Robust optimization of multistage process: response surface and multi-response optimization approaches

A multistage system refers to a system contains multiple components or stages which are necessary to finish the final product or service. To analyze these problems, the first step is model building and the other is optimization. Response surfaces are used to model multistage problem as an efficient procedure. One regular approach to estimate a response surface using experimental results is the ordinary least squares (OLS) method. OLS method is very sensitive to outliers, so some multivariate robust estimation methods have been discussed in the literature in order to estimate the response surfaces accurately such as multivariate M-estimators. In optimization phase, multi-response optimization methods such as global criterion (GC) method and ε-constraints approaches are different methods to optimize the multi-objective-multistage problems. An example of the multistage problem had been estimated considering multivariate robust approaches, besides applying multi-response optimization approaches. The results show the efficiency of the proposed approaches.

Multistage Constructed Wetland in the Treatment of Greywater under Tropical Conditions: Performance, Operation, and Maintenance

Greywater (GW) can be separated in different fractions where the kitchen component might be included. Constructed wetland (CW) systems are commonly used for the onsite treatment of GW, and the fraction treated might impact the performance, operation, and maintenance. These aspects are still poorly explored in the literature and are of importance for a proper design and system sustainability. In this study, a multi-stage household-scale CW system composed of a horizontal flow (HF), followed by a vertical flow (VF) unit, was monitored over 1330 days, focusing on different GW fractions and hydraulic and organic loading rates. The biochemical oxygen demand (BOD) was ~50% lower without the kitchen sink component (GWL) in the system inlet, while no drop was observed in the chemical oxygen demand (COD). Treatment with the GWL component caused a sudden drop in the hydraulic loading rate applied at the HF-CW (~114 to 35 mm per day) and the VF-CW (~230 to 70 mm per day). Even when the HF-CW received ~90 gCOD m−2 per day (GW), the multistage system reached a COD removal of 90%. The lower BOD load when treating GWL avoids clogging and decreases the frequency of maintenance. These variables can be used for the optimal design and operation of a CW, contributing with empirical data to CW guidelines in Brazil, and could additionally be expanded for application in other countries with similar climates.

Assessment of an Integrated and Sustainable Multistage System for the Treatment of Poultry Slaughterhouse Wastewater

This paper assesses the performance of an integrated multistage laboratory-scale plant, for the treatment of poultry slaughterhouse wastewater (PSW). The system was comprised of an eco-flush dosed bio-physico pre-treatment unit for fats, oil, and grease (FOG) hydrolysis prior to the PSW being fed to a down-flow expanded granular bed reactor (DEGBR), coupled to a membrane bioreactor (DEGBR-MBR). The system’s configuration strategy was developed to achieve optimal PSW treatment by introducing the enzymatic pre-treatment unit for the lipid-rich influent (PSW) in order to treat FOG including odour causing constituents such as H2S known to sour anaerobic digestion (AD) such that the PSW pollutant load is alleviated prior to AD treatment. This was conducted to aid the reduction in clogging and sludge washout in the DEGBR-MBR systems and to achieve the optimum reactor and membrane system performance. A performance for the treatment of PSW after lipid reduction was conducted through a qualitative analysis by assessing the pre- and post-pre-treatment units’ chemical oxygen demand (COD), total suspended solids (TSS), and FOG concentrations across all other units and, in particular, the membrane units. Furthermore, a similar set-up and operating conditions in a comparative study was also performed. The pre-treatment unit’s biodelipidation abilities were characterised by a mean FOG removal of 80% and the TSS and COD removal reached 38 and 56%, respectively. The final acquired removal results on the DEGBR, at an OLR of ~18–45 g COD/L.d, was 87, 93, and 90% for COD, TSS, and FOG, respectively. The total removal efficiency across the pre-treatment-DEGBR-MBR units was 99% for COD, TSS, and FOG. Even at a high OLR, the pre-treatment-DEGBR-MBR train seemed a robust treatment strategy and achieved the effluent quality set requirements for effluent discharge in most countries.

An efficient method for vibration equations with time varying coefficients and nonlinearities

An efficient method for solving vibration equations is the basis of the vibration analysis of a cracked multistage blade–disk–shaft system. However, dynamic equations are usually time varying and nonlinear, and the time required for solving is greatly increased accompanied by an increase in the model order caused by the multistage system and the nonlinearity caused by cracks. In this article, an efficient method for solving the time varying and nonlinear vibration equation is investigated. In the proposed method, the time varying terms are transformed into constant terms, while the local nonlinear matrix of the cracked blade is separated from the assembly stiffness matrix under the constraint of proper orthogonal decomposition (POD) transformation rules. Furthermore, the POD transformations of the constant terms and the linear assembled stiffness matrix can be implemented in the pretreatment steps to achieve a more efficient POD reduction operation. This research provides a method for efficiently performing the comprehensive and rapid analysis of nonlinear vibration characteristics of rotor systems.

