Direct Correlation Method Research Articles

Wavelength dependences of the optical/UV and X-ray luminosity correlations of quasars

ABSTRACT The interband correlations between optical/ultraviolet (UV) and X-ray luminosities of active galactic nuclei (AGNs) are important for understanding the disc–coronal connection, as well as using AGN as standard candles for cosmology. It is conventional to measure the X-ray luminosity at rest-frame 2 keV and compare to the UV luminosity at the rest-frame 2500 Å, but the wavelength dependence was never well explored. In this work, we adopt a well-defined sample of 1169 unobscured quasars in the redshift range 0.13–4.51, and apply the direct-correlation method to explore how the correlation with the 2 keV luminosity changes at different optical/UV wavelengths, from 1280 to 5550 Å where the spectral quality is high. We find that the luminosity at all UV continuum wavelengths correlates with the X-ray luminosity similarly to that at 2500 Å, and that these correlations are better than at the optical wavelengths. Strong self-correlation is also found in the broad-band optical/UV continuum, supporting the scenario that it is dominated by the disc emission. Correlations of various emission lines are also investigated (e.g. C iv, C iii], Mg ii, Hβ, and [O iii]λλ4959/5007), including the Baldwin effect and correlations involving linewidths. We find the forms of these line correlations are different, and they are also different from their underlying continua, suggesting various complexities in the line-generation process. We discuss these results in the disc-wind scenario. Our study confirms that the rest-frame 2500 Å is a good wavelength to represent the optical/UV continual properties of quasars, and shows the advantages of the direct-correlation method.

Application of a Phase Resolved Partial Discharge Pattern Analysis for Acoustic Emission Method in High Voltage Insulation Systems Diagnostics

An alternative method for analysis of acoustic emission (AE) signals generated by partial discharges (PD), based on a correlation between voltage phase run and AE pulses, so called phase resolved PD pattern (PRPD), is presented in the paper. PRPD pattern is a well-known analysis tool commonly used in such PD diagnostic methods as conventional electrical and UHF ones. Moreover, it yields various signal analysis abilities and allows a direct correlation indication between measurement results achieved using different methods. An original PRPD measurement methodology applied for AE method as well as some exemplary measurement results and further data analysis capabilities are presented in the paper. Also a comparative analysis of PRPD patterns achieved using various measurement methods and different PD source configurations have been investigated. All presented experiments were done under laboratory conditions using PD model sources immersed in the insulation oil. The main purpose of the presented research is to indicate an all-embracing analytical tool that yields an ability to direct comparison (qualitative as well as quantitative) of the AE measurement results with other commonly applied PD measurement methods. The presented results give a solid fundamental for further research work concerning a direct correlation method for AE and other described in the paper diagnostic techniques, mainly in order to continue PD phenomena analysis and assessment in real life high voltage apparatus insulation systems under normal onsite operation conditions.

SHALLOW FOUNDATION BEARING CAPACITY ANALYSIS BASED ON CONE PENETRATION TEST

In the simple buildings, shallow foundations can be used to support the construction above them. This shallow foundation has various types, including the type of footplate which can be calculated using the Terzaghi equation. In the Terzaghi equation, it requires dimension parameters of the footing and soil material parameters such as cohesion and soil volume weight which requires laboratory testing to obtain it. Meanwhile, Schmertmann provides an equation to obtain the Terzaghi bearing capacity factor in the form of Nq and Nγ by using the Cone Penetration Test (CPT). This bearing capacity factor value can be used to calculate the bearing capacity using the Terzaghi Equation. In addition, Schmertmann also provides an equation to directly calculate the bearing capacity value based on CPT data. Based on this problem, this study analyzes the bearing capacity of various footplate dimensions using the Schmertmann approach. The study took place in the Argoboga, Salatiga which the type of soil based on the CPT test value generally is sandy soil. The results show that the bearing capacity calculated by the Nq correlation method is greater than the Nγ correlation method and the direct correlation method. In addition, the greater the difference between the dimensions and the depth of the foundation, the greater the deviation of the bearing capacity results between each method.

