Control Of Composition Research Articles

Fixed-time anti-disturbance control for nonlinear turbofan engine with impulsive prescribed performance

To analyze the robust control problem of turbofan engine within a large flight envelope, a fixed-time prescribed performance control scheme is proposed for the nonlinear turbofan engine in presence of unknown disturbances and possibly discontinuous reference signals. Firstly, the equilibrium manifold expansion (EME) modeling method is adopted for the turbofan engine to construct an affine nonlinear model. Then, considering the possibly discontinuous reference signals, a novel fixed-time prescribed performance function (FxTPPF) with impulsive characteristic is presented to successfully deal with the singularity problem caused by its discontinuity situation. In what follows, a fixed-time nonlinear disturbance observer (FxTNDO) is developed to realize fast estimation of disturbances within fixed time. According to the transformed error system and disturbance estimations, a fixed-time anti-disturbance composite controller is further developed. By borrowing Lyapunov stability theory, the boundedness of all error signals in the impulsive closed-loop system is proved. Finally, simulation results indicate that this control scheme can ensure rotor speeds effectively to track the desired commands within a predefined time after the appearance of a discontinuity and the tracking errors are limited to the performance bound all along.

A composite control method of PWM and phase shift for a three-level DC-DC converter

Abstract This research introduces a control strategy for the Three Level Active Half Bridge (TL-DAHB) DC-DC converter that integrates PWM combined with phase-shift control. This composite control method precisely regulates the output voltage by adjusting the phase-shift duty cycle between the input and output sides. Additionally, the application of the PWM control loop optimizes the duty cycle of the switches, effectively reducing the current stress on the converter during operation, improving transmission efficiency, and decreasing conduction losses of the switches. These enhancements boost the overall performance and the reliability of the converter. With its excellent voltage regulation capabilities and safety features, this converter is an ideal choice in the field of power conversion, especially in applications that demand high levels of stability and safety.

Synthesis and challenges of fluorinated divinyl urethane monomers as a strategy for masking hydrolytic sensitive methacrylate groups in resin composites

ObjectiveThe biodegradation of methacrylate (MA)-based dental restoratives has been suggested to contribute to a loss of adhesion and subsequent detachment, or secondary caries, both major causes of restoration failure. Previous studies have demonstrated that intermolecular interactions between resin monomers may affect the hydrolytic-susceptibility of composites. Altering the intermolecular interactions by shielding or masking the hydrolytically-susceptible ester groups found in MA monomers could be an effective strategy to mitigate the biodegradation of resin composites. The objective of this work was to assess whether shielding/masking MAs using fluorinated groups could improve the biostability of experimental composites. MethodsEight fluorinated monomers (FM) were synthesized, characterized (1H NMR), and formulated into experimental resin composites (FC, 65 wt%, microfill). FCs were assessed for interactions with water (water contact angle, water sorption, gel fraction), mechanical properties (both compressive and flexural strength and modulus), cytocompatibility, resistance to biodegradation using simulated human salivary esterase (SHSE) and compared to a control composite (CC) without FM. ResultsIntegration of FMs was found to generally decrease both the physical and mechanical properties under all incubation conditions when compared to the CC. Additionally, all FCs had a negative influence on composite biodegradation following immersion in SHSE when compared to the CC. SignificanceShielding/masking MA-esters inherently inserts molecular spaces between the polymer chains within the resin network, and shielding is likely not possible while also maintaining the necessary cohesive forces that regulate the physical and mechanical properties of resin composites. Novel dental resin development should seek to remove/replace vulnerable ester-containing MAs rather that adopting a shielding/masking approach.

