Phenomenon Of Stratification Research Articles

Protetores solares, pele negra e mídia em aulas de química

A exposição solar proporciona sensação de bem-estar físico, estimula a produção de melanina e a síntese de vitamina D pelo organismo. As civilizações antigas da África utilizavam base de mamona, extrato de magnólia, jasmim e óleo de amêndoas como protetores solares. Com características de uma pesquisa participante, este estudo teve como objetivo aproximar alunas/os do Ensino Médio de cientistas negras contemporâneas. Os resultados estabeleceram um diálogo sobre as radiações ultravioletas que incidem sobre a Terra pelos raios solares. Pessoas de pele negra representam a maioria da população do Brasil e, ainda assim, a veiculação de comerciais sobre protetores solares apresentam como alvo somente o corpo branco. A/o aluna/o reconhece o fenômeno da estratificação racial da população como construção ideológica realizada por meio de um conjunto de práticas materiais de discriminação racial. Portanto, cabe-nos como professoras/res de Química e sujeitos desta sociedade mediar o discurso que combata o racismo na educação.

Preparation and thermal properties of sodium acetate trihydrate as a novel phase change material for energy storage

As phase change thermal storage material, sodium acetate trihydrate (CH3COONa·3H2O) exhibits large thermal capacity and holds tremendous promise. However, main problems of undercooling of solidification and phase stratification constrained its application in energy storage. Thus, present work prepared a new composite phase change thermal storage material of sodium acetate trihydrate mixed with nucleating agent and thickening agent. The initial research results showed that addition of an appropriate proportion of nucleating agent tetrasodium pyrophosphate decahydrate led to a good restrain to the undercooling of CH3COONa·3H2O. A certain amount of thickening agent polyacrylamide could also avoid the phenomenon of phase stratification and maintain the heat storage capacity of samples. Meanwhile, the additions little affected the melting point and would not decrease the enthalpy of fusion of sodium acetate trihydrate as established from Differential Scanning Calorimetry study, which indicated that this novel composite material possessed excellent and stable performance suitable for its application for thermal energy storage systems.

Movement rules and screening characteristics of rice-threshed mixture separation through a cylinder sieve

The rice-threshed mixture presents the phenomenon of axial flow and radial stratification under the impact of airflow field, gravitational field, and sieve. We used the method that couples computational fluid dynamics (CFD) with the discrete element method (DEM) to numerically calculate the process described above, and investigated the influence of inlet airflow velocity, diameter and rotating speed of cylindrical sieve on the movement rules and screening characteristics of rice-threshed mixture components (grains, shriveled grains, and short stalks). The nonlinear fitting curve showed that inlet airflow velocity had a significant influence on the axial average velocity of mixture components, the sifting grain mass distribution, and screening loss rate. The greatest screening efficiency give with an inlet airflow velocity of 9.67 m/s. The diameter of cylindrical sieve has a large influence on the axial average velocity of grains and short stalks. Cylindrical sieve rotating speed has a great influence on the axial average velocity of the short stalks, screening loss rate, and screening efficiency. Validation test for one of parameters shown that the error for the screening cleaning rate of each collection area is below 5%, while the screening loss rate and screening efficiency error are 8.11% and 3.3%, respectively. The research result indicates that the CFD-DEM coupling method has scientific and practical value in calculating the movement rules and screening characteristics of rice-threshed mixture in a cylindrical sieve.

DESIGUALDADE SOCIAL, RESPONSABILIDADE E RESPONSIVIDADE DA PESQUISA

Inequality is one of the classic problems of the social sciences. It is recurrently associated with the phenomenon of social stratification because it manifests itself as a hierarchical and unequal arrangement of positions based on socially defined features, such as power, property, and prestige (Eisenstadt, 1995) or as a “structure of regularized inequalities” (Almeida, 1984, p. 175). Although concerns over the economic basis of income and class inequality predominate, attention on the subject has been intensified by its association with other dimensions, such as gender, race, and ethnicity (Dodd, Lamont, & Savage, 2017).

