1,721,058 research outputs found
Comfort-driven target setting
No full textSince the first appearance of hand-tools, artisans and engineers have attempted to make handwork
as comfortable as possible. In the second half of twentieth century, awareness raising by industrialists about
ergonomics and safety made the preventive evaluation of workplace ergonomics/comfort an essential element
of product/process design. ISO 11228 provided guidelines for improving overall operator performance, as
well as reducing the risk of muscle-skeletal disease. Companies, designers and engineers use their knowledge
to improve work environments and artefacts to enhance worker performance and improve user safety. In the
digital era (since the 1990s) new virtual prototyping (VP) techniques and their development and deployment
in industrial environments have allowed products, processes and workplaces to be designed and redesigned in
a virtual environment. Similarly, Digital Human Modelling (DHM) techniques and instruments allow designers
and engineers to virtualise the human/machine interaction (HMI) and to preventively assess ergonomic elements,
resulting in an improved appeal to the market. Nevertheless, the ‘comfort’ issue is still an open problem
due to the subjectivity of performances and to the difficulty in developing a ‘model’ of perception that is
both easily integrated in VP and can be used for designing new products/processes/workplaces. The introduction
of comfort-driven design into the product/process development plan remains a challenge for scientists,
engineers, designers and others. This paper gives an overview of the state of the art concerning ergonomicdriven
and comfort-driven design in companies’ innovation activities. It also proposes a general ‘comfort
model’ and a general ‘design framework’ for introducing a comfort-driven step to product target setting
Majorana Solutions to the Two-Electron Problem
No full textThe two-electron atom is the simplest nontrivial quantum system not amenable to exact solutions. Today, its relevance in the development of quantum mechanics and its pedagogical value within the realm of atomic physics are widely recognized. In this work, an historical review of the known different methods and results devised to study such a problem is presented, with an emphasis to the calculations of the ground state energy of helium. Then we discuss several, related, unpublished results obtained around the same years by Ettore Majorana, which remained unknown till recent times. Among them a general variant of the variational method appears to be particularly interesting, even for current research in atomic and nuclear physics: it takes directly into account, already in the trial wavefunction, the action of the full Hamiltonian operator of a given quantum system. Further relevant contributions, specialized to the two-electron problem, include the introduction of the remarkable concept of an effective nuclear charge different for the two electrons (thus generalizing previous known results) and an application of the perturbative method, where the atomic number Z was treated effectively as a continuous variable. Finally a survey of results, relevant mainly for pedagogical reasons, is given; in particular we focus on simple broad range estimates of the helium ionization potential, obtained by suitable choices for the wavefunction, as well as on a simple alternative to Hylleraas’ method, which led Majorana to first order calculations comparable in accuracy with well-known order 11 results derived, in turn, by Hylleraas
Comfort driven design of innovative products: A personalized mattress case study
No full textBACKGROUND: Human-centred design asks for wellbeing and comfort of the customer/worker when interacting with a product. Having a good perception-model and an objective method to evaluate the experienced (dis)comfort by the product user is needed for performing a preventive comfort evaluation as early as possible in the product development plan. The mattress of a bed is a typical product whose relevance in everyday life of people is under-evaluated. Fortunately, this behaviour is quickly changing, and the customer wants to understand the product he/she buys and asks for more comfortable and for scientifically assessed products. No guidelines for designing a personalized mattress are available in the literature. OBJECTIVES: This study deals with the experience of designing an innovative product whose product-development-plan is focused on the customer perceived comfort: a personalized mattress. The research question is: which method can be used to innovate or create a comfort-driven human-centred product? METHODS: Virtual prototyping was used to develop a correlated numerical model of the mattress. A comfort model for preventively assessing the perceived comfort was proposed and experimentally tested. Mattress testing sessions with subjects were organized, and collected data were compared with already tested mattresses. Brainstorming and multi-expert methods were used to propose, realize, and test an archetype of a new mattress for final comfort assessment. RESULTS: A new reconfigurable mattress was developed, resulting in two patents. The mattress design shows that personalized products can be tuned according to the anthropometric data of the customer in order to improve the comfort experience during sleep. CONCLUSIONS: A 'comfort-driven design guideline' was proposed; this method has been based on the use of virtual prototyping, virtual optimization and physical prototyping and testing. It allowed to improve an existing product in a better way and to bring innovation in it
Teaching quantum physics in the footsteps of Einstein
No full textA teaching-learning sequence designed to introduce some fundamental concepts of quantum physics to high school teachers is proposed. Some parts of the proposal can be adapted to be taught to advanced high school students themselves. The inspiration came from the recognition of the fact that the roots of many pivotal concepts of quantum physics, namely light quanta, wave-particle duality, and probability, were introduced for the first time in some paper by Albert Einstein. Moreover, this was done in a characteristically deep and illuminating way. A critical study of Einstein's papers should therefore be useful for teachers and students as well, in view of the fact that such concepts are often misconceived. The teaching-learning sequence can supplement usual historically oriented treatments of elementary quantum physics and can in turn be complemented by a discussion of some elementary tools of statistical physics, which may be not part of the learners' background. Preliminary results obtained with both teachers and pupils in high schools in southern Italy, which are very promising, are presented
Phase time and transmission probability in the traversal of a PT-symmetric potential: The case of an electromagnetic waveguide
No full textWe study the unconventional transmission properties of a wave packet through a PT-symmetric potential region as describing the actual electromagnetic wave propagation along a waveguide filled with gain and loss media. The nontrivial behavior of the transmission probability manifests in the giant amplification of the incident electromagnetic signal of given wavelengths for well-defined configurations, depending on the gain/loss contrast. Maximum transmission peaks are related to spectral singularities and a strict correlation exists between the "resonant" wavelengths and the gain/loss contrast. The transit times are as well calculated, showing their surprising vanishing in the opaque barrier limit, independently of the gain/loss contrast, which is reminiscent of some sort of Hartman effect. Also, nonlocal effects manifest in the presence of negative delay times for given configurations, while a correlation is apparent between maximum delay times and transmission probability peaks, though appreciably depending on the gain/loss contrast
A road map for Feynman’s adventures in the land of gravitation
No full textRichard P. Feynman’s work on gravitation, as can be inferred from several published and unpublished sources, is reviewed. Feynman was involved with this subject at least from late 1954 to the late 1960s, giving several pivotal contributions to it. Even though he published only three papers, much more material is available, beginning with the records of his many interventions at the Chapel Hill conference in 1957, which are here analyzed in detail, and show that he had already considerably developed his ideas on gravity. In addition, he expressed deep thoughts about fundamental issues in quantum mechanics which were suggested by the problem of quantum gravity, such as superpositions of the wave functions of macroscopic objects and the role of the observer. Feynman also lectured on gravity several times. Besides the famous lectures given at Caltech in 1962–1963, he extensively discussed this subject in a series of lectures delivered at the Hughes Aircraft Company in 1966–1967, whose focus was on astronomy and astrophysics. All this material allows to reconstruct a detailed picture of Feynman’s ideas on gravity and of their evolution until the late sixties. According to him, gravity, like electromagnetism, has quantum foundations, therefore general relativity has to be regarded as the classical limit of an underlying quantum theory; this quantum theory should be investigated by computing physical processes, as if they were experimentally accessible. The same attitude is shown with respect to gravitational waves, as is evident also from an unpublished letter addressed to Victor F. Weisskopf. In addition, an original approach to gravity, which closely mimics (and probably was inspired by) the derivation of the Maxwell equations given by Feynman in that period, is sketched in the unpublished Hughes lectures
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