Science.gov

Sample records for employing transport layer

  1. W-doped TiO2 mesoporous electron transport layer for efficient hole transport material free perovskite solar cells employing carbon counter electrodes

    NASA Astrophysics Data System (ADS)

    Xiao, Yuqing; Cheng, Nian; Kondamareddy, Kiran Kumar; Wang, Changlei; Liu, Pei; Guo, Shishang; Zhao, Xing-Zhong

    2017-02-01

    Doping of TiO2 by metal elements for the scaffold layer of the perovskite solar cells has been proved to be one of the effective methods to improve the power conversion efficiency. In the present work, we report the impact of doping of TiO2 nanoparticles with different amounts of tungsten (W) on the photovoltaic properties of hole transport material free perovskite solar cells (PSCs) that employ carbon counter electrode. Light doping with W (less than 1000 ppm) improves the power conversion efficiencies (PCEs) of solar cells by promoting the electron conductivity in the TiO2 layer which facilitates electron transfer and collection. With the incorporation of W, average efficiency of PSCs is increased from 9.1% for the un-doped samples to 10.53% for the 1000 ppm W-doped samples, mainly originates from the increase of short circuit current density and fill factor. Our champion cell exhibits an impressive PCE of 12.06% when using the 1000 ppm W-doped TiO2 films.

  2. Scalar transport in plane mixing layers

    NASA Astrophysics Data System (ADS)

    Vanormelingen, J.; Van den Bulck, E.

    This paper describes the application of the Eulerian, single-point, single-time joint-scalar probability density function (PDF) equation for predicting the scalar transport in mixing layer with a high-speed and a low-speed stream. A finite-volume procedure is applied to obtain the velocity field with the k-ɛ closure being used to describe turbulent transport. The scalar field is represented through the modelled evolution equation for the scalar PDF and is solved using a Monte Carlo simulation. The PDF equation employs gradient transport modelling to represent the turbulent diffusion, and the molecular mixing term is modelled by the LMSE closure. There is no source term for chemical reaction as only an inert mixing layer is considered here. The experimental shear layer data published by Batt is used to validate the computational results despite the fact that comparisons between experiments and computational results are difficult because of the high sensitivity of the shear layer to initial conditions and free stream turbulence phenomena. However, the bimodal shape of the RMS scalar fluctuation as was measured by Batt can be reproduced with this model, whereas standard gradient diffusion calculations do not predict the dip in this profile. In this work for the first time an explanation is given for this phenomenon and the importance of a micromixing model is stressed. Also it is shown that the prediction of the PDF shape by the LMSE model is very satisfactory.

  3. Issues in designing transport layer multicast facilities

    NASA Technical Reports Server (NTRS)

    Dempsey, Bert J.; Weaver, Alfred C.

    1990-01-01

    Multicasting denotes a facility in a communications system for providing efficient delivery from a message's source to some well-defined set of locations using a single logical address. While modem network hardware supports multidestination delivery, first generation Transport Layer protocols (e.g., the DoD Transmission Control Protocol (TCP) (15) and ISO TP-4 (41)) did not anticipate the changes over the past decade in underlying network hardware, transmission speeds, and communication patterns that have enabled and driven the interest in reliable multicast. Much recent research has focused on integrating the underlying hardware multicast capability with the reliable services of Transport Layer protocols. Here, we explore the communication issues surrounding the design of such a reliable multicast mechanism. Approaches and solutions from the literature are discussed, and four experimental Transport Layer protocols that incorporate reliable multicast are examined.

  4. Guide to transportation-demand management plans for employers

    SciTech Connect

    Anderson, S.M.; Gerwig, K.L.; Shirazi, E.

    1988-09-01

    This guide is designed to introduce employers, transportation agencies, consultants, government officials and others to the elements of transportation demand management (TDM) plans. TDM plans use a variety of strategies to orchestrate employees' commute-related activities, including use of carpools, vanpools, bicycles, and buses, use of variable work hours to spread or reduce peak hour congestion, and telecommuting (working from home or a satellite office). The guide contains a description of the typical elements in a TDM plan, including an assessment of the current employee transportation program, methods for measuring vehicle occupancy, strategies for program improvement, and implementing and monitoring the transportation program. The procedure is illustrated for a fictitious employer in the Los Angeles Central Business District.

  5. Aeolian Sand Transport by Boundary Layer Turbulence

    NASA Astrophysics Data System (ADS)

    Baas, A. C.

    2007-12-01

    The erratic and intermittent nature of wind-driven sand transport challenges our current transport models, which lack physical mechanisms for explaining and taking into account this spatio-temporal variability. This paper presents a collective overview of results from investigations into the nature of spatio-temporal variability in sand transport generally, and the formation and behaviour of aeolian streamers specifically. This includes three principal studies. First, the results of field investigations into the formation and behaviour of aeolian streamers in coastal and desert environments, where spatio-temporal transport variability and associated turbulence characteristics were assessed with an extensive instrument array. Streamers were measured with a transverse array of Safires, while the wind field and associated turbulent structures were monitored with cup-anemometry and a rake of hot-film probes. Second, these field data were used to assess the statistical trends in transport variability as a function of spanwise scale of measurement and the temporal scale of time-averaging transport rates. Third, spectral wavelet analysis of high-frequency collocated wind speed (hot- film probes) and transport flux (Safires) time-series revealed distinct forcing-response regimes at different temporal scales. The transitions between these regimes and their ranges compare favourably with physically meaningful scales, such as the minimum temporal scale of saltation response to wind speed fluctuations, and the integral time-scale of the observed internal boundary layer turbulence dynamics. The paper concludes with a tentative conceptual framework that attempts to integrate the results and insights from these studies towards an improved understanding of aeolian sediment transport processes.

  6. Stacking-dependent transport properties in few-layers graphene

    NASA Astrophysics Data System (ADS)

    Lima, Matheus Paes; Padilha, José Eduardo; Pontes, Renato Borges; Fazzio, Adalberto; Silva, Antônio José Roque da

    2017-01-01

    By performing ab initio electronic structure and transport calculations, we investigated the effects of the stacking order (Bernal (AB) and rhombohedral (ABC)) as well as the number of layers, in the electronic structure and charge transport of few-layers graphene (FLG). We observed that for the ABC stack the transport properties are derived from surface states close to the Fermi level connected to dispersive states with an exponential penetration towards the inner layers, whereas for the AB stacking the transport is distributed over all layers. We present a simple model for the resistances as a function of the number of layers which contemplates the different contribution of the surface and inner layers for the transport. However, even if the stackings AB and ABC present completely different electronic and transport properties, both present the same cohesive energies, showing the absence of a thermodynamical preference for a given kind of stacking.

  7. Optoelectronic device with nanoparticle embedded hole injection/transport layer

    DOEpatents

    Wang, Qingwu [Chelmsford, MA; Li, Wenguang [Andover, MA; Jiang, Hua [Methuen, MA

    2012-01-03

    An optoelectronic device is disclosed that can function as an emitter of optical radiation, such as a light-emitting diode (LED), or as a photovoltaic (PV) device that can be used to convert optical radiation into electrical current, such as a photovoltaic solar cell. The optoelectronic device comprises an anode, a hole injection/transport layer, an active layer, and a cathode, where the hole injection/transport layer includes transparent conductive nanoparticles in a hole transport material.

  8. Compact Layer Free Perovskite Solar Cells with a High-Mobility Hole-Transporting Layer.

    PubMed

    Zhu, Qianqian; Bao, Xichang; Yu, Jianhua; Zhu, Dangqiang; Qiu, Meng; Yang, Renqiang; Dong, Lifeng

    2016-02-03

    A high-mobility diketopyrrolopyrrole-based copolymer (P) was employed in compact layer free CH3NH3PbI3 perovskite solar cells as a hole-transporting layer (HTL). By using the P-HTL, the 6.62% device efficiency with conventional poly-3-hexylthiophene was increased to 10.80% in the simple device configuration (ITO/CH3NH3PbI3/HTL/MoO3/Ag). With improved short circuit current density, open circuit voltage, and fill factor, the higher power conversion efficiency of P-HTL device is ascribed to the higher carrier mobility, more suitable energy level, and lower interfacial charge recombination. Advantages of applying P-HTL to perovskite solar cells, such as low cost, low-temperature processing, and excellent performance with simple cell structure, exhibit a possibility for commercial applications.

  9. Turbulent transport across shear layers in magnetically confined plasmas

    SciTech Connect

    Nold, B.; Ramisch, M.; Manz, P.; Birkenmeier, G.; Ribeiro, T. T.; Müller, H. W.; Scott, B. D.; Fuchert, G.; Stroth, U.

    2014-10-15

    Shear layers modify the turbulence in diverse ways and do not only suppress it. A spatial-temporal investigation of gyrofluid simulations in comparison with experiments allows to identify further details of the transport process across shear layers. Blobs in and outside a shear layer merge, thereby exchange particles and heat and subsequently break up. Via this mechanism particles and heat are transported radially across shear layers. Turbulence spreading is the immanent mechanism behind this process.

  10. Wave mediated angular momentum transport in astrophysical boundary layers

    NASA Astrophysics Data System (ADS)

    Hertfelder, Marius; Kley, Wilhelm

    2015-07-01

    Context. Disk accretion onto weakly magnetized stars leads to the formation of a boundary layer (BL) where the gas loses its excess kinetic energy and settles onto the star. There are still many open questions concerning the BL, for instance the transport of angular momentum (AM) or the vertical structure. Aims: It is the aim of this work to investigate the AM transport in the BL where the magneto-rotational instability (MRI) is not operating owing to the increasing angular velocity Ω(r) with radius. We will therefore search for an appropriate mechanism and examine its efficiency and implications. Methods: We perform 2D numerical hydrodynamical simulations in a cylindrical coordinate system (r,ϕ) for a thin, vertically integrated accretion disk around a young star. We employ a realistic equation of state and include both cooling from the disk surfaces and radiation transport in radial and azimuthal direction. The viscosity in the disk is treated by the α-model; in the BL there is no viscosity term included. Results: We find that our setup is unstable to the sonic instability which sets in shortly after the simulations have been started. Acoustic waves are generated and traverse the domain, developing weak shocks in the vicinity of the BL. Furthermore, the system undergoes recurrent outbursts where the activity in the disk increases strongly. The instability and the waves do not die out for over 2000 orbits. Conclusions: There is indeed a purely hydrodynamical mechanism that enables AM transport in the BL. It is efficient and wave mediated; however, this renders it a non-local transport method, which means that models of a effective local viscosity like the α-viscosity are probably not applicable in the BL. A variety of further implications of the non-local AM transport are discussed.

  11. Holographic recording medium employing a photoconductive layer and a low molecular weight microcrystalline polymeric layer

    NASA Technical Reports Server (NTRS)

    Gange, Robert Allen (Inventor)

    1977-01-01

    A holographic recording medium comprising a conductive substrate, a photoconductive layer and an electrically alterable layer of a linear, low molecular weight hydrocarbon polymer has improved fatigue resistance. An acrylic barrier layer can be interposed between the photoconductive and electrically alterable layers.

  12. Nonlocal thermal transport across embedded few-layer graphene sheets.

    PubMed

    Liu, Ying; Huxtable, Scott T; Yang, Bao; Sumpter, Bobby G; Qiao, Rui

    2014-12-17

    Thermal transport across the interfaces between few-layer graphene sheets and soft materials exhibits intriguing anomalies when interpreted using the classical Kapitza model, e.g. the conductance of the same interface differs greatly for different modes of interfacial thermal transport. Using atomistic simulations, we show that such thermal transport follows a nonlocal flux-temperature drop constitutive law and is characterized jointly by a quasi-local conductance and a nonlocal conductance instead of the classical Kapitza conductance. The nonlocal model enables rationalization of many anomalies of the thermal transport across embedded few-layer graphene sheets and should be used in studies of interfacial thermal transport involving few-layer graphene sheets or other ultra-thin layered materials.

  13. Nonlocal thermal transport across embedded few-layer graphene sheets

    SciTech Connect

    Liu, Ying; Huxtable, Scott T.; Yang, Bao; Sumpter, Bobby G.; Qiao, Rui

    2014-11-13

    Thermal transport across the interfaces between few-layer graphene sheets and soft materials exhibits intriguing anomalies when interpreted using the classical Kapitza model, e.g., the conductance of the same interface differs greatly for different modes of interfacial thermal transport. Using atomistic simulations, we show that such thermal transport follows a nonlocal flux-temperature drop constitutive law and is characterized jointly by a quasi-local conductance and a nonlocal conductance instead of the classical Kapitza conductance. Lastly, the nonlocal model enables rationalization of many anomalies of the thermal transport across embedded few-layer graphene sheets and should be used in studies of interfacial thermal transport involving few-layer graphene sheets or other ultra-thin layered materials.

  14. Ionic transport in passivation layered on the lithium electrode

    NASA Astrophysics Data System (ADS)

    Nimon, Eugeny S.; Churikov, Alexei V.; Shirokov, Alexander V.; Lvov, Arlen L.; Chuvashkin, Anatoly N.

    1993-04-01

    The processes of ionic transport in passivating layers on the surface of the lithium electrode in solutions based on thionyl chloride, propylene carbonate and gamma -butyrolactone have been studied by means of pulse electrochemical methods. The data obtained are quantitatively described by a model which takes into account transport of both the intrinsic mobile lithium ions of the passivating layer and lithium ions injected into the passivating layer from the electrode or from the electrolyte solution under anodic or cathodic current directions, respectively. The values of mobility and concentration of mobile lithium ions in passivating layers formed on lithium in various solutions under open-circuit conditions have been determined.

  15. Nonlocal thermal transport across embedded few-layer graphene sheets

    DOE PAGES

    Liu, Ying; Huxtable, Scott T.; Yang, Bao; ...

    2014-11-13

    Thermal transport across the interfaces between few-layer graphene sheets and soft materials exhibits intriguing anomalies when interpreted using the classical Kapitza model, e.g., the conductance of the same interface differs greatly for different modes of interfacial thermal transport. Using atomistic simulations, we show that such thermal transport follows a nonlocal flux-temperature drop constitutive law and is characterized jointly by a quasi-local conductance and a nonlocal conductance instead of the classical Kapitza conductance. Lastly, the nonlocal model enables rationalization of many anomalies of the thermal transport across embedded few-layer graphene sheets and should be used in studies of interfacial thermal transportmore » involving few-layer graphene sheets or other ultra-thin layered materials.« less

  16. Ion transport through electrolyte/polyelectrolyte multi-layers

    PubMed Central

    Femmer, Robert; Mani, Ali; Wessling, Matthias

    2015-01-01

    Ion transport of multi-ionic solutions through layered electrolyte and polyelectrolyte structures are relevant in a large variety of technical systems such as micro and nanofluidic devices, sensors, batteries and large desalination process systems. We report a new direct numerical simulation model coined EnPEn: it allows to solve a set of first principle equations to predict for multiple ions their concentration and electrical potential profiles in electro-chemically complex architectures of n layered electrolytes E and n polyelectrolytes PE. EnPEn can robustly capture ion transport in sub-millimeter architectures with submicron polyelectrolyte layers. We proof the strength of EnPEn for three yet unsolved architectures: (a) selective Na over Ca transport in surface modified ion selective membranes, (b) ion transport and water splitting in bipolar membranes and (c) transport of weak electrolytes. PMID:26111456

  17. Mass transport in a thin layer of power-law mud under surface waves

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Bai, Yuchuan; Xu, Dong

    2017-02-01

    The mass transport velocity in a two-layer system is studied theoretically. The wave motion is driven by a periodic pressure load on the free water surface, and mud in the lower layer is described by a power-law rheological model. Perturbation analysis is performed to the second order to find the mean Eulerian velocity. A numerical iteration method is employed to solve the non-linear governing equation at the leading order. The influence of rheological properties on fluid motion characteristics including the flow field, the surface displacement, the mass transport velocity, and the net discharge rates are investigated based on theoretical results. Theoretical analysis shows that under the action of interfacial shearing, a recirculation structure may appear near the interface in the upper water layer. A higher mass transport velocity at the interface does not necessarily mean a higher discharge rate for a pseudo-plastic fluid mud.

  18. 49 CFR 40.409 - What does the issuance of a PIE mean to transportation employers?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false What does the issuance of a PIE mean to... What does the issuance of a PIE mean to transportation employers? (a) As an employer, you are deemed to have notice of the issuance of a PIE when it appears on the List mentioned in § 40.401(a) or the...

  19. Pore Network Modeling of Multiphase Transport in Polymer Electrolyte Membrane Fuel Cell Gas Diffusion Layers

    NASA Astrophysics Data System (ADS)

    Fazeli, Mohammadreza

    In this thesis, pore network modeling was used to study how the microstructure of the polymer electrolyte membrane (PEM) fuel cell gas diffusion layer (GDL) influences multiphase transport within the composite layer. An equivalent pore network of a GDL was used to study the effects of GDL/catalyst layer condensation points and contact quality on the spatial distribution of liquid water in the GDL. Next, pore networks extracted from synchrotron-based micro-computed tomography images of compressed GDLs were employed to simulate liquid water transport in GDL materials over a range of compression pressures, and favorable GDL compression values for preferred liquid water distributions were found for two commercially available GDL materials. Finally, a technique was developed for calculating the oxygen diffusivity in carbon paper substrates with a microporous layer (MPL) coating through pore network modeling. A hybrid network was incorporated into the pore network model, and effective diffusivity predictions of MPL coated GDL materials were obtained.

  20. Transport Processes in the Coastal Atmospheric Boundary Layer

    DTIC Science & Technology

    2016-06-07

    coastlines or boundary layer processes at the coast. The transported constituents may be properties of the marine boundary layer, e.g. humidity, air ... pollution or aerosols, the latter both of natural and man-made origin. In particular I am interested in the cross-coast mixing potential. By this I mean...speed maximas. Also some properties of the coastal marine air , e.g. the presence of aerosol and low clouds, are detrimental to remote sensing based on

  1. Location Management in a Transport Layer Mobility Architecture

    NASA Technical Reports Server (NTRS)

    Eddy, Wesley M.; Ishac, Joseph

    2005-01-01

    Mobility architectures that place complexity in end nodes rather than in the network interior have many advantageous properties and are becoming popular research topics. Such architectures typically push mobility support into higher layers of the protocol stack than network layer approaches like Mobile IP. The literature is ripe with proposals to provide mobility services in the transport, session, and application layers. In this paper, we focus on a mobility architecture that makes the most significant changes to the transport layer. A common problem amongst all mobility protocols at various layers is location management, which entails translating some form of static identifier into a mobile node's dynamic location. Location management is required for mobile nodes to be able to provide globally-reachable services on-demand to other hosts. In this paper, we describe the challenges of location management in a transport layer mobility architecture, and discuss the advantages and disadvantages of various solutions proposed in the literature. Our conclusion is that, in principle, secure dynamic DNS is most desirable, although it may have current operational limitations. We note that this topic has room for further exploration, and we present this paper largely as a starting point for comparing possible solutions.

  2. Chloride transport in layered soil systems with hydraulic trap effect.

    PubMed

    Badv, K; Mahooti, A A

    2005-08-01

    The natural and engineered hydraulic trap systems in sanitary-engineered solid waste landfills were investigated using three layer one dimensional laboratory models. The models consisted of a top reservoir containing a sodium chloride source solution, a compacted upper silt layer as a primary liner, a coarse sand layer as a secondary leachate collection system or a hydraulic control layer, a compacted lower silt layer as a secondary liner, and a bottom water reservoir as a groundwater aquifer. In the first test, the natural hydraulic trap system (upward flow through the lower silt layer) was modeled. In this case, the contaminant transport mechanisms through the upper silt layer were downward advection and diffusion, and through the lower silt layer, diffusion was downward and advection was upward. The results showed that the implementation of the natural hydraulic control system could effectively reduce chloride transport to the bottom reservoir. In the second test, the natural and engineering hydraulic trap systems were simulated (upward flow from the bottom reservoir to the upper reservoir). In the third test, the engineered hydraulic trap system (downward flow through the upper silt layer and upward flow through the lower silt layer) was modeled. The results showed that the natural and engineered hydraulic trap systems have an important effect in reducing chloride migration toward the underlying aquifer. In all experiments the chloride concentrations in the silt and coarse sand layers and top and bottom reservoirs were measured and the observed concentrations were compared with concentrations calculated by a theoretical model. A good agreement was obtained between the observed and theoretical data confirming the acceptable accuracy of the experimental methodologies, observations, and the theoretical model.

  3. The Employment of Airships for the Transport of Passengers

    NASA Technical Reports Server (NTRS)

    Nobile, Umberto

    1921-01-01

    It was a conclusion of this detailed study of the practicality of using airships for carrying passengers that, although slow, airships are capable of carrying useful loads over long distances. However, it is noted that there is a certain limit to the advantages of large cubature. Beyond a certain point, the maximum altitude of the airship goes on decreasing, in spite of the fact that the range of action in the horizontal plane and the useful load go on increasing. The possibility of rapid climb is an essential factor of security in aerial navigation in the case of storms, as is velocity. To rise above and run ahead of storms are ways of avoiding them. However, high altitude and high speed are antithetical. This investigation concluded that a maximum velocity of 120 km/h is as far as we ought to go. This figure can only be exceeded by excessive reduction of the altitude of ceiling, range of flight, and useful load. The essential requisites of a public transport service are discussed, as are flight security, regularity of service, competition with other forms of passenger transportation, and the choice between rigid and semi-rigid airships.

  4. Inorganic Nanowires-Assembled Layered Paper as the Valve for Controlling Water Transportation.

    PubMed

    Chen, Fei-Fei; Zhu, Ying-Jie; Xiong, Zhi-Chao; Sun, Tuan-Wei; Shen, Yue-Qin; Yang, Ri-Long

    2017-03-29

    Layered materials with open interlayer channels enable various applications such as tissue engineering, ionic and molecular sieving, and electrochemical devices. However, most reports focus on the two-dimensional nanosheets-assembled layered materials, whose interlayer spacing is limited at the nanometer scale. Herein, we demonstrate that one-dimensional inorganic nanowires are the ideal building blocks for the construction of layered materials with open interlayer channels as well, which has not aroused much attention before. It is found that the relatively long inorganic nanowires are capable of assembling into free-standing layered paper with open interlayer channels during the filtration process. The spacings of interlayer channels between adjacent layers are up to tens of micrometers, which are much larger than those of the two-dimensional nanosheets-assembled layered materials. But the closed interlayer channels are observed when the relatively short inorganic nanowires are used as building blocks. The mechanism based on the relationship between the structural variation and the nanowires used is proposed, including the surface charge amplified effect, surface charge superimposed effect, and pillarlike supporting effect. According to the proposed mechanism, we have successfully fabricated a series of layered paper sheets whose architectures (including interlayer channels of cross section and pores on the surface) show gradient changes. The as-prepared layered paper sheets are employed as the valves for controlling water transportation. Tunable water transportation is achieved by the synergistic effect between in-plane interlayer channels (horizontal transportation) from the open to the closed states, and through-layer pores (vertical transportation) without surface modification or intercalation of any guest species.

  5. Nonlinear Surface Transport in the Thin Double-Layer Limit

    NASA Astrophysics Data System (ADS)

    Chu, Kevin; Bazant, Martin

    2006-03-01

    At high applied electric fields, ionic transport within the double layer plays a significant role in the overall response of electrokinetic systems. It is well-known that surface transport processes, including surface electromigration, surface diffusion and surface advection, may impact the strength of electrokinetic phenomena by affecting both the zeta-potential and the magnitude of the tangential electric field. Therefore, it is important to include these effects when formulating the effective boundary conditions for the equations that govern electrokinetic flow outside of the double layer. In this talk, we discuss the application of a general formulation of ``surface conservation laws'' for diffuse boundary layers to derive effective boundary conditions that capture the physics of electrokinetic surface transport. Previous analyses (e.g. Deryagin & Dukhin 1969) are only valid for weak applied fields and are based on a linearization of the concentration and potential about a reference solution, but our results are fully nonlinear and hold at large applied fields as long as the double layer is sufficiently thin. We compare our nonlinear surface transport theory with existing linear analogues and apply it to the canonical problem of induced-charge electro-osmosis around a metal sphere or cylinder in a strong DC field.

  6. Modeling Metallic Ion Transport During the Lifetime of an Intermediate Layer

    NASA Astrophysics Data System (ADS)

    Bishop, R. L.; Earle, G. D.

    2001-05-01

    Intermediate layers are one of several phenomena that occur at midlatitudes in the nighttime E region. These ionization layers which typically form on the bottomside of the F region, are frequently observed by the Arecibo Incoherent Scatter Facility. Although their occurrence is relatively common, they exhibit diverse structure. Their altitude of formation, vertical thickness, and motion show significant nightly variations. Layer structure is influenced by a number of factors including composition, electric fields, and fluctuations in the neutral wind field. A numerical simulation has been employed to investigate the effects of composition on layer development. Specifically, the simulation, named LEAD (Layer Evolution And Dynamics), explores the transport of metallic ions during the formation and subsequent motion of a layer due to a time varying meridional wind field. We discuss the relative molecular/metallic ratio inside the layer during its evolution, the time scales for metallic ion dominance within the layer, and the motion of metallic ions in the adjacent altitude regions. We present animated results from LEAD which allow detailed inspection of ion composition variations throughout the process of layer evolution and descent.

  7. Drift-wave transport in the velocity shear layer

    NASA Astrophysics Data System (ADS)

    Rosalem, K. C.; Roberto, M.; Caldas, I. L.

    2016-07-01

    Particle drift driven by electrostatic wave fluctuations is numerically computed to describe the transport in a gradient velocity layer at the tokamak plasma edge. We consider an equilibrium plasma in large aspect ratio approximation with E × B flow and specified toroidal plasma velocity, electric field, and magnetic field profiles. A symplectic map, previously derived for infinite coherent time modes, is used to describe the transport dependence on the electric, magnetic, and plasma velocity shears. We also show that resonant perturbations and their correspondent islands in the Poincaré maps are much affected by the toroidal velocity profiles. Moreover, shearless transport barriers, identified by extremum values of the perturbed rotation number profiles of the invariant curves, allow chaotic trajectories trapped into the plasma. We investigate the influence of the toroidal plasma velocity profile on these shearless transport barriers.

  8. Effective transport rates and transport-induced melting and solidification in mushy layers

    NASA Astrophysics Data System (ADS)

    Butler, S. L.

    2011-01-01

    Mushy layers are known to occur in magma chambers, sea-ice, and metal castings. They are often modeled as a porous layer in which a fluid and solid matrix exist in thermal and compositional equilibria. In nonreactive porous media, both advective and diffusive transport rates for heat and solute differ. In mushy layers, however, the temperature and composition of the fluid phase are constrained by the liquidus relationship giving rise to effective transport rates that are intermediate between those for heat and solute in passive porous layers. The transport of heat and solute, even if the invading fluid is itself in equilibrium, is also accompanied by a degree of solidification or melting due to the difference in the transport rates for these two quantities. In this paper, analytical expressions for the effective velocity and diffusivity in a mushy layer and for the degree of melting or solidification accompanying the passage of a front with a different temperature and composition are derived and compared with the predictions of a numerical model and found to be in very good agreement. Characteristic parameters for a few mushy systems are calculated and appropriate transport and melting/freezing regimes are indicated.

  9. Near independence of OLED operating voltage on transport layer thickness

    SciTech Connect

    Swensen, James S.; Wang, Liang; Polikarpov, Evgueni; Rainbolt, James E.; Koech, Phillip K.; Cosimbescu, Lelia; Padmaperuma, Asanga B.

    2013-01-01

    We report organic light emitting devices (OLEDs) with weak drive voltage dependence on the thickness of the hole transport layer (HTL) for thicknesses up to 1150 Å using the N,N'-Bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (α-NPD) and N,N'-bis(3-methyl phenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'diamine (TPD), both of which have hole mobilities in the range of 2 × 10-3 cm2V-1s-1. Lower mobility HTL materials show larger operating voltage dependence on thickness. The near independence of the operating voltage for high mobility transport material thickness was only observed when the energy barrier for charge injection into the transport material was minimized. To ensure low injection barriers, a thin film of 2-(3-(adamantan-1-yl)propyl)-3,5,6-trifluorotetracyanoquinodimethane (F3TCNQ-Adl) was cast from solution onto the ITO surface. These results indicate that thick transport layers can be integrated into OLED stacks without the need for bulk conductivity doping.

  10. SUPPRESSION OF ENERGETIC ELECTRON TRANSPORT IN FLARES BY DOUBLE LAYERS

    SciTech Connect

    Li, T. C.; Drake, J. F.; Swisdak, M.

    2012-09-20

    During flares and coronal mass ejections, energetic electrons from coronal sources typically have very long lifetimes compared to the transit times across the systems, suggesting confinement in the source region. Particle-in-cell simulations are carried out to explore the mechanisms of energetic electron transport from the corona to the chromosphere and possible confinement. We set up an initial system of pre-accelerated hot electrons in contact with ambient cold electrons along the local magnetic field and let it evolve over time. Suppression of transport by a nonlinear, highly localized electrostatic electric field (in the form of a double layer) is observed after a short phase of free-streaming by hot electrons. The double layer (DL) emerges at the contact of the two electron populations. It is driven by an ion-electron streaming instability due to the drift of the back-streaming return current electrons interacting with the ions. The DL grows over time and supports a significant drop in temperature and hence reduces heat flux between the two regions that is sustained for the duration of the simulation. This study shows that transport suppression begins when the energetic electrons start to propagate away from a coronal acceleration site. It also implies confinement of energetic electrons with kinetic energies less than the electrostatic energy of the DL for the DL lifetime, which is much longer than the electron transit time through the source region.

  11. Costs and benefits of employment transportation for low-wage workers: an assessment of job access public transportation services.

    PubMed

    Thakuriah Vonu, Piyushimita; Persky, Joseph; Soot, Siim; Sriraj, P S

    2013-04-01

    This paper focuses on an evaluation of public transportation-based employment transportation (ET) services to transport low-wage workers to jobs in the US. We make an attempt to capture a more comprehensive range of intended and unintended outcomes of ET services than those traditionally considered in the case of public transportation services. Using primary data from 23 locations across the country, we present a framework to evaluate how transportation improvements, in interaction with labor markets, can affect users' short-run economic welfare, users' long-run human capital accumulation and non-users' short-run economic welfare. These services were partially funded by a specialized program - the Job Access and Reverse Commute (JARC) program - which was consolidated into larger transit funding programs by recent legislation. In the sites examined, we found that low wage users benefited from self-reported increased access to jobs, improvements in earnings potential, as well as from savings in transport cost and time. Simulations show the potential of users to accrue long-term worklife benefits. At the same time, users may have accrued changes in leisure time as a result of transitioning from unemployment to employment, and generated a range of societal impacts on three classes of non-users: the general tax-paying public, the general commuting public in the service operating area and other low-wage workers in local labor markets.

  12. Effects of double-layer polarization on ion transport.

    PubMed Central

    Hainsworth, A H; Hladky, S B

    1987-01-01

    It has been proposed that changes in ionic strength will alter the shape of current-voltage relations for ion transport across a lipid membrane. To investigate this effect, we measured currents across glyceryl monooleate membranes at applied potentials between 10 and 300 mV using either gramicidin and 1 mM NaCl or valinomycin and 1 mM KCl. A bridge circuit with an integrator as null detector was used to separate the capacitative and ionic components of the current. The changes in the current-voltage relations when ionic strength is varied between 1 and 100 mM are compared with predictions of Gouy-Chapman theory for the effects of these variations on polarization of the electrical diffuse double-layer. Double-layer polarization accounts adequately for the changes observed using membranes made permeable by either gramicidin or valinomycin. PMID:2432953

  13. Effects of double-layer polarization on ion transport.

    PubMed

    Hainsworth, A H; Hladky, S B

    1987-01-01

    It has been proposed that changes in ionic strength will alter the shape of current-voltage relations for ion transport across a lipid membrane. To investigate this effect, we measured currents across glyceryl monooleate membranes at applied potentials between 10 and 300 mV using either gramicidin and 1 mM NaCl or valinomycin and 1 mM KCl. A bridge circuit with an integrator as null detector was used to separate the capacitative and ionic components of the current. The changes in the current-voltage relations when ionic strength is varied between 1 and 100 mM are compared with predictions of Gouy-Chapman theory for the effects of these variations on polarization of the electrical diffuse double-layer. Double-layer polarization accounts adequately for the changes observed using membranes made permeable by either gramicidin or valinomycin.

  14. Understanding thermal transport in asymmetric layer hexagonal boron nitride heterostructure

    NASA Astrophysics Data System (ADS)

    Zhang, Jingchao; Wang, Xinyu; Hong, Yang; Xiong, Qingang; Jiang, Jin; Yue, Yanan

    2017-01-01

    In this work, thermal transport at the junction of an asymmetric layer hexagonal boron-nitride (h-BN) heterostructure is explored using a non-equilibrium molecular dynamics method. A thermal contact resistance of 3.6 × 10-11 K · m2 W-1 is characterized at a temperature of 300 K with heat flux from the trilayer to monolayer regions. The mismatch in the flexural phonon modes revealed by power spectra analysis provides the driving force for the calculated thermal resistance. A high thermal rectification efficiency of 360% is calculated at the layer junction surpassing that of graphene. Several modulators, i.e. the system temperature, contact pressure and lateral dimensions, are applied to manipulate the thermal conductance and rectification across the interfaces. The predicted thermal rectification sustains positive correlations with temperature and phonon propagation lengths with little change to the coupling strength.

  15. Transport measurements on monolayer and few-layer WSe2

    NASA Astrophysics Data System (ADS)

    Palomaki, Tauno; Zhao, Wenjin; Finney, Joe; Fei, Zaiyao; Nguyen, Paul; McKay, Frank; Cobden, David

    The behavior of the electrical contacts often dominates transport measurements in mono and few-layer transition metal dichalcogenide (TMD) devices. Creating good contacts for some TMDs is particularly challenging since the fabrication procedure should prevent the TMD from oxidizing or chemically interacting with the contacts. In this talk, we discuss our progress on creating mono and few-layer WSe2 devices with both good electrical contacts and minimal effects from the substrate, polymer contamination, oxidation and other chemistry. For example, we have developed a technique for encapsulating metallic contacts and WSe2 flakes together in hexagonal boron nitride with multiple gates to separate and control the contributions from the channel and the Schottky barriers at the contacts. Research supported in part by Samsung GRO grant US 040814

  16. The design and performance of axially symmetrical contoured wall diffusers employing suction boundary layer control

    NASA Technical Reports Server (NTRS)

    Nelson, C. D., Jr.; Hudson, W. G.; Yang, T.

    1974-01-01

    This paper presents a procedure for the design and the performance prediction of axially symmetrical contoured wall diffusers employing suction boundary layer control. An inverse problem approach was used in the potential flow design of the diffuser wall contours. The experimentally observed flow characteristics and the stability of flows within the diffuser are also described. Guidelines for the design of low suction (less than 10 percent of the inlet flow) and thus high effectiveness contoured wall diffusers are also provided based on the results of the experimental program.

  17. Investigation of hole transport layer in relation to the properties of organic solar cells.

    PubMed

    Chou, Dei-Wei; Huang, Chien-Jung; Tsai, Chi-Chu; Meen, Teen-Hang; Chen, Wen-Ray; Yang, Cheng-Fu

    2012-04-01

    Organic solar cells based on a blend of copper phthalocyanine and bulk fullerene are fabricated with a double hole transport layer system. The double hole transport layer was composed of poly3,4-ethylenedioxythiophene:polystyrenesulfonate, and copper phthalocyanine and inserted between the anode and active layer. The double hole transport layer system utilizes advantages of both layer. The poly3,4-ethylenedioxythiophene:polystyrenesulfonate layer modifies the surface morphology of the ITO anode and the copper phthalocyanine layer enhances hole transport. In order to enhance the conductivity of the modification layer, the optimal amount of glycerol is doped into poly3,4-ethylenedioxythiophene:polystyrenesulfonate. Furthermore, the photovoltaic characteristics are further improved. Insertion of the double hole transport layer with a 4 nm-thick copper phthalocyanine layer resulted in open circuit voltage, short current, and power conversion efficiency as high as 0.46 V, 8.8 mA/cm2 and 1.37%, respectively.

  18. Electron transport in molecular junctions with graphene as protecting layer

    SciTech Connect

    Hüser, Falco; Solomon, Gemma C.

    2015-12-07

    We present ab initio transport calculations for molecular junctions that include graphene as a protecting layer between a single molecule and gold electrodes. This vertical setup has recently gained significant interest in experiment for the design of particularly stable and reproducible devices. We observe that the signals from the molecule in the electronic transmission are overlayed by the signatures of the graphene sheet, thus raising the need for a reinterpretation of the transmission. On the other hand, we see that our results are stable with respect to various defects in the graphene. For weakly physiosorbed molecules, no signs of interaction with the graphene are evident, so the transport properties are determined by offresonant tunnelling between the gold leads across an extended structure that includes the molecule itself and the additional graphene layer. Compared with pure gold electrodes, calculated conductances are about one order of magnitude lower due to the increased tunnelling distance. Relative differences upon changing the end group and the length of the molecule on the other hand, are similar.

  19. Carbon transport in the bottom boundary layer. Final report

    SciTech Connect

    Lohrenz, S.E.; Asper, V.L.

    1997-09-01

    The authors objective was to characterize distributions of chloropigment fluorescence in relation to physical processes in the benthic boundary layer in support of the Department of Energy (DOE) Ocean Margins Program`s (OMP) goal of quantifying carbon transport across the continental shelf. Their approach involved participation in the Ocean Margins Program (OMP) field experiment on the continental shelf off Cape Hatteras by conducting multi-sensor fluorescence measurements of photosynthetic pigments. Specific tasks included (1) pre- and post-deployment calibration of multiple fluorescence sensors in conjunction with Woods Hole personnel; (2) collection and analysis of photosynthetic pigment concentrations and total particulate carbon in water column samples to aid in interpretation of the fluorescence time-series during the field experiment; (3) collaboration in the analysis and interpretation of 1994 and 1996 time-series data in support of efforts to quantify pigment and particulate organic carbon transport on the continental shelf off Cape Hatteras. This third component included analysis of data obtained with a multi-sensor fiber-optic fluorometer in the benthic boundary layer of the inner shelf off Cape Hatteras during summer 1994.

  20. Influence of Cemented Layers on Contaminant Transport in Mine Tailings

    NASA Astrophysics Data System (ADS)

    Ptacek, C.; Blowes, D.; Jambor, J.; Moncur, M.; Gunsinger, M.; Doerr, N.

    2004-12-01

    Exposure of sulfide-mine tailings to atmospheric oxygen leads to the initiation of a series of reactions, including sulfide oxidation, acid neutralization and metal attenuation reactions. As oxygen ingresses into the tailings, the oxidation front moves downward and inward from the edges of the tailings surface. At or near the acid neutralization front, secondary phases can accumulate, leading to the formation of hardpan layers. Field studies were conducted at three mine sites to evaluate the role of cemented layers in influencing contaminant transport from oxidized tailings. Detailed field measurements were made, including collection of water and gas samples from the vadose and groundwater zones. Cores were collected for mineralogical and chemical analyses to evaluate the extent of sulfide mineral oxidation and accumulation of secondary phases. Calculations of mineral saturation indices were made using ion-pair and ion-interaction models that were modified to account for the very high solute concentrations observed in the tailings pore waters. At a site that has been oxidizing for 25 years, a massive Fe(III)-bearing hardpan, containing gypsum, goethite and jarosite, has formed over the last 15 years. At a site that has been oxidizing for 35 years, an Fe(III)-bearing hardpan is also present. At a site that has been oxidizing for 70 years, a massive Fe(II)-bearing hardpan containing melanterite and gypsum is present below the zone of active oxidation. Above this zone, there are discontinuous Fe(III)-bearing cemented layers that are likely oxidized remnants of the original Fe(II) hardpan. Calculated mineral saturation indices are consistent with the observed accumulations of secondary phases. Transient perched water table conditions have developed above the massive Fe(II) hardpan, leading to the lateral transport of sulfide oxidation products along the hardpan and the formation of seepage zones above the permanent water table. Chemical extractions and mineralogical

  1. Stereospecific micellar electrokinetic chromatography assay of methionine sulfoxide reductase activity employing a multiple layer coated capillary.

    PubMed

    Zhu, Qingfu; El-Mergawy, Rabab G; Heinemann, Stefan H; Schönherr, Roland; Jáč, Pavel; Scriba, Gerhard K E

    2013-09-01

    A micellar electrokinetic chromatography method for the analysis of the l-methionine sulfoxide diastereomers employing a successive multiple ionic-polymer layer coated fused-silica capillary was developed and validated in order to investigate the stereospecificity of methionine sulfoxide reductases. The capillary coating consisted of a first layer of hexadimethrine and a second layer of dextran sulfate providing a stable strong cathodic EOF and consequently highly repeatable analyte migration times. The methionine sulfoxide diastereomers, methionine as product as well as β-alanine as internal standard were derivatized by dabsyl chloride and separated using a 35 mM sodium phosphate buffer, pH 8.0, containing 25 mM SDS as BGE and a separation voltage of 25 kV. The method was validated in the range of 0.15-2.0 mM with respect to linearity and precision. The LODs of the analytes ranged between 0.04 and 0.10 mM. The assay was subsequently applied to determine the stereospecificity of methionine sulfoxide reductases as well as the enzyme kinetics of human methionine sulfoxide reductase A. Monitoring the decrease of the l-methionine-(S)-sulfoxide Km = 411.8 ± 33.8 μM and Vmax = 307.5 ± 10.8 μM/min were determined.

  2. Combined core/boundary layer transport simulations in tokamaks

    SciTech Connect

    Prinja, A.K.; Schafer, R.F. Jr.; Conn, R.W.; Howe, H.C.

    1986-04-01

    Significant new numerical results are presented from self-consistent core and boundary or scrape-off layer plasma simulations with 3-D neutral transport calculations. For a symmetric belt limiter it is shown that, for plasma conditions considered here, the pump limiter collection efficiency increases from 11% to 18% of the core efflux as a result of local reionization of blade deflected neutrals. This hitherto unobserved effect causes a significant amplification of upstream ion flux entering the pump limiter. Results from coupling of an earlier developed two-zone edge plasma model ODESSA to the PROCTR core plasma simulation code indicates that intense recycling divertor operation may not be possible because of stagnation of upstream flow velocity. This results in a self-consistent reduction of density gradient in an intermediate region between the central plasma and separatrix, and a concomitant reduction of core-efflux. There is also evidence of increased recycling at the first wall.

  3. Vertical transport of water in the Martian boundary layer

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Haberle, R. M.; Houben, Howard C.

    1993-01-01

    We are continuing our examination of the transport of H2O through the martian boundary layer, and we have written a one-dimensional numerical model of the exchange of H2O between the atmosphere and subsurface of Mars through the planetary boundary layer (PBL). Our goal is to explore the mechanisms of H2O exchange, and to elucidate the role played by the regolith in the local H2O budget. The atmospheric model includes effects of Coriolis, pressure gradient, and frictional forces for momentum, as well as radiation, sensible heat flux, and advection for heat. The model differs from Flasar and Goody by use of appropriate Viking-based physical constants and inclusion of the radiative effects of atmospheric dust. We specify the pressure gradient force or compute it from a simple slope model. The subsurface model accounts for conduction of heat and diffusion of H2O through a porous adsorbing medium in response to diurnal forcing. The model is initialized with depth-independent H2O concentrations (2 kg M(exp -3)) in the regolith, and a dry atmosphere. The model terminates when the atmospheric H2O column abundance stabilizes at 0.1 percent per sol.

  4. Fulleropyrrolidinium Iodide As an Efficient Electron Transport Layer for Air-Stable Planar Perovskite Solar Cells.

    PubMed

    Huang, Jiabin; Yu, Xuegong; Xie, Jiangsheng; Li, Chang-Zhi; Zhang, Yunhai; Xu, Dikai; Tang, Zeguo; Cui, Can; Yang, Deren

    2016-12-21

    Organic-inorganic halide perovskite solar cells have attracted great attention in recent years. But there are still a lot of unresolved issues related to the perovskite solar cells such as the phenomenon of anomalous hysteresis characteristics and long-term stability of the devices. Here, we developed a simple three-layered efficient perovskite device by replacing the commonly employed PCBM electrical transport layer with an ultrathin fulleropyrrolidinium iodide (C60-bis) in an inverted p-i-n architecture. The devices with an ultrathin C60-bis electronic transport layer yield an average power conversion efficiency of 13.5% and a maximum efficiency of 15.15%. Steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements show that the high performance is attributed to the efficient blocking of holes and high extraction efficiency of electrons by C60-bis, due to a favorable energy level alignment between the CH3NH3PbI3 and the Ag electrodes. The hysteresis effect and stability of our perovskite solar cells with C60-bis become better under indoor humidity conditions.

  5. Computation of turbulent boundary layers employing the defect wall-function method. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Brown, Douglas L.

    1994-01-01

    In order to decrease overall computational time requirements of spatially-marching parabolized Navier-Stokes finite-difference computer code when applied to turbulent fluid flow, a wall-function methodology, originally proposed by R. Barnwell, was implemented. This numerical effort increases computational speed and calculates reasonably accurate wall shear stress spatial distributions and boundary-layer profiles. Since the wall shear stress is analytically determined from the wall-function model, the computational grid near the wall is not required to spatially resolve the laminar-viscous sublayer. Consequently, a substantially increased computational integration step size is achieved resulting in a considerable decrease in net computational time. This wall-function technique is demonstrated for adiabatic flat plate test cases from Mach 2 to Mach 8. These test cases are analytically verified employing: (1) Eckert reference method solutions, (2) experimental turbulent boundary-layer data of Mabey, and (3) finite-difference computational code solutions with fully resolved laminar-viscous sublayers. Additionally, results have been obtained for two pressure-gradient cases: (1) an adiabatic expansion corner and (2) an adiabatic compression corner.

  6. Perpendicular Magnetic Anisotropy in FePt Patterned Media Employing a CrV Seed Layer.

    PubMed

    Kim, Hyunsu; Noh, Jin-Seo; Roh, Jong Wook; Chun, Dong Won; Kim, Sungman; Jung, Sang Hyun; Kang, Ho Kwan; Jeong, Won Yong; Lee, Wooyoung

    2011-12-01

    A thin FePt film was deposited onto a CrV seed layer at 400°C and showed a high coercivity (~3,400 Oe) and high magnetization (900-1,000 emu/cm(3)) characteristic of L 10 phase. However, the magnetic properties of patterned media fabricated from the film stack were degraded due to the Ar-ion bombardment. We employed a deposition-last process, in which FePt film deposited at room temperature underwent lift-off and post-annealing processes, to avoid the exposure of FePt to Ar plasma. A patterned medium with 100-nm nano-columns showed an out-of-plane coercivity fivefold larger than its in-plane counterpart and a remanent magnetization comparable to saturation magnetization in the out-of-plane direction, indicating a high perpendicular anisotropy. These results demonstrate the high perpendicular anisotropy in FePt patterned media using a Cr-based compound seed layer for the first time and suggest that ultra-high-density magnetic recording media can be achieved using this optimized top-down approach.

  7. Transition Metal-Oxide Free Perovskite Solar Cells Enabled by a New Organic Charge Transport Layer.

    PubMed

    Chang, Sehoon; Han, Ggoch Ddeul; Weis, Jonathan G; Park, Hyoungwon; Hentz, Olivia; Zhao, Zhibo; Swager, Timothy M; Gradečak, Silvija

    2016-04-06

    Various electron and hole transport layers have been used to develop high-efficiency perovskite solar cells. To achieve low-temperature solution processing of perovskite solar cells, organic n-type materials are employed to replace the metal oxide electron transport layer (ETL). Although PCBM (phenyl-C61-butyric acid methyl ester) has been widely used for this application, its morphological instability in films (i.e., aggregation) is detrimental. Herein, we demonstrate the synthesis of a new fullerene derivative (isobenzofulvene-C60-epoxide, IBF-Ep) that serves as an electron transporting material for methylammonium mixed lead halide-based perovskite (CH3NH3PbI(3-x)Cl(x)) solar cells, both in the normal and inverted device configurations. We demonstrate that IBF-Ep has superior morphological stability compared to the conventional acceptor, PCBM. IBF-Ep provides higher photovoltaic device performance as compared to PCBM (6.9% vs 2.5% in the normal and 9.0% vs 5.3% in the inverted device configuration). Moreover, IBF-Ep devices show superior tolerance to high humidity (90%) in air. By reaching power conversion efficiencies up to 9.0% for the inverted devices with IBF-Ep as the ETL, we demonstrate the potential of this new material as an alternative to metal oxides for perovskite solar cells processed in air.

  8. Calculation of effective transport properties of partially saturated gas diffusion layers

    NASA Astrophysics Data System (ADS)

    Bednarek, Tomasz; Tsotridis, Georgios

    2017-02-01

    A large number of currently available Computational Fluid Dynamics numerical models of Polymer Electrolyte Membrane Fuel Cells (PEMFC) are based on the assumption that porous structures are mainly considered as thin and homogenous layers, hence the mass transport equations in structures such as Gas Diffusion Layers (GDL) are usually modelled according to the Darcy assumptions. Application of homogenous models implies that the effects of porous structures are taken into consideration via the effective transport properties of porosity, tortuosity, permeability (or flow resistance), diffusivity, electric and thermal conductivity. Therefore, reliable values of those effective properties of GDL play a significant role for PEMFC modelling when employing Computational Fluid Dynamics, since these parameters are required as input values for performing the numerical calculations. The objective of the current study is to calculate the effective transport properties of GDL, namely gas permeability, diffusivity and thermal conductivity, as a function of liquid water saturation by using the Lattice-Boltzmann approach. The study proposes a method of uniform water impregnation of the GDL based on the "Fine-Mist" assumption by taking into account the surface tension of water droplets and the actual shape of GDL pores.

  9. Atomic layer deposition of NiO hole-transporting layers for polymer solar cells

    NASA Astrophysics Data System (ADS)

    Hsu, Che-Chen; Su, Heng-Wei; Hou, Cheng-Hung; Shyue, Jing-Jong; Tsai, Feng-Yu

    2015-09-01

    NiO is an attractive hole-transporting material for polymer solar cells (PSCs) owing to its excellent stability and electrical/optical properties. This study demonstrates, for the first time, fabrication of uniform, defect-free, and conformal NiO ultra-thin films for use as hole-transporting layers (HTLs) in PSCs by atomic layer deposition (ALD) through optimization of the ALD processing parameters. The morphological, optical, and electrical properties of ALD NiO films were determined to be favorable for their HTL application. As a result, PSCs containing an ALD NiO HTL with an optimized thickness of 4 nm achieved a power conversion efficiency (PCE) of 3.4%, which was comparable to that of a control device with a poly(3,4-ethylenedioxy-thiophene):poly(styrene-sulfonate) HTL. The high quality and manufacturing scalability of ALD NiO films demonstrated here will facilitate the adoption of NiO HTLs in PSCs.

  10. Employing lidar to detail vegetation canopy architecture for prediction of aeolian transport

    USGS Publications Warehouse

    Sankey, Joel B.; Law, Darin J.; Breshears, David D.; Munson, Seth M.; Webb, Robert H.

    2013-01-01

    The diverse and fundamental effects that aeolian processes have on the biosphere and geosphere are commonly generated by horizontal sediment transport at the land surface. However, predicting horizontal sediment transport depends on vegetation architecture, which is difficult to quantify in a rapid but accurate manner. We demonstrate an approach to measure vegetation canopy architecture at high resolution using lidar along a gradient of dryland sites ranging from 2% to 73% woody plant canopy cover. Lidar-derived canopy height, distance (gaps) between vegetation elements (e.g., trunks, limbs, leaves), and the distribution of gaps scaled by vegetation height were correlated with canopy cover and highlight potentially improved horizontal dust flux estimation than with cover alone. Employing lidar to estimate detailed vegetation canopy architecture offers promise for improved predictions of horizontal sediment transport across heterogeneous plant assemblages.

  11. 49 CFR 372.103 - Motor vehicles employed solely in transporting school children and teachers to or from school.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... school children and teachers to or from school. 372.103 Section 372.103 Transportation Other Regulations... Exemptions § 372.103 Motor vehicles employed solely in transporting school children and teachers to or from... motor vehicles being used at the time of operation in the transportation of schoolchildren and...

  12. 49 CFR 372.103 - Motor vehicles employed solely in transporting school children and teachers to or from school.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... school children and teachers to or from school. 372.103 Section 372.103 Transportation Other Regulations... Exemptions § 372.103 Motor vehicles employed solely in transporting school children and teachers to or from... motor vehicles being used at the time of operation in the transportation of schoolchildren and...

  13. 49 CFR 372.103 - Motor vehicles employed solely in transporting school children and teachers to or from school.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... school children and teachers to or from school. 372.103 Section 372.103 Transportation Other Regulations... Exemptions § 372.103 Motor vehicles employed solely in transporting school children and teachers to or from... motor vehicles being used at the time of operation in the transportation of schoolchildren and...

  14. 49 CFR 372.103 - Motor vehicles employed solely in transporting school children and teachers to or from school.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... school children and teachers to or from school. 372.103 Section 372.103 Transportation Other Regulations... Exemptions § 372.103 Motor vehicles employed solely in transporting school children and teachers to or from... motor vehicles being used at the time of operation in the transportation of schoolchildren and...

  15. 49 CFR 372.103 - Motor vehicles employed solely in transporting school children and teachers to or from school.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... school children and teachers to or from school. 372.103 Section 372.103 Transportation Other Regulations... Exemptions § 372.103 Motor vehicles employed solely in transporting school children and teachers to or from... motor vehicles being used at the time of operation in the transportation of schoolchildren and...

  16. Real-time dosimeter employed to evaluate the half-value layer in CT

    NASA Astrophysics Data System (ADS)

    McKenney, Sarah E.; Seibert, J. Anthony; Burkett, George W.; Gelskey, Dale; Sunde, Paul B.; Newman, James D.; Boone, John M.

    2014-01-01

    Half-value layer (HVL) measurements on commercial whole body computer tomography (CT) scanners require serial measurements and, in many institutions, the presence of a service engineer. An assembly of aluminum filters (AAF), designed to be used in conjunction with a real-time dosimeter, was developed to provide estimates of the HVL using clinical protocols. Two real-time dose probes, a solid-state and air ionization chamber, were examined. The AAF consisted of eight rectangular filters of high-purity aluminum (Type 1100), symmetrically positioned to form a cylindrical ‘cage’ around the probe's detective volume. The incident x-ray beam was attenuated by varying thicknesses of aluminum filters as the gantry completed a minimum of one rotation. Measurements employing real-time chambers were conducted both in service mode and with a routine abdomen/pelvis protocol for several combinations of x-ray tube potentials and bow tie filters. These measurements were validated against conventional serial HVL measurements. The average relative difference between the HVL measurements using the two methods was less than 5% when using a 122 mm diameter AAF; relative differences were reduced to 1.1% when the diameter was increased to 505 mm, possibly due to reduced scatter contamination. Use of a real-time dose probe and the AAF allowed for time-efficient measurements of beam quality on a clinical CT scanner using clinical protocols.

  17. Applicants' preference for impression management tactic in employment interviews by Transportation Security Administration.

    PubMed

    Scudder, Joseph N; Lamude, Kevin G

    2009-04-01

    Following past findings on employment interviews, this study hypothesized applicants would have a preference for using self-promoting tactics of impression management over other focuses. Self-reports of impression management tactics were collected from 124 applicants who had interviews for screener positions with the Transportation Security Administration. Contrary to the hypothesis, analysis indicated participants reported they used more ingratiation tactics attempting to praise the interviewer than self-promotion tactics which focused on their own accomplishments. Special qualifications for security jobs which required well-developed perceptual abilities and the controlling structure of the interview context were perhaps responsible for present results differing from prior findings.

  18. Particle Swarm Transport through Immiscible Fluid Layers in a Fracture

    NASA Astrophysics Data System (ADS)

    Teasdale, N. D.; Boomsma, E.; Pyrak-Nolte, L. J.

    2011-12-01

    Immiscible fluids occur either naturally (e.g. oil & water) or from anthropogenic processes (e.g. liquid CO2 & water) in the subsurface and complicate the transport of natural or engineered micro- or nano-scale particles. In this study, we examined the effect of immiscible fluids on the formation and evolution of particle swarms in a fracture. A particle swarm is a collection of colloidal-size particles in a dilute suspension that exhibits cohesive behavior. Swarms fall under gravity with a velocity that is greater than the settling velocity of a single particle. Thus a particle swarm of colloidal contaminants can potentially travel farther and faster in a fracture than expected for a dispersion or emulsion of colloidal particles. We investigated the formation, evolution, and break-up of colloidal swarms under gravity in a uniform aperture fracture as hydrophobic/hydrophyllic particle swarms move across an oil-water interface. A uniform aperture fracture was fabricated from two transparent acrylic rectangular prisms (100 mm x 50 mm x 100 mm) that are separated by 1, 2.5, 5, 10 or 50 mm. The fracture was placed, vertically, inside a glass tank containing a layer of pure silicone oil (polydimethylsiloxane) on distilled water. Along the length of the fracture, 30 mm was filled with oil and 70 mm with water. Experiments were conducted using silicone oils with viscosities of 5, 10, 100, or 1000 cSt. Particle swarms (5 μl) were comprised of a 1% concentration (by mass) of 25 micron glass beads (hydrophilic) suspended in a water drop, or a 1% concentration (by mass) of 3 micron polystyrene fluorescent beads (hydrophobic) suspended in a water drop. The swarm behavior was imaged using an optical fluorescent imaging system composed of a CCD camera and by green (525 nm) LED arrays for illumination. Swarms were spherical and remained coherent as they fell through the oil because of the immiscibility of oil and water. However, as a swarm approached the oil-water interface, it

  19. Solution processed metal oxide thin film hole transport layers for high performance organic solar cells

    DOEpatents

    Steirer, K. Xerxes; Berry, Joseph J.; Chesin, Jordan P.; Lloyd, Matthew T.; Widjonarko, Nicodemus Edwin; Miedaner, Alexander; Curtis, Calvin J.; Ginley, David S.; Olson, Dana C.

    2017-01-10

    A method for the application of solution processed metal oxide hole transport layers in organic photovoltaic devices and related organic electronics devices is disclosed. The metal oxide may be derived from a metal-organic precursor enabling solution processing of an amorphous, p-type metal oxide. An organic photovoltaic device having solution processed, metal oxide, thin-film hole transport layer.

  20. Detecting Man-in-the-Middle Attacks against Transport Layer Security Connections with Timing Analysis

    DTIC Science & Technology

    2011-09-15

    2.4. The Transport Layer Security Protocol In the early 1990‟s, Netscape introduced a web browser named Navigator, which used the proprietary...Transport Layer Security connection to a secure website. The server refers to the machine that hosts the web server that the client is connecting to...Layer Security (TLS) protocol is responsible for protecting nearly all secure web browsing on the Internet today. From e-commerce websites to Virtual

  1. Color stabilization in white organic light emitting devices utilizing trapping layers inserted in both an electron transport layer and an emitting layer.

    PubMed

    Kwack, Byoung Chan; Lee, Kwang Seop; Choo, Dong Chul; Kim, Tae Whan; Seo, Ji Hyun; Kim, Young Kwan

    2008-10-01

    The electrical and the optical properties of white organic light emitting devices (OLEDs) utilizing trapping layers inserted into both an electron transport layer (ETL) and an emitting layer (EML) were investigated. The current density of OLEDs with an ETL containing a 5,6,11,12-tetraphenylnaphthacene (rubrene) layer was slightly smaller than those of other devices. The luminance-current density and luminance efficiency-current density of the OLEDs with rubrene layers embedded in only an ETL or an EML were similar to the blue reference device. While the electroluminescence (EL) spectrum for the OLEDs with a rubrene layer in the ETL in the low voltage range showed the white color, that with rubrene layers in both the EML and the ETL exhibited white color, regardless of the applied voltage. The Commission International de l'Eclairage coordinates of the white OLEDs became stabilized by inserting rubrene layers into both the EML and the ETL.

  2. A simple parameterization for the turbulent kinetic energy transport terms in the convective boundary layer derived from large eddy simulation

    NASA Astrophysics Data System (ADS)

    Puhales, Franciano Scremin; Rizza, Umberto; Degrazia, Gervásio Annes; Acevedo, Otávio Costa

    2013-02-01

    In this work a parametrization for the transport terms of the turbulent kinetic energy (TKE) budget equation, valid for a convective boundary layer (CBL) is presented. This is a hard task to accomplish from experimental data, especially because of the difficulty associated to the measurements of pressure turbulent fluctuations, which are necessary to determine the pressure correlation TKE transport term. Thus, employing a large eddy simulation (LES) a full diurnal planetary boundary layer (PBL) cycle was simulated. In this simulation a forcing obtained from experimental data is used, so that the numerical experiment represents a more realistic case than a stationary PBL. For this study all terms of the TKE budget equation were determined for a CBL. From these data, polynomials that describe the TKE transport terms’ vertical profiles were adjusted. The polynomials found are a good description of the LES data, and from them it is shown that a simple formulation that directly relates the transport terms to the TKE magnitude has advantages on other parameterizations commonly used in CBL numerical models. Furthermore, the present study shows that the TKE turbulent transport term dominates over the TKE transport by pressure perturbations and that for most of the CBL these two terms have opposite signs.

  3. A composite nanostructured electron-transport layer for stable hole-conductor free perovskite solar cells: design and characterization

    NASA Astrophysics Data System (ADS)

    Yu, Zhenhua; Qi, Fei; Liu, Pei; You, Sujian; Kondamareddy, Kiran Kumar; Wang, Changlei; Cheng, Nian; Bai, Sihang; Liu, Wei; Guo, Shishang; Zhao, Xing-Zhong

    2016-03-01

    A novel composite nanostructured titanium dioxide (TiO2) based electron-transport layer (ETL) is designed by combining size blended nanoparticles (SBNP) and nanoarrays (NA) for efficient perovskite solar cell (PSC) applications. The composite nanostructured (SBNP + NA) ETL is successfully employed in hole-conductor free PSCs, there by achieving a stable device with a maximum efficiency of 13.5%. The improvement in the performance is attributed to the better charge transport and lower recombination in the SBNP + NA ETL. Despite the stable high efficiency, SBNP + NA ETL based PSCs are advantageous owing to their low cost, ease of all-solution fabrication process in an open environment and good reproducibility.A novel composite nanostructured titanium dioxide (TiO2) based electron-transport layer (ETL) is designed by combining size blended nanoparticles (SBNP) and nanoarrays (NA) for efficient perovskite solar cell (PSC) applications. The composite nanostructured (SBNP + NA) ETL is successfully employed in hole-conductor free PSCs, there by achieving a stable device with a maximum efficiency of 13.5%. The improvement in the performance is attributed to the better charge transport and lower recombination in the SBNP + NA ETL. Despite the stable high efficiency, SBNP + NA ETL based PSCs are advantageous owing to their low cost, ease of all-solution fabrication process in an open environment and good reproducibility. Electronic supplementary information (ESI) available: Details of the experimental section and ESI figures. See DOI: 10.1039/c5nr09045h

  4. ANGULAR MOMENTUM TRANSPORT BY ACOUSTIC MODES GENERATED IN THE BOUNDARY LAYER. I. HYDRODYNAMICAL THEORY AND SIMULATIONS

    SciTech Connect

    Belyaev, Mikhail A.; Rafikov, Roman R.; Stone, James M.

    2013-06-10

    The nature of angular momentum transport in the boundary layers of accretion disks has been one of the central and long-standing issues of accretion disk theory. In this work we demonstrate that acoustic waves excited by supersonic shear in the boundary layer serve as an efficient mechanism of mass, momentum, and energy transport at the interface between the disk and the accreting object. We develop the theory of angular momentum transport by acoustic modes in the boundary layer, and support our findings with three-dimensional hydrodynamical simulations, using an isothermal equation of state. Our first major result is the identification of three types of global modes in the boundary layer. We derive dispersion relations for each of these modes that accurately capture the pattern speeds observed in simulations to within a few percent. Second, we show that angular momentum transport in the boundary layer is intrinsically nonlocal, and is driven by radiation of angular momentum away from the boundary layer into both the star and the disk. The picture of angular momentum transport in the boundary layer by waves that can travel large distances before dissipating and redistributing angular momentum and energy to the disk and star is incompatible with the conventional notion of local transport by turbulent stresses. Our results have important implications for semianalytical models that describe the spectral emission from boundary layers.

  5. Ultrathin ammonium heptamolybdate films as efficient room-temperature hole transport layers for organic solar cells.

    PubMed

    Qiu, Weiming; Hadipour, Afshin; Müller, Robert; Conings, Bert; Boyen, Hans-Gerd; Heremans, Paul; Froyen, Ludo

    2014-09-24

    Ammonium heptamolybdate (NH4)6Mo7O24·4H2O (AHM) and its peroxo derivatives are analyzed as solution-processed room temperature hole transport layer (HTL) in organic solar cells. Such AHM based HTLs are investigated in devices with three different types of active layers, i.e., solution-processed poly(3-hexylthiophene)/[6,6]-phenyl C61-butyric acid methyl ester(P3HT/PC60BM), poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]/[6,6]-phenyl C70-butyric acid methyl ester(PCDTBT/PC70BM) and evaporated small molecule chloro(subphthalocyaninato)boron(III) (SubPc)/C60. By virtue of their high work functions, AHM based HTLs outperform the commonly used poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) HTL for devices employing deep HOMO level active materials. Moreover, devices using AHM based HTLs can achieve higher short circuit current (Jsc) than the ones with evaporated molybdenum oxide(eMoO3), and thus better power conversion efficiency (PCE). In addition, P3HT/PC60BM devices with AHM based HTLs show air stability comparable to those with eMoO3, and much better than the ones with PEDOT:PSS.

  6. A nano-grid structure made of perovskite SrTiO3 nanowires for efficient electron transport layers in inverted polymer solar cells.

    PubMed

    Kim, Jeong Won; Suh, Yo-han; Lee, Chang-Lyoul; Kim, Yong Seok; Kim, Won Bae

    2015-03-14

    A nano-grid structure of perovskite SrTiO3 NWs is developed for a novel electron transport layer in inverted polymer solar cells. Due to the excellent charge transporting properties of the SrTiO3 nano-grid structure, the device employing this nanostructure showed ∼32% enhanced photovoltaic performance, compared to the solar cell using a TiO2 thin film.

  7. Spinel-structured surface layers for facile Li ion transport and improved chemical stability of lithium manganese oxide spinel

    NASA Astrophysics Data System (ADS)

    Lee, Hae Ri; Seo, Hyo Ree; Lee, Boeun; Cho, Byung Won; Lee, Kwan-Young; Oh, Si Hyoung

    2017-01-01

    Li-ion conducting spinel-structured oxide layer with a manganese oxidation state close to being tetravalent was prepared on aluminum-doped lithium manganese oxide spinel for improving the electrochemical performances at the elevated temperatures. This nanoscale surface layer provides a good ionic conduction path for lithium ion transport to the core and also serves as an excellent chemical barrier for protecting the high-capacity core material from manganese dissolution into the electrolyte. In this work, a simple wet process was employed to prepare thin LiAlMnO4 and LiMg0.5Mn1.5O4 layers on the surface of LiAl0.1Mn1.9O4. X-ray absorption studies revealed an oxidation state close to tetravalent manganese on the surface layer of coated materials. Materials with these surface coating layers exhibited excellent capacity retentions superior to the bare material, without undermining the lithium ion transport characteristics and the high rate performances.

  8. Color stable white phosphorescent organic light emitting diodes with red emissive electron transport layer

    SciTech Connect

    Wook Kim, Jin; Yoo, Seung Il; Sung Kang, Jin; Eun Lee, Song; Kwan Kim, Young; Hwa Yu, Hyeong; Turak, Ayse; Young Kim, Woo

    2015-06-28

    We analyzed the performance of multi-emissive white phosphorescent organic light-emitting diodes (PHOLEDs) in relation to various red emitting sites of hole and electron transport layers (HTL and ETL). The shift of the recombination zone producing stable white emission in PHOLEDs was utilized as luminance was increased with red emission in its electron transport layer. Multi-emissive white PHOLEDs including the red light emitting electron transport layer yielded maximum external quantum efficiency of 17.4% with CIE color coordinates (−0.030, +0.001) shifting only from 1000 to 10 000 cd/m{sup 2}. Additionally, we observed a reduction of energy loss in the white PHOLED via Ir(piq){sub 3} as phosphorescent red dopant in electron transport layer.

  9. Color stable white phosphorescent organic light emitting diodes with red emissive electron transport layer

    NASA Astrophysics Data System (ADS)

    Wook Kim, Jin; Yoo, Seung Il; Sung Kang, Jin; Eun Lee, Song; Kwan Kim, Young; Hwa Yu, Hyeong; Turak, Ayse; Young Kim, Woo

    2015-06-01

    We analyzed the performance of multi-emissive white phosphorescent organic light-emitting diodes (PHOLEDs) in relation to various red emitting sites of hole and electron transport layers (HTL and ETL). The shift of the recombination zone producing stable white emission in PHOLEDs was utilized as luminance was increased with red emission in its electron transport layer. Multi-emissive white PHOLEDs including the red light emitting electron transport layer yielded maximum external quantum efficiency of 17.4% with CIE color coordinates (-0.030, +0.001) shifting only from 1000 to 10 000 cd/m2. Additionally, we observed a reduction of energy loss in the white PHOLED via Ir(piq)3 as phosphorescent red dopant in electron transport layer.

  10. Formation of Al/B4C Surface Nano-composite Layers on 7075 Al Alloy Employing Friction Stir Processing

    NASA Astrophysics Data System (ADS)

    Kashani-Bozorg, S. F.; Jazayeri, K.

    2009-06-01

    Al/B4C surface nano-composite layers was achieved on commercial 7075 Al substrate employing friction stir processing technique. Agglomeration of B4C particles was occurred after a single pass. The dispersion of B4C particles was found to be affected by the number of FSP passes. A distribution of nano-size B4C particle was achieved after four passes. Moreover, the increasing in number of FSP passes causes a decreasing in matrix grain size of the surface nano-composite layer. The micro hardness of the surface nano-composite layer improves by almost two times as compared to that of the as-received substrate; this is attributed to the finer matrix grains and dispersion of nano-sized B4C particles.

  11. Modeling pollutant transport in the atmosphere boundary layer

    SciTech Connect

    O`Steen, B.L.

    1990-12-31

    The two basic methods for modeling the atmospheric transport of pollutants (diagnostic and prognostic) are examined along with the current models utilized at SRS for emergency response (WINDS). The ability of a limited-area (mesoscale) model, nested within a synoptic scale model, to represent a wide range of flow behavior, makes it the method of choice for predicting pollutant transport. Such a mesoscale model can provide an invaluable research tool and, with a periodic processing strategy for wind field calculation and/or sufficient computer capability, can be utilized in an emergency response capacity. Various models are compared.

  12. Modeling pollutant transport in the atmosphere boundary layer

    SciTech Connect

    O'Steen, B.L.

    1990-01-01

    The two basic methods for modeling the atmospheric transport of pollutants (diagnostic and prognostic) are examined along with the current models utilized at SRS for emergency response (WINDS). The ability of a limited-area (mesoscale) model, nested within a synoptic scale model, to represent a wide range of flow behavior, makes it the method of choice for predicting pollutant transport. Such a mesoscale model can provide an invaluable research tool and, with a periodic processing strategy for wind field calculation and/or sufficient computer capability, can be utilized in an emergency response capacity. Various models are compared.

  13. High-performance quantum dot light-emitting diodes with hybrid hole transport layer via doping engineering.

    PubMed

    Huang, Qianqian; Pan, Jiangyong; Zhang, Yuning; Chen, Jing; Tao, Zhi; He, Chao; Zhou, Kaifeng; Tu, Yan; Lei, Wei

    2016-11-14

    Here, we report on the hybrid hole transport materials 4,4'-bis-(carbazole-9-yl)biphenyl (CBP) or poly-N-vinylcarbazole (PVK) doped into poly(4-butyl-phenyl-diphenyl-amine) (Poly-TPD) as the hybrid hole transport layer (HTL) to tailor the energy band alignment between hole injection layer (HIL) and quantum dot (QD) light emitting layer in order to realize efficient quantum dot light emitting diodes (QLEDs) in all solution-processed fabrication. Compared to the pristine Poly-TPD based device, it is found that the electroluminescence (EL) performance of QLEDs can be significantly improved by 1.5 fold via addition of CBP into Poly-TPD, which can be attributed to the lowered highest occupied molecular orbital (HOMO) level of Poly-TPD to reduce the energy barrier between HTL and valance band (VB) of QDs. Thus, after doping small molecules into polymer under optimized proportion (Poly-TPD:CBP = 2:1 by weight), the hole transport rate can be balanced, facilitating the carrier injection from HTL to QDs and enhancing the efficiency of QLEDs. As a result, a maximum luminance, a maximum current efficiency and a maximum power efficiency of 7600 cd/m2, 5.41 cd/A and 4.25 lm/W can be obtained based on this variety of hybrid HTL employed QLEDs.

  14. Water Transport in the Micro Porous Layer and Gas Diffusion Layer of a Polymer Electrolyte Fuel Cell

    NASA Astrophysics Data System (ADS)

    Qin, C.; Hassanizadeh, S. M.

