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1. Optimum Antenna Characteristics for Maximally Harvesting Ambient RF Energy

Author

Constant M. A. Niamien

Subjects
Dipole antennas, directive antennas, isotropic antennas, energy harvesting, receiving antennas, Telecommunication, TK5101-6720
Abstract

This paper investigates the best antenna characteristics to harvest ambient RF waves maximally. The proposed approach analyzes and compares key design aspects, including multi-polarization, multi-port, multi-band, omnidirectional, quasi-isotropic, and non-quasi-isotropic pattern options, over the same antenna size defined by the enclosing sphere radius. First, the ideal isotropic and the Dirac-directive antennas are theoretically analyzed and compared within a general Gaussian channel to derive the most suitable design options. Then, several test antennas, covering the design options, are designed, fabricated, characterized, and compared within a full-wave antenna simulator under spherical incidences and polarizations. Further experiments in real ambient environments complete the tests. Two optimum antenna solutions emerge from the results: the quasi-isotropic antenna and the collocated LP-port diversity system with a power combiner. The crucial feature is optimizing antenna solutions for lower frequency bands with significant power densities that compensate for the available power ${\lambda }^{2}$ -factor.

Published
2022
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2. Unique-Solution Single-Sample Complex Dielectric Characterization Through Linear Phase Approximation

Author

Constant M. A. Niamien

Subjects
Dielectric constant, dielectric losses, transmission line measurements, Telecommunication, TK5101-6720
Abstract

This paper presents a transmission-only (TO) approach that solves the long-standing problem of transmission phase ambiguity. The approach considers a linear frequency-dependent phase approximation to derive the phase mode value analytically and uniquely based on three parameters: the first phase jump frequency, the start frequency, and the start phase value. This formulation leads to a unique propagation constant, easy-to-compute for low-band and wideband applications. In addition, the approach presents a non-iterative loss extraction method based on analytical formulation and curve-fitting. Beyond, the approach corrects standing waves’ effect, making it suitable for matched and mismatched lines without any initial guess of the material properties. Numerical and experimental validations confirm the proposed approach for weakly and highly dispersive microstrip samples, including low- and high-loss dielectrics.

Published
2022
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3. 2-D WFS Approach Through Field Transformation—Application to Performance Prediction in Standard Antenna Simulators

Author

Constant M. A. Niamien

Subjects
Antenna arrays, dipole antennas, electromagnetic propagation, wavefield synthesis, Telecommunication, TK5101-6720
Abstract

This paper presents a 2-D wavefield synthesis approach directly implementable in standard antenna simulation software. The approach uses a field transformation matrix and two array sets to design vertically and horizontally polarized wavefields, implemented with thin electric dipoles for their simple geometry. The synthesized wavefields positively correlate with numerical methods (FIT, FEM) obtained from full-wave simulations over various array sets (size, number, polarization, frequency). Synthesizing 2-D isotropic wavefields in both polarizations under an error vector magnitude (EVM) equal to or smaller than −30 dB is demonstrated over the largest test zone radius of $\lambda $ /10 with just three dipoles located at a minimum distance of $5\lambda $ far from the phase center. Application to a test antenna (folded dipole) anticipates the received power and MEG directly inside the antenna simulator in receiving mode. This valuable design option, not handled by most antenna simulators, helps optimize the antenna with the propagation medium characteristics during the design stage.

Published
2021
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4. Chemical Speciation of Copper in a Salt Marsh Estuary and Bioavailability to Thaumarchaeota

Author

Hannah Whitby, James T. Hollibaugh, and Constant M. G. van den Berg

Subjects
copper speciation, cathodic stripping voltammetry, humic substances, thiols, thiourea, organic ligands, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Abstract

The concentrations of dissolved copper (Cud), copper-binding ligands, thiourea-type thiols, and humic substances (HSCu) were measured in estuarine waters adjacent to Sapelo Island, Georgia, USA, on a monthly basis from April to December 2014. Here we present the seasonal cycle of copper speciation within the estuary and compare it to the development of an annually occurring bloom of Ammonia Oxidizing Archaea (AOA), which require copper for many enzymes. Two types of complexing ligands (L1 and L2) were found to dominate with mean complex stabilities (log KCuL′) of 14.5 and 12.8. Strong complexation resulted in lowering the concentration of free cupric ion (Cu2+) to femtomolar (fM) levels throughout the study and to sub-fM levels during the summer months. A Thaumarchaeota bloom during this period suggests that this organism manages to grow at very low Cu2+ concentrations. Correlation of the concentration of the L1 ligand class with a thiourea-type thiol and the L2 ligand class with HSCu provide an interesting dimension to the identity of the ligand classes. Due to the stronger complex stability, 82–99% of the copper was bound to L1. Thiourea-type thiols typically form Cu(I) species, which would suggest that up to ~90% copper could be present as Cu(I) in this region. In view of the very low concentration of free copper (pCu > 15 at the onset and during the bloom) and a reputedly high requirement for copper, it is likely that the Thaumarchaeota are able to access thiol-bound copper directly.

