Order Autocorrelation Research Articles

Contribution of Teachers’ Qualification Level on Employability in African Economies, through Econometric Estimation of the Generalized Method of Moments, 2016–2020 — A Secondary Publication

Both education and its quality supply are closely linked to employability and labour productivity. The present study aimed to analyze the contribution of the level of teacher qualification on the employability variable in African economies, for the period 2016–2020. Regarding the methodology, a quantitative analysis of the data was conducted through the Generalized Method of Moments in Differences, two stages and with standard error correction. Based on the results, it was possible to determine the existence of a negative, inverse and significant relationship between the degree of qualification of teachers on the unemployment rate; therefore, it could be concluded that a higher level of qualification of teachers has a direct contribution on the increase in the levels of employability for the African business sector. Through the results of Hansen’s Test (P-value = 0.540), the validity of the model’s specificity in terms of instrument utilization was tested. Based on the first (P-value = 0.009) and second order (P-value = 0.148) autocorrelation tests, the validity of the consistency of the Generalized Method of Moments econometric estimators in differences, two stages and with corrected standard errors was tested.

Measurement of third order coherence by in situ autocorrelation for determining three-photon cross-sections.

We show theoretically that the third order coherence at zero delay can be obtained by measuring the second and third order autocorrelation traces of a pulsed laser. Our theory enables the measurement of a fluorophore's three-photon cross-section without prior knowledge of the temporal profile of the excitation pulse by using the same fluorescent medium for both the measurement of the third order coherence at zero delay as well as the cross-section. Such an in situ measurement needs no assumptions about the pulse shape nor group delay dispersion of the optical system. To verify the theory experimentally, we measure the three-photon action cross-section of Alexa Fluor 350 and show that the measured value of the three-photon cross-section remains approximately constant despite varied amounts of chirp on the excitation pulses.

Single photon emission from in situ created nitrogen-vacancies in chemical vapor deposition grown single crystal diamond

The work reports the manipulation of nitrogen-vacancy centres in chemical vapor deposition grown single crystal diamonds by incorporation of nitrogen, boron and oxygen during the growth process. Single photon emission measurements were performed on diamond samples by using continuous wave and pulsed laser of wavelength 532 nm. The second order auto-correlation measurement 0.3<g2(0)<0.6 on nitrogen incorporated diamond sample shows the anti-bunching behavior of photons emerging from the population of one- and two-color centres. However, the correlation measurement 0.6<g2(0)<0.8 on oxygen and boron incorporated diamond samples show the anti-bunching behaviour of photons due to population of two- and three-color centres present in the samples. The result opens the possibilities of in situ development of nitrogen-vacancy centres in diamond during the growth process for next generation quantum computing devices.

Applying Time Series Analysis to Study the Development Trend and Influencing Factors of Ethnic Folk Dance

Abstract In this paper, firstly, we propose to use time series analysis to observe the development and change process of social events, using the DF test and ADF test to eliminate the random autocorrelation in order to exclude the interference of white noise series. Secondly, the instantaneous frequency of non-smooth data is defined by analyzing the signal, and the constraints are modified from global constraints to local constraints. The Fourier-transformed eigenmode function is used to satisfy the four necessary conditions of completeness, orthogonality, localization, and adaptability. Finally, the development trend of ethnic folk dances and the change in communication dynamics are analyzed. The results show that the change of language on the spreading attitude of folk dance is 4.381, the change of custom on the spreading attitude is 5.943, the change of culture on the spreading attitude is 10.866, and the change of culture on the spreading attitude of folk dance is the largest, which shows that the development of folk dance away from the development of folk dance is not separated from the support of culture. The study will have a positive impact on passing on the distinctive art of ethnic folk dance and enriching Chinese traditional culture and art.

Maximum Likelihood Estimation for Non-Stationary Location Models with Mixture of Normal Distributions

We consider an observation-driven location model where the unobserved location variable is modeled as a random walk process and where the error variable is from a mixture of normal distributions. The time-varying location can be extended with a stationary process to account for cyclical and/or higher order autocorrelation. The mixed normal distribution can accurately approximate many continuous error distributions. We obtain a flexible modeling framework for the robust filtering and forecasting based on time-series models with non-stationary and nonlinear features. We provide sufficient conditions for strong consistency and asymptotic normality of the maximum likelihood estimator of the parameter vector in the specified model. The asymptotic properties are valid under correct model specification and can be generalized to allow for potential misspecification of the model. A simulation study is carried out to monitor the forecast accuracy improvements when extra mixture components are added to the model. In an empirical study we show that our approach is able to outperform alternative observation-driven location models in forecast accuracy for a time-series of electricity spot prices.

