Applied Sciences

1535 KiB

Open AccessArticle

Front-End Light Source for aWaveform-Controlled High-Contrast Few-Cycle Laser System for High-Repetition Rate Relativistic Optics

by Aurélien Ricci, Aurélie Jullien, Jean-Philippe Rousseau and Rodrigo Lopez-Martens

Appl. Sci. 2013, 3(1), 314-324; https://doi.org/10.3390/app3010314 - 18 Mar 2013

Cited by 14 | Viewed by 6459

Abstract

We present the current development of an injector for a high-contrast, ultrashort laser system devoted to relativistic laser-plasma interaction in the few-cycle regime. The front-end is based on CEP-stabilized Ti:Sa CPA followed by XPW filter designed at the mJ level for temporal cleaning [...] Read more.

We present the current development of an injector for a high-contrast, ultrashort laser system devoted to relativistic laser-plasma interaction in the few-cycle regime. The front-end is based on CEP-stabilized Ti:Sa CPA followed by XPW filter designed at the mJ level for temporal cleaning and shortening. Accurate characterization highlights the fidelity of the proposed injector. Measured CEP drift is 170 mrad rms. Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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Graphical abstract

2150 KiB

Open AccessReview

Recent Developments in Experimental Techniques for Measuring Two Pulses Simultaneously

by Tsz Chun Wong and Rick Trebino

Appl. Sci. 2013, 3(1), 299-313; https://doi.org/10.3390/app3010299 - 18 Mar 2013

Cited by 5 | Viewed by 7313

Abstract

As many high-intensity ultrafast-optical measurements involve more than one pulse—typically one to excite a medium under study and another to probe it—a technique for measuring two pulses simultaneously is highly desirable. In two decades, two-pulse measurement techniques have advanced from ambiguity-laden to a [...] Read more.

As many high-intensity ultrafast-optical measurements involve more than one pulse—typically one to excite a medium under study and another to probe it—a technique for measuring two pulses simultaneously is highly desirable. In two decades, two-pulse measurement techniques have advanced from ambiguity-laden to a recently developed technique that can measure a pulse pair with arbitrary central wavelengths, complexities and bandwidths. Here, we review recent efforts to simultaneously measure two ultrashort laser pulses using a single device. Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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326 KiB

Open AccessArticle

Numerical Simulation of High-Energy, Ytterbium-Doped Amplifier Tunability

by Celso P. João, João Wemans and Gonçalo Figueira

Appl. Sci. 2013, 3(1), 288-298; https://doi.org/10.3390/app3010288 - 13 Mar 2013

Cited by 5 | Viewed by 8110

Abstract

The study of wavelength tunability for the gain media Yb:CaF₂ and Yb:YAG in a regenerative amplifier configuration, was performed by using a simulation code previously benchmarked with real data. The results demonstrate that both materials have potential for amplifying pulses up to [...] Read more.

The study of wavelength tunability for the gain media Yb:CaF₂ and Yb:YAG in a regenerative amplifier configuration, was performed by using a simulation code previously benchmarked with real data. The results demonstrate that both materials have potential for amplifying pulses up to the milijoule level for wavelengths around 1048–1049 nm. In light of this, we propose and evaluate their performance as gain media in the pre-amplifier of a hybrid chain operating at 1053 nm. Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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792 KiB

Open AccessArticle

Laser Induced Multiphoton Effects in Nano-Graphene Molecules

by Mingqiang Gu, Guoping Zhang and Xiaoshan Wu

Appl. Sci. 2013, 3(1), 278-287; https://doi.org/10.3390/app3010278 - 13 Mar 2013

Cited by 3 | Viewed by 6032

Abstract

We perform first-principles calculations to study the high-order harmonic generation induced in graphene nanostructures by the laser field. Three distinct signals are noticed: the integer higher-order harmonic generation (HHG), the shifted fractional order peaks from the integer order harmonics, and the intrinsic emissions. [...] Read more.