Published
2017
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5. Monitoring macroplastics in aquatic and terrestrial ecosystems: Expert survey reveals visual and drone-based census as most effective techniques

Author

Gallitelli, L., Girard, P., Andriolo, U., Liro, M., Suaria, G., Martin, C., Lusher, A.L., Hancke, K., Blettler, MCM, Garcia-Garin, O., Napper, I.E., Corbari, L., Cózar, A., Morales-Caselles, C., González-Fernández, D., Gasperi, J., Giarrizzo, T., Cesarini, G., De, K., Constant, M., Koutalakis, P., Gonçalves, G., Sharma, P., Gundogdu, S., Kumar, R., Garello, N.A., Camargo, A.L.G., Topouzelis, K., Galgani, F., Royer, S.J., Zaimes, G.N., Rotta, F., Lavender, S., Nava, V., Castro-Jiménez, J., Mani, T., Crosti, R., Azevedo-Santos, V.M., Bessa, F., Tramoy, R., Costa, M.F., Corbau, C., Montanari, A., Battisti, C., and Scalici, M.

Published
2024
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14. Observation of Quantum Interference in Molecular Charge Transport

Author

Guedon, Constant M., Valkenier, Hennie, Markussen, Troels, Thygesen, Kristian S., Hummelen, Jan C., and van der Molen, Sense Jan

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

As the dimensions of a conductor approach the nano-scale, quantum effects will begin to dominate its behavior. This entails the exciting possibility of controlling the conductance of a device by direct manipulation of the electron wave function. Such control has been most clearly demonstrated in mesoscopic semiconductor structures at low temperatures. Indeed, the Aharanov-Bohm effect, conductance quantization and universal conductance fluctuations are direct manifestations of the electron wave nature. However, an extension of this concept to more practical emperatures has not been achieved so far. As molecules are nano-scale objects with typical energy level spacings (~eV) much larger than the thermal energy at 300 K (~25 meV), they are natural candidates to enable such a break-through. Fascinating phenomena including giant magnetoresistance, Kondo effects and conductance switching, have previously been demonstrated at the molecular level. Here, we report direct evidence for destructive quantum interference in charge transport through two-terminal molecular junctions at room temperature. Furthermore, we show that the degree of interference can be controlled by simple chemical modifications of the molecule. Not only does this provide the experimental demonstration of a new phenomenon in quantum charge transport, it also opens the road for a new type of molecular devices based on chemical or electrostatic control of quantum interference.

Published
2011
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22. List of Contributors

