Effective Tuning Method Research Articles

Defect Engineering Advances Thermoelectric Materials.

Defect engineering is an effective method for tuning the performance of thermoelectric materials and shows significant promise in advancing thermoelectric performance. Given the rapid progress in this research field, this Review summarizes recent advances in the application of defect engineering in thermoelectric materials, offering insights into how defect engineering can enhance thermoelectric performance. By manipulating the micro/nanostructure and chemical composition to introduce defects at various scales, the physical impacts of diverse types of defects on band structure, carrier and phonon transport behaviors, and the improvement of mechanical stability are comprehensively discussed. These findings provide more reliable and efficient solutions for practical applications of thermoelectric materials. Additionally, the development of relevant defect characterization techniques and theoretical models are explored to help identify the optimal types and densities of defects for a given thermoelectric material. Finally, the challenges faced in the conversion efficiency and stability of thermoelectric materials are highlighted and a look ahead to the prospects of defect engineering strategies in this field is presented.

Piezo-modulated interface field facilitating hydroxyl radical formation of SrTiO3/ZnO heterojunction for water purification

Piezo-modulated interface engineering is an effective method for tuning the charge transfer process to enhance piezocatalytic dynamics. In this study, SrTiO3/ZnO heterojunctions were successfully synthesized via hydrothermal methods to degrade carbamazepine in water. The optimal SrTiO3/ZnO-5 % sample exhibited a remarkable 99.9 % degradation efficiency of carbamazepine within 60 min under ultrasonic vibration. The piezocatalytic reaction rate (k value = 0.0746 min−1) was 4.63 times and 10.97 times higher than that of pure SrTiO3 and pure ZnO, respectively. Reactive species scavenger tests, electron paramagnetic resonance techniques, and bands gap analysis revealed that the enhanced activity can be attributed to the construction of an interfacial electric field in SrTiO3/ZnO heterojunctions and the modification of an internal piezoelectric polarized field. This allowed charge redistribution and transport across the SrTiO3/ZnO heterojunction interface, and facilitated the generation of hydroxyl radicals (HO•) through simultaneous hole oxidation and electron reduction. This study provides a comprehensive mechanistic understanding about piezoelectric heterojunctions in the catalytic redox reactions, and offers valuable insights for designing more effective piezoelectric heterojunctions for the degradation of pharmaceutical organic pollutants.

Trajectory control and optimization of PID controller parameters for dual-arms with a single-link underwater robot manipulator

ABSTRACT This paper focuses on the modeling, simulation, and control of the trajectories of a dual-arm single-link underwater robot manipulator (DS-URM), having dual arms (left and right) with a single link each. The dynamic coupling between the base and the dual arms makes trajectory control of the end effector difficult. This study attempts to simulate and control dual arms with a single-link underwater robotic manipulator using a hybrid controller. To reduce the error for a sinusoidal wave and a cycloid trajectory, a hybrid controller is the combination of the Proportional-Integral-Derivative (PID) controller and overwhelm controller. The underwater dynamic’s buoyancy, gravity, and hydrostatic forces acting on the underwater robot are modeled in an integrated SIMULINK model, including the DS-URM. The DS-URM has been investigated, revealing some significant trajectories of the left and right tips. Effective tuning methods include Ziegler-Nicholas (Z-N), genetic algorithms, Ant Colony Optimization (ACO), and Particle Swarm Optimization (PSO). The Integral of Time multiplied by Absolute Error (ITAE) criteria has been used to improve trajectory tracking via particle swarm optimization. Results show significant improvements in trajectory tracking, with ITAE error reduction by 96.44% and 98.6% for left and right arms, respectively, achieving stability in 0.000645s.

Vanadium Metal Doping of Monolayer MoS2 for p-Type Transistors and Fast-Speed Phototransistors.

