Modeling of heat transfer for energy efficiency prediction of solar receivers

© 2019 Elsevier. This manuscript is made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International licence (CC BY-NC-ND 4.0). Please see https://creativecommons.org/licenses/by/4.0/ for further details.In this article, a new heat transfer model for solar receivers with metal foam is developed for design optimization. The proposed model facilitates analysis of heat transfer processes in terms of forced convection, natural convection, heat conduction and radiation, accurately predicting the energy efficiency and percentage contribution of each form of heat loss. The results show good agreement between the predicted results and the experimental data. Specifically, sensitivity analysis is performed to predict the energy efficiency of solar receivers under different operating conditions. To explore the influence of inlet temperature, a series of simulations under high inlet temperature are carried out, resulting in poorer energy performance and heavier radiant heat loss. Non-radiant heat loss, however, accounts for less than 1.1% of the total energy loss in all cases. The results reveal that reduction of radiant loss is conducive to energy efficiency improvement.Peer reviewe

Diversity of NC10 bacteria associated with sediments of submerged Potamogeton crispus (Alismatales: Potmogetonaceae)

Background The nitrite-dependent anaerobic methane oxidation (N-DAMO) pathway, which plays an important role in carbon and nitrogen cycling in aquatic ecosystems, is mediated by “Candidatus Methylomirabilis oxyfera” (M. oxyfera) of the NC10 phylum. M. oxyfera-like bacteria are widespread in nature, however, the presence, spatial heterogeneity and genetic diversity of M. oxyfera in the rhizosphere of aquatic plants has not been widely reported. Method In order to simulate the rhizosphere microenvironment of submerged plants, Potamogeton crispus was cultivated using the rhizobox approach. Sediments from three compartments of the rhizobox: root (R), near-rhizosphere (including five sub-compartments of one mm width, N1–N5) and non-rhizosphere (>5 mm, Non), were sampled. The 16S rRNA gene library was used to investigate the diversity of M. oxyfera-like bacteria in these sediments. Results Methylomirabilis oxyfera-like bacteria were found in all three sections, with all 16S rRNA gene sequences belonging to 16 operational taxonomic units (OTUs). A maximum of six OTUs was found in the N1 sub-compartment of the near-rhizosphere compartment and a minimum of four in the root compartment (R) and N5 near-rhizosphere sub-compartment. Indices of bacterial community diversity (Shannon) and richness (Chao1) were 0.73–1.16 and 4–9, respectively. Phylogenetic analysis showed that OTU1-11 were classified into group b, while OTU12 was in a new cluster of NC10. Discussion Our results confirmed the existence of M. oxyfera-like bacteria in the rhizosphere microenvironment of the submerged plant P. crispus. Group b of M. oxyfera-like bacteria was the dominant group in this study as opposed to previous findings that both group a and b coexist in most other environments. Our results indicate that understanding the ecophysiology of M. oxyfera-like bacteria group b may help to explain their existence in the rhizosphere sediment of aquatic plant

Research progress of hydrogels as delivery systems and scaffolds in the treatment of secondary spinal cord injury

Secondary spinal cord injury (SSCI) is the second stage of spinal cord injury (SCI) and involves vasculature derangement, immune response, inflammatory response, and glial scar formation. Bioactive additives, such as drugs and cells, have been widely used to inhibit the progression of secondary spinal cord injury. However, the delivery and long-term retention of these additives remain a problem to be solved. In recent years, hydrogels have attracted much attention as a popular delivery system for loading cells and drugs for secondary spinal cord injury therapy. After implantation into the site of spinal cord injury, hydrogels can deliver bioactive additives in situ and induce the unidirectional growth of nerve cells as scaffolds. In addition, physical and chemical methods can endow hydrogels with new functions. In this review, we summarize the current state of various hydrogel delivery systems for secondary spinal cord injury treatment. Moreover, functional modifications of these hydrogels for better therapeutic effects are also discussed to provide a comprehensive insight into the application of hydrogels in the treatment of secondary spinal cord injury

Intellectual Capital Performance of the Textile Industry in Emerging Markets: A Comparison with China and South Korea

In this study, the Value Added Intellectual Capital (VAICTM) and Modified Value Added Intellectual Capital (MVAICTM) models are utilized to analyze intellectual capital (IC) performance of the textile industry in China and South Korea during 2012–2017, and measure the contribution of IC sub-components to companies’ performance. The results show that the aggregate IC positively affects earnings, profitability, and productivity of textile companies in China and South Korea. At the sub-components level, the contribution of capital employed efficiency (CEE) is the largest, followed by structural capital efficiency (SCE), and relational capital efficiency (RCE) in China’s textile industry. In addition, Korea’s textile industry relies heavily on CEE and human capital efficiency (HCE), while the contribution of RCE is relatively small. Finally, relevant policies are put forward to promote the sustainable development of the textile industry in these two emerging markets

