Concept Of Tuning Research Articles

Quantum Dots Array: An Approach to Multipixel Devices

Abstract Graphene has been proven to be an excellent material for high-frequency electromagnetic radiation detection. Here, we are reporting the graphene quantum dots (GQDs) devices designed as multi-parallel arrays of the dots (200 nm in diameter) between the source and drain electrodes. These state-of-the-art devices provide a novel concept of tuning the total device area and impedance while maintaining superior performance. The GQDs devices have been fabricated on silicon oxide substrate and analyzed for their transport properties. The multi-parallel array of GQDs on SiO2/Si substrates has depicted the possibility of tuning the activation energy depending on the back gate bias and the number of parallelly arranged GQDs while keeping the temperature dependence of resistance higher than 75 MΩ K-1 and 5 GΩ K-1 (for 2-dots and 8-dots devices). The results presented here pave the way for further optimization and realization of chip-scale arrays of GQDs-based multipixel devices, enhancing the applications in imaging and magneto-optical spectroscopy.

Molecular Orbital Tuning of Pentacene-Based Organic Semiconductors through N-Ethynylation of Dihydrodiazapentacene.

This study explores the concept of molecular orbital tuning for organic semiconductors through the use of N,N'-diethynylated derivatives of 6,13-dihydro-6,13-diazapentacene (2a and 2b). These novel molecules maintain the same molecular geometry and π-π stacking as their parent pentacene derivatives (1a and 1b), as confirmed by X-ray crystallography. However, they exhibit altered frontier molecular orbitals in terms of the phase, nodal properties, and energy levels. Theoretical calculations based on crystal structures indicate that 2a and 2b could significantly enhance the hole mobilities of the parent compounds by improving the hole transfer integral. Organic field-effect transistors (OFETs) of 1a and 2a were fabricated by using dip-coating and bar-coating methods. Both types of devices for 2a demonstrated a hole mobility exceeding 1 cm2 V-1 s-1, more than twice that of the respective devices for 1a. Additionally, unlike its pentacene parent, 2a is transparent to visible light and exhibits significantly enhanced environmental stability against light and air, making it a promising candidate for broader applications in organic electronic devices.

Ultrafast laser frequency tuning based on equivalent optical phase sampling and accumulation

Ultrafast laser frequency tuning is a crucial function in numerous applications, including light detection and ranging (LiDAR), optical coherence tomography (OCT), and spectroscopy. In general, laser frequency tuning is realized via the motion of mechanical structures, frequency-swept optical filters, or the Pockels effect in the laser cavity. Nevertheless, the maximum frequency tuning rate and sweep rate are smaller than 107 THz/s and 1 GHz, respectively, due to the inherent speed limitation of the existing tuning mechanisms. Here, we propose and demonstrate a brand-new concept for ultrafast laser frequency tuning, which is realized based on equivalent optical phase sampling and accumulation in the laser cavity. By inserting an electro-optic phase modulator (PM) into the laser cavity and properly setting the period of the driving signal applied to the PM to make its integer multiple slightly deviate from the round trip time of the laser cavity, a linear mapping from the voltage of the driving signal to the output laser frequency is realized via equivalent optical phase sampling and accumulation. This remarkable feature provides a rapid way to manipulate the laser frequency, breaking the frequency tuning speed limitation of the existing approaches. In the experiment, a record-breaking frequency tuning rate of 1.522 × 109 THz/s and a sweep rate of 2223.97 MHz are simultaneously realized. Moreover, the center wavelength and the frequency tuning range can be easily reconfigured. This work paves the way for ultrafast laser frequency tuning in a customized wavelength range.

Highly Solvating Electrolytes with Core-Shell Solvation Structure for Lean-Electrolyte Lithium-Sulfur Batteries.

The practical energy density of lithium-sulfur batteries is limited by the low sulfur utilization at lean electrolyte conditions. The highly solvating electrolytes (HSEs) promise to address the issue at harsh conditions, but the conflicting challenges of long-term stability of radical-mediated sulfur redox reactions (SRR) and the poor stability with lithium metal anode (LMA) have dimmed the efforts. We now present a unique core-shell solvation structured HSE formulated with classical ether-based solvents and phosphoramide co-solvent. The unique core-shell solvation structure features confinement of the phosphoramide in the first solvation shell, which prohibits severe contact reactions with LMA and endows prolonged stability for [S3]⋅- radical, favoring a rapid radical-mediated solution-based SRR. The cell with the proposed electrolyte showing a high capacity of 864 mAh gsulfur -1 under high sulfur loading of 5.5 mgsulfur cm-2 and low E/S ratio of 4 μL mgsulfur -1. The strategy further enables steady cycling of a 2.71-A h pouch cell with a high specific energy of 307 W h kg-1. Our work highlights the fundamental chemical concept of tuning the solvation structure to simultaneously tame the SRR and LMA stability for metal-sulfur batteries wherein the electrode reactions are heavily coupled with electrolyte chemistry.

