bluuebunny/crossref_metadata_2025 huggingface dataset:
A possible interpretation of Λ baryon spectrum with pentaquark components
Authors: Xu Kai , Kaewsnod Attaphon , Zhao Zheng , Htun Thiri Yadanar , Limphirat Ayut , Yan Yupeng
Published: May 2023

The Λ baryon spectrum is studied within the SU(3) flavor symmetry in a constituent quark model. We found that it is rather difficult to accommodate some negative-parity Λ resonances as single q
2
s (q = u, d quarks) states in the conventional three-quark picture. The ground

q

3

s

q

¯

pentaquark mass spectrum is evaluated and a possible interpretation is proposed in the work: the observed Λ(1405)1/2−, Λ(1670)1/2− and Λ(1800)1/2− are three-state mixtures of two p-wave q
2
s states and one ground

q

3

s

q

¯

pentaquark state, so are the Λ(1520)3/2−, Λ(1690)3/2− and Λ(2050)3/2− resonances. Both Λ(1405)1/2− and Λ(1520)3/2− contain considerable

q

3

s

q

¯

pentaquark components.
Synchronous fault feature extraction for rolling bearings in a generalized demodulation framework
Authors: Liu Kangning , Shi Juanjuan , Shen Changqing , Huang Weiguo , Zhu Zhongkui
Published: May 2023

Generalized demodulation (GD) has the potential to process non-stationary vibration signals since it can demodulate a signal with a curved time–frequency (TF) ridge into a signal, with a TF ridge parallel to a time axis with an improved time-frequency representation (TFR) energy concentration level. However, current GD methods require iteration operations and cannot simultaneously deal with vibrations from multiple components of rolling bearings. This paper proposes a method based on the GD framework, which can simultaneously demodulate multiple components of interest using the Hadamard product between matrices. A synchronous extractor is also constructed to post-process TFRs of generalized demodulated signals to further improve the TF aggregation. Unlike the conventional synchronous extraction transform, the synchronous extractor in this paper can be directly applied to TF ridges parallel to the time axis without the estimation of instantaneous frequencies (IFs). Then, the post-processed TF ridges are backward demodulated to restore the actual IF. The proposed synchronous fault feature extraction method in the GD framework also allows for the signal reconstruction. Both simulated and experimental signals are applied to validate the effectiveness of the proposed method for rolling bearing fault diagnosis.
Third-order nonlinear Hall effect in two-dimensional Dirac systems
Authors: Gao Yang , Zhang Zhi-Qiang , Ding Kai-He
Published: May 2023

We theoretically investigate the third-order nonlinear Hall effect by employing the quantum kinetic equation and present an analytic formula for the third-order harmonic conductivity, where the intraband and the mixed inter-band contributions caused by the external electric field as well as the multiphoton process dressed Berry curvature are unveiled. These results are applied in a two-dimensional Dirac system. We find that the third-order harmonic conductivity exhibits a crossover from the negative to positive value due to the intraband transition of the electrons in the low-frequency region, whereas a kink or dip structure due to the multiphoton process between the conduction and valence bands in the high-frequency region. In experiment, these features can be identified by detecting the transverse current. Our work deepens the understanding of the multiphoton process in the nonlinear transport of topological materials and enlightens a possible way to its characterization in experiments.
Prospects for constraining interacting dark energy models from gravitational wave and gamma ray burst joint observation
Authors: Hou Wan-Ting , Qi Jing-Zhao , Han Tao , Zhang Jing-Fei , Cao Shuo , Zhang Xin
Published: May 2023

With the measurement of the electromagnetic (EM) counterpart, a gravitational wave (GW) event could be treated as a standard siren. As a novel cosmological probe, GW standard sirens will bring significant implications for cosmology. In this paper, by considering the coincident detections of GW and associated γ ray burst (GRB), we find that only about 400 GW bright standard sirens from binary neutron star mergers could be detected in a 10-year observation of the Einstein Telescope and the THESEUS satellite mission. Based on this mock sample, we investigate the implications of GW standard sirens on the interaction between dark energy and dark matter. In our analysis, four viable interacting dark energy (IDE) models, with interaction forms Q = 3βHρ
de and Q = Q = 3βHρ
c, are considered. Compared with the traditional EM observational data such as CMB, BAO, and SN Ia, the combination of both GW and EM observations could effectively break the degeneracies between different cosmological parameters and provide more stringent cosmological fits. We find that the GW data could play a more important role for determining the interaction in the models with Q = 3βHρ
c, compared with the models with Q = 3βHρ
de. We also show that constraining IDE models with mock GW data based on different fiducial H
0 values yield different results, indicating that accurate determination of H
0 is significant for exploring the interaction between dark energy and dark matter.
Prediction of multifaceted asymmetric radiation from the edge movement in density-limit disruptive plasmas on Experimental Advanced Superconducting Tokamak using random forest
Authors: Hu Wenhui , Hou Jilei , Luo Zhengping , Huang Yao , Chen Dalong , Xiao Bingjia , Yuan Qiping , Duan Yanmin , Hu Jiansheng , Zuo Guizhong , Li Jiangang
Published: May 2023

