BOUNDARY LAYER ON FLAT PLATE WITH LEADING EDGE PATTERNS

Ph.DDOCTOR OF PHILOSOPH

Utilizing Modern Experimentation Method to Quantify Jet-Breaker Dimension Effects on Drop Manhole Pool Height

Drop manholes are commonly employed in sewer and drainage systems to reduce pipes slope. The operation of these structures is dominated by their flow regime. Poor hydraulic performance of them under Regime R2 was improved with the jet-breaker, which intersects the inlet jet; yet its proper dimensions were needed to be precisely determined. In this paper, effects of jet-breaker length, width, sagitta, and angle on drop manhole pool free-surface height were experimentally studied under 80% filling ratio of the inlet pipe. The modern statistical Design of Experiment (DoE) methodology and dimensional analysis were utilized to design the experiments in accordance with the 24-1IV fractional factorial design. Consequently, nine specific jet-breakers were built and examined at two different angles, and under various flow rates. The statistical analysis of the results shown that manhole pool height was significantly decreased when jet-breaker length, width, and sagitta were 1, 1.4, and 0.7 times the inlet pipe diameter, respectively, and its angle was at 70°. The use of DoE resulted in 21% reduction in experimental runs, cost, and time, while it provided comprehensive data analysis and objective conclusion

Impact of verbal explanation on parental acceptance level of different behavior management techniques in dental office

BACKGROUND AND AIM: Parents’ attitudes towards different aspects of dentistry especially the use of behavior management techniques (BMTs) can greatly effect a child’s cooperation in a dental office. The present quasi-experimental study was conducted with the aim to assess the effect of a verbal explanation on parents’ acceptance level of the most common BMTs used in pediatric dentistry. METHODS: A videotaped presentation showing the 6 most commonly used BMTs in Iran was presented to 60 parents recruited by a convenient sampling method. Using visual analogue scale (VAS), the acceptance level of each BMT was measured before and after an explanation on the reasons of each BMT. Paired t-test, repeated measures analysis of variance (ANOVA) and independent t-test were used for statistical analysis of data. Significance level was set as 0.050. RESULTS: Giving a verbal explanation on BMTs had a statistically significant effect on the acceptance of BMTs. Tell-show-do (TSD) and hand-over-mouth (HOM) techniques achieved the highest and lowest mean scores of parental acceptance, respectively. The acceptance of physical restraint (P = 0.013) and parental presence/absence (PPA) (P = 0.015) of parents was obtained higher among men compared to women using t-test. CONCLUSION: Giving an explanation to parents while performing a BMT is effective in raising parents' acceptance of the technique. Non-invasive methods such as TSD and PPA of parents are the more favorable methods to parents. KEYWORDS: Pediatric Dentistry; Behavior Control; Parental Consen

Dynamic Response of a Thick Piezoelectric Circular Cylindrical Panel: An Exact Solution

One of the interesting fields that attracted many researchers in recent years is the smart structures. The piezomaterials, because of their ability in converting both mechanical stress and electricity to each other, are very applicable in this field. However, most of the works available used various inexact two-dimensional theories with certain types of simplification, which are inaccurate in some applications such as thick shells while, in some applications due to request of large displacement/stress, thick piezoelectric panel is needed and two-dimensional theories have not enough accuracy. This study investigates the dynamic steady state response and natural frequency of a piezoelectric circular cylindrical panel using exact three-dimensional solutions based on this decomposition technique. In addition, the formulation is written for both simply supported and clamped boundary conditions. Then the natural frequencies, mode shapes, and dynamic steady state response of the piezoelectric circular cylindrical panel in frequency domain are validated with commercial finite element software (ABAQUS) to show the validity of the mathematical formulation and the results will be compared, finally

Integration and Performance Improvement of Green Supply Chain Management Using Green Human Resource Management

Nowadays, managers in the public and private sectors consider having knowledge of green laws and issues are essential in surviving of their organizations. Although researchers have promoted each issue of green human resource management and green supply chain management separately, but there has been a great delay in integrating these two issues. Therefore, this study first attempts to provide an integrated and coherent framework for linking green human resource management and green supply chain management (GHRM-GSCM). For this purpose, firstly, using a comprehensive literature review of the research, interviews and expert opinion on the ornamental industry, the initial identification of evaluation indicators in green supply chain management and green human resources management was undertaken. In the next step, the causal relations were determined by using the fuzzy DEMATEL method and the weight of each of the criteria and sub-criteria were determined with the fuzzy ANP method. The results of this assessment show leadership, flexibility, and environmental factors based on their importance are identified as effective factors, and optimizing these factors by the Arya array industry could lead to other factors optimization (influencing factors)

Chemical characterization of volatile components of Thymus serpyllium L. using Microwave Distillation (MD) and Hydro-distillation (HD) methods. Green chemistry

ABSTRACT In this paper, Microwave distillation a new method of essential oil extraction has been compared with a conventional technique, hydro-distillation (HD). The compositions of essential oil extracted by applying kinds of extraction methods were identified by using GC-MS system. There was no obvious difference in the quality of essential oils obtained by the kinds of extraction methods. The major components of MD and HD methods are as Thymol (20.74%,21.70%), Camphene(6.60%,6.65%), Limonene(3.17%,3.26%) camphor(1.09% , 20 %) limonene (3.17% , 3.26 %) respectively