We perform first-principles calculations to study the high-order harmonic generation induced in graphene nanostructures by the laser field. Three distinct signals are noticed: the integer higher-order harmonic generation (HHG), the shifted fractional order peaks from the integer order harmonics, and the intrinsic emissions. Due to the small gap between HOMO and LUMO of graphene molecule, the HHG can be generated for the infrared laser pulse with the photon energy ranging from 20 meV to 1 eV. The intrinsic emission corresponds to the electron excitation between eigenstates. Using a laser pulse with a photon energy of 0.042 eV and amplitude of 0.2 V/A° , HHGs up to 19th order are identified. Unsaturated graphene molecule is an excellent media for HHG. Moreover, the HHG signals are very sensitive to the hydrogen passivation. Our results also indicate that HHG can be a promising method for detecting the product in the fabrication of graphene molecules. Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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1334 KiB

Open AccessReview

Spectral Shifts of Nonadiabatic High-Order Harmonic Generation

by Xue-Bin Bian and André D. Bandrauk

Appl. Sci. 2013, 3(1), 267-277; https://doi.org/10.3390/app3010267 - 13 Mar 2013

Cited by 17 | Viewed by 8404

Abstract

High-order harmonic generation (HHG) is a nonlinear nonperturbative process in ultrashort intense laser-matter interaction. It is the main source of coherent attosecond (1 as = 10⁻¹⁸ s) laser pulses to investigate ultrafast electron dynamics. HHG has become an important table-top source covering [...] Read more.

High-order harmonic generation (HHG) is a nonlinear nonperturbative process in ultrashort intense laser-matter interaction. It is the main source of coherent attosecond (1 as = 10⁻¹⁸ s) laser pulses to investigate ultrafast electron dynamics. HHG has become an important table-top source covering a spectral range from infrared to extreme ultraviolet (XUV). One way to extend the cutoff energy of HHG is to increase the intensity of the laser pulses. A consequence of HHG in such intense short laser fields is the characteristic nonadiabatic red and blue shifts of the spectrum, which are reviewed in the present work. An example of this nonperturbative light-matter interaction is presented for the one-electron nonsymmetric molecular ion HeH²⁺, as molecular systems allow for the study of the laser-molecule orientation dependence of such new effects including a four-step model of MHOHG (Molecular High-order Harmonic Generation). Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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801 KiB

Open AccessReview

Attosecond Hard X-ray Free Electron Laser

by Sandeep Kumar, Heung-Sik Kang and Dong-Eon Kim

Appl. Sci. 2013, 3(1), 251-266; https://doi.org/10.3390/app3010251 - 12 Mar 2013

Cited by 7 | Viewed by 7951

Abstract

In this paper, several schemes of soft X-ray and hard X-ray free electron lasers (XFEL) and their progress are reviewed. Self-amplified spontaneous emission (SASE) schemes, the high gain harmonic generation (HGHG) scheme and various enhancement schemes through seeding and beam manipulations are discussed, [...] Read more.

In this paper, several schemes of soft X-ray and hard X-ray free electron lasers (XFEL) and their progress are reviewed. Self-amplified spontaneous emission (SASE) schemes, the high gain harmonic generation (HGHG) scheme and various enhancement schemes through seeding and beam manipulations are discussed, especially in view of the generation of attosecond X-ray pulses. Our recent work on the generation of attosecond hard X-ray pulses is also discussed. In our study, the enhanced SASE scheme is utilized, using electron beam parameters of an XFEL under construction at Pohang Accelerator Laboratory (PAL). Laser, chicane and electron beam parameters are optimized to generate an isolated attosecond hard X-ray pulse at 0.1 nm (12.4 keV). The simulations show that the manipulation of electron energy beam profile may lead to the generation of an isolated attosecond hard X-ray of 150 attosecond pulse at 0.1 nm. Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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2757 KiB

Open AccessReview

Ultra-Intense, High Spatio-Temporal Quality Petawatt-Class Laser System and Applications

by Hiromitsu Kiriyama, Takuya Shimomura, Michiaki Mori, Yoshiki Nakai, Manabu Tanoue, Shuji Kondo, Shuhei Kanazawa, Alexander S. Pirozhkov, Timur Z. Esirkepov, Yukio Hayashi, Koichi Ogura, Hideyuki Kotaki, Masayuki Suzuki, Izuru Daito, Hajime Okada, Atsushi Kosuge, Yuji Fukuda, Mamiko Nishiuchi, Masaki Kando, Sergei V. Bulanov, Keisuke Nagashima, Mitsuru Yamagiwa, Kiminori Kondo, Akira Sugiyama, Paul R. Bolton, Shinichi Matsuoka and Hirofumi Kan Show full author list Hide full author list

