bluuebunny/crossref_metadata_2025 huggingface dataset:
Incorporating interface permeability into the diffusion MRI signal representation while using impermeable Laplace eigenfunctions
Authors: Yang Zheyi , Fang Chengran , Li Jing-Rebecca
Published: August 2023

Objective. The complex-valued transverse magnetization due to diffusion-encoding magnetic field gradients acting on a permeable medium can be modeled by the Bloch–Torrey partial differential equation. The diffusion magnetic resonance imaging (MRI) signal has a representation in the basis of the Laplace eigenfunctions of the medium. However, in order to estimate the permeability coefficient from diffusion MRI data, it is desirable that the forward solution can be calculated efficiently for many values of permeability. Approach. In this paper we propose a new formulation of the permeable diffusion MRI signal representation in the basis of the Laplace eigenfunctions of the same medium where the interfaces are made impermeable. Main results. We proved the theoretical equivalence between our new formulation and the original formulation in the case that the full eigendecomposition is used. We validated our method numerically and showed promising numerical results when a partial eigendecomposition is used. Two diffusion MRI sequences were used to illustrate the numerical validity of our new method. Significance. Our approach means that the same basis (the impermeable set) can be used for all permeability values, which reduces the computational time significantly, enabling the study of the effects of the permeability coefficient on the diffusion MRI signal in the future.
Synthesis of possible room temperature superconductor LK-99: Pb9Cu(PO4)6O
Authors: Kumar Kapil , Karn N K , Awana V P S
Published: August 2023

The quest for room temperature superconductors has been teasing scientists and physicists, since its inception in 1911 itself. Several assertions have already been made about room temperature superconductivity, but have never been verified or reproduced across the labs. The cuprates were the earliest high transition temperature (T
c) superconductors, and it seems that copper has done the magic once again. In July 2023, a Korean group synthesized a lead apatite based compound LK-99, showing a T
c of above 400 K (Lee et al 2023 arXiv: 2307.12008; 2023 arXiv: 2307.12037; Lee et al 2023 J. Korean Cryst. Growth Cryst.
33 61). The signatures of superconductivity in the compound are very promising, in terms of resistivity (ρ = 0) and diamagnetism at T
c. Although, the heat capacity (C
p) did not show the obvious transition at T
c. Inspired by the interesting claims of the above room temperature superconductivity in LK-99, in this article, we report the synthesis of polycrystalline samples of LK-99, by following the same heat treatment as reported in Lee et al (2023 arXiv: 2307.12008; 2023 arXiv: 2307.12037) using a two-step precursor method. The phase is confirmed through x-ray diffraction measurements, performed after each heat treatment. The room temperature diamagnetism is not evidenced by the levitation of a permanent magnet over the sample or vice versa. The isothermal magnetization measurement at 280 K shows that as synthesized sample of LK-99 is paramagnetic. Further measurements for the confirmation of bulk superconductivity in variously synthesized samples are underway. Our results on the present LK-99 sample, synthesized at 925 °C, as of now do not confirm the appearance of bulk superconductivity at room temperature. Further studies with different heat treatments are underway.
Effect of spin-orbit coupling within the spin-filter layer on the tunnel magneto-resistance in spin-filter magnetic tunnel junctions
Authors: Mehrparvar Dariush , Ghobadi Nader , Daqiq Reza
Published: August 2023

The tunnel magneto-resistance ratio is investigated for spin-filter magnetic tunnel junctions in the presence of spin–orbit coupling within a spin-filter layer. The non-equilibrium Green’s function formalism is utilized to calculate the transmission function in the linear-response limit. The results show that a larger tunnel magneto-resistance is achieved for spin-filter magnetic tunnel junctions compared to that for conventional magnetic tunnel junctions due to the existence of a spin-filter layer. Therefore, the current findings can be introduced new routes to improve the field of spintronics.
Effects of vacancies and doping on the sensitivity of arsenene/graphene heterostructure toward NH3
Authors: Ye Shiyang , Zhou Qingxiao , Ju Weiwei , Liu Yijia , Li Pengcheng , Cai Sitong , Wang Yajing
Published: August 2023

Using the first-principle calculation method, this study analyzed the geometrical properties, electron transfer, magnetic properties, and recovery time of NH3 molecules of pristine, vacancy-defected, and doped (N, Al, S, Ti, Cr, Co) arsenene/graphene (As/G) heterostructures. Introducing vacancy defects did not enhance the activity of the As/G heterostructure. However, the adsorption ability of the structure doped with N, Al, Cr, and Co atoms on NH3 molecules was enhanced. Furthermore, the magnetic state of As/G changed as a result of Cr doping. The improvements in the absorption energy and recovery time indicated that Cr-doped As/G heterostructures are suitable for fabricating reusable gas sensors for detecting NH3 molecules.
Inverse design of electromagnetically induced transparency(EIT) metasurface based on deep convolutional generative adversarial network
Authors: Zhu Lei , Zhang Cong , Dong Liang , Rong Miao Xin , Gong Jin Yue , Meng Fan-Yi
Published: August 2023

