bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Information Technology in Teaching Chinese as a Second Language
Authors: Ding Lei
Published: October 2022

Using information technology to create a teaching environment for TCSL and developing TCSL in an all-round way is not only
a supplement to offline teaching mode, but also an important innovation of TCSL teaching mode. Facing the new environment of Wisdom
Education, in order to better carry out the teaching of Chinese as a foreign language, it is necessary to build an intelligent platform focusing
on the teaching of Chinese as a foreign language based on the advantages of the application of information technology, improving the
quality of teaching Chinese as a foreign language. Based on the teaching environment of Chinese as a foreign language (TCFL) and the
advantages of information technology in TCFL, this paper puts forward a multi-platform construction mechanism.
The Promotion of Modern Information Technology to the Transformation and Marketization of Regional Scientific and Technological Achievements
Authors: Liu Xin
Published: October 2022

In the process of promoting the transformation of regional scientific and technological achievements, the unclear property right system restricts the market transformation process of regional scientific and technological achievements, and it is difficult to give full play to the application advantages of scientific and technological achievements. In the intelligent environment, by giving full play to the advantages of information technology, in the process of regional transformation of scientific and technological achievements, by constructing the transformation model led by scientific and technological personnel, and by providing the relevant scientific and technological personnel with complete rights and interests, give full impetus to the market development of scientific and technological achievements. Based on the analysis of the background of the transformation of regional scientific and technological achievements into market and the advantages of the application of modern information technology, this paper puts forward some strategies for accelerating the transformation of regional scientific and technological achievements into market.
An Analysis of the Artistic Elements of TV Anchor in the Perspective of the Development of Modern Information Technology
Authors: Kuang Suping
Published: October 2022

TV anchor is a key profession in radio and television industry, and its artistic expression is of great practical significance to the development of the whole industry. In order to fully meet the needs of the current social development and the progress of the industry, we should, on the basis of improving the expression of individual language of TV anchorpersons, master the necessary communication and interaction skills, and integrate into the development features of modern information technology, improve the overall quality of the art of television broadcast hosting, effectively meet the public’s psychological expectations of television broadcast hosting. Based on the development of modern information technology, this paper makes a detailed analysis of the artistic elements of TV broadcasting.
Art Form and New Fashion Style of Virtual Reality Design
Authors: Shi Jiayi
Published: October 2022

With the application of virtual reality technology matures, the integration with art design deepens day by day. This technology presents a wonderful experience space for the public on the basis of a better life for the public, leading the field of art and design continue to develop. On the basis of actively breaking the traditional two-dimensional one-sided design, we should actively explore new fashion style by giving full play to the advantages of virtual reality design. Based on the future trend of virtual reality technology, this paper interprets the art form and new fashion style of virtual reality design.
Effective Integration of Computer and Ideological and Political Education Based on Intelligent Teaching Platform
Authors: Wang Yongzhi
Published: October 2022

The traditional mechanism of ideological and political education is relatively single, no matter it is teaching idea, or teaching method, there are great limitations, which affect the effectiveness of ideological and political education. In the environment of wisdom education, we will give full play to the advantages of computer technology and reconstruct the system of ideological and political education. We will innovate the effectiveness of ideological and political education on the basis of accurately grasping students' demands for ideological and political study, improving students' understanding of ideological and political education. Based on the intelligence teaching environment, this paper puts forward the effective integration path of computer and ideological and political education based on the intelligence teaching platform.
Research on the Application of Computer Digital Technology in the Protection of Security Language
Authors: Bai Aruna
Published: October 2022

Making full use of computer digital technology to carry out machine translation research, will realize the language variety conversion between national language and document information, and make the security language language realize the communication goal with no limit, it also lays a good foundation for the protection of security language and writing information and the construction of barrier-free national cultural exchange system. Based on the analysis of the current situation of the security language and characters, this paper probes into the concrete methods of protecting the security language and characters by using digital recording technology, Digital Image Processing Technology and other computer digital technologies.
Research on Digital Protection Strategy of Traditional Sports Culture in the View of Computer Network Communication
Authors: Gao Lan , Geng Nannan , Wang Chaoqun
Published: October 2022

Facing the new cultural ecology, the traditional sports culture has many problems, such as single communication subject, imperfect communication system and so on, which directly affects the healthy survival of sports culture. Under the new vision of computer network communication, in order to better adapt to the new multi-cultural form, and to solve the survival pressure of traditional sports culture, it is necessary to take computer network communication ecology as the basis, in order to improve the communication efficiency of traditional sports culture, the inner gene of traditional sports culture is excavated, the traditional sports culture is developed in digital form, and the cultural protection mechanism of the integration of digital tradition is constructed. Based on the communication environment of computer network and the current situation of traditional sports culture, the digital protection strategy is put forward.
Sports Diplomacy of Socialism with Chinese Characteristics in the New Era: Opportunities and Challenge
Authors: Jinghui Zhao
Published: October 2022

