Synchronous Sampling Research Articles

Sine-fitting multiharmonic algorithms implemented by artificial neural networks

A new method designed to perform high-accuracy spectral analysis, based on ADALINE artificial neural networks (ANNs), is proposed. The proposed network is able to accurately calculate the fundamental frequency and the harmonic content of an input signal. The method is especially useful in high-precision digital measurement systems in which periodical signals are involved, i.e. digital watt meters. Most of these systems use spectral analysis algorithms as an intermediate step for the computation of the magnitudes of interest. The traditional spectral analysis methods require synchronous sampling, which introduce limitations to the sampling circuitry. Sine-fitting multiharmonics algorithms resolve the hardware limitations concerning the synchronous sampling but have some limitations with regard to the phase of the array of samples. The new implementation of sine-fitting multiharmonics algorithms based on ANN eliminates these limitations.

On-Chip Measurement of Jitter Transfer and Supply Sensitivity of PLL/DLLs

This brief describes low-cost on-chip measurement circuits for jitter transfer and supply sensitivity of phase-locked loops (PLLs) and delay-locked loops (DLLs). Unlike previous works that measured the frequency-domain responses, the proposed circuits measure the time-domain responses of the PLL/DLL to the periodic disturbances applied to either its input clock phase or its supply voltage. A synchronous sampling technique accurately measures the PLL/DLL's periodic response while suppressing the unrelated noises and interferences via averaging. The synchronous sampler outputs either DC voltage or digital values, making it suitable for low-cost characterization and production tests. The procedure for estimating the frequency-domain transfer functions from the measured time-domain responses is outlined. The jitter transfer and supply sensitivity measurements were demonstrated with a PLL fabricated in 0.13-mum CMOS. Compared with the PLL that occupied 1.1x0.46 mm2 and dissipated 36 mW from a 1.2-V supply, the on-chip measurement circuits occupied only 0.014 mm2 and dissipated only 2.6 mW.

Non-preemptible last section assignment for reducing feedback latency in real-time control systems

A real-time control system design procedure consists of the controller design stage and the implementation stage. In the controller design stage, various digital control theories are used with assumptions, such as synchronous sampling, no sampling jitter and negligible feedback latency (latency from sensing to actuation). However, in the implementation stage, multiple control tasks are usually scheduled on a processor, which creates a finite sampling period, varying feedback latency and sampling jitter, and therefore the controller's performance is degraded. In this article, we investigate the relationship between control performance and timing parameters. In the course of this investigation, we found that the feedback latency is the dominant factor affecting control performance. In addition, we propose a rate monotonic (RM) scheduler with non-preemptible last section algorithm, which can reduce the feedback latency considerably. The proposed algorithm provides better control performance than a preemptive RM scheduler, in most cases. The effectiveness of the proposed algorithm is shown in illustrative examples.

Simple Algorithm for Sampling Synchronization of ADCs

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper describes an algorithm for synchronizing analog-to-digital converters (ADCs) to the fundamental of a continuous periodic signal. It operates like a digital phase-locked loop, is based mainly on discrete Fourier transform (DFT) on sampled data, and uses DFT-leakage detection to ensure synchronous sampling. It may be applied to distorted waveforms in general, irrespective of the type of ADC used, and no windowing functions on the sampled data need to be applied. Measurements in ac metrology in the microvolt-per-volt and microradian uncertainty levels can be done without tight hardware synchronization. </para>

Definition of Instantaneous Dielectric Loss Factor and Digital Algorithm for Online Monitoring

Among the digital algorithms currently available for online monitoring of the dielectric loss factor of power apparatus, there are unavoidable limitations, such as that most of them must strictly meet the synchronous sampling criterion simultaneously with a precondition that the power frequency must be invariable in the sampling periods. This paper presents a unique definition and a corresponding digital algorithm of the instantaneous dielectric loss factor. The theoretical basis of the algorithm is also deduced. In a nonstationary signal environment where power frequencies are randomly variable, the algorithm can accurately track the instantaneous frequency of power signals, recursively calculate the parameters of parallel equivalent circuit, and, finally, figure out the waveform of the instantaneous dielectric loss factor. Simulations and experimental results show that the proposed algorithm renders good application performance without being affected by the limitations incurred from synchronous sampling and harmonics.