    2015-12-01

    In this work, a recently developed dynamic pore-network model is presented [1]. The model explicitly solves for both water pressure and capillary pressure. A semi-implicit scheme is used in updating water saturation in each pore body, which considerably increases the numerical stability at low capillary number values. Furthermore, a multiple-time-step algorithm is introduced to reduce the computational effort. A number of case studies of water transport in the micro porous layer (MPL) and gas diffusion layer (GDL) are conducted. We illustrate the role of MPL in reducing water flooding in the GDL. Also, the dynamic water transport through the MPL-GDL interface is explored in detail. This information is essential to the reduced continua model (RCM), which was developed for multiphase flow through thin porous layers [2, 3]. C.Z. Qin, Water transport in the gas diffusion layer of a polymer electrolyte fuel cell: dynamic pore-network modeling, J Electrochimical. Soci., 162, F1036-F1046, 2015. C.Z. Qin and S.M. Hassanizadeh, Multiphase flow through multilayers of thin porous media: general balance equations and constitutive relationships for a solid-gas-liquid three-phase system, Int. J. Heat Mass Transfer, 70, 693-708, 2014. C.Z. Qin and S.M. Hassanizadeh, A new approach to modeling water flooding in a polymer electrolyte fuel cell, Int. J. Hydrogen Energy, 40, 3348-3358, 2015.

  15. Two stacked tandem white organic light-emitting diodes employing WO3 as a charge generation layer

    NASA Astrophysics Data System (ADS)

    Bin, Jong-Kwan; Lee, Na Yeon; Lee, SeungJae; Seo, Bomin; Yang, JoongHwan; Kim, Jinook; Yoon, Soo Young; Kang, InByeong

    2016-09-01

    Recently, many studies have been conducted to improve the electroluminescence (EL) performance of organic lightemitting diodes (OLEDs) by using appropriate organic or inorganic materials as charge generation layer (CGL) for their application such as full color displays, backlight units, and general lighting source. In a stacked tandem white organic light-emitting diodes (WOLEDs), a few emitting units are electrically interconnected by a CGL, which plays the role of generating charge carriers, and then facilitate the injection of it into adjacent emitting units. In the present study, twostacked WOLEDs were fabricated by using tungsten oxide (WO3) as inorganic charge generation layer and 1,4,5,8,9,11- hexaazatriphenylene hexacarbonitrile (HAT-CN) as organic charge generation layer (P-CGL). Organic P-CGL materials were used due to their ease of use in OLED fabrication as compared to their inorganic counterparts. To obtain high efficiency, we demonstrate two-stacked tandem WOLEDs as follows: ITO/HIL/HTL/HTL'/B-EML/ETL/N-CGL/P-CGL (WO3 or HAT-CN)/HTL″/YG-EML/ETL/LiF/Al. The tandem devices with blue- and yellow-green emitting layers were sensitive to the thickness of an adjacent layer, hole transporting layer for the YG emitting layer. The WOLEDs containing the WO3 as charge generation layer reach a higher power efficiency of 19.1 lm/W and the current efficiency of 51.2 cd/A with the white color coordinate of (0.316, 0.318) than the power efficiency of 13.9 lm/W, and the current efficiency of 43.7 cd/A for organic CGL, HAT-CN at 10 mA/cm2, respectively. This performance with inserting WO3 as CGL exhibited the highest performance with excellent CIE color coordinates in the two-stacked tandem OLEDs.

  16. First principles calculations of solid-state thermionic transport in layered van der Waals heterostructures.

    PubMed

    Wang, Xiaoming; Zebarjadi, Mona; Esfarjani, Keivan

    2016-08-21

    This work aims at understanding solid-state energy conversion and transport in layered (van der Waals) heterostructures in contact with metallic electrodes via a first-principles approach. As an illustration, a graphene/phosphorene/graphene heterostructure in contact with gold electrodes is studied by using density functional theory (DFT)-based first principles calculations combined with real space Green's function (GF) formalism. We show that for a monolayer phosphorene, quantum tunneling dominates the transport. By adding more phosphorene layers, one can switch from tunneling-dominated transport to thermionic-dominated transport, resulting in transporting more heat per charge carrier, thus, enhancing the cooling coefficient of performance. The use of layered van der Waals heterostructures has two advantages: (a) thermionic transport barriers can be tuned by changing the number of layers, and (b) thermal conductance across these non-covalent structures is very weak. The phonon thermal conductance of the present van der Waals heterostructure is found to be 4.1 MW m(-2) K(-1) which is one order of magnitude lower than the lowest value for that of covalently-bonded interfaces. The thermionic coefficient of performance for the proposed device is 18.5 at 600 K corresponding to an equivalent ZT of 0.13, which is significant for nanoscale devices. This study shows that layered van der Waals structures have great potential to be used as solid-state energy-conversion devices.

  17. Phonon transport in single-layer boron nanoribbons

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongwei; Xie, Yuee; Peng, Qing; Chen, Yuanping

    2016-11-01

    Inspired by the successful synthesis of three two-dimensional (2D) allotropes, the boron sheet has recently been one of the hottest 2D materials around. However, to date, phonon transport properties of these new materials are still unknown. By using the non-equilibrium Green’s function (NEGF) combined with the first principles method, we study ballistic phonon transport in three types of boron sheets; two of them correspond to the structures reported in the experiments, while the third one is a stable structure that has not been synthesized yet. At room temperature, the highest thermal conductance of the boron nanoribbons is comparable with that of graphene, while the lowest thermal conductance is less than half of graphene’s. Compared with graphene, the three boron sheets exhibit diverse anisotropic transport characteristics. With an analysis of phonon dispersion, bonding charge density, and simplified models of atomic chains, the mechanisms of the diverse phonon properties are discussed. Moreover, we find that many hybrid patterns based on the boron allotropes can be constructed naturally without doping, adsorption, and defects. This provides abundant nanostructures for thermal management and thermoelectric applications.

  18. Solution-processable graphene oxide as an efficient hole transport layer in polymer solar cells.

    PubMed

    Li, Shao-Sian; Tu, Kun-Hua; Lin, Chih-Cheng; Chen, Chun-Wei; Chhowalla, Manish

    2010-06-22

    The utilization of graphene oxide (GO) thin films as the hole transport and electron blocking layer in organic photovoltaics (OPVs) is demonstrated. The incorporation of GO deposited from neutral solutions between the photoactive poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM) layer and the transparent and conducting indium tin oxide (ITO) leads to a decrease in recombination of electrons and holes and leakage currents. This results in a dramatic increase in the OPV efficiencies to values that are comparable to devices fabricated with PEDOT:PSS as the hole transport layer. Our results indicate that GO could be a simple solution-processable alternative to PEDOT:PSS as the effective hole transport and electron blocking layer in OPV and light-emitting diode devices.

  19. Structural design of a double-layered porous hydrogel for effective mass transport.

    PubMed

    Kim, Hyejeong; Kim, Hyeon Jeong; Huh, Hyung Kyu; Hwang, Hyung Ju; Lee, Sang Joon

    2015-03-01

    Mass transport in porous materials is universal in nature, and its worth attracts great attention in many engineering applications. Plant leaves, which work as natural hydraulic pumps for water uptake, have evolved to have the morphological structure for fast water transport to compensate large water loss by leaf transpiration. In this study, we tried to deduce the advantageous structural features of plant leaves for practical applications. Inspired by the tissue organization of the hydraulic pathways in plant leaves, analogous double-layered porous models were fabricated using agarose hydrogel. Solute transport through the hydrogel models with different thickness ratios of the two layers was experimentally observed. In addition, numerical simulation and theoretical analysis were carried out with varying porosity and thickness ratio to investigate the effect of structural factors on mass transport ability. A simple parametric study was also conducted to examine unveiled relations between structural factors. As a result, the porosity and thickness ratio of the two layers are found to govern the mass transport ability in double-layered porous materials. The hydrogel models with widely dispersed pores at a fixed porosity, i.e., close to a homogeneously porous structure, are mostly turned out to exhibit fast mass transport. The present results would provide a new framework for fundamental design of various porous structures for effective mass transport.

  20. Sediment transport under wave groups: Relative importance between nonlinear waveshape and nonlinear boundary layer streaming

    USGS Publications Warehouse

    Yu, X.; Hsu, T.-J.; Hanes, D.M.

    2010-01-01

    Sediment transport under nonlinear waves in a predominately sheet flow condition is investigated using a two-phase model. Specifically, we study the relative importance between the nonlinear waveshape and nonlinear boundary layer streaming on cross-shore sand transport. Terms in the governing equations because of the nonlinear boundary layer process are included in this one-dimensional vertical (1DV) model by simplifying the two-dimensional vertical (2DV) ensemble-averaged two-phase equations with the assumption that waves propagate without changing their form. The model is first driven by measured time series of near-bed flow velocity because of a wave group during the SISTEX99 large wave flume experiment and validated with the measured sand concentration in the sheet flow layer. Additional studies are then carried out by including and excluding the nonlinear boundary layer terms. It is found that for the grain diameter (0.24 mm) and high-velocity skewness wave condition considered here, nonlinear waveshape (e.g., skewness) is the dominant mechanism causing net onshore transport and nonlinear boundary layer streaming effect only causes an additional 36% onshore transport. However, for conditions of relatively low-wave skewness and a stronger offshore directed current, nonlinear boundary layer streaming plays a more critical role in determining the net transport. Numerical experiments further suggest that the nonlinear boundary layer streaming effect becomes increasingly important for finer grain. When the numerical model is driven by measured near-bed flow velocity in a more realistic surf zone setting, model results suggest nonlinear boundary layer processes may nearly double the onshore transport purely because of nonlinear waveshape. Copyright 2010 by the American Geophysical Union.

  1. Vorticity Transport in a Two Layer, Double Gyre Ocean Basin

    NASA Astrophysics Data System (ADS)

    Kaiser, Bryan; Clayson, Carol Anne; Jayne, Steve

    2016-11-01

    The double gyre ocean circulations predicted by strongly frictional, barotropic, linearized ocean models qualitatively agree with the patterns of large scale gyres in the world ocean. However, nonlinear ocean models featuring less intense eddy diffusion parameterization can converge to an infinite number of statistically stationary circulations, depending on the parameterization of dissipation of energy and vorticity. Patterns of vorticity flux and dissipation in a barotropic ocean have been examined previous studies; in this work the inclusion of the first baroclinic mode is examined. The first vertical mode permits the model to be split into two layers, the top approximating the thermocline and the bottom approximating the abyssal circulation. The separation into two layers not only adds realism and but also removes the nonphysical direct restraint of the upper ocean by bottom friction. Steady state circulations for various boundary conditions, sources and sinks of vorticity, and Reynolds numbers are simulated using a parallel pseudo-spectral quasi-geostrophic flow solver and mechanisms of vorticity flux and dissipation are discussed.

  2. Improved Ambient-Stable Perovskite Solar Cells Enabled by a Hybrid Polymeric Electron-Transporting Layer.

    PubMed

    Zhu, Zonglong; Chueh, Chu-Chen; Zhang, Guangye; Huang, Fei; Yan, He; Jen, Alex K-Y

    2016-09-22

    In this work, an efficient inverted perovskite solar cell with decent ambient stability is successfully demonstrated by employing an n-type polymer, poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalene diimide-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (N2200), as the electron-transporting layer (ETL). The device performance can be further enhanced from a power conversion efficiency (PCE) of 15 to 16.8 % by tailoring the electronic properties of N2200 with a polymeric additive, poly[9,9-bis(6'-(N,N-diethylamino)propyl)-fluorene-alt-9,9-bis(3-ethyl(oxetane-3-ethyloxy)-hexyl) fluorene] (PFN-Ox). More importantly, the device derived from this hybrid ETL can maintain good ambient stability inherent from the pristine N2200 ETL, for which 60-70 % of initial PCE can be retained after being stored in air with 10-20 % humidity for 45 days.

  3. Improved ambient-stable perovskite solar cells enabled by a hybrid polymeric electron-transporting layer

    DOE PAGES

    Zhu, Zonglong; Chueh, Chu -Chen; Zhang, Guangye; ...

    2016-08-26

    In this study, an efficient inverted perovskite solar cell with decent ambient stability is successfully demonstrated by employing an n-type polymer, poly{[N,N’-bis(2-octyldodecyl)- 1,4,5,8-naphthalene diimide-2,6-diyl]-alt-5,5’-(2,2’-bithiophene)} (N2200), as the electron-transporting layer (ETL). The device performance can be further enhanced from a power conversion efficiency (PCE) of 15 to 16.8% by tailoring the electronic properties of N2200 with a polymeric additive, poly[9,9-bis(6’- (N,N’-diethylamino)propyl)-fluorene-alt-9,9-bis(3-ethyl(oxetane- 3-ethyloxy)-hexyl) fluorene] (PFN-Ox). More importantly, the device derived from this hybrid ETL can maintain good ambient stability inherent from the pristine N2200 ETL, for which 60–70% of initial PCE can be retained after being stored in air with 10–20% humiditymore » for 45 days.« less

  4. Improved ambient-stable perovskite solar cells enabled by a hybrid polymeric electron-transporting layer

    SciTech Connect

    Zhu, Zonglong; Chueh, Chu -Chen; Zhang, Guangye; Huang, Fei; Yan, He; Jen, Alex K. -Y.

    2016-08-26

    In this study, an efficient inverted perovskite solar cell with decent ambient stability is successfully demonstrated by employing an n-type polymer, poly{[N,N’-bis(2-octyldodecyl)- 1,4,5,8-naphthalene diimide-2,6-diyl]-alt-5,5’-(2,2’-bithiophene)} (N2200), as the electron-transporting layer (ETL). The device performance can be further enhanced from a power conversion efficiency (PCE) of 15 to 16.8% by tailoring the electronic properties of N2200 with a polymeric additive, poly[9,9-bis(6’- (N,N’-diethylamino)propyl)-fluorene-alt-9,9-bis(3-ethyl(oxetane- 3-ethyloxy)-hexyl) fluorene] (PFN-Ox). More importantly, the device derived from this hybrid ETL can maintain good ambient stability inherent from the pristine N2200 ETL, for which 60–70% of initial PCE can be retained after being stored in air with 10–20% humidity for 45 days.

  5. A composite nanostructured electron-transport layer for stable hole-conductor free perovskite solar cells: design and characterization.

    PubMed

    Yu, Zhenhua; Qi, Fei; Liu, Pei; You, Sujian; Kondamareddy, Kiran Kumar; Wang, Changlei; Cheng, Nian; Bai, Sihang; Liu, Wei; Guo, Shishang; Zhao, Xing-zhong

    2016-03-21

    A novel composite nanostructured titanium dioxide (TiO2) based electron-transport layer (ETL) is designed by combining size blended nanoparticles (SBNP) and nanoarrays (NA) for efficient perovskite solar cell (PSC) applications. The composite nanostructured (SBNP + NA) ETL is successfully employed in hole-conductor free PSCs, there by achieving a stable device with a maximum efficiency of 13.5%. The improvement in the performance is attributed to the better charge transport and lower recombination in the SBNP + NA ETL. Despite the stable high efficiency, SBNP + NA ETL based PSCs are advantageous owing to their low cost, ease of all-solution fabrication process in an open environment and good reproducibility.

  6. 41 CFR 102-34.210 - May I use a Government motor vehicle for transportation between places of employment and mass...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... motor vehicle for transportation between places of employment and mass transit facilities? 102-34.210... of employment and mass transit facilities? Yes, you may use a Government motor vehicle for transportation between places of employment and mass transit facilities under the following conditions: (a)...

  7. 41 CFR 102-34.210 - May I use a Government motor vehicle for transportation between places of employment and mass...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... motor vehicle for transportation between places of employment and mass transit facilities? 102-34.210... of employment and mass transit facilities? Yes, you may use a Government motor vehicle for transportation between places of employment and mass transit facilities under the following conditions: (a)...

  8. 41 CFR 102-34.210 - May I use a Government motor vehicle for transportation between places of employment and mass...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... motor vehicle for transportation between places of employment and mass transit facilities? 102-34.210... of employment and mass transit facilities? Yes, you may use a Government motor vehicle for transportation between places of employment and mass transit facilities under the following conditions: (a)...

  9. 41 CFR 102-34.210 - May I use a Government motor vehicle for transportation between places of employment and mass...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... motor vehicle for transportation between places of employment and mass transit facilities? 102-34.210... of employment and mass transit facilities? Yes, you may use a Government motor vehicle for transportation between places of employment and mass transit facilities under the following conditions: (a)...

  10. 41 CFR 102-34.210 - May I use a Government motor vehicle for transportation between places of employment and mass...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... motor vehicle for transportation between places of employment and mass transit facilities? 102-34.210... of employment and mass transit facilities? Yes, you may use a Government motor vehicle for transportation between places of employment and mass transit facilities under the following conditions: (a)...

  11. Transportation & Work: Exploring Car Usage and Employment Outcomes in the LSAL Data. NCSALL Occasional Paper

    ERIC Educational Resources Information Center

    Sullivan, Kerri

    2003-01-01

    This analysis addresses the role of car usage in employment outcomes such as employment status, average weekly wages, and weeks worked per year. It postulates that car ownership is an important employment tool for adults of low educational attainment in Portland, even in the context of other factors such as social networks/resources (social…

  12. A Two-Layered Model for Dynamic Supply Chain Management Considering Transportation Constraint

    NASA Astrophysics Data System (ADS)

    Tanimizu, Yoshitaka; Harada, Kana; Ozawa, Chisato; Iwamura, Koji; Sugimura, Nobuhiro

    This research proposes a two-layered model for dynamic supply chain management considering transportation constraint. The model provides a method for suppliers to estimate suitable prices and delivery times of products based on not only production schedules but also transportation plans in consideration of constraints about shipping times and loading capacities for transportation. A prototype of dynamic supply chain simulation system was developed and some computational experiments were carried out in order to verify the effectiveness of the model. The prototype system is available to determine suitable shipping times and loading capacities of transportation vehicles.

  13. Small particle transport across turbulent nonisothermal boundary layers

    NASA Technical Reports Server (NTRS)

    Rosner, D. E.; Fernandez De La Mora, J.

    1982-01-01

    The interaction between turbulent diffusion, Brownian diffusion, and particle thermophoresis in the limit of vanishing particle inertial effects is quantitatively modeled for applications in gas turbines. The model is initiated with consideration of the particle phase mass conservation equation for a two-dimensional boundary layer, including the thermophoretic flux term directed toward the cold wall. A formalism of a turbulent flow near a flat plate in a heat transfer problem is adopted, and variable property effects are neglected. Attention is given to the limit of very large Schmidt numbers and the particle concentration depletion outside of the Brownian sublayer. It is concluded that, in the parameter range of interest, thermophoresis augments the high Schmidt number mass-transfer coefficient by a factor equal to the product of the outer sink and the thermophoretic suction.

  14. Expression of digestive enzymes and nutrient transporters in Eimeria acervulina-challenged layers and broilers.

    PubMed

    Su, S; Miska, K B; Fetterer, R H; Jenkins, M C; Wong, E A

    2014-05-01

    Avian coccidiosis is a disease caused by intestinal protozoa in the genus Eimeria. Clinical signs of coccidiosis include intestinal lesions and reduced feed efficiency and BW gain. This growth reduction may be due to changes in expression of digestive enzymes and nutrient transporters in the intestine. The objective of this study was to examine the differential expression of digestive enzymes, transporters of amino acids, peptides, sugars, and minerals, and an antimicrobial peptide in the small intestine of Eimeria acervulina-infected broilers and layers. Uninfected broilers and layers, in general, expressed these genes at comparable levels. Some differences included 3-fold and 2-fold greater expression of the peptide transporter PepT1 and the antimicrobial peptide LEAP2 (liver expressed antimicrobial peptide 2), respectively, in the jejunum of layers compared with broilers and 17-fold greater expression of LEAP2 in the duodenum of broilers compared with layers. In the duodenum of Eimeria-infected broilers and layers, there was downregulation of aminopeptidase N; sucrase-isomaltase; the neutral, cationic, and anionic amino acid transporters b(o,+)AT/rBAT, B(o)AT, CAT2, and EAAT3; the sugar transporter GLUT2; the zinc transporter ZnT1; and LEAP2. In the jejunum of infected layers there was downregulation of many of the same genes as in the duodenum plus downregulation of PepT1, b(o,+)AT/rBAT, and the y(+) L system amino acid transporters y(+) LAT1 and y(+) LAT2. In the ileum of infected layers there was downregulation of CAT2, y(+)LAT1, the L type amino acid transporter LAT1, and the sugar transporter GLUT1, and upregulation of APN, PepT1, the sodium glucose transporter SGLT4, and LEAP2. In E. acervulina-infected broilers, there were no gene expression changes in the jejunum and ileum. These changes in intestinal digestive enzyme and nutrient transporter gene expression may result in a decrease in the efficiency of protein digestion, uptake of important amino acids

  15. Spin Transport in Single Layer Transition Metal Dichalcogenides

    NASA Astrophysics Data System (ADS)

    Phillips, Michael; Aji, Vivek

    Inversion symmetry breaking and strong spin orbit coupling in two dimensional transition metal dichalcogenides leads to interesting new phenomena such as the valley hall and spin hall effects. The nontrivial Berry curvature of the bands yields transverse spin currents in applied field. In this talk we characterize the spin transport in hole-doped systems. Due to the large spin-splitting, time-reversal invariance, and the large separation of hole pockets in momentum space, spin flip scattering involves inter-valley processes with large momentum. As such, one expects large spin life times and a large spin hall angle. We analyze the robustness of the phenomena to various scattering processes and explore the viability of transition metal dichalcogenides for spintronic applications. We acknowledge the support of the NSF via Grant NSF DMR-1506707.

  16. Multifunctional Inverse Opal-Like TiO2 Electron Transport Layer for Efficient Hybrid Perovskite Solar Cells.

    PubMed

    Chen, Xiao; Yang, Shuang; Zheng, Yi Chu; Chen, Ying; Hou, Yu; Yang, Xiao Hua; Yang, Hua Gui

    2015-09-01

    A novel multifunctional inverse opal-like TiO2 electron transport layer (IOT-ETL) is designed to replace the traditional compact layer and mesoporous scaffold layer in perovskite solar cells (PSCs). Improved light harvesting efficiency and charge transporting performance in IOT-ETL based PSCs yield high power conversion efficiency of 13.11%.

  17. Ion transport in complex layered graphene-based membranes with tuneable interlayer spacing

    PubMed Central

    Cheng, Chi; Jiang, Gengping; Garvey, Christopher J.; Wang, Yuanyuan; Simon, George P.; Liu, Jefferson Z.; Li, Dan

    2016-01-01

    Investigation of the transport properties of ions confined in nanoporous carbon is generally difficult because of the stochastic nature and distribution of multiscale complex and imperfect pore structures within the bulk material. We demonstrate a combined approach of experiment and simulation to describe the structure of complex layered graphene-based membranes, which allows their use as a unique porous platform to gain unprecedented insights into nanoconfined transport phenomena across the entire sub–10-nm scales. By correlation of experimental results with simulation of concentration-driven ion diffusion through the cascading layered graphene structure with sub–10-nm tuneable interlayer spacing, we are able to construct a robust, representative structural model that allows the establishment of a quantitative relationship among the nanoconfined ion transport properties in relation to the complex nanoporous structure of the layered membrane. This correlation reveals the remarkable effect of the structural imperfections of the membranes on ion transport and particularly the scaling behaviors of both diffusive and electrokinetic ion transport in graphene-based cascading nanochannels as a function of channel size from 10 nm down to subnanometer. Our analysis shows that the range of ion transport effects previously observed in simple one-dimensional nanofluidic systems will translate themselves into bulk, complex nanoslit porous systems in a very different manner, and the complex cascading porous circuities can enable new transport phenomena that are unattainable in simple fluidic systems. PMID:26933689

  18. Ion transport in complex layered graphene-based membranes with tuneable interlayer spacing.

    PubMed

    Cheng, Chi; Jiang, Gengping; Garvey, Christopher J; Wang, Yuanyuan; Simon, George P; Liu, Jefferson Z; Li, Dan

    2016-02-01

    Investigation of the transport properties of ions confined in nanoporous carbon is generally difficult because of the stochastic nature and distribution of multiscale complex and imperfect pore structures within the bulk material. We demonstrate a combined approach of experiment and simulation to describe the structure of complex layered graphene-based membranes, which allows their use as a unique porous platform to gain unprecedented insights into nanoconfined transport phenomena across the entire sub-10-nm scales. By correlation of experimental results with simulation of concentration-driven ion diffusion through the cascading layered graphene structure with sub-10-nm tuneable interlayer spacing, we are able to construct a robust, representative structural model that allows the establishment of a quantitative relationship among the nanoconfined ion transport properties in relation to the complex nanoporous structure of the layered membrane. This correlation reveals the remarkable effect of the structural imperfections of the membranes on ion transport and particularly the scaling behaviors of both diffusive and electrokinetic ion transport in graphene-based cascading nanochannels as a function of channel size from 10 nm down to subnanometer. Our analysis shows that the range of ion transport effects previously observed in simple one-dimensional nanofluidic systems will translate themselves into bulk, complex nanoslit porous systems in a very different manner, and the complex cascading porous circuities can enable new transport phenomena that are unattainable in simple fluidic systems.

  19. A data-driven approach to establishing microstructure-property relationships in porous transport layers of polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Çeçen, A.; Fast, T.; Kumbur, E. C.; Kalidindi, S. R.

    2014-01-01

    The diffusion media (DM) has been shown to be a vital component for performance of polymer electrolyte fuel cells (PEFCs). The DM has a dual-layer structure composed of a macro-substrate referred to as the gas diffusion layer (GDL) coated with a micro-porous layer (MPL). Efficient prediction of the effective transport properties of the DM from its internal structure is essential to optimizing the multifunctional characteristics of this critical component. In this work, a unique data-driven approach to establishing structure-property correlations is introduced and applied to the case of gas diffusion in the GDL and MPL. This new approach provides an automated process to produce unbiased estimators to microstructural variance, in contrast to many process-related (hence biased) parameters employed by prominent correlations in the field. The present approach starts with a rigorous quantification of microstructure in the form of n-point statistics. It is followed by the identification of the key aspects of the internal structure through the use of principle component analysis. A data-driven correlation is established when the principal components are related to effective diffusivity by multivariate linear regression. This data-driven approach is compared to the conventional correlations and shown to achieve a very high accuracy for capturing the diffusive transport in the tested PEFC components.

  20. Effects of hole-transporting layers of perovskite-based solar cells

    NASA Astrophysics Data System (ADS)

    Suzuki, Atsushi; Kida, Tomoyasu; Takagi, Tatsuru; Oku, Takeo

    2016-02-01

    Fabrication and characterization of the photovoltaic and optical properties, and microstructure of perovskite-based solar cells with lead phthalocyanine (PbPc), zinc phthalocyanine, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], and copper(I) thiocyanate as hole-transporting layers were investigated. X-ray diffraction analysis and energy-dispersive X-ray spectroscopy were used to identify surface morphologies of the crystal structure and the elemental composition. Introducing PbPc into perovskite solar cells extended the retaining period of photovoltaic activity and performance. The effects of the hole-transporting layer on incident photon-to-current efficiency were investigated. The energy diagram and photovoltaic mechanism of the perovskite solar cells with the hole-transporting layer are discussed.

  1. Activated Transport in the Separate Layers that Form the νT=1 Exciton Condensate

    NASA Astrophysics Data System (ADS)

    Wiersma, R. D.; Lok, J. G.; Kraus, S.; Dietsche, W.; von Klitzing, K.; Schuh, D.; Bichler, M.; Tranitz, H.-P.; Wegscheider, W.

    2004-12-01

    We observe the total filling factor νT=1 quantum Hall state in a bilayer two-dimensional electron system with virtually no tunneling. We find thermally activated transport in the balanced system with a monotonic increase of the activation energy with decreasing d/ℓB below 1.65. In the imbalanced system we find activated transport in each of the layers separately, yet the activation energies show a striking asymmetry around the balance point, implying a different excitation spectrum for the separate layers forming the condensed state.

  2. Magneto-transport properties of a random distribution of few-layer graphene patches

    NASA Astrophysics Data System (ADS)

    Iacovella, Fabrice; Trinsoutrot, Pierre; Mitioglu, Anatolie; Conédéra, Véronique; Pierre, Mathieu; Raquet, Bertrand; Goiran, Michel; Vergnes, Hugues; Caussat, Brigitte; Plochocka, Paulina; Escoffier, Walter

    2014-11-01

    In this study, we address the electronic properties of conducting films constituted of an array of randomly distributed few layer graphene patches and investigate on their most salient galvanometric features in the moderate and extreme disordered limit. We demonstrate that, in annealed devices, the ambipolar behaviour and the onset of Landau level quantization in high magnetic field constitute robust hallmarks of few-layer graphene films. In the strong disorder limit, however, the magneto-transport properties are best described by a variable-range hopping behaviour. A large negative magneto-conductance is observed at the charge neutrality point, in consistency with localized transport regime.

  3. Diffusion across a layered medium and relation to transport in thermonuclear plasmas

    SciTech Connect

    Lopes Cardozo, N.J.; Peters, M.

    1995-11-01

    The generic characteristics of diffusion in a medium exhibiting strong variations of the diffusivity are considered. The varying diffusivity is parametrized by alternating layers of high and low diffusivity. The limiting case is considered that the insulating layers determine the net transport. Some salient features of tokamak transport, such as the fact that perturbative experiments yield a higher diffusivity than a steady-state power balance, are shown to be a natural result of the inhomogeneity. The importance of a possible inhomogeneous diffusivity for the comparison of measurements with theoretical expressions for the diffusivity is discussed. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  4. Coherent Structures in the Turbulent Atmospheric Boundary Layer: modulation by static stability and role in transport

    NASA Astrophysics Data System (ADS)

    Bou-Zeid, E.; Li, D.; Shah, S.

    2012-12-01

    Understanding the turbulent transport of momentum, scalars, and particles in the atmospheric boundary layer is important in many disciplines such as meteorology, hydrology, and desert morphodynamics. At present, similarity theories that rely on a significant degree of empiricism remain the main approach to understand and model these fluxes. One of the hurdles to developing more fundamental and robust theories is our lack of understanding of the topology and dynamics of turbulent coherent structures, which perform these fluxes, and how they are modulated by atmospheric stability. Using field data sets and numerical simulations of atmospheric surface layer flows under a range of stabilities, we revisit these links between coherent structures, atmospheric stability, and turbulent transport. The results confirm that the topology of the coherent structures is very sensitive to stability. The findings point to a gradual transformation of the structures from hairpin vortices under neutral stability, to thermals under unstable conditions, and to more horizontal structures under stable conditions. Under unstable conditions, this change then induces a decorrelation of the momentum and scalar fluxes in the surface layer: the eddies transporting heat and momentum become distinct leading to an increase in the transport efficiency of heat and a decrease in the transport efficiency of momentum. Under stable conditions, the reduction in the transport of momentum to the surface leads to reductions in the friction velocity and the turbulent kinetic energy (TKE) production. The effect of reduced production can be more important than the effect of direct TKE destruction in the stable ABL.

  5. First principles calculations of solid-state thermionic transport in layered van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoming; Zebarjadi, Mona; Esfarjani, Keivan

    2016-08-01

    This work aims at understanding solid-state energy conversion and transport in layered (van der Waals) heterostructures in contact with metallic electrodes via a first-principles approach. As an illustration, a graphene/phosphorene/graphene heterostructure in contact with gold electrodes is studied by using density functional theory (DFT)-based first principles calculations combined with real space Green's function (GF) formalism. We show that for a monolayer phosphorene, quantum tunneling dominates the transport. By adding more phosphorene layers, one can switch from tunneling-dominated transport to thermionic-dominated transport, resulting in transporting more heat per charge carrier, thus, enhancing the cooling coefficient of performance. The use of layered van der Waals heterostructures has two advantages: (a) thermionic transport barriers can be tuned by changing the number of layers, and (b) thermal conductance across these non-covalent structures is very weak. The phonon thermal conductance of the present van der Waals heterostructure is found to be 4.1 MW m-2 K-1 which is one order of magnitude lower than the lowest value for that of covalently-bonded interfaces. The thermionic coefficient of performance for the proposed device is 18.5 at 600 K corresponding to an equivalent ZT of 0.13, which is significant for nanoscale devices. This study shows that layered van der Waals structures have great potential to be used as solid-state energy-conversion devices.This work aims at understanding solid-state energy conversion and transport in layered (van der Waals) heterostructures in contact with metallic electrodes via a first-principles approach. As an illustration, a graphene/phosphorene/graphene heterostructure in contact with gold electrodes is studied by using density functional theory (DFT)-based first principles calculations combined with real space Green's function (GF) formalism. We show that for a monolayer phosphorene, quantum tunneling dominates the

  6. Temperature Dependence of Electric Transport in Few-layer Graphene under Large Charge Doping Induced by Electrochemical Gating

    PubMed Central

    Gonnelli, R. S.; Paolucci, F.; Piatti, E.; Sharda, Kanudha; Sola, A.; Tortello, M.; Nair, Jijeesh R.; Gerbaldi, C.; Bruna, M.; Borini, S.

    2015-01-01

    The temperature dependence of electric transport properties of single-layer and few-layer graphene at large charge doping is of great interest both for the study of the scattering processes dominating the conductivity at different temperatures and in view of the theoretically predicted possibility to reach the superconducting state in such extreme conditions. Here we present the results obtained in 3-, 4- and 5-layer graphene devices down to 3.5 K, where a large surface charge density up to about 6.8·1014 cm−2 has been reached by employing a novel polymer electrolyte solution for the electrochemical gating. In contrast with recent results obtained in single-layer graphene, the temperature dependence of the sheet resistance between 20 K and 280 K shows a low-temperature dominance of a T2 component – that can be associated with electron-electron scattering – and, at about 100 K, a crossover to the classic electron-phonon regime. Unexpectedly, this crossover does not show any dependence on the induced charge density, i.e. on the large tuning of the Fermi energy. PMID:25906088

  7. Carrier-mediated placental transport of cimetidine and valproic acid across differentiating JEG-3 cell layers.

    PubMed

    Ikeda, K; Ueda, C; Yamada, K; Nakamura, A; Hatsuda, Y; Kawanishi, S; Nishii, S; Ogawa, M

    2015-07-01

    Human choriocarcinoma has been used as a model to study trophoblast transcellular drug transport in the placenta. Previous models had limitations regarding low molecular weight drug transport through the intracellular gap junction. The purpose of this study was to evaluate placental carrier-mediated transport across a differentiating JEG-3 choriocarcinoma cell (DJEGs) layer model in which the intracellular gap junction was restricted. Cimetidine is the substrate of an efflux transporter, breast cancer resistance protein (BCRP). BCRP highly expressed in the placenta, and its function in the DJEGs model was investigated. In addition, the placental drug transport of another efflux transporter, multidrug resistance-associated proteins (MRPs), and an influx transporter, monocarboxylate transporter (MCT), were examined with various substrates. Cimetidine permeated from the fetal side to the maternal side at significantly high levels and saturated in a dose-dependent manner. The permeability coefficient of a MRP substrate, fluorescein, across the DJEGs model was significantly increased by inhibiting MRP function with probenecid. On the other hand, permeation in the influx direction to the fetal side with a substrate of MCT, valproic acid, had a gentle dose-dependent saturation. These findings suggest that the DJEGs model could be used to evaluate transcellular placental drug transport mediated by major placental transporters.

  8. Exclusion of metal oxide by an RF sputtered Ti layer in flexible perovskite solar cells: energetic interface between a Ti layer and an organic charge transporting layer.

    PubMed

    Ameen, Sadia; Akhtar, M Shaheer; Seo, Hyung-Kee; Nazeeruddin, Mohammad Khaja; Shin, Hyung-Shik

    2015-04-14

    In this work, the effects of a titanium (Ti) layer on the charge transport and recombination rates of flexible perovskite solar cells were studied. Ti as an efficient barrier layer was deposited directly on PET-ITO flexible substrates through RF magnetic sputtering using a Ti-source and a pressure of ∼5 mTorr. A Ti coated PET-ITO was used for the fabrication of a flexible perovskite solar cell without using any metal oxide layer. The fabricated flexible perovskite solar cell was composed of a PET-ITO/Ti/perovskite (CH3NH3PbI3)/organic hole transport layer of 2,2',7,7'-tetrakis [N,N'-di-p-methoxyphenylamine]-9,9'-spirobifluorene (spiro-OMeTAD)-Li-TFSI/Ag. A high conversion efficiency of ∼8.39% along with a high short circuit current (JSC) of ∼15.24 mA cm(-2), an open circuit voltage (VOC) of ∼0.830 V and a high fill factor (FF) of ∼0.66 was accomplished by the fabricated flexible perovskite solar cell under a light illumination of ∼100 mW cm(-2) (1.5 AM). Intensity-modulated photocurrent (IMPS)/photovoltage spectroscopy (IMVS) studies demonstrated that the fabricated flexible perovskite solar cell considerably reduced the recombination rate.

  9. Impact of Soil Layering on Evaporation Driven Flow and Transport in Arid Soils

    NASA Astrophysics Data System (ADS)

    Nie, W.; Nicholl, M. J.; Young, M. H.; Yu, Z.

    2008-12-01

    Coupling between soil development, hydrologic processes, and plant growth in arid regions is not well understood. Here, we integrate field, lab and numerical investigations to study the impact of soil layering on evaporation driven flow and transport in arid soils. Specifically, two hypotheses are proposed: 1) soil horizon development may significantly impact evaporation rate and spatio-temporal chemical species redistribution in arid soils; 2) differences in layering between soils beneath plant canopies and nearby interspace (bare soils) may significantly influence evaporation-driven upward water flow and solute transport. Field samples were collected from two 1-m deep soil pits in Eldorado Valley, approximately 50 km from Las Vegas, Nevada. One soil pit was located beneath a creosote bush, the other from the adjacent interspace. The overall concentrations of K+, Na+, Ca2+, Mg2+, SO42-, and soluble salts in soils under plant canopy are much higher than those from the interspace. Salts accumulated at depths from 60 to 90 cm under the canopy; in contrast, the salt concentrations in bare soils were more uniform and may accumulate in relatively deeper layers. Soil samples taken from the pits will be packed into layered and non- layered columns, respectively, to examine the effects of soil layering on evaporation flow and transport. Evaporation rate, soil-water matric/osmotic potential, and temperature gradients in each column will be continuously monitored. Upward flow and transport in different soil layering under various conditions will be simulated using the HYDRUS model. It is expected that less soil horizon development will lead to higher evaporation rates, resulting in lower volumetric water content and higher accumulation of salts in the uppermost soil horizons.

  10. Low-temperature solution-processed hydrogen molybdenum and vanadium bronzes for an efficient hole-transport layer in organic electronics.

    PubMed

    Xie, Fengxian; Choy, Wallace C H; Wang, Chuandao; Li, Xinchen; Zhang, Shaoqing; Hou, Jianhui

    2013-04-11

    A simple one-step method is reported to synthesize low-temperature solution-processed transition metal oxides (TMOs) of molybdenum oxide and vanadium oxide with oxygen vacancies for a good hole-transport layer (HTL). The oxygen vacancy plays an essential role for TMOs when they are employed as HTLs: TMO films with excess oxygen are highly undesirable for their application in organic electronics.

  11. Quantitative characterization of water transport and flooding in the diffusion layers of polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Casalegno, A.; Colombo, L.; Galbiati, S.; Marchesi, R.

    Optimization of water management in polymer electrolyte membrane fuel cells (PEMFC) and in direct methanol fuel cells (DMFC) is a very important factor for the achievement of high performances and long lifetime. A good hydration of the electrolyte membrane is essential for high proton conductivity; on the contrary water in excess may lead to electrode flooding and severe reduction in performances. Many studies on water transport across the gas diffusion layer (GDL) have been carried out to improve these components; anyway efforts in this field are affected by lack of effective experimental methods. The present work reports an experimental investigation with the purpose to determine the global coefficient of water transport across different diffusion layers under real operating conditions. An appropriate and accurate experimental apparatus has been designed and built to test the single GDL under a wide range of operating conditions. Data analysis has allowed quantification of both the water vapor transport across different diffusion layers, and the effects of micro-porous layers; furthermore flooding onset and its consequences on the mass transport coefficient have been characterized by means of suitably defined parameters.

  12. Charge transport and device physics of layered-crystalline organic semiconductors (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Hasegawa, Tatsuo

    2015-10-01

    Here we present and discuss our recent investigations into the understanding of microscopic charge transport, novel film processing technologies, and a development of layered-crystalline organic semiconductors for high performance OTFTs. We first discuss the microscopic charge transport in the OTFTs, as investigated by field-induced electron spin resonance spectroscopy. The technique can detect signals due to tiny amount of field-induced carriers, accumulated at the semiconductor-insulator interfaces. Following aspects are presented and discussed; 1) Carrier motion within the crystalline domains can be understood in terms of the trap-and-release transport, 2) charge trap states are spatially extended over several sites depending on the trap levels, and 3) the intra- and inter-domain transport can be discriminated by anisotropic electron spin resonance measurements. Next we discuss novel print production technologies for organic semiconductors showing high layered crystallinity. The concept of "printed electronics" is now regarded as a realistic paradigm to manufacture light-weight, thin, and impact-resistant electronics devices, although production of highly crystalline semiconductor films may be incompatible with conventional printing process. We here present printing techniques for manufacturing high performance OTFTs; 1) double-shot inkjet printing for small-molecule-based semiconductors, and 2) push-coating for semiconducting polymers. We demonstrate that both processes are useful to manufacture high quality semiconductor layers with the high layered crystallinity.

  13. Analytical solution for the advection-dispersion transport equation in layered media

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The advection-dispersion transport equation with first-order decay was solved analytically for multi-layered media using the classic integral transform technique (CITT). The solution procedure used an associated non-self-adjoint advection-diffusion eigenvalue problem that had the same form and coef...

  14. Water Transport Characteristics of Gas Diffusion Layer in a PEM Fuel Cell

    SciTech Connect

    Damle, Ashok S; Cole, J Vernon

    2008-12-01

    A presentation addressing the following: Water transport in PEM Fuel Cells - a DoE Project 1. Gas Diffusion Layer--Role and Characteristics 2. Capillary Pressure Determinations of GDL Media 3. Gas Permeability Measurements of GDL Media 4. Conclusions and Future Activities

  15. Interrelated structures of the transport shock and collisional relaxation layer in a multitemperature, multilevel ionized gas

    NASA Technical Reports Server (NTRS)

    Vinolo, A. R.; Clarke, J. H.

    1973-01-01

    The gas dynamic structures of the transport shock and the downstream collisional relaxation layer are evaluated for partially ionized monatomic gases. Elastic and inelastic collisional nonequilibrium effects are taken into consideration. In the microscopic model of the atom, three electronic levels are accounted for. By using an asymptotic technique, the shock morphology is found on a continuum flow basis. This procedure gives two distinct layers in which the nonequilibrium effects to be considered are different. A transport shock appears as the inner solution to an outer collisional relaxation layer. The results show four main interesting points: (1) on structuring the transport shock, ionization and excitation rates must be included in the formulation, since the flow is not frozen with respect to the population of the different electronic levels; (2) an electron temperature precursor appears at the beginning of the transport shock; (3) the collisional layer is rationally reduced to quadrature for special initial conditions, which (4) are obtained from new Rankine-Hugoniot relations for the inner shock.

  16. On effective transport coefficients in PEM fuel cell electrodes: Anisotropy of the porous transport layers

    NASA Astrophysics Data System (ADS)

    Pharoah, J. G.; Karan, K.; Sun, W.

    This paper reviews the approach taken in the literature to model the effective transport coefficients - mass diffusivity, electrical conductivity, thermal conductivity and hydraulic permeability - of carbon-fibre based porous electrode of polymer electrolyte membrane fuel cells (PEMFCs). It is concluded that current PEMFC model do not account for the inherent anisotropic microstructure of the fibrous electrodes. Simulations using a 2-D PEMFC cathode model show that neglecting the anisotropic nature and associated transport coefficients of the porous electrodes significantly influences both the nature and the magnitude of the model predictions. This emphasizes the need to appropriately characterize the relevant anisotropic properties of the fibrous electrode.

  17. Pore network modeling to explore the effects of compression on multiphase transport in polymer electrolyte membrane fuel cell gas diffusion layers

    NASA Astrophysics Data System (ADS)

    Fazeli, Mohammadreza; Hinebaugh, James; Fishman, Zachary; Tötzke, Christian; Lehnert, Werner; Manke, Ingo; Bazylak, Aimy

    2016-12-01

    Understanding how compression affects the distribution of liquid water and gaseous oxygen in the polymer electrolyte membrane fuel cell gas diffusion layer (GDL) is vital for informing the design of improved porous materials for effective water management strategies. Pore networks extracted from synchrotron-based micro-computed tomography images of compressed GDLs were employed to simulate liquid water transport in GDL materials over a range of compression pressures. The oxygen transport resistance was predicted for each sample under dry and partially saturated conditions. A favorable GDL compression value for a preferred liquid water distribution and oxygen diffusion was found for Toray TGP-H-090 (10%), yet an optimum compression value was not recognized for SGL Sigracet 25BC. SGL Sigracet 25BC exhibited lower transport resistance values compared to Toray TGP-H-090, and this is attributed to the additional diffusion pathways provided by the microporous layer (MPL), an effect that is particularly significant under partially saturated conditions.

  18. Interrelated structures of the transport shock and collisional relaxation layer in a multitemperature, multilevel ionized gas

    NASA Technical Reports Server (NTRS)

    Vinolo, A. R.; Clarke, J. H.

    1972-01-01

    The gas dynamic structures of the transport shock and the downstream collisional relaxation layer are evaluated for partially ionized monatomic gases. Elastic and inelastic collisional nonequilibrium effects are taken into consideration. Three electronic levels are accounted for in the microscopic model of the atom. Nonequilibrium processes with respect to population of levels and species plus temperature are considered. By using an asymptotic technique the shock morphology is found on a continuum flow basis. The asymptotic procedure gives two distinct layers in which the nonequilibrium effects to be considered are different. A transport shock appears as the inner solution to an outer collisional relaxation layer in which the gas reaches local equilibrium. A family of numerical examples is displayed for different flow regimes. Argon and helium models are used in these examples.

  19. Transport numbers in the surface layers of asymmetric membranes from initial time measurements

    SciTech Connect

    Compan, V.; Lopez, M.L. ); Sorensen, T.S. ); Garrido, J. )

    1994-09-08

    The initial time asymmetry potentials of two ultra filtration membranes (cellulose acetate and polysulfone membranes) were measured in electrochemical cells using Ag/AgCl electrodes and NaCl solutions. The concentration in the two electrode chambers differed slightly by a fixed concentration difference. Either the membranes were brought to equilibrium with the left-hand solution and subsequently exposed to the right-hand solution at the right-hand face, or the procedure was reversed. From such measurements it is possible to evaluate the transport numbers corresponding to each of the two surface layers of the membrane under conditions such that the effects of autoprotolysis of water and of foreign ions may be neglected. These measurements permit a description of each of the surface layers of the membranes and make possible an electrochemical characterization of the asymmetry of ultrafiltration membranes. The asymmetry is given by the difference between surface layer transport numbers. 31 refs., 13 figs., 4 tabs.

  20. Phase Conjugated and Transparent Wavelength Conversions of Nyquist 16-QAM Signals Employing a Single-Layer Graphene Coated Fiber Device

    PubMed Central

    Hu, Xiao; Zeng, Mengqi; Long, Yun; Liu, Jun; Zhu, Yixiao; Zou, Kaiheng; Zhang, Fan; Fu, Lei; Wang, Jian

    2016-01-01

    We fabricate a nonlinear optical device based on a fiber pigtail cross-section coated with a single-layer graphene grown by chemical vapor deposition (CVD) method. Using the fabricated graphene-assisted nonlinear optical device and employing Nyquist 16-ary quadrature amplitude modulation (16-QAM) signal, we experimentally demonstrate phase conjugated wavelength conversion by degenerate four-wave mixing (FWM) and transparent wavelength conversion by non-degenerate FWM in graphene. We study the conversion efficiency as functions of the pump power and pump wavelength and evaluate the bit-error rate (BER) performance. We also compare the time-varying symbol sequence for graphene-assisted phase conjugated and transparent wavelength conversions of Nyquist 16-QAM signal. PMID:26932470

  1. Phase Conjugated and Transparent Wavelength Conversions of Nyquist 16-QAM Signals Employing a Single-Layer Graphene Coated Fiber Device

    NASA Astrophysics Data System (ADS)

    Hu, Xiao; Zeng, Mengqi; Long, Yun; Liu, Jun; Zhu, Yixiao; Zou, Kaiheng; Zhang, Fan; Fu, Lei; Wang, Jian

    2016-03-01

    We fabricate a nonlinear optical device based on a fiber pigtail cross-section coated with a single-layer graphene grown by chemical vapor deposition (CVD) method. Using the fabricated graphene-assisted nonlinear optical device and employing Nyquist 16-ary quadrature amplitude modulation (16-QAM) signal, we experimentally demonstrate phase conjugated wavelength conversion by degenerate four-wave mixing (FWM) and transparent wavelength conversion by non-degenerate FWM in graphene. We study the conversion efficiency as functions of the pump power and pump wavelength and evaluate the bit-error rate (BER) performance. We also compare the time-varying symbol sequence for graphene-assisted phase conjugated and transparent wavelength conversions of Nyquist 16-QAM signal.

  2. Phase Conjugated and Transparent Wavelength Conversions of Nyquist 16-QAM Signals Employing a Single-Layer Graphene Coated Fiber Device.

    PubMed

    Hu, Xiao; Zeng, Mengqi; Long, Yun; Liu, Jun; Zhu, Yixiao; Zou, Kaiheng; Zhang, Fan; Fu, Lei; Wang, Jian

    2016-03-02

    We fabricate a nonlinear optical device based on a fiber pigtail cross-section coated with a single-layer graphene grown by chemical vapor deposition (CVD) method. Using the fabricated graphene-assisted nonlinear optical device and employing Nyquist 16-ary quadrature amplitude modulation (16-QAM) signal, we experimentally demonstrate phase conjugated wavelength conversion by degenerate four-wave mixing (FWM) and transparent wavelength conversion by non-degenerate FWM in graphene. We study the conversion efficiency as functions of the pump power and pump wavelength and evaluate the bit-error rate (BER) performance. We also compare the time-varying symbol sequence for graphene-assisted phase conjugated and transparent wavelength conversions of Nyquist 16-QAM signal.

  3. Study of the effect of the charge transport layer in the electrical characteristics of the organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Rahimi, Ronak; Roberts, Alex; Narang, V.; Kumbham, Vamsi Krishna; Korakakis, D.

    2013-09-01

    Significant progress in fabrication and optimization of organic photovoltaics (OPVs) has been made during the last decade. The main reason for popularity of OPVs is due to their low production cost, large area devices and compatibility with flexible substrates 1-3. Various approaches including optimizing morphology of the active layers 1, 2, introducing new materials as the donor and acceptor 3,4, new device structures such as tandem structure 5, 6 have been adapted to improve the efficiency of the organic photovoltaics. However, electrical characteristics of the OPVs do not only depend on the active layer materials or device structure. They can also be defined by the interface properties between active layers and the charge transport layers or the metal contacts. Within this paper, the effect of the thickness variation of the charge transport layer in the electrical properties of the bilayer heterojunction OPVs has been studied. Several devices with CuPc/PTCDI-C8 as the donor/acceptor layers have been fabricated with different thicknesses of electron transport layer. MoO3 and Alq3 have been used respectively as the hole transport layer (HTL) and the electron transport layer (ETL). It has been shown that the S-shape effect in the current-voltage curve is attributed to the accumulation of the charge carriers at the interface between the active layer and the charge transport layer 5, 7.

  4. Study of the effect of the charge transport layer in the electrical characteristics of the organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Rahimi, Ronak; Roberts, Alex; Narang, V.; Kumbham, Vamsi Krishna; Korakakis, D.

    2013-03-01

    Significant progress in fabrication and optimization of organic photovoltaics (OPVs) has been made during the last decade. The main reason for popularity of OPVs is due to their low production cost, large area devices and compatibility with flexible substrates [1-3]. Various approaches including optimizing morphology of the active layers [1,2], introducing new materials as the donor and acceptor [3,4], new device structures such as tandem structure [5,6] have been adapted to improve the efficiency of the organic photovoltaics. However, electrical characteristics of the OPVs do not only depend on the active layer materials or device structure. They can also be defined by the interface properties between active layers and the charge transport layers or the metal contacts. Within this paper, the effect of the thickness variation of the charge transport layer in the electrical properties of the bilayer heterojunction OPVs has been studied. Several devices with CuPc/PTCDI-C8 as the donor/acceptor layers have been fabricated with different thicknesses of electron transport layer. MoO3 and Alq3 have been used respectively as the hole transport layer (HTL) and the electron transport layer (ETL). It has been shown that the S-shape effect in the current-voltage curve is attributed to the accumulation of the charge carriers at the interface between the active layer and the charge transport layer [5,7].

  5. Charge Transport in Field-Effect Transistors based on Layered Materials and their Heterostructures

    NASA Astrophysics Data System (ADS)

    Kumar, Jatinder

    In the quest for energy efficiency and device miniaturization, the research in using atomically thin materials for device applications is gaining momentum. The electronic network in layered materials is different from 3D counterparts. It is due to the interlayer couplings and density of states because of their 2D nature. Therefore, understanding the charge transport in layered materials is fundamental to explore the vast opportunities these ultra-thin materials offer. Hence, the challenges targeted in the thesis are: (1) understanding the charge transport in layered materials based on electronic network of quantum and oxide capacitances, (2) studying thickness dependence, ranging from monolayer to bulk, of full range-characteristics of field-effect transistor (FET) based on layered materials, (3) investigating the total interface trap charges to achieve the ultimate subthreshold slope (SS) theoretically possible in FETs, (4) understanding the effect of the channel length on the performance of layered materials, (5) understanding the effect of substrate on performance of the TMDC FETs and studying if the interface of transition metal dichalcogenides (TMDCs)/hexagonalboron nitride (h-BN) can have less enough trap charges to observe ambipolar behavior, (6) Exploring optoelectronic properties in 2D heterostructures that includes understanding graphene/WS2 heterostructure and its optoelectronic applications by creating a p-n junction at the interface. The quality of materials and the interface are the issues for observing and extracting clean physics out of these layered materials and heterostructures. In this dissertation, we realized the use of quantum capacitance in layered materials, substrate effects and carrier transport in heterostructure.

  6. Improving the efficiency of organic photovoltaics by tuning the work function of graphene oxide hole transporting layers

    NASA Astrophysics Data System (ADS)

    Stratakis, Emmanuel; Savva, Kyriaki; Konios, Dimitrios; Petridis, Constantinos; Kymakis, Emmanuel

    2014-05-01

    A facile, fast, non-destructive and roll-to-roll compatible photochemical method for simultaneous partial reduction and doping of graphene oxide (GO) films through ultraviolet laser irradiation in the presence of a Cl2 precursor gas is demonstrated. The photochemical chlorinated GO-Cl films were fully characterized by XPS and Raman measurements, in which grafting of chloride to the edges and the basal plane of GO was confirmed. By tuning the laser exposure time, it is possible to control the doping and reduction levels and therefore to tailor the work function (WF) of the GO-Cl layers from 4.9 eV to a maximum value of 5.23 eV. These WF values match with the HOMO level of most polymer donors employed in OPV devices. Furthermore, high efficiency poly(2,7-carbazole) derivative (PCDTBT):fullerene derivative (PC71BM) based OPVs with GO-Cl as the hole transporting layer (HTL) were demonstrated with a power conversion efficiency (PCE) of 6.56% which is 17.35% and 19.48% higher than that of the pristine GO and PEDOT:PSS based OPV devices, respectively. The performance enhancement was attributed to more efficient hole transportation due to the energy level matching between the GO-Cl and the polymer donor.

  7. Design and application of carbon nanomaterials for photoactive and charge transport layers in organic solar cells

    NASA Astrophysics Data System (ADS)

    Jin, Sunghwan; Jun, Gwang Hoon; Jeon, Seokwoo; Hong, Soon Hyung

    2016-04-01

    Commercialization of organic solar cell (OSC) has faltered due to their low power conversion efficiency (PCE) compared to inorganic solar cell. Low electrical conductivity, low charge mobility, and short-range light absorption of most organic materials limit the PCE of OSCs. Carbon nanomaterials, especially carbon nanotubes (CNTs) and graphenes, are of great interest for use in OSC applications due to their high electrical conductivity, mobility, and unique optical properties for enhancing the performance of OSCs. In this review, recent progress toward the integration of carbon nanomaterials into OSCs is described. The role of carbon nanomaterials and strategies for their integration into various layers of OSCs, including the photoactive layer and charge transport layer, are discussed. Based on these, we also discuss the prospects of carbon nanomaterials for specific OSC layers to maximize the PCE.

  8. Design and application of carbon nanomaterials for photoactive and charge transport layers in organic solar cells.

    PubMed

    Jin, Sunghwan; Jun, Gwang Hoon; Jeon, Seokwoo; Hong, Soon Hyung

    2016-01-01

    Commercialization of organic solar cell (OSC) has faltered due to their low power conversion efficiency (PCE) compared to inorganic solar cell. Low electrical conductivity, low charge mobility, and short-range light absorption of most organic materials limit the PCE of OSCs. Carbon nanomaterials, especially carbon nanotubes (CNTs) and graphenes, are of great interest for use in OSC applications due to their high electrical conductivity, mobility, and unique optical properties for enhancing the performance of OSCs. In this review, recent progress toward the integration of carbon nanomaterials into OSCs is described. The role of carbon nanomaterials and strategies for their integration into various layers of OSCs, including the photoactive layer and charge transport layer, are discussed. Based on these, we also discuss the prospects of carbon nanomaterials for specific OSC layers to maximize the PCE.

  9. Efficiency Enhancement of Inverted Structure Perovskite Solar Cells via Oleamide Doping of PCBM Electron Transport Layer.

    PubMed

    Xia, Fei; Wu, Qiliang; Zhou, Pengcheng; Li, Yi; Chen, Xiang; Liu, Qing; Zhu, Jun; Dai, Songyuan; Lu, Yalin; Yang, Shangfeng

    2015-06-24

    An amphiphilic surfactant, oleamide, was applied to dope the PCBM electron transport layer (ETL) of inverted structure perovskite solar cells (ISPSCs), resulting in a dramatic efficiency enhancement. Under the optimized oleamide doping ratio of 5.0 wt %, the power conversion efficiency of the CH3NH3PbIxCl(3-x) perovskite-based ISPSC device is enhanced from 10.05% to 12.69%, and this is primarily due to the increases of both fill factor and short-circuit current. According to the surface morphology study of the perovskite/PCBM bilayer film, oleamide doping improves the coverage of PCBM ETL onto the perovskite layer, and this is beneficial for the interfacial contact between the perovskite layer and the Ag cathode and consequently the electron transport from perovskite to the Ag cathode. Such an improved electron transport induced by oleamide doping is further evidenced by the impedance spectroscopic study, revealing the prohibited electron-hole recombination at the interface between the perovskite layer and the Ag cathode.

  10. Epitaxial 1D electron transport layers for high-performance perovskite solar cells.

    PubMed

    Han, Gill Sang; Chung, Hyun Suk; Kim, Dong Hoe; Kim, Byeong Jo; Lee, Jin-Wook; Park, Nam-Gyu; Cho, In Sun; Lee, Jung-Kun; Lee, Sangwook; Jung, Hyun Suk

    2015-10-07

    We demonstrate high-performance perovskite solar cells with excellent electron transport properties using a one-dimensional (1D) electron transport layer (ETL). The 1D array-based ETL is comprised of 1D SnO2 nanowires (NWs) array grown on a F:SnO2 transparent conducting oxide substrate and rutile TiO2 nanoshells epitaxially grown on the surface of the 1D SnO2 NWs. The optimized devices show more than 95% internal quantum yield at 750 nm, and a power conversion efficiency (PCE) of 14.2%. The high quantum yield is attributed to dramatically enhanced electron transport in the epitaxial TiO2 layer, compared to that in conventional nanoparticle-based mesoporous TiO2 (mp-TiO2) layers. In addition, the open space in the 1D array-based ETL increases the prevalence of uniform TiO2/perovskite junctions, leading to reproducible device performance with a high fill factor. This work offers a method to achieve reproducible, high-efficiency perovskite solar cells with high-speed electron transport.

  11. Development of Layered Sediment Structure and its Effects on Pore Water Transport and Hyporheic Exchange

    SciTech Connect

    Packman, Aaron I.; Marion, Andrea; Zaramella, Mattia; Chen, Cheng; Gaillard, Jean-François; Keane, Denis T.

    2008-04-15

    Hyporheic exchange is known to provide an important control on nutrient and contaminant fluxes across the stream-subsurface interface. Similar processes also mediate interfacial transport in other permeable sediments. Recent research has focused on understanding the mechanics of these exchange processes and improving estimation of exchange rates in natural systems. While the structure of sediment beds obviously influences pore water flow rates and patterns, little is known about the interplay of typical sedimentary structures, hyporheic exchange, and other transport processes in fluvial/alluvial sediments. Here we discuss several processes that contribute to local-scale sediment heterogeneity and present results that illustrate the interaction of overlying flow conditions, the development of sediment structure, pore water transport, and stream-subsurface exchange. Layered structures are shown to develop at several scales within sediment beds. Surface sampling is used to analyze the development of an armor layer in a sand-and-gravel bed, while innovative synchrotron-based X-ray microtomography is used to observe patterns of grain sorting within sand bedforms. We show that layered bed structures involving coarsening of the bed surface increase interfacial solute flux but produce an effective anisotropy that favors horizontal pore water transport while limiting vertical penetration.

  12. Effect of benthic boundary layer transport on the productivity of Mono Lake, California.

    PubMed

    Bruce, Louise C; Jellison, Robert; Imberger, Jörg; Melack, John M

    2008-08-19

    The significance of the transport of nutrient-rich hypolimnetic water via the benthic boundary layer (BBL) to the productivity of Mono Lake was studied using a coupled hydrodynamic and ecological model validated against field data. The coupled model enabled us to differentiate between the role of biotic components and hydrodynamic forcing on the internal recycling of nutrients necessary to sustain primary productivity. A 4-year period (1991-1994) was simulated in which recycled nutrients from zooplankton excretion and bacterially-mediated mineralization exceeded sediment fluxes as the dominant source for primary productivity. Model outputs indicated that BBL transport was responsible for a 53% increase in the flux of hypolimnetic ammonium to the photic zone during stratification with an increase in primary production of 6% and secondary production of 5%. Although the estimated impact of BBL transport on the productivity of Mono Lake was not large, significant nutrient fluxes were simulated during periods when BBL transport was most active.

  13. Effect of benthic boundary layer transport on the productivity of Mono Lake, California

    PubMed Central

    Bruce, Louise C; Jellison, Robert; Imberger, Jörg; Melack, John M

    2008-01-01

    The significance of the transport of nutrient-rich hypolimnetic water via the benthic boundary layer (BBL) to the productivity of Mono Lake was studied using a coupled hydrodynamic and ecological model validated against field data. The coupled model enabled us to differentiate between the role of biotic components and hydrodynamic forcing on the internal recycling of nutrients necessary to sustain primary productivity. A 4-year period (1991–1994) was simulated in which recycled nutrients from zooplankton excretion and bacterially-mediated mineralization exceeded sediment fluxes as the dominant source for primary productivity. Model outputs indicated that BBL transport was responsible for a 53% increase in the flux of hypolimnetic ammonium to the photic zone during stratification with an increase in primary production of 6% and secondary production of 5%. Although the estimated impact of BBL transport on the productivity of Mono Lake was not large, significant nutrient fluxes were simulated during periods when BBL transport was most active. PMID:18710583

  14. 28 CFR 79.63 - Proof of employment as an ore transporter.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... RADIATION EXPOSURE COMPENSATION ACT Eligibility Criteria for Claims by Ore Transporters § 79.63 Proof of... Public Health Service (PHS) in the course of any health studies of uranium workers during or including the period 1942-1990; (2) Records of a uranium worker census performed by the PHS at various...

  15. 28 CFR 79.63 - Proof of employment as an ore transporter.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... RADIATION EXPOSURE COMPENSATION ACT Eligibility Criteria for Claims by Ore Transporters § 79.63 Proof of... Public Health Service (PHS) in the course of any health studies of uranium workers during or including the period 1942-1990; (2) Records of a uranium worker census performed by the PHS at various...

  16. Solution of transport equations in layered media with refractive index mismatch using the PN-method.

    PubMed

    Phillips, Kevin G; Jacques, Steven L

    2009-10-01

    The PN-method is a spectral discretization technique used to obtain numerical solutions to the radiative transport equation. To the best of our knowledge, the PN-method has yet to be generalized to the case of refractive index mismatch in layered slabs used to numerically simulate skin. Our main contribution is the application of a collocation method that takes into account refractive index mismatch at layer interfaces. The stability, convergence, and accuracy of the method are established. Example calculations demonstrating the flexibility of the method are performed.

  17. A way for studying the impact of PEDOT:PSS interface layer on carrier transport in PCDTBT:PC71BM bulk hetero junction solar cells by electric field induced optical second harmonic generation measurement

    NASA Astrophysics Data System (ADS)

    Ahmad, Zubair; Abdullah, Shahino Mah; Taguchi, Dai; Sulaiman, Khaulah; Iwamoto, Mitsumasa

    2015-04-01

    Electric-field-induced optical second-harmonic generation (EFISHG) measurement was employed to study the impact of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) interface layer on the carrier transport mechanism of the PCDTBT:PC71BM bulk heterojunction (BHJ) organic solar cells (OSCs). We revealed that the electric fields in the PCDTBT and PC71BM were allowed to be measured individually by choosing fundamental laser wavelengths of 1000 nm and 1060 nm, respectively, in dark and under illumination. The results showed that the direction of the internal electric fields in the PCDTBT:PC71BM BHJ layer is reversed by introducing the PEDOT:PSS layer, and this results in longer electron transport time in the BHJ layer. We conclude that TR-EFISHG can be used as a novel way for studying the impact of interfacial layer on the transport of electrons and holes in the bulk-heterojunction OSCs.

  18. Efficiency enhancement of blue phosphorescent organic light-emitting diodes using mixed electron transport layer

    NASA Astrophysics Data System (ADS)

    Yoo, Seung Il; Yoon, Ju-An; Kim, Nam Ho; Kim, Jin Wook; Lee, Ho Won; Kim, Young Kwan; He, Gufeng; Kim, Woo Young

    2015-01-01

    Blue phosphorescent organic light-emitting diodes (OLED) using mixed electron transport layer (ETL) were fabricated with the device structure of ITO/NPB/mCP:Firpic-8%/TPBi:BCP or TPBi:3TPYMB/Liq/Al to observe mixed ETL's influence on their electrical and optical characteristics. OLED device with mixed ETL of TPBi with BCP or 3TPYMB significantly improved its current efficiency to 30.4 and 34.2 cd/A comparing to 19.8 cd/A of single ETL with BCP only. We examined mixed ETL's capability of electron transport and triplet exciton confinement enhancing phosphorescent OLED's luminance and luminous efficiency.

  19. Doped hole transport layer for efficiency enhancement in planar heterojunction organolead trihalide perovskite solar cells

    DOE PAGES

    Wang, Qi; Bi, Cheng; Huang, Jinsong

    2015-05-06

    We demonstrated the efficiency of a solution-processed planar heterojunction organometallic trihalide perovskite solar cell can be increased to 17.5% through doping the hole transporting layer for reducing the resistivity. Doped Poly(triaryl amine) (PTAA) by 2,3,5,6-Tetrafluoro-7,7,8,8-Tetracyanoquinodimethane (F4-TCNQ) reduced device series resistance by three-folds, increasing the device fill factor to 74%, open circuit voltage to 1.09 V without sacrificing the short circuit current. As a result, this study reveals that the high resistivity of currently broadly applied polymer hole transport layer limits the device efficiency, and points a new direction to improve the device efficiency.

  20. Investigation on polymer solar cells by using calcium as an Electron Transportation Layer

    NASA Astrophysics Data System (ADS)

    Liu, Guilin; Guo, Ying; Yan, Huimin; Zhu, Bingjie; Li, Guohua

    2015-10-01

    This work investigated the transportation and recombination mechanisms of carriers in organic photovoltaic by using calcium (Ca 10 to 50 nm) as the Electron Transportation Layer (ETL). Compared with the sample without ETL layer, the Fermi Energy Level (EF) moved at least 0.4 eV towards the Lowest Unoccupied Molecular Orbit (LUMO) of P3HT after Ca was inserted. Ca-S bonds at the interface resulted in the shift of Highest Occupied Molecular Orbit (HOMO) which increased Voc to 0.58 V. Meanwhile, the shift of HOMO and low work function of Ca decreased the recombination possibility (from 1.38% to 0.403%), which resulted in 1% improvement of Fill Factor (FF). The experimental results were coincide with theoretical explanation. Additionally, the existence of accumulative error during the thermal evaporation cannot be neglected. This is the main reason for the decrease of Iscand FF.

  1. Phosphorescent white organic light-emitting diodes by electron transporting layer engineering.

    PubMed

    Lee, Seok Jae; Koo, Ja Ryong; Lee, Dong Hyung; Lee, Ho Won; Lee, Kum Hee; Yoon, Seung Soo; Kim, Young Kwan

    2014-10-01

    The authors describe the fabrication of white organic light-emitting diodes (WOLEDs) with dual electron transporting layers (D-ETL) using 2,9-dimethyl-4,7-diphenyl-1,10-phenanhroline/ 4,7-diphenyl-1,10-phenanthroline (BPhen) and bis-(2-methyl-8-quinolinolate)-4-(phenylphenolato) aluminum/BPhen. Stepwise D-ETL easily transports electrons easily to the emitting layer and reduces the leakage of electrons. Therefore, WOLEDs with D-ETL show higher external quantum efficiency (EQE) when compared to a control WOLED with a single ETL device. The optimized WOLEDs showed a peak EQE of 13.0%, luminous efficiency of 27.4 cd/A, and Commission Internationale de L'Eclairage coordinates of (0.40, 0.39) at 1000 cd/m2.

  2. Efficient organic solar cells using copper(I) iodide (CuI) hole transport layers

    SciTech Connect

    Peng, Ying; Yaacobi-Gross, Nir; Perumal, Ajay K.; Faber, Hendrik A.; Bradley, Donal D. C.; Anthopoulos, Thomas D. E-mail: t.anthopoulos@imperial.ac.uk; Vourlias, George; Patsalas, Panos A.; He, Zhiqun E-mail: t.anthopoulos@imperial.ac.uk

    2015-06-15

    We report the fabrication of high power conversion efficiency (PCE) polymer/fullerene bulk heterojunction (BHJ) photovoltaic cells using solution-processed Copper (I) Iodide (CuI) as hole transport layer (HTL). Our devices exhibit a PCE value of ∼5.5% which is equivalent to that obtained for control devices based on the commonly used conductive polymer poly(3,4-ethylenedioxythiophene): polystyrenesulfonate as HTL. Inverted cells with PCE >3% were also demonstrated using solution-processed metal oxide electron transport layers, with a CuI HTL evaporated on top of the BHJ. The high optical transparency and suitable energetics of CuI make it attractive for application in a range of inexpensive large-area optoelectronic devices.

  3. On Theory of Dispersive Transport in a Two-Layer Polymer Structure

    NASA Astrophysics Data System (ADS)

    Sibatov, R. T.; Morozova, E. V.

    2016-09-01

    Dispersive transport of charge carriers in a two-layer polymer structure is modeled on the basis of the integrodifferential equation of hereditary diffusion. The model of multiple trapping in a bilayer is generalized to the case of an arbitrary density of localized states. With the help of an efficient Monte Carlo algorithm, curves of the transient current are calculated and their features are explained within the framework of a stochastic interpretation of the process.

  4. Viscous dissipation effects on thermophoretically augmented aerosol particle transport across laminar boundary layers

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Rosner, D. E.

    1985-01-01

    The effect of viscous dissipation on mass transport across nonisothermal low-mass-loading laminar boundary layers of dusty gas is investigated theoretically by means of numerical simulations. The derivation of the model is outlined, and numerical results are presented in extensive graphs and characterized in detail. The dissipation effects are found to be significant, increasing total particle-deposition rates; the intensity of the effects depends on the ratio of wall temperature to mainstream static temperature.

  5. The impacts of moisture transport on drifting snow sublimation in the saltation layer

    NASA Astrophysics Data System (ADS)

    Huang, Ning; Dai, Xiaoqing; Zhang, Jie

    2016-06-01

    Drifting snow sublimation (DSS) is an important physical process related to moisture and heat transfer that happens in the atmospheric boundary layer, which is of glaciological and hydrological importance. It is also essential in order to understand the mass balance of the Antarctic ice sheets and the global climate system. Previous studies mainly focused on the DSS of suspended snow and ignored that in the saltation layer. Here, a drifting snow model combined with balance equations for heat and moisture is established to simulate the physical DSS process in the saltation layer. The simulated results show that DSS can strongly increase humidity and cooling effects, which in turn can significantly reduce DSS in the saltation layer. However, effective moisture transport can dramatically weaken the feedback effects. Due to moisture advection, DSS rate in the saltation layer can be several orders of magnitude greater than that of the suspended particles. Thus, DSS in the saltation layer has an important influence on the distribution and mass-energy balance of snow cover.

  6. Polyethers with pendent phenylvinyl substituted carbazole rings as polymers for hole transporting layers of OLEDs

    NASA Astrophysics Data System (ADS)

    Griniene, R.; Liu, L.; Tavgeniene, D.; Sipaviciute, D.; Volyniuk, D.; Grazulevicius, J. V.; Xie, Z.; Zhang, B.; Leduskrasts, K.; Grigalevicius, S.

    2016-01-01

    Polyethers containing pendent 3-(2-phenylvinyl)carbazole moieties have been synthesized by the multi-step synthetic routes. Full characterization of their structures is presented. The polymers represent materials of high thermal stability with initial thermal degradation temperatures exceeding 370 °C. The glass transition temperatures of the amorphous materials were in the range of 56-658 °C. The electron photoemission spectra of thin layers of the polymers showed ionization potentials of about 5.6 eV. Hole-transporting properties of the polymeric materials were tested in the structures of organic light emitting diodes with Alq3 as the green emitter and electron transporting layer. The device containing hole-transporting layers of poly{9-[6-(3-methyloxetan-3-ylmethoxy)hexyl]-3-(2-phenylvinyl)carbazole} exhibited the best overall performance with a maximum photometric efficiency of about 4.0 cd/A and maximum brightness exceeding 6430 cd/m2.