In 2005, former Foreign Minister Qian Qichen put forward and defined the concept of "sports diplomacy" in his Dictionary of World Diplomacy. "Sports diplomacy" is defined as "the foreign sports exchanges and exchanges conducted by a country's sports authorities or sports circles for the purpose of promoting relations between countries." It is reasonable to have different understanding and cognition to sports diplomacy. Due to different historical backgrounds, national rights and interests and international environments, China's diplomacy has different strategic aspirations and specific goals. Even if there are common interests, they differ in scope and emphasis. However, there are two common points: the target of foreign participants; For the purpose of fulfilling national interests. To sum up, sports diplomacy in the new era can be defined as the sum total of all external sports activities carried out by the participants through sports and sports culture exchanges with the participants for the purpose of realizing national political or diplomatic goals, promoting inter-state relations and safeguarding national interests.
Research on the Application of Information Technology in Chinese Distance Multimedia Teaching
Authors: Zhang Xinyue , Liu Hui
Published: October 2022

With the integration of Internet technology and educational activities, it is increasingly urgent to integrate information technology into distance multimedia teaching. In order to effectively improve the quality of Chinese distance multimedia teaching, it is necessary to take the new context of intelligent teaching as the basis, to focus on enhancing and improving the learning experience of students, and to give full play to the advantages of multimedia teaching, the project of Chinese distance multimedia teaching is reconstructed actively. This paper analyzes the advantages of the application of information technology in Chinese distance multimedia teaching, and puts forward some relevant suggestions.
The mode transformation of modern information technology in higher education management
Authors: Liu Chao , Wu Jienan
Published: October 2022

With the development of "Internet + Education", higher education management has entered a new stage of intelligent and intelligent development. By giving full play to the advantages of modern information technology, actively restructuring the process of university education management, innovating the mode of university education management and the thinking of governance, the quality of university education management will be substantially improved, better realize the consistent integration of wisdom education and all-round education. This paper analyzes the background and advantages of the application of modern information technology in higher education management, and puts forward some suggestions on the reform of the mode.
Analysis and research of computer information security technology under big data background
Authors: Wang Jun , Huang Hong
Published: October 2022

Big Data optimizes the process of information processing, expands the scale of information processing, and improves the application effect of big data and computer information technology. However, big data has also triggered data leakage, network viruses and other security risks. In the context of big data, in order to give full play to the application advantages of computer information security technology, it is necessary to give full play to all kinds of technology to avoid the problems such as system failures, external attacks and so on, then ensure that the computer system in a safe and stable operating environment. This paper analyzes the problems of computer information security technology under the background of big data, and puts forward the corresponding application strategies based on the concrete superiority technology.
Research on the methods of cultivating and managing students' learning by computer technology under the network environment
Authors: Wang Wei , Wu Jienan
Published: October 2022

The training and management of Students' learning is a dynamic and continuous optimization process, which is the comprehensive result of combining students' reality and growing environment. In the network environment, with the continuous advancement of intelligence education, the application of computer technology to give full play to the advantages of positive change and innovation in student learning training and management strategies, will be on the basis of improving the education ecology, to provide students with high-quality learning resources to achieve the fundamental optimization of student training process. This paper analyzes the influence of computer technology on the cultivation and management of Students' study under the network environment, and advances some corresponding suggestions.
Research on the role of modern information technology in promoting the leadership of informationization of higher education
Authors: Jing Yuhuan , Wu Jienan
Published: October 2022

The construction of information-based leadership is of great practical significance in driving the development of higher education. By giving full play to the application advantages of modern information technology, an educational system covering all levels of higher education is constructed, we will comprehensively improve the level of informationization and intellectualization of higher education, and help to realize high-quality development of higher education. This paper analyzes the role of modern information technology in improving the leadership of information-based education in colleges and universities, and puts forward some relevant strategies to improve the leadership of information-based education in colleges and universities by using modern information technology.
Numerically modelling temperature deformations and stresses in the exhaust system of a gas compressor unit
Authors: Demianenko Maryna , Volf Michal , Banias Myron , Starynskyi Oleksandr
Published: October 2022

During the operation of a gas compressor unit, the temperature of the exhaust system can cause failure or burnout of the inner facing sheets of the unit. The article describes a technique for determining the maximum temperature deformations of these elements. The technique enables more accurate calculation of the temperature deformations by determining the influence of the contacts between the inner facing and the power frame on the temperature distribution and mobility of the exhaust system. The temperature deformations and stresses of the exhaust system elements are determined, and the level of the permissible stresses is evaluated. The results of the work can be used to prevent possible ruptures and burning of the inner facing, as well as to calculate the design dimensions of the lens expansion joint.
Development of a micro ORC power unit using digital prototyping methods
Authors: Pejchal Jan , Kolář Petr
Published: October 2022

