bluuebunny/crossref_metadata_2025 huggingface dataset:
VEGF-C prophylaxis favors lymphatic drainage and modulates neuroinflammation in a stroke model
Authors: Boisserand Ligia Simoes Braga , Geraldo Luiz Henrique , Bouchart Jean , El Kamouh Marie-Renee , Lee Seyoung , Sanganahalli Basavaraju G. , Spajer Myriam , Zhang Shenqi , Lee Sungwoon , Parent Maxime , Xue Yuechuan , Skarica Mario , Yin Xiangyun , Guegan Justine , Boyé Kevin , Saceanu Leser Felipe , Jacob Laurent , Poulet Mathilde , Li Mingfeng , Liu Xiaodan , Velazquez Sofia E. , Singhabahu Ruchith , Robinson Mark E. , Askenase Michael H. , Osherov Artem , Sestan Nenad , Zhou Jiangbing , Alitalo Kari , Song Eric , Eichmann Anne , Sansing Lauren H. , Benveniste Helene , Hyder Fahmeed , Thomas Jean-Leon
Published: March 2024

Meningeal lymphatic vessels (MLVs) promote tissue clearance and immune surveillance in the central nervous system (CNS). Vascular endothelial growth factor-C (VEGF-C) regulates MLV development and maintenance and has therapeutic potential for treating neurological disorders. Herein, we investigated the effects of VEGF-C overexpression on brain fluid drainage and ischemic stroke outcomes in mice. Intracerebrospinal administration of an adeno-associated virus expressing mouse full-length VEGF-C (AAV-mVEGF-C) increased CSF drainage to the deep cervical lymph nodes (dCLNs) by enhancing lymphatic growth and upregulated neuroprotective signaling pathways identified by single nuclei RNA sequencing of brain cells. In a mouse model of ischemic stroke, AAV-mVEGF-C pretreatment reduced stroke injury and ameliorated motor performances in the subacute stage, associated with mitigated microglia-mediated inflammation and increased BDNF signaling in brain cells. Neuroprotective effects of VEGF-C were lost upon cauterization of the dCLN afferent lymphatics and not mimicked by acute post-stroke VEGF-C injection. We conclude that VEGF-C prophylaxis promotes multiple vascular, immune, and neural responses that culminate in a protection against neurological damage in acute ischemic stroke.
Meningeal lymphatics can influence stroke outcome
Authors: Koh Gou Young , McDonald Donald M.
Published: March 2024

Meningeal lymphatics are conduits for cerebrospinal fluid drainage to lymphatics and lymph nodes in the neck. In this issue of JEM, Boisserand et al. (https://doi.org/10.1084/jem.20221983) provide evidence that expansion of meningeal lymphatics protects against ischemic stroke.
Bulk viscous late acceleration under near equilibrium conditions in f(R, T) gravity with mixed dark matter
Authors: Pai Vishnu A , Mathew Titus K
Published: March 2024

Numerous studies have tried to explain the observed late acceleration of the Universe as being caused by the bulk viscosity associated with the dark matter (DM) component. However, for driving the said accelerated expansion, all such models require a violation of near equilibrium conditions (NECs) associated with the background viscous theory. But recently, it was found that, with the aid of a cosmological constant, it is possible to maintain NEC for the bulk viscous warm DM during certain evolutionary epochs of the Universe. Nevertheless, this negated the possibility of having a ‘solely’ viscous-driven late acceleration in Einstein gravity within the NEC limit. In the present study, we investigate a model of the Universe composed of mixed DM components, with viscous DM, and inviscid cold DM as its constituents, in the context of

R
+
2
λ

T

v
m

gravity, and show that the model predicts late acceleration by satisfying NEC, critical energy condition and second law of thermodynamics (SLT) throughout the evolution, even in the absence of a cosmological constant. One intriguing feature observed in this model is the possibility of having a negative bulk viscous coefficient and yet satisfying the SLT. Finally, by applying both theoretical and observational constraints on the model parameters, we determined the best-fit values of model parameters and thereby analyzed the evolutionary behavior of some relevant cosmological observables.
Stable determination of an impedance obstacle by a single far-field measurement
Authors: Diao Huaian , Liu Hongyu , Tao Longyue
Published: March 2024

We establish sharp stability estimates of logarithmic type in determining an impedance obstacle in

R

2

. The obstacle is the polygonal shape and the surface impedance parameter is non-zero constant. We establish the stability results using a single far-field pattern, constituting a longstanding problem in the inverse scattering theory. This is the first stability result in the literature in determining an impedance obstacle by a single far-field measurement. The stability in simultaneously determining the obstacle and the boundary impedance is established in terms of the classical Hausdorff distance. Several technical novelties and developments in the mathematical strategy developed for establishing the aforementioned stability results exist. First, the stability analysis is conducted around a corner point in a micro-local manner. Second, our stability estimates establish explicit relationships between the obstacle’s geometric configurations and the wave field’s vanishing order at the corner point. Third, we develop novel error propagation techniques to tackle singularities of the wave field at a corner with the impedance boundary condition.
Theoretical valley-polarized subgap transport and intravalley pairing states in a silicene-based antiferromagnet–superconductor junction
Authors: Ding Zixuan , Wang Donghao , Huang Chuanshuai , Li Mengyao , Tao Yongchun , Huang Fengliang
Published: March 2024

