Stiffener Design for Interior Sound Reduction Using a Topology Optimization Based Approach

2003 ◽  
Vol 125 (3) ◽  
pp. 267-273 ◽  
Author(s):  
Jianhui Luo ◽  
Hae Chang Gea
Keyword(s):  
Topology Optimization ◽  
Optimization Problem ◽  
Low Frequency ◽  
Coupled System ◽  
Conservative System ◽  
Sound Level ◽  
Single Frequency ◽  
Frequency Noise ◽  
Topology Optimization Problem ◽  
Sound Reduction

A topology optimization based approach is proposed to study the optimal configuration of stiffeners for the interior sound reduction. Since our design target is aimed at reducing the low frequency noise, a coupled acoustic-structural conservative system without damping effect is considered. Modal analysis method is used to evaluate the interior sound level for this coupled system. To formulate the topology optimization problem, a recently introduced Microstructure-based Design Domain Method (MDDM) is employed. Using the MDDM, the optimal stiffener configurations problem is treated as a material distribution problem and sensitivity analysis of the coupled system is derived analytically. The norm of acoustic excitation is used as the indicator of the interior sound level. The optimal stiffener design is obtained by solving this topology optimization problem using a sequential convex approximation method. Examples of acoustic box under single frequency excitation and a band of low frequency excitations are presented and discussed.

scholarly journals Evidence that ship noise increases stress in right whales

2012 ◽  
Vol 279 (1737) ◽  
pp. 2363-2368 ◽  
Author(s):  
Rosalind M. Rolland ◽  
Susan E. Parks ◽  
Kathleen E. Hunt ◽  
Manuel Castellote ◽  
Peter J. Corkeron ◽  
...  
Keyword(s):  
Low Frequency ◽  
Acoustic Signals ◽  
Frequency Noise ◽  
Underwater Noise ◽  
Baleen Whales ◽  
Ship Traffic ◽  
Right Whale ◽  
Right Whales ◽  
North Atlantic Right Whales ◽  
Shipping Traffic

Baleen whales ( Mysticeti ) communicate using low-frequency acoustic signals. These long-wavelength sounds can be detected over hundreds of kilometres, potentially allowing contact over large distances. Low-frequency noise from large ships (20–200 Hz) overlaps acoustic signals used by baleen whales, and increased levels of underwater noise have been documented in areas with high shipping traffic. Reported responses of whales to increased noise include: habitat displacement, behavioural changes and alterations in the intensity, frequency and intervals of calls. However, it has been unclear whether exposure to noise results in physiological responses that may lead to significant consequences for individuals or populations. Here, we show that reduced ship traffic in the Bay of Fundy, Canada, following the events of 11 September 2001, resulted in a 6 dB decrease in underwater noise with a significant reduction below 150 Hz. This noise reduction was associated with decreased baseline levels of stress-related faecal hormone metabolites (glucocorticoids) in North Atlantic right whales ( Eubalaena glacialis ). This is the first evidence that exposure to low-frequency ship noise may be associated with chronic stress in whales, and has implications for all baleen whales in heavy ship traffic areas, and for recovery of this endangered right whale population.

Theoretical End Experimental Evaluation of Perforations Effect on Sound Insulation

2017 ◽  
Author(s):  
Olga Khrystoslavenko ◽  
Raimondas Grubliauskas
Keyword(s):  
Noise Reduction ◽  
High Frequency ◽  
Sound Absorption ◽  
Low Frequency ◽  
Experimental Methods ◽  
Glass Wool ◽  
Acoustic Properties ◽  
Sound Insulation ◽  
Frequency Noise ◽  
Sound Reduction

To design a sound-absorbing panel, it is important to identify factors that affect the maximum sound absorption of low, middle and high frequency sounds. Perforation effect is very important for the noise-reducing and noiseabsorbing panels. Perforations are often used for sound reduction. Experimental data shows that the perforation is very effective to absorb low-frequency noise. In the presented study, influence of perforation coefficient of noise reduction was analyzed with theoretical and experimental methods. The experiments were conducted in noise reduction chamber using an perforated construction with glass wool filler. Sound reductions index of 15 dB indicates good acoustic properties of the panel.

