| 1. |
- Akbar, Nabeela, et al.
(författare)
-
Tunning tin-based perovskite as an electrolyte for semiconductor protonic fuel cells
- 2022
-
Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 47:8, s. 5531-5540
-
Tidskriftsartikel (refereegranskat)abstract
- The use of ceramic semiconductors to serve as an efficient proton conductor is an evolving approach in the novel emerging field of semiconductor protonic fuel cells (SPFCs). One of the most critical challenges in SPFCs is to design a sufficient proton-conductivity of 0.1 S cm(-1) below <600 degrees C. Here we report to tune the perovskite BaSnO3 (BSO), a semi-conductor single-phase material, to be applied as a proton-conducting electrolyte for SPFC. It was found that the oxygen vacancies play a vital role to promote proton transport while the electronic short-circuiting issue of BSO semiconductor has been justified by the Schottky junction mechanism at the anode/electrolyte interface. We have demonstrated a SPFC device to deliver a maximum power density of 843 mW cm(-2) with an ionic conductivity of 0.23 S cm(-1) for BSO at 550 degrees C. The oxygen vacancy formation by increasing the annealing temperature helps to understand the proton transport mechanism in BSO and such novel low-temperature SPFC (LT-SPFC).
|
|
| 2. |
- Sarfraz, Amina, et al.
(författare)
-
Catalytic Effect of Silicon Carbide on the Composite Anode of Fuel Cells
- 2021
-
Ingår i: ACS Applied Energy Materials. - : AMER CHEMICAL SOC. - 2574-0962. ; 4:7, s. 6436-6444
-
Tidskriftsartikel (refereegranskat)abstract
- High efficiency, fuel flexibility, and sustainable energy conversion make fuel cells attractive compared to conventional energy systems. The direct ethanol fuel cells have attracted much attention because of the direct utilization of ethanol fuel. Anode materials are required to enhance the catalytic activity of the liquid fuel, which oxidize the fuel at lower operating temperature. Therefore, the catalytic effect using silicon carbide has been investigated in the LiNiO2-delta anode. The material has been characterized, and it is found that SiC shows a cubic structure and LiNiO2-delta exhibits a hexagonal structure, while the LiNiO2-delta-SiC composite exhibits a mixed cubic and hexagonal phase. Scanning electron microscopy depicts that the material is porous. The Fourier transform infrared spectroscopy analysis shows the presence of Si-O-Si, Si-C, C=O, and Si-OH bonding. The LiNiO2-delta-SiC composite (1:0.3) exhibited a maximum electrical conductivity of 1.34 S cm(-1) at 650 degrees C with an electrical band gap of 0.84 eV. The fabricated cell with the LiNiO2-delta-SiC anode exhibits a power density of 0.20 W cm(-2) at 650 degrees C with liquid ethanol fuel. The results show that there is a promising catalytic activity of SiC in the fuel cell anode.
|
|
| 3. |
- Ali Ahmad, Syed Ossama, et al.
(författare)
-
Application of two-dimensional materials in perovskite solar cells: recent progress, challenges, and prospective solutions
- 2021
-
Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 9:40, s. 14065-14092
-
Forskningsöversikt (refereegranskat)abstract
- Perovskite solar cells (per-SCs) with high performance and cost-effective solution processing have been the center of interest for researchers in the past decade. Power conversion efficiencies (PCEs) have been gradually improved up to 25.2% with relatively improved stability, which is an unparalleled progress in all generations of solar cell (SC) technology. However, there are still some prevailing challenges regarding the stability and upscaling of these promising devices. Recently, 2D layered materials (LMs) have been extensively explored to overcome the prevailing challenges of poor stability (under moisture, light soaking and high temperature), halide segregation, hysteresis, involvement of toxic materials (i.e., lead), and upscaling of devices. A critical review addressing the recent developments in the use of 2D materials, especially transition metal dichalcogenides (TMDCs), is hence necessary. The development of novel synthesis and deposition techniques including liquid-metal synthesis and ultrasonic assisted spray pyrolysis has offered more efficient fabrication of 2D-LMs with controlled thickness and morphology. Effective functionalization approaches to increase the dispersability of 2D-LMs in non-polar solvents has boosted their potential application in solar cell technology as well. Moreover, compositing 2D TMDCs with suitable organic/inorganic compounds has enabled superior charge kinetics in all functional parts of per-SCs. In addition, newly developed materials such as graphyne and graphdyine along with 2D metal organic frameworks (MOFs) and covalent organic frameworks (COFs) have been employed in per-SCs to achieve PCEs up to 20%. This review summarizes the recent progress and challenges in the application of 2D-LMs in per-SCs and outlines the future pathways to further extend the PCE of per-SCs beyond 25%. This review particularly focuses on 2D-LMs as electrode materials and additives, the underlying charge (electron-hole) transport phenomenon in the functional layers, and their chemical and structural stability.
|
|
| 4. |
- Khokhar, Javeria, et al.
