Saturation Corrections Research Articles

Image Dehazing Based on Improved Color Channel Transfer and Multiexposure Fusion

Image dehazing is one of the problems that need to be solved urgently in the field of computer vision. In recent years, more and more algorithms have been applied to image dehazing and achieved good results. However, the image after dehazing still has color distortion, contrast and saturation disorder, and other challenges; in order to solve these problems, in this paper, an effective image dehazing method is proposed, which is based on improved color channel transfer and multiexposure image fusion to achieve image dehazing. First, the image is preprocessed using a color channel transfer method based on k-means. Second, gamma correction is introduced on the basis of guided filtering to obtain a series of multiexposure images, and the obtained multiexposure images are fused into a dehazed image through a Laplacian pyramid fusion scheme based on local similarity of adaptive weights. Finally, contrast and saturation corrections are performed on the dehazed image. Experimental verification is carried out on synthetic dehazed images and natural dehazed images, and it is verified that the method proposed is superior to existing dehazed algorithms from both subjective and objective aspects.

Gluon quasiparticles and the CGC density matrix

We revisit and extend the calculation of the density matrix and entanglement entropy of a color glass condensate (CGC) by including the leading saturation corrections in the calculation. We show that the density matrix is diagonal in the quasiparticle basis, where it has the Boltzmann form. The quasiparticles in a wide interval of momenta behave as massless two-dimensional bosons with the temperature proportional to the typical semihard scale $T={Q}_{s}/\sqrt{{\ensuremath{\alpha}}_{s}{N}_{c}}$. Thus, the semihard momentum region ${Q}_{s}<k<{Q}_{s}/\sqrt{{\ensuremath{\alpha}}_{s}{N}_{c}}$ arises as a well-defined intermediate regime between the perturbatively hard momenta and the nonperturbative soft momenta $k<{Q}_{s}$ in the CGC description of a hadronic wave function.

First saturation correction in high energy proton-nucleus collisions. Part III. Ensemble averaging

In high energy proton-nucleus collisions, the gluon saturation effects from the nucleus are fully incorporated into the light-like Wilson lines. The gluon saturation effects from the proton, which are anticipated to be important either in the extreme high energy limit or towards the dense-dense (nucleus-nucleus) collision regimes, have been studied perturbatively within the Color Glass Condensate effective theory in previous papers of this series. A configuration-by-configuration expression for the single inclusive semi-hard gluon production including the first saturation correction was obtained. In this paper, we perform ensemble averaging in the McLerran-Venugopalan model and the Dipole Approximation. We find that, in the saturation correction, the effects of the initial state interactions are negligible while the final state interactions play most important role and give a positive-valued contribution to the semi-hard gluon spectrum. Furthermore, we show that the single gluon spectrum scales approximately 1/ {k}_{perp}^4 at small k⊥, suggesting that a resummation of higher order saturation corrections is required to regulate the infrared region of the gluon spectrum.

Phantom development for daily checks in electron intraoperative radiotherapy with a mobile linac

PurposeIORT with mobile linear accelerators is a well-established modality where the dose rate and, therefore, the dose per pulse are very high. The constancy of the dosimetric parameters of the accelerator has to be checked daily. The aim of this work is to develop a phantom with embedded detectors to improve both accuracy and efficiency in the daily test of an IORT linac at the surgery room. MethodsThe developed phantom is manufactured with transparent polymethyl methacrylate (PMMA), allocating 6 parallel-plate chambers: a central one to evaluate the on-axis beam output, another on-axis one placed at a fixed depth under the previous one to evaluate the energy constancy and four off-axis chambers to evaluate the flatness and symmetry. To analyse the readings a specific application has been developed. ResultsFor all chambers and energies, the mean saturation and polarization corrections were smaller than 0.7%. The beam is monitored at different levels of the clinical beam. Output, energy constancy and flatness correlate very well with the correspondent values with the complete applicator. During the first six months of clinical use the beam dosimetric parameters showed excellent stability. ConclusionsA phantom has been developed with embedded parallel plate chambers attached to the upper applicator part of an IORT linac. The phantom allows a very efficient setup reducing the time to check the parameters. It provides complete dosimetric information (output, energy and flatness) with just one shot and using ionization chambers with minimum saturation effect, as this highly pulsed beam requires.

