Proposed Synthesis Procedure Research Articles

[formula omitted] gain-scheduled dynamic output feedback control with transient performance applied to electrical microgrid

This paper introduces an approach for designing gain-scheduled dynamic output feedback controllers for continuous-time Linear Parameter-Varying (LPV) systems. The aim is to improve transient response by incorporating both D-stability and H∞ criteria into the synthesis conditions. We achieve this by employing changes of variables and congruence transformations, which lead to new synthesis conditions expressed as linear matrix inequalities. Additional fine-tuned scalar parameters can be used to enhance further the controller performance in terms of less conservative H∞ guaranteed costs. To assess the effectiveness of our proposed synthesis procedure, we conduct computational experiments in the context of a microinverter-based distributed power generation system. These experiments take into account real-world operational characteristics, providing a comprehensive evaluation of our approach. The results demonstrate that the designed controller effectively ensures the desired closed-loop system behavior, even when dealing with state noise and discretization errors originating from digital implementation.

Sensor deception attacks against security in supervisory control systems

This paper investigates the problem of synthesizing sensor deception attacks against security in the context of supervisory control of discrete-event systems (DES). We consider a DES plant controlled by a supervisor, whose security requirement is to maintain the initial-secret of the system undetected, i.e., it does not want to reveal the fact that it was initiated from a secret state. On the other hand, there exists an active attacker that can tamper with the observations received by the supervisor by, e.g., hacking into the communication channel between the sensors and the supervisor. The objective of the attacker is to deceive the supervisor such that the initial-secret is revealed due to incorrect control actions. We investigate the problem from the attacker’s point of view and focus on synthesizing attack strategies that threaten the security of the system. We consider two levels of success of the attacker: one requires that the attacker can detect the initial-secret of the system “almost surely” and the other only requires that the attacker has the possibility to detect the initial-secret of the system. For both cases, we present algorithms for synthesizing successful attack strategies. Our approach is based on the All Attack Structure (AAS) which records state estimates for both the supervisor and the attacker. Structural properties of the security requirements are also leveraged to reduce the synthesis complexity. A running academic example is provided to illustrate the proposed synthesis procedures.

Time dependence in the synthesis of Cu2FeSnS4 and some of its properties

Polycrystalline Cu2FeSnS4 materials (abbreviated CFTS) were synthesized by a hydrothermal route implementing a one-step thermal treatment to measure dependence on different reaction times in the stabilization and structural, vibrational, and optoelectronic properties. The structural results have shown a tetragonal system with I-42m spatial group. The vibrational analysis by Raman spectroscopy allowed the identification of additional crystal phases arising from the synthesis procedure and corroborated the presence of a stannite phase. This evaluation showed that the reaction time gave the proposed synthesis procedure, significantly affects the semiconductor behavior of the solids; consequently, the conductivity measurements evidence a decrease from 1.02x106 to 9.84x105 W at 573 K as the synthesis time increases. These results described above, corroborated that the control of the reaction time provide a tool to successful fine-tune of the structural and conductivity properties of CFTS materials.

Highly efficient synthesis of titanium phosphate precursor for electroactive materials

In recent years titanium phosphates (TiPs) have aroused considerable interest as multi-functional materials. Known methods of TiPs synthesis are rather complicated because they are based on wet chemistry in terms of which one-step synthesis of pure TiP fails. It is highly welcomed to develop a new approach to TiP production. In this work the novel minimalistic approach to the synthesis of two titanium phosphates of different composition from a solid TiOSO 4 ·H 2 O precursor has been proposed. Despite the fact that the TiOSO 4 solutions are widely used for the synthesis of titanium phosphates, the solid compound as a titanium source has never been used before. The new mechanochemistry-based synthesis provides easy access to obtaining TiO(OH)(H 2 PO 4 )·H 2 O and Ti(HPO 4 ) 2 ·H 2 O (α-TiP) for 3 h and 5 h, respectively. The substitution of protons in α-TiP with Li + and Al 3+ by ion-exchange reactions provide the formation of Li 1.5 Al 0.5 Ti 1.5 (PO 4 ) 3 which is electroactive material. The proposed synthesis procedure is more technologically attractive compared with traditional methods, and enables direct production of highly dispersed monophasic powder (100–300 nm) of desired composition at 823 K. The material obtained demonstrates high conductivity value of 7.8·10 −4 S cm −1 at 298 K, low activation energy of 0.27 eV, and can be used as a solid electrolyte for practical application in all-solid-state lithium batteries.

