Stabilization Coefficient Research Articles

Fluorine-free foaming extinguishing agent: Design route, fire extinguishing performance, foam stability mechanism

The development of fluorine-free foaming extinguishing agent, abbreviation FFEA, has become an urgent scientific challenge in the field of fire protection engineering due to the fact that the key component of existing aqueous film-forming foams is listed as a persistent organic pollutant. A study was conducted on foam performance and fire extinguishing efficiency of FFEA prepared by hydrocarbon and silicone surfactants with low-carbon alcohol modulation, using three selected silicone surfactants. The results show that the FFEA, including low-carbon alcohol-modulated Silok8141/SDS and Silok8008/SDS, exhibit low surface tension, good foam stabilization coefficient and long foam drainage time. Laboratory foam extinguishing experiments demonstrate that the FFEA produced by Silok8141/SDS/Isobutanol ternary system has better cooling effect and fire extinguishing performance. And the study of FFEA mechanism reveals that the addition of isobutanol blocks the foam liquid channel and increases the foam stability. The wide applicability of the design route for FFEA prepared by low-carbon alcohol-regulated hydrocarbon and silicone surfactants has been demonstrated.

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The article relates to the field of research of the physics of the transition of the amplifier from the aggregate state of amplification to the aggregate state of generation. The aim of the study is to find the possibility of controlling the process of transition from one state of aggregation to another, to implement a stable retention of the device at a given point. The latter will make it possible to implement the construction of stable regenerators. A theoretical conclusion is obtained about the possibility of stable signal regeneration, for which the stabilization coefficient of negative feedback on a constant, zero component should be greater than the regeneration coefficient or gain in gain due to positive feedback at the maximum gain frequency, and for a resonant amplifier – at a resonant frequency. The information confirming the theoretical conclusions and conditions on the example of some technical solutions and implementations of practical devices is given. The multiple technical advantages of stable regenerators over traditional amplifying devices are demonstrated, including resistance to excitation of parasitic generation in a wide dynamic range and temperature range. This is explained by the fact that a stable regenerator cannot be excited twice, a stable excitation is a normal state of aggregation of the regeneration of the input signal. There is also a significant increase in sensitivity and, accordingly, a decrease in intrinsic noise by 9-10 orders of magnitude, an improvement in the width of the linear dynamic range by 8-9 orders of magnitude. An improvement in the amplified frequency bandwidth is demonstrated, not only in the area of minimization, but also in the region of significant expansion, more than an order of magnitude, relative to the maximum achievable for specific samples of the amplifying element, the transistor. The fact that the dependence of the regeneration coefficient and the quality factor of the LC circuit is a special case, only for LC regenerators, is shown and explained. The presented broadband regenerators use strip valves or broadband transformers without an LC circuit and have a regeneration coefficient, which does not contradict the theory and is useful in practice. Multiple improvements are predicted in the construction of systems and devices for low-power signals, as well as an improvement by several orders of magnitude of the main technical characteristics of communication and location systems, measuring systems and devices.

Optimization of laser stabilization via self-injection locking to a whispering-gallery-mode microresonator: experimental study.

Self-injection locking of a diode laser to a high-quality-factor microresonator is widely used for frequency stabilization and linewidth narrowing. We constructed several microresonator-based laser sources with measured instantaneous linewidths of 1 Hz and used them for investigation and implementation of the self-injection locking effect. We studied analytically and experimentally the dependence of the stabilization coefficient on tunable parameters such as locking phase and coupling rate. It was shown that precise control of the locking phase allows fine-tuning of the generated frequency from the stabilized laser diode. We also showed that it is possible for such laser sources to realize fast continuous and linear frequency modulation by injection current tuning inside the self-injection locking regime. We conceptually demonstrate coherent frequency-modulated continuous wave LIDAR over a distance of 10 km using such a microresonator-stabilized laser diode in the frequency-chirping regime and measure velocities as low as sub-micrometer per second in the unmodulated case. These results could be of interest to cutting-edge technology applications such as space debris monitoring and long-range object classification, high-resolution spectroscopy, and others.

