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Design and Equivalent Circuit Model Extraction of a Fractal Slot-Loaded 3–40 GHz Super Wideband Antenna
(2024-11) Alamro, Wasan; Seet, Boon Chong; Wang, Lulu; Parthiban, Prabakar; Department of Engineering
In this paper, we present the design and equivalent circuit model (ECM) of a fractal slot-loaded super wideband (SWB) antenna for compact and high-performance applications operating in the 3–40 GHz range. The proposed antenna features a compact dimension of 40 × 35 × 1.57 mm³, a measured bandwidth ratio of 13:1, a peak gain of 9.7 dBi, an average radiation efficiency of 94%, and a low cross-polarization level across the entire bandwidth. The presented ECM is derived using transmission line theory and incorporates the individual behavior of each constituting element of the antenna. A dual sequential optimization approach is employed to determine the optimal element values. The ECM results show good agreement with both simulated and measured results in terms of the magnitude of reflection coefficient | (Formula presented.) | and both real and imaginary impedances with low mean absolute percentage errors of 4.9%, 7.5%, and 7.7%, respectively, demonstrating the model’s ability to accurately predict the antenna’s performance.
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Design and Characterization of a Compact Four-Element Microstrip Array Antenna for WiFi-5/6 Routers
(2023) Paul, Liton Chandra; Ankan, Sarker Saleh Ahmed; Rani, Tithi; Jim, Md Tanvir Rahman; Karaaslan, Muharrem; Shezan, Sk A.; Wang, Lulu; Department of Engineering
The WiFi-5 band was the most popular WiFi band until the Federal Communications Commission (FCC) announced a new spectrum of 6 GHz WiFi (5.925-7.125 GHz) for unlicensed users. Our proposed work is about to cover both the 5 GHz and 6 GHz WiFi bands. These two bands have a great impact in the wireless communication field. A low-loss Rogers RT 5880 material is used as the substrate layer, which helps us to make the antenna compact (23×40×0.79 mm3) keeping a good performance profile over the latest high-speed WiFi-5/6 band. The proposed antenna covers a huge bandwidth (simulated BW: 2.85 GHz ranging from 4.50 to 7.35 GHz and measured BW: 2.83 GHz ranging from 4.50 to 7.33 GHz), which can be used for the latest WiFi-5 and WiFi-6 routers. The antenna also has omnidirectional properties. Besides that, the gain and directivity of the antenna are quite good, and the measured results buttress the simulated results. The presented different detail parametric studies indicate the antenna's optimization level, which is excellent. The minimum values of reflection coefficient and voltage standing wave ratio make it a compatible candidate for the implementation of high-speed WiFi-5/6 routers.
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Demographic characteristics, gambling engagement, mental health, and associations with harmful gambling risk among UK Armed Forces serving personnel
(2025-12-01) Jones, Matthew; Champion, H.; Dighton, G.; Larcombe, J.; Fossey, M.; Dymond, S.; Department of Psychology
Introduction Harmful gambling negatively impacts individuals, families and communities. Growing international evidence indicates that the Armed Forces (AF) community may be at a comparatively higher risk of experiencing harm from gambling than the general population. The current study sought to identify general predictors of harmful gambling and gambling engagement among UK AF serving personnel (AFSP). Methods We conducted a cross-sectional, exploratory survey to identify associations between demographic factors, mental health, gambling engagement and gambling type in a sample (N=608) of AFSP. Results Most of the sample reported past-year gambling, with 23% having experienced harm. Male gender, younger age and lower educational attainment all predicted harmful gambling, as did mental health variables of prior generalised anxiety and post-traumatic stress symptomatology. Strategy-based gambling and online sports betting were also predictive of experiencing harm from gambling. Conclusions The risk of harm from gambling is associated with demographic, mental health and gambling engagement variables among AFSP. Better understanding of these predictors is important for the development of individualised treatment approaches for harmful gambling.
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Deep Reinforcement Adversarial Learning against Botnet Evasion Attacks
(2020-12) Apruzzese, Giovanni; Andreolini, Mauro; Marchetti, Mirco; Venturi, Andrea; Colajanni, Michele; Department of Computer Science
As cybersecurity detectors increasingly rely on machine learning mechanisms, attacks to these defenses escalate as well. Supervised classifiers are prone to adversarial evasion, and existing countermeasures suffer from many limitations. Most solutions degrade performance in the absence of adversarial perturbations; they are unable to face novel attack variants; they are applicable only to specific machine learning algorithms. We propose the first framework that can protect botnet detectors from adversarial attacks through deep reinforcement learning mechanisms. It automatically generates realistic attack samples that can evade detection, and it uses these samples to produce an augmented training set for producing hardened detectors. In such a way, we obtain more resilient detectors that can work even against unforeseen evasion attacks with the great merit of not penalizing their performance in the absence of specific attacks. We validate our proposal through an extensive experimental campaign that considers multiple machine learning algorithms and public datasets. The results highlight the improvements of the proposed solution over the state-of-the-art. Our method paves the way to novel and more robust cybersecurity detectors based on machine learning applied to network traffic analytics.
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Compressive sensing holographic microwave random array imaging of dielectric inclusion
(2018) Wang, Lulu; Fatemi, Mostafa; Department of Engineering
Holographic microwave imaging is an innovative method to image biological objects based on their dielectric properties, which has the advantages of high spatial resolution. However, the image reconstruction method is always a critical issue in holographic microwave imaging. This research aims to investigate the feasibility and effectiveness of applying compressive sensing (CS) technique to the holographic microwave imaging for small dielectric object detection. This paper presents a compressive sensing holographic microwave random array imaging (CS-HMRAI) method for imaging of dielectric objects. A numerical system consists of various dielectric models and imaging processing model are developed to evaluate the proposed approach. The split Bregman (SB) and orthogonal matching pursuit (OMP) algorithms are applied to HMRAI for evaluation of small inclusions embedded in dielectric objects. Various experiments are conducted to identify lesions using the proposed CS-HMRAI method and results are compared with HMRAI and HMRAI via OMP methods. Both simulation and experimental results demonstrate that CS-HMRAI via SB can produce high-quality images and detect arbitrarily shaped small inclusions with random sizes and locations by using significantly fewer sensors and scanning times than the HMRAI and CS-HMRAI via OMP approaches. The proposed approach has the potential for further investigation for breast tumor detection in a fast and cost-effective manner.

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