Unlike consumers in the mall or supermarkets, online consumers are “intangible” and their purchasing behaviors are affected by multiple factors, including product pricing, promotion and discounts, quality of product...Unlike consumers in the mall or supermarkets, online consumers are “intangible” and their purchasing behaviors are affected by multiple factors, including product pricing, promotion and discounts, quality of products and brands, and the platforms where they search for the product. In this research, I study the relationship between product sales and consumer characteristics, the relationship between product sales and product qualities, demand curve analysis, and the search friction effect for different platforms. I utilized data from a randomized field experiment involving more than 400 thousand customers and 30 thousand products on JD.com, one of the world’s largest online retailing platforms. There are two focuses of the research: 1) how different consumer characteristics affect sales;2) how to set price and possible search friction for different channels. I find that JD plus membership, education level and age have no significant relationship with product sales, and higher user level leads to higher sales. Sales are highly skewed, with very high numbers of products sold making up only a small percentage of the total. Consumers living in more industrialized cities have more purchasing power. Women and singles lead to higher spending. Also, the better the product performs, the more it sells. Moderate pricing can increase product sales. Based on the research results of search volume in different channels, it is suggested that it is better to focus on app sales. By knowing the results, producers can adjust target consumers for different products and do target advertisements in order to maximize the sales. Also, an appropriate price for a product is also crucial to a seller. By the way, knowing the search friction of different channels can help producers to rearrange platform layout so that search friction can be reduced and more potential deals may be made.展开更多
Although the efficacy of tuberculosis (TB) vaccines is tightly linked to cell-mediated immunity, some functions of T and B cells in TB patients remain unclear. To address how Mycobacterium tuberculosis infection inhib...Although the efficacy of tuberculosis (TB) vaccines is tightly linked to cell-mediated immunity, some functions of T and B cells in TB patients remain unclear. To address how Mycobacterium tuberculosis infection inhibits T effector responses, we assessed the proportions of T cell subsets and B cells in peripheral blood from pulmonary TB (PTB) patients, pleural TB (PLTB) patients, and healthy subjects (HS, who showed purified protein derivative (PPD)-positive reactions) with flow cytometry. Compared to HS, PTB and PLTB patients exhibited higher proportions of B cells and Th17 cells, and lower proportions of Th2 cells and ratios of Th1 to Th17 cells and of Th2 to Th17 cells. PTB patients had higher CD4+ T cells and PD-1+ CD4+ T cells than HS. Newly diagnosed PTB patients (nPTB) had higher proportions of B cells than HS;in contrast, PTB patients subjected to effective treatments (oPTB) and HS shared similar proportions of B cells. oPTB patients had higher proportions of CD4+ T cells, Th17 cells, and PD-1+ CD4+ T cells than HS, but this difference did not occur in nPTB patients. These findings suggest that shifting ratios of Th1 to Th17 cells may be beneficial for M. tuberculosis to amplify.展开更多
Visual navigation is imperative for successful asteroid exploration missions.In this study,an integrated visual navigation system was proposed based on angles-only measurements to robustly and accurately determine the...Visual navigation is imperative for successful asteroid exploration missions.In this study,an integrated visual navigation system was proposed based on angles-only measurements to robustly and accurately determine the pose of the lander during the final landing phase.The system used the lander's global pose information provided by an orbiter,which was deployed in space in advance,and its relative motion information in adjacent images to jointly estimate its optimal state.First,the landmarks on the asteroid surface and markers on the lander were identified from the images acquired by the orbiter.Subsequently,an angles-only measurement model concerning the landmarks and markers was constructed to estimate the orbiter's position and lander's pose.Subsequently,a method based on the epipolar constraint was proposed to estimate the lander's inter-frame motion.Then,the absolute pose and relative motion of the lander were fused using an extended Kalman filter.Additionally,the observability criterion and covariance of the state error were provided.Finally,synthetic image sequences were generated to validate the proposed navigation system,and numerical results demonstrated its advance in terms of robustness and accuracy.展开更多