Numerical and Experimental Study of Thermal Stratification Outside a Small SMR Containment Vessel

A Small Modular Reactor’s (SMR) containment vessel (CNV) is submerged in the reactor cooling pool, which supplies a passive heat sink for containment to remove heat during Loss of Coolant Accident (LOCA). The heat transfer efficiency of passive safety systems is affected by thermal stratification processes. This study aims to explain the phenomenon of thermal stratification in SMR’s reactor pool. A small scaled containment vessel with an electric heater inside immersed in a pool of water was used to simulate this phenomenon. The results show how the thermal stratification formed. Moreover, a three-dimensional computational fluid dynamic (CFD) model was built using ANSYS FLUENT. Experimental data were compared with simulation results, and the standard k-ε model was found to be suitable for calculating thermal stratification in the pool outside the containment.

ENVIRONMENTALLY SAFE AUTOMATED PRODUCTION PROCESS FOR COMPRESSED AIR IN CONSTRUCTION INDUSTRY

The article in accordance with the adoption of the Federal law dated 23 November 2009 No. 261-FZ "On energy saving and increase of ecological safety and on amendments to certain legislative acts of the Russian Federation" the authors have developed and proposed for implementation of innovative solution for the environmentally safe production of compressed air, widely used in the construction industry in the Russian Federation and in the near and far abroad. Due to the fact that the production of a building material , its transportation and use in the creation of building elements is accompanied by considerable allocations of dirt, especially in the form of solid particles, which have a significant effect on the environmental parameters in the industrial zones, the problem of ecological safety of the population is important and requires your decision. On the basis of the conducted at the Department of "Teplogazosnabzhenie" research work in the framework of the strategic development of the University of the proposed technical device for the production of compressed air of normalized parameters ensuring the environmentally friendly production of pneumatic energy. The novelty of technical solutions, protected by patents of the Russian Federation and can be effectively used in various sectors of the economy.. This is achieved by processing the intake of atmospheric air into the air filter of the compressor, which uses the phenomenon of turbulence and thermodynamic stratification with intensification of purification from fine-dispersed contaminants in the form of dust and droplet of moisture. The mathematical model of the environmental process for the production of compressed air by cleaning the stream of intake atmospheric air, which became the basis for the development of a number of technical solutions to air filters compressors.

Design and experimental assessment of thermal stratification effects on operational loading of surge line of Unit 5, Novovoronezh NPP

One of the key tasks in substantiating NPP service life extension consists in detailed examination of all factors affecting the remaining lifespan of critical NPP components. Particular attention must be paid to studying the phenomenon of thermal stratification (TS) which is the effect of coolant lamination into the “cold” and “hot” layers in horizontal pipelines when flows with different temperatures propagate at slow velocities. Special importance of this issue is explained by the fact that cyclic loads caused by TS contribute in accumulation of metal damage due to thermal fatigue and can provoke formation and accelerated growth of defects.This study is dedicated to implementing complex analysis of coolant TS observed in horizontal sections of the surge line (SL) on WWER-1000 units from the viewpoint of assessment of TS effects on the stressed-deformed conditions of metal and accumulation of cyclic damages. The experimental data on the distribution of temperature fields in horizontal SL sections, as well as cyclic loading history during several reactor fuel residence campaigns were recorded by the on-line diagnostic monitoring system put into operation on Unit 5 Novovoronezh NPP. Certain distinguishing features of TS in SL of Unit 5 were identified as the result of data analysis depending on operational modes. The most significant TS effects were observed in the control cross-section located within the first horizontal section from the pressurizer.Calculation and experimental assessment of effects of thermal loading factors on the stress-deformed state of SL demonstrated that effects of thermal stratification and thermal fatigue significantly affect the operational loading of the pipeline. It is noted that zones with maximum accumulated damage determined according to the results of calculations coincide with places where factual operational defects were detected. Procedure involving treatment of SL welded joints by the method of surface plastic deformation is suggested as the compensatory measure aimed at extending the SL residual lifespan.

