114 research outputs found
Design and characterization of the tensile properties of 3-d braid-twist ligament scaffolds
No full textThere are roughly between 100,000 -250,000 anterior cruciate ligament (ACL) injuries that are annually diagnosed in the U.S. alone. Around 50,000 of these require surgical reconstruction and replacement of the ACL [1-2]. The current treatment of choice is the use of an autograft harvested from the patellar tendon, the hamstring tendon or quadriceps tendons. However, autologous grafts are associated with a number of drawbacks including donor site morbidity and the requirement of two surgeries to carry out the ACL replacement. Therefore, alternative techniques need to be developed for ACL reconstruction. Recently tissue engineering-based scaffolds have received wide attention as potentially viable alternatives to autografts. This report discusses the development and characterization of the tensile properties of a 3-D braid twist scaffold fabricated using an automated braiding machine. The braiding angle of the scaffolds was altered in a controllable manner. Scaffolds with three different braiding angles; 53°, 63° and 72° were obtained to determine the effect of braiding angle on the tensile properties of the braid-twist scaffolds. Based on these studies scaffolds with a braiding angle of 72° were determined to have tensile characteristics most suitable for ligament replacement. Future studies will further evaluate the mechanical and biological properties of these scaffolds.M.S.Includes bibliographical referencesby Rohit Ra
Automatically learning optimal formula simplifiers and database entity matching rules
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 153-161).Traditionally, machine learning (ML) is used to find a function from data to optimize a numerical score. On the other hand, synthesis is traditionally used to find a function (or a program) that can be derived from a grammar and satisfies a logical specification. The boundary between ML and synthesis has been blurred by some recent work [56,90]. However, this interaction between ML and synthesis has not been fully explored. In this thesis, we focus on the problem of finding a function given large amounts of data such that the function satisfies a logical specification and also optimizes a numerical score over the input data. We present a framework to solve this problem in two impactful application domains: formula simplification in constraint solvers and database entity matching (EM). First, we present a system called Swapper based on our framework that can automatically generate code for efficient formula simplifiers specialized to a class of problems. Formula simplification is an important part of modern constraint solvers, and writing efficient simplifiers has largely been an arduous manual task. Evaluation of Swapper on multiple applications of the Sketch constraint solver showed 15-60% improvement over the existing hand-crafted simplifier in Sketch. Second, we present a system called EM-Synth based on our framework that generates as effective and more interpretable EM rules than the state-of-the-art techniques. Database entity matching is a critical part of data integration and cleaning, and it usually involves learning rules or classifiers from labeled examples. Evaluation of EM-Synth on multiple real-world datasets against other interpretable (shallow decision trees, SIFI [116]) and noninterpretable (SVM, deep decision trees) methods showed that EM-Synth generates more concise and interpretable rules without sacrificing too much accuracy.by Rohit Singh.Ph. D
Modified Lifting Scheme for DWT along with Parallel scanning Architecture 1
Get PDFAbstract To overcome the inefficiencies in the JPEG standard and serve emerging areas of mobile and Internet communications, the new Lifting Scheme and processing element has been developed based on the principles of DWT. Previous DWT architectures are mostly based on the lift ing scheme/flipping structure where at least four pipelining stages were required for each multiplier or a large temporal buffer is needed. In this brief, modifications are made to the lifting scheme, and the intermediate results are recombined in the processing element and stored to get three number of pipelining stages and with reduced design complexity, computational time and to get the result in 2Dimensional image. Through optimizing the lifting scheme, Wu and Lin [10] implemented the parallel 2-D DWT. The design is a pipelined two-input/two-output architecture, and a 2×2 transposing module with four registers was developed. In addition, the critical path delay is one Tm. Nevertheless, it needs eight pipelining stages to complete the 1-D DWT and makes the total number of registers reach 22. The flipping structure is another important DWT architecture that was proposed by Huang et al. In this brief, further optimization on the processing element is proposed to overcome shortages in previous works and minimize sizes of the logic units and the memory without loss of the throughput. By recombining the intermediate results of the row and column transforms, the number of pipelining stages and registers is reduced, while keeping the critical path delay as Tm. In addition, a novel architecture is developed to implement the 2-D DWT based on the above modified scheme. The parallel scanning method is employed to reduce the computational time. As a result, our design achieves higher efficiency. The rest of this brief is organized as follows. Section II reviews the lifting scheme of the DWT in and Section III presents the proposed architecture for the 2-D DWT, and Section IV provides implementation results and comparisons with previous architectures. Conclusion is drawn in Section
L-C filter design implementation and comparative study with various PWM techniques for DCMLI
No full textUse of Public Library Services by Differently abled Persons: A Pilot Study of City Central Library, Dharwad
Get PDFIn this article, an attempt has been made to investigate whether differently abled persons effectively using public library services or not. For the study, 50 questionnaires were distributed to differently abled persons and finally 43 (86%) questionnaires were considered for analysis based on the merit of the filled questionnaires. The analysis of the data revealed that, differently abled persons use City Central Library services very rarely and majority rather all of them were physically disabled persons. Another finding is that, Information needs of differently abled persons are same as other abled persons. It is rather disappointing that majority i.e. 69.77% of information needs of differently abled persons remain un-satisfied. Inaccessibility, Lack of reading materials in alternative formats, special services and Lack of assistive technologies with access to computers are the major problems faced by the differently abled persons. The study concludes with some of the important suggestions for development of information resources, services and infrastructure facilities of the CCL in order to provide better services and to improve the collection to satisfy the needs of differently abled persons