The development of the prototype of the ORC micro turbine includes already in the design phase the creation of a digital prototype based on the use of computational simulations, especially the CFD flow program Simcenter STAR CCM +, strength and rotor-dynamic FEA analyses of system behaviour Simcenter 3D. This is followed by the optimization of the device by increasing its efficiency and improving the mechanical properties of the system. For this purpose, we used the optimization program HEEDS and the topological optimization method Simcenter 3D. This was followed by the production of a prototype, where 3D printing technology was used to produce turbine housing moulds and other components. A huge attention of this contribution is devoted to these additive production processes.
Experimental Investigation of 3D Dynamical Effects in a Wake behind Circular Cylinder
Authors: Uruba Václav , Procházka Pavel
Published: October 2022

A circular cylinder in crossflow is subjected to the study of 3D dynamical structure of its wake. The typical dynamics is characterized by quasi-periodic behaviour called Kármán – Bénard vortex street with the typical frequency in dimensionless form known as Strouhal number. The experimental study relies on stereo Particle Image Velocimetry method, the plane of measurement is perpendicular to the flow in the distance 3.8 cylinder diameters in streamwise direction. Reynolds number was around 5 thousand. The structure and dynamical behaviour of the wake along the cylinder axis is studied in details. On the top of the known streamwise velocity deficit definition of the wake, the streamwise oriented dynamically evolving vortices are detected. For the detailed dynamics examination, the Oscillation Pattern Decomposition method was used. Waves of various structures travelling along the cylinder axis as well as some pulsations were identified. The wake dynamics is characterised by the streamwise velocity component deficit and the streamwise vorticity concentration. Both structures are moving periodically in transversal direction with the same frequency, the velocity deficit is shifted by a quarter of period behind the vorticity concentration in the shedding process.
Turbulence topology behind different sections of the wind turbine blade
Authors: Yanovych Vitalii , Duda Daniel , Uruba Václav , Kosiak Pavlo , Horáček Vít
Published: October 2022

This work aimed to investigate the turbulence characteristics behind different parts of the wind turbine blade. Airfoils S807, S813, S817, and S803, which characterize the shape of the blade at different lengths, were selected for estimation. During the experiment, the chord-based Reynolds number was 2.6×105, while the angle of attack was zero. Measuring crosssections were placed behind the trailing edge at x·c-1≈0.2, 0.4 and 1.0. For the determination flow topology, we used a Hotwire anemometry with a split fiber probe 55R55 and a miniature X-wire probe 55P64. The obtained data allowed us to determine and compare the evolution of the wake behind different types of airfoils in streamwise and spanwise directions. Thus, the largest and smallest velocity deficit located behind S817 and S803 airfoils, respectively. This trend is also evident in the Normalized Reynolds shear stress distributions. Finally, we determined the spectrum and calculated the Integral length scale, the Taylor and Kolmogorov microscale of turbulent flow. According to the results, profile S817 contributes to the formation of a flow with a large scale of turbulence, while the S803 is contrary.
Preservation of adiabatic invariants and geometric numerical algorithm for disturbed nonholonomic systems
Authors: Xia Li-Li , Wu Meng-Meng , Bai Long
Published: October 2022

Perturbations to Mei symmetry and the numerical algorithm of disturbed nonholonomic systems are studied under total variational discretization. The discrete equations on regular lattices of nonholonomic systems in the undisturbed and the disturbed cases are presented. The determining equations of Mei symmetry are established for undisturbed and disturbed systems. The exact invariants of Noether type led by Mei symmetry for undisturbed nonholonomic systems are given under infinitesimal transformations of Lie groups. For discrete disturbed nonholonomic systems, the condition of existence of adiabatic invariants led by perturbation to Mei symmetry and their forms are presented. The numerical simulations demonstrate that the geometric numerical algorithm has a higher precision and longer time stability than the standard numerical method.
Real-time time-dependent DFT study of laser-enhanced atomic layer etching of silicon for damage-free nanostructure fabrication
Authors: Wang Peizhi , Fang Fengzhou
Published: October 2022

