20,351 research outputs found
Development and Validation of an In‐Line API Quantification Method Using AQbD Principles Based on UV‐Vis Spectroscopy to Monitor and Optimise Continuous Hot Melt Extrusion Process
open access journalA key principle of developing a new medicine is that quality should be built in, with a
thorough understanding of the product and the manufacturing process supported by appropriate
process controls. Quality by design principles that have been established for the development of
drug products/substances can equally be applied to the development of analytical procedures. This
paper presents the development and validation of a quantitative method to predict the
concentration of piroxicam in Kollidon® VA 64 during hot melt extrusion using analytical quality
by design principles. An analytical target profile was established for the piroxicam content and a
novel in‐line analytical procedure was developed using predictive models based on UV‐Vis
absorbance spectra collected during hot melt extrusion. Risks that impact the ability of the analytical
procedure to measure piroxicam consistently were assessed using failure mode and effect analysis.
The critical analytical attributes measured were colour (L* lightness, b* yellow to blue colour
parameters—in‐process critical quality attributes) that are linked to the ability to measure the API
content and transmittance. The method validation was based on the accuracy profile strategy and
ICH Q2(R1) validation criteria. The accuracy profile obtained with two validation sets showed that
the 95% β‐expectation tolerance limits for all piroxicam concentration levels analysed were within
the combined trueness and precision acceptance limits set at ±5%. The method robustness was tested
by evaluating the effects of screw speed (150–250 rpm) and feed rate (5–9 g/min) on piroxicam
content around 15% w/w. In‐line UV‐Vis spectroscopy was shown to be a robust and practical PAT
tool for monitoring the piroxicam content, a critical quality attribute in a pharmaceutical HME
process
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Scaling Effects in Laser-Based Additive Manufacturing Processes
Mechanical Engineerin
Thermophysical Phenomena in Metal Additive Manufacturing by Selective Laser Melting: Fundamentals, Modeling, Simulation and Experimentation
Among the many additive manufacturing (AM) processes for metallic materials,
selective laser melting (SLM) is arguably the most versatile in terms of its
potential to realize complex geometries along with tailored microstructure.
However, the complexity of the SLM process, and the need for predictive
relation of powder and process parameters to the part properties, demands
further development of computational and experimental methods. This review
addresses the fundamental physical phenomena of SLM, with a special emphasis on
the associated thermal behavior. Simulation and experimental methods are
discussed according to three primary categories. First, macroscopic approaches
aim to answer questions at the component level and consider for example the
determination of residual stresses or dimensional distortion effects prevalent
in SLM. Second, mesoscopic approaches focus on the detection of defects such as
excessive surface roughness, residual porosity or inclusions that occur at the
mesoscopic length scale of individual powder particles. Third, microscopic
approaches investigate the metallurgical microstructure evolution resulting
from the high temperature gradients and extreme heating and cooling rates
induced by the SLM process. Consideration of physical phenomena on all of these
three length scales is mandatory to establish the understanding needed to
realize high part quality in many applications, and to fully exploit the
potential of SLM and related metal AM processes
Random field sampling for a simplified model of melt-blowing considering turbulent velocity fluctuations
In melt-blowing very thin liquid fiber jets are spun due to high-velocity air
streams. In literature there is a clear, unsolved discrepancy between the
measured and computed jet attenuation. In this paper we will verify numerically
that the turbulent velocity fluctuations causing a random aerodynamic drag on
the fiber jets -- that has been neglected so far -- are the crucial effect to
close this gap. For this purpose, we model the velocity fluctuations as vector
Gaussian random fields on top of a k-epsilon turbulence description and develop
an efficient sampling procedure. Taking advantage of the special covariance
structure the effort of the sampling is linear in the discretization and makes
the realization possible
Kaedah pembelajaran lukisan kejuruteraan berasaskan simulasi
