Problems of distance education in high school

В статье рассматриваются проблемы развития системы дистанционного образования. Внедрение инновационных технологий в высшей школе требует значительных финансовых затрат. Однако развитие дистанционного образования дает возможность большинству людей получать образование, экономить деньги, выбирать удобное время для обучения, повышать квалификацию.This article discusses the development of distance education. Introduction of innovative technologies in higher education requires considerable financial costs. However, the development of distance education makes it possible for most people to get an education, to save money, choose a convenient time for learning, improve their qualifications

The role of fragmentation in interaction of meteoroids with the Earth's atmosphere

As a rule, when analyzing the mechanism of quasi continuous fragmentation (QCF) it is assumed that fragments separated from the parent meteoroid (PM) are of equal initial mass. In reality, this may not be so. A major difficulty is the lack of observational data on the function of the fragment initial mass distribution and so one must resort to theoretical modeling. A discrete distribution is considered which excluded to a certain extent some mathematical difficulties. The calculation results are given and discussed

Study of a novel type of the optical modes in VCSELs

We study novel side-emitting modes in VCSEL microcavities. These modes correspond to π-shaped propagation along the mesa diameter, reflection from angled mesa walls and bottom Bragg reflector. We believe this study of π-modes is important for optimization of VCSEL design for improvement of efficiency

Cross-sections for nuclide production in 56Fe target irradiated by 300, 500,750, 1000, 1500, and 2600 MeV protons compared with data on hydrogen target irradiation by 300, 500, 750, 1000, and 1500 MeV/nucleon 56Fe ions

Cross-sections for radioactive nuclide production in 56Fe(p,x) reactions at 300, 500, 750, 1000, 1500, and 2600 MeV were measured using the ITEP U-10 proton accelerator. In total, 221 independent and cumulative yields of products of half-lives from 6.6 min to 312 days have been obtained via the direct-spectrometry method. The measured data have been compared with the experimental data obtained elsewhere by the direct and inverse kinematics methods and with calculations by 15 codes, namely: MCNPX (INCL, CEM2k, BERTINI, ISABEL), LAHET (BERTINI, ISABEL), CEM03 (.01, .G1, .S1), LAQGSM03 (.01, .G1, >.S1), CASCADE-2004, LAHETO, and BRIEFF. Most of our data are in a good agreement with the inverse kinematics results and disprove the results of some earlier activation measurements that were quite different from the inverse kinematics measurements. The most significant calculation-to-experiment differences are observed in the yields of the A<30 light nuclei, indicating that further improvements in nuclear reaction models are needed, and pointing out as well to a necessity of more complete measurements of such reactions.Comment: 53 pages, 9 figures, 6 tables, only pdf file, submitted to Phys. Rev.

Design of electrically driven single photon source based on dielectric passive cavity structure at 1.3 μm

A combination of advanced concepts is applied for designing micro-cavity structures aimed for single-photon sources with high photon-extraction efficiency in the telecom O-band at ~1.3 μm. The device design consists of a broad stop-band bottom distributed Bragg reflector (DBR), a top DBR formed in a dielectric micropillar with additional circular Bragg grating and a central dielectric passive cavity. This combination of photonic elements is compatible with electric carrier injection and provides overall photon-extraction efficiency of ~83% as shown by 3D finite-difference time-domain simulations

