Drop Configuration Research Articles

Mercury Detection in Novel Foods by a Smart Pocket Sensor

AbstractMercury is one of the most well‐known toxic contaminants of natural and anthropogenic origin in aquatic ecosystems that can bioaccumulate in vegetal and animal organisms. In this work, we propose a smart detection system for Hg(II) ions by square wave anodic stripping voltammetry at nanocomposite graphite screen‐printed electrodes, as an analytical tool to be applied in food quality control. The nanocomposite surfaces were obtained by the modification of screen‐printed graphite electrodes with poly(l‐aspartic acid) and gold nanoparticles and were characterized by means of electrochemical techniques. An exhaustive study of the experimental conditions involved both in the electropolymerization and in the voltammetric stripping measurements was addressed to develop a reliable method capable of measuring Hg(II) concentration in the low μg/L range, both in conventional and drop configurations. The sensor was integrated in a smart setup, comprising a Sensit Smart pocket instrument connected to a smartphone, thus proving its applicability for in situ analysis due to its cost‐effectiveness. The analytical significance of the developed sensor was assessed by detecting Hg(II) in novel food samples.

Determination of delamination-related material properties and sensitivities in a ply drop composite using a semi-numerical approach

The aims of this paper are to investigate damage initiation and propagation in the vicinity of a ply drop focusing on delamination, to extract delamination-related material properties without conducting classical single and mixed mode fracture tests, and to analyze the sensitivities of delamination evolution with respect to these material properties. Quasi-static tensile tests were conducted on the coupon level for a UD composite with a ply drop. A combined numerical/experimental approach was followed to identify the material properties associated with delamination evolution. For that purpose, a finite element model was created using the cohesive zone model. The delamination-related properties were characterized by fitting the numerical model to the experiments by calibrating the cohesive zone parameters such that the global coupon response and the delamination extent for different load levels were in good agreement. Based on the identified parameter set, a sensitivity analysis was carried out to raise awareness of the influence of material properties on damage evolution. Damage around the ply drop was governed by mode II delamination. Several sensitivities were found to be non-linear with respect to a variation of input parameters. The methodology can be used in future work focusing on different ply drop configurations, and the results so far can serve as a database for benchmark simulations of delamination evolution in the vicinity of ply drops.

Numerical study of compound drop mobility over a surface having wettability difference

Three-dimensional numerical simulations have been performed to analyze the effect of wettability difference on a compound droplet through biphilic and wettability gradient surfaces. Three distinct drop–drop configuration regimes during translation are found in both types of surfaces, as the contact angle difference on the surface is varied. Along with these advancing, rear, and central locations of core drop regimes, lens like drop–drop configuration is also realized over the biphilic surface by considering hydrophobic contact angle variation. On the biphilic surface, drop–drop configurations are also reported from simulation with different core-to-shell volume ratios and inversion of core and shell liquids.

Two-phase flow in a vertical concentric annulus: Pressure drop and flow configuration

This paper presents experimental investigation of flow configurations and pressure drop of single-phase water flow and two-phase air-water flow in a vertical annulus. The annular test section had a concentric geometry with a casing and tubing diameter of 50 and 33.7 mm, respectively. The superficial velocity conditions of the liquid and gas were ranged 0.08–1.56 and 0–3.56 m/s, respectively. The combination of these superficial velocities produces the bubbly, slug and churn flow regimes. The identification of the flow patterns shows that the Mishima and Ishii model is the most relevant to highlight the flow transition. The measured friction factors were compared to prediction models from the literature. It was deduced that the model proposed by Gunn and Darling underestimates the liquid friction factor in the annulus. The measured pressure drops and the dimensionless pressure gradient evolution exhibits different slopes that characterize each flow pattern. The standard deviation and structure frequency describe specific ranges for each flow pattern. These two parameters can also be used for the prediction of flow patterns.

