22264 research outputs found
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Build an app and they will come? Lessons learnt from trialling the GetThereBus app in rural communities
No full textReal-time passenger information (RTPI) systems have been identified as having benefits in terms of passenger willingness to travel by public transport and their satisfaction levels with services provided. The lack of this amenity in rural areas, however, may hamper public transport use, thus reinforcing patterns of over-reliance on personal vehicles. To explore the potential impacts of providing RTPI in rural areas, a smartphone application (GetThereBus) was developed to allow rural bus passengers to share real-time public transport data, and access real-time and timetable information. Through user testing of GetThereBus, this work aimed to address questions related to the impact of the limited availability of rural digital infrastructure on the provision of RTPI; the potential for crowdsourced information to supplement published timetable information given digital limitations; and the potential impacts of such a system on the traveller experience. This study describes the GetThereBus development and evaluation phases. The authors found it was possible to design and develop a system that overcame many of the technological limitations experienced in rural areas, and users reported a positive response to the system. However, despite a campaign of user engagement, it proved difficult to recruit and motivate sufficient users to provide the data needed to achieve area-wide coverage
A study of KL1 X-ray satellite spectrum of the elements 27Z31 by photon excitation
No full textK X-ray satellite spectra of Co, Ni, Cu, Zn, and Ga generated by photon excitation are analyzed using a wavelength dispersion spectrometer. Spectra of Ni, Cu, Zn, and Ga are studied for the first time using a LiF420 crystal. Spectrum of Co was studied with LiF200 crystal in second order. KL1 X-ray satellite energies and relative intensities are measured. The energy shifts relative to diagram line are computed and are compared with theoretical and semi-empirical values. Dependence of energy shifts and relative intensities on Z and mode of excitation is analyzed
Friction Hydro-Pillar Processing of a High Carbon Steel: Joint Structure and Properties
No full textA coupled experimental and theoretical study is reported here on friction hydro-pillar processing of AISI 4140 steel, which is a novel solid-state joining technique to repair and fill crack holes in thick-walled components by an external stud. The stud is rotated and forced to fill a crack hole by plastic flow. During the process, frictional heating occurs along the interface of the stud and the wall of crack hole leading to thermal softening of the stud that eases its plastic deformation. The effect of the stud force, its rotational speed and the total processing time on the rate of heat generation and resulting transient temperature field is therefore examined to correlate the processing variables with the joint structure and properties in a systematic and quantitative manner, which is currently scarce in the published literature. The results show that a gentler stud force rate and greater processing time can promote proper filling of the crack hole and facilitate a defect-free joint between the stud and original component
An in situ study on the solid state decomposition of ammonia borane: unmitigated by-product suppression by a naturally abundant layered clay mineral
No full textBorazine is a by-product often encountered in the thermal decomposition of ammonia borane, which leads to an inescapable hindrance towards sustainability and cost effectiveness. In this study, a low cost, low surface area clay mineral, bentonite, was modified and introduced as a support material. Bentonite (42.4 m(2) g(-1)) revealed decomposition characteristics comparable to previously reported high surface area (usually 700-1000 m(2) g(-1)) support materials. In addition, borazine formation from bentonite supported ammonia borane was observed to be completely eliminated. Extensive size strain analysis (Williamson-Hall and Warren-Averbach) indicated that the crystalline parameters were observed to be a considerable factor affecting the dehydrogenation reaction along with the high surface area. However, using in situ XRD and MS characterization, the supported decomposition was attributed to a facile pathway, which was dominated by DADB formation. The proposed pathway justifies the borazine elimination and more steady hydrogen release from AB
Almost global asymptotic stability of a grid-connected synchronous generator