We theoretically study the valley-polarized subgap transport and intravalley pairing states in silicene-based antiferromagnet/superconductor (AF/SC) junctions. It is found that in the absence of an electric field, the antiferromagnetic order induced in silicene can give rise to valley-polarized states that strongly affect the subgap conductance. With the increasing antiferromagnetic exchange field, the gap-edge Andreev-resonant peak is replaced by broadened features for the homo-SC model whereas by a sharp conductance dip for the bulk-SC one. This significant difference arises from the intravalley Andreev reflection caused by the valley-mixing scattering in the bulk-SC model, which can be enhanced by the antiferromagnetic order. Particularly, this intravalley pairing process can be switched on or off by adjusting the spin polarization through the electric field applied in the AF region. Our findings not only pave a new road to employ antiferromagnetic materials in valleytronics, but also facilitate the verification and detection of potential intravalley pairing state and valley polarization in silicene.
Complex energy-based description of alpha-cluster lifetime in intense laser fields
Authors: Szilvási Réka , Kis Dániel P
Published: March 2024

The phenomenon of laser-assisted alpha decay is studied within the framework of non-Hermitian quantum theory integrated with the (t, t′)-formalism. The width and the lifetime of the alpha cluster of a specific isotope is extracted from the spectrum of the complex-scaled Hamiltonian operator of the nuclear system and estimated numerically. The laser-field-induced correction to the lifetime is computed by first-order (t, t′)-perturbation calculation with regard to different polarization states and control parameters of the external laser field, adjusting appropriate intensity and photon energy pairs by examining the limit of the non-relativistic approximation of the problem.
Silica-based scintillators: basic properties of radioluminescence kinetics
Authors: Grandvillain Marjorie , Vidal Marie , Hérault Joël , Benabdesselam Mourad , Hofverberg Petter , Mady Franck
Published: March 2024

Radioluminescent silica-based fiber dosimeters offer great advantages for designing miniaturized realtime sensors for high dose-rate dosimetry. Rise and fall kinetics of their response must be properly understood to better assess their performances in terms of measurement speed and repeatability. A standard model of radioluminescence (RL) has already been quantitatively validated for doped silica glasses, but beyond conclusive comparisons with specific experiments, a comprehensive understanding of the processes and parameters determining transient and equilibrium kinetics of RL is still lacking. We analyze in detail the kinetics inherent in the standard RL model. Several asymptotical regimes in the RL growth are demonstrated in the case of a pristine sample (succesive quadratic, linear and power-law time dependencies before the plateau is reached). We show how this situation is modified when a pre-irradiation partly fills traps beforehand. RL growth is then greatly accelerated because of the pre-formation of recombination centers (RCs) from dopant ions, but not due to pre-filling of trapping levels. In all cases, the RL intensity eventually tends to a constant level equal to the pair generation rate, long before all carrier densities themselves reach equilibrium. This occurs late under irradiation, when deep traps get to saturation. The fraction of dopants converted into RCs is then ‘frozen’ at a lower level the smaller the density of deep traps. Controlling RL kinetics through the engineering of material traps is not an option. Pre-irradiation appears to be the simplest way to obtain accelerated and repeatable kinetics.
Improved metric-based meta learning with attention mechanism for few-shot cross-domain train bearing fault diagnosis
Authors: Zhong Hao , He Deqiang , Lao Zhenpeng , Jin Zhenzhen , Shen Guoqiang , Chen Yanjun
Published: March 2024

Traction motor bearings, as a crucial component of subway trains, play a pivotal role in ensuring the safety of train operations. Therefore, intelligent diagnosis of train bearings holds significant importance. However, due to the complex and dynamic nature of bearing conditions coupled with limited fault data availability, traditional diagnostic methods fail to yield satisfactory results. To address this issue, we propose an improved metrics-based meta-learning approach for accurate few-shot cross-domain fault diagnosis of train bearings. Firstly, we introduce a 1D-signal channel attention mechanism that effectively extracts latent features and enhances recognition accuracy. Secondly, by incorporating the Adabound algorithm into our model framework, we further enhance its classification performance. Finally, through several case studies, we demonstrate the effectiveness of our proposed method in comparison to other approaches within similar settings.
Fabrication of thin inorganic temperature-sensitive paint using ball milling and its temporal response delay
Authors: Jung Juyong , Saito Shimpei , Someya Satoshi , Baba Soumei , Takada Naoki
Published: March 2024

Temperature-sensitive paint (TSP) is widely used to measure the temperature distribution. A TSP is advantageous in terms of cost and spatiotemporal resolution. However, regardless of its thickness, a finite thickness introduces errors. An important issue regarding the thickness of the TSP is the temporal response delay. In this study, a thin TSP was fabricated using ball milling, and TSPs with a thickness <2 µm could be produced. However, the phosphorescence intensity decreased drastically after ball milling. A special system was designed to measure the temporal response delay caused by the TSP layer. A high-resolution measurement technique (210 kHz and 1.05 µm/pixel) was employed. Time delays were defined and calculated using both experimental and numerical approaches. Numerical simulations were conducted using the experimental data and the thermal properties of ZnO:Zn and epoxy, given that the thermal properties of TSP are unknown. From the time delay, it was found that the thermal diffusivity of the TSP was between those of ZnO:Zn and epoxy, and this result was considered reasonable. Although this study provides only a rough estimation of the thermal diffusivity of TSPs, it reveals a relationship between the time delay and thermal diffusivity, opening up the possibility of calculating the thermal diffusivity from the time delay. Our results can help advance the application of TSPs for temperature measurements in highly dynamic environments.
Type A standard uncertainty evaluation in one measurement through uncertainty propagation from voxel values’ distribution for computed tomography metrology
Authors: Ou Dongsheng , Xiao Yongshun , Lan Dini , Wang Yingxin
Published: March 2024

