| 1. |
- Khan, Sabih Ahmad, et al.
(författare)
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Investigation of the mechanical behavior of FDM processed CFRP/Al hybrid joint at elevated temperatures
- 2023
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Ingår i: Thin-walled structures. - : Elsevier BV. - 0263-8231 .- 1879-3223. ; 192
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Tidskriftsartikel (refereegranskat)abstract
- This research is focused on investigating the mechanical behavior of Fused Deposition Modeling (FDM) processed CFRP/Al hybrid riveted joints at elevated temperatures. A two-pronged approach was adopted entailing experimental and computational domains. In the experimental thrust, the developed joint was evaluated for its mechanical behavior by employing Digital Image Correlation, micro-XCT, and fractographic analysis. The tensile testing was performed at four different temperatures, i.e., Room Temperature (RT), 50°C, 75°C, and 100 °C. At RT, the joint experienced net-sectioning in the CFRP sheet along with minute secondary bending. Further, distinct failure modes were noticed for each ply orientation where the inherent porosity/voids appeared as the governing factor for the damage progression. Novel constitutive models were developed using accrued strain and change in energy dissipation to estimate the damage progression. The damage accumulation was found to be more uniform in the 0° layer as compared to 90°. Moreover, the 90° layer exhibited a more catastrophic damage pattern toward final failure. At elevated temperatures, a significant reduction in mechanical properties along with a non-uniform warping/bending of the plies was noticed due to viscoelastic behavior change. The computational analysis, having a hierarchical approach, was performed for the validation of the experimental results, and both were found to be in good agreement.
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| 2. |
- Khan, Muhammad Ahsan Iqbal, et al.
(författare)
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An Experimental and Comparative Performance Evaluation of a Hybrid Photovoltaic-Thermoelectric System
- 2021
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Ingår i: Frontiers in Energy Research. - : FRONTIERS MEDIA SA. - 2296-598X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The majority of incident solar irradiance causes thermalization in photovoltaic (PV) cells, attenuating their efficiency. In order to use solar energy on a large scale and reduce carbon emissions, their efficiency must be enhanced. Effective thermal management can be utilized to generate additional electrical power while simultaneously improving photovoltaic efficiency. In this work, an experimental model of a hybrid photovoltaic-thermoelectric generation (PV-TEG) system is developed. Ten bismuth telluride-based thermoelectric modules are attached to the rear side of a 10 W polycrystalline silicon-based photovoltaic module in order to recover and transform waste thermal energy to usable electrical energy, ultimately cooling the PV cells. The experiment was then carried out for 10 days in Lahore, Pakistan, on both a simple PV module and a hybrid PV-TEG system. The findings revealed that a hybrid system has boosted PV module output power and conversion efficiency. The operating temperature of the PV module in the hybrid system is reduced by 5.5%, from 55 degrees C to 52 degrees C. Due to a drop in temperature and the addition of some recovered energy by thermoelectric modules, the total output power and conversion efficiency of the system increased. The hybrid system's cumulative output power increased by 19% from 8.78 to 10.84 W, compared to the simple PV system. Also, the efficiency of the hybrid PV-TEG system increased from 11.6 to 14%, which is an increase of 17% overall. The results of this research could provide consideration for designing commercial hybrid PV-TEG systems.
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| 3. |
- Saif-Ul-Allah, Muhammad Waqas, et al.
(författare)
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Computationally Inexpensive 1D-CNN for the Prediction of Noisy Data of NOx Emissions From 500 MW Coal-Fired Power Plant
- 2022
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Ingår i: Frontiers in Energy Research. - : FRONTIERS MEDIA SA. - 2296-598X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Coal-fired power plants have been used to meet the energy requirements in countries where coal reserves are abundant and are the key source of NOx emissions. Owing to the serious environmental and health concerns associated with NOx emissions, much work has been carried out to reduce NOx emissions. Sophisticated artificial intelligence (AI) techniques have been employed during the past few decades, such as least-squares support vector machine (LSSVM), artificial neural networks (ANN), long short-term memory (LSTM), and gated recurrent unit (GRU), to develop the NOx prediction model. Several studies have investigated deep neural networks (DNN) models for accurate NOx emission prediction. However, there is a need to investigate a DNN-based NOx prediction model that is accurate and computationally inexpensive. Recently, a new AI technique, convolutional neural network (CNN), has been introduced and proven superior for image class prediction accuracy. According to the best of the author's knowledge, not much work has been done on the utilization of CNN on NOx emissions from coal-fired power plants. Therefore, this study investigated the prediction performance and computational time of one-dimensional CNN (1D-CNN) on NOx emissions data from a 500 MW coal-fired power plant. The variations of hyperparameters of LSTM, GRU, and 1D-CNN were investigated, and the performance metrics such as RMSE and computational time were recorded to obtain optimal hyperparameters. The obtained optimal values of hyperparameters of LSTM, GRU, and 1D-CNN were then employed for models' development, and consequently, the models were tested on test data. The 1D-CNN NOx emission model improved the training efficiency in terms of RMSE by 70.6% and 60.1% compared to LSTM and GRU, respectively. Furthermore, the testing efficiency for 1D-CNN improved by 10.2% and 15.7% compared to LSTM and GRU, respectively. Moreover, 1D-CNN (26 s) reduced the training time by 83.8% and 50% compared to LSTM (160 s) and GRU (52 s), respectively. Results reveal that 1D-CNN is more accurate, more stable, and computationally inexpensive compared to LSTM and GRU on NOx emission data from the 500 MW power plant.
