Wallis Correlation Research Articles

An assessment of scaling methods for ECC behavior in downcomer of UPTF with RELAP5 code

Various experimental investigations in scaled-down test facilities have been conducted to observe the ECC behaviors during a Large-Break Loss of Coolant Accident (LBLOCA). The ability of the scaling method to describe the similarity between the prototype and the scaled models required validation. In this paper, a series of simulations were performed to investigate the characteristics of ECC penetration in UPTF and the models scaled by four scaling methods including three-level scaling method, linear method, modified linear method and Hierarchical Two-tiered Scaling (H2TS) method. The ECC behaviors, such as the inventory and pressure in lower plenum, steam mass flow at the break, have been analyzed. And the applicability of the scaling method has been evaluated based on the analysis of the ECC behaviors in both of the prototype and scaled models. The results showed that the transient process in the model scaled by H2TS method with aspect ratio of 1.87 and modified linear was in good agreement with the prototype during ECC injection. Moreover, in order to investigate the effect of the aspect ratio, different aspect ratio in H2TS method was applied to scale the model and the inventory in the lower plenum between the UPTF and the model has been compared. In addition, the modified Wallis correlation for CCFL accounting for the condensation effect has been performed.

Overexpression of phosphatidylethanolamine-binding protein 4 (PEBP4) associates with recurrence of meningiomas

Background and purposeAbnormal expression of phosphatidylethanolamine-binding protein 4 (PEBP4) has been identified in various types of malignant tumors. In the present study, we investigated the expression of PEBP4 in meningioma cases and examined whether PEBP4 expression was correlated with outcomes among these patients. Materials and methodsThe expression levels of PEBP4 and Ki-67 in human meningioma tissues from 65 patients were evaluated by immunohistochemical staining. The correlation between PEBP4 immunoreactivity in meningioma samples and patients’ clinical outcomes was examined using the Kruskal–Wallis correlation test. The prognostic value of PEBP4 expression in meningiomas patients also was investigated. ResultsImmunohistochemical analysis revealed up-regulated PEBP4 expression in both atypical and anaplastic meningiomas compared with classical meningiomas (13.38 ± 4.19% vs. 3.64 ± 2.04%, P < 0.001). PEBP4 immunoreactivity in meningioma samples was closely correlated with that for Ki-67 (Spearman r = 0.7922, P < 0.0001). PEBP4 expression was also associated with tumor differentiation grade and clinical recurrence (P < 0.05). Multivariate regression analysis showed with high PEBP4 expression was associated with a longer recurrence-free survival (hazard ratio=0.252, 95% confidence interval: 0.067–0.940, P = 0.040). ConclusionPEBP4 may play an important role in the progression of meningioma, as high PEBP4 expression was associated with a higher pathological grade of meningioma. Moreover, PEBP4 expression may be a meaningful prognostic biomarker in meningioma.

RECURSOS DO AMBIENTE FAMILIAR E DESEMPENHO DE LEITURA EM ADOLESCENTES

ABSTRACT This study aimed to verify the association between the resources of the family environment and teenage reading. A total of 106 adolescents of both sexes, aged between 11 and 16 years, without learning difficulties, participated in the study. For data collection, a narrative text, a multiple-choice questionnaire about the text and an adapted Family Environment Resources questionnaire were used. Descriptive and inferential analysis was performed using Spearman, Mann-Whitney and Kruskal Wallis correlation tests, with a significance level of 5%. Resources that promote proximal processes and parenting practices contributed to better reading performance. In contrast, the predictable activities category contributed negatively. Thus, the environment and resources influenced the adolescents’ reading performance. It is concluded that the elaboration of school measures and public policies is important to strengthen the family-school relationship, expand family resources and make the environment favorable to teaching.