According to the guide to the expression of uncertainty in measurement, ‘type A evaluation’ generally requires repeated measurements, which are time-consuming for CT scans. To solve this problem, we developed a method for estimating the standard deviation of measurement results in one measurement through uncertainty propagation, which can be regarded as repeatability standard deviation to evaluate the type A standard uncertainty. The method first fits the CT voxel value distribution, uses the ISO50 method to determine the spatial distribution of surface points from the voxel value distribution and edge shape interpolation, and then derives the measurement results by fitting geometric parameters with the least square algorithm. Finally, the standard deviation of the measurement results is evaluated according to the distribution of the surface point position through uncertainty propagation. We performed simulations and experiments using the hole-plate with 28 holes to compare the uncertainty evaluated by our method and the type A standard uncertainty evaluated on the basis of a series of observations obtained under repeatability conditions. Both simulation and experimental results show that these two uncertainties follow the same statistical variation pattern. The Pearson correlation coefficients of the two uncertainties in simulation and experiment are 0.79 and 0.33, respectively, indicating that the uncertainty evaluated by the proposed method can directly replace the type A uncertainty or provide a reference similar to type A uncertainty for the evaluation of the combined uncertainty.
Acoustic tunnel lining cavity detection using cepstral coefficients with optimized filter bank
Authors: Wu Ting , Cheng Xiaobin , Yan Zhaoli , Yang Jun , Chai Xuesong , Dai Xiaojing
Published: March 2024

Tunnels are an essential component of modern transportation infrastructure, and their structural health is critical to traffic safety, which can be seriously affected by tunnel lining cavities. In this paper, an acoustic-based detection approach for assessing the integrity of tunnel linings is studied. By tapping the tunnel lining surface, acoustic signals are sampled and analyzed using a novel feature parameter extraction algorithm-the energy-frequency cepstral coefficient, which uses wavelet packet decomposition to obtain energy distribution statistics in the frequency domain of the signal, and constructs a signal-dependent filter bank to achieve the cepstral coefficient extraction. Compared with the traditional Mel filter bank, this method can adaptively adjust the resolution of the filter bank according to the frequency characteristics of the classified samples. This allows for higher frequency resolution in regions where the energy distribution is concentrated. As a result, the extracted feature parameters achieve both dimensional compression and superior information retention. Experimental results show that the proposed energy-frequency cepstral coefficient feature outperforms the traditional Mel-frequency cepstral coefficient feature, resulting in a higher accuracy of tunnel lining detection. The convolutional neural network model achieves an accuracy of 99.2%, with a 78.9% reduction in error rate compared with the traditional Mel-frequency cepstral coefficient feature parameters. Additionally, a particle swarm optimization support vector machine model is trained to achieve an accuracy rate of 99.6% and an error rate reduction of 76.5%.
Coupling between the Alfvén eigenmode and edge-coherent mode on the experimental advanced superconducting tokamak
Authors: Wang M Y , Liu A D , Zhou C , Zhuang G , Feng X , Zhang J , Zhong X M , Zhang R B , Wang Y H , Yang J X , Li H , Lan T , Xie J L , Liu H Q , Liu Z X , Mao W Z , Ding W X , Liu W D
Published: March 2024

High-frequency electromagnetic fluctuations and edge-coherent modes (ECMs) have been detected by Doppler reflectometry (DR) in the pedestal region of the Experimental Advanced Superconducting Tokamak. The frequency of the electromagnetic fluctuations was proportional to the Alfvén velocity and localized in the ellipticity-induced Alfvén eigenmodes (EAEs) gap in the Alfvén continuum. Therefore, the fluctuations are presumed to be EAE. The DR measurements of poloidal flow fluctuations show that EAEs and ECMs have amplitude envelopes that are localized near the bottom of the radial electric field well. Simultaneous EAE and ECM activity generates sidebands at

f

E
A
E

±

f

E
C
M

, the strengths of the upper and lower sidebands are unequal, with the upper sideband being stronger. This is consistent with the theoretical prediction of Chen et al. Compared with ECM-only discharges, the inclusion of EAEs leads to an increase in

D
α

intensity, thus indicating enhanced outward particle transport.
Weyl points and anomalous transport effects tuned by the Fe doping in Mn3Ge Weyl semimetal
Authors: Rai V , Jana S , Perßon J , Nandi S
Published: March 2024

The discovery of a significantly large anomalous Hall effect in the chiral antiferromagnetic system—Mn3Ge—indicates that the Weyl points are widely separated in phase space and positioned near the Fermi surface. In order to examine the effects of Fe substitution in Mn3Ge on the presence and location of the Weyl points, we synthesized (Mn