Digital monitoring and health diagnosis for mechanical equipment operation safety based on fiber Bragg grating sensor

This paper introduces fiber Bragg grating (FBG) based on a fiber optic grating sensor developed to be embedded on mechanical equipment for digital monitoring and health diagnosis. The theoretical and experimental researches on the new-style FBG sensor (FBGS) technology, high-speed demodulation, and data transmission are discussed. The transmission characteristics between the FBG and the detection interface, modeling and compensation method for online distributed multi-parameter digital monitoring and methods for data processing, synchronous sampling, and long-term dynamic digital monitoring using embedded technology are also presented. The acquired information by an FBGS can be used for the optimization of maintenance schedules and refinement of mechanical equipment design. It is a challenge to gather real-time data from components working at high speed and in a severe environment of high temperature, high pressure, and high rotation speed. Currently, there are no sensors or technologies available for digital monitoring and health diagnosis under this rigorous situation for use in mechanical engineering operation safety. As a result, this paper introduces an online distributed and integrated digital monitoring system and health diagnosis. The new principle and new method will contribute to modern measurements in science and technology, mechanical engineering, and large mechanical equipment operation safety.

Sampling design for compliance monitoring of surface water quality: A case study in a Polder area

International agreements such as the EU Water Framework Directive (WFD) ask for efficient sampling methods for monitoring natural resources. In this paper a general methodology for designing efficient, statistically sound monitoring schemes is described. An important decision is the choice between a design‐based and a model‐based method, implying the choice between probability (random) sampling and purposive sampling. For mapping purposes, model‐based methods are more appropriate, whereas to obtain valid results for the universe as a whole, such as in testing water quality standards against legal standards, we generally prefer a design‐based method. Four basic sampling patterns in space‐time universe are described: static, synchronous, static‐synchronous, and rotational. A case study is carried out for monitoring the quality of surface water at two farms in western Netherlands, wherein a synchronous sampling design is applied, with stratified simple random sampling in both space and time. To reduce laboratory costs the aliquots taken at the locations of a given sampling round are bulked to form a composite. To test the spatiotemporal mean N‐total concentration during the summer half‐year against the MAR standard with a power of 80% at a concentration 15% below the MAR standard and with a confidence of 95%, six to nine sampling rounds are needed with 50 to 75 locations per sampling round. For P‐total the required number of sampling rounds differs strongly between the two farms, but is for both farms much larger than for N‐total.

Tumor heterogeneity in ovarian cancer as demonstrated by in vitro chemoresistance assays

Objective Tumor heterogeneity has been demonstrated in solid tumors. In vitro assays were developed in an effort to predict in vivo tumor response to therapy. We compare the in vitro assay results from multiple synchronous tumor samples in primary and recurrent ovarian cancers. Methods 38 patients underwent surgery for primary (18) or recurrent (20) ovarian cancer. Two (22) or three (16) samples were obtained per patient and tested using the EDR assay (Oncotech, Inc.). The percentage of Extreme (E), Intermediate (I) and Low (L) drug resistance for each chemotherapy was compared between synchronous specimens. Results A total of 92 samples were collected and 787 drug assays were performed. Tumor heterogeneity was seen in 22.4% of all cases, including 18.6% primary and 26.1% recurrent diseases ( p = 0.01). Two category differences (L vs. E) were seen in 4.1% primary and 11.3% recurrent cases (7.8% of all cases). Overall, an increased frequency in EDR was seen in recurrent disease as compared to primary for all agents tested (22.9% primary vs. 31.6% recurrent, p = 0.006). Marked heterogeneity of the drug resistance profiles was seen with paclitaxel as compared with cisplatin/gemcitabine ( p = 0.03), taxotere ( p = 0.04) or topotecan ( p = 0.04). No association was demonstrated between assay results and clinicopathologic parameters collected in this cohort. Conclusions Treatment failure is often attributed to the development of chemoresistance. These results suggest that tumor heterogeneity may play an equally important role in treatment failure. Recurrent lesions exhibit greater heterogeneity and more frequent EDR. These data can influence therapeutic strategy i.e., multiple samples, sequential, or consolidation therapy.

