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The progress of digital audio technology has enabled the familiar use of products such as CD and DAT in acoustic measurement. For example, a signal reproduced with a CD player is inputted into a subject for measurement and a DAT r...
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The progress of digital audio technology has enabled the familiar use of products such as CD and DAT in acoustic measurement. For example, a signal reproduced with a CD player is inputted into a subject for measurement and a DAT recorder records its response. However, the sampling cannot be synchronized completely with the input signal, although both nominal sample rates are set up equally, because the player and recorder work independently. The most popular solution is to use software to perform the synchronous addition after converting the recorded signal into the original sampling rate. However, the rate conversion also has an error due to the windowing in the high-frequency region of the processed signal. This paper proposes a new method for averaging asynchronous sampling data to solve these problems. To evaluate performance, the transfer function of only measuring equipment estimated from asynchronous sampling data was compared with the measurement results in synchronous sampling conditions. Both results agreed within 0.1 dB, so the effectiveness of the new method was confirmed. In measuring the frequency response of a BPF when white noise is introduced, the proposed method was compared with the method using rate conversion. As a result, the noise reduction was almost the same, and the processing time was reduced to about one-fourth.
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Passive sampling is an emerging tool for monitoring micropollutants in surface waters and enables the determination of time-weighted average (TWA) concentration over extended sampling periods. For the determination of TWA concentr...
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Passive sampling is an emerging tool for monitoring micropollutants in surface waters and enables the determination of time-weighted average (TWA) concentration over extended sampling periods. For the determination of TWA concentration, the sampling rates (R-s) for the compounds of interest are required. Laboratory calibration experiments were conducted in order to determine the sampling rates of 12 selected pesticides using Polar Organic Chemical Integrative Samplers (pest-POCIS). The experiments were performed on the basis of static renewal exposure of pest-POCIS under stirred conditions for different time intervals up to 28days. The recoveries of target pesticides ranged between 71 % and 120 % with relative standard deviation (RSD) <18%. Detection limits (LODs) and quantification limits (LOQs) ranged between 0.5 and 6ng L-1 and 1.6 and 19.7ng L-1, respectively. The uptake in POCIS for the studied pesticides followed a linear pattern throughout the 28days of exposure, except for fipronil. The calculated sampling rates ranged from 0.030L day(-1) to 0.223L day(-1). The pesticides pirimiphos methyl, clofentezine, cyprodinil, fipronil and kresoxim methyl have never been studied before in calibration experiments using pest-POCIS passive samplers. Using the described analytical procedure, trace levels (ng L-1) of the target pesticides could be determined in surface waters.
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This paper introduces Manhattan sampling in two and higher dimensions, and proves sampling theorems for them. In 2-D, Manhattan sampling, which takes samples densely along a Manhattan grid of lines, can be viewed as sampling on th...
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This paper introduces Manhattan sampling in two and higher dimensions, and proves sampling theorems for them. In 2-D, Manhattan sampling, which takes samples densely along a Manhattan grid of lines, can be viewed as sampling on the union of two rectangular lattices, one dense horizontally and the other vertically, with the coarse spacing of each being a multiple of the fine spacing of the other. The sampling theorem shows that the images bandlimited to the union of the Nyquist regions of the two rectangular lattices can be recovered from their Manhattan samples, and an efficient procedure for doing so is given. Such recovery is possible even though there is an overlap among the spectral replicas induced by Manhattan sampling. In three and higher dimensions, there are many possible configurations for Manhattan sampling, each consisting of the union of special rectangular lattices called bi-step lattices. This paper identifies them, proves a sampling theorem showing that the images bandlimited to the union of the Nyquist regions of the bi-step rectangular lattices are recoverable from Manhattan samples, presents an efficient onion-peeling procedure for doing so, and shows that the union of Nyquist regions is as large as any bandlimited region, such that all images supported by such can be stably reconstructed from samples taken at the rate of the Manhattan sampling. It also develops a special representation for the bi-step lattices with a number of useful properties. While most of this paper deals with continuous-space images, Manhattan sampling of discrete-space images is also considered, for infinite, as well as finite, support images.
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This contribution deals with the design of a fully digital multi-rate receiver, operating on non-synchronized bandpass samples. Issues related to aliasing, sample rate conversion and timing correction are considered. We compare va...
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This contribution deals with the design of a fully digital multi-rate receiver, operating on non-synchronized bandpass samples. Issues related to aliasing, sample rate conversion and timing correction are considered. We compare various receiver alternatives in terms of the BER degradation caused by aliasing and non-ideal timing correction. In particular, we focus on a low-complexity receiver performing sample rate conversion prior to matched filtering by means of an interpolator. We show that the BER degradation can be reduced to about 0.1 dB by careful selection of the system parameters, but at the expense of a large oversampling factor. A similar BER degradation can be achieved at a considerably smaller oversampling factor by including a simple digital anti-aliasing filter in front of the interpolator. We will develop a new type of anti-aliasing filter based on CIC filters. The distortion introduced by this CIC-type filter can be compensated for, by replacing the matched filter by an optimized receiver filter.
