Search Results (17,630)

This study introduces a novel approach for transforming the cationic surfactant, cetyltrimethylammonium bromide (CTAB), into fluorescent carbon dots (CDs) capable of detecting cadmium ions at ultralow concentrations. The current approach involves preparing CDs through hydrothermal process at various pH levels. The CDs synthesized using pH 10, CTAB-CDs-10, exhibited the highest fluorescence quantum yield (QY), 14.22%. UV-Vis spectroscopy helped identify specific peaks between 210 and 300 nm, corresponding to the π–π* transitions of the aromatic C=C bonds. Transmission electron microscopic (TEM) analysis verified the uniform spherical morphology with a particle size < 2.45 nm. FT-IR analysis confirmed the presence of C=C stretching vibrations. The Box–Behnken (BB) Design was used to reconnoiter the influence of three variables on the response parameter: the F₀/F ratio. The best performance could be achieved at a pH of 9, after only 300 s, and a temperature of 50 °C. The developed CTAB-CDs-based nanoprobe showed an ON–OFF behavior when came in contact with cadmium (II) and demonstrated high sensitivity with a limit of detection as low as 0.06 µM (0.007 ppm) over a wide linear range of 2–103 µM. Validation tests confirmed the applicability of the CTAB-CDs-based nanoprobe for detecting cadmium (II) in tap and drinking waters with high accuracy and precision. Full article

Materials for the conservation of cultural heritage must meet specific demands, such as high durability, service life, and compatibility with other materials used in the original building structures. Due to their low permeability to water and water vapor and their high rigidity, the use of Portland cement (PC) mortars, despite their high mechanical resistance and durability, does not represent an appropriate solution for the repair of historic masonry and structures. Their incompatibility with the original materials used in the past, often on a lime basis, is therefore a serious deficiency for their application. On the other hand, lime-based mortars, compared to PC-based materials, are more susceptible to mechanical stress, but they possess high porosity, a high water vapor transmission rate, and moderate liquid water transport. This study aims at the development of two types of lime-based mortars, calcium lime (CL) and hydraulic lime (HL). The modification of mortars was conducted with a carbon-based nanoadditive and graphene nanoplatelets (GNs) in three dosages: 0.1%, 0.3%, and 0.5% of the binder weight. The enhancement of CL mortars by GNs greatly increased mechanical strength and affected heat transport characteristics, while other characteristics such as porosity, water absorption, and drying rate remained almost similar. The application of GNs to HL not only enhanced the strength of mortars but also decreased their porosity, influenced pore size distribution, and other dependent characteristics. It can be concluded that the use of graphene nanoplatelets as an additive of lime-based composites can be considered a promising method to reinforce and functionalize these composite materials. The improved mechanical resistance while maintaining other properties may be favorable in view of the increasing requirements of building materials and may prolong the life span of building constructions. Full article

As the world’s largest producer of construction waste, China’s recycling and related policies are of the biggest concern to the world. However, the effective disposal and reuse of this waste has become an important issue since currently China still has a very low recycling ratio compared to developed countries, and most of the waste concrete was only simply broken and used as low-grade recycled aggregates for subgrade cushion, cement stabilized crushed stone, and filler wall. In this paper, a concrete cycle model focusing on how to effectively recycle and utilize waste concrete is put forward to prepare high quality recycled concrete, especially through a series of technical means, such as effective separation, carbon sequestration, and reactivation. Producing high quality recycled concrete can not only replace traditional concrete but also effectively reduce the consumption and waste of raw materials. What’s more, the calculation results show a potential of significantly carbon sink; for every ton of recycled cement produced, the CO₂ emission could be reduced by 0.35–0.77 tons compared to ordinary Portland cement, corresponding to a reduction of 47%–94%; and for every ton of recycled concrete produced, the CO₂ emission could be reduced by 0.186 tons compared to normal concrete. A yearly CO₂ sequestration of 1.4–3.08 gigatonnes could happen if the ordinary Portland cement could be replaced by the recycled cement around the world. Taking the currently accumulated construction and demolition (C&D) wastes globally, the production of recycled cement, recycled aggregates, and recycled concrete could induce a significant carbon sink in the world. Full article