Error analysis of a stable reduced order model based on the proper orthogonal decomposition method for the Allen–Cahn–Navier–Stokes system

In this paper, we develop a stable reduced order model based on the proper orthogonal decomposition method, and conduct rigorous theoretical analyses for the Allen–Cahn–Navier–Stokes system. Firstly, the full order model and the reduced order model are constructed. The full order model uses finite element discretization for space and explicit–implicit discretization for time, where the same degree of Lagrange polynomials are used to discretize phase function ϕ, velocity u and pressure p for the spatial discretization. Such spatial discretization leads to unstable schemes due to the loss of inf–sup stability condition. Therefore, we consider adding some stability terms to increase the stability of the whole system. The local projection stabilization method is added to the gradient of velocity and pressure. It should be emphasized that the local projection stabilization method relaxes the constraints of the stabilization coefficient compared with the previous research. Secondly, on the basis of full order model, we obtain the reduced order model by using proper orthogonal decomposition method. Then, we theoretically validate the energy stabilities and the error estimate of the full order model and the reduced order model, respectively. After that, some numerical experiments are performed to verify the numerical accuracy and the computational efficiency of the reduced order model.

Mirror-Assisted Self-Injection Locking of a Laser to a Whispering-Gallery-Mode Microresonator

Self-injection locking is a dynamic phenomenon, which provides passive stabilization of a laser emission frequency via resonant optical feedback. The stabilization coefficient depends on the level of the feedback and quality factor of the external resonant structure creating the feedback. A conventional self-injection locked laser (SIL) based on a dielectric cavity involves barely tunable resonant Rayleigh scattering (RRS). In this work we study theoretically a scheme of a SIL via a high-$Q$ microresonator with a drop-port coupled mirror, in which the optical feedback level is optimally adjusted by tuning the drop-port mirror coupling. We show that the additional reflector can improve the laser stabilization and power handling efficiency if compared with the classic RRS-based scheme.

Thermal Properties of Shape-Stabilized Phase Change Materials Based on Porous Supports for Thermal Energy Storage

The use of phase change materials (PCM) for thermal energy storage (TES) is of great relevance, especially for the exploitation, in various ways, of the major ecological resource offered by solar energy. Unfortunately, the transition to the liquid state of PCM requires complex systems and limits their application. The goal of producing shape-stabilized phase change materials (SSPCM) is mainly pursued with the use of media capable of containing PCM during solid/liquid cycles. In this work, four cheap shape stabilizers were considered: sepiolite, diatomite, palygorskite and zeolite and two molten salts as PCM, for medium (MT) and high temperature (HT). The SSPCM, produced with an energy saving method, showed good stability and thermal storage performances. Diatomite reaches up to 400% wt. of encapsulated PCM, with a shape stabilization coefficient (SSc) of 97.7%. Zeolite exhibits a SSc of 87.3% with 348% wt. of HT-PCM. Sepiolite contains 330% wt. of MT-PCM with an SSc of 82.7. Therefore, these materials show characteristics such that they can be efficiently used in thermal energy storage systems, both individually and inserted in a suitable matrix (for example a cementitious matrix).

Analysis of dynamic characteristics of the inverter operating on a complex load

A simulation model of a converter with soft switching of transistors has been created. New calculation methods and means of measuring the equivalent frequency characteristics of converting devices with negative feedback to the problems of stability analysis have been applied. A comparative analysis of the calculated frequency characteristics of the converter in the normal operation mode with the characteristics of its linear model is presented. The features of calculating the equivalent frequency characteristics of the loop amplification of key devices are considered. It is noted that it is the equivalent frequency characteristics of the loop amplification that describe the relationship of frequency properties with the dynamics of voltage converters with pulse-width modulation and make it possible to reliably determine the real stability margins, predict the generation modes and open up the possibility of obtaining maximum negative feedback in a given frequency band of key devices. The non-minimal phase properties of the converter significantly complicate the achievement of high-quality stabilization of the output current (stabilization coefficient) of pulse stabilizers using only the deflection control principle. A successful solution to the problem is provided by the use of the principle of combined control. Compensation of the disturbance effect (changes in the supply voltage) gives a much better result than countering it through the feedback loop. It is quite realistic to exclude the influence of the input voltage u ( t ) on the output current i 2 in a static mode ( u =const) and in the absence of a negative feedback loop, which provides for u =const in a steady state, and to provide better dynamic properties of the converter. The influence of the nonlinear properties of pulse width modulation on stability is manifested in the considered characteristics in the form of an additional phase shift and resonant bursts in the vicinity of the clock frequency subharmonics. Additional feedbacks introduced into the control loop make it possible to solve synthesis problems using the most simple technical means

Water Chemistry Development for a Thermal Power Plant Circulating Cooling System Using the VTIAMIN EKO-1 Chemical Agent