1
−
α

Fe

α

)
3

Ge (

α
=
0
−
0.30

) compounds. The AHE was observed in compounds up to α = 0.22, but only within the temperature range where the magnetic structure remains the same as the Mn3Ge. Additionally, positive longitudinal magnetoconductance and planar Hall effect (PHE) were detected within the same temperature and doping range. These findings strongly suggest the existence of Weyl points in (Mn

1
−
α

Fe

α

)
3

Ge (

α
=
0
−
0.22

) compounds. Further, we observed that with an increase in Fe doping fraction, there is a significant reduction in the magnitude of anomalous Hall conductivity, PHE, and positive longitudinal magnetoconductance, indicating that the Weyl points move further away from the Fermi surface. Consequently, it can be concluded that suitable dopants in the parent Weyl semimetals have the potential to tune the properties of Weyl points and the resulting anomalous electrical transport effects.
First-principles study on the electronic structure of n-type magnetic semiconductor Ba(Zn 1−x
Co x
)2As2
Authors: Zhi Guo-Xiang , Xu Chenchao , Zhao Xueqin , Dong Jinou , Guo Shengli , Man Huiyuan , Ding Cui , Fu Licheng , Gu Yilun , Xie Lingfeng , Pan Xun , Cao Chao , Ning Fanlong
Published: March 2024

We perform systematic first-principles calculations on the electronic structure of n-type magnetic semiconductor Ba(Zn

1
−
x

Co
x
)2As2 with the facilitation of HSE06 hybrid functional. Supercells are used to consider the doping of Co atoms, and the first-principles band structures are unfolded for clarity. Based on the calculation results, magnetic states are preferred by individual Co atoms doped in Ba(Zn

1
−
x

Co
x
)2As2 at diluted limit, and carriers are originated mainly from situations where only one Co atom exists in the nearest neighbor Zn sites out of certain doped Co atoms. The origination of carriers can be explained by the density of states and the unfolded band structure, where it is found that the scattering effects from single Co atom is small but quite large when more Co atoms are located at adjacent Zn sites. The large scattering effects of two adjacent Co atoms will alter the band structures near the Fermi-level. Carriers in Ba(Zn

1
−
x

Co
x
)2As2 mainly originate from the As-4p orbitals, with partial contributions from the Co-3d orbitals. Our work provides new insights into the origin of the n-type carriers in magnetic semiconductors and will inspire the development of new magnetic semiconducting systems.
Study on current-carrying tribological characteristics of C-Cu sliding electric contacts under water accumulation from rainfall condition
Authors: Gao Guoqiang , Wang Qingsong , Wang Hong , Qian Pengyu , Peng Wei , Ma Yaguang , Dong Deliang , Wang Xiangfei , He Shuhang , Yang Zefeng , Wu Guangning
Published: March 2024

Pantograph-OCS system sliding electrical contact is the only way for train energy transmission, which determines the safety and stability of energy transfer. And the current-carrying wear is the core factor that affecting the service performance of C-Cu contact pairs. C-Cu mate pairs often work for a long time in rainy/humid environments due to its exposed nature of work, and the contact interface often accumulates a large amount of water. Existing operating experience has shown that the carbon sliding plate of the pantograph experiences abnormal wear and frequent failure during rainfall, resulting in a significant decrease in service performance and lifespan. This article found that the thickness of the water film at the contact interface has a significant impact on the current carrying friction and wear performance of C-Cu contact pairs. When the thickness of the water film exceeds a certain range, the carbon skateboard will cause abnormal wear under high current, with the wear amount being more than three times the minimum value. The contact resistance also increases by 53.9%, which is related to the obstruction of current transmission. It also proves that the water film lubrication effect can be restored during the process of rainfall decreasing from large to small. The research can help to provide a suitable maintenance policy for pantograph and catenary system during the rainy season.
Synthesis of cerium-doped gadolinium gallium aluminum garnet (GGAG:Ce) scintillating powder via solvothermal method
Authors: Oad Nisha , Pandya Divya , Rawat Sheetal , Chandra Prakash , Tyagi Mohit , Tripathi Brijesh , Gurrala Pavan
Published: March 2024

The powder material Gd3Ga3Al2O12:Ce (GGAG doped with Cerium) has garnered significant attention in radiation detection due to its high light yield and rapid decay time. Despite its potential, the synthesis of high-quality and reproducible GGAG:Ce scintillating powder remains a considerable challenge. In this study, we present a solvothermal approach with an annealing temperature of 1300 °C for producing cerium-doped GGAG powder with varying concentrations (4, 2, and 0.5 mol%). The structural and luminescent characteristics were meticulously examined using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence (PL), radioluminescence (RL) spectroscopy, and X-ray photoelectron spectroscopy (XPS). XRD analysis confirmed the single-cubic phase garnet structure of the synthesized powder. By comparing the intermediate solvothermal products synthesized at different sintering temperatures (900 °C for 3 h and 1300 °C for 1 and 3 h), a direct correlation between solvothermal conditions and the structure/property relationships of the product was established. FESEM images revealed an ellipsoidal to irregular morphology of the as-synthesized GGAG:Ce microparticles, ranging from 0.1 to 0.3 μm, regardless of the Ce concentration. PL spectra demonstrated a strong emission peak at approximately 550 nm, characteristic of Ce3+ ions. RL data confirmed the peak luminescence at around 550 nm, with an almost twofold increase in intensity as the concentration of Ce3+ increased from 0.5 mol% to 4 mol%. XPS data disclosed the Ce3+/Ce4+ ratio in solvothermally synthesized GGAG:Ce, wherein Ce loading of 4 mol% demonstrated the increase in Ce3+ concentration to 95%, whereas the concentration of Ce4+ decreased to 5%. Notably, the highest luminescence efficiency was achieved with GGAG:Ce at a 4 mol% concentration. Thus, the solvothermal method employed in GGAG:Ce synthesis presents a straightforward approach, yielding rapid results with precise control over particle morphology and size.
Investigation of optical and electrical properties of TiO2, SiO2, and Ag single and multilayer thin films using spectroscopic ellipsometry and spectrophotometry methods: prepared by spin coating and DC magnetron sputtering
Authors: Entezarmahdi Hamid , Sedghi Hassan
Published: March 2024

