1,720,980 research outputs found
On the applicability of algebraic statistics to regression models with errors in variables
No full textShape Partitioning Based on Symmetries Detection
No full textFeature partitioning is one of the most frustrating problems in measurement processes. Currently the solution relies on technician's skills and experience but industries and metrological laboratories are searching for more rigorous procedures. The Geometrical Product Specification (GPS) project, whose goal is the formulation of a unique, coherent and mathematical-based framework for product shape control, is facing the problem. According to the mathematical approach adopted several years ago, the ISO/TC213, sponsor of the GPS project, proposed a classification of three-dimensional surfaces according to their invariance properties under the action of rigid motions (i.e. symmetries). This methodology requires the development and implementation of proper algorithms for feature classification and several approaches has been developed to partition surfaces on the basis of symmetries detection. Currently three different methods, available in scientific literature, are investigated to address the feature partitioning process: the Stanford method, the Wien method and the Turin method. Many other methods are available to solve the partitioning problem but only these methods rely on the feature classification adopted in the ISO/TC213 GPS projec
Analysis of the Covariance Structure in Manufactured Parts
No full textWe discuss on a technological case study the use of estimators of covariance in a Kriging model to assess tolerances in a mechanical production process. It is a tricky issue to decide which class of covariance models is the best among the available options. The variogram is very informative about the spatial dependence and its estimation is essential in the spatial prediction, because it allows the computation of the weights assigned to the measured points in the Kriging prediction. In the paper we use various literature estimators for variograms for evaluating their estimation propertie
Introductory notes to algebraic statistics
Full text linkThese are the notes of a short course on algebraic
statistics, a new discipline across the fields of statistical modeling
and computational commutativa algebra. The basics of the
theory are provided together with brief reference to applications to
design of experiments, to exponential and graphical models, and
to computational biology
Strategic factors affecting warehouse maintenance costs
No full textPurpose - The purpose of this paper is to determine the fundamental factors influencing maintenance costs of logistic buildings and to provide benchmark indications for designing maintenance efficient warehouses that contribute to the enhancement of business performance. Design/methodology/approach - The relations between factors and indicators of building facilities maintenance costs are examined using regression analysis of a dataset collected from about 100 distribution warehouses leased by a leading global freight provider throughout Italy. Findings - Maintenance cost reduction can only be achieved by making appropriate design decisions on the strategic characteristics of warehouse facilities. In particular, the location and the age of a building are relevant factors of breakdown maintenance, while the monthly volume of freight transiting the warehouse is a significant cost factor of maintenance due to damage. Research limitations/implications - This paper is limited to logistic service providing organisations, has local impact, and does not consider operational requirements in suggesting design criteria. Further research may gainfully generalise the model by examining other businesses, geographical areas and industrial operations issues. Leasing and frequently relocating facilities have emerged as appropriate distribution management strategies to control location, size and age of a building, and thus to face dynamic business conditions. Originality/value - This paper provides maintenance cost benchmarks and supports design decision making of distribution warehouse facilities
Research on feature partitioning: analysis of efficiency and reliability of ISO algorithms
No full text
Drilling experiments on a gamma titanium aluminide obtained via electron beam melting
No full textGamma titanium aluminides are intermetallic structural alloys with many advantages like high temperature and oxidation resistance, low density, high specific strength, rigidity, etc. This makes them promising candidates for critical applications where both mechanical and thermal properties are required. Unfortunately, their machinability is demanding, generating low cutting life and poor surface conditions. A deeper knowledge on the machining parameters is essential for a wider application of these heat resistant light-weight alloys in aircraft and automotive industry. In this paper, the performance of uncoated carbide drills in drilling a gamma titanium aluminide was analysed. The workpiece material was obtained via electron beam melting (EBM) process, a versatile technology for additive manufacturing of complex metal parts from metal powders. EBM is highly appealing in the field of aeroengine components, and it is particularly interesting in processing gamma titanium aluminides. Cutting performances were measured in terms of tool wear, surface roughness, dimensional and geometric errors. The experimental results show strong dependence of tool wear and part quality on cutting parameters, with poor tool life compared with other work material
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