Fast multi-phase processes in methane hydrate bearing samples pose a challenge for quantitative micro-computed tomography study and experiment steering due to complex tomographic data analysis ...involving time-consuming segmentation procedures. This is because of the sample's multi-scale structure, which changes over time, low contrast between solid and fluid materials, and the large amount of data acquired during dynamic processes. Here, a hybrid approach is proposed for the automatic segmentation of tomographic data from time-resolved imaging of methane gas-hydrate formation in sandy granular media, which includes a deep-learning 3D U-Net model. To prepare a training dataset for the 3D U-Net, a technique to automate data labeling based on sample-specific information about the mineral matrix immobility and occasional fluid movement in pores is proposed. Automatic segmentation allowed for studying properties of the hydrate growth in pores, as well as dynamic processes such as incremental flow and redistribution of pore brine. Results of the quantitative analysis showed that for typical gas-hydrate stability parameters (100 bar methane pressure, 7°C temperature) the rate of formation is slow (less than 1% per hour), after which the surface area of contact between brine and gas increases, resulting in faster formation (2.5% per hour). Hydrate growth reaches the saturation point after 11 h of the experiment. Finally, the efficacy of the proposed segmentation scheme in on-the-fly automatic data analysis and experiment steering with zooming to regions of interest is demonstrated.
Kurokawa's method of calculating the power reflection coefficient from the Smith chart in the situation when one complex impedance is directly connected to another is applied to passive RFID tag ...design, where power reflection is important, as it determines the tag characteristics. The performance analysis of a specific RFID tag is presented together with experimental data, which is in close agreement with the theory.
The article presents unknown evidence of epistolary communication of S. I. Ozhegov and his “correspondents” — Professor A. M. Egolin, Prince P. Obolenskiy, Mr Nedzvetskiy. The linguistic ...informativeness of the letters is noted. The value of the presented materials for the study of lexicology, stylistics, author’s punctuation and speech culture is indicated. Attention is drawn to the range of problems discussed in the letters, including the selection and interpretation of definitions in dictionaries (pilyonyi sakhar ‘sawn sugar’, plavlenyi syr ‘processed cheese’, gromootvod ‘lightning rod’), haplology, the formation of appellatives from the names of writers (nekrasovoved or nekrasoved), social and phonetic adaptation of foreign language vocabulary (t’emp — temp), etc. The facts given in the correspondence are commented on from the standpoint of the history of philological science, the necessary references are given, possible comparisons are made with the events and persons mentioned in the epistolary. The texts are evaluated as a fragment of a special linguistic picture of the world, in which the main place is occupied by the linguistic personality of S. I. Ozhegov, who attracted scientists of different schools and generations. The conclusion is made about the relevance of the publication of archival sources that reveal interesting circumstances of the scientific life of philologists, exposing their searches and discoveries. These materials supplement the available information about the linguistic discussions of the 1950s and 1960s, represent living portraits of scientists.
M-ary Aggregate Spread Pulse Modulation (M-ASPM) is the physical layer (PHY) modulation technique that is well suited for use in low-power wide-area networks (LPWANs). Notably, M-ASPM combines high ...energy-per-bit efficiency, robustness, resistance to interference, and a number of other favorable technical characteristics, with the spread-spectrum ability to maintain the capacity of an uplink-focused network while extending its range. However, when all M-ASPM nodes transmit with the same average power, implementation of such capacity-preserving range extension may become impractical in complicated propagation environments with greatly varying path losses. Favorably, the efficiency of M-ASPM with constant-envelope pulses can be maintained effectively the same as the efficiency of transmitting a continuous constant-envelope waveform. Then the transmit power of different nodes can be adjusted, without sacrificing the transmission efficiency, to compensate for differences in the path attenuation. This enables us to significantly simplify planning and management of the network. In addition, such a variable-power approach generally increases the network capacity and the average energy efficiency of the nodes, as compared with the arrangement of the nodes with a constant transmit power. In this paper, we outline a practical approach to implementing such an energy-efficient M-ASPM power control, that can be used for scaling LPWANs with realistic desired and/or actual areal distributions of the uplink nodes under diverse propagation conditions.