Transition metal promoted combustion of rice husk and rice straw towards an energy optimized synthesis of biogenic silica

The classical approach for the synthesis of catalysts based on biogenic silica from rice husk or rice straw involves a high temperature (600 °C) calcination step to remove the organic matrix from the silica backbone. The remaining silica can then be impregnated with a variety of active components in the form of Mn-, Fe- and Ce-precursors, followed by subsequent thermal treatment to form the corresponding metal oxides. In this work, we introduce a novel energy optimized route for the preparation of biogenic silica supported metal oxides. The proposed synthesis procedure aims towards the reduction of pyrolysis steps by infiltrating metal salts into the biomass lignocellulosic matrix. The modified rice husk or rice straw can then be calcined to directly yield the desired metal oxide supported on biogenic silica. To evaluate the described method, as model system manganese oxide modified rice husk silica was compared to a set of materials synthesized via classical calcination-impregnation by means of textural (N2-Sorption, SEM/EDX), structural (XRD), thermal (TG/DTA) and elemental (ICP-OES; XRF) analysis. Results indicate that the introduction of transition metals into biomass powder promotes the combustion of the organic matrix in terms of temperature requirements for its complete removal. In addition, catalytic tests of the materials obtained by the novel synthesis route clearly show similar or even improved performance as compared to catalysts prepared via impregnation method.

Biodistribution of Quantum Dots-Labelled Halloysite Nanotubes: A Caenorhabditis elegans In Vivo Study.

Halloysite is a promising building block in nanoarchitectonics of functional materials, especially in the development of novel biomaterials and smart coatings. Understanding the behavior of materials produced using halloysite nanotubes within living organisms is essential for their safe applications. In this study, quantum dots of different compositions were synthesized on the surface of modified clay nanotubes, and the biodistribution of this hybrid material was monitored within Caenorhabditis elegans nematodes. The influence of the modification agent as well as the particles’ composition on physicochemical properties of hybrid nanomaterials was investigated. Several microscopy techniques, such as fluorescence and dark-field microscopy, were compared in monitoring the distribution of nanomaterials in nematodes’ organisms. The effects of QDs-halloysite composites on the nematodes’ life cycle were investigated in vivo. Our fluorescent hybrid probes induced no acute toxic effects in model organisms. The stable fluorescence and low toxicity towards the organisms suggest that the proposed synthesis procedure yields safe nanoarchitectonic materials that will be helpful in monitoring the behavior of nanomaterials inside living cells and organisms.

TiO2/Au/TiO2 plasmonic photocatalyst with enhanced photocatalytic activity and stability under visible-light irradiation

Plasmonic photocatalysis, i.e., photocatalysis with activity under visible-light (vis) irradiation due to plasmonic feature of noble metals (NMs), has been intensively studied as promising method for solar energy conversion. Although various plasmonic photocatalysts have already been investigated, the vis activity is usually low, and thus should be improved for commercial application. Moreover, considering charge carriers’ mechanism, the stability of NMs during long-term irradiation should be also considered. Accordingly, this study has focused on the improvement of photocatalytic activity and stability of gold-modified titania photocatalysts under vis irradiation. Among a few proposed synthesis procedures, modified photodeposition method has resulted in the formation of TiO2/Au/TiO2 composites with high level of photoactivity. Large gold nanoparticles (NPs), formed on large rutile titania particles, are partially covered with fine anatase titania NPs, and thus the interface between titania and gold has been enlarged. Moreover, partial coverage of gold by fine titania NPs hinders gold aggregation, resulting in improved stability of these samples. Action spectrum of 2-propanol oxidation and numerical 3D-FDTD simulations of field distribution have indicated that the enhanced utilization of incident photons is responsible for high activity of TiO2/Au/TiO2 photocatalysts.

