Transverse Channel Research Articles

Drainage network evolution and patterns of sedimentation in an experimental wedge

In fold and thrust belts drainage organization and patterns of sedimentation depend conceptually on the ability or not for preexisting reaches to incise uplifting thrust sheets. In this study we investigate experimentally the dynamics of drainage network in a wedge submitted to shortening and erosion. It allows us to reproduce and to monitor the interactions between tectonics, erosion and sedimentation during the development of up to five successive thrust sheets. In the experiments channels adjust to uplift rate by both increasing their slope and narrowing their channels as it is observed in nature. The series of experiments shows that the proportion of persistent preexisting transverse channels increases with the ratio of rainfall over shortening rates. The experiments confirm the view that the competition between discharge and tectonic uplift controls along-strike variations in sediment flux in sedimentary basins by controlling the drainage organization. If the transverse channels draining a wedge are not diverted, a line-source dispersal system develops in front of the active structure. If channels are diverted in the backlimb of the frontal structure it results in point-sourced depositional systems separated by areas fed only by small channels developing in the front of the wedge. Fans accumulated in front of the active structures reveal two stages of sedimentation, one of progradation, while the frontal structure is active and a second one of valley backfilling and thrust sealing during internal deformation of the wedge. The experiments also suggest that spatial variations in rock uplift rate along a thrust front may be evidenced by minimum-discharge variations of persistent transverse channels.

Responsive composite Janus cages

pH responsive composite Janus cages of PS-silica-PEO are prepared using silica nanoparticles to crosslink two PAA contained di-block copolymers at an emulsion interface sequentially. Transverse channels are in situ created across the shell, which facilitates mass transfer. Shell is pH responsive owing to the presence of residual PAA chains tethered onto the silica nanoparticles. The Janus cages are capable to preferentially capture oil from their aqueous surroundings. The saturation absorption capacity is determined by pH and oil property. Other composite Janus cages are expected by extension the method using other copolymers and functional nanoparticles.

Contribution of two-particle–two-hole final states to the nuclear response

The excitation of two particle-two hole final states in neutrino-nucleus scattering has been advocated by many authors as the source of the excess cross section observed by the MiniBooNE Collaboration in the quasi elastic sector. We analyse the mechanisms leading to the appearance of these final states, and illustrate their significance through the results of accurate calculations of the nuclear electromagnetic response in the transverse channel. A novel approach, allowing for a consistent treatment of the amplitudes involving one- and two-nucleon currents in the kinematical region in which the non relativistic approximation breaks down, is outlined.

Modelling rip current flow and bather escape strategies across a transverse bar and rip channel morphology

Rip currents are a hazard to bathers on surf beaches worldwide, yet due to logistical and ethical concerns there has been minimal examination of how bathers caught in them should attempt to escape. This study presents the first numerical model of simulated bathers escaping from a rip current. An understanding of the underlying coastal geomorphology and hydrodynamics form a critical basis for the model, with the intention that outcomes of the model should be evaluated from a physical science perspective. Field observations of a transverse bar rip channel were used as model inputs. Escape simulations were performed with moderate energy (Hs≈1m), oblique offshore wave forcing, used to generate two non-stationary, asymmetric flow fields (dominant surfzone exits and dominant recirculation). The model treats bathers as particles that move with the underlying flow, with an additional swimming velocity added, iterating until a safety condition, based on depth and current speed, is satisfied or until a maximum time limit is reached. Simulations compared the strategies of “stay afloat” and various fixed swim directions, using two bather heights and four swim speeds (up to 0.4m/s). The overall optimal escape strategy was to swim parallel in the direction of alongshore flow. Time to safety was less for: (i) recirculating flow; (ii) taller bathers; and (iii) greater swim speeds. Across all simulations, 44% of “floaters” reached safety within 10min, while 80% of slow swimmers (0.2m/s) succeeded in the same time interval. This suggests that slow sustainable swimming may be a preferable escape action to floating. Optimal swim direction varied with start location, from onshore (near the shoreline), parallel to shore (mid-rip channel) and diagonally onshore (outer rip channel). At lower swim speeds, the optimal swim direction had greater dependence on the underlying flow field, as opposed to distance to safety, therefore choice of direction is more complex for slower swimmers. Critically, no strategy succeeded in all scenarios at all locations across the surfzone, and small changes to input conditions (water level, start time and location, swim direction) had major impacts on outcomes. Future modelling efforts should examine additional surf zone rip current morphologies and wave-tide inputs, with a goal of determining generalised rip escape principles that may be communicated to the general public.