Effects of jet-breaker dimensional characteristics on drop manhole hydraulic performance

Drop manholes prevent excessive flow velocity and provide energy dissipation in steep urban sewer and drainage systems. Their poor hydraulic performance under Regime R2, in which the inlet jet collides with the manhole outlet, was improved by the jet-breaker. However, this device should still be properly sized to efficiently enhance manhole operation. In this paper, effects of jet-breaker length, width, sagitta, angle, and inlet pipe filling ratio on drop manhole performance, were investigated experimentally. Two-level factorial design and dimensional analysis were both utilized to design the experiments to study drop manhole energy dissipation and air demand as responses. Statistical analysis of the results revealed both significant design factors and regression models for each response. Neither jet-breaker length nor width had significant effects. However, the responses were improved by increasing both jet-breaker angle and inlet pipe filling ratio. Jet-breaker sagitta had a different effect on each response; a flat plate was more appropriate for energy dissipation while a curved plate decreased air demand. Simultaneous analysis of regression models determined the proper levels of significant design factors as 80% filling ratio of the inlet pipe, jet-breaker angle at 70°, and its sagitta equal to 0.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Modeling and experimental verification of a 25W fabricated PEM fuel cell by parametric and GMDH-type neural network

In this paper two artificial intelligence techniques to predict and control behavior of a 25W fabricated proton exchange membrane (PEM) fuel cell, have been investigated. These approaches are: “Parametric Neural Network (PNN)” and “Group Method of Data Handling (GMDH)” for the first time. A PNN model is developed by introducing a “p” parameter in the activation function of the neural network. PNN model with its specific tangent hyperbolic transfer function have the ability to be with different nonlinearity degrees of input data. To develop GMDH network, quadratic polynomial was utilized. To determine proper weights of GMDH network, back propagation algorithm has been used. The input layer consists of gas pressure, fuel cell temperature and input current experimental data, to predict the output voltage. The results show that both generalized Parametric and GMDH-type neural networks are reliable tools to predict the output voltage of PEM fuel cell with high coefficient of determination values of 0.96 and 0.98

Aspirin administration from early pregnancy versus initiation after 11 weeks of gestation for prevention of pre-eclampsia in high-risk pregnant women: Study protocol for randomized controlled trial

Background: Pre-eclampsia (PE) is a multiorgan disorder that affects 2–5% of all pregnant women. Present recommendations for when to start aspirin in high-risk women are after 11 wk of gestation. Objective: We present a protocol to investigate the effectiveness of aspirin use from early pregnancy, which is a randomized controlled trial to assess whether prescribed low-dose aspirin from early pregnancy reduces the prevalence of early and late-onset PE. Additionally, to compare the effectiveness of aspirin administration before and after 11 wk in reducing the occurrence of PE? Materials and Methods: All pregnancies at risk of PE, according to demographic and midwifery history, who are referred to the Maternal-Fetal Clinic of Tehran University hospital, Tehran, Iran were invited to take part in the trial. The outcomes of pregnancy and newborns will be gathered and analyzed. The first registration for the pilot study was in January 2023, and the participants were recognized as high-risk for PE. In addition, enrollment in the main study will begin as of October 2023. Key words: Pre-eclampsia, Aspirin, Color doppler ultrasonography, Pregnancy, First trimester, Pregnancy-associated plasma protein-A. Key words: Pre-eclampsia, Aspirin, Color doppler ultrasonography, Pregnancy, First-trimester, Pregnancy-associated plasma protein-A

Regional Analysis of Dust Day Duration in Central Iran

The duration of dust days (DDD) is one of the most important parameters that may worsen the effects of the presence of dust in the affected areas. Persistent pollution over consecutive dusty days can have particularly negative effects on the human respiratory system. The present analysis was conducted in Central Iran, where the phenomenon of dust is one of the most important problems. In this study, using dust codes recorded at 35 synoptic stations, the homogeneity of DDD across the region was investigated using the L-moments method. Then, characteristics of DDD over the period 1999–2018 were calculated. The results showed that the region is statistically homogeneous. Furthermore, Zabol and Zahdan are the stations worst affected, with the longest durations of 22 and 21 days in 2014. Additionally, the values of DDD with return periods of 5, 10, 25, and 50 years were calculated using fitted statistical distributions and kriging and mapped. Finally, using the K nearest neighbor method the most important factor affecting DDD of the spatial characteristics, including longitude, latitude, elevation, average daily temperature (tm), dew point (td), wind altitude (u), maximum wind speed (ffmax), and direction of the fastest wind (ddmax), was determined. It was found that the southeastern parts of the study area are affected by the longest dust storm duration in all return periods; over longer return periods, long dust storms are also found in the central parts, especially the central desert of Iran. Therefore, these areas should be given priority in fighting and controlling wind erosion. Furthermore, the results showed that the maximum wind speed has the greatest effect on DDD