Heart Rate Detection From Plantar Bioimpedance Measurements

In this paper, a novel technique for heart rate measurement on a standing subject is proposed that relies on electrical impedance variations detected by a plantar interface with booth feet, such as those in some bathroom weighting scales for body composition analysis. Heart-related impedance variations in the legs come from arterial blood circulation and are below 500 mOmega. To detect them, we have implemented a system with a gain in excess of 600, and whose fully differential AC input amplifier has a gain of 4.5 and a common-mode rejection ratio (CMRR) higher than 90 dB at 10 kHz. Differential coherent demodulation based on synchronous sampling yields a signal-to-noise ratio (SNR) of about 54 dB . The system sensitivity is 610 mV/Omega. The technique has been demonstrated on 18 volunteers, whose bioimpedance signal and ECG were simultaneously recorded. A Bland-Altman plot shows a mean bias of -0.2 ms between the RR time intervals obtained from these two signals, which is negligible. The technique is simple and user friendly and does not require any additional sensors or electrodes attached to the body, hence no conductive gel or skin preparation.

Data Collection System of EEG Based on USB Interface

This article introduces a EEG synchronous sampling system and its hardware composing principle and software design method which is based on USB interface IC FT245BM, simultaneous and high speed 16 bit ADC IC ADS8320 with 16 channels, and 8 bit SCM AT89C51. This system can fully enhance the veracity of data measuring, and show its superiority in the precise measurement of the EEG parameters. This system has come into operation and produced good effect.

Hedgehog Pathway Expression in Heterogeneous Pancreatic Adenocarcinoma: Implications for the Molecular Analysis of Clinically Available Biopsies

Recent studies suggest that hedgehog (HH)-pathway signaling is required for the initiation and continued growth of pancreatic adenocarcinoma (PAC). Definitive gene expression analysis of PAC remains difficult, owing to the host desmoplastic stromal interaction and subsequent tumor heterogeneity. The primary goal of this study was to evaluate the effect of heterogeneity within a series (n=5) of matched clinical PAC biopsies [snap-frozen, formalin-fixed paraffin-embedded (FPE), endoscopic ultrasound-guided fine-needle aspirate (EUS-FNA)]. Differential expressions, specific to tumor cells, were evaluated by comparisons of uninvolved pancreas (n=9), EUS-FNA (n=14), and macrodissected (tumor-cell-enriched) biopsies (n=16). To determine whether treatment modulates gene expression, a unique (independent) set of synchronous EUS-FNA samples (n=4) was obtained before, and 2 weeks after, chemoradiation. mRNA levels were evaluated using real-time quantitative polymerase chain reaction formatted in a TaqMan low-density array, which was capable of simultaneously quantifying 46 independent genes in the HH pathway. Protein levels for Patched, Smoothened, and glioma-associated oncogene 1 (Gli-1) in FPE tissues were determined, using immunohistochemistry. A significant concordance (P<0.0001) was observed in the HH-pathway mRNA levels between matched surgically resected (both snap-frozen and FPE) and EUS-FNA biopsies. HH-pathway mRNA levels changed (increased) only after macrodissection, suggesting localization to tumor cells. Immunohistochemical staining for Patched, Smoothened, and Gli-1 confirmed the increased (P<0.001) levels of protein in the PAC cells, compared with cells from uninvolved pancreas. EUS-FNA biopsies that were obtained before and during chemoradiation demonstrated no significant changes in HH-pathway gene expression. Collectively, these studies demonstrate presence of HH-pathway expression in all the clinical PAC biopsies examined, suggesting that this is a significant tumor-associated target and offering the possibility that specific molecular profiling might be attempted from these heterogeneous tissues.