Multifaceted asymmetric radiation from the edge (MARFE) movement which can cause density limit disruption is often encountered during high density operation on many tokamaks. Therefore, identifying and predicting MARFE movement is meaningful to mitigate or avoid density limit disruption for the steady-state high-density plasma operation. A machine learning method named random forest (RF) has been used to predict the MARFE movement based on the density ramp-up experiment in the 2022’s first campaign of Experimental Advanced Superconducting Tokamak (EAST). The RF model shows that besides Greenwald fraction which is the ratio of plasma density and Greenwald density limit, dβ
p/dt, H
98 and dW
mhd/dt are relatively important parameters for MARFE-movement prediction. Applying the RF model on test discharges, the test results show that the successful alarm rate for MARFE movement causing density limit disruption reaches ∼85% with a minimum alarm time of ∼40 ms and mean alarm time of ∼700 ms. At the same time, the false alarm rate for non-disruptive and non-density-limit disruptive discharges can be kept below 5%. These results provide a reference to the prediction of MARFE movement in high density plasmas, which can help the avoidance or mitigation of density limit disruption in future fusion reactors.
Quantum tunneling in the surface diffusion of single hydrogen atoms on Cu(001)
Authors: Yu Xiaofan , Tong Yangwu , Yang Yong
Published: May 2023

The adsorption and diffusion of hydrogen atoms on Cu(001) are studied using first-principles calculations. By taking into account the contribution of zero-point energy (ZPE), the originally identical barriers are shown to be different for H and D, which are respectively calculated to be ∼158 meV and ∼139 meV in height. Using the transfer matrix method (TMM), we are able to calculate the accurate probability of transmission across the barriers. The crucial role of quantum tunneling is clearly demonstrated at low-temperature region. By introducing a temperature-dependent attempting frequency prefactor, the rate constants and diffusion coefficients are calculated. The results are in agreement with the experimental measurements at temperatures from ∼50 K to 80 K.
Dynamic decision and its complex dynamics analysis of low-carbon supply chain considering risk-aversion under carbon tax policy
Authors: Lin 林 Jin-Chai 金钗 , Fan 范 Ru-Guo 如国 , Wang 王 Yuan-Yuan 圆缘 , Du 杜 Kang 康
Published: May 2023

This study establishes a low-carbon supply chain game model under the centralized decision situation and the decentralized decision situation considering the manufacturer risk-aversion behavior, and discusses the influence of the manufacturer risk-aversion behavior on the optimal decision, profit, coordination, and complex dynamics of the supply chain. We find that comparing with the risk-neutral decentralized decision, the increase of manufacturer’s risk tolerance attitude can narrow the gap between the supply chain profit and the centralized decision, but it will further reduce the carbon emission reduction level. The increase of risk tolerance of the manufacturer and carbon tax will narrow the stable region of the system. Under this situation, the manufacturer should carefully adjust parameters to prevent the system from losing stability, especially the adjustment parameters for carbon emission reduction level. When the system is in a chaotic state, the increase of carbon tax rate makes the system show more complex dynamic characteristics. Under the chaotic state, it is difficult for the manufacturer to make correct price decision and carbon emission reduction strategy for the next period, which damages its profit, but increases the profit of the retailer and the supply chain. Finally, the carbon emission reduction cost-sharing contract is proposed to improve the carbon emission reduction level and the supply chain efficiency, achieving Pareto improvement. The stability region of the system is larger than that in the centralized decision situation, but the increase of the cost sharing coefficient will reduce the stability of the system in the decentralized decision-making situation.
Pressure-induced phase transition and electronic structure evolution in layered semimetal HfTe2
Authors: Zhang Mei-Guang , Chen Lei , Feng Long , Tuo Huan-Huan , Zhang Yun , Wei Qun , Li Pei-Fang
Published: May 2023

Motivated by the recent experimental work, the pressure-induced structural transition of well-known two-dimensional (2D) 1T-HfTe2 was investigated up to 50 GPa through the advanced CALYPSO structure search technique combined with the first-principles calculations. Our calculations suggested that the 1T-HfTe2 will first transform to C2/m phase at 3.6 GPa with a volume reduction of 7.6% and then to

P

6
¯

2
m

phase at 9.6 GPa with a volume collapse of 4.6%. The occurrences of 3D C2/m and

P

6
¯

2
m

phases mainly originated from the enhanced Te–Te interlayer coupling and the drastic distortions of Hf–Te polyhedrons in

P

3
¯

m
1

phase under compression. Concomitantly, the coordination number of Hf atoms increased from six in

P

3
¯

m
1

to eight in C2/m and eventually to nine in

P

6
¯

2
m

at elevated pressure. The metallic and semimetallic nature of C2/m and

P

6
¯

2
m

phases were characterized, and the evidence of the reinforced covalent interactions of Te–Hf and Te–Te orbitals in these two novel high-pressure phases were manifested by the atom-projected electronic DOS and Bader charge.
Ab initio study of chemical effect on structural properties of Ti–Al melts
Authors: Feng 冯 Yun 运 , Feng 冯 Yan 艳 , Peng 彭 Hai-Long 海龙
Published: May 2023

