Simultaneous Sources Research Articles

Automation in geophysical data acquisition: From ocean-bottom nodes to RoboNodes

The future of seismic data acquisition clearly dictates increased sampling in both receiver and shot domains. A significant amount, almost 80%, of the total cost of an exploration and development seismic project is spent on data acquisition. It is, therefore, extremely important that we reduce acquisition-related costs and at the same time we strive to improve seismic data quality. Indeed, the number of seismic channels follows a form of Moore's law; that is, the number of channels laid out in the field is steadily increasing by an order of magnitude every 10 years (Figure 1) while the recent introduction of simultaneous sources provides improved spatial sampling in the shot domain. Figure 2 shows three time slices that clearly demonstrate the link between increased number of channels recorded and improved resolution and image quality.

Control of two-dimensional growth of AlN and high Al-content AlGaN-based MQWs for deep-UV LEDs

Dense and atomically flat AlN film with root-mean-square roughness value of 0.32 nm was grown on sapphire substrate at a relatively lower temperature by using a three-step epitaxy technique. On the basis of this AlN template, AlGaN-based multiple quantum wells (MQWs) with atomically flat hetero-interfaces were epitaxially grown to suppress nonradiative recombination by introducing In as a surfactant during simultaneous source supply. As a result, single intense- and narrow-peaked photoluminescence was obtained from the MQWs. Finally, the deep ultraviolet light emitting diodes with well-behaved I-V characteristic and strong electroluminescence in the range of 256–312 nm were fabricated successfully.

MOMENT PRESERVING FINITE VOLUME SCHEMES FOR SOLVING POPULATION BALANCE EQUATIONS INCORPORATING AGGREGATION, BREAKAGE, GROWTH AND SOURCE TERMS

In this work we present some moment preserving finite volume schemes (FVS) for solving population balance equations. We are considering unified numerical methods to simultaneous aggregation, breakage, growth and source terms, e.g. for nucleation. The criteria for the preservation of different moments are given. The property of conservation is a special case of preservation. First we present a FVS which shows the preservation with respect to one-moment depending upon the processes under consideration. In case of the aggregation and breakage it satisfies first-moment preservation whereas for the growth and nucleation we observe zeroth-moment preservation. This is due to the well-known property of conservativity of FVS. However, coupling of all the processes shows no preservation for any moments. To overcome this issue, we reformulate the cell average technique into a conservative formulation which is coupled together with a modified upwind scheme to give moment preservation with respect to the first two-moments for all four processes under consideration. This allows for easy coupling of these processes. The preservation is proven mathematically and verified numerically. The numerical results for the first two-moments are verified for various coupled processes where analytical solutions are available.

An ICA-SCT-PHD Filter Approach for Tracking and Separation of Unknown Time-Varying Number of Sources

In this paper we present a solution to the problem of tracking and separation of a mixture of concurrent sources in a reverberant environment where the number of sources is unknown and varies with time: new sources can appear and existing sources can disappear or undergo silence periods. In order to deal with this challenging problem, we synergistically combine two key ideas, one in the front end and the other at the back end. In the front end we employ independent component analysis (ICA) to demix the mixtures and the state coherence transform (SCT) to represent the signals in a direction of arrival (DOA) detection framework. By exploiting the frequency sparsity of the sources, ICA/SCT is even effective when the number of simultaneous sources is greater than the number of sensors therefore allowing for minimal number of sensors to be used. At the back end, the probability hypothesis density (PHD) filter is incorporated in order to track the multiple DOAs and determine the number of sources. The PHD filter is based on random finite sets (RFS) where the multi-target states and the number of targets are integrated to form a set-valued variable with uncertainty in the number of sources. A Gaussian mixture implementation of the PHD filter (GM-PHD) is utilized that solves the data association problem intrinsically, hence providing distinct DOA tracks. The distinct tracks also make the separation task possible by going back and rearranging the outputs of the ICA stage. The tracking and separation capabilities of the proposed method is demonstrated using simulations of multiple sources in reverberant environments.

