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34 results on '"Li, Bixiong"'

1. Pre-insertion resistors temperature prediction based on improved WOA-SVR

Author

Dai, Honghe, Mo, Site, Wang, Haoxin, Yin, Nan, Fan, Songhai, and Li, Bixiong

Subjects
Computer Science - Machine Learning, Computer Science - Computational Engineering, Finance, and Science, Physics - Applied Physics
Abstract

The pre-insertion resistors (PIR) within high-voltage circuit breakers are critical components and warm up by generating Joule heat when an electric current flows through them. Elevated temperature can lead to temporary closure failure and, in severe cases, the rupture of PIR. To accurately predict the temperature of PIR, this study combines finite element simulation techniques with Support Vector Regression (SVR) optimized by an Improved Whale Optimization Algorithm (IWOA) approach. The IWOA includes Tent mapping, a convergence factor based on the sigmoid function, and the Ornstein-Uhlenbeck variation strategy. The IWOA-SVR model is compared with the SSA-SVR and WOA-SVR. The results reveal that the prediction accuracies of the IWOA-SVR model were 90.2% and 81.5% (above 100$^\circ$C) in the 3$^\circ$C temperature deviation range and 96.3% and 93.4% (above 100$^\circ$C) in the 4$^\circ$C temperature deviation range, surpassing the performance of the comparative models. This research demonstrates the method proposed can realize the online monitoring of the temperature of the PIR, which can effectively prevent thermal faults PIR and provide a basis for the opening and closing of the circuit breaker within a short period.

Published
2024

2. Dance of Channel and Sequence: An Efficient Attention-Based Approach for Multivariate Time Series Forecasting

Author

Wang, Haoxin, Mo, Yipeng, Yin, Nan, Dai, Honghe, Li, Bixiong, Fan, Songhai, and Mo, Site

Subjects
Computer Science - Machine Learning, Computer Science - Artificial Intelligence
Abstract

In recent developments, predictive models for multivariate time series analysis have exhibited commendable performance through the adoption of the prevalent principle of channel independence. Nevertheless, it is imperative to acknowledge the intricate interplay among channels, which fundamentally influences the outcomes of multivariate predictions. Consequently, the notion of channel independence, while offering utility to a certain extent, becomes increasingly impractical, leading to information degradation. In response to this pressing concern, we present CSformer, an innovative framework characterized by a meticulously engineered two-stage self-attention mechanism. This mechanism is purposefully designed to enable the segregated extraction of sequence-specific and channel-specific information, while sharing parameters to promote synergy and mutual reinforcement between sequences and channels. Simultaneously, we introduce sequence adapters and channel adapters, ensuring the model's ability to discern salient features across various dimensions. Rigorous experimentation, spanning multiple real-world datasets, underscores the robustness of our approach, consistently establishing its position at the forefront of predictive performance across all datasets. This augmentation substantially enhances the capacity for feature extraction inherent to multivariate time series data, facilitating a more comprehensive exploitation of the available information.

Published
2023

3. TimeSQL: Improving Multivariate Time Series Forecasting with Multi-Scale Patching and Smooth Quadratic Loss

Author

Mo, Site, Wang, Haoxin, Li, Bixiong, Fan, Songhai, Wu, Yuankai, and Liu, Xianggen

Subjects
Computer Science - Machine Learning
Abstract

Time series is a special type of sequence data, a sequence of real-valued random variables collected at even intervals of time. The real-world multivariate time series comes with noises and contains complicated local and global temporal dynamics, making it difficult to forecast the future time series given the historical observations. This work proposes a simple and effective framework, coined as TimeSQL, which leverages multi-scale patching and smooth quadratic loss (SQL) to tackle the above challenges. The multi-scale patching transforms the time series into two-dimensional patches with different length scales, facilitating the perception of both locality and long-term correlations in time series. SQL is derived from the rational quadratic kernel and can dynamically adjust the gradients to avoid overfitting to the noises and outliers. Theoretical analysis demonstrates that, under mild conditions, the effect of the noises on the model with SQL is always smaller than that with MSE. Based on the two modules, TimeSQL achieves new state-of-the-art performance on the eight real-world benchmark datasets. Further ablation studies indicate that the key modules in TimeSQL could also enhance the results of other models for multivariate time series forecasting, standing as plug-and-play techniques.

