Analysis of the hydrodynamic torque effects on large size butterfly valves and comparing results with AWWA C504 standard recommendations

Butterfly valves are widely used in various industries such as water distribution, sewage, oil and gas plants. The hydrodynamic torque applied on the butterfly valve disk is one of the most important factors which should be considered in their design and application. Although several methods have been used to calculate the total torque on these valves, most of them are based on hydrostatic analysis and ignore the hydrodynamic effect which has a major role to determine the torque of the large-size valves. For finding the dynamic-valvetorque, some empirical formulas and methods have been proposed; for example in AWWA C504 standard, a relationship for calculating the dynamic torque has been given and its variation versus disk angle has been stated. However, the use of these empirical relationships is restricted due to the conditions defined in the standards. In this paper, the dynamic-valve-torque has been calculated for a large butterfly valve under different conditions and also at the different opening angles of the valve disk. For this purpose a computational fluid dynamics (CFD) method has been used. The results have been compared with those given in the AWWA C504 standard recommendations. Moreover, the effects of the disk shape and its deformation, surface roughness, upstream/downstream pressure variation and disk-offset value have been studied.     

Kinetic Investigation of Rosemary Essential Oil by Two Methods: Solvent-Free Microwave Extraction and Hydrodistillation

Depending on the use area of rosemary essential oil, pharmaceutical, cosmetic, or in food, the choice of both method and extraction time is fundamental, and the sample characterization is mainly based on comparing a few compounds that act as markers of a defined quality for a precise application. In the present work, the kinetic study of major components of Rosmarinus officinalis L. essential oils obtained by solvent-free microwave extraction (SMFE) and by hydrodistillation (HD) has been followed in order to determine the optimum extraction time of a defined bioactive molecule or its chemical family as well as its recommended extraction technique, either SFME or HD. The monoterpene hydrocarbons were nearly extracted completely in the first instants by SFME and progressively by HD. In contrast, the oxygenated monoterpenes were substantially extracted during the first minutes by HD and progressively by SFME. While the extraction of trans-caryophyllene was achieved at the beginning with SFME, it required more than 2 h with HD. A substantial gain in the extraction time has been obtained using SFME. Even though the essential oils extracted by SFME (30 min) and HD (3 h) are qualitatively similar, the oil fractions obtained during extraction time are very different.     

Evaluation of PMSG‐based drivetrain technologies for 10‐MW floating offshore wind turbines: Pros and cons in a life cycle perspective

This paper presents an in depth evaluation and comparison of three different drivetrain choices based on permanent‐magnet synchronous generator (PMSG) technology for 10‐MW offshore wind turbines. The life cycle approach is suggested to evaluate the performance of the different under consideration drivetrain topologies. Furthermore, the design of the drivetrain is studied through optimized designs for the generator and gearbox. The proposed drivetrain analytical optimization approach supported by numerical simulations shows that application of gearbox in 10‐MW offshore wind turbines can help to reduce weight, raw material cost, and size and simultaneously improve the efficiency. The possibility of resonance with the first torsional natural frequency of drivetrain for the different designed drivetrain systems, the influence of gear ratio, and the feasibility of the application for a spar floating platform are also discussed. This study gives evidence on how gearbox can mitigate the torque oscillation consequences on the other components and how the latter can influence the reliability of drivetrain.     

Mechanism of Browning in Fresh Highbush Blueberry Fruit (Vaccinium corymbosum L). Role of Blueberry Polyphenol Oxidase,Chlorogenic Acid and Anthocyanins

Browning reactions which occurred after crushing fresh blueberries (Vaccinium corymbosum L) were followed by determination of chlorogenic acid colour density, polymer colour and the level of polymers. A polyphenol oxidase (PPO) activity plays a dominant role in enzymatic browning. Peroxidase (POD) does not contribute to brown colour formation. The loss of 29% of the colour in a model system containing PPO and blueberry anthocyanins indicated that PPO could act directly on these pigments. However, the rate of anthocyanin degradation was stimulated by the addition of chlorogenic acid. © 1997 SCI.     

Effects of strain rate and temperature on the mechanical behavior of high-density polyethylene

The objective of this work is to initiate the discussion about multiphysics relationships between the molten and solid states of high-density polyethylene (HDPE). The extrusion and the injection processes are employed to prepare samples, and the experimental procedures, using differential scanning calorimetry, dynamic thermomechanical analysis (DMTA), thermal gravimetric analysis, and rheological measurements, are defined to choose the optimal variables. After different characterizations, the extrusion and injection temperatures of 220 and 230 °C have been chosen. To investigate the viscoelastic behavior of HDPE, the DMTA is used. To perform the high strain rate tensile tests, tensile machine was equipped with a specific furnace. Two temperatures, −20 and 20 °C, with strain rates varying from 0.001 to 100 seconds⁻¹ were used to compare the flow characteristics. Results showed that by increasing the strain rate the molecular mobility of the HDPE chains is decreased. In addition, to the tests at −20 °C, the increase of Young's modulus can be properly observed, under high strain rates. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48778.     

