Estimation of stresses in atmospheric ice during aeolian vibration of power transmission lines

Aeolian vibration in bare and iced cable was simulated using the theory of cable vibration. High frequency vibration creates stresses in the cable and consequently in the ice covering that cable, which may result in ice failure and eventually ice shedding. These stresses were estimated in this study. Displacement of the cable during vibration was determined; furthermore, instantaneous wind loads in vertical and transverse directions, additional stresses induced by the motion in the cable and in the atmospheric ice, as well as torque due to cable springback were calculated. In order to simulate the loading conditions of a chunk of atmospheric ice in the middle of a span, a new model was developed using ABAQUS. Results from this model show in spite of high frequency vibration, the resulting level of stress in atmospheric ice is far less than its failure limit. In other words, the atmospheric ice under the condition assumed in this investigation does not shed due to aeolian vibration.     

Power quality impacts of high-penetration electric vehicle stations and renewable energy-based generators on power distribution systems

High-penetration renewable energy-based generators (REGs) in distribution systems have increased the importance of impact assessment involving these systems. This assessment focuses on power quality (PQ) and compatibility between REGs and existing system components. Electric vehicle (EV) technology has also recently achieved a substantial market share. This technology requires the development of charging stations similar to current petroleum fuelling stations in the near future. Thus, the effect of EV stations (EVSs) on PQ must also be considered. This study presents a PQ analysis on the effects of high-penetration EVS and REG systems, including wind turbines, grid-connected photovoltaics (PVs), and fuel cell (FC) power generation units on a modified 16-bus distribution system under different loading and weather conditions. All data on EVS, wind farm, PV, and FC units as well as weather conditions presented in this paper were collected from different power companies and the Malaysian Meteorological Department. The system is modelled and simulated using the MATLAB/Simulink software to study the effects of these technologies on system performances at various penetration levels. Simulation results indicated that the presence of high-penetration EVSs and REGs can cause severe PQ problems such as frequency and voltage fluctuations, voltage drop, harmonic distortion and power factor reduction.     

Characterization of Tribofilms Generated from Serpentine and Commercial Oil Using X-ray Absorption Spectroscopy

The chemical and tribological properties of serpentine particles suspended in lubricating oil were investigated using a pin-on-disk high frequency friction machine at 100 °C. The wear scar width of the upper steel pins was measured by an optical microscope. The tribofilm was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) elemental mapping, and X-ray absorption near-edge structure (XANES) spectroscopy. It was found that the addition of serpentine to commercial engine oil improves its tribological properties. The SEM and EDX elemental mapping shows that a tribofilm formed by the commercial oil with serpentine contains silicon, magnesium, oxygen, phosphorus, sulfur, zinc, calcium, and carbon on the worn surface, which is different from the tribofilm formed by the commercial oil without serpentine. The results of the XANES analysis show that the addition of serpentine to the commercial oil changes the chemical compositions of the tribofilms. This change may account for the better tribological properties of the lubricating oil containing serpentine. The formation mechanism of the tribofilm is discussed.     

Host (nanopores of zeolite Y)-guest (oxovanadium(IV) tetradentate schiff-base complexes) nanocomposite materials: synthesis,characterization and liquid phase hydroxylation of phenol with hydrogen peroxide

Oxovanadium(IV) tetradentate Schiff-base complexes; [VO(X₂-haacac)] (X = H, Cl, CH₃ and NO₂), X₂-haacac = substituted bis(2-hydroxyanil)acetylacetone; and encapsulated in the nanopores of zeolite NaY; [VO(X₂-haacac)]-NaY; have been synthesized and characterized. The host-guest nanocomposite materials; [VO(X₂-haacac)]-NaY; was characterized by chemical analysis and spectroscopic methods (FT-IR, UV/VIS, XRD, BET and DRS). The analytical data indicated a composition corresponding to the mononuclear complex of Schiff-base ligand. The characterization data showed the absence of extraneous complexes, retention of zeolite crystalline structure and encapsulation in the nanopores. Substitution of the aromatic hydrogen atoms of the Schiff-base ligand by electron withdrawing groups like −Cl, and −NO₂ has two major effects: (1) retention and concentration of the oxovanadium(IV) complex in the zeolite cavities is enhanced (due to the larger size of the substituents) and (2) the electronic and spectral properties of the encapsulated complex are modified. Liquid-phase selective hydroxylation of phenol with H₂O₂ to a mixture of catechol and hydroquinone in CH₃CN has been reported using oxovanadium(IV) Schiff-base complexes encapsulated in zeolite-Y as catalysts. Reaction conditions have been optimized by considering the concentration of substrate and oxidant, amount of catalyst, effect of time, volume of solvent and temperature. Under the optimized reaction conditions, [VO((NO₂)₂-haacac)]-NaY has shown the highest conversion of 42.3% after 6 h. All these catalysts are more selective toward catechol formation. Encapsulated oxovanadium(IV) complex is catalytically very efficient as compared to other neat complexes for the hydroxylation of phenol and is stable to be recycled without much deterioration.     

