Now showing items 1-20 of 55886

    • Muscle Fatigue Sensor Based on Ti 3 C 2 T x MXene Hydrogel

      Lee, Kanghyuck; Zhang, Yi-Zhou; Kim, Hyunho; Lei, Yongjiu; Hong, Seunghyun; Wustoni, Shofarul; Hama, Adel; Inal, Sahika; Alshareef, Husam N. (Small Methods, Wiley, 2021-10-26) [Article]
      MXene-based hydrogels have received significant attention due to several promising properties that distinguish them from conventional hydrogels. In this study, it is shown that both strain and pH level can be exploited to tune the electronic and ionic transport in MXene-based hydrogel (M-hydrogel), which consists of MXene (Ti3C2Tx)-polyacrylic acid/polyvinyl alcohol hydrogel. In particular, the strain applied to the M-hydrogel changes MXene sheet orientation which leads to modulation of ionic transport within the M-hydrogel, due to strain-induced orientation of the surface charge-guided ionic pathway. Simultaneously, the reorientation of MXene sheets under the axial strain increases the electronic resistance of the M-hydrogel due to the loss of the percolative network of conductive MXene sheets during the stretching process. The iontronic characteristics of the M-hydrogel can thus be tuned by strain and pH, which allows using the M-hydrogel as a muscle fatigue sensor during exercise. A fully functional M-hydrogel is developed for real-time measurement of muscle fatigue during exercise and coupled it to a smartphone to provide a portable or wearable digital readout. This concept can be extended to other fields that require accurate analysis of constantly changing physical and chemical conditions, such as physiological changes in the human body.
    • A novel zero-liquid discharge desalination system based on the humidification-dehumidification process: a preliminary study

      Chen, Qian; Akhtar, Faheem; Burhan, Muhammad; Kumja, M; Ng, Kim Choon (Water Research, Elsevier BV, 2021-10-25) [Article]
      As a byproduct of desalination plants, brine is increasingly becoming a threat to the environment, and the design of zero-liquid discharge desalination (ZLDD) systems is gaining increasing attention. Existing ZLDD systems are limited by a high energy intensity and high plant costs of their crystallizers. This study proposes a novel crystallization method based on the humidification-dehumidification (HDH) process, which exhibits the advantages of a low energy consumption, low component costs and a reduced scaling and fouling potential. A simple experimental setup is first designed to demonstrate the feasibility of the proposed system. Brine concentration and salt crystallization are successfully achieved with air heated to 40 ℃ as the heat source. Afterwards, a thermo-economic analysis is conducted for the whole system. The specific thermal energy and electricity consumption levels are found to range from 700-900 and 5-11 kJ, respectively, per kg of feed brine. The energy consumption is 56% lower than that of a conventional evaporative crystallizer, and the initial plant cost is reduced by 58%. Keywords: zero-liquid discharge desalination; crystallization; humidification-dehumidification.
    • Printed Memtransistor Utilizing a Hybrid Perovskite/Organic Heterojunction Channel

      Ma, Chun; Chen, Hu; Yengel, Emre; Faber, Hendrik; Khan, Jafar Iqbal; Tang, Ming-Chun; Li, Ruipeng; Loganathan, Kalaivanan; Lin, Yuanbao; Zhang, Weimin; Laquai, Frédéric; McCulloch, Iain; Anthopoulos, Thomas D. (ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2021-10-25) [Article]
      Neuromorphic computing has the potential to address the inherent limitations of conventional integrated circuit technology, ranging from perception, pattern recognition, to memory and decision-making ( Acc. Chem. Res. 2019, 52 (4), 964−974) ( Nature 2004, 431 (7010), 796−803) ( Nat. Nanotechnol. 2013, 8 (1), 13−24). Despite their low power consumption ( Nano Lett. 2016, 16 (11), 6724−6732), traditional two-terminal memristors can perform only a single function while lacking heterosynaptic plasticity ( Nanotechnology 2013, 24 (38), 382001). Inspired by the unconditioned reflex, multiterminal memristive transistors (memtransistor) were developed to realize complex functions, such as multiterminal modulation and heterosynaptic plasticity ( Nature 2018, 554, (7693), 500−504). Here we combine a hybrid metal halide perovskite with an organic conjugated polymer to form heterojunction transistors that are responsive to both electrical and optical stimuli. We show that the synergistic effects of photoinduced ion migration in the perovskite and electronic transport in the polymer layers can be exploited to realize memristive functions. The device combines reversible, nonvolatile conductance modulation with large switching current ratios, high endurance, and long retention times. Using in situ scanning Kelvin probe microscopy and variable-temperature charge transport measurement, we correlate the collective effects of bias-induced and photoinduced ion migration with the heterosynaptic behavior observed in this hybrid memtransistor. The hybrid heterojunction channel concept is expected to be applicable to other material combinations making it a promising platform for deployment in innovative neuromorphic devices of the future.
    • Electrode metallization for scaled perovskite/silicon tandem solar cells: Challenges and opportunities

