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Visible quantum cutting in green-emitting BaF2: Gd3+, Tb3+ phosphor: An approach toward mercury-free lamps 绿色发光BaF2: Gd3+， Tb3+荧光粉的可见量子切割:迈向无汞灯的途径
IF 0.2
St Petersburg Polytechnic University Journal-Physics and Mathematics Pub Date : 2017-10-01 DOI: 10.1016/j.spjpm.2017.06.005
Shreeniwas K. Omanwar , Shailesh R. Jaiswal , Niraj S. Sawala , Kishor A. Koparkar , Pankaj A. Nagpure , Vinod B. Bhatkar
{"title":"Visible quantum cutting in green-emitting BaF2: Gd3+, Tb3+ phosphor: An approach toward mercury-free lamps","authors":"Shreeniwas K. Omanwar ,&nbsp;Shailesh R. Jaiswal ,&nbsp;Niraj S. Sawala ,&nbsp;Kishor A. Koparkar ,&nbsp;Pankaj A. Nagpure ,&nbsp;Vinod B. Bhatkar","doi":"10.1016/j.spjpm.2017.06.005","DOIUrl":"https://doi.org/10.1016/j.spjpm.2017.06.005","url":null,"abstract":"<div><p>Visible quantum cutting (QC) has been observed in green emitting BaF<sub>2</sub> co-doped with Gd<sup>3+</sup>, Tb<sup>3+</sup> phosphor via down-conversion (DC) synthesized by wet chemical method. Powder X-ray diffraction (XRD) analysis shows structural purity of synthesized phosphors. The excitation (PLE) and PL spectra in the vacuum ultraviolet (VUV) or UV region were measured with the help of 4B8-VUV spectroscopy experimental station of the Beijing Synchrotron Radiation Facility (BSRF). In the QC process, one VUV–UV photon absorbed is cut into more than one visible photons emitted by Tb<sup>3+</sup> through cross relaxation (CR) and direct energy transfer (DET) between Tb<sup>3+</sup> and Tb<sup>3+</sup> or Tb<sup>3+</sup> and Gd<sup>3+</sup>, depending on the excitation wavelength. From the emission spectra monitored at different wavelength excitation, the two-step energy transfer process is investigated and theoretically calculated quantum efficiency observed 148% and 177% at the excitation wavelength of 174 nm and 219 nm respectively.</p></div>","PeriodicalId":41808,"journal":{"name":"St Petersburg Polytechnic University Journal-Physics and Mathematics","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2017-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.spjpm.2017.06.005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91778996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 4
The contribution of the albedo for photons to the intensity of hard X-ray emission of solar flares 光子反照率对太阳耀斑硬x射线发射强度的贡献
IF 0.2
St Petersburg Polytechnic University Journal-Physics and Mathematics Pub Date : 2017-10-01 DOI: 10.1016/j.spjpm.2017.09.008
Evgeniya P. Ovchinnikova, Yuri E. Charikov, Aleksander N. Shabalin, Gennady I. Vasilyev
{"title":"The contribution of the albedo for photons to the intensity of hard X-ray emission of solar flares","authors":"Evgeniya P. Ovchinnikova,&nbsp;Yuri E. Charikov,&nbsp;Aleksander N. Shabalin,&nbsp;Gennady I. Vasilyev","doi":"10.1016/j.spjpm.2017.09.008","DOIUrl":"10.1016/j.spjpm.2017.09.008","url":null,"abstract":"<div><p>The albedo contribution to the total hard X-ray solar-flare emission has been considered. First, the distribution of primary hard X-ray photons localized along the flare loop was found, and finally, the Monte Carlo calculations of the Compton scattered hard X-ray photons were performed. The albedo for photons was shown to contribute to the total X-ray flux only in the energy range from 30 to 100 keV. The backscattered photon flux depends on the loop's position and on the localization of the source of primary radiation along the loop<em>.</em> For an isotropic distribution of primary photons, the backscattered photons’ contribution to the total flux is maximal for the loop in the center of the Sun and reduces when shifting to a limb. In the case of an anisotropic source the angle at which the contribution is maximal depends on the degree of anisotropy and on X-ray directivity in the source.</p></div>","PeriodicalId":41808,"journal":{"name":"St Petersburg Polytechnic University Journal-Physics and Mathematics","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2017-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.spjpm.2017.09.008","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85498417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
The EOS choice effect on the simulated results obtained for an underwater electrical explosion of conductors EOS选择对导体水下电爆炸模拟结果的影响
IF 0.2
St Petersburg Polytechnic University Journal-Physics and Mathematics Pub Date : 2017-10-01 DOI: 10.1016/j.spjpm.2017.09.001
