Organically (octyl amine, OA) surface modified electrocatalyst (OA-Pt/CB) was studied for its oxygen reduction reaction (ORR) activity via dc methods and its charge and mass transfer properties were studied via electrochemical impedance spectroscopy (EIS). Comparison with a commercial catalyst (TEC10V30E) with similar Pt content was also carried out. In EIS, both the catalysts showed a single time-constant with an emerging high-frequency semicircle of very small diameter which was fitted using suitable equivalent circuits. The organically modified catalyst showed lower charge-transfer resistance and hence, low polarization resistance in high potential region as compared to the commercial catalyst. The dominance of kinetic processes was observed at 0.925-1.000 V, whereas domination of diffusion based processes was observed at lower potential region for the organic catalyst. No effect due to the presence of carbon was observed in the EIS spectra. Using the hydrodynamic method, higher current penetration depth was obtained for the organically modified catalyst at 1600 rpm. Exchange current density and Tafel slopes for both the electrocatalysts were calculated from the polarization resistance obtained from EIS which was in correlation with the results obtained from dc methods.
Two imines of different molecular sizes namely 3-(phenylimino) indolin-2-one (PII) and 3,3- (1,4-phenylenebis (azan-1-yl-1-ylidene) diindolin-2-one (PDI) were investigated for their corrosion inhibition on mild steel in 1 M HCl solution using electrochemical impedance spectroscopy (EIS). The bigger molecule PDI containing double the amount of isatin moiety exhibited higher inhibition efficiency of 87.3% while PII that contained monoisatin moiety showed a lower inhibition efficiency of 74.8%. Both compounds had an increase in inhibition efficiencies percentage as concentrations increased. Density functional theory (DFT) was used to determine the correlation between the corrosion inhibition efficiency and electronic parameters. The DFT calculations indicated that the corrosion inhibition efficiency was mainly dependant on the frontier orbital energy gap and the chemical softness/hardness of the imines.
The rheological properties, microstructure, textural properties, colour and droplet size distribution of mayonnaise-like emulsion models prepared using 10-30wt.% of palm olein-based diacylglycerol (POL-DAG) oil were compared with those of the control (100wt.% VCO) model. There were significant (P<0.05) differences in the particle size distribution of the oil droplets, the textural properties, and the rheological properties of the various emulsion models. The rheological analysis included the determination of the flow curves, yield stress, thixotropy, apparent viscosity, and viscoelastic parameters. The concentrated oil-in-water (O/W) emulsion with 30wt.% POL-DAG substitution exhibited high thixotropy. The POL-DAG content had a substantial effect on the rheological properties of yield stress, storage modulus (G') and loss modulus (G″). The pseudoplastic behaviour of the emulsions was demonstrated. The size of the particles in the 30% POL-DAG-substituted emulsion was dramatically increased after one day and 30days of storage. All of the emulsion samples with POL-DAG substituted for VCO showed a relatively non-uniform bimodal droplet size distribution after one day of storage. In general, substitution of 10-20wt.% POL-DAG oil is appropriate for preparing O/W emulsions that had flow curves and textural properties similar to those of the control sample.
The observation of Higgs boson production in association with a top quark-antiquark pair is reported, based on a combined analysis of proton-proton collision data at center-of-mass energies of sqrt[s]=7, 8, and 13 TeV, corresponding to integrated luminosities of up to 5.1, 19.7, and 35.9 fb^{-1}, respectively. The data were collected with the CMS detector at the CERN LHC. The results of statistically independent searches for Higgs bosons produced in conjunction with a top quark-antiquark pair and decaying to pairs of W bosons, Z bosons, photons, τ leptons, or bottom quark jets are combined to maximize sensitivity. An excess of events is observed, with a significance of 5.2 standard deviations, over the expectation from the background-only hypothesis. The corresponding expected significance from the standard model for a Higgs boson mass of 125.09 GeV is 4.2 standard deviations. The combined best fit signal strength normalized to the standard model prediction is 1.26_{-0.26}^{+0.31}.
A search for a heavy neutral lepton N of Majorana nature decaying into a W boson and a charged lepton is performed using the CMS detector at the LHC. The targeted signature consists of three prompt charged leptons in any flavor combination of electrons and muons. The data were collected in proton-proton collisions at a center-of-mass energy of 13 TeV, with an integrated luminosity of 35.9 fb^{-1}. The search is performed in the N mass range between 1 GeV and 1.2 TeV. The data are found to be consistent with the expected standard model background. Upper limits are set on the values of |V_{eN}|^{2} and |V_{μN}|^{2}, where V_{ℓN} is the matrix element describing the mixing of N with the standard model neutrino of flavor ℓ. These are the first direct limits for N masses above 500 GeV and the first limits obtained at a hadron collider for N masses below 40 GeV.