  7. Modeling reactive transport of reclaimed water through large soil columns with different low-permeability layers

    NASA Astrophysics Data System (ADS)

    Hu, Haizhu; Mao, Xiaomin; Barry, D. A.; Liu, Chengcheng; Li, Pengxiang

    2015-03-01

    The efficacy of different proportions of silt-loam/bentonite mixtures overlying a vadose zone in controlling solute leaching to groundwater was quantified. Laboratory experiments were carried out using three large soil columns, each packed with 200-cm-thick riverbed soil covered by a 2-cm-thick bentonite/silt-loam mixture as the low-permeability layer (with bentonite mass accounting for 12, 16 and 19 % of the total mass of the mixture). Reclaimed water containing ammonium (NH4 +), nitrate (NO3 -), organic matter (OM), various types of phosphorus and other inorganic salts was applied as inflow. A one-dimensional mobile-immobile multi-species reactive transport model was used to predict the preferential flow and transport of typical pollutants through the soil columns. The simulated results show that the model is able to predict the solute transport in such conditions. Increasing the amount of bentonite in the low-permeability layer improves the removal of NH4 + and total phosphorous (TP) because of the longer contact time and increased adsorption capacity. The removal of NH4 + and OM is mainly attributed to adsorption and biodegradation. The increase of TP and NO3 - concentration mainly results from discharge and nitrification in riverbed soils, respectively. This study underscores the role of low-permeability layers as barriers in groundwater protection. Neglect of fingers or preferential flow may cause underestimation of pollution risk.

  8. Diagnosis of energy transport in iron buried layer targets using an extreme ultraviolet laser

    NASA Astrophysics Data System (ADS)

    Shahzad, M.; Culfa, O.; Rossall, A. K.; Wilson, L. A.; Guilbaud, O.; Kazamias, S.; Delmas, O.; Demailly, J.; Maitrallain, A.; Pittman, M.; Baynard, E.; Farjardo, M.; Tallents, G. J.

    2015-02-01

    We demonstrate the use of extreme ultra-violet (EUV) laboratory lasers in probing energy transport in laser irradiated solid targets. EUV transmission through targets containing a thin layer of iron (50 nm) encased in plastic (CH) after irradiation by a short pulse (35 fs) laser focussed to irradiances 3 × 1016 Wcm-2 is measured. Heating of the iron layer gives rise to a rapid decrease in EUV opacity and an increase in the transmission of the 13.9 nm laser radiation as the iron ionizes to Fe5+ and above where the ion ionisation energy is greater than the EUV probe photon energy (89 eV). A one dimensional hydrodynamic fluid code HYADES has been used to simulate the temporal variation in EUV transmission (wavelength 13.9 nm) using IMP opacity values for the iron layer and the simulated transmissions are compared to measured transmission values. When a deliberate pre-pulse is used to preform an expanding plastic plasma, it is found that radiation is important in the heating of the iron layer while for pre-pulse free irradiation, radiation transport is not significant.

  9. Diagnosis of energy transport in iron buried layer targets using an extreme ultraviolet laser

    SciTech Connect

    Shahzad, M.; Culfa, O.; Rossall, A. K.; Tallents, G. J.; Wilson, L. A.; Guilbaud, O.; Kazamias, S.; Delmas, O.; Demailly, J.; Maitrallain, A.; Pittman, M.; Baynard, E.; Farjardo, M.

    2015-02-15

    We demonstrate the use of extreme ultra-violet (EUV) laboratory lasers in probing energy transport in laser irradiated solid targets. EUV transmission through targets containing a thin layer of iron (50 nm) encased in plastic (CH) after irradiation by a short pulse (35 fs) laser focussed to irradiances 3 × 10{sup 16} Wcm{sup −2} is measured. Heating of the iron layer gives rise to a rapid decrease in EUV opacity and an increase in the transmission of the 13.9 nm laser radiation as the iron ionizes to Fe{sup 5+} and above where the ion ionisation energy is greater than the EUV probe photon energy (89 eV). A one dimensional hydrodynamic fluid code HYADES has been used to simulate the temporal variation in EUV transmission (wavelength 13.9 nm) using IMP opacity values for the iron layer and the simulated transmissions are compared to measured transmission values. When a deliberate pre-pulse is used to preform an expanding plastic plasma, it is found that radiation is important in the heating of the iron layer while for pre-pulse free irradiation, radiation transport is not significant.

  10. A nano-grid structure made of perovskite SrTiO3 nanowires for efficient electron transport layers in inverted polymer solar cells

    NASA Astrophysics Data System (ADS)

    Kim, Jeong Won; Suh, Yo-Han; Lee, Chang-Lyoul; Kim, Yong Seok; Kim, Won Bae

    2015-02-01

    A nano-grid structure of perovskite SrTiO3 NWs is developed for a novel electron transport layer in inverted polymer solar cells. Due to the excellent charge transporting properties of the SrTiO3 nano-grid structure, the device employing this nanostructure showed ~32% enhanced photovoltaic performance, compared to the solar cell using a TiO2 thin film.A nano-grid structure of perovskite SrTiO3 NWs is developed for a novel electron transport layer in inverted polymer solar cells. Due to the excellent charge transporting properties of the SrTiO3 nano-grid structure, the device employing this nanostructure showed ~32% enhanced photovoltaic performance, compared to the solar cell using a TiO2 thin film. Electronic supplementary information (ESI) available: Experimental details, HR-TEM images with EDX atomic ratio analysis, FE-SEM images, transmittance spectra and light absorbance spectra. See DOI: 10.1039/c4nr06720g

  11. Interface modified thermally stable hole transporting layer for efficient organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Grover, Rakhi; Srivastava, Ritu; Dagar, Janardan; Kamalasanan, M. N.; Mehta, D. S.

    2014-08-01

    Electrical transport in thermally stable 2, 7-bis [N, N-bis (4-methoxy-phenyl) amino]-9, 9-spirobifluorene (MeO-Spiro-TPD) thin films has been investigated as a function of temperature and organic layer thickness. ITO/MeO-Spiro-TPD interface was found to be injection limited and has been studied in detail to find barrier height for hole injection. The thickness of tetra-fluoro-tetracyano-quinodimethane thin films were optimized to be used as hole injection buffer layer which resulted in switching of charge transport mechanism from injection limited to space charge limited conduction above a critical thickness of 3 nm. Hole mobility has been measured using transient space charge limited conduction (SCLC), field dependent SCLC, and top contact transistor characteristics. The charge carrier transport in interface modified hole only devices was analysed using Gaussian disorder model. The thermal stability of MeO-Spiro-TPD has been investigated by atomic force microscopy and X-ray diffraction studies. The study indicates a thermally stable and highly efficient hole transport material for application in organic semiconductor based devices.

  12. Estuarine sediment transport by gravity-driven movement of the nepheloid layer, Long Island Sound

    USGS Publications Warehouse

    Poppe, L.J.; McMullen, K.Y.; Williams, S.J.; Crocker, J.M.; Doran, E.F.

    2008-01-01

    Interpretation of sidescan-sonar imagery provides evidence that down-slope gravity-driven movement of the nepheloid layer constitutes an important mode of transporting sediment into the basins of north-central Long Island Sound, a major US East Coast estuary. In the Western Basin, this transport mechanism has formed dendritic drainage systems characterized by branching patterns of low backscatter on the seafloor that exceed 7.4 km in length and progressively widen down-slope, reaching widths of over 0.6 km at their southern distal ends. Although much smaller, dendritic patterns of similar morphology are also present in the northwestern part of the Central Basin. Because many contaminants display affinities for adsorption onto fine-grained sediments, and because the Sound is affected by seasonal hypoxia, mechanisms and dispersal pathways by which inorganic and organic sediments are remobilized and transported impact the eventual fate of the contaminants and environmental health of the estuary. ?? Springer-Verlag 2008.

  13. Comparison of scrape-off layer transport in inner and outer wall limited JET plasmas

    NASA Astrophysics Data System (ADS)

    Silva, C.; Arnoux, G.; Devaux, S.; Frigione, D.; Groth, M.; Horacek, J.; Lomas, P. J.; Marsen, S.; Matthews, G.; Pitts, R. A.; JET-EFDA Contributors

    2013-07-01

    The JET scrape-off layer has been characterized with a reciprocating probe in inner wall, IW, and outer wall, OW, limited plasmas. Broad SOL profiles are observed for IW limited plasmas with power e-folding length substantially larger (by a factor of ˜5-7.5) than in OW limited plasmas. The properties of the fluctuations in the SOL parameters indicate larger turbulent transport for IW limited plasmas. The striking differences observed between IW and OW limited plasmas on the power e-folding length, parallel flow, turbulent transport as well as the characteristics of the fluctuations support the existence of a poloidally localized region of enhanced radial transport near the outboard midplane. The dependence of the SOL power e-folding length on the main plasma parameters was also investigated for IW limited plasmas and a modest negative dependence on both the plasma current and the line-averaged density found.

  14. Fabrication and characterization of perovskite based solar cells using phthalocyanine and naphthalocyanine as hole-transporting layer

    NASA Astrophysics Data System (ADS)

    Okada, Yuki; Suzuki, Atsushi; Yamasaki, Yasuhiro; Oku, Takeo

    2017-01-01

    Organic-inorganic hybrid heterojunction solar cells containing CH3NH3PbI3 perovskite compound were fabricated using TiO2 as an electronic transporting layer and spirobifluorence as a hole-transporting layer. The purpose of the present study is to investigate a role of the hole-transporting layer on the photovoltaic properties and microstructures of CH3NH3PbI3 perovskite solar cells. The X-ray diffraction identified crystal structures of the perovskite layer in the solar cells. Optical microscopy showed different surface morphologies, and the perovskite structures on the TiO2 mesoporous structure depended on addition of phthalocyanine into the hole-transporting layer. The photovoltaic properties and hole-transporting behavior was depending on carrier mobility, electron structures of the perovskite crystal and band gaps related with the photovoltaic parameters. Energy diagram and photovoltaic mechanism of the perovskite solar cells using hole-transporting layers were discussed by experimental results. Perovskite based solar cells using phthalocyanines as hole-transporting layers have advantages to provide a high photovoltaic performance with a wide region of optical absorption.

  15. Elevated Ozone Levels in Denmark: Analysis Employing Trajectory and Chemical Transport Modelling

    NASA Astrophysics Data System (ADS)

    Mahura, A.; Gross, A.; Petrova, I.

    2009-09-01

    In our study, among 9 Danish measurement sites, 3 sites having long-term ozone measurement (with a time resolution of 1 hour and starting in early 1990s) records were selected - Ulborg (DK31; 56.28°N, 8.43°E) and Frederiksborg (DK32; 55.97°N, 12.33°E) and Lille Valby (DK41; 55.69°N, 12.13°E) located on Jutland Peninsula and Zealand Island of Denmark, respectively. After pre-screening of the time series (covering almost 15 year period and including almost 543 thousand valid observations), the measurements with high ozone level (using threshold as 150 µg/m3) were selected accounting in total for 508 cases for these 3 locations. Among these, 42 (for DK41) and 59 (for DK31 and DK32) cases showed very high ozone concentrations (i.e. above 180 µg/m3). For all these cases, at first, the trajectory modelling approach was applied in order to estimate atmospheric transport pathway of air mass arrival at the measurement sites and potential source regions from where the elevated ozone level can be associated. In our study the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) model using REANALYSIS meteorological dataset (global, 1948-present) was run to calculate a set of backward trajectories (in total 508, with duration of 5 day backward in time and arriving at altitude of 100 m) and divide into groups with respect to potential source regions and dominating atmospheric transport pathways using cluster analysis technique. Several relatively long-term episodes with continuous elevated ozone were identified in the analyzed time series; in particular, for DK31 - 7 episodes (having longest duration and observed in Jun 1996 and Jun 2000), DK32 - 5 (Jul 1992 and Jun 2000), and DK41 - 4 (Jul 1992 and Jun 2000). For selected episodes the off-line Eulerian Chemistry-Aerosol-Cloud (CAC) model was run over the European domain. As meteorological driver, the High Resolution Limited Area Model (HIRLAM) generated output with 3D meteorological fields was used

  16. Charge-transport anisotropy in black phosphorus: critical dependence on the number of layers.

    PubMed

    Banerjee, Swastika; Pati, Swapan K

    2016-06-28

    Phosphorene is a promising candidate for modern electronics because of the anisotropy associated with high electron-hole mobility. Additionally, superior mechanical flexibility allows the strain-engineering of various properties including the transport of charge carriers in phosphorene. In this work, we have shown the criticality of the number of layers to dictate the transport properties of black phosphorus. Trilayer black phosphorus (TBP) has been proposed as an excellent anisotropic material, based on the transport parameters using Boltzmann transport formalisms coupled with density functional theory. The mobilities of both the electron and the hole are found to be higher along the zigzag direction (∼10(4) cm(2) V(-1) s(-1) at 300 K) compared to the armchair direction (∼10(2) cm(2) V(-1) s(-1)), resulting in the intrinsic directional anisotropy. Application of strain leads to additional electron-hole anisotropy with 10(3) fold higher mobility for the electron compared to the hole. Critical strain for maximum anisotropic response has also been determined. Whether the transport anisotropy is due to the spatial or charge-carrier has been determined through analyses of the scattering process of electrons and holes, and their recombination as well as relaxation dynamics. In this context, we have derived two descriptors (S and F(k)), which are general enough for any 2D or quasi-2D systems. Information on the scattering involving purely the carrier states also helps to understand the layer-dependent photoluminescence and electron (hole) relaxation in black phosphorus. Finally, we justify trilayer black phosphorus (TBP) as the material of interest with excellent transport properties.

  17. Dispersed solar thermal generation employing parabolic dish-electric transport with field modulated generator systems

    NASA Technical Reports Server (NTRS)

    Ramakumar, R.; Bahrami, K.

    1981-01-01

    This paper discusses the application of field modulated generator systems (FMGS) to dispersed solar-thermal-electric generation from a parabolic dish field with electric transport. Each solar generation unit is rated at 15 kWe and the power generated by an array of such units is electrically collected for insertion into an existing utility grid. Such an approach appears to be most suitable when the heat engine rotational speeds are high (greater than 6000 r/min) and, in particular, if they are operated in the variable speed mode and if utility-grade a.c. is required for direct insertion into the grid without an intermediate electric energy storage and reconversion system. Predictions of overall efficiencies based on conservative efficiency figures for the FMGS are in the range of 25 per cent and should be encouraging to those involved in the development of cost-effective dispersed solar thermal power systems.

  18. The impact of ice layers on gas transport through firn at the North Greenland Eemian Ice Drilling (NEEM) site, Greenland

    NASA Astrophysics Data System (ADS)

    Keegan, K.; Albert, M. R.; Baker, I.

    2014-10-01

    Typically, gas transport through firn is modeled in the context of an idealized firn column. However, in natural firn, imperfections are present, which can alter transport dynamics and therefore reduce the accuracy of reconstructed climate records. For example, ice layers have been found in several firn cores collected in the polar regions. Here, we examined the effects of two ice layers found in a NEEM, Greenland firn core on gas transport through the firn. These ice layers were found to have permeability values of 3.0 and 4.0 × 10-10 m2, and are therefore not impermeable layers. However, the shallower ice layer was found to be significantly less permeable than the surrounding firn, and can therefore retard gas transport. Large closed bubbles were found in the deeper ice layer, which will have an altered gas composition than that expected because they were closed near the surface after the water phase was present. The bubbles in this layer represent 12% of the expected closed porosity of this firn layer after the firn-ice transition depth is reached, and will therefore bias the future ice core gas record. The permeability and thickness of the ice layers at the North Greenland Eemian Ice Drilling (NEEM) site suggest that they do not disrupt the firn-air concentration profiles and that they do not need to be accounted for in gas transport models at NEEM.

  19. Multi-dimensional Simulations of Core Collapse Supernovae employing Ray-by-Ray Neutrino Transport

    NASA Astrophysics Data System (ADS)

    Hix, W. R.; Mezzacappa, A.; Liebendoerfer, M.; Messer, O. E. B.; Blondin, J. M.; Bruenn, S. W.

    2001-12-01

    Decades of research on the mechanism which causes core collapse supernovae has evolved a paradigm wherein the shock that results from the formation of the proto-neutron star stalls, failing to produce an explosion. Only when the shock is re-energized by the tremendous neutrino flux that is carrying off the binding energy of this proto-neutron star can it drive off the star's envelope, creating a supernova. Work in recent years has demonstrated the importance of multi-dimensional hydrodynamic effects like convection to successful simulation of an explosion. Further work has established the necessity of accurately characterizing the distribution of neutrinos in energy and direction. This requires discretizing the neutrino distribution into multiple groups, adding greatly to the computational cost. However, no supernova simulations to date have combined self-consistent multi-group neutrino transport with multi-dimensional hydrodynamics. We present preliminary results of our efforts to combine these important facets of the supernova mechanism by coupling self-consistent ray-by-ray multi-group Boltzmann and flux-limited diffusion neutrino transport schemes to multi-dimensional hydrodynamics. This research is supported by NASA under contract NAG5-8405, by the NSF under contract AST-9877130, and under a SciDAC grant from the DoE Office of Science High Energy and Nuclear Physics Program. Work at Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.

  20. Analysis of quadratic nonlinearities in hydrodynamic transport systems employing numerical simulations

    NASA Astrophysics Data System (ADS)

    Bicken, Gurcan

    This dissertation deals with the analysis and identification of quadratic non-linearities in hydrodynamic transport problems arising in engineering and science. As representative application areas, homogenous oscillations of electron and ion plasmas in a 1-D periodic domain and the forced voltage-current dynamics of a semiconductor device are considered. The time series data obtained from numerical solutions of the associated hydrodynamic equations are used for the spectral analysis of the quadratic nonlinearities in these respective systems. More specifically, electron plasma oscillations are analyzed using power spectra and cross-bicoherency spectra to gain insight into the quadratic interactions predicted by a simple model of the energy transfer that cascades from lower modes to higher modes within a small amplitude range of oscillations. The efficiency of the bicoherency function in detecting the quadratic wave interactions from the complex time series of the mode amplitudes is observed. The difference in the modal interactions for isentropic and isothermal plasma models are investigated based on numerical 'experiments' simulating the modal dynamics in each case. Furthermore, the concentration oscillations of cold ion plasmas in a Lagrangian frame are analyzed for different Debye lengths. The detailed effects of linear and nonlinear mechanisms in the hydrodynamic model on the power spectra of the oscillations are investigated. Second-order Volterra models are considered for approximating the dynamics of input-output systems with quadratic nonlinear terms. The linear and quadratic kernels of the Volterra model are estimated using multi- tone inputs and least-squares minimization. The implications of the non-orthogonality of the model are investigated in detail. To circumvent the negative effects of non-orthogonality on the accuracy of the kernel estimation, an 'odd-even' separation technique is utilized in the kernel estimation. This approach for estimating an

  1. Epitaxial 1D electron transport layers for high-performance perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Han, Gill Sang; Chung, Hyun Suk; Kim, Dong Hoe; Kim, Byeong Jo; Lee, Jin-Wook; Park, Nam-Gyu; Cho, In Sun; Lee, Jung-Kun; Lee, Sangwook; Jung, Hyun Suk

    2015-09-01

    We demonstrate high-performance perovskite solar cells with excellent electron transport properties using a one-dimensional (1D) electron transport layer (ETL). The 1D array-based ETL is comprised of 1D SnO2 nanowires (NWs) array grown on a F:SnO2 transparent conducting oxide substrate and rutile TiO2 nanoshells epitaxially grown on the surface of the 1D SnO2 NWs. The optimized devices show more than 95% internal quantum yield at 750 nm, and a power conversion efficiency (PCE) of 14.2%. The high quantum yield is attributed to dramatically enhanced electron transport in the epitaxial TiO2 layer, compared to that in conventional nanoparticle-based mesoporous TiO2 (mp-TiO2) layers. In addition, the open space in the 1D array-based ETL increases the prevalence of uniform TiO2/perovskite junctions, leading to reproducible device performance with a high fill factor. This work offers a method to achieve reproducible, high-efficiency perovskite solar cells with high-speed electron transport.We demonstrate high-performance perovskite solar cells with excellent electron transport properties using a one-dimensional (1D) electron transport layer (ETL). The 1D array-based ETL is comprised of 1D SnO2 nanowires (NWs) array grown on a F:SnO2 transparent conducting oxide substrate and rutile TiO2 nanoshells epitaxially grown on the surface of the 1D SnO2 NWs. The optimized devices show more than 95% internal quantum yield at 750 nm, and a power conversion efficiency (PCE) of 14.2%. The high quantum yield is attributed to dramatically enhanced electron transport in the epitaxial TiO2 layer, compared to that in conventional nanoparticle-based mesoporous TiO2 (mp-TiO2) layers. In addition, the open space in the 1D array-based ETL increases the prevalence of uniform TiO2/perovskite junctions, leading to reproducible device performance with a high fill factor. This work offers a method to achieve reproducible, high-efficiency perovskite solar cells with high-speed electron transport

  2. Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall

    SciTech Connect

    Wang, Jian; Krejci, Radovan; Giangrande, Scott; Kuang, Chongai; Barbosa, Henrique M. J.; Brito, Joel; Carbone, Samara; Chi, Xuguang; Comstock, Jennifer; Ditas, Florian; Lavric, Jost; Manninen, Hanna E.; Mei, Fan; Moran-Zuloaga, Daniel; Pöhlker, Christopher; Pöhlker, Mira L.; Saturno, Jorge; Schmid, Beat; Souza, Rodrigo A. F.; Springston, Stephen R.; Tomlinson, Jason M.; Toto, Tami; Walter, David; Wimmer, Daniela; Smith, James N.; Kulmala, Markku; Machado, Luiz A. T.; Artaxo, Paulo; Andreae, Meinrat O.; Petäjä, Tuukka; Martin, Scot T.

    2016-10-24

    A necessary prerequisite of cloud formation, aerosol particles represent one of the largest uncertainties in computer simulations of climate change1,2, in part because of a poor understanding of processes under natural conditions3,4. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions5-7. Cloud condensation nuclei (CCN) in clean Amazonia are mostly produced by the growth of smaller particles in the boundary layer8-10, whereas these smaller particles themselves 31 appear to be produced elsewhere5,11. Key questions are in what part of the atmosphere they might 32 be produced and what could be the transport processes that deliver them to the boundary layer, where they grow into CCN. Here, using recent aircraft measurements above central Amazonia, we show high concentrations of small particles in the lower free troposphere. The particle size spectrum shifts towards larger sizes with decreasing altitude, implying particle growth as air descends from the free troposphere towards Earth's surface. Complementary measurements at ground sites show that free tropospheric air having high concentrations of small particles (diameters of less than 50 nm) is transported into the boundary layer during precipitation events, both by strong convective downdrafts and by weaker downward motions in the trailing stratiform region. This vertical transport helps maintain the population of small particles and ultimately CCN in the boundary layer, thereby playing an important role in controlling the climate state under natural conditions. In contrast, this mechanism becomes masked under polluted conditions, which sometimes prevail at times in Amazonia as well as over other tropical continental regions5,12.

  3. The essential role of the poly(3-hexylthiophene) hole transport layer in perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Liu, Wenqiang; Tan, Furui; Gu, Yuzong

    2015-01-01

    The compact and oriented TiO2 films are prepared by a solvothermal method, and used as electron transporting layers in perovskite CH3NH3PbI3-xClx based solar cells incorporating poly(3-hexylthiophene-2,5-diyl) (P3HT) as the hole transporting material layer. The devices with P3HT exhibit a substantial increase in power conversion efficiency, open circuit voltage, and fill factor, compared with the reference device without P3HT. Impedance spectroscopy measurements demonstrate that the present P3HT layer decreases the internal resistance in solar cells and allows the interface between oriented TiO2 and CH3NH3PbI3-xClx to form more perfect in electronics. It is also found that the electron lifetime in the devices with P3HT is much longer than that of the device without P3HT. Thus, the charge collection efficiency of the device with P3HT is markedly enhanced, compared with the devices without P3HT. Analysis of the energy levels of the involved materials indicates that the P3HT film between the CH3NH3PbI3-xClx layer and the Au electrode provides a better energy level matching for efficient transporting holes to the anode. Meanwhile, the stability of such P3HT solar cells is enhanced because of the compact and oriented TiO2 film preventing the possible interaction between TiO2 and perovskite as time went on.

  4. Synthesis and characterization of polymer layers for control of fluid transport

    NASA Astrophysics Data System (ADS)

    Vatansever, Fehime

    The level of wetting of fiber surface with liquids is an important characteristic of fibrous materials. It is related to fiber surface energy and the structure of the material. Surface energy can be changed by surface modification via the grafting methodologies that have been reported for introducing new and stable functionality to fibrous substrates without changing bulk properties. Present work is dedicated to synthesis and characterization of macromolecular layers grafted to fiber surface in order to achieve directional liquid transport for the modified fabric. Modification technique used here is based on formation of stable polymer layer on fabric surface using "grafting to" technique. Specifically, modification of fabric with wettability gradient for facilitated one way-liquid transport, and pointed modification of yarn-based channels on textile microfluidic device for directional liquid transport are reported here. First, fabric was activated with alkali (NaOH) solution. Second, poly (glycidyl methacrylate) (PGMA) was deposited on fabric as an anchoring layer. Finally, polymers of interest were grafted to surface through the epoxy functionality of PGMA. Effect of polymer grafting on the wicking property of the fabric has been evaluated by vertical wicking technique at the each step of surface modification. The results shows that wicking performance of fabric can be altered by grafting of a thin nanoscale polymeric film. For the facilitated liquid transport, the gradient polymer coating was created using "grafting to" technique and its dependence on the grafting temperature. Wettability gradient from hydrophilic to hydrophobic (change in water contact angle from 0 to 140 degrees on fabric) was achieved by grafting of polystyrene (PS) and polyacrylic acid (PAA) sequentially with concentration gradient. This study proposes that fabric with wettability gradient property can be used to transfer sweat from skin and support moisture management when it is used in a

  5. Measurements and theory for transport layer structure in intense bed-load

    NASA Astrophysics Data System (ADS)

    Fraccarollo, L.; Capart, H.

    2012-04-01

    We focus on sediment laden flows driven by turbulent open-channel flows where the bed surface is fully mobilized and nonetheless the thickness of the bedload layer is conveniently smaller than the flow depth. This regime presents dynamic and kinematic features which persist in the range of applied Shields stress between about 0.3 and 3. Below the lower limit the moving grains do not develop significant stresses compared to the applied ones; above the upper limit, debris-flow type frictional contacts develop in a non negligible portion of the bedload layer. We report laboratory experiments in which, using high-speed cameras and a laser light sheet, detailed profiles of granular velocity and concentration have been measured. We checked that the transversal bed profile is flat and that the sidewall measurements are representative of the interior domain. The profiles provide new information on transport layer structure and its relation to the applied Shields stress. Contrary to expectations, we find that intense bed-load layers respond to changes in flow conditions by adjusting their granular concentration at the base. Two mechanisms account for the resulting behavior: stresses generated by immersed granular collisions, and equilibration by density stratification. Without parameter adjustment, the deduced constitutive relations capture the responses of velocity, concentration, and layer thickness in the above reported ten-fold increase Shields-stress range. Away from this intermediate range, in both directions, we show how the flow features rapidly change and the theoretical inferences decay.

  6. Sources and Transport of Aerosol above the Boundary Layer over the Mediterranean Basin

    NASA Astrophysics Data System (ADS)

    Roberts, Greg; Corrigan, Craig; Ritchie, John; Pont, Veronique; Claeys, Marine; Sciare, Jean; Mallet, Marc; Dulac, François; Mihalopoulos, Nikos

    2015-04-01

    The Mediterranean Region has been identified as sensitive to changes in the hydrological cycle, which could affect the water resources for millions of people by the turn of the century. However, prior to recent observations, most climate models have not accounted for the impacts of aerosol in this region. Past airborne studies have shown that aerosol sources from Europe and Africa are often transported throughout the lower troposphere; yet, because of their complex vertical distribution, it is a challenge to capture the variability and quantify the contribution of these sources to the radiative budget and precipitation processes. The PAEROS ChArMEx Mountain Experiment (PACMEx) complemented the regional activities by collecting aerosol data from atop a mountain on the island of Corsica, France in order to assess boundary layer / free troposphere atmospheric processes. In June/July 2013, PACMEx instruments were deployed at 2000 m.asl near the center of Corsica, France to complement ground-based aerosol observations at 550 m.asl on the northern peninsula, as well as airborne measurements. Comparisons between the peninsula site and the mountain site show similar general trends in aerosol properties; yet, differences in aerosol properties reveal the myriad transport mechanisms over the Mediterranean Basin. Using aerosol physicochemical data coupled with back trajectory analysis, different sources have been identified including Saharan dust transport, residual dust mixed with sea salt, anthropogenic emissions from Western Europe, and a period of biomass burning from Eastern Europe. Each period exhibits distinct signatures in the aerosol related to transport processes above and below the boundary layer. In addition, the total aerosol concentrations at the mountain site revealed a strong diurnal cycling the between the atmospheric boundary layer and the free troposphere, which is typical of mountain-top observations. PACMEx was funded by the National Science Foundation

  7. Transport and Evolution of Aerosol Above/Below the Boundary Layer in the Western Mediterranean Basin

    NASA Astrophysics Data System (ADS)

    Roberts, G. C.; Corrigan, C.; Ritchie, J.; Pont, V.; Claeys, M.; Sciare, J.; Mallet, M.; Dulac, F.

    2014-12-01

    The Mediterranean Region has been identified as sensitive to changes in the hydrological cycle, which could affect the water resources for millions of people by the turn of the century. However, prior to recent observations, most climate models have not accounted for the impacts of aerosol in this region. Past airborne studies have shown that aerosol sources from Europe and Africa are often transported throughout the lower troposphere; yet, because of their complex vertical distribution, it is a challenge to capture the variability and quantify the contribution of these sources to the radiative budget and precipitation processes. The PAEROS ChArMEx Mountain Experiment (PACMEx) complemented the regional activities of the ChArMEx/ADRIMED summer 2013 campaign by collecting aerosol data from atop a mountain on the island of Corsica, France in order to assess boundary layer / free troposphere atmospheric processes. In June/July 2013, PACMEx instruments were deployed at 2000 m.asl near the center of Corsica to complement ground-based aerosol observations at 550 m.asl on the northern peninsula, as well as airborne measurements. Comparisons between the peninsula site and the mountain site show similar general trends in aerosol properties; yet, differences in aerosol properties reveal the myriad transport mechanisms over the Mediterranean Basin. Using aerosol physicochemical data coupled with back trajectory analysis, different sources have been identified including Saharan dust transport, residual dust mixed with sea salt, anthropogenic emissions from Western Europe, and a period of biomass burning from Eastern Europe. Each period exhibits distinct signatures in the aerosol related to transport processes above and below the boundary layer. In addition, the total aerosol concentrations at the mountain site revealed a strong diurnal cycling between the atmospheric boundary layer and the free troposphere, which is typical of mountain-top observations. PACMEx was funded by the

  8. ANGULAR MOMENTUM TRANSPORT BY ACOUSTIC MODES GENERATED IN THE BOUNDARY LAYER. II. MAGNETOHYDRODYNAMIC SIMULATIONS

    SciTech Connect

    Belyaev, Mikhail A.; Rafikov, Roman R.; Stone, James M.

    2013-06-10

    We perform global unstratified three-dimensional magnetohydrodynamic simulations of an astrophysical boundary layer (BL)-an interface region between an accretion disk and a weakly magnetized accreting object such as a white dwarf-with the goal of understanding the effects of magnetic field on the BL. We use cylindrical coordinates with an isothermal equation of state and investigate a number of initial field geometries including toroidal, vertical, and vertical with zero net flux. Our initial setup consists of a Keplerian disk attached to a non-rotating star. In a previous work, we found that in hydrodynamical simulations, sound waves excited by shear in the BL were able to efficiently transport angular momentum and drive mass accretion onto the star. Here we confirm that in MHD simulations, waves serve as an efficient means of angular momentum transport in the vicinity of the BL, despite the magnetorotational instability (MRI) operating in the disk. In particular, the angular momentum current due to waves is at times larger than the angular momentum current due to MRI. Our results suggest that angular momentum transport in the BL and its vicinity is a global phenomenon occurring through dissipation of waves and shocks. This point of view is quite different from the standard picture of transport by a local anomalous turbulent viscosity. In addition to angular momentum transport, we also study magnetic field amplification within the BL. We find that the field is indeed amplified in the BL, but only by a factor of a few, and remains subthermal.

  9. Characterization of scrape-off layer transport in JET limiter plasmas

    NASA Astrophysics Data System (ADS)

    Silva, C.; Arnoux, G.; Devaux, S.; Frigione, D.; Groth, M.; Horacek, J.; Lomas, P. J.; Marsen, S.; Matthews, G.; Meneses, L.; Pitts, R. A.; Contributors, JET-EFDA

    2014-08-01

    The JET scrape-off layer (SOL) has been characterized with a reciprocating probe in inner wall (IW), and outer wall (OW), limited plasmas. Experiments revealed that SOL profiles are substantially broader (by a factor of ˜5-7.5 in the power e-folding length) for IW limited than in OW limited plasmas. Results are consistent with the larger radial turbulent transport found for IW limited plasmas. Major differences are observed between IW and OW limited plasmas on the density and electron temperature e-folding lengths, parallel flow, radial turbulent transport as well as on the temporal and spatial characteristics of the fluctuations. Experimental findings on JET suggest that the differences in the SOL characteristics for both configurations are due to a combination of a poloidal asymmetry in radial transport with a reduced cross-field transport across the last closed flux surface associated with the confinement improvement observed for OW limited plasmas. The dependence of the SOL power e-folding length on the main plasma parameters was also investigated for IW limited plasmas and a modest negative dependence on both the plasma current and the line-averaged density found. Finally, it is shown that the SOL radial transport and the amplitude of the fluctuations increase with plasma current and decrease with line-averaged density for IW limited plasmas.

  10. Thermal transport in bismuth telluride quintuple layer: mode-resolved phonon properties and substrate effects

    PubMed Central

    Shao, Cheng; Bao, Hua

    2016-01-01

    The successful exfoliation of atomically-thin bismuth telluride (Bi2Te3) quintuple layer (QL) attracts tremendous research interest in this strongly anharmonic quasi-two-dimensional material. The thermal transport properties of this material are not well understood, especially the mode-wise properties and when it is coupled with a substrate. In this work, we have performed molecular dynamics simulations and normal mode analysis to study the mode-resolved thermal transport in freestanding and supported Bi2Te3 QL. The detailed mode-wise phonon properties are calculated and the accumulated thermal conductivities with respect to phonon mean free path (MFP) are constructed. It is shown that 60% of the thermal transport is contributed by phonons with MFP longer than 20 nm. Coupling with a-SiO2 substrate leads to about 60% reduction of thermal conductivity. Through varying the interfacial coupling strength and the atomic mass of substrate, we also find that phonon in Bi2Te3 QL is more strongly scattered by interfacial potential and its transport process is less affected by the dynamics of substrate. Our study provides an in-depth understanding of heat transport in Bi2Te3 QL and is helpful in further tailoring its thermal property through nanostructuring. PMID:27263656

  11. The design, fabrication and maintenance of semi-trailers employed in the highway transport of weight-concentrated radioactive loads

    SciTech Connect

    Huffman, D.S.

    1991-12-31

    Transportation of weight-concentrated radioactive loads by truck is an essential part of a safe and economical nuclear industry. This proposed standard presents guidance and performance criteria for the safe transport of these weight-concentrated radioactive loads. ANSI N14.30 will detail specific requirements for the design, fabrication, testing, in-service inspections, maintenance and certification of the semi-trailers to be employed in said service. Furthermore, guidelines for a quality assurance program are also enumerated. This standard would apply to any semi-trailer that may or may not be specifically designed to carry weight-concentrated loads. Equipment not suitable per the criteria established in the standard would be removed from service. The nature of the nuclear industry and the need for a positive public perception of the various processes and players, mandates that the highway transportation of weight-concentrated radioactive loads be standardized and made inherently safe. This proposed standard takes a giant step in that direction.

  12. Turbulent transport in the atmospheric boundary layer with application to wind farm dynamics

    NASA Astrophysics Data System (ADS)

    Waggy, Scott B.

    With the recent push for renewable energy sources, wind energy has emerged as a candidate to replace some of the power produced by traditional fossil fuels. Recent studies, however, have indicated that wind farms may have a direct effect on local meteorology by transporting water vapor away from the Earth's surface. Such turbulent transport could result in an increased drying of soil, and, in turn, negatively affect the productivity of land in the wind farm's immediate vicinity. This numerical study will analyze four scenarios with the goal of understanding turbulence transport in the wake of a turbine: the neutrally-stratified boundary layer with system rotation, the unstably-stratified atmospheric boundary layer, and wind turbine simulations of these previous two cases. For this work, the Ekman layer is used as an approximation of the atmospheric boundary layer and the governing equations are solved using a fully-parallelized direct numerical simulation (DNS). The in-depth studies of the neutrally and unstably-stratified boundary layers without introducing wind farm effects will act to provide a concrete background for the final study concerning turbulent transport due to turbine wakes. Although neutral stratification rarely occurs in the atmospheric boundary layer, it is useful to study the turbulent Ekman layer under such conditions as it provides a limiting case when unstable or stable stratification are weak. In this work, a thorough analysis was completed including turbulent statistics, velocity and pressure autocorrelations, and a calculation of the full turbulent energy budget. The unstably-stratified atmospheric boundary layer was studied under two levels of heating: moderate and vigorous. Under moderate stratification, both buoyancy and shearing contribute significantly to the turbulent dynamics. As the level of stratification increases, the role of shearing is shown to diminish and is confined to the near-wall region only. A recent, multi

  13. Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall.

    PubMed

    Wang, Jian; Krejci, Radovan; Giangrande, Scott; Kuang, Chongai; Barbosa, Henrique M J; Brito, Joel; Carbone, Samara; Chi, Xuguang; Comstock, Jennifer; Ditas, Florian; Lavric, Jost; Manninen, Hanna E; Mei, Fan; Moran-Zuloaga, Daniel; Pöhlker, Christopher; Pöhlker, Mira L; Saturno, Jorge; Schmid, Beat; Souza, Rodrigo A F; Springston, Stephen R; Tomlinson, Jason M; Toto, Tami; Walter, David; Wimmer, Daniela; Smith, James N; Kulmala, Markku; Machado, Luiz A T; Artaxo, Paulo; Andreae, Meinrat O; Petäjä, Tuukka; Martin, Scot T

    2016-11-17

    The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin (for example, ref. 2) and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear. Here we present aircraft- and ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. This rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.

  14. Spin transport in tantalum studied using magnetic single and double layers

    NASA Astrophysics Data System (ADS)

    Montoya, Eric; Omelchenko, Pavlo; Coutts, Chris; Lee-Hone, Nicholas R.; Hübner, René; Broun, David; Heinrich, Bret; Girt, Erol

    2016-08-01

    We report on spin transport in sputter-grown Ta films measured by ferromagnetic resonance. Spin diffusion length and spin mixing conductance are determined from magnetic damping measurements for a varying thickness of Ta layer 0 ≤dTa≤10 nm. The different boundary conditions of single- and double-magnetic-layer heterostructures Py |Ta and Py |Ta | [Py |Fe ] allow us to significantly narrow down the parameter space and test various models. We show that a common approach of using bulk resistivity value in the analysis yields inconsistent spin diffusion length and spin mixing conductance values for magnetic single- and double-layer structures. X-ray diffraction shows that bulk Ta is a combination of β -Ta and bcc-Ta . However, in the region of significant spin transport, ≲2 nm, there is an intermediate region of growth where the Ta lacks long-range structural order, as observed by transmission electron microscopy. Thickness-dependent resistivity measurements confirm that the bulk and intermediate regions have significantly different resistivity values. We find that the data can be well represented if the intermediate region resistivity value is used in the analysis. Additionally, the data can be fit if resistivity has the measured thickness dependence and spin diffusion length is restricted to be inversely proportional to resistivity. Finally, we rule out a model in which spin diffusion length is a constant, while the resistivity has the measured thickness dependence.

  15. Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Krejci, Radovan; Giangrande, Scott; Kuang, Chongai; Barbosa, Henrique M. J.; Brito, Joel; Carbone, Samara; Chi, Xuguang; Comstock, Jennifer; Ditas, Florian; Lavric, Jost; Manninen, Hanna E.; Mei, Fan; Moran-Zuloaga, Daniel; Pöhlker, Christopher; Pöhlker, Mira L.; Saturno, Jorge; Schmid, Beat; Souza, Rodrigo A. F.; Springston, Stephen R.; Tomlinson, Jason M.; Toto, Tami; Walter, David; Wimmer, Daniela; Smith, James N.; Kulmala, Markku; Machado, Luiz A. T.; Artaxo, Paulo; Andreae, Meinrat O.; Petäjä, Tuukka; Martin, Scot T.

    2016-11-01

    The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin (for example, ref. 2) and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear. Here we present aircraft- and ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. This rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.

  16. Vertical electron transport in van der Waals heterostructures with graphene layers

    NASA Astrophysics Data System (ADS)

    Ryzhii, V.; Otsuji, T.; Ryzhii, M.; Aleshkin, V. Ya.; Dubinov, A. A.; Mitin, V.; Shur, M. S.

    2015-04-01

    We propose and analyze an analytical model for the self-consistent description of the vertical electron transport in van der Waals graphene-layer (GL) heterostructures with the GLs separated by the barriers layers. The top and bottom GLs serve as the structure emitter and collector. The vertical electron transport in such structures is associated with the propagation of the electrons thermionically emitted from GLs above the inter-GL barriers. The model under consideration describes the processes of the electron thermionic emission from and the electron capture to GLs. It accounts for the nonuniformity of the self-consistent electric field governed by the Poisson equation which accounts for the variation of the electron population in GLs. The model takes also under consideration the cooling of electrons in the emitter layer due to the Peltier effect. We find the spatial distributions of the electric field and potential with the high-electric-field domain near the emitter GL in the GL heterostructures with different numbers of GLs. Using the obtained spatial distributions of the electric field, we calculate the current-voltage characteristics. We demonstrate that the Peltier cooling of the two-dimensional electron gas in the emitter GL can strongly affect the current-voltage characteristics resulting in their saturation. The obtained results can be important for the optimization of the hot-electron bolometric terahertz detectors and different devices based on GL heterostructures.

  17. Vertical electron transport in van der Waals heterostructures with graphene layers

    SciTech Connect

    Ryzhii, V.; Otsuji, T.; Ryzhii, M.; Aleshkin, V. Ya.; Dubinov, A. A.; Mitin, V.; Shur, M. S.

    2015-04-21

    We propose and analyze an analytical model for the self-consistent description of the vertical electron transport in van der Waals graphene-layer (GL) heterostructures with the GLs separated by the barriers layers. The top and bottom GLs serve as the structure emitter and collector. The vertical electron transport in such structures is associated with the propagation of the electrons thermionically emitted from GLs above the inter-GL barriers. The model under consideration describes the processes of the electron thermionic emission from and the electron capture to GLs. It accounts for the nonuniformity of the self-consistent electric field governed by the Poisson equation which accounts for the variation of the electron population in GLs. The model takes also under consideration the cooling of electrons in the emitter layer due to the Peltier effect. We find the spatial distributions of the electric field and potential with the high-electric-field domain near the emitter GL in the GL heterostructures with different numbers of GLs. Using the obtained spatial distributions of the electric field, we calculate the current-voltage characteristics. We demonstrate that the Peltier cooling of the two-dimensional electron gas in the emitter GL can strongly affect the current-voltage characteristics resulting in their saturation. The obtained results can be important for the optimization of the hot-electron bolometric terahertz detectors and different devices based on GL heterostructures.

  18. Intrinsic transport of h-BN encapsulated few-layer black phosphorus

    NASA Astrophysics Data System (ADS)

    Arefe, Ghidewon; Kim, Young Duck; Chenet, Daniel; Cui, Xu; Chang, Damien; Hone, James

    2015-03-01

    Few-layer black phosphorus (BP) is an exciting two-dimensional material with ambipolar behavior, large on/off ratio, and high mobility with a direct bandgap. The anisotropic atomic nature of black phosphorus exhibits unique angle dependent electronic and optical features. One of the primary difficulties in fabricating few-layer BP devices to study transport is the reactive nature of the material in ambient conditions as it degrades in the presence of air and moisture. In order to characterize the intrinsic physical properties of BP, we fabricated few-layer BP flakes that are fully encapsulated by hexagonal boron nitride (h-BN) with a clean stacking technique. We also characterized the electrical transport of h-BN encapsulated BP devices that show greatly improved environmental stability and high mobility at low temperature due to the suppression of extrinsic scattering effects such as charge impurities, surface polar optical phonons, and absorbents from air. H-BN encapsulated BP devices will be an essential platform for the observation of new physics from BP and realization of BP based advanced opto-electronic application devices body.

  19. Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall

    SciTech Connect

    Wang, Jian; Krejci, Radovan; Giangrande, Scott; Kuang, Chongai; Barbosa, Henrique M. J.; Brito, Joel; Carbone, Samara; Chi, Xuguang; Comstock, Jennifer; Ditas, Florian; Lavric, Jost; Manninen, Hanna E.; Mei, Fan; Moran-Zuloaga, Daniel; Pöhlker, Christopher; Pöhlker, Mira L.; Saturno, Jorge; Schmid, Beat; Souza, Rodrigo A. F.; Springston, Stephen R.; Tomlinson, Jason M.; Toto, Tami; Walter, David; Wimmer, Daniela; Smith, James N.; Kulmala, Markku; Machado, Luiz A. T.; Artaxo, Paulo; Andreae, Meinrat O.; Petäjä, Tuukka; Martin, Scot T.

    2016-10-24

    The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear. Here we present aircraft- and ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. Lastly, this rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.

  20. Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall

    DOE PAGES

    Wang, Jian; Krejci, Radovan; Giangrande, Scott; ...

    2016-10-24

    The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear. Here we present aircraft- andmore » ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. Lastly, this rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.« less

  1. Vertical structure of aeolian turbulence in a boundary layer with sand transport

    NASA Astrophysics Data System (ADS)

    Lee, Zoe S.; Baas, Andreas C. W.

    2016-04-01

    Recently we have found that Reynolds shear stress shows a significant variability with measurement height (Lee and Baas, 2016), and so an alternative parameter for boundary layer turbulence may help to explain the relationship between wind forcing and sediment transport. We present data that were collected during a field study of boundary layer turbulence conducted on a North Atlantic beach. High-frequency (50 Hz) 3D wind velocity measurements were collected using ultrasonic anemometry at thirteen different measurement heights in a tight vertical array between 0.11 and 1.62 metres above the surface. Thanks to the high density installation of sensors a detailed analysis of the boundary layer flow can be conducted using methods more typically used in studies where data is only available from one or just a few measurement heights. We use quadrant analysis to explore the vertical structure of turbulence and track the changes in quadrant signatures with measurement elevation and over time. Results of quadrant analysis, at the 'raw' 50 Hz timescale, demonstrates the tendency for event clustering across all four quadrants, which implies that at-a-point quadrant events are part of larger-scale turbulent structures. Using an HSV colour model, applied to the quadrant analysis data and plotted in series, we create colour maps of turbulence, which can provide a clear visualisation of the clustering of event activity at each height and illustrate the shape of the larger coherent flow structures that are present within the boundary layer. By including a saturation component to the colour model, the most significant stress producing sections of the data are emphasised. This results in a 'banded' colour map, which relates to clustering of quadrant I (Outward Interaction) and quadrant IV (Sweep) activity, separate from clustering of quadrant II (Burst) and quadrant III (Inward Interaction). Both 'sweep-type' and 'burst-type' sequences are shown to have a diagonal structure

  2. Glassy Metal Alloy Nanofiber Anodes Employing Graphene Wrapping Layer: Toward Ultralong-Cycle-Life Lithium-Ion Batteries.

    PubMed

    Jung, Ji-Won; Ryu, Won-Hee; Shin, Jungwoo; Park, Kyusung; Kim, Il-Doo

    2015-07-28

    Amorphous silicon (a-Si) has been intensively explored as one of the most attractive candidates for high-capacity and long-cycle-life anode in Li-ion batteries (LIBs) primarily because of its reduced volume expansion characteristic (∼280%) compared to crystalline Si anodes (∼400%) after full Li(+) insertion. Here, we report one-dimensional (1-D) electrospun Si-based metallic glass alloy nanofibers (NFs) with an optimized composition of Si60Sn12Ce18Fe5Al3Ti2. On the basis of careful compositional tailoring of Si alloy NFs, we found that Ce plays the most important role as a glass former in the formation of the metallic glass alloy. Moreover, Si-based metallic glass alloy NFs were wrapped by reduced graphene oxide sheets (specifically Si60Sn12Ce18Fe5Al3Ti2 NFs@rGO), which can prevent the direct exposure of a-Si alloy NFs to the liquid electrolyte and stabilize the solid-electrolyte interphase (SEI) layers on the surfaces of rGO sheets while facilitating electron transport. The metallic glass nanofibers exhibited superior electrochemical cell performance as an anode: (i) Si60Sn12Ce18Fe5Al3Ti2 NFs show a high specific capacity of 1017 mAh g(-1) up to 400 cycles at 0.05C with negligible capacity loss as well as superior cycling performance (nearly 99.9% capacity retention even after 2000 cycles at 0.5C); (ii) Si60Sn12Ce18Fe5Al3Ti2 NFs@rGO reveals outstanding rate behavior (569.77 mAh g(-1) after 2000 cycles at 0.5C and a reversible capacity of around 370 mAh g(-1) at 4C). We demonstrate the potential suitability of multicomponent a-Si alloy NFs as a long-cycling anode material.

  3. Large eddy simulation study of scalar transport in fully developed wind-turbine array boundary layers

    NASA Astrophysics Data System (ADS)

    Calaf, Marc; Parlange, Marc B.; Meneveau, Charles

    2011-12-01

    Wind harvesting is fast becoming an important alternative source of energy. As wind farms become larger, they begin to attain scales at which two-way interactions with the atmospheric boundary layer (ABL) must be taken into account. Several studies have shown that there is a quantifiable effect of wind farms on the local meteorology, mainly through changes in the land-atmosphere fluxes of heat and moisture. In particular, the observed trends suggest that wind farms increase fluxes at the surface and this could be due to increased turbulence in the wakes. Conversely, simulations and laboratory experiments show that underneath wind farms, the friction velocity is decreased due to extraction of momentum by the wind turbines, a factor that could decrease scalar fluxes at the surface. In order to study this issue in more detail, a suite of large eddy simulations of an infinite (fully developed) wind turbine array boundary layer, including scalar transport from the ground surface without stratification, is performed. Results show an overall increase in the scalar fluxes of about 10%-15% when wind turbines are present in the ABL, and that the increase does not strongly depend upon wind farm loading as described by the turbines' thrust coefficient and the wind turbines spacings. A single-column analysis including scalar transport shows that the presence of wind farms can be expected to increase slightly the scalar transport from the bottom surface and that this slight increase is due to a delicate balance between two strong opposing trends.

  4. Band offset of vanadium-doped molybdenum oxide hole transport layer in organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Chang, Feng-Kuei; Huang, Yi-Chi; Jeng, Jiann-Shing; Chen, Jen-Sue

    2016-08-01

    Solution-processed vanadium-doped molybdenum oxide films (V)MoOx films with mole ratios of Mo:V = 1:0, 1:0.05, 1:0.2, 1:0.5, 0:1, are fabricated as hole transport layer (HTL) in organic photovoltaics with active layer blend comprising poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM). The device structure is ITO/(V)MoOx/P3HT:PCBM/ZnO NP/Al, and the working area is 0.16 cm2. The result shows that the device using V0.05MoOx HTL has the best performance, including power conversion efficiency of 2.16%, Voc of 0.6 V, Jsc of 6.93 mA/cm2, and FF of 51.9%. Using ultraviolet photoelectron spectroscopy (UPS), we can define the energy levels of valence band edge and Fermi level of (V)MoOx films. UPS analysis indicates that V0.05MoOx has the smallest energy band offset between its valence band edge to the HOMO of P3HT, which is advantageous for hole transporting from P3HT to ITO anode via the V0.05MoOx HTL. In addition, V0.05MoOx film shows the lowest electrical resistivity among all (V)MoOx films, which is further beneficial for hole transportation.

  5. Thermal Transport Phenomena in the Quasi-laminarization Process of Turbulent Boundary Layers

    NASA Astrophysics Data System (ADS)

    Castillo, Luciano; Araya, Guillermo; Hussain, Fazle

    2014-11-01

    Direct Numerical Simulation of a spatially evolving turbulent boundary layer subject to strong favorable pressure gradient (SFPG) with eventual quasi-laminarization has been performed to include the thermal field. In this talk, the following questions will be addressed: i) to which extend the Reynolds analogy is satisfied during flow laminarization? ii) can the thermal boundary layer under quasi-laminarization be described as two quasi-independent inner/outer regions? To the best of our knowledge, documented investigation regarding heat transfer phenomena associated with quasi-laminarization process of spatially developing boundary layers is rather scarce. In order to introduce realistic thermal inlet fluctuations in a SFPG we employed the multi-scale technique for thermal boundary layers devised by Araya and Castillo PoF (2013). Such methodology enable us to more effective capture the pressure gradient and thermal field than using a single scaling approach. It is shown that the Reynolds normal stresses for the streamwise component remains frozen in space while the wall-normal and spanwise components continue to decrease as the flow moves downstream and never becomes laminar due to the survival of the upstream turbulence during dissipation on viscous time scales.

  6. Architecture of the Interface between the Perovskite and Hole-Transport Layers in Perovskite Solar Cells.

    PubMed

    Moriya, Masahiro; Hirotani, Daisuke; Ohta, Tsuyoshi; Ogomi, Yuhei; Shen, Qing; Ripolles, Teresa S; Yoshino, Kenji; Toyoda, Taro; Minemoto, Takashi; Hayase, Shuzi

    2016-09-22

    The interface between the perovskite (PVK, CH3 NH3 PbI3 ) and hole-transport layers in perovskite solar cells is discussed. The device architecture studied is as follows: F-doped tin oxide (FTO)-coated glass/compact TiO2 /mesoporous TiO2 /PVK/2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-MeOTAD)/Au. After a thin layer of 4,4,4-trifluorobutylammonium iodide (TFBA) was inserted at the interface between PVK and Spiro-MeOTAD, the photovoltaic efficiency increased from 11.6-14.5 % to 15.1-17.6 %. TFBA (10 ppm) was added in the PVK solution before coating. Owing to the low surface tension of TFBA, TFBA rose to the surface of the PVK layer spontaneously during spin-coating to make a thin organic layer. The PVK grain boundaries also seemed to be passivated with the addition of TFBA. However, large differences in Urbach energies and valence band energy level were not observed for the PVK layer with and without the addition of TFBA. The charge recombination time constant between the PVK and the Spiro-MeOTAD became slower (from 8.4 to 280 μsec) after 10 ppm of TFBA was added in the PVK. The experimental results using TFBA conclude that insertion of a very thin layer at the interface between PVK and Spiro-MeOTAD is effective for suppressing charge recombination and increasing photovoltaic performances.

  7. High-Mobility Transport Anisotropy in Few-Layer MoO3 and Its Origin.

    PubMed

    Zhang, Wei-Bing; Qu, Qian; Lai, Kang

    2017-01-18

    The novel two-dimensional semiconductors with high carrier mobility and excellent stability are essential to the next-generation high-speed and low-power nanoelectronic devices. Because of the natural abundance, intrinsic gap, and chemical stability, metal oxides were also recently suggested as potential candidates for electronic materials. However, their carrier mobilities are typically on the order of tens of square centimeters per volt per second, much lower than that for commonly used silicon. By using first-principles calculations and deformation potential theory, we have predicted few-layer MoO3 as chemically stable wide-band-gap semiconductors with a considerably high acoustic-phonon-limited carrier mobility above 3000 cm(2) V(-1) s(-1), which makes them promising candidates for both electron- and hole-transport applications. Moreover, we also find a large in-plane anisotropy of the carrier mobility with a ratio of about 20-30 in this unusual system. Further analysis indicates that, because of the unique charge density distribution of whole valence electrons and the states near the band edge, both the elastic modulus and deformation potential are strongly directionally dependent. Also, the predicted high-mobility transport anisotropy of few-layer MoO3 can be attributed to the synergistic effect of the anisotropy of the elastic modulus and deformation potential. Our results not only give an insightful understanding for the high carrier mobility observed in few-layer MoO3 systems but also reveal the importance of the carrier-transport direction to the device performance.

  8. Effective Transport Properties Accounting for Electrochemical Reactions of Proton-Exchange Membrane Fuel Cell Catalyst Layers

    SciTech Connect

    Pharoah, Jon; Choi, Hae-Won; Chueh, Chih-Che; Harvey, David

    2011-07-01

    There has been a rapidly growing interest in three-dimensional micro-structural reconstruction of fuel cell electrodes so as to derive more accurate descriptors of the pertinent geometric and effective transport properties. Due to the limited accessibility of experiments based reconstruction techniques, such as dual-beam focused ion beam-scanning electro microscopy or micro X-Ray computed tomography, within sample micro-structures of the catalyst layers in polymer electrolyte membrane fuel cells (PEMFCs), a particle based numerical model is used in this study to reconstruct sample microstructure of the catalyst layers in PEMFCs. Then the reconstructed sample structure is converted into the computational grid using body-fitted/cut-cell based unstructured meshing technique. Finally, finite volume methods (FVM) are applied to calculate effective properties on computational sample domains.

  9. A TiO2 nanotube network electron transport layer for high efficiency perovskite solar cells.

    PubMed

    Gao, Xianfeng; Li, Jianyang; Gollon, Sam; Qiu, Ming; Guan, Dongsheng; Guo, Xiaoru; Chen, Junhong; Yuan, Chris

    2017-02-15

    The electron transport layer (ETL) plays a critical role in high efficiency perovskite solar cells. In this study, an anodic TiO2 nanotube film was transformed into a TiO2 nanotube network film, which maintained its advantage as an efficient ETL for perovskite solar cells. Compared with the mesoporous TiO2 nanoparticle ETL, the TiO2 nanotube network ETL can increase the efficiency of perovskite solar cells by 26.6%, which is attributed to its superior charge collection property and light trapping ability. The results confirm the importance of optimizing the electron collecting layer and suggest another way to design and fabricate novel perovskite solid state solar cells, potentially by using a TiO2 nanotube network film as an alternative high efficiency electrode.

  10. Nb2O5 as a new electron transport layer for double junction polymer solar cells.

    PubMed

    Siddiki, Mahbube K; Venkatesan, Swaminathan; Qiao, Qiquan

    2012-04-14

    Nb(2)O(5) as a new electron transport layer (ETL) was used for double junction polymer solar cells. The Nb(2)O(5) ETL was prepared by spin coating a Nb(2)O(5) sol-gel solution onto the active layer of the optical front subcell. The double junction devices using Nb(2)O(5) ETL exhibit an open circuit voltage (V(oc)) of 1.30 V, which is close to the sum of the s of the individual subcells. The current density-voltage (J-V) simulation showed that the double junction device performance using Nb(2)O(5) as ETL could be significantly increased by reducing the series resistance (R(se)) and matching the current densities of the individual subcells.

  11. Cross-layer restoration with software defined networking based on IP over optical transport networks

    NASA Astrophysics Data System (ADS)

    Yang, Hui; Cheng, Lei; Deng, Junni; Zhao, Yongli; Zhang, Jie; Lee, Young

    2015-10-01

    The IP over optical transport network is a very promising networking architecture applied to the interconnection of geographically distributed data centers due to the performance guarantee of low delay, huge bandwidth and high reliability at a low cost. It can enable efficient resource utilization and support heterogeneous bandwidth demands in highly-available, cost-effective and energy-effective manner. In case of cross-layer link failure, to ensure a high-level quality of service (QoS) for user request after the failure becomes a research focus. In this paper, we propose a novel cross-layer restoration scheme for data center services with software defined networking based on IP over optical network. The cross-layer restoration scheme can enable joint optimization of IP network and optical network resources, and enhance the data center service restoration responsiveness to the dynamic end-to-end service demands. We quantitatively evaluate the feasibility and performances through the simulation under heavy traffic load scenario in terms of path blocking probability and path restoration latency. Numeric results show that the cross-layer restoration scheme improves the recovery success rate and minimizes the overall recovery time.

  12. Thermal transport across few-layer boron nitride encased by silica

    SciTech Connect

    Ni, Yuxiang; Dumitricǎ, Traian; Jiang, Jiechao; Meletis, Efstathios

    2015-07-20

    Two dimensional hexagonal boron nitride (h-BN) attracted attention for use in applications. Using equilibrium molecular dynamics, we examine the phonon transport in few-layer h-BN encased by silica (SiO{sub 2}). We report large interfacial thermal resistances, of about 2.2 × 10{sup −8} m{sup 2} K W{sup −1}, which are not sensitive to the number of h-BN layers or the SiO{sub 2} crystallinity. The h-BN/SiO{sub 2} superlattices exhibit ultra-low thermal conductivities across layers, as low as 0.3 W/m K. They are structurally stable up to 2000 K while retaining the low-thermal conductivity attributes. Our simulations indicate that incorporation of h-BN layers and nanoparticles in silica could establish thermal barriers and heat spreading paths, useful for high performance coatings and electronic device applications.

  13. Angular Momentum Transport and Variability in Boundary Layers of Accretion Disks Driven by Global Acoustic Modes

    NASA Astrophysics Data System (ADS)

    Belyaev, Mikhail A.; Rafikov, Roman R.; Stone, James M.

    2012-11-01

    Disk accretion onto a weakly magnetized central object, e.g., a star, is inevitably accompanied by the formation of a boundary layer near the surface, in which matter slows down from the highly supersonic orbital velocity of the disk to the rotational velocity of the star. We perform high-resolution two-dimensional hydrodynamical simulations in the equatorial plane of an astrophysical boundary layer with the goal of exploring the dynamics of non-axisymmetric structures that form there. We generically find that the supersonic shear in the boundary layer excites non-axisymmetric quasi-stationary acoustic modes that are trapped between the surface of the star and a Lindblad resonance in the disk. These modes rotate in a prograde fashion, are stable for hundreds of orbital periods, and have a pattern speed that is less than and of the order of the rotational velocity at the inner edge of the disk. The origin of these intrinsically global modes is intimately related to the operation of a corotation amplifier in the system. Dissipation of acoustic modes in weak shocks provides a universal mechanism for angular momentum and mass transport even in purely hydrodynamic (i.e., non-magnetized) boundary layers. We discuss the possible implications of these trapped modes for explaining the variability seen in accreting compact objects.

  14. ANGULAR MOMENTUM TRANSPORT AND VARIABILITY IN BOUNDARY LAYERS OF ACCRETION DISKS DRIVEN BY GLOBAL ACOUSTIC MODES

    SciTech Connect

    Belyaev, Mikhail A.; Stone, James M.; Rafikov, Roman R.

    2012-11-20

    Disk accretion onto a weakly magnetized central object, e.g., a star, is inevitably accompanied by the formation of a boundary layer near the surface, in which matter slows down from the highly supersonic orbital velocity of the disk to the rotational velocity of the star. We perform high-resolution two-dimensional hydrodynamical simulations in the equatorial plane of an astrophysical boundary layer with the goal of exploring the dynamics of non-axisymmetric structures that form there. We generically find that the supersonic shear in the boundary layer excites non-axisymmetric quasi-stationary acoustic modes that are trapped between the surface of the star and a Lindblad resonance in the disk. These modes rotate in a prograde fashion, are stable for hundreds of orbital periods, and have a pattern speed that is less than and of the order of the rotational velocity at the inner edge of the disk. The origin of these intrinsically global modes is intimately related to the operation of a corotation amplifier in the system. Dissipation of acoustic modes in weak shocks provides a universal mechanism for angular momentum and mass transport even in purely hydrodynamic (i.e., non-magnetized) boundary layers. We discuss the possible implications of these trapped modes for explaining the variability seen in accreting compact objects.

  15. The design and optimization of two low frequency energy harvesters employing 3C-SiC/AlN/Mo composite layers

    SciTech Connect

    Iqbal, Abid Mohd-Yasin, Faisal Dimitrijev, Sima

    2014-10-24

    This paper presents the design and simulation of twocantilever-based energy harvesters that employs cubic silicon carbide on silicon (3C-SiC-on-Si) wafer as the base material and bottom electrode. Aluminum Nitride (AlN) is employed as the piezoelectric/middle layer due to its excellent material properties and high stability in varying temperature and harsh environment. Molybdenum (Mo) serves as the top layer/electrode. The thickness of the structural layers are optimized through MATLAB and also analyzed via Finite Element Analysis using Intellisuite. Two designs are proposed at low resonant frequency, one with conventional cantilever beam, the other being a T-shaped cantilever beam. Both structures are simulated and their performances are compared.

  16. Crystal structure and electrical transport properties of single layered perovskite LaSrCoO4

    NASA Astrophysics Data System (ADS)

    Ahad, Abdul; Shukla, D. K.; Rahman, F.; Majid, S.; Tarachand; Okram, G. S.; Phase, D. M.

    2016-10-01

    We present here investigations on the influence of structure on electrical transport properties of polycrystalline LaSrCoO4 that is single layered perovskite with K2NiF4 type structure synthesized using solid state reaction route. Using Reitveld refinement of X-ray diffraction (XRD) data, it is found that the sample is in single phase with tetragonal structure (space group I4/mmm). Electrical resistivity performed in the temperature range 140-300K shows semiconducting character of the sample. Considerable contrasts in the Co-O bond length is associated with the intermediate spin (IS) state of Co ion that correlates the structural and transport properties. Detailed analysis indicates that the temperature dependent electrical resistivity follows the three-dimensional variable range hopping (VRH) model in low temperature region below 225K. The high temperature (225-300K) resistivity data has been found to follow the thermally activated behaviour.

  17. Numerical Computation of Mass Transport in Low Reynolds Number Flows and the Concentration Boundary Layer

    NASA Astrophysics Data System (ADS)

    Licata, Nicholas A.; Fuller, Nathaniel J.

    Understanding the physical mechanisms by which an individual cell interacts with its environment often requires detailed information about the fluid in which the cell is immersed. Mass transport between the interior of the cell and the external environment is influenced by the flow of the extracellular fluid and the molecular diffusivity. Analytical calculations of the flow field are challenging in simple geometries, and not generally available in more realistic cases with irregular domain boundaries. Motivated by these problems, we discuss the numerical solution of Stokes equation by implementing a Gauss-Seidel algorithm on a staggered computational grid. The computed velocity profile is used as input to numerically solve the advection-diffusion equation for mass transport. Special attention is paid to the case of two-dimensional flows at large Péclet number. The numerical results are compared with a perturbative analytical treatment of the concentration boundary layer.

  18. Conductive conjugated polyelectrolyte as hole-transporting layer for organic bulk heterojunction solar cells.

    PubMed

    Zhou, Huiqiong; Zhang, Yuan; Mai, Cheng-Kang; Collins, Samuel D; Nguyen, Thuc-Quyen; Bazan, Guillermo C; Heeger, Alan J

    2014-02-01

    Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been extensively used as the hole-transporting layer (HTL) in bulk heterojunction (BHJ) solar cells, however, its anisotropic electrical conduction and intrinsic acidic nature generally limit the device performance. Here we demonstrate the application of a water/alcohol soluble CPE (CPE-K) as HTLs in BHJ solar cells, achieving a PCE up to 8.2%. The more superior and uniform vertical electrical conductivity found in CPE-K reduces the series resistance and provides efficient hole extraction.

  19. Tunneling transport of mono- and few-layers magnetic van der Waals MnPS3

    NASA Astrophysics Data System (ADS)

    Lee, Sungmin; Choi, Ki-Young; Lee, Sangik; Park, Bae Ho; Park, Je-Geun

    2016-08-01

    We have investigated the tunneling transport of mono- and few-layers of MnPS3 by using conductive atomic force microscopy. Due to the band alignment of indium tin oxide/MnPS3/Pt-Ir tip junction, the key features of both Schottky junction and Fowler-Nordheim tunneling (FNT) were observed for all the samples with varying thickness. Using the FNT model and assuming the effective electron mass (0.5 me) of MnPS3, we estimate the tunneling barrier height to be 1.31 eV and the dielectric breakdown strength as 5.41 MV/cm.

  20. Evaluating the transport layer of the ALFA framework for the Intel® Xeon Phi™ Coprocessor

    NASA Astrophysics Data System (ADS)

    Santogidis, Aram; Hirstius, Andreas; Lalis, Spyros

    2015-12-01

    The ALFA framework supports the software development of major High Energy Physics experiments. As part of our research effort to optimize the transport layer of ALFA, we focus on profiling its data transfer performance for inter-node communication on the Intel Xeon Phi Coprocessor. In this article we present the collected performance measurements with the related analysis of the results. The optimization opportunities that are discovered, help us to formulate the future plans of enabling high performance data transfer for ALFA on the Intel Xeon Phi architecture.

  1. Numerical Modeling Studies of Wake Vortex Transport and Evolution Within the Planetary Boundary Layer

    NASA Technical Reports Server (NTRS)

    Lin, Yuh-Lang; Arya, S. Pal; Kaplan, Michael L.; Shen, Shaohua

    1998-01-01

    In support of the wake vortex effect of the Terminal Area Productivity program, we have put forward four tasks to be accomplished in our proposal. The first task is validation of two-dimensional wake vortex-turbulence interaction. The second task is investigation of three-dimensional interaction between wake vortices and atmospheric boundary layer (ABL) turbulence. The third task is ABL studies. The, fourth task is addition of a Klemp-Durran condition at the top boundary for TASS model. The accomplishment of these tasks will increase our understanding of the dynamics of wake vortex and improve forecasting systems responsible for air safety and efficiency. The first two tasks include following three parts: (a) Determine significant length scale for vortex decay and transport, especially the length scales associated with the onset of Crow instability (Crow, 1970); (b) Study the effects of atmospheric turbulence on the decay of the wake vortices; and (c) Determine the relationships between decay rate, transport properties and atmospheric parameters based on large eddy simulation (LES) results and the observational data. These parameters may include turbulence kinetic energy, dissipation rate, wind shear and atmospheric stratification. The ABL studies cover LES modeling of turbulence structure within planetary boundary layer under transition and stable stratification conditions. Evidences have shown that the turbulence in the stable boundary layer can be highly intermittent and the length scales of eddies are very small compared to those in convective case. We proposed to develop a nesting grid mesh scheme and a modified Klemp-Durran conditions (Klemp and Wilhelmson, 1978) at the top boundary for TASS model to simulate planetary boundary layer under stable stratification conditions. During the past year, our group has made great efforts to carry out the above mentioned four tasks simultaneously. The work accomplished in the last year will be described in the next

  2. Investigation of silver and iodine transport through silicon carbide layers prepared for nuclear fuel element cladding

    NASA Astrophysics Data System (ADS)

    Friedland, E.; van der Berg, N. G.; Malherbe, J. B.; Hancke, J. J.; Barry, J.; Wendler, E.; Wesch, W.

    2011-03-01

    Transport of silver and iodine through polycrystalline SiC layers produced by PBMR (Pty) Ltd. for cladding of TRISO fuel kernels was investigated using Rutherford backscattering analysis and electron microscopy. Fluences of 2 × 10 16 Ag + cm -2 and 1 × 10 16 I + cm -2 were implanted at room temperature, 350 °C and 600 °C with an energy of 360 keV, producing an atomic density of approximately 1.5% at the projected ranges of about 100 nm. The broadening of the implantation profiles and the loss of diffusors through the front surface during vacuum annealing at temperatures up to 1400 °C was determined. The results for room temperature implantations point to completely different transport mechanisms for silver and iodine in highly disordered silicon carbide. However, similar results are obtained for high temperature implantations, although iodine transport is much stronger influenced by lattice defects than is the case for silver. For both diffusors transport in well annealed samples can be described by Fickian grain boundary diffusion with no abnormal loss through the surface as would be expected from the presence of nano-pores and/or micro-cracks. At 1100 °C diffusion coefficients for silver and iodine are below our detection limit of 10 -21 m 2 s -1, while they increase into the 10 -20 m 2 s -1 range at 1300 °C.

  3. Three-dimensional scrape off layer transport in the helically symmetric experiment HSX

    NASA Astrophysics Data System (ADS)

    Akerson, A. R.; Bader, A.; Hegna, C. C.; Schmitz, O.; Stephey, L. A.; Anderson, D. T.; Anderson, F. S. B.; Likin, K. M.

    2016-08-01

    The edge topology of helically symmetric experiment (HSX) in the quasi-helically symmetric configuration is characterized by an 8/7 magnetic island remnant embedded in a short connection length scrape-off layer (SOL) domain. A 2D mapping of edge plasma profiles within this heterogeneous SOL has been constructed using a movable, multi-pin Langmuir probe. Comparisons of these measurements to edge simulations using the EMC3-EIRENE 3D plasma fluid and kinetic neutral gas transport model have been performed. The measurements provide strong evidence that particle transport is diffusive within the island region and dominantly convective in the SOL region. Measurements indicate that phenomenological cross-field diffusion coefficients are low in the SOL region between the last closed flux surface and edge island (i.e. {{D}\\bot}≈ 0.03 m2 s-1). This level of transport was found to increase by a factor of two when a limiter is inserted almost completely into the magnetic island. A reduction in gradients of the edge electrostatic plasma potential was also measured in this configuration, suggesting that the reduced electric field may be linked to the increased cross-field transport observed.