Atomic layer etching (ALE) has emerged as a promising technique that enables the manufacturing of atomically controlled nanostructures toward next-generation nanoelectronics. However, the high-energy ion bombardment (typically 40–60 eV for Si) in current plasma ALE would cause damage to structures and even underlying substrates, which is detrimental to processing controllability as well as device performances. This problem could be addressed by introducing an additional laser source into the plasma ALE process to reduce the required ion energy, namely, laser-enhanced ALE. To elucidate the fundamental role of photons in laser-enhanced ALE, we explored the laser–matter interaction in laser-enhanced ALE of Si using real-time time-dependent density functional theory. The results show that with time evolution the incident laser would produce repulsive forces between the modified and bulk Si atoms. The magnitude of these forces can be up to 1.94 eV/Å when a large laser intensity and a short wavelength are employed. Under such large forces, the corresponding bonds are weakened with electron distribution decreasing significantly and can be even broken directly as time propagates. Low-energy ions can, therefore, be used to selectively remove the modified Si atoms whose bonds are already weakened by the additional laser, thereby minimizing and even eliminating the unwanted surface damage.
JPL/Caltech ArtCenter
Authors: Hendrie Maggie , Mushkin Hillary , Lombeyda Santiago , Davidoff Scott
Published: October 2022

Data visualization frequently provides audiences with novel semantic and computational presentations. How does a
multifaceted team expand this scope by harnessing the power of visualization as a tool to think with? The NASA JPL/Caltech/
ArtCenter data visualization program demonstrates how scientific knowledge, shaped from data and theory, is equally co-constructed
from diverse human perspectives. We will share case studies from Mars Rover Path planning and PIXLISE, a visual reasoning tool for
understanding planetary geology. Working from source data through mixed media artifacts, these projects explore co-design methods
for complex scientific domains with real-world applications. Our methodology emphasizes that all participants in the co-design
process are both learners and experts. In this dynamic, the design and coding process are unique modes of critical discovery.
Study of the adiabatic passage in tripod atomic systems in terms of the Riemannian geometry of the Bloch sphere
Authors: Cinins Arturs , Bruvelis Martins , Bezuglov Nikolai N
Published: October 2022

We present an analysis of the stimulated Raman adiabatic passage (STIRAP) processes based on the methods of differential geometry. The present work was inspired by an excellent article by Shore et al (Unanyan et al 1999 Phys. Rev. A 59 2910). We demonstrate how a purely geometric interpretation of the adiabatic passage in quantum tripod systems as a Riemannian parallel transport of the dark state vector along the Bloch sphere allows describing the evolution of the system for a given sequence of Stokes, pump and control laser excitation pulses. In combination with the Dykhne–Davis–Pechukas adiabaticity criterion and the minimax principle for circles on a sphere, this approach allows obtaining the analytical form of the optimal laser pulse sequences for a high fidelity tripod fractional STIRAP. In contrast to the conventional STIRAP in Λ-systems, the Gaussian approximations of the optimal laser pulse sequences allow reaching the infidelity of 10−7 for the adiabaticity parameter of 300 without noticeable oscillatory or other detrimental effects on population transfer accuracy.
Tunable polyvinyl chloride (PVC) and thermoplastic polyurethane (TPU)-based soft polymer gel sensors
Authors: Neubauer Justin , Cho H Jeremy , Kim Kwang J
Published: October 2022

Polyvinyl chloride (PVC) gels have recently been found to exhibit mechanoelectrical transduction under mechanical deformation. These mechanoelectrical properties of PVC gels are largely uncharacterized and the underlying transduction mechanisms are currently unknown. These soft electroactive polymers have tunable properties such as modulus and response voltage based on physical dimensions and the amount of plasticizer content within the material making them ideal candidates for complaint sensors. This study aims to investigate PVC gels comprised of various plasticizers to further investigate underlying mechanisms of mechanoelectrical transduction and broaden possible sensing applications. Plasticizers used in this study include dibutyl adipate, dibutyl phthalate, dioctyl phthalate, otherwise known as bis(2-ethylhexyl) phthalate, diisodecyl adipate, and the environmentally friendly biodegradable plasticizer acetyl tributyl citrate (ATBC). ATBC is often used in cosmetics and food packaging applications and is even used as a food additive which may lead to future biocompatibility for these gel sensors. These plasticizers are used to produce PVC gel sensors that are experimentally tested for mechanoelectrical transduction properties and sensing performance. In this study, a Langmuir adsorptive model is fit to the collected mechanoelectrical transduction data. These results are also nondimensionalized and compared to the characteristic dimensionless Langmuir adsorptive model. This simple model agrees very well with the experimental data. Additionally, a study on the mechanoelectrical transduction of an alternative polymer lattice structure, thermoplastic polyurethane (TPU), is discussed. This is a novel electroactive polymer investigated for mechanoelectrical transduction properties. This portion of the study aims to further knowledge of underlying mechanisms of mechanoelectrical transduction as well as show feasibility of additional lattices for soft polymer gel sensors. These TPU gel sensors show strikingly similar mechanoelectrical transduction properties to analogous PVC gels, insinuating that the polymer structure has a limited role in the underlying sensing mechanism and PVC itself is not unique to polymer gel sensing. The TPU-based soft polymer gel sensors however do display some level of mechanoelectrical hysteresis which may be attributed to viscoelastic properties and display a small amount of fatigue possibly due to exudation of liquid plasticizer. This study provides further characterization of mechanoelectrical response for varying plasticizers, provides a theoretical framework for underlying mechanisms, and displays the potential for further polymeric gel sensors.
Incommensurate magnetic states induced by ordering competition in

