Dynamic characteristics of centrifugal pump induced by fluid and motor excitation forces

The combined dynamic characteristics of the centrifugal pump induced by the fluid and motor excitation forces are investigated in this paper. The coupling vibrations of a centrifugal pump during the operation are mainly caused by the fluid excitation and the motor excitation forces. The finite element model was constructed in this paper under the consideration of the fluid excitation which was obtained from the numerical simulation and the motor excitation force which came from the experiments; compared with the experimental results and well agreement, the components of the whole model were validated to be accurate enough for simulation. Applying the approach of the modal dynamics, the dynamic analysis was conducted to study the influence of the flow rate, the blade number, the exit installation angle and the outside diameter of impeller on the responses. The suggested optimal parameters were provided from the perspective of the vibration reduction. The results of the calculation are helpful to the designation and the safe operation of the centrifugal pumps

Synchronous and subsynchronous vibration under the combined effect of bearings and seals: numerical simulation and its experimental validation

A three-dimensional computational fluid dynamics (CFD) model of a labyrinth seal was established in order to investigate the influence mechanism of combined effects between bearings and labyrinth seals on the dynamic characteristics of the rotor-bearing-seal system. The dynamic coefficients of the labyrinth seal for various rotating speeds were calculated. Results show that the absolute values of cross-coupled coefficients increase with the increasing rotating speed, while the absolute values of direct coefficients decrease slightly. The positive preswirl at the inlet tends to intensify the increase of cross-coupled coefficients and the decrease of direct coefficients. The negative preswirl shows the opposite effect. A finite element model was further setup. Results show that the labyrinth seal has a large influence on the synchronous response of rotor in the resonant region due to its damping effect. For other speeds, it has a minor effect. The labyrinth seal may promote the instability of the rotor-bearing-seal system. The subsynchronous vibration increases significantly when the seal force is taken into account. The system stability can be generally enhanced by introducing the negative preswirl at the inlet. Results also show that the detrimental influence of the labyrinth seal can be compensated by using suitable bearings. A proper bearing configuration can be designed to reduce the risks of rotordynamic instabilities due to seals. An experimental test was finally performed, and it shows good agreements with the numerical simulation

Study on the Effect of Cuisine Tourism Resource on Tourists’ Willingness to Visit

This article aims at examining if tourists’ evaluation of cuisine tourism resource has a positive effect on their willingness to visit (WTV) the destination (H1). In Study 1, the content analysis of travelogues of 60 Chinese major tourist cities shows that the scenic spots have a significant effect on WTV, while the effect of cuisine tourism resource on WTV is not supported. Moreover, the tourist city Chengdu with both abundant scenic spots and cuisine resources is chosen for further research of how cuisine resources influence tourist’ decisions. In term of 276 questionnaires (Study 2) and 30 interviewee (Study 3), the results show that the impact of the cuisine resource on WTV is moderated by the tourists’ evaluation on the scenic spots. Only when tourists have a high evaluation on scenic spots, the cuisine resource plays a positive impact on WTV, showing the auxiliary attraction of cuisine resource to tourists

Decelerated non-relativistic expansion in a tidal disruption event with a potential neutrino association

A tidal disruption event (TDE) involves the tidal shredding of a star in the vicinity of a dormant supermassive black hole. The nearby ($\approx$230 mega-parsec) radio-quiet (radio luminosity of $4 \times 10^{38}$ erg s$^{-1}$) AT2019dsg is the first TDE potentially associated with a neutrino event. The origin of the non-thermal emission in AT2019dsg remains inconclusive; possibilities include a relativistic jet or a sub-relativistic outflow. Distinguishing between them can address neutrino production mechanisms. High resolution very long baseline interferometry monitoring provides uniquely constraining flux densities and proper motion of the ejecta. A non-relativistic (outflow velocity of $\approx$0.1 $c$) decelerated expansion in a relatively dense environment is found to produce the radio emission. Neutrino production may be related to the acceleration of protons by the outflow. The present study thus helps exclude jet-related origins for the non-thermal emission and neutrino production, and constrains non-jetted scenarios.Comment: 40 pages, 3 figures, 2 tables. Submitted after revisio

In vitro evaluation of a novel pH neutral calcium phosphosilicate bioactive glass that does not require preconditioning prior to use

It is well known that bioactive glasses can cause a significant increase in pH due to the rapid release of calcium and/or sodium ions. Consequently, preconditioning of the glass is usually required prior to surgery to negate the effect of this sudden release of ions. However, preconditioning for several days is far from ideal and also preconditioning is not practical for novel organic/inorganic sol-gel hybrids currently being developed since the organic phase will start to hydrolyze and dissolve. This study describes a bioactive glass that dissolves without causing a significant change in pH from physiologically optimal values and requires no preconditioning prior to use. The bioactivity of the pH neutral glass, hydroxyapatite formation, and cellular responses, are measured and compared directly with results from archetypal 45S5 and S70C30 bioactive glasses. A hydroxyapatite layer was found to rapidly form (within 1 day) on the surface of the pH neutral glass upon reacting with simulated body fluid. In addition, improved cell compatibility was observed compared with 45S5 and S70C30 glasses. Therefore, this pH neutral glass has significant potential for bone repair applications

