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Records with Keyword: Optimization
Showing records 1 to 25 of 29. [First] Page: 1 2 Last
Earliest Deadline Control of a Group of Heat Pumps with a Single Energy Source
Jiří Fink, Richard P. van Leeuwen
January 7, 2019 (v1)
Keywords: combined heat and power control, domestic hot water, floor heating, heat pump control, Model Predictive Control, Optimization, renewable energy integration, smart grids, smart control, thermal storage
In this paper, we develop and investigate the optimal control of a group of 104 heat pumps and a central Combined Heat and Power unit (CHP). The heat pumps supply space heating and domestic hot water to households. Each house has a buffer for domestic hot water and a floor heating system for space heating. Electricity for the heat pumps is generated by a central CHP unit, which also provides thermal energy to a district heating system. The paper reviews recent smart grid control approaches for central and distributed levels. An online algorithm is described based on the earliest deadline first theory that can be used on the aggregator level to control the CHP and to give signals to the heat pump controllers if they should start or should wait. The central controller requires only a limited amount of privacy-insensitive information from the heat pump controllers about their deadlines, which the heat pump controllers calculate for themselves by model predictions. In this way, a robust he... [more]
Real Time Information Based Energy Management Using Customer Preferences and Dynamic Pricing in Smart Homes
Muhammad Babar Rasheed, Nadeem Javaid, Muhammad Awais, Zahoor Ali Khan, Umar Qasim, Nabil Alrajeh, Zafar Iqbal, Qaisar Javaid
January 7, 2019 (v1)
Keywords: demand side management, energy management, genetic algorithm (GA), knapsack, microgird, Optimization, programmable communication thermostat, real time pricing, smart grid (SG)
This paper presents real time information based energy management algorithms to reduce electricity cost and peak to average ratio (PAR) while preserving user comfort in a smart home. We categorize household appliances into thermostatically controlled (tc), user aware (ua), elastic (el), inelastic (iel) and regular (r) appliances/loads. An optimization problem is formulated to reduce electricity cost by determining the optimal use of household appliances. The operational schedules of these appliances are optimized in response to the electricity price signals and customer preferences to maximize electricity cost saving and user comfort while minimizing curtailed energy. Mathematical optimization models of tc appliances, i.e., air-conditioner and refrigerator, are proposed which are solved by using intelligent programmable communication thermostat ( iPCT). We add extra intelligence to conventional programmable communication thermostat (CPCT) by using genetic algorithm (GA) to control tc a... [more]
Optimal Planning of Sustainable Buildings: Integration of Life Cycle Assessment and Optimization in a Decision Support System (DSS)
Fabio Magrassi, Adriana Del Borghi, Michela Gallo, Carlo Strazza, Michela Robba
December 3, 2018 (v1)
Keywords: decision support system (DSS), life cycle assessment (LCA), nearly-zero energy buildings, Optimization, sustainable buildings
Energy efficiency measures in buildings can provide for a significant reduction of greenhouse gas (GHG) emissions. A sustainable design and planning of technologies for energy production should be based on economic and environmental criteria. Life Cycle Assessment (LCA) is used to quantify the environmental impacts over the whole cycle of life of production plants. Optimization models can support decisions that minimize costs and negative impacts. In this work, a multi-objective decision problem is formalized that takes into account LCA calculations and that minimizes costs and GHG emissions for general buildings. A decision support system (DSS) is applied to a real case study in the Northern Italy, highlighting the advantage provided by the installation of renewable energy. Moreover, a comparison among different optimal and non optimal solution was carried out to demonstrate the effectiveness of the proposed DSS.
