446494 research outputs found
Sort by
Effect of Density Irregularities on Radio Frequency Wave Propagation in Ionospheric Plasmas
No full textDensity irregularities play a vital role in determining how radio frequency (RF) waves travel through plasmas. In the Earth’s ionosphere, these density irregularities also impact radio communication. In this study, we conduct a detailed numerical analysis of RF wave propagation in small-scale ionospheric density irregularities using the advanced Petra-M code. We focus specifically on high-frequency (HF) waves, ranging from 3 to 30 MHz, which are essential for military, amateur radio operators, and emergency communications. By introducing density structures, such as equatorial plasma bubbles derived from fluid simulations, we demonstrate that HF waves can scatter in multiple directions when they encounter these irregularities. Additionally, we observe significant mode conversion, where incoming electromagnetic waves transform into electrostatic modes within the density gradient layer. This shows that smaller density irregularities can greatly weaken signals or cause complete signal loss for receivers, emphasizing the need for increased awareness and innovative solutions in radio communication transmission
Strength characterization and microstructure of untreated and cryo treated CrMoV low alloy steel
No full textThis study examines the impact of various cryogenic treatments compared to traditional vacuum heat treatment on the development of mechanical characteristics and microstructure of CrMoV Steel. The mechanical characteristics of the samples were analysed to determine the impact of untreated and cryogenically treated materials on hardness, toughness, tensile strength, and microstructure. Experimental evidence showed that the cryogenically treated samples exhibited improved mechanical characteristics compared to the traditionally treated ones. The findings indicated that specimens subjected to cryogenic treatment at a temperature of -100°C for a soaking period of 2 hours, followed by furnace tempering at 200°C for 2 hours, exhibited an 81% increase in tensile strength, an 18% increase in hardness, and a 123% increase in toughness. The confirmation of numerous phases and complicated carbides was achieved using X-ray diffraction, while the shape of microstructure and cracked surfaces was examined using field emission scanning electron microscopy methods
First Experiments on 3D Plasma Calculations Using Positive Maxwellian Operator
No full textA new form of time-harmonic Maxwell’s equations [1] based on the standard formulation is used for the numerical modelling of RF fields in non-uniform plasmas without an external magnetic field. This formulation expresses the equations in terms of magnetic field strength, electric displacement, the vector and scalar potential. It offers several advantages. First, the differential operators act directly on these quantities with positive definiteness. Second, curl operators are absent in the leading-order terms of the equations. The Laplacian appears as the leading-order operator in the equations for potentials and magnetic field, while the gradient of a divergence is the leading-order operator for the electric displacement. Third, the absence of spatially varying coefficients in the leading-order differential operators ensures diagonal dominance of the discretized matrix. Following the approach of [1], the computational domain is chosen as a rectangular parallelepiped. A lowest-order 3D finite-difference method is applied for discretization. The antenna model is represented by a divergence-free electric current directed along the y axis. The plasma is treated as three-dimensional, non-uniform, and unmagnetized
Preventive effect of
No full textPersistent liver injury leads to liver fibrosis, a pathological condition distinguished by the excessive deposition of extracellular matrix components, especially collagen. This condition is a critical stage leading to cirrhosis and hepatocellular carcinoma, so prevention at the early stage is essential. Moringa oleifera seed oil (MOSEIL) contains bioactive compounds such as oleic acid, kaempferol, and quercetin, which exhibit antioxidant, anti-inflammatory, and antifibrotic activities. This research aimed to investigate MOSEIL's preventive potential against liver fibrosis in mice. Hepatocyte injury was assessed by hematoxylin eosin (HE) staining, while collagen accumulation was evaluated with Picrosirius red staining. The results showed that the fibrosis model group experienced changes in liver architecture, hepatocyte degeneration, and inflammatory cell infiltration. In contrast, the MOSEIL treatment group showed histological structure improvement with reduced cell damage and inflammatory infiltration. Picrosirius red staining demonstrated marked collagen deposition in the fibrosis group, whereas the MOSEIL-treated group exhibited a pronounced reduction in collagen accumulation, especially within the perisinusoidal and periportal regions. In conclusion, MOSEIL has potential as a preventive agent for liver fibrosis through histological improvement and inhibition of collagen deposition, thereby supporting its use as a candidate for natural-based therapy
Cogon Grass Root Extract
No full textAngiotensin II (Ang II) stimulates oxidative stress in endothelial cells, leading to cell dysfunction. The active substances of Imperata cylindrica roots (IC) extract inhibit oxidative stress. This study aimed to evaluate whether IC extract treatment increases Ang II-induced endothelial cell viability (ECV). The in vitro model on human umbilical vein endothelial cells culture (HUVECs) treated with 0.1 μM Ang II. There were five groups: control (CTL), Ang II, and three groups each given Ang II and 5, 10, and 15 μg/ml IC extract, respectively. Cell Counting Kit-8 (CCK-8) was used to assess ECV at 0, 24, and 48 hours, respectively. The data were analysed using one-way ANOVA. A p-value less than 0.05 was considered significant. ECV percentage at 24-hour observation in the CTL, Ang II, 5, 10, 15 μg/ml IC extract groups was 100±1.17; 94.91±0.75; 96.16±0.76; 95.87±1.75, and 95.65±0.97%, respectively. At 24-hour observation was 100±0.89; 78.71±0.38; 98.84±0.99; 111.99±0.99, and 101.77±1.76%, respectively. Further, at 48-hour observation was 100±0.83; 59.23±2.21; 107.83±3.94; 129.39±0.62, and 136.51±2.99%, respectively. Ang II reduces ECV compared to the control group at time-dependent observations (p<0.000). However, IC extract significantly improved ECV at all doses compared to the Ang II group (p < 0.000). IC extract increases Ang II-induced ECV