      Rehman, Atteq Ur; Van Kerschaver, Emmanuel P.; Aydin, Erkan; Raja, Waseem; Allen, Thomas; De Wolf, Stefaan (Progress in Photovoltaics: Research and Applications, Wiley, 2021-10-25) [Article]
      Monolithic perovskite/silicon tandem solar cells have the potential to reach very high power conversion efficiencies (PCEs) in a cost-effective manner. In the last decade, significant technological advancements have been made for lab-scale devices (~1 cm2), with PCEs now higher than the theoretical PCE limit of single-junction silicon solar cells. For market entry of such tandems, the involved processing steps need to be scaled to industrial wafer dimensions, typically >244 cm2, which also mandates the development of adequate electrode-metallization strategies. Here we discuss challenges and opportunities related to this, including the required properties of the front metal grid for perovskite/silicon tandems, as well as key motivations and challenges in adopting screen-printed metallization, which is the current standard for mainstream silicon solar cells. We give a cost estimation for the front metal grid by considering the cost of low-temperature metal pastes that are compatible with the thermal budget limitations imposed by the perovskite top cell. We also consider opportunities to employ alternative metallization schemes that arise from the reduction in current density in tandem solar cells compared to single-junction devices. Lastly, we discuss possible routes to replace or minimize the silver content in costly silver-based metallization for industrial applications.
    • Shape and Reflectance Reconstruction in Uncontrolled Environments by Differentiable Rendering

      Li, Rui; Zang, Guangmin; Qi, Miao; Heidrich, Wolfgang (arXiv, 2021-10-25) [Preprint]
      Simultaneous reconstruction of geometry and reflectance properties in uncontrolled environments remains a challenging problem. In this paper, we propose an efficient method to reconstruct the scene's 3D geometry and reflectance from multi-view photography using conventional hand-held cameras. Our method automatically builds a virtual scene in a differentiable rendering system that roughly matches the real world's scene parameters, optimized by minimizing photometric objectives alternatingly and stochastically. With the optimal scene parameters evaluated, photo-realistic novel views for various viewing angles and distances can then be generated by our approach. We present the results of captured scenes with complex geometry and various reflection types. Our method also shows superior performance compared to state-of-the-art alternatives in novel view synthesis visually and quantitatively.
    • Local combustion regime identification using machine learning

      Malpica Galassi, Riccardo; Ciottoli, Pietro P.; Valorani, Mauro; Im, Hong G. (Combustion Theory and Modelling, Informa UK Limited, 2021-10-24) [Article]
      A new combustion regime identification methodology using the neural networks as supervised classifiers is proposed and validated. As a first proof of concept, a binary classifier is trained with labelled thermochemical states obtained as solutions of prototypical one-dimensional models representing premixed and nonpremixed regimes. The trained classifier is then used to associate the regime to any given thermochemical state originating from a multi-dimensional reacting flow simulation that shares similar operating conditions with the training problems. The classification requires local information only, i.e. no gradients are required, and operates on reduced-dimension thermochemical states, in order to cope with experimental data as well. The validity of the approach is assessed by employing a two-dimensional laminar edge flame data as a canonical configuration exhibiting multi-regime combustion behaviour. The method is readily extendable to additional classes to identify criticality phenomena, such as local extinction and re-ignition. It is anticipated that the proposed classifier tool will be useful in the development of turbulent multi-regime combustion closure models in large scale simulations.
    • A versatile framework to solve the Helmholtz equation using physics-informed neural networks