  4. Non-Newtonian effects of blood on LDL transport inside the arterial lumen and across multi-layered arterial wall with and without stenosis

    NASA Astrophysics Data System (ADS)

    Deyranlou, Amin; Niazmand, Hamid; Sadeghi, Mahmood-Reza; Mesri, Yaser

    2016-06-01

    Blood non-Newtonian behavior on low-density lipoproteins (LDL) accumulation is analyzed numerically, while fluid-multilayered arteries are adopted for nonstenotic and 30%-60% symmetrical stenosed models. Present model considers non-Newtonian effects inside the lumen and within arterial layers simultaneously, which has not been examined in previous studies. Navier-Stokes equations are solved along with the mass transport convection-diffusion equations and Darcy’s model for species transport inside the luminal flow and across wall layers, respectively. Carreau model for the luminal flow and the modified Darcy equation for the power-law fluid within arterial layers are employed to model blood rheological characteristics, appropriately. Results indicate that in large arteries with relatively high Reynolds number Newtonian model estimates LDL concentration patterns well enough, however, this model seriously incompetent for regions with low WSS. Moreover, Newtonian model for plasma underestimates LDL concentration especially on luminal surface and across arterial wall. Therefore, applying non-Newtonian model seems essential for reaching to a more accurate estimation of LDL distribution in the artery. Finally, blood flow inside constricted arteries demonstrates that LDL concentration patterns along the stenoses inside the luminal flow and across arterial layers are strongly influenced as compared to the nonstenotic arteries. Additionally, among four stenosis severity grades, 40% stenosis is prone to more LDL accumulation along the post-stenotic regions.

  5. What Supergranule Flow Models Tell Us About the Sun's Surface Shear Layer and Magnetic Flux Transport

    NASA Technical Reports Server (NTRS)

    Hathaway, David

    2011-01-01

    Models of the photospheric flows due to supergranulation are generated using an evolving spectrum of vector spherical harmonics up to spherical harmonic wavenumber l1500. Doppler velocity data generated from these models are compared to direct Doppler observations from SOHO/MDI and SDO/HMI. The models are adjusted to match the observed spatial power spectrum as well as the wavenumber dependence of the cell lifetimes, differential rotation velocities, meridional flow velocities, and relative strength of radial vs. horizontal flows. The equatorial rotation rate as a function of wavelength matches the rotation rate as a function of depth as determined by global helioseismology. This leads to the conclusions that the cellular structures are anchored at depths equal to their widths, that the surface shear layer extends to at least 70 degrees latitude, and that the poleward meridional flow decreases in amplitude and reverses direction at the base of the surface shear layer (approx.35 Mm below the surface). Using the modeled flows to passively transport magnetic flux indicates that the observed differential rotation and meridional flow of the magnetic elements are directly related to the differential rotation and meridional flow of the convective pattern itself. The magnetic elements are transported by the evolving boundaries of the supergranule pattern (where the convective flows converge) and are unaffected by the weaker flows associated with the differential rotation or meridional flow of the photospheric plasma.

  6. Current transport mechanisms in plasma-enhanced atomic layer deposited AlN thin films

    SciTech Connect

    Altuntas, Halit E-mail: biyikli@unam.bilkent.edu.tr; Ozgit-Akgun, Cagla; Donmez, Inci; Biyikli, Necmi E-mail: biyikli@unam.bilkent.edu.tr

    2015-04-21

    Here, we report on the current transport mechanisms in AlN thin films deposited at a low temperature (i.e., 200 °C) on p-type Si substrates by plasma-enhanced atomic layer deposition. Structural characterization of the deposited AlN was carried out using grazing-incidence X-ray diffraction, revealing polycrystalline films with a wurtzite (hexagonal) structure. Al/AlN/ p-Si metal-insulator-semiconductor (MIS) capacitor structures were fabricated and investigated under negative bias by performing current-voltage measurements. As a function of the applied electric field, different types of current transport mechanisms were observed; i.e., ohmic conduction (15.2–21.5 MV/m), Schottky emission (23.6–39.5 MV/m), Frenkel-Poole emission (63.8–211.8 MV/m), trap-assisted tunneling (226–280 MV/m), and Fowler-Nordheim tunneling (290–447 MV/m). Electrical properties of the insulating AlN layer and the fabricated Al/AlN/p-Si MIS capacitor structure such as dielectric constant, flat-band voltage, effective charge density, and threshold voltage were also determined from the capacitance-voltage measurements.

  7. Unusual isotope effect on thermal transport of single layer molybdenum disulphide

    SciTech Connect

    Wu, Xufei; Yang, Nuo; Luo, Tengfei

    2015-11-09

    Thermal transport in single layer molybdenum disulfide (MoS{sub 2}) is critical to advancing its applications. In this paper, we use molecular dynamics simulations with first-principles force constants to study the isotope effect on the thermal transport of single layer MoS{sub 2}. Through phonon modal analysis, we found that isotopes can strongly scatter phonons with intermediate frequencies, and the scattering behavior can be radically different from that predicted by conventional scattering model based on perturbation theory, where Tamura's formula is combined with Matthiessen's rule to include isotope effects. Such a discrepancy becomes smaller for low isotope concentrations. Natural isotopes can lead to a 30% reduction in thermal conductivity for large size samples. However, for small samples where boundary scattering becomes significant, the isotope effect can be greatly suppressed. It was also found that the Mo isotopes, which contribute more to the phonon eigenvectors in the intermediate frequency range, have stronger impact on thermal conductivity than S isotopes.

  8. Numerical study on exciton transport and light emission for organic light emitting diodes with an emission layer.

    PubMed

    Kim, K S; Hwang, Y W; Won, T Y

    2013-12-01

    This paper reports the results of a numerical study on carrier injection and exciton transport in an organic light emitting diode (OLED) structure based on tris (8-hydroxyquinolinato) aluminum (Alq3). Because charge accumulation at the interfaces between the emission layer (EML) and transport layer are believed to increase the recombination rate, which also increases the exciton density, a numerical study was performed on the effect of inserting an EML in the bilayer structure. In the first case considered, the lowest unoccupied molecular orbital (LUMO) of the EML was aligned with the LUMO of the hole transport layer (HTL), whereas the highest occupied molecular orbital (HOMO) of the EML was aligned with the HOMO of the electron transport layer (ETL). In the second case, the LUMO of the EML was aligned with the LUMO of the ETL and the HOMO of the EML was aligned with the HOMO of the HTL. In case of a charge-blocking device, most of the recombination appeared to occur at both edges of the EML because the electric field exhibited a peak in these areas. On the other hand, in the case of the charge-confining device, the electric field was confined at the interface between the EML and ETL. This paper also discussed the effect of the insertion of a doping layer as transport layer.

  9. Tail-ion transport and Knudsen layer formation in the presence of magnetic fields

    SciTech Connect

    Schmit, P. F.; Molvig, Kim; Nakhleh, C. W.

    2013-11-15

    Knudsen layer losses of tail fuel ions could reduce significantly the fusion reactivity of highly compressed cylindrical and spherical targets in inertial confinement fusion (ICF). With the class of magnetized ICF targets in mind, the effect of embedded magnetic fields on Knudsen layer formation is investigated for the first time. The modified energy scaling of ion diffusivity in magnetized hot spots is found to suppress the preferential losses of tail-ions perpendicular to the magnetic field lines to a degree that the tail distribution can be at least partially, if not fully, restored. Two simple threshold conditions are identified leading to the restoration of fusion reactivity in magnetized hot spots. A kinetic equation for tail-ion transport in the presence of a magnetic field is derived, and solutions to the equation are obtained numerically in simulations. Numerical results confirm the validity of the threshold conditions for restored reactivity and identify two different asymptotic regimes of the fusion fuel. While Knudsen layer formation is shown to be suppressed entirely in strongly magnetized cylindrical hot spot cavities, uniformly magnetized spherical cavities demonstrate remnant, albeit reduced, levels of tail-ion depletion.

  10. Anomalous transport in discrete arcs and simulation of double layers in a model auroral circuit

    NASA Technical Reports Server (NTRS)

    Smith, Robert A.

    1987-01-01

    The evolution and long-time stability of a double layer in a discrete auroral arc requires that the parallel current in the arc, which may be considered uniform at the source, be diverted within the arc to charge the flanks of the U-shaped double-layer potential structure. A simple model is presented in which this current re-distribution is effected by anomalous transport based on electrostatic lower hybrid waves driven by the flank structure itself. This process provides the limiting constraint on the double-layer potential. The flank charging may be represented as that of a nonlinear transmission. A simplified model circuit, in which the transmission line is represented by a nonlinear impedance in parallel with a variable resistor, is incorporated in a 1-d simulation model to give the current density at the DL boundaries. Results are presented for the scaling of the DL potential as a function of the width of the arc and the saturation efficiency of the lower hybrid instability mechanism.

  11. Anomalous transport in discrete arcs and simulation of double layers in a model auroral circuit

    NASA Technical Reports Server (NTRS)

    Smith, Robert A.

    1987-01-01

    The evolution and long-time stability of a double layer (DL) in a discrete auroral arc requires that the parallel current in the arc, which may be considered uniform at the source, be diverted within the arc to charge the flanks of the U-shaped double layer potential structure. A simple model is presented in which this current redistribution is effected by anomalous transport based on electrostatic lower hybrid waves driven by the flank structure itself. This process provides the limiting constraint on the double layer potential. The flank charging may be represented as that of a nonlinear transmission line. A simplified model circuit, in which the transmission line is represented by a nonlinear impedance in parallel with a variable resistor, is incorporated in a one-dimensional simulation model to give the current density at the DL boundaries. Results are presented for the scaling of the DL potential as a function of the width of the arc and the saturation efficiency of the lower hybrid instability mechanism.

  12. Low band gap polymeric solar cells using solution-processable copper iodide as hole transporting layer

    NASA Astrophysics Data System (ADS)

    Chaudhary, Neeraj; Kesari, J. P.; Chaudhary, Rajiv; Patra, Asit

    2016-08-01

    In the present work, we have shown the performance of solution-processable copper iodide (CuI) as an alternative hole transporting layer (HTL) for polymeric solar cells. Optical spectra of the CuI thin film reveal highly transparent and practically no absorption in the range vis-NIR region (450-1110 nm). X-ray diffraction (XRD) patterns of CuI exhibits as a p-type semiconductor as well as crystalline nature. The photovoltaic devices were fabricated using PCDTBT and PTB7 as donor materials blended with PC71BM as an acceptor material. The power conversion efficiencies (PCEs) based on CuI as an HTL have been achieved to up to 3.04% and 4.48% for PCDTBT and PTB7 based donor materials respectively with a configuration based on ITO/CuI(40 nm)/active layer (60 nm)/Al (120 nm). This study clearly indicated that the devices made with CuI as an HTL showed superior performance than the device fabricated from PEDOT:PSS layer as an HTL. Morphological characterization of the HTL using scanning electron microscopy (SEM) and atomic force microscope (AFM) were carried for better understanding.

  13. Amorphous indium-gallium-zinc-oxide as electron transport layer in organic photodetectors

    NASA Astrophysics Data System (ADS)

    Arora, H.; Malinowski, P. E.; Chasin, A.; Cheyns, D.; Steudel, S.; Schols, S.; Heremans, P.

    2015-04-01

    Amorphous indium-gallium-zinc-oxide (a-IGZO) is demonstrated as an electron transport layer (ETL) in a high-performance organic photodetector (OPD). Dark current in the range of 10 nA/cm2 at a bias voltage of -2 V and a high photoresponse in the visible spectrum were obtained in inverted OPDs with poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester active layer. The best results were obtained for the optimum a-IGZO thickness of 7.5 nm with specific detectivity of 3 × 1012 Jones at the wavelength of 550 nm. The performance of the best OPD devices using a-IGZO was shown to be comparable to state-of-the-art devices based on TiOx as ETL, with higher rectification achieved in reverse bias. Yield and reproducibility were also enhanced with a-IGZO, facilitating fabrication of large area OPDs. Furthermore, easier integration with IGZO-based readout backplanes can be envisioned, where the channel material can be used as photodiode buffer layer after additional treatment.

  14. Amorphous indium-gallium-zinc-oxide as electron transport layer in organic photodetectors

    SciTech Connect

    Arora, H.; Malinowski, P. E. Chasin, A.; Cheyns, D.; Steudel, S.; Schols, S.; Heremans, P.

    2015-04-06

    Amorphous indium-gallium-zinc-oxide (a-IGZO) is demonstrated as an electron transport layer (ETL) in a high-performance organic photodetector (OPD). Dark current in the range of 10 nA/cm{sup 2} at a bias voltage of −2 V and a high photoresponse in the visible spectrum were obtained in inverted OPDs with poly(3-hexylthiophene) and phenyl-C{sub 61}-butyric acid methyl ester active layer. The best results were obtained for the optimum a-IGZO thickness of 7.5 nm with specific detectivity of 3 × 10{sup 12} Jones at the wavelength of 550 nm. The performance of the best OPD devices using a-IGZO was shown to be comparable to state-of-the-art devices based on TiO{sub x} as ETL, with higher rectification achieved in reverse bias. Yield and reproducibility were also enhanced with a-IGZO, facilitating fabrication of large area OPDs. Furthermore, easier integration with IGZO-based readout backplanes can be envisioned, where the channel material can be used as photodiode buffer layer after additional treatment.

  15. Front surface field formation for majority carriers by functional p-NiO layer employed Si solar cell

    NASA Astrophysics Data System (ADS)

    Patel, Dipal B.; Kim, Hong-Sik; Patel, Malkeshkumar; Chauhan, Khushbu R.; Park, Jeong Eun; Lim, Donggun; Kim, Joondong

    2016-09-01

    An optically transparent and electrically conductive p-NiO layer was deposited on a conventional n-Si/p-Si solar cell, which improved the device performance. The transmittance and reflectance properties of the p-NiO layer were found to be much better than the SiNx layer in the visible light region. Impedance spectroscopic study under varying bias and illumination conditions was carried out to understand the underlying mechanisms governing the device performance. An AC signal analysis revealed that the p-NiO layer acted as a front surface field region for majority charge carriers. In addition, the p-NiO layer significantly improved Si solar cell performances due to the improved properties of parasitic resistances. The optically transparent NiO layered Si device (p-NiO/n-Si/p-Si) spontaneously enhanced the electrical properties, resulting in the substantially improved fill factor value of 74% from 34.3% of the bare n-Si/p-Si device. The existence of a front surface field increased the lifetime of carriers to 92 μs for the p-NiO/n-Si/p-Si solar cell compared to only 43 μs for an n-Si/p-Si cell. We may suggest a functional NiO layer to the efficient designs for Si solar cells.

  16. Colloidal metal oxide nanocrystals as charge transporting layers for solution-processed light-emitting diodes and solar cells.

    PubMed

    Liang, Xiaoyong; Bai, Sai; Wang, Xin; Dai, Xingliang; Gao, Feng; Sun, Baoquan; Ning, Zhijun; Ye, Zhizhen; Jin, Yizheng

    2017-02-28

    Colloidal metal oxide nanocrystals offer a unique combination of excellent low-temperature solution processability, rich and tuneable optoelectronic properties and intrinsic stability, which makes them an ideal class of materials as charge transporting layers in solution-processed light-emitting diodes and solar cells. Developing new material chemistry and custom-tailoring processing and properties of charge transporting layers based on oxide nanocrystals hold the key to boosting the efficiency and lifetime of all-solution-processed light-emitting diodes and solar cells, and thereby realizing an unprecedented generation of high-performance, low-cost, large-area and flexible optoelectronic devices. This review aims to bridge two research fields, chemistry of colloidal oxide nanocrystals and interfacial engineering of optoelectronic devices, focusing on the relationship between chemistry of colloidal oxide nanocrystals, processing and properties of charge transporting layers and device performance. Synthetic chemistry of colloidal oxide nanocrystals, ligand chemistry that may be applied to colloidal oxide nanocrystals and chemistry associated with post-deposition treatments are discussed to highlight the ability of optimizing processing and optoelectronic properties of charge transporting layers. Selected examples of solution-processed solar cells and light-emitting diodes with oxide-nanocrystal charge transporting layers are examined. The emphasis is placed on the correlation between the properties of oxide-nanocrystal charge transporting layers and device performance. Finally, three major challenges that need to be addressed in the future are outlined. We anticipate that this review will spur new material design and simulate new chemistry for colloidal oxide nanocrystals, leading to charge transporting layers and solution-processed optoelectronic devices beyond the state-of-the-art.

  17. Ion transport through a charged cylindrical membrane pore contacting stagnant diffusion layers

    NASA Astrophysics Data System (ADS)

    Andersen, Mathias B.; Biesheuvel, P. M.; Bazant, Martin Z.; Mani, Ali

    2012-11-01

    Fundamental understanding of the ion transport in membrane systems by diffusion, electromigration and advection is important in widespread processes such as de-ionization by reverse osmosis and electrodialysis and electro-osmotic micropumps. Here we revisit the classical analysis of a single cylindrical pore, see e.g. Gross and Osterle [J Chem Phys 49, 228 (1968)]. We extend the analysis by including the well-established concept of contacting stagnant diffusion layers on either side of the pore; thus, the pore is not in direct equilibrium with the reservoirs. Inside the pore the ions are assumed to be in quasi-equilibrium in the radial direction with the surface charge on the pore wall and we obtain a 1D model by area-averaging. We demonstrate that in some extreme limits this model reduces to simpler models studied in the literature; see e.g. Yaroshchuk [J Membrane Sci 396, 43 (2012)]. Using our model we present predictions of important transport effects such as variation of transport numbers inside the membrane, onset of limiting current, and transient dynamics described by the method of characteristics.

  18. The impact of thermal conductivity and diffusion rates on water vapor transport through gas diffusion layers

    NASA Astrophysics Data System (ADS)

    Burlatsky, Sergei F.; Atrazhev, Vadim V.; Gummalla, Mallika; Condit, Dave A.; Liu, Fuqiang

    Proper water management in a hydrogen-fueled polymer electrolyte membrane (PEM) fuel cell is critical for performance and durability. A mathematical model has been developed to elucidate the effect of thermal conductivity and water vapor diffusion coefficient in the gas diffusion layers (GDLs). The fraction of product water removed in the vapor phase through the GDL as a function of GDL properties/set of material and component parameters and operating conditions has been calculated. The current model enables identification of conditions wherein condensation occurs in each GDL component. The model predicts the temperature gradient across various components of a PEM fuel cell, providing insight into the overall mechanism of water transport in a given cell design. The water condensation conditions and transport mode in the GDL components depend on the combination of water vapor diffusion coefficients and thermal conductivities of the GDL components. Different types of GDLs and water transport scenarios are defined in this work, based on water condensation in the GDL and fraction of water that the GDL removes through the vapor phase, respectively.

  19. Block Copolymer-Tuned Fullerene Electron Transport Layer Enhances the Efficiency of Perovskite Photovoltaics.

    PubMed

    Lin, Hsi-Kuei; Su, Yu-Wei; Chen, Hsiu-Cheng; Huang, Yi-Jiun; Wei, Kung-Hwa

    2016-09-21

    In this study, we enhanced the power conversion efficiency (PCE) of perovskite solar cells by employing an electron transfer layer (ETL) comprising [6,6]phenyl-C61-butyric acid methyl ester (PC61BM) and, to optimize its morphology, a small amount of the block copolymer polystyrene-b-poly(ethylene oxide) (PS-b-PEO), positioned on the perovskite active layer. When incorporating 0.375 wt % PS-b-PEO into PC61BM, the PCE of the perovskite photovoltaic device increased from 9.4% to 13.4%, a relative increase of 43%, because of a large enhancement in the fill factor of the device. To decipher the intricate morphology of the ETL, we used synchrotron grazing-incidence small-angle X-ray scattering for determining the PC61BM cluster size, atomic force microscopy and scanning electron microscopy for probing the surface, and transmission electron microscopy for observing the aggregation of PC61BM in the ETL. We found that the interaction between PS-b-PEO and PC61BM resulted in smaller PC61BM clusters that further aggregated into dendritic structures in some domains, a result of the similar polarities of the PS block and PC61BM; this behavior could be used to tune the morphology of the ETL. The optimal PS-b-PEO-mediated PC61BM cluster size in the ETL was 17 nm, a large reduction from 59 nm for the pristine PC61BM layer. This approach of incorporating a small amount of nanostructured block copolymer into a fullerene allowed us to effectively tune the morphology of the ETL on the perovskite active layer and resulted in enhanced fill factors of the devices and thus their device efficiency.

  20. Campylobacter fetus Surface Layer Proteins Are Transported by a Type I Secretion System

    PubMed Central

    Thompson, Stuart A.; Shedd, Omer L.; Ray, Kevin C.; Beins, Michael H.; Jorgensen, Jesse P.; Blaser, Martin J.

    1998-01-01

    The virulence of Campylobacter fetus, a bacterial pathogen of ungulates and humans, is mediated in part by the presence of a paracrystalline surface layer (S-layer) that confers serum resistance. The subunits of the S-layer are S-layer proteins (SLPs) that are secreted in the absence of an N-terminal signal sequence and attach to either type A or B C. fetus lipopolysaccharide in a serospecific manner. Antigenic variation of multiple SLPs (encoded by sapA homologs) of type A strain 23D occurs by inversion of a promoter-containing DNA element flanked by two sapA homologs. Cloning and sequencing of the entire 6.2-kb invertible region from C. fetus 23D revealed a probable 5.6-kb operon of four overlapping genes (sapCDEF, with sizes of 1,035, 1,752, 1,284, and 1,302 bp, respectively) transcribed in the opposite direction from sapA. The four genes also were present in the invertible region of type B strain 84-107 and were virtually identical to their counterparts in the type A strain. Although SapC had no database homologies, SapD, SapE, and SapF had predicted amino acid homologies with type I protein secretion systems (typified by Escherichia coli HlyBD/TolC or Erwinia chrysanthemi PrtDEF) that utilize C-terminal secretion signals to mediate the secretion of hemolysins, leukotoxins, or proteases from other bacterial species. Analysis of the C termini of four C. fetus SLPs revealed conserved structures that are potential secretion signals. A C. fetus sapD mutant neither produced nor secreted SLPs. E. coli expressing C. fetus sapA and sapCDEF secreted SapA, indicating that the sapCDEF genes are sufficient for SLP secretion. C. fetus SLPs therefore are transported to the cell surface by a type I secretion system. PMID:9851986

  1. Structural, optical, and electrical-transport properties of Al-P-O inorganic layer coated on flexible stainless steel substrate

    NASA Astrophysics Data System (ADS)

    Kim, Moojin; Min, Jinhyuk; Kwak, Yongsu; Kim, Doori; Kim, Kyoung-Bo; Song, Jonghyun

    2017-03-01

    We coated inorganic layer containing oxygen, aluminium, phosphorus, and negligible sodium (APO) on stainless steel (STS) by using slot-die coating method and studied its application prospects as a substrate for flexible devices. The APO layer was compositionally uniform in overall area with an amorphous crystal structure. Surface morphology characterization of STS exhibited an improved flatness after the APO layer coating process. The optical property characterization of the APO film carried out by measuring optical reflectance spectrum and refractive index. We also investigated the electrical-transport mechanism in the APO layer. These experimental observations imply the possibility of potential application of APO-STS as a substrate for flexible devices.

  2. Large-eddy transport in the surface layer over heterogeneous terrain

    NASA Astrophysics Data System (ADS)

    Mauder, M.; Eder, F.; De Roo, F.; Brugger, P.; Schmid, H. P. E.; Rotenberg, E.; Yakir, D.

    2015-12-01

    Surface heterogeneity and complex terrain invalidate to a certain extent basic assumptions behind the classical turbulence theory. One important classical concept is Townsend's hypothesis, which postulates that outer layer scale and inner layer scale turbulence do not interact. However, there is little knowledge to what extent large-scale eddies can affect near-surface fluxes. We shall investigate the relevance of large-eddy transport in the surface layer by an integrated approach combining field measurements and numerical simulations. Doppler lidar and tower-based turbulence measurements were conducted at the Yatir forest in Israel, which is surrounded by semi-arid shrubland. Vertical profiles of vertical and horizontal wind speed and direction were determined from Doppler lidar data. Eddy-covariance measurements were conducted at two sites. In addition, idealized large-eddy simulations (LES) were performed. A virtual control volume method allowed us to disentangle all components of the total surface flux. The daytime sensible heat flux over the forest was almost twice as large as over the surrounding shrubland. These very large differences in surface heating generated a secondary circulation, which was detected by the Doppler lidar measurements. Persistent updrafts were detected above the forest. Tower measurements at the shrubland site showed generally larger low-frequency contributions in spectra and co-spectra, and the energy balance ratio over the forest was 1.00, while it was only 0.81 at the shrubland site. LES results indicate that advection is the main cause for the lack of energy balance closure at the shrubland site. Over the forest, an equally large advective flux (in the opposite direction as over the shrubland) is almost completely balanced by horizontal flux divergence. We conclude that secondary circulations indeed exist over the Yatir forest, and that they can be detected from Doppler lidar data. Against the prediction of Townsend's hypothesis

  3. Synthesis of transport layers with controlled anisotropy and application thereof to study proton exchange membrane fuel cell performance

    NASA Astrophysics Data System (ADS)

    Todd, Devin; Mérida, Walter

    2016-04-01

    We report on a novel method for the synthesis of fibre-based proton exchange membrane (PEM) fuel cell porous transport layers (PTLs) with controllable fibre alignment. We also report the first application of such layers as diagnostics tools to probe the effect of within-plane PTL anisotropy upon PEM fuel cell performance. These structures are realized via adaptation of electrospinning technology. Electrospun layers with progressive anisotropy magnitude are produced and evaluated. This novel approach is distinguished from the state-of-the-art because an equivalent study using commercially available materials is impossible due to lack of structurally similar substrates with different anisotropies. The anisotropy is visualized via scanning electron microscopy, and quantified using electrical resistivity. The capacity is demonstrated to achieve fibre alignment, and the associated impact on transport properties. A framework is presented for assessing the in-situ performance, whereby transport layer orientation versus bipolar plate flow-field geometry is manipulated. While an effect upon the commercial baseline cannot be discerned, electrospun transport layers with greater anisotropy magnitude suggest greater sensitivity to orientation; where greater performance is obtained with fibres cross-aligned to flow-field channels. Our approach of electrospun transport enables deterministic structures by which fuel cell performance can be explained and optimized.

  4. High-Performance Regular Perovskite Solar Cells Employing Low-Cost Poly(ethylenedioxythiophene) as a Hole-Transporting Material.

    PubMed

    Jiang, Xiaoqing; Yu, Ze; Zhang, Yuchen; Lai, Jianbo; Li, Jiajia; Gurzadyan, Gagik G; Yang, Xichuan; Sun, Licheng

    2017-02-13

    Herein, we successfully applied a facile in-situ solid-state synthesis of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) as a HTM, directly on top of the perovskite layer, in conventional mesoscopic perovskite solar cells (PSCs) (n-i-p structure). The fabrication of the PEDOT film only involved a very simple in-situ solid-state polymerisation step from a monomer 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) made from a commercially available and cheap starting material. The ultraviolet photoelectron spectroscopy (UPS) demonstrated that the as-prepared PEDOT film possesses the highest occupied molecular orbital (HOMO) energy level of -5.5 eV, which facilitates an effective hole extraction from the perovskite absorber as confirmed by the photoluminescence measurements. Optimised PSC devices employing this polymeric HTM in combination with a low-cost vacuum-free carbon cathode (replacing the gold), show an excellent power conversion efficiency (PCE) of 17.0% measured at 100 mW cm(-2) illumination (AM 1.5G), with an open-circuit voltage (Voc) of 1.05 V, a short-circuit current density (Jsc) of 23.5 mA/cm(2) and a fill factor (FF) of 0.69, respectively. The present finding highlights the potential application of PEDOT made from solid-state polymerisation as a HTM for cost-effective and highly efficient PSCs.

  5. High-Performance Regular Perovskite Solar Cells Employing Low-Cost Poly(ethylenedioxythiophene) as a Hole-Transporting Material

    NASA Astrophysics Data System (ADS)

    Jiang, Xiaoqing; Yu, Ze; Zhang, Yuchen; Lai, Jianbo; Li, Jiajia; Gurzadyan, Gagik G.; Yang, Xichuan; Sun, Licheng

    2017-02-01

    Herein, we successfully applied a facile in-situ solid-state synthesis of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) as a HTM, directly on top of the perovskite layer, in conventional mesoscopic perovskite solar cells (PSCs) (n-i-p structure). The fabrication of the PEDOT film only involved a very simple in-situ solid-state polymerisation step from a monomer 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) made from a commercially available and cheap starting material. The ultraviolet photoelectron spectroscopy (UPS) demonstrated that the as-prepared PEDOT film possesses the highest occupied molecular orbital (HOMO) energy level of ‑5.5 eV, which facilitates an effective hole extraction from the perovskite absorber as confirmed by the photoluminescence measurements. Optimised PSC devices employing this polymeric HTM in combination with a low-cost vacuum-free carbon cathode (replacing the gold), show an excellent power conversion efficiency (PCE) of 17.0% measured at 100 mW cm‑2 illumination (AM 1.5G), with an open-circuit voltage (Voc) of 1.05 V, a short-circuit current density (Jsc) of 23.5 mA/cm2 and a fill factor (FF) of 0.69, respectively. The present finding highlights the potential application of PEDOT made from solid-state polymerisation as a HTM for cost-effective and highly efficient PSCs.

  6. High-Performance Regular Perovskite Solar Cells Employing Low-Cost Poly(ethylenedioxythiophene) as a Hole-Transporting Material

    PubMed Central

    Jiang, Xiaoqing; Yu, Ze; Zhang, Yuchen; Lai, Jianbo; Li, Jiajia; Gurzadyan, Gagik G.; Yang, Xichuan; Sun, Licheng

    2017-01-01

    Herein, we successfully applied a facile in-situ solid-state synthesis of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) as a HTM, directly on top of the perovskite layer, in conventional mesoscopic perovskite solar cells (PSCs) (n-i-p structure). The fabrication of the PEDOT film only involved a very simple in-situ solid-state polymerisation step from a monomer 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) made from a commercially available and cheap starting material. The ultraviolet photoelectron spectroscopy (UPS) demonstrated that the as-prepared PEDOT film possesses the highest occupied molecular orbital (HOMO) energy level of −5.5 eV, which facilitates an effective hole extraction from the perovskite absorber as confirmed by the photoluminescence measurements. Optimised PSC devices employing this polymeric HTM in combination with a low-cost vacuum-free carbon cathode (replacing the gold), show an excellent power conversion efficiency (PCE) of 17.0% measured at 100 mW cm−2 illumination (AM 1.5G), with an open-circuit voltage (Voc) of 1.05 V, a short-circuit current density (Jsc) of 23.5 mA/cm2 and a fill factor (FF) of 0.69, respectively. The present finding highlights the potential application of PEDOT made from solid-state polymerisation as a HTM for cost-effective and highly efficient PSCs. PMID:28211919

  7. Graphene oxide hole transport layers for large area, high efficiency organic solar cells

    SciTech Connect

    Smith, Chris T. G.; Rhodes, Rhys W.; Beliatis, Michail J.; Imalka Jayawardena, K. D. G.; Rozanski, Lynn J.; Mills, Christopher A.; Silva, S. Ravi P.

    2014-08-18

    Graphene oxide (GO) is becoming increasingly popular for organic electronic applications. We present large active area (0.64 cm{sup 2}), solution processable, poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1, 3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]:[6,6]-Phenyl C{sub 71} butyric acid methyl ester (PCDTBT:PC{sub 70}BM) organic photovoltaic (OPV) solar cells, incorporating GO hole transport layers (HTL). The power conversion efficiency (PCE) of ∼5% is the highest reported for OPV using this architecture. A comparative study of solution-processable devices has been undertaken to benchmark GO OPV performance with poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) HTL devices, confirming the viability of GO devices, with comparable PCEs, suitable as high chemical and thermal stability replacements for PEDOT:PSS in OPV.

  8. Understanding the Role of the Electron-Transport Layer in Highly Efficient Planar Perovskite Solar Cells.

    PubMed

    Liu, Jiang; Wang, Gang; Luo, Kun; He, Xulin; Ye, Qinyan; Liao, Cheng; Mei, Jun

    2017-03-17

    Solar cells based on perovskite absorbers are rapidly emerging as attractive candidates for photovoltaics development. Understanding the role of the electron-transport layer (ETL) is very important to obtain highly efficient perovskite solar cells. Herein, the effect of the ETL on device performance in planar perovskite solar cells is investigated in detail, and the band bending in different situations is discussed. The ET barrier is shown to be responsible for the poor fill factor (FF) of J-V curves. Introduction of a thin bathocuproine interlayer increases the interface inversion and results in an increase of FF from 56 to 76 %. Some experimental and theoretical results verify these conclusions. Furthermore, this study can provide an interface-engineering strategy to improve device performance.

  9. Tungsten injector for scrape-off layer impurity transport experiments in the Tore Supra tokamak

    SciTech Connect

    Kočan, M.; Lunt, T.; Gunn, J. P.; Meyer, O.; Pascal, J.-Y.

    2013-07-15

    This paper describes the design and operation of a new tungsten (W) injection system for impurity transport experiments in the Tore Supra tokamak. The system is mounted on a reciprocating manipulator and injects a controlled amount of gaseous tungsten hexacarbonyl, W(CO){sub 6} at arbitrary depth in the scrape-off layer, using an inertially activated valve. Injected W(CO){sub 6} is dissociated in the plasma, forming a radially localized plume of W atoms. The injector does not require an external gas feed and can perform a large number of injections from an on-board reservoir of W(CO){sub 6}. Some examples of W injections in Tore Supra are included, demonstrating successful operation and discussing some technical issues of the injector prototype.

  10. Helium transport in the core and stochastic edge layer in LHD

    NASA Astrophysics Data System (ADS)

    Ida, K.; Yoshinuma, M.; Goto, M.; Schmitz, O.; Dai, S.; Bader, A.; Kobayashi, M.; Kawamura, G.; Moon, C.; Nakamura, Y.; The LHD Experiment Group

    2016-07-01

    Radial profiles of the density ratio of helium to hydrogen ions are measured using charge exchange spectroscopy with a two-wavelength spectrometer in the large helical device. Helium transport at the last closed flux surface (LCFS) and stochastic magnetic field layer outside the LCFS as well as in the core plasma is studied for a wide range of helium fractions, i.e. from hydrogen-dominated plasmas up to helium-dominated plasmas. The helium density profile becomes more peaked and inward convection velocity increases in the hydrogen-dominant plasma, while it becomes flat or hollow and the convection velocity is in the outward direction in the helium-dominant plasmas. The density gradient of helium at the LCFS is twice that of hydrogen and becomes steeper as the hydrogen becomes more dominant.

  11. Copper thiocyanate: An attractive hole transport/extraction layer for use in organic photovoltaic cells

    SciTech Connect

    Treat, Neil D. E-mail: t.anthopoulos@imperial.ac.uk; Stingelin, Natalie; Yaacobi-Gross, Nir; Faber, Hendrik; Perumal, Ajay K.; Bradley, Donal D. C.; Anthopoulos, Thomas D. E-mail: t.anthopoulos@imperial.ac.uk

    2015-07-06

    We report the advantageous properties of the inorganic molecular semiconductor copper(I) thiocyanate (CuSCN) for use as a hole collection/transport layer (HTL) in organic photovoltaic (OPV) cells. CuSCN possesses desirable HTL energy levels [i.e., valence band at −5.35 eV, 0.35 eV deeper than poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS)], which produces a 17% increase in power conversion efficiency (PCE) relative to PEDOT:PSS-based devices. In addition, a two-fold increase in shunt resistance for the solar cells measured in dark conditions is achieved. Ultimately, CuSCN enables polymer:fullerene based OPV cells to achieve PCE > 8%. CuSCN continues to offer promise as a chemically stable and straightforward replacement for the commonly used PEDOT:PSS.

  12. Effect of collisional temperature isotropisation on ELM parallel transport in a tokamak scrape-off layer

    NASA Astrophysics Data System (ADS)

    Coulette, David; Hirstoaga, Sever A.; Manfredi, Giovanni

    2016-08-01

    We develop a hybrid model to describe the parallel transport in a tokamak scrape-off layer following an edge-localized mode (ELM) event. The parallel dynamics is treated with a kinetic Vlasov-Poisson model, while the evolution of the perpendicular temperature {{T}\\bot} is governed by a fluid equation. The coupling is ensured by isotropising collisions. The model generalises an earlier approach where {{T}\\bot} was constant in space and time (Manfredi et al 2011 Plasma Phys. Control. Fusion 53 015012). Numerical results show that the main effect comes from electron-electron collisions, which limit the decrease of the parallel electron temperature and increase the potential drop in the Debye sheath in front of the surface. Ion-ion collisions have an almost negligible impact. The net effect is an increased peak power load on the target plates.

  13. Transport of desert dust mixed with North African industrial pollutants in the subtropical Saharan Air Layer

    NASA Astrophysics Data System (ADS)

    Rodríguez, S.; Alastuey, A.; Alonso-Pérez, S.; Querol, X.; Cuevas, E.; Abreu-Afonso, J.; Viana, M.; Pérez, N.; Pandolfi, M.; de La Rosa, J.

    2011-07-01

    An analysis of chemical composition data of particulate matter samples (TSP, PM10 and PM2.5) collected from 2002 to 2008 in the North Atlantic free troposphere at the Izaña Global Atmospheric Watch (GAW) observatory (Tenerife, Canary Islands) shows that desert dust is very frequently mixed with particulate pollutants in the Saharan Air Layer (SAL). The study of this data set with Median Concentrations At Receptor (MCAR) plots allowed the identification of the potential source regions of the dust and particulate pollutants. Areas located at the south of the southern slope of the Atlas mountains emerge as the most frequent source of the soil desert dust advected to the northern edge of the SAL in summer. Industrial emissions occurring in Northern Algeria, Eastern Algeria, Tunisia and the Atlantic coast of Morocco appear as the most important source of the nitrate, ammonium and a fraction of sulphate (at least 60 % of the sulphate <10 μm transported from some regions) observed in the SAL. These emissions are mostly linked to crude oil refineries, phosphate-based fertilizer industry and power plants. Although desert dust emissions appear as the most frequent source of the phosphorous observed in the SAL, high P concentrations are observed when the SAL is affected by emissions from open mines of phosphate and phosphate based fertilizer industry. The results also show that a significant fraction of the sulphate (up to 90 % of sulphate <10 μm transported from some regions) observed in the SAL may be influenced by soil emissions of evaporite minerals in well defined regions where dry saline lakes (chotts) are present. These interpretations of the MCAR plots are consistent with the results obtained with the Positive Matrix Factorization (PMF2) receptor modelling. The results of this study show that North African industrial pollutants may be mixed with desert dust and exported to the North Atlantic in the Saharan Air Layer.

  14. Transport of desert dust mixed with North African industrial pollutants in the subtropical Saharan Air Layer

    NASA Astrophysics Data System (ADS)

    Rodríguez, S.; Alastuey, A.; Alonso-Pérez, S.; Querol, X.; Cuevas, E.; Abreu-Afonso, J.; Viana, M.; Pandolfi, M.; de La Rosa, J.

    2011-03-01

    The chemical composition of particulate matter samples (TSP, PM10 and PM2.5) collected from 2002 to 2008 in the North Atlantic free troposphere at Izaña Global Atmospheric Watch (GAW) observatory (Tenerife, The Canary Islands) was studied. The analysis of the samples collected in the Saharan Air Layer (SAL) shows that soil desert dust is very frequently mixed with particulate pollutants. An analysis of this data set with Median Concentrations At Receptor (MCAR) plots allowed to identify the potential source regions of the dust and particulate pollutants. Areas located at the south of the Southern slope of Atlas emerge as the most frequent source of the soil desert dust advected to the northern edge of the SAL in summer. Industrial emissions occurring along the Atlantic coast of Morocco, Northern Algeria, Eastern Algeria and Tunisia appear as the most important source of the nitrate, ammonium and a fraction of sulphate (at least a 60% of the sulphate <10 μm transported from some regions) observed in the SAL. These emissions are mostly linked to crude oil refineries, phosphate-based fertilizer industry and power plants. Although desert dust emissions appear as the most frequent source of the phosphorous observed in the SAL, high P concentrations are observed when the SAL is affected by emissions from open mines of phosphate and phosphate based fertilizer industry. The results also show that a significant fraction of the sulphate (up to 90% of sulphate <10 μm transported from some regions) observed in the SAL is linked to soil emissions of evaporite minerals in well defined regions where dry saline lakes (chotts) are present. These interpretations of the MCAR plots are consistent with the results obtained with the Positive Matrix Factorization receptor modelling. The results of this study show that North African industrial pollutants may be mixed with desert dust and exported to the North Atlantic in the Saharan Air Layer.

  15. Parameterizing Urban Canopy Layer transport in an Lagrangian Particle Dispersion Model

    NASA Astrophysics Data System (ADS)

    Stöckl, Stefan; Rotach, Mathias W.

    2016-04-01

    The percentage of people living in urban areas is rising worldwide, crossed 50% in 2007 and is even higher in developed countries. High population density and numerous sources of air pollution in close proximity can lead to health issues. Therefore it is important to understand the nature of urban pollutant dispersion. In the last decades this field has experienced considerable progress, however the influence of large roughness elements is complex and has as of yet not been completely described. Hence, this work studied urban particle dispersion close to source and ground. It used an existing, steady state, three-dimensional Lagrangian particle dispersion model, which includes Roughness Sublayer parameterizations of turbulence and flow. The model is valid for convective and neutral to stable conditions and uses the kernel method for concentration calculation. As most Lagrangian models, its lower boundary is the zero-plane displacement, which means that roughly the lower two-thirds of the mean building height are not included in the model. This missing layer roughly coincides with the Urban Canopy Layer. An earlier work "traps" particles hitting the lower model boundary for a recirculation period, which is calculated under the assumption of a vortex in skimming flow, before "releasing" them again. The authors hypothesize that improving the lower boundary condition by including Urban Canopy Layer transport could improve model predictions. This was tested herein by not only trapping the particles, but also advecting them with a mean, parameterized flow in the Urban Canopy Layer. Now the model calculates the trapping period based on either recirculation due to vortex motion in skimming flow regimes or vertical velocity if no vortex forms, depending on incidence angle of the wind on a randomly chosen street canyon. The influence of this modification, as well as the model's sensitivity to parameterization constants, was investigated. To reach this goal, the model was

  16. Transport of chemical tracers from the boundary layer to stratosphere associated with the dynamics of the Asian summer monsoon

    NASA Astrophysics Data System (ADS)

    Pan, Laura L.; Honomichl, Shawn B.; Kinnison, Douglas E.; Abalos, Marta; Randel, William J.; Bergman, John W.; Bian, Jianchun

    2016-12-01

    Chemical transport associated with the dynamics of the Asian summer monsoon (ASM) system is investigated using model output from the National Center for Atmospheric Research (NCAR) Whole Atmosphere Community Climate Model run in specified dynamics mode. The 3-D day-to-day behavior of modeled carbon monoxide is analyzed together with dynamical fields and transport boundaries to identify preferred locations of uplifting from the boundary layer, the role of subseasonal-scale dynamics in the upper troposphere and lower stratosphere (UTLS), and the relationship of ASM transport and the stratospheric residual circulation. The model simulation of CO shows the intraseasonal east-west oscillation of the anticyclone may play an essential role in transporting convectively pumped boundary layer pollutants in the UTLS. A statistical analysis of 11 year CO also shows that the southern flank of the Tibetan plateau is a preferred location for boundary layer tracers to be lofted to the tropopause region. The vertical structure of a model tracer (E90) further shows that the rapid ASM vertical transport is only effective up to the tropopause level (around 400 K). The efficiency of continued vertical transport into the deep stratosphere is limited by the slow ascent associated with the zonal-mean residual circulation in the lower stratosphere during northern summer. Quasi-isentropic transport near the 400 K potential temperature level is likely the most effective process for ASM anticyclone air to enter the stratosphere.

  17. Highly efficient electroluminescence from a heterostructure device combined with emissive layered-perovskite and an electron-transporting organic compound

    NASA Astrophysics Data System (ADS)

    Hattori, Toshiaki; Taira, Takahiro; Era, Masanao; Tsutsui, Tetsuo; Saito, Shugu

    1996-05-01

    Two Pbl-based layer perovskite compounds, which possess cyclohexenylethylamine or phenylbutylamine as an organic ammonium layer, were newly found to exhibit efficient exciton emission due to their self-organized quantum well structure where a lead halide semiconducting layer and an organic ammonium dielectric layer are alternately piled up. We prepared heterostructure electroluminescent devices using the combination of the emissive layered perovskite and an electron-transporting oxadiazole. When the heterostructure devices were driven at 110 K, greenish emission, which corresponded well to the exciton emission, was observed. In the device using the perovskite with an organic layer of cyclohexenythylamine, a high luminance exceeding 4000 cd m -2 and high external EL quantum efficiency of 2.8% were attained at a current density of 50 mA cm -2 at an applied voltage of 24 V.

  18. Substrate-Electrode Interface Engineering by an Electron-Transport Layer in Hematite Photoanode.

    PubMed

    Ding, Chunmei; Wang, Zhiliang; Shi, Jingying; Yao, Tingting; Li, Ailong; Yan, Pengli; Huang, Baokun; Li, Can

    2016-03-23

    The photoelectrochemical water oxidation efficiency of photoanodes is largely limited by interfacial charge-transfer processes. Herein, a metal oxide electron-transport layer (ETL) was introduced at the substrate-electrode interface. Hematite photoanodes prepared on Li(+)- or WO3-modified substrates deliver higher photocurrent. It is inferred that a Li-doped Fe2O3 (Li:Fe2O3) layer with lower flat band potential than the bulk is formed. Li:Fe2O3 and WO3 are proved to function as an expressway for electron extraction. Via introducing ETL, both the charge separation and injection efficiencies are improved. The lifetime of photogenerated electrons is prolonged by 3 times, and the ratio of surface charge transfer and recombination rate is enhanced by 5 times with Li:Fe2O3 and 125 times with WO3 ETL at 1.23 V versus reversible hydrogen electrode. This result indicates the expedited electron extraction from photoanode to the substrate can suppress not only the recombination at the back contact interface but also those at the surface, which results in higher water oxidation efficiency.

  19. A simple stochastic quadrant model for the transport and deposition of particles in turbulent boundary layers

    SciTech Connect

    Jin, C.; Potts, I.; Reeks, M. W.

    2015-05-15

    We present a simple stochastic quadrant model for calculating the transport and deposition of heavy particles in a fully developed turbulent boundary layer based on the statistics of wall-normal fluid velocity fluctuations obtained from a fully developed channel flow. Individual particles are tracked through the boundary layer via their interactions with a succession of random eddies found in each of the quadrants of the fluid Reynolds shear stress domain in a homogeneous Markov chain process. In this way, we are able to account directly for the influence of ejection and sweeping events as others have done but without resorting to the use of adjustable parameters. Deposition rate predictions for a wide range of heavy particles predicted by the model compare well with benchmark experimental measurements. In addition, deposition rates are compared with those obtained from continuous random walk models and Langevin equation based ejection and sweep models which noticeably give significantly lower deposition rates. Various statistics related to the particle near wall behavior are also presented. Finally, we consider the model limitations in using the model to calculate deposition in more complex flows where the near wall turbulence may be significantly different.

  20. Statistics of fluctuation induced transport in the scrape-off layer of Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Kube, Ralph; Garcia, Odd Erik; Theodorsen, Audun; Labombard, Brian; Terry, James

    2016-10-01

    The fluctuation induced transport in the scrape-off layer of Alcator C-Mod is investigated in an ohmically heated lower single-null discharge using Mirror Langmuir Probes. The probes are connected to a horizontal scanning probe which dwells at the outboard mid plane limiter radius and to electrodes in the outer divertor baffle. At the limiter radius the electron density, electron temperature and plasma potential are correlated with linear correlation coefficients r of approximately r=0.8. The bursts show a steep rise and a decay on a time scales of approximately 5 and 10 microseconds respectively. Amplitudes of bursts in the density, temperature, and plasma potential time series are correlated with r approximately 0.7-0.8. Conditionally averaged bursts in the radial particle and heat flux time series are less coherent and less reproducible, their amplitudes are correlated to the amplitude of bursts in the density time series with r=0.4. Statistics of the fluctuating plasma parameters at the outer divertor baffle are qualitatively similar to those at outboard midplane. Histograms, as well as statistics for level crossings and excess times spent above a given threshold for the time series compare favorably to a stochastic model for time series of scrape-off layer plasmas.

  1. Study of effective transport properties of fresh and aged gas diffusion layers

    NASA Astrophysics Data System (ADS)

    Bosomoiu, Magdalena; Tsotridis, Georgios; Bednarek, Tomasz

    2015-07-01

    Gas diffusion layers (GDLs) play an important role in proton exchange membrane fuel cells (PEMFCs) for the diffusion of reactant and the removal of product water. In the current study fresh and aged GDLs (Sigracet® GDL34BC) were investigated by X-ray computed tomography to obtain a representative 3D image of the real GDL structure. The examined GDL samples are taken from areas located under the flow channel and under the land. Additionally, a brand new Sigracet® GDL34BC was taken as a reference sample in order to find out the impact of fuel cell assembly on GDL. The produced 3D image data were used to calculate effective transport properties such as thermal and electrical conductivity, diffusivity, permeability and capillary pressure curves of the dry and partially saturated GDL. The simulation indicates flooding by product water occurs at contact angles lower than 125° depending on sample porosity. In addition, GDL anisotropy significantly affects the permeability as well as thermal and electrical conductivities. The calculated material bulk properties could be next used as input for CFD modelling of PEM fuel cells where GDL is usually assumed layer-like and homogeneous. Tensor material parameters allow to consider GDL anisotropy and lead to more realistic results.

  2. Ozone Transport and Mixing Processes in the Boundary Layer Observed with Lidar during Discover-AQ

    NASA Astrophysics Data System (ADS)

    Senff, C. J.; Langford, A. O.; Alvarez, R. J. _II, II; Choukulkar, A.; Brewer, A.; Weickmann, A. M.; Kirgis, G.; Sandberg, S.; Hardesty, M.; Delgado, R.; Long, R.; Brown, S. S.

    2014-12-01

    The final two Discover-AQ air quality studies were conducted in Houston, TX in September 2013 and the Colorado Front Range in July/August 2014. These two regions are characterized by different ozone precursor sources and exhibit unique regional wind flow patterns. During these studies, NOAA deployed its truck-based, scanning TOPAZ ozone lidar to document the vertical structure and temporal evolution of ozone concentrations from near the surface up to about 2.5 km above ground level. In Houston, TOPAZ was located next to a radar wind profiler while during the Colorado campaign, Doppler wind lidars collocated with TOPAZ measured wind profiles and vertical velocity statistics throughout the boundary layer (BL). For both studies, nearby in situ sensors provided continuous observations of surface ozone and NOx. These combinations of remote and in situ sensors lend themselves to study the influence of BL transport and mixing processes on surface-level ozone. In this presentation, we focus on characterizing and quantifying changes in surface ozone due to several BL processes, including the Houston land-sea breeze circulation, the terrain-driven BL flow in the Colorado Front Range area, thunderstorm outflows, BL growth rate and depth, and entrainment of air from the residual layer or lower free troposphere into the BL.

  3. Ultraviolet-enhanced light emitting diode employing individual ZnO microwire with SiO{sub 2} barrier layers

    SciTech Connect

    Xu, Yingtian; Xu, Li; Dai, Jun; Ma, Yan; Chu, Xianwei; Zhang, Yuantao; Du, Guotong; Zhang, Baolin; Yin, Jingzhi

    2015-05-25

    This paper details the fabrication of n-ZnO single microwire (SMW)-based high-purity ultraviolet light-emitting diodes (UV-LEDs) with an added SiO{sub 2} barrier layer on the p-Si substrate. However, the current-voltage (I-V) curve exhibited non-ideal rectifying characteristics. Under forward bias, both UV and visible emissions could be detected by electroluminescence (EL) measurement. When bias voltage reached 60 V at room temperature, a UV emission spike occurred at 390 nm originating from the n-ZnO SMW. Compared with the EL spectrum of the n-ZnO SMW/p-Si heterojunction device without the SiO{sub 2} barrier layer, we saw improved UV light extraction efficiency from the current-blocking effect of the SiO{sub 2} layer. The intense UV emission in the n-ZnO SMW/SiO{sub 2}/p-Si heterojunction indicated that the SiO{sub 2} barrier layer can restrict the movement of electrons as expected and result in effective electron-hole recombination in ZnO SMW.

  4. Molecular self ordering and charge transport in layer by layer deposited poly (3,3‴-dialkylquarterthiophene) films formed by Langmuir-Schaefer technique

    SciTech Connect

    Pandey, Rajiv K.; Singh, Arun Kumar; Upadhyay, C.; Prakash, Rajiv

    2014-09-07

    The performance of π-conjugated polymer based electronic devices is directly governed by the molecular morphology of polymer aggregation, the extent to which a molecule is electronically coupled (self ordered and interacted) to neighboring molecules, and orientation. The well electronic coupled and crystalline/ordered polymer films have the potential to enhance the charge transport properties up to a benchmark. However, there is insufficient knowledge about the direct formation of large area, oriented, crystalline, and smooth films. In this study, we have presented Langmuir Schaefer technique to obtain the large area, oriented, crystalline, and smooth film of Poly (3,3‴-dialkylquarterthiophene) (PQT-12) polymer. The effect of self ordering and orientation of PQT-12 polymer on optical, morphological, and charge transport properties has been investigated. The prepared films have been characterized by UV-vis spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM), selected area diffractions pattern (SAED), and atomic force microscopy (AFM) techniques. UV-vis spectra, TEM, SAED, and AFM images of monolayer films reveal the formation of well ordered and electronically coupled polymer domains. Layer by layer deposited films reveal the change in the orientation, which is confirmed by Raman spectra. Electronic properties and layer dependent charge transport properties are investigated using sandwiched structure Al/PQT-12/ITO Schottky configuration with perpendicular to the deposited films. It is observed that the charge transport properties and device electronic parameters (ideality factor and turn on voltage) are significantly changing with increasing the number of PQT-12 layers. Our study also demonstrates the charge transport between polymer crystallites and cause of deviation of ideal behavior of organic Schottky diodes. It may be further explored for improving the performance of other organic and optoelectronic devices.

  5. Layering Networked and Symphonic Selves: A Critical Role for e-Portfolios in Employability through Integrative Learning

    ERIC Educational Resources Information Center

    Cambridge, Darren

    2008-01-01

    Purpose: E-portfolios, which document and facilitate learning and performance, have recently attracted interest in the USA, UK, and Europe as means to increase employability and support lifelong learning. This article aims to critically examine these objectives in order to guide the future e-portfolio practice. Design/methodology/approach: Social…

  6. Flow and suspended particulate transport in a tidal bottom layer, south San Francisco Bay, California

    USGS Publications Warehouse

    Cheng, R.T.; Gartner, J.W.; Cacchione, D.A.; Tate, G.B.

    1998-01-01

    Field investigations of the hydrodynamics and the resuspension and transport of particulate matter in a bottom boundary layer were carried out in South San Francisco Bay, California during March-April 1995. The GEOPROBE, an instrumented bottom tripod, and broad-band acousti Doppler current profilers were used in this investigation. The instrument assemblage provided detailed measurements of 1) turbulent mean velocity distribution within 1.5 m of sediment-w interface; 2) characteristics of 3-D tidal current in the water column; 3) friction velocity u* or bottom shear stress and bottom roughness length zo; 4) hydrodynamic conditions conducive for s resuspension; and 5) circulation patterns which are responsible for transporting suspended particulate matter in South San Francisco Bay. An unusual flow event was recorded by the instruments during March 8-11, 1995. A 3-D numerical model was implemented which re qualitatively, the unusual observations and supported the hypothesis that the unusual flow event caused by a combination of wind driven circulation and weak neap tides.

  7. Turbulent transport regimes and the scrape-off layer heat flux width

    SciTech Connect

    Myra, J. R.; D'Ippolito, D. A.; Russell, D. A.

    2015-04-15

    Understanding the responsible mechanisms and resulting scaling of the scrape-off layer (SOL) heat flux width is important for predicting viable operating regimes in future tokamaks and for seeking possible mitigation schemes. In this paper, we present a qualitative and conceptual framework for understanding various regimes of edge/SOL turbulence and the role of turbulent transport as the mechanism for establishing the SOL heat flux width. Relevant considerations include the type and spectral characteristics of underlying instabilities, the location of the gradient drive relative to the SOL, the nonlinear saturation mechanism, and the parallel heat transport regime. We find a heat flux width scaling with major radius R that is generally positive, consistent with the previous findings [Connor et al., Nucl. Fusion 39, 169 (1999)]. The possible relationship of turbulence mechanisms to the neoclassical orbit width or heuristic drift mechanism in core energy confinement regimes known as low (L) mode and high (H) mode is considered, together with implications for the future experiments.

  8. Towards printed perovskite solar cells with cuprous oxide hole transporting layers: a theoretical design

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Xia, Zhonggao; Liang, Jun; Wang, Xinwei; Liu, Yiming; Liu, Chuan; Zhang, Shengdong; Zhou, Hang

    2015-05-01

    Solution-processed p-type metal oxide materials have shown great promise in improving the stability of perovskite-based solar cells and offering the feasibility for a low cost printing fabrication process. Herein, we performed a device modeling study on planar perovskite solar cells with cuprous oxide (Cu2O) hole transporting layers (HTLs) by using a solar cell simulation program, wxAMPS. The performance of a Cu2O/perovskite solar cell was correlated to the material properties of the Cu2O HTL, such as thickness, carrier mobility, mid-gap defect, and doping concentrations. The effect of interfacial defect densities on the solar cell performance was also investigated. Our simulation indicates that, with an optimized Cu2O HTL, high performance perovskite solar cells with efficiencies above 13% could be achieved, which shows the potential of using Cu2O as an alternative HTL over other inorganic materials, such as NiOx and MoOx. This study provides theoretical guidance for developing perovskite solar cells with inorganic hole transporting materials via a printing process.

  9. Solution-Processed Metal Oxides as Efficient Carrier Transport Layers for Organic Photovoltaics.

    PubMed

    Choy, Wallace C H; Zhang, Di

    2016-01-27

    Carrier (electron and hole) transport layers (CTLs) are essential components for boosting the performance of various organic optoelectronic devices such as organic solar cells and organic light-emitting diodes. Considering the drawbacks of conventional CTLs (easily oxidized/unstable, demanding/costly fabrication, etc.), transition metal oxides with good carrier transport/extraction and superior stability have drawn extensive research interest as CTLs for next-generation devices. In recent years, many research efforts have been made toward the development of solution-based metal oxide CTLs with the focus on low- or even room-temperature processes, which can potentially be compatible with the deposition processes of organic materials and can significantly contribute to the low-cost and scale-up of organic devices. Here, the recent progress of different types of solution-processed metal oxide CTLs are systematically reviewed in the context of organic photovoltaics, from synthesis approaches to device performance. Different approaches for further enhancing the performance of solution-based metal oxide CTLs are also discussed, which may push the future development of this exciting field.

  10. SPREADING LAYERS IN ACCRETING OBJECTS: ROLE OF ACOUSTIC WAVES FOR ANGULAR MOMENTUM TRANSPORT, MIXING, AND THERMODYNAMICS

    SciTech Connect

    Philippov, Alexander A.; Rafikov, Roman R.; Stone, James M.

    2016-01-20

    Disk accretion at a high rate onto a white dwarf (WD) or a neutron star has been suggested to result in the formation of a spreading layer (SL)—a belt-like structure on the object's surface, in which the accreted matter steadily spreads in the poleward (meridional) direction while spinning down. To assess its basic characteristics, we perform two-dimensional hydrodynamic simulations of supersonic SLs in the relevant morphology with a simple prescription for cooling. We demonstrate that supersonic shear naturally present at the base of the SL inevitably drives sonic instability that gives rise to large-scale acoustic modes governing the evolution of the SL. These modes dominate the transport of momentum and energy, which is intrinsically global and cannot be characterized via some form of local effective viscosity (e.g., α-viscosity). The global nature of the wave-driven transport should have important implications for triggering Type I X-ray bursts in low-mass X-ray binaries. The nonlinear evolution of waves into a system of shocks drives effective rearrangement (sensitively depending on thermodynamical properties of the flow) and deceleration of the SL, which ultimately becomes transonic and susceptible to regular Kelvin–Helmholtz instability. We interpret this evolution in terms of the global structure of the SL and suggest that mixing of the SL material with the underlying stellar fluid should become effective only at intermediate latitudes on the accreting object's surface, where the flow has decelerated appreciably. In the near-equatorial regions the transport is dominated by acoustic waves and mixing is less efficient. We speculate that this latitudinal nonuniformity of mixing in accreting WDs may be linked to the observed bipolar morphology of classical nova ejecta.

  11. Solution-processed 2D niobium diselenide nanosheets as efficient hole-transport layers in organic solar cells.

    PubMed

    Gu, Xing; Cui, Wei; Song, Tao; Liu, Changhai; Shi, Xiaoze; Wang, Suidong; Sun, Baoquan

    2014-02-01

    Thin-layer, two-dimensional NbSe2 nanosheets with lower trap density have been obtained and act as an alternative hole-transporting layer to replace MoO3 in organic solar cells. If poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}):[6,6]-phenyl-C71-butyric acid methyl ester acts as an active layer, a power conversion efficiency of 8.10 % has been achieved without any further thermal treatment. The properties of this hole-transporting layer were investigated and the improvements in the devices are discussed.

  12. The importance of subsurface nepheloid layers in transport and delivery of sediments to the eastern Cariaco Basin, Venezuela

    NASA Astrophysics Data System (ADS)

    Lorenzoni, Laura; Thunell, Robert C.; Benitez-Nelson, Claudia R.; Hollander, David; Martinez, Nahysa; Tappa, Eric; Varela, Ramón; Astor, Yrene; Muller-Karger, Frank E.

    2009-12-01

    Optical transmissometer measurements were coupled with particulate organic matter (POM) observations to understand suspended sediment composition and distribution in the eastern Cariaco Basin during the rainy seasons of September 2003 and 2006. Our results suggest that nepheloid layers originating at the mouth of small mountainous rivers discharging into the eastern Basin are a major delivery mechanism of terrigenous sediments to the Basin interior. Intermediate nepheloid layers (INL) were observed near the shelf break (˜100 m) and appear to effectively transport terrigenous material laterally from the shelf to deep waters, thereby providing a plausible supply mechanism of the terrestrial material observed in sediment traps. These findings highlight the importance of small, local rivers in the Cariaco Basin as sources of terrestrial material. In contrast, these nepheloid layers contained only limited POM. When this information is combined with published sediment trap POM data, it suggests that nepheloid layers may not be a primary mechanism for delivering terrigenous POM to the deeper waters of the basin during the rainy season. Rather, BNL may redistribute marine-derived POM from shallow waters to the Basin's interior by providing ballast materials, particularly during episodic events driven by wind and precipitation. Though we have determined that nepheloid layers play an important role in the seaward transport of particulate material in the Cariaco Basin, their composition and temporal variability have not been fully characterized. This is critical to understand lateral particle transport, since nepheloid layers constitute a significant source of sediment to the deep Cariaco Basin.

  13. Numerical modeling studies of wake vortex transport and evolution within the planetary boundary layer

    NASA Technical Reports Server (NTRS)

    Lin, Yuh-Lang; Arya, S. Pal; Kaplan, Michael L.

    1994-01-01

    The proposed research involves four tasks. The first of these is to simulate accurately the turbulent processes in the atmospheric boundary layer. TASS was originally developed to study meso-gamma scale phenomena, such as tornadic storms, microbursts and windshear effects in terminal areas. Simulation of wake vortex evolution, however, will rely on appropriate representation of the physical processes in the surface layer and mixed layer. This involves two parts. First, a specified heat flux boundary condition must be implemented at the surface. Using this boundary condition, simulation results will be compared to experimental data and to other model results for validation. At this point, any necessary changes to the model will be implemented. Next, a surface energy budget parameterization will be added to the model. This will enable calculation of the surface fluxes by accounting for the radiative heat transfer to and from the ground and heat loss to the soil rather than simple specification of the fluxes. The second task involves running TASS with prescribed wake vortices in the initial condition. The vortex models will be supplied by NASA Langley Research Center. Sensitivity tests will be performed on different meteorological environments in the atmospheric boundary layer, which include stable, neutral, and unstable stratifications, calm and severe wind conditions, and dry and wet conditions. Vortex strength may be varied as well. Relevant non-dimensional parameters will include the following: Richardson number or Froude number, Bowen ratio, and height to length scale ratios. The model output will be analyzed and visualized to better understand the transport, decay, and growth rates of the wake vortices. The third task involves running simulations using observed data. MIT Lincoln Labs is currently planning field experiments at the Memphis airport to measure both meteorological conditions and wake vortex characteristics. Once this data becomes available, it can be

  14. Investigation of AlGaN/GaN high electron mobility transistor structures on 200-mm silicon (111) substrates employing different buffer layer configurations

    NASA Astrophysics Data System (ADS)

    Lee, H.-P.; Perozek, J.; Rosario, L. D.; Bayram, C.

    2016-11-01

    AlGaN/GaN high electron mobility transistor (HEMT) structures are grown on 200-mm diameter Si(111) substrates by using three different buffer layer configurations: (a) Thick-GaN/3 × {AlxGa1‑xN}/AlN, (b) Thin-GaN/3 × {AlxGa1‑xN}/AlN, and (c) Thin-GaN/AlN, so as to have crack-free and low-bow (<50 μm) wafer. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, high resolution-cross section transmission electron microscopy, optical microscopy, atomic-force microscopy, cathodoluminescence, Raman spectroscopy, X-ray diffraction (ω/2θ scan and symmetric/asymmetric ω scan (rocking curve scan), reciprocal space mapping) and Hall effect measurements are employed to study the structural, optical, and electrical properties of these AlGaN/GaN HEMT structures. The effects of buffer layer stacks (i.e. thickness and content) on defectivity, stress, and two-dimensional electron gas (2DEG) mobility and 2DEG concentration are reported. It is shown that 2DEG characteristics are heavily affected by the employed buffer layers between AlGaN/GaN HEMT structures and Si(111) substrates. Particularly, we report that in-plane stress in the GaN layer affects the 2DEG mobility and 2DEG carrier concentration significantly. Buffer layer engineering is shown to be essential for achieving high 2DEG mobility (>1800 cm2/V•s) and 2DEG carrier concentration (>1.0 × 1013 cm‑2) on Si(111) substrates.

  15. Investigation of AlGaN/GaN high electron mobility transistor structures on 200-mm silicon (111) substrates employing different buffer layer configurations

    PubMed Central

    Lee, H.-P.; Perozek, J.; Rosario, L. D.; Bayram, C.

    2016-01-01

    AlGaN/GaN high electron mobility transistor (HEMT) structures are grown on 200-mm diameter Si(111) substrates by using three different buffer layer configurations: (a) Thick-GaN/3 × {AlxGa1−xN}/AlN, (b) Thin-GaN/3 × {AlxGa1−xN}/AlN, and (c) Thin-GaN/AlN, so as to have crack-free and low-bow (<50 μm) wafer. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, high resolution-cross section transmission electron microscopy, optical microscopy, atomic-force microscopy, cathodoluminescence, Raman spectroscopy, X-ray diffraction (ω/2θ scan and symmetric/asymmetric ω scan (rocking curve scan), reciprocal space mapping) and Hall effect measurements are employed to study the structural, optical, and electrical properties of these AlGaN/GaN HEMT structures. The effects of buffer layer stacks (i.e. thickness and content) on defectivity, stress, and two-dimensional electron gas (2DEG) mobility and 2DEG concentration are reported. It is shown that 2DEG characteristics are heavily affected by the employed buffer layers between AlGaN/GaN HEMT structures and Si(111) substrates. Particularly, we report that in-plane stress in the GaN layer affects the 2DEG mobility and 2DEG carrier concentration significantly. Buffer layer engineering is shown to be essential for achieving high 2DEG mobility (>1800 cm2/V∙s) and 2DEG carrier concentration (>1.0 × 1013 cm−2) on Si(111) substrates. PMID:27869222

  16. Membranes with well-defined ions transport channels fabricated via solvent-responsive layer-by-layer assembly method for vanadium flow battery

    PubMed Central

    Xu, Wanxing; Li, Xianfeng; Cao, Jingyu; Zhang, Hongzhang; Zhang, Huamin

    2014-01-01

    In this work we presented a general strategy for the fabrication of membranes with well-defined ions transport channels through solvent-responsive layer-by-layer assembly (SR-LBL). Multilayered poly (diallyldimethylammonium chloride) (PDDA) and poly (acrylic acid) (PAA) complexes were first introduced on the inner pore wall and the surface of sulfonated poly (ether ether ketone)/poly (ether sulfone) (PES/SPEEK) nanofiltration membranes to form ions transport channels with tuned radius. This type of membranes are highly efficient for the separators of batteries especially vanadium flow batteries (VFBs): the VFBs assembled with prepared membranes exhibit an outstanding performance in a wide current density range, which is much higher than that assembled with commercial Nafion 115 membranes. This idea could inspire the development of membranes for other flow battery systems, as well as create further progress in similar areas such as fuel cells, electro-dialysis, chlor-alkali cells, water electrolysis and so on. PMID:24500376

  17. Membranes with well-defined ions transport channels fabricated via solvent-responsive layer-by-layer assembly method for vanadium flow battery

    NASA Astrophysics Data System (ADS)

    Xu, Wanxing; Li, Xianfeng; Cao, Jingyu; Zhang, Hongzhang; Zhang, Huamin

    2014-02-01

    In this work we presented a general strategy for the fabrication of membranes with well-defined ions transport channels through solvent-responsive layer-by-layer assembly (SR-LBL). Multilayered poly (diallyldimethylammonium chloride) (PDDA) and poly (acrylic acid) (PAA) complexes were first introduced on the inner pore wall and the surface of sulfonated poly (ether ether ketone)/poly (ether sulfone) (PES/SPEEK) nanofiltration membranes to form ions transport channels with tuned radius. This type of membranes are highly efficient for the separators of batteries especially vanadium flow batteries (VFBs): the VFBs assembled with prepared membranes exhibit an outstanding performance in a wide current density range, which is much higher than that assembled with commercial Nafion 115 membranes. This idea could inspire the development of membranes for other flow battery systems, as well as create further progress in similar areas such as fuel cells, electro-dialysis, chlor-alkali cells, water electrolysis and so on.

  18. Membranes with well-defined ions transport channels fabricated via solvent-responsive layer-by-layer assembly method for vanadium flow battery.

    PubMed

    Xu, Wanxing; Li, Xianfeng; Cao, Jingyu; Zhang, Hongzhang; Zhang, Huamin

    2014-02-06

    In this work we presented a general strategy for the fabrication of membranes with well-defined ions transport channels through solvent-responsive layer-by-layer assembly (SR-LBL). Multilayered poly (diallyldimethylammonium chloride) (PDDA) and poly (acrylic acid) (PAA) complexes were first introduced on the inner pore wall and the surface of sulfonated poly (ether ether ketone)/poly (ether sulfone) (PES/SPEEK) nanofiltration membranes to form ions transport channels with tuned radius. This type of membranes are highly efficient for the separators of batteries especially vanadium flow batteries (VFBs): the VFBs assembled with prepared membranes exhibit an outstanding performance in a wide current density range, which is much higher than that assembled with commercial Nafion 115 membranes. This idea could inspire the development of membranes for other flow battery systems, as well as create further progress in similar areas such as fuel cells, electro-dialysis, chlor-alkali cells, water electrolysis and so on.

  19. Rapid Transport of Stratospheric Ozone into the Planetary Boundary Layer over the Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Skerlak, B.; Sprenger, M.; Pfahl, S.; Wernli, H.

    2013-12-01

    Stratosphere-troposphere exchange (STE) has important impacts on atmospheric chemistry: it changes the oxidative capacity of the troposphere and affects the climate system through the exchange of water vapor and ozone. Although a large part of tropospheric ozone is produced photochemically, significant amounts of stratospheric ozone can be brought into the troposphere during STE events. The relative importance of these two sources depends on the location of interest and transport characteristics. Of particular interest are so-called deep exchange events where ozone-rich stratospheric air reaches the planetary boundary layer (PBL) within a few days (deep STT). This rapid vertical transport can contribute to ozone concentrations at ground level which can impair plant and human physiology. It is therefore not only important to quantify the ozone flux across the tropopause but also to investigate the transport pathways after the crossing to identify affected areas at ground. Using a Lagrangian methodology and 33 years of ERA-Interim reanalysis data, we have compiled a global climatology of STE from which the mountainous areas in western North America can be identified as a 'hot spot' of deep STT, especially in boreal spring. To address the question of how the stratospheric air masses are transported into the PBL in more detail, we investigate case studies in this region with the mesoscale numerical weather prediction model COSMO. On this account, we initialize a passive tracer in the stratosphere using an elaborated 3D-labeling algorithm which applies the dynamical 2 pvu/380 K tropopause definition. This tracer is then advected by both resolved and parameterized processes and allows us to follow the stratospheric air masses along their journey into the mountainous PBL. Although this tracer does not directly represent a specific chemical species, its concentrations at the lowest model level can indicate when and where ozone levels at ground are likely to be influenced

  20. Meeting Skills Needs in a Market-Based Training System: A Study of Employer Perceptions and Responses to Training Challenges in the Australian Transport and Logistics Industry

    ERIC Educational Resources Information Center

    Gekara, Victor O.; Snell, Darryn; Chhetri, Prem; Manzoni, Alex

    2014-01-01

    Many countries are adopting market-based training systems to address industry skills needs. This paper examines the marketisation of Australia's training system and the implications for training provision and outcomes in the Transport and Logistics industry. Drawing on qualitative interviews from industry employers and training providers, we…

  1. Optimization of an Electron Transport Layer to Enhance the Power Conversion Efficiency of Flexible Inverted Organic Solar Cells.