Saturation corrections to dilute-dense particle production and azimuthal correlations in the Color Glass Condensate

We perform a numerical study of higher order saturation corrections to the dilute-dense approximation for multi-particle production in high-energy hadronic collisions in the framework of the Color Glass Condensate. We compare semi-analytical results obtained by performing a leading order expansion in the dilute field of the projectile with numerical simulations of the full Classical Yang-Mills dynamics for a number of phenomenologically relevant observables. By varying the saturation momentum of the target and the projectile, we establish the regime of validity of the dilute-dense approximation and assess the magnitude and basic features of higher order saturation corrections. In particular, we find that dilute-dense approximation faithfully reproduces dense-dense results if restricted to the range of its validity.

On-flight intercomparison of three miniature aerosol absorption sensors using unmanned aerial systems (UASs)

Abstract. The present study investigates and compares the ground and in-flight performance of three miniaturized aerosol absorption sensors integrated on board small-sized Unmanned Aerial Systems (UASs). These sensors were evaluated during two contrasted field campaigns performed at an urban site, impacted mainly by local traffic and domestic wood burning sources (Athens, Greece), and at a remote regional background site, impacted by long-range transported sources including dust (Cyprus Atmospheric Observatory, Agia Marina Xyliatou, Cyprus). The miniaturized sensors were first intercompared at the ground-level against two commercially available instruments used as a reference. The measured signal of the miniaturized sensors was converted into the absorption coefficient and equivalent black carbon concentration (eBC). When applicable, signal saturation corrections were applied, following the suggestions of the manufacturers. The aerosol absorption sensors exhibited similar behavior against the reference instruments during the two campaigns, despite the diversity of the aerosol origin, chemical composition, sources, and concentration levels. The deviation from the reference during both campaigns concerning (eBC) mass was less than 8 %, while for the absorption coefficient it was at least 15 %. This indicates that those sensors that report black carbon mass are tuned and corrected to measure eBC more accurately than the absorption coefficient. The overall potential use of miniature aerosol absorption sensors on board small UASs is also illustrated. UAS-based absorption measurements were used to investigate the vertical distribution of eBC over Athens up to 1 km above sea level during January 2016, exceeding the top of the planetary boundary layer (PBL). Our results reveal a heterogeneous boundary layer concentration of absorbing aerosol within the PBL intensified in the early morning hours due to the concurrent peak traffic emissions at ground-level and the fast development of the boundary layer. After the full development of the PBL, homogenous concentrations are observed from 100 m a.g.l. to the PBL top.

62. Detectors comparison for absorbed dose and output factors determination in high dose per pulse electron beams produced by a mobile linac for Intra Operative Radiation Therapy (IORT)

Purpose Evaluating the level of agreement of measurements by different types of ionization chambers and solid state detectors in IORT electron beams with high dose per pulse. Methods Two electron beams (R50 2.59 and 3.05 cm) by a Novac7 Hitesys linac were used. Absorbed dose to water (Dw) and output factors (OF) were determined for the reference applicator of diameter 10 cm and the clinical applicators of diameter from 4 to 7 cm. The dose per pulse ranged between 29 and 77 mGy. Six types of plane parallel ionization chambers (PTW Markus, Advanced Markus and Roos; IBA PPC05, PPC40 and NACP02) were utilized. OF measurements were also made using a PTW microDiamond type 60019 and silicon diodes PTW type 60017 and IBA-EFG-3D. The IAEA TRS-398 dosimetry protocol was applied except for the saturation corrections applied to the ionization chambers that were determined according to [1] . Results The PPC05 and the Advanced Markus chambers exhibited the lowest ion recombination effects, being the corrections to be applied lower than 0.5% and 1.5%, respectively. Corrections larger than 15% were obtained for the Roos, the and PPC40 and the NACP02. Agreement among ionization chamber OF values was generally better than 1.5% except for the largest chambers in the smallest beams, where beam non uniformity likely caused dose underestimation, and for some discrepancies relevant to the Markus and the NACP02 chambers. OF values obtained using the solid state detectors typically agreed within 1.5%, while differences from PPC05 and Advanced Markus OFs were within 2%. Dw measurements by means of different ionization chambers agree to each other within the stated uncertainties (2.5%, 1SD). Conclusions Results of this work show that, at the high dose per pulse of NOVAC7 beams, dosimetry based on ionimetric measurements is feasible, if ion recombination effects are properly taken into account, and the studied solid state detectors are suitable for relative dosimetry.

