МЕТОДЫ РАСЧЕТА ОПТИМАЛЬНЫХ НАСТРОЕК СИСТЕМ УПРАВЛЕНИЯ ПО КАНАЛУ ВОЗМУЩЕНИЯ

In the process of automatic control system debugging the great attention is paid to determining formulas’ parameters of optimal dynamic adjustment of regulators, taking into account the dynamics of Objects control. In most cases the known formulas are oriented on design of automatic control system through channel “input-output definition”. But practically in all continuous processes the main task of all regulators is stabilization of output parameters. The Methods of parameters calculation for dynamic adjustment of regulations were developed. These methods allow to optimize the analog and digital regulators, taking into account minimization of regulated influences. There were suggested to use the fact of detuning and maximum value of regulated influence. As the automatic control system optimization with proportional plus reset controllers on disturbance channel is an unimodal task, the main algorithm of optimization is realized by Hooke – Jeeves method. For controllers optimization through channel external disturbance there were obtained functional dependences of parameters calculations of dynamic proportional plus reset controllers from dynamic characteristics of Object control. The obtained dependences allow to improve the work of controllers (regulators) of automatic control on external disturbance channel and so it allows to improve the quality of regulation of transient processes. Calculation formulas provide high accuracy and convenience in usage. In suggested method there are no nomographs and this fact expels subjectivity of investigation in determination of parameters of dynamic adjustment of proportional plus reset controllers. Functional dependences can be used for calculation of adjustment of PR controllers in a great range of change of dynamic characteristics of Objects control.В процессе наладки систем автоматического управления обычно отдают предпочтение элементарным формулам определения параметров оптимальной динамической настройки регуляторов, учитывающим динамику объектов управления. В большинстве случаев известные формулы ориентированы на расчет систем автоматического управления по каналу «задание – выход». Однако практически для всех непрерывных процессов основной задачей регуляторов является стабилизация выходных параметров на заданных значениях.Разработана методика расчета параметров динамических настроек регуляторов, учитывающая динамику крайнего внешнего возмущения. Данная методика позволяет оптимизировать аналоговые и цифровые регуляторы с учетом минимизации регулирующих воздействий. При этом для оптимизации регуляторов предлагается использовать функционал, учитывающий рассогласование и максимальную величину регулирующего воздействия. Так как оптимизация системы автоматического управления с ПИ-регулятором по каналу возмущения является унимодальной задачей, то основной алгоритм оптимизации реализован по методу Хука – Дживса. Для оптимизации регуляторов по каналу внешнего возмущения получены функциональные зависимости расчета параметров динамической настройки ПИ-регулятора от динамических свойств объекта управления. В отличие от существующих методов полученные зависимости позволяют оптимизировать регуляторы автоматического управления по каналу внешнего возмущения как с учетом динамических характеристик объекта управления по каналу регулирующего воздействия, так и по динамическим характеристикам канала крайнего внешнего возмущения, что, несомненно, улучшает качество регулирования переходных процессов. Расчетные формулы обеспечивают высокую точность и удобны для практического использования. В предложенном методе отсутствуют графические номограммы, что исключает субъективность исследователя при определении параметров динамической настройки ПИ-регуляторов. Функциональные зависимости могут применяться для расчета настройки ПИ-регуляторов в широком диапазоне изменения динамических свойств объектов управления

Баланс льда в Северном Ледовитом океане в 1979–2019 гг. (по данным моделирования)

The results of numerical experiments on the model of joint water and ice circulation for the period from September 1979 to December 2019, aimed at studying the interannual variability of the ice balance in the Arctic Ocean, are considered. The results obtained made it possible to analyze the geographical features of the processes of ice formation and melting in the Arctic Ocean and to identify key areas that determine the volume of ice in the ocean. It is established that the main quantity of ice is formed in waters of the Siberian seas, and the most intense melting occurs in the North European Basin, where the ice transported by the Transpolar Current through the Fram Strait enters the relatively warm water of the Greenland Sea, heated by the North Atlantic Current. The formation of the absolute minimum of ice coverage in 2012 was promoted by the anomalous position of the anticyclonic hydrological cycle – much closer to the Canadian coast. This resulted in the fact that only a small part of the ice formed in the Siberian seas was involved into a weakened circulation, while most of the ice in the stream of the Transpolar Current was transported through the Fram Strait to the Greenland Sea. Statistical analysis of the results of numerical experiments demonstrated that the trend towards a decrease in the volume of ice in the Arctic Ocean is primarily determined by the global warming, and dynamic forcing exerts significant effect on local extremes.Для исследования изменчивости баланса льда Северного Ледовитого океана использовалась модель совместной циркуляции вод и льдов. Результаты специальных численных экспериментов для периода с сентября 1979 г. по декабрь 2019 г. позволили установить некоторые географические особенности процессов образования и таяния льда. Статистический анализ результатов показал, что тренд на уменьшение объёма льда в Северном Ледовитом океане определяется в первую очередь глобальным потеплением, а на локальные экстремумы сильное влияние оказывает динамический форсинг

