Layer-based Approach Research Articles

Performance evaluation of Python and MATLAB for CGH generation using layer-based approach

Performance evaluation of Python and MATLAB for CGH generation using layer-based approach

Vortex technique to track 3D object displacement in CGH

In this work, we introduce and test a technique to track the movement of objects from computer-generated holographic videos, without the need for reconstruction. To achieve this, we first generated holographic videos of moving 3D objects using a random phase layer-based approach. Then, we analyzed the hologram phase to determine the locations of the optical vortices. We used the core properties of each vortex to track its movement over all the frames of the video, and then establish a relationship between the object and the vortex movement. We also tested the vortex tracking over a pseudo-phase obtained by performing the Laguerre–Gauss transform of the hologram, which enables more precise control over the number of optical vortices that can be tracked. Our proposal was tested with holographic videos generated with one and two objects, using two different hologram generation approaches.

A Probabilistic Fatigue Strength Assessment in AlSi-Cast Material by a Layer-Based Approach

An advanced lightweight design in cast aluminium alloys features complexly shaped geometries with strongly varying local casting process conditions. This affects the local microstructure in terms of porosity grade and secondary dendrite arm spacing distribution. Moreover, complex service loads imply changing local load stress vectors within these components, evoking a wide range of highly stressed volumes within different microstructural properties per load sequence. To superimpose the effects of bulk and surface fatigue strength in relation to the operating load sequence for the aluminium alloy EN AC 46200, a layer-based fatigue assessment concept is applied in this paper considering a non-homogeneous distribution of defects within the investigated samples. The bulk fatigue property is now obtained by a probabilistic evaluation of computed tomography results per investigated layer. Moreover, the effect of clustering defects of computed tomography is studied according to recommendations from the literature, leading to a significant impact in sponge-like porosity layers. The highly stressed volume fatigue model is applied to computed tomography results. The validation procedure leads to a scattering of mean fatigue life from −2.6% to 12.9% for the investigated layers, inheriting strongly varying local casting process conditions.

Security and Privacy Issues in Autonomous Vehicles: A Layer-Based Survey

Artificial Intelligence (AI) is changing every technology we are used to deal with. Autonomy has long been a sought-after goal in vehicles, and now more than ever we are very close to that goal. Big auto manufacturers as well are investing billions of dollars to produce Autonomous Vehicles (AVs). This new technology has the potential to provide more safety for passengers, less crowded roads, congestion alleviation, optimized traffic, fuel-saving, less pollution as well as enhanced travel experience among other benefits. But this new paradigm shift comes with newly introduced privacy issues and security concerns. Vehicles before were dumb mechanical devices, now they are becoming smart, computerized, and connected. They collect huge troves of information, which needs to be protected from breaches. In this work, we investigate security challenges and privacy concerns in AVs. We examine different attacks launched in a layer-based approach. We conceptualize the architecture of AVs in a four-layered model. Then, we survey security and privacy attacks and some of the most promising countermeasures to tackle them. Our goal is to shed light on the open research challenges in the area of AVs as well as offer directions for future research.

An improved air entrainment model for stepped spillways

This work considers the application of the air entrainment model developed in [P. Lopes et al. Int. J. Nonlin. Sci. Num., vol. 18, pp. 559-574, 2017] to simulation of flows in stepped spillways. Four Froude numbers are considered for the flow, with parameters selected to match available experimental data. An extensive simulation campaign led to the identification of several deficiencies in the model, most importantly, its strong grid dependence. An improvement to the interface detection algorithm used in the model is proposed, and simulations reveal improved robustness with respect to the grid density. Furthermore, two criteria for predicting the inception point of air entrainment are tested, based on energy balance and boundary layer state, respectively. The boundary layer-based approach is recommended due to superior accuracy and robustness with respect to turbulence model selection.

Photocuring-while-writing: A 3D printing strategy to build free space structure and freeform surface texture

Parts are fabricated layer-by-layer in most three-dimensional (3D) printing methods. Such a layer-based approach brings obstacles to fabricate layer-sensitive objects, such as space structures and surface textures. We present a photocuring-while-writing strategy for 3D printing. A nozzle is used to extrude photocurable material, and a laser is used to dynamically solidify the newly extruded materials instantly into desired features. Two scanning galvo mirrors control the laser spot based on a developed mathematical model. As a proof of concept, we successfully built free-standing structures and surface textures. The developed strategy may shed light on fabricating conformal features, free-standing scaffolds, and multi-material textures.

