Boron-doped TiO 2 nanotube arrays were produced by forming a nanotube-like TiO 2 film in an anodization process on a Ti sheet, followed by chemical vapor deposition treatment using trimethyl borate as the boron source with N 2 as the carrier gas, and were characterized by ESEM, XPS, XRD, and UV-vis methods. The highly ordered vertically oriented nanotube arrays were obtained, and the nanotubes were open at the top end with an average diameter of approximately 80 nm. Analysis by XPS indicated that the introduced boron was probably incorporated into TiO 2 and that the chemical environmental surrounding boron might be Ti-B-O. The boron-doped sample with a mixture of anatase and rutile was identified by X-ray diffraction. A shift of the absorption edge to a lower energy in the spectrum of the UV-vis absorption was observed. Under both UV and 400-620 nm visible light irradiation, the B-doped TiO 2 nanotube array electrode exhibited a higher photoconversion efficiency than the non-doped one, a notable photoconversion efficiency of 31.5% was achieved under high-pressure mercury lamp irradiation, and a photoconversion efficiency of 15.1% on the B-doped electrode was obtained under λ > 290 nm light irradiation. The photoelectrocatalytic activity of the prepared electrode was evaluated using pentachlorophenol as a test substance under UV and visible light irradiation.
Satellites will play an indispensable part in 5G roll out and the common use of new radio (NR) air interface will enable this. Satellite-terrestrial integration requires adaptations to the existing NR standards and demands further study on the potential areas of impact. From a physical layer perspective, the candidate waveform has a critical role in addressing design constraints to support non-terrestrial networks (NTN). In this paper, the adaptability of frequency-localized orthogonal frequency division multiplexing (OFDM)-based candidate waveforms and solutions are discussed in the context of physical layer attributes of non-linear satellite channel conditions. The performance of the new air interface waveforms are analysed in terms of spectral confinement, peak-to-average power ratio (PAPR), power amplifier efficiency, robustness against non-linear distortions and carrier frequency offset (CFO).
The rotary control orifice, in which the relative angular openings are adjusted by the rotary motion of the spool, thus controlling the flow area and the flow passing through, is a basic control element of hydraulic control valve. It has several advantages, such as little minimal steady flow rate, good anti-contamination, small driving power, small opening and shutting shock, and etc., over the translational control orifice. The working medium is tap water. A model is developed and numerical studies are carried out to investigate the hydrodynamic characteristics of the rotary control orifice, including flow and pressure field, flow characteristics, flow torque. The relationships between the flow and the pressure drops, the efflux angle and the angular openings, the steady-state flow torque and the pressure drops as well as the angular openings are obtained. The results show that a) the orifice geometries have great effects on the efflux angle and the steady-state flow torque; b) Under the same openings and flow direction, the efflux angle is almost constant under different pressure drops. It is larger for meter-in flow than for meter-out flow and decreases with the increase of openings; c) The steady-state flow torque (including meter-in flowTsfinand meter-out flowTsfout) is proportional to the pressure drops and first increases and then decreases with the increase of openings, finally reaches zero at the fully opened position; d) The friction moment is proportional to the rotary speed so as the transient flow induced moment to the rotary acceleration. The in-depth study of the drag moment of rotary control orifice helps to design high performance rotary servo valve for robots. The in-depth study of the rotary control orifice provides a basis for developing high performance rotary control valve.
Composition segregation and microstructure nonuniform of H13 steel have been obviously improved though adding nitrogen element. The microstructure and property of H13 steel with nitrogen contents of 0, 0.021%, 0.058% and 0.085% are studied under various quenching and tempering states. Dual quenching that is quenching between 1000~1010°C twice is employed in order to increase the tensile strength and hardness of coupons. The temperature and time are explored for improving the toughness under optimal quenching treatment. For extruding die steel, the tensile strength can reach a satisfactory level and impact toughness are met the requirements of NADCA at the temperature.
As revealed by previous experiments, protein mechanical stability can be effectively regulated by ligand binding with the binding site distant from the force-bearing region. However, the mechanism for such long-range allosteric control of protein mechanics is still largely unknown. In this work, we use protein topology-based elastic network model (ENM) and all-atomic steered molecular dynamics (SMD) simulations to study the impact of ligand binding on protein mechanical stability in two systems, i.e., GB1 and CheY-binding P2-domain of CheA (CBDCheA). Both ENM and SMD results show that the ligand binding has considerable and negligible effects on the mechanical stability of these two proteins, respectively. These results are consistent with the experimental observations. A physical mechanism for the enhancement of protein mechanical stability was then proposed: the correlated deformations of the force-bearing region and the binding site are handcuffed by the binding of ligand. The handcuff effect suppresses the propagation of internal force in the force-bearing region, thus improving the resistance to the loading force. Our study indicates that ENM method can effectively identify the structure motifs allosterically related to the deformation in the force bearing region, as well as the force propagation pathway within the structure of the studied proteins. Hence, it should be helpful to understand the molecular origin of the different mechanical properties in response to ligand binding for GB1 and CBDCheA.
Thixoforming or Semi-Solid Metal Forming offers many advantages in comparison with casting and conventional forging. The purpose of the present study is to provide the basic microstructure and deformation data for austenitic and ferritic stainless steel under mushy state. As well known, the stainless steels solidify in different modes according to the different chemical compositions. In this paper, microstructural evolution of austenitic stainless steel type 304 which solidifies in FA mode ( L → L +δ → L +δ +γ →δ +γ →γ ),austenitic stainless steel type 310S which solidifies in A mode ( L → L +γ →γ ), and ferritic stainless steel type 430 which solidifies in F mode ( L → L +δ →δ )are investigated during partial remelting by way of SIMA (Strain Induced Melted Activation). The results show that A and F mode of stainless steels melt directly at the grain boundary without phase transformation during reheating. A banded structure, originating from the primary dendritic segregation of the original ingots, is observed in type 310S steel during further heating. On the other hand, a perfect globular and insegregative two-phase semi-solid structure L +δ can be obtained while heated beyond the banded three-phase L +δ +γ semi-solid state in FA mode austenitic stainless steel type 304. This spheroidization can be attributed to the peritectic reaction occurred in the L +δ +γ semi-solid state. In addition, simple compression tests of these alloys in semi-solid state for varied combination of deformation rate and deformation temperature are conducted to examine the deformation behavior of stainless steel. Flow stress curves exhibit abrupt change in various alloys, even though in the same alloy such as type 304, various flow stresses are observed according to the difference in inner microstructure or morphology. Stress of type 310S steel shows the most reduction as the deformation temperature increasing at the same strain rate condition. The Liquid is centralized to periphery by the compression force in all deformed test pieces. Fracture, observed in all alloys except type 304 steel in globular L +δ semi-solid state, should be resulted from the lack of liquid in L +δ +γ state of type 304 steel and solidification crack in type 310S and type 430 steel. Deformation of solid particles occurs only in L +δ +γ state of type 304 steel. Last in this paper, various deformation mechanisms are proposed for various microstructures.
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