Anisotropic Heterobimetallic Nanomaterials with Controlled Composition for Efficient Oxygen Reduction at Ultralow Loading

AbstractHydrogen fuel cells represent a leading technology in developing green energy targeting net‐zero emissions goals by mid‐century. However, the sluggish kinetics of the oxygen reduction reaction (ORR) have hitherto demanded substantial quantities of expensive platinum (Pt) group metals. Advances in catalyst design, including the controllable fabrication of highly branched morphologies to increase the surface area‐to‐volume ratio, intermixing Pt with more affordable transition metals, and controlling composition, offer solutions that can further enhance activity and reduce expense. In this context, Pt/M (M = Fe, Ni, Co) nanopods and nanodendrites with precise composition control using more affordable starting materials are designed and crafted. The method is highly efficient, taking only 30 min and avoiding the need for high‐pressure equipment, making it highly scalable. These catalysts show superior ORR performance at an electrode loading as low as 0.0022 mgPt cm−2. One, nanodendritic Pt/Ni, achieves a mass activity of at 0.9 V versus RHE, making it 87 times more efficient in terms of Pt‐content than a commercial 10 wt% Pt/C nanoparticle standard. These findings provide new opportunities for developing next‐generation, cost‐efficient Pt‐based catalysts, by potentially advancing hydrogen fuel cell technology through performance enhancement and addressing cost challenges through catalyst design.

Composition control of additively manufactured color-graded temporary veneer

ObjectiveThe aim of this study was to design and assess composite resin composition for patient-specific esthetic color-graded temporary veneer. MethodsVarious compositions of composite structures (assorted by Ba2SiO4 filler, TiO2 pigment, and photoinitiator) were prepared via additive manufacturing with 3 s UV exposure (405 nm, 10 W/cm2) per 50 µm thick layer followed by 20 min post-curing treatment after fabrication. The effect of each component on the generated color shades was observed and compared to the commonly used VITA shade guide. The coloration was explored by staining aging treatment under dry, wet, artificial saliva environments, coffee, and cola. The mechanical properties were also evaluated. Color measurement and comparison were done using a colorimeter (lightness (L*), green-red color (a*), and blue-yellow color (b*)), and the changes were calculated by CIEDE2000 (ΔE00), translucency parameter (TP) and whiteness index (WID). The composition color analysis results were then applied to produce a color-graded temporary veneer for mimicking a natural look. ResultMechanically, all composition result in adequate bending strength with maximum achievable strength of 111.64 MPa. At the same time, the composite color was affected by each constituent differently. The L* value, which indicates the color lightness of the composite, was considerably tuned by the TiO2 pigment, whereas Ba2SiO4 filler only triggered minor changes. Photoinitiator concentration significantly affected the yellowness, indicated by the increased b* value. Similar tendency also observed toward the calculated TP and WID as well. Based on these evaluations, color-graded temporary veneer successfully generated, matching the VITA A3, A2, and B1 shades gradation. However, the stability of the composite color decreased at high amounts of Ba2SiO4 and photoinitiator. SignificanceThe study presents a composition guide for fabricating temporary patient-specific color-graded veneer. It provides insights on the effect of the constituent material on dental esthetics.

Metal-Organic Framework on Fullerene (MOFOF) as a Hierarchical Composite by the Integration of Coordination Chemistry and Supramolecular Chemistry.

There is a synergy between coordination chemistry and supramolecular chemistry that has led to the development of innovative hierarchical composites with diverse functionalities. Here, we present a novel approach for the synthesis and characterization of a metal-organic framework on fullerene (MOFOF) composites, achieved through the integration of coordination chemistry and supramolecular chemistry principles. The hierarchical nature of the MOFOF harnesses the inherent properties of metal-organic frameworks and fullerenes. The two-step synthesis procedure involves controlled assembly of fullerenes as tube-like nanostructures (fullerene nanotube: FNT), their surface functionalization, and the on-surface growth of the MOF (in this case, ZIF-67). The method permits the precise tuning of morphology, effective distribution of MOF-on-FNT, and tight compositional control. The materials were comprehensively structurally characterized using electron microscopy, spectroscopic techniques, and other methods to elucidate the unique features and interactions within the MOFOF composites. The main findings reveal that the novel synthesis and characterization of MOFOF composites demonstrate the successful integration of coordination chemistry and supramolecular chemistry for the designing and fabricating of advanced hierarchical composites with tailored properties, including micro- and mesopore channels, interfacial facets, and defect sites. These properties are expected to lead to numerous potential applications such as gas storage and separation, catalysis, sensing, energy storage, and environmental remediation. However, only the capability of acid vapor sensing was tested and is described here.

