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Prediction of oxygen concentration and temperature distribution in loose coal based on BP neural network

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Mining Science and Technology 2009年第2期19卷 216-219页

作者： ZHANG Yong-jian wu guo-guang XU Hong-feng MENG Xian-liang WANG guang-you School of Chemical Engineering and Technology China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China

An effective method for preventing spontaneous combustion of coal stockpiles on the ground is to control the air-flow in loose coal. In order to determine and predict accurately oxygen concentrations and temperatures within coal stockpiles, it is vital to obtain information of self-heating conditions and tendencies of spontaneous coal combustion. For laboratory conditions, we designed our own experimental equipment composed of a control-heating system, a coal column and an oxygen concentration and temperature monitoring system, for simulation of spontaneous combustion of block coal （13-25 mm） covered with fine coal （0-3 mm）. A BP artificial neural network （ANN） with 150 training samples was gradually established over the course of our experiment. Heating time, relative position of measuring points, the ratio of fine coal thickness, artificial density, voidage and activation energy were selected as input variables and oxygen concentration and temperature of coal column as output variables. Then our trained network was applied to predict the trend on the untried experimental data. The results show that the oxygen concentration in the coal column could be reduced below the minimum still able to induce spontaneous combustion of coal - 6% by covering the coal pile with fine coal, which would meet the requirement to prevent spontaneous combustion of coal stockpiles. Based on the prediction of this ANN, the average errors of oxygen concentration and temperature were respectively 0.5% and 7 ℃, which meet actual tolerances. The implementation of the method would provide a practical guide in understanding the course of self-heating and spontaneous combustion of coal stockpiles.

关键词： loose coal neural netwOrk spontaneous combustion of coal oxygen concentration temperature prediction

A model reduction approach for discrete-time linear time-variant systems with delayed inputs

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Science China(Information Sciences) 2024年第4期67卷 197-217页

作者： Ai-guo wu guang-Ren DUAN Yu WANG Jie ZHANG School of Mechanical Engineering and Automation Harbin Institute of Technology(Shenzhen) HIT wuhu Robot Technology Research Institute Center for Control Science and Technology Southern University of Science and Technology

A model reduction approach is presented for discrete-time linear time-variant input-delayed systems. According to this proposed approach, a dynamical variable is constructed by taking advantage of the current state and historical information of input. It is revealed that the behavior of this dynamical variable is governed by a discrete-time linear delay-free system. It is worth noting that the presented variable transformation does not require the system matrix to be invertible. Based on the reduced delay-free models,stabilizing control laws can be easily obtained for the original delayed system. For the case with a single input delay, the constructed variable is an exact prediction for the future state, and thus the stabilizing control law could be designed by replacing the future state with its prediction. Finally, three discrete-time periodic systems with delayed input are employed to illustrate how to utilize the presented model reduction approaches.

关键词： reduction approach predictor-based feedback time-varying systems delayed input periodic system

Blended coals for improved coal water slurries

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Journal of China University of Mining and Technology 2008年第1期18卷 50-54页

作者： GU Tian-ye wu guo-guang LI Qi-hui SUN Zhi-qiang ZENG Fang WANG guang-you MENG Xian-liang School of Chemical Engineering and Technology China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China

Three coal samples of different ranks were used to study the effect of coal blending on the preparation of Coal Water Slurry (CWS). The results show that by taking advantage of two kinds of coal, the coal concentration in slurry made from hard-to-pulp coal can be effectively improved and increased by 3%–5% generally. DLT coal (DaLiuTa coal mine) is very poor in slurryability and the stability and rheology of the resulting slurry are not very good. When the amount of easily slurried coal is more than 30%, all properties of the CWS improve and the CWS meets the requirements for use as fuel. Coalification, porosity, surface oxygenic functional groups, zeta potential and grindability have a great effect on the performance of blended coal CWS. This leads to some differences in performance between the slurry made from a single coal and slurry made from blended coal.

