The effect of different inlet conditions of air in a rectangular channel on convection heat transfer: Turbulence flow

Theoretical and empirical correlations for duct flow are given for hydrodynamically and thermally developed flow in most of previous studies. However, this is commonly not a realistic inlet configuration for heat exchanger, in which coolant flow generally turns through a serpentine shaped passage before entering heat sinks. Accordingly, an experimental investigation was carried out to determine average heat transfer coefficients in uniformly heated rectangular channel with 45° and 90° turned flow, and with wall mounted a baffle. The channel was heated through bottom side with the baffle. In present work, a detailed study was conducted for three different height of entry channel (named as the ratio of the height of entry channel to the height of test section (${\overline{H}}_{\text{c}}=h_{\text{c}}/H$)) by varying Reynolds number (${\mathit{Re}}_{\text{Dh}}$). Another variable parameter was the ratio of the baffle height to the channel height (${\overline{H}}_{\text{b}}=h_{\text{b}}/H$). Only one baffle was attached on the bottom (heating) surface. The experimental procedure was validated by comparing the data for the straight channel with no baffle. Reynolds number $({\mathit{Re}}_{\text{Dh}})$ was varied from 2800 to 30,000, so the flow was considered as only turbulent regime. All experiments were conduced with air accordingly; Prandtl number (Pr) was approximately fixed at 0.71. The results showed that average Nusselt number for θ = 45° and θ = 90° were 9% and 30% higher, respectively, than that of the straight channel without baffle. Likewise, the pressure drop increased up to 4.4 to 5.3 times compare to the straight channel.     

Polysaccharide-based hemostats: recent developments,challenges, and future perspectives

Cellulose - Excessive hemorrhage is a leading cause of death to trauma patients, especially in combat and civilian accidents. The main priority in the medical treatment of trauma patients is to...     

Reactions of aldehyde with collagen: a DFT study

Structural Chemistry - The reaction mechanisms of several amino acids (Asn, Gln, Arg, His, and Lys) in the collagen with aldehyde were studied using density functional theory method. Based on the...     

Asymptotic analysis of microscopic impenetrability constraints for atomistic systems

We analyze systems of atomistic interactions on a triangular lattice allowing for fracture under a geometric condition on the triangles corresponding to a microscopic impenetrability constraint. Such systems can be thought as a computational simulation of materials undergoing brittle fracture. We show that in the small-deformation regime such approximation can be validated analytically in the framework of variational models of fracture. Conversely, in a finite-deformation regime various pathologies show that the continuum approximation of such a system differs from the usual variational representations of fracture and either needs new types of formulations on the continuum, or a proper interpretation of the atomistic constraints limiting their range and adapting them to a dynamical framework.     

Preparation of Bi<Subscript>2</Subscript>WO<Subscript>6</Subscript> by Electrospinning: Researching Their Synthesis Mechanism and Photocatalytic Activity

The novel Bi₂WO₆ nanomaterials, which consist of nanosheets and nanoparticles, were successfully synthesized by a combination of electrospinning and calcining processes. The Bi₂WO₆ with different morphologies and microstructures had been obtained in the same experimental conditions. The growth mechanism of such special nanostructures was investigated, and citric acid played an important role in the formation of Bi₂WO₆ nanostructures. The Bi₂WO₆ nanomaterials exhibited excellent photocatalytic property in the photodegradation of the pulping and papermaking wastewater under visible light irradiation. Besides, preparation of the photocatalyst using electrospinning was beneficial for separation and recycling. So, the Bi₂WO₆ nanomaterials have a great potential in application for wastewater treatment in the future.     

A DFT Study on the Stable Structures and Dissociation Mechanism of C3O6 Cluster

Using geometrical optimization and DFT method at the B3LYP/6-31G (d) level, nineteen equilibrium geometries were identified, and three transition states of dissociation reaction of C3O6 clusters were also found. The vibrational frequencies and intrinsic reaction coordinate (IRC) verification at the same level were computed to verify the transitions. And then we calculated the dissociation energies and analyzed the dissociation channels. The computational results show that the dissociation energies of C3O6 isomers relative to three CO2 are between 1.509 × 103 and 10.61 × 103 kJ·kg-1, and the energy barriers of the reactions are 92.857, 131.138 and 185.793 kJ·mol-1. Both the high dissociation energies and high energy barriers show that C3O6 clusters studied in this paper are stable enough to be used as high-energy-density materials.     

Photocatalytic property of surface-modified TiO<Subscript>2</Subscript> nanobelts under visible light irradiation

A novel plasmonic photocatalyst, i.e., acid-etched TiO₂ nanobelts attached with Ag/AgI nanoparticles (NPs) was prepared by deposition–precipitation-photoreduction method. Such surface-modified nanobelts had larger area than the normal one. Ag NPs were formed from AgI by photo-reduction under Xenon lamp irradiation. X-ray diffraction, scanning electron microscopy analysis, UV–Vis diffuse reflectance spectra and fluorescence spectra were used to characterize the structure and optical properties of the sample. The obtained sample exhibited strong photodegradation of methyl orange (MO) under visible light irradiation, which were attributed to both the surface plasmon resonance of Ag NPs and the visible light actived AgI. The photodegradation was accomplished by the transfer of photoexcited electrons from the Ag NPs to the acid-etched TiO₂ nanobelts. After four cycles of photodegradation the photocatalyst was still stable. This novel photocatalyst had a high potential application in wastewater-treatment and biomedical engineering.     

静电纺丝结合溶胶-凝胶法制备MgNb2O6陶瓷纤维

以五氧化二铌(Nb2O5)和氧化镁(MgO)为原料,柠檬酸作配位剂,采用静电纺丝结合溶胶-凝胶法制备了铌酸镁(MgNb2O6)陶瓷纤维。在本合成体系中,高质量Nb5+溶液的获得是形成MgNb2O6前驱体溶胶的关键步骤。通过TGA,FTIR,XRD,TEM以及SEM技术对纤维的形貌,微观结构以及组成进行了表征。结果表明,900℃烧结以后得到的MgNb2O6纤维长度约为10 cm,具有中空结构,壁厚约为800 nm。     

Spatially Responsive Multicolor Lanthanide-MOF Heterostructures for Covert Photonic Barcodes

Micro/nanoscale photonic barcodes based on multicolor luminescent segmented heterojunctions hold potential for applications in information security. However, such multicolor heterojunctions reported thus far are exclusively based on static luminescent signals, thus restricting their application in advanced confidential information protection. Reported here is a strategy to design responsive photonic barcodes with heterobimetallic (Tb³⁺/Eu³⁺) metal—organic framework multicolor heterostructures. The spatial colors could be precisely controlled by thermally manipulating the energy-transfer process between the two lanthanides, thus achieving responsive covert photonic barcodes. Also demonstrated is that spatially resolved responsive barcodes with multi-responsive features could be created in a single heterostructure. These findings offer unique opportunities to purposely design highly integrated responsive microstructures and smart devices toward advanced anti-counterfeiting applications.