scholarly journals Low Noise Programmable DC Amplifier with Remote Control

2019 ◽  
Vol 22 (4) ◽  
pp. 99-108
Author(s):  
Viktor E. Ivanov ◽  
Chye En Un
Keyword(s):  
Flicker Noise ◽  
Experimental Studies ◽  
Low Frequency ◽  
Intrinsic Noise ◽  
Measuring Channel ◽  
Low Noise ◽  
Measuring System ◽  
Frequency Noise ◽  
Measuring Systems ◽  
Wide Range

Introduction. In modern experimental technology, the direction associated with the development of information-measuring systems for recording, pre-processing and analyzing excess low-frequency noise (flicker noise) is well known. Currently, such measuring systems are mainly presented in the form of particular solutions, due to the large variety of research goals and objectives. At the same time, for automation of the experiment, multichannel measuring complexes with the possibility of flexible reconfiguration of the measuring channel according to the task are highly demanded. It is obvious that any distributed measuring channel is represented as a multi-stage scheme with given functions and parameters of each stage, which makes it difficult for the measuring system to adapt to different conditions and tasks of the experiment. The logical solution to this problem is a deep unification of all components of the measuring channel while maintaining good performance characteristics. One of the main problems with this is the evaluation of the intrinsic noise of electronic elements, which provide for changing the parameters of the amplifier.Objective. Experimental analysis of the intrinsic noise of electronic potentiometers, development of the concept and study of parameters of a low-noise DC amplifier with a high degree of unification, the possibility of external electronic control and the use of built-in characteristics correction algorithms.Materials and methods. To achieve the set result, a method for measuring the noise of electronic potentiometers was proposed and experimental studies were carried out.Results. According to the calculation results and experimental studies, it was shown that the specific noise of the electronic potentiometers corresponds to the noise of the metal-film resistors, which makes it possible to use them in low-noise amplification stages. The developed circuit solutions allow the implementation of a unified amplifying module with cascading to build low-noise measuring DC paths based on electronic potentiometers. External and internal digital control allows you to significantly improve the performance of the measuring path as a whole and allows you to adapt it to a wide range of tasks.Conclusion. As part of the study, a method was proposed for measuring the noise of electronic potentiometers, analytical and experimental studies were carried out, and a prototype of a low-noise amplifier was developed and investigated.

scholarly journals Rigid DNA nanotube tethers suppress high frequency noise in dual-trap optical tweezers systems

2021 ◽  
Author(s):  
Alan Shaw ◽  
Rohit Satija ◽  
Eduardo Antunez de Mayolo De la Matta ◽  
Susan Marqusee ◽  
Carlos Bustamante
Keyword(s):  
Optical Tweezers ◽  
Molecular Motors ◽  
High Frequency ◽  
Low Frequency ◽  
Frequency Noise ◽  
High Frequency Noise ◽  
Wide Range ◽  
Length Changes ◽  
Force Range ◽  
Dna Nanotube

Dual trap optical tweezers are a powerful tool to trap and characterize the biophysical properties of single biomolecules such as the folding pathways of proteins and nucleic acids, and the chemomechanical activity of molecular motors. Despite its vastly successful application, noise from drift and fluctuation of the optics, and Brownian motion of the trapped beads still hinder the technique's ability to directly visualize folding of small biomolecules or the single nucleotide stepping of polymerases, especially at low forces (<10 pN) and sub-millisecond timescales. Rigid DNA nanotubes have been used to replace the conventional dsDNA linker to reduce optical tweezers noise in the low force range. However, optical tweezers are used to study a wide range of biophysical events, with timescales ranging from microseconds to seconds, and length changes ranging from sub nanometers to tens of nanometers. In this study, we systematically evaluate how noise is distributed across different frequencies in dual trap optical tweezers systems and show that rigid DNA nanotube tethers suppress only high frequency noise (kHz), while the low frequency noise remains the same when compared to that of dsDNA tethers.

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