Technical and Economic Criteria to Select Pavement Surfaces of Port Handling Plants

A port is an intermodal system in which many logistics activities requiring properly constructed areas occur. The large extension of these areas poses a major problem in choosing materials with technical and economic implications. Choice and design of pavements are directly related to the port handling systems and procedures for the disposal of the cargo units. The paper presents the design and verification procedures for three equivalent pavements for a handling pavement in an Italian medium-sized port trafficked by reach stackers moving containers. An asphalt pavement, a concrete pavement, and a concrete block pavement have been considered during the 20-year service life. Empirical and analytical methods have been adopted to design and verify the pavements. The structures have been examined in terms of economic concerns during the overall service life, considering both construction and maintenance costs, in order to determine the most cost-effective option. The results demonstrate the inappropriateness of asphalt pavement, in the examined case, from a construction costs point of view. Furthermore, the overall discounted costs show an inversion of convenience between block concrete pavement and cast in situ concrete: the latter is the cheaper solution. The proposed methodology can balance often conflicting objectives in matters of durability and funds management, providing answers to a complex topic

Mechanical loss in state-of-the-art amorphous optical coatings

We present the results of mechanical characterizations of many different high-quality optical coatings made of ion-beam-sputtered titania-doped tantala and silica, developed originally for interferometric gravitational-wave detectors. Our data show that in multi-layer stacks (like high-reflection Bragg mirrors, for example) the measured coating dissipation is systematically higher than the expectation and is correlated with the stress condition in the sample. This has a particular relevance for the noise budget of current advanced gravitational-wave interferometers, and, more generally, for any experiment involving thermal-noise limited optical cavities.Comment: 31 pages, 14 figure

Analysis of systems hardware flown on LDEF. Results of the systems special investigation group

The Long Duration Exposure Facility (LDEF) was retrieved after spending 69 months in low Earth orbit (LEO). LDEF carried a remarkable variety of mechanical, electrical, thermal, and optical systems, subsystems, and components. The Systems Special Investigation Group (Systems SIG) was formed to investigate the effects of the long duration exposure to LEO on systems related hardware and to coordinate and collate all systems analysis of LDEF hardware. Discussed here is the status of the LDEF Systems SIG investigation through the end of 1991

Advanced characterization and optical simulation for the design of solar selective coatings based on carbon: transition metal carbide nanocomposites

Solar selective coatings based on carbon transition metal carbide nanocomposite absorber layers were designed. Pulsed filtered cathodic arc was used for depositing amorphous carbon:metal carbide (a-C:MeC, Me = V, Mo) thin films. Composition and structure of the samples were characterized by ion beam analysis, X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The optical properties were determined by ellipsometry and spectrophotometry. Three effective medium approximations (EMA), namely Maxwell-Garnett, Bruggeman, and Bergman, were applied to simulate the optical behaviour of the nanocomposite thin films. Excellent agreement was achieved between simulated and measured reflectance spectra in the entire wavelength range by using the Bergman approach, where in-depth knowledge of the nanocomposite thin film microstructure is included. The reflectance is shown to be a function of the metal carbide volume fraction and its degree of percolation, but not dependent on whether the nanocomposite microstructure is homogeneous or a self-organized multilayer. Solar selective coatings based on an optimized a-C:MeC absorber layer were designed exhibiting a maximum solar absorptance of 96% and a low thermal emittance of ~5% and 15% at 25 and 600 °C, respectively. The results of this study can be considered as a predictive design tool for nanomaterial-based optical coatings in general

External Insulation Systems for Cryogenic Storage Systems

Multilayer dielectric film reflector applied to cryogenic insulation material

LDEF: A bibliography with abstracts

The Long Duration Exposure Facility (LDEF) was a free-flying cylindrical structure that housed self-contained experiments in trays mounted on the exterior of the structure. Launched into orbit from the Space Shuttle Challenger in 1984, the LDEF spent almost six years in space before being recovered in 1990. The 57 experiments investigated the effects of the low earth orbit environment on materials, coatings, electronics, thermal systems, seeds, and optics. It also carried experiments that measured crystals growth, cosmic radiation, and micrometeoroids. This bibliography contains 435 selected records from the NASA aerospace database covering the years 1973 through June of 1992. The citations are arranged within subject categories by author and date of publication