(författare)
-
Prevalence and determinants of anemia among resident female university students from Southern Punjab, Pakistan
- 2022
-
Ingår i: Women and Health. - : Informa UK Limited. - 0363-0242 .- 1541-0331. ; 62:6, s. 488-501
-
Tidskriftsartikel (refereegranskat)abstract
- Health and nutritional status of the women of reproductive age (WRA) is expected to be influenced with women literacy status alongside other sociodemographic indicators. However, data are scant to validate if literate young women have lower incidence of anemia prevalence. Nexus to the problem stated, a cross-sectional study was conducted on 1,541 female resident university students (FRUS) aged 17–35 years from a public sector university located in Southern Punjab, Pakistan. Hemoglobin (Hb) led screening for anemia was performed followed by nutritional assessment and structured questionnaire-based sociodemographic and dietary assessment. The data generated were analyzed using independent t-test, Chi-square, and response surface regression models. Response rate for the prevalence of anemia in FRUS was 38 percent with mean Hb levels 10.5 g/dL. With a significant effect (p =.001) of participants’ weight on anemia prevalence, 22.45 percent of the sample population was recorded as underweight. Sociodemographic and dietary parameters analyzed suggested low daily food expenditure (x 2 = 20.59; p =.000) and reduced intake of meat (x 2 = 12.14; p =.01), beans & pulses (x 2 = 18.56; p =.001) to significantly influence rate of anemia prevalence in FRUS. The study concludes high prevalence rate of anemia among FRUS to strongly relate with students’ low monthly stipend, little daily food expenditure, and substandard dietary quality.
|
|
| 5. |
- Qu, Gang, et al.
(författare)
-
Enhancing the Performance of the p-n Heterostructure Electrolyte for Solid Oxide Fuel Cells via A-Site-Deficiency Engineering
- 2023
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 15:42, s. 49154-49169
-
Tidskriftsartikel (refereegranskat)abstract
- Semiconductor ionic electrolytes are attracting growing interest for developing low-temperature solid oxide fuel cells (LT-SOFCs). Our recent study has proposed a p-n heterostructure electrolyte based on perovskite oxide BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) and ZnO, achieving promising fuel cell performance. Herein, to further improve the performance of the heterostructure electrolyte, an A-site-deficiency strategy is used to solely modify BCFZY for regulating the ionic conduction and catalytic activity of the heterostructure. Two new electrolytes, B0.9CFZY-ZnO and B0.8CFZY-ZnO, were developed and systematically studied. The results show that the two samples gain improved ionic conductivity and auxiliary catalytic activity after A-site deficiency as a result of the increment of the surface and interface oxygen vacancies. The single cells with B0.9CFZY-ZnO and B0.8CFZY-ZnO exhibit enhanced peak power outputs at 450-550 °C compared to the cell based on B1.0CFZY-ZnO (typically, 745 and 795 vs 542 mW cm-2 at 550 °C). Particular attention is paid to the impact of A-site deficiency on the interface energy band alignment between BxCFZY and ZnO, which suggests that the p-n heterojunction effect of BxCFZY-ZnO for charge carrier regulation can be tuned by A-site deficiency to enable high proton transport while avoiding fuel cell current leakage. This study thus confirms the feasibility of A-site-deficiency engineering to optimize the performance of the heterostructure electrolyte for developing LT-SOFCs.
|
|
| 6. |
- Sohail, Muhammad Tayyab, et al.
(författare)
-
Impacts of urbanization, LULC, LST, and NDVI changes on the static water table with possible solutions and water policy discussions: A case from Islamabad, Pakistan
- 2023
-
Ingår i: Frontiers in Environmental Science. - : Frontiers Media S.A.. - 2296-665X. ; 11
-
Tidskriftsartikel (refereegranskat)abstract
- Rapid urbanization, coupled with land use land cover changes (LULC), has caused stress on freshwater resources around the globe. As in the case of Islamabad, the capital of Pakistan, the population has increased significantly, creating a deficit of natural resources and affecting the environment adversely. Therefore, the purpose of this study is to examine the effects of urbanization and LULC on the decline of the static water table in Islamabad. It also seeks to analyze water policy issues in order to achieve sustainable water resource development. The excessive pumping of the existing groundwater has exceeded the safe limit, which is justified by the constantly growing population. However, the changes in the LULC of the study area have turned many green pastures into barren land. Our research data were obtained from the Capital Development Authority (CDA), Pakistan Meteorological Department (PMD), and Landsat Satellite images. After analyzing PMD and CDA data for the last 20 years (2000–2020), the results were interpreted using Arc GIS. It has been observed that the Normalized Difference Vegetation Index (NDVI) value increases as the Land Surface Temperature (LST) decreases. Therefore, the overall observation is a decreasing trend in Islamabad temperatures due to the increased vegetation in the study area during the period of 2000–2020. It was observed that there has been a considerable drop in water levels due to over-pumping in a few areas. It is primarily associated with the increasing population of the capital in the last 2 decades. This study uses a survey to explore the potential locations for check dams to enhance and recharge the groundwater aquifers in the capital, Islamabad. It suggests catchment areas throughout the Margalla Hills along with different localities, such as Rumli Village, Trail 5, and Shahdara.
|
|
| 7. |
- Abbafati, Cristiana, et al.
