648 research outputs found
Generalized small-signal modelling of dual active bridge DC/DC converter
this paper presents a novel generalised approach of the small-signal modelling of dual active bridge (DAB) DC/DC converter. The adopted analysis is based on a per-unit fundamental frequency representation of the DAB. The outcome of the proposed modelling approach is a small signal, linearised, state-space DAB model; which is considered as a main building block for future control applications. The developed small signal DAB model includes all possible degrees of freedom affecting the performance of the DAB; this includes the voltage conversion ratio to allow the study of all DAB operation modes (i.e.: unity-gain and buck/boost modes.). Furthermore, since triple phase shift control (TPS) is used in this development work, the proposed model incorporates phase shift in addition to duty ratios. This feature allows for bridge voltage regulation, which is essential for efficient DAB operation in the case of buck/boost operation. Another key achievement is that the proposed small signal modelling methodology can be applied to any bidirectional DC-DC converter regardless of ratings, parameter values and number of ports. Extensive simulation is carried out to verify the proposed analysis
Tunneling and Non-Universality in Continuum Percolation Systems
The values obtained experimentally for the conductivity critical exponent in
numerous percolation systems, in which the interparticle conduction is by
tunnelling, were found to be in the range of and about , where
is the universal conductivity exponent. These latter values are however
considerably smaller than those predicted by the available ``one
dimensional"-like theory of tunneling-percolation. In this letter we show that
this long-standing discrepancy can be resolved by considering the more
realistic "three dimensional" model and the limited proximity to the
percolation threshold in all the many available experimental studiesComment: 4 pages, 2 figure
LPAR1 (lysophosphatidic acid receptor 1)
Review on LPAR1 (lysophosphatidic acid receptor 1), with data on DNA, on the protein encoded, and where the gene is implicated
ENHANCEMENT OF SOLUBILITY AND DISSOLUTION RATE OF ACETYLSALICYLIC ACID VIA CO-CRYSTALLIZATION TECHNIQUE: A NOVEL ASA-VALINE COCRYSTAL
Objective: This study aims to synthesize acetylsalicylic acid (ASA) cocrystals using valine as a coformer via a co-crystallization technique to increase the solubility and dissolution rate of ASA.
Methods: The ASA-valine cocrystal (1:1 molar ratio) was prepared using the solvent evaporation technique with ethanol: water (50:50). The cocrystal was characterized using Fourier transform infrared spectroscopy (FT-IR), Differential scanning calorimetry (DSC), Powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM), melting point to confirm the formation of cocrystal. The evaluation of cocrystal was done by drug content determination, solubility and dissolution studies.
Results: The prepared cocrystal was successfully confirmed for the formation of a hydrogen bond. The melting point of prepared cocrystal was decreased compared to pure ASA and valine, which indicated the formation of a new crystalline form. The FT-IR studies showed the formation of a new hydrogen bond by shifting the-O-H,-C=O and-N-H functional groups. SEM studies ensured that the prepared cocrystals were in needle-like appearance. Finally, DSC and PXRD studies were also indicated the successful formation of ASA-valine cocrystal. The drug release of cocrystal was found to be 100% at 60th min. Where in the case of pure ASA and marketed product of ASA exhibited the dissolution rate of 59% and 69% at 60th min respectively.
Conclusion: The co-crystallization technique can be adopted as the best strategy to increase the solubility and dissolution rate of BCS class 2 drugs. Therefore the prepared ASA-valine cocrystal can be a greater alternative to increase the solubility and dissolution rate compared with pure and marketed ASA
The 3s Proton Occupancy in 206-Pb
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
Test of the DWBA Description of Transfer Reactions at Intermediate Energies by Measuring a Complete Set of Single Nucleon and Elastic Scattering Data
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
Investigation of pulsed laser induced dewetting in nanoscopic metal films
Hydrodynamic pattern formation (PF) and dewetting resulting from pulsed laser
induced melting of nanoscopic metal films have been used to create spatially
ordered metal nanoparticle arrays with monomodal size distribution on
SiO_{\text{2}}/Si substrates. PF was investigated for film thickness h\leq7 nm
< laser absorption depth \sim11 nm and different sets of laser parameters,
including energy density E and the irradiation time, as measured by the number
of pulses n. PF was only observed to occur for E\geq E_{m}, where E_{m} denotes
the h-dependent threshold energy required to melt the film. Even at such small
length scales, theoretical predictions for E_{m} obtained from a
continuum-level lumped parameter heat transfer model for the film temperature,
coupled with the 1-D transient heat equation for the substrate phase, were
consistent with experimental observations provided that the thickness
dependence of the reflectivity of the metal-substrate bilayer was incorporated
into the analysis. The spacing between the nanoparticles and the particle
diameter were found to increase as h^{2} and h^{5/3} respectively, which is
consistent with the predictions of the thin film hydrodynamic (TFH) dewetting
theory. These results suggest that fast thermal processing can lead to novel
pattern formation, including quenching of a wide range of length scales and
morphologies.Comment: 36 pages, 11 figures, 1 tabl
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