62,215 research outputs found
Application of wavelet analysis in tool wear evaluation using image processing method
Tool wear plays a significant role for proper planning and control of machining parameters to maintain the product quality. However, existing tool wear monitoring methods using sensor signals still have limitations. Since the cutting tool operates directly on the work-piece during machining process, the machined surface provides valuable information about the cutting tool condition. Therefore, the objective of present study is to evaluate the tool wear based on the workpiece profile signature by using wavelet analysis. The effect of wavelet families, scale of wavelet and statistical features of the continuous wavelet coefficient on the tool wear is studied. The surface profile of workpiece was captured using a DSLR camera. Invariant moment method was applied to extract the surface profile up to sub-pixel accuracy. The extracted surface profile was analyzed by using continuous wavelet transform (CWT) written in MATLAB. The re-sults showed that average, RMS and peak to valley of CWT coefficients at all scale increased with tool wear. Peak to valley at higher scale is more sensitive to tool wear. Haar was found to be more effective and significant to correlate with tool wear with highest R2 which is 0.9301
Considerations on the physical and mechanical properties of lime-stabilized rammed earth walls and their evaluation by ultrasonic pulse velocity testing
This study examines the influence of moulding moisture content on the compressive strength, dry density and porosity of a rammed earth wall, using ultrasound as a complementary technique. Non-parametric and multivariate statistical techniques were applied to analyse the behaviour of variables with a sufficiently large population. The statistical analysis demonstrated that excessive or insufficient moulding moisture content directly determines the physical-mechanical properties of such walls. Ultrasound was confirmed as a valid technique for assessing the quality of a wall, since its response, albeit with certain limitations, was consistent with physical-mechanical properties
Porous Titanium for Biomedical Applications: Evaluation of the Conventional Powder Metallurgy Frontier and Space-Holder Technique
Titanium and its alloys are reference materials in biomedical applications because of
their desirable properties. However, one of the most important concerns in long-term prostheses
is bone resorption as a result of the stress-shielding phenomena. Development of porous titanium
for implants with a low Young’s modulus has accomplished increasing scientific and technological
attention. The aim of this study is to evaluate the viability, industrial implementation and potential
technology transfer of different powder-metallurgy techniques to obtain porous titanium with
stiffness values similar to that exhibited by cortical bone. Porous samples of commercial pure titanium
grade-4 were obtained by following both conventional powder metallurgy (PM) and space-holder
technique. The conventional PM frontier (Loose-Sintering) was evaluated. Additionally, the technical
feasibility of two different space holders (NH4HCO3 and NaCl) was investigated. The microstructural
and mechanical properties were assessed. Furthermore, the mechanical properties of titanium porous
structures with porosities of 40% were studied by Finite Element Method (FEM) and compared with
the experimental results. Some important findings are: (i) the optimal parameters for processing
routes used to obtain low Young’s modulus values, retaining suitable mechanical strength; (ii) better
mechanical response was obtained by using NH4HCO3 as space holder; and (iii) Ti matrix hardening
when the interconnected porosity was 36–45% of total porosity. Finally, the advantages and limitations
of the PM techniques employed, towards an industrial implementation, were discussed.Ministry of Economy and Competitiveness of Spain Grant MAT2015-71284-PJunta de AndalucĂa Grant P12-TEP-1401ComisiĂłn Nacional de InvestigaciĂłn, CientĂfica y TecnolĂłgica (CONICYT) of the Chilean government project FONDECYT 1116086
Correlation of Solid Dosage Porosity and Tensile Strength with Acoustically Extracted Mechanical Properties
Currently, the compressed tablet and its oral administration is the most popular drug delivery modality in medicine. The accurate porosity and tensile strength characterization of a tablet design is vital for predicting its performance such as disintegration, dissolution, and drug-release efficiency upon administration as well as ensuring its mechanical integrity. In current work, a non-destructive contact ultrasonic approach and an associated testing procedure are presented and employed to quantify and relate the acoustically extracted mechanical properties of pharmaceutical compacts to direct porosity and tensile strength measurements. Based on a comprehensive set of experimental data, it is demonstrated how strongly the acoustic wave propagation is modulated and correlated to the tablet porosity and tensile strength of a compact made using spray-dried lactose and microcrystalline cellulose with varying mixture ratios. The effect of mixing ratio on the porosity and tensile strength on the resulting compacts is quantified and, with the acoustic experimental data, mixing ratio is related to the compact ultrasonic characteristics. The ultrasonic techniques provide a rapid, non-destructive means for evaluating compacts in formulation development and manufacturing. The presented approach and data could find critical applications in continuous tablet manufacturing, its real-time quality monitoring, as well as minimizing batch-to-batch quality variations
Soil Stabilization Manual 2014 Update
Soil Stabilization is used for a variety of activities including temporary wearing curses, working platforms, improving poor subgrade materials,
upgrading marginal materials, dust control, and recycling old roads containing marginal materials. There are a number methods of stabilizing soils
including modifying the gradation, the use of asphalt or cement stabilizers, geofiber stabilization and chemical stabilization. Selection of the method
depends on the soil type, environment and application. This manual provide tools and guidance in the selection of the proper stabilization method and
information on how to apply the method.
