scholarly journals Statistical analysis of vapor distribution in a cavitation flow based on an ensemble of instantaneous liquid velocity fields

2021 ◽  
Vol 2119 (1) ◽  
pp. 012046
Author(s):  
A S Severin ◽  
M V Timoshevskiy ◽  
B B Ilyushin ◽  
K S Pervunin
Keyword(s):  
Statistical Analysis ◽  
Vapor Phase ◽  
Liquid Velocity ◽  
Continuous Phase ◽  
Velocity Fields ◽  
Cavitating Flow ◽  
New Method ◽  
Exponential Dependence ◽  
Chi Square ◽  
Cloud Cavitation

Abstract A new method was developed for statistical analysis of ensembles of instantaneous velocity fields measured by PIV in liquid (continuous phase) to determine the distribution of the vapor phase in cavitating flow. The method is based on two main principles: the absence of tracers used for PIV measurements in vapor, and the statistical independence of individual measurements. This allowed establishing an exponential dependence of repeatability of the vapor phase at a certain point of a cavitating flow. Compliance with this theoretical law was verified using the Pearson chi-square test. All theoretical distributions were divided into several groups depending on the time-averaged local vapor content calculated over the entire ensemble of realizations and the probability of a single event. As a result, dimensions of the stationary part of an attached cavity and the place of detachments of cloud cavities from the hydrofoil surface were determined using the new method of statistical analysis for an unsteady cloud cavitation regime.

scholarly journals Relationships between Final Purchasers and Offerors in the Context of Their Perception by Final Purchasers

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3271
Author(s):  
Agnieszka Izabela Baruk
Keyword(s):  
Factor Analysis ◽  
Statistical Analysis ◽  
World Literature ◽  
Empirical Studies ◽  
Primary Data ◽  
Survey Method ◽  
Chi Square ◽  
Marketing Process ◽  
Research Gap

The aim of this article was to identify the role of good mutual relationships with offerors for final purchasers, as well as define the meaning of the perception of offerors in the scope of listening to purchasers’ opinions and profiting from purchasers’ readiness to cooperate for the specificities of the prosumeric activity. A deep analysis of the world literature was used to prepare the theoretical part of this paper. The results of this analysis confirm the existing cognitive gap and research gap regarding mentioned aspects, including energy market. Empirical studies were conducted to reduce identified gaps. The survey method was used to collect primary data. The collected data were subjected to quantitative analysis, during which statistical analysis methods and tests were applied (Pearson chi-square independence test, V-Cramer factor analysis, Kruskal–Wallis test (KW), and exploratory factor analysis). The results of the statistical analysis and testing allowed the three research hypotheses formulated to be checked. Between the significance of good relationships with offerors and their perception, a statistically significant dependence was identified for all groups of offerors. The perception of offerors was a feature differentiating respondents’ opinions about the significance of good relationships with offerors for the two following groups: producers and traders. Additionally, the perception of offerors was a feature differentiating forms of prosumeric activity of respondents only for three interpurchase behaviors. The results obtained have a visible cognitive and applicability value. They contribute to the theory of marketing, as well as possibly facilitating the formation of good mutual relationships between offerors (including offerors of energy) and final purchasers as key partners cooperating with offerors in the marketing process. The approach presented in this paper has not been studied and analyzed so far, either in theoretical or in practical terms. This fact confirms its originality and value.

scholarly journals Statistical Analysis of Ordered Tetrads

Genetics ◽  
1998 ◽  
Vol 150 (1) ◽  
pp. 459-472 ◽  
Author(s):  
Hongyu Zhao ◽  
Terence P Speed
Keyword(s):  
Statistical Analysis ◽  
Genetic Markers ◽  
Chi Square ◽  
Yield Information ◽  
Data Yield ◽  
Interference Models ◽  
Chiasma Interference

Abstract Ordered tetrad data yield information on chromatid interference, chiasma interference, and centromere locations. In this article, we show that the assumption of no chromatid interference imposes certain constraints on multilocus ordered tetrad probabilities. Assuming no chromatid interference, these constraints can be used to order markers under general chiasma processes. We also derive multilocus tetrad probabilities under a class of chiasma interference models, the chi-square models. Finally, we compare centromere map functions under the chi-square models with map functions proposed in the literature. Results in this article can be applied to order genetic markers and map centromeres using multilocus ordered tetrad data.

