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Search Results: 1 - 10 of 7474 matches for " Ivan Kasik "
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Fabrication and Properties of Er-Doped Nanocrystalline Phase-Seperated Optical Fibers
Anirban Dhar,Ivan Kasik,Ondrej Podrazky,Vlastimil Matejec
Advances in Electrical and Electronic Engineering , 2013,
Abstract: The fabrication of Er-doped ZrO2-based nanocrystalline phase-separated optical fiber preforms using the MCVD and solution doping techniques is presented and discussed in details in the paper. Preforms with nearly transparent cores containing Er-doped nanocrystals with dimensions mainly within 20-80 nm have been prepared. Fibers drawn from the preforms exhibit good luminescent properties around 1550 nm suitable for applications in lasers and amplifiers.
Preparation and Properties of Er-Doped ZrO2 Nanocrystalline Phase-Separated Preforms of Optical Fibers by MCVD Process
Anirban Dhar,Ivan Kasik,Ondrej Podrazky,Vlastimil Matejec,Bernard Dussardier
Physics , 2011, DOI: 10.1111/j.1744-7402.2011.00669.x
Abstract: The fabrication of Er-doped ZrO2-based nanocrystalline phase-separated silica optical preforms by the MCVD and solution doping techniques is presented. Fabricated preform cores are nearly transparent and contain phase-separated rare-earth doped nanocrystalline particles with diameters mainly in a range from 20 to 80 nm. High concentrations of erbium and aluminium in preform cores of about 0.3 and 14 mol%, respectively have been achieved without defects on the core-cladding interface. Spectral losses in a range 800-1600 nm and fluorescence spectra of erbium ions around 1550 nm measured on a fibre drawn from the preform are reported.
Thulium-doped silica fibers with enhanced 3H4 level lifetime: modelling the devices for 800-820 nm band
Pavel Peterka,Ivan Kasik,Anirban Dhar,Bernard Dussardier,Wilfried Blanc
Physics , 2012, DOI: 10.1117/12.871756
Abstract: Silica-based thulium-doped fiber devices operating around 810 nm would extend the spectral range covered by high- power fiber devices. Using a comprehensive numerical model of the fiber we have shown that efficient lasing at 810 nm can be achieved for specific ranges of the laser cavity parameters in silica-based thulium-doped fibers with enhanced 3H4 lifetime up to 58 \mus as measured in our highly alumina-codoped fibers. We present optimization of the thulium-doped fiber and laser cavity parameters and also potential applications of the developed host material in amplifiers and broadband sources.
Preparation and characterization of highly thulium- and alumina-doped optical fibers for single-frequency fiber lasers
Pavel Honzatko,Anirban Dhar,Ivan Kasik,Ondrej Podrazky,Vlastimil Matejec,Pavel Peterka,Wilfried Blanc,Bernard Dussardier
Physics , 2012, DOI: 10.1117/12.912536
Abstract: Thulium-doped fibers suitable for core-pumped single-frequency lasers were fabricated by the modified chemical vapor deposition (MCVD) method. Refractive index profile, doping profile and spectral absorption was measured. High doping concentration of thulium ions should be achieved to allow for high absorption of light at a pump wavelength while the thulium ions clustering should be avoided to prevent the cooperative upconversion and quenching processes. The fabricated fibers featured pump absorption up to 70dB/m at a pump wavelength of 1611nm. The single-frequency master oscillator with a resonator composed of a pair of fiber Bragg gratings and a thulium-doped fiber was demonstrated with predominantly single ended operation. We achieved a slope efficiency of 22% and a threshold of 22mW at a lasing wavelength of 1944nm.
T helepanekuid soome ja eesti keele liitnimis nadest
Reet Kasik
L?hiv?rdlusi. L?hivertailuja , 2010,
Abstract: The article compares compound noun formation in Finnish and Estonian. On the basis of published grammars, the basic patterns of noun compounding are described. Their application in text is analysed on the material of the Finnish daily Helsingin Sanomat, examining the compound nouns used in the titles and their possible translations into Estonian. Th e regularities and restrictions behind the compounding differences between the two languages are pointed out.
Effects of sesame and bitter almond seed oils on mycelium growth of Agaricus bisporus (Lange) Sing.
kalyoncu, Ismail Hakki,KaSik, Giyaseddin,?zcan, Musa,?zturk, Celaleddin
Grasas y Aceites , 1999,
Abstract: Secondary mycelium growth of Agaricus bisporus from Nigde University Mushroom Research Centre (Aksaray-Nigde) was monitored in malt extract agar medium containing sesame or bitter almond seed oils. With 1 % sesame oil, highest growth was established and less growth period was determined as 27.4 days. All of the samples with sesame oil showed better growth according to the control, being the stimulative effect of sesame oil higher than that of bitter almond oil. El crecimiento secundario de micelios de Agaricus bisporus del Centro de Investigación de Hongos de la Universidad de Nigde (Aksaray-Nigde) se siguió en agar con extracto de malta conteniendo aceites de semillas de almendra amarga o sésamo. El mayor crecimiento se obtuvo con aceite de sésamo al 1%, y el periodo más corto para dicho crecimiento se estableció en 27.4 días. Todas las muestras con aceite de sésamo mostraron mejor crecimiento que el control, siendo el efecto estimulante del aceite de sésamo mayor que el del aceite de almendra amarga.
