Calorimetric measurements are performed to determine the specific heat of Si-xat.% Ge(where x = 0, 10, 30,50, 70, 90 and 100) alloys within a broad temperature range from 123 to 823 K. The measured specific heat incre...Calorimetric measurements are performed to determine the specific heat of Si-xat.% Ge(where x = 0, 10, 30,50, 70, 90 and 100) alloys within a broad temperature range from 123 to 823 K. The measured specific heat increases dramatically at low temperatures, and the composition dependence of specific heat is evaluated from the experimental results. Meanwhile, the specific heat at constant volume, the thermal expansion, and the bulk modulus of Si and Ge are investigated by the first principle calculations combined with the quasiharmonic approximation. The negative thermal expansion is observed for both Si and Ge. Furthermore, the isobaric specific heat of Si and Ge is calculated correspondingly from OK to their melting points, which is verified by the measured results and accounts for the temperature dependence in a still boarder range.展开更多
With the modernization of industrial production,various automatic following technologies have gradually penetrated into people's lives.Among them,the application fields that follow mobile balancing vehicles range ...With the modernization of industrial production,various automatic following technologies have gradually penetrated into people's lives.Among them,the application fields that follow mobile balancing vehicles range from the structured environment of factories to the daily living environment.The purpose of this subject is to be able to use UWB positioning technology to realize that the balanced trolley is an automatic following function,which mainly uses the ranging function in UWB positioning technology,uses the TOF ranging principle and embedded basic knowledge,and changes the positioning algorithm to a following algorithm.The distance between the target object and the person is effectively determined by two tags set on the trolley and a base station in the hand to determine the distance,and the distance information is transmitted through the serial port.By writing an algorithm,the distance information is converted to the driving information of the trolley,and the driving information is sent to the trolley to control the trolley,thereby realizing the task of balancing the trolley to follow the specified target in a simple indoor environment.展开更多
This paper analyzes the control mechanism of coal and gas outbursts and proposes the concept of an effective pressure relief protection range, based on the stress relief of the underlying coal-rock mass and the develo...This paper analyzes the control mechanism of coal and gas outbursts and proposes the concept of an effective pressure relief protection range, based on the stress relief of the underlying coal-rock mass and the development of a plastic zone. Also this study developed a stress change and fracture development model of the underlying coal-rock mass. In addition, the stress and depth of fracture of any point in the floor were deduced with the application of Maple Calculation Software. The specific engineering parameters of the Pingdingshan No. 12 colliery were applied to determine the relationship between the depth of fracture in the floor and the mining height. The pressure-relief principle of the underlying coal-rock mass was analyzed while varying the mining height of the upper protective seam. The findings indicate that as the depth of fracture in the floor increases, the underlying coal-rock mass experiences a limited amount of pressure relief, and the pressure relief protection range becomes narrower.Additionally, the stress distribution evolves from a ‘‘U" shape into a ‘‘V" shape. A 2.0 m mining height of protective seam situates the outburst-prone seam, Ji_(15), within the effective pressure relief protection range. The fracture development and stress-relief ratio rises to 88%, ensuring the pressure-relief effect as well as economic benefits. The measurement data show that: after mining the upper protective seam, the gas pressure of Ji_(15) dropped from 1.78 to 0.35 MPa, demonstrating agreement between the engineering application and the theoretical calculation.展开更多
The precision of Earth＇s gravitational field from GRACE up to degree and order 120 was studied for different inter-satellite ranges using the improved energy conservation principle. Our simulated result shows that： ...The precision of Earth＇s gravitational field from GRACE up to degree and order 120 was studied for different inter-satellite ranges using the improved energy conservation principle. Our simulated result shows that： For long wavelength （L≤20） at degree 20, the cumulative geoid-height error gradually decreased with increasing range, from 0. 052 cm for 110 km to 1. 156 times and 1. 209 times as large for 220 km and 330 kin, respectively. For medium-wavelength （ 100 ≤ L ≤ 120） at degree 120, the cumulative geoid-height error de- creased from 13. 052 cm for 110 km, to 1. 327 times and 1. 970 times as large for the ranges of 220 km and 330 km, respectively; By adopting an optimal range of 220 ± 50 km, we can suppress considerably the loss of precision in the measurement of the Earth＇ s long-wavelength and medium-wavelength gravitational field.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 51522102,51734008,51327901 and 51474175
文摘Calorimetric measurements are performed to determine the specific heat of Si-xat.% Ge(where x = 0, 10, 30,50, 70, 90 and 100) alloys within a broad temperature range from 123 to 823 K. The measured specific heat increases dramatically at low temperatures, and the composition dependence of specific heat is evaluated from the experimental results. Meanwhile, the specific heat at constant volume, the thermal expansion, and the bulk modulus of Si and Ge are investigated by the first principle calculations combined with the quasiharmonic approximation. The negative thermal expansion is observed for both Si and Ge. Furthermore, the isobaric specific heat of Si and Ge is calculated correspondingly from OK to their melting points, which is verified by the measured results and accounts for the temperature dependence in a still boarder range.
