On the accuracy of the ALI method for solving the radiative transfer equation

We solve the integral equation describing the propagation of light in an isothermal plane-parallel atmosphere of optical thickness $\tau^*$, adopting a uniform thermalization parameter $\epsilon$. The solution given by the ALI method, widely used in the field of stellar atmospheres modelling, is compared to the exact solution. Graphs are given that illustrate the accuracy of the ALI solution as a function of the parameters $\epsilon$, $\tau^*$ and optical depth variable $\tau$.Comment: 7 pages, 11 figures, A&A, accepted 30 July 2003, minor correction

MIX DESIGN AND MECHANICAL CHARACTERIZATION OF STABILIZED COMPRESSED EARTH BLOCKS AND ASSEMBLIES FOR THE JEMEZ PUEBLO IN NEW MEXICO

Earthen structures have a long architectural and cultural heritage in New Mexico. Similar structures are evident around the world. With the current depletion of natural resources and high cost of materials, compressed earth block construction offers a sustainable building material alternative. Stabilized compressed earth blocks (SCEB) are compressed earth blocks with additives such as, hydrated lime or Portland cement to protect the earth block from absorbing water. SCEBs are being produced using native soils for residential construction on the Jemez Pueblo in New Mexico. The primary goal of this research is to enable production of SCEBs with native soils from the Jemez Pueblo. The objectives of this research are to identify suitable local soils to be used to develop a compressed earth block mix design, compare the mechanical characteristics of SCEB to commercial adobe blocks, and investigate the mechanical behavior of SCEB prism and wall assemblies. Close to 50 native soil locations at the Jemez reservation in New Mexico were investigated. These soils were classified according to the Unified Soil Classification System (USCS) considering their grain size distribution, plasticity limit and swelling potential. A method for down selection of the soils suitable for compressed earth block production was developed. In addition, the clay mineralogy of the suitable soils and soil mix designs were determined using X-ray Diffraction (XRD) and Scanning electron microscopy (SEM). SCEB mix design included two selected native soils, two sands and either Type S hydrated lime or Type II Portland cement. These materials were mixed to fabricate SCEBs of nine different SCEB mix designs. Compressive and flexural strength tests of the SCEBs were performed and compared to commercial adobe blocks. Tests to determine water absorption characteristics in SCEBs including initial rate of absorption, total absorption and sorptivity were also carried out. The mechanical and absorption characteristics of SCEBs were correlated to the mix design and the native soil classification. The ratio of clay and sand in the compressed earth block mix has a significant correlation with the mechanical and absorption characteristics of SCEBs. The results from all the testing showed that an optimum mix design was found for the nine blocks evaluated. SCEB assemblies, including prisms and wall panels were produced with standard type S mortar. Prisms made of SCEB units were tested to determine the compressive strength, bond strength, and shear strength. The time-dependent creep of the SCEB prism at 56 days of age was also evaluated. These measurements showed that creep displacement has a significant effect on the total displacement of the prism assembly. The approximately 570 mm x 570 mm (22 in. x 22 in.) SCEB wall panels made of the optimum SCEB were tested under in-plane shear using a diagonal compression test. The results of the diagonal compression test show that the SCEB wall assembly obtained a lateral strength comparable to rammed earth. The results showed that some SCEBs have higher compressive and flexural strengths than commercial stabilized adobe. SCEBs provide a resilient, sustainable building material and are suitable for use in residential construction for the Jemez Pueblo in New Mexico

In-flight load testing of advanced shuttle thermal protection systems

NASA Ames Research Center has conducted in-flight airload testing of some advanced thermal protection systems (TPS) at the Dryden Flight Research Center. The two flexible TPS materials tested, felt reusable surface insulation (FRSI) and advanced flexible reusable surface insulation (AFRSI), are currently certified for use on the Shuttle orbiter. The objectives of the flight tests were to evaluate the performance of FRSI and AFRSI at simulated launch airloads and to provide a data base for future advanced TPS flight tests. Five TPS configurations were evaluated in a flow field which was representative of relatively flat areas without secondary flows. The TPS materials were placed on a fin, the Flight Test fixture (FTF), that is attached to the underside of the fuselage of an F-104 aircraft. This paper describes the test approach and techniques used and presents the results of the advanced TPS flight test. There were no failures noted during post-flight inspections of the TPS materials which were exposed to airloads 40 percent higher than the design launch airloads

The European port industry: an analysis of its economic efficiency

Because of their critical strategic role, ports have all traditionally been subject to some form of government control even if the legal form and the intensity of this control have varied across countries. The member countries of the European Union have not been different from the rest of the world in this respect. A significant difference however is the recurrent effort to integrate, in a coordinated way, the port sector in a trans-European transport network (TEN-T) through the adoption of a common legal framework. In this context, if the objective of the reforms is to ensure that port networks, integrated in combined transport networks, become competitors of the road network, the concept of port efficiency becomes central. This paper provides an overview of the evolution of the European Port Legislation and shows how comparative economic measures can be used to highlight the scope for port efficiency improvements, essential to allow short sea shipping transport to compete with road transport in Europe. To our knowledge, this paper is also the first effort of estimating technical efficiency of European Port Authorities. The average port efficiency in 2002 was estimated to be around 60%, denoting that ports could have handled 40% more traffic with the same resources. Maritime Economics & Logistics (2007) 9, 148â171. doi:10.1057/palgrave.mel.910017

