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Trajectory inference of unknown linear systems based on partial states measurements
Get PDFProliferation of cheaper autonomous system prototypes has magnified the threat space for attacks across the manufacturing, transport, and smart living sectors. An accurate trajectory inference algorithm is required for monitoring and early detection of autonomous misbehavior and to take relevant countermeasures. This article presents a trajectory inference algorithm based on a CLOE approach using partial states measurements. The approach is based on a physics informed state parameteterization that combines the main advantages of state estimation and identification algorithms. Noise attenuation and parameter estimates convergence are obtained if the output trajectories fulfill a persistent excitation condition. Known and unknown desired reference/destination cases are considered. The stability and convergence of the proposed approach are assessed via Lyapunov stability theory under the fulfillment of a persistent excitation condition. Simulation studies are carried out to verify the effectiveness of the proposed approach.IEEE Transactions on Systems, Man, and Cybernetics: System
Dynamics modeling of multirotor type UAV with the blade element momentum theory and nonlinear controller design for a wind environment
Get PDFThis paper presents an aerodynamics modeling of a rotary type Vertical Take-Off and Landing (VTOL) aircraft using the Blade Element Momentum Theory (BEMT). The BEMT is incorporated into the rigid body dynamics to describe main force and its reactive torque by rotor of the multirotor UAV. The dynamics modeling can demonstrate the motion of the multirotor UAV in the presence of gust or wind in an unsteady environment effectively. In order to operate the multirotor UAV, a robust nonlinear control technique is designed to track the desired command and stabilize the UAV subject to uncertainties such as modeling error, external disturbances. The hierarchical Sliding Mode Control (SMC) is adopted to organize a multi-loop structure: the outer-loop and inner-loop mode. Actual control input is distributed by physical configuration of the multirotor UAV with the described thrust and torque modeling by the BEMT in the control allocation. Numerical simulation evaluates the feasibility of the dynamic modeling of the multrirotor UAV with BEMT in the presence of external wind effects, which enables to understand a motion of rotary type UAV in a windy environment.AIAA SCITECH 2024 Foru
Composite model reference adaptive control under finite excitation with unstructured uncertainties
Get PDFThis paper presents an online parameter update algorithm in the context of composite model reference adaptive control based on intermittent signal holding to improve convergence properties of the parameters representing the unstructured uncertainties in the absence of persistent excitation. The present study extends the algorithm which was previously developed by considering only the structured uncertainties for which the basis functions are known a priori. The proposed extension utilises the Gaussian radial basis function neural network as the model for the uncertainty assuming appropriate placement of the local basis functions in the state space. A notable distinction from the case with full knowledge of the features constituting the linearly-parameterised uncertainty model is that the extended algorithm introduces a robustifying modification in the earlier phase of operation to deal with the inevitable learning residual.2023 62nd IEEE Conference on Decision and Control (CDC
Lifting the lid on manipulative website contents: a framework mapping contextual and informational feature combinations against associated social cognitive vulnerabilities
Get PDFWebsite contents can be designed to influence individual and group decision-making for social, political or financial gain. A novel working theoretical framework was developed to provide insights into where website contents have been designed to exploit common cognitive vulnerabilities (CVs) amongst audiences; a form of social cognitive hacking. A literature synthesis on CVs, website content design and credibility identified features on a context credibility (CC) dimension that were mapped against features on an information validity (IV) dimension. Alignment of CC and IV feature pairings with CVs enables evaluation and interpretation of nuanced website content for identification of attempted influence undetectable by machine algorithms. Subjective responses to prompts about features on each dimension generate pairs of numerical values. The value pairs indicate within a quad-graph the possible presence and extent of CV exploitation. Each value pair can be traced to the underlying CC-IV features and CVs being targeted. External prima facie assessment suggests the framework can form the basis for standardised human analysis of website contents. Application of the framework provides insights into what and how feature combinations may be manipulated for CV exploitation. It has potential for application in fields such as intelligence analysis, education, and marketing.Defence Science and Technology Laboratory, Grant/Award Number: DSTLX1000133521Social and Personality Psychology Compas