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| 4. |
- Abdelfattah, Ahmed, et al.
(författare)
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Global analysis of the apple fruit microbiome : are all apples the same?
- 2021
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Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 23:10, s. 6038-6055
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Tidskriftsartikel (refereegranskat)abstract
- We present the first worldwide study on the apple (Malus x domestica) fruit microbiome that examines questions regarding the composition and the assembly of microbial communities on and in apple fruit. Results revealed that the composition and structure of the fungal and bacterial communities associated with apple fruit vary and are highly dependent on geographical location. The study also confirmed that the spatial variation in the fungal and bacterial composition of different fruit tissues exists at a global level. Fungal diversity varied significantly in fruit harvested in different geographical locations and suggests a potential link between location and the type and rate of postharvest diseases that develop in each country. The global core microbiome of apple fruit was represented by several beneficial microbial taxa and accounted for a large fraction of the fruit microbial community. The study provides foundational information about the apple fruit microbiome that can be utilized for the development of novel approaches for the management of fruit quality and safety, as well as for reducing losses due to the establishment and proliferation of postharvest pathogens. It also lays the groundwork for studying the complex microbial interactions that occur on apple fruit surfaces.
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| 5. |
- Aslam, Bilal, et al.
(författare)
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A compact implantable RFID tag antenna dedicated to wireless health care
- 2017
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Ingår i: International Journal of RF and Microwave Computer-Aided Engineering. - : John Wiley & Sons. - 1096-4290 .- 1099-047X. ; 27:5
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Tidskriftsartikel (refereegranskat)abstract
- Implantable tag antennas are an integral component of contemporary pervasive patient monitoring setups envisioned to reduce the medical errors and improve the quality of health care facilities. These tags, embedded into the human body, transmit critical patient information to the external equipment via a wireless communication link. This research article presents an implantable compact folded dipole antenna of size 10 mm 3 15 mm 3 2 mm, designed to operate in the industrial-scientificmedical band (2.4-2.48GHz). A three-layered phantom representing the human arm is used to evaluate the subcutaneous antenna performance. The tag antenna embedded in the middle of the fat layer offers a maximum gain of 216.3 dBi. The tag antenna performance as a function of implant position and phantom dimensions is analyzed. Link budget calculations show that with the achieved antenna gain the link power exceeds the required power by 38.37 dBm, and hence wireless communication is viable.
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| 6. |
- Khan, Safia, et al.
(författare)
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Kinetic and thermodynamic analysis of ammonia electro-oxidation over alumina supported copper oxide (CuO/Al2O3) catalysts for direct ammonia fuel cells
- 2024
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Ingår i: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 52, s. 1206-1216
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Tidskriftsartikel (refereegranskat)abstract
- In this work, ammonia electrooxidation (AEO) is studied to probe the electrochemical behavior of aqueous NH3 as direct fuel by implication of gamma alumina supported copper oxide catalysts (CuO/Al2O3). Precipitation and impregnation techniques are adapted to synthesize the substrate Al2O3, and loading of different ratios (1%, 2%, 3%, 4%) of active precursor i.e., CuO, respectively. Small average crystallite sizes (DAvg) in range of 1.46–6.76 nm and smaller particle sizes from micrographs proposed a superb activity of the catalysts. Modified GCE exhibited the excellent conductive properties towards standard redox probe K4[Fe(CN)6] and KCl, displaying a high active electrochemical surface area of up to 0.0021 cm2. Current profiles in response to increase in scan rates, concentrations of ammonia and temperature have been observed in 0.1 M KOH, thereby estimating the thermodynamic and kinetic constraints of the AEO process. Attributed to the electroactive properties towards AEO, CuO/Al2O3 is found to exhibit the desirable physiochemical properties owing to large oxidation current, large diffusion coefficient “D°” (3.6 × 10-9 cm2 s-1), large rate constant “ko” (1.2 × 10-5 cm s-1), large system entropy “ΔS” (-108 J K-1 mol-1), high change in enthalpy “ΔH” (72.3 J mol-1) and low activation energy “ΔG” (32.8 kJ mol-1). Resultingly, the oxidation of ammonia is found to be facile and robust by incorporation of CuO/Al2O3 catalysts owing to large ko, ΔH and ΔH. This study opened a gateway towards eco-benign and economical efficient energy generation and viable market entry of direct ammonia fuel cells.