How classical gluon fields generate odd azimuthal harmonics for the two-gluon correlation function in high-energy collisions

We show that, in the saturation/Color Glass Condensate framework, odd azimuthal harmonics of the two-gluon correlation function with a long-range separation in rapidity are generated by the higher-order saturation corrections in the interactions with the projectile and the target. At the very least, the odd harmonics require three scatterings in the projectile and three scatterings in the target. We derive the leading-order expression for the two-gluon production cross section which generates odd harmonics: the expression includes all-order interactions with the target and three interactions with the projectile. We evaluate the obtained expression both analytically and numerically, confirming that the odd-harmonics contribution to the two-gluon production in the saturation framework is non-zero.

The behavior of the heavy quarks structure functions at small-x

The behavior of the charm and bottom structure functions [Formula: see text], where i = c, and b; k = 2, and L) at small-x is considered with respect to the hard-Pomeron and saturation models. Having checked that this behavior predicate the heavy flavor reduced cross-sections concerning the unshadowed and shadowed corrections. We will show that the effective exponents for the unshadowed and saturation corrections are independent of x and Q2, and also the effective coefficients are dependent to ln Q2 compared to Donnachie–Landshoff (DL) and color dipole models (CDMs).

Classical gluon production amplitude for nucleus-nucleus collisions: First saturation correction in the projectile

We calculate the classical single-gluon production amplitude in nucleus-nucleus collisions including the first saturation correction in one of the nuclei (the projectile) while keeping multiple-rescattering (saturation) corrections to all orders in the other nucleus (the target). In our approximation only two nucleons interact in the projectile nucleus: the single-gluon production amplitude we calculate is order-g 3 and is leading-order in the atomic number of the projectile, while resumming all order-one saturation corrections in the target nucleus. Our result is the first step towards obtaining an analytic expression for the first projectile saturation correction to the gluon production cross section in nucleus-nucleus collisions.

Next-to-leading and resummed BFKL evolution with saturation boundary

We investigate the effects of the saturation boundary on small-x evolution at the next-to-leading order accuracy and beyond. We demonstrate that the instabilities of the next-to-leading order BFKL evolution are not cured by the presence of the nonlinear saturation effects, and a resummation of the higher order corrections is therefore needed for the nonlinear evolution. The renormalization group improved resummed equation in the presence of the saturation boundary is investigated, and the corresponding saturation scale is extracted. A significant reduction of the saturation scale is found, and we observe that the onset of the saturation corrections is delayed to higher rapidities. This seems to be related to the characteristic feature of the resummed splitting function which at moderately small values of x possesses a minimum.

