Search Results (176)

Strategic petroleum reserves are critical for energy security. In Japan, 0.5 million kiloliters of crude oil (12% of the state-owned reserves) is stored using underground rock-cavern tanks, which comprise unlined horizontal tunnels bored into bedrock. Crude oil is held within the tank by water inside the tank, the pressure of which is kept higher than that of the crude oil by natural groundwater and irrigation water. This study applied microbial DNA-based monitoring to assess the water environments in and around national petroleum-stockpiling bases (the Kuji, Kikuma, and Kushikino bases) using the rock-cavern tanks. Forty-five water samples were collected from the rock-cavern tanks, water-supply tunnels, and observation wells. Principal-component analysis and hierarchical clustering indicated that microbial profiles of the water samples reflect the local environments of their origins. Particularly, the microbial profiles of water inside the rock-cavern tanks were distinct from other samples, revealing biological conditions and hence environmental characteristics within the tanks. Moreover, the clustering analysis indicated distinct features of water samples that have not been detected by other monitoring methods. Thus, microbial DNA-based monitoring provides valuable information on the in situ environments of rock-cavern tanks and can serve as an extremely sensitive measurement to monitor the underground oil storage. Full article

An altermagnet, characterized by its distinctive magnetic properties, may hold potential applications in diverse fields such as magnetic materials, spintronics, data storage, and quantum computing. As a prototypical altermagnet, RuO₂ exhibits spin polarization and demonstrates the advantageous characteristics of high electrical conductivity and low thermal conductivity. These exceptional properties endow it with considerable promise in the emerging field of thermal spintronics. We studied the electronic structure and thermoelectric properties of RuO₂; the constructed RuO₂/TiO₂/RuO₂ all-antiferromagnetic tunnel junction (AFMTJ) exhibited thermally induced magnetoresistance (TIMR), reaching a maximum TIMR of 1756% at a temperature gradient of 5 K. Compared with prior studies on RuO₂-based antiferromagnetic tunnel junctions, the novelty of this work lies in the thermally induced magnetoresistance based on its superior thermoelectric properties. In parallel structures, the spin-down current dominates the transmission spectrum, whereas in antiparallel structures, the spin-up current governs the transmission spectrum, underscoring the spin-polarized thermal transport. In addition, thermoelectric efficiency emphasizes the potential of RuO₂ to link antiferromagnetic robustness with ferromagnetic spin functionality. These findings promote the development of efficient spintronic devices and spin-based storage technology for waste heat recovery and emphasize the role of spin splitting in zero-magnetization systems. Full article

Organic nonvolatile transistor memories (ONVMs) using a hybrid spiro [fluorene-9,7′-dibenzo [c, h] acridine]-5′-one (SFDBAO)/polystyrene (PS) film as bulk-heterojunction-like tunneling and trapping elements were fabricated. From the characterization of the 10% SFDBAO/PS based on ONVM, a sterically hindered small-molecule SFDBAO with rigid orthogonal configuration and a donor–acceptor (D-A) structure as a molecular-scale charge storage element demonstrated significantly higher charge trapping ability than other small-molecule materials such as C₆₀ and Alq₃. The ONVM based on 10% SFDBAO/PS presents ambipolar memory behaviors with a wide memory window (146 V), a fast-switching speed (20 ms), an excellent retention time (over 5 × 10⁴ s), and stable reversibility (36 cycles without any noticeable decay). By applying different gate voltages, the above ONVM shows reliable four-level data storage characteristics. The investigation demonstrates that the strategical bulk-heterojunction-like tunneling and trapping elements composed of small-molecule materials and polymers exhibit promising potential for high-performance ambipolar ONVMs. Full article

Three-dimensional NAND Flash has adopted the cell-over-peripheral (COP) structure to increase storage density. Unlike the conventional structure, the COP structure cannot directly increase the channel potential via substrate bias during the erase operation. Therefore, the gate-induced drain leakage (GIDL) erase method, which utilizes band-to-band tunneling (BTBT) to raise the channel potential, is employed. However, compared to bulk erase, the BTBT-based erase method requires a longer time to generate holes in the channel, leading to erase speed degradation. To address this issue, we propose a structure which enhances the erase speed by surrounding the bitline (BL) PAD with SiGe. In the case of a SiGe thickness (t_SiGe) of 13 nm, the lower bandgap of SiGe increases the BTBT generation rate, boosting the channel potential rise at the end of the erase voltage ramp-up by 861% compared to the Si-only structure, while limiting the reduction in read on-current to within 4%. We modeled the voltage and electric field across the SiGe layer, as well as BTBT generation rate and GIDL current in the SiGe layer, by varying t_SiGe, Ge composition ratio (SiGe_X), and the voltage difference between V_BL and V_{GIDL_TR}. Full article