Author

Abbas, B., primary, Abreu, A., additional, Adams, R., additional, Adolfsson-Erici, M., additional, Afonso, A., additional, Afonso-Olivares, C., additional, Agirbas, E., additional, Aguiló, J.M., additional, Airoldi, L., additional, Aksoy, H., additional, Albentosa, M., additional, Alcaro, L., additional, Aliani, S., additional, Al-Maslamani, I., additional, Alomar, C., additional, Altin, D., additional, Álvarez, E., additional, Amaral-Zettler, L.A., additional, Amato, E., additional, Anderson, A., additional, Andrady, A.L., additional, Andrius, G., additional, Angel, D., additional, Ariese, F., additional, Arp, H.P., additional, Asensio, M., additional, Assidqi, K., additional, Avio, C.G., additional, Aytan, U., additional, Bahri, T., additional, Baini, M., additional, Bakir, A., additional, Ball, H., additional, Baranyi, C., additional, Barboza, L.G.A., additional, Barg, U., additional, Bargelloni, L., additional, Barras, H., additional, Barrera, C., additional, Barria, P., additional, Barrows, A., additional, Barth, A., additional, Batel, A., additional, Baztan, J., additional, Baztan, P., additional, Beiras, R., additional, Benedetti, M., additional, Berber, A.A., additional, Berber, N., additional, Bergmann, M., additional, Berlino, M., additional, Berrow, S., additional, Bessa, F., additional, Besseling, E., additional, Beyer, B., additional, Binaglia, M., additional, Bizjak, T., additional, Bjorndal, K.A., additional, Blust, R., additional, Boertien, M., additional, Bolten, A.B., additional, Booth, A.M., additional, Bounoua, B., additional, Bourseau, P., additional, Brahimi, N., additional, Bramini, M., additional, Brennholt, N., additional, Breuninger, E., additional, Bried, J., additional, Broderick, A., additional, Broglio, E., additional, Browne, M.A., additional, Bruzaud, S., additional, Buceta, J., additional, Buchinger, S., additional, Budimir, S., additional, Budzin-ski, H., additional, Butter, E., additional, Cachot, J., additional, Caetano, M., additional, Callaghan, A., additional, Camedda, A., additional, Capella, S., additional, Cardelli, L., additional, Carpentieri, S., additional, Carrasco, A., additional, Carriço, R., additional, Caruso, A., additional, Cassone, A.-L., additional, Castillo, A., additional, Castro, R.O., additional, Catarino, A.I., additional, Cazenave, P.W., additional, Çelik, İ., additional, Cerralbo, P., additional, César, G., additional, Chouinard, O., additional, Chubarenko, I., additional, Chubarenko, I.P., additional, Cicero, A.M., additional, Clarindo, G., additional, Clarke, B., additional, Clérandeau, C., additional, Clüsener-Godt, M., additional, Codina-García, M., additional, Cole, M., additional, Collard, F., additional, Collignon, A., additional, Collins, T., additional, Compa, M., additional, Conan, P., additional, Constant, M., additional, Cordier, M., additional, Courtene-Jones, W., additional, Cousin, X., additional, Covelo, P., additional, Cózar, A., additional, Crichton, E., additional, Crispi, O., additional, Cronin, M., additional, Croot, P.L., additional, Cruz, M.J., additional, d’Errico, G., additional, Dâmaso, C., additional, Das, K., additional, de Alencastro, L.F., additional, de Araujo, F.V., additional, de Boer, J.F., additional, de Lucia, G.A., additional, Debeljak, P., additional, Dehaut, A., additional, Deudero, S., additional, Devrieses, L., additional, Di Vito, S., additional, Díaz, A., additional, Donohue, J., additional, Doumenq, P., additional, Doyle, T.K., additional, Dris, R., additional, Druon, J.-N., additional, Duarte, C.M., additional, Duflos, G., additional, Dumontier, M., additional, Duncan, E., additional, Dussud, C., additional, Eckerlebe, A., additional, Egelkraut-Holtus, M., additional, Eidsvoll, D.P., additional, Ek, C., additional, Elena, S., additional, Elineau, A., additional, Enevoldsen, H., additional, Eppe, G., additional, Eriksen, M., additional, Ernsteins, R., additional, Espino, M., additional, Estévez-Calvar, N., additional, Ewins, C., additional, Fabre, P., additional, Faimali, M., additional, Fattorini, D., additional, Faure, F., additional, Ferrando, S., additional, Ferreira, J.C., additional, Ferreira-da-Costa, M., additional, Fileman, E., additional, Fischer, M., additional, Fortunato, A.B., additional, Fossi, M.C., additional, Foulon, V., additional, Frank, A., additional, Frenzel, M., additional, Frère, L., additional, Frias, J.P.G.L., additional, Frick, H., additional, Froneman, P.W., additional, Gabet, V.M., additional, Gabrielsen, G.W., additional, Gago, J., additional, Gajst, T., additional, Galgani, F., additional, Gallinari, M., additional, Galloway, T.S., additional, Gamarro, E.G., additional, Gambardella, C., additional, Garaventa, F., additional, Garcia, S., additional, Garrabou, J., additional, Garrido, P., additional, Gary, S.F., additional, Gasperi, J., additional, Gaze, W., additional, Geertz, T., additional, Gelado-Caballero, M.D., additional, George, M., additional, Gercken, J., additional, Gerdts, G., additional, Ghiglione, J.-F., additional, Gies, E., additional, Gilbert, B., additional, Giménez, L., additional, Glassom, D., additional, Glockzin, M., additional, Godley, B., additional, Goede, K., additional, Goksøyr, A., additional, Gómez, M., additional, Gómez-Parra, A., additional, González-Marco, D., additional, González-Solís, J., additional, Gorbi, S., additional, Gorokhova, E., additional, Gorsky, G., additional, Gosch, M., additional, Grose, J., additional, Guebitz, G.M., additional, Guedes-Alonso, R., additional, Guijarro, B., additional, Guilhermino, L., additional, Gundry, T., additional, Gutow, L., additional, Haave, M., additional, Haeckel, M., additional, Haernvall, K., additional, Hajbane, S., additional, Hamann, M., additional, Hämer, J., additional, Hamm, T., additional, Hansen, B.H., additional, Hardesty, B.D., additional, Harth, B., additional, Hartikainen, S., additional, Hassellöv, M., additional, Hatzky, S., additional, Healy, M.G., additional, Hégaret, H., additional, Henry, T.B., additional, Hermabessiere, L., additional, Hernández-Brito, J.J., additional, Hernandez-Gonzalez, A., additional, Hernandez-Milian, G., additional, Hernd, G., additional, Herrera, A., additional, Herring, C., additional, Herzke, D., additional, Heussner, S., additional, Hidalgo-Ruz, V., additional, Himber, C., additional, Holland, M., additional, Hong, N.-H., additional, Horton, A.A., additional, Horvat, P., additional, Huck, T., additional, Huhn, M., additional, Huvet, A., additional, Iglesias, M., additional, Igor, C., additional, Isachenko, I.A., additional, Ivar do Sul, J-A., additional, Jahnke, A., additional, Janis, B., additional, Janis, K., additional, Janis, U., additional, Jemec, A., additional, Jiménez, J.C., additional, Johnsen, H., additional, Jorgensen, B., additional, Jørgensen, J.H., additional, Jörundsdóttir, H., additional, Jung, Y.