Quasi-stationary Conditions Research Articles

Assessment of Quasi-Stationary Power Quality Phenomena in DC Power Systems

The adoption of dc architectures for electricity distribution has been increasingly considered to reduce the number of energy conversions and to exploit their inherent ability to cope with peaks in energy supply and demand. Furthermore, dc systems have been commonly and widely adopted for high-voltage transmission systems and public transport for many years. Despite this, the Power Quality (PQ) assessment in dc power networks is still unstandardized. In the scientific literature, various indices have been proposed for the quantification of dc PQ. However, not all the aspects encountered in practical applications are adequately accounted for, and their effects regarding the impact on the measurement results are not fully analysed. This paper focuses on signal processing for the analysis of PQ of dc networks in stationary or quasi-stationary conditions aimed at compatibility level assessment. The influence quantities that affect the measurement results of the most commonly adopted procedures for determining the PQ index determination are identified and modelled, and their impact is analytically calculated. Advanced signal processing methods, suitable to be adopted in standards for dc PQ compatibility level surveys, are proposed to improve the accuracy and reliability of results. The rationality and effectiveness of the proposed procedures are shown with analytical calculations and in real measurement situations.

ОЦЕНКА ВОЗМОЖНОСТИ ЭСКАЛАЦИИ ПОЖАРА ПРИ ХРАНЕНИИ МОТОРНЫХ ТОПЛИВ В ПОЛИМЕРНЫХ ЭЛАСТИЧНЫХ РЕЗЕРВУАРАХ

Due to the increase in oil production and production of petroleum products, as well as their transportation and storage, the range and sizes of reservoirs are increasing. For this purpose, polymer tanks are widely used at Russian enterprises of the fuel and energy complex, including mobile tank farmsand oil depots for the operational storage of oil and petroleum products. However, the polymer materials from which the tanks are made are flammable, which increases their fire hazard level. An assessment of the possibility of fire escalation has been carried out using the example of an oil depot model for storing motor fuels in polymer elastic tanks. The results 
 of calculating the dangerous factors of a spill fire during depressurization of polymer elastic tanks with gasoline and diesel fuel, as well as a graph of the dependence of the intensity of thermal radiation during the ignition of these tanks, are presented in tabular form, and an event tree is constructed. The parameters characterizing the possible escalation of a fire at a motor fuel storage site under quasi-stationary conditions have been determined.
 A methodology is proposed that allows assessing the possibility of realizing the escalating nature of a fire at facilities for storing and handling motor fuels in polymer elastic tanks, and recommendations are also given to prevent the progressive nature of the development of negative events and reduce damage in case of fire.

The specific current action integral for conductors exploded by high-frequency currents

The explosive emission processes that occur at electrode surface microprotrusions may have harmful effects in a variety of electrodynamic and acceleration systems exposed to high-power radio frequency electromagnetic waves. This paper presents the results of a radiative magnetohydrodynamic simulation of the explosion of copper conductors that occur under conditions inherent in the explosion of electrode microprotrusions, i.e., at current densities of the order of 109 A/cm2. Explosions occurring under quasi-stationary and radio frequency conditions (hereinafter referred to as quasi-stationary and radio frequency explosions, respectively) were considered. It was shown that in all the considered cases, the explosion occurred at high temperatures, so that the energy deposited in the conductor by the time of explosion exceeded the sublimation energy of the conductor material. It turned out, however, that the energy deposited in the conductor under radio frequency conditions, regardless of the frequency of current oscillations, was more than two times less than that deposited under quasi-stationary conditions. The explosion time was also virtually independent of the frequency, and it was approximately three times longer than that calculated for quasi-stationary conditions. For a radio frequency explosion, the specific current action integral was somewhat less (by about 25%) than that for a quasi-stationary explosion, and its value was actually independent of frequency. At the same time, in the radio frequency regime, the radiation power coming out of the conductor substance drops strongly, and it is almost two orders of magnitude smaller compared to the radiation power in the quasistationary regime.