High temperature epsilon-near-zero and epsilon-near-pole metamaterial emitters for thermophotovoltaics

We propose a method for engineering thermally excited far field electromagnetic radiation using epsilon-near-zero metamaterials and introduce a new class of artificial media: epsilon-near-pole metamaterials. We also introduce the concept of high temperature plasmonics as conventional metamaterial building blocks have relatively poor thermal stability. Using our approach, the angular nature, spectral position, and width of the thermal emission and optical absorption can be finely tuned for a variety of applications. In particular, we show that these metamaterial emitters near 1500 K can be used as part of thermophotovoltaic devices to surpass the full concentration Shockley-Queisser limit of 41%. Our work paves the way for high temperature thermal engineering applications of metamaterials.Comment: 15 pages, 8 figure

Investigations of the properties of materials for the optics and suspensions of future gravitational wave detectors

Future generations of gravitational wave detectors will require significant progress in the reduction of all forms of noise affecting the system. One form of noise it is critical to reduce is thermal noise, which can be described as the consequence of the atoms which make up the measurement optics experiencing vibrations because of their non-zero temperature. The dielectric multilayer coatings of the mirror in an interferometric gravitational wave detector are known to contribute significantly to the overall levels of thermal noise. The next generation of gravitational wave detectors may need to use exotic coatings, cryogenic operating temperatures and silicon mirror substrates in an effort to mitigate the effects of thermal noise. Chapter Two describes thermal noise in detail, and introduces the concepts of substrate noise, coating noise, thermoelastic dissipation, mechanical loss and the formulae used to calculate them. Chapter Three describes the current state of research on the factors affecting mechanical loss in dielectric coatings. The technique of probing the structure and dissipation characteristics of materials by assessing the shape and position of the low temperature excess loss feature known as a Debye peak is introduced. The cryogenic mechanical loss measurement apparatus used in Chapters Four, Five and Six is described and characterised. Chapter Four concerns the variation of mechanical loss of ion-beam sputtered silica coatings with temperature and investigates the effects of heat-treatment upon them. The low-temperature Debye peak was found in some modes of a sample heat treated at 300oC and an Arrhenius analysis provided a characteristic energy for the dissipation process of (17.3 ± 2.3)meV. Further heat treatment of silica at 600oC and 800oC appears to narrow the Debye peak, which is thought to be indicative of the narrowing of the distribution of bond angles in the amorphous silica network. Hafnia is investigated as an alternative coating material in Chapter Five. The mechanical loss of hafnia heat-treated at 300oC was measured and two excess loss features were discovered, one below 100K and one above 200K. Electron scattering measurements indicate that this sample may already have developed polycrystalline regions which are known to be connected to high levels of mechanical loss. The mechanical loss of an un-heat-treated hafnia coating is also measured and an extremely low coating loss of 1.87 × 10−5 is found at 20K. Chapter Six describes an experiment to find the mechanical loss of a hydroxycatalysis bond between silicon cantilevers at temperatures between 10K and 300K.This new technique for the measurement of the mechanical loss of bond material produced a minimum upper limit of the bond loss of (0.13 ± 0.03) occurring in the fundamental mode at 80K and upper limit of the bond loss of (0.19 ± 0.07) occurring in the third mode at 15K. Chapter Seven describes the development and testing of a nodal support system to enable cryogenic measurements of cylindrical bulk mirror substrates to be made. The efficacy of the support varied significantly with the frequency of the mode and the cryogenic measurements were partially successful. The major results in this work are the successful measurements of the mechanical loss of amorphous hafnia coatings at low temperatures and the use of a structure made from hydroxy-catalysis bonded silicon cantilevers to obtain an upper limit for the mechanical loss of the bond material. These results may inform technological advances that reduce the level of thermal noise experienced in future gravitational wave detectors