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Relationship between body habitus and image quality and radiation dose in chest X-ray examinations: A phantom study
摘要： Purpose: To evaluate the influence of being overweight on image quality (IQ), radiation dose and acquisition parameters when undertaking adult chest X-ray (CXR) examinations using routine acquisition protocols. Methods: The Lungman chest phantom, with and without chest plates, was used to simulate the chest region for larger size and average adult patients, respectively. Radiographic acquisitions were conducted using 17 X-ray machines located in eight hospitals using their routine clinical protocols. IQ was assessed using relative visual grading analysis (VGA) and 2 alternative forced choice (2AFC) by six observers. Incident air kerma (IAK) was measured using a solid-state dosimeter. Results: IQ mean (range) scores between the hospitals were 16.2 (12.0–21.3) with a 56.0% difference and 20.9 (14.1–23.6) with a 50.2% difference for the standard and larger size phantoms, respectively. IAK mean (range) scores 63 μGy (19–136 μGy) with a 150% difference and 159 μGy (27–384 μGy) with a 173% difference for the standard and larger size phantoms, respectively. The chest plates had a significant negative impact on IQ (P = 0.001) and lead to an increased in IAK by approximately 50%. Conclusion: Visual measures of IQ and IAK showed large differences between hospitals for standard and larger phantom sizes; differences within the hospitals was lower. Overall, Lungman with chest plates was found to degrade IQ and increase radiation dose by a factor of two. Further optimisation is required especially for the larger sized patient’s imaging protocols for all eight hospitals.
关键词： Overweight,Image quality,Obesity,Adult chest radiography,Dose optimisation,Radiation dose
更新于2025-09-23 15:23:52
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An Improved Optical Parameter Optimisation Approach Using Taguchi and Genetic algorithm for High Transmission Optical Filter Design
摘要： High transmission optical filters require specific filter characteristics and set of optimisation methods since precision in output performance plays a vital role in such applications. In this paper, an improved genetic algorithm approach to optimise high transmission optical filter is described. High transmission of around 99% in the wavelength region of 525-575 nm without any dips in between is the main performance requirement desired. The optimisation parameters are layer thickness, refractive index and number of layers and design wavelength is 550 nm in visible region. The method integrates the Taguchi method and genetic algorithm. First, Taguchi method is used to reduce the number of design experiments and find the minimum possible number of optimised set of values that represents the quality performance of the system. Then, genetic algorithm is applied to search the optimal design parameters. The performance is determined in terms of transmittance. Three levels for each optimisation parameter were considered. The total number of design experiments to be performed (in worst case) using genetic algorithm only with three optimisation variables and three levels is approximately 33=27 for obtaining the best design that matches the desired performance whereas Taguchi integrated genetic method helped in finding the best matching design with 9 design experiments. The best transmission performance was obtained for 24 layers, with thickness range 10-123.75 nm and high and low refractive index of 2.1 and 1.38. This method is a very robust approach that can be used for design parameter optimisation of optical filters for high transmission applications.
关键词： Optical filters,Genetic algorithm,Taguchi,Optimisation
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference on Radar (RADAR) - Brisbane, Australia (2018.8.27-2018.8.31)] 2018 International Conference on Radar (RADAR) - Real Aperture Imaging Using Sparse Optimisation with Application to Low-Angle Tracking
摘要： Estimating the angle of arrival of a low-altitude target over the sea surface is made difficult due to the coherent multipath interference caused by the target image. A real aperture imaging technique for estimating azimuth and elevation of targets using a phased array multichannel radar, as described by Berry et al [1], is applied to this classical problem of suppressing low-angle multipath signals received by a naval radar from a low-flying target. The degree of spatial resolution which can be usefully attained is explored; this depends on many factors and the nonlinear problem formulation is not easily amenable to analysis. It is found that the technique is feasible for resolving the direct target signal, its specular reflection and multiple diffuse reflections even when the signals would be combined by a conventional beamformer to form a multipath null.
