Development and analysis of mineral based coatings for buildings and urban structures

Commonly used materials in the construction of the building façades located in warm climates, often entrap a great amount of heat from the incoming solar radiation, leading to a respective thermal increase in the interior. The aim of the present study is to examine mineral-based coatings as a passive solar technique that contributes to buildings’ energy efficiency. A series of mineral based samples are developed and tested. Their thermal performance is estimated by infrared thermography and surface temperature measurements. Their optical properties are also measured while the energy efficiency is quantified using simulation techniques. The results revealed that renders based on hydraulic and/or hydrated lime with additions of calcium carbonate powder, as well as mineral paints comprised either of lime wash or silicate minerals can behave as cool coatings and contribute to a significant reduction of the cooling demand in warm climates.     

Assessment of the strain monitoring reliability of fiber Bragg grating sensor (FBGs) in advanced composite structures

Fiberoptic Bragg grating sensors were embedded in composite structures in order to be used as the detection system for structural health monitoring purposes. Firstly, optical fibers had been embedded in several locations in between the layers of composite material and for the typical tensile testing coupon configuration. It has been shown experimentally and with finite element analysis that embedding the optical fiber out of the neutral axis of the coupon, downgrades significantly the composite’s ultimate tensile strength. Secondly, a composite patch with embedded FBG has been used to restore a typical damage case on aluminum structure currently applied on advanced ‘aging’ vehicles. Data values taken from the FBG system during the experimental tension tests of the composite structures were calculated to axial strain values with the aid of an interrogator. Theoretical axial strain values of the composite patch had been calculated by exploiting a newly-developed finite element model. Discussion has been made on the correlation between experimental and theoretical results for the verification of sensing sensitivity and accuracy.     

Insights into the molecular organization of the neuron by cryo-electron tomography

Despite great progress in the identification and characterization of the key molecular players in neuronal function, remarkably little is known about their supramolecular organization. Cryo-electron tomography (cryo-ET), providing three-dimensional views of the molecular components of the cell in their native, fully hydrated environment, is uniquely positioned to elucidate the native architecture of the molecular machinery of the neuron. In our laboratory, we employ cryo-ET to study neuronal morphology in a variety of experimental systems and develop methods to extract quantitative and functional information from tomographic data. This approach has allowed us to shed light onto the intricate organization of the molecules of the synaptic cleft and the presynaptic cytomatrix, providing evidence for their functional roles. Also, cryo-ET of cultured neurons is beginning to open new perspectives on neuronal ultrastructure and the architecture of synaptic complexes in situ. Here, we will review these findings and discuss future directions towards the elucidation of the molecular landscape of the neuron.     

ATM traffic engineering for ABR service provisioning

The Available Bit Rate (ABR) service is being designed as a low-cost transport service over ATM, which will be using the bandwidth left available after servicing connections of another, high-priority class. The implementation of the ABR service requires large buffers at each multiplexing/switching stage to keep cell-loss rates down to a minimum, and a feedback mechanism from the network to the terminals in order for the latter to adjust their traffic profiles according to the prevailing congestion conditions. Thus, an enhanced set of traffic control functions is necessary to support this new service. In this paper the main traffic analysis and control problems related with the ABR service are addressed, modelled and answered on the basis of effective rates defined for the multiplexed connections. Emphasis is given to a simple CAC scheme which consists in allocating peak rates to the high-priority class and effective rates to the ABR class. An adaptive shaping mechanism is then required to enforce the contracted effective rates for the ABR streams. Producing ON/OFF streams facilitates the control functions by allowing the use of approximate closedform calculations.This work has been carried out partly in the framework of the RACE EXPLOIT project.     

Wheel+legs-a new solution for traction enhancement without additivesoil compaction

This paper presents the tractive performance of a one-wheeled vehicle equipped with a rotative leg appendage. Traction tests of the vehicle are performed and the maximum coefficient of traction is determined. Tests to measure the pressure distribution created by the legs on a soil bin are conducted to illustrate traction enhancement     

Parameterized complex dielectric functions of CuIn1−xGaxSe2: applications in optical characterization of compositional non‐uniformities and depth profiles in materials and solar cells