-J., additional, Kedzierski, M., additional, Keiter, S., additional, Kershaw, P., additional, Kerhervé, P., additional, Kesy, K., additional, Khan, F., additional, Khatmullina, L.I., additional, Kirby, J., additional, Kiriakoulakis, K., additional, Klein, R., additional, Klunderud, T., additional, Knudsen, C.M.H., additional, Knudsen, T.B., additional, Kochleus, C., additional, Koelmans, A.A., additional, Kögel, T., additional, Koistinen, A., additional, Kopke, K., additional, Korez, Š., additional, Kowalski, N., additional, Kreikemeyer, B., additional, Kroon, F., additional, Krumpen, T., additional, Krzan, A., additional, Kržan, A., additional, Labrenz, M., additional, Lacroix, C., additional, Ladirat, L., additional, Laforsch, C., additional, Lagarde, F., additional, Lahive, E., additional, Lambert, C., additional, Lapucci, C., additional, Lattin, G., additional, Law, K.L., additional, Le Roux, F., additional, Le Souef, K., additional, Le Tilly, V., additional, Lebreton, L., additional, Leemans, E., additional, Lehtiniemi, M., additional, Lenz, M., additional, Leskinen, J., additional, Leslie, H., additional, Leslie, H.A., additional, Levasseur, C., additional, Lewis, C., additional, Licandro, P., additional, Lind, K., additional, Lindeque, P., additional, Lindeque, P.K., additional, Lips, I., additional, Liria, A., additional, Liria-Loza, A., additional, Llinás, O., additional, Loiselle, S.A., additional, Long, M., additional, Lorenz, C., additional, Lorenzo, S.M., additional, Loubar, K., additional, Luna-Jorquera, G., additional, Lusher, A.L., additional, Macchia, V., additional, MacGabban, S., additional, Mackay, K., additional, MacLeod, M., additional, Maes, T., additional, Magaletti, E., additional, Maggiore, A., additional, Magnusson, K., additional, Mahon, A.M., additional, Makorič, P., additional, Mallow, O., additional, Marques, J., additional, Marsili, L., additional, Martí, E., additional, Martignac, M., additional, Martin, J., additional, Martínez, I., additional, Martínez, J., additional, Martinez-Gil, M., additional, Martins, H.R., additional, Matiddi, M., additional, Maximenko, N., additional, Mazlum, R., additional, Mcadam, R., additional, Mcknight, L., additional, McNeal, A.W., additional, Measures, J., additional, Mederos, M.S., additional, Mendoza, J., additional, Meyer, M.S., additional, Miguelez, A., additional, Milan, M., additional, Militão, T., additional, Miller, R.Z., additional, Mino-Vercellio-Verollet, M., additional, Mir, G., additional, Miranda-Urbina, D., additional, Misurale, F., additional, Montesdeoca-Esponda, S., additional, Mora, J., additional, Morgana, S., additional, Moriceau, B., additional, Morin, B., additional, Morley, A., additional, Morrison, L., additional, Murphy, F., additional, Naidoo, T., additional, Näkki, P., additional, Napper, I.E., additional, Narayanaswamy, B.E., additional, Nash, R., additional, Negri, A., additional, Nel, H.A., additional, Nerheim, M.S., additional, Nerland, I.L., additional, Neto, J., additional, Neves, V., additional, Nies, H., additional, Noel, M., additional, Nor, N.H.M., additional, Noren, F., additional, O’ Connell, B., additional, O’ Connor, I., additional, Obbard, J.P., additional, Oberbeckmann, S., additional, Obispo, R., additional, Officer, R., additional, Ogonowski, M., additional, Orbea, A., additional, Ortlieb, M., additional, Osborn, A.M., additional, Ostiategui-Francia, P., additional, Packard, T., additional, Pahl, S., additional, Palatinus, A., additional, Palmqvist, A., additional, Pannetier, P., additional, Panti, C., additional, Parmentier, E., additional, Pasanen, P., additional, Patarnello, T., additional, Pattiaratchi, C., additional, Pauletto, M., additional, Paulus, M., additional, Pavlekovsky, K., additional, Pedersen, H.B., additional, Pedrotti, M.-L., additional, Peeken, I., additional, Peeters, D., additional, Peeters, E., additional, Pellegrini, D., additional, Perales, J.A., additional, Perez, E., additional, Perz, V., additional, Petit, S., additional, Pflieger, M., additional, Pham, C.K., additional, Piazza, V., additional, Pinto, M., additional, Planells, O., additional, Plaza, M., additional, Pompini, O., additional, Potthoff, A., additional, Prades, L., additional, Primpke, S., additional, Proietti, M., additional, Proskurowski, G., additional, Puig, C., additional, Pujo-Pay, M., additional, Pullerits, K., additional, Queirós, A.M., additional, Quinn, B., additional, Raimonds, E., additional, Ramis-Pujol, J., additional, Rascher-Friesenhausen, R., additional, Reardon, E., additional, Regoli, F., additional, Reichardt, A.M., additional, Reifferscheid, G., additional, Reilly, K., additional, Reisser, J., additional, Riba, I., additional, Ribitsch, D., additional, Rinnert, E., additional, Rios, N., additional, Rist, S.E., additional, Rivadeneira, M.M., additional, Rivière, G., additional, Robbens, J., additional, Robertson, C.J.R., additional, Rocher, V., additional, Rochman, C.M., additional, Rodrigues, M., additional, Rodriguez, Y., additional, Rodríguez, A., additional, Rodríguez, G., additional, Rodríguez, J.R.B., additional, Rodríguez, S., additional, Rodríguez, Y., additional, Rogan, E., additional, Rojo-Nieto, E., additional, Romeo, T., additional, Ross, P.S., additional, Roveta, A., additional, Rowland, S.J., additional, Ruckstuhl, N.A., additional, Ruiz-Fernández, A-C., additional, Ruiz-Orejón, L.F., additional, Runge, J., additional, Russell, M., additional, Saavedra, C., additional, Saborowski, R., additional, Sahin, B.E., additional, Sailley, S., additional, Sakaguchi-Söder, K., additional, Salaverria, I., additional, Sánchez-Arcilla, A., additional, Sánchez-Nieva, J., additional, Sanderson, W., additional, Santana-Rodríguez, J.J., additional, Santana-Viera, S., additional, Santos, M.B., additional, Santos, M.R., additional, Sanz, M.R., additional, Sardá, R., additional, Savelli, H., additional, Schoeneich-Argent, R., additional, Scholz-Böttcher, B.M., additional, Sciacca, F., additional, Scofield, R.P., additional, Setälä, O., additional, Selenius, M., additional, Sempere, R., additional, Senturk, Y., additional, Shashoua, Y., additional, Sherman, P., additional, Sick, C., additional, Siegel, D., additional, Sierra, J.P., additional, Silva, F., additional, Silvestri, C., additional, Sintija, G., additional, Sire, O., additional, Slat, B., additional, Smit, A., additional, Sobral, P., additional, Sorvari, J., additional, Sosa-Ferrera, Z., additional, Sotillo, M.G., additional, Soudant, P., additional, Speidel, L., additional, Spurgeon, D.J., additional, Steer, M.K., additional, Steindal, C.C., additional, Stifanese, R., additional, Štindlová, A., additional, Stuurman, L., additional, Suaria, G., additional, Suazo, C.G., additional, Sureda, A., additional, Surette, C., additional, Svendsen, C., additional, Syberg, K., additional, Tairova, Z., additional, Talvitie, J., additional, Tassin, B., additional, Tazerout, M., additional, Tekman, M.B., additional, ter Halle, A., additional, Thiel, M., additional, Thomas, K.V., additional, Thompson, R.C., additional, Tinkara, T., additional, Tirelli, V., additional, Tomassetti, P., additional, Toorman, E., additional, Toppe, J., additional, Tornambè, A., additional, Torres, R., additional, Torres-Padrón, M.E., additional, Underwood, A.J., additional, Urbina, M., additional, Usategui-Martín, A., additional, Usta, R., additional, Valdés, L., additional, Valente, A., additional, Valentina, T., additional, van Arkel, K., additional, Van Colen, C., additional, Van Der Hal, N., additional, van Franeker, J.A., additional, Van Herwerden, L., additional, Van Loosdrecht, M., additional, van Oyen, A., additional, Vandeperre, F., additional, Vanderlinden, J-P., additional, Vani, D., additional, Vasconcelos, L., additional, Vega-Moreno, D., additional, Ventero, A., additional, Vethaak, A.D., additional, Vianello, A., additional, Vicioso, M., additional, Vieira, L.R., additional, Viršek, M.K., additional, Vos, M., additional, Wahl, M., additional, Wallace, N., additional, Walton, A., additional, Waniek, J.J., additional, Watts, A., additional, Webster, L., additional, Wesch, C., additional, Whitfield, E., additional, Wichels, A., additional, Wieczorek, A.M., additional, Wilcox, C., additional, Williams, R.J., additional, Wong-Wah-Chung, P., additional, Wright, S., additional, Wyles, K.J., additional, Young, R., additional, Yurtsever, M., additional, Yurtsever, U., additional, Zada, L., additional, Zamani, N.P., additional, and Zampetti, G., additional

