The Horizontal Tunnelability Graph is Dual to Level Set Trees

Time series data, reflecting phenomena like climate patterns and stock prices, offer key insights for prediction and trend analysis. Contemporary research has independently developed disparate geometric approaches to time series analysis. These include tree methods, visibility algorithms, as well as persistence-based barcodes common to topological data analysis. This thesis enhances time series analysis by innovatively combining these perspectives through our concept of horizontal tunnelability. We prove that the level set tree gotten from its Harris Path (a time series), is dual to the time series' horizontal tunnelability graph, itself a subgraph of the more common horizontal visibility graph. This technique extends previous work by relating Merge, Chiral Merge, and Level Set Trees together along with visibility and persistence methodologies. Our method promises significant computational advantages and illuminates the tying threads between previously unconnected work. To facilitate its implementation, we provide accompanying empirical code and discuss its advantages

Novel Algorithm for Hand Gesture Modeling Using Genetic Algorithm with Variable Length Chromosome

Many languages the people can exploit for them in order to communicate among them and get the message delivered, but, these languages should be known by those people in order to understand and speak, contrarily, gesture system is the common language that can be adopted for this objective and need less knowledge as compared with spoken languages that need the grammatically and semantically rules, in this paper we applied a novel algorithm for capturing hand gesture shape using one of the evolutionary algorithms in order to fit the hand segment. Previous techniques in the literature that fully captured hand shape applied some artificial intelligent methods [1] or some statistical methods [2]. Genetic Algorithms (GAs) with variable length of chromosomes is used to model the hand structure. The most effective GA parameters used for this purpose are; the generation of initial population, tournament selection, crossover with variable position of the cutting points in the parents, artificial mutation operator, deleting of the repetitive genes in same individual, and elitism strategy. Experimental results shows the robust and efficiency of applying the proposed algorithm

Pulsed Nd:YAG Laser Processing of Nitinol

The excellent pseudoelasticity, shape memory and biocompatibility of Nitinol have made it a leading candidate for applications in various fields, including aerospace, micro-electronics and medical devices. Challenges associated with laser processing need to be resolved before its full potential in practical applications can be realized. The current thesis details the effects of pulsed Nd:YAG laser processing on Ni-rich (Ni-49.2. at.% Ti) Nitinol. First, the mechanical, pseudoelastic and cyclic loading properties for varying process parameters have been compared to those of the base metal. Process parameters were shown to greatly influence the mechanical performance. This was due to local yielding occurring within the processed material during tensile straining. In addition, laser processed samples showed higher permanent residual strain and exhibited a slightly higher efficiency for energy storage during the initial 5 cycles compared to base material. Fracture surfaces of base material revealed ductile dimpled surfaces while welded specimens exhibited both brittle (low peak power) and ductile (high peak power) failure modes. DSC analyses conducted on the processed metal revealed additional high temperature transformation peaks. These peaks were attributed to the local phase conversion induced by laser processing. Further corroboration was made with room temperature XRD analysis, showing only austenite in the base metal and added martensite peaks in the melted metal. Temperature controlled TEM observations confirmed high temperature transformation peaks to be associated with processed metal. Furthermore, TEM analysis aided in identifying the submicron second phase particles observed in fracture surfaces as Ti2Ni. Finally, local phase conversion was correlated to change in local chemical composition. Preferential vaporization of nickel was determined to cause the change in Ni/Ti ratio. This in turn explained the altered mechanical performance and presence of the Ti-rich intermetallic (Ti2Ni). Consequently, a novel method using a high power density energy source to alter transformation temperature of shape memory alloys (SMA’s) was developed. Results were used to successfully demonstrate a novel technology that can embed additional memories in Nitinol and other SMA’s. Possessing the ability to control local transformation temperatures and as a result the shape memory effect of SMA’s promises to enhance their functionality while enabling new applications to be realized

Spot Welding of Advanced High Strength Steels (AHSS)

Efforts to reduce vehicle weight and improve crash performance have resulted in increased application of advanced high strength steels (AHSS) and a recent focus on the weldability of these alloys. Resistance spot welding (RSW) is the primary sheet metal welding process in the manufacture of automotive assemblies. Integration of AHSS into the automotive architecture has brought renewed challenges for achieving acceptable welds. The varying alloying content and processing techniques has further complicated this initiative. The current study examines resistance spot welding of high strength and advance high strength steels including high strength low alloy (HSLA), dual phase (DP) and a ferritic-bainitic steel (590R). The mechanical properties and microstructure of these RSW welded steel alloys are detailed. Furthermore a relationship between chemistries and hardness is produced. The effect of strain rate on the joint strength and failure mode is also an important consideration in the design of welded structures. Current literature, however, does not explain the effects of weld microstructure and there are no comprehensive comparisons of steels. This work details the relationship between the joint microstructure and impact performance of spot welded AHSS. Quasi-static and impact tests were conducted using a universal tensile tester and an instrumented drop tower, respectively. Results for elongation, failure load and energy absorption for each material are presented. Failure modes are detailed by observing weld fracture surfaces. In addition, cross-sections of partially fractured weldments were examined to detail fracture paths during static loading. Correlations between the fracture path and mechanical properties are developed using observed microstructures in the fusion zone and heat-affected-zone. Friction stir spot welding (FSSW) has proven to be a potential candidate for spot welding AHSS. A comparative study of RSW and FSSW on spot welding AHSS has also been completed. The objective of this work is to compare the microstructure and mechanical properties of Zn-coated DP600 AHSS (1.2mm thick) spot welds conducted using both processes. This was accomplished by examining the metallurgical cross-sections and local hardnesses of various spot weld regions. High speed data acquisition was also used to monitor process parameters and attain energy outputs for each process