Ba1−xNaxFe2As2
Authors: Wang Jing
Published: October 2022

Quantum criticality near a certain magnetic phase transition beneath the superconducting (SC) dome of

B
a

1
−

x

N
a

x

F
e

2

A
s

2

is attentively studied by virtue of a phenomenological theory in conjunction with the renormalization group approach. We report that ordering competition between magnetic and SC fluctuations is capable of coaxing incommensurate (IC) magnetic states to experience distinct fates depending upon their spin configurations. The C
2-symmetry IC magnetic stripe with a perpendicular magnetic helix dominates over other C
2-symmetry magnetic competitors and hints at a potential candidate for the unknown C
2-symmetry magnetic state. Of the C
4-symmetry IC magnetic phases, the IC charge spin density wave is substantiated to be superior, shedding light on the significant intertwining of charge and spin degrees of freedom. Meanwhile, ferocious fluctuations render a sharp fall in superfluid density alongside a dip in critical temperature as well as intriguing behavior of the London penetration depth.
Analysis of cosmic aspects through string-inspired teleparallel gravity models
Authors: Jawad Abdul , Bilal Amin Sulehri M , Rani Shamaila
Published: October 2022

We consider a generic string inspired gravitational theory in the framework of teleparallel gravity whose stringy action based on a particular function which depends on the scalar field, its kinetic energy, the boundary and torsion terms as well as the Gauss-Bonnet terms We examine some cosmographic parameters like the equation of state parameter (ω
tot),

ω

tot

−

ω

tot

′

plane behavior and their stability with the help of squared speed of sound parameter (v2

s
). Under the choice of some specific values of model parameters, the equation of state parameter ω
tot indicates the range of cosmological constant and quintessence region of the evolving universe for the past, present and near future times while phantom phase in the far future times. The phase plane

ω

tot

−

ω

tot

′

expresses the super accelerated phase (the freezing region) whereas

v

s

2

gives the stability of each underlying model in the realm of accelerated universe.
Constraining the charge-sign and rigidity-dependence of solar modulation
Authors: Cholis Ilias , Hooper Dan , Linden Tim
Published: October 2022

Our ability to identify the sources of cosmic rays and understand how these particles
propagate through the interstellar medium is hindered by the combined effects of the solar wind
and its embedded magnetic field, collectively known as solar modulation. In this paper, we build
upon our previous work to model and constrain the effects of solar modulation on the cosmic-ray
spectrum, using data from AMS-02 and BESS Polar II collected between 2007 and 2012,
during which the heliospheric magnetic field was in a state of negative polarity. Our model uses
measurements of the heliospheric magnetic field and the tilt angle of the heliospheric current
sheet to accurately predict the effects of solar modulation as a function of time, charge, and
rigidity. By incorporating data from a period of negative polarity, we have been able to robustly
observe and constrain the charge-dependent effects of solar modulation.
Effect of potassium bubbles on the thermal shock fatigue behavior of large-volume potassium-doped tungsten alloy
Authors: Ma Xiaolei , Feng Fan , Zhang Xiaoxin , Wang Ting , Liu Xiang , Lv Wei , Lang Shaoting , Ge Changchun , Yan Qingzhi
Published: October 2022

A newly developed large-volume potassium-doped tungsten (W–K) plate with a thickness of 15 mm and a weight of 25 kg by powder metallurgy plus hot rolling was prepared to meet the requirements of the International Thermonuclear Experimental Reactor (ITER) in engineering application. In order to clarify the effect of K doping on the thermal shock performance of W–K alloy, transient thermal shock tests with a single-pulse duration of 1 ms for 100 shots at room temperature were performed. The absorbed power density is set to 0.33, 0.44, 0.55 and 0.66 GW m−2, respectively. Furthermore, the microstructure, Vickers micro-hardness before and after the transient thermal shock, thermal conductivity and relative density were also characterized. The results indicate that the cracking threshold of rolled W–K is 0.44–0.55 GW m−2, which possesses a better transient thermal shock resistance compared with the most of advanced W-based materials. This is mainly because K doping can significantly improve the high-temperature stability and mechanical properties of W material without reducing its thermal conductivity. In particular, K bubbles can also effectively inhibit the formation and propagation of cracks during thermal shock. Moreover, the cracking mechanism of rolled W–K alloy is also discussed in detail. This study is helpful for building a trusted ITER database on advanced W-based materials that provides useful references for the selection of future plasma-facing materials.
Unprecedented differences in phytoplankton community structures in the Amundsen Sea Polynyas, West Antarctica
Authors: Lee Youngju , Park Jisoo , Jung Jinyoung , Kim Tae Wan
Published: October 2022

