Gravitation is one of the basic phenomena of the world. Tremendous number of theoretical works on origin, nature, essentials, consequences, etc. of the gravitation and related phenomena were published so far. The most...Gravitation is one of the basic phenomena of the world. Tremendous number of theoretical works on origin, nature, essentials, consequences, etc. of the gravitation and related phenomena were published so far. The most prominent ones are based on the Albert Einstein＇s general theory of relativity. The author of this communication based his approach to the gravitation on Isaac Newton＇s law of the universal gravitation and related quantities, i.e. gravitational forces of matter objects, distance and motion. Namely on the fact, that the gravitation force is - as well as the inertia, mass, space ＂occupied＂ and other properties are - principal features/attributes/properties of matter objects. Gravitation is an additive property of matter objects. Taking into account other positivistic quantities like mass of the Earth, standard acceleration of gravity, and the value of the atomic unit of mass, the author defined a gravitational force of atomic unit （or ＂the Gravitational Force Quantum＂） as a gravitational force which exerts one atomic unit of Earth＇s mass on 1 kilogram of a mass on Earth＇s surface, and he calculated its value： GFO = 1.4958 × 10^-54 N. This quantity can be useful for further development of the ＂quantum mechanical＂ approach to the description and general notion about the world.展开更多
In the article ＂The Gravitational Force Quantum and its Value＂ [1 ], the author defined a gravitational force of the atomic unit （＂the Gravitational Force Quantum＂） as a gravitational force which exerts one atom...In the article ＂The Gravitational Force Quantum and its Value＂ [1 ], the author defined a gravitational force of the atomic unit （＂the Gravitational Force Quantum＂） as a gravitational force which exerts one atomic unit of the Earth＇s mass on l kilogram of a mass on the Earth＇s surface, and he calculated its value as： GFQEarth = 1.4958 × 10.54 N. In the present contribution, he extended the Gravitational Force Quantum concept to further Objects of the Solar Planetary System and for the Pluto. He calculated values of the GFQo on the analogous basis, i.e. of the mass and the standard acceleration of the gravity of individual objects and of the atomic unit of the mass. He received GFQo values for the Mercury 102.1427 × 1055N, the Venus 16,60012 × 10-55N, the Earth 14.97839 × l0-55 N, the Mars 52.91869 × 10-55N, the Jupiter 0.124391×1055 N, the Saturn 0.17929 ×1055N, the Uranus 0.945178 ×1055N, the Neptune 1.002845 × 10-55N, for the Pluto 458.9124 × 10-55N, and for the Sun 0.001257 × 10-55N, respectively. He multiplied the GFQo values by second power of the radii of the individual objects （O）, receiving values denoted as the ＂Elementary Gravitational Charge＂ （Go）. The Elementary Gravitational Charge represents a gravitational force of one atomic unit of mass in the （radius） distance of 1 meter. They were found of the same value： GMe= Gv = GE= GMa= Gj= Gs = Gp= GSun= 6.079675463 × 10-41N. The values were the same as the calculated one on the basis of the ＂classical＂ Newton＇s formula： FG = И × M × m / R2, for the gravitational force between the atomic unit mass and a mass of 1 kg at a distance of 1 meter, which value was calculated as G = 6.079675463 ×1041 N. The quantity of the Elementary Gravitational Charge can be supposed to be analogous to the Elementary （Electric） Charge （e =1.6021766208（98） × 10-19 C） quantity.展开更多
In this paper the influence of a knot on the structure of a polymethylene （PM） strand in the tensile process is investigated by using the steered molecular dynamics （SMD） method. The gradual increasing of end-to-e...In this paper the influence of a knot on the structure of a polymethylene （PM） strand in the tensile process is investigated by using the steered molecular dynamics （SMD） method. The gradual increasing of end-to-end distance, R, results in a tighter knot and a more stretched contour. That the break in a knotted rope almost invariably occurs at a point just outside the ＇entrance＇ to the knot, which has been shown in a good many experiments, is further theoretically verified in this paper through the calculation of some structural and thermodynamic parameters. Moreover, it is found that the analyses on bond length, torsion angle and strain energy can facilitate to the study of the localization and the size of a knot in the tensile process. The symmetries of torsion angles, bond lengths and bond angles in the knot result in the whole symmetry of the knot in microstructure, thereby adapting itself to the strain applied. Additionally, the statistical property of the force-dependent average knot size illuminates in detail the change in size of a knot with force f, and therefore the minimum size of the knot in the restriction of the potentials considered in this work for a PM chain is deduced. At the same time, the difference in response to uniaxial strain, between a knotted PM strand and an unknotted one is also investigated. The force-extension profile is easily obtained from the simulation. As expected, for a given f, the knotted chain has an R significantly smaller than that of an unknotted polymer. However, the scaled difference becomes less pronounced for larger values of N, and the results for longer chains approach those of the unknotted chains.展开更多
