Attenuation Methods Research Articles

A brief history of underwater construction noise

Underwater sound from marine construction became an important issue around the year 2000 because of the potential impacts to marine mammals and fish that are protected by the Endangered Species Act. While protections were in place for marine mammals, there was no guidance for protecting fish. Early on, pile driving was found to visibly injure fish, leading to efforts to reduce sounds, develop protective regulatory thresholds, and research the effects of sound on aquatic species. Over the last 16 years, extensive measurements have been conducted and compiled, protective thresholds have been developed and updated, noise attenuation systems or methods have been improved and tested, and research has been conducted. This paper provides an overview of the different types of sounds characterized, thresholds for protecting animals and the types of noise mitigation strategies employed. Sounds characterized include various types of pile driving in and near water, use of explosives in and near water, mechanical demolition, and dredging-type sounds. The various types of thresholds and methodology for applying those thresholds are discussed. Finally, sounds measured from the various types of attenuation systems are summarized.

Noise Reduction Disturbance Observer for Disturbance Attenuation and Noise Suppression

In most research works on the disturbance observer (DOB)-based controller, stability conditions are only sufficient and not effective for handling large uncertainties. To deal with large uncertainties, a necessary and sufficient condition for robust stability has been recently provided by utilizing a novel design technique for the Q -filter. Although this design method can deal with large uncertainties, it is not capable of suppressing the effect of sensor noise. To achieve noise suppression as well as disturbance attenuation, this paper proposes a robust controller by utilizing a modified DOB structure. In contrast to the conventional DOB structure, noise suppression ability of the proposed controller can be adjusted by an appropriate choice of the Q -filter. Moreover, a necessary and sufficient condition for the modified DOB system to be robustly stable is newly presented. To show the effectiveness of the proposed controller, the performance is compared with other disturbance attenuation methods through simulation studies. Finally, in order to verify the validity of the proposed method, laboratory experiments are also conducted with brushless dc motor drives, which confirms that the proposed controller is quite useful for attenuating both input disturbance and sensor noise, while DOB controller is not capable of suppressing sensor noise.

Time-invariant radon transform by generalized Fourier slice theorem

Time-invariant Radon transforms play an important role in many fields of imaging sciences, whereby a function is transformed linearly by integrating it along specific paths, e.g. straight lines, parabolas, etc. In the case of linear Radon transform, the Fourier slice theorem establishes a simple analytic relationship between the 2-D Fourier representation of the function and the 1-D Fourier representation of its Radon transform. However, the theorem can not be utilized for computing the Radon integral along paths other than straight lines. We generalize the Fourier slice theorem to make it applicable to general time-invariant Radon transforms. Specifically, we derive an analytic expression that connects the 1-D Fourier coefficients of the function to the 2-D Fourier coefficients of its general Radon transform. For discrete data, the model coefficients are defined over the data coefficients on non-Cartesian points. It is shown numerically that a simple linear interpolation provide satisfactory results and in this case implementations of both the inverse operator and its adjoint are fast in the sense that they run in $O(N \;\text{log}\; N)$ flops, where $N$ is the maximum number of samples in the data space or model space. These two canonical operators are utilized for efficient implementation of the sparse Radon transform via the split Bregman iterative method. We provide numerical examples showing high-performance of this method for noise attenuation and wavefield separation in seismic data.

Development of Silencer for Low-Power Internal Combustion Engines

This article relates to the field of acoustics and deals with the problem of noise attenuation of low-power internal combustion engines. Due to the fact that the flow resistance increases when the noise decreases, the authors elaborated and researched various configurations of silencers and the methods of noise attenuation. During the study on a test bench in the form of a chainsaw the acoustic characteristics and the hydraulic resistances of the created silencers were determined. According to the obtained results of the research the most effective method of silencing the low-power internal combustion engine was identified.

Continuous Glucose Monitoring Sensors: Past, Present and Future Algorithmic Challenges.

