514 research outputs found
Functionally heterogeneous porous scaffold design for tissue engineering
Most of the current tissue scaffolds are mainly designed with homogeneous porosity which does not represent the spatial heterogeneity found in actual tissues. Therefore engineering a realistic tissue scaffolds with properly graded
properties to facilitate the mimicry of the complex elegance of native tissues are critical for the successful tissue regeneration. In this work, novel bio-mimetic heterogeneous porous scaffolds have been modeled. First, the geometry of the scaffold is extracted along with its internal regional heterogeneity. Then the model has been discretized with planner slices suitable for layer based fabrication. An optimum filament deposition angle has been determined for each slice based on the contour geometry and the internal heterogeneity. The internal region has been discritized considering the homogeneity factor along the deposition direction. Finally, an area weight based approach has been used to generate the spatial porosity function that
determines the filament deposition location for desired biomimetic porosity. The proposed methodology has been implemented and illustrative examples are provided. The effective porosity has been compared between the proposed
design and the conventional homogeneous scaffolds. The result shows a significant error reduction towards achieving the biomimetic porosity in the scaffold design and provides better control over the desired porosity level. Moreover, sample designed structures have also been fabricated with a NC motion
controlled micro-nozzle biomaterial deposition system
N-fold Supersymmetry in Quantum Systems with Position-dependent Mass
We formulate the framework of N-fold supersymmetry in one-body quantum
mechanical systems with position-dependent mass (PDM). We show that some of the
significant properties in the constant-mass case such as the equivalence to
weak quasi-solvability also hold in the PDM case. We develop a systematic
algorithm for constructing an N-fold supersymmetric PDM system. We apply it to
obtain type A N-fold supersymmetry in the case of PDM, which is characterized
by the so-called type A monomial space. The complete classification and general
form of effective potentials for type A N-fold supersymmetry in the PDM case
are given.Comment: 18 pages, no figures; Refs. updated, typos correcte
New approach to (quasi)-exactly solvable Schrodinger equations with a position-dependent effective mass
By using the point canonical transformation approach in a manner distinct
from previous ones, we generate some new exactly solvable or quasi-exactly
solvable potentials for the one-dimensional Schr\"odinger equation with a
position-dependent effective mass. In the latter case, SUSYQM techniques
provide us with some additional new potentials.Comment: 11 pages, no figur
Modeling of multifunctional porous tissue scaffolds with continuous deposition path plan
A novel modeling technique for porous tissue scaffolds with targeting the functionally gradient variational porosity with continuous material deposition planning has been proposed. To vary the porosity of the designed scaffold
functionally, medial axis transformation is used. The medial axis of each layers of the scaffold is calculated and used as an internal feature. The medial axis is then used connected to the outer contour using an optimum matching. The desired pore size and hence the porosity have been achieved by discretizing the sub-regions along its peripheral direction based on the pore
size while meeting the tissue scaffold design constraints. This would ensure the truly porous nature of the structure in every direction as well as controllable porosity with interconnected pores. Thus the desired controlled variational porosity along the scaffold architecture has been achieved with the combination of two geometrically oriented consecutive layers. A continuous,
interconnected and optimized tool-path has been generated for successive layers for additive-manufacturing or solid free form fabrication process. The proposed methodology has been computationally implemented with illustrative examples.
Furthermore, the designed example scaffolds with the desired pore size and porosity has been fabricated with an extrusion based bio-fabrication process
Spectrum generating algebras for position-dependent mass oscillator Schrodinger equations
The interest of quadratic algebras for position-dependent mass Schr\"odinger
equations is highlighted by constructing spectrum generating algebras for a
class of d-dimensional radial harmonic oscillators with and a
specific mass choice depending on some positive parameter . Via some
minor changes, the one-dimensional oscillator on the line with the same kind of
mass is included in this class. The existence of a single unitary irreducible
representation belonging to the positive-discrete series type for and
of two of them for d=1 is proved. The transition to the constant-mass limit
is studied and deformed su(1,1) generators are constructed.
These operators are finally used to generate all the bound-state wavefunctions
by an algebraic procedure.Comment: 21 pages, no figure, 2 misprints corrected; published versio
Moving forward with combinatorial interaction testing
Combinatorial interaction testing (CIT) is an efficient and effective method of detecting failures that are caused by the interactions of various system input parameters. In this paper, we discuss CIT, point out some of the difficulties of applying it in practice, and highlight some recent advances that have improved CIT’s applicability to modern systems. We also provide a roadmap for future research and directions; one that we hope will lead to new CIT research and to higher quality testing of industrial systems
Position-dependent mass models and their nonlinear characterization
We consider the specific models of Zhu-Kroemer and BenDaniel-Duke in a
sech-mass background and point out interesting correspondences with the
stationary 1-soliton and 2-soliton solutions of the KdV equation in a
supersymmetric framework.Comment: 8 Pages, Latex version, Two new references are added, To appear in
J.Phys.A (Fast Track Communication
Jointly learning trajectory generation and hitting point prediction in robot table tennis
This paper proposes a combined learning framework for a table tennis robot. In a typical robot table tennis setup, a single striking point is predicted for the robot on the basis of the ball's initial state. Subsequently, the desired Cartesian racket state and the desired joint states at the striking time are determined. Finally, robot joint trajectories are generated. Instead of predicting a single striking point, we propose to construct a ball trajectory prediction map, which predicts the ball's entire rebound trajectory using the ball's initial state. We construct as well a robot trajectory generation map, which predicts the robot joint movement pattern and the movement duration using the Cartesian racket trajectories without the need of inverse kinematics, where a correlation function is used to adapt these joint movement parameters according to the ball flight trajectory. With joint movement parameters, we can directly generate joint trajectories. Additionally, we introduce a reinforcement learning approach to modify robot joint trajectories such that the robot can return balls well. We validate this new framework in both the simulated and the real robotic systems and illustrate that a seven degree-of-freedom Barrett WAM robot performs well
Morphometric properties of the tensor fascia lata muscle in human foetuses
Background: In neonatal and early childhood surgeries such as meningomyelocele repairs, closing deep wounds and oncological treatment, tensor fasciae lata (TFL) flaps are used. However, there are not enough data about structural properties of TFL in foetuses, which can be considered as the closest to neonates in terms of sampling. This study’s main objective is to gather data about morphological structures of TFL in human foetuses to be used in newborn surgery. Materials and methods: Fifty formalin-fixed foetuses (24 male, 26 female) with gestational age ranging from 18 to 30 weeks (mean 22.94 ± 3.23 weeks) were included in the study. TFL samples were obtained by bilateral dissection and then surface area, width and length parameters were recorded. Digital callipers were used for length and width measurements whereas surface area was calculated using digital image analysis software. Results: No statistically significant differences were found in terms of numerical value of parameters between sides and sexes (p > 0.05). Linear functions for TFL surface area, width, anterior and posterior margin lengths were calculated as y = –225.652 + 14.417 × age (weeks), y = –5.571 + 0.595 × age (weeks), y = –4.276 + 0.909 × age (weeks), and y = –4.468 + 0.779 × age (weeks), respectively. Conclusions: Linear functions for TFL surface area, width and lengths can be used in designing TFL flap dimensions in newborn surgery. In addition, using those described linear functions can also be beneficial in prediction of TFL flap dimensions in autopsy studies
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