Dispersion Monitoring Research Articles

On efficient use of auxiliary information for control charting in SPC

In Statistical Process Control (SPC), monitoring of the process dispersion has a major impact on the performance of processes like manufacturing, management and services. Control charts act as the most important SPC tool, used to differentiate between common and special cause variations in the process. The use of auxiliary information can enhance the detection ability of control charts and hence an efficient monitoring of process parameter(s) can be done. This study deals with the Shewhart type variability control charts based on auxiliary characteristics for the non-cascading processes, assuming stability of auxiliary parameters. The control chart structures of these variability charts are provided and their performance evaluations are carried out in terms of average run length (ARL), relative average run length (RARL) and extra quadratic loss (EQL) under the normal and t distributed process environments. The comparisons have been made among different variability charts and superiorities are established based on their detection abilities for different amounts of shifts in process dispersion. An illustrative example is also provided in support of the theory, and finally the study ends with concluding remarks and suggestions for future research.

In-Service Monitoring of Chromatic Dispersion With Filter-Bank Digitally Sub-Banded OFDM

We propose to use the recent filter-bank based receivers for robust, accurate, and low-complexity in-service chromatic dispersion estimation for quasi-Nyquist-shaped channels, impervious to channel impairments.

CSRZ 신호의 클럭 성분을 이용한 색분산 감시법에서 송수신단 대역폭의 영향 분석

광통신 시스템에서는 제한된 대역폭에서 최상의 성능을 얻기 위해 다양한 신호형태가 사용되고 있다. 그중에서도 CSRZ (carrier-suppressed return-to-zero) 신호는 스펙트럼 효율이 높으면서도 색분산에 대해 비교적 강인한 특성을 지니고 있어 많이 사용되고 있다. 우리는 이러한 CSRZ 신호의 중요성을 파악하고, 이전의 연구에서 CSRZ 신호의 클럭 (clock) 성분을 이용하여 색분산을 감시하는 방법을 제시한 바가 있다. 하지만, 클럭 성분을 이용하여 색분산을 감시하는 방법은 송수신단의 대역폭에 의해 그 영향을 받을 수 있다. 따라서, 본 논문에서는 CSRZ 신호에서 송수신단의 대역폭이 클럭 성분을 이용한 색분산 감시법에 미치는 영향을 분석하고, 송수신단의 대역폭이 변하더라도 그 성능이 유지될 수 있는 강인한 클럭 추출법을 제시한다. In optical fiber communications, several newly-developed signal formats are used to obtain the best performance within limited spectral bandwidth. CSRZ (carrier-suppressed return-to-zero) format is one of the new signal formats, which has better spectral efficiency and better robustness to dispersion than RZ (return-to-zero) format. Thus it is widely used for demonstrating high-speed optical communication systems. In an earlier research, we proposed a clock-extraction method of CSRZ signal to monitor chromatic dispersion. However, the clock-frequency component extracted by the clock-extraction method can be affected by the bandwidth of a transmitter or a receiver. Therefore, in this paper, we investigate the effect of bandwidth on the chromatic dispersion monitoring of CSRZ signal based on clock-frequency component. As a result, we propose a couple of robust clock-extraction methods to monitor chromatic dispersion in CSRZ signal.

Randomly Detected Genetically Modified (GM) Maize (Zea mays L.) near a Transport Route Revealed a Fragile 45S rDNA Phenotype

Monitoring of genetically modified (GM) crops has been emphasized to prevent their potential effects on the environment and human health. Monitoring of the inadvertent dispersal of transgenic maize in several fields and transport routes in Korea was carried out by qualitative multiplex PCR, and molecular analyses were conducted to identify the events of the collected GM maize. Cytogenetic investigations through fluorescence in situ hybridization (FISH) of the GM maize were performed to check for possible changes in the 45S rDNA cluster because this cluster was reported to be sensitive to replication and transcription stress. Three GM maize kernels were collected from a transport route near Incheon port, Korea, and each was found to contain NK603, stacked MON863 x NK603, and stacked NK603 x MON810 inserts, respectively. Cytogenetic analysis of the GM maize containing the stacked NK603 x MON810 insert revealed two normal compact 5S rDNA signals, but the 45S rDNA showed a fragile phenotype, demonstrating a “beads-on-a-string” fragmentation pattern, which seems to be a consequence of genetic modification. Implications of the 45S rDNA cluster fragility in GM maize are also discussed.