Fano resonances in high energy electron transport in nanowires of variable cross-section

Electron ballistic transport in 2D quantum waveguide with two narrowings is considered. For longitudinal electron motion such narrowings play the role of effective potential barriers and conditions for resonant tunneling arise. If the electron energy is sufficiently high the electron wave can scatter into different quantum states (transverse channels of the leads) which results in complicated E-dependence of the scattering amplitudes. Numerical simulations have shown that the scattering amplitudes resonances are of Fano type. The form of the transmission probability curve is conditioned by interference of the quantum states into which the electron wave is scattered by the narrowings. The suggested interference model makes possible to find the resonance parameters with high precision and to link them to the closed resonator eigenvalues.

Carbohydrate-mediated purification of petrochemicals.

Metal-organic frameworks (MOFs) are known to facilitate energy-efficient separations of important industrial chemical feedstocks. Here, we report how a class of green MOFs-namely CD-MOFs-exhibits high shape selectivity toward aromatic hydrocarbons. CD-MOFs, which consist of an extended porous network of γ-cyclodextrins (γ-CDs) and alkali metal cations, can separate a wide range of benzenoid compounds as a result of their relative orientation and packing within the transverse channels formed from linking (γ-CD)6 body-centered cuboids in three dimensions. Adsorption isotherms and liquid-phase chromatographic measurements indicate a retention order of ortho- > meta- > para-xylene. The persistence of this regioselectivity is also observed during the liquid-phase chromatography of the ethyltoluene and cymene regioisomers. In addition, molecular shape-sorting within CD-MOFs facilitates the separation of the industrially relevant BTEX (benzene, toluene, ethylbenzene, and xylene isomers) mixture. The high resolution and large separation factors exhibited by CD-MOFs for benzene and these alkylaromatics provide an efficient, reliable, and green alternative to current isolation protocols. Furthermore, the isolation of the regioisomers of (i) ethyltoluene and (ii) cymene, together with the purification of (iii) cumene from its major impurities (benzene, n-propylbenzene, and diisopropylbenzene) highlight the specificity of the shape selectivity exhibited by CD-MOFs. Grand canonical Monte Carlo simulations and single component static vapor adsorption isotherms and kinetics reveal the origin of the shape selectivity and provide insight into the capability of CD-MOFs to serve as versatile separation platforms derived from renewable sources.

Nernst and Seebeck effects in HgTe/CdTe topological insulator

The Seebeck and Nernst effects in HgTe/CdTe quantum wells are studied using the tight-binding Hamiltonian and the nonequilibrium Green's function method. The Seebeck coefficient, Sc, and the Nernst coefficient, Nc, oscillate as a function of EF, where EF is the Fermi energy. The Seebeck coefficient shows peaks when the Fermi energy crosses the discrete transverse channels, and the height of the nth peak of the Sc is [ln2/(12+|n|)] for EF > 0. For the case EF < 0, the values of the peaks are negative, but the absolute values of the first five peaks are the same as those for EF > 0. The 6th peak of Sc reaches the value [ln2/1.35] due to a higher density of states. When a magnetic field is applied, the Nernst coefficient appears. However, the values of the peaks for Nc are all positive. For a weak magnetic field, the temperature suppresses the oscillation of the Seebeck and Nernst coefficients but increases their magnitude. For a large magnetic field, because of the highly degenerate Landau levels, the peaks of the Seebeck coefficient at position EF=−12, 10, 28meV, and Nernst coefficient at EF=−7, 10meV are robust against the temperature.