Modulating the electrical properties of two-dimensional (2D) materials is a fundamental prerequisite for their development to advanced electronic and optoelectronic devices. Substitutional doping has been demonstrated as an effective method for tuning the band structure in monolayer 2D materials. Here, we demonstrate a facile selective-area growth of vanadium-doped molybdenum disulfide (V-doped MoS2) flakes via pre-patterned vanadium-metal-assisted chemical vapor deposition (CVD). Optical microscopy characterization revealed the presence of flake arrays. Transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were employed to identify the chemical composition and crystalline structure of as-grown flakes. Electrical measurements indicated a light p-type conduction behavior in monolayer V-doped MoS2. Furthermore, the response time of phototransistors based on V-doped MoS2 monolayers exhibited a remarkable capability of 3 ms, representing approximately 3 orders of magnitude faster response than that observed in pure MoS2 phototransistors. This work hereby provides a feasible approach to doping of 2D materials, promising a scalable pathway for the integration of these materials into emerging electronic and optoelectronic devices.

Out-of-Sample Tuning for Causal Discovery.

Causal discovery is continually being enriched with new algorithms for learning causal graphical probabilistic models. Each one of them requires a set of hyperparameters, creating a great number of combinations. Given that the true graph is unknown and the learning task is unsupervised, the challenge to a practitioner is how to tune these choices. We propose out-of-sample causal tuning (OCT) that aims to select an optimal combination. The method treats a causal model as a set of predictive models and uses out-of-sample protocols for supervised methods. This approach can handle general settings like latent confounders and nonlinear relationships. The method uses an information-theoretic approach to be able to generalize to mixed data types and a penalty for dense graphs to penalize for complexity. To evaluate OCT, we introduce a causal-based simulation method to create datasets that mimic the properties of real-world problems. We evaluate OCT against two other tuning approaches, based on stability and in-sample fitting. We show that OCT performs well in many experimental settings and it is an effective tuning method for causal discovery.

Faradaic and Non-Faradaic Self-Discharge Mechanisms in Carbon-Based Electrochemical Capacitors.

Electrochemical capacitors (ECs) play a crucial role in electrical energy storage, offering great potential for efficient energy storage and power management. However, they face challenges such as moderate energy densities and rapid self-discharge. Addressing self-discharge necessitates a fundamental understanding of the underlying processes. This review sets itself apart from other reviews by focusing on the basic principles of self-discharge processes in carbon-based ECs, particularly examining the nature of the process and the involvement of redox reactions. This study delineates the potential conditions for various self-discharge processes and proposes plausible criteria for differentiation, complemented by mathematical modeling. Additionally, the model selection, curve fitting, and effective tuning methods are explored to control self-discharge processes.

Improving Arabic Spam classification in social media using hyperparameters tuning and Particle Swarm Optimization

Online social networks continue to evolve, serving a variety of purposes, such as sharing educational content, chatting, making friends and followers, sharing news, and playing online games. However, the widespread flow of unwanted messages poses significant problems, including reducing online user interaction time, extremist views, reducing the quality of information, especially in the educational field. The use of coordinated automated accounts or robots on social networking sites is a common tactic for spreading unwanted messages, rumors, fake news, and false testimonies for mass communication or targeted users. Since users (especially in the educational field) receive many messages through social media, they often fail to recognize the content of unwanted messages, which may contain harmful links, malicious programs, fake accounts, false reports, and misleading opinions. Therefore, it is vital to regulate and classify disturbing texts to enhance the security of social media. This study focuses on building an Arabic disturbing message dataset extracted from Twitter, which consists of 14,250 tweets. Our proposed methodology includes applying new tag identification technology to collected tweets. Then, we use prevailing machine learning algorithms to build a model for classifying disturbing messages in Arabic, using effective parameter tuning methods to obtain the most suitable parameters for each algorithm. In addition, we use particle swarm optimization to identify the most relevant features to improve the classification performance. The results indicate a clear improvement in the classification performance from 0.9822 to 0.98875, with a 50% reduction in the feature set. Our study focuses on Arabic spam messages, classifying spam messages, tuning effective parameters, and selecting features as key areas of investigation.

Tunable-performance all-oxide structure field-effect transistor based atomic layer deposited Hf-doped In2O3 thin films.

