english EUGENIA TANASĂ
Rezumat
Separarea fotoelectrochimică (PEC) a apei folosind energia solară apare ca o strategie extrem de promițătoare pentru generarea durabilă de hidrogen și stocarea energiei. Cercetările actuale în acest domeniu evidențiază hematitul ca material fotoanod adecvat pentru separarea apei datorită proprietăților sale favorabile: este un semiconductor de tip n, posedă o bandă interzisă adecvată pentru absorbția luminii vizibile, prezintă o stabilitate chimică ridicată și este disponibil din abundență pe Pământ. Acest review prezintă diverse strategii de modificare a hematitului pentru a-i îmbunătăți performanța. Aceste modificări includ doparea elementelor, proiectarea și fabricarea nanostructurilor, integrarea co-catalizatorilor, formarea heterostructurilor și interdependența dintre structura și performanța hematitului.
Cuvinte cheie
energie solară, hematită, fotoanozi
XIANWU JING, XIAOJIN ZHOU, TENG GONG, TAO WANG, YANG WANG, GUOQING LIU, KAIJUN WANG
Rezumat
This research employed molecular dynamics simulations to explore the distribution of sodium dodecyl sulfate (SDS) at the n-hexane/water interface. Once the SDS concentration surpasses the critical micelle concentration(cmc), a large portion of SDS migrates to the n-hexane/water interface, establishing a thin layer where sulfonic acid groups are oriented towards the water phase and carbon-hydrogen chains are directed towards n-hexane, a small amount of SDS forms spherical micelle with sulfonic acid groups facing the water phase, while carbon-hydrogen chains aggregate in the interior of these spherical structures. The sulfonic acid group of SDS forms multiple h-bonds with water, shows strong interaction energy; while the carbon hydrogen chain itself has only weak van der Waals interactions with surrounding molecules. The thickness of SDS- layer at the n-hexane/water interface is about 2.06 nm, with a maximum number density of about 0.25 per nm3, and average area occupied by a single SDS- is about 0.21 nm2. According to radial distribution function (RDF) result, due to the attractive effect of positive and negative charges, the first coordination layer of Na+ ions and oxygen atoms on sulfonic acid groups is about 0.21 nm. This study investigated the distribution of SDS at n-hexane/water interface, vividly demonstrating the mechanism by which SDS reduces the interfacial tension between oil and water, and providing guidance for oilfield development.
Cuvinte cheie
Interfață N-hexan/apă; Simulare dinamică moleculară; Dodecil sulfat de sodiu; Analiza interacțiunii slabe
S. DHANALAKSHMI, T. JESUDAS, M. PRADEEP KUMAR
Rezumat
The objective of this research study is focused to improve the wear resistance of the reinforced Al6063 hybrid metal matrix composite. The secondary particles like Al2O3 /TiO2are used as a reinforcement particle and the samples fabricated using stir casting technique with the base material Al6063 alloy. The fabricated samples were analyzed using Energy Dispersive Spectroscopy (EDS) and Scanning Electron Microscope (SEM) for understanding the potential of fabricated samples. Dry sliding wear test was conducted for the composite samples. The major wear process parameters such as load, sliding distance were considered for analysis work. The reinforcement particles such as Al2O3 /TiO2 also were considered as one of process parameter for wear analysis. The results of Variance of analysis clearly statethat reinforced secondary particles were the most influencing wear process parameter. The validation of desirability function analysis results reveals that the obtained optimal solutions were effectively enhance the wear resistance property for fabricated hybrid metal matrix composite (Al6063/Al2O3 /TiO2).
Cuvinte cheie
Al 6063, Al2O3 /TiO2, DFA, Wear, RSM.
CHIENTA CHEN, SHINGWEN TSAI
Rezumat
The rapid increase in terrain variability, climatic factors, axle load, and traffic volume has significantly affected the performance of asphalt pavements on expressways, particularly in harsh environmental conditions. In some cases, the service life of expressway pavements is far shorter than the expected design time. Certain sections of expressways face pavement failures just one or two years after opening, including cracks, potholes, rutting, and oil flooding. These problems not only disrupt the normal flow of traffic but also substantially increase maintenance and repair costs. This study focuses on diagnosing and addressing the causes of asphalt pavement failures, specifically in Jiangsu Province, China, where various asphalt pavement diseases were reported in 2020. By calculating the porosity of asphalt mixtures, we assess the water permeability, strength, and durability of the materials. Applying Mohr-Coulomb theory, we evaluate the high-temperature shear strength of asphalt mixtures and analyze rutting depth. Our findings indicate that rutting is the primary distress type on expressways in Jiangsu, with a rut depth of [3-8] mm observed in 67% of the total road network. Additionally, the pavement smoothness of expressways remains within a range of 0.5-1m/km for 85% of the highway network. We also analyze lateral and longitudinal fractures, which constitute 97% of repairs, with transverse cracks becoming prevalent after 6 years of service under high axle loads. This suggests the need for early preventive measures within the first 6 years of service to mitigate the development of cracks.
Cuvinte cheie
pavaj asfaltic, autostradă, diagnosticarea pavajelor, tehnologie de reparare, impact asupra mediului, formarea șanțurilor, formarea fisurilor, sarcina traficului.