The powered-descent landing(PDL)phase of the Tianwen-1 mission began with composite backshell–parachute(CBP)separation and ended with landing-rover touchdown.The main tasks of this phase were to reduce the velocity o...The powered-descent landing(PDL)phase of the Tianwen-1 mission began with composite backshell–parachute(CBP)separation and ended with landing-rover touchdown.The main tasks of this phase were to reduce the velocity of the lander,perform the avoidance maneuver,and guarantee a soft touchdown.The PDL phase overcame many challenges:performing the divert maneuver to avoid collision with the CBP while simultaneously avoiding large-scale hazards;slowing the descent from approximately 95 to 0 m/s;performing the precise hazard-avoidance maneuver;and placing the lander gently and safely on the surface of Mars.The architecture and algorithms of the guidance,navigation,and control system for the PDL phase were designed;its execution resulted in Tianwen-1’s successful touchdown in the morning of 15 May 2021.Consequently,the Tianwen-1 mission achieved a historic autonomous landing with simultaneous hazard and CBP avoidance.展开更多
The entry vehicle for the Tianwen-1 mission successfully landed on the surface of Mars at 7:18 AM BJT on May 15,2021.This successful landing made China the first country to orbit,land,and release a rover in their firs...The entry vehicle for the Tianwen-1 mission successfully landed on the surface of Mars at 7:18 AM BJT on May 15,2021.This successful landing made China the first country to orbit,land,and release a rover in their first attempt at the Mars exploration.The guidance,navigation,and control(GNC)system plays a crucial role in the entry,descent,and landing(EDL)phases.This study focused on the attitude control component of the GNC system design.The EDL phase can be divided into several sub-phases,namely the angle of attack control phase,lift control phase,parachute descent phase,and powered descent phase.Each sub-phase has unique attitude control requirements and challenges.This paper introduces the key aspects of designing attitude controllers for each phase.Furthermore,flight results are presented and analyzed.展开更多
To meet the requirements of the Tianwen-1 mission,adaptive entry guidance for entry vehicles,with low lift-to-drag ratios,limited control authority,and large initial state bias,was presented.Typically,the entry guidan...To meet the requirements of the Tianwen-1 mission,adaptive entry guidance for entry vehicles,with low lift-to-drag ratios,limited control authority,and large initial state bias,was presented.Typically,the entry guidance law is divided into four distinct phases:trim angle-of-attack phase,range control phase,heading alignment phase,and trim-wing deployment phase.In the range control phase,the predictor–corrector guidance algorithm is improved by planning an on-board trajectory based on the Mars Science Laboratory(MSL)entry guidance algorithm.The nominal trajectory was designed and described using a combination of the downrange value and other states,such as drag acceleration and altitude rate.For a large initial state bias,the nominal downrange value was modified onboard by weighing the landing accuracy,control authority,and parachute deployment altitude.The biggest advantage of this approach is that it allows the successful correction of altitude errors and the avoidance of control saturation.An overview of the optimal trajectory design process,including a discussion of the design of the initial flight path angle,relevant event trigger,and transition conditions between the four phases,was also presented.Finally,telemetry data analysis and post-flight assessment results were used to illustrate the adaptive guidance law,create good conditions for subsequent parachute reduction and power reduction processes,and gauge the success of the mission.展开更多
On May 15,2021,the Tianwen-1 lander successfully touched down on the surface of Mars.To ensure the success of the landing mission,an end-to-end Mars entry,descent,and landing(EDL)simulator is developed to assess the g...On May 15,2021,the Tianwen-1 lander successfully touched down on the surface of Mars.To ensure the success of the landing mission,an end-to-end Mars entry,descent,and landing(EDL)simulator is developed to assess the guidance,navigation,and control(GNC)system performance,and determine the critical operation and lander parameters.The high-fidelity models of the Mars atmosphere,parachute,and lander system that are incorporated into the simulator are described.Using the developed simulator,simulations of the Tianwen-1 lander EDL are performed.The results indicate that the simulator is valid,and the GNC system of the Tianwen-1 lander exhibits excellent performance.展开更多
