1,597 research outputs found
Sensitivity of semiclassical vibrational spectroscopy to potential energy surface accuracy: A test on formaldehyde.
A set of permutationally invariant potential energy surfaces for the electronic ground state of formaldehyde is built at several levels of electronic theory and atomic orbital basis sets starting from a database of more than 34000 ab initio energies. The reliability of the fitted surfaces is determined by comparing the calculated harmonic frequencies with the corresponding ab initio values. Semiclassical estimates of the quantum frequencies of vibration are presented, and their dependence on the employed level of theory, type of atomic orbital basis set, and complexity of the fit is investigated. Comparisons to experimental data show that anharmonic frequencies are influenced by the precision of the fit, while accurate frequency values are obtained also with density functional theory. Results and conclusions support the use of ab initio \u201con-the-fly\u201d semiclassical dynamics as a means of spectroscopic investigation when high level analytical potential energy surfaces are not available
The role of mediterranean fruit tree orchards and vineyards in maintaining the traditional agricultural landscape
The Mediterranean area represents one of the most suitable and diversified
environments for horticultural crops, being this propriety well expressed in the
commonly accepted definition of “Mediterranean cultivated garden”. In Italy, fruit
crops have been in the past introduced and expanded in different environments
depending on the species and adaptability to the physiographic characteristics of the
regions. The climate and the diversity of environmental contexts, the specificity of
soils, the plasticity of the cultivated genotypes, have allowed a tight and typical
relationship among land and farmers. Since the past centuries olive and fruit
orchards, vineyards and Citrus plantations have represented the typicity of the Italian
rural landscape. The physiognomy of tree cropping systems has been changed rapidly
starting from half of the past century owing to the introduction of new genetic
resources, the change in the concepts of quality, the modernization and intensification
of the agronomical techniques, resulting in loss of environmental and biological
diversity. Nonetheless, some historic fruit orchards and vineyards have survived. The
research is focused: a) on the recognition and mapping of the traditional landscapes of
fruit crops in two representative Mediterranean regions; b) on the identification of
their typological traits; c) on the definition of their environmental and technical
sustainability based on an interdisciplinary methodology. Through a multi-criterial
analysis it was possible to recognize and measure the sustainability of these cropping
models and their ecological function, turning into preservation of environmental
resources, environmental quality and quality of life. The study also underlined the
crucial role of the traditional agricultural landscapes in the maintenance of local
identity, history and economy. By representing a cultural heritage, traditional agricultural
landscapes and traditional farming might justify preservation and valorisation
actions
Knowledge Acquisition by Networks of Interacting Agents in the Presence of Observation Errors
In this work we investigate knowledge acquisition as performed by multiple
agents interacting as they infer, under the presence of observation errors,
respective models of a complex system. We focus the specific case in which, at
each time step, each agent takes into account its current observation as well
as the average of the models of its neighbors. The agents are connected by a
network of interaction of Erd\H{o}s-Renyi or Barabasi-Albert type. First we
investigate situations in which one of the agents has a different probability
of observation error (higher or lower). It is shown that the influence of this
special agent over the quality of the models inferred by the rest of the
network can be substantial, varying linearly with the respective degree of the
agent with different estimation error. In case the degree of this agent is
taken as a respective fitness parameter, the effect of the different estimation
error is even more pronounced, becoming superlinear. To complement our
analysis, we provide the analytical solution of the overall behavior of the
system. We also investigate the knowledge acquisition dynamic when the agents
are grouped into communities. We verify that the inclusion of edges between
agents (within a community) having higher probability of observation error
promotes the loss of quality in the estimation of the agents in the other
communities.Comment: 10 pages, 7 figures. A working manuscrip
Participative ergonomics for the improvement of occupational health and safety in industry: a focus group-based approach
This paper introduces a participative approach to the investigation and promotion of health and safety in industry. The proposed methodology promotes the active participation of the workers in the analysis of consequences and causes of unsafe behaviours that may result in work-related musculoskeletal disorders, accidents, injuries or near-misses. The developed participative technique is the Focus Group with Workers, based on the Fault Tree Analysis method (FGW-FTA). Focus groups are conventionally used by social and behavioural researchers to understand opinions, motivations, attitudes, and mental processes that underlie people behaviours. The innovative procedure in this paper addresses researchers and safety professionals during the focus groups with the workers for the identification of critical risk factors in the workplace. The result is a structured analysis, operated by and with the workers, for the identification of consequences and causes of unsafe behaviours. Finally, the developed methodology addresses the definition of a set of preventive and protective measures, and corrective actions for the improvement of health and safety in the workplace.