Highly Solvating Electrolytes with Core‐Shell Solvation Structure for Lean‐Electrolyte Lithium‐Sulfur Batteries

The practical energy density of lithium‐sulfur batteries is limited by the low sulfur utilization at lean electrolyte conditions. The highly solvating electrolytes (HSEs) promise to address the issue at harsh conditions, but the conflicting challenges of long‐term stability of radical‐mediated sulfur redox reactions (SRR) and the poor stability with lithium metal anode (LMA) have dimmed the efforts. We now present a unique core‐shell solvation structured HSE formulated with classical ether‐based solvents and phosphoramide co‐solvent. The unique core‐shell solvation structure features confinement of the phosphoramide in the first solvation shell, which prohibits severe contact reactions with LMA and endows prolonged stability for [S3]•– radical, favoring a rapid radical‐mediated solution‐based SRR. The cell with the proposed electrolyte showing a high capacity of 864 mA h gsulfur−1 under high sulfur loading of 5.5 mgsulfur cm−2 and low E/S ratio of 4 µL mgsulfur−1. The strategy further enables steady cycling of a 2.71‐A h pouch cell with a high specific energy of 307 W h kg−1. Our work highlights the fundamental chemical concept of tuning the solvation structure to simultaneously tame the SRR and LMA stability for metal‐sulfur batteries wherein the electrode reactions are heavily coupled with electrolyte chemistry.

Investigation of anti-windup Proportional-Integral controller with semi-decoupled tuning gains in motor speed control

Abstract Integral windup refers to a prevalent phenomenon that can occur in Proportional-Integral-Derivative (PID) control systems that employ integral control where the control output generated exceeds the operating limit of an actuator. Despite the system’s inability to respond further due to control output limitations, the integral controller perseveres in accumulating errors. The accumulation of error can lead to system instability and undesirable oscillations. Additionally, the dynamic response of the PID controller is also limited by the coupled tuning gain characteristics, complicating the process of gain tuning. The coupling and decoupling of the tuning gains are depending on the separation of the gains in the error dynamics of the system. In this study, a concept of semi-decoupled tuning gains in anti-windup controllers is proposed. The performance of the proposed controller was investigated through hardware simulation against conventional PI and existing anti-windup schemes and has demonstrated an overall improvement in its dynamic behaviour such as faster settling time and its ability to tune the system without significantly altering its damping ratio.

Hierarchical Composites Patterned via 3D Printed Cellular Fluidics

AbstractAdditive manufacturing of freeform structures containing multiple materials with deterministic spatial arrangement and interactions remains a challenge for most 3D printing processes, due to complex fabrication tool requirements and limitations in printability of some material classes. Here, a versatile method is reported to produce architected composites using the concept of cellular fluidics, in which lattices of unit cells are used as templating scaffolds to guide flowable infill materials in a programmed spatial pattern, upon which they are cured in place to produce a deterministically ordered multimaterial solid. The lattice design relies on the unit cell size, type, strut diameter, surface wetting, and distribution of cellular structures to control liquid flow and retention. Individual unit cells are tuned to achieve reliable infilling and combined into higher‐order architectures to achieve multiscale composite materials with disparate mechanical properties, including those considered non‐printable. Lattice design considerations for leveraging capillary phenomena and demonstrate several methods of patterning polymers in 3D‐printed cellular fluidic structures are presented. The concept of tuning the compressive response of an architected composite using a flexible‐elastomer as the lattice and a stiff‐epoxy as the infill material is illustrated.

Discharging a capacitor

Discharging a capacitor is a standard experiment in physics education. Here it is described in a form that challenges students’ preconceptions, since the voltage across the capacitor is observed to oscillate after switching off the power supply. The aim is to demonstrate the importance and relevance of experiments and measurements, even if these are in contradiction with expectations and textbooks. Students have the opportunity to develop a quantitative model for the observations and explore the transition from oscillatory to overdamped behaviour—with the latter being the standard in textbook presentations—in further measurements. The experiment can also be used in schools, since the concept of tuning the damping by resistance variation is rather intuitive and insightful even without a formal mathematical background.

