bluuebunny/crossref_metadata_2025_split huggingface dataset:
A novel calibration method based on fixed multi-plane targets for cameras with large field of view
Authors: Shi Xiancong , Peng Tao , Huang Zhenzhen , Zhang Zhijiang 
Published: May 2024

Abstract
For camera calibration with large field of view (FOV), the accuracy is impacted by the size of the calibration targets. Considering the challenges associated with producing and carrying large targets, existing methods resort to using small targets to achieve calibration without high accuracy. In order to solve this problem, a photogrammetric calibration method based on the fixed multi-plane targets (FMPT) is proposed in this paper for cameras with large FOV. The FMPT is composed by multiple identical small planar targets (PTs), with fixed pose transformation relationships among PTs. The proposed calibration method involves the following main steps. Firstly, the camera is moved several times to capture a series of images of FMPT. Secondly, the fixed pose transformation matrices of different small PTs in FMPT are calculated through the initial parameters of camera. Finally, calibration based on photogrammetry is conducted, with a continuous optimization of camera intrinsic and extrinsic parameters based on the multiple 2D and 3D constraint in the FMPT. Simulation and real data experiments show that the calibration accuracy using the proposed method is much higher than that using a small target, and sightly higher than that using a large target. Furthermore, the experiments demonstrate the robust stability of this method, maintaining high calibration accuracy even in the presence of increased noise and error in target production.
Long Term X-Ray Spectral Variations of the Seyfert-1 Galaxy Mrk 279
Authors: Akhila K. , Misra Ranjeev , Ezhikode Savithri H. , Jeena K. 
Published: May 2024

Abstract
We present the results from a long term X-ray analysis of Mrk 279 during the period 2018–2020. We use data from multiple missions – AstroSat, NuSTAR and XMM-Newton, for the purpose. The X-ray spectrum can be modeled as a double Comptonization along with the presence of neutral Fe Kα line emission, at all epochs. We determined the source’s X-ray flux and luminosity at these different epochs. We find significant variations in the source’s flux state. We also investigate the variations in the source’s spectral components during the observation period. We find that the photon index and hence the spectral shape follow the variations only over longer time periods. We probe the correlations between fluxes of different bands and their photon indices, and found no significant correlations between the parameters.
Classification of motor imagery using chaotic entropy based on sub-band EEG source localization
Authors: Bi Jicheng , Gao Yunyuan , Peng Zheng , Ma Yuliang 
Published: May 2024

Abstract

Objective. Electroencephalography (EEG) has been widely used in motor imagery (MI) research by virtue of its high temporal resolution and low cost, but its low spatial resolution is still a major criticism. The EEG source localization (ESL) algorithm effectively improves the spatial resolution of the signal by inverting the scalp EEG to extrapolate the cortical source signal, thus enhancing the classification accuracy. Approach. To address the problem of poor spatial resolution of EEG signals, this paper proposed a sub-band source chaotic entropy feature extraction method based on sub-band ESL. Firstly, the preprocessed EEG signals were filtered into 8 sub-bands. Each sub-band signal was source localized respectively to reveal the activation patterns of specific frequency bands of the EEG signals and the activities of specific brain regions in the MI task. Then, approximate entropy, fuzzy entropy and permutation entropy were extracted from the source signal as features to quantify the complexity and randomness of the signal. Finally, the classification of different MI tasks was achieved using support vector machine. Main result. The proposed method was validated on two MI public datasets (brain–computer interface (BCI) competition III IVa, BCI competition IV 2a) and the results showed that the classification accuracies were higher than the existing methods. Significance. The spatial resolution of the signal was improved by sub-band EEG localization in the paper, which provided a new idea for EEG MI research.
Experimental study on spatial distribution law of traffic noise on urban viaduct
Authors: Li Xingang , Wang Lujie , Ding Yong 
Published: May 2024

