Comparative Evaluation of the Condition of Academic Graduate School (Middle 2000s – Late 2010s)

The main task of the article was to identify the dynamics of changing social characteristics of graduate students from research institutes of Novosibirsk Academgorodok. For the comparative analysis we used the data of polls conducted in 2005 and 2018. We compared such variables as the reasons for admission to graduate school, assessments of the current state of the main elements of scientific activity, the expectations of graduate students about their future profession, primarily a scientific career, criteria and factors of its success. Based on these results we planned to identify the main trends inherent in graduate studies as the main method of training personnel for Russian science. It is concluded that at present the system of training highly qualified scientific personnel in the country is in an unstable state. As a result, there is an active discussion in the professional community about ways of further reforming graduate school.

Effects of Intrinsic Flame Instabilities On Thermoacoustic Oscillations in Lean Premixed Gas Turbines

Thermoacoustic instabilities are commonly encountered in the development of aeroengines and rocket motors. Research on the fundamental mechanism of thermoacoustic instabilities is beneficial for the optimal design of these engine systems. In the present study, a thermoacoustic instability model based on the lean premixed gas turbines (LPGT) combustion system was established. The longitudinal distribution of heat release caused by the intrinsic instability of flame front is considered in this model. Effects of different heat release distributions and characteristics parameters of the premixed gas (Lewis number Le, Zeldovich Number and Prandtl number Pr) on thermoacoustic instability behaviors of the LPGT system are investigated based on this model. Results show that the LPGT system features with two kinds of unstable thermoacoustic modes. The first one corresponds to the natural acoustic mode of the plenum and the second one corresponds to that of the combustion chamber. The characteristic parameters of premixed gases have a large impact on the stability of the system and even can change the system from stable to unstable state.

Periplasmic bacterial biomineralization of copper sulfide nanoparticles

Metal sulfides are a common group of extracellular bacterial biominerals. Only few cases of intracellular biomineralization have been reported in this group, mostly limited to greigite (Fe3S4) in magnetotactic bacteria. Here, we report the intracellular but periplasmic biomineralization of copper sulfide by the magnetotactic bacterium Desulfamplus magnetovallimortis (strain BW-1) that is known to mineralize greigite and magnetite (Fe3O4) in the cytoplasm. BW-1 produces hundreds of spherical nanoparticles, composed of 1-2 nm substructures of a poorly crystalline hexagonal copper sulfide that remains in a thermodynamically unstable state. Differential proteomics suggests that periplasmic proteins, such as a DegP-like protein and a heavy metal-binding protein, could be involved in this process. The unexpected periplasmic formation of copper sulfide nanoparticles in BW-1 reveals previously unknown possibilities for intracellular biomineralization.

Early Combination Therapy of Ketamine and Midazolam in Patients with Refractory Status Epilepticus in Hemodynamic Unstable State

The use of anesthetics is inevitable to suppress seizure activity in refractory status epilepticus (RSE). Hypotension, which is a critical side effect observed when treating RSE using a higher dosage of anesthetics that enhance γ-aminobutyric acid (GABA) activity, often requires vasopressor agents. Concomitant treatment with N-methyl-D-aspartate (NMDA) receptor antagonists, such as ketamine, could be effective in prolonged refractory SE, while maintaining stable blood pressure owing to the blockage of catecholamine reuptake in the systemic circulation. We report two cases of patients who had RSE with hemodynamic instability treated promptly with an early combination of ketamine and low-dose midazolam. The combination treatment effectively suppressed epileptic discharge with less hemodynamic side effects; moreover, a low dose of midazolam was required when combined with ketamine therapy. The initial combination of a third-line therapy that blocks NMDA receptors with enhanced GABAergic activity could be useful in RSE. Further studies are necessary in many variable etiologies of SE.