关键词： low rank coal coal water slurry coal blending slurryability zeta potential

Properties of p-NiO/n-GaN Diodes Fabricated by Magnetron Sputtering

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Chinese Physics Letters 2012年第10期29卷 190-192页

作者： WANG Hui ZHANG Bao-Lin wu guo-guang wu Chao SHI Zhi-Feng ZHAO Yang WANG Jin MA Yan DU guo-Tong DONG Xin State Key Laboratory on Integrated Optoelectronics College of Electronic Science and EngineeringJilin UniversityChangchun 130012 College of Physics and Engineering Henan University of Science and TechnologyLuoyang 471003

The p-NiO thin film is prepared by radio frequency magnetron sputtering on the n-GaN/sapphire substrate to form p-NiO/n-GaN heterojunction *** structural,optical and electrical properties of the p-NiO thin film are *** results indicate that the NiO film has good crystal qualities and stable p-type *** current-voltage measurement of the p-NiO/n-GaN diode exhibits typical rectifying behaviour with a turn-on voltage of about 2.2 *** forward bias,a prominent ultraviolet emission centered at 375 nm is observed at room ***,the mechanism of the light emission is discussed in terms of the band diagrams of the heterojunction in detail.

关键词： temperature heterojunction sapphire

Advances in ice avalanches on the Tibetan Plateau

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Journal of Mountain Science 2024年第6期21卷 1814-1829页

作者： TANG Minggao LI guang ZHAO Huanle XU Qiang wu guangjian YANG Wei guo Daojing State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of TechnologyChengdu 610059China College of Environment and Civil Engineering Chengdu University of TechnologyChengdu 610059China Institute of Tibetan Plateau Research Chinese Academy of SciencesBeijing 100101China

As some of the greatest natural disasters in the cryosphere,ice avalanches(IAs)seriously threaten lives and cause catastrophic damage to the resource environment,but a comprehensive overview of the state of knowledge on IAs remains *** summarized 63 IAs on the Tibetan Plateau(TP)since the 20th century,of which,over 20 IAs occurred after the 21st *** distributions of IAs are mainly concentrated in the southeastern and northwestern TP,and the occurrence time of IAs is mostly concentrated from July to *** highlight recent advances in mechanical properties and genetic mechanisms of IAs and emphasize that temperature,rainfall,and seismicity are the inducing *** failure modes of IAs are summarized into 6 categories by examples:slip pulling type,slip toppling type,slip breaking type,water level collapse type,cave roof collapse type,and wedge failure ***,we deliver recommendations concerning the risk assessment and prediction of *** results provide important scientific value for addressing climate change and resisting glacier-related hazards.

关键词： Ice avalanche Global warming Genetic mechanism Risk assessment Tibetan Plateau

Conduction-convection coupled heat transfer around a hollow cylinder under different buoyancy forces

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Chinese Journal of Aeronautics 2024年第4期37卷 216-228页

作者： Wanyu ZHANG Jingyi wu guang YANG Institute of Refrigeration and Cryogenics Shanghai Jiao Tong UniversityShanghai 200240China

In order to clarify the effect of a buoyancy force on conduction–convection coupled heat transfer in a hollow cylinder, the flow and thermal characteristics were analyzed using an RNG k-ε turbulence model. The Reynolds number was fixed at 1.014 × 10^(6), and the Rayleigh number varied from 1.122 × 10^(10)to 1.088 × 10^(11). Results have shown that, when considering the effect of an opposed buoyancy force, increasing the Rayleigh number has a positive impact on the rate of change and uniformity of the cylinder temperature. The temperature distributions along the axial and circumferential directions are similar for different Rayleigh numbers, but extreme values *** the axial direction, the maximum temperature is obtained at the interface between the variable-diameter part and the constant-diameter part. The maximum dimensionless temperature value decreases to 0.12 when the Rayleigh number increases to 1.088 × 10^(11). Along the circumferential direction, the temperature distribution is affected by the buoyancy force, which results in the temperature of the upper part being higher than that of the lower part. After nondimensionalization of the temperature and time, a correlation was proposed to illustrate the transient heat transfer process quantitatively. The standard deviation of the maximum relative temperature, representing the temperature uniformity, was also calculated. It was found that the difference in the direction of the buoyancy force made a huge difference. Compared with the opposed buoyancy force, the maximum dimensionless temperature is almost two times higher with an assisted buoyancy force. Similarly, the heat transfer coefficient with an assisted buoyancy force is half of that with an opposed buoyancy force. Overall, an assisted buoyancy force plays a negative role in terms of thermal characteristics. The flow field around the hollow cylinder was also illustrated to reveal the mechanism of the buoyancy force on magnitude and direction aspects

