This paper presents the findings of a study on the helpful approaches to write essentially defectfree code among senior students majored in software engineering.In the first phase of the lab study,we prepared 9 coding...This paper presents the findings of a study on the helpful approaches to write essentially defectfree code among senior students majored in software engineering.In the first phase of the lab study,we prepared 9 coding projects for students which will help them to find their own best practices or principles to write essentially defect-free code before unit test.These students were interviewed regarding the use of their own best practices,their principles,and problems arising from the coding projects.We present qualitative and quantitative findings as well as our plans for second study phase including an industry field study.展开更多
Block-based visual programming languages enable programmers to focus on programming thinking without excessive coding or syntax attention.We find that projects written in visual programming languages like Scratch also...Block-based visual programming languages enable programmers to focus on programming thinking without excessive coding or syntax attention.We find that projects written in visual programming languages like Scratch also have bugs and code smells that cannot be avoided automatically.Existing studies analyze these problems by converting code into Abstract Syntax Trees(ASTs)before analysis.This process is time-consuming and analyzing the AST directly can be complex.In this paper,we propose a novel code image-based static analysis approach for visual programming languages,which mines code patterns in images to pre-determine whether there are problems in projects without parsing them first.We train a code image object detection network to judge whether the input projects are likely to have bugs or smells.Further analysis is performed only on potentially problematic projects.Based on the proposals of the detection network,we analyze the key areas of the AST and identify the specific code problems.Experiments show that compared with others,our method can quickly determine code problems and accurately locate them.For the code image detection task,the improved model can achieve higher mean average precision(MAP)faster in the training phase,while the model is smaller and faster in inference.展开更多
Global navigation satellite system(GNSS) comes with potential unavoidable application risks such as the sudden distortion or failure of navigation signals because its satellites are generally operated until failure. I...Global navigation satellite system(GNSS) comes with potential unavoidable application risks such as the sudden distortion or failure of navigation signals because its satellites are generally operated until failure. In order to solve the problems associated with these risks, receiver autonomous integrity monitoring(RAIM) and ground-based signal quality monitoring stations are widely used. Although these technologies can protect the user from the risks, they are expensive and have limited region coverage. Autonomous monitoring of satellite signal quality is an effective method to eliminate these shortcomings of the RAIM and ground-based signal quality monitoring stations; thus, a new navigation signal quality monitoring receiver which can be equipped on the satellite platform of GNSS is proposed in this paper. Because this satellite-equipped receiver is tightly coupled with navigation payload, the system architecture and its preliminary design procedure are first introduced. In theory, code-tracking loop is able to provide accurate time delay estimation of received signals. However, because of the nonlinear characteristics of the navigation payload, the traditional code-tracking loop introduces errors. To eliminate these errors, the dummy massive parallel correlators(DMPC) technique is proposed. This technique can reconstruct the cross correlation function of a navigation signal with a high code phase resolution. Combining the DMPC and direct radio frequency(RF) sampling technology, the satellite-equipped receiver can calibrate the differential code bias(DCB) accurately. In the meantime, the abnormities and failures of navigation signal can also be monitored. Finally, the accuracy of DCB calibration and the performance of fault monitoring have been verified by practical test data and numerical simulation data, respectively. The results show that the accuracy of DCB calibration is less than 0.1 ns and the novel satellite-equipped receiver can monitor the signal quality effectively.展开更多
文摘This paper presents the findings of a study on the helpful approaches to write essentially defectfree code among senior students majored in software engineering.In the first phase of the lab study,we prepared 9 coding projects for students which will help them to find their own best practices or principles to write essentially defect-free code before unit test.These students were interviewed regarding the use of their own best practices,their principles,and problems arising from the coding projects.We present qualitative and quantitative findings as well as our plans for second study phase including an industry field study.
基金supported by the National Natural Science Foundation of China(Nos.62272052 and 62172051).
文摘Block-based visual programming languages enable programmers to focus on programming thinking without excessive coding or syntax attention.We find that projects written in visual programming languages like Scratch also have bugs and code smells that cannot be avoided automatically.Existing studies analyze these problems by converting code into Abstract Syntax Trees(ASTs)before analysis.This process is time-consuming and analyzing the AST directly can be complex.In this paper,we propose a novel code image-based static analysis approach for visual programming languages,which mines code patterns in images to pre-determine whether there are problems in projects without parsing them first.We train a code image object detection network to judge whether the input projects are likely to have bugs or smells.Further analysis is performed only on potentially problematic projects.Based on the proposals of the detection network,we analyze the key areas of the AST and identify the specific code problems.Experiments show that compared with others,our method can quickly determine code problems and accurately locate them.For the code image detection task,the improved model can achieve higher mean average precision(MAP)faster in the training phase,while the model is smaller and faster in inference.
基金supported by the National Basic Research Program of China(“973”Project)(Grant No.6132XX)the National Hi-Tech Research and Development Program of China(“863”Project)(Grant No.2015AA7054032)the National Natural Science Foundation of China(Grant No.60901017)
文摘Global navigation satellite system(GNSS) comes with potential unavoidable application risks such as the sudden distortion or failure of navigation signals because its satellites are generally operated until failure. In order to solve the problems associated with these risks, receiver autonomous integrity monitoring(RAIM) and ground-based signal quality monitoring stations are widely used. Although these technologies can protect the user from the risks, they are expensive and have limited region coverage. Autonomous monitoring of satellite signal quality is an effective method to eliminate these shortcomings of the RAIM and ground-based signal quality monitoring stations; thus, a new navigation signal quality monitoring receiver which can be equipped on the satellite platform of GNSS is proposed in this paper. Because this satellite-equipped receiver is tightly coupled with navigation payload, the system architecture and its preliminary design procedure are first introduced. In theory, code-tracking loop is able to provide accurate time delay estimation of received signals. However, because of the nonlinear characteristics of the navigation payload, the traditional code-tracking loop introduces errors. To eliminate these errors, the dummy massive parallel correlators(DMPC) technique is proposed. This technique can reconstruct the cross correlation function of a navigation signal with a high code phase resolution. Combining the DMPC and direct radio frequency(RF) sampling technology, the satellite-equipped receiver can calibrate the differential code bias(DCB) accurately. In the meantime, the abnormities and failures of navigation signal can also be monitored. Finally, the accuracy of DCB calibration and the performance of fault monitoring have been verified by practical test data and numerical simulation data, respectively. The results show that the accuracy of DCB calibration is less than 0.1 ns and the novel satellite-equipped receiver can monitor the signal quality effectively.
