The study area is located around Guider and belongs to the Northern Cameroon Pan-African fold belt.It is essentially made of three generations of granitoids.The first generation G1 comprises diorites,tonalites and gra...The study area is located around Guider and belongs to the Northern Cameroon Pan-African fold belt.It is essentially made of three generations of granitoids.The first generation G1 comprises diorites,tonalites and granodiorites.The second one G2 is constituted by biotite granites and biotite-muscovite granites deformed in the solid-state.The third generation G3 is constituted by biotite-syenites,monzosyenites,and leucogranites. All the granitoids are cross cut by aplite veins展开更多
Traditional plastic scintillator has respectively low gamma energy resolution.Space radiation detection need the plastic scintillator to keep a relatively better energy resolution for gamma.Thus we did experiments to ...Traditional plastic scintillator has respectively low gamma energy resolution.Space radiation detection need the plastic scintillator to keep a relatively better energy resolution for gamma.Thus we did experiments to study how to get it enhanced by adding light guider and chamfer.A 9000 Bq radioactive source 60 Co has been utilized to make the experiment and results came that when keeping other conditions same,the height of poly methyl methacrylate(PMMA)light guider changes from 12 mm to 40 mm and the energy resolutions varied from 72.3%to63.5% respectively.Furthermore,another contrast experiment was made to decide whether plastic scintillator with light guiders or integrated chamfer can get better energy resolution.In conclusion the plastic scintillator with integrated chamfer got 55.0%.Through the study of adding light guider or chamfer to plastic scintillator,the gamma energy resolution has been improved greatly from 72.3%to 55.0%.展开更多
In the syenitic pluton of Guider (593 ± 4 Ma) in the North-West Cameroon domain of Central African Fold Belt, mineralized N-S to NE-SW vertical or sub-vertical quartz and quartz feldspar veins has been recently i...In the syenitic pluton of Guider (593 ± 4 Ma) in the North-West Cameroon domain of Central African Fold Belt, mineralized N-S to NE-SW vertical or sub-vertical quartz and quartz feldspar veins has been recently identified. In this contribution, we present petrography and mineralogy of these veins, in order to constrain their genesis and emplacement mechanisms based on detailed field work, petrographic studies and chemical characterization of minerals by using an electron probe microanalyser (EPMA). Field observations and vein microstructures show that the emplacement of the veins has been controlled by the dextral N-S trending strike-slip shear zones related to the regional D2 deformation phase. The results of mineralogical analysis reveal the co-presence of silicates and metallic minerals that include magnetite, ilmenite, pyrite, bismuthite, galena (very rare) and sulphide complexes (BiPbS, BiAgPbS, FeBiPbCuS, BiFe(TeS), FeBiPbS, BiPbCuS). The gangue is represented by quartz (quartz 1, quartz 2 and quartz 3), feldspars, sericite, chlorite, yellowish brown clay minerals, and hematite. The textural relationships between sulphides, quartz and alteration products show that the mineralization is essentially syn- to late-D2 and suggest that syenitic country rock and dextral shear zones have played an important role in the metallogenesis of these veins. This mineralization shows characteristics for copper-bearing calc-alkaline deposits, but differs from these by its more extensive alteration and its abundance in hematite. Substitutions of Al(IV) by Si(IV) in sericite associated with the sulphide mineralization and cataclastic deformation suggest that the temperature of trapping of the fluids is between 230°C and 275°C.展开更多
In an emergency evacuation,the free evacuation of pedestrians can make the entire evacuation process slow and dangerous.To limit the free behavior of pedestrians and reduce the interaction between pedestrians,a reason...In an emergency evacuation,the free evacuation of pedestrians can make the entire evacuation process slow and dangerous.To limit the free behavior of pedestrians and reduce the interaction between pedestrians,a reasonable layout of the guider can improve the efficiency and safety of evacuation.How to set the number,location,and exit allocation of guiders requires further investigation.In the current study,we transform the evacuation into a multiobjective optimization problem.A two-layer optimization framework is developed.In the upper level,the improved NSGA-II multi-objective algorithm is introduced to generate the favorable guider layout,and a chromosome fragment deletion operator is added to improve the optimization efficiency.In the lower layer,the agent movement simulation model is used to simulate the evacuation dynamic of crowd under the favorable guider layout.The variables of this multi-objective solution model in the upper layer are the number and location of the guiders.The evacuation time and agent movement cost are calculated by the lower layer simulation as the objective values of the solution sample,and guide the iterative search process to obtain more reasonable optimization results.The developed model is verified and then applied to a fictional scenario.The number,initial position and exit allocation of guiders are obtained by optimizing the iterative process.The results show that the near optimal solution can be applied in various visibility conditions,and the evacuation efficiency is much higher than that of unguided evacuation.This optimization framework can provide theoretical and methodological support for emergency evacuation planning.展开更多