Review of special features of determining resistance to heat transfer under natural conditions and in a climate chamber

The current study aims to review methods of experimental determination of the resistance to heat transfer. In order to study the special features of determining thermal resistance under natural conditions and in a climate chamber, modern patents have been reviewed. Two studies by Mureev P.N. et al. discussed in this article were intended to study the determination of the resistance to heat transfer and the influence of counter heat flows arising in the thickness of the wall enclosure under quasistationary conditions in full scale. The authors’ experiment has been analyzed, the distinctive feature of which is the introduction of sensors inside the wall enclosure, which makes it possible to more accurately determine the temperature distribution and direction of heat flows inside the enclosure. In his research, Budadin O.N. together with colleagues examined the issues of improving the quality and reliability of determining the thermal resistance of a building envelope when tested in a climate chamber, and succeded in obtaining a very low error in determining the thermal resistance. A modified climatic chamber presented as a stand with a mobile cassette for installing a sample patented by Verkhovsky A.A. and co-others has also been considered. These methods were justified by the achievement of technical research results.

Repulsive, but sticky – Insights into the non-ionic foam stabilization mechanism by superchaotropic nano-ions

HypothesisThe superchaotropic Keggin polyoxometalate α-SiW12O404− (SiW) was recently shown to stabilize non-ionic surfactant (C18:1E10) foams owing to electrostatic repulsion that arises from the adsorption of SiW-ions to the foam interfaces. The precise mechanism of foam stabilization by SiW however remained unsolved. ExperimentsImaging and conductimetry were used on macroscopic foams to monitor the foam collapse under free drainage and small angle neutron scattering (SANS) at a given foam height allowed for the tracking of the evolution of film thickness under quasi-stationary conditions. Thin film pressure balance (TFPB) measurements enabled to quantify the resistance of single foam films to external pressure and to identify intra-film forces. FindingsAt low SiW/surfactant ratios, the adsorption of SiW induces electrostatic repulsion within foam films. Above a concentration threshold corresponding to an adsorption saturation, excess of SiW screens the electrostatic repulsion that leads to thinner foam films. Despite screened electrostatics, the foam and single foam films remain very stable caused by an additional steric stabilizing force consistent with the presence of trapped micelles inside the foam films that bridge between the interfaces. These trapped micelles can serve as a surfactant reservoir, which promotes self-healing of the interface leading to much more resilient foam films in comparison to bare surfactant foams/films.

Interaction of a tubular charged-particle beam with eigenwaves of a plasma solid-state cylinder located in strong longitudinal magnetic field

An electrodynamic system in which a magnetized tubular electron beam blows around a cylindrical solid-state plasma waveguide located coaxially in a longitudinal magnetic field is theoretically studied. It has been established, when quasi-stationary conditions are satisfied, hybrid bulk-surface or surface electromagnetic waves of helicon origin are excited in the waveguide. The waveguide eigenwaves are excited by the space-charge field of beam with matching of the longitudinal spectral components of electric field. It is noted that helicons and waves of their nature are formed in a conducting plasma medium in the assistance of an external magnetic field. It is shown the instability of coupled waves of the electrodynamic system is due to the Vavilov–Cherenkov effect.

Experimental determination of the resistance to heat transfer of various building envelope constructions

The aim of the current research is to examine instruments for measuring heat flow and temperature, and to present methods for calculating resistance to heat transfer in accordance with regulatory documents. Requirements for constructions chosen as samples, and the conditions for their testing under stationary, quasi-stationary, and non-stationary conditions, are discussed. The study investigates devices for measuring thermal characteristics based on the research conducted by Yaping Cui, Jingchao Xie, Jiaping Liu, Peng Xue. An experiment performed by Chinese scientists to determine heat transfer coefficients using a naphthalene sample is analyzed. The research also presents a field experiment conducted by E.A. Gnezdilova to calculate the design characteristics of heat loss through floor constructions and building envelope constructions in direct contact with the soil. The validity and reliability of applying various methodologies are justified.

Start-up behavior and the ignition limit of passive hydrogen recombiners with various catalytic elements

The paper gives the results of experiments aimed to study start-up characteristics and the ignition limit of recombiners containing two various types of catalysts, namely ceramic rods and high porosity cell material. Both types of catalysts were produced by Redkino Catalyst Company. Experiments were carried out using a 15 m3 BM-P chamber located at the FSUE “RFNC-VNIITF named after Academ. E.I. Zababakhin” test site. The recombiner was tested in a homogeneous hydrogencontaining gas mixture under the quasi-stationary conditions with a stepwise increase in hydrogen concentration.Experimental results demonstrated that similar physical processes were observed for both types of catalysts. The recombiner was shown to start up when natural convection flow was activated through its case. Ignition was proved to be caused not only by a heated catalyst, but also by particles escaping from catalytic surface due to spallation and thus decreasing the ignition limit from 10% down to 5%.