Appl. Sci. 2013, 3(1), 214-250; https://doi.org/10.3390/app3010214 - 7 Mar 2013

Cited by 15 | Viewed by 10229

Abstract

This paper reviews techniques for improving the temporal contrast and spatial beam quality in an ultra-intense laser system that is based on chirped-pulse amplification (CPA). We describe the design, performance, and characterization of our laser system, which has the potential for achieving a [...] Read more.

This paper reviews techniques for improving the temporal contrast and spatial beam quality in an ultra-intense laser system that is based on chirped-pulse amplification (CPA). We describe the design, performance, and characterization of our laser system, which has the potential for achieving a peak power of 600 TW. We also describe applications of the laser system in the relativistically dominant regime of laser-matter interactions and discuss a compact, high efficiency diode-pumped laser system. Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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1351 KiB

Open AccessArticle

Photoelectron Angular Distribution and Phase in Two-Photon Single Ionization of H and He by a Femtosecond and Attosecond Extreme-Ultraviolet Pulse

by Kenichi L. Ishikawa and Kiyoshi Ueda

Appl. Sci. 2013, 3(1), 189-213; https://doi.org/10.3390/app3010189 - 5 Mar 2013

Cited by 28 | Viewed by 9313

Abstract

We theoretically study the photoelectron angular distribution (PAD) from the two-photon single ionization of H and He by femtosecond and attosecond extreme-ultraviolet pulses, based on the time-dependent perturbation theory and simulations with the full time-dependent Schrodinger equation. The PAD is formed by the [...] Read more.

We theoretically study the photoelectron angular distribution (PAD) from the two-photon single ionization of H and He by femtosecond and attosecond extreme-ultraviolet pulses, based on the time-dependent perturbation theory and simulations with the full time-dependent Schrodinger equation. The PAD is formed by the interference of the s and d continuum wave packets, and, thus, contains the information on the relative phase and amplitude ratio between them. We find that, when a spectrally broadened femtosecond pulse is resonant with an excited level, the PAD substantially changes with pulse width, since the competition between resonant and nonresonant ionization paths, leading to distinct from the scattering phase shift difference, changes with it. In contrast, when the Rydberg manifold is excited, and for the case of above-threshold two-photon ionization, and the PAD do not depend much on pulse width, except for the attosecond region. Thus, the Rydberg manifold and the continuum behave similarly in this respect. For a high-harmonic pulse composed of multiple harmonic orders, while the value is different from that for a single-component pulse, the PAD still rapidly varies with pulse width. The present results illustrate a new way to tailor the continuum wave packet. Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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1374 KiB

Open AccessArticle

Linear Electro Optic Effect for High Repetition Rate Carrier Envelope Phase Control of Ultra Short Laser Pulses

by Olivier Gobert, Daniele Rovera, Gabriel Mennerat and Michel Comte

Appl. Sci. 2013, 3(1), 168-188; https://doi.org/10.3390/app3010168 - 26 Feb 2013

Cited by 2 | Viewed by 9512

Abstract

This paper is devoted to analyzing the principle and applications of the linear electro-optic (EO) effect for the control of the carrier-envelope-phase (CEP). We introduce and detail here an original method, which relies on the use of an EO dispersive prism pair in [...] Read more.