Can crisis management teams mitigate COVID-19's effects? A comparative case study between China and the United States

The COVID-19 pandemic has been the world's greatest challenge since World War II. As an unprecedented global public health crisis, crisis management teams (CMTs) in the infected countries need to rethink to cope with the similar uncertainty and urgency of the ongoing COVID-19 pandemic. The shared context of COVID-19 allows us to explore a cross-nation study of different constructs and CMT to communicate information about crises with the public effectively. Since the pandemic affected all countries, the comparison is warranted. Can CMTs mitigate the effects of COVID-19? Based on the analysis of China and the US cases, our study explores how shared and common knowledge cognition among crisis responders plays a pivotal role in effective CMTs' communication while technological failures and inadequate information disrupt the system, worsening pandemics like COVID-19. Furthermore, organizational dysfunction, such as institutional fragmentation, regulatory hurdles and bureaucratic arrogance, impede effective communication between CMTs. However, effective coordination and decisive leadership could improve coordination effectiveness and reduce crisis costs.     

Impact of Silicon Foliar Application on the Growth and Physiological Traits of Carthamus tinctorius L. Exposed to Salt Stress

Silicon - Althought safflower is a tolerant crop against many environmental stresses, but its yield and performance reduce under stress. The aim of this experiment was to investigate the effect of...     

Epoxy resin/plasticized carbon black composites. Part II. Correlation among network structure and mechanical properties

The network structure, mechanical properties, and thermal gravimetric of epoxy resin filled with plasticized carbon black (CB) have been studied. The effect of CB concentration on composite morphology as well as cross linking density (n), volume fraction of resin (V_r), degree of crystallinity (X_c), mean gap among conductive particles (g), aspect ratio (F), and mechanical property such as modulus of elasticity (Y_m), hardness (H_A), and elongation at break (EB) have been examined and correlated to establish structure–property relationships. According to the thermal gravimetric analysis, the thermal decomposition of the composite took place at a slightly higher temperature than that of green epoxy. It proved that the inclusion of plasticized CB improves the quality of the network structure and enhances the mechanical properties of the composites. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers.     

Double diffusive Buoyancy-driven flow in a fluid-saturated elliptical annulus with a neural network-based prediction of heat and mass transfer

This paper presents a numerical study of buoyancy-driven double-diffusive convection within an elliptical annulus enclosure filled with a saturated porous medium. An in-house built FORTRAN code has been developed, and computations are carried out in a range of values of Darcy–Rayleigh number Ra_m (10 ≤ Ra_m ≤ 500), Lewis number Le (0.1 ≤ Le ≤ 10), and the ratio of buoyancy forces N (−5 ≤ N ≤ 5). In addition, three methods are used, namely the multi-variable polynomial regression, the group method of data handling (GMDH), and the artificial neural network (ANN) for the predictions of heat and mass transfer rates. First, results are successfully validated with existing numerical and experimental data. Then, the results indicated that temperature and concentration distributions are sensitive to the Lewis number and thermal and mass plumes are developing in proportion to the Lewis number. Two particular values of Lewis number Le = 2.735 and Le = 2.75 captured the flow's transition toward an asymmetric structure with a bifurcation of convective cells. The average Nusselt number tends to have an almost asymptotic value for Le » 5. For the case of aiding buoyancies N > 1, the average Nusselt Number $\overline{\mathit{Nu}}$ decreased by 33% when the Lewis number increased to its maximum value. Then, it increased by 10% when the Lewis number increased to Le = 1 for the case of opposing buoyancies N < 1 and then decreased by 33% when the Lewis number increased to its maximum value., contrary to the behavior of the average Sherwood number $\overline{\mathit{Sh}}$ that increased by 700% for both cases N > 1 and N < 1. New correlations of $\overline{\mathit{Nu}}$, and $\overline{\mathit{Sh}}$ as a function of Ra_m, Le, and N are derived and compared with GMDH and ANN methods, and the ANN method showed higher performance for the prediction of $\overline{\mathit{Nu}}$ and $\overline{\mathit{Sh}}$ with R² exceeding 0.99.     

Research on the Effects of Yttrium on Bismuth Titanate Borosilicate Glass System

Silicon - Glasses with the chemical composition of 52B2O3 – 12SiO2–26Bi2O3 – (10 − x)TiO2 - xY2O3, :(0 ≤ x ≤ 10) prepared...