Heat Transfer of Helix Energy Pile: Part 2—Novel Truncated Cone Helix Energy Pile

Owing to the fact that severe thermal interferences exist in the radial and generatrix directions of the traditional cylinder helix energy pile due to the limited thermal heat capacity of the pile and small ratio between coil pitch and radius of pile, therefore, a novel truncated cone helix energy pile (CoHEP) is presented to weaken the thermal interferences and improve the heat transfer efficiency. Further, both the analytical solution model and numerical solution model for CoHEP are built to discuss the dynamic characteristics of thermal interferences and heat transfer performance. The results indicate that the thermal interference of CoHEP is dynamic. The thermal interference in the upper part of the CoHEP is much smaller than the traditional CyHEP. And in general the heat flux per unit pipe length of the novel CoHEP is larger than that of the traditional CyHEP. Heat flux per unit pipe length of the CoHEP increases linearly with inlet water temperature. For the same inlet water temperature, the thermal short circuit is serious at the bottom of the CoHEP, and it’s weak in the upper part of CoHEP. Also it’s obvious that as the inlet water temperature increases, the thermal short circuit becomes more serious

Heat Transfer of Helix Energy Pile: Part 1: Traditional Cylinder Helix Energy Pile

Helix energy pile (HEP) is a new popular ground heat exchanger that has the advantages of large heat exchange rate and low initial cost. As for the traditional helix energy pile, the tube is wound on the cylindrical wall, which is called the cylinder helix energy pile (CyHEP). Further, both analytical solution model and numerical solution model for CyHEP are built to discuss the dynamic characteristics of thermal interferences and heat transfer performance. The results indicate that four heat exchange stages for the spiral pile geothermal heat exchanger along the fluid flow direction are revealed: inlet heat exchange stage, grout thermal short-circuiting stage, small temperature difference stage and outlet heat exchange stage. Each stage has corresponding heat transfer characteristics, and reducing the length of small temperature difference stage and increasing the other stages would enhance the heat exchange of spiral geothermal ground heat exchanger. As the pile diameter increases, the heat transfer per unit tube length decreases, and the heat exchange per unit pile depth increases. As the pile depth increases, the heat transfer per unit tube length and the heat exchange per unit pile depth are reduced. And as the pitch increases, the heat transfer per unit tube length increases, and the heat exchange per unit pile depth decreases

Species invasions threaten the antiquity of China's freshwater fish fauna

AimHuman-mediated species introductions and extirpations have resulted in the homogenization of biotas over time. However, there remains considerable uncertainty in our understanding of homogenization process for megadiverse regions of the world. Here, we investigate the consequences of widespread species invasions and extirpations for the biogeography of China&#39;s unique freshwater fish fauna. LocationChina. MethodsBy assembling a comprehensive dataset for distribution of Chinese freshwater fishes, we quantify how non-native fish species, from both overseas introductions and domestic translocations, has led to taxonomic homogenization of fish faunas at watershed, basin, ecoregion and country scales. We explore how the observed patterns in homogenization vary geographically, and identify those species most responsible for the faunal changes. Lastly, we simulate how China&#39;s fish fauna may continue to homogenize according to different scenarios of anticipated species introductions and extirpations. ResultsWe demonstrate that species introductions and extirpations have homogenized freshwater fish faunas across China. Overall compositional similarity of watersheds increased by 7.0% (from a historical 14.9% to 21.9% in the present day; SOrensen index). Compositional similarity of 96 of 103 (93.2%) watersheds increased, with western basins exhibiting the highest magnitude. Translocated non-native species associated with aquaculture practices contributed the most to faunal homogenization when compared to alien species (7.3% and 0.4%, respectively). Furthermore, faunal homogenization is predicted to intensify an additional 0.5-4.2% with increasing numbers of new non-native species introductions and the extirpation of native species. Main conclusionsSpecies introductions and extirpations have resulted in the significant impoverishment, and thus the loss of antiquity, of China&#39;s freshwater fish fauna over the past century. In the light of the growing realization that species composition (not richness) defines the role that biodiversity plays in maintaining ecosystem function, our study highlights the need for conservation strategies in China that consider changing patterns of diversity.</p

Species distribution models have limited spatial transferability for invasive species

The reliability of transferring species distribution models (SDMs) to new ranges and future climates has been widely debated. Biological invasions offer the unique opportunity to evaluate model transferability, as distribution data between species' native and introduced ranges are geographically independent of each other. Here, we performed the first global quantitative synthesis of the spatial transferability of SDMs for 235 invasive species and assessed the association of model transferability with the focal invader, model choice and parameterisation. We found that SDMs had limited spatial transferability overall. However, model transferability was higher for terrestrial endotherms, species introduced from or to the Southern Hemisphere, and species introduced more recently. Model transferability was also positively associated with the number of presences for model calibration and evaluation, respectively, but negatively with the number of predictors. These findings highlight the importance of considering the characteristics of the focal invader, environment and modelling in the application and assessment of SDMs

