This paper presents observations on the WAAS L1 and L5 signals quality and their impact on the robustness of the navigation solution by quantifying the contributions of each broadcasted differential correction. This w...This paper presents observations on the WAAS L1 and L5 signals quality and their impact on the robustness of the navigation solution by quantifying the contributions of each broadcasted differential correction. This work is undertaken with the intent of defining performance benefits of L5 by dual frequency WAAS users and is to provide useful material for Minimum Operational Performance Standard (MOPS) development. In this perspective, a study of the WAAS signal characteristics is first carried out. The information gathered is then used to compare various GPS solutions in terms of frequency diversity, satellite diversity, pseudorange noise and different signal corrections and their impacts. These solutions are compared against a reference standalone GPS solution. All statistics are computed with respect to a post-processed Novatel Waypoint Real-Time Kinematics (RTK) GPS L1/L2 semi-codeless static solution, considered as the reference. A discussion on some simplifications with respect to specifications (i.e. MOPS) that could be considered by receiver manufacturers closes the paper. It is confirmed that the current WAAS navigation message definition is the same on both the L1 and L5 frequencies, the latter further being Manchester coded, thus avoiding data ambiguity. The +5 dB SNR on L5 has minor impacts in terms of reliability and continuous availability in the presented scenarios, but would become especially beneficial in hostile environments, despite a greater number of pulsed interferers. Another demonstration is that the WAAS message varies slightly from one WAAS satellite to another, even if corrections are generated centrally. Finally, it is observed that WAAS and GPS signals pseudorange noise are comparable on a “per frequency” basis.展开更多
Evolutionary algorithms have been shown to be very successful in solving multi-objective optimization problems(MOPs).However,their performance often deteriorates when solving MOPs with irregular Pareto fronts.To remed...Evolutionary algorithms have been shown to be very successful in solving multi-objective optimization problems(MOPs).However,their performance often deteriorates when solving MOPs with irregular Pareto fronts.To remedy this issue,a large body of research has been performed in recent years and many new algorithms have been proposed.This paper provides a comprehensive survey of the research on MOPs with irregular Pareto fronts.We start with a brief introduction to the basic concepts,followed by a summary of the benchmark test problems with irregular problems,an analysis of the causes of the irregularity,and real-world optimization problems with irregular Pareto fronts.Then,a taxonomy of the existing methodologies for handling irregular problems is given and representative algorithms are reviewed with a discussion of their strengths and weaknesses.Finally,open challenges are pointed out and a few promising future directions are suggested.展开更多
Eliminating the nonselective permeation path inside the mixed-matrix membranes(MMMs)is critical for fabrication of gas separation membranes.We demonstrate that by utilizing the phase separation of block copolymers,we ...Eliminating the nonselective permeation path inside the mixed-matrix membranes(MMMs)is critical for fabrication of gas separation membranes.We demonstrate that by utilizing the phase separation of block copolymers,we are able to introduce metal-organic polyhedrons(MOPs)with precise pore sizes into a polymer matrix and form an ordered layered structure.We also prove that,by arranging MOP cages into a continuous nanosheet-like layer structure,we are able to generate repeated MOP-effective pathways and deplete the MOP-free permeation pathways,thus enhancing the gas-separation efficiency of MMMs.展开更多
文摘This paper presents observations on the WAAS L1 and L5 signals quality and their impact on the robustness of the navigation solution by quantifying the contributions of each broadcasted differential correction. This work is undertaken with the intent of defining performance benefits of L5 by dual frequency WAAS users and is to provide useful material for Minimum Operational Performance Standard (MOPS) development. In this perspective, a study of the WAAS signal characteristics is first carried out. The information gathered is then used to compare various GPS solutions in terms of frequency diversity, satellite diversity, pseudorange noise and different signal corrections and their impacts. These solutions are compared against a reference standalone GPS solution. All statistics are computed with respect to a post-processed Novatel Waypoint Real-Time Kinematics (RTK) GPS L1/L2 semi-codeless static solution, considered as the reference. A discussion on some simplifications with respect to specifications (i.e. MOPS) that could be considered by receiver manufacturers closes the paper. It is confirmed that the current WAAS navigation message definition is the same on both the L1 and L5 frequencies, the latter further being Manchester coded, thus avoiding data ambiguity. The +5 dB SNR on L5 has minor impacts in terms of reliability and continuous availability in the presented scenarios, but would become especially beneficial in hostile environments, despite a greater number of pulsed interferers. Another demonstration is that the WAAS message varies slightly from one WAAS satellite to another, even if corrections are generated centrally. Finally, it is observed that WAAS and GPS signals pseudorange noise are comparable on a “per frequency” basis.
基金supported in part by the National Natural Science Foundation of China(61806051,61903078)Natural Science Foundation of Shanghai(20ZR1400400)+2 种基金Agricultural Project of the Shanghai Committee of Science and Technology(16391902800)the Fundamental Research Funds for the Central Universities(2232020D-48)the Project of the Humanities and Social Sciences on Young Fund of the Ministry of Education in China(Research on swarm intelligence collaborative robust optimization scheduling for high-dimensional dynamic decisionmaking system(20YJCZH052))。
文摘Evolutionary algorithms have been shown to be very successful in solving multi-objective optimization problems(MOPs).However,their performance often deteriorates when solving MOPs with irregular Pareto fronts.To remedy this issue,a large body of research has been performed in recent years and many new algorithms have been proposed.This paper provides a comprehensive survey of the research on MOPs with irregular Pareto fronts.We start with a brief introduction to the basic concepts,followed by a summary of the benchmark test problems with irregular problems,an analysis of the causes of the irregularity,and real-world optimization problems with irregular Pareto fronts.Then,a taxonomy of the existing methodologies for handling irregular problems is given and representative algorithms are reviewed with a discussion of their strengths and weaknesses.Finally,open challenges are pointed out and a few promising future directions are suggested.
基金supported by Guangdong Natural Science Foundation(No.2018B030306039)the Recruitment Program of Guangdong(No.2016ZT06C322)and the 111 Project(No.B18023).
文摘Eliminating the nonselective permeation path inside the mixed-matrix membranes(MMMs)is critical for fabrication of gas separation membranes.We demonstrate that by utilizing the phase separation of block copolymers,we are able to introduce metal-organic polyhedrons(MOPs)with precise pore sizes into a polymer matrix and form an ordered layered structure.We also prove that,by arranging MOP cages into a continuous nanosheet-like layer structure,we are able to generate repeated MOP-effective pathways and deplete the MOP-free permeation pathways,thus enhancing the gas-separation efficiency of MMMs.