•DNA methylation inhibitors do not influence memory reconsolidation.•MK-801/reminding cause memory reconsolidation impairment and amnesia development.•DNA methylation inhibitors/reminding caused ...amnesia impairment and memory recovery.•DNA methylation inhibitors in 3, but not in 9h after reminding impaired amnesia.•DNA methylation inhibitors/reminding don’t affect the late amnesia stage.
Current considerations suggest that the mechanisms of long term memory are based on the changes of the neuronal genetic algorithms. Process of the enzyme DNA methylation have great importance to the differential genes expression, and is likely to be one of the key mechanisms of the consolidation and memory storage. The present study aimed to investigate the DNA methylation processes role in the mechanisms of the conditioned food aversion memory reconsolidation and also in the amnesia development mechanisms, caused by disturbances of the reconsolidation in Helix lucorum. It was found that DNA–methyltransferase inhibitors zebularine and RG108 had no influence on the memory reconsolidation. We investigated the effects of the DNA–methyltransferase inhibitors on different amnesia stage. The amnesia was induced by NMDA glutamate receptors antagonists. At the early stage of amnesia (3rd day after its induction) injections of the DNA–methyltransferase inhibitors in combination with reminder by conditioned food stimuli led to memory recall. Memory was recovered by the DNA–methyltransferase inhibitors injections before the reminder and also 3h, but not 9h after the reminder. In case when enzyme inhibitors or reminders were applied separately, no effect on memory was revealed. At the late stage of amnesia (10th day) the DNA–methyltransferase inhibitors didn’t affects amnesia development. It might be hypothesized that presentation of reminding stimuli result in the reactivation/reconsolidation of molecular processes, involved in amnesia development, one of the key mechanisms of which could be the DNA methylation/demethylation of neural cells.
M-ary Aggregate Spread Pulse Modulation (M-ASPM) is a recently introduced physical layer (PHY) modulation technique that is well suited for use in low-power wide-area networks (LPWANs). Notably, ...M-ASPM combines high energy-per-bit efficiency, robustness, resistance to interference, and a number of other favorable technical characteristics, with the spread-spectrum ability to maintain the capacity of an uplink-focused network while extending its range. However, while the essential tools for detection and synchronization of pulsed spread-spectrum waveforms in general, and the M-ASPM signals in particular, have been previously provided, a practical framework for combining the detection, synchronization, and decoding of an M-ASPM packet has not yet been suggested. In this paper, we outline such a framework, and describe a prototype algorithm for its implementation. This implementation can be subsequently adapted, under given technical constraints, to specific practical complications such as, for example, significant delay spreads, external technogenic interference, or co-channel and inter-channel collisions. In addition to low latency and computational complexity, the main requirement for this prototype algorithm is that the signal quality remains effectively invariant, for a given path loss, and for a wide range of the data rates, payload sizes, lengths of pulse shaping filters (PSFs), and pulse duty cycles, for a relatively large carrier frequency offset (CFO) between the transmitter (TX) and the receiver (RX). Further, this needs to be achieved without any feedback communications between the TX and the RX, and performed entirely in the RX software.
The process of starting the rotating detonation engine initially filled with air in low outer pressure conditions was studied. Such engines can be used for bringing satellites into the Earth orbit. A ...three-dimensional numerical simulation of an engine combustion chamber with a rotating detonation wave of a cylindrical type with an internal body fed by a hydrogen-oxygen mixture or an acetylene-oxygen mixture was performed. The influence of the lengths of the combustion chamber channel on the stability of the detonation wave and thrust characteristics was considered. An author's computer code was used in simulations, the code was based on a model of multicomponent gas dynamics with chemical transformations and turbulence. The code was tested by comparing it with experiments and analytical solutions for simple cases. To describe the kinetics of acetylene combustion, a simplified chemical scheme of interaction of 10 components was used, without “heavy” radical species: C2H2, CO, CO2, H2, O2, H2O, OH, O, H, N2. The influence of the chosen kinetic mechanism in case of hydrogen-oxygen mixture on the simulation results was studied. Various modes of the process in the detonation engine were obtained, including those with a stable detonation wave.