In this work, spectroscopic ellipsometry was used to study the optical and electrical properties of TiO2 and SiO2 thin films deposited by spin-coating at different coating rotation speeds and annealed at various temperatures. In addition, Ag thin films of different thicknesses were deposited by DC magnetron sputtering at ambient temperature. In this method, the optical band gap for TiO2 thin films is between 3.15–3.85 eV, and for SiO2 thin films, it is between 3.2–3.8 eV. The optical properties, including reflectance, transmittance, and absorbance, of TiO2, SiO2, and Ag thin films in the form of single and multilayer thin films in the wavelength range of 200–2500 nm, were investigated using an ultraviolet-visible-near infrared (UV–vis-NIR) dual-beam spectrophotometer. In the TiO2/Ag/SiO2 multilayer thin film, the rejection was 58.6% −73.6% in the NIR wavelength range (800–2500 nm), and a transmittance of 40%–45% was achieved in the visible light range (400–700 nm).
Tribological behavior of autocatalytic Ni-P based duplex coatings
Authors: Biswas Palash , Das Suman Kalyan , Sahoo Prasanta
Published: March 2024

The present research evaluates the tribological performance of different Ni-P based duplex autocatalytic coatings (electroless coatings). The study investigates coatings including Ni-P/Ni-W-P, Ni-P/Ni-Mo-P, and Ni-P/Ni-Cu-P, examining various factors such as heat treatment conditions, sample composition, and their influence on the coatings’ performance. The phase structure of the coatings is influenced by heat treatment parameters viz. temperature and duration as well as phosphorus content. Notably, at temperatures above 400 °C, all duplex coatings form a robust nickel phosphide phase, enhancing hardness and wear resistance which is almost double of that in as-deposited state in some cases. When subjected to a temperature of 400 °C for duration of 1 h, the Ni-P/Ni-W-P coating displays the highest microhardness (1440 HV0.1) and the lowest wear rate (10.62 × 10−5. mm3. N−1. m−1) among all the duplex coatings. In all three duplex systems, the wear typically involves a combination of abrasive and adhesive mechanisms. Among the as-deposited coatings, the Ni-P/Ni-Cu-P demonstrates higher corrosion potential (E
corr −302 mV) and lower corrosion current (i
corr 1.83 × 10−5 mA cm−2) which imply superior corrosion resistance compared to the other duplex coatings. In the heat-treated state, the Ni-P/Ni-Mo-P duplex coating generally exhibits better corrosion resistance when compared to the other two types of duplex coatings.
Discover an accurate approximation of dynamical system without prior information and customized design
Authors: Wang Bochen , Wang Liang , Peng Jiahui , Dong Shuangqi , Xu Wei
Published: March 2024

Modeling dynamical systems is fraught with challenges when data can be collected but thorough analysis of the mechanism is absent. We design a method to discover unknown dynamical systems from data. The method discovers an accurate approximation of the model without the prior information and the customized design for each problem. The identification steps are straightforward as bringing in the data and then obtaining the model. The method begins with the simple idea that the equations of motion of many practical problems are Riemann integrable functions. For this reason, the Fourier series can decompose the equations of motion. In order to improve the accuracy, we design an extension that helps us to approximate unknown functions by the Fourier series with a high rate of convergence. The idea converts the difficulty of modeling the dynamical system into finding its Fourier series approximation. Convenient procedures enable the modeling of different problems. Numerical examples show that the new method discovers linear and nonlinear dynamical systems in the same steps and without the prior information.
Effective field theory of black hole perturbations in vector-tensor gravity
Authors: Aoki Katsuki , Gorji Mohammad Ali , Mukohyama Shinji , Takahashi Kazufumi , Yingcharoenrat Vicharit
Published: March 2024

