Design and analysis of a direct transfer trajectory from a near rectilinear halo orbit to a low lunar orbit

2020 ◽  
Author(s):  
Lin Lu ◽  
Haiyang Li ◽  
Wanmeng Zhou ◽  
Jianghui Liu
Keyword(s):  
Halo Orbit ◽  
Lunar Orbit ◽  
Direct Transfer ◽  
Transfer Trajectory

Method for calculating the perturbed trajectoryof a two-impulse flight between the halo orbit in the vicinity of the L2 point of the Sun — Earth systemand the near-lunar orbit

2020 ◽  
Author(s):  
Zhou Rui
Keyword(s):  
Boundary Value Problem ◽  
Boundary Value ◽  
Continuation Method ◽  
Initial Approximation ◽  
Halo Orbit ◽  
Lunar Orbit ◽  
The Sun ◽  
Zonal Harmonic ◽  
The Earth ◽  
Parameter Continuation

The paper introduces a new method for solving the problem of calculating the perturbed trajectory of a two-impulse flight between a near-lunar orbit and a halo orbit in the vicinity of the L2 point of the Sun — Earth system. Unlike traditional numerical methods, this method has better convergence. Accelerations from the gravitational forces of the Earth, the Moon and the Sun as point masses and acceleration from the second zonal harmonic of the geopotential are taken into account at all sections of the trajectory. The calculation of the flight path is reduced to solving a two-point boundary value problem for a system of ordinary differential equations. The developed method is based on the parameter continuation method and does not require the choice of an initial approximation for solving the boundary value problem. The last section of the paper provides examples and results of the analysis based on this method.

scholarly journals Design and Analysis of Korean Lunar Orbiter Mission using Direct Transfer Trajectory

2013 ◽  
Vol 41 (12) ◽  
pp. 950-958 ◽  
Author(s):  
Su-Jin Choi ◽  
Young-Joo Song ◽  
Jonghee Bae ◽  
Eunhyeuk Kim ◽  
Gwanghyeok Ju
Keyword(s):  
Direct Transfer ◽  
Lunar Orbiter ◽  
Transfer Trajectory ◽  
Orbiter Mission

Parallelly generating halo orbit and its transfer trajectory in the full ephemeris model

2019 ◽  
Vol 364 (1) ◽  
Author(s):  
Tao Wu ◽  
Xiao Pan ◽  
Ming Xu ◽  
Qingyu Qu ◽  
Qianhui Xia ◽  
...  
Keyword(s):  
Halo Orbit ◽  
Transfer Trajectory ◽  
Full Ephemeris Model

scholarly journals Diagnostic value of transcranial ultrasonography for selecting subjects with large vessel occlusion: a systematic review

2019 ◽  
Vol 11 (1) ◽  
Author(s):  
Daria Antipova ◽  
Leila Eadie ◽  
Ashish Stephen Macaden ◽  
Philip Wilson
Keyword(s):  
Systematic Review ◽  
Diagnostic Accuracy ◽  
Acute Stroke ◽  
Clinical Assessment ◽  
Assessment Tools ◽  
Large Vessel ◽  
Cochrane Library ◽  
Direct Transfer ◽  
Large Vessel Occlusion ◽  
Vessel Occlusion

Abstract Introduction A number of pre-hospital clinical assessment tools have been developed to triage subjects with acute stroke due to large vessel occlusion (LVO) to a specialised endovascular centre, but their false negative rates remain high leading to inappropriate and costly emergency transfers. Transcranial ultrasonography may represent a valuable pre-hospital tool for selecting patients with LVO who could benefit from rapid transfer to a dedicated centre. Methods Diagnostic accuracy of transcranial ultrasonography in acute stroke was subjected to systematic review. Medline, Embase, PubMed, Scopus, and The Cochrane Library were searched. Published articles reporting diagnostic accuracy of transcranial ultrasonography in comparison to a reference imaging method were selected. Studies reporting estimates of diagnostic accuracy were included in the meta-analysis. Results Twenty-seven published articles were selected for the systematic review. Transcranial Doppler findings, such as absent or diminished blood flow signal in a major cerebral artery and asymmetry index ≥ 21% were shown to be suggestive of LVO. It demonstrated sensitivity ranging from 68 to 100% and specificity of 78–99% for detecting acute steno-occlusive lesions. Area under the receiver operating characteristics curve was 0.91. Transcranial ultrasonography can also detect haemorrhagic foci, however, its application is largely restricted by lesion location. Conclusions Transcranial ultrasonography might potentially be used for the selection of subjects with acute LVO, to help streamline patient care and allow direct transfer to specialised endovascular centres. It can also assist in detecting haemorrhagic lesions in some cases, however, its applicability here is largely restricted. Additional research should optimize the scanning technique. Further work is required to demonstrate whether this diagnostic approach, possibly combined with clinical assessment, could be used at the pre-hospital stage to justify direct transfer to a regional thrombectomy centre in suitable cases.

scholarly journals Identification of the ‘Streptococcus anginosus group’ by matrix-assisted laser desorption ionization – time-of-flight mass spectrometry

2014 ◽  
Vol 63 (9) ◽  
pp. 1143-1147 ◽  
Author(s):  
Katherine Woods ◽  
David Beighton ◽  
John L. Klein
Keyword(s):  
Species Level ◽  
Direct Transfer ◽  
Laser Desorption Ionization ◽  
Ionization Time ◽  
Maldi Tof Ms ◽  
Streptococcus Anginosus ◽  
Maldi Tof ◽  
Flight Mass Spectrometry ◽  
Transfer Method ◽  
Tof Ms

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) provides rapid, accurate and cost-effective identification of a range of bacteria and is rapidly changing the face of routine diagnostic microbiology. However, certain groups of bacteria, for example streptococci (in particular viridans or non-haemolytic streptococci), are less reliably identified by this method. We studied the performance of MALDI-TOF MS for identification of the ‘Streptococcus anginosus group’ (SAG) to species level. In total, 116 stored bacteraemia isolates identified by conventional methods as belonging to the SAG were analysed by MALDI-TOF MS. Partial 16S rRNA gene sequencing, supplemented with sialidase activity testing, was performed on all isolates to provide ‘gold standard’ identification against which to compare MALDI-TOF MS performance. Overall, 100 % of isolates were correctly identified to the genus level and 93.1 % to the species level by MALDI-TOF MS. However, only 77.6 % were correctly identified to the genus level and 59.5 % to the species level by a MALDI-TOF MS direct transfer method alone. Use of a rapid in situ extraction method significantly improved identification rates when compared with the direct transfer method (P<0.001). We recommend routine use of this method to reduce the number of time-consuming full extractions required for identification of this group of bacteria by MALDI-TOF MS in the routine diagnostic laboratory. Only 22 % (1/9) of Streptococcus intermedius isolates were reliably identified by MALDI-TOF MS to the species level, even after full extraction. MALDI-TOF MS reliably identifies S. anginosus and Streptococcus constellatus to the species level but does not reliably identify S. intermedius.

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