A deformation criterion of pressurized non-circular cross-section cabin and its effects on cruise performance of BWB civil aircraft

Blended-Wing-Body(BWB)aircraft is promoted as one of the most possible layouts to achieve more sustainable civil aviation.Due to the non-circular cross-section of the center-body,a bulge deformation forms over the upper surface of the body under the coupled loads of the internal pressurization of the cabin and the aerodynamic bending moments of the wing,which reduces the lift-to-drag ratio of BWB aircraft.Under a limited deformation,the relationship between the aerodynamic performance and the structural weight needs to be studied.In this work,the effects of stiffness constraints on the center-body deformation,structural weight of the airframe and aerodynamic performance were investigated by using an analytical model of the Pultruded Rod Stitched Efficient Unitized Structure(PRSEUS)for the airframe and the computational fluid dynamics method,respectively.The results show that as the stiffness constraint increases,the spacings between the rod stringers and the frame stiffeners decrease,and the structural weight increases inversely.A 5.2% reduction of the lift-to-drag ratio is encountered at cruise for a medium deformation design of 42.8 mm/m.A higher aerodynamic penalty is suffered when the stiffness constraint is further released.The final deformation criterion is different when the weight vector of the aerodynamic performance and structural weight is different.

西藏地区糖尿病视网膜病变患病率及危险因素的分析

目的了解西藏地区糖尿病视网膜病变(DR)患病率及相关危险因素。方法选取2017年12月至2018年12月到西藏自治区人民政府驻成都办事处医院内分泌科就诊的来自西藏地区的糖尿病患者239例为观察对象,按民族将患者分为藏族患者和汉族患者。采用免散瞳眼底照相机照片,根据视网膜病变严重程度的分期标准来评估DR病情。结果西藏地区DR患病率为18.0%,其中,藏族患者DR患病率为17.5%,汉族患者DR患病率为19.2%,差异无统计学意义(χ^(2)=0.10,P=0.754)。通过logistic回归分析显示,西藏地区DR患者的危险因素包括糖尿病病程(OR=1.14,95%CI:1.05~1.24,P<0.05)、胰岛素治疗(OR=2.74,95%CI:1.09~6.89,P<0.05)、空腹血糖(OR=1.37,95%CI:1.07~1.75,P<0.05)、高血压(OR=1.98,95%CI:1.02~3.86,P<0.05),其中糖尿病病程、空腹血糖是DR患者的独立危险因素。然而,西藏地区糖尿病患者糖化血红蛋白(HBA1c)虽升高,但并不能预测DR的发生风险(OR=1.01,95%CI:0.82~1.25,P>0.05)。结论高血糖是西藏地区糖尿病患者发生DR的重要危险因素,然而,HBA1c水平并不能作为预测西藏高原地区DR发生风险的血糖评估指标。该研究填补了西藏地区DR患病率及民族差异的研究领域空白,为高原DR的防治提供科学依据。