Abstract
Traffic noise is the main environmental pollution of the elevated line. In order to prevent and control this noise, it is necessary to understand the spatial distribution of the noise. In this paper, the noise monitoring and data fitting of representative points near the Ningbo viaduct are carried out by means of the field test. By setting measuring points at different distances and heights perpendicular to and parallel to the elevated line, the spatial distribution law of noise near the elevated line is studied. The results show that: (1) The noise in the transverse direction of the bridge decreases in a logarithmic curve with the increase of the vertical distance between the measuring point and the viaduct; (2) The noise along the bridge decreases in a logarithmic curve with the increase of the vertical distance between the measuring point and the intersection; (3) The noise in the elevated direction first increases with the rise of the floor, reaching the maximum on floors 10-12, and the sound pressure on floors 12-20 is basically stable.
The impact of contamination on audible noise in AC transmission lines
Authors: Xie Lianke , Cui Xiangyu , Shi Xin , Hou Xiaobang , Hu Yanglin , Wei Qingquan 
Published: May 2024

Abstract
The objective of this study is to investigate the impact of accumulated pollutants on the surface of a 1000 kV AC transmission line in a specific location in China on its audible noise generation. The line with diatomaceous earth, kaolin, and other pollutants attached to it is modeled by using finite element software, and the study results indicate that the conductivity of the material plays a significant role in influencing the audible noise. In addition, diatomaceous earth has the least effect on the amplitude and lateral attenuation of audible noise, and sodium chloride and carbon powder have the greatest effect. The research in this paper can be used for the reason that dirt particles affect the magnitude of audible noise and these findings offer valuable insights for the management of audible noise.
Research on numerical simulation of tandem thrusters flow-induced noise
Authors: Ma Fuqiang , Xie Lixun , Liu Yansen 
Published: May 2024

Abstract
A tandem propeller is a kind of propulsion device that is installed on the outer axis and the inner axis with the same axis respectively and rotates positively and negatively. Taking DTMB tandem thrusters as an example, which consists of propeller3689 and propeller3849, the hydrodynamic characteristic simulation of the tandem thrusters is completed, using sound analogy theory. The simulation results are consistent with the experimental results. The speed distribution of the tandem thrusters and the hydrodynamic wake of the tandem thrusters are analyzed. Through the analysis of acoustic radiation characteristics, it can be concluded that the noise characteristics of tandem thrusters are more complex than those of ordinary propellers, and there are more line spectrum characteristics in them.
Development of an acoustic doppler flow profiler and flow testing
Authors: Zou Jun , Liu Yanping 
Published: May 2024

Abstract
The flow test with acoustic Doppler current profiler (ADCP) is a new flow test method developed and applied only in the last decade or so. However, because it involves many disciplines such as hydroacoustic physics, ultrasonic transducer technology, electronics, and signal processing, most of the ADCPs used at the present stage are imported, and the domestically produced high-precision ADCPs have a lot of space in the domestic market. This paper introduces the measurement principle of ADCP. Based on this principle, we have overcome the weak signal processing circuit and successfully developed a domestic horizontal fixed acoustic Doppler flow profiler. The instrument is used for flow tests in Yixing (South) Hydrological Station, and the results of the comparison and error analysis meet the requirements of the national first-class precision hydrological station in the “Hydrological Data Compilation Specification” to satisfy the needs of the daily test in the station. The “Horizontal Fixed Acoustic Doppler Profile Flow Rate System” was selected as one of the 100 typical cases of popularizing and applying the achievements of the Ministry of Water Resources in 2020, and it can replace the imported instruments.
Experimental study on cavitation water jet cleaning of marine fouling
Authors: Ji Zitao , Fang Zhenlong , Kang Ding 
Published: May 2024

Abstract
The accumulation of marine fouling on a ship’s hull can increase its fuel consumption, necessitating removal. The use of a cavitation water jet as an efficient method for cleaning marine fouling has been widely adopted. In the research, experiments are conducted on water jet cleaning of marine fouling to investigate the influence of water jet parameters on cleaning efficiency. The findings reveal that the surface damage to specimens was minimized when maintaining an erosion pressure of 16 MPa, employing a 25 mm standoff distance, and applying a 90° incidence angle. This research can provide theoretical guidance for subsequent optimization of cavitation water jet cleaning parameters.
Heat transfer mechanism of different vortex generators arrangements embedded in heat exchange tubes
Authors: Liu Kai , Guo Yangyang , Wang Jiangbo 
Published: May 2024