Synthesis of nitrogen-doped crystalline Ga2O3 thin films via trimethylgallium doped NH3/H2/N2/O2 premixed stagnation flames

This study presents a novel and cost-effective technique for fabricating nitrogen-doped crystalline α-Ga2O3 and β-Ga2O3 thin films under atmospheric pressure conditions through flame synthesis for the first time. We employ metal–organic ammonia (NH3)-assisted flame synthesis (MO-NAFS) in a quasi-one-dimensional trimethylgallium (TMG) doped NH3/H2/N2/O2 flat flame to achieve a one-step deposition of Ga2O3 onto c-plane α-Al2O3 substrates. We found that hydrogen (H2) addition directly impacts the crystallinity of the Ga2O3 thin film. When only NH3 is employed as the fuel, a thin-film single-crystal nitrogen-doped β-Ga2O3 was observed. Blending the NH3 with 5 % of H2 yields a single-crystal nitrogen-doped α-Ga2O3, while a further increase of H2 fraction up to 10 % results in a mixture of both α-Ga2O3 and β-Ga2O3 crystals. Remarkably, the nitrogen doping through MO-NAFS was found to persistently result in an N/O atomic ratio as high as 1.12, as determined by the XPS analysis. This approach paves the way to a simple and scalable means for producing crystalline nitrogen-doped Ga2O3 thin films with potential control of crystal phase composition through parameter adjustments.

MXene Supported Surface Plasmon Polaritons for Optical Microfiber Ammonia Sensing.

The properties of surface plasmons are notoriously dependent on the supporting materials system. However, new capabilities cannot be obtained until the technique of surface plasmon enabled by advanced two-dimensional materials is well understood. Herein, we present the experimental demonstration of surface plasmon polaritons (SPPs) supported by single-layered MXene flakes (Ti3C2Tx) coating on an optical microfiber and its application as an ammonia gas sensor. Enabled by its high controllability of chemical composition, unique atomistically thin layered structure, and metallic-level conductivity, MXene is capable of supporting not only plasmon resonances across a wide range of wavelengths but also a selective sensing mechanism through frequency modulation. Theoretical modeling and optics experiments reveal that, upon adsorbing ammonia molecules, the free electron motion at the interface between the SiO2 microfiber and the MXene coating is modulated (i.e., the modulation of the SPPs under applied light), thus inducing a variation in the evanescent field. Consequently, a wavelength shift is produced, effectively realizing a selective and highly sensitive ammonia sensor with a 100 ppm detection limit. The MXene supported SPPs open a promising path for the application of advanced optical techniques toward gas and chemical analysis.

Impacts of the energy transition on public health in the context of country risk: From an international perspective

The global climate issue is becoming increasingly serious, and studying the energy transition (ET) has proven to be an effective solution to this problem. The essence of climate mitigation is to address the issue of ensuring the public health (pH) of human beings. Still, the definitions of ET in existing literature are inconsistent, and Many researches overlook the definitions of ET in official documents and discuss the relationship between ET and pH. Therefore, this research utilizes panel data from 107 countries over the period 2000–2020 to construct an energy transition indicator based on the definition from the World Economic Forum (WEF). It also examines the link between ET and pH using a two-way fixed effects regression. In the current turbulent international environment, this paper also investigates this link in the context of composite risk control (CRC), financial risk control (FRC), economic risk control (ERC), and political risk control (PRC). The results show that ET can significantly improve pH, a conclusion that remains significant after being subjected to a range of robustness tests. The study exploring the mechanism impact on the relationship between ET and pH shows that CRC, FRC, ERC, and PRC all strengthen the effect of ET on pH, and the mechanism effect varies considerably between high-income and low- and middle-income countries (LMICs); ET is more significantly affected by the mechanism in LMICs than in high-income countries. Furthermore, this paper illustrates that ET does not differ by gender in improving pH among infants, while there are gender differences in adults by using the instrumental variable regression and GMM regression to mitigate the endogenous and heteroscedasticity issue for heterogeneity test. The study in this paper can not only inspire policy researchers on which aspects to promote ET, but also provide a direction for improving pH.

