Modeling and experimental evaluation of the effective bulk modulus for a mixture of hydraulic oil and air

The bulk modulus of pure hydraulic oil and its dependency on pressure and temperature has been studied extensively over the past years. A comprehensive review of some of the more common definitions of fluid bulk modulus is conducted and comments on some of the confusion over definitions and different methods of measuring the fluid bulk modulus are presented in this thesis. In practice, it is known that there is always some form of air present in hydraulic systems which substantially decreases the oil bulk modulus. The term effective bulk modulus is used to account for the effect of air and/or the compliance of transmission lines. A summary from the literature of the effective bulk modulus models for a mixture of hydraulic oil and air is presented. Based on the reviews, these models are divided into two groups: “compression only” models and “compression and dissolve” models. A comparison of various “compression only” models, where only the volumetric compression of air is considered, shows that the models do not match each other at the same operating conditions. The reason for this difference is explained and after applying some modifications to the models, a theoretical model of the “compression only” model is suggested. The “compression and dissolve” models, obtained from the literature review, include the effects of the volumetric compression of air and the volumetric reduction of air due to the dissolving of air into the oil. It is found that the existing “compression and dissolve” models have a discontinuity at some critical pressure and as a result do not match the experimental results very well. The reason for the discontinuity is discussed and a new “compression and dissolve” model is proposed by introducing some new parameters to the theoretical model. A new critical pressure (PC) definition is presented based on the saturation limit of oil. In the new definition, the air stops dissolving into the oil after this critical pressure is reached and any remaining air will be only compressed afterwards. An experimental procedure is successfully designed and fabricated to verify the new proposed models and to reproduce the operating conditions that underlie the model assumptions. The pressure range is 0 to 6.9 MPa and the temperature is kept constant at °C. Air is added to the oil in different forms and the amount of air varies from about 1 to 5%. Experiments are conducted in three different phases: baseline (without adding air to the oil), lumped air (air added as a pocket of air to the top of the oil column) and distributed air (air is distributed in the oil in the form of small air bubbles). The effect of different forms and amounts of air and various volume change rates are investigated experimentally and it is shown that the value of PC is strongly affected by the volume change rate, the form, and the amount of air. It is also shown that the new model can represent the experimental data with great accuracy. The new proposed “compression and dissolve” model can be considered as a general model of the effective bulk modulus of a mixture of oil and air where it is applicable to any form of a mixture of hydraulic oil and air. However, it is required to identify model parameters using experimental measurements. A method of identifying the model parameters is introduced and the modeling errors are evaluated. An attempt is also made to verify independently the value of some of the parameters. The new proposed model can be used in analyzing pressure variations and improving the accuracy of the simulations in low pressure hydraulic systems. The new method of modeling the air dissolving into the oil can be also used to improve the modeling of cavitation phenomena in hydraulic systems

Evaluation of Relation between Rainfall and El Nino Phenomena in Iran

In this study El Nino effects on rainfall in Iran is evaluated. Annual rainfall data of the selected rain gauging stations for the years when El Nino phenomenon has taken place (1973-2012), have been picked up. Next, annual rainfall of the years with and without El Nino phenomenon were compared and then analyzed (correlation is significant at the 0.01 level). Finally, percentage-frequency of the rainfalls influenced by warm Enso condition was obtained. Regarding that El Nino has different affect on rainfall under different regions of the world, the results approved that El Nino, increases rainfall across Iran plateau as annual rainfall is increased from south to north. While less increasing of rainfall is seen for coastal area. Results showed that El Nino causes increasing of annual rainfall in Iran

THE RELATIONSHIP BETWEEN COMMUNICATION SKILLS AND MANAGERS' THINKING STYLE FUNCTIONS WITH THE JOB PERFORMANCE OF ELEMENTARY SCHOOL TEACHERS IN URMIA, IRAN IN THE ACADEMIC YEAR 2018-2019