The influence of coronal EUV irradiance on the emission in the He I 10830 A and D3 multiplets

Two of the most attractive spectral windows for spectropolarimetric investigations of the physical properties of the plasma structures in the solar chromosphere and corona are the ones provided by the spectral lines of the He I 10830 A and 5876 A (or D3) multiplets, whose polarization signals are sensitive to the Hanle and Zeeman effects. However, in order to be able to carry out reliable diagnostics, it is crucial to have a good physical understanding of the sensitivity of the observed spectral line radiation to the various competing driving mechanisms. Here we report a series of off-the-limb non-LTE calculations of the He I D3 and 10830 A emission profiles, focusing our investigation on their sensitivity to the EUV coronal irradiation and the model atmosphere used in the calculations. We show in particular that the intensity ratio of the blue to the red components in the emission profiles of the He I 10830 A multiplet turns out to be a good candidate as a diagnostic tool for the coronal irradiance. Measurements of this observable as a function of the distance to the limb and its confrontation with radiative transfer modeling might give us valuable information on the physical properties of the solar atmosphere and on the amount of EUV radiation at relevant wavelengths penetrating the chromosphere from above.Comment: 19 pages, 11 figures (pre-print format). Accepted for publication in Ap

Fractional Order Continuity and Some Properties about Integrability and Differentiability of Real Functions

AbstractIn this paper a certain function spaceCα, 0≤α≤1, larger than the space of continuous functions, is introduced in order to study new properties and the extension of some already known results about the Riemann–Liouville fractional integral and derivative operators.Sufficient conditions for the continuity ofI1−αafare given. Furthermore, necessary conditions are given for the pointwise existence of fractional derivatives. The existence of a derivative of order β, from the existence of a certain derivative of order α, β<α, is also analyzed

Channeling 5-min photospheric oscillations into the solar outer atmosphere through small-scale vertical magnetic flux tubes

We report two-dimensional MHD simulations which demonstrate that photospheric 5-min oscillations can leak into the chromosphere inside small-scale vertical magnetic flux tubes. The results of our numerical experiments are compatible with those inferred from simultaneous spectropolarimetric observations of the photosphere and chromosphere obtained with the Tenerife Infrared Polarimeter (TIP) at 10830 A. We conclude that the efficiency of energy exchange by radiation in the solar photosphere can lead to a significant reduction of the cut-off frequency and may allow for the propagation of the 5 minutes waves vertically into the chromosphere.Comment: accepted by ApJ

On a Riemann–Liouville Generalized Taylor's Formula

AbstractIn this paper, a generalized Taylor's formula of the kindfx=∑j=0najx−a(j+1)α−1+Tnx,whereaj∈R,x>a, 0≤α≤1, is established. Such expression is precisely the classical Taylor's formula in the particular case α=1. In addition, detailed expressions forTn(x) andaj, involving the Riemann–Liouville fractional derivative, and some applications are also given

Observations of solar scattering polarization at high spatial resolution

The weak, turbulent magnetic fields that supposedly permeate most of the solar photosphere are difficult to observe, because the Zeeman effect is virtually blind to them. The Hanle effect, acting on the scattering polarization in suitable lines, can in principle be used as a diagnostic for these fields. However, the prediction that the majority of the weak, turbulent field resides in intergranular lanes also poses significant challenges to scattering polarization observations because high spatial resolution is usually difficult to attain. We aim to measure the difference in scattering polarization between granules and intergranules. We present the respective center-to-limb variations, which may serve as input for future models. We perform full Stokes filter polarimetry at different solar limb positions with the CN band filter of the Hinode-SOT Broadband Filter Imager, which represents the first scattering polarization observations with sufficient spatial resolution to discern the granulation. Hinode-SOT offers unprecedented spatial resolution in combination with high polarimetric sensitivity. The CN band is known to have a significant scattering polarization signal, and is sensitive to the Hanle effect. We extend the instrumental polarization calibration routine to the observing wavelength, and correct for various systematic effects. The scattering polarization for granules (i.e., regions brighter than the median intensity of non-magnetic pixels) is significantly larger than for intergranules. We derive that the intergranules (i.e., the remaining non-magnetic pixels) exhibit (9.8 \pm 3.0)% less scattering polarization for 0.2<u<0.3, although systematic effects cannot be completely excluded. These observations constrain MHD models in combination with (polarized) radiative transfer in terms of CN band line formation, radiation anisotropy, and magnetic fields.Comment: Accepted for publication in A&