The use of a rock-bed accumulator for a short-term heat storage and air exchange in a building facility is an economical and energy-efficient technological solution to balance and optimize the energy supplied to the facility. Existing scientific studies have not addressed, as yet, the environmental impacts of using a rock bed for heat storage. The purpose of the research is the environmental life cycle assessment (LCA) of a heat storage system in a rock-bed accumulator supported by a photovoltaic installation. The boundaries of the analyzed system include manufacturing the components of the storage device, land preparation for the construction of the accumulator, the entire construction process, including transportation of materials, and its operation in cooperation with a horticultural facility (foil tunnel) during one growing season, as well as the photovoltaic installation. The functional unit in the analysis is 1 square meter of rock-bed accumulator surface area. SimaPro 8.1 software and Ecoinvent database were used to perform the LCA, applying the ReCiPe model to analyze environmental impact. The analysis showed the largest negative environmental impact occurs during raw materials extraction and component manufacturing (32.38 Pt). The heat stored during one season (April to October) at a greenhouse facility reduces this negative impact by approx. 7%, mainly due to the reduction in the use of fossil fuels to heat the facility. A 3 °C increase in average air temperature results in an average reduction of 0.7% per year in the negative environmental impact of the rock-bed thermal energy storage system. Full article

This paper presents a comparative study examining the effects of carbon nanotubes (CNTs) and expanded graphite (EG) on the thermal, mechanical, morphological, electrical, and piezoresistive properties of poly(ethylene-co-methacrylic acid) (EMAA) nanocomposites. To this end, different amounts of carbonaceous fillers (EG and CNTs separately) were added to the EMAA thermoplastic matrix, and the relative electrical percolation thresholds (EPTs) were determined. The effect of filler concentration on thermo-oxidative degradation and the EMAA crystallinity was investigated via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. Dynamic mechanical analysis (DMA) demonstrated that both fillers enhance the Young’s and storage moduli, as well as the glass transition temperature, with a greater improvement for the bidimensional nanofiller, most likely due to the cumulative effect of more extensive EG-matrix interactions. In tensile tests, a very relevant difference was detected in the Gauge Factor (G.F.) and the elongation at break of the two typologies of nanocomposites. The G.F. of EMAA 10% CNT and EMAA 15% EG were found to be 0.5 ± 0.08 and 165 ± 14, respectively, while elongation at break was about 68% for EMAA 10% CNT and 8% for EMAA 15% EG. Emission Scanning Electron Microscopy (FESEM) and Tunneling Atomic Force Microscopy (TUNA) have contributed to explaining the differences between EG- and CNT-based nanocomposites from a morphological point of view, underlying the pivotal role of the filler aspect ratio and its structural features in determining different mechanical and piezoresistive performance. The comprehensive analysis of EMAA-EG and EMAA-CNT nanocomposites provides a guide for selecting the best self-sensing system for the specific application. More specifically, EMAA-CNT nanocomposites with high elongation at break and lower sensitivity to small strains are suitable for movement sensors in the soft robotic field, where high deformation has to be detected. On the other hand, the high sensitivity at a low strain of EMAA-EG systems makes them suitable for integrated sensors in more rigid composite structures, such as aeronautical and automotive components or wind turbines. Full article

The Industry Foundation Class (IFC)-based sensor monitoring information expression mechanism is discussed, and an IFC-based tunnel entity definition and sensor monitoring information expansion method are proposed. Based on the existing IFC standards, by introducing the description dimensions of the tunnel’s spatial and geometric structure, the definition of IFC tunnel entities is creatively supplemented. For the first time, the expansion of IFCs in the field of tunnels is achieved, significantly expanding the boundaries of IFCs in complex underground engineering applications. The IFC-based tunnel monitoring information model is constructed using IfcSensor as the sensor entity and extending the sensor entity attribute set. Aiming at the problems of complicated tunnel monitoring data and difficult storage, this paper studies the tunnel monitoring information integration and visual early warning method based on IFCs. A Building Information Modeling (BIM)-based monitoring information integration system is developed, and the engineering application is carried out with the Jianyuan–Kaiyuan Road tunnel project in Xi‘an as a demonstration case. The advantages of BIM technology in a model visualization application are verified, and the risk perception and visual warning of tunnel construction are realized. Full article