CONSTRUCTION OF COMPLEX SCHEDULES FOR EXECUTION OF TASK PACKAGES AT FORMING SETS IN SPECIFIED DIRECTIVE TERMS

The current state with the solution of the problem complex planning of the execution of task packets in multistage system is characterized by the absence of universal methods of forming decisions on the composition of packets, the presence of restrictions on the dimension of the problem and the impossibility of guaranteed obtaining effective solutions for various values of its input parameters, as well the impossibility of registration the condition of the formation of sets from the results. The solution of the task of planning the execution of task packets in multistage systems with the formation of sets of results within the specified deadlines has been realized of authors in article. To solve the planning problem, the generalized function of the system was decomposed into a set of hierarchically interrelated subfunctions. The use of decomposition made it possible to use a hierarchical approach for planning the execution of task packets in multistage systems, which involves defining solutions based on the composition of packets at the top level of the hierarchy and scheduling the execution of packages at the bottom level of the hierarchy. The theory of hierarchical games is used to optimize solutions for the compositions of task packets and schedules for their execution is built, which is a system of criteria at the decision-making levels. Evaluation of the effectiveness of decisions by the composition of packets at the top level of the hierarchy is ensured by the distribution of the results of task execution by packets in accordance with the formed schedule. To evaluate the effectiveness of decisions on the composition of packets, method for ordering the identifiers of the types of sets with registration of the deadlines and a method for distributing the results of the tasks performed by packets has been formulated, which calculates the moments of completion of the formation of sets and delays with their formation relative to the specified deadlines. The studies of planning the process of the executing task packages in multistage systems have been carried out, provided that the sets are formed within specified deadlines. On their basis, conclusions, regarding the dependence of the planning efficiency from the input parameters of the problem, were formulated.

Education in the Age of Marginalism and the Alienation of Knowledge

Global changes of contemporary education are so large-scale that they need a se­rious reconsideration. Philosophy of education has viewed education as a highly valued human activity and form of socialization, though philosophers may have had different views on the aims and methods of education. The importance of ed­ucation was based on the fact that a society could develop if and only if its mem­bers had an appropriate education. Nowadays education is discussed in journals, like the Philosophy of Education published in Novosibirsk, in annual confer­ences and by various associations of thinkers, teachers and professors. The abso­lute majority of philosophers since Plato emphasizes the fundamental value of education and wants to make its quality better. But a current state of humankind does not require a universal education of population. Robots and neural networks force the humans out of production. The humans are lacking a long-time mem­ory as information turns easily accessible by means of Internet. Growth rates of innovations, discoveries and changes are so high that adaptation to them requires daily efforts of any individual. Many professions are dying. The current trend of social development is growing marginalization of humans, their societies and countries. Knowledge alienates from its creators and, in a much greater degree, from public. Humans are first of all consumers but consumers do not need edu­cation: why one should spend many years in school and institute to buy food or see a clip on a smartphone? A multistage system of education looks outdated. The need of such an institution is dying step by step, as complex operations may be more effectively made by machines with stable, reliable and efficient neural networks, than by humans who have to spend years to become specialists. Colos­sal growth of information makes its learning by an individual impossible. Alien­ated knowledge turns external force regarding an individual.

Reverse Electrodialysis: Co- and Counterflow Optimization of Multistage Configurations for Maximum Energy Efficiency

Reverse electrodialysis (RED) is one of the techniques able to harvest energy from the salinity gradient between different salt solutions. There is a tradeoff between efficiency and generated power in a RED stack. This paper focuses on efficiency. A simple model is presented to calculate the efficiency in a co-flow or counterflow operated stack. Moreover, the efficiency can be improved by applying multistaging; the stacks in such a system can also be interconnected externally in co- and counterflow. The four combinations of internally and externally flow modes are the base of further considerations concerning procedures for optimization of these configurations. Three methods for optimization the energy efficiency in a multistage system are discussed: (A) successively maximizing the power of each individual stage, (B) maximizing the power of the whole system by adjusting the electrical current in all stages simultaneously, and (C) maximizing the power of the whole system by adjusting the same current through each stage. Method C is the most attractive because it only requires one converter (cheaper and easier to control) while the results are hardly inferior to B and much better than A. An alternative to multistaging is electrode segmentation and the advantages and disadvantages of both systems are briefly discussed.