bluuebunny/crossref_metadata_2025 huggingface dataset:
Visualising vapours
Authors: Stahl-Timmins Will
Published: November 2022

The case study describes the process of designing an interactive visualisation tool to help people understand the likelihood of Covid-19 transmission in different situations. This visualisation was created as part of a 13 month long collaborative project between scientific experts from a UK government advisory group, and a multimedia team at The BMJ (British Medical Journal). The data underpinning the graphic was collected from 27 experts via a knowledge elicitation study. It includes discussion of lessons learned about collecting and visualising uncertain data, and the benefits of user testing.
Progressives in present and past
Authors: Vafaeian Ghazaleh
Published: November 2022

This study investigates the relationship between progressive patterns and present and past time reference. First,
it looks at the shared distribution of more than 90 progressives in two parallel corpora and discusses the characteristics of
these contexts. It is shown that while progressives are used for dramatic and topical events in the present, they are typically
used as backgrounding, supportive material in the past. Second, it is shown that progressives generally have more occurrences in
contexts with present time reference than past, this is especially true for progressives with many uses, i.e. more grammaticalized
progressives. And third, a number of progressives temporally restricted are presented. Two historical explanations for these
restrictions are provided, both of which result from the higher frequency of present uses over past.
A hitherto unnoticed type of verb-framed construction in Lithuanian and the typology of event conflation
Authors: Holvoet Axel
Published: November 2022

The article starts out from a Lithuanian construction denoting achievement of an excessive value of some parameter of an incremental event. It is verb-framed, that is, the main-clause verb denotes motion along a path towards a normative value of the parameter involved. Its implications for our understanding of the Talmyan typology of event conflation are discussed. Event conflation in the domains of spatial motion and change of state has received most attention in the literature; differences in saliency and elaboration, and the importance of constraints on the lexicalization of path (result) and manner, have been pointed out. The Lithuanian verb-framed constructions discussed here are, however, similar to those in the domain of ‘temporal contouring’ in that they involve an incremental path superimposed on the path-to-result lexicalized in the embedded predicate. This extension beyond the core domains of spatial motion and change of state represents another dimension of the Talmyan typology, largely overlooked until now.
Quasi-Two-Dimensional Nature of High-T
c Superconductivity in Iron-Based (Li,Fe)OHFeSe
Authors: Li Dong , Liu Yue , Lu Zouyouwei , Li Peiling , Zhang Yuhang , Ma Sheng , Liu Jiali , Lu Jihu , Zhang Hua , Liu Guangtong , Zhou Fang , Dong Xiaoli , Zhao Zhongxian
Published: November 2022

The intercalated iron selenide (Li,Fe)OHFeSe has a strongly layered structure analogous to the quasi-two-dimensional (2D) bismuth cuprate superconductors, and exhibits both high-temperature (T
c) and topological superconductivity. However, the issue of its superconductivity dimensionality has not yet been fully investigated so far. Here we report that the quasi-2D superconductivity features, including the high anisotropy γ = 151 and the associated quasi-2D vortices, are also revealed for (Li,Fe)OHFeSe, based on systematic experiments of the electrical transport and magnetization and model fittings. Thus, we establish a new vortex phase diagram for (Li,Fe)OHFeSe, which delineates an emergent quasi-2D vortex-liquid state, and a subsequent vortex-solid dimensional crossover from a pancake-like to a three-dimensional state with decreasing temperature and magnetic field. Furthermore, we find that all the quasi-2D characteristics revealed here for the high-T
c iron selenide superconductor are very similar to those reported for high-T
c bismuth cuprate superconductors.
Effect of Mn doping and charge transfer on LaTi1−x
Mn
x
O3
Authors: Cao Guixin , Weng Yakui , Yao Xinyu , Ward T Zac , Gai Zheng , Mandrus David , Dong Shuai
Published: November 2022

We report the magnetic and electronic transport properties of Mn-doped LaTi1−x
Mn
x
O3 (x= 0, 0.1, 0.3, 0.5) as a function of temperature and an applied magnetic field. It was found that the Mn-doped samples show a magnetic transition which is not present in the parent LaTiO3. The Mn-doped samples showed fluctuations in magnetization at low fields below their Néel transition temperature indicating electronic phase separation in the material. Increased Mn content in the sample strengthens the ferromagnetic-like moment while maintaining G-type antiferromagnetic phase by charge transfer from Mn to Ti and influencing orbital ordering of the Ti3+ t2g orbitals. The results are discussed in parallel with transport and bulk magnetization measurements detailing the electronic behavior. An additional context for the mechanism is supported by first-principles density-function theory calculations.
Autonomous image background removal for accurate and efficient close-range photogrammetry
Authors: Eastwood J , Leach R K , Piano S
Published: November 2022