Continuous glucose monitoring (CGM) sensors are portable devices that allow measuring and visualizing the glucose concentration in real time almost continuously for several days and are provided with hypo/hyperglycemic alerts and glucose trend information. CGM sensors have revolutionized Type 1 diabetes (T1D) management, improving glucose control when used adjunctively to self-monitoring blood glucose systems. Furthermore, CGM devices have stimulated the development of applications that were impossible to create without a continuous-time glucose signal, e.g., real-time predictive alerts of hypo/hyperglycemic episodes based on the prediction of future glucose concentration, automatic basal insulin attenuation methods for hypoglycemia prevention, and the artificial pancreas. However, CGM sensors’ lack of accuracy and reliability limited their usability in the clinical practice, calling upon the academic community for the development of suitable signal processing methods to improve CGM performance. The aim of this paper is to review the past and present algorithmic challenges of CGM sensors, to show how they have been tackled by our research group, and to identify the possible future ones.

Damping of VFTO in Gas-Insulated Switchgear by a New Coating Material

Several methods of attenuation of very-fast transient overvoltages (VFTOs) in gas-insulated switchgear (GIS) are under development. An approach that is currently gaining high attention among researchers is based on the application of magnetic cores dissipating the energy associated with VFTO due to eddy current losses and magnetic hysteresis losses. This paper presents an advancement in this approach by introducing a new material type (denoted in this paper as “nanoflakes”). This new material comprises macro pieces of nanocrystalline ribbons (with the size ranging in square millimeters), acquired from crumbled nanocrystalline cores of a standard design. The material is characterized by relatively high magnetic permeability, poor electrical conductivity, and high saturation flux level. The material is suitable for application as a coating layer applied to the surfaces of an inner and/or an outer GIS conductor, as a fill-in material in the GIS shielding elements, or as a standard shaped core. This paper presents the material major features, outlines its development process, and reports on validation of the material effectiveness in real VFTO conditions. The validation is based on the measurement of VFTO attenuation in a full-scale 550 kV GIS test setup.

Seismic arrival enhancement through the use of noise whitening

A constant feature in seismic data, noise is particularly troublesome for passive seismic monitoring where noise commonly masks microseismic events. We propose a statistics-driven noise suppression technique that whitens the noise through the calculation and removal of the noise’s covariance. Noise whitening is shown to reduce the noise energy by a factor of 3.5 resulting in microseismic events being observed and imaged at lower signal to noise ratios than originally possible – whilst having negligible effect on the seismic wavelet. The procedure is shown to be highly resistant to most changes in the noise properties and has the flexibility of being used as a stand-alone technique or as a first step before standard random noise attenuation methods.

Comparison of electrostatic charge and beta attenuation mass monitors for continuous airborne PM10 monitoring under field conditions

An electrostatic PM10 mass monitor (EPMM) used for wireless continuous airborne particulate matter monitoring was developed and evaluated in our previous work. However, differences in measured PM10 mass concentrations between the electrostatic charge and the beta ray attenuation methods due to the frequent occurrence of high humidity and temperature in the ambient air in Thailand’s have not been extensively studied in our previous work; and in the literature, it would be necessary to compare the output of the EPMM against the beta ray attenuation mass monitor. In this study, we evaluated the performance of the EPMM simultaneously with a commercially available FH62C14 Beta gauge continuous ambient particulate monitor, Thermo Fisher Scientific Inc., for PM10 measurements at ambient condition in the field. The measurements were made at Yupparaj Wittayalai School, Si Phum, Mueang, Chiang Mai, Thailand from November 16-23, 2015. They showed that the averages of PM10 mass concentrations measured by the EPMM linearly correlate very well with the PM10 mass concentrations measured by the FH62C14. The slopes were 0.9620 and 1.0649 for 1 and 24-hour, respectively, and R2 of 0.8634 and 0.9889 for 1 and 24-hour, respectively. Finally, this comparison proved to be particularly useful in the refinement and design of the EPMM.

