The Evolution of Asymmetries in the Tropical Cyclone Boundary Layer Wind Field during Landfall

The evolution of the tropical cyclone boundary layer (TCBL) wind field before landfall is examined in this study. As noted in previous studies, a typical TCBL wind structure over the ocean features a supergradient boundary layer jet to the left of motion and Earth-relative maximum winds to the right. However, the detailed response of the wind field to frictional convergence at the coastline is less well known. Here, idealized numerical simulations reveal an increase in the offshore radial and vertical velocities beginning once the TC is roughly 200 km offshore. This increase in the radial velocity is attributed to the sudden decrease in frictional stress once the highly agradient flow crosses the offshore coastline. Enhanced advection of angular momentum by the secondary circulation forces a strengthening of the supergradient jet near the top of the TCBL. Sensitivity experiments reveal that the coastal roughness discontinuity dominates the friction asymmetry due to motion. Additionally, increasing the inland roughness through increasing the aerodynamic roughness length enhances the observed asymmetries. Lastly, a brief analysis of in-situ surface wind data collected during the landfall of three Gulf of Mexico hurricanes is provided and compared to the idealized simulations. Despite the limited in-situ data, the observations generally support the simulations. The results here imply that assumptions about the TCBL wind field based on observations from over horizontally-homogeneous surface types - which have been well-documented by previous studies - are inappropriate for use near strong frictional heterogeneity.

Ridge-type roughness: from turbulent channel flow to internal combustion engine

While existing engineering tools enable us to predict how homogeneous surface roughness alters drag and heat transfer of near-wall turbulent flows to a certain extent, these tools cannot be reliably applied for heterogeneous rough surfaces. Nevertheless, heterogeneous roughness is a key feature of many applications. In the present work we focus on spanwise heterogeneous roughness, which is known to introduce large-scale secondary motions that can strongly alter the near-wall turbulent flow. While these secondary motions are mostly investigated in canonical turbulent shear flows, we show that ridge-type roughness—one of the two widely investigated types of spanwise heterogeneous roughness—also induces secondary motions in the turbulent flow inside a combustion engine. This indicates that large scale secondary motions can also be found in technical flows, which neither represent classical turbulent equilibrium boundary layers nor are in a statistically steady state. In addition, as the first step towards improved drag predictions for heterogeneous rough surfaces, the Reynolds number dependency of the friction factor for ridge-type roughness is presented. Graphic abstract

Experimental assessment on preparation of biodegradable polythylene/polylatic acid-chithosan composite from renewable resources

Due to poor degradability and contamination risk of synthetic plastics, utilization of renewable resources is encouraged. Biobased thermoplastic polymers from renewable resource that is inexpensive, biodegradable, compostable and renewably non-toxic, is focused. In this paper mixtures of synthetic and natural polymers were used as a potential option to reduce pollution by plastic waste. The study is aimed at assessing utilization of sweet potato waste as a source of bioplastic for package application, the polymer was modified with a biopolymer chitosan to obtain polylactic acid-chitosan plastic. The developed polymer matrix was blended with polyethylene to obtain biodegradable packaging material. The bioplastic was characterized using Fourier Transformed Infra-Red Spectroscopy (FTIR) and scaning electron microscope (SEM). Physical and mechanical properties of the composites were evaluated by measuring enzymatic degradation, tensile strength, and elongation at break. The results have shown that the film obtained have homogeneous surface by (SEM). Mechanical properties of the bio plastics revealed that tensile strength increases with increases in the concentration of chitosan and hence, the elongation at break decreases with increase in chitosan content. While the fastest enzymatic degradation was observed to have high microbial growth on the bio plastics with high content of Chitosan-Polylactic acid.