In the Antarctic coast, ice shelves are rapidly thinning and retreating due to global warming. Basal melt water influences marine life, particularly the phytoplankton, which are directly affected by changes in physicochemical environments. However, there is limited in situ data over large areas in the Amundsen Sea, which is currently a hotspot for rapidly thinning ice shelves in West Antarctica. During the austral summer cruise of 2020, phytoplankton species abundance was investigated along the Amundsen Sea coast using an automated continuous observation instrument, the Imaging FlowCytobot. The phytoplankton community was dominated by Phaeocystis antarctica in most coastal waters of the Amundsen Sea, as previously reported; however, unexpected blooms of diatom Dactyliosolen tenuijunctus were observed throughout the Pine Island Bay region at a high dominance rate (∼90%) and abundance (>107 cells l−1). D. tenuijunctus is a weakly silicified diatom and its massive bloom in the water column has been rarely reported from the Antarctic Ocean. The dramatic difference in phytoplankton compositions between these adjacent polynyas probably indicates an unstable response of phytoplankton to ice melting conditions. They could play a different role in the marine food web and carbon flux compared to other diatoms and P. antarctica. Therefore, further research is warranted to predict the biological and biogeochemical impacts of future melting conditions.
Nonlinear stability and dynamic characteristics of hydropower station under fluctuation of downstream channel water level
Authors: Zhang Tianyu , Zhou Jianzhong , Huang Yan , Li Mengyao
Published: October 2022

This paper aims to investigate the hydropower station with downstream channel (HSDC) and reveal the effect of fluctuation from downstream channel on its stability and dynamic characteristics under load disturbance. Firstly, a novel mathematical model of HSDC considering the fluctuation of downstream channel water level is established. Then, the stability and dynamic characteristics of HSDC are analysed by Hopf bifurcation. Finally, it is revealed that the effect of the fluctuation from downstream channel water level on the stability and dynamic characteristics of hydropower station. The results indicate that the HSDC is a supercritical system, and the stable domain is on the lower left to the bifurcation line in K

p
-K

i
plane. Considering the fluctuation of downstream water level, the stable domain of HSDC is wider than the reference where downstream channel water level is constant. The fluctuation of downstream water level has two-sided effect on the dynamic characteristics of HSDC, which makes the attenuation rate lager but setting time longer. Moreover, the more obviously the downstream water level changes with flow, the stronger the influence on stability and dynamic characteristics of HSDC are. Therefore, it is safer to design hydropower station and select the parameters of governor according to constant water level in engineering.
AI-based approach to predict nozzle instability in Pelton turbine model test.
Authors: Andolfatto L , Morisod M , Dodier A , Gervais N
Published: October 2022

Over past experience on reduced scale physical models of Pelton turbines, it has been noticed that a few models exhibited disturbed performance curves over a given domain of speed factor and discharge factor under specific test head values, while the same performance curves were smooth at other test heads. Cross-checking of different model component combinations helped identify that those disturbances occur with specific nozzles independently from other model components. The experienced disturbances have been understood to be consequences of instabilities attributed to the nozzle.

Attempts to understand root causes and predict such instabilities with physics-based approaches first proved unsuccessful. The proposed research presents the analysis performed on an available model test results database to predict the occurrence of instability thanks to neural network classifiers, the so-called AI-based approach.

A model test campaign including a nozzle known to be subject to instabilities but not part of the database used to train the classifier has been designed and conducted. The agreement between the operating domain with predicted disturbance and the operating domain with measured disturbance is finally discussed.
Draft Tube Vortex Rope Analysis of a Pump-turbine Unit under Different Operating Conditions
Authors: He Qilian , Huang Xingxing , Bi Huili , Yang Mengqi , Yang Haixia , Wang Zhengwei
Published: October 2022