Close-range photogrammetry can be used to reconstruct dense point clouds of an object with very high surface coverage, making it useful for manufacturing metrology tasks such as part inspection and validation. However, compared to competing techniques, data processing times can be slow. In this paper we present a method to autonomously remove the background from the images within a photogrammetric dataset. We show that using masked images directly in the reconstruction results in much lower data processing times, with lower memory utilisation. Furthermore, we show that the point density on the object surface is increased while the number of superfluous background points is reduced. Finally, a set of reconstruction results are compared to a set of tactile coordinate measurements. Reconstructions with the background removed are shown to have a standard deviation in the point to mesh distance of up to 30 µm lower than if the background is not removed. This improvement in standard deviation is likely due to the static background, relative to the object on the rotation stage, causing triangulation errors when points are detected and matched on this background data. The proposed approach is shown to be robust over several example artefacts and can, therefore, be implemented to improve the measurement efficiency and measurement results of photogrammetry coordinate measurement systems.
High-frequency ultrasound-based thickness measurement of highly attenuating materials
Authors: Wang Jishuo , Lai Quanqing , Xu Caibin , Hu Ning , Deng Mingxi
Published: November 2022

This paper investigates an effective method for measuring the thickness of highly attenuating materials using the acoustic radiation-induced quasi-static component (QSC) of a primary longitudinal wave (PLW) at high frequency. The generated QSC features lower attenuation than the high-frequency PLW, so the generated QSC pulse with zero carrier frequency can propagate a longer distance at the same group velocity, even in highly attenuating materials. In addition, the method based on the QSC of a high-frequency PLW has better directivity than the low-frequency PLW-based method, making it more suitable for highly attenuated material local thickness measurement. The thickness of highly attenuating materials can be accurately measured by measuring the pulse-echo time-of-flight of the generated QSC pulse using an ultrasound pulse-echo technique. The experimental examinations conducted for highly attenuating silicone rubber blocks with different thicknesses demonstrate that their thicknesses can be accurately measured with the QSC-based method. This paper provides an effective method for thickness measurements of highly attenuating materials.
Exploiting coherence for quantum thermodynamic advantage
Authors: Hammam Kenza , Leitch Heather , Hassouni Yassine , De Chiara Gabriele
Published: November 2022

The introduction of the quantum analogue of a Carnot engine based on a bath comprising of particles with a small amount of coherence initiated an active line of research on the harnessing of different quantum resources for the enhancement of thermal machines beyond the standard reversible limit, with an emphasis on non-thermal baths containing quantum coherence. In our work, we investigate the impact of coherence on the thermodynamic tasks of a collision model which is composed of a system interacting, in the continuous time limit, with a series of coherent ancillas of two baths at different temperatures. Our results show the advantages of utilising coherence as a resource in the operation of the machine, and allows it: (a) to exhibit unconventional behaviour such as the appearance of a hybrid refrigerator, capable of simultaneous refrigeration and generation of work, and (b) to function as an engine or a refrigerator with efficiencies larger than the Carnot bound. Moreover, we find an effective upper bound to the efficiency of the thermal machine operating as an engine in the presence of a coherent reservoir.
A novel quantum recommender system
Authors: Gao Shang , Yang Yu-Guang
Published: November 2022

Recommendation system is a kind of information filtering system, which plays an increasingly important role in the era of big data. In this work, we present a novel quantum recommender system, which can also be regarded as a quantum version of the matrix reconstruction algorithm. In order to obtain two factors in the quantum state form, a quantum version of the alternating least squares algorithm is designed. And based on the factor matrices, the reconstruction matrix of the original rating matrix is calculated. The complexity analysis shows that our quantum algorithm may achieve an exponential speedup relative to the classical counterpart under certain conditions.
Pulsar and cosmic variances of pulsar timing-array correlation measurements of the stochastic gravitational wave background
Authors: Bernardo Reginald Christian , Ng Kin-Wang
Published: November 2022

Pulsar timing-array correlation measurements offer an exciting opportunity to test the nature of gravity in the cosmologically novel nanohertz gravitational wave regime. The stochastic gravitational wave background is assumed Gaussian and random, while there are limited pulsar pairs in the sky. This brings theoretical uncertainties to the correlation measurements, namely the pulsar variance due to pulsar samplings and the cosmic variance due to Gaussian signals. We demonstrate a straightforward calculation of the mean and the variances on the Hellings-Downs correlation relying on a power spectrum formalism. We keep arbitrary pulsar distances and consider gravitational wave modes beyond Einstein gravity as well as off the light cone throughout, thereby presenting the most general and, most importantly, numerically efficient calculation of the variances.
Holographic dark energy from acceleration of particle horizon
Authors: Fazlollahi H. R.
Published: November 2022

Following the holographic principle, which suggests that the energy density of dark energy may be inversely proportional to the area of the event horizon of the Universe, we propose a new energy density of dark energy through the acceleration of the particle horizon scaled by the length of this parameter. The proposed model depends only on one free parameter:

. For values of

near zero, the deviation between the proposed model and the

CDM model is significant, while for

, the suggested model has no conflict with the

CDM theory. Regardless of the value of

, the model considers dark energy to behave as matter with positive pressure in high redshifts,