Test of Scintillometer Saturation Correction Methods Using Field Experimental Data

Boundary Layer Meteorology manuscript No. (will be inserted by the editor) Test of scintillometer saturation correction methods using field experimental data J. Kleissl, O.K. Hartogensis, J.D. Gomez Received: Aug. 11, 2009 / Accepted: date Abstract Saturation of large aperture scintillometer (LAS) signals can result in sen- sible heat flux measurements that are biased low. A field study with LASs of different aperture sizes and path lengths was performed to investigate the onset of and correc- tions for signal saturation. Saturation already occurs at C n 2 ≈ 0.074D 5/3 λ 1/3 L −8/3 , where C n 2 is the structure parameter of the refractive index, D is the aperture size, λ is the wavelength, L is the transect length, which is smaller than theoretically de- rived saturation limits. At a transect length of 1 km, a height of 2.5 m, and aperture ≈ 0.15 m the correction factor exceeds 5% already at C n 2 = 2 × 10 −12 m −2/3 , which will affect many practical applications of scintillometry. The Clifford correction method, which only depends on C n 2 and transect geometry, provides good saturation corrections over the range of conditions observed in our study. The saturation correction proposed by Ochs and Hill results in correction factors that are too small in large saturation regimes. An inner length scale dependence of the sat- uration correction factor was not observed. Thus for practical applications the Clifford correction method should be applied. Keywords Large aperture scintillometer · Sensible heat flux · Signal saturation · Wave propagation 1 Introduction A major challenge for the validation of surface energy balance fluxes from remote sens- ing images is the ground measurement at a scale similar to their spatial resolution. While the pixel size of daily thermal remote sensing images is on the order of km, J. Kleissl Dept. of Mechanical and Aerospace Engineering, University of California, San Diego, USA Tel.: +1-443-527-2740 E-mail: jkleissl@ucsd.edu J.D. Gomez Dept. of Earth and Environmental Sciences, New Mexico Tech, Socorro, New Mexico, USA O.K. Hartogensis Dept of Meteorology and Air Quality, Wageningen University, Wageningen, The Netherlands

KECK ECHELLETTE SPECTROGRAPH AND IMAGER OBSERVATIONS OF METAL-POOR DAMPED Lyα SYSTEMS

We present the first results from a survey of SDSS quasars selected for strong H I damped Lyα (DLA) absorption with corresponding low equivalent width absorption from strong low-ion transitions (e.g., C II λ1334 and Si II λ1260). These metal-poor DLA candidates were selected from the SDSS fifth release quasar spectroscopic database, and comprise a large new sample for probing low-metallicity galaxies. Medium-resolution echellette spectra from the Keck Echellette Spectrograph and Imager spectrograph for an initial sample of 35 systems were obtained to explore the metal-poor tail of the DLA distribution and to investigate the nucleosynthetic patterns at these metallicities. We have estimated saturation corrections for the moderately underresolved spectra, and systems with very narrow Doppler parameters (b ≤ 5 km s^(–1)) will likely have underestimated abundances. For those systems with Doppler parameters b > 5 km s^(–1), we have measured low-metallicity DLA gas with [X/H] < –2.4 for at least one of C, O, Si, or Fe. Assuming non-saturated components, we estimate that several DLA systems have [X/H] < –2.8, including five DLA systems with both low equivalent widths and low metallicity in transitions of both C II and O I. All of the measured DLA metallicities, however, exceed or are consistent with a metallicity of at least 1/1000 of solar, regardless of the effects of saturation in our spectra. Our results indicate that the metal-poor tail of galaxies at z ~ 3 drops exponentially at [X/H] ≾ –3. If the distribution of metallicity is Gaussian, the probability of identifying interstellar medium gas with lower abundance is extremely small, and our results suggest that DLA systems with [X/H] < –4.0 are extremely rare, and could comprise only 8 × 10^(–7) of DLA systems. The relative abundances of species within these low-metallicity DLA systems are compared with stellar nucleosynthesis models, and are consistent with stars having masses of 30 M_⊙ < M * < 100 M_⊙. The observed ratio of [C/O] for values of [O/H] < –2.5 exceeds values seen in moderate metallicity DLA systems, and also exceeds theoretical nucleosynthesis predictions for higher mass Population III stars. We also have observed a correlation between the column density N(C IV) with [Si/H] metallicity, suggestive of a trend between mass of the DLA system and its metallicity.

