Maximum Spread Research Articles

The Integral Dense-gas Dispersion Model (IDDM) and comparison with Jack Rabbit II data

The Integral Dense-gas Dispersion Model (IDDM) is presented and used to predict the maximum concentrations and spread of a dense-gas cloud from a short-term release. IDDM is based on integrated conservation equations and includes spreading due to source momentum and density effects, cloud-top air entrainment, height changes with time, and wind transport. The equations are solved numerically but some useful analytical results are found showing the dependence of cloud radius and height on source conditions, entrainment, and time. IDDM comparisons with the Jack Rabbit (JR) II experiments are made for two smooth-terrain Trials (6, 7) and one with a Mock Urban Array (MUA) of Conex containers (Trial 1). For the smooth-terrain cases, predicted concentrations (C) follow the observed JR II data trends with distance x, and for x>1 km are consistent with a -5/3 empirical correlation. In the near field, analytical results for C show excellent agreement with the IDDM numerical solution. For Trial 1, an internal boundary layer (IBL) model is added to obtain the modified winds, friction velocity, and IBL depth due to the MUA. With the IBL and a mean depth (10 m) included, IDDM concentrations agree with the data. Over all Trials (1,6,7), IDDM exhibits good statistical performance with 83% of the predictions within a factor of 2 of the observations. An elliptical horizontal cloud geometry is added to estimate the lateral cloud width given an anisotropy ratio (ani) of along-wind (x) to lateral (y) cloud width. With constant ani (=3), the agreement between predicted and observed width is good with a geometric mean (GM) of predicted-to-observed width of 1.02 and a geometric standard deviation (GSD) of 1.35. However, with a trial-specific ani (=0.5−3) and longitudinal wind shear included, the mean model agreement (GM) is about the same, but the model-data scatter is reduced to a GSD of ≃1.1.

Maximum spread of graphs and bipartite graphs

Given any graph G G , the spread of G G is the maximum difference between any two eigenvalues of the adjacency matrix of G G . In this paper, we resolve a pair of 20-year-old conjectures of Gregory, Hershkowitz, and Kirkland regarding the spread of graphs. The first states that for all positive integers n n , the n n -vertex graph G G that maximizes spread is the join of a clique and an independent set, with ⌊ 2 n / 3 ⌋ \lfloor 2n/3 \rfloor and ⌈ n / 3 ⌉ \lceil n/3 \rceil vertices, respectively. Using techniques from the theory of graph limits and numerical analysis, we prove this claim for all n n sufficiently large. As an intermediate step, we prove an analogous result for a family of operators in the Hilbert space over L 2 [ 0 , 1 ] \mathscr {L}^2[0,1] . The second conjecture claims that for any fixed m ≤ n 2 / 4 m \leq n^2/4 , if G G maximizes spread over all n n -vertex graphs with m m edges, then G G is bipartite. We prove an asymptotic version of this conjecture. Furthermore, we construct an infinite family of counterexamples, which shows that our asymptotic solution is tight up to lower-order error terms.

Droplet lift-off from hydrophobic surfaces from impact with soft-hydrogel spheres

Droplet impacts on superhydrophobic surfaces may result in complete bouncing, with the absence of contact hysteresis and viscous dissipation leading the droplet to fully rebound off the surface. This rebound usually happens in the retraction phase, when the droplet retracts back after reaching a maximum spread diameter. Here, we present experimental evidence of a bouncing phenomenon where a sessile droplet on a hydrophobic surface bounces off the surface in its spreading phase when a soft deformable hydrogel sphere axisymmetrically impacts the droplet. We term this as ‘Lift-Off’ and propose a simple force balance based on the deformation characteristics of the hydrogel sphere to explain the out-of-plane jump of the droplet during spreading. We observe three different impact regimes, and propose their dependency on a modified elastic ‘Mach’ number (Ma*) with Ma* ≈ 0.1 corresponding to the onset of lift-off. We also report on the unique acoustic signatures of lift-off cases, associated with the capture of air-bubbles through the air-borne retracting droplet rim. These results may have potential applications for drainage and surface cleaning, non-stick surface coating, industrial mixing and plant disease spreading.