With the increasing complexity of electromagnetically induced transparency (EIT) metasurface structure and the limitations of traditional optimization methods, there is an urgent need for an advanced design approach to accelerate the design of complex EIT metasurface. In this study, we propose an improved deep learning model based on deep convolutional generative adversarial network (DCGAN) to simplify the design process of EIT metasurface. The proposed model enables the optimization of metasurface with eight structural parameters, obtaining single-band or dual-band EIT effects for y polarization incidence. The training of the network model achieves convergence with a mean square error (MSE) of 0.2 for the generator and 0.41 for the discriminator. The average errors between the predicted results and the target parameters are within 0.6 μm. The relative spectral error (RSE) is utilized to quantify the deviation between the simulated spectra obtained from the predicted structures and the target spectra, exhibiting a minimum RSE of 6.26%. Furthermore, comparisons between the proposed model and two other convolutional neural networks validate the superior prediction capability and higher accuracy of our proposed model.
Research on accelerated coding absorber design with deep learning
Authors: Tian Feng , Zhang Shiao , Cao Miao , Huang Xiaojun
Published: August 2023

The traditional design of metamaterials requires a large amount of prior knowledge in electromagnetism and is time-consuming and labour-intensive, but these challenges can be addressed by using trained neural networks to accelerate the forward design process. However, when it comes to coded absorbers, there is no clear ‘guidance manual’ on which neural network is most effective for this task. In this paper, three basic neural networks (full connection, one-dimensional convolution and two-dimensional convolution) are designed considering the apparent pattern and structural parameters of the coded absorber, trained under the same conditions, and evaluated for performance.The two-dimensional convolutional neural network achieved the highest accuracy on the test set, with an average accuracy of 92.37% and 70.3% of groups with accuracy greater than 95%. These results indicate that trained neural networks have great potential to approximate the functionality of traditional electromagnetic simulation software, and the two-dimensional convolutional neural network is the best choice for accelerating the forward design of coded absorbers.
Structure, optical transition analysis and magnetic study of lanthanide based metal-organic framework: holmium bi-tartrate trihydrate
Authors: Dar Faheem A , Want Basharat
Published: August 2023

This study presents the hydrothermal synthesis of holmium bi-tartrate trihydrate single crystals. The crystal structure and morphology were determined using single crystal x-ray analysis and field emission scanning electron microscopy, respectively. Fourier transform infrared spectroscopy was employed to identify the ligand phase. The thermal stability was assessed through differential scanning calorimetry. The effect of ligand on the incorporated paramagnetic center is discerned by reckoning the magnetic moment of the same. Judd-Ofelt theory was utilized to analyze optical transitions and calculate excited state properties. The complex exhibited violet and red emissions, attributed to ligand-based and metal-based luminescence , respectively. The absence of antenna effect was due to a significant energy gap between the resonance energy state, 5
S
2 of the Ho(III) ion and the triplet state of the coordinated tartrate ligand. The synthesized MOF's prolonged radiative lifetime holds promise for laser technologies and environmental monitoring applications.
Transient properties of grazing ecosystem driven by Lévy noise and Gaussian noise
Authors: Mi Lina , Guo Yongfeng , Ding Jiaxin
Published: August 2023

This paper explores how Lévy noise and Gaussian noise affect the ecological grazing system by using the fourth-order Runge–Kutta method to simulate dynamic system and the Janicki-Weron algorithm to produce Lévy noise. Two deterministic quantities, the mean first passage time (MFPT) and the probability density function (PDF) of the first passage time (FPT), are utilized to explore the transient properties of grazing ecosystem. Our research results show that: (i) The transitions between two alternative stable states can be induced by the Gaussian noise intensity, Lévy noise intensity, Lévy stability index and Lévy skewness parameter. (ii) A higher Lévy noise intensity and a larger Lévy stability index or Lévy skewness parameter make the MFPT from desert state to sustainable vegetated state shorter; a higher Gaussian noise intensity makes it longer, which indicates that increased Lévy noise intensity can mitigate ecosystem degradation; increased Gaussian noise intensity will lead to desertification of vegetation. (iii) For larger Lévy noise intensity, the MFPT from sustainable vegetated state to desert state as a function of Gaussian noise intensity exhibits one maximum value when it transformation from the sustainable vegetated state to the desert state, the noise enhanced stability (NES) phenomena of grazing ecosystems are observed.
OpenFOAM modeling of beryllium melt motion and splashing from first wall in ITER
Authors: Zhang Cheng , Miloshevsky Gennady
Published: August 2023