Aleksey I. Ryakhovskiy, Valeriy I. Antonov, Nikolay V. Kalinin
{"title":"The EOS choice effect on the simulated results obtained for an underwater electrical explosion of conductors","authors":"Aleksey I. Ryakhovskiy,&nbsp;Valeriy I. Antonov,&nbsp;Nikolay V. Kalinin","doi":"10.1016/j.spjpm.2017.09.001","DOIUrl":"https://doi.org/10.1016/j.spjpm.2017.09.001","url":null,"abstract":"<div><p>In the paper, the effect of the choice of equations of state (EOSs) depicting the states of metal plasma and water on the simulated results obtained for an underwater electrical explosion of conductors has been analyzed. In order to compare various EOSs, a one-dimensional, cylindrically symmetrical, magnetohydrodynamic model of an underwater wire explosion was employed. The simulated results were compared with the experimental data on both micro- and nanosecond explosions of aluminum and copper wires. The right choice of EOSs and the model of transportation coefficients allowed us to improve the agreement between the experimental and simulated data and to replicate the thermodynamic evolution of the system more closely. The comparison revealed the most appropriate EOSs for application to simulation of an electrical explosion.</p></div>","PeriodicalId":41808,"journal":{"name":"St Petersburg Polytechnic University Journal-Physics and Mathematics","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2017-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.spjpm.2017.09.001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91770276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Stabilization of the NOP ferroelectric phase in potassium nitrate–barium titanate ferroelectric composites 硝酸钾-钛酸钡铁电复合材料中NOP铁电相的稳定性
IF 0.2
St Petersburg Polytechnic University Journal-Physics and Mathematics Pub Date : 2017-10-01 DOI: 10.1016/j.spjpm.2017.09.006
Olga A. Alekseeva , Aleksandr А. Naberezhnov , Elena V. Stukova , Valeriy G. Simkin
{"title":"Stabilization of the NOP ferroelectric phase in potassium nitrate–barium titanate ferroelectric composites","authors":"Olga A. Alekseeva ,&nbsp;Aleksandr А. Naberezhnov ,&nbsp;Elena V. Stukova ,&nbsp;Valeriy G. Simkin","doi":"10.1016/j.spjpm.2017.09.006","DOIUrl":"https://doi.org/10.1016/j.spjpm.2017.09.006","url":null,"abstract":"<div><p>The study of temperature evolution of KNO<sub>3</sub> (NOP) structure in ferroelectric (1−<em>x</em>)KNO<sub>3</sub> + (<em>x</em>)BaTiO<sub>3</sub> composites with BaTiO<sub>3</sub> concentrations <em>х</em> = 0.25, 0.50 and 0.53 has been carried out on cooling with the use of the neutron diffraction technique. It was shown that, on cooling, the phase transition temperature (<em>T</em><sub>c</sub>) from the high-temperature paraelectric phase into the ferroelectric one did not depend on barium titanate concentration and practically coincided with <em>T</em><sub>c</sub> for pure NOP. Moreover, it was found that the admixture of BaTiO<sub>3</sub> essentially enlarged the temperature range of NOP ferroelectric phase stability in the composites with BaTiO<sub>3</sub> concentrations <em>x</em> = 0.25 and 0.50. The suppression of the ferroelectric phase was observed for the composite with <em>x</em> = 0.53.</p></div>","PeriodicalId":41808,"journal":{"name":"St Petersburg Polytechnic University Journal-Physics and Mathematics","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2017-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.spjpm.2017.09.006","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91770277","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
The splitting features of a frequency spectrum of a gyroscope based on elastic waves in solids: An isolated imperfect ring as an example 基于固体中弹性波的陀螺仪频谱的分裂特征:一个孤立的不完美环为例
IF 0.2
St Petersburg Polytechnic University Journal-Physics and Mathematics Pub Date : 2017-10-01 DOI: 10.1016/j.spjpm.2017.09.004
Sergei V. Seregin
