Recent Submissions

  • Optical force decoration of 3D microstructures with plasmonic particles

    Donato, M. G.; Rajamanickam, Vijayakumar Palanisamy; Foti, A.; Gucciardi, P. G.; Liberale, Carlo; Maragò, O. M. (The Optical Society, 2018-10-12)
    Optical forces are used to push and aggregate gold nanorods onto several substrates creating surface-enhanced Raman scattering (SERS) active hot spots for Raman-based identification of proteins. By monitoring the increase of the protein SERS signal, we observe different aggregation times for different curvatures of the substrates. The slower aggregation dynamics on curved surfaces is justified by a simple geometrical model. In particular, this technique is used to decorate three-dimensional microstructures and to quickly realize hybrid micro/nanosensors for highly sensitive detection of biological material directly in a liquid environment.
  • Surrogate formulation for diesel and jet fuels using the minimalist functional group (MFG) approach

    Abdul Jameel, Abdul Gani; Naser, Nimal; Emwas, Abdul-Hamid M.; Sarathy, Mani (Elsevier BV, 2018-10-12)
    Surrogate fuels aim to reproduce real fuel combustion characteristics in order to enable predictive simulations and fuel/engine design. In this work, surrogate mixtures were formulated for three diesel fuels (Coryton Euro and Coryton US-2D certification grade and Saudi pump grade) and two jet fuels (POSF 4658 and POSF 4734) using the minimalist functional group (MFG) approach, a method recently developed and tested for gasoline fuels. The diesel and jet fuel surrogates were formulated by matching five important functional groups, while minimizing the surrogate components to two species. Another molecular parameter, called as branching index (BI), which denotes the degree of branching was also used as a matching criterion. The present works aims to test the ability of the MFG surrogate methodology for high molecular weight fuels (e.g., jet and diesel). 1H Nuclear Magnetic Resonance (NMR) spectroscopy was used to analyze the composition of the groups in diesel fuels, and those in jet fuels were evaluated using the molecular data obtained from published literature. The MFG surrogates were experimentally evaluated in an ignition quality tester (IQT), wherein ignition delay times (IDT) and derived cetane number (DCN) were measured. Physical properties, namely, average molecular weight (AMW) and density, and thermochemical properties, namely, heat of combustion and H/C ratio were also compared. The results show that the MFG surrogates were able to reproduce the combustion properties of the above fuels, and we demonstrate that fewer species in surrogates can be as effective as more complex surrogates. We conclude that the MFG approach can radically simplify the surrogate formulation process, significantly reduce the cost and time associated with the development of chemical kinetic models, and facilitate surrogate testing.
  • Differential diffusion effect on the stabilization characteristics of autoignited laminar lifted methane/hydrogen jet flames in heated coflow air

    Jung, Ki Sung; Kim, Seung Ook; Lu, Tianfeng; Chung, Suk-Ho; Lee, Bok Jik; Yoo, Chun Sang (Elsevier BV, 2018-10-10)
    The characteristics of autoignited laminar lifted methane/hydrogen jet flames in heated coflow air are numerically investigated using laminarSMOKE code with a 57-species detailed methane/air chemical kinetic mechanism. Detailed numerical simulations are performed for various fuel jet velocities, U0, with different hydrogen ratio of the fuel jet, RH, and the inlet temperature, T0. Based on the flame characteristics, the autoignited laminar lifted jet flames can be categorized into three regimes of combustion mode: the tribrachial edge flame regime, the Moderate or Intense Low-oxygen Dilution (MILD) combustion regime, and the transition regime in between. Under relatively low temperature and high hydrogen ratio (LTHH) conditions, an unusual decreasing liftoff height, HL, behavior with increasing U0 is observed, qualitatively similar to those of previous experimental observations. From additional simulations with modified hydrogen mass diffusivity, it is substantiated that the unusual decreasing HL behavior is primarily attributed to the high diffusive nature of hydrogen molecules. The species transport budget, autoignition index, and displacement speed analyses verify that the autoignited lifted jet flames are stabilized by autoignition-assisted flame propagation or autoignition depending on the combustion regime. Chemical explosive mode analysis (CEMA) identifies important variables and reaction steps for the MILD combustion and tribrachial edge flame regimes.
  • Predator Avoidance in the European Seabass After Recovery From Short-Term Hypoxia and Different CO2 Conditions