Non-Destructive Possibilities of Thermal Performance Evaluation of the External Walls.

Identification of the actual thermal properties of the partitions of building enclosures has a significant meaning in determining the actual energy consumption in buildings and in their thermal comfort parameters. In this context, the total thermal resistance of the exterior walls (and therefore their thermal transmittance) in the building is a major factor which influences its heat losses. There are many methods to determine the total thermal resistance of existing walls, including the quantitative thermography method (also used in this study). This paper presents a comparison of the calculated total thermal resistance values and the measured ones for three kinds of masonry walls without thermal insulation and the same walls insulated with expanded polystyrene boards. The measurements were carried out in quasi-stationary conditions in climate chambers. The following three test methods were used: the temperature-based method (TBM), the heat flow meter method (HFM) and the infrared thermography method (ITM). The measurement results have been found to be in good agreement with the theoretically calculated values: 61% of the measured values were within 10% difference from the mean value of total thermal resistance for a given external wall and 79% of the results were within 20% difference. All of the used measuring methods (TBM, HFM and ITM) have proven to be similarly approximate in obtained total thermal resistances, on average between 6% and 11% difference from the mean values. It has also been noted that, while performing measurements, close attention should be paid to certain aspects, because they can have a major influence on the quality of the result.

Waves of a Magnetoplasma Solid-State Cylinder Under Quasi-Stationary Conditions

The theory of electromagnetic eigenwaves of a cylindrical plasma waveguide located in a constant coaxial magnetic field is developed. The dispersion equation for a waveguide with high electronic conductivity is obtained. It is shown that the waveguide supports the propagation of bulk and bulk-surface hybrid waves of helicon origin. The nonreciprocity effect of waveguide eigenwaves with the identical field distributions, but differing in the direction of propagation along the azimuthal coordinate and also when the direction of the external magnetic field is reversed, is discovered.

Study of Array of Mems Inertial Measurement Units Under Quasi-Stationary and Dynamic Conditions

Abstract A measurement system includes all components in a chain of hardware and software that leads from a measured variable to processed data. In that context, the type and quality of the sensors or measuring devices are critical to any measurement system. MEMS/IMU sensors lag behind leading technologies in this respect, but the MEMS/IMU performance rapidly changes while is relatively inexpensive. For this reason, the paper proposes some investigations of currently available MEMS/IMUs, but in an array configuration. The article presents the results of research undertaken on this type of IMU sensor configuration under quasi-stationary and dynamic conditions and answers the question of whether the precision of current MEMS technologies for acceleration and angular velocity sensors is still improved using this kind of approach.

Atmospheric blocking events in the North Atlantic: trends and links to climate anomalies and teleconnections

Atmospheric blockings are generally associated with large-scale high-pressure systems that interrupt west-to-east atmospheric flow in mid and high latitudes. Blockings cause several days of quasi-stationary weather conditions, and therefore can result in monthly or seasonal climate anomalies and extreme weather events on the affected regions. In this paper, the long-term coupled CERA-20C reanalysis data from 1901 to 2010 are used to evaluate the links between blocking events over the North Atlantic north of 35° N, and atmospheric and oceanic modes of climate variability on decadal time scales. This study indicates more frequent and longer lasting blocking events than previous studies using other reanalyses products. A strong relationship was found between North Atlantic blocking events and North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO) and Baffin Island–West Atlantic (BWA) indices, in fall, winter and spring. More blocking events occur during the negative phases of the NAO index and positive phases of the BWA mode. In some situations, the BWA patterns provide clearer links with the North Atlantic blocking occurrence than with the NAO alone. The correlation between the synchronous occurrences of AMO and blocking is generally weak, although it does increase for a lag of about 6–10 years. Convergent cross mapping (CCM) furthermore demonstrates a significant two-way causal effect between blocking occurrences and the NAO and BWA indices. Finally, while we find no significant trends in blocking frequencies over the last 110 years in the Northern Hemisphere, these events become longer lasting in summer and fall, and more intense in spring in the North Atlantic.