MR1 Tetramer-Based Artificial APCs Expand MAIT Cells from Human Peripheral Blood That Effectively Kill Glioblastoma Cells.

Immunotherapy for cancer treatment requires the activation of cytotoxic effector lymphocytes. Mucosal-associated invariant T (MAIT) cells are innate T cells that recognize the MHC class I-like molecule MR1. MAIT cells play an important role in the immune response against microbial infections and can directly kill tumor cells. Although MAIT cells can be expanded ex vivo, this method is time-consuming, expensive, and requires allogenic feeder layers. To overcome the limitations of conventional dendritic cell-based vaccines and ex vivo expansion of human T cells, an artificial APC (aAPC) approach to expand antitumor effector cells has several advantages. In this study, we explored an efficient in vitro method to amplify MR1-specific MAIT cells from human peripheral blood using aAPCs made by coating cell-sized latex beads with an Ag-loaded MR1 tetramer complex and anti-CD28 Ab. We further elucidated the cytotoxic potential of such expanded MAIT cells against three human glioblastoma multiforme (GBM) cell lines to explore their potential use as a novel immunotherapeutic tool, as the mostly lethal GBM poorly responds to conventional chemotherapy. When aAPCs were compared with the standard allogenic feeder layer-based approach for MAIT cell expansion, they were significantly more effective. Our results indicate that the aAPC-expanded MAIT cells remained functional, retained their original phenotype, secreted proinflammatory cytokines, and showed cytotoxicity against the GBM cell lines. Hence, MAIT cells have the potential to be a novel tool in immunotherapy approaches for the treatment of human GBM.

‘MR1 Tetramer-based Artificial Antigen Presenting Cells Expand MAIT Cells from Human Peripheral Blood that Effectively Kill Glioblastoma Cells.’

Abstract Immunotherapy for cancer treatment requires the activation of cytotoxic effector lymphocytes. Mucosal-associated invariant T (MAIT) cells are innate T cells that recognize the MHC class I-like molecule, MR1. MAIT cells play an important role in the immune response against microbial infections and can directly kill tumor cells. Although MAIT cells can be expanded ex vivo, this method is time-consuming, expensive and requires allogenic feeder layers. To overcome the limitations of conventional dendritic cell-based vaccines and ex vivo expansion of human T cells, an artificial antigen presenting cell (aAPC) approach to expand antitumor effector cells has several advantages. In this study, we explored an efficient in vitro method to amplify MR1-specific MAIT cells from human peripheral blood using aAPCs made by coating cell-sized latex beads with an antigen-loaded MR1 tetramer complex and anti-CD28 antibody. We further elucidated the cytotoxic potential of such expanded MAIT cells against three human glioblastoma (GBM) cell lines to explore their potential use as a novel immunotherapeutic tool, as the mostly lethal GBM poorly responds to conventional chemotherapy. When aAPCs were compared to the standard allogenic feeder layer-based approach for MAIT cell expansion, they were significantly more effective. Our results indicate that the aAPC-expanded MAIT cells remained functional, retained their original phenotype, secrete pro-inflammatory cytokines, and showed cytotoxicity against the GBM cell lines. Hence, MAIT cells have the potential to be a novel tool in immunotherapy approaches for the treatment of human GBM.

An Approach for Mitigation of Beam Blockage in mmWave-Based Indoor Networks

The rapidly evolving scenario around cellular networks, Internet of Things (IoT), and the associated services ecosystem has generated a wide range of expectations for the future networks. However, the unavailability of sufficient bandwidth and severe interference prohibit the existing commercially used radio-frequency (RF) bands from supporting some of these services. In this respect, the millimeter wave (mmWave)-based systems are seen as promising alternatives for supporting various high data rate enhanced mobile broadband (eMBB) services. Nevertheless, the adverse wave propagation characteristics in these bands and the resulting media access control (MAC) layer problems of beam blockage restrict these systems from operating in a reliable manner. Therefore, in this article, we propose a MAC layer-based approach of control delegation to tackle the problem of beam blockage. The mechanism uses policy-based relinquishment of access point (AP) control from the default AP to other AP capable member nodes to improve node visibility and alleviate the blockage scenario without requiring any additional network infrastructure. To account for the dynamic behavior of the network, a discrete-time Markov decision process (MDP)-based model is proposed. It uses a dynamic optimization methodology to accommodate multiple reconfigurable performance metrics, which can then be adjusted to cater to different performance criteria. Using computer simulations, we evaluate the effectiveness of our proposed solution for some alternate static and dynamic control policies. Our simulation results show that our proposed solution can significantly reduce the blockage in a network while satisfying a variety of performance objectives over different classes of indoor IoT scenarios.

