A study of micro-channel size and spatter dispersion for laser beam micro-milling

During micromachining the accuracy of micro-feature is always a major concern. Using laser beam micro-milling (LBMM) the produced size is generally larger than the input design size. Another important drawback of LBMM is the formation of melt spatter around the feature geometry. The spatter adheres within the premises of the machined feature and influences the machining results, especially the geometry of previously machined features by adhering inside or around the feature. Determination of spatter size is very important when the objective is to produce an array of micro-features such as micro-channels. Thus, the minimum distance between two consecutive micro-features is necessary to be known in order to achieve safe geometry for which the size of spatter plays a significant role. The knowledge of spatter scattering and pre-calculated distance of dispersing spatter could certainly assist the machinist in estimating the safe distance between adjacent micro-channels. In this study, the micro-channel size and average spatter size are studied during the micro-milling of Ti-6AL-4V by Nd:YAG laser beam machining (LBM). Response surface methodology (RSM) has been utilized to plan a set of experiments and mathematical models are proposed to pre-calculate the channel size and spatter dispersion. Finally, the models are validated through confirmatory tests showing an acceptable range of error.     

Experimental Visualization and Investigation of Multiphase Flow Regime Transitions in Two-Dimensional Trickle Bed Reactors

Different flow regimes are known to occur in the interaction of multiphase gas–liquid flows over packed beds of solid particles, such as those observed in trickle bed reactors (TBRs). There are four major flow regimes that are known to occur in downward cocurrent flow in TBRs, namely: trickle, pulse, bubble, and mist flow regimes. In this work, the focus is on macro-scale experimental visualizations and investigations of the flow regimes in a two-dimensional TBR.

Experimental observations are made to investigate the development and transition of these flow regimes over a wide range of liquid and gas velocities. Cylindrical particles are placed between two glass plates that are sealed on the sides, and water and air are injected over them using an injection manifold to simulate multiphase flow in a TBR. A diffused light emitting device (LED) light table is used to illuminate the experimental window, while real time images are obtained using a high-speed camera. Flow maps are reported depicting all four regimes and the transition regions between them. Transition regions occur where the characteristics of more than one flow regime coexist.

The 2D experimental results are then compared with the existing literature data of three dimensional results and found to be in good agreement. Emphasis is placed on the transition between the trickle and pulse regimes, since that is the most important mode of operation in industrial TBRs. It is observed that the change in diameters of the cylindrical particles in a two-dimensional TBR has little effect on the transition between the flow regimes when the porosity of the bed is kept constant.     

Prediction of COVID-19 Pandemic Spread in Kingdom of Saudi Arabia

A significant increase in the number of coronavirus cases can easily be noticed in most of the countries around the world. Inspite of the consistent preventive initiatives being taken to contain the spread of this virus, the unabated increase in the cases is both alarming and intriguing. The role of mathematical models in predicting and estimating the spread of the virus, and identifying various preventive factors dependencies has been found important and effective in most of the previous pandemics like Severe Acute Respiratory Syndrome (SARS) 2003. In this research work, authors have proposed the Susceptible-Infectected-Removed (SIR) model variation in order to forecast the pattern of coronavirus disease (COVID-19) spread for the upcoming eight weeks in perspective of Saudi Arabia. The study has been performed by using SIR model with a proposed simplification using average progression for further estimation of β and γ values for better curve fittings ratios. The predictive results of this study clearly show that under the current public health interventions, there will be an increase in the COVID-19 cases in Saudi Arabia in the next four weeks. Hence, a set of strong health primitives and precautionary measures are recommended in order to avoid and prevent the further spread of COVID-19 in Saudi Arabia.     

A generic demand‐side management model for smart grid

The demand‐side management (DSM) is one of the most important aspects in future smart grids: towards electricity generation cost by minimizing the expensive thermal peak power plants. The DSM greatly affects the individual users' cost and per unit cost. The main objective of this research article is to develop a generic demand‐side management (G‐DSM) model for residential users to reduce peak‐to‐average ratio (PAR), total energy cost, and waiting time of appliances (WTA) along with fast execution of the proposed algorithm. We propose a system architecture and mathematical formulation for total energy cost minimization, PAR reduction, and WTA. The G‐DSM model is based on genetic algorithm (GA) for appliances scheduling and considers 20 users having a combination of appliances with different operational characteristics. Simulation results show the effectiveness of G‐DSM model for both single and multiple user scenarios. Copyright © 2015 John Wiley & Sons, Ltd.     