Risk assessment for sUAS in urban environments: a comprehensive analysis, modelling and validation for safe operations
Get PDFThe rapidly growing number of applications for small Unmanned Aerial Systems (sUAS) in last-mile applications within metropolitan environments creates a complex airspace and ground safety scenario, where numerous risks must be considered to accomplish safe operations. The built-up and heterogeneously shaped geometry, together with the densely populated and transited nature of urban scenes, define a challenging scene for piloted and autonomous missions, where operators need to consider performance-based and third-party risks. In response to the increasing requirements inherent from urban scenarios, this paper proposes an integrated and comprehensive risk model for urban sUAS operations, composed by different risk layers designed for real-world scenarios, and validated through simulated drone flights and 3D risk-based navigation. By identifying the different risk requirements for sUAS operations, first party risks – including navigation performance, data link monitoring and collision avoidance – are computed within a photorealistic simulation environment for a discretized airspace representation. On top of this, trajectory based third party risks are modelled to identify potential routes subject to drone failure and consequent fatality and third party damage, as well as societal impact in terms of noise and privacy. Risk-based navigation techniques are implemented to validate the resulting model, including classical path planning and reinforcement learning. The results enable the perception of urban scenes associated risks through the lenses of risk modelling, providing a valuable methodology for sUAS urban operations and contributing to safer drone flights.AIAA SCITECH 2024 Foru
Representing, re-presenting, or producing the past? memory work amongst museum employees
Get PDFThough it is widely understood that the past can be an important resource for organizations, less is known about the micro-level skills and choices that help to materialize different representations of the past. We understand these micro-level skills and choices as a practice: ‘memory work’ – a banner term gathering various activities that provide the scaffolding for a shared past. Seeking to learn from a context where memory work is central, we share insights from a quasi-longitudinal study of UK museum employees. We theorize three ideal-typic regimes of memory work, namely representing, re-presenting and producing the past, and detail the micro-practices through which these regimes are enacted. Through explaining the key features of memory work in this context, our paper offers novel, broader insights into the relationship between occupations and memory work, showing how occupations differ in their understanding of memory and how this shapes their memory work.Journal of Management Studie
A scalable optical meta-surface glazing design for agricultural greenhouses
Get PDFOptical meta-surfaces allow controllable reflection and transmission spectra in both optical and infrared regions. In this study, we explore their potential in enhancing the performance of low-emission glazing designed for improved energy efficiency, for agricultural greenhouses in cold climates. The low-emission glazing employs thin film optics to retain heat by allowing solar radiation while reflecting radiation emitted by room-temperature objects. The incorporation of metamaterials that can be scalably manufactured and designed for capturing solar energy in the mid-infrared spectrum, offers an opportunity to further enhance the glazing's energy efficiency. Based on existing literature, the finite difference time domain (FDTD) method and the transfer matrix method are utilised to propose a metamaterial structure, with spherical silver nanoparticles and thin-films. We compare the performance of this proposed design against existing materials. The outcome of this study offers insights into the potential of metamaterials in optimizing the energy efficiency of cold-climate agricultural greenhouses.Physica Script
A low-cost miniature immunosensor for haemoglobin as a device for the future detection of gastrointestinal bleeding
