Model Results Research Articles

Abnormally large radiational S2 tides in the Gulf of Tonkin and implications for other diurnal resonant seas

Radiational tides derived from solar radiation are important components of ocean tides. Understanding dynamical features of radiational tides can be beneficial for further promoting the accuracy of water level prediction. Generally, radiational S2 amplitudes are only 10%–30% of gravitational S2 amplitudes, which has been verified by numerous studies. However, a previous study indicated that radidational S2 amplitudes can reach 60% of gravitational S2 amplitudes in the Gulf of Tonkin and related physical processes are unknown. In this paper, we revisit this abnormal phenomenon and find that such large radiational S2 amplitudes are not real, but artifacts induced by the inadaptation of the method based on the credo of smoothness. Specifically, observed semi-diurnal tidal admittances in the Gulf of Tonkin are not smooth due to strong nonlinear interactions between large main diurnal tides. We quantitatively estimate and remove the contributions of quadratic and quartic nonlinear interactions to main semi-diurnal tides and find that the real ratio of radiational S2 amplitude to astronomical S2 amplitude is only 0.17 at Beihai, which is basically consistent with previous model results. Our study highlights the importance of eliminating the interference of nonlinear interactions to semi-diurnal tidal admittances in all diurnal resonant sea areas like the Gulf of Tonkin and the Gulf of Thailand when extracting radiational S2 tides from sea level observations.

Unveiling the Impact of Geopolitical Risks on Turkish Economy and Fiscal Dynamics

This research aims to examine the impact of geopolitical risks on Türkiye's trade openness, household consumption, investment, government debt, and budget deficit for the quarters 2006:I–2022:IV. There are no empirical studies in the literature that examine the relationship between geopolitical risks and Turkish fiscal policy. The vector autoregressive (VAR) approach is utilized to examine the relationships among the variables. Geopolitical risks contribute to a very serious increase in inflation in Türkiye. The increase in geopolitical risks negatively affects consumption and investment and increases budget deficits and government debt. Additionally, Türkiye's trade volume has also decreased as a result of rising geopolitical risks, according to the VAR model's results. These findings demonstrate how vulnerable the Turkish economy is to geopolitical risks. Succinctly, Türkiye's public finances and economy are negatively impacted by geopolitical risks according to the analysis's findings. As a matter of fact, taking precautionary fiscal policy measures against geopolitical risks is important in eliminating the fiscal and economic losses that may arise. In this respect, this study has the potential to make a new contribution to the fiscal policy literature and to guide fiscal policy makers.

Improved BIO-Based Chinese Automatic Abstract-Generation Model

With its unique information-filtering function, text summarization technology has become a significant aspect of search engines and question-and-answer systems. However, existing models that include the copy mechanism often lack the ability to extract important fragments, resulting in generated content that suffers from thematic deviation and insufficient generalization. Specifically, Chinese automatic summarization using traditional generation methods often loses semantics because of its reliance on word lists. To address these issues, we proposed the novel BioCopy mechanism for the summarization task. By training the tags of predictive words and reducing the probability distribution range on the glossary, we enhanced the ability to generate continuous segments, which effectively solves the above problems. Additionally, we applied reinforced canonicality to the inputs to obtain better model results, making the model share the sub-network weight parameters and sparsing the model output to reduce the search space for model prediction. To further improve the model’s performance, we calculated the bilingual evaluation understudy (BLEU) score on the English dataset CNN/DailyMail to filter the thresholds and reduce the difficulty of word separation and the dependence of the output on the word list. We fully fine-tuned the model using the LCSTS dataset for the Chinese summarization task and conducted small-sample experiments using the CSL dataset. We also conducted ablation experiments on the Chinese dataset. The experimental results demonstrate that the optimized model can learn the semantic representation of the original text better than other models and performs well with small sample sizes.

A moderated-mediation model of training transfer from leadership intervention

PurposeGrounding on the goal-setting theory and flow theory, this study explored the mechanism underlying the association between transfer design (TD); identical elements and training transfer (TT). Specifically, the authors explored a moderated mediation process of trainer performance and motivation to improve work through learning (MTIWL) that has received less consideration in the TT literature.Design/methodology/approachData were collected using the retro-perspective survey method. The first survey was administered offline (t1: the day when leadership intervention was completed. Subsequently, trainees were requested to participate in an online survey (t2: 12–14 weeks later). In all, 355 executives participated.FindingsThe results of structural equation modeling (SEM) analyses suggested that trainees’ MTIWL mediational impact between leadership intervention triggers (transfer design and identical elements), and TT was supported. In addition, the indirect impact of these variables on TT was found to be significant when the trainer had high performance than when it was low. This confirmed the trainer’s performance as a potential moderator in the TT process.Practical implicationsThis study is limited to the exploration of leadership intervention variables on TT. The findings have implications for leadership professionals and scholars who use leadership intervention and motivation metrics to predict TT.Originality/valueThis study offers a moderated mediation mechanism for enhancing TT through leadership intervention triggers. The proposed conceptual model included MTIWL as mediator and trainer performance during leadership intervention as moderator.

