Effect of size and strain rate on deformation behaviour of Cu50Zr50 metallic glass: A molecular dynamics simulation study

Metallic glasses or amorphous metals have attracted considerable attention due to their unique properties and have been evolved as a potential field of research in recent years. The recent discovery of new glass-forming compositions makes it possible to produce metallic glasses in bulk shapes. Bulk metallic glasses provides a promising future to revolutionize the field of structural materials with combinations of strength, elastic limit, toughness, wear resistance and corrosion resistance. Some of their superior properties over crystalline metals have made them a versatile engineering material for many commercial applications now-a-days. Since the fabrication of metallic glasses require high cooling rates and sometimes practically impossible in laboratory conditions, so computational approaches are extensively used to explore various properties and behaviour of metallic glasses. This project work presents a molecular dynamics simulation study on deformation behaviour of Cu50Zr50 metallic glass where the effect of parameters like sample-size and strain rate on the tensile deformation behaviour have been thoroughly studied. Computational methods to create alloy models, subsequent quenching and further tensile deformation have been mentioned. Stress-strain plots were drawn at same strain rate for different sizes of alloy models and at different strain rates for a particular size. Reasons for getting different stress-stress curves for different conditions have also been discussed

Combinatorial Path Planning for a System of Multiple Unmanned Vehicles

In this dissertation, the problem of planning the motion of m Unmanned Vehicles (UVs) (or simply vehicles) through n points in a plane is considered. A motion plan for a vehicle is given by the sequence of points and the corresponding angles at which each point must be visited by the vehicle. We require that each vehicle return to the same initial location(depot) at the same heading after visiting the points. The objective of the motion planning problem is to choose at most q(≤ m) UVs and find their motion plans so that all the points are visited and the total cost of the tours of the chosen vehicles is a minimum amongst all the possible choices of vehicles and their tours. This problem is a generalization of the wellknown Traveling Salesman Problem (TSP) in many ways: (1) each UV takes the role of salesman (2) motion constraints of the UVs play an important role in determining the cost of travel between any two locations; in fact, the cost of the travel between any two locations depends on direction of travel along with the heading at the origin and destination, and (3) there is an additional combinatorial complexity stemming from the need to partition the points to be visited by each UV and the set of UVs that must be employed by the mission. In this dissertation, a sub-optimal, two-step approach to motion planning is presented to solve this problem:(1) the combinatorial problem of choosing the vehicles and their associated tours is based on Euclidean distances between points and (2) once the sequence of points to be visited is specified, the heading at each point is determined based on a Dynamic Programming scheme. The solution to the first step is based on a generalization of Held-Karp’s method. We modify the Lagrangian heuristics for finding a close sub-optimal solution. In the later chapters of the dissertation, we relax the assumption that all vehicles are homogenous. The motivation of heterogenous variant of Multi-depot, Multiple Traveling Salesmen Problem (MDMTSP) derives form applications involving Unmanned Aerial Vehicles (UAVs) or ground robots requiring multiple vehicles with different capabilities to visit a set of locations

Optimizing the Performance of X-Ray Optics for MaGIXS

The Marshall Grazing Incidence X-Ray Spectrometer (MaGIXS) is an X-ray imaging spectrometer that will observe the solar corona in the soft X-ray regime with both spatial and spectral resolution. The science goal of MaGIXS is to better understand the problem of coronal heating by measuring the temperature distribution, composition, and temporal variability of hot plasmas (>4 MK) in active regions. In order to do this, the instrument will observe the corona with a fast cadence (~5 seconds) in wavelengths between 6-24 A with a 6” spatial resolution and a 0.1 A spectral resolution. To ensure that this instrument can achieve such a resolution, it is crucial to have exact measurements of the focal lengths of the mirrors. The mirrors will be aligned and mounted using the Centroid Detector Assembly (CDA) (a steerable laser originally developed for aligning the AXAF mirrors), a CMM Romer arm, and Hartmann aperture masks to perform the focal length measurements. We have designed metrology supports that elevate the aperture mask and mirror up to the height of the optical axis defined by the CDA of the laser, allows the aperture mask 3 translational degrees of freedom, and the allows the mirror 3 translational and 3 rotational degrees of freedom needed for alignment. The measured and verified focal lengths will then be used to carry out the alignment of the mirrors as the MaGIXS instrument is assembled for launch