Unsteady-state thermal stress and thermal deformation analysis for a pressurizer surge line subjected to thermal stratification based on a coupled CFD-FEM method

In the pressurizer surge line, the phenomenon of thermal stratification may induce thermal stress and thermal deformation. Excessive thermal stress may result in thermal fatigue of the pipe structure, and excessive thermal deformation may destroy the pipe supports. The phenomenon of thermal stratification, and the induced thermal stress and thermal deformation in the pressurizer surge line would pose a threat on the safe operation of the nuclear power plants (NPPs). Therefore, it is very important to make an analysis to the thermal stratification, thermal stress and thermal deformation of the pressurizer surge line. In this study, a detailed unsteady-state computational fluid dynamics (CFD) analysis involving conjugate heat transfer (CHT) analysis is performed to obtain the transient temperature distributions of the pressurizer surge line under an overall out-surge case, and the thermal loads from the CFD calculations are then transferred to ANSYS Workbench Mechanical as body temperature loads for obtaining the transient thermal stress and the transient thermal deformation. With the coupled computational fluid dynamics-finite element method (CFD-FEM) analysis, the transient response characteristic of the surge line subjected to transient thermal stratification loadings are investigated and analyzed quantitatively. The positions where the maximal thermal stress occurs and where the maximal pipeline displacement occurs are determined, and the method for determining the degree of thermal deformation in the cross-section has been proposed. The coupled CFD-FEM method and the obtained conclusions in this study will be helpful for the design of the pipeline structures and the pipe supports to reduce the structural failure related safety accident.

Preparation research of novel composite phase change materials based on sodium acetate trihydrate

As phase change thermal storage material, sodium acetate trihydrate (SAT) exhibits certain problems such as large undercooling, stratification in phase change, and small thermal conductivity. To overcome these problems, in this study, a new composite phase change thermal storage material was prepared by adding a certain amount of nucleating agent, thickening agent, and high thermal conductivity medium. The research results showed that addition of an appropriate proportion of nucleating agent disodium phosphate dodecahydrate(DSP) and thickening agent carboxymethyl cellulose(CMC) or gelatin led to a good restrain to the undercooling of SAT, while maintaining the heat storage capacity of sample, and avoiding the phenomenon of phase stratification at room temperature cooling. A certain proportion of expanded graphite could also be used in combination with the thermal storage materials, which resulted in relatively small undercooling of the SAT thermal storage materials and a relatively large thermal conductivity.

Motor Oil Viscosity Stratification in Friction Units of Marine Diesel Motors

The phenomenon of the motor oil viscosity stratification in lubricating the cylinder-piston units of marine diesel engines has been investigated. The correlations for determining the shear stress and the velocity, occurring in the liquid flow between the parallel planes, have been given. The modes of the hydrodynamic and the boundary lubrication, taking place in the cylinder assembly of the marine diesel engine operation, have been considered. The methodology has been introduced for determining the viscosity of the boundary layer, which separates the surfaces of the piston ring and that of the cylinder bushing in the marine diesel motor operation. The results of the experiments, confirming the presence of the viscosity stratification in the boundary lubrication layer of the marine motor oil, have been submitted.

Investigation on thermal stratification and turbulent penetration in a pressurizer surge line with an overall out-surge flow

Excessive thermal stresses caused by temperature fluctuations can result in thermal fatigue in the piping system of a nuclear power plants (NPPs). The phenomenon of thermal stratification and turbulent penetration in a pipe can lead to temperature fluctuations, and have attracted much attention of the researchers who deal with NPPs. In particular, this phenomenon in the pressurizer surge line has been assessed as one of the significant safety and technical issues due to its high rate of occurrence. This work focuses on a fundamental description of the thermal stratification and turbulent penetration in a pressurizer surge line using experiment and computational fluid dynamics (CFD) simulation based on the FLUENT 6.3.26 code. In this study, CFD simulation with the LES turbulence model is proved to be an accurate and effective method of studying thermal stratification in a pressurizer surge line. Details of turbulent penetration have also been studied in this paper. A criterion of determining the depth of turbulent penetration has been proposed, and the main frequency of the velocity fluctuations of turbulent penetration in a surge line is found to be a continuous frequency band, and not a fixed value.

International Trade Modelling Using Open Flow Networks: A Flow-Distance Based Analysis.