Comparing some panel data estimators in the presence of autocorrelation

In this work, panel data that were characterized by features of no first order autocorrelation was modelled using three estimation models: Pool Regression, Fixed Effect, Random Effect models. Panel data like other aspects of econometrics, exploits regression analysis as one of the statistical tools to formulate and illustrate models. The regression analysis requires some assumptions which, if violated, results to one problem or the other. In such case, the Pooling method of estimation remains linear, unbiased and normally distributed but might not be efficient as the estimates of the parameters might become indeterminate, the confidence intervals may be too wide and the standard errors might become large. Simulation studies were carried out at different panel structures and autocorrelation level. The experiment was repeated for 10,000 times and Root Mean Square Error (RMSE) was used to judge the performance of the models. The results from this work showed that for small sample panel structure N = 25, T = 5 and n = 5, irrespective of autocorrelation levels, fixed effect model is preferable at all level. But when moderate for N = 50, T = 10, n = 5, irrespective of autocorrelation level, random effect model is preferred, while for large panel structure for N = 450, T = 30, n = 15, irrespective of autocorrelation level, random effect model is preferred.

Machine learning assisted quantum super-resolution microscopy

One of the main characteristics of optical imaging systems is spatial resolution, which is restricted by the diffraction limit to approximately half the wavelength of the incident light. Along with the recently developed classical super-resolution techniques, which aim at breaking the diffraction limit in classical systems, there is a class of quantum super-resolution techniques which leverage the non-classical nature of the optical signals radiated by quantum emitters, the so-called antibunching super-resolution microscopy. This approach can ensure a factor of sqrt{n} improvement in the spatial resolution by measuring the n -th order autocorrelation function. The main bottleneck of the antibunching super-resolution microscopy is the time-consuming acquisition of multi-photon event histograms. We present a machine learning-assisted approach for the realization of rapid antibunching super-resolution imaging and demonstrate 12 times speed-up compared to conventional, fitting-based autocorrelation measurements. The developed framework paves the way to the practical realization of scalable quantum super-resolution imaging devices that can be compatible with various types of quantum emitters.

COMPARING VALUE - BASED AND TRADITIONAL MEASURING TOOLS. EVIDENCE FROM PAKISTAN

This paper's primary goal is to evaluate the assertion that value-based measures are preferable to traditional accounting based financial-performance measures, such as profit after tax (PAT), earnings per share (EPS), return on assets (ROA), return on equity (ROE), and return on investment (ROI), in the non-financial sector of Pakistan, while also providing empirical evidence to support the claim. Additionally, it evaluates and tests the informational value of different performance measures and how they relate to stock return. The sample of 97 non-financial Pakistani companies included in this study was obtained from the Pakistan Stock Exchange (PSX) between 2016 and 2021. The information richness of value-based measurements and conventional performance measures in explaining shareholders' returns is investigated using a variety of regression models. Relative information content tests shows that traditional accounting-based measures such as EPS, ROE and ROA performed better than value based measures in explaining the returns of Pakistan non-financial companies. Incremental information content of value based measures doesn’t have any contribution to information content above traditional performance measures. The claim of superiority of value based measures over accounting-based measures in association with shareholder returns is proved invalid in Pakistan non-financial companies. According to the study's findings, value-based financial performance indicators are not any better at explaining stock returns of Pakistani non-financial enterprises than traditional accounting-based financial performance measures. Panel data are tested using the Hausman's test for fixed and random effects, the variance inflation factor (VIF) test for multicollinearity, and the Durbin-Watson test for autocorrelation in order to ensure substantial results.

Motion Robust MR Fingerprinting Scan to Image Neonates With Prenatal Opioid Exposure.

