Search results for "compression"
showing 10 items of 774 documents
All-Normal-Dispersion Photonic Crystal Fibers Under Prism of Supercontinuum Generation and Pulse Compression
2015
We discuss properties of all-normal-dispersion photonic crystal fibers in context of supercontinuum generation and compression of ultrashort pulses. The application of pump pulses typical for the state of the art Ti:Sapphire lasers allows obtaining quite flat and broad spectra extending more than one octave in this fiber. The influence of initial pump pulse parameters such as pulse energy, duration, and pump wavelength on the SC generation was investigated. It was shown that compression of pulses with such SC spectra allows obtaining a few cycle pulses up to 8.1 fs, if a simple quadratic compressor is used and single cycle pulses up to 2.5 fs, if full phase compensation is provided.
Predicting ultrafast nonlinear dynamics in optical fiber using neural networks
2021
We show how neural networks can be used to model complex and predict nonlinear propagation dynamics in optical fibres for a widerange of input conditions and fibre systems, including pulse compression, ultra-broadband supercontinuum generation, and multimode fiber systems. Our results open up novel perspectives to model and optimize complex nonlinear dynamics and systems.
Multiple four-wave mixing in optical fibers: 1.5–3.4-THz femtosecond pulse sources and real-time monitoring of a 20-GHz picosecond source
2010
International audience; In this work, we report recent progress on the design of all-fibered ultra-high repetition-rate pulse sources for telecommunication applications around 1550 nm. The sources are based on the non-linear compression of an initial beat-signal through a multiple four-wave mixing process taking place into an optical fiber. We experimentally demonstrate real-time monitoring of a 20 GHz pulse source having an integrated phase noise 0.01 radian by phase locking the initial beat note against a reference RF oscillator. Based on this technique, we also experimentally demonstrate a well-separated high-quality 110 fs pulse source having a repetition rate of 2 THz. Finally, we show…
Nonlinear repolarization dynamics in optical fibers: transient polarization attraction
2011
International audience; In this work, we present a theoretical and experimental study of the response of a lossless polarizer to a signal beam with a time-varying state of polarization (SOP). By lossless polarizer, we mean a nonlinear conservative medium (e.g., an optical fiber) that is counterpumped by an intense and fully polarized pump beam. Such a medium transforms input uniform or random distributions of the SOP of an intense signal beam into output distributions that are tightly localized around a well-defined SOP. We introduce and characterize an important parameter of a lossless polarizer--its response time. Whenever the fluctuations of the SOP of the input signal beam are slower th…
Compression of Polarized 3He
1991
This article gives a status report on the polarized 3He target development work at Mainz. It is based on the optical pumping of the 3S1 state of 3He with subsequent metastability spin exchange to the ground state atoms. This pumping scheme is very efficient at 3He pressures of about 1 Torr; for high density targets, however, a mechanical compression of the polarized gas is needed in a second step. First results with a Toepler compression pump look promising and will be discussed in the following.
He-3 spin filter for neutrons
2005
The strongly spin-dependent absorption of neutrons in nuclear spin-polarized (3)He opens up the possibility of polarizing neutrons from reactors and spallation sources over the full kinematical range of cold, thermal and hot neutrons. This paper gives a report on the neutron spin filter (NSF) development program at Mainz. The polarization technique is based on direct optical pumping of metastable (3)He atoms combined with a polarization preserving mechanical compression of the gas up to a pressure of several bar, necessary to run a NSF. The concept of a remote type of operation using detachable NSF cells is presented which requires long nuclear spin relaxation times of order 100 hours. A sh…
Scope Oriented Thermoeconomic analysis of energy systems. Part II: Formation Structure of Optimality for robust design
2010
This paper represents the Part II of a paper in two parts. In Part I the fundamentals of Scope Oriented Thermoeconomics have been introduced, showing a scarce potential for the cost accounting of existing plants; in this Part II the same concepts are applied to the optimization of a small set of design variables for a vapour compression chiller. The method overcomes the limit of most conventional optimization techniques, which are usually based on hermetic algorithms not enabling the energy analyst to recognize all the margins for improvement. The Scope Oriented Thermoeconomic optimization allows us to disassemble the optimization process, thus recognizing the Formation Structure of Optimal…
Comparison of pharyngeal airway volume in different skeletal facial patterns using cone beam computed tomography
2018
Background This study aimed to compare the pharyngeal airway volume in class I,II and III skeletal malocclusion patients using cone beam computed tomography (CBCT). Material and Methods This retrospective, cross sectional study was conducted on lateral cephalograms of 71 patients derived from their CBCT scans. Using the ANB angle, the patients were divided into class I,II and III malocclusion. Two observers used Dolphin 3D software to calculate the pharyngeal airway volume, airway area, minimum axial area, minimum area location, airway length and morphology. Data were analyzed using one-way ANOVA, Kruskal-Wallis test, Tukey's test, Spearman's correlation coefficient and multiple regression …
Customised pressure profiles of made-to-measure sports compression garments
2021
AbstractThe purpose of this study was to make made-to-measure compression garments that elicit pressures within and below clinical standards. The study also examined whether pressures and gradients can be replicated within and between participants’ legs, and between separate compression garment conditions. Ten males volunteered to participate. Based on three-dimensional scans of the participants’ lower body, three different made-to-measure garments were manufactured: control, symmetrical and asymmetrical. Garment pressures were assessed from the malleolus to the gluteal fold using a pressure monitoring device. A root mean squared difference analysis was used to calculate the in vivo linear …
In vitro assessment of retention and resistance failure loads of complete coverage restorations made for anterior maxillary teeth restored with two d…
2019
Background The purpose of this in vitrostudy was to evaluate the retention and resistance form of complete coverage restorations supported by two different cast post and core designs. Material and methods Forty extracted maxillary central incisors were randomly divided into four groups of 10 specimens each (namely A, B, C and D). All specimens were endodontically treated and a uniform post space of 9mm was created. All prepared teeth had a 360o chamfer ferrule of 2mm in axial height measured 0.5mm coronally from the cementoenamel junction (CEJ) and an axial wall thickness of 1.5 mm. Specimens in groups A and C received cast post and cores with the standardized core design, where the core en…