The Batailing Au deposit is a vein-type deposit in central Jilin Province, situated in the southern sector of the Lesser Xing’an–Zhangguangcai Range within the eastern Central Asian Orogenic Belt. NE-trending fault-controlled orebodies occur in the Upper Permian Yangjiagou Formation and quartz diorite–porphyrite. The mineralisation process was delineated into three stages: (I) quartz–arsenopyrite–pyrite, (II) quartz–polymetallic sulphides (main Au mineralisation stage), and (III) quartz–pyrite–carbonate. Fluid inclusions (FIs) in quartz were identified as four types: PC-type (pure CO₂), C₁-type (CO₂-bearing), C₂-type (CO₂-rich), and W-type (aqueous two-phase). Raman spectroscopy analysis revealed that the vapor components of the FIs predominantly comprised CO₂ with minor quantities of CH₄ in stages I–II. Stages I and II encompassed four types of FIs with homogenisation temperature ranging from 264 to 332 °C and 213 to 292 °C and salinity spanning from 4.7 to 11.2 wt% and 1.8 to 11.6 wt%, respectively. Stage III exclusively contained W-type FIs with homogenisation temperature ranging from 152 to 215 °C and salinity spanning from 1.4 to 6.4 wt%. H-O isotopic values (δD = −84 to −79.6‰, δ¹⁸O_H2O = 6.2 to 6.4‰ in stage I and δD = −96.4 to −90.4‰, δ¹⁸O_H2O = 2.8 to 4.4‰ in stage II) and microthermometric data indicated that the ore-forming fluids are initially from a magmatic source, with later meteoric water input. Low C isotopic data from CO₂ in FIs in quartz (−24.4 to −24.3‰ in stage I and −23.7 to −22.6‰ in stage II) indicated an organic carbon source. Ore precipitation is mainly attributable to fluid immiscibility. S-Pb isotopic data (δ³⁴S = −3.5 to −1.6‰; ²⁰⁶Pb/²⁰⁴Pb = 18.325–18.362, ²⁰⁷Pb/²⁰⁴Pb = 15.523–5.562, ²⁰⁸Pb/²⁰⁴Pb = 38.064–38.221) revealed that ore metals primarily originated from magma. Based on this research, the origin of the Batailing Au deposit is of the mesothermal magmatic–hydrothermal lode type. Full article

In the context of global climate change and energy and resource scarcity, understanding the factors that influence the adoption of green production technology by rice farmers and promoting a transformation in agricultural practices towards low-carbon and environmentally friendly methods represent a crucial step towards achieving sustainable development. This study employs an ordered logit model to comprehensively explore the influence mechanism of social capital and risk preference within the adoption of green production technology by rice farmers. Research indicates that social capital can significantly and positively affect rice farmers’ uptake of green production technology. Among various dimensions, it can be seen that the role of social participation emerges as a particularly salient factor. The analysis of risk preference demonstrates that it exerts a negative moderating influence. The heterogeneity analysis results indicate that new-generation and part-time rice farmers prefer adopting new technologies if they possess higher social capital. In light of the findings above, it is recommended that the organizational support of cooperatives and collective action be reinforced; the use of digital technologies in agriculture should be increased; the livelihood changes of rice farmers be considered to meet their heterogeneous needs accurately; and the integration of carbon emission reduction policies and green production technologies be strengthened to promote the widespread adoption of green technologies among rice farmers. Full article