OPTIMIZATION OF THE BLADE PROFILE AND COOLING STRUCTURE IN A GAS TURBINE STAGE CONSIDERING BOTH THE AERODYNAMICS AND HEAT TRANSFER

The need to design high performance of a cooled gas turbine is considered with emphasis made on coupled aerodynamic and heat transfer optimization of the vane, blade, and single stage cooled gas turbine by using a multiobjective optimization method. The aerodynamic profile is designed to have three sections and the cooling structure to consist of a serpentine passage, with a tail transverse channel and trailing edge slots. The optimization platform is built up in an in-house code using a cooling structure parametric method based on MATLAB, as well as automatic grid generation methods, a blade profile parametric program in FORTRAN, the soft ware ISIGHT and ANSYS-CFX. The optimization platform evaluates the aerodynamic effects through the aerodynamic efficiency and presents the cooling effect by the high-temperature coefficient. The pressure drop is described by a pressure drop function. The multiobjective optimization method is accomplished by optimizing the inlet flow angle, installation angle, and the post-corner angle of the vane and blade profiles, while the position of partition is the optimized variable of the cooling structure. The results show that there exists an optimum case in aerodynamic efficiency, high-temperature coefficient, and pressure drop in a Pareto-optimal front. (Less)

Performance of a plate-fin heat exchanger with vortex-generator channels: 3D-CFD simulation and experimental validation

A type of plate-fin channel with rectangular wings as a transverse vortex-generator channel was considered. The heat transfer and fluid flow characteristics of the vortex-generator channel were systematically analyzed by 3D-CFD simulations. As the first part of project, a precise and reliable experimental setup was designed and fabricated to generate a constant temperature boundary condition. Inlet–outlet bulk and surface temperatures along with flow rate data were acquired by using pt-100 and K series calibrated thermocouples and an ultrasonic flow meter, respectively. Hence, boundary conditions for the CFD simulations were well defined, and data for the validation of a reference model were generated. Comparing the experimental data with the predicted results by CFD simulation implies that the applied CFD approach can properly predict the thermal-hydraulic specifications of the vortex-generator channel. In the second part of the project, the influences of seven effective geometrical parameters (i.e. wings height, wings width, channel length, longitudinal wings pitch, transverse wings pitch, wings attach angle, and wings attack angle) for three conventional coolants flow (i.e. water, oil, and ethylene glycol) at the laminar flow regime were evaluated. As the third part of the project, general correlations were derived for Nusselt number of the coolants flow inside the plate-fin heat exchangers with vortex-generator channels.

Numerical investigation of the nonreacting and reacting flow fields in a transverse gaseous injection channel with different species

The mixing and combustion process has an important impact on the engineering realization of the scramjet engine. The nonreacting and reacting flow fields in a transverse injection channel have been investigated numerically, and the predicted results have been compared with the available experimental data in the open literature, the wall pressure distributions, the separation length, as well as the penetration height. Further, the influences of the molecular weight of the fuel and the jet-to-crossflow pressure ratio on the wall pressure distribution have been studied. The obtained results show that the predicted results show reasonable agreement with the experimental data, and the variable trends of the penetration height and the separation distance are almost the same as those obtained in the experiment. The vapor pressure model is suitable to fit the relationship between the penetration height, the separation distance and the jet-to-crossflow pressure ratio. The combustion process mainly occurs upstream of the injection port, and it makes a great difference to the wall pressure distribution upstream of the injection port, especially when the jet-to-crossflow pressure ratio is large enough, namely 17.72 and 25.15 in the range considered in the current study. For hydrogen, the combustion downstream of the injection port occurs more intensively, and this may be induced by its smaller molecular weight.

Transverse Electric Mode for Near‐Field Radiative Heat Transfer in Graphene–Metamaterial Systems

Heat transfer via radiation can be enhanced across short distances when the system supports resonant tunneling of surface electromagnetic modes. For certain metamaterials, the transverse electric mode is available. Such magnetically active artificial composites can facilitate coupling with the transverse electric mode of graphene. Graphene transverse electric or magnetic channels for the near-field radiation can be emphasized or inhibited by design.

