三维动态非结构重叠网格Navier-Stokes方程并行算法

 提出了一种三维动态非结构重叠网格Navier-Stokes(N-S)方程的并行计算方法。N-S方程的空间离散采用格点有限体积方法,时间离散采用隐式的双时间步长方法。应用一方程Spalart-Allmaras(S-A)模型来计算湍流黏性。并行计算采用动态的区域分裂方法,在每一物理时间步利用METIS网格分区系统对网格进行分区。为了实现各CPU之间的负载均衡,每块网格都按CPU个数进行分区并对活动节点和非活动节点进行了加权处理。最后,通过对外挂物投放无黏流动的数值模拟和内埋武器弹舱开启黏性流动的数值模拟,验证了该并行程序的准确性、高性能并行计算以及处理复杂几何外形的能力。     

乘波飞行器的优化设计和气动热计算研究

以高超声速技术为研究背景,开展高超声速乘波飞行器设计方法研究.在已有乘波构型生成方法基础上,采用相交楔锥生成多级压缩的乘波构形.并通过对乘波器的前缘进行钝化,进行了气动热特性数值研究.使乘波体在气动力层面上具有尖前缘,保持高升阻比特性,而在气动热层面上具有钝前缘,降低气动加热强度.结果表明,这为高超声速飞行器的气动防热设计开辟了新途径.     

Fast calibration of between-receiver GPS/Galileo/BDS differential phase bias with millimeter accuracy based on short baseline mode

The differential code and phase biases induced by the receiver hardware (including receiver, antenna, firmware, etc.) of the Global Navigation Satellite System (GNSS) have significant effects on precise timing and ionosphere sensing, thus deserve careful treatment. In this contribution, we propose an approach to fast fix the single-difference ambiguity to finally obtain the unbiased estimates of between-receiver differential phase bias (BR-DPB) and between-receiver differential code-phase bias (BR-DCPB) based on the short baseline mode. The key to this method is that the error sources can be significantly eliminated due to the length of the baseline is very short. At the same time, the empirical constraints and random characteristics of BR-DPB/BR-DCPB were considered, which is conducive to the resolution of single-difference ambiguity. Several sets of GNSS data (GPS L1/L2, Galileo E1/E5b, and BDS B1/B3), recorded by the short baselines in an interval of 30 s and covered a broad range of receiver/antenna types (JAVA, SEPT, LEIC, and TRIM), were used to verify the effectiveness of the proposed method. The numerical tests show that the proposed method is capable of fast fixing the single-difference ambiguity successfully within a few epochs and then providing the unbiased estimates of BR-DPB and BR-DCPB in an epoch-by-epoch manner. Experiments show that the estimated BR-DPB is in millimeter accuracy, which is of great significance for the millimeter-accuracy phase time transfer and ionospheric delay estimation. Furthermore, the calibrated BR-DPB/BR-DCPB can be treated as the known products for long-distance precise timing and ionosphere sensing based on the inter-station single-difference model.     

NB-IoT模块与电信物联网开放平台的通信研究

中国电信物联网开放平台实现对各种NB-IoT设备数据的统一管理,同时向第三方应用系统开发接口,让各种应用能快速构建自己的物联网业务。本文构建物联网系统,终端利用DS18B20温度传感器采集环境温度,通过BC35-G模块以CoAP协议将温度传输至电信物联网开放平台。     

Comparison of RO tropopause height based on different tropopause determination methods

The tropopause is an important boundary in the Earth’s atmosphere, and has been the subject of close attention from atmosphere and climate researchers. To monitor the global tropopause using radio occultation (RO) data, there are two primary methods, one is the widely used temperature lapse rate method, and the other is the bending angle covariance transform method which is unique to RO data. We use FengYun3-C (FY3C) and Meteorological Operational Satellite Program (MetOp) RO data and European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis data to determine differences in RO tropopause height calculated by these two methods. We compute biases of the RO lapse rate tropopause height (LRTH) and the RO bending angle tropopause height (BATH) relative to the ECMWF LRTH. The dependences of the tropopause height biases on tropopause height (TPH) retrieval method, latitude, season and RO mission are investigated. The results indicate that BATH show a consistent 0.8–1.2 km positive bias over the tropics and high latitude regions compared with LRTH, however, over 25° to 40° latitude in both hemisphere, BATH results are less stable. Furthermore, the mean bias between BATH and LRTH displayed a different symmetrical characteristic from 2017.12 to 2018.2 (DJF) compared to 2018.6–2018.8 (JJA). However, except for some bias over Antarctica, the mean value of both LRTH and BATH show a similar tropopause variation, indicating the consistency of both methods.     

固液混合火箭发动机固体燃料的燃速计算

分析了固液混合火箭发动机的燃烧特点、燃烧中气相过程和固体燃料内部的传热过程,利用由传热理论得出的固体燃料燃速公式和阿累尼乌斯(Arrhenius)燃速公式耦合计算,得到了燃速与氧化剂流率、轴向距离、装药初温和时间的变化规律.计算结果表明固体燃料燃速主要受氧化剂流率和轴向距离的影响,随氧化剂流率的增加而增加,随轴向距离的增加而减小.固体燃料燃速温度敏感性小,在设计发动机时可以不考虑装药初温的影响.利用热力计算得到了绝热燃烧温度与氧化剂流率和药柱长度的变化规律,绝热燃烧温度随氧化剂流率的增加存在一最大值.计算结果与相关文献的报道比较吻合,为进一步研究固液混合火箭发动机的燃烧及流动问题打好了基础.     

一种CCSDS深空标准的LDPC码高效实现

针对CCSDS(空间数据系统咨询委员会)深空通信标准LDPC(低密度奇偶校验码),为减少定点量化后的译码性能损失,提出了一种改进的译码修正算法。通过分析矩阵结构特点,并引入交错译码结构以及流水结构,设计了一种适合该标准深空通信LDPC码编译码器的高效实现结构。使用此结构,在Xilinx公司的XC5VSX95T芯片上实现了CCSDS深空通信标准的(8 192,4 096)LDPC码,在40次迭代情况下可以达到47m的吞吐率。实践表明:该设计可以灵活地移植应用于其他码率的CCSDS深空通信标准LDPC编译码器设计。     

Performance simulation of high altitude scientific balloons

The design and operation of a high altitude scientific balloon requires adequate knowledge of the thermal characteristics of the balloon to make it safe and reliable. The thermal models and dynamic models of altitude scientific balloons are established in this paper. Based on the models, a simulation program is developed. The thermal performances of a super pressure balloon are simulated. The influence of film radiation property and clouds on balloon thermal behaviors is discussed in detail. The results are helpful for the design and operate of safe and reliable high altitude scientific balloons.     

贝叶斯网络在飞控系统可靠性评估中的应用

把一种基于贝叶斯网络的故障树分析法应用于飞控系统俯仰控制功能的可靠性评估中,突破传统故障树分析法的局限性——各部件独立、状态为二值,不但可以计算系统的可靠性指标,而且可以定量给出某个事件或某几个事件在系统可靠性中所占的地位,找出系统的薄弱环节。