In order to analyze and learn the difference in car-following behavior between normal and rainy days, we first collect car-following trajectory data of an urban elevated road on normal and rainy days by microwave rada...In order to analyze and learn the difference in car-following behavior between normal and rainy days, we first collect car-following trajectory data of an urban elevated road on normal and rainy days by microwave radar and analyze the differences in speed, relative speed, acceleration, space headway, and time headway among data through statistics. Secondly, owing to the time-series characteristics of car-following data, we use the long short-term memory(LSTM) neural network optimized by attention mechanism(AM) and sparrow search algorithm(SSA) to learn the different car-following behaviors under different weather conditions and build corresponding models(ASL-Normal, ASL-Rain, where ASL stands for AM-SSA-LSTM), respectively. Finally, the simulation test shows that the mean square error(MSE) and reciprocal of time-to-collision(RTTC) of the ASL model are better than those of LSTM and intelligent diver model(IDM), which is closer to the real data. The ASL model can better learn different driving behaviors on normal and rainy days. However,it has a higher sensitivity to weather conditions from cross test on normal and rainy data-sets which need classification training or sample diversification processing. In the car-following platoon simulation, the stability performances of two models are excellent, which can describe the basic characteristics of traffic flow on normal and rainy days. Comparing with ASL-Rain model, the convergence time of ASL-Normal is shorter, reflecting that cautious driving behavior on rainy days will reduce traffic efficiency to a certain extent. However, ASL-Normal model produces a more severe and frequent traffic oscillation within a shorter period because of aggressive driving behavior on normal days.展开更多
Assessing and accounting for material consumption and environmental impact are necessary to measure environmental externalities of the aluminum industry and to construct an ecological civilization.In this research,lif...Assessing and accounting for material consumption and environmental impact are necessary to measure environmental externalities of the aluminum industry and to construct an ecological civilization.In this research,life cycle assessment(LCA)theory was used to assess the environmental impact of primary aluminum based on the lime soda Bayer process and different power generation modes,and the sources and distributions of the four selected impact categories were analyzed.The results show that,(1)Negative environmental impact of aluminum industry generally occurs from alumina extraction,carbon anode fabrication and electrolysis,particularly electrolysis and alumina extraction.Primary energy demand(PED),water use(WU),global warming potential(GWP)and freshwater eutrophication potential(FEP)are main environmental impact categories.(2)The environmental load with thermal power is higher than that with hydropower,e.g.,for the former,the greenhouse gas emission coefficient of 21800 kg CO2 eq/t(Al)will be generated,while for the latter,4910 kg CO2 eq/t(Al)will be generated.(3)Both power mode methods reflect the energy structure,whereas direct emissions reflect the technical level,indicating the potential for large energy savings and emission reductions,and some policies,related to clean power,energy efficiency and technological progress,should be made for emission reduction.展开更多
Objective To evaluate left atrial function in essential hypertension patients with different patterns of left ventricular geometric models by real-time three-dimensional echocardiography （RT-3DE） and left atrial tra...Objective To evaluate left atrial function in essential hypertension patients with different patterns of left ventricular geometric models by real-time three-dimensional echocardiography （RT-3DE） and left atrial tracking （EAT）.展开更多
Using the International Country Risk Guide(ICRG)index to represent countries’political risk,the time-varying effect of political risk on copper prices was examined based on the time-varying parameter structural vecto...Using the International Country Risk Guide(ICRG)index to represent countries’political risk,the time-varying effect of political risk on copper prices was examined based on the time-varying parameter structural vector autoregression with stochastic volatility(TVP-SVAR-SV)model.The empirical results show that the impact of political risk on copper prices is time-varying and has tended to increase gradually in recent years.There are significant country-level differences in the impact of political risk on copper prices.Political risk has a stronger and longer-lasting impact on copper prices in exporting countries.In terms of risk sources,external and internal conflicts contribute most to international copper price fluctuations in the sample period.The impact of political risk on copper prices reaches an extreme level during the international financial crisis,the European debt crisis,and the election of Donald Trump.展开更多
Two-dimensional(2D) magnetic crystals have attracted great attention due to their emerging new physical phenomena. They provide ideal platforms to study the fundamental physics of magnetism in low dimensions. In this ...Two-dimensional(2D) magnetic crystals have attracted great attention due to their emerging new physical phenomena. They provide ideal platforms to study the fundamental physics of magnetism in low dimensions. In this research,magnetic tunneling junctions(MTJs) based on XSe2(X = Mn, V) with room-temperature ferromagnetism were studied using first-principles calculations. A large tunneling magnetoresistance(TMR) of 725.07% was obtained in the MTJs based on monolayer MnSe2. Several schemes were proposed to improve the TMR of these devices. Moreover, the results of our non-equilibrium transport calculations showed that the large TMR was maintained in these devices under a finite bias.The transmission spectrum was analyzed according to the orbital components and the electronic structure of the monolayer XSe2(X = Mn, V). The results in this paper demonstrated that the MTJs based on a 2D ferromagnet with room-temperature ferromagnetism exhibited reliable performance. Therefore, such devices show the possibility for potential applications in spintronics.展开更多
