童话之城——哥本哈根

哥本哈根位于波罗的海和北海之间的厄勒海峡西岸,集聚着充满童话气质的古堡与皇宫、乡村与庄园。不论是沉淀了古老历史的还是延续着皇族传奇的各类建筑,都鳞次栉比地坐落在这里。哥本哈根融合了古典与现代的艺术气息,阿肯艺术中心、路易斯安娜博物馆、国家博物馆、丹麦国家美术馆等众多艺术博物馆各领风骚。富有皇族气质的哥本哈根,贯穿着全年度的各种主题节庆,令狂欢从夏季一直延续到冬季。最著名的莫过于哥本哈根国际爵士音乐节,在每年7月将持续整整10天,着实是不容错过的年度盛会!     

Bioelectrochemical degradation of urea at platinized boron doped diamond electrodes for bioregenerative systems

The recovery of potable water from space mission wastewater is critical for the life support and environmental health of crew members in long-term missions. NASA estimates reveal that at manned space missions 1.91 kg/person day of urine is produced, with urea and various salts as its main components. In this research we explore the utilization of urease (EC 3.5.1.5, 15,000 U/g) along with a platinized boron doped diamond electrode (Pt-BDD) to degrade urea. Urea is directly degraded to nitrogen by the in situ utilization of the reaction products as a strategy to increase the amount of clean water in future space expeditions. The biochemical reaction of urease produces ammonia and carbon dioxide from urea. Thereafter, ammonia is electrooxidized at the interface of the Pt-BDD producing molecular nitrogen. The herein presented system has been proven to have 20% urea conversion efficiency. This research has potential applications for future long-term space missions since the reaction byproducts could be used for a biomass subsystem (in situ resource recovery), while generating electricity from the same process.     

The Evolving Sigmoid: Evidence for Magnetic Flux Ropes in the Corona Before, During, and After CMES

It is generally accepted that the energy that drives coronal mass ejections (CMEs) is magnetic in origin. Sheared and twisted coronal fields can store free magnetic energy which ultimately is released in the CME. We explore the possibility of the specific magnetic configuration of a magnetic flux rope of field lines that twist about an axial field line. The flux rope model predicts coronal observables, including heating along forward or inverse S-shaped, or sigmoid, topological surfaces. Therefore, studying the observed evolution of such sigmoids prior to, during, and after the CME gives us crucial insight into the physics of coronal storage and release of magnetic energy. In particular, we consider (1) soft-X-ray sigmoids, both transient and persistent; (2) The formation of a current sheet and cusp-shaped post-flare loops below the CME; (3) Reappearance of sigmoids after CMEs; (4) Partially erupting filaments; (5) Magnetic cloud observations of filament material.     

中层大气受迫Rossby波包的非线性相互作用：Ⅱ.数值计算

本文对中层大气受迫Ｒｏｓｓｂｙ波包的非线性三波相互作用问题作了进一步的数值分析，结果表明，三个波包随时间演化达到的平衡态与文献［１］的理论结果完全一致，而且仅当系统中只有中等波长波包不受外源强迫时，系统运动有可能出现两个稳定平衡态，在一定外源强度范围内，平衡态会产生尖点突变，平衡态随外源的变化有滞后分岔的特征，系统运动最终达到的平衡态不仅与外源强度的变化方式有关，而且依赖于初始状态。     

不同介质下高速铣削钛合金时切屑的变形研究

开展了不同介质下钛合金切屑变形的高速铣削试验研究,分析比较了不同介质、不同铣削速度对切屑宏观和微观形貌的影响及其原因,得出了干铣削、空气油雾和氮气油雾介质下切屑变形的各自特点以及切屑变形随速度而变化的规律。     

浮动零点法及其在声表面波（SAW）传感器中的应用

温度是影响传感器精度的重要因素。本文介绍了一种新的温度误差校正方法，即浮动零点法。该方法以差动原理和浮动坐标为基础，是实现温度校正较为理想的方法。     

航改燃气轮机改用柴油的适应性试验研究

采用试验手段,完成了QD128航改燃气轮机燃用轻柴油燃料的适应性研究。结果表明:喷嘴雾化锥角对燃料物性改变不敏感,基本稳定;流量受粘度、密度共同影响,设计工况流量减小约3%;粘度增加导致雾化粒度增大约8μm;改用柴油后点火性能依旧良好,贫油点火范围宽;进气温度升高,贫油点火极限略为增加。以上结果为QD128航改燃气轮机柴油燃料机型设计提供了可靠的技术依据。     

基于虚拟样机的起落架收放系统仿真

通过建立某飞机起落架机构动力学模型和液压及控制系统模型,构建了完整的起落架收放系统的虚拟样机。基于虚拟样机,进行了起落架收放系统仿真分析,并与试验结果进行了对比。结果表明:仿真结果与试验结果基本一致,仿真模型可以用于起落架系统收放时间的模拟。     

Linux路由实现机制分析

通过对Linux2.4.20版内核路由模块代码的分析和研究,详尽地阐述了Linux路由机制的实现思想和技术特点,对于更好地使用Linux的路由功能和在Linux路由上进行二次开发都具有实际的指导意义。     

A Class of TVD Type Combined Numerical Scheme for MHD Equations With a Survey About Numerical Methods in Solar Wind Simulations

It has been believed that three-dimensional, numerical, magnetohydrodynamic (MHD) modelling must play a crucial role in a seamless forecasting system. This system refers to space weather originating on the sun; propagation of disturbances through the solar wind and interplanetary magnetic field (IMF), and thence, transmission into the magnetosphere, ionosphere, and thermosphere. This role comes as no surprise to numerical modelers that participate in the numerical modelling of atmospheric environments as well as the meteorological conditions at Earth. Space scientists have paid great attention to operational numerical space weather prediction models. To this purpose practical progress has been made in the past years. Here first is reviewed the progress of the numerical methods in solar wind modelling. Then, based on our discussion, a new numerical scheme of total variation diminishing (TVD) type for magnetohydrodynamic equations in spherical coordinates is proposed by taking into account convergence, stability and resolution. This new MHD model is established by solving the fluid equations of MHD system with a modified Lax-Friedrichs scheme and the magnetic induction equations with MacCormack II scheme for the purpose of developing a combined scheme of quick convergence as well as of TVD property. To verify the validation of the scheme, the propagation of one-dimensional MHD fast and slow shock problem is discussed with the numerical results conforming to the existing results obtained by the piece-wise parabolic method (PPM). Finally, some conclusions are made. This revised version was published online in August 2006 with corrections to the Cover Date.