Tubes with their features optimized to enhance heat transfer are routinely used in industry. A series of experimental investigations of evaporation heat transfer of widely used refrigerants inside a horizontal micro-fin cooper tube have been conducted and are reported here. The micro-fin tubes have different geometric parameters with inner diameter ranging from 4.98mm to 7.14mm. The helix angle of the tested tubes ranges from 18.858° to 35°. The apex angle of the tested tubes ranges from 11° to 40°. In addition, other geometric parameters of the tubes vary, such as the fin height, fin pitch and starts. Evaporation heat transfer experiments were conducted with the tubes and the working fluids include R22, R32 and R410A. The evaporation experiments were taken at a constant temperature of 6 °C for R22 and R410A, but 10 °C for R32. Moreover, the working conditions of the experiments varied with the mass flux ranging from 100 kg/(m2.s) to 400 kg/(m2.s). For the evaporation experiments, the inlet vapor quality is set as 0.1, while the outlet vapor quality is set as 0.9. The experimental data reveals that tubes with different geometric parameters have different heat transfer performance. The heat transfer coefficients, the reduced pressure and the changing trend of the heat transfer coefficients vary among these tubes. The experimental data has been compared with available models in the literature and an analysis of the effect of geometric parameters on the performance of the tubes undertaken. The influence of each geometric parameter on the heat transfer performance of the micro-fin tube has been analyzed and is reported.
Abstract The aim of this study is to investigate a robust and stable calcium-phosphorus system to remineralize human early enamel caries lesions with nanocomplexes of carboxymethyl chitosan/L-serine/amorphous calcium phosphate (CMC-Ser-ACP) to develop an effective method for mimicking the amelogenin (AMEL) mineralization pattern through ACP assembly. A CMC-Ser-ACP nanocomplex solution was first synthesized by a chemical precipitation method, and then 1% sodium hypochlorite (NaClO) was added to induce ACP phase formation. The morphologies of the nanocomplexes were characterized by transmission electron microscopy (TEM), and zeta potential analysis and Fourier transform infrared spectroscopy (FTIR) were performed to detect surface charge and functional group changes. The subtle changes of the demineralized enamel models induced by the remineralization effect were observed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The CMC-Ser-ACP nanocomplex solution could be preserved without any precipitation for 45 days. After the application of NaClO and through the guidance of Ser, ACP nanoparticles transformed into relatively orderly arranged hydroxyapatite (HAP) crystals, generating an aprismatic enamel-like layer closely integrated with the demineralized enamel, which resulted in enhanced mechanical properties for the treatment of early enamel caries lesions. The CMC-Ser-ACP nanocomplex solution is a remineralization system with great solution stability, and when NaClO is added, it can rapidly regenerate an aprismatic enamel-like layer in situ on the demineralized enamel surface. This novel remineralization system has stable chemical properties and can greatly increase the therapeutic effects against early enamel caries. Graphical Abstract
Escherichia coli (E. coli) bloodstream infections (BSIs) are among the most predominant causes of death in infants and children worldwide. NDM-5 (New Delhi Metallo-lactamase-5) is responsible for one of the main mechanisms of carbapenem resistance in E. coli. To analyze the phenotypic and genomic characteristics of NDM-5-producing E. coli from bloodstream infections (BSIs), a total of 114 E. coli strains was collected from a children's hospital in Jiangsu province, China. Eight blaNDM-5-carrying E. coli strains were identified which were all carbapenem-resistant and carried diverse antimicrobial resistance genes apart from blaNDM-5. They belonged to six distinct sequence types (STs) and serotypes including one each for ST38/O7:H8, ST58/O?:H37, ST131/O25:H4, ST156/O11:H25 and ST361/O9:H30 and three strains are originating from a single clone belonging to ST410/O?:H9. Apart from blaNDM-5, the E. coli strains isolated from BSIs also carried other β-lactamase genes, including blaCMY-2 (n = 4), blaCTX-M-14 (n = 2), blaCTX-M-15 (n = 3), blaCTX-M-65 (n = 1), blaOXA-1 (n = 4) and blaTEM-1B (n = 5). The blaNDM-5 genes were located on three different types of plasmids, which were IncFII/I1 (n = 1), IncX3 (n = 4) and IncFIA/FIB/FII/Q1 (n = 3). The former two types were conjugatively transferable at frequencies of 10-3 and 10-6, respectively. The dissemination of NDM-producing strains, which exhibit resistance to the last-line antibiotics, carbapenems, may increase the muti-antimicrobial resistance burden among E. coli BSIs and further threaten public health.
Microbial communities and soil organic carbon (SOC) fractions are sensitive indicators for monitoring soil quality and crop yield. But the effects of fertilization on relationship between SOC fractions and microbial community in black soil are remain unclear. Focused on this point, we performed the present study with a maize monocropping system suffered different fertilization treatments, including non-fertilization (CK), chemical fertilization (CF), chemical fertilizer with straw (CFS) and organic manure (OM). The contents and fractions of SOC were measured, whereas the microbial community structure was assessed by Illumina sequencing technology. As results, the highest contents of active SOC fractions were found in the OM treatment, while the highest maize yield was obtained in the CFS treatment. Proteobacteria were widely distributed in all the fertilization treatments. The dominant fungal phyla were Ascomycota in CK, CF and OM, and Basidiomycota in CFS treatment. Principal coordinate analysis revealed similar bacterial communities in CF and CFS, and similar fungal communities in CF and CK. Redundancy analysis demonstrated that microbial biomass carbon (MBC) and easily oxidized organic carbon (EOC) had relatively large influences on bacterial communities, while light fraction of organic carbon (LFOC) and dissolved organic carbon (DOC) were the primary factors affecting soil fungal communities. Correlations between soil bacterial/fungal communities and the active SOC fractions evidenced that fertilization, especially organic manure application, stimulated soil bacteria and fungi to participate in SOC turnover. The understanding of bacterial/fungal community structure linked to active SOC fractions under different fertilization managements will contribute to improving the productivity and quality of black soil under the sustainable management.
In this article, a modular linear permanent-magnet (PM) vernier machine is presented and optimized for high-precision and safety-critical direct-drive applications. The novelty of this article is to not only propose a multi-objective optimization method, but also present a modular linear PM vernier machine. The presented machine has the merit of desired fault-tolerant capability and improved force performances by mainly adopting the modular mover structure. And, the design principle of modular mover structure is introduced in detail in this article. To realize low detent force, high thrust force, low force ripple, and good fault tolerance, modular mover structure, PM array with flux-intensifying effect and six-phase structure are adopted in machine design. Furthermore, a new multi-objective optimization method is proposed to obtain a set of tradeoff solutions among multiple optimization objectives in machine optimization. First, to decompose the high dimension design space, the design variables are stratified into nonsensitive and sensitive levels by utilizing a comprehensive sensitivity analysis. Second, combined approximation models are implemented to decrease the large amount of computations. Then, to enhance the efficiencies of two multi-objective optimization processes, multi-objective differential evolution algorithm with ranking-based mutation operator is employed. After the optimization by the proposed multi-objective optimization method, the desired comprehensive performances with high optimization efficiency and accuracy can be obtained. Finally, to verify the results of theoretical analysis, a prototype machine is fabricated.
Menthol (MT) can effectively promote ordered molecular arrangement of acceptors in non-halogenated solvent, contributing to the large-area organic photovoltaic modules (19.31 cm 2 ) with a notable power conversion efficiency (PCE) of 15.74%.
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