Distribution of hydrogen and oxygen stable isotope of water in soil-plant-atmosphere continuum (SPAC)system of a typical forest area

Water cycle in the soil-plant-atmosphere continuum (SPAC) is an important research topic in hydrology and ecology. The differences in the composition of hydrogen and oxygen stable isotopes in different water bodies can indicate water cycle process. Based on the measurements of isotopic compositions in precipitation, soil water, and plant water, we analyzed water isotope evolution in a SPAC system located in a subtropical evergreen broad-leaved forest in Chengdu Plain. The different interface processes of regional water cycle was revealed. The results showed that the local meteoric water line (LMWL) equation was δD=7.13 δ18O+2.35 (R2=0.99), and the soil evaporation line (SEL) equation was δD=6.98δ18O-0.32 (R2=0.92). In the water transportation process of precipitation-soil water-plant water, hydrogen and oxygen isotopes were gradually enriched. The δ18O in water of the surface soil layer (0-35 cm) was sensitive to precipitation input, as it was directly affected by precipitation. In contrast, the δ18O in water of the middle and deep layers (35-100 cm) was relatively stable. The isotopes of plant xylem water were slightly more enriched than those of soil water, indicating the possibility of slight evaporation or transpiration through phloem or bark in plant water transportation. The estimation of plant water intake from different soil layers was performed by direct correlation method. Cinnamomum camphora mainly used water from the middle layer, Broussonetia papyrifera mainly used that from the surface layer, and Parathelypteris glanduligera tended to use surface soil water and precipitation intercepted by plants because of the shallow root system. Compared with P. glanduligera, C. camphora and B. papyrifera experienced stronger water evaporation and the isotopes were influenced by more intense dynamic fractionation.

A computatively effective method for determining the parameters of nonharmonic sinusoidal signal spectrum components by direct correlation method

A computatively effective method for determining the parameters of nonharmonic sinusoidal signal spectrum components by direct correlation method

光阱中微粒位置高精度检测技术

Precision sensing and measuring based on optical trap technology is innovation and deepening for application of optical force effect from micro-precise manipulation to precise measurement of physical quantities. Precision measurement of position information of the particle in optical trap is key technology of precise sensing and measuring. The method was put forward, which used digital image processing and curve fitting algorithm to detect particle positions in optical trap. The normalized self-correlation function of particle positions was obtained by digital image correlation, and the quadratic curve fitting was used to the normalized self-correlation function curve by least-square method to realize particle position detection of sub-pixel accuracy. Experiments show that the method described in this paper can effectively suppress the quantization effect of hardware and realize fast and high-precision detection of particle position in optical traps. Compared with the direct correlation method, the detection accuracy can be improved by at least one order of magnitude to 0.03 pixel.

Relationship between solar activity and flood/drought disasters of the Second Songhua river basin

Based on the direct correlation method, this paper analyzes the correlation of sunspot number (SSN) and western Pacific subtropical high (WPSH) ridge index with flood/drought disasters in the Second Songhua River (SSHR) basin, combined with long sequences of SSN, WPSH ridge index, precipitation and other data. Results show that SSN is clearly correlated with flood/drought disasters, what is more, flood years mainly appear in three phases: Solar Maximum Year, years after Solar Maximum Year and Solar Minimum Year. In addition, there is an alternate change of flood/drought with a 10-year cycle. This paper uses the commensurable method to identify the periods of floods and droughts in the study area. According to the commensurable diagram, catastrophic nodes of the future floods or droughts in SSHR basin can be primarily predicted as follows: 2021 will be a flood year, while 2013, 2016 and 2024 will be high flow years; 2012 and 2022 will be dry years, while 2014, 2018 and 2027 will be low flow years. Moreover, forecast accuracy of flood/dry years is higher than the one of high/low flow years. Prediction of flood/drought has an error of ±1 year, which can be tracked and corrected with a scatter diagram.

Lightning VHF radiation location system based on short-baseline TDOA technique — Validation in rocket-triggered lightning

A lightning VHF radiation location system based on short-baseline time-difference of arrival (TDOA) technology is newly developed. Based on the orthogonal 10m-baseline antenna array with four identical broadband flat plane antennas, this system receives the lightning broadband VHF radiation signals and calculates TDOA between antennas in order to determine the location of lightning radiation sources in two dimensions (elevation and azimuth). To reduce noise and improve estimation accuracy of time delay, a general correlation time delay estimation algorithm based on direct correlation method and wavelet transform is proposed. Moreover, parabolic interpolation algorithm is used in the fractional delay estimation to improve the time resolution of the positioning system. In this paper, a rocket-triggered lightning discharge and a cloud lightning discharge are analyzed respectively, combining with simultaneous observations of high-speed camera and fast/slow electric field changes. The results indicate that the TDOA location system could effectively map the lightning radiation sources in 2 dimensions and are in a good agreement with the high-speed video camera images.

