The authors admire Poincaré’s idea that the convention on the nature for light propagation is the foundation of the measurement of time and point out that the conventions on the light velocity is just the conven...The authors admire Poincaré’s idea that the convention on the nature for light propagation is the foundation of the measurement of time and point out that the conventions on the light velocity is just the convention on the symmetries of space time.The conditions on the transitivity of synchronization of clock rate are shown.With the condition,not only the question about the definition of the synchronization of rate of clocks located at different places is answered,but also find the solution to the definition of the equality of two durations is found.展开更多
A Carnot cycle outside a Schwarzschild black hole is investigated in detail. We propose a reversible Carnot cycle with a black hole being the cold reservoir. In our model, a Carnot engine operates between a hot reserv...A Carnot cycle outside a Schwarzschild black hole is investigated in detail. We propose a reversible Carnot cycle with a black hole being the cold reservoir. In our model, a Carnot engine operates between a hot reservoir with temperature Ti and a black hole with Hawking temperature TH. By naturally extending the ordinary Carnot cycle to the black hole system, we show that the thermal efficiency for a reversible process can reach the maximal efficiency 1 - TH/T1. Consequently, black holes can be used to determine the thermodynamic temperature by means of the Carnot cycle. The role of the atmosphere around the black hole is discussed. We show that the thermal atmosphere provides a necessary mechanism to make the process reversible.展开更多
目的分析2016年度宁夏吴忠市重点职业病危害因素。方法采用描述性流行病学方法,对所收集数据进行汇总、分析。结果吴忠市接触重点职业病危害因素的劳动者6 755例,其中血压异常者307例,不同性别血压异常差异有统计学意义(χ~2=19.25,P<...目的分析2016年度宁夏吴忠市重点职业病危害因素。方法采用描述性流行病学方法,对所收集数据进行汇总、分析。结果吴忠市接触重点职业病危害因素的劳动者6 755例,其中血压异常者307例,不同性别血压异常差异有统计学意义(χ~2=19.25,P<0.05),不同年龄血压异常差异有统计学意义(χ~2=100.51,P<0.05);接触煤尘的工人共941例,胸片异常61例;苯作业人员共935例,专项检查结果异常79例,不同性别检测项异常差异有统计学意义(χ~2=19.92,P<0.05),不同年龄检测项异常差异有统计学意义(χ~2=14.03,P<0.05);接触噪声的工人有6 573例,双耳高频听阈≥40 d B 610例。检出职业禁忌证12例,疑似职业病13例,新发重点职业病2例为煤工尘肺病和布鲁氏菌病。结论综合判定吴忠市重点职业病危害因素为煤尘、矽尘、苯、噪声和布鲁氏菌。应加大监管力度,加强日常培训和宣传,做好防治工作。展开更多
文摘The authors admire Poincaré’s idea that the convention on the nature for light propagation is the foundation of the measurement of time and point out that the conventions on the light velocity is just the convention on the symmetries of space time.The conditions on the transitivity of synchronization of clock rate are shown.With the condition,not only the question about the definition of the synchronization of rate of clocks located at different places is answered,but also find the solution to the definition of the equality of two durations is found.
基金Supported by the National Natural Science Foundations of China under Grant Nos 10373003, 10475013 and 10375087, and the National Key Basic Research of China under Grant No 2003CB716300.
基金supported by the National Natural Science Foundation of China (Grant No 10605006)the Scientific Research Starting Foundation for the Returned Overseas Chinese Scholars,Ministry of Education,Chinathe Undergraduate Research Foundation from Beijing Normal University,China
文摘A Carnot cycle outside a Schwarzschild black hole is investigated in detail. We propose a reversible Carnot cycle with a black hole being the cold reservoir. In our model, a Carnot engine operates between a hot reservoir with temperature Ti and a black hole with Hawking temperature TH. By naturally extending the ordinary Carnot cycle to the black hole system, we show that the thermal efficiency for a reversible process can reach the maximal efficiency 1 - TH/T1. Consequently, black holes can be used to determine the thermodynamic temperature by means of the Carnot cycle. The role of the atmosphere around the black hole is discussed. We show that the thermal atmosphere provides a necessary mechanism to make the process reversible.
文摘目的分析2016年度宁夏吴忠市重点职业病危害因素。方法采用描述性流行病学方法,对所收集数据进行汇总、分析。结果吴忠市接触重点职业病危害因素的劳动者6 755例,其中血压异常者307例,不同性别血压异常差异有统计学意义(χ~2=19.25,P<0.05),不同年龄血压异常差异有统计学意义(χ~2=100.51,P<0.05);接触煤尘的工人共941例,胸片异常61例;苯作业人员共935例,专项检查结果异常79例,不同性别检测项异常差异有统计学意义(χ~2=19.92,P<0.05),不同年龄检测项异常差异有统计学意义(χ~2=14.03,P<0.05);接触噪声的工人有6 573例,双耳高频听阈≥40 d B 610例。检出职业禁忌证12例,疑似职业病13例,新发重点职业病2例为煤工尘肺病和布鲁氏菌病。结论综合判定吴忠市重点职业病危害因素为煤尘、矽尘、苯、噪声和布鲁氏菌。应加大监管力度,加强日常培训和宣传,做好防治工作。
