The Development Status and Prospect of Hydrogen Fuel Cell Powered Tram

The problem of energy and environmental pollution is a huge challenge for the development of contemporary society. Hydrogen energy has emerged as a prominent area of current research to address this issue. Researchers have found that applying hydrogen fuel cells to trams can solve the problem, but the feasibility of this technology has yet to be analyzed. Herein, this paper explores the power system and commercial feasibility of hydrogen-fueled trams regarding their technical issues, security assessment, and cost estimation. It is found that compared with traditional trams, hydrogen energy trams have the advantages of high energy utilization and long driving range and achieve zero emission in the operation process. At the same time, with the continuous development of technology, issues related to the safety of hydrogen use will be verified, and the cost will be further reduced with the development of low-platinum fuel cell catalysts and Type IV hydrogen storage tanks. The feasibility of hydrogen-fueled trams has been confirmed as multiple trains have rolled off the assembly line, and with the determination of relevant industry norms, it will definitely be widely used

Responses of Soil Organic Carbon to Long-Term Understory Removal in Subtropical Cinnamomum camphora Stands

We conducted a study on a 48-year-old Cinnamomum camphora plantation in the subtropics of China, by removing understory gradually and then comparing this treatment with a control (undisturbed). This study analyzed the content and storage soil organic carbon (SOC) in a soil depth of 0-60 cm. The results showed that SOC content was lower in understory removal (UR) treatment, with a decrease range from 5% to 34%, and a decline of 10.16 g⋅kg −1 and 8.58 g⋅kg −1 was noticed in 0-10 cm and 10-20 cm layers, respectively, with significant differences ( < 0.05). Carbon storage was reduced in UR, ranging from 2% to 43%, with a particular drastic decline of 15.39 t⋅hm −2 and 11.58 t⋅hm −2 in 0-10 cm ( < 0.01) and 10-20 cm ( < 0.01) layers, respectively. Content of SOC had an extremely significant ( < 0.01) correlation with soil nutrients in the two stands, and the correlation coefficients of CK were higher than those of UR. Our data showed that the presence of understory favored the accumulation of soil organic carbon to a large extent. Therefore, long-term practice of understory removal weakens the function of forest ecosystem as a carbon sink

Responses of Soil Organic Carbon to Long-Term Understory Removal in Subtropical Cinnamomum camphora

We conducted a study on a 48-year-old Cinnamomum camphora plantation in the subtropics of China, by removing understory gradually and then comparing this treatment with a control (undisturbed). This study analyzed the content and storage soil organic carbon (SOC) in a soil depth of 0–60 cm. The results showed that SOC content was lower in understory removal (UR) treatment, with a decrease range from 5% to 34%, and a decline of 10.16 g·kg−1 and 8.58 g·kg−1 was noticed in 0–10 cm and 10–20 cm layers, respectively, with significant differences (P<0.05). Carbon storage was reduced in UR, ranging from 2% to 43%, with a particular drastic decline of 15.39 t·hm−2 and 11.58 t·hm−2 in 0–10 cm (P<0.01) and 10–20 cm (P<0.01) layers, respectively. Content of SOC had an extremely significant (P<0.01) correlation with soil nutrients in the two stands, and the correlation coefficients of CK were higher than those of UR. Our data showed that the presence of understory favored the accumulation of soil organic carbon to a large extent. Therefore, long-term practice of understory removal weakens the function of forest ecosystem as a carbon sink

Towards understanding Android system vulnerabilities: Techniques and insights

National Research Foundation (NRF) Singapor

Gut microbiota-derived metabolite Trimethylamine-N-oxide (TMAO) and multiple health outcomes:an umbrella review and updated meta-analysis

BACKGROUND: Trimethylamine-N-oxide (TMAO) is a gut microbiota-derived metabolite produced from dietary nutrients. Many studies have discovered that circulating TMAO levels are linked to a wide range of health outcomes. OBJECTIVES: This study aimed to summarize health outcomes related to circulating TMAO levels. METHODS: We searched Embase, Medline, Web of Science and Scopus databases from inception to 15 February 2022 to identify and update meta-analyses examining the associations between TMAO and multiple health outcomes. For each health outcome, we estimated the summary effect size, 95% prediction confidence interval (CI), between-study heterogeneity, evidence of small-study effects, and evidence of excess-significance bias. These metrics were used to evaluate the evidence credibility of the identified associations. RESULTS: This umbrella review identified 24 meta-analyses that investigated the association between circulating TMAO levels and health outcomes including all-cause mortality, cardiovascular diseases, diabetes mellitus, cancer, and renal function. We updated these meta-analyses by including a total of 82 individual studies in 18 unique health outcomes. Among them, 14 associations were nominally significant. After evidence credibility assessment, we found six (33%) associations (i.e., all-cause mortality, cardiovascular disease mortality, major adverse cardiovascular events, hypertension, diabetes mellitus, and glomerular filtration rate) to present highly suggestive evidence. CONCLUSIONS: TMAO might be a novel biomarker related to human health conditions including all-cause mortality, hypertension, cardiovascular disease, diabetes, cancer and kidney function. Further studies are needed to investigate whether circulating TMAO levels could be an intervention target for chronic disease

Systematic meta-analyses, field synopsis and global assessment of the evidence of genetic association studies in colorectal cancer