Online Power Management with Embedded Offline-Optimized Parameters for a Three-Source Hybrid Powertrain with an Experimental Emulation Application
Bedatri Moulik, Dirk Söffker
November 28, 2018 (v1)
Keywords: HEV, Optimization, rule-based power management
Real-time power management in the presence of one or more reversible energy storage systems is a current issue with hybrid electric vehicles (HEVs). To evaluate the potentials of rule-based power management, optimization with respect to two conflicting objectives, fuel consumption and state of charge (SoC) deviation, is considered in this contribution. A modular structure of power management with decoupled offline and online parts is presented. The online part incorporates look-up tables (LUTs) with parameters from the offline optimization part. This permits an inclusion of more LUTs corresponding to different drive patterns. The goal of this contribution is to combine the real-time applicability of rule-based power management and the multi-objective optimization property of genetic algorithms in a single control strategy. Component aging problems are addressed by suitable design. The influence of sizing is investigated. Finally, an experimental setup consisting of components capable o... [more]
Quantifying the Impact of Feedstock Quality on the Design of Bioenergy Supply Chain Networks
Krystel K. Castillo-Villar, Hertwin Minor-Popocatl, Erin Webb
November 27, 2018 (v1)
Subject: Biosystems
Keywords: bioenergy, bioethanol, Biomass, logging residues, logistics, Optimization, quality costing, supply chain network design
Logging residues, which refer to the unused portions of trees cut during logging, are important sources of biomass for the emerging biofuel industry and are critical feedstocks for the first-type biofuel facilities (e.g., corn-ethanol facilities). Logging residues are under-utilized sources of biomass for energetic purposes. To support the scaling-up of the bioenergy industry, it is essential to design cost-effective biofuel supply chains that not only minimize costs, but also consider the biomass quality characteristics. The biomass quality is heavily dependent upon the moisture and the ash contents. Ignoring the biomass quality characteristics and its intrinsic costs may yield substantial economic losses that will only be discovered after operations at a biorefinery have begun. This paper proposes a novel bioenergy supply chain network design model that minimizes operational costs and includes the biomass quality-related costs. The proposed model is unique in the sense that it suppor... [more]
Distributed Renewable Generation and Storage System Sizing Based on Smart Dispatch of Microgrids
Raji Atia, Noboru Yamada
November 27, 2018 (v1)
Keywords: demand response (DR), distributed power generation, energy management, Energy Storage, microgrid (MG), Optimization
This paper considers the contribution of independent owners (IOs) operating within microgrids (MGs) toward green power generation in deregulated energy markets. An optimization scheme is introduced for sizing distributed renewable generation (DRG) and a distributed energy storage system (DESS) based on a novel energy management system (EMS) that accounts for demand response (DR), DESS dispatch and performance degradation, dynamic pricing environments, power distribution loss and irregular renewable generation. The proposed EMS utilizes an iterative Newton-Raphson linear programming algorithm that schedules resources in order to minimize the objective function, to deal with the complicated nonlinear nature of the problem and to enable efficient long-term assessments. The EMS is used to evaluate candidate solutions that are generated by a genetic algorithm (GA) to determine the optimal combination of DRG and DESS. A case study for IEEE 34-bus distribution MG in Okinawa, Japan, is used fo... [more]
Optimal Power Management Strategy for Energy Storage with Stochastic Loads
Stefano Pietrosanti, William Holderbaum, Victor M. Becerra
November 27, 2018 (v1)
Keywords: Energy Storage, flywheel, Optimization, power management, RTG crane, stochastic loads
In this paper, a power management strategy (PMS) has been developed for the control of energy storage in a system subjected to loads of random duration. The PMS minimises the costs associated with the energy consumption of specific systems powered by a primary energy source and equipped with energy storage, under the assumption that the statistical distribution of load durations is known. By including the variability of the load in the cost function, it was possible to define the optimality criteria for the power flow of the storage. Numerical calculations have been performed obtaining the control strategies associated with the global minimum in energy costs, for a wide range of initial conditions of the system. The results of the calculations have been tested on a MATLAB/Simulink model of a rubber tyre gantry (RTG) crane equipped with a flywheel energy storage system (FESS) and subjected to a test cycle, which corresponds to the real operation of a crane in the Port of Felixstowe. The... [more]
Diesel-Minimal Combustion Control of a Natural Gas-Diesel Engine
Florian Zurbriggen, Richard Hutter, Christopher Onder
October 23, 2018 (v1)
Keywords: closed-loop control, combustion control, Diesel, dual fuel, engine control, extremum seeking, internal combustion engine, Natural Gas, Optimization
This paper investigates the combustion phasing control of natural gas-diesel engines. In this study, the combustion phasing is influenced by manipulating the start and the duration of the diesel injection. Instead of using both degrees of freedom to control the center of combustion only, we propose a method that simultaneously controls the combustion phasing and minimizes the amount of diesel used. Minimizing the amount of diesel while keeping the center of combustion at a constant value is formulated as an optimization problem with an equality constraint. A combination of feedback control and extremum seeking is used to solve this optimization problem online. The necessity to separate the different time scales is discussed and a structure is proposed that facilitates this separation for this specific example. The proposed method is validated by experiments on a test bench.
