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Comparative study on the flame retardancy of CO_(2) and N_(2) during coal adiabatic oxidation process

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International Journal of Coal Science & Technology 2023年第4期10卷 254-264页

作者： Xiyang Fang bo tan Haiyan Wang School of Emergency Management and Safety Engineering China University of Mining and Technology(Beijing)Beijing 100083China School of Civil and Resources Engineering University of Science and TechnologyBeijing 100083China

To test the effectiveness of N_(2) and CO_(2) in preventing coal from spontaneously combusting,researchers used an adiabatic oxidation apparatus to conduct an experiment with different temperature starting ***-adsorbed helium(He)was used as a reference gas,and coal and oxygen concentration temperature variations were analyzed after *** results showed that He had the best cooling effect,N_(2) was second,and CO_(2) was the *** 70℃and 110℃,the impact of different gases on reducing oxygen concentration and the cooling effect was the ***,at the starting temperature of 150℃,CO_(2) was less effective in lowering oxygen concentration at the later stage than He and N_(2).N_(2) and CO_(2) can prolong the flame retardation time of inert gas and reduce oxygen displacement with an initial temperature *** the starting temperature is the same,N_(2) injection cools coal samples and replaces oxygen more effectively than CO_(2) *** flame retardancy of inert gas is the combined result of the cooling effect of inert gas and the replacement of *** findings are essential for using inert flame retardant technology in the goaf.

关键词： Coal spontaneous combustion Adiabatic oxidation Inert gas flame retardant Flame retardant efficiency Replacement

The distribution of the large partial quotients in continued fraction expansions

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Science China Mathematics 2023年第5期66卷 935-956页

作者： bo tan Chen Tian Baowei Wang School of Mathematics and Statistics Huazhong University of Science and TechnologyWuhan 430074China

The existence of large partial quotients destroys many limit theorems in the metric theory of continued *** achieve some variant forms of limit theorems,a common approach mostly used in practice is to discard the largest partial quotient,while this approach works in obtaining limit theorems only when there cannot exist two terms of large partial quotients in a metric *** by this,we are led to consider the metric theory of points with at least two large partial *** precisely,denoting by[a1(x),a2(x),...]the continued fraction expansion of x∈[0,1)and lettingψ:N→R+be a positive function tending to in nity as n→∞,we present a complete characterization on the metric properties of the set,i.e.,E(ψ)={x∈[0,1):∃16 k̸=ℓ6 n,ak(x)>ψ(n),aℓ(x)>ψ(n)for in nitely many n∈N}in the sense of the Lebesgue measure(the borel-Bernstein type result)and the Hausdor dimension(the Jarnik type result).The main result implies that any nite deletion from a1(x)+……+an(x)cannot result in a law of large numbers.

关键词： continued fraction Hausdor dimension borel-Bernstein theorem

Condition-based maintenance policy for gamma deteriorating systems

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Journal of Systems Engineering and Electronics 2010年第1期21卷 57-61页

作者： Lin tan Zhijun Cheng bo Guo Shiyu Gong School of Information System and Management National University of Defense Technology Changsha 410073 E R. China

A condition-based maintenance model for gamma deteriorating system under continuous inspection is studied. This methodology uses a gamma distribution to model the material degradation, and the impact of imperfect maintenance actions on the system reliability is investigated. The state of a degrading system immediately after the imperfect maintenance action is assumed as a random variable and the maintenance time follows a geometric process. Furthermore, the explicit expressions for the long-run average cost and availability per unit time of the system are evaluated, an optimal policy （ε^＊） could be determined numeri- cally or analytically according to the optimization model. At last, a numerical example for a degrading system modeled by a gamma process is presented to demonstrate the use of this policy in practical applications.

关键词： condition-based maintenance gamma process imperfect maintenance deteriorating system geometrical process.

