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Showing records 51 to 75 of 1602. [First] Page: 1 2 3 4 5 6 7 Last
Numerical Simulations of Polymer Solution Droplet Impact on Surfaces of Different Wettabilities
Moussa Tembely, Damien Vadillo, Arthur Soucemarianadin, Ali Dolatabadi
December 16, 2019 (v1)
Keywords: droplet impact, viscoelasticity, volume of fluid method
This paper presents a physically based numerical model to simulate droplet impact, spreading, and eventually rebound of a viscoelastic droplet. The simulations were based on the volume of fluid (VOF) method in conjunction with a dynamic contact model accounting for the hysteresis between droplet and substrate. The non-Newtonian nature of the fluid was handled using FENE-CR constitutive equations which model a polymeric fluid based on its rheological properties. A comparative simulation was carried out between a Newtonian solvent and a viscoelastic dilute polymer solution droplet. Droplet impact analysis was performed on hydrophilic and superhydrophobic substrates, both exhibiting contact angle hysteresis. The effect of substrates’ wettability on droplet impact dynamics was determined the evolution of the spreading diameter. While the kinematic phase of droplet spreading seemed to be independent of both the substrate and fluid rheology, the recoiling phase seemed highly influenced by th... [more]
The Effect of Fines on Hydraulic Conductivity of Lawrencepur, Chenab and Ravi Sand
Tanveer Ahmed Khan, Khalid Farooq, Mirza Muhammad, Mudasser Muneer Khan, Syyed Adnan Raheel Shah, Muhammad Shoaib, Muhammad Asif Aslam, Syed Safdar Raza
December 16, 2019 (v1)
Subject: Other
Keywords: fines, fluid, permeability, sand, soil, transport
The amount of fines in sand greatly influence the permeability of sandy soils. Thus, this research was conducted to study the effect of plastic and non-plastic fines on the permeability of three types of sands (Lawrencepur sand, Chenab sand and Ravi sand). For this purpose, plastic and non-plastic fines were collected from different location of Lahore. Samples were prepared by mixing plastic and non-plastic fines into each type of sand separately, in amounts ranging from 0% to 50% with increments of five percent. Overall 63 samples were prepared. Sieve analysis and hydrometric analysis were performed to obtain particle size distribution for each sample. Atterberg’s limits were also determined and each sample was classified according to the Unified Soil Classification System (USCS). Compaction tests were performed on all samples as per the procedure in a standard Proctor test. The test samples were compacted in permeability molds with optimum moisture contents to obtain the density, as... [more]
Oil Recovery from Palm Kernel Meal Using Subcritical Water Extraction in a Stirred Tank Reactor
Johnnys Bustillo Maury, Andrés Aldana Rico, Cindy García Pinto, Ingrid Hernández Medina, Juan Urueta Urueta, Jerry W. King, Antonio Bula Silvera
December 16, 2019 (v1)
Keywords: clean separation, oil recovery, palm kernel meal, subcritical water extraction
Palm kernel meal (PKM) is one of the main byproducts of the oil palm industry. PKM can be obtained as the result of solvent or mechanical extraction of palm kernel oil; in both cases, meal has a remaining oil content that could be recovered. In this work, PKM coming from a mechanical pressing extraction system with an initial oil content between 7 to 8% (wt.) was treated with subcritical water in a batch stirred reactor. To find the proper operational conditions, a three-step experimental process was performed. Extraction temperature, reaction time, particle size and alkaline catalyst usage were selected as process factors. After subcritical extraction, the system was cooled down and depressurized; then oil phase was separated by centrifugation. After extraction, meal was oven-dried at 80 °C. A maximum recovery of 0.034 kg-oil/kg-meal was obtained at 423 K, 720 s and particles smaller than 0.001 m. The experimental procedure showed consistent extraction yields of 40% without modifying... [more]
The Fast Potential Evaluation Method of Enhanced Oil Recovery Based on Statistical Analysis
Zhengbo Wang, Qiang Wang, Desheng Ma, Wanchun Zhao, Xiaohan Feng, Zhaoxia Liu
December 16, 2019 (v1)
Keywords: grey correlation, potential evaluation, rapid analogy, screening method, tertiary oil recovery
