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Incorporating carbon nanotubes (CNTs) into Al-Si alloy to prepare in-situ SiC/Al-Si composites enhances thermal conductivity (TC) and reduces the coefficient of thermal expansion (CTE). However, challenges include CNTs aggregation and uneven SiC distribution. This study uses fluidized bed chemical vapor deposition (FBCVD) to achieve uniform CNTs coverage on Al-50Si powder. Subsequent powder hot extrusion and heat treatment above the eutectic temperature enable a gradual reaction between CNTs and Al/Si atoms, resulting in uniformly dispersed SiC within the SiC/Al-50Si composite. The formation mechanism of in-situ SiC particles and their impact on the microstructure, thermal and mechanical properties of the composite are further investigated. The formation process involves a two-step chemical reaction: lamellar Al4C3 phases transform into lamellar eutectic SiC + Al phases, which then transition into polyhedral SiC particles through epitaxial growth. This in-situ formation of SiC particles also impedes Si growth during heat treatment, refining Si particles and enhancing the composite’s properties. The resulting in-situ SiC/Al-50Si composite exhibits excellent thermal and mechanical properties, including a high TC of ∼162 Wm-1K−1, a low CTE of ∼ 8.7 × 10-6/K, and a good bending strength of approximately 253 MPa at room temperature.

The Al–50Si alloy, designed for effective heat dissipation in electronic components, was subjected to a two-stage heat treatment process to optimize its microstructure and achieve high thermal conductivity (TC). Two distinct temperature stages were strategically chosen: 850 °C and 550 °C, respectively, with the former operating above and the latter below the eutectic point. The first stage at 850 °C led to the isolation of independent Si particles, each closely associated with individual Al crystal with grain size of approximately 1 mm. Subsequent heat treatment at 550 °C skillfully eliminated introduced eutectic Si through Ostwald ripening. Consequently, the impediments posed by grain boundaries to the movement of electrons and phonons were significantly reduced, yielding an exceptionally high TC of approximately 180 Wm−1K−1, closely approaching the theoretical TC value (∼193 Wm−1K−1) for the Al–50Si alloy. This work paved a new path for the design of outstanding thermal properties in Al–Si electronic packaging materials.

Al–50Si alloys were prepared by powder extrusion and characterized for electronic packaging. The optimization of powder size, extrusion temperature, and heat treatment parameters was performed to enhance the microstructure and thermo-physical properties. The alloy exhibits a high relative density >99 %, a low coefficient of thermal expansion (CTE)

Deep shale gas resources in the Sichuan Basin have great potential, and this is a major area for future shale gas exploration and development. Deep shale gas wells face problems with liquid loading throughout the production cycle. Regarding deliquification techniques, it is necessary to consider the requirements of gas wells over the full life cycle, as well as the main form of artificial lift used at different stages, to achieve economically efficient development. This paper divides the life cycle of a deep shale gas well into two stages: early production and middle/late production. Pressure-control production is conducted in the early stage of production, whereas investigations on critical liquid-carrying models, the flow distribution in the wellbore, and the main form of artificial lift are conducted in the middle and late stages of production. A recommended scheme of deliquification techniques over the full life cycle has been developed to guide the development and enhancement of artificial lift methods in deep shale gas reservoirs. As of March 2022, in the PetroChina Southwest Oil & Gasfield Company managed-pressure production has been implemented in 14 wells in the early stage of deep shale gas production. In eight wells, plunger gas lift has been implemented in the middle and late stages of production. In seven wells, foam lift has been implemented. The abovementioned techniques are effective in increasing and stabilizing production and achieving deliquification in deep shale gas reservoirs.

3D photonic crystals (PCs) attract attention due to their unique optical properties but printing of colloidal particles is limited by lack of control over the assembly. Here, the authors demonstrate a continuous digital light processing 3D printing strategy using hydrogen bond assisted colloidal inks for fabricating well-assembled 3D PC structures.