Statistical modeling and optimization of pretreatment of Bombax ceiba with KOH through Box–​Behnken design of response surface methodology

Bioethanol is considered the cleanest liquid fuel used as a substitute for depleting fossil fuels. Various technologies have been introduced to form bioethanol from lignocellulosic biomass. Seed pods of Bombax ceiba, which are produced and wasted in large amount annually, were used as a source of cellulose. In this study, response surface methodology was used to explore the effects of KOH concentrations, substrate loading, and residence time on cellulose exposure and liberation of reducing sugars (RS), total sugars (TS), and total phenolic compounds from seed pods of B. ceiba. Box–Behnken design with three variables and three levels showed maximum release of total phenolic compounds (394.04 mg/ml) and RS (50.06 mg/ml) corresponding to 3% KOH concentration, 15% substrate level with residence time of 8 h at 121°C, and maximum cellulose exposure (64%), and TS (206.65 mg/ml) liberation was observed at 5% KOH concentration and 10% substrate level at same temperature for same soaking time. While at room temperature maximum cellulose exposed (46%), TS (146.1480 mg/ml), total phenol (300.3901 mg/ml), and RS (9.0075 mg/ml) were observed at 3% KOH, 15% substrate concentration, and 8-h residence time. These results suggested that thermochemical pretreatment is more effective than chemical pretreatment alone. The second-order polynomial equation using analysis of variance was employed for analyzing the results.     

Design and fabrication of electro‐conductive polymer nanocomposites with mechanical and thermal resistance

The commencement of the industrial revolution paved the way for the fabrication of flexible polymers with high‐strength metalloceramics as novel materials of all kinds. Fabricating metal–ceramic/polymer conductive composites is one such dimension followed for the present research work making use of the properties of the three components. Electroless deposition, for permanent metallic coating, was performed to coat Al₂O₃ with metallic Cu followed by the inclusion of the Cu–Al₂O₃ filler into a poly(vinyl chloride) (PVC) matrix. X‐ray diffraction and energy‐dispersive X‐ray studies predicted a prominent growth of metallic Cu crystallites onto Al₂O₃ with an increased average size and variation in elemental composition, respectively, when compared to pristine Al₂O₃. Morphological behaviour via scanning electron microscopy also envisioned uniform Cu coating onto Al₂O₃ and a homogeneous dispersion throughout the polymer matrix. When incorporated into PVC, electrical conductivity analysis highlighted a distinct variation in composite phases from insulating (7.14 × 10^?16 S cm^?1) to semiconducting behaviour (8.33 × 10^?5 S cm^?1) as a function of Cu–Al₂O₃ filler. Mechanical behaviour (tensile strength, Young's modulus and elongation at break) and thermal properties of the prepared composites also indicated a substantial improvement in material strength with Cu–Al₂O₃ incorporation. The enhanced electrical conductivity along with improved thermomechanical status with significant filler–matrix interaction permits the potential usage of such novel composites in a range of state‐of‐the‐art semiconducting electronic devices. © 2018 Society of Chemical Industry     

Development of paracetamol-caffeine co-crystals to improve compressional,formulation and in vivo performance

Paracetamol, a frequently used antipyretic and analgesic drug, has poor compression moldability owing to its low plasticity. In this study, new co-crystals of paracetamol (PCM) with caffeine (as a co-former) were prepared and delineated. Co-crystals exhibited improved compaction and mechanical behavior. A screening study was performed by utilizing a number of methods namely dry grinding, liquid assisted grinding (LAG), solvent evaporation (SE), and anti-solvent addition using various weight ratios of starting materials. LAG and SE were found successful in the screening study. Powders at 1:1 and 2:1 weight ratio of PCM/CAF by LAG and SE, respectively, resulted in the formation of co-crystals. Samples were characterized by PXRD, DSC, and ATR-FTIR techniques. Compressional properties of PCM and developed co-crystals were analyzed by in-die heckle model. Mean yield pressure (Py), an inverse measure of plasticity, obtained from the heckle plots decreased significantly (p?In vitro dissolution studies on tablets also showed enhanced dissolution profiles (～90–97%) in comparison to the tablets of PCM prepared by direct compression (～55%) and wet granulation (～85%) methods. In a single dose sheep model study, co-crystals showed up to twofold increase in AUC and C_max. A significant (p?in vitro and in vivo profile. Enhancement in AUC and C_max of PCM by co-crystallization might suggest the dose reduction and avoidance of side effects.     

Energy management in residential buildings using energy hub approach

Building Simulation - Building-owned micro energy hubs (EHs) usually focus on optimal energy consumption cost and emission, whereas, macro energy hubs (MEHs) mainly concentrate on utility’s...