Format transparent, wide range and independent dispersion monitoring method based on four-wave mixing

In this paper we propose an improved all optical chromatic dispersion (CD) monitoring method based on highly nonlinear power transfer function (PTF) provided by four-wave mixing (FWM) in highly nonlinear fibers (HNLFs). This method can be applied for various modulation formats, including on–off keying and advanced multi-level modulation formats, without necessitating any changes of the hardware or software. Furthermore, it can expand the CD monitoring range beyond the limitation of Talbot effects and is insensitive to optical signal-to-noise ratio (OSNR) and polarization mode dispersion (PMD). These improvements are achieved by optimizing the profile of the PTF curve and utilizing a sweeping tunable dispersion compensator (TDC) in combination with an extremely simple digital signal processing (DSP) to find the zero residual dispersion point. Numerical simulations are then used to demonstrate the effectiveness of this method.

Particulate matter pollution over a Mediterranean urban area

The main purpose of this study is to investigate the aerosols' (PM10, PM2.5, and PM1) spatial and temporal distribution in different types of environment in a Mediterranean urban region, the Greater Athens Area based on data from a sampling campaign that took place during the cold and warm period of 2008. The influence of the atmospheric circulation patterns, the possible local transport mechanisms, as well as the differentiation of the PM behaviour from that of the inorganic pollutants (NOx, O3), are analysed and discussed. Furthermore, the Comprehensive Air Quality Model with extensions (CAMx) was applied for selected sampling dates and its results were evaluated against measurements in order to interpret qualitatively the configured picture of the air pollution above the GAA. Analysis of the measurement data show that local sources such as traffic and industry dominate over the prevailing PM loads, especially at the ‘hot spot’ areas. Moreover, the synoptic circulation patterns associated with calm conditions and southerly flows lead to high particulate pollution levels that also affect the urban background stations. Saharan dust outbreaks appeared to increase the particles' diameter as well as the number of E.U. limit value exceedances within the stations of our network. Without any dependence on the characteristics of the investigated atmosphere, PM1 always constituted the greatest part of the PM2.5 mass while PM10, especially during the Saharan dust episodes, was mainly constituted by the coarse fraction. The numerical modelling approach of the geographical distribution of PM10, PM2.5, NOx and O3 justified the design of the sampling campaign, indicating the need for the systematic and parallel monitoring and modelling of the pollutants' dispersion in order to understand the particulate pollution problem in the GAA and to aid to the formulation of pollution control strategies.

Research on Sustainable Environmental Monitoring System Based on GSM

Along with the high development of economy, the environment pollution is more serious because of the lack of Environment Control Unit (ECU) and the lag of the monitoring means. At the same time, with the fast development of mobile communication network, the remote monitoring system based on global system for mobile communication (GSM) is well applied in the environmental monitoring fields etc. which requires abroad overcast, less data transmission and dispersed monitoring points. To this question, the remote ECU based on GSM was designed and the control scheme of data-collecting system was emphasized introduced using of module TC35i and W78E516B, also the serial communication programs with Visual C++ was studied. This system is characterized by simple structure, high reliability and easy operation and will be extensive used in environmental monitoring, fire monitoring for electric power system, temperature monitoring for barn and material warehouse etc.

A novel chromatic dispersion monitoring technique for 16/64-QAM system based on asynchronous amplitude histogram

A novel chromatic dispersion (CD) monitoring technique based on asynchronous amplitude histogram (AAH) for higher order modulation formats is proposed in this paper. Without demodulating the signal, in the monitoring scheme, the received signal is sampled asynchronously, and thus clock information and high-speed sampling units are unnecessary, resulting in low cost and high reliability. Simulations of CD monitoring technique for non-return-to-zero/return-to-zero (NRZ/RZ) 16- and 64-quadrature amplitude modulation (QAM) systems with different optical signal-to-noise ratios (OSNRs) and duty cycles are investigated, and the tolerance of the scheme is also discussed. Simulation results show that the presented CD monitoring technique with high sensitivity can be applied to monitor the residual CD of a transmission link in the next-generation optical networks.

MDEWMA chart: an efficient and robust alternative to monitor process dispersion

Control chart is the most important statistical process control tool used to monitor changes in process location and dispersion. In this study, an EWMA control chart is proposed for efficient and robust monitoring of process dispersion. The proposed chart, namely the MDEWMA chart, is based on estimating the process standard deviation (σ) using the mean absolute deviations (MD), taken from the sample median. The performance of the proposed chart has been compared with the EWMASR chart (a dispersion EWMA chart based on sample range) and MD chart (a Shewhart-type dispersion chart based on MD), under the existence and violation of normality assumption. It has been observed that the proposed MDEWMA chart is more efficient and robust when compared with both EWMASR and MD charts in terms of run length (RL) characteristics such as average RL, median RL and standard deviation of the RL distribution.