    Steckbauer, Alexandra; Díaz-Gil, Carlos; Alós, Josep; Catalán, Ignacio A.; Duarte, Carlos M. (Frontiers Media SA, 2018-10-09)
    Short-term hypoxia that lasts just a few days or even hours is a major threat for the marine ecosystems. The single effect of the human-induced levels of hypoxia and other anthropogenic impacts such as elevated pCO2 can reduce the ability of preys to detect their predators across taxa. Moreover, both processes, hypoxia and elevated pCO2, are expected to co-occur in certain habitats, but the synergic consequences of both processes and the ability of fish to recover remain unknown. To provide empirical evidence to this synergy, we experimentally evaluated the risk-taking behavior in juveniles of the European seabass (Dicentrachus labrax), an important commercial fisheries species after recovering from short-term hypoxia and different pH scenarios. The behavior of seabass juveniles was monitored in an experimental arena before and after the exposure to a simulated predator and contrasted to control fish (BACI design) (current levels of hypoxia and elevated pCO2) using a mechanistic function-valued modeling trait approach. Results revealed that fish recovering from elevated pCO2, alone or combined with hypoxia, presented less avoidance behavior in failing to seek refuge when a simulated predator was present in the arena compared to those exposed to control pCO2 levels. Our results show that recovery from short-term exposure to acidification and hypoxia was not synergistic and suggest that recovery from acidification takes longer than from short-term hypoxia treatment through a potential effect on the sensorial and hence behavioral capacities of fish.
  • Flexible Lightweight CMOS-Enabled Multisensory Platform for Plant Microclimate Monitoring

    Khan, Sherjeel M.; Shaikh, Sohail F.; Qaiser, Nadeem; Hussain, Muhammad Mustafa (Institute of Electrical and Electronics Engineers (IEEE), 2018-10-09)
    We report an ultralightweight flexible sensory platform using bare die CMOS chips having a light, temperature, and humidity sensor on a flexible polymer substrate. An application-specified integrated circuit designed and fabricated in a 0.35-μm process is used for signal acquisition, conditioning, and further transfer of data to a bare die microcontroller. The whole platform is powered by a bare die solid-state battery. This extremely lightweight (0.44 g), compact (3 x 1.5 cm²), flexible, and mostly transparent platform can be unobtrusively placed on a leaf of a plant to monitor microclimate conditions surrounding a plant for accurate plant growth monitoring. The latter is successfully demonstrated by placing the platform on a plant leaf and monitoring changing environmental conditions (light, temperature, and humidity) for a whole day.
  • Absorptive hydrogen scavenging for enhanced aromatics yield during non-oxidative methane dehydroaromatization on Mo/H-ZSM-5 catalysts

    Kumar, Anurag; Song, Kepeng; Liu, Lingmei; Han, Yu; Bhan, Aditya (Wiley, 2018-10-08)
    The addition of Zr metal particles to MoCx/ZSM-5 in interpellet mixtures (2:1 weight ratio) resulted in maximum single-pass methane conversion of ~27% for dehydroaromatization at 973 K - in significant excess of the equilibrium prescribed ~10% conversion at these conditions - and a concurrent 1.4 - 5.6 fold increase in aromatic product yields due to circumvention of thermodynamic equilibrium limitations by absorptive hydrogen removal by Zr while retaining the cumulative aromatic product selectivity. The absorptive function of the polyfunctional catalyst formulation can be regenerated by thermal treatment in helium flow at 973 K yielding above equilibrium methane conversion in successive regeneration cycles. Hydrogen uptake experiments demonstrate formation of bulk ZrH₁.₇₅ on hydrogen absorption by zirconium at 973 K. Cooperation between absorption and catalytic centers distinct in location and function enables circumvention of persistent thermodynamic challenges in non-oxidative methane dehydrogenation.
  • Uncertainty quantification of groundwater contamination

