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In the course of this study we defined conditions for the rational utilization of intermittent heat supply for public buildings of various types: administrative and educational institutions, and other public buildings. Known results of theoretical and experimental research do not take into consideration the dynamics of cooling a building and the appropriateness of employing a standby heating mode. And this is very important for a model of control over a heat supply system. We modeled mathematically a change in temperature indoors for various types of buildings under variable climatic parameters, of different levels of modernization and operating parameters of buildings, all of which defines the appropriateness of employing a standby regime. By cancelling a standby mode, it becomes possible to achieve an additional energy saving effect. This paper shows the impact of enclosing structures of buildings on the dynamics of heating and cooling premises under variable climatic conditions for various operational modes. A mathematical model has been proposed for the basic operational modes when an intermittent heating supply is used. A structure of the mathematical model consists of two inertial links: low­inertial and highly­inertial. The first link reflects the process of heating air indoors. The second link reflects the process of heating a premise’s enclosing structures. Parameters of the proposed model are the coefficients of the transfer of an object along the channel “heating power – change in air temperature”, as well as the time constants for each of the links. The input variables for a given model are the ambient temperature and the premises’ utilization mode (switch time of alternating regimes). The output change is a room temperature in accordance with the current mode. We have defined boundary conditions for employing a standby mode of an intermittent heating system for various types of buildings at different degrees of thermal modernization. The results of this research could be used when designing new public buildings and while modifying heating systems at existing administrative and educational institutions. In this case, it is necessary to take into consideration the degree of thermal modernization of a building, the type of heating systems, as well as modes of utilization

Максимально досяжна ефективність парогазових енергетичних установок визначається, в першу чергу, початковими і кінцевими параметрами (тиском, температурою) комбінованого циклу. В даний час, практично вичерпані технічні та доцільні техніко-економічні можливості істотного розширення діапазону цих параметрів. Викликає певний інтерес можливість підвищення показників ПГУ з котлами-утилізаторами за рахунок зниження незворотності в процесі теплообміну між продуктами згоряння і робочим тілом (вода, пара) паротурбінної частини, Застосування паралельного потоку газів в котлі-утилізаторі дозволяє досягти поставленої мети і дещо підняти ефективність ПГУ без суттевого її ускладнення і подорожчання.

We describe the design and implementation of a stable high-power 1064 nm laser system to generate optical lattices for experiments with ultracold quantum gases. The system is based on a low-noise laser amplified by an array of four heavily modified, high-power fiber amplifiers. The beam intensity is stabilized and controlled with a nonlinear feedback loop. Using real-time monitoring of the resulting optical lattice, we find the stability of the lattice site positions to be well below the lattice spacing over the course of hours. The position of the harmonic trap produced by the Gaussian envelope of the lattice beams is stable to about one lattice spacing and the long-term (six-month) relative RMS stability of the lattice spacing itself is 0.5%., Comment: 13 pages, 13 figures

Предложены перспективные схемные решения альтернативной системы горячего водоснабжения. Выполнено моделирование тепловых процессов в аккумуляторах теплоты при различных способах подключения генераторов теплоты и потребителей. Проведены экспериментальные исследования системы горячего водоснабжения на базе теплового насоса при различных температурных режимах

Exotic phases of matter can emerge from strong correlations in quantum many-body systems. Quantum gas microscopy affords the opportunity to study these correlations with unprecedented detail. Here we report site-resolved observations of antiferromagnetic correlations in a two-dimensional, Hubbard-regime optical lattice and demonstrate the ability to measure the spin-correlation function over any distance. We measure the in-situ distributions of the particle density and magnetic correlations, extract thermodynamic quantities from comparisons to theory, and observe statistically significant correlations over three lattice sites. The temperatures that we reach approach the limits of available numerical simulations. The direct access to many-body physics at the single-particle level demonstrated by our results will further our understanding of how the interplay of motion and magnetism gives rise to new states of matter., Comment: 6 + 12 pages, 4 + 6 figures, 1 table

Accessing new regimes in quantum simulation requires the development of new techniques for quantum state preparation. We demonstrate the quantum state engineering of a strongly correlated many-body state of the two-component repulsive Fermi-Hubbard model on a square lattice. Our scheme makes use of an ultralow entropy doublon band insulator created through entropy redistribution. After isolating the band insulator, we change the underlying potential to expand it into a half-filled system. The final many-body state realized shows strong antiferromagnetic correlations and a temperature below the exchange energy. We observe an increase in entropy, which we find is likely caused by the many-body physics in the last step of the scheme. This technique is promising for low-temperature studies of cold-atom-based lattice models., 6+4 pages, 4+4 figures

