Electrochemistry of Dihalogenated Nicotonic Acids in Aqueous and Aprotic Media

The electrochemical reduction of several 2,5- and 5,6- dihalonicotinic acids have been studied in dimethyl sulfoxide as well as in aqueous buffers of different pH. The polarographic half-wave potentials for the reduction of these compounds in both media are reported here. The compounds appear to reduce at the carboxyl group. The presence of halogen atoms on the pyridine ring facilitates reduction

A Modified Algorithm of Improved Explicit Euler’s Method To Solve Initial Value Problems.

Details can be found in the PDF of the article

Oxidation-Reduction Characteristics of Chlorophenols in an Aprotic Medium

Eighteen chlorophenols, containing from one to five chlorine atoms on the benzene ring at various positions, have been studied by cyclic voltammetric methods to evaluate their oxidation-reduction characteristics in an aprotic medium. The compounds were dissolved in dimethylsulfoxide containing 0.10 M tetrabutylammonium perchlorate as the supporting electrolyte and were then both oxidized and reduced on a glassy carbon electrode. The results indicate that phenols oxidize in a one-step process to phenoxium ion which dimerizes to quinone ether. The ether can be reduced back to phenol in a two-step reduction process. The oxidation potential of the chlorophenols varies with the number and the position of the chlorine substitution. It may also have a relationship with the toxicity of the compound. The main purpose of this study is to understand low chlorophenols, classified as environmental pollutants for their toxicity and carcinogenicity, are oxidized by cytochrome P450 in the metabolic activation process in living systems

Analysis of Inertia Effect on Axisymmetric Squeeze Flow of Slightly Viscoelastic Fluid Film between Two Disks by Recursive Approach

In this study, we analyzed the inertia effect on the axisymmetric squeeze flow of slightly viscoelastic fluid film between two disks. A system of nonlinear partial differential equations (PDEs) in cylindrical coordinates, along with nonhomogenous boundary conditions, illustrates the phenomenon of fluid flow caused by squeezing with the inertia effect. The Langlois recursive approach was applied to obtain the analytical solution of the system having a stream function, axial and radial velocities, pressure distribution, normal and tangential stresses and normal squeeze force. These flow variables are also portrayed graphically to describe the effects of the Reynolds number and slightly viscoelastic parameter. The results show that by increasing the Reynolds number, the velocity profile decreases, and both the pressure distribution and shear stresses increase. Moreover, there is a small increase in normal squeeze force. When the slightly viscoelastic parameter approaches zero, the obtained solution of flow variables matches with the classical results. This study can be applied to understand the mechanism of load-bearing features in thrust bearings and in arthrodial human joint (knee and hip) diseases.Basque Government Grants IT1555-22 and KK-2022/00090; and MCIN/AEI 269.10.13039/501100011033 for Grant PID2021-1235430B-C21/C22

Racemic methyl 3,10-dioxa-2-aza­tri­cyclo­[6.2.1.02,6]undecane-4-carboxyl­ate

The structure of the racemic title compound, C10H15NO4, consists of a tricyclic skeleton comprising a six-membered piperidine ring and five-membered isoxazolidine and tetra­hydro­furan rings. The piperidine ring adopts a distorted chair conformation, while the isoxazolidine and tetra­hydro­furan rings have envelope conformations

Modelling performance of ocean-thermal energy conversion cycle according to different working fluids

Ocean Thermal Energy Conversion (OTEC) is a promising renewable energy technology with the concept to harness the energy stored at the surface seawater (SSW) and the cold deep seawater (DSW). The operation is based on the Rankine cycle, and involves at a minimum temperature difference of 20 K of the SSW and DSW to generate electricity. This research focuses on the economic efficiency of different working fluids used in the OTEC Rankine cycle. The various working fluids include ammonia, ammonia-water mixture (0.9), propane, R22, R32, R134a, R143a, and R410a. Most of the existing commercial OTEC systems use ammonia as the working medium despite its toxic nature. This study shows that the ammonia-water mixture still gives the best results in terms of heat transfer characteristics because of its greater transport properties and stability compared to other fluids. However, fluids such as propane and R32 can also be used as a substitute for ammonia-water mixture despite having slightly lower efficiency, because they are non-toxic and safer towards the environment. The same developmental model was used to present the proposed modified OTEC Rankine cycle, which shows a 4% increase in thermal cycle efficiency. This study reveals economically efficient and environmentally friendly working fluids