Synthesis of cosecant-squared pattern in substrate integrated waveguide leaky-wave antennas

A synthesis procedure for realizing a cosecant-squared pattern in leaky-wave antennas (LWAs) is presented. In this method, the antenna is divided into a number of sections, each with an appropriate phase constant, length and leakage rate. The phase constant of the radiating sections is obtained such that their beam pointing angles would arrange on an appropriate layout in the shaped region. The two latter parameters are determined such that the radiation intensity of each section would decay with a cosecant-squared profile. Finally, using an optimization algorithm, i.e., a genetic algorithm (GA) optimization, the initial values of the leakage rate are adjusted to achieve the desired shaped region. The synthesis procedure is applied to a slotted substrate integrated waveguide (SIW) LWA, and a prototype of the antenna is designed to achieve the cosecant-squared pattern within the range of 10° to 30°. The results show that the antenna has low ripples (≤2 dB) in the shaped region with a low level of sidelobes (≤-18 dB) outside the region. The antenna is fabricated and measured. Measurements show a good agreement with the simulation results. The obtained results reveal that the proposed synthesis procedure can be utilized in designing cosecant-squared pattern LWAs to use in air-surveillance radar systems.

Catalysing the Combustion of Rice Husk and Rice Straw Towards an Energy Optimized Synthesis of Metal Modified Biogenic Silica

The classical approach for the synthesis of catalysts based on biogenic silica from rice husk or rice straw involves a high temperature (600 °C) calcination step to remove the organic matrix from the silica backbone. The remaining silica can then be impregnated with a variety of active components in the form of Mn-, Fe- and Ce-precursors, followed by subsequent thermal treatment to form the corresponding metal oxides. In this work, we introduce a novel energy optimized route for the preparation of biogenic silica supported metal oxides. The proposed synthesis procedure aims towards the reduction of pyrolysis steps by infiltrating metal salts into the biomass lignocellulosic matrix. The modified rice husk or rice straw can then be calcined to directly yield the desired metal oxide supported on biogenic silica. To evaluate the described method, as model system manganese oxide modified rice husk silica was compared to a set of materials synthesized via classical calcination-impregnation by means of textural (N2-Sorption, SEM/EDX), structural (XRD), thermal (TG/DTA) and elemental (ICP-OES; XRF) analysis. Results indicate that the introduction of transition metals into biomass powder promotes the combustion of the organic matrix in terms of temperature requirements for its complete removal. In addition, catalytic tests of the materials obtained by the novel synthesis route clearly show similar or even improved performance as compared to catalysts prepared via impregnation method.

Flat-topped pattern synthesis of optical leaky-wave antennas

In this article, a synthesis procedure is proposed to achieve a flat-topped radiation pattern in optical leaky-wave antennas (OLWAs). In the proposed procedure, the antenna is divided into sections, each with an appropriate phase constant, length and leakage constant. By determining a proper value for these parameters, the desired flat-topped pattern is achieved. The phase constant of the sections is obtained such that their beam pointing angle follows an appropriate layout in the region of interest. Further, by introducing the same beamwidth and the same radiation power for the radiating sections, the two latter parameters, i.e., the length and the leakage constant of the sections are determined. The proposed synthesis procedure is applied to a conventional OLWA, i.e., grating waveguide (GWG), to achieve a flat-topped pattern in the angular region of -30°to -11°. Results show that the desired radiation pattern is well synthesized. Finally, the effects of beam spacing and the sections’ beamwidth on the angular rejection slope, symmetry level, -3 dB and -10 dB beamwidth are investigated. The reflection coefficient of the synthesized antenna is also examined, indicating an excellent operation below -38 dB at the entire frequency band. The proposed synthesis procedure can be applied to any type of OLWA, through which a uniform illumination can be achieved in a desired angular region.

Fixed-Dynamics Antiwindup Design: Application to Pitch-Limited Position Control of Multirotor Unmanned Aerial Vehicles

In this brief, we present and validate an antiwindup (AW) control design suitable to deal with saturated discrete-time linear plants. Following the modern approach to AW design, the proposed synthesis procedure is based on the compensator paradigm in which the AW controller acts on top of a baseline one, tuned to achieve desirable performance in the unsaturated regime. After extending existing ideas for continuous-time plants to their discrete-time counterparts, the design of the AW compensator is carried out with a focus on computational efficiency and optimized performance in practical operating scenarios. The proposed approach allows one to design fixed-dynamics AW compensators for possibly open-loop unstable plants using generalized sector conditions. Then, the synthesis procedure is applied to tune a fixed-dynamics compensator having the structure of a static compensator cascaded with a unit delay to avoid algebraic loops. Finally, the benefits of such AW augmentation are assessed experimentally to counteract windup effects arising in the position control of multirotor unmanned aerial vehicles (UAVs) when pitch limitations are imposed.

