Ambient Interface Research Articles

Gravity currents propagating up a slope in a two-layer fluid

Gravity currents produced by partial-depth lock-release and travelling along the base of a two-layer stratified ambient are investigated as they propagate along a rising slope. The initial gravity current front speed is found to be consistent with a theory adapted from Shin et al. [“Gravity currents produced by lock exchange,” J. Fluid Mech. 521, 1-34 (2004)] to the case of partial-depth currents in two-layer ambients. The subsequent evolution depends on the gravity current speed relative to the speed of the interfacial disturbance it creates. The deceleration of supercritical gravity currents, which travel faster than the interfacial disturbance, is gradual and agrees well with the relationship developed by Marleau et al. [“Gravity currents propagating up a slope,” Phys. Fluids 26, 046605 (2014)] for upslope gravity currents in uniform density ambients. In several subcritical cases, the gravity current suddenly came to rest as a consequence of interactions with the interfacial disturbance. The disturbance amplitude, speed, and width are found to be nearly constant during its evolution. In cases for which the ambient interface intersected the bottom slope, the amplitude, speed, and width were nearly constant up to the point where the lower layer shallowed and the disturbance transformed into an upslope-propagating gravity current.

Microstructure Measurements from an Underwater Glider in the Turbulent Faroe Bank Channel Overflow

AbstractMeasurements of ocean microstructure are made in the turbulent Faroe Bank Channel overflow using a turbulence instrument attached to an underwater glider. Dissipation rate of turbulent kinetic energy ε is measured using airfoil shear probes. A comparison is made between 152 profiles from dive and climb cycles of the glider during a 1-week mission in June 2012 and 90 profiles collected from the ship using a vertical microstructure profiler (VMP). Approximately one-half of the profiles are collocated. For 96% of the dataset, measurements are of high quality with no systematic differences between dives and climbs. The noise level is less than 5 × 10−11 W kg−1, comparable to the best microstructure profilers. The shear probe data are contaminated and unreliable at the turning depth of the glider and for U/ut < 20, where U is the flow past the sensor, ut = (ε/N)1/2 is an estimate of the turbulent velocity scale, and N is the buoyancy frequency. Averaged profiles of ε from the VMP and the glider agree to better than a factor of 2 in the turbulent bottom layer of the overflow plume, and beneath the stratified and sheared plume–ambient interface. The glider average values are approximately a factor of 3 and 9 times larger than the VMP values in the layers defined by the isotherms 3°–6° and 6°–9°C, respectively, corresponding to the upper part of the interface and above. The discrepancy is attributed to a different sampling scheme and the intermittency of turbulence. The glider offers a noise-free platform suitable for ocean microstructure measurements.

Influence of lock aspect ratio upon the evolution of an axisymmetric intrusion

AbstractThrough theory and numerical simulations in an axisymmetric geometry, we examine evolution of a symmetric intrusion released from a cylindrical lock in stratified fluid as it depends upon the ambient interface thickness, $h$, and the lock aspect ratio ${R}_{c} / H$, in which ${R}_{c} $ is the lock radius and $H$ is the ambient depth. Whereas self-similarity and shallow-water theory predicts that intrusions, once established, should decelerate shortly after release from the lock, we find that the intrusions rapidly accelerate and then enter a constant-speed regime that extend between $2{R}_{c} $ and $5{R}_{c} $ from the gate, depending upon the relative interface thickness ${\delta }_{h} \equiv h/ H$. This result is consistent with previously performed laboratory experiments. Scaling arguments predict that the distance, ${R}_{a} $, over which the lock fluid first accelerates increases linearly with ${R}_{c} $ if ${R}_{c} / H\ll 1$ and ${R}_{a} / H$ approaches a constant for high aspect ratios. Likewise in the constant-speed regime, the speed relative to the rectilinear speed, $U/ {U}_{\infty } $, increases linearly with ${R}_{c} / H$ if the aspect ratio is small and is of order unity if ${R}_{c} / H\gg 1$. Beyond the constant-speed regime, the intrusion front decelerates rapidly, with power-law exponent as large as $0. 7$ if the relative ambient interface thickness, ${\delta }_{h} \lesssim 0. 2$. For intrusions in uniformly stratified fluid (${\delta }_{h} = 1$), the power-law exponent is close to $0. 2$. Except in special cases, the exponents differ significantly from the $1/ 2$ power predicted from self-similarity and the $1/ 3$ power predicted for intrusions from partial-depth lock releases.