Advances in the Application of Nanozymes in Joint Disease Therapy

Nanozymes are nanoscale materials with enzyme-mimicking catalytic properties. Nanozymes can mimic the mechanism of natural enzyme molecules. By means of advanced chemical synthesis technology, the size, shape, and surface characteristics of nanozymes can be accurately regulated, and their catalytic properties can be customized according to the specific need. Nanozymes can mimic the function of natural enzymes, including catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx), to scavenge reactive oxygen species (ROS). Reported findings have shown that nanozymes have the advantages of excellent stability, low cost, and adjustable catalytic activity, thereby showing great potential and broad prospects in the application of disease treatment. Herein, we reviewed the advances in the application of nanozymes in the treatment of joint diseases. The common clinical manifestations of joint diseases include joint pain, swelling, stiffness, and limited mobility. In severe cases, joint diseases may lead to joint destruction, deformity, and functional damage, entailing crippling socioeconomic burdens. ROS is a product of oxidative stress. Increased ROS in the joints can induce macrophage M1 type polarization, which in turn induces and aggravates arthritis. Therefore, the key to the treatment of joint diseases lies in ROS scavenging and increasing oxygen (O2) content. Nanozymes have demonstrated promising application potential in the treatment of joint diseases, including rheumatoid arthritis, osteoarthritis, and gouty arthritis. However, how to ensure their biosafety, reduce the toxicity, and increase enzyme activity remains the main challenge in current research. Precise control of the chemical composition, size, shape, and surface modification of nanomaterials is the main development direction for the future.

Synchronous control method for the walking system of the dual forging manipulators based on triangular velocity planning

The primary function of the dual forging manipulators’ walking system is to precisely control the axial feeding of forgings. The stability and control accuracy of this system significantly impact forging quality and production efficiency. To achieve synchronized position control, a mathematical model was developed using two 20 kN forging manipulators as the research subjects. Subsequently, a triangular velocity trajectory planner was devised to examine the effects of acceleration, start–stop coefficient, and peak coefficient on the control behavior of the system. Lastly, the efficacy of this control method, which employing triangular velocity planning (TVP) for displacement–velocity composite control, was confirmed through equivalent experiments. The results indicate that this method can effectively regulate the response dynamics of two walking systems, with a displacement difference of less than 1 mm between the two manipulators.

Microscopic methods to study meat and meat product quality

Reliable information about meat quality at all stages of the production process is necessary to ensure high quality of meat products. The structure of muscle, connective and fat tissues plays a direct role in formation of meat quality. Microscopic methods allow investigating the meat structure and determining its change depending on a range of endo- and exogenous factors (animal species, breed, sex, conditions of raising and slaughter) and on a type of technological processing. The paper presents the main directions of using microscopic analysis in investigation of meat and finished meat products. An advantage of microscopy is presentation of results in a visual form as well as a possibility of performing morphometry, including with the use of computer systems of image analysis, and obtaining quantitative characteristics of structures. Most common are light microscopy and electron microscopy. Due to various staining procedures, light microscopy enables detecting different components of a sample, studying topography and morphology of tissues and cells. Electron microscopy gives information about the ultrastructure of cells and their chemical composition. The paper discusses possibilities of microscopy in assessment of composition and detection of falsification of finished meat products. It has been noted that the use of several approaches and methods of staining allows reliable identification of many components, including components of plant origin. Histological methods can ensure detection of falsification and control of meat product composition at the state level.