Previous research has primarily focused on soil erosion issues in arid and semi-arid regions, with a limited understanding of soil erosion mechanisms in tropical areas. Additionally, there is a lack of a holistic perspective to determine the spatial attribution of soil erosion. The conversion of tropical rainforests into economically driven plantations, like rubber and pulpwood, has resulted in distinct soil erosion characteristics in specific regions. To enhance our knowledge of soil erosion patterns and mechanisms in tropical regions, it is necessary to examine soil erosion in the three major watersheds of Hainan Island from 1991 to 2021, which encompass significant geographical features such as tropical island water sources and tropical rainforest national parks. The study employed the China Soil Loss Equation (CSLE) model, slope trend analysis, Pearson correlation analysis, land-use transfer matrix, and spatial attribution analysis to examine soil erosion under different scenarios. The research results indicate that scenarios driven by the combination of natural and human factors have the greatest impact on soil erosion changes in the entire study area. Co-driven increases affected 53.56% of the area, while co-driven decreases affected 21.74%. The 31-year soil erosion showed an overall increasing trend. Human factors were identified as the primary drivers of increased soil erosion in the Nandu River basin, while a combination of climate and anthropogenic factors influenced the decrease in soil erosion. In the Changhua River basin, climate and human activities contributed to the soil erosion increase, while human activities primarily caused the decrease in soil erosion. In the Wanquan River basin, climate intensified soil erosion, whereas human activities mitigated it. This study underscores the significant combined impact of human activities and natural factors on soil erosion in tropical regions. It emphasizes the importance of considering human-induced factors when implementing soil erosion control measures in tropical regions.

Snow cover is a sensitive indicator of global climate change, and optical images are an important means for monitoring its spatiotemporal changes. Due to the high reflectivity, rapid change, and intense spatial heterogeneity of mountainous snow cover, Sentinel-2 (S2) and Landsat 8 (L8) satellite imagery with both high spatial resolution and spectral resolution have become major data sources. However, optical sensors are more susceptible to cloud cover, and the two satellite images have significant spectral differences, making it challenging to obtain snow cover beneath clouds and cloud shadows (CCSs). Based on our previously published approach for snow reconstruction on S2 images using the Google Earth Engine (GEE), this study introduces two main innovations to reconstruct snow cover: (1) combining S2 and L8 images and choosing different CCS detection methods, and (2) improving the cloud shadow detection algorithm by considering land cover types, thus further improving the mountainous-snow-monitoring ability. The Babao River Basin of the Qilian Mountains in China is chosen as the study area; 399 scenes of S2 and 35 scenes of L8 are selected to analyze the spatiotemporal variations of snow cover from September 2019 to August 2022 in GEE. The results indicate that the snow reconstruction accuracies of both images are relatively high, and the overall accuracies for S2 and L8 are 80.74% and 88.81%, respectively. According to the time-series analysis of three hydrological years, it is found that there is a marked difference in the spatial distribution of snow cover in different hydrological years within the basin, with fluctuations observed overall.

A novel and highly efficient adsorbent was prepared by loading La/Fe/Al oxides onto rice straw biochar (RSBC), which was tested for the ability to remove fluoride from drinking water. Characterized by SEM, XRD, Zeta potential and FTIR, it was found that the ternary metal oxides were successfully loaded on the surface of biochar in amorphous form, resulting in the formation of hydroxyl active adsorption sites and positive charges, which played a synergistic role in fluoride removal. Through batch adsorption tests, key factors including contact time, initial fluoride concentration, initial pH and co-existing anions effects were investigated. Results showed that the tri-metallic modified biochar (La/Fe/Al-RSBC) had excellent fluoride removal performance with an adsorption capacity of 111.11 mg/g. Solution pH had little impact on the removal of fluoride, the adsorbent retained excellent fluoride removal capacity in a wide pH range of 3.0–11.0. The co-existing anions had almost no effect on the fluoride removal by La/Fe/Al-RSBC. In addition, La/Fe/Al-RSBC could be regenerated and reused. Electrostatic adsorption and ion exchange were responsible for this adsorption behavior. These findings suggested the broad application prospect of a prepared biochar adsorbent based on rare earth and aluminum impregnation for the fluoride removal from drinking water. HIGHLIGHTS A novel tri-metal oxide loaded rice straw biochar (La/Fe/Al-RSBC) was successfully prepared by simple co-precipitation.; La/Fe/Al-RSBC has excellent fluoride adsorption performance with wide pH range.; The mechanism of fluoride adsorption involves in electric attraction and ion exchange.;