Transfer matrix methods for sound attenuation in resonators with perforated intruding inlets

A resonator with perforated intruding inlet (PII) is a superior silencer element, since the use of perforated inlet extensions can dramatically improve the acoustic performance. In this work, both a one-dimensional (1D) and a two-dimensional (2D) transfer matrix methods are developed to predict the transmission loss of the resonator without considering the mean flow. Based on the two groups of comparisons with tests, it is found out that the applicability of 1D method is limited by the resonator geometry even when the frequency is below the cut-off value of plane wave. Whereas the 2D approach is much more accurate while predicting the transmission losses within entire frequency range. Subsequently, five groups of resonators are chosen to determine the effects of structure parameters to transmission loss based on the 2D approach. The resonant frequency decreases and more resonant peaks appear when the length of inlet extension increases. A higher perforation rate leads to a shift of resonant peak towards higher frequencies. Besides, better acoustic performance could be obtained with the perforation being properly designed. Reducing the inlet/outlet radius can obviously improve the transmission loss without changing the frequency of resonant peak. The theories and conclusions in this study can be used for the design and optimization of resonators in various engineering applications.

Determination of the Absorption Coefficient and Cloudiness Multiplicity Attenuation During the Gamma-Radiation Passage

The paper presents background value equivalent dose of gamma-radiation investigation in different weather: clear cloudy and overcast. The change of the dose rate of gamma radiation, depending on the weather and the ability cloudiness to shield gamma rays is shown. A new method for eliminating the consequences of accidents at nuclear power plants or plants using radioactive elements is proposed. A calculation method of cloudiness coefficient absorption and cloudiness gamma-radiation multiplicity attenuation is developed. The gamma- radiation multiplicity attenuation and the absorption coefficient of gamma radiation were calculated.

Lifetime measurements in the yrast band of the gamma-soft nuclei 131Ce and 133Pr

Lifetimes of excited states in the yrast band of the gamma-soft nuclei 131Ce and 133Pr have been measured using the recoil distance Doppler shift and Doppler shift attenuation methods. The yrast bands in 131Ce and 133Pr are based on odd decoupled neutron νh 11/2 high Ω and proton π h 11/2 low Ω orbitals, respectively. The triaxiality parameter extracted from the experimentally deduced values of transition quadrupole moments, within the framework of cranked Hartree–Fock–Bogoliubov (CHFB) and total Routhian surface (TRS) calculatons, is γ ∼ −80∘ for the band in 131Ce at high spins, while for the band in 133Pr, the value of γ is close to 0∘. This agrees well with the γ shape polarization property of high and low Ωh 11/2 orbitals in these gamma-soft nuclei.

Free-surface multiple attenuation for blended data

Blended data sets are now being acquired because of improved efficiency and reduction in cost compared with conventional seismic data acquisition. We have developed two methods for blended data free-surface multiple attenuation. The first method is based on an extension of surface-related multiple elimination (SRME) theory, in which free-surface multiples of the blended data can be predicted by a multidimensional convolution of the seismic data with the inverse of the blending operator. A least-squares inversion method is used, which indicates that crosstalk noise existed in the prediction result due to the approximate inversion. An adaptive subtraction procedure similar to that used in conventional SRME is then applied to obtain the blended primary — this can damage the energy of primaries. The second method is based on inverse data processing (IDP) theory adapted to blended data. We derived a formula similar to that used in conventional IDP, and we attenuated free-surface multiples by simple muting of the focused points in the inverse data space (IDS). The location of the focused points in the IDS for blended data, which can be calculated, is also related to the blending operator. We chose a singular value decomposition-based inversion algorithm to stabilize the inversion in the IDP method. The advantage of IDP compared with SRME is that, it does not have crosstalk noise and is able to better preserve the primary energy. The outputs of our methods are all blended primaries, and they can be further processed using blended data-based algorithms. Synthetic data examples show that the SRME and IDP algorithms for blended data are successful in attenuating free-surface multiples.

