Future heavy duty trucking engine requirements

Developers of advanced heavy duty diesel engines are engaged in probing the opportunities presented by new materials and techniques. This process is technology driven, but there is neither assurance that the eventual users of the engines so developed will be comfortable with them nor, indeed, that those consumers will continue to exist in either the same form, or numbers as they do today. To ensure maximum payoff of research dollars, the equipment development process must consider user needs. This study defines motor carrier concerns, cost tolerances, and the engine parameters which match the future projected industry needs. The approach taken to do that is to be explained and the results presented. The material to be given comes basically from a survey of motor carrier fleets. It provides indications of the role of heavy duty vehicles in the 1998 period and their desired maintenance and engine performance parameters

Free-space and underwater GHz data transmission using AlGaInN laser diode technology

Laser diodes fabricated from the AlGaInN material system is an emerging technology for defence and security applications; in particular for free space laser communication. Conventional underwater communication is done acoustically with very slow data rates, short reach, and vulnurable for interception. AlGaInN blue-green laser diode technology allows the possibility of both airbourne links and underwater telecom that operate at very fast data rates (GHz), long reach (100’s of metres underwater) and can also be quantum encrypted. The latest developments in AlGaInN laser diode technology are reviewed for defence and security applications. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well. Ridge waveguide laser diode structures are fabricated to achieve single mode operation with optical powers of <100mW. Visible light communications at high frequency (up to 2.5 Gbit/s) using a directly modulated 422nm Galliumnitride (GaN) blue laser diode is reported in free-space and underwate

Lateral grating DFB AlGaInN laser diodes for optical communications and atomic clocks

AlGaInN laser diode technology is of considerable interest for telecom applications and next generation atomic optical clocks based on Sr (by using 422nm & 461nm) and Rb at 420.2nm.Very narrow linewidths (<1MHz) are required for such applications. We report lateral gratings on AlGaInN ridge waveguide laser diodes to achieve a single wavelength device with a good side mode suppression ratio (SMSR) that is suitable for atomic clock and telecom applications

AlGaInN Laser Diode Technology for Systems Applications

Gallium Nitride (GaN) laser diodes fabricated from the AlGaInN material system is an emerging technology that allows laser diodes to be fabricated over a very wide wavelength range from u.v. to the visible, and is a key enabler for the development of new system applications such as (underwater and terrestrial) telecommunications, quantum technologies, display sources and medical instrumentation

Detection and characterization of hydraulically active fractures in a carbonate aquifer: results from self-potential, temperature and fluid electrical conductivity logging in the Combioula hydrothermal system in the southwestern Swiss Alps

A geophysical and geochemical study has been conducted in a fractured carbonate aquifer located at Combioula in the southwestern Swiss Alps with the objective to detect and characterize hydraulically active fractures along a 260-m-deep borehole. Hydrochemical analyses, borehole diameter, temperature and fluid electrical conductivity logging data were integrated in order to relate electrokinetic self-potential signals to groundwater flow inside the fracture network. The results show a generally good, albeit locally variable correlation of variations of the self-potential signals with variations in temperature, fluid electrical conductivity and borehole diameter. Together with the hydrochemical evidence, which was found to be critical for the interpretation of the self-potential data, these measurements not only made it possible to detect the hydraulically active fractures but also to characterize them as zones of fluid gain or fluid loss. The results complement the available information from the corresponding litholog and illustrate the potential of electrokinetic self-potential signals in conjunction with temperature, fluid electrical conductivity and hydrochemical analyses for the characterization of fractured aquifers, and thus may offer a perspective for an effective quantitative characterization of this increasingly important class of aquifers and geothermal reservoir

High Speed Visible Light Communication Using Blue GaN Laser Diodes

GaN-based laser diodes have been developed over the last 20 years making them desirable for many security and defence applications, in particular, free space laser communications. Unlike their LED counterparts, laser diodes are not limited by their carrier lifetime which makes them attractive for high speed communication, whether in free space, through fiber or underwater. Gigabit data transmission can be achieved in free space by modulating the visible light from the laser with a pseudo-random bit sequence (PRBS), with recent results approaching 5 Gbit/s error free data transmission. By exploiting the low-loss in the blue part of the spectrum through water, data transmission experiments have also been conducted to show rates of 2.5 Gbit/s underwater. Different water types have been tested to monitor the effect of scattering and to see how this affects the overall transmission rate and distance. This is of great interest for communication with unmanned underwater vehicles (UUV) as the current method using acoustics is much slower and vulnerable to interception. These types of laser diodes can typically reach 50-100 mW of power which increases the length at which the data can be transmitted. This distance could be further improved by making use of high power laser arrays. Highly uniform GaN substrates with low defectivity allow individually addressable laser bars to be fabricated. This could ultimately increase optical power levels to 4 W for a 20-emitter array. Overall, the development of GaN laser diodes will play an important part in free space optical communications and will be vital in the advancement of security and defence applications

On the Crystal and Magnetic Behavior of ScFe4Al8 Single Crystal

Nuclear and magnetic properties of the ScFe4Al8 single crystal were found to exhibit unparalleled complexity of nuclear and magnetic structures. Our previous neutron measurements revealed presence of two modulation vectors, both along [", ", 0], however with dfferent critical temperatures. Recent experiments forced us to revise our knowledge of the structural ordering in the sample. So far, the crystal structure of this alloy, being of ThMn12-type, has never been questioned