Complex research of the unclosed HTS shield for improving homogeneity of the magnetic field

Homogeneous magnetic fields are required in different applications. The resolution of MRI techniques depends on the quality of the magnetic field, as well as the efficiency of electron cooling systems used at particle accelerators. Unclosed magnetic shield made of superconducting tapes is able to nullify the radial component of a solenoidal magnetic field, forming the long region of the homogeneous magnetic field. The shield is a lengthwise winding made from YBCO tapes are wound along a carcass generatrix. Then it is positioned coaxially inside an electromagnet. The measurements were carried out under quasistationary conditions, magnetic fields up to 1 kG at 77K. This paper discusses the design of the superconducting shield and presents experimental and numerical studies into the homogeneity of the magnetic field in solenoids with the superconducting shield.

Special modes of diffusion mass transfer in isothermal triple gas mixtures

In isothermal three-component gas mixtures in quasi-stationary conditions the procedure of numerical solution of Stefan-Maxwell diffusion equations using the software package “MathCad” is considered. It is shown that one of the specific features of multicomponent diffusion is the appearance of nonlinear concentration distributions of components in vertical channels. Due to the difference in the coefficients of mutual diffusion of gases in some systems under certain conditions, nonlinear distributions of component concentrations lead to a non-monotonic distribution of the density of the gas mixture. By the example of hydrogen – nitrogen – methane and methane – n-butane – nitrogen systems at a constant temperature T = 298 K, the influence of the content of the component with the highest molecular weight in the triple gas mixture on the degree of nonlinearity of the density distribution in the diffusion channel is analyzed. It is suggested that the inversion of the density distribution of the mixture may be the cause of convective instability in triple gas systems. The results of calculations are compared with experimental data.

Laser welding with side-gas application and its impact on spatter formation and weld seam shape

Spattering is a quality issue within deep penetration laser welding processes resulting in time-consuming and cost-intensive post-processing. In this study, the formation of unconventional weld shapes, e.g. with bulge formation was observed in a lap-joint, while using a side-gas jet to enlargen the capillary opening. During quasi-stationary conditions, spattering could not be detected. It was found that in addition to a side-gas jet, the implementation of conventional center-gas is required. However, the type of shielding gas (N2, Ar, He) used for both, the center- as well as the side-gas does not impact on the formation of the characteristic bulge shape. Furthermore, bulge characteristics strongly depend on the welding speed. Therefore, the formation of latter is attributed to surface tension driven melt flows. In conclusion, spattering can be virtually non-existent if the capillary enlargement resulting from the side-gas jet is kept above a certain threshold.

NATURAL RISKS AND STRATEGY OF THE WATER AVAILABILITY RESEARCH OF TERRITORIES

According to the “Water strategy” accepted by the Government of Russian Federation in 2009, risks of the negative influence of natural water on the environment mostly are related with the peak flood runoff. The water deficit is not in the list of risks. The water deficit has begun to increase during the past decades even in humid zones mainly due to the climate change. Therefore, there is a necessity to assess reasons and trends of water regimes and water resources changes for different territories. The twofold of the runoff distribution in the different chains of the river network displayed for the modern decades. The low flows in the lower river chains (so-called “the large rivers”) increased substantially since 1987-1990. The same situation was in “the small rivers” until 2000’s, but low flows there became decrease later (however, it is still more than it was during 1950-1970’s). The favorable conditions of the water leakage keeping for the long period had led to the disturbance of the water balance components, when water leakage in rivers became exceed their feeding, and water has “outflow” from the basins of small rivers. Nonsynchronous changes of the water regimes of river net chains of different order can’t be explained by “global approaches” to the climate changes. Therefore, there is a different suggested way to solve this problem, related to nonlinear reaction of the river basins water system to the climate long-term variations, when one quasi-stationary conditions (definite relative stable period of climate conditions) change to another. It is useful to add to “The water strategy” more detailed hydrological basis. It should include all aspects of the standard and special hydrological network development, problems of the scientific study hydrological processes, spatial-temporary nonuniformity of the different order river basins water turnover reaction on the climate change.