Beryllium (Be) is a material which will be used as a plasma facing component in ITER due to its unique properties of high thermal conductivity, low density, and high strength. However, under extreme conditions of high temperature and pressure, Be can melt at the surface of tiles and molten droplets can be ejected into the reactor leading to disruption of fusion plasma. The pressure, mass density, velocity of Be vapor, and variations of temperature at the melt layer interface can influence the splashing of Be melt. The Computational Fluid Dynamics (CFD) model based on the OpenFOAM toolbox, a free open source CFD software package, was developed to treat the coupled flow of liquid Be metal and its vapor. The vapor-melt interface is modeled using the volume of fluid (VOF) approach implemented in the interCondensatingEvaporatingFoam solver that solves the continuity, momentum, heat conduction, and VOF equations. This CFD model is capable to predict the hydrodynamic effects of Be vapor on the melt layer motion, splashing, non-linear growth of melt waves, and ejection of molten droplets. The modeling accounts for the effects of thermal, viscous, gravitational, and surface tension forces at the vapor-melt interface. In this research, we used the interCondensatingEvaporatingFoam solver to simulate the effects of Be phase change and the development of melt motion with the droplets ejected from the surface. The CFD model accounts for inter-phase change between Be liquid and Be vapor. The evaporation model was validated against the Stefan phase-change problems. The influence of heat and mass transfer across the vapor-melt interface on melt layer stability is also investigated. The results provide an understanding of how the rate of phase change affects the development of melt structures and waves at the vapor-melt interface.
Asymptotic steady state of a dissipative long-range interacting spin system at finite temperature
Authors: Sadiek Gehad , Almalki Samaher
Published: August 2023

Many of the recently developed quantum systems that are considered promising candidates for the underlying technology of quantum computing enjoy long-range interaction, which is even tunable in some of them. Most of these systems can be described using the Heisenberg spin model to represent their interaction with the same system or a different one in hybrid structures. We consider here a finite two-dimensional spin system with a varying spin-spin long-range interaction under the effect of an external uniform magnetic field. We investigate the dynamics of the system and its asymptotic behavior at different degrees of anisotropy and interaction range under coupling to a thermal dissipative environment, starting from different initial states. We show that the system spin state and bipartite entanglement evolve in time to reach asymptotic values that are enhanced significantly by the degree of anisotropy and interaction range, whereas the thermal dissipative environment degrades the entanglement asymptotic equilibrium value as the temperature increases. Interestingly, while the robustness of the spin system against the environment’s thermal dissipative effects increases with the interaction range and degree of anisotropy, the entanglement between the far sites on the lattice shows its highest resilience in the partially anisotropic system, which might be attributed to a critical behavior taking place in the system. While the system’s early dynamics varies significantly depending on the initial state, the asymptotic equilibrium value is found to be completely independent.
Study of antiprotons as drivers in inertial confinement fusion by fast ignition method
Authors: Azizi Maryam , Khanbabaei Babak
Published: August 2023

Inertial confinement fusion is a promising approach to achieve controlled nuclear fusion for clean and abundant energy production. One of the key challenges in Inertial confinement fusion is achieving efficient ignition of the fusion fuel. Fast ignition offers a potential solution to this challenge by using an ultra-high intensity laser or a charged particle beam to directly ignite a pre-compressed fusion fuel. In this manuscript, we propose an approach for fast ignition in ICF, utilizing an antiproton beam to drive ignition in a deuteron-tritium fuel with a uranium-238 seed. The use of antiproton beams in Inertial confinement fusion offers unique advantages, including their ability to deposit energy deeply into the fuel, leading to enhanced energy coupling and heating. The addition of uranium-238 as a seed material in the fuel can further improve ignition conditions by enhancing energy deposition and facilitating ignition reactions. We present detailed simulations and analyses to demonstrate the feasibility and potential benefits of this approach. We investigate the effects of antiproton beam parameters, such as energy, intensity, and pulse duration, on ignition conditions, as well as the impact of uranium-238 seed concentration and distribution in the fuel. Our results show that fast ignition driven by an antiproton beam in DT with uranium-238 seed has the potential to significantly improve ignition performance in Inertial confinement fusion, leading to enhanced energy output and higher gain. The use of antiproton beams allows for efficient energy deposition and heating of the fuel, while the inclusion of uranium-238 seed promotes ignition reactions and improves ignition conditions. This concept presents a promising pathway towards achieving practical and efficient ignition in Inertial confinement fusion, and could pave the way for next-generation fusion power plants.
Reviewing the prospect of fermion triplets as dark matter and source of baryon asymmetry in non-standard cosmology
Authors: Biswas Anirban , Chakraborty Mainak , Khan Sarif
Published: August 2023