The annex A of the United Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR)2020/2021 Report presented a comprehensive global estimate of frequencies and doses from medical exposure to ionizing r...The annex A of the United Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR)2020/2021 Report presented a comprehensive global estimate of frequencies and doses from medical exposure to ionizing radiation,their distribution and trends for the period 2009-2018.The annex considered four general categories of medical practice using ionizing radiation:(a)diagnostic radiology,including dental radiology and computed tomography,(b)interventional radiology(image-guided interventional procedures),(c)nuclear medicine,and(d)radiation therapy.In the period 2009-2018,about 4.2 billion medical radiological examinations were performed annually,resulting in an annual effective dose of 0.57 mSv per caput.The use of computed tomography has continued to grow and the contribution from interventional radiology has increased rapidly in recent years.The annual number of radionuclide therapy treatments has increased by 60% since the UNSCEAR 2008 Report,while the number of courses of radiation therapy has increased by 22%.Medical exposure remains by far the largest human-made source of radiation exposure to the public.The Committee's evaluation relies on the collection of up-to-date and representative exposure data from all Member States of the United Nations.Future exposure survey should be more relevant and useful and adapted to changing data sources and changing uses of radiation across the world.展开更多
The annex D of the United Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR)2020/2021 Report presented a comprehensive global estimate of occupational exposure to ionizing radiation.The worldwide...The annex D of the United Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR)2020/2021 Report presented a comprehensive global estimate of occupational exposure to ionizing radiation.The worldwide annual number of workers exposed to natural and human-made sources of ionizing radiation was estimated to be approximately 24 million in the period 2010-2014.About 52% of those were employed in the sectors that involve exposure to natural sources of radiation.The worldwide average annual effective dose for all workers during the period 2010-2014 was estimated to be around 1.2 mSv-about two thirds of the value estimated for the period 1995-1999.The annual effective dose was estimated to be around 2.0 mSv for workers exposed to natural sources and 0.5 mSv for workers exposed to human-made sources.The overriding limitation of current evaluation was the low rate of participation by United Nations Member States in providing occupational exposure monitoring data,especially data from non-nuclear sectors and occupational sectors involving naturally occurring radioactive materials.As the assessment of the worldwide occupational exposure is a complex task,the Committee relies on the collection of up-to-date data on occupational exposure from United Nations Member States in a broad range of occupational sectors,and continues collaboration with international organizations.展开更多
The annex B of the UNSCEAR 2019 Report presented a comprehensive review of dosimetric and epidemiological assessments published in the period 2006 to 2017 for deriving conversion factors for calculating the dose from ...The annex B of the UNSCEAR 2019 Report presented a comprehensive review of dosimetric and epidemiological assessments published in the period 2006 to 2017 for deriving conversion factors for calculating the dose from a given exposure to radon(222Rn).The conversion factor is needed for comparison purposes with other sources of radiation exposure.Even though extensive research has been conducted,uncertainties remain large.Given that the uncertainties from both dosimetric and epidemiological studies give rise to a broad range of risk estimates and the fact that values from the current dosimetry and epidemiological reviews are consistent with those used in previous UNSCEAR reports,the Committee recommends the continued use of the dose conversion factor of 9 nSv·(h·Bq·m^(-3))^(-1) equilibrium equivalent concentration of ^(222)Rn for estimating radon exposure levels to a population.This paper summarizes the findings of UNSCEAR's scientific evaluations and its decision regarding the dose conversion factor for population exposure to radon.Research needs for better assessing doses to the lung and risks of lung cancer from exposure to radon are also discussed.展开更多