关键词： Buoyancy Conduction-convection heat transfer Transient analysis Hollow cylinder Non-dimensionalization

Porous Ti_(3)C_(2)T_(x) MXene nanosheets sandwiched between polyimide fiber mats for electromagnetic interference shielding

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Nano Research 2024年第3期17卷 2070-2078页

作者： Wenhao Liang Juntao wu Shan Zhang Pei-Yan Zhao Yi Cong Yongqiang guo guang-Sheng Wang Key Laboratory of Bioinspired Smart Interfacial Science and Technology of Ministry of Education School of ChemistryBeihang UniversityBeijing 100191China

With the rapid development of wireless communication technology and electronic devices,the issue of electromagnetic interference(EMI)is becoming increasingly *** a new and flexible electromagnetic interference shielding material has become a challenging ***,a sandwich-structured EMI shielding composite film was prepared using electrospinning and vacuum filtration *** this process,a porous MXene was synthesized through a reaction with cobalt acetate and served as the intermediate layer in the composite film to shield electromagnetic *** electrospun polyimide(PI)fibers were used as the top and bottom layers of the composite film,which can protect the porous MXene from *** lightweight and flexible composite film integrates electromagnetic interference shielding and thermal insulation capabilities,showing excellent comprehensive *** composite film achieves an EMI shielding effectiveness of 48.8 dB in X-band(8.2–12.4 GHz),and absolute shielding effectiveness of the composite film reached a satisfying 4142.43(dB·cm^(2))/*** to the design of a multi-layer porous structure,the density of the composite film is 0.65 g/***,the thermal conductivity of the film is 0.042 W/(m·K)due to the clamping of electrospun PI fibers,showing excellent thermal insulation ***,the composite film exhibits excellent high and low-temperature *** summary,this work provides a feasible strategy for preparing a lightweight polymer-based EMI shielding film.

关键词： porous MXene polyimide electromagnetic interference shielding thermal insulation

Differentially private SGD with random features

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Applied Mathematics(A Journal of Chinese Universities) 2024年第1期39卷 1-23页

作者： WANG Yi-guang guo Zheng-chu Polytechnic Institute of Zhejiang University Zhejiang UniversityHangzhou 310015China School of Mathematical Sciences Zhejiang UniversityHangzhou 310058China

In the realm of large-scale machine learning,it is crucial to explore methods for reducing computational complexity and memory demands while maintaining generalization ***,since the collected data may contain some sensitive information,it is also of great significance to study privacy-preserving machine learning *** paper focuses on the performance of the differentially private stochastic gradient descent(SGD)algorithm based on random *** begin,the algorithm maps the original data into a lowdimensional space,thereby avoiding the traditional kernel method for large-scale data storage ***,the algorithm iteratively optimizes parameters using the stochastic gradient descent ***,the output perturbation mechanism is employed to introduce random noise,ensuring algorithmic *** prove that the proposed algorithm satisfies the differential privacy while achieving fast convergence rates under some mild conditions.

关键词： learning theory differential privacy stochastic gradient descent random features reproducing kernel Hilbert spaces

A molecular insight into coke formation process of vacuum residue in thermal cracking reaction

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Petroleum Science 2024年第3期21卷 2130-2138页

作者： Ji-guang Li Xin guo Huan-Di Hou Heavy Oil Processing Department Sinopec Research Institute of Petroleum Processing Co.LtdBeijing100083China

Understanding the coking behaviors has been considered to be really essential for developing better vacuum residue processing technologies.A battery of thermal cracking tests of typical vacuum residue at 410℃ with various reaction time were performed to evaluate the coke formation *** total yields of ideal components including naphtha,atmospheric gas oil(AGO)and vacuum gas oil(VGO)of thermal cracking reactions increased from 10.89%to 40.81%,and the conversion ratios increased from8.05%to 43.33%with increasing the reaction time from 10 to 70 *** asphaltene content increased from 12.14%to a maximum of 22.39%and then decreased,and this maximum of asphaltene content occurred at the end of the coking induction *** asphaltenes during the coking induction period,at the end and after coking induction period of those tested thermal cracking reactions were characterized to disclose the structure changing rules for coke formation process,and the coke formation pathways were discussed to reveal the coke formation process at molecular level.

关键词： Vacuum residue Thermal cracking Asphaltene Coking induction period Sulfur Nitrogen