We study chemical effect on the structural properties of Ti–Al melts, with the Al concentration systematically changed, via ab initio molecular dynamics simulations. By calculating the partial coordination numbers, we find a preferred connection between the nearest neighbors for Al–Ti pairs. This induces an excess Ti coordination in the cluster characterized by local five-fold symmetry in Voronoi tessellation. Structural entropy measured from the diversity of Voronoi polyhedrons shows an intriguing non-monotonic tendency with concentration: it first decreases to a minimum value at Ti40Al60, and then increases beyond this concentration. This implies a more ordered local structure induced by the chemical interaction at the intermediate compositions. The spatial correlation among the crystalline-like or the icosahedral-like clusters also exhibits the highest intensity for Al–Ti pairs, verifying the important role played by the chemical interaction in the local structure connectivity.
Processing composite materials with lasers
Authors: Teirumnieka Ē , Pīgožnis K , Blumberga D , Teirumnieks E , Lazov L
Published: May 2023

Composite materials, consisting of fibers and binders of natural and artificial origin, are increasingly used in various fields of industry. Processing of the obtained materials into finished forms is often difficult and expensive. Treatment of composite materials, such as milling, cutting, or grinding, is currently dominant.

At present, lasers are increasingly used in production processes. It should be noted that modern industrial production is unthinkable without the use of laser equipment. However, when using lasers, initial adjustment of their laser parameters is required for optimal material processing. When considering different lasers and materials to be processed, the setting parameters are different and the obtained processing quality is varied.

In the research, samples of composite materials have been made, consisting of epoxy resin as a binder and hemp, flax, and carbon fibers as reinforcing materials. The obtained composite materials have been studied with fiber laser for their processing quality.
Polarization properties of two-dimensional polarization holographic gratings inscribed in azopolymer thin films
Authors: Mateev G , Nedelchev L , Nazarova D , Nikolova L , Ivanov B , Strijkova V , Stoykova E
Published: May 2023

Azopolymers are efficient photoanisotropic materials and for this reason are commonly used for inscription of polarization-selective diffraction gratings by polarization holography. More often however, the characteristics of one-dimensional (1D) gratings are studied. Here, we present real time diffraction efficiency kinetics and polarization properties of two-dimensional (2D) polarization holographic gratings, each of them obtained by overlapping two perpendicular 1D gratings. The gratings are consecutively inscribed using as recording medium the azopolymer poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt], or PAZO. To record the gratings, He-Cd laser (λ = 442 nm) was used with left and right circular polarizations (LCP and RCP) of the recording beams. Our results show that the volume polarization grating has lower influence on the polarization properties of the 2D grating than the surface relief scalar grating.
Case study of biomass-burning aerosol events over Sofia, Bulgaria, based on AERONET sun photometer data
Authors: Evgenieva Ts , Gurdev L , Toncheva E , Dreischuh T
Published: May 2023

In the present work, the peculiarities were analyzed of aerosol events over Sofia, Bulgaria, characterized by a daily-mean aerosol optical depth (AOD) exceeding 0.3 and Ångström exponent (AE) above unity. Such aerosol situations arise most frequently in summer and early autumn, and sometimes in late autumn and winter. The analysis was based on AERONET sun photometer data and showed that the corresponding aerosol ensembles consisted mainly of fine-fraction biomass-burning (BB) smoke particles due to summer wildfires or domestic heating in winter, with a high sphericity factor (SF) that reached unity and a low linear particle depolarization ratio (LDR) of the order of thousandths. In the cases of aged BB smoke particles, the values of AE decrease without essential changes in SF and LDR. The presence or the periodic appearance of desert dust and/or marine aerosols during the day will also lead to a lower AE, accompanied however by a decreasing SF and an increasing LDR.
Optical properties of 3D printed orthodontic retainers
Authors: Uzunov T , Yordanova-Ignatova T , Grozdanova-Uzunova R , Stoyanova N , Stoev Y , Apostolov N , Taneva I , Bogdanov V
Published: May 2023

The orthodontic retainers, used after orthodontic treatment are mainly produced by thermoforming. Studies and knowledge regarding directly printed orthodontic retainers and their optical properties are limited. The optical properties were tested using a source of monochromatic light and a spectrometer, which measures the intensity of the light passing through the specimens at different wavelengths. The best optical properties are seen with thermoformed specimens, whereas with 3D printed specimens polishing diminished the intensity of light passing through. The transparency of thermoformed materials is superior to that of 3D printed ones. Polishing the materials reduced their optical properties. Despite the fact that less light is transmitted through the 3D printed specimens, the materials offer clinically acceptable and satisfying optical properties.
Nonparaxial solitons in air
Authors: Dakova A , Kasapeteva Z , Dakova D , Kovachev L
Published: May 2023