Exploration of the Relationships between the Spraying Condition and Wetting Behavior on Coal Surface of Dust Suppression Droplet: Improving the Utilization Rate

Dust suppression through water-based media is an important technical means, which is of great significance to industrial process safety and environmental protection. In order to improve the utilization rate of droplets, the dynamic spreading process of droplets impacting the coal surface was studied by the coupled level-set and volume-of-fluid methods (CLSVOF) method. The spread area was calculated by the binary method to characterize the wetting effect. Dimensionless spread area per unit volume (DSAPUV) was proposed to represent the utilization of droplets. The results show that the droplet spreading fracture process can be divided into three stages: initial deformation period, spreading fracture period, and stable period. When the particle size was not being changed, the area of dimensionless spread does not increase consistently with velocities, but there exists an optimal critical velocity of impingement, which is 17 m/s for the maximum dimensionless spread area reached by droplets with a diameter of 30 μm and 19 m/s for the maximum dimensionless spread area reached by droplets with a diameter of 50 μm. Droplet size is directly proportional to the dimensionless spread area. The maximum dimensionless spread areas of the droplets were all reached during spreading, and the time required increased gradually with increasing particle sizes. It was found that the effect of droplet size on the utilization of droplets was obvious when their size ranged from 10 μm to 50 μm, and their velocity ranged from 15 m/s to 20 m/s.

Vegetative Growth, Yield and Quality of Broccoli As Influenced by Application of Gibberellic Acid

Field experiments on broccoli cv. ‘BARI Broccoli-1’ was carried out during two consecutive rabi seasons of 2014-15 and 2015-16 at the field of Plant Physiology Section of HRC, BARI. 30 days old seedlings were treated before transplanting by dipping their roots for 24 h in different concentrations of GA3 (Gibberellic acid) viz., 20, 40, 60, 80 and 100 ppm along with control (distilled water). The experiment was laid out in a Randomized complete block Design with three replications. GA3 concentrations significantly influenced the growth parameters, yield and yield attributes and quality parameters of broccoli. In regard to the average data of two years, GA3 @ 60 ppm gave the maximum leaf length (46.58 cm), spread diameter (52.38 cm), head circumference (38.2cm cm), head length (16.60 cm), head diameter (15.45 cm), primary and secondary head weight/plant (289.85 g and 192.80 g). The maximum head yield (18.82 t/ha in 2014-15 and 21.39 t/ha in 2015-16) with an average of 20.11 t/ha was recorded at GA3 @ 60 ppm followed by GA3 @ 40 ppm. Application of GA3 @ 60 ppm also produced the highest head compactness index (18.77 g/cm), maximum vitamin C (82.88 mg/100 g FW), vitamin A (601.90 IU/100 g FW) contents and the highest total soluble solid (10.10%). From the investigation it was also observed that application of more than 60 ppm GA3 reduced the yield attributes and yield of broccoli.
 Bangladesh J. Agril. Res. 45(3): 247-259, September 2020

Coalescence Dynamics of a Droplet Impacting on a Rectangular Pixel for Inkjet Printing.

A droplet impacting on a rectangular pixel with an offset is prone to cause the liquid to spread out of the pixel and adhere to adjacent pixels in organic light-emitting diode (OLED) inkjet printing. Therefore, the coalescence of a droplet impacting on a rectangular pixel is crucial in understanding the reliable OLED inkjet printing. In this paper, an assumption is established that the rectangular coalescence process is divided into the fusion part and spread part. On this basis, a dynamics model is introduced to analyze the coalescence behavior of a droplet impacting on a rectangular pixel. According to the law of conservation of mass and energy, dynamic equations are developed to obtain the maximum spread length as a function of time. In addition, the volume of the fluid method is used to simulate coalescence dynamics of a droplet impacting on a rectangular pixel by using the software of FLUENT, and the analytical solutions are consistent with the simulation results. Furthermore, the effects of the positioning error and initial velocity on the coalescence dynamics are analyzed. The results show that small initial velocity and positioning error of the droplet are helpful for the reliable OLED inkjet printing.