This paper models and analyzes international trade flows using open flow networks (OFNs) with the approaches of flow distances, which provide a novel perspective and effective tools for the study of international trade. We discuss the establishment of OFNs of international trade from two coupled viewpoints: the viewpoint of trading commodity flow and that of money flow. Based on the novel model with flow distance approaches, meaningful insights are gained. First, by introducing the concepts of trade trophic levels and niches, countries’ roles and positions in the global supply chains (or value-added chains) can be evaluated quantitatively. We find that the distributions of trading “trophic levels” have the similar clustering pattern for different types of commodities, and summarize some regularities between money flow and commodity flow viewpoints. Second, we find that active and competitive countries trade a wide spectrum of products, while inactive and underdeveloped countries trade a limited variety of products. Besides, some abnormal countries import many types of goods, which the vast majority of countries do not need to import. Third, harmonic node centrality is proposed and we find the phenomenon of centrality stratification. All the results illustrate the usefulness of the model of OFNs with its network approaches for investigating international trade flows.

Examination of ossification of the distal radial epiphysis using magnetic resonance imaging. New insights for age estimation in young footballers in FIFA tournaments

Alongside a variety of clinical and forensic issues, age determination in living persons also plays a decisive role in the field of professional sport. Only methods of determining skeletal age which do not expose individuals to ionizing radiation are suitable for this purpose. The present study examines whether MRI diagnosis of the distal radial epiphysis can be utilised to monitor internationally relevant age limits in professional football.The wrist area of 152 male footballers aged 18 to 22years belonging to regional clubs was prospectively examined using MRI. The ossification stage of the distal radial epiphysis was subsequently determined on the basis of established criteria used in determining the maturity of the medial clavicular epiphysis.For the first time, we ascertained evidence of an increase in the prevalence of the phenomenon of threefold linear stratification (hypointense line, hyperintense line, and hypointense line) in the representation of the fused epiphyseal plate of the radius using magnetic resonance imaging with increasing chronological age. Within our study population, test persons with an ossified epiphyseal plate without any verifiable epiphyseal scar were not represented. The presumably high minimum age of entry into this final stage of development (>22years) must be verified in the course of further studies.According to the results of the present study, the fused epiphyseal plate of the distal radius provides potential maturation criteria which appear suitable for reliable monitoring of all relevant age limits in international football with the aid of magnetic resonance imaging.

典型亚热带热分层水库秋季细菌群落垂直分布

水库在我国东南沿海地区是重要的饮用水水源地,对地区经济发展和社会稳定起到重要作用.选择亚热带地区典型的热分层水库——福建莆田东圳水库,于2011年秋季稳定分层期,以水体温度的垂直变化特征为依据进行分层采样.应用PCR-DGGE和克隆测序的方法研究浮游细菌群落的垂直分布特征,利用多元统计分析揭示细菌群落与热分层水体理化指标之间的关系.结果显示:溶解氧、电导率、叶绿素a、总氮、氨氮及硝氮在上下层水体中的分布有显著差异,下层缺氧区细菌的Shannon-Wiener指数和DGGE条带数明显高于上层好氧区,表明东圳水库热分层水体中存在明显的物理、化学及生物分层现象.测序结果表明β-变形菌可能是东圳水库中占优势的细菌类群,统计结果提示溶解氧是显著影响细菌群落组成的环境因子.热分层水体的物理化学分层与水体细菌群落结构密切相关,提示水库生态学研究应对水体热分层给予重视.;Fujian reservoirs in southeast China are important water resources for economic and social sustainable development, although few have been studied previously. Dongzhen Reservoir, a typical subtropical stratified reservoir in Fujian, was chosen for investigation of bacterial distribution, composition and diversity in autumn 2011. As the only built large reservoir in Putian City, it plays an important role in irrigation, flood control, hydroelectric power, and water supply. Dongzhen Reservoir shows an obvious phenomenon of water thermal stratification during summer and autumn, thus creates a unique gradient of environmental variables along the water column. We investigated the bacterial community and its relation to environmental variables in this study for a better understanding of vertical distribution of bacterial community and the primary environmental drivers in a stratified reservoir. Five water samples were collected from five different depths according to the vertical changes of temperature. Both PCR-DGGE and sequencing were used to investigate the bacterial community and diversity. Moreover, physical and chemical parameters were measured according to the national standard methods. Multivariate statistical techniques were used to examine the relationship between bacterial community and environmental variables. Principal component analysis (PCA) clearly showed that water temperature, dissolved oxygen (DO), chlorophyll a (Chl a), total nitrogen (TN), ammonia nitrogen (NH₄-N), nitrite/nitrate nitrogen (NO_<em>x</em>-N) and electric conductivity of the upper aerobic zone were differed from those of the deeper anoxic zone. Both the number of DGGE bands and the Shannon-Wiener index of the deeper anoxic zone were higher than those of the upper aerobic zone. Further, two groups were distinguished by the cluster analysis of bacterial communities based on the Bray-Curtis similarity. Thus, Dongzhen Reservoir presented an obviously physical, chemical, and biological stratified phenomenon. Seven bands that common to all sampling depths were extracted and sequenced, and among which four were identified as Betaproteobacteria, indicating that Betaproteobacteria were the most dominant taxa in Dongzhen Reservoir in autumn. Bacterial community composition and diversity differed greatly among different sampling depths, and these differences were closely related to the physical and chemical stratification of the water body. Redundancy analysis (RDA) demonstrated DO was the significant environmental variable that shaping the bacterial community and diversity (<em>P</em> < 0.01). Therefore, we should pay more attention to DO and thermal stratification of reservoirs for sustainable reservoir management.