The Cross Country Effect of Patent Applications on Ease of Doing Business

Innovation and technological progress have long played a critical role in the economic growth of countries. While this relationship has been studied many times, it is not clear exactly how patents play into this equation. We believe that patents have a direct relationship with innovation, and thus, business growth and progress. Therefore, we hypothesized that countries with a greater number of patent applications will have better ease of business scores as measured by the World Bank. To analyze this relationship, we have used World Bank data and created economical and statistical models to understand this crucial relationship to get a better sense of the role patents play in a country’s economy. Contrary to our original hypothesis, no evidence could be found to support a statistically significant effect of the number of patent applications in a country’s economy on that country’s ease of business score

Synovial chondromatosis of knee joint: a case report

Synovial chondromatosis is a benign condition encountered infrequently within joints which is also known as synovial osteochondromatosis. They present as multiple nodules in the synovium which are either fibrin type or cartilaginous type. The fibrin type usually results from bleeding within the joint, rheumatoid arthritis and tuberculosis. The cartilaginous type is usually due to trauma or osteoarthritis. This typically involves large joints, knee being the most common, rarely small joints also may be involved. Here we report a case of 30-year-old female who presented to us with symptoms of swelling, restriction of movement and pain in the right knee. After clinical and radiological assessment, arthroscopic exploration with loose body removal and synovectomy done, following which patient achieved painless complete range of movements. Histopathological examination confirmed the diagnosis as synovial chondromatosis

Non-Random Sister Chromatid Segregation During Stem Cell Division in Drosophila Melanogaster Testis.

Adult stem cells undergo asymmetric cell division to self-renew and to produce differentiated cells throughout the life of an organism. This increases the risk of replicative senescence or neoplastic transformation due to mutations that accumulate over many rounds of DNA replication. The immortal strand hypothesis proposes that stem cells reduce the accumulation of replication-induced mutations by retaining all the older template DNA strands. In addition, other models have also been proposed in which stem cells non-randomly segregate only a subset of chromosomes for different reasons, such as retention of epigenetic memories. However, the mechanism and the biological relevance of these chromosome asymmetries remain elusive. The Drosophila melanogaster testis is one of the few well-characterized model systems that enable a detailed study of the regulation of stem cells. To elaborate, unlike many other model systems Drosophila male germline stem cells (GSCs) can be unambiguously identified at single-cell resolution. Further, GSCs divide asymmetrically giving rise to a stem cell and a differentiating cell, which can be readily identified in vivo enabling unambiguous identification of both asymmetric stem cell division and any other potential asymmetries such as nonrandom sister chromatid segregation. In this thesis, I describe work where I first showed that the bulk of chromosomes are not segregated asymmetrically in dividing Drosophila GSCs, suggesting that GSCs do not retain all the older template DNA strands to maintain their genomic integrity. However, these initial results did not exclude the possibility that GSCs might be non-randomly segregating individual chromosomes. In order to unambiguously study the segregation patterns of individual chromosomes, I adapted the CO-FISH (chromosome orientation fluorescence in situ hybridization) protocol, which allows strand-specific identification of sister chromatids. Using this method, I found that sister chromatids of X and Y chromosomes, but not autosomes, are segregated non-randomly during asymmetric divisions of GSCs. These results provide the first direct evidence that sister chromatids of certain chromosomes can be segregated non-randomly during asymmetric stem cell divisions. Further, in this work I also showed that centrosomal proteins, nuclear envelope proteins, and methyltransferase are all required for non-random sister chromatid segregation of X and Y chromosomes.PHDCell and Developmental BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/102306/1/swathi_1.pd

On the information flow required for the scalability of the stability of motion of approximately rigid formation