An experimental study in an Italian boiler manufacturer describes the proposed methodology and the results of the focus groups with the workers. An evaluation questionnaire was elaborated to investigate the workers’ knowledge on occupational health and safety. A second questionnaire was developed to understand the workers’ perception on occupational risks. Each participant was invited to fill in both the questionnaires before and after the focus groups with the workers. The results of the study proved the effectiveness of the developed methodology in improving workers knowledge and perceptions on occupational health and safety
Semiclassical vibrational spectroscopy with Hessian databases
We report on a new approach to ease the computational overhead of ab initio "on-the-fly" semiclassical dynamics simulations for vibrational spectroscopy. The well known bottleneck of such computations lies in the necessity to estimate the Hessian matrix for propagating the semiclassical pre-exponential factor at each step along the dynamics. The procedure proposed here is based on the creation of a dynamical database of Hessians and associated molecular geometries able to speed up calculations while preserving the accuracy of results at a satisfactory level. This new approach can be interfaced to both analytical potential energy surfaces and on-the-fly dynamics, allowing one to study even large systems previously not achievable. We present results obtained for semiclassical vibrational power spectra of methane, glycine, and N-acetyl-L-phenylalaninyl-L-methionine-amide, a molecule of biological interest made of 46 atoms
Efficient calculation of van der Waals dispersion coefficients with time-dependent density functional theory in real time: application to polycyclic aromatic hydrocarbons
The van der Waals dispersion coefficients of a set of polycyclic aromatic
hydrocarbons, ranging in size from the single-cycle benzene to circumovalene
(C66H20), are calculated with a real-time propagation approach to
time-dependent density functional theory (TDDFT). In the non-retarded regime,
the Casimir-Polder integral is employed to obtain C6, once the dynamic
polarizabilities have been computed at imaginary frequencies with TDDFT. On the
other hand, the numerical coefficient that characterizes the fully retarded
regime is obtained from the static polarizabilities. This ab initio strategy
has favorable scaling with the size of the system - as demonstrated by the size
of the reported molecules - and can be easily extended to obtain higher order
van der Waals coefficients.Comment: submitted to J. Chem. Phy
Identification of a chemical fingerprint linking the undeclared 2017 release of 106Ru to advanced nuclear fuel reprocessing
The undeclared release and subsequent detection of ruthenium-106 (106Ru) across Europe from late September to early October of 2017 prompted an international effort to ascertain the circumstances of the event. While dispersion modeling, corroborated by ground deposition measurements, has narrowed possible locations of origin, there has been a lack of direct empirical evidence to address the nature of the release. This is due to the absence of radiological and chemical signatures in the sample matrices, considering that such signatures encode the history and circumstances of the radioactive contaminant. In limiting cases such as this, we herein introduce the use of selected chemical transformations to elucidate the chemical nature of a radioactive contaminant as part of a nuclear forensic investigation. Using established ruthenium polypyridyl chemistry, we have shown that a small percentage (1.2 ± 0.4%) of the radioactive 106Ru contaminant exists in a polychlorinated Ru(III) form, partly or entirely as β-106RuCl3, while 20% is both insoluble and chemically inert, consistent with the occurrence of RuO2, the thermodynamic endpoint of the volatile RuO4. Together, these findings present a clear signature for nuclear fuel reprocessing activity, specifically the reductive trapping of the volatile and highly reactive RuO4, as the origin of the release. Considering that the previously established 103Ru:106Ru ratio indicates that the spent fuel was unusually young with respect to typical reprocessing protocol, it is likely that this exothermic trapping process proved to be a tipping point for an already turbulent mixture, leading to an abrupt and uncontrolled release
ENVIRONMENTAL ASSESSMENT OF AN INNOVATIVE PLANT FOR THE WASTEWATER PURIFICATION IN THE BEVERAGE INDUSTRY
Nowadays, efforts to reduce the resource depletion and environmental emissions from the anthropic activities, are mandatory for sustainable development pattern. Among the key resources to save, pure water is as important as critic due to its scarcity and its essential role for life and growth. Furthermore, during the last decades, rising attention from institutions and industries is toward solutions for the water intensity decrease and wastewater recovery. This paper proposes the environmental assessment of an innovative wastewater collection and purification plant tailored to a mid-size beverage industry aiming at locally closing the loop of the water chain, allowing its recirculation and local reuse. After the description of the functional module features, sizes and design, based on a prototype actually working in Italy, the paper follows the ISO 14040 standards to develop an environmental assessment of the industrial system, quantifying the impact rising from the manufacturing and the assembly phases
Cu-exchanged 3D-printed geopolymer/ZSM-5 monolith for selective catalytic reduction of NOx
Cu-exchanged zeolites with MFI structure, such as ZSM-5, represent effective catalysts for SCR processes when the application requires a good thermal stability under a wide range of temperature as for the after-treatment of exhaust gas from diesel engine. The production of zeolite in a structured form, mandatorily required for mobile applications, is quite complex due to the poor adhesion of the material. In this paper 3D-printed geopolymers containing about 37 % ZSM-5 are proposed as potentially structured catalysts for SCR applications. The production of the monolith and the pre-treatment necessary to introduce copper as active exchanged cation are investigated. The effect of pre-treatments on the physical and morphological structure of both geopolymer and zeolite and on the nature of copper introduced in the subsequent step was studied using characterization techniques such as SEM, XRD, N2 physisorption and Temperature Programmed Reduction (TPR)
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