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Numerical simulation to determine the gas explosion risk in longwall goaf areas:A case study of Xutuan Colliery

International Journal of Mining Science and Technology 2020年第6期30卷 875-882页

作者： Yunzhuo Li Hetao Su Huaijun ji Wuyi cheng School of Engineering and Technology China University of Geosciences(Beijing)Beijing 100083China Key Laboratory of Deep Geodrilling Technology Ministry of Land and ResourcesChina University of Geosciences(Beijing)Beijing 100083China

Underground gassy longwall mining goafs may suffer potential gas explosions during the mining process because of the irregularity of gas emissions in the goaf and poor ventilation of the working face,which are risks difficult to *** this work,the 3235 working face of the Xutuan Colliery in Suzhou City,China,was researched as a case *** effects of air quantity and gas emission on the three-dimensional distribution of oxygen and methane concentration in the longwall goaf were *** on the revised Coward’s triangle and linear coupling region formula,the coupled methane-oxygen explosive hazard zones(CEHZs)were ***,a simple practical index was proposed to quantitatively determine the gas explosion risk in the longwall *** results showed that the CEHZs mainly focus on the intake side where the risk of gas explosion is *** CEHZ is reduced with increasing air ***,the higher the gas emission,the larger the CEHZ,which moves towards the intake side at low goaf heights and shifts to the deeper parts of the goaf at high *** addition,the risk of gas explosion is reduced as air quantities increase,but when gas emissions increase to a higher level(greater than 50 m3/min),the volume of the CEHZ does not decrease with the increase of air quantity,and the risk of gas explosion no longer shows a linear downward *** study is of significance as it seeks to reduce gas explosion accidents and improve mine production safety.

关键词： Longwall goaf Gas explosion Air quantity Gas emission Hazard zone Quantitative risk analysis

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Solidification in Soft-Contact Continuous Casting Mold with Alternating Electromagnetic Field

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Journal of Iron and Steel Research International 2003年第1期10卷 15-19页

作者： DENG An-yuan HE ji-cheng Northeastern University

The mechanical behavior of the mushy zone was studied in detail. Based on the analysis of conventional high temperature mechanical model, considering the physical phenomenon in casting process, a mechanical model suitable for describing the mechanical behavior of the casting material in twin roll casting process was built. Comparing experimental results to the numerical simulated ones, the mechanical model was proved to be correct.

关键词： strip casting mushy zone mechanical model constitutive equation

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Approximate Data Aggregation in Sensor Equipped IoT Networks

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Tsinghua Science and Technology 2020年第1期25卷 44-55页

作者： ji Li Madhuri Siddula Xiuzhen cheng Wei cheng Zhi Tian Yingshu Li Kennesaw State University MariettaGA 30060USA Georgia State University AtlantaGA 30303USA George Washington University WashingtonDC 20052USA Department of Computer Science Virginia Commonwealth UniversityRichmondVA 23284USA Department of Electrical&Computer Engineering George Mason UniversityFairfaxVA 22030USA

As Internet-of-Things(IoT) networks provide efficient ways to transfer data, they are used widely in data sensing applications. These applications can further include wireless sensor networks. One of the critical problems in sensor-equipped IoT networks is to design energy efficient data aggregation algorithms that address the issues of maximum value and distinct set query. In this paper, we propose an algorithm based on uniform sampling and Bernoulli sampling to address these issues. We have provided logical proofs to show that the proposed algorithms return accurate results with a given probability. Simulation results show that these algorithms have high performance compared with a simple distributed algorithm in terms of energy consumption.