Vertical stratification in marine sediment profiles indicates physical and chemical sedimentary processes and, thus, is the first step in sedimentary research and in studying their relationship with global climate change. Traditional technologies for studying vertical stratification have low efficiency; thus, new technologies are highly needed. Recently, visible and near-infrared spectroscopy (VNIR) has been explored to rapidly determine sediment parameters, such as clay content, particle size, total carbon (TC), total nitrogen (TN), and so on. Here, we explored vertical stratification in a sediment column in the South China Sea using VNIR. The sediment column was 160 cm and divided into 160 samples by 1 cm intervals. All samples were classified into three layers by depth, that is, 0–50 cm (the upper layer), 50–100 cm (the middle layer), and 100–160 cm (the bottom layer). Concentrations of TC and TN in each sample were measured by Elementa Vario EL III. Visible and near-infrared reflectance spectra of each sample were collected by Agilent Cary 5000. A global model and several classification models for vertical stratification in sediments were established by a Support Vector Machine (SVM) after the characteristic spectra were identified using Competitive Adaptive Reweighted Sampling. In the classification models, K-means clustering and Density Peak Clustering (DPC) were employed as the unsupervised clustering algorithms. The results showed that the stratification was successful by VNIR, especially when using the combination of unsupervised clustering and machine learning algorithms. The correct classification rate (CCR) was much higher in the classification models than in the global model. And the classification models had a higher CCR using K-means combined with SVM (94.8%) and using DPC combined with SVM (96.0%). The higher CCR might be derived from the chemical classification. Indeed, similar results were also found in the chemical stratification. This study provided a theoretical basis for the rapid and synchronous measurement of chemical and physical parameters in sediment profiles by VNIR. Full article

Fruit photosynthesis occurs in an internal microenvironment seldom encountered by a leaf (hypoxic and extremely CO₂-enriched) due to its metabolic and anatomical features. In this study, the anatomical and photosynthetic traits of fully exposed green fruits of Quercus coccifera L. were assessed during the period of fruit production (summer) and compared to their leaf counterparts. Our results indicate that leaf photosynthesis, transpiration and stomatal conductance drastically reduced during the summer drought, while they recovered significantly after the autumnal rainfalls. In acorns, gas exchange with the surrounding atmosphere is hindered by the complete absence of stomata; hence, credible CO₂ uptake measurements could not be applied in the field. The linear electron transport rates (ETRs) in ambient air were similar in intact leaves and pericarps (i.e., when the physiological internal atmosphere of each tissue is maintained), while the leaf NPQ was significantly higher, indicating enhanced needs for harmless energy dissipation. The ETR measurements performed on leaf and pericarp discs at different CO₂/O₂ partial pressures in the supplied air mixture revealed that pericarps displayed significantly lower values at ambient gas levels, yet they increased by ~45% under high CO₂/O₂ ratios (i.e., at gas concentrations simulating the fruit’s interior). Concomitantly, NPQ declined gradually in both tissues as the CO₂/O₂ ratio increased, yet the decrease was more pronounced in pericarps. Furthermore, net CO₂ assimilation rates for both leaf and pericarp segments were low in ambient air and increased almost equally at high CO₂, while pericarps exhibited significantly higher respiration. It is suggested that during summer, when leaves suffer from photoinhibition, acorns could contribute to the overall carbon balance, through the re-assimilation of respiratory CO₂, thereby reducing the reproductive cost. Full article

As global carbon reduction initiatives progress and the new energy sector rapidly develops, photovoltaic (PV) power generation is playing an increasingly significant role in renewable energy. Accurate PV output forecasting, influenced by meteorological factors, is essential for efficient energy management. This paper presents an optimal hybrid forecasting strategy, integrating bidirectional temporal convolutional networks (BiTCN), dynamic convolution (DC), bidirectional long short-term memory networks (BiLSTM), and a novel mixed-state space model (Mixed-SSM). The mixed-SSM combines the state space model (SSM), multilayer perceptron (MLP), and multi-head self-attention mechanism (MHSA) to capture complementary temporal, nonlinear, and long-term features. Pearson and Spearman correlation analyses are used to select features strongly correlated with PV output, improving the prediction correlation coefficient (R²) by at least 0.87%. The K-Means++ algorithm further enhances input data features, achieving a maximum R² of 86.9% and a positive R² gain of 6.62%. Compared with BiTCN variants such as BiTCN-BiGRU, BiTCN-transformer, and BiTCN-LSTM, the proposed method delivers a mean absolute error (MAE) of 1.1%, root mean squared error (RMSE) of 1.2%, and an R² of 89.1%. These results demonstrate the model’s effectiveness in forecasting PV power and supporting low-carbon, safe grid operation. Full article