It is known in the literature on Automated Highway Systems that information flow can significantly affect the propagation of errors in spacing in a collection of vehicles. This thesis investigates this issue further for a homogeneous collection of vehicles. Specifically, we consider the effect of information flow on the propagation of errors in spacing and velocity in a collection of vehicles trying to maintain a rigid formation. The motion of each vehicle is modeled using a Linear Time Invariant (LTI) system. We consider undirected and connected information flow graphs, and assume that that each vehicle can communicate with a maximum of q(n) vehicles, where q(n) may vary with the size n of the collection. The feedback controller of each vehicle takes into account the aggregate errors in position and velocity of the vehicles, with which it is in direct communication. The controller is chosen in such a way that the resulting closed loop system is a Type-2 system. This implies that the loop transfer function must have at least two poles at the origin. We then show that if the loop transfer function has three or more poles at the origin, and if the size of the formation is sufficiently large, then the motion of the collection is unstable. Suppose l is the number of poles of the transfer function relating the position of a vehicle with the control input at the origin of the complex plane, and if the number (q(n)l+1)/(nl) -> 0 as n -> (Infinity), then we show that there is a low frequency sinusoidal disturbance with unity maximum amplitude acting on each vehicle such that the maximum errors in spacing response increase at least as much as O (square_root(n^l/(q(n)^(l+1)) ) consequence of the results presented in this paper is that the maximum of the error in spacing and velocity of any vehicle can be made insensitive to the size of the collection only if there is at least one vehicle in the collection that communicates with at least O(square_root(n)) other vehicles in the collection

Open posteromedial dislocation of ankle without associated fractures

Dislocation of ankle without associated malleoli or talar fractures is a rare presentation. There is no established standard treatment for this condition. Most of them are treated by immediate reduction followed by immobilisation for 6-9 weeks. Majority of them recover without any complications. Here we reported a case of 33 year old man who was injured due to fall from a height, His ankle was deformed with a laceration over lateral side of ankle. Plain radiograph revealed posteromedial tibiotalar dislocation without any associated fractures. Immediate reduction and suturing was performed. At 5 months postoperative review patient was able to perform his daily routine without any instability or complaints

Combinatorial Path Planning for a System of Multiple Unmanned Vehicles

In this dissertation, the problem of planning the motion of m Unmanned Vehicles (UVs) (or simply vehicles) through n points in a plane is considered. A motion plan for a vehicle is given by the sequence of points and the corresponding angles at which each point must be visited by the vehicle. We require that each vehicle return to the same initial location(depot) at the same heading after visiting the points. The objective of the motion planning problem is to choose at most q(≤ m) UVs and find their motion plans so that all the points are visited and the total cost of the tours of the chosen vehicles is a minimum amongst all the possible choices of vehicles and their tours. This problem is a generalization of the wellknown Traveling Salesman Problem (TSP) in many ways: (1) each UV takes the role of salesman (2) motion constraints of the UVs play an important role in determining the cost of travel between any two locations; in fact, the cost of the travel between any two locations depends on direction of travel along with the heading at the origin and destination, and (3) there is an additional combinatorial complexity stemming from the need to partition the points to be visited by each UV and the set of UVs that must be employed by the mission. In this dissertation, a sub-optimal, two-step approach to motion planning is presented to solve this problem:(1) the combinatorial problem of choosing the vehicles and their associated tours is based on Euclidean distances between points and (2) once the sequence of points to be visited is specified, the heading at each point is determined based on a Dynamic Programming scheme. The solution to the first step is based on a generalization of Held-Karp’s method. We modify the Lagrangian heuristics for finding a close sub-optimal solution. In the later chapters of the dissertation, we relax the assumption that all vehicles are homogenous. The motivation of heterogenous variant of Multi-depot, Multiple Traveling Salesmen Problem (MDMTSP) derives form applications involving Unmanned Aerial Vehicles (UAVs) or ground robots requiring multiple vehicles with different capabilities to visit a set of locations