The traditional drought and flood analysis method had not fully considered the proportion analysis of different drought and flood grades in the historical years of each rainfall station. This made results unconvincing and made it difficult to deeply understand the characteristics and applicability of various methods. Based on the daily rainfall data of 88 stations in Hainan Island from 1970 to 2019, the China-Z index and the Standardized Precipitation Index (SPI) were used to compare and analyze the spatial and temporal distribution characteristics of droughts and floods from three different time scales (flood season, non-flood season and the whole year). The results showed that both SPI and China-Z index can well reflect the actual drought and flood situations in Hainan Island. The analysis of the proportions of different drought and flood grades in the historical years of each rainfall station and regional historical drought and flood statistics suggested that the China-Z index had a better indication effect than SPI on the extreme drought and flood grades. The alternation of drought and flood between different eras were obvious. Hainan Island generally presented an east-west reverse drought-flood variation trend, as well as a north-south reverse drought-flood variation trend. The drought and flood in the central mountainous area of Hainan Island had been relatively stable. The distribution pattern of drought and flood had a good spatial consistency in the three periods. On the whole, Hainan Island had shown a trend of flood in the east and drought in the west in the past 50 years.

Different regions exhibit different response patterns of hydrological process changes under changing environments. The hydrological response mechanism of underlying surface changes in tropical rainforest regions remains uncertain, so there is an urgent need to study the causes of hydrological changes in typical tropical watersheds. The sequential clustering analysis and Pettitt-Mann-Whitney test were employed to detect abrupt change points of runoff series for the Wanquan River Basin in the tropics, and the series was then divided into pre-impact period (1967–1990) and post-impact period (1991–2014). And the Soil and Water Assessment Tool (SWAT) model was used to simulate the runoff to quantify the impact of climate change, land use change and other human activities on runoff, which the latter two collectively referred to as “human activities” in this study. The findings reveal: 1) runoff series showed an abrupt change and a downward trend around the year 1990; the SWAT model has a good simulation in the Wanquan River Basin during the pre-impact period; the coefficients of determination (R2) for the calibration and validation periods are both 0.91, and the Nash-Sutcliffe model efficiency coefficients (NSE) for the calibration and validation periods are 0.89 and 0.86, respectively. 2) There was a considerable change in land use between 1967 and 2014, as evidenced by a decrease of 29.54% in natural forest and an increase of 54.90% in rubber. These land use changes were mostly caused by the transformation of tropical rainforests into rubber forests and orchards. 3) Runoff declined in the post-impact period from the pre-impact period, with climate change, land use change, and other human activities contributing 44.05%, 10.83%, and 45.12% to the runoff change, respectively. The conversion of tropical rain forests to rubber forests and orchards has indirectly led to a reduction in runoff. These results can provide a reference for understanding the evolution of water cycle for other tropical rivers.

Flexible and stretchable electronic devices are indispensable parts of wearable devices. However, these electronics employ electrical transducing modes and lack the ability to visually respond to external stimuli, restricting their versatile application in the visualized human–machine interaction. Inspired by the color variation of chameleons’ skin, we developed a series of novel mechanochromic photonic elastomers (PEs) with brilliant structural colors and a stable optical response. Typically, these PEs with a sandwich structure were prepared by embedding PS@SiO2 photonic crystals (PCs)within the polydimethylsiloxane (PDMS) elastomer. Benefiting from this structure, these PEs exhibit not only bright structural colors, but also superior structural integrity. Notably, they possess excellent mechanochromism through lattice spacing regulation, and their optical responses are stably maintained even when suffering from 100 stretching–releasing cycles, showing superior stability and reliability and excellent durability. Moreover, a variety of patterned PEs were successfully obtained through a facile mask method, which provides great inspiration to create intelligent patterns and displays. Based on these merits, such PEs can be utilized as visualized wearable devices for detecting various human joint movements in real time. This work offers a new strategy for realizing visualized interactions based on PEs, showing huge application prospects in photonic skins, soft robotics, and human–machine interactions.

Shear relaxation commonly occurs in shock compressed metals at the plastic wave front, but no consensus has ever been reached on its origin due to the multiscale nature of high rate plasticity. To this end, this work takes a top-down approach by conducting a theoretical and numerical investigation on the macroscale, and then simulations on the mesoscale with crystal plasticity, followed by a brief discussion on the microscale mechanisms based on dislocation theory. On the macroscale, theoretical derivation through isotropic elasticity and von-Mises plasticity, as well as continuum simulations of shocked aluminum employing Johnson-Cook plasticity and equations of state for nonlinear elasticity at high pressures, uncovers that strain rate hardening decisively leads to shear relaxation when the equivalent plastic strain rate is greater than two-thirds of the total strain rate (ε̇p>2/3∙ε̇1). Other factors play subsidiary roles, including limited or conditioned promotive effect of thermal softening and suppressive effect of strain hardening. On the mesoscale, simulations with crystal plasticity and hyperelasticity perfectly verify the macroscopic discoveries, and additionally revealed the subordinate stimulative effect of deformation heterogeneity of polycrystals. On the microscale, dislocation nucleation and multiplication are identified as the dominant factors by evaluating contributions of micro-mechanisms to strain rate hardening.

