Article
Computer Science, Information Systems
Weigang Lv, Jiale Bai, Qingli Yan, Hui Ming Wang
Summary: This study proposes an active RIS-aided multi-antenna physical layer secrecy transmission scheme, which can effectively resist the double fading effect and is more energy efficient than passive RIS.
IEEE WIRELESS COMMUNICATIONS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Zijian Zhang, Linglong Dai, Xibi Chen, Changhao Liu, Fan Yang, Robert Schober, H. Vincent Poor
Summary: This paper proposes the concept of active reconfigurable intelligent surfaces (RISs) to overcome the capacity limitation of passive RISs in strong direct link scenarios. By integrating amplifiers into the elements, active RISs can amplify the reflected signals. The signal model of active RISs is developed and verified through experimental measurements, and the significant capacity gain they provide for wireless communications is analyzed. A joint transmit beamforming and reflect precoding scheme is proposed to maximize the sum-rate in an active RIS aided multi-user multiple-input single-output (MU-MISO) system. Simulation results show that active RISs can achieve a significant sum-rate gain of 130% in comparison to the limited 22% gain of passive RISs, thus overcoming the multiplicative fading effect.
IEEE TRANSACTIONS ON COMMUNICATIONS
(2023)
Article
Chemistry, Physical
Michael Rudolf Koblischka, Anjela Koblischka-Veneva, Quentin Nouailhetas, Ghazi Hajiri, Kevin Berger, Bruno Douine, Denis Gokhfeld
Summary: Superconducting YBCO foams were prepared and their superconducting and mechanical properties were simulated. The investigation of the foam microstructures provided insights into the specific characteristics of the foam samples.
Article
Engineering, Electrical & Electronic
Anastasios Papazafeiropoulos, Ahmet M. Elbir, Pandelis Kourtessis, Ioannis Krikidis, Symeon Chatzinotas
Summary: Reconfigurable intelligent surface (RIS) is a cost-effective and promising solution to extend wireless signal coverage and improve performance. This paper proposes a cooperative double-RIS with simultaneously transmitting and reflecting RIS (STAR-RIS) architecture, denoted as RIS/STAR-RIS, under correlated Rayleigh fading conditions, to assist communication in a massive multiple-input multiple-output (mMIMO) setup.
IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY
(2023)
Article
Construction & Building Technology
Manisha Malik, S. K. Bhattacharyya, Sudhirkumar Barai
Summary: The study investigates the thermal and mechanical properties of coarse aggregates, cement mortar, and cement concrete specimens after exposure to high temperatures. It is found that the degradation in concrete strength at high temperatures is primarily due to nonuniform thermal expansion, leading to changes in porosity. The crack initiation and propagation were studied using scanning electron microscopy to analyze the micrographs.
JOURNAL OF MATERIALS IN CIVIL ENGINEERING
(2021)
Article
Metallurgy & Metallurgical Engineering
Ya-jie Wang, Hai-bin Zuo, Jun Zhao, Guang-wei Wang
Summary: The study showed that the gasification reactivity of coal chars is influenced by coal rank and carbonaceous structure, with higher coal ranks leading to lower gasification reactivity and higher reaction orders.
JOURNAL OF IRON AND STEEL RESEARCH INTERNATIONAL
(2021)
Article
Materials Science, Coatings & Films
Y. Gaillard, E. Jimenez-Pique, M. Oliva-Ramirez, V. J. Rico, A. R. Gonzalez-Elipe
Summary: This work focused on the indentation analysis of nanocolumnar thin films and revealed the importance of microstructure in determining mechanical properties. The study found that a unique analytical thin-film nanoindentation model did not exist and developed a numerical finite element model to understand the contributions of different physical phenomena. By incorporating two length scales and considering densification and buckling of nanocolumnar units, a parametrical representation was developed to accurately predict the elastic modulus variation with depth during indentation tests, leading to a better agreement with experimentally determined values.