Discrete Leslie's model with bifurcations and control

We explored a local stability analysis at fixed points, bifurcations, and a control in a discrete Leslie's prey-predator model in the interior of $\mathbb{R}_+^2$. More specially, it is examined that for all parameters, Leslie's model has boundary and interior equilibria, and the local stability is studied by the linear stability theory at equilibrium. Additionally, the model does not undergo a flip bifurcation at the boundary fixed point, though a Neimark-Sacker bifurcation exists at the interior fixed point, and no other bifurcation exists at this point. Furthermore, the Neimark-Sacker bifurcation is controlled by a hybrid control strategy. Finally, numerical simulations that validate the obtained results are given

HAND GESTURE RECOGNITION: A LITERATURE REVIEW

ABSTRAC

Randomize to Generalize: Domain Randomization for Runway FOD Detection

Tiny Object Detection is challenging due to small size, low resolution, occlusion, background clutter, lighting conditions and small object-to-image ratio. Further, object detection methodologies often make underlying assumption that both training and testing data remain congruent. However, this presumption often leads to decline in performance when model is applied to out-of-domain(unseen) data. Techniques like synthetic image generation are employed to improve model performance by leveraging variations in input data. Such an approach typically presumes access to 3D-rendered datasets. In contrast, we propose a novel two-stage methodology Synthetic Randomized Image Augmentation (SRIA), carefully devised to enhance generalization capabilities of models encountering 2D datasets, particularly with lower resolution which is more practical in real-world scenarios. The first stage employs a weakly supervised technique to generate pixel-level segmentation masks. Subsequently, the second stage generates a batch-wise synthesis of artificial images, carefully designed with an array of diverse augmentations. The efficacy of proposed technique is illustrated on challenging foreign object debris (FOD) detection. We compare our results with several SOTA models including CenterNet, SSD, YOLOv3, YOLOv4, YOLOv5, and Outer Vit on a publicly available FOD-A dataset. We also construct an out-of-distribution test set encompassing 800 annotated images featuring a corpus of ten common categories. Notably, by harnessing merely 1.81% of objects from source training data and amalgamating with 29 runway background images, we generate 2227 synthetic images. Subsequent model retraining via transfer learning, utilizing enriched dataset generated by domain randomization, demonstrates significant improvement in detection accuracy. We report that detection accuracy improved from an initial 41% to 92% for OOD test set.Comment: 29 pages, 9 figure

Deconvolution of overlapping peaks from differential scanning calorimetry analysis for multi-phase NiTi alloys

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.tca.2018.05.014 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/An adaptive function capable of fitting the curve of Differential Scanning Calorimetry (DSC) data for any NiTi phase transformation peak has been developed. A novel methodology was applied in conjunction with this new equation, allowing for the deconvolution of multiple overlapping NiTi phase transformation peaks. Characteristic transformation properties determine by this methodology closely matched those ascertainable by current analysis techniques. This novel analysis technique allows for better determination of characteristic properties of complex NiTi materials with overlapping phase transformations or multiple embedded memories.Natural Sciences and Engineering Research Council of CanadaCanadian Foundation for Innovatio

Effects of post-processing on the thermomechanical fatigue properties of laser modified NiTi

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.ijfatigue.2017.11.012 © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/The multifunctional capabilities needed for advanced shape memory alloys (SMA) actuators has been shown to be achievable by locally tuning the properties through laser processing. Before the wide-spread use of these SMAs is realized, a detailed understanding on the long-term stability and functional life span of these material must be achieved. The current study systematically investigates the effects of thermomechanical treatment on laser modified NiTi wires, while comparing them to the original base material. Surface analysis was done using a scanning electron microscope (SEM), while microstructure analysis was performed using transmission electron microscopy (TEM). Mechanical properties were assessed using standard tensile tests and a custom built thermomechanical fatigue. Results showed that the coarse-grains, large inclusions and surface defects associated with as laser modified NiTi resulted in reduced mechanical performance. However, subsequent thermomechanical treatment restored the refined microstructure and mechanical performance similar to the base material while providing the added functionality, thus allowing for laser processed NiTi to be used for manufacturing multiple memory NiTi actuators.Natural Sciences and Engineering Research Council of CanadaCanada Research ChairsOntario Centres of Excellenc