Based on a large number of empirical statistics of tertiary oil recovery technology in China, including polymer flooding, chemical flooding, gas flooding, in situ combustion, steam flooding, ect., 22 key reservoir parameters were filterized. Five levels of quantitative screening criteria were developed for different tertiary oil recovery methods. The mean algorithm for the downward approximation and the grey correlation theory were used in this paper to quickly select the appropriate tertiary oil recovery method for the target blocks, which provides a preferred development method for subsequent potential evaluation. In the rapid analogy evaluation method of tertiary oil recovery potential, the total similarity ratio between the target block and the example block is determined. The target block is matched with the appropriate instance block according to the total similarity ratio value, using 80% as the boundary. The ratio of the geological reserves is used to predict the oil recovery i... [more]
Physical and Thermal Studies of Carbon-Enriched Silicon Oxycarbide Synthesized from Floating Plants
Guan-Ting Pan, Siewhui Chong, Yi Jing Chan, Timm Joyce Tiong, Jun Wei Lim, Chao-Ming Huang, Pradeep Shukla, Thomas Chung-Kuang Yang
December 16, 2019 (v1)
Subject: Materials
Keywords: floating plants, silica, silicon oxycarbide, SiOC, thermal conductivity
In the present study, amorphous mesoporous silicon oxycarbide materials (SiOC) were successfully synthesized via a low-cost facile method by using potassium hydroxide activation, high temperature carbonization, and acid treatment. The precursors were obtained from floating plants (floating moss, water cabbage, and water caltrops). X-ray diffraction (XRD) results confirmed the amorphous Si−O−C structure and Raman spectra revealed the graphitized carbon phase. Floating moss sample resulted in a rather rough surface with irregular patches and water caltrops sample resulted in a highly porous network structure. The rough surface of the floating moss sample with greater particle size is caused by the high carbon/oxygen ratio (1: 0.29) and low amount of hydroxyl group compared to the other two samples. The pore volumes of these floating moss, water cabbage, and water caltrops samples were 0.4, 0.49, and 0.63 cm3 g−1, respectively, resulting in thermal conductivities of 6.55, 2.46, and 1.14 W... [more]
The Synthesis of N-(Pyridin-2-yl)-Benzamides from Aminopyridine and Trans-Beta-Nitrostyrene by Fe2Ni-BDC Bimetallic Metal−Organic Frameworks
Trinh Duy Nguyen, Oanh Kim Thi Nguyen, Thuan Van Tran, Vinh Huu Nguyen, Long Giang Bach, Nhan Viet Tran, Dai-Viet N. Vo, Tuyen Van Nguyen, Seong-Soo Hong, Sy Trung Do
December 16, 2019 (v1)
Subject: Materials
Keywords: bimetallic metal–organic frameworks, decarboxylative amidation, metal–organic framework
A bimetallic metal−organic framework material, which was generated by bridging iron (III) cations and nickel (II) cations with 1,4-Benzenedicarboxylic anions (Fe2Ni-BDC), was synthesized by a solvothermal approach using nickel (II) nitrate hexahydrate and iron (III) chloride hexahydrate as the mixed metal source and 1,4-Benzenedicarboxylic acid (H2BDC) as the organic ligand source. The structure of samples was determined by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and nitrogen physisorption measurements. The catalytic activity and recyclability of the Fe2Ni-BDC catalyst for the Michael addition amidation reaction of 2-aminopyridine and nitroolefins were estimated. The results illustrated that the Fe2Ni-BDC catalyst demonstrated good efficiency in the reaction under optimal conditions. Based on these results, a reaction mechanism was proposed. When the molar ratio of 2-aminopyridine and trans-β-nitrostyrene was 1:1, and the sol... [more]
Numerical Study of the Unsteady Flow Characteristics of a Jet Centrifugal Pump under Multiple Conditions
Rong Guo, Rennian Li, Renhui Zhang, Wei Han
December 16, 2019 (v1)
Keywords: jet centrifugal pump (JCP), numerical calculation, pressure fluctuation, rotor–stator interaction, unsteady flow
To study the reasons for the low efficiency of jet centrifugal pumps (JCPs) and the mechanism of unsteady flow characteristics under multiple conditions, taking a JET750G1 JCP as the object, three-dimensional steady and unsteady numerical calculations of the model pump were carried out using the k−ω turbulence model. The transient fluctuation characteristics of the flow field in the major flow passage components and the spatial and temporal evolution laws of vortices in the rotor−stator cascades were analyzed. The accuracy of the numerical method was verified by experiments. The results show that there are various scales of flow distortion phenomena in the chamber of the JCP, such as eddies, blockage of the flow passage, recirculation, secondary flow, and circulation, which not only cause great hydraulic loss, but also destroy the flow stability, symmetry, and balance in the other flow passage components. This is an important reason for the obviously lower efficiency of a JCP compared... [more]