SURFACE & COATINGS TECHNOLOGY
(2021)
Article
Chemistry, Multidisciplinary
Gabor Varhegyi, Liang Wang, Oyvind Skreiberg
Summary: The study adapted an empirical kinetic model for CO2 gasification of biomass chars and tested its applicability through reevaluation of experiments. Two evaluation strategies were explored for analyzing the kinetic parameters and the results were compared based on 12 experiments.
Article
Engineering, Electrical & Electronic
Siqi Ma, Wenqian Shen, Xinyu Gao, Jianping An
Summary: This research establishes a communication system model considering blocked RIS and proposes a variational Bayesian based channel estimation algorithm that is robust in estimating both channel information and RIS blockage.
IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY
(2022)
Article
Engineering, Biomedical
Z. Lin, M. Sivaguru, H. Phillips, B. L. McFarlin, K. C. Toussaint, A. J. Wagoner Johnson
Summary: This study investigates the remodeling process of the rat cervix using 3D microscopy and reveals that the changes in different regions are heterogeneous. The study also finds that microstructural differences between regions become more similar as pregnancy progresses.
ACTA BIOMATERIALIA
(2022)
Article
Computer Science, Information Systems
Sonia Pala, Keshav Singh, Mayur Katwe, Chih-Peng Li
Summary: This letter proposes a novel resource allocation design for a multi-RIS-aided MISO URLLC system. An alternating optimization framework is provided to solve the sum-rate maximization problem by decoupling it into two sub-problems and using convex approximations. Numerical results show the fast convergence and superior performance of the proposed solution, with up to 40% improvement compared to random resource allocation and 3-5% rate performance boost for each RIS deployment.
IEEE WIRELESS COMMUNICATIONS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Sifan Liu, Rang Liu, Ming Li, Yang Liu, Qian Liu
Summary: Reconfigurable intelligent surface (RIS) is a revolutionary technology for manipulating wireless environments in sixth-generation (6G) networks. Due to its frequency-selective nature, RIS can effectively shape signals only within a certain frequency band, which complicates the association between base stations (BS), RIS, and users in cellular networks. This paper aims to jointly optimize BS-RIS-user association, active beamforming at base stations, and passive beamforming of RIS to maximize the sum-rate of RIS-assisted cellular networks, taking into account the frequency-selective characteristics of RIS. Efficient algorithms based on l(0)-norm approximation, majorization-minimization (MM), and alternating direction method of multipliers (ADMM) are proposed to solve the sub-problems. Extensive simulation results demonstrate the importance of BS-RIS-user association optimization and validate the effectiveness of the proposed joint association and beamforming design algorithm in RIS-assisted cellular networks.
IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY
(2023)
Article
Biophysics
Laura Miller, Raimondo Penta
Summary: In this study, we investigate the impact of microstructural changes induced by myocardial infarction on the elastic parameters of the heart. We use a poroelastic composite model to describe the myocardium microstructure and consider changes such as loss of myocyte volume and increased matrix fibrosis in the areas surrounding the infarct. Our simulations show that the infarcted heart is stiffer than the healthy heart, but with reperfusion, it begins to soften. We also observe that an increase in myocyte volume leads to a softer myocardium. These findings provide insights into predicting the stiffness and volume changes in the heart post-infarction.
BIOMECHANICS AND MODELING IN MECHANOBIOLOGY
(2023)
Article
Telecommunications
Hong Wang, Haitao Zhao, Zheng Shi, Yaru Fu
Summary: A brand-new framework for cascaded-reconfigurable intelligent surface (RIS) empowered multi-antenna non-orthogonal multiple access (NOMA) system is proposed in this paper, where RISs are deployed to serve their associated users and assist data transmission for the farther RISs as well. A new concept of RIS-level successive interference cancellation (RSIC) is developed to eliminate the inter-RIS interference. With the devised framework, a transmit power minimization problem is formulated by collaboratively designing each user's transmit power, the RISs' phase shifts, and the BS's equalizers. Specifically, a parallel iteration method is developed to solve the subproblem of jointly optimizing transmit power and equalizers, whereas a sequential phase-rotation algorithm is proposed to address the subproblem of phase shift optimization. Simulations show that the proposed scheme outperforms the existing benchmark schemes in terms of total transmit power.