关键词： data aggregation sampling Internet-of-Things(IoT) networks

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Malnutrition Prevalence in Lasa Xizang Children and Adolescents

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Biomedical and Environmental Sciences 2014年第8期27卷 614-626页

作者： YIN Xiao jian ji cheng Ye Key Laboratory of Adolescent Health Assessment and Exercise Intervention Ministry of Education College of Physical Education & Health East China Normal University Institute of Child and Adolescent Health Peking University Health Science Center

Objective To assess the prevalence of malnutrition among children and adolescents in Xizang （Tibet）. Methods We analyzed data from the Chinese National Survey on Students＇ Constitution and Health for the years 1995, 2000, 2005, and 2010 pertaining to Tibetan children and adolescents in Lase （Lhasa）, aged 7-18 years old. Numbers of survey subjects for these years were：2 393, 2 754, 2 397, and 2 643, respectively. Results Our results indicated that the rate of occurrence of stunting in Tibet has evidenced a gradual decline：for boys, from 26.8%in 2000 to 9.3%in 2010;and for girls, from 25.8%in 2000 to 10.8%in 2010. In general, the wasting rate for both boys and girls in Tibet has gradually decreased over time：for boys, from 17.7%in 1995 to 4.6%in 2005;and for girls from 12.5%in 1995 to 2.3%in 2005. The stunting rates of boys aged 7-13 years old and of girls aged 7-11 years old were 67.5%and 53.1%, respectively, while these rates for boys aged 14-18 years old and girls aged 12-18 years old were 32.5%and 46.9%, respectively. Conclusion Stunting and wasting rates of Tibetan children and adolescents indicate a gradual declining trend over time. The stunting rates of both boys and girls during early puberty were significantly higher than those during late puberty.

关键词： Tibetan children and adolescents Malnutrition Stunting Wasting

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Secular Change in Stature of Urban Chinese Children and Adolescents, 1985-2010

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Biomedical and Environmental Sciences 2013年第1期26卷 13-22页

作者： CHEN Tian jiao ji cheng Ye Institute of Child and Adolescent Health School of Public HealthPeking University Health Science Center

Objective Research evidence shows a secular trend in Chinese physical growth in recent *** aim of this study was to analyze and assess changes in stature of children and adolescents during the 25 years from 1985‐2010,using national *** Data came from successive cycles of the Chinese National Survey on Students＇ Constitution and Health（CNSSCH）.Subjects were 7‐ to 18‐year‐old children and *** An overall positive secular trend occurred in urban China during 1985‐*** overall average rates of increment were 2.4 and 1.7 cm/decade for boys and girls,*** increases in adult stature for boys and girls were 2.6 and 1.7 cm,yielding rates of 1.0 and 0.7 cm/decade,*** with different socioeconomic levels had different characteristic *** stature increases in big cities were larger than those in moderate and small cities,and boys and girls in moderate and small cities showed greater potential for growth in *** An overall positive secular growth trend was associated with socioeconomic progress and differed with area socioeconomic *** policies and strategies should be developed based on increased stature,and should continue narrowing the inequity between different socioeconomic populations.

关键词： Secular change Stature Growth Socioeconomic disparity Children and adolescents

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Secular Changes of Stature in Rural Children and Adolescents in China, 1985-2010

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Biomedical and Environmental Sciences 2014年第8期27卷 573-581页

作者： CHEN Tian jiao ji cheng Ye Institute of Child and Adolescent Health School of Public Health Peking University Health Science Center

Objective To analyze and assess secular change in stature in rural children and adolescents in China from 1985 to 2010. Methods Data were obtained from the 6 rounds of the Chinese National Survey on Student＇s Constitution and Health. The subjects enrolled in the study were children and adolescents aged 7-18 years in rural areas of provincial capitals. Results An overall positive secular trend in stature occurred in rural areas of provincial capitals in China from 1985 to 2010. The overall average increase rates were 3.1 and 2.4 cm/decade for boys and girls, respectively. The total body height increases for grown up boys and girls were 3.6 and 2.3 cm and the increase rates were 1.4 and 0.9 cm/decade, respectively. There were differences in body height increase among eastern, central and western regions. The average body height of the children or adolescents in eastern region was highest, followed by central region and western region. The overall increase rates in central region were highest among the three regions. The difference between eastern/central region and western region was obvious. 〈br〉 Conclusion Positive secular trend in stature of children or adolescents has occurred in rural area of China, and rural boys and girls showed a great potential for continuous growth. More attention should be paid to the differences in children＇s body height between western region and eastern/central region.