Poetic Portraits of a Revolution by Will McInerney and Kane Smego (review)

Reviewed by: Poetic Portraits of a Revolution by Will McInerney and Kane Smego Jeanmarie Higgins Poetic Portraits of a Revolution. Written and performed by Will McInerney and Kane Smego of the Sacrificial Poets, in collaboration with translator Mohammad Moussa. Directed by Joseph Megel. Photography and videography by Sameer Abdelkhalek. Presented by StreetSigns Center for Literature and Performance, Carrboro, NC.10 March 2012. Cultural theorist Jean Baudrillard’s infamous declaration that the Gulf War “did not take place” characterized that conflict’s news coverage as a proliferation of images in which long-range weapons stood in for the bodies of soldiers who used them and the civilians who were killed by them. Twenty years later, “taking place” is an increasingly contested phrase. One can argue, for example, that something takes place in a geographical location as it simultaneously takes place on the Internet. In the wake of the 2011 Arab uprising, American spoken-word poets Will McInerney and Kane Smego traveled to Egypt and Tunisia to interview participants in the 2011 revolution to learn what happened from people—not from news reports. The multimedia performance they created from their experiences, Poetic Portraits of a Revolution, exposed the falsity of the live/mediated binary they articulated and instead foregrounded how the Arab Spring engaged the many ways that an event can take place: from violent group protests on the street to collective consciousness-raising on the Internet. McInerney and Smego’s performance further emphasized how the history of this revolution is being written—as an impermanent, uncurated archive of YouTube videos, Facebook posts, and tweets. Smego and McInerney interviewed witnesses to the ongoing revolutionary actions that began with the December 2010 self-immolation of Tunisian protester Mohamed Bouazizi, and has since included the overthrow of Tunisian leader Zine El Abidine Ben Ali and Egypt’s Hosni Mubarak. Structured as a series of episodic slam poems with alternating photographic portraits and filmed interviews, the performance included subjects who reflected a range of views, from those who continue to participate in political actions to others who contend either that the revolution is over or that it “changed nothing.” The poets asked their interviewees whether the Arab uprising was indeed the “Facebook Revolution.” As Amina Zaki, a young woman “with a mind so sharp hidden beneath her headscarf/it could have qualified as a concealed weapon,” told her interviewers, “Twitter changed everything.” Others thought that the power of social media was drastically overstated: “Facebook and Twitter did not sleep in the streets. Facebook didn’t say ‘Shut up, Mubarak.’ That was me.” Denying the notion of a youth revolution altogether, 76-year-old labor organizer Fathallah insisted that the events of 2011 were the product of years of work by political organizations, the media, and laborers: “Revolution is like your fingernails or your hair, you don’t see it growing.” Click for larger view View full resolution Will McInerney and Kane Smego in Poetic Portraits of a Revolution. (Photo: Nicholas Graetz.) One fraught moment illustrated the overdeter-mined effect of multiple simultaneous news sources on individual experiences of revolution: a moment from an evening the poets spent in Tunisia with the Mubarki family, whose teenaged son Mohammad Amin was killed in Kasserine. They described what happened that evening: the poets entered the Mubarki house through a door painted with Mohammad’s name; in the back of the house, a television played: “An elderly man is watching Al Jazeera in the far room—/the Syrian uprising can be heard in sound bites and political commentary/from confident Kevlar vested reporters”; Mohammad’s mother and brother showed them pictures of him; his sister played a YouTube video of his funeral procession. The following poem described the moment that the video froze on the image of Mohammad’s bloodied head: “It’s stuck in time/The bloody face is frozen on the screen/Mrs. Mubarki doesn’t blink/It’s the same still shot as the photo sitting beside me/Mrs. Mubarki closes her eyes/The [End Page 117] video never finished loading that day/The photo is still sitting on the table/His name still written in white paint on the door.” This poem drew out the...