      Song, Chao; Alkhalifah, Tariq Ali; Waheed, Umair bin (Geophysical Journal International, Oxford University Press (OUP), 2021-10-23) [Article]
      Solving the wave equation to obtain wavefield solutions is an essential step in illuminating the subsurface using seismic imaging and waveform inversion methods. Here, we utilize a recently introduced machine-learning based framework called physics-informed neural networks (PINNs) to solve the frequency-domain wave equation, which is also referred to as the Helmholtz equation, for isotropic and anisotropic media. Like functions, PINNs are formed by using a fully-connected neural network (NN) to provide the wavefield solution at spatial points in the domain of interest, in which the coordinates of the point form the input to the network. We train such a network by back propagating the misfit in the wave equation for the output wavefield values and their derivatives for many points in the model space. Generally, a hyperbolic tangent activation is used with PINNs, however, we use an adaptive sinusoidal activation function to optimize the training process. Numerical results show that PINNs with adaptive sinusoidal activation functions are able to generate frequency-domain wavefield solutions that satisfy wave equations. We also show the flexibility and versatility of the proposed method for various media, including anisotropy, and for models with strong irregular topography.
    • Composite nanofiltration membrane comprising one-dimensional erdite, two-dimensional reduced graphene oxide, and silkworm pupae binder

      Balaji, K.R.; Hardian, Rifan; Dileep Kumar, V.G.; Viswanatha, R.; Kumar, Suneel; Kumar, Surender; Singh, Archana; Santosh, Mysore Sridhar; Szekely, Gyorgy (Materials Today Chemistry, Elsevier, 2021-10-23) [Article]
      Composite nanofiltration membranes offer advantages because of synergetic effects among the constituent materials’ properties. However, the sustainability of both the membrane fabrication and the raw materials has been a drawback of this energy-efficient separation technology. We report the facile fabrication of a nanocomposite membrane composed of a two-dimensional (2D) material of reduced graphene oxide (rGO) combined with a one-dimensional (1D) material of a ternary metal-based chalcogenide (NaFeS2 or NFS), using silkworm pupae protein as a natural binder. All the source materials can be derived from either nature or waste, ensuring the sustainability of the membrane and its production method. The structural characteristics of the synthesized membranes were analyzed, and the morphology of the composite membranes was studied thoroughly. Thermogravimetric analysis, differential scanning calorimetry, and nanoindentation characterizations indicated that the composite membranes were mechanically and thermally stable. The water and acetone fluxes; salt, dye, and pollutant rejections; and long-term membrane performance were evaluated using a cross-flow filtration system. Solute rejection was observed to increase (up to 98%, 94%, 95%, and 78% for Rhodamine B, 2,4-dichlorophenol, MgCl2, and NaCl, respectively) with increasing concentration of the nanomaterials in the membrane. The fine-tuning of the molecular weight cut-off from 794 to 600 g mol–1 was achieved by varying the concentration of the nanomaterials from 1 to 3 mg mL–1 . Our research findings demonstrate the synergetic effects of combining 1D and 2D materials using silkworm pupae binder. The composite membrane was stable in different classes of organic solvents, including hydrocarbons, alcohols, esters, ethers, polar aprotic solvents, halogenated solvents, and ketones. This first use of natural pupae binder in constructing membrane materials paves the way toward the development of more sustainable membranes.
    • COP26 Futures We Want – Regional Profile for the Arabian Peninsula

      Short, Samuel; Molini, Annalisa; Santamarina, Carlos; Friedrich, Luiz; Shuckburgh, Emily (Cambridge University Press (CUP), 2021-10-23) [Preprint]
      This regional profile for the Arabian Peninsula was developed in the context of the BEIS COP26 Futures We Want project. It covers the United Arab Emirates (UAE) and the Kingdom of Saudi Arabia (KSA), and has been developed with the input from in- country academic experts Prof. Annalisa Molini and Mr Luiz Friedrich (Khalifa University, UAE) and Prof. Juan Carlos Santamarina (King Abdullah University of Science and Technology, KSA). It sets out a synthesis of the available evidence base on regional challenges and opportunities for mitigation, adaptation, and resilience measures for both KSA and UAE and the wider Arabian Peninsula associated with climate change and a global transition to an inclusive, desirable, and resilient net-zero future.
    • Be-Be π bonding and predicted superconductivity in MBe2 (M=Zr, Hf)

