Spelling suggestions: "subject:" stratification"" "subject:" atratification""
371 |
Numerical and experimental study of the fluid flow in porous medium in charging process of stratified thermal storage tank / Numerisk och experimentell studie av fluidströmning i porösa medier under laddning av stratifierad värmelagringstankBerg, Anders January 2013 (has links)
In order to increase the efficiency of an adsorption heat pump system, a stratified thermal heat storage can be used to enable regeneration of heat between the different phases of the process. It’s crucial to avoid mixing and to keep layers intact inside the storage tank. As mixing generally occurs during charging and discharging, the aim of this project is minimizing these effects by introducing porous media into the region of the inlet ports. The impact of porous media on laminar and turbulent flow inside stratified thermal storage tanks is qualitatively and quantitatively investigated. Two thermal storage tanks are examined in which polyurethane foam is used as porous medium. Numerical results are compared with experimental results in order to study the effects of the porous medium and validating numerical models. For the quantitative investigation, equations describing flow in porous media are obtained and implemented into computational fluid dynamics (CFD) models. Simulations of storage tanks are performed by means of 2D-axisymmetric domain models. Tanks are investigated qualitatively using two methods; background oriented schlieren (BOS) and ink colored inlet water, in order to visualize flow and mixing inside tanks. Thermo elements are also used to measure temperatures at given locations. Results from experimental- and numerical cases show how porous media influence stratification in a positive way. Flow visualizing experiments (using ink and BOS) showed decrease in thermocline thickness when using polyurethane foam. This could also be seen for the numerical cases. Experimental- and numerical investigations of the ability of porous media to damp turbulence intensity and kinetic energy, showed a positive effect. Further improvements have to be done, adjusting numerical models to experimental results. Comparison between the numerical- and experimental results showed differences both in flow fields and temperature distributions. Results indicate however, that porous media could play an increasing role in the development of stratified heat storages. / Stratifierade värmelagringstankar kan användas för att öka effektiviteten hos adsorptionsvärmepumpsprocesser genom att möjliggöra regeneration av värme mellan faserna. För att dessa effektivt ska kunna användas är det viktigt att temperaturskikt hålls intakta inuti lagringstankarna och att omröring undviks. Då omröring oftast uppstår vid laddning och tömning av lagringstankarna är målet för det här projektet att minska denna effekt genom att använda porösa medier vid deras inlopp. Porösa mediers inverkan på flöden och temperaturskikt inuti värmelagringstankar undersöks både kvalitativt och kvantitativt i det här projektet. Två tankar undersöks där polyuretanskum används som poröst medium. Numeriska resultat jämförs med experimentella för att undersöka effekterna av de porösa medierna, samt för att validera de numeriska modeller som används. Ekvationer som beskriver flödet genom porösa medier implementeras i CFD (computational fluid dynamics) modeller och lagringstankarna modelleras som 2D-axelsymmetriska domäner. Bakgrundsorienterad schlierenteknik (BOS) och färgning av inloppsvatten används för den kvalitativa undersökningen och termoelement används för att mäta temperaturer vid olika positioner. Numeriska och experimentella resultat visar hur porösa medier har en positiv inverkan på temperaturskiktningen. Resultat från experiment då BOS teknik och färgning av vatten används visar en minskning av det termoklina skiktets tjocklek med en ökad polyuretanskumtjocklek. Detta kunde också ses för de numeriska fallen. Numeriska och experimentella resultat visar även att porösa medier har en positiv inverkan på dämpningen av turbulens och kinetisk energi. Fortsatt arbete krävs för att anpassa numeriska modeller till experimentella data. Jämförelser mellan numeriska och experimentella resultat uppvisar skillnader både hos flödesfält samt hos temperaturfördelningar inuti tankarna. Resultaten visar dock att porösa medier skulle kunna spela en betydande roll för utvecklingen av stratifierade värmelagringstankar.