Numerous substances and complex chemical agents, as well as various biocides for inhibiting the growth of microbial colonies and algae, are commercially available in the market of water treatment chemicals. In frequent cases, the chemicals offered in the market are not adapted to the water chemistry conditions of power plant circulating cooling systems (CCSs), and attempts of using them may lead to violation of the circulating water or effluent (blowdown) water quality standards. The aims of this study were to investigate the effectiveness of the VTIAMIN EKO-1 chemical agent and to select its optimal dose to reduce the corrosion rate of heat transfer surfaces and prevent mineral deposits from forming on them under the conditions of the experimental bench facility simulating the operation of CCSs for the condensers of steam turbines used at combined heat and power plants (CHPPs) equipped with a PGU-450 combined-cycle power unit. During the bench tests, the circulating and makeup water quality in terms of main indicators was monitored on a daily basis. For evaluating the corrosiveness of circulating water flowing in the experimental bench facility, a pair of corrosion rate surveillance specimens (coupons) made of St. 20 carbon steel and one brass coupon were installed at all test stages. The circulating water scale-forming properties were evaluated based on the results from visual examination and weighing of the thermal electric heater and the surveillance specimen made of stainless steel as well as the stabilization coefficient (calcium transport) calculation results. After having been evaporated, the CHPP makeup water that has not been subjected to corrective (reactant) treatment has increased scale-forming and corrosive properties with respect to carbon steels and medium-level scale-forming and corrosive properties with respect to brass. By using the VTAMIN EKO-1 chemical agent in the optimal dose, the carbon steel corrosion rate was slowed down by a factor of 3.7; the linear deposit-formation rate was decreased by a factor of 27.5, and the stabilization coefficient was kept at a level of 95.72%. In so doing, the requirements posed to the chemical agent’s key components by the standards for fishery water bodies were not violated. With the average content of the VTIAMIN EKO-1 reagent in circulating water at a level of 9.54 mg/dm3, its effectiveness in terms of corrosion protection and prevention of scale formation has been demonstrated. The estimated demand for the chemical agent is 33 397 kg/year.

Codon stabilization coefficient as a metric to gain insights into mRNA stability and codon bias and their relationships with translation.

The codon stabilization coefficient (CSC) is derived from the correlation between each codon frequency in transcripts and mRNA half-life experimental data. In this work, we used this metric as a reference to compare previously published Saccharomyces cerevisiae mRNA half-life datasets and investigate how codon composition related to protein levels. We generated CSCs derived from nine studies. Four datasets produced similar CSCs, which also correlated with other independent parameters that reflected codon optimality, such as the tRNA abundance and ribosome residence time. By calculating the average CSC for each gene, we found that most mRNAs tended to have more non-optimal codons. Conversely, a high proportion of optimal codons was found for genes coding highly abundant proteins, including proteins that were only transiently overexpressed in response to stress conditions. We also used CSCs to identify and locate mRNA regions enriched in non-optimal codons. We found that these stretches were usually located close to the initiation codon and were sufficient to slow ribosome movement. However, in contrast to observations from reporter systems, we found no position-dependent effect on the mRNA half-life. These analyses underscore the value of CSCs in studies of mRNA stability and codon bias and their relationships with protein expression.

Adaptive Physiological and Morphological Adjustments Mediated by Intestinal Stem Cells in Response to Food Availability in Mice

Several studies have evaluated plastic changes in the morphology of the digestive tract in rodents subjected to caloric restriction or restricted availability. Nevertheless, studies that link these morphological responses to physiological consequences are scarce. In order to investigate short-term plastic responses in the intestine, we acclimated adult Mus musculus (BALB/c) males for 20 days to four distinctive treatments: two caloric regimens (ad libitum and 60% of calorie ingestion) and two levels of periodicity of the regimens (continuous and stochastic treatment). At the end of the treatment we analyzed the cell proliferation and cell death dynamics of small intestinal crypts in these animals. In addition, we measured organ masses and lengths, hydrolytic digestive enzyme activities, and energy output from feces. Finally, in order to explore the metabolic changes generated by these dietary conditions we assessed the catabolic activity (i.e., enzymes) of the liver. Our results show that individuals acclimated to a continuous and 60% regimen presented longer intestines in comparison to the other treatments. Indeed, their intestines grew with a rate of 0.22 cm/day, generating a significant caloric reduction in the content of their feces. Besides, both mass and intestinal lengths were predicted strongly by the stabilization coefficient of BrdU+ proliferating cells per crypt, the latter correlating positively with the activity of n-aminopeptidases. Interestingly, by using pharmacological inhibition of the kinase mammalian target of rapamycin complex 1 (mTORC1) by Rapamycin, we were able to recapitulate similar changes in the proliferation dynamics of intestinal stem cells. Based on our results, we propose that the impact of caloric restriction on macroscopic variation in morphology and functional changes in digestive n-aminopeptidases occurs through synchronization in the proliferation rate of stem and/or progenitor cells located in the small intestinal crypts and requires mTORC1 as a key mediator. Hence, we suggest that an excessive stem and progenitor activity could result in increased crypts branching and might therefore underlie the reported intestinal tissue expansion in response to short-term caloric restriction. Summarizing, we demonstrate for the first time that short-term caloric restriction induces changes in the level of cell proliferation dynamics explaining in part digestive tract plasticity in adaptive performance.