Indirect searches of Dark Matter (DM), in conjugation with 'missing track searches' at the collider seem to confine SU(2)
L
fermion triplet DM (FTDM) mass within a narrow range around 1 TeV. The canonical picture of the pure FTDM is in tension since it is under-abundant for the said mass range. Several preceding studies have reported that an extra species (ϕ), redshifts faster than the radiation (∼ a
(4+n) where n > 0), leads to a faster expanding early Universe by dominating in the energy density with an enhanced Hubble parameter. This has the potential to revive the under-abundant FTDM (ℤ2 odd, lightest generation) by causing freeze-out earlier without modifying the interaction strength between DM and thermal bath. On the other hand, although the CP asymmetry produced due to the decay of ℤ2 even heavier generations of the triplet remains unaffected, its evolution is greatly affected by the non-standard cosmology. It has been observed through numerical estimations that the minimum mass of the triplet, required to produce sufficient baryon asymmetry of the Universe (BAU), can be lowered up to two orders (compared to the standard cosmology) in this fast expansion scenario. The non-standard parameters n and Tr
(a reference temperature below which radiation dominance prevails), which simultaneously control DM abundance as well as the frozen value of BAU, are tightly constrained from the observed experimental values. We have found that n is strictly bounded within the interval 0.4 ≲ n ≲ 1.8 where the upper bound is imposed by the BAU constraint whereas the lower bound arises to satisfy the correct DM abundance. It has been noticed that the restriction on Tr
is not so stringent as it can vary from sub GeV to a few tens of GeV.
Hunting the stochastic gravitational wave background in pulsar timing array cross correlations through theoretical uncertainty
Authors: Bernardo Reginald Christian , Ng Kin-Wang
Published: August 2023

Incredible progress on the theoretical uncertainty of the spatial correlations of the stochastic gravitational wave (GW) background were recently made. However, it remains to realize the impact of this theoretical uncertainty on PTA cross correlations analysis. This paper pushes forward in this direction, as a proof-of-principle: showing the potential role that theoretical uncertainty has on unburying the stochastic GW background signal in noisy PTA cross correlation measurements. We consider both a mock data set and the noise-marginalized 12.5 years NANOGrav spatial correlation measurements, and find optimistic conclusions regardless of the physical content of the GW background and the nature of the noise in the data. Very briefly, we show through various cases a modest result that looking out for a stochastic signal is better when two of its moments are utilized. Or, in terms of GWs, we show that the theoretical uncertainty can play a substantial role in the hunt for the stochastic GW background.
Inflation caused by a potential valley with 𝖢𝖯 violation
Authors: Suematsu Daijiro
Published: August 2023

We propose an inflation scenario caused by an inflaton identified with a potential
valley which brings about CP violation in the standard model (SM).
If singlet scalars have nonminimal couplings with the Ricci scalar in a suitable way,
favorable inflation could be derived through the potential
valley composed of such scalars.
We study dynamics of the scalars during and after the inflation, which suggests
that it could be described as a single field inflation approximately.
If these scalars make suitable ingredients of the SM couple with
vectorlike fermions and
right-handed neutrinos, a CKM phase could be induced and also leptogenesis
could occur successfully even at a rather low reheating temperature.
Peaky production of light dark photon dark matter
Authors: Nakai Yuichiro , Namba Ryo , Obata Ippei
Published: August 2023

We explore a mechanism to produce a light dark photon dark matter through a coupling between
the dark photon field and a spectator scalar field which plays no role in
the inflationary expansion of the Universe while rolling down its potential during the inflation.
The motion of the spectator field efficiently produces dark photons with large wavelengths
which become non-relativistic before the time of matter-radiation equality.
The spectrum of the wavelengths is peaky
so that the constraint from the isocurvature perturbation can be evaded.
The correct relic abundance is then achieved over a wide range of the dark photon mass down to 10-13 eV.
Our mechanism favors high-scale inflation models which can be tested in future observations.
Furthermore, fluctuations of the dark photon field during inflation produce gravitational waves
detectable at future space-based interferometers and/or pulsar timing array experiments.
The AGN Feedback in Compact Galaxies: On the Impact of a More Massive Central Black Hole
Authors: Di Yihuan , Yuan Feng , Ji Suoqing
Published: August 2023

We conduct high-resolution hydrodynamical simulations using the MACER framework to investigate the interplay between the interstellar medium, active galactic nuclei (AGN) feedback and black hole (BH) feeding in a massive compact galaxy, with an emphasis on the impact of different central BH masses. We find that with a more massive central BH, high-speed outflows are more prominent, and the gas fraction in the compact galaxy is reduced. Due to the lower gas density and higher gas temperature, the compact galaxy with a more massive BH (MAS galaxy) remains predominantly single-phase with the cooling time t
cool ≳ 100t
ff. In contrast, the compact galaxy with the reference BH mass (REF galaxy) maintains a higher gas fraction with a shorter cooling time, slightly more multiphase gas and less prominent outflows. We further demonstrate that the difference in gas thermal states and kinematics is caused by the stronger AGN feedback in the compact galaxy with a more massive BH, where the AGN wind power is twice as much as that with the reference BH. Since the AGN feedback efficiently suppresses the inflow rate and the BH feeding rate, the BH mass growth is significant in neither the compact galaxy with the reference BH nor that with the more massive BH, only by 24% and 11% of the initial BH mass, respectively, over the entire evolution time of 10 Gyr. We thus posit that without ex situ mass supply from mergers, the massive BHs in compact galaxies cannot grow significantly via gas accretion during the late phase, but might have already formed by the end of the rapid early phase of galaxy formation.
Motion analysis and power output optimization design of wave energy device
Authors: Chen Lijie , Liu Xiao , Yan Weimin , Shi Guoyong , Gao Zhibing , Huang Zexian
Published: August 2023