Automatic Hybrid Attack Graph (AHAG) Generation for Complex Engineering Systems
Mariam Ibrahim, Ahmad Alsheikh
December 16, 2019 (v1)
Keywords: Hybrid Attack Graph, Level-of-Resilience, stability, topology
Complex Engineering Systems are subject to cyber-attacks due to inherited vulnerabilities in the underlying entities constituting them. System Resiliency is determined by its ability to return to a normal state under attacks. In order to analyze the resiliency under various attacks compromising the system, a new concept of Hybrid Attack Graph (HAG) is introduced. A HAG is a graph that captures the evolution of both logical and real values of system parameters under attack and recovery actions. The HAG is generated automatically and visualized using Java based tools. The results are illustrated through a communication network example.
Determination of the Least Impactful Municipal Solid Waste Management Option in Harare, Zimbabwe
Trust Nhubu, Edison Muzenda
December 16, 2019 (v1)
Subject: Energy Policy
Keywords: acidification, eutrophication, global warming, Harare, human health, life cycle assessment, life cycle impacts, life cycle stages, municipal solid waste management, Zimbabwe
Six municipal solid waste management (MSWM) options (A1−A6) in Harare were developed and analyzed for their global warming, acidification, eutrophication and human health impact potentials using life cycle assessment methodology to determine the least impactful option in Harare. Study findings will aid the development of future MSWM systems in Harare. A1 and A2 considered the landfilling and incineration, respectively, of indiscriminately collected MSW with energy recovery and byproduct treatment. Source-separated biodegradables were anaerobically treated with the remaining non-biodegradable fraction being incinerated in A3 and landfilled in A4. A5 and A6 had the same processes as in A3 and A4, respectively, except the inclusion of the recovery of 20% of the recoverable materials. The life cycle stages considered were collection and transportation, materials recovery, anaerobic digestion, landfilling and incineration. A5 emerged as the best option. Materials recovery contributed to imp... [more]
Optimal Design of Experiments for Liquid−Liquid Equilibria Characterization via Semidefinite Programming
Belmiro P.M. Duarte, Anthony C. Atkinson, José F.O. Granjo, Nuno M.C. Oliveira
December 13, 2019 (v1)
Keywords: approximate designs, liquid–liquid equilibria, optimal design of experiments, semidefinite programming, ternary systems
Liquid−liquid equilibria (LLE) characterization is a task requiring considerable work and appreciable financial resources. Notable savings in time and effort can be achieved when the experimental plans use the methods of the optimal design of experiments that maximize the information obtained. To achieve this goal, a systematic optimization formulation based on Semidefinite Programming is proposed for finding optimal experimental designs for LLE studies carried out at constant pressure and temperature. The non-random two-liquid (NRTL) model is employed to represent species equilibria in both phases. This model, combined with mass balance relationships, provides a means of computing the sensitivities of the measurements to the parameters. To design the experiment, these sensitivities are calculated for a grid of candidate experiments in which initial mixture compositions are varied. The optimal design is found by maximizing criteria based on the Fisher Information Matrix (FIM). Three op... [more]
Experimental and Numerical Analysis of a Sustainable Farming Compartment with Evaporative Cooling System
M. Sina Mousavi, Siamak Mirfendereski, Jae Sung Park, Jongwan Eun
December 13, 2019 (v1)
Keywords: dynamic numerical simulation, evaporative cooling system, heat transport, humidity, optimized design, temperature, water recycling
The United Arab Emirates (UAE) relies on groundwater as well as desalinated water which are very expensive and energy-concentrated. Despite the lack of water resources, only 54% of wastewater was recycled in the UAE in 2016. In this study, a Sustainable Farming Compartment (SFC) with an evaporative cooling system is investigated as an alternative to reusing wastewater and the optimal design is identified experimentally and numerically. First, the applicability of the SFC was examined to reduce the ambient temperature in the system. A prototype SFC was tested in the environmentally constrained laboratory and field site considering an extreme climate condition (with high temperature and humidity) in Abu Dhabi to evaluate the temperature drop and humidity change of the SFC. The experimental results showed that the temperature of the SFC significantly decreases by 7−15 °C when the initial relative humidity is 50%. For validation, an energy modeling using dynamic numerical simulations was p... [more]