, while for present and near-future Universe, it is considered to behave similar to that in the cosmological constant model and phantom field. Comparing the model with the Ricci dark energy model, we show that our model reduces the errors of the Ricci dark energy model concerning the calculation of the age of old supernovae and evolution of different cosmic components in high redshifts. Moreover, we calculated matter structure formation parameters such as the CMB temperature and matter power spectrum of the model to consider the effects of matter-like dark energy during the matter-dominated era.
Decreased surface blistering and deuterium retention in potassium-doped tungsten exposed to deuterium plasma following ion irradiation
Authors: Ma Xiaolei , Zhang Xiaoxin , Wang Ting , Gao Yuan , Yuan Yue , Cheng Long , Zhu Jipeng , Lv Wei , Lang Shaoting , Ge Changchun , Yan Qingzhi
Published: November 2022

A large-size potassium-doped tungsten (KW) plate with a thickness of 15 mm was fabricated via powder metallurgy technology and hot rolling. In order to appraise the irradiation resistance of KW, the surface deuterium (D) blistering and D retention were studied on Fe11+ pre-damaged (0, 0.05 and 0.5 dpa) KW and pure tungsten (PW), which were exposed to ∼60 eV and ∼5 × 1021 m−2 s−1 D plasmas at 500 K at a fluence of ∼5.76 × 1025 m−2. The results indicate that the KW alloy can better inhibit the generation of vacancy defects after Fe11+ ion damage compared with PW because K bubbles can restrain the migration of W self-interstitial atoms and the accumulation of vacancies caused during Fe11+ ion irradiation. The Fe11+ ion pre-damage can relieve the surface blistering and D retention of PW and KW at the same time, and the KW has a better effect of inhibiting D retention, while it does not show a significant advantage in inhibiting surface blistering compared with PW. In addition, the causes of the discrepancy in total D retention and the surface morphology evolution of PW and KW are discussed in detail.
Intelligent diagnosis of rolling bearings with imbalanced data based on the ConVAE-CNN model
Authors: Xing Zhikai , Liu Yongbao , Wang Qiang , Li Jun
Published: November 2022

Data-driven intelligent diagnosis method has been widely used in mechanical equipment fault identification. However, the data set imbalance is still one of the critical problems affecting the effect of intelligent diagnosis in the practical work of rotating machinery. To solve the problem of fault identification of rolling bearings with imbalanced data sets, a rolling bearing intelligent diagnosis method based on the ConVAE-CNN model was proposed in this paper. In this method, a convolutional variational autoencoder network (ConVAE) model is constructed. In the coding stage, the convolutional layer is used to extract the features of minority samples. In the decoding stage, full connection layers are used to expand the dataset of minority samples. Bearing fault features were extracted by convolution and pooling operations of the convolutional neural network model, and the performance of the proposed method was tested using rolling bearing experimental data. The results show that the proposed method effectively solves the bearing fault classification problem with imbalanced data sets. Compared with the other diagnosis methods, the performance of the proposed method is better, and it has a broad application prospect in the diagnosis of imbalanced data.
Nonlinear dynamic analysis of liquid-solid coupling and rubbing on drill string
Authors: Ren Fushen , Sun Pengyu , Wang Baojin , Fang Tiancheng
Published: November 2022

Natural deposit of natural gas hydrate (NGH) exists in the colder regions on the earth, which is an unconventional energy and has great potential. About 97% of the NGH is located in the offshore and only 3% is located on the land. Due to its sensitivity to the external environment and easy decomposition, it is necessary to suppress the external environment changes caused by the complex vibration of the drill string during its exploitation. In this paper, the fluid-solid coupling nonlinear vibration of drill string is studied. The nonlinear dynamic model of drill string with drilling fluid is established. The relationship between variable parameters of drill string and complex dynamics of drill string is analyzed. Furthermore, the bifurcation diagram is given. The results have certain significance for discussing the non-linear dynamic mechanism of drill string under complex conditions and reasonably selecting the drilling process parameters of NGH.
Control of droplet transfer during in-situ synthesis of NiTi alloys by dual-wire electron beam additive manufacturing
Authors: Pu Ze , Chang Baohua
Published: November 2022

In this paper, the droplet transfer mode during in-situ synthesis of NiTi alloys by dual-wire electron beam additive manufacturing by pure Ni and Ti wires was comprehensively studied. This work shows that the droplet transfer was jointly determined by the droplet transfer distance together with spatial position between two wires and electron beam. By reasonable control of the above factors, an ideal stable continuous liquid bridge transfer mode could be achieved. In this mode, Ni wire and Ti wire could be melted together and form a shared molten pool, which avoids the occurrence of spatter and guarantee the credibility of wire fed amount. Results show that NiTi alloys in-situ synthesized by liquid bridge transfer mode could obtain NiTi alloys with good forming quality and typical phase transformation behavior.
Design of ultrasonic leak location detector based on FPGA for spacecraft based on orbit
Authors: Sun Wei , Pan Ying , Hou Xuyan , Li Zheng , Ren Guohua , Sun Lichen , Qi Guangming , Yan Rongxin , Meng Donghui , Qi Lei , Su Liang , Wang Hao , Qiang Zhou
Published: November 2022

