348 research outputs found
Measurement of small rotation angle of flange joints by a novel flexure magnifying mechanism
Bolted flange joints are indispensable components in process industries due to the good sealing, assemble and disassemble capacities. Generally, the flange rigidity characterized by the rotation angle is a key index to evaluate the sealing tightness of flange joints. However, the rotation angle of flange is usually too small (less than 1º) to monitor during the assemble and operation stages. Accordingly, a novel flexure magnifying mechanism is designed to measure the small rotation angle of flange joints under internal pressure and external bending moment. The magnification factor and calculation approach of the flexure amplification mechanism are deduced and verified by experimental data and finite element simulation. Results indicate that the proposed measuring apparatus has good performance to monitor the maximum rotation angle. It is of great interest that the measured location of the maximum rotation angle is in good agreement with that in the experiment, and the average error is 7.3%, which is acceptable for practical application. Additionally, the leakage rate at the top of flange joints slowly and almost linearly increases with the increment of external bending moment ascribing to the decrease the gasket stress near the top of flange joints
Numerical and Experimental Studies of a Two-Stage Pulse Tube Cryocooler Working Around 20K
The absence of cold moving parts in pulse tube cryocoolers has allowed it to has advantages of low vibration, high reliability, and low cost, which can meet requirements of many high-temperature superconducting applications. However, Stirling type pulse tube cryocoolers working around 20 K are still not commerally aviable due to low efficiency and low power density. With Comprehensive consideration of higher specific power of whole system and performance in relative lower working temperature of 20K, this paper proposes a thermally coupled two stage co-axial pulse tube cryocooler to pursue several watts cooling power around 20K.At the first stage, an ultrahigh frequency operation of 100 Hz is utilized to precoo the second stage for seeking a higher power density. At the second stage, a relative lower frequency of around 30Hz is used for improving system efficiency. Firstly, a quasi-one-dimensional numeric model based on the thermoacoustic theory is used to optimize the operating and structure parameters and some simulation results are briefly introduced. The influences of different phase shifters such as doule-inlet and room temperature displacers are also also investigated numerically. Then, in the experiments, typically a lowest no-load temperature of 13 K has been obtained and the cooling power at 20K was 2 W with an input electric power of 500 W, which mean an efficiency of 5.6% of Carnot. The influences of different operating and structure parameters such as frequency, mean pressure and precooling temperature were also investigated numerically and experimentally
Self-supervised Learning to Bring Dual Reversed Rolling Shutter Images Alive
Modern consumer cameras usually employ the rolling shutter (RS) mechanism,
where images are captured by scanning scenes row-by-row, yielding RS
distortions for dynamic scenes. To correct RS distortions, existing methods
adopt a fully supervised learning manner, where high framerate global shutter
(GS) images should be collected as ground-truth supervision. In this paper, we
propose a Self-supervised learning framework for Dual reversed RS distortions
Correction (SelfDRSC), where a DRSC network can be learned to generate a high
framerate GS video only based on dual RS images with reversed distortions. In
particular, a bidirectional distortion warping module is proposed for
reconstructing dual reversed RS images, and then a self-supervised loss can be
deployed to train DRSC network by enhancing the cycle consistency between input
and reconstructed dual reversed RS images. Besides start and end RS scanning
time, GS images at arbitrary intermediate scanning time can also be supervised
in SelfDRSC, thus enabling the learned DRSC network to generate a high
framerate GS video. Moreover, a simple yet effective self-distillation strategy
is introduced in self-supervised loss for mitigating boundary artifacts in
generated GS images. On synthetic dataset, SelfDRSC achieves better or
comparable quantitative metrics in comparison to state-of-the-art methods
trained in the full supervision manner. On real-world RS cases, our SelfDRSC
can produce high framerate GS videos with finer correction textures and better
temporary consistency. The source code and trained models are made publicly
available at https://github.com/shangwei5/SelfDRSC. We also provide an
implementation in HUAWEI Mindspore at
https://github.com/Hunter-Will/SelfDRSC-mindspore.Comment: Accepted by ICCV 2023, available at
https://github.com/shangwei5/SelfDRS
Semi-Cycled Generative Adversarial Networks for Real-World Face Super-Resolution
Real-world face super-resolution (SR) is a highly ill-posed image restoration
task. The fully-cycled Cycle-GAN architecture is widely employed to achieve
promising performance on face SR, but prone to produce artifacts upon
challenging cases in real-world scenarios, since joint participation in the
same degradation branch will impact final performance due to huge domain gap
between real-world and synthetic LR ones obtained by generators. To better
exploit the powerful generative capability of GAN for real-world face SR, in
this paper, we establish two independent degradation branches in the forward
and backward cycle-consistent reconstruction processes, respectively, while the
two processes share the same restoration branch. Our Semi-Cycled Generative
Adversarial Networks (SCGAN) is able to alleviate the adverse effects of the
domain gap between the real-world LR face images and the synthetic LR ones, and
to achieve accurate and robust face SR performance by the shared restoration
branch regularized by both the forward and backward cycle-consistent learning
processes. Experiments on two synthetic and two real-world datasets demonstrate
that, our SCGAN outperforms the state-of-the-art methods on recovering the face
structures/details and quantitative metrics for real-world face SR. The code
will be publicly released at https://github.com/HaoHou-98/SCGAN
Neurogenesis is enhanced by stroke in multiple new stem cell niches along the ventricular system at sites of high BBB permeability