Assessing the Potential of Plug-in Electric Vehicles in Active Distribution Networks
Reza Ahmadi Kordkheili, Seyyed Ali Pourmousavi, Mehdi Savaghebi, Josep M. Guerrero, Mohammad Hashem Nehrir
October 23, 2018 (v1)
Keywords: Optimization, photovoltaic (PV) panels, plug-in electric vehicle (PEV), state of charge (SoC), vehicle to grid (V2G)
A multi-objective optimization algorithm is proposed in this paper to increase the penetration level of renewable energy sources (RESs) in distribution networks by intelligent management of plug-in electric vehicle (PEV) storage. The proposed algorithm is defined to manage the reverse power flow (PF) from the distribution network to the upstream electrical system. Furthermore, a charging algorithm is proposed within the proposed optimization in order to assure PEV owner’s quality of service (QoS). The method uses genetic algorithm (GA) to increase photovoltaic (PV) penetration without jeopardizing PEV owners’ (QoS) and grid operating limits, such as voltage level of the grid buses. The method is applied to a part of the Danish low voltage (LV) grid to evaluate its effectiveness and capabilities. Different scenarios have been defined and tested using the proposed method. Simulation results demonstrate the capability of the algorithm in increasing solar power penetration in the grid up t... [more]
Optimal Coordinated Control of Power Extraction in LES of a Wind Farm with Entrance Effects
Jay P. Goit, Wim Munters, Johan Meyers
October 23, 2018 (v1)
Keywords: adjoints, large eddy simulations, Optimization, turbulent boundary layers, wind farm, wind farm control
We investigate the use of optimal coordinated control techniques in large eddy simulations of wind farm boundary layer interaction with the aim of increasing the total energy extraction in wind farms. The individual wind turbines are considered as flow actuators, and their energy extraction is dynamically regulated in time, so as to optimally influence the flow field. We extend earlier work on wind farm optimal control in the fully-developed regime (Goit and Meyers 2015, J. Fluid Mech. 768, 5⁻50) to a ‘finite’ wind farm case, in which entrance effects play an important role. For the optimal control, a receding horizon framework is employed in which turbine thrust coefficients are optimized in time and per turbine. Optimization is performed with a conjugate gradient method, where gradients of the cost functional are obtained using adjoint large eddy simulations. Overall, the energy extraction is increased 7% by the optimal control. This increase in energy extraction is related to faster... [more]
Approximating Nonlinear Relationships for Optimal Operation of Natural Gas Transport Networks
Kody Kazda, Xiang Li
October 13, 2018 (v1)
Subject: Optimization
Keywords: Compressors, Fuel Cost Minimization Problem, GAMS, Matlab, Natural Gas, Optimization
Source code for the case study presented in the paper "Approximating Nonlinear Relationships for Optimal Operation of Natural Gas Transport Networks". The case study involves solving the compressor fuel cost minimization problem (FCMP) on three simple natural gas networks. For each gas network three different formulations of the FCMP are tested: a common simplified FCMP model (FCMP_S), the novel approximation FCMP model (FCMP_N) that is developed in the paper, and a partially rigorous FCMP model (FCMP_PR) that models components of the model using their most rigorous calculations where feasible. The FCMP for each of these tests was optimized using GAMS, for which the code is provided. The accuracy of each of the three models was then assessed by comparing them to a rigorous simulation. The rigorous simulation was coded in Matlab and is provided, where separate files are used to calculate the rigorous gas pressure drop along a pipeline, and the energy input required for gas compression... [more]