      Goesten, Maarten Gerard (Angewandte Chemie International Edition, Wiley, 2021-10-23) [Article]
      Beryllium, an s-block element, forms an aromatic network of delocalized Be-Be π bonds in alloys ZrBe2 and HfBe2. This gives rise to a structure that fits description as stacked [Be2]4- layers with tetravalent cations in between. The [Be2]4- sublattice is isoelectronic and isostructural to graphite, as well as the [B]-2 sublattice in MgB2, and it bears identical manifestations of π bonding in its electronic band structure. These come in the form of degeneracies at K and H in the Brillouin zone, separated in energy as the result of interlayer orbital interactions. Zr and Hf use their valence d orbitals to form bonds with the layers, leading to nearly identical band structures. Like MgB2, ZrBe2 and HfBe2 are computed to be phonon-mediated superconductors at ambient pressures, with respective critical temperatures of 11.4 K and 8.8 K. The coupling strength between phonons and free electrons is very similar, so that the difference in critical temperatures is controlled by the mass of constituent interlayer ions.
    • Thermal treatment of hydroxyl functionalized polytriazole and its effect on gas transport: From crosslinking to carbon molecular sieve

      Chisca, Stefan; Bettahalli Narasimha, Murthy Srivatsa; Musteata, Valentina-Elena; Vasylevskyi, Serhii; Hedhili, Mohamed N.; Abou-Hamad, Edy; Karunakaran, Madhavan; Genduso, Giuseppe; Nunes, Suzana Pereira (Journal of Membrane Science, Elsevier BV, 2021-10-22) [Article]
      We propose hydroxyl-functionalized polytriazole as a precursor for the preparation of highly crosslinked membranes and carbon molecular sieves (CMS) for gas separation. We studied the effect of the treatment temperature on the chemical structure and gas separation properties. A progressing crosslinking structure was formed when polytriazole films were treated in the range of 300–400 °C. Above 425 °C, CMSs with multi-layered nitrogen-graphene-like structures were obtained. The CO2 permeability increased by increasing the temperature, while the CO2/CH4 selectivity was maintained. Permeability increases up to 37-fold compared to the untreated polymer film were obtained, aligned with a CO2/CH4 selectivity of 75. The single-gas CO2 permeability vs. CO2/CH4 selectivity data obtained for films treated at 475 and 550 °C are among the highest reported in the literature. Moreover, the mixed gas performance of these membranes is far above previously reported CO2/CH4 data plotted as mixed-gas trade-off curves, demonstrating the potential of polytriazole materials for these applications.
    • Deep characterization of paired chromatin and transcriptomes in four immune cell types from multiple sclerosis patients

      Fernandes, Sunjay Jude; Ericsson, Matilda; Khademi, Mohsen; Jagodic, Maja; Olsson, Tomas; Gomez-Cabrero, David; Kockum, Ingrid; Tegner, Jesper (Epigenomics, Future Medicine Ltd, 2021-10-22) [Article]
      Background: The putative involvement of chromatin states in multiple sclerosis (MS) is thus far unclear. Here we determined the association of chromatin-accessibility with concurrent genetic, epigenetic and transcriptional events. Material & methods: We generated paired assay for transposase-accessible chromatin sequencing and RNA-seq profiles from sorted blood immune CD4$^{+}$ and CD8$^{+}$ T cells, CD14$^{+}$ monocytes and CD19$^{+}$ B cells from healthy controls (HCs) and MS patients. Results: We identified differentially accessible regions between MS and HCs, primarily in CD4$^{+}$ and CD19$^{+}$. CD4$^{+}$ regions were enriched for MS-associated single nucleotide polymorphisms and differentially methylated loci. In the vicinity of differentially accessible regions of CD4$^{+}$ cells, 42 differentially expressed genes were identified. The top two dysregulated genes identified in this multilayer analysis were CCDC114 and SERTAD1. Conclusion: These findings provide new insight into the primary role of CD4$^{+}$ and CD19$^{+}$ cells in MS.
    • Optical diagnostics and multi-point pressure sensing on the knocking combustion with multiple spark ignition

