黏性彻体力建模方法及其应用

研究了将Navier-Stokes方程中黏性项简化为黏性彻体力的建模方法,并将该模型加入已有的计算流体力学(CFD)程序中,实现了用三维欧拉方程加黏性彻体力模型快速模拟叶轮机三维非定常流动的方法.使用该方法对进气周向总压畸变条件下的某双级压气机非定常流场进行了模拟,并与雷诺平均的Navier-Stokes(RANS)程...     

用Ce~(3+):YVO_4晶体荧光粉与蓝光LED制造自然白光LED

本文报导了通过结合自行制备的掺铈钒酸钇晶体(Ce3 :YVO4)荧光粉与InGaN／GaN蓝光发光二极管(LED)结合而得的白光发光二极管(W-LED)。在室温、正向电压3.5V、正向电流20mA时W-LED的CIE色坐标为(0．32,0．37),接近纯白色(0．33,0．33)。     

基于TM1300的AC-3定点解码算法的设计与优化

TM1300是专为处理高质量的视频、音频数据而开发的高效多媒体处理器。本文主要介绍了AC-3音频解码算法在TM1300上的设计及优化。     

基于多模PPP-AR技术的大气水汽探测性能分析

精密单点定位（precise point positioning，PPP）反演大气可降水量（precipitable water vapor，PWV）具有精度高、实时性强等优点，能够在灾害监测、降雨预报及探测降水信息等方面发挥重要作用。为评估整周模糊度固定模式下PPP-AR（PPP ambiguity resolution）反演PWV的性能，选取全球范围16个MGEX站2022年4个时段的观测数据，采用最终精密星历解算，设置不同星座组合（GPS,BDS-3,GPS+BDS-3,GPS+GLO+GAL+BDS-3）获取对流层延迟（zenith total delay，ZTD）估值，并转换为PWV。从PPP-ZTD与IGS-ZTD的相关性、PPP-ZTD收敛时间、ZTD估值精度和PPP-PWV估值精度4个方面评价多模PPP-AR探测水汽的性能。结果表明，与单（G、C）、双系统（GC）固定解相比，多系统（GREC）固定解获取ZTD估值更加精确，相关系数更高。相较于单、双系统，多系统具有更快的收敛速度，收敛时间分别缩短了27%,25%和20%，多系统固定解与浮点解相比收敛时间缩短11%。此外，对GNSS PPP反演的PWV与探空站PWV（RS-PWV）进行对比，结果表明，WUH2站与HOB2站单、双、多系统固定解、多系统浮点解（float-GREC）的平均均方根误差分别为6.40 mm,6.48 mm,6.19 mm,6.17 mm,6.19 mm和5.82 mm,5.77 mm,5.72 mm,5.62 mm,5.70 mm。多模下得到的PWV估值精度最高，可为高精度的水汽反演提供支持。     

飞机燃油系统全尺寸地面模拟试验

飞机燃油系统全尺寸地面模拟试验是保证燃油系统设计的正确性、合理性，检验系统及其成品工作性能协调性，及时发现系统设计缺陷和理论计算无法解决的问题，排除系统故障，保证飞机飞行安全、工作可靠的重要和必不可少的手段。现代飞机燃油系统的设计越来越复杂，加之新技术的采用，不仅给系统的设计提出了相当高的要求，同时也给系统的全尺寸地面模拟试验带了诸多前所未有的难题。针对飞机燃油系统的特点，阐述了其试验边界条件的模拟方法和海量数据计算机测控系统的设计策略，已成功应用于多个型号飞机燃油系统的研制，具有一定的工程实用价值。     

GMRT monitoring of Cyg X-1 and Cyg X-3

We present the results of low frequency radio observations of the X-ray binaries, Cygnus X-1 and Cygnus X-3, during different X-ray states. The low frequency observations were made for the first time for these sources at 0.61 and 1.28 GHz using the Giant Meter-wave Radio Telescope (GMRT) between 2003 and 2004. Both Cyg X-1 and Cyg X-3 are highly variable at low radio frequencies. We also compare our data with the observations at 15 GHz conducted by the Ryle telescope. Spectral turnover is seen for both the sources below 2 GHz. The data suggest that the change in the radio flux density in both the sources is correlated to the X-ray hardness ratio and follows a similar behavior pattern.     

Progress in tropospheric ammonia retrieval from the MIPAS satellite instrument

The Michelson Interferometer for Passive Atmospheric Sounding is a polar orbiting high resolution mid-infrared emission limb sounder with a nominal vertical resolution of 3 km. Work to extend the list of routinely retrieved species led to the examination of ammonia, NH₃. In this paper, we explore the feasibility of upper tropospheric retrievals around 6-km altitude, discussing appropriate methods. We demonstrate a weak north to south gradient outside the error bars, using co-addition to improve signal-to-noise and compare these first results with a model.     

三维全五向编织复合材料的切边效应

对切割与未切割的三维全五向(3DF5D)编织复合材料进行了纵向拉伸力学性能研究。首先分别对2种编织角下3种不同情况(未切割、沿厚度方向切边和沿宽度方向切边)的试件进行了力学性能实验,实验结果表明,沿着厚度方向切边使材料的刚度和强度分别下降了约10%和25%;沿着宽度方向切边使材料刚度和强度分别下降了约3%和18%;进一步通过有限元数值模拟对上述实验过程进行了仿真计算,得到了单胞的损伤演化过程、破坏机理以及应力-应变曲线。最后对实验结果和计算结果进行了对比,结果显示二者吻合良好。研究结果表明,三维全五向编织复合材料的编织角越大,拉伸刚度和强度会越小;试件尺寸越大,厚度方向和宽度方向切边的影响越小,并趋于定值。     

基于AutoCAD的线切割自动编程接口软件设计

在分析DXF文件格式、3B指令代码的基础上,提出了基于AutoCAD的线切割自动编程流程,并重点讨论了自动编程过程中的基本加工路线生成、间隙补偿、计数长度计算等关键技术。     

GRB 980425, SN1998BW and the EMBH model

The EMBH model, previously developed using GRB 991216 as a prototype, is here applied to GRB 980425. We fit the luminosity observed in the 40–700 keV, 2–26 keV and 2–10 keV bands by the BeppoSAX satellite. In addition we present a novel scenario in which the supernova SN1998bw is the outcome of an “induced gravitational collapse” triggered by GRB 980425, in agreement with the GRB-Supernova Time Sequence (GSTS) paradigm [Ruffini, R., Bianco, C.L., Chardonnet, P., Fraschetti, F., Xue, S.-S. On a possible GRB-supernova time sequence. Astrophys. J. 555, L117–L120, 2001c]. A further outcome of this astrophysically exceptional sequence of events is the formation of a young neutron star generated by the SN1998bw event. A coordinated observational activity is recommended to further enlighten the underlying scenario of this most unique astrophysical system.