The research on the ultrasonic leak location technology for the spacecraft on orbit environment is of great significance to ensure the long-term on orbit normal operation, eliminate the leakage in time, maintain the cabin environment and ensure the life safety of astronauts. Taking the leakage of the cabin wall structure and gas pipeline of the space station as the research object, the aerodynamic sound source characteristics of on orbit gas leakage are analyzed, and the acoustic characteristics are analyzed and extracted. Based on the theoretical basis, an ultrasonic on orbit leak detector is developed with non-contact ultrasonic sensor and camera as the probe and FPGA as the core processor. The tests are carried out to simulate the vacuum leakage of the sealed cabin structure and the positive pressure leakage of the sealed pipeline, and the leakage ultrasonic signals under different leakage holes are analyzed and processed. According to the magnitude of Eigen values, the leakage point position is determined by patrol inspection to form the detection process. The results show that the aerodynamic ultrasonic signal of gas leakage to vacuum is weak, and the amplitude of sound source signal increases with the increase of leakage hole. The signal characteristic of leakage ultrasound is that there will be an obvious main peak in the frequency band of 40KHz ± 3kHz. The leakage of more than 0.2mm can be effectively detected through patrol inspection, and the positioning accuracy is better than ± 20mm. The research results lay a foundation for on orbit leak detection and rapid positioning of the space station.
Research on selection of control points for vibration test of radar servo system
Authors: Cheng Liang , Zhou Junyu
Published: November 2022

In this paper, the influence of control points on vibration results in random vibration test for radar servo system is studied through simulation and destructive experiment. Results show that if the control points are not selected properly, resonance is easy to occur, which makes the response of structure out of tolerance as well as leads to strength failure of the structure. According to the response results of pre-vibration test, properly control points can be selected for the actual vibration test. The result has important reference for reasonable selection of control points in vibration test.
Numerical visualisation on the impact of setting convective velocity of outflow boundary on a parallel grid-generated flow
Authors: Suzuki Hiroki
Published: November 2022

This study approaches a widely used convective outflow condition for analysing turbulent flow fields with a freestream to clarify effects of the convection velocity setting. Previous studies have often used a local velocity at the outflow boundary. This study uses the setting of the outflow condition described in the previous Orlanski’s study. In this study, a two-dimensional flow induced by a parallel grid is analysed. The governing equations are spatially discretised by a second-order central difference method and integrated in the time domain using the fourth-order Runge-Kutta method. We can observe wavy profiles near the outflow boundary that vary in the streamwise direction. These wavy profiles are more evident when the local velocity is used as the convective velocity. The effect of the setting outflow velocity on the turbulence structure characterised using the second invariant of the velocity gradient tensor is also investigated.
Stability analysis of the turbine rotor system with foundation support under impact excitation
Authors: Xu Siyu , Wang Mingxin , Li Kai , Han Qingpeng , Tong Xin , He Keyuan , Zhu Rui
Published: November 2022

Considering the stability changes of the whole steam turbine system with and without shock excitation, based on the combined methods of modeling simulation, multi-point analysis and multi-feature map analysis, the support structure of the whole steam turbine rotor under the action of unbalance and shock excitation is analyzed. Stability changes were analyzed. By analyzing the time-domain waveform, frequency spectrum and axis locus of the model casing, the typical support points of the high-pressure rotor section and the low-pressure rotor section under the sudden shock excitation and unbalanced force, the time-domain waveform, frequency spectrum and axis locus of the axis can be grasped. The influence on the structural stability and vibration characteristics of the steam turbine can provide a reference for the shock resistance design of the whole steam turbine system.
A polyurethane binder with excellent mechanical properties based on copolymerization and dynamic bond crosslinking
Authors: Zhang Yu , Zheng Jian , Zhang Xiao , Yu Guibo , Jia Yunfei
Published: November 2022

Hydroxyl-terminated polybutadiene (HTPB) based polymer binder is expected to possess exceptional mechanical performances, as the matrix of composite solid propellant. In this study, HTPB and hydroxyl-terminated polyether (HTPE) were copolymerized by isocyanate (IPDI) to form HTPB-HTPE, and then ZnCl2 was added to prepare a polyurethane binder (HTPB-HTPE-Zn) with excellent mechanical performances. The thermal properties and dynamic mechanical characteristics of the synthesized polyurethane were characterized by a differential scanning calorimeter, dynamic thermomechanical analyser, and Instron universal testing machine. The experimental results show that HTPB-HTPE-Zn exhibits significantly enhanced elongation at break (1122.52%) and basically unchanged tensile strength (0.37 MPa), compared with pure HTPB (503.42%/0.38 MPa). This work provides a method for preparing binders with high mechanical properties and broadens the application field of HTPB-based polyurethane.
Analysis of thermal-stress behavior during the process of in-situ fabricating Ti-22Al-25Nb parts by twin-wire electron beam freeform fabrication
Authors: Li Zixiang , Zhang Haoyu , Liang Zhiyue , Chang Shuhe , Du Dong , Wang Li
Published: November 2022