No full textWe study the global asymptotic behavior of a grid-connected constant field current synchronous generator (SG). The grid is regarded as an "infinite bus," i.e., a three-phase AC voltage source. The generator does not include any controller other than the frequency droop loop. This means that the mechanical torque applied to this generator is an affine function of its angular velocity. The negative slope of this function is the frequency droop constant. We derive sufficient conditions on the SG parameters under which there exist exactly two periodic state trajectories for the SG, one stable and another unstable, and for almost all initial states, the state trajectory of the SG converges to the stable periodic trajectory (all the angles are measured modulo ). Along both periodic state trajectories, the angular velocity of the SG is equal to the grid frequency. Our sufficient conditions are easy to check computationally. An important tool in our analysis is an integro-differential equation called the exact swing equation, which resembles a forced pendulum equation and is equivalent to our fourth-order model of the grid-connected SG. Apart from our objective of providing an analytical proof for a global asymptotic behavior observed in a classical dynamical system, a key motivation for this work is the development of synchronverters which are inverters that mimic the behavior of SGs. Understanding the global dynamics of SGs can guide the choice of synchronverter parameters and operation. As an application we find a set of stable nominal parameters for a 500-kW synchronverter
Solution processable truxene based blue emitters: Synthesis, characterization and electroluminescence studies
No full textTruxene (10,15-dihydro-5H-diindeno[ 1,2-a; 1', 2'-c] fluorene) derived blue emitting materials were designed and developed utilizing Suzuki and Buchwald-Hartwig type cross-coupling reactions. The target molecules T-1, T-2 and T-3 bearing N-carbazolyl, 1-pyrenyl and N-phenyl-N-(pyren-1-yl) substituents, respectively at 2,7,12-positions, were synthesized under mild conditions by palladium-catalyzed reactions in good yields. To improve the solution processability of the material, n-hexyl chains were used as substituents at 5,5'-, 10,10'-, 15,15'-positions. From UV-vis measurements, the absorption maxima were found to be at 330 nm for T-1, 356 nm for T-2 and 412 nm for T-3. The materials were found to be blue emitting with their emission maxima at 385 nm, 425 nm and 490 nm for T-1, T-2 and T-3, respectively. The excited state lifetimes were investigated using time correlated single photon counting and were found to be 10 ns, 1.4 ns and 5.4 ns for T-1, T-2 and T-3, respectively. The highest photoluminescence quantum yield was observed in the case of T-2 corresponding to a value of 0.97. The compounds T-2 and T-3 were used as active materials for the fabrication of solution processed, single layer blue light emitting diodes, with low turn-on voltage (2-3.3 V) and Commission Internationale de l'eclairage (CIE) coordinates corresponding to (0.16, 0.23) and (0.17, 0.36) for T-2 and T-3, respectively
Enhanced luminescence and optical performance through strain minimization in self-assembled InAs QDs using dual quaternary-ternary/ternary-quaternary capping
No full textTheoretical simulations are necessary to scientifically progress, envisage and gain the first hand knowledge of the properties of semiconductor quantum dot (QD) structure. The impact of dual ternary-quaternary/quaternary-ternary capping layers on the square based truncated pyramidal InAs QD and their influence on the energy band structure as well as the strain profile has been investigated in this study. A comparative analysis has been demonstrated with binary, ternary and quaternary capping layer counterparts. The capping layers are: GaAs (binary), InGaAs/GaAs (ternary), InAlGaAs/GaAs (quaternary), InGaAs/InAlGaAs/GaAs (dual ternary-quaternary) and InAlGaAs/InGaAs/GaAs (dual quaternary-ternary). The hydrostatic and biaxial strain for all the heterostructures have also been computed and compared. The biaxial strain was highest for the QD capped with InAlGaAs/GaAs and InAlGaAs/InGaAs/GaAs, leading to the red shift of the ground state emission in the photoluminescence (PL) spectrum. The possible absorption peaks were also calculated for all QDs from the electron (EL) and hole (HL) eigenstates. The lowest energy transition (EL1-HL1) at 300 K is near to the communication wavelength for the optimum (InAlGaAs/InGaAs/GaAs capped) QD, which is at 1.35 mu m. The optimized QD heterostructure claimed the highest electrostatic potential of 0.4986 V. This study will be helpful in predicting few optical and electrical characteristics based on the strain distribution inside the structure. The optimized QD structure having a consistent strain profile inside it would render superior luminescence characteristics. Finally, to verify the accuracy of the simulation, the simulated transition peaks at 19 K and 300 K were validated with the experimental PL data, and the percentage error was within 5%