Quantitative cardiac 31P spectroscopy at 3 Tesla using adiabatic pulses

Cardiac phosphorus magnetic resonance spectroscopy (MRS) with surface coils promises better quantification at 3 Tesla (T) from improved signal-to-noise ratios and spectral resolution compared with 1.5 T. However, Bloch equation and field analyses at 3T show that for efficient quantitative MRS protocols using small-angle adiabatic (BIR4/BIRP) pulses the excitation-field is limited by radiofrequency (RF) power requirements and power deposition. When BIR4/BIRP pulse duration is increased to reduce power levels, T2-decay can introduce flip-angle dependent errors in the steady-state magnetization, causing errors in saturation corrections for metabolite quantification and in T1s measured by varying the flip-angle. A new dual-repetition-time (2TR) T1 method using frequency-sign-cycled adiabatic-half-passage pulses is introduced to alleviate power requirements, and avoid the problem related to T2 relaxation during the RF pulse. The 2TR method is validated against inversion-recovery in phantoms using a practical transmit/receive coil set designed for phosphorus MRS of the heart at depths of 9-10 cm with 4 kW of pulse power. The T1s of phosphocreatine (PCr) and adenosine triphosphate (gamma-ATP) in the calf-muscle (n=9) at 3 T are 6.8+/-0.3 s and 5.4+/-0.6 s, respectively. For heart (n=10) the values are 5.8+/-0.5 s (PCr) and 3.1+/-0.6 s (gamma-ATP). The 2TR protocol measurements agreed with those obtained by conventional methods to within 10%.

Experimental demonstration of quantitation errors in MR spectroscopy resulting from saturation corrections under changing conditions

Metabolite concentration measurements in in vivo NMR are generally performed under partially saturated conditions, with correction for partial saturation performed after data collection using a measured saturation factor. Here, we present an experimental test of the hypothesis that quantitation errors can occur due to application of such saturation factor corrections in changing systems. Thus, this extends our previous theoretical work on quantitation errors due to varying saturation factors. We obtained results for two systems frequently studied by 31 P NMR, the ischemic rat heart and the electrically stimulated rat gastrocnemius muscle. The results are interpreted in light of previous theoretical work which defined the degree of saturation occurring in a one-pulse experiment for a system with given spin–lattice relaxation times, T 1s, equilibrium magnetizations, M 0s, and reaction rates. We found that (i) the assumption of constancy of saturation factors leads to quantitation errors on the order of 40% in inorganic phosphate; (ii) the dominant contributor to the quantitation errors in inorganic phosphate is most likely changes in T 1; (iii) T 1 and M 0 changes between control and intervention periods, and chemical exchange contribute to different extents to quantitation errors in phosphocreatine and γ-ATP; (iv) relatively small increases in interpulse delay substantially decreased quantitation errors for metabolites in ischemic rat hearts; (v) random error due to finite SNR led to approximately 4% error in quantitation, and hence was a substantially smaller contributor than were changes in saturation factors.

On neglecting chemical exchange effects when correcting in vivo (31)P MRS data for partial saturation.

Signal acquisition in most MRS experiments requires a correction for partial saturation that is commonly based on a single exponential model for T(1) that ignores effects of chemical exchange. We evaluated the errors in (31)P MRS measurements introduced by this approximation in two-, three-, and four-site chemical exchange models under a range of flip-angles and pulse sequence repetition times (T(R)) that provide near-optimum signal-to-noise ratio (SNR). In two-site exchange, such as the creatine-kinase reaction involving phosphocreatine (PCr) and gamma-ATP in human skeletal and cardiac muscle, errors in saturation factors were determined for the progressive saturation method and the dual-angle method of measuring T(1). The analysis shows that these errors are negligible for the progressive saturation method if the observed T(1) is derived from a three-parameter fit of the data. When T(1) is measured with the dual-angle method, errors in saturation factors are less than 5% for all conceivable values of the chemical exchange rate and flip-angles that deliver useful SNR per unit time over the range T(1)/5 < or = T(R) < or = 2T(1). Errors are also less than 5% for three- and four-site exchange when T(R) > or = T(1)(*)/2, the so-called "intrinsic" T(1)'s of the metabolites. The effect of changing metabolite concentrations and chemical exchange rates on observed T(1)'s and saturation corrections was also examined with a three-site chemical exchange model involving ATP, PCr, and inorganic phosphate in skeletal muscle undergoing up to 95% PCr depletion. Although the observed T(1)'s were dependent on metabolite concentrations, errors in saturation corrections for T(R) = 2 s could be kept within 5% for all exchanging metabolites using a simple interpolation of two dual-angle T(1) measurements performed at the start and end of the experiment. Thus, the single-exponential model appears to be reasonably accurate for correcting (31)P MRS data for partial saturation in the presence of chemical exchange. Even in systems where metabolite concentrations change, accurate saturation corrections are possible without much loss in SNR.