This paper is devoted to analyzing the principle and applications of the linear electro-optic (EO) effect for the control of the carrier-envelope-phase (CEP). We introduce and detail here an original method, which relies on the use of an EO dispersive prism pair in a compressor-like configuration. We show that, by choosing an adequate geometry, it is possible to shift the CEP without changing the group delay (isochronous carrier-envelope-phase shifter) or change the induced group delay without varying the CEP. According to our calculations, when applying an electric field around 400 V/cm to the rubidium titanyle phosphate (RTP) prisms in a double pass configuration (2 × 40 mm total length), one obtains a CEP shift of π rad at 800 nm without inducing a group delay. In contrast, this CEP shift is obtained for an electric field around 1.4 kV/cm in a RTP rectangular slab of the same total length and, in this case, the group delay is of the order of a few fs. Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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1100 KiB

Open AccessArticle

Pulse Compression of Ultrashort UV Pulses by Self-Phase Modulation in Bulk Material

by Nils Krebs, Igor Pugliesi and Eberhard Riedle

Appl. Sci. 2013, 3(1), 153-167; https://doi.org/10.3390/app3010153 - 8 Feb 2013

Cited by 27 | Viewed by 11030

Abstract

The bandwidth of ultrafast pulses in the UV is limited by the finite acceptance bandwidth of the nonlinear crystals used for their generation. For fundamental laser pulses it is well established that spectral broadening can be used to overcome intrinsic bandwidth limits. We [...] Read more.

The bandwidth of ultrafast pulses in the UV is limited by the finite acceptance bandwidth of the nonlinear crystals used for their generation. For fundamental laser pulses it is well established that spectral broadening can be used to overcome intrinsic bandwidth limits. We show that self-phase modulation of UV pulses in bulk materials leads to large spectral broadening and allows for a significant reduction of the pulse duration. We find that for pulse energies in the range of a few μJ, a thin crystal is favorable due to the strong dispersion in the UV and the limitations set by self-focusing. In contrast to spectral broadening in gaseous media, the self-focus has to lie outside the crystal to avoid beam break up. We focus UV pulses into a 1 mm thick CaF₂ crystal. For moderately short input pulses, a shortening factor up to 2.4 is achieved: the 120 fs long third harmonic output of a Ti:sapphire amplifier is compressed down to 50 fs FWHM. For a central wavelength of 315 nm, we generate pulses as short as 14.9 fs after compression with an UV pulse shaper. In both cases the resulting beam shape is close to Gaussian and fully usable for spectroscopic experiments. We use the pulses in a collinear 2D-UV experiment and clearly resolve vibronic off-diagonal peaks of the S₂ ¹B_2u vibronic progression of pyrene. Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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1392 KiB

Open AccessArticle

Adaptive Generation and Diagnostics of Linear Few-Cycle Light Bullets

by Martin Bock and Ruediger Grunwald

Appl. Sci. 2013, 3(1), 139-152; https://doi.org/10.3390/app3010139 - 8 Feb 2013

Cited by 8 | Viewed by 9148

Abstract

Recently we introduced the class of highly localized wavepackets (HLWs) as a generalization of optical Bessel-like needle beams. Here we report on the progress in this field. In contrast to pulsed Bessel beams and Airy beams, ultrashort-pulsed HLWs propagate with high stability in [...] Read more.

Recently we introduced the class of highly localized wavepackets (HLWs) as a generalization of optical Bessel-like needle beams. Here we report on the progress in this field. In contrast to pulsed Bessel beams and Airy beams, ultrashort-pulsed HLWs propagate with high stability in both spatial and temporal domain, are nearly paraxial (supercollimated), have fringe-less spatial profiles and thus represent the best possible approximation to linear “light bullets”. Like Bessel beams and Airy beams, HLWs show self-reconstructing behavior. Adaptive HLWs can be shaped by ultraflat three-dimensional phase profiles (generalized axicons) which are programmed via calibrated grayscale maps of liquid-crystal-on-silicon spatial light modulators (LCoS-SLMs). Light bullets of even higher complexity can either be freely formed from quasi-continuous phase maps or discretely composed from addressable arrays of identical nondiffracting beams. The characterization of few-cycle light bullets requires spatially resolved measuring techniques. In our experiments, wavefront, pulse and phase were detected with a Shack-Hartmann wavefront sensor, 2D-autocorrelation and spectral phase interferometry for direct electric-field reconstruction (SPIDER). The combination of the unique propagation properties of light bullets with the flexibility of adaptive optics opens new prospects for applications of structured light like optical tweezers, microscopy, data transfer and storage, laser fusion, plasmon control or nonlinear spectroscopy. Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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1951 KiB