Wave energy is an essential marine renewable energy. Improving the energy conversion efficiency of wave energy devices is the key aspect of wave energy utilization research. This paper deals with the movement status of the wave energy device and its power optimization. Depending on Newton’s second law, the second-order ordinary differential equation model is established for the float and oscillator respectively. According to whether the damping coefficient is constant, the pending method coefficient is utilized to solve the general second-order solution ordinary differential equation model, and the drooping displacement and velocity graphs under different damping coefficients are obtained. The analysis shows that the oscillating wave energy device improved by the second-order ordinary differential equation model could become stable within a very short time. The motion displacement and velocity of the wave energy device at five random moments were taken to check the accuracy of the model, and the results show that the model has an excellent promoting effect on the motion state of the wave energy device at sea and reduces the depletion of the device in terms of accuracy of motion displacement and velocity.
Temporal and Spatial Variation Characteristics of Hydrodynamic Forces in Urban Shallow Lakes
Authors: Xiao Tingting , Yu Can , Zhang Kui , Zhang Ya , Zhang Qin
Published: August 2023

To study the temporal and spatial variation characteristics of hydrodynamic forces in Rule Lake, a two-dimensional mathematical model of shallow water lake was established based on MIKE 21, and the flow field characteristics of Rule Lake under the action of topography, wind field and inflow were simulated and analyzed. The results show that the spatial and temporal heterogeneity of hydrodynamics in the Rule Lake area is obvious, the velocity in the lake area presents a gradient change characteristic of high in the west and low in the east, and the velocity in the middle of the lake area is greater than that in the bends of shorelines on both sides of the lake area; Under the driving of wind field, there is a reverse circulation area in the lake area. The existence of the circulation area can disturb the dead water area at the shoreline bend and improve the local water mobility; The flow velocity in summer and autumn is slightly higher than that in spring and winter. It is suggested that during the operation and maintenance period, attention should be paid to the fluidity of the water body in the southwest of the lake area, the change in water quality and the timely removal of floating garbage on the water surface.
Hydrodynamic Performance of Soft Robotic Fish Actuated by Ionic Polymer-Metal Composite Pectoral Caudal Fin
Authors: Wu Jinxian , Chen Kun , Zhang Tian , Fu Yong
Published: August 2023

Soft robotic fish has a lot of benefits. This paper aims to create a robotic fish with a soft pectoral caudal fin which was powered by IPMC material. The soft robotic fish’s hydrodynamic performance during straight swimming is numerically computed using the overset grid approach. Compared with the soft tail fin driven with a driving frequency of 0.05 Hz and those driven together with three soft pectoral fins with different driving frequencies and amplitude, the hydrodynamic coefficients and pressure of the bionic robotic fish are analyzed. We can find the regions of distinct positive and negative pressure during the IPMC soft caudal fin flapping. And the forward pressure component provides forward propulsion for the bionic fish. The greater the flapping frequency of the IPMC soft pectoral fin is, the smaller the amplitude is, and the greater the drag force receives. It is concluded that while the driving frequency of soft pectoral fins is 0.05 Hz, the amplitude is 5.64 mm, and the soft pectoral fin driving effect is good. Further research into how soft pectoral caudal fin frequency and amplitude affect the hydrodynamic capabilities of bionic fish was also made.
The Influence of Different Diving Angles on the Hydrodynamic Noise of Submarine Enclosures
Authors: Lv Bangjun , Chen Yonghong
Published: August 2023

The hull is an important component of the submarine structure, and it is also one of the factors that affect the concealment of the submarine. By using the finite element method, a submarine model was established to analyze the hydrodynamic noise at the contact points between the front and rear of the hull and the hull under different diving angles. The results show that when the diving angle is about 10°, the hydrodynamic noise at the front and rear positions of the enclosure is relatively small. The research results provide a reference for ensuring the stealth operation conditions of submarines and have practical significance for improving the stealth of submarines.
The effect of seasonal variation of medium viscosity on centrifugal desanding in shaft seal water system of suction dredger: Numerical simulation and mechanism study
Authors: Tan Shaohuan , Wang Bingjie , Bai Zhishan
Published: August 2023

As a lubrication medium, the shaft-seal water often carries substantial sand particles in the cutter suction dredger, causing severe wear and tear of the internal components of the slurry pump. It has been proved that the shaft seal water system could be optimized by introducing a hydro cyclone to prolong the service life of the slurry pump. However, it was found that the seasonal variation of water viscosity would produce an obvious effect on the centrifugal separation of sand particles. Therefore, in this study, the influence of seasonal viscosity change on the flow field characteristics and sand particle separation was systematically studied by computational fluid dynamics (CFD). The simulation results showed that the fluid and pressure field in hydro cyclone has good symmetry under different viscosity. While with the increase of viscosity, the fluid resistance coefficient increases, resulting in a downward trend of turbulent kinetic energy and an upward trend of negative pressure zone, which is not conducive to sand particle separation. Moreover, to verify the consistency between simulation and actual industry, the grade efficiency of sand particles was studied and discussed. The average particle size of sand could be reduced from 37.8 μm to 8.1 μm, and the separation efficiency could reach 90% under better suitable dredging conditions (Salinity: 34%, Temperature: 20 °C). Further, the experimental and industrial results showed that the fish hook effect inevitably existed in practice due to the entrainment of coarse particles. This study would provide theoretical support for the subsequent optimization of the shaft seal water system.
Study on Influence of Flow Inertia of Pressure Pipe on Critical Stable Sectional Area of Surge Tank
Authors: Li Gaohui , Yang Shaojia , Cui Weijie , Xue Kaizhen
Published: August 2023