Published
2023

16. The Influence of Excitation Method on the Strength of Glass Powder High-Strength Cementitious Materials.

Author

Li, Bixiong, Wei, Xin, Zhang, Zhibo, and Peng, Bo

Subjects
FLEXURAL strength, POWDERED glass, GLASS waste, WASTE recycling, COMPRESSIVE strength, SOLID waste, POWDERS
Abstract

Recycling economy and the re-utilization of solid waste have become important parts of sustainable development strategy. To improve the utilization rate of waste glass, glass powder high-strength cementitious material (GHSC) was prepared by replacing part of the cement in the cementitious material with ground waste glass powder. Firstly, the effect of glass powder particle size on the flexural and compressive strength of GHSC was investigated by the gray correlation method, and the optimal grinding time was obtained. Additionally, the effect of the magnitude of steam curing temperature and the length of steam curing time on the compressive strength and flexural strength of GHSC was investigated, and the mechanism of the effect of the curing regime on the strength was explored by examination of the microstructure. Finally, to simplify the curing process of GHSC, the effects of Ca(OH)2 and Na2SO4 as excitation agents on the compressive strength and flexural strength of GHSC at different dosing levels were compared. The results showed that glass powder with a particle size of less than 20 μm would improve the compressive strength and flexural strength of the specimen. Steam curing can significantly improve the flexural strength and compressive strength of GHSC specimens. At a steam curing temperature of 90 °C for a duration of three days, the compressive strength and flexural strength of GHSC increased by 76.7% and 98.2%, respectively, compared with the standard curing specimens. Ca(OH)2 and Na2SO4 as excitation agents significantly enhanced the compressive and flexural strengths of GHSC under standard curing conditions. [ABSTRACT FROM AUTHOR]

Published
2024
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17. Early strength development of mortar with addition of calcium formate and electric field curing in cold climates.

Author

Yang, Zhouzhou, Mao, Jianghong, Li, Bixiong, Li, Sili, Qian, Wei, Li, Hao, and Ren, Jun

Subjects
MORTAR, ELECTRIC fields, CALCIUM, POROSITY, SCANNING electron microscopy, COLD regions
Abstract

The rapid development of early strength of concrete in cold regions is the primary measure to ensure its resistance to frost damage. In this context, this paper incorporates 2 wt% calcium formate into a mortar and electrically cures it by passing an alternating current (AC) at a temperature of −10°C. During testing, a temperature probe monitors the real-time changes in the internal temperature of the mortar under different energisation parameters. The strength of the mortar energised for 1 day is analysed under different energisation parameters. Then, the mortar specimens are moved to a standard curing box to be cured for 3 and 7 days. X-ray diffraction (XRD), TG/DTG (thermogravimetry/derivative thermogravimetry), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) characterise the hydration products, microstructure and pore structure of the electrically cured mortar specimens. The results show that the initial resistance of the mortar specimen with calcium formate is 25% of that of the mortar without calcium formate. The 3- and 7-day strengths of the calcium formate mortar increase by 59 and 29%, respectively, compared with the mortar without calcium formate under the same energisation parameters. The combined effect of adding calcium formate and applying electrical curing densifies the pore structure of the electrically cured mortar. [ABSTRACT FROM AUTHOR]

Published
2024
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21. Microstructure and mechanical behaviors of engineered cementitious composites with high-volume fly ash.

Author

Liao, Qiao, Li, Bixiong, and You, Yang

Subjects
FLY ash, CEMENT composites, POLYVINYL alcohol, MICROSTRUCTURE, PORE size distribution, SCANNING electron microscopes
Abstract

To study the effects of fly ash, polyvinyl alcohol (PVA) fibers and curing schemes on the microstructure and mechanical behaviors of Engineered Cementitious Composites (ECC) with high-volume fly ash, two kinds of fly ash and two PVA fibers were used in ECC. Besides, two curing schemes were adopted. The microstructure and mechanical properties of ECC were investigated by mercury intrusion porosimetry (MIP), scanning electron microscope (SEM), uniaxial compression test and three-point bending test. The results show that curing schemes and adding PVA fibers have a great influence on the differential curves of the pore size distribution of ECC and matrix in the range of 0–100 nm. There is a positive relationship between the deflection capacity or ultimate tensile strain of ECC and its macro pore volume fraction. Number of cracks increases with increasing the capillary pore volume fraction. On the contrary, the deflection capacity, ultimate tensile strain and number of cracks decrease when the transitional pore volume percent in ECC increases. [ABSTRACT FROM AUTHOR]