Published
2017
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24. Extending NMR Tortuosity Measurements to Paramagnetic Catalyst Materials Through the Use of Low Field NMR

Author

Jordan A. Ward‐Williams, Vivian Karsten, Constant M. Guédon, Timothy A. Baart, Peter Munnik, Andrew J. Sederman, Mick D. Mantle, Qingyuan Zheng, Lynn F. Gladden, Ward‐Williams, Jordan A [0000-0001-8969-1239], Sederman, Andrew J [0000-0002-7866-5550], Gladden, Lynn F [0000-0001-9519-0406], and Apollo - University of Cambridge Repository

Subjects
3402 Inorganic Chemistry, 34 Chemical Sciences, General Medicine
Abstract

Funder: Shell United States; Id: http://dx.doi.org/10.13039/100004378, Pulsed Field Gradient (PFG) NMR is recognised as an analytical technique used to characterise the tortuosity of porous media by measurement of the self‐diffusion coefficient of a fluid contained within the pore space of the material of interest. Such measurements are usually performed on high magnetic field NMR hardware (>300 MHz). However, many materials of interest, in particular heterogeneous catalysts, contain significant amounts of paramagnetic species, which make such measurements impossible due to their characteristic short spin‐spin relaxation times. Here it is demonstrated that by performing PFG NMR measurements on a low field magnet (2 MHz), tortuosity measurements can be obtained for a range of titania (TiO2) based carriers and catalyst precursors containing paramagnetic species up to a 20 wt.% loading. The approach is also used to compare the tortuosity of two catalyst precursors of the same metal loading prepared by different methods.