Neural Interactive Keypoint Detection

This work proposes an end-to-end neural interactive keypoint detection framework named Click-Pose, which can significantly reduce more than 10 times labeling costs of 2D keypoint annotation compared with manual-only annotation. Click-Pose explores how user feedback can cooperate with a neural keypoint detector to correct the predicted keypoints in an interactive way for a faster and more effective annotation process. Specifically, we design the pose error modeling strategy that inputs the ground truth pose combined with four typical pose errors into the decoder and trains the model to reconstruct the correct poses, which enhances the self-correction ability of the model. Then, we attach an interactive human-feedback loop that allows receiving users' clicks to correct one or several predicted keypoints and iteratively utilizes the decoder to update all other keypoints with a minimum number of clicks (NoC) for efficient annotation. We validate Click-Pose in in-domain, out-of-domain scenes, and a new task of keypoint adaptation. For annotation, Click-Pose only needs 1.97 and 6.45 NoC@95 (at precision 95%) on COCO and Human-Art, reducing 31.4% and 36.3% efforts than the SOTA model (ViTPose) with manual correction, respectively. Besides, without user clicks, Click-Pose surpasses the previous end-to-end model by 1.4 AP on COCO and 3.0 AP on Human-Art. The code is available at https://github.com/IDEA-Research/Click-Pose.Comment: Accepted to ICCV 202

Prevalence of Depression and Anxiety Symptoms of High School Students in Shandong Province During the COVID-19 Epidemic

© Copyright © 2020 Zhang, Zhai, Yang, Zhang, Zhou, Yang, Duan and Zhou. Background: The coronavirus disease 2019 (covid-19) has brought physical risks as well as psychological challenges to the whole world. High school students are a special group suffering from both the academic pressure and the threat of the epidemic. The present study aims to conduct an online survey to investigate the psychological status of high school students in Shandong Province. Methods: Using a web-based cross-sectional survey, data was collected from 1,018 voluntary high school students assessed with demographic information, the Patient Health Questionnaire-9 (PHQ-9), the Generalized Anxiety Disorder-7 (GAD-7) and a self-designed online-study effect survey. Correlation analysis was performed to explore the relationships between depression symptoms, anxiety symptoms, and study effect. Result: The prevalence of depressive symptoms, anxiety symptoms, and a combination of depressive and anxiety symptoms was 52.4, 31.4, and 26.8%, respectively, among high school students in Shandong Province during the COVID-19 epidemic. And from moderate to severe severity level, the rates of depressive symptoms and anxious symptoms were 17.6 and 4.6%. Female students exhibited a higher rate and severity of mental symptoms than male, and grade one senior high school students got a higher rate and severity of mental symptoms than the other two grades. Nearly half of the students were not satisfied with their online-study effect. The PHQ-9 score had a strong positive correlation with the GAD-7 score. Both the PHQ-9 score the GAD-7 score had a negative correlation with the study-effect survey score. Conclusion: Quite a number of high school students suffered from depression and anxiety symptoms during the COVID-19 epidemic. Sufficient attentions should be paid, and necessary supports should be provided, to protect the mental health of this special group

GPAvatar: Generalizable and Precise Head Avatar from Image(s)

Head avatar reconstruction, crucial for applications in virtual reality, online meetings, gaming, and film industries, has garnered substantial attention within the computer vision community. The fundamental objective of this field is to faithfully recreate the head avatar and precisely control expressions and postures. Existing methods, categorized into 2D-based warping, mesh-based, and neural rendering approaches, present challenges in maintaining multi-view consistency, incorporating non-facial information, and generalizing to new identities. In this paper, we propose a framework named GPAvatar that reconstructs 3D head avatars from one or several images in a single forward pass. The key idea of this work is to introduce a dynamic point-based expression field driven by a point cloud to precisely and effectively capture expressions. Furthermore, we use a Multi Tri-planes Attention (MTA) fusion module in the tri-planes canonical field to leverage information from multiple input images. The proposed method achieves faithful identity reconstruction, precise expression control, and multi-view consistency, demonstrating promising results for free-viewpoint rendering and novel view synthesis.Comment: ICLR 2024, code is available at https://github.com/xg-chu/GPAvata

Synchronous and subsynchronous vibration under the combined effect of bearings and seals: numerical simulation and its experimental validation

A three-dimensional computational fluid dynamics (CFD) model of a labyrinth seal was established in order to investigate the influence mechanism of combined effects between bearings and labyrinth seals on the dynamic characteristics of the rotor-bearing-seal system. The dynamic coefficients of the labyrinth seal for various rotating speeds were calculated. Results show that the absolute values of cross-coupled coefficients increase with the increasing rotating speed, while the absolute values of direct coefficients decrease slightly. The positive preswirl at the inlet tends to intensify the increase of cross-coupled coefficients and the decrease of direct coefficients. The negative preswirl shows the opposite effect. A finite element model was further setup. Results show that the labyrinth seal has a large influence on the synchronous response of rotor in the resonant region due to its damping effect. For other speeds, it has a minor effect. The labyrinth seal may promote the instability of the rotor-bearing-seal system. The subsynchronous vibration increases significantly when the seal force is taken into account. The system stability can be generally enhanced by introducing the negative preswirl at the inlet. Results also show that the detrimental influence of the labyrinth seal can be compensated by using suitable bearings. A proper bearing configuration can be designed to reduce the risks of rotordynamic instabilities due to seals. An experimental test was finally performed, and it shows good agreements with the numerical simulation