Synthesizing a synthesis tool
Get PDFThesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 85-87).SMT/SAT solvers are used by many tools for program verification and analysis. Most of these tools have an optimization layer which applies transformations (or "rewrite rules") to simplify the internal representation of the problem. These hard coded rules can drastically affect the performance of the solver. They are usually hand-picked by experts and verified using trial and error. These rules are very domain-specific as well (the domain from which the tool receives its inputs) and leverage the recurring patterns in the domain. The goal of this thesis is to automatically synthesize this optimization layer by learning an optimal set of rules from a corpus of problems taken from a given domain. To achieve this goal, we will use two key technologies: Machine Learning and Program Synthesis (Sketch tool). Sketch is a state of the art tool for generating programs automatically from high level specifications. We propose a Machine Learning and Sketch based method to automatically generate "statistically significant" optimization rules (rules that can be applied at significant number of places in benchmarks from a particular domain) and then generate efficient code to apply the rules for that particular domain. In addition to using Sketch as a tool, we will also use it as a target for this technology. Sketch uses SAT/SMT solver in its back-end, and, like any other tool it has its own hand-built optimization layer. In particular, Sketch uses a set of pre- determined optimization rules to modify the internal representation of the formula in a way that results in faster SAT/SMT solving. Sketch is being used for synthesizing programs in various domains like Storyboard Programming[21], SQL queries for databases[5], MPI based Parallel Programming, Autograder for MOOCs[20]; The current optimizer has to work well for each one of these domains and one of our goals is to have a domain specific optimizer that can take advantage of specific features of each domain. Hence, Sketch is an ideal use-case for our analysis and all our experiments are conducted on the Sketch tool for various domains.by Rohit Singh.S.M
Associations of micronutrients and lipids with prediabetes and glycemic parameters in adolescent girls of the rural DERVAN cohort (DERVAN-9)
Get PDFBackgroundWe investigated the associations of micronutrients and lipids with prediabetes, glycemic parameters, and glycemic indices among the adolescent girls of the DERVAN (aDolescent and prEconception health peRspectiVe of Adult Non-communicable diseases) cohort study from rural India.MethodsWe recruited 1,520 adolescent girls aged 16–18 years. We measured glycemic parameters (glucose, insulin and HbA1C), lipids (total cholesterol, high-density lipoprotein [HDL], low-density lipoprotein [LDL], and triglycerides), and micronutrients (vitamin B12, folate, and vitamin D). Prediabetes was defined using American Diabetes Association criteria (fasting glucose ≥100 mg/dL or HbA1C ≥5.7%). Glycemic indices (insulin resistance, insulin sensitivity, and β cell function) were calculated using the homeostasis model. Associations of prediabetes, glycemic parameters and glycemic indices with micronutrients and lipids were analyzed by multiple logistic regressions.ResultsThe median age and Body Mass Index (BMI) were 16.6 years and 17.6 kg/m2, respectively. Overall, 58% of girls had a low BMI. Median vitamin B12, folate, and vitamin D concentrations were 249.0 pg/mL, 6.1 ng/mL, and 14.2 ng/mL, respectively. The deficiencies observed were 32.1% for vitamin B12, 11.8% for folate, and 33.0% for vitamin D. Median total cholesterol, LDL, HDL, and triglyceride concentrations were 148.0 mg/dL, 81.5 mg/dL, 50.8 mg/dL, and 61.5 mg/dL, respectively. Elevated total cholesterol, LDL, and triglycerides were observed in 4.8, 4.0, and 3.8%, respectively, while low HDL was observed in 12.8%. Prediabetes was observed in 39.7% of the girls. Among lipids, total cholesterol and LDL were higher in girls with prediabetes (p < 0.01 for both). In a multivariate model containing cholesterol and vitamin B12/folate/vitamin D, prediabetes was associated with high cholesterol. Prediabetes was also associated with high LDL, independent of folate and vitamin D. Poor insulin secretion was high in those with low vitamin B12. Elevated insulin resistance was associated with low HDL. The likelihood of high insulin sensitivity was reduced in those with high triglycerides. The likelihood of poor β cell function was high in those with high LDL. Statistical interactions between micronutrients and lipids for prediabetes and glycemic outcomes were not significant.ConclusionThere was a substantial deficiency of micronutrients and an absence of dyslipidemia. Our results indicate the need for lipid and micronutrient-based interventions in adolescence to improve glycemic outcomes. Maintaining adequate storage of not only micronutrients but also lipids in adolescent girls is likely to reduce diabetes risk in adulthood
Periodicity in the cohomology of symmetric groups via divided powers
Get PDFA famous theorem of Nakaoka asserts that the cohomology of the symmetric group stabilizes. The first author generalized this theorem to non‐trivial coefficient systems, in the form of FI‐modules over a field, though one now obtains periodicity of the cohomology instead of stability. In this paper, we further refine these results. Our main theorem states that if M is a finitely generated FI‐module over a noetherian ring k then ⨁n⩾0Ht(Sn,Mn) admits the structure of a D‐module, where D is the divided power algebra over k in a single variable, and moreover, this D‐module is ‘nearly’ finitely presented. This immediately recovers the periodicity result when k is a field, but also shows, for example, how the torsion varies with n when k=Z. Using the theory of connections on D‐modules, we establish sharp bounds on the period in the case where k is a field. We apply our theory to obtain results on the modular cohomology of Specht modules and the integral cohomology of unordered configuration spaces of manifolds.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143618/1/plms12107.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/143618/2/plms12107_am.pd
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