Mode Conversion of the Edge Modes in the Graphene Double-Ribbon Bend

In this paper, a new kind of graphene double-ribbon bend structure, which can support two edge graphene surface plasmons (EGSPs) modes, is proposed. In this double-ribbon bend, one edge mode can be partly converted into another one. We attribute the mode conversion mechanism to the interference between the two edge plasmonic modes. Based on the finite element method (FEM), we calculate the transmission and loss of EGSPs propagating along this graphene double-ribbon bend in the mid-infrared range under different parameters

The impact of a metacognitive self-regulation inventory in translator self-training: a pre-post study with English-Chinese translation students

The goal of this study was to investigate the impact of repeated use of a metacognitive self-regulation inventory (MSRI) in translator self-training. Designed by the researchers, the MSRI includes the cognitive management strategies of planning, monitoring and evaluation. A pre-post comparison study was conducted with two groups of students. The data obtained from students’ responses to the inventory, think-aloud protocols (TAPs), post-task interviews, and translation products assessments were analysed for triangulation purposes. The results show that an MSRI can be used as an effective tool for translator self-training. Specifically, repeated practice with the inventory in students’ self-training processes can effectively increase their awareness of metacognitive self-regulation by diagnosing their strengths and weaknesses, assist them to transform declarative knowledge into procedural knowledge, promote top-down processing mode, and eventually influence the balance of their patterns of metacognitive self-regulation. Furthermore, the strengthening of metacognitive self-regulation encourages students to pay more attention to the communicative function of the translation, and ultimately enhances their translation quality, particularly in the aspects of clarity, vocabulary, morphosyntax, genre conventions, and translation’s purpose and target audience

A Fast Image Stitching Algorithm via Multiple-Constraint Corner Matching

Video panoramic image stitching is in general challenging because there is small overlapping between original images, and stitching processes are therefore extremely time consuming. We present a new algorithm in this paper. Our contribution can be summarized as a multiple-constraint corner matching process and the resultant faster image stitching. The traditional Random Sample Consensus (RANSAC) algorithm is inefficient, especially when stitching a large number of images and when these images have quite similar features. We first filter out many inappropriate corners according to their position information. An initial set of candidate matching-corner pairs is then generated based on grayscales of adjacent regions around each corner. Finally we apply multiple constraints, e.g., their midpoints, distances, and slopes, on every two candidate pairs to remove incorrectly matched pairs. Consequently, we are able to significantly reduce the number of iterations needed in RANSAC algorithm so that the panorama stitching can be performed in a much more efficient manner. Experimental results demonstrate that (i) our corner matching is three times faster than normalized cross-correlation function (NCC) rough match in traditional RANSAC algorithm and (ii) panoramas generated from our algorithm feature a smooth transition in overlapping image areas and satisfy human visual requirements

A Scaled Boundary Finite-Element Method with B-Differentiable Equations for 3D Frictional Contact Problems

Contact problems are among the most difficult issues in mathematics and are of crucial practical importance in engineering applications. This paper presents a scaled boundary finite-element method with B-differentiable equations for 3D frictional contact problems with small deformation in elastostatics. Only the boundaries of the contact system are discretized into surface elements by the scaled boundary finite-element method. The dimension of the contact system is reduced by one. The frictional contact conditions are formulated as B-differentiable equations. The B-differentiable Newton method is used to solve the governing equation of 3D frictional contact problems. The convergence of the B-differentiable Newton method is proven by the theory of mathematical programming. The two-block contact problem and the multiblock contact problem verify the effectiveness of the proposed method for 3D frictional contact problems. The arch-dam transverse joint contact problem shows that the proposed method can solve practical engineering problems. Numerical examples show that the proposed method is a feasible and effective solution for frictional contact problems

Efficient video panoramic image stitching based on an improved selection of Harris corners and a multiple-constraint corner matching.

Video panoramic image stitching is extremely time-consuming among other challenges. We present a new algorithm: (i) Improved, self-adaptive selection of Harris corners. The successful stitching relies heavily on the accuracy of corner selection. We fragment each image into numerous regions and select corners within each region according to the normalized variance of region grayscales. Such a selection is self-adaptive and guarantees that corners are distributed proportional to region texture information. The possible clustering of corners is also avoided. (ii) Multiple-constraint corner matching. The traditional Random Sample Consensus (RANSAC) algorithm is inefficient, especially when handling a large number of images with similar features. We filter out many inappropriate corners according to their position information, and then generate candidate matching pairs based on grayscales of adjacent regions around corners. Finally we apply multiple constraints on every two pairs to remove incorrectly matched pairs. By a significantly reduced number of iterations needed in RANSAC, the stitching can be performed in a much more efficient manner. Experiments demonstrate that (i) our corner matching is four times faster than normalized cross-correlation function (NCC) rough match in RANSAC and (ii) generated panoramas feature a smooth transition in overlapping image areas and satisfy real-time human visual requirements