Periodic optimal control for biomass productivity maximization in a photobioreactor using natural light

We address the question of optimization of the microalgal biomass long term productivity in the framework of production in photobioreactors under the influence of day/night cycles. For that, we propose a simple bioreactor model accounting for light attenuation in the reactor due to biomass density and obtain the control law that optimizes productivity over a single day through the application of Pontryagin's maximum principle, with the dilution rate being the main control. An important constraint on the obtained solution is that the biomass in the reactor should be at the same level at the beginning and at the end of the day so that the same control can be applied everyday and optimizes some form of long term productivity. Several scenarios are possible depending on the microalgae's strain parameters and the maximal admissible value of the dilution rate: bang-bang or bang-singular-bang control or, if the growth rate of the algae is very strong in the presence of light, constant maximal dilution. A bifurcation diagram is presented to illustrate for which values of the parameters these different behaviors occur. Finally, a simple sub-optimal bang-bang strategy is proposed that numerically achieves productivity levels that almost match those of the optimal strategy

Компьютерное моделирование напряженно-деформированного состояния сварных конструкций

В данной работе показано, что при оценке и обеспечении живучести сварныхметаллоконструкций важную роль играют технологические факторы. Учет их влияния реализуется на основе применения метода конечных элементов. Описана численная методика расчета остаточных сварочных напряжений и деформаций в элементах сварных металлоконструкций.Численнообосновантехнологическийметодповышенияживучестиуказанногоклассаметаллоконструкций

Optimal life-history strategies in seasonal consumer-resource dynamics.

International audienceThe interplay between individual adaptive life histories and populations dynamics is an important issue in ecology. In this context, we considered a seasonal consumer-resource model with nonoverlapping generations. We focused on the consumers decision-making process through which they maximize their reproductive output via a differential investment into foraging for resources or reproducing. Our model takes a semi-discrete form, and is composed of a continuous time within-season part, similar to a dynamic model of energy allocation, and of a discrete time part, depicting the between seasons reproduction and mortality processes. We showed that the optimal foraging-reproduction strategies of the consumers may be "determinate" or "indeterminate" depending on the season length. More surprisingly, it depended on the consumers population density as well, with large densities promoting indeterminacy. A bifurcation analysis showed that the long-term dynamics produced by this model were quite rich, ranging from both populations' extinction, coexistence at some season-to-season equilibrium or on (quasi)-periodic motions, to initial condition-dependent dynamics. Interestingly, we observed that any long-term sustainable situation corresponds to indeterminate consumers' strategies. Finally, a comparison with a model involving typical nonoptimal consumers highlighted the stabilizing effects of the optimal life histories of the consumers

Применение МКЭ для анализа сварных конструкций с дефектами типа трещин

В данной работе исследован нелинейный процесс деформирования сварных конструкций с трещиноподобными дефектами. В качестве основного параметра используется энергетический J-интеграл и эквивалентная пластическая деформация. Величину J-интеграла для элемента конструкции с трещиной можно определить численными методами, например методом конечных элементов. Автоматизированный анализ изделий с трещиноподобными дефектами осуществлялся с использованием программного комплекса ANSYS и программного комплекса CRACK, разработанным в Карагандинском государственном техническом университете (КарГТУ)

Coal Supply Chain Management and Economic Efficiency of using High-Ash Coking Coal in Ferroalloy Manufacturing

In the global competitive environment, metallurgical industries reach progress through cuts in production costs. In this light, the priorities to boost ferroalloy manufacturing include the effective innovative material- and energy-saving technologies, which are applied to alternative carbonaceous reducing agents used in ferroalloy production. Additionally to a regression model for predicting the average annual world prices for steel, this article assesses the economic efficiency of using weak coking coals in ferroalloy manufacturing. This study also explores the relationship between supply chain management and production cost considered a key factor in supply chain management. The factors influencing price behaviour are the capacity of the world metallurgical plants and the price for coking coal. The economic efficiency of using high-ash coking coal to produce ferroalloys was studied on the ferrosilicoaluminium (FeSiAl) FS55A20 against the ferrosilicon FS75. The comparative analysis was performed using economic-mathematical modelling. The commercial efficiency of investment projects was studied using statistical (payback period) and dynamic (net present value) methods. Based on these factors, the steel price forecast was made for 2019–2023. In ferroalloy manufacturing, the shift from ferrosilicon FS75 to ferrosilicoaluminium FS55A20 will bring a profit of USD 2.1 million annually. The average payback period for investments in the project was 2 years. The calculated net present value of the project was USD 2.4 million. The analysis resulted in the outline of the main factors to consider when choosing a strategy of supply chain management

Optimization of a photobioreactor biomass production using natural light

We address the question of optimization of the biomass long term productivity in the framework of microalgal biomass production in photobioreactors under the influence of day/night cycles. For that, we propose a simple bioreactor model accounting for light attenuation in the reactor due to biomass density and obtain the control law that optimizes productivity over a single day through the application of Pontryagin's maximum principle, with the dilution rate being the control. An important constraint on the obtained solution is that the biomass in the reactor should be at the same level at the beginning and at the end of the day so that the same control can be applied everyday and optimizes the long term productivity. Several scenarios are possible depending on the microalgae's strain parameters and the maximal admissible value of the dilution rate: bang-bang or bang-singular-bang control or, if the growth rate of the algae is very strong in the presence of light, constant maximal dilution. A bifurcation diagram is presented to illustrate for which values of the parameters these different behaviors occur