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| 3. |
- Kaya, Sarp, et al.
(författare)
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Highly Compressed Two-Dimensional Form of Water at Ambient Conditions
- 2013
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- The structure of thin-film water on a BaF2(111) surface under ambient conditions was studied using x-ray absorption spectroscopy from ambient to supercooled temperatures at relative humidity up to 95%. No hexagonal ice-like structure was observed in spite of the expected templating effect of the lattice-matched (111) surface. The oxygen K-edge x-ray absorption spectrum of liquid thin-film water on BaF2 exhibits, at all temperatures, a strong resemblance to that of high-density phases for which the observed spectroscopic features correlate linearly with the density. Surprisingly, the highly compressed, high-density thin-film liquid water is found to be stable from ambient (300 K) to supercooled (259 K) temperatures, although a lower-density liquid would be expected at supercooled conditions. Molecular dynamics simulations indicate that the first layer water on BaF2(111) is indeed in a unique local structure that resembles high-density water, with a strongly collapsed second coordination shell.
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| 4. |
- Ketteler, Guido, et al.
(författare)
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The nature of water nucleation sites on TiO2(110) surfaces revealed by ambient pressure X-ray photoelectron spectroscopy
- 2007
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 111:23, s. 8278-8282
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Tidskriftsartikel (refereegranskat)abstract
- X-ray photoelectron spectroscopy at ambient conditions of pressure (up to 1.5 Torr) and temperature (265 K < T < 800 K) was used to study the adsorption of water on rutile TiO2(110) under conditions of thermodynamic equilibrium. It was found that OH groups in bridging positions, normally present in small amounts due to residual O-vacancies, act as nucleation sites for subsequent water adsorption. The adsorption enthalpy of water binding to these sites is similar to 70 kJ/mol, much stronger than that in the bulk liquid (45 kJ/mol). A model is proposed that relates the structure of the oxide surface to its hydrophilic character.
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| 5. |
- Shibata, Naotaka, et al.
(författare)
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Channel-Gain-Based Transmission Scheduling for Cooperative Relaying
- 2010
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Ingår i: IEICE transactions on communications. - 0916-8516 .- 1745-1345. ; E93B:3, s. 776-779
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Tidskriftsartikel (refereegranskat)abstract
- A cooperative relaying. system with transmission scheduling is investigated Cooperative relaying, is composed of multiple links because the source;ends the data to more than one receiver, and the destination receive; multiple data transmitted by more than one transmitter Therefore. tithe source can transmit the data when the channel gains of the links are high, it is not clear which channel gains should he high in order to achieve high spectral efficiency In the present letter. the spectral efficiency of a cooperative relay me system is theoretically derived under the assumption that the source transmits the data only when the channel gains of links are above certain threshold values Numerical results reveal that a high spectral efficiency can be achieved by assuring a high channel gain for the link with the highest average received power among links to the destination.
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- Starr, David E., et al.
(författare)
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NO2 Adsorption on Ag(100) Supported MgO(100) Thin Films : Controlling the Adsorption State with Film Thickness
- 2009
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:17, s. 7355-7363
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Tidskriftsartikel (refereegranskat)abstract
- Using photoemission and X-ray absorption spectroscopy, we compare the adsorption properties of NO2 at 300 K on MgO(100)/Ag(100) films with thicknesses varying from 2 to 8 ML and NO2 exposures ranging from 0 L to over 25 000 L. We find that NO2 is stable on 2 ML MgO(100) films, where it is the most abundant adsorbate on the surface (similar to 0.35 ML) for exposures up to at least similar to 25 000 L. At high exposures, NO3 also forms on the surface of 2 ML thick films but is a minority species. In contrast, films thicker than similar to 5 ML show conversion to NO3 beginning already at low exposures. At high exposure to NO2, NO3 is the only species present on the surface. Shifts to lower binding energy of the O 1s spectra with adsorbed species indicate that the NO2 adsorbed on the thin MgO(100) films is likely negatively charged and forms NO2-. A more gradual binding energy shift is observed on thicker films and is likely associated with the slower formation of NO3- Measurements on MgO(1.00) films of various thicknesses indicate that for films thicker than 5 ML, the NO2 adsorption properties are similar and most likely correspond to surfaces of bulk MgO(100). We discuss potential mechanisms for NO2 charging and stabilization on the thin MgO(100) films in the context of recent literature.
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| 7. |
- Teshima, Kunihiko, et al.
(författare)
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Capacity Analysis of Cooperative Relaying Networks with Adaptive Relaying Scheme Selection
- 2009
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Ingår i: IEICE transactions on communications. - 0916-8516 .- 1745-1345. ; E92B:12, s. 3744-3752
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Tidskriftsartikel (refereegranskat)abstract
- In the present paper, the performance of cooperative relaying networks with adaptive relaying scheme selection is analyzed. Cooperative relaying is a new technique to achieve spatial diversity gain by using neighboring stations. However, when multiple stations transmit simultaneously, the number of interference signals increases. Therefore, the introduction of cooperative relaying in radio communication systems does not always increase the network capacity due to the co-channel interference. Therefore, in order to achieve high spectral efficiency, it is necessary to select cooperative relaying or non-cooperative relaying adaptively. Assuming both centralized and decentralized adaptive controls, the spectrum efficiency is evaluated. The performance under decentralized control is evaluated using a game-theoretic approach. Simulation results show that the introduction of cooperative relaying with centralized control always increases the spectral efficiency. On the other hand, Simulation results also show that, when each source selects a relaying scheme independently and selfishly to maximize its own spectral efficiency, the introduction of the co-operative relaying may reduce the spectral efficiency due to the increase in the number of interference signals.
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| 9. |
- Yi, Chuixiang, et al.
(författare)
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Climate control of terrestrial carbon exchange across biomes and continents
- 2010
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2 exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid-and high-latitudes, (2) a strong function of dryness at mid-and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45 degrees N). The sensitivity of NEE to mean annual temperature breaks down at similar to 16 degrees C (a threshold value of mean annual temperature), above which no further increase of CO2 uptake with temperature was observed and dryness influence overrules temperature influence.
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