THIACALIX[4]ARENES DERIVATIVES: FROM SELF-ASSEMBY TO FUNCTIONAL MATERIALS

This work was supported by the by Russian Science Foundation, project # 19-13-00095

Cross-relaxation and phonon bottleneck effects on magnetization dynamics in LiYF4:Ho3+

Frequency and dc magnetic field dependences of dynamic susceptibility in diluted paramagnets LiYF$_4$:Ho$^{3+}$ have been measured at liquid helium temperatures in the ac and dc magnetic fields parallel to the symmetry axis of a tetragonal crystal lattice. Experimental data are analyzed in the framework of microscopic theory of relaxation rates in the manifold of 24 electron-nuclear sublevels of the lowest non-Kramers doublet and the first excited singlet in the Ho$^{3+}$ ground multiplet $^5I_8$ split by the crystal field of S$_4$ symmetry. The one-phonon transition probabilities were computed using electron-phonon coupling constants calculated in the framework of exchange charge model and were checked by optical piezospectroscopic measurements. The specific features observed in field dependences of the in- and out-of-phase susceptibilities (humps and dips, respectively) at the crossings (anti-crossings) of the electron-nuclear sublevels are well reproduced by simulations when the phonon bottleneck effect and the cross-spin relaxation are taken into account

Self-Organization in Multimode Microwave Phonon Laser (Phaser): Experimental Observation of Spin-Phonon Cooperative Motions

An unusual nonlinear resonance was experimentally observed in a ruby phonon laser (phaser) operating at 9 GHz with an electromagnetic pumping at 23 GHz. The resonance is manifested by very slow cooperative self-detunings in the microwave spectra of stimulated phonon emission when pumping is modulated at a superlow frequency (less than 10 Hz). During the self-detuning cycle new and new narrow phonon modes are sequentially ``fired'' on one side of the spectrum and approximately the same number of modes are ``extinguished'' on the other side, up to a complete generation breakdown in a certain final portion of the frequency axis. This is usually followed by a short-time refractority, after which the generation is fired again in the opposite (starting) portion of the frequency axis. The entire process of such cooperative spectral motions is repeated with high degree of regularity. The self-detuning period strongly depends on difference between the modulation frequency and the resonance frequency. This period is incommensurable with period of modulation. It increases to very large values (more than 100 s) when pointed difference is less than 0.05 Hz. The revealed phenomenon is a kind of global spin-phonon self- organization. All microwave modes of phonon laser oscillate with the same period, but with different, strongly determined phase shifts - as in optical lasers with antiphase motions.Comment: LaTeX2e file (REVTeX4), 5 pages, 5 Postscript figures. Extended and revised version of journal publication. More convenient terminology is used. Many new bibliographic references are added, including main early theoretical and experimental papers on microwave phonon lasers (in English and in Russian

Calixarene-based supramolecular systems: a platform for nanomaterials design by self-assembly

Lower rim thiacalix[4]arenes derivatives in cone and 1,3-alternate conformations have many advantages to create a wide range of precursors for the design of very sophisticated supramolecular architectures. These compounds can be considered as technological platform for nanomaterials design by self-assembly method. Particular attention will be paid to the application of calixarene derivatives for the construction of various supramolecular and nanosystems, devices and smart materials: colloid nanoparticles, catalytic systems, metalcoordinated networks, Langmuir-Blodgett nanolayers, molecular magnets etc.The authors gratefully acknowledge of the RSF (19-13-00095 and 18-73-10033) for the financial support

Power quality problems and ways of modeling the electrotechnological installations for identification of negative phenomena and factors arising from the operation of this equipment