Scaling of Anisotropic Wetting Behavior of Water Drop Configuration Arising from Parallel Groove-Textured Stainless Steel Surfaces

Understanding the wetting behavior of stainless steel surfaces can help in resolving many socio-economic challenges faced by modern day engineering developments. In this research paper, investigations have been carried out to understand the role of surface unidirectional microgrooves on the wetting behavior by the water drop liquid using the liquid drop shape configuration, captured in the view direction parallel and orthogonal to surface microgrooves. Because of the variation in wetting characteristics between these two directions, i.e., anisotropic wetting behavior, the liquid drop has attained ellipsoidal shape configuration in the microgroove-textured stainless steel surfaces. Detailed investigation has been carried out in understanding the role of microgroove geometrical sizes, i.e., width and depth and the spacing between the grooves on the wetting behavior in terms of contact diameter (D) and contact angle (θ). Overall, the wetting dynamics has been characterized by looking at the variation of eccentricity (ε, as a ratio between D in the direction parallel to microgroove and the spreading diameter in the direction orthogonal to microgroove) and wetting anisotropy (Δθ, as a difference in θ between the direction orthogonal and parallel to microgroove) with the microgroove depth parameter (ϕ as a ratio between the microgroove depth and width) and the groove spacing parameter (ξ as a ratio of the spacing between the grooves and the groove width). By and large, with increase in surface non-dimensional geometrical parameters, ϕ and ξ, the parameters quantifying eccentricity, ε and Δθ decrease, so the liquid drop shape configuration shifts towards spherical cap from ellipsoidal cap.

Investigation of the Impact Resistance Behavior of Customized Hair Clipper Comb Fabricated by Fused Deposition Modeling

This study consists of the development of a hair clipper comb finite element (FE) model, impact test analysis on the FE model, fabrication of the product using commercially available materials, followed by physical impact testing of the comb. Moreover, microscopic examination of the combs was performed to analyze the quality of the product and correlate the defects with the failure mechanism. The 3D model of comb for a Philips hair clipper was developed using ONSHAPE software, followed by a design study to understand the impact resistance of the product. The design study was performed using finite element analysis (FEA) explicit dynamic module, where two hair clipper comb designs, one with a solid body and the other with a shell were subjected to drop test simulation in two orientations: leg and head drop. Two readily available 3D printable plastic materials, Acrylonitrile Butadiene Styrene (ABS) and Polylactic acid (PLA) were selected for the FEA simulation while the comb was subjected to free fall from a height of 5 ft (1.67 m). The comb was dropped in two orientations: the head drop configuration and the leg drop configuration. For all combinations, the maximum stresses generated as a result of impact were noted and experiments performed to validate the simulation results. The four models were fabricated using fused deposition modeling (FDM) technique and were manually dropped from the same height. In line with the simulated results, models prepared from PLA material failed upon the impact while ABS samples having a comparatively better impact resistance sustained the impact without failure. Finally, fracture surface morphologies of the failed PLA component and the surface of ABS in as-printed condition were analyzed using Scanning Electron Microscopy (SEM). Based on the obtained results, the shell model made of ABS material turns out to be the most suitable choice out of all the designs considered.

Modeling the evaporation of multicomponent drops of general shape on the basis of an analytical solution to the Stefan–Maxwell equations

This paper proposes an analytical approach to model the evaporation of multicomponent drops of general shape, which is based on the solution to Stefan–Maxwell equations. The model predicts the quasi-steady molar fractions and temperature distributions in the gas phase as well as the heat rate and the species evaporation rates. The model unifies previous approaches to this problem, namely, for spherical and spheroidal drops, under a unique model and proposes solutions for other shapes and geometries, such as sessile drops and drop pairs. To assess the model, a comparison with a numerical solution to the conservation equations is also reported for both different drop configurations and different compositions.

Dielectrophoretic stretching of drops of silicone oil: Experiments and multi-physical modeling

It is shown experimentally that drops of two pure silicone oils of different viscosities on a polypropylene substrate do not react to the in-plane electric field. Pre-treatment of silicone oil in a humid atmosphere at 80% relative humidity enriches oil with water-related ions and results in subsequent drop slight stretching under the action of the in-plane electric field. These phenomena demonstrate that the original silicone oils do not contain a sufficient concentration of any ions and counter-ions for the appearance of any Coulomb force or Maxwell stresses, which would result in drop stretching. However, a stronger stretching of silicone oil drops on the polypropylene substrate subjected to the in-plane electric field was experimentally demonstrated when 5 wt. % of TiO2 particles was suspended in oil. The particles behave as electric dipoles and, when subjected to a nonlinear symmetric electric field, experience dielectrophoretic force, which attracts them to both electrodes in air and oil. 3D simulations of the dielectrophoretically driven evolution of silicone oil drops laden with TiO2 particles also revealed a significant drop stretching in the inter-electrode direction in qualitative agreement with the experimental data. Still, numerical simulations predict an unbounded stretching with two tongues developing at the two drop sides. This prediction disagrees with the experiments where the dielectrophoretically driven stretching ceases and steady-state drop configurations without tongues are attained. This disagreement is probably related to the fact that in the experiments, TiO2 particles settle onto the substrate and are subjected to significant additional friction forces, which could ultimately arrest them.

