Analysis of mesoscopic mechanical dynamic characteristics of ballast bed with under sleeper pads

The meso-dynamical behaviour of a high-speed rail ballast bed with under sleeper pads(USPs)was studied.The geometrically irregular refined discrete element model of the ballast particles was constructed using 3D scanning techniques,and the 3D dynamic model of the rail-sleeper-ballast bed was constructed using the coupled discrete element method-multiflexible-body dynamics(DEM-MFBD)approach.We analyse the meso-mechanical dynamics of the ballast bed with USPs under dynamic load on a train and verify the correctness of the model in laboratory tests.It is shown that the deformation of the USPs increases the contact area between the sleeper and the ballast particles,and subsequently the number of contacts between them.As the depth of the granular ballast bed increases,the contact area becomes larger,and the contact force between the ballast particles gradually decreases.Under the action of the elastic USPs,the contact forces between ballast particles are reduced and the overall vibration level of the ballast bed can be reduced.The settlement of the granular ballast bed occurs mainly at the shallow position of the sleeper bottom,and the installation of the elastic USPs can be effective in reducing the stress on the ballast particles and the settlement of the ballast bed.

Effect of FeSi additive in dual-chamber sample cup on thermal analysis characteristic values and vermiculating rate of compacted graphite iron

Thermal analysis plays a key role in the online inspection of molten iron quality.Different solidification process of molten iron can be reflected by thermal analysis curves,and silicon is one of important elements affecting the solidification of molten iron.In this study,FeSi75 was added in one chamber of the dual-chamber sample cup,and the influences of FeSi75 additive on the characteristic values of thermal analysis curves and vermiculating rate were investigated.The results show that with the increase of FeSi75,the start temperature of austenite formation TALfirstly decreases and then increases,but the start temperature of eutectic growth TSEF,the lowest eutectic temperature TEU,temperature at maximum eutectic reaction rate TEM,and highest eutectic temperature TERkeep always an increase.The temperature at final solidification point TEShas little change.The FeSi75 additive has different influences on the vermiculating rate of molten iron with different vermiculation,and the vermiculating rate increases for lower vermiculation molten iron while decreases for higher one.According to the thermal analysis curves obtained by a dual-chamber sample cup with 0.30wt.%FeSi75 additive in one chamber,the vermiculating rate of molten iron can be evaluated by comparing the characteristic values of these curves.The time differenceΔtERcorresponding to the highest eutectic temperature TERhas a closer relationship with the vermiculating rate,and a parabolic regression curve between the time differenceΔtERand vermiculating rateηhas been obtained within the range of 65%to 95%,which is suitable for the qualified melt.

Numerical Analysis of Explosion Characteristics of Vent Gas From 18650 LiFePO_(4) Batteries With Different States of Charge

The combustion and explosion characteristics of lithium-ion battery vent gas is a key factor in determining the fire hazard of lithium-ion batteries.Investigating the combustion and explosion hazards of lithium-ion batteries vent gas can provide guidance for rescue and protection in explosion accidents in energy storage stations and new energy vehicles,thereby promoting the application and development of lithium-ion batteries.Based on this understanding and combined with previous research on gas production from lithium-ion batteries,this article conducted a study on the combustion and explosion risks of vent gas from thermal runaway of 18650 LFP batteries with different states of charge(SOCs).The explosion limit of mixed gases affected by carbon dioxide inert gas is calculated through the“elimination”method,and the Chemkin-Pro software is used to numerically simulate the laminar flame speed and adiabatic flame temperature of the battery vent gas.And the concentration of free radicals and sensitivity coefficients of major elementary reactions in the system are analyzed to comprehensively evaluate the combustion explosion hazard of battery vent gas.The study found that the 100%SOC battery has the lowest explosion limit of the vent gas.The inhibitory elementary reaction sensitivity coefficient in the reaction system is lower and the concentration of free radicals is higher.Therefore,it has the maximum laminar flame speed and adiabatic flame temperature.The combustion and explosion hazard of battery vent gas increases with the increase of SOC,and the risk of explosion is the greatest and most harmful when SOC reaches 100%.However,the related hazards decrease to varying degrees with overcharging of the battery.This article provides a feasible method for analyzing the combustion mechanism of vent gas from lithium-ion batteries,revealing the impact of SOC on the hazardousness of battery vent gas.It provides references for the safety of storage and transportation of lithium-ion batteries,safety protection of energy storage stations,and the selection of related fire extinguishing agents.