To address issues such as large surface roughness, coarse grains, and poor mechanical properties in low-carbon steel parts produced through wire arc additive manufacturing (WAAM), this paper proposes a method combining multi-directional incremental forming with the WAAM process. The additive manufacturing and cooling processes were simulated using the finite element software Abaqus to analyze the effects of multi-directional additive manufacturing on the stress field of the fabricated parts. The results indicate that after multi-directional incremental forming, the residual stress in the fabricated parts shifts from tensile stress to compressive stress, thereby reducing the risk of defects such as cracks. Moreover, the equivalent plastic strain of the processed parts increases, and the surface microhardness improves, with the most significant impact of multi-directional incremental forming observed in the contact area of the rolling head. Full article

Capillary water absorption plays a critical role in the ingress of corrosive elements during the construction of concrete structures in corrosive environments. This study presented a novel approach for analyzing capillary water flow within unsaturated concrete based on the principle of stationary action. The flow of water within the concrete capillary pores can be regarded as a variational problem, while the principle of stationary action provides a method for determining the path solution. The evolution and distribution characteristics of water content and wetting front were explicitly determined using the exponential and power hydraulic functions. A simplistic yet effective approach for determining these hydraulic parameters was put forward based on the relationship between the position of the wetting front and the diffusivity parameters. The proposed approach exhibited enhanced theoretical robustness and entailed fewer hypotheses compared to existing methodologies. Furthermore, the material hydraulic parameters in the proposed approach can be determined explicitly. The governing equations for capillary water flow were derived in accordance with the principle of stationary action. Numerical simulations were carried out to verify the effectiveness of the proposed approach. The results demonstrated that the proposed approach can accurately predict capillary water flow and diffusivity parameters within unsaturated concrete. The findings of this study contribute to developing more effective strategies to mitigate moisture-related damage in concrete structures. Full article

Recent observations of superconductivity in low-dimensional systems composed of twisted, untwisted, or rhombohedral graphene have attracted significant attention. One-dimensional moiré superlattices and flat bands have interestingly been identified in collapsed chiral carbon nanotubes (CNTs), opening up new avenues for the tunability of the electronic properties in these systems. The nucleation of hexagonal moiré superlattices and other types of stacking faults has also been demonstrated in partially collapsed and uncollapsed carbon nano-onions (CNOs). Here, we report a novel investigation on the dynamics of stacking fault nucleation within the multilayered lattices of micrometer-scale vertically oriented films of multiwall CNTs (MWCNTs), resulting from the pyrolysis of molecular precursors consisting of ferrocene or dimethyl ferrocene, at low vapor flow rates of ~5–20 mL/min. Interestingly, local nucleation of moiré-like superlattices (as stacking faults) was found when employing dimethyl ferrocene as the pyrolysis precursor. The morphological and structural properties of these systems were investigated with the aid of scanning and transmission electron microscopies, namely SEM, TEM, and HRTEM, as well as X-ray diffraction (XRD) and Raman point/mapping spectroscopy. Deconvolution analyses of the Raman spectra also demonstrated a local surface oxidation, possibly occurring on defect-rich interfaces, frequently identified within or in proximity of bamboo-like graphitic caps. By employing high-temperature Raman spectroscopy, we demonstrate a post-growth re-graphitization, which may also be visualized as an alternative way of depleting the oxygen content within the MWCNTs’ interfaces through recrystallization. Full article