Carbonaceous and inorganic species in atmospheric aerosols during wintertime over urban and high‐altitude sites in North India

Synchronous sampling of bulk‐aerosols, carried out during wintertime from the two strategically located sites in North India, reveals that total suspended particulates (TSP) over an urban site (Hisar: 29.2°N 75.7°E; 219 m asl) ranged from 67 to 396 μg m−3; in contrast, TSP at Manora Peak (a high‐altitude station: 29.4°N 79.5°E; 1950 m asl) was relatively low (range: 13.7 to 42.7 μg m−3). At Hisar, on average, water‐soluble ionic species (WSIS, range: 14.1 to 78.3 μg m−3) contribute nearly one‐fourth by weight to TSP, with dominant contribution from SO42−, NO3− and NH4+. The time series analysis over a span of 30 days shows somewhat uniform distribution of organic carbon/elemental carbon (OC/EC) ratio centering around 8.5 ± 2.2 at this urban site; and the water‐soluble organic components (WSOC range: 6.7 to 42.0 μg m−3) account for 11.5 % to the TSP concentration. Both WSOC and OC exhibit significant positive correlation with water‐soluble K+ (r = 0.88 and 0.79 respectively), suggesting their dominant contribution from biomass burning. At Manora Peak, the chemical composition of ambient aerosols show characteristically lower abundances of WSIS (range: 2.0 to 9.9 μg m−3) and WSOC (range: 1.4 to 6.0 μg m−3); together they account for one‐third of the TSP. The characteristic low abundances of OC (range: 2.8 to 6.9 μg C m−3) and EC (range: 0.34 to 1.4 μg C m−3) at this high‐altitude site and their significant correlation with K+ and SO42− suggest contribution from long‐range transport of anthropogenic species. This study represents a first comprehensive data set for documenting the chemical characteristics of ambient aerosols and source apportionment of EC, OC, WSIS and mineral dust over urban and high‐altitude sites in north India, an important data set required for the south Asian region. If the observed OC/EC ratios far greater than ∼2 (unlike reported values in the literature for urban sites) and the semi‐empirical estimates of secondary OC are typical of the annual average abundances in the ambient aerosols over north India, then the temporal and regional analyses of primary and secondary OC using the existing emission models require reassessment for this region.

Reproducibility of blood tests of liver fibrosis in clinical practice

Objectives: To evaluate the inter-laboratory reproducibility of blood test for liver fibrosis: FibroMeter, Fibrotest, APRI and their composites variables. Design and methods: Four studies, including 147 patients, were performed: study #1 included 2 metachronous blood samples and 2 laboratories; studies #2, #3 and #4 included synchronous samples with assays delayed at day 1 in 12 laboratories, at day 0 in 10 laboratories and at day 0 or 1 in 2 laboratories, respectively. Agreement was evaluated by the intraclass correlation coefficient ( r ic). Results: In studies #1, #2 and #4, r ic for FibroMeter was 0.893, 0.942 and 0.991, respectively. In study #3, the r ic were: FibroMeter: 0.963, Fibrotest: 0.984, APRI: 0.949. Large simulated variations in composite variables had a weak impact on FibroMeter. Conclusions: When blood marker limits are controlled, inter-laboratory agreement of blood tests is excellent in clinical practice conditions. Blood tests are robust against the variability of composite blood variables.

Synchronous Sampling and Demodulation in an Instrument for Multifrequency Bioimpedance Measurement

Direct sampling of known carriers is the preferred digital method for measuring biomodulation of tissue impedance. Due to limited resolution and conversion rate of analog-to-digital converters and limited processing power of available digital processors and/or lack of energy resources, conventional discrete-Fourier-transform-based algorithms are not efficient in small medical devices. Knowing exactly the frequencies of carriers (and excitations), an energy-saving fast signal processing method can be developed and implemented. When sampling synchronously with a carrier, it is possible to minimize the complexity of calculations and to introduce a digital-to-analog feedback for enhancement of resolution by digitizing only the small variations between adjacent samples. The proposed system is qualified on proprietary hardware.