Термодинамические свойства L-ментола в кристаллическом и газообразном состояниях

Objectives. Menthol causes a cooling sensation and reduces the nerve activity when it is applied locally, ingested, or inhaled. This feature explains its extensive use as both an aromatizer and a flavoring agent in food manufacturing, tobacco industry, cosmetics production, as well as a mild anesthetic and antiseptic in dentistry. This work aimed to perform a comprehensive thermodynamic study of L-menthol in both crystalline and gaseous states.Methods. To determine the combustion energy of L-menthol in the crystalline state, combustion bomb calorimetry was used. The temperature dependence of L-menthol’s heat capacity in the range of 5–370 K and the melting (fusion) parameters were determined using adiabatic calorimetry. Quantum chemical calculations were performed on a standalone virtual machine in the Google Cloud Platform using an eight-core Intel Xeon Scalable Processor (Skylake) with a 2.0 GHz (up to 2.7 GHz at peak load) clock frequency and 8 GB RAM.Results. The energy and enthalpy of L-menthol combustion in the crystalline state were determined, and the standard enthalpy of L-menthol formation in the gaseous state was calculated using the standard enthalpy of sublimation. The standard thermodynamic functions (reduced enthalpy, entropy, and reduced Gibbs energy) of L-menthol in both crystalline and liquid states were obtained based on the smoothed values of heat capacity and melting parameters. The group of isodesmic reactions for the ab initio calculation of the enthalpy of formation for gaseous L-menthol was substantiated. Electronic energy and frequencies of normal modes of the molecules involved in these reactions were calculated using the Gaussian 4 composite quantum chemical method. Further, the sublimation enthalpy of L-menthol was calculated using the extended Politzer equation according to the electrostatic potential model.Conclusions. The first comprehensive thermodynamic study of L-menthol in various states of aggregation was performed, and the values calculated using semiempirical methods were consistent with the experimental values within error limits, which confirms the reliability of the results.Цели. Ментол при местном воздействии, употреблении в пищу или вдыхании вызывает ощущение охлаждения и снижает нервную активность, что объясняет его широкое применение в качестве отдушки и вкусовой добавки в пищевой и табачной промышленности, косметике, а также в качестве мягкого анестетика и антисептика в стоматологии. Цель работы заключалась в комплексном термодинамическом исследовании L-ментола в кристаллическом и газообразном состояниях.Методы. Методом бомбовой калориметрии сгорания была определена энергия сгорания L-ментола в кристаллическом состоянии. Методом адиабатической калориметрии была получена температурная зависимость теплоемкости L-ментола в интервале 5–370 К и найдены его параметры плавления. Квантово-химические вычисления производились на выделенной виртуальной машине в облачном сервисе Google Cloud Platform с использованием 8 вычислительных ядер Intel Xeon Scalable Processor (Skylake) с тактовой частотой 2.0 ГГц (до 2.7 ГГц при пиковой нагрузке) и 8 ГБ оперативной памяти.Результаты. Были определены энергия и энтальпия сгорания L-ментола в кристаллическом состоянии. С использованием величины стандартной энтальпии сублимации был выполнен расчет стандартной энтальпии образования L-ментола в газообразном состоянии. На основании сглаженных значений теплоемкости и параметров плавления получены стандартные термодинамические функции (приведенная энтальпия, энтропия и приведенная энергия Гиббса) L-ментола в кристаллическом и жидком состояниях. Обоснована группа изодесмических реакций для ab initio расчета энтальпии образования газообразного L-ментола, и с использованием композитного квантово-химического метода Gaussian 4 вычислены электронная энергия и частоты нормальных колебаний молекул–участников этих реакций. В рамках модели электростатического потенциала по расширенному уравнению Политцера рассчитана энтальпия сублимации L-ментола.Выводы. Впервые было проведено комплексное термодинамическое исследование L-ментола в различных агрегатных состояниях. Величины, рассчитанные с помощью полуэмпирических методов, согласуются в пределах погрешностей с опытными величинами, что подтверждает достоверность полученных результатов

Thermodynamic similarity of stacked-cup multiwall carbon nanotubes and graphite

When conducting photo elicitation interviews (PEI), researchers introduce photographs into the interview context. Although PEI has been employed across a wide variety of disciplines and participants, little has been written about the use of photographs in interviews with children. In this article, the authors review the use of PEI in a research study that explored the perspectives on camp of children with cancer. In particular, they review some of the methodological and ethical challenges, including (a) who should take the photographs and (b) how the photographs should be integrated into the interview. Although some limitations exist, PEI in its various forms can challenge participants, trigger memory, lead to new perspectives, and assist with building trust and rapport

Criticality analysis of pyrochemical reprocessing apparatuses for mixed uranium-plutonium nitride spent nuclear fuel using the MCU-FR and MCNP program codes

A preliminary criticality analysis for novel pyrochemical apparatuses for the reprocessing of mixed uranium-plutonium nitride spent nuclear fuel from the BREST-OD-300 reactor was performed. High-temperature processing apparatuses, “metallization” electrolyzer, refinery remelting apparatus, refining electrolyzer, and “soft” chlorination apparatus are considered in this work. Computational models of apparatuses for two neutron radiation transport codes (MCU-FR and MCNP) were developed and calculations for criticality were completed using the Monte Carlo method. The criticality analysis was performed for different loads of fissile material into the apparatuses including overloading conditions. Various emergency situations were considered, in particular, those associated with water ingress into the chamber of the refinery remelting apparatus. It was revealed that for all the considered computational models nuclear safety rules are satisfied. © 2022 Korean Nuclear Societ

Anomalous lasing of high-speed 850 nm InGaAlAs oxide-confined vertical-cavity surface-emitting lasers with a large negative gain-to-cavity wavelength detuning

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 105, 061104 (2014) and may be found at https://doi.org/10.1063/1.4892885.The impact of a large negative quantum well gain-to-cavity etalon wavelength detuning on the static and dynamic characteristics of 850 nm InGaAlAs high-speed oxide-confined vertical-cavity surface-emitting lasers (VCSELs) was investigated. Three distinct lasing regimes were revealed in large square aperture (≥7 μm per side) devices with large detuning including: (1) an anomalous lasing via higher order Hermite–Gaussian modes at low forward bias current; (2) lasing via the lowest order Hermite–Gaussian modes at high bias current; and (3) simultaneous lasing via both types of transverse modes at intermediate bias currents. In contrast to conventional multimode VCSELs a two-resonance modulation response was observed for the case of co-lasing via multiple transverse modes with high spectral separation. The reduction in the oxide aperture area resulted in classical lasing via the lowest order modes with a conventional single-resonance frequency response.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement

Spatial structure of felodipine dissolved in DMSO by 1D NOE and 2D NOESY NMR spectroscopy

Small organic molecules in dissolved state exist as an ensemble of conformers. In this work conformation of felodipine in dimethyl sulphoxide was studied and dominant stable conformers were determined. Effective interatomic distances were obtained by means of NOE spectroscopy. Fractions of different conformers were estimated by comparing effective distances and those obtained from quantum-chemical calculation [8]; averaging of distances was made following the N-site jump model. © 2012 Elsevier B.V. All rights reserved