A new method of LES verification and validation for attached turbulent cavitating flow

2021 ◽  
Vol 33 (1) ◽  
pp. 170-174
Author(s):  
Yun Long ◽  
Lin-feng Deng ◽  
Jun-qiang Zhang ◽  
Bin Ji ◽  
Xin-ping Long
Keyword(s):  
Cavitating Flow ◽  
Verification And Validation ◽  
New Method

scholarly journals NUMERICAL SIMULATION OF AIR – WATER FLOWS IN AN EVAPORATIVE CONDENSER

2009 ◽  
Vol 8 (1) ◽  
pp. 24 ◽  
Author(s):  
I. C. Acunha Jr ◽  
P. S. Schneider
Keyword(s):  
Turbulent Flows ◽  
Simple Algorithm ◽  
Continuous Phase ◽  
Velocity Fields ◽  
Temperature Fields ◽  
Two Phase ◽  
Equipment Manufacturer ◽  
Functional Aspects ◽  
Water Behavior ◽  
Complex Phenomena

Evaporative condensers present a hard problem for numerical modeling because of the complex phenomena of heat and mass transfer outside of the bundle tubes in turbulent flows. The goal of this work is to study the air and water behavior inside an evaporative condenser operating with ammonia as the refrigerant fluid. A commercial CFD software package (FLUENT) is employed to predict the two-phase flow of air and water droplets in this equipment. The air flow is modeled as a continuous phase using the Eulerian approach while the droplets water flow is modeled as a disperse phase with Lagrangian approach. The coupling between pressure and velocity fields is performed by the SIMPLE algorithm. The pressure, velocity and temperature fields are used to perform qualitative analyses to identify functional aspects of the condenser, while the temperature and the relative humidity evolution contributed to verify the agreement between the results obtained with the numerical model and those presented by equipment manufacturer.

A New Cavitation-Induced-Momentum-Defect (CIMD) Correction Approach to Track Cavitation Events

2007 ◽  
Author(s):  
Vedanth Srinivasan ◽  
Abraham J. Salazar ◽  
Kozo Saito
Keyword(s):  
Liquid Phase ◽  
Transport Equation ◽  
Vapor Phase ◽  
Incompressible Flows ◽  
Vapor Transport ◽  
Source Terms ◽  
Local Pressure ◽  
Cloud Cavitation ◽  
Tracking Model ◽  
The Impact

A new unsteady cavitation event tracking model is developed for predicting vapor dynamics occurring in multi-dimensional incompressible flows. The procedure solves incompressible Navier-Stokes equations for the liquid phase with an additional vapor transport equation for the vapor phase. The model tracks regions of liquid vaporization and applies compressibility effects to compute the local variation in speed of sound using the Homogeneous Equilibrium Model (HEM) assumptions. The variation of local cell density as a function of local pressure is used to construct the source term in the vapor fraction transport equation. The novel Cavitation-Induced-Momentum-Defect (CIMD) correction methodology developed in this study serves to account for cavitation inception and collapse events as relevant momentum source terms in the liquid phase momentum equations. Effects of vapor phase accumulation and diffusion are incorporated by detailed relaxation models. A modified RNG K-ε model, including the effects of compressibility in the vapor regions, is employed for modeling turbulence effects. Turbulent kinetic energy and dissipation contributions from the vapor regions are integrated with the liquid phase turbulence using relevant source terms. Numerical simulations are carried out using a Finite Volume methodology available within the framework of commercial CFD software code Fluent v.6.2. Simulation results are in qualitative agreement with experiments for unsteady cloud cavitation behavior in planar nozzle flows. Multitude of mechanisms such as formation of vortex cavities, vapor cluster shedding and coalescence, cavity pinch off are sharply captured by the supplemented vapor transport equation. Our results concur with previously established theories concerning sheet and cloud cavitation such as the re-entrant jet motion, cavity closure and the impact of adverse pressure gradients on cavitation dynamics.