We formulate the effective field theory (EFT) of vector-tensor gravity for perturbations around an arbitrary background with a timelike vector profile, which can be applied to study black hole perturbations. The vector profile spontaneously breaks both the time diffeomorphism and the U(1) symmetry, leaving their combination and the spatial diffeomorphism as the residual symmetries in the unitary gauge. We derive two sets of consistency relations which guarantee the residual symmetries of the EFT. Also, we provide the dictionary between our EFT coefficients and those of generalized Proca (GP) theories, which enables us to identify a simple subclass of the EFT that includes the GP theories as a special case. For this subclass, we consider the stealth Schwarzschild(-de Sitter) background solution with a constant temporal component of the vector field and study the decoupling limit of the longitudinal mode of the vector field, explicitly showing that the strong coupling problem arises due to vanishing sound speeds. This is in sharp contrast to the case of gauged ghost condensate, in which perturbations are weakly coupled thanks to certain higher-derivative terms, i.e., the scordatura terms. This implies that, in order to consistently describe this type of stealth solutions within the EFT, the scordatura terms must necessarily be taken into account in addition to those already included in the simple subclass.
Polarized images of charged particles in vortical motions around a magnetized Kerr black hole
Authors: Zhang Zhenyu , Hou Yehui , Hu Zezhou , Guo Minyong , Chen Bin
Published: March 2024

In this work, we study the images of a Kerr black hole (BH) immersed in uniform magnetic
fields, illuminated by the synchrotron radiation of charged particles in the jet. We particularly
focus on the spontaneously vortical motions (SVMs) of charged particles in the jet region and
investigate the polarized images of electromagnetic radiations from the trajectories along
SVMs. We notice that there is a critical value ω_c for charged particle released at a given
initial position and subjected an outward force, and once |qB_0/m|=|ω_B|>|ω_c| charged
particles can move along SVMs in the jet region. We obtain the polarized images of the
electromagnetic radiations from the trajectories along SVMs. Our simplified model suggests that
the SVM radiations can act as the light source to illuminate the BH and form a photon
ring structure.
A study of U-isotope ground state properties with covariant energy density functional*
Authors: Wang 王 Junchen 俊辰 , Tian 田 Yuan 源 , Xu 续 Ruirui 瑞瑞 , Cui 崔 Ying 莹 , Tao 陶 Xi 曦 , Sun 孙 Xiaodong 小东 , Zhang 张 Zhi 智 , Zhang 张 Yue 玥 , Han 韩 Yinlu 银录 , Ge 葛 Zhigang 智刚 , Shu 舒 Nengchuan 能川
Published: March 2024

In this study, we systematically analyzed the ground state of uranium isotopes from 225 to 240. In our calculations, we used the covariant energy density functional of density-dependent meson exchange interaction (DD-ME2) with separable pairing interaction (TMR). Using the multiple deformation constraint, we calculated the potential energy surface (PES) of the uranium isotopes for both even-even and even-odd nuclei with quadrupole and octupole deformation. Based on our calculation and upon comparing the experimental data and Hartree-Fock-Bogoliubov calculations with Gogny D1S calculation data, the ground state of uranium isotopes with reflection-asymmetric deformation was found to be preferred.
Numerical study on the effect of radial inlet chamber on the performance of oblique flow compressor
Authors: Chen Jixiang , Zuo Zhitao , Zhou Xin , Guo Wenbin , Sun Jianting , Chen Haisheng
Published: March 2024

The oblique flow compressor is one of the key components in compressed air energy storage (CAES) system, which has the advantages of high single-stage pressure ratio, wide operating range, high efficiency and large mass flow. In this paper, a numerical method is used to study the first-stage oblique flow compressor in a compressor group with radial inlet chamber (RIC), and the oblique flow compressor performance with axial inlet is compared. The results show that the RIC makes the overall performance curve of compressor shift downward, the stable working range is reduced by 15.75%, and the isentropic efficiency and pressure ratio are reduced by 1.54% and 1.57% respectively under the design conditions. The RIC makes the impeller inlet aerodynamic parameters circumferential distribution non-uniformity, which declines the compressor performance. And the rotation of the impeller also destroys the original symmetrical flow distribution of the RIC.
Pressurization process and performance analysis of gear-claw hydrogen circulating pump used in PEMFC system
Authors: Pan Shiyang , Wang Jun , Zhao Xin , Ren Chunji , Xin Yuanjie , Wang Zengli , Cui Dong
Published: March 2024

Owing to the structure of the gear-claw rotor, working chambers of claw pumps are divided into small multi-chambers by a pair of intermeshing claw rotors in the mixing process, and the transient flow in multi-chambers is complicated, which results in the increase of the pump consumption. Hence, it is necessary to study the transient flow and working process of gear-claw hydrogen circulating pumps to optimize the pump performance. In this study, the meshing model of a high-order curve and its conjugate curve was proposed, and the profile composition of the gear-claw rotor was introduced. The influence of the radius ratio of claw addendum arc on the performance including relative carryover, built-in volume ratio and volume utilization was analyzed. The flow field of gear-claw hydrogen circulating pump including pressure and velocity field was analyzed by using numerical simulations. Furthermore, the p-V diagram of pumps was obtained. It is found that the gas in the compression chamber is mixed with the gas in the carryover, and the initial pressure in the compression chamber is 130.78kPa, which increases by 29.07% compared to the original initial pressure in the compression chamber. Therefore, an overcompression phenomenon at the end of the compression process (at the beginning of the discharge process) occurs.
Effect of the number of guide vanes on cavitation characteristics and pressure pulsation of centrifugal pumps
Authors: Dong Wei , He Fan , Ai Gaigai , Liang Wuke , Li Peixuan , Fan Xugang
Published: March 2024

