In this paper, two control strategies are presented for the study of the control of a large-scale electric power system. In the first, the control is obtained by decomposition of the system to what are called I e-ccupled ' subsystems, and in the second, e. control strategy using closed-loop hierarchical control techniques is introduced. Finally, these two approaches are applied to a system consisting of three plants. IntroductionThe electric power system is a complex one consisting of a large number of units of energy production interconnected by the network of transmission and distribution; the complexity of this system is increasing every day due to the exponential rise in its demand and increased dependence on its reliability and security. Due to economical and technical reasons, interconnections become vital to electric power systems, these interconnections increase the degree of complexity of the system-operating problem. Hence the problem of the control of a large-scale system will be an important one. The system is usually subjected to perturbations and it is necessary to bring it back to a steady state in an optimal or suboptimal manner; this is the role of the system regulators which include speed and voltage regulators. But the numerical calculation of the exact optimal control is impracticable for a large-scale power system. The purpose of this paper is to show two methods allowing a large-scale design problem to be split into a set of simpler subsystem problems. Recently, the problem of decomposition of a large-scale system has received the attention of many authors (Kokotovic et al. (1969) developed a method for computing near-optimal regulators for a linear system with quadratic performance indices. The first part of this paper is a generalization of this method as applied to a power system. Singh et al. (1976) and developed a method for providing the optimal feedback gain matrix for high-order linear quadratic problems using multi-level computation techniques. In the second part of this paper this method is applied to the electric power system.

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Background: Systemic arterial hypertension (SAH) is an important cause of chronic systolic heart failure (CHF) in underdeveloped countries. It would be desirable to know predictors of mortality for patients with this condition in order to provide proper scientific treatment.

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Prostate cancer is the most common invasive cancer in men. Radical prostatectomy (RP) is a definitive treatment option, but biochemical recurrence can reach 40%. Salvage lymphadenectomy is a relatively recent approach to oligometasis and has been rapidly diffused primarily due to improvement in imaging diagnosis and results showing possibly promising therapy. A systematic literature review was performed in March 2020, according to the PRISMA statement. We excluded studies with patients with suspicion or confirmation of visceral and / or bone metastases. A total of 27 articles were included in the study. All studies evaluated were single arm, and there were no randomized studies in the literature. A total of 1,714 patients received salvage lymphadenectomy after previous treatment for localized prostate cancer. RP was the most used initial therapeutic approach, and relapses were based on PET / CT diagnosis, with Coline-11C being the most widely used radiopharmaceutical. Biochemical response rates ranged from 0% to 80%. The 5 years -Free Survival Biochemical recurrence was analyzed in 16 studies with rates of 0% up to 56.1%. The articles do not present high levels of evidence to draw strong conclusions. However, even if significant rates of biochemical recurrence are not evident in all studies, therapy directed to lymph node metastases may present good oncological results and postpone the onset of systemic therapy. The long-term impact in overall survival and quality of life, as well as the best strategies for case selection remains to be determined.