Three‐dimensional mapping of lingual myoarchitecture by diffusion tensor MRI

This study was performed to assess the feasibility of investigating the complex lingual myoarchitecture through segmentation of muscles from diffusion tensor imaging (DTI) data. The primary eigenvectors were found to be adequate for delineating the superior and inferior longitudinalis, genioglossus, and hyoglossus. The tertiary eigenvector orientations effectively revealed the homogeneous and systematic change of muscle orientation in the tongue core. In the longitudinalis near the tongue tip, the secondary eigenvectors were oriented in the radial direction. Lingual muscles were segmented using two methods: modified directional correlation (DC) and tensor coherence (TC) methods. The DC method, based on one eigenvector, was found to be inadequate for lingual muscle segmentation, whereas the TC method, based on the tensor shape and orientation, was used successfully to segment most lingual muscles. The segmentation result was used to report the diffusion tensor properties of individual lingual muscles. Also found was a continuous change in skewness of the intrinsic tongue core from negative in the anterior region to positive in the posterior region. DTI and the proposed segmentation method provide an adequate means of imaging and visualizing the complex, compartmentalized musculature of the tongue. The potential for in vivo research and clinical applications is demonstrated.

Development and investigation of real-time robust algorithms for estimating the parameters of geometric transformations of video-sequence frames

The problem of estimating the parameters of geometric transformations of the frames in a video sequence is considered. The solution to this problem is found through a combination of three basic approaches: the optical-flow feature-point methods and the direct correlation methods. A procedure for the detailed analysis of the behavior of the correlation function is used to ensure stable real-time operation of the proposed algorithms on modern (even unspecialized) computing systems for a wide range of shooting conditions.

画像の時空間微分を利用した流場の計測手法

Application of so-called gradient method to sub-pixel analysis was described, and the effects of the higher-order terms including external factors are considered. The authors has developed an algorithm by combining the direct correlation method and the gradient method. The new algorithm utilizes the merits of both methods, and the final accuracy is dominated with the accuracy of gradient method. In the present paper, the mechanism of error occurrence and its truncation procedure were considered theoretically, and the characteristics of errors caused by the external factor such as the change of the illumination strength were considered.

Testing of the bandpass eddy covariance method for a long-term measurement of water vapour flux over a forest

The bandpass eddy covariance method has been used to measure the turbulent flux of scalar quantities using a slow-responsescalar sensor. The method issimilar in principle to the traditional eddy correlation method but includes the estimation of high-frequency components of the flux on the basis of cospectral similarity in the atmospheric surface layer. In order to investigate the performance of the method, measurements of the water vapour flux over a forest with the bandpass eddy covariance method and the direct eddy correlation method were compared. The flux obtained by the bandpass eddy covariance method agreed with that by the eddy correlation method within ±20% for most cases, in spite of a rather slow sensor-response of the adopted hygrometer. This result supports its relevance to a long-term continuous operation, since a stable, low-maintenance,general-purpose sensor canbe utilized for scalar quantities. Oneweak point of the method isits difficulty in principle to measure the correct flux when the magnitude of the sensible heat flux is very small, because the method uses the sensible heat flux as a standard reference for the prediction of undetectable high-frequency components of the scalar flux. An advanced method is then presented to increase its robustness. In the new method, output signals from a slow-response sensor are corrected using empirical frequency-responsefunctions for the sensor,thereby extending the width of the bandpass frequency region where components of the flux are directly measured (not predicted). The advanced method produced correct fluxes for all cases including the cases of small sensible heat flux. The advanced bandpass eddy covariance method is thus appropriate for along-term measurement of the scalar fluxes.

