A Large Goaf Group Treatment by means of Mine Backfill Technology

There are few studies on the management methods of large-scale goaf groups per the specific surrounding rock mass conditions of each goaf. This paper evaluates comprehensively the stability of the multistage large-scale goaf group in a Pb-Zn mine in Inner Mongolia, China, via the modified Mathews stability diagram technique. The volume of each goaf to be backfilled was quantitatively analyzed in the combination of theoretical analysis and three-dimensional laser scanning technology. The corresponding mechanical characteristics of the filling were determined by laboratory testing while formulating the treatment scheme of the large goaf group using the backfill method. The applicability of the treatment scheme using the backfill was verified by the combination of the numerical results of the distribution of the surrounding rock failure zone and the monitored data of the surface subsidence. The research results and treatment scheme using the backfill can provide a reference for similar conditions of mines worldwide.

Indicators of the critical state of the ship’s stability

According to the main criterion, the vessel stability according to the main criterion is standardized by the Rules of the Russian Register by the assumption that the units of the stability margin are practically equal, which is the ratio of listing and restoring moments characterizing the equality of their work. That is, the current domestic and international standards allow the achievement of a shipborne borderline hazardous state, after which it will either capsize, or an uncontrolled inflow of water into the hull and emergency flooding will begin. The characteristics of the vessel that affect stability during its assessment, both at the design stages and during operation, are determined with some error. It is caused by the assumptions of the Rules to the displacement value determination and the coordinates of the gravity center, incomplete compliance with the predicted cruise conditions, due to the ship falling into possible more severe conditions, the construction of a static stability diagram, which is the dependence of the reduced restoring moment on the inclination angle, with a flat waterline, while it is three-dimensional, and other factors related to the vessel’s type and purpose, which are not taken into account when calculating stability. In this paper, we consider a group of such factors, in relation to ships of inland and mixed (river-sea) navigation, the features and reasons for their occurrence, taking into account in verification calculations. A mathematical stability safety factor form, reflecting the expected increments of permissible values, which will improve the safety of the ship, is proposed.

Model of a single-electron transistor based on endohedral fullerene (Sc3N)@C80

In this work within the framework of the density functional theory and the method of nonequilibrium Green’s functions the dependences of the total energy of molecules C80-SET and (Sc3N)@C80 - SET on their total charge, the dependence of the total energy from the gate voltage and the stability diagram of the single-electron transistor have been determined. It is noted that for transition to switch to on mode (Sc3N)@C80-SET it is necessary to apply the gate voltage in the range from 0.019 ≤ VG ≤ 5.940 with the bias voltage -2.040 ≤ VSD ≤ 2.155 V. Considering that at values of bias voltage equal to –0.381 ≤ VSD ≤ 0.533 V there is no voltage on the substrate (VG = 0 V) and electric current does not flow. It is shown that the total energy at negative values of charge is higher than at positive charges and that the area of the Coulomb rhombus in fullerene with scandium nitride is 5.3 times larger than in “pure” fullerene.

Emergence of Stripe-Core Mixed Spiral Chimera on a Spherical Surface of Nonlocally Coupled Oscillators

We report on a stripe-core mixed spiral chimera in a system of nonlocally coupled phase oscillators, located on the spherical surface, where the spiral wave consisting of phase-locked oscillators is separated by a stripe-type region of incoherent oscillators into two parts. We analyze the existence and stability of the stripe-core mixed spiral chimera state rigorously, on the basis of the Ott–Antonsen reduction theory. The stability diagram for the stationary states including the spiral chimeras as well as incoherent state is presented. Our stability analysis reveals that the stripe-core mixed spiral chimera state emerges as a unique attractor and loses its stability via the Hopf bifurcation. We verify our theoretical results using direct numerical simulations of the model system.

An Operation Guide of Si-MOS Quantum Dots for Spin Qubits

In the last 20 years, silicon quantum dots have received considerable attention from academic and industrial communities for research on readout, manipulation, storage, near-neighbor and long-range coupling of spin qubits. In this paper, we introduce how to realize a single spin qubit from Si-MOS quantum dots. First, we introduce the structure of a typical Si-MOS quantum dot and the experimental setup. Then, we show the basic properties of the quantum dot, including charge stability diagram, orbital state, valley state, lever arm, electron temperature, tunneling rate and spin lifetime. After that, we introduce the two most commonly used methods for spin-to-charge conversion, i.e., Elzerman readout and Pauli spin blockade readout. Finally, we discuss the details of how to find the resonance frequency of spin qubits and show the result of coherent manipulation, i.e., Rabi oscillation. The above processes constitute an operation guide for helping the followers enter the field of spin qubits in Si-MOS quantum dots.

Evaluating the Potential of Polylactide Nonwovens as Bio-Based Media for Air Filtration

The presented research aims to characterize hydrolytic resistance of highly crystalline and oriented polylactide (PLA) as a prerequisite for exploiting this bio-based material in durable applications. Industrially melt-spun PLA monofilaments and nonwovens have been subjected to environmental aging in a temperature range of 50–70 °C at a wide range of relative humidity (RH) in order to identify the onset of the material degradation under application conditions. Along with the measurements of mechanical and thermal behavior of the aged samples, the suitability of FTIR spectroscopy to probe the initial changes in the crystalline structure and in chemical composition of the fibers, caused by hydrolytic degradation, has been evaluated. The diagrams of stability and hydrolytic degradation under employed environmental aging for 7–14 days are presented for both types of PLA materials. Assessment of filtration performance of the artificially aged fibrous PLA media indicated a good agreement with the established stability diagram and confirmed the application potential of PLA nonwoven media, spun from currently available PLA grades, in air filtration under moderate climatic conditions up to max 50 °C and 50% RH. The presented results advance the knowledge on hydrolytic resistance of bio-based industry-relevant fibers and therefore open new application areas for sustainable materials with biodegradable components.