Preparation and Characterization of Bragg Fibers for Delivery of Laser Radiation at 1064 nm
V. Matejec,I. Kasik,O. Podrazky,J. Aubrecht
Radioengineering , 2013,
Abstract: Bragg fibers offer new performance for transmission of high laser energies over long distances. In this paper theoretical modeling, preparation and characterization of Bragg fibers for delivery laser radiation at 1064 nm are presented. Investigated Bragg fibers consist of the fiber core with a refractive index equal to that of silica which is surrounded by three pairs of circular layers. Each pair is composed of one layer with a high and one layer with a low refractive index and characterized by a refractive-index difference around 0.03. Propagation constants and radiation losses of the fundamental mode in such a structure were calculated on the basis of waveguide optics. Preforms of the Bragg fibers were prepared by the MCVD method using germanium dioxide, phosphorous pentoxide and fluorine as silica dopants. The fibers with a diameter of 170 m were drawn from the preforms. Refractive-index profiles, angular distributions of the output power and optical losses of the prepared fibers were measured. Results of testing the fibers for delivery radiation of a pulse Nd:YAG laser at 1064 nm are also shown.
Cyclic Operator Decomposition for Solving the Differential Equations  [PDF]
Ivan Gonoskov
Advances in Pure Mathematics (APM) , 2013, DOI: 10.4236/apm.2013.31A025

We present an approach how to obtain solutions of arbitrary linear operator equation for unknown functions. The particular solution can be represented by the infinite operator series (Cyclic Operator Decomposition), which acts the generating function. The method allows us to choose the cyclic operators and corresponding generating function selectively, depending on initial problem for analytical or numerical study. Our approach includes, as a particular case, the perturbation theory, but generally does not require inside any small parameters and unperturbed solutions. We demonstrate the applicability of the method to the analysis of several differential equations in mathematical physics, namely, classical oscillator, Schrodinger equation, and wave equation in dispersive medium.

Dyscirculatory Angiopathy of Alzheimer's Type  [PDF]
Ivan V. Maksimovich
Journal of Behavioral and Brain Science (JBBS) , 2011, DOI: 10.4236/jbbs.2011.12008
Abstract: Purpose: We assess the significance of dyscirculatory angiopathy of Alzheimer’s type (DAAT) in identify- ing the predisposition to the development and diagnosis of Alzheimer’s disease (AD) different stages. Meth- ods: 108 patients took part in the research:1) 49 aged 34-79 suffering from AD or running an increased risk of its development (those not diagnosed with AD but having growing memory disorders without any mani- festations of dementia or specific cognitive impairments, and having 2 or more immediate relatives with AD) - Test Group; 2) 59 aged 28-78 suffering from different types of brain lesions accompanied by dementia but not suffering from AD or corresponding to their age norm - Control Group. All the patients underwent MRI, CT with subsequent calculation of the temporal lobes atrophy degree, brain scintigraphy (SG), rheoencepha- lography (REG), and MUGA. Results: Characteristic features of patients with an increased risk of AD as well as at its various stages are: 1) Temporal lobes and hippocampus atrophy ranging from 4% among those with an increased risk of AD to 62% among those at its advanced stages; 2) DAAT manifestations: reduction of the capillary bed in the temporal and frontoparietal regions with the development of multiple arterioven- ous shunts of the same localization and correspondent early venous discharge accompanied by venous stasis on the border of the frontal and parietal region; 3) DAAT phenomena equally develop both among those with an increased risk of developing AD and those at various AD stages. Similar changes are not observed among Control Group patients with other brain lesions, regardless of the severity of dementia, as well as among practically healthy people of the corresponding age group. Conclusion: Timely identification of the above- mentioned changes can reveal a predisposition to AD development long before its initial manifestations, and it allows differentiating AD from other diseases attended by dementia. In both cases, timely diagnosis allows beginning timely treatment and thus achieving more stable results.
Helping Oncology Nurses Advise Younger Patients about Self Care: Feasibility of Using Animated and DVD Formats for Nurse Instruction  [PDF]
Ivan Beale, Vivien Lane
Creative Education (CE) , 2010, DOI: 10.4236/ce.2010.11008
Abstract: This study explored the perceptions of oncology nurses about the usefulness of a video-game or an animated DVD intervention designed to teach young patients about self care. The study also measured the effects of these interventions on nurses’ cancer knowledge and perceived self-efficacy to communicate with patients about self-care. Twenty-two oncology nurses were randomly assigned either to use a video game “Re-Mission” or to view instructional animations from the game on DVD. They completed tests and rating scales before and after, then rated the acceptability of the game or DVD. Only ten participants completed the study. For these ten, ratings of the acceptability and credibility of the game or DVD were moderately positive, regardless of age or nursing experience. Self-efficacy for communicating to patients about self-care increased following use of the game or DVD. Cancer knowledge was not affected. It was concluded that oncology nurses in Australia are not generally enthusiastic about the concept of instruction via video game and animated DVD formats, although those who participated rated the experience positively.
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