文摘Gravitation is one of the basic phenomena of the world. Tremendous number of theoretical works on origin, nature, essentials, consequences, etc. of the gravitation and related phenomena were published so far. The most prominent ones are based on the Albert Einstein＇s general theory of relativity. The author of this communication based his approach to the gravitation on Isaac Newton＇s law of the universal gravitation and related quantities, i.e. gravitational forces of matter objects, distance and motion. Namely on the fact, that the gravitation force is - as well as the inertia, mass, space ＂occupied＂ and other properties are - principal features/attributes/properties of matter objects. Gravitation is an additive property of matter objects. Taking into account other positivistic quantities like mass of the Earth, standard acceleration of gravity, and the value of the atomic unit of mass, the author defined a gravitational force of atomic unit （or ＂the Gravitational Force Quantum＂） as a gravitational force which exerts one atomic unit of Earth＇s mass on 1 kilogram of a mass on Earth＇s surface, and he calculated its value： GFO = 1.4958 × 10^-54 N. This quantity can be useful for further development of the ＂quantum mechanical＂ approach to the description and general notion about the world.
文摘In the article ＂The Gravitational Force Quantum and its Value＂ [1 ], the author defined a gravitational force of the atomic unit （＂the Gravitational Force Quantum＂） as a gravitational force which exerts one atomic unit of the Earth＇s mass on l kilogram of a mass on the Earth＇s surface, and he calculated its value as： GFQEarth = 1.4958 × 10.54 N. In the present contribution, he extended the Gravitational Force Quantum concept to further Objects of the Solar Planetary System and for the Pluto. He calculated values of the GFQo on the analogous basis, i.e. of the mass and the standard acceleration of the gravity of individual objects and of the atomic unit of the mass. He received GFQo values for the Mercury 102.1427 × 1055N, the Venus 16,60012 × 10-55N, the Earth 14.97839 × l0-55 N, the Mars 52.91869 × 10-55N, the Jupiter 0.124391×1055 N, the Saturn 0.17929 ×1055N, the Uranus 0.945178 ×1055N, the Neptune 1.002845 × 10-55N, for the Pluto 458.9124 × 10-55N, and for the Sun 0.001257 × 10-55N, respectively. He multiplied the GFQo values by second power of the radii of the individual objects （O）, receiving values denoted as the ＂Elementary Gravitational Charge＂ （Go）. The Elementary Gravitational Charge represents a gravitational force of one atomic unit of mass in the （radius） distance of 1 meter. They were found of the same value： GMe= Gv = GE= GMa= Gj= Gs = Gp= GSun= 6.079675463 × 10-41N. The values were the same as the calculated one on the basis of the ＂classical＂ Newton＇s formula： FG = И × M × m / R2, for the gravitational force between the atomic unit mass and a mass of 1 kg at a distance of 1 meter, which value was calculated as G = 6.079675463 ×1041 N. The quantity of the Elementary Gravitational Charge can be supposed to be analogous to the Elementary （Electric） Charge （e =1.6021766208（98） × 10-19 C） quantity.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 20274040,20574052 and 20774066)the Program for New Century Excellent Talents in University,China (Grant No NCET-05-0538)the Natural Science Foundation of Zhejiang Province,China (Grant No R404047)
文摘In this paper the influence of a knot on the structure of a polymethylene （PM） strand in the tensile process is investigated by using the steered molecular dynamics （SMD） method. The gradual increasing of end-to-end distance, R, results in a tighter knot and a more stretched contour. That the break in a knotted rope almost invariably occurs at a point just outside the ＇entrance＇ to the knot, which has been shown in a good many experiments, is further theoretically verified in this paper through the calculation of some structural and thermodynamic parameters. Moreover, it is found that the analyses on bond length, torsion angle and strain energy can facilitate to the study of the localization and the size of a knot in the tensile process. The symmetries of torsion angles, bond lengths and bond angles in the knot result in the whole symmetry of the knot in microstructure, thereby adapting itself to the strain applied. Additionally, the statistical property of the force-dependent average knot size illuminates in detail the change in size of a knot with force f, and therefore the minimum size of the knot in the restriction of the potentials considered in this work for a PM chain is deduced. At the same time, the difference in response to uniaxial strain, between a knotted PM strand and an unknotted one is also investigated. The force-extension profile is easily obtained from the simulation. As expected, for a given f, the knotted chain has an R significantly smaller than that of an unknotted polymer. However, the scaled difference becomes less pronounced for larger values of N, and the results for longer chains approach those of the unknotted chains.