In the present work the soliton regime of propagation in air of ultra-short long-wavelength infrared laser pulses is investigated. The dispersion of atmospheric air in mid-infrared and long-wavelength infrared shows anomalous group velocity dispersion regions for wavelengths in the ranges of 3.5 to 4.2μm and 9.3 to 13.5μm. In these spectral regions the atmospheric air is transparent. From other hand, the nonparaxiality leads to waveguiding regime of propagation for femtosecond pulses with shape of light disks (the transverse size is much bigger than the longitudinal one). It allows reducing this 3D + 1 task to 1D + 1 problem in the same manner as in optical fibers. The combination between anomalous group velocity dispersion and atmospheric nonlinearity is a base for the observation of optical solitons in the air transparency regions for the indicated wavelengths. The main equation in our research is the 1D + 1 nonlinear nonparaxial amplitude equation, written in Galilean and Laboratory coordinate systems. New analytical solution in the form of bright soliton is found. The critical power, needed for the observation of these solitons is of two orders of magnitudes less than the critical one for self-focusing. That is why there are no conditions for ionization of the media.
Effect of carbon content on resistance to cavitation erosion of Cr-C coatings deposited by Arc PVD method
Authors: Safonov V , Zykova A , Steller J , Tolmachova G , Donkov N
Published: May 2023

The aim of the study is a comparative analysis of effect of the carbon content in the range from 2 to 25 at.% on the resistance to cavitation erosion of Cr-C coated samples by means of the rotating disk method. The effect of carbon concentration in the range from 2 to 25 at % on the structure, properties and cavitation resistance of Cr-C vacuum-arc coatings deposited in argon with toluene at a pressure of 0.08 to 0.23 Pa on 12Cr18Ni10Ti stainless steel samples has been studied. It has been established that the application of coatings leads to a decrease in the rate of cavitation erosion of steel from 4 to 6 times. Chromium coatings with a two-phase structure containing carbide Cp7C3show maximum durability.
Low temperature electrical transport in thin carbon films deposited on SiO2/Si substrates by pulsed laser deposition
Authors: Valcheva E , Kirilov K , Dikovska A , Milenov T
Published: May 2023

In this paper electrical transport studies are performed on thin carbon films deposited on SiO2/Si substrates by pulsed laser deposition (PLD) applying laser ablation of micro-crystalline graphite target. Experiments were carried out on 320 - 420 nm thick SiO2 on Si substrates as well as on hydrogenated diamond-like carbon (DLC) films deposited on SiO2/Si. Structural studies by means of XPS, SEM and Raman spectroscopy revealed that the films can be characterized as nano-sized carbon phases possessing different phase composition (i.e. the ratio sp3/sp2 hybridized carbon, etc.). The electrical conductivity/resistivity of the films was measured in the temperature range 10 K < T < 300 K. Four-contact Van der Pauw method as well as two contact schemes have been applied. Some films have low room temperature resistivity in the range ρ = (0.1–1.5)×10-3 Ω.·m and consist predominantly of sp2 hybridized carbon with Raman spectra, which resemble that of nano-sized graphene depending on the deposition conditions and substrates used. The thinnest only 0.5 nm layer deposited directly on SiO2 exhibits relatively low specific resistance (~10-3 Ω. m), which can be taken as an indication of good deposition conditions of graphene-like layers. The current flow mechanism was explored at temperatures from 300 K down to 10K. The temperature dependence reveals non-metallic behavior - the conductivity decreases at decreasing temperature as opposed to typical metal behaviour. A model of variable range hopping (VRH) mechanism is applied to explain the low temperature conductivity drawn from transport in nanocrystalline disordered systems.
Surface structuring of β-TCP and transition to α-TCP induced by femtosecond laser processing
Authors: Aceti D M , Filipov E , Sotelo L , Fontanot T , Christiansen S , Lasgorceix M , Leriche A , Buchvarov I , Daskalova A
Published: May 2023

Tricalcium phosphate (Ca3(PO4)2, TCP), is one of the most studied and used as material for bioresorbable implants. The β phase has a slower dissolution dynamic and ensures mechanical support for a longer time in biological environment, while a faster release of ions characterize the α phase that trigger a stronger biological response. In this work a femtosecond laser system was used to process β-TCP pellets surface. The femtosecond laser processing results in surface morphology modification, by turning the flat mirror polished surface into a rough and opaque one. The morphological and phisycochemical characteristics of material surface were studied by means of SEM, AFM, Raman, XRD and contact angle measurement. The processed surface showed the formation of micro and nano roughness alongside, furthermore a partial phase transformation from β-TCP to α-TCP was detected. A significant improvement in surface wettability for three different liquids (i.e.water, ethylene glycol and diiodo-methane) is reported. This implies an increase in surface free energy as well. The combination of α and β phase, together with the increased roughness obtained by laser processing, could positively affect the cell adhesion and metabolic activity.
Decomposition of Carbon Emission Influencing Factors and Peak Prediction in Ningxia Region
Authors: Yan Zhenhua , Li Yongliang , Luo Hairong , Zhang Shuang , Zhu Dongge
Published: May 2023

To meet the demand for carbon emission prediction, it is necessary to master the measurement criteria and influencing factors of carbon emission and improve the accuracy of prediction results in the form of a combined application of multiple algorithmic models. This paper proposes a carbon emission impact factor decomposition model based on LMDI and a carbon emission prediction model based on the EEMD-BSO-GPR model. The study of carbon emission forecasting within the study region allows the study of the stage in which carbon emissions are located, the relationship between emissions and influencing factors such as industrial structure, affluence, energy structure, technology level, degree of openness to the outside world, and population size. The combined forecasting model can also meet the demand for carbon emission forecasting in the region with higher forecasting accuracy.
Functional Positioning and Configuration of Wind Energy Storage in the Power System
Authors: Du Yiyue
Published: May 2023