{"title":"The splitting features of a frequency spectrum of a gyroscope based on elastic waves in solids: An isolated imperfect ring as an example","authors":"Sergei V. Seregin","doi":"10.1016/j.spjpm.2017.09.004","DOIUrl":"https://doi.org/10.1016/j.spjpm.2017.09.004","url":null,"abstract":"<div><p>The calculation results on dynamic characteristics of a geometrically imperfect ring turning out of shape in its plane have been exemplified by a simpler computational model for a ring resonator of a gyroscope based on elastic waves in solids. The specific malconformations were shown to be responsible for a splitting of the bending frequency spectrum of such rings. In so doing the spectral mismatch may appear in cases different from the ideas of modern theory.</p><p>The splitting of the bending frequency spectrum was established to occur not only in the cases when the number of formative waves being equal to that of malconformation waves of the ring (as it is commonly believed at present) but also in the cases when the number of formative waves being two, three, four and so on times more than that of malconformation waves.</p></div>","PeriodicalId":41808,"journal":{"name":"St Petersburg Polytechnic University Journal-Physics and Mathematics","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2017-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.spjpm.2017.09.004","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91707736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 4
Stage-by-stage modeling of the mechanism of semiconductor–metal phase transition in vanadium dioxide 二氧化钒中半导体-金属相变机理的逐级模拟
IF 0.2
St Petersburg Polytechnic University Journal-Physics and Mathematics Pub Date : 2017-10-01 DOI: 10.1016/j.spjpm.2017.09.002
Aleksander V. Il'inskiy , Marina E. Pashkevich , Eugeniy B. Shadrin
{"title":"Stage-by-stage modeling of the mechanism of semiconductor–metal phase transition in vanadium dioxide","authors":"Aleksander V. Il'inskiy ,&nbsp;Marina E. Pashkevich ,&nbsp;Eugeniy B. Shadrin","doi":"10.1016/j.spjpm.2017.09.002","DOIUrl":"https://doi.org/10.1016/j.spjpm.2017.09.002","url":null,"abstract":"<div><p>The algorithm of stage-by-stage qualitative modeling of the mechanism of a semiconductor–metal phase transition in vanadium dioxide has been proposed. The basis for the model is a statement that the transition is complex in character and consists of the anhysteretic, purely electronic Моtt transition occurring over a wide temperature range, and the temperature-abrupt structural Peierls transition having a thermal hysteresis. The initial stage of the model is based on the solution of a quantum-mechanical problem of an electronic spectrum of a linear vanadium-ion's chain. The model is completed by consideration of correlation effects and a martensitic character of the structural transition through taking consecutively account of results obtained by X-ray, spectroscopic, impedansmetric and magnetic resonance methods.</p></div>","PeriodicalId":41808,"journal":{"name":"St Petersburg Polytechnic University Journal-Physics and Mathematics","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2017-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.spjpm.2017.09.002","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91770280","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Operational matrices to solve nonlinear Riccati differential equations of arbitrary order 求解任意阶非线性Riccati微分方程的运算矩阵
IF 0.2
St Petersburg Polytechnic University Journal-Physics and Mathematics Pub Date : 2017-10-01 DOI: 10.1016/j.spjpm.2017.08.001
Kourosh Parand , Mehdi Delkhosh
{"title":"Operational matrices to solve nonlinear Riccati differential equations of arbitrary order","authors":"Kourosh Parand ,&nbsp;Mehdi Delkhosh","doi":"10.1016/j.spjpm.2017.08.001","DOIUrl":"10.1016/j.spjpm.2017.08.001","url":null,"abstract":"<div><p>In this paper, an effective numerical method to achieve the numerical solution of nonlinear Riccati differential equations of arbitrary (integer and fractional) order has been developed. For this purpose, the fractional order of the Chebyshev functions (FCFs) based on the classical Chebyshev polynomials of the first kind have been introduced, that can be used to obtain the solution of these equations. Also, the operational matrices of fractional derivative and product for the FCFs have been constructed. The obtained results illustrated demonstrate that the suggested approaches are applicable and valid.</p></div>","PeriodicalId":41808,"journal":{"name":"St Petersburg Polytechnic University Journal-Physics and Mathematics","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2017-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.spjpm.2017.08.001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87426324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 8
Testing of various schemes with quasi-one-dimensional reconstruction of gasdynamic variables in the case of unstructured-grid calculations 非结构网格计算中各种气体动力变量准一维重建方案的测试
IF 0.2
St Petersburg Polytechnic University Journal-Physics and Mathematics Pub Date : 2017-10-01 DOI: 10.1016/j.spjpm.2017.09.010