Kajian yang dijalankan ini adalah untuk melihat kebolehgunaan sebuah perisian pendidikan yang menerapkan Kaedah Pembelajaran Lukisan Kejuruteraan Berasaskan Simulasi bagi menyelesaikan masalah kurang faham , kurang minat dan kebergantungan yang terlalu memusat kepada guru di kalangan pelajar Tingkatan 4, Sekolah Menengah Ungku Aziz, Sabak Bernam, Selangor . Justeru, penyampaian isi kandungan yang bersesuaian dengan tahap pemikiran atau kognitif pelajar, aspek minat dan motivasi serta pembelajaran ala akses kendiri dirasakan sebagai faktor utama yang ingin dikenal pasti dalam perisian yang dibangunkan bagi menyelesaikan masalah tersebut. Macromedia Authorware versi 6.5 dipilih sebagai bahasa pengarangan bagi membangunkan perisian pendidikan ini. Seramai 30 responden dipilih untuk mendapatkan maklum balas terhadap kajian ini. Data yang didapati telah dianalisis menggunakan perisian Statistical Package for Social Science (SPSS) versi 11.0 menggunakan kaedah deskriptif min. Hasil kajian mendapati bahawa maklum balas adalah positif terhadap faktor-faktor yang telah dikaji
Accurate prediction of melt pool shapes in laser powder bed fusion by the non-linear temperature equation including phase changes - isotropic versus anisotropic conductivity
In this contribution, we validate a physical model based on a transient
temperature equation (including latent heat) w.r.t. the experimental set
AMB2018-02 provided within the additive manufacturing benchmark series,
established at the National Institute of Standards and Technology, USA. We aim
at predicting the following quantities of interest: width, depth, and length of
the melt pool by numerical simulation and report also on the obtainable
numerical results of the cooling rate. We first assume the laser to posses a
double ellipsoidal shape and demonstrate that a well calibrated, purely thermal
model based on isotropic thermal conductivity is able to predict all the
quantities of interest, up to a deviation of maximum 7.3\% from the
experimentally measured values.
However, it is interesting to observe that if we directly introduce, whenever
available, the measured laser profile in the model (instead of the double
ellipsoidal shape) the investigated model returns a deviation of 19.3\% from
the experimental values. This motivates a model update by introducing
anisotropic conductivity, which is intended to be a simplistic model for heat
material convection inside the melt pool. Such an anisotropic model enables the
prediction of all quantities of interest mentioned above with a maximum
deviation from the experimental values of 6.5\%.
We note that, although more predictive, the anisotropic model induces only a
marginal increase in computational complexity
The effects of impurities on the performance of silicon solar cells
The major factors that determine the tolerable concentrations of impurities in silicon feedstock for solar cells used in power generation are discussed in this report. It is concluded that a solar-grade silicon can be defined only for a specific manufacturing process. It is also concluded that it is the electrical effects, efficiency and resistivity, that are dominant in determining tolerable concentrations of impurities in the silicon feedstock. Crystal growth effects may become important when faster growth rates and larger crystal diameters are developed and used
Thermooxidative stability of PMMA composites
Tato práce se zabývá studiem termooxidační stability kompozitů polymethylmethakrylátu (PMMA) plněného mikro a nanočásticemi siliky. V připravených vzorcích byly použity různé objemové zlomky a různé velikosti částic siliky. Studium stability bylo prováděno pomocí termogravimetrie, která umožňuje simulovat podmínky termooxidační degradace. Indukční perioda byla stanovena za použití různých rychlostí ohřevu a aplikací izokonverzních metod. Závislosti teplot degradací na rychlostech ohřevu sloužily pro určení parametrů odvozených ze čtyř různých teplotních funkcí, které dovolují předpověď stability materiálu (indukční periody) při zvoleném rozsahu teplot. Zjištěné výsledky ukazují, že větší částice siliky snižuji stabilitu PMMA, zatímco nanočástice v nízkých koncentracích ji nijak neovlivňují.In this work the thermooxidative stability of poly(methyl metacrylate) (PMMA) composites reinforced with silica micro and nanoparticles was studied. Different volume fractions and particles sizes of silica particles were used. PMMA/silica composites were analysed by thermogravimetry which simulated the conditions of thermooxidative degradation. The induction periods were determined using different heating rates and applying the isoconversional methods. The dependence of degradation temperatures on heating rates were used for the determination of adjustable parameters derived for four different temperature functions allowing the prediction of material stability (induction periods) at chosen temperatures. Results showed that the larger silica particles destabilized the PMMA structure while smallest nanoparticles at low concentration had no effect on the stability.
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