Wind power as a renewable energy source has both strong fluctuations in output power affecting the power balance in real-time operation of the system. In power systems with high wind power penetration, energy storage devices are used to dissipate wind energy and achieve optimal allocation of resources for generating units and storage devices to meet economic requirements. In this paper, we mainly use horizontal planning and vertical planning to calculate the total cost of power generation and the optimal wind power access to optimize the output quota of each unit.
Experimental study of coupled solar and air source heat pump heating system
Authors: Li Xu Lin , Wang Xing , Wang Yun Long
Published: May 2023

To increase the heating stability and system energy efficiency as well as to offer technical assistance for promoting and deploying multi-energy coupled heating technology in village and township buildings, a solar-air source coupled heating system is suggested and developed. The experiment was conducted on a multi-energy coupled heating system for a village and town office building in Hun nan New Area, Shenyang City, over a period of 15 days, with an average daily solar radiation intensity of 558.62 w/m2-h and an average outdoor temperature ranging from -18.3 °C to -2.7 °C. The trial findings demonstrated that all indoor temperatures could exceed 18 °C while the system was in use, and the average value of the system’s overall energy efficiency was 2.45.
Development and Application of Laser Cleaner for Disconnecting Switch Rust
Authors: Zhang Jing , Zhang Xu , Zhang Min , Zhang Haoyu , Zhu Shengrong
Published: May 2023

The timely and regularly clean for long-time use disconnecting switches are important for prolonging their lifetime. Laser cleaning for metal rust has the advantage of zero pollution. Fast speed and parameters can be adjusted to various sites. This paper introduces the development of laser cleaner for rust on disconnecting switches. Comparing results under different parameters in labs and sites, this paper concludes that when the laser power is 20W and the scanning speed is 2500mm/s, the device has a better cleaning effect.
Research on Distributed Photovoltaic Grid-connected Mode Based on PSASP
Authors: Wang Wenlong , Cai Nan , Song Baiyue , Guan Wanlin , Xu Mingyu , Liu Yanlong , You Chao , Ma Jiancheng
Published: May 2023

With the continuous implementation of the carbon peak and carbon neutrality, a large number of distributed solar power stations have been integrated into the grid, which has caused a strong impact on the safe and stable operation of the traditional power system. Based on this, the grid-connected mode of distributed solar power stations is studied, and three types of grid connection are proposed. Mode A is merged into the 66 kV bus side of the 220 kV substation through the 66 kV dedicated line; Mode B is merged into the 66 kV bus side of the 66 kV substation through the 66 kV dedicated line; Mode C is T-connected to the 66 kV transmission line through 66 kV dedicated line. By using a power system analysis software package (PSASP), we can build a model of a certain regional power grid and study the effects of the above three grid-connected modes on system voltage stability, short-circuit current, and network loss. The study shows that the three modes are all feasible. Mode A has the smallest change in voltage quality and short-circuit current of the grid-connected substation and has the smallest network loss of the three modes.
Photovoltaic Power Generation Based on Three-port DC-DC Step-down Circuit
Authors: Wang Lulu , Xu Handan , Li Wenjing , Song Mingxin
Published: May 2023

In this paper, the photovoltaic cell is combined with the analog battery pack and the load through a three-port DC-DC Buck circuit, which gives power to the analog battery pack and load. From the perspective of simulation, the photovoltaic cell is lowered to reach respective specific values through the two Buck circuits at the output end of it and to give power to the load and the simulated battery pack. The influence of Pulse Width Modulation (PWM) duty ratio output on voltage and the influence of PWM frequency on load voltage and current limiting resistance of the power supply system is studied from the angle of power conversion. The results show that when the PWM duty ratio is changed, the actual output voltage does not reach the theoretical value, and is somewhat less than the theoretical value. When the frequency is less than 100 KHz and the inductance value is less than or equal to 100 uH, under the same other conditions, the load voltage decreases first and then increases with the increase of frequency. The larger the inductance value is, the faster the voltage drops, and the smaller the inductance value is, the faster the voltage increases. When the inductance reaches 250 uH, the inductance value continues to increase, which has little influence on the load voltage, and the load voltage generated by different inductance values only has a small error. If the output frequency of PMW is too high or too low, the output voltage will be reduced. The maximum voltage value is between 90 and 100 KHz. When the current limiting resistance is 18.5 Ω, it is close to and does not exceed the maximum charging voltage of the analog battery string.
Analysis of Laser Cleaning and Rust Removal Technology for Substation Isolator Switches
Authors: Zhang Haoyu , Zhang Jing , Zhang Xu , Zhu Shengrong , Zhang Min
Published: May 2023

After running for a long time, isolator switches are prone to be covered with dirt and corrosion. Switch cleaning is necessary for good operation and safety. Laser cleaning technology for rust removal is emerging in recent years. This paper introduces the technical principles of laser cleaning for rust removal in detail, designs a specific process scheme and takes a steel plate sample cleaning and rust removal as a case. The application effect of laser cleaning and rust removal technology is tested and shows that the technology analyzed in this paper can play a great cleaning effect without damaging the equipment base.
Assessment method of large-scale distributed power consumption capacity for rural grids
Authors: Li Chao , Lu Tianguang , Han Xueshan
Published: May 2023

