Optimal dividend strategies for two collaborating insurance companies

We consider a two-dimensional optimal dividend problem in the context of two insurance companies with compound Poisson surplus processes, who collaborate by paying each other's deficit when possible. We solve the stochastic control problem of maximizing the weighted sum of expected discounted dividend payments (among all admissible dividend strategies) until ruin of both companies, by extending results of univariate optimal control theory. In the case that the dividends paid by the two companies are equally weighted, the value function of this problem compares favorably with the one of merging the two companies completely. We identify this optimal value function as the smallest viscosity supersolution of the respective Hamilton-Jacobi-Bellman equation and provide an iterative approach to approximate it numerically. Curve strategies are identified as the natural analogue of barrier strategies in this two-dimensional context. A numerical example is given for which such a curve strategy is indeed optimal among all admissible dividend strategies, and for which this collaboration mechanism also outperforms the suitably weighted optimal dividend strategies of the two stand-alone companies

Optimal dividend strategies for a catastrophe insurer

In this paper we study the problem of optimally paying out dividends from an insurance portfolio, when the criterion is to maximize the expected discounted dividends over the lifetime of the company and the portfolio contains claims due to natural catastrophes, modelled by a shot-noise Cox claim number process. The optimal value function of the resulting two-dimensional stochastic control problem is shown to be the smallest viscosity supersolution of a corresponding Hamilton-Jacobi-Bellman equation, and we prove that it can be uniformly approximated through a discretization of the space of the free surplus of the portfolio and the current claim intensity level. We implement the resulting numerical scheme to identify optimal dividend strategies for such a natural catastrophe insurer, and it is shown that the nature of the barrier and band strategies known from the classical models with constant Poisson claim intensity carry over in a certain way to this more general situation, leading to action and non-action regions for the dividend payments as a function of the current surplus and intensity level. We also discuss some interpretations in terms of upward potential for shareholders when including a catastrophe sector in the portfolio.Este artículo se encuentra originalmente publicado en Frontiers of Mathematical Finance (e- ISSN:2769-6715

Experience of the cleft lip and palate clinic at the hospital general de México 2017-2023

Background: The care of cleft lip and palate patients at the general hospital of Mexico has nearly 70 years of experience. Methods: An observational study of a 7-year cohort of resolved cases of cleft lip and palate by the plastic and reconstructive surgery service of the general hospital of Mexico (2017-2023) was conducted. Results: The 121 patients were recorded, with 47 palatoplasties, 44 primary cheiloplasties, 24 secondary cheiloplasties, and 11 veloplasties performed. All patients are evaluated by a multidisciplinary team composed of plastic surgery, dentistry, clinical nutrition, speech therapy, audiology, genetics, and psychology to determine a comprehensive treatment plan. Conclusions: The data reported by the cohort in this work aligns with international reports. The frequency of cases decreased due to the COVID-19 pandemic, but has increased in recent years

A Deadbeat Controller for Doubly-Fed Induction Generator Power Control

A deadbeat power control scheme for doubly-fed induction generator for variable speed was proposed. The deadbeat controller algorithm calculates the voltage vector to be supplied to the rotor in order to eliminate the active and reactive power errors in each period using and stator field orientation and the doublyfed induction generator dynamic model. The deadbeat controller uses the rotor current control to the power control of the machine. This control technique can be applied to the wind energy systems. Experimental results are carried out to validate of the deadbeat controller operation

Alternative approach to the optimality of the threshold strategy for spectrally negative Levy processes

Consider the optimal dividend problem for an insurance company whose uncontrolled surplus precess evolves as a spectrally negative Levy process. We assume that dividends are paid to the shareholders according to admissible strategies whose dividend rate is bounded by a constant. The objective is to find a dividend policy so as to maximize the expected discounted value of dividends which are paid to the shareholders until the company is ruined. Kyprianou, Loeffen and Perez [28] have shown that a refraction strategy (also called threshold strategy) forms an optimal strategy under the condition that the Levy measure has a completely monotone density. In this paper, we propose an alternative approach to this optimal problem.Comment: 16 page

The Uranus multi-experiment radiometer for haze and clouds characterization

The aerosols (clouds and hazes) on Uranus are one of the main elements for understanding the thermal structure and dynamics of its atmosphere. Aerosol particles absorb and scatter the solar radiation, directly affecting the energy balance that drives the atmospheric dynamics of the planet. In this sense, aerosol information such as the vertical distribution or optical properties is essential for characterizing the interactions between sunlight and aerosol particles at each altitude in the atmosphere and for understanding the energy balance of the planet’s atmosphere. Moreover, the distribution of aerosols in the atmosphere provides key information on the global circulation of the planet (e.g., regions of upwelling or subsidence). To address this challenge, we propose the Uranus Multi-experiment Radiometer (UMR), a lightweight instrument designed to characterize the aerosols in Uranus’ atmosphere as part of the upcoming Uranus Flagship mission’s descending probe payload. The scientific goals of UMR are: (1) to study the variation of the solar radiation in the ultra-violet (UV) with altitude and characterize the energy deposition in the atmosphere; (2) to study the vertical distribution of the hazes and clouds and characterize their scattering and optical properties; (3) to investigate the heating rates of the atmosphere by directly measuring the upward and downward fluxes; and (4) to study the cloud vertical distribution and composition at pressures where sunlight is practically negligible (p > 4-5 bars). The instrument includes a set of photodetectors, field-of-view masks, a light infrared lamp, and interference filters. It draws on the heritage of previous instruments developed at the Instituto Nacional de Técnica Aeroespacial (INTA) that participated in the exploration of Mars, where similar technology has demonstrated its endurance in extreme environments while utilizing limited resources regarding power consumption, mass and volume footprints, and data budget. The radiometer’s design and characteristics make it a valuable complementary payload for studying Uranus’ atmosphere with a high scientific return

Toxic Metals (Pb and Cd) and Their Respective Antagonists (Ca and Zn) in Infant Formulas and Milk Marketed in Brasilia, Brazil

In non-ideal scenarios involving partial or non-breastfeeding, cow’s milk-based dairy products are mainstream in infant feeding. Therefore, it is important to study the concentrations of potentially neurotoxic contaminants (Pb and Cd) and their respective counteracting elements (Ca and Zn) in infant dairy products. Fifty-five brands of infant formulas and milk sold in Brasilia, Brazil were analyzed. The dairy products came from areas in the central-west (26%), southeast (29%) and south of Brazil (36%) extending as far as Argentina (7%) and the Netherlands (2%). For toxic Pb and Cd, median concentrations in powdered samples were 0.109 mg/kg and 0.033 mg/kg, respectively; in fluid samples median Pb concentration was 0.084 mg/kg, but median Cd concentration was below the limit of detection and overall values were below reference safety levels. However, 62% of these samples presented higher Pb concentration values than those established by FAO/WHO. Although the inverse correlation between Cd and Zn (Spearman r = −0.116; P = 0.590) was not statistically significant, the positive correlation between Ca and Pb was (Spearman r = 0.619; P < 0.0001). Additionally, there was a significant correlation between Pb and Cd. Furthermore, the study also revealed that provision of the essential trace element Zn in infant formulas can provide adequate amounts of the recommended daily requirements. Infant formulas and milk sold for consumption by infants and children can be an efficient tool to monitor neurotoxic metal risk exposure among young children