Si in GaN -- On the Nature of the Background Donor

A characterization of the Si impurity in GaN is performed by Raman spectroscopy. Applying hydrostatic pressure up to 25 GPa the authors study the behavior of the LO phonon-plasmon mode in a series of high mobility Si doped GaN films. In contrast to earlier results on unintentionally doped bulk GaN crystals no freeze out of the free carriers could be observed in Si doped samples. The authors find that Si is a shallow hydrogenic donor throughout the pressure range studied. This result positively excludes Si incorporation as a dominant source of free electrons in previously studied bulk GaN samples

High-pressure lattice dynamics in wurtzite and rocksalt indium nitride investigated by means of Raman spectroscopy

We present an experimental and theoretical lattice-dynamical study of InN at high hydrostatic pressures. We perform Raman scattering measurements on five InN epilayers, with different residual strain and free electron concentrations. The experimental results are analyzed in terms of ab initio lattice-dynamical calculations on both wurtzite InN (w-InN) and rocksalt InN (rs-InN) as a function of pressure. Experimental and theoretical pressure coefficients of the optical modes in w-InN are compared, and the role of residual strain on the measured pressure coefficients is analyzed. In the case of the LO band, we analyze and discuss its pressure behavior considering the double-resonance mechanism responsible for the selective excitation of LO phonons with large wave vectors in w-InN. The pressure behavior of the L− coupled mode observed in a heavily doped n-type sample allows us to estimate the pressure dependence of the electron effective mass in w-InN. The results thus obtained are in good agreement with k⋅p theory. The wurtzite-to-rocksalt phase transition on the upstroke cycle and the rocksalt-to-wurtzite backtransition on the downstroke cycle are investigated, and the Raman spectra of both phases are interpreted in terms of DFT lattice-dynamical calculations. ©2013 American Physical SocietyWork was supported by the Spanish Ministerio de Economia y Competitividad through Projects MAT2010-16116, MAT2010-21270-C04-04 and MALTA Consolider Ingenio 2010 (CSD2007-00045).Ibánez, J.; Oliva, R.; Manjón Herrera, FJ.; Segura, A.; Yamaguchi, T.; Nanishi, Y.; Cuscó, R.... (2013). High-pressure lattice dynamics in wurtzite and rocksalt indium nitride investigated by means of Raman spectroscopy. Physical Review B. 88:115202-1-115202-13. https://doi.org/10.1103/PhysRevB.88.115202S115202-1115202-1388Wu, J. (2009). When group-III nitrides go infrared: New properties and perspectives. 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High-pressure behavior of the bond-bending mode of AIN. Journal of Experimental and Theoretical Physics, 98(5), 981-985. doi:10.1134/1.1767565Ibáñez, J., Segura, A., García-Domene, B., Oliva, R., Manjón, F. J., Yamaguchi, T., … Artús, L. (2012). High-pressure optical absorption in InN: Electron density dependence in the wurtzite phase and reevaluation of the indirect band gap of rocksalt InN. Physical Review B, 86(3). doi:10.1103/physrevb.86.035210Serrano, J., Romero, A. H., Manjón, F. J., Lauck, R., Cardona, M., & Rubio, A. (2004). Pressure dependence of the lattice dynamics of ZnO: Anab initioapproach. Physical Review B, 69(9). doi:10.1103/physrevb.69.094306Cuscó, R., Ibáñez, J., Domenech-Amador, N., Artús, L., Zúñiga-Pérez, J., & Muñoz-Sanjosé, V. (2010). Raman scattering of cadmium oxide epilayers grown by metal-organic vapor phase epitaxy. 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Raman scattering by LO phonon-plasmon coupled modes inn-type InP. Physical Review B, 60(8), 5456-5463. doi:10.1103/physrevb.60.5456Ib��ez, J., Cusc�, R., & Art�s, L. (2001). Raman Scattering Determination of Free Charge Density Using a Modified Hydrodynamical Model. physica status solidi (b), 223(3), 715-722. doi:10.1002/1521-3951(200102)223:33.0.co;2-oKasic, A., Schubert, M., Saito, Y., Nanishi, Y., & Wagner, G. (2002). Effective electron mass and phonon modes inn-type hexagonal InN. Physical Review B, 65(11). doi:10.1103/physrevb.65.115206Demangeot, F., Pinquier, C., Frandon, J., Gaio, M., Briot, O., Maleyre, B., … Gil, B. (2005). Raman scattering by the longitudinal optical phonon in InN: Wave-vector nonconserving mechanisms. Physical Review B, 71(10). doi:10.1103/physrevb.71.104305Thakur, J. S., Haddad, D., Naik, V. M., Naik, R., Auner, G. W., Lu, H., & Schaff, W. J. (2005). A1(LO)phonon structure in degenerate InN semiconductor films. 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Physical Review B, 50(7), 4397-4415. doi:10.1103/physrevb.50.4397Ovsyannikov, S. V., Shchennikov, V. V., Karkin, A. E., Polian, A., Briot, O., Ruffenach, S., … Moret, M. (2010). Pressure cycling of InN to 20 GPa: In situ transport properties and amorphization. Applied Physics Letters, 97(3), 032105. doi:10.1063/1.3466913Davydov, V. Y., Klochikhin, A. A., Smirnov, M. B., Emtsev, V. V., Petrikov, V. D., Abroyan, I. A., … Inushima, T. (1999). Phonons in Hexagonal InN. Experiment and Theory. physica status solidi (b), 216(1), 779-783. doi:10.1002/(sici)1521-3951(199911)216:13.0.co;2-