Volatile and thermally stable tungsten organometallic complexes (RCp)W(CO)2(η3-2-tert-butylallyl) as potential thin film deposition precursor

Two organometallic tungsten complexes (RCp)W(CO)2(η3-2-tert-butylallyl) (R = methyl or ethyl, Cp = cyclopentadienyl) as precursors capable of growing tungsten-containing thin films, are constructed bearing heteroleptic ligand system. The syntheses adopt a rationally designed approach excluding the use of extreme conditions and involving facile purification procedures. The two complexes are authenticated by nuclear magnetic resonance (NMR) and elemental analysis, as well as Fourier transform-infrared (FT-IR) spectroscopy. Thermal property evaluations, including thermogravimetric and vapor pressure tests, reveal favorable thermal stability and volatility which are essential for a typical ALD process. It is noteworthy that both precursors possess relatively low-melting point and specifically, the one bearing ethyl-Cp group is in liquid phase at room temperature. Such design concept of heteroleptic ligand system and substructure tuning pave the way to develop liquid precursors which are imperative demand in microelectronic industry.

Tuning Strong Metal‐Support Interactions for Enhancing Direct Deoxygenation of Biomass‐Lignin Derived Phenolics

AbstractCatalytic direct deoxygenation (DDO) of phenolic compounds to aromatics is an appealing approach for utilization of biomass‐lignin with minimal amount of H2 consumption. Metal/reducible metal oxide catalysts provide two functionalities, i. e., C−H bond formation (hydrogenation) and C−O bond breakage (deoxygenation), required for this reaction that takes place at the interfacial perimeter sites. Strong metal‐support interactions (SMSI) can profoundly alter the density and property of such sites. This short review summarized recent advances in tuning SMSI for enhancing DDO of phenolics. The approaches of varying reduction temperature, modulation of crystal facets and crystal phases of metal oxide, and reduction of mixed metal oxide were discussed for the origin for formation of SMSI, the degree of SMSI, and its consequence on the DDO performance. The analysis revealed that intermediate degree of SMSI with maximal density of metal/oxide interfacial perimeter site enhances DDO while minimizing unfavorable side reactions. This short review highlights the concept of tuning the interfacial perimeter sites via SMSI for reactions which require multiple functionalities and take place at the metal/oxide interface.

Fuzzy logic applied to mutation size in evolutionary strategies

Tuning of algorithm parameters is a complex but very important issue in the design of Evolutionary Algorithms. This paper discusses a new concept of mutation size tuning in Evolutionary Strategies. The proposed algorithm uses data on evolutionary history in earlier generations to tune the mutation size. A Fuzzy Logic Part examines this historical data and tunes the mutation size of individuals to improve the algorithm’s convergence and its resistance to getting stuck in a local optimum. The Fuzzy Logic Part tunes the mutation size and keeps an appropriate relation of algorithm’s exploration and exploitation. The proposed concept is discussed, and several tests on Function Optimization Problems are performed. In tests, we use a set of data and functions with different difficulties recommended in the commonly used benchmarks. The results of experiments suggest that the proposed method is more efficient and resistant to getting stuck in suboptimal solutions. The proposed algorithm has been used in recognizing the type of ultra-high energy cosmic ray particle that initiates the Extensive Air Showers when hit the Earth atmosphere. It could be used for a wide range of similar problems. It is possible that the proposed method could be adapted to other types of optimization methods, inspired by natural evolution, for example, Evolutionary Algorithms.

Co-culture platform for tuning of cancer receptor density allows for evaluation of bispecific immune cell engagers

Cancer immunotherapy, where a patient’s immune system is harnessed to eradicate cancer cells selectively, is a leading strategy for cancer treatment. However, successes with immune checkpoint inhibitors (ICI) are hampered by reported systemic and organ-specific toxicities and by two-thirds of the patients being non-responders or subsequently acquiring resistance to approved ICIs. Hence substantial efforts are invested in discovering novel targeted immunotherapies aimed at reduced side-effects and improved potency. One way is utilizing the dual targeting feature of bispecific antibodies, which have made them increasingly popular for cancer immunotherapy. Easy and predictive screening methods for activation ranking of candidate drugs in tumor contra non-tumor environments are however lacking. Herein, we present a cell-based assay mimicking the tumor microenvironment by co-culturing B cells with engineered human embryonic kidney 293 T cells (HEK293T), presenting a controllable density of platelet-derived growth factor receptor β (PDGFRβ). A target density panel with three different surface protein levels on HEK293T cells was established by genetic constructs carrying regulatory elements limiting RNA translation of PDGFRβ. We employed a bispecific antibody-affibody construct called an AffiMab capable of binding PDGFRβ on cancer cells and CD40 expressed by B cells as a model. Specific activation of CD40-mediated signaling of immune cells was demonstrated with the two highest receptor-expressing cell lines, Level 2/3 and Level 4, while low-to-none in the low-expressing cell lines. The concept of receptor tuning and the presented co-culture protocol may be of general utility for assessing and developing novel bi-specific antibodies for immuno-oncology applications.