Comparison of algorithms to suppress artifacts from the natural lens in fluorescence lifetime imaging ophthalmoscopy (FLIO).

Fluorescence lifetime imaging ophthalmoscopy (FLIO) has developed as a new diagnostic tool in ophthalmology. FLIO measurements are taken from 30° retinal fields in two spectral channels (short spectral channel (SSC): 498-560 nm, long spectral channel (LSC): 560-720 nm). Because of the layered structure of the eye, the detected signal is an interaction of the fluorescence decay of the anterior part and of the fundus. By comparing FLIO measurements before and after cataract surgery, the impact of the natural lens was proven, despite the application of a confocal laser scanning (cSLO) technique. The goal of this work was to determine the best algorithmic solution to isolate the sole fundus fluorescence lifetime from the measured signal, suppressing artifacts from the natural lens. Three principles based on a tri-exponential model were investigated: a tailfit, a layer-based approach with a temporally shifted component, and the inclusion of a separately measured fluorescence decay of the natural lens. The mean fluorescence lifetime τm,12 is calculated using only the shortest and the intermediate exponential component. τm,all is calculated using all three exponential components. The results of tri-exponential tailfit after cataract surgery were considered as a reference, because the implanted artificial lens can be assumed as non-fluorescent. In SSC, the best accordance of τm,all of the reference was determined with τm,12 of the tailfit before surgery. If high-quality natural lens measurements are available, the correspondence of τm,12 is best with τm,all of the reference. In LSC, there is a good accordance for all models between τm,12 before and after surgery. To study the pure fundus fluorescence decay in eyes with natural lenses, we advise to utilize fluorescence lifetime τm,12 of a triple-exponential tailfit, as it corresponds well with the mean fluorescence lifetime τm,all of eyes with fluorescence-less artificial intraocular lenses.

SIMURG_CITIES: Meta-Analysis for KPI's of Layer-Based Approach in Sustainability Assessment

SIMURG_CITIES, is the research and development project that is developed under the main project named as SIMURG: “A performance-based and Sustainability-oriented Integration Model Using Relational database architecture to increase Global competitiveness of Turkish construction industry in industry 5.0 era”, is the relational database model that is currently being developed in a dissertation for performance-based development and assessment of sustainable and sophisticated solutions for the built environment. This study aims to analyze the key performance indicators (KPIs) at «Cities Level» for the smart city concept that is referred to as «Layers» in the master project. KPIs for the concept of a smart city is determined by using the meta-analysis technique. Hence, the three most reputable urban journals issued from 2017 through 2020 are reviewed in this study. In addition to this, models of smart city frameworks/assessment tools/KPIs are reviewed within the context of this paper; environment, economy and governance were found to have domain themes on the urban sustainability according to the literature review. Consequently, efficient and integrated urban management, environmental monitoring and management, public and social services of urban development and sustainability are found to be the most important dimensions in urban and regional planning. SIMURG_CITIES evaluation models for urban projects can use the findings of this paper.

NB-IoT Security: A Survey

In the past few years, the term Internet of Things (IoT) has become very prevalent. In IoT, aggregation of data (from sensors) to processing the data (to the cloud) is energy constraint. To address this challenge, Narrowband- Internet of Things (NB-IoT) is becoming a popular choice for smart devices manufacturer due to its characteristics of high energy-efficient and long battery life. Researchers and academia have addressed the problem related to energy constraints, but it opens the door for security issues related to NB-IoT devices. In this paper, we have done a survey closely related to security issues related to NB-IoT technologies like RFID, WSN, WoT, and IoT. IoT is enabled with five-layered architectures, and each layer is prone to different security attacks. In this paper, we have provided a comparative analysis of security issues in a layer-based approach. We propose the different possible security attacks like shared node attack, synchronization attack, node failure attack, source code attack, and battery drainage attack associated with NB-IoT. To do the performance analysis of security attacks, related matrix, and their mathematical formulation is based on Secrecy Rate and Secrecy Outage Probability for the smart home application. This paper also raises security issues related to smart health and smart agriculture applications.