Impacts of climate change on the hydrologic processes under future climate change conditions were assessed over Muda and Dungun watersheds of Peninsular Malaysia by means of a coupled regional climate and physically-based hydrology model utilizing an ensemble of future climate change projections. An ensemble of 15 different future climate realizations from coarse resolution global climate models' (GCMs) projections for the 21st century was dynamically downscaled to 6km resolution over Peninsular Malaysia by a regional climate model, which was then coupled with the watershed hydrology model WEHY through the atmospheric boundary layer over Muda and Dungun watersheds. Hydrologic simulations were carried out at hourly increments and at hillslope-scale in order to assess the impacts of climate change on the water balances and flooding conditions in the 21st century. The coupled regional climate and hydrology model was simulated for a duration of 90years for each of the 15 realizations. It is demonstrated that the increase in mean monthly flows due to the impact of expected climate change during 2040-2100 is statistically significant from April to May and from July to October at Muda watershed. Also, the increase in mean monthly flows is shown to be significant in November during 2030-2070 and from November to December during 2070-2100 at Dungun watershed. In other words, the impact of the expected climate change will be significant during the northeast and southwest monsoon seasons at Muda watershed and during the northeast monsoon season at Dungun watershed. Furthermore, the flood frequency analyses for both watersheds indicated an overall increasing trend in the second half of the 21st century.
Substitutional clusters of multiple light element dopants are a promising route to the elusive shallow donor in diamond. To understand the behaviour of co-dopants, this report presents an extensive first principles study of possible clusters of boron and nitrogen. We use periodic hybrid density functional calculations to predict the geometry, stability and electronic excitation energies of a range of clusters containing up to five N and/or B atoms. Excitation energies from hybrid calculations are compared to those from the empirical marker method, and are in good agreement.
When a boron-rich or nitrogen-rich cluster consists of 3 - 5 atoms, the minority dopant element - a nitrogen or boron atom respectively - can be in either a central or peripheral position. We find B-rich clusters are most stable when N sits centrally, whereas N-rich clusters are most stable with B in a peripheral position. In the former case, excitation energies mimic those of the single boron acceptor, while the latter produce deep levels in the band-gap. Implications for probable clusters that would arise in high-pressure high-temperature (HPHT) co-doped diamond and their properties are discussed.
The χ_{b1}(3P) and χ_{b2}(3P) states are observed through their ϒ(3S)γ decays, using an event sample of proton-proton collisions collected by the CMS experiment at the CERN LHC. The data were collected at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 80.0 fb^{-1}. The ϒ(3S) mesons are identified through their dimuon decay channel, while the low-energy photons are detected after converting to e^{+}e^{-} pairs in the silicon tracker, leading to a χ_{b}(3P) mass resolution of 2.2 MeV. This is the first time that the J=1 and 2 states are well resolved and their masses individually measured: 10513.42±0.41(stat)±0.18(syst) MeV and 10524.02±0.57(stat)±0.18(syst) MeV; they are determined with respect to the world-average value of the ϒ(3S) mass, which has an uncertainty of 0.5 MeV. The mass splitting is measured to be 10.60±0.64(stat)±0.17(syst) MeV.
The elliptic azimuthal anisotropy coefficient (v_{2}) is measured for charm (D^{0}) and strange (K_{S}^{0}, Λ, Ξ^{-}, and Ω^{-}) hadrons, using a data sample of p+Pb collisions collected by the CMS experiment, at a nucleon-nucleon center-of-mass energy of sqrt[s_{NN}]=8.16 TeV. A significant positive v_{2} signal from long-range azimuthal correlations is observed for all particle species in high-multiplicity p+Pb collisions. The measurement represents the first observation of possible long-range collectivity for open heavy flavor hadrons in small systems. The results suggest that charm quarks have a smaller v_{2} than the lighter quarks, probably reflecting a weaker collective behavior. This effect is not seen in the larger PbPb collision system at sqrt[s_{NN}]=5.02 TeV, also presented.