Direct correlation method for OH, NH and CH local modes: vibrational overtone spectroscopy of biphenyl, anthracene, isobutanol, 2-chloroethanol and ethylenediamine at the third overtone region

The vibrational overtone spectra of gaseous biphenyl, anthracene, isobutanol, 2-chloroethanol and ethylenediamine at the Δv=4 vibrational overtone region have been recorded and assigned using the local mode model. For the spectral assignments, linear correlations were determined between the ab initio bond lengths (calculated in this work) and the overtone transition energies (taken from the literature) of aromatic and nonaromatic hydrocarbons, alcohols and amines. The bond lengths were obtained from ab initio geometry optimizations using both the 3-21G * and the 6-31G ** basis sets. The bond length–overtone transition wavenumber correlations for the OH, NH and aromatic, methyl and methylenic CH oscillators are presented for the Δv=4 region for both basis sets. The bond lengths (CH for biphenyl and anthracene, OH for isobutanol and 2-chloroethanol and NH for ethylenediamine) were also determined. These bond lengths were used to predict the transition wavenumbers for Δv=4 transitions which could then be compared to the experimental values. These predictions which accounted for the possibility of various conformations agreed well with the experiment.

Vibrational Overtone Spectroscopy of Cycloheptatriene-d6 at the Third and Fourth Overtone Regions

In a previous report1 the vibrational overtone spectrum of gaseous cycloheptatriene (CHT) was presented. The main absorption features at the third and fourth overtones were assigned to the CH olefinic oscillators of CHT using a direct correlation method. Assignments were also suggested for the methylenic CH absorptions; however, further confirmation of these spectral assignments was required. In CHT-d6 the CH olefinic transitions are eliminated, and only features due to the methylenic group of the CHT ring will remain in the spectrum. The CHT-d6 was synthesized by refluxing 12 mL of C6D6 (99.6 atom % d, Aldrich) in the presence of CuBr for 3.5 h with dropwise addition of 40 mL of diazomethane (CH2N2) solution in C6D6 as was described by Muler et al.2 The diazomethane solution was generated from nitrosomethylurea according to the procedure proposed by Arndt.3 Nitrosomethylurea was prepared from acetamide and bromine as was recommended by Amstutz and Myers.4 The resulting reaction mixture contained about 2.4% CHT-d6 dissolved in the deuterated benzene. The 1H NMR of the mixture displayed the single broad peak around 2.1 ppm corresponding to the CH2 group of the CHT-d6. The amount of solvent was reduced using rotatory evaporation to bring the CHT-d6 content to 43%. Then the CHT-d6 sample (91%) was collected using preparative gas chromatography. The third and fourth overtone spectra of CHT-d6 were obtained using the photoacoustic spectrometer described previously.1 The sample pressure was 14 Torr, and 300 Torr of argon was added to increase the photoacoustic signal. The spectra of CHT-d6 and CHT at the third and fourth overtone regions are shown in Figures 1 and 2, respectively. Peak positions and vibrational assignments are tabulated in Table 1. At the third overtone the absence of the olefinic CH bond stretch absorptions in the CHT-d6 spectrum around 11 30011 400 cm-1 leaves only two well-resolved peaks associated with the methylenic CH bonds of the CHT-d6 ring (Figure 1). Based on the general pattern reported for the CH methylenic bond in cyclic hydrocarbons5 (rCHax > rCHeq) and ab initio geometry optimization for CHT,1 the lower energy peak at 11 096 cm-1 can be assigned to the CHax of CHT-d6, while the higher energy transition, located at 11 215 cm-1, belongs to the CHeq. Similar arguments can be made for the two peaks recorded in the next overtone region (Figure 2), where the CHax peak appeared at 13 643 cm-1 and the CHeq transition appeared at 13 785 cm-1. Thus, the spectral results for CHT-d6 confirmed the assignments suggested for the CHT third and fourth overtone methylenic peaks. Acknowledgment. The authors wish to thank Dr. Thomas Kinstle for assistance in the synthetic part of work and J. Romanowitz for the GCMS analysis of the samples.

A112 フーリエ位相相関法による流速測定について

New PTV measurement using a Fourier-Transform phase correlation method is attempted on the experimental flows showing a 2-D circular cylinder wake. To make a good use of the qualities of this phase correlation method, the image templates for pattern matching are not described by the original particle dots, but by single polygons connecting all the particles in each template, followed by 2-D normal FFT and phase-component inverse FFT processes. The results obtained are not so revo-lutionary when compared to ordinary direct correlation methods, but there exists apparent improvement in the rotating flow regions.