Determinants of mothers knowledge about breastfeeding in neonatology intensive care

Abstract Background Breastfeeding (BF) is one of the most effective ways to ensure child health and survival. In Morocco the BF rate decreased from 51% to 27,8% between 1992 and 2011. The breast feeding rate in neonatal intensive care unit (NICU) is lower 12,4%. Studies showed if we improve the mothers knowledge, the BF practice rate increase in NICU. We aim to determine associated factors of mothers knowledge about BF in NICU of Ibn Rochd teaching hospital in Casablanca (Morocco). Methods A cross-sectional study was conducted between 04 January and 23 April 2021 in NICU ward of teaching hospital Ibn Roch of Casablanca (Morocco). We included Moroccan mothers who can practice the BF presents during the study period. We used face to face interview using questionnaire. A scoring system from 0 to 16 points was used to measure the knowledge. The student, ANOVA, Mann-Whitney-Wilcoxon, Kruskal Wallis, Pearson and spearman correlation tests were used to test association between BF and potential associated factors. Associated factors with p ≤ 0.05 were considered as determinants of BF. Data were analyzed using R 3.6.3. Results We included 111 mothers. The mean score of knowledge was 10.38 ± 2.31. Associated factors with BF knowledge were: healthcare staffs support (yes mean score =11.06 and no = 9.72; p = 0.002); getting prior information about BF (yes mean score =10.53 and no = 9; p = 0.012). The knowledge increase with age of mother (correlation coefficient = 0.26; p = 0.005) and parity (correlation coefficient = 0.30; P = 0.001). Conclusions Mothers and specifically younger primiparous should receive more attention from training program and healthcare staffs in NICU to improve the knowledge and practice of BF. Key messages we can enhance significantly the survival and health of newborn hospitalized in NICU by simple actions as advices, encouragement toward the newborn mothers to improve their knowledge about BF. Healthcare staffs and facilities have to be the teachers and school about breast feeding.

Effect of Ambient Temperature Variation on Pressure Drop During Condensation in Long Inclined Tubes

Abstract Two-phase flow pressure drop during condensation of steam inside inclined tube heat exchangers was investigated over a wide range of ambient temperature. The ambient temperature changes from 3 to 45 °C, the steam mass flux varies from 3 to 18 kg/(m2 · s), vapor quality ranges from 0.51 to 0.86. 608 data points were experimentally obtained and compared with eight commonly used correlations from the available literatures. Frictional pressure drop increases with increasing temperature difference and fan speed. For the full experimental dataset, the best overall performing correlation was obtained by using the Wallis correlation (MAPE = 17.60%, NRMSE = 14.87%). For cold ambient temperatures, (Tamb &amp;lt; 20 °C, N = 298), the best overall performing correlation was obtained by using the Carey correlation (MAPE = 11.02%, NRMSE = 14.71%). For hot ambient temperatures (Tamb &amp;gt; 30 °C, N = 196), the Lockhart and Martinelli correlation has shown the best performance (MAPE = 16.84%, NRMSE = 20.45%). An improved two-phase frictional pressure drop correlation based on the Wallis correlation (Wallis, 1969, One Dimensional Two-Phase Flow, McGraw-Hill, New York) is proposed.

Investigation of Pre-Service Teachers’ Tolerance Tendencies and Democratic Tendencies

The current study aims to investigate whether pre-service teachers&amp;rsquo; tolerance tendencies and democratic tendencies vary significantly depending on gender and mother and father&amp;rsquo;s education level and the relationship between their tolerance tendencies and democratic tendencies. A total of 417 second-year students from the departments of Turkish teaching, social studies teaching, elementary school teacher training, pre-school teacher training, science teaching, elementary school math teaching, arts, music, psychological counselling and guidance, English teaching and German teaching participated in the current study. In the analysis of the collected data, frequencies, percentages, Mann Whitney U test, Kruskall Wallis test and correlation analysis were used. As a result of the analyses, the pre-service teachers&amp;rsquo; tolerance tendencies were found to be very high. The female pre-service teachers&amp;rsquo; tolerance tendencies were found to be higher than those of the male pre-service teachers. The pre-service teachers&amp;rsquo; tolerance tendencies were found to be not varying significantly depending on mother and father&amp;rsquo;s education level. The pre-service teachers&amp;rsquo; democratic tendencies were found to be higher than the medium level. The female pre-service teachers&amp;rsquo; democratic tendencies were found to be higher than those of the male pre-service teachers. The pre-service teachers&amp;rsquo; democratic tendencies were found to be not varying significantly depending on mother and father&amp;rsquo;s education level. A positive, medium and significant correlation was found between the pre-service teachers&amp;rsquo; tolerance tendencies and democratic tendencies.