Synchronous averaging for asynchronous sampling data

AbstractThe 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. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(2): 33– 41, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20455

Models and Algorithms for Tracking of Maneuvering Objects Using Variable Rate Particle Filters

Standard algorithms in tracking and other state-space models assume identical and synchronous sampling rates for the state and measurement processes. However, real trajectories of objects are typically characterized by prolonged smooth sections, with sharp, but infrequent, changes. Thus, a more parsimonious representation of a target trajectory may be obtained by direct modeling of maneuver times in the state process, independently from the observation times. This is achieved by assuming the state arrival times to follow a random process, typically specified as Markovian, so that state points may be allocated along the trajectory according to the degree of variation observed. The resulting variable dimension state inference problem is solved by developing an efficient variable rate particle filtering algorithm to recursively update the posterior distribution of the state sequence as new data becomes available. The methodology is quite general and can be applied across many models where dynamic model uncertainty occurs on-line. Specific models are proposed for the dynamics of a moving object under internal forcing, expressed in terms of the intrinsic dynamics of the object. The performance of the algorithms with these dynamical models is demonstrated on several challenging maneuvering target tracking problems in clutter.

Development of a Cryogen-Free Terahertz Time-Domain Magnetooptical Measurement System

We have developed a terahertz time-domain magnetooptical measurement system for investigating the carrier transport of semiconductors at low temperatures and high magnetic fields. To cool a superconducting magnet and a sample, Gifford–McMahon-type refrigerators were employed to avoid the use of liquid cryogen. However, the vibration of the refrigerator is a critical problem because it induces oscillation noise in measured waveforms of terahertz pulses. In order to overcome this problem, a synchronous data sampling method has been developed utilizing the sound of the refrigerator as a trigger for the waveform acquisition. This sampling method succeeded in eliminating the oscillation noise completely. Our measurement system enables us to obtain the magnetooptical spectra in the frequency range from 0.2 to 1.5 THz at temperatures between 5 and 300 K in magnetic fields of up to ±10 T. As an example, the measurement of the cyclotron resonances of a two-dimensional electron gas in a GaAs/AlGaAs heterostructure is demonstrated.

High-Accuracy Methods and Measurement Procedures for Power Quality Parameters Using the Digital Synchronous Sampling Technique

This paper describes the accurate methods for the determination of power quality parameters. The methods and procedures described apply to the measurement of harmonics, flicker, fluctuating harmonics, and interharmonics and allow uncertainties of some parts in 106 to be attained

Implementation of an OFDM underwater acoustic communication system on an underwater vehicle with multiprocessor structure

Orthogonal frequency division multiplexing (OFDM) can fully use the frequency band and transmit data at high speeds. The ADSP-TS101 is a high performance digital signal processor (DSP) with good properties that include parallel processing and a high speed. Aimed at the real-time processing requirement of the OFDM algorithm, an underwater acoustic communication system with real-time processing capability is carried out. The system is mainly composed of multiple ADSP-TS101s, a multi-channel synchronous sample module and a field programmable gate array (FPGA) chip. The multiprocessor structure is made up of a cluster/data flow associated multiprocessing parallel processing structure as the operation kernel, and a multi-channel synchronous sample module is designed to realize no phase warp among the multiple channels’ data at the same time. The digital modulation/demodulation methods are applied to the OFDM algorithm. Through experiments in a lake, the results show that the system has good stability and real-time processing capability, thus satisfying the design requirements.

Frequency-Offset PLL for Synchronous Optical Sampling of OTDM Signals

We demonstrate a novel synchronization scheme for optical sampling which is based on a nonstandard phase-locked loop (PLL). Phase comparison is performed at a 10-GHz optical time-division-multiplexing (OTDM) base rate, thus avoiding ultrafast detectors and electronics. The employed frequency-offset PLL allows synchronous sampling of OTDM signals (or any other signals with bit rates given by integer multiples of the base rate), which would be impossible using a standard PLL. This provides a higher degree of flexibility for problem-specific sweeping than asynchronous sampling