An internal power angle control strategy for high-speed sensorless brushless DC motors

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Chinese Journal of Aeronautics 2022年第11期35卷 309-321页

作者： bo tan Xingyuan GUO Jun ZHAO Xiaofeng DING Wei FANG School of Electronic Information Engineering Xi'an Technological UniversityXi'an 71021China Marketing Service Center of State Grid Hebei Electric Power Co.LtdShijiazhuang 050021China Xi'an Aviation Institute of Computing Technology Aviation Industry Corporation of ChinaXi'an 710065China School of Automation Science and Electrical Engineering Beihang UniversityBejing 100083China Chinese Flight Test Establishment Xi'an 710089China

High-speed Brushless DC Motors(BLDCMs)usually adopt a sensorless control strategy and operate in three-phase six-state drive ***,the sampling errors of the rotor position and the driving method increase the Internal Power Angle(IPA),resulting in a decrease in the efficiency of the *** IPA reduction strategies are either sensitive to motor parameters,or ignore diode freewheeling during the commutation process,or require additional current *** this paper,a new strategy to reduce the IPA is ***,a Zero-Crossing Point(ZCP)detection method for the back-EMF without filter is proposed to reduce the sampling errors of the rotor ***,the relationship between the non-energized terminal voltage and the ZCP of the corresponding back-EMF is *** non-energized terminal voltage that has completed the diode freewheeling is divided into two triangles by half of the bus *** the IPA is suppressed,the areas of the two triangles are ***,an advanced angle for reducing the IPA is obtained through a PI regulator which can eliminate the deviation between the two ***,both a simulation model and an experimental circuit are built to verify the proposed control strategy.

关键词： Back-EMF detection Brushless DC motors Commutation control Electric drive Internal power angle

Quantitative Poincar recurrence in continued fraction dynamical system

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Science China Mathematics 2012年第1期55卷 131-140页

作者： PENG Li tan bo WANG BaoWei School of Mathematics and Statistics Huazhong University of Science and TechnologyWuhan 430074China

Let T ： X → X be a transformation. For any x C [0, 1） and r 〉 O, the recurrence time Tr（x） of x under T in its r-neighborhood is defined as Tr（X） = inf{k ≥ 1： d（Tk（x）,x）〈 r}.For 0 ≤ α ≤ β ∞ co, le... 详细信息

Let T ： X → X be a transformation. For any x C [0, 1） and r 〉 O, the recurrence time Tr（x） of x under T in its r-neighborhood is defined as Tr（X） = inf{k ≥ 1： d（Tk（x）,x）〈 r}.For 0 ≤ α ≤ β ∞ co, let E（α,β） be the set of points with prescribed recurrence time as follows E（α,β）={x∈X：lim inf r→0 logTr（x）/-logr=α,lim sup r→0 logTr（x）/-logr=β}.In this note, we consider the Gauss transformation T on [0, 1）, and determine the size of E（α,β）by showing that dimH E（α,β） = 1 no matter what a and/~ are. This can be compared with Feng and Wu＇s result [Nonlinearity, 14 （2001）, 81-85] on the symbolic space.

关键词： recurrence continued fraction Hausdorff dimension

Theoretical Study of the Sensitivity-Improvement Effect of Phosphoryl Group in Mass Spectrometry of Small Peptides

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Chinese Chemical Letters 2001年第9期12卷 807-808页

作者： Yang JIANG bo tan Yu Fen ZHAO The Key Laboratory of Bioorganic Phosphorus Chemistry Ministry of EducationDepartment of ChemistrySchool of Life Sciences and EngineeringTsinghua UniversityBeijing 100084

It was found that phosphorylation of small peptide could improve the sensitivity in mass spectrometry. Density functional theory calculations showed that the energy for the protonation of N-(O,O'-dimethyl) phosphoryl ... 详细信息

关键词： Phosphoryl group small peptide mass spectrometry relative energy

A parameterization scheme for upward lightning in the cloud model and a discussion of the initial favorable environmental characteristics in the cloud

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Science China Earth Sciences 2016年第7期59卷 1440-1453页

作者： tan Yong bo CHEN Chao ZHOU Jie Chen ZHOU bo Wen ZHANG DongDong GUO XiuFeng Key Laboratory of Meteorological Disaster Ministry of Education (KLME)/Joint International Research Laboratory of Climate and Environment Change (ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD)/Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration Nanjing University of Information Science & Technology