Tianwen-1,the first mission of China’s planetary exploration program,accomplished its goals of orbiting,landing,and roving on the Mars.The entry,descent,and landing(EDL)phase directly determines the success of the en...Tianwen-1,the first mission of China’s planetary exploration program,accomplished its goals of orbiting,landing,and roving on the Mars.The entry,descent,and landing(EDL)phase directly determines the success of the entire mission,of which the guidance,navigation,and control(GNC)system is crucial.This paper outlines the Tianwen-1 EDL GNC system design by introducing the GNC requirements followed by presenting the GNC system architecture and algorithms to meet such requirements.The actual flight results for the whole EDL phase are also provided in this paper.展开更多
In the article titled“The Tianwen-1 Guidance,Navigation,and Control for Mars Entry,Descent,and Landing”[1],there was an error in Figure 9(b).On the y-axis,the data read q1,q2,and q1.It should have read q1,q2,and q3....In the article titled“The Tianwen-1 Guidance,Navigation,and Control for Mars Entry,Descent,and Landing”[1],there was an error in Figure 9(b).On the y-axis,the data read q1,q2,and q1.It should have read q1,q2,and q3.This is updated as shown in Figure 1 below.展开更多
Dear authors and readers,Mars is the outer neighboring planet to our planet,the Earth,which has long been the destination of the deep space exploration.Through decades of exploration since the 1960s,mankind has learne...Dear authors and readers,Mars is the outer neighboring planet to our planet,the Earth,which has long been the destination of the deep space exploration.Through decades of exploration since the 1960s,mankind has learned a lot about Mars.Two main scientific reasons for exploring Mars at least can be summarized,including the search for life,and understanding the planet’s evolution.Particularly,Mars can help us to discover the evolution of the Earth and its history,in other words,learning more about our home planet.展开更多
Given that chemotherapy as a stand-alone therapeutic strategy may not be sufficient to effectively treat cancer,there is increasing interest in combination of chemotherapy and alternative therapies.Photodynamic therap...Given that chemotherapy as a stand-alone therapeutic strategy may not be sufficient to effectively treat cancer,there is increasing interest in combination of chemotherapy and alternative therapies.Photodynamic therapy has the advantages of high selectivity and low side effects,so the combination of photodynamic therapy and chemotherapy has become one of the most appealing strategies for tumor treatment.In this work,we constructed a nano drug codelivery system(PPDC)to realize the combined treatment of chemotherapy and photodynamic therapy through encapsulating chemotherapeutic drug dihydroartemisinin and photosensitizer chlorin e6 in PEG-PCL.The potentials,particle size and morphology of nanoparticles were characterized by dynamic light scattering and transmission electron microscopy.We also investigated the reactive oxygen species(ROS)generation and drug release ability.The antitumor effect in vitro was investigated by methylthiazolyldiphenyl-tetrazolium bromide assays and cell apoptosis experiments,and the potential cell death mechanisms were explored by ROS detection and Western blot analysis.The in vivo antitumor effect of PPDC was evaluated under the guidance of fluorescence imaging.Our work provides a potential antitumor treatment approach and expands the application of dihydroartemisinin for breast cancer therapy.展开更多
文摘Unlike consumers in the mall or supermarkets, online consumers are “intangible” and their purchasing behaviors are affected by multiple factors, including product pricing, promotion and discounts, quality of products and brands, and the platforms where they search for the product. In this research, I study the relationship between product sales and consumer characteristics, the relationship between product sales and product qualities, demand curve analysis, and the search friction effect for different platforms. I utilized data from a randomized field experiment involving more than 400 thousand customers and 30 thousand products on JD.com, one of the world’s largest online retailing platforms. There are two focuses of the research: 1) how different consumer characteristics affect sales;2) how to set price and possible search friction for different channels. I find that JD plus membership, education level and age have no significant relationship with product sales, and higher user level leads to higher sales. Sales are highly skewed, with very high numbers of products sold making up only a small percentage of the total. Consumers living in more industrialized cities have more purchasing power. Women and singles lead to higher spending. Also, the better the product performs, the more it sells. Moderate pricing can increase product sales. Based on the research results of search volume in different channels, it is suggested that it is better to focus on app sales. By knowing the results, producers can adjust target consumers for different products and do target advertisements in order to maximize the sales. Also, an appropriate price for a product is also crucial to a seller. By the way, knowing the search friction of different channels can help producers to rearrange platform layout so that search friction can be reduced and more potential deals may be made.