A vorticity-and-stability diagram as a means to study potential vorticity nonconservation

The study of atmospheric circulation from a potential vorticity (PV) perspective has advanced our mechanistic understanding of the development and propagation of weather systems. The formation of PV anomalies by nonconservative processes can provide additional insight into the diabatic-to-adiabatic coupling in the atmosphere. PV nonconservation can be driven by changes in static stability, vorticity or a combination of both. For example, in the presence of localized latent heating, the static stability increases below the level of maximum heating and decreases above this level. However, the vorticity changes in response to the changes in static stability (and vice versa), making it difficult to disentangle stability from vorticity-driven PV changes. Further diabatic processes, such as friction or turbulent momentum mixing, result in momentum-driven, and hence vorticity-driven, PV changes in the absence of moist diabatic processes. In this study, a vorticity-and-stability diagram is introduced as a means to study and identify periods of stability- and vorticity-driven changes in PV. Potential insights and limitations from such a hyperbolic diagram are investigated based on three case studies. The first case is an idealized warm conveyor belt (WCB) in a baroclinic channel simulation. The simulation allows only condensation and evaporation. In this idealized case, PV along the WCB is first conserved, while stability decreases and vorticity increases as the air parcels move poleward near the surface in the cyclone warm sector. The subsequent PV modification and increase during the strong WCB ascent is, at low levels, dominated by an increase in static stability. However, the following PV decrease at upper levels is due to a decrease in absolute vorticity with only small changes in static stability. The vorticity decrease occurs first at a rate of 0.5 f per hour and later decreases to approximately 0.25 f per hour, while static stability is fairly well conserved throughout the period of PV reduction. One possible explanation for this observation is the combined influence of diabatic and adiabatic processes on vorticity and static stability. At upper levels, large-scale divergence ahead of the trough leads to a negative vorticity tendency and a positive static stability tendency. In a dry atmosphere, the two changes would occur in tandem to conserve PV. In the case of additional diabatic heating in the mid troposphere, the positive static stability tendency caused by the dry dynamics appears to be offset by the diabatic tendency to reduce the static stability above the level of maximum heating. This combination of diabatically and adiabatically driven static stability changes leads to its conservation, while the adiabatically forced negative vorticity tendency continues. Hence, PV is not conserved and reduces along the upper branch of the WCB. Second, in a fullfledged real case study with the Integrated Forecasting System (IFS), the PV changes along the WCB appear to be dominated by vorticity changes throughout the flow of the air. However, accumulated PV tendencies are dominated by latent heat release from the large-scale cloud and convection schemes, which mainly produce temperature tendencies. The absolute vorticity decrease during the period of PV reduction lasts for several hours, and is first in the order of 0.5 f per hour and later decreases to 0.1f per hour when latent heat release becomes small, while static stability reduces moderately. PV and absolute vorticity turn negative after several hours. In a third case study of an air parcel impinging on the warm front of an extratropical cyclone, changes in the horizontal PV components dominate the total PV change along the flow and thereby violate a key approximation of the two-dimensional vorticity-and-stability diagram. In such a situation where the PV change cannot be approximated by its vertical component, a higher-dimensional vorticity-and-stability diagram is required. Nevertheless, the vorticity-and-stability diagram can provide supplementary insights into the nature of diabatic PV changes.

An overstability analysis of vertically vibrated suspension of active swimmers subjected to thermal stratification

The present article focuses on the analytical approach to discuss the thermo–vibrational convection in a suspension of the active (gyrotactic) swimmers. The onset of instability criterion is investigated for the stationary and oscillatory modes of convection in a shallow fluid layer with no–slip and rigid–free walls. The eigenvalue problem is tackled by Galerkin scheme to get the desired stability diagram and the correlation between the critical Rayleigh numbers. The overstability in suspension is possible when the unstable density gradient of the gyrotactic particles is opposed by the density variation due to thermo–vibrational influence. The suspension is destabilized due to gyrotactic up–swimming while the increase in Péclet number stabilizes the system. The stabilizing influence of vertical vibration is considerably affected due to thermal gradient which destabilizes the suspension. An interesting result of this study is the influence of thermo–vibrational parameter which is associated with applied thermal and vibrational properties. We reported that the destabilizing nature of thermo–vibrational parameter becomes thermally or vibrationally governed when the suspension is heated or cooled from below. When compared to the rigid–rigid boundaries, the displayed profiles for rigid–free walls yielded less stableness in the suspension.

Diagrams of static stability of a ship in rough conditions

Static stability diagram, solid-state model of a ship when constructing a static diagram of a ship in accordance with the requirements Of the rules of classification societies, it is necessary to take into account special navigation conditions: icing, the presence of liquid cargo in tanks, etc. In this case, the presence of the ship's side pitching caused by the action of waves is taken into account only at the time of determining the restoring moments. This article analyzes the influence on the stability diagram of the shape of the water surface (wave profile) on which the inclination occurs. Building a complex form of volume displacement, caused not only by the form of a surface ship, but a change in waterline, made with the use of solid modeling theoretical hull and volume of the water pool in the environment of Autodesk AutoCAD and Visual Lisp. For test calculations, it is found that the possible deviation of the static stability arm and the area under the positive part of the diagram can reach twelve percent.