Summary

Eng (ISSN 2673-4117) is an international, peer-reviewed open access journal which publishes original papers, critical reviews, rapid communications, technical notes, and discussions on all areas of engineering. Eng's aim is to encourage scientists to publish their experimental and theoretical research relating to engineering science and technology in as much detail as possible. There is no restriction on the maximum length of the papers. Launched in 2020, Eng was indexed in Scopus in 2023. The journal was subsequently included in the Emerging Sources Citation Index (ESCI, Web of Science) in March 2024 and Ei Compendex in April 2025. It holds a 2025 Impact Factor of 3.5 and is ranked JCR Q1 in the “ENGINEERING, MULTIDISCIPLINARY” category. Its 2025 CiteScore is 4.1, and it currently ranks Q2 in Scopus’ “Engineering (miscellaneous)” category.

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Topic Review
One-Dimensional Solar Cell
A one-dimensional solar cell is a computational or physical model in which the photovoltaic device structure and its governing equations are treated as varying only along a single spatial coordinate—usually the depth normal to the illuminated surface—while material properties are assumed uniform in the lateral directions [1]. The model solves, along that coordinate, Poisson’s equation for the electrostatic potential coupled to the electron and hole continuity equations and the drift–diffusion current equations, together with optical generation as a function of depth and wavelength [2]. Carrier transport, recombination (radiative, Shockley–Read–Hall, Auger), and the resulting current–voltage and quantum-efficiency characteristics are computed under boundary conditions at the front and back contacts [3]. The one-dimensional approximation reduces a multilayer thin-film or crystalline device to a stack of homogeneous layers and is the conceptual basis of standard solar-cell simulators, distinguishing it from two- or three-dimensional models that resolve lateral fingers, shunts, and microstructural inhomogeneities [4].
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  • 18 Sep 2026
Topic Review
Charge Carrier Dynamics
Charge carrier dynamics describes the generation, transport, and recombination of electrons and holes—the mobile charge carriers—in a semiconductor following an external excitation such as photon absorption or electrical injection [1]. After generation, excess carriers drift under internal electric fields and diffuse down concentration gradients, with mobilities and diffusion coefficients linked by the Einstein relation, until they are lost through recombination, quantified by the minority-carrier lifetime and the associated diffusion length [2]. Recombination may be radiative, non-radiative through trap states (Shockley–Read–Hall), or via Auger three-body processes, each characterized by a distinct rate and time scale [3]. In photoexcited materials, the temporal evolution of excess populations is commonly described by rate equations linking generation, drift, diffusion, and recombination, while transient optical probes follow the decay of photoluminescence or photoconductivity. The dynamic quantities—lifetimes, mobilities, diffusion lengths, and internal quantum yields—determine how efficiently photogenerated carriers are collected and therefore set the performance of photovoltaic, photoconductive, and other semiconductor devices [4].
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  • 18 Sep 2026
Topic Review
Surrounding Rock Deformation
Surrounding rock deformation refers to the time-dependent change in shape and position of the rock mass immediately adjacent to an underground excavation — such as a tunnel, roadway, cavern, or borehole — caused by the redistribution of in-situ stress after excavation [1]. Before excavation, the rock is in equilibrium under the virgin stress field; removal of material at the opening boundary causes stress concentration around the opening and induces displacements — radial convergence, wall displacement, roof sag, and floor heave — that may be elastic, elastoplastic, or viscoelastic depending on rock-mass quality, depth, and groundwater conditions [2]. The deformation field is governed by the stiffness, strength, and discontinuity geometry of the rock mass and is commonly analyzed using the convergence–confinement method, in which a ground-reaction curve relates radial displacement at the wall to the support pressure provided by linings, rock bolts, or shotcrete [3]. The term is distinguished from intact-rock deformation measured on laboratory specimens and from surface subsidence by its scale and by its location within the rock mass around the opening.