This paper investigates the field-dependent rheological properties of magnetorheological (MR) fluid used to fill in MR dampers after long-term cyclic operation. For testing purposes, a meandering MR valve was customized to create a double-ended MR damper in which MR fluid flowed inside the valve due to the magnetic flux density. The test was conducted for 170,000 cycles using a fatigue dynamic testing machine which has 20 mm of stroke length and 0.4 Hz of frequency. Firstly, the damping force was investigated as the number of operating cycles increased. Secondly, the change in viscosity of the MR fluid was identified as in-use thickening (IUT). Finally, the morphological observation of MR particles was undertaken before and after the long-term operation. From these tests, it was demonstrated that the damping force increased as the number of operating cycles increases, both when the damper is turn on (on-state) and off (off-state). It is also observed that the particle size and shape changed due to the long operation, showing irregular particles.
A novel dual-pulse actuation voltage that reduces dielectric charging in micro-electromechanical system (MEMS) switch and thus leading to a longer switch lifetime, are shown to simultaneously mitigate MEMS switch contact bouncing. A simple mass-spring-damper mathematical model is used to simulate movement of the switch contact as the excitation voltage is applied. The model shows that the novel dual-pulse voltages damped the acceleration of the switch membrane as it approaches the contact point, eventually slowing it down and minimizes the impact force. This has the effect of minimizing the occurrence of contact bouncing. Practical experiment on the commercial TeraVicta TT712-68CSP MEMS switch corroborates that the novel excitation voltages reduced bouncing.
An electron beam (EB) flue gas test rig and a dielectric barrier discharge (DBD) reactor were tested for the removal of nitric oxide (NO) from gas stream in separate experiments. In both systems, energised electrons were used to produce radicals that reacted with the pollutants. The EB system was a laboratory scale test rig used to treat emission from a diesel run generator. At 1.0 MeV and 10 mA more than 90% NO removal from flue gases flowing at 120 Nm3/h can be achieved. For higher removal percentage, higher beam current was required. In a related effort, a table top, two tubes DBD reactor was used to process bottled gases containing 106 ppm NO. Total removal (>99%) was achieved when the inlet gas contained only NO and N2. Additional SO2 in the in let gas stream lowered the removal rate but was overcame by scaling up the system to 10 DBD tubes. The system was operated with input AC voltage of 35 kV peak to peak. In the EB treatment system, the amount of NO2 increased at high beam current, showing that the NO was also oxidised in the process. Whereas in the DBD reactor, the amount of NO2 remained insignificant throughout the process. This leads to the conclusion that the DBD reactor is capable of producing total removal of NO. This is highly desirable as post treatment will not be necessary.
In this paper, we report the effect of BaAl2O4 addition (0-30 wt. %) on power consumption and oxygen sensing response of hot-spots developed on short Er123 ceramic rods of around 12 mm length synthesized using standard solid-state reaction. All the sensor rods showed increase in output current with increasing voltage followed by sudden reduction in output current and appearance of hot spot. After appearance of hot spot, for each rod, output current was observed to decrease gradually with increasing voltage with the slope of the I-V curve gradually approaching zero. Output current after the hot spot formation showed sensitivity to oxygen partial pressure, pO2 between 1 to 100 kPa. Addition of 30 wt. % BaAl2O4 reduced the fluctuation of current and increased the sensitivity for pO2 below 10 kPa. In addition, overshoot current was also reduced and resulted in improvement of response time from around 10 s to 5 s. Our result also showed that minimum power consumption was significantly reduced in the Er123 rods with 30 wt. % BaAl2O4.
The suction between soil particles is the basis and core problem in the study of unsaturated soil. However, is the suction between soil particles just the matrix suction (which has been widely used since the discipline of unsaturated soil mechanics was established). In fact, the concept of matrix suction is from soil science and reflects the water-absorbing capacity of the soil. Matrix suction characterizes the interaction between soil particles and pore water rather than the interactions between soil particles, which were not in conformity with the principle of effective stress of soils. The suction of unsaturated soil, in essence, is the intergranular suction composed of absorbed suction and structural suction. In this paper, first, the basic concepts of absorbed suction and structural suction were briefly introduced. Then, with soil mechanics, powder science, crystal chemistry, granular material mechanics and other related disciplines of knowledge for reference, the quantitative calculation formulas were theoretically deduced for the absorbed suction for equal-sized and unequal-sized unsaturated soil particles with arbitrary packing and the variable structural suction for equal-sized unsaturated soil particles with arbitrary packing and unequal-sized unsaturated soil particles with close tetrahedral packing. The factors that influence these equations were discussed. Then, the shear strength theory of unsaturated soil was established based on the theory of intergranular suction through the analysis of the effective stress principle of unsaturated soil. This study demonstrates that the shear strength of unsaturated soil consists of three parts: The effective cohesive force, the additional strength caused by external loads and the strength caused by intergranular suction. The contribution of the three parts to the shear strength of unsaturated soil depends on the following influence factors: Soil type, confining pressure, water content and density. Therefore, these factors must be comprehensively considered when determining the strength of an unsaturated soil.