Association Between Positive Occipital Sharp Transients of Sleep and Lambda Waves

2018 ◽  
Vol 50 (3) ◽  
pp. 219-221
Author(s):  
Ushtar Amin ◽  
Lucy Sullivan ◽  
Pat Trudeau ◽  
Selim R. Benbadis
Keyword(s):  
Statistical Analysis ◽  
Chi Square ◽  
High Association ◽  
Similar Morphology ◽  
Strong Similarity ◽  
Continuity Correction ◽  
Chi Square Test

Positive occipital sharp transients of sleep (POSTS) and lambda waves have similar morphology and location. We studied a possible association between these 2 normal EEG patterns. We reviewed a series of consecutive unselected ambulatory EEGs during a 3-month period (October 16, 2017 to January 19, 2018) and identified records with POSTS and records with lambda waves. Statistical analysis was performed using a chi-square test. A total of 140 ambulatory EEGs were reviewed. Duration of EEGs ranged from 24 to 168 hours (mean 76 hours). The population was 34% males, with ages ranging from 3 to 93 years (mean 48 years). Of the 140 records, 30 were abnormal, including 20 with epileptiform abnormalities. A chi-square test for independence (with Yates continuity correction) indicated a significant association between POSTS and lambda waves, χ2(1, n = 140) = 69.208, p < .001, φ = 0.72. In addition, 100% of records with lambda waves had POSTS, and 72% of records with POSTS had lambda waves. There is a high association between lambda waves and POSTS. This suggests a strong similarity between the 2 waveforms, and possibly a common occipital generator.

scholarly journals To Evaluate the Effect of Nasal Packing on Blood Oxygen Saturation

2015 ◽  
Vol 7 (2) ◽  
pp. 41-44
Author(s):  
Jagat Singh ◽  
SPS Yadav ◽  
Ankit Gulati ◽  
Surender Singh ◽  
Anamika Bishnoi
Keyword(s):  
Statistical Analysis ◽  
Oxygen Saturation ◽  
Pulse Oximetry ◽  
Nasal Packing ◽  
Blood Oxygen ◽  
Deviated Nasal Septum ◽  
Blood Oxygen Saturation ◽  
Chi Square ◽  
Old Patients ◽  
Digital Pulse

ABSTRACT Objective To study the effect of nasal packing on blood oxygen saturation. Materials and methods Study was conducted on 30 patients of deviated nasal septum, who underwent septoplasty under local anesthesia followed by anterior nasal packing. The pulse oximetry was carried out three times on each patient to record the blood oxygen saturation (SpO2) by using digital pulse oximeter. The first reading of SpO2 was taken before nasal packing, second after 24 hours of nasal packing and third 3 weeks after surgery. Statistical analysis was done by Chi-square test and paired t-test. Results A total of 33.3% patients were below 20 years of age, whereas 60% were between 20 and 30 years of age and 6.7% were above 30 years. Males were 80%. It was observed that preoperative mean SpO2 was 98.3 ± 0.794%, after 24 hours of nasal packing was 97.17 ± 1.744% and 3 weeks after surgery was 98.87 ± 0.629%. On statistical analysis, the difference in SpO2 was highly significant (p < 0.001). Conclusion The application of nasal packs can be risky in old patients, more so having cardiopulmonary disease. The use of packs with airflow is recommended in these patients who should ideally be monitored with pulse oximetry. How to cite this article Singh S, Singh J, Kakkar V, Yadav SPS, Bishnoi A, Kathuria B, Gulati A, Sharma C. To Evaluate the Effect of Nasal Packing on Blood Oxygen Saturation. Int J Otorhinolaryngol Clin 2015;7(2):41-44.

scholarly journals The Relationship between Demographical Characteristic and Central Obesity with Hypertension

2018 ◽  
Vol 6 (1) ◽  
pp. 43
Author(s):  
Desy Amanda ◽  
Santi Martini
Keyword(s):  
Risk Factors ◽  
Statistical Analysis ◽  
Observational Study ◽  
Central Obesity ◽  
Chi Square ◽  
Cross Sectional ◽  
Independent Variables ◽  
Obesity Status ◽  
Observational Study Design ◽  
The Relationship