Abstract
Heat exchange is widely used in many fields to improve heat transfer efficiency and save energy, while longitudinal vortex generator (VG) is widely used in many heat transfer heat exchangers. In this work, the effect of VGs with different numbers and different pitch ratios (PR) on the heat transfer characteristics in the tube was studied numerically. The results show that when the fluid flows through the VG, the reflux region will be generated, and the fluid velocity in the reflux region will be inhibited, resulting in uneven temperature distribution and increased Nu. When multiple VGs are arranged in a row, the number of vortices is increased, and the area affected is increased. This improves the overall heat transfer performance. With the decrease of PR, the number of VG rows increases, and the heat transfer performance increases first and then decreases with the decrease of PR.
Study of long-term in-orbit pressure control of liquid krypton cryogenic storage tank
Authors: Chen Jidong , Zhu Jianbing , Chen Jie , Duan Luobin , Xu Guowen 
Published: May 2024

Abstract
Due to its high specific impulse, low toxicity, contamination, safety, and cost, krypton has gradually replaced other propellants as the primary choice for electric thrusters on deep-space exploration and large-orbit transfer missions with long-range, long-duration, and large-thrust requirements. However, due to the cryogenic propellant itself having a low boiling point, controlling the pressure change of krypton cryogenic propellant during the process of long-term cryogenic storage has emerged as one of the most important issues that must be resolved and proven to achieve non-destructive storage of cryogenic propellant. This paper examines the necessity and viability of a cryogenic gas propellant liquefaction storage scheme and quantifies the effectiveness of tank pressure control of the supercooled liquid krypton injection mixing scheme to solve the problem at present. Its purpose is to offer scheme examples for the design of a krypton thruster propellant storage unit and the in-tank pressure control during the long-term application process.
Optimization of sustainable distributed power generation in distribution networks: a comprehensive analysis of location, capacity, and environmental impact
Authors: Guo Guangchuan , Xu Limei , Maihemutijiang Maiheliya , Wang Yao 
Published: May 2024

Abstract
With the increasing integration of distributed generation (DG) into distribution networks, the impact of its output and configuration on the environment and overall benefits has become more pronounced. To enhance environmental benefits while minimizing costs, an optimization model for DG location and capacity considering environmental benefits (LCEB) is proposed. Initially, a mathematical model for DG location and capacity is established, with optimization objectives including voltage deviation, network loss, and environmental benefit. Subsequently, modified particle swarm optimization (MPSO) with a single-dimension search probability mutation is employed to solve this model, obtaining an optimized DG output and layout scheme. Finally, the feasibility and effectiveness of the proposed model are demonstrated through simulation and analysis by using the IEEE33 node system as an example. The results highlight the model’s capability to improve environmental and economic benefits, enhance voltage levels, and reduce network losses within the distribution network.
Current-sensorless model predictive control for DAB converter based on back-flow power optimization
Authors: Tang Kaile , Chen Quan , Ding Jinjin , Hui Hui , Zhang Qian 
Published: May 2024

Abstract
To solve problems such as high back-flow power, low system efficiency and poor dynamic properties of dual-active-full-bridge DC-DC converters in energy routers under traditional single-phase-shift modulation, the present paper introduces a current-sensorless-based model predictive control method combining back-flow power optimization based on Extended-Phase-Shift (EPS) modulation strategy. The transmission power model of the DAB converter is analyzed, taking into account the extended phase shift and the optimal shift comparison combination is found by the Lagrange multiplier method with the return power as the objective function. Then, the cost function is constructed to track the output voltage to achieve model predictive control without a current sensor. Finally, the accuracy and efficiency of the proposed strategy are verified by simulation. The results demonstrate the efficacy of this approach in mitigating system back-flow power and enhancing dynamic performance.
Reactive power optimization of distribution network with photovoltaic power based on sparrow search algorithm
Authors: He Beibei , Xiao Jianmei , Yi Puting , Gu Shuangnan 
Published: May 2024