Improving enhanced geothermal systems performance using adaptive fracture conductivity

Maximizing heat extraction from enhanced geothermal systems (EGS) depends heavily on an efficient heat sweeping or basically an effective circulation of water through fracture networks. Fracture hydraulic conductivity can play a critical role in controlling potential thermal breakthroughs; however, the exact geometry and properties of these fractures cannot be determined in practice. Thermal breakthrough remains a main challenge for maintaining efficient heat extraction throughout the lifespan of an EGS project. In this work, we explore the concept of fracture conductivity tuning using temperature-sensitive proppants to extract more heat and delay thermal breakthrough from the particle scale to the reservoir scale. We derive an empirical equation to describe fracture conductivity as a function of proppant properties and in-situ conditions including closure stress and temperature. Sensitivity analysis are performed to determine which parameters are the most crucial in determining the temperature-sensitive proppant permeability. Temperature and thermal expansion coefficient are the main contributing factors to the change in proppant permeability. Poisson’s ratio is found to have negligible impact on the proppant permeability. The derived equation is used to quantify the improvement in heat extraction from EGS at the field scale. The outcome shows that using temperature-sensitive proppant can increase the heat extracted by 47.8% compared to using typical proppant. This work assesses the feasibility of using temperature-sensitive proppants to effectively delay thermal breakthrough and sweep larger amounts of heat from EGS. In addition, this paper provides a quick and robust method to determine the required properties of such temperature-sensitive proppants to achieve uniform thermal gradient along different flow paths in the subsurface autonomously.

Cation Substitution Induced d‐Band Center Modulation on Cobalt‐Based Spinel Oxides for Catalytic Ozonation

AbstractCo3O4 spinel is a promising transition metal oxide (TMO) catalyst for the catalytic ozonation of volatile organic compounds (VOCs). Herein, metal–organic frameworks (MOFs)‐derived Ni‐ and Mg‐ substituted Co3O4 catalysts retain similar spinel structures, but display improved and reduced ozonation performance of methyl mercaptan (CH3SH), respectively. Remarkably, the NiCo2O4 catalyst can still ≈90% removal of CH3SH after running for 20 h at room temperature under an initial concentration of 50 ppm CH3SH and 40 ppm O3, relative humidity of 60%, and space velocity of 300 000 mL h−1 g−1, exceeding the reported values. Experimental characterizations have unveiled that the substitution of Ni and Mg into the Co3O4 spinel altered surface acidity, oxygen species mobility, and Co2+/Co3+ ratio. The in situ Raman spectra reveal the dynamic formation Co(III)‐Oad* via the transformation of O3 into surface atomic oxygen (Oad*) and peroxide species (O2*). Theoretical calculations verify that Ni‐substitution increases nonuniform charges and Fermi density, leading to a moderate increase in d‐band center energy levels, thereby promoting O3 specific adsorption/activation to convert Oad*/O2* and •OH/1O2/•O2−, which contributes to eliminate CH3SH and prevent poisoning. The concept of tuning the d‐band center can provide valuable insights for the design of other catalysts for catalytic ozonation.

Tuning the self: Revisiting health inequities through the lens of social interaction

AbstractIn this article, we examine the subjective experiences of people who, according to their education level and income, belong to the lowest social classes—indicators that are commonly associated with poor health behaviors and poor health status. Drawing on 18 months of fieldwork among white, working‐class people in Denmark, we draw attention to the negative stereotypes connected to health inequities and how people attempt to navigate and mitigate perceived bias. We draw particular attention to the proposed concept of tuning, which we identify as acts intended to mitigate practitioner bias and secure higher esteem and adequate care by differentiating oneself from stereotypes. Ultimately, we aim to contribute to more nuanced conversations on health inequity and how it is conceptualized and acted upon by individuals through the concept of tuning.