The relocation of peripheral transistors from the front-end-of-line (FEOL) to the back-end-of-line (BEOL) in fabrication processes is of significant interest, as it allows for the introduction of novel functionality in the BEOL while providing additional die area in the FEOL. Oxide semiconductor-based transistors serve as attractive candidates for BEOL. Within these categories, In2O3 material is particularly notable; nonetheless, the excessive intrinsic carrier concentration poses a limitation on its broader applicability. Herein, the deposition of Hf-doped In2O3 (IHO) films via atomic layer deposition for the first time demonstrates an effective method for tuning the intrinsic carrier concentration, where the doping concentration plays a critical role in determine the properties of IHO films and all-oxide structure transistors with Au-free process. The all-oxide transistors with In2O3: HfO2 ratio of 10:1 exhibited optimal electrical properties, including high on-current with 249 µA, field-effect mobility of 13.4cm2V-1s-1, and on/off ratio exceeding 106, and also achieved excellent stability under long time positive bias stress and negative bias stress. These findings suggest that this study not only introduces a straightforward and efficient approach to improve the properties of In2O3 material and transistors, but as well paves the way for development of all-oxide transistors and their integration into BEOL technology.

CONFIGURATIONS OF ULTRASONIC EMITTER RESONANCE MODES FOR UNILATERAL ACCESS TO AN OBJECT

Link for citation: Azin A.V., Bogdanov E.P., Vasilyev A.V., Ponomarev S.A., Ponomarev S.V., Rikkonen S.V. Configurations of ultrasonic emitter resonance modes for unilateral access to an object. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 10, рр. 199-209. In Rus. Relevance. To prepare high-viscosity oil for transport, a number of methods are used in practice: thermal, chemical and the method of physical influences. Ultrasonic exposure of hydrocarbon raw materials is one of the physical methods. It is necessary to develop an effective method for tuning an ultrasonic emitter for maximum energy transfer into a multilayer technological medium. Aim: to study resonant operating modes of an ultrasonic emitter in a multilayer system with unilateral access to the object with simplified design of a resonance type ultrasonic emitter. Objects: oscillating system of an ultrasonic resonant type emitter, multilayer system, physical model of a system «ultrasonic emitter – multilayer system». Methods: mathematical modeling of linear oscillating system to determine the properties of oscillating system influence and technological factors on the form of vibration oscillations and on the amplitude-frequency characteristics of the system; experimental research on the basis of the physical model «ultrasonic emitter – multilayer system». Results. The authors have revealed a physical feature of the oscillatory system operation, which consists in the fact that at resonance the form of oscillations of the force signals of a multilayer piezoactor and vibration acceleration signals are purely harmonic in nature. This effect extends to operation of a resonant-type ultrasonic emitter in a short-circuit mode on a multilayer system. It was found that force and vibration acceleration amplitude-frequency characteristics of a multilayer piezoactor are similar to each other. Based on the analysis of theoretical and experimental data, the authors developed the method for adjusting the resonant operating modes of an ultrasonic emitter with unilateral access to an object. This allows simplification and reduction in the emitter design cost. The method for setting up oscillatory systems is applicable for laboratory and industrial installations. Conclusion. The research results show that in practice, harmonic shape of acceleration and force signals, as well as force amplitude of a multilayer piezoactor can be used as criteria for determining and adjusting the resonance of an oscillatory system. The oscillatory system of a resonant-type ultrasonic emitter can be tuned to resonance according to the shape and amplitude of the signal from the force sensor of the multilayer piezoactor. The force sensor is located in series with the multilayer piezoactor and does not require additional structural elements for its fastening. The ultrasonic emitter design is greatly simplified due to the absence of a vibration acceleration sensor. The method of adjusting the resonance of an oscillatory system using only a force sensor is also applied when operating a resonant-type ultrasonic emitter to a multilayer mechanical system. The developed design and technique for tuning the oscillatory system of a resonant-type ultrasonic emitter can be conveniently used when influencing process fluids through the walls of tanks and storage tanks.