On the Measurements of Individual Particle Properties Via Compression and Crushing

An experimental study is presented to measure the elastic, yielding, and crushing properties of individual particles under compression using substrates made of aluminum alloy, stainless steel, and sapphire. Carefully selected, highly spherical individual Ottawa sand particles of 0.75-1.1 mm in nominal diameter were compressed between two smooth substrates, and the load-deformation curves were analyzed by Hertz elastic contact theory to derive their reduced modulus and Young\u27s modulus as well as yielding and crushing strengths, which vary significantly with the type of substrate materials. Further analysis of the yielding and plastic deformation at the particle-substrate contact shows that the yield strength or hardness of the substrate materials dominates the local contact behavior and hence affects the measured apparent yielding and crushing strengths. The two softer substrates (aluminum alloy and stainless steel) actually lead to underestimated apparent shear yield strengths of quartz particles by 60.4% and 54.2%, respectively, which are actually the yielding of substrates, while the true particle yielding occurs in the sapphire-particle contact. Moreover, the two softer substrates cause much overestimated crushing strengths of the quartz particles by 50.4% and 36.4%, respectively. Selection of inappropriate substrate materials and inappropriate interpretation of the particle-substrate contact can lead to significant errors in the measured yielding and crushing strengths. It is recommended that single particle compression testing uses substrates with yield strength greater than that of the tested particles and result interpretation also considers the elastic and yielding behaviors of the substrates. (C) 2021 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V

Diet-induced bacterial immunogens in the gastrointestinal tract of dairy cows: Impacts on immunity and metabolism

Dairy cows are often fed high grain diets to meet the energy demand for high milk production or simply due to a lack of forages at times. As a result, ruminal acidosis, especially subacute ruminal acidosis (SARA), occurs frequently in practical dairy production. When SARA occurs, bacterial endotoxin (or lipopolysaccharide, LPS) is released in the rumen and the large intestine in a large amount. Many other bacterial immunogens may also be released in the digestive tract following feeding dairy cows diets containing high proportions of grain. LPS can be translocated into the bloodstream across the epithelium of the digestive tract, especially the lower tract, due to possible alterations of permeability and injuries of the epithelial tissue. As a result, the concentration of blood LPS increases. Immune responses are subsequently caused by circulating LPS, and the systemic effects include increases in concentrations of neutrophils and the acute phase proteins such as serum amyloid-A (SAA), haptoglobin (Hp), LPS binding protein (LBP), and C-reactive protein (CRP) in blood. Entry of LPS into blood can also result in metabolic alterations. Blood glucose and nonesterified fatty acid concentrations are enhanced accompanying an increase of blood LPS after increasing the amount of grain in the diet, which adversely affects feed intake of dairy cows. As the proportions of grain in the diet increase, patterns of plasma β-hydoxybutyric acid, cholesterol, and minerals (Ca, Fe, and Zn) are also perturbed. The bacterial immunogens can also lead to reduced supply of nutrients for synthesis of milk components and depressed functions of the epithelial cells in the mammary gland. The immune responses and metabolic alterations caused by circulating bacterial immunogens will exert an effect on milk production. It has been demonstrated that increases in concentrations of ruminal LPS and plasma acute phase proteins (CRP, SAA, and LBP) are associated with declines in milk fat content, milk fat yield, 3.5% fat-corrected milk yield, as well as milk energy efficiency

Simultaneous Resonant and Broadband Detection for Dark Sectors

Electromagnetic resonant systems, such as cavities or LC circuits, have emerged as powerful detectors for probing ultralight boson dark matter and high-frequency gravitational waves. However, the limited resonant bandwidth of conventional single-mode resonators, imposed by quantum fluctuations, necessitates numerous scan steps to cover broad unexplored frequency regions. The incorporation of multiple auxiliary modes can realize a broadband detector while maintaining a substantial signal response. The broadened sensitive width can be on the same order as the resonant frequency, encompassing several orders of the source frequency for heterodyne detection, where a background cavity mode transitions into another. Consequently, our approach enables significantly deeper exploration of the parameter space within the same integration time compared to single-mode detection.Comment: 18 pages, 6 figure

Conditional Well-Posedness for an Inverse Source Problem in the Diffusion Equation Using the Variational Adjoint Method

This article deals with an inverse problem of determining a linear source term in the multidimensional diffusion equation using the variational adjoint method. A variational identity connecting the known data with the unknown is established based on an adjoint problem, and a conditional uniqueness for the inverse source problem is proved by the approximate controllability to the adjoint problem under the condition that the unknowns can keep orders locally. Furthermore, a bilinear form is set forth also based on the variational identity and then a norm for the unknowns is well-defined by which a conditional Lipschitz stability is established