Fuel-Optimal Thrust-Allocation Algorithm Using Penalty Optimization Programing for Dynamic-Positioning-Controlled Offshore Platforms
Se Won Kim, Moo Hyun Kim
September 21, 2018 (v1)
Subject: Optimization
Keywords: dynamic positioning, fuel consumption, Genetic Algorithm, Optimization, penalty programming, pseudo-inverse, quadratic-programming, thrust allocation, thruster arrangement, turret-moored FPSO
This research, a new thrust-allocation algorithm based on penalty programming is developed to minimize the fuel consumption of offshore vessels/platforms with dynamic positioning system. The role of thrust allocation is to produce thruster commands satisfying required forces and moments for position-keeping, while fulfilling mechanical constraints of the control system. The developed thrust-allocation algorithm is mathematically formulated as an optimization problem for the given objects and constraints of a dynamic positioning system. Penalty programming can solve the optimization problems that have nonlinear object functions and constraints. The developed penalty-programming thrust-allocation method is implemented in the fully-coupled vessel⁻riser⁻mooring time-domain simulation code with dynamic positioning control. Its position-keeping and fuel-saving performance is evaluated by comparing with other conventional methods, such as pseudo-inverse, quadratic-programming, and genetic-alg... [more]
Identification of the Heat Equation Parameters for Estimation of a Bare Overhead Conductor’s Temperature by the Differential Evolution Algorithm
Mirza Sarajlić, Jože Pihler, Nermin Sarajlić, Gorazd Štumberger
September 21, 2018 (v1)
Keywords: conductor temperature, measurement, Optimization, overhead transmission line, parameter identification, Simulation
This paper deals with the Differential Evolution (DE) based method for identification of the heat equation parameters applied for the estimation of a bare overhead conductor`s temperature. The parameters are determined in the optimization process using a dynamic model of the conductor; the measured environmental temperature, solar radiation and wind velocity; the current and temperature measured on the tested overhead conductor; and the DE, which is applied as the optimization tool. The main task of the DE is to minimise the difference between the measured and model-calculated conductor temperatures. The conductor model is relevant and suitable for the prediction of the conductor temperature, as the agreement between measured and model-calculated conductor temperatures is exceptional, where the deviation between mean and maximum measured and model-calculated conductor temperatures is less than 0.03 °C.
The Optimization of Hybrid Power Systems with Renewable Energy and Hydrogen Generation
Fu-Cheng Wang, Yi-Shao Hsiao, Yi-Zhe Yang
September 20, 2018 (v1)
Keywords: cost, fuel cell, hybrid power system, Hydrogen, Optimization, reliability, solar, Wind
This paper discusses the optimization of hybrid power systems, which consist of solar cells, wind turbines, fuel cells, hydrogen electrolysis, chemical hydrogen generation, and batteries. Because hybrid power systems have multiple energy sources and utilize different types of storage, we first developed a general hybrid power model using the Matlab/SimPowerSystemTM, and then tuned model parameters based on the experimental results. This model was subsequently applied to predict the responses of four different hybrid power systems for three typical loads, without conducting individual experiments. Furthermore, cost and reliability indexes were defined to evaluate system performance and to derive optimal system layouts. Finally, the impacts of hydrogen costs on system optimization was discussed. In the future, the developed method could be applied to design customized hybrid power systems.