True three-dimensional (3D) displays are the best display technologies and their breakthrough is primarily due to advancements in display media. In this paper, we propose two luminescent materials for a static volumetric 3D display based on photoactivated phosphorescence. The luminescent materials include (1) dimethyl sulfoxide (DMSO)/1-methyl-2-pyrrolidinone (NMP) or tetramethylene sulfoxide (TMSO) as the solvent and photochemically-deoxygenating reagent; (2) a metal phthalocyanine complex as the sensitizer; (3) a phosphorescent platinum complex as the emitter. The metal phthalocyanine complex, PdPrPc (PdBuPc), absorbs the light beam of 635 nm and the solvent scavenges the sensitized singlet oxygen. Light beams pass through a deoxygenated zone. The phosphorescent emitter, PtNI, absorbs the 440 nm light beam and phosphoresces only in the deoxygenated zone generated by the sensitizer. Phosphorescent voxels and high-contrast 3D images are well-defined at the intersection of 635 and 440 nm light beams.

In this work, we provide a fabrication method for dual-responsive electrochromic (EC) polymer dispersed liquid crystal (PDLC) devices. The EC PDLC device was developed by combing the PDLC technique and a colored complex formed via a redox reaction without a specific EC molecule in a simple preparation method. The mesogen played dual roles in the device for scattering in the form of microdroplets and participating in the redox reactions. Orthogonal experiments were performed with the acrylate monomer concentration, the ionic salt concentration, and the cell thickness as factors to investigate the electro-optical performance for the achievement of optimized fabrication conditions. The optimized device presented four switchable states modulated by external electric fields. The light transmittance of the device was changed by an alternative current (AC) electric field while the color change was realized by a direct current (DC) electric field. Variations of mesogen and ionic salt species can modulate the color and hue of devices, which solves the disadvantage of a single color for traditional EC devices. This work lays the foundation for realizing patterned multi-colored patterned displays and anti-counterfeiting via screen printing and inkjet printing techniques.

Fluorinated or fluoroalkylated allenes are versatile building blocks for medicinal and material chemistry. Here, the authors show a regioselective trifunctionalization of 1,3-enynes proceeding through double C-F bond formation and concomitant installation of a -NSO2Ph group to the allene moiety.

Background: Acute myocardial infarction (AMI) is a rare complication of acute organophosphorus pesticide poisoning. Although chlorpyrifos has been widely used as an organophosphate insecticide, a few cases of AMI complicated by chlorpyrifos poisoning have been reported thus far. Hence, a suitable treatment strategy remains to be explored.Case Presentation: Based on the clinical manifestations, medical history, results of an auxiliary examination, and serum biomarkers, a 65-year-old male farmer with complaints of nausea, vomiting, chest tightness, and pain was clearly diagnosed as having a severe chlorpyrifos self-poisoning with acute non-ST-segment elevation MI. Because the patient and his family confirmedly refused a coronary intervention, conservative treatment was used instead. It should be noted that there were some conflicts of the management for chlorpyrifos poisoning and AMI. Although rapid atropinization would contribute to the relief of muscarinic symptoms, it would also lead to an increased heart rate and myocardial oxygen consumption in AMI. Furthermore, the reduction of platelet aggregation, which is necessary for coronary recanalization of an AMI patient, is known to aggravate the gastrointestinal injury caused by poisoning. In this case, these conflicts were properly addressed, which led to an excellent effect and prognosis of the patient.Conclusions: To our knowledge, this is the first case report of acute chlorpyrifos poisoning with AMI. It is emphasized that patients with chest pain or coronary heart disease should be treated with atropine more cautiously because of the possible AMI. Moreover, proper resolution of conflicts in the management for chlorpyrifos poisoning and AMI played contributing roles in patient improvement.

A copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction for the synthesis of 1,4-disubstituted 1,2,3-triazoles from alkyl diacyl peroxides, azidotrimethylsilane, and terminal alkynes is reported. The alkyl carboxylic acids is for the first time being used as the alkyl azide precursors in the form of alkyl diacyl peroxides. This method avoids the necessity to handle organic azides, as they are generated in situ, making this protocol operationally simple. The Cu(I) catalyst not only participates in the alkyl diacyl peroxides decomposition to afford alkyl azides but also catalyzes the subsequent CuAAC reaction to produce the 1,2,3-triazoles.

In order to apply the electric submersible pump (ESP) based drainage gas recovery technology commonly used in conventional gas wells to high-sulfur gas wells, and meet the requirements of casing protection in high-sulfur gas wells, we conducted a series of technical researches on casing protection, gas interference and vibration of deep-well ESP set in terms of a completion string design and support tools based on the completion modes of high-sulfur gas wells and the technical characteristics of ESP drainage gas recovery technologies. Simultaneously, drainage gas recovery technology was designed for Well L2. The research and application results show: firstly, the completion string system of high-sulfur gas wells composed of a canned ESP system and an anchor intubation packer can realize the normal operation of ESP and meet the requirements of casing protection; secondly, multiphase pump and bleeder line can be used to solve the problem of gas interference, the automatic reverse valve can be used to reduce the effect of ESP complex flow path on the flowing of the gas well, and the anchor intubation packer can be used to reduce the string vibration; thirdly, the canned ESP system designed in this paper is applicable to Ø244.5 mm and Ø177.8 mm casings, specifically, the ESP corresponding to Ø244.5 mm casing has the maximum flow rate of 900 m3/d and the maximum lift height of 4500 m, and that corresponding to Ø177.8 mm casing has the maximum flow rate of 300 m3/d and the maximum lift height of 3000 m. It is concluded that this research result provides a technical support for the implementation of ESP based drainage gas recovery technology in high-sulfur gas wells. Keywords: High-sulfur gas well, Electric submersible pump, Drainage gas recovery, Canned system, Well completion method, Casing protection, Intubation packer, Multiphase pump

Background: We previously designed an electrospinning chitosan (CS) nanofiber-based carrier, using polyvinyl alcohol (PVA) as an adjuvant to deliver doxorubicin (DOX) and MoS2 nanosheets for postoperative tumor re-occurrence inhibition. However, owing to that the nanofibrous mat is un-injectable, this composite nanofiber is far from being clinically applicable. Materials and Methods: Via modulating the electrospray parameters, polyvinyl alcohol (PVA) beads string doped with DOX and MoS2 (PVA/MoS2/DOX microspheres) were prepared, which were further crosslinked with glutaraldehyde to obtain the water-stability. Results: Under the 808-nm laser irradiation, MoS2 nanosheets rendered the prepared PVA/MoS2/DOX microspheres an excellent light-to-heat conversion performance with η of 23.2%. Besides, the heat generated by near-infrared laser irradiation can improve the effect of chemotherapy by promoting the release rate of DOX. HT29 cell and tumor-bearing nude mice were used to systematically study the combined tumor treatment efficiency of composite nanospheres. Conclusion: PVA/MoS2/DOX nanospheres have excellent photothermal effect and chemotherapy effect, which can completely suppress the tumor recurrence. Therefore, the PVA/MoS2/DOX nanospheres are anticipated to find potential applications in the treatment of local colorectal cancer.

The stationarity assumption of hydrological processes has long been compromised by human disturbances in river basins. The traditional hydrological extreme-value analysis method, i.e., “extreme value theory” which assumes stationarity of the time series, needs to be amended in order to adapt to these changes. In this paper, taking the East River basin, south China as a case study, a framework was put forward for selection of a suitable distribution curve for non-stationary flood series by using the time-varying moments (TVM). Data used for this study are the annual maximum daily flow of 1954–2009 at the Longchuan, Heyuan and Boluo Stations in the study basin. Five types of distribution curves and eight kinds of trend models, for a combination of 40 models, were evaluated and compared. The results showed that the flood series and optimal distribution curves in the East River basin have been significantly impacted by a continuously changing environment. With the increase of the degree of human influence, the thinner tails of distributions are more suitable for fitting the observed flow data, and the trend models are changed from CP (mean and standard deviation fitted by parabolic trend model) to CL (mean and standard deviation fitted by linear trend model) from upstream to downstream of the catchment. The design flood flow corresponding to a return period of more than 10 years at the Longchuan, Heyuan and Boluo Stations was overestimated by more than 28.36%, 53.24% and 26.06%, respectively if the non-stationarity of series is not considered and the traditional method is still used for calculation. The study reveals that in a changing environment, more advanced statistical methods that explicitly account for the non-stationarity of extreme flood characteristics are required.