    PubMed

    Lee, Kang Hyuck; Kumar, Brijesh; Park, Hye-Jeong; Kim, Sang-Woo

    2010-08-31

    The photovoltaic (PV) performance of flexible inverted organic solar cells (IOSCs) with an active layer consisting of a blend of poly(3-hexylthiophene) and [6, 6]-phenyl C(61)-butlyric acid methyl ester was investigated by varying the thicknesses of ZnO seed layers and introducing ZnO nanorods (NRs). A ZnO seed layer or ZnO NRs grown on the seed layer were used as an electron transport layer and pathway to optimize PV performance. ZnO seed layers were deposited using spin coating at 3,000 rpm for 30 s onto indium tin oxide (ITO)-coated polyethersulphone (PES) substrates. The ZnO NRs were grown using an aqueous solution method at a low temperature (90°C). The optimized device with ZnO NRs exhibited a threefold increase in PV performance compared with that of a device consisting of a ZnO seed layer without ZnO NRs. Flexible IOSCs fabricated using ZnO NRs with improved PV performance may pave the way for the development of PV devices with larger interface areas for effective exciton dissociation and continuous carrier transport paths.

  2. Surface-initiated poly(3-methylthiophene) as a hole-transport layer for polymer solar cells with high performance.

    PubMed

    Yang, Liqiang; Sontag, S Kyle; LaJoie, Travis W; Li, Wentao; Huddleston, N Eric; Locklin, Jason; You, Wei

    2012-10-24

    In this work, uniform poly(3-methylthiophene) (P3MT) films are fabricated on indium-tin oxide (ITO) surfaces using surface-initiated Kumada catalyst-transfer polycondensation (SI-KCTP) from surface-bound arylnickel(II) bromide initiators. The P3MT interfacial layer is covalently bound to the ITO surface, thereby preventing possible delamination during the processing of additional layers. These surface-bound P3MT layers successfully serve as the hole-transport layer for solution-processed bulk heterojunction polymer solar cells. Efficiencies greater than 5% have been achieved on devices based on doped thin P3MT interfacial layers. Moreover, because of the excellent stability of the covalently immobilized P3MT on ITO substrates, devices based on reused P3MT/ITO substrates extracted from old devices exhibit efficiencies similar to those of the original devices.

  3. Solution-Processed Hybrid Light-Emitting Devices Comprising TiO2 Nanorods and WO3 Layers as Carrier-Transporting Layers

    NASA Astrophysics Data System (ADS)

    Tsai, Tsung-Yan; Yan, Po-Ruei; Yang, Sheng-Hsiung

    2016-11-01

    The goal of this research is to prepare inverted light-emitting devices with improved performance by combining titanium dioxide (TiO2) nanorods and tungsten trioxide (WO3) layer. TiO2 nanorods with different lengths were established directly on the fluorine-doped tin oxide (FTO) substrates by the hydrothermal method. The prepared TiO2 nanorods with lengths shorter than 200 nm possess transmittance higher than 80% in the visible range. Inverted light-emitting devices with the configuration of FTO/TiO2 nanorods/ionic PF/MEH-PPV/PEDOT:PSS/WO3/Au were constructed. The best device based on 100-nm-height TiO2 nanorods achieved a max brightness of 4493 cd/m2 and current efficiency of 0.66 cd/A, revealing much higher performance compared with those using TiO2 compact layer or nanorods with longer lengths as electron-transporting layers.

  4. Fate and Transport of Methane Formed in the Active Layer of Alaskan Permafrost

    NASA Astrophysics Data System (ADS)

    Conrad, M. E.; Curtis, J. B.; Smith, L. J.; Bill, M.; Torn, M. S.

    2015-12-01

    Over the past 2 years a series of tracer tests designed to estimate rates of methane formation via acetoclastic methanogenesis in the active layer of permafrost soils were conducted at the Barrow Environmental Observatory (BEO) in northernmost Alaska. The tracer tests consisted of extracting 0.5 to 1.0 liters of soil water in gas-tight bags from different features of polygons at the BEO, followed by addition of a tracer cocktail including acetate with a 13C-labeled methyl group and D2O (as a conservative tracer) into the soil water and injection of the mixture back into the original extraction site. Samples were then taken at depths of 30 cm (just above the bottom of the active layer), 20 cm, 10 cm and surface flux to determine the fate of the 13C-labeled acetate. During 2014 (2015 results are pending) water, soil gas, and flux gas were sampled for 60 days following injection of the tracer solution. Those samples were analyzed for concentrations and isotopic compositions of CH4, DIC/CO2 and water. At one site (the trough of a low-centered polygon) the 13C acetate was completely converted to 13CH4 within the first 2 days. The signal persisted for throughout the entire monitoring period at the injection depth with little evidence of transport or oxidation in any of the other sampling depths. In the saturated center of the same polygon, the acetate was also rapidly converted to 13CH4, but water turnover caused the signal to rapidly dissipate. High δ13C CO2 in flux samples from the polygon center indicate oxidation of the 13CH4 in near-surface waters. Conversely, CH4 production in the center of an unsaturated, flat-centered polygon was relatively small 13CH4 and dissipated rapidly without any evidence of either 13CH4 transport to shallower levels or oxidation. At another site in the edge of that polygon no 13CH4 was produced, but significant 13CO2/DIC was observed indicating direct aerobic oxidation of the acetate was occurring at this site. These results suggest that

  5. Large Eddy Simulation and Field Experiments of Pollen Transport in the Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Chamecki, M.; Meneveau, C.; Parlange, M. B.; van Hout, R.

    2006-12-01

    Dispersion of airborne pollen by the wind has been a subject of interest for botanists and allergists for a long time. More recently, the development of genetically modified crops and questions about cross-pollination and subsequent contamination of natural plant populations has brought even more interest to this field. A critical question is how far from the source field pollen grains will be advected. Clearly the answer depends on the aerodynamic properties of the pollen, geometrical properties of the field, topography, local vegetation, wind conditions, atmospheric stability, etc. As a consequence, field experiments are well suited to provide some information on pollen transport mechanisms but are limited to specific field and weather conditions. Numerical simulations do not have this drawback and can be a useful tool to study pollen dispersal in a variety of configurations. It is well known that the dispersion of particles in turbulent fields is strongly affected by the large scale coherent structures. Large Eddy Simulation (LES) is a technique that allows us to study the typical distances reached by pollen grains and, at the same time, resolve the larger coherent structures present in the atmospheric boundary layer. The main objective of this work is to simulate the dispersal of pollen grains in the atmospheric surface layer using LES. Pollen concentrations are simulated by an advection-diffusion equation including gravitational settling. Of extreme importance is the specification of the bottom boundary conditions characterizing the pollen source over the canopy and the deposition process everywhere else. In both cases we make use of the theoretical profile for suspended particles derived by Kind (1992). Field experiments were performed to study the applicability of the theoretical profile to pollen grains and the results are encouraging. Airborne concentrations as well as ground deposition from the simulations are compared to experimental data to validate the

  6. A novel alignment mechanism employing orthogonal connected multi-layered flexible hinges for both leveling and centering

    NASA Astrophysics Data System (ADS)

    Zhao, Jian; Wang, Hongxi; Gao, Renjing; Hu, Ping; Yang, Yintang

    2012-06-01

    To eliminate the effects of motion coupling for measuring cylindrical work pieces, a novel alignment mechanism integrating functions of both leveling and centering is designed and fabricated by introducing multi-layered orthogonal connected flexible hinges as the key supporting and joining elements. Different from traditional leveling mechanisms with many separate parts fabricated together, all of the flexible hinges were integrated in one three-dimensioned machining part without assembling process, and thus synchronously simplifying the structure and reducing assembly errors. Based on the screw theory, the mathematic model of the proposed alignment mechanism is established for any resolution requirements depending on screw characteristics. A millimeter-sized device is fabricated with the alignment precision of 1.0 μm for centering within the range of ±1 mm and 1 in. for leveling within ±1°. The experiment results are in very close agreement to those obtained by simulation, which validate the feasibility of introducing multi-layered orthogonal flexible hinges in the centering and leveling mechanisms.

  7. Co-precipitation of tobramycin into biomimetically coated orthopedic fixation pins employing submicron-thin seed layers of hydroxyapatite.

    PubMed

    Sörensen, Jan H; Lilja, Mirjam; Åstrand, Maria; Sörensen, Torben C; Procter, Philip; Strømme, Maria; Steckel, Hartwig

    2014-01-01

    The migration, loosening and cut-out of implants and nosocomial infections are current problems associated with implant surgery. New innovative strategies to overcome these issues are emphasized in today's research. The current work presents a novel strategy involving co-precipitation of tobramycin with biomimetic hydroxyapatite (HA) formation to produce implant coatings that control local drug delivery to prevent early bacterial colonization of the implant. A submicron- thin HA layer served as seed layer for the co-precipitation process and allowed for incorporation of tobramycin in the coating from a stock solution of antibiotic concentrations as high as 20 mg/ml. Concentrations from 0.5 to 20 mg/ml tobramycin and process temperatures of 37 °C and 60 °C were tested to assess the optimal parameters for a thin tobramycin- delivering HA coating on discs and orthopedic fixation pins. The morphology and thickness of the coating and the drug-release profile were evaluated via scanning electron microscopy and high performance liquid chromatography. The coatings delivered pharmaceutically relevant amounts of tobramycin over a period of 12 days. To the best of our knowledge, this is the longest release period ever observed for a fast-loaded biomimetic implant coating. The presented approach could form the foundation for development of combination device/antibiotic delivery vehicles tailored to meet well-defined clinical needs while combating infections and ensuring fast implant in-growth.

  8. A novel alignment mechanism employing orthogonal connected multi-layered flexible hinges for both leveling and centering.

    PubMed

    Zhao, Jian; Wang, Hongxi; Gao, Renjing; Hu, Ping; Yang, Yintang

    2012-06-01

    To eliminate the effects of motion coupling for measuring cylindrical work pieces, a novel alignment mechanism integrating functions of both leveling and centering is designed and fabricated by introducing multi-layered orthogonal connected flexible hinges as the key supporting and joining elements. Different from traditional leveling mechanisms with many separate parts fabricated together, all of the flexible hinges were integrated in one three-dimensioned machining part without assembling process, and thus synchronously simplifying the structure and reducing assembly errors. Based on the screw theory, the mathematic model of the proposed alignment mechanism is established for any resolution requirements depending on screw characteristics. A millimeter-sized device is fabricated with the alignment precision of 1.0 μm for centering within the range of ±1 mm and 1 in. for leveling within ±1°. The experiment results are in very close agreement to those obtained by simulation, which validate the feasibility of introducing multi-layered orthogonal flexible hinges in the centering and leveling mechanisms.

  9. Employing PEDOT as the p-Type Charge Collection Layer in Regular Organic-Inorganic Perovskite Solar Cells.

    PubMed

    Liu, Jiewei; Pathak, Sandeep; Stergiopoulos, Thomas; Leijtens, Tomas; Wojciechowski, Konrad; Schumann, Stefan; Kausch-Busies, Nina; Snaith, Henry J

    2015-05-07

    Organic-inorganic halide perovskite solar cells have recently emerged as high-performance photovoltaic devices with low cost, promising for affordable large-scale energy production, with laboratory cells already exceeding 20% power conversion efficiency (PCE). To date, a relatively expensive organic hole-conducting molecule with low conductivity, namely spiro-OMeTAD (2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine) 9,9'- spirobifluorene), is employed widely to achieve highly efficient perovskite solar cells. Here, we report that by replacing spiro-OMeTAD with much cheaper and highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) we can achieve PCE of up to 14.5%, with PEDOT cast from a toluene based ink. However, the stabilized power output of the PEDOT-based devices is only 6.6%, in comparison to 9.4% for the spiro-OMeTAD-based cells. We deduce that accelerated recombination is the cause for this lower stabilized power output and postulate that reduced levels of p-doping are required to match the stabilized performance of Spiro-OMeTAD. The entirely of the materials employed in the perovskite solar cell are now available at commodity scale and extremely inexpensive.

  10. TURBULENT TRANSPORT IN A STRONGLY STRATIFIED FORCED SHEAR LAYER WITH THERMAL DIFFUSION

    SciTech Connect

    Garaud, Pascale

    2016-04-10

    This work presents numerical results on the transport of heat and chemical species by shear-induced turbulence in strongly stratified, thermally diffusive environments. The shear instabilities driven in this regime are sometimes called “secular” shear instabilities, and can take place when the Richardson number of the flow is large, provided the Péclet number is small. We have identified a set of simple criteria to determine whether these instabilities can take place or not. Generally speaking, we find that they may be relevant whenever the thermal diffusivity of the fluid is very large (typically larger than 10{sup 14} cm{sup 2} s{sup −1}), which is the case in the outer layers of high-mass stars (M ≥ 10 M{sub ⊙}), for instance. Using a simple model setup in which the shear is forced by a spatially sinusoidal, constant-amplitude body-force, we have identified several regimes ranging from effectively unstratified to very strongly stratified, each with its own set of dynamical properties. Unless the system is in one of the two extreme regimes (effectively unstratified or completely stable), however, we find that (1) only about 10% of the input power is used toward heat transport, while the remaining 90% is viscously dissipated; (2) that the effective compositional mixing coefficient is well-approximated by the model of Zahn, with D ≃ 0.02κ{sub T}/J where κ{sub T} is the thermal diffusivity and J is the Richardson number. These results need to be confirmed, however, with simulations in different model setups and at higher effective Reynolds number.

  11. Pristine fullerenes mixed by vacuum-free solution process: Efficient electron transport layer for planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Dai, Si-Min; Tian, Han-Rui; Zhang, Mei-Lin; Xing, Zhou; Wang, Lu-Yao; Wang, Xin; Wang, Tan; Deng, Lin-Long; Xie, Su-Yuan; Huang, Rong-Bin; Zheng, Lan-Sun

    2017-01-01

    Discovery of organic-inorganic hybrid perovskites ignites the dream of next-generation solar cells fabricated by low-cost solution processing. To date, fullerene derivative [6,6]-phenyl-C61- butyric acid methyl ester (PC61BM), is the most prevalently used electron transport layer for high efficiency p-i-n planar heterojunction perovskite solar cells. Compared with PC61BM, pristine fullerenes, such as C60 and C70, have shown superiority of higher electron mobility and much lower costs. Due to the poor solubility and strong tendency to crystallize for pristine fullerenes in solution process, it is still a challenge to deposit compact and continuous film of pristine fullerenes for p-i-n type perovskite solar cells by solution processing. Herein, solution processed pristine fullerenes (C60 and C70) were used as electron transport layers to replace PC61BM in perovskite solar cells with high performance and enhanced stability. Power conversion efficiency of 14.04% was obtained by using mixture of C60 and C70 as electron transport layer, which is comparable to that of PC61BM based device (13.74%). We demonstrated that the strong tendency of pristine fullerenes to crystallize during solvent removal can be largely mitigated by mixing different kinds of pristine fullerenes. These findings implicate pristine fullerenes as promising electron transport layers for high performance perovskite solar cells.

  12. Verification of the multi-layer SNOWPACK model with different water transport schemes

    NASA Astrophysics Data System (ADS)

    Wever, N.; Schmid, L.; Heilig, A.; Eisen, O.; Fierz, C.; Lehning, M.

    2015-12-01

    The widely used detailed SNOWPACK model has undergone constant development over the years. A notable recent extension is the introduction of a Richards equation (RE) solver as an alternative for the bucket-type approach for describing water transport in the snow and soil layers. In addition, continuous updates of snow settling and new snow density parameterizations have changed model behavior. This study presents a detailed evaluation of model performance against a comprehensive multiyear data set from Weissfluhjoch near Davos, Switzerland. The data set is collected by automatic meteorological and snowpack measurements and manual snow profiles. During the main winter season, snow height (RMSE: < 4.2 cm), snow water equivalent (SWE, RMSE: < 40 mm w.e.), snow temperature distributions (typical deviation with measurements: < 1.0 °C) and snow density (typical deviation with observations: < 50 kg m-3) as well as their temporal evolution are well simulated in the model and the influence of the two water transport schemes is small. The RE approach reproduces internal differences over capillary barriers but fails to predict enough grain growth since the growth routines have been calibrated using the bucket scheme in the original SNOWPACK model. However, the agreement in both density and grain size is sufficient to parameterize the hydraulic properties successfully. In the melt season, a pronounced underestimation of typically 200 mm w.e. in SWE is found. The discrepancies between the simulations and the field data are generally larger than the differences between the two water transport schemes. Nevertheless, the detailed comparison of the internal snowpack structure shows that the timing of internal temperature and water dynamics is adequately and better represented with the new RE approach when compared to the conventional bucket scheme. On the contrary, the progress of the meltwater front in the snowpack as detected by radar and the temporal evolution of the vertical

  13. Employing X-ray Photoelectron Spectroscopy for Determining Layer Homogeneity in Mixed Polar Self-Assembled Monolayers

    PubMed Central

    2016-01-01

    Self-assembled monolayers (SAMs) containing embedded dipolar groups offer the particular advantage of changing the electronic properties of a surface without affecting the SAM–ambient interface. Here we show that such systems can also be used for continuously tuning metal work functions by growing mixed monolayers consisting of molecules with different orientations of the embedded dipolar groups. To avoid injection hot-spots when using the SAM-modified electrodes in devices, a homogeneous mixing of the two components is crucial. We show that a combination of high-resolution X-ray photoelectron spectroscopy with state-of-the-art simulations is an ideal tool for probing the electrostatic homogeneity of the layers and thus for determining phase separation processes in polar adsorbate assemblies down to inhomogeneities at the molecular level. PMID:27429041

  14. Employing X-ray Photoelectron Spectroscopy for Determining Layer Homogeneity in Mixed Polar Self-Assembled Monolayers.

    PubMed

    Hehn, Iris; Schuster, Swen; Wächter, Tobias; Abu-Husein, Tarek; Terfort, Andreas; Zharnikov, Michael; Zojer, Egbert

    2016-08-04

    Self-assembled monolayers (SAMs) containing embedded dipolar groups offer the particular advantage of changing the electronic properties of a surface without affecting the SAM-ambient interface. Here we show that such systems can also be used for continuously tuning metal work functions by growing mixed monolayers consisting of molecules with different orientations of the embedded dipolar groups. To avoid injection hot-spots when using the SAM-modified electrodes in devices, a homogeneous mixing of the two components is crucial. We show that a combination of high-resolution X-ray photoelectron spectroscopy with state-of-the-art simulations is an ideal tool for probing the electrostatic homogeneity of the layers and thus for determining phase separation processes in polar adsorbate assemblies down to inhomogeneities at the molecular level.

  15. Electric double layer capacitors employing nitrogen and sulfur co-doped, hierarchically porous graphene electrodes with synergistically enhanced performance

    NASA Astrophysics Data System (ADS)

    Kannan, Aravindaraj G.; Samuthirapandian, Amaresh; Kim, Dong-Won

    2017-01-01

    Hierarchically porous graphene nanosheets co-doped with nitrogen and sulfur are synthesized via a simple hydrothermal method, followed by a pore activation step. Pore architectures are controlled by varying the ratio of chemical activation agents to graphene, and its influence on the capacitive performance is evaluated. The electric double layer capacitor (EDLC) assembled with optimized dual-doped graphene delivers a high specific capacitance of 146.6 F g-1 at a current density of 0.8 A g-1, which is higher than that of cells with un-doped and single-heteroatom doped graphene. The EDLC with dual-doped graphene electrodes exhibits stable cycling performance with a capacitance retention of 94.5% after 25,000 cycles at a current density of 3.2 A g-1. Such a good performance can be attributed to synergistic effects due to co-doping of the graphene nanosheets and the presence of hierarchical porous structures.

  16. Solution processed deposition of electron transport layers on perovskite crystal surface-A modeling based study

    NASA Astrophysics Data System (ADS)

    Mortuza, S. M.; Taufique, M. F. N.; Banerjee, Soumik

    2017-02-01

    The power conversion efficiency (PCE) of planar perovskite solar cells (PSCs) has reached up to ∼20%. However, structural and chemicals defects that lead to hysteresis in the perovskite based thin film pose challenges. Recent work has shown that thin films of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) deposited on the photo absorption layer, using solution processing techniques, minimize surface pin holes and defects thereby increasing the PCE. We developed and employed a multiscale model based on molecular dynamics (MD) and kinetic Monte Carlo (kMC) to establish a relationship between deposition rate and surface coverage on perovskite surface. The MD simulations of PCBMs dispersed in chlorobenzene, sandwiched between (110) perovskite substrates, indicate that PCBMs are deposited through anchoring of the oxygen atom of carbonyl group to the exposed lead (Pb) atom of (110) perovskite surface. Based on rates of distinct deposition events calculated from MD, kMC simulations were run to determine surface coverage at much larger time and length scales than accessible by MD alone. Based on the model, a generic relationship is established between deposition rate of PCBMs and surface coverage on perovskite crystal. The study also provides detailed insights into the morphology of the deposited film.

  17. Nonlinearity and hysteresis in longitudinal current transport in CoSi/GaAs alloy layers deposited from laser plasma

    NASA Astrophysics Data System (ADS)

    Demidov, E. S.; Gusev, S. N.; Podol'skii, V. V.; Lesnikov, V. P.; Sdobnyakov, V. V.; Budarin, L. I.; Tronov, A. A.; Skopin, E. V.

    2013-07-01

    The electron transport properties of nanosized CoSi alloy layers deposited at a lowered temperature (350°C) from laser plasma onto single-crystalline gallium arsenide have been studied. An asymmetry of the current-voltage characteristic (CVC) in the longitudinal current transport in such layers has been found, which indicates the spin polarization of charge carriers, and a substantial (up to 18%) nonlinearity and a hysteresis (up to 4%) have been revealed both at room temperature and at 77 K for comparatively low current densities (up to 5 × 104 A/cm2). In repeated cycles of CVC measurements at 77 K, irreversible changes in the properties of the layers have been observed.

  18. Universality of intermittent convective transport in the scrape-off layer of magnetically confined devices

    NASA Astrophysics Data System (ADS)

    Antar, Ghassan Y.; Counsell, Glenn; Yu, Yang; Labombard, Brian; Devynck, Pascal

    2003-02-01

    The nature of intermittency, long observed in magnetic fusion devices, was revisited lately [G. Antar et al., Phys. Rev. Lett. 87, 065001 (2001)]. It was shown that intermittency is caused by large-scale events with high radial velocity reaching about 1/10th of the sound speed. These type of structures were named "avaloids." In the present article, the universality of convective turbulence in magnetically confined plasmas is investigated. Turbulence properties in the scrape-off layer of four different magnetic fusion devices are compared. Namely, the Tore Supra tokamak [Tore Supra Team, Nuclear Fusion, 40, 1047 (2000)] with circular cross-section limiter-bounded plasma, the Alcator C-Mod tokamak [B. LaBombard et al., Phys. Plasmas 8, 2107 (2001)] which is a divertor device, the Mega-Ampere Spherical Tokamak (MAST) [A. Sykes et al., Phys. Plasmas 8, 2101 (2001)] with vacuum chamber walls far from the plasma last closed flux surface and the PISCES linear plasma device [D. Geobel et al., Rev. Sci. Istrum. 56, 1717 (1985)]. The statistical properties of the turbulent signals in the four devices are found to be identical allowing us to conclude that intermittent convective transport by avaloids is universal in the sense that it occurs and has the same properties in many confinement devices with different configurations.

  19. Influence of electron transport layer thickness on optical properties of organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Liu, Guohong; Liu, Yong; Li, Baojun; Zhou, Xiang

    2015-06-01

    We investigate experimentally and theoretically the influence of electron transport layer (ETL) thickness on properties of typical N,N'-diphenyl-N,N'-bis(1-naphthyl)-[1,1'-biphthyl]-4,4'-diamine (NPB)/tris-(8-hydroxyquinoline) aluminum (Alq3) heterojunction based organic light-emitting diodes (OLEDs), where the thickness of ETL is varied to adjust the distance between the emitting zone and the metal electrode. The devices showed a maximum current efficiency of 3.8 cd/A when the ETL thickness is around 50 nm corresponding to an emitter-cathode distance of 80 nm, and a second maximum current efficiency of 2.6 cd/A when the ETL thickness is around 210 nm corresponding to an emitter-cathode distance of 240 nm. We adopt a rigorous electromagnetic approach that takes parameters, such as dipole orientation, polarization, light emitting angle, exciton recombination zone, and diffusion length into account to model the optical properties of devices as a function of varying ETL thickness. Our simulation results are accurately consistent with the experimental results with a widely varying thickness of ETL, indicating that the theoretical model may be helpful to design high efficiency OLEDs.

  20. Intermittent transport across the scrape-off layer: latest results from ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Kočan, M.; Müller, H. W.; Nold, B.; Lunt, T.; Adámek, J.; Allan, S. Y.; Bernert, M.; Conway, G. D.; de Marné, P.; Eich, T.; Elmore, S.; Gennrich, F. P.; Herrmann, A.; Horacek, J.; Huang, Z.; Kallenbach, A.; Komm, M.; Maraschek, M.; Mehlmann, F.; Müller, S.; Ribeiro, T. T.; Rohde, V.; Schrittwieser, R.; Scott, B.; Stroth, U.; Suttrop, W.; Wolfrum, E.; the ASDEX Upgrade Team

    2013-07-01

    We report the latest results of turbulence and transport studies in the ASDEX Upgrade scrape-off layer (SOL). Dissimilarity between the plasma and the floating potential fluctuations is studied experimentally and by gyrofluid simulations. Measurements by a retarding field analyser reveal that both, edge-localized mode (ELM) and turbulent filaments, convey hot ions over large radial distances in the SOL. The measured far SOL ELM ion temperature increases with the ELM energy, consistent with earlier observations that large ELMs deposit a large fraction of their energy outside the divertor. In the SOL, the ELM suppression by magnetic perturbations (MPs) results in lower ELM ion energy in the far SOL. At the same time, large filaments of ion saturation current are replaced by more continuous bursts. Splitting of the divertor strike zones observed by the infrared imaging in H-mode with MPs agree with predictions from the EMC3-Eirene simulations. This suggests that the ‘lobe’ structures due to perturbation fields observed near the X-point are not significantly affected by plasma screening, and can be described by a vacuum approach, as in the EMC3-Eirene. Finally, some effects of the MPs on the L-mode SOL are addressed.

  1. Photodiode Based on CdO Thin Films as Electron Transport Layer

    NASA Astrophysics Data System (ADS)

    Soylu, M.; Kader, H. S.

    2016-11-01

    Cadmium oxide (CdO) thin films were synthesized by the sol-gel method. The films were analyzed by means of XRD, AFM, and UV/Vis spectrophotometry. X-ray diffraction patterns confirm that the films are formed from CdO with cubic crystal structure and consist of nano-particles. The energy gap of the prepared film was found to be 2.29 eV. The current-voltage ( I- V) characteristics of the CdO/ p-Si heterojunction were examined in the dark and under different illumination intensities. The heterojunction showed high rectifying behavior and a strong photoresponse. Main electrical parameters of the photodiode such as series and shunt resistances ( R s and R sh), saturation current I 0, and photocurrent I ph, were extracted considering a single diode equivalent circuit of a photovoltaic cell. Results indicate that the application of CdO thin films as an electron transport layer on p-Si acts as a photodetector in the field of the UV/visible.

  2. Carbon materials with quasi-graphene layers: The dielectric, percolation properties and the electronic transport mechanism

    NASA Astrophysics Data System (ADS)

    Lu, Ming-Ming; Yuan, Jie; Wen, Bo; Liu, Jia; Cao, Wen-Qiang; Cao, Mao-Sheng

    2013-03-01

    We investigate the dielectric properties of multi-walled carbon nanotubes (MWCNTs) and graphite filling in SiO2 with the filling concentration of 2-20 wt.% in the frequency range of 102-107 Hz. MWCNTs and graphite have general electrical properties and percolation phenomena owing to their quasi-structure made up of graphene layers. Both permittivity ɛ and conductivity σ exhibit jumps around the percolation threshold. Variations of dielectric properties of the composites are in agreement with the percolation theory. All the percolation phenomena are determined by hopping and migrating electrons, which are attributed to the special electronic transport mechanism of the fillers in the composites. However, the twin-percolation phenomenon exists when the concentration of MWCNTs is between 5-10 wt.% and 15-20 wt.% in the MWCNTs/SiO2 composites, while in the graphite/SiO2 composites, there is only one percolation phenomenon in the graphite concentration of 10-15 wt.%. The unique twin-percolation phenomenon of MWCNTs/SiO2 is described and attributed to the electronic transfer mechanism, especially the network effect of MWCNTs in the composites. The network formation plays an essential role in determining the second percolation threshold of MWCNTs/SiO2.

  3. Influence of electron transport layer thickness on optical properties of organic light-emitting diodes

    SciTech Connect

    Liu, Guohong; Liu, Yong; Li, Baojun; Zhou, Xiang

    2015-06-07

    We investigate experimentally and theoretically the influence of electron transport layer (ETL) thickness on properties of typical N,N′-diphenyl-N,N′-bis(1-naphthyl)-[1,1′-biphthyl]-4,4′-diamine (NPB)/tris-(8-hydroxyquinoline) aluminum (Alq{sub 3}) heterojunction based organic light-emitting diodes (OLEDs), where the thickness of ETL is varied to adjust the distance between the emitting zone and the metal electrode. The devices showed a maximum current efficiency of 3.8 cd/A when the ETL thickness is around 50 nm corresponding to an emitter-cathode distance of 80 nm, and a second maximum current efficiency of 2.6 cd/A when the ETL thickness is around 210 nm corresponding to an emitter-cathode distance of 240 nm. We adopt a rigorous electromagnetic approach that takes parameters, such as dipole orientation, polarization, light emitting angle, exciton recombination zone, and diffusion length into account to model the optical properties of devices as a function of varying ETL thickness. Our simulation results are accurately consistent with the experimental results with a widely varying thickness of ETL, indicating that the theoretical model may be helpful to design high efficiency OLEDs.

  4. New Physical Deposition Approach for Low Cost Inorganic Hole Transport Layer in Normal Architecture of Durable Perovskite Solar Cells.

    PubMed

    Nejand, Bahram Abdollahi; Ahmadi, Vahid; Shahverdi, Hamid Reza

    2015-10-07

    In this work we reported sputter deposited NiOx/Ni double layer as an HTM/contact couple in normal architecture of perovskite solar cell. A perovskite solar cell that is durable for more than 60 days was achieved, with increasing efficiency from 1.3% to 7.28% within 6 days. Moreover, low temperature direct deposition of NiOx layer on perovskite layer was introduced as a potential hole transport material for an efficient cost-effective solar cell applicable for various morphologies of perovskite layers, even for perovskite layers containing pinholes, which is a notable challenge in perovskite solar cells. The angular deposition of NiOx layers by dc reactive magnetron sputtering showed uniform and crack-free coverage of the perovskite layer with no negative impact on perovskite structure that is suitable for nickel back contact layer, surface shielding against moisture, and mechanical damages. Replacing the expensive complex materials in previous perovskite solar cells with low cost available materials introduces cost-effective scalable perovskite solar cells.

  5. Role of Metal Oxide Electron-Transport Layer Modification on the Stability of High Performing Perovskite Solar Cells.

    PubMed

    Singh, Trilok; Singh, Jai; Miyasaka, Tsutomu

    2016-09-22

    Organic-inorganic hybrid perovskite light absorbers have recently emerged as a "holy grail" for next generation thin-film photovoltaics with excellent optoelectronics properties and low fabrication cost. In a very short span of time, we have witnessed a pronounced and unexpected progress in organic- inorganic perovskite solar cells (PSCs) with a vertical rise in power conversion efficiency from 3.8 to 22.1 %. In this manuscript we focus specifically on the recent development of metal oxide-based electron-transporting layer (ETL) modification for high performing PSCs and their stability. This review highlights various methodologies to modify existing compact/scaffold layers for improving device performance and stability. Various aspects of the ETL are discussed with different metal oxide compact layers in their relation to modification in mesoporous layers towards the design of a cell structure with high performance and stability.

  6. Effect of aging-induced disorder on the quantum transport properties of few-layer WTe2

    NASA Astrophysics Data System (ADS)

    Lai Liu, Wei; Chen, Mao Lin; Li, Xiao Xi; Dubey, Sudipta; Xiong, Ting; Dai, Zhi Ming; Yin, Jun; Guo, Wan Lin; Ma, Jin Long; Chen, Ya Ni; Tan, Jun; Li, Da; Wang, Zhen Hua; Li, Wu; Bouchiat, Vincent; Sun, Dong Ming; Han, Zheng; Zhang, Zhi Dong

    2017-03-01

    The emerging physical phenomena found in transition metal dicalcogenides (TMDCs) have triggered vast investigations in recent years. Among them, nanoelectronics in WTe2 devices have attracted particular attentions due to its exotic band structure that leads to exciting phenomena such as the predicted type-II Weyl semimetallic state. However, the thickness dependence of its quantum transport properties in the two-dimensional limit remains under debate. The major missing ingredient in the previous studies is the aging-induced disorder, as atomically thin layers of TMDCs are often known to be metastable in the ambient atmosphere. Here, we show systematic performance of low temperature quantum electronic transport of few-layer WTe2. It is observed that aging-induced localized electronic states explains the low temperature Coulomb gap in transport measurements, leading to the anomalous magnetotransport which appears to be extrinsic. While few-layered WTe2 shows clear metallic tendency in the fresh state, degraded devices first exhibited a re-entrant insulating behavior, and finally entered a fully insulating state. Correspondingly, a crossover from parabolic to linear magnetoresistance, and, upon further aging, leads to the observation of weak anti-localization. Our study reveals for the first time the correlation between the unusual magnetotransport and disorder in few-layered WTe2, which is indispensable in providing guidance on its future device applications.

  7. Suspended particulate loads and transports in the nepheloid layer of the abyssal Atlantic Ocean

    USGS Publications Warehouse

    Biscaye, P.E.; Eittreim, S.L.

    1977-01-01

    Vertical profiles of light scattering from over 1000 L-DGO nephelometer stations in the Atlantic Ocean have been used to calculate mass concentrations of suspended particles based on a calibration from the western North American Basin. From these data are plotted the distributions of particulate concentrations at clear water and in the more turbid near-bottom water. Clear water is the broad minimum in concentration and light scattering that occurs at varying mid-depths in the water column. Concentrations at clear water are as much as one-to-two orders of magnitude lower than those in surface water but still reflect a similar geographic distribution: relatively higher concentrations at ocean margins, especially underneath upwelling areas, and the lowest concentrations underneath central gyre areas. These distributions within the clear water reflect surface-water biogenic productivity, lateral injection of particles from shelf areas and surface circulation patterns and require that the combination of downward vertical and horizontal transport processes of particles retain this pattern throughout the upper water column. Below clear water, the distribution of standing crops of suspended particulate concentrations in the lower water column are presented. The integration of mass of all particles per unit area (gross particulate standing crop) reflects a relative distribution similar to that at the surface and at clear water levels, superimposed on which is the strong imprint of boundary currents along the western margins of the Atlantic. Reducing the gross particulate standing crop by the integral of the concentration of clear water yields a net particulate standing crop. The distribution of this reflects primarily the interaction of circulating abyssal waters with the ocean bottom, i.e. a strong nepheloid layer which is coincident with western boundary currents and which diminishes in intensity equatorward. The resuspended particulate loads in the nepheloid layer of the

  8. Methane distributions and transports in the nocturnal boundary layer at a rural station

    NASA Astrophysics Data System (ADS)

    Schäfer, Klaus; Zeeman, Matthias; Brosy, Caroline; Münkel, Christoph; Fersch, Benjamin; Mauder, Matthias; Emeis, Stefan

    2016-10-01

    To investigate the methane distributions and transports, the role of related atmospheric processes by determination of vertical profiles of wind, turbulence, temperature and humidity as well as nocturnal boundary layer (NBL) height and the quantification of methane emissions at local and plot scale the so-called ScaleX-campaign was performed in a pre-alpine observatory in Southern Germany from 01 June until 31 July 2015. The following measurements from the ground up to the free troposphere were performed: layering of the atmosphere by a ceilometer (Vaisala CL51); temperature, wind, turbulence profiles from 50 m up to 500 m by a Radio-Acoustic Sounding System (RASS, Metek GmbH); temperature, humidity profiles in situ by a hexacopter; methane farm emissions by two open-path laser spectrometers (Boreal GasFinder2); methane concentrations in situ (Los Gatos DLT-100) with tubes in 0.3 m agl and 5 sampling heads; and methane soil emissions by a big chamber (10 m length, 2.60 m width, up to 0.61 m height) with a plastic cover. The methane concentrations near the surface show a daily variation with a maximum and a frequent double-peak structure during night-time. Analysis of the variation of the nocturnal methane concentration together with the hexacopter and RASS data indicates that the first peak in the nocturnal methane concentration is probably due to local cooling and stabilization which keeps the methane emissions from the soil near the ground. The second peak seems to be due to advection of methane-enriched air which had formed in the environment of the nearby farm yards. These dairy farm emissions were determined by up-wind and down-wind open-path concentration measurements, turbulence data from an EC station nearby and Backward Lagrangian Simulation (WindTrax software). The methane fluxes at plot scale (big chamber) are characterized by emissions at water saturated grassland patches, by an exponential decrease of these emissions during grassland drying, and by an

  9. Climatology of wintertime long-distance transport of surface-layer air masses arriving urban Beijing in 2001-2012

    NASA Astrophysics Data System (ADS)

    Chen, Bin; Xiang-De, XU

    2017-02-01

    In this study, the FLEXPART-WRF coupled modeling system is used to conduct 12-year Lagrangian modeling over Beijing, China, for the winters of 2001-2012. Based on large trajectory tracking ensembles, the long-range air transport properties, in terms of geographic source regions within the atmospheric planetary boundary layer (PBL) and large-scale ventilation, and its association with air quality levels were quantified from a climatological perspective. The results show the following: (1) The air masses residing in the near-surface layer over Beijing potentially originate from broader atmospheric boundary-layer regions, which cover vast areas with the backward tracking time elapsed. However, atmospheric transport from northeastern China and, to a lesser extent, from the surrounding regions of Beijing is important. (2) The evolution of air quality over Beijing is negatively correlated with large-scale ventilation conditions, particularly at a synoptic timescale. Thus, the simple but robust backward-trajectory ventilation (BV) index defined in this study could facilitate operational forecasting of severe air pollution events. (3) By comparison, the relatively short-range transport occurring over transport timescales of less than 3 days from southern and southeastern Beijing and its surrounding areas plays a vital role in the formation of severe air pollution events during the wintertime. (4) Additionally, an interannual trend analysis suggests that the geographic sources and ventilation conditions also changed, at least over the last decade, corresponding to the strength variability of the winter East Asian monsoon.

  10. Low-cost copper complexes as p-dopants in solution processable hole transport layers

    SciTech Connect

    Kellermann, Renate; Taroata, Dan; Maltenberger, Anna; Hartmann, David; Schmid, Guenter; Brabec, Christoph J.

    2015-09-07

    We demonstrate the usage of the Lewis-acidic copper(II)hexafluoroacetylacetonate (Cu(hfac){sub 2}) and copper(II)trifluoroacetylacetonate (Cu(tfac){sub 2}) as low-cost p-dopants for conductivity enhancement of solution processable hole transport layers based on small molecules in organic light emitting diodes (OLEDs). The materials were clearly soluble in mixtures of environmentally friendly anisole and xylene and spin-coated under ambient atmosphere. Enhancements of two and four orders of magnitude, reaching 4.0 × 10{sup −11} S/cm with a dopant concentration of only 2 mol% Cu(hfac){sub 2} and 1.5 × 10{sup −9} S/cm with 5 mol% Cu(tfac){sub 2} in 2,2′,7,7′-tetra(N,N-ditolyl)amino-9,9-spiro-bifluorene (spiro-TTB), respectively, were achieved. Red light emitting diodes were fabricated with reduced driving voltages and enhanced current and power efficiencies (8.6 lm/W with Cu(hfac){sub 2} and 5.6 lm/W with Cu(tfac){sub 2}) compared to the OLED with undoped spiro-TTB (3.9 lm/W). The OLED with Cu(hfac){sub 2} doped spiro-TTB showed an over 8 times improved LT{sub 50} lifetime of 70 h at a starting luminance of 5000 cd/m{sup 2}. The LT{sub 50} lifetime of the reference OLED with PEDOT:PSS was only 8 h. Both non-optimized OLEDs were operated at similar driving voltage and power efficiency.

  11. A way for studying the impact of PEDOT:PSS interface layer on carrier transport in PCDTBT:PC{sub 71}BM bulk hetero junction solar cells by electric field induced optical second harmonic generation measurement

    SciTech Connect

    Ahmad, Zubair Abdullah, Shahino Mah; Sulaiman, Khaulah; Taguchi, Dai; Iwamoto, Mitsumasa

    2015-04-28

    Electric-field-induced optical second-harmonic generation (EFISHG) measurement was employed to study the impact of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) interface layer on the carrier transport mechanism of the PCDTBT:PC{sub 71}BM bulk heterojunction (BHJ) organic solar cells (OSCs). We revealed that the electric fields in the PCDTBT and PC{sub 71}BM were allowed to be measured individually by choosing fundamental laser wavelengths of 1000 nm and 1060 nm, respectively, in dark and under illumination. The results showed that the direction of the internal electric fields in the PCDTBT:PC{sub 71}BM BHJ layer is reversed by introducing the PEDOT:PSS layer, and this results in longer electron transport time in the BHJ layer. We conclude that TR-EFISHG can be used as a novel way for studying the impact of interfacial layer on the transport of electrons and holes in the bulk-heterojunction OSCs.

  12. Effects of physical processes on structure and transport of thin zooplankton layers in the coastal ocean

    USGS Publications Warehouse

    McManus, M.A.; Cheriton, O.M.; Drake, P.J.; Holliday, D.V.; Storlazzi, C.D.; Donaghay, P.L.; Greenlaw, C.F.

    2005-01-01

    Thin layers of plankton are recurrent features in a variety of coastal systems. These layers range in thickness from a few centimeters to a few meters. They can extend horizontally for kilometers and have been observed to persist for days. Densities of organisms found within thin layers are far greater than those above or below the layer, and as a result, thin layers may play an important role in the marine ecosystem. The paramount objective of this study was to understand the physical processes that govern the dynamics of thin layers of zooplankton in the coastal ocean. We deployed instruments to measure physical processes and zooplankton distribution in northern Monterey Bay; during an 11 d period of persistent upwelling-favorable winds, 7 thin zooplankton layers were observed. These zooplankton layers persisted throughout daylight hours, but were observed to dissipate during evening hours. These layers had an average vertical thickness of 1.01 m. No layers were found in regions where the Richardson number was <0.25. In general, when the Richardson number is <0.25 the water column is unstable, and incapable of supporting thin layers. Thin zooplankton layers were also located in regions of reduced flow. In addition, our observations show that the vertical depth distribution of thin zooplankton layers is modulated by high-frequency internal waves, with periods of 18 to 20 min. Results from this study clearly show an association between physical structure, physical processes and the presence of thin zooplankton layers in Monterey Bay. With this new understanding we may identify other coastal regions that have a high probability of supporting thin layers. ?? Inter-Research 2005.

  13. Electrical Transport and Low-Frequency Noise in Chemical Vapor Deposited Single-Layer MoS2 Devices

    DTIC Science & Technology

    2014-03-18

    vapor deposited (CVD) single-layer molybdenum disulfide ( MoS2 ) based back-gated field-effect transistors (FETs). Electrical characterization and LFN...measurements were conducted on MoS2 FETs with Al2O3 top-surface passivation. We also studied the effect of top-surface passivation etching on the...is unlimited. Electrical transport and low-frequency noise in chemical vapor deposited single-layer MoS2 devices The views, opinions and/or findings

  14. 41 CFR 109-38.301-1.50 - Authorization for transportation between residence and place of employment.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... ENERGY PROPERTY MANAGEMENT REGULATIONS AVIATION, TRANSPORTATION, AND MOTOR VEHICLES 38-MOTOR EQUIPMENT... eligible for prior approval of home-to-work motor vehicle use which would be appropriate to include in...

  15. 41 CFR 109-38.301-1.50 - Authorization for transportation between residence and place of employment.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... ENERGY PROPERTY MANAGEMENT REGULATIONS AVIATION, TRANSPORTATION, AND MOTOR VEHICLES 38-MOTOR EQUIPMENT... eligible for prior approval of home-to-work motor vehicle use which would be appropriate to include in...

  16. Transport driven plasma flows in the scrape-off layer of ADITYA Tokamak in different orientations of magnetic field

    SciTech Connect

    Sangwan, Deepak; Jha, Ratneshwar; Brotankova, Jana; Gopalkrishna, M. V.

    2014-06-15

    Parallel plasma flows in the scrape-off layer of ADITYA tokamak are measured in two orientations of total magnetic field. In each orientation, experiments are carried out by reversing the direction of the toroidal magnetic field and the plasma current. The transport-driven component is determined by averaging flow Mach numbers, measured in two directions of the toroidal magnetic field and the plasma current for the same orientation. It is observed that there is a significant transport-driven component in the measured flow and the component depends on the field orientation.

  17. Impact of compression on gas transport in non-woven gas diffusion layers of high temperature polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Froning, Dieter; Yu, Junliang; Gaiselmann, Gerd; Reimer, Uwe; Manke, Ingo; Schmidt, Volker; Lehnert, Werner

    2016-06-01

    Gas transport in non-woven gas diffusion layers of a high-temperature polymer electrolyte fuel cell was calculated with the Lattice Boltzmann method. The underlying micro structure was taken from two sources. A real micro structure was analyzed in the synchrotron under the impact of a compression mask mimicking the channel/rib structure of a flow field. Furthermore a stochastic geometry model based on synchrotron X-ray tomography studies was applied. The effect of compression is included in the stochastic model. Gas transport in these micro structures was simulated and the impact of compression was analyzed. Fiber bundles overlaying the micro structure were identified which affect the homogeneity of the gas flow. There are significant deviations between the impact of compression on effective material properties for this type of gas diffusion layers and the Kozeny-Carman equation.

  18. Facile thiol-ene thermal crosslinking reaction facilitated hole-transporting layer for highly efficient and stable perovskite solar cells

    SciTech Connect

    Li, Zhong'an; Zhu, Zonglong; Chueh, Chu -Chen; Luo, Jingdong; Jen, Alex K. -Y.

    2016-08-08

    A crosslinked organic hole-transporting layer (HTL) is developed to realize highly efficient and stable perovskite solar cells via a facile thiol-ene thermal reaction. This crosslinked HTL not only facilitates hole extraction from perovskites, but also functions as an effective protective barrier. Lastly, a high-performance (power conversion efficiency: 18.3%) device is demonstrated to show respectable photo and thermal stability without encapsulation.

  19. An experimental study of the turbulent boundary layer on a transport wing in subsonic and transonic flow

    NASA Technical Reports Server (NTRS)

    Spaid, Frank W.; Roos, Frederick W.; Hicks, Raymond M.

    1990-01-01

    The upper surface boundary layer on a transport wing model was extensively surveyed with miniature yaw probes at a subsonic and a transonic cruise condition. Additional data were obtained at a second transonic test condition, for which a separated region was present at mid-semispan, aft of mid-chord. Significant variation in flow direction with distance from the surface was observed near the trailing edge except at the wing root and tip. The data collected at the transonic cruise condition show boundary layer growth associated with shock wave/boundary layer interaction, followed by recovery of the boundary layer downstream of the shock. Measurements of fluctuating surface pressure and wingtip acceleration were also obtained. The influence of flow field unsteadiness on the boundary layer data is discussed. Comparisons among the data and predictions from a variety of computational methods are presented. The computed predictions are in reasonable agreement with the experimental data in the outboard regions where 3-D effects are moderate and adverse pressure gradients are mild. In the more highly loaded mid-span region near the trailing edge, displacement thickness growth was significantly underpredicted, except when unrealistically severe adverse pressure gradients associated with inviscid calculations were used to perform boundary layer calculations.

  20. Dependence of light-emitting and photovoltaic properties of dual-function organic diodes on carrier-transporting layers

    NASA Astrophysics Data System (ADS)

    Lee, Ho-Nyeon; Choi, Mun Soo

    2013-10-01

    Dual-function photovoltaic organic light-emitting diodes (PVOEDs) have been investigated in this work. The PVOLEDs emit light when forward biased and generate electricity when backward biased. This dual function is based on the half-gap junction composed of 5,6,11,12-tetraphenylnaphthacene (rubrene) and C 60. The device structure was optimized through experiments using various organic materials for the electron-transporting layer (ETL) and electron-injection layer (EIL). Through this work, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), C 60 and LiF were selected as the ETL, electron-accepting layer and EIL, respectively. Using this device structure, we obtained a current efficiency of 0.27 cd/A for the light-emitting mode and a power-conversion efficiency of 1.95% for the photovoltaic mode.

  1. Application of Hybrid Fillers for Improving the Through-Plane Heat Transport in Graphite Nanoplatelet-Based Thermal Interface Layers

    PubMed Central

    Tian, Xiaojuan; Itkis, Mikhail E.; Haddon, Robert C.

    2015-01-01

    The in-plane alignment of graphite nanoplatelets (GNPs) in thin thermal interface material (TIM) layers suppresses the though-plane heat transport thus limiting the performance of GNPs in the geometry normally required for thermal management applications. Here we report a disruption of the GNP in-plane alignment by addition of spherical microparticles. The degree of GNP alignment was monitored by measurement of the anisotropy of electrical conductivity which is extremely sensitive to the orientation of high aspect ratio filler particles. Scanning Electron Microscopy images of TIM layer cross-sections confirmed the suppression of the in-plane alignment. The hybrid filler formulations reported herein resulted in a synergistic enhancement of the through-plane thermal conductivity of GNP/Al2O3 and GNP/Al filled TIM layers confirming that the control of GNP alignment is an important parameter in the development of highly efficient GNP and graphene-based TIMs. PMID:26279183

  2. Investigation of chemical properties and transport phenomena associated with pollutants in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Holmes, Heather A.

    Under the Clean Air Act, the U.S. Environmental Protection Agency is required to determine which air pollutants are harmful to human health, then regulate, monitor and establish criteria levels for these pollutants. To accomplish this and for scientific advancement, integration of knowledge from several disciplines is required including: engineering, atmospheric science, chemistry and public health. Recently, a shift has been made to establish interdisciplinary research groups to better understand the atmospheric processes that govern the transport of pollutants and chemical reactions of species in the atmospheric boundary layer (ABL). The primary reason for interdisciplinary collaboration is the need for atmospheric processes to be treated as a coupled system, and to design experiments that measure meteorological, chemical and physical variables simultaneously so forecasting models can be improved (i.e., meteorological and chemical process models). This dissertation focuses on integrating research disciplines to provide a more complete framework to study pollutants in the ABL. For example, chemical characterization of particulate matter (PM) and the physical processes governing PM distribution and mixing are combined to provide more comprehensive data for source apportionment. Data from three field experiments were utilized to study turbulence, meteorological and chemical parameters in the ABL. Two air quality field studies were conducted on the U.S./Mexico border. The first was located in Yuma, AZ to investigate the spatial and temporal variability of PM in an urban environment and relate chemical properties of ambient aerosols to physical findings. The second border air quality study was conducted in Nogales, Sonora, Mexico to investigate the relationship between indoor and outdoor air quality in order to better correlate cooking fuel types and home activities to elevated indoor PM concentrations. The final study was executed in southern Idaho and focused on

  3. Investigating the source, transport, and isotope composition of water vapor in the planetary boundary layer

    NASA Astrophysics Data System (ADS)

    Griffis, Timothy J.; Wood, Jeffrey D.; Baker, John M.; Lee, Xuhui; Xiao, Ke; Chen, Zichong; Welp, Lisa R.; Schultz, Natalie M.; Gorski, Galen; Chen, Ming; Nieber, John

    2016-04-01

    Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle - an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understand feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor at a very tall tower (185 m) in the upper Midwest, United States, to diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotope observations for this region. Several simple isotope models and cross-wavelet analyses were used to assess the importance of the Rayleigh distillation process, evaporation, and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a large seasonal amplitude (mean monthly δ18Ov ranged from -40.2 to -15.9 ‰ and δ2Hv ranged from -278.7 to -113.0 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio when considering the entire hourly data set. However, this relation was strongly modulated by evaporation and PBL entrainment processes at timescales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess (dv) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that evaporation often leads changes in dv, confirming that it is a potential tracer of regional evaporation. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional evaporation. However, isoforcing calculations and mixing model analyses for high PBL water vapor mixing ratio events ( > 25 mmol mol-1) indicate that regional evaporation can account

  4. Investigating the source, transport, and isotope composition of water vapor in the planetary boundary layer

    DOE PAGES

    Griffis, Timothy J.; Wood, Jeffrey D.; Baker, John M.; ...

    2016-04-25

    Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle – an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understand feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor at a very tall tower (185 m) in the upper Midwest, United States, to diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotopemore » observations for this region. Several simple isotope models and cross-wavelet analyses were used to assess the importance of the Rayleigh distillation process, evaporation, and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a large seasonal amplitude (mean monthly δ18Ov ranged from –40.2 to –15.9 ‰ and δ2Hv ranged from –278.7 to –113.0 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio when considering the entire hourly data set. However, this relation was strongly modulated by evaporation and PBL entrainment processes at timescales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess (dv) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that evaporation often leads changes in dv, confirming that it is a potential tracer of regional evaporation. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional evaporation. However, isoforcing calculations and mixing model analyses for high PBL water vapor mixing ratio events ( > 25 mmol mol–1) indicate that regional

  5. Investigating the source, transport, and isotope composition of water vapor in the planetary boundary layer

    SciTech Connect

    Griffis, Timothy J.; Wood, Jeffrey D.; Baker, John M.; Lee, Xuhui; Xiao, Ke; Chen, Zichong; Welp, Lisa R.; Schultz, Natalie M.; Gorski, Galen; Chen, Ming; Nieber, John

    2016-04-25

    Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle – an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understand feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor at a very tall tower (185 m) in the upper Midwest, United States, to diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotope observations for this region. Several simple isotope models and cross-wavelet analyses were used to assess the importance of the Rayleigh distillation process, evaporation, and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a large seasonal amplitude (mean monthly δ18Ov ranged from –40.2 to –15.9 ‰ and δ2Hv ranged from –278.7 to –113.0 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio when considering the entire hourly data set. However, this relation was strongly modulated by evaporation and PBL entrainment processes at timescales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess (dv) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that evaporation often leads changes in dv, confirming that it is a potential tracer of regional evaporation. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional evaporation. However, isoforcing calculations and mixing model analyses for

  6. Transportation as a Factor in the Delivery of Rural Manpower Services in Public Service Employment. Final Report.

    ERIC Educational Resources Information Center

    Lawrence, Frederick T.; And Others

    The Vermont Experimental and Demonstration Manpower Pilot Project placed low income unemployed individuals in wage subsidized job slots in public and nonprofit agencies, anticipating that the work experience and related job skills gained would enable them to acquire nonsubsidized employment. A quantitative analysis is presented of 196 Special Work…

  7. Model Simulation of Ionosphere Electron Density with Dynamic Transportation and Mechanism of Sporadic E Layers in Lower Part of Ionosphere

    NASA Astrophysics Data System (ADS)

    Lin, Y. C.; Chu, Y. H.

    2015-12-01

    There are many physical theories responsible for explanation the generation mechanism of sporadic E (Es) plasma irregularities. In middle latitude, it's generally believed that sporadic E layers occur in vertical ion convergent areas driven by horizontal neutral wind shear. The sporadic E layers appear characteristic of abundant metallic ion species (i.e., Fe+, Mg+, Na+), that lifetime are longer than molecular ions by a factor of several orders, have been demonstrated by rocket-borne mass spectrometric measurements. On the basic of the GPS Radio Occultation (RO), using the scintillations of the GPS signal-to-noise ratio and intense fluctuation of excess phase, the global and seasonal sporadic E layers occurrence rates could be retrieved. In our previous study we found there is averaged 10 kilometers shift in height between the COSMIC-retrieved sporadic E layer occurrence rate and the sporadic E occurrence rate modeled from considering the convergence/divergence of Fe+ vertical flux. There are many reasons that maybe result in the altitude differences, e.g., tidal wind with phase shift, electric field driven force, iron species distributions. In this research, the quantitative analyses for electric field drives Es layers translations in vertical direction are presented. The tidal wind driven sporadic E layers have been simulating by modeling several nonmetallic ions (O+(4S), O+(2D), O+(2p), N+, N2+, O2+, NO+) and metallic ions (Fe+, FeO2+, FeN2+, FeO+) with wind shear transportation. The simulation result shows the Fe+ particles accumulate at zonal wind shear convergent regions and form the thin sporadic E layers. With the electric field taking into account, the whole shape of sporadic E layers vertical shift 2~5 km that depending on what magnitude and direction of electric field is added.

  8. Methane transport from the active layer to lakes in the Arctic using Toolik Lake, Alaska, as a case study.

    PubMed

    Paytan, Adina; Lecher, Alanna L; Dimova, Natasha; Sparrow, Katy J; Kodovska, Fenix Garcia-Tigreros; Murray, Joseph; Tulaczyk, Slawomir; Kessler, John D

    2015-03-24

    Methane emissions in the Arctic are important, and may be contributing to global warming. While methane emission rates from Arctic lakes are well documented, methods are needed to quantify the relative contribution of active layer groundwater to the overall lake methane budget. Here we report measurements of natural tracers of soil/groundwater, radon, and radium, along with methane concentration in Toolik Lake, Alaska, to evaluate the role active layer water plays as an exogenous source for lake methane. Average concentrations of methane, radium, and radon were all elevated in the active layer compared with lake water (1.6 × 10(4) nM, 61.6 dpm⋅m(-3), and 4.5 × 10(5) dpm⋅m(-3) compared with 1.3 × 10(2) nM, 5.7 dpm⋅m(-3), and 4.4 × 10(3) dpm⋅m(-3), respectively). Methane transport from the active layer to Toolik Lake based on the geochemical tracer radon (up to 2.9 g⋅m(-2)⋅y(-1)) can account for a large fraction of methane emissions from this lake. Strong but spatially and temporally variable correlations between radon activity and methane concentrations (r(2) > 0.69) in lake water suggest that the parameters that control methane discharge from the active layer also vary. Warming in the Arctic may expand the active layer and increase the discharge, thereby increasing the methane flux to lakes and from lakes to the atmosphere, exacerbating global warming. More work is needed to quantify and elucidate the processes that control methane fluxes from the active layer to predict how this flux might change in the future and to evaluate the regional and global contribution of active layer water associated methane inputs.

  9. Methane transport from the active layer to lakes in the Arctic using Toolik Lake, Alaska, as a case study

    PubMed Central

    Paytan, Adina; Lecher, Alanna L.; Dimova, Natasha; Sparrow, Katy J.; Kodovska, Fenix Garcia-Tigreros; Murray, Joseph; Tulaczyk, Slawomir; Kessler, John D.

    2015-01-01

    Methane emissions in the Arctic are important, and may be contributing to global warming. While methane emission rates from Arctic lakes are well documented, methods are needed to quantify the relative contribution of active layer groundwater to the overall lake methane budget. Here we report measurements of natural tracers of soil/groundwater, radon, and radium, along with methane concentration in Toolik Lake, Alaska, to evaluate the role active layer water plays as an exogenous source for lake methane. Average concentrations of methane, radium, and radon were all elevated in the active layer compared with lake water (1.6 × 104 nM, 61.6 dpm⋅m−3, and 4.5 × 105 dpm⋅m−3 compared with 1.3 × 102 nM, 5.7 dpm⋅m−3, and 4.4 × 103 dpm⋅m−3, respectively). Methane transport from the active layer to Toolik Lake based on the geochemical tracer radon (up to 2.9 g⋅m−2⋅y−1) can account for a large fraction of methane emissions from this lake. Strong but spatially and temporally variable correlations between radon activity and methane concentrations (r2 > 0.69) in lake water suggest that the parameters that control methane discharge from the active layer also vary. Warming in the Arctic may expand the active layer and increase the discharge, thereby increasing the methane flux to lakes and from lakes to the atmosphere, exacerbating global warming. More work is needed to quantify and elucidate the processes that control methane fluxes from the active layer to predict how this flux might change in the future and to evaluate the regional and global contribution of active layer water associated methane inputs. PMID:25775530

  10. Solution-Processed Hybrid Light-Emitting Devices Comprising TiO2 Nanorods and WO3 Layers as Carrier-Transporting Layers.

    PubMed

    Tsai, Tsung-Yan; Yan, Po-Ruei; Yang, Sheng-Hsiung

    2016-12-01

    The goal of this research is to prepare inverted light-emitting devices with improved performance by combining titanium dioxide (TiO2) nanorods and tungsten trioxide (WO3) layer. TiO2 nanorods with different lengths were established directly on the fluorine-doped tin oxide (FTO) substrates by the hydrothermal method. The prepared TiO2 nanorods with lengths shorter than 200 nm possess transmittance higher than 80% in the visible range. Inverted light-emitting devices with the configuration of FTO/TiO2 nanorods/ionic PF/MEH-PPV/PEDOT:PSS/WO3/Au were constructed. The best device based on 100-nm-height TiO2 nanorods achieved a max brightness of 4493 cd/m(2) and current efficiency of 0.66 cd/A, revealing much higher performance compared with those using TiO2 compact layer or nanorods with longer lengths as electron-transporting layers.

  11. Morphology and Transport Properties of Novel Polymer Nanocomposites Resulted from Melt Processing of Polyvinylacetate Substrates Coated with Layer-by-Layer Assemblies

    NASA Astrophysics Data System (ADS)

    Soltani, Iman; Spontak, Richard J.

    Novel polymer nanocomposites (PNCs) were processed through layer-by-layer (LBL) deposition of clay and polyethylene terephthalate ionomer layers on polyvinylacetate (PVAc) substrates, followed by repetitive melt pressing of coated samples to crush LBL assemblies into the polymeric matrix. The increase in the clay content in resulted PNCs prepared through similar LBL coatings, relative to previously studied hydrophobic polystyrene-based nanocomposites, postulated superiority of PVAc, with relatively higher hydrophilicity, to interact with LBL assemblies. Also, these PNCs showed relatively good barrier improvement against transport of oxygen and carbon dioxide gases, proposing the scavenging effect of LBL assemblies crushed portions as highly tortuous labyrinths with high aspect ratios, comprising edge-edge flocculated exfoliated clay platelets, observed through transmission electron micrographs. However, combinative morphological investigations through optical microscopy, x-ray diffractometry, and transmission electron microscopy proposed low global dispersion of clay throughout polymeric matrix, conjecturing insufficient intensity of stress applied through cyclic melt pressing, and/or slight thermal degradation of samples via extended times of processing at high temperatures.

  12. A bill to require the Transportation Security Administration to comply with the Uniformed Services Employment and Reemployment Rights Act.

    THOMAS, 112th Congress

    Sen. Lieberman, Joseph I. [ID-CT

    2011-12-14

    12/14/2011 Read twice and referred to the Committee on Commerce, Science, and Transportation. (text of measure as introduced: CR S8604) (All Actions) Notes: For further action, see H.R.3670, which became Public Law 112-171 on 8/16/2012. Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

  13. Effects of disorder state and interfacial layer on thermal transport in copper/diamond system

    SciTech Connect

    Sinha, V.; Gengler, J. J.; Muratore, C.; Spowart, J. E.

    2015-02-21

    The characterization of Cu/diamond interface thermal conductance (h{sub c}) along with an improved understanding of factors affecting it are becoming increasingly important, as Cu-diamond composites are being considered for electronic packaging applications. In this study, ∼90 nm thick Cu layers were deposited on synthetic and natural single crystal diamond substrates. In several specimens, a Ti-interface layer of thickness ≤3.5 nm was sputtered between the diamond substrate and the Cu top layer. The h{sub c} across Cu/diamond interfaces for specimens with and without a Ti-interface layer was determined using time-domain thermoreflectance. The h{sub c} is ∼2× higher for similar interfacial layers on synthetic versus natural diamond substrate. The nitrogen concentration of synthetic diamond substrate is four orders of magnitude lower than natural diamond. The difference in nitrogen concentration can lead to variations in disorder state, with a higher nitrogen content resulting in a higher level of disorder. This difference in disorder state potentially can explain the variations in h{sub c}. Furthermore, h{sub c} was observed to increase with an increase of Ti-interface layer thickness. This was attributed to an increased adhesion of Cu top layer with increasing Ti-interface layer thickness, as observed qualitatively in the current study.

  14. O2-Filled Swimbladder Employs Monocarboxylate Transporters for the Generation of O2 by Lactate-Induced Root Effect Hemoglobin

    PubMed Central

    Umezawa, Takahiro; Kato, Akira; Ogoshi, Maho; Ookata, Kayoko; Munakata, Keijiro; Yamamoto, Yoko; Islam, Zinia; Doi, Hiroyuki; Romero, Michael F.; Hirose, Shigehisa

    2012-01-01

    The swimbladder volume is regulated by O2 transfer between the luminal space and the blood In the swimbladder, lactic acid generation by anaerobic glycolysis in the gas gland epithelial cells and its recycling through the rete mirabile bundles of countercurrent capillaries are essential for local blood acidification and oxygen liberation from hemoglobin by the “Root effect.” While O2 generation is critical for fish flotation, the molecular mechanism of the secretion and recycling of lactic acid in this critical process is not clear. To clarify molecules that are involved in the blood acidification and visualize the route of lactic acid movement, we analyzed the expression of 17 members of the H+/monocarboxylate transporter (MCT) family in the fugu genome and found that only MCT1b and MCT4b are highly expressed in the fugu swimbladder. Electrophysiological analyses demonstrated that MCT1b is a high-affinity lactate transporter whereas MCT4b is a low-affinity/high-conductance lactate transporter. Immunohistochemistry demonstrated that (i) MCT4b expresses in gas gland cells together with the glycolytic enzyme GAPDH at high level and mediate lactic acid secretion by gas gland cells, and (ii) MCT1b expresses in arterial, but not venous, capillary endothelial cells in rete mirabile and mediates recycling of lactic acid in the rete mirabile by solute-specific transcellular transport. These results clarified the mechanism of the blood acidification in the swimbladder by spatially organized two lactic acid transporters MCT4b and MCT1b. PMID:22496829

  15. Downscaling the Sample Thickness to Sub-Micrometers by Employing Organic Photovoltaic Materials as a Charge-Generation Layer in the Time-of-Flight Measurement

    PubMed Central

    Liu, Shun-Wei; Lee, Chih-Chien; Su, Wei-Cheng; Yuan, Chih-Hsien; Lin, Chun-Feng; Chen, Kuan-Ting; Shu, Yi-Sheng; Li, Ya-Ze; Su, Tsung-Hao; Huang, Bo-Yao; Chang, Wen-Chang; Liu, Yu-Hsuan

    2015-01-01

    Time-of-flight (TOF) measurements typically require a sample thickness of several micrometers for determining the carrier mobility, thus rendering the applicability inefficient and unreliable because the sample thicknesses are orders of magnitude higher than those in real optoelectronic devices. Here, we use subphthalocyanine (SubPc):C70 as a charge-generation layer (CGL) in the TOF measurement and a commonly hole-transporting layer, N,N’-diphenyl-N,N’-bis(1,1’-biphenyl)-4,4’-diamine (NPB), as a standard material under test. When the NPB thickness is reduced from 2 to 0.3 μm and with a thin 10-nm CGL, the hole transient signal still shows non-dispersive properties under various applied fields, and thus the hole mobility is determined accordingly. Only 1-μm NPB is required for determining the electron mobility by using the proposed CGL. Both the thicknesses are the thinnest value reported to data. In addition, the flexibility of fabrication process of small molecules can deposit the proposed CGL underneath and atop the material under test. Therefore, this technique is applicable to small-molecule and polymeric materials. We also propose a new approach to design the TOF sample using an optical simulation. These results strongly demonstrate that the proposed technique is valuable tool in determining the carrier mobility and may spur additional research in this field. PMID:25999238

  16. Propagation and fluid transport of fault-related mineral veins in layered rocks

    NASA Astrophysics Data System (ADS)

    Brenner, S. L.; Gudmundsson, A.

    2003-04-01

    Mineral veins are normally hydrofractures, that is fractures generated by internal fluid pressure, formed by geothermal water. The generation of hydrofractures is, together with the formation of shear fractures, presumably one of the main mechanisms for developing permeability in fractured reservoirs, such as those for petroleum, gas, geothermal or groundwater. We present field data on calcite veins related to normal faults in a Liassic limestone-shale sequence from Kilve at the Somerset Coast, SW-England. The veins are injected into the limestone layers along the faults; most veins are subvertical extension fractures restricted to these layers. Such arrested, stratabound fractures are common in layered fluid reservoirs. When fractures are stratabound, the temporary permeability in a heterogeneous fluid reservoir is much lower than when fractures propagate through many layers (non-stratabound). Numerical models on the effects of mechanical layering, such as abrupt changes in layer stiffness, indicate that soft layers can contribute to the arrest of hydrofractures such as mineral veins. For example, at Kilve, comparatively few veins dissect the soft shale layers. These veins are commonly thinner in the shale than in the limestone layers, partly because they commonly follow inclined shear fractures and are thus inclined to the minimum compressive principal stress. By contrast, numerical models of the aperture variation of vertical hydrofractures with the fluid overpressure as the only loading indicate that the apertures of hydrofractures tend to be smaller in stiff layers than in soft layers. Aperture changes between layers with different mechanical properties suggest that in certain layers in a fluid reservoir preferential flow (flow channelling) may occur. Using analytical models based on the vein length/thickness ratios in the limestone layers, we calculate the fluid overpressure at the time of vein formation. The veins at Kilve presumably formed during normal

  17. Effects of Surface Heat Flux Anomalies on Stratification, Convective Growth and Vertical Transport within the Saharan Boundary Layer

    NASA Astrophysics Data System (ADS)

    Huang, Qian; Marsham, John; Parker, Doug; Tian, Wenshou; Grams, Christian; Cuesta, Juan; Flamant, Cyrille

    2010-05-01

    The very large surface sensible and very low latent heat fluxes in the Sahara desert lead to its unusually deep, almost dry-adiabatic boundary layer, that often reaches 6 km. This is often observed to consist of a shallow convective boundary layer (CBL) with a near neutral residual layer above (the Saharan Residual Layer, or SRL). It has been shown that the SRL can be both spatially extensive and persist throughout the day. Multiple near-neutral layers are frequently observed within the SRL, or within the SAL, each with a different water vapour and/or dust content, and each separated by a weak lid (e.g., Figure 1). A local maximum in not only relative humidity, but also water vapour mixing ratio (WVMR) is often seen at the top of the SRL or SAL. This structure suggests that in some locations, at some times, convection from the surface is mixing the full depth of the Saharan boundary layer, but in most locations and times this is not the case, and varying horizontal advection leads to the multiple layering observed. During the GERBILS (GERB Intercomparison of Longwave and Shortwave radiation) field campaign in the Sahara, coherent couplings were observed between surface albedo, CBL air temeperatures and CBL winds. Using two cases based on observations from GERBILS, large eddy model (LEM) simulations have been used to investigate the effects of surface flux anomalies on the growth of the summertime Saharan CBL into the Saharan Residual layer (SRL) above, and transport from the CBL into the SRL. Hot surface anomalies generated updraughts and convergence in the CBL that increased transport from the CBL into the SRL. The induced subsidence in regions away from the anomalies inhibited growth of the CBL there. If the domain-averaged surface fluxes were kept constant this led to a shallower, cooler CBL. If fluxes outside the anomalies were kept constant, so that stronger anomalies led to increased domain-averaged fluxes, this gave a warmer, shallower CBL. These effects

  18. Charge transport dependent high open circuit voltage tandem organic photovoltaic cells with low temperature deposited HATCN-based charge recombination layers.

    PubMed

    Wei, Huai-Xin; Zu, Feng-Shuo; Li, Yan-Qing; Chen, Wen-Cheng; Yuan, Yi; Tang, Jian-Xin; Fung, Man-Keung; Lee, Chun-Sing; Noh, Yong-Young

    2016-02-07

    Mechanisms of charge transport between the interconnector and its neighboring layers in tandem organic photovoltaic cells have been systematically investigated by studying electronic properties of the involving interfaces with photoelectron spectroscopies and performance of the corresponding devices. The results show that charge recombination occurs at HATCN and its neighboring hole transport layers which can be deposited at low temperature. The hole transport layer plays an equal role to the interconnector itself. These insights provide guidance for the identification of new materials and the device architecture for high performance devices.