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We want to evaluate the performance of two FDR-based multiple testing procedures by Benjamini and Hochberg (1995, J. R. Stat. Soc. Ser. B, 57, 289-300) and Storey (2002, J R. Stat Soc. Ser. B, 64, 479-498) in analyzing real microa...
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We want to evaluate the performance of two FDR-based multiple testing procedures by Benjamini and Hochberg (1995, J. R. Stat. Soc. Ser. B, 57, 289-300) and Storey (2002, J R. Stat Soc. Ser. B, 64, 479-498) in analyzing real microarray data. These procedures commonly require independence or weak dependence of the test statistics. However, expression levels of different genes from each array are usually correlated due to coexpressing genes and various sources of errors from experiment-specific and subject-specific conditions that are not adjusted for in data analysis. Because of high dimensionality of microarray data, it is usually impossible to check whether the weak dependence condition is met for a given dataset or not. We propose to generate a large number of test statistics from a simulation model which has asymptotically (in terms of the number of arrays) the same correlation structure as the test statistics that will be calculated from the given data and to investigate how accurately the FDR-based testing procedures control the FDR on the simulated data. Our approach is to directly check the performance of these procedures for a given dataset, rather than to check the weak dependency requirement. We illustrate the proposed method with real microarray datasets, one where the clinical endpoint is disease group and another where it is survival.
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In this paper, we present a rigorous mathematical proof on the minimum sampling rate as well as all acceptable sampling rates (independent of band position) for the first-order sampling of bandpass signals. It is shown that the mi...
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In this paper, we present a rigorous mathematical proof on the minimum sampling rate as well as all acceptable sampling rates (independent of band position) for the first-order sampling of bandpass signals. It is shown that the minimum sampling rate is between 2 sigma (Nyquist rate) and 3 sigma, where a is the bandwidth of a bandpass signal. It is also noted that the Nyquist rate is actually an asymptotic sampling rate for the first-order sampling of bandpass signals. A so-called csinc interpolator is used in the reconstruction of a bandpass signal from its samples, which makes the sampling theorem for bandpass signals congruent with the sampling theorem for lowpass signals. (c) 2007 Elsevier Inc. All rights reserved.
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Changes in the accounting and auditing environments since the passage of Sarbanes-Oxley (SOX) and the creation of the Public Accounting Oversight Board (PCAOB) have likely impacted accounting population error rates and audit sampl...
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Changes in the accounting and auditing environments since the passage of Sarbanes-Oxley (SOX) and the creation of the Public Accounting Oversight Board (PCAOB) have likely impacted accounting population error rates and audit sampling procedures. We investigate accounting population error rates and auditor sampling performance for a unique proprietary post-SOX dataset of 160 audit sampling applications for a large auditing firm. Compared to previous research, we find that in the post-SOX period, accounting data error rates are significantly lower in magnitude and frequency, sample sizes are significantly larger, and auditor performance has improved in evaluating sample errors. The low error rates suggest criticisms in prior research regarding audit sampling techniques may not be a serious concern for most audit sampling applications. Furthermore, we provide evidence that auditors' application of audit sampling is more consistent with the requirements in professional standards than previously reported.
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Integrative passive sampling with devices such as semipermeable membrane devices generally relies on rigs for month-long static exposures in water. We evaluate here whether mobile exposures of passive samplers can provide reliable...
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Integrative passive sampling with devices such as semipermeable membrane devices generally relies on rigs for month-long static exposures in water. We evaluate here whether mobile exposures of passive samplers can provide reliable estimates of dissolved contaminant concentrations. Mobile exposures were obtained by towing samplers fastened to the end of a benthic trawl net. Significant and reproducible absorption of polycyclic aromatic hydrocarbons during 5 h-long deployments was made possible by high sampling rates resulting from high water turbulences during towing at 1.2-1.5 knots. Sampling rates (72-215 L d~(-1)) estimated from the dissipation of performance reference compounds were supported by in situ calibration with samplers exposed for a 30 days in the vicinity of the test site. Higher fluoranthene and pyrene absorption in samplers exposed to the trawling-induced sediment plume could be attributed to desorption from re-suspended sediments. This mode of exposure has the potential to be used in monitoring programmes.
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For discrete time systems, the sampling rate is an important design issue. On the one hand, a sampling rate below the Nyquist rate results in spectral aliasing, on the other hand, a sampling rate chosen higher than necessary incre...
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For discrete time systems, the sampling rate is an important design issue. On the one hand, a sampling rate below the Nyquist rate results in spectral aliasing, on the other hand, a sampling rate chosen higher than necessary increases the computational burden. We show in this paper that aliased spectra, arising from sampling a random process below the Nyquist rate, may be completely eliminated. We show that a deterministic or random waveform that is sampled at a rate less than the classical Nyquist rate may be successfully reconstructed if two arbitrarily closely spaced samples are retained each sampling instant. A convergence proof is given for the random waveform case. We suggest a diagonally loaded maximum likelihood estimator approach to reduce the reconstruction errors resulting from timing jitter between the pairs of impulse samples as an area of future research.
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