Mechanism and Kinetics of Ammonium Sulfate Roasting of Boron-Bearing Iron Tailings for Enhanced Metal Extraction
Xiaoshu Lv, Fuhui Cui, Zhiqiang Ning, Michael L. Free, Yuchun Zhai
December 13, 2019 (v1)
Keywords: ammonium sulfate roasting process, iron tailings, kinetics, reaction mechanism
The large amount of boron-bearing iron tailings in China is a resource for metals that needs to be more completely and efficiently utilized. In this evaluation, the ammonium sulfate roasting process was used to make a controllable phase transformation to facilitate the subsequent extraction of valuable metals from boron-bearing iron tailings. The effects of roasting temperature, roasting time, the molar ratio of ammonium sulfate to tailings, and the particle size on the extraction of elements were investigated. The orthogonal experimental design of experiments was used to determine the optimal processing conditions. XRD (X-Ray Diffractomer), scanning electron microscope (SEM), and simultaneous DSC−TG analyzer were used to assist in elucidating the mechanism of ammonium sulfate roasting. The experimental results showed that nearly all Fe, Al, and Mg were extracted under the following conditions: (1) the molar ratio of ammonium sulfate to iron tailings was 3:1; (2) the roasting temperatu... [more]
Additive Manufacturing for Repair and Restoration in Remanufacturing: An Overview from Object Design and Systems Perspectives
Rahito, D. A. Wahab, A. H. Azman
December 13, 2019 (v1)
Subject: Energy Policy
Keywords: additive manufacturing, circular economy, direct energy deposition, remanufacturing, repair, restoration
Repair and restoration is an important step in remanufacturing as it ensures end-of-life products are returned to as-new condition before entering the subsequent life cycle. Currently, such processes are carried out manually by skilled workers. The advent of additive manufacturing (AM) has encouraged researchers to investigate its potential in automated repair and restoration, thus rendering it as a more effective method for remanufacturing. However, the application of this widespread technology for repair and restoration in remanufacturing is still new. This paper provides an overview of the principles and capabilities offered by the existing metal AM technology for object repair and restoration namely, direct energy deposition, powder bed fusion, and cold spray technology. Their applications in the repair and restoration of remanufacturable components are presented and discussed along with issues requiring attention from the perspectives of object design and process systems capabilit... [more]
Reliability Evaluation Method Considering Demand Response (DR) of Household Electrical Equipment in Distribution Networks
Hongzhong Chen, Jun Tang, Lei Sun, Jiawei Zhou, Xiaolei Wang, Yeying Mao
December 13, 2019 (v1)
Keywords: capacity constraint, demand response, household electrical equipment, incentive mechanism, real-time electricity price, reliability evaluation
The load characteristic of typical household electrical equipment is elaborately analyzed. Considering the electric vehicles’ (EVs’) charging behavior and air conditioning’s thermodynamic property, an electricity price-based demand response (DR) model and an incentive-based DR model for two kinds of typical high-power electrical equipment are proposed to obtain the load curve considering two different kinds of DR mechanisms. Afterwards, a load shedding strategy is introduced to improve the traditional reliability evaluation method for distribution networks, with the capacity constraints of tie lines taken into account. Subsequently, a reliability calculation method of distribution networks considering the shortage of power supply capacity and outages is presented. Finally, the Monte Carlo method is employed to calculate the reliability index of distribution networks with different load levels, and the impacts of different DR strategies on the reliability of distribution networks are an... [more]
Numerical and Experimental Investigation on Radiated Noise Characteristics of the Multistage Centrifugal Pump
Qiaorui Si, Biaobiao Wang, Jianping Yuan, Kaile Huang, Gang Lin, Chuan Wang
December 13, 2019 (v1)
Keywords: acoustic analogy, flow-induced noise, multistage centrifugal pump, numerical calculation
