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Three-dimensional guidance method with course modification for altitude shaping in endoatmospheric interception
Get PDFThis study presents a three-dimensional guidance law for the interception of an endoatmospheric target. The proposed method takes an empirical design approach which first specifies the structure of the lateral acceleration command as that of a linear optimal guidance law for zero-effort-miss nullifcation. Then, the direction of pursuit and the guidance gain are designed in accordance with the physical understandings of the motion characteristics of an aerodynamically-controlled interceptor. More specifically, the proposed method induces an intentional increase in the flight altitude around the initial phase while respecting the maximum altitude constraint, all of which are realised through modification of the desired flight path angle in the vertical plane. The proposed guidance method does not rely on explicit definition of design elements such as engagement planes, guidance phases, complicated time-to-go estimation, and waypoints. Moreover, the proposed design approach of modifying the desired course based on the collision courses naturally facilitates smooth handover to the terminal phase near the collision condition. Numerical simulation shows that the proposed guidance method is effective in intercepting a nonmanoeuvring target over a wide range of engagement conditions to the target in comparison to the existing guidance laws developed for homing and midcourse flight.IEEE Transactions on Aerospace and Electronic System
Strain controlled fatigue behaviour of a wire + arc additive manufactured Ti-6Al-4V
Get PDFThis paper presents the cyclic deformation behaviour and fatigue properties of a wire + arc additive manufactured Ti-6Al-4V alloy in the as built condition under strain-controlled test condition. Higher local energy input used to build the material has resulted in a coarser primary columnar β grain structure along with a coarser α microstructure compared to Ti-6Al-4V alloys produced by other additive manufacture processes. Test specimens were manufactured in horizontal and vertical orientations with respect to the deposited layers. Isotropic fatigue property was observed at lower applied strain values. When the strain amplitude was above 0.6%, the vertical samples, where the loading axis was parallel with the primary columnar β grains, showed marginally higher fatigue life owing to the material being more ductile in this direction. Moreover, higher cyclic softening rate by a factor of two was measured in the vertical samples. No porosity defects were found in the material. Cracks were initiated from either the α laths or α/β interface due to cyclic slip localisation.International Journal of Fatigu
Structured urban airspace capacity analysis: four drone delivery cases
Get PDFA route network-based urban airspace is one of the initial operational concepts of managing the high-density very low-level (VLL) urban airspace for unmanned aircraft system (UAS) traffic management (UTM). For the conceptual urban airspace, it is necessary to perform a quantitative analysis of urban airspace to stakeholders for designing rules and regulations. This study aims to discuss the urban airspace capacity for four different operation types by applying different sequencing algorithms and comparing its results to provide insight and suggestions for different operation cases to assist airspace designers, regulators, and policymakers. Four drone delivery operation types that can be applied in the high-density VLL urban airspace are analysed using the suggested four metrics: total flight time; total flight distance; mission completion time; the number of conflicts. The metrics can be calculated from a flight planning algorithm that we proposed in our previous studies. The algorithm for multiple agents flight planning problems consists of an inner loop algorithm, which calculates each agent’s flight plan, and an outer loop algorithm, which determines the arrival and departure sequences. For each operation type, we apply two different outer loops with the same inner loop to suggest an appropriate sequencing algorithm. Numerical simulation results show tendencies for each type of operation with regard to the outer loop algorithms and the number of agents, and we analyse the results in terms of airspace capacity, which could be utilised for designing structures depending on urban airspace situations and environments. We expect that this study could give some intuition and support to policymakers, urban airspace designers, and regulators.Applied Science
Socio-technical barriers to domestic hydrogen futures: repurposing pipelines, policies, and public perceptions
Get PDFThe feasibility of the global energy transition may rest on the ability of nations to harness hydrogen's potential for cross-sectoral decarbonization. In countries historically reliant on natural gas for domestic heating and cooking such as the UK, hydrogen may prove critical to meeting net-zero targets and strengthening energy security. In response, the UK government is targeting industrial decarbonization via hydrogen, with parallel interest in deploying hydrogen-fueled appliances for businesses and homes. However, prospective hydrogen futures, and especially the domestic hydrogen transition, face multiple barriers which reflect the cross-sectoral dynamics of achieving economies of scale and social acceptance. Addressing these challenges calls for a deep understanding of socio-technical factors across different scales of the hydrogen economy. In response, this paper develops a socio-technical systems framework for overcoming barriers to the domestic transition, which is applied to the UK context. The paper demonstrates that future strategies should account for interactions between political, techno-economic, technical, market, and social dimensions of the hydrogen transition. In parallel to techno-economic feasibility, the right policies will be needed to create an even playing field for green hydrogen technologies, while also supporting stakeholder symbiosis and consumer buy-in. Future studies should grapple with how an effective repurposing of pipelines, policies, and public perceptions can be aligned to accelerate the development of the hydrogen economy, with maximum net benefits for society and the environment.Engineering and Physical Sciences Research Council (EPSRC): EP/T518104/1
Cadent Gas Ltd.Applied Energ
Techno-economic assessment of wireless charging systems for airport electric shuttle buses
