We study quantum motion around a classical heteroclinic point of a single trapped ion interacting with a strong laser standing wave. We construct a set of exact coherent states of the quantum system and from the exact...We study quantum motion around a classical heteroclinic point of a single trapped ion interacting with a strong laser standing wave. We construct a set of exact coherent states of the quantum system and from the exact solutions reveal that quantum signatures of chaos can be induced by the adiabatic interaction between the trapped ion and the laser standing wave, where the quantum expectation values of position and momentum correspond to the classically chaotic orbit. The chaotic region on the phase space is illustrated. The energy crossing and quantum resonance in time evolution and the exponentially increased Heisenberg uncertainty are found. The results suggest a theoretical scheme for controlling the unstable regular and chaotic motions.展开更多
Organophosphorus flame retardants(OPFRs) are gradually replacing brominated flame retardants(BFRs), which are widely used in the world. The increasing output of OPFRs and the increasing detection of OPFRs in environme...Organophosphorus flame retardants(OPFRs) are gradually replacing brominated flame retardants(BFRs), which are widely used in the world. The increasing output of OPFRs and the increasing detection of OPFRs in environmental media have attracted wide attention of scholars at home and abroad. OPFRs are generally semi-volatile, easy to enter the environment and accumulate in organisms,causing potential hazards to the environment and human health. In this paper, the pollution status and toxic effects of OPFRs in aquatic environment were introduced,and the research progress of human health risk caused by them was summarized.The existing problems were pointed out, and the future research was prospected. In the future, the analytical methods of various environmental and biological media should be improved, and comprehensive and in-depth environmental investigation and ecological and health risk assessment should be carried out. Attention should be paid to the effects of combined pollution on organisms and the study of biological acceptability.展开更多
Based on an internationally recognized concept of food security, this paper has created a system of eight indicators to analyze China's food security. For the proper control and analysis of this study, the authors of...Based on an internationally recognized concept of food security, this paper has created a system of eight indicators to analyze China's food security. For the proper control and analysis of this study, the authors of this paper have chosen these indicators: supply, distribution, consumption, utilization efficiency, food security results, stability, sustainability and controllability. Results indicate that China's food security is currently at a high level and has been increasing in recent years. China's food security has multiple advantages with various indicators that include a self-sufficiency ratio, per capita calorie intake and protein supply that are above world average levels, even exceeding the average level of some developed countries. Major challenges facing China's food security include an unreasonable nutrition structure and poor environmental sustainability. In order to increase China's food security level, efforts must be made to adjust output structure, adopt an environmentally friendly pattern of production, attach importance to demand management, reduce unreasonable consumption and loss and moderately lower China's food reserve ratio.展开更多
A methodology for the evaluation of the economic impact of overweight permitted vehicles hauling agricultural products on state highways is presented in this study. The different gross vehicle weight scenarios that ar...A methodology for the evaluation of the economic impact of overweight permitted vehicles hauling agricultural products on state highways is presented in this study. The different gross vehicle weight scenarios that are selected for this investigation range between 80,000 lb. and 100,000 lb. Uniform distribution of axle loads and lumped loads are considered in this study. This study evaluates the proposed higher truck loads and their economic impact to the highways and to the industry. The effects of adapting higher truck loads on the existing highways are evaluated using a deterministic load capacity evaluation as well as a reliability assessment. The target reliability level is derived from AASHTO (American Association of State Highway and Transportation Officials) standard design specifications to satisfy safe and adequate performance level. The overlay thickness required to carry traffic from each gross vehicle weight scenario for the overlay design period is determined. Differences in overlay life were calculated for different gross vehicle weight scenarios with uniform and lumped axle loads. The overlay thickness and costs were determined for a twenty year analysis period using statistical methods. The result showed that lumped loads with allowable axle load of 48,000 lb. produce more pavement damage than the current permitted gross vehicle weight for timber trucks with equally loaded axles.展开更多