Wire-based in-situ additive manufacturing (AM) technology is famous for the integration of material preparation and structure manufacturing. In the current study, the simulation method was adopted to study the thermal-stress evolution behavior during the process of the in-situ AM Ti-22Al-25Nb component. A single-layer multi-pass component was deposited firstly to prove the credibility of the simulation model. Then, the temperature-stress field evolution of the multi-layer single-pass component was revealed and analyzed systematically. This research is of great significance for suppressing the generation of cracks during forming process and promoting the wide application of Ti-22Al-25Nb alloys.
Robust path following control for autonomous vehicle considering actuator fault
Authors: Chen Mengyuan , Ren Yue , Ou Minghui
Published: November 2022

The development of drive-by-wire chassis technology increases the flexibility of vehicle dynamic control. However, more actuators have higher potential failure risk and lead model mismatch, which brings a severe challenge for the control precision and system robustness. Regarding to the potential failure risk of the steering actuator, this research presents a feedback gain scheduling H∞ controller for autonomous vehicle path tracking. Firstly, the linear parameter-varying (LPV) model is established considering the speed variation and potential actuator fault. Then the state feedback control algorithm is proposed to maintain the tracking performance and system robustness. The control gain matrix is optimized via linear matrix inequation (LMI). Finally, the closed loop system is proved to be asymptotic stable by Lyapunov function and the simulation results demonstrate that the proposed controller has satisfactory tracking performance under unpredictable actuator fault degree, which provides good robustness and better reliability for autonomous vehicle in complex conditions.
Analysis of power system angle stability based on Heun algorithm under gauss and jump excitation
Authors: Li Lijuan , Li Yuange , Chen Yongdong , Liu Hongliang , Zhang Qingsong
Published: November 2022

In the process of promoting the dual-carbon goals, the “double-high” character of the power system is gradually becoming obvious and brings a lot of random factors, such as high proportion of new energy access and cut out power system, brings gauss excitation from continuous fluctuations and jump excitation from shock fluctuations, affecting the power system safety operation. Combining the effects of gauss excitation and jump excitation, described as excitation terms acting on gauss white noise and poisson white noise. Constructing the stochastic dynamic model with jump of power system, Heun method is constructed to solve the model, and the comprehensive influence of stochastic excitation and jump excitation under different intensities on stability analysis is analyzed quantitatively. The simulation results of one-machine infinite-bus (OMIB) system shows the correctness and rationality of the method constructed, and provides ideas for the analysis of power system stability under the combined influence of multiple types of random factors.
Static voltage stability prediction for PCCs of new energy power stations in the grid-connected system
Authors: Li Sheng , Ma Yanan , Zhang Can , Yu Jiawei
Published: November 2022

To estimate the static voltage stability of the PCC (Points of Common Coupling) of wind/PV (Photovoltaic) in the new energy resources grid-connected system, a modified static voltage stability index NVSI that adds the stochastic wind/PV power to calculate the index values is proposed, based on the IVSI index that is derived from the power flow equations of the traditional power system. A short-term wind/PV power prediction model considering several meteorological factors and using the RF (Random Forest) algorithm is presented. The RF’s prediction accuracy is affirmed by comparing with the BP-ANN algorithm on a typical day, and the predicted wind/PV power values are substituted into the NVSI index to predict and estimate the PCC’s voltage stability in the IEEE 14-bus system with wind/PV, the practicability and effectiveness of the NVSI index are affirmed.
Development and application of unplanned automatic shutdown fault tree model of nuclear power plant
Authors: Cheng Bin , Yang Xiaohu , Qing Chen , Jiang Hong
Published: November 2022

In order to improve the operation performance of nuclear power plants, this paper introduces a modeling method of unplanned automatic shutdown of nuclear power units based on Fault Tree Analysis, and takes the shutdown signal of steam generator water level low-low as an example, analyzes the development process and application scenarios of unplanned automatic shutdown fault tree in detail. The results show that this method solves the huge and complex problems in the fault tree model of unplanned automatic shutdown in nuclear power units, and can be used to comprehensively and systematically identify the components that affect unit power generation. At the same time, combined with quantitative data, it can monitor the risk of unit power generation, and achieve targeted and efficient improvement of equipment reliability management level and power generation performance level.
Structure design and performance research of the radar antenna array
Authors: Meng Guojun , Chen Jianping , Zhao Chengsan , Hu Feng
Published: November 2022