Communication skills and managers' thinking style have a significant impact on teachers' job performance toward organizational goals. The purpose of this study was to investigate the relationship between communication skills level and leadership style of principals with job performance of primary school teachers in Urmia. This is a descriptive correlational study. The statistical population of this study consisted of principals and teachers of public primary schools in Urmia city in 2017-2018 with a total of 60 people. Thus, the districts and schools were first selected by cluster sampling then, by stratified sampling, gender and school type were observed and using a simple random sampling method, a number of principals and teachers were selected from the selected schools. Data were collected using three communication skills questionnaires: Kaufman (1999), Sternberg-Wagner (1997), and Paterson Job Performance (2000). Descriptive and inferential statistics were used for data analysis by SPSS software version 24. Pearson correlation coefficient and regression analysis were used to investigate the correlation between research variables. Research results show that; there is a positive and significant relationship between communication skills and managers' thinking style with teachers' job performance. Among the components of communication skills, perceptual skills and among the components of thinking style, judgmental thinking style has the most roles in explaining the prediction of teachers' job performance. Evidence from this study shows that in order to improve teachers' job performance, the high impact of perceptual skills and managers' judgmental thinking style is among the issues that should be seriously considered.  Article visualizations

Socioeconomic Status and Coronary Heart Disease

Background: Iran has undergone a remarkable demographic transition over the last threedecades. Socioeconomic status (SES) indicators including education, income, and occupationare associated with coronary heart disease (CHD) risk factors, morbidity, and mortality. Theaim of the present study was to describe demographic and socioeconomic characteristics, theirassociation to the diseases, and to explore the predictive risk of CHD in Tabriz, the fourthlargest city in Iran and the capital of East Azerbaijan Province.Methods: This cross-sectional descriptive study was carried out to explore and analyze thecurrent SES status of CHD patients. The study was conducted in Tabriz and all patients(n=189) refereed to the Central Referral Hospital for cardiac patients (Shahid Madani Hospital)from 2009 to 2010 were considered. A researcher structured questionnaire with 15 questionswas used to collect data. Descriptive statistics were used to describe the basic SES featuresof the CHD patients and data analysis was done using SPSS ver. 16.Results: Less educated participants were more susceptible to CHD. Regarding to occupationalstatus, housewives and retired men were in higher risk of CHD than the rest of the people.Studied patients also reported to be mostly from urban areas that were living in apartmentcomplexes.Conclusion: In line with some international research evidence the study results suggested thatpeople from lower/middle social classes were in greater CHD risk than higher social classes.This epidemic might be halted through the promotion of healthier lifestyles and the support ofenvironmental and policy changes

Schema modes in cluster B personality disorders

Summary Aim: The present study aimed to investigate the role of schema modes in cluster B personality disorders. Materials and methods: The participants were 220 individuals -38 men and 137 women -selected from psychiatric and psychological clinics in Tabriz, Iran. Among the participants, 153 individuals were diagnosed with cluster B personality disorder (44 with borderline disorder, 16 with antisocial disorder, 56 with histrionic disorder and 37 with narcissistic personality disorder). The remaining 67 participants had no personality disorder. The diagnosis was based on the Structured Clinical Interview for DSM-IV Axis II disorders (SCID-II). All participants (with or without personality disorder) were assessed with Millon Clinical Multiaxial Inventory-III (MC-MI-III) and Schema Mode Inventory (SMI). Results: Vulnerable, angry and impulsive child modes are predictors of borderline personality disorder, and angry child, self-soother and healthy adult modes are predictors of antisocial personality disorder. The impulsive and happy child, the attack-bully and healthy adult schema modes predict histrionic personality disorder. Finally, the angry child, happy child, self-soother and self-aggrandizer schema modes could predict narcissistic personality disorder. Conclusions: Special schema modes have a role in explaining cluster B personality disorders, and yet these disorders may overlap with regard to some dimensions, especially in terms of cognitions and beliefs. This can be interpreted as a lack of specificity in categorical classification systems such as the DSM. personality disorder/cluster B/schema modes/cognitive theory of personality disorde

Tetra­kis{4-[(2H-tetra­zol-5-yl)meth­yl]morpholin-4-ium} dodeca­tungstosilicate hexa­hydrate

The crystal structure of the title compound, (C6H12N5O)4[W12(SiO4)O36]·6H2O, consists of an α-Keggin-type [W12(SiO4)O36]4− polyoxidoanion, four [(2H-tetra­zol-5-yl)meth­yl]morpholinium cations and six uncoordinated water mol­ecules. In the cations, the morpholine rings display chair conformations. Extensive N—H⋯O, N—H⋯N, O—H⋯O and O—H⋯N hydrogen bonds are present in the crystal structure