An extended finite element method model for carbon sequestration

SummaryA two‐phase flow eXtended Finite Element Method (XFEM) model is presented to analyse the injection and sequestration of carbon dioxide (CO2) in deep saline aquifers. XFEM is introduced to accurately approximate near‐injection well pressure behaviour with elements significantly larger than the injection well diameter. We present a vertically averaged multiphase flow model that combines XFEM to approximate the pressure field, with a Streamline Upwind/Finite Element Method/Finite Difference Method (SU‐FEM‐FDM) to approximate the distribution of CO2 in the aquifer. Near‐well enrichment functions are presented along with the solution procedure for the coupled problem. Two examples are presented: in the first, CO2 injection into a perfectly horizontal aquifer is modelled with both XFEM and FEM‐based methods. The results suggest that XFEM is able to provide low relative errors in the pressure near the well at a reduced computational cost compared with FEM. The impact and selection of the stabilization coefficient of the SU‐FEM‐FDM is also discussed. In the second example, the XFEM and SU‐FEM‐FDM model is applied to a more realistic problem of an inclined aquifer to demonstrate the ability of the model to capture the buoyancy‐driven migration of CO2 in a deep saline aquifer. Copyright © 2014 John Wiley & Sons, Ltd.

Acousto-Optic Stabilization of Laser Beam Intensity

The results from studying a system for stabilizing laser beam intensity based on an acousto-optic modulator are presented. An equation that describes the dynamic processes and the system’s operating modes is obtained. It is shown that the stabilization coefficient is determined by the signal transmission coefficient in the feedback circuit and the position of the operating point on the amplitude characteristic of acousto-optic interaction.

Acousto-optic stabilization of the intensity of a laser beam

A system for stabilization of the intensity of a laser beam based on an acousto-optic modulator is theoretically and experimentally studied. An equation that describes dynamic processes in the system and various working regimes is derived. It is demonstrated that the stabilization coefficient depends on the transfer coefficient of the feedback circuit and the position of the working point on the amplitude characteristic of the acoustooptic interaction. An experimental prototype of the stabilization system is based on a paratellurite acousto-optic cell. The system stabilizes the intensity with a coefficient of 78 in a frequency band of 15–180 Hz.

The Relationship between Power Resources and the Procedures of Overcoming Employers’ Resistance against Organizational Changes among Managers of the University of Isfahan and Isfahan University of Medical Sciences, Iran

The purpose of this study was to examine the relationship between power resources and the procedures of overcoming employers' resistance against organizational changes among managers of the University of Isfahan as well as Isfahan University of Medical Sciences in 2012-2013 academic years. The research was descriptive-correlative and samples consisted of all the managers of the university of Isfahan as well as Isfahan University of Medical Sciences in 2012-2013 academic years using random sampling by which 108 managers were selected. The instruments used to collect data were two questionnaires designed by the researcher consisting of 30 questions related to power resources of managers extracted from French and Raven viewpoint and 28 questions covering procedures of overcoming employers' resistance against changes according to Likert scale and classification. Stabilization coefficient was obtained by means of Cronbach alpha (0.86) in the two questionnaires. The analysis of data was performed in descriptive (frequency, percent, mean, and deviation) as well as inferential (analysis of multi -variable variance, and regression coefficient) statistics through SPSS. The results of the study showed that there were no significant differences between the legal power of managers and the procedures used to overcome the resistance of employers against organizational changes. There was a negative and significant relationship between obligatory power and cooperation procedure. There was a positive and significant relationship between referential power and cooperation procedure.