Flexible transmission control of mode conversion in a TiO2 cladding silicon subwavelength waveguide by engineering inter-waveguide mode coupling

Mode conversions can be effectively accomplished in coupled mode silicon photonic waveguide systems when specific phase-matching conditions are fulfilled. However, conventional device using such principles is optimized to a certain coupling length, which can only achieve a fixed energy transmission. Moreover, the conventional method to tune the refractive index is insufficient for effective transmission manipulation. In this paper, we systematically analyze the coupling strategy in the silicon-based dual-waveguide coupled-mode system, and propose an effective transmission tuning method by engineering the inter-waveguide mode coupling. We introduce titanium dioxide as cladding material to a subwavelength waveguide-based directional coupler to change the refractive index variable, which is both CMOS compatible and has negative thermo-optical coefficient. By implementing different temperature on waveguide, the dispersion curves of stripe waveguide and subwavelength waveguide can be tailored independently, thus the coupling coefficient can be changed without changing the geometry of waveguide. We demonstrate prototype of TE0-TE1 multi-mode variable optical attenuator. The output can be tuning 0.05%–96.4% of input energy when the temperature rises 0-400 K. We extend the device to TE2 and TE3 with output intensities of 0.04-91.4% and 0.04-88.8% over the temperature rise range of 317 K and 214 K, respectively. Cascading mode converters for different mode-order, we can arbitrarily mix the mode percentage in output waveguide to generate different interference patterns. We demonstrate a reconfigurable optical tweezer using this setup, which is capable of manipulating nanoscale particles. We envision that such methodology can be implemented in flexible multimode optical networks and labs on chip.

Proximity effects in graphene-supported single-atom catalysts for hydrogen evolution reaction.

The interaction between adjacent active sites is crucial to balance the efficiency and utilization of functional atoms in single-atom catalysts. Herein, the catalytic activity of hydrogen evolution reaction at different site (nitrogen coordinated transition metal centers embedded in graphene) distances was comprehensively investigated by density functional theory calculations. The results show that a proximity effect of reactivity and site spacing can be identified in the Co-series single-atom catalysts. Although the proximity effect is more linearly responded with the site spacing along x direction, an optimal distance of ∼0.8 and ∼2.8nm are found for Co and Rh, Ir atoms, respectively. An in-depth analysis of the electronic property reveals that the proximity effect is caused by the distinct net charge of the active site, which is affected by the dz2 position relative to EF. Subsequently, an excess electron nodal channel in x direction was found to serve as a communication pathway between the active sites. Through the finding in this work, an optimal Fe-N2C2 structure was deliberately designed and has shown prominent proximity effect as Co-series do. The results reported in this work provide a simple and effective tuning method for the reactivity of a single-atom catalyst.

Enhancing adsorption capacity and herbicidal efficacy of 2,4-D through supramolecular self-assembly: Insights from cocrystal engineering to solution chemistry

Highly water-soluble pesticides have garnered significant attention due to their poor durability and severe environmental damage caused by easy leaching. Cocrystallization based on a supramolecular self-assembly mechanism has been demonstrated to be an effective method for tuning the dissolution of pharmaceuticals and agrochemicals. However, as a strategy to tune the properties of solid materials, cocrystal engineering appears to be challenging to apply to many liquid formulations of pesticides. Herein, cocrystal of the 2,4-dichlorophenoxyacetic acid (2,4-D) and phenazine (PHE) were developed to explore whether supramolecular assembly in the solid state could be extended to the solution. In the crystalline state, the cocrystal reduced the solubility and dissolution rate of 2,4-D by 71.51 % and 50.55 %, respectively. Notably, when applied in solution, 2,4-D - PHE cocrystal exhibits greater soil adsorption capacity and lower leaching characteristics than pure 2, 4-D. Specifically, only 75% of the cocrystal was leached when 2,4-D was fully leached. Under simulated rainfall, the biological activity experiments in the greenhouse demonstrated that the control efficacy of cocrystal was almost twice as that of the pure 2,4-D. Additionally, two-dimensional NOE Spectroscopy (2D NOESY) and molecular simulations were employed to reveal the mechanism of supramolecular assembly in crystal lattice and aqueous solution. This work reveals that cocrystal engineering is a promising strategy for bridging solid-state and solution chemistry through supramolecular self-assembly to improve the persistence and decrease the off-target threat of highly water-soluble pesticides.