As the scale of photovoltaic (PV) access continues to expand, both transmission and distribution grids are experiencing systemic consumption problems, with rural distribution grids being particularly prominent. An accurate assessment of distributed power consumption capacity is crucial to the improvement of distributed power consumption capacity. Firstly, taking into account the uncertainty of the output of the distributed power supply and comprehensive consideration of power quality, reliability of the electricity supply and operational influences, A comprehensive index evaluation system has been established to assess the ability of distributed power sources to consume; secondly, hierarchical analysis and improved gray correlation analysis are used to assign weights to the indexes; finally, a Monte Carlo model is used to identify the consumption capacity of rural power grids. This method can provide a comprehensive and accurate assessment of the consumption capacity of large-scale distributed power sources in new rural power grids, and also provide data support for solving the problem of new energy consumption in power grids.
Study on the Operation Scheme of Distribution Network Considering Voltage Stability and High Permeability Photovoltaic Access
Authors: Dong Anqi , Gao Hui , Li Huailiang
Published: May 2023

With the introduction of high-density distributed photovoltaic (DPV) into the distribution network, the reasonable evaluation of the voltage stability during the operation of the distribution network has become a research hotspot. In this paper, firstly, the influence of distributed photovoltaic on the voltage after it is connected to the distribution network is analyzed. Then, by building the hybrid simulation platform of MATLAB and Opendss, the change of the operation state of the typical distribution network when it is connected to the photovoltaic energy of different permeability and different capacity is analyzed. Two key nodes affecting the photovoltaic access capacity are introduced. The accuracy of the theoretical analysis was verified by the time series simulation analysis, and the general rule of the high-capacity photovoltaic access scheme was obtained based on the simulation results.
Virtual Oscillator Control for inverters based on reduced-order Andronov-Hopf oscillator
Authors: Guo Xiaolong , Kang Pengpeng , Yang Guixing , Song Pengfei , Shi Yafan
Published: May 2023

This paper proposes a virtual oscillator control method by reducing the order of the amplitude term of the Andronov-Hopf dynamic process. The proposed oscillator retains its steady-state droop characteristic and power dispatchability in grid-connected mode, but with less nonlinearity. At the same time, based on the steady-state performance criterion of the inverter, the detailed parameter selection principle of the proposed controller is given, and its dispatchability is verified by simulation. Finally, we compared the proposed controller with the full-order virtual oscillation controller. The results show that the proposed controller has a stronger load capacity.
A full-automatic test system for the intelligent substation based on GOOSE/SV signal simulation
Authors: Chen Yongxin , Li Hengxuan , Yang Gang , Xiao Yeqing , Wu Hao , Shi Yichuan , Chen Chongxiang
Published: May 2023

With the wide application of one-key sequence control in intelligent substations, the testing of one-key sequential control and error prevention logic has become an important work before production. Due to the limitation of testing methods, most of the tests are conducted during on-site commissioning, which has a large workload, lower efficiency, and a high probability of missed testing. Therefore, this paper proposes a full-automatic test system for the intelligent substation based on GOOSE/SV signal simulation. It can automatically verify the error prevention logic and the one-key sequence control of the monitoring system through the combination of GOOSE/SV signals at different statuses, which provides technical support for the site to improve efficiency and safety.
Research on refined prediction of coastal wind power based on dynamic downscale and deep learning prediction
Authors: Zhang Yi , Zhang Feng , Qiu Yutao , Yao Xudong , Liu Ang , Mo Jianguo , Xie Xiahui
Published: May 2023

With the expansion of the installed capacity of offshore wind power, its impact on the safe operation of the power grid is increasingly obvious, and improving the prediction accuracy of offshore wind power power has become a key problem to be solved in the industry. The improvement of prediction accuracy, on the one hand, can facilitate the operation control of power grid, on the other hand, can also significantly improve the economic benefits of wind power plants. Based on power downscaling and deep learning methods, this paper carries out localized short-term and ultra-short-term power prediction modeling and optimization technologies for coastal offshore wind power. Comprehensive statistical prediction method, artificial intelligence prediction method, multi-model integration method and other combined prediction model, multi-source fusion information, to realize the refined prediction of Zhejiang offshore wind power, and improve the overall prediction accuracy. The research method is generally applicable and can guide the output prediction of the same type of offshore wind power.
Study on the start-up control strategy of DFIG wind farm via MMC-HVDC grid connection
Authors: Wang Qian , Wu Shouyuan , Song Yu
Published: May 2023

The flexible DC transmission technology proposed in recent years has significant technical advantages over other transmission methods for long-distance grid-connected transmission of large-capacity wind farms. However, as the scale of wind farms continues to expand, new problems have emerged, mainly in the form of start-up control as the basis for the reliable grid-connected operation of wind turbines. In this paper, a start-up control strategy for DFIG wind farms connected to the grid via MMC-HVDC is proposed for DFIG wind farms via flexible DC outgoing transmission scenarios, mainly including MMC-HVDC controlled rectifier start-up control and single DFIG start-up control. Finally, the correctness and feasibility of the proposed control strategy are verified by simulation.
Study on the aerodynamic performance of inlet pipe different bending radius of ram air system
Authors: Liu Xiaohong , Xia Fuming
Published: May 2023