Published
2022
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28. Experimental Determination of H2 and CO Diffusion Coefficients in a Wax Mixture Confined in a Porous Titania Catalyst Support

Author

Lynn F. Gladden, Qingyuan Zheng, T. A. Baart, Constant M. Guedon, Andrew J. Sederman, Jack Williams, and Mick D. Mantle

Subjects
Wax, Molecular diffusion, Materials science, Hydrogen, Catalyst support, Diffusion, Analytical chemistry, chemistry.chemical_element, Hard spheres, Tortuosity, Surfaces, Coatings and Films, chemistry, visual_art, Materials Chemistry, visual_art.visual_art_medium, Physical and Theoretical Chemistry, Porosity
Abstract

The ability to measure and predict molecular diffusion coefficients in multicomponent mixtures is not only of fundamental scientific interest but also of significant relevance in understanding how catalytic processes proceed. In the present work, the direct measurement of the molecular diffusion of H2 and CO gas-phase species diffusing in n-alkane mixtures using pulsed-field gradient (PFG) nuclear magnetic resonance (NMR) methods is reported. The work is of direct relevance to Fischer-Tropsch (FT) catalysis, with the measurements being made of the gas-wax system with the wax in both the bulk liquid state and when confined within a titania catalyst support, at temperatures and pressures typical of low-temperature FT synthesis. Molecular diffusion coefficients of H2 and CO within wax-saturated porous titania in the range (1.00-2.43) × 10-8 and (6.44-8.50) × 10-9 m2 s-1, respectively, were measured in the temperature range of 140-240 and 200-240 °C for H2 and CO, respectively, at a pressure of 40 bar. The wax mixture was typical of a wax produced during FT catalysis and had a molar average carbon number of 36. It is shown that the hydrogen diffusion coefficient within this wax mixture is consistent, to within experimental error, with the hydrogen diffusion coefficient measured in pure single-component n-hexatriacontane (n-C36) wax; this result held with the waxes in the bulk liquid state and when confined within the porous titania. The tortuosity of the porous titania was also measured using PFG NMR and found to be 1.77; this value is independent of temperature. The ability of existing correlations to predict these experimentally determined data was then critically evaluated. Although the Wilke-Chang correlation was found to underestimate the molecular diffusion coefficients of both H2 and CO diffusing in the wax in both the bulk state and when confined within the porous titania, parameterized correlations based on the rough hard sphere model, having accounted for the experimentally determined tortuosity factor, predicted the H2 and CO diffusion within bulk and confined wax to within 3%.

Published
2020
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29. In Situ Determination of Carbon Number Distributions of Mixtures of Linear Hydrocarbons Confined within Porous Media Using Pulsed Field Gradient NMR

Author

Lynn F. Gladden, Mick D. Mantle, Jack Williams, Qingyuan Zheng, Constant M. Guedon, T. A. Baart, and Andrew J. Sederman

Subjects
In situ, chemistry.chemical_classification, Hydrocarbon mixtures, chemistry.chemical_compound, Hydrocarbon, chemistry, Calibration, Analytical chemistry, Heterogeneous catalysis, Pulsed field gradient, Mole fraction, Porous medium, Analytical Chemistry
Abstract

Pulsed field gradient (PFG) NMR measurements, combined with a novel optimization method, are used to determine the composition of hydrocarbon mixtures of linear alkanes (C7-C16) in both the bulk liquid state and when imbibed within a porous medium of mean pore diameter 28.6 nm. The method predicts the average carbon number of a given mixture to an accuracy of ±1 carbon number and the mole fraction of a mixture component to within an average root-mean-square error of ±0.036 with just three calibration mixtures. Given that the method can be applied at any conditions of temperature and pressure at which the PFG NMR measurements are made, the method has the potential for application in characterizing hydrocarbon liquid mixtures inside porous media and at the operating conditions relevant to, for example, hydrocarbon recovery and heterogeneous catalysis.

Published
2020
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34. Water-wax behaviour in porous silica at low temperature Fischer-Tropsch conditions

Author

T. A. Baart, Qingyuan Zheng, Constant M. Guedon, Lynn F. Gladden, Jacob L. Brown, Mick D. Mantle, Andrew J. Sederman, Mantle, Mick [0000-0001-7977-3812], Sederman, Andy [0000-0002-7866-5550], Gladden, Lynn [0000-0001-9519-0406], and Apollo - University of Cambridge Repository

Subjects
Wax, Capillary condensation, Chemistry, Process Chemistry and Technology, Condensation, Porous media, Water, Fischer–Tropsch process, Fischer-Tropsch synthesis, Thermal diffusivity, NMR, Catalysis, Phase behaviour, Adsorption, Chemical engineering, visual_art, Phase (matter), visual_art.visual_art_medium, Porosity
Abstract