To explore whether MR fingerprinting (MRF) scans provide motion-robust and quantitative brain tissue measurements for non-sedated infants with prenatal opioid exposure (POE). Prospective. 13 infants with POE (3 male; 12 newborns (age 7-65 days) and 1 infant aged 9-months). 3T, 3D T1-weighted MPRAGE, 3D T2-weighted TSE and MRF sequences. The image quality of MRF and MRI was assessed in a fully crossed, multiple-reader, multiple-case study. Sixteen image quality features in three types-image artifacts, structure and myelination visualization-were ranked by four neuroradiologists (8, 7, 5, and 8 years of experience respectively), using a 3-point scale. MRF T1 and T2 values in 8 white matter brain regions were compared between babies younger than 1 month and babies between 1 and 2 months. Generalized estimating equations model to test the significance of differences of regional T1 and T2 values of babies under 1 month and those older. MRI and MRF image quality was assessed using Gwet's second order auto-correlation coefficient (AC2) with confidence levels. The Cochran-Mantel-Haenszel test was used to assess the difference in proportions between MRF and MRI for all features and stratified by the type of features. A P value <0.05 was considered statistically significant. The MRF of two infants were excluded in T1 and T2 value analysis due to severe motion artifact but were included in the image quality assessment. In infants under 1 month of age (N = 6), the T1 and T2 values were significantly higher compared to those between 1 and 2 months of age (N = 4). MRF images showed significantly higher image quality ratings in all three feature types compared to MRI images. MR Fingerprinting scans have potential to be a motion-robust and efficient method for nonsedated infants. 2 TECHNICAL EFFICACY STAGE: 1.

Inequality, population growth, and hunger in Sub-Saharan Africa.

Despite increasing population and inequality in most countries in Sub-Saharan Africa (SSA) and their tendencies to aggravate hunger there is still dearth of knowledge on their effects on hunger in the region. Therefore, the study used data for 46 SSA countries from 2007 to 2017 to examine the effects of inequality and population on hunger by adopting the System Generalized Method of Moment approach as it is specifically applicable in this situation. Results showed that inequality (p < 0.01) and population growth (p < 0.1) significantly increased the level of hunger, while GDP per capita (p < 0.01) and Food Production index (p < 0.1) significantly reduced hunger in the region. Arellano-Bond test confirmed the validity of the GMM results by rejecting the null hypothesis of non-existence of autocorrelation of the first order and accepting that of the second order in the disturbance term, while the Hansen and Sargan tests affirmed that variables used as instruments were valid in line with expectations. Robustness of the result was also confirmed as the coefficient of the lagged response variable (0.8701) fell between the fixed effect model estimate (0.5165) and pooled OLS estimate (0.9571) in line with theory. The study recommended policies capable of reducing inequality, boosting economic growth, and controlling excessive population growth, while food production and value addition are encouraged in order to avert hunger in the region.

Attosecond stable dispersion-free delay line for easy ultrafast metrology

We demonstrate a dispersion-free wavefront splitting attosecond resolved interferometric delay line for easy ultrafast metrology of broadband femtosecond pulses. Using a pair of knife-edge prisms, we symmetrically split and later recombine the two wavefronts with a few tens of attosecond resolution and stability and employ a single-pixel analysis of interference fringes with good contrast using a phone camera without any iris or nonlinear detector. Our all-reflective delay line is theoretically analyzed and experimentally validated by measuring 1st and 2nd order autocorrelations and the SHG-FROG trace of a NIR femtosecond pulse. Our setup is compact, offers attosecond stability with flexibility for independent beam-shaping of the two arms. Furthermore, we suggest that our compact and in-line setup can be employed for attosecond resolved pump-probe experiments of matter with few-cycle pulses.

A novel targeted method of informative frequency band selection based on lagged information for diagnosis of gearbox single and compound faults

Detection of compound faults in rotating machinery remained a challenge in the field of fault diagnosis since the presence of multiple faults at the same time acts as an interference in the isolation of a specific fault signature. One of the widely used methods in rotating machinery fault diagnosis is envelope analysis. The envelope spectrum of a properly band-pass filtered signal could be informative about the presence of a fault. The main challenge in envelope analysis is the selection of appropriate criteria to choose the most informative frequency band. A novel targeted informative frequency band selection method have been proposed in this work, which will be referred as Lagged Information Spectrum (LIS). Lagged information inspired by the fractional lower order autocorrelation and its logarithm-based derivation results in a close relation to the concept of negentropy. The proposed method can reduce the effect of both Gaussian and non-Gaussian noise in the signal, and in the same time, separate the signatures of compound faults. The performance of the proposed method has been evaluated under both simulated and experimental gearbox vibration signals and compared to a wide range of other previously established methods of informative frequency band selection. The results of simulated signal verify that the proposed method is more robust than other methods in the presence of Gaussian noise for noise to signal ratios up to 3 dB while its efficiency under moderate non-Gaussian impulsive noise is acceptable (up to 11 dB noise to signal ratio). One experimental case study of single chipping fault and two experimental case studies of compound wear/crack and chipping/spalling faults have been accomplished to show the performance of the proposed method in separation of fault signatures. The proposed method outperforms other methods in isolation of fault characteristic frequencies and generating higher quality spectra based on Fault Feature Coefficient (FFC) criterion, especially, in two compound fault case studies.