In this paper, the bending radius deviation of the intake duct is studied. The computational fluid dynamics (CFD) method is used to evaluate the performance of the inlet by the coupling calculation of the internal and external flow of aircraft. Firstly, the CFD method is used to calculate the theoretical numerical model. The results show that when the pipeline flow is constant and the pipeline R/D decreases, such as from 1.84 to 1.3, the total pressure recovery decreases, especially when the pipeline R/D is less than 1.5, the total pressure recovery decreases rapidly. At the same time, the drag force of the pipeline does not change much, and the flow field of the inlet pipeline is analyzed to analyze the internal reasons for the total pressure recovery and flow rate change with R/D, which has important guiding significance for the application of batch production in future.
Temperature Field and Thermal Stress Analysis of Rocket Engine Composite Structure Nozzles
Authors: Liu Yunpeng , Feng Feng , Shen Xiaodong , Chen Chao
Published: May 2023

As one of the core components of the rocket engine, the working conditions of the nozzle are very bad. Ensuring the nozzle works normally is an important prerequisite for the normal operation of the rocket engine. To ensure the safety of the solid rocket motor nozzle in use, the temperature distribution and thermal stress of the nozzle must be preliminarily analyzed. Therefore, the three-dimensional model of an L-shaped nozzle is established. The temperature field and stress field of the structure is numerically simulated by FLUENT and Static Structural. The influence of gas temperature and material thermal conductivity on temperature distribution and thermal stress of solid structures are analyzed. The results show that the throat has the highest temperature and maximum thermal stress. When the gas temperature is 2600K, the maximum temperature of the throat is 1400K, and the thermal stress is 158MPa. When the thermal conductivity of the insulation layer is 2.8 W/(m·K), the thermal stress on the throat is 170 MPa. The conclusion can provide an important reference for the thermal protection design of the nozzle.
Research on the influence of pilot workload on local route path planning of helicopters in low-altitude penetration
Authors: Li Shen , Li Pan
Published: May 2023

Targeting the problem of high pilot workload caused by trajectory planning of low altitude penetration, this paper proposed a trajectory planning method considering the pilot workload. Firstly, by decomposing the three-dimensional trajectory into horizontal and vertical directions, the trajectory tree method based on the dynamic programming technique is used for horizontal trajectory planning, and the comprehensive slope-curvature limitation method is used for altitude trajectory planning. Then, a method was proposed to quantify the control inputs and pilot workload based on trajectory tracking simulation. The pilot workload cost, together with flight altitude cost and route length cost, was added to the local planning of a reference trajectory. To solve the problem of dimension explosion in trajectory tree search, a segmented optimal route tree algorithm is proposed. Finally, the simulation results show that the proposed method can effectively consider the pilot workload in trajectory planning, which is helpful to improve the flight ability of the planning trajectory and reduce the pilot workload at the same time.
High-fidelity Modelling Approach for Investigating the Tightening Torque Effect in Thread Connection
Authors: Zhang Hui , Yu Fei , Wang Houbin
Published: May 2023

Accurate replication of the torque-tightening effect is important when simulating the mechanical behavior of composite joints using the finite element (FE) approach. In this study, a parametric mesh construction strategy was developed to automatically build a high-fidelity 3D FE model with lift angle to simulate bolt thread interactions. An experimental approach was proposed to calibrate the FE model. The relation between tightening torque and the axial force was studied by the FE method, experiment, and engineering algorithm. Results showed that traditional empirical formula overestimate the clamping force. By using the proposed model to calculate the axial force of the bolt, the accuracy of the axial force can be significantly improved when analyzing the composite bolted joints. Finally, parametric simulations were performed to investigate the influence of coefficients of friction at thread interfaces and the nut/washer interfaces. The pre-tightening force was significantly influenced by the frictional coefficients at these interfaces. Results indicated that increasing the coefficient of friction (CoF) at the nut/washer interface from 0.1 to 0.2 can lead up to 28% reduction in the clamping force, while this increase was 23% for the threads interfaces.
Feasibility of autonomous orbit keeping with optimal fuel consumption using drag-free CubeSat
Authors: Liu Rui , Wei Donghua , Liu Yingying , Liu Yiheng
Published: May 2023

In this paper, the composition of the drag-free CubeSat platform was introduced first. Then the control strategy of drag-free CubeSat orbit keeping was proposed. Finally, the simulation with the control scheme of the Homan transfer orbit was compared. By comparing and analyzing the fuel consumption of the drag-free track and Homan transfer track, it is demonstrated that the continuous drag compensation of the drag-free control scheme can significantly reduce the consumption of thruster mass, and the drag-free technology has good advantages in track stability.
Key Failure Mode Identification Method of LED System Based on Fuzzy TOPSIS
Authors: Zhang Bing , Hao Zhaojun , Wang Lifang , Li Lexiao
Published: May 2023