Strategies for electron correlation calculations on large molecular systems

AbstractThe two main problems in applying common methods for electron correlation to large systems are (1) the steep dependency of the computational task with the size of the system and (2) the large and often prohibitive number of two‐electron integrals that must be stored and retrieved during the calculation. The direct local correlation method eliminates both these problems. This method is a combination of the local correlation method that eliminates the steep computational dependency with the size of the system and extension of the direct SCF approach to electron correlation methods. The latter method eliminates external storage of the electron repulsion integrals. In this review, the direct local correlation approach and its computer implementation will be described in detail, including computational examples and comparisons to similar methods developed in other groups. The feasibility of future applications to extended systems is discussed.

Comparative studies of time differential and integral directional correlation methods on delayed γ-ray cascades

A time differential directional correlation method using a slow-fast coincidence setup consisting of four BaF 2 detectors was applied to measure the anisotropy of a number of γ-ray cascades in the β decay of 140La and the EC decay of 75Se. Such a four-detector arrangement combined with a proper data reduction method makes it possible to accurately separate prompt, random and delayed events, and to eliminate instrumental effects such as detector efficiencies to a large extent. In addition, hyperfine interaction attenuation could be accurately corrected for. Accordingly the achieved results: A 22(329–487) = −0.109(4) A 22(329–1596) = −0.103(3) and A 22(433–487) = +0.168(12) for 140 Ce and A 22(121–280) = −0.431(10) for 75 As are considered to be more reliable than values previously determined by means of conventional time integral methods.

Strategies for lot acceptance testing using CMOS transistors and ICs

Direct-correlation and simple overstress methods for estimating IC response in strategic and space environments from laboratory transistor and IC data are investigated. Transistors and ICs were irradiated at dose rates from 0.2 rad(SiO/sub 2/)/s to 10/sup 6/ rad(SiO/sub 2/)/s. Over a wide range of process conditions and hardness levels, laboratory measurements of threshold voltage shift due to oxide trapped charge correlate well with IC leakage current at high dose rates for ICs with gate-oxide-dominated response. For ICs whose response is dominated by parasitic field-oxide structures, laboratory measurements of both transistor and IC leakage currents correlate well with IC hardness at high dose rates. For dose levels up to approximately=500 krad(SiO/sub 2/), it is shown that a simple factor-of-three overtest can be used as a conservative estimate of radiation hardness for strategic applications, provided that both functional and parametric testing is performed following X-ray irradiation at a dose rate of approximately=2000 rad(SiO/sub 2/)/s. For space environments, a laboratory irradiation to 1.5 times the required system level followed by a one-week 100 degrees C biased anneal gave conservative estimates of IC hardness. >

Multipole admixtures of electromagnetic transitions in165Er

165Er is in the deformed region, and follows the decay of165Tm by more than 100 transitions. The multipole mixing ratios of these transitions are measured by the γ-γ(θ) directional correlation method. In eight different experiments about 20 gamma-rays were investigated, and it is shown that: excepting the 47 keV, the transitions which are predominantlyE1 have largeM2 mixing, and excepting the 806 keV, the transitions which are predominantlyM1 have largeE2 mixing. The 77 keV transition is pureE2 and the 460 keV transition might have anM3 component. Excepting the 196 keV transition theE2/M1 mixing ratios are positive for the gamma-rays connecting the levels which have equal spins, otherwise they are negative. There are two 564 keV transitions, the spin of the 608 keV level is 3/2, and the 590 keV level has spin 1/2 or 3/2.

A Detection Algorithm for Optical Targets in Clutter

There is active interest in the development of algorithms for detecting weak stationary optical and IR targets in a heavy opticalclutter background. Often only poor detectability of low signal-to-noise ratio (SNR) targets is achieved when the direct correlation method is used. In many cases, this is partly obviated by using detection with correlated reference scenes [1, 2].This paper uses the experimentally justified assumption that most optical clutter can be modeled as a whitened Gaussian randomprocess with a rapidly space-varying mean and a more slowlyvarying covariance [2]. With this assumption, a new constant falsealarm rate (CFAR) detector is developed as an application of the classical generalized maximum likelihood ratio test of Neyman and Pearson. The final CFAR test is a dimensionless ratio. This test exhibits the desirable property that its probability of a false alarm(PFA) is independent of the covariance matrix of the actual noiseencountered. When the underlying noise processes are complex intime, similar considerations can yield a sidelobe canceler CFARdetection criterion for radar and communications. Performance analyses based on the probability of detection (PD)versus signal-to-noise ratio for several given fixed false alarm probabilities are presented. Finally these performance curves are validated by computer simulations of the detection process which use real image data with artificially implanted signals.