Effect of spirometer temperature on FEV1 in a longitudinal epidemiological study.

OBJECTIVES: To assess the magnitude of error in pulmonary function measurements introduced by variation in spirometer temperature under field conditions. In a large scale epidemiological study of school children, the...

Simulations of laser imprint for Nova experiments and for ignition capsules

In direct drive inertial confinement fusion (ICF), nonuniformities in laser illumination seed ripples at the ablation front in a process called “imprint.” These nonuniformities grow during the capsule implosion and, if initially large enough, can penetrate the capsule shell, impede ignition, or degrade burn. Imprint has been simulated for recent experiments performed on the Nova laser [Campbell et al., Rev. Sci. Instrum. 57, 2101 (1986)] examining a variety of beam smoothing conditions. Most used laser intensities similar to the early part of an ignition capsule pulse shape, I≅1013 W/cm2. The simulations matched most of the measurements of imprint modulation. The effect of imprint upon National Ignition Facility (NIF) direct drive ignition capsules has also been simulated. Imprint is predicted to give modulation comparable to an intrinsic surface finish of ∼10 nm rms. Modulation growth was examined using the Haan [Phys. Rev. A 39, 5812 (1989)] model, with linear growth factors as a function of spherical harmonic mode number obtained from an analytic dispersion relation. Ablation front amplitudes are predicted to become substantially nonlinear, so that saturation corrections are large. Direct numerical simulations of two-dimensional multimode growth were also performed. The capsule shell is predicted to remain intact, which gives a basis for believing that ignition can be achieved.

Large multiplicity fluctuations and saturation effects in onium collisions

This paper studies two related questions in high energy onium-onium scattering: the probability of producing an unusually large number of particles in a collision, where it is found that the cross section for producing a central multiplicity proportional to k should decrease exponentially in √ k. Secondly, the nature of gluon (dipole) evolution when dipole densities become so high that saturation effects due to dipole-dipole interactions become important: measures of saturation are developed to help understand when saturation becomes important, and further information is obtained by exploiting changes of frame, which interchange unitarity and saturation corrections.

The Impact of CN Line Profile Measurements on the Cosmic Microwave Background Temperature

We present moderate to high signal-to-noise high-resolution (R ≈ 150,000–170,000) optical spectra toward ζ Oph. Gaussian fits to our data indicate a value of the line-width parameter b, of b = 1.4 ± 0.2 km s−1, along this line of sight. When CN is used as an indirect probe of the cosmic microwave background (CMB) temperature, the line profile is used to determine saturation corrections in the line. This affects column density calculations, which are reflected in the excitation temperature. Current measurements of the b-value along this line of sight range from 0.88 ± 0.02 km s−1 (Crane et al. 1986) to 1.3 ± 0.1 km s−1 (Hegyi, Traub, and Carleton 1972). The extreme range of these b-values yield saturation corrections to the CMB temperature that differ by 0.05 K, which is equal to the quoted precision of current measurements. Preliminary analysis of observations toward HD 29647 indicate that TCMB = 2.70 ± 0.14 K at 2.64 mm toward this line of sight.