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To achieve uniform heating of heat‐not‐burn cigarettes, the ANSYS Workbench was used to verify the calculation rule of the resistance value of the mesh heating element. To provide a theoretical basis for improving the design of mesh heating elements, the effect of rounded corners on the resistance value and that of key parameters such as the number of mesh heat emitters in series and parallel, mesh density, and heating power on the heating uniformity were investigated. The deviation of all calculation results is less than 2.4%, indicating that the total resistance value of the mesh heating element conforms to the calculation rule of the series and parallel connections of single‐module resistors. The heating power increases by 3.2%, which has a relatively small impact on the overall heating element when a rounded corner with a radius equal to the line width is added to the corner of the heating element. The area of the heating body increases when increasing the number of series connections and reducing the number of parallel connections, which is conducive to uniform heating. While maintaining the ratio of the number of series connections to the number of parallel connections constant, reducing the module size will not change the area of the mesh heating element, but it will improve the temperature uniformity. Under different power conditions, the heating uniformity of the same heating element does not change. [ABSTRACT FROM AUTHOR]

To realize stable heating of a heated cigarette while effectively controlling the outer‐wall temperature of an electric heating‐type appliance, a vacuum‐insulated tube (VIT) is currently widely used for thermal insulation against the heating element. The effects of the critical parameters of the VIT, gases at different pressures, wall thickness, and material on its thermal insulation performance, were simulated using Fluent to provide guidance on the structure and performance optimization of the EHD. When the absolute pressure of gas in the VIT was <0.5 Pa, increasing the degree of vacuum did not improve the thermal insulation performance. The thermal insulation performance of VITs made from different materials (stainless steel, copper, aluminium, brass, and titanium alloy) was closely related to the emissivity and thermal conductivity of the material. Stainless steel yielded better overall thermal insulation owing to its low thermal conductivity and emissivity. Highly emissive materials, such as brass and titanium alloy, contributed to higher heat transfers through the radiation inside the vacuum chamber and external radiation from the VIT, decreasing the thermal insulation performance of the VIT. Stainless steel VITs yielded an improved thermal insulation performance as the wall thickness decreased, but at the cost of decreased mechanical stability. For a wall thickness of 0.05–0.30 mm, stainless steel yielded the best structural stability. VITs with different wall thicknesses were made from stainless steel, copper, and aluminium, and the thermal insulation performance and structural stability of the EHD were optimized. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have been attracting intense research due to their permanent porosity, designable architecture, and high stability. However, COFs are challenging to crystallize and their synthesis often results in tiny crystal sizes and low crystallinities, which hinders an unambiguous structure determination. Herein, we demonstrate that the structure of low-crystallinity COF Py-1P nanocrystals can be solved by coupling three-dimensional electron diffraction (3DED) with simulated annealing (SA). The resulting model is comparable to that obtained from high-crystallinity samples by dual-space method. Moreover, for low-resolution 3DED data, the model obtained by SA shows a better framework than those provided by classic direct method, dual-space method, and charge flipping. We further simulate data with different resolutions to understand the reliability of SA under different crystal quality conditions. The successful determination of Py-1P structure by SA compared to other methods provides new knowledge for using 3DED to analyze low-crystallinity and nanosized materials. Covalent organic frameworks have demonstrated promise for a wide variety of applications, but their synthesis often results in materials with low crystallinity that are challenging to characterize. Here, coupling three dimensional electron diffraction with simulated annealing is shown to enable the structural determination of a low crystallinity pyrene-containing covalent organic framework. [ABSTRACT FROM AUTHOR]

Acidic compounds constitute a group of chemicals present in mainstream cigarette smoke, among which organic acids contribute to flavoring. In order to obtain a comprehensive understanding of the constituents of acidic compounds in both the particulate and gaseous phases of the mainstream smoke of commercial cigarettes, and to delineate the difference between two types of cigarettes, the yields of acidic constituents from nine cigarettes of two commercial brands (L- and M-types) were collected and analyzed in detail by gas chromatography–mass spectrometry (GC-MS). The results identified and quantitatively analyzed 46 compounds, grouped according to the substituent groups. Compositional differences between the two cigarette types were evaluated with statistical approaches. Comparison between individual, grouped, and total acid contents, between the particulate and the gaseous phases, and between the commercial L- and M-type tobaccos were conducted and characterized by the p values obtained from Student's t-test. Multivariate analysis was performed using principal component analysis (PCA) and orthogonal projections to latent structures discriminant analysis (OPLS-DA) models to identify the acids that enable a reliable differentiation of the two types. Seventeen acidic compounds whose p < 0.05 and variable importance in projection (VIP) > 1 were identified as key components that could discriminate between the two groups of commercial cigarettes. This study may be beneficial for the development of non-combusted tobacco products, which could serve as alternatives to traditional cigarettes. [ABSTRACT FROM AUTHOR]