Bhavin V. Mehta

Comparison of image processing techniques (Magnetic resonance imaging, computed tomography scan and ultrasound) for 3D modeling and analysis of the human bones

Magnetic resonance imaging (MRI), computed tomography scanning (CT scan), and ultrasound imaging techniques (UI) were used for data acquisition to construct/develop a 3D solid model of the human tibia, femur, and skull. CT scan was found to be an acceptable technique for cadavers. CT scans are harmful to the human body in large doses, while MRIs and ultrasound are known to be safe. However, MRIs form a better tool in performing this image generation task for living beings because of its high resolution capacity when compared with images obtained using ultrasound techniques. High resolution poses to be a very important factor, as the consideration of various material properties of the bones was part of the emphasis of this research. MRIs have the capacity of displaying a distinct boundary between the muscles and the bone, in addition to the boundary between the cortical and the cancellous region within the bone. Ultrasound was found to be the cheapest technique and gave reasonably good results for just the outside boundaries of the bone. The models of the human bones were generated on a Computer Aided Design (CAD) system. The cross-sections obtained from (MRI, CT, or UI) were scanned into the computer. Image processing software was used to detect the boundaries of the bones. A C + + program was used to read the coordinates of the edges and construct a B-spline curve on the CAD system. The curves were converted to a B-rep solid using skinning. The solid models were meshed, constrained, and material properties were assigned to different regions of the models for Finite Element Analysis (FEM).

3D flow analysis inside shear and streamlined extrusion dies for feeder plate design

Abstract The extrusion process is one of the commonly used metals forming processes. In this paper, shear dies with a feeder plate are analyzed using a 3D metal forming simulation package — MSC/SuperForge. This package uses the finite-volume analysis method. Twelve simulations using different die shapes (streamlined, shear and shear with feeder plate) for producing a complex shaped product — I-shape — were performed. The results indicated that shear dies with feeder plates can have the same flow characteristics and better surface finish as compared to streamlined dies, which are more difficult to design and manufacture for aluminum extrusions. It is shown that the MSC/SuperForge package using the finite-volume method provides results very close to those obtained from a validated analysis package. However, the simulation time using MSC/SuperForge was almost half the time consumed by the other package in performing identical simulations using the same computer. Moreover, the finite-volume technique used in MSC/SuperForge eliminates the remeshing problems that make simulating a metal-forming process with severe deformation, such as the extrusion process using a shear die, so difficult.

Prediction of Secondary Structures of Proteins

Artificial neural network techniques and Statistical techniques have been used for the prediction of secondary structures of proteins. Back-error propagation was used initially. However it has some inherent shortcomings in its implementation, one being a long convergence time for training and the other being the occurrence of local minima. To overcome the above mentioned drawbacks, a different algorithm called Fuzzy-Adaptive Resonance Theory Mapping (ARTMAP) was employed for our complex pattern mapping problem. Fuzzy ARTMAP is an incremental supervised learning algorithm which combines fuzzy logic and adaptive resonance theory neural network for the recognition of pattern categories.

Modified Upper Bound Elemental Technique (MUBET) for Preform Design in Closed Die Forging

The objective of this research was to develop mathematical models based on modified UBET (MUBET) using backward simulations for forging preform design of axis‐symmetric parts. In the modified UBET, the velocity fields are derived based on volume mapping approach and evaluated by minimizing the total energy rate of UBET. FEM forward simulations were conducted in order to validate the developed model. The significance of various process parameters such as the intermediate/preform geometry, the optimum aspect ratio of billet, and forming load were determined using the developed method. The results showed that this research was successful in predicting the optimal preform geometry which minimizes material waste.

A new methodology of using design of experiments as a precursor to neural networks for material processing: extrusion die design

Extrusion die design and making is an art and a science. In present day extrusions using composites, polymers, and other new alloys, the product geometries are extremely complicated. The flow analysis inside an extrusion die using finite element analysis (FEA) is tedious and time consuming. To optimize the design of a die one needs to perform hundreds of runs, requiring several weeks or months of computer time. In the past researchers have used neural networks (NN) to optimize the design and predict flow patterns for newly designed dies of similar geometries. But, even for NN it has been proven that one needs a few thousand runs to train a network and accurately predict the flow. This paper shows a new methodology of using design of experiments (DOE) as a precursor to identify the importance of some variables and thus reduce the data set needed for training a NN. Based on the DOE results, a neural network training set is generated with more variations for the most significant inputs. A comparison of design using only NN versus using DOE and then NN is shown. The results indicate a significant reduction in the size of the training set, the time required for training and improvement in accuracy of the predicted results. To reduce the analysis time, a newly developed upper bound technique was used for generating the training set. The DOE model is extremely fast and can be used for real time (online) control of the process.

Human Vocal Tract Modeling and Geometric Parameterization

This investigation uses a multi disciplinary approach to standardize a non-invasive method for measuring human vocal tract morphology. A series of Magnetic Resonance Imaging (MRI) scans are performed on the subject’s vocal tract and a detailed three-dimensional model is created through image processing and computer modeling. This information is compared with the vocal tract measurements obtained with Eccovision Acoustic Pharyngometer, in order to establish the accuracy of the instrument. The model is then used to develop other specific models through parametric modeling. This method is useful in creating solid models with limited geometrical information and helps researchers study the human vocal tract changes due to aging and degenerative diseases.Copyright

Improved Prosthetic Bone Implants

An improved method for manufacturing prosthetic bones is examined. We are developing a new improved method for designing and manufacturing prosthetic bones that have a porous interior core covered by a solid outer shell, more closely matching the morphology of natural bone. The new method is compatible with a wide variety of materials, including polymers, metals, composites, and biodegradable scaffold materials. Use of biodegradable scaffold material holds the potential for eventual bone regeneration within and throughout the prosthesis. Regardless of the material selection, this improved type of prosthesis is expected to more closely mimic the overall material and structural properties of natural bone, including shape, strength, weight, and weight distribution. By fabricating prosthetic bones that duplicate the material and structural properties of natural bone, implants could be made to operate as precision replacements, feeling and functioning exactly like natural bone. In addition to improving patient comfort, these new prostheses are expected to reduce the occurrence of unnatural secondary wear patterns caused by current style prosthetic bones that function in unnatural fashions due to their non-matching material and structural properties.Copyright