Optimal Control of Underactuated Mechanical Systems: A Geometric Approach

In this paper, we consider a geometric formalism for optimal control of underactuated mechanical systems. Our techniques are an adaptation of the classical Skinner and Rusk approach for the case of Lagrangian dynamics with higher-order constraints. We study a regular case where it is possible to establish a symplectic framework and, as a consequence, to obtain a unique vector field determining the dynamics of the optimal control problem. These developments will allow us to develop a new class of geometric integrators based on discrete variational calculus.Comment: 20 pages, 2 figure

Design of a high power production target for the Beam Dump Facility at CERN

The Beam Dump Facility (BDF) project is a proposed general-purpose facility at CERN, dedicated to beam dump and fixed target experiments. In its initial phase, the facility is foreseen to be exploited by the Search for Hidden Particles (SHiP) experiment. Physics requirements call for a pulsed 400 GeV/c proton beam as well as the highest possible number of protons on target (POT) each year of operation, in order to search for feebly interacting particles. The target/dump assembly lies at the heart of the facility, with the aim of safely absorbing the full high intensity Super Proton Synchrotron (SPS) beam, while maximizing the production of charmed and beauty mesons. High-Z materials are required for the target/dump, in order to have the shortest possible absorber and reduce muon background for the downstream experiment. The high average power deposited on target (305 kW) creates a challenge for heat removal. During the BDF facility Comprehensive Design Study (CDS), launched by CERN in 2016, extensive studies have been carried out in order to define and assess the target assembly design. These studies are described in the present contribution, which details the proposed design of the BDF production target, as well as the material selection process and the optimization of the target configuration and beam dilution. One of the specific challenges and novelty of this work is the need to consider new target materials, such as a molybdenum alloy (TZM) as core absorbing material and Ta2.5W as cladding. Thermo-structural and fluid dynamics calculations have been performed to evaluate the reliability of the target and its cooling system under beam operation. In the framework of the target comprehensive design, a preliminary mechanical design of the full target assembly has also been carried out, assessing the feasibility of the whole target system.Comment: 17 pages, 18 figure

Maternal perception of emotional expressiveness. A cross-cultural comparison

The parents' perception of children is a crucial aspect involving the relationship between caregiver and children (Stern, 2007) that represents an important area of investigation during the clinical assessment in developmental age. Although maternal perception is conceived as a mixture of objective and subjective judgments (Regan et al., 1974; Taylor e Koivumaki, 1976; Goldberg, 1981), influenced by multiple factors, such as the personal experience with the baby and parents' own personality, little is known about the influence of the cultural context. The present research explored the cultural influence on the parental perspectives by means of a cross-cultural approach. In particular, this study investigated parents' perception of different ethnic groups and compared them with the direct emotional expression of children. Participants were 165 mothers and 165 children, aged between 6 and 18 years, divided in three samples: Italians, African and Latin-American. Parents' perception was measured by means of the Child Behavior Checklist (Achenbach, 1991), whereas children emotional expression was derived by spontaneous narratives to the Roberts-2 (Roberts e Gruber, 2005). Results showed cultural differences in CBCL profile, related to the ethnic group and to gender, as well as in the emotions expressed in the test Robert-2