Psychological Well-being Family Affected by Tidal Flood in Pekalongan City

Tidal floods affect the surrounding community not only on social, economic, environmental aspects, but also psychological aspects. This phenomenon becomes very important for families in achieving psychological well-being. The purpose of this study was to analyze the psychological well-being of families affected by tidal flooding. Quantitative methods was used in this research with cross sectional study approaches. A total of 84 respondents were taken by purposive sampling. Spearman Rank and Kruskal Wallis correlations was used for data analysis. The result showed that the psychological well-being of respondents averaged 159 197.39 with the lowest value and the highest value of 228. The Kruskal Wallis test results obtained ρ: 0.340> 0.05, meaning that there is no difference in psychological well-being in the three villages. The psychological well-being of families affected by tidal floods is in the low category, so it needs guidance, and cooperation between related institutions in handling psychological aspects.

Intraoperative bacterial analysis in nasal polyposis: Clinical and functional impact

BackgroundThe impact of Staphylococcus aureus on onset of nasal polyposis has been the focus of numerous studies, but there have been few studies of other germs found in the ethmoid of operated patients or of their impact on post-operative results. Material and methodsAll patients undergoing endoscopic radical ethmoidectomy for nasal polyposis in the teaching hospital of Nantes (France) between 2006 and 2016 had intraoperative ethmoid cavity bacterial sampling. Phenotypic characteristics, pre- and post-operative symptoms and endoscopic findings were analyzed. Mann–Whitney tests and Kruskal–Wallis correlation analysis were used to assess clinical/bacteriological correlations. ObjectivesThe main objective was to describe bacterial colonization of patients undergoing surgery for nasal polyposis, and to assess correlations with phenotypic features, functional results and postoperative clinical course. ResultsOne hundred and seven patients were included. A total of 26% were not infected, 55% mono-infected and 19% multi-infected. In 27.3%, staphylococci were isolated; in 30.5%, isolates were gram-negative bacilli. There were no significant correlations between presence or type of pathogen and symptom profile. ConclusionThis study confirmed the high rate of pathogenic bacteria in nasal cavities in case of polyposis, with high frequencies of S. aureus but also of gram-negative bacilli, raising the question of their involvement in the inflammatory reactions underlying the nasal polyposis.

A Study of Pressure Gradient in Multiphase Flow in Vertical Pipes

The study of multiphase flow in vertical pipes is aimed at effective and accurate design of tubing, surface facilities and well performance optimization for the production of oil and gas in the petroleum industry by developing a better approach for predicting pressure gradient. In this study, field data was analyzed using mathematical model, multiphase flow correlations, statistical model, and computer programming to predict accurately the flow regime, liquid holdup and pressure drop gradient which are important in the optimization of well. A Computer programme was used to prediction pressure drop gradient. Four dimensionless parameters liquid velocity number (Nlv), gas velocity number (Ngv), pipe diameter number (Nd), liquid viscosity number (Nl), were chosen because they represent an integration of the two dominant components that influence pressure drop in pipes. These dominant component are flow channel/media and the flowing fluid. The model was found to give a fit of 100% to the selected data points. Hagedorn &amp; Brown, Griffith &amp;Wallis correlations and model were compared with field data and the overall pressure gradient for a total depth of 10000ft was predicted. The predicted pressure gradient measured was found to be 0.320778psi/ft, Graffith&amp; Wallis gave 0.382649Psi/ft, Hagedorn &amp; Brown gave 0.382649Psi/ft; whereas generated model gave 0.271514Psi/ft. These results indicate that the model equation generated is better and leads to a reasonably accurate prediction of pressure drop gradient according to measured pressure gradient.