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  • 18 Sep 2026
Topic Review
Global Carbon Emissions
Global carbon emissions denote the annual or cumulative mass of carbon dioxide released to the atmosphere by human activities, reported globally and usually expressed in gigatonnes of CO2 (GtCO2) or of carbon (GtC) [1]. In the standard IPCC and Global Carbon Project accounting, the term comprises CO2 from fossil-fuel combustion and industrial processes, notably cement production (CO2-FFI), together with net CO2 emissions from land-use, land-use change, and forestry (CO2-LULUCF) [2]. Fossil emissions are estimated primarily from national fuel-use statistics and emission factors, whereas land-use emissions are derived from satellite-based land-cover change [3]. Emissions are further reported by sector—energy supply, transport, industry, buildings, and agriculture—and decomposed by fuel type (coal, oil, gas) and by country or region, with net flows balanced against ocean and land sinks in the global carbon budget. Global carbon emissions are distinguished from total greenhouse-gas emissions, which also include methane, nitrous oxide, and fluorinated gases; CO2 is the principal anthropogenic long-lived greenhouse gas and the reference gas against which global-warming potentials are defined [4].
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  • 18 Sep 2026
Topic Review
Electric Vehicle Charging Stations
An electric vehicle charging station (also termed electric vehicle supply equipment, EVSE) is an installation that delivers electrical energy—alternating or direct current—to recharge the traction battery of an electric road vehicle [1]. Conductive charging stations are classified by IEC 61851 into charging modes according to the degree of control and protection, ranging from simple connection to a standard socket-outlet to dedicated DC fast-charge installations with a dedicated converter and a control-pilot signal [2]. Stations may be installed on private premises or in public access points, operate at power levels from slow AC to high-power DC, and incorporate safety functions such as protective earthing, current supervision, and communication between vehicle and equipment [3]. Charging is grouped as AC or DC according to where the power-conversion electronics are located, and each standard mode specifies the rated current and voltage together with the protective functions that must be verified before energization. They are distinguished from inductive (wireless) charging systems by physical conductive contact, and from ordinary electrical outlets by dedicated control, protection, and metering functions [4].
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  • 18 Sep 2026
Topic Review
Gas Turbine Engines
A gas turbine engine is a rotary internal combustion engine in which energy is extracted from a continuous flow of gas that is compressed, combusted, and expanded through a turbine to produce shaft power or jet thrust [1]. Its core consists of an air compressor that raises the pressure of incoming air, a combustor that burns fuel in the compressed air to raise gas temperature, and a turbine that extracts work from the expanding hot gas to drive the compressor; the remaining energy is delivered either as rotational shaft output to a driven load or as exhaust jet momentum for propulsion [1]. The engine operates on a continuous open Brayton (Joule) cycle, with air continuously entering the compressor and combustion products continuously leaving the turbine, rather than on the intermittent reciprocating cycles of piston engines [2]. Gas turbines are configured as turbojet, turbofan, turboprop, turboshaft, or industrial gas turbine variants depending on how the extracted work is used, and are distinguished by their continuous-flow rotary operation and by the high ratio of turbine inlet temperature to compressor delivery pressure that governs their cycle efficiency [3].
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  • 18 Sep 2026
Topic Review
Construction and Demolition Waste
Construction and demolition waste (C&D waste) is the waste stream arising from the construction, renovation, and demolition of buildings, civil-engineering structures, and infrastructure, including excavated soil and residues from road planning and maintenance [1]. Under European waste legislation, C&D waste is formally identified with the waste codes listed in Chapter 17 of the European List of Wastes and comprises materials such as concrete, bricks, tiles, ceramics, wood, glass, metals, plastics, gypsum plasterboard, and uncontaminated excavated soil from construction and demolition operations, while explicitly excluding naturally occurring material and specified hazardous fractions that are classified separately [1]. The category is distinguished from municipal solid waste and from industrial-process waste by its origin in building and civil-engineering works, and it is typically heterogeneous, bulky, and dense relative to domestic waste; individual components may be hazardous (e.g., asbestos-containing materials or chemically treated wood) or non-hazardous, and the stream is commonly managed by source separation, sorting, crushing, and recycling into aggregates, fill, or backfill [2][3].