Ambient laser ablation sampling for capillary electrophoresis mass spectrometry

Ambient laser ablation with mass spectrometric detection is a powerful method for direct analysis of biological samples in their native environment. Capillary electrophoresis (CE) can separate complex mixtures of biological molecules prior to mass spectrometry (MS) analysis and an ambient sampling interface for CE/MS will allow the detection of minor components. An infrared (IR) laser ablated and transferred sample materials under ambient conditions for direct loading onto the CE separation column. Samples were deposited on a transparent target and ablated in transmission geometry using a pulsed mid-IR laser. The ablated materials were captured in the exposed sampling solvent and then loaded into a capillary by electrokinetic injection for separation and analysis by electrospray ionization (ESI)-MS. The system was tested using mixtures of peptide and protein standards. It is estimated that tens of fmol of material was transferred from the ablation target for injection into the CE system and the theoretical plate number was between 1000 and 3000. A novel interface for ambient sampling to CE/MS was developed. The interface is generally applicable and has potential utility for mass spectrometry imaging as well as the loading of microfluidic devices from untreated ambient samples.

Label-free fiber-optic interferometric immunosensors based on waist-enlarged fusion taper

Label-free, all-fiber immunosensors based separately on Mach–Zehnder interferometry (MZI) and Michelson interferometery (MI) implemented using only single mode fiber (SMF) are proposed and experimentally demonstrated. The proposed SMF–MZI and SMF–MI sensors rely on intermodal interference between the core mode and cladding modes to detect ambient refractive index changes due to protein absorption on the cladding–ambient interface. The fiber surfaces were functionalized with self-assembled polyelectrolyte layers (chitosan (CS)/polysodium styrene sulfonate (PSS)). Immunoglobulin G (IgG) was immobilized on the polyelectrolyte layer and anti-immunoglobulin G (anti-IgG) molecular binding events were monitored through measurement of wavelength shifts. The proposed immunosensors exhibit anti-IgG detection sensitivities of 27.37nm/(ng/mm2) and 5.91nm/(ng/mm2) with concentration detection limits of 0.181nM and 4.941nM for MZI and MI sensor respectively. The specificities of the sensors were investigated using correlated/non-correlated anti-IgG–IgG pairs. These results demonstrate the feasibility of these sensors for various bio/chemical applications such as DNA hybridization detection and immunosensing.

User Experience Design using the Ambient interface In order to make pleasant the eating habits of a person living alone

User Experience Design using the Ambient interface In order to make pleasant the eating habits of a person living alone

Gravity currents in a two-layer stratified ambient: The theory for the steady-state (front condition) and lock-released flows, and experimental confirmations

We consider the propagation of a gravity current of density ρc at the bottom of a two-layer stratified ambient in a horizontal channel of height H, in the high-Reynolds number Boussinesq domain. The study emphasizes theoretical-analytical modeling, however, experimental and Navier-Stokes simulation data are also presented and their comparison with theory is discussed. The stratification parameters are S = (ρ1 − ρ2)/(ρc − ρ2) where ρ is the fluid density, and φ = h1R/H where h1R is the (unperturbed) ambient interface height. Here, 1 and 2 denote, respectively, the lower and upper layer and c denotes the gravity current. The reduced gravity is defined as g′ = (ρc/ρ2 − 1)g. Rigorous results are obtained for the steady-state analogue of the classical problem of Benjamin [J. Fluid Mech. 31, 209 (1968)]10.1017/S0022112068000133, in which the half-infinite gravity current has thickness h and speed U. We thereby demonstrate that the Froude number \documentclass[12pt]{minimal}\begin{document}${\cal F}= U/(g^{\prime } h)^{1/2}$\end{document}F=U/(g′h)1/2 is a function of a = h/H, S, and φ. In general, two solutions (or modes) may be realized. Issues of energy dissipation, sub- vs. supercriticality with respect to long internal waves and, more generally, the influence of upstream-propagating disturbances are discussed. For a gravity current released from a lock of height h0 and length x0, we derive an approximate shallow-water model and show that the motion is in this case governed by Ξ = H/h0, S, and φ. Although the shallow-water model neglects motion in the ambient layers and ignores the impact of propagation on stratification, the gravity current front speed in the slumping stage is in excellent agreement with measured data. Our theoretical solutions are consistent with previous results (in particular, Holyer and Huppert [J. Fluid Mech. 100, 739 (1980)] and Tan et al. [Environ. Fluid Mech. 11, 203 (2011)]), but have the advantages of being (i) derived without reliance on adjustable constants and ad hoc closures; (ii) applicable to a significantly broader range of dimensionless parameters; and (iii) better assessed by comparison against measured data. The present one-layer shallow-water approximation turns out to be a simple and versatile extension of existing models for homogeneous and linearly stratified ambients, and can be straightforwardly incorporated into the available prediction tools for gravity currents.