Due to the limited amount of funds available for bridge inspection, maintenance and rehabilitation, the evaluation of load capacity for existing bridges is crucial to the Louisiana Department of Transportation and Dev...Due to the limited amount of funds available for bridge inspection, maintenance and rehabilitation, the evaluation of load capacity for existing bridges is crucial to the Louisiana Department of Transportation and Development. This paper includes the development of a methodology to assess the economic impact of overweight vehicles with permits, hauling Louisiana harvest products on state bridges. The proposed higher truck loads are applied on the existing bridges and their effects are determined using deterministic load capacity evaluations as well as reliability assessments. The target rehability level is derived from bridge structures designed to satisfy AASHTO Standard Design Specifications and also satisfy safe and adequate performance levels. The amount of harvest produced is used to select a representative sample of bridges to provide specific examples of expected changes in load ratings and safety levels. The bridges include simple and continuous span behavior. Strength and serviceability criteria are investigated under current legal loads and the expected changes, due to the proposed new weights, are determined. The results are used to assess the cost of crossing a bridge and the permit fees for the proposed truck weight regulation.展开更多
As a result of more than two thousand nuclear tests performed since 1945, two war actions and few accidents in nuclear reactor, it does already exist a radioactive contamination at global scale. This contamination has...As a result of more than two thousand nuclear tests performed since 1945, two war actions and few accidents in nuclear reactor, it does already exist a radioactive contamination at global scale. This contamination has been accumulated mainly in marine sediments, because sea is about 80% of planet surface, and solid fission products released by nuclear explosions are transported by wind first and then by rain to liquid and solid portions on earth, while gaseous fission products are diffused in the atmosphere. In this way, heavy, high yielding fission products, such as 137Cs, get marine sediments, where they are found mixed with heavy radioactive natural elements such as U, Th and their also radioactive decay products. But since alkaline are so abundant on earth, it is also found natural radioactive isotope 4~K, 0.0118% of isotopes forming K element, with half life 1.28 ~ l09, in the time range of planet age and elements origin. So, one easy way to assess both the importance and evaluation of radioactive contamination at global scale should be to establish a RCF (radioactive contamination factor) as a percentage of 137Cs contaminant radioactivity in marine sediments, compared to 4~K natural radioactivity present from the very beginning of earth, both expressed as Bq per gram of sediment. In the frame of these rather general considerations, a research project has started in Mexico whose varied purposes are: to characterize sea regions in both vast littorals in the country, by its natural 4~K radioactivity present in sea salts, as well as to determine if 137Cs traces produced by recent radioactive contamination have reached their coasts. Also, to assess the 137Cs traces already present in marine sediments as a result of more than two thousand nuclear test explosions performed till now, rather than contamination produced by four main accidents in nuclear reactors during the last 60 years. It is proposed a radioactive contamination factor obtained from samples taken up in both coasts during the last two years, which should be very useful in two ways: first to assess the real danger of radioactive contamination already present by comparing with natural radioactivity, and second to assess the growth, equilibrium or drop of radioactive contamination, given that nuclear energy is still the best option to solve the large energy demand foreseen in the near future.展开更多
Studies on radiation level and radionuclide distribution in Yemen were studied. The samples were collected from eight locations: Ma'rib, A1 Jawf, Sana'a, Dhamar, Amran, Ibb, Al Bayda and Al Dalea. The purpose of th...Studies on radiation level and radionuclide distribution in Yemen were studied. The samples were collected from eight locations: Ma'rib, A1 Jawf, Sana'a, Dhamar, Amran, Ibb, Al Bayda and Al Dalea. The purpose of this study is to provide a baseline map of radioactivity background levels in the investigated area and this study will be used as reference information to assess any change in the radioactive background level due to geological processes. The highest values of 22~ and 2~l'h concentrations (8797.2 and 24984.1 Bq.kg"l, respectively) were observed at A1 Jawf, region, whereas the highest average value of 40K concentration was 1561.9 Bq.kg-1. The investigation of the geological maps of the area under study showed that the surface rock outcrops consist mainly of granites, diorite, granodiorite, gneisses, and schists. All these rock types arc known to be rich in radioactive materials, which are considered natural sources for gamma radiation. The low mdiological background characterizing some Yemeni rocks could be attributed to nature of these rocks which consist of lime stone (sands and gravels). The absorbed dose rate in air was found to be in the range between 5.40 and 45.11 nGy.h-1 depending on the geological features, and radium equivalent activity concentration was found in the range between 29.57 and 71.85 Bq.kg-1. Also the representative extcmal hazard index values for the corresponding samples were also estinlated and given.展开更多
基金The project supported by National Natural Science Foundation of China under Grant No.10575034the Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics of China under Grant No.T152504
文摘We study quantum motion around a classical heteroclinic point of a single trapped ion interacting with a strong laser standing wave. We construct a set of exact coherent states of the quantum system and from the exact solutions reveal that quantum signatures of chaos can be induced by the adiabatic interaction between the trapped ion and the laser standing wave, where the quantum expectation values of position and momentum correspond to the classically chaotic orbit. The chaotic region on the phase space is illustrated. The energy crossing and quantum resonance in time evolution and the exponentially increased Heisenberg uncertainty are found. The results suggest a theoretical scheme for controlling the unstable regular and chaotic motions.