Flow induced vibration of a square cylinder with high scruton number

Flow over a square cylinder is numerically studied to understand the effect of reduced velocity to the transverse oscillation under the influence of high Scruton number elastic system of 4.316. For low reduced velocities, the transverse oscillation behavior can be grouped in the initial branch region. In this region, the motion is mainly controlled by the lift fluctuation. For intermediate reduced velocities, the transverse oscillation behavior is grouped in the lower branch region. In this region, its natural frequency slowly becomes significant. For high reduced velocities, the galloping region is observed. In this region, the natural frequency dominated the shape of the amplitude oscillation

Aerodynamics characteristics around simplified high speed train model under the effect of crosswinds

The aerodynamics problems of train commonly come when the flow pass through train body. The increasing speed of train to achieve highly technology demands has led to increase the forces and moments and increase sensitivity of train stability and may cause the train to overturn. In this paper, two prisms arranged in tandem represent a simplified model of high speed train are performed at different yaw angle ranging from 0° to 90° by using the unsteady Reynolds- Averaged Navier Stokes (URANS) equation combined with k-ω SST turbulence model. The Reynolds number is 3.14x105based on height of the train and the free stream velocity. The aerodynamic quantities such as the side force, lift force and drag force coefficient show a similar trend where the forces increase with the yaw angle until a certain critical yaw angle before start to decrease till the yaw angle of 90°. The flow structure around the train under the effect of crosswind is visualized. The vorticiticy start to form from the nose and slowly drifts away further towards the trailing edge. The two-dimensional mean streamlines on the cross-section of train at different yaw angle show that the size of vortex increase as the yaw angle increase. Time averaged pressure contour plotted on the cross section along x-axis show the variation of region between high pressure and low pressure region on the leeward and windward side of the train model that may cause train to overturn. © 2006-2017 Asian Research Publishing Network (ARPN)

Aerodynamics characteristics around simplified high speed train model under the effect of crosswinds

The aerodynamics problems of train commonly come when the flow pass through train body. The increasing speed of train to achieve highly technology demands has led to increase the forces and moments and increase sensitivity of train stability and may cause the train to overturn. In this paper, two prisms arranged in tandem represent a simplified model of high speed train are performed at different yaw angle ranging from 0° to 90° by using the unsteady Reynolds- Averaged Navier Stokes (URANS) equation combined with k-ω SST turbulence model. The Reynolds number is 3.14x105based on height of the train and the free stream velocity. The aerodynamic quantities such as the side force, lift force and drag force coefficient show a similar trend where the forces increase with the yaw angle until a certain critical yaw angle before start to decrease till the yaw angle of 90°. The flow structure around the train under the effect of crosswind is visualized. The vorticiticy start to form from the nose and slowly drifts away further towards the trailing edge. The two-dimensional mean streamlines on the cross-section of train at different yaw angle show that the size of vortex increase as the yaw angle increase. Time averaged pressure contour plotted on the cross section along x-axis show the variation of region between high pressure and low pressure region on the leeward and windward side of the train model that may cause train to overturn. © 2006-2017 Asian Research Publishing Network (ARPN)

Utilizing open source software running in inexpensive high performance computing system for cfd applications

The high cost of conducting research is a significant issue for the successfulness of any research project. For research activities involving flow simulation, the licensing fee for the numerical software and the cost to acquire powerful machine are the main factors contributing to the high cost. This paper reports our experiences in setting up a cost effective way of doing computational fluid dynamics (CFD). The actions involve two areas, i.e., software and hardware. For the software, open source softwares are utilized, particularly the OpenFOAM(r) as the CFD package. For the hardware, a parallel computer made from a cluster of inexpensive desktop computer is constructed. This architecture is found able to meet our requirement in investigating various flow problems that include aeroacoustics, vibration and wind engineering for ventilation