In order to realize the compatibility of various transportation modes and rapid erection requirements of a large-aperture radar, this study takes a large-aperture high-spanning ratio P-band radar antenna array as the research object, and designs the array’s retraction, locking and synchronization control in detail. On this basis, the simulation analysis of the rigidity of the surface is carried out, and the accuracy of the face is actually measured. The simulation and actual measurement results show that the erection and retraction time are controlled within 11 minutes, and the synchronization error is controlled within 2mm. The retractor can meet the requirements of large-caliber P-band radar precision measurement, and has the characteristics of strong reliability, high synchronization accuracy, good maneuverability, high surface accuracy, and has broad application prospects.
Analysis and research on the influence of multiple factors on the steady operation area of large-capacity MMC-HVDC transmission system
Authors: Zhang Longen , Chen Kun , Han Hongling , Wang Ting , Zhu Shuai
Published: November 2022

Aiming at the MMC-HVDC (modular multilevel converter based high voltage direct current), this paper studies the influence of multiple factors such as the AC system and converter characteristic limits on the steady-state operating range of the MMC-HVDC transmission system. First, a mathematical model based on the steady-state operation of the MMC-HVDC transmission system is established, and the AC-side power quality requirements and stability limiting factors of the MMC-HVDC system are analyzed and summarized, as well as the constraints of multiple limiting factors on the converter side. Based on this, the power operation range of MMC-HVDC transmission project under different conditions is obtained. Finally, combined with the actual project, the effects of modulation ratio, equivalent reactance between the AC outlets of the converter and AC system equivalent impedance on the steady-state power operating range are analyzed and studied separately.
Error analysis of multi-step day-ahead PV production forecasting with chained regressors
Authors: Sarajcev Petar , Meglic Antun
Published: November 2022

This paper presents a comprehensive error analysis of the day-ahead photovoltaic (PV) production multi-step forecasting model that uses a chained support vector regression (SVR). A principal component analysis (PCA) is also implemented to investigate possible improvements of the SVR prediction accuracy. Special attention was given to the hyper-parameter tuning of the chained SVR and PCA+SVR models; specifically, the dispersion of the prediction errors when fine-tuning the model with an experimental halving random search algorithm implemented within scikit-learn, i.e. the HalvingRandomSearchCV (HRSCV). The obtained results were compared with the traditional randomized search technique, i.e. the RandomizedSearchCV (RSCV). The chained SVR model prediction errors were analysed for several different parameter distribution settings. After doing repetitive fine-tuning and predictions, it was observed that the HRSCV tends to choose sub-optimal hyper-parameters for certain scenarios, as will be elaborated in the paper. Moreover, when analysing prediction errors of the same model fine-tuned repetitively with the HRSCV and RSCV, it was found that HRSCV creates larger errors and more inconsistency (variability) in the prediction results. The introduction of the PCA to the chained SVR model, at the same time, reduces the influence of exogenous variables and, on average, increases its performance and decreases prediction errors regardless of the optimization technique used.
Analysis of typical fault characteristics of modular multilevel converter for flexible HVDC transmission
Authors: Hu Xingyang , Chen Kun , Wang Ting , Huang Zengrui
Published: November 2022

Modular multilevel converter (MMC) has been widely used in VSC-HVDC system for its smooth output waveform, low harmonic content and low switching loss. But compared with the conventional LCC-HVDC system, modular multilevel converter has a short development history, few engineering applications, high failure rate and lacks of very effective protection strategies, which limits its further development. Therefore, this paper firstly introduces topological structure of MMC and its working principle. Then the commonly used control policy of dual-terminal MMC-HVDC project is elaborated. Finally, the transient electrical characteristics of the typical faults are detailedly analyzed through the combination of theoretical analysis and simulation, such as three phase short circuit of converter valve, single phase grounding of converter valve, and the bridge arm short circuit. The conclusion provides an essential theory for the research of the converter protection strategy in the MMC-HVDC project.
PSO-SVR-based voltage stability online monitoring method for large-scale power grids
Authors: Li Shuaihu , Li Jie , Hou Jie , Tong Xing
Published: November 2022

With the power load increasing, the issue of voltage stability and voltage collapse is getting greater attention. Online monitoring of grid voltage stability is therefore a necessary requirement. In this paper, a PSO-SVR-based voltage stability online monitoring method for large-scale power grid is proposed. Initially, the load impedance modulus margin (LIMM) method is used to identify weak nodes in the system and thereby determine the best installation locations of the phase measurement units (PMUs). Afterwards, a particle swarm optimization modified support vector regression (PSO-SVR) algorithm is trained by using the state variables of the weak nodes where the PMUs are installed as input features and the calculated LIMM values as output features. In this way, the PSO-SVR model learns the non-linear relationship between the operating state of the power system and the corresponding LIMM values. The LIMM values of the nodes are obtained from the respective state-variables. The method proposed in this paper not only accurately assesses the stable voltage level of the load node, but also avoids the problems of parameter drift and misjudgement that can occur in the original LIMM method. Therefore, it has significantly advantages for online applications. Lastly, it is tested on an IEEE 118 system to verify the effectiveness and accuracy of the proposed method in this paper.
Optical fiber hydrogen sensing system based on dual photodetectors
Authors: Xiao Shiyun
Published: November 2022