Water is a major product of Fischer-Tropsch synthesis, and hence the behaviour of water within Fischer-Tropsch synthesis catalysts and its potential influence on catalyst rate and selectivity are questions of long-standing interest. The present work applies three different magnetic resonance techniques to study how water interacts with a model wax, n-octacosane, within the pore space of a porous silica of mean pore size ∼18 nm. 1H magnetic resonance spectroscopy, spin-lattice relaxation time and pulsed-field gradient measurements were performed at 195 °C, and for water pressure in the range 3–13.6 bar, conditions relevant to low temperature Fischer-Tropsch synthesis. The uptake of water within this system is shown to be very similar to that observed for capillary condensation of water within the empty pore space of the same porous silica under the same experimental conditions; suggesting that capillary condensation of water within the wax-saturated pores is occurring. The behaviour of water is characterised by two regimes. At low water relative pressures of ∼0.3 ≤ P/P0 ≤ ∼0.8 water moves into the pore space, displacing wax from the pore surface and existing as a water-rich layer between the pore surface and an oil-rich phase in the centre of the pore; the strong interaction with the pore surface is evidenced by the short nuclear spin relaxation time values of water at the lowest pressures which then increase slightly as multi-layer adsorption at the pore surface occurs with increase in pressure. In the water relative pressure range ∼0.8 ≤ P/P0 ≤ ∼0.97, condensation of water within the pores is observed, characterised by increases in both spin-lattice relaxation time and molecular diffusivity. Analysis of the data suggests that as much as ∼40% of the pore surface is occupied by condensed water after condensation has occurred. It is suggested that these two regimes of water behaviour inside initially wax-filled pores might explain previously reported aspects of the behaviour of Fischer-Tropsch catalyst performance as a function of pore size and amount of co-fed water.

Published
2019
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35. Floating macrolitter leaked from Europe into the ocean

Author

González-Fernández, D., Cózar, A., Hanke, G., Viejo, J., Morales-Caselles, C., Bakiu, R., Barceló, D., Bessa, F., Bruge, A., Cabrera, M., Castro-Jiménez, C., Constant, M., Crosti, R., Galletti, Y., Kideys, A.E., Machitadze, N., de Brito, J.P., Pogojeva, M., Ratola, N., Rigueira, J., Rojo-Nieto, Elisa, Savenko, O., Schöneich-Argent, R.I., Siedlewicz, G., Suaria, G., Tourgeli, M., González-Fernández, D., Cózar, A., Hanke, G., Viejo, J., Morales-Caselles, C., Bakiu, R., Barceló, D., Bessa, F., Bruge, A., Cabrera, M., Castro-Jiménez, C., Constant, M., Crosti, R., Galletti, Y., Kideys, A.E., Machitadze, N., de Brito, J.P., Pogojeva, M., Ratola, N., Rigueira, J., Rojo-Nieto, Elisa, Savenko, O., Schöneich-Argent, R.I., Siedlewicz, G., Suaria, G., and Tourgeli, M.

Abstract

Riverine systems act as converging pathways for discarded litter within drainage basins, becoming key elements in gauging the transfer of mismanaged waste into the ocean. However, riverine litter data are scarce and biased towards microplastics, generally lacking information about larger items. Based on the first ever database of riverine floating macrolitter across Europe, we have estimated that between 307 and 925 million litter items are released annually from Europe into the ocean. The plastic fraction represented 82% of the observed litter, mainly fragments and single-use items (that is, bottles, packaging and bags). Our modelled estimates show that a major portion of the total litter loading is routed through small-sized drainage basins (<100 km2), indicating the relevance of small rivers, streams and coastal run-off. Moreover, the major contribution of high-income countries to the macrolitter inputs suggests that reducing ocean pollution cannot be achieved only by improving waste management, but also requires changing consumption habits and behaviour to curb waste generation at source. The inability of countries with well-developed recovery systems to control the leakage of waste into the environment further supports the need to regulate the production and use of plastic on a global scale.

Published
2021

37. Experimental Determination of H

Author

Qingyuan, Zheng, Jack, Williams, Mick D, Mantle, Andrew J, Sederman, Timothy A, Baart, Constant M, Guédon, and Lynn F, Gladden

Abstract

The ability to measure and predict molecular diffusion coefficients in multicomponent mixtures is not only of fundamental scientific interest but also of significant relevance in understanding how catalytic processes proceed. In the present work, the direct measurement of the molecular diffusion of H

Published
2020

38. Time-Average Behaviors of Indoor Propagation Channels on Wireless Applications

Author

Shirin Aghabeiki, Moncef Kadi, Constant M. A. Niamien, Pôle Electronique et Systèmes, Institut de Recherche en Systèmes Electroniques Embarqués (IRSEEM), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-École Supérieure d’Ingénieurs en Génie Électrique (ESIGELEC)-Université de Rouen Normandie (UNIROUEN), and Normandie Université (NU)-Normandie Université (NU)-École Supérieure d’Ingénieurs en Génie Électrique (ESIGELEC)