(författare)
-
- 2020
-
Tidskriftsartikel (refereegranskat)
|
|
| 8. |
- Akbar, Muhammad Usman, 1990-, et al.
(författare)
-
Brain tumor segmentation using synthetic MR images - A comparison of GANs and diffusion models
- 2024
-
Ingår i: Scientific Data. - : Nature Publishing Group. - 2052-4463. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Large annotated datasets are required for training deep learning models, but in medical imaging data sharing is often complicated due to ethics, anonymization and data protection legislation. Generative AI models, such as generative adversarial networks (GANs) and diffusion models, can today produce very realistic synthetic images, and can potentially facilitate data sharing. However, in order to share synthetic medical images it must first be demonstrated that they can be used for training different networks with acceptable performance. Here, we therefore comprehensively evaluate four GANs (progressive GAN, StyleGAN 1–3) and a diffusion model for the task of brain tumor segmentation (using two segmentation networks, U-Net and a Swin transformer). Our results show that segmentation networks trained on synthetic images reach Dice scores that are 80%–90% of Dice scores when training with real images, but that memorization of the training images can be a problem for diffusion models if the original dataset is too small. Our conclusion is that sharing synthetic medical images is a viable option to sharing real images, but that further work is required. The trained generative models and the generated synthetic images are shared on AIDA data hub.
|
|
| 9. |
- Baharin, Shamsul Ammar Shamsul, et al.
(författare)
-
Electromagnetic Interference From Natural Lightning on 4G Communication Links
- 2024
-
Ingår i: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 12, s. 14870-14881
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, microwave radiation pulses emitted from natural lightning have been found to interfere with the Fourth Generation Long Term Evolution (4G LTE) mobile communication data transmission. Two sets of measurement instruments have been synchronized where lightning electric field sensor together with 4G LTE network were evaluated its performance under two conditions namely fair-weather (four cases) and storm (four lightning cases). The microwave radiation emitted from lightning was directly measured without the use of a mixer and down-convertor to ensure the preservation of information such as the number of pulses and amplitude. A client-server architecture has been set up for data transmission utilizing User Datagram Protocol (UDP) where the packets have been generated by using Internet Performance Working Group Third Version (Iperf3) platform. Under fair-weather conditions, the 4G LTE connection at both the client and server nodes demonstrated stability and experienced minimal impact. On the other hand, natural lightning electromagnetic interference disrupted the 4G LTE communication links. Among the four reported storms, three storms have affected the 4G LTE data transmission. The first and fourth storms resulted in a complete connection drop to zero, lasting for 4 minutes and 2 seconds and for 44 seconds, respectively. The observation of hundreds microwave radiation pulses, each characterized by individual oscillating features suggests a potential disruption to packet transmission. Moreover, negative could-to-ground (-CG) and intra-cloud (IC) lightning flashes have been identified as the primary sources of interference to the 4G LTE data transmission. This information could be useful for future studies and for developers working on improving the reliability and performance of 4G LTE networks, particularly in areas prone to thunderstorms.
|
|
| 10. |
- Jönemo, Johan, 1974-, et al.
(författare)
-
Efficient Brain Age Prediction from 3D MRI Volumes Using 2D Projections
- 2023
-
Ingår i: Brain Sciences. - : MDPI. - 2076-3425. ; 13:9
-
Tidskriftsartikel (refereegranskat)abstract
- Using 3D CNNs on high-resolution medical volumes is very computationally demanding, especially for large datasets like UK Biobank, which aims to scan 100,000 subjects. Here, we demonstrate that using 2D CNNs on a few 2D projections (representing mean and standard deviation across axial, sagittal and coronal slices) of 3D volumes leads to reasonable test accuracy (mean absolute error of about 3.5 years) when predicting age from brain volumes. Using our approach, one training epoch with 20,324 subjects takes 20–50 s using a single GPU, which is two orders of magnitude faster than a small 3D CNN. This speedup is explained by the fact that 3D brain volumes contain a lot of redundant information, which can be efficiently compressed using 2D projections. These results are important for researchers who do not have access to expensive GPU hardware for 3D CNNs.
|
|