BACKGROUND The number of patients with bronchial trauma(BT)who survived to hospital admission has increased with the improvement of prehospital care;early diagnosis and treatment should be considered,especially among ...BACKGROUND The number of patients with bronchial trauma(BT)who survived to hospital admission has increased with the improvement of prehospital care;early diagnosis and treatment should be considered,especially among blunt trauma patients,whose diagnosis is frequently delayed.AIM To describe the early recognition and surgical management considerations of blunt and penetrating BTs,and to elaborate the differences between them.METHODS All patients with BTs during the past 15 years were reviewed,and data were retrospectively analyzed regarding the mechanism of injury,diagnostic and therapeutic procedures,and outcomes.According to the injury mechanisms,the patients were divided into two groups:Blunt BT(BBT)group and penetrating BT(PBT)group.The injury severity,treatment procedures,and prognoses of the two groups were compared.RESULTS A total of 73 patients with BT were admitted during the study period.The proportion of BTs among the entire cohort with chest trauma was 2.4%(73/3018),and all 73 underwent thoracotomy.Polytrauma patients accounted for 81.6% in the BBT group and 22.9%in the PBT group,and the mean Injury Severity Score was 38.22±8.13 and 21.33±6.12,respectively.Preoperative three-dimensional spiral computed tomography(CT)and/or fiberoptic bronchoscopy(FB)were performed in 92.1% of cases in the BBT group(n=38)and 34.3% in the PBT group(n=35).In the BBT group,a delay in diagnosis for over 48 h occurred in 55.3% of patients.In the PBT group,31 patients underwent emergency thoracotomy due to massive hemothorax,and BT was confirmed during the operation.Among them,22 underwent pulmo-tractotomy for hemostasis,avoiding partial pneumonectomy.In this series,the overall mortality rate was 6.9%(5/73),and it was 7.9%(3/38)and 5.7%(2/35)in the BBT group and PBT group,respectively(P>0.05).All 68 survivors were followed for 6 to 42(23±6.4)mo,and CT,FB,and pulmonary function examinations were performed as planned.All patients exhibited normal lung function and healthy conditions except three who required reoperations.CO展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 52072108)the Natural Science Foundation of Anhui Province, China (Grant No. 2208085ME148)the Open Fund for State Key Laboratory of Cognitive Intelligence, China (Grant No. W2022JSKF0504)。
文摘In order to analyze and learn the difference in car-following behavior between normal and rainy days, we first collect car-following trajectory data of an urban elevated road on normal and rainy days by microwave radar and analyze the differences in speed, relative speed, acceleration, space headway, and time headway among data through statistics. Secondly, owing to the time-series characteristics of car-following data, we use the long short-term memory(LSTM) neural network optimized by attention mechanism(AM) and sparrow search algorithm(SSA) to learn the different car-following behaviors under different weather conditions and build corresponding models(ASL-Normal, ASL-Rain, where ASL stands for AM-SSA-LSTM), respectively. Finally, the simulation test shows that the mean square error(MSE) and reciprocal of time-to-collision(RTTC) of the ASL model are better than those of LSTM and intelligent diver model(IDM), which is closer to the real data. The ASL model can better learn different driving behaviors on normal and rainy days. However,it has a higher sensitivity to weather conditions from cross test on normal and rainy data-sets which need classification training or sample diversification processing. In the car-following platoon simulation, the stability performances of two models are excellent, which can describe the basic characteristics of traffic flow on normal and rainy days. Comparing with ASL-Rain model, the convergence time of ASL-Normal is shorter, reflecting that cautious driving behavior on rainy days will reduce traffic efficiency to a certain extent. However, ASL-Normal model produces a more severe and frequent traffic oscillation within a shorter period because of aggressive driving behavior on normal days.
基金Projects(71633006,71403298) supported by the National Natural Science Foundation of ChinaProjects(14YJCZH045,15YJCZH019) supported by the Ministry of Education of Humanities and Social Science,China
文摘Assessing and accounting for material consumption and environmental impact are necessary to measure environmental externalities of the aluminum industry and to construct an ecological civilization.In this research,life cycle assessment(LCA)theory was used to assess the environmental impact of primary aluminum based on the lime soda Bayer process and different power generation modes,and the sources and distributions of the four selected impact categories were analyzed.The results show that,(1)Negative environmental impact of aluminum industry generally occurs from alumina extraction,carbon anode fabrication and electrolysis,particularly electrolysis and alumina extraction.Primary energy demand(PED),water use(WU),global warming potential(GWP)and freshwater eutrophication potential(FEP)are main environmental impact categories.(2)The environmental load with thermal power is higher than that with hydropower,e.g.,for the former,the greenhouse gas emission coefficient of 21800 kg CO2 eq/t(Al)will be generated,while for the latter,4910 kg CO2 eq/t(Al)will be generated.(3)Both power mode methods reflect the energy structure,whereas direct emissions reflect the technical level,indicating the potential for large energy savings and emission reductions,and some policies,related to clean power,energy efficiency and technological progress,should be made for emission reduction.
