QCD-scale modified-gravity universe

A possible gluon-condensate-induced modified-gravity model with f(R) ∝ ∣R∣^1/2 has been suggested previously. Here, a simplified version is presented using the constant flat-spacetime equilibrium value of the QCD gluon condensate and a single pressureless matter component (cold dark matter, CDM). The resulting dynamical equations of a spatially-flat and homogeneous Robertson-Walker universe are solved numerically. This simple empirical model allows, in fact, for a careful treatment of the boundary conditions and does not require a further scaling analysis as the original model did. Reliable predictions are obtained for several observable quantities of the homogeneous model universe. In addition, the estimator E_G, proposed by Zhang et al. to search for deviations from standard Einstein gravity, is calculated for linear sub-horizon matter-density perturbations. The QCD-scale modified-gravity prediction for E_G(z) differs from that of the ΛCDM model by about ±10% depending on the redshift z.     

球载高能天文望远镜的超视距自动跟踪

本文在HAPI-4原有系统的基础上，利用80C196超16位单片机，首次实现了球载姿态指向控制系统的数字化；借助于全球卫星定位系统GPS，实现了气球位置的高精度定位和时间的绝对定标；采用小型高密度磁带机作为球载数据流存储器，利用海事卫星实现超视距测控，形成了新一代的球载高能望远镜控制系统．     

飞机刹车能量确定方法和计算公式比较

介绍了飞机机轮刹车能量确定方法,分析了不同规范估算公式的精度.结果表明,民用航空标准要求高于军用标准,按美国军用标准MIL-W-5013计算的刹车能量小约5%,提出了修改建议.     

LED新型光源的应用与发展前景分析

本文主要叙述了LED作为新型光源与传统光源相比所具有的优势，以及目前各国将LED技术应用于照明、通讯等领域的突出优点，最后文章指出目前困扰我国LED技术发展的几点问题。     

舰尾流环境中载机纵向QFT/TECS控制系统设计

为了消除舰尾流对载机着舰过程产生的影响,同时完成低动压状态下飞行速度与高度的解耦工作,基于定量反馈理论/总能量控制理论(QFT/TECS)设计了纵向着舰控制系统。针对着舰过程中数学模型所具有的不确定因素及舰尾流对下滑航迹的影响,以载机高度变化率为控制对象,使用定量反馈理论结合推力补偿系统进行了内回路鲁棒控制律设计。外回路控制律设计是以总能量控制理论为基础,通过粒子群优化算法对待调控制参数进行寻优,进而实现了对高度、速度等参数的精确控制,完成了载机纵向着舰轨迹与速度的解耦工作。仿真结果表明,该控制律在拥有较强的鲁棒性的基础上具有良好的解耦控制能力,实现了载机着舰段的高度与速度的解耦控制,明显提高了载机对着舰轨迹的跟踪能力,可满足不确定条件下载机的着舰要求。     

基于增量学习的高光谱图像目标检测

高光谱图像目标检测是高光谱图像分析中的重要研究内容之一。本文从经典有效的约束能量最小化算法出发,提出了一种基于增量学习的高光谱目标检测方法。当获得新的样本时,不需要重新计算所有样本的自相关矩阵即可对检测器模型进行更新,减轻了星上有限计算资源的负担。实验结果表明:本文提出的目标检测算法在压制背景光谱的同时可以更好地适应目标光谱,提高了算法的检测性能。     

带弹性元件扑翼机构的动力学分析及实验

为研究扑翼飞行器传动机构的能量特性，以特拉华大学机械系统实验室所研制样机为原型进行了建模。引入气动项和拉力弹簧建立了完整的动力学模型。分析发现，气动项的力矩峰值为惯性项的4.8倍，对电机的转矩峰值的影响起主要作用。运用正交法进行仿真发现，引入拉力弹簧可以使电机转矩峰值最大降低77.5%，与理论分析相符合。进一步的物理实验验证了理论分析和仿真结果的正确性，并得到了当弹簧的连接点位置为185 mm、原长为200 mm及刚度为0.1 N/mm时实验结果取得最优值，可为扑翼机传动机构的优化设计提供依据。此外，引入弹性元件也可有效降低电机的转速波动，进而为仿生扑翼飞行器的生产和实践应用提供理论指导。     

摆锤式冲击试验机能量损失检测方法的比较与分析

摆锤式冲击试验机的能量损失包括：指针的摩擦（或接触式电子角位移传感器的摩擦）、空气阻力和摆轴轴承的摩擦所引起的能量损失；基础的冲击、机架和摆锤的振动所引起的能量损失。国内外还没有成熟的测量方法和测量仪器测定基础的冲击、机架和摆锤的振动所引起的能量损失，没有形成技术文件，目前摆锤式冲击试验机能量损失的检测主要针对前者。本文针对国内计量部门计量摆锤式冲击试验机所依据的常用标准和规程，比较能量损失的检测方法和计算公式，做出简要分析，指出某些计算公式值得商榷之处。     

中国电动飞机技术创新与实践观点

电动飞机极大地提高了飞机的环保性、舒适性、维修性和经济性，是航空工业未来的发展方向。电动飞机应具备高气动效率、高推进效率、高结构效率、高能量密度，以提高航时。"十三五"期间，中国已完成2机首飞，2机取证。"十四五"期间，电动飞机研发应该以高功率高效率电推进系统为研发重点，以混合电推进系列飞机为研发核心，以现有新能源型号全寿命保障体系研究为关键，以拓展新型电动飞行器研发和标准构建为目标。     

Minimizing energy utilization for growing strawberries during long-duration space habitation

Strawberry is a candidate crop for space that is rich in protective antioxidants and could also have psychological benefits as a component of crew diets during long-duration space habitation. Energy for electric lighting is a major input to a controlled-environment crop-production system for space habitation. Day-neutral strawberry cultivars were evaluated at several different photoperiods to determine minimum lighting requirements without limiting yield or negatively impacting fruit quality. The cultivars ‘Tribute’, ‘Seascape’, and ‘Fern’ were grown at 14, 17, or 20 h of light per day, and fruit yield was evaluated over a 31-week production period. This amounted to a difference of 2418 kWh m⁻² in energy usage between the longest and shortest photoperiods. All cultivars produced similar total fresh weight of fruit regardless of photoperiod. Volunteer tasters rated organoleptic characteristics including sweetness, tartness, texture, and overall appeal as measures of fruit quality. Generally, organoleptic attributes were not affected by photoperiod, but these attributes were somewhat dependent upon cultivar and harvest time. Cultivars under different photoperiods varied in their production of fruit over time. ‘Seascape’ was the most consistent producer, typically with the largest, most palatable fruit. ‘Seascape’ plants subsequently were grown at 10-, 12-, or 14-h photoperiods over a treatment period of 33 weeks. Photoperiod again had no significant effect on total fruit weight, although there were periodic flushes of productivity. Fruit under all photoperiods had acceptable approval ratings. A large-fruited, day-neutral strawberry cultivar such as ‘Seascape’ remains productive under shortened photoperiods, allowing reductions in energy and crew labor while maintaining flexibility for mixed-cropping scenarios in space.