Transferring the calibration of direct solar irradiance to diffuse-sky radiance measurements for CIMEL Sun-sky radiometers

Two types of sunphotometric measurement are considered in this study: direct-Sun irradiance and diffuse-sky radiance. Based on CIMEL CE318 Sun-sky radiometer characteristics, we introduce a gain-corrected solid angle that allows interconverting calibration coefficients of these two types of measurement, thus realizing a "vicarious" radiance calibration. The accuracy of the gain-corrected solid angle depends on the number of available historical calibration records. The method is easy to use, provided that at least one laboratory calibration has been made previously. Examples coming from three distinct CE318 versions belonging to the AERONET/PHOTONS network are presented to provide details on the vicarious calibration method and protocols. From the error propagation analysis and the comparison with laboratory results, the uncertainty of the vicarious radiance calibration is shown to be comparable with the laboratory one, e.g., 3%-5%.     

An axiomatic characterization of the ranking based on the h-index and some other bibliometric rankings of authors

In the last few years, many new bibliometric rankings or indices have been proposed for comparing the output of scientific researchers. We propose a formal framework in which rankings can be axiomatically characterized. We then present a characterization of some popular rankings. We argue that such analyses can help the user of a ranking to choose one that is adequate in the context where she/he is working.     

The behavior of statically-indeterminate structural members and frames with cracks present

Crack stability is discussed as affected by their presence in statically-indeterminate beams, frames, rings, etc. loaded into the plastic range. The stability of a crack in a section, which has become plastic, is analyzed with the remainder of the structure elastic and with subsequent additional plastic hinges occurring. The reduction of energy absorption characteristics for large deformations is also discussed. The methods of elastic-plastic tearing instability are incorporated to show that in many cases the fully plastic collapse mechanism must occur for complete failure.     

Temperature Modulation Measurements of the Thermal Properties of Nanosystems at Low Temperatures

We report on the dynamic measurements of thermal properties of nanosystems at very low temperatures. These techniques are based on the modulation of the temperature and hence leads to highly sensitive measurements. We will discuss the intrinsic limitations of these methods when the thermal properties of nano-objects are studied at very low temperatures, much below 1 K. Firstly, we will present thermal conductance measurements using the 3ω method. This technique is limited at low temperatures due to the significant increase of the mean free path. Secondly, heat capacity measurements using ac calorimetry are outlined, and again restrictions occur due to the continuous temperature gradient inherent to that technique. Propositions are made in order to overcome these limitations.     

Finite-range topical functions and uniformly topical functions

We introduce a remarkable subclass of the class of topical functions, the class of uniformly topical functions, whose dynamical behaviour is investigated. Every uniformly topical endofunction has a spectral vector, related to some special fixed points (possibly at infinity), about which we establish various properties. In the stochastic case, we prove a multiplicative ergodic theorem, asserting that the stochastic spectral vector exists in all cases.     

Direct extraction of the mean particle size from a digital hologram

Digital holography, which consists of both acquiring the hologram image in a digital camera and numerically reconstructing the information, offers new and faster ways to make the most of a hologram. We describe a new method to determine the rough size of particles in an in-line hologram. This method relies on a property that is specific to interference patterns in Fresnel holograms: Self-correlation of a hologram provides access to size information. The proposed method is both simple and fast and gives results with acceptable precision. It suppresses all the problems related to the numerical depth of focus when large depth volumes are analyzed.     

A finite macro-element for corroded reinforced concrete

This paper proposes a model of the mechanical behaviour of corroded reinforced concrete members subjected to bending under service load. The model is based on the formulation of a macro-element to be used in FEM analysis, having a length equal to the distance between two consecutive flexural cracks and a cross-section equal to the member cross-section. The mechanical formulation is directly written in generalized variables (bending moment and curvature) and is based on the concept of the transfer length necessary for the transmission of tensile load from re-bar to tensile concrete thanks to the bond. It is thus possible to take into account the effect of reinforcement corrosion on the bond between re-bar and concrete, by increasing the transfer length versus intensity of corrosion. The variation of the transfer length versus corrosion is expressed using a scalar damage parameter. A first experimental validation is performed on a 17-year-old beam kept in a chloride environment under its service load.     

Estimation of the total uncertainty of sky-radiance measurements in field experimental conditions: implications for the aerosol single-scattering albedo

We compare the spectral sky radiance measured by three ground-based optical radiometers during the second Aerosol Characterization Experiment (ACE-2) to estimate the total uncertainty of the radiance in field experimental conditions. The propagation of this uncertainty on the column-integrated aerosol single-scattering albedo omega0 at 868 nm is investigated. The radiance measurements are affected by a systematic gain uncertainty of less than 2% in the visible spectral region and within 6% in the near-IR region. Correcting the measured radiance by a systematic uncertainty reduces the dispersion of the omega0 from 0.07 to 0.03. Besides, the total relative uncertainty of the radiance measurements in field experimental conditions is within 4% at any wavelength. The corresponding uncertainty delta omega0 is 4% for an aerosol optical thickness of 0.2.     

Retrieval of the ultraviolet aerosol optical depth during a spring campaign in the Bavarian Alps

A measurement campaign was organized in March 1999 in the Bavarian Alps as part of the European project, Characteristics of the UV Radiation Field in the Alps (CUVRA), to analyze the effect of altitude, aerosols, and snow cover on ground-level UV spectral irradiance. We present the results of simultaneous measurements of aerosol optical depth (AOD) made at various sites on two cloudless days in March 1999. The two days exhibited different aerosol conditions. Results derived from spectral measurements of UV irradiance are compared with data from filter radiometer measurements made at discrete wavelengths extending from the UV to the near IR. The different methods generated values for the AOD that were in good agreement. This result confirms that one can use either method to retrieve the AOD with an uncertainty of approximately 0.03-0.05. On 18 March, high turbidity was observed at low altitude (400-nm AOD approximately 0.5 at 700 m above sea level), and the AOD decreased regularly with altitude; on 24 March, the turbidity was much less (0.11 at 700 m above sea level). On both days very low AODs (0.05-0.09) were measured at 3000 m above sea level. The spectral dependence of the AOD is often parameterized by the angstrom relationship; the alpha parameter is generally difficult or impossible to retrieve from spectral measurements because of the relatively narrow wavelength range (320-400 nm), and only one of the spectro-radiometers used during the campaign permits this retrieval. In most cases, during this field campaign, alpha was found by filter sunphotometers to be 1.1-1.5.