With research on the carrier phase synchronization and symbol synchronization algorithm of demodulation module, a synchronization circuit system is designed for GPS software receiver based on field programmable gate a...With research on the carrier phase synchronization and symbol synchronization algorithm of demodulation module, a synchronization circuit system is designed for GPS software receiver based on field programmable gate array （FPGA）, and a series of experiment is done on the hardware platform. The result shows the all-digital synchronization and demodulation of GPS intermediate frequency （IF） signal can be realized and applied in embedded real-time GPS software receiver system. It is verified that the decision-directed joint tracking algorithm of carrier phase and symbol timing for received signals from GPS is reasonable. In addition, the loop works steadily and can be used for receiving GPS signals using synchronous demodulation. The synchronization circuit for GPS software receiver designed based on FPGA has the features of low cost, miniaturization, low power and real-time. Surely, it will become one of the development directions for GPS and even GNSS embedded real-time software receiver.展开更多
An effective autonomous navigation system for the integration of star sensor,infrared horizon sensor,magnetometer,radar altimeter and ultraviolet sensor is developed.The requirements of the integrated navigation syste...An effective autonomous navigation system for the integration of star sensor,infrared horizon sensor,magnetometer,radar altimeter and ultraviolet sensor is developed.The requirements of the integrated navigation system manager make optimum use of the various navigation sensors and allow rapid fault detection,isolation and recovery.The normal full fusion feedback method of federated unscented Kalman filter（UKF） cannot meet the needs of it.So a no-reset feedback federated Kalman filter architecture is developed and used in the autonomous navigation system.The minimal skew sigma points are chosen to improve the calculation speed.Simulation results are presented to demonstrate the advantages of the algorithm.These advantages include improved failure detection and correction,improved computational efficiency,and reliability.Additionally,its＇ accuracy is higher than that of the full fusion feedback method.展开更多
Advanced Receiver Autonomous Integrity Monitoring(ARAIM) is a new technology that will provide worldwide coverage of vertical guidance in aviation navigation. The ARAIM performance and improvement under depleted const...Advanced Receiver Autonomous Integrity Monitoring(ARAIM) is a new technology that will provide worldwide coverage of vertical guidance in aviation navigation. The ARAIM performance and improvement under depleted constellations is a practical problem that needs to be faced and researched further. It is a shortcut that improves the availability in position domain whose key idea is to replace the conventional least squares process with a non-least-squares estimator to lower the integrity risk in exchange for a slight increase in nominal position error. The contributions given in this paper include two parts: First, the impacts of one satellite outage on different constellations are analyzed and compared. The conclusion is that GPS is more sensitive and vulnerable to one satellite outage. Second, a constellation weighted ARAIM(CW-ARAIM)position estimator is proposed. The position solution is replaced by a constellation weighted average solution to eliminate the constellation difference. The new solution will move close to the constellation solutions with respect to the accuracy requirement. The simulation results under baseline GPS and Galileo dual-constellation show that the one GPS satellite outage will knock the availability from 91% to only 50%. The performance remains stable with one Galileo satellite outage. With the assistance of the CW-ARAIM method, the availability can increase from 50% to more than80% under depleted GPS configurations. Even without any satellite outage, the proposed method can effectively improve the availability from 91.29% to 98.75%. The test results under optimistic constellations further verify that a balanced constellation is more important than more satellites on orbit and the superiority of CW-ARAIM method is still effective.展开更多
WC–Co cemented carbides, well-known as the conventional tooling materials, have not been successfully produced by one step additive manufacturing processes such as selective laser melting(SLM) yet. The microstructure...WC–Co cemented carbides, well-known as the conventional tooling materials, have not been successfully produced by one step additive manufacturing processes such as selective laser melting(SLM) yet. The microstructure evolution as well as WC grain growth behavior has rarely been investigated in detail during SLM process. In this study, the WC–Co cemented carbides with different Co contents(12–32 wt%) were prepared by optimized SLM processes for comparative investigation of densification behavior, microstructure characterization and mechanical property. The increase in Co content in feedstock carbide granules can improve the densification behavior during SLM process. The SLM processed WC-12 Co shows larger average WC grain size and higher percentage of coarser WC grains as compared with both WC-20 Co and WC-32 Co. The microstructure characterization, combined with finite element simulation, shows the WC grain growth mechanisms include agglomeration and dissolution-deposition of WC during SLM process and agglomeration of WC is an important mechanism especially for WC–Co cemented carbides with Co content as low as 12 wt%. The comparison between horizontal(perpendicular to the SLM laser beam) and vertical(parallel to the SLM laser beam) cross sections of carbides shows that SLM process introduces a certain degree of microstructure and mechanical behavior anisotropy for WC-12 Co, WC-20 Co, and WC-32 Co.展开更多
