The wavelength dependence of laser induced breakdown spectroscopy (LIBS) in the analysis of the carbon contents of coal was studied using 266 nm and 1064 nm laser radiations. Compared with the 1064 nm wavelength laser ablation, the 266 nm wavelength laser ablation has less thermal effects, resulting in a better crater morphology on the coal pellets. Besides, the 266 nm wavelength laser ablation also provides better laser-sample coupling and less plasma shielding, resulting in a higher carbon line intensity and better signal reproducibility. The carbon contents in the bituminous coal samples have better linearity with the line intensities of atomic carbon measured by the 266 nm wavelength than those measured by the 1064 nm wavelength. The partial least square (PLS) model was established for the quantitative analysis of the carbon content in coal samples by LIBS. The results show that both of the 266 nm and 1064 nm wavelengths are capable of achieving good performance for the quantitative analysis of carbon content in coal using the PLS method.
Abstract Polysulfide shuttling and uncontrollable lithium dendrite growth have hampered the application of lithium–sulfur (Li–S) batteries. Although various materials have been utilized to overcome these obstacles, simple and scalable methods are still needed for Li–S battery commercialization. It is shown for the first time that the layer‐by‐layer (LbL) self‐assembly of 2D nanomaterials can be used to controllably fabricate multifunctional separators that simultaneously trap polysulfides and suppress lithium dendrite growth. The double‐sided “nanobrick wall” structure, constructed by MoS 2 /poly(diallyl dimethyl ammonium chloride) hybrid in conjunction with poly(acrylic acid) (PAA), provides a physical shield against polysulfides and the chemical adsorption of such species by MoS 2 and PAA. At the same time, the robust and Li‐ion conducting MoS 2 layers strengthen the separator and regulate Li deposition, thereby effectively suppressing Li dendrite formation. As a result, a simple sulfur cathode battery with an ultralight separator coating (0.10 mg cm −2 ) is able to achieve an outstanding cycle stability with a capacity decay as low as 0.029% per cycle over 2000 cycles and a reversible areal capacity ≈2.0 mAh cm −2 at 1 C. The proposed LbL approach opens the door to the simple, scalable, and economic fabrication of advanced functional separators for use in the real world.
The significant fire hazards on the polymer-based thermal interface materials (TIM) used in electronic devices are but often neglected. Also, high filler loading with the incident deterioration of mechanical, thermal, and processing properties limits the further application of the traditional polymer-based TIMs. In this work, a ternary TIMs with epoxy resin (EP) matrix, silver nanowires (AgNWs), and a small amount of flame-retardant functionalized graphene (GP-DOPO) were proposed to address the above questions. Briefly, a facile "branch-like" strategy with a polymer as the backbone and flame-retardant molecule as the branch was first used to functionalize reduced graphene oxide (RGO) toward increasing the flame-retardant grafting ratio and RGO's compatibility in matrix, and the resulted GP-DOPO was then in situ introduced into the EP/AgNW composites. As expected, the incorporation of GP-DOPO (2 wt %) can increase the thermal conductivity to 1.413 W/(m K) at a very low AgNW loading (4 vol %), which is 545 and 56% increments compared to pure EP and EP/AgNW, respectively. The prominent improvement in thermal conductivity was put down to the synergetic effect of AgNW and GP-DOPO, i.e., the improving dispersion and bridging effect for AgNWs by adding GP-DOPO. Moreover, the high flame-retardant grafting amount and the excellent compatibility of GP-DOPO resulted in a strong catalytic charring effect on EP matrix, which further formed a robust protective char layer by combining the AgNW and graphene network. Therefore, the flame retardancy of EP/AgNW was significantly improved by introducing GP-DOPO, i.e., the peak heat release rate, total heat release and total smoke production reduced by 27.0, 32.4, and 30.9% reduction compared to EP/AgNW, respectively.
Measurement of coal carbon content using laser-induced breakdown spectroscopy (LIBS) is limited by its low precision and accuracy. A modified spectrum standardization method was proposed to achieve both reproducible and accurate results for the quantitative analysis of carbon content in coal using LIBS. The proposed method used the molecular emissions of diatomic carbon (C 2 ) and cyanide (CN) to compensate for the diminution of atomic carbon emissions in high volatile content coal samples caused by matrix effect. The compensated carbon line intensities were further converted into an assumed standard state with standard plasma temperature, electron number density, and total number density of carbon, under which the carbon line intensity is proportional to its concentration in the coal samples. To obtain better compensation for fluctuations of total carbon number density, the segmental spectral area was used and an iterative algorithm was applied that is different from our previous spectrum standardization calculations. The modified spectrum standardization model was applied to the measurement of carbon content in 24 bituminous coal samples. The results demonstrate that the proposed method has superior performance over the generally applied normalization methods. The average relative standard deviation was 3.21%, the coefficient of determination was 0.90, the root mean square error of prediction was 2.24%, and the average maximum relative error for the modified model was 12.18%, showing an overall improvement over the corresponding values for the normalization with segmental spectrum area, 6.00%, 0.75, 3.77%, and 15.40%, respectively.
Considering the effect of atmosphere, the natural permeability variation process of expensive soil is simulated by lab test. The method of Fredlund & Xing is also used to predict the permeability coefficient of unsaturated expensive soil. The results show that drying-wetting cyclic action may increase the permeability of expensive soil, which illuminates the atmosphere influence depth evolution of cut slope. The results can supply parameter reference in design and numerical calculation.
The swelling-shrinking deformation, deformation modulus and permeability of expansive soil are tracked and measured in Nanning, Guangxi considering the effect of atmosphere. The test results are just as follows. Firstly, a low rainfall may lead water content and swelling state to the limit value, and the influence depth of infiltration is finite while raining. Secondly, the deformation modulus is decreased with the increase of water content following the forms of power function. Finally, when the water content is low, the fissure is developed and the permeability is improved greatly; meanwhile, the permeability is also strengthened with the vegetation covered, which is useful to recognize the disastrous mechanism of expansive soil slope.
The rapid development of renewable energy has made hydropower's role as a flexible resource increasingly important in power systems. However, hydropower generation capability highly depends on water inflows, particularly during dry seasons, making it difficult to independently meet growing load demands. The application of hydro-wind-photovoltaic-storage systems offers a promising solution, yet faces challenges from the high-dimensional uncertainties in natural conditions. This paper proposes a capacity planning method that considers high-dimensional uncertainties characterized by spatiotemporal correlations of natural factors. Firstly, a scenario generation method based on the transition probability matrix and C-Vine Copula model is developed. The constructed scenario sets capture the temporal correlations of natural conditions and spatial correlations between different parameters. Secondly, a bi-level optimization model for capacity planning is established. The upper level minimizes the deviation of operational cost and grid supply revenue to determine optimal capacity allocation, while the lower level optimizes both economic and safe objectives for operational dispatch. The normal boundary intersection method is employed to obtain Pareto front solutions that balance economy and safety. Different case studies are conducted to validate the effectiveness of the proposed method. Compared with the fixed ratio and variable ratio capacity allocation strategies without uncertainty, the optimal total system cost is reduced by 2.90% and 3.88%, respectively.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)