关键词： Secular change Stature Rural population Regional difference Child and adolescent

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Mappings between balls with geometric and degeneracy rank two

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Science China Mathematics 2019年第10期62卷 1947-1960页

作者： Xiaoliang cheng Shanyu ji Wanke Yin Department of Mathematics Jilin Normal UniversitySiping136000China Department of Mathematics University of HoustonHoustonTX77204USA School of Mathematics and Statistics Wuhan UniversityWuhan430072China

The paper is devoted to the study of rational proper holomorphic maps from the unit ball B^n to the unit ball B^N. We classify these maps with both the geometric rank and the degeneracy rank less than or equal to two.

关键词： proper holomorphic maps holomorphic classification geometric rank degeneracy rank

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Temporal and spatial characteristics of monopole acoustic energy dominated by unsteady thermodynamic cavitating flow

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Journal of Hydrodynamics 2021年第4期33卷 867-871页

作者： Xin-cheng Wang Xiao-rui Bai Huai-yu cheng Bin ji State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan430072China

The acoustic propagation characteristics of the cavitating flow are essential for the noise suppression, but were not well studied. In the current paper, a new technique concerning the propagation path of the monopole acoustic energy is presented and two typical thermodynamic cavitation modes (the inertial and thermal modes) are selected to investigate the effect of the cavity shedding dynamics on the acoustic propagation path. In the inertial mode, the temporal variation and the spatial distributions of the monopole acoustic energy as well as the divergence of the monopole acoustic pressure are both more powerful and concentrated than that in the thermal mode. The acoustic propagation path in the thermal mode strictly satisfies the feature of the convective amplification, while there exists another propagation direction close to the normal direction of the foil surface in the inertial mode. Furthermore, the occurrence of the normal direction propagation will make the path deviate from the convective direction.

关键词： Thermodynamic cavitation acoustic propagation path hydroacoustic inertial mode thermal mode

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Dependence of microstructure and mechanical properties on solidification condition of directionally solidified Zn-55Al-1.6Si alloys

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China Foundry 2024年第6期21卷 685-692页

作者： ji-peng Li De-gao Qiao jian Li Peng Peng Kai-di Hu Xian-tao Yan shu-sen cheng Yuan-li Xu School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China Gansu jiu Steel Group Hongxing Iron and Steel Co. Ltd.Jiayuguan 735100GansuChina School of Materials and Energy Lanzhou UniversityLanzhou 730000China

In this study,directional solidification was utilized to explore the relationship between microstructure,mechanical properties,and withdrawal speeds of Zn-55Al-1.6Si *** order to assess the characteristics of Zn-55Al-1.6Si alloys,both the microstructure and mechanical properties were thoroughly *** involved conducting room temperature tensile tests on samples with different withdrawal speeds(5,10,100,200,and 400μm·s^(-1)).The results reveal that both the as-cast alloy and samples after directional solidification are composed of zinc,aluminum,and silicon *** the withdrawal speed increases,an evident decrease in the size of the primary dendrites is *** results of tensile experiments show that Zn-55Al-1.6Si alloys after directional solidification exhibit brittle fracture characteristics,both the tensile strength and elongation of the alloys increase with withdrawal speed.

关键词： Zn-55Al-1.6Si alloy directional solidification microstructure mechanical properties

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A Pair Correlation Function Characterizing the Anisotropy of Force Networks

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Chinese Physics Letters 2011年第6期28卷 176-178页

作者： SUN Qi-cheng ji shun-Ying State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing 100084 State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian 116023

Force networks may underlie the constitutive relations among granular solids and granular flows and inter-state ***,it is difficult to effectively describe the anisotropy of force *** propose a new pair correlation function g(r,θ)to describe the characteristic lengths and orientations of force chains that are composed of particles with contact forces greater than the threshold values.A formulation g(r,θ)≈a(r)+b(r)cos2(θ−π/2)is used to fit the g(r,θ)*** characteristic lengths and orientations of force networks are then elucidated.

关键词： networks characteristic anisotropy

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