Simultaneous location of two partial discharge sources in power transformers based on acoustic emission using the modified binary partial swarm optimisation algorithm

One of the main methods for partial discharge (PD) source localisation in power transformers is acoustic emission measurements. This study describes a new method for detection and location of two simultaneous partial discharge sources in three-phase power transformer. In this method, acoustic signals are detected by sensors first and are then denoised using a wavelet transform. Finally, the two PD sources are localised using the modified binary partial swarm optimisation (MBPSO) method. To prove the efficiency of the two simultaneous PD localisations, the proposed algorithm is used to localise PD sources of the arc furnace transformer at Isfahan's Mobarakeh steel company. For this purpose, the PD localisation problem converts to an optimisation problem. To prove the efficiency of the MBPSO algorithm, its performance is compared with a genetic algorithm. The PD localisation results confirm the efficiency of the proposed method for the detection and location of PD sources.

Stroke caused auditory attention deficits in children

To verify the auditory selective attention in children with stroke. Dichotic tests of binaural separation (non-verbal and consonant-vowel) and binaural integration - digits and Staggered Spondaic Words Test (SSW) - were applied in 13 children (7 boys), from 7 to 16 years, with unilateral stroke confirmed by neurological examination and neuroimaging. The attention performance showed significant differences in comparison to the control group in both kinds of tests. In the non-verbal test, identifications the ear opposite the lesion in the free recall stage was diminished and, in the following stages, a difficulty in directing attention was detected. In the consonant- vowel test, a modification in perceptual asymmetry and difficulty in focusing in the attended stages was found. In the digits and SSW tests, ipsilateral, contralateral and bilateral deficits were detected, depending on the characteristics of the lesions and demand of the task. Stroke caused auditory attention deficits when dealing with simultaneous sources of auditory information.

Collaborative Blind Source Separation Using Location Informed Spatial Microphones

This letter presents a new Collaborative Blind Source Separation (CBSS) technique that uses a pair of location informed coincident microphone arrays to jointly separate simultaneous speech sources based on time-frequency source localization estimates from each microphone recording. While existing BSS approaches are based on localization estimates of sparse time-frequency components, the proposed approach can also recover non-sparse (overlapping) time-frequency components. The proposed method has been evaluated using up to three simultaneous speech sources under both anechoic and reverberant conditions. Results from objective and subjective measures of the perceptual quality of the separated speech show that the proposed approach significantly outperforms existing BSS approaches.

Simultaneous sources in marine acquisition: experiences to date

A modified inversion approach is presented for the effective separation of sources in marine simultaneous shooting acquisition. The method aims to distribute all energy in the simultaneous shot records by reconstructing the individual shot records at their respective locations. The method is applied to a simulated simultaneous long offset data set, where two sources are used to acquire long offsets with conventional cables. In the second example, the performance is investigated on a data set from Western Australia, where two sources where located within close proximity, with only a small cross line distance between them. Results demonstrate that the individual sources can be separated satisfactory for both simultaneous source configurations.

Simultaneous sources: The inaugural full-field, marine seismic case history from Australia

SummarySimultaneous (blended) sources have attracted a great deal of attention recently because of their potential to increase significantly the rate at which seismic data can be acquired. The viability of the method was previously demonstrated through the use of small-scale tests on synthetic and field data. In this paper, we present a case history from Australia of the first field-development-scale use of this technology in the world.Concept studies involving simulations of simultaneoussource data from conventional data indicated that the proposed survey design would yield data that were separable into components for each source. The resultant data set contains twice as many traces as its conventional equivalent, and provides improved sampling for important processing steps such as coherent noise attenuation.Simultaneous-source acquisition requires quality control methods that are specific to the technique to ensure that the data are acquired as planned. New QC methods were developed specifically for this project, and showed that no problems related to the simultaneous-source technique were encountered.Data processing involved source separation at an early stage, after which a conventional processing sequence could be used on the resultant, densely-sampled data set. Separation was performed using a sparse inversion technique, which proved very effective. Very little signal leakage was observed, and the interference was almost completely suppressed.Through this case history, we demonstrate the viability of simultaneous sources as an effective marine seismic acquisition method.

