At present, the main problem faced by ground-based augment system （GBAS） is that though carder smoothing filter and local differential global positioning system （LDGPS） improve the accuracy of the pseudorange by r...At present, the main problem faced by ground-based augment system （GBAS） is that though carder smoothing filter and local differential global positioning system （LDGPS） improve the accuracy of the pseudorange by reducing the noise in it and eliminating almost all the common errors between the user and the reference station, they also cause extra errors on account of the effects of the ionosphere temporal and spatial gradients. Based on the analysis of these errors as well as the smoothing noise, this article suggests a new algorithm to design the optimal Hatch filter, whose smoothing window width varies real-time with the satellite elevation, ionosphere variation, and distance from the user to the reference station. By conducting the positioning process in the GBAS emulation platform for several hours and after its comparison with the performances of traditional Hatch filters, it is found that the errors in the differential correction become smaller and the positioning accuracy gets heightened with this new method.展开更多
Background HATCH score is an established predictor of progression from paroxysmal to persistent atrial fibrillation （AF）. The purpose of this study was to determine if HATCH score could predict recurrence after cath...Background HATCH score is an established predictor of progression from paroxysmal to persistent atrial fibrillation （AF）. The purpose of this study was to determine if HATCH score could predict recurrence after catheter ablation of AF. Methods The data of 488 consecutive paroxysmal AF patients who underwent an index circumferential pulmonary veins （PV） ablation were retrospectively analyzed. Of these patients, 250 （51.2%） patients had HATCH score=0, 185 （37.9%） patients had HATCH score=l, and 53 （10.9%） patients had HATCH score 〉2 （28 patients had HATCH score=2, 23 patients had HATCH score=3, and 2 patients had HATCH score=4）. Results The patients with HATCH score 〉2 had significantly larger left atrium size, the largest left ventricular end systolic diameter, and the lowest ejection fraction. After a mean follow-up of （823＋532） days, the recurrence rates were 36.4%, 37.8% and 28.3% from the HATCH score=0, HATCH score=l to HATCH score 〉2 categories （P=0.498）. Univariate analysis revealed that left atrium size, body mass index, and failure of PV isolation were predictors of AF recurrence. After adjustment for body mass index, left atrial size and PV isolation, the HATCH score was not an independent predictor of recurrence （HR=0.92, 95% confidence interval=0.76-1.12, P=0.406） in multivariate analysis. Conclusion HATCH score has no value in prediction of AF recurrence after catheter ablation.展开更多
It has been proven that carrier smoothing and differential global positioning system （DGPS） are effective to improve the accuracy of pseudorange by reducing the noise in it and eliminating almost all the common mode...It has been proven that carrier smoothing and differential global positioning system （DGPS） are effective to improve the accuracy of pseudorange by reducing the noise in it and eliminating almost all the common mode errors between the ground station and user. However, another issue coming with local area augmentation system （LAAS） is how to find an adaptive smoothing window width to minimize the error on account of ionosphere delay and multipath. Based on the errors analysis in carrier smoothing process, a novel algorithm is formulated to design adaptive Hatch filter whose smoothing window width flexibly varies with the characteristic of ionosphere delay and multipath in the differential carrier smoothing process. By conducting the simulation in LAAS and after compared with traditional Hatch filers, it reveals that not only the accuracy of differential correction, but also the accuracy and the robustness of positioning results are significantly improved by using the designed adaptive Hatch filter.展开更多
This article introduces the working principles of a spacecraft hatch including its operating process and moving trajectory. On this basis, an operating mechanism is designed to execute automatic open and close action ...This article introduces the working principles of a spacecraft hatch including its operating process and moving trajectory. On this basis, an operating mechanism is designed to execute automatic open and close action of the hatch and measure the operating torques. Analysis on the mechanism＇s configuration and topological structure of each phase of movement proves that it is a typical variable freedom mechanism. The mechanism manipulates the hatch in accordance with the moving trajectory requirements through configuration transformation. Kinematic analysis and simulation of some typical configurations show that the velocity differences among mechanism components themselves and the components and their abutting components could exert influences on its working stability during configuration transformation. To solve the problem, stability conditions of configuration transformation are proposed. Appropriate control models are established for the output velocity curves of the driving servo motor and solved based on the stability conditions and rules of movement. Results from another simulation demonstrate that the proposed control models ensure smooth configuration transform and stable operation.展开更多
基金National Natural Science Foundation of China (60672181)National High-tech Research and Development Program (2006AA12A101)
文摘At present, the main problem faced by ground-based augment system （GBAS） is that though carder smoothing filter and local differential global positioning system （LDGPS） improve the accuracy of the pseudorange by reducing the noise in it and eliminating almost all the common errors between the user and the reference station, they also cause extra errors on account of the effects of the ionosphere temporal and spatial gradients. Based on the analysis of these errors as well as the smoothing noise, this article suggests a new algorithm to design the optimal Hatch filter, whose smoothing window width varies real-time with the satellite elevation, ionosphere variation, and distance from the user to the reference station. By conducting the positioning process in the GBAS emulation platform for several hours and after its comparison with the performances of traditional Hatch filters, it is found that the errors in the differential correction become smaller and the positioning accuracy gets heightened with this new method.
