1,720,996 research outputs found
SUNLIGHT-BASED SUN IMITATING ILLUMINATION
No full textA sunlight-based projector system (3) is disclosed for providing a direct light beam (5). The projector system (3) comprises a sunlight receiving unit (9) with a collector system (13), a plurality of optical fibers (15), and a plurality of fiber output channels (44). The collector system (13) collects natural outdoor light, and couples the collected light into the plurality of optical fibers (15). The projector system (3) comprises further a sunlight forming unit (11) with a plurality of optical collimator units (47) arranged in a two-dimensional array, wherein each optical collimator unit (47) receives the respective fiber output light (45) and comprises at least one optical collimator (49) for reducing the angular distribution width of the received divergent fiber output light (45). Output areas of the plurality of optical collimator units (47) form essentially a continuously extending large light- emitting face (53) of the sunlight forming unit (11) for emitting an essentially collimated light beam (5). The generated direct light beam (5) may be used together with diffused light generating areal units to provide a sun-sky imitating lighting system with a sun-like appearance
Commercial counterboard for 10 ns software correlator for photon and fluorescence correlation spectroscopy
No full textA 10 ns time resolution, multi-tau software correlator, capable of computing simultaneous autocorrelation (A-A, B-B) and cross (A-B) correlation functions at count rates up to similar to 10 MHz, with no data loss, has been developed in LabVIEW and C++ by using the National Instrument timer/counterboard (NI PCIe-6612) and a fast Personal Computer (PC) (Intel Core i7-4790 Processor 3.60 GHz). The correlator works by using two algorithms: for large lag times (tau greater than or similar to 1 mu s), a classical time-mode scheme, based on the measure of the number of pulses per time interval, is used; differently, for tau less than or similar to 1 mu s a photon-mode (PM) scheme is adopted and the correlation function is retrieved from the sequence of the photon arrival times. Single auto- and cross-correlation functions can be processed online in full real time up to count rates of similar to 1.8 MHz and similar to 1.2 MHz, respectively. Two autocorrelation (A-A, B-B) and a cross correlation (A-B) functions can be simultaneously processed in full real time only up to count rates of similar to 750 kHz. At higher count rates, the online processing takes place in a delayed modality, but with no data loss. When tested with simulated correlation data and latex spheres solutions, the overall performances of the correlator appear to be comparable with those of commercial hardware correlators, but with several nontrivial advantages related to its flexibility, low cost, and easy adaptability to future developments of PC and data acquisition technology. Published by AIP Publishing
Role of microstructure in the exploitation of self-healing potential in form-stable composite phase change materials based on immiscible alloys
Full text linkMetallic Phase Change Materials (PCMs), based on solid-liquid transitions, represents one of the most promising technologies for efficient Thermal Energy Storage (TES), due to their superior thermal conductivity and energy storability per unit volume, but suffer of limited solutions for their handling at the molten state. The use of Miscibility Gap Alloys (MGAs) allows to manage PCM volume expansion and keep it confined when molten, preventing interaction with the environment. A relevant example is provided by the Al-Sn system, where Al covers the role of the high-temperature stable and highly thermal-conductive passive matrix and Sn the active PCM. The alloy can thus be considered a Composite PCM (C-PCM). The response fastness of these systems depends on their thermal diffusivity, subjected to abrupt variations under the presence of discontinuities and damages. In this sense, the authors investigated the possibility to employ molten Sn mobility in a potentially damaged C-PCM for self-healing purposes, aimed to restore, at least partially, the material continuity and thus its thermal diffusivity. Exudation heat treatments above the melting temperature of Sn were performed on sets of Al-40%wt. Sn metallic composites, produced either with powder metallurgy or liquid metal routes, in order to quantify and assess the mobility of the Sn under simulated operating conditions. Exudation tests assess Simple Mixed powders and liquid metal routes sample as the ones with the highest healing potential. Al dissolution and re-deposition was established by EDS analyses as one of the principal Sn mobility mechanisms. Laser Flash Analysis tests, as well as microstructural investigations, were performed on the samples before and after both healing-focused and simulated service heat treatments to evaluate the changes of thermal diffusivity. Healing-focused treatment at 250°C for 1 hour generally displayed a moderate thermal diffusivity recovery and simulated service by shorter cycles between 170°C and 270°C slightly reduce it. The beneficial role of healing focused heat treatments at 250°C for 1 hour suggests that the presence of fully molten Sn phase during service for relatively long time could be beneficial for functional healing. The requirements of suitable Al-Sn microstructures for self-healing purposes, granting at the same time the C-PCM functionalities, i.e., thermal energy storage and form-stability, were set
COMBINED SYSTEM FOR SUN-SKY IMITATING ILLUMINATION