The safe use of hydrogen energy is expected to solve the dual problems of the environment and energy in the future. However, because of the flammable and explosive characteristics of hydrogen, new sensing technologies that can reliably monitor the concentration of hydrogen are urgently needed. Fiber optic sensing technology has the advantages of good electrical insulation performance, strong anti-electromagnetic interference ability, non-invasive, high sensitivity, easy to realize the long-distance monitoring of the measured signal, corrosion resistance, explosion-proof, flexible optical path, easy to connect with the computer and so on. Based on the above advantages, this paper uses the hydrogen-induced discoloration effect of WO3-Pd2Pt-Pt nanocomposite films to construct a fiber-optic hydrogen sensing system based on dual photodetectors, which is closely integrated with Internet technology. It can realize the real-time monitoring of hydrogen concentration in life and production and is of great significance to the safe operation of national defense security and national economic construction.
Machine learning for materials classifications from images
Authors: Zhang Lei , Li Zhenyu
Published: November 2022

Computer-aided materials recognition from images is critical for automation in materials industry. In this manuscript, we perform machine learning studies to recognize common materials from images. To this end, an annotated materials image database consisting of typical materials including metal, plastic, glass, fabric, leather and wood is provided. Subsequently, a PSPNET-based deep learning model is constructed to classify these materials from images. The model achieves decent recognition accuracies above 0.60 for leather and wood, which are comparable to human. The machine learning process is also attempted for videos and small-size images to further demonstrate the viability of the image-based machine learning techniques. This study highlights the importance of image-based deep learning studies for materials science, and calls for further machine learning studies to automate and expedite the materials recognition process.
A novel structural design technology of highly integrated antenna in missile
Authors: Hong Zhaobin , Zhu Xian , Zhou Zhijian , Zhao Kai
Published: November 2022

High integration and low-profile integrated design technology need to be proposed to meet the modern tactical requirements of highly integrated antenna in missile, which put forward strict requirements for volume, weight, reliability, and environmental adaptability, etc. A vertical blind matching non-cable connection between T/R module and radiating surface of the antenna is presented to realize low-profile antenna. An analysis method based on the missile-borne environment and electromechanical thermal coupling is proposed for highly integrated active antenna in missiles. Low-profile and high integrated unit design technology, parameterized high-precision blind matching technology, electromechanical thermal coupling technology have been broken out in this paper.
Based on NXUG10 Research on automatic programming and simulation machining of integral split impeller
Authors: Ye Xuanlin
Published: November 2022

Taking the programming and simulation processing of integral split impeller in nxug10.0 software as an example, this paper introduces a method that can realize the automatic programming of parts and components to call out five axis machine tool for simulation processing in ug10.0 software. This paper introduces the whole process of ug10.0 impeller machining module from automatic programming parameter setting of integral split impeller to generating tool path files for machining integral split impeller parts and calling out five axis machine tool for simulation machining. The correctness of the automatic programming program is verified. The phenomenon of Tool Collision and interference in the machining process is avoided, and the machining efficiency of the impeller is greatly improved.
Failures statistics of on-line monitoring devices for gases dissolved in oil
Authors: Liu Shuang , Wang Wenhao , Han Rui , Wang Shaohe , Zou Guoping
Published: November 2022

The on-line monitoring device of dissolved gas in oil is an important starting point to understand the internal operation condition of large oil filled equipment such as transformer. However, the device has no unified maintenance strategy. At present, it basically adopts the strategy of “repair only when it is broken”, which seriously affects the real-time perception ability of the device to the health state of primary equipment. According to the components of the device, the device faults were divided into four categories: Status information access controller (CAC) fault, carrier gas fault, communication fault and monitoring device body fault. In addition, they were subdivided into eight secondary faults according to the detection principle and process. Through the big data analysis of the operation and maintenance records of a province in recent three years, it was found that the main causes of the device faults were the under voltage of the carrier gas and the fault of the monitoring device body. It was suggested to popularize the device using carrier gas maintenance free type or photoacoustic spectrum principle to reduce the frequency of device failure. At the same time, it was suggested that the device design should be transformed to modularization to facilitate the fault operation and maintenance of the device body. The degassing module and intelligent monitoring module of the unit should be focused when formulating the maintenance strategy of the unit in the future.
Energy-conscious maintenance and production scheduling for single machine systems under time-of-use tariffs
Authors: An Xiangxin , Cao Lei , Si Guojin , Chen Zhen , Zheng Meimei , Tao Jianfeng , Xia Tangbin
Published: November 2022

In view of the joint optimization problem of preventive maintenance and production scheduling for modern production systems under time-of-use tariffs, a two-stage joint decision-making policy is proposed to achieve the peak-shifting reduction of production power. In the first stage, a dynamic preventive maintenance schedule is sequentially obtained based on the availability of machine. In the second stage, the production scheduling optimization of multi-workpiece processing is further carried out. The power consumption cost and the delay penalty cost under the time-of-use electricity tariff are considered, and the mixed integer programming model is established to achieve the balance of energy consumption and production delay. Numerical experiments have shown that by reasonably planning the idle time at the time of production batch conversion, the proposed model can effectively shift the on-peak power demand to off-peak, meet the stable electricity demand of enterprises, and improve the sustainable utilization level of power.
Argonne Pixel Tracking Telescope at the Fermilab Test Beam Facility
Authors: Bhopatkar V. , Benoit M. , Dong B. , Kiehn M. , Lambert J. , Metcalfe J. , Muse J. , Wilbern D.
Published: November 2022