Though promoting ferroptosis can reduce cisplatin resistance in tumor cells,ferroptosis and cisplatin resistance in bladder urothelial carcinoma(BUC)following long non-coding RNAs(lncRNAs)is largely unknown.Here,we fo...Though promoting ferroptosis can reduce cisplatin resistance in tumor cells,ferroptosis and cisplatin resistance in bladder urothelial carcinoma(BUC)following long non-coding RNAs(lncRNAs)is largely unknown.Here,we found the highly expressed lncRNA MAF transcription factor G antisense RNA 1(MAFG-AS1)in BUC,and its inhibition increased the sensitivity of BUC cells to cisplatin by promoting ferroptosis.Mechanically,binding to iron chaperone poly(rC)-binding protein 2(PCBP2)facilitated the recruitments of MAFG-AS1 to deubiquitinase ubiquitin carboxyl-terminal hydrolase isozyme L5(UCHL5),thus stabilizing PCBP2 protein itself.Then PCBP2 was confirmed to interact with ferroportin 1(FPN1),an iron export protein,leading to inhibition of ferroptosis.Moreover,the expression of MAFG-AS1 was regulated by the transcriptional factor MAFG.Interestingly,MAFG-AS1 stimulated MAFG transcription by recruiting histone acetyltransferase p300(EP300)to promote the histone 3 at lysine 27(H3K27ac)at genomic locus of MAFG,forming a MAFG-AS1/MAFG positive feedback loop.In patient samples,higher expression of MAFG-AS1 and MAFG in BUC tissues was significantly correlated with T status and N status,such that MAFG-AS1,MAFG,and the combination of the two were independent prognostic indicators and chemotherapy sensitivity predictive biomarkers for BUC patients.These findings suggest that inhibition of MAFG-AS1 and MAFG can increase the sensitivity of BUC cells to cisplatin through promoting ferroptosis,indicating the novel chemotherapy sensitivity biomarkers and therapeutic target for BUC.展开更多
High dynamic conditions impose critical challenges on Global Navigation Satellite System(GNSS)receivers,leading to large tracking errors or even loss of tracking.Current methods that intend to improve receivers’adapt...High dynamic conditions impose critical challenges on Global Navigation Satellite System(GNSS)receivers,leading to large tracking errors or even loss of tracking.Current methods that intend to improve receivers’adaptability for high dynamics require either complicated structures or prior statistical information of noises.This paper proposes a high dynamics algorithm based on steepest ascent method that can circumvent the deficiencies of existing methods.First,the relationship between the error of carrier tracking and the maximum of Fast Fourier Transform(FFT)outputs is established,and a performance function based on the steepest ascent method is designed.It can keep stable in high dynamics.Second,a new carrier-tracking loop is constructed by deploying the performance function.When the variation of GPS receiver acceleration ranges from 10 g to 100 g,compared with the PLL that either loses lock or keeps tracking accuracy less than 33.89 Hz,the experimental results show that the proposed method can not only keep tracking,but also achieve tracking accuracy more than 2.77 Hz.展开更多
The Unmanned Aerial Helicopter(UAH)has attracted increasing attention in the military and civil areas with the unique flight performance.The significant impact on the attitude measurement performance of UAHs by the st...The Unmanned Aerial Helicopter(UAH)has attracted increasing attention in the military and civil areas with the unique flight performance.The significant impact on the attitude measurement performance of UAHs by the strong airflow disturbance is an essential factor threatening flight safety.To improve the attitude measurement performance of UAHs under atmospheric disturbance,an attitude fusion method over the factor graph is applied and provides the plug-and-play capability.Based on the relationship between position,velocity and attitude,a new attitude correction algorithm for the Modified Attitude Factor Graph Fusion(MAFGF)navigation method is designed and constructed through the fused position and velocity information.Finally,results of simulation and experiment are given to show the effectiveness of the proposed method.展开更多
Multipath interference seriously degrades the performance of Global Navigation Satellite System(GNSS)positioning in an urban canyon.Most current multipath mitigation algorithms suffer from heavy computational load or ...Multipath interference seriously degrades the performance of Global Navigation Satellite System(GNSS)positioning in an urban canyon.Most current multipath mitigation algorithms suffer from heavy computational load or need external assistance.We propose a multipath mitigation algorithm based on the steepest descent approach,which has the merits of less computational load and no need for external aid.A new ranging code tracking loop is designed based on the steepest descent method,which can save an early branch or a late branch compared with the narrow-spacing correlation method.The power of the Non-Line-of-Sight(NLOS)signal is weaker than that of the Line-of-Sight(LOS)signal when the LOS signal is not obstructed and with a relatively high Carrier Noise Ratio(CNR).The peak position in the X-axis of the ranging code autocorrelation function does not move with the NLOS interference.Meanwhile,the cost function is designed according to this phenomenon.The results demonstrate that the proposed algorithm outperforms the narrow-spacing correlation and the Multipath Estimated Delay Locked Loop(MEDLL)in terms of the code multipath mitigation and computation time.The Standard Deviation(STD)of the tracking error with the proposed algorithm is less than 0.016 chips.Moreover,the computation time of the proposed algorithm in a software defined receiver is shortened by 24.21%compared with the narrow-spacing correlation.展开更多