Disturbance observers and applications

The control performance of practical systems has inevitably suffered from various disturbances and uncertainties, including external environmental disturbances, unknown model uncertainties (possibly caused by unmodelled dynamics) and parameter perturbations. The development of disturbance observation and attenuation methods and technologies has received a great deal of attention for practical engineering systems. The new generations of control systems require increasingly higher control performance accuracy, and thus higher disturbance rejection abilities. In addition, the complexity of practical systems is much greater than those currently dealt with, for example, the extremely high dimensionality of these complex systems. This will result in the degraded disturbance rejection performance of the existing methods and technologies. The main objective of this Special Issue (SI) on ‘Disturbance Observers and Applications’ of the Transactions of the Institute of Measurement and Control is to present recent advances in disturbance observers and applications for practical control systems. The present SI will facilitate faster uptake of advanced disturbance observer technologies, as well as addressing new challenges arising from complex control systems, in order to give rise to new theories and methodologies. The interplay of disturbance observers and complex practical systems will largely advance the knowledge in both fields, resulting in much smarter methodologies and technologies to enhance the performance of the practical control systems. This SI consists of 16 papers selected from many highquality submissions through a strict peer-reviewed procedure. It covers some recent new progress in disturbance estimation and attenuations in both theoretical and application aspects. The contributions of the selected papers are categorised into four categories, which are briefly summarised as follows.

Frequency Effect on Shielding Quality of Closed Superconducting Magnetic Shields Made of Superconducting Tapes

Magnetic fields can be effectively shielded with superconducting tapes. They can be used either to attenuate a magnetic field or to improve its homogeneity. In this paper, magnetic field changes, due to the presence of a superconducting shield, are investigated. Both experimental and model results are shown. Specimens were subjected to a low-frequency ac magnetic field (up to 45 Hz). Attenuation of the field inside a shielded cavity was observed. The dependence of the shielding effect on the magnetic field strength and frequency was analyzed. A computer model of a shield has been developed. The additional increase of the shielding effect was observed above a certain threshold frequency depending on the geometry and material properties of a screen. The size and limits of this increase were investigated. It was observed to be linear in some frequency intervals. The interval of magnetic field amplitude, in which magnetic field attenuation is constant, becomes thinner at higher frequencies. Analyzed shields may find multiple applications in devices where dc and low-frequency magnetic fields are present. Their construction is uncomplicated, and they are relatively cheap. Medicine and science can greatly benefit from this simple and reliable method of magnetic field attenuation.

The impact of surface‐wave attenuation on 3‐D seismic survey design

ABSTRACTThree‐dimensional seismic survey design should provide an acquisition geometry that enables imaging and amplitude‐versus‐offset applications of target reflectors with sufficient data quality under given economical and operational constraints. However, in land or shallow‐water environments, surface waves are often dominant in the seismic data. The effectiveness of surface‐wave separation or attenuation significantly affects the quality of the final result. Therefore, the need for surface‐wave attenuation imposes additional constraints on the acquisition geometry. Recently, we have proposed a method for surface‐wave attenuation that can better deal with aliased seismic data than classic methods such as slowness/velocity‐based filtering. Here, we investigate how surface‐wave attenuation affects the selection of survey parameters and the resulting data quality. To quantify the latter, we introduce a measure that represents the estimated signal‐to‐noise ratio between the desired subsurface signal and the surface waves that are deemed to be noise. In a case study, we applied surface‐wave attenuation and signal‐to‐noise ratio estimation to several data sets with different survey parameters. The spatial sampling intervals of the basic subset are the survey parameters that affect the performance of surface‐wave attenuation methods the most. Finer spatial sampling will reduce aliasing and make surface‐wave attenuation easier, resulting in better data quality until no further improvement is obtained. We observed this behaviour as a main trend that levels off at increasingly denser sampling. With our method, this trend curve lies at a considerably higher signal‐to‐noise ratio than with a classic filtering method. This means that we can obtain a much better data quality for given survey effort or the same data quality as with a conventional method at a lower cost.