The radiated noise of the centrifugal pump acts as a disturbance in many applications. The radiated noise is closely related to the hydraulic design. The hydraulic parameters in the multistage pump are complex and the flow interaction among different stages is very strong, which in turn causes vibration and noise problems because of the strong hydraulic excitation. Hence, the mechanism of radiated noise and its relationship with hydraulics must be studied clearly. In order to find the regular pattern of the radiated noise at different operational conditions, a hybrid numerical method was proposed to obtain the flow-induced noise source based on Lighthill acoustic analogy theory, which divided the computational process into two parts: computational fluid dynamics (CFD) and computational acoustics (CA). The unsteady flow field was solved by detached eddy simulation using the commercial CFD code. The detailed flow information near the surface of the vane diffusers and the calculated flow-... [more]
Sustainable Design and Engineering: A Relationship Analysis between Digital Destructive and Non-Destructive Testing Process for Lightweight Concrete
Muhammad Ahmed Qurashi, Syyed Adnan Raheel Shah, Muhammad Farhan, Muhammad Taufiq, Waleed Khalid, Hunain Arshad, Muhammad Tayyab, Gullnaz Shahzadi, Muhammad Waseem
December 13, 2019 (v1)
Subject: Materials
Keywords: concrete, EPS-beads, lightweight, non-destructive testing, process, sustainable
The development of sustainable lightweight materials is a promising field solution in this era. The production of sustainable materials by replacing coarse aggregates with some lightweight alternative provides a good quality construction material. In this study, rocky coarse aggregates were replaced by an ultra-lightweight material (i.e., expanded polystyrene beads) to produce an equivalent rock-solid mass of concrete. Using an M15 grade of concrete composition, expanded polystyrene (EPS) beads were added in place of aggregates in amounts ranging from 5% to 40% at a water−cement (w/c) ratio of 0.60. The specimen size as per American Society for Testing and Materials (ASTM) specification was 150 mm in diameter and 300 mm in length. Furthermore, statistical analysis for the relationship study for destructive testing (DT) (i.e., compressive test machine) and non-destructive testing (NDT) (i.e., rebound hammer and ultrasonic pulse velocity (UPV)) has been performed at developed specimens u... [more]
Experimental Investigation of Sludge Treatment Using a Rotor-Stator Type Hydrodynamic Cavitation Reactor and an Ultrasonic Bath
Hyunsoo Kim, Xun Sun, Bonchan Koo, Joon Yong Yoon
December 13, 2019 (v1)
Keywords: performance comparison, rotor-stator type hydrodynamic cavitation reactor, sludge treatment, ultrasonication
In the present work, the sludge treatment performance of a sludge treatment using a rotor-stator type hydrodynamic cavitation reactor (HCR) was investigated. To verify the performance, a comparison with an ultrasonic bath was conducted in four experimental cases using three assessment factors. The HCR consisted of a rotor and three covers with inserted dimples resulting in variation of the cross-sectional area in a flow. The experimental cases were established using the same energy consumption for each device. Disintegration performance was analyzed with assessment factors using particle size distribution and sludge volume index (SVI), oxidation performance using total chemical oxygen demand (TCOD) and volatile suspended solids (VSS) reduction rate, as well as solubilization rate using soluble chemical oxygen demand (SCOD). As a result, the particle disintegration and oxidation performance of the HCR were generally superior to those of the ultrasonic bath. However, due to the contradic... [more]
Design, Simulation, and Experiment of an LTCC-Based Xenon Micro Flow Control Device for an Electric Propulsion System
Chang-Bin Guan, Yan Shen, Zhao-Pu Yao, Zhao-Li Wang, Mei-Jie Zhang, Ke Nan, Huan-Huan Hui
December 13, 2019 (v1)
Keywords: electric propulsion system, flow characteristic, low-temperature co-fired ceramic (LTCC), xenon feeding system, xenon micro flow control device (XMFCD)
A xenon micro flow control device (XMFCD) is the key component of a xenon feeding system, which controls the required micro flow xenon (µg/s−mg/s) to electric thrusters. Traditional XMFCDs usually have large volume and weight in order to achieve ultra-high fluid resistance and have a long producing cycle and high processing cost. This paper proposes a miniaturized, easy-processing, and inexpensive XMFCD, which is fabricated by low-temperature co-fired ceramic (LTCC) technology. The design of the proposed XMFCD based on complex three-dimensional (3D) microfluidic channels is described, and its fabrication process based on LTCC is illustrated. The microfluidic channels of the fabricated single (9 mm diameter and 1.4 mm thickness) and dual (9 mm diameter and 2.4 mm thickness) XMFCDs were both checked by X-ray, which proved the LTCC method’s feasibility. A mathematical model of flow characteristics is established with the help of finite element analysis, and the model is validated by the e... [more]