文摘With the modernization of industrial production,various automatic following technologies have gradually penetrated into people's lives.Among them,the application fields that follow mobile balancing vehicles range from the structured environment of factories to the daily living environment.The purpose of this subject is to be able to use UWB positioning technology to realize that the balanced trolley is an automatic following function,which mainly uses the ranging function in UWB positioning technology,uses the TOF ranging principle and embedded basic knowledge,and changes the positioning algorithm to a following algorithm.The distance between the target object and the person is effectively determined by two tags set on the trolley and a base station in the hand to determine the distance,and the distance information is transmitted through the serial port.By writing an algorithm,the distance information is converted to the driving information of the trolley,and the driving information is sent to the trolley to control the trolley,thereby realizing the task of balancing the trolley to follow the specified target in a simple indoor environment.
基金supported by the Foundation for Distinguished professor of Jiangsu Provincethe Foundation for Innovative Research Groups of the National Natural Science Foundation of China (No.51421003)
文摘This paper analyzes the control mechanism of coal and gas outbursts and proposes the concept of an effective pressure relief protection range, based on the stress relief of the underlying coal-rock mass and the development of a plastic zone. Also this study developed a stress change and fracture development model of the underlying coal-rock mass. In addition, the stress and depth of fracture of any point in the floor were deduced with the application of Maple Calculation Software. The specific engineering parameters of the Pingdingshan No. 12 colliery were applied to determine the relationship between the depth of fracture in the floor and the mining height. The pressure-relief principle of the underlying coal-rock mass was analyzed while varying the mining height of the upper protective seam. The findings indicate that as the depth of fracture in the floor increases, the underlying coal-rock mass experiences a limited amount of pressure relief, and the pressure relief protection range becomes narrower.Additionally, the stress distribution evolves from a ‘‘U" shape into a ‘‘V" shape. A 2.0 m mining height of protective seam situates the outburst-prone seam, Ji_(15), within the effective pressure relief protection range. The fracture development and stress-relief ratio rises to 88%, ensuring the pressure-relief effect as well as economic benefits. The measurement data show that: after mining the upper protective seam, the gas pressure of Ji_(15) dropped from 1.78 to 0.35 MPa, demonstrating agreement between the engineering application and the theoretical calculation.
基金supported by the Main Direction Program of Knowledge Innovation of Chinese Academy of Sciences for Distinguished Young Scholar(KZCX2-EW-QN114)the National Natural Science Foundation of China(41004006,41131067,11173049)+5 种基金the Merit-based Scientific Research Foundation of the State Ministry of Human Resources and Social Security of China for Returned Overseas Chinese Scholars(2011)the Open Research Fund Program of the Key Laboratory of Geo-Informatics of State Bureau of Surveying and Mapping(201031)the Open Research Fund Program of the Key Laboratory of Computational Geodynamics of Chinese Academy of Sciences(2011-04)the Frontier Field Program of Knowledge Innovation of Institute of Geodesy and Geophysics of Chinese Academy of Sciencesthe Open Fund of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(PLN1113)the Hubei Province Key Laboratory of Refractories and Ceramics Ministry-Province jointly-Constructed Cultivation Base for State key Laboratory(G201009)
文摘The precision of Earth＇s gravitational field from GRACE up to degree and order 120 was studied for different inter-satellite ranges using the improved energy conservation principle. Our simulated result shows that： For long wavelength （L≤20） at degree 20, the cumulative geoid-height error gradually decreased with increasing range, from 0. 052 cm for 110 km to 1. 156 times and 1. 209 times as large for 220 km and 330 kin, respectively. For medium-wavelength （ 100 ≤ L ≤ 120） at degree 120, the cumulative geoid-height error de- creased from 13. 052 cm for 110 km, to 1. 327 times and 1. 970 times as large for the ranges of 220 km and 330 km, respectively; By adopting an optimal range of 220 ± 50 km, we can suppress considerably the loss of precision in the measurement of the Earth＇ s long-wavelength and medium-wavelength gravitational field.