Sparse time-frequency representation for seismic noise reduction using low-rank and sparse decomposition

Attenuation of random noise is a major concern in seismic data processing. This kind of noise is usually characterized by random oscillation in seismic data over the entire time and frequency. We introduced and evaluated a low-rank and sparse decomposition-based method for seismic random noise attenuation. The proposed method, which is a trace by trace algorithm, starts by transforming the seismic signal into a new sparse subspace using the synchrosqueezing transform. Then, the sparse time-frequency representation (TFR) matrix is decomposed into two parts: (a) a low-rank component and (b) a sparse component using bilateral random projection. Although seismic data are not exactly low-rank in the sparse TFR domain, they can be assumed as being of semi-low-rank or approximately low-rank type. Hence, we can recover the denoised seismic signal by minimizing the mixed [Formula: see text] norms’ objective function by considering the intrinsically semilow-rank property of the seismic data and sparsity feature of random noise in the sparse TFR domain. The proposed method was tested on synthetic and real data. In the synthetic case, the data were contaminated by random noise. Denoising was carried out by means of the [Formula: see text] classical singular spectrum analysis (SSA) and [Formula: see text] deconvolution method for comparison. The [Formula: see text] deconvolution and the classical [Formula: see text] SSA method failed to properly reduce the noise and to recover the desired signal. We have also tested the proposed method on a prestack real data set from an oil field in the southwest of Iran. Through synthetic and real tests, the proposed method is determined to be an effective, amplitude preserving, and robust tool that gives superior results over classical [Formula: see text] SSA as conventional algorithm for denoising seismic data.

Effect of Attenuation Correction on Regional Quantification Between PET/MR and PET/CT: A Multicenter Study Using a 3-Dimensional Brain Phantom.

A spatial bias in brain PET/MR exists compared with PET/CT, because of MR-based attenuation correction. We performed an evaluation among 4 institutions, 3 PET/MR systems, and 4 PET/CT systems using an anthropomorphic brain phantom, hypothesizing that the spatial bias would be minimized with CT-based attenuation correction (CTAC). The evaluation protocol was similar to the quantification of changes in neurologic PET studies. Regional analysis was conducted on 8 anatomic volumes of interest (VOIs) in gray matter on count-normalized, resolution-matched, coregistered data. On PET/MR systems, CTAC was applied as the reference method for attenuation correction. With CTAC, visual and quantitative differences between PET/MR and PET/CT systems were minimized. Intersystem variation between institutions was +3.42% to -3.29% in all VOIs for PET/CT and +2.15% to -4.50% in all VOIs for PET/MR. PET/MR systems differed by +2.34% to -2.21%, +2.04% to -2.08%, and -1.77% to -5.37% when compared with a PET/CT system at each institution, and these differences were not significant (P ≥ 0.05). Visual and quantitative differences between PET/MR and PET/CT systems can be minimized by an accurate and standardized method of attenuation correction. If a method similar to CTAC can be implemented for brain PET/MRI, there is no reason why PET/MR should not perform as well as PET/CT.