Dynamical Modeling and Dynamic Characteristics Analysisof a Coaxial Dual-Rotor System

The dual-rotor structure serves as the primary source of vibration in aero-engines. Understanding itsdynamical model and analyzing dynamic characteristics, such as critical speed and unbalanced response, arecrucial for rotor system dynamics. Previous work introduced a coaxial dual-rotor-support scheme for aeroengines,and a physical model featuring a high-speed flexible inner rotor with a substantial length-to-diameter ratiowas designed. Then a finite element (FE) dynamic model based on the Timoshenko beam elements and rigid bodykinematics of the dual-rotor system is modeled, with the Newmark method and Newton–Raphson method used forthe numerical calculation to study the dynamic characteristics of the system. Three different simulation models,including beam-based FE (1D) model, solid-based FE (3D) model, and transfer matrix model, were designed tostudy the characteristics of mode and the critical speed characteristic of the dual-rotor system. The unbalancedresponse of the dual-rotor system was analyzed to study the influence of mass unbalance on the rotor system. Theeffect of different disk unbalance phases and different speed ratios on the dynamic characteristics of the dual-rotorsystem was investigated in detail. The experimental result shows that the beam-based FE model is effective andsuitable for studying the dual-rotor system.

Analysis and Research on Aerodynamic Characteristics of Quad Tilt Rotor Aircraft

For the quad tilt rotor aircraft, a computational fluid dynamics method based on multiple reference frames (MRF) was used to analyze the influence of aerodynamic layout parameters on the aerodynamic characteristics of the quad tilt rotor aircraft. Firstly, a numerical simulation method for the interference flow field of the quad tilt rotor aircraft is established. Based on this method, the aerodynamic characteristics of isolated rotors, rotor combinations at different lateral positions on the wing, and rotor rotation directions under different inflow velocities were calculated and analyzed, in order to grasp their aerodynamic interference laws and provide reference for the design and control theory research of such aircraft.

Study of Pyrolysis Characteristics and Kinetic Analysis of Shenmu Coal at a High Heating Rate Using TG-FTIR

Coal pyrolysis is a fundamental reaction in the thermal processing and utilization of coal.Investigating the behavior and kinetics of coal pyrolysis is crucial for optimizing,designing,and developing a composite riser for the staged pyrolysis gasification process of pulverized coal.In this study,the non-isothermal pyrolysis behavior and kinetics of coal were examined at different heating rates(30,50,100,300,500,700,and 900℃/min)using thermogravimetry(TG)coupled with Fourier-transform infrared spectroscopy.Analysis of the TG/derivative TG(TG/DTG)curves indicated that coal pyrolysis mainly occurred between 300℃ and 700℃.Higher heating rates led to more volatiles being released from the coal,and a higher temperature was required to achieve rapid pyrolysis.Kinetic analysis showed that both the model-free methods(Friedman,Flynn-Wall-Ozawa,and Kissinger-Akahira-Sunose)and the model-based method(Coats-Redfern)effectively describe the coal pyrolysis process.The change in the Ea values between the two kinetic models was consistent throughout the pyrolysis process,and the most probable mechanism was the F2 model(secondary chemical reaction).In addition,the heating rate did not change the overall reaction order of the pyrolysis process;however,a higher heating rate resulted in a decrease in the Ea value during the initial pyrolysis stage.

Quantitative analysis of laser-generated ultrasonic wave characteristics and their correlation with grain size in polycrystalline materials

Quantitative relationship between nanosecond pulsed laser parameters and the characteristics of laser-generated ultrasonic waves in polycrystalline materials was evaluated.The high energy of the pulsed laser with a large irradiation spot simultaneously generated ultrasonic longitudinal and shear waves at the epicenter under the slight ablation regime.An optimized denoising technique based on wavelet thresholding and variational mode decomposition was applied to reduce noise in shear waves with a low signal-to-noise ratio.An approach for characterizing grain size was proposed using spectral central frequency ratio(SCFR)based on time-frequency analysis.The results demonstrate that the generation regime of ultrasonic waves is not solely determined by the laser power density;even at high power densities,a high energy with a large spot can generate an ultrasonic waveform dominated by the thermoelastic effect.This is ascribed to the intensification of the thermoelastic effect with the proportional increase in laser irradiation spot area for a given laser power density.Furthermore,both longitudinal and shear wave SCFRs are linearly related to grain size in polycrystalline materials;however,the shear wave SCFR is more sensitive to finer-grained materials.This study holds great significance for evaluating metal material properties using laser ultrasound.

