Terahertz Topological Waveguide and Waveguide based Grating

The upcoming sixth-generation (6G) communication which could emerge as an intelligent platform, is expected to deliver ubiquitous wireless technology. The use of the terahertz (THz) region of the spectrum has the potential to support high data rates (over 100 Gbit/s) and wider bandwidth enabling future 6G wireless technologies and the internet of things. Nevertheless, the THz frequencies have a set of technical challenges including the adequate high power from THz sources and the lack of integrated THz systems with high bandwidth and low cost. The latter can be enabled by a compact planar platform through integrated waveguides and functional components with low loss and low dispersion. Several planar THz waveguides have been proposed for routing THz waves including promising solutions such as metallic parallel-plate waveguides, dielectric two-dimensional photonic crystal waveguides, and hybrid photonic crystal waveguides. Due to THz waveguide interconnection with different components in an integrated THz system, flexibility is required to have the waveguides with bends. However, these current THz waveguides show a lack of robustness and high loss against sharp bends arising from reflection. This results in a narrow transmission bandwidth in the waveguide and waveguides with functional components, i.e., bends, intersections, and junctions. The recent realization of quantum spin Hall photonic topological insulator rises as an avenue to enable robust propagation insensitive to structural impurities and sharp bends through a topological waveguiding solution. Prior topological waveguides are mainly reported either on the microwave or optical frequencies. While we initiate working for topological waveguides in the THz region, since then, a few reports have appeared mostly all-silicon-based topological waveguides. However, these reports present relatively narrow topological single-mode bandwidth due to the high refractive index of silicon. In addition, the need for access to clean rooms and photolithography machines makes the fabrication process expensive. This thesis is structured into two parts: development of THz waveguide and waveguide-based device towards THz integrated system. In the context of a waveguide, this thesis reports low-cost and broad-bandwidth air channel topological integrated waveguide in the THz region which is considered a new field of application stemming from the recent breakthrough in photonic topological insulators. The topological waveguide, composed of hexagonally arranged photonic crystal metallic pillars confined between two metallic parallel plates offers broader relative topological bandwidth beating the previously reported silicon-based THz topologically guided bandwidth with a 60% increase in terms of the actual frequency range. The topological waveguide is fabricated with low-cost 3D printing and a gold sputtering method, for the first time, to the best of our knowledge. The waveguide supports single-mode, linear dispersion, and topological robustness, confirming the low-loss transmission through sharp corners and defects in the measurements. Another crucial point for realizing an integrated THz system is the development of waveguide-based functional devices. The waveguide devices provide the advantage of manipulating THz waves effectively and increase stability compared to free-space isolated optical components. In this development, various waveguide devices are still in demand such as the THz filter, an essential signal-processing device. To realize a passive filter, a common approach is to exploit Bragg grating, a fundamental component, which has been widely demonstrated in the optical range due to low loss silica but less explored in THz due to high absorption losses of polymers. In the context of the waveguide-based device, this thesis reports dual-frequency filtering and dispersion compensating THz waveguide subwavelength grating. The grating is realized using a subwavelength birefringent dielectric core in a cross-section where the periodicity is introduced along the propagation direction. The fabrication of subwavelength waveguide grating is performed using micromachining techniques in a low-loss polymer material, cyclic olefin copolymer. The waveguide grating demonstrates filtering of two orthogonally polarized modes (x- and y- polarizations) with average 8-dB extinction ratios and 5-GHz 3-dB bandwidth for both polarizations. Due to strong index modulation in a subwavelength grating, a large negative group velocity dispersion of -188/ps/mm/THz is achieved which confirms a 7.5 times increase in comparison to the state-of-the-art reported until now in the THz range. In addition, this dispersion is reported in a very compact length of 43 mm which is less than half of the length reported to date, to the best of our knowledge. This thesis shines a light on the development of future integrated THz systems. This is realized by examining the possibility of exploiting a robust waveguide for the short-range broadband THz wireless communication and compact polarization maintaining waveguide-based grating for the THz long-haul wireless/fiber-based links, respectively

Video-GroundingDINO: Towards Open-Vocabulary Spatio-Temporal Video Grounding

Video grounding aims to localize a spatio-temporal section in a video corresponding to an input text query. This paper addresses a critical limitation in current video grounding methodologies by introducing an Open-Vocabulary Spatio-Temporal Video Grounding task. Unlike prevalent closed-set approaches that struggle with open-vocabulary scenarios due to limited training data and predefined vocabularies, our model leverages pre-trained representations from foundational spatial grounding models. This empowers it to effectively bridge the semantic gap between natural language and diverse visual content, achieving strong performance in closed-set and open-vocabulary settings. Our contributions include a novel spatio-temporal video grounding model, surpassing state-of-the-art results in closed-set evaluations on multiple datasets and demonstrating superior performance in open-vocabulary scenarios. Notably, the proposed model outperforms state-of-the-art methods in closed-set settings on VidSTG (Declarative and Interrogative) and HC-STVG (V1 and V2) datasets. Furthermore, in open-vocabulary evaluations on HC-STVG V1 and YouCook-Interactions, our model surpasses the recent best-performing models by $4.88$ m_vIoU and $1.83\%$ accuracy, demonstrating its efficacy in handling diverse linguistic and visual concepts for improved video understanding. Our codes will be publicly released

