Line maintenance is a part of aircraft MRO, which refers to the works on discrepancies as per the requirements of the flight crew in order to ensure airworthy condition of the aircraft. These works are conducted before or in between flight operations on a regular basis. Line maintenance involves two components: labor and materials. Some of the line maintenance activities are A checks, weekly/overnight checks, daily checks, transit checks, and pre-flight checks.

The global baby stroller and pram market has been registering positive growth over the last few years and is shaping up to become one of the top competitive markets at a global level. With the rise in globalization, ample growth opportunities are being created in the market.

An aerostat uses gases lighter than air such as hydrogen, helium, as well as hot air, which helps the aerostat to generate airlift. Aerostats include powered airships and unpowered balloons that are tethered to the ground. These are generally used for intelligence, surveillance, and reconnaissance (ISR) purposes by the military forces and also for tourism and civilian observations. An aerostat surveillance system possesses the long-endurance capability, which is not feasible with a fixed-wing aircraft. The alternatives to aerostats (such as unmanned aerial vehicles (UAVs)) are battery dependent, which results in operational failures.

Aerospace fasteners have evolved over the years with the constantly changing aerospace industry. These components are widely used in commercial and military aircraft, ballistic missiles, rockets, and associated aftermarket services. The aerospace industry employs a wide range of fasteners such as bolts, nuts, screws, rivets, and pins.

据报道，4月20日19时41分，搭载着天舟一号货运飞船的长征七号遥二运载火箭成功点火发射，此后与天宫二号成功完成对接。此次任务是我国载人航天工程第二步收官之战，将为18年开建正式空间站奠定坚实基础。未来十年我国载人航天驶入快车道，市场规模接近500亿元，重点推荐航天电子、中国卫星。

航母下水和 C919 首飞预期，或带动军工行情。腾讯网报道，4 月23 日，国产大型客机Ｃ919 进行高滑抬前轮试验取得成功；辽宁省大连市香炉礁码头观察发现，国产航母的船坞开始注水。我们认为 C919 首飞和国产航母下水的时间越来越近了，短期两大重器标志性的时间结点或将带动军工行情。当前，中证军工指数已经回到了 2015 年牛市启动前的水平。

我们认为，2017 年外部不确定性增强——4 月 7 日美国打击叙利亚，而本周朝鲜半岛局势持续发酵，也都印证了随着特朗普上台并开始执政日益加强。我们认为，地缘政治紧张刺激军工板块走势，今年对军工板块具有刺激性的事件数量将大幅度增加。

本期商业航天研究专题三：《“一带一路”战略下我国北斗导航“走出去”对策研究》，首先分析了我国北斗导航产业“走出去”基础条件。第二，重点对北斗产业“走出去”面临的机遇和挑战做了系统梳理，围绕国外卫星导航产业发展、全球地缘政治、全球科技革命、国家发展战略、北斗产业核心技术进行了阐述。第三，研究了高铁、核电等高端装备产业国际化发展的经验和启示。第四，以解决制约我国北斗导航产业“走出去”的问题为导向，提出了“一带一路”沿线国家和地区推动北斗系统应用和产业化发展四点对策建议：加强军地深度合作机制建设，推动北斗产业的国内市场创新发展；注重开展“一带一路”国际合作，提升北斗产业的国际竞争力；充分发挥企业主体作用，支持开展强强联合；加快境内外示范基地建设，不断完善支撑产业发展的载体。

4月11日，中车株洲电力机车有限公司与马来西亚交通部在长沙签订两款“米轨”（1米宽轨距）动车组购销合同，包括 13列混合动力电动车组和 9列现代超级动车组。这是自 2014 年以来中国再次获得马来西亚的“米轨”动车组订单。近年来，中国轨道交通装备企业在“一带一路”合作中不断取得突破，由最初的输出产品升级到输出产品+技术+制造+服务+管理，由最初的企业单一出海升级到带动轨道交通产业集群联合出海。 

我国载人航天工程实施“三步走”发展战略，第一步为载人飞船阶段，第二步为空间实验室阶段，第三步为空间站阶段。当前第二步战略已进入最后的关键阶段—空间补给技术的验证，这一历史性任务，预计于 4 月下旬，由“天宫二号”、“天舟一号”和“长征七号”共同完成，这是我国载人航天“三步走”战略中第二步的收官之战，将为后续空间站阶段奠定坚实基础。