Centrifugal pumps play an important role in the national economy, they usually have complex flow fields and abundant flow structures. Based on the K-ε turbulence model and Zwart cavitation model, ANSYS was used to analyze the large guide vane centrifugal pump. Four schemes are proposed, each with 11, 13, 15, and 17 guide vanes respectively. When operating under different flow conditions, the external characteristics of the pump were analyzed and compared. The cavitation characteristics of the pump at the design flowrate and the pressure pulsation in the vaneless zone were analyzed. The influence of guide vane number on cavitation performance and pressure fluctuation in the vaneless region of the pump was studied. The final results show that the cavitation variation patterns of different schemes are similar. Z
0=13 has the best cavitation performance, and Z
0=17 has the worst cavitation performance. The change in guide vane numbers will affect the number of peaks and valleys at each monitoring point in the cycle, which correspond to guide vane numbers. Appropriately increasing guide vane numbers can reduce the amplitude of pressure fluctuation to a certain extent and reduce the pressure difference, which is beneficial for maintaining a stable state during unit operation.
Investigation on the operation and gas-liquid two phase flow characteristics of vane type deep-sea pump
Authors: Luo Xingqi , Yan Sina , Feng Jianjun , Li Chenhao , Sun Shuaihui , Zhu Guojun , Zhang Lefu , Xie Hang
Published: March 2024

The development of oil and gas resources towards the deep sea is an inevitable trend in international energy development. Due to its advantages of high production and transportation efficiency, good flow safety and low investment cost, oil and gas mixed transportation technology has become the preferred technology for deep-sea oil and gas production and transportation system. The core device of the oil-gas mixed transportation system is the gas-liquid two-phase flow pump. Under the gas-liquid two-phase condition, the pressure surging will occur with the increase of the inlet gas volume fraction (IGVF) in the pump. At this time, the pressurization capacity of the pump decreases significantly, accompanied by violent vibration, resulting in extremely unstable operation. To solve this problem, the numerical simulation and experiment of the two-phase operation characteristics of a centrifugal pump and a semi-open mixed-flow pump were carried out in this study. The influence of operating parameters on its pressurization capacity was clarified, and the internal gas-liquid distribution was visually tested, revealing the distribution and its spatiotemporal evolution of gas-phase in the impeller. Finally, the unsteady characteristics of pressure surging were analyzed in detail.
Investigation of the influence of the gap between impeller and diffuser in the pressure pulsation characteristics of a centrifugal pump
Authors: Sun J , Yan W Z , Wang W J
Published: March 2024

The volute centrifugal pump is the core equipment in large-scale water transfer project. The instability of the unit during operation is mainly due to the hydraulic vibration inside the mechanical parts, and pressure pulsation in the “bladeless area” of impeller and diffuser is the main reason for the hydraulic vibration. This paper investigated the change of pump efficiency and head on different values impeller-diffuser gap, and comparatively analyzed the pressure pulsation characteristics of centrifugal pump. The findings demonstrated that the large gap between the impeller and diffuser, the higher pump efficiency and the lower head. The high pressure regions at the impeller outlet and diffuser inlet were significantly narrowed at gap values of 10 mm and 12 mm. With the increase of the gap, the distribution of the flow field in the impeller and diffuser region became more uniform and the intensity of pressure pulsation was decreased. While the gap value was 12 mm, for the impeller monitoring point on the pressure coefficient ranged within ±0.05. This study illustrated the impact of impeller-diffuser gap value on the internal pressure pulsation of centrifugal pumps, it offered as a certain reference for improving the operational stability of the pumps.
Optimization method investigation for centrifugal pump performance based on 3D inviscid inverse design
Authors: Shen Zhenhua , Wang Chao , Ye Daoxing , Zhang Libin , Wang Peng
Published: March 2024

Centrifugal pump is widely used in many important fields such as large hydropower station, urban central heating, aerospace engineering, etc. It has high requirements for cavitation performance and hydraulic performance in actual use. This study centers around on a pipeline pump with a specific speed of 360, reconstructs the impeller in TURBOdesign, takes important parameters of the impeller as the input conditions for optimization, aims at enhancing the blade’s minimum pressure and curtailing the flow losses in the blade channel and progressively optimize the meridional-blade loading based on the inviscid flow which was carried out by using genetic algorithm. The optimization leverages genetic algorithm, progressively optimizing the impeller using meridional and blade loading. By analyzing the effects of meridional and blade loading parameters on cavitation and hydraulic performance, it is found that the optimized models’ NPSH are much better than the original one. It’s approved that this optimization method is valid.
Numerical research on performance failure caused by gas blocking in multiphase mixed-transport pump under non-uniform inflow conditions
Authors: Wang Zhisheng , Quan Hui , Feng Bing , Lan Jianying
Published: March 2024