Analysis and Zonation of Freeze–Thaw Action in the Chinese Plateau Region Considering Spatiotemporal Climate Characteristics

Concerns about the durability of transportation infrastructure due to freeze-thaw(F-T)cycles are particu-larly significant in the Chinese plateau region,where concrete aging and performance deterioration pose substantial challenges.The current national standards for the frost resistance design of concrete struc-tures are based predominantly on the coldest monthly average temperature and do not adequately address the comprehensive effects of the spatiotemporal variance,amplitude,and frequency of F-T cycles.To address this issue,this study introduced a spatiotemporal distribution model to analyze the long-term impact of F-T action on concrete structures by employing statistical analysis and spatial inter-polation techniques.Cluster analysis was applied to create a nationwide zonation of F-T action level from data on the freezing temperature,temperature difference,and the number of F-T cycles.Furthermore,this study explored the similarity between natural environmental conditions and laboratory-accelerated tests using hydraulic pressure and cumulative damage theories.A visualization platform that incorporates tools for meteorological data queries,environmental characteristic analyses,and F-T action similarity calculations was designed.This research lays theoretical groundwork and provides technical guidance for assessing service life and enhancing the quantitative durability design of concrete structures in the Chinese plateau region.

Analysis of combustion characteristics and chemical properties for biocoke fuel

Analyses of the characteristics and properties of biocoke fuel from several biomass wastes were carried out to determine the energy potential of the fuel.Biocoke production in this research uses heating and pressure methods simultaneously under constant conditions.Experimental results using thermogravimetric analysis show that biocoke empty-fruit-bunches(EFB)have a higher energy potential of 26.57 MJ/kg.Meanwhile,mangrove biocoke recorded the lowest ash content at 1.81%compared to EFB at 5.09%.The carbon content of mangrove biocoke is 58.02%,slightly higher than that of EFB,56.70%,but EFB is higher than that of other biomass.Overall,the energy content recorded in biocoke increased significantly compared to raw biomass.

Analysis of the Variability of the Characteristics of Water Resources in the Diani Watershed: Case of the Silissou District

This study aims to analyze the spatio-temporal variability of the characteristics of water resources in the Diani watershed,located in the southeast of the Republic of Guinea.The objective is to assess the availability and quantity of water for sustainable management of this essential resource.The results obtained show a slight variability of hydro-climatic parameters.The most remarkable wet periods by their intensity of(1982-1998)and(2005-2012)are moderate and that of 1986-1990 is extremely severe during which they are felt on all the stations of the South of Guinea.In addition,the dry years,the end of 1970 and 1980 to 1987 recognized by the WMO(World Meteorological Organization)as drought years were highlighted in the Diani watershed in the South of the Republic of Guinea.

Clinical characteristics of patients with early gastric prematurity cancer and analysis of complications by endoscopic resection