The Argonne Pixel Tracking Telescope is installed at the
Fermilab Test Beam Facility. The telescope consists of six planar
n+-in-n silicon sensors with a pixel size of
250 × 50 μm2. The instrumentation of the
telescope is described including the electrical and mechanical
setups. A 120 GeV proton beam is used to evaluate the telescope
performance using criteria such as cluster size, pixel tracking
efficiency, and spatial resolution. The spatial resolution of the
telescope is measured to be
72 μm × 13 μm and is consistent
with the resolution determined from the simulation. This telescope
will be used to test the performance of the various silicon pixel
technology as well as to study the effects and the performance of
the detectors after being irradiated.
Effects of sterilization methods on gelatin methacryloyl hydrogel properties and macrophage gene expression in vitro
Authors: Zhang Fan , Scull Grant , Gluck Jessica M , Brown Ashley C , King Martin W
Published: November 2022

To assure the long-term safety and functional performance after implantation, it is of critical importance to completely sterilize a biomaterial implant. Ineffective sterilization can cause severe inflammation and infection at the implant site, leading to detrimental events of morbidity and even mortality. Macrophages are pivotal players in the inflammatory and foreign body response after implanting a biomaterial in the body. However, the relationship between the sterilization procedure and macrophage response has not been established. In this study, three commonly used sterilization methods, including autoclaving, ethylene oxide gas and ethanol treatment, were used to sterilize a gelatin methacryloyl hydrogel. The impacts of different sterilization methods on the structure and physical properties of the hydrogel were compared. Macrophage responses to the sterilized hydrogel were analyzed based on their morphology, viability and in vitro gene expression. It was found that the sterilization methods only marginally altered the hydrogel morphology, swelling behavior and elastic modulus, but significantly impacted macrophage gene expression within 48 h and over 7 d in vitro. Therefore, when selecting sterilization methods for GelMA hydrogel, not only the sterility and hydrogel properties, such as material destruction and degradation caused by temperature and moisture, should be taken into consideration, but also the cellular responses to the sterilized material which could be substantially different.
Effects of cryospheric hydrological processes on future flood inundation and the subsequent socioeconomic exposures in Central Asia
Authors: Wang Ning , Sun Fubao , Wang Hong , Liu Wenbin
Published: November 2022

Floods and their subsequent socioeconomic exposures are increasing in most parts of the world due to global warming. However, less attention is given in the arid Central Asia (CA), in which floods usually occur in data-scarce high-mountainous regions with complex cryospheric hydrological processes (CHP). In this study, an improved hydrologic-hydrodynamic model coupled with a glacier mass balance module was developed to enhance flood simulations in CA. The effects of the CHP on future flood inundation and the subsequent socioeconomic exposures were also investigated. We found that the simulations of daily streamflow and flood magnitudes improved significantly over the selected hydrological stations after considering the glacier mass balance. Our estimations indicated that the flood inundation and its dynamic evolution generally agreed with satellite observations. Moreover, CHP-induced (rainfall-induced) flood inundation plays a significant role in China’s Xinjiang and Tajikistan (other regions of CA). The CHP would amplify the effects of future flood on socioeconomics in CA, with population (Gross Domestic Productivity, GDP) exposure up to 2.25 million persons/year (150 billion $ PPP/year) for 2071–2100. These findings could provide scientific evidence to improve the understanding of CHP effects on future floods and the subsequent exposures, informing the prioritization and design of flood mitigation strategies in CA.
A new grinding surface roughness measurement method based on image quality algorithm and BP neural network
Authors: Lu Enhui , Guo Yaocun , Zhu Xinglong , Wang Yunan , Ren Wenxiang , Yang Yong
Published: November 2022

Due to the problem of single factor and no benchmark in the design of image characteristic index, the measurement results of machine vision-based grinding surface roughness measurement are greatly influenced by the light source brightness, and the accuracy is limited. To address this problem, a method based on the combination of a full-reference (FR) image quality algorithm visual saliency-induced index (VSI) and a backward propagation (BP) neural network for grinding surface roughness measurement is proposed. First, the VSI is applied to characterize grinding surface roughness. Its performance is then compared with the mainstream color image-based indices. Meanwhile, the ability of anti-interference to light source is analyzed for the VSI. Furthermore, in order to improve the prediction accuracy, the BP neural network is selected and applied to construct the roughness prediction model. The experimental results show that the VSI has significant advantages in the abilities of measurement accuracy and anti-interference to light source brightness levels. BP can significantly improve the prediction accuracy for VSI.