Acceptance of Internet-Based Health Care Services Among Households in Poland: Secondary Analysis of a Population-Based Survey

BackgroundPolish society is benefiting from growing access to the Internet, but the use of advanced e-services is still limited. The provision of Internet-based health services depends not only on the penetration of the Internet into society, but also on the acceptance of this technology by potential users.ObjectiveThe main objective of this study was focused on the assessment of predictors of acceptance of Internet use for provision of health services (eg, sociodemographic status, the use of information technologies, and consumption of health care services) among households in Poland.MethodsThe study was based on a secondary analysis of the dataset from the 2011 Social Diagnosis survey (a biannual survey conducted since 2001 about economic and non-economic aspects of household and individual living conditions in Poland). Analysis of the questionnaire results focused on the situations of the households included in the study. The predictors for 2 outcome variables describing the acceptance of households for Internet use for provision of a full health care service, or at least access to information and download of required forms, were assessed using multivariate logistic regression. ResultsAfter excluding those households that would not consider the use of health care services or for which predictor variables assumed missing values, the final analyses were conducted on data from 8915 households. Acceptance of the use of the Internet for provision of full health care services in Polish households was significantly higher among households in urban locations with ≥ 200,000 inhabitants than among households in rural areas; it was also higher with salaried employment as the source of income than with self-employment in agriculture (odds ratio [OR] = 0.53, 95% CI 0.40 - 0.70), retirement pension (OR = 0.46, 95% CI 0.39 - 0.54), disability pension (OR = 0.48, 95% CI 0.34 - 0.68), or with several simultaneous income sources (OR = 0.66; 95% CI 0.57 - 0.79). Furthermore, acceptance of Internet-based health care was higher in households with a higher monthly net income per capita (OR = 2.11, 95% CI 1.75 - 2.53 for households from the lowest and the highest income interval), among households with > 1 child aged < 15 years (OR = 1.38, 95% CI 1.20 - 1.59), among households with at least some books (with OR = 3.33, 95% CI 2.39 - 4.64 for household with no books and those with over 500 books). Acceptance was also higher in households with a computer (OR = 1.86, 95% CI 1.35 - 2.56), Internet access (OR = 1.95, 95% CI 1.37 - 2.76), and Internet access for a longer duration (OR = 1.36, 95% CI 1.06 - 1.75 and OR = 1.81, 95% CI 1.40 - 2.33 for households with access < 1 year versus those with access for 1-5 years and > 5 years, respectively). Greater self-declared confidence in using technology was also associated with higher acceptance of the Internet for health care services (OR = 2.94, 95% CI 2.21 - 3.91 for the least confident households versus those with the highest confidence). Furthermore, recent use of health care services increased acceptance of using the Internet for at least some health-related services (OR = 1.49, 95% CI 1.16 - 1.91), but not for full provision of online health care services (OR = 1.20, 95% CI 0.92 - 1.55). Neither the hospitalization of a member of a household nor the opinion about satisfying health care needs of a household affected the degree of acceptance.ConclusionsThe acceptance of health care services through the Internet is higher in households from larger cities, with stable income from an employee salary, as well as with higher income levels per capita. Furthermore, general computer and Internet use in the household influenced the perception of eHealth. Paradoxically, the use of health care services or the level of satisfaction with the coverage of the household’s health needs has a limited influence on acceptance of Internet-based health care services.