Underwater localization and node mobility estimation

<p><span lang="EN-US">In this paper, localizing a moving node in the context of underwater wireless sensor networks (UWSNs) is considered. Most existing algorithms have had designed to work with a static node in the networks. However, in practical case, the node is dynamic due to relative motion between the transmitter and receiver. The main idea is to record the time of arrival message (ToA) stamp and estimating the drift in the sampling frequency accordingly. It should be emphasized that, the channel conditions such as multipath and delay spread, and ambient noise is considered to make the system pragmatic. A joint prediction of the node mobility and speed are estimated based on the sampling frequency offset estimation. This sampling frequency offset drift is detected based on correlating an anticipated window in the orthogonal frequency division multiplexing (OFDM) of the received packet. The range and the distance of the mobile node is predicted from estimating the speed at the received packet and reused in the position estimation algorithm. The underwater acoustic channel is considered in this paper with 8 paths and maximum delay spread of 48 ms to simulate a pragmatic case. The performance is evaluated by adopting different nodes speeds in the simulation in two scenarios of expansion and compression. The results show that the proposed algorithm has a stable profile in the presence of severe channel conditions. Also, the result shows that the maximum speed that can be adopted in this algorithm is 9 km/h and the expansion case profile is more stable than the compression scenario. In addition, a comparison with a dynamic triangular algorithm (DTN) is presented in order to evaluate the proposed system.</span></p>

On the instability of water-in-oil emulsion drop lamella and rim moving over a heated surface in the film boiling regime

The experimental study deals with the nature of interrelated unstable equilibrium of lamella and rim of an emulsion drop based on n-dodecane and bidistilled water after its collision with a solid surface heated to 350–400 °C at Weber numbers We =160–310 and in the presence of a stable boundary vapor layer. The relationship between the delay time of the onset of emulsion lamella destabilization relative to maximum drop spreading time and the ratio of the characteristics of diffusive and convective heat transfer at unstable equilibrium of the liquid is revealed. The combined effect of We and the emulsion concentration on the critical Rayleigh and Marangoni numbers characterizing the lamella perforation is demonstrated. A mechanism is proposed where the fingering causes the lamella rupture near attachment to the rim. Liquid wettability is partially restored and the liquid periodically contacts the surface, resulting in the vapor bubbles formation and growth, as well as their collapse, which ensures the cascade of the lamella destruction and the liquid bridges formation. The proposed physical model develops ideas about the complexity and interconnectedness of the destabilization mechanisms of the emulsion drop rim and lamella, including not only rim instabilities, but also the long-wave Marangoni instability taking into account the emulsion concentration and, in some cases, Rayleigh-Benard instability.

3-D Ray Launching MIMO Channel Geometric Estimation

The complete multiple-input–multiple-output (MIMO) channel simulation in deterministic techniques can be a computationally intensive task, due to the inherent scenario's complexity and number of antennas. The spatial coherence among MIMO elements is a reasonable assumption to approximate the channel from a single point simulation. In this letter, a novel method to incorporate a geometrical approximation of the MIMO channel into a three-dimensional ray launching (3D-RL) algorithm is presented. The method is antenna type independent and the orientation of the array is embedded in the antenna representation. Relevant information of the MIMO channel characteristics like the root mean square (rms) delay spread, the maximum delay spread, phase and channel capacity are obtained and compared with the full 3D-RL simulation of the entire MIMO array, achieving 93.4% reduction in computational time.

Aquifer depths and thickness in Ogba/Egbema/Ndoni local government area of Rivers State, Nigeria from vertical electrical soundings

Most parts of the world depend on groundwater for domestic and other uses. Different geophysical methods can be used to exploit these groundwater. In this study aquifer depths and thickness spread in parts of Ogba/Egbema/Ndoni Local Government Area of Rivers State, Nigeria have been determined from 30 vertical electrical sounding survey. An ABEM Terrameter (SAS 300C) was used with Schlumberger array configuration of maximum electrode spread of 500 m. The data were analyzed with an IP2WIN ID software to obtain the strata resistivities, geoelectric layers, aquifer depths and thickness from which the isopach and iso-resistivity maps of the region were obtained. The results show two to four layer formations with resistivity values ranging from 350 to 3895 . Aquifer depths of between 20 m to 75 m and thickness varying from 17 m to 48 m. The isopach map indicates that regions in the north-central part of the study area have shallower aquifer thickness with an average value of 25 m while in the other parts of the study area, the average value is 41 m. The iso-resistivity contour maps at depth intervals of 50 m, 100 m, 150 m and 200 m reveal the trending of the resistivity values for these depths across the region. The general results indicate that the study area has productive aquifers of reasonable thickness at moderate depths from 20 m as in the other parts of the Niger delta region, therefore portable boreholes can be drilled from this depth.