•Under low external pressure conditions, the detonation engine starting was investigated.•A simulation of an engine powered by acetylene oxygen was carried out.•The influence of the fuel concentration on the processes in the chamber is studied.•Combustion chambers of two lengths are considered.•Traction characteristics were obtained and analyzed for all cases.
The free linear shrinkage of samples from PLA, HIPS, and ABS filaments, used for 3D printing by FDM technology in extrusion operating temperature ranges, has been studied. It is found that the PLA ...filament is characterized by shrinkage values in the range of 0.2–0.6% in operating extrusion temperatures of 200–220°C. HIPS filaments (operating temperature range of 220–240°C) and ABS filaments (operating temperature range of 240–270°C) have shrinkage in the range of 0.3–0.8%. The values of linear shrinkage must be taken into account when designing mathematical models of the future cast product. The influence of print density
d
p
(the degree of filling of the internal structure) on the value of the ash residue A during the burning of samples obtained from the studied filaments is studied. It is shown that, with an increase in
d
p
(5–15–30%), the value of
A
also increases. The minimum values of
A
(0.19–0.48%) have a filament of the PLA. It is concluded that, for the 3D printing of castings models by the FDM technology for casting into refractory ceramic molds (RCM), the PLA filament is the most technologically advanced according to the set of indicators of free linear shrinkage and ash residue. Model blocks are 3D printed from PLA filament by FDM technology to produce Branch Pipes by casting into an RCM. The RCMs are formed according to the model blocks. In the process of burning out the model blocks from the RCM, it was found that part of the RCM cracked under linear heating. This was due to the excessive pressure of the expanding material of the model block during heating to its softening temperature, and the gas pressure formed during the subsequent burning of the model block. With an increase in the heating rate, the proportion of cracked RCMs increased. In order to prevent cracking, a stepwise mode of heating the RCM, combined with their calcination, has been developed. When removing the model blocks according to the stepwise mode, the RCM did not crack. Experimental Branch Pipe castings were obtained from bronze of the BrA9ZH3L brand. The quality of the castings met the requirements of the design documentation.
In this paper we present an overview of the M-ary Aggregate Spread Pulse Modulation (M-ASPM), and provide an assessment of its suitability and advantages for use in low-power wide-area networks ...(LPWANs). Notably, M-ASPM combines high energy-per-bit efficiency, robustness, resistance to interference, and a number of other favorable technical characteristics, with the spread-spectrum ability to maintain the network capacity while extending its range. We quantify the impact of mutual interference of multiple M-ASPM transmitters and demonstrate how such capacity-preserving range extension can be achieved for numerous desired areal distributions of the uplink nodes. Throughout the paper, LoRa is used for benchmark comparison and quantification of various M-ASPM features. In particular, we show that, while sharing many essential properties with LoRa, M-ASPM provides far more effective network range extension. When used in the same manner as LoRa, M-ASPM can serve as an appealing LoRa alternative. In addition, while being different LPWAN solutions, M-ASPM and LoRa can be designed to concurrently operate in the same spectral band and geographical area, cooperatively complementing each other's coverage.
Within the balanced approximation of fiber lasers (FLs) considered as distributed systems, an improved mathematical model is constructed that describes the low-frequency dynamics of FLs with mirrors ...based on optomechanical micro-oscillators (MOs), taking into account the effect of spontaneous emission (SE) localized in the cladding modes of the active fiber (AF). The mechanisms of the effect of SE on the synchronous self-oscillations (SSOs) in the FL–MO laser system are revealed: additional inversion removal in the AF due to the finite path length of SE cladding mode photons in the FL active medium, violation of the condition for the internal resonance in the laser system, and perturbation of MO oscillations by photoinduced force caused by SE. By means of numerical simulation of SSOs in an erbium–ytterbium FL with an MO and experimental studies, the dependence of the SSO frequency on the geometric-optical parameters of the AF and the reflectivity of the AF–environment interface has been established, which can be used to improve the frequency stability of laser pulses in fiber sources of pulsed radiation and create a new class of resonant fiber-optic sensors.