Open AccessArticle

Generation of Phase-Stable Sub-Cycle Mid-Infrared Pulses from Filamentation in Nitrogen

by Takao Fuji and Yutaka Nomura

Appl. Sci. 2013, 3(1), 122-138; https://doi.org/10.3390/app3010122 - 6 Feb 2013

Cited by 51 | Viewed by 8609

Abstract

Sub-single-cycle pulses in the mid-infrared (MIR) region were generated through a laser-induced filament. The fundamental (ω₁) and second harmonic (ω₂) output of a 30-fs Ti:sapphire amplifier were focused into nitrogen gas and produce phase-stable broadband MIR pulses (ω₀ [...] Read more.

Sub-single-cycle pulses in the mid-infrared (MIR) region were generated through a laser-induced filament. The fundamental (ω₁) and second harmonic (ω₂) output of a 30-fs Ti:sapphire amplifier were focused into nitrogen gas and produce phase-stable broadband MIR pulses (ω₀) by using a four-wave mixing process (ω₁ + ω₁ - ω₂→ ω₀) through filamentation. The spectrum spread from 400 cm^-1 to 5500 cm^-1, which completely covered the MIR region. The low frequency components were detected by using an electro-optic sampling technique with a gaseous medium. The efficiency of the MIR pulse generation was very sensitive to the delay between the fundamental and second harmonic pulses. It was revealed that the delay dependence of the efficiency came from the interference between two opposite parametric processes, ω₁ + ω₁ - ω₂ → ω₀ and ω₂ - ω₁ - ω₁ → ω₀. The pulse duration was measured as 6.9 fs with cross-correlation frequency-resolved optical gating by using four-wave mixing in nitrogen. The carrier-envelope phase of the MIR pulse was passively stabilized. The instability was estimated as 154 mrad rms in 2.5 h. Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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319 KiB

Open AccessArticle

An Appropriate Wind Model for Wind Integrated Power Systems Reliability Evaluation Considering Wind Speed Correlations

by Rajesh Karki, Dinesh Dhungana and Roy Billinton

Appl. Sci. 2013, 3(1), 107-121; https://doi.org/10.3390/app3010107 - 6 Feb 2013

Cited by 39 | Viewed by 8074

Abstract

Adverse environmental impacts of carbon emissions are causing increasing concerns to the general public throughout the world. Electric energy generation from conventional energy sources is considered to be a major contributor to these harmful emissions. High emphasis is therefore being given to green [...] Read more.

Adverse environmental impacts of carbon emissions are causing increasing concerns to the general public throughout the world. Electric energy generation from conventional energy sources is considered to be a major contributor to these harmful emissions. High emphasis is therefore being given to green alternatives of energy, such as wind and solar. Wind energy is being perceived as a promising alternative. This source of energy technology and its applications have undergone significant research and development over the past decade. As a result, many modern power systems include a significant portion of power generation from wind energy sources. The impact of wind generation on the overall system performance increases substantially as wind penetration in power systems continues to increase to relatively high levels. It becomes increasingly important to accurately model the wind behavior, the interaction with other wind sources and conventional sources, and incorporate the characteristics of the energy demand in order to carry out a realistic evaluation of system reliability. Power systems with high wind penetrations are often connected to multiple wind farms at different geographic locations. Wind speed correlations between the different wind farms largely affect the total wind power generation characteristics of such systems, and therefore should be an important parameter in the wind modeling process. This paper evaluates the effect of the correlation between multiple wind farms on the adequacy indices of wind-integrated systems. The paper also proposes a simple and appropriate probabilistic analytical model that incorporates wind correlations, and can be used for adequacy evaluation of multiple wind-integrated systems. Full article

(This article belongs to the Special Issue Renewable Energy)

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568 KiB

Open AccessArticle

Double Relativistic Electron Accelerating Mirror

by Alexander Andreev, Konstantin Platonov and Saltanat Sadykova

Appl. Sci. 2013, 3(1), 94-106; https://doi.org/10.3390/app3010094 - 4 Feb 2013

Cited by 5 | Viewed by 5934

Abstract

In the present paper, the possibility of generation of thin dense relativistic electron layers is shown using the analytical and numerical modeling of laser pulse interaction with ultra-thin layers. It was shown that the maximum electron energy can be gained by optimal tuning [...] Read more.