文摘The study area is located around Guider and belongs to the Northern Cameroon Pan-African fold belt.It is essentially made of three generations of granitoids.The first generation G1 comprises diorites,tonalites and granodiorites.The second one G2 is constituted by biotite granites and biotite-muscovite granites deformed in the solid-state.The third generation G3 is constituted by biotite-syenites,monzosyenites,and leucogranites. All the granitoids are cross cut by aplite veins
基金supported by the National Natural Science Foundation of China including Research on the Technology of Fast Neutron Location Sensitive Detector Based on GEM and Data Acquisition(No.11575073)the Space Neutron Telescope Detection Technology(No.11775114)
文摘Traditional plastic scintillator has respectively low gamma energy resolution.Space radiation detection need the plastic scintillator to keep a relatively better energy resolution for gamma.Thus we did experiments to study how to get it enhanced by adding light guider and chamfer.A 9000 Bq radioactive source 60 Co has been utilized to make the experiment and results came that when keeping other conditions same,the height of poly methyl methacrylate(PMMA)light guider changes from 12 mm to 40 mm and the energy resolutions varied from 72.3%to63.5% respectively.Furthermore,another contrast experiment was made to decide whether plastic scintillator with light guiders or integrated chamfer can get better energy resolution.In conclusion the plastic scintillator with integrated chamfer got 55.0%.Through the study of adding light guider or chamfer to plastic scintillator,the gamma energy resolution has been improved greatly from 72.3%to 55.0%.
文摘In the syenitic pluton of Guider (593 ± 4 Ma) in the North-West Cameroon domain of Central African Fold Belt, mineralized N-S to NE-SW vertical or sub-vertical quartz and quartz feldspar veins has been recently identified. In this contribution, we present petrography and mineralogy of these veins, in order to constrain their genesis and emplacement mechanisms based on detailed field work, petrographic studies and chemical characterization of minerals by using an electron probe microanalyser (EPMA). Field observations and vein microstructures show that the emplacement of the veins has been controlled by the dextral N-S trending strike-slip shear zones related to the regional D2 deformation phase. The results of mineralogical analysis reveal the co-presence of silicates and metallic minerals that include magnetite, ilmenite, pyrite, bismuthite, galena (very rare) and sulphide complexes (BiPbS, BiAgPbS, FeBiPbCuS, BiFe(TeS), FeBiPbS, BiPbCuS). The gangue is represented by quartz (quartz 1, quartz 2 and quartz 3), feldspars, sericite, chlorite, yellowish brown clay minerals, and hematite. The textural relationships between sulphides, quartz and alteration products show that the mineralization is essentially syn- to late-D2 and suggest that syenitic country rock and dextral shear zones have played an important role in the metallogenesis of these veins. This mineralization shows characteristics for copper-bearing calc-alkaline deposits, but differs from these by its more extensive alteration and its abundance in hematite. Substitutions of Al(IV) by Si(IV) in sericite associated with the sulphide mineralization and cataclastic deformation suggest that the temperature of trapping of the fluids is between 230°C and 275°C.
基金support by the National Natural Science Foundations of China(No.52208204,No.12272284)the Shaanxi science and technology innovation team(No.2022TD-05)Shaanxi“Sanqin Scholar”innovation team.
文摘In an emergency evacuation,the free evacuation of pedestrians can make the entire evacuation process slow and dangerous.To limit the free behavior of pedestrians and reduce the interaction between pedestrians,a reasonable layout of the guider can improve the efficiency and safety of evacuation.How to set the number,location,and exit allocation of guiders requires further investigation.In the current study,we transform the evacuation into a multiobjective optimization problem.A two-layer optimization framework is developed.In the upper level,the improved NSGA-II multi-objective algorithm is introduced to generate the favorable guider layout,and a chromosome fragment deletion operator is added to improve the optimization efficiency.In the lower layer,the agent movement simulation model is used to simulate the evacuation dynamic of crowd under the favorable guider layout.The variables of this multi-objective solution model in the upper layer are the number and location of the guiders.The evacuation time and agent movement cost are calculated by the lower layer simulation as the objective values of the solution sample,and guide the iterative search process to obtain more reasonable optimization results.The developed model is verified and then applied to a fictional scenario.The number,initial position and exit allocation of guiders are obtained by optimizing the iterative process.The results show that the near optimal solution can be applied in various visibility conditions,and the evacuation efficiency is much higher than that of unguided evacuation.This optimization framework can provide theoretical and methodological support for emergency evacuation planning.