Cellulose-based carbon membranes for gas separations - Unraveling structural parameters and surface chemistry for superior separation performance

Carbon molecular sieve membranes were prepared from the carbonization of a cellulose-based polymeric precursor doped with urea. The addition of urea to the cellulose precursor induces an increase in structural disorder and an increase in pore volume inside the structure of prepared membranes. This unique preparation procedure proved to be an extremely effective method for tuning the pore size of carbon membranes to the desired separations. Urea acts as a pore-forming agent that allows the fabrication of carbon membranes with high porosity. The addition of 2.8 wt% of urea doubled the permeability of the prepared carbon membrane to hydrogen. In addition, a permeability to oxygen of 333 barrer was obtained, without impairing the selectivity. The proposed preparation procedure is compatible with industrial production and scaling, hopefully making carbon membranes a viable solution to produce oxygen-enriched air, recovering of hydrogen from hydrocarbon streams and carbon dioxide removal from natural gas/biogas.

Visible Light Effects on Photostrictive/Magnetostrictive PMN‐PT/Ni Heterostructure

AbstractThe possibility of modifying the ferromagnetic response of a multiferroic heterostructure via fully optical means exploiting the photovoltaic/photostrictive properties of the ferroelectric component is an effective method for tuning the interfacial properties. In this study, the effects of 405 nm visible‐light illumination on the ferroelectric and ferromagnetic responses of (001) Pb(Mg1/3Nb2/3)O3‐0.4PbTiO3 (PMN‐PT)/Ni heterostructures are presented. By combining electrical, structural, magnetic, and spectroscopic measurements, how light illumination above the ferroelectric bandgap energy induces a photovoltaic current and the photostrictive effect reduces the coercive field of the interfacial magnetostrictive Ni layer are shown. Firstly, a light‐induced variation in the Ni orbital moment as a result of sum‐rule analysis of x‐ray magnetic circular dichroic measurements is reported. The reduction of orbital moment reveals a photogenerated strain field. The observed effect is strongly reduced when polarizing out‐of‐plane the PMN‐PT substrate, showing a highly anisotropic photostrictive contribution from the in‐plane ferroelectric domains. These results shed light on the delicate energy balance that leads to sizeable light‐induced effects in multiferroic heterostructures, while confirming the need of spectroscopy for identifying the physical origin of interface behavior.

Optimised Sliding Mode Control of a Hexacopter: Simulation and Experiments

Hexacopters are a kind of unmanned aerial vehicle (UAV) with six actuators and six degrees-of-freedom motions. The control of a hexacopter drone is a critical challenge. This paper presents a nonlinear dynamical model for a hexacopter and complete control approaches based on sliding mode control theory. Furthermore, this study proposed an effective control tuning method based on an optimisation algorithm. The controller has been improved by the grey wolf optimisation (GWO) algorithm, an iteration algorithm inspired by the social hierarchy and hunting behaviour of grey wolves. The improvement of the controller has been verified both experimentally and in simulations. The performance of the sub-controller for an attitude angle was tested in a test bench, and the whole flight controller was tested in simulation hexacopters, which are highly manoeuvrable, nonlinear aerial vehicles with six independent rotors and capacity for vertical take-off and landing. This article presents a derivation of the nonlinear dynamical model for a hexacopter, which includes the aerodynamic drag, and inertia counter torques. Flight control based on sliding mode control theory, which generally shows good performance on nonlinear systems, is developed and implemented. Given the need to simultaneously tune controller parameters, two nature inspired optimisation routines (GWO and PSO) are applied and compared for effectiveness in controller tuning. Results indicate that GWO-based tuning produces superior outcomes in terms of controller performance. This is in addition to the fact that PSO parameters require tuning rather than random selection of algorithm parameters. A reduced-order physical prototype is presented for the validation of the tuning routine on the roll/pitch control. The results indicate good agreement between simulation and experimental outcomes, with about 10.4% improvement in the tracking performance of roll DOF when GWO is applied to tune the controller.

Tuning Method of a Grid-Following Converter for the Extremely-Weak-Grid Connection

This letter proves that a grid-following converter can stably connect to a weak grid even short-circuit ratio (SCR) is 1. Root instability causes of this grid-following control are identified including fast control response, insufficient damping, and slow voltage support. A simple and effective tuning method is proposed to stabilize this connection. Three control modes are considered in this tuning method including current control, active power and voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ PV$</tex-math></inline-formula> ) control, and active power and reactive power ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ PQ$</tex-math></inline-formula> ) control. The switching model of a two-level converter is used for the simulation validation.

