The computation of the eddy along the upper wall in the three‐dimensional flow over a backward‐facing step

A three‐dimensional laminar flow over a backward‐facing step is studied as a numerical experiment by solving the steady‐state, isothermal and incompressible Navier–Stokes equations using two different finite element codes. The Reynolds number ranges from 100 to 1050. The expansion ratio is 1:1.94, and the aspect ratio is 1:36.7. The numerical experiment reveals both eddies along the lower and upper walls downstream of the step. Results of computations regarding positions of detachment of the eddy along the upper wall and positions of reattachments of the eddies along both the lower and upper walls are tabulated along with positions and magnitudes of global extrema of shear rate within the eddies. The wall effects are shown by calculating streamlines along planes parallel/normal to the lateral walls of the domain and depicting how the streamlines are distorted close to the walls and how they assume a two‐dimensional configuration in the plane of symmetry. Comparisons are made with available numerical results and laboratory measurements

Neural network: an instrument to study flow and packing properties of pharmaceutical powders

In the present study five brands of microcrystalline cellulose (Ph101, Vivapur, Ph 301, Emcocel and Prosolv), three brands of Crospovidone (XL, XL-10 and INF) and pregelatinized Starch were mixed with 2% w/w of Aerosil 200, Aerosil R972 (two different kinds of colloidal silicon dioxide) or Mg stearate, to obtain 27 distinct mixtures. Flow rate, bulk and tapped density of mixtures were measured and tablets were prepared

Powder Compaction: Compression Properties of Cellulose Ethers

Effective development of matrix tablets requires a comprehensive understanding of different raw material attributes and their impact on process parameters. Cellulose ethers (CE) are the most commonly used pharmaceutical excipients in the fabrication of hydrophilic matrices. The innate good compression and binding properties of CE enable matrices to be prepared using economical direct compression (DC) techniques. However, DC is sensitive to raw material attributes, thus, impacting the compaction process. This article critically reviews prior knowledge on the mechanism of powder compaction and the compression properties of cellulose ethers, giving timely insight into new developments in this field

A new outflow boundary condition

Boundary conditions come from Nature. Therefore these conditions exist at natural boundaries. Often, owing to limitations in computing power and means, large domains are truncated and confined between artificial synthetic boundaries. Then the required boundary conditions there cannot be provided naturally and there is a need to fabricate them by intuition, experience, asymptotic behaviour and numerical experimentation. In this work several kinds of outflow boundary conditions, including essential, natural and free boundar conditions, are evaluated for two flow and heat transfer model problems. A new outflow boundary condition, called hereafter the free boundary condition , is introduced and tested. This free boundary condition is equivalent to extending the validity of the weak form of the governing equations to the synthetic outflow instead of replacing them there with unknown essential or natural boundary conditions. In the limit of zero Reynolds number the free boundary condition minimizes the energy functional among all possible choices of outflow boundary conditions. A review of results from applications of the same boundary conditions to several other flow situations is also presented and discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50207/1/1650140506_ftp.pd

Dissolution Enhancement and Formulation of Rapid-Release Lornoxicam Mini-Tablets

The aim was to enhance the dissolution of lornoxicam (LOR) and to produce mini-tablets with an optimised system to provide a rapid-release multi-particulate formulation. LOR systems were prepared through co-evaporation with either polyethylene glycol 6000 or Pluronic® F-68 (PLU) and adsorption onto Neusilin® US2 alone or co-adsorption in the presence of different amounts of polysorbate 80. All systems were characterised by FT-IR, differential scanning calorimetry, X-ray diffraction, flowability and dissolution techniques. Mini-tablets were prepared using the system with the optimum dissolution profile and flowability. Tensile strengths, content uniformity and dissolution profiles of the mini-tablets were evaluated. The effects of different excipients and storage conditions on mini-tablet properties were also studied. The optimised rapid-release LOR mini-tablets were further evaluated for their in vivo pharmacokinetic profile. The co-evaporate of LOR with PLU showed significantly faster dissolution and superior flowability and was evaluated together with three directly compressible excipients (Cellactose® 80, StarLac® (STA) and Emcompress®) for mini-tablet formulation. The formulation with STA provided the optimum results in terms of tensile strength content uniformity and rapid drug release following a 3-month stability study and was selected for further in vivo evaluation. The pharmacokinetic profile indicated the potential of the mini-tablets achieving rapid release and increased absorption of LO

Pharmaceutical nanocrystals: production by wet milling and applications

Nanocrystals are regarded as an important nanoformulation approach exhibiting advantages of increased dissolution and saturation solubility with chemical stability and low toxicity. Nanocrystals are produced in the form of nanosuspensions using top-down (e.g., wet milling or high pressure homogenization) and bottom-up methods (e.g., antisolvent precipitation). Wet milling is a scalable method applicable to drugs with different physicochemical and mechanical properties. Nanocrystalline-based formulations, either as liquid nanosuspensions or after downstream processing to solid dosage forms, have been developed as drug delivery systems for various routes of administration (i.e., oral, parenteral, pulmonary, ocular, and dermal). In this review, we summarize and discuss the features, preparation methods, and therapeutic applications of pharmaceutical nanocrystals, highlighting their universality as a formulation approach for poorly soluble drugs

Three-dimensional streamlined finite elements: Design of extrusion dies

A method to determine three-dimensional die shapes from extrudate swell and vice versa is presented using a three-dimensional Galerkin finite element method based on a streamlined formulation with the fluid velocities and pressures represented by triquadratic and trilinear basis functions respectively. The three-dimensional streamlined method, an extension of the two-dimensional formulation, uses successive streamsurfaces to form a boundary-conforming co-ordinate system. This produces a fixd, computational domain leaving the spatial location of the elements as unknowns to be determined with the standard primary variables ( u , v , w , p ). The extrudate produced by a die of a given shape is considered for moderate Reynolds numbers. Finally, the method is extended to address the problem of die design, where a die profile is sought to produce a target extrudate shape.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50206/1/1650140103_ftp.pd

Neural network: an instrument to study flow and packing properties of pharmaceutical powders

In the present study five brands of microcrystalline cellulose (Ph101, Vivapur, Ph 301, Emcocel and Prosolv), three brands of Crospovidone (XL, XL-10 and INF) and pregelatinized Starch were mixed with 2% w/w of Aerosil 200, Aerosil R972 (two different kinds of colloidal silicon dioxide) or Mg stearate, to obtain 27 distinct mixtures. Flow rate, bulk and tapped density of mixtures were measured and tablets were prepared

Analysis of high-speed continuous casting with inverse finite elements

A recently proposed inverse isotherm finite element method is further extended in order to account for processes with distorted isotherms. With this method a variety of problems can be solved which require the explicit calculation of characteristic material lines along with the common field of unknowns in transport phenomena. The method is applied to high-speed metal casting, where the location and shape of the extensive solidification front is calculated simultaneously with the primary unknowns, the velocity and the pressure, whereas the temperature is fixed at the moving nodes of the finite element tessellation. This is achieved by solving the energy equation inversely along with the rest of the conservation equations, i.e. the temperature field is fixed and its location is calculated. Empirical correlations may be derived which give the shape of the solidification front as a function of the process parameters. This may be used to improve the control means of metal casting, which is currently based on one-dimensional approximate analyses.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50204/1/1650131002_ftp.pd