Статья описывает проблему снижения качества электроэнергии, возникающую в процессе наращивания энергетических мощностей. Снижение качества электроэнергии может быть вызвано множеством различных факторов, проявляющихся при определенных обстоятельствах, и имеют поэтому разные решения по их устранению. Наиболее остро стоит проблема влияния качества электроэнергии на энергетические параметры электрооборудования и электроприемников в металлургической отрасли и в области механической обработки, широко эксплуатирующих различные электротехнологические установки. Важным элементом при подготовке специалистов в области электроэнергетики и электротехники является формирование компетенций, направленных на выявление и устранение причин, вызывающих снижение качества электроэнергии. Наиболее эффективно эти компетенции могут быть сформированы при выполнении действий на реальном оборудовании или на физической модели.The article describes the problem of reducing power quality, arising in the process of building energy capacity. Reduced power quality can be caused by many different factors, manifested in certain circumstances, and therefore have different solutions for their elimination. The most acute problem of the influence of power quality parameters on energy and electrical power consumers in the steel industry and in the field of machining, widely different operating electrotechnological installation. An important element in the preparation of specialists in the field of electricity and electrical engineering is the formation of competences, aimed at identifying and eliminating the causes of decline in power quality. The most effective of these competencies can be formed when performing actions on real hardware or on a physical model

Development and testing the exciter of synchronous machine based on high frequency regulator of current

В статье обосновывается целесообразность применения возбудителей синхронных машин малой мощности на основе источника тока. Показаны особенности характеристик синхронных машин малой мощности. Описана блочная функциональная схема системы возбуждения, позволяющая регулировать величину тока. Описаны технологические особенности схемы, представлены преимущества такой схемы относительно традиционных систем.The article explains the usefulness of agents of low-power synchronous machines based on the current source. The features of low power characteristics of synchronous machines. Be described a functional block diagram of the excitation system, which allows to regulate the amount of current. Described technological features of the scheme, presented the benefits of such a scheme with respect to traditional systems

Application compensating devices and resonant filters to suppress the voltage higher harmonics in the electric grid

В статье обосновывается целесообразность применения компенсирующих устройств, в том числе конденсаторных батарей и резонансных фильтров высших гармоник. Описаны особенности применения данных устройств при комплексном использовании. Описана схема разработанных фильтров, приведены результаты сравнения применяемых компенсирующих устройств. Проведены расчеты по нахождению величин тока основной гармоники нагрузки и фильтра.The article proves the feasibility of compensating devices, including capacitor banks and harmonic filter resonance. The features of the application of these devices with the integrated use. The scheme developed by the filters, given the results of comparison used compensating devices. The calculations for finding the values of the fundamental harmonic current load and filter

Development intellectual of laboratory for trainees on electrical engineering courses

Проведение лабораторных практикумов является существенным этапом подготовки специалистов любого профиля. В настоящее время многими производителями предлагаются лабораторные стенды, отвечающие широкому спектру изучаемых дисциплин, как общего профиля, так и специализированных, однако охватить обширную тематику вопросов обсуждаемых в рамках дисциплин электроэнергетического профиля достаточно сложно. Некоторые вопросы специальных дисциплин требуют более пристального внимания, чем сейчас, что объясняет потребность в разработке специализированных лабораторных стендов для этих дисциплин.The article explains the usefulness of agents of low-power synchronous machines based on the current source. The features of low power characteristics of synchronous machines. Be described a functional block diagram of the excitation system, which allows to regulate the amount of current. Described technological features of the scheme, presented the benefits of such a scheme with respect to traditional systems

Temperature dependence of the EPR linewidth of Yb3+ - ions in Y0.99Yb0.01Ba2Cu3OX compounds: Evidence for an anomaly near TC

Electron paramagnetic resonance experiments on doped Yb3+ ions in YBaCuO compounds with different oxygen contents have been made. We have observed the strong temperature dependence of the EPR linewidth in the all investigated samples caused by the Raman processes of spin-lattice relaxation. The spin-lattice relaxation rate anomaly revealed near TC in the superconducting species can be assigned to the phonon density spectrum changesComment: 10 pages, 4 figures Renewed versio