In the present paper, the possibility of generation of thin dense relativistic electron layers is shown using the analytical and numerical modeling of laser pulse interaction with ultra-thin layers. It was shown that the maximum electron energy can be gained by optimal tuning between the target width, intensity and laser pulse duration. The optimal parameters were obtained from a self-consistent system of Maxwell equations and the equation of motion of electron layer. For thin relativistic electron layers, the gaining of maximum electron energies requires a second additional overdense plasma layer, thus cutting the laser radiation off the plasma screen at the instant of gaining the maximum energy (DREAM-schema). Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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1937 KiB

Open AccessReview

Direct Electron Acceleration with Radially Polarized Laser Beams

by Charles Varin, Stéphane Payeur, Vincent Marceau, Sylvain Fourmaux, Alexandre April, Bruno Schmidt, Pierre-Louis Fortin, Nicolas Thiré, Thomas Brabec, François Légaré, Jean-Claude Kieffer and Michel Piché

Appl. Sci. 2013, 3(1), 70-93; https://doi.org/10.3390/app3010070 - 30 Jan 2013

Cited by 74 | Viewed by 10820

Abstract

In the past years, there has been a growing interest in innovative applications of radially polarized laser beams. Among them, the particular field of laser-driven electron acceleration has received much attention. Recent developments in high-power infrared laser sources at the INRS Advanced Laser [...] Read more.

In the past years, there has been a growing interest in innovative applications of radially polarized laser beams. Among them, the particular field of laser-driven electron acceleration has received much attention. Recent developments in high-power infrared laser sources at the INRS Advanced Laser Light Source (Varennes, Qc, Canada) allowed the experimental observation of a quasi-monoenergetic 23-keV electron beam produced by a radially polarized laser pulse tightly focused into a low density gas. Theoretical analyses suggest that the production of collimated attosecond electron pulses is within reach of the actual technology. Such an ultrashort electron pulse source would be a unique tool for fundamental and applied research. In this paper, we propose an overview of this emerging topic and expose some of the challenges to meet in the future. Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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220 KiB

Open AccessReview

Glycerol: A promising Green Solvent and Reducing Agent for Metal-Catalyzed Transfer Hydrogenation Reactions and Nanoparticles Formation

by Alba E. Díaz-Álvarez and Victorio Cadierno

Appl. Sci. 2013, 3(1), 55-69; https://doi.org/10.3390/app3010055 - 23 Jan 2013

Cited by 112 | Viewed by 21183

Abstract

Glycerol is a non-toxic, non-hazardous, non-volatile, biodegradable, and recyclable liquid that is generated as a byproduct in the manufacture of biodiesel fuel from vegetable oils. Due to its easy availability, along with its unique combination of physical and chemical properties, glycerol has recently [...] Read more.

Glycerol is a non-toxic, non-hazardous, non-volatile, biodegradable, and recyclable liquid that is generated as a byproduct in the manufacture of biodiesel fuel from vegetable oils. Due to its easy availability, along with its unique combination of physical and chemical properties, glycerol has recently emerged as an economically appealing and safe solvent for organic synthesis. Recent works have also demonstrated that glycerol can be used as a hydrogen source in metal-catalyzed transfer hydrogenation of organic compounds, such as aldehydes, ketones, olefins and nitroarenes. Herein, the advances reached in this emerging field are reviewed. The utility of glycerol as solvent and reducing agent for the generation of metal nanoparticles is also briefly discussed. Full article

(This article belongs to the Special Issue Greener and Sustainable Chemistry)

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1733 KiB

Open AccessArticle

Field Deployable Fiber Bragg Grating Strain Patch for Long-Term Stable Health Monitoring Applications

by Vivien Schukar, Nadine Kusche, Gerhard Kalinka and Wolfgang Habel

Appl. Sci. 2013, 3(1), 39-54; https://doi.org/10.3390/app3010039 - 16 Jan 2013

Cited by 11 | Viewed by 7664

Abstract

A fiber Bragg grating (FBG) strain patch specially adapted for long-term and high-strain applications has been developed and characterized. The design concept for the patch is based on a glass-fiber reinforced plastic (gfrp) carrier material. The developed concept for the FBG integration into [...] Read more.