基金Supported by National Science and Technology Major Project of China(2017ZX07202004)~~
文摘Organophosphorus flame retardants(OPFRs) are gradually replacing brominated flame retardants(BFRs), which are widely used in the world. The increasing output of OPFRs and the increasing detection of OPFRs in environmental media have attracted wide attention of scholars at home and abroad. OPFRs are generally semi-volatile, easy to enter the environment and accumulate in organisms,causing potential hazards to the environment and human health. In this paper, the pollution status and toxic effects of OPFRs in aquatic environment were introduced,and the research progress of human health risk caused by them was summarized.The existing problems were pointed out, and the future research was prospected. In the future, the analytical methods of various environmental and biological media should be improved, and comprehensive and in-depth environmental investigation and ecological and health risk assessment should be carried out. Attention should be paid to the effects of combined pollution on organisms and the study of biological acceptability.
基金sponsored by the Chinese Academy of Social Sciences(CASS)Innovation Programme
文摘Based on an internationally recognized concept of food security, this paper has created a system of eight indicators to analyze China's food security. For the proper control and analysis of this study, the authors of this paper have chosen these indicators: supply, distribution, consumption, utilization efficiency, food security results, stability, sustainability and controllability. Results indicate that China's food security is currently at a high level and has been increasing in recent years. China's food security has multiple advantages with various indicators that include a self-sufficiency ratio, per capita calorie intake and protein supply that are above world average levels, even exceeding the average level of some developed countries. Major challenges facing China's food security include an unreasonable nutrition structure and poor environmental sustainability. In order to increase China's food security level, efforts must be made to adjust output structure, adopt an environmentally friendly pattern of production, attach importance to demand management, reduce unreasonable consumption and loss and moderately lower China's food reserve ratio.
文摘A methodology for the evaluation of the economic impact of overweight permitted vehicles hauling agricultural products on state highways is presented in this study. The different gross vehicle weight scenarios that are selected for this investigation range between 80,000 lb. and 100,000 lb. Uniform distribution of axle loads and lumped loads are considered in this study. This study evaluates the proposed higher truck loads and their economic impact to the highways and to the industry. The effects of adapting higher truck loads on the existing highways are evaluated using a deterministic load capacity evaluation as well as a reliability assessment. The target reliability level is derived from AASHTO (American Association of State Highway and Transportation Officials) standard design specifications to satisfy safe and adequate performance level. The overlay thickness required to carry traffic from each gross vehicle weight scenario for the overlay design period is determined. Differences in overlay life were calculated for different gross vehicle weight scenarios with uniform and lumped axle loads. The overlay thickness and costs were determined for a twenty year analysis period using statistical methods. The result showed that lumped loads with allowable axle load of 48,000 lb. produce more pavement damage than the current permitted gross vehicle weight for timber trucks with equally loaded axles.