Modulational Instability of Ion-Acoustic Waves in Pair-Ion Plasma

The modulational instability (MI) of ion-acoustic waves (IAWs) is examined theoretically in a four-component plasma system containing inertialess electrons featuring a non-thermal, non-extensive distribution, iso-thermal positrons, and positively as well as negatively charged inertial ions. In this connection, a non-linear Schrödinger equation (NLSE), which dominates the conditions for MI associated with IAWs, is obtained by using the reductive perturbation method. The numerical analysis of the NLSE reveals that the increment in non-thermality leads to a more unstable state, whereas the enhancement in non-extensivity introduces a less unstable state. It also signifies the bright (dark) ion-acoustic (IA) envelope solitons mode in the unstable (stable) domain. The conditions for MI and its growth rate in the unstable regime of the IAWs are vigorously modified by the different plasma parameters (viz., non-thermal, non-extensive q-distributed electron, iso-thermal positron, the ion charge state, the mass of the ion and positron, non-thermal parameter α, the temperature of electron and positron, etc.). Our findings may supplement and add to prior research in non-thermal, non-extensive electrons and iso-thermal positrons that can co-exist with positive as well as negative inertial ions.

Paleovegetation dynamics in an alternative stable states landscape in the montane Western Ghats, India

Peat deposits (>50 ka) in the montane Nilgiris (Western Ghats, India), have been central to the reconstruction of late Quaternary paleoclimate using paleovegetation changes in the forest-grassland vegetation mosaic that coexist here. However, it is well-known that short-term disturbances can also cause vegetation switches when multiple stable vegetation states exist. We studied paleovegetation changes within the alternative stable states framework using stable carbon isotopes (relative abundance of C3-C4 vegetation) on the cellulose fraction from two high-resolution radiocarbon-dated peat cores ~170 m apart in the Sandynallah valley: Core 1 closer to the hillslope (32,000 years old) and Core 2 from the centre of the valley (45,000 years old). Core 1 is located in an ecotone showing shola-sedgeland dynamics with vegetation switching at c.22 ka from shola (possibly due to fire) to a prolonged unstable state until 13 ka sustained by low waterlogging. Following a hiatus c.13 ka, sedgeland dominates, with a shift into shola at 3.75 ka driven by increasing aridity. Core 2 shows a stable sedgeland mixed C3-C4 composition responding to temperature, enriched in C3-vegetation in the last glacial with C4-dominance beginning c.18.5 ka, indicative of deglacial warming. The distinctive vegetation states at corresponding times in Cores 1 and 2 within the same valley, responding independently to disturbances and climate, respectively, is the first paleo-record from an alternative stable states landscape in the montane tropics. Thus, short-term disturbances and site attributes need to be accounted for before ascribing vegetation change to changing climate in such vegetation mosaics.

Reinforcement-learning-based control of confined cylinder wakes with stability analyses

This work studies the application of a reinforcement learning (RL)-based flow control strategy to the flow past a cylinder confined between two walls to suppress vortex shedding. The control action is blowing and suction of two synthetic jets on the cylinder. The theme of this study is to investigate how to use and embed physical information of the flow in the RL-based control. First, global linear stability and sensitivity analyses based on the time-mean flow and the steady flow (which is a solution to the Navier–Stokes equations) are conducted in a range of blockage ratios and Reynolds numbers. It is found that the most sensitive region in the wake extends itself when either parameter increases in the parameter range we investigated here. Then, we use these physical results to help design RL-based control policies. We find that the controlled wake converges to the unstable steady base flow, where the vortex shedding can be successfully suppressed. A persistent oscillating control seems necessary to maintain this unstable state. The RL algorithm is able to outperform a gradient-based optimisation method (optimised in a certain period of time) in the long run. Furthermore, when the flow stability information is embedded in the reward function to penalise the instability, the controlled flow may become more stable. Finally, according to the sensitivity analyses, the control is most efficient when the probes are placed in the most sensitive region. The control can be successful even when few probes are properly placed in this manner.

