Additive Manufacturing of Porous Structures for Unmanned Aerial Vehicles Applications

Unmanned aerial vehicles (UAVs) have shown promising benefits in many applications. This has been enabled by the emergence of additive manufacturing (AM), which give the designers a large amount of geometrical freedom. In this paper, a novel design process of fused deposition modeling (FDM) combining both topology and infill optimization is introduced for AM of high performance porous structures. Tensile testing of FDM printed samples is first carried out to study the effect of the build orientation on the mechanical properties of acrylonitrile butadiene styrene (ABS) samples. It is found that samples built perpendicular to the load axis are the weakest with a tensile strength of 29 MPa and Young's modulus of 1960 MPa. The materials properties are fed to the finite elements analysis (FEA) for geometrical topology optimization, aiming to maximize stiffness and reduce weight of those parts. Afterwards, an infill optimization is carried out on the topology optimized parts using different mesostructures such as honeycomb, triangular, and rectangular to achieve high structural performance. The results showed that triangular pattern with 50% infill density had the lowest developed stresses, less mass, and strain energy when compared to other structures. Optimum UAVs parts of a quadcopter are successfully manufactured, assembled, and tested.

     

Hyperparameter Tuned Deep Learning Enabled Cyberbullying Classification in Social Media

Cyberbullying (CB) is a challenging issue in social media and it becomes important to effectively identify the occurrence of CB. The recently developed deep learning (DL) models pave the way to design CB classifier models with maximum performance. At the same time, optimal hyperparameter tuning process plays a vital role to enhance overall results. This study introduces a Teacher Learning Genetic Optimization with Deep Learning Enabled Cyberbullying Classification (TLGODL-CBC) model in Social Media. The proposed TLGODL-CBC model intends to identify the existence and non-existence of CB in social media context. Initially, the input data is cleaned and pre-processed to make it compatible for further processing. Followed by, independent recurrent autoencoder (IRAE) model is utilized for the recognition and classification of CBs. Finally, the TLGO algorithm is used to optimally adjust the parameters related to the IRAE model and shows the novelty of the work. To assuring the improved outcomes of the TLGODL-CBC approach, a wide range of simulations are executed and the outcomes are investigated under several aspects. The simulation outcomes make sure the improvements of the TLGODL-CBC model over recent approaches.     

Predicting the Crushing Behavior of Axially Loaded Elliptical Composite Tubes Using Artificial Neural Networks

In this research work, the artificial neural networks (ANN) technique is used in predicting the crushing behavior and energy absorption characteristics of axially-loaded glass fiber/epoxy composite elliptical tubes. Predictions are compared to actual experimental results obtained from the literature and are shown to be in good agreement. Effects of parameters such as network architecture, number of hidden layers and number of neurons per hidden layer are also considered. The study shows that ANN techniques can effectively be used to predict the crushing response and the energy absorption characteristics of elliptical composite tubes with various ellipticity ratios subjected to axial loading.     

Producing of AA5083/ZrO2 Nanocomposite by Friction Stir Processing (FSP)

In this study, friction stir processing (FSP) was used to produce AA5083/ZrO₂ nanocomposite layer. Optical microscopy and SEM were used to probe the microstructures formed in the composite layer. In addition, the mechanical properties of each sample are characterized using both tensile and hardness tests. Results showed that FSP is an effective process to fabricate AA5083/ZrO₂ nanocomposite layer with uniform distribution of ZrO₂ particles, good interfacial integrity, and significant grain refinement. On processing, in the proper combination of process parameters, the metal matrix composite layer was observed to have increased tensile and hardness properties.     

Can lanthanum doping enhance catalytic performance of silver in direct propylene epoxidation over NaMoAg/SiO_2?

In the attempt to reduce surface free energy of silica to improve interaction of silica with silver, silica was doped by different amounts of low surface energy lanthanum, La_2O_3, through impregnation. The doped and undoped silica were used as supports for preparation of Na/Ag/Mo/La_2O_3-SiO_2 catalysts. Catalytic performances of the catalysts were evaluated in direct epoxidation of propylene(DPO) using molecular oxygen under atmospheric pressure and without adding hydrogen. Adding 5 wt%La to the Na/Ag/Mo/SiO_2 catalyst improves both the catalysts electivity in DPO and its stability over 20h of time-on-stream.The characterization results show that La_2O_3 species interact strongly with silver particles on the silica surface which result in significant improvement in the dispersion profile of silver and marked decrease in the size of silver nanoparticles(AgNPs). The estimated mean diameter of AgNPs is ca. 4.0 nm in Na/Ag/Mo/5 wt%La_2O_3-SiO_2, which is smaller than that(53.9 nm) found in Na/Ag/SiO_2. The presence of subnanometer AgNPs on Ag/La_2O_3-SiO_2 prior addition of MoO_3 and NaCl to the sample can enhance the mutual electronic synergism between Ag, MoO_3 and Na for selective production of propylene oxide.     