Published
2023
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31. An experimental investigation on the performance of TEGs with a compact heat exchanger design towards low-grade thermal energy recovery

Author

Hongtao Liu, Licheng Sun, Li Bixiong, Yang Wei, Heping Xie, Cheng Ju, Cunbao Li, and Zhang Hongyin

Subjects
Materials science, business.industry, 020209 energy, Energy Engineering and Power Technology, Mechanical engineering, Tapering, 02 engineering and technology, Modular design, Industrial and Manufacturing Engineering, Thermoelectric generator, 020401 chemical engineering, Heat recovery ventilation, Heat exchanger, Thermal, 0202 electrical engineering, electronic engineering, information engineering, 0204 chemical engineering, business, Thermal energy, Power density
Abstract

Thermoelectric generator (TEG) is a promising technology for low-grade heat recovery, whereas the scalability of TEGs remains challenging. Modular design with an ideal thermal design provides a potential solution for large scale application of TEG system in harvesting low-grade thermal energy. In this paper, a concept of modular design with a compact thermal design was proposed for the cold and hot sides of TEG system. A compact heat exchanger was fabricated by using diffusion welding technique for the TEG system. The inlet and outlet of the heat exchanger are designed with a tapering geometry to achieve a uniform fluid flow and temperature distribution among the flow channels, and the inlets of the hot-side heat exchangers and the outlets of cold-side heat exchangers can be arranged at the same side to realize a counter-flow thermal design. With the design of compact heat exchanger, the modularization assembly of a TEG system can be achieved and the TEG system can be scaled up by alternately arranging hot- and cold-side heat exchangers. To evaluate the TEG performance with current design, a single unit with five TEG modules was tested at various temperature differences. Despite that a thermoelectric conversion efficiency of 1.64% was obtained at a temperature difference of 96.4 °C, the unit exhibited a high volumetric power density (86.4 kW/m3) and a negligible power consumption (0.64% of the total power output). Furthermore, the measurements were also carried out to evaluate the temperature distribution across the contacting surface of the heat exchanger and the flow resistance between inlet outlet of the heat exchanger. A low temperature variation (

Published
2021

32. Experimental study on improving shrinkage properties of lightweight EPS concrete in composite wall panels.

Author

SU Liuyue and LI Bixiong

Abstract

Expanded polystyrene (EPS) based lightweight concrete sandwich wall panel is widely used as a new type of wall materials in engineering. However, the shrinkage of EPS concrete becomes a key factor to restrict the development of sandwich wall panel. In order to improve the shrinkage property of EPS concrete, the influence of sodium alginate, xanthan gum and diatomite on EPS concrete was researched, based on shrinkage test and characterization of microstructure by the Scanning Electron Microscopy (SEM) . The results show that the sodium alginate, xanthan gum and diatomite can reduce the water loss rate and shrinkage of EPS concrete and improve the EPS concretes microstructure, so as to reduce the number of harmful holes, and improve the density. [ABSTRACT FROM AUTHOR]

Published
2020

33. Investigations of the spin-Hamiltonian parameters for Yb3+in the tetragonal phase of SrTiO3crystal

Author

Wei Zheng, Li Bixiong, Weiqing Yang, and Hong-Gang Liu

Subjects
Zeeman effect, Condensed matter physics, Chemistry, Diagonalizable matrix, Condensed Matter Physics, Molecular physics, law.invention, Ion, symbols.namesake, Tetragonal crystal system, law, symbols, Hamiltonian (quantum mechanics), Electron paramagnetic resonance, Hyperfine structure, Matrix method
Abstract

The spin-Hamiltonian parameters (g factors, , , and hyperfine structure constants, , ) for Yb3+ at the 12-fold coordinated Sr2+ site of tetragonal SrTiO3 crystal at T ≈ 2 and 50 K were calculated using the completed diagonalization (of the energy matrix) method (CDM). Differing from the conventional CDM, the Hamiltonian concerning the energy matrix in this CDM contains the Zeeman and hyperfine interaction terms and so the spin-Hamiltonian parameters can be calculated directly from CDM. The crystal parameters used in the energy matrix are calculated from the superposition model, in which the tetragonal distortions and hence the order parameters φ at both temperatures are applied. From the calculations, the spin-Hamiltonian parameters at both temperatures are explained reasonably and the signs of hyperfine structure constants for the 171Yb3+ and 173Yb3+ isotopes in SrTiO3 are suggested. The results are discussed.

Published
2010

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