Implementation of Simulation Modeling of Single and High-Volume Machine-Building Productions

The authors of this article analyze the existing methods and models of technological preparation of machine-building industries. The structure of a three-level simulation model with network-centric control, the structures of individual elements of the simulation model, and the process of simulation modeling are described. The criteria for choosing a rational option for the processing technological route have been determined. During this research, a simulation program was implemented in C++. It allows you to select the optimal scenario for the operation of a production site based on two criteria: time and cost. The volume of implementation is about 2 × 103 lines of code. A diagram of the modeling algorithm for the implemented program and a description of the classes and their interactions are given in the article. The developed simulation model was tested at a machine-building enterprise using the example of the “Pusher” part, manufactured under single-unit production conditions. The technological equipment used for the manufacture of this part was formed in the form of input data of the simulation model. The results of simulation modeling for the selected part are described. For each variant of the technological processing route, the values of variable costs and the duration of the production cycle were determined.

A random mathematical model to describe the antibiotic resistance depending on the antibiotic consumption: the Acinetobacter baumannii colistin-resistant case in Valencia, Spain

ABSTRACT The increase in antibiotic resistance in recent years, mainly due to the non-rational use of antibiotics, is one of the most important global public health threats. In this paper, we propose a mathematical dynamic random model describing the antibiotic resistance evolution of a bacteria and where antibiotic consumption is included is the main driving force in the resistance increase. The random model is solved using the Random Variable Transformation technique and is applied to study the case of Acinetobacter baumannii bacterium resistant to the antibiotic colistin in Valencia, Spain. Using the Multi-Objective Particle Swarm Optimization algorithm, the model has been calibrated with the A. baumannii colistin-resistance and colistin consumption data series. With the optimal model, four possible 7-year future scenarios with different antibiotic consumption trends have been simulated. The model results show how reducing antibiotic consumption does not easily stop the increase in resistance.

Traceability Analysis and Environmental Quality Assessment of Soil Heavy Metal Pollution in West Hunan Province

In order to explore the status of soil heavy metal pollution and environmental quality in west Hunan, relevant areas of Phoenix County were selected as the study area. Using data from 440 soil samples collected in the study area from June to August 2022, the pH value of the soil and contents of eight heavy metal elements, namely, As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, were analyzed. The PMF model was used for traceability analysis and geochemical evaluation of soil environmental quality. The results showed that the average values of soil heavy metals ω(Zn), ω(Cr), ω(Pb), ω(Ni), ω(Cu), ω(As), ω(Cd), and ω(Hg) were 81.02, 64.67, 31.63, 29.27, 25.52, 9.93, 0.28, and 0.13 mg·kg-1, respectively. The soil in the study area was mainly weakly acidic, and the contents of the Cd and Hg elements were relatively high compared to the national soil background values and were highly variable. The contents of the Hg and Cd elements in forest land were higher than that in other land uses. The PMF model results showed that the contribution rates of heavy metal pollution sources in the study area were mining sources (37.4%), atmospheric sedimentation sources (7.7%), natural sources (41.1%), and agricultural activity sources (13.8%) and provided suggestions on pollution control measures according to the spatial distribution of the four types of pollution sources. Through the comprehensive assessment of soil environmental geochemistry, the study area was divided into three types of plots, namely, non-risk areas (94.27 km2), accounting for 76.38%; risk-controllable areas (27.45 km2), accounting for 22.24%; and high-risk areas (1.7 km2), accounting for 1.38%. This study provided data support for the prevention and control measures of land pollution in the research area, as well as the delineation of the prevention and control scope.

Results of numerical modeling of the effect of vertical fractures on electrical logging data

Based on the results of numerical modeling, the effect of vertical drilling-induced fractures on the data of galvanic electrical logging methods is considered. Geoelectric models represent a space with different resistivity values, a well and axisymmetric fractures filled with drilling fluid. The effect of fractures limited in radial depth on galvanic logging data leads to a change in signals similar to the change opposite the formation with a penetration zone located within the fracture interval. Based on the on gradient probes and focused logging data, a model of both a formation with an invaded zone and an impermeable formation with a vertical resistivity less than the horizontal one is selected. Thin vertical fractures do not affect the signals of induction probes, which may be a sign of their presence.