Video-FocalNets: Spatio-Temporal Focal Modulation for Video Action Recognition

Recent video recognition models utilize Transformer models for long-range spatio-temporal context modeling. Video transformer designs are based on self-attention that can model global context at a high computational cost. In comparison, convolutional designs for videos offer an efficient alternative but lack long-range dependency modeling. Towards achieving the best of both designs, this work proposes Video-FocalNet, an effective and efficient architecture for video recognition that models both local and global contexts. Video-FocalNet is based on a spatio-temporal focal modulation architecture that reverses the interaction and aggregation steps of self-attention for better efficiency. Further, the aggregation step and the interaction step are both implemented using efficient convolution and element-wise multiplication operations that are computationally less expensive than their self-attention counterparts on video representations. We extensively explore the design space of focal modulation-based spatio-temporal context modeling and demonstrate our parallel spatial and temporal encoding design to be the optimal choice. Video-FocalNets perform favorably well against the state-of-the-art transformer-based models for video recognition on five large-scale datasets (Kinetics-400, Kinetics-600, SS-v2, Diving-48, and ActivityNet-1.3) at a lower computational cost. Our code/models are released at https://github.com/TalalWasim/Video-FocalNets.Comment: Accepted to ICCV-2023. Camera-Ready version. Project page: https://TalalWasim.github.io/Video-FocalNets

En bloc resection of a giant retroperitoneal liposarcoma: A surgical challenge

Liposarcomas are exceedingly rare entities that evoke malignant transformation of connective tissue and fat cells.These tumours occur throughout the soft tissues of the body, afflicting a myriad of regions. In the adult population, liposarcomas represent the most prevalent subtype of sarcomas, and often arise de novo. Retroperitoneal liposarcomas (RLS) are a ubiquitous subset of sarcomas that, due to their deep location in the hollow abdomen, can grow to astronomical proportions before manifesting any noticeable symptoms; a prompt diagnosis of RLS is therefore often rendered dilatory. We hereby delineate the case of a 43-year-old woman who presented with vague left hemiabdominal distention and discomfort. A subsequent computed tomography scan divulged a giant retroperitoneal growth impaling on and thus displacing the pancreas. A compartmental, en bloc resection was performed, with subsequent histopathology of the excised specimen revealing a well-differentiated liposarcoma. The surgical intervention was curative and led to an uneventful recovery. This paper highlights the pertinence of surgical management as an appropriate treatment modality for a complete resection of RLS

Primary somatosensory cortex in chronic low back pain – a 1H-MRS study

The goal of this study was to investigate whether certain metabolites, specific to neurons, glial cells, and the neuronal-glial neurotransmission system, in the primary somatosensory cortex (SSC), are altered and correlated with clinical characteristics of pain in patients with chronic low back pain (LBP). Eleven LBP patients and eleven age-matched healthy controls were included. N-acetylaspartate (NAA), choline (Cho), myo-inositol (mI), and glutamine/glutamate (Glx) were measured with proton magnetic resonance spectroscopy (1H-MRS) in left and right SSC. Differences in metabolite concentrations relative to those of controls were evaluated as well as analyses of metabolite correlations within and between SSCs. Relationships between metabolite concentrations and pain characteristics were also evaluated. We found decreased NAA in the left SSC (P = 0.001) and decreased Cho (P = 0.04) along with lower correlations between all metabolites in right SSC (P = 0.007) in LBP compared to controls. In addition, we found higher and significant correlations between left and right mI (P < 0.001 in LBP vs P = 0.1 in controls) and between left mI and right Cho (P = 0.048 vs P = 0.6). Left and right NAA levels were negatively correlated with pain duration (P = 0.04 and P = 0.02 respectively) while right Glx was positively correlated with pain severity (P = 0.04). Our preliminary results demonstrated significant altered neuronal-glial interactions in SSC, with left neural alterations related to pain duration and right neuronal-glial alterations to pain severity. Thus, the 1H-MRS approach proposed here can be used to quantify relevant cerebral metabolite changes in chronic pain, and consequently increase our knowledge of the factors leading from these changes to clinical outcomes

DSP Based Digital Controller Design and Implementation for Energy Systems

This paper presents a comprehensive study on the design and implementation of DSP-based digital controllers for energy systems, with a specific focus on utilizing the TMS320F28335 microcontroller from Texas Instruments. Energy systems play a critical role in various domains and improving their control strategies using advanced digital signal processing (DSP) techniques is of utmost importance. The paper begins with an overview of energy systems and the significance of efficient control mechanisms. It then explores the fundamental concepts of DSP and highlights the relevance of using the TMS320F28335 microcontroller for digital control applications in energy systems. The microcontroller offers a powerful combination of performance, features, and flexibility, making it suitable for implementing complex control algorithms

Searching Heuristically Optimal Path Using a New Technique of Bug0 Algorithm in Swarm Robotics

Bug Algorithms in robotics field play an important role in path planning. The main challenge in conventional bug algorithms is searching the cluttered environment. To solve this problem a method is introduced which uses the concept of swarm robotics that helps in finding path using coordination between robots in swarm. The challenge in this research article is to find a path which is heuristically optimal. A type of bug algorithm is introduced in which parent bug sends two of its child bugs. Each of them has capability of searching in different directions. After searching the path from both sides, parent bug follows the path which is heuristically optimal. Parent and child bugs are equipped with tactile sensors to follow the perimeter of an obstacle. Illustrative simulation results show two test cases in which different scenarios are presented. Results are compared with of bug0 algorithm that is visualized in configuration space as well as in workspace to find the heuristically optimal path