Optimization of Coke Oven Gas Desulphurization and Combined Cycle Power Plant Electricity Generation
焦炉煤气除硫以及联合循环发电的优化
LINGYAN DENG, Thomas A. Adams II
September 12, 2018 (v3)
Subject: Optimization
Keywords: carbon tax, coke oven gas valorization, combined cycle power plant, desulphurization, net present value, Optimization, steel refinery
Many steel refineries generate significant quantities of coke oven gas (COG), which is in some cases used only to generate low pressure steam and small amounts of electric power. In order to improve energy efficiency and reduce net greenhouse gas emissions, a combined cycle power plant (CCPP) where COG is used as fuel is proposed. However, desulphurization is necessary before the COG can be used as a fuel input for CCPP. Using a local steel refinery as a case study, a proposed desulphurization process is designed to limit the H2S content in COG to less than 1 ppmv, and simulated using ProMax. In addition, the proposed CCPP plant is simulated in Aspen Plus and is optimized using GAMS to global optimality with net present value as the objective function. Furthermore, carbon tax is considered in this study. The optimized CCPP plant was observed to generate more than twice the electrical efficiency when compared to the status quo for the existing steel refinery. Thus, by generating more e... [more]
很多炼钢厂排放大量焦炉煤气。大部分焦炉煤气被用于燃烧来生产低压蒸汽以及通过汽轮机生产少量的电。为了提高发电效率并减少温室效应,本文提出运用联合循环发电来替代蒸汽发电。不同于现有的蒸汽发电的是,在联合循环发电过程中,焦炉煤气必须经过脱硫处理。基于当地炼钢厂的情况,本文提出并设计了焦炉煤气脱硫方案,使得焦炉煤气中H2S含量低于1 ppmv。该脱硫过程采用ProMax模拟。联合循环发电采用Aspen Plus模拟。并且整个联合循环发电过程又用GAMS软件模拟,以最大化纯现价为目标来优化整个联合循环发电过程。本文还考虑了二氧化碳排放税对纯现价的影响。优化后的联合循环发电效率是现有的低压蒸汽发电的两倍多。因此,通过提高发电效率,钢铁厂所需购买电量降低,也因而从生命周期的角度来说大大减少了二氧化碳的排放量。
A Cybernetic Approach to Modeling Lipid Metabolism in Mammalian Cells
Lina Aboulmouna, Shakti Gupta, Mano R. Maurya, Frank T. DeVilbiss, Shankar Subramaniam, Doraiswami Ramkrishna
August 28, 2018 (v1)
Keywords: cybernetic modeling, lipids, metabolic objective functions, omics data, Optimization, prostaglandin metabolism
The goal-oriented control policies of cybernetic models have been used to predict metabolic phenomena such as the behavior of gene knockout strains, complex substrate uptake patterns, and dynamic metabolic flux distributions. Cybernetic theory builds on the principle that metabolic regulation is driven towards attaining goals that correspond to an organism’s survival or displaying a specific phenotype in response to a stimulus. Here, we have modeled the prostaglandin (PG) metabolism in mouse bone marrow derived macrophage (BMDM) cells stimulated by Kdo2-Lipid A (KLA) and adenosine triphosphate (ATP), using cybernetic control variables. Prostaglandins are a well characterized set of inflammatory lipids derived from arachidonic acid. The transcriptomic and lipidomic data for prostaglandin biosynthesis and conversion were obtained from the LIPID MAPS database. The model parameters were estimated using a two-step hybrid optimization approach. A genetic algorithm was used to determine the p... [more]
Modelling of a Naphtha Recovery Unit (NRU) with Implications for Process Optimization
Jiawei Du, William R. Cluett
July 31, 2018 (v1)
Keywords: naphtha recovery unit, Optimization, Simulation, statistical model
The naphtha recovery unit (NRU) is an integral part of the processes used in the oil sands industry for bitumen extraction. The principle role of the NRU is to recover naphtha from the tailings for reuse in this process. This process is energy-intensive, and environmental guidelines for naphtha recovery must be met. Steady-state models for the NRU system are developed in this paper using two different approaches. The first approach is a statistical, data-based modelling approach where linear regression models have been developed using Minitab® from plant data collected during a performance test. The second approach involves the development of a first-principles model in Aspen Plus® based on the NRU process flow diagram. A novel refinement to this latter model, called “withdraw and remix„, is proposed based on comparing actual plant data to model predictions around the two units used to separate water and naphtha. The models developed in this paper suggest some interesting ideas for the... [more]
Optimal Multiscale Capacity Planning in Seawater Desalination Systems
Hassan Baaqeel, Mahmoud M. El-Halwagi
July 31, 2018 (v1)
Subject: Optimization
Keywords: desalination, membrane distillation, multi-effect distillation, Optimization, process integration, Scheduling