|
372 |
Ventilation systems in Low Energy Houses: augmentation of mixing in a small-scale water model by generating resonanceChocarro de Erauso, Borja January 2022 (has links)
Some passive houses are provided a warm supply flow inlet coming from a mechanical ventilation system, creating issues of shortcut ventilation as a result of an originated density layer stratification, since the supplied warm air is confined to the ceiling level. In this way, there exist several complaints of thermal discomfort and poor indoor environmental quality in passive houses. Thus, a method of periodic variation of the ventilation supply frequency is an option to increase mixing, aimed at de-stratifying the room conditions. A small-scale water model is employed in order to systematically explore the influence of the created standing waves from the supply input frequency and its interaction with stratification characteristics in the studied volume, hence operating with water as a working fluid and a paddle as an oscillating mechanical input. Measurements at three different input frequencies and at three input paddle locations have been performed, gathering vertical temperature gradients and visualization data from them. Thus, ventilation efficiency of passive houses is set to improve, consequently increasing their public acceptability, via reaching buoyancy resonance, i.e., matching the input frequency with the internal Brunt-Väisäla frequency of the fluid. Consequently, the shortcut ventilation issues may be mitigated and the public acceptability of passive houses increased, achieving a higher thermal comfort and economic and energy demand savings, while enhancing sustainable and renewable heating alternatives such as the heat recovery from the outgoing exhaust flow.
|
373 |
Universal Suicide Risk Screening in the Parkland Health and Hospital System: Evaluation of the Parkland Algorithm for Suicide ScreeningGoans, Christian 08 1900 (has links)
Suicide is a significant public health issue in the US. Despite national and international prioritization since 1996, little definitive progress has been made in terms of identification and intervention in cases of elevated suicide risk. Forty percent of those who died by suicide attended an emergency department within a year of death. Therefore, universal suicide risk screening in emergency departments could prove a vital component to a national suicide prevention strategy. The present study empirically evaluated the universal suicide risk screening program recently implemented at Parkland Health and Hospital System. The sample consisted of patients over 18 years of age (N=333,855; Mage=42.7, 32% male) screened as part of routine clinical care from May 4th, 2015, through November 3rd, 2015. The Parkland Algorithm for Suicide Screening (PASS) is part of a clinical decision support system for responses to Columbia - Suicide Severity Rating Scale Clinical Practice Screener (C-SSRS) items, leading to an automated clinical response via three suicide risk stratification levels: no action for no risk identified, psychiatric social worker assessment for moderate risk identified, and psychiatrist/psychologist interview for high risk identified. The present study used receiver operating characteristic (ROC) curve analysis, which found the PASS predicted disposition (z=30.46, p<.001, AUC=.78, CI95=.77, .81). This study also evaluated the cutpoints separating suicide risk stratification and levels of clinical response. The results supported the first cutpoint and highlighted a need for additional data to address the second cutpoint. The results of the present study suggest that the universal suicide risk screening program at Parkland Health and Hospital System is an important step toward addressing suicide prevalence in the US.
|
374 |
Proměna ruské střední třídy v letech 1998 - 2008 / Evolution of Russian Middle Class in 1998-2008Vojtíšková, Kristýna January 2012 (has links)
The existence of Russian middle class is often perceived as a condition for Russia's democratization and the country's economic progress is often mentioned in connection with the growth of the middle class and henceforth increased popular demand for transparent functioning of public institutions. However economic growth does not necessarily lead to more extensive middle class, especially not when the income inequality rises as was the case of Russia in the particular period. This thesis proves that Russian middle class grew between the years 1998 and 2008, it identifies its specific features and explains its evolution from the perspective of occupation and income. The data from Russian Longitudinal Monitoring Survey, which the thesis is based on, confirm that while the Russian middle class was growing in size, growth in inequality was also observed, especially between cities and countryside and between individual economic sectors.