The asymmetric effects of changes in price and income on renewable and nonrenewable energy

Due to the ongoing climate change and environmental pollution, renewable energy supply has been overemphasized in many countries. Since an increase in the prices of non-renewable energy sources or the country's income might shift energy demand from non-renewable energy sources to renewable energy sources, this study examines the relationship of renewable and non-renewable energy consumptions with income and price. Whether price and income have an asymmetric effect on energy consumption was tested in the models constructed for 42 net energy exporter countries from 2000 to 2018. The asymmetry test indicates that only price has an asymmetric effect on solar, wind, and geothermal energy consumption among renewable energy sources, whereas both price and income have an asymmetric effect on oil consumption among non-renewable energy sources. According to the results of using specific heteroscedasticity and individual-specific first order autocorrelation to estimate the symmetric and asymmetric panel regression model, the income elasticity in the wind and solar energy models was more than one. Moreover, although the consumption of all energy sources is sensitive to the price of crude oil, positive shocks in prices are more effective on consumption than negative shocks in prices.

Statistical Analysis of Nigeria’s Price Sector: An Econometric Approach

This study analyzed Nigeria’s price sector using a formulated model for the price sector of the Nigeria economy. A set of simultaneous equations were used to reflect the implicit gross domestic product deflators for each of the sectors of the Nigeria economy and was found to be over identified under the order condition for identification. The model was estimated by ordinary least square method and two stage least square methods. All the variables have expected signs and as indicated by the F –statistic, the overall performance of the entire regression is significant. The high measure of R2 and Ṝ2, in each case indicates that the explanatory variables included in the equation jointly account for the entire variation. The small RMSE also indicates that the equations have good fit. Durbin –Watson statistics shows that there is no positive first order autocorrelation. The small value of the Theil’s inequality indicates that the equation has good predictive performance. The researcher therefore recommends that government should employ the model so as to be able to monitor price of each of the sectors of the economy and put proper mechanism in place to control those sectors that affect the overall price sector of the economy.

Eco-efficiency measurement and spatial–temporal evolution of forest tourism

Our study uses the SBM-undesirable output model of DEA to measure the eco-efficiency of 28 national forest parks and spatial autocorrelation in order to analyze the evolution of spatial–temporal evolution. The conclusions are as follows: (1) the average eco-efficiency of forest tourism in Liaoning is 0.88 between 2007 and 2016, at a relatively high level. The trend is upward although there is a small fluctuation. (2) The eco-efficiency in eastern and southern regions is obviously higher than that in northern and western ones. Fenghuang, Dahe, Huancheng, and Hemu have always been in effective frontier. The eco- efficiency increases greatly in eastern and southern regions but slowly or even stagnantly in northern and western ones. (3) According to the Moran index of forest tourism, regions with a similar level of eco-efficiency show the phenomenon of volatility agglomeration in space. From the local analysis, due to the positive radiation in eastern and southern regions, the eco-efficiency of forest tourism in Liaoning has been constantly improving. The original regional polarization situation has been improved, and the regional differences have been reduced.

Photon Statistics of Incoherent Cathodoluminescence with Continuous and Pulsed Electron Beams

Photon bunching in incoherent cathodoluminescence (CL) spectroscopy originates from the fact that a single high-energy electron can generate multiple photons when interacting with a material, thus, revealing key properties of electron–matter excitation. Contrary to previous works based on Monte Carlo modeling, here we present a fully analytical model describing the amplitude and shape of the second order autocorrelation function (g(2)(τ)) for continuous and pulsed electron beams. Moreover, we extend the analysis of photon bunching to ultrashort electron pulses, in which up to 500 electrons per pulse excite the sample within a few picoseconds. We obtain a simple equation relating the bunching strength (g(2)(0)) to the electron beam current, emitter decay lifetime, pulse duration, in the case of pulsed electron beams, and electron excitation efficiency (γ), defined as the probability that an electron creates at least one interaction with the emitter. The analytical model shows good agreement with the experimental data obtained on InGaN/GaN quantum wells using continuous, ns-pulsed (using beam blanker) and ultrashort ps-pulsed (using photoemission) electron beams. We extract excitation efficiencies of 0.13 and 0.05 for 10 and 8 keV electron beams, respectively, and we observe that nonlinear effects play no compelling role, even after excitation with ultrashort and dense electron cascades in the quantum wells.