In the process of calculating the analytical formula of the critical stable section area of the surge tank, the influence of the time constant of the flow inertia in the pressure pipe is ignored by all the formulas, including Thoma’s formula and the E/N correction formula. In this paper, a fifth-order analytical model of a hydraulic turbine generator set with a surge tank is established after considering the inertia of the flow in the pressure pipe. Then, the relationship between the flow inertia in the pressure pipe and the critical stable section area of the surge tank is systematically analyzed by using this fifth-order analytical model. Finally, combined with a typical hydropower station, the influence of flow inertia of the pressure pipe on the stable section of the surge tank caused by the changes of head, flow and the length of the pressure channel is analyzed.
Design and Seakeeping Performance of a Shallow-sea Surface Litter Collection Device
Authors: Zhang Xiangyu , Zhang Sheng , Lei Yu , Zheng Xiangyuan
Published: August 2023

In recent years, the pollution of ecological waters, especially the litter floating on the ocean surface, has emerged as a pressing economic, political, and environmental concern of the international society. The development of a widely applicable, safe, reliable and cost-saving marine surface litter collection device has drawn considerable attention. In this paper, an innovative shallow-sea floating surface litter collection device (later referred to as SFSLCD) is proposed first, including its concept design, dimensions and key parameters, working scheme, and mooring system. Second, the hydrostatic and hydrodynamic characteristics of SFSLCD are derived through numerical modeling. Last, the safety of SFSLCD in normal and rough sea states is validated in terms of its good seakeeping performance using the coastal condition of Dapeng Bay, Shenzhen, China. It is proven that this litter collection device equipped with photovoltaic panels to supply power can operate in waters of depth between 5 and 15 m in seas, rivers and lakes.
Unsteady Simulation and Mode Analysis of Disturbed Cylinder Flow
Authors: Gong Ziqiao
Published: August 2023

The unsteady simulation of cylinder flow with inlet velocity disturbance is simulated and compared with that without disturbance. POD is adopted to analyze and capture the dominant modes of the vortex street in the cylinder wake. The results show that the POD method is efficient in reconstructing the flow field. When the inlet velocity disturbance exists, the number of modes required to reconstruct the flow field accurately is almost unchanged, but the energy proportion of each mode changes. The larger the disturbance frequency is, the smaller the shape and vorticity magnitude of the vortex street is, and the slower the generation speed is. If the frequency deviates too much from the original frequency of the flow field, the effect of inlet velocity disturbance will be shielded.
Numerical simulation study on noise pollution of the solenoid valve in pressure water-air system of pumped storage power station
Authors: Long Zhe , Shu Lingfeng , Li Chengjun , Zheng Yingxia , Huang Jingqian
Published: August 2023

To explore the noise problem of the solenoid valve in the pressurized water-air system of a pumped storage power station when operating under the discharge condition, a full-channel unsteady numerical simulation was carried out on the medium-pressure gas storage tank and its discharge facilities. Firstly, the large eddy simulation (LES) method was used to calculate the sound source, and then the finite element method (FEM) was used to solve the internal sound field. The flow field and sound field distribution of the solenoid valve in the pressure water-air system are analyzed in detail. Then the near-field noise analysis method is used to trace the source of the noise problem of the solenoid valve. Finally, according to the noise intensity distribution, the location of the noise source and the noise mechanism is clarified, which provides the basis for the selection of a technical route for the subsequent optimization design of the solenoid valve in the exhaust pressure water system.
Study on Hydrodynamics of Fish-Friendly Open-Channel Flow
Authors: Jiang Dingguo , Lu Peng , Gao Huan , Yang Ji
Published: August 2023

To elucidate the hydrodynamic characteristics of a fish-friendly open channel, a three-dimensional numerical hydrodynamic model is constructed in this study employing the Large-eddy Simulation (LES) technique. The reliability of this numerical model is thoroughly validated by incorporating periodic boundaries in the flow direction, allowing for the recurrent development of water flow within the computational domain and utilizing experimental data from a flume. The results demonstrate that the fish-friendly channel is partitioned into a high-velocity mainstream zone and a low-velocity habitat zone. The time-averaged flow velocity in the mainstream zone is approximately 2.0 times the cross-sectional average flow velocity. In the low-velocity habitat zone, the average hourly flow velocity and turbulence are at a relatively low level, rendering the zone suitable for fish habitation and the incubation of adhesive fish eggs. A significant vortex structure is present in the mixing layer at the junction of the main flow area and the habitat area, which not only markedly increases the turbulence intensity but also serves as the primary driver of momentum exchange within the open channel.
Modelling Study of EMBr Effect on Interface Fluctuation and Melt Flow in a Thin Slab Mould
Authors: Lv Xin-sheng , Xu Lin , Liu Cong , Guan Duo-jiao , Pei Qun-wu , Xu He-yuan
Published: August 2023