  19. Significantly improved photovoltaic performance in polymer bulk heterojunction solar cells with graphene oxide /PEDOT:PSS double decked hole transport layer

    PubMed Central

    Rafique, Saqib; Abdullah, Shahino Mah; Shahid, Muhammad Mehmood; Ansari, Mohammad Omaish; Sulaiman, Khaulah

    2017-01-01

    This work demonstrates the high performance graphene oxide (GO)/PEDOT:PSS doubled decked hole transport layer (HTL) in the PCDTBT:PC71BM based bulk heterojunction organic photovoltaic device. The devices were tested on merits of their power conversion efficiency (PCE), reproducibility, stability and further compared with the devices with individual GO or PEDOT:PSS HTLs. Solar cells employing GO/PEDOT:PSS HTL yielded a PCE of 4.28% as compared to either of individual GO or PEDOT:PSS HTLs where they demonstrated PCEs of 2.77 and 3.57%, respectively. In case of single GO HTL, an inhomogeneous coating of ITO caused the poor performance whereas PEDOT:PSS is known to be hygroscopic and acidic which upon direct contact with ITO reduced the device performance. The improvement in the photovoltaic performance is mainly ascribed to the increased charge carriers mobility, short circuit current, open circuit voltage, fill factor, and decreased series resistance. The well matched work function of GO and PEDOT:PSS is likely to facilitate the charge transportation and an overall reduction in the series resistance. Moreover, GO could effectively block the electrons due to its large band-gap of ~3.6 eV, leading to an increased shunt resistance. In addition, we also observed the improvement in the reproducibility and stability. PMID:28084304

  20. Significantly improved photovoltaic performance in polymer bulk heterojunction solar cells with graphene oxide /PEDOT:PSS double decked hole transport layer

    NASA Astrophysics Data System (ADS)

    Rafique, Saqib; Abdullah, Shahino Mah; Shahid, Muhammad Mehmood; Ansari, Mohammad Omaish; Sulaiman, Khaulah

    2017-01-01

    This work demonstrates the high performance graphene oxide (GO)/PEDOT:PSS doubled decked hole transport layer (HTL) in the PCDTBT:PC71BM based bulk heterojunction organic photovoltaic device. The devices were tested on merits of their power conversion efficiency (PCE), reproducibility, stability and further compared with the devices with individual GO or PEDOT:PSS HTLs. Solar cells employing GO/PEDOT:PSS HTL yielded a PCE of 4.28% as compared to either of individual GO or PEDOT:PSS HTLs where they demonstrated PCEs of 2.77 and 3.57%, respectively. In case of single GO HTL, an inhomogeneous coating of ITO caused the poor performance whereas PEDOT:PSS is known to be hygroscopic and acidic which upon direct contact with ITO reduced the device performance. The improvement in the photovoltaic performance is mainly ascribed to the increased charge carriers mobility, short circuit current, open circuit voltage, fill factor, and decreased series resistance. The well matched work function of GO and PEDOT:PSS is likely to facilitate the charge transportation and an overall reduction in the series resistance. Moreover, GO could effectively block the electrons due to its large band-gap of ~3.6 eV, leading to an increased shunt resistance. In addition, we also observed the improvement in the reproducibility and stability.

  1. Steady-state and time-dependent modelling of parallel transport in the scrape-off layer

    NASA Astrophysics Data System (ADS)

    Havlíčková, E.; Fundamenski, W.; Naulin, V.; Nielsen, A. H.; Zagórski, R.; Seidl, J.; Horáček, J.

    2011-06-01

    The one-dimensional fluid code SOLF1D has been used for modelling of plasma transport in the scrape-off layer (SOL) along magnetic field lines, both in steady state and under transient conditions that arise due to plasma turbulence. The presented work summarizes results of SOLF1D with attention given to transient parallel transport which reveals two distinct time scales due to the transport mechanisms of convection and diffusion. Time-dependent modelling combined with the effect of ballooning shows propagation of particles along the magnetic field line with Mach number up to M ≈ 1 and supersonic transport when plasma-neutral interactions are not present. Asymmetric heat and particle fluxes are analysed for a case with poloidally asymmetric radial outflow (ballooning) and for a radial outflow with parallel momentum (rotation). In addition, parallel damping of the density and electron temperature calculated in SOLF1D is compared with the approximative model used in the turbulence code ESEL both for steady-state and turbulent SOL. Dynamics of the parallel transport are investigated for a simple transient event simulating the propagation of particles and energy to the targets from a blob passing across the flux tube at the outboard midplane and for more complex time-dependent data provided by ESEL.

  2. Efficiency improvement of organic solar cells by tuning hole transport layer with germanium oxide.

    PubMed

    Choi, Moon Kee; Kim, Ju-Hyung; Yoon, Hyunsik; Tahk, Dongha; Seo, Soonmin; Shin, Kyusoon; Lee, Hong H

    2012-01-01

    Improving optical property is critical for optimizing the power conversion efficiency of organic solar cells. In the present research, we show that modification of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) layer with GeO2 leads to 15% improvement of power conversion efficiency in a polymer solar cells through enhancement of short circuit currents. Modified PEDOT:PSS layer with optimized concentration of GeO2 assists active layer absorbing much light by playing a role of optical spacer. Using AFM and grazing incidence X-ray diffraction (GIXD) data, we also present the evidence that an addition of GeO2 does not affect crystallinity of active layer.

  3. Defect chemistry and charge transport properties of mixed bismuth oxides with layer lattices

    NASA Astrophysics Data System (ADS)

    Palanduz, Ahmet Cengiz

    Undoped SrBi2Ta2O9 (SBT) displays a broad ionic conductivity plateau and p-type conductivity at lower and higher oxygen activities, respectively, which is consistent with an oxide that has a net acceptor center concentration of 1--2%. Undoped SrBi2Nb 2O9 (SBN) displays n-type conductivity behaviour that is consistent with that of an oxide which has a net donor center concentration of 1--2% SBN also undergoes an unprecedented abrupt conductivity rise at very low oxygen activities. Recent structural studies indicate that there is substantial place exchange between Bi3+ and Sr2+ in the alternating layers of the structure and that there is significant distortion of Ta (Nb) octahedral environment. In a crystal with a 'homogeneous' unit cell the cation place exchange would be self-compensating. Defect chemistry studies suggest that in SBN and SBT, where there are two distinct layers, Bi ˙Sr and Sr 'Bi are locally compensated by strontium vacancies in the perovskite-like layers and by oxygen vacancies in the bismuth oxide layers, respectively. In SBT, where electron density is low due to its large band gap, oxygen vacancies in the bismuth oxide layers dominate the total conductivity. In SBN, which due to its easier reducibility is expected to have a lower band gap, n-type conductivity prevails. SBN displays thermally activated electron mobility. Superior ferroelectric fatigue resistance of SBT is attributed to the following: (i) large band gap and (ii) heavy donor presence suppress electron and oxygen vacancy formation in the perovskite-like layers; (iii) electron mobility is thermally activated; (iv) oxygen vacancies in the bismuth oxide layers can not enter the perovskite-like layer. Thus there are no mobile defects that could drift to the domain walls and pin their movement.

  4. Lidar Characterization of Boundary Layer Transport and Mixing for Estimating Urban-Scale Greenhouse Gas Emissions

    NASA Astrophysics Data System (ADS)

    Hardesty, R. Michael; Brewer, W. Alan; Sandberg, Scott P.; Weickmann, Ann M.; Shepson, Paul B.; Cambaliza, Maria; Heimburger, Alexie; Davis, Kenneth J.; Lauvaux, Thomas; Miles, Natasha L.; Sarmiento, Daniel P.; Deng, A. J.; Gaudet, Brian; Karion, Anna; Sweeney, Colm; Whetstone, James

    2016-06-01

    A compact commercial Doppler lidar has been deployed in Indianapolis for two years to measure wind profiles and mixing layer properties as part of project to improve greenhouse measurements from large area sources. The lidar uses vertical velocity variance and aerosol structure to measure mixing layer depth. Comparisons with aircraft and the NOAA HRDL lidar generally indicate good performance, although sensitivity might be an issue under low aerosol conditions.

  5. Interface architecture between TiO2/perovskite, perovskite/hole transport layer, and perovskite grain boundary(Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hayase, Shuzi; Hirotani, Daisuke; Moriya, Masahiro; Ogomi, Yuhei; Shen, Qing; Yoshino, Kenji; Toyoda, Taro

    2016-09-01

    surface was much more passivated by PbCl2 than by PbI2. This may explain partially the high efficiency when the perovskite layer was fabricated by one step process consisting of MAI and PbCl2 solution. We also observed that the crystal size increased with an increase in the amount of Cl anion which of course one of the explanation of the high efficiency. The interface of hole transport layer/perovskite layer, and between perovskite layer /perovskite layer (grain boundary) was passivated with organic amines. The passivation was also effective for increasing Voc and Jsc. This was explained by the results of transient absorption spectroscopy that the charge recombination time between hole transport payer/perovskite layer increased from 0.3 μsec to 60 μsec.

  6. Solute transport in a single fracture involving an arbitrary length decay chain with rock matrix comprising different geological layers.

    PubMed

    Mahmoudzadeh, Batoul; Liu, Longcheng; Moreno, Luis; Neretnieks, Ivars

    2014-08-01

    A model is developed to describe solute transport and retention in fractured rocks. It accounts for advection along the fracture, molecular diffusion from the fracture to the rock matrix composed of several geological layers, adsorption on the fracture surface, adsorption in the rock matrix layers and radioactive decay-chains. The analytical solution, obtained for the Laplace-transformed concentration at the outlet of the flowing channel, can conveniently be transformed back to the time domain by the use of the de Hoog algorithm. This allows one to readily include it into a fracture network model or a channel network model to predict nuclide transport through channels in heterogeneous fractured media consisting of an arbitrary number of rock units with piecewise constant properties. More importantly, the simulations made in this study recommend that it is necessary to account for decay-chains and also rock matrix comprising at least two different geological layers, if justified, in safety and performance assessment of the repositories for spent nuclear fuel.

  7. Lattice and transport properties of the misfit-layered oxide thermoelectric Ca3Co4O9 from first principles

    NASA Astrophysics Data System (ADS)

    Rebola, Alejandro; Klie, Robert; Zapol, Peter; Ogut, Serdar

    2013-03-01

    The misfit-layered oxide Ca3Co4O9 (CCO) has recently been the subject of many experimental and some theoretical investigations due to its remarkable thermoelectric properties. CCO is composed of two incommensurate subsystems, a distorted rocksalt-type Ca2CoO3 layer sandwiched between hexagonal CoO2 layers. Taking into account that the composition ratio between these subsystems is very close to the golden mean, which is the limit of the sequence of the ratios of consecutive Fibonacci numbers F (n) , we model CCO from first principles[1] by using rational approximants of composition [Ca2CoO3]2 F (n)[CoO2]2 F (n + 1). In the present study, we use 3/2 and 5/3 rational approximants and PBE+U computations to calculate the ab initio phonon dispersion curves, related thermal properties, as well as ab initio electronic transport properties such as DC conductivity and thermopower within the relaxation time approximation by applying the Boltzmann transport theory. Results are compared with available experimental data and potential routes for increasing the thermopower of CCO are discussed.

  8. Hierarchically Structured Hole Transport Layers of Spiro-OMeTAD and Multiwalled Carbon Nanotubes for Perovskite Solar Cells.

    PubMed

    Lee, Jiyong; Menamparambath, Mini Mol; Hwang, Jae-Yeol; Baik, Seunghyun

    2015-07-20

    The low electrical conductivity of spiro-OMeTAD hole transport layers impedes further enhancements of the power conversion efficiency (PCE) of perovskite solar cells. We embedded multiwalled carbon nanotubes (MWNTs) in spiro-OMeTAD (spiro-OMeTAD/MWNTs) to increase carrier mobility and conductivity. However, direct electrical contact between CH3 NH3 PbI3 and the MWNTs created pathways for undesirable back-electron transfer, owing to the large work function of MWNTs, limiting enhancements of the PCE. A hierarchical structure of pure spiro-OMeTAD and spiro-OMeTAD/MWNTs was designed to block back-electron transfer and fully exploit the enhanced charge transport of spiro-OMeTAD/MWNTs. The enhanced fill factor, short-circuit current density, open-circuit voltage, and PCE (15.1 %) were achieved by using this hierarchical hole transport layer structure (MWNT concentration=2 wt %). The perovskite solar cells were fabricated by a low-temperature solution process, further decreasing their per-Watt cost.

  9. Improved color purity and electroluminescent efficiency obtained by modulating thicknesses and evaporation rates of hole block and electron transport layers

    NASA Astrophysics Data System (ADS)

    Zhou, Liang; Deng, Ruiping; Feng, Jing; Li, Xiaona; Li, Xiyan; Zhang, Hongjie

    2011-01-01

    In this work, a series of electroluminescent (EL) devices based on trivalent europium (Eu3+) complex Eu(TTA)3phen (TTA = thenoyltrifluoroacetone, phen = 1,10-phenanthroline) were fabricated by selecting 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) and tris(8-hydroxyquinoline) aluminum (Alq3) as hole block and electron transport materials, respectively. Interestingly, we found the transport of electrons decreases gradually with increasing thicknesses and evaporation rates of BCP and Alq3 layers. Analyzing carrier distribution and EL spectra, we conclude that appropriately modulating the thicknesses and evaporation rates is an efficient way to decrease the accumulation of electrons in HBL, thus suppressing the EL of hole block material. On the other hand, decreasing the transport of electrons can also facilitate the balance of holes and electrons on Eu(TTA)3phen molecules, thus further enhancing the EL efficiency. As a result, pure Eu3+ emission with the efficiency as high as 8.49 cd/A was realized by controlling the thicknesses and evaporation rates of BCP and Alq3 layers to be 30 nm and 0.10 nm/s, 40 nm and 0.10 nm/s, respectively.

  10. On statistical properties of transport barriers in magnetospheric and laboratory boundary layers

    NASA Astrophysics Data System (ADS)

    Savin, Sergey; Budaev, Viacheslav; Zeleniy, Lev; Amata, Ermanno; Kozak, Lyudmila; Buechner, Joerg; Romanov, Stanislav; Blecki, Jan; Balikhin, Michael A.; Lezhen, Liudmila

    Transport barriers at outer magnetospheric boundaries have a dualistic feature: being effec-tive in limitation of the momentum transfer and serving as an effective obstacle, they display the super-diffusive statistical properties and provide partial exchange of plasmas. In tokamaks namely the statistical properties of transport barriers look to control the high and low heating modes, while small size of the barriers prevents their detailed studies. We tend to use magne-tospheric multi-spacecraft data to improve understanding of common physics in the transport barriers. We show examples from Interball-1 and Cluster with quiet solar wind. The inherently turbulent crossings in this equilibrium cases demonstrate ion heating namely in the transport barrier. It agrees with the kinetic energy transformation into the thermal one inside the barrier -the turbulent dissipation of the magnetosheath kinetic energy -as simultaneously with the ion temperature rise, the general velocity component drops from its model prediction. In sense of the momentum transfer the transport turbulent barriers effectively isolate the high-alti-tude cusp from fast-flowing magnetosheath. Contrary to that, several examples from different missions and different plasma parameters demonstrate the super-diffusive transport character. The individual coherent structures inside the barriers, which we call Alfvenic 'collapsons', have similar scale chains to that of high kinetic plasma pressure jets, showing mutual interaction features. We think that the interacting jets and barriers, accompanying by classic and/ or micro-reconnection, have rather general importance for the plasma physics, and for understanding of turbulence and mechanisms of magnetic field generation. These coherent, nonlinear interacting structures, most probably, provide intermittency a long-range correlations inside the transport barriers (c.f. blobs and flow spikes in fusion devices). We recall that very high-amplitude turbulence in

  11. Moisture Transport, Lower-Tropospheric Stability, and Decoupling of Cloud-Topped Boundary Layers.

    NASA Astrophysics Data System (ADS)

    Bretherton, Christopher S.; Wyant, Matthew C.

    1997-01-01

    Decoupling during the `Lagrangian' evolution of a cloud-topped boundary layer advected equatorward by the trade winds in an idealized eastern subtropical ocean is studied using a mixed-layer model (MLM). The sea surface temperature is gradually warmed while the free tropospheric sounding remains unchanged, causing the boundary layer to deepen, the surface relative humidity to decrease, and surface latent heat fluxes to increase. Diurnally averaged insolation is used.For entrainment closures in which entrainment rate is related to a large-eddy convective velocity scale w(, the MLM predicts an increasingly prominent layer of negative buoyancy fluxes below cloud base as the sea surface temperature warms. Decoupling of the mixed layer can be inferred when the MLM-predicted negative buoyancy fluxes become too large for the internal circulations to sustain. The authors show that decoupling is mainly driven by an increasing ratio of the surface latent heat flux to the net radiative cooling in the cloud, and derive a decoupling criterion based on this ratio. Other effects such as drizzle, the vertical distribution of radiative cooling in the cloud, and sensible heat fluxes, also affect decoupling but are shown to be less important in typical subtropical boundary layers. A comparison of MLM results with a companion numerical study with a cloud-resolving model shows that the decoupling process is similar and the same decoupling criterion applies. A regional analysis of decoupling using Lagrangian trajectories based on summertime northeast Pacific climatology predicts decoupling throughout the subtropical stratocumulus region except in coastal zones where the boundary layer is under 750 m deep.A `flux-partitioning' entrainment closure, in which the entrainment rate is chosen to maintain a specified ratio of some measure of negative subcloud buoyancy fluxes to positive buoyancy fluxes within the cloud and near the surface, was also considered. By construction, such an MLM

  12. Polyoxometalate-based layered structures for charge transport control in molecular devices.

    PubMed

    Douvas, Antonios M; Makarona, Eleni; Glezos, Nikos; Argitis, Panagiotis; Mielczarski, Jerzy A; Mielczarski, Ela

    2008-04-01

    Hybrid organic-inorganic films consisted of molecular layers of a Keggin-structure polyoxometalate (POM: 12-tungstophosphoric acid, H(3)PW(12)O(40)) and 1,12-diaminododecane (DD) on 3-aminopropyl triethoxysilane (APTES)-modified silicon surface, fabricated via the layer-by-layer (LBL) self-assembly method are evaluated as molecular materials for electronic devices. The effect of the fabrication process parameters, including primarily compositions of deposition solutions, on the structural characteristics of the POM-based multilayers was studied extensively with a combination of spectroscopic methods (UV, FTIR, and XPS). Well-characterized POM-based films (both single-layers and multilayers) in a controlled and reproducible way were obtained. The conduction mechanisms in single-layered and multilayered structures were elucidated by the electrical characterization of the produced films supported by the appropriate theoretical analysis. Fowler-Nordheim (FN) tunneling and percolation mechanisms were encountered in good correlation with the structural characteristics of the films encouraging further investigation on the use of these materials in electronic and, in particular, in memory devices.

  13. Model representations of aerosol layers transported from North America over the Atlantic Ocean during the Two-Column Aerosol Project

    NASA Astrophysics Data System (ADS)

    Fast, Jerome D.; Berg, Larry K.; Zhang, Kai; Easter, Richard C.; Ferrare, Richard A.; Hair, Johnathan W.; Hostetler, Chris A.; Liu, Ying; Ortega, Ivan; Sedlacek, Arthur; Shilling, John E.; Shrivastava, Manish; Springston, Stephen R.; Tomlinson, Jason M.; Volkamer, Rainer; Wilson, Jacqueline; Zaveri, Rahul A.; Zelenyuk, Alla

    2016-08-01

    The ability of the Weather Research and Forecasting model with chemistry (WRF-Chem) version 3.7 and the Community Atmosphere Model version 5.3 (CAM5) in simulating profiles of aerosol properties is quantified using extensive in situ and remote sensing measurements from the Two-Column Aerosol Project (TCAP) conducted during July of 2012. TCAP was supported by the U.S. Department of Energy's Atmospheric Radiation Measurement program and was designed to obtain observations within two atmospheric columns; one fixed over Cape Cod, Massachusetts, and the other several hundred kilometers over the ocean. The performance is quantified using most of the available aircraft and surface measurements during July, and 2 days are examined in more detail to identify the processes responsible for the observed aerosol layers. The higher-resolution WRF-Chem model produced more aerosol mass in the free troposphere than the coarser-resolution CAM5 model so that the fraction of aerosol optical thickness above the residual layer from WRF-Chem was more consistent with lidar measurements. We found that the free troposphere layers are likely due to mean vertical motions associated with synoptic-scale convergence that lifts aerosols from the boundary layer. The vertical displacement and the time period associated with upward transport in the troposphere depend on the strength of the synoptic system and whether relatively high boundary layer aerosol concentrations are present where convergence occurs. While a parameterization of subgrid scale convective clouds applied in WRF-Chem modulated the concentrations of aerosols aloft, it did not significantly change the overall altitude and depth of the layers.

  14. Model representations of aerosol layers transported from North America over the Atlantic Ocean during the Two-Column Aerosol Project

    SciTech Connect

    Fast, Jerome D.; Berg, Larry K.; Zhang, Kai; Easter, Richard C.; Ferrare, Richard A.; Hair, Johnathan W.; Hostetler, Chris A.; Liu, Ying; Ortega, Ivan; Sedlacek, Arthur; Shilling, John E.; Shrivastava, Manish; Springston, Stephen R.; Tomlinson, Jason M.; Volkamer, Rainer; Wilson, Jacqueline; Zaveri, Rahul A.; Zelenyuk, Alla

    2016-08-22

    The ability of the Weather Research and Forecasting model with chemistry (WRF-Chem) version 3.7 and the Community Atmosphere Model version 5.3 (CAM5) in simulating profiles of aerosol properties is quantified using extensive in situ and remote sensing measurements from the Two Column Aerosol Project (TCAP) conducted during July of 2012. TCAP was supported by the U.S. Department of Energy’s Atmospheric Radiation Measurement program and was designed to obtain observations within two atmospheric columns; one fixed over Cape Cod, Massachusetts and the other several hundred kilometers over the ocean. The performance is quantified using most of the available aircraft and surface measurements during July, and two days are examined in more detail to identify the processes responsible for the observed aerosol layers. The higher resolution WRF-Chem model produced more aerosol mass in the free troposphere than the coarser resolution CAM5 model so that the fraction of aerosol optical thickness above the residual layer from WRF-Chem was more consistent with lidar measurements. We found that the free troposphere layers are likely due to mean vertical motions associated with synoptic-scale convergence that lifts aerosols from the boundary layer. The vertical displacement and the time period associated with upward transport in the troposphere depend on the strength of the synoptic system and whether relatively high boundary layer aerosol concentrations are present where convergence occurs. While a parameterization of subgrid scale convective clouds applied in WRF-Chem modulated the concentrations of aerosols aloft, it did not significantly change the overall altitude and depth of the layers.

  15. Model representations of aerosol layers transported from North America over the Atlantic Ocean during the Two-Column Aerosol Project

    SciTech Connect

    Fast, Jerome D.; Berg, Larry K.; Zhang, Kai; Easter, Richard C.; Ferrare, Richard A.; Hair, Johnathan W.; Hostetler, Chris A.; Liu, Ying; Ortega, Ivan; Sedlacek, Arthur; Shilling, John E.; Shrivastava, Manish; Springston, Stephen R.; Tomlinson, Jason M.; Volkamer, Rainer; Wilson, Jacqueline; Zaveri, Rahul A.; Zelenyuk, Alla

    2016-08-22

    The ability of the Weather Research and Forecasting model with chemistry (WRF-Chem) version 3.7 and the Community Atmosphere Model version 5.3 (CAM5) in simulating profiles of aerosol properties is quantified using extensive in situ and remote sensing measurements from the Two-Column Aerosol Project (TCAP) conducted during July of 2012. TCAP was supported by the U.S. Department of Energy's Atmospheric Radiation Measurement program and was designed to obtain observations within two atmospheric columns; one fixed over Cape Cod, Massachusetts, and the other several hundred kilometers over the ocean. The performance is quantified using most of the available aircraft and surface measurements during July, and 2 days are examined in more detail to identify the processes responsible for the observed aerosol layers. The higher-resolution WRF-Chem model produced more aerosol mass in the free troposphere than the coarser-resolution CAM5 model so that the fraction of aerosol optical thickness above the residual layer from WRF-Chem was more consistent with lidar measurements. We found that the free troposphere layers are likely due to mean vertical motions associated with synoptic-scale convergence that lifts aerosols from the boundary layer. The vertical displacement and the time period associated with upward transport in the troposphere depend on the strength of the synoptic system and whether relatively high boundary layer aerosol concentrations are present where convergence occurs. In conclusion, while a parameterization of subgrid scale convective clouds applied in WRF-Chem modulated the concentrations of aerosols aloft, it did not significantly change the overall altitude and depth of the layers.

  16. Model representations of aerosol layers transported from North America over the Atlantic Ocean during the Two-Column Aerosol Project

    DOE PAGES

    Fast, Jerome D.; Berg, Larry K.; Zhang, Kai; ...

    2016-08-22

    The ability of the Weather Research and Forecasting model with chemistry (WRF-Chem) version 3.7 and the Community Atmosphere Model version 5.3 (CAM5) in simulating profiles of aerosol properties is quantified using extensive in situ and remote sensing measurements from the Two-Column Aerosol Project (TCAP) conducted during July of 2012. TCAP was supported by the U.S. Department of Energy's Atmospheric Radiation Measurement program and was designed to obtain observations within two atmospheric columns; one fixed over Cape Cod, Massachusetts, and the other several hundred kilometers over the ocean. The performance is quantified using most of the available aircraft and surface measurementsmore » during July, and 2 days are examined in more detail to identify the processes responsible for the observed aerosol layers. The higher-resolution WRF-Chem model produced more aerosol mass in the free troposphere than the coarser-resolution CAM5 model so that the fraction of aerosol optical thickness above the residual layer from WRF-Chem was more consistent with lidar measurements. We found that the free troposphere layers are likely due to mean vertical motions associated with synoptic-scale convergence that lifts aerosols from the boundary layer. The vertical displacement and the time period associated with upward transport in the troposphere depend on the strength of the synoptic system and whether relatively high boundary layer aerosol concentrations are present where convergence occurs. In conclusion, while a parameterization of subgrid scale convective clouds applied in WRF-Chem modulated the concentrations of aerosols aloft, it did not significantly change the overall altitude and depth of the layers.« less

  17. Solution-Processable Ionic Liquid as an Independent or Modifying Electron Transport Layer for High-Efficiency Perovskite Solar Cells.

    PubMed

    Wu, Qiliang; Zhou, Weiran; Liu, Qing; Zhou, Pengcheng; Chen, Tao; Lu, Yalin; Qiao, Qiquan; Yang, Shangfeng

    2016-12-21

    Inorganic metal oxide, especially TiO2, has been commonly used as an electron transport layer (ETL) in regular-structure (n-i-p) planar heterojunction perovskite solar cells (PHJ-PSCs) but generally suffers from high electron recombination rate and incompatibility with low-temperature solution processability. Herein, by applying an ionic liquid (IL, 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM]PF6)) as either a TiO2-modifying interlayer or an independent ETL, we investigated systematically IL interface engineering for PHJ-PSCs. Upon spin-coating [EMIM]PF6-IL onto TiO2 ETL as a modification layer, the average power conversion efficiency (PCE) of CH3NH3PbI3 PHJ-PSC devices reaches 18.42 ± 0.65%, which dramatically surpasses that based on commonly used TiO2 ETL (14.20 ± 0.43%), and the highest PCE (19.59%) is almost identical to that of the record PCE for planar CH3NH3PbI3 PSCs (19.62%) reported very recently. On the other hand, by applying [EMIM]PF6-IL as an independent ETL, we achieved an average PCE of 13.25 ± 0.55%, and the highest PCE (14.39%) approaches that obtained for PHJ-PSCs based on independent TiO2 ETL (14.96%). Both IL interface engineering methods reveal the effective electron transport of [EMIM]PF6-IL. The effects of [EMIM]PF6-IL on the surface morphology, crystallinity, and optical absorption of the perovskite film and the interface between the perovskite layer and substrate were investigated and compared with the case of independent TiO2 ETL, revealing the role of [EMIM]PF6-IL in efficient electron transport.

  18. Optimized inverted polymer solar cells incorporating Cs2CO3-doped C60 as electron transport layer

    NASA Astrophysics Data System (ADS)

    Barbot, A.; Lucas, B.; Di Bin, C.; Ratier, B.; Aldissi, M.

    2013-05-01

    An efficient charge transfer between co-sublimed cesium carbonate (Cs2CO3) and fullerene C60 provides an n-type material exhibiting an electrical conductivity above 1 S/cm. This type of doped layers can be used in organic optoelectronic devices to reduce ohmic losses at organic-electrode interfaces. We report here an analysis of inverted polymer-based solar cells incorporating Cs2CO3 doped C60 as electron transport layer (ETL). The optimization of both dopant concentration and thickness resulted in a maximum efficiency of 3.79% compared to 3% for similar devices using undoped C60 as ETL and 2.13% for devices without any ETL.

  19. Solution-Processed Nb:SnO2 Electron Transport Layer for Efficient Planar Perovskite Solar Cells.

    PubMed

    Ren, Xiaodong; Yang, Dong; Yang, Zhou; Feng, Jiangshan; Zhu, Xuejie; Niu, Jinzhi; Liu, Yucheng; Zhao, Wangen; Liu, Shengzhong Frank

    2017-01-25

    Electron transport layer (ETL), facilitating charge carrier separation and electron extraction, is a key component in planar perovskite solar cells (PSCs). We developed an effective ETL using low-temperature solution-processed Nb-doped SnO2 (Nb:SnO2). Compared to the pristine SnO2, the power conversion efficiency of PSCs based on Nb:SnO2 ETL is raised to 17.57% from 15.13%. The splendid performance is attributed to the excellent optical and electronic properties of the Nb:SnO2 material, such as smooth surface, high electron mobility, appropriate electrical conductivity, therefore making a better growth platform for a high quality perovskite absorber layer. Experimental analyses reveal that the Nb:SnO2 ETL significantly enhances the electron extraction and effectively suppresses charge recombination, leading to improved solar cell performance.

  20. Impact of the electron-transport layer on the performance of solution-processed small-molecule organic solar cells.

    PubMed

    Long, Guankui; Wan, Xiangjian; Kan, Bin; Hu, Zhicheng; Yang, Xuan; Zhang, Yi; Zhang, Mingtao; Wu, Hongbing; Huang, Fei; Su, Shijian; Cao, Yong; Chen, Yongsheng

    2014-08-01

    Although the performance of polymer solar cells has been improved significantly recently through careful optimization with different interlayers for the same materials, more improvement is needed in this respect for small-molecule-based solar cells, particularly for the electron-transport layers (ETLs). In this work, three different solution-processed ETLs, PFN, ZnO nanoparticles, and LiF, were investigated and compared in the performance of small-molecule-based devices, and power conversion efficiencies (PCEs) of 8.32, 7.30, and 7.38% were achieved, respectively. The mechanism for the ETL-induced enhancement has been studied, and different ETLs have a significantly different impact on the device performance. The clearly improved performance of PFN is attributed to the combination of reduced bimolecular recombination and increased effective photon absorption in the active layer.

  1. Formation of BaSi{sub 2} heterojunction solar cells using transparent MoO{sub x} hole transport layers

    SciTech Connect

    Du, W.; Takabe, R.; Baba, M.; Takeuchi, H.; Toko, K.; Hara, K. O.; Usami, N.; Suemasu, T.

    2015-03-23

    Heterojunction solar cells that consist of 15 nm thick molybdenum trioxide (MoO{sub x}, x < 3) as a hole transport layer and 600 nm thick unpassivated or passivated n-BaSi{sub 2} layers were demonstrated. Rectifying current-voltage characteristics were observed when the surface of BaSi{sub 2} was exposed to air. When the exposure time was decreased to 1 min, an open circuit voltage of 200 mV and a short circuit current density of 0.5 mA/cm{sup 2} were obtained under AM1.5 illumination. The photocurrent density under a reverse bias voltage of −1 V reached 25 mA/cm{sup 2}, which demonstrates the significant potential of BaSi{sub 2} for solar cell applications.

  2. Formation of BaSi2 heterojunction solar cells using transparent MoOx hole transport layers

    NASA Astrophysics Data System (ADS)

    Du, W.; Takabe, R.; Baba, M.; Takeuchi, H.; Hara, K. O.; Toko, K.; Usami, N.; Suemasu, T.

    2015-03-01

    Heterojunction solar cells that consist of 15 nm thick molybdenum trioxide (MoOx, x < 3) as a hole transport layer and 600 nm thick unpassivated or passivated n-BaSi2 layers were demonstrated. Rectifying current-voltage characteristics were observed when the surface of BaSi2 was exposed to air. When the exposure time was decreased to 1 min, an open circuit voltage of 200 mV and a short circuit current density of 0.5 mA/cm2 were obtained under AM1.5 illumination. The photocurrent density under a reverse bias voltage of -1 V reached 25 mA/cm2, which demonstrates the significant potential of BaSi2 for solar cell applications.

  3. Simplified organic light-emitting devices utilizing ultrathin electron transport layers and new insights on their roles.

    PubMed

    Zhang, Yingjie; Wang, Qi; Aziz, Hany

    2014-02-12

    The lifetime of organic light-emitting devices (OLEDs) can be limited by exciton-polaron interactions at the organic/organic interfaces. In this work, we show that simplified phosphorescent OLEDs (PHOLEDs) are subjected to this phenomenon. By reducing the exciton concentration at the emission layer (EML)/electron transport layer (ETL) interface by means of increasing the EML thickness, hence broadening the recombination zone, the device lifetime can indeed be improved. Moreover, we report a device that displays the same extended lifetime, but with only 1 nm thin ETL. Studying the roles of this ultrathin ETL in increasing device efficiency reveals that electron injection, hole blocking, and triplet exciton blocking are all important factors. Hole blocking of the ETL can be achieved by highest occupied molecular orbitals level mismatch, where a layer thickness as low as 1 nm is sufficient, or by low hole mobility of the ETL, where a much thicker layer is required (> 5 nm). This ultrathin ETL also enables devices with only 50 nm total organic stacks, which is more than 50% thinner than the typical. This structure opens up opportunities for much shorter processing time and lower fabrication costs in the OLED industry.

  4. Transitions metal dichalcogenides: Growth, fermiology studies, and few-layered transport properties

    NASA Astrophysics Data System (ADS)

    Rhodes, Daniel

    Transition metal dichalcogenides (TMDs or TMDCs) have garnered much interest recently due to their weakly layered structures, allowing for mechanical exfoliation down to a single atomic layer. As such, it is pertinent to re-examine the bulk properties of these materials in order to completely understand and predict what is happening in the few-layered limit. A large majority of these systems were first investigated in the 1950s and 1960s. As such, many of the current growth methods rely on these reports, making new growth techniques for lowering defects of importance as well. In this thesis, both topics are taken into consideration and discussed, though the latter remains to be investigated in much more detail and should be the work of future research efforts. (Abstract shortened by ProQuest.).

  5. Quantum-Transport Characteristics of a p-n Junction on Single-Layer TiS3.

    PubMed

    Iyikanat, Fadil; Senger, Ramazan T; Peeters, Francois M; Sahin, Hasan

    2016-12-05

    By using density functional theory and non-equilibrium Green's function-based methods, we investigated the electronic and transport properties of a TiS3 monolayer p-n junction. We constructed a lateral p-n junction on a TiS3 monolayer using Li and F adatoms. An applied bias voltage caused significant variability in the electronic and transport properties of the TiS3 p-n junction. In addition, the spin-dependent current-voltage characteristics of the constructed TiS3 p-n junction were analyzed. Important device characteristics were found, such as negative differential resistance and rectifying diode behaviors for spin-polarized currents in the TiS3 p-n junction. These prominent conduction properties of the TiS3 p-n junction offer remarkable opportunities for the design of nanoelectronic devices based on a recently synthesized single-layered material.

  6. Phase-coherent electron transport in (Zn, Al)O{sub x} thin films grown by atomic layer deposition

    SciTech Connect

    Saha, D. E-mail: pmisra@rrcat.gov.in; Misra, P. E-mail: pmisra@rrcat.gov.in; Ajimsha, R. S.; Joshi, M. P.; Kukreja, L. M.

    2014-11-24

    A clear signature of disorder induced quantum-interference phenomena leading to phase-coherent electron transport was observed in (Zn, Al)O{sub x} thin films grown by atomic layer deposition. The degree of static-disorder was tuned by varying the Al concentration through periodic incorporation of Al{sub 2}O{sub 3} sub-monolayer in ZnO. All the films showed small negative magnetoresistance due to magnetic field suppressed weak-localization effect. The temperature dependence of phase-coherence length (l{sub φ}∝T{sup −3/4}), as extracted from the magnetoresistance measurements, indicated electron-electron scattering as the dominant dephasing mechanism. The persistence of quantum-interference at relatively higher temperatures up to 200 K is promising for the realization of ZnO based phase-coherent electron transport devices.

  7. Detailed analysis of charge transport in amorphous organic thin layer by multiscale simulation without any adjustable parameters

    PubMed Central

    Uratani, Hiroki; Kubo, Shosei; Shizu, Katsuyuki; Suzuki, Furitsu; Fukushima, Tatsuya; Kaji, Hironori

    2016-01-01

    Hopping-type charge transport in an amorphous thin layer composed of organic molecules is simulated by the combined use of molecular dynamics, quantum chemical, and Monte Carlo calculations. By explicitly considering the molecular structure and the disordered intermolecular packing, we reasonably reproduce the experimental hole and electron mobilities and their applied electric field dependence (Poole–Frenkel behaviour) without using any adjustable parameters. We find that the distribution of the density-of-states originating from the amorphous nature has a significant impact on both the mobilities and Poole–Frenkel behaviour. Detailed analysis is also provided to reveal the molecular-level origin of the charge transport, including the origin of Poole–Frenkel behaviour. PMID:28000728

  8. Detailed analysis of charge transport in amorphous organic thin layer by multiscale simulation without any adjustable parameters

    NASA Astrophysics Data System (ADS)

    Uratani, Hiroki; Kubo, Shosei; Shizu, Katsuyuki; Suzuki, Furitsu; Fukushima, Tatsuya; Kaji, Hironori

    2016-12-01

    Hopping-type charge transport in an amorphous thin layer composed of organic molecules is simulated by the combined use of molecular dynamics, quantum chemical, and Monte Carlo calculations. By explicitly considering the molecular structure and the disordered intermolecular packing, we reasonably reproduce the experimental hole and electron mobilities and their applied electric field dependence (Poole–Frenkel behaviour) without using any adjustable parameters. We find that the distribution of the density-of-states originating from the amorphous nature has a significant impact on both the mobilities and Poole–Frenkel behaviour. Detailed analysis is also provided to reveal the molecular-level origin of the charge transport, including the origin of Poole–Frenkel behaviour.

  9. High-Efficiency Perovskite Solar Cells Employing a S,N-Heteropentacene-based D-A Hole-Transport Material.

    PubMed

    Bi, Dongqin; Mishra, Amaresh; Gao, Peng; Franckevičius, Marius; Steck, Christopher; Zakeeruddin, Shaik Mohammed; Nazeeruddin, Mohammad Khaja; Bäuerle, Peter; Grätzel, Michael; Hagfeldt, Anders

    2016-03-08

    We developed a new donor-π-acceptor-type hole-transport material (HTMs) incorporating S,N-heteropentacene as π-spacer, triarylamine as donor, and dicyanovinylene as acceptor. In addition to appropriate frontier molecular orbital energies, the new HTM showed high photo absorptivity in the visible region. Without the use of p-dopants, solution-processed mixed perovskite devices using the HTM achieved power conversion efficiencies of up to 16.9% and high photocurrents of up to 22.2 mA cm(-2). These results demonstrate that heteroacene can be an excellent building block to prepare alternative HTMs for perovskite solar cells and hold promise for further advancement through fine-tuning the molecular structure.

  10. The Turbulent Boundary Layer: An Experimental Study of the Transport of Momentum and Heat with the Effect of Roughness

    DTIC Science & Technology

    1975-05-01

    COMMERCE TIlE TURBULENT BOUNDARY LAYER: AN EXPERIMENTAL STUDY OF THE TRANSPORT OF 1 M(IMENTUM AND HEAT W\\ ITHl THE EFFECT OF ROUGIINESS I • • 11. . 1 ...1975 NATIONAL TECHNICAL INFORMATION SERVICE US D.l’. 2 C....51.3’ tt.VA. 22t51 II Unclassified - SECURTY CLAISSIFICATION OF TUIS PAGE 1 --. 0- 1 ...EoI1*’*dl REPORT DOCUMENTATION4 PAGE BEOECMLEIGFR REPO T N] 1 :ER:.10VT ACCESSION NO. 3 RsECIPIENT Sl CATALOG NUMBER 4 TITLE (sI4S.btIIII.) 5. TYPE OF

  11. Well-Defined Nanostructured, Single-Crystalline TiO2 Electron Transport Layer for Efficient Planar Perovskite Solar Cells.

    PubMed

    Choi, Jongmin; Song, Seulki; Hörantner, Maximilian T; Snaith, Henry J; Park, Taiho

    2016-06-28

    An electron transporting layer (ETL) plays an important role in extracting electrons from a perovskite layer and blocking recombination between electrons in the fluorine-doped tin oxide (FTO) and holes in the perovskite layers, especially in planar perovskite solar cells. Dense TiO2 ETLs prepared by a solution-processed spin-coating method (S-TiO2) are mainly used in devices due to their ease of fabrication. Herein, we found that fatal morphological defects at the S-TiO2 interface due to a rough FTO surface, including an irregular film thickness, discontinuous areas, and poor physical contact between the S-TiO2 and the FTO layers, were inevitable and lowered the charge transport properties through the planar perovskite solar cells. The effects of the morphological defects were mitigated in this work using a TiO2 ETL produced from sputtering and anodization. This method produced a well-defined nanostructured TiO2 ETL with an excellent transmittance, single-crystalline properties, a uniform film thickness, a large effective area, and defect-free physical contact with a rough substrate that provided outstanding electron extraction and hole blocking in a planar perovskite solar cell. In planar perovskite devices, anodized TiO2 ETL (A-TiO2) increased the power conversion efficiency by 22% (from 12.5 to 15.2%), and the stabilized maximum power output efficiency increased by 44% (from 8.9 to 12.8%) compared with S-TiO2. This work highlights the importance of the ETL geometry for maximizing device performance and provides insights into achieving ideal ETL morphologies that remedy the drawbacks observed in conventional spin-coated ETLs.

  12. Climatic variability of transport in the upper layer of the Antarctic Circumpolar Current from hydrological and satellite data

    NASA Astrophysics Data System (ADS)

    Artamonov, Ju. V.; Fedirko, A. V.; Skripaleva, E. A.

    2016-12-01

    Based on the satellite altimetry dataset of sea level anomalies, the climatic hydrological database World Ocean Atlas-2009, ocean reanalysis ECMWF ORA-S3, and wind velocity components from NCEP/NCAR reanalysis, the interannual variability of Antarctic Circumpolar Current (ACC) transport in the ocean upper layer is investigated for the period 1959-2008, and estimations of correlative connections between ACC transport and wind velocity components are performed. It has been revealed that the maximum (by absolute value) linear trends of ACC transport over the last 50 years are observed in the date-line region, in the Western and Eastern Atlantic and the western part of the Indian Ocean. The greatest increase in wind velocity for this period for the zonal component is observed in Drake Passage, at Greenwich meridian, in the Indian Ocean near 90° E, and in the date-line region; for the meridional component, it is in the Western and Eastern Pacific, in Drake Passage, and to the south of Africa. It has been shown that the basic energy-carrying frequencies of interannual variability of ACC transport and wind velocity components, as well as their correlative connections, correspond to the periods of basic large-scale modes of atmospheric circulation: multidecadal and interdecadal oscillations, Antarctic Circumpolar Wave, Southern Annual Mode, and Southern Oscillation. A significant influence of the wind field on the interannual variability of ACC transport is observed in the Western Pacific (140° E-160° W) and Eastern Pacific; Drake Passage and Western Atlantic (90°-30° W); in the Eastern Atlantic and Western Indian Ocean (10°-70° E). It has been shown in the Pacific Ocean that the ACC transport responds to changes of the meridional wind more promptly than to changes of the zonal wind.

  13. Identification and semi-quantitative determination of anti-oxidants in lubricants employing thin-layer chromatography-spray mass spectrometry.

    PubMed

    Kreisberger, Georg; Himmelsbach, Markus; Buchberger, Wolfgang; Klampfl, Christian W

    2015-02-27

    A quick and simple method for identification and semi-quantitative determination of nine antioxidants commonly used in lubricants is presented. A dual step thin-layer chromatography (TLC) separation, removes in a first step the oil matrix whereas in a second step the antioxidants are separated. Cutting the spots out of the TLC-plate in the form of triangles allows direct-spray mass spectrometric (MS) measurements, providing MS and MS(n) spectra (if an appropriate MS instrument is employed) of the antioxidants, allowing their identification but also giving information about potential oxidation or degradation of these additives. Calibration curves within the concentration range relevant for the analysis of real oil samples (0.2-1.2gL(-1)) were constructed with R(2) values above 0.98 (when using an appropriate internal standard). This allowed the semi-quantitative determination of the selected antioxidants in real oils samples. Comparison with results from HPLC-UV measurement showed acceptable agreement for all analytes.

  14. Lattice Boltzmann method for short-pulsed laser transport in a multi-layered medium

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Yi, Hong-Liang; Tan, He-Ping

    2015-04-01

    We construct a lattice Boltzmann method (LBM) for transient radiative transfer in one-dimensional multi-layered medium with distinct refractive index in each layer. The left boundary is irradiated normally by a short-pulsed laser. The Fresnel interfaces conditions, which incorporate reflection and refraction, are used at the boundaries and the interfaces. Based on the Fresnel's law and Snell's law, the interfacial intensity formulas are introduced. The collimated and diffuse intensities are treated individually. At a transient time step, the collimated component is first solved by LBM and then embedded into the transient radiative transfer equation as a source term. To keep the consistency of the directions in all the layers, angular interpolation of the intensities at the interfaces is adopted. The transient radiative transfer in a two-layer medium is first investigated, and the time-resolved results are validated by comparing with those by the Monte Carlo method (MCM). Of particular interest, the angular intensities along the slab at different times are presented to illustrate a variety of interesting phenomena, and the discontinuous nature of the intensity at the interfaces is discussed. The effects of various parameters on the time-resolved signals are examined.

  15. Electron Transport, Chemistry and Optical Emissions in the Auroral E-Layer.

    DTIC Science & Technology

    1981-01-01

    and ionization rates for monoenergetic and energy dis- tributed sources with various pitch angle dependences. Walt et al. (1967) were the first to...Phys. Rev. A], 834 (1970). Borst, W.L., Phys. Rev. A5, 648 (1972). Davidson, B., Neutron Transport Theory, Oxford Press, London (1957). Donahue, T.M

  16. Nonlinear Response of Layer Growth Dynamics in the Mixed Kinetics-Bulk-Transport Regime

    NASA Technical Reports Server (NTRS)

    Vekilov, Peter G.; Alexander, J. Iwan D.; Rosenberger, Franz

    1996-01-01

    In situ high-resolution interferometry on horizontal facets of the protein lysozyme reveal that the local growth rate R, vicinal slope p, and tangential (step) velocity v fluctuate by up to 80% of their average values. The time scale of these fluctuations, which occur under steady bulk transport conditions through the formation and decay of step bunches (macrosteps), is of the order of 10 min. The fluctuation amplitude of R increases with growth rate (supersaturation) and crystal size, while the amplitude of the v and p fluctuations changes relatively little. Based on a stability analysis for equidistant step trains in the mixed transport-interface-kinetics regime, we argue that the fluctuations originate from the coupling of bulk transport with nonlinear interface kinetics. Furthermore, step bunches moving across the interface in the direction of or opposite to the buoyancy-driven convective flow increase or decrease in height, respectively. This is in agreement with analytical treatments of the interaction of moving steps with solution flow. Major excursions in growth rate are associated with the formation of lattice defects (striations). We show that, in general, the system-dependent kinetic Peclet number, Pe(sub k) , i.e., the relative weight of bulk transport and interface kinetics in the control of the growth process, governs the step bunching dynamics. Since Pe(sub k) can be modified by either forced solution flow or suppression of buoyancy-driven convection under reduced gravity, this model provides a rationale for the choice of specific transport conditions to minimize the formation of compositional inhomogeneities under steady bulk nutrient crystallization conditions.

  17. Transport and retention of TiO2 and polystyrene nanoparticles during drainage from tall heterogeneous layered columns

    NASA Astrophysics Data System (ADS)

    Hoggan, James L.; Sabatini, David A.; Kibbey, Tohren C. G.

    2016-11-01

    Recent developments in nanotechnology have seen an increase in the use of manufactured nanomaterials. Although their unique physicochemical properties are desirable for many products and applications, concern continues to exist about their environmental fate and potential to cause risk to human and ecological health. The purpose of this work was to examine one aspect of nanomaterial environmental fate: transport and retention in the unsaturated zone during drainage. The work made use of tall segmented columns packed with layers of two different porous media, one medium sand and one fine sand. The use of tall columns allowed drainage experiments to be conducted where the water table remained within the height of the column, permitting control of final saturation profiles without the need for capillary barrier membranes which can potentially complicate analyses. Experiments were conducted with titanium dioxide (TiO2) and polystyrene nanomaterials. For the strongly negatively-charged polystyrene nanomaterials, little retention was observed under the conditions studied. For the TiO2 nanomaterials, results of the work suggest that while saturated fine sand layers may retain more nanomaterials than saturated coarse sand layers, significantly greater retention is possible in unsaturated media. Furthermore, unsaturated medium sand layers exhibited significantly greater retention than adjacent saturated fine sand layers when present at low saturations high above the water table. Retention by unsaturated media were found to correlate strongly with elevation. Free drainage experiments including both primary and secondary drainages in homogeneous columns showed evidence of redistribution during imbibition and secondary drainage, but still showed substantial unsaturated retention of TiO2 nanoparticles high in the column, despite re-saturation with- and drainage of nanoparticle-free water.

  18. Organic solar cells with graphene electrodes and vapor printed poly(3,4-ethylenedioxythiophene) as the hole transporting layers.

    PubMed

    Park, Hyesung; Howden, Rachel M; Barr, Miles C; Bulović, Vladimir; Gleason, Karen; Kong, Jing

    2012-07-24

    For the successful integration of graphene as a transparent conducting electrode in organic solar cells, proper energy level alignment at the interface between the graphene and the adjacent organic layer is critical. The role of a hole transporting layer (HTL) thus becomes more significant due to the generally lower work function of graphene compared to ITO. A commonly used HTL material with ITO anodes is poly(3,4-ethylenedioxythiophene) (PEDOT) with poly(styrenesulfonate) (PSS) as the solid-state dopant. However, graphene's hydrophobic surface renders uniform coverage of PEDOT:PSS (aqueous solution) by spin-casting very challenging. Here, we introduce a novel, yet simple, vapor printing method for creating patterned HTL PEDOT layers directly onto the graphene surface. Vapor printing represents the implementation of shadow masking in combination with oxidative chemical vapor deposition (oCVD). The oCVD method was developed for the formation of blanket (i.e., unpatterened) layers of pure PEDOT (i.e., no PSS) with systematically variable work function. In the unmasked regions, vapor printing produces complete, uniform, smooth layers of pure PEDOT over graphene. Graphene electrodes were synthesized under low-pressure chemical vapor deposition (LPCVD) using a copper catalyst. The use of another electron donor material, tetraphenyldibenzoperiflanthene, instead of copper phthalocyanine in the organic solar cells also improves the power conversion efficiency. With the vapor printed HTL, the devices using graphene electrodes yield comparable performances to the ITO reference devices (η(p,LPCVD) = 3.01%, and η(p,ITO) = 3.20%).

  19. Predictions of Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions Using an Intermittency Transport Equation

    NASA Technical Reports Server (NTRS)

    Suzen, Y. Bora; Huang, P. G.; Hultgren, Lennart S.; Ashpis, David E.

    2001-01-01

    A new transport equation for the intermittency factor was proposed to predict separated and transitional boundary layers under low-pressure turbine airfoil conditions. The intermittent behavior of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, mu(sub t), with the intermittency factor, gamma. Turbulent quantities are predicted by using Menter's two-equation turbulence model (SST). The intermittency factor is obtained from a transport equation model, which not only can reproduce the experimentally observed streamwise variation of the intermittency in the transition zone, but also can provide a realistic cross-stream variation of the intermittency profile. In this paper, the intermittency model is used to predict a recent separated and transitional boundary layer experiment under low pressure turbine airfoil conditions. The experiment provides detailed measurements of velocity, turbulent kinetic energy and intermittency profiles for a number of Reynolds numbers and freestream turbulent intensity conditions and is suitable for validation purposes. Detailed comparisons of computational results with experimental data are presented and good agreements between the experiments and predictions are obtained.

  20. Predictions of Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions Using an Intermittency Transport Equation

    NASA Technical Reports Server (NTRS)

    Suzen, Y. B.; Huang, P. G.; Hultgren, Lennart S.; Ashpis, David E.

    2003-01-01

    A new transport equation for the intermittency factor was proposed to predict separated and transitional boundary layers under low-pressure turbine airfoil conditions. The intermittent behavior of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, t , with the intermittency factor, y. Turbulent quantities are predicted by using Menter s two-equation turbulence model (SST). The intermittency factor is obtained from a transport equation model, which not only can reproduce the experimentally observed streamwise variation of the intermittency in the transition zone, but also can provide a realistic cross-stream variation of the intermittency profile. In this paper, the intermittency model is used to predict a recent separated and transitional boundary layer experiment under low pressure turbine airfoil conditions. The experiment provides detailed measurements of velocity, turbulent kinetic energy and intermittency profiles for a number of Reynolds numbers and freestream turbulent intensity conditions and is suitable for validation purposes. Detailed comparisons of computational results with experimental data are presented and good agreements between the experiments and predictions are obtained.

  1. Phonon and electron temperature and non-Fourier heat transport in thin layers

    NASA Astrophysics Data System (ADS)

    Carlomagno, I.; Cimmelli, V. A.; Sellitto, A.

    2017-04-01

    We present a thermodynamic model of heat conductor which allows for different temperatures of phonons and electrons. This model is applied to calculate the steady-state radial temperature profile in a circular thin layer. The compatibility of the obtained temperature profiles with the second law of thermodynamics is investigated in view of the requirement of positive entropy production and of a nonlocal constitutive equation for the entropy flux.

  2. Numerical Modeling of the Vertical Heat Transport Through the Diffusive Layer of the Arctic Ocean

    DTIC Science & Technology

    2013-03-01

    DIFFUSIVE LAYER OF THE ARCTIC OCEAN 5 . FUNDING NUMBERS 6. AUTHOR(S) Angela S. Lefler 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval...1 A. ARCTIC OCEAN AND CLIMATE CHANGE ....................1 1. Heat Required to Melt Arctic Sea-Ice .......... 5 2...29 2. Testing the 4/3 Exponent ..................... 31 C. COMPARISON OF TWO- AND THREE-DIMENSIONAL EXPERIMENTS

  3. The horizontal transport of pollutants from a slope wind layer into the valley core as a function of atmospheric stability

    NASA Astrophysics Data System (ADS)

    Leukauf, Daniel; Gohm, Alexander; Rotach, Mathias W.; Posch, Christian

    2016-04-01

    Slope winds provide a mechanism for the vertical exchange of air between the valley and the free atmosphere aloft. By this means, heat, moisture and pollutants are exported or imported. However, it the static stability of the valley atmosphere is strong, one part of the up-slope flow is redirected towards the valley center and pollutants are recirculated within the valley. This may limit the venting potential of slope winds severely. The main objective of this study is to quantify the horizontal transport of pollutants from the slope wind layer into the stable valley core and to determine the dependency of this flux as a function of the initial stability of the atmosphere. For this purpose, we conducted large eddy simulations with the Weather Research and Forecasting (WRF) model for a quasi-two-dimensional valley. The valley geometry consists of two slopes with constant slope angle rising to a crest height of 1500 m and a 4 km wide flat valley floor in between. The valley is 20 km long and homogeneous in along-valley direction. Hence, only slope winds but no valley winds can evolve. The surface sensible heat flux is prescribed by a sine function with an amplitude of 125 W m-2. The initial sounding characterized by an atmosphere at rest and by a constant Brunt-Väisälä frequency which is varied between 0.006 s-1 and 0.02 s-1. A passive tracer is released with an arbitrary but constant rate at the valley floor. As expected, the atmospheric stability has a strong impact on the vertical and horizontal transport of tracer mass. A horizontal intrusion forms at the top of the mixed layer due to outflow from the slope wind layer. Tracer mass is transported from the slope towards the center of the valley. The efficiency of this mechanism increases with increasing stability N. For the lowest value of N, about 70% of the tracer mass released at the valley bottom is exported out of the valley. This value drops to about 12% in the case of the strongest stability. Hence, most

  4. Contacts and transport characteristics of few-layer transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Wang, Junjie; Li, Jing; Shevrin, Jacob; Nguyen, An; Mallouk, Tom; Zhu, J.; Rhodes, Daniel; Balicas, Luis; Watanabe, K.; Taniguchi, T.

    2014-03-01

    Two-dimensional layered transition metal dichalcogenides (TMDs) are potentially useful for electronic and optoelectronic applications. However, the lack of reliable methods to make ohmic contacts has been a major challenge. This work addresses two aspects of this challenge, i.e. interface cleanness and conductivity of the material in the contact area. Using gentle Ar ion milling immediately before the deposition of metal electrodes, we can completely remove polymer residue from prior lithography without significantly damaging the few-layer TMD sheet. Gate stacks made of Au and HfO2 films can inject carriers up to 3 ×1013 cm-2. We make van der Pauw devices of few-layer (< 5 L) TMD (MoS2, WS2, WSe2) sheets using Ti/Au contacts with area < 2 (um)2 and observe contact resistance less than 10 k Ω at high carrier densities, where the sheet conductance is well above 2e2/h. We eliminate hysteresis in the transfer curve of TMD devices by pulsing the gate voltage. Ambipolar conduction is observed in WSe2 devices, with an on/off ratio exceeding 106 for both electrons and holes. WSe2 devices supported on h-BN show field-effect (hole) mobility > 100 cm2/(Vs) at 300K. We discuss the effects of the various approaches taken above.

  5. Fission Product Transport in TRISO Particle Layers under Operating and Off-Normal Conditions

    SciTech Connect

    Van der Ven, Anton; Was, Gary; Wang, Lumin; Taheri, Mitra

    2014-04-26

    The objective of this project is to determine the diffusivity and chemical behavior of key fission products (ag, Cs, I. Te, Eu and Sr) through SiC and PyC both thermally, under irradiation, and under stress using FP introduction techniques that avoid the pitfalls of past experiments. The experimental approach is to create thin PyC-SiC couples containing the fission product to be studied embedded in the PyC layer. These samples will then be subjected to high temperature exposures in a vacuum and also to irradiation at high temperature, and last, to irradiation under stress at high temperature. The PyC serves as a host layer, providing a means of placing the fission product close to the SiC without damaging the SiC layer by its introduction or losing the FP during heating. Experimental measurements of grain boundary structure and distribution (EBSD, HRTEM, APT) will be used in the modeling effort to determine the qualitative dependence of FP diffusion coefficients on grain boundary orientation, temperature and stress.

  6. Enhanced efficiency and stability of inverted perovskite solar cells using highly crystalline SnO2 nanocrystals as the robust electron-transporting layer

    SciTech Connect

    Zhu, Zonglong; Bai, Yang; Liu, Xiao; Chueh, Chu -Chen; Yang, Shihe; Jen, Alex K. -Y.

    2016-05-11

    Here highly crystalline SnO2 is demonstrated to serve as a stable and robust electron-transporting layer for high-performance perovskite solar cells. Benefiting from its high crystallinity, the relatively thick SnO2 electron-transporting layer (≈120 nm) provides a respectable electron-transporting property to yield a promising power conversion efficiency (PCE)(18.8%) Over 90% of the initial PCE can be retained after 30 d storage in ambient with ≈70% relative humidity.

  7. Enhanced efficiency and stability of inverted perovskite solar cells using highly crystalline SnO2 nanocrystals as the robust electron-transporting layer

    DOE PAGES

    Zhu, Zonglong; Bai, Yang; Liu, Xiao; ...

    2016-05-11

    Here highly crystalline SnO2 is demonstrated to serve as a stable and robust electron-transporting layer for high-performance perovskite solar cells. Benefiting from its high crystallinity, the relatively thick SnO2 electron-transporting layer (≈120 nm) provides a respectable electron-transporting property to yield a promising power conversion efficiency (PCE)(18.8%) Over 90% of the initial PCE can be retained after 30 d storage in ambient with ≈70% relative humidity.

  8. Implications of Convective Scrape-Off Layer Transport for Fusion Reactors with Solid and Liquid Walls

    SciTech Connect

    Kotschenreuther, M; Rognlien, T D; Valanju, P

    2003-11-13

    Recent experimental observations in tokamaks indicate enhanced convection of plasma blobs toward the main chamber wall. Potential implications of these observations for reactors are examined here. Two dimensional plasma edge calculations are performed with UEDGE, including convective transport consistent with present experiments. This is coupled to a kinetic neutral calculation using the code NUT, to compute the hot neutral flux to the wall. The inclusion of convection increases sputtering of the wall by roughly an order of magnitude. For tungsten walls, erosion (neglecting re-deposition) is estimated to be {approx}0.6 mm per year. Plasma contamination could be serious for high Z walls of W or Sn, and might preclude ignition (based on empirical screening estimates). Low Z liquid materials offer much better prospects for acceptable plasma contamination. Rough estimates of dust generation from such erosion rates imply significant safety issues. Plasma transport via blobs can also significantly modify models of impurity redeposition.

  9. Nitrate in the atmospheric boundary layer of the tropical South Pacific - Implications regarding sources and transport

    NASA Technical Reports Server (NTRS)

    Savoie, Dennis L.; Prospero, Joseph M.; Merrill, John T.; Uematsu, Mitsuo

    1989-01-01

    Weekly bulk aerosol samples collected at three sites in the tropical South Pacific from 1983 to 1987 are analyzed. The mean nitrate concentrations obtained for the sites range from 0.107 to 0.117 microg/cu m. The results suggest that the region is minimally affected by the transport of soil material and pollutants from the continents. Measurements from sites in the tropical North Pacific show mean nitrate concentrations that are about three times higher than those in the South Pacific, showing that the North Pacific is significantly impacted by the transport of material from Asia and North America. The relationships between the nitrate concentrations to other constituents at American Samoa are discussed, including nonseasalt sulfate, Pb-210, and Be-7.

  10. Fluvial Erosion and Transportation of an Impact Regolith Layer: Implications for Titan

    NASA Astrophysics Data System (ADS)

    Moore, Jeffrey M.; Howard, Alan D.; Breton, Sylvain

    2014-11-01

    Large regions of Titan appear to be eroded cratered terrain. If this is correct, then Titan’s surface could have been characterized by a regolith hundreds of meters thick with abundant unconsolidated debris in the size range that could be fluvially transported and serving as tools for bedrock incision. We utilized a variant on our Landform Evolution Model, originally developed to understand fluvial erosion on Mars, to study this issue. We see two end-member results. Slopes covered with coarse grained material develop a drainage network that essentially becomes stabilized after a sufficient time. They become paved with gravel that can only be eroded very slowly, if at all, after some degree of erosion. Simulations with finer sediment (for example with the maximum grain size only 16 mm) the flow can transport a good bit of sediment throughout the simulation, and drainage basins are initially created, but the topography evolves into a gentle slope of parallel drainage. For gravel channel systems under high sediment transport situations, there is no downstream concavity - the channels are essentially uniform in slope so that no drainage basins form. However, for coarser sediment we are near the threshold of motion near the end of the simulation, and channel gradients decrease downstream, implying a well-developed drainage network will form. However, if boulders are intermixed with the fines (which is reasonable), upland surfaces could eventually become mantled with a pavement of coarse debris after differential removal of transportable sediment, thus limiting net erosion unless a weathering (rock-disintegrating) process occurs on Titan. Titan’s fluvial networks could have been quickly established, then become somewhat impervious to further landscape evolution even if the precipitation rates and intensities persisted for long times.

  11. Modeling and analysis of HTM-free perovskite solar cells based on ZnO electron transport layer

    NASA Astrophysics Data System (ADS)

    Lin, Lingyan; Jiang, Linqin; Qiu, Yu; Yu, Yunlong

    2017-04-01

    On the road towards high-efficiency and low-cost photovoltaic technology, perovskite solar cells (PSCs) emerge as the most promising candidate. Their application is, however, limited by the expensive hole transport material(HTM) and electrode material (e.g. spiro-OMeTAD and gold) and the high-temperature processed electron transport layer (e.g. TiO2) in the common device structure. In this paper, device modeling of HTM free perovskite solar cells having the structure of FTO/ZnO/CH3NH3PbI3/carbon is performed. Various factors that influence the solar cell performance have been investigated, such as doping concentration and thickness of CH3NH3PbI3 absorber layer, the interface defect density and work function of the back contact (φ). The reasonable thickness of CH3NH3PbI3 absorber is around 500 nm. The doping concentrations in the CH3NH3PbI3 layer significantly affect the electron potential barrier height at the junction interface. Meanwhile, to achieve high photovoltaic performance, the defect densities at the CH3NH3PbI3/ZnO interface should be controlled under the order of ∼1017 cm-3 by interface modification. Finally, the φ matching is a requirement to obtain high device performance. We found that an efficiency over 15% can be obtained under the moderate simulation conditions. Moreover, the conversion efficiency of 18.11% can be obtained when the doping concentration of absorber is improved to 1016 cm-3. These findings will provide important guidelines for the manufacturing of low-temperature low-cost perovskite solar cells.

  12. Composite oxygen ion transport element

    DOEpatents

    Chen, Jack C.; Besecker, Charles J.; Chen, Hancun; Robinson, Earil T.

    2007-06-12

    A composite oxygen ion transport element that has a layered structure formed by a dense layer to transport oxygen ions and electrons and a porous support layer to provide mechanical support. The dense layer can be formed of a mixture of a mixed conductor, an ionic conductor, and a metal. The porous support layer can be fabricated from an oxide dispersion strengthened metal, a metal-reinforced intermetallic alloy, a boron-doped Mo.sub.5Si.sub.3-based intermetallic alloy or combinations thereof. The support layer can be provided with a network of non-interconnected pores and each of said pores communicates between opposite surfaces of said support layer. Such a support layer can be advantageously employed to reduce diffusion resistance in any type of element, including those using a different material makeup than that outlined above.

  13. Low driving voltage in polymer light-emitting diodes with CdS nanoparticles as an electron transport layer

    NASA Astrophysics Data System (ADS)

    Mohsennia, Mohsen; Bidgoli, Maryam Massah; Boroumand, Farhad Akbari

    2015-01-01

    Water-soluble cadmium sulfide (CdS) nanoparticles were synthesized through aqueous thermochemical method using thioglycolic acid as a capping agent. The resulting CdS nanoparticles were characterized using x-ray diffraction, field-emission scanning electron microscopy, ultraviolet-visible, and photoluminescence spectroscopy. The CdS prepared has been used as an electron transport layer (ETL) in a polymer light-emitting diode (PLED) with the structure of poly(ethylene terephthalate)/indium tin oxide/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate/poly[2-methoxy-5-(2‧-ethyl-hexyloxy)-1,4-phenylene vinylene/CdS/aluminium (PET/ITO/PEDOT:PSS/MEH-PPV/CdS/Al). The performance of the fabricated device containing CdS nanoparticles as an ETL was compared with the device with the structure of PET/ITO/PEDOT:PSS/MEH-PPV/Al. According to the obtained results, it was shown that the ETL yields a higher current and lower turn-on voltage. The improvement was ascribed to the step barrier theory and hole blocking effect of the CdS layer. These results show that the CdS layer could be very useful in the fabrication of efficient PLEDs.

  14. In-situ measurement of the heat transport in defect- engineered free-standing single-layer graphene

    PubMed Central

    Wang, Haidong; Kurata, Kosaku; Fukunaga, Takanobu; Takamatsu, Hiroshi; Zhang, Xing; Ikuta, Tatsuya; Takahashi, Koji; Nishiyama, Takashi; Ago, Hiroki; Takata, Yasuyuki

    2016-01-01

    Utilizing nanomachining technologies, it is possible to manipulate the heat transport in graphene by introducing different defects. However, due to the difficulty in suspending large-area single-layer graphene (SLG) and limited temperature sensitivity of the present probing methods, the correlation between the defects and thermal conductivity of SLG is still unclear. In this work, we developed a new method for fabricating micro-sized suspended SLG. Subsequently, a focused ion beam (FIB) was used to create nanohole defects in SLG and tune the heat transport. The thermal conductivity of the same SLG before and after FIB radiation was measured using a novel T-type sensor method on site in a dual-beam system. The nanohole defects decreased the thermal conductivity by about 42%. It was found that the smaller width and edge scrolling also had significant restriction on the thermal conductivity of SLG. Based on the calculation results through a lattice dynamics theory, the increase of edge roughness and stronger scattering on long-wavelength acoustic phonons are the main reasons for the reduction in thermal conductivity. This work provides reliable data for understanding the heat transport in a defective SLG membrane, which could help on the future design of graphene-based electrothermal devices. PMID:26906476

  15. Fabrication and characteristics of CH3NH3PbI3 perovskite solar cells with molybdenum-selenide hole-transport layer

    NASA Astrophysics Data System (ADS)

    Chen, Lung-Chien; Tseng, Zong-Lieng; Chen, Cheng-Chiang; Hsiung Chang, Sheng; Ho, Cheng-Han

    2016-12-01

    We present a solar cell with an FTO/MoSe2/perovskite/C60/bathocuproine (BCP)/silver structure. The hole-transport material (HTM), active photovoltaic layer, electron-transport layer, and electron-buffer layer were made of MoSe2, perovskite, C60, and BCP, respectively. The domain sizes of the CH3NH3PbI3 (MAPbI3) perovskite films that were deposited on the MoSe2 HTM films following annealing at 500, 600, and 700 °C were determined to be 23, 25, and 27 nm, respectively, revealing that the domain size of the MAPbI3 perovskite film increased with the annealing temperature of the MoSe2 HTM film under it. Therefore, the crystallinities of the perovskite layers were improved by increasing the annealing temperatures of the HTM layers. Following optimization, the maximum power-conversion efficiency was 8.23%.

  16. Electrical and thermal transport properties of layered Bi2YO4Cu2Se2

    NASA Astrophysics Data System (ADS)

    Xiao, Yu; Pei, Yanling; Chang, Cheng; Zhang, Xiao; Tan, Xing; Ye, Xinxin; Gong, Shengkai; Lin, Yuanhua; He, Jiaqing; Zhao, Li-Dong

    2016-07-01

    Bi2YO4Cu2Se2 possesses a low thermal conductivity and high electrical conductivity at room temperature, which was considered as a potential thermoelectric material. In this work, we have investigated the electrical and thermal transport properties of Bi2YO4Cu2Se2 system in the temperature range from 300 K to 873 K. We found that the total thermal conductivity decreases from 1.8 W m-1 K-1 to 0.9 W m-1 K-1, and the electrical conductivity decreases from 850 S/cm to 163 S/cm in the measured temperature range. To investigate how potential of Bi2YO4Cu2Se2 system, we prepared the heavily Iodine doped samples to counter-dope intrinsically high carrier concentration and improve the electrical transport properties. Interestingly, the Seebeck coefficient could be enhanced to +80 μV/K at 873 K, meanwhile, we found that a low thermal conductivity of 0.7 W m-1 K-1 could be achieved. The intrinsically low thermal conductivity in this system is related to the low elastic properties, such as Young's modulus of 70-72 GPa, and Grüneisen parameters of 1.55-1.71. The low thermal conductivity makes Bi2YO4Cu2Se2 system to be a potential thermoelectric material, the ZT value 0.06 at 873 K was obtained, a higher performance is expected by optimizing electrical transport properties through selecting suitable dopants, modifying band structures or by further reducing thermal conductivity through nanostructuring etc.

  17. Role of 4- tert -Butylpyridine as a Hole Transport Layer Morphological Controller in Perovskite Solar Cells

    SciTech Connect

    Wang, Shen; Sina, Mahsa; Parikh, Pritesh; Uekert, Taylor; Shahbazian, Brian; Devaraj, Arun; Meng, Ying Shirley

    2016-09-14

    Hybrid organic-inorganic materials for high efficiency, low cost photovoltaic devices have seen rapid progress since the introduction of lead based perovskites and solid-state hole transport layers. Although majority of the materials used for perovskite solar cells (PSC) are introduced from dye-sensitized solar cells (DSSCs), the presence of a perovskite capping layer as opposed to a single dye molecule (in DSSCs) changes the interactions between the various layers in perovskite solar cells. 4-tert-butylpyridine (tBP), commonly used in PSCs, is assumed to function as a charge recombination inhibitor, similar to DSSCs. However, the presence of a perovskite capping layer calls for a re-evaluation of its function in PSCs. Using TEM (transmission electron microscopy), we first confirm the role of tBP as a HTL morphology controller in PSCs. Our observations suggest that tBP significantly improves the uniformity of the HTL and avoids accumulation of Li salt. We also study degradation pathways by using FTIR (Fourier transform infrared spectroscopy) and APT (atom probe tomography) to investigate and visualize in 3-dimensions the moisture content associated with the Li salt. Long term effects, over 1000 hours, due to evaporation of tBP have also been studied. Based on our findings, a PSC failure mechanism associated with the morphological change of the HTL is proposed. tBP, the morphology controller in HTL, plays a key role in this process and thus this study highlights the need for additive materials with higher boiling points for consistent long term performance of PSCs.

  18. The skaergaard layered series. Part IV. reaction-transport simulations of foundered blocks.

    SciTech Connect

    Sonnenthal, Eric L.; McBirney, Alexander R.

    1996-01-02

    During the middle stages of crystallization of the Skaergaard Layered Series large numbers of blocks became detached from the Upper Border Series and settled into the mush of crystals on the floor. It has been recognized for some time that these blocks now have compositions and textures that differ markedly from those of the units from which they came. They tend to be more plagioclase rich and seem to have lost mafic components to the surrounding gabbro. Numerical simulations coupling crystallization, melting, and heat and mass transfer for a multicomponent system show how the blocks reacted with the mush in which they were emplaced. Enhanced cooling and crystallization of a compositionally stratified mush adjacent to the blocks resulted in patterns of melt compositions similar to those of layering around the blocks. Volume changes during crystallization and melting induced convection of the interstitial melt leading to changes in the bulk compositions of the blocks and the surrounding mush. Inhomogeneities such as inclusions are likely to facilitate the onset of compositional convection in a chemically stratified solidification zone.