Pumped-storage power stations which can be flexibly adjusted for power generation and energy storage, are widely constructed worldwide. Pumped-storage units work under different operating conditions according to the demand of the power grid, and vortex ropes in the draft tube will appear and show different shapes under the partial load conditions of the unit in generation mode. The unstable pressure pulsation caused by the eccentric vortex ropes inside the draft tube may cause the vibration of the unit during operation. So it is important to study the characteristics of draft tube vortex ropes for flow and vibration analysis. In this paper, a three-dimensional model of the unit is fully established, and the unsteady calculations of 60 %, 86.7%, and 100 % load conditions in turbine mode are carried out by numerical calculations to obtain the flow characteristics of the full flow field. The pressure and velocity distributions, shapes of vortex rope in the draft tube under different load conditions are extracted from the CFD analyses, respectively. The pressure pulsations of different monitoring points set up inside the draft tube are evaluated in the time domain and frequency domain. The results show that the vortex rope in the draft tube is more obvious under small flow discharge, and the vortex rope itself is not sensitive to the selection of Q criterion threshold, but the vortex on the draft tube wall is greatly affected by the selection of the threshold. The influence of draft tube vortex ropes on the vibration of the pumped-storage unit is also discussed.
Development of blade element momentum (BEM) method for hydropower
Authors: Abedi H , Uribe C I , Fahlbeck J , Nilsson H
Published: October 2022

The BEM method is extensively used for analyzing the aerodynamic performance of wind turbines and marine propellers. It is computationally fast and is easily implemented while it can give fairly accurate results. Application of the BEM method to predict the forces acting on rotor blades for a model scale axial shaft-driven Counter-Rotating Pump-Turbine (CRPT) is investigated. Some modifications have been proposed to adopt the classical BEM method for CRPT machine and the results are validated against results from Computational Fluid Dynamics (CFD). The results display that the proposed modifications can improve the loading predicted by BEM. However, the improvements are more pronounced in pump mode rather than turbine mode.
Experimental investigation of small axial hydro-kinetic turbines
Authors: Bucur D M , Dunca G , Bunea F , Chihaia R A , Grecu I S , Mitruţ R
Published: October 2022

In the present paper the prototypes of small axial hydro-kinetic turbines are designed, built and tested in laboratory conditions in order to demonstrate their operability. The hydrokinetic turbine prototypes have a 0.2 m tip diameter, three blades and are meant to be used in a free water stream flowing with 1 m/s velocity. Two geometries of the turbine runner are studied in order to determine the best correlation between the water flow velocity and the cross-sectional area of the turbine. The 3D designs of the turbine are used for the prototype printing in order to obtain a lightweight compact assembly of reduced dimensions. The experimental measurements are conducted in a closed-loop laboratory setup, specially designed for hydro-kinetic turbines prototypes testing. The flow velocity, runner speed and shaft torque are measured. The aim of the experimental testing is to determine the characteristic parameters for the tested turbines as power coefficient and mechanical power output.
Sensitivity analysis of a swirling flow to the GEKO model
Authors: Kranenbarg J , Jonsson P P , Mulu B G , Cervantes M J
Published: October 2022

Accurate numerical models for hydraulic turbine applications are highly coveted. They must be able to correctly capture the swirling flow found at off-design operating conditions in the turbine draft tube. The GEKO model is a relatively fast and flexible eddy viscosity turbulence model with adjustable coefficients to tune the model to different flow scenarios. In this study, the GEKO model is tested on a swirling flow inside a diffusor similar to the flow conditions found at part-load operation of a propeller turbine. The diffusor investigated corresponds to the Porjus U9 draft tube cone section, including the runner cone. Results showed that the near-wall coefficient, with a value of 2, increased the wall shear stress and moved the separation point from the runner cone further downstream. Moreover, with a value of 0.7, the separation coefficient increased the eddy viscosity, which also moved the separation point from the runner cone further downstream. Both coefficients gave velocity profiles closer to experimental values and increased the swirl number at the outlet of the diffusor by up to 36.9 % compared to the GEKO default model. Overall, the near-wall coefficient with a value of 2 gave the best results. The GEKO model provides an opportunity to tweak numerical models to swirling flow.
Repeatability and operational setting of Newly Developed Francis Turbine Test Rig
Authors: Kumar Sandeep , Khullar Subodh , Gandhi Bhupendra K
Published: October 2022

A small-scale test rig is developed to study the flow phenomena during off-design operations of a Francis turbine. The test rig can be operated in open and closed loops for a maximum head and discharge of 8 meters and 0.055 m3/s. The runner outlet diameter is 200 mm and rotates at 500 rpm. However, the test rig is not a model turbine test rig as per IEC 600193. Therefore, the repeatability of parameters is the key to establishing reliability in measurement and performance estimation. This paper presents the repeatability results of the turbine unit performed at a constant head. A control system is developed in the LABVIEW program with PID (Proportional, Integral, and Derivative) to run the turbine at the constant head with variable discharge and constant discharge at the variable head.
Numerical simulation of cavitating flows: comparison between two-fluid and homogeneous approaches
Authors: Ferhat J , Leclercq C , Fortes-Patella R , Archer A , Mimouni S , Aiouaz T.
Published: October 2022

