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17. Design of Draw Resistance of Pressure Drop Standards for Tobacco Products Based on the Flow Distribution

Author

Zhang Pengfei, Li Congcong, Yang Rongchao, Shi Zhandong, Chen Zhihao, Zhang Kai, and Miao Qian

Subjects
structural parameters, pressure drop standard, design, capillaries size, length, Science
Abstract

Cigarette draw resistance and filter pressure drop are both critical physical indicators for the tobacco industry, which use testing equipment to measure the two parameters. Pressure drop standards are used as transfer standards to ensure the accuracy and reliability of the testing equipment. Pressure drop standards are generally cylindrical rods having a certain number of parallel capillaries. To address the issue of how to design and fabricate pressure drop standards quickly and conveniently, this paper proposes a design method for pressure drop standards based on structural parameters. The method uses a mathematical model of the internal airflow of the standard including the entrance effect into a circular capillary and uses an iterative calculation algorithm accordingly. By iterative calculation, the structural parameters of the pressure drop standard, namely, diameter and length of the capillaries, were obtained, along with the relationship between the draw resistance of the standard and the flow rate in each capillary. The accuracy of the mathematical model was validated by comparing and analyzing the experimental and theoretical draw resistance of standards with different structural parameters. The experimental results showed that the relative error between the measured draw resistance and the calculated draw resistance was below 8%, which proves the reliability and validity of the mathematical model, and provides theoretical support for the design and fabrication of pressure drop standards.

Published
2024
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22. Oxypeucedanin hydrate alleviates rheumatoid arthritis by inhibiting the TLR4-MD2/NF-κB/MAPK signaling axis

Author

Liu Mengdan, Huo Xueyan, Li Congcong, Hu Yunjie, Lei Haoran, Wang Dong, Zhu Lin, Gu Yucheng, Guo Dale, Huang Lijun, and Deng Yun

Subjects
oxypeucedanin hydrate, rheumatoid arthritis, TLR4-MD2 complex, NF-κB/MAPK pathway, Biochemistry, QD415-436, Genetics, QH426-470
Abstract

Rheumatoid arthritis (RA) is an idiopathic and chronic autoimmune disease for which there are currently no effective treatments. Oxypeucedanin hydrate (OXH) is a natural coumarin known for its potent anti-inflammatory properties. However, further investigations are needed to determine its therapeutic efficacy in treating RA. In this study, we evaluate the anti-inflammatory activity of OXH by treating LPS-induced RAW264.7 macrophages. Our results show that OXH treatment reverses the changes in iNOS, COX-2, IL-1β, IL-6, and TNF-α levels. Additionally, OXH reduces ROS production. Further analysis reveals that OXH suppresses the activation of the NF-κB/MAPK pathway. CETSA results show that OXH competes with LPS for binding to the TLR4/MD2 complex. MST experiments demonstrate the specific affinity of OXH for the TLR4/MD2 complex, with a Kd value of 33.7 μM. Molecular docking analysis suggests that OXH binds to the pocket of the TLR4/MD2 complex and interacts with specific amino acids, such as GLY-343, LYS-388, and PHE-345. Molecular dynamics simulations further confirm this conclusion. Finally, we investigate the potential of OXH in treating RA using a collagen-induced arthritis (CIA) model in rats. OXH effectively ameliorates the symptoms of CIA, including improving body weight, reducing swelling and redness, increasing talus volume, and decreasing bone erosion. OXH also decreases the mRNA levels of pro-inflammatory factors in synovial tissue. Transcriptome enrichment analysis and western blot analysis confirm that OXH suppresses the NF-κB/MAPK pathway, which is consistent with our in vitro findings.

Published
2024
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23. Efficient and accurate assessment of fire spread over external claddings in high-rise buildings

Author

Li, Congcong, Craft, Timothy, and Wang, Yong

Subjects
BS 8414, Fire development model, Facade, Regulation
Abstract

The general aim of this thesis is to develop an efficient and accurate model to simulate upward flame spread in unventilated and ventilated cladding systems. The validated model is then used to assess the current Euroclass system of selecting external materials and proposes guidelines on how to improve external material selection while still within the simplistic framework of regulations. The model consists of the following main sub-models: a one-dimensional combined heat and mass transfer model to compute gaseous fuel production due to decomposition, and a simplified model to calculate surface heat flux and transient flame growth. To demonstrate the capability of the new model, vertical burning and upward flame spread on 2.4m high panels of wood and 5.0 m high panels of PMMA are carried out and compared with experimental results and FDS simulations. The new model calculation results, including propagation of the pyrolysis front, total heat flux, and heat release rate are in good agreement with experimental and FDS's results. However, the new model requires a fraction (a few minutes of CPU time) of that for carrying out the corresponding FDS simulation (CPU time of 2 days). The validated fire spread model was used to quantify the realistic ranges of combustible materials represented by the same SBI classification. The material properties were obtained by inverse analysis so that their combinations would exactly achieve the relevant thresholds for Class B and Class C materials according to SBI test. This thesis assessed fire spread behaviour of these materials in Full-scale test (BS 8414) when used as cladding, either on its own, or in combination with another material, both with and without cavity ventilation. The majority, but not all Class B materials would be able to pass the BS 8414 full-scale fire test criterion for flame height. The Class B materials that do not pass the acceptance criterion are combinations of high density (>120kg/m3) and high heat of combustion (>16 MJ/kg). Many Class C materials could still pass the BS 8414 full-scale fire test criterion for flame height. Such materials are characterized by low density (< 60kg/m³) and low heat of combustion (< 16 MJ/kg). The SBI-based material specification for multi-layered façade is severely restrictive if the insulation material is encapsulated by a non-combustible external surface. Instead of achieving Class A2, even Class C insulation materials can be used provided the thickness of the external layer is not lower than a critical thickness. This critical thickness is no more than a few mms and can be easily achieved in practice.

Published
2023

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