Using Chinese General Social Survey(CGSS)in 2005,2008 and 2013,this study investigates health determinants and health inequality in China.The ordinal complementary log-log model is used firstly to examine the impact o...Using Chinese General Social Survey(CGSS)in 2005,2008 and 2013,this study investigates health determinants and health inequality in China.The ordinal complementary log-log model is used firstly to examine the impact of individual and contextual factors on self-rated health status.The study further checks the health inequality among subgroups divided by health determinants considered in the determinant model.We find that there are significant gender,residential,ethnic,socioeconomic,emotional,regional,and periodic differences.Moreover,the health status of sub-groups defined by factors used in this research is affected by health determinants in different ways which indicates the impact of these health determinants on health is moderated by each other.We conclude that while the health status generally varies with individual factors and social contexts,each group characterized by individual and contextual features has its own unique needs to improve and maintain their health status in China.The public policies aiming to increase Chinese health status and reduce health inequality must pay close attention to these needs while equalizing the availability,accessibility,and affordability of health facilities and health care system.展开更多
基金supported in part by the National High Technology Research and Development Program of China (863 Program)(2006AA12A108)CSC International Scholarship (2008104769)
文摘With research on the carrier phase synchronization and symbol synchronization algorithm of demodulation module, a synchronization circuit system is designed for GPS software receiver based on field programmable gate array （FPGA）, and a series of experiment is done on the hardware platform. The result shows the all-digital synchronization and demodulation of GPS intermediate frequency （IF） signal can be realized and applied in embedded real-time GPS software receiver system. It is verified that the decision-directed joint tracking algorithm of carrier phase and symbol timing for received signals from GPS is reasonable. In addition, the loop works steadily and can be used for receiving GPS signals using synchronous demodulation. The synchronization circuit for GPS software receiver designed based on FPGA has the features of low cost, miniaturization, low power and real-time. Surely, it will become one of the development directions for GPS and even GNSS embedded real-time software receiver.
基金supported by the Aviation Science Foundation(20070852009)
文摘An effective autonomous navigation system for the integration of star sensor,infrared horizon sensor,magnetometer,radar altimeter and ultraviolet sensor is developed.The requirements of the integrated navigation system manager make optimum use of the various navigation sensors and allow rapid fault detection,isolation and recovery.The normal full fusion feedback method of federated unscented Kalman filter（UKF） cannot meet the needs of it.So a no-reset feedback federated Kalman filter architecture is developed and used in the autonomous navigation system.The minimal skew sigma points are chosen to improve the calculation speed.Simulation results are presented to demonstrate the advantages of the algorithm.These advantages include improved failure detection and correction,improved computational efficiency,and reliability.Additionally,its＇ accuracy is higher than that of the full fusion feedback method.
基金funded by the National Natural Science Foundation of China (Nos. 61533008, 61374115, 61328301 and 61603181)the Funding of Jiangsu Innovation Program for Graduate Education of China (No. KYLX16_0379)the Open Fund of State Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University of China (No.17P02)
文摘Advanced Receiver Autonomous Integrity Monitoring(ARAIM) is a new technology that will provide worldwide coverage of vertical guidance in aviation navigation. The ARAIM performance and improvement under depleted constellations is a practical problem that needs to be faced and researched further. It is a shortcut that improves the availability in position domain whose key idea is to replace the conventional least squares process with a non-least-squares estimator to lower the integrity risk in exchange for a slight increase in nominal position error. The contributions given in this paper include two parts: First, the impacts of one satellite outage on different constellations are analyzed and compared. The conclusion is that GPS is more sensitive and vulnerable to one satellite outage. Second, a constellation weighted ARAIM(CW-ARAIM)position estimator is proposed. The position solution is replaced by a constellation weighted average solution to eliminate the constellation difference. The new solution will move close to the constellation solutions with respect to the accuracy requirement. The simulation results under baseline GPS and Galileo dual-constellation show that the one GPS satellite outage will knock the availability from 91% to only 50%. The performance remains stable with one Galileo satellite outage. With the assistance of the CW-ARAIM method, the availability can increase from 50% to more than80% under depleted GPS configurations. Even without any satellite outage, the proposed method can effectively improve the availability from 91.29% to 98.75%. The test results under optimistic constellations further verify that a balanced constellation is more important than more satellites on orbit and the superiority of CW-ARAIM method is still effective.