Synchronization And State Estimation Of Nonlinear Systems With Unknown Time-Delays: Adaptive Identification Method

The paper studies a novel adaptive identifier proposed in IFAC World Congress 2020 for nonlinear time-delay systems composed of linear, Lipschitz and non-Lipschitz components. To begin with, an identifier is designed for uncertain systems with a priori known delay values, and then it is generalized for systems with unknown delay values. The algorithm ensures the asymptotic parameter estimation and state observation by using gradient algorithms. The unknown delays and plant parameters are estimated by using a special equivalent extension of the plant equation. The algorithms stability is presented by solvability of linear matrix inequalities. Simulation results are invoked to support the developed identifier design and to illustrate the efficiency of the proposed synthesis procedure.

Hierarchical diagnostic model synthesis for dataflow real-time computing system

Subject of Research. The paper considers design issues for diagnostic tools of fault detection in addressing information exchanges between software modules for real-time dataflow computing systems. Despite the decomposition of the design processes in such systems, the issues of diagnostics and fault tolerance remain relevant for each hierarchy level. Method. The proposed synthesis procedures for the hierarchical model of a dataflow computing system are the result of the test diagnostics method development based on the parallel model application. Main Results. The paper presents a brief description of the test diagnostics method based on the parallel model. An algorithm for hierarchical diagnostics model synthesis is developed. The model minimizes the amount of diagnostic data transmitted through the exchange channels, reducing the redundancy level introduced into the system and thereby increasing the level of reliability. Practical Relevance. The developed hierarchical model reduces significantly the design time for diagnostic tools as a result of reducing the required number of diagnostic modules included in it.

A Decoupling and Matching Network Design for Single- and Dual-Band Two-Element Antenna Arrays

This article presents a new decoupling and matching network (DMN) design for symmetric, single- and dual-band two-element antenna arrays. The DMNs use parallel-line-based coupling elements. The decoupling between the output ports of the proposed DMN and the reflection coefficients at these ports is obtained using the scattering parameters of the coupled antenna array and those of the DMN. These are clearly expressed as functions of the DMN's design parameters. These design parameters are determined using a simple numerical method to provide high inter-element isolation and good impedance matching for the array. To verify the proposed synthesis procedure, three DMN example designs are considered. These include one for a single-band array and two for dual-band arrays having different frequency ratios. Prototypes of these antennas along with their DMNs were designed, fabricated, and experimentally characterized. In each case, a good agreement between the measured and theoretical results is achieved. Simulation and measurement results show that the proposed DMN design and its associated synthesis procedure can be employed to significantly improve the interelement isolation of single- and dual-band, two-element arrays in various scenarios.

Population Synthesis for a City in a Developing Country

Activity-based approach in transportation studies increased the demand for detailed disaggregate data. To overcome the tedious and costly data collection, synthesized data are widely used in activity based modeling practices in developed countries. In the case of developing economies, time, resource and monetary constraints hinder the development of new generation travel demand models. Population synthesis practices are the need of the hour in developing countries. Through this study, the authors proposed a method for population synthesis for a medium sized city, in a developing country. Details from 9901 households, collected through home-interview survey in 2011 formed the database for this work. The proposed synthesis procedure makes use of Monte Carlo process along with logit modeling technique to simulate population attributes using the survey data. The procedure is developed as a Visual Basic Application in spreadsheet platform. By adopting this method, various household level and person level attributes are simulated. Comparison of observed data from survey and simulated data showed consistent results and low differences. It is expected that this study will assist the planning authorities to better understand the city′s population characteristics.

A Strategy To Prepare Peptide Heterodimers in the Solid Phase with an Acid-Labile Linker.

The currently synthetic methods of peptide heterodimer involve tedious synthesis and purification steps. An acid-labile traceless linker was prepared, which is highly compatible with the Fmoc strategy and could be used to prepare peptide heterodimer on resin. The linker could be cleaved concomitantly with peptide cleavage, and two model heterodimers were synthesized. The proposed synthesis procedure is simple, straightforward, and provides great convenience for preparing disulfide-linked peptide heterodimers.