Spectroscopic Ellipsometry Analysis of a Thin Film Composite Membrane Consisting of Polysulfone on a Porous α-Alumina Support

Exposure of a thin polymer film to a fluid can affect properties of the film such as the density and thickness. In particular in membrane technology, these changes can have important implications for membrane performance. Spectroscopic ellipsometry is a convenient technique for in situ studies of thin films, because of its noninvasive character and very high precision. The applicability of spectroscopic ellipsometry is usually limited to samples with well-defined interfacial regions, whereas in typical composite membranes, often substantial and irregular intrusion of the thin film into the pores of a support exists. In this work, we provide a detailed characterization of a polished porous alumina membrane support, using variable-angle spectroscopic ellipsometry in combination with atomic force microscopy and mercury porosimetry. Two Spectroscopic ellipsometry optical models are presented that can adequately describe the surface roughness of the support. These models consider the surface roughness as a distinct layer in which the porosity gradually increases toward the outer ambient interface. The first model considers the porosity profile to be linear; the second model assumes an exponential profile. It is shown that the models can be extended to account for a composite membrane geometry, by deposition of a thin polysulfone film onto the support. The developed method facilitates practicability for in situ spectroscopic ellipsometry studies of nonequilibrium systems, i.e., membranes under actual permeation conditions.

X-ray spectroscopy characterization of self-assembled monolayers of nitrile-substituted oligo(phenylene ethynylene)s with variable chain length.

Self-assembled monolayers (SAMs) of nitrile-substituted oligo(phenylene ethynylene) thiols (NC-OPEn) with a variable chain length n (n ranging from one to three structural units) on Au(111) were studied by synchrotron-based high-resolution X-ray photoelectron spectroscopy and near-edge absorption fine-structure spectroscopy. The experimental data suggest that the NC-OPEn molecules form well-defined SAMs on Au(111), with all the molecules bound to the substrate through the gold–thiolate anchor and the nitrile tail groups located at the SAM–ambient interface. The packing density in these SAMs was found to be close to that of alkanethiolate monolayers on Au(111), independent of the chain length. Similar behavior was found for the molecular inclination, with an average tilt angle of ~33–36° for all the target systems. In contrast, the average twist of the OPEn backbone (planar conformation) was found to depend on the molecular length, being close to 45° for the films comprising the short OPE chains and ~53.5° for the long chains. Analysis of the data suggests that the attachment of the nitrile moiety, which served as a spectroscopic marker group, to the OPEn backbone did not significantly affect the molecular orientation in the SAMs.

Oscillating Dense Plumes

Abstract The flow of dense polar shelf waters down continental slopes is a critical component of the global ocean circulation. Recent observations suggest that such plumes can be heavily impacted by tidal variability, and many of the world’s important dense-water sources are located in tidally active areas. Tides affect the source of dense water (by modulating the location of hydrographic gradients) and control the subsequent plume mixing and flow path. In an effort to separate these effects, dense plumes are modeled here by extending a classical one-dimensional plume model to two unsteady scenarios in which the plume path is fixed. The first case features a pulsed release of dense water into a stagnant ambient, and the model predicts that gravity waves propagate down the plume. Advective waves in plume density travel with the mean velocity of the current and thus have a wavelength of , the product of plume velocity and the oscillation period P. The second case is of a steady-sourced plume flowing through an ambient that has uniformly oscillating flow. This drives fluctuating shear at the plume–ambient interface (and/or seabed) that leads to variable entrainment of ambient fluid into the plume. Perturbed properties are subsequently advected by the plume, leading to standing “entrainment waves” that also have a wavelength of . Pulsed-source effects may be distinguished from variable-entrainment effects by the phase difference between waves in the different state variables of each plume. Both effects are maximized when the ratio , where L is the plume length. This condition is satisfied in the Ross Sea, Antarctica, where observations show dense plumes that are strongly affected by tides. Modeled pulsed-source effects qualitatively agree with the observations, implying that hydrographic variability in Ross Sea plumes is associated with variability in their dense-water source rather than unsteady plume mixing. These results might help inform the gathering and interpretation of oceanographic data in tidally active dense-water source regions.

