DEVELOPMENT OF RESOURCE-SAVING TECHNOLOGY OF POROUS-HOLLOW CERAMIC STONES

A resource-saving technology of porous ceramic materials using low-quality non-sintering sandy loam as a basic raw material has been developed. Based on the analysis of the plastic properties of two- and three-component ceramic masses, including sandy loam, expanded clay and fuel slag in various ratios, it was found that the required level of their plasticity provides the content of the main raw material in the following range (wt%): fuel slag – 15 – 20; sandy loam – 50 – 65; expanded clay – 20 – 30. By the method of planning the experiment, the rational composition of the three-component ceramic mass was substantiated. This which contains: 62.5 wt. % sandy loam, 20 wt. % medium-sintering plastic clay as a plasticizer and 17.5 wt. % fuel slag of TPP as a porous agent. For the developed mass, the main technological properties were investigated, which made it possible to recommend the drying mode of the raw material – 60 hours, the optimal firing temperature – 950 °С. Such conditions ensure that samples are obtained without drying cracks and signs of deformation. Оn the results of dilatometric analysis of mass the rational mode of firing high-hollow semifinished products was designed. The firing mode provides for a 44-hour firing and a decrease in the heating rates in the areas of dehydration of clay minerals, direct quartz transition and intensive sintering of the mass, as well as a decrease in the cooling rate in the area of the reverse quartz transition. The proposed firing mode provides the degree of sintering and their properties necessary for ceramic materials. Based on the developed mass under the recommended drying and firing modes, porous ceramic materials with an apparent density of 1.48 g/cm3, a compressive strength of 18.2 MPa and frost resistance of 30 cycles were obtained. The developed materials belong to the group of conditionally effective, and if 50% of the voids are organized, they can be classified as effective.

STUDY OF THE INFLUENCE OF CALCIUM OXIDES IN LIGHT-FUSION RAW MATERIALS ON THE PROPERTIES OF A CERAMIC PRODUCT

One of the main problems of modern building ceramics based on low-melting raw materials is the increased CaO content in the charge. This deviation from the normative values of the technological parameters of production leads to defects - underburning / overburning, quirks, looseness, low strength. Firing mode, molding parameters, addition of additives, preparation of raw materials are the factors for solving this problem. The Alekseevsk low-melting clay and the Yarmysh (Uzbekistan) loess-like loam were investigated, the destruction of the sample structure upon absorption of moisture from the CaO air was graphically modeled, the diagrams of the dependence of the fi ring temperature on the compressive strength were plott ed, the infl uence of molding and the fi neness of grinding of raw materials on the compressive strength and the nature of the formation of ceramic defects was derived.

Integration, coincidence detection and resonance in networks of spiking neurons expressing Gamma oscillations and asynchronous states

Gamma oscillations are widely seen in the awake and sleeping cerebral cortex, but the exact role of these oscillations is still debated. Here, we used biophysical models to examine how Gamma oscillations may participate to the processing of afferent stimuli. We constructed conductance-based network models of Gamma oscillations, based on different cell types found in cerebral cortex. The models were adjusted to extracellular unit recordings in humans, where Gamma oscillations always coexist with the asynchronous firing mode. We considered three different mechanisms to generate Gamma, first a mechanism based on the interaction between pyramidal neurons and interneurons (PING), second a mechanism in which Gamma is generated by interneuron networks (ING) and third, a mechanism which relies on Gamma oscillations generated by pacemaker chattering neurons (CHING). We find that all three mechanisms generate features consistent with human recordings, but that the ING mechanism is most consistent with the firing rate change inside Gamma bursts seen in the human data. We next evaluated the responsiveness and resonant properties of these networks, contrasting Gamma oscillations with the asynchronous mode. We find that for both slowly-varying stimuli and precisely-timed stimuli, the responsiveness is generally lower during Gamma compared to asynchronous states, while resonant properties are similar around the Gamma band. We could not find conditions where Gamma oscillations were more responsive. We therefore predict that asynchronous states provide the highest responsiveness to external stimuli, while Gamma oscillations tend to overall diminish responsiveness.

Influence of Additive’s Concentration on the Temperature Conditions for the Formation of the Solid Solutions of the System MgAl2O4-Ga2O3

The production of a precursor of magnesium aluminate spinel (AMS) by thermic synthesis to obtain a material with high-performance properties is reviewed in the work. The temperature synthesis of AMS is determined, the introduction of the additive is described in the range of concentrations of 3, 5, and 7 mol.%. The current processes during the firing of products have been investigated with a view to the further selection of the firing mode of the ceramic samples, which can be obtained.