It has been found in engineering practice that the degree of rockburst risk increases when roadway excavation occurs near the stratigraphical boundary of different lithologies. This study uses the 1276 m deep-buried roadway of a lead–zinc mine in Yunnan, China, as its engineering background. Based on a numerical analysis of this case, it investigates the mechanical behavior of surrounding rocks in different lithological formations and explores the causes of excavation-induced rockburst. Additionally, by changing the excavation strategy in a numerical simulation, the influence of the direction of roadway excavation on the degree of rockburst risk in the construction of different lithological formations is assessed. The results are summarized as follows: (1) When the tunnel passes from the C₁b stratum (limestone) to the D₃zg stratum (dolomite), an abnormal stress zone forms in the roof rock strata of the D₃zg stratum (the lower plate of the stratum boundary). The rockburst risk level was evaluated by introducing the numerical rockburst index in this abnormal stress zone, which aligns closely with on-site rockburst investigation results. The rockburst risk is the greatest in the abnormal stress zone, which provides an external energy storage environment for the development of rockburst disasters. (2) Near the stratum boundary, the rockburst risk level when excavating from the D₃zg stratum to the C₁b stratum is greater than that when excavating from the C₁b stratum to the D₃zg stratum. The direction of tunnel excavation significantly affects the rockburst risk level during construction that crosses different lithological strata. These findings can provide a theoretical basis for the construction design of similar underground projects. Full article

This paper presents a novel transposed MRAM architecture (WinEdge) specifically optimized for Winograd convolution acceleration in edge computing devices. Leveraging Magnetic Tunnel Junctions (MTJs) with Spin Hall Effect (SHE)-assisted Spin-Transfer Torque (STT) writing, the proposed design enables a single SHE current to simultaneously write data to four MTJs, substantially reducing power consumption. Additionally, the integration of stacked MTJs significantly improves storage density. The proposed WinEdge efficiently supports both standard and transposed data access modes regardless of bit-width, achieving up to 36% lower power, 47% reduced energy consumption, and 28% faster processing speed compared to existing designs. Simulations conducted in 45 nm CMOS technology validate its superiority over conventional SRAM-based solutions for convolutional neural network (CNN) acceleration in resource-constrained edge environments. Full article

Selecting the type of lined rock cavern (LRC) is a critical aspect in the construction of compressed air energy storage (CAES) plants. Present research on CAES has mainly focused on site selection, sealing performance, and stability of underground LRCs. Insufficient attention has been given to the selection of LRC type, which is a prerequisite for further detailed analyses of LRCs. To overcome this limitation, based on reliable numerical simulation, in this study, we simulate the mechanical responses of two popular types of LRCs: tunnel-type and silo-type LRCs. Parameter sensitivity analysis is then conducted based on the mechanical response, including parameters such as the deformation modulus of the surrounding rock mass, Poisson’s ratio, cohesion, friction angle, crustal stress, and lateral stress coefficient. Based on the simulated results, the analytical hierarchy process (AHP) method is used to propose scoring systems for the two types of LRCs. This scoring system can be used for quantitative estimation of an appropriate LRC in CAES systems. Full article

The high water head of some pumped storage power stations will induce the cracking of the concrete lining of their diversion tunnel and the leakage of high-pressure water, which will affect the safety of the tunnel and the surrounding rock. At present, there is no solution to the problem of impermeability of concrete materials after cracking. This paper proposes a composite lining to solve this problem. The composite lining with modified polydimethylsiloxane coating can effectively prevent high-pressure water, but its crack resistance needs to be further studied. Therefore, the tensile mechanical properties, constitutive relationship of modified polydimethylsiloxane impermeable coating, and the crack resistance mechanical properties of modified polydimethylsiloxane impermeable composite lining were studied by laboratory tests and numerical simulations. The results show that the true fracture elongation of the modified polydimethylsiloxane impermeable coating is as high as 118.98%, and its mechanical behavior can be described by a simplified polynomial hyperelastic constitutive model. The in situ stress will affect the crack width of the concrete lining. When the lateral pressure coefficient is less than 1, the crack width decreases with the increase in the lateral pressure coefficient. When the lateral pressure coefficient is greater than 1, the crack width increases with the increase in the lateral pressure coefficient. To prevent the cracking of modified polydimethylsiloxane coating, its spraying thickness needs to increase with the increase in crack width. The ratio of the coating’s thickness to crack width is recommended from 0.162 to 1.930 for internal water pressure from 1 MPa to 10 MPa, respectively. The suggestion provides a reference for designing the impermeable composite lining structure subjected to high internal water pressure. Full article