Synthesis of eco-compatible bimetallic silver/iron nanoparticles for water remediation and reactivity assessment on bromophenol blue

In the last decade, zero-valent iron nanoparticles (nZVI) have been applied for groundwater remediation and they proved to be effective towards a wide range of contaminants, both organic and inorganic. One of the critical aspects related to the synthesis of this material concerns the use of borohydride, which increases the cost of the final product and generates toxic borates. In this paper, a new synthesis method of bimetallic nanoscale zero-valent silver/iron (nZVSI), its properties and its reactivity towards a model compound are presented. The novel synthesis protocol employs benign hydrosulfite as reducing agent and it is of easy implementation and scalability. The resulting nanoparticles have narrow size distribution and show appropriate colloidal stability. They consist of a core of zerovalent iron and a thin shell of iron oxide, while silver is homogeneously distributed within the material. The nanoparticles showed effective reactivity, able to degrade bromophenol blue with suitable kinetics and using a low amount of material. Additionally, the bimetallic nanomaterial significantly outperformed nanometric zero-valent silver (nZVS) and nZVI obtained with the same protocol. The proposed synthesis would allow to significantly reduce the environmental and health impact of the stage prior to product application via injection in the subsoil. Also, the simplicity and the safety of the proposed synthesis procedure would allow the production of the bimetallic reactant directly on-site, thus streamlining the remediation process and maximizing its efficiency.

Event‐triggered state‐dependent switching rule design for switched linear systems

SummaryThis paper is devoted to the synthesis problem of switched linear systems. We come up with a novel state‐dependent switching rule in terms of an event‐triggered mechanism. This switching rule is able to expand the degree of freedom of bilinear matrix inequality where the synthesis problem is constructively formulated. It is overwhelmingly critical that the number of decision variables, which determines the conservativeness of our results under the proposed event‐triggered state‐dependent switching rule, is larger than the previous ones when a switched system consisted of three or more subsystems. The implementation complexity of a switching law is greatly reduced, as well as the number of switchings. Finally, two examples illustrate that the proposed synthesis procedure is valid.

Structural synthesis of a class of kinematically redundant parallel manipulators based on modified G–K criterion and RDOF criterion

Based on the modified Grübler–Kutzbach (G–K) criterion and relative degrees of freedom (RDOF) criterion, a novel method is proposed for structural synthesis of a class of kinematically redundant parallel manipulators (KR-PMs) with spherical joints attached to a moving platform. First, a formula that can be used to calculate the number of kinematic joints not limited to basic joints is proposed, which is affected by the number of links including fixed base, links with multi-node, compound hinges, and the INTERNAL independent loops in parallel manipulators. Furthermore, the sum degrees of all the kinematic joints possesses a direct relationship with the number of kinematic joints, the number of spherical joints, and the type combination of spherical joints attached to the moving platform. Then, the relationship between the mobility M and the RDOF with intermediate variables is derived based on modified G-K criterion and RDOF criterion, which is the base of the proposed synthesis procedure. Next, the proposed synthesis procedure is performed with the synthesis conditions RDOF = 3 or 4, and some typical KR-PMs are obtained. Finally, the condition for proper selection of actuators for KR-PM is revealed. And the reasons for large configuration randomness of the synthesized KR-PMs are discussed.

Synthesis of ternary distillation process structures featuring minimum utility cost using the IDEAS approach

A synthesis method for ternary distillation process structures is proposed on the basis of the infinite‐dimensional state‐space (IDEAS) approach. The proposed synthesis procedure consists of two steps. At the first step, the utility cost is minimized. The result of the first step contains many tiny flows among the modules because the number of flows is not included in the objective function. Then, at the second step, an evolutionary procedure for process simplification is executed. In this step, the weighted sum of flow rates is minimized recursively while updating the weights at each iteration. The practical process structure is finally determined from the result of the second simplification step. The developed synthesis procedure was applied to the separation problem of a ternary mixture consisting of benzene, toluene, and o‐xylene. It demonstrated that the proposed procedure provides a process whose liquid composition profile is quite similar to that of a Petlyuk column. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1285–1294, 2018