基金financially supported by the Science and Technology Project of Guangdong Province,China(Grant Nos.2017B090911006 and 2017B090913006)the Key Project of Basic Research and Applied Basic Research in Universities of Guangdong Province,China(Grant No.2018KZDXM043)+3 种基金the Jihua Laboratory Project“Additive Manufacturing for Difficulty-to-Machine Materials”(Grant No.X190061UZ190)the Heyuan Science and Technology Project(Grant No.HEKE 000781)the Young Innovative Talents Program of Universities in Guangdong Province(Grant No.2018KQNCX141)the Guangzhou Science and Technology Project(Grant No.202002030259)。
文摘WC–Co cemented carbides, well-known as the conventional tooling materials, have not been successfully produced by one step additive manufacturing processes such as selective laser melting(SLM) yet. The microstructure evolution as well as WC grain growth behavior has rarely been investigated in detail during SLM process. In this study, the WC–Co cemented carbides with different Co contents(12–32 wt%) were prepared by optimized SLM processes for comparative investigation of densification behavior, microstructure characterization and mechanical property. The increase in Co content in feedstock carbide granules can improve the densification behavior during SLM process. The SLM processed WC-12 Co shows larger average WC grain size and higher percentage of coarser WC grains as compared with both WC-20 Co and WC-32 Co. The microstructure characterization, combined with finite element simulation, shows the WC grain growth mechanisms include agglomeration and dissolution-deposition of WC during SLM process and agglomeration of WC is an important mechanism especially for WC–Co cemented carbides with Co content as low as 12 wt%. The comparison between horizontal(perpendicular to the SLM laser beam) and vertical(parallel to the SLM laser beam) cross sections of carbides shows that SLM process introduces a certain degree of microstructure and mechanical behavior anisotropy for WC-12 Co, WC-20 Co, and WC-32 Co.
基金This work was supported by the National Natural Science Foundation of China(81874137)the Outstanding Youth Foundation of Hunan Province(2018JJ1047)+4 种基金the Huxiang Young Talent Project(2016RS3022)the Hunan Province Science and Technology Talent Promotion Project(2019TJ-Q10)the Project of Scientific Research Plan of Health and Family Planning Commission of Hunan Province(c20180476)the Fundamental Research Funds for the Central South University(2018zzts938)the Wisdom Accumulation and Talent Cultivation Project of the Third Xiangya Hosipital of Central South University(ZC060001 and YX202007).
文摘Though promoting ferroptosis can reduce cisplatin resistance in tumor cells,ferroptosis and cisplatin resistance in bladder urothelial carcinoma(BUC)following long non-coding RNAs(lncRNAs)is largely unknown.Here,we found the highly expressed lncRNA MAF transcription factor G antisense RNA 1(MAFG-AS1)in BUC,and its inhibition increased the sensitivity of BUC cells to cisplatin by promoting ferroptosis.Mechanically,binding to iron chaperone poly(rC)-binding protein 2(PCBP2)facilitated the recruitments of MAFG-AS1 to deubiquitinase ubiquitin carboxyl-terminal hydrolase isozyme L5(UCHL5),thus stabilizing PCBP2 protein itself.Then PCBP2 was confirmed to interact with ferroportin 1(FPN1),an iron export protein,leading to inhibition of ferroptosis.Moreover,the expression of MAFG-AS1 was regulated by the transcriptional factor MAFG.Interestingly,MAFG-AS1 stimulated MAFG transcription by recruiting histone acetyltransferase p300(EP300)to promote the histone 3 at lysine 27(H3K27ac)at genomic locus of MAFG,forming a MAFG-AS1/MAFG positive feedback loop.In patient samples,higher expression of MAFG-AS1 and MAFG in BUC tissues was significantly correlated with T status and N status,such that MAFG-AS1,MAFG,and the combination of the two were independent prognostic indicators and chemotherapy sensitivity predictive biomarkers for BUC patients.These findings suggest that inhibition of MAFG-AS1 and MAFG can increase the sensitivity of BUC cells to cisplatin through promoting ferroptosis,indicating the novel chemotherapy sensitivity biomarkers and therapeutic target for BUC.