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| 7. |
- Khan, Umar Hasan, et al.
(författare)
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Compact RFID Enabled Moisture Sensor
- 2016
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Ingår i: Radioengineering. - : Spolecnost Pro Radioelektronicke Inzenyrstvi. - 1210-2512 .- 1805-9600. ; 25:3, s. 449-456
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Tidskriftsartikel (refereegranskat)abstract
- This research proposes a novel, low-cost RFID tag sensor antenna implemented using commercially available Kodak photo-paper. The aim of this paper is to investigate the possibility of stable, RFID centric communication under varying moisture levels. Variation in the frequency response of the RFID tag in presence of moisture is used to detect different moisture levels. Combination of unique jaw shaped contours and T-matching network is used for impedance matching which results in compact size and minimal ink consumption. Proposed tag is 1.4x9.4 cm(2) in size and shows optimum results for various moisture levels upto 45 % in FCC band with a bore sight read range of 12.1 m.
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| 8. |
- Khan, Umar Hasan, et al.
(författare)
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Novel chipless displacement sensor circuit using spurline resonantor
- 2016
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Ingår i: IEICE Electronics Express. - : Institute of Electronics Information Communication Engineers. - 1349-2543. ; 13:23
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Tidskriftsartikel (refereegranskat)abstract
- A novel uni-dimensional chipless displacement sensor circuit based on spurline resonators is presented. Sensor circuit design consists of two components: series of spurline resonators and a selector element. In response to displacement, the selector element slides over the spurline resonator slots that translating this movement into a corresponding change in the circuit's frequency response. The designed circuit offers a capacity of 16 bits in the 2-4.2 GHz frequency band. Half of the bits are designated as the sensory bits, while the other half are attributed as the ID bits. The formulated sensor has a dynamic range from 0-3.75 mm and a minimum resolution of 0.25 mm. The proposed sensor is a prime candidate for deployment in smart cities for ubiquitous infrastructural health monitoring.
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| 9. |
- Khan, Wali Ullah, et al.
(författare)
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Opportunities for Physical Layer Security in UAV Communication Enhanced with Intelligent Reflective Surfaces
- 2022
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Ingår i: IEEE Wireless Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1284. ; 29:6, s. 22-28
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Tidskriftsartikel (refereegranskat)abstract
- Unmanned aerial vehicles (UAVs) are an important component of next-generation wireless networks that can assist in high data rate communications and provide enhanced coverage.Their high mobility and aerial nature offer deployment flexibility and low-cost infrastructure support to existing cellular networks and provide many applications that rely on mobile wireless communications. However, security is a major challenge in UAV communications, and physical layer security (PLS) is an important technique to improve the reliability and security of data shared with the assistance of UAVs. Recently, the intelligent reflective surface (IRS) has emerged as a novel technology to extend and/or enhance wireless coverage by reconfiguring the propagation environment of communications. This article provides an overview of how the IRS can improve the PLS of UAV networks. We discuss different use cases of PLS for IRS-enhanced UAV communications and briefly review the recent advances in this area. Then, based on the recent advances, we also present a case study that utilizes alternate optimization to maximize the secrecy capacity for an IRS-enhanced UAV scenario in the presence of multiple Eves. Finally, we highlight several open issues and research challenges to realize PLS in IRS-enhanced UAV communications.
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| 10. |
- Malik, Shairyar, et al.
(författare)
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An Improved Skin Lesion Boundary Estimation for Enhanced-Intensity Images Using Hybrid Metaheuristics
- 2023
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Ingår i: Diagnostics. - : MDPI. - 2075-4418. ; 13:7, s. 1285-1285
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Tidskriftsartikel (refereegranskat)abstract
- The demand for the accurate and timely identification of melanoma as a major skin cancer type is increasing daily. Due to the advent of modern tools and computer vision techniques, it has become easier to perform analysis. Skin cancer classification and segmentation techniques require clear lesions segregated from the background for efficient results. Many studies resolve the matter partly. However, there exists plenty of room for new research in this field. Recently, many algorithms have been presented to preprocess skin lesions, aiding the segmentation algorithms to generate efficient outcomes. Nature-inspired algorithms and metaheuristics help to estimate the optimal parameter set in the search space. This research article proposes a hybrid metaheuristic preprocessor, BA-ABC, to improve the quality of images by enhancing their contrast and preserving the brightness. The statistical transformation function, which helps to improve the contrast, is based on a parameter set estimated through the proposed hybrid metaheuristic model for every image in the dataset. For experimentation purposes, we have utilised three publicly available datasets, ISIC-2016, 2017 and 2018. The efficacy of the presented model is validated through some state-of-the-art segmentation algorithms. The visual outcomes of the boundary estimation algorithms and performance matrix validate that the proposed model performs well. The proposed model improves the dice coefficient to 94.6% in the results.
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