Get PDFFlightpath 2050, the European Commission's vision for aviation, requires that the aviation industry achieves a 75 % reduction in CO2 emissions per passenger mile and airports become emission-free by 2050. Airport shuttle buses in the airfields are going to be electrified to reduce ground emissions. Simultaneously, the airfield movement space and time schedules are becoming more limited for adopting stationary charging facilities for electrified ground vehicles. Therefore, the dynamic wireless charging technology becomes a promising technology to help improve the stability of electrification of the airfield transport network. This paper proposes a techno-economic assessment of wireless charging, wired charging, and conventional technologies for electrifying airport shuttle buses. A bi-level planning optimisation approach combines the multi-objective Non-dominated Sorting Genetic Algorithm (NSGA-III) and mixed integer linear programming (MILP) algorithm to handle a large number of decision variables and constraints generated from the investigated problem. The airport shuttle bus transport is simulated through a multi-agent-based model (MABM) approach. Four case studies are analysed for illustrating the techno-economic feasibility of wireless charging technology for airport electric shuttle buses. The results show that the wireless charging technology enables the electric shuttle buses to carry smaller batteries while conducting the same as tasks conventional diesel/petrol vehicles and the bi-directional wireless charging technology could help mitigate the impact of electrification of shuttle buses on the distribution network.Engineering and Physical Sciences Research Council (EPSRC): EP/S032053/1Journal of Energy Storag
Nonlinear asset pricing in Chinese stock market: a deep learning approach
Get PDFThe redesign of asset pricing models failed to integrate the frequent financial phenomenon that stock markets exhibit a non-linear long- and short-term memory structure. The difficulty lies in developing a nonlinear pricing structure capable of depicting the memory influence of the pricing variable. This paper presents a Long- and Short-Term Memory Neural Network Model (LSTM) to capture the non-linear pricing structure among five elements in the Chinese stock market, including market portfolio return, market capitalization, book-to-market ratio, earnings factor, and investment factor. The long-short-term memory structure implies that the autocorrelation function of the stock return series decays slowly and has a long-term characteristic. The LSTM model surpasses the standard Fama–French five-factor model in terms of out-of-sample goodness-of-fit and long-short strategy performance. The empirical findings indicate that the LSTM nonlinear model properly represents the nonlinear relationships between the five components
Exchange rates, bond yields and the stock market: nonlinear evidence of Indonesia during the COVID-19 period
Get PDFPurpose
The authors explore the relationship between the exchange rate, bond yield and the stock market as well as the effect of capital market dynamics on the exchange rate before and during the COVID-19 pandemic.
Design/methodology/approach
The authors employ a non-linear autoregressive distributed lag (NARDL) methodology using daily data of the Indonesian economy over the period 2012–2021.
Findings
Whilst, over the full sample period, the authors find no cointegration between the exchange rate, the 10-year bond yield and stock market, for the COVID-19 period, evidence of cointegration is present. Furthermore, the results suggest that asymmetric effects are evident both in the short as well as the long run.
Originality/value
To the best of the authors’ knowledge, this is the first time that the relationship between the exchange rate, bond yield and the stock market as well as the effect of capital market dynamics on the exchange rate before and during the COVID-19 pandemic has been explored in the case of the Indonesian economy
Transforming industrial manipulators via kinesthetic guidance for automated inspection of complex geometries
Get PDFThe increased demand for cost-efficient manufacturing and metrology inspection solutions for complex-shaped components in High-Value Manufacturing (HVM) sectors requires increased production throughput and precision. This drives the integration of automated robotic solutions. However, the current manipulators utilizing traditional programming approaches demand specialized robotic programming knowledge and make it challenging to generate complex paths and adapt easily to unique specifications per component, resulting in an inflexible and cumbersome teaching process. Therefore, this body of work proposes a novel software system to realize kinesthetic guidance for path planning in real-time intervals at 250 Hz, utilizing an external off-the-shelf force–torque (FT) sensor. The proposed work is demonstrated on a 500 mm2 near-net-shaped Wire–Arc Additive Manufacturing (WAAM) complex component with embedded defects by teaching the inspection path for defect detection with a standard industrial robotic manipulator in a collaborative fashion and adaptively generating the kinematics resulting in the uniform coupling of ultrasound inspection. The utilized method proves superior in performance and speed, accelerating the programming time using online and offline approaches by an estimate of 88% to 98%. The proposed work is a unique development, retrofitting current industrial manipulators into collaborative entities, securing human job resources, and achieving flexible production.Sensor
Role of dynamic response in inclined transverse crack inspection for 3D-printed polymeric beam with metal stiffener
Get PDFThis paper aims to quantify the relationship between the dynamic response of 3D-printed polymeric beams with metal stiffeners and the severity of inclined transverse cracks under mechanical loading. Very few studies in the literature have focused on defects starting from bolt holes in light-weighted panels and considered the defect’s orientation in an analysis. The research outcomes can be applied to vibration-based structure health monitoring (SHM). In this study, an acrylonitrile butadiene styrene (ABS) beam was manufactured through material extrusion and bolted to an aluminium 2014-T615 stiffener as the specimen. It simulated a typical aircraft stiffened panel geometry. The specimen had seeded and propagated inclined transverse cracks of different depths (1/1.4 mm) and orientations (0°/30°/45°). Then, their dynamic response was investigated numerically and experimentally. The fundamental frequencies were measured with an experimental modal analysis. The numerical simulation provided the modal strain energy damage index (MSE-DI) to quantify and localise the defects. Experimental results showed that the 45° cracked specimen presented the lowest fundamental frequency with a decreased magnitude drop rate during crack propagation. However, the 0° cracked specimen generated a more significant frequency drop rate with an increased crack depth ratio. On the other hand, several peaks were presented at various locations where no defect was present in the MSE-DI plots. This suggests that the MSE-DI approach for assessing damage is unsuitable for detecting cracks beneath stiffening elements due to the restriction of the unique mode shape at the crack’s location.Material