A fiber Bragg grating (FBG) strain patch specially adapted for long-term and high-strain applications has been developed and characterized. The design concept for the patch is based on a glass-fiber reinforced plastic (gfrp) carrier material. The developed concept for the FBG integration into the carrier material was derived from reliable integration procedure of FBG sensors into composite structures. The patches’ temperature sensitivity, strain gauge factor, fiber–matrix interface adhesion and fatigue behavior were characterized. As a result, FBG strain patches with linear temperature and strain behavior, as well as excellent fatigue resistance, were developed and can be used as part of a monitoring system for advanced composite materials in aerospace structures or wind turbine power plants. Full article

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1690 KiB

Open AccessArticle

Biofuels and Land Use Change: Applying Recent Evidence to Model Estimates

by Farzad Taheripour and Wallace E. Tyner

Appl. Sci. 2013, 3(1), 14-38; https://doi.org/10.3390/app3010014 - 11 Jan 2013

Cited by 66 | Viewed by 10399

Abstract

Biofuels impact on global land use has been a controversial yet important topic. Up until recently, there has not been enough biofuels to have caused major land use change, so the evidence from actual global land use data has been scant. However, in [...] Read more.

Biofuels impact on global land use has been a controversial yet important topic. Up until recently, there has not been enough biofuels to have caused major land use change, so the evidence from actual global land use data has been scant. However, in the past decade, there have been 72 million hectares added to global crop cover. In this research we take advantage of this new data to calibrate the Global Trade Analysis Project (GTAP) model and parameters. We make two major changes. First, we calibrate the land transformation parameters (called constant elasticity of transformation, CET) to global regions so that the parameters better reflect the actual land cover change that has occurred. Second, we alter the land cover nesting structure. In the old GTAP model, cropland, pasture, and forest were all in the same nest suggesting, everything else being equal, that pasture or forest convert to cropland with equal ease and cost. However, we now take advantage of the fact that pasture converts to cropland at lower cost than forest. The paper provides the theoretical and empirical justification for these two model improvements. Then it re-evaluates the global land use impacts due to the USA ethanol program using the improved model tuned with actual observations. Finally, it shows that compared to the old model, the new model projects: (1) less expansion in global cropland due to ethanol expansion; (2) lower U.S. share in global cropland expansion; (3) and lower forest share in global cropland expansion. Full article

(This article belongs to the Special Issue Renewable Energy)

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277 KiB

Open AccessArticle

Single-Grating Monochromators for Extreme-Ultraviolet Ultrashort Pulses

by Luca Poletto and Fabio Frassetto

Appl. Sci. 2013, 3(1), 1-13; https://doi.org/10.3390/app3010001 - 27 Dec 2012

Cited by 11 | Viewed by 7809

Abstract

A single-grating monochromator can be used for the spectral selection of ultrashort pulses without altering in a significant way the pulse duration, provided that the number of illuminated grooves is equal to the resolution. Two configurations are compared: the classical-diffraction mount (CDM) and [...] Read more.

A single-grating monochromator can be used for the spectral selection of ultrashort pulses without altering in a significant way the pulse duration, provided that the number of illuminated grooves is equal to the resolution. Two configurations are compared: the classical-diffraction mount (CDM) and the off-plane mount (OPM). The advantages and drawbacks of both configurations are presented. The two geometries can be joined in a new and innovative design of a monochromator with two interchangeable diffracting stages both used at grazing incidence, one with the gratings in the CDM and the other in the OPM. The use of two stages gives great flexibility: the OPM stage is used for sub-50 fs time response and low spectral resolution and the CDM stage for 100-200 fs time response and high spectral resolution. The design overcomes the limits of the two single configurations, giving on the same instrument either ultrafast response with low spectral resolution or slower response with higher resolution. Full article

(This article belongs to the Special Issue Ultraintense Ultrashort Pulse Lasers)

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Appl. Sci., Volume 3, Issue 1 (March 2013) – 19 articles , Pages 1-324

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