Tectono-Metamorphic Evolution of the Cretaceous Kluane Schist, Southwest Yukon

Abstract A wealth of information regarding the Mesozoic evolution of the Northern Canadian and Alaskan Cordillera is held within a series of variably metamorphosed and deformed rocks that formed in Jura-Cretaceous basins. Located at the interface between the pericratonic Intermontane and exotic Insular terranes, these basinal rocks are key to understanding the timing and tectonic style of Insular terrane accretion, a topic of longstanding debate. This study unravels the structural and metamorphic evolution of one of these basins, the Kluane Basin, within southwest Yukon Territory. The Kluane Schist is the primary assemblage of the Kluane Basin. It consists of metamorphosed and deformed low-Al pelites that were intruded by granodioritic plutons of the Paleocene Ruby Range batholith. Previous workers have suggested the variable metamorphic character of the Kluane Schist represents an extensive and static thermal aureole related to Ruby Range batholith emplacement. Our work, however, indicates that the Kluane Schist experienced Buchan-style metamorphism coeval with protracted deformation and can be divided into seven distinct petrologic zones, which, based on their unique combination of mineral assemblage and structure, are incompatible with static thermal metamorphism. Instead, we propose the Kluane Schist experienced two distinct metamorphic phases: (1) an early greenschist-facies phase that resulted in the development of a bedding-parallel chlorite-muscovite-titanite fabric, preserved by its lowest-grade units, and (2) a later amphibolite-facies phase that manifests as the progressive transposition of the earlier chlorite-muscovite-titanite fabric into a penetrative biotite-rich schistosity that transitions upgrade into a segregated gneissic fabric comprised of biotite-cordierite and plagioclase-quartz (± sillimanite-K-feldspar-melt). By integrating the results of detailed petrography and petrological modeling, we demonstrate that the second main metamorphic phase experienced by the Kluane Schist preserves a record of pressures and temperatures that align with other Buchan-style terranes worldwide. Our data defines a field gradient across the Kluane Schist ranging from 3.0–3.5 kbar at 375–400 °C to 4–4.5 kbar at 700–750 °C. This record of a coupled Buchan-style metamorphic-deformational evolution and tops-to-the SW non-coaxial shear structures is consistent with the override of the thermally mature Yukon-Tanana terrane as the principal driver of Kluane Schist metamorphism, with some limited heat likely contributed by the late-syn- to post-tectonic intrusion of the Ruby Range batholith.

Theory and Empirical Analysis of Bridge Load Limitation Under the Action of Typical Heavy-Duty Vehicles

Abstract With the continuous growth of transportation demands, in-service highway bridges face greater challenges in their long-term operational lifespans, and bridge collapse accidents caused by vehicle overloading occur from time to time. Additionally, under the influence of loads and environmental factors, various wear patterns inevitably lead to degraded reinforced concrete bridges. In view of this problem, it is reasonable and feasible to limit the vehicle loads passing over highway bridges, and the key basis for limitation is determining the load limit value of a bridge. To determine a reasonable load limit value of a bridge, this paper has carried out the following research: Based on a classification of vehicle types, this paper explores the load parameters of several heavy-duty vehicles with large traffic volumes through traffic flow information and summarizes the load spectra of typical heavy-duty vehicles. On the basis of the theory of structural reliability, a method for determining the limit load of bridges is proposed. Given a structural target reliability index, the theoretical load limit value of a bridge can be calculated. To ensure the rationality of the theory of bridge load limit value, by relying on the engineering example, the theoretical load limit value is calculated. By comparing actual bridge load test data with the finite element model results, the rationality of the bridge load limiting theory is verified. Finally, the paper notes that it is safer and more reliable to define the load limit value according to the bending stress state for bridges.