基金Supported by the Natural Science Foundation of Liaoning ProvinceChina(2013023010)
文摘Objective To evaluate left atrial function in essential hypertension patients with different patterns of left ventricular geometric models by real-time three-dimensional echocardiography （RT-3DE） and left atrial tracking （EAT）.
基金financial supports from the National Natural Science Foundation of China(Nos.71633006,71874210,71874207,71974208)the Natural Science Founda-tion of Hunan Province,China(No.2020JJ5784)the Innovation-Driven Foundation of Central South University,China(No.2020CX049)。
文摘Using the International Country Risk Guide(ICRG)index to represent countries’political risk,the time-varying effect of political risk on copper prices was examined based on the time-varying parameter structural vector autoregression with stochastic volatility(TVP-SVAR-SV)model.The empirical results show that the impact of political risk on copper prices is time-varying and has tended to increase gradually in recent years.There are significant country-level differences in the impact of political risk on copper prices.Political risk has a stronger and longer-lasting impact on copper prices in exporting countries.In terms of risk sources,external and internal conflicts contribute most to international copper price fluctuations in the sample period.The impact of political risk on copper prices reaches an extreme level during the international financial crisis,the European debt crisis,and the election of Donald Trump.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61571415 and 61622406)the National Key Research and Development Program of China(Grant No.2017YFA0207500)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB30000000)Beijing Academy of Quantum Information Sciences,China(Grant No.Y18G04)
文摘Two-dimensional(2D) magnetic crystals have attracted great attention due to their emerging new physical phenomena. They provide ideal platforms to study the fundamental physics of magnetism in low dimensions. In this research,magnetic tunneling junctions(MTJs) based on XSe2(X = Mn, V) with room-temperature ferromagnetism were studied using first-principles calculations. A large tunneling magnetoresistance(TMR) of 725.07% was obtained in the MTJs based on monolayer MnSe2. Several schemes were proposed to improve the TMR of these devices. Moreover, the results of our non-equilibrium transport calculations showed that the large TMR was maintained in these devices under a finite bias.The transmission spectrum was analyzed according to the orbital components and the electronic structure of the monolayer XSe2(X = Mn, V). The results in this paper demonstrated that the MTJs based on a 2D ferromagnet with room-temperature ferromagnetism exhibited reliable performance. Therefore, such devices show the possibility for potential applications in spintronics.
文摘BACKGROUND The number of patients with bronchial trauma(BT)who survived to hospital admission has increased with the improvement of prehospital care;early diagnosis and treatment should be considered,especially among blunt trauma patients,whose diagnosis is frequently delayed.AIM To describe the early recognition and surgical management considerations of blunt and penetrating BTs,and to elaborate the differences between them.METHODS All patients with BTs during the past 15 years were reviewed,and data were retrospectively analyzed regarding the mechanism of injury,diagnostic and therapeutic procedures,and outcomes.According to the injury mechanisms,the patients were divided into two groups:Blunt BT(BBT)group and penetrating BT(PBT)group.The injury severity,treatment procedures,and prognoses of the two groups were compared.RESULTS A total of 73 patients with BT were admitted during the study period.The proportion of BTs among the entire cohort with chest trauma was 2.4%(73/3018),and all 73 underwent thoracotomy.Polytrauma patients accounted for 81.6% in the BBT group and 22.9%in the PBT group,and the mean Injury Severity Score was 38.22±8.13 and 21.33±6.12,respectively.Preoperative three-dimensional spiral computed tomography(CT)and/or fiberoptic bronchoscopy(FB)were performed in 92.1% of cases in the BBT group(n=38)and 34.3% in the PBT group(n=35).In the BBT group,a delay in diagnosis for over 48 h occurred in 55.3% of patients.In the PBT group,31 patients underwent emergency thoracotomy due to massive hemothorax,and BT was confirmed during the operation.Among them,22 underwent pulmo-tractotomy for hemostasis,avoiding partial pneumonectomy.In this series,the overall mortality rate was 6.9%(5/73),and it was 7.9%(3/38)and 5.7%(2/35)in the BBT group and PBT group,respectively(P>0.05).All 68 survivors were followed for 6 to 42(23±6.4)mo,and CT,FB,and pulmonary function examinations were performed as planned.All patients exhibited normal lung function and healthy conditions except three who required reoperations.CO