基金funded by National Natural Science Foundation of China(Nos.61533008,61603181,61673208,61873125)。
文摘High dynamic conditions impose critical challenges on Global Navigation Satellite System(GNSS)receivers,leading to large tracking errors or even loss of tracking.Current methods that intend to improve receivers’adaptability for high dynamics require either complicated structures or prior statistical information of noises.This paper proposes a high dynamics algorithm based on steepest ascent method that can circumvent the deficiencies of existing methods.First,the relationship between the error of carrier tracking and the maximum of Fast Fourier Transform(FFT)outputs is established,and a performance function based on the steepest ascent method is designed.It can keep stable in high dynamics.Second,a new carrier-tracking loop is constructed by deploying the performance function.When the variation of GPS receiver acceleration ranges from 10 g to 100 g,compared with the PLL that either loses lock or keeps tracking accuracy less than 33.89 Hz,the experimental results show that the proposed method can not only keep tracking,but also achieve tracking accuracy more than 2.77 Hz.
基金co-supported by the National Natural Science Foundation of China (Nos. 61533008, 61603181)the Fundamental Research Funds for the Central Universities of China (No. NS2018021)the Priority Academic Program Development of Jiangsu Higher Education Institutions, China
文摘The Unmanned Aerial Helicopter(UAH)has attracted increasing attention in the military and civil areas with the unique flight performance.The significant impact on the attitude measurement performance of UAHs by the strong airflow disturbance is an essential factor threatening flight safety.To improve the attitude measurement performance of UAHs under atmospheric disturbance,an attitude fusion method over the factor graph is applied and provides the plug-and-play capability.Based on the relationship between position,velocity and attitude,a new attitude correction algorithm for the Modified Attitude Factor Graph Fusion(MAFGF)navigation method is designed and constructed through the fused position and velocity information.Finally,results of simulation and experiment are given to show the effectiveness of the proposed method.
基金National Natural Science Foundation of China(NO.61533008,61603181,61673208,61873125).
文摘Multipath interference seriously degrades the performance of Global Navigation Satellite System(GNSS)positioning in an urban canyon.Most current multipath mitigation algorithms suffer from heavy computational load or need external assistance.We propose a multipath mitigation algorithm based on the steepest descent approach,which has the merits of less computational load and no need for external aid.A new ranging code tracking loop is designed based on the steepest descent method,which can save an early branch or a late branch compared with the narrow-spacing correlation method.The power of the Non-Line-of-Sight(NLOS)signal is weaker than that of the Line-of-Sight(LOS)signal when the LOS signal is not obstructed and with a relatively high Carrier Noise Ratio(CNR).The peak position in the X-axis of the ranging code autocorrelation function does not move with the NLOS interference.Meanwhile,the cost function is designed according to this phenomenon.The results demonstrate that the proposed algorithm outperforms the narrow-spacing correlation and the Multipath Estimated Delay Locked Loop(MEDLL)in terms of the code multipath mitigation and computation time.The Standard Deviation(STD)of the tracking error with the proposed algorithm is less than 0.016 chips.Moreover,the computation time of the proposed algorithm in a software defined receiver is shortened by 24.21%compared with the narrow-spacing correlation.
基金Social Sciences and Humanities Research Council(SSHRC)of Canada(Grant no.410-2007-1315).
文摘Using Chinese General Social Survey(CGSS)in 2005,2008 and 2013,this study investigates health determinants and health inequality in China.The ordinal complementary log-log model is used firstly to examine the impact of individual and contextual factors on self-rated health status.The study further checks the health inequality among subgroups divided by health determinants considered in the determinant model.We find that there are significant gender,residential,ethnic,socioeconomic,emotional,regional,and periodic differences.Moreover,the health status of sub-groups defined by factors used in this research is affected by health determinants in different ways which indicates the impact of these health determinants on health is moderated by each other.We conclude that while the health status generally varies with individual factors and social contexts,each group characterized by individual and contextual features has its own unique needs to improve and maintain their health status in China.The public policies aiming to increase Chinese health status and reduce health inequality must pay close attention to these needs while equalizing the availability,accessibility,and affordability of health facilities and health care system.
