基于查表的开环MPM预失真器

提出了一种基于查表的开环记忆多项式模型(MPM,Memory Polynomial Model)预失真器.从MPM预失真器系数估计和执行信号预失真处理两方面加以考虑.首先,利用预失真器和高功率放大器(HPA,High Power Amplifier)传输特性的互补性,由采集到的HPA输入、输出基带数据进行单次最小二乘估计得到MPM预失真器的系数,避免了以往递归结构的收敛性和计算量大等问题.然后,利用MPM预失真器的特点,建立了基于输入信号强度索引的一维向量表,通过查表实现MPM预失真器的幂次累加项,极大地减少了实现预失真器所需的计算量及硬件开销.仿真显示,采用提出的预失真器可以有效补偿HPA对信号的记忆非线性失真,有效带宽内获得了近20 dB的功率改善,也显著改善了系统误码性能.     

On a non-primordial origin of the cosmic background radiation and pregalactic density fluctuations

Dusty pregalactic Population III objects may provide a mechanism for an effective thermalization of the star radiation. They may generate the observed microwave background and so the high cosmic photon entropy. Assuming a tepid universe a smaller primordial entropy contribution results in reasonable mass scales and amplification factors of pregalactic density fluctuations.     

质量管理在中国香港的应用(英文)

香港工商企业的质量管理大部分都采用西方的质量管理概念。每当范畴扩展到建立人的优质思想和意识时,便遇到不少困难,基于上述问题,作者进行了一系列的研究,希望了解‘文化’与‘优质管理’之间的关系,并将中国的优良文化传统应用于现代质量管理之中。研究结果显示,‘管理哲学’是重要的一环,而我国的哲学极为丰富,作者借此文章,希望引起更多中国人在这方面的兴趣,从而进行更深入地研究和推广。     

高速航空拖靶的总体方案和气动外形优化

针对某高速、低空恒高拖靶系统研制的需求,设计了一种有良好气动特性、结构简单、工艺性好、成本低的拖靶总体方案.为了进一步减少气动阻力,采用基于Kriging模型的优化方法对高速拖靶气动外形进行了优化设计.优化结果表明:在满足操纵力和稳定性要求前提下,优化后拖靶的气动阻力明显减小.本文研究结果为整个拖靶系统的进一步设计和论证奠定了基础.     

Regolith X-Ray Imaging Spectrometer (REXIS) Aboard the OSIRIS-REx Asteroid Sample Return Mission

The Regolith X-ray Imaging Spectrometer (REXIS) is the student collaboration experiment proposed and built by an MIT-Harvard team, launched aboard NASA’s OSIRIS-REx asteroid sample return mission. REXIS complements the scientific investigations of other OSIRIS-REx instruments by determining the relative abundances of key elements present on the asteroid’s surface by measuring the X-ray fluorescence spectrum (stimulated by the natural solar X-ray flux) over the range of energies 0.5 to 7 keV. REXIS consists of two components: a main imaging spectrometer with a coded aperture mask and a separate solar X-ray monitor to account for the Sun’s variability. In addition to element abundance ratios (relative to Si) pinpointing the asteroid’s most likely meteorite association, REXIS also maps elemental abundance variability across the asteroid’s surface using the asteroid’s rotation as well as the spacecraft’s orbital motion. Image reconstruction at the highest resolution is facilitated by the coded aperture mask. Through this operation, REXIS will be the first application of X-ray coded aperture imaging to planetary surface mapping, making this student-built instrument a pathfinder toward future planetary exploration. To date, 60 students at the undergraduate and graduate levels have been involved with the REXIS project, with the hands-on experience translating to a dozen Master’s and Ph.D. theses and other student publications.     

Changes in the amino acid code.

The genetic code is characterized by a pattern arising from "wobble-pairing" between codons and anticodons, so that one nucleotide in the first anticodon position can pair with more than one nucleotide in the third position of a codon. Earlier codes may have existed in which there were fewer anticodons than at present, so that these earlier codes contained fewer amino acids. The universal code was formerly thought to be the only currently existing code used by terrestrial species. It is now known that differences exist from the universal code in mitochondrial coding systems, and also that mitochondrial systems differ from each other. These findings lend support to the proposal that archetypal codes preceded the present universal code. Such archetypal codes may have had some resemblances to mitochondrial codes.     

模糊变分原理在求解结构固有频率中的应用

在处理含模糊参数的结构固有频率问题时,现有的方法局限于先将模糊参数转化为区间数求解,再由区间解构造出相应的模糊解.由于现有方法计算量较大,所以提出了基于模糊变分原理的模糊里兹法和模糊有限元法.通过在瑞利商变分中直接引入模糊参数,得到了结构固有频率问题的模糊变分原理.作为模糊变分原理的应用,推导了模糊里兹法和模糊有限元法.这两种方法都可以直接得到问题的模糊解,与传统的区间解法相比,提高了计算效率.算例表明,这两种方法不但具有较高的计算精度,而且可以很大程度上减少计算量.     

The image/poetry education and public outreach program

Education and public outreach are viewed by NASA as significant undertakings for all of its space missions. The IMAGE satellite is one of the first missions to explicitly include `E&PO in its original proposal to NASA in 1996. We will discuss what IMAGE has accomplished in this area to date, and what new activities it will conduct following a successful launch.     

运载火箭测发控网络设计

运载火箭测试发射控制系统对数据处理能力、数据通信能力的要求越来越高。本文采用最新的网络通信技术,结合CZ-3A运载火箭测发控网络的实际设计需求和设计原则,概要介绍了运载火箭测发控网络的特点,着重从测发控网络的拓扑结构、双网卡捆绑技术、静态路由技术等五方面详细阐述了测发控网络的设计,最后通过测发控网络的功能测试验证了该设计的可靠性和先进性。     

基于联邦滤波的异质异步多传感器组合导航算法

针对多源组合导航中各导航子系统数据更新频率不一致导致滤波器量测信息非等间隔,以及动力学模型受到干扰量测信息异常的问题,提出一种基于多尺度模型的自适应组合导航信息融合算法.利用不同尺度上的观测信息在各尺度上进行Kalman滤波,并经过融合最终获得基于全局的状态估计值.且以飞行器为应用对象,设计了适用于飞行器的惯导/卫星/...