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

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

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

The Sigmoid function, where it is clearly demonstrated that the critical value range of is [−5, 5].

<p>The Sigmoid function, where it is clearly demonstrated that the critical value range of is [−5, 5].</p

Status of the Science and Technology Award of the Chinese Nursing Association and analysis of the development trend of nursing research

Aims and objective: This study focuses on the status quo and development trend of nursing research in our country to provide a reference for nursing research workers and improve the development of nursing research in China. Methods: The official website of the Chinese Nursing Association was searched to obtain the total number, category, geographical distribution, and job of project leaders of winning projects of the Chinese Nursing Association Technology Award. Findings were analyzed using webometrics and content analysis approach to understand the “study hotspots,” “study level,” and “development trend” of nursing research in China. Results: The total number of winning projects was 144. Among them, the number of first, second, and third prizes were 8, 36, and 100, respectively. Beijing is the area with the largest number of winners (21), followed by Shanghai (17) and Jiangsu (13). Among the winning projects, the top 3 research areas were specialty nursing, nursing management, and nursing education, with percentages of 50%, 27%, and 18%, respectively. Among the 144 project leaders, 96% were academic or hospital directors and only 4% were ordinary staff. Conclusions: The geographical distribution of winning projects presented a regional concentration trend. The categories of winning projects are diverse, and our country has made great achievements in every category, particularly in specialty nursing. Most of the project leaders were academic or hospital directors. The stumbling block to nursing research is the lack of high-quality research projects with international influence. Future research should learn from the experiences of developed countries, focus on the in-depth refinement of specialty nursing, and highlight the importance of collaboration to coordinate and promote nursing development in all regions

Experiments on the entire image-stitching algorithm (II): (a) Video image 1; (b) Video image 2 (reference image); (c) Video image 3; (d) Generated video panoramic image.

<p>Experiments on the entire image-stitching algorithm (II): (a) Video image 1; (b) Video image 2 (reference image); (c) Video image 3; (d) Generated video panoramic image.</p

Experiments on the entire image-stitching algorithm (V): (a) Video image 1; (b) Video image 2 (reference image); (c) Video image 3; (d) Generated video panoramic image.

<p>Experiments on the entire image-stitching algorithm (V): (a) Video image 1; (b) Video image 2 (reference image); (c) Video image 3; (d) Generated video panoramic image.</p