Regional Reform and Its Impact on the Electoral Behavior during 2012 and 2017 Presidential Elections in France

The article deals with the 2015 territorial reform in France which reduced the number of regions and changed jurisdiction of the center and regions. In the paper the authors try to learn whether and how this reform affected electoral behavior in the regions during the first round of 2012 and 2017 presidential elections, whether there is a difference between them, and what are the voting patterns in French regions. The author used Moran’s index of spatial autocorrelation in order to answer the questions and analyze “neighborhood effect”. Besides the researcher employed multivariate explanatory data analysis to uncover the electoral patterns. Among the variables underlying the patterns the author selected socio-economic and demographic ones, as well as the number of criminal acts against Muslim-migrants in the context of the 2015 migrant crisis in Europe. The scholar concludes that territorial reform mitigated the neighborhood effect in regional electoral behavior which indicates the process of decentralization. As for electoral patterns, it is in the Eastern regions where the citizens vote for Marin Le Pen given high levels of migration and unemployment there. In the West where migration and unemployment are low people tend to choose a candidate whose agenda is not centered around migrants. The winner usually gets support from the capital region where migration and unemployment are low but many criminal acts against Muslim-migrants were reported. Consequently, the reform itself did not change electoral patterns in the regions which indicates the tendency towards recentralization and leaves the capital region in the center of political process.

Deterministic assembly of a charged-quantum-dot–micropillar cavity device

Developing future quantum communication may rely on the ability to engineer cavity-mediated interactions between photons and solid-state artificial atoms, in a deterministic way. Here, we report a set of technological and experimental developments for the deterministic coupling between the optical mode of a micropillar cavity and a quantum dot trion transition. We first identify a charged transition through in-plane magnetic field spectroscopy, and then tune the optical cavity mode to its energy via in-situ lithography. In addition, we design an asymmetric tunneling barrier to allow the optical trapping of the charge, assisted by a quasi-resonant pumping scheme, in order to control its occupation probability. We evaluate the generation of a positively-charged quantum dot through second order auto-correlation measurements of its resonance fluorescence, and the quality of light-matter interaction for these spin-photon interfaces is assessed by measuring the performance of the device as a single-photon source.

Autocorrelation-Based Quickest Change Detection

We consider the utilization of the autocorrelation information for aiding the quickest detection problem. Specifically, we investigate the problem of quickly detecting a Gaussian source with autocorrelation such that some of its symbols are repeated as cyclic prefixes. Based on the cumulative sum algorithm, we propose a method which takes advantage of this autocorrelation in order to provide performance improvement compared to the classical energy based detection of the uncorrelated source.

Are young trees suitable for climate-growth analysis? A trial with Pinus nigra in the central Apennines treeline

In the context of ecological research, tree-ring analysis often deals with short time series (< 30 years). Their crossdating and averaging can be difficult but crucial to use such data for ecological modelling, multivariate statistics, and climate-growth analysis. Several studies were conducted in the Central Apennines (Italy) on recent encroachment of European black pine (Pinus nigra J.F. Arnold) on treeless areas above the current forestline. Growth of young trees is mainly controlled by endogenous or microclimatic factors making usual dendrochronology methods less applicable and crossdating very difficult or even impossible. The potential ecological information deriving from tree-ring growth in short series is therefore limited by this methodological bias. The aim of this study is to test suitable methods for optimizing the use of short ring series for further analytical use. A dataset of 734 tree-ring series of young European black pines (mean cambial age 15 years) growing at high altitude in 8 sites was used in this analysis. At each site tree-ring series were divided in two groups based on inter-series correlation: the crossdated or selected series (SEL), and non-crossdated or rejected ones (REJ). The following dendrochronological parameters were calculated for SEL and REJ series: mean tree-ring width, mean sensitivity, Gini coefficient, first order autocorrelation, inter-series correlation, and Gleichläufigkeit (GLK). Two methods of pointer years analysis were tested in order to detect years with synchronous growth: i) Normalization in a moving Window (NW) and ii) the RElative growth change method (RE). The two methods were applied to the raw series varying the standard thresholds, in order to detect synchronous growth-years in SEL and REJ group. A sensitivity analysis was included to assess how the threshold choice in the analysis could affect the results obtained. The term “common” was used to indicate years with similar tree growth response. Differences in the detected number of common years within SEL and REJ were obtained using different time windows with the RE and NW methods. The 47 % of all series were classified as SEL, showing more common years than the REJ series. However, a similar result occurred considering all the series together without SEL/REJ discrimination. In general, a significant occurrence of common years could be a tool to select series to be averaged for a site mean chronology. These are preliminary but encouraging results contributing to a more efficient use of the ecological information provided by short time series from young trees.