Mg-doped LaAlO3 structure: a theoretical investigation of indirect to direct bandgap and brittle to ductile transition

Integrating chemical dopants into a pure lattice has fueled a novel concept of tuning the physical and chemical properties of existing materials under and beyond ambient conditions. By using density functional theory (DFT) calculations, we report the structural, electronic, elastic, and optical properties of pure and Mg-doped LaAlO3 structure (La1- xMgxAlO3 and LaAl1- xMgxO3), respectively, with the doping concentrations of x = 0%, 20%, 40%, 60%, 80%, and 100%. Our results show that the doping of Mg along La sites introduce new band (s, p) in the valence bands that is moved towards the conduction bands with increase of doping ration (at x = 60% with a reduced bandgap of 0.04 eV), as well as indirect to direct bandgap transition along Al sites. The density of states shows that the valence band shifts towards the Fermi level by inducing a metallicity in La1-xMgxAlO3 format at 60% configuration. Elastically, LaAlO3 experiences brittle to ductile transition for both doping systems except LaAl1-xMgxO3 at 40% configuration. The higher ranges of optical peaks for both systems are identified for 0%‒40% ranges as compared to other configurations. Fortunately, this study reveals the tunability of LaAlO3 structure in structural, electronic, elastic, and optical aspects, and also extends the availability of this material for future optoelectronic and mechanical applications.

Targeted Micro-Phase separation – A generic design concept to control the elasticity of extrudable hydrogels

Hydrogels are ubiquitous in nature and technology. Controlling their mechanical properties and under-standing their complex microstructure is critical e.g. for 3D bioprinting or tissue engineering applications. Here a generic design concept for tuning the elasticity of extrudable gels at given polymer or particle concentration is presented. Targeted micro-phase separation leading to micro-heterogeneities (1–100 µm) yields high gel strength allowing for extrusion of uniform filaments with high shape accuracy as long as the heterogeneity length scale is small compared to the extruded filament diameter (>500 μm). Micro-mechanical and structural heterogeneity was enhanced in alginate hydrogels by accelerating crosslinking kinetics, corresponding to gel elasticity variation of more than two orders of magnitude (17 Pa to 2300 Pa), enabling filament extrusion (1046 µm) with high shape fidelity. Introducing poly(vinylalcohol) into gelatin gels resulted in more heterogeneous materials with a 2-fold increase in elasticity (951 Pa to 1993 Pa) and thinner filaments (908 µm to 590 µm). Higher ionic strength in Laponite-based hydrogels induced nanoparticle aggregation, leading to higher elasticity (857 Pa to 2316 Pa) enabling smooth filament extrusion. Eliminating the often tacitly assumed hydrogel uniformity on the microscale provides additional degrees of freedom to achieve high gel strength without increasing polymer, particle or crosslinker concentration.

A nonlinear tunable piezoelectric resonant shunt using a bilinear component: theory and experiment

In this article, we propose a new concept for tuning a resonant piezoelectric shunt absorber thanks to the use of a nonsmooth electronic component. It consists in adding a voltage source in the resonant shunt circuit, which is a bilinear function of the voltage across the piezoelectric patch. The main advantage is the ability to change the electrical resonance frequency with the bilinear component gain, enabling a tuning as well as a possible reduction in the required inductance value. Furthermore, because of the intrinsic nonlinear nature of the bilinear component, a multi-harmonic response is at hand, leading to a nonlinear coupling between the mechanical and electrical modes. Two particular tunings between the electrical and the mechanical resonance frequencies are tested. The first one is one-to-one, for which the electrical resonance is tuned close to the mechanical one. It is proved to be similar to a classical linear resonant shunt, with the additional tuning ability. The second case consists in tuning the electrical circuit at half the mechanical resonance, leading to a two-to-one (2:1) internal resonance. The obtained response is also found to be similar to a classical resonant shunt near the main resonance. In either case, the shunt performances are analytically and numerically studied, leading to optimal values of the design parameters as well as an estimation of the amplitude reduction provided by the shunt. Finally, experimental validation is proposed, targeting the damping of the twisting mode of a hydrofoil structure, in which the bilinear component is realized with a diode.

A novel concept of extreme fine tuning in harmonic profile improvement in multilevel inverter for electrical drives

A novel concept of extreme fine tuning in harmonic profile improvement in multilevel inverter for electrical drives

A Novel Concept of Extreme Fine Tuning in Harmonic Profile Improvement in Multilevel Inverter for Electrical Drives

A Novel Concept of Extreme Fine Tuning in Harmonic Profile Improvement in Multilevel Inverter for Electrical Drives