The increasing demands for water and the dwindling resources of fresh water create a critical need for continually enhancing desalination capacities. This poses a challenge in distressed desalination network, with incessant water demand growth as the conventional approach of undertaking large expansion projects can lead to low utilization and, hence, low capital productivity. In addition to the option of retrofitting existing desalination units or installing additional grassroots units, there is an opportunity to include emerging modular desalination technologies. This paper develops the optimization framework for the capacity planning in distressed desalination networks considering the integration of conventional plants and emerging modular technologies, such as membrane distillation (MD), as a viable option for capacity expansion. The developed framework addresses the multiscale nature of the synthesis problem, as unit-specific decision variables are subject to optimization, as well... [more]
An Optimization Scheme for Water Pump Control in Smart Fish Farm with Efficient Energy Consumption
Israr Ullah, DoHyeun Kim
July 31, 2018 (v1)
Subject: Optimization
Keywords: Energy Efficiency, fish farm, IoT, Kalman filter, Optimization
Healthy fish production requires intensive care and ensuring stable and healthy production environment inside the farm tank is a challenging task. An Internet of Things (IoT) based automated system is highly desirable that can continuously monitor the fish tanks with optimal resources utilization. Significant cost reduction can be achieved if farm equipment and water pumps are operated only when required using optimization schemes. In this paper, we present a general system design for smart fish farms. We have developed an optimization scheme for water pump control to maintain desired water level in fish tank with efficient energy consumption through appropriate selection of pumping flow rate and tank filling level. Proposed optimization scheme attempts to achieve a trade-off between pumping duration and flow rate through selection of optimized water level. Kalman filter algorithm is applied to remove error in sensor readings. We observed through simulation results that optimization sc... [more]
An Integrated Approach to Water-Energy Nexus in Shale-Gas Production
Fadhil Y. Al-Aboosi, Mahmoud M. El-Halwagi
July 31, 2018 (v1)
Keywords: cogeneration, desalination, Optimization, process integration, solar energy, thermal storage
Shale gas production is associated with significant usage of fresh water and discharge of wastewater. Consequently, there is a necessity to create proper management strategies for water resources in shale gas production and to integrate conventional energy sources (e.g., shale gas) with renewables (e.g., solar energy). The objective of this study is to develop a design framework for integrating water and energy systems including multiple energy sources, the cogeneration process and desalination technologies in treating wastewater and providing fresh water for shale gas production. Solar energy is included to provide thermal power directly to a multi-effect distillation plant (MED) exclusively (to be more feasible economically) or indirect supply through a thermal energy storage system. Thus, MED is driven by direct or indirect solar energy and excess or direct cogeneration process heat. The proposed thermal energy storage along with the fossil fuel boiler will allow for the dual-purpos... [more]
Fuel Gas Network Synthesis Using Block Superstructure
Jianping Li, Salih Emre Demirel, M. M. Faruque Hasan
July 31, 2018 (v1)
Keywords: block superstructure, fuel gas network synthesis, MINLP, Optimization, process integration
Fuel gas network (FGN) synthesis is a systematic method for reducing fresh fuel consumption in a chemical plant. In this work, we address FGN synthesis problems using a block superstructure representation that was originally proposed for process design and intensification. The blocks interact with each other through direct flows that connect a block with its adjacent blocks and through jump flows that connect a block with all nonadjacent blocks. The blocks with external feed streams are viewed as fuel sources and the blocks with product streams are regarded as fuel sinks. An additional layer of blocks are added as pools when there exists intermediate operations among source and sink blocks. These blocks can be arranged in a I × J two-dimensional grid with I = 1 for problems without pools, or I = 2 for problems with pools. J is determined by the maximum number of pools/sinks. With this representation, we formulate FGN synthesis problem as a mixed-integer nonlinear... [more]
Methanol Synthesis: Optimal Solution for a Better Efficiency of the Process
Grazia Leonzio
July 31, 2018 (v1)
Keywords: ANOVA analysis, equilibrium reactions, methanol reaction, Optimization, response surface methodology