Parametric and numerical study of a solar system for heating a greenhouse equipped with a buried exchanger

This paper presents a TRNSYS simulation to evaluate the performances of a solar water heating system (SWHS) used for greenhouses according to Tunisian weather. The SWHS is mainly composed of two solar collectors, with a 4m2 total surface, related to a 200L storage tank and a capillary polypropylene heat exchanger integrated to the greenhouse. During the simulation all combinations possible of the two solar collectors (series and parallels) are investigated. The parameters which have influence on the storage system, like the inlet flow rate, tank volume and collector area are also investigated. The results of simulation show that, by increasing the tank volume, the temperature at the collector outlet decreases. In addition, high flow rate minimizes the phenomenon of stratification and increases the efficiency of the system. We notice that decreasing the exchanger inlet flow rate is good solution to reduce heating loses. The best storage system we found will be used as our greenhouse heating system. In fact, the choosen heating system according to this parametric analysis, mainly composed of a flat plate collector and a 200L tank, can increase the inside air temperature of the greenhouse by 5°C and make it suitable for tomatoes agriculture.

Collaboration in Buyer-Seller Relationships as a New Approach to Competitive Advantage

Although recent academic work on business relationships often discusses relationship quality as a major subject, particularly with regard to the phenomenon of seller stratification, there is still little empirical research on this important construct. In this paper, the authors provide a thorough conceptualization of relationship quality and its possible antecedents, i.e., bond relationship, Temporal, Social, and Structural bond, drawing on an empirical base of 219 buyers questionnaires, Structural equations modeling (SEM) is used to assess the simultaneous effects of the predictive variables. An empirical survey confirms the impact of the relational bond dimension on the satisfaction. The satisfaction has an effect on the customer trust witch influence his commitment. The findings are discussed and the authors provide managerial implications for decision-makers from both buyer and supplier organizations.

Environmental Case Study of Water Quality of Ancient WellsMasabi Boudi and Narasimha Temple Well of Bijapur

Ancient historic wells or boudies, built by Adil Shahi kings in Bijapur are the huge sources of water in the drought place of northern Karnataka (India). They stand neglected and polluted. Masabi Boudi and Narasimha Temple well are two wells selected for the study. We have studied the water quality in terms of physico-chemical, biochemical, phytoplanktonic and bacteriological properties depthwise. Masabi Boudi exhibited a rare phenomenon of vertical inverse thermal stratification whereas in Narasimha Temple well winter thermal stratification broke in summer and monsoon. Phytoplankton occurrence was rare in Masabi Boudi. Desmids showed their pollution tolerance throughout the study in Masabi Boudi. Glucose, protein, creatinine, urea and uric acid in the water reads the utrophication, which resulted the growth of E-coli. Algal maximum was followed soon after the E-coli were in excess in both the wells. Chlorides, nitrates and nitrogenous content stated the rich nutritional status. The self purification of water takes place naturally as a quality control. There is a natural symmetry in the biological science between bacterioplankton and phytoplankton and high enrichment with organic matter provided a measure of stabilization to this eco-system. In all, Masabi Boudi shows better water quality than Narasimha Temple well.