No full textIn an aspect, a combined system (300) comprises a sun-sky imitating device (310) that is configured as an artificial illumination device (20) for generating light with a luminance profile and an appearance, which feature a directed-light component (314) and a first diffused-light component (316) that are emitted from a sun-sky imitating output area (312) for imitating the natural light from the sun and the sky, respectively, and the sun-sky imitating output area (312) has a transversal dimension (D310) of at least 7 cm, wherein the transversal dimension as the longest line segment joining two points of a perimeter of the sun- sky imitating output area (312). Moreover, the combined system (300) comprises a sky imitating device (320) that is configured as an additional diffused- light emitter to emit a second diffused-light component (326) from a sky imitating output area (322) for imitating the natural light from the sky only
Erratum: Modeling of Fibrin Gels Based on Confocal Microscopy and Light-Scattering Data (Biophysical Journal (2013) 104(5) (1151–1159)(S0006349513000945)(10.1016/j.bpj.2013.01.024))
No full text(Biophysical Journal 104, 1151–1159; March, 2013) In the original Supporting Material Supplement there was a typographical error in Eq. (S-7a): This was a typographical error and does not affect the results reported on this supplement and in the main article. We thank F. Burla (AMOLF, Amsterdam, The Netherlands) for having brought the error to our attention
Microstructural features and thermal response of granulated Al and A356 alloy with relevant Sn additions
Full text linkThe aim of the work was to explore the possibility of producing Sn-bearing composite phase change materials (C-PCMs) intended to be used as Latent Heat Thermal Energy Storage (LH-TES) systems. To this purpose, pure Al and A356 Al alloy, with 40%mass Sn, were produced by granulating process. They were composed by an Al (and other phases) matrix and a low melting Sn-rich phase that can store/release latent heat by its melting/solidification. Pure Al and A356 were produced as reference materials. Finite Element Analyses was used to estimate the cooling rate experienced by the alloys during granulation. Microstructural features of the produced materials were discussed as for C-PCM. Granules thermal characterization was performed with Differential Scanning Calorimetry and dilatometry tests. Results show that Sn addition delays the solidification and increase microstructural refinement. Phase transition of the Sn-rich phase occurs at about 230 °C in Al-Sn alloy and in the 200–230 °C range for A356-Sn alloy, as also assessed by CALPHAD modelling. The stability of the thermal response for all the systems, as well as the form stability, is achieved after the first cycle. Moreover, A356-Sn exhibits suitable microstructure for limiting the exudation of the Sn-rich phase, making this alloy very attractive for C-PCMs
Development of a Microstructure-Based Finite Element Model of Thermomechanical Response of a Fully Metallic Composite Phase Change Material
No full textResponse to "A Simplified Implementation of the Bubble Analysis of Biopolymer Networks Pores''
No full textFast two-dimensional bubble analysis of biopolymer filamentous networks pore size from confocal microscopy thin data stacks
No full textThe average pore size ξ0 of filamentous networks assembled from biological macromolecules is one of the most important physical parameters affecting their biological functions. Modern optical methods, such as confocal microscopy, can noninvasively image such networks, but extracting a quantitative estimate of ξ0 is a nontrivial task. We present here a fast and simple method based on a two-dimensional bubble approach, which works by analyzing one by one the (thresholded) images of a series of three-dimensional thin data stacks. No skeletonization or reconstruction of the full geometry of the entire network is required. The method was validated by using many isotropic in silico generated networks of different structures, morphologies, and concentrations. For each type of network, the method provides accurate estimates (a few percent) of the average and the standard deviation of the three-dimensional distribution of the pore sizes, defined as the diameters of the largest spheres that can be fit into the pore zones of the entire gel volume. When applied to the analysis of real confocal microscopy images taken on fibrin gels, the method provides an estimate of ξ0 consistent with results from elastic light scattering data. © 2013 Biophysical Society
Modeling of Fibrin Gels Based on Confocal Microscopy and Light-Scattering Data
No full textFibrin gels are biological networks that play a fundamental role in blood coagulation and other patho/physiological processes, such as thrombosis and cancer. Electron and confocal microscopies show a collection of fibers that are relatively monodisperse in diameter, not uniformly distributed, and connected at nodal points with a branching order of ∼3-4. Although in the confocal images the hydrated fibers appear to be quite straight (mass fractal dimension Dm = 1), for the overall system 1<Dm<2. Based on the confocal images, we developed a method to generate three-dimensional (3D) in silico gels made of cylindrical sticks of diameter d, density ρ, and average length 〈L〉, joined at randomly distributed nodal points. The resulting 3D network strikingly resembles real fibrin gels and can be sketched as an assembly of densely packed fractal blobs, i.e., regions of size ξ, where the fiber concentration is higher than average. The blobs are placed at a distance ξ0 between their centers of mass so that they are overlapped by a factor η = ξ/ξ0 and have Dm ∼1.2-1.6. The in silico gels' structure is quantitatively analyzed by its 3D spatial correlation function g3D(r) and corresponding power spectrum I(q) = FFT3D[g3D(r)], from which ρ, d, Dm, η, and ξ0 can be extracted. In particular, ξ0 provides an excellent estimate of the gel mesh size. The in silico gels' I(q) compares quite well with real gels' elastic light-scattering measurements. We then derived an analytical form factor for accurately fitting the scattering data, which allowed us to directly recover the gels' structural parameters. © 2013 Biophysical Society
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