Abstract
With the construction of new power systems centered around new energy, distributed photovoltaic power generation has been rapidly popularized. Photovoltaic power generation with volatility and randomness is connected to the distribution network, causing voltage fluctuations in the distribution network to exceed allowable values and an increase in system losses. The objective of this article is to establish a mathematical model for optimizing the distribution of reactive power using distributed photovoltaic power generation, to minimize system losses and voltage fluctuations. Using an improved sparrow search algorithm to solve the model and taking the IEEE30 node system as an example for simulation analysis, the feasibility of the model and algorithm is verified through case analysis.
An optimized design for power inspection
Authors: Fan Jiashu , Huang Qiaoliang 
Published: May 2024

Abstract
This paper realizes attitude tracking, speed tracking, fixed-point tracking, path tracking, and trajectory tracking by adjusting the relevant parameters of the UAV motor controller. In the practical application of UAVs, we will design some flight modes according to the actual use requirements, such as stabilization mode, fixed point mode, and mission mode. From the essence of control, these modes are to expect the state of the aircraft and allow it to fly in a given desired state. For example, in the stabilization mode, the remote control outputs pitch angle expectation, roll angle expectation, yaw rate expectation, and throttle expectation, and then the controller controls the above expectation by controlling the motor throttle.
A study of the performance of SPEEK electrolyte of a novel PEMFC
Authors: Awulachew S S , Nigussa K N 
Published: May 2024

Abstract
Analysis of performance of fuel cell is carried out by considering non-fluorinated electrolyte and variety of potential electrodes. The study spans low temperature regions and carried out MD investigation of transport of ions in a novel PEM fuel cell (PEMFC), which is composed of electrodes and SPEEK as a non-fluorinated electrolyte. Typical values of ion conductivity σ near room temperature are σ = 8.5 × 10−2 S cm−1 when Pt is used as electrode, σ = 26 × 10−2 S cm−1 when Pd3Ag is used as electrode, and σ = 0.34 × 10−2 S cm−1 when Pd is used as electrode. Thus, this study reveals a twofold implications. Firstly, the choice of electrolyte affects whether the traditional Pt electrode remains to be superior for the overall fuel cell performance. Secondly, using SPEEK electrolyte has a potential to yield a closely matching ion conductivity with the one obtained from the costly Nafion electrolyte.
Bioremediation potential of microalgae for copper ion from wastewater and its impact on growth and biochemical contents: equilibrium isotherm studies
Authors: Fawzy Mustafa A , Abdelsalam Shereen , Hafez Wafaa A , Fathi Adel A 
Published: May 2024

Abstract
The use of microalgae to remediate heavy metal-contaminated wastewater has attracted more and more interest. In this investigation, the green microalgae Chloroidium ellipsoideum and Desmodesmus subspicatus were used to study copper uptake from nutrient media and its effect on algal growth and metabolism. The growth of C. ellipsoideum and D. subspicatus generally decreased with increasing copper concentrations. There was a decrease in the carbohydrate content of C. ellipsoideum, but an increase was observed in D. subspicatus by treatment with various copper concentrations. Low concentrations of copper helped to increase the protein content of C. ellipsoideum, but a decline in protein content was reported for D. subspicatus. By increasing the copper concentrations, an increase in the free amino acids and a decrease in the total lipid content of C. ellipsoideum and D. subspicatus were recorded. At 0.1 mgl–1 copper concentration, pH of 6.8, and algal dose of 1 g L−1, the maximum biosorption capacity of C. ellipsoideum was 0.398 mg g−1, corresponding to the maximum reduction of 68.66% of Cu2+, and 0.396 mg/g for D. subspicatus, corresponding to the maximum reduction of 59.52%. The Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models were applied to describe the isothermal biosorption of Cu2+ ions in studied algae. The Dubinin–Radushkevich model indicated that the copper biosorption mechanism was physical in nature. Cu2+ has a greater affinity for D. subspicatus than C. ellipsoideum, suggesting that C. ellipsoideum was relatively more resistant to Cu2+ toxicity than D. subspicatus. Moreover, FT-IR analysis revealed that carboxyl, amide, amino, carbonyl, hydroxyl, methyl and alkyl groups were the key groups responsible for the biosorption process. Therefore, D. subspicatus and C. ellipsoideum are efficient biosorbents for Cu2+ and can be used as biosorbents for heavy metals removal from wastewater.
Performance and stability of hybrid organic-inorganic perovskite photovoltaics in outdoor illuminations conditions
Authors: Meheretu Getnet M , Yihunie Moges T , Wubetu Getasew A 
Published: May 2024