Relationship between Maximum Voltage Drop and Configuration Cost for Low‐Voltage Distribution‐System

Owing to the large number of power distribution equipment, the supply voltage is managed independently in 6.6‐kV medium‐voltage (MV) and 100‐V low‐voltage (LV) systems in Japanese distribution systems. Both systems have their respective independent allowable voltage range. We have studied the optimum allowable voltage range for MV and LV systems in order to reduce the equipment cost. In this study, we analyze the relationship between the maximum voltage drop and system configuration in an LV systems from the viewpoint of investment costs. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Interface Reactions Responsible for Run-Out in Active Brazing: Part 4

This study examined the interface reaction between Ag-xAl filler metals h˜ving x = 0.2, 0.5, or 1.0 wt-% and Kovar™ base materials. The present investigation used the braze joint test sample configuration. The brazing conditions were 965°C (1769°F), 5 min; 995°C (1823°F), 20 min, and a vacuum of 10–7 Torr. Run-out was absent from all test samples. Combining these results with those of the Part 2 study that used high-Al, Ag-xAl filler metals (x = 2.0, 5.0, and 10 wt-%) established these conditions for run-out: Ag-xAl filler metals having x ≥ 2.0 wt-% Al, which result in reaction layer compositions, and (Fe, Ni, Co)yAlz, having z ≥ 26 at.-% Al. The limited occurrences of run-out lobes resulted from the surface tension effect that quickly reduced the driving force for additional run-out events. The interface reactions were controlled by a driving force that was an expressed function of filler metal composition (Ag-xAl) and brazing temperature, as opposed to simply thermally activated rate kinetics. The differences of reaction layer composition and thickness confirmed that the interface reactions differed between the braze joint and sessile drop configurations. Collectively, the findings from the Parts 1–4 investigations concluded that the most-effective means to mitigate run-out is to place a barrier coating on the Kovar base material that will prevent formation of the (Fe, Ni, Co)yAlz reaction layer.

Flexible Manipulation of Lasing Modes in an Erbium-Doped Microcavity via an Add–Drop Configuration

Flexible Manipulation of Lasing Modes in an Erbium-Doped Microcavity via an Add–Drop Configuration

Delamination suppression in tapered unidirectional laminates with multiple ply drops using a tape scarfing technique

Composite laminate thickness tapering is essential for weight efficient structures. This is achieved by terminating specific plies, but these can in turn act as sites for delamination initiation. One area of importance is the spacing between adjacent ply drops, which can have a significant impact on the delamination stress. In this work, a novel tape scarfing method that applies a tapered profile to dropped ply ends was used on unidirectional tapered laminate specimens with multiple ply drops. The effect of ply drop spacing on the delamination stress of both conventional and scarfed plies in tension was studied experimentally. The results showed that the scarfed ply drop configurations can completely suppress delamination in certain configurations. The scarfed ply drops also retained higher performance with smaller ply drop spacings. This indicates that in using scarfed plies, conventional laminate design rules could be relaxed and the weight of the structure could be further reduced. The underlying failure mechanisms were also investigated using both analytical and numerical methods. A simple stress-based formula for estimating the delamination stress of scarfed plies was introduced and shown to be consistent with both experimental and numerical results, which could be used (and further developed) to make tapered laminate design easier.

Controllable dried patterns of colloidal drops

HypothesisWhen an aqueous colloidal drop dries on a solid substrate, the final pattern of the dried deposit can be manipulated through controlling the internal flow states of the drop. ExperimentsWe report a strategy to control the dried patterns of aqueous colloidal drop by controlling the drop configurations and relative humidity. For this purpose, both sessile and pendant drops are studied. FindingThe capillary flow, which is responsible for coffee-ring, is suppressed by increasing the relative humidity. Then, surprisingly, the internal convection in the pendant drop is significantly stronger than that in the sessile drop. This phenomenon leads to the formation of the disc-like and spot-like dried patterns in the sessile and pendant drop, respectively, which are the results of different interactions between the Marangoni and (buoyancy-induced) natural convections in the sessile and pendant drops. In the sessile drop, the Marangoni and natural convections mutually restrain each other due to their opposite flow directions. In contrast, in the pendant drop, the two convections mutually enhance each other, due to their same flow directions. Thisnew strategy offers a foreign-material-free and external-force-free means to control the dried patterns of the drop.