  19. Statistical evidence of anasymptotic geometric structure to the momentum transporting motions in turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    Morrill-Winter, Caleb; Philip, Jimmy; Klewicki, Joseph

    2017-03-01

    The turbulence contribution to the mean flow is reflected by the motions producing the Reynolds shear stress (<-uv>) and its gradient. Recent analyses of the mean dynamical equation, along with data, evidence that these motions asymptotically exhibit self-similar geometric properties. This study discerns additional properties associated with the uv signal, with an emphasis on the magnitudes and length scales of its negative contributions. The signals analysed derive from high-resolution multi-wire hot-wire sensor data acquired in flat-plate turbulent boundary layers. Space-filling properties of the present signals are shown to reinforce previous observations, while the skewness of uv suggests a connection between the size and magnitude of the negative excursions on the inertial domain. Here, the size and length scales of the negative uv motions are shown to increase with distance from the wall, whereas their occurrences decrease. A joint analysis of the signal magnitudes and their corresponding lengths reveals that the length scales that contribute most to <-uv> are distinctly larger than the average geometric size of the negative uv motions. Co-spectra of the streamwise and wall-normal velocities, however, are shown to exhibit invariance across the inertial region when their wavelengths are normalized by the width distribution, W(y), of the scaling layer hierarchy, which renders the mean momentum equation invariant on the inertial domain.

  20. Turbulent transport and production/destruction of ozone in a boundary layer over complex terrain

    NASA Technical Reports Server (NTRS)

    Greenhut, Gary K.; Jochum, Anne M.; Neininger, Bruno

    1994-01-01

    The first Intensive Observation Period (IOP) of the Swiss air pollution experiment POLLUMET took place in 1990 in the Aare River Valley between Bern and Zurich. During the IOP, fast response measurements of meteorological variables and ozone concentration were made within the boundary layer aboard a motorglider. In addition, mean values of meteorological variables and the concentrations of ozone and other trace species were measured using other aircraft, pilot balloons, tethersondes, and ground stations. Turbulent flux profiles of latent and sensible heat and ozone are calculated from the fast response data. Terms in the ozone mean concentration budget (time rate of change of mean concentration, horizontal advection, and flux divergence) are calculated for stationary time periods both before and after the passage of a cold front. The source/sink term is calculated as a residual in the budget, and its sign and magnitude are related to the measured concentrations of reactive trace species within the boundary layer. Relationships between concentration ratios of trace species and ozone concentration are determined in order to understand the influence of complex terrain on the processes that produce and destroy ozone.

  1. Effect of Mechanical Agitation on Cationic Liposome Transport across an Unstirred Water Layer in Caco-2 Cells.

    PubMed

    Kono, Yusuke; Iwasaki, Ayu; Matsuoka, Kenta; Fujita, Takuya

    2016-01-01

    To develop an effective oral delivery system for plasmid DNA (pDNA) using cationic liposomes, it is necessary to clarify the characteristics of uptake and transport of cationic liposome/pDNA complexes into the intestinal epithelium. In particular, evaluation of the involvement of an unstirred water layer (UWL), which is a considerable permeability barrier, in cationic liposome transport is very important. Here, we investigated the effects of a UWL on the transfection efficiency of cationic liposome/pDNA complexes into a Caco-2 cell monolayer. When Caco-2 cells were transfected with cationic liposome/pDNA complexes in shaking cultures to reduce the thickness of the UWL, gene expression was significantly higher in Caco-2 cells compared with static cultures. We also found that this enhancement of gene expression by shaking was not attributable to activation of transcription factors such as activator protein-1 and nuclear factor-kappaB (NF-κB). In addition, the increase in gene expression by mechanical agitation was observed at all charge ratios (1.5, 2.3, 3.1, 4.5) of cationic liposome/pDNA complexes. Transport experiments using Transwells demonstrated that mechanical agitation increased the uptake of cationic liposome/pDNA complexes by Caco-2 cells, whereas transport of the complexes across a Caco-2 cell monolayer did not occurr. Moreover, the augmentation of the gene expression of cationic liposome/pDNA complexes by shaking was observed in Madin-Darby canine kidney cells. These results indicate that a UWL greatly affects the uptake and transfection efficiency of cationic liposome/pDNA complexes into an epithelial monolayer in vitro.

  2. Microstructure of Josephson junctions: Effect on supercurrent transport in YBCO grain boundary and barrier layer junctions

    SciTech Connect

    Merkle, K.L.; Huang, Y.

    1998-01-01

    The electric transport of high-temperature superconductors, such as YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (YBCO), can be strongly restricted by the presence of high-angle grain boundaries (GB). This weak-link behavior is governed by the macroscopic GB geometry and the microscopic grain boundary structure and composition at the atomic level. Whereas grain boundaries present a considerable impediment to high current applications of high T{sub c} materials, there is considerable commercial interest in exploiting the weak-link-nature of grain boundaries for the design of microelectronic devices, such as superconducting quantum interference devices (SQUIDs). The Josephson junctions which form the basis of this technology can also be formed by introducing artificial barriers into the superconductor. The authors have examined both types of Josephson junctions by EM techniques in an effort to understand the connection between microstructure/chemistry and electrical transport properties. This knowledge is a valuable resource for the design and production of improved devices.

  3. TRANSPORT

    EPA Science Inventory

    Presentation outline: transport principles, effective solubility; gasoline composition; and field examples (plume diving).
    Presentation conclusions: MTBE transport follows from - phyiscal and chemical properties and hydrology. Field examples show: MTBE plumes > benzene plu...

  4. Thermal transport in three-dimensional foam architectures of few-layer graphene and ultrathin graphite.

    PubMed

    Pettes, Michael Thompson; Ji, Hengxing; Ruoff, Rodney S; Shi, Li

    2012-06-13

    At a very low solid concentration of 0.45 ± 0.09 vol %, the room-temperature thermal conductivity (κ(GF)) of freestanding graphene-based foams (GF), comprised of few-layer graphene (FLG) and ultrathin graphite (UG) synthesized through the use of methane chemical vapor deposition on reticulated nickel foams, was increased from 0.26 to 1.7 W m(-1) K(-1) after the etchant for the sacrificial nickel support was changed from an aggressive hydrochloric acid solution to a slow ammonium persulfate etchant. In addition, κ(GF) showed a quadratic dependence on temperature between 11 and 75 K and peaked at about 150 K, where the solid thermal conductivity (κ(G)) of the FLG and UG constituents reached about 1600 W m(-1) K(-1), revealing the benefit of eliminating internal contact thermal resistance in the continuous GF structure.

  5. Large Eddy Simulation of Pollen Transport in the Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Chamecki, Marcelo; Meneveau, Charles; Parlange, Marc B.

    2007-11-01

    The development of genetically modified crops and questions about cross-pollination and contamination of natural plant populations enhanced the importance of understanding wind dispersion of airborne pollen. The main objective of this work is to simulate the dispersal of pollen grains in the atmospheric surface layer using large eddy simulation. Pollen concentrations are simulated by an advection-diffusion equation including gravitational settling. Of great importance is the specification of the bottom boundary conditions characterizing the pollen source over the canopy and the deposition process everywhere else. The velocity field is discretized using a pseudospectral approach. However the application of the same discretization scheme to the pollen equation generates unphysical solutions (i.e. negative concentrations). The finite-volume bounded scheme SMART is used for the pollen equation. A conservative interpolation scheme to determine the velocity field on the finite volume surfaces was developed. The implementation is validated against field experiments of point source and area field releases of pollen.

  6. Magnetically dependent superconducting transport in oxide heterostructures with an antiferromagnetic layer

    NASA Astrophysics Data System (ADS)

    Kislinskii, Y. V.; Konstantinian, K. Y.; Ovsyannikov, G. A.; Komissinskiy, P. V.; Borisenko, I. V.; Shadrin, A. V.

    2008-04-01

    The superconducting current in hybrid superconducting structures Nb/Au/Ca1- x Sr x CuO2/YBa2Cu3O7- δ with an antiferromagnetic layer is experimentally shown to have a Josephson nature, and the deviation from the sinusoidal dependence of the superconducting current on the phase difference between superconducting electrodes is about 20% of the second harmonic. These heterostructures are found to have sensitivity to an applied magnetic field that is much higher than that of conventional Josephson junctions. The experimental shape of the magnetic-field dependence of the critical current in the heterostructures differs from the usual Fraunhofer shape by oscillation with a significantly smaller period along a magnetic field.

  7. Bulk transport measurements in ZnO: The effect of surface electron layers

    NASA Astrophysics Data System (ADS)

    Allen, M. W.; Swartz, C. H.; Myers, T. H.; Veal, T. D.; McConville, C. F.; Durbin, S. M.

    2010-02-01

    Magnetotransport measurements and x-ray photoemission spectroscopy were used to investigate the surface conductivity of ZnO. Near-surface downward band bending, consistent with electron accumulation, was found on the polar and nonpolar faces of bulk ZnO single crystals. A significant polarity effect was observed in that the downward band bending was consistently stronger on the Zn-polar face and weaker on the O-polar face. The surface electron accumulation layer was found to significantly influence the electrical properties of high resistivity, hydrothermally grown bulk ZnO crystals at temperatures below 200 K, and is largely responsible for the anomalously low electron mobility reported for this material.

  8. Statistical analysis and modeling of intermittent transport events in the tokamak scrape-off layer

    SciTech Connect

    Anderson, Johan; Halpern, Federico D.; Ricci, Paolo; Furno, Ivo; Xanthopoulos, Pavlos

    2014-12-15

    The turbulence observed in the scrape-off-layer of a tokamak is often characterized by intermittent events of bursty nature, a feature which raises concerns about the prediction of heat loads on the physical boundaries of the device. It appears thus necessary to delve into the statistical properties of turbulent physical fields such as density, electrostatic potential, and temperature, focusing on the mathematical expression of tails of the probability distribution functions. The method followed here is to generate statistical information from time-traces of the plasma density stemming from Braginskii-type fluid simulations and check this against a first-principles theoretical model. The analysis of the numerical simulations indicates that the probability distribution function of the intermittent process contains strong exponential tails, as predicted by the analytical theory.

  9. A systematic study of transport, magnetic and thermal properties of layered iridates

    NASA Astrophysics Data System (ADS)

    Korneta, Oleksandr

    A unique feature of the 5d-iridates is that the spin-orbit interaction (SOI) and Coulomb interactions U are of comparable strength and therefore compete vigorously. The relative strength of these interactions stabilizes new exotic ground states that provide a fertile ground for studying new physics. SOI is proportional to Z4 (Z is the atomic number), and it is now recognized that strong SOI can drive novel narrow-gap insulating states in heavy transition metal oxides such as iridates. Indeed, strong SOI necessarily introduces strong lattice degrees of freedom that become critical to new physics in the iridates. This dissertation thoroughly examines a wide array of newly observed novel phenomena induced by adjusting the relative strengths of U and SOI interactions via slight chemical doping and application of hydrostatic pressure in the layered iridates, particularly, BaIrO3 and Sr2IrO4. KEYWORDS: spin-orbit interaction, Mott insulator, iridates, magnetism, pressure

  10. Statistical evidence of anasymptotic geometric structure to the momentum transporting motions in turbulent boundary layers.

    PubMed

    Morrill-Winter, Caleb; Philip, Jimmy; Klewicki, Joseph

    2017-03-13

    The turbulence contribution to the mean flow is reflected by the motions producing the Reynolds shear stress (〈-uv〉) and its gradient. Recent analyses of the mean dynamical equation, along with data, evidence that these motions asymptotically exhibit self-similar geometric properties. This study discerns additional properties associated with the uv signal, with an emphasis on the magnitudes and length scales of its negative contributions. The signals analysed derive from high-resolution multi-wire hot-wire sensor data acquired in flat-plate turbulent boundary layers. Space-filling properties of the present signals are shown to reinforce previous observations, while the skewness of uv suggests a connection between the size and magnitude of the negative excursions on the inertial domain. Here, the size and length scales of the negative uv motions are shown to increase with distance from the wall, whereas their occurrences decrease. A joint analysis of the signal magnitudes and their corresponding lengths reveals that the length scales that contribute most to 〈-uv〉 are distinctly larger than the average geometric size of the negative uv motions. Co-spectra of the streamwise and wall-normal velocities, however, are shown to exhibit invariance across the inertial region when their wavelengths are normalized by the width distribution, W(y), of the scaling layer hierarchy, which renders the mean momentum equation invariant on the inertial domain.This article is part of the themed issue 'Toward the development of high-fidelity models of wall turbulence at large Reynolds number'.

  11. Electronic, transport, and optical properties of bulk and mono-layer PdSe2

    DOE PAGES

    Sun, Jifeng; Shi, Hongliang; Siegrist, Theo; ...

    2015-10-13

    In this study, the electronic and optical properties of bulk and monolayer PdSe2 are investigated using firstprinciples calculations. Using the modified Becke-Johnson potential, we find semiconductor behavior for both bulk and monolayer PdSe2 with indirect gap values of 0.03 eV for bulk and 1.43 eV for monolayer, respectively. Our sheet optical conductivity results support this observation and show similar anisotropic feature in the 2D plane. We further study the thermoelectric properties of the 2D PdSe2 using Blotzmann transport model and find interestingly high Seebeck coefficients (>200 μV/K) for both p- and n-type up to high doping level (–2 x 1013more » cm2) with an anisotropic character in an electrical conductivity suggesting better thermoelectric performance along y direction in the plane.V« less

  12. Type-controlled nanodevices based on encapsulated few-layer black phosphorus for quantum transport

    NASA Astrophysics Data System (ADS)

    Long, Gen; Xu, Shuigang; Shen, Junying; Hou, Jianqiang; Wu, Zefei; Han, Tianyi; Lin, Jiangxiazi; Wong, Wing Ki; Cai, Yuan; Lortz, Rolf; Wang, Ning

    2016-09-01

    We demonstrate that encapsulation of atomically thin black phosphorus (BP) by hexagonal boron nitride (h-BN) sheets is very effective for minimizing the interface impurities induced during fabrication of BP channel material for quantum transport nanodevices. Highly stable BP nanodevices with ultrahigh mobility and controllable types are realized through depositing appropriate metal electrodes after conducting a selective etching to the BP encapsulation structure. Chromium and titanium are suitable metal electrodes for BP channels to control the transition from a p-type unipolar property to ambipolar characteristic because of different work functions. Record-high mobilities of 6000 cm2 V-1 s-1 and 8400 cm2 V-1 s-1 are respectively obtained for electrons and holes at cryogenic temperatures. High-mobility BP devices enable the investigation of quantum oscillations with an indistinguishable Zeeman effect in laboratory magnetic field.

  13. A kinetic model for the transport of electrons in a graphene layer

    NASA Astrophysics Data System (ADS)

    Fermanian Kammerer, Clotilde; Méhats, Florian

    2016-12-01

    In this article, we propose a new numerical scheme for the computation of the transport of electrons in a graphene device. The underlying quantum model for graphene is a massless Dirac equation, whose eigenvalues display a conical singularity responsible for non-adiabatic transitions between the two modes. We first derive a kinetic model which takes the form of two Boltzmann equations coupled by a collision operator modeling the non-adiabatic transitions. This collision term includes a Landau-Zener transfer term and a jump operator whose presence is essential in order to ensure a good energy conservation during the transitions. We propose an algorithmic realization of the semi-group solving the kinetic model, by a particle method. We give analytic justification of the model and propose a series of numerical experiments studying the influences of the various sources of errors between the quantum and the kinetic models.

  14. Recent Progress in the Development of a Multi-Layer Green's Function Code for Ion Beam Transport

    NASA Technical Reports Server (NTRS)

    Tweed, John; Walker, Steven A.; Wilson, John W.; Tripathi, Ram K.

    2008-01-01

    To meet the challenge of future deep space programs, an accurate and efficient engineering code for analyzing the shielding requirements against high-energy galactic heavy radiation is needed. To address this need, a new Green's function code capable of simulating high charge and energy ions with either laboratory or space boundary conditions is currently under development. The computational model consists of combinations of physical perturbation expansions based on the scales of atomic interaction, multiple scattering, and nuclear reactive processes with use of the Neumann-asymptotic expansions with non-perturbative corrections. The code contains energy loss due to straggling, nuclear attenuation, nuclear fragmentation with energy dispersion and downshifts. Previous reports show that the new code accurately models the transport of ion beams through a single slab of material. Current research efforts are focused on enabling the code to handle multiple layers of material and the present paper reports on progress made towards that end.

  15. Magnetization and magneto-transport staircaselike behavior in layered perovskite Sr2CoO4 at low temperature

    PubMed Central

    Li, Qiuhang; Yuan, Xueping; Xing, Lei; Xu, Mingxiang

    2016-01-01

    Polycrystalline layered perovskite Sr2CoO4 sample was synthesized by high temperature and high pressure method. The staircaselike behavior has been observed in the magnetization and resistivity versus field curves of Sr2CoO4 at low temperature. The main features of the steps can be obtained from the measured results: (i) the positions of the external magnetic field at which steps occur are varying in different measurement runs, (ii) the steps only appear at low temperature and disappear with a slight increase of the temperature, (iii) the steps are dependent on the temperature and field sweep rate. Based on the features of the magnetization and magneto-transport staircaselike behavior in Sr2CoO4, the unusual phenomenon can be ascribed to an avalanche of flipping domains in terms of the random field theory. PMID:27293142

  16. Satellite Sounder Observations of Contrasting Tropospheric Moisture Transport Regimes: Saharan Air Layers, Hadley Cells, and Atmospheric Rivers

    SciTech Connect

    Nalli, Nicholas R.; Barnet, Christopher D.; Reale, Tony; Liu, Quanhua; Morris, Vernon R.; Spackman, J. Ryan; Joseph, Everette; Tan, Changyi; Sun, Bomin; Tilley, Frank; Leung, L. Ruby; Wolfe, Daniel

    2016-12-01

    This paper examines the performance of satellite sounder atmospheric vertical moisture proles (AVMP) under tropospheric conditions encompassing moisture contrasts driven by convection and advection transport mechanisms, specifically Atlantic Ocean Saharan air layers (SALs) and Pacific Ocean moisture conveyer belts (MCBs) commonly referred to as atmospheric rivers (ARs), both of these being mesoscale to synoptic meteorological phenomena within the vicinity of subtropical Hadley subsidence zones. Operational AVMP environmental data records retrieved from the Suomi National Polar-orbiting Partnership (SNPP) NOAA-Unique Combined Atmospheric Processing System (NUCAPS) are collocated with dedicated radiosonde observations (RAOBs) obtained from ocean-based intensive field campaigns; these RAOBs provide uniquely independent correlative truth data not assimilated into numerical weather prediction models for satellite sounder validation over open ocean. Using these marine-based data, we empirically assess the performance of the operational NUCAPS AVMP product for detecting and resolving these tropospheric moisture features over otherwise RAOB-sparse regions.

  17. Effects of oxide electron transport layer on quantum dots light emitting diode with an organic/inorganic hybrid structure

    NASA Astrophysics Data System (ADS)

    Kim, Jiwan; Park, Yu Jin; Kim, Yohan; Kim, Yong-Hoon; Han, Chul Jong; Han, Jeong In; Oh, Min Suk

    2013-11-01

    We report on the effects of an oxide semiconductor as an electron transport layer (ETL) on a quantum dots light emitting diode (QD-LED). To improve the properties of QD-LED, we optimized the process parameters for the deposition and post-annealing steps of an oxide ETL. When zinc tin oxide (ZTO) was deposited by radio-frequency magnetron sputtering in a gas mixture of argon and oxygen (Ar : O2 = 2 : 1) and then annealed under 760 Torr O2 for 10 min, our QD-LED showed improved luminescence characteristics. Additionally, to overcome the problem of non-uniform luminescence, we optimized the concentration and process conditions of colloidal quantum dot materials. Finally, we fabricated QD-LED devices with luminescence of 4,874 cd/m2 and luminous efficiency of 2.68 cd/A.

  18. Thermally Stable Mesoporous Perovskite Solar Cells Incorporating Low-Temperature Processed Graphene/Polymer Electron Transporting Layer.

    PubMed

    Tong, Shi Wun; Balapanuru, Janardhan; Fu, Deyi; Loh, Kian Ping

    2016-11-02

    In the short time since its discovery, perovskite solar cells (PSCs) have attained high power conversion efficiency but their lack of thermal stability remains a barrier to commercialization. Among the experimentally accessible parameter spaces for optimizing performance, identifying an electron transport layer (ETL) that forms a thermally stable interface with perovskite and which is solution-processable at low-temperature will certainly be advantageous. Herein, we developed a mesoporous graphene/polymer composite with these advantages when used as ETL in CH3NH3PbI3 PSCs, and a high efficiency of 13.8% under AM 1.5G solar illumination could be obtained. Due to the high heat transmission coefficient and low isoelectric point of mesoporous graphene-based ETL, the PSC device enjoys good chemical and thermal stability. Our work demonstrates that the mesoporous graphene-based scaffold is a promising ETL candidate for high performance and thermally stable PSCs.

  19. Electron Transport Layer-Free Solar Cells Based on Perovskite-Fullerene Blend Films with Enhanced Performance and Stability.

    PubMed

    Pascual, Jorge; Kosta, Ivet; Tuyen Ngo, T; Chuvilin, Andrey; Cabanero, German; Grande, Hans J; Barea, Eva M; Mora-Seró, Iván; Delgado, Juan Luis; Tena-Zaera, Ramon

    2016-09-22

    The solution processing of pinhole-free methylammonium lead triiodide perovskite-C70 fullerene (MAPbI3 :C70 ) blend films on fluorine-doped tin oxide (FTO)-coated glass substrates is presented. Based on this approach, a simplified and robust protocol for the preparation of efficient electron-transport layer (ETL)-free perovskite solar cells is described. Power conversion efficiency (PCE) of 13.6 % under AM 1.5 G simulated sunlight is demonstrated for these devices. Comparative impedance spectroscopy and photostability analysis of the MAPbI3 :C70 and single MAPbI3 films compared with conventional compact TiO2 ETL-based devices are shown. The beneficial impact of using MAPbI3 :C70 blend films is emphasized.

  20. Stable and null current hysteresis perovskite solar cells based nitrogen doped graphene oxide nanoribbons hole transport layer

    PubMed Central

    Kim, Jeongmo; Mat Teridi, Mohd Asri; Mohd Yusoff, Abd. Rashid bin; Jang, Jin

    2016-01-01

    Perovskite solar cells are becoming one of the leading technologies to reduce our dependency on traditional power sources. However, the frequently used component poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) has several shortcomings, such as an easily corroded indium-tin-oxide (ITO) interface at elevated temperatures and induced electrical inhomogeneity. Herein, we propose solution-processed nitrogen-doped graphene oxide nanoribbons (NGONRs) as a hole transport layer (HTL) in perovskite solar cells, replacing the conducting polymer PEDOT:PSS. The conversion efficiency of NGONR-based perovskite solar cells has outperformed a control device constructed using PEDOT:PSS. Moreover, our proposed NGONR-based devices also demonstrate a negligible current hysteresis along with improved stability. This work provides an effective route for substituting PEDOT:PSS as the effective HTL. PMID:27277388

  1. Low-temperature solution-processed tin oxide as an alternative electron transporting layer for efficient perovskite solar cells.

    PubMed

    Ke, Weijun; Fang, Guojia; Liu, Qin; Xiong, Liangbin; Qin, Pingli; Tao, Hong; Wang, Jing; Lei, Hongwei; Li, Borui; Wan, Jiawei; Yang, Guang; Yan, Yanfa

    2015-06-03

    Lead halide perovskite solar cells with the high efficiencies typically use high-temperature processed TiO2 as the electron transporting layers (ETLs). Here, we demonstrate that low-temperature solution-processed nanocrystalline SnO2 can be an excellent alternative ETL material for efficient perovskite solar cells. Our best-performing planar cell using such a SnO2 ETL has achieved an average efficiency of 16.02%, obtained from efficiencies measured from both reverse and forward voltage scans. The outstanding performance of SnO2 ETLs is attributed to the excellent properties of nanocrystalline SnO2 films, such as good antireflection, suitable band edge positions, and high electron mobility. The simple low-temperature process is compatible with the roll-to-roll manufacturing of low-cost perovskite solar cells on flexible substrates.

  2. Subsonic Investigation of a Leading-Edge Boundary Layer Control Suction System on a High-Speed Civil Transport Configuration

    NASA Technical Reports Server (NTRS)

    Campbell, Bryan A.; Applin, Zachary T.; Kemmerly, Guy T.; Coe, Paul L., Jr.; Owens, D. Bruce; Gile, Brenda E.; Parikh, Pradip G.; Smith, Don

    1999-01-01

    A wind tunnel investigation of a leading edge boundary layer control system was conducted on a High Speed Civil Transport (HSCT) configuration in the Langley 14- by 22-Foot Subsonic Tunnel. Data were obtained over a Mach number range of 0.08 to 0.27, with corresponding chord Reynolds numbers of 1.79 x 10(exp 6) to 5.76 x 10(exp 6). Variations in the amount of suction, as well as the size and location of the suction area, were tested with outboard leading edge flaps deflected 0 and 30 deg and trailing-edge flaps deflected 0 and 20 deg. The longitudinal and lateral aerodynamic data are presented without analysis. A complete tabulated data listing is also presented herein.

  3. Improved memory characteristics of charge trap memory by employing double layered ZrO2 nanocrystals and inserted Al2O3

    NASA Astrophysics Data System (ADS)

    Tang, Z. J.; Li, R.; Zhang, X. W.; Hu, D.; Zhao, Y. G.

    2016-07-01

    The charge trap memory capacitors incorporating a stacked charge trapping layer consisting of double layered ZrO2 nanocrystals (NCs) and inserted Al2O3 have been fabricated and investigated. It is observed that the memory capacitor with stacked trapping layer exhibits a hysteresis window as large as 14.3 V for ±10 V sweeping gate voltage range, faster program/erase speed, improved endurance performance, and good data retention characteristics with smaller extrapolated ten years charge loss at room temperature and 125 °C compared to single layered NCs. The special energy band alignment and the introduced additional traps of double layered ZrO2 NCs and inserted Al2O3 change the trapping and loss behavior of charges, and jointly contribute to the remarkable memory characteristics. Therefore, the memory capacitor with a stacked charge trapping layer is a promising candidate in future nonvolatile charge trap memory device design and application.

  4. Enhanced electrical property of Ni-doped CoOx hole transport layer for inverted perovskite solar cells.

    PubMed

    Huang, Aibin; Yu, Yu; Liu, Yan; Yang, Songwang; Lei, Lei; Bao, Shanhu; Cao, Xun; Jin, Ping

    2017-03-15

    Ultrathin Ni doped CoOx (Ni:CoOx) films were demonstrated by direct current (DC) co-sputtering at room temperature and employed as inorganic hole transport materials for inverted perovskite solar cells. P-type Ni2+ doping introduced in this work was designed to adjust the valence band position of CoOx to match the highest occupied molecular orbital of perovskite absorber material (CH3NH3PbI3), which would effectively inhibit recombination of photo-induced electrons and holes. Moreover, the hole extraction capacity would be further enhanced as a result of the appropriate Ni2+ doping, and hence the power conversion efficiency (PCE) of the devices increased from 3.68% to 9.60%. The optimized performance was also accompanied by decent stability as a result of its intrinsic stability and conductivity.

  5. The Observed Relationship Between Water Vapor and Ozone in the Tropical Tropopause Saturation Layer and the Influence of Meridional Transport

    NASA Technical Reports Server (NTRS)

    Selkirk, Henry B.; Schoeberl, M. R.; Olsen, M. A.; Douglass, A. R.

    2011-01-01

    We examine balloonsonde observations of water vapor and ozone from three Ticosonde campaigns over San Jose, Costa Rica [10 N, 84 W] during northern summer and a fourth during northern winter. The data from the summer campaigns show that the uppermost portion of the tropical tropopause layer between 360 and 380 K, which we term the tropopause saturation layer or TSL, is characterized by water vapor mixing ratios from proximately 3 to 15 ppmv and ozone from approximately 50 ppbv to 250 ppbv. In contrast, the atmospheric water vapor tape recorder at 380 K and above displays a more restricted 4-7 ppmv range in water vapor mixing ratio. From this perspective, most of the parcels in the TSL fall into two classes - those that need only additional radiative heating to rise into the tape recorder and those requiring some combination of additional dehydration and mixing with drier air. A substantial fraction of the latter class have ozone mixing ratios greater than 150 ppbv, and with water vapor greater than 7 ppmv this air may well have been transported into the tropics from the middle latitudes in conjunction with high-amplitude equatorial waves. We examine this possibility with both trajectory analysis and transport diagnostics based on HIRDLS ozone data. We apply the same approach to study the winter season. Here a very different regime obtains as the ozone-water vapor scatter diagram of the sonde data shows the stratosphere and troposphere to be clearly demarcated with little evidence of mixing in of middle latitude air parcels.

  6. Convective heat transport in a rotating fluid layer of infinite Prandtl number: optimum fields and upper bounds on Nusselt number.

    PubMed

    Vitanov, Nikolay K

    2003-02-01

    By means of the Howard-Busse method of the optimum theory of turbulence we investigate numerically upper bounds on convective heat transport for the case of infinite fluid layer with stress-free vertical boundaries rotating about a vertical axis. We discuss the case of infinite Prandtl number, 1-alpha solution of the obtained variational problem and optimum fields possessing internal, intermediate, and boundary layers. We investigate regions of Rayleigh and Taylor numbers R and Ta, where no analytical bounds can be derived, and compare the analytical and numerical bounds for these regions of R and Ta where such comparison is possible. The increasing rotation has a different influence on the rescaled optimum fields of velocity w(1), temperature theta(1) and the vertical component of the vorticity f(1). The increasing Ta for fixed R leads to vanishing of the boundary layers of w(1) and theta(1). Opposite to this, the increasing Ta leads first to a formation of boundary layers of the field f(1) but further increasing the rotation causes vanishing of these boundary layers. We obtain optimum profiles of the horizontal averaged total temperature field which could be used as hints for construction of the background fields when applying Doering-Constantin method to the problems of rotating convection. The wave number alpha(1) corresponding to the optimum fields follows the asymptotic relationship alpha(1)=(R/5)(1/4) for intermediate Rayleigh numbers. However, when R becomes large with respect to Ta, after a transition region, the power law for alpha(1) becomes close to the power law for the case without rotation. The Nusselt number Nu is close to the nonrotational bound 0.32R(1/3) for the case of large R and small Ta. Nu decreases with increasing Taylor number. Thus, the upper bounds reflect the tendency of inhibiting thermal convection by increasing rotation for a fixed Rayleigh number. For the regions of Rayleigh and Taylor numbers where the numerical and asymptotic

  7. Transport of ion beam in an annular magnetically expanding helicon double layer thruster

    SciTech Connect

    Zhang, Yunchao Charles, Christine; Boswell, Rod

    2014-06-15

    An ion beam generated by an annular double layer has been measured in a helicon thruster, which sustains a magnetised low-pressure (5.0 × 10{sup −4} Torr) argon plasma at a constant radio-frequency (13.56 MHz) power of 300 W. After the ion beam exits the annular structure, it merges into a solid centrally peaked structure in the diffusion chamber. As the annular ion beam moves towards the inner region in the diffusion chamber, a reversed-cone plasma wake (with a half opening angle of about 30°) is formed. This process is verified by measuring both the radial and axial distributions of the beam potential and beam current. The beam potential changes from a two-peak radial profile (maximum value ∼ 30 V, minimum value ∼ 22.5 V) to a flat (∼28 V) along the axial direction; similarly, the beam current changes from a two-peak to one-peak radial profile and the maximum value decreases by half. The inward cross-magnetic-field motion of the beam ions is caused by a divergent electric field in the source. Cross-field diffusion of electrons is also observed in the inner plume and is determined as being of non-ambipolar origin.

  8. Tail-ion transport and Knudsen layer formation in the presence of magnetic fields

    NASA Astrophysics Data System (ADS)

    Schmit, Paul; Molvig, Kim

    2013-10-01

    The impact of magnetic fields on Knudsen layer formation in ICF-relevant plasma is investigated for the first time. Magnetic fields change the energy scaling of the ion diffusivity in a way that eliminates the preferential losses of fast ions compared to thermal ions. Simple threshold criteria give conditions such that the restoration of the ion tail distribution is sufficient to recover much of the lost fusion reactivity. The tail-ion kinetic equations are solved for hot fuel bounded by a cold, nonreacting wall using a numerical stochastic differential equation solver, and the modified fusion reactivities are calculated. We find that modest magnetic fields too weak to magnetize thermal ions are still sufficient to restore much of the lost reactivity, consistent with the threshold conditions. We also find that the Maxwell-averaged fusion reactivities are recovered more fully in cylindrical targets compared to spherical targets. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  9. Numerical Modeling Studies of Wake Vortex Transport and Evolution Within the Planetary Boundary Layer

    NASA Technical Reports Server (NTRS)

    Lin, Yuh-Lang; Arya, S. Pal; Kaplan, Michael L.; Han, Jongil

    2000-01-01

    The fundamental objective of this research is study behavior of aircraft wake vortices within atmospheric boundary layer (ABL) in support of developing the system, Aircraft VOrtex Spacing System (AVOSS), under NASA's Terminal Area Productivity (TAR) program that will control aircraft spacing within the narrow approach corridors of airports. The purpose of the AVOSS system is to increase airport capacity by providing a safe reduction in separation of aircraft compared to the now-existing flight rules. In our first funding period (7 January 19994 - 6 April 1997), we have accomplished extensive model development and validation of ABL simulations. Using the validated model, in our second funding period (7 April 1997 - 6 April 2000) we have investigated the effects of ambient atmospheric turbulence on vortex decay and descent, Crow instability, and wake vortex interaction with the ground. Recognizing the crucial influence of ABL turbulence on wake vortex behavior, we have also developed a software generating vertical profiles of turbulent kinetic energy (TKE) or energy dissipation rate (EDR), which are, in turn, used as input data in the AVOSS prediction algorithms.

  10. Electron transport in Al-doped ZnO nanolayers obtained by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Blagoev, B. S.; Dimitrov, D. Z.; Mehandzhiev, V. B.; Kovacheva, D.; Terziyska, P.; Pavlic, J.; Lovchinov, K.; Mateev, E.; Leclercq, J.; Sveshtarov, P.

    2016-03-01

    Al-doped ZnO thin films with different Al content were prepared by atomic layer deposition (ALD). To carry out thermal ALD, diethyl zinc (DEZ) and tri-methyl aluminium (TMA) were used as Zn and Al precursors, respectively, and water vapor as oxidant. Various numbers n of DEZ and m TMA cycles was used to obtain different [ZnO] n [Al2O3] m films, where n = 100 - 95, m = 1 - 5. The X-ray diffraction analysis showed a predominantly (100) oriented polycrystalline phase for the ZnO:Al films with a low Al content (m = 1 - 3) and an amorphous structure for pure Al2O3. In ZnO:Al with a higher Al content (m = 4 - 6) the (100) reflection disappeared and the (002) peak increased. The resistivity of the films decreased with the increase in the Al content, reaching a minimum of 3.3×10-3 Ω cm at about 1.1 % Al2O3 for the [ZnO]99[Al2O3]2 sample; for higher dopant concentrations, the resistivity increased because of the increased crystal inhomogeneity due to axis reorientation.

  11. Assessing the transport of PAH in the surficial sediment layer by passive sampler approach.

    PubMed

    Belles, Angel; Alary, Claire; Criquet, Justine; Ivanovsky, Anastasia; Billon, Gabriel

    2017-02-01

    A new method based on passive samplers has been developed to assess the diffusive flux of fluorene, fluoranthene and pyrene in the sediment bed and across the sediment-water interface. The dissolved compound concentration gradient in the sediment in the vertical direction was measured at the outlet of a storm water pond by using polyethylene strips as passive samplers. Simultaneously, the dissipation of a set of tracer compounds preloaded in the passive samplers was measured to estimate the effective diffusion coefficients of the pollutants in the sediment. Both measurements were used to evaluate the diffusive flux of the compounds according to Fick's first law. The diffusive fluxes of the 3 studied compounds have been estimated with a centimetre-scale resolution in the upper 44cm of the sediment. According to the higher compound diffusion coefficient and the steeper concentration gradient in the surficial sediment layer, the results show that the net flux of compounds near the sediment interface (1cm depth) is on average 500 times higher than in the deep sediment, with average fluxes at 1cm depth on the order of 5, 0.1 and 0.1ng/m(2)/y for fluorene, fluoranthene and pyrene, respectively.

  12. Synthesis and high temperature transport properties of new quaternary layered selenide NaCuMnSe{sub 2}

    SciTech Connect

    Pavan Kumar, V.; Varadaraju, U.V.

    2014-04-01

    Synthesis and high temperature transport properties of NaCu{sub 1+x}Mn{sub 1−x}Se{sub 2}, (x=0−0.75) a new quaternary layered selenide, are reported. NaCuMnSe{sub 2} crystallizes in a trigonal unit cell with space group of P-3m1 (a=4.1276 Å, c=7.1253 Å). The isovalent substitution of Mn{sup 2+} by Cu{sup 2+} is carried out. All the compositions show semiconducting nature, whereas the Seebeck coefficient increases gradually over the entire measured temperature range. Compositions with x=0 and 0.025 follow thermally activated behavior. With increase in copper concentration the conduction mechanism transforms to 2D variable range hopping (VRH) for x=0.05 and 0.075. - Graphical abstract: Crystal structure of NaCuMnSe{sub 2}. - Highlights: • A new quaternary layered selenide NaCuMnSe{sub 2} is synthesized. • All the compositions show semiconducting nature, whereas the Seebeck coefficient increases gradually over the entire measured temperature range. • Conduction mechanism transforms from thermally activated behavior to 2D variable range hopping with increase in copper concentration.

  13. TiO2-ZnS Cascade Electron Transport Layer for Efficient Formamidinium Tin Iodide Perovskite Solar Cells.

    PubMed

    Ke, Weijun; Stoumpos, Constantinos C; Logsdon, Jenna Leigh; Wasielewski, Michael R; Yan, Yanfa; Fang, Guojia; Kanatzidis, Mercouri G

    2016-11-16

    Achieving high open-circuit voltage (Voc) for tin-based perovskite solar cells is challenging. Here, we demonstrate that a ZnS interfacial layer can improve the Voc and photovoltaic performance of formamidinium tin iodide (FASnI3) perovskite solar cells. The TiO2-ZnS electron transporting layer (ETL) with cascade conduction band structure can effectively reduce the interfacial charge recombination and facilitate electron transfer. Our best-performing FASnI3 perovskite solar cell using the cascaded TiO2-ZnS ETL has achieved a power conversion efficiency of 5.27%, with a higher Voc of 0.380 V, a short-circuit current density of 23.09 mA cm(-2), and a fill factor of 60.01%. The cascade structure is further validated with a TiO2-CdS ETL. Our results suggest a new approach for further improving the performance of tin-based perovskite solar cells with a higher Voc.

  14. An analytical model for solute transport through a GCL-based two-layered liner considering biodegradation.

    PubMed

    Guan, C; Xie, H J; Wang, Y Z; Chen, Y M; Jiang, Y S; Tang, X W

    2014-01-01

    An analytical model for solute advection and dispersion in a two-layered liner consisting of a geosynthetic clay liner (GCL) and a soil liner (SL) considering the effect of biodegradation was proposed. The analytical solution was derived by Laplace transformation and was validated over a range of parameters using the finite-layer method based software Pollute v7.0. Results show that if the half-life of the solute in GCL is larger than 1 year, the degradation in GCL can be neglected for solute transport in GCL/SL. When the half-life of GCL is less than 1 year, neglecting the effect of degradation in GCL on solute migration will result in a large difference of relative base concentration of GCL/SL (e.g., 32% for the case with half-life of 0.01 year). The 100-year solute base concentration can be reduced by a factor of 2.2 when the hydraulic conductivity of the SL was reduced by an order of magnitude. The 100-year base concentration was reduced by a factor of 155 when the half life of the contaminant in the SL was reduced by an order of magnitude. The effect of degradation is more important in approving the groundwater protection level than the hydraulic conductivity. The analytical solution can be used for experimental data fitting, verification of complicated numerical models and preliminary design of landfill liner systems.

  15. Turbulent transport of heat and momentum in a boundary layer subject to deceleration, suction and variable wall temperature

    NASA Technical Reports Server (NTRS)

    Orlando, A. F.; Moffat, R. J.; Kays, W. M.

    1974-01-01

    The relationship between the turbulent transport of heat and momentum in an adverse pressure gradient boundary layer was studied. An experimental study was conducted of turbulent boundary layers subject to strong adverse pressure gradients with suction. Near-equilibrium flows were attained, evidenced by outer-region similarity in terms of defect temperature and defect velocity profiles. The relationship between Stanton number and enthalpy thickness was shown to be the same as for a flat plate flow both for constant wall temperature boundary conditions and for steps in wall temperature. The superposition principle used with the step-wall-temperature experimental result was shown to accurately predict the Stanton number variation for two cases of arbitrarily varying wall temperature. The Reynolds stress tensor components were measured for strong adverse pressure gradient conditions and different suction rates. Two peaks of turbulence intensity were found: one in the inner and one in the outer regions. The outer peak is shown to be displaced outward by an adverse pressure gradient and suppressed by suction.

  16. Characterizing the Asian Tropopause Aerosol Layer (ATAL) Using Satellite Observations, Balloon Measurements and a Chemical Transport Model

    NASA Technical Reports Server (NTRS)

    Fairlie, T. D.; Vernier, J.-P.; Liu, H.; Deshler, T.; Natarajan, M.; Bedka, K.; Wegner, T.; Baker, N.; Gadhavi, H.; Ratnam, M. V.; Jayaraman, A.; Pandit, A.; Raj, A.; Kumar, H.; Kumar, S.; Singh, A.; Stenchikov, G.; Wienhold, F.; Bian, J.

    2016-01-01

    Satellite observations and numerical modeling studies have demonstrated that the Asian Summer Monsoon (ASM) provide a conduit for gas-phase pollutants in south Asia to reach the lower stratosphere. Now, observations from the CALIPSO satellite have revealed the Asian Tropopause Aerosol Layer (ATAL), a summertime accumulation of aerosols in the upper troposphere and lower stratosphere (UTLS), associated with the ASM anticyclone. The ATAL has potential implications for regional cloud properties, climate, and chemical processes in the UTLS. Here, we show in situ measurements from balloon-borne instruments, aircraft, and satellite observations, together with trajectory and chemical transport model (CTM) simulations to explore the origin, composition, physical, and optical properties of aerosols in the ATAL. In particular, we show balloon-data from our BATAL-2015 field campaign to India and Saudi Arabia in summer 2015, which includes in situ backscatter measurements from COBALD instruments, and the first observations of size and volatility of aerosols in the ATAL layer using optical particle counters (OPCs). Back trajectory calculations initialized from CALIPSO observations point to deep convection over North India as a principal source of ATAL aerosols. Available aircraft observations suggest significant sulfur and carbonaceous components to the ATAL, which is supported by simulations using the GEOS-Chem CTM. Source elimination studies conducted with the GEOS-Chem indicate that ATAL aerosols originate primary from south Asian sources, in contrast with some earlier studies.

  17. Growth, characterization, and transport properties of ternary (Bi1-x Sb x )2Te3 topological insulator layers.

    PubMed

    Weyrich, C; Drögeler, M; Kampmeier, J; Eschbach, M; Mussler, G; Merzenich, T; Stoica, T; Batov, I E; Schubert, J; Plucinski, L; Beschoten, B; Schneider, C M; Stampfer, C; Grützmacher, D; Schäpers, Th

    2016-12-14

    Ternary (Bi1-x Sb x )2Te3 films with an Sb content between 0 and 100% were deposited on a Si(1 1 1) substrate by means of molecular beam epitaxy. X-ray diffraction measurements confirm single crystal growth in all cases. The Sb content is determined by x-ray photoelectron spectroscopy. Consistent values of the Sb content are obtained from Raman spectroscopy. Scanning Raman spectroscopy reveals that the (Bi1-x Sb x )2Te3 layers with an intermediate Sb content show spatial composition inhomogeneities. The observed spectra broadening in angular-resolved photoemission spectroscopy (ARPES) is also attributed to this phenomena. Upon increasing the Sb content from x  =  0 to 1 the ARPES measurements show a shift of the Fermi level from the conduction band to the valence band. This shift is also confirmed by corresponding magnetotransport measurements where the conductance changes from n- to p-type. In this transition region, an increase of the resistivity is found, indicating a location of the Fermi level within the band gap region. More detailed measurements in the transition region reveals that the transport takes place in two independent channels. By means of a gate electrode the transport can be changed from n- to p-type, thus allowing a tuning of the Fermi level within the topologically protected surface states.

  18. Time-resolved soft-x-ray studies of energy transport in layered and planar laser-driven targets

    SciTech Connect

    Stradling, G.L.

    1982-04-19

    New low-energy x-ray diagnostic techniques are used to explore energy-transport processes in laser heated plasmas. Streak cameras are used to provide 15-psec time-resolution measurements of subkeV x-ray emission. A very thin (50 ..mu..g/cm/sup 2/) carbon substrate provides a low-energy x-ray transparent window to the transmission photocathode of this soft x-ray streak camera. Active differential vacuum pumping of the instrument is required. The use of high-sensitivity, low secondary-electron energy-spread CsI photocathodes in x-ray streak cameras is also described. Significant increases in sensitivity with only a small and intermittant decrease in dynamic range were observed. These coherent, complementary advances in subkeV, time-resolved x-ray diagnostic capability are applied to energy-transport investigations of 1.06-..mu..m laser plasmas. Both solid disk targets of a variety of Z's as well as Be-on-Al layered-disk targets were irradiated with 700-psec laser pulses of selected intensity between 3 x 10/sup 14/ W/cm/sup 2/ and 1 x 10/sup 15/ W/cm/sup 2/.

  19. Growth, characterization, and transport properties of ternary (Bi1-x Sb x )2Te3 topological insulator layers

    NASA Astrophysics Data System (ADS)

    Weyrich, C.; Drögeler, M.; Kampmeier, J.; Eschbach, M.; Mussler, G.; Merzenich, T.; Stoica, T.; Batov, I. E.; Schubert, J.; Plucinski, L.; Beschoten, B.; Schneider, C. M.; Stampfer, C.; Grützmacher, D.; Schäpers, Th

    2016-12-01

    Ternary (Bi1-x Sb x )2Te3 films with an Sb content between 0 and 100% were deposited on a Si(1 1 1) substrate by means of molecular beam epitaxy. X-ray diffraction measurements confirm single crystal growth in all cases. The Sb content is determined by x-ray photoelectron spectroscopy. Consistent values of the Sb content are obtained from Raman spectroscopy. Scanning Raman spectroscopy reveals that the (Bi1-x Sb x )2Te3 layers with an intermediate Sb content show spatial composition inhomogeneities. The observed spectra broadening in angular-resolved photoemission spectroscopy (ARPES) is also attributed to this phenomena. Upon increasing the Sb content from x  =  0 to 1 the ARPES measurements show a shift of the Fermi level from the conduction band to the valence band. This shift is also confirmed by corresponding magnetotransport measurements where the conductance changes from n- to p-type. In this transition region, an increase of the resistivity is found, indicating a location of the Fermi level within the band gap region. More detailed measurements in the transition region reveals that the transport takes place in two independent channels. By means of a gate electrode the transport can be changed from n- to p-type, thus allowing a tuning of the Fermi level within the topologically protected surface states.

  20. Magnetism and transport properties of layered rare-earth cobaltates Ln0.3CoO2

    NASA Astrophysics Data System (ADS)

    Knížek, K.; Novák, P.; Jirák, Z.; Hejtmánek, J.; Maryško, M.; Buršík, J.

    2015-05-01

    The ab-initio (GGA+U) electronic structure calculations of layered cobaltates Ln0.3CoO2 (Ln = La, Pr, Nd) prepared by ionic exchange from Na0.90CoO2 precursors have been performed. The data are used for numerical modeling of Seebeck coefficient within Boltzmann transport theory using BoltzTraP program [G. K. H. Madsen and D. J. Singh, Comput. Phys. Commun. 175, 67 (2006)], as well as for determination of the crystal field split levels of rare-earth ions using a method based on a transformation of Bloch states into the basis of Wannier functions [P. Novák et al., Phys. Rev. B 87, 205139 (2013)]. An overall agreement with observed magnetism and transport properties is obtained. In particular, the high p-type thermopower is well reproduced in a broad temperature range, but instead of theoretical linear decrease down to the lowest temperatures, the real systems exhibit an anomalous change of Seebeck sign, which might be related to the change of bare metallic carriers into the polaronic ones.

  1. Electron Beam-Blip Spectroscopic Diagnostics of the Scrape-off-Layer Parallel Transport in C-2

    NASA Astrophysics Data System (ADS)

    Osin, Dmitry; Thompson, Matthew; Garate, Eusebio; TAE Team

    2015-11-01

    C-2 is a microscopically stable, high-performance field-reversed configuration (FRC), where high plasma temperatures with significant fast ion population and record lifetimes were achieved by a combination of tangential neutral beam injection, electrically biased plasma guns at the ends and wall conditioning. FRC confinement depends on the properties of both the open and closed field lines, therefore, understanding the electron transport in the scrape-of-layer (SOL) is critical. To study parallel heat conduction in SOL, a high-energy pulsed electron beam (e-beam) was injected on-axis into C-2 to produce a heat pulse, which causes a fast rise and slower decay of the electron temperature, Te, in the SOL. The heat-blip was observed by means of He-jet spectroscopy. A small fraction of the total deposited e-beam energy is necessary to explain the measured Te increase. The electron thermal conductivity along the magnetic field lines can be inferred from the Te decay. Experiments suggest that a high energy e-beam pulse can serve as a direct diagnostic of heat transport in the SOL.

  2. Nano-structural analysis of effective transport paths in fuel-cell catalyst layers by using stochastic material network methods

    NASA Astrophysics Data System (ADS)

    Shin, Seungho; Kim, Ah-Reum; Um, Sukkee

    2016-02-01

    A two-dimensional material network model has been developed to visualize the nano-structures of fuel-cell catalysts and to search for effective transport paths for the optimal performance of fuel cells in randomly-disordered composite catalysts. Stochastic random modeling based on the Monte Carlo method is developed using random number generation processes over a catalyst layer domain at a 95% confidence level. After the post-determination process of the effective connectivity, particularly for mass transport, the effective catalyst utilization factors are introduced to determine the extent of catalyst utilization in the fuel cells. The results show that the superficial pore volume fractions of 600 trials approximate a normal distribution curve with a mean of 0.5. In contrast, the estimated volume fraction of effectively inter-connected void clusters ranges from 0.097 to 0.420, which is much smaller than the superficial porosity of 0.5 before the percolation process. Furthermore, the effective catalyst utilization factor is determined to be linearly proportional to the effective porosity. More importantly, this study reveals that the average catalyst utilization is less affected by the variations of the catalyst's particle size and the absolute catalyst loading at a fixed volume fraction of void spaces.

  3. Solution-processed zinc oxide/polyethylenimine nanocomposites as tunable electron transport layers for highly efficient bulk heterojunction polymer solar cells.

    PubMed

    Chen, Hsiu-Cheng; Lin, Shu-Wei; Jiang, Jian-Ming; Su, Yu-Wei; Wei, Kung-Hwa

    2015-03-25

    In this study, we employed polyethylenimine-doped sol-gel-processed zinc oxide composites (ZnO:PEI) as efficient electron transport layers (ETL) for facilitating electron extraction in inverted polymer solar cells. Using ultraviolet photoelectron spectroscopy, synchrotron grazing-incidence small-angle X-ray scattering and transmission electron microscopy, we observed that ZnO:PEI composite films' energy bands could be tuned considerably by varying the content of PEI up to 7 wt %-the conduction band ranged from 4.32 to 4.0 eV-and the structural order of ZnO in the ZnO:PEI thin films would be enhanced to align perpendicular to the ITO electrode, particularly at 7 wt % PEI, facilitating electron transport vertically. We then prepared two types of bulk heterojunction systems-based on poly(3-hexylthiophene) (P3HT):phenyl-C61-butryric acid methyl ester (PC61BM) and benzo[1,2-b:4,5-b́]dithiophene-thiophene-2,1,3-benzooxadiazole (PBDTTBO):phenyl-C71-butryric acid methyl ester (PC71BM)-that incorporated the ZnO:PEI composite layers. When using a composite of ZnO:PEI (93:7, w/w) as the ETL, the power conversion efficiency (PCE) of the P3HT:PC61BM (1:1, w/w) device improved to 4.6% from a value of 3.7% for the corresponding device that incorporated pristine ZnO as the ETL-a relative increase of 24%. For the PBDTTBO:PC71BM (1:2, w/w) device featuring the same amount of PEI blended in the ETL, the PCE improved to 8.7% from a value of 7.3% for the corresponding device that featured pure ZnO as its ETL-a relative increase of 20%. Accordingly, ZnO:PEI composites can be effective ETLs within organic photovoltaics.

  4. Co-functionalized organic/inorganic hybrid ZnO nanorods as electron transporting layers for inverted organic solar cells.

    PubMed

    Ambade, Swapnil B; Ambade, Rohan B; Eom, Seung Hun; Baek, Myung-Jin; Bagde, Sushil S; Mane, Rajaram S; Lee, Soo-Hyoung

    2016-03-07

    In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM-ZnO NRs) leads to higher aggregation owing to the weaker solubility of SMs in solutions of ZnO NRs dispersed in chlorobenzene (CB). A prior addition of organic 2-(2-methoxyethoxy)acetic acid (MEA) over ZnO NRs not only inhibits aggregation of SMs over ZnO NRs, but also provides enough sites for the SM to strongly couple with the ZnO NRs to yield transparent SM-MEA-ZnO NRs hybrids that exhibited excellent capability as electron transporting layers (ETLs) in inverted organic solar cells (iOSCs) of P3HT:PC60BM bulk-heterojunction (BHJ) photoactive layers. A strongly coupled SM-MEA-ZnO NR hybrid reduces the series resistance by enhancing the interfacial area and tunes the energy level alignment at the interface between the (indium-doped tin oxide, ITO) cathode and BHJ photoactive layers. A significant enhancement in power conversion efficiency (PCE) was achieved for iOSCs comprising ETLs of SM-MEA-ZnO NRs (3.64%) advancing from 0.9% for pristine ZnO NRs, while the iOSCs of aggregated SM-ZnO NRs ETL exhibited a much lower PCE of 2.6%, thus demonstrating the potential of the co-functionalization approach. The superiority of the co-functionalized SM-MEA-ZnO NRs ETL is also evident from the highest PCE of 7.38% obtained for the iOSCs comprising BHJ of PTB7-Th:PC60BM compared with extremely poor 0.05% for non-functionalized ZnO NRs.

  5. Thermoelectric transport in the layered Ca3Co4-xRhxO9 single crystals

    NASA Astrophysics Data System (ADS)

    Ikeda, Yusuke; Saito, Kengo; Okazaki, Ryuji

    2016-06-01

    We have examined an isovalent Rh substitution effect on the transport properties of the thermoelectric oxide Ca3Co4O9 using single-crystalline form. With increasing Rh content x, both the electrical resistivity and the Seebeck coefficient change systematically up to x = 0.6 for Ca3Co4-xRhxO9 samples. In the Fermi-liquid regime where the resistivity behaves as ρ = ρ 0 + A T 2 around 120 K, the A value decreases with increasing Rh content, indicating that the correlation effect is weakened by Rh 4d electrons with extended orbitals. We find that, in contrast to such a weak correlation effect observed in the resistivity of Rh-substituted samples, the low-temperature Seebeck coefficient is increased with increasing Rh content, which is explained with a possible enhancement of a pseudogap associated with the short-range order of spin density wave. In high-temperature range above room temperature, we show that the resistivity is largely suppressed by Rh substitution while the Seebeck coefficient becomes almost temperature-independent, leading to a significant improvement of the power factor in Rh-substituted samples. This result is also discussed in terms of the differences in the orbital size and the associated spin state between Co 3d and Rh 4d electrons.

  6. Efficiency Enhancement of Hybrid Perovskite Solar Cells with MEH-PPV Hole-Transporting Layers

    PubMed Central

    Chen, Hsin-Wei; Huang, Tzu-Yen; Chang, Ting-Hsiang; Sanehira, Yoshitaka; Kung, Chung-Wei; Chu, Chih-Wei; Ikegami, Masashi; Miyasaka, Tsutomu; Ho, Kuo-Chuan

    2016-01-01

    In this study, hybrid perovskite solar cells are fabricated using poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and poly(3-hexylthiophene-2,5-diyl) (P3HT) as dopant-free hole-transporting materials (HTMs), and two solution processes (one- and two-step methods, respectively) for preparing methylammonium lead iodide perovskite. By optimizing the concentrations and solvents of MEH-PPV solutions, a power conversion efficiency of 9.65% with hysteresis-less performance is achieved, while the device with 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′spirobifluorene (Spiro-OMeTAD) doped with lithium salts and tert-butylpyridine (TBP) exhibits an efficiency of 13.38%. This result shows that non-doped MEH-PPV is a suitable, low-cost HTM for efficient polymer-based perovskite solar cells. The effect of different morphologies of methylammonium lead iodide perovskite on conversion efficiency is also investigated by incident photon-to-electron conversion efficiency (IPCE) curves and electrochemical impedance spectroscopy (EIS). PMID:27698464

  7. Efficiency Enhancement of Hybrid Perovskite Solar Cells with MEH-PPV Hole-Transporting Layers

    NASA Astrophysics Data System (ADS)

    Chen, Hsin-Wei; Huang, Tzu-Yen; Chang, Ting-Hsiang; Sanehira, Yoshitaka; Kung, Chung-Wei; Chu, Chih-Wei; Ikegami, Masashi; Miyasaka, Tsutomu; Ho, Kuo-Chuan

    2016-10-01

    In this study, hybrid perovskite solar cells are fabricated using poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and poly(3-hexylthiophene-2,5-diyl) (P3HT) as dopant-free hole-transporting materials (HTMs), and two solution processes (one- and two-step methods, respectively) for preparing methylammonium lead iodide perovskite. By optimizing the concentrations and solvents of MEH-PPV solutions, a power conversion efficiency of 9.65% with hysteresis-less performance is achieved, while the device with 2,2‧,7,7‧-tetrakis(N,N-di-p-methoxyphenylamine)-9,9‧spirobifluorene (Spiro-OMeTAD) doped with lithium salts and tert-butylpyridine (TBP) exhibits an efficiency of 13.38%. This result shows that non-doped MEH-PPV is a suitable, low-cost HTM for efficient polymer-based perovskite solar cells. The effect of different morphologies of methylammonium lead iodide perovskite on conversion efficiency is also investigated by incident photon-to-electron conversion efficiency (IPCE) curves and electrochemical impedance spectroscopy (EIS).

  8. How non-adiabatic passing electron layers of linear microinstabilities affect turbulent transport

    NASA Astrophysics Data System (ADS)

    Dominski, J.; Brunner, S.; Görler, T.; Jenko, F.; Told, D.; Villard, L.

    2015-06-01

    The response of passing electrons in ion temperature gradient and trapped electron mode microturbulence regimes is investigated in tokamak geometry making use of the flux-tube version of the gyrokinetic code GENE. Results are obtained using two different electron models, fully kinetic and hybrid in which passing particles are forced to respond adiabatically, while trapped are handled kinetically. Comparing linear eigenmodes obtained with these two models enables to systematically isolate fine radial structures located at corresponding mode rational surfaces, clearly resulting from the non-adiabatic passing-electron response. Non-linear simulations show that these fine structures on the non-axisymmetric modes survive in the turbulent phase. Furthermore, through non-linear coupling to axisymmetric modes, they induce radial modulations in the effective profiles of density, ion/electron temperature, and E × B shearing rate. Finally, the passing-electron channel is shown to significantly contribute to the transport levels, at least in our ion temperature gradient case. Also shown is that the passing electrons significantly influence the E × B saturation mechanism of turbulence fluxes.

  9. Quantum transport modeling of the symmetric Fe/FeO0.5/MgO magnetic tunnel junction: the effects of correlations in the buffer layer.

    PubMed

    Timoshevskii, Vladimir; Hu, Yibin; Marcotte, Étienne; Guo, Hong

    2014-01-08

    We report ab initio simulations of quantum transport properties of Fe/MgO/Fe trilayer structures with FeO0.5 buffer iron oxide layer, where on-site Coulomb interaction is explicitly taken into account by local density approximation + Hubbard U approach. We show that on-site Coulomb repulsion in the iron-oxygen layer can cause a dramatic drop of the tunnel magnetoresistance of the system. We present an understanding of microscopic details of this phenomenon, connecting it to localization of electronic states of particular symmetry, which takes place in the buffer Fe-O layer, when on-site Coulomb repulsion is introduced. We further study the possible influence of the symmetry reduction in the buffer Fe-O layer on the transport properties of the Fe/MgO/Fe interface.

  10. Trace surface-clean palladium nanosheets as a conductivity enhancer in hole-transporting layers to improve the overall performances of perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Cao, Jing; Mo, Shiguang; Jing, Xiaojing; Yin, Jun; Li, Jing; Zheng, Nanfeng

    2016-02-01

    Surface-clean Pd nanosheets were synthesized and embedded in a hole transport material (HTM) matrix to improve the conductivity of the HTM layer. Applying only a trace amount of Pd nanosheets readily led to a remarkably enhanced performance of perovskite solar cells (PSCs). This finding provides an effective strategy to build efficient charge-transport materials for improving the overall performance of PSCs.Surface-clean Pd nanosheets were synthesized and embedded in a hole transport material (HTM) matrix to improve the conductivity of the HTM layer. Applying only a trace amount of Pd nanosheets readily led to a remarkably enhanced performance of perovskite solar cells (PSCs). This finding provides an effective strategy to build efficient charge-transport materials for improving the overall performance of PSCs. Electronic supplementary information (ESI) available: Details of the XRD, UV-vis spectra, cross-sectional SEM images and the EQE spectra of the cells. See DOI: 10.1039/c5nr07789c

  11. Focused helium-ion beam irradiation effects on electrical transport properties of few-layer WSe2: Enabling nanoscale direct write homo-junctions

    SciTech Connect

    Stanford, Michael; Noh, Joo Hyon; Koehler, Michael R.; Mandrus, David G.; Duscher, Gerd; Rondinone, Adam Justin; Ivanov, Ilia N.; Ward, Thomas Zac; Rack, Philip D.; Pudasaini, Pushpa Raj; Belianinov, Alex; Cross, Nicholas

    2016-06-06

    Atomically thin transition metal dichalcogenides (TMDs) are currently receiving significant attention due to their promising opto-electronic properties. Tuning optical and electrical properties of mono and few-layer TMDs, such as tungsten diselenide (WSe2), by controlling the defects, is an intriguing opportunity to synthesize next generation two dimensional material opto-electronic devices. Here, we report the effects of focused helium ion beam irradiation on the structural, optical and electrical properties of few-layer WSe2, via high resolution scanning transmission electron microscopy, Raman spectroscopy, and electrical transport measurements. By controlling the ion irradiation dose, we selectively introduce precise defects in few-layer WSe2 thereby locally tuning the resistivity and transport properties of the material. Hole transport in the few layer WSe2 is degraded more severely relative to electron transport after helium ion irradiation. Moreover, by selectively exposing material with the ion beam, we demonstrate a simple yet highly tunable method to create lateral homo-junctions in few layer WSe2 flakes, which constitutes an important advance towards two dimensional opto-electronic devices.

  12. Focused helium-ion beam irradiation effects on electrical transport properties of few-layer WSe2: enabling nanoscale direct write homo-junctions

    NASA Astrophysics Data System (ADS)

    Stanford, Michael G.; Pudasaini, Pushpa Raj; Belianinov, Alex; Cross, Nicholas; Noh, Joo Hyon; Koehler, Michael R.; Mandrus, David G.; Duscher, Gerd; Rondinone, Adam J.; Ivanov, Ilia N.; Ward, T. Zac; Rack, Philip D.

    2016-06-01

    Atomically thin transition metal dichalcogenides (TMDs) are currently receiving significant attention due to their promising opto-electronic properties. Tuning optical and electrical properties of mono and few-layer TMDs, such as tungsten diselenide (WSe2), by controlling the defects, is an intriguing opportunity to synthesize next generation two dimensional material opto-electronic devices. Here, we report the effects of focused helium ion beam irradiation on the structural, optical and electrical properties of few-layer WSe2, via high resolution scanning transmission electron microscopy, Raman spectroscopy, and electrical transport measurements. By controlling the ion irradiation dose, we selectively introduce precise defects in few-layer WSe2 thereby locally tuning the resistivity and transport properties of the material. Hole transport in the few layer WSe2 is degraded more severely relative to electron transport after helium ion irradiation. Furthermore, by selectively exposing material with the ion beam, we demonstrate a simple yet highly tunable method to create lateral homo-junctions in few layer WSe2 flakes, which constitutes an important advance towards two dimensional opto-electronic devices.

  13. Focused helium-ion beam irradiation effects on electrical transport properties of few-layer WSe2: Enabling nanoscale direct write homo-junctions

    DOE PAGES

    Stanford, Michael; Noh, Joo Hyon; Koehler, Michael R.; ...

    2016-06-06

    Atomically thin transition metal dichalcogenides (TMDs) are currently receiving significant attention due to their promising opto-electronic properties. Tuning optical and electrical properties of mono and few-layer TMDs, such as tungsten diselenide (WSe2), by controlling the defects, is an intriguing opportunity to synthesize next generation two dimensional material opto-electronic devices. Here, we report the effects of focused helium ion beam irradiation on the structural, optical and electrical properties of few-layer WSe2, via high resolution scanning transmission electron microscopy, Raman spectroscopy, and electrical transport measurements. By controlling the ion irradiation dose, we selectively introduce precise defects in few-layer WSe2 thereby locally tuningmore » the resistivity and transport properties of the material. Hole transport in the few layer WSe2 is degraded more severely relative to electron transport after helium ion irradiation. Moreover, by selectively exposing material with the ion beam, we demonstrate a simple yet highly tunable method to create lateral homo-junctions in few layer WSe2 flakes, which constitutes an important advance towards two dimensional opto-electronic devices.« less

  14. Efficient Planar Perovskite Solar Cells with Reduced Hysteresis and Enhanced Open Circuit Voltage by Using PW12-TiO2 as Electron Transport Layer.

    PubMed

    Huang, Chun; Liu, Canjun; Di, Yunxiang; Li, Wenzhang; Liu, Fangyang; Jiang, Liangxing; Li, Jie; Hao, Xiaojing; Huang, Haitao

    2016-04-06

    An electron transport layer is essential for effective operation of planar perovskite solar cells. In this Article, PW12-TiO2 composite was used as the electron transport layer for the planar perovskite solar cell in the device structure of fluorine-doped tin oxide (FTO)-glass/PW12-TiO2/perovskite/spiro-OMeTAD/Au. A proper downward shift of the conduction band minimum (CBM) enhanced electron extraction from the perovskite layer to the PW12-TiO2 composite layer. Consequently, the common hysteresis effect in TiO2-based planar perovskite solar cells was significantly reduced and the open circuit voltage was greatly increased to about 1.1 V. Perovskite solar cells using the PW12-TiO2 compact layer showed an efficiency of 15.45%. This work can contribute to the studies on the electron transport layer and interface engineering for the further development of perovskite solar cells.

  15. Interfacial Engineering of Perovskite Solar Cells by Employing a Hydrophobic Copper Phthalocyanine Derivative as Hole-Transporting Material with Improved Performance and Stability.

    PubMed

    Jiang, Xiaoqing; Yu, Ze; Lai, Jianbo; Zhang, Yuchen; Hu, Maowei; Lei, Ning; Wang, Dongping; Yang, Xichuan; Sun, Licheng

    2017-02-15

    In high-performance perovskite solar cells (PSCs), hole-transporting materials (HTMs) play an important role in extracting and transporting the photo-generated holes from the perovskite absorber to the cathode, thus reducing unwanted recombination losses and enhancing the photovoltaic performance. Herein, solution-processable tetra-4-(bis(4-tert-butylphenyl)amino)phenoxy-substituted copper phthalocyanine (CuPc-OTPAtBu) was synthesized and explored as a HTM in PSCs. The optical, electrochemical, and thermal properties were fully characterized for this organic metal complex. The photovoltaic performance of PSCs employing this CuPc derivative as a HTM was further investigated, in combination with a mixed-ion perovskite as a light absorber and a low-cost vacuum-free carbon as cathode. The optimized devices [doped with 6 % (w/w) tetrafluoro-tetracyano-quinodimethane (F4TCNQ)] showed a decent power conversion efficiency of 15.0 %, with an open-circuit voltage of 1.01 V, a short-circuit current density of 21.9 mA cm(-2) , and a fill factor of 0.68. Notably, the PSC devices studied also exhibited excellent long-term durability under ambient condition for 720 h, mainly owing to the introduction of the hydrophobic HTM interlayer, which prevents moisture penetration into the perovskite film. The present work emphasizes that solution-processable CuPc holds a great promise as a class of alternative HTMs that can be further explored for efficient and stable PSCs in the future.

  16. Coffee-Ring-Free Quantum Dot Thin Film Using Inkjet Printing from a Mixed-Solvent System on Modified ZnO Transport Layer for Light-Emitting Devices.

    PubMed

    Jiang, Congbiao; Zhong, Zhiming; Liu, Baiquan; He, Zhiwei; Zou, Jianhua; Wang, Lei; Wang, Jian; Peng, JunBiao; Cao, Yong

    2016-10-05

    Inkjet printing has been considered an available way to achieve large size full-color RGB quantum dots LED display, and the key point is to obtain printed film with uniform and flat surface profile. In this work, mixed solvent of 20 vol % 1,2-dichlorobenzene (oDCB) with cyclohexylbenzene (CHB) was used to dissolve green quantum dots (QDs) with CdSe@ZnS/ZnS core/shell structure. Then, by inkjet printing, a flat dotlike QDs film without the coffee ring was successfully obtained on polyetherimide (PEI)-modified ZnO layer, and the printed dots array exhibited great stability and repeatability. Here, adding oDCB into CHB solutions was used to reduce surface tension, and employing ZnO nanoparticle layer with PEI-modified was used to increase the surface free energy. As a result, a small contact angle is formed, which leads to the enhancement of evaporation rate, and then the coffee ring effect was suppressed. The printed dots with flat surface profile were eventually realized. Moreover, inverted green QD-LEDs with PEI-modified ZnO film as electron transport layer (ETL) and printed green QDs film as emission layer were successfully fabricated. The QD-LEDs exhibited the maximum luminance of 12 000 cd/m(2) and the peak current efficiency of 4.5 cd/A at luminance of 1500 cd/m(2).

  17. Measurements of the turbulent transport of heat and momentum in convexly curved boundary layers - Effects of curvature, recovery and free-stream turbulence

    NASA Technical Reports Server (NTRS)

    Kim, J.; Simon, T. W.

    1987-01-01

    The effects of streamwise convex curvature, recovery, and freestream turbulence intensity on the turbulent transport of heat and momentum in a mature boundary layer are studied using a specially designed three-wire hot-wire probe. Increased freestream turbulence is found to increase the profiles throughout the boundary layer on the flat developing wall. Curvature effects were found to dominate turbulence intensity effects for the present cases considered. For the higher TI (turbulence intensity) case, negative values of the turbulent Prandtl number are found in the outer half of the boundary layer, indicating a breakdown in Reynolds analogy.

  18. The effect of employing the p/i buffer layers and in-situ hydrogen treatment for transparent a-Si:H solar cells.

    PubMed

    Lee, Da Jung; Yun, Sun Jin; Park, Min A; Lim, Jung Wook

    2014-05-01

    In this study, we describe the effects of various thicknesses of triple p/i buffer layers and hydrogen treatment on various performances in the fabrication of transparent a-Si:H solar cells. For the increment of buffer layer thickness, V(oc) increases steadily and J(sc) firstly increases and then decreases. The triple buffer layers also enhance the transmittance as well as conversion efficiency. For hydrogen plasma treatment, overall performances were enhanced with plasma power due to the passivation of dangling bonds at p/i interface. Therefore, the usage of triple buffer layers with proper treatment is beneficial to obtaining transparent a-Si:H solar cells with high quality.

  19. Light-emitting diodes based on solution-processed nontoxic quantum dots: oxides as carrier-transport layers and introducing molybdenum oxide nanoparticles as a hole-inject layer.

    PubMed

    Bhaumik, Saikat; Pal, Amlan J

    2014-07-23

    We report fabrication and characterization of solution-processed quantum dot light-emitting diodes (QDLEDs) based on a layer of nontoxic and Earth-abundant zinc-diffused silver indium disulfide (AIZS) nanoparticles as an emitting material. In the QDLEDs fabricated on indium tin oxide (ITO)-coated glass substrates, we use layers of oxides, such as graphene oxide (GO) and zinc oxide (ZnO) nanoparticles as a hole- and electron-transport layer, respectively. In addition, we introduce a layer of MoO3 nanoparticles as a hole-inject one. We report a comparison of the characteristics of different device architectures. We show that an inverted device architecture, ITO/ZnO/AIZS/GO/MoO3/Al, yields a higher electroluminescence (EL) emission, compared to direct ones, for three reasons: (1) the GO/MoO3 layers introduce barriers for electrons to reach the Al electrode, and, similarly, the ZnO layers acts as a barrier for holes to travel to the ITO electrode; (2) the introduction of a layer of MoO3 nanoparticles as a hole-inject layer reduces the barrier height for holes and thereby balances charge injection in the inverted structure; and (3) the wide-bandgap zinc oxide next to the ITO electrode does not absorb the EL emission during its exit from the device. In the QDLEDs with oxides as carrier inject and transport layers, the EL spectrum resembles the photoluminescence emission of the emitting material (AIZS), implying that excitons are formed in the quaternary nanocrystals and decay radiatively.