      Shi, Hao; Tang, Qinglong; Uddeen, Kalim; Magnotti, Gaetano; Turner, James W. G. (Combustion and Flame, Elsevier BV, 2021-10-22) [Article]
      Engine knock is an abnormal combustion phenomenon that limits the thermal efficiency and service life of spark-ignition engines. A better understanding of the knock mechanisms and characteristics is beneficial to knock alleviation and engine efficiency improvement. In this study, a metal liner with four evenly-spaced spark plugs in the periphery of the combustion chamber is designed to initiate knock from different positions. Four spark strategies are applied to the single-cylinder optical research engine and six pressure sensors are utilized to analyze the local pressure oscillations in the cylinder. The knocking combustion is investigated by simultaneous 72 kHz high-speed imaging and 6-point pressure sensing. The experimental results indicate that using multiple spark-ignition could promote knock intensity, advance the start of auto-ignition and introduce more acoustic resonance modes. The center pressure sensor is more sensitive to the first radial resonant mode (0, 1) of the knock pressure oscillation, while the side sensors are more sensitive to the first and second circumferential resonant modes (1, 0) and (2, 0). The knock onset judged by natural flame photography is earlier than that by pressure analysis because the auto-ignition event happens first and induces the subsequent pressure fluctuation. Natural flame luminosity analysis demonstrates that the initial auto-ignition sites only cause weak pressure oscillations, and the instantaneous combustion of the remaining end-gas increases the heat release rate significantly and gives rise to more violent pressure oscillations. Statistically, the maximum amplitude of pressure oscillation follows an exponential relationship with the peak mean flame luminosity. The end-gas resides in the gaps among the flame fronts generated by different spark strategies while the first auto-ignition sites are not evenly distributed in the end-gas zone. This fact gives insights into the local temperature non-uniformity of the end gas zone that affects the spatial distributions of the initial auto-ignition sites in the cylinder.
    • Etch-free additive lithographic fabrication methods for reflective and transmissive micro-optics

      Fu, Qiang; Amata, Hadi; Heidrich, Wolfgang (Optics Express, The Optical Society, 2021-10-22) [Article]
      With the widespread application of micro-optics in a large range of areas, versatile high quality fabrication methods for diffractive optical elements (DOEs) have always been desired by both the research community and by industry. Traditionally, multi-level DOEs are fabricated by a repetitive combination of photolithography and reactive-ion etching (RIE). The optical phase accuracy and micro-surface quality are severely affected by various etching artifacts, e.g., RIE lag, aspect ratio dependent etching rates, and etching artifacts in the RIE steps. Here we propose an alternative way to fabricate DOEs by additively growing multi-level microstructures onto the substrate. Depth accuracy, surface roughness, uniformity and smoothness are easily controlled to high accuracy by a combination of deposition and lift-off, rather than etching. Uniform depths can be realized for both micrometer and millimeter scale features that are simultaneously present in the designs. The grown media can either be used directly as a reflective DOE, or as a master stamp for nanoimprinting refractive designs. We demonstrate the effectiveness of the fabrication methods with representative reflective and transmissive DOEs for imaging and display applications.
    • Photovoltage-Competing Dynamics in Photoelectrochemical Devices: Achieving Self-Powered Spectrally Distinctive Photodetection