In‐situ spectroscopic ellipsometry (SE) was employed to extract the complex dielectric functions ε = ε₁ + iε₂ over the spectral range of 0.75–6.5 eV for a set of polycrystalline CuIn_1−xGa_xSe₂ (CIGS) thin films with different alloy compositions x = [Ga]/{[In] + [Ga]}. For highest possible accuracy in ε for each CIGS thin film, specialized SE procedures were adopted including (i) deposition to a thickness of ~600 Å on smooth native oxide covered crystal silicon wafers, which minimizes the surface roughness on the film and thus the required corrections in data analysis, and (ii) measurement in‐situ, which minimizes ambient contamination and oxidation of the film surface. Assuming an analytical form for each of the ε spectra for these CIGS films, oscillator parameters were obtained in best fits, and these parameters were fit in turn to polynomials in x. With the resulting database of polynomial coefficients, the ε spectra for any composition of CIGS can be generated from the single parameter, x. In addition to enabling accurate contactless determination of bulk and surface roughness layer thicknesses of CIGS films by high speed multichannel SE, the database enables characterization of the composition and its profile with depth into these films, and even how the depth profile varies spatially within the plane of the films. In this study, depth profile parameters were found to correlate spatially with solar cell performance parameters. As a result, SE provides the capability of contactless compositional analysis of production‐scale CIGS photovoltaic modules at high speed. Copyright © 2016 John Wiley & Sons, Ltd.     

Engineering scalable, cache and space efficient tries for strings

Storing and retrieving strings in main memory is a fundamental problem in computer science. The efficiency of string data structures used for this task is of paramount importance for applications such as in-memory databases, text-based search engines and dictionaries. The burst trie is a leading choice for such tasks, as it can provide fast sorted access to strings. The burst trie, however, uses linked lists as substructures which can result in poor use of CPU cache and main memory. Previous research addressed this issue by replacing linked lists with dynamic arrays forming a cache-conscious array burst trie. Though faster, this variant can incur high instruction costs which can hinder its efficiency. Thus, engineering a fast, compact, and scalable trie for strings remains an open problem. In this paper, we introduce a novel and practical solution that carefully combines a trie with a hash table, creating a variant of burst trie called HAT-trie. We provide a thorough experimental analysis which demonstrates that for large set of strings and on alternative computing architectures, the HAT-trie—and two novel variants engineered to achieve further space-efficiency—is currently the leading in-memory trie-based data structure offering rapid, compact, and scalable storage and retrieval of variable-length strings.     

Colloidal Stability of Zirconia-Doped Yttria–Silica Binary Aqueous Suspensions

Minor amounts of zirconia (up to 5 wt%) were fused with yttria and their effect on water solubility of yttria, and colloidal stability of yttria–silica aqueous binary suspensions, was examined. It is shown that incorporated zirconia reduces the water sensitivity of yttria while maintaining the hydrophilic nature of the surface. This fusion procedure makes yttria particles suitable for production of longlasting yttria–silica aqueous suspensions.     

Atomistic Modeling of Solidification Phenomena Using the Phase-Field-Crystal Model

In recent years, a fundamental understanding of solidification and its behavior has been gained through molecular dynamics simulations and the phase-field method, the first of which is limited to short time scales and the latter of which does not represent interface and elastoplastic properties accurately. Recently, the phase-field-crystal (PFC) method, a continuum method operating on atomistic length scales and diffusive time scales, has helped bridge the multiple scale gap between molecular dynamics and phase field. This review surveys the advances of PFC models in the context of various solidification phenomena.     

Complex dielectric functions of anodic bi-layer tantalum oxide

The optical properties and structure of anodic oxides are dependent on the anodization conditions. For tantalum oxide formed in dilute phosphoric acid, the anodic oxide forms as two chemically distinct layers, referred to as a bi-layer, where the inner layer is pure tantalum oxide and the outer layer contains incorporated phosphate. The complex dielectric functions of the individual inner and outer layers are determined using spectroscopic ellipsometry. The dielectric functions of the bi-layers are compared to mono-layer oxides formed in sodium sulfate, and the effects of hydrothermal sealing are explored. For bi-layer oxides formed to 70 V in phosphoric acid, the inner layer band gap is 4.37 ± 0.02 eV and the outer layer band gap is 3.86 ± 0.06 eV. Thin anodic oxides (∼6-15 nm) are best described by a mono-layer oxide model and exhibit higher optical absorption with a band gap of 3.98 ± 0.08 eV. This study shows that spectroscopic ellipsometry is a valuable tool in assessing processing-property relationships of multi-layer anodic films.