Functional scheme of the automated laser vibration measuring systems with two optical channels converted to monitor and control the parameters of vibration

Mathematical modeling involves the search for optimal solutions. Control of the parameters of objects vibration and structures can extend their service life. The analysis of parameters influence such as channel power ratio m, the angle of non-parallelism β, and the error angle of optical access α to the stabilization coefficient K.

Numerical assessment of stability of interface discontinuous finite element pressure spaces

The stability of two recently developed pressure spaces has been assessed numerically: The space proposed by Ausas et al. [R.F. Ausas, F.S. Sousa, G.C. Buscaglia, An improved finite element space for discontinuous pressures, Comput. Methods Appl. Mech. Engrg. 199 (2010) 1019–1031], which is capable of representing discontinuous pressures, and the space proposed by Coppola-Owen and Codina [A.H. Coppola-Owen, R. Codina, Improving Eulerian two-phase flow finite element approximation with discontinuous gradient pressure shape functions, Int. J. Numer. Methods Fluids, 49 (2005) 1287–1304], which can represent discontinuities in pressure gradients. We assess the stability of these spaces by numerically computing the inf–sup constants of several meshes. The inf–sup constant results as the solution of a generalized eigenvalue problems. Both spaces are in this way confirmed to be stable in their original form.An application of the same numerical assessment tool to the stabilized equal-order P1/P1 formulation is then reported. An interesting finding is that the stabilization coefficient can be safely set to zero in an arbitrary band of elements without compromising the formulation’s stability. An analogous result is also reported for the mini-element P1+/P1 when the velocity bubbles are removed in an arbitrary band of elements.

A system of capacity stabilization for the forage harvesters

The results of laboratory and field tests of forage harvester КСК-100А equipped with a system of capacity stabilization are given. Advantages of modernized harvester are revealed. Its performance increased and total load on the engine decreased. The stabilization coefficient of loading is 1.14, stabilization coefficient of vegetative mass layer thickness is 1.35.

Emulational Analysis of Concrete Pouring in Steel-Pipe Arch Rib of Fei Shuiya Bridge

Fei Shuiya Bridge is a half-through steel-pipe concrete arch bridge with uniform catenary. Based on sufficiently considering the principle of symmetrically loading rib concrete, the pouring process of concrete is calculated through MIDAS/Civil 6.71. Structural distortion, bearing-force characteristics and stabilization coefficient of each phase are given. Structural security is discussed too. Conclusions have a certain reference value for the same bridge in pouring the rib concrete.

A voltage stabilizer on a storage capacitor

A voltage stabilizer on a storage capacitor is intended for converting constant unstabilized voltages into pulsed voltages with stabilized amplitudes in power supply circuits for lasers. The principle of operation of this stabilizer is based on preliminarily charging of the storage capacitor to a voltage intended for compensating for an alternating component of the input voltage. The proposed technical decision significantly increases the laser emission stability. A voltage Uout = 1000 ± 1 V was obtained across the storage capacior, and the stabilization coefficient was ∼100.

Geno-mathematical identification of the multi-layer perceptron

In this paper, we will focus on the use of the three-layer backpropagation network in vector-valued time series estimation problems. The neural network provides a framework for noncomplex calculations to solve the estimation problem, yet the search for optimal or even feasible neural networks for stochastic processes is both time consuming and uncertain. The backpropagation algorithm—written in strict ANSI C—has been implemented as a standalone support library for the genetic hybrid algorithm (GHA) running on any sequential or parallel main frame computer. In order to cope with ill-conditioned time series problems, we extended the original backpropagation algorithm to a K nearest neighbors algorithm (K-NARX), where the number K is determined genetically along with a set of key parameters. In the K-NARX algorithm, the terminal solution at instant t can be used as a starting point for the next t, which tends to stabilize the optimization process when dealing with autocorrelated time series vectors. This possibility has proved to be especially useful in difficult time series problems. Following the prevailing research directions, we use a genetic algorithm to determine optimal parameterizations for the network, including the lag structure for the nonlinear vector time series system, the net structure with one or two hidden layers and the corresponding number of nodes, type of activation function (currently the standard logistic sigmoid, a bipolar transformation, the hyperbolic tangent, an exponential function and the sine function), the type of minimization algorithm, the number K of nearest neighbors in the K-NARX procedure, the initial value of the Levenberg–Marquardt damping parameter and the value of the neural learning (stabilization) coefficient α. We have focused on a flexible structure allowing addition of, e.g., new minimization algorithms and activation functions in the future. We demonstrate the power of the genetically trimmed K-NARX algorithm on a representative data set.