Development of a disposable sensor for electrocatalytic detection of guanine and ss-DNA using a modified sol-gel screen-printed carbon electrode

The electrocatalytic oxidation of guanine and DNA is demonstrated on a sol-gel coated carbon screen printed electrode modified with {MeReO(edt)}₂ using cyclic and differential pulse voltammetric techniques. An oxidation peak at 370 mV was found, but no corresponding reduction peaks could be detected in the negative scan, which indicates that the oxidation of guanine is completely irreversible process. The oxidation peak potentials are shifted to more negative values with increasing pH. The utility of applying the sensor for determination of guanine and ss-DNA were investigated. The linear ranges were 0.19-10.8 and 0.45-7.8 μg ml⁻¹ for guanine and DNA, respectively. Detection limits of 0.1 and 0.32 μg ml⁻¹ were obtained for guanine and ss-DNA, respectively.     

Modification of isotactic polypropylene by the free‐radical grafting of 1,1,1‐trimethylolpropane trimethacrylate

The chemical modification of isotactic polypropylene was performed by the free‐radical‐promoted grafting of 1,1,1‐trimethylolpropane trimethacrylate (TMPTMA) in the presence of dicumyl peroxide (DCP) as the initiator. The reaction was carried out both in a batch internal mixer and in a corotating twin‐screw extruder; the effects of the peroxide and monomer concentrations on the extent of modification in terms of the grafting efficiency and polymer chain structure variations were investigated. The modified samples were characterized with Fourier transform infrared to determine the structure of the grafted groups and the degree of functionalization, with gel permeation chromatography and the melt flow index to evaluate changes in the molecular weight, and with differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis to measure the final thermal properties. In addition, solvent extraction with xylene was performed to highlight the presence of gel and its extent. The structure of the grafted groups was determined, and the number of grafted groups was quantitatively evaluated. The degree of functionalization increased with an increasing TMPTMA/DCP molar ratio. Thermal analysis results hinted at the presence of grafted chains with an increased percentage of TMPTMA. Although degradation reactions predominated at high amounts of peroxide, grafting and branching processes became competitive at high levels of TMPTMA. The balance between competing β‐scission and grafting/branching reactions could be adjusted on the basis of feed conditions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 950–958, 2007     

CFD Modeling of Micromixing and Velocity Distribution in a 1.7‐MHz Tubular Sonoreactor

The effect of high‐frequency (1.7 MHz) ultrasound waves on the mixing rate in a new continuous tubular sonoreactor was investigated by CFD modeling. Modeling of piezoelectric transducer (PZT) vibrations was done based on the dynamic mesh model. Results indicate that the acoustic streams were in the direction of wave propagation and their maximum velocity near the PZT surface agreed well with experimental measurements. The micromixing efficiency of the sonoreactor was studied by adopting the Villermaux/Dushman reaction in the modeling. Comparison of the calculated relative segregation index from modeling results with experimental data revealed reasonable accordance.     

The Effect of Particle Size on the Mechanical and Microstructural Properties of Freeze‐Casted Macroporous Hydroxyapatite Scaffolds

Two different hydroxyapatites with the particle sizes of 3.9 and 1.69 μm were chosen. Slurries with initial hydroxyapatite concentration of 15 vol% were prepared. Different cooling rates from 2 to 14°C/min were utilized. The specimens were sintered at different temperatures of 1250–1350°C. The phase composition (by X‐Ray Diffraction), microstructure (by Scanning Electron Microscopy), mechanical characteristics, and the porosity of sintered samples were assessed. The porosity of the sintered samples was in range of ~57–83%, and the compressive strength varied from ~1.7 to 15 MPa. The mechanical strength of the scaffolds increased as a function of cooling rate and sintering temperature.     

Optical absorption of dilute nitride alloys using self-consistent Green’s function method

We have calculated the optical absorption for InGaNAs and GaNSb using the band anticrossing (BAC) model and a self-consistent Green’s function (SCGF) method. In the BAC model, we include the interaction of isolated and pair N levels with the host matrix conduction and valence bands. In the SCGF approach, we include a full distribution of N states, with non-parabolic conduction and light-hole bands, and parabolic heavy-hole and spin-split-off bands. The comparison with experiments shows that the first model accounts for many features of the absorption spectrum in InGaNAs; including the full distribution of N states improves this agreement. Our calculated absorption spectra for GaNSb alloys predict the band edges correctly but show more features than are seen experimentally. This suggests the presence of more disorder in GaNSb alloys in comparison with InGaNAs.     

Effect of parameters on roll dynamic response of an articulated vehicle carrying liquids

Directional response and roll stability characteristics of a partly filled tractor semi-trailer vehicle, with cylindrical tank, under different parameters and conditions are investigated. The effective parameters and conditions in the stability of a tractor semi-trailer carrying liquid can be considered as filled volume, kinematic viscosity of liquid cargo and vehicle steering input. The dynamic interaction of liquid cargo with the tractor semi-trailer vehicle is evaluated by integrating a dynamic slosh model of the partly filled tank with five-degrees-offreedom of a tractor semi-trailer tank model. The dynamic fluid slosh within the tank is modeled using three-dimensional Navier-Stokes equations, coupled with the volume-of-fluid equations and analyzed using FLUENT software. The coupled tank-vehicle model is subsequently analyzed to determine the roll stability characteristics for different conditions and maneuvers. The results show effects of parameter variations on roll stability of the vehicle carrying liquid and also fluid’s behavior in interaction with a vehicle’s dynamics.