High workability together with a good resistance to segregation is needed for cement based composites, specifically fresh self-compacting mortars (SCM); in this prospect, the amount of coarse materials has to be reduced and replaced by fine material. Several limestone fillers are here compared and analysed. These by-products are issued from different industrial sectors, such as the aggregate and lime production industry (quarrying operations) and the ornamental stones industry (sawing operations).Particular attention has been paid to clay content, as consistency of fresh mortars was varying, while other physical characteristics like granulometry remained the same. Relationship between the physico-chemical properties of the fillers and the properties of fresh and hardened mortars are brought forward. Even if it may affect fresh properties of mortars, results clearly show that clay type and content has minor influence than limestone filler itself. 相似文献
We investigate the localization of a camera subject to a planar motion with horizontal optical axis in the presence of known vertical landmarks. Under these assumptions, a calibrated camera can measure the distance to the viewed landmarks. We propose to replace the trilateration method by intersecting a pair of Chasles-Apollonius circles. In the case of square pixels but unknown focal length we introduce a new method to recover the camera position from one image with three vertical landmarks. To this end we consider virtual landmarks and Apollonius-like circles. We extend this method in order to deal with an unknown principal point by using four landmarks. 相似文献
Concrete is a complex multi-scale composite involving multi-physics processes. As it is the only evolving component of concrete, the cement paste has a major influence on the mechanical properties of concrete at early age. This paper focuses on the increase of the elastic properties of a cement paste during its hydration. The homogenization theory for disordered media is used in order to estimate the evolution of the effective elastic moduli of the hydrating paste. The morphological model refers to two types of C-S-H (calcium silicate hydrates, main hydration products of Portland cements) distinguished by many authors: inner products or high density C-S-H build up layers surrounding the anhydrous particles, while the outer products or low density C-S-H play the role of a porous matrix.The simulations of the effective Young's modulus at late age during hydration and at the end of hydration prove to be in excellent agreement with the experimental results available in the literature. 相似文献
This paper presents a computational model for studying the mechanical properties of skin with aging. In particular, attention is given to the folding capacity of skin, which may be manifested as wrinkles. The simulation provides visual results demonstrating the form and density of folds under the various conditions. This can help in the consideration of proper measures for a cosmetic product for the skin. 相似文献
We propose to find the propagation constants of modes in layered media by means of signal identification methods. To this effect we employ Cauchy's theorem, conformal mapping and Fast Fourier Transform (FFT) techniques to generate relevant Hankel moments, afterwards to be processed with selected signal identification algorithms. The method, terminated by a few Newton steps, provides a batch of highly accurate roots in appropriate disks or half-disks. 相似文献
A pleasant and consistent bitterness is an essential flavour attribute of beer. Hop‐derived iso‐α‐acids are largely responsible for beer bitterness and accurate determination of these primary flavour compounds is very important in relation to quality control. The most widely used way to determine beer bitterness is based on spectrophotometry, measuring the absorbance of an iso‐octane extract of acidified beer. However, this approach is far from specific as it measures all of the extracted compounds, including non‐bittering principles. For that particular reason, High Performance Liquid Chromatography (HPLC) is increasingly applied for the quantitative determination of hop‐derived iso‐α‐acids and, if present, reduced iso‐α‐acids. However, to obtain accurate data on beer bitterness profiles, both quantitative sample preparation and state‐of‐the‐art HPLC are essential. In this paper, several extraction procedures based on solid phase extraction (SPE) and liquid‐liquid extraction (LLE), respectively, were evaluated and an optimised extraction methodology using H3PO4 for sample acidification prior to extraction is presented. The proposed extraction/HPLC methodology allows for the quantitative recovery and analysis of hop‐derived beer bitterness. 相似文献
A copper‐catalysed multicomponent coupling reaction between readily available (Z)‐3‐iodoacrylic acids, terminal alkynes, and primary amines was developed to smoothly access a small library of 5‐hydroxy‐1H‐pyrrol‐2(5H)‐ones in good yields. This practical and general process was applied to a short‐steps synthesis of the natural product pulchellalactam.