Challenges of x-ray spectroscopy in investigations of matter under extreme conditions

Advanced X-ray spectroscopic methods provide unique and critical data to study matter under extreme environmental conditions induced by high-intensity and high-energy lasers. The aim of this paper is to contribute to a contemporary discussion of the role of X-ray spectroscopy in the investigation of radiative properties of strongly coupled, highly correlated, and frequently weakly emissive plasma systems formed in matter irradiated by sub-petawatt and petawatt class lasers. After reviewing the properties of different X-ray crystal spectrometers, high-resolution X-ray diagnostic methods are surveyed with respect to their potential to study plasma-induced and externally induced radiation fields, suprathermal electrons, and strong electromagnetic field effects. Atomic physics in dense plasmas is reviewed with emphasis on non-Maxwellian non-LTE atomic kinetics, quasi-stationary and highly-transient conditions, hollow ion X-ray emission, and field-perturbed atoms and ions. Finally, we discuss the role of X-ray free electron lasers with respect to supplementary investigations of matter under extreme conditions via the use of controlled high-intensity radiation fields.

Oxidation-influenced crystallization in (GeSe2)x(Sb2Se3)1-x chalcogenide glasses

Influence of oxygen atmosphere on crystallization of (GeSe2)x(Sb2Se3)1-x glasses (for x = 0.3, 0.4 and 0.5) was investigated by differential scanning calorimetry, X-ray diffraction analysis and infrared microscopy. Particle-size-dependent study was performed to reveal the role of mechanically induced defects. The presence of oxygen led to an early formation of a thin surface crystalline layer (smoothly structured) that significantly influenced further crystal growth. The most pronounced consequence was surprisingly found in case of the (GeSe2)0.3(Sb2Se3)0.7 composition that crystallizes in volume. The thin surface crystalline layer hindered the macroscopic viscous flow, so that the samples retained their original shape, and these quasi-stationary conditions accelerated the initial nucleation and growth rates. At the same time, however, these conditions prevented the samples from reaching full crystallinity. In case of the compositions with x = 0.4 and 0.5, the crystal growth proceeded only at the surface and presence of external interfaces and mechanically induced defects took over the major role driving the crystallization kinetics. Correlation of the calorimetric, microscopic and viscosity data is discussed in detail.

Crystallization of (GeSe2)0.3(Sb2Se3)0.7 chalcogenide glass - Influence of reaction atmosphere

Differential scanning calorimetry, infrared microscopy and X-ray diffraction analysis and were used to investigate the influence of reaction atmosphere (air versus pure nitrogen) on crystallization behavior of (GeSe2)0.3(Sb2Se3)0.7 glass. The presence of oxygen was found to accelerate the crystal growth both on surface and in bulk material, with a similar effect in case of powders and bulk samples. Detailed crystallization kinetics study was performed, revealing that the presence of oxygen leads to a lowered activation energy and steeper onset of the process – single-curve-averaged masterplot approach was used to deal with the temperature-differentiated complexity of the crystallization. Direct observations by infrared microscopy have shown that the presence of oxygen leads to a formation of robust surface crystalline layer, which prevents powder sintering and bulk samples deformation by viscous flow, and to a more rapid nucleation and crystal growth within the sample volume. Based on the viscosity values estimated for the crystallization temperatures, an explanation for the accelerated volume crystallization was proposed, employing the quasi-stationary conditions contributing to better cohesivity of critical nuclei and crystal/glass interface. The existence of the surface crystalline layer however prevents the sample from reaching full crystallinity.

Kinetics of growth of non-equilibrium fluctuations during thermodiffusion in a polymer solution.

A thermal diffusion process occurring in a binary liquid mixture is accompanied by long ranged non-equilibrium concentration fluctuations. The amplitude of these fluctuations at large length scales can be orders of magnitude larger than that of equilibrium ones. So far non-equilibrium fluctuations have been mainly investigated under stationary or quasi-stationary conditions, a situation that allows to achieve a detailed statistical characterization of their static and dynamic properties. In this work we investigate the kinetics of growth of non-equilibrium concentration fluctuations during a transient thermodiffusion process, starting from a configuration where the concentration of the sample is uniform. The use of a large molecular weight polymer solution allows to attain a slow dynamics of growth of the macroscopic concentration profile. We focus on the development of fluctuations at small wave vectors, where their amplitude is strongly limited by the presence of gravity. We show that the growth rate of non-equilibrium fluctuations follows a power law [Formula: see text] as a function of time, without any typical time scale and independently of the wave vector. We formulate a phenomenological model that allows to relate the rate of growth of non-equilibrium fluctuations to the growth of the macroscopic concentration profile in the absence of arbitrary parameters.