A fiber optic communication shield based on a two-dimensional molybdenum disulfide broadband absorber

We propose a broadband absorber in the infrared band using a two-dimensional molybdenum disulfide with a patterned gold array. The light absorption enhancement effect of the local surface plasmon resonance (LSPR) is utilized to greatly enhance the light absorption of the monolayer MoS2. Our absorber has 99.62% absorption in the most important band for fiber optic communication (i.e. 1550 nm), a result calculated by the finite-difference time-domain method. Our absorber can serve as an excellent shield for fiber optic communication. At the same time, our absorber is also polarization and light incidence angle insensitive, which greatly expands the application location of our absorber. In addition, we demonstrate that our absorber structure can be widely used in absorbers based on transition-metal dichalcogenides (TMDCs), which is a guideline for the design of such absorbers. In order to solve the tuning difficulties of MoS2-based absorbers, we also propose an effective method for tuning the absorber, which is able to tune the absorber over a large wavelength range without a significant decrease in the absorber's optical absorption. We believe that our absorber can play an important role in fiber optic communication shielding systems, detection systems in the infrared band.

Origin and strain tuning of charge density wave in LaTe3

We study the origin of charge density wave (CDW) in rare-earth tritelluride LaTe3 and the strain tuning effect on CDW in monolayer LaTe3 by first-principles calculations. The calculations of the electronic structure, phonon spectrum, electron susceptibility, and electron-phonon coupling (EPC) matrix show that the origin of CDW in LaTe3 is momentum-dependent EPC rather than Fermi-surface nesting. The unidirectional CDW with a wave-vector QCDW≈2/7c∗ is the most stable state. We study the biaxial strain effect on CDW in monolayer LaTe3 by evaluating the total energy, CDW-related lattice distortions, and phonon spectra. Our results show that the tensile strain can enhance CDW order, while the compressive strain can inhibit CDW order. As the CDW order is fully suppressed, superconductivity could be induced. Our study may help to clarify the mechanism of CDW in LaTe3 and find the effective tuning method of CDW in monolayer or few-layer configuration.

Improving the thermal reliability of photonic chiplets on multicore processors

Silicon photonics is a promising technology for high-performance inter/intra-chip networks. Although chiplet technologies help to integrate photonic network with processors and memories, thermal reliability remains a major challenge for photonic networks. Thermal variations are common in chiplet-based systems. Due to thermo-optic effects, photonic switches, such as microresonators (MRs), suffer from temperature-dependent wavelength shifts. To improve the thermal reliability of photonic chiplets, we propose an effective bridging and tuning method, called BAT. Our method enhances the temperature channel transition among MRs and minimize bit errors during temperature changes. BAT is integrated with thermal tuning, electrical tuning, laser tuning, and receiver tuning. We optimize MR design, control logic, tuning circuit, thermal floorplan, and network protection mechanism for BAT. Compared to state-of-the-art methods, BAT achieves a 10−12 bit-error-rate for photonic chiplets, saves up to 70.0% of the thermal tuning power, and improves up to a 1.17X system energy efficiency.

Giant Bandgap Engineering in Two-Dimensional Ferroelectric α-In2Se3.

Bandgap engineering is an efficient strategy for controlling the physical properties of semiconductor materials. For flexible two-dimensional (2D) materials, strain provides a nondestructive and adjustable method for bandgap adjustment. Here, we propose that, in 2D materials with out-of-plane ferroelectricity, the antibonding nature of the valence band maximum and conduction band minimum and polarized charge distribution induced by ferroelectricity give rise to giant changes of the bandgap under curvature strain field. This hypothesis was proven by scanning tunneling microscopy/spectroscopy measurements on monolayer α-In2Se3 that revealed that the bandgap of α-In2Se3 increases significantly due to bending. Both experiments and theoretical calculations indicated that the bandgap increases monotonically with the degree of bending of the α-In2Se3 layer. Our work suggests that bending is an effective method for tuning the gaps of 2D ferroelectric materials, providing a new platform for bandgap engineering under the combination of ferroelectricity and strain field.