Thermal analysis and measurement of a solar pond prototype to study the non-convective zone salt gradient stability

Solar ponds combine solar energy collection with long-term storage and can provide reliable thermal energy at temperature ranges from 50 to 90 °C. A solar pond consists of three distinct zones. The first zone, which is located at the top of the pond and contains the less dense saltwater mixture, is the absorption and transmission region, also known as the upper convective zone (UCZ). The second zone, which contains a variation of saltwater densities increasing with depth, is the gradient zone or non-convective zone (NCZ). The last zone is the storage zone or lower convective zone (LCZ). In this region, the density is uniform and near saturation. The stability of a solar pond prototype was experimentally performed. The setup is composed of an acrylic tube with a hot plate emulating the solar thermal energy input. A study of various salinity gradients was performed based on the Stability Margin Number (SMN) criterion, which is used to satisfy the dynamic stability criterion. It was observed that erosion of the NCZ was accelerated due to mass diffusion and convection in the LCZ. It can be determined that for this prototype the density of the NCZ is greatly affected as the SMN reaches 1.5.     

Hydrodynamic and mass transfer evaluation of post-combustion CO2 capture process for power plants

Clean Technologies and Environmental Policy - The present work is a comparative evaluation on CO2 capture process post-combustion by chemical absorption with alkanolamines, of three Mexican power...     

Single-mode—multimode—single-mode and lossy mode resonance-based devices: a comparative study for sensing applications

In this work, a thin-film consisting of 15 bilayers (estimated thickness: 210 nm) of titanium (IV) oxide and poly(sodium 4-styrenesulfonate) is simultaneously deposited onto two optical fiber structures: a single-mode—multimode—single-mode (SMS) device and a lossy mode resonance (LMR)-based device. The performance of both structures, as refractometers and relative humidity sensors, is studied and compared. In both cases, the sensitivity of the LMR-based device (955 nm/RIU and 3.54 nm/RH %, respectively) highly improves the one of the SMS (142 nm/RIU and 0.3 nm/RH %). These facts can be taken into account when developing sensors based on either SMS or LMR technologies.     

Diamond Surface Modification to Enhance Interfacial Thermal Conductivity in Al/Diamond Composites

Diamond/metal composites are very attractive materials for electronics because their excellent thermal properties make them suitable for use as heat sink elements in multifunctional electronic packaging systems. To enlarge the potential applications of these composites, current efforts are mainly focused on investigating different ways to improve the contact between metal and diamond. In the present work, a theoretical study has been carried out to determine the differences between the interfacial thermal conductance of aluminum/diamond and aluminum/graphite interfaces. Additionally, diamond particles were surface modified with oxygen to observe how it affects the quality of the diamond surface. The characterization of the surface of diamonds has been performed using different surface analysis techniques, especially x-ray photoelectron spectroscopy and temperature-programmed desorption.     

Designing antimicrobial bioactive glass materials with embedded metal ions synthesized by the sol–gel method

Bioactive glasses (SiO₂–P₂O₅–CaO) having tailored concentrations of different biocide metal ions (copper or silver) were produced by the sol–gel method. All the particles release phosphorous ions when immersed in water and simulated body fluid (SBF). Moreover, a surface layer of polycrystalline hydroxy-carbonate apatite was formed on the particle surfaces after 10 day immersion in SBF as confirmed by X-ray diffraction and scanning electron microscopy (SEM) showing the bioactive materials. Samples with embedded either copper or silver ions were able to further release the biocide ions with a release rate that depends on the metal embedded and the dissolution medium: water or SBF. This biocide ion release from the samples explains the antimicrobial effect of our active particles against Escherichia coli DH5α ampicillin-resistant (Gram-negative) and Streptococcus mutans (Gram-positive) as determined by the Minimum Bactericidal Concentration (MBC) method. The antimicrobial behavior of the particles depends on the bacteria and the biocide ion used. Noteworthy, although samples with copper are able to release more metal ion than samples with silver, they present higher MBC showing the high effect of silver against these bacteria.     

Weak convergence to a modified fractional Brownian motion

This article discusses the weak convergence of a particular version of a fractional process (appropriately normalized) to a modified fractional Brownian motion which has not been previously reported in the literature. Additionally, we illustrate a specific case in which this type of fractional Brownian motion characterizes the limiting behaviour of processes which might arise in practice. This is related to the situation termed by Hualde (2006) as ‘unbalanced cointegration’, where the integration orders of the observables are different, but their corresponding balanced versions (where one of the series is filtered adequately so it has identical integration order to the other one) are cointegrated in the usual sense.     

Construction of interval-valued fuzzy entropy invariant by translations and scalings

In this paper, we propose a method to construct interval-valued fuzzy entropies (Burillo and Bustince 1996). This method uses special aggregation functions applied to interval-contrasts. In this way, we are able to construct interval-valued fuzzy entropies from automorphisms and implication operators. Finally, we study the invariance of our constructions by scaling and translation.     

双侧延伸端板半刚性组合节点的抗震性能(1):试验研究

与钢结构相比,相同延性下,组合结构具有较高的刚度及较好的抗火性能。因此,在地震高发区大量采用组合结构。研究了双侧延伸端板半刚性组合节点的抗震性能,对节点进行单调、循环、准静力试验,以描述这种节点的抗震性能。试验包括内节点和外节点,并提供了关于节点延性、能量耗散、退化影响的实用数据。采用这些数据构建和校验基于构件的节点模型。节点由双向弹簧组成,其中一个代表剪切板的性能,另一个代表连接的性能。模型能精确模拟节点的性能及在循环荷载下的破坏形式。     

Partition-Based Lower Bound for Max-CSP

In this paper we address Max-CSP, a constraint optimization problem typically solved using a branch and bound scheme. It is well known that the efficiency of branch and bound greatly depends on the quality of the available lower bound. Previous approaches aggregate to the lower bound individual contributions of unassigned variables. In this paper, we augment this approach by adding global contributions of disjoint subsets of unassigned variables, which requires a partition of the set of unassigned variables. Using this idea, we introduce the partition-based lower bound. It improves previous approaches based on individual contributions in the sense that our method can be added up to previous bounds, possibly increasing their value. We demonstrate our method presenting two new algorithms, PFC-PRDAC and PFC-MPRDAC, which are the natural successors of PFC-RDAC and PFC-MRDAC augmented with our approach. We provide experimental evidence for the superiority of the new algorithms on random problems and real instances of weighted over-constrained problems.