Z-Spec: A MM-Wave Spectrometer For Measuring Redshifts Of Submillimeter Galaxies

We are building a background-limited, broadband millimeter-wave spectrometer (Z-Spec) for observations of CO rotational transitions from high-redshift dusty galaxies. The large instantaneous bandwidth (195 to 310 GHz) will enable redshifts of dust obscured galaxies to be unambiguously measured. Z-Spec uses a waveguide-coupled grating architecture in which the light propagation is confined within a parallel-plate waveguide. The grating is extremely compact compared to a classical free-space system. An array of silicon nitride bolometers cooled to 100 mK will provide background-limited performance. Z-Spec serves as a technology demonstration for a future space-borne far-infrared grating spectrometer

WaFIRS: a waveguide far-IR spectrometer: enabling spectroscopy of high-z galaxies in the far-IR and submillimeter

The discovery of galaxies beyond z~1 which emit the bulk of their luminosity at long wavelengths has demonstrated the need for high-sensitivity, broad-band spectroscopy in the far-IR/submm/mm bands. Because many of these sources are not detectable in the optical, long-wavelength spectroscopy is key to measuring their redshifts and ISM conditions. The continuum source list will increase in the coming decade with new ground-based instruments (SCUBA2, Bolocam, MAMBO), and the surveys of HSO and SIRTF. Yet the planned spectroscopic capabilities lag behind, in part due to the difficulty in scaling existing IR spectrograph designs to longer wavelengths. To overcome these limitations, we are developing WaFIRS, a novel concept for long-wavelength spectroscopy which utilizes a parallel-plate waveguide and a curved diffraction grating. WaFIRS provides the large (~60%) instantaneous bandwidth and high throughput of a conventional grating system, but offers a dramatic reduction in volume and mass. WaFIRS requires no space overheads for extra optical elements beyond the diffraction grating itself, and is two-dimensional because the propagation is confined between two parallel plates. Thus several modules could be stacked to multiplex either spatially or in different frequency bands. The size and mass savings provide opportunities for spectroscopy from space-borne observatories which would be impractical with traditional spectrographs. With background-limited detectors and a cooled 3.5 m telescope, the line sensitivity would be comparable to that of ALMA, with instantaneous broad-band coverage. We present the spectrometer concept, performance verification with a mm-wave prototype, and our progress toward a cryogenic astronomical instrument

Dispersion of traffic exhausts in urban street canyons with tree plantings : experimental and numerical investigations

Wind tunnel experiments and numerical computations have been performed in order to investigate the influence of avenuelike tree plantings on the dispersion of traffic exhaust in an urban street canyon. Reduced natural ventilation and enhanced pollutant concentrations have been found in the presence of trees. A comparison of experimental and numerical results shows qualitative good, but quantitative rather poor agreement. In the numerical computations, flow velocities are underestimated and pollutant concentrations are overestimated

Wind erosion

No abstract

Renaturing Cities: Green and Blue Urban Spaces as Paradigms of Urban Planning

Green in cities does not only play an aesthetic role but also contributes greatly to making the urban environment more sustainable in all senses of the term: environmental, energy-wise, economic and social. The purpose of this chapter is to tackle the issue of green in cities by highlighting the connections that exist between having a nature base or renaturing of cities and sustainable planning, stimulating the necessary in-depth analysis of a topic that must constitute an information resource for those who deal with green planning. The chapter, after an introduction that highlights the need to seek a new alliance between urban spaces and natural spaces, deals with the issue of urban infrastructure, highlighting its potential. The final part of the chapter deals with the issue of urban heat islands providing some improvement strategies