Under the “dual-carbon” strategy, accurately quantifying carbon emissions in water conservancy projects is crucial to promoting low-carbon construction. However, existing life cycle assessment (LCA) methods for carbon emissions during the mechanical construction stage often fail to reflect actual processes and are limited by high costs and lengthy data collection, potentially leading to inaccurate estimates. To address these challenges, this paper proposes a carbon emission evaluation method for the mechanical construction stage, based on carbon footprint theory and discrete event simulation (DES). This method quantifies equipment operation time and energy consumption during the drilling and blasting processes, enabling a detailed and dynamic emission analysis. Using the Fumin Pumped Storage Power Station Tunnel Project as a case study, a comparative analysis is conducted to examine the carbon emission characteristics of drilling and blasting operations under different surrounding rock conditions based on DES. The validity of the proposed model is confirmed by comparing its results with monitoring data and LCA results. The results show a clear upward trend in carbon emission intensity as surrounding rock conditions deteriorate, with emission intensity rising from 8405.82 kgCO₂e/m for Class II to 16,189.30 kgCO₂e/m for Class V in the headrace tunnel. The total carbon emissions of the water conveyance tunnels reach 40,019.64 tCO₂e, with an average intensity of 13,565.98 kgCO₂e/m. This study presents a refined and validated framework for assessing the carbon emissions of pumped storage tunnels. It addresses key limitations of traditional LCA methods in the mechanical construction stage and provides a practical tool to support the green transition of hydraulic infrastructure. Full article

Tunnel-structured Na_0.44MnO₂ (NMO) has been extensively studied as a potential cathode for sodium-ion batteries (SIBs) due to its favorable cycling endurance, cost-effectiveness, environmental benignity, and notable air-moisture stability. However, limitations, such as sluggish ion diffusion kinetics, an insufficient Na⁺ storage capacity, and an unsatisfactory Jahn–Teller effect, impede its widespread application. To address these problems, this study proposes a co-doping strategy that involves the simultaneous introduction of a cation and an anion. The optimized cathode Na_0.44Mn_0.99Ni_0.01O_1.985F_0.015 demonstrates remarkable rate capabilities with average discharge capacities of 136.2, 133.0, 129.6, 124.0, 115.9, and 95.8 mAh g⁻¹ under current rates ranging from 0.1 to 5 C. Furthermore, it also exhibits exceptional long-term cyclability, retaining 86.5% and 89.4% capacity retention at 1 and 5 C after 200 and 400 cycles, respectively, accompanied by nearly 100% Coulombic efficiency. A comprehensive structural characterization and experimental analysis reveal that the synergistic incorporation of Ni and F can effectively adjust the lattice parameters and alleviate the Jahn–Teller distortion of the NMO cathode, thereby resulting in enhanced structural integrity, rapid ion transfer dynamics, and excellent sodium storage performance. Consequently, this investigation establishes a significant approach for optimizing tunnel-phase Mn-based cathodes through the synergistic effect of cation and anion co-doping, which promotes the practical implementation of advanced SIBs. Full article

This study aims to ensure that the maximum crack width of underground working linings for compressed air energy storage (CAES) meets the allowable limit under high internal pressure conditions. Drawing on crack width calculation methods from hydraulic tunnels, this study proposes a design method for segmented linings with preset seams. The method accounts for the shear mechanical behavior of the sliding layer, with parameters determined through laboratory testing. A typical case study validates the reliability of the crack width calculation method that accounts for lining damage and plasticity. The study determined, from an engineering case, that six seams are optimal when the lateral pressure coefficient λ is below 1, while four seams are more suitable when λ > 1. Additionally, reinforcement ratios and retractable joints of the segmented lining were designed for the case. When the surrounding rock quality is lower than that of hard rock mass and gas pressure exceeds 12 MPa, monolithic cast-reinforced concrete linings often fail to meet the allowable crack width limits. However, segmented linings offer greater flexibility, as they can still meet the requirements even with fair-quality rock mass. These findings provide critical theoretical foundations for the design of CAES workings under high internal pressure. Full article

Under extremely low-head conditions, the performance and stability of pump-turbine units are strongly influenced by the flow distortion caused by variations in guide vane opening. In this study, a pump-turbine model—representative of a domestic pumped storage power station—was investigated through a combination of experimental observations and three-dimensional unsteady numerical simulations employing the SST k-ω turbulence model. The analysis focused on characterizing the variations in turbulence kinetic energy, pressure pulsations, and impeller force fluctuations as the guide vane opening was altered. The results reveal that, with increasing guide vane opening, the turbulence kinetic energy within the impeller region is notably reduced. This reduction is primarily attributed to a decrease in energy losses along the suction surfaces of the blades and within the straight pipe section of the tailwater tunnel. Simultaneously, pressure pulsations were detected at multiple locations including the volute inlet, the blade-free zone, downstream of the conical pipe, and along the inner surface of the shaft tube. While most regions experienced a decline in pressure pulsation intensity with larger openings, the bladeless zone exhibited a significant increase. Moreover, force analysis at four distinct guide vane settings indicated that an opening of 41 mm resulted in relatively uniform fluctuations in the impeller forces. This uniformity suggests that an optimal guide vane configuration exists, which minimizes uneven stress distributions and enhances the operational stability of the pump-turbine under extremely low-head conditions. These findings offer valuable insights for the design and operational optimization of pump-turbine systems in pumped storage power stations. Full article