Prevalence of Salmonella in broilers at retail outlets, processing plants and farms in Malaysia

A study was conducted to estimate the prevalence of Salmonella among broilers retailed at wet-markets and processing plants. Litter and feed samples obtained from both broiler and breeder farms were also examined for Salmonella. A total of 158 out of 445 (35.5%) and 52 out of 104 (50.0%) broiler carcasses obtained from wet-markets and processing plants were contaminated with Salmonella, respectively. Salmonella was isolated from 14 out of 98 (14.3%) samples of intestinal content. Litter samples from broiler and breeder farms were positive for Salmonella, 8/40 (20%) and 2/10 (20%), respectively. Salmonella isolates (230) belonging to 15 different serovars were isolated. Predominant serovars were S. enteritidis, S. muenchen, S. kentucky and S. blockley.     

Postprocessing techniques for gadolinium-enhanced three-dimensional MR angiography

Contrast material-enhanced three-dimensional (3D) magnetic resonance (MR) angiography is rapidly gaining acceptance as a versatile noninvasive alternative to conventional angiography. The technique has proved useful in the visualization and assessment of complex pathologic entities in the thoracic and abdominal aorta, renal arteries, pelvic arterial system, and pulmonary arteries. Several postprocessing techniques are available for reformation of the imaging data, including maximum intensity projection (MIP), surface rendering, and virtual intraluminal endoscopy (VIE). MIP and subvolume MIP reconstructions can be produced quickly and are useful for demonstration and archiving purposes. Because of its unique ability to display vessels without overlap, surface rendering is especially useful in depicting diseases that influence either the outer shape of the vessels or their topographic arrangement. VIE allows assessment of the inside of the vascular wall and is helpful in detecting wall-bound thrombus and evaluating the degree of stenosis. Most clinically relevant questions (eg, presence of pulmonary embolism, aortic aneurysm, renal artery stenosis) can be fully answered if analysis is based on MIP and thin multiplanar reformations of contrast-enhanced 3D MR angiograms. In some cases, the use of additional postprocessing techniques enhances diagnostic confidence.     

Dynamic modeling and simulation of a riser-type fluid catalytic cracking unit

A dynamic model is developed for a fluid catalytic cracking (FCC) unit to describe the dynamic behavior of both the riser and the regenerator reactors and their interactions. The cracking reactions are simulated by the four-lumped kinetic model [1]. The reactions in the riser occur in a transported bed with the fluid and the solids in ideal plug flow. The two-phase nature of the regenerator-fluidized bed is considered and the kinetic model for the coke combustion on the cracking catalyst [2,3] is incorporated. The proposed model is validated using steady-state plant data from an industrial unit and the results are found to be in good agreement. One of the main advantages of the model is that it does not include any partial differential equations. This facilitates the solution of the equations and makes the model particularly suitable for control studies. Simulation studies are performed to investigate the effect of changing various process variables, such as catalyst circulation rate, gas oil feed rate, and oxygen feed concentration.     

El Niño-Southern Oscillation and Rainfall Variability in Central and Southern Sudan

Abstract

In this study, the effects of the El Niño-Southern Oscillation (ENSO) on the rainfall variability in the central (Savannah) and southern (Equatorial) regions of Sudan are examined. The annual rainfall data from 12 rainfall stations for 49 years are used in this examination. The results of the study show that the areal annual regionally averaged rainfall values in the two regions have decreased markedly since the early 1960s, with co-existence between the driest years and the warm ENSO events. The correlation between the annual regional rainfall values and the ENSO events is found to be relatively higher for the Savannah region than for the Equatorial region. Two regional ENSO-rainfall prediction models are developed, one for each region. These models use the ENSO sea surface temperature. The results of the models test show that both models can significantly improve the predictability of the annual rainfall values, which is essential for the planning and the management of water resources in Sudan