关键词： radar signal processing,low-angle tracking,sparse optimisation,multipath propagation,phased array multichannel radar
更新于2025-09-23 15:22:29
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Designing and exergetic analysis of a solar power tower system for Iskenderun region
摘要： In this paper, a steam cycle assisted solar tower power system is designed and parametrically optimised for Iskenderun region by considering the weather conditions. After the optimisation, exergy-based analysis of the compounds and overall plant is performed for the best-performing cycle conditions. As a result of the annual-based monthly parametric optimisation, the design parameters, working performance, energy and exergy efficiencies of system are compared to obtain the best-performing cycle conditions which are found in July at the tower outlet pressure and temperature of 100 bar and 1,000°C. The net power production and thermal efficiency of the system at the best-performing conditions are calculated as 47,046.60 kW and 45.814%, respectively. After the exergetic analysis of compounds and overall system, the highest exergetic efficiency is evaluated in 2nd turbine (T-2) as 99.23% and the lowest exergetic efficiency is found in 1st heat exchanger (HeX-1) as 74.16%. Moreover, the overall exergetic efficiency is calculated as 47.19%.
关键词： SPT,steam cycle,solar power tower,exergy analysis,parametric optimisation,energy analysis
更新于2025-09-23 15:22:29
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On-line estimation of local oscillator noise and optimisation of servo parameters in atomic clocks
摘要： For atomic frequency standards in which fluctuations of the local oscillator (LO) frequency are the dominant noise source, we examine the role of the the servo algorithm that predicts and corrects these frequency fluctuations. We derive the optimal linear prediction algorithm, showing how to measure the relevant spectral properties of the noise and optimise servo parameters while the standard is running, using only the atomic error signal. We find that, for realistic LO noise spectra, a conventional integrating servo with a properly chosen gain performs nearly as well as the optimal linear predictor. Using simple analytical models and numerical simulations, we establish optimum probe times as a function of clock atom number and of the dominant noise type in the local oscillator. We calculate the resulting LO-dependent scaling of achievable clock stability with atom number for product states as well as for maximally-correlated states.
关键词： quantum projection noise,servo optimisation,local oscillator noise,atomic frequency standards
更新于2025-09-23 15:22:29
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Multi-fidelity EM simulations and constrained surrogate modelling for low-cost multi-objective design optimisation of antennas
摘要： In this study, a technique for low-cost multi-objective design optimisation of antenna structures has been proposed. The proposed approach is an enhancement of a recently reported surrogate-assisted technique exploiting variable-fidelity electromagnetic (EM) simulations and auxiliary kriging interpolation surrogate, the latter utilised to produce the initial approximation of the Pareto set. A bottleneck of the procedure for higher-dimensional design spaces is a large number of training data samples necessary to construct the surrogate. Here, the authors propose a procedure that allows us to confine the model domain to the subset spanned by the reference points, including the extreme Pareto-optimal designs obtained by optimising the individual objectives as well as an additional design that determines the Pareto front curvature. Setting up the surrogate in the constrained domain leads to a dramatic reduction of the required number of data samples, which results in lowering the overall cost of the optimisation process. Furthermore, the model domain confinement is generic, i.e. applicable for any number of design goals considered. The proposed technique is demonstrated using an ultra-wideband monopole antenna optimised with respect to three objectives. Significant reduction of the design cost is obtained as compared to the reference surrogate-assisted algorithm.
关键词： Pareto set,antenna structures,variable-fidelity EM simulations,kriging interpolation surrogate,multi-objective design optimisation,ultra-wideband monopole antenna
更新于2025-09-23 15:21:21
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Optimisation for large-scale photovoltaic arraysa?? placement based on Light Detection And Ranging data
摘要： The availability of high-resolution LiDAR (Light Detection And Ranging) geospatial data has increased immensely, providing new opportunities to solve challenges in the field of spatial energy planning. This paper presents a new method for large-scale placement of photovoltaic arrays over buildings’ rooftops in an optimal manner by using the global optimisation approach. The position, aspect and slope are the key geometrical parameters being optimised for each photovoltaic array. The predicted energy generation (i.e. photovoltaic potential) is simulated by using state-of-the-art hourly shadowing estimation from the surroundings, anisotropic diffuse, reflected, and direct irradiances that are based on a Typical Meteorological Year, and non-linear efficiency characteristics of a considered photovoltaic system configuration. The optimisation performs multiple simulation scenarios throughout an entire year for each photovoltaic array, in order to maximise its photovoltaic potential. The method was tested over three LiDAR datasets with different landscape topographies and urban densities. In comparison to the methods for photovoltaic arrays’ fixed optimal slope estimation, the proposed method is substantially more suitable for application in urban environments.