IEEE COMMUNICATIONS LETTERS
(2023)
Article
Telecommunications
Fatih Kilinc, Recep A. Tasci, Abdulkadir Celik, Asmaa Abdallah, Ahmed M. Eltawil, Ertugrul Basar
Summary: This paper introduces a reconfigurable intelligent surface (RIS)-assisted grant-free non-orthogonal multiple access (GF-NOMA) scheme. The proposed approach maximizes the network sum rate by jointly clustering user equipment (UE) and assigning RISs. By decoupling UE clustering and RIS assignment/alignment subproblems, the computational complexity is significantly reduced.
IEEE TRANSACTIONS ON COGNITIVE COMMUNICATIONS AND NETWORKING
(2023)
Article
Geochemistry & Geophysics
Ana Claudia Santos, Alexandra Guedes, David French, Aurora Futuro, Bruno Valentim
Summary: The increasing demand and supply risk of rare earth elements (REEs) have led to the research on alternative secondary sources. This study focuses on coal and coal combustion ash as potential raw materials for REEs. The results show that the concentrations of REEs in ash are higher than in feed coals. The fine and nonmagnetic fractions of the ash are found to be enriched with REEs. However, the concentrations of REE oxides are still below the economical cutoff of 1000 ppm.
Article
Archaeology
Patricia Jordao, Alexandra Guedes, Nuno Pimentel
Summary: In this study, the mineralogical characteristics of both archaeological and geological flint were investigated using Raman microspectroscopy and X-ray diffraction (XRD). The degree of quartz crystallinity in archaeological materials could be inferred by evaluating its crystallinity through Raman analysis. The evaluation of moganite content allowed for better differentiation among Cenomanian flints from different locations.
Article
Energy & Fuels
R. Esmailpour, S. Alipour, F. Doulati Ardejani, S. Rodrigues, J. Esterle
Summary: The Tabas Basin in Iran has the country's largest coal deposits, primarily in the Parvadeh Coalfield. The basin is structurally characterized by thrust faults and strike-slip faults that separate the coalfields. The study examines the coalification history and the occurrence of pseudovitrinite in the Parvadeh coals.
INTERNATIONAL JOURNAL OF COAL GEOLOGY
(2022)
Article
Energy & Fuels
Xiaoxiao Mao, Sandra Rodrigues, Joan S. Esterle, Suzanne D. Golding
Summary: Open file data and new laboratory data were integrated to interpret reservoir properties of the Toolebuc Formation. The formation is divided into an upward deepening cycle (UDC) followed by an upward shallowing cycle (USC), with different lithofacies present. Facies 1 is clay and silica-rich with low TOC, Facies 2 has mixed mineralogical composition with high TOC, and Facies 3 is enriched in carbonates. The lithofacies stacking pattern corresponds to changes in GR response, TOC, Brittleness Index (BI), and clay content.
INTERNATIONAL JOURNAL OF COAL GEOLOGY
(2023)
Article
Chemistry, Analytical
R. Silva, A. Guedes, D. Ribeiro, C. Vale, A. Meixedo, A. Mosleh, P. Montenegro
Summary: This study aims to develop a methodology to automatically identify unbalanced vertical loads in freight trains circulation, which is crucial for railways management companies and operators to prevent service interruptions or derailments with high financial costs.
Article
Green & Sustainable Science & Technology
Elsayed Mousa, Xianfeng Hu, Ludvig Annhagen, Guozhu Ye, Antonella Cornelio, Ario Fahimi, Elza Bontempi, Patrizia Frontera, Charlotte Badenhorst, Ana Claudia Santos, Karen Moreira, Alexandra Guedes, Bruno Valentim
Summary: This paper reports on the characterization of two grades of black mass from spent lithium-ion batteries and their behavior during heating trials. The study provides important insights for optimizing lithium-ion battery recycling processes by fully characterizing black mass samples before and after heating.