Characteristic features of the temperature dependence of the surface impedance in polycrystalline MgB2_2 samples

The real $R_s(T)$ and imaginary $X_s(T)$ parts of the surface impedance $Z_s(T)=R_s(T)+iX_s(T)$ in polycrystalline MgB$_2$ samples of different density with the critical temperature $T_c\approx 38$ K are measured at the frequency of 9.4 GHz and in the temperature range $5\le T<200$ K. The normal skin-effect condition $R_s(T)=X_s(T)$ at $T\ge T_c$ holds only for the samples of the highest density with roughness sizes not more than 0.1 $\mu$m. For such samples extrapolation $T\to 0$ of the linear at $T<T_c/2$ temperature dependences $\lambda_L(T)=X_s(T)/\omega\mu_0$ and $R_s(T)$ results in values of the London penetration depth $\lambda_L(0)\approx 600$ \AA and residual surface resistance $R_{res}\approx 0.8$ m$\Omega$. In the entire temperature range the dependences $R_s(T)$ and $X_s(T)$ are well described by the modified two-fluid model.Comment: 7 pages, 3 figures. Europhysics Letters, accepted for publicatio

Electron transport, penetration depth and upper critical magnetic field of ZrB12 and MgB2

We report on the synthesis and measurements of the temperature dependence of resistivity, R(T), the penetration depth, l(T), and upper critical magnetic field, Hc2(T), for polycrystalline samples of dodecaboride ZrB12 and diboride MgB2. We conclude that ZrB12 as well as MgB2 behave like simple metals in the normal state with usual Bloch-Gruneisen temperature dependence of resistivity and with rather low resistive Debye temperature, TR=280 K, for ZrB12 (as compared to MgB2 with TR=900 K). The R(T) and l(T) dependencies of ZrB12 reveal a superconducting transition at Tc=6.0 K. Although a clear exponential l(T)dependence in MgB2 thin films and ceramic pellets was observed at low temperatures, this dependence was almost linear for ZrB12 below Tc/2. These features indicate s-wave pairing state in MgB2, whereas a d-wave pairing state is possible in ZrB12. A fit to the data gives a reduced energy gap 2D(0)/kTc=1.6 for MgB2 films and pellets, in good agreement with published data for 3D \pi - sheets of the Fermi surface. Contrary to conventional theories we found a linear temperature dependence of Hc2(T) for ZrB12 (Hc2(0)=0.15 T).Comment: 8 pages, 10 figures, submitted to JET

Экспресс-методы определения коэффициентов передаточных функций пароперегревательных участков котлов при различных нагрузках

The paper proposes rapid methods for transfer function coefficient determination of superheater sections under various loads while using a universal nomogram based on initial data of one load. The rapid methods make it possible to obtain analytical nonlinear dependences pertaining to changes of superheater transfer function parameters through the channel of regulatory impact, that provides parameter optimization of the dynamic knob injection adjustment throughout the whole range of power block load changes.Предложены экспресс-методы определения коэффициентов передаточных функций пароперегревательных участков при различных нагрузках с использованием универсальной номограммы на основе исходных данных одной нагрузки. Экспресс-методы дают возможность получить аналитические нелинейные зависимости изменения параметров передаточных функций пароперегервателей по каналу регулирующего воздействия, что позволяет оптимизировать параметры динамической настройки регуляторов впрысков во всем диапазоне изменения нагрузки энергоблоков

Isolation of Flow and Nonflow Correlations by Two- and Four-Particle Cumulant Measurements of Azimuthal Harmonics in sNN=\sqrt{s_{_{\rm NN}}} = 200 GeV Au+Au Collisions