      Liu, Xin; Wang, Danhao; Kang, Yang; Fang, Shi; Yu, Huabin; Zhang, Haochen; Memon, Muhammad Hunain; He, Jr-Hau; Ooi, Boon S.; Sun, Haiding; Long, Shibing (Advanced Functional Materials, Wiley, 2021-10-22) [Article]
      Multiple-band and spectrally distinctive photodetection play critical roles in building next-generation colorful imaging, spectroscopy, artificial vision, and optically controlled logic circuits of the future. Unfortunately, it remains challenging for conventional semiconductor photodetectors to distinguish different spectrum bands with photon energy above the bandgap of the material. Herein, for the first time, a photocurrent polarity-switchable photoelectrochemical device composed of group III-nitride semiconductors, demonstrating a positive photocurrent density of 10.54 µA cm−2 upon 254 nm illumination and a negative photocurrent density of −0.08 µA cm−2 under 365 nm illumination without external power supply, is constructed. Such bidirectional photocurrent behavior arises from the photovoltage-competing dynamics across two photoelectrodes. Importantly, a significant boost of the photocurrent and corresponding responsivity under 365 nm illumination can be achieved after decorating the counter electrode of n-type AlGaN nanowires with platinum (Pt) nanoparticles, which promote a more efficient redox reaction in the device. It is envisioned that the photocurrent polarity-switch behavior offers new routes to build multiple-band photodetection devices for complex light-induced sensing systems, covering a wide spectrum band from deep ultraviolet to infrared, by simply engineering the bandgaps of semiconductors.
    • Effects of nano- and microplastics on kidney: Physicochemical properties, bioaccumulation, oxidative stress and immunoreaction

      Meng, Xuemei; Zhang, Jiawei; Wang, Wenjing; Gonzalez-Gil, Graciela; Vrouwenvelder, Johannes S.; Li, Zhenyu (Chemosphere, Elsevier BV, 2021-10-21) [Article]
      The potential toxicity of nanoplastics (NPs) and microplastics (MPs) has raised concerns. However, knowledge of the effects of NPs/MPs on the health of mammals is still limited. Here we investigated the alteration of the physicochemical properties of polystyrene NPs (PS-NPs: 50 nm) and MPs (PS-MPs: 300 nm, 600 nm, 4 μm) in the gastrointestinal tract. Moreover, we investigated the uptake and bioaccumulation and the toxic effects of these plastic particles in the kidneys of mice. The results revealed that their digestion promoted the aggregation of PS-NPs and PS-MPs and increased the Zeta-potential value. Both PS-NPs and PS-MPs bioaccumulated in the kidneys, and the aggregation of 600 nm PS-MPs exacerbated their biotoxicity. The PS-NPs and PS-MPs caused mice weight loss, increased their death rate, significantly alternated several biomarkers, and resulted in histological damage of the kidney. We also found that exposure to PS-NPs and PS-MPs induced oxidative stress and the development of inflammation. These findings provide new insights into the toxic effects of NPs and MPs on mice.
    • Cyanamide Passivation Enables Robust Elemental Imaging of Metal Halide Perovskites at Atomic Resolution

      Liu, Jiakai; Song, Kepeng; Zheng, Xiaopeng; Yin, Jun; Yao, Ke Xin; Chen, Cailing; Yang, Haoze; Hedhili, Mohamed N.; Zhang, Wang; Han, Peigang; Mohammed, Omar F.; Han, Yu; Bakr, Osman (The Journal of Physical Chemistry Letters, American Chemical Society (ACS), 2021-10-21) [Article]
      Lead halide perovskites (LHPs) have attracted a tremendous amount of attention because of their applications in solar cells, lighting, and optoelectronics. However, the atomistic principles underlying their decomposition processes remain in large part obscure, likely due to the lack of precise information about their local structures and composition along regions with dimensions on the angstrom scale, such as crystal interfaces. Aberration-corrected scanning transmission electron microscopy combined with X-ray energy dispersive spectroscopy (EDS) is an ideal tool, in principle, for probing such information. However, atomic-resolution EDS has not been achieved for LHPs because of their instability under electron-beam irradiation. We report the fabrication of CsPbBr3 nanoplates with high beam stability through an interface-assisted regrowth strategy using cyanamide. The ultrahigh stability of the nanoplates primarily stems from two contributions: defect-healing self-assembly/regrowth processes and surface modulation by strong electron-withdrawing cyanamide molecules. The ultrahigh stability of as-prepared CsPbBr3 nanoplates enabled atomic-resolution EDS elemental mapping, which revealed atomically and elementally resolved details of the LHP nanostructures at an unprecedented level. While improving the stability of LHPs is critical for device applications, this work illustrates how improving the beam stability of LHPs is essential for addressing fundamental questions on structure–property relations in LHPs.
    • Applying heat flux method to laminar burning velocity measurements of NH3/CH4/air at elevated pressures and kinetic modeling study