Integration, coincidence detection and resonance in networks of spiking neurons expressing gamma oscillations and asynchronous states

Gamma oscillations are widely seen in the awake and sleeping cerebral cortex, but the exact role of these oscillations is still debated. Here, we used biophysical models to examine how gamma oscillations may participate to the processing of afferent stimuli. We constructed conductance-based network models of gamma oscillations, based on different cell types found in cerebral cortex. The models were adjusted to extracellular unit recordings in humans, where gamma oscillations always coexist with the asynchronous firing mode. We considered three different mechanisms to generate gamma, first a mechanism based on the interaction between pyramidal neurons and interneurons (PING), second a mechanism in which gamma is generated in interneuron networks (ING) and third, a mechanism which relies on gamma oscillations generated by pacemaker Chattering neurons (CHING). We find that all three mechanisms generate features consistent with human recordings, but that the ING mechanism is most consistent with the firing rate change inside Gamma bursts seen in the human data. We next evaluated the responsiveness and resonant properties of these networks, contrasting gamma oscillations with the asynchronous mode. We find that for both slowly-varying stimuli and precisely-timed stimuli, the responsiveness is generally lower during Gamma compared to asynchronous states, while resonant properties are similar around the Gamma band. We could not find conditions where Gamma oscillations were more responsive. We therefore predict that asynchronous states provide the highest responsiveness to external stimuli, while Gamma oscillations tend to overall diminish responsiveness.

Pupil size dynamics predict dLGN firing mode over a wide range of timescales

Pupil size is a commonly used proxy for waking brain states such as arousal, and has been related to activity modulations in cortical sensory areas. Here, we asked whether the dorsolateral geniculate nucleus (dLGN), which provides sensory input to the visual cortex, is modulated by pupil-indexed arousal. Observing that the pupil size oscillates at multiple timescales, we developed a method to show that the spiking mode of the dLGN is predicted by pupil size oscillations over several of these timescales. Overall, we found that tonic spikes preferentially occurred during pupil dilation, while bursts occurred during contraction. These preferences could not be explained solely by pupil size per se or by the locomotion of the animal, and were also present during periods of stimulus viewing. We conclude that dLGN spiking activity is modulated by pupil-indexed arousal processes on various timescales, influencing the mode in which sensory signals are passed on to the cortex.

Tonic firing mode of midbrain dopamine neurons continuously tracks reward values changing moment-by-moment

Animal behavior is regulated based on the values of future rewards. The phasic activity of midbrain dopamine neurons signals these values. Because reward values often change over time, even on a subsecond-by-subsecond basis, appropriate behavioral regulation requires continuous value monitoring. However, the phasic dopamine activity, which is sporadic and has a short duration, likely fails continuous monitoring. Here, we demonstrate a tonic firing mode of dopamine neurons that effectively tracks changing reward values. We recorded dopamine neuron activity in monkeys during a Pavlovian procedure in which the value of a cued reward gradually increased or decreased. Dopamine neurons tonically increased and decreased their activity as the reward value changed. This tonic activity was evoked more strongly by non-burst spikes than burst spikes producing a conventional phasic activity. Our findings suggest that dopamine neurons change their firing mode to effectively signal reward values in a given situation.

Recoil Reduction Method of Gun with Side to Rear Jet Controlled by Piston Motion

Excessive recoil severely restricts the loading of high-power traditional guns on modern vehicles. To reduce the recoil without breaking the continuous firing mode and reducing the projectile velocity, a recoil reduction method that controls the lateral ejecting of propellant gas by a piston was proposed. The recoil reduction device is symmetric about the barrel axis. First, a one-dimensional two-phase flow model of interior ballistic during the gun firing cycle was established. Next, the MacCormack scheme was used to simulate, and the piston motion was gained. Then the propagation of the rarefaction wave in the barrel was presented. Finally, the propulsion difference between the piston-controlled gun and the traditional gun was discussed. The results showed that the recoil momentum was reduced by 31.80%, and the muzzle velocity was decreased by just 1.30% under the reasonable matching of structural parameters.

Determination of the influence of aluminum phosphate on the properties of quartz ceramics

One of the significant disadvantages of quartz glass-based materials is their tendency to crystallize cristobalite during firing and, as a consequence, a significant deterioration in performance. In order to prevent crystallization of quartz ceramics during sintering, a number of additives are used. However, all known options some disadvantages, namely, relatively low strength values and increased coefficient of linear thermal expansion of products.In this regard, a promising area of research is to study the effect of aluminum phosphate additives on the properties of quartz ceramics. According to the totality of properties, the addition of AlPO4 in an amount of 20 wt % has the most positive effect on the characteristics of quartz ceramics. According to differential thermal analysis, it is noted that up to a temperature of 1,200 °C, no noticeable phase and modification transformations occur in the base mixtures. In the course of the work, it was found that the most appropriate firing mode is as follows: oxidizing medium; the products are immersed in a hot furnace, after being held at the maximum temperature, they are removed from the hot furnace, cooling occurs slowly in the air. The materials obtained in this way are characterized by the following properties: α=31.6·10-7 deg-1; σcomp=153 MPa; P=2.7 %; tgδ and ε (frequency 1010 Hz, temperature 20 °C) 0.001 and 10, respectively. It is noted that the main crystal phase prevailing in the samples is aluminum phosphate. The microstructure of the material is characterized by the presence of a small number of residual pores and a densely sintered shard.The proposed solution will significantly reduce power consumption, improve production performance and increase the basic properties of polyfunctional quartz ceramic products