The upward lightning(UL) initiated from the top of tall buildings(at least above 100 m) is a type of atmospheric discharge. Currently, we understand the nature of the UL from ground observations, but the corresponding theoretical research is lacking. Based on an existing bidirectional leader stochastic model, a stochastic parameterization scheme for the UL has been built and embedded in an existing two-dimensional thundercloud charge/discharge model. The ULs simulated from the experiments with two-dimensional high resolution agree generally with the observation results. By analyzing the charge structure of thunderstorm clouds, we determined the in-cloud environmental characteristics that favor the initiation of conventional cloud-to-ground(CG) flashes and analyzed the differences and similarities of some characteristics of the positive and the negative UL. Simulation results indicate that the positive ULs are typically other-lightning-triggered ULs(OLTUL) and are usually a discharge phenomenon between the ground and the lower positive charge region appearing below the main middle negative charge region. The effect of the previous in-cloud lightning(IC) process of space electrical field provides favorable conditions for the initiation of a positive UL. Its entire discharge process is limited, and the branches of the leader are fewer in number as its discharge is not sufficient. A negative UL is generally a discharge phenomenon of the dipole charge structure between the ground and the main negative charge region. The lower temperature stratification and the sinking of the hydrometeors typically initiate a negative UL. Negative ULs develop strongly and have more branches. The OLTUL is initiated mainly during the development stage of a thunderstorm, while the self-triggered UL(STUL) is initiated mainly during the dissipation stage of a thunderstorm.

关键词： Upward lightning Numerical simulation Initial conditions Propagation characteristics Thunderstorm cloud model

Research Progress of Metal-Based Shielding Materials for Neutron and Gamma Rays

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Acta Metallurgica Sinica(English Letters) 2021年第12期34卷 1609-1617页

作者： Bin Gan Shichang Liu Zhen He Fucai Chen Haoxuan Niu Jingchang Cheng bo tan bo Yu Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of ChinaChengdu610213China State Key Laboratory of Light Alloy Casting Technology for High-End Equipment Shenyang Research Institute of Foundry Co.Ltd.Shenyang110022China

The radiation generated by nuclear reaction is harmful to human body and equipment,thus the radiation shielding materials that employ the shielding ability from neutron and gamma rays are the best candidates according to application situations and radiation *** this paper,the researches of metal-based neutron and gamma rays or multiple purpose shielding materials are systematically summarized,and the respective and principal problems of these materials with respect to shielding effectiveness and other performances,such as corrosion,mechanical properties,manufacture,etc.,are ***,the prospect of shielding materials is outlined,which suggests that the development of highly efficient and multiply functional radiation shielding materials with good environmental compatibility is one of the future development trends.

关键词： Radiation shielding materials Metal-based boron-containing shielding materials High density alloys

Comparative study of the explosion pressure characteristics of micro- and nano-sized coal dust and methane–coal dust mixtures in a pipe

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International Journal of Coal Science & Technology 2020年第1期7卷 68-78页

作者： bo tan Huilin Liu Bin Xu Tian Wang School of Emergency Management and Safety Engineering China University of Mining and Technology(Beijing)Beijing 100083China

Coal dust explosion accidents often cause substantial property damage and casualties and frequently involve nano-sized coal *** order to study the impact of nano-sized coal on coal dust and methane–coal dust explosions,a pipe test apparatus was used to analyze the explosion pressure characteristics of five types of micro-nano particle dusts(800 nm,1200 nm,45μm,60μm,and 75μm)at five concentrations(100 g/m3,250 g/m3,500 g/m3,750 g/m3,and 1000 g/m3).The explosion pressure characteristics were closely related to the coal dust particle size and *** maximum explosion pressure,maximum rate of pressure rise,and deflagration index for nano-sized coal dust were larger than for its micro-sized counterpart,indicating that a nano-sized coal dust explosion is more *** highest deflagration index Kst for coal dust was 13.97 MPa/(m·s),indicating weak *** 7%methane was added to the air,the maximum deflagration index Kst for methane–coal dust was 42.62 MPa/(m·s),indicating very strong *** indicates that adding methane to the coal dust mixture substantially increased the hazard grade.

关键词： A pipe test apparatus Nano-sized Coal dust explosion Methane/coal dust explosion Pressure characteristics