Electromagnetic brakes (EMBrs) are regularly used in continuous casting to control interface fluctuations in a mould. In the research, to appraise the damping effect of EMBr technique, namely EMBr-ruler technique, the influence of magnetic field intensity on behaviours of melt flow and interface fluctuation in a Compact Strip Production (CSP) thin slab funnel mould are numerically simulated. The numerical results illustrate that the existence of the EMBr-ruler technique is conducive to inhibiting the impact of the ascending circulation on the interface in the CSP funnel mould. With the gradual enhancement of magnetic intensity, the service efficiency of the EMBr-ruler on the fluctuation of two-phase steel/slag interface is enhanced. For instance, by applying a magnetic induction intensity of 0.5 T, the maximum fluctuation height of two-phase steel/slag interface is decreased to 6.4 mm. This can well prevent surface defects, such as slag entrapment.
Optimization of multi-objective integrated energy efficient utilization based on the digital twin
Authors: Zhao Lin , Hou Yixin , Jiang Haiwei , Liu Guangshuo , Yang Fangyuan
Published: August 2023

To address the effect of non-determinacy on power system scheduling patterns, a comprehensive multipurpose optimization scheduling method is proposed. First, region mathematical methods are used to describe many uncertain factors, such as unit performance, connectors, prices, user response, and changes in the power system. Second, considering the differences in production methods and conversions of high-quality intensity, the built-in electrical system scheduling, multi-objective gold standard scheduling methods to align built-in power equipment under multiple uncertainties. Finally, based on the multipurpose linear programming method, the most effective scheduling model range of forced equipment is integrated. Many symptoms can occur under uncertain conditions. The numerical results indicate that the proposed multipurpose scheduling model can meet most needs, improve the economic and energy efficiency of the machine, and enhance the system’s ability to cope with uncertainties.
Application of digital intelligent construction in the field of water conservancy and hydropower engineering
Authors: Liu Rongrong , Luo Zuliang
Published: August 2023

The application of intelligent construction technology is gradually penetrating the field of water conservancy and hydropower engineering. This article systematically summarizes the application research of intelligent construction in water conservancy and hydropower engineering, including intelligent design, intelligent construction, and intelligent monitoring. In terms of intelligent design, the use of BIM technology to establish three-dimensional modeling of water conservancy and hydropower projects can achieve collaboration, communication, and management of multiple aspects of information and improve design efficiency and quality in terms of intelligent construction. The use of robot technology and automation equipment can achieve construction automation and digitization, reduce human errors and safety risks, and improve construction efficiency and quality. In terms of intelligent monitoring, real-time monitoring, and intelligent management of water conservancy and hydropower projects can be achieved through the Internet of Things and big data technology, timely detection of problems, and early warning processing, ensuring the safe and stable operation of the project. A sound management system is established with standard specifications to promote the widespread application of intelligent construction in the field of water conservancy and hydropower engineering.
Multi-Objective Location Method for Small Capacity Distributed Generation under Timing Characteristics
Authors: Tang Yi , Wu Hanjiang , Wu Kehan , Chen Cai , Ma Luyao , Huang Jie
Published: August 2023

The conventional multi-objective location method of distributed generation mainly uses the static stability index to determine the load of distributed generation, which is vulnerable to the impact of load timing characteristics, resulting in a high active power loss of different nodes. Therefore, it is necessary to design the multi-objective location method of small-capacity distributed power sources based on the timing characteristics. That is, the multi-objective location algorithm of small capacity distributed generation is designed based on the multi-objective function, and the multi-objective location model of small capacity distributed generation is constructed according to the timing characteristics to achieve the multi-objective location of small capacity distributed generation. The experimental results show that the designed multi-objective location method has low active power loss, which proves that the designed location method has good location effect, energy saving and certain application value, and has made a certain contribution to saving the comprehensive operation cost of distributed power generation.
Experimental study of a hydraulic model of the side inlet and outlet of a pumped storage power station
Authors: Li Gaohui , Lu Ting , Chen Funan , Yang Shaojia , Jiang Lei , Zhen Haolei
Published: August 2023

Inlets/outlets have bi-directional characteristics and complex structures, which have important implications for practical operational safety and efficiency. In this paper, the hydraulic characteristics of the lateral inlet/outlet of a pumped storage power station are studied by means of model tests. The flow velocity distribution at the leading edge of the inlet/outlet orifice and the barrage section is more uniform, and the flow velocity distribution at the left, middle, and right of each orifice is the same. The formation of swirl is related to the relative submergence depth s/d and the Froude number Fr, with the inlet/outlet Fr< 0.23, relative submergence depth s/d> 0.5 and it has no harmful eddies.
The Motion Response of Trailing Suction Hopper Dredger under the Influence of Swell
Authors: Zhu Ping , Wang Sheng , Lyu Hanghang , Hao Yuchi
Published: August 2023