In this research, an ANOVA analysis and a response surface methodology are applied to analyze the equilibrium of methanol reaction from pure carbon dioxide and hydrogen. In the ANOVA analysis, carbon monoxide composition in the feed, reaction temperature, recycle and water removal through a zeolite membrane are the analyzed factors. Carbon conversion, methanol yield, methanol productivity and methanol selectivity are the analyzed responses. Results show that main factors have the same effect on responses and a common significant interaction is not present. Carbon monoxide composition and water removal have a positive effect, while temperature and recycle have a negative effect on the system. From central composite design, an optimal solution is found in order to overcome thermodynamic limit: the reactor works with a membrane at lower temperature with carbon monoxide composition in the feed equal to 10 mol % and without recycle. In these conditions, carbon conversion, methanol yield, me... [more]
Optimization of Stimulation Parameters for Targeted Activation of Multiple Neurons Using Closed-Loop Search Methods
Michelle L. Kuykendal, Stephen P. DeWeerth, Martha A. Grover
July 31, 2018 (v1)
Subject: Optimization
Keywords: closed-loop, dissociated culture, extracellular electrical stimulation, feedback, micro-electrode array (MEA), Optimization, Powell
Differential activation of neuronal populations can improve the efficacy of clinical devices such as sensory or cortical prostheses. Improving stimulus specificity will facilitate targeted neuronal activation to convey biologically realistic percepts. In order to deliver more complex stimuli to a neuronal population, stimulus optimization techniques must be developed that will enable a single electrode to activate subpopulations of neurons. However, determining the stimulus needed to evoke targeted neuronal activity is challenging. To find the most selective waveform for a particular population, we apply an optimization-based search routine, Powell’s conjugate direction method, to systematically search the stimulus waveform space. This routine utilizes a 1-D sigmoid activation model and a 2-D strength⁻duration curve to measure neuronal activation throughout the stimulus waveform space. We implement our search routine in both an experimental study and a simulation study to characterize... [more]
Optimization through Response Surface Methodology of a Reactor Producing Methanol by the Hydrogenation of Carbon Dioxide
Grazia Leonzio
July 31, 2018 (v1)
Subject: Optimization
Keywords: ANOVA analysis, carbon capture and utilization, methanol production, Optimization, process simulation, response surface methodology
Carbon dioxide conversion and utilization is gaining significant attention worldwide, not only because carbon dioxide has an impact on global climate change, but also because it provides a source for potential fuels and chemicals. Methanol is an important fuel that can be obtained by the hydrogenation of carbon dioxide. In this research, the modeling of a reactor to produce methanol using carbon dioxide and hydrogen is carried out by way of an ANOVA and a central composite design. Reaction temperature, reaction pressure, H₂/CO₂ ratio, and recycling are the chosen factors, while the methanol production and the reactor volume are the studied responses. Results show that the interaction AC is common between the two responses and allows improvement of the productivity in reducing the volume. A mathematical model for methanol production and reactor volume is obtained with significant factors. A central composite design is used to optimize the process. Results show that a higher productivity... [more]
Improving Bioenergy Crops through Dynamic Metabolic Modeling
Mojdeh Faraji, Eberhard O. Voit
July 31, 2018 (v1)
Keywords: biochemical systems theory, biofuel, lignin biosynthesis, Optimization, plant metabolism, recalcitrance
Enormous advances in genetics and metabolic engineering have made it possible, in principle, to create new plants and crops with improved yield through targeted molecular alterations. However, while the potential is beyond doubt, the actual implementation of envisioned new strains is often difficult, due to the diverse and complex nature of plants. Indeed, the intrinsic complexity of plants makes intuitive predictions difficult and often unreliable. The hope for overcoming this challenge is that methods of data mining and computational systems biology may become powerful enough that they could serve as beneficial tools for guiding future experimentation. In the first part of this article, we review the complexities of plants, as well as some of the mathematical and computational methods that have been used in the recent past to deepen our understanding of crops and their potential yield improvements. In the second part, we present a specific case study that indicates how robust models... [more]
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