BACKGROUND Gastric cancer,a prevalent malignancy,poses a severe threat to the health of residents in China.Timely intervention in early stages can extend patients’survival.AIM To analyze clinical characteristics of patients with early gastric cancer and efficacy and risk of complications associated with endoscopic resection.METHODS This study included 175 patients with early gastric cancer treated at our hospital,with no restrictions on sex or age.General data,pathological information,and endoscopic biopsy results were obtained.The clinical characteristics of early gastric cancer were analyzed,and endoscopic resection was performed.Postoperative efficacy and incidence of complications were monitored.Statistical analysis was performed using SPSS 26.0 and GraphPad Prism 8.0 software.RESULTS A total of 175 patients with early gastric cancer were included,with 75.43%(n=132)males and 24.57%(n=43)females.38.29%(n=67)and 35.43%(n=62)of patients had a history of smoking and alcohol consumption,respectively.Comorbidities included diabetes(8.57%,n=15),coronary heart disease(10.29%,n=18),and hypertension(43.43%,n=76),which was highly prevalent.A history of abdominal surgery and family history of digestive system cancer accounted for 21.14%and 17.14%,respectively.The most common lesion location was the antral part of the stomach(52.00%,n=91),followed by the gastric angle,body,and fundus.The pathological types were predominantly high-grade intraepithelial neoplasia(28.00%,n=49)and well-differentiated adenocarcinoma(26.86%,n=47),followed by moderately differentiated adenocarcinoma,high-moderately differentiated adenocarcinoma,and moderate-lowly differentiated adenocarcinoma.89.14%of the patients had intestinal metaplasia and 85.14%had atrophy.After endoscopic resection,re-examination revealed that 13 patients had cancer cells at the tissue margin,with a positive margin rate of 7.43%.Postoperative complications included no cases of gastrointestinal obstruction,but incisional infection(2.86%,n=5),gastric perforation(1.14%,n=2),and gastric bleeding(4%,n=7)were present,with an overall incidence of 8.00%.CONCLUSION Analysis of the clinical characteristics indicated that early gastric cancer is more prevalent in males with a history of hypertension,with lesions most commonly occurring in the antral region of the stomach.The pathological types are often high-grade intraepithelial neoplasia and well-differentiated adenocarcinoma,with over 85%of patients having comorbid intestinal metaplasia and atrophy.Despite endoscopic resection,a positive margin rate persisted,indicating a probability of residual cancer at the margins.Postoperative complications,such as gastrointestinal obstruction,incisional infection,gastric perforation,and gastric bleeding can occur and require timely symptomatic treatment.

Inter-stage performance and energy characteristics analysis of electric submersible pump based on entropy production theory

The electric submersible pump(ESP) is a crucial apparatus utilized for lifting in the oil extraction process.Its lifting capacity is enhanced by the multi-stage tandem structure, but variations in energy characteristics and internal flow across stages are also introduced. In this study, the inter-stage variability of energy characteristics in ESP hydraulic systems is investigated through entropy production(EP) analysis,which incorporates numerical simulations and experimental validation. The EP theory facilitates the quantification of energy loss in each computational subdomain at all ESP stages, establishing a correlation between microscopic flow structure and energy dissipation within the system. Furthermore, the underlying causes of inter-stage variability in ESP hydraulic systems are examined, and the advantages and disadvantages of applying the EP theory in this context are evaluated. Consistent energy characteristics within the ESP, aligned with the distribution of internal flow structure, are provided by the EP theory, as demonstrated by our results. The EP theory also enables the quantitative analysis of internal flow losses and complements existing performance analysis methods to map the internal flow structure to hydraulic losses. Nonetheless, an inconsistency between the energy characterization based on EP theory and the traditional efficiency index when reflecting inter-stage differences is identified. This inconsistency arises from the exclusive focus of the EP theory on flow losses within the flow field, disregarding the quantification of external energy input to the flow field. This study provides a reference for the optimization of EP theory in rotating machinery while deeply investigating the energy dissipation characteristics of multistage hydraulic system, which has certain theoretical and practical significance.

Analysis of pulse-wave propagation characteristics in abdominal aortic sclerosis disease

In this work,a bidirectional fluid-structure coupling finite element analysis model of the abdominal aorta was established,with the various vascular elastic modulus as the main parameters for atherosclerosis,taking into consideration blood's dynamic viscosity and compressibility.Pressure and velocity pulse-wave propagation were investigated through the application of a full-coupling analysis algorithm.The effect of atherosclerosis degree on the propagation characteristics of pulse waves in the bifurcated abdominal aorta was quantitatively analyzed.Arterial bifurcation can cause substantial attenuation on the peak of pressure pulse waveform and an increase in wave velocity during the cardiac cycle.The elastic modulus and bifurcation properties of the arterial wall directly affected the peak value and wave propagation velocity of the pressure pulse wave.The preliminary results of this work will be crucial in guiding the evolution of the pressure pulse wave and the initial diagnosis of atherosclerotic disease through the waveform.