Web Based Cross Layer Optimization Technique for Energy Efficient WSN

In recent days, wireless sensor networks (WSN) plays a major role in the real time applications like military battlefield surveillance, industrial process monitoring, machine health monitoring and so on. In WSN, selecting the cluster head (CH) is the challenging task. CH selection is done by considering parameters of single layer only. In cross layer protocol more than one layers are considered for inter related parameters such as integration of MAC/physical layer and integration routing/MAC/physical layers. The main drawback of layer-based approach is not considering the effect on improvement of particular layer parameter to other layer parameters. In this paper, new cross layer technique for energy efficient module is designed to address the energy efficiency issues, which is common to all layers and used to optimize the energy from one layer parameter by others. Nowadays everything is possible with the help of Internet, so sharing the information between WSN and TCP through the energy efficient cross layer can be done. It is done with transport layer to enhance the application filed to be reliably connected to the web. In this paper, dynamically adapted sleep scheduling mechanism is used with residual energy of each node. Virtual end-to-end packet rate selection and congestion control feedback mechanism are considered for end to end delay. This reduces the packet loss with the support of data-rate adaptation technique.

A Novel Hybrid Intrusion Detection Using Flow-Based Anomaly Detection and Cross-Layer Features in Wireless Sensor Network

The emerging technology of Wireless sensor network is expected to provide Intrusion detection technique for all kind of attacks. This article models and analyzes intrusion detection using flow-based IDS and cross-layered approach. The Critical application needs to replace cryptographic technique with flow-based anomaly detection for secure communication and single layer detection method with multi-layer detection method for efficient attack detection. The proposed detection system has a two-phase approach. In the first phase, flow-based anomaly detection method is used to detect potential anomalies in the network traffic. During second phase cross–layer features are correlated to narrow down the possible attacks. Simulation results clearly show that the proposed detection technique has an excellent performance in terms of detection accuracy, the energy consumption, and the false positive rate will reduce than the layer-based approach and packet-based approach.

Exploring an innovative evaluation method to ensure the quality of spatial data needed at the distribution stage: focused on building and road map in South Korea

This paper aimed to suggest a method to evaluate the quality of spatial data in order to increase the interoperability of national geospatial data. The national geospatial data is managed by the government and is provided to the public according to the Spatial Data Industry Promotion Act. Although the quality control is necessary in the every processing steps including data production, processing, distribution, and service. This paper focused data quality only on the distribution stage. The evaluation rules suitable for national geospatial data were derived by comparing and analyzing domestic and foreign standards for data quality. Then, the quality diagnosis were carried out using commercial software. Two diagnostic methods were applied to test data quality. One is ‘Layer-based Approach’ that requires a comparison between two layers and the other is ‘Geometry-based Approach’ that diagnose feature geometries in a single layer. The diagnostic methods have been applied to the building and road layers in Seoul. In conclusion, this paper presented the standard quality evaluation rules and criteria that could be applied immediately for spatial data distribution industry, although some of items checked by direct visual inspection. Later, it is expected all quality evaluation rules are fully automated.

Secure Communications in Tiered 5G Wireless Networks With Cooperative Jamming

Cooperative jamming is deemed as a promising physical layer-based approach to secure wireless transmissions in the presence of eavesdroppers. In this paper, we investigate cooperative jamming in a two-tier 5G heterogeneous network (HetNet), where the macrobase stations (MBSs) at the macrocell tier are equipped with large-scale antenna arrays to provide space diversity and the local base stations (LBSs) at the local cell tier adopt non-orthogonal multiple access (NOMA) to accommodate dense local users (LUs). In the presence of imperfect channel state information, we propose three robust secrecy transmission algorithms that can be applied to various scenarios with different security requirements. The first algorithm employs robust beamforming (RBA) that aims to optimize the secrecy rate of a marcouser (MU) in a macrocell. The second algorithm provides robust power allocation (RPA) that can optimize the secrecy rate of an LU in a local cell. The third algorithm tackles a robust joint optimization (RJO) problem across tiers that seek the maximum secrecy sum rate of a target MU and a target LU robustly. We employ convex optimization techniques to find feasible solutions to these highly non-convex problems. The numerical results demonstrate that the proposed algorithms are highly effective in improving the secrecy performance of a two-tier HetNet.