A Study on Design and Implementation of Remote Fire Monitoring System for Buildings

Abstract The paper discusses how to design and implement the remote fire monitoring system based on the widely used dispersed fire monitoring method. The study analyses the division of system functions, which have been utilized to build monitoring centres, public security and fire departments and buildings in need of fire-monitoring system. It also establishes a basic structure of a remote frre monitoring system and focuses on describing the intemetworking technology of the equipment in remote fire monitoring system. The network connection schemes for frre controller and video monitoring system are provided as well.

Improved all optical chromatic dispersion monitoring method for WDM systems

In this paper we propose an improved all optical chromatic dispersion (CD) monitoring method applicable to wavelength division multiplexing (WDM) systems with intensity or phase modulation format. This method can operate over a much larger bandwidth and CD monitoring range and is insensitive to optical signal-to-noise ratio (OSNR) and polarization mode dispersion (PMD). These improvements are achieved by utilizing a wavelength tunable laser as the probe to maintain the appropriate phase-matching condition and a loop-back controlled tunable CD compensator to discriminate CD distortions from PMD and OSNR influences. Numerical simulations show that by this method the operational bandwidth and CD monitoring range can be expanded to cover C+L bands and ±1600ps/nm, respectively, for different modulation formats and the sensitivity is higher than the other methods proposed before.

CD-insensitive PMD monitoring using electronic domain orthogonal coherent processing for OOK optical link at 40 Gbits/s

We theoretically and experimentally demonstrated the polarization mode dispersion (PMD) monitoring of 40Gbit/s NRZ and RZ links by using a electronic domain orthogonal coherent technique; this method can detect the spectrum phase difference between the fast axes and slow axes. In my experiments, the radio frequency (RF) of local oscillator (LO) is set to 5GHz, the monitoring range is around 0–100 ps, the maximum fluctuation range of measured phase difference is better than 0.05rad for 40Gbit/s NRZ link. This method is independent on data rate for intensity modulation direct detection (IM/DD) links.

Application of Photothermal and Photoacoustic Spectroscopy for the Monitoring of Aqueous Dispersions of Carbon Nanomaterials

Photothermal and optoacoustic spectroscopy in their state-of-the-art techniques—multiwavelength, scanning and transient—are used for complex investigation and analysis (chemical analysis and the estimation of physicochemical properties and size) of novel carbon materials—fullerenes and nanodiamonds—and their aqueous dispersions as promising biomedical nanosystems. The estimation of the cluster size and the possibilities to determine subnanogram amounts of both nanodiamonds and fullerenes by these techniques are shown. The comparison of fullerene solutions in various solvents, toluene, N-methylpyrrolydone and water, is made. The advantages of the photothermal and optoacoustic techniques over conventional spectroscopies and the current limitation are discussed. The necessity to develop robust models for transient and imaging photothermal techniques is outlined.

Range Control Charts Revisited: Simpler Tippett-like Formulae, Its Practical Implementation, and the Study of False Alarm

This article presents simpler alternative formulae and procedures of implementation to deal with the relative range statistic used in the range control chart for process dispersion monitoring. The chart performance is assessed considering false alarm comparison between our exact limits charts versus normal approximated ones, which shows the serious drawbacks of such misplaced control limits. These much simple tools introduced here, we believe, will permit the presentation of R charts more transparently and without unrealistic normal approximations, avoiding the serious limitations of such “ad hoc” practice.

Experimental Demonstration and Analytic Derivation of Chromatic Dispersion Monitoring Technique Based on Clock-frequency Component

In an earlier work, we proposed the chromatic dispersion monitoring technique of non-return to zero (NRZ) signal based on clock-frequency component (CFC) through numerical simulations. However, we have not yet shown any experimental demonstration or analytic derivation of it. In this paper, we show an experimental demonstration and analytic derivation of the proposed chromatic dispersion monitoring technique. We confirm that the experimental results and the analytic results correspond with the simulation results. We also demonstrate that monitoring range and accuracy can be improved by using a simple clock-extraction method.

Chromatic Dispersion Monitoring for NRZ-DPSK System Using Asynchronous Amplitude Histogram Evaluation

We propose and demonstrate a chromatic dispersion (CD) monitoring technique for a nonreturn-to-zero differential phase-shift keying (NRZ-DPSK) signal generated with a Mach-Zehnder modulator at 40 Gb/s by analyzing the waveform overshoot after transmission. Without demodulating the NRZ-DPSK signal, the CD up to 120 ps/nm is monitored experimentally via the amplitude of the overshoot. Furthermore, based on the asynchronous amplitude histogram (AAH) evaluation method, a novel histogram processing method, which is more convenient, is proposed and investigated. Experimental results show that the monitoring scheme for CD is independent of optical signal-to-noise ratio (OSNR) within a certain range. This technique needs neither demodulating the signal nor extracting the synchronous clock, and it can be applied to high-order modulation formats at different bit rates.

