National Engineering and Scientific Commission

Rotating Detonation Engines (RDEs) operate on continuous detonation waves, offering superior thermodynamic efficiency and compactness compared to traditional deflagration-based combustion systems. This study investigates the feasibility of RDEs for suborbital and hypersonic cruise flight vehicles through a combined theoretical and computational approach. A fractional-factorial Design of Experiments (DoE) method is applied to evaluate the influence of key parameters such as propellant type (methane, acetylene), thrust, and thermal stability. The performance impact of nozzle geometry, particularly aerospike configurations, is also assessed. A two-dimensional computational fluid dynamics (CFD) simulation in ANSYS Fluent is used to visualize detonation wave propagation, pressure rise, and flow field dynamics. Results show that detonation wave characteristics are highly sensitive to specific impulse and nozzle geometry, with CFD confirming hypersonic wave speeds and effective detonation front propagation. The study demonstrates the potential of RDEs as efficient, compact propulsion systems for suborbital applications. Future work will focus on real-gas effects, improved cooling strategies, and enhancing detonation stability under variable flow conditions.

Background and Study AimThe proliferation of synchronous videoconferencing platforms (e.g., Zoom) in educational settings has precipitated concern over “Zoom fatigue” psychological and cognitive exhaustion following extended online interaction (Bailenson, 2021; Fauville et al., 2023). PMC+3Stanford News+3Virtual Human Interaction Lab+3 Concurrently, in online learning environments, the concept of cognitive load, the working-memory burden on learners has gained critical significance (Skulmowski & Rey, 2022). SpringerLink+1 The present study thus aimed to (1) estimate the prevalence of Zoom fatigue among adolescents engaged in remote/virtual schooling, (2) identify key predictors of Zoom fatigue (e.g., session frequency, screen time, socio-demographic variables), and (3) examine the association between Zoom fatigue and cognitive load (intrinsic, extraneous, germane) in this population.Material and MethodsA cross-sectional survey was administered to N = 780 adolescents aged 13–18 years enrolled in urban public secondary schools during an online-learning period. Inclusion criteria required at least two synchronous videoconference lessons per day; exclusion included diagnosed neurological or psychiatric disorders. A stratified cluster sampling frame (by school, grade) was used. The instrument comprised the adapted Zoom Exhaustion & Fatigue Scale (ZEF) and the Cognitive Load Questionnaire (adapted from Sweller et al., 1998), with sociodemographic and usage-pattern items. Data were analysed using descriptive statistics, chi-square tests, t-tests, and linear regression models (α=.05) ResultsThe prevalence of moderate-to-high Zoom fatigue (ZEF ≥ 4 on a 5-point scale) was 22.4%. Significant predictors (p < .01) included female gender (β = 0.18), ≥ 4 videoconf. sessions/day (β = 0.25), self-view on during sessions (β = 0.12), and lower break-time between sessions (β = –0.14). Regression analysis indicated that extraneous cognitive load mediated the relationship between session frequency and Zoom fatigue (indirect effect β = 0.09, 95% CI [.05, .14]).ConclusionZoom fatigue is prevalent among adolescents in virtual schooling, and is meaningfully associated with increased extraneous cognitive load, supporting a cognitive-load theoretical framework for videoconference exhaustion. Educational policymakers and EdTech designers should consider scheduling constraints, interface settings (e.g., self-view disablement), and cognitive-load reduction in virtual pedagogy.

Both natural and man-made soil salinity is a chief geological disaster in semi-arid and arid parts. In cultivated land, it has a negative impact on plant development and harvests, while in semi-arid and arid non-agricultural zones, due to subsidence, corrosion and groundwater quality, it affects urban structures, leading to additional soil erosion and land deprivation. The study was conducted at central Punjab, Pakistan with the aim to develop a baseline and to show the precision and accuracy of Geographic Information System (GIS) technology for delineating soil salinity in no data region. The samples of soil were gathered at deepness of 0-15 and 15-30 cm, and three factors (pH, Electrical Conductivity, and Sodium Adsorption Ratio) were analyzed in the laboratory. Landsat 8 OLI imagery were used for salinity indices development. A statistical index association was found between soil salinity noted in soil samples of field and 13 GIS-based salinity indices. The effect importance and model parameters for various soil salinity indices were assessed using regression model fitting. The data were divided into 3 categories: i) ground or field data, ii) brightness/intensity indicators, and iii) salinity indicators. Data were analyzed using principal component analysis (PCA). The results indicated that salinity indices were favorably related with ground data sets, but brightness/intensity indices had no significant relationship with ground or field data.

The construction industry plays a vital role in the economic development and overall progress of any country. Construction activities have significant impact on the economy, but their environmental consequences cannot be overlooked. The excessive use of construction materials particularly cement and steel, which are among the most commonly used construction materials, has become a major environmental concern, as these materials are also key sources of carbon emissions. Moreover, the raw materials required for the preparation of cement and Steel are also depleting at a rapid pace. Therefore, it is necessary to conduct research studies to find new alternative materials which can reduce the consumption of cement and steel in the concrete. Fly ash can be used as binding agent in concrete as it has good cementation properties and is abundantly available. To enhance the mechanical performance of geopolymer concrete (GPC), polypropylene fibers (PPFs) were incorporated in varying ratios (0.5% to 1.5% by volume). The samples were prepared to test the mechanical and durability properties of the concrete. Compressive Strength, Flexural Strength, and Split Tensile Strength test was carried out to conclude the mechanical properties of the geopolymer concrete against different percentages of polypropylene Fiber. Acid attack and rapid chloride permeability tests were conducted out to evaluate the durability of the concrete. The research findings depicted that the greatest compressive strength and split tensile strength are obtained at 1% PPFs GPC. The least amount of chloride penetration was demonstrated by GPC, at 1.5% PPFs.

Long-term organic amendments are a key strategy to build soil organic carbon (SOC) stocks in semiarid agroecosystems, where low biomass inputs and calcareous parent material constrain carbon accumulation. This 14-year field experiment in central Iraq (2000–2014) evaluated how a gradient of organic matter (OM) additions (0, 1, 2.5, 5, 10, and 20%) affects SOC dynamics, nutrient availability, and soil organic matter composition in clay-dominated, semiarid soils. Surface and subsurface samples (0–30, 30–60, and 60–90 cm) were analysed for SOC, nutrients, and mid-infrared Fourier transform infrared (FTIR) spectra, which were then integrated with Partial Least Squares (PLS) regression and RothC simulations. Moderate OM inputs (5–10%) were most effective in increasing surface SOC from 0.71% to 2.11%, while electrical conductivity, pH, and total nitrogen remained within agronomically acceptable ranges. FTIR spectra showed enhanced C–H and C=O bands in surface horizons, indicating concurrent accumulation of labile and more stable organic fractions, whereas low- and mid-wavenumber bands (1080–670 cm⁻¹) confirmed the persistence of clay and silicate mineral structures across depths. PLS models predicted SOC and total N with high accuracy (R² = 0.84–0.995), low RMSEP, and excellent predictive performance (RPD = 3.05–41), particularly under higher OM inputs. RothC simulations reproduced the observed depth-dependent SOC gradients, with deviations typically ranging from −22% to +10%, and confirmed that most carbon gains are concentrated in surface layers, while deeper horizons change only slightly. The combined use of FTIR spectroscopy, spectral PLS modelling, and RothC provides a robust framework for quantifying and predicting SOC responses to organic amendments in semiarid, calcareous soils. These findings highlight that sustained, moderate OM applications can substantially enhance SOC sequestration and soil fertility in degraded Iraqi soils, with broader relevance for semiarid agroecosystems worldwide.