Economic assessment of hydrogen production from solar driven high-temperature steam electrolysis process
No full textA key prerequisite for the hydrogen economy is cost-effective renewable hydrogen supply. This paper provides a framework for the thermodynamic and economic assessment of solar hydrogen production from the high-temperature steam electrolysis (HTSE) route. A system configuration for the solar-driven steam electrolysis plant is proposed. The thermodynamic and economic analysis is done for varying temperature and current density conditions of the solid oxide electrolyzer powered by concentrated solar (CSP) and photovoltaic (PV) power plants. Based on the expected reductions in the cost of plant components, the levelized cost of hydrogen (LCOH2) for the 2030 scenario is evaluated. Conditions for the viability of this route are checked by comparing the results with the polymer electrolyte membrane electrolysis (PEME) process. The optimum energy efficiency of a PV driven process increases from 9.1% at 873 K, 1500 A/m(2) to 12.1% at 1273 K. 8000 A/m(2). For the electrolyzer operating at 873 K, the optimum LCOH2 of 22 /kg at 5000 A/m(2) to 12.1 /kg is achievable if the component costs reduce to 2030 level. Thus, the process has potential to be commercially viable and should be pursued further by creating prototype and pilot scale demonstrations. (C) 2018 Elsevier Ltd. All rights reserved
Engineering interfacial migration by collective tuning of adhesion anisotropy and stiffness
No full textInterfacial migration is central to multiple processes including morphogenesis and wound healing. However, the sensitivity of interfacial migration to properties of the interfacial microenvironment has not been adequately explored. Here, we address this question by tracking motility of 3T3 fibroblasts at the interface of two hydrogels. By sandwiching cells between two adhesive gels (composed of methacrylated gelatin) or between an adhesive and a non-adhesive gel (composed of gellan), we show that cells are more motile in case of the latter. By tuning the bulk stiffness of the gellan gel, we then show that motility is tuned in a stiffness-dependent manner. Fastest motility observed in case of the stiffest gel was associated with increased cell height, suggestive of stiffness-mediated cytoskeletal assembly. Inhibition of cell motility by contractile agonists and actin depolymerizing drugs is indicative of a mode of migration wherein cells combine contractile tractions exerted at their base and actin-based pushing forces on the top surface to propel themselves forward. Together, our results suggest that dorso-ventral adhesion anisotropy and stiffness can be collectively tuned to engineer interfacial migration. Statement of Significance It is increasingly understood that cells migrate in vivo through confining spaces which typically occur as pores in the matrix and through naturally occurring interfaces that exist between neighbouring ECM fibers, or between the stroma and the vasculature. Such interfaces are also created when treating wounds on the skin surface by covering the wounds with adhesives. How multiple cues impact interfacial migration has not been adequately addressed. By studying cell migratory behaviour at the interface of two hydrogel substrates, we identify adhesivity and stiffness as two critical factors that can be tuned to maximize cell migration. We foresee a potential use of this knowledge in the design of tissue adhesives for wound healing applications. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved
Dissociation cross section for high energy O-2-O-2 collisions
No full textCollision-induced dissociation cross section database for high energy O-2-O-2 collisions (up to 30 eV) is generated and published using the quasiclassical trajectory method on the singlet, triplet, and quintet spin ground state O-4 potential energy surfaces. At equilibrium conditions, these cross sections predict reaction rate coefficients that match those obtained experimentally. The main advantage of the cross section database based on ab initio computations is in the study of complex flows with high degree of non-equilibrium. Direct simulation Monte Carlo simulations using the reactive cross section databases are carried out for high enthalpy hypersonic oxygen flow over a cylinder at rarefied ambient conditions. A comparative study with the phenomenological total collision energy chemical model is also undertaken to point out the difference and advantage of the reported ab initio reaction model. Published by AIP Publishing