AbstractPrevious studies have established the subventricular (SVZ) and subgranular (SGZ) zones as sites of neurogenesis in the adult forebrain (Doetsch et al., 1999a; Doetsch, 2003a). Work from our laboratory further indicated that midline structures known as circumventricular organs (CVOs) also serve as adult neural stem cell (NSC) niches (Bennett et al., 2009, 2010). In the quiescent rat brain, NSC proliferation remains low in all of these sites. Therefore, we recently examined whether ischemic stroke injury (MCAO) or sustained intraventricular infusion of the mitogen bFGF could trigger an up-regulation in NSC proliferation, inducing neurogenesis and gliogenesis. Our data show that both stroke and bFGF induce a dramatic and long-lasting (14day) rise in the proliferation (BrdU+) of nestin+Sox2+GFAP+ NSCs capable of differentiating into Olig2+ glial progenitors, GFAP+nestin-astrocyte progenitors and Dcx+ neurons in the SVZ and CVOs. Moreover, because of the upsurge in NSC number, it was possible to detect for the first time several novel stem cell niches along the third (3V) and fourth (4V) ventricles. Importantly, a common feature of all brain niches was a rich vasculature with a blood–brain-barrier (BBB) that was highly permeable to systemically injected sodium fluorescein. These data indicate that stem cell niches are more extensive than once believed and exist at multiple sites along the entire ventricular system, consistent with the potential for widespread neurogenesis and gliogenesis in the adult brain, particularly after injury. We further suggest that because of their leaky BBB, stem cell niches are well-positioned to respond to systemic injury-related cues which may be important for stem-cell mediated brain repair
Nuclear Magnetic Resonance Measurements in High Flat-top Pulsed Magnetic Field up to 40 T at WHMFC
Nuclear magnetic resonance (NMR) technique benefits from high magnetic field
not only due to the field-enhanced measurement sensitivity and resolution, but
also because it is a powerful tool to investigate field-induced physics in
modern material science. In this study, we successfully performed NMR
measurements in high flat-top pulsed magnetic field (FTPMF) up to 40 T. A
two-stage corrected FTPMF with fluctuation less than 10 mT and duration longer
than 9 ms was established. Besides, a Giga-Hz NMR spectrometer and a sample
probe suitable for pulsed-field condition were developed. Both
free-induction-decay and spin-echo sequences were exploited for the
measurements. The derived Nb NMR results show that the stability and
homogeneity of the FTPMF reach an order of 10 ppm / 10 ms and 10 ppm /
10 mm respectively, which is approaching a degree of maturity for some
researches on condensed matter physics.Comment: 8 pages, 9 figure
β-diversity in temperate grasslands is driven by stronger environmental filtering of plant species with large genomes
Elucidating mechanisms underlying community assembly and biodiversity patterns is central to ecology and evolution. Genome size (GS) has long been hypothesized to potentially affect species' capacity to tolerate environmental stress and might therefore help drive community assembly. However, its role in driving β-diversity (i.e., spatial variability in species composition) remains unclear. We measured GS for 161 plant species and community composition across 52 sites spanning a 3200-km transect in the temperate grasslands of China. By correlating the turnover of species composition with environmental dissimilarity, we found that resource filtering (i.e., environmental dissimilarity that includes precipitation, and soil nitrogen and phosphorus concentrations) affected β-diversity patterns of large-GS species more than small-GS species. By contrast, geographical distance explained more variation of β-diversity for small-GS than for large-GS species. In a 10-year experiment manipulating levels of water, nitrogen, and phosphorus, adding resources increased plant biomass in species with large GS, suggesting that large-GS species are more sensitive to the changes in resource availability. These findings highlight the role of GS in driving community assembly and predicting species responses to global change
Development of a High Efficiency Pulse Tube Cryocooler Using Room Temperature Displacers for HTS Applications
The compact and high efficiency coolers working in the liquid nitrogen temperature region play an important role in HTS Applications. Stirling type pulse tube cooler servers as a promising candidate for cooling HTS devices for its advantages such as low vibration, high reliability and low cost due to absence of the moving parts in the cold head compared with traditional coolers. However, phase shift mechanisms used in a conventional pulse tube cryocooler need to dissipate expansion power at the ambient end of the pulse tube, which leads to a lower thermodynamic efficiency than that of a Stirling cryocooler. In order to improve the efficiency and obtain a reliable cryocooler system, this article presents a pulse tube cryocooler which uses room temperature displacers as the phase shifter, which aims at providing more than 10 W cooling power at 77 K. The cryocooler with a model number of TC4189 consists of linear compressor, coaxial pulse tube and two dual-opposed ambient displacers. High pressure ratio and high frequency operation are used to increase the power density. The whole system has a total mass of 4.3 kg. At an optimum working point, a lowest no-load temperature of 44 K has been obtained and the cooling power at 80K reaches 15 W with an input electric power of 240 W, which means an efficiency of 17.1% of Carnot. The influence of displacers operating and structural parameters were investigated through simulations and experiments
Deformed Two-Mode Quadrature Operators in Noncommutative Space
Starting from noncommutative quantum mechanics algebra, we investigate the
variances of the deformed two-mode quadrature operators under the evolution of
three types of two-mode squeezed states in noncommutative space. A novel
conclusion can be found and it may associate the checking of the variances in
noncommutative space with homodyne detecting technology. Moreover, we analyze
the influence of the scaling parameter on the degree of squeezing for the
deformed level and the corresponding consequences.Comment: 11 pages, no figure
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