Mo–Nb–Si–B Alloy: Synthesis, Composition, and Structure

Cast refractory alloys Mo–Nb–Si–B were prepared by centrifugal self-propagating high-temperature synthesis (SHS) from metallothermic mixtures containing MoO3, Nb2O5, Al, Si, and B powders, and additive of Al2O3 as a temperature-moderating and chemically inert agent. Variation in the centrifugal acceleration and amount of the additive affected the composition and structure of cast Mo–Nb–Si–B alloys. In a wide range of values, the combustion temperature was found to exceed 3000 K, and the combustion products were obtained as two-layer ingots of target Mo–Nb–Si–B alloy (lower) and Al2O3 slag (upper).

The effect of the centrifugal acceleration on period spacings of gravito-inertial modes in intermediate-mass stars

Context. The Kepler and Transiting Exoplanet Survey Satellite (TESS) space telescopes delivered high-precision, long-duration photometric time series for hundreds of main-sequence stars, revealing their numerous gravito-inertial (g) pulsation modes. This high precision allows us to evaluate increasingly detailed theoretical stellar models. Recent theoretical work extended the traditional approximation of rotation, a framework to evaluate the effect of the Coriolis acceleration on g modes, to include the effects of the centrifugal acceleration in the approximation of slightly deformed stars, which so far have mostly been neglected in asteroseismology. This extension of the traditional approximation was conceived by re-deriving the traditional approximation in a centrifugally-deformed, spheroidal coordinate system. Aims. We explore the effect of the centrifugal acceleration on g modes and assess its detectability in space-based photometric observations. Methods. We implemented the new theoretical framework to calculate the centrifugal deformation of pre-computed 1D spherical stellar structure models and computed the corresponding g-mode frequencies, assuming uniform rotation. The framework was evaluated for a grid of stellar structure models covering a relevant parameter space for observed g-mode pulsators. Results. The centrifugal acceleration modifies the effect of the Coriolis acceleration on g modes, narrowing the equatorial band in which they are trapped. Furthermore, the centrifugal acceleration causes the pulsation periods and period spacings of the most common g modes (prograde dipole modes and r modes) to increase with values similar to the observational uncertainties of the measured period spacing values in Kepler and TESS data. Conclusions. The effect of the centrifugal acceleration on g modes is formally detectable in modern space photometry. The implementation of the used theoretical framework in stellar structure and pulsation codes will allow for more precise asteroseismic modelling of centrifugally deformed stars in order to assess its effect on mode excitation, trapping, and damping.

Relativistic Effects of Rotation in γ-ray Pulsars—Invited Review

In this paper, we consider the relativistic effects of rotation in the magnetospheres of γ-ray pulsars. The paper reviews the progress achieved in this field during the last three decades. For this purpose, we examine the direct centrifugal acceleration of particles and the corresponding limiting factors: the constraints due to the curvature radiation and the inverse Compton scattering of electrons against soft photons. Based on the obtained results, the generation of parametrically excited Langmuir waves and the corresponding Landau–Langmuir centrifugal drive are studied.

Analysis of metrological characteristics of elbow flowmeter under rotating state

The application of elbow flowmeter in rotary equipments is beneficial to reduce the pipeline complexity. However, the intervention of centrifugal acceleration will lead to the change of metrological characteristics of elbow flowmeter. Based on the analysis of the differential pressure formation mechanism of the environmental acceleration on the elbow flowmeter, the calculation formula of the flow rate measurement with the elbow flowmeter in the rotating state is derived, and the fitting method of the discharge coefficient is put forward. The CFD method was used to analyze the internal flow field of the elbow flowmeter under rotating state, summarize the pressure distribution characteristics of the pipe wall, and verify the feasibility of the discharge coefficient fitting strategy by simulation. The results show that for the elbow flowmeters with diameters of 10 mm and 15 mm and the radius to diameter ratio of 1.5, as long as the water flow rate is between 1.5 m/s and 5 m/s, the measurement accuracy can be guaranteed to be above 4%.