Study of Pressure Gradient in Multiphase Flow in Vertical Pipes

The study of multiphase flow in vertical pipes is aimed at effective and accurate design of tubing, surface facilities and well performance optimization for the production of oil and gas in the petroleum industry by developing a better approach for predicting pressure gradient. In this study, field data was analyzed using mathematical model, multiphase flow correlations, statistical model, and computer programming to predict accurately the flow regime, liquid holdup and pressure drop gradient which are important in the optimization of well. A Computer programme was used to prediction pressure drop gradient. Four dimensionless parameters liquid velocity number (Nlv), gas velocity number (Ngv), pipe diameter number (Nd), liquid viscosity number (Nl), were chosen because they represent an integration of the two dominant components that influence pressure drop in pipes. These dominant component are flow channel/media and the flowing fluid. The model was found to give a fit of 100% to the selected data points. Hagedorn &amp; Brown, Griffith &amp;Wallis correlations and model were compared with field data and the overall pressure gradient for a total depth of 10000ft was predicted. The predicted pressure gradient measured was found to be 0.320778psi/ft, Graffith&amp; Wallis gave 0.382649Psi/ft, Hagedorn &amp; Brown gave 0.382649Psi/ft; whereas generated model gave 0.271514Psi/ft. These results indicate that the model equation generated is better and leads to a reasonably accurate prediction of pressure drop gradient according to measured pressure gradient.

Effects of prophylactic ketamine and pethidine to control postanesthetic shivering: A comparative study

Background: Shivering is an undesirable complication following general anesthesia and spinal anesthesia, whose early control can reduce postoperative metabolic and respiratory complications. Therefore, this study aims to compare the effects of prophylactic injection of ketamine and pethidine on postoperative shivering.&#x0D; Methods: This double-blind clinical trial was performed on 105 patients with short-term orthopedic and ENT surgery. The patients were randomly divided into three groups; 20 minutes before the end of the surgery, 0.4 mg/kg of pethidine was injected to the first group, 0.5 mg/kg of ketamine was injected to the second group, and normal saline was injected to the third group. After the surgery, the tympanic membrane temperature was measured at 0, 10, 20, and 30 minutes. The shivering was also measured by a four-point grading from zero (no shivering) to four (severe shivering). Data were analyzed by one-way ANOVA, Kruskal Wallis, Chi-square and Pearson correlation.&#x0D; Results: The mean age of patients was 35.8+/-11.45 years in the ketamine group, 34.8+/-11.64 years in the normal saline group, and 33.11+/-10.5 years in the pethidine group. The one-way ANOVA showed no significant difference in the mean age between the three groups (P=0.645). The incidence and intensity of shivering were significantly higher in the normal saline group than in the ketamine and pethidine groups (p=0.001). However, there was no significant difference in the incidence and the intensity of shivering between the ketamine and the pethidine groups (p=0.936).&#x0D; Conclusion: The results showed that the 0.5 mg/kg of ketamine could control the post-anesthetic shivering.&#x0D;

The Effect of the Coach-Athlete Relationship on Passion for Sports: The Case of Male Handball Players in Super League

The purpose of this study is to reveal out the relationship between the team players' perceived coach-athlete relationship and their passion in sports. This is a research carried out with sectional screening model. The study group consisted of 200 male handball players in super league in Turkey. Participants were asked questions with demographic information to obtain personal information. Additionally, 11 question “Coach-Athlete Relationship Scale” developed by Jowett &amp; Ntoumanis (2004) and adapted to Turkish by Altıntaş et al. (2012) and 12 question “Athlete Passion Scale” developed by Vallerand et al. (2003) and adapted to Turkish by Kelecek &amp; Aşçı (2013) was applied. To evaluate the obtained data SPSS 20 package program was used and percentage (%), frequency (f), Kruskal Wallis test, correlation analysis, and regression analysis were conducted. There was a positive relationship between the coach-athlete relationship and its sub-dimensions of commitment, closeness and complementarity and also between the passion for sports and its sub-dimensions of harmonious passion and obsessive passion. Besides, the regression analysis has shown that the coach-athlete relationship has a relatively high impact on the passion for sports. In other words, as the effectiveness and quality of the coach-athlete relationship increase, so does "passion", which is one of the most important motivation sources for the athletes. At the end of our research it was found that, the coach-athlete relationship was at high level. As a result, there is a relationship between coach-athlete relationship and sport passion.

Effect of wall friction model on predicting emergency core coolant behavior in upper downcomer with direct vessel safety injection using MARS-KS

For predicting more realistic flow behaviors, nuclear safety analysis code, MARS has adopted multi-dimensional module. However, most of the constitutive models in the module were developed based on onedimensional experimental results. In this study, the wall friction models in MARS were validated with two benchmark tests which were conducted by Korea Atomic Energy Research Institute (KAERI) for describing the direct ECC bypass phenomenon in the upper downcomer of the Advanced Power React 1400 (APR1400) during the reflood phase of a large-break LOCA (LBLOCA). One is the two-dimensional film flow experiment and the other is the MIDAS (multi-dimensional investigation on downcomer annulus simulation) test. Both simulation results showed that the Wallis correlation could improve the predictability yielding a stronger wall friction force than the H.T.F.S. correlation did.

