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Sensory evaluation of the sound of rolling office chairs: An exploratory study for sound design
No full textOnly an infinitesimal part of the sounds from everyday objects that surround us has been designed specifically. This study has dealt with a sensory test for sounds produced by objects interacting with other objects, which can be performed during the concept design phase, where only some parts of the product can be tested. The aim of the study has been to prove the reliability of this preliminary test and compare it to the full-product test con- dition. The concept for an office-chair was considered, and the sound of a chair-wheel moving across flooring tiles was tested as a simplification of chair-flooring interactions. Sixty participants took part in a listening test and described the acoustic stimuli of the wheels of two office chairs, one of high quality and the other of low quality, rolling over polyvinyl chloride (PVC), ceramic and wood floorings. The listeners were asked to assign descriptors to stimuli from a list of 26 adjectives, according to a forced ordered scale. Comparisons were made with sounds from the rolling of real office chairs. The sound of wheel rolling was prevalently judged "rough" on ceramics, "dull" on PVC and "smooth" on wood, and some cross-modal audio-tactile verbal interactions between the sounds and flooring surfaces emerged. No statistically significant difference was found between the concept and full product test conditions, thus proving the efficacy of the concept sound test during the early design phase
Free-vibration tailoring of single- and multi-bay laminated box structures by refined beam theories
No full textImproved dynamic programming and approximation results for the knapsack problem with setups
No full textWe consider the 0-1 Knapsack Problem with Setups (KPS). Items are grouped into families and if any items of a family are packed, this induces a setup cost as well as a setup resource consumption. We introduce a new dynamic programming algorithm which performs much better than a previous dynamic program and turns out to be also a valid alternative to an exact approach based on the use of an ILP solver. Then we present a general inapproximability result. Furthermore, we investigate several relevant special cases which still permit fully polynomial time approximation schemes (FPTASs) and others where the problem remains hard to approximate
Cost Evaluation of Synchronization Algorithms for Multicore Architectures
No full textIn a multicore environment, a major focus is represented by synchronization. Since synchronization mechanisms strongly affect the performance of multithread algorithms, the selection of an effective synchronization approach is critical for multicore environments. In this chapter, the cost of the main existing synchronization techniques is estimated. The current investigation covers both hardware and software solutions. A comparative analysis highlights benefits and drawbacks of the considered approaches. The results are intended to represent a useful aid for researchers and practitioners interested in optimization of parallel algorithms
Workload models and performance evaluation of cloud storage services
No full textCloud storage systems are currently very popular with many companies offering services, including worldwide providers such as Dropbox, Microsoft and Google. These companies as well as providers entering the market could greatly benefit from a deep understanding of typical workload patterns their services have to face in order to develop cost-effective solutions. Yet, despite recent studies of usage and performance of these systems, the underlying processes that generate workload for the system have not been deeply studied. This paper presents a thorough investigation of the workload generated by Dropbox customers. We propose a hierarchical model that captures user sessions, file system modifications and content sharing patterns. We parameterize our model using passive measurements gathered from fourdifferent networks. Next, we use the proposed model to drive the development of CloudGen, a new synthetic workload generator that allows the simulation of the network traffic created by cloud storage services in various realistic scenarios. We validate CloudGen by comparing synthetic traces with actual data from operational networks. We then show its applicability by investigating the impact of the continuing growth in cloud storage popularity on bandwidth consumption. Our results indicate that a hypothetical 4-fold increase in both user population and content sharing could lead to 30 times more network traffic. CloudGen is a valuable tool for administrators and developers interested in engineering and deploying cloud storage service
Non-stationary transport phenomena in networks of fractures: effective simulations and stochastic analysis
No full textAmong the major challenges in performing underground flow simulations in fractured media are geometrical complexities in the domain and uncertainty in the problem parameters, including the geometrical configuration. The Discrete Fracture Network (DFN) model is largely applied in order to properly account for the directionality of the flow in fractured media. Generation of DFN configurations is usually based on stochastic data and this contributes to generate very complex geometrical configurations for which a conforming mesh generation is often infeasible. Moreover, uncertainty in the geometrical and hydro-geological properties calls for a deep uncertainty quantification analysis; the corresponding huge computational cost of the simulations requires modern efficient approaches faster and cheaper than the classical Monte Carlo approach. In this paper we numerically investigate both these aspects, proposing a viable solution for dealing with geometrical complexities arising in the computation of the hydraulic head and in the solution of the unsteady transport problem of a passive scalar in the DFN, and for dealing with uncertainties in hydro-geological parameters of the fracture distribution considered
Shell elements with through-the-thickness variable kinematics for the analysis of laminated composite and sandwich structures
No full textEvaluation of energy and failure parameters in composite structures via a Component-Wise approach
No full textThis paper deals with the static analysis of fiber reinforced composites via the Component-Wise approach (CW). The main aim of this work is the investigation of the CW capabilities for the evaluation of integral quantities such as the strain energy, or integral failure indexes. Such quantities are evaluated in the global structures and local volumes. The integral failure indexes, in particular, are proposed as alternatives to point-wise failure indexes. The CW approach has been recently developed as an extension of the 1D Carrera Unified Formulation (CUF). The CUF provides hierarchical higher-order structural models with arbitrary expansion orders. In this work, Lagrange-type polynomials are used to interpolate the displacement field over the element cross-sections. The CW makes use of the 1D CUF finite elements to model simultaneously different scale components (fiber, matrix, laminae and laminates) with a reduced computational cost. CW models do not require the homogenization of the material characteristics nor the definition of mathematical lines or surfaces. In other words, the material characteristics of each component, e.g. fibers and matrix, are employed, and the problem unknowns are placed above the physical surface of the body. In the perspective of failure analyses, the integral evaluation of failure parameters is introduced to determine critical portions of the structure where failure could take place. Integral quantities are evaluated using 3D integration sub-domains that may cover macro- and micro-volumes of the structure. The integral quantities can be evaluated directly on fiber and matrix portions. Numerical results are provided for different configurations and compared with solid finite element models. The results prove the accuracy of the CW approach and its computational efficiency. In particular, 3D local effects can be detected. The use of the integral failure index provides qualitatively reliable results; however, experimental campaigns should be carried out to relate such indexes to the failure occurrenc