Blending Ratio Effect of ZnPc/ZnO Hybrid Nanocomposite on Surface Morphology and Structural Properties

Recently, organic/inorganic hybrid nanocomposites being the future in electronic applications. In this paper, we have investigated hybrid nanocomposite zinc phthalocyanine (ZnPc)/zinc oxide nanoparticles (ZnO). ZnPc/ZnO hybrid nanocomposites were prepared with different ratios (wt/wt) (1/0), (0/1), (0.75/0.25), (0.5/0.5), (0.25/0.75), and, deposited on glass substrates by spin coating technique. X-Ray diffraction investigate the structural of ZnPc/ZnO thin films and studied the morphological properties using field emission scan electron microscopy, the surface of ZnPc/ZnO hybrid nanocomposites shows the presence of nanorod-like structures represented the organic material (ZnPc) and spherical nanoparticles for (ZnO), that is depending on the ratio of the blend. In ratio (0.5/0.5) we get the preferred homogeneous surface between like-nanorod and spherical shapes were show various properties from pure compounds which used to prepare the blend. The distribution of ZnO nanoparticles on ZnPc particles nanorods led to the disappearance feature of ZnO morphological characterize and ZnPc decorated was dominated on the hybrid nanocomposite structure.

Design and implementation of an illumination system to mimic skyglow at ecosystem level in a large-scale lake enclosure facility

Light pollution is an environmental stressor of global extent that is growing exponentially in area and intensity. Artificial skyglow, a form of light pollution with large range, is hypothesized to have environmental impact at ecosystem level. However, testing the impact of skyglow at large scales and in a controlled fashion under in situ conditions has remained elusive so far. Here we present the first experimental setup to mimic skyglow at ecosystem level outdoors in an aquatic environment. Spatially diffuse and homogeneous surface illumination that is adjustable between 0.01 and 10 lx, resembling rural to urban skyglow levels, was achieved with white light-emitting diodes at a large-scale lake enclosure facility. The illumination system was enabled by optical modeling with Monte-Carlo raytracing and validated by measurements. Our method can be adapted to other outdoor and indoor skyglow experiments, urgently needed to understand the impact of skyglow on ecosystems.

Synthesis of Adsorbent from Bagasse for Methylene Blue Adsorption

The ability of bagasse adsorbents to adsorb methylene blue without activation using 0.5 M H2SO4 solution was examined. Methylene blue is widely used in the textile industry because it produces bright colors, and the dyeing process is fast and easy. This research aims to determine the optimum adsorption conditions, namely the variations in contact time, dye concentration, adsorbent mass, and pH effect on methylene blue, which were carried out using the batch method. Furthermore, the adsorbents were characterized by FT-IR and SEM. The optimum state of the bagasse adsorbent to adsorb methylene blue dye has a mass of 0.5 grams, a contact time of 30 minutes, a concentration of 50 ppm, and a pH of 5. The character of the adsorbent after activation with H2SO4 was better than without activation. The highest adsorption efficiency of methylene blue dye in the batch method was 99.67%. The FTIR spectrum of the bagasse adsorbent showed OH, C-H, C=O, C=C, and C-O functional groups. The adsorption isotherm model for methylene blue dye follows the Langmuir isotherm since the graph obtained is linear with the correlation coefficient (R2) = 1, where the adsorbent has a homogeneous surface.

A reusable mesoporous adsorbent for efficient treatment of hazardous triphenylmethane dye wastewater: RSM-CCD optimization and rapid microwave-assisted regeneration

In this research, mesoporous calcium aluminate nanostructures (meso-CaAl2O4) were synthesized using a citric acid-assisted sol–gel auto-combustion process as the potential adsorbent to eliminate toxic triphenylmethane dye malachite green (MG) from synthetic/real effluent. The surface morphology of meso-CaAl2O4 was highly porous with nanometric size and non-homogeneous surface. The specific surface area, total pore volume, and BJH pore diameter of meso-CaAl2O4 were 148.5 m2 g−1, 1.39 cm3 g−1, and 19 nm, respectively. The meso-CaAl2O4 also showed a very high heat resistance, due to losing only 7.95% of its weight up to 800 °C, which is mainly related to the moisture loss. The optimal adsorption conditions were obtained based on response surface methods (RSM)-central composite design (CCD) techniques. The Langmuir isotherm model was used for fitting the adsorption measurements, which presented 587.5 mg g–1 as the maximum adsorption capacity of the dye. The data obtained from the adsorption kinetics model were found to correspond to the pseudo-second-order model. Also, the thermodynamic parameters including enthalpy change (ΔH°), entropy change (ΔS°), and Gibbs free energy change (ΔG°) indicated that MG dye adsorption by the meso-CaAl2O4 was feasible, endothermic, and occurred spontaneously. Furthermore, the meso-CaAl2O4 was regenerated by microwave irradiation under 900 W at 6 min, and the MG dye removal efficiency was remained over 90% after the five cycles of microwave regeneration.