A comparative study on nano La2O3 suspension treated by ultrasonic and ball milling

This paper presented a scientific study of the effects of four dispersion methods on the dispersion capability of nano La2O3 suspensions, which are ball milling, ultrasonic, ultrasonic followed by ball milling and ball milling followed by ultrasonic. For the purposes of comparing their dispersion capability, sedimentation test, Zeta-potential measurement test, particles size measurement test and transmission electron microscopy (TEM) test were carried out. Suspension ability coefficient was also defined with expectation to estimate the stability of nano La2O3 suspension through granularity size, and their relationship curve was worked out. The results showed that ultrasonic followed by ball milling enjoyed an excellent capability of dispersion for nano La2O3 suspension. Its mechanism was discussed, and breakage models of nano La2O3 particles were developed. The study results indicated that ultrasonic followed by ball milling could break through both the limits of ultrasonic dispersion size range and thermo-effect, and thus was able to overcome the problem of the secondary aggregation of nanoparticles. Moreover, aggregations could be further de-agglomerated. As a result, dispersion capability of nano La2O3 suspension could be improved more greatly by ultrasonic followed by ball milling. And its suspension stability was the best with the highest suspension ability coefficient of the nanoparticles. It was found in the experiment that there was almost no obvious phenomenon of stratification for the suspension with a little sediment after being deposited for 8 d.

ASSESSMENT OF STELLAR STRATIFICATION IN THREE YOUNG STAR CLUSTERS IN THE LARGE MAGELLANIC CLOUD

(abridged) We present a comprehensive study of stellar stratification in young star clusters in the Large Magellanic Cloud (LMC). We apply our recently developed effective radius method for the assessment of stellar stratification on imaging data obtained with the Advanced Camera for Surveys of three young LMC clusters to characterize the phenomenon and develop a comparative scheme for its assessment in such clusters. The clusters of our sample, NGC 1983, NGC 2002 and NGC 2010, are selected on the basis of their youthfulness, and their variety in appearance, structure, stellar content, and surrounding stellar ambient. Our photometry is complete for magnitudes down to m_814 ~ 23 mag, allowing the calculation of the structural parameters of the clusters, the estimation of their ages and the determination of their stellar content. Our study shows that each cluster in our sample demonstrates stellar stratification in a quite different manner and at different degree from the others. Specifically, NGC 1983 shows to be partially segregated only for the faintest stars of the cluster, NGC 2002 shows evidence of strong stellar stratification for both bright and faint stars, and NGC 2010 is found not to be segregated. For the parametrization of the phenomenon of stellar stratification and its quantitative comparison among these clusters, we propose the slope derived from the change in the effective radius over the corresponding magnitude range as indicative parameter of the degree of stratification in the clusters. A positive value of this slope indicates mass segregation in the cluster, while a negative or zero value signifies the lack of the phenomenon.

Foams and Emulsions: the Importance of Structural Forces

We present a brief summary of the salient findings of our recent research delivered as a keynote lecture at the Australian Conference on Colloid and Interface Science held in Sydney in February 2007. We have developed a hybrid surface force apparatus (thin film capillary force balance) in conjunction with differential interference microscopy to show the phenomenon of microstructuring or stratification in thin films containing surfactant micelles, proteins, and nanoparticles separating two bubbles or droplets, as in foam and emulsion systems. The structural disjoining pressure, i.e. the structural force, arising because of the ordered microstructure formation inside thin liquid films between bubbles or drops, offers a new stabilization mechanism for foams, emulsions, and fluid-particle suspensions. In addition to the thin film approach, we also used both the Kossel diffraction and direct digitized optical imaging methods to directly observe the structure and stability of foam and emulsion systems. Our experiments were complemented by computations involving Monte Carlo simulations and the integral equation of statistical mechanics.