A New Algorithm of Iterative MIMO Detection and Decoding Using Linear Detector and Enhanced Turbo Procedure in Iterative Loop

In the paper we develop and evaluate a novel low complexity algorithm of iterative detection and decoding in multiple input multiple output (MIMO) system. It is based on a new enhanced Turbo procedure. Although the algorithm utilizes well-known components such as linear minimum mean square error (MMSE) detector and channel decoder with soft bits feedback, the new original procedure of getting extrinsic data essentially allows improving the receiver performance and reducing its complexity. Moreover, it is shown that proposed Turbo approach works even without channel decoder in the iteration loop. Thus, we ob-tain pure iterative MMSE detector with improved performance. Utilization of combined scheme with MMSE detector and channel decoder feedback demonstrates really outstanding performance. It is confirmed with simulations that the performance of proposed architecture exceeds traditional ML MIMO detector schemes that are designed with channel decoder but without iterative loop

Flat liquid jet as a highly efficient source of terahertz radiation

Polar liquids are strong absorbers of electromagnetic waves in the terahertz range, therefore, historically such liquids have not been considered as good candidates for terahertz sources. However, flowing liquid medium has explicit advantages, such as a higher damage threshold compared to solid-state sources and more efficient ionization process compared to gases. Here we report systematic study of efficient generation of terahertz radiation in flat liquid jets under sub-picosecond single-color optical excitation. We demonstrate how medium parameters such as molecular density, ionization energy and linear absorption contribute to the terahertz emission from the flat liquid jets. Our simulation and experimental measurements reveal that the terahertz energy has quasi-quadratic dependence on the optical excitation pulse energy. Moreover, the optimal pump pulse duration, which depends on the thickness of the jet is theoretically predicted and experimentally confirmed. The obtained optical-to-terahertz energy conversion efficiency is more than 0.05%. It is comparable to the commonly used optical rectification in most of electro-optical crystals and two-color air filamentation. These results, significantly advancing prior research, can be successfully applied to create a new alternative source of terahertz radiation

3D biodegradable scaffolds of polycaprolactone with silicate-containing hydroxyapatite microparticles for bone tissue engineering: high-resolution tomography and in vitro study

To date, special interest has been paid to composite scaffolds based on polymers enriched with hydroxyapatite (HA). However, the role of HA containing different trace elements such as silicate in the structure of a polymer scaffold has not yet been fully explored. Here, we report the potential use of silicate-containing hydroxyapatite (SiHA) microparticles and microparticle aggregates in the predominant range from 2.23 to 12.40 µm in combination with polycaprolactone (PCL) as a hybrid scaffold with randomly oriented and well-aligned microfibers for regeneration of bone tissue. Chemical and mechanical properties of the developed 3D scaffolds were investigated with XRD, FTIR, EDX and tensile testing. Furthermore, the internal structure and surface morphology of the scaffolds were analyzed using synchrotron X-ray µCT and SEM. Upon culturing human mesenchymal stem cells (hMSC) on PCL-SiHA scaffolds, we found that both SiHA inclusion and microfiber orientation affected cell adhesion. The best hMSCs viability was revealed at 10 day for the PCL-SiHA scaffolds with well-aligned structure (~82%). It is expected that novel hybrid scaffolds of PCL will improve tissue ingrowth in vivo due to hydrophilic SiHA microparticles in combination with randomly oriented and well-aligned PCL microfibers, which mimic the structure of extracellular matrix of bone tissue

Author Correction: 3D biodegradable scaffolds of polycaprolactone with silicate-containing hydroxyapatite microparticles for bone tissue engineering: high-resolution tomography and in vitro study

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper

Distributed GNSS-Based Time Synchronization and Applications

The paper deals with synchronization standards, applications and challenges in the modern packet switched telecommunication networks. In recent years, the number of time-dependent services and systems only increases with the development of such areas as Internet of Things (IoT), industrial Internet, remote automation and robotics, precise positioning etc. In the paper, these emerging applications are discussed. An alternative way to the traditional centralized synchronization infrastructure is proposed. Compact and low-priced devices equipped with a Global Navigation Satellite System (GNSS) receiver and a reliable internal clock can be installed specifically in the places where they are needed without additional intelligence in the network itself. Thus, distributed synchronization approach brings together the providers of time-critical information and sources of precise timing.peerReviewe