The upper tail of a flood frequency distribution is always specifically concerned with flood control. However, different model selection criteria often give different optimal distributions when the focus is on the upper tail of distribution. With emphasis on the upper-tail behavior, five distribution selection criteria including two hypothesis tests and three information-based criteria are evaluated in selecting the best fitted distribution from eight widely used distributions by using datasets from Thames River, Wabash River, Beijiang River and Huai River. The performance of the five selection criteria is verified by using a composite criterion with focus on upper tail events. This paper demonstrated an approach for optimally selecting suitable flood frequency distributions. Results illustrate that (1) there are different selections of frequency distributions in the four rivers by using hypothesis tests and information-based criteria approaches. Hypothesis tests are more likely to choose complex, parametric models, and information-based criteria prefer to choose simple, effective models. Different selection criteria have no particular tendency toward the tail of the distribution; (2) The information-based criteria perform better than hypothesis tests in most cases when the focus is on the goodness of predictions of the extreme upper tail events. The distributions selected by information-based criteria are more likely to be close to true values than the distributions selected by hypothesis test methods in the upper tail of the frequency curve; (3) The proposed composite criterion not only can select the optimal distribution, but also can evaluate the error of estimated value, which often plays an important role in the risk assessment and engineering design. In order to decide on a particular distribution to fit the high flow, it would be better to use the composite criterion.

Predicting pressure drop in gas wells is one of the most important issues for designing deliquification technologies and optimizing gas production. Current pressure-drop prediction methods can be divided into analytical and empirical models. Although various models have been proposed to predict pressure drop in wellbores, no model has offered stable performance over wide liquid and gas flowrate ranges. Especially for gas wells with low liquid – gas ratios, very few models have been developed specifically. In this study, a simple and accurate three-point model is developed for predicting liquid holdup in wellbores. The model is based on the liquid holdups and gas velocities at the annular – churn, churn – slug and slug – bubble boundaries and is comprehensive for calculating the liquid holdup in vertical wellbores at different liquid/gas flowrates and pressures. The proposed method was verified with 39 collected laboratory and 182 field measured data points from the literature, which have wide parameter ranges. For comparison, some widely used models in the petroleum industry were also evaluated. In validation with the laboratory data with pipe diameters of 50.8 and 101.6 mm, although the new model has an average percentage error (E3) of 220.1% in the churn flow, ranking fourth of all the evaluated models, the other five indicators in the churn flow and six indicators in the annular flow are lowest of all these evaluated models, resulting in relative performance factors (RPFs) of 0.2 and 0, respectively. In the field measured data, gas and liquid productions range between 0.34 × 104 —77.6 × 104 m³/d and 1—347.8 m³/d, tubinghead pressure ranges from 0.7 to 84.7 MPa, which can cover most gas wells. The validation demonstrates that the new model still has good performance with five indicators being lowest. The RPF of the new pressuredrop model in the field measured data ranges is 0.29, still lowest of all these evaluated models, showing better performance than these widely used models in petroleum industry for vertical gas wells. This indicates that the new model can accurately predict pressure drop under different conditions in vertical gas wells. [ABSTRACT FROM AUTHOR]

The flow behavior of shale gas horizontal wells is relatively complex, and this should be regarded as the main reason for which conventional pipe flow models are not suitable to describe the related dynamics. In this study, numerical simulations have been conducted to determine the gas-liquid distribution in these wells. In particular, using the measured flow pressure data related to 97 groups of shale gas wells as a basis, 9 distinct pipe flow models have been assessed, and the models displaying a high calculation accuracy for different water-gas ratio (WGR) ranges have been identified. The results show that: (1) The variation law of WGR in gas well satisfies a power function relation. (2) The well structure is the main factor affecting the gas-liquid distribution in the wellbore. (3) The Beggs & Brill, Hagedorn & Brown and Gray models exhibit a high calculation accuracy. [ABSTRACT FROM AUTHOR]