    Litvinenko, Alexander; Logashenko, Dmitry (2018-10-08)
    In many countries, groundwater is the strategic reserve, which is used as drinking water and as an irrigation resource. Therefore, accurate modeling of the pollution of the soil and groundwater aquifer is highly important. As a model, we consider a density-driven groundwater flow problem with uncertain porosity and permeability. This problem may arise in geothermal reservoir simulation, natural saline-disposal basins, modeling of contaminant plumes and subsurface flow. This strongly non-linear problem describes how salt or polluted water streams down building ''fingers". The solving process requires a very fine unstructured mesh and, therefore, high computational resources. Consequently, we run the parallel multigrid solver UG4 (https://github.com/UG4/ughub.wiki.git) on Shaheen II supercomputer. The parallelization is done in both - the physical space and the stochastic space. The novelty of this work is the estimation of risks that the pollution will achieve a specific critical concentration. Additionally, we demonstrate how the multigrid UG4 solver can be run in a black-box fashion for testing different scenarios in the density-driven flow. We solve Elder's problem in 2D and 3D domains, where unknown porosity and permeability are modeled by random fields. For approximations in the stochastic space, we use the generalized polynomial chaos expansion. We compute different quantities of interest such as the mean, variance and exceedance probabilities of the concentration. As a reference solution, we use the solution, obtained from the quasi-Monte Carlo method.
  • Self-Assembled Membranes with Featherlike and Lamellar Morphologies Containing α-Helical Polypeptides

    Sutisna, Burhannudin; Bilalis, Panagiotis; Musteata, Valentina-Elena; Smilgies, Detlef-M.; Peinemann, Klaus-Viktor; Hadjichristidis, Nikolaos; Nunes, Suzana Pereira (American Chemical Society (ACS), 2018-10-08)
    Biological systems are the ultimate model for an effective selective permeation device. Biomimetic artificial channels based on the assembly of peptides have been previously integrated in vesicles and lipid layers with the expectation of leading in the future to a more efficient water purification and biological separation. We demonstrate here the design of scalable membranes constituted by synthesized copolymers with α-helical polypeptide blocks. They have unique featherlike and lamellar structures and were obtained from poly(styrene-b-γ-benzyl-l-glutamate) copolymers via phase inversion or spin-coating. The membranes were then hydrolyzed using acid vapor annealing, which preserved the helical morphology after hydrolysis. Water permeation up to 3.5 L m–2 h–1 bar–1 was obtained. Dialysis experiments with membranes prepared via phase inversion had high retention of cytochrome c. High rejection of cytochrome c and the negatively charged dye Brilliant Blue was demonstrated for the spin-coated membranes. The bioinspired membranes are developed for effective molecular separation, aiming at applications in the biotech industry.
  • Dynamic responses of counterflow nonpremixed flames to AC electric field

    Park, Daegeun; Chung, Suk-Ho; Cha, Min (Elsevier BV, 2018-10-08)
    Although ionic wind has been observed to play important roles in the effects of electric fields on flames, there is a lack of systematic quantification of ionic wind that allows interpretation of a flame's responses to electric fields. Here, we report on various responses of nonpremixed flames, such as the flame's dynamic responses and the generation of bidirectional ionic wind, in relation to the applied voltage and frequency of an alternating current (AC) in a counterflow burner. We find that although the Lorentz force acting on charged molecules initiates related effects, each effect is both complex and different. When the applied voltage is in the sub-saturated regime (small) as determined by the voltage-current behavior, flame movements and flow motion are minimally affected. However, when the applied voltage is in the saturated regime (large), flame oscillation occurs and a bidirectional ionic wind is generated that creates double-stagnation planes. The flame's oscillatory motion could be categorized in the transport-limited regime and in the oscillatory decaying regime, suggesting a strong dependence of the motion on the configuration of the burner. We also observed bidirectional ionic wind in visibly stable flames at higher AC frequencies. We present detailed explanations for flame behaviors, electric currents, and flow characteristics under various experimental conditions.
  • Spectral-Efficiency - Illumination Pareto Front for Energy Harvesting Enabled VLC System