Article
Energy & Fuels
Sandra Rodrigues, Lionel Fonteneau, Joan Esterle
Summary: Commercially available hyperspectral drill core scanning systems were used to characterise coal samples of varying rank with different preparations. The observed spectral features of the coals changed with increasing coalification. The ratio of the area of the aromatic absorption feature to that of the aliphatic absorption features, called Rank Spectral Index, displayed a strong linear correlation with coal rank parameters.
INTERNATIONAL JOURNAL OF COAL GEOLOGY
(2023)
Article
Geology
P. Caldevilla, L. Gonzalez-Menendez, T. Martin-Crespo, E. Vindel, A. Guedes, E. Berrezueta, A. M. Castanon, F. Gomez-Fernandez
Summary: The Pen deposit in NW Iberia is mainly composed of quartz veins containing wolframite, cassiterite, and minor molybdenite. The study combined whole rock geochemistry, mineral characterization, fluid inclusions, and stable isotope geochemistry to understand the hydrothermal mineralization conditions. Four stages of mineralization were identified, including an alteration stage, three mineralization stages, and a supergene stage.
ORE GEOLOGY REVIEWS
(2023)
Article
Geochemistry & Geophysics
Helena Sant'Ovaia, Claudia Cruz, Alexandra Guedes, Helena Ribeiro, Patricia Santos, Sonia Pereira, Jorge Espinha Marques, Maria dos Anjos Ribeiro, Catarina Mansilha, Helena Cristina Brites Martins, Bruno Valentim, Joana Torres, Ilda Abreu, Fernando Noronha, Deolinda Flores
Summary: The study focused on the tungsten Regoufe mine, which stopped operations in the 1970s. The research evaluated the contamination of soil, plants, and water in the mining area, specifically looking at potentially toxic elements (PTEs). The results showed that the area had a high level of contamination, posing ecological risks, particularly due to contributions from arsenic (As) and cadmium (Cd). However, it was difficult to establish a direct link between As contamination and mining activities, as the soils were already enriched in metals and metalloids from natural geological processes. The study also found that PTE levels in plants were lower than in soil, but bioaccumulation was influenced by site-specific soil concentrations of As and Pb. Magnetic studies indicated the presence of technogenic particles, likely formed during ore processing/mining activities. Overall, the levels of PTEs in surface and groundwater samples were relatively low, with the exception of As, which exceeded drinking water standards.
Article
Energy & Fuels
Tara Congo, Sandra Rodrigues, Joan Esterle, Karen Steel, Silvio Maranha
Summary: This paper briefly reviews the founding research in coal petrography as a tool for predicting coke quality and proposes a technique for direct optical comparison of a semicoke to its precursory coal. The method involves imaging a polished block sample of coal, pyrolysing it in a furnace, embedding the resulting semicoke in resin, and re-imaging the surface of interest. The observations of two Permian coals are also presented.
Article
Biochemistry & Molecular Biology
Susana L. H. Rebelo, Cesar A. T. Laia, Monika Szefczyk, Alexandra Guedes, Ana M. G. Silva, Cristina Freire
Summary: Unveiling and shaping the molecular connectivity in (metallo)porphyrin-carbon nanotube hybrids is crucial for their various applications in medicine, photoelectronics, catalysis, and photocatalysis. This study successfully modified multi-walled carbon nanotubes through 1,3-dipolar cycloaddition reactions and demonstrated the presence of different porphyrin-carbon nanotube connectivity in the resulting nanohybrid. Photophysical studies further confirmed energy/charge transfer in the photoactivated nanohybrid.
Article
Green & Sustainable Science & Technology
Charlotte Badenhorst, Iwona Kuzniarska-Biernacka, Alexandra Guedes, Elsayed Mousa, Violeta Ramos, Gavin Rollinson, Guozhu Ye, Bruno Valentim
Summary: This paper presents a separation process for recovering graphite from spent lithium-ion batteries, along with the recovery of LMO, Cu, and Al as by-products. The process is simple, environmentally friendly, and cost-effective, using readily available equipment in the market.