Contribution to manufacturing control of particle-filled composites by RTM process

Contribution to manufacturing control of particle-filled composites by RTM process

Portable near-infrared (NIR) spectroscopy and multivariate calibration for reliable quality control of maize and sorghum grain chemical composition

Portable near-infrared (NIR) spectroscopy combined with multivariate calibration was used to determine the chemical composition of maize and sorghum grains of different genotypes cultivated in Brazil. Partial least squares (PLS) models were built, and the maize models exhibited R2 > 0.90 for all constituents except starch. For sorghum, the R2 was > 0.8 for all componentes. The Residual Prediction to Deviation (RPD) values and the Range Error Ratio (RER) values for all maize and sorghum calibration models exceeded 2.5 and 10, respectively, indicating the models’ reliability for routine laboratory implementation. No significant differences were found between the results obtained by the PLS models and the reference methods for any analyzed constituents in the maize and sorghum grains. These results demonstrate that the MicroNIR instrument is a viable tool for quality control of chemical composition in maize and sorghum grain samples. It offers the advantages of speed, non-destructiveness, and being a green alternative to standard methods.

Theoretical regulating the T-site composition of Janus MXenes achieving efficient bifunctional ORR/OER catalysts

The development of metal-air batteries relies heavily on efficient bifunctional catalysts for oxygen reduction/evolution reactions (ORR/OER). Herein, we employ first-principles calculations to investigate the structure-activity relationship between the composition of terminal atoms and the catalytic activity of Pt-doped VCl-Ti2CO2-xClx single-atom catalysts (SACs). Firstly, the results demonstrate clear linear correlations between the composition and the work function, interlayer average transfer charges (Δq), and the integrated crystal orbital Hamilton population (ICOHP) of the Pt-O bond that adsorbs OH. Besides, the difference in the average transferred charge between the Ti and the C layers (Δq5–3) and the ICOHP of Pt-O bond adsorbing OH can be used as effective descriptors of bifunctional performance of Pt-doped VCl-Ti2CO2-xClx. Furthermore, the bonding and charge transfer between the active site Pt and adsorbed intermediate OH are elucidated, revealing the bridging role of dxz and dz2 orbitals of Pt during the activation process. Based on the above understanding, we reported a catalyst of Pt-VCl-Ti2CO0.22Cl1.78 with a low bifunctional overpotential (ηBi = 1.00 V), effectively reducing the overpotential of Pt-doped Ti2CO2. This study extensively investigates the impact of terminal composition control on the ORR/OER activity, providing robust support for the design of highly active Janus MXene-based SACs.

Developing an online composition prediction for an HI–I2–H2O system using deep neural network

We developed a deep neural network (DNN) method to predict the composition of the HI–I2–H2O system in the iodine–sulfur (IS) process of thermochemical water-splitting hydrogen production using measurable properties. Unlike conventional titration analysis, this approach allows for a quick understanding of fluid composition, providing essential information for controlling operating conditions. This study focused on the HI–I2–H2O three-component system within the IS process. Gibbs’ phase rule was used to construct the DNN model using online measurement parameters, such as temperature, pressure, and density, as input conditions. The model was trained with experimental data, and the structural parameters were tuned. Composition prediction using actual trend data correlated well with titration analysis measurements. The local interpretable model-agnostic explanations method was incorporated to acquire insights into the significance of input parameters for compositions from the DNN model, providing valuable information on crucial parameters for effective composition control.

Hierarchical metal–organic framework nanoarchitectures for catalysis

Metal–organic frameworks (MOFs) have garnered significant attention in the field of catalysis due to their unique advantages such as diverse coordination geometry, variable metal nodes, and organic linkers, facilitating precise structural and compositional control for achieving programmable catalytic functionalities. Although their inherent microporous structure could provide excellent shape selectivity during catalysis, it typically impedes the mass transfer process, thereby reducing the use of internal active sites and overall catalytic efficiency. Additionally, employing single MOFs as catalysts presents challenges in achieving complex catalytic reactions that require multifunctional active sites. In recent years, considerable research efforts have focused on designing and constructing hierarchical nanostructured MOFs to alleviate substrate diffusion limitations by introducing secondary nanopores, shortening diffusion distances via the construction of low-dimensional nanoarchitectures, and constructing multifunctional catalysts by integrating distinct MOFs with suitable functions. This review provides a comprehensive overview of the design, synthesis methods, and formation mechanisms of MOF-based hierarchical nanostructures in recent years. Subsequently, it further highlights their applications in thermal catalysis, electrocatalysis, and photocatalysis, along with the relationship between their hierarchical nanostructures and catalytic performances. Finally, it provides an outlook on the challenges and potential development directions of hierarchically structured MOF nanocatalysts.