    Abdelhady, Amr Mohamed Abdelaziz; Amin, Osama; Chaaban, Anas; Shihada, Basem; Alouini, Mohamed-Slim (2018-10-07)
    The continuous improvement in optical energy harvesting devices motivates visible light communication (VLC) system developers to utilize such available free energy sources. An outdoor VLC system is considered where an optical base station sends data to multiple users that are capable of harvesting the optical energy. The proposed VLC system serves multiple users using time division multiple access (TDMA) with unequal time and power allocation, which are allocated to improve the system performance. The adopted optical system provides users with illumination and data communication services. The outdoor optical design objective is to maximize the illumination, while the communication design objective is to maximize the spectral efficiency (SE). The design objectives are shown to be conflicting, therefore, a multiobjective optimization problem is formulated to obtain the Pareto front performance curve for the proposed system. To this end, the marginal optimization problems are solved first using low complexity algorithms. Then, based on the proposed algorithms, a low complexity algorithm is developed to obtain an inner bound of the Pareto front for the illumination-SE tradeoff. The inner bound for the Pareto-front is shown to be close to the optimal Pareto-frontier via several simulation scenarios for different system parameters.
  • An N-parallel FENE-P constitutive model and its application in large-eddy simulation of viscoelastic turbulent drag-reducing flow

    Li, Jingfa; Yu, Bo; Sun, Shuyu; Sun, Dongliang; Kawaguchi, Yasuo (Elsevier BV, 2018-10-05)
    In this paper, an N-parallel FENE-P constitutive model based on multiple relaxation times is proposed, it can be viewed as a simplified version of the multi-mode FENE-P model under the assumption of identical deformation rate. The proposed model holds the merit of multiple relaxation times to preserve good computational accuracy but could reduce the computational cost, especially in the application of high-fidelity numerical simulation of viscoelastic turbulent drag-reducing flow. Firstly the establishment of N-parallel FENE-P model and the numerical approach to calculate the apparent viscosity are introduced. Then the proposed model is compared with the experimental data and the conventional FENE-P model in estimating rheological properties of two common-used viscoelastic fluids to validate its performance. This work is an extended version of our ICCS conference paper [1]. To further judge the performance of the proposed FENE-P model in complex turbulent flows, the extended application of the proposed model in large-eddy simulation of viscoelastic turbulent drag-reducing channel flow is carried out.
  • Crystalline 2D Covalent Organic Framework Membranes for High-Flux Organic Solvent Nanofiltration

    Shinde, Digambar B.; Sheng, Guan; Li, Xiang; Ostwal, Mayur; Emwas, Abdul-Hamid; Huang, Kuo-Wei; Lai, Zhiping (American Chemical Society (ACS), 2018-10-05)
    Two-dimensional (2D) covalent organic framework (COF) materials have the most suitable microstructure for membrane applications in order to achieve both high flux and high selectivity. Here, we report the synthesis of a crystalline TFP-DHF 2D COF membrane constructed from two precursors of 1,3,5-triformylphloroglucinol (TFP) and 9,9-dihexylfluorene-2,7-diamine (DHF) through the Langmuir–Blodgett (LB) method, for the first time. A single COF layer is precisely four-unit-cell thick and can be transferred to different support surfaces layer-by-layer. The TFP-DHF 2D COF membrane supported on anodic aluminum oxide (AAO) porous supports displayed remarkable permeabilities for both polar and nonpolar organic solvents, which were approximately 100 times higher than that of the amorphous membranes prepared by the same procedure and similar to the best of the reported polymer membranes. The transport mechanism through the TFP-DHF 2D COF membrane was found to be a viscous flow coupled with a strong slip boundary enhancement, which was also different from those of the amorphous polymer membranes. The membrane exhibited a steep molecular sieving with a molecular weight retention onset of approximately 600 Da and a molecular weight cut-off of approximately 900 Da. The substantial performance enhancement was attributed to the structural change from an amorphous structure to a well-defined ordered porous structure, which clearly demonstrated the high potential for the application of 2D COFs as the next generation of membrane materials.
  • Energy-resolved Photoconductivity Mapping in a Monolayer-bilayer WSe2 Lateral Heterostructure