Willingness of healthcare workers to treat COVID-19 patients during the pandemic: Extended theory of planned behavior

During the COVID-19 pandemic, healthcare workers played a significant role in minimizing the maximum spread of the virus. This study aims to investigate the relationship between healthcare workers’ attitudes, subjective norms, perceived behavioral control, perceived effectiveness of the pandemic, risk perception of the COVID-19 pandemic, and willingness to treat COVID-19 patients in Lahore, Pakistan. However, the extended theory of planned behavior was applied and included two key constructs (perceived effectiveness and risk perception of the COVID-19 pandemic). Data were collected from 253 male and female respondents working in public, private, and semi-government hospitals. Structural equation modeling (SEM) was applied to test the proposed hypotheses. Overall, the findings show that healthcare workers’ attitudes, social norms, and perceived behavioral control significantly impact healthcare workers’ willingness to treat COVID-19 patients. In contrast, perceived effectiveness and risk perception of the pandemic showed a negative effect. The results suggested that healthcare workers showed positive attitudes, subjective norms, and perceived behavioral control to COVID-19 patients. On the other hand, due to the virus novelty, effectiveness and risk perception of the pandemic was very high, which shows that healthcare workers feel stressed and scared to treat COVID-19 patients.

Dynamics of drops on hygroscopic ionic liquid aqueous solution-wetted porous surfaces

The impact dynamics of water drops on porous surfaces wetted by a hygroscopic ionic liquid aqueous solution are investigated. Firstly, to better illustrate the different dynamic characteristics of water drops on ionic liquid-wetted porous surfaces, it is compared with that on the dry and water-wetted porous surfaces. The results indicate that, the water drop barely penetrates on the dry porous surface at ambient temperature, but penetrate when the surface temperature is raised or the surface is pre-wetted. The maximum spreading and penetration of the droplet on the ionic liquid-wetted surface is larger and faster than that on the water-wetted surface. Then, the effect of the mass fraction of aqueous ionic liquid, impact velocity, porosity on the spreading and penetration is explored. The larger the mass fraction of aqueous ionic liquid on the porous surface, the faster the droplet spreading factor, height, and residual volume decrease. The effect of impact velocity is even more pronounced for the water droplets impacting on pure ionic liquid-wetted porous surfaces. A higher porosity contributes to a smaller spreading diameter but a larger volume decreasing rate on the wetted porous surface.

Dynamical behaviors of water drop impact on superhydrophobic surfaces with the macro-textured cavity

Drop impact on superhydrophobic surfaces (SHSs) is of significant importance to many engineering applications. Drop impact dynamics on micro-nano structured SHSs has been widely investigated, however, that on macro-textured SHSs is still lacking, especially the macro-textured cavities. In this work, water drops impact on rigid SHSs with or without cavities were experimentally investigated through a high-speed camera. We number (We = ρdu2/σ) is chosen to quantify the drop impact intensity. Compared to plane SHSs, the cavity with different geometries reduces both the maximum spreading diameter and the contact time, and leads to complex drop deformation with two times expanding process under higher We numbers. The maximum spreading ratios increase with We numbers and are scaled by a power-law with exponents of 0.20 for plane SHSs and 0.17 for cavity-textured SHSs. The dimensionless contact time on plane SHSs remains constant about 0.88, while that on the cavity-textured SHSs is about 0.82. Drop impact on SHSs with macro-textured cavities exhibits different behaviors, which anticipates to throw an insight into the applications of self-cleaning, anti-icing and so on.