Performance verification test of coaxial centrifugal clutch for motorcycle transmission system

With the popularization of motorcycles, the demand for motorcycles is getting higher and higher. Therefore, the improvement of power output, the reduction of pollutants discharged, the replacement of waste, the improvement of efficiency and the reduction of fuel use, are also relatively important. Stop-and-go on urban driving will keep the clutch in a state of being engaged and not engaged. The clutch cannot be engaged and is constantly worn. The output efficiency of the CVT belt-type continuously variable transmission system clutch used in the transmission is only about 70~80%. Transmission efficiency. Furthermore, since the traditional CVT belt-type system clutch mainly relies on the action of the centrifugal roller to change the reduction ratio, when encountering different driving conditions and need to accelerate and decelerate, this will make the working area of the internal combustion engine in an unstable state. The matching structure between the automatic clutch weight and the telescopic spring in the reciprocating separation state and the fitted state is replaced, which effectively reduces the problem of uneven contact surfaces of the plates in the past, and prevents the elastic aging from affecting the uniform transmission of power, resulting in the entire dry clutch The life span of the engine is improved and the efficiency of power transmission is maintained, thereby reducing fuel consumption and producing more complete engine power. Therefore, the “Design Performance Verification of Coaxial Contact Centrifugal Ball Clutch” is proposed mainly to verify that the coaxial contact centrifugal ball clutch has better performance than the CVT belt-type clutch.

Longitudinal-transverse thermal- force bending and stability layered inhomogeneous profiled rod

The solution to the problem of the stress-strain state of an inhomogeneous profiled rod is based on the use of nonlinear equilibrium conditions and physical relations of a layered thermo elastic thin rod. A differential equation of bifurcation inhomogeneous rod stability of variable cross-section is obtained. The equation has variable functional coefficients. In the initial state, the rod is subjected to bending with the implementation of one of the asymmetric shapes. The critical state occurs under the action of a longitudinal load corresponding to one of the lowest symmetrical shapes, orthogonal to the initial shape. In the first series, numerical calculations of an inhomogeneous I-rod with a variable cross section height are performed. Shelves and wall I-rod are made of steel, aluminum and titanium alloys. The graphs of maximum deflection and normal stresses acting at the calculate points at the boundaries of the layers are plotted depending on the longitudinal load at the given levels of transverse loads and thermal field. A significant influence of the rod physical structure, the profiling its form and the factor of nonlinearity of static relations on the stress fields has been established. A homogeneous temperature field with a nominal value of 80°C creates fields of self-balanced stresses in an inhomogeneous rod. The components of normal stresses in this case reach 20-40% of the materials permissible resistance level. The presence of rod parts with a significant difference in the coefficients of thermal expansion in the composition enhances this effect. In the second, the stability analysis of an inhomogeneous I-rod with a variable width cross section was performed. The transition of the initial S-shaped bend to an unstable state is shown.

Improving the accuracy of predicting the hazard of the earth’s surface failure formation during underground mining of mineral deposits

Purpose. Development of a new approach to improving the accuracy of predicting situations in which the earth’s surface failures occur as a result of undermining a rock mass during the development of mineral deposits. Methods. The critical situations, including the earth’s surface failures, are predicted on the basis of assessing the value of geoenergy and studying its change as large volumes of rock mass are involved in mining. Analytical solutions based on the fundamental laws of physics and mechanics of continuous media are used. The research is performed using methods of cause-and-effect analysis. Findings. Based on the cause-effect relationship, determined between the change in the value of the mass geoenergy and deformation processes on the daylight surface of the field, an effective method has been developed for ranking it according to the degree of hazard of failure formation with the simultaneous use of two criteria. One of the criteria is determined by the relative change in geoenergy during the system transition from the initial (stable) state to the current one, which becomes unstable under certain conditions. The second criterion is formed on the basis of the change in geoenergy during the transition from the current (possibly unstable) state to the final (stable) state. Originality. For the first time, when zoning the daylight surface of a field according to the degree of hazard of failure formation, two ranking criteria are used simultaneously, based on the assessment of geoenergy accumulated in a heterogeneous mass, when it is undermined in the conditions of triaxial compression. Practical implications. The territory ranking method, developed on the basis of the used criteria for hazard of failure formation, allows improving the quality of situational control, predicting risk situations and their development, as well as optimizing the short-term and long-term plans for the development of mining operations.