    Chu, Zhaodong; Han, Ali; Lei, Chao; Lopatin, Sergei; Li, Peng; Wannlund, David; Wu, Di; Herrera, Kevin; Zhang, Xixiang; MacDonald, Allan H; Li, Xiaoqin; Li, Lain-Jong; Lai, Keji (American Chemical Society (ACS), 2018-10-05)
    Vertical and lateral heterostructures of van der Waals materials provide tremendous flexibility for band structure engineering. Since electronic bands are sensitively affected by defects, strain, and interlayer coupling, the edge and heterojunction of these two-dimensional (2D) systems may exhibit novel physical properties, which can be fully revealed only by spatially resolved probes. Here, we report the spatial mapping of photoconductivity in a monolayer-bilayer WSe2 lateral heterostructure under multiple excitation lasers. As the photon energy increases, the light-induced conductivity detected by microwave impedance microscopy first appears along the hetero-interface and bilayer edge, then along the monolayer edge, inside the bilayer area, and finally in the interior of the monolayer region. The sequential emergence of mobile carriers in different sections of the sample is consistent with the theoretical calculation of local energy gaps. Quantitative analysis of the microscopy and transport data also reveals the linear dependence of photoconductivity on the laser intensity and the influence of interlayer coupling on carrier recombination. Combining theoretical modeling, atomic scale imaging, mesoscale impedance microscopy, and device-level characterization, our work suggests an exciting perspective to control the intrinsic band-gap variation in 2D heterostructures down to the few-nanometer regime.
  • The transport of nanoparticles in subsurface with fractured, anisotropic porous media: Numerical simulations and parallelization

    Chen, Meng-Huo; Salama, Amgad; Sun, Shuyu (Elsevier BV, 2018-10-05)
    The flow of fluids through fractured porous media has been an important topic in the research of subsurface flow. The several orders of magnitude in size between the fractures and the rock matrix causes difficulties for simulating such flow scenario. The fluid velocities in fractures are also several orders of magnitude higher than that in the rock matrix due to high permeability and porosity. If there exists pollutant such as nanoparticles in the fluids, the pollutant may be transported rapidly and the rock matrix’s properties near the fractures are hence changed. In this research, we simulate the transport phenomena of nanoparticles in the fluid flow through fractured porous media. The permeability fields which contain different anisotropy angles are considered in the simulation. Fractures are represented explicitly by volumetric grid cells and the numerical algorithm is parallelized in order to reduce the simulation time. We investigate the effect of the appearance of fractures and rotated anisotropy on the transport of nanoparticles, particles deposition, entrapment and detachment. The results show that flow directions are affected by the direction of anisotropy and the transport of nanoparticles in the fractures is significantly faster than that in rock matrix due to high fluid velocities. The direction of anisotropy distorted the pressure field and changed the fluid flow directions, which determined the time needed for the pollutant front to reach the fractures. The parallel efficiency of the overall algorithm is also discussed and the experimental results show that it is deeply affected by the performance of the multigrid solver.
  • Early biofouling detection using fluorescence-based extracellular enzyme activity

    Khan, Babar K.; Fortunato, Luca; Leiknes, Torove (Elsevier BV, 2018-10-05)
    Membrane-based filtration technologies have seen rapid inclusion in a variety of industrial processes, especially production of drinking water by desalination. Biological fouling of membranes is a challenge that leads to increased costs from efficiency reductions, membrane damage and ultimately, membrane replacement over time. Such costs can be mitigated by monitoring and optimizing cleaning processes for better prognosis. Monitoring bacterial accumulation in situ can therefore advance understanding of cleaning efficiency. A fluorescence-based sensor for early biofouling detection capable of measuring extracellular enzyme activity was developed and tested in a lab-scale seawater reverse osmosis (SWRO) biofouling model for use in monitoring bacterial accumulation proximal to the surface of a membrane. We tracked bacterial biomass accumulation rapidly and non-invasively using exogenously applied fluorogen-substrates and corroborated with optical coherence tomography imaging of the membrane surface in real-time. The selected fluorogen and fluorogen-substrate were characterized and down selected by high throughput screening in vitro for compatibility in seawater and profiled over relevant Red Sea desalination parameters (pH and temperature). This approach demonstrates the practicality of prototyping an early-detection biofouling sensor in membrane based processes, such as seawater desalination, using extracellular enzyme activity as a measure of bacterial abundance.
  • Tunable self-injection locked green laser diode

