Touchdown dynamic modeling and simulation of lunar lander
In this paper, the key influences of lunar lander landing model are illuminated systematic. Then the touchdown dynamic model of lunar module is built. And the simulation model for lunar landing described on ADAMS is discussed. As an example, one kind of lunar module model with four cantilever truss style landing gear is built by ADAMS and the simulations are focused on the influences on landing by the characteristics of buffers in primary and secondary struts of the landing gear. The conclusions can be used for the design of lunar lander.
Modeling and Simulation of Landing Leg for the Lunar Landing Gear System
The mathematical model of landing dynamics was presented.Based on analysis of aluminum honeycomb characteristics,an Al-honeycomb shock absorber model was derived.The model was utilized in one-leg impacting simulation of the landing gear.Analysis results show nice agreement with test data in these aspects: stroke displacement,energy absorption,acceleration response and its peak value.It is referable to modeling of shock absorber with Al-honeycomb for investigation on landing dynamics of landing gear system.
Access to antenatal care and children’s cognitive development: a comparative analysis in Ethiopia, Peru, Vietnam and India
ObjectivesEarly life interventions are considered essential for reducing the burden of health inequalities over the life course. This paper tests this issue empirically focusing on whether access to antenatal care can later reduce children’s health and educational inequalities.MethodsData came from the Young Lives Project for Ethiopia, Peru, Vietnam, and the State of Andhra Pradesh in India. We selected children born in early 2001/2002 and who were followed longitudinally in 2006/2007. We used multilevel mixed effects linear regression models to estimate the parameters of interest.ResultsWe found a positive and significant relationship between mothers’ access to antenatal care and their children’s cognitive development in all countries. In addition, we found a positive and significant relationship between antenatal care and children’s cognitive development for stunted children but only in Peru and Vietnam.ConclusionsWe conclude that (1) antenatal care has the potential to change the negative consequences of early nutritional deficiencies on later cognitive development in Peru and Vietnam; (2) differentials in the quality of antenatal care services could explain the cross-country differentials in the role of early life interventions found here.