文摘Although the efficacy of tuberculosis (TB) vaccines is tightly linked to cell-mediated immunity, some functions of T and B cells in TB patients remain unclear. To address how Mycobacterium tuberculosis infection inhibits T effector responses, we assessed the proportions of T cell subsets and B cells in peripheral blood from pulmonary TB (PTB) patients, pleural TB (PLTB) patients, and healthy subjects (HS, who showed purified protein derivative (PPD)-positive reactions) with flow cytometry. Compared to HS, PTB and PLTB patients exhibited higher proportions of B cells and Th17 cells, and lower proportions of Th2 cells and ratios of Th1 to Th17 cells and of Th2 to Th17 cells. PTB patients had higher CD4+ T cells and PD-1+ CD4+ T cells than HS. Newly diagnosed PTB patients (nPTB) had higher proportions of B cells than HS;in contrast, PTB patients subjected to effective treatments (oPTB) and HS shared similar proportions of B cells. oPTB patients had higher proportions of CD4+ T cells, Th17 cells, and PD-1+ CD4+ T cells than HS, but this difference did not occur in nPTB patients. These findings suggest that shifting ratios of Th1 to Th17 cells may be beneficial for M. tuberculosis to amplify.
基金supported by the National Natural Science Foundation of China(Grant Nos.61673057 and 61803028)。
文摘Visual navigation is imperative for successful asteroid exploration missions.In this study,an integrated visual navigation system was proposed based on angles-only measurements to robustly and accurately determine the pose of the lander during the final landing phase.The system used the lander's global pose information provided by an orbiter,which was deployed in space in advance,and its relative motion information in adjacent images to jointly estimate its optimal state.First,the landmarks on the asteroid surface and markers on the lander were identified from the images acquired by the orbiter.Subsequently,an angles-only measurement model concerning the landmarks and markers was constructed to estimate the orbiter's position and lander's pose.Subsequently,a method based on the epipolar constraint was proposed to estimate the lander's inter-frame motion.Then,the absolute pose and relative motion of the lander were fused using an extended Kalman filter.Additionally,the observability criterion and covariance of the state error were provided.Finally,synthetic image sequences were generated to validate the proposed navigation system,and numerical results demonstrated its advance in terms of robustness and accuracy.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.61673057 and 61803028)and the Civil Aerospace Advance Research Project.
文摘The powered-descent landing(PDL)phase of the Tianwen-1 mission began with composite backshell–parachute(CBP)separation and ended with landing-rover touchdown.The main tasks of this phase were to reduce the velocity of the lander,perform the avoidance maneuver,and guarantee a soft touchdown.The PDL phase overcame many challenges:performing the divert maneuver to avoid collision with the CBP while simultaneously avoiding large-scale hazards;slowing the descent from approximately 95 to 0 m/s;performing the precise hazard-avoidance maneuver;and placing the lander gently and safely on the surface of Mars.The architecture and algorithms of the guidance,navigation,and control system for the PDL phase were designed;its execution resulted in Tianwen-1’s successful touchdown in the morning of 15 May 2021.Consequently,the Tianwen-1 mission achieved a historic autonomous landing with simultaneous hazard and CBP avoidance.
基金This work was supported by the National Natural Science Foundation of China(Grant No.61673057)and the Civil Aerospace Advance Research Project.
文摘The entry vehicle for the Tianwen-1 mission successfully landed on the surface of Mars at 7:18 AM BJT on May 15,2021.This successful landing made China the first country to orbit,land,and release a rover in their first attempt at the Mars exploration.The guidance,navigation,and control(GNC)system plays a crucial role in the entry,descent,and landing(EDL)phases.This study focused on the attitude control component of the GNC system design.The EDL phase can be divided into several sub-phases,namely the angle of attack control phase,lift control phase,parachute descent phase,and powered descent phase.Each sub-phase has unique attitude control requirements and challenges.This paper introduces the key aspects of designing attitude controllers for each phase.Furthermore,flight results are presented and analyzed.
文摘To meet the requirements of the Tianwen-1 mission,adaptive entry guidance for entry vehicles,with low lift-to-drag ratios,limited control authority,and large initial state bias,was presented.Typically,the entry guidance law is divided into four distinct phases:trim angle-of-attack phase,range control phase,heading alignment phase,and trim-wing deployment phase.In the range control phase,the predictor–corrector guidance algorithm is improved by planning an on-board trajectory based on the Mars Science Laboratory(MSL)entry guidance algorithm.The nominal trajectory was designed and described using a combination of the downrange value and other states,such as drag acceleration and altitude rate.For a large initial state bias,the nominal downrange value was modified onboard by weighing the landing accuracy,control authority,and parachute deployment altitude.The biggest advantage of this approach is that it allows the successful correction of altitude errors and the avoidance of control saturation.An overview of the optimal trajectory design process,including a discussion of the design of the initial flight path angle,relevant event trigger,and transition conditions between the four phases,was also presented.Finally,telemetry data analysis and post-flight assessment results were used to illustrate the adaptive guidance law,create good conditions for subsequent parachute reduction and power reduction processes,and gauge the success of the mission.