Behaviors of the water droplet impacting on subcooled superhydrophobic surfaces in the electrostatic field

The impact dynamic behavior of rainwater and the subsequent freezing process on the transmission line cause significant damage to the power grid. Therefore, a good understanding of the droplet impact and freezing process on a subcooled superhydrophobic surface under an electric field is crucial. In this study, the dynamic behavior of a droplet impacting a subcooled superhydrophobic surface at various surface temperatures and electric field strengths was visually studied. Moreover, the influence of the surface temperature and electric field strength on the contact time, maximum spread factor, rebound mode, and nucleation rate were investigated. Furthermore, the variation in rebound modes with electric field strength and surface temperature was clarified in the phase diagram. Eventually, the nucleation rate exponentially increases with an increase in the electric field strength and a decrease in the surface temperature. This study can aid in the anti-icing design of power grid systems.

Multi-objective scheduling of a single mobile robot based on the grey wolf optimization algorithm

During the last decades, intelligent mobile robots have been recognized as one of the most promising and emerging solutions used for fulfilling material transport demands in intelligent manufacturing systems. One of the most significant characteristics of those demands is their multi-objectivity, where identified objectives might usually conflict. Therefore, obtaining the optimally scheduled robotic-based material transport system that is simultaneously facing several conflicting objectives is a highly challenging task. To address such a challenge, this paper proposes a novel multi-objective Grey Wolf Optimizer (MOGWO) methodology to efficiently schedule material transport systems based on an intelligent single mobile robot. The proposed optimization methodology includes the comprehensive analysis and the mathematical formulation of 13 novel fitness functions combined to form a Pareto front of the multi-objective optimization problem and a novel strategy for optimal exploration of multi-objective search space. Moreover, four metrics, i.e., Generational Distance (GD), Inverted Generational Distance (IGD), Spacing (SP), and Maximum Spread (MS), are employed to quantitively evaluate and compare the effectiveness of the proposed enhanced MOGWO algorithm with three state-of-the-art metaheuristic methods (MOGA, MOAOA, and MOPSO) on 25 benchmark problems. The results achieved through two experimental scenarios indicate that the enhanced MOGWO algorithm outperforms other algorithms in terms of convergence, coverage, and the robust optimal Pareto solution. Finally, transportation paths based on obtained scheduling plans are experimentally corroborated by the mobile robot RAICO (Robot with Artificial Intelligence based Cognition) within a physical model of the intelligent manufacturing environment. The achieved experimental results successfully demonstrate the efficiency of the proposed methodology for optimal multi-objective scheduling of material transport tasks based on a single mobile robotic system.

Impact of Slope Orientation on Inlet Spacing: Gutter Flow Analyses

A roadway’s capacity to drain itself is of utmost importance for the safety and comfort of its users. Standing water and any amount of channelized flow on roadways create nuisances to the users, and the extent of encroachment into the lanes and the water-film thickness over the lanes are crucial for motorists with relatively high speed. Guidelines cover a wide range of subjects from size and type of inlets, which capture the channelized flow for conveyance into enclosed drains, to the decision for slope orientation, but the guidelines seem to lack in checking the depth of channelized flow. HEC-22 (the urban drainage design manual of US Department of Transportation) endorses limiting the flow depths to curb height (as if the concern is no longer the roadway users) and fixes the criterion for the inlet spacing (restricted to 90 to 150 m) to maximum allowable flow spreads. This study analyzed the maximum allowable inlet spacing via setting three criteria: fixed maximums to flow depth, spread for the channel flow, and to over-lane water-film thickness. The impact of slope orientation on inlet spacing is tested along with some other factors for roadways of two types (local and highway). The results were graphed for various uniform slope orientations under a wide range of rainfall intensities for the determined inlet spacing values. This was performed by combining a kinematic wave equation solution to dismiss the conditions that lead to hydroplaning depths when using the Rational Method and Manning’s equation to obtain water depths and inlet spacings for an inlet of full capture capacity. It is found that the allowable spacing values do not constitute any major restrictions in highway setting (3 m shoulder) in terms of recommended spacing. In the local setting, however, with a maximum spread of 1.8 m, maximum allowable inlet spacing becomes a limitation in many orientations, and slope optimization under such conditions becomes crucial at times when providing the same spacing for two orientations.