The paper presents a new two-phase flow approach to simulate unsteady cavitating flows. The study applied the in-house codeneptune_cfd, which allows two-fluid modelling of liquid-vapor flows [1]. The code solves the ensemble-averaged equations of mass, momentum and energy conservation for each phase (liquid and vapour) for a total of six conservation equations. The equations system requires closure laws for the interfacial terms that represent the mass, momentum and energy transfers occurring between the liquid and vapor phases. An original approach is implemented by using an energy-source term based on the difference between the local enthalpy and its saturation value. 2D and 3D simulations are carried out for a NACA 65−012 hydrofoil with an angle of attack of 6°, a cavity length of 40% of the hydrofoil chord and different flow velocities. The methodology to obtain the cavity length and the main frequency of its periodic behavior is presented. Then the numerical results are compared with those previously obtained by a homogeneous approach [2] and with the available experimental data [3]. The quantitative predictions of the hydrodynamic characteristics (i.e. cavitation sigma number, cavity length, shedding frequency and cavity shape) obtained from two-phase flow modeling appear in better accordance with experimental data.
Flow-induced vibration analysis of a prototype pump-turbine runner during turbine start-stop transient process
Authors: Zhou Xijun , Yin Xilong , Wang Wenlong , Huang Xingxing , Zhang Shaozheng , Bi Huili , Wang Zhengwei
Published: October 2022

Recently more start-stops per day of the pump-turbine units are required by the power grid for load regulation. During the turbine start-up and shut-down transient processes, the flow and pressure of the prototype pump-turbine change dramatically at different guide vane opening angles. The extremely unsteady pressure fluctuation in the flow passages can induce large deformation, stress concentration, and strong vibration of the pump-turbine runner. Therefore, it is significantly important to study the unsteady flow characteristics and the corresponding flow-Induced vibration of the runner during turbine start-up and shut-down transient process. In this investigation, a 3D model of the pump-turbine unit including the flow passages of the spiral casing, stay vane, guide vane, runner, and draft tube, crown chamber, band chamber, labyrinth seals, and balance pipes are constructed. The flow characteristics of the unit during the turbine start-up and shut-down process were analysed by coupling the 1D pipeline calculation and 3D turbine flow domain calculation. By mapping the pressure distribution of the fluid domain to the runner structure domain, the flow-induced dynamic behavior of the pump-turbine runner is performed, and the large deformation and stress concentration of the runner are investigated in detail. The flow-induced vibration results achieved are able to provide meaningful suggestions for safe operation and for improving the pump-turbine runner design.
Numerical investigation of the pressure-time method
Authors: Kalantar M , Jonsson P , Dunca G , Cervantes M J
Published: October 2022

The flow rate is a challenging hydrodynamic parameter to measure in order to determine turbine efficiency. The pressure-time method is a cost-effective alternative to estimate the flow rate. Its principle is based on the transformation of momentum into pressure during the deceleration of the liquid mass. Numerical simulations give valuable information to develop the method. One of the challenges in the numerical study of the pressure-time method is modelling the valve movement. In previous numerical studies, the dynamic mesh has been used for valve closure modelling. The dynamic mesh may lead to divergence, and re-meshing makes this method more time-consuming.

In this paper, the valve closure is modelled considering immersed solid method. The results’ sensitivity is studied by different time-step, grid, and boundary conditions at the inlet. It is shown that the result is independent of the time-step size smaller than 0.1 ms. Furthermore, it is observed that only the opening boundary condition at the inlet can predict the oscillation of variables during water hammer phenomenon. Then, the numerical results are validated with experimental data. Finally, the pressure-time method is applied to the data, and the flow rate is estimated.
Numerical fatigue damage analysis of a variable speed Francis pump-turbine during start-up in generating mode
Authors: Biner Daniel , Alligné Sebastien , Nicolet Christophe , Dujic Drazen , Münch-Alligné Cécile
Published: October 2022

Variable speed hydropower units offer a large spectrum of grid regulation services and may therefore contribute to the stability of future power supply systems. Full Size Frequency Converters (FSFC) already found real world application in Pumped Storage Hydropower Plants up to a rated power of 100 MW and are even considered scalable up to a few hundred MW. Apart from the extension of the power range and grid regulation capacities, the FSFC technology also provides new control possibilities during transient operations such as start-up in generating mode. Thus, harsh conditions with damaging impact on the hydromechanical components may be avoided by tuning the operating point trajectory in the start-up phase. In this paper, runner fatigue damage during start-up in generating mode of a 5 MW variable speed Francis pump-turbine prototype equipped with a FSFC is numerically analyzed. The fixed speed solution is compared to a variable speed solution following a BEP tracking control strategy. 1D hydraulic transient simulations provide boundary conditions for detailed 3-D CFD/FEA simulations. Full and reduced numerical domains are used and compared. The overall outcome of the present numerical study indicates an important reduction of partial damages using variable speed drives for turbine start-up manoeuvres.