Cost-effectiveness analysis of minimally invasive surgical treatments for benign prostatic hyperplasia: implications for Japan’s public healthcare system

Aims Benign prostatic hyperplasia (BPH) represents a significant public health issue in Japan. This study evaluated the lifetime cost-effectiveness of water vapor energy therapy (WAVE) versus prostatic urethral lift (PUL) for men with moderate-to-severe BPH from a public healthcare payer’s perspective in Japan. Materials and methods A decision analytic model compared WAVE to PUL among males in Japan. Clinical effectiveness and adverse event (AE) inputs were obtained from a systematic literature review. Resource utilization and cost inputs were derived from the Medical Data Vision database and medical service fee national data in Japan. Experts reviewed and validated model input parameters. One-way and probabilistic sensitivity analyses were conducted to determine how changes in the values of uncertain parameters affect the model results. Results Throughout patients’ lifetimes, WAVE was associated with higher quality-adjusted life years (0.920 vs. 0.911 year 1; 15.564 vs. 15.388 lifetime) and lower total costs (¥734,134 vs. ¥888,110 year 1; ¥961,595 vs. ¥1,429,458 lifetime) compared to PUL, indicating that WAVE is a more effective and less costly (i.e. dominant) treatment strategy across all time horizons. Lifetime cost-savings for the Japanese healthcare system per patient treated with WAVE instead of PUL were ¥467,863. The 32.7% cost difference between WAVE and PUL was predominantly driven by lower WAVE surgical retreatment rates (4.9% vs. 19.2% for WAVE vs PUL, respectively, at 5 years) and AE rates (hematuria 11.8% vs. 25.7%, dysuria 16.9% vs. 34.3%, pelvic pain 2.9% vs. 17.9%, and urinary incontinence 0.4% vs. 1.3% for WAVE vs PUL, respectively, at 3 months). Model findings were robust to changes in parameter input values. Limitations The model represents a simplification of complex factors involved in resource allocation decision-making. Conclusions Driven by lower retreatment and AE rates, WAVE was a cost-effective and cost-saving treatment for moderate-to-severe BPH in Japan compared to PUL, providing better outcomes at lower costs to the healthcare system.

Comparison of Degassing Efficiency on a Foundry Degassing Unit Using Different Rotor Types

The present paper describes a comparison of the efficiency of different types of rotors used in the refining of aluminium melt at a foundry degassing unit (FDU). Physical modelling was used to obtain data for six different rotor types under defined experimental conditions. In order to evaluate the data from the physical model, an evaluation method based on the interpolation of degassing curves was developed in such a way that the resulting characteristic can be expressed by a single parameter. Using the new methodology, the datasets were replaced by a single dimensionless parameter, a, which characterizes the rotor performance at a given gas flow rate. Based on the comparison of these performance parameters, it was possible to mutually compare the rotor efficiency depending on the selected conditions. The comparison is also demonstrated on the expected degassing time to a certain required concentration. Based on the physical model results, the study found that rotor D had the highest degassing efficiency, followed by rotors F and A. Rotors B and E had similar efficiency at a flow rate of 17 Nl·min−1. However, rotor B showed better efficiency at higher inert gas flow rates (19 and 21 Nl·min−1), while rotor E showed better efficiency at lower flow rates (13 and 15 Nl·min−1).

Simulating the Volcanic Sulfate Aerosols From the 1991 Eruption of Cerro Hudson and Their Impact on the 1991 Ozone Hole

AbstractThe Chilean volcano Cerro Hudson erupted between August 8th and 15th, 1991, injecting between 1.7 and 2.9 Tg of SO2 into the upper troposphere and lower stratosphere. We simulate this injection using the Goddard Earth Observing System Earth system model with detailed sulfur chemistry and sectional aerosol microphysics, focusing on the resulting aerosols and their contribution to the 1991 Antarctic Austral Springtime ozone hole. The simulations show a column ozone deficit (12 DU) in the Southern Hemisphere vortex collar region. The majority of this effect is between 10 and 20 km and due to heterogeneous chemistry. The model shows a 26% decrease in ozone from background levels at these altitudes, compared with in‐situ observations of a 50% decrease. Above 20 km, the dynamical response to the eruption also causes lower ozone values, a novel modeling result. This experiment highlights potential interactions between proposed solar radiation management geoengineering aerosols and volcanic eruptions.

Using radial basis function for estimating the high-performance concrete compressive strength with optimizing AVOA and SSA

Compressive strength (CS) is concrete’s most important mechanical property, as it plays an important role in setting design criteria. Thus, an accurate and early assessment of the CS of concrete can minimize time, labor, and cost. This paper investigated the ability of the Radial Basis Function (RBF) to handle the prediction of CS. The nonlinearities raised from the novel utilized admixtures between the input variables and output CS is tried to be conducted with the RBF model. In order to make a flexible framework combination of the RBF model with the African Vulture Optimization (AVOA) and Salp Swarm Algorithm (SSA) techniques are considered. The results achieved from the RBF-AVOA model indicated good agreement between the actual and predicted values. The proposed model provides a very accurate HPC compressive strength prediction. In addition, the correlation coefficient R2 is equal to (0.997), and the values of mean absolute error (MAE) (0.1917 MPa), root mean square error (RMSE) (0.937 MPa), and variance account coefficient (VAF) (99.73%) are low. The performance of the RBF-AVOA model, compared to other models, provided the desired advantage and more stable predictions. AVOA plays a key role in modeling results, improving generalization capabilities, avoiding redundant data, and decreasing uncertainty.