关键词： LiDAR data,Optimisation,Photovoltaic potential,Environmental simulation
更新于2025-09-23 15:19:57
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Laser Welding of ZE41 Mg Alloy: Experimental Investigations on the Effect of Parameters and Nondestructive Testing
摘要： Laser beam welding is an essential metal joining method for magnesium and its alloys with their growing applications in automotive, aerospace, marine, etc. In this research paper, the experimental modelling for laser beam welding of ZE41 Mg alloy and the mechanical and metallurgical characterisation after welding are reported. The effects of weld scan speed and laser beam power on the weld geometry for bead on plates of ZE41 Mg alloy using a continuous-wave CO2 laser system were analysed in this work. The microstructure, hardness, and radiography analysis were discussed. The results indicate the in?uence of laser parameters and the validity of the regression equations developed for the optimisation of process parameters.
关键词： ZE41 magnesium alloy,Hardness,Optimisation,X-ray radiography,Laser beam welding
更新于2025-09-23 15:19:57
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Contour scanning, multi-leaf collimation and the combination thereof for proton pencil beam scanning
摘要： In proton therapy, the lateral fall-off is often used to spare critical organs. It is therefore crucial to improve the penumbra for proton pencil beam scanning. However, previous work has shown that collimation may not be necessary for depths of >15 cm in water. As such, in this work we investigate the effectiveness of a thin multi leaf collimator (just thick enough to completely stop protons with ranges of <15 cm in water) for energy layer specific collimation in patient geometries, when applied in combination with both grid and contour scanned PBS proton therapy. For this, an analytical model of collimated beam shapes, based solely on data available in the treatment planning system, has been included in the optimization, with the resulting optimised plans then being recalculated using Monte Carlo in order to most accurately simulate the full physics effects of the collimator. For grid based scanning, energy specific collimation has been found to reduce the V30 outside the PTV by 19.8% for an example patient when compared to the same pencil beam placement without collimation. V30 could be even reduced by a further 5.6% when combining collimation and contour scanning. In addition, mixed plans, consisting of contour scanning for deep fields (max range >15 cm WER) and collimated contour scanning for superficial fields (<15 cm), have been created for four patients, by which V30 could be reduced by 0.8% to 8.0% and the mean dose to the brain stem by 1.5% to 3.3%. Target dose homogeneity however is not substantially different when compared to the best un-collimated scenario. In conclusion, we demonstrate the potential advantages of a thin, multi leaf collimator in combination with contour scanning for energy layer specific collimation in PBS proton therapy.
关键词： collimation,optimisation,pencil beam scanning,proton therapy,penumbra
更新于2025-09-19 17:15:36
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Shaping of a laser-accelerated proton beam for radiobiology applications via genetic algorithm
摘要： Laser-accelerated protons have a great potential for innovative experiments in radiation biology due to the sub-picosecond pulse duration and high dose rate achievable. However, the broad angular divergence makes them not optimal for applications with stringent requirements on dose homogeneity and total flux at the irradiated target. The strategy otherwise adopted to increase the homogeneity is to increase the distance between the source and the irradiation plane or to spread the beam with flat scattering systems or through the transport system itself. Such methods considerably reduce the proton flux and are not optimal for laser-accelerated protons. In this paper we demonstrate the use of a Genetic Algorithm (GA) to design an optimal non-flat scattering system to shape the beam and efficiently flatten the transversal dose distribution at the irradiated target. The system is placed in the magnetic transport system to take advantage of the presence of chromatic focusing elements to further mix the proton trajectories. The effect of a flat scattering system placed after the transport system is also presented for comparison. The general structure of the GA and its application to the shaping of a laser-accelerated proton beam are presented, as well as its application to the optimisation of dose distribution in a water target in air.
关键词： Genetic algorithm,Beam shaping,Laser-driven protons,Monte Carlo simulations,Dose optimisation
更新于2025-09-16 10:30:52