ABSTRACT
Considering that it satisfies high strength and stiffness at a low weight, the grid structure is the ideal option for meeting the requirements for developing the wall panel structure for the satellite. The most attractive grid structures for the satellite wall panel industry are isogrid and honeycomb structures. The first part of this work involves studying the mechanical and dynamic performance of five designs for the satellite wall panel made of 7075-T0 Al-alloy. These designs include two isogrid structures with different rib widths, two honeycomb structures with different cell wall thicknesses, and a solid structure for comparison. The performance of these designs was evaluated through compression, bending, and vibration testing using both finite element analysis (FEA) with the Ansys workbench and experimental testing. The FEA results are consistent with the experimental ones. The results show that the isogrid structure with a lower rib thickness of 2 mm is the best candidate for manufacturing the satellite wall panel, as this design reveals the best mechanical and dynamic performance. The second part of this work involves studying the influence of the length of the sides of the best isogrid structure in the range of 12 mm-24 mm on its mechanical and dynamic performance to achieve the lowest possible mass while maintaining the structure's integrity. Then, a modified design of skinned wall panels was introduced and dynamically tested using FEA. Finally, a CAD model of a hexagonal satellite prototype using the best-attained design of the wall panel, i.e., the isogrid structure with a 2 mm rib width and 24 mm-long sides, was built and dynamically tested to ensure its safe design against vibration. Then, the satellite prototype was manufactured, assembled, and successfully assessed.
ABSTRACT
BACKGROUND: Clinical Risk Index for Babies scoring system (CRIB II) score is a recently developed tool to predict initial risk of mortality amongst low birth weight babies, the utility of which is scarce in many developing countries. OBJECTIVE: To assess the efficiency of CRIB II score as a tool to predict the risk for neonatal mortality among the LBW babies admitted to neonatal intensive care unit (NICU) at a tertiary care facility Kasr El-Aini paediatric hospital, Cairo, Egypt. MATERIALS AND METHODS: Prospective cohort study design where 113 neonates, admitted during the first 24 hours to the NICU of Kasr El-Aini Hospital, from November 2013 till May 2014 were included. On admission, history taking, neonatal examination, arterial blood gas analysis and variables of CRIB II score were done. Subjects were followed up from admission till discharge or death. RESULTS: Male to female ratio was 1.1:1. Gestational age ranged from 25-32 weeks, the birth weight ranged from 700-1500 gm with mean of 1134.5 (± 202). CRIB II score ranged from 1-19 with a mean of 9.9 (± 4.0). The total mortality in the included cohort was 34.5% (31/113). Significant positive correlations were found between gestational age, birth weight, temperature, excess base, CRIB II score and the occurrence of mortality and with progressive increase in mortality with increasing CRIB II score (p=0.001). CRIB II score ≥ 11, gestational age ≤ 28 and birth weight ≤ 1100 were all found to be significantly associated with neonatal mortality. Area under ROC curve for CRIB II, gestational age and birth weight were found to be (0.968, 0.900 and 0.834) respectively. CRIB II score with cutoff point of ≥ 11 was the most sensitive (94.9%) with the predictive value (74.0%) and specificity (82.4%) compared to birth weight and gestational age. CRIB II score showed good calibration to predict neonatal mortality as demonstrated with Hosmer-lemeshow goodness of fit test (p= 0.952). CONCLUSION: CRIB II score is a valid tool of initial risk assessment in LBW, predicting outcome more accurately than birth weight or gestational age alone. It is easily applicable and should replace the traditional models as predictor of neonatal outcome.