  20. Spin dependent transport properties of Mn-Ga/MgO/Mn-Ga magnetic tunnel junctions with metal(Mg, Co, Cr) insertion layer

    SciTech Connect

    Liang, S. H.; Tao, L. L.; Liu, D. P. Han, X. F.; Lu, Y.

    2014-04-07

    We report a first principles theoretical investigation of spin polarized quantum transport in Mn{sub 2}Ga/MgO/Mn{sub 2}Ga and Mn{sub 3}Ga/MgO/Mn{sub 3}Ga magnetic tunneling junctions (MTJs) with the consideration of metal(Mg, Co, Cr) insertion layer effect. By changing the concentration of Mn, our calculation shows a considerable disparity in transport properties: A tunneling magnetoresistance (TMR) ratio of 852% was obtained for Mn{sub 2}Ga-based MTJs, however, only a 5% TMR ratio for Mn{sub 3}Ga-based MTJs. In addition, the influence of insertion layer has been considered in our calculation. We found the Co insertion layer can increase the TMR of Mn{sub 2}Ga-based MTJ to 904%; however, the Cr insertion layer can decrease the TMR by 668%; A negative TMR ratio can be obtained with Mg insertion layer. Our work gives a comprehensive understanding of the influence of different insertion layer in Mn-Ga based MTJs. It is proved that, due to the transmission can be modulated by the interfacial electronic structure of insertion, the magnetoresistance ratio of Mn{sub 2}Ga/MgO/Mn{sub 2}Ga MTJ can be improved by inserting Co layer.

  1. Edge transport studies in the edge and scrape-off layer of the National Spherical Torus Experiment with Langmuir probes

    SciTech Connect

    Boedo, J. A. Rudakov, D. L.; Myra, J. R.; D'Ippolito, D. A.; Zweben, S.; Maingi, R.; Maqueda, R. J.; Bell, R.; Kugel, H.; Leblanc, B.; Roquemore, L. A.; Soukhanovskii, V. A.; Ahn, J. W.; Canik, J.; Crocker, N.

    2014-04-15

    Transport and turbulence profiles were directly evaluated using probes for the first time in the edge and scrape-off layer (SOL) of NSTX [Ono et al., Nucl. Fusion 40, 557 (2000)] in low (L) and high (H) confinement, low power (P{sub in}∼ 1.3 MW), beam-heated, lower single-null discharges. Radial turbulent particle fluxes peak near the last closed flux surface (LCFS) at ≈4×10{sup 21} s{sup −1} in L-mode and are suppressed to ≈0.2×10{sup 21} s{sup −1} in H mode (80%–90% lower) mostly due to a reduction in density fluctuation amplitude and of the phase between density and radial velocity fluctuations. The radial particle fluxes are consistent with particle inventory based on SOLPS fluid modeling. A strong intermittent component is identified. Hot, dense plasma filaments 4–10 cm in diameter, appear first ∼2 cm inside the LCFS at a rate of ∼1×10{sup 21} s{sup −1} and leave that region with radial speeds of ∼3–5 km/s, decaying as they travel through the SOL, while voids travel inward toward the core. Profiles of normalized fluctuations feature levels of 10% inside LCFS to ∼150% at the LCFS and SOL. Once properly normalized, the intermittency in NSTX falls in similar electrostatic instability regimes as seen in other devices. The L-H transition causes a drop in the intermittent filaments velocity, amplitude and number in the SOL, resulting in reduced outward transport away from the edge and a less dense SOL.

  2. 3D effects of edge magnetic field configuration on divertor/scrape-off layer transport and optimization possibilities for a future reactor

    NASA Astrophysics Data System (ADS)

    Kobayashi, M.; Xu, Y.; Ida, K.; Corre, Y.; Feng, Y.; Schmitz, O.; Frerichs, H.; Tabares, F. L.; Evans, T. E.; Coenen, J. W.; Liang, Y.; Bader, A.; Itoh, K.; Yamada, H.; Ghendrih, Ph.; Ciraolo, G.; Tafalla, D.; Lopez-Fraguas, A.; Guo, H. Y.; Cui, Z. Y.; Reiter, D.; Asakura, N.; Wenzel, U.; Morita, S.; Ohno, N.; Peterson, B. J.; Masuzaki, S.

    2015-10-01

    This paper assesses the three-dimensional (3D) effects of the edge magnetic field structure on divertor/scrape-off layer transport, based on an inter-machine comparison of experimental data and on the recent progress of 3D edge transport simulation. The 3D effects are elucidated as a consequence of competition between transports parallel (\\parallel ) and perpendicular (\\bot ) to the magnetic field, in open field lines cut by divertor plates, or in magnetic islands. The competition has strong impacts on divertor functions, such as determination of the divertor density regime, impurity screening and detachment control. The effects of magnetic perturbation on the edge electric field and turbulent transport are also discussed. Parameterization to measure the 3D effects on the edge transport is attempted for the individual divertor functions. Based on the suggested key parameters, an operation domain of the 3D divertor configuration is discussed for future devices.

  3. Study of ethanolamine surface treatment on the metal-oxide electron transport layer in inverted InP quantum dot light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Jang, Ilwan; Kim, Jiwan; Park, Chang Jun; Ippen, Christian; Greco, Tonino; Oh, Min Suk; Lee, Jeongno; Kim, Won Keun; Wedel, Armin; Han, Chul Jong; Park, Sung Kyu

    2015-11-01

    The present work shows the effect of ethanolamine surface treatment on inverted InP quantum dot light-emitting diodes (QD-LEDs) with inorganic metal oxide layers. In the inverted structure of ITO/ZnO/InP QDs/CBP/MoO3/Al, a sol-gel derived ZnO film was used as an electron transport layer (ETL) and MoO3 was used as a hole injection layer (HIL). First, ethanolamine was treated as a surface modifier on top of the ZnO electron transport layer. The optical performance of the QD-LED device was improved by the ethanolamine surface treatment. Second, low temperature annealing (<200°C) was performed on the ZnO sol-gel electron transport layer, followed by an investigation of the effect of the ZnO annealing temperature. The efficiency of the inverted QD-LEDs was significantly enhanced (more than 3-fold) by optimization of the ZnO annealing temperature. [Figure not available: see fulltext.

  4. The Origin of the Terra Meridiani Sediments: Volatile Transport and the Formation of Sulfate Bearing Layered Deposits on Mars

    NASA Technical Reports Server (NTRS)

    Niles, P.B.

    2008-01-01

    formation process which must have acted over a large area of Mars. The results of this study suggest a mechanism for volatile transport on Mars without invoking an early greenhouse. They also imply a common formation mechanism for most of the sulfate minerals and layered deposits on Mars, which explains their common occurrence.

  5. STC-SAB program users manual for the turbulent boundary layer and turbulent separation prediction methods employed in the NASA Langley streamtube curvature computer program

    NASA Technical Reports Server (NTRS)

    Ferguson, D. R.

    1972-01-01

    The streamtube curvature program (STC) has been developed to predict the inviscid flow field and the pressure distribution about nacelles at transonic speeds. The effects of boundary layer are to displace the inviscid flow and effectively change the body shape. Thus, the body shape must be corrected by the displacement thickness in order to calculate the correct pressure distribution. This report describes the coupling of the Stratford and Beavers boundary layer solution with the inviscid STC analysis so that all nacelle pressure forces, friction drag, and incipient separation may be predicted. The usage of the coupled STC-SAB computer program is outlined and the program input and output are defined. Included in this manual are descriptions of the principal boundary layer tables and other revisions to the STC program. The use of the viscous option is controlled by the engineer during program input definition.

  6. Aqueous boundary layers related to oral absorption of a drug: from dissolution of a drug to carrier mediated transport and intestinal wall metabolism.

    PubMed

    Sugano, Kiyohiko

    2010-10-04

    The aqueous boundary layer (ABL) affects various aspects of oral absorption of a drug, from dissolution of the drug to the apparent K(m) value of intestinal wall metabolism and carrier mediated transport. However, the importance of ABL has often been entirely ignored in oral absorption investigation. In this minireview, the effect of ABL on oral absorption of a drug is discussed in an easy-to-understand manner. This review starts with an introduction of the boundary layer theory with many illustrations (and links to public web movies visualizing the ABL), and then discusses some specific cases of interest in pharmaceutical science, such as dissolution of floating drug particles in the USP paddle apparatus. The effect of the boundary layer on the membrane permeation is also discussed from the viewpoint of structure permeability relationship, carrier mediated transport/metabolism and estimation of the fraction of a dose absorbed for poor solubility compounds.

  7. Toward Revealing the Critical Role of Perovskite Coverage in Highly Efficient Electron-Transport Layer-Free Perovskite Solar Cells: An Energy Band and Equivalent Circuit Model Perspective.

    PubMed

    Huang, Like; Xu, Jie; Sun, Xiaoxiang; Du, Yangyang; Cai, Hongkun; Ni, Jian; Li, Juan; Hu, Ziyang; Zhang, Jianjun

    2016-04-20

    Currently, most efficient perovskite solar cells (PVKSCs) with a p-i-n structure require simultaneously electron transport layers (ETLs) and hole transport layers (HTLs) to help collecting photogenerated electrons and holes for obtaining high performance. ETL free planar PVKSC is a relatively new and simple structured solar cell that gets rid of the complex and high temperature required ETL (such as compact and mesoporous TiO2). Here, we demonstrate the critical role of high coverage of perovskite in efficient ETL free PVKSCs from an energy band and equivalent circuit model perspective. From an electrical point of view, we confirmed that the low coverage of perovskite does cause localized short circuit of the device. With coverage optimization, a planar p-i-n(++) device with a power conversion efficiency of over 11% was achieved, implying that the ETL layer may not be necessary for an efficient device as long as the perovskite coverage is approaching 100%.

  8. Effect of fluorine plasma treatment with chemically reduced graphene oxide thin films as hole transport layer in organic solar cells

    NASA Astrophysics Data System (ADS)

    Yu, Youn-Yeol; Kang, Byung Hyun; Lee, Yang Doo; Lee, Sang Bin; Ju, Byeong-Kwon

    2013-12-01

    The inorganic materials such as V2O5, MoO3 and WO3 were investigated to replace PEDOT:PSS as hole transport layer (HTL) in organic electronic devices such as organic solar cells (OSCs) and organic lighting emission diodes. However, these methods require vacuum techniques that are long time process and complex. Here, we report about plasma treatment with SF6 and CF4 using reactive ion etching on reduced graphene oxide (rGO) thin films that are obtained using an eco-friendly method with vitamin C. The plasma treated rGO thin films have dipoles since they consist of covalent bonds with fluorine on the surface of rGO. This means it is possible to increase the electrostatic potential energy than bare rGO. Increased potential energy on the surface of rGO films is worth applying organic electronic devices as HTL such as OSCs. Consequently, the power conversion efficiency of OSCs increased more than the rGO films without plasma treatment.

  9. Doping ZnO with Water/Alcohol-Soluble Small Molecules as Electron Transport Layers for Inverted Polymer Solar Cells.

    PubMed

    Liu, Chang; Zhang, Lin; Xiao, Liangang; Peng, Xiaobin; Cao, Yong

    2016-10-03

    By doping ZnO with porphyrin small molecules (FNEZnP-OE and FNEZnP-T) as cathode electron transport layers (ETLs), the inverted polymer solar cells (i-PSC) with PTB7:PC71BM (PTB7: polythieno[3,4-b]-thiophene-co-benzodithiophene, PC71BM: [6, 6]-phenyl-C71-butyric acid methyl ester) as the active materials exhibit enhanced device performance. While the power conversion efficiency (PCE) of the PSCs with pure ZnO ETL is 7.52%, that of the devices with FNEZnP-T-doped ZnO ETL shows a slightly improved PCE of 8.09%, and that of the PSCs with FNEZnP-OE-doped ZnO ETL is further enhanced up to 9.24% with an over 20% improvement compared to that with pure ZnO ETL. The better performance is contributed by the better interfacial contact and reduced work function induced by 9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorenes and 3,4-bis-(2-(2-methoxy-ethoxy)-ethoxy)-phenyls in the porphyrin small molecules. More importantly, the PCE is still higher than 8% even when the thickness of FNEZnP-OE-doped ZnO ETL is up to 110 nm, which are important criteria for eventually making organic photovoltaic modules with roll-to-roll coat processing.

  10. Carbon Quantum Dots/TiOx Electron Transport Layer Boosts Efficiency of Planar Heterojunction Perovskite Solar Cells to 19.

    PubMed

    Li, Hao; Shi, Weina; Huang, Wenchao; Yao, En-Ping; Han, Junbo; Chen, Zhifan; Liu, Shuangshuang; Shen, Yan; Wang, Mingkui; Yang, Yang

    2017-03-06

    In planar n-i-p heterojunction perovskite solar cells, the electron transport layer (ETL) plays important roles in charge extraction and determine the morphology of the perovskite film. Here, we report a solution-processed carbon quantum dots (CQDs)/TiO2 composite that has negligible absorption in the visible spectral range, a very attractive feature for perovskite solar cells. Using this novel CQDs/TiO2 ETL in conjunction with a planar n-i-p heterojunction, we achieved an unprecedented efficiency of ∼19% under standard illumination test conditions. It was found that a CQDs/TiO2 combination increases both the open circuit voltage and short-circuits current density as compared to using TiO2 alone. Various advanced spectroscopic characterizations including ultrafast spectroscopy, ultraviolet photoelectron spectroscopy, and electronic impedance spectroscopy elucidate that the CQDs increases the electronic coupling between the CH3NH3PbI3-xClx and TiO2 ETL interface as well as energy levers that contribute to electron extraction.

  11. Nonreduction-Active Hole-Transporting Layers Enhancing Open-Circuit Voltage and Efficiency of Planar Perovskite Solar Cells.

    PubMed

    Liu, Tiefeng; Jiang, Fangyuan; Qin, Fei; Meng, Wei; Jiang, Youyu; Xiong, Sixing; Tong, Jinhui; Li, Zaifang; Liu, Yun; Zhou, Yinhua

    2016-12-14

    Inverted planar perovskite solar cells using poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the hole-transporting layer (HTL) are very attractive because of their low-temperature and easy processing. However, the planar cells with the PEDOT:PSS HTL typically display lower open-circuit voltage (VOC) (about 0.90 V) than that of devices with TiO2-based conventional structure (1.0-1.1 V). The underlying reasons are still not clear. In this work, we report the PEDOT:PSS that is intrinsically p-doped can be chemically reduced by methylamine iodide (MAI) and MAPbI3. The reaction reduces the work function (WF) of PEDOT:PSS, which suppresses the efficient hole collection and yields lower VOC. To overcome this issue, we adopt undoped semiconducting polymers that are intrinsically nonreduction-active (NRA) as the HTL for inverted planar perovskite solar cells. The cells display enhanced VOC from 0.88 ± 0.04 V (PEDOT:PSS HTL, reference cells) to 1.02 ± 0.03 V (P3HT HTL) and 1.04 ± 0.03 V (PTB7 and PTB-Th HTL). The power conversion efficiency (PCE) of the devices with these NRA HTL reaches about 17%.

  12. Screening of inorganic wide-bandgap p-type semiconductors for high performance hole transport layers in organic photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Ginley, David; Zakutayev, Andriy; Garcia, Andreas; Widjonarko, Nicodemus; Ndione, Paul; Sigdel, Ajaya; Parilla, Phillip; Olson, Dana; Perkins, John; Berry, Joseph

    2011-03-01

    We will report on the development of novel inorganic hole transport layers (HTL) for organic photovoltaics (OPV). All the studied materials belong to the general class of wide-bandgap p-type oxide semiconductors. Potential candidates suitable for HTL applications include SnO, NiO, Cu2O (and related CuAlO2, CuCrO2, SrCu2O4 etc) and Co3O4 (and related ZnCo2O4, NiCo2O4, MgCo2O4 etc.). Materials have been optimized by high-throughput combinatorial approaches. The thin films were deposited by RF sputtering and pulsed laser deposition at ambient and elevated temperatures. Performance of the inorganic HTLs and that of the reference organic PEDOT:PSS HTL were compared by measuring the power conversion efficiencies and spectral responses of the P3HT/PCBM- and PCDTBT/PCBM-based OPV devices. Preliminary results indicate that Co3O4-based HTLs have performance comparable to that of our previously reported NiOs and PEDOT:PSS HTLs, leading to a power conversion efficiency of about 4 percent. The effect of composition and work function of the ternary materials on their performance in OPV devices is under investigation.

  13. Influence of Metal Contacts on Graphene Transport Characteristics and Its Removal with Nano-carbon Interfacial Layer

    NASA Astrophysics Data System (ADS)

    Kanda, Akinobu; Ito, Yu; Katakura, Kenta; Sonoda, Hiroki; Higuchi, Shoma; Tomori, Hikari; Ootuka, Youiti

    Graphene is a promising candidate for the next-generation electronic material. While considerable effort has been devoted to achieve higher mobility in graphene films, relatively little attention has been paid to the effect of metal contacts, which are indispensable to the electric devices. At a graphene/metal interface, mainly due to the difference in work functions, carriers are injected from the metal to graphene. The resulting shift of local Dirac point is not limited at the graphene/metal interface but extends into the graphene channel. This carrier doping affects more significantly the performance of graphene field effect devices with shorter channel, as well as may conceal Dirac physics at the graphene/metal interface. Here, we experimentally investigate the channel length dependence of graphene transport properties in a wide gate-voltage range and extract the effect of metal contact. Several metal species are investigated. We reveal the origin of electron-hole asymmetry and the effect of the chemical interaction between graphene and metal, and derive the effective work function of graphene (4.93 eV). Furthermore, we succeed in reducing the influence of metal contact by inserting a thin nano-carbon layer (amorphous carbon or multilayer graphene (MLG)) at the interface.

  14. Modified Fullerenes for Efficient Electron Transport Layer-Free Perovskite/Fullerene Blend-Based Solar Cells.

    PubMed

    Sandoval-Torrientes, Rafael; Pascual, Jorge; García-Benito, Inés; Collavini, Silvia; Kosta, Ivet; Tena-Zaera, Ramón; Martín, Nazario; Delgado, Juan Luis

    2017-03-15

    A variety of novel chemically modified fullerenes, showing different electron-accepting capabilities, has been synthesized and used to prepare electron transport layer (ETL)-free solar cells based on perovskite/fullerene blends. In particular, isoxazolino[60] fullerenes are proven to be a good candidate for processing blend films with CH3 NH3 PbI3 and obtaining enhanced power conversion efficiency (PCE) ETL-free perovskite solar cells (PSCs), improving the state-of-the-art PCE (i.e., 14.3 %) for this simplified device architecture. A beneficial effect for pyrazolino and methano[60]fullerene derivatives versus pristine [60]/fullerene is also shown. Furthermore, a clear correlation between the LUMO energy level of the fullerene component and the open circuit voltage of the solar cells is found. Apart from the new knowledge on innovative fullerene derivatives for PSCs, the universality and versatility of perovskite/fullerene blend films to obtain efficient ETL-free PSCs is demonstrated.

  15. Co-functionalized organic/inorganic hybrid ZnO nanorods as electron transporting layers for inverted organic solar cells

    NASA Astrophysics Data System (ADS)

    Ambade, Swapnil B.; Ambade, Rohan B.; Eom, Seung Hun; Baek, Myung-Jin; Bagde, Sushil S.; Mane, Rajaram S.; Lee, Soo-Hyoung

    2016-02-01

    In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM-ZnO NRs) leads to higher aggregation owing to the weaker solubility of SMs in solutions of ZnO NRs dispersed in chlorobenzene (CB). A prior addition of organic 2-(2-methoxyethoxy)acetic acid (MEA) over ZnO NRs not only inhibits aggregation of SMs over ZnO NRs, but also provides enough sites for the SM to strongly couple with the ZnO NRs to yield transparent SM-MEA-ZnO NRs hybrids that exhibited excellent capability as electron transporting layers (ETLs) in inverted organic solar cells (iOSCs) of P3HT:PC60BM bulk-heterojunction (BHJ) photoactive layers. A strongly coupled SM-MEA-ZnO NR hybrid reduces the series resistance by enhancing the interfacial area and tunes the energy level alignment at the interface between the (indium-doped tin oxide, ITO) cathode and BHJ photoactive layers. A significant enhancement in power conversion efficiency (PCE) was achieved for iOSCs comprising ETLs of SM-MEA-ZnO NRs (3.64%) advancing from 0.9% for pristine ZnO NRs, while the iOSCs of aggregated SM-ZnO NRs ETL exhibited a much lower PCE of 2.6%, thus demonstrating the potential of the co-functionalization approach. The superiority of the co-functionalized SM-MEA-ZnO NRs ETL is also evident from the highest PCE of 7.38% obtained for the iOSCs comprising BHJ of PTB7-Th:PC60BM compared with extremely poor 0.05% for non-functionalized ZnO NRs.In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM

  16. C70/C70:pentacene/pentacene organic heterojunction as the connecting layer for high performance tandem organic light-emitting diodes: Mechanism investigation of electron injection and transport

    NASA Astrophysics Data System (ADS)

    Guo, Qingxun; Yang, Dezhi; Chen, Jiangshan; Qiao, Xianfeng; Ahamad, Tansir; Alshehri, Saad M.; Ma, Dongge

    2017-03-01

    A high performance tandem organic light-emitting diode (OLED) is realized by employing a C70/C70:pentacene/pentacene organic heterojunction as the efficient charge generation layer (CGL). Not only more than two time enhancement of external quantum efficiency but also significant improvement in both power efficiency and lifetime are well achieved. The mechanism investigations find that the electron injection from the CGL to the adjacent electron transport layer (ETL) in tandem devices is injection rate-limited due to the high interface energy barrier between the CGL and the ETL. By the capacitance-frequency (C-F) and low temperature current density-voltage (J-V) characteristic analysis, we confirm that the electron transport is a space-charge-limited current process with exponential trap distribution. These traps are localized states below the lowest unoccupied molecular orbital edge inside the gap and would be filled with the upward shift of the Fermi level during the n-doping process. Furthermore, both the trap density (Ht) and the activation energy (Ea) could be carefully worked out through low temperature J-V measurements, which is very important for developing high performance tandem OLEDs.

  17. EMC3-EIRENE modelling of edge impurity transport in the stochastic layer of the large helical device compared with extreme ultraviolet emission measurements

    NASA Astrophysics Data System (ADS)

    Dai, Shuyu; Kobayashi, M.; Kawamura, G.; Morita, S.; Zhang, H. M.; Oishi, T.; Feng, Y.; Wang, D. Z.; Suzuki, Y.; the LHD Experimental Group

    2016-06-01

    The transport properties and line emissions of carbon impurity in the stochastic layer of the Large Helical Device have been investigated with the 3D edge transport code EMC3-EIRENE. A parameter study has been performed to examine the sensitivity of the simulation results on each transport term in the impurity transport model and the impurity source characteristics, i.e. the source amount and the location. The modelling has revealed that in order to reproduce the experimental results of the emission distribution, the impurity perpendicular transport coefficient (D imp) and the first wall source play important roles, while changes to the ion thermal and the friction forces are rather irrelevant. The detailed study of flux tube tracing and magnetic field structure in the edge stochastic layer, in relation to impurity transport, has shown that the deeper penetration of impurity into the higher plasma density region due to the enhanced D imp and the first wall source is responsible for the change of emission pattern as well as the intensity. The analysis indicates that D imp might be larger than that of background plasma by a few factors and also that there probably exists a substantial amount of first wall impurity source.

  18. A NEW MODEL FOR MIXING BY DOUBLE-DIFFUSIVE CONVECTION (SEMI-CONVECTION). II. THE TRANSPORT OF HEAT AND COMPOSITION THROUGH LAYERS

    SciTech Connect

    Wood, T. S.; Garaud, P.; Stellmach, S.

    2013-05-10

    Regions of stellar and planetary interiors that are unstable according to the Schwarzschild criterion, but stable according to the Ledoux criterion, are subject to a form of oscillatory double-diffusive (ODD) convection often called ''semi-convection''. In this series of papers, we use an extensive suite of three-dimensional (3D) numerical simulations to quantify the transport of heat and composition by ODD convection, and ultimately propose a new 1D prescription that can be used in stellar and planetary structure and evolution models. The first paper in this series demonstrated that under certain conditions ODD convection spontaneously transitions from an initial homogeneous state of weak wave-breaking turbulence into a staircase of fully convective layers, which results in a substantial increase in the transport of heat and composition. Here, we present simulations of ODD convection in this layered regime, we describe the dynamical behavior of the layers, and we derive empirical scaling laws for the transport through layered convection.

  19. Low Work-function Poly(3,4-ethylenedioxylenethiophene): Poly(styrene sulfonate) as Electron-transport Layer for High-efficient and Stable Polymer Solar Cells

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Chen, Lie; Hu, Xiaotian; Zhang, Lin; Chen, Yiwang

    2015-08-01

    Low-work-function poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) modified with polyethylenimine (PEIE) was used as an electron transport layer (ETL) for polymer solar cells (PSCs). A thin layer of PEIE film was spin-coated onto the surface on the PEDOT:PSS films, thus substantially changing their charge selectivity from supporting hole transport to supporting electron transport. It was also found that the PEDOT:PSS/PEIE ETL exhibited higher interfacial contact, a more favorable active morphology, and improved charge mobility. By virtue of these beneficial properties, inverted PSCs based on low-bandgap semiconducting photoactive layers achieved a notably improved power conversion efficiency (PCE) of 7.94%, superior even to the corresponding performance of devices with only a ZnO layer. Surpassing our expectations, compared with the extreme degradation of device stability observed when pure PEDOT:PSS is used, PEIE-modified PEDOT:PSS can considerably suppress device degradation because of the hydrophobic and alkaline nature of PEIE, which not only reduces the hygroscopicity of the PEDOT:PSS but also neutralizes the acidic PEDOT:PSS and thus prevents the corrosion of the ITO cathode. These results demonstrate the potential of PEIE-modified PEDOT:PSS for use as an efficient ETL in commercial printed electronic devices.

  20. Low Work-function Poly(3,4-ethylenedioxylenethiophene): Poly(styrene sulfonate) as Electron-transport Layer for High-efficient and Stable Polymer Solar Cells

    PubMed Central

    Zhang, Yong; Chen, Lie; Hu, Xiaotian; Zhang, Lin; Chen, Yiwang

    2015-01-01

    Low-work-function poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) modified with polyethylenimine (PEIE) was used as an electron transport layer (ETL) for polymer solar cells (PSCs). A thin layer of PEIE film was spin-coated onto the surface on the PEDOT:PSS films, thus substantially changing their charge selectivity from supporting hole transport to supporting electron transport. It was also found that the PEDOT:PSS/PEIE ETL exhibited higher interfacial contact, a more favorable active morphology, and improved charge mobility. By virtue of these beneficial properties, inverted PSCs based on low-bandgap semiconducting photoactive layers achieved a notably improved power conversion efficiency (PCE) of 7.94%, superior even to the corresponding performance of devices with only a ZnO layer. Surpassing our expectations, compared with the extreme degradation of device stability observed when pure PEDOT:PSS is used, PEIE-modified PEDOT:PSS can considerably suppress device degradation because of the hydrophobic and alkaline nature of PEIE, which not only reduces the hygroscopicity of the PEDOT:PSS but also neutralizes the acidic PEDOT:PSS and thus prevents the corrosion of the ITO cathode. These results demonstrate the potential of PEIE-modified PEDOT:PSS for use as an efficient ETL in commercial printed electronic devices. PMID:26239868

  1. The Formation of Incisional Boundary Layers In Bedrock-Alluvial Rivers Subjected to Spatiotemporally Varying Alluvial Transport

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Parker, G.; Stark, C. P.; Inoue, T.; Viparelli, E.; Fu, X.; Izumi, N.

    2015-12-01

    The Capacity-based Saltation Abrasion (CSA) bedrock incision introduced by Sklar and Dietrich (2004) has opened new horizons in the study of the morphodynamics of mixed bedrock-alluvial rivers. The CSA formulation has a major limitation, however, in that it relates bedrock cover only to the sediment supply rate, without providing a mechanism to route this sediment downstream. As a result, the formulation cannot treat the morphodynamics of bedrock incision under the condition of waves of alluviation passing down the river. The Macro-Roughness-based Saltation-Abrasion-Alluviation (MRSAA) model introduced here a) relates areal fraction of alluvial cover to the thickness to which characteristic bedrock roughness elements are buried in alluvium (rather than sediment supply rate), and b) tracks alluvial thickness via an Exner equation of sediment conservation modified to capture both at-capacity and below-capacity transport. MRSAA thus has the ability to track the waves of alluviation and rarification that are likely to characterize the morphodyamics of bedrock-alluvial landscapes subject to dynamic relative base level change (e.g. rock uplift), where discrete landslides and debris flows may be common. Here we apply MRSAA to the case of a 1D channel subject to repeated "sedimentographs" of sediment supply at the upstream end. We show that under such conditions, an "incisional boundary layer" forms in the first ~ 20 km downstream of the sediment feed point, where the mean bedrock slope can differ substantially from that associated with constant sediment feed rate. Farther downstream, the sediment wave is damped and smeared out, and the long-term bedrock morphodynamics differ little from that associated with a constant feed rate. Here we consider both the cases of a repeated periodic sedimentograph and a randomized sedimentograph.

  2. Amorphous Tin Oxide as a Low-Temperature-Processed Electron-Transport Layer for Organic and Hybrid Perovskite Solar Cells.

    PubMed

    Barbé, Jérémy; Tietze, Max L; Neophytou, Marios; Murali, Banavoth; Alarousu, Erkki; Labban, Abdulrahman El; Abulikemu, Mutalifu; Yue, Wan; Mohammed, Omar F; McCulloch, Iain; Amassian, Aram; Del Gobbo, Silvano

    2017-04-05

    Chemical bath deposition (CBD) of tin oxide (SnO2) thin films as an electron-transport layer (ETL) in a planar-heterojunction n-i-p organohalide lead perovskite and organic bulk-heterojunction (BHJ) solar cells is reported. The amorphous SnO2 (a-SnO2) films are grown from a nontoxic aqueous bath of tin chloride at a very low temperature (55 °C) and do not require postannealing treatment to work very effectively as an ETL in a planar-heterojunction n-i-p organohalide lead perovskite or organic BHJ solar cells, in lieu of the commonly used ETL materials titanium oxide (TiO2) and zinc oxide (ZnO), respectively. Ultraviolet photoelectron spectroscopy measurements on the glass/indium-tin oxide (ITO)/SnO2/methylammonium lead iodide (MAPbI3)/2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene device stack indicate that extraction of photogenerated electrons is facilitated by a perfect alignment of the conduction bands at the SnO2/MAPbI3 interface, while the deep valence band of SnO2 ensures strong hole-blocking properties. Despite exhibiting very low electron mobility, the excellent interfacial energetics combined with high transparency (Egap,optical > 4 eV) and uniform substrate coverage make the a-SnO2 ETL prepared by CBD an excellent candidate for the potentially low-cost and large-scale fabrication of organohalide lead perovskite and organic photovoltaics.

  3. A comparative study on the performance of hybrid solar cells containing ZnSTe QDs in hole transporting layer and photoactive layer

    NASA Astrophysics Data System (ADS)

    Najeeb, Mansoor Ani; Abdullah, Shahino Mah; Aziz, Fakhra; Ahmad, Zubair; Shakoor, R. A.; Mohamed, A. M. A.; Khalil, Uzma; Swelm, Wageh; Al-Ghamdi, Ahmed A.; Sulaiman, Khaulah

    2016-12-01

    In this paper, ZnSTe quantum dots-based hybrid solar cells (HSC) with two different device architectures have been investigated. The improved performance of the poly(3-hexylthiophene) (P3HT) and [6,6]phenyl C71 butyric acid methyl ester (PC71BM)-based bulk heterojunction (BHJ) solar cells by the incorporation of ZnSTe quantum dots (QDs) with an average size of 2.96 nm in PEDOT:PSS layer and active layer that have been demonstrated. Although the efficiency of both types of devices is almost the same, a close comparison reveals different reasons behind their improved performance. The device prepared with QDs in the HTL has shown reduced series resistance, increased shunt resistance, and improved mobility. On the other hand, QDs in the photoactive layer demonstrates increased photo-generation leading to improved efficiency.

  4. Soil Transport Implement

    NASA Technical Reports Server (NTRS)

    Dixon, William; Fan, William; Lloyd, Joey; Pham, Nam-Anh; Stevens, Michael

    1988-01-01

    The design of the Soil Transport Implement (STI) for SKITTER is presented. The purpose of STI is to provide a protective layer of lunar soil for the lunar modules. The objective is to cover the lunar module with a layer of soil approximately two meters thick within a two week period. The amount of soil required to cover the module is roughly 77 dump truck loads or three million earth pounds. A spinning disk is employed to accomplish its task. STI is an autonomous, teleoperated system. The design incorporates the latest advances in composite materials and high strength, light weight alloys to achieve a high strength to weight ratio. The preliminary design should only be used to assess the feasibility of employing a spinning wheel as a soil transport implement. A mathematical model of the spinning wheel was used to evaluate the performance of this design.

  5. p-i-n/n-i-p type planar hybrid structure of highly efficient perovskite solar cells towards improved air stability: synthetic strategies and the role of p-type hole transport layer (HTL) and n-type electron transport layer (ETL) metal oxides.

    PubMed

    Mali, Sawanta S; Hong, Chang Kook

    2016-05-19

    There has been fast recent progress in perovskite solar cells (PSCs) towards low cost photovoltaic technology. Organometal mixed halide (MAPbX or FAPbX) perovskites are the most promising light absorbing material sandwiched between the electron transport layer (ETL) and hole transport layer (HTL). These two layers play a critical role in boosting the power conversion efficiency (PCE) and maintaining air stability. However, the device stability is a serious issue in regular as well as p-i-n inverted type perovskite solar cells. This mini-review briefly outlines the state-of-art of p-i-n/n-i-p type planar hybrid perovskite solar cells using MAPbX/FAPbX perovskite absorbing layers. Later, we will focus on recent trends, progress and further opportunities in exploring the air stable hybrid planar structure PSCs.

  6. p-i-n/n-i-p type planar hybrid structure of highly efficient perovskite solar cells towards improved air stability: synthetic strategies and the role of p-type hole transport layer (HTL) and n-type electron transport layer (ETL) metal oxides

    NASA Astrophysics Data System (ADS)

    Mali, Sawanta S.; Hong, Chang Kook

    2016-05-01

    There has been fast recent progress in perovskite solar cells (PSCs) towards low cost photovoltaic technology. Organometal mixed halide (MAPbX or FAPbX) perovskites are the most promising light absorbing material sandwiched between the electron transport layer (ETL) and hole transport layer (HTL). These two layers play a critical role in boosting the power conversion efficiency (PCE) and maintaining air stability. However, the device stability is a serious issue in regular as well as p-i-n inverted type perovskite solar cells. This mini-review briefly outlines the state-of-art of p-i-n/n-i-p type planar hybrid perovskite solar cells using MAPbX/FAPbX perovskite absorbing layers. Later, we will focus on recent trends, progress and further opportunities in exploring the air stable hybrid planar structure PSCs.

  7. Industry Employment

    ERIC Educational Resources Information Center

    Occupational Outlook Quarterly, 2012

    2012-01-01

    This article illustrates projected employment change by industry and industry sector over 2010-20 decade. Workers are grouped into an industry according to the type of good produced or service provided by the establishment for which they work. Industry employment projections are shown in terms of numeric change (growth or decline in the total…

  8. Industry Employment

    ERIC Educational Resources Information Center

    Occupational Outlook Quarterly, 2010

    2010-01-01

    This article illustrates projected employment change from an industry perspective over the 2008-2018 decade. Workers are grouped into an industry according to the type of good produced or service provided by the establishment in which they work. Industry employment projections are shown in terms of numeric change (growth or decline in the total…

  9. Flexible ITO-free organic solar cells applying aqueous solution-processed V2O5 hole transport layer: An outdoor stability study

    NASA Astrophysics Data System (ADS)

    Lima, F. Anderson S.; Beliatis, Michail J.; Roth, Bérenger; Andersen, Thomas R.; Bortoti, Andressa; Reyna, Yegraf; Castro, Eryza; Vasconcelos, Igor F.; Gevorgyan, Suren A.; Krebs, Frederik C.; Lira-Cantu, Mónica

    2016-02-01

    Solution processable semiconductor oxides have opened a new paradigm for the enhancement of the lifetime of thin film solar cells. Their fabrication by low-cost and environmentally friendly solution-processable methods makes them ideal barrier (hole and electron) transport layers. In this work, we fabricate flexible ITO-free organic solar cells (OPV) by printing methods applying an aqueous solution-processed V2O5 as the hole transport layer (HTL) and compared them to devices applying PEDOT:PSS. The transparent conducting electrode was PET/Ag/PEDOT/ZnO, and the OPV configuration was PET/Ag/PEDOT/ZnO/P3HT:PC60BM/HTL/Ag. Outdoor stability analyses carried out for more than 900 h revealed higher stability for devices fabricated with the aqueous solution-processed V2O5.

  10. Surface conductivity of Si(100) and Ge(100) surfaces determined from four-point transport measurements using an analytical N -layer conductance model

    NASA Astrophysics Data System (ADS)

    Just, Sven; Soltner, Helmut; Korte, Stefan; Cherepanov, Vasily; Voigtländer, Bert

    2017-02-01

    An analytical N -layer model for charge transport close to a surface is derived from the solution of Poisson's equation and used to describe distance-dependent electrical four-point measurements on the microscale. As the N -layer model comprises a surface channel, multiple intermediate layers, and a semi-infinite bulk, it can be applied to semiconductors in combination with a calculation of the near-surface band bending to model very precisely the measured four-point resistance on the surface of a specific sample and to extract a value for the surface conductivity. For describing four-point measurements on sample geometries with mixed 2D-3D conduction channels, often a very simple parallel-circuit model has so far been used in the literature, but the application of this model is limited, as there are already significant deviations, when it is compared to the lowest possible case of the N -layer model, i.e., the three-layer model. Furthermore, the N -layer model is applied to published distance-dependent four-point resistance measurements obtained with a multitip scanning tunneling microscope (STM) on germanium(100) and silicon(100) with different bulk doping concentrations resulting in the determination of values for the surface conductivities of these materials.

  11. A survey of surface hemorheological experiments on the inhibition of fibrinogenin formation employing surface layers of fibrinogen systems with heparins and other substances. A contribution on antithrombogenic action.

    PubMed

    Copley, A L; King, R G

    1984-08-01

    In earlier studies using a modified Weissenberg Rheogoniometer, we found decreased rigidity or torque values (tau) in surface layers of heparin plasma, when compared to tau of oxalate plasma from the same blood withdrawal (Thrombosis Res. 1, 1-17, 1972). In subsequent studies of the viscoelasticity of surface layers of highly purified fibrinogen (97-100% clottability) of human and bovine origin, we found, with some heparins, marked lowering of surface viscous moduli (eta's) and of surface elastic moduli (Gs). With some heparins no changes in tau, eta's and Gs occurred. Certain low molecular weight (LMW) preparations of heparins showed decreases, but some did not. This is also the case with heparins of low and high affinity for antithrombin. Calcium heparin and Ca2+ alone always increased eta's and Gs, when added to the fibrinogen system. N-desulfated heparin both decreased or did not change eta's and Gs. Preparations of fibrinogen in dog plasma, to which sodium heparin was added, resulted in a decrease of tau values. These results appear to emphasize that plasma proteins other than fibrinogen, and other plasma constituents, may affect surface hemorheological values. These findings suggest needed interface studies of fibrinogen systems to which plasma or plasma constituents are added. We found also that other substances, i.e., dextran MW 20,000; dextran sulfate MW 17,000; sodium hyaluronate and depolymerized hyaluronate decreased tau, eta's and Gs markedly. Recent findings in the literature are discussed in relation to thrombogenesis in which fibrinogenin gelation is considered as the initial phase of blood clotting. Fibrinogenin is the new term for initial fibrinogen aggregation and subsequent fibrinogen gelation without thrombin participation. The inhibition of fibrinogenin formation extra vivum is considered to be a valid indicator of antithrombogenic activity of substances which play a significant role in investigations on the therapy and prevention of

  12. In Situ Formation of ZnO in Graphene: A Facile Way To Produce a Smooth and Highly Conductive Electron Transport Layer for Polymer Solar Cells.

    PubMed

    Hu, Aifeng; Wang, Qingxia; Chen, Lie; Hu, Xiaotian; Zhang, Yong; Wu, Yinfu; Chen, Yiwang

    2015-07-29

    A novel electron transport layer (ETL) based on zinc oxide@graphene:ethyl cellulose (ZnO@G:EC) nanocomposite is prepared by in situ formation of zinc oxide (ZnO) nanocrystals in a graphene matrix to improve the performance of polymer solar cells. Liquid ultrasound exfoliation by ethyl cellulose as stabilizer not only allows for uniform dispersion of graphene solution but also maintains an original structure of graphene gaining a high conductivity. The ZnO@G:EC ETL displays a quite smooth morphology and develops the energy-level alignment for the electron extraction and transportation. Subsequently, the device based on poly(3-hexylthiophene) (P3HT):(6,6)-phenyl-C61 butyric acid methyl ester (PC61BM) with the ZnO@G:EC as ETL obtains a power conversion efficiency (PCE) of 3.9%, exhibiting a ∼20% improvement compared to the familiar device with bare ZnO nanocrystals as ETL. Replacing the active layer with polythieno[3,4-b]thiophene/benzodithiophene (PTB7): (6,6)-phenyl-C71 butyric acid methyl ester (PC71BM), the PCE can be dramatically improved to 8.4%. This facile and fascinating method to produce a smooth and highly conductive electron transport layer provides an anticipated approach to obtain high performance polymer solar cells.

  13. Seasonal Ozone Variations in the Isentropic Layer between 330 and 380 K as Observed by SAGE 2: Implications of Extratropical Cross-Tropopause Transport

    NASA Technical Reports Server (NTRS)

    Wang, Pi-Huan; Cunnold, Derek M.; Zawodny, Joseph M.; Pierce, R. Bradley; Olson, Jennifer R.; Kent, Geoffrey S.; Skeens, Kristi, M.

    1998-01-01

    To provide observational evidence on the extratropical cross-tropopause transport between the stratosphere and the troposphere via quasi-isentropic processes in the middleworld (the part of the atmosphere in which the isentropic surfaces intersect the tropopause), this report presents an analysis of the seasonal variations of the ozone latitudinal distribution in the isentropic layer between 330 K and 380 K based on the measurements from the Stratospheric Aerosol and Gas Experiment (SAGE) II. The results from SAGE II data analysis are consistent with (1) the buildup of ozone-rich air in the extratropical middleworld through the large-scale descending mass circulation during winter, (2) the spread of ozone-rich air in the isentropic layer from midlatitudes to subtropics via quasi-isentropic transport during spring, (3) significant photochemical ozone removal and the absence of an ozone-rich supply of air to the layer during summer, and (4) air mass exchange between the subtropics and the extratropics during the summer monsoon period. Thus the SAGE II observed ozone seasonal variations in the middleworld are consistent with the existing model calculated annual cycle of the diabatic circulation as well as the conceptual role of the eddy quasi-adiabatic transport in the stratosphere-troposphere exchange reported in the literature.

  14. Inverted InP quantum dot light-emitting diodes using low-temperature solution-processed metal-oxide as an electron transport layer

    NASA Astrophysics Data System (ADS)

    Jang, Ilwan; Kim, Jiwan; Ippen, Christian; Greco, Tonino; Oh, Min Suk; Lee, Jeongno; Kim, Won Keun; Wedel, Armin; Jong Han, Chul; Park, Sung Kyu

    2015-02-01

    The present work shows the inverted InP quantum dot light-emitting diodes (QD-LEDs) with inorganic metal oxide layers. In the inverted structure of ITO/ZnO/InP QDs/CBP/MoO3/Al, a sol-gel derived ZnO film was used as an electron transport layer (ETL) and MoO3 was used as a hole injection layer (HIL). In contrary to high annealing temperature (>200 °C) for conventional ZnO films, low temperature annealing (˜150 °C) was performed for sol-gel derived ZnO film. The performance of the inverted QD-LEDs was efficiently improved by optimization of the annealing time and temperature of ZnO ETL. The current efficiency was significantly improved about 215% by lowering annealing temperature of ZnO ETL.

  15. Carrier transport in flexible organic bistable devices of ZnO nanoparticles embedded in an insulating poly(methyl methacrylate) polymer layer

    NASA Astrophysics Data System (ADS)

    Son, Dong-Ick; Park, Dong-Hee; Choi, Won Kook; Cho, Sung-Hwan; Kim, Won-Tae; Kim, Tae Whan

    2009-05-01

    The bistable effects of ZnO nanoparticles embedded in an insulating poly(methyl methacrylate) (PMMA) polymer single layer by using flexible polyethylene terephthalate (PET) substrates were investigated. Transmission electron microscopy (TEM) images revealed that ZnO nanoparticles were formed inside the PMMA polymer layer. Current-voltage (I-V) measurement on the Al/ZnO nanoparticles embedded in an insulating PMMA polymer layer/ITO/PET structures at 300 K showed a nonvolatile electrical bistability behavior with a flat-band voltage shift due to the existence of the ZnO nanoparticles, indicative of trapping, storing, and emission of charges in the electronic states of the ZnO nanoparticles. The carrier transport mechanism of the bistable behavior for the fabricated organic bistable device (OBD) structures is described on the basis of the I-V results by analyzing the effect of space charge.

  16. Perovskite solar cells with a DMSO-treated PEDOT:PSS hole transport layer exhibit higher photovoltaic performance and enhanced durability.

    PubMed

    Huang, Di; Goh, Tenghooi; Kong, Jaemin; Zheng, Yifan; Zhao, Suling; Xu, Zheng; Taylor, André D

    2017-03-14

    Despite being the most commonly used hole transport layer for p-i-n perovskite solar cells, the conventional PEDOT:PSS layer is far from being optimal for the best photovoltaic performance. Herein, we demonstrate highly conductive thin DMSO-doped PEDOT:PSS layers which significantly enhance the light harvesting, charge extraction, and photocurrent production of organo-lead iodide devices. Both imaging and X-ray analysis reveal that the perovskite thin films grown on DMSO-doped PEDOT:PSS exhibit larger grains with increased crystallinity. Altogether, these improvements result in a 37% boost in the power conversion efficiency (PCE) compared to standard p-i-n photovoltaics with pristine PEDOT:PSS. Furthermore, we demonstrate that DMSO-doped PEDOT:PSS devices possess enhanced PCE durability over time which we attribute primarily to fill factor stability.

  17. First field demonstration of cloud datacenter workflow automation employing dynamic optical transport network resources under OpenStack and OpenFlow orchestration.

    PubMed

    Szyrkowiec, Thomas; Autenrieth, Achim; Gunning, Paul; Wright, Paul; Lord, Andrew; Elbers, Jörg-Peter; Lumb, Alan

    2014-02-10

    For the first time, we demonstrate the orchestration of elastic datacenter and inter-datacenter transport network resources using a combination of OpenStack and OpenFlow. Programmatic control allows a datacenter operator to dynamically request optical lightpaths from a transport network operator to accommodate rapid changes of inter-datacenter workflows.

  18. Solution-processed inverted organic solar cell using V2O5 hole transport layer and vacuum free EGaIn anode

    NASA Astrophysics Data System (ADS)

    Ongul, Fatih

    2015-12-01

    In this study, the sol-gel V2O5 derived by a hydrothermal method to replace the PEDOT:PSS which is a hole transport layer between organic active layer and two different anodes in inverted organic solar cells with TiO2 as an electron transport layer was investigated. The power conversion efficiencies of inverted organic photovoltaic cells increased approximately twofold with using V2O5 instead of PEDOT:PSS on top of the photoactive layer. It was demonstrated that the power conversion efficiencies of inverted organic solar cells prepared with V2O5 solution which was diluted with isopropanol in certain proportions by volume were decreased by increasing ratio of isopropanol in total volume. It was reported for the first time that the inverted organic photovoltaic cells prepared using V2O5 interlayer and Eutectic Gallium-Indium alloy which was prepared using vacuum free simple brush-painted method and can be used as anode electrode as Ag electrode.

  19. Radiation Transport

    SciTech Connect

    Urbatsch, Todd James

    2015-06-15

    We present an overview of radiation transport, covering terminology, blackbody raditation, opacities, Boltzmann transport theory, approximations to the transport equation. Next we introduce several transport methods. We present a section on Caseology, observing transport boundary layers. We briefly broach topics of software development, including verification and validation, and we close with a section on high energy-density experiments that highlight and support radiation transport.

  20. Highly Durable Supportless Pt Hollow Spheres Designed for Enhanced Oxygen Transport in Cathode Catalyst Layers of Proton Exchange Membrane Fuel Cells.

    PubMed

    Dogan, Didem C; Cho, Seonghun; Hwang, Sun-Mi; Kim, Young-Min; Guim, Hwanuk; Yang, Tae-Hyun; Park, Seok-Hee; Park, Gu-Gon; Yim, Sung-Dae

    2016-10-10

    Supportless Pt catalysts have several advantages over conventional carbon-supported Pt catalysts in that they are not susceptible to carbon corrosion. However, the need for high Pt loadings in membrane electrode assemblies (MEAs) to achieve state-of-the-art fuel cell performance has limited their application in proton exchange membrane fuel cells. Herein, we report a new approach to the design of a supportless Pt catalyst in terms of catalyst layer architecture, which is crucial for fuel cell performance as it affects water management and oxygen transport in the catalyst layers. Large Pt hollow spheres (PtHSs) 100 nm in size were designed and prepared using a carbon template method. Despite their large size, the unique structure of the PtHSs, which are composed of a thin-layered shell of Pt nanoparticles (ca. 7 nm thick), exhibited a high surface area comparable to that of commercial Pt black (PtB). The PtHS structure also exhibited twice the durability of PtB after 2000 potential cycles (0-1.3 V, 50 mV/s). A MEA fabricated with PtHSs showed significant improvement in fuel cell performance compared to PtB-based MEAs at high current densities (>800 mA/cm(2)). This was mainly due to the 2.7 times lower mass transport resistance in the PtHS-based catalyst layers compared to that in PtB, owing to the formation of macropores between the PtHSs and high porosity (90%) in the PtHS catalyst layers. The present study demonstrates a successful example of catalyst design in terms of catalyst layer architecture, which may be applied to a real fuel cell system.

  1. Entrainment and Optical Properties of an Elevated Forest Fire Plume Transported into the Planetary Boundary Layer near Washington, D.C.

    NASA Technical Reports Server (NTRS)

    Colarco, P. R.; Schoeberl, M. R.; Marufu, L. T.; Torres, O.; Welton, E. J.; Doddridge, B. G.

    2003-01-01

    Smoke and pollutants from Canadian forest fires were transported over the northeastern United States in July 2002. Lidar observations at the NASA Goddard Space Flight Center show the smoke from these fires arriving in an elevated plume that was subsequently transported to the surface. Trajectory and three-dimensional model calculations confirm the origin of the smoke and show that it mixed to the surface after it was intercepted by the turbulent planetary boundary layer. Modeled smoke optical properties agreed well with aircraft and remote sensing observations provided coagulation of smoke particles was accounted for in the model. Our results have important implications for the long-range transport of pollutants and their subsequent entrainment to the surface, as well as the evolving optical properties of smoke from boreal forest fires.

  2. Spin transport in epitaxial magnetic manganite/ruthenate heterostructures with an LaMnO{sub 3} layer

    SciTech Connect

    Petrzhik, A. M. Ovsyannikov, G. A.; Shadrin, A. V.; Khaidukov, Yu. N.; Mustafa, L.

    2014-12-15

    Epitaxial La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/LaMnO{sub 3}/SrRuO{sub 3} (LSMO/LMO/SRO) heterostructures with an LMO layer 0–35 nm thick are grown by laser ablation on an NdGaO{sub 3} substrate at a high temperature. X-ray diffraction and transmission electron microscopy demonstrate sharp interfaces and epitaxial growth of the LSMO and SRO layers in the heterostructures at an LMO layer thickness of 0–35 nm. SQUID measurements of the magnetic moment of the heterostructures with an LMO layer and the data obtained with reflectometry of polarized neutrons show that the manganite LMO layer is a ferromagnet at a temperature below 150 K and strongly affects the magnetic moment of the heterostructures at low temperatures. The magnetoresistance of the mesostructure created from the heterostructure using lithography and ion etching decreases with increasing LMO layer thickness and weakly depends on the direction of an applied magnetic field. If the LMP layer is absent, a negative magnetoresistance is detected; it is likely to be caused by a negative magnetization of the SRO layer.

  3. The osmotolerant fructophilic yeast Zygosaccharomyces rouxii employs two plasma-membrane fructose uptake systems belonging to a new family of yeast sugar transporters.

    PubMed

    Leandro, Maria José; Sychrová, Hana; Prista, Catarina; Loureiro-Dias, Maria C

    2011-02-01

    Owing to its high resistance to weak-acid preservatives and extreme osmotolerance, Zygosaccharomyces rouxii is one of the main spoilage yeasts of sweet foods and beverages. In contrast with Saccharomyces cerevisiae, Z. rouxii is a fructophilic yeast; it consumes fructose faster than glucose. So far, to our knowledge, no specific Z. rouxii proteins responsible for this fructophilic behaviour have been characterized. We have identified two genes encoding putative fructose transporters in the Z. rouxii CBS 732 genome. Heterologous expression of these two Z. rouxii ORFs in a S. cerevisiae strain lacking its own hexose transporters (hxt-null) and subsequent kinetic analysis of sugar transport showed that both proteins are functionally expressed at the plasma membrane: ZrFfz1 is a high-capacity fructose-specific facilitator (K(m)∼400 mM and V(max)∼13 mmol h(-1) g(-1)) and ZrFfz2 is a facilitator transporting glucose and fructose with similar capacity and affinity (K(m)∼200 mM and V(max)∼4 mmol h(-1) g(-1)). These two proteins together with the Zygosaccharomyces bailii Ffz1 fructose-specific transporter belong to a new family of sugar transport systems mediating the uptake of hexoses via the facilitated diffusion mechanism, and are more homologous to drug/H(+) antiporters (regarding their primary protein structure) than to other yeast sugar transporters of the Sugar Porter family.

  4. The Role of African Easterly Wave on Dust Transport and the Interaction Between Saharan Dust Layer and Atlantic ITCZ During Boreal Summer

    NASA Technical Reports Server (NTRS)

    Lau, William K. M.; Kim, Kyu-Myong

    2012-01-01

    In this paper, we investigate the relationships among Saharan dust outbreak and transport, African easterly waves (AEW), African easterly jet (AEJ) and associated convective activities of Atlantic Intertropical Convergence Zone (ITCZ) using Cloudsat-Calipso, MODIS and MERRA data. We find that a major Saharan dust outbreak is associated with the formation of a westward propagating strong cyclone around 15-25N over the western part northern Saharan. The strong cyclonic flow mobilizes and lifts the dust from the desert surface to a high elevation. As the cyclone propagate westward, it transports a thick elevated dust layer between 900 -500 hPa from the African continent to the eastern Atlantic. Cloudiness is reduced within the warm, dry dusty layer, but enhanced underneath it, possibly due to the presence of a shallow inversion layer over the marine boundary layer. The dust outbreak is linked to enhanced deep convection in the northern part of Atlantic ITCZ, abutting the southern flank of the dust layer, and a strengthening of the northward flank of the AEJ. As the dust layer spreads westward, it loses elevation and becomes increasing diffused as it reaches the central and western Atlantic. Using band pass filtered EOF analysis of MERRA winds, we find that AEWs propagating westward along two principal tracks, centered at 15-25N and 5-10N respectively. The easterly waves in the northern track are highly correlated with major dust outbreak over North Africa and associated with slower moving systems, with a quasi-periodicity of 6-9 day. On the other hand, easterly waves along the southern track are faster, with quasi-periodicity of 3-5 days. These faster easterly waves are closely tied to rainfall/cloud variations along the Atlantic ITCZ. Dust transport along the southern track by the faster waves generally leads rainfall/cloud anomalies in the same region by one or two days, suggesting the southern tracks of dust outbreak are regions of strong interaction between

  5. Ternary Oxides in the TiO2-ZnO System as Efficient Electron-Transport Layers for Perovskite Solar Cells with Efficiency over 15.

    PubMed

    Yin, Xiong; Xu, Zhongzhong; Guo, Yanjun; Xu, Peng; He, Meng

    2016-11-02

    Perovskite solar cells, which utilize organometal-halide perovskites as light-harvesting materials, have attracted great attention due to their high power conversion efficiency (PCE) and potentially low cost in fabrication. A compact layer of TiO2 or ZnO is generally applied as electron-transport layer (ETL) in a typical perovskite solar cell. In this study, we explored ternary oxides in the TiO2-ZnO system to find new materials for the ETL. Compact layers of titanium zinc oxides were readily prepared on the conducting substrate via spray pyrolysis method. The optical band gap, valence band maximum and conduction band minimum of the ternary oxides varied significantly with the ratio of Ti to Zn, surprisingly, in a nonmonotonic way. When a zinc-rich ternary oxide was applied as ETL for the device, a PCE of 15.10% was achieved, comparable to that of the device using conventional TiO2 ETL. Interestingly, the perovskite layer deposited on the zinc-rich ternary oxide is stable, in sharp contrast with that fabricated on a ZnO layer, which will turn into PbI2 readily when heated. These results indicate that potentially new materials with better performance can be found for ETL of perovskite solar cells in ternary oxides, which deserve more exploration.

  6. Improving the performance of organic solar cells using an electron transport layer of B4PyMPM self-assembled nanostructures

    NASA Astrophysics Data System (ADS)

    Ji, Chan-Hyuk; Oh, Il-Soo; Oh, Se-Young

    2015-09-01

    The electron transport (ETL) layer improves power conversion efficiency (PCE) in organic photovoltaic cells (OPVs) through the incorporation of the cathode interfacial layers. Here, we introduce [bis-4,6-(3,5-di-4-pyridylphenyl)-2-methylpyrimidine] (B4PyMPM) as an n-type buffer layer consisting of a self-organized layer with a horizontal configuration in bulk heterojunction OPVs. It is demonstrated that self-organization of this B4PyMPM compound in which molecules adopt a horizontal orientation parallel to the organic semiconducting substrate induces a large local interfacial electric field that results in a significant enhancement of exciton dissociation. The device using B4PyMPM as an ETL layers has a significantly high open circuit voltage ( V oc = 0.64 V), good short circuit current ( J sc = 8.24 mA/cm2), good fill factor ( FF = 0.65) and good PCE (3.42%). The physical properties of the device have also been studied from the measurements of impedance spectroscopy and photocurrent, which directly show the mechanisms occurring inside OPVs. [Figure not available: see fulltext.

  7. Modelling and simulation of low-density lipoprotein transport through multi-layered wall of an anatomically realistic carotid artery bifurcation.

    PubMed

    Kenjereš, Saša; de Loor, Alexander

    2014-02-06

    A high concentration of low-density lipoprotein (LDL) is recognized as one of the principal risk factors for development of atherosclerosis. This paper reports on modelling and simulations of the coupled mass (LDL concentration) and momentum transport through the arterial lumen and the multi-layered arterial wall of an anatomically realistic carotid bifurcation. The mathematical model includes equations for conservation of mass, momentum and concentration, which take into account a porous layer structure, the biological membranes and reactive source/sink terms in different layers of the arterial wall, as proposed in Yang & Vafai (2006). A four-layer wall model of an arterial wall with constant thickness is introduced and initially tested on a simple cylinder geometry where realistic layer properties are specified. Comparative assessment with previously published results demonstrated proper implementation of the mathematical model. Excellent agreement for the velocity and LDL concentration distributions in the arterial lumen and in the artery wall are obtained. Then, an anatomically realistic carotid artery bifurcation is studied. This is the main novelty of the presented research. We find a strong dependence between underlying blood flow pattern (and consequently the wall shear stress distributions) and the uptake of the LDL concentration in the artery wall. The radial dependency of interactions between the diffusion, convection and chemical reactions within the multi-layered artery wall is crucial for accurate predictions of the LDL concentration in the media. It is shown that a four-layer wall model produced qualitatively good agreement with the experimental results of Meyer et al. (1996) in predicting levels of LDL within the media of a rabbit aorta under identical transmural pressure conditions. Finally, it is demonstrated that the adopted model represents a good initial platform for future numerical investigations of the initial stage of atherosclerosis for

  8. A theoretical discussion of the use of the Lineweaver-Burk plot to estimate kinetic parameters of intestinal transport in the presence of unstirred water layers.

    PubMed

    Thomson, A B

    1981-09-01

    Transport of a solute molecule from the bulk phase in the intestinal lumen into the mucosal cells is determined by the rate of movement of the solute molecule across two barriers, the unstirred water layers (UWL) and the microvillus membrane. Failure to account for the effect of the resistance offered by the UWL introduces significant errors into the estimate of kinetic constants of carrier-mediated transport, and these errors may be further magnified by the use of the Lineweaver-Burk plot. This study was under taken to determine use of this plot under conditions that depict the effect of varying the effective resistance of the UWL, the distribution of transport sites along the villus (fn), the passive permeability coefficient (P), the maximal transport rate (Jdm), and the Michaelis constant (Km). Theoretical curves derived from a new equation demonstrate that (1) the Lineweaver-Burk plot is linear under only a limited number of conditions, and even then may lead to serous over- or under-estimation of Jdm and Km; (2) failure to correct for passive permeation may give rise to additional quantitative discrepancies between the true and apparent values of Jdm and Km; and (3) the qualitative characteristics of a carrier-mediated intestinal transport system may be ascertained only after correction for the contribution of passive permeation, and after correction for the effective resistance of the UWL.

  9. Occupational Employment

    ERIC Educational Resources Information Center

    Occupational Outlook Quarterly, 2012

    2012-01-01

    When choosing a career, jobseekers often want to know which occupations offer the best prospects. Generally, occupations that have rapid job growth, many new jobs, or many job openings--and good wages--promise better opportunities. This paper shows how employment in particular occupations is projected to change from 2010 to 2020. It presents…

  10. Transport properties of interfacial Si-rich layers formed on silicate minerals during weathering: Implications for environmental concerns

    NASA Astrophysics Data System (ADS)

    Daval, Damien; Rémusat, Laurent; Bernard, Sylvain; Wild, Bastien; Micha, Jean-Sébastien; Rieutord, François; Fernandez-Martinez, Alejandro

    2015-04-01

    The dissolution of silicate minerals is of primary importance for various processes ranging from chemical weathering to CO2 sequestration. Whether it determines the rates of soil formation, CO2 uptake and its impact on climate change, channeling caused by hydrothermal circulation in reservoirs of geothermal power plants, durability of radioactive waste confinement glasses or geological sequestration of CO2, the same strategy is commonly applied for determining the long term evolution of fluid-rock interactions. This strategy relies on a bottom-up approach, where the kinetic rate laws governing silicate mineral dissolution are determined from laboratory experiments. However, a long-standing problem regarding this approach stems from the observation that laboratory-derived dissolution rates overestimate their field counterparts by orders of magnitude, casting doubt on the accuracy and relevance of predictions based on reactive-transport simulations. Recently [1], it has been suggested that taking into account the formation of amorphous Si-rich surface layers (ASSL) as a consequence of mineral dissolution may contribute to decrease the large gap existing between laboratory and natural rates. Our ongoing study is aimed at deciphering the extent to which ASSL may represent a protective entity which affects the dissolution rate of the underlying minerals, both physically (passivation) and chemically (by promoting the formation of a local chemical medium which significantly differs from that of the bulk solution). Our strategy relies on the nm-scale measurement of the physicochemical properties (diffusivity, thickness and density) of ASSL formed on cleavages of a model mineral (wollastonite) and their evolution as a function of reaction progress. Our preliminary results indicate that the diffusivity of nm-thick ASSL formed on wollastonite surface is ~1,000,000 times smaller than that reported for an aqueous medium, as estimated from the monitoring of the progression of a

  11. Roles of blocking layer and anode bias in processes of impurity-band transition and transport for GaAs-based blocked-impurity-band detectors

    NASA Astrophysics Data System (ADS)

    Wang, Xiaodong; Wang, Bingbing; Chen, Xiaoyao; Chen, Yulu; Hou, Liwei; Xie, Wei; Pan, Ming

    2016-11-01

    Recently, GaAs-based BIB detector has attracted a lot of attention in the area of THz photovoltaic detection due to potential application values in security check and drug inspection. However, the physical mechanisms involving in carrier transition and transport are still unclear due to the poor material quality and immature processing technique. In this paper, the dark current and THz response characteristics have thus been numerically studied for GaAs-based blocked-impurity-band (BIB) detectors. The key parameters and physical models are constructed by simultaneously considering carrier freeze-out and impurity-band broadening effects. Roles of blocking layer and anode bias in processes of impurity-band transition and transport are intensively investigated, and the results can be well explained by numerical models. It is demonstrated that the effective electric field for the detector is only located in the absorbing layer, and can determine to a large extent the magnitude of the dark current and THz response. While the blocking layer not only can suppress dark current but also can attenuate responsivity due to its electric-field modulation effect.

  12. The China Clipper - Fast advective transport of radon-rich air from the Asian boundary layer to the upper troposphere near California

    NASA Technical Reports Server (NTRS)

    Kritz, Mark A.; Le Roulley, Jean-Claude; Danielsen, Edwin F.

    1990-01-01

    A series of upper tropospheric radon concentration measurements made over the eastern Pacific and west coast of the U.S. during the summers of 1983 and 1984 has revealed the occurrence of unexpectedly high radon concentrations for 9 of the 61 measurements. A frequency distribution plot of the set of 61 observations shows a distinct bimodal distribution, with approximately 2/5 of the observations falling close to 1 pCi/SCM, and 3/5 falling in a high concentration mode centered at about 11 pCi/SCM. Trajectory and synoptic analyses for two of the flights on which such high radon concentrations were observed indicate that this radon-rich air originated in the Asian boundary layer, ascended in cumulus updrafts, and was carried eastward in the fast moving air on the anticyclonic side of the upper tropospheric jet. The results suggest that the combination of rapid vertical transport from the surface boundary layer to the upper troposphere, followed by rapid horizontal transport eastward represents an efficient mode of long-transport for other, chemically reactive atmospheric trace constituents.

  13. Stochastic microstructural modeling of fuel cell gas diffusion layers and numerical determination of transport properties in different liquid water saturation levels

    NASA Astrophysics Data System (ADS)

    Tayarani-Yoosefabadi, Z.; Harvey, D.; Bellerive, J.; Kjeang, E.

    2016-01-01

    Gas diffusion layer (GDL) materials in polymer electrolyte membrane fuel cells (PEMFCs) are commonly made hydrophobic to enhance water management by avoiding liquid water blockage of the pores and facilitating reactant gas transport to the adjacent catalyst layer. In this work, a stochastic microstructural modeling approach is developed to simulate the transport properties of a commercial carbon paper based GDL under a range of PTFE loadings and liquid water saturation levels. The proposed novel stochastic method mimics the GDL manufacturing process steps and resolves all relevant phases including fiber, binder, PTFE, liquid water, and gas. After thorough validation of the general microstructure with literature and in-house data, a comprehensive set of anisotropic transport properties is simulated for the reconstructed GDL in different PTFE loadings and liquid water saturation levels and validated through a comparison with in-house ex situ experimental data and empirical formulations. In general, the results show good agreement between simulated and measured data. Decreasing trends in porosity, gas diffusivity, and permeability is obtained by increasing the PTFE loading and liquid water content, while the thermal conductivity is found to increase with liquid water saturation. Using the validated model, new correlations for saturation dependent GDL properties are proposed.

  14. Transport and distribution of bacteria and diatoms in the aqueous surface micro-layer of a salt marsh

    USGS Publications Warehouse

    Harvey, Ronald W.; Lion, Leonard W.; Young, Lily Y.

    1983-01-01

    The effects of tide and wind upon the distribution and transport of bacteria and diatoms in the aqueous surface microlayers of a Massachusetts and San Francisco Bay salt marsh were examined. The compression of the surface films by both tide and wind resulted in significant enrichments of bacterioneuston. At the San Francisco Bay site, significant numbers of diatoms were transported within the microlayer over a tidal cycle.

  15. Gate-tunable and thickness-dependent electronic and thermoelectric transport in few-layer MoS2

    NASA Astrophysics Data System (ADS)

    Kayyalha, Morteza; Maassen, Jesse; Lundstrom, Mark; Shi, Li; Chen, Yong P.

    2016-10-01

    Over the past few years, there has been a growing interest in layered transition metal dichalcogenides such as molybdenum disulfide (MoS2). Most studies so far have focused on the electronic and optoelectronic properties of single-layer MoS2, whose band structure features a direct bandgap, in sharp contrast to the indirect bandgap of thicker MoS2. In this paper, we present a systematic study of the thickness-dependent electrical and thermoelectric properties of few-layer MoS2. We observe that the electrical conductivity ( σ) increases as we reduce the thickness of MoS2 and peaks at about two layers, with six-times larger conductivity than our thickest sample (23-layer MoS2). Using a back-gate voltage, we modulate the Fermi energy ( E F ) of the sample where an increase in the Seebeck coefficient ( S ) is observed with decreasing gate voltage ( E F ) towards the subthreshold (OFF state) of the device, reaching as large as 500 μ V / K in a four-layer MoS2. While previous reports have focused on a single-layer MoS2 and measured Seebeck coefficient in the OFF state, which has vanishing electrical conductivity and thermoelectric power factor ( P F = S 2 σ ), we show that MoS2-based devices in their ON state can have P F as large as > 50 /μ W cm K 2 in the two-layer sample. The P F increases with decreasing thickness and then drops abruptly from double-layer to single-layer MoS2, a feature we suggest as due to a change in the energy dependence of the electron mean-free-path according to our theoretical calculation. Moreover, we show that care must be taken in thermoelectric measurements in the OFF state to avoid obtaining erroneously large Seebeck coefficients when the channel resistance is very high. Our study paves the way towards a more comprehensive examination of the thermoelectric performance of two-dimensional (2D) semiconductors.

  16. Employment of High-Performance Thin-Layer Chromatography for the Quantification of Oleuropein in Olive Leaves and the Selection of a Suitable Solvent System for Its Isolation with Centrifugal Partition Chromatography.

    PubMed

    Boka, Vasiliki-Ioanna; Argyropoulou, Aikaterini; Gikas, Evangelos; Angelis, Apostolis; Aligiannis, Nektarios; Skaltsounis, Alexios-Leandros

    2015-11-01

    A high-performance thin-layer chromatographic methodology was developed and validated for the isolation and quantitative determination of oleuropein in two extracts of Olea europaea leaves. OLE_A was a crude acetone extract, while OLE_AA was its defatted residue. Initially, high-performance thin-layer chromatography was employed for the purification process of oleuropein with fast centrifugal partition chromatography, replacing high-performance liquid-chromatography, in the stage of the determination of the distribution coefficient and the retention volume. A densitometric method was developed for the determination of the distribution coefficients, KC = CS/CM. The total concentrations of the target compound in the stationary phase (CS) and in the mobile phase (CM) were calculated by the area measured in the high-performance thin-layer chromatogram. The estimated Kc was also used for the calculation of the retention volume, VR, with a chromatographic retention equation. The obtained data were successfully applied for the purification of oleuropein and the experimental results confirmed the theoretical predictions, indicating that high-performance thin-layer chromatography could be an important counterpart in the phytochemical study of natural products. The isolated oleuropein (purity > 95%) was subsequently used for the estimation of its content in each extract with a simple, sensitive and accurate high-performance thin-layer chromatography method. The best fit calibration curve from 1.0 µg/track to 6.0 µg/track of oleuropein was polynomial and the quantification was achieved by UV detection at λ 240 nm. The method was validated giving rise to an efficient and high-throughput procedure, with the relative standard deviation % of repeatability and intermediate precision not exceeding 4.9% and accuracy between 92% and 98% (recovery rates). Moreover, the method was validated for robustness, limit of quantitation, and limit of detection. The amount of oleuropein for

  17. Two case studies on the interaction of large-scale transport, mesoscale photochemistry, and boundary-layer processes on the lower tropospheric ozone dynamics in early spring

    NASA Astrophysics Data System (ADS)

    Brönnimann, S.; Siegrist, F. C.; Eugster, W.; Cattin, R.; Sidle, C.; Hirschberg, M. M.; Schneiter, D.; Perego, S.; Wanner, H.

    2001-04-01

    The vertical distribution of ozone in the lower troposphere over the Swiss Plateau is investigated in detail for two episodes in early spring (February 1998 and March 1999). Profile measurements of boundary-layer ozone performed during two field campaigns with a tethered balloon sounding system and a kite are investigated using regular aerological and ozone soundings from a nearby site, measurements from monitoring stations at various altitudes, backward trajectories, and synoptic analyses of meteorological fields. Additionally, the effect of in situ photochemistry was estimated for one of the episodes employing the Metphomod Eulerian photochemical model. Although the meteorological situations were completely different, both cases had elevated layers with high ozone concentrations, which is not untypical for late winter and early spring. In the February episode, the highest ozone concentrations of 55 to 60 ppb, which were found at around 1100 m asl, were partly advected from Southern France, but a considerable contribution of in situ photochemistry is also predicted by the model. Below that elevation, the local chemical sinks and surface deposition probably overcompensated chemical production, and the vertical ozone distribution was governed by boundary-layer dynamics. In the March episode, the results suggest that ozone-rich air parcels, probably of stratospheric or upper tropospheric origin, were advected aloft the boundary layer on the Swiss Plateau.