A major portion of this manual is devoted to the use of stabilizing agents. The methods described here are considered best practices for Alaska.State of Alaska, Alaska Dept. of Transportation and Public Facilitie
Comparison of ibuprofen release from minitablets and capsules containing ibuprofen: β-Cyclodextrin complex
NOTICE: this is the author’s version of a work that was accepted for publication in European Journal of Pharmaceutics and Biopharmaceutics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Eur J Pharm Biopharm. 2011 May;78(1):58-66. Epub 2010 Dec 30.Mixtures containing ibuprofen (IB) complexed with b-cyclodextrin (bCD) obtained by two complexation methods [suspension/solution (with water removed by air stream, spray- and freeze-drying) and kneading technique] were processed into pharmaceutical dosage forms (minitablets and capsules). Powders (IB, bCD and IBbCD) were characterized for moisture content, densities (true and bulk), angle of repose and Carr’s index, X-ray and NMR. From physical mixtures and IBbCD complexes without other excipients were prepared 2.5-mm-diameter minitablets and capsules. Minitablets were characterized for the energy of compaction, tensile strength, friability, density and IB release (at pH 1.0 and 7.2), whereby capsules were characterized for IB release. The results from the release of IB were analyzed using different parameters, namely, the similarity factor (f2), the dissolution efficiency (DE) and the amounts released at a certain time (30, 60 and 180 min) and compared statistically (a = 0.05). The release of IB from the minitablets showed no dependency on the amount of water used in the formation of the complexes. Differences were due to the compaction force used or the presence of a shell for the capsules. The differences observed were mostly due to the characteristics of the particles (dependent on the method considered on the formation of the complexes) and neither to the dosage form nor to the complex of the IB
Uncertainty Quantification of geochemical and mechanical compaction in layered sedimentary basins
In this work we propose an Uncertainty Quantification methodology for
sedimentary basins evolution under mechanical and geochemical compaction
processes, which we model as a coupled, time-dependent, non-linear,
monodimensional (depth-only) system of PDEs with uncertain parameters. While in
previous works (Formaggia et al. 2013, Porta et al., 2014) we assumed a
simplified depositional history with only one material, in this work we
consider multi-layered basins, in which each layer is characterized by a
different material, and hence by different properties. This setting requires
several improvements with respect to our earlier works, both concerning the
deterministic solver and the stochastic discretization. On the deterministic
side, we replace the previous fixed-point iterative solver with a more
efficient Newton solver at each step of the time-discretization. On the
stochastic side, the multi-layered structure gives rise to discontinuities in
the dependence of the state variables on the uncertain parameters, that need an
appropriate treatment for surrogate modeling techniques, such as sparse grids,
to be effective. We propose an innovative methodology to this end which relies
on a change of coordinate system to align the discontinuities of the target
function within the random parameter space. The reference coordinate system is
built upon exploiting physical features of the problem at hand. We employ the
locations of material interfaces, which display a smooth dependence on the
random parameters and are therefore amenable to sparse grid polynomial
approximations. We showcase the capabilities of our numerical methodologies
through two synthetic test cases. In particular, we show that our methodology
reproduces with high accuracy multi-modal probability density functions
displayed by target state variables (e.g., porosity).Comment: 25 pages, 30 figure
Early detection of capping risk in pharmaceutical compacts
Capping is a common mechanical defect in tablet manufacturing, exhibited during or after the compression process. Predicting tablet capping in terms of process variables (e.g. compaction pressure and speed) and formulation properties is essential in pharmaceutical industry. In current work, a non-destructive contact ultrasonic approach for detecting capping risk in the pharmaceutical compacts prepared under various compression forces and speeds is presented. It is shown that the extracted mechanical properties can be used as early indicators for invisible capping (prior to visible damage). Based on the analysis of X-ray cross-section images and a large set of waveform data, it is demonstrated that the mechanical properties and acoustic wave propagation characteristics is significantly modulated by the tablet’s internal cracks and capping at higher compaction speeds and pressures. In addition, the experimentally extracted properties were correlated to the directly-measured porosity and tensile strength of compacts of Pearlitol®, Anhydrous Mannitol and LubriTose® Mannitol, produced at two compaction speeds and at three pressure levels. The effect compaction speed and pressure on the porosity and tensile strength of the resulting compacts is quantified, and related to the compact acoustic characteristics and mechanical properties. The detailed experimental approach and reported wave propagation data could find key applications in determining the bounds of manufacturing design spaces in the development phase, predicting capping during (continuous) tablet manufacturing, as well as online monitoring of tablet mechanical integrity and reducing batch-to-batch end-product quality variations
Rammed Earth Construction: A Proposal for a Statistical Quality Control in the Execution Process
Unlike other common contemporary construction materials such as concrete, mortars,
or fired clay bricks, which are widely supported by international standards and regulations,
building with rammed earth is barely regulated. Furthermore, its quality control is usually problematic,
which regularly encourages the rejection of this technique. In the literature, many authors have
suggested ways to safely build a rammed earth wall, but only a few of them have delved into its
quality control before and during the construction process. This paper introduces a preliminary
methodology and establishes unified criteria, based in a statistical analysis, for both the production
and the quality control of this constructive technique in cases dealing with both samples and walls
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