Diagnosing climatic and tectonic controls on topography: Eastern flank of the northern Bolivian Andes

High relief and steep rainfall gradients make the eastern flank of the northern Bolivian Andes an excellent location for deciphering the relative roles of tectonics and climate on erosion and landscape evolution. We seek to resolve the climate versus tectonics debate in this location by linking topographic analyses and erosion rate data with fluvial bedrock incision theory and numerical landscape evolution modeling. We find that patterns in the channel steepness index (channel slope normalized for drainage area) in both transverse channels that drain across the rainfall gradient through the driest and wettest parts of the landscapes, and frontal channels that drain only the wettest regions are indicative primarily of a gradient in rock uplift rate, although climate likely plays a secondary role in shaping these channel profiles. Previously published erosion rates from 23 watersheds vary with the proposed rock uplift gradient and inversely with rainfall rate, suggesting that increased rainfall is not driving increased rock uplift and erosion. The channel steepness index in an additional 35 tributary watersheds increases with the proposed rock uplift gradient. Simulations from a landscape evolution model that isolate the signatures of rainfall and uplift patterns on landscape morphology corroborate our interpretation that the morphology of this landscape is primarily controlled by a gradient in rock uplift rate, with rainfall rates playing a secondary role. Model results also suggest that the differences between channel steepness values in the transverse and frontal channels cannot be explained by the uplift and rainfall patterns alone. Differences in lithology may be contributing to the higher channel steepness values in the transverse channels, or the transverse channels may be affected by a transient oversteepening phenomenon seen in tools-and-cover river incision models. The conclusions are possible only after detailed comparisons among real and modeled rivers of different sizes that drain different locations. We present best practices for future studies that seek to resolve the relative imprint of rock uplift and rainfall on a landscape.

Design and fabrication of a holey fiber microfluidic device with transverse micro-channel

In this report, we present a design of holey fiber structure with six air holes in the cladding and a transverse microfluidic channel intersecting the silica core for liquid detection purpose. The simulation results suggest an improved refractive index sensitivity of the proposed structure compared to that of a single mode fiber with similar transverse channel. The proposed holey fiber structures are fabricated and characterized. Full Text: PDF References J.C. Knight, J. Arriaga, T.A. Birks, A. Ortigosa-Blanch, W.J. Wadsworth and P.St.J. Russell, "Anomalous dispersion in photonic crystal fiber", IEEE Photon. Technol. Lett. 12, 807 (2000) CrossRef D.J.J. Hu, P. Shum, G. Ren and C. Lu, "Hole-assisted lightguide fibers with small negative dispersion and low dispersion slope", App. Opt. 47, 5061 (2008) CrossRef P.St.J. Russell, P. H&ouml;lzer, W. Chang, A. Abdolvand and J. C. Travers, "Hollow-core photonic crystal fibres for gas-based nonlinear optics", Nature Photonics, 8, 278 (2014) CrossRef D. J. J. Hu, P. Shum, C. Lu and G. Ren, "Dispersion-flattened polarization-maintaining photonic crystal fiber for nonlinear applications", Opt. Comm. 282, 4072 (2009) CrossRef K. Milenko, D. J. J. Hu, P. P. Shum, T. Zhang, J. L. Lim, Y. Wang, T. R. Wolinski, H. Wei and W. Tong, "Photonic crystal fiber tip interferometer for refractive index sensing", Opt. Lett., 37, 1373 (2012) CrossRef D. J. J. Hu, Y. Wang, J. L. Lim, T. Zhang, K. Mileńko, Z. Chen, M. Jiang, G. Wang, F. Luan, P. P. Shum, Q. Sun, H. Wei, W. Tong and T. R. Woliński, "Novel Miniaturized Fabry&ndash;Perot Refractometer Based on a Simplified Hollow-Core Fiber With a Hollow Silica Sphere Tip", IEEE Sensors Journal, 12, 1239 (2012) CrossRef M.T. Myaing, J.Y. Ye and T.B. Norris, "Enhanced two-photon biosensing with double-clad photonic crystal fibers", Opt. Lett., 28, 1224 (2003) CrossRef D. J. J. Hu, J. L. Lim, M. K. Park, L. T.-H. Kao and Y. Wang, "Photonic Crystal Fiber-Based Interferometric Biosensor for Streptavidin and Biotin Detection", IEEE J. Sel. Top. Quant. Electron., 18, 1293 (2012) CrossRef D. J. J. Hu, J. L. Lim, Y. Cui, K. Milenko, Y. Wang, P. P. Shum and T. Wolinski, "Fabrication and Characterization of a Highly Temperature Sensitive Device Based on Nematic Liquid Crystal-Filled Photonic Crystal Fiber", IEEE Photonics Journal, 4, 1248 (2012). CrossRef Y. Cui, P.P. Shum, D. J. J. Hu, G. Wang, G. Humbert and X.-Q Dinh, "Temperature Sensor by Using Selectively Filled Photonic Crystal Fiber Sagnac Interferometer", IEEE Photonics Journal, 4, 1801 (2012) CrossRef D. J. J. Hu, P.P. Shum, J.L. Lim, Y. Cui, K. Milenko, Y. Wang and T. Wolinski, "A Compact and Temperature-Sensitive Directional Coupler Based on Photonic Crystal Fiber Filled With Liquid Crystal 6CHBT", IEEE Photonics Journal, 4, 2010 (2012) CrossRef Dinish U. S, Chit Yaw Fu, Kiat Seng Soh, Ramaswamy Bhuvaneswari, Anil Kumar and Malini Olivo, "Highly sensitive SERS detection of cancer proteins in low sample volume using hollow core photonic crystal fiber", Biosensors and Bioelectronics, 33, 293 (2012) CrossRef K. Zhou, Z. Yan, L. Zhang, and I. Bennion, "Refractometer based on fiber Bragg grating Fabry-P&eacute;rot cavity embedded with a narrow microchannel," Opt. Express 19, 11769-11779 (2011). CrossRef J. Petrovic, Y. Lai, and I. Bennion, "Numerical and experimental study of microfluidic devices in step-index optical fibers", Appl. Opt. 47, 1410-1416 (2008). CrossRef