Simultaneous identification of the pollutant release history and the source location in groundwater by means of a geostatistical approach

This paper describes an innovative procedure that is able to simultaneously identify the release history and the source location of a pollutant injection in a groundwater aquifer (simultaneous release function and source location identification, SRSI). The methodology follows a geostatistical approach: it develops starting from a data set and a reliable numerical flow and transport model of the aquifer. Observations can be concentration data detected at a given time in multiple locations or a time series of concentration measurements collected at multiple locations. The methodology requires a preliminary delineation of a probably source area and results in the identification of both the sub-area where the pollutant injection has most likely originated, and in the contaminant release history. Some weak hypotheses have to be defined about the statistical structure of the unknown release function such as the probability density function and correlation structure. Three case studies are discussed concerning two-dimensional, confined aquifers with strongly non-uniform flow fields. A transfer function approach has been adopted for the numerical definition of the sensitivity matrix and the recent step input function procedure has been successfully applied.

Perception of Mixture of Musical Instruments with Spectral Overlap Removed

Abstract The issue of auditory segregation of simultaneous sound sources has been addressed in speech research but was given less attention in musical acoustics. In perception of concurrent speech, or speech with noise, the operation of time-frequency masking was often used as a research tool. In this work, an ex- tension of time-frequency masking, leading to the removal of spectro-temporal overlap between sound sources, was applied to musical instruments playing together. The perception of the original mixture was compared with the perception of the same mixture with all spectral overlap electronically removed. Ex- periments differed in the method of listening (headphones or a loudspeaker), sets of instruments mixed, and populations of participants. The main findings were: (i) in one of the experimental conditions the removal of spectro-temporal overlap was imperceptible, (ii) perception of the effect increased when removal of spectro-temporal overlap was performed in larger time-frequency regions rather than in small ones, (iii) perception of the effect decreased in loudspeaker listening. The results support both the multiple looks hypothesis and the “glimpsing” hypothesis known from speech perception.

Source Localization with Acoustic Sensor Arrays Using Generative Model Based Fitting with Sparse Constraints

This paper presents a novel approach for indoor acoustic source localization using sensor arrays. The proposed solution starts by defining a generative model, designed to explain the acoustic power maps obtained by Steered Response Power (SRP) strategies. An optimization approach is then proposed to fit the model to real input SRP data and estimate the position of the acoustic source. Adequately fitting the model to real SRP data, where noise and other unmodelled effects distort the ideal signal, is the core contribution of the paper. Two basic strategies in the optimization are proposed. First, sparse constraints in the parameters of the model are included, enforcing the number of simultaneous active sources to be limited. Second, subspace analysis is used to filter out portions of the input signal that cannot be explained by the model. Experimental results on a realistic speech database show statistically significant localization error reductions of up to 30% when compared with the SRP-PHAT strategies.

Source Localization with Acoustic Sensor Arrays Using Generative Model Based Fitting with Sparse Constraints

This paper presents a novel approach for indoor acoustic source localization using sensor arrays. The proposed solution starts by defining a generative model, designed to explain the acoustic power maps obtained by Steered Response Power (SRP) strategies. An optimization approach is then proposed to fit the model to real input SRP data and estimate the position of the acoustic source. Adequately fitting the model to real SRP data, where noise and other unmodelled effects distort the ideal signal, is the core contribution of the paper. Two basic strategies in the optimization are proposed. First, sparse constraints in the parameters of the model are included, enforcing the number of simultaneous active sources to be limited. Second, subspace analysis is used to filter out portions of the input signal that cannot be explained by the model. Experimental results on a realistic speech database show statistically significant localization error reductions of up to 30% when compared with the SRP-PHAT strategies.

Robust acoustic source localization based on modal beamforming and time–frequency processing using circular microphone arrays

Uniform circular array processing has been shown to be a very useful tool for broadband acoustic source localization over 360°. Specifically, beamforming methods based on circular harmonics have attracted a lot of research attention in the last several years, as modal array signal processing is a very active research topic. On the other hand, due to the sparsity properties of speech, source localization methods in the time-frequency (T-F) domain have also demonstrated their capability to locate several simultaneous sources with high accuracy. In this paper, a localization framework based on circular harmonics beamforming and T-F processing that provides accurate localization performance under very adverse acoustic conditions is presented. Modal processing and sparsity-based localization are jointly addressed to estimate the direction-of-arrival of multiple concurrent speech sources. Experiments in real and simulated environments with different microphone setups are discussed, showing the validity of the proposed approach and comparing its performance with other state-of-the-art methods.