Розробка методики побудови математичних моделей стану ґрунту під впливом клину

Studies of the technique of construction of mathematical models on the condition of soil under the action of wedge are presented. Based on hypothesis about separation of the layer of soil by a wedge through its bending, we constructed a mathematical model of determining normal and tangential stresses in soil under the action of wedge. Using mathematical dependencies, we obtained patterns of the distribution of maximum tensile and compression stresses, dependent on the depth of motion of wedge at different angles of crushing the soil. It was found that crushing of soil, which is determined by the size of lumps and chunks, formed under the action of the soil­cultivating working bodies, has a direct dependence on the covered path to reaching limiting stresses in soil. The increase in the distance of the passage of working bodies until the start of the process of cleaving the soil layer contributes to formation of lumps and chunks of larger size. The studies revealed that the wedge, depending on the angle of crushing, strength indices of soil and depth of cultivation, may create in it stresses, necessary for the cleaving, at the initial moment of motion after covering the distance equal to 10 mm and longer. Stresses in soil grow with an increase in the angle of crushing and depth of cultivation. To substantiate parameters of a chisel blade, in particular geometric profile of the rack, we used the method of the calculus of variations. Substantiation of the point of a chisel blade was carried out in two stages. At the first stage we substantiated the profile of chisel of the point taking into account the provision of necessary deepening into soil at minimum energy consumption, at the second stage – the profile of the point with minimum energy consumption by the results of studies, connected with substantiation of the chisel. Analysis of traction resistance of chisel working bodies established that the improvement in the profile of the point ensures reduction in traction resistance of a chisel working body. The data analysis of experiment demonstrated that the coefficient of structuredness of soil after its treatment by standard and experimental points has practically identical value; the improvement of profiles of the points of chisel organs does not lead to worsening the quality of soil treatment. The data analysis on determining traction resistance of chisel working bodies showed that, compared to the standard one, the experimental working body has lower traction resistance. Thus, experimental studies confirm reliability of results of theoretical studies on the substantiation of the profile of the chisel of a chisel working body from the point of view of reduction in their energy consumption while providing for the quality of crushing the soil.Описана математическая модель для определения напряжений, которые возникают в почве под воздействием клина. Получены зависимости, с помощью которых для разной глубины обработки и прочностных показателей почвы в зависимости от заданных параметров качества проведения операции можно определить необходимый угол крошения. Полученные зависимости позволили определить параметры динамических систем, которые способствуют снижению их энергоемкости, повышению качественных показателей работы и созданию условий для повышения производительности агрегатовОписано математичну модель для визначення напружень, які виникають в ґрунті під впливом клина. Отримано залежності, за допомогою яких для різної глибини обробітку і показників міцності ґрунту в залежності від заданих параметрів якості проведення операцій можна визначити необхідний кут кришення. Отримані залежності дозволили визначити параметри динамічних систем, які сприяють зниженню їх енергоємності, підвищенню якісних показників роботи і створенню умов для підвищення продуктивності агрегаті

Regulation and control in cooling systems of internal combustion engines

The paper is devoted to the urgent problem of improving the automatic regulation of the thermal state of internal combustion engines and controlling the water-chemical cooling regimes during the transition to high-temperature cooling. Principal and functional diagrams of cooling systems with improved control are presented. The prospects of controlling the pressure in the internal circuit of high-temperature engine cooling systems and the automatic control of the physicochemical characteristics of the coolant have been proved

Quasi-Orthogonal Space-Time Block Coding with Closed-Loop Control in MIMO Communication Systems

In the paper, we proposed a method of space-time diversity on the transmitting side, combining a closed feedback and quasi-orthogonal space-time coding technique called closed- loop control with quasi-orthogonal space-time block coding (QO- STBC). For a configuration 4x1-4x4 with four transmit and one receive antennas and four symbols per four resource elements, our method allows the QO-STBC to be completely orthogonalized what maximizes the diversity gain. It is shown that the developed approach can also be used for the 4x2-4x2 configuration. In this case, it is not possible to orthogonalize QO-STBC completely, but the level of inter-channel correlation is considerably reduced. A statistical modeling was carried out to study the characteristics of noise immunity of the proposed transmission scheme. We show that it is sufficient to use a one-bit command to control the phase of two transmitting antennas. A gain of 1.4 dB is achieved for the 4x1-4x4 scenario and 2.5 dB - for the 4x2-4x2 case. Phase control of transmitting antennas used in this method of signal transmission does not change the interference conditions