The helical-axial multiphase mixed-transport pump fails due to gas blocking caused by gas-liquid separation caused by cavitation under complex conditions with high gas volume fraction. This is an urgent engineering problem that needs to be addressed in the application of this pump. In order to simulate the flow structure characteristics in the channel, two types of non-uniform inflow boundary conditions were introduced. The bubble structure, velocity, and pressure under different inflow conditions were compared and analyzed, and the variation patterns affected by non-uniform boundary conditions were obtained. At the same time, the internal flow characteristics and mechanisms of multiphase mixed-transport pump are analyzed based on the velocity changes at the inlet of the impeller and the pressure fluctuations at the outlet of the guide vanes, leading to the intensification of gas-liquid separation and eventually the development of gas blocking. Research has shown that through programmatic control of the inlet boundary conditions, a linear change in inlet pressure has a more significant effect on the intensification of gas-liquid separation in the flow channel of the mixed-transport pump than a sinusoidal change, ultimately leading to significant performance failure when generating gas blocking. The research conclusion provides reference value for solving gas blocking in engineering applications of helical-axial multiphase mixed-transport pump.
Integrated design and hydraulic model optimization of model horizontal main pump based on CFD fluid dynamics analysis
Authors: Lu Jinqi , Wang Dezhong
Published: March 2024

There are few studies and reports related to horizontal main pumps for nuclear power plants. The installation of vertical main pumps for small reactors requires the design of special elbows on the pressure vessel. Horizontal main pump, as a new main pump structure, can reduce the diameter of the main pressure vessel and simplify the structure of the pressure vessel. Compared with the vertical main pump, the horizontal main pump needs to control its axial dimension to improve its stiffness, which makes it impossible to set a long straight pipe section at the inlet, which has an impact on the pump performance. On the other hand, the compression of the axial dimension of the pump casing makes the overflow area of the press-out chamber small, resulting in large hydraulic losses. In this paper, in order to improve the efficiency of the pump and reduce the influence of non-uniform incoming flow, the optimization design is carried out with the SST k-ω model, and it is shown that: 1. the suction port of the curved impeller is easier for the fluid to enter into the impeller in the axial direction; and 2. the axially symmetric worm gear produces more vortex flow losses.
Research on prediction method of sensorless measurement of centrifugal pump operational state based on hybrid model
Authors: Gong X B , Gan X C
Published: March 2024

Centrifugal pumps are widely used in various fields such as industrial production and urban water supply. In order to achieve the monitoring of operational state of pumping systems, as well as the problems of inability to install sensors or high cost of sensors in practical engineering, the sensorless estimation method of centrifugal pump operational state provides a new opportunity for the monitoring and control of pumping systems. In this paper, a hybrid model based on QP model and neural network model is proposed to estimate the flow rate of rational pump by dividing the speed region. Taking a centrifugal pump as the research object, the operational points of the pump at different rotational speeds are acquired by experiments. Using the proposed method, a prediction model is established to predict the operational state of the pump. The prediction results are verified through experiments, and the error analysis of the prediction results is carried out. The results show that the proposed hybrid model can improve the prediction accuracy of centrifugal pump operational state and has certain practical value of engineering.
Experiment of cavitating flow characteristics of inducer with inflow entrained air
Authors: Lin R H , Chen H , Xiang L , Qu N C
Published: March 2024

To study the effect of inflow entrained non-condensable LOX tank pressurization gas on cavitating flow inside inducer pumps, a series of experiment were performed. The cavitation head breakdown point and cavitation instability characteristics of an inducer pump under different inlet gas volume fraction(IGVF) were investigated. It was found that head breakdown occurred at higher cavitation number under higher IGVF condition. Analysis of low frequency pulsating pressure suggested that cavitation surge was supressed by extra compressibility provided by non-condensable gas at operating point near head breakdown.
Design and numerical simulation of elliptical claw-type hydrogen circulation pump rotor
Authors: Feng Bing , Quan Hui , Wang Zhisheng
Published: March 2024

The claw-type hydrogen circulation pump has the advantages of smooth gas delivery, wide range of adapted working conditions, high efficiency, etc., which is the key equipment of the fuel cell system. In this paper, a new type of elliptical claw rotor is proposed by the combination of elliptical line, circular arc and pendulum line, and the equation of the line is calculated and deduced, and the distribution law of the flow field in the working chamber is obtained based on numerical simulation, and the internal flow characteristics, the working process, the change rule of the pressure, speed and the resisting moment are analysed. The results show that the elliptical claw rotor is subjected to a smaller gas resisting moment compared with the traditional cycloidal hydrogen circulating pump.
CFD study on the effect of particle properties on the performance of annular jet pump
Authors: Liu Wenhui , Lai Xinjie , Zhou Qiwei , Zhu Chenbin , Yang Xuelong
Published: March 2024

The annular jet pump is a type of fluid mechanical pump that operates by exchanging momentum with the fluid. Annular jet pumps possess distinctive advantages in the transportation of solid particles. However, the efficiency of these pumps is significantly impacted by both the physical properties of the particles and their initial concentration, thereby limiting their practical applications. In this paper, by combining other scholars’ designs of annular jet pumps, the effects of different physical densities and different initial concentrations of particles on the flow field, pressure and efficiency of an annular jet pump were analysed based on the RNG k-ε turbulence model and the Mixture multiphase flow model. The efficiency of the annular jet pump decreases with a higher particle bulk density. Specifically, at an initial concentration of 20% and a flow ratio (M) of 0.5, the efficiency of the annular jet pump fluctuates as follows: it changes from 28.736% under single-phase flow conditions to 25.011%, 24.369%, 23.637%, 22.950%, and 21.733% as the density of particulate matter increases. The findings of this study offer valuable theoretical insights for the implementation of annular jet pumps in engineering discharge applications.