A Study of the English Translation of Characteristic Cuisines of the Hexi Corridor from the Perspective of Multimodal Discourse Analysis

Given the diversity of geographical and cultural backgrounds,it is difficult to find precise counterparts of many food-related vocabularies in the unique dietary culture of the Hexi Corridor in the target language,making it challenging to fully convey the essence of its local dietary culture in translation.To achieve the purpose of translation,the theory of multimodal discourse analysis provides an ideal translation approach through the language mode,image mode,sound mode,and the synergistic effect of multimodalities,which can accurately address the deficiencies in the translation of dietary culture.Through this research,it is not only possible to highlight the unique charm of the dietary culture of the Hexi Corridor but also to build a bridge for its international dissemination,promoting cross-border cultural exchanges and mutual understanding.

Simulation and Analysis of Cascading Faults in Integrated Heat and Electricity Systems Considering Degradation Characteristics

Cascading faults have been identified as the primary cause of multiple power outages in recent years.With the emergence of integrated energy systems(IES),the conventional approach to analyzing power grid cascading faults is no longer appropriate.A cascading fault analysis method considering multi-energy coupling characteristics is of vital importance.In this study,an innovative analysis method for cascading faults in integrated heat and electricity systems(IHES)is proposed.It considers the degradation characteristics of transmission and energy supply com-ponents in the system to address the impact of component aging on cascading faults.Firstly,degradation models for the current carrying capacity of transmission lines,the water carrying capacity and insulation performance of thermal pipelines,as well as the performance of energy supply equipment during aging,are developed.Secondly,a simulation process for cascading faults in the IHES is proposed.It utilizes an overload-dominated development model to predict the propagation path of cascading faults while also considering network islanding,electric-heating rescheduling,and load shedding.The propagation of cascading faults is reflected in the form of fault chains.Finally,the results of cascading faults under different aging levels are analyzed through numerical examples,thereby verifying the effectiveness and rationality of the proposed model and method.

Clinical characteristics and north-south differences of inflammatory bowel disease in China: A cross-sectional study and meta-analysis

Objective:This study aimed to estimate the incidence rate and clinical characteristics of inflammatory bowel disease(IBD)in the Chinese population,specially comparing the North and South regions.Methods:We designed a questionnaire survey for patients diagnosed with IBD and conducted a systematic literature search in PubMed,China National Knowledge Internet,and Wanfang digital database,covering studies published between 2012 and 2022.Meta-analysis was performed to determine the overall incidence rate and prevalence of clinical manifestations of Crohn's disease(CD)and ulcerative colitis(UC)in China's Mainland.Clinical phenotypes and demographic characteristics were calculated with 95%confidence intervals(CI).A comparison between the northern and southern regions was also conducted.Results:The questionnaire survey included 440 patients,and 64 publications were included for Meta-analysis.The overall incidence rates of IBD,CD,and UC were 1.36(95%CI:0.79-2.33)per 100,000 person-years,0.23(95%CI:0.09-0.58)per 100,000 person-years,and 1.12(95%CI:0.69-1.80)per 100,000 person-years,respectively.The incidence rates of IBD,CD,and UC were all higher in southern China compared to the North.Clinical characteristics of 440 IBD patients from the questionnaire and 2,821 CD patients and 12,809 UC patients from the literature were analyzed.There were more male patients compared to female patients.CD cases in the North exhibited earlier disease diagnosis(P<0.01),more upper gastrointestinal lesions(P<0.01),and higher hospitalizations rates(P<0.01)compared to the South.UC cases in the North had higher severity(P<0.01),anemia rates(P<0.01),and weight loss(P<0.01)compared to the South.Conclusions:The incidence rates of IBD,CD,and UC were higher in southern China than in the North.Northern patients exhibited more severe symptoms compared to their southern counterparts.