Exotic phenomena in systems with strongly correlated electrons emerge from the interplay between spin and motional degrees of freedom. For example, doping an antiferromagnet is expected to give rise to pseudogap states and high-temperature superconductors. Quantum simulation using ultracold fermions in optical lattices could help to answer open questions about the doped Hubbard Hamiltonian, and has recently been advanced by quantum gas microscopy. Here we report the realization of an antiferromagnet in a repulsively interacting Fermi gas on a two-dimensional square lattice of about 80 sites at a temperature of 0.25 times the tunnelling energy. The antiferromagnetic long-range order manifests through the divergence of the correlation length, which reaches the size of the system, the development of a peak in the spin structure factor and a staggered magnetization that is close to the ground-state value. We hole-dope the system away from half-filling, towards a regime in which complex many-body states are expected, and find that strong magnetic correlations persist at the antiferromagnetic ordering vector up to dopings of about 15 per cent. In this regime, numerical simulations are challenging and so experiments provide a valuable benchmark. Our results demonstrate that microscopy of cold atoms in optical lattices can help us to understand the low-temperature Fermi-Hubbard model.

The complexity of quantum many-body systems originates from the interplay of strong interactions, quantum statistics, and the large number of quantum-mechanical degrees of freedom. Probing these systems on a microscopic level with single-site resolution offers important insights. Here we report site-resolved imaging of two-component fermionic Mott insulators, metals, and band insulators using ultracold atoms in a square lattice. For strong repulsive interactions we observe two-dimensional Mott insulators containing over 400 atoms. For intermediate interactions, we observe a coexistence of phases. From comparison to theory we find trap-averaged entropies per particle of $1.0\,k_{\mathrm{B}}$. In the band-insulator we find local entropies as low as $0.5\,k_{\mathrm{B}}$. Access to local observables will aid the understanding of fermionic many-body systems in regimes inaccessible by modern theoretical methods., 6+7 pages

High resolution digital micro-mirror devices (DMD) make it possible to produce nearly arbitrary light fields with high accuracy, reproducibility and low optical aberrations. However, using these devices to trap and manipulate ultracold atomic systems for e.g. quantum simulation is often complicated by the presence of kHz-frequency switching noise. Here we demonstrate a simple hardware extension that solves this problem and makes it possible to produce truly static light fields. This modification leads to a 47 fold increase in the time that we can hold ultracold $^6$Li atoms in a dipole potential created with the DMD. Finally, we provide reliable and user friendly APIs written in Matlab and Python to control the DMD., Comment: Minor updates to address the reviewers' comments. 3 Pages, 3 Figures. Supplemental Material might be found on the Rev. Sci. Intrum. webpage

Removal of groundwater with further use of it for potable water supply and heat supply with the use of heat pump is an important problem. A new revolutionary approach to the decision of energy and water saving that provides rational accommodation of groundwater boreholes ensuring the required flow rate of water through the heat pump evaporator with simultaneously high intensity of heat exchange process is proposed. The method of calculation which allows determining the necessary depth of borehole, quantity of boreholes, in consideration of flow rate and temperature of subsoil water determining capacity of heat pump installation is worked out.

We demonstrate stable, long-term trapping of fermionic $^6$Li atoms in an optical lattice with MHz trap frequencies for use in a quantum gas microscope. Adiabatic release from the optical lattice in the object plane of a high-numerical-aperture imaging system allows a measurement of the population distribution among the lowest three bands in both radial directions with atom numbers as low as $7\times 10^2$. We measure exponential ground band heating rates as low as 0.014(1) s$^{-1}$ corresponding to a radial ground state $1/e$ lifetime of 71(5) s, fundamentally limited by scattering of lattice photons. For all lattice depths above 2 recoil, we find radial ground state lifetimes $\ge 1.6 \times 10^6$ recoil times., Comment: 5 pages, 4 figures, 3 pages supplemental material

Two new quantum gas microscopes demonstrate the imaging of fermionic atoms in an optical lattice, providing a step towards simulating complex electronic systems.

We demonstrate site-resolved imaging of individual fermionic ^{6}Li atoms in a single layer of a 3D optical lattice. To preserve the density distribution during fluorescence imaging, we simultaneously cool the atoms with 3D Raman sideband cooling. This laser cooling technique, demonstrated here for the first time for ^{6}Li atoms, also provides a pathway to rapid low-entropy filling of an optical lattice. We are able to determine the occupation of individual lattice sites with a fidelity95%, enabling direct, local measurement of particle correlations in Fermi lattice systems. This ability will be instrumental for creating and investigating low-temperature phases of the Fermi-Hubbard model, including antiferromagnets and d-wave superfluidity.