文摘Due to the limited amount of funds available for bridge inspection, maintenance and rehabilitation, the evaluation of load capacity for existing bridges is crucial to the Louisiana Department of Transportation and Development. This paper includes the development of a methodology to assess the economic impact of overweight vehicles with permits, hauling Louisiana harvest products on state bridges. The proposed higher truck loads are applied on the existing bridges and their effects are determined using deterministic load capacity evaluations as well as reliability assessments. The target rehability level is derived from bridge structures designed to satisfy AASHTO Standard Design Specifications and also satisfy safe and adequate performance levels. The amount of harvest produced is used to select a representative sample of bridges to provide specific examples of expected changes in load ratings and safety levels. The bridges include simple and continuous span behavior. Strength and serviceability criteria are investigated under current legal loads and the expected changes, due to the proposed new weights, are determined. The results are used to assess the cost of crossing a bridge and the permit fees for the proposed truck weight regulation.
文摘As a result of more than two thousand nuclear tests performed since 1945, two war actions and few accidents in nuclear reactor, it does already exist a radioactive contamination at global scale. This contamination has been accumulated mainly in marine sediments, because sea is about 80% of planet surface, and solid fission products released by nuclear explosions are transported by wind first and then by rain to liquid and solid portions on earth, while gaseous fission products are diffused in the atmosphere. In this way, heavy, high yielding fission products, such as 137Cs, get marine sediments, where they are found mixed with heavy radioactive natural elements such as U, Th and their also radioactive decay products. But since alkaline are so abundant on earth, it is also found natural radioactive isotope 4~K, 0.0118% of isotopes forming K element, with half life 1.28 ~ l09, in the time range of planet age and elements origin. So, one easy way to assess both the importance and evaluation of radioactive contamination at global scale should be to establish a RCF (radioactive contamination factor) as a percentage of 137Cs contaminant radioactivity in marine sediments, compared to 4~K natural radioactivity present from the very beginning of earth, both expressed as Bq per gram of sediment. In the frame of these rather general considerations, a research project has started in Mexico whose varied purposes are: to characterize sea regions in both vast littorals in the country, by its natural 4~K radioactivity present in sea salts, as well as to determine if 137Cs traces produced by recent radioactive contamination have reached their coasts. Also, to assess the 137Cs traces already present in marine sediments as a result of more than two thousand nuclear test explosions performed till now, rather than contamination produced by four main accidents in nuclear reactors during the last 60 years. It is proposed a radioactive contamination factor obtained from samples taken up in both coasts during the last two years, which should be very useful in two ways: first to assess the real danger of radioactive contamination already present by comparing with natural radioactivity, and second to assess the growth, equilibrium or drop of radioactive contamination, given that nuclear energy is still the best option to solve the large energy demand foreseen in the near future.
文摘Studies on radiation level and radionuclide distribution in Yemen were studied. The samples were collected from eight locations: Ma'rib, A1 Jawf, Sana'a, Dhamar, Amran, Ibb, Al Bayda and Al Dalea. The purpose of this study is to provide a baseline map of radioactivity background levels in the investigated area and this study will be used as reference information to assess any change in the radioactive background level due to geological processes. The highest values of 22~ and 2~l'h concentrations (8797.2 and 24984.1 Bq.kg"l, respectively) were observed at A1 Jawf, region, whereas the highest average value of 40K concentration was 1561.9 Bq.kg-1. The investigation of the geological maps of the area under study showed that the surface rock outcrops consist mainly of granites, diorite, granodiorite, gneisses, and schists. All these rock types arc known to be rich in radioactive materials, which are considered natural sources for gamma radiation. The low mdiological background characterizing some Yemeni rocks could be attributed to nature of these rocks which consist of lime stone (sands and gravels). The absorbed dose rate in air was found to be in the range between 5.40 and 45.11 nGy.h-1 depending on the geological features, and radium equivalent activity concentration was found in the range between 29.57 and 71.85 Bq.kg-1. Also the representative extcmal hazard index values for the corresponding samples were also estinlated and given.