Time filter

Source Type

Littringer E.M.,Research Center Pharmaceutical Engineering GmbH | Mescher A.,Institute of Mechanical Engineering | Schroettner H.,Austrian Center for Electronic Microscopy and Nanoanalysis | Achelis L.,University of Bremen | And 2 more authors.
European Journal of Pharmaceutics and Biopharmaceutics | Year: 2012

The aim of this work was to study the performance of mannitol carrier particles of tailored surface roughness in dry powder inhaler formulations. Carrier particles of different surface roughness were prepared by spray drying of aqueous mannitol solutions at different outlet temperatures at a pilot-scale spray dryer. However, the carrier particles did not only change in surface roughness but also in shape. This is why the impact of carrier shape on the performance of carrier based dry powder inhalates was evaluated also. The highest fine particle fraction (FPF), that is the amount of active pharmaceutical substance, delivered to the deep lung, is achieved when using rough, spherical carrier particles (FPF = 29.23 ± 4.73%, mean arithmetic average surface roughness (mean Ra) = 140.33 ± 27.75 nm, aspect ratio = 0.925). A decrease of surface roughness (mean Ra = 88.73 ± 22.25 nm) leads to lower FPFs (FPF = 14.62 ± 1.18%, aspect ratio = 0.918). The FPF further decreases when irregular shaped particles are used. For those particles, the micronized active accumulates within the cavities of the carrier surface during the preparation of the powder mixtures. Upon inhalation, the cavities may protect the active from being detached from the carrier. © 2012 Elsevier B.V. All rights reserved.


Zhu Y.,Institute of Mechanical Engineering
Jixie Qiangdu/Journal of Mechanical Strength | Year: 2016

Diagnosis and resolution faults of gas bearing turbo-expander influences the operation of refrigeration system. Through the analysis of the structure of gas bearing turbo-expander is of great importance for fault diagnosis. Crashes, caused by the rotor imbalance, was eliminated by static balance and dynamic balance test, when gas bearing turbo-expander was started and run, it should be regulated not to overspeed to ensure that rotor were not overloaded. The reason of gas bearing stability was analyzed, caused by the radial load and frequent start-stop and flash power outage. The relationship between gas supply pressure, radial clearance and the rotor balance was analyzed. Clearance, between the machine shell and wheel, could be adjusted to avoid the increase of the internal leakage. Measures was adopt to reduce external leaks, such as adjusting the sealing gap at the back of the wheel and providing plenty of sealing gas. The causes of liquid impact fault was analyzed, and processing method was put forward. Failures caused by gas pipeline jam and unclean bearing gas were analyzed. Methods are proposed to ensure safe and stable operation of the turbo-expander gas bearing, such as rigorous test of dynamic and static balance, the correct assembly, standardized operation, and regular maintenance. © 2016, Journal of Mechanical Strength. All right reserved.


Dinis L.M.J.S.,University of Porto | Jorge R.M.N.,University of Porto | Belinha J.,Institute of Mechanical Engineering
Computers and Structures | Year: 2011

The Natural Neighbour Radial Point Interpolation Method (NNRPIM), an improved meshless method, is used in the numerical implementation of an Unconstrained Third-Order Plate Theory applied to laminates. The nodal connectivity and the node dependent integration background mesh are constructed resorting to the Voronoï tessellation and to the Delaunay triangulation. Within NNRPIM the obtained interpolation functions, constructed with the Radial Point Interpolators, pass through all nodes inside the influence-cell providing the interpolation functions with the delta Kronecker property. In order to prove the high accuracy and convergence rate of the proposed meshless method several well-known benchmark static and dynamic laminate examples are solved. The numerical results obtained with the NNRPIM are compared with the Unconstrained Third-Order Plate Theory exact solution, when available, and with exact solutions of other plate deformation theories. © 2010 Civil-Comp Ltd and Elsevier Ltd. All rights reserved.


Belinha J.,Institute of Mechanical Engineering | Jorge R.M.N.,University of Porto | Dinis L.M.J.S.,University of Porto
Computer Methods in Biomechanics and Biomedical Engineering | Year: 2013

In this work, a novel anisotropic material law for the mechanical behaviour of the bone tissue is proposed. This new law, based on experimental data, permits to correlate the bone apparent density with the obtained level of stress. Combined with the proposed material law, a biomechanical model for predicting bone density distribution was developed, based on the assumption that the bone structure is a gradually self-optimising anisotropic biological material that maximises its own structural stiffness. The strain and the stress field required in the iterative remodelling process are obtained by means of an accurate meshless method, the Natural Neighbour Radial Point Interpolation Method (NNRPIM). Comparing with other numerical approaches, the inclusion of the NNRPIM presents numerous advantages such as the high accuracy and the smoother stress and strain field distribution. The natural neighbour concept permits to impose organically the nodal connectivity and facilitates the analysis of convex boundaries and extremely irregular meshes. The viability and efficiency of the model were tested on several trabecular benchmark patch examples. The results show that the pattern of the local bone apparent density distribution and the anisotropic bone behaviour predicted by the model for the microscale analysis are in good agreement with the expected structural architecture and bone apparent density distribution. © 2013 © 2013 Taylor & Francis.