文摘The annex A of the United Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR)2020/2021 Report presented a comprehensive global estimate of frequencies and doses from medical exposure to ionizing radiation,their distribution and trends for the period 2009-2018.The annex considered four general categories of medical practice using ionizing radiation:(a)diagnostic radiology,including dental radiology and computed tomography,(b)interventional radiology(image-guided interventional procedures),(c)nuclear medicine,and(d)radiation therapy.In the period 2009-2018,about 4.2 billion medical radiological examinations were performed annually,resulting in an annual effective dose of 0.57 mSv per caput.The use of computed tomography has continued to grow and the contribution from interventional radiology has increased rapidly in recent years.The annual number of radionuclide therapy treatments has increased by 60% since the UNSCEAR 2008 Report,while the number of courses of radiation therapy has increased by 22%.Medical exposure remains by far the largest human-made source of radiation exposure to the public.The Committee's evaluation relies on the collection of up-to-date and representative exposure data from all Member States of the United Nations.Future exposure survey should be more relevant and useful and adapted to changing data sources and changing uses of radiation across the world.
文摘The annex D of the United Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR)2020/2021 Report presented a comprehensive global estimate of occupational exposure to ionizing radiation.The worldwide annual number of workers exposed to natural and human-made sources of ionizing radiation was estimated to be approximately 24 million in the period 2010-2014.About 52% of those were employed in the sectors that involve exposure to natural sources of radiation.The worldwide average annual effective dose for all workers during the period 2010-2014 was estimated to be around 1.2 mSv-about two thirds of the value estimated for the period 1995-1999.The annual effective dose was estimated to be around 2.0 mSv for workers exposed to natural sources and 0.5 mSv for workers exposed to human-made sources.The overriding limitation of current evaluation was the low rate of participation by United Nations Member States in providing occupational exposure monitoring data,especially data from non-nuclear sectors and occupational sectors involving naturally occurring radioactive materials.As the assessment of the worldwide occupational exposure is a complex task,the Committee relies on the collection of up-to-date data on occupational exposure from United Nations Member States in a broad range of occupational sectors,and continues collaboration with international organizations.
文摘The annex B of the UNSCEAR 2019 Report presented a comprehensive review of dosimetric and epidemiological assessments published in the period 2006 to 2017 for deriving conversion factors for calculating the dose from a given exposure to radon(222Rn).The conversion factor is needed for comparison purposes with other sources of radiation exposure.Even though extensive research has been conducted,uncertainties remain large.Given that the uncertainties from both dosimetric and epidemiological studies give rise to a broad range of risk estimates and the fact that values from the current dosimetry and epidemiological reviews are consistent with those used in previous UNSCEAR reports,the Committee recommends the continued use of the dose conversion factor of 9 nSv·(h·Bq·m^(-3))^(-1) equilibrium equivalent concentration of ^(222)Rn for estimating radon exposure levels to a population.This paper summarizes the findings of UNSCEAR's scientific evaluations and its decision regarding the dose conversion factor for population exposure to radon.Research needs for better assessing doses to the lung and risks of lung cancer from exposure to radon are also discussed.
