Impact of atmospheric clutter on Doppler-limited gas sensors in the submillimeter/terahertz

It is well known that clutter (spectral interference) from atmospheric constituents can be a severe limit for spectroscopic point sensors, especially where high sensitivity and specificity are required. In this paper, we will show for submillimeter/terahertz (SMM/THz) sensors that use cw electronic techniques the clutter limit for the detection of common target gases with absolute specificity (probability of false alarm ? 10?1?) is in the ppt (1 part in 1012) range or lower. This is because the most abundant atmospheric gases are either transparent to SMM/THz radiation (e.g., CO?) or have spectra that are very sparse relative to the 10? Doppler-limited resolution elements available (e.g., H?O). Moreover, the low clutter limit demonstrated for cw electronic systems in the SMM/THz is independent of system size and complexity.     

梁之歌

北地里,千宅万户的屋梁受尽风欺雪压犹自温柔地抱着一团小小的燕巢。这是最温情的守候。人世间,千秋万代的屋梁穷尽一生之力,默默擎起身下各异的居所。这是最无私的担当。可古往今来,自喻有情的世人皆赞梁间燕,梁     

散记（10）

原来以为,21世纪遥远,代表未来。进入21世纪的头几年,没什么特殊感觉。转眼十年过去,快。不留神,整个21世纪可能就这么稀里糊涂地滑过去。     

散记（11）

春节后,有几节设计理论课。长时间磨设计,新鲜一回,调剂调剂。学生们大概认为跟老头儿真没公共语言。我没问。中国学生,问了也不会告诉你。我喜欢小孩儿,愿意跟学生聊天。时间有限,上来就布置作业：选个亲眼见过的建筑作品,观察和观点是自己的,图片是自己拍的,如果引用他人成果要详细注明,按你们学校论文的标准格式,工作量不大,3000字,也不小,因为都得是自己的话。     

A review of the impact of the RingRing study for multifunctional motorway tunnels in the Netherlands and beyond

In the early 1990s, it became clear that tunnelling as Dutch engineers knew was about to change fundamentally. Local governments, pressure groups and individuals had become aware of the added value that underground space technology (tunnelling) could bring, giving rise to the next generation of multifunctional road and rail tunnel projects. This article reports on the outcome of a landmark study that focused on the new opportunities that multifunctional tunnels for motorways offer: RingRing. The RingRing study includes a concise state-of-the-art exploration of path-finding projects, delivers a solid methodology for dealing with the many design decisions during the conceptual phase of the multidisciplinary project, proposes a set of generic concepts that respond to the four key challenges faced by multifunctional tunnels, conducts two showcase design study projects, and provides an overall analysis of the applicability of multifunctional tunnels for integrating orbital motorways in large cities such as Amsterdam and Rotterdam. Eight years after the publication of the RingRing study, the first projects it identified are built. Others projects have not yet made it off the drawing board. This article looks back to assess what has been accomplished and draws lessons learned in order to be able to improve future projects.