Real-time layer-based computer-generated hologram calculation for the Fourier transform optical system.

With the growing interest for augmented reality devices, holography is often considered as a promising technology to overcome the focus issues of conventional stereoscopic displays. To enlarge the field of view of holographic head-mounted displays, a Fourier transform optical system (FTOS) has been proposed. However, since the scene geometry is distorted by the FTOS, it is necessary to compensate the position of each scene point during the hologram computation, resulting in long calculation times. In this paper, we propose a real-time computer-generated hologram calculation method for the FTOS. Whereas previously proposed methods used a ray-tracing approach to compensate the distortion induced by the FTOS, our proposed method relies on a layer-based approach. Experimental results show that our method is able to compute holograms of resolution (3840×2160) in real time at 24 frames per second, enabling its use in augmented reality applications.

An Enhanced Cross-Layer Approach Based on Fuzzy-Logic for Securing Wireless Ad-Hoc Networks from Black Hole Attacks

Black holes attack in wireless ad-hoc networks can obstruct network functions, e.g.; successful packets delivery ratio to destinations. Current conventional detection mechanisms are based on single layer information, lack of appropriate performance metrics, and/or the adequate accuracy. In this paper, a new cross-layer Intrusion Detection System (IDS) is proposed, in order to mitigate the black hole attack in wireless ad-hoc networks. The proposed work modifies ad-hoc routing protocol for black hole attacks detection through extracting information from different OSI layers, and use these information as inputs into the fuzzy logic system, in which the algorithm precisely detects existing malicious nodes. Using NS2 simulation tool, a comprehensive simulation is conducted in order to compare our proposed approach performance with a recent cross layer-based approach for black hole intrusion detection. Simulation results reveal that our proposed system has a tremendous accuracy in detecting black holes with an acceptable additional overhead. Our proposed IDS outperforms studied IDS in terms of successful packet delivery ratio (PDR).

Three-Dimensional Printing and Cell Therapy for Wound Repair.

Significance: Skin tissue damage is a major challenge and a burden on healthcare systems, from burns and other trauma to diabetes and vascular disease. Although the biological complexities are relatively well understood, appropriate repair mechanisms are scarce. Three-dimensional bioprinting is a layer-based approach to regenerative medicine, whereby cells and cell-based materials can be dispensed in fine spatial arrangements to mimic native tissue. Recent Advances: Various bioprinting techniques have been employed in wound repair-based skin tissue engineering, from laser-induced forward transfer to extrusion-based methods, and with the investigation of the benefits and shortcomings of each, with emphasis on biological compatibility and cell proliferation, migration, and vitality. Critical issues: Development of appropriate biological inks and the vascularization of newly developed tissues remain a challenge within the field of skin tissue engineering. Future Directions: Progress within bioprinting requires close interactions between material scientists, tissue engineers, and clinicians. Microvascularization, integration of multiple cell types, and skin appendages will be essential for creation of complex skin tissue constructs.

Generalized Layerings for Arbitrary and Fixed Drawing Areas

The Directed Layering Problem (DLP) solves a step of the widely used layer-based approach to automatically draw directed acyclic graphs. To cater for cyclic graphs, usually a preprocessing step is used that solves the Feedback Arc Set Problem (FASP) to make the graph acyclic before a layering is determined. Here we present the Generalized Layering Problem (GLP), which solves the combination of DLP and FASP simultaneously, allowing general graphs as input. We present an integer programming model and a heuristic to solve the NP-complete GLP and perform thorough evaluations on different sets of graphs and with different implementations for the steps of the layer-based approach. We observe that GLP reduces the number of dummy nodes significantly, can produce more compact drawings, and improves on graphs where DLP yields poor aspect ratios. The drawings resulting from GLP also turn out to be more suitable for making the best possible use of a given drawing area. However, we show that a specialized variant of GLP can yield considerable improvements w.r.t. this particular optimization goal.