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- Lappalainen, H. K., et al.
(författare)
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Overview: Recent advances in the understanding of the northern Eurasian environments and of the urban air quality in China - a Pan-Eurasian Experiment (PEEX) programme perspective
- 2022
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 22:7, s. 4413-4469
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Tidskriftsartikel (refereegranskat)abstract
- The Pan-Eurasian Experiment (PEEX) Science Plan, released in 2015, addressed a need for a holistic system understanding and outlined the most urgent research needs for the rapidly changing Arctic-boreal region. Air quality in China, together with the long-range transport of atmospheric pollutants, was also indicated as one of the most crucial topics of the research agenda. These two geographical regions, the northern Eurasian Arctic-boreal region and China, especially the megacities in China, were identified as a "PEEX region". It is also important to recognize that the PEEX geographical region is an area where science-based policy actions would have significant impacts on the global climate. This paper summarizes results obtained during the last 5 years in the northern Eurasian region, together with recent observations of the air quality in the urban environments in China, in the context of the PEEX programme. The main regions of interest are the Russian Arctic, northern Eurasian boreal forests (Siberia) and peatlands, and the megacities in China. We frame our analysis against research themes introduced in the PEEX Science Plan in 2015. We summarize recent progress towards an enhanced holistic understanding of the land-atmosphere-ocean systems feedbacks. We conclude that although the scientific knowledge in these regions has increased, the new results are in many cases insufficient, and there are still gaps in our understanding of large-scale climate-Earth surface interactions and feedbacks. This arises from limitations in research infrastructures, especially the lack of coordinated, continuous and comprehensive in situ observations of the study region as well as integrative data analyses, hindering a comprehensive system analysis. The fast-changing environment and ecosystem changes driven by climate change, socio-economic activities like the China Silk Road Initiative, and the global trends like urbanization further complicate such analyses. We recognize new topics with an increasing importance in the near future, especially "the enhancing biological sequestration capacity of greenhouse gases into forests and soils to mitigate climate change" and the "socio-economic development to tackle air quality issues".
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| 2. |
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| 3. |
- Lioubtchenko, Dmitri V., et al.
(författare)
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W-band phase shifter based on optimized optically controlled carbon nanotube layer
- 2017
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Ingår i: 2017 IEEE MTT-S International Microwave Symposium (IMS). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509063604 ; , s. 1188-1191
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Konferensbidrag (refereegranskat)abstract
- Phase shifting in a dielectric rod waveguide (DRW), loaded with carbon nanotube (CNT) layers of different thickness, was studied experimentally under light illumination in the frequency range of 75-110 GHz. The dependence of efficiency of the phase shifting, in terms of phase shift per light intensity and millimeter wave attenuation, on the optical transparency of the CNT-layer is investigated in this paper. The best result, a phase shifter of 0-15° with less than 0.1 dB additional signal loss in the W-band was achieved for a 95% transparent CNT layer at 23 mW/mm2 light intensity of a tungsten halogen lamp (main radiation spectrum is 550-680 nm). The overall insertion loss of the phase shifter including two DRW tapering sections serving as transitions to rectangular waveguides are 3 to 5 dB in the W-band, about 2 dB is attributed to the CNT DRW section. This comprises, for the first time, an optically-controlled CNT-based DRW phase shifter with phase shift and insertion loss levels suitable for practical applications.
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| 5. |
- Chicherin, Dmitry, et al.
(författare)
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Micro-fabricated High-impedance Surface for Millimeter Wave Beam Steering Applications
- 2008
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Ingår i: 33RD INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER AND TERAHERTZ WAVES. - NEW YORK : IEEE. - 9781424421190 ; , s. 574-576
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Konferensbidrag (refereegranskat)abstract
- A multi-layer high-impedance surface has been micro-fabricated and measured in W band. It consists of an array of capacitors placed on a dielectric substrate with a ground plane. Reconfigurability of the effective surface impedance of this structure can be enabled by applying control voltage to the tunable capacitors. Tunable impedance surfaces can be used in phase shifters for a phased array antenna, and directly as a smart beam steering surface.
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| 6. |
- Chicherini, D., et al.
(författare)
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Analog type millimeter wave phase shifters based on MEMS tunable high-impedance surface in rectangular metal waveguide
- 2010
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Ingår i: 2010 IEEE MTT-S International Microwave Symposium. - : IEEE. - 9781424460571 ; , s. 61-64
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Konferensbidrag (refereegranskat)abstract
- Possibility of compact low loss analog type millimeter wave phase shifter was demonstrated. The phase shifter is controlled by a MEMS tunable high-impedance surface placed, e.g., as a backshort or as sidewall inclusions of a rectangular metal waveguide. Reflection type phase shifter can provide differential analog phase shift from O to up to 240. Reliable and tunable MEMS based high-impedance surface has been demonstrated for the first time. The insertion loss of the fabricated MEMS tunable high-impedance surface varies from 0.7 dB to a maximum of3.5 dB (at a resonance frequency), which is a dramatic improvement over our previous non-tunable prototype.
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| 7. |
- Frisk, U., et al.
(författare)
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The Odin satellite - I. Radiometer design and test
- 2003
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 402:3, s. L27-L34
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Tidskriftsartikel (refereegranskat)abstract
- The Sub-millimetre and Millimetre Radiometer (SMR) is the main instrument on the Swedish, Canadian, Finnish and French spacecraft Odin. It consists of a 1.1 metre diameter telescope with four tuneable heterodyne receivers covering the ranges 486-504 GHz and 541-581 GHz, and one fixed at 118.75 GHz together with backends that provide spectral resolution from 150 kHz to 1 MHz. This Letter describes the Odin radiometer, its operation and performance with the data processing and calibration described in Paper II.
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