      Wang, Shixing; Wang, Zhihua; Chen, Chenlin; Elbaz, Ayman M.; Sun, Zhiwei; Roberts, William L. (Combustion and Flame, Elsevier BV, 2021-10-21) [Article]
      Combustion of ammonia (NH3) blended fuels under elevated pressure conditions is critical for adopting this non-carbon fuel in the energy system for decarbonization. In the present work, laminar burning velocities of ammonia/methane(CH4)/air mixtures were measured using the heat-flux method at the pressure from 1 to 5 atm with the mixture equivalence ratios ranging from 0.6 to 1.6 and the mole fraction of NH3 ranging from 0 to 1.0. The relatively completed results obtained at elevated pressures were then used for validating and modifying the kinetic mechanisms (CEU-NH3-Mech 1.0) leading to a new version (CEU-NH3-Mech-1.1). Experimental results of NH3/H2/air in the present work, NH3/H2/CO/air mixtures measured on the same setup and reported in our previous works were also considered in the development of the kinetic mechanism. It was found that the CEU-NH3−Mech-1.1 can predict well the laminar flame speed, ignition delay time and species concentration in the ammonia oxidation at high temperatures for both NH3/CH4/air and NH3/H2/CO/air mixtures in a wide range of equivalence ratios and elevated pressures, including oxygen-enriched combustion conditions. The present experimental results also show that the value of pressure exponent (β) varies with the mole fraction of ammonia and behaves differently for the mixtures of ammonia blending into CH4 and H2. The kinetic and sensitivity analyses show that the sensitive reactions for β are weakly correlated to those for the laminar burning velocity, indicating that β can also work as a potential parameter for validating kinetic mechanisms. Ammonia content in the NH3/CH4/air mixtures determines the pressure exponent variation at over-rich equivalence ratios and reaction pathway variation in the post-flame zone. This work also clarifies the utilization of ammonia containing fuels in rich-lean combustion strategies.
    • Analytical and Experimental Study of the Dynamics of a Micro-Electromechanical Resonator Based Digital-to-Analog Converter

      Zhao, Wen; Ahmed, Sally; Fariborzi, Hossein; Younis, Mohammad I. (Journal of Micromechanics and Microengineering, IOP Publishing, 2021-10-21) [Article]
      In this paper, an analytical model of a micro-electromechanical (MEM) resonator used as a 4-bit digital-to-analog converter (DAC) is presented. First, we derive the dynamic equation of the 4-bit DAC device, and the nonlinear governing equation is solved by the Galerkin method combined with a shooting technique to simulate the static response, linear eigenvalue problem, and forced vibration response of the device for various electrostatic actuation cases. Also, we optimize the air gaps in the linear domain to ensure enhanced performance of the DAC. Further, to analyze the operation of the DAC in the nonlinear regime, two experimental samples powered by -2dBm and -12dBm AC inputs are examined. Forward and backward frequency sweeps are conducted experimentally and analytically. The proposed analytical results are validated by comparison with experimental data. The results indicate that the presented modeling, simulations, and optimization are effective tools for the design of MEM resonator-based circuits. Keywords: Digital to Analog Converter (DAC); MEMS Resonator; Optimization; Nonlinear Dynamics.
    • MemSor: Emergence of the In-Memory Sensing Technology for the Digital Transformation

      Elatab, Nazek (physica status solidi (a), Wiley, 2021-10-21) [Article]
      Since Moore’s law is facing several bottlenecks, electron devices are currently developing towards the trend of “More than Moore” which is based on functional diversifcation in terms of sensing, storage and processing of information. This multifunctionality is thought of as another form of miniaturization of the electronic devices, where noncomputing devices are merged with digital ones, leading to faster and more energy efficient processing of data. Complementary to the in-memory computing and in-sensor computing approaches, here, we examine the concept of in-memory sensing in which the roles of both analog sensors and digital memory devices are integrated and achieved using a single “MemSor“ device. We review the demonstrated optoelectronic memory devices which can sense and store optical signals, next, we provide perspectives on the potential integration of other sensing capabilities such as pressure and gas. We also discuss the implementation of the in-memory sensing technology in future energy efficient and scaled down electronic systems. We finally analyze the challenges in the field and present potential solutions for the implementation of the merged sensing and storage functions using advanced manufacturing technologies.