Solar constraints on hidden photons re-visited

We re-examine solar emission of hidden photons γ′(mass m) caused by kinetic γ–γ′ mixing. Wecalculate the emission rate with thermal field theory methods andwith a kinetic equation that includes γ–γ′ ''flavoroscillations'' and γ absorption and emission by the thermalmedium. In the resonant case both methods yield identical emissionrates which, in the longitudinal channel, are enhanced by a factorωP2/m2 (plasma frequency ωP) inagreement with An, Pospelov and Pradler (2013). The Sun must notemit more energy in a ``dark channel'' than allowed by solarneutrino measurements, i.e., not more than 10% of its photonluminosity. Together with the revised emission rate, thisconservative requirement implies χ < 4 × 10−12(eV/m) for the kinetic mixing parameter. This is the mostrestrictive stellar limit below m ∼ 3eV,whereas for larger masses the transverse channel dominates togetherwith limits from other stars. A recent analysis of XENON10 datamarginally improves the solar limit, leaving open the opportunity todetect solar hidden photons with future large-scale dark matterexperiments. Detecting low-mass hidden photons with the ALPS-IIphoton-regeneration experiment also remains possible.

Investigation of slip boundary conditions in the T-shaped microchannel

Flow regimes and mixing performance in a T-type micromixer at high Reynolds numbers were studied by numerical solution of the Navier–Stokes equations. The Reynolds number was varied from 1 to 1000. The cross section of the mixing channel was 100μm×200μm, and its length was 1400μm. The transverse inlet channels were symmetric about the mixing channel, and their cross-section was 100μm×100μm, and the total length was 800μm. Five different flow regimes were identified: (i) stationary vortex-free flow (Re<5); (ii) stationary symmetric vortex flow with two horseshoe vortices (5<Re<150); (iii) stationary asymmetric vortex flow (150<Re<240); (iv) non-stationary periodic flow (240<Re<400); and (v) stochastic flow (Re>400). Maximum mixing efficiency is obtained for nonstationary asymmetric vortex flow. In this case, an S-shaped vortex structure is formed in the flow field. The effect of the slip conditions on the flow pattern and mixing efficiency is studied. The slip length varied from 1 to 70μm in the calculations. It was shown that the mixing can be controlled by hydrophobic coating.

Janus Cages of Bilayered Polymer–Inorganic Composites

Janus cages with a bilayer polymer–inorganic composite shell are synthesized by an emulsion interfacial self-organized sol–gel process followed by a polymer grafting onto the interior surface containing a vinyl group. Binary surfactants experience a phase separation to create transverse channels across the shell. The Janus cages can be functionalized by either growing responsive polymers or integrating with functional nanoparticles. They are promising in controlled loading and triggered release of desired materials under guidance.