Belinha J.,Institute of Mechanical Engineering | Dinis L.M.J.S.,University of Porto | Natal Jorge R.M.,University of Porto
International Journal for Numerical Methods in Engineering | Year: 2013

SUMMARY: In this work an innovative numerical approach is proposed, which combines the simplicity of low-order finite elements connectivity with the geometric flexibility of meshless methods. The natural neighbour concept is applied to enforce the nodal connectivity. Resorting to the Delaunay triangulation a background integration mesh is constructed, completely dependent on the nodal mesh. The nodal connectivity is imposed through nodal sets with reduce size, reducing significantly the test function construction cost. The interpolations functions, constructed using Euclidian norms, are easily obtained. To prove the good behaviour of the proposed interpolation function several data-fitting examples and first-order partial differential equations are solved. The proposed numerical method is also extended to the elastostatic analysis, where classic solid mechanics benchmark examples are solved. © 2013 John Wiley & Sons, Ltd.


Belinha J.,Institute of Mechanical Engineering | Dinis L.M.J.S.,University of Porto | Natal Jorge R.M.,University of Porto
International Journal of Mechanical Sciences | Year: 2013

An innovative numerical approach, combining the simplicity of low-order finite elements connectivity with the geometric flexibility of Meshless methods, is extended to the elastostatic analysis of thick plates. The nodal connectivity is enforced using the natural neighbour mathematical concept and the background integration mesh is constructed uniquely depending on the nodal mesh. The nodal connectivity is imposed through nodal sets with reduced size, reducing significantly the test function construction cost. The interpolation functions are constructed using Euclidean norms and easily obtained. It is considered as the Reissner-Mindlin plate shear deformation theory. Several thick plate elastostatic benchmark examples are solved. © 2013 Elsevier Ltd.


Dinis L.M.J.S.,University of Porto | Jorge R.M.N.,University of Porto | Belinha J.,Institute of Mechanical Engineering
Composite Structures | Year: 2010

A three-dimensional shell-like approach for the analysis of composite thin plates and shells using a meshless method, the natural neighbour radial point interpolation method (NNRPIM), is presented. In the NNRPIM the nodal connectivity is enforced using the natural neighbour concept. The node-depending background mesh used in the numerical integration of the NNRPIM interpolation functions is entirely created from the unstructured nodal arrangement. The radial point interpolators are used to construct the NNRPIM interpolation functions, which possesses the delta Kronecker property, used in the Galerkin weak form. The novelty of this work lays on the development of a unique NNRPIM approach when 3D thin structures are considered. This new approach leads to remarkable results and it is extremely suitable to the composite structure problem. In order to demonstrate the effectiveness of the method the 3D shell-like NNRPIM analysis is used to solve several isotropic and orthotropic thin plates and shells problems. © 2009 Elsevier Ltd. All rights reserved.


Filippenko G.V.,Institute of Mechanical Engineering
Proceedings of the International Conference Days on Diffraction, DD 2010 | Year: 2010

Shells are the elements of various constructions, particulary partially submerged into the water (see [1], Fig. 1). They are subjected to external forces of different kind. It is important to estimate the level of vibration fields in these composite systems and analyze energy and energy flow in them. Different shell models were considered in [2], [3], [4] for example. The shell models of Timoshenko and Kirchhoff-Love type, approach and results received in [2] are considered here. © 2010 Days on Diffraction.


Dinis L.M.J.S.,University of Porto | Natal Jorge R.M.,University of Porto | Belinha J.,Institute of Mechanical Engineering
Thin-Walled Structures | Year: 2011

This work presents the dynamic analysis of three-dimensional plate and shell structures based on an improved meshless method, the Natural Neighbour Radial Point Interpolation Method (NNRPIM) using a shell-like formulation. In the NNRPIM, the nodal connectivity is imposed using the natural neighbours concept. An integration background mesh is constructed, totally node-dependent, and used in the numerical integration of the NNRPIM interpolation functions, which possess the delta Kronecker property. Several dynamic plate and shell problems are studied to demonstrate the effectiveness of the method. © 2010 Elsevier Ltd.


Belinha J.,Institute of Mechanical Engineering | Natal Jorge R.M.,University of Porto | Dinis L.M.J.S.,University of Porto
Engineering Analysis with Boundary Elements | Year: 2012

In this work the natural neighbour radial point interpolation method (NNRPIM), an improved meshless method, is extended to the bone remodelling analysis. A biomechanical model for predicting the bone density distribution was developed. The proposed gradient remodelling algorithm considers an anisotropic material law for the mechanical behaviour of the bone tissue, based on experimental data available in the literature, allowing to gradually correlate the bone density with the obtained level of stress. The viability and efficiency of the model were successfully tested on the classical femur bone example and a novel calcaneus bone example under multiple loading conditions. © 2012 Elsevier Ltd. All rights reserved.

Loading Institute of Mechanical Engineering collaborators
Loading Institute of Mechanical Engineering collaborators