Subjects
Computer science, business.industry, [SPI.NRJ]Engineering Sciences [physics]/Electric power, 020206 networking & telecommunications, 020302 automobile design & engineering, 02 engineering and technology, Spatial distribution, [SPI.TRON]Engineering Sciences [physics]/Electronics, [SPI]Engineering Sciences [physics], Distribution function, 0203 mechanical engineering, Incident wave, 0202 electrical engineering, electronic engineering, information engineering, Electronic engineering, Wireless, Time average, Graphical model, Radio frequency, business, ComputingMilieux_MISCELLANEOUS
Abstract

This paper investigates the three-dimensional spatial distribution of incident waves within an indoor environment over commonly used wireless bands such as GSM900, GSM1800, IMT2000 and WiFi 2.4 GHz. Unlike previous works, the proposed approach derives the time-average behavior of the channels from the received powers coming from common existing RF transmitters. It is seen that the 3D-spatial envelopes of the channels over wireless bands are Gaussian-type only for downlinks.

Published
2020
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39. PSO-Algorithm-Based Design of Arbitrary Focal Distance Reflectarrays for Beam Collimation Objective

Author

Zouheir Riah, Jiawei Han, and Constant M. A. Niamien

Subjects
Electromagnetics, Computer science, Surface wave, 0202 electrical engineering, electronic engineering, information engineering, Particle swarm optimization, Focal length, 020206 networking & telecommunications, 02 engineering and technology, Beam collimation, Topology, Array factor, Microstrip
Abstract

This paper presents an efficient PSO-algorithm-based approach to design arbitrary focal distance (AFD) reflectarrays. The approach is based on the array factor formulation, which can manage both infinite and finite focal distances, and any kinds of sources and polarizations. It helps reducing the design time and complexity of this kind of electromagnetic problem. An optimized reflectarray is designed by considering a mushroom-type structure with delay lines as the unit cell. Theoretical results compare well with full-wave simulations.

Published
2020
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40. Multi-Mode Cavity-Backed Slot Ring Antenna for Multi-band Applications

Author

Hong Phuong Phan and Constant M. A. Niamien

Subjects
Physics, Ring (mathematics), Frequency band, Acoustics, 010401 analytical chemistry, Mode (statistics), 020206 networking & telecommunications, Reflector (antenna), 02 engineering and technology, 01 natural sciences, 0104 chemical sciences, law.invention, Wavelength, Capacitor, Multi band, law, 0202 electrical engineering, electronic engineering, information engineering, Antenna (radio)
Abstract

This paper presents a multi-mode approach for designing multi-band cavity-backed slot antennas. The approach is based on the analysis of the fundamental and first higher-order mode of a slot ring structure. In addition, cavity modes can be introduced by adding a floating reflector underneath the slot at a small distance of around one-eleventh wavelength, which is much less than the conventional requirement for quarter-wavelength separation distance. The first higher-order mode of the slot can be controlled by placing, at particular locations, one or more capacitors inside the slot. Simulated IEEE gains of the designed antennas are around 9 dBi over the entire frequency band of 900 MHz-3 GHz. Prototypes and measurements will be further detailed.

Published
2020
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42. Auteurs

Author

Adamsbaum, C., primary, André, C., additional, Ardaens, K., additional, Ardaens, Y., additional, Baranzelli, M.-C., additional, Benoit, B., additional, Bigot, J., additional, Castelain, B., additional, Catteu-Jonard, S., additional, Ceugnart, L., additional, Chevalier, A., additional, Coquel, Ph., additional, Constant, M., additional, Cosson, M., additional, Dewailly, D., additional, Gauthier, H., additional, Grandbastien, B., additional, Gougeon, A., additional, Guérin du Masgenêt, B., additional, Haag, Th., additional, Hancart-Destée, C., additional, Kalifa, G., additional, Laurent, N., additional, Leblanc, E., additional, Lefebvre, C., additional, Lernout, M., additional, Levaillant, J.-M., additional, Lions, Ch., additional, Mauroy, B., additional, Mestdagh, P., additional, Millischer-Bellaïche, A.-E., additional, Narducci, F., additional, Perrot, N., additional, Poncelet, E., additional, Renan, C.-A., additional, Rocourt, N., additional, Taieb, S., additional, Thomas, P., additional, and Thomassin-Naggara, I., additional

Published
2010
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50. Isotope effect on the reactivation of neutralized Si dopants in hydrogenated or deuterated GaAs: the role of hot electrons

Author

Constant, E., Bernard-Loridant, D., Meziere, S., Constant, M., and Chevallier, J.

Subjects
Diodes, Schottky-barrier -- Research, Gallium arsenide semiconductors -- Research, Semiconductor doping -- Research, Physics
Abstract

Research was conducted to examine hydrogenated and deuterated Si doped n-type GaAs Schottky diodes by means of room-temperature bias stress and annealing experiments. The variation of the active doping concentration and the reactivation of neutralized dopants was analyzed from a careful study of capacitance-voltage characteristics. Results demonstrate that hot electron excitation apparently plays an important role in the dissociation of SiH complexes in reverse bias Schottky GaAs diodes at room temperature.

Published
1999

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