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  • 18 Sep 2026
Topic Review
Energy-Efficient Building Envelopes
A building envelope (or building envelope assembly) is the physical separator between the conditioned interior and the exterior environment, comprising exterior walls, roofs, floors on grade or over unconditioned space, windows, doors, and associated air, vapor, and moisture-control layers [1]. An energy-efficient building envelope is designed to reduce unwanted heat transfer, air leakage, and moisture accumulation while maintaining acceptable indoor environmental conditions. Key performance considerations include thermal resistance, airtightness, moisture control, solar control, and, where appropriate, thermal mass [1][2][3]. Thermal transmittance (U-value), expressed in W/(m²·K), can be calculated for applicable building components and elements from the thermal resistances of their constituent layers and the relevant surface resistances in accordance with ISO 6946 [4]. ISO 6946 applies principally to relevant building components and elements and excludes windows, doors and other glazed units, curtain walling, building components involving heat transfer to the ground, and components through which air is designed to permeate [4]. Energy-efficient envelopes are therefore defined by their ability to achieve appropriate thermal, air, moisture, and solar-control performance while supporting energy-efficient building operation, rather than by a prescribed material or construction method [1][2].
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  • 22 Sep 2026
Topic Review
Low-Carbon Cementitious Materials
Low-carbon cementitious materials are a family of cementitious binders and constituents formulated or selected to reduce greenhouse-gas emissions expressed as CO₂-equivalent associated with cement and concrete production, relative to a specified conventional baseline, while providing the binding performance required for their intended applications [1]. Emission reductions can be achieved primarily by lowering the Portland-clinker fraction through partial replacement with supplementary cementitious materials, such as fly ash, ground granulated blast-furnace slag, silica fume, metakaolin, and calcined clay, or by using alternative binder chemistries, including alkali-activated binders, calcium sulfoaluminate cements, belite-rich cements, and magnesium-based cements, which may require lower calcination temperatures or reduce reliance on limestone calcination [2]. Because conventional Portland cement production generates greenhouse-gas emissions from both the calcination of calcium carbonate and fuel combustion during clinker production, the low-carbon performance of a cementitious material is generally assessed by comparing greenhouse-gas emissions with those of an appropriate baseline, using a defined system boundary and functional unit [3][4][5]. Such comparisons should also consider equivalent performance requirements, including strength, durability, and expected service life, to ensure that emission reductions are evaluated on a functionally comparable basis. Low-carbon cementitious materials therefore do not correspond to a single composition, clinker-substitution level, or strength class, and conventional blended cements may also be considered low-carbon when they demonstrate a meaningful reduction in greenhouse-gas emissions relative to an appropriate reference system.
  • 25
  • 21 Sep 2026
Topic Review
Gibbs Energy Minimization
Gibbs energy minimization is a thermodynamic computational method that determines the equilibrium composition of a closed multiphase, multicomponent system by finding the set of phase amounts and species mole numbers that minimize the total Gibbs free energy subject to elemental mass-balance constraints at specified temperature and pressure [1]. At fixed temperature and pressure, the second law requires the total Gibbs energy G to reach a global minimum at equilibrium, equivalently requiring equality of the chemical potential of each species among all phases in which it appears [2]. The formulation does not require selection of independent chemical reactions; instead, G is expressed as a function of the unknown mole numbers using ideal or non-ideal mixing models, and the minimum is found by constrained optimization, commonly via Lagrange multipliers or the RAND algorithm [3]. It is distinguished from equilibrium-constant methods, which solve reaction stoichiometry explicitly, by treating equilibrium as an optimization over the distribution of phases and species rather than over reaction extents [4].
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