MĂDĂLINA-OANA MIHĂILĂ, DENISA FICAI, OANA DAMIAN, BOGDAN ȘTEFAN VASILE, ALEXANDRA CRISTINA BURDUȘEL, ANDREI PĂDURARU, ECATERINA ANDRONESCU
Rezumat
Înainte de a discuta despre materialele și nanomaterialele inovative de conservare și restaurare a patrimoniului național arheologic este necesară indentificarea și caracterizarea materiilor prime principale (plastice și neplastice) și auxiliare folosite pentru obținerea corpului ceramic (partea I) și decorației de pe suprafață: sculpturală – simultană cu fasonarea și picturală (partea a II-a), existente pe suprafața interioară sau exterioară a pieselor ceramice. Astfel, după originea lor și modul de formare, prin sedimentare, procesare termică – sintetizare și vitrificare sau recristalizare, ce determină compoziția, proprietățile, culoarea și gradul de refractibilitate, acestea sunt clasificate în argile comune și argile superioare, diferențiate prin indicele de plasticitate, vitrifierea fiind influențată de raporturile oxizilor componenți, de temperaturile de ardere și de tipurile de atmosfera din interiorul cuptoarelor: oxidantă în cazul ceramicii albe și colorate sau reducătoare în cazul ceramicii negre, parțială sau completă, realizată într-o singură fază sau în două etape.
Cuvinte cheie
argilă plastică, decorație sculpturală, decorație policromă, angobe ceramice, glazuri ceramice, culoarea, oxizi coloranți, oxizi alcalini și oxizi alcalinopământoși.
SALEM MERABTI, LAYACHI GUELMINE, MEZIANE KACI
Rezumat
This study investigates the seismic performance of reinforced concrete buildings ranging from 5 to 20 stories using nonlinear static pushover analysis. Four shear wall bracing configurations are considered: L-shaped peripheral walls, central core, double central core, and double peripheral core systems, with wall thicknesses of 15, 20, and 25 cm, all subjected to unidirectional lateral loading. Although these configurations are widely implemented in both moderate and high seismicity regions, few comparative studies have assessed their nonlinear seismic resistance. The results indicate that central core configurations provide superior control of inter-storey drift, with a significant reduction in lateral displacements—up to 48% compared to peripheral wall systems. In contrast, peripheral wall systems exhibit higher drift demands, reaching a maximum of 0.124% for 15 cm thick walls. The analysis also highlights the effectiveness of L-shaped walls in mid-rise buildings, particularly those with wall thicknesses of 20 and 25 cm. The study of deformation mechanisms reveals a concentration of plastic hinges and thus stress in L-shaped wall systems and at beam-wall joint regions.
Cuvinte cheie
Clădire cu mai multe etaje, Analiză neliniară de tip pushover, Perete de forfecare din beton armat, Derivă interetajată, Tensiune de forfecare, Moment de răsturnare.
ALI SABERI VARZANEH, MAHMOOD NADERI
Rezumat
In concrete design, durability is as vital as strength, especially in aging structures exposed to harsh environmental conditions. Increased permeability over time compromises structural integrity. Polypropylene (PP) fibers help limit cracking, which in turn reduces permeability. Traditionally, assessing permeability requires destructive core sampling. This study introduces a novel approach—the “cylindrical chamber” test—to evaluate permeability directly on structures. Validation of this method confirmed its reliability. Results indicated that incorporating PP fibers reduced permeability in C25, C35, and C45 concretes by 22.5%, 20.2%, and 16.3%, respectively. XRD analysis revealed that PP fibers influenced Ca(OH)₂ crystallization and enhanced C-S-H formation. MIP results showed a 24.5% increase in pore volume and 32.8% rise in pore surface area in C45 concrete with fibers, yet overall permeability declined. This confirms the effectiveness of PP fibers in improving durability without the need for invasive testing.
Cuvinte cheie
Beton, durabilitate, fibră, rezistență, metodă inovatoare.
KARTHIKEYAN R, PARTHEEBAN P, THOLKAPIYAN.M, SIVAKUMAR, SUGUNA K, GAAYATHRI KK
Rezumat
This work discusses the outcome of Finite Element Analysis using ANSYS Workbench, to analyse the cyclic behavior of rubberized concrete beams with steel fiber reinforcement. The investigation focuses on substituting coarse aggregate with sand coated rubber shreds, obtained from waste conveyor belt, with the sand coating applied using resin. The study examines rubber shreds in proportion of 2.5%, 5% and 7.5%, combined with steel fibres at volume fraction of 0.5% and 1%, total of seven beams were cast and tested under cyclic loading in a standard loading frame of 500kN capacity. The FEA outcomes revealed that reinforced concrete beams with steel fibres and sand coated rubber shreds reveal boosted cyclic efficiency regarding number of cycle’s sustained, maximum deflection and total energy absorption capacity. Load – deflection curves were plotted to compare experimental and FEA for all seven beams. These results have proved very helpful for better understanding the rubberized concrete with fiber reinforcement under cyclic loading, for its use in structural applications.
Cuvinte cheie
Fâșii de cauciuc acoperite cu nisip, deformare maximă, fibră de oțel, absorbție de energie și curbă sarcină-deformare.