Environmentally Friendly Polyvinyl alcohol−alginate/bentonite Nanocomposite Hydrogel Beads as Efficient Adsorbents for Removal of Toxic Methylene Blue from Aqueous Solution

Hazardous chemicals like toxic organic dyes are very harmful to the environment and their removal is quite challenging. Therefore there is a necessity to develop techniques, which are environment friendly, cost-effective and easily available in nature for water purification and re-mediation. The present research work is focused on the development` and characterization of the ecofriendly polyvinyl alcohol (PVA) and alginate (Alg) hydrogel beads incorporating natural bentonite (Bent) clay as beneficial adsorbents for removal of toxic methylene blue (MB) from industrial water. PVA−Alg/Bent nanocomposite hydrogel beads with different Bent content (0, 10, 20, and 30 wt%) were synthesized via external ionic gelation method. The designed porous and steady structure beads were characterized by the use of Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The performance of the beads as MB adsorbents was investigated by treating batch aqueous solutions. The experimental results indicated that the incorporation of Bent (30 w%) in the nanocomposite formulation sustained porous structure, preserved water uptake, and increased MB removal effi-ciency by 230 % compared to empty beads. Designed beads possessed higher affinity to MB at high pH 8, 30 °C, and fitted well to pseudo-second-order kinetic model a high correlation coefficient. Moreover, designed beads had a good stability and reusability as they exhibited excellent removal efficiency (90%) after six consecutive adsorption-desorption cycles. Adsorption process was found be combination of both monolayer adsorption on homogeneous surface and multilayer adsorption on heterogeneous surface. The maximum adsorption capacity of the designed beads system as calculated by Langmuir isotherm was found to be 51.34 mg/g, which is in good agreement with the reported clay-related adsorbents. The designed PVA−Alg/Bent nanocomposite hydrogel beads demonstrated good adsorbent properties and could be potentially used for MB removal from polluted water.

Defluoridation of Groundwater Using Formaldehyde-Treated Agricultural Waste - Wheat, Oats, And Pea Straw

The present study investigates the potential of acid-treated agricultural waste (Wheat, Oat, and Pea straw) for the defluoridation of groundwater following the chemical treatment using formaldehyde in 1:5 w/v ratio at 50℃. The effects of operational parameters (pH, dose, time, and initial fluoride concentration) were investigated in the batch mode. Response surface methodology (RSM) was employed to predicted and validated the experimental findings. The efficiency of developed adsorbents was compared with commercially available activated carbon (CAC) and found suitable for working at neutral pH conditions. The better applicability of Langmuir isotherm on adsorption data reflects monolayer adsorption over the homogeneous surface of adsorbents. Further, the experimental data can better be modeled by the pseudo-second-order kinetics (R2 = 0.996). The simple synthesis technique and massive raw material availability made these adsorbents a promising and cost-effective tecnhiqe for removing the fluoride from groundwater.

Evaluation of Nb2O5 Ceramic Nanofibers Efficacy to Promote CO2 Photoconversion

The increase in global warming due to NOx, CO2, and CH4 harmfully different ecosystems and significantly prejudice world life. A promising methodology in this sense is the pollutant conversion into valuable chemicals from photocatalytic processes by reusable photocatalyst. In this way, the present work aimed to produce a Nb2O5 photocatalyst nanofibers system to convert CO2 by the electrospinning method. Based on the collected data, the nanofibers calcination at 600°C for 2 h resulted in the best condition to obtain a homogeneous surface with an average diameter of 84 nm. As a result, the Nb2O5 nanofibers converted CO2 mostly into CO and CH4, reaching values around 8.5 μmol g−1 and 0.55 μmol g−1, respectively.