Potential of Nanoparticels Dayak Onion
No full textThe aim is to analyse the potential of nanoparticles in Dayak Onion as an immunomodulator in supporting spleen tissue growth and improving broiler production performance. The research material is nanoparticles Dayak Onion (NPDO) and broiler. The treatment was administered of NPDO 1%, 2%, 3%, positive and negative (control). The research method is experimental. The variable are immune response, spleen tissue and broiler production performance. The Research design is completely randomized. Data were analysed using Analysis of Variance and followed by the Duncan Test (5%). The treatment had a significant effect (P < 0.05) on the immune response (Ig G and Ig Y). The highest concentration of Ig G was in the Negative Control (36.64 g/L), while the highest concentration of Ig Y was in NPDO 3% (22 g/L). The best increase in spleen weight was observed at NPDO 3% (2.81g), and the lowest tissue damage score was recorded at NPDO 3% (1.7%). NPDO does not affect broiler performance, as measured by average weight gain (AWG) and index performance (IP). The conclusion is that NPDO provide a good response to immunity and supporting spleen tissue, but not to broiler performance production. NPDO as a feed additive for immunomodulators' broilers is recommended to be given at 3% of the basal feed
Wind environment optimization of traditional villages using Sware numerical simulations: A case study of Shuicheping old street, Chongqing
No full textTraditional mountainous villages embody regional ecological wisdom through their wind environments, yet face challenges including blocked natural wind corridors, increased building density, and inadequate ventilation during modernization. This study investigates Shuicheping Old Street using Sware numerical simulations integrated with field measurements and CFD modeling to establish a 3D wind environment model. Quantitative analysis revealed disorderly construction caused 42% wind speed attenuation between clusters, 35% vortex-dominated street areas, and substandard ventilation (0.5 ACH) in dwellings.On this basis we propose a tripartite strategy—hierarchical wind corridor restoration, building interface optimization, and microclimate regulation—improved cluster ventilation efficiency by 28.6%, reduced street vortices to 22%, and enhanced indoor ventilation to 1.2 ACH.And an economic feasibility analysis was conducted on the adopted three in one strategy, estimating the construction and maintenance costs of different optimization measures as well as the subsequent economic benefits, providing a more comprehensive decision-making basis for practical engineering applications.The final proposed framework balances heritage preservation with climate adaptation, offering a replicable design paradigm for sustainable renewal of Southwestern China's mountainous settlements
Research on optimized mud wall protection tchnology for rotary drilling in deep soft soil formations
No full textBorehole stability is a major technical challenge during rotary drilling of cast-in-place piles in deep soft soil layers , particularly those characterized by high water content, high compressibility, low shear strength, and pronounced flow plasticity. Conventional wall protection methods often fail to counteract the strong disturbance caused by dynamic drilling operations, frequently leading to hole collapse or diameter reduction, which compromises pile quality and project safety. To address this, a mud wall protection technology compatible with rotary drilling characteristics was developed. Through numerical modeling, the influence of key mud parameters on borehole stability was analyzed, showing that appropriately enhanced mud performance effectively balances soil pressure and controls deformation. Experimental design methods were then used to optimize a bentonite-based mud formulation with specific chemical additives, significantly improving mud cake quality and stability. Validated in field projects, the optimized mud demonstrated improved borehole stability. This research provides a scientific basis for mud design and a practical technical solution for rotary drilling in deep soft soils, contributing significantly to ensuring pile bearing capacity and project safety
Turnpike property of nonzero-sum linear-quadratic differential games
No full textThis paper investigates the turnpike properties of deterministic nonzero-sum linearquadratic (LQ) differential games. Under certain assumptions on the Hamiltonian matrix of the nonzero-sum LQ differential game, we establish the solvability of both the coupled non-symmetric differential Riccati equation (DRE) and the algebraic Riccati equation (ARE). Moreover, we identify the convergence relationship between the DRE and ARE, which is essential for understanding the turnpike properties. Over a finite but sufficiently long time horizon, the open-loop Nash equilibrium is shown to remain exponentially close to the solution of a two-objective optimization problem for the majority of the time horizon
Bolon tectonics concept in Batak Toba
No full textThe focus of this tectonic research is to assess how structures and building construction respond to climatic and natural influences. Understanding the Jabu Bolon timber buildings in Toba is vital given the region's earthquake-prone terrain. The study used a qualitative method with a correlational explanation strategy, namely describing the tectonic phenomenology of Jabu Bolon. The selected object of study was Jabu Bolon in Jangga Dolok village, based on field observations, literature, and articles. Qualitative descriptive analysis was used to connect the phenomenology of tectonic vernacular architecture with Jabu Bolon Batak Toba. The concept of Jabu Bolon is geometrically structured into three distinct parts. Pillars along its sides support the building. A series of roof ridges, sloping wall installation techniques, and the arrangement of the base pillars contribute to the structure's overall aesthetic. The connecting details used to reinforce the building include a dowel system for the pillars and beams, as well as a tie system made from natural materials linking the roof to the wall coverings. The building is both sturdy and aesthetically pleasing, making it resilient against natural elements