Abstract
In this study, we conducted real-world outdoor performance and stability tests on two different configurations of perovskite solar cells in the climate conditions of Bahir Dar, Ethiopia. Under outdoor illumination with an incident power of 69 mW cm−2, this device demonstrated a power conversion efficiency (PCE) of 15% for an active area of 0.1 cm2. The maximum power generated, measured at a solar irradiance of 72 mW/ cm2, and was 1.23 mW. The second perovskite device has planar p-i-n configuration. This device achieved a PCE of 18% without masking, but the PCE dropped to 11% when the device was covered with circular aperture mask. Maximum power tracking and stability measurements of the device were conducted. Maximum power generation occurred at operating voltages ranging from 0.8 V to 1.2 V for a device with an active area of 0.095 to 0.1cm2. After 30 days of environmental exposure, the device maintained more than 90% of its initial PCE.
Building Partnerships
Authors: Williams Abiodun 
Published: May 2024

AbstractChapter 8 discusses the partnerships that Kofi Annan built with nongovernmental organizations, universities, think tanks, Nobel laureates, and other opinion shapers. He saw the potential of civil society as advocates and partners in achieving the goals of the UN. He believed that the engagement of civil society was a way to enhance the legitimacy, accountability, and transparency of intergovernmental decision-making. The chapter also examines his groundbreaking engagement with the business community and the creation of the Global Compact. Opening the UN to the private sector entailed risks and opportunities. The risk was that member states would see this form of engagement as a threat to their autonomy in economic governance. The opportunity derived from the fact that the private sector had enormous resources and expertise which could contribute to the UN’s work, especially on development. The chapter concludes with a discussion of Annan’s eponymous lecture series which he launched in 2002 as part of his goal to engage broader constituencies.
Lianas in tropical dry seasonal forests have a high hydraulic efficiency but not always a higher embolism resistance than lianas in rainforests
Authors: Gerolamo Caian S , Pereira Luciano , Costa Flavia R C , Jansen Steven , Angyalossy Veronica , Nogueira Anselmo 
Published: May 2024

Abstract

Background and Aims
Lianas have higher relative abundance and biomass in drier seasonal forests than in rainforests, but whether this difference is associated with their hydraulic strategies is unclear. Here, we investigate whether lianas of seasonally dry forests are safer and more efficient in water transport than rainforest lianas, explaining patterns of liana abundance.

Methods
We measured hydraulic traits on five pairs of congeneric lianas of the tribe Bignonieae in two contrasting forest sites: the wet ‘Dense Ombrophilous Forest’ in Central Amazonia (~2 dry months) and the drier ‘Semideciduous Seasonal Forest’ in the inland Atlantic Forest (~6 dry months). We also gathered a broader database, including 197 trees and 58 liana species from different tropical forests, to compare hydraulic safety between habits and forest types.

Key Results
Bignonieae lianas from both forests had high and similar hydraulic efficiency but exhibited variability in resistance to embolism across forest types when phylogenetic relationships were taken into account. Three genera had higher hydraulic safety in the seasonal forest than in the rainforest, but species across both forests had similar positive hydraulic safety margins despite lower predawn water potential values of seasonal forest lianas. We did not find the safety–efficiency trade-off. Merging our results with previously published data revealed a high variability of resistance to embolism in both trees and lianas, independent of forest types.

Conclusions
The high hydraulic efficiency of lianas detected here probably favours their rapid growth across tropical forests, but differences in hydraulic safety highlight that some species are highly vulnerable and may rely on other mechanisms to cope with drought. Future research on the lethal dehydration threshold and the connection between hydraulic resistance strategies and liana abundance could offer further insights into tropical forest dynamics under climatic threats.