Performance Improvement of a Grid-Tied Neutral-Point-Clamped 3-φ Transformerless Inverter Using Model Predictive Control
Hani Albalawi, Sherif A. Zaid
December 13, 2019 (v1)
Keywords: 3-φ transformerless inverter, boost converter, maximum power point tracking, Model Predictive Control, NPC, PV
Grid-connected photovoltaic (PV) systems are now a common part of the modern power network. A recent development in the topology of these systems is the use of transformerless inverters. Although they are compact, cheap, and efficient, transformerless inverters suffer from chronic leakage current. Various researches have been directed toward evolving their performance and diminishing leakage current. This paper introduces the application of a model predictive control (MPC) algorithm to govern and improve the performance of a grid-tied neutral-point-clamped (NPC) 3-φ transformerless inverter powered by a PV panel. The transformerless inverter was linked to the grid via an inductor/capacitor (LC) filter. The filter elements, as well as the internal impedance of the grid, were considered in the system model. The discrete model of the proposed system was determined, and the algorithm of the MPC controller was established. Matlab’s simulations for the proposed system, controlled by the MPC... [more]
Development of an Electric Arc Furnace Simulator Based on a Comprehensive Dynamic Process Model
Thomas Hay, Thomas Echterhof, Ville-Valtteri Visuri
December 13, 2019 (v1)
Keywords: electric arc furnace, process model, Simulation, steelmaking
A simulator and an algorithm for the automatic creation of operation charts based on process conditions were developed on the basis of an existing comprehensive electric arc furnace process model. The simulator allows direct user input and real-time display of results during the simulation, making it usable for training and teaching of electric arc furnace operators. The automatic control feature offers a quick and automated evaluation of a large number of scenarios or changes in process conditions, raw materials, or equipment used. The operation chart is adjusted automatically to give comparable conditions at tapping and allows the assessment of the necessary changes in the operating strategy as well as their effect on productivity, energy, and resource consumption, along with process emissions.
Dynamic Semi-Quantitative Risk Research in Chemical Plants
Qiusheng Song, Peng Jiang, Song Zheng, Yaguang Kong, Ye Zhao, Gang Shen
December 13, 2019 (v1)
Keywords: analytical hierarchy process, chemical plants, dynamic semi-quantitative calculation, risk value
When a major accident occurs in a chemical industry park, it directly affects the personal safety of operators and neighboring residents and causes major losses; therefore, we should take measures to strengthen the management of chemical industry parks. This article proposes and analyzes a new dynamic semi-quantitative risk calculation model for chemical plants that can be applied digitally. This model provides a sustainable, standardized, and comprehensive management strategy for the safety management of chemical plants and chemical industry park managers. The model and its determined parameters were applied to the safety management of chemical companies within the chemical industry park of Quzhou, Zhejiang Province. From the point of view of the existing semi-quantitative model, the existing problems of the current model are analyzed, the current model is optimized, and a new dynamic semi-quantitative calculation model scheme is proposed. The new model uses an analytical hierarchy pr... [more]
Salp Swarm Optimization Algorithm-Based Controller for Dynamic Response and Power Quality Enhancement of an Islanded Microgrid
Touqeer Ahmed Jumani, Mohd. Wazir Mustafa, Madihah Md. Rasid, Waqas Anjum, Sara Ayub
December 13, 2019 (v1)
Keywords: dynamic response enhancement, microgrid, Optimization, power quality, salp swarm optimization algorithm, voltage and frequency regulation
