Relative Curves Research Articles

Study on strength characteristics of soft and hard rock masses based on thermal-mechanical coupling

For deep resource exploitation and engineering construction, the mechanical properties of soft and hard interbedded rock masses are important factors impacting engineering stability. Simultaneously, the influence of temperature on the strength of deep rock masses poses a significant obstacle to the exploitation of deep resources and the utilization of underground space. In this paper, the particle flow code (PFC2D) is utilized to establish the thermal-mechanical coupling numerical model of soft and hard interbedded rock masses, and then the uniaxial compression response of soft and hard interbedded rock masses following thermal damage is studied. The displacement and contact force produced by applying temperature, as well as the failure strength, strain, and crack development of the specimen after uniaxial compression is analyzed. The findings reveal that: 1) The peak displacement caused by applied temperature increases first and subsequently decreases with the increase of soft rock thickness ratio (Hs/H), whereas the peak displacement increases linearly with increasing temperature. The peak contact force varies in two stages with the increase of the soft rock thickness ratio (Hs/H), and with the same trends. 2) As the soft rock thickness ratio increases (Hs/H), the number of cracks decreases steadily. When the soft rock thickness ratio Hs/H < 0.5, the relationship curve between vertical strain and crack changes in two stages: the stage of crack development along with the stage of vertical strain gradually increases with crack development. When the thickness ratio of soft rock Hs/H > 0.5, the relationship curve changes in three stages: crack development stage, vertical strain increase stage, and vertical strain increase stage with crack development. 3) When the soft rock thickness ratio Hs/H < 0.5, the failure strength gradually decreases as soft rock thickness increases at T = 100°C, 200°C. The failure strength gradually increases as the soft rock thickness increases in general at T = 400°C. Soft rock thickness ratio Hs/H > 0.5, the failure strength increases with the increase of soft rock thickness at T = 300°C, 400°C. At T = 100°C, 200°C, the tendency of the failure strength changes less.

Dynamic Compressive Mechanical Properties of UR50 Ultra-Early-Strength Cement-Based Concrete Material under High Strain Rate on SHPB Test

UR50 ultra-early-strength cement-based self-compacting high-strength material is a special cement-based material. Compared with traditional high-strength concrete, its ultra-high strength, ultra-high toughness, ultra-impact resistance, and ultra-high durability have received great attention in the field of protection engineering, but the dynamic mechanical properties of impact compression at high strain rates are not well known, and the dynamic compressive properties of materials are the basis for related numerical simulation studies. In order to study its dynamic compressive mechanical properties, three sets of specimens with a size of Φ100 × 50 mm were designed and produced, and a large-diameter split Hopkinson pressure bar (SHPB) with a diameter of 100 mm was used to carry out impact tests at different speeds. The specimens were mainly brittle failures. With the increase in impact speed, the failure mode of the specimens gradually transits from larger fragments to small fragments and a large amount of powder. The experimental results show that the ultra-early-strength cement-based material has a greater impact compression brittleness, and overall rupture occurs at low strain rates. Its dynamic compressive strength increases with the increase of strain rates and has an obvious strain rate strengthening effect. According to the test results, the relationship curve between the dynamic enhancement factor and the strain rate is fitted. As the impact speed increases, the peak stress rises, the energy absorption density increases, and its growth rate accelerates. Afterward, based on the stress–strain curve, the damage variables under different strain rates were fitted, and the results show that the increase of strain rate has a hindering effect on the increase of damage variables and the increase rate.

Low ambient temperature might trigger the symptom onset of pulmonary embolism: A nationwide case-crossover study at hourly level in China

BackgroundPulmonary embolism (PE) is an important cause of death and its seasonality has long been observed. Very few epidemiological studies have explored the potential role of ambient temperature in PE symptom onset, especially at the hourly level. MethodsWe conducted a time-stratified case-crossover study among 17,903 PE patients with hourly onset of symptom from 1590 hospitals across China between January 2015 and September 2020. Conditional logistic regression model combined with distributed lag non-linear models were used to explore the associations between hourly ambient temperature and PE symptom onset. The attributable fractions due to non-optimum temperature were calculated. ResultsThe exposure-response relationship curve was inverse and almost linear. Lower temperature was significantly associated with higher risk of PE symptom onset when temperature was below 18 °C. This risk occurred immediately at the same hour, attenuated thereafter, and became nonsignificant at approximately 72 h after exposure. Compared with the referent temperature (P99, 34.1 °C), the odds ratio of PE symptom onset associated with extremely low temperature (P1, −16.1 °C) over lag 0–72 h was 1.63 (95%CI: 1.23, 2.16). Low temperature may account for 16.19 % of the symptom onset nationally with higher proportion in the south of China. The effects were stronger in older adults, males, and cold seasons. ConclusionsWe provided the first-hand robust evidence that transient exposure (at the hourly level) to low temperature might trigger the symptom onset of PE and constitute a considerable burden for PE patients. Targeted protections and health education are needed for susceptible populations.

