李家云副总设计师

目前,直升机在民用领域的应用越来越广,作为中航工业直升机所副总设计师,请您谈谈在通用航空领域,中航直升机所将开发哪些新型民用直升机型号? 李家云:中国直升机行业在研制军用直升机满足国防建设的同时,也在积极开发民用直升机,直9、直11两型直升机先后取得中国民航型号合格证,由于方方面面的原因,占据国内民用直升机市场份额较小.     

徐朝梁 中国著名直升机总设计师

在此次珠海航展上,大型民用直升机AC313的精彩表演吸引了观众热切的目光,作为总设计师,您眼中的AC313是怎样的定位?徐朝梁:AC313是借鉴原有型号平台的成功设计经验、采用成熟的先进技术、按照国际最新的适航标准、采用与国际接轨的适航审定程序自主研发的全新民用直升机,是目前国内最大吨位的直升机。     

Dynamics of space welding impact and corresponding safety welding study

This study was undertaken in order to be sure that no hazard would exist from impingement of hot molten metal particle detachments upon an astronauts space suit during any future electron beam welding exercises or experiments. The conditions under which molten metal detachments might occur in a space welding environment were analyzed. The safety issue is important during welding with regards to potential molten metal detachments from the weld pool and cold filler wire during electron beam welding in space. Theoretical models were developed to predict the possibility and size of the molten metal detachment hazards during the electron beam welding exercises at low earth orbit. Some possible ways of obtaining molten metal drop detachments would include an impulse force, or bump, to the weld sample, cut surface, or filler wire. Theoretical models were determined for these detachment concerns from principles of impact and kinetic energies, surface tension, drop geometry, surface energies, and particle dynamics. A weld pool detachment parameter for specifying the conditions for metal weld pool detachment by impact was derived and correlated to the experimental results. The experimental results were for the most part consistent with the theoretical analysis and predictions.     

Gating Functions for Multipath Mitigation in GNSS BOC Signals

A new multipath mitigation technique is proposed for binary offset carrier (BOC) signals in global navigation satellite systems (GNSS) using the concept of gating function originally conceived for the GPS coarse-acquisition (C/A) code. Specially-tailored pulses are utilized to diminish the number of false-lock points of the code discriminator response and to improve the multipath mitigation capability. The code loop includes only four real correlators (two extra correlators are required for the simplified bump-jumping algorithm with BOC(n,n) signals). Results obtained with BOC(n,n) and BOC(2n,n) signals show that this technique eliminates the multipath ranging errors for reflected rays with relative delays typically above twenty percent of the spreading code chip duration, thus comparing favorably with the conventional receiver correlation techniques.     

Tropospheric delays from GNSS for application in coastal altimetry

In the scope of the development of an improved methodology for the computation of the wet tropospheric correction for coastal altimetry, based on the use of tropospheric delays derived from GNSS (Global Navigation Satellite Systems), various studies have been conducted aiming to improve the estimation, at global scale, of GNSS-derived tropospheric delays.