|
375 |
Sportování a česká společnost: zdroje rozdílů ve sportovní participaci / Sport and Czech Society: Sources of Differences in Sports ParticipationŠpaček, Ondřej January 2014 (has links)
The thesis examines changes in sports participation in Czech society in last decades. Sports activities are conceptualized as a practice, routinized habit that is shared in a society's culture (Reckwitz 2002; Warde 2005). Bourdieu's (1984) also shows how different social positions generate different taste and preferences, which are simultaneously classified and base for symbolic borders between social classes. The empirical analysis focuses on sports participation during the last three decades and deeper understanding of differentiation and meanings of today's sports activity. The results clearly show profound increase in sports participation, from 25 % in 1984 to 67 % in 2009. The cohort analysis confirms that dynamics of sports practices' spread have roots in the socialization process and cohort exchange, because younger cohorts have a stable higher level of sports participation irrespective of their aging. Lasting impact of cultural capital on sports participation is particularly striking, especially in the light of the major change in society's regime in the 1989 and after. This brings attention to the question, how mechanisms of social inequalities - especially cultural capital - worked in a similar way across supposedly different social orders. Next chapter deals with patterns of participation in...
|
376 |
A concept of the elements of juvenile criminality from a sociological aspectSmith, Frank Burchard 01 January 1931 (has links)
The conditions that have prevailed in the United States in the last twenty-five years, compel thoughtful citizens to give careful attention to the disrespect for law that is so marked a characteristic of the period.
Crime and disorder are spread theoughout the length and breadth of the land. This produces problems which should be studies and solved for the good of society. The reaction which accompanies this evil will eventually cause social demoralization.
While attempting to treat this particular evil, social workers have been largely content to deal with surface conditions. Attention has been focused upon the symptom rather than the cause.
Hardened criminals are not made in a day. They are the result of contacts and environment, plus hereditary forces, which have influenced them through years of time. Therefore, a study should be made of delinquent youth for the purpose of understanding the criminal.
For years the criminal acts of delinquent individuals have been catalogued and graded according to the respective felonies and misdemeanors committed. Little has been done however, relative to understanding the cause of delinquency. This statement is not made for the purpose of discounting any good work which has been accomplished; but the accomplishments have been almost negligible in comparison with those in other fields of research.
It is the desire of the writer to set forth in an accurate manner the elements of juvenile criminality, more commonly called delinquency. The terms, criminality and delinquency, will be used interchangeably to designate and infraction against, or a nonconformity to, law and order.
|
377 |
Ischemic Heart Disease in WomenAshley, Kellan E., Geraci, Stephen A. 01 July 2013 (has links)
Cardiovascular disease is the leading cause of death in women. Although overall mortality from coronary heart disease (CHD) has decreased, there are subsets of patients, particularly youngwomen, in whom the mortality rate has increased. Underlying sex differences in CHD may be an explanation. Women have more frequent symptoms, more ischemia, and higher mortality than men, but less obstructive coronary artery disease (CAD). Despite this, traditional risk factor assessment has been ineffective in risk stratifying women, prompting the emergence of novel markers and prediction scores to identify a population at risk. Sex differences inmanifestations and the pathophysiology of CHD also have led to differences in the selection of diagnostic testing and treatment options for women, having profound effects on outcomes. The frequent finding of nonobstructive CAD in women with ischemia suggests microvascular dysfunction as an underlying cause; therefore, coronary reactivity and endothelial function testing may add to diagnostic accuracy in female patients. In spite of evidence that women benefit from the same therapies as men, they continue to receive lessaggressive therapy, which is reflected in higher healthcare resource utilization and adverse outcomes. More sex-specific research is needed in the area of symptomatic nonobstructive CAD to define the optimal therapeutic approach.