Experimental and Numerical Investigation on the Dynamics of Impacting Droplet Spreading at Small Weber Numbers

The dynamic of droplet spreading on a free-slip surface was studied experimentally and numerically, with particularly interest in the impacts under relatively small droplet inertias (We≤30). Our experimental results and numerical predictions of dimensionless droplet maximum spreading diameter βmax agree well with those of Wildeman et al.’s widely-used model at We>30. The “1/2 rule” (i.e., approximately one half of the initial kinetic energy Ek0 finally transferred into surface energy) was found to break down at small Weber numbers (We≤30) and droplet height is non-negligible when the energy conservation approach is employed to estimate βmax. As We increases, surface energy and kinetic energy alternately dominates the energy budget. When the initial kinetic energy is comparable to the initial surface energy, competition between surface energy and kinetic energy finally results in the non-monotonic energy budget. In this case, gas viscous dissipation contributes the majority of the dissipated energy under relatively large Reynolds numbers. A practical model for estimating βmax under small Weber numbers (We≤30) was proposed by accounting for the influence of impact parameters on the energy budget and the droplet height. Good agreement was found between our model predictions and previous experiments.

PDMS 표면에서 충돌 액적의 점도에 따른 거동의 주기성

Periodicity behavior was observed after droplet collision in viscous solutions with controlled glycerol concentrations onto a PDMS surface. No periodic movement was observed in the droplets at glycerol concentrations of 50% or more. In contrast, the vertical diameter of the droplets increased and decreased periodically at glycerol solution concentrations of 40% or less. Moreover, there was little change in the periodicity of the impacting droplet movement, and the vibration frequency was measured at approximately 80 to 98 Hz in the entire range. The maximum droplet spreading factor after collision decreased significantly with increasing glycerol concentrations of 40% or more (Ohnesorge number 1.4 × 10SUP-2/SUP or more). The results suggest that the effect of viscosity became greater than that of the solution surface tension with increasing glycerol concentrations.

Thermal Performance Analysis of Mempool RISC-V Multicore SoC

The presence of multiple cores in modern multicore architectures makes thermal management and temperature estimation a really challenging task for enhancing reliability and lifespan. Due to the presence of many cores, the core/tile spacing needs to be optimized in order to enhance the thermal coupling between interconnect routing blocks and active tiles. In addition, the tiles activity patterns under partial workload conditions significantly affect the maximum on-chip temperature which results in nonuniform temperature distribution. This is due to poor thermal coupling between neighboring tiles owing to the decrease in spacing between cores. In this article, we investigate the thermal performance analysis of a 256-core (i.e., 64 tiles) Mempool reduced instruction set computer (RISC) V-based architecture considering the impact of inter tiles spacing. Simulation results reveal that lateral heat spreading predominantly affects the thermal performance in multicore architectures under partial workload conditions. We also optimize the thermal performance with different tiles activity pattern. Simulation results reveal that both the maximum on-chip temperature and lateral heat spreading are improved for specific tiles activity patterns. Also the thermal performance analysis considering the “tile-insite effect” reveals that there is little impact on on-chip maximum temperature ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\text {max}}$ </tex-math></inline-formula> ), but the on-chip thermal gradient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta T$ </tex-math></inline-formula> ) and the thermal profile pattern are predominantly affected. Finally, the effect of the secondary heat path toward printed circuit board (PCB) is studied in this work.

Spreading and retraction of the concentric impact of a drop with a sessile drop of the same liquid: Effect of surface wettability

The concentric impact on a sessile drop is relevant in many applications, including spray coating and icing phenomena. Herein, the spreading and retraction phases yielded during the impact of a coaxial drop with a sessile drop on a solid substrate were empirically and analytically examined. We analyzed the effects of surface wettability on the impact outcomes utilizing five distinctive surfaces (i.e., smooth glass, aluminum, copper, Teflon, and coated glass). The results showed that the merged drop takes longer to attain its maximum spreading diameter at a relatively higher contact angle of the sessile drop with the solid surface. Furthermore, based on energy balance, a model for predicting the maximum spreading diameter of the drop with varying surface wettability was presented. This model considers the assumption of viscous energy loss during the merging of falling and sessile drops and at the maximum spreading diameter. Additionally, the maximum retraction height during the impact on the coated glass surface was investigated. Our model results matched well with the experimental data.