The farmland system in the global terrestrial ecosystem has dual attributes as both a carbon source and a carbon sink, playing a crucial role in controlling carbon emissions and mitigating global warming. Using carbon source and sink accounting of farmland ecosystems, we applied methods such as standard deviation ellipse, Tapio decoupling theory, and Markov chain to analyze the spatiotemporal changes, response mechanisms, and evolutionary trends of regional carbon effects. The results indicated that from 2011 to 2021, the farmland ecosystem in the middle and lower reaches of the Yangtze River consistently acted as a carbon sink. However, the net carbon sink showed slight fluctuations and significant spatial differences. The migration range of the net carbon sink center in the farmland ecosystem of the middle and lower reaches of the Yangtze River was relatively small, ranging from 115.52 to 115.77° E and 30.14 to 30.27° N. The decomposition of the Tapio decoupling index between the net carbon sink of the farmland ecosystem and agricultural output value showed the order of effects on their coupling relationship as follows: agricultural mechanization level > agricultural mechanization efficiency > agricultural output value > planting scale. The probability of maintaining the original state of net carbon sink in various cities in the middle and lower reaches of the Yangtze River (over 77%) was much higher than the probability of transfer, making it difficult to achieve a leapfrog growth in net carbon sink. The net carbon sink at the city scale exhibits the Matthew effect and spatial spillover effect. The above research results clarify the spatiotemporal changes in carbon effects in agricultural production at multiple levels, including city, province, and region. They also provide a theoretical basis for formulating differentiated regional emission reduction and sink enhancement strategies in the middle and lower reaches of the Yangtze River, promoting the rapid development of low-carbon agriculture in China. Full article

Nuclear energy is increasingly being considered for such targeted energy applications as data centers in light of their high capacity factors and low carbon emissions. This paper focuses on assessing the tradeoffs between economies of scale versus mass production to identify promising reactor sizes to meet data center demands. A framework is then built using the best cost estimates from the literature to identify ideal reactor power sizes for the needs of the given data center. Results should not be taken to be deterministic but highlight the variability of ideal reactor power output against the required demand. While certain advocates claim that with the gigawatts of clean, firm energy needed, large plants are ideal, others advocate for SMRs that can be deployed in large quantities and reap the benefits from learning effects. The findings of this study showcase that identifying the optimal size for a reactor is likely more nuanced and dependent on the application and its requirements. Overall, the study does show potential economic promise for coupling nuclear reactors to data centers and industrial heat applications under certain key conditions and assumptions. Full article

As an important energy source to achieve carbon neutrality, green hydrogen has always faced the problems of high use cost and unsatisfactory environmental benefits due to its remote production areas. Therefore, a liquid-gaseous cascade green hydrogen delivery scheme is proposed in this article. In this scheme, green hydrogen is liquefied into high-density and low-pressure liquid hydrogen to enable the transport of large quantities of green hydrogen over long distances. After long-distance transport, the liquid hydrogen is stored and then gasified at transfer stations and converted into high-pressure hydrogen for distribution to the nearby hydrogen facilities in cities. In addition, this study conducted a detailed model evaluation of the scheme around the actual case of hydrogen energy demand in Chengdu City in China and compared it with conventional hydrogen delivery methods. The results show that the unit hydrogen cost of the liquid-gaseous cascade green hydrogen delivery scheme is only 51.58 CNY/kgH₂, and the dynamic payback periods of long- and short-distance transportation stages are 13.61 years and 7.02 years, respectively. In terms of carbon emissions, this scheme only generates indirect carbon emissions of 2.98 kgCO₂/kgH₂ without using utility electricity. In sum, both the economic and carbon emission analyses demonstrate the advantages of the liquid-gaseous cascade green hydrogen delivery scheme. With further reductions in electricity prices and liquefication costs, this scheme has the potential to provide an economically/environmentally superior solution for future large-scale green hydrogen applications. Full article

Drawing from A-share listed companies’ data from the Shanghai and Shenzhen stock markets in China (2013–2022), this paper adopts the differential model to test the impact and mechanism of a green supply chain (GSC) pilot on pilot enterprises. The results show that the GSC pilot effectively improved the carbon performance of the pilot enterprises and passed a series of robustness tests. Mechanism analysis finds that green innovation, efficiency improvement, and environmental information disclosure (EID) can reduce the carbon emissions of enterprises. The moderating effect discovers that environmental regulation and environmental attention effectively strengthened the role of the GSC pilot in improving carbon performance. In addition, this paper finds that the pilot had a better carbon reduction effect on mature, technology-intensive, and non-state-owned enterprises. The above research conclusions provide strong support for the government to build a GSC and promote low-carbon development. Full article