Elizaveta V. Kolesnik, Evgueni M. Smirnov
{"title":"Testing of various schemes with quasi-one-dimensional reconstruction of gasdynamic variables in the case of unstructured-grid calculations","authors":"Elizaveta V. Kolesnik,&nbsp;Evgueni M. Smirnov","doi":"10.1016/j.spjpm.2017.09.010","DOIUrl":"10.1016/j.spjpm.2017.09.010","url":null,"abstract":"<div><p>Several schemes of the second-order approximation worked out in the literature for unstructured-grid-based computations of gasdynamic flows are described. The convective fluxes on the control-volume's faces are evaluated using Roe's approximate Riemann solver. The MUSCL approach with the use of various quasi-one-dimensional schemes of reconstruction of gasdynamic variables and limiters making the solution monotonic is applied in order to improve the approximation accuracy. Comparative analysis of the working capacity of the schemes under consideration has been carried out through solving two problems of inviscid gas flow. Namely, the transonic NACA-0012 airfoil flow and the superpersonic flow in a duct with a central ramp were computed<em>.</em> The smoothness of solution, obtained with different schemes, dissipativity features of the schemes and computational process stability were evaluated.</p></div>","PeriodicalId":41808,"journal":{"name":"St Petersburg Polytechnic University Journal-Physics and Mathematics","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2017-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.spjpm.2017.09.010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87590288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
High-efficiency and robust M-estimates of the scale parameter on the Q-estimate basis 在q估计的基础上对尺度参数进行高效稳健的m估计
IF 0.2
St Petersburg Polytechnic University Journal-Physics and Mathematics Pub Date : 2017-10-01 DOI: 10.1016/j.spjpm.2017.09.012
Pavel O. Smirnov, Ivan S. Shirokov, Georgiy L. Shevlyakov
{"title":"High-efficiency and robust M-estimates of the scale parameter on the Q-estimate basis","authors":"Pavel O. Smirnov,&nbsp;Ivan S. Shirokov,&nbsp;Georgiy L. Shevlyakov","doi":"10.1016/j.spjpm.2017.09.012","DOIUrl":"https://doi.org/10.1016/j.spjpm.2017.09.012","url":null,"abstract":"<div><p>The commonly employed highly efficient and robust <em>Q</em>-estimate of the scale parameter proposed by Rousseeuw and Croux has been approximated using computationally fast Huber <em>M</em>-estimates. The suggested <em>M</em>-estimates were shown to be robust and highly efficient for an arbitrary underlying data distribution due to correctly choosing the approximation parameters. The following indicators of the efficiency and robustness of <em>M</em>-estimates of scale were computed: their asymptotic variances, influence functions and breakdown points. Special attention was given to the particular cases of the Gaussian and Cauchy distributions. It is noteworthy that for the Cauchy distribution, the suggested robust estimate of scale coincides with the maximal likelihood estimate. Finally, the computation time of these highly efficient and robust estimates of scale is 3–4 times less than for the corresponding <em>Q</em>-estimates.</p></div>","PeriodicalId":41808,"journal":{"name":"St Petersburg Polytechnic University Journal-Physics and Mathematics","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2017-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.spjpm.2017.09.012","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91770275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Simulation of an on-the-fly measuring system of a descent module under uncertainty of the lunar-surface composition 月面成分不确定条件下下降舱实时测量系统仿真
IF 0.2
St Petersburg Polytechnic University Journal-Physics and Mathematics Pub Date : 2017-10-01 DOI: 10.1016/J.SPJPM.2017.09.003
Irina A. Kislitsyna, G. Malykhina
{"title":"Simulation of an on-the-fly measuring system of a descent module under uncertainty of the lunar-surface composition","authors":"Irina A. Kislitsyna, G. Malykhina","doi":"10.1016/J.SPJPM.2017.09.003","DOIUrl":"https://doi.org/10.1016/J.SPJPM.2017.09.003","url":null,"abstract":"","PeriodicalId":41808,"journal":{"name":"St Petersburg Polytechnic University Journal-Physics and Mathematics","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2017-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74516605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
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