Objective: To provide an understanding of the role of common genetic variations in colorectal cancer (CRC) risk, we report an updated field synopsis and comprehensive assessment of evidence to catalogue all genetic markers for CRC (CRCgene2). Design: We included 869 publications after parallel literature review and extracted data for 1063 polymorphisms in 303 different genes. Meta-Analyses were performed for 308 single nucleotide polymorphisms (SNPs) in 158 different genes with at least three independent studies available for analysis. Scottish, Canadian and Spanish data from genome-wide association studies (GWASs) were incorporated for the meta-Analyses of 132 SNPs. To assess and classify the credibility of the associations, we applied the Venice criteria and Bayesian False-Discovery Probability (BFDP). Genetic associations classified as â € positive' and â € less-credible positive' were further validated in three large GWAS consortia conducted in populations of European origin. Results: We initially identified 18 independent variants at 16 loci that were classified as â € positive' polymorphisms for their highly credible associations with CRC risk and 59 variants at 49 loci that were classified as â € less-credible positive' SNPs; 72.2% of the â € positive' SNPs were successfully replicated in three large GWASs and the ones that were not replicated were downgraded to â € less-credible' positive (reducing the â € positive' variants to 14 at 11 loci). For the remaining 231 variants, which were previously reported, our meta-Analyses found no evidence to support their associations with CRC risk. Conclusion: The CRCgene2 database provides an updated list of genetic variants related to CRC risk by using harmonised methods to assess their credibility.</p

Research on the Relationship between Resistivity and Resistance between Two Points on RCS Test Model

Surface conductivity is one of the key factors in judging whether the RCS (Radar Cross Section) test model is qualified, but the accuracy of traditional detection methods is insufficient. Furthermore, the resistance between two points obtained by traditional methods cannot be directly applied to the electromagnetic simulation analysis of the test model. In this paper, the theoretical model of the relationship between resistivity and resistance between two points on the model surface is proposed. The simulation method for the resistance between two points on the model surface is established. The advantage of the method proposed in this paper compared with the traditional method in detecting the surface resistance of the model is demonstrated intuitively. The experiments are carried out on ITO (Indium Tin Oxide) conductive films with several dimensions and resistivity. Results show that the measured resistance between two points on the model surface is highly consistent with the theoretical and simulated values. Moreover, the comparison of experiments shows that the measurement error of the traditional method is 150% to 200% higher than that of the method proposed in this paper

Research on the Relationship between Resistivity and Resistance between Two Points on RCS Test Model

Surface conductivity is one of the key factors in judging whether the RCS (Radar Cross Section) test model is qualified, but the accuracy of traditional detection methods is insufficient. Furthermore, the resistance between two points obtained by traditional methods cannot be directly applied to the electromagnetic simulation analysis of the test model. In this paper, the theoretical model of the relationship between resistivity and resistance between two points on the model surface is proposed. The simulation method for the resistance between two points on the model surface is established. The advantage of the method proposed in this paper compared with the traditional method in detecting the surface resistance of the model is demonstrated intuitively. The experiments are carried out on ITO (Indium Tin Oxide) conductive films with several dimensions and resistivity. Results show that the measured resistance between two points on the model surface is highly consistent with the theoretical and simulated values. Moreover, the comparison of experiments shows that the measurement error of the traditional method is 150% to 200% higher than that of the method proposed in this paper

Aerodynamic Shape Optimization of Subsonic/Supersonic Flows Integrating Variable-Fidelity Longitudinal Trim Analysis

Most existing studies on aerodynamic shape optimization have not considered longitudinal trim under control surface deflection, typically achieving self-trim through a constraint of zero pitching moment or adjusting the optimized configuration for longitudinal trim. However, adjustments to the optimized configuration might introduce additional drag, reducing overall optimization benefits. In this paper, a novel approach of incorporating control surface deflection for longitudinal trim in aerodynamic optimization is proposed. Firstly, an aerodynamic computation program based on the high-order panel method was developed, introducing velocity perturbations on specific mesh surfaces to simulate actual control surface deflections. Subsequently, a comprehensive optimization framework was established, encompassing parametric modeling, aerodynamic computation, and variable-fidelity control surface deflection analysis. Finally, aerodynamic optimization analysis was conducted under both subsonic and supersonic conditions. Thirty-one design variables were selected with the trimmed lift-to-drag ratio in cruising condition as the objective function and the control surface deflection angle as the constraint. The results indicated an 8.52% increase in the trimmed lift-to-drag ratio compared to the baseline model under subsonic conditions and an 8.1% increase under supersonic conditions

Impact and usage of the shear thickening fluid (STF) material in damping vibration of bolted flange joints

Bolted flange joints in fuzes undergo high acceleration during penetration, along with nonlinear responses which are forced reaction, structural vibrations, and shock effects. Vibrations of high frequencies aggregate noises and make it harder for the signal processing of fuzes. This study proposed an effective and innovative method of suppressing vibrations of high frequencies caused by impact loading. Shear thickening fluids (STFs) were stuffed into bolted flange joints. A damper of 57 vol/vol% dense silica particle-ethylene glycol suspension was inserted into gaps between the surfaces of the incident bar and the flange. Based on a modified split Hopkinson pressure bar, pulse widths, amplitudes, and structural frequencies of both impact and vibrational response regions were evaluated to examine the effectiveness of the STF damper. The amplitude and pulse width in the vibrational response region were significantly reduced, since this suspension forms jamming clusters subjected to impulses, attenuating the shockwaves. The STF fillers under various lengths of projectiles from 50 mm-400 mm were discussed to validate effectiveness. Further comparisons with epoxy resin fillers with various curing times indicated that the STF inhibited high frequency oscillations as a protector, and damped the dominant frequency of the original structure. However, experimental data showed that the transmission pulse of the incident bar was similar to joints without protection, indicating that the force transmission ratio was not affected by the fillers. These results show the feasibility of STFs as energy absorbers for vibration reduction of bolted flange joints