The Influence of Flooding Phenomenon to Pressure Drop on Hotleg Simulator with L/D=25

Cooling system in nuclear reactor is much influenced by counter-current flow. When a leakage is occured, coolant in primary circuit of hotleg and hot steam from reactor will flows in counter-current condition. An experimental investigation has been performed to examine the effect of flooding phenomenon on the pressure drop. It was observed using acrylic complex pipe as hotleg simulator consisting of three parts: horizontal, bend and inclined pipe. Geometrical sizes of pipes was in scale of 1/30 of the actual hotleg geometrical size in the PWR with inner diameter=25.4 mm, the horizontal pipe length L=635 mm, and inclined pipe length was 20 mm with an angle of 50o. Pressure drop was meassured by using differential pressure sensor installed in the lower-tank (RPV simulator) dan upper-tank (SG simulator). Pressure drop was observed before, during and after flooding. Based on the observation, it was found that the change of flow pattern is followed by the change of pressure drop. The results of this study were also compared with some correlations using the dimensionless superficial velocity parameter by Wallis correlation. Wallis correlation can be written as JG*1/2 + 0,3974 JL*1/2 = 0,4832 .

&lt;b&gt;Balance in seniors who exercise, considering different levels of fear of falling

The aging process brings changes to one’s body balance and may trigger a fear of falling. The aim of this study was to compare and verify correlation between different methods that assess body balance among elderly individuals who exercise, according to different levels of fear of falling. The sample was composed of 186 individuals (68.28±6.years) who exercise. Balance assessment used Timed Up and Go, Unipedal Stance, Sitting-Rising and Functional Reach tests. A question about fear of falling was applied in the form of an interview. Statistical analysis used Spearman and Kruskall Wallis correlation. In results, Timed Up and Go (7.13±1.6s), Unipedal Stance (20.52±9.9s), Sitting-Rising (12.43s±3.2s) and Functional Reach (29.51±6.5) showed significant correlation with fear of falling. Individuals less afraid of falling showed better balance performance when compared to those not afraid of falling. In conclusion, better balance performance can contribute to decreasing fear of falling.

Pressure drop in dairy evaporators: Experimental study and friction factor modelling

The pressure drop that occurs during the falling film evaporation of dairy products is related to the downward co-flowing vapour and directly affects the saturation temperature of the product, resulting in a non-constant thermal driving force of the process along the evaporator. Frictional forces are the major contributor to the pressure drop, and the friction factor is a crucial parameter in reliably estimating the pressure drop. In the present study, the absolute vapour flow pressure losses during falling film evaporation of dairy products were measured using an experimental internal tube evaporator set-up. To simulate real industrial conditions, experiments were conducted by varying the co-flow inlet velocity (from 0 to 37 ms−1) over a wide range of product dry solid content DC (from DC = 0%–50%). Results obtained at DC = 0% show that the experimental approach is consistent when measurements are compared to the well-known Wallis correlation. A large number of experimental data has been obtained for DC between 13 and 40% for which the pressure losses have a strong dependence from the co-flowing vapour rate; in some specific cases, the influence of the surface bubbling phenomena has been put in evidence. The presented results, have been used to calibrate a new accurate correlation for the friction factor (4flv) coefficient showing a squared residual of R2 = 0.93.

鉛直管内における気液対向流制限

Characteristics of counter-current flow limitation (CCFL) inside vertical pipes with sharp-edged upper end (CCFL-P/SE) and with round-edged upper and lower ends (CCFL-P) were evaluated to clarify the dependence of the limiting locations. The CCFL is defined by the relationship between the gas and liquid volumetric fluxes (JG and JL) under a quasi-steady state after onset of flooding. CCFL correlations were constructed for CCFL-P/SE and CCFL-P based on the previous experimental data. The correlations were compared to the characteristics of CCFL at the vertical pipes of the sharp-edged upper end (CCFL-U) and the sharp-edged lower end (CCFL-L). CCFL-P has the highest liquid volumetric flux when CCFL occurs, and the lowest is CCFL-L. For the Wallis correlation, selection of the characteristic length of w = D(1-β)Lβ (where D and L respectively denote the diameter and the Laplace capillary length) is quite important. Our results have indicated that CCFL-P/SE and CCFL-P are also expressed by β ≈ 0.5, CCFL-U is expressed by β = 1, and CCFL-L is expressed by β = 0.