Model independent analysis of interactions between dark matter and various quarks

Present and future expected limits on interactions between dark matter and various quarks are thoroughly investigated in a model-independent way. In particular, the constraints on the interactions from the Large Hadron Collider (LHC) experiment are carefully considered with focusing on mono jet + missing transverse energy, mono b-jet + missing transverse energy, and top quark(s) + missing transverse energy channels. Model-independent upper limits (expected limits) on the cross section times acceptance for non-standard model events are derived at 7 TeV (8 or 14 TeV) running of the LHC experiment. With assuming that the dark matter is a singlet real scalar or a singlet Majorana fermion, we also put constraints on several operators describing its interactions with up, down, strange, charm, bottom and top quarks. These constraints are compared to those obtained by cosmological and astrophysical observations of the dark matter.

Winding branes and persistent currents

A D5 brane winding around a stack of D3 branes can be used as a model of persistent current in a thin superconducting ring, with the number N of D3s corresponding to the number of transverse channels in the ring. We consider, in the large N limit, existence and properties of a gapped superconducting state with a uniform winding number density q. We find that there is a gapped classical solution for any q, no matter how large, but when q is larger than a certain q_m the state is unstable with respect to decay by phase slips. We argue that this decay produces strings via a version of the Hanany-Witten effect (in a non-transverse, non-supersymmetric arrangement of branes). This parallels the requirement of quasiparticle production in a clean (disorder-free) wire in field theory of superconductivity.

Critical current of a superconducting wire via gauge/gravity duality

We describe application of the gauge/gravity to study of depairing current in thin superconducting wires. The large number N of colors of the gauge theory is identified with the number of filled transverse channels in the wire. On the gravity side, the physics is described by a system of D3 and D5 branes intersecting over a line. We consider the ground state of the system at fixed electric current and find that there is a continuous phase transition at a critical current, in the universality class of the dissipative XY model. We discuss relation of our results to recent experiments on statistics of the switching current in nanowires.

Karst subsidence as a control on the accumulation and preservation of aeolian deposits: A Pleistocene example from a proglacial outwash setting, Ebro Basin, Spain

AbstractMeltwater flows emanating from the Pyrenees during the Pleistocene constructed a braided outwash plain in the Ebro Basin and led to the karstification of the Neogene gypsum bedrock. Synsedimentary evaporite dissolution locally increased subsidence rates and generated dolines and collapses that enabled the accumulation and preservation of outwash gravels and associated windblown deposits that were protected from erosion by later meltwater flows. In these localized depocentres, maximum rates of wind deceleration resulted from airflow expansion, enabling the accumulation of cross‐stratified sets of aeolian strata climbing at steep angles and thereby preserving up to 5 m thick sets. The outwash plain was characterized by longitudinal and transverse fluvial gravel bars, channels and windblown facies organized into aeolian sand sheets, transverse and complex aeolian dunes, and loess accumulations. Flat‐lying aeolian deposits merge laterally to partly deformed aeolian deposits encased in dolines and collapses. Synsedimentary evaporite dissolution caused gravels and aeolian sand deposits to subside, such that formerly near‐horizontal strata became inclined and generated multiple internal angular unconformities. During episodes when the wind was undersaturated with respect to its potential sand transporting capacity, deflation occurred over the outwash plain and coarse‐grained lags with ventifacts developed. Subsequent high‐energy flows episodically reached the aeolian dune field, leading to dune destruction and the generation of hyperconcentrated flow deposits composed in part of reworked aeolian sands. Lacustrine deposits in the distal part of the outwash plain preserve rhythmically laminated lutites and associated Gilbert‐type gravel deltas, which developed when fluvial streams reached proglacial lakes. This study documents the first evidence of an extensive Pleistocene proglacial aeolian dune field located in the Ebro Basin (41˙50° N), south of what has hitherto been considered to be the southern boundary of Pleistocene aeolian deposits in Europe. A non‐conventional mechanism (evaporite karst‐related subsidence) for the preservation of aeolian sands in the stratigraphic record is proposed.