The islanded mode of the microgrid (MG) operation faces more power quality challenges as compared to grid-tied mode. Unlike the grid-tied MG operation, where the voltage magnitude and frequency of the power system are regulated by the utility grid, islanded mode does not share any connection with the utility grid. Hence, a proper control architecture of islanded MG is essential to control the voltage and frequency, including the power quality and optimal transient response during different operating conditions. Therefore, this study proposes an intelligent and robust controller for islanded MG, which can accomplish the above-mentioned tasks with the optimal transient response and power quality. The proposed controller utilizes the droop control in addition to the back to back proportional plus integral (PI) regulator-based voltage and current controllers in order to accomplish the mentioned control objectives efficiently. Furthermore, the intelligence of the one of the most modern soft... [more]
Extremum Seeking Control for Discrete-Time with Quantized and Saturated Actuators
Martin Guay, Daniel J. Burns
December 13, 2019 (v1)
Keywords: constrained systems, extremum-seeking control, real-time optimization
This paper proposes an extremum-seeking controller (ESC) design for a class of discrete-time nonlinear control systems subject to input constraints or quantized inputs. The proposed method implements a proportional-integral ESC design along with a discrete-time anti-windup mechanism. The anti-windup enforces input saturation while preserving the input dither signal. The technique incorporates a mechanism for adjusting the amplitude of the extremum seeking control dither signal. This mechanism ensures that any violation of constraints due to the dither signal is removed while maintaining the probing signal active. An amplitude update routine is also proposed. The amplitude update is coupled with a saturation bias estimation algorithm that correctly accounts for the inherent bias associated with systems operated at or near saturation conditions. The amplitude update is designed to remove the dither signal when the system approaches the optimum. It also ensures that a lower bound of the a... [more]
A Review of Convex Approaches for Control, Observation and Safety of Linear Parameter Varying and Takagi-Sugeno Systems
Francisco-Ronay López-Estrada, Damiano Rotondo, Guillermo Valencia-Palomo
December 13, 2019 (v1)
Keywords: convex systems, fault diagnosis, fault tolerant control (FTC), linear matrix inequalities (LMIs), linear parameter varying (LPV) systems, Takagi-Sugeno systems
This paper provides a review about the concept of convex systems based on Takagi-Sugeno, linear parameter varying (LPV) and quasi-LPV modeling. These paradigms are capable of hiding the nonlinearities by means of an equivalent description which uses a set of linear models interpolated by appropriately defined weighing functions. Convex systems have become very popular since they allow applying extended linear techniques based on linear matrix inequalities (LMIs) to complex nonlinear systems. This survey aims at providing the reader with a significant overview of the existing LMI-based techniques for convex systems in the fields of control, observation and safety. Firstly, a detailed review of stability, feedback, tracking and model predictive control (MPC) convex controllers is considered. Secondly, the problem of state estimation is addressed through the design of proportional, proportional-integral, unknown input and descriptor observers. Finally, safety of convex systems is discusse... [more]
Adaptive Control of Biomass Specific Growth Rate in Fed-Batch Biotechnological Processes. A Comparative Study
Vytautas Galvanauskas, Rimvydas Simutis, Vygandas Vaitkus
December 13, 2019 (v1)
Keywords: adaptive control, biotechnological processes, fed-batch process, gain scheduling technique, model-free adaptive control, specific growth rate control
This article presents a comparative study on the development and application of two distinct adaptive control algorithms for biomass specific growth rate control in fed-batch biotechnological processes. A typical fed-batch process using Escherichia coli for recombinant protein production was selected for this research. Numerical simulation results show that both developed controllers, an adaptive PI controller based on the gain scheduling technique and a model-free adaptive controller based on the artificial neural network, delivered a comparable control performance and are suitable for application when using the substrate limitation approach and substrate feeding rate manipulation. The controller performance was tested within the realistic ranges of the feedback signal sampling intervals and measurement noise intensities. Considering the efforts for controller design and tuning, including development of the adaptation/learning algorithms, the model-free adaptive control algorithm prov... [more]
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