Get PDFGastrointestinal bleeding (GIB) is a serious medical condition, which requires immediate attention to establish the cause of the bleeding. Here, we present the development of a miniaturised electrochemical impedance spectroscopy (EIS) device for the detection of GIB. The device performs EIS measurements up to 100 kHz. Following the development of an immunosensor for haemoglobin (Hb) on screen printed electrodes, the EIS device was used for detecting Hb as an early indication of bleeding. The sensor was able to detect Hb in a redox solution in a linear range between 5 μg mL−1 and 60 μg mL−1, with a limit of detection of 13.3 μg mL−1. It was also possible to detect Hb in simulated intestinal fluid, without the need for a redox solution, within a range of 10 μg mL−1 to 10 mg mL−1 with a limit of detection of 2.31 mg mL−1. The miniature EIS device developed in this work is inexpensive, with an estimated cost per unit of £30, and has shown a comparable performance to existing commercial tools, demonstrating its potential to be used in the future as an ingestible sensor to detect GIB. All these measurements were carried out in a purpose built flow cell with supporting hardware electronics outside the cell. Integration of the hardware and the sensing electrodes was demonstrated in pill form. This pill after integration sampling fluidics has potential to be used in detecting gastrointestinal bleeding.Analys
Analyses of the brown stain on the Parthenon Centaur head in Denmark
Get PDFIn 1688 two sculptural fragments, a head of bearded man and a head of an unbearded youth, arrived in Copenhagen, sent from Athens as a gift to King Christian 5. They were placed in the Royal Kunstkammer, their provenance given as the Temple of Artemis in Ephesos, one of the Seven Wonders of the World. Almost a hundred and fifty years later, in the early 1820’s they were noticed and studied by two scholars independently visiting the Kunstkammer. However, both concluded that the two heads belonged to one of the metopes decorating the south side of the Parthenon temple on the Acropolis in Athens, showing fighting between Greeks and the mythical Centaurs, part man and part horse. In the 1830’s another sculptural fragment, a horse’s hoof, obtained through the German archaeologist and state antiquary of Greece, Ludwig Ross, reached Copenhagen. It was forwarded by the Danish consul to Athens, C.T. Falbe, as a gift to King Christian 8. The inventory reads: ‘… was found on the Acropolis near the Parthenon temple and is supposed to belong to one the Centaurs on the metopes.’ The present paper focuses solely on the head of the Centaur.
A brown stain was noticed on the Parthenon marbles as early as 1830 by the British Museum and has ever since eluded a deeper understanding of its genesis despite many investigations and attempts of analyses. A quite similar brown stain can be observed on the Centaur’s head in Copenhagen as well.
The present study reports analyses by LA-ICP-MS, SEM–EDX, µXRD, GC–MS, and LC–MS-MS, as well as optical microscopy of five small samples sequestered in 1999 from the Centaur head curated by the National Museum of Denmark. Our analyses show that the brown stain consists of two consecutively added surficial layers of the calcium oxalate minerals whewellite and weddellite. Despite a thorough search using proteomics, we have found no viable organic precursor material for the oxalates. Our results do not solve the mystery of the formation of the brown stain, but they do further qualify the structure and characterization of the brown stain.Heritage Scienc
Long-term network structure evolution investigation for sustainability improvement: an empirical analysis on global top full-service carriers
Get PDFThe continuous and strategic planning of full-service carriers plays a prominent role in transferring and adapting them into resilient full-service carrier network structures. The exploration of full-service carrier network structures using the latest long-term empirical data facilitates enhancing cognitive capabilities in aspects of identifying network development tendencies, readjusting network structures, and supporting determinations of strategic business routes. Aiming at providing sustainable transport network solutions with historical long-term network structure analysis, this paper researches the global top 10 full-service carriers’ air transport networks from 2007 to 2022, applied using social network analysis (SNA). The static metrics from local to path-based perspectives are adopted to explore the global network evolution trend, along with competitiveness characteristics over critical airports. The cascading failure model is applied as a key indicator to analyze the dynamic robustness capability for the network. The similarity changing feature among the selected networks over the past years from 2007 to 2022 is measured using the autocorrelation function (ACF). The results indicate that, from 2011 to 2019, the majority of full-service carrier networks belong to the network types of closed, structural symmetry and two-way transitivity. The critical airports in North America present superiority in terms of network efficiency over those in Europe, Asia, and Oceania. The 10 full-service carriers’ air transport networks all show the trend of being more destruction-resistant. During the COVID-19 pandemic period, the merger with other airlines and the signing of a joint venture agreement led to higher temporal variability in the network structure.Aerospac