Impact of electric charge and motion of water drops on the inception field strength of partial discharges.

Strong electric fields may deform drops and induce their oscillation or motion on the substrate. Moreover, they can initiate partial discharges (PDs) because of the enhancement of the electric field in the vicinity of the three-phase contact lines. The partial discharges affect the drop spreading which can result in unusual drop shapes. In addition, the partial discharges can also deteriorate the surface properties of the substrate, e.g., of high-voltage composite insulators. In this study the occurrence of partial discharges due to stationary or oscillating sessile drops under the influence of an alternating electric field is investigated using a generic insulator model under well-defined conditions. Drops of a yield stress fluid (a gelatin-water mixture) are used to determine the PD inception field strength for stationary drop shapes. The influence of the volume as well as the distance between the individual drops for two drop configurations on the PD inception threshold is determined. The inception field strength of the partial discharges is measured for various drop volumes, drop charges, as well as for different resonance modes of drop oscillations. Besides the electrical measurement, the location of the partial discharges is optically determined by a UV camera. The detailed knowledge of the influencing factors of the partial discharges improves the understanding of the drop behavior under the impact of strong electric fields.

Sessile drop response to a single wave electrokinetic excitation

The response time for maximum drop deformation and its comparison with different time scales is established and verified with experiments. The applied fluctuation is achieved by applying a single wave perturbation of electrowetting with desired amplitude and frequency. To pinpoint the importance of the initial actuation conditions, the variance in the maximum drop deformation for a single wave perturbation is studied. The focus of this study was to analyze the maximum deformation of a drop for a wide range of actuation mechanism with a varied drop or surrounding medium viscosities. The drop response to this cyclic actuation is compared with the equivalent mass–spring–dampener system, and limitations of this approach are identified. Interestingly, the qualitative results were similar between the air and liquid medium cases, but the attainment of equilibrium configuration was dissimilar. As anticipated, the higher actuation magnitude and frequency deformed the drop significantly and thus altered the drop configuration. Higher viscosity of drops and the surrounding medium delayed the time to achieve the maximum deformation. Accurately predicting the time required for a drop to attain the maximum deformation is paramount for optimizing processes and based on microfluidics technology.

Particle size and substrate wettability dependent patterns in dried pendant drops

The particle laden sessile drops when dried on solid surfaces under certain conditions leave a deposit pattern wherein all the particles are confined to a narrow region close to the edge of the deposit. Such patterns which often form when coffee drops dry are referred to as the coffee ring patterns or the coffee stains. Recent research points to the formation of intriguing patterns when colloidal particle laden drops are dried in configurations other than sessile mode. In this article, the combined effect of particle size and wettability of the substrate on the patterns formed by drying drops in sessile and pendant configurations is investigated via experiments. Our results demonstrate a transition from coffee ring to central dome-like deposit morphology with decrease in wettability of the substrates when drops containing 3 μm diameter particles are dried in pendent mode. A similar transition in the deposit morphology is observed with increase in the diameter of the particles in pendant drops dried on substrates of near neutral wettability (θ = 86 ± 3°). The influence of particles size, substrate wettability and drop configuration on the kinetics of deposition of particles at the three phase contact line will also be discussed. We compare our experimental observations with particle based simulations wherein the dried patterns are generated by accounting for three particle transport modes, namely, advective particle transport resulting from capillary flow, gravity driven settling of particles and particle capture by descending interface.

MINIMIZED VOLTAGE DROP RECTIFIER CIRCUIT USING PIEZOELECTRIC TRANSDUCER FOR ENERGY HARVESTING

Piezoelectric systems produce an AC voltage signal at the output and to utilize this voltage, It is required to convert this AC signal into DC with the assistance of the rectifying circuit. The aim of this research is to minimize the voltage drop VD of the conventional diode by designing a diode circuit with the help of MOSFETs to be used in the rectifier. In conventional full bridge rectifier (Con-FBR) the power losses are very high because of diodes drop VD. To minimize these losses the Con-FBR circuit is altered with the employment of both n-type and p-type MOSFETs to be operated in the deep triode (ohmic) region while blocking the reverse leakage which results in reducing the threshold voltage VTH to few mV. Both positive and negative cycles are availed and investigated to extract the maximum output voltage. It is simulated in NI-Multisim (version 14.0) and is implemented using discrete components. The results show that the bridge rectifier using proposed low diode drop configuration has a better power conversion efficiency and can extract power ‘4’ four times more than the Con-FBR.