Clinorotation as a promising and environmentally friendly biotechnology in agriculture and some industries

Aim. To investigate the direct and indirect impact of clinorotation on vital activity of gilled mushrooms (Agaricales) using the mycelium of the model organism Agaricus bisporus, clinorotated by the ground-based facility Ekoloh, as the example. Methods. The mycelium of Agaricus bisporus was cultivated on the medium with agar and compost extract. The microgravitational environment was simulated using the method of uniaxial clinorotation at the ground-based facility Ekoloh. The mycelia of Agaricus bisporus from the experimental group were clinorotated for 4 h a day for 12 days. The samples from the control group were cultivated in normal (1 g) conditions. The simulated gravitational acceleration value was 3.5 × 10–4 g at the rotational velocity of 2.5 rpm and the rotation radius of 0.05 m. The centrifugal acceleration, affecting the mycelium of Agaricus bisporus under clinorotation, was 0.00343 m/s2. The two-way ANOVA analysis demonstrated that the effects of g-level, the duration of the impact and their interaction were all statistically signifi cant. At the same time, 73.1 % of the variance in mycelium growth coeffi cient was triggered by the simulated value of the g, i.e. the duration of the impact was a minor factor. Results. Clinorotation stimulated growth and development of gilled mushroom (Agaricales) mycelium. In particular, in this study the clinorotated mycelium of Agaricus bisporus had approximately 3.4, 2.5, 1.6 times higher coeffi cients of mycelium growth compared against the mycelium, cultivated in stationary conditions (1 g) on day 5, 10, and 15 of the cultivation respectively. Contrary to the control mycelial colonies, the growth of clinorotated mycelial colonies of Agaricus bisporus was asymmetric. The direction of the gravitational acceleration vector regarding mycelium colonies was constantly changing in the microgravitational environment, simulated by the ground-based facility Ekoloh. At the same time, different organs of Agaricus bisporus are characterized by gravitropism of different orientation. Therefore, constant changes in the direction of gravitational acceleration vector regarding mycelium could have caused constant re-orientation of mycelium cells in terms of the gravitational acceleration vector, and thus, multidirectional asymmetric growth. In addition, the centrifugal acceleration, generated during clinorotation, is a mechanostimulator, capable of triggering stress responses in different living systems. The accelerated growth is one of the stress responses. At the same time, mycelium could expand in the environment mechanically due to the impact of centrifugal acceleration. However, the centrifugal acceleration was insignifi cant, thus, we believe that the main effect was caused by microgravity. Conclusions. Since clinorotation stimulates the growth and development of gilled mushrooms and is an effi cient way of forming virus-free planting material of different plants, this technology may have a wide scope of application. It may be used in agriculture, forestry and different industries, using raw plants or mushrooms, for instance, in food, pharmaceutical and textile industries, etc.

Heat Transport Capacity of an Axial-Rotating Single-Loop Oscillating Heat Pipe for Abrasive-Milling Tools

In order to enhance heat transfer in the abrasive-milling processes to reduce thermal damage, the concept of employing oscillating heat pipes (OHPs) in an abrasive-milling tool is proposed. A single-loop OHP (SLOHP) is positioned on the plane parallel to the rotational axis of the tool. In this case, centrifugal accelerations do not segregate the fluid between the evaporator and condenser. The experimental investigation is conducted to study the effects of centrifugal acceleration (0–738 m/s2), heat flux (9100–31,850 W/m2) and working fluids (methanol, acetone and water) on the thermal performance. Results show that the centrifugal acceleration has a positive influence on the thermal performance of the axial-rotating SLOHP when filled with acetone or methanol. As for water, with the increase of centrifugal acceleration, the heat transfer performance first increases and then decreases. The thermal performance enhances for higher heat flux rises for all the fluids. The flow inside the axial-rotating SLOHP is analyzed by a slow-motion visualization supported by the theoretical analysis. Based on the theoretical analysis, the rotation will increase the resistance for the vapor to penetrate through the liquid slugs to form an annular flow, which is verified by the visualization.

Ground Simulation Test of 2D Dynamic Overload Environment of Fuze Launching

The fuze launch process is subjected to backseat and spin overloads. To address this issue, a loading method of a 2D dynamic acceleration environment was developed in this study for testing fuze antioverload performance on ground. The techniques of flywheel energy storage, high-speed impact, and centrifugal rotation in the track are combined in a dynamic analysis and simulation. First, the flywheel is rotated at a constant speed by a variable-frequency motor to obtain high kinetic energy. Second, an impact hammer is instantaneously released on the specimen at a high speed, loading the backseat acceleration environment. Finally, the impact hammer is retracted, and the specimen is rotated in the track instead of spinning around its axis, thereby loading the centrifugal acceleration environment. The peak value and pulse width of the 2D overload acceleration can be adjusted by changing the speed of the flywheel and buffers in the abovementioned process. The experimental and simulation results observed that the peak value of backseat acceleration could reach 34,559 g, the pulse width was approximately 400 μs, and the peak value of the centrifugal acceleration was 1,020 g. The study results showed that the proposed approach fulfills the requirements of the 2D overload simulation test of the micro-electromechanical system (MEMS) fuze safety and arming mechanism. The proposed loading method has been successfully applied to ground simulation tests of the MEMS fuze safety and arming mechanism.