Ambient Interface Design (AID) for the Ergonomically Challenged

Mobile devices offer convenient communication capabilities and have the potential to create intermediary support for ergonomically challenged users. With the global proliferation of increasing longevity, assisting the elderly and those living with impediments through human engineering and computing technology is pivotal to biotechnological attainment. To remain independently empowered, seamless integrations through efficient affable interfaces are required to provide sedulous location-independent and appliance-sensitive media viewing for the user. The Ambient Interface Design (AID) system assists with finding personal preferences and provides a synchronisation framework, coordinating connectivity across various environmentally distributed devices via sensor data mapping. Cooperative interface communication coupled with context awareness will be abstracted to a representation that facilitates optimisation and customisation to these displays. To overcome personal challenges in the efficient selection and acquisition of online information, AID mediates between the needs of the user and the constraints of the technology to provide a singular customised encapsulation of ‘ability preference and device’ for each authenticated member. A particular emphasis is the application of a human-centered design ethos.

Designing a usable ambient intelligence system

The design of the ambient intelligence service interface should be seen as an evolutionary object that continually changes to adapt to the emerging needs of the users. Context-awareness is a key feature of ambient computing. There is currently very little research conducted on how we can support the design of usable context-aware homes through ambient intelligence. Although principles of traditional interface design can be useful, we need to go beyond usability by looking at design parameters that deal with the contextual issues of these systems. Activity theory incorporates the notions of intentionality, history, mediation, motivation, understanding, culture and community into design. In particular, it provides a framework in which the critical issue of context can be taken into account. This paper studies how activity theory can be used for analysing user needs in order to design an ambient intelligence home.

2207 アンビエントな車内情報空間の設計方式(OS3-1 設計・デザイン論I,OS3 設計・デザイン論)

Although such information services as FM-VICS, gas stations, sales at department stores etc., contribute to car drivers for their safety and satisfaction in driving situation, it is hard for them to retrieve such information while driving. It is also difficult to push all such information without any control which should disturb driver's concentration on driving. The authors have been investigating a task-oriented menu, which enables users to search for mobile internet services by what they want to do and not by category. We have built a task model of the mobile users' daily activities and reorganized "contexts" in the model to develop a menu hierarchy from the view point of the task. We have applied the framework to modeling car drivers' activities. Such models indicate when and what kind of information should be provided in the car, which in turn contribute to design ambient interface for the drivers.

Research for Embodied Interaction Based Ambient Interface

Research for Embodied Interaction Based Ambient Interface

A prototype home robot with an ambient facial interface to improve drug compliance

We have developed a prototype home robot to improve drug compliance. The robot is a small mobile device, capable of autonomous behaviour, as well as remotely controlled operation via a wireless datalink. The robot is capable of face detection and also has a display screen to provide facial feedback to help motivate patients and thus increase their level of compliance. An RFID reader can identify tags attached to different objects, such as bottles, for fluid intake monitoring. A tablet dispenser allows drug compliance monitoring. Despite some limitations, experience with the prototype suggests that simple and low-cost robots may soon become feasible for care of people living alone or in isolation.

Onset of entrainment in transitional round fountains

It is of fundamental interest to understand the behavior of transitional fountains with intermediate Froude and Reynolds numbers, together with the associated entrainment and turbulence. In this work, the transient behavior of axisymmetric fountains with 1 ⩽ Fr ⩽ 8 and 200 ⩽ Re ⩽ 800 is studied by direct numerical simulation. It is found that at Re ⩽ 200, there is little entrainment present at the upflow–downflow interface and at the downflow–ambient interface, even for a value of Fr as high as 8; however, at Re > 200, entrainment is present at these interfaces and the extent increases with Re, which clearly demonstrates that entrainment is strongly dependent on Re whereas the contribution from the Fr effect is relatively much smaller. The DNS results also show that z m, which is the maximum fountain penetration height, fluctuates, even when the flow reaches full development, due to the entrainment at the upflow–downflow and the downflow–ambient interfaces, and the averaged z m scales with Fr 3 2 Re 1 4 for 1 < Fr ⩽ 8 and 100 ⩽ Re ⩽ 800.