With the continuous development of the dredging business to overseas markets, dredging ships are faced with a more and more complex hydrodynamic environment. Swell with long wave periods has a great impact on the adaptability of ship operations. Focused on the Trailing Suction Hopper Dredger (TSHD), this paper studied the motion response characteristics of the TSHD under the influence of swell. The result shows that the motion response of the TSHD is severely affected by swell. The amplitude of the ship motion response increases with the increase of wave height. When subjected to the transverse swell with the 90° wave direction, both the heave and roll response amplitude of TSHD is the most significant. While under the influence of swell with the 0° wave direction, the TSHD only pitches violently. The results can guide the suitability assessment of dredging ships in the swell area.
Modeling and Analysis of Aluminum Cable Joints in Steady State for New Energy Stations
Authors: Gao Zhao , Wang Le , Zhang Haoran , Li Boyi , Fan Lijun
Published: August 2023

Compared with copper cables, aluminum cables have certain advantages in engineering costs and transportation costs, but have installation difficulties in the application process. However, limited by the manufacturing process, installation technology, and operating conditions, the intermediate joint of the aluminum cable is prone to failures such as insulation deterioration caused by abnormal temperature. The temperature of the core of the conductor in a steady state in the cable joint is the most direct and effective physical quantity, which can reflect the operating state. So modeling and analysis of the aluminum cable joint, as well as the study of its internal temperature change mechanism and influencing factors, are to improve the process and installation level of the aluminum cable joint and to develop the basis of the corresponding temperature monitoring system. In this paper, the thermal conduction mechanism of aluminum cable joints in a steady state is analyzed by using the thermal circuit theory. Then, the thermal circuit model of aluminum cable joints in a steady state based on the equivalent thermal circuit model and its parameter calculation method are proposed. By building an experimental platform, the validation experiment finally proved the accuracy of the method proposed in this paper.
Renewable Energy Power System Unit Commitment Considering Regional Frequency Stability Requirement
Authors: Cao Bin , Miao Lifang , Liu Hongqing , Lai Shuyu , Wang Cheng
Published: August 2023

With the development of new power systems, the formation of a “double high” pattern in frequency has made frequency security a prominent problem. It is particularly important to formulate a unit power generation plan with frequency security constraints at the day-ahead scale. However, a unit commitment model with frequency security constraints based on a unified frequency for the entire network cannot be used because the frequency exhibits spatial variations. This problem is solved in this study by establishing a single-machine aggregation model for the frequency response of a partitioned power system. In the unit commitment model, the frequency support between individual regions is established based on the distribution of the disturbance power over individual subregions. The index of the initial frequency change rate is introduced for each subregion to establish an analytical expression for the relationship between the frequency security constraints and the unit commitment scheme. Finally, the effectiveness of the model and the solution algorithm is verified for the improved IEEE39 node system.
Design and Verification for Measurement and Control System of Large-scale Ship Model
Authors: Shi Panhao , Li Dehai , Shen Jiacheng , Huang Lei , Wu Yongshun , Yang Sujun
Published: August 2023

The navigation performance of the ship model is generally studied by the hydrodynamic parameters of ship models with the help of test chamber towing tanks or external waters. Considering the difference among the conditions of the indoor field towing tank or the outer field water area and the actual sea state, to solve the problem of the large-scale ship model series test under the actual sea state in this article, a large-scale ship model measurement and the control system was designed, including heading control system, controller, propeller propulsion device, rudder actuator and power supply module and others. It is used to test the maneuvering performance of large-scale ship models in the sea. On this basis, the reliability and effectiveness of the system were verified by testing the speed and maneuverability of the model in open water.
A Robust Parameter Identification Approach with Anti-Outlier Characteristics for Lithium-Ion Batteries
Authors: Ning Xuefeng , Shi Zhenglu , Xu Jiazhu
Published: August 2023

Accurate acquisition of model parameters of lithium-ion batteries (LIBs) is imperative for precious estimation state of charge. However, due to the interference of noise, the inevitable uncertainty may lead to outliers appearing in measurement data, which often leads to inaccurate parameter identification. To solve the problem, a robust Kalman filter (RKF) that uses the Mahalanobis Distance Criterion (MDC) is proposed for the parameter identification of LIBs. Firstly, the one-order equivalent circuit model of the LIBs is created. Subsequently, the gain of robust factor is implemented into the Kalman filter to decrease filter gain and swell the measurement noise covariance when facing the outlier measurements. Finally, the dynamic stress test condition of the electric vehicle is used to prove the effectiveness of the RKF-MDC approach. The simulation reveals that the RKF-MDC can reduce the influence of outlier values for the parameter identification of LIBs.