A data-driven method was applied to measurements of Au+Au collisions at $\sqrt{s_{_{\rm NN}}} =$ 200 GeV made with the STAR detector at RHIC to isolate pseudorapidity distance $\Delta\eta$-dependent and $\Delta\eta$-independent correlations by using two- and four-particle azimuthal cumulant measurements. We identified a component of the correlation that is $\Delta\eta$-independent, which is likely dominated by anisotropic flow and flow fluctuations. It was also found to be independent of $\eta$ within the measured range of pseudorapidity $|\eta|<1$. The relative flow fluctuation was found to be $34\% \pm 2\% (stat.) \pm 3\% (sys.)$ for particles of transverse momentum $p_{T}$ less than $2$ GeV/$c$. The $\Delta\eta$-dependent part may be attributed to nonflow correlations, and is found to be $5\% \pm 2\% (sys.)$ relative to the flow of the measured second harmonic cumulant at $|\Delta\eta| > 0.7$

Observation of charge asymmetry dependence of pion elliptic flow and the possible chiral magnetic wave in heavy-ion collisions

We present measurements of $\pi^-$ and $\pi^+$ elliptic flow, $v_2$, at midrapidity in Au+Au collisions at $\sqrt{s_{_{\rm NN}}} =$ 200, 62.4, 39, 27, 19.6, 11.5 and 7.7 GeV, as a function of event-by-event charge asymmetry, $A_{ch}$, based on data from the STAR experiment at RHIC. We find that $\pi^-$ ($\pi^+$) elliptic flow linearly increases (decreases) with charge asymmetry for most centrality bins at $\sqrt{s_{_{\rm NN}}} = \text{27 GeV}$ and higher. At $\sqrt{s_{_{\rm NN}}} = \text{200 GeV}$, the slope of the difference of $v_2$ between $\pi^-$ and $\pi^+$ as a function of $A_{ch}$ exhibits a centrality dependence, which is qualitatively similar to calculations that incorporate a chiral magnetic wave effect. Similar centrality dependence is also observed at lower energies.Comment: 6 pages, 4 figure

Centrality and transverse momentum dependence of elliptic flow of multi-strange hadrons and ϕ\phi meson in Au+Au collisions at sNN\sqrt{s_{NN}} = 200 GeV

We present high precision measurements of elliptic flow near midrapidity ($|y|<1.0$) for multi-strange hadrons and $\phi$ meson as a function of centrality and transverse momentum in Au+Au collisions at center of mass energy $\sqrt{s_{NN}}=$ 200 GeV. We observe that the transverse momentum dependence of $\phi$ and $\Omega$ $v_{2}$ is similar to that of $\pi$ and $p$, respectively, which may indicate that the heavier strange quark flows as strongly as the lighter up and down quarks. This observation constitutes a clear piece of evidence for the development of partonic collectivity in heavy-ion collisions at the top RHIC energy. Number of constituent quark scaling is found to hold within statistical uncertainty for both 0-30$\%$ and 30-80$\%$ collision centrality. There is an indication of the breakdown of previously observed mass ordering between $\phi$ and proton $v_{2}$ at low transverse momentum in the 0-30$\%$ centrality range, possibly indicating late hadronic interactions affecting the proton $v_{2}$.Comment: 7 pages and 4 figures, Accepted for publication in Physical Review Letter

Beam energy dependent two-pion interferometry and the freeze-out eccentricity of pions in heavy ion collisions at STAR

We present results of analyses of two-pion interferometry in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV measured in the STAR detector as part of the RHIC Beam Energy Scan program. The extracted correlation lengths (HBT radii) are studied as a function of beam energy, azimuthal angle relative to the reaction plane, centrality, and transverse mass ($m_{T}$) of the particles. The azimuthal analysis allows extraction of the eccentricity of the entire fireball at kinetic freeze-out. The energy dependence of this observable is expected to be sensitive to changes in the equation of state. A new global fit method is studied as an alternate method to directly measure the parameters in the azimuthal analysis. The eccentricity shows a monotonic decrease with beam energy that is qualitatively consistent with the trend from all model predictions and quantitatively consistent with a hadronic transport model.Comment: 27 pages; 27 figure