基金This work was supported by the National Science Foundation Council of China （No. 30900628, 81070147）, Beijing Natural Science Foundation （No. 7102048） and Beijing Nova Program （No. 2009B32） and Training Program for Excellent Talent of Beijing （No. 2010D003034000025）.
文摘Background HATCH score is an established predictor of progression from paroxysmal to persistent atrial fibrillation （AF）. The purpose of this study was to determine if HATCH score could predict recurrence after catheter ablation of AF. Methods The data of 488 consecutive paroxysmal AF patients who underwent an index circumferential pulmonary veins （PV） ablation were retrospectively analyzed. Of these patients, 250 （51.2%） patients had HATCH score=0, 185 （37.9%） patients had HATCH score=l, and 53 （10.9%） patients had HATCH score 〉2 （28 patients had HATCH score=2, 23 patients had HATCH score=3, and 2 patients had HATCH score=4）. Results The patients with HATCH score 〉2 had significantly larger left atrium size, the largest left ventricular end systolic diameter, and the lowest ejection fraction. After a mean follow-up of （823＋532） days, the recurrence rates were 36.4%, 37.8% and 28.3% from the HATCH score=0, HATCH score=l to HATCH score 〉2 categories （P=0.498）. Univariate analysis revealed that left atrium size, body mass index, and failure of PV isolation were predictors of AF recurrence. After adjustment for body mass index, left atrial size and PV isolation, the HATCH score was not an independent predictor of recurrence （HR=0.92, 95% confidence interval=0.76-1.12, P=0.406） in multivariate analysis. Conclusion HATCH score has no value in prediction of AF recurrence after catheter ablation.
基金supported by the National Natural Science Foundationof China (60974104)the National Defense Technical Foundation of Shipbuilding Industry (08J3.8.8)
文摘It has been proven that carrier smoothing and differential global positioning system （DGPS） are effective to improve the accuracy of pseudorange by reducing the noise in it and eliminating almost all the common mode errors between the ground station and user. However, another issue coming with local area augmentation system （LAAS） is how to find an adaptive smoothing window width to minimize the error on account of ionosphere delay and multipath. Based on the errors analysis in carrier smoothing process, a novel algorithm is formulated to design adaptive Hatch filter whose smoothing window width flexibly varies with the characteristic of ionosphere delay and multipath in the differential carrier smoothing process. By conducting the simulation in LAAS and after compared with traditional Hatch filers, it reveals that not only the accuracy of differential correction, but also the accuracy and the robustness of positioning results are significantly improved by using the designed adaptive Hatch filter.
基金National Natural Science Foundation of China (50675006,50720135503)
文摘This article introduces the working principles of a spacecraft hatch including its operating process and moving trajectory. On this basis, an operating mechanism is designed to execute automatic open and close action of the hatch and measure the operating torques. Analysis on the mechanism＇s configuration and topological structure of each phase of movement proves that it is a typical variable freedom mechanism. The mechanism manipulates the hatch in accordance with the moving trajectory requirements through configuration transformation. Kinematic analysis and simulation of some typical configurations show that the velocity differences among mechanism components themselves and the components and their abutting components could exert influences on its working stability during configuration transformation. To solve the problem, stability conditions of configuration transformation are proposed. Appropriate control models are established for the output velocity curves of the driving servo motor and solved based on the stability conditions and rules of movement. Results from another simulation demonstrate that the proposed control models ensure smooth configuration transform and stable operation.
