•A cavitation structure of double-hump PTLVC is firstly observed in mixed flow pump.•Double-hump PTLVC is classified: incepting, growing, merging, propagating stage.•Propagating velocity of the front ...hump of PTLVC reaches the maximum of 0.38 Utip.•Empirical function proposed for projected area, axial thickness, collapse position.
Tip leakage cavitation remains an unsolved problem that threatens the safe operation of hydraulic machines and plagues researchers worldwide. The objective of this work is to investigate the classification and spatial-temporal evolution of tip leakage cavitation, and even to provide additional insights into the flow physics. Experiments are conducted in a mixed flow pump installed on a closed-loop test rig. High-speed visualizations are performed to capture the flow patterns of tip leakage cavitation at rated flow rate. It is demonstrated that tip leakage vortex cavitation can be categorized as primary tip leakage vortex cavitation (PTLVC) and secondary tip leakage vortex cavitation (STLVC). A new tip leakage cavitation structure, named as the double-hump PTLVC, is firstly observed in the mixed flow pump under severe cavitation conditions. The spatial-temporal evolution of the double-hump PTLVC is classified into four stages: incepting stage, growing stage, merging stage and propagating stage. The averaged propagating velocity of the front hump of PTLVC increases with decreasing net positive suction head (NPSH), and reaches the maximum of 0.38 Utip in the present experiment. Three empirical functions are proposed to describe the relationship between projected area, the maximum axial thickness, circumferential collapse position and NPSH, respectively. It is found that for every 0.1 m drop in NPSH, the projected area increases by about 2.1%, the maximum axial thickness increases by about 2.7%, and the circumferential length of the PTLVC increases by about 3.5%, respectively.
Scanning tunneling microscopy and atomic force microscopy can provide detailed information about the geometric and electronic structure of molecules with submolecular spatial resolution. However, an ...essential capability to realize the full potential of these techniques for chemical applications is missing from the scanning probe toolbox: chemical recognition of organic molecules. Here, we show that maps of the minima of frequency shift-distance curves extracted from 3D data cubes contain characteristic contrast. A detailed theoretical analysis based on density functional theory and molecular mechanics shows that these features are characteristic for the investigated species. Structurally similar but chemically distinct molecules yield significantly different features. We find that the van der Waals and Pauli interaction, together with the specific adsorption geometry of a given molecule on the surface, accounts for the observed contrast.
This article presents a contemporary overview of tip suturing and tip structural grafting techniques used to refine the wide nasal tip. Previous reductive techniques have proved to produce unnatural ...results over time. It is imperative to correctly evaluate the nose and assess all possible pitfalls during the preoperative period before outlining a surgical plan. Intraoperatively, an algorithmic approach helps obtain a reproducible and refined yet properly narrowed domal tip region with graceful contours that extend laterally to the alar lobule with proper shadowing.
Scanning tunneling microscopy‐based tip‐enhanced Raman spectroscopy (TERS) is a powerful analytical technique for surface characterization, providing both topological and chemical information with ...sub‐nm spatial resolution, well below the diffraction limit of light. In order to take advantage of plasmonic activity, it is necessary to use silver (Ag) probes due to their plasmonic range in the visible region. However, the Ag probe fabrication process remains challenging and is not yet standardized in practice, leading to inconsistent enhancements even for two similar types of tips prepared consecutively. In this work, we demonstrate an alternative way to reuse and recycle a plasmonic tip for distinct molecular systems inside an ultrahigh vacuum (UHV). We provide evidence of the ability to recycle tips without compromising the TERS experimental results. A long‐term preservation (>2 months) of plasmonically active probes inside UHV is demonstrated.
Ar+ ion sputtering is shown here as an effective way to eliminate the contaminations resulting from the tip etching process for tip‐enhanced Raman spectroscopy (TERS) experiments. Furthermore, this method is extremely useful to get rid of molecular contaminations while preserving plasmonic activity. The effectiveness of these probes has been demonstrated for different sets of TERS experiments with different excitation lasers, providing a routine technique to reuse, recycle, and preserve the enhancing plasmonic probes for a relatively much longer time (>2 months in this case).
Tip‐enhanced Raman spectroscopy can provide molecular fingerprint information with ultrahigh spatial resolution, but the tip will be easily contaminated, thus leading to artifacts. It also remains a ...great challenge to establish tip‐enhanced fluorescence because of the quenching resulting from the proximity of the metal tip. Herein, we report shell‐isolated tip‐enhanced Raman and fluorescence spectroscopies by employing ultrathin shell‐isolated tips fabricated by atomic layer deposition. Such shell‐isolated tips not only show outstanding electromagnetic field enhancement in TERS but also exclude interference by contaminants, thus greatly promoting applications in solution. Tip‐enhanced fluorescence has also been achieved using these shell‐isolated tips, with enhancement factors of up to 1.7×103, consistent with theoretical simulations. Furthermore, tip‐enhanced Raman and fluorescence signals are acquired simultaneously, and their relative intensities can be manipulated by changing the shell thickness. This work opens a new avenue for ultrahigh resolution surface analysis using plasmon‐enhanced spectroscopies.
