Research on FMC analytic algorithm of PBN track transition coding

Airborne navigation database(NavDB)coding directly affects the result of analysis on the instrument flight procedure by the modern aircraft flight management computer(FMC).A reasonable flight track transition mode can improve the track tracking accuracy and flight quality of the aircraft.According to the path terminator(PT)and track transition characteristics of the performance based navigation(PBN)instrument flight procedure and by use of the world geodetic system(WGS)-84 ellipsoidal coordinate system,the algorithms for“fly by”and“fly over”track transition connections are developed,together with the algorithms for coordinates of fix-to-altitude(FA)altitude termination point and heading-to-an-intercept(VI)track entry point and for track transition display of the navigation display(ND).According to the simulation carried out based on the PBN instrument approach procedure coding of a certain airport and the PBN route data at a high altitude,the algorithm results are consistent with the FMC-calculated results and the actual ND results.

Dynamics Performance of Subgrade-Tunnel Transition on Chongqing-Suining Ballastless Track

Experiments were conducted on China railway high speed electrical multiple units （EMUs） CRH2 and freight car C80 on Chongqing-Suining high-speed ballastless track. Based on the experimental results, the dynamics performance of cement concrete transition and cement stabilized aggregate transition was analyzed. The results show that the dynamic stress, vibration displacement, vibration velocity, vibration acceleration and other vibration parameters vary steadily on the profile section of transitions, and that at the adjoining position between subgrade and tunnel portal, cement concrete transition has gradual hardness change, whereas cement stabilized aggregate transition exhibits good elasticity, small shock, and small dynamic effect of the cars.

Performance analysis of a novel chip tracking loop used for regenerative pseudo-noise ranging clock recovery

To improve the performance of composite pseudo-noise （PN） code clock recovery in a regenerative PN ranging system at a low symbol signal-to-noise ratio （SNR）, a novel chip tracking loop （CTL） used for regenerative PN ranging clock recovery is adopted. The CTL is a modified data transition tracking loop （DTTL）. The difference between them is that the Q channel output of the CTL is directly multiplied by a clock component, while that of the DTTL is multiplied by the Ⅰ channel transition detector output. Under the condition of a quasi-squareware PN ranging code, the tracking （ mean square timing jitter） performance of the CTL is analyzed. The tracking performances of the CTL and the DTTL, are compared over a wide range of symbol SNRs. The result shows that the CTL and the DTTL have the same performance at a large symbol SNR, while at a low symbol SNR, the former offers a noticeable enhancement.

Investigation of differential movement at railroad bridge approaches through geotechnical instrumentation

Railway transitions experience differential movements due to differences in track system stiffness,track damping characteristics,foundation type,ballast settlement from fouling and/or degradation,as well as fill and subgrade settlement.This differential movement is especially problematic for high speed rail infrastructure as the 'bump' at the transition is accentuated at high speeds.Identification of different factors contributing towards this differential movement,as well as development of design and maintenance strategies to mitigate the problem is imperative for the safe and economical operation of both freight and passenger rail networks.This paper presents the research framework and initial instrumentation details from an ongoing research effort at the University of Illinois at Urbana-Champaign.Three bridge approaches experiencing recurrent geometry problems were instrumented using multidepth deflectometers(MDDs) and strain gages to identify different factors contributing to the development of differential movements.