Clinical characteristics and risk factors of post-operative intestinal flora disorder following laparoscopic colonic surgery:A propensityscore-matching analysis

BACKGROUND Intestinal flora disorder(IFD)poses a significant challenge after laparoscopic colonic surgery,and no standard criteria exists for its diagnosis and treatment.AIM To analyze the clinical features and risk factors of IFD.METHODS Patients with colon cancer receiving laparoscopic surgery were included using propensity-score-matching(PSM)methods.Based on the occurrence of IFD,patients were categorized into IFD and non-IFD groups.The clinical characteristics and treatment approaches for patients with IFD were analyzed.Multivariate regression analysis was performed to identify the risk factors of IFD.RESULTS The IFD incidence after laparoscopic surgery was 9.0%(97 of 1073 patients).After PSM,97 and 194 patients were identified in the IFD and non-IFD groups,respectively.The most common symptoms of IFD were diarrhea and abdominal,typically occurring on post-operative days 3 and 4.All patients were managed conservatively,including modulation of the intestinal flora(90.7%),oral/intravenous application of vancomycin(74.2%),and insertion of a gastric/ileus tube for decompression(23.7%).Multivariate regression analysis identified that preoperative intestinal obstruction[odds ratio(OR)=2.79,95%CI:1.04–7.47,P=0.041]and post-operative antibiotics(OR=8.57,95%CI:3.31–23.49,P<0.001)were independent risk factors for IFD,whereas pre-operative parenteral nutrition(OR=0.12,95%CI:0.06–0.26,P<0.001)emerged as a protective factor.CONCLUSION A stepwise approach of probiotics,vancomycin,and decompression could be an alternative treatment for IFD.Special attention is warranted post-operatively for patients with pre-operative obstruction or early use of antibiotics.

Contrastive Analysis of Lightning Characteristics and Lightning Parameters in Hongya County

Based on the data of cloud-to-ground lightning obtained by the lightning detection system in Hongya County during 2011-2015,the parameters of lightning current intensity and steepness in Hongya County were analyzed,and the lightning parameters and the annual average density of lightning stroke to earth were discussed in combination with the Design Code for Protection of Structures against Lightning(GB 50057-2010),so as to provide scientific guidance for lightning disaster prevention in Hongya County.

Isogeometric Analysis of Hyperelastic Material Characteristics for Calcified Aortic Valve

This study explores the implementation of computed tomography(CT)reconstruction and simulation techniques for patient-specific valves,aiming to dissect the mechanical attributes of calcified valves within transcatheter heart valve replacement(TAVR)procedures.In order to facilitate this exploration,it derives pertinent formulas for 3D multi-material isogeometric hyperelastic analysis based on Hounsfield unit(HU)values,thereby unlocking foundational capabilities for isogeometric analysis in calcified aortic valves.A series of uniaxial and biaxial tensile tests is executed to obtain an accurate constitutive model for calcified active valves.To mitigate discretization errors,methodologies for reconstructing volumetric parametric models,integrating both geometric and material attributes,are introduced.Applying these analytical formulas,constitutive models,and precise analytical models to isogeometric analyses of calcified valves,the research ascertains their close alignment with experimental results through the close fit in displacement-stress curves,compellingly validating the accuracy and reliability of the method.This study presents a step-by-step approach to analyzing themechanical characteristics of patient-specific valves obtained fromCT images,holding significant clinical implications and assisting in the selection of treatment strategies and surgical intervention approaches in TAVR procedures.

Analysis of Characteristics and Meteorological Influencing Factors of Air Pollution in Luojiang District,Deyang City

Based on the monitoring data of ambient air quality and meteorological observation data,the characteristics and meteorological influencing factors of air pollution in Luojiang District of Deyang City from 2018 to 2022 were analyzed.The results show that from 2018 to 2022,the main air pollutants affecting the air quality of Luojiang District of Deyang City were PM_(2.5) and PM_(10),and the primary pollutant on heavy pollution days was basically PM_(2.5).PM_(2.5) and PM_(10) pollution showed obvious seasonal differences,and PM_(2.5) concentration exceeded the limit mainly in spring and winter,among which it was the most serious in early spring,especially in January and February,followed by December.PM_(10) exceeding the standard had a high seasonal correlation with PM_(2.5) exceeding the standard,mainly in spring and winter,among which it was the most serious in winter,especially in December,followed by January.PM_(2.5) and PM_(10) pollution showed an overall weakening trend.PM_(2.5) and PM_(10) concentration were closely related to meteorological factors such as temperature,relative humidity,wind speed,precipitation and air pressure,and were mainly affected by rainfall.