Excess electron relaxation dynamics at water/air interfaces

We have performed mixed quantum-classical molecular dynamics simulations of the relaxation of a ground state excess electron at interfaces of different phases of water with air. The investigated systems included ambient water/air, supercooled water/air, Ih ice/air, and amorphous solid water/air interfaces. The present work explores the possible connections of the examined interfacial systems to finite size cluster anions and the three-dimensional infinite, fully hydrated electron. Localization site analyses indicate that in the absence of nuclear relaxation the electron localizes in a shallow potential trap on the interface in all examined systems in a diffuse, surface-bound (SB) state. With relaxation, the weakly bound electron undergoes an ultrafast localization and stabilization on the surface with the concomitant collapse of its radius. In the case of the ambient liquid interface the electron slowly (on the 10 ps time scale) diffuses into the bulk to form an interior-bound state. In each other case, the excess electron persists on the interface in SB states. The relaxation dynamics occur through distinct SB structures which are easily distinguishable by their energetics, geometries, and interactions with the surrounding water bath. The systems exhibiting the most stable SB excess electron states (supercooled water/air and Ih ice/air interfaces) are identified by their characteristic hydrogen-bonding motifs which are found to contain double acceptor-type water molecules in the close vicinity of the electron. These surface states correlate reasonably with those extrapolated to infinite size from simulated water cluster anions.

Cellular automata model of density currents

Cellular automata (CA) represent an interesting approach to the modelling of dynamical systems evolving on the basis of local interactions and internal transformations. The CA model, specially developed for simulating density currents, is described. The objective is to predict the formation and evolution of channels and the structure of deposits associated to the flow path. For simulation purposes, currents are represented as a dynamical system subdivided into elementary parts, whose state evolves as a consequence of local interactions and internal transformations within a spatial discrete domain. The model is developed for unsteady, two-dimensional, depth-averaged, particle-laden turbulent underflows driven by gravity, acting on density gradients created by non-uniform and non-cohesive sediment. CA is defined as a tessellation of finite-state automata (cells). The attributes of each cell (substates) describe physical characteristics. The natural phenomenon is decomposed into a number of elementary processes, with a particular composition that makes up the transition function of the CA. By applying this function to all the cells simultaneously, the evolution of the phenomenon can be simulated in terms of modification of the substates. The transition function includes the effects of water incorporation at the suspension–ambient fluid interface, a transport equation for the particle volume concentration, and a toppling rule for the deposited sediments. Simple and flexible, the obtained model constitutes a first step toward quantitative comprehension of the impact of external parameters on the turbidity current dynamics and on the organisation of the subsequent depositional sequences.

A 3D Vision-Based Ambient User Interface

This article proposes a 3-dimensional (3D) vision-based ambient user interface as an interaction metaphor that exploits a user's personal space and its dynamic gestures. In human-computer interaction, to provide natural interactions with a system, a user interface should not be a bulky or complicated device. In this regard, the proposed ambient user interface utilizes an invisible personal space to remove cumbersome devices where the invisible personal space is virtually augmented through exploiting 3D vision techniques. For natural interactions with the user's dynamic gestures, the user of interest is extracted from the image sequences by the proposed user segmentation method. This method can retrieve 3D information from the segmented user image through 3D vision techniques and a multiview camera. With the retrieved 3D information of the user, a set of 3D boxes (SpaceSensor) can be constructed and augmented around the user; then the user can interact with the system by touching the augmented SpaceSensor. In the user's dynamic gesture tracking, the computational complexity of SpaceSensor is relatively lower than that of conventional 2-dimensional vision-based gesture tracking techniques, because the touched positions of SpaceSensor are tracked. According to the experimental results, the proposed ambient user interface can be applied to various systems that require real-time user's dynamic gestures for their interactions both in real and virtual environments.

Abrupt change in the structure of self-assembled monolayers upon metal evaporation

We have studied the interaction of vapor-deposited nickel with thiol-terminated self-assembled monolayers (SAMs) of oligophenylthiolates on Au, which can be considered as model systems for molecular electronics. Instead of usually observed disordering of the molecular layer, a drastic decrease in molecular tilt was observed at the initial stage of the deposition. This was attributed to the formation of Ni-thiol complexes at the SAM–ambient interface. The reorientation resulted in the appearance of transient channels for the metal diffusion into the SAM and to the SAM–substrate interface.