The steady laminar combined convective flow with heat and mass transfer of a Newtonian viscous incompressible fluid over a permeable flat plate with linear hydrodynamic and thermal slips has been investigated numerically. The velocity of the external flow, the suction/injection velocity and the temperature of the plate surface are assumed to vary nonlinearly following the power law with the distance along the plate from the origin. Lie group analysis is used to develop the similarity transformations and the governing momentum, the energy conservation and the mass conservation equations are converted to a system of coupled nonlinear ordinary differential equations with the associated boundary conditions. The resulting equations are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order numerical method. The effects of hydrodynamic slip parameter (a), thermal slip parameter (b), suction/injection parameter (fw), power law parameter (m), buoyancy ratio parameter (N), Prandtl number (Pr) and Schmidt number (Sc) on the fluid flow, heat transfer and mass transfer characteristics are investigated and presented graphically. We have also shown the effects of the Reynolds number (Re) and the power law parameter (m) on the velocity slip and the thermal slip factors. Good agreement is found between the numerical results of the present paper and published results.
A steady laminar mixed convection boundary layer flow about an isothermal solid sphere embedded in a porous medium filled with a nanofluid has been studied for both cases of assisting and opposing flows. The transformed boundary layer equations were solved numerically using an implicit finite-difference scheme. Three different types of nanoparticles, namely Cu, Al2O3 and TiO2 in water-based fluid were considered. Numerical solutions were obtained for the skin friction coefficient, the velocity and temperature profiles. The features of the flow and heat transfer characteristics for various values of the nanoparticle volume fraction and the mixed convection parameters were analyzed and discussed.
Aluminum foams were fabricated by sintering dissolution process (SDP) using sodium chloride (NaCl) as space holder. The compositions of space holder, used in this study were 40 and 60 wt. % with different dissolution times; 1, 2 and 3 h. The effect of different dissolution times on compressive behavior and energy absorption of foams were evaluated. The result showed that by increasing space holder and dissolution times, energy absorption capability increases. For aluminum foam contains 60 wt. % NaCl, longer dissolution times resulted in thinner cell wall and cell structure become more unstable which lead to lower plateau region.
Three different designs of heat exchanger, V-groove, honeycomb and stainless steel wool had been tested to study their effectiveness in improving the overall performance of a photovoltaic/thermal (PV/T) air base solar collector. Heat exchangers were installed horizontally into the channel located at the back side of the PV module. The system was tested at irradiance of 828 W/m2 with mass flow rate spanning from 0.02 kg/s to 0.13 kg/s. It was observed that at mass flow rate of 0.11 kg/s, the maximum thermal efficiency of the system with V-groove is 71%, stainless steel wool is 86% and honeycomb is 87%. The electrical efficiency of the systems is 7.04%, 6.88% and 7.13%, respectively. The experimental results showed that honeycomb design is the most efficient design as heat exchanger. The design which is simple and compact is suitable for building integration.
A series of (Li20)x(B203)1-x has been synthesized with mole fraction x=0.10, 0.15,020,025 and 0.30 mol% using melt quenching method. The structure of the glass system was determined by FTIR and X-ray diffraction. The density and molar volume were determined and the density increases with Li20 content whereas molar volume decreases with Li20. Refractive index of glass samples were measured by ellipsometer. Refractive index increases with increase of Li20. The absorption spectra of the studied glass showed that position of fundamental absorption edge shifts to longer wavelength with Li20. Optical band gap varies from 0.10 to 222 eV and Urbach energy varies from 2.91 to 1.55 eV. The variation in optical band gap and Urbach energy were due to the variation in the glass structure.
In the present study, we report the size distribution study on the iron oxide (Fe304) magnetic nanocrystals (Ncs), which have been synthesized by using green chemistry approach with palm-oil based carboxylic compound (oleic acid) as capping ligands . The Fe304 Ncs were prepared by one pot reaction under non-hydrolytic approach. With the assistance of oleic acid that plays the role as effective capping-ligands , we showed that the Fe304 NCs that are highly monodispersed in size and shape can be synthesized by scrupulously controlling the reaction time. The diameter of Fe304 Ncs can be tuned within the range of 4.0-18.0 nm and exhibit very uniform morphology, which are spherical in shape. Current synthetic approach offers a cheap, environmentally benign and excellent repeatability route in large-scale production of high-quality magnetic Fe304 Ncs if compared to the preceding reports.