Using a multi-frequency acoustic backscatter system as an in situ high concentration dispersion monitor

This paper demonstrates the potential of an in situ acoustic backscatter system (ABS) to measure particle dispersion concentrations in small and large scale mixing vessels. The ABS unit employs 1, 2, 4 and 5MHz transducers that emit ultrasonic pulses and receive the resultant echo backscatter signals, with the strength of the return being related to particle concentration. In small scale studies (where the effect of depth-wise attenuation is effectively ignored), a peak is measured in the strength of the echo responses at intermediate concentrations, due to a balance of the backscatter and attenuation components on the overall signal. The average measured responses were then compared to backscatter theory, which suggested that such analysis is invalid for systems with particle levels greater than ∼2.5g/L and qualitative approaches may be necessary to correlate concentration.More detailed analysis is undertaken in a larger-scale system, where the deviation between expected depth-wise theoretical response and real experimental echo decays are quantified for individual frequencies. It is shown that theoretical estimations heavily over-predict the strength of backscatter echoes at higher particle concentrations, likely due to increasing inter-particle scattering, and such effects are most evident for the highest frequency tested. Because of these limitations, dispersion concentration is correlated using qualitative approaches. For the 4 and 5MHz responses, which had approximated linear depth-wise decays (on a dB scale), it is found that the gradient of the attenuation decay slope (in dB/m) increases linearly with respect to particle concentration, which allowed the formation of a direct correlation relationship. For the 1 and 2MHz responses, the interpolated differential is calculated for specific depth points. Again, a linear correlation is established between the gradient of attenuation and particle concentration, where importantly, it was found that this gradient is independent of dispersion depth. This result highlights the possibility of measuring concentration variation in larger scale systems, simply from the associated differential attenuation changes, and indicates the potential of acoustic techniques for the monitoring and characterisation of industrial multiphase systems.

Optical Performance Monitoring Using Artificial Neural Networks Trained With Empirical Moments of Asynchronously Sampled Signal Amplitudes

We propose a low-cost technique for simultaneous and independent optical signal-to-noise ratio (OSNR), chromatic dispersion (CD), and polarization-mode dispersion (PMD) monitoring in 40/56-Gb/s return-to-zero differential quadrature phase-shift keying (RZ-DQPSK) and 40-Gb/s RZ-DPSK systems, using artificial neural networks (ANN) trained with empirical moments of asynchronously sampled signal amplitudes. The proposed technique employs an extremely simple hardware and digital signal processing to enable multi-impairment monitoring at different data rates and for various modulation formats without necessitating hardware changes. Simulation results demonstrate wide dynamic ranges and good monitoring accuracies.

Simultaneous chromatic dispersion monitoring, extinction ratio enhancement and wavelength conversion using four-wave mixing

This paper presents a multi-functional all-optical device performs simultaneous chromatic dispersion (CD) monitoring, extinction ratio (ER) improvement and tunable wavelength conversion using four-wave mixing (FWM) in a single piece of highly nonlinear optical fiber (HNLF). The multi-functional ability arises from the nonlinear power transfer function (PTF) between the input signal and the output idler wave, which not only maps the CD information of the signal onto the average power of idler wave, but also transfers the data information to the idler wave with ER enhancement, making the device compact and cost effective. Furthermore within the wavelength tuning range the monitoring sensitivity and output ER can be much higher compared to all optical monitors and regenerators proposed before. Numerical simulations are then used to demonstrate the efficiency of this method.

On Efficient Monitoring of Process Dispersion using Interquartile Range

The presence of dispersion/variability in any process is understood and its careful monitoring may furnish the performance of any process. The interquartile range (IQR) is one of the dispersion measures based on lower and upper quartiles. For efficient monitoring of process dispersion, we have proposed auxiliary information based Shewhart-type IQR control charts (namely IQRr and IQRp charts) based on ratio and product estimators of lower and upper quartiles under bivariate normally distributed process. We have developed the control structures of proposed charts and compared their performances with the usual IQR chart in terms of detection ability of shift in process dispersion. For the said purpose power curves are constructed to demonstrate the performance of the three IQR charts under discussion in this article. We have also provided an illustrative example to justify theory and finally closed with concluding remarks.