Modelling the centrifugal mixing process of minced meat to optimise the production of chopped meat semi-finished products

One of the most important problems in ensuring the quality of mincemeat preparation in the production of sausages is the effective structuring of components and mixing of their ingredients. To solve this problem, researchers added a multifunctional admixture based on whey protein in the process of centrifugal mixing of the components, which determined the composition of the factor space of the investigated process. Based on the results of the research, the effective content of whey protein, sodium alginate, and soy fiber in the developed recipe was proven, which showed high characteristics in terms of fat-retaining and moisture-retaining ability, digestibility, pH level – activity, and other parameters. The developed formulation made it possible to improve the general indicator of the balance of amino acids in the product and increase the functional-technological and quality parameters of the developed products. The physical and mechanical characteristics of the obtained meat product were evaluated based on the results of physical and mathematical modelling. Modelling was carried out using Federman-on-Buckingham's second similarity theory and the "dimension theory" method, which allows the processing of the obtained experimental data in the form of a criterion equation, which was compiled using Froude, Euler, and Sherwood criteria. The purpose of this study was to obtain dependencies between such process factors as product density, the coefficient of dynamic viscosity of the technological medium, the ultimate shear stress, the change in the concentration of the main impurities of lactic acid in the raw material, the value of the diffusion coefficient and the coefficient of mass transfer in the loading mass, the weight of one load of products, the angular frequency of rotation of the screws of the minced meat mixer, the radius of the rotating working bodies, the characteristic size of the products after grinding. Using the complex criterion equation and the developed program, we find a recommended set of operating mode parameters for preparing minced meat under the conditions of centrifugal influence on the mixing process and the action of the specified factors.

Stresses in silicon dioxide films deposited from dielectric targets: results of atomistic modeling

The previously proposed method of molecular dynamics simulation of the deposition of thin films from metal targets is adapted to the case of dielectric targets and applied to silicon dioxide films. The possibility of not only silicon atoms leaving the target, but also clusters with oxygen atoms was taken into account by adding O=Si=O molecules to the flow of deposited atoms. Atomistic film clusters were obtained by high-energy and low-energy deposition at different percentages of molecules in the flow of deposited atoms. The values of the stress tensor components are calculated. With high-energy deposition, compressive stresses are observed, with low-energy deposition, tensile stresses are observed. The absolute values of the diagonal components of the stress tensor increase with increasing proportion of molecules in the flow of deposited atoms.

Integrating space syntax and CPTED in assessing outdoor physical activity

AbstractThe relationship between the spatial configuration of the built environment and outdoor physical activity is supported in the literature. However, the role of crime prevention elements and safety is neglected in that relationship. Using structural equation modelling and considering the effect of demographic factors, this study combined concepts of space syntax for analysis of spatial configuration and Crime Prevention through Environmental Design (CPTED) at property and street scales to investigate the direct and indirect relationships between neighbourhoods’ environments and levels of outdoor physical activity. The theoretical purposes have been to measure CPTED elements in two scales and each as a second‐order construct and to gauge pedestrians’ feeling of safety as mediators in the relationship between space syntax measures and physical activity. The results of structural equation modelling suggest that streets’ CPTED elements mediate the relationship between space syntax measures and feelings of safety. The mediation role of feelings of safety in the relationship between CPTED at the street scale and physical activity is also supported. Thus, the study shows that space syntax measures cannot be considered in relation to physical activity without also thinking about its consequent effects on neighbourhoods’ physical environments andalso provides novel insights into the effects of demographic variables on outdoor physical activity.