The premise of the system reliability analysis is to effectively discern the patterns of product failures at all levels. To deal with the problem that the diversity of failure modes of complex products represented by LED systems cannot be analyzed comprehensively, in this paper, a key failure mode identification method based on Fuzzy TOPSIS is proposed. First, the construction method of the failure relevance tree is given to support the comprehensive identification of potential failure modes. Then, the decision rule of node failure weight is mined by the rough set method, the systematic evaluation of the node failure weight is realized with the TOPSIS method, and the key failure modes are identified. Finally, a case validation of the proposed method in this paper is performed.
Effectiveness Evaluation of Medium-sized Carrier Rockets Based on ADC Method
Authors: Wang Jianjun , Xu Zhensen , Zhou Tao , Zhang Jun , Wu Xiangqing
Published: May 2023

Using scientific evaluation methods to evaluate the mission effectiveness and cost-efficiency of rockets is one of the important topics in the development of rocket models. Aiming at the problem that the effectiveness evaluation of carrier rockets cannot be quantitatively analyzed, this paper takes the medium-sized carrier rockets, covering both new and old generation ones in service, as the object of establishing a simplified inherent capability index system. The ADC method is utilized to quantitatively evaluate the availabilities, dependabilities, and capabilities of various types of rockets and calculates the corresponding effectiveness and cost efficiencies when performing launch missions in LEO, GTO, and SSO orbits. The results show that Model II has excellent mission effectiveness, which is particularly suitable for medium and high orbit missions; the cost-efficiency of Model III is as good as that of the former, and it can complete many tasks; but Model I is outdated.
Pseudo-Theory-Based Optimization Design Method for Lunar Gravity-Assisted Human Earth-Mars Transfer Trajectory
Authors: Yuan Yiting , Zhao Zichen , Dong Yue
Published: May 2023

The lunar gravity assist (LGA) is recognized as one of the potential ways to reduce the energy demand of human Mars exploration. Nevertheless, it indeed increases the difficulty of designing the exploration trajectory due to its inevitable considerations of a more complex gravitational environment and additional flying stages. Focusing on this issue, an efficient pre-design method is proposed on the basis of the pseudo-state theory. By embedding the pseudo-sweep back step into the dynamical propagation, the accuracy of two-body trajectories can be recovered to a high level, which brings significant convenience of initially designing high-precision trajectory, rapidly searching the departure window, and fast evaluating the LGA effect. A large amount of simulation results show that the application of the pseudo theory could enhance at least 88% trajectory accuracy, increase the 60% success rate, and decrease 5% the necessary cost when optimizing the Earth-Mars transfer trajectory, with comparisons to the two-body trajectory.
Simulation and analysis of drag for inflatable aerodynamic decelerator
Authors: Yun Chenghu , Liu Danghui
Published: May 2023

Inflatable aerodynamic decelerator, as a novel deceleration and recovery technology, has received attention due to its lightweight and freedom from the launch vehicle fairing size constraints for the space mission. Aimed at the aerodynamic characteristics of the inflatable aerodynamic decelerator, this work studied the effect of the cone angle on its drag and discussed the drag varied with the angle of attack under the different cone angles. The simulation showed that the drag was affected by the cone angle and increased locally with the angle of attack. Furthermore, the larger cone angle was beneficial to the stability of the flow field on its leeward in the case of a high Mach number. The math model of drag with the Mach number and the angle of attack was obtained by fitting the data, which provided favorable support for the prospective discussion of the flight dynamics characteristics.
Technical analysis on airworthiness compliance of lighting components for civil aircraft emergency evacuation slides
Authors: Song Hongyuan , Li Feng , Tang Xiaoliang
Published: May 2023

The emergency landing safety of emergency evacuation slides can be improved greatly by using lighting components, especially in dark environments. To design a required lighting system, two problems need to be solved, which are also the focus of this paper. Firstly, what airworthiness compliance work should be planned and how to do it. Secondly, how to design to meet the airworthiness requirements should be considered. A complete and effective airworthiness compliance method was proposed by analyzing various performance characteristics such as self-opening function, lighting duration, illuminance, and installation environment. Airworthiness requirements are decomposed into design features, and the design requirements of lighting components are put forward. This study can provide verification methods and design ideas for the lighting components of civil aircraft emergency evacuation slides.
Traffic Participant Classification Method Based on Decision Tree for Point Cloud Data Detected by Event Camera
Authors: Zhang Yu , Liu Haiqing
Published: May 2023

Event camera has the advantage of accurately identifying moving targets while being insensitive to stationary targets, which makes up for the lack of traditional video streaming camera and has a wide range of applications in the field of traffic flow detection. In this paper, a traffic participant classification method based on a decision tree for point cloud data acquired by an event camera in a roadside installation scenario is proposed. For traffic identification, 5 basic features to describe the geometrical and quantitative characteristics, and 8 Gaussian projection features to describe the point distribution characteristics are extracted and analyzed. Furthermore, the CART decision tree is used to identify four kinds of traffic participants, including the large vehicle, the compact vehicle, the non-motor vehicle, and the pedestrian. By modulating parameters of the maximum layer and feature weighting values, the proposed method can reach equilibrium in generalization ability and accuracy. Experimental results show that the proposed method demonstrates high accuracy of 97.49% in target participant classification.