Relationship between body mass index and physical fitness of children and adolescents in Xinjiang, China: a cross-sectional study

BackgroundXinjiang is an economically underdeveloped area in China, but the obesity rate of children and adolescents is increasing year by year. Physical fitness and body mass index (BMI) are very important factors for healthy development, whereas few studies focus on the relationship between them in this region. This study aimed to explore the relationship between physical fitness and BMI of children and adolescents aged 7 to 18 in Xinjiang.MethodA total of 17,356 children and adolescents aged 7–18 years were involved. BMI was divided into five levels by percentiles, from very low to very high. Physical fitness was evaluated by five indicators: grip strength, standing long jump, sit-and-reach, 50 m dash, and endurance running. Single-factor analysis of variance was used to compare the Z-scores of the five physical fitness indicators among different BMI levels for the four age groups by gender. A nonlinear quadratic regression model was used to evaluate the relationship between BMI and each indicator in the four age groups.ResultThere is a significant correlation between the five health-related indicators (grip strength, standing long jump, sit and reach, 50 m dash, endurance run) at two age groups (13-15 yrs., 16-18 yrs) of children and adolescents in Xinjiang, China. The range of the Pearson coefficient is 0.048 ~ 0.744. For the other two age groups (7-9 yrs., 10-12 yrs.,) significant correlations are found only in some indicators, and the Pearson coefficient ranges from 0.002 to 0.589. The relationship between BMI and physical fitness presents an U-shaped or inverted U-shaped curve in most age groups(R2 ranges from − 0.001 to 0.182. Children and adolescents with normal BMI score higher on physical fitness tests, and boys (R2 ranges from − 0.001 to 0.182) are more pronounced than girls (R2 ranges from 0.001 to 0.031).ConclusionChildren and adolescents with a BMI above or below the normal ranges have lower physical fitness than those with normal BMI. BMI and physical fitness have an U-shaped or inverted U-shaped curve relationship, and the impact is more evident in boys than girls. Targeted actions such as improving the quality of physical education classes, advocating students to keep a balanced diet and physical exercise should be taken designedly.

Research of Water Consumption Rate Measurement Based on Thermodynamic Method

As an important index which can be used to evaluate the economic operation result for hydropower station, the water consumption rate of hydropower unit can be acquired with hill chart curve of hydraulic turbine, the relationship curve between flow discharge of hydropower station and water level of reservoir. However, considering that the hill chart curve of turbine is calculated and converted by the model test, there are certain errors when used on the prototype machine, which also brings limitations to the applicability. According to the definition of water consumption rate, it can be determined by the unit’s net head and efficiency. The static water head of the unit can be obtained by measuring pressure for spiral case inlet and draft tube outlet. Therefore, the key issue for the measurement of unit water consumption rate is the measurement of turbine flow discharge. Therefore, according to the operating characteristics of high-head turbines, this article adopts thermodynamics to measure the flow discharge of turbine, studies the installation and implementation of high- and low-pressure section test instruments with the site condition of a hydropower project, and analyses of the water consumption rate of units under different conditions such as the multiple-unit’s operation, various water heads, etc. The analysis results show the relationship and trend for the water consumption rate and unit operation condition, which can provide references for the optimal dispatch operation of multi-units’ hydropower stations, achieving the purpose of reducing the water consumption rate of power generation and improving the efficiency of power generation.

Nonlinear threshold approach for asymmetric effects of government size on economic growth in an emerging Asian economy: the Malaysian experience

This paper discovers the asymmetric relation between government size and economic growth in Malaysia, an emerging Asian economy, by utilising a dynamic threshold nonlinear approach. The study finds empiric evidence that the threshold effect linking government size to economic growth in Malaysia exists when two different proxies of government size are set as the threshold variable. On closer inspection, it is found that an inverted U-shaped Armey curve is present when allowing for endogenous government size threshold proxied by government operating/real GDP. However, a U-shaped curve of nonlinear relationship exists instead when the government investment/real GDP serves as the threshold variable. In general, this paper gives policymakers a real insight into the optimal government size in Malaysia especially when designing an effectual fiscal policy to advance sustainable economic growth to materialise its Shared Prosperity Vision by the year 2030.

Does resource environment carrying capacity have a coercive effect on urbanization quality? Evidence from the Yangtze River Economic Belt, China

Understanding the relationship between resource environment carrying capacity (RECC) and urbanization quality (UQ) is of great significance for the new urbanization strategy. Different from previous studies which mainly focused on the coordination degree between urbanization and RECC, this study explores the environmental Kuznets curve relationship between UQ and RECC pressure by considering the nonlinear relationship between systems. The 11 sub-regions in the Yangtze River Economic Belt of China are selected as the study area. Results show that: (1) All 11 sub-regions witness UQ growth during the survey period of 2005–2017, among which Shanghai, Jiangsu, and Zhejiang take the three top positions. (2) The levels of RECC in the 11 sub-regions follow a gradual increasing trend from 2005 to 2017. Shanghai has the highest RECC value, and Guizhou province has the lowest RECC. (3) Except for Zhejiang, the other three sub-regions downstream of the Yangtze River present an N-shaped relationship between UQ and RECC pressure. The relationship for the three midstream regions presents a U shape, while that for upstream regions is either a U shape or an inverted N shape. These findings provide a valuable reference for governments to formulate effective measures for promoting the coordination of UQ and RECC in the Yangtze River Economic Belt. Moreover, new insights for conducting research on the relationship between UQ and RECC in other economic systems on a global level are given.

Numerical Simulation of Multifunctional Projectile Penetrating Reinforced Concrete Target Plate Based on Sensor Data Acquisition

The main material of a type of multifunctional warhead is energy-containing material, which mainly relies on the projectile’s own kinetic energy to hit the target plate to achieve the function of penetrating reinforced concrete, so it needs the bullet material to have high strength and be able to withstand the high overload when penetrating reinforced concrete. At present, the composite energy-containing material structure with Al, Zr, Ti, and other materials as PTFE-based reducing agents is the mainstream direction of research on high-strength energy-containing materials. LS-DYNA is used to establish a simulation model to simulate and analyze the tapping power. The relationship curve between material strength and attack depth is established and compared with the experimental data of traditional steel material attack ammunition to finally determine the strength limit of energy-containing material compared with traditional attack ammunition. The simulation results show that the composite energy-containing material multifunctional projectile can accomplish the tapping task of penetrating 1.2 m reinforced concrete under the premise of ensuring that the percentage of W powder is not higher than 80%. This study has a certain reference value for the selection of energy-containing materials for multifunctional