Background: The prevalence of hypertension in Indonesia was 25,80% in 2013 found in people aged above 18 years old. One of the risk factors is obesity. Purpose: This study aimed to analyze the relationship between the demographical characteristic and central obesity with the risk of hypertension in the health center of Sidoarjo. Methods: This analytical observational study design was cross sectional. There were 50 respondents selected through accidental sampling. The independent variables of this study were respondents’ characteristic and central obesity status. However, the dependent variable was hypertension. Overall, respondents were divided into two groups based on sex (female and male) and age (> 59 years old and ≤ 59 years old). Data were analyzed with chi-square statistical analysis. Results: Respondents with central obesity had a higher risk to get hypertension, with majority male respondents aged above 59 years old. Conclusion: There was a correlation between age and hypertension (p = 0,01), sex and hypertension (p = 0,04), also between central obesity status and hypertension (p = 0,01). 

scholarly journals A Study on the impact of Coping Strategies over Stress Management – An Empirical Study

2021 ◽  
Vol 12 (3) ◽  
pp. 5566-5573
Author(s):  
Ch.Narahari Et. al.
Keyword(s):  
Statistical Analysis ◽  
Empirical Study ◽  
Stress Management ◽  
Emotional Support ◽  
Positive Emotion ◽  
Software Industry ◽  
Total Sample ◽  
Chi Square ◽  
Chi Square Test ◽  
The Impact

In the present study we analyze the employees’ perception towards coping measures adopted byfirms in software industry. The considered coping constructs adopted for the study in stress abatement areVenting of Emotions,Problem Focused, Seeking Information and emotional support, Positive Emotion-Focused, were, employee perception was acquired by a systematic survey.A total sample of 800 employees’perceptions have been collected through simple random technique and out of which survey respondents, irregular responses are eliminated finally 756 samples are determined for statistical analysis. Chi-square test was performed to determine the association between perceptions and model constructs. Results are reported and discussions are made as per the results and in correlation between results of previous literature.Finally, suggestions and future indication for extension of the study are proposed.

scholarly journals Knowledge, Attitude and Practices Regarding First Aid against Domestic Injuries in Mothers of Children less than 5 Years of Age Attending Fauji Foundation Hospital Islamabad

2021 ◽  
Vol 11 (3) ◽  
pp. 151-157
Author(s):  
Raima Asif ◽  
Naila Azam ◽  
Fatima Ali Raza ◽  
Mehwish Riaz ◽  
Shaista Zulfiqar ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Tertiary Care ◽  
First Aid ◽  
Cross Sectional Study ◽  
Care Hospital ◽  
Chi Square ◽  
Cross Sectional ◽  
Co Morbidity ◽  
Strongly Agree ◽  
Home Accidents

Background: The objective is to assess the knowledge, attitude and practices regarding first aid towards home related injuries among mothers of children less than 5 years of age at tertiary care hospital of Islamabad. Methods: A questionnaire based cross sectional study was conducted in Fauji Foundation Hospital Islamabad. 400 participants were selected using convenience sampling the mother of children under 5 years of age were included and mother of children with any major co morbidity, congenital abnormalities and who didn’t give consent were excluded from the study. A pretested, structured, self-administered questionnaire was used for data collection after obtaining permission from Institutional Ethical Committee. Statistical analysis was carried using SPSS version 20. Frequencies and percentages were computed, descriptive statistical analysis was done. Chi- Square was applied for association between socio demographic variables and knowledge of mothers regarding first aid. Results: About 44% of the mothers and 63% children fall in age group of 31 and 2-5 years respectively. Half of the mothers (48%) are below intermediate level of education. About 34% of the respondents stated bleeding as most urgent and important injury requiring first aid. Regarding attitudes, 50% of the mothers strongly agree towards necessity of first aid and lack of awareness about dealing with domestic injuries. Sixty-five (65%) of the mothers had given first aid to their child. About 33%, 75%, 44% and 39% of the mothers have faced a child with difficulty in breathing; bleeding, burning and insect/sibling bite respectively. Age of mother (p=0.041), education of mother (p=0.001) and total no of children (p=0.001) were significantly associated with knowledge of first aid. Conclusion: Although home accidents are a common problem, mother’s knowledge regarding home accidents was deficient although majority of the respondents have positive attitude.

Sign in / Sign up

Export Citation Format

Share Document