某型机载导航计算机系统检测平台的硬件设计

为解决导航计算机系统飞行训练故障多、排故难的问题,满足大修厂对航空导航计算机系统 的检测需求,以工控计算机为平台,采用高精度的14位旋转变压器和大规模数字集成电路,设 计出一种检测速度 快、故障定位准确的自动检测平台,模拟角度精度可达到1.3′。通过模拟机载设备之间的 通信信号,可实现对数字计算机、控制台和代码转换装置的功能性能检测。     

Link16数据链导航功能实现与改进

基于同步的相对导航与精确定位技术是Link16数据链运行的关键。针对国内文献对该 技术介绍较少的情况,分析了相对导航的基本原理,研究了利用往返计时报文实现精确同步 的方法和步骤,建立了相对导航解算方程以及相对栅格与地理栅格坐标之间的数据转换模型 ,最后提出了一种用GPS/IMU数据融合和卡尔曼滤波方法提高导航精度的方案。应用结果表 明,该方案能显著提高数据链的导航精度。     

基于ADS-B报文的“北斗”便携式终端实现

针对单个广播式自动相关监视（Automatic Dependent Surveillance-Broadcast,ADS-B）发射机传输距离受限、多地面站组网复杂以及成本较高等问题,在分析ADS-B报文编码与解码算法的基础上,探讨了基于无线网络传输的ADS-B报文信息技术,并设计了基于“北斗”卫星导航（BeiDou Satellite Navigation System,BDS）/嵌入式控制器以及无线网络的便携式监视终端系统。利用实测ADS-B数据联合搭建的监视中心对算法和系统进行测试,结果表明数据传输稳定,实现了低空空域通用航空飞机ADS-B态势信息的网络传输功能,丰富了监视信息的链路传输方式,为低空通航飞行器安全飞行和全面监视提供了新的方法。     

汽车空气滤清器数值仿真分析与结构改进设计

降低空气滤清器流动阻力是提高滤清效率、延长滤清器寿命、提高发动机动力性与经济性的主要方法。利用计算流体力学(Computational Fluid Dynamic,CFD)数值仿真分析方法对某型号汽车空气滤清器进行流动阻力仿真分析与研究。通过调整滤清器的进气角度以及圆角设计,提高了滤清器内部气流流动的均匀性,有效降低了滤清器的流动阻力。     

Urban air pollution in China: destination image and risk perceptions

Inbound tourist arrivals into China have been declining in recent years, possibly in response to increasing levels of urban air pollution. To examine Westerners’ contemporary views on China as a travel destination, with a particular focus on air pollution, this research surveyed 600 US and Australian residents. An online panel survey collected data on cognitive and affective destination image, cognitive and affective risk perceptions, intention to visit China and key demographic variables. The findings show that, while China's cognitive image attributes were perceived positively, potential travellers expressed negative views about travel risks in China in general and about air quality in particular. Importantly, feelings towards the risk of air quality had a significant negative impact on destination image as well as intention to visit China. The research contributes to theory by highlighting the importance of considering affective risk perceptions in destination image studies. While some market segments seemed less sensitive to air pollution than others, this paper concludes that unless China proactively addresses the problem of air pollution, for example by seeking to stimulate positive feelings, international arrivals may continue to be compromised.     

空分产品放空-供气自动调节的PID控制方法

本文使用一种分段控制方法,将空分产品管线的放空、供气阀门使用同一PID模块进行电流分段控制,从而解决了两阀门相关性问题,降低了控制成本,简化了控制难度。     

水下高速气体射流的实验研究

本文对高速空气射流在受限约束下的动力学行为进行了实验研究。通过流动可视化揭示了高速空气射流在单筒和同心筒发射筒底部滞止、反转、而后向上绕经航行体或同心筒间隙向上喷入水中的演化过程。主要观察了单筒底部有无导流锥、同心筒三种间隙在不同压比和不同流量下的气水两相流态,并测量了航行体与发射筒的壁面压力分布。给出了航行体壁表面压力的动态变化规律,和沿轴向的分布规律。     

Economies of traffic density and scale in the integrated air cargo industry: The cost structures of FedEx Express and UPS Airlines

This paper examines the cost structures of the leading integrated air cargo carriers, FedEx Express and UPS Airlines. A total cost model is estimated for the two carriers using quarterly data on domestic operations and costs over a nine-year period (2003–2011). The estimated model indicates that the integrated industry exhibits increasing returns to traffic density and constant returns to scale. Accounting for carrier-specific differences in cost structure and network size, FedEx Express is found to be more cost-efficient than UPS Airlines. Looking at the carriers individually, UPS Airlines exhibits substantial economies of traffic density and constant returns to scale while FedEx Express' cost structure is characterized by weak economies of density and constant returns to scale. The combined effect of returns to density and returns to scale on the cost structures of integrated carriers is captured by economies of size. Both FedEx Express and UPS Airlines exhibit economies of size, indicating that carriers in the integrated industry can be more cost efficient by making appropriate adjustments to their network size as their output grows. Moreover, the relative cost-efficiencies of the carriers are reversed when their network-size differences are not controlled.     

Warehouse location problems for air freight forwarders: a challenge created by the airport relocation

The move of Hong Kong International Airport from the city centre to a suburban area in July 1998 provided sufficient capacity to meet the increasing demand of passenger and air-cargo flows in Hong Kong in the foreseeable future. However, the move has adverse side effects such as causing the readjustment of many existing systems and creating many imminent strategic problems. One of such problems is the warehouse location of freight forwarders: they have to decide whether they should locate their warehouses in the new airport, in current locations, or in new locations somewhere in the city. This paper delineates the results of a survey conducted in the summer of 1997 before the airport was relocated. The survey asked what decisions the freight forwarders had made and how they evaluated some potential warehouse locations. The paper also considers two mathematical models, which explain and predict, respectively, the location pattern of freight forwarder warehouses before and after the relocation of the airport.     

The impact of Air Service Agreement liberalisation: The case of Nigeria

The positive impact of air transport liberalisation as suggested by economic theories and empirical studies has inspired many developing countries like Nigeria to liberalise some of its Air Service Agreements (ASAs). This paper seeks to examine the extent to which international air service liberalisation has impacted upon Nigeria ten years after it was introduced. The research developed a cross-sectional model with passenger traffic as the dependent variable, while macroeconomic factors (trade and GDP), historical links, distance and ASAs (a proxy for liberalisation) served as independent or predictor variables. The analysis revealed a set of ASA stages in the country's policy-making process (restricted Bilateral Air Service Agreement, Open Skies Agreement and Yamoussoukro Declaration). Further analysis showed that the predictor variables were all significant in explaining passenger demand. The model demonstrated that the liberalisation of market access to the Open Skies Agreement level could stimulate traffic growth by at least 65 percent. The findings can assist in guiding policy and industry stakeholders in future decisions relating to liberalisation and ASAs.