Neural-based fixed-time composite learning control for multiagent systems with intermittent faults

In this paper, a distributed fixed-time composite learning control problem is addressed for nonlinear multiagent systems (MASs) subject to intermittent actuator faults. First, a distributed estimator is constructed for followers that are unable to communicate directly with the leader. Then, instead of using the traditional adaptive neural network (NN) algorithm, a predictor-based composite learning technique is proposed, which incorporates the prediction error into the NN update law to enhance the estimation accuracy of the unknown nonlinearity. Furthermore, an adaptive fault-tolerant control compensation mechanism is developed for intermittent faults that may occur indefinitely and frequently. To guarantee that all signals of the closed-loop system are bounded in fixed time, a nonsingular fixed-time fault-tolerant controller in the form of quadratic function is established. Finally, simulation results confirm the effectiveness of the presented algorithm.

Inertia–Active Power Filter Design Based on Repetitive Control

The advent of distributed generation has brought with it a plethora of challenges for the nascent power systems that are being deployed on a large scale. Firstly, the majority of power electronic converters connected to the grid are in current source mode, which results in a lack of inertia and an inability to provide effective inertia or achieve damping support during fluctuations in grid frequency. Secondly, the issue of power quality, caused by the presence of harmonics, is becoming increasingly severe. This is particularly problematic in microgrids or systems with high line impedance, where harmonics can be amplified, thereby further compromising the stability of the power system. To address the deficiency in system inertia, numerous scholars are currently utilizing grid-forming (GFM) technology to achieve virtual inertia. In order to address the issue of system harmonics, it is possible to install active power filter (APF) devices at the point of common coupling (PCC), which serve to mitigate the effects of harmonics. This paper puts forth a proposal for the implementation of an APF with virtual inertia, based on PR + RC composite control. This composite control mechanism serves to enhance the harmonic suppression capabilities of the APF. The introduction of a frequency droop enables the capacitor voltage amplitude to be adjusted during fluctuations in system frequency, thereby achieving virtual inertia and providing active support for system frequency. The experimental results demonstrate that this strategy not only reduces the total harmonic distortion (THD) by 13% in comparison to PI control, indicating excellent harmonic suppression performance, but also allows the system to be inert, achieving positive results in suppressing frequency fluctuations during transients.

Physico-mechanical properties of halite and gypsum–mudstone crushed rock backfills of the Mercia Mudstone Group

Permanent disposal of radioactive waste in deep geological repositories (DGRs) relies on engineered barriers, such as crushed rock backfills, to ensure that wastes are isolated and contained. The performance of crushed rock backfill, during construction, operation and closure, relies on optimizing its mechanical properties. This paper explores how density and composition influence the strength of (i) crushed halite and (ii) crushed gypsum–mudstone mixtures of the Triassic Mercia Mudstone Group, which is a potential DGR host rock in the UK. Unconfined compressive strength (UCS) testing of compacted halite demonstrated that strength correlated with compaction density, with UCS increasing from 220 kPa at a density of 1.72 g cm −3 up to 6600 kPa at the maximum achieved density of 1.83 g cm −3 . Direct shear testing revealed an angle of internal friction for crushed halite samples of 39°–40° at a density of 1.5 g cm −3 . Direct shear testing of gypsum–mudstone composites from 100% gypsum to 100% mudstone revealed that higher gypsum percentages provide greater frictional shearing resistance, whilst higher mudstone percentages promote more cohesive strength. Data are also presented on bulk materials characterization by X-ray fluorescence (XRF), scanning electron microscopy with energy-dispersive spectrometry (SEM-EDS) and optical microscopy. This research provides insights into how the strength properties of compacted crushed halite and gypsiferous mudstone backfills can be engineered through control of density and composition.