|
378 |
Ischemic Heart Disease in WomenAshley, Kellan E., Geraci, Stephen A. 01 July 2013 (has links)
Cardiovascular disease is the leading cause of death in women. Although overall mortality from coronary heart disease (CHD) has decreased, there are subsets of patients, particularly youngwomen, in whom the mortality rate has increased. Underlying sex differences in CHD may be an explanation. Women have more frequent symptoms, more ischemia, and higher mortality than men, but less obstructive coronary artery disease (CAD). Despite this, traditional risk factor assessment has been ineffective in risk stratifying women, prompting the emergence of novel markers and prediction scores to identify a population at risk. Sex differences inmanifestations and the pathophysiology of CHD also have led to differences in the selection of diagnostic testing and treatment options for women, having profound effects on outcomes. The frequent finding of nonobstructive CAD in women with ischemia suggests microvascular dysfunction as an underlying cause; therefore, coronary reactivity and endothelial function testing may add to diagnostic accuracy in female patients. In spite of evidence that women benefit from the same therapies as men, they continue to receive lessaggressive therapy, which is reflected in higher healthcare resource utilization and adverse outcomes. More sex-specific research is needed in the area of symptomatic nonobstructive CAD to define the optimal therapeutic approach.
|
379 |
Examining the Impact of Maternal Health, Race, and Socioeconomic Status on Daughter's Self-Rated Health Over Three DecadesShippee, Tetyana P., Rowan, Kathleen, Sivagnanam, Kamesh, Oakes, J. Michael 01 September 2015 (has links)
This study examines the role of mother's health and socioeconomic status on daughter's self-rated health using data spanning three decades from the National Longitudinal Surveys of Mature Women and Young Women (N = 1,848 matched mother-daughter pairs; 1,201 White and 647 African American). Using nested growth curve models, we investigated whether mother's self-rated health affected the daughter's self-rated health and whether socioeconomic status mediated this relationship. Mother's health significantly influenced daughters' self-rated health, but the findings were mediated by mother's socioeconomic status. African American daughters reported lower self-rated health and experienced more decline over time compared with White daughters, accounting for mother's and daughter's covariates. Our findings reveal maternal health and resources as a significant predictor of daughters' self-rated health and confirm the role of socioeconomic status and racial disparities over time.
|
380 |
Comparing Nonlinear and Nonparametric Modeling Techniques for Mapping and Stratification in Forest Inventories of the Interior Western USAMoisen, Gretchen Gengenbach 01 May 2000 (has links)
Recent emphasis has been placed on merging regional forest inventory data with satellite-based information both to improve the efficiency of estimates of population totals, and to produce regional maps of forest variables. There are numerous ways in which forest class and structure variables may be modeled as functions of remotely sensed variables, yet surprisingly little work has been directed at surveying modem statistical techniques to determine which tools are best suited to the tasks given multiple objectives and logistical constraints. Here, a series of analyses to compare nonlinear and nonparametric modeling techniques for mapping a variety of forest variables, and for stratification of field plots, was conducted using data in the Interior Western United States. The analyses compared four statistical modeling techniques for predicting two discrete and four continuous forest inventory variables. The modeling techniques include generalized additive models (GAMs), classification and regression trees (CARTs), multivariate adaptive regression splines (MARS), and artificial neural networks (ANNs). Alternative stratification schemes were also compared for estimating population totals. The analyses were conducted within six ecologically different regions using a variety of satellite-based predictor variables. The work resulted in the development of an objective modeling box that automatically models spatial response variables as functions of any assortment of predictor variables through the four nonlinear or nonparametric modeling techniques. In comparing the different modeling techniques, all proved themselves workable in an automated environment, though ANNs were more problematic. When their potential mapping ability was explored through a simple simulation, tremendous advantages were seen in use of MARS and ANN for prediction over GAMs, CART, and a simple linear model. However, much smaller differences were seen when using real data. In some instances, a simple linear approach worked virtually as well as the more complex models, while small gains were seen using more complex models in other instances. In real data runs, MARS performed (marginally) best most often for binary variables, while GAMs performed (marginally) best most often for continuous variables. After considering a subjective "ease of use" measure, computing time and other predictive performance measures, it was determined that MARS had many advantages over other modeling techniques. In addition, stratification tests illustrated cost-effective means to improve precision of estimates of forest population totals. Finally, the general effect of map accuracy on the relative precision of estimates of population totals obtained under simple random sampling compared to that obtained under stratified random sampling was established and graphically illustrated as a tool for management decisions.
|
Page generated in 0.1444 seconds