Development of a critical heat flux mapping method for fin-structured surfaces

ABSTRACTIn this study, we performed critical heat flux (CHF) experiments using structured surfaces to validate the parameter effects and understand their physical meanings. Experimental results showed that the CHF has a peak value as the fin geometry changes. Fins with height of 0.5 mm produced the largest CHF, 1.7 MW/m2, and fins longer than 2 mm reduced the CHF values. To explain the results, a CHF mapping method was developed describing the liquid supply-side and demand-side limits. The liquid demand-side limit is governed by the heat removal capability, mainly the nucleate boiling, calculated using the hot spot model. We consider three liquid supply-side limits restricting the liquid supply to the heating surface: capillary limit and counter-current flow limitations (CCFLs). The capillary limit is determined by balancing the capillary pressure and viscous dissipation in the liquid film on the fin side. The CCFL in the structure is calculated using the Wallis correlation and the CCFL in the free volume limits the liquid downward flow by the vapor jetting from the heating surface. The CHF map for our experimental results successfully describes the CHF trend of the structured surfaces. As a result, we concluded that CHF mapping method is an effective means of explaining CHF in pool boiling.

Considering the uncertainties in empirical correlations for vertical countercurrent flow limitation (CCFL) with TRACE

Abstract TRACE is used to calculate the thermal-hydraulic sequence in nuclear power plants for accident analysis. In some postulated accidents, countercurrent flow limitation (CCFL) phenomena can occur. This phenomenon is calculated by means of empirical relationships in TRACE. Usually, not all empirical relationships used in TRACE are accessible to the user who develops the computational model for accident analysis, but in the case of CCFL, the user must specify the parameters of the empirical relationship. Additional preliminary work is needed for fitting the parameters so that experimental data matches the computational calculations and the accident analysis can be performed. Furthermore, uncertainties in measurement errors from experimental data lead to user-based variations in the parameters of the empirical relationship for CCFL. Therefore, an alternative procedure in which accident analysis is performed with consideration of the uncertainties in the empirical relationships is presented. The uncertainty was quantified by means of a stochastic linear regression model for the Wallis correlation and the Bankoff correlation. An uncertainty analysis was subsequently performed to demonstrate the influence of uncertainty in certain cases of CCFL.

Experimental study of gas–liquid two-phase flow through packed bed under natural circulation conditions

Dry-out phenomena in packed beds or porous media may cause a significant digression of cooling/reaction performance in heat transfer/chemical reactor systems. One of the phenomena responsible for the dry-out in packed beds is known as the counter-current flow limitation (CCFL). In order to investigate the CCFL phenomena induced by gas–liquid two-phase flow in packed beds inside a pool, a natural circulation packed bed test facility was designed and constructed. A total of 27 experimental conditions covering various packing media sizes (sphere diameters: 3.0, 6.4 and 9.5 mm), packed bed heights (15, 35 and 50 cm) and water level heights (1.0, 1.5 and 2.0 m) were tested to examine the CCFL criteria with adiabatic air–water two-phase flow under natural circulation conditions. Both CCFL and flow reversal phenomena were observed, and the experimental data including instantaneous and time-averaged void fraction, differential pressure and superficial gas–liquid velocities were collected. The CCFL criteria were determined when periodical oscillations of void fraction and differential pressure appear. In addition, the Wallis correlation for CCFL was utilized for data analysis, and the Wallis coefficient, C, was determined experimentally from the packed bed CCFL tests. Compared to the existing data-sets in literature, the higher C values obtained in the present experiment suggest a possibly higher dry-out heat flux for natural circulation debris systems, which may be due to the water supply from both top and bottom surfaces of the packed beds. Considering the effects of bed height and hydraulic diameter of the packing media, a newly developed model for the Wallis coefficient, C, under natural circulation CCFL is presented. The present model can predict the experimental data with an averaged absolute error of ±7.9%.