Review on attenuation of nanotoxicity and the mechanisms

Nanoparticles (NPs) with excellent properties have been rapidly developed and applied in various fields such as phototherapy, early cancer diagnosis, drug carriers, electronic components, cosmetics, food additives, water treatment, and soil remediation. Humans could be directly exposed to these NPs via these applications. These NPs or NP-containing products could also be released into the environment, leading to potential environmental risks. Therefore, the environmental and health risks of nanomaterials urgently need to be assessed, especially for the development of control methodologies. Methods for control or regulation of nanomaterial risks are still in the developmental stages, and some knowledge gaps and ambiguities still exist. To address these knowledge gaps and to guarantee the sustainable development of nanote- chnology, this review discusses the attenuation of nanotoxicity and mechanisms thereof. Physicochemical properties of NPs, such as size, purity, and surface properties (surface charge, hydrophilicity, and surface modification) influence their interactions with biological systems. Environmental conditions during the interaction of NPs with cells, such as exposure dose and time and reaction media, also affect nanotoxicity. Optimization of these physicochemical properties and environmental conditions is expected to aid the design of ideal NPs and control adverse effects of NPs. Nanotoxicity has been reported to be reduced by adjusting size, purity, surface properties (surface charge, hydrophilicity, and surface modification), exposure dose and time, and reaction media of NPs. Herein, the corresponding progress and challenges are also discussed individually. Moreover, this review elaborates on toxic mechanisms and attenuation of nanotoxicity involving five aspects: chemophysiological damage of cellular and subcellular structures, oxidative stress, genes, proteins, and metabolism. Understanding mechanisms underlying the interaction of NPs with biological systems would be conducive to the prediction of nanotoxicity and the design of experiments to attenuate this nanotoxicity. Currently, further studies need be conducted to explore NP uptake, absorption, distribution, interaction, and elimination in biological systems or cells. Globally, the methods of nanotoxicity attenuation remain immature, and well-corroborated methods are unavailable. Finally, perspectives on future research in nanotoxicity attenuation are proposed. An understanding of nanotoxicology and the development of related control methods affect multiple disciplines, including medicine, chemistry, physics, biology, and environmental science. Therefore, multidisciplinary experts need to urgently work together to ensure the sustainable development of nanotechnology.

Comparison between dot-immunoblotting assay and clinical sign determination method for quantifying avian infectious bronchitis virus vaccine by titration in embryonated eggs

A sensitive and specific method for measuring the vaccine titer of infectious bronchitis virus (IBV) is important to commercial manufacturers for improving vaccine quality. Typically, IBV is titrated in embryonated chicken eggs, and the infectivity of the virus dilutions is determined by assessing clinical signs in the embryos as evidence of viral propagation. In this study, we used a dot-immunoblotting assay (DIA) to measure the titers of IBV vaccines that originated from different pathogenic strains or attenuation methods in embryonated eggs, and we compared this assay to the currently used method, clinical sign evaluation. To compare the two methods, we used real-time reverse transcription-PCR, which had the lowest limit of detection for propagated IBV. As a clinical sign of infection, dwarfism of the embryo was quantified using the embryo: egg (EE) index. The DIA showed 9.41% higher sensitivity and 15.5% higher specificity than the clinical sign determination method. The DIA was particularly useful for measuring the titer of IBV vaccine that did not cause apparent stunting but propagated in embryonated chicken eggs such as a heat-adapted vaccine strain. The results of this study indicate that the DIA is a rapid, sensitive, reliable method for determining IBV vaccine titer in embryonated eggs at a relatively low cost.

Ozonation of Cylindrospermopsin (Cyanotoxin): Degradation Mechanisms and Cytotoxicity Assessments.

Cylindrospermopsin (CYN) is a potent toxic alkaloid produced by a number of cyanobacteria frequently found in lakes and reservoirs used as drinking water sources. We report for the first time detailed pathways for the degradation of CYN by treatment with ozone. This was accomplished by use of ultra-high-performance liquid chromatography (UHPLC)-quadrupole time-of-flight mass spectrometry (QTOF MS), which revealed that CYN is readily degraded by ozone with at least 36 transformation products. Structural similarities among the major products indicated that the carbon-carbon double bond in the uracil ring of CYN was most susceptible to attack by ozone. Furthermore, the nitrogen functionality associated with the tricyclic guanidine moiety is also involved via a degradation pathway that has not been previously observed. To assess the potential toxicity of ozonation products of CYN, the cytotoxicity of CYN and the mixture of its ozonation products was measured in a human hepatoma cell line (HepG2). The IC50 for CYN at 24 and 48 h incubations was approximately 64.1 and 12.5 μM, respectively; however, the ozonation products of CYN did not exhibit measurable cytotoxicity to human cells. The results indicate ozone is an effective and practical method for CYN attenuation in water treatment without formation of overtly toxic transformation products.