Beam steering response matrix inversion method: Accurate localization of simultaneous high and low frequency sources using a small line array

The Beam Steering Response (BSR) Matrix Inversion Method is a technique using a small line array that, when mathematically steered to populate a BSR matrix, can simultaneously resolve the locations of multiple sources. Using this technique, high directivity over a wide frequency range may be achieved with a small array. Simultaneous tracking of multiple low and high frequency sources is demonstrated using the BSR Matrix Inversion Method with an acoustic video camera having a 49 inch, 8 element line array. This paper addresses 1) the derivation of the Beam Steering Response matrix, 2) line array design considerations, 3) processing limitations, and 4) a practical demonstration of the BSR Matrix Inversion Method.

Robust pixel-based source and mask optimization for inverse lithography

A robust pixel-based simultaneous source and mask optimization (SMO) method is proposed. A three dimensional (3D) partially coherent imaging model is used in this method. The process variations, such as defocus, exposure dose, aberrations, radiometric correction and apodization are incorporated in the 3D imaging model and the optimization framework. The pattern error is calculated with respect to the 3D image in the photoresist. The expectation of the pattern error is used as the cost function. The sensitivity of the cost function is employed to guide cost function in the decedent direction during optimization. The framework is finally solved by joint optimization of the source and mask patterns. Numerical results verify the validity of the proposed method. Influences caused by the aberrations are also shown by simulations.

Fast waveform inversion without source‐encoding

ABSTRACTRandomized source‐encoding has recently been proposed as a way to dramatically reduce the costs of full waveform inversion. The main idea is to replace all sequential sources by a small number of simultaneous sources. This introduces random cross‐talk in model updates and special stochastic optimization strategies are required to deal with this. Two problems arise with this approach: i) source‐encoding can only be applied to fixed‐spread acquisition setups and ii) stochastic optimization methods tend to converge very slowly, relying on averaging to suppress the cross‐talk. Although the slow convergence is partly off‐set by a low iteration cost, we show that conventional optimization strategies are bound to outperform stochastic methods in the long run. In this paper we argue that we do not need randomized source‐encoding to reap the benefits of stochastic optimization and we review an optimization strategy that combines the benefits of both conventional and stochastic optimization. The method uses a gradually increasing batch of sources. Thus, iterations are initially very cheap and this allows the method to make fast progress in the beginning. As the batch‐size grows, the method behaves like conventional optimization, allowing for fast convergence. Stylized numerical examples suggest that the stochastic and hybrid methods perform equally well with and without source‐encoding and that the hybrid method outperforms both conventional and stochastic optimization. The method does not rely on source‐encoding techniques and can thus be applied to marine data. We illustrate this on a realistic synthetic model.

Simultaneous sources separation via multidirectional vector-median filtering

Simultaneous source acquisition technology, also referred to as “blended acquisition,” involves recording two or more shots simultaneously. Despite the fact that the recorded data has crosstalk from different shots, conventional processing procedures can still produce acceptable images for interpretation. This is due to the power of the stacking process using blended data with its increased data redundancy and inherent time delays between various shots. It is still desirable to separate the blended data into single shot gathers and reduce the crosstalk noise to achieve the highest seismic image quality and for standard prestack processing, such as filtering, statics computation, and velocity analysis. This study introduced a new and simple multidirectional vector-median filter (MD-VMF) to separate the blended seismic shot gathers. This method extended the well-known conventional median filter from a scalar implementation to a vector version. More specifically, a vector median filter was applied in many trial directions and the median vector was chosen from among these. We demonstrated the effectiveness of our proposed MD-VMF on simulated data generated by blending synthetic and real marine seismic data.