Assessing Work Zone Traffic Control Options for 3-to-1 Lane Closures

The presence of highway construction zones hinders mobility and affects traffic operations. A 2002 study by Wunderlich & Hardesty reported that nearly 20% of the National Highway System roads have scheduled construction work during the peak construction season. Additionally, approximately 24% of non-recurring delays on freeways are caused by work zones. To minimize time lost by travelers due to work zone induced traffic congestion, it is important to efficiently plan temporary traffic control (TTC) at work zones. Earlier research conducted by Sisiopiku & Ramadan, 2017 confirms that the majority of State Departments of Transportation currently rely on their earlier experience when planning for work zones, rather than consider operational and safety impacts. Using a study corridor in Birmingham, Alabama as a test bed, this study investigated the operational impacts of TTC options for work zones with 3-to-1 lane drop configuration using traffic data collected from the Alabama Department of Transportation. The VISSIM simulation platform was used to conduct the experiments. The experimental design considered two TTC strategies (i.e., static late and early merge) under 3-to-1 lane drop configuration for work-space length of 500 ft for long- and short-term lane closures. The study concluded that the 3-to-1 lane-drop configuration should not be scheduled for long-term duration. Maintenance work can be scheduled from midnight to early morning and under the 3-to-1 lane closure scenario the performance of early and late merge traffic control is similar. Overall, this study used simulation modeling to compare the effectiveness of two traffic control strategies at work zones on the basis of different performance measures. The results provide information about the impact of each control strategy on density, speed, travel time etc. They also help determine what time of the day is best for lane closings in order to reduce adverse impacts from capacity reduction. Thus, the findings are expected to provide valuable guidance for agencies responsible for planning, design, and operations of work zones in the future.

Three dimensional numerical simulation of drops suspended in a channel under uniform electric field

Abstract In this paper, numerical study of emulsion of drops in a channel under uniform electric field is investigated. The electric field is created by imposing an electric potential difference across the channel walls. The leaky dielectric model developed by Taylor is used to compute the electric force. The electric conductivity ratio σ r = σ i σ o and electric permittivity ratio e r = e i e o are used to study oblate and prolate drops The interaction of drop-to-wall and drop-to-drop are investigated by changing the dimensionless numbers. Oblate drops and prolate drops with σ r e r , are always attracted to the walls, but prolate drops with σ r > e r , are attracted by or repelled from the walls depending on the initial distance and electric properties. Drop-to-drop interaction depends on the initial configuration of drops. Drop pairs that are placed at an angle relative to the direction of the electric field, are always attracted towards each other. If they have an initial separation distance in the direction of the electric field, they are attracted to the walls or towards each other depending on their separation distance. Prolate drops with σ r > e r , obtain a different configuration in their final state. They may stick together or have a small separation distance, depending on their electric properties. Increasing the electric capillary number, changes the vertical and horizontal separation distance of drop pairs at steady state configuration. It also decreases the time required to reach steady state configuration. The behavior of emulsion of drops is studied by considering oblate drops, prolate drops with σ r e r and prolate drops with σ r > e r . All drops form fiber chains in the direction of the electric field that will break in stronger Poiseuille flow. Oblate drops either settle on the walls or migrate to the channel center line, but prolate drops form chains of fibers that sometimes extend between the walls. Presence of drops will change the well-known parabolic velocity profile especially for prolate drops that are suspended in the channel. The channel flow rate is also studied for different emulsion of drops and electric field. At a constant electric field and pressure gradient, the channel flow rate for oblate emulsion is higher than prolate ones. As the electric field strength increases, the channel flow rate will also increase for oblate emulsions.

Oxidation during fuel-coolant interaction: Advances and modeling

Following the OECD SERENA phase 2 program and EC SARNET-2 network conclusions, oxidation was identified as a major issue for a comprehensive modelling of Fuel Coolant Interaction (FCI). Indeed, the topic is very complex, involving hydrogen and void generation, strong heat release and change of material properties, in particular regarding solidification. Based on a literature review and recent experimental data, the mechanisms related to oxidation are revisited. Following this work, a kinetic model of oxidation is being built and applied to the thermohydraulic code MC3D, based on the competition between H2/vapor inter-diffusion in the boundary layer and oxygen diffusion in the melt. Two drop configurations are considered here, in subcooled water and in superheated steam. Faced with the paucity of experimental data in terms of kinetics of reaction above the metal melting point, direct numerical simulations are performed in order to compare the reaction rates with those given by the macroscopic model and to provide a local scale observation of the boundary layer surrounding the drop during the process of oxidation.