    Shamim, Md Hosne Mobarok; Ng, Tien Khee; Ooi, Boon S.; Khan, Mohammed Zahed Mustafa (The Optical Society, 2018-10-05)
    We report, to the best of our knowledge, the first employment of a self-injection locking scheme for the demonstration of a tunable InGaN/GaN semiconductor laser diode. We have achieved a 7.11 nm (521.10–528.21 nm) tunability in a green color with different injection currents and temperatures. The system exhibited mode spectral linewidth as narrow as ∼69 pm and a side mode suppression ratio as high as ∼28 dB, with a maximum optical power of ∼16.7 mW. In the entire tuning window, extending beyond 520 nm, a spectral linewidth of ≤100 pm, high power, and stable performance were consistently achieved, making this, to the best of our knowledge, the first-of-its-kind compact tunable laser system attractive for spectroscopy, imaging, sensing systems, and visible light communication.
  • Ultraviolet FSO to laser-based VLC – the role of group-III-nitride devices

    Ooi, Boon S.; Sun, Xiaobin; Shen, Chao; Guo, Yujian; Liu, Guangyu; Ng, Tien Khee (2018-10-04)
  • Multimode Excitation of a Metal Organics Frameworks Coated Microbeam for Smart Gas Sensing and Actuation

    Jaber, N.; Ilyas, S.; Shekhah, O.; Eddaoudi, M.; Younis, M.I. (Elsevier BV, 2018-10-04)
    Smart sensing systems suffer complexity requiring interface circuits, microcontrollers, switches, and actuators to detect and sense, process the signal and take a decision, and trigger an action upon demand. This increases the device footprint and boosts significantly the power required to actuate the system. Here, we present a hybrid sensor and switch device, which is capable of accurately measuring gas concentration and perform switching when the concentration exceeds specific (safe) threshold. The device is based on a clamped-clamped microbeam coated with metal-organic frameworks (MOFs). Using the electrostatic harmonic voltage, we employ dynamic multi-modal actuation in which the microbeam is simultaneously excited at the first mode of vibration, near the pull-in band, and at the third mode. We demonstrate experimentally the effectiveness of this technique in measuring the concentration of water vapor and achieving switching when the concentration exceeds a threshold value. In contrast to the first mode operation, we show that monitoring the third mode enhances sensitivity, improves accuracy, and lowers the sensor sensitivity to noise.
  • Overview of Low-rank and Sparse Techniques in Spatial Statistics and Parameter Identification

    Litvinenko, Alexander (2018-10-03)
    Motivation: improve statistical model by implementing more efficient numerical tools Major Goal: Develop new statistical tools to address new problems. Overview: Low-rank matrices, Sparse matrices, Hierarchical matrices. Approximation of Matern covariance functions and joint Gaussian likelihood, Identification of unknown parameters via maximizing Gaussian log-likelihood, Low-rank tensor methods
  • Reduction and Increase in Thermal Conductivity of Si Irradiated with Ga+ via Focused Ion Beam

    Alaie, Seyedhamidreza; Ghasemi Baboly, Mohammadhosein; Jiang, Ying Bing; Rempe, Susan B.; Anjum, Dalaver H.; Chaieb, Sahraoui; Donovan, Brian Francis; Giri, Ashutosh; Szwejkowski, Chester J; Gaskins, John Thomas; Elahi, Mirza; Goettler, Drew; Braun, Jeffrey L.; Hopkins, Patrick E.; Leseman, Zayd Chad (American Chemical Society (ACS), 2018-10-03)
    Focused Ion Beam (FIB) technology has become a valuable tool for the microelectronics industry and for the fabrication and preparation of samples at the micro/nanoscale. Its effects on the thermal transport properties of Si, however are not well understood, nor do experimental data exist. This paper presents a carefully designed set of experiments for the determination of the thermal conductivity of Si samples irradiated by Ga+ FIB. Generally, the thermal conductivity decreases with increasing ion dose. For doses of >1016 (Ga+/cm2), a reversal of the trend was observed due to recrystallization of Si. This report provides insight on the thermal transport considerations relevant to engineering of Si nanostructures and interfaces fabricated or prepared by FIB.

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