基金This work was supported by the National Natural Science Foundation of China(No.61803028)and Civil Aerospace Advance Research Project.
文摘On May 15,2021,the Tianwen-1 lander successfully touched down on the surface of Mars.To ensure the success of the landing mission,an end-to-end Mars entry,descent,and landing(EDL)simulator is developed to assess the guidance,navigation,and control(GNC)system performance,and determine the critical operation and lander parameters.The high-fidelity models of the Mars atmosphere,parachute,and lander system that are incorporated into the simulator are described.Using the developed simulator,simulations of the Tianwen-1 lander EDL are performed.The results indicate that the simulator is valid,and the GNC system of the Tianwen-1 lander exhibits excellent performance.
基金supported by the International Cooperation Fund of the Science and Technology Commission of Shanghai(19520744500)the National Natural Science Foundation of China(51903045 and 52173031)+3 种基金the Program of Shanghai Academic/Technology Research Leader(20XD1400100)the Basic Research Project of the Science and Technology Commission of Shanghai(21JC1400100)the Fundamental Research Funds for the Central UniversitiesGraduate Student Innovation Fund of Donghua University(CUSF-DH-D-2020048)。
基金This work is supported by the Chinese National Space Administration(CNSA).Parts of the work are supported by the National Natural Science Foundation of China(Grant No.61503023,No.61673057,No.61803028,and No.61903032).
文摘Tianwen-1,the first mission of China’s planetary exploration program,accomplished its goals of orbiting,landing,and roving on the Mars.The entry,descent,and landing(EDL)phase directly determines the success of the entire mission,of which the guidance,navigation,and control(GNC)system is crucial.This paper outlines the Tianwen-1 EDL GNC system design by introducing the GNC requirements followed by presenting the GNC system architecture and algorithms to meet such requirements.The actual flight results for the whole EDL phase are also provided in this paper.
文摘In the article titled“The Tianwen-1 Guidance,Navigation,and Control for Mars Entry,Descent,and Landing”[1],there was an error in Figure 9(b).On the y-axis,the data read q1,q2,and q1.It should have read q1,q2,and q3.This is updated as shown in Figure 1 below.
文摘Dear authors and readers,Mars is the outer neighboring planet to our planet,the Earth,which has long been the destination of the deep space exploration.Through decades of exploration since the 1960s,mankind has learned a lot about Mars.Two main scientific reasons for exploring Mars at least can be summarized,including the search for life,and understanding the planet’s evolution.Particularly,Mars can help us to discover the evolution of the Earth and its history,in other words,learning more about our home planet.
基金approved by the Ethical Committee of Fujian Medical University(No.FJMU IACUC 2021-0317)conducted by following the guidelines from the Ethics Committee and national regulations of China.
文摘Given that chemotherapy as a stand-alone therapeutic strategy may not be sufficient to effectively treat cancer,there is increasing interest in combination of chemotherapy and alternative therapies.Photodynamic therapy has the advantages of high selectivity and low side effects,so the combination of photodynamic therapy and chemotherapy has become one of the most appealing strategies for tumor treatment.In this work,we constructed a nano drug codelivery system(PPDC)to realize the combined treatment of chemotherapy and photodynamic therapy through encapsulating chemotherapeutic drug dihydroartemisinin and photosensitizer chlorin e6 in PEG-PCL.The potentials,particle size and morphology of nanoparticles were characterized by dynamic light scattering and transmission electron microscopy.We also investigated the reactive oxygen species(ROS)generation and drug release ability.The antitumor effect in vitro was investigated by methylthiazolyldiphenyl-tetrazolium bromide assays and cell apoptosis experiments,and the potential cell death mechanisms were explored by ROS detection and Western blot analysis.The in vivo antitumor effect of PPDC was evaluated under the guidance of fluorescence imaging.Our work provides a potential antitumor treatment approach and expands the application of dihydroartemisinin for breast cancer therapy.