Combined tip‐enhanced Raman and fluorescence spectroscopy using shell‐isolate tips is presented. With this method, clear and strong Raman and fluorescence signals can be obtained, and their relative intensities can be tuned by changing the shell thickness.
The phenomenon of dysplasia describes the mathematical model. The model that shows the behaviour of the growth of bilateral branching, lateral branching, filament tip anastomosis, limb anastomosis, ...and limb death due to overcrowd- ing with thread death. The study shows energy consumption; in general that the growth of fungi needs to be resolved until its goal becomes a correction. More- over the study reduced the cost, effort by predicting the best class of plants for cultivation according to the results. Herein we suggest mathematical solution using the solution of Partial Differential Equations (PDEs). Furthermore, Matlab software codes were utilized numerical analysis because of some of the difficulties we face in the direct mathematical solution. Finally, the study mod- els shows the success or failure of the growth of the studied fungi
The unsteady tip leakage flow (UTLF) is experimentally studied to observe the circumferential propagation in axial flow compressors. The evolutionary process of the circumferential propagation is ...captured by utilizing a collection of time-resolved pressure transducers on the casing with circumferential and chord-wise spatial resolution. Results show that the circumferential propagation dominated by the UTLF exists and occurs only after the emergence of the UTLF in the throttling process. Since then, the propagating speed and the scale of disturbance gradually augment, until the transition to the propagating speed and scale of stall inception. The tip air injection is applied to further verify the aforementioned circumferential propagation. Two kinds of injected momentum ratios, namely, micro and macro injection adopted in single-rotor compressor, and two types of injected methods, i.e., external air source and self-recirculation applied in single-stage and three-stage compressor demonstrate that either micro injection with a small stall margin improvement (SMI) or macro injection with a large SMI, or the different injected types in single- and three-stage compressor, with the increasing stability-enhancing capability of tip air injection, the UTLF is effectively weakened, and the circumferentially propagating speed and the scale of the disturbance dominated by UTLF accordingly shows a decreasing trend. The above results provide guidance for understanding the relationship between the UTLF and stall inception in terms of circumferential propagation that can be used to predict the compressor stability.
Degradation in the service or manufacturing tolerances can cause tip clearance variation, which adversely affects the stability and performance of compressors. In particular, for a miniature gas ...turbine, the size of the tip clearance ratio (the ratio of tip clearance to the tip chord length) is relatively large, thus it is more likely to operate at low Reynolds number. This study, therefore, numerically investigated the effect of tip clearance variation on the aerodynamic performance of a 1.5-stage transonic compressor at high and low Reynolds numbers using a 3D Reynolds averaged Navier-Stokes (RANS) solver that incorporates the SST k-ω turbulence model coupled with the γ-θ transition model. The results show that the aerodynamic performance and the tip flow field structure of the compressor change significantly with varying tip clearance.
At high Reynolds number, the performance curves are essentially negatively linear with tip clearance, but the slopes sharply increase at medium tip clearance (0.9% C, C represents the tip chord length). At low Reynolds number, the varying trends of the sensitive curves for large tip clearances (0.9% C–1.8% C) are basically the same as that at high Reynolds number. However, for small tip clearances (0.3% C–0.9% C), the aerodynamic performance parameters fluctuate, namely, there is a peak aerodynamic performance at low Reynolds number. When considering the performance and surge margin of the compressor comprehensively, the best tip clearance is 0.6% C at high Reynolds number, but 0.9% C at low Reynolds number.
Abstract
We use data from the ESA Gaia mission Early Data Release 3 (EDR3) to measure the trigonometric parallax of
ω
Cen, the first high-precision parallax measurement for the most massive globular ...cluster in the Milky Way. We use a combination of positional and high-quality proper motion data from EDR3 to identify over 100,000 cluster members, of which 67,000 are in the magnitude and color range where EDR3 parallaxes are best calibrated. We find the estimated parallax to be robust, demonstrating good control of systematics within the color–magnitude diagram of the cluster. We find a parallax for the cluster of 0.191 ± 0.001 (statistical) ±0.004 (systematic) mas (2.2% total uncertainty) corresponding to a distance of 5.24 ± 0.11 kpc. The parallax of
ω
Cen provides a unique opportunity to directly and geometrically calibrate the luminosity of the tip of the red giant branch (TRGB) because it is the only cluster with sufficient mass to provide enough red giant stars, more than 100 one magnitude below the tip, for a precise, model-free measurement of the tip. Combined with the preexisting and most widely used measurements of the tip and foreground Milky Way extinction, we find
M
I
,TRGB
=−3.97 ± 0.06 mag for the
I
-band luminosity of the blue edge. Using the TRGB luminosity calibrated from the Gaia EDR3 parallax of
ω
Cen to calibrate the luminosity of Type Ia supernovae results in a value for the Hubble constant of
H
0
= 72.1 ± 2.0 km s
−1
Mpc
−1
. We make the data for the stars in
ω
Cen available electronically and encourage independent analyses of the results presented here.
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