DEVELOPMENT OF A VORTEX CHAMBER MODEL TO ESTIMATE THE VALUES OF THE LIQUID AND GASEOUS PHASES

When preparing well products from gas fields at complex gas treatment plants, dry stripped gas and unstable condensate are separated. During the exploitation of a field, development indicators (flow rate, reservoir pressure, composition of extracted products, etc.) change. At the same time, the efficiency of the apparatus for separating the gas and liquid phases decreases, which is accompanied by an increase in the entrainment of the liquid phase from the gaseous phase and can reach about 30–40 % of the total volume. This affects economic efficiency indicators, since the volume of unstable condensate decreases, and, consequently, the profit from its sale.The article is devoted to studying the effectiveness of using vortex chambers to reduce the entrainment of the liquid phase from the gaseous phase during the preparation of well products. The results of the research analysis are presented, methods for assessing phase transitions in vortex chambers and the mathematical models used are described.The work defines the basic equations that describe the process of entrainment of the liquid phase from the gaseous phase. Thus, to describe the phase boundaries, the volume of fluid model is used, and the standard k – ε is used as a flow turbulence model. A model of a vortex chamber is being developed in ANSYS FLUENT, the mesh model is built using elements – tetrahedrons. The size of the mesh elements was determined from the condition of stability of the resulting solution and amounted to 10 mm.The influence of chamber geometry, liquid mass velocity and other parameters on the process of phase entrainment is considered.A comparison of the results of experimental studies and modeling results shows the possibility of reducing the entrainment of the liquid phase as a result of the use of vortex chambers and justify the selected parameters for developing the model.

Redox condition changes caused by impacts: Insights from Chang’e-5 lunar glass beads

Lunar materials are overall more reducing compared with their terrestrial counterparts, but the mechanism remains to be elucidated. In this study, we present a possible explanation for the changes in redox state of the lunar regolith caused by impact events, based on our investigations of the impact glass beads from Chang’e-5 mission. These glass beads contain iron metal grains and show concentration gradients of FeO and K2O (with or without Na2O) from their rims to centers. The compositional profiles exhibit error-function-like shapes, which indicates a diffusion-limited mechanism. Our numerical modeling results suggest that the iron metal grains on the surface of the glass beads were generated through the reduction of FeO by elemental K and (or) Na produced during the impact events. Meanwhile, the iron metal grains inside the bead may have formed due to oxygen diffusion driven by redox potential gradients. Furthermore, our study suggests that impact processes intensify the local reducing conditions, as evidenced by the presence of calcium sulfide particles within troilite grains that coexist with iron metal grains on the surface of the glass beads. This study provides insights into the oxygen diffusion kinetics during the formation of iron metal spherules and sheds light on the changes in redox conditions of lunar materials caused by impact events.

Chemical composition, sources and formation mechanism of urban PM2.5 in Southwest China: a case study at the beginning of 2023

Abstract. Despite significant improvements in air quality in recent years, the Sichuan Basin (SCB) is still facing frequent haze pollution in winter, and the causes of severe haze formation have not yet been fully investigated. In this study, the chemical components of PM2.5 (i.e., particulate matter with an aerodynamic diameter of less than 2.5 µm) in a typical pollution period at the beginning of 2023 in Chengdu, a megacity in the SCB, were characterized by bulk-chemical and single-particle analysis, and the PM2.5 sources and formation mechanism of pollution were analyzed. The average mass concentration of PM2.5 during the study period was 95.6 ± 28.7 µg m−3. Organic matter (OM) was the most abundant component (35.3 %), followed by nitrate (22.0 %), sulfate (9.2 %) and ammonium (7.8 %). The individual aerosol particles were classified into five categories, i.e., mineral, OM, secondary inorganic aerosol (SIA), soot and fly ash/metal particles, and most of them were in the state of being internally mixed. The entire observation period could be divided into two non-pollution periods (NP-1 and NP-2) and two haze periods (Haze-1 and Haze-2). With the evolution of pollution, the bulk-chemical and single-particle analysis exhibited similar characteristics, suggesting that Haze-1 was mainly caused by pollutants related to fossil fuel combustion, especially local mobile sources, while Haze-2 was triggered by the rapidly increasing secondary pollutants, which mainly came from regional transmission. The PM2.5 sources included dust (8.5 %), biomass burning (3.5 %), coal combustion (15.4 %), industrial processes (6.5 %), vehicular emissions (25.6 %) and secondary sources (40.5 %). Analysis of Weather Research and Forecasting model with Chemistry (WRF-Chem) model results showed that the average contributions of local sources and regional transmission to pollution in Chengdu were the same (50 % vs. 50 %). In addition, the source composition and WRF-Chem simulation results in different periods confirmed our analysis of the formation mechanisms of the two haze events. This study confirms that further significant reductions in PM2.5 in Chengdu are still needed, and more effective policies for local emission reduction or joint prevention and control of regional air pollution will be necessary in the future.