Variance Allocation and Shapley Value

Motivated by the problem of utility allocation in a portfolio under a Markowitz mean-variance choice paradigm, we propose an allocation criterion for the variance of the sum of $n$ possibly dependent random variables. This criterion, the Shapley value, requires to translate the problem into a cooperative game. The Shapley value has nice properties, but, in general, is computationally demanding. The main result of this paper shows that in our particular case the Shapley value has a very simple form that can be easily computed. The same criterion is used also to allocate the standard deviation of the sum of $n$ random variables and a conjecture about the relation of the values in the two games is formulated.Comment: 20page

Implementation of an economic MPC with robustly optimal steady-state behavior

Designing an economic model predictive control (EMPC) algorithm that asymptotically achieves the optimal performance in presence of plant-model mismatch is still an open problem. Starting from previous work, we elaborate an EMPC algorithm using the offset-free formulation from tracking MPC algorithms in combination with modifier-adaptation technique from the real-time optimization (RTO) field. The augmented state used for offset-free design is estimated using a Moving Horizon Estimator formulation, and we also propose a method to estimate the required plant steady-state gradients using a subspace identification algorithm. Then, we show how the proposed formulation behaves on a simple illustrative example

Understanding the perceptions, roles and interactions of stakeholder networks managing health-care waste: a case study of the Gaza Strip

The sustainable management of waste requires a holistic approach involving a range of stakeholders. What is often difficult is to understand the manner in which different networks, like information and interaction, are composed and work, and to enhance their effectiveness. Using social network analysis and stakeholder analysis of healthcare waste management stakeholders in the case study region of the Gaza Strip, this study aimed to understand and examine the manner in which the networks functioned. The Ministry of Health was found to be the most important stakeholder, followed by municipalities and solid waste management councils. Some international agencies were also mentioned, with specific roles, while other local institutions had a limited influence. Finally health-care facilities had a high interested in waste management, but were poorly informed and linked each other. The manner in which the network operated was complicated and influenced by differences in perception, sharing of information, access to finance and levels of awareness. In particular the lack of a clear legal framework generated various mistakes about roles and responsibilities in the system, and evidently regulation was not an effective driver for improvement. Finally stakeholders had different priorities according to the waste management phases they were involved into, however segregation at the source was identified as a key requirement. Areas for improving the effectiveness of the networks are suggested. The analysis utilized an innovative methodology, which involved a large number of stakeholders. Such an approach raised interest and awareness at different levels (public authorities, health providers, supporting actors, others), and stimulated the discussion about the adoption of specific policies, and the identification of the effective way forward

Model predictive control design for multivariable processes in the presence of valve stiction

This paper presents different formulations of Model Predictive Control (MPC) to handle static friction in control valves for industrial processes. A fully unaware formulation, a stiction embedding structure, and a stiction inversion controller are considered. These controllers are applied to multivariable systems, with linear and nonlinear process dynamics. A semiphysical model is used for valve stiction dynamics and the corresponding inverse model is derived and used within the stiction inversion controller. The two-move stiction compensation method is revised and used as warm-start to build a feasible trajectory for the MPC optimal control problem. Some appropriate choices of objective functions and constraints are used with the aim of improving performance in set-points tracking. The different MPC formulations are reviewed, compared, and tested on several simulation examples. Stiction embedding MPC proves to guarantee good performance in set-points tracking and also stiction compensation, at the expense of a lower robustness with respect to other two formulations

A valve stiction tolerant formulation of MPC for industrial processes

This paper presents three different formulations of MPC to face static friction in control valves for industrial processes. A pure linear formulation, a stiction embedding structure, and a stiction inversion controller are designed. The controllers are derived for SISO systems with linear process dynamics, where valve stiction is the only nonlinearity present in the control loop. A novel smoothed stiction model is introduced to improve and fasten the dynamic optimization module of stiction embedding MPC. A stiction compensation method is revised and used as a warm-start to build a suitable trajectory for the predictive controller. The different MPC formulations are tested and compared on some simulation examples

Estimation technique for offset-free economic MPC based on modifier adaptation

Economic model predictive control formulations that combine online optimizing control with offset-free methodologies such as modifier adaptation have been proposed recently. These new algorithms are able to achieve asymptotic optimal performance despite the presence of plant-model mismatch. However, there is a major requirement stemming from the modifier-adaptation part, namely, the necessity to know the static plant gradients at the sought (and therefore still unknown) steady-state operating point. Hence, for implementation purposes, the algorithms need to be enhanced with plant gradient estimation techniques. This work proposes to estimate modifiers directly, based on steady-state perturbations and using Broyden’s approximation. The proposed economic MPC algorithm has been tested in simulation on the Williams-Otto reactor and provides plant optimality upon convergence

Generation of mouse oocytes defective in cAMP synthesis and degradation: Endogenous cyclic AMP is essential for meiotic arrest

AbstractAlthough it is established that cAMP accumulation plays a pivotal role in preventing meiotic resumption in mammalian oocytes, the mechanisms controlling cAMP levels in the female gamete have remained elusive. Both production of cAMP via GPCRs/Gs/adenylyl cyclases endogenous to the oocyte as well as diffusion from the somatic compartment through gap junctions have been implicated in maintaining cAMP at levels that preclude maturation. Here we have used a genetic approach to investigate the different biochemical pathways contributing to cAMP accumulation and maturation in mouse oocytes. Because cAMP hydrolysis is greatly decreased and cAMP accumulates above a threshold, oocytes deficient in PDE3A do not resume meiosis in vitro or in vivo, resulting in complete female infertility. In vitro, inactivation of Gs or downregulation of the GPCR GPR3 causes meiotic resumption in the Pde3a null oocytes. Crossing of Pde3a−/− mice with Gpr3−/− mice causes partial recovery of female fertility. Unlike the complete meiotic block of the Pde3a null mice, oocyte maturation is restored in the double knockout, although it occurs prematurely as described for the Gpr3−/− mouse. The increase in cAMP that follows PDE3A ablation is not detected in double mutant oocytes, confirming that GPR3 functions upstream of PDE3A in the regulation of oocyte cAMP. Metabolic coupling between oocytes and granulosa cells was not affected in follicles from the single or double mutant mice, suggesting that diffusion of cAMP is not prevented. Finally, simultaneous ablation of GPR12, an additional receptor expressed in the oocyte, does not modify the Gpr3−/− phenotype. Taken together, these findings demonstrate that Gpr3 is epistatic to Pde3a and that fertility as well as meiotic arrest in the PDE3A-deficient oocyte is dependent on the activity of GPR3. These findings also suggest that cAMP diffusion through gap junctions or the activity of additional receptors is not sufficient by itself to maintain the meiotic arrest in the mouse oocyte

A seismological and engineering perspective on the 2016 Central Italy earthquakes

The strong earthquake (M 6.0-6.2) that hit the central Apennines on August 24, 2016, occurred in one of the most seismically active areas in Italy. Field surveys indicated severe damage in the epicentral area where, in addition to the loss of human life, widespread destruction of cultural heritage and of critical buildings occurred. Using the neo-deterministic seismic hazard assessment (NDSHA), we apply the maximum deterministic seismic input (MDSI) procedure at two of the most relevant sites in the epicentral area, comparing the results with the current Italian building code. After performing an expeditious engineering analysis, we interpret as a possible cause of the reported damages the high seismic vulnerability of the built environment, combined with the source and site effects characterising the seismic input. Therefore, it is important to design and retrofit with appropriate spectral acceleration levels compatible with the possible future scenarios, like the ones provided by MDSI

A comprehensive review and classification of unit operations with assessment of outputs quality in lithium-ion battery recycling

Lithium-ion batteries (LIBs) are the core component of the electrification transition, being used in portable electronics, electric vehicles, and stationary energy storage. The exponential growth of LIB use generates a large flow of spent batteries which must be recycled. This paper provides a comprehensive review of industrial realities of LIB recycling companies in Europe, North America, and Asia. An in-depth description of representative pyrometallurgy-based and hydrometallurgy-based processes is reported, providing classification of unit operations, their industrial readiness, and quality of output materials. The analysis shows that the pyrometallurgical route can treat different LIB chemistries without pre-sorting, but Li is not recovered unless the slag is refined. Hydrometallurgy-based processes are more chemistry-specific and in, although being affected by losses of electrode active materials during the mechanical pre-treatments for black mass separation. Efforts are required to promote in Europe the industrial capacity and readiness of hydrometallurgical processes by facilitating sorting and mechanical separations. There is also the need for harmonization of criteria for outputs definitions and rules for calculating recycling efficiency indicators. This represents an opportunity for modeling to support quantitative techno-economic and environmental assessments of the entire LIB recycling chain

Rigorous Simulation Model of a KCl Food Production Plant to Address Impurity Precipitation

Potassium chloride (KCl) is widely used in many fields of the processing industry. The application in the food industry, as well the one in the pharmaceutic sector, requires very pure KCl crystals (not less than 99.0%), therefore the elimination of impurities in the production process is a mandatory task. The case study analyzed in this work is a real pilot plant for producing high-purity KCl developed by an Italian chemical company. The major issue of this process is given by the occasional presence of potassium sulfate (K2SO4) in the final product which invalidates the stringent purity specifications required. The actual socio-economic situation linked to the energy and raw materials markets makes it very difficult for the industries to spend efforts for experimental investigations that are normally often long and expensive. Therefore, a rigorous simulation model of the plant has been built using UniSim Design® with the thermodynamic package OLI® that enables the possibility to consider different liquid-solid equilibria. The developed model has been used to verify the formation of the impurities in three different ways: checking the process normal operation, verifying the fluid dynamics design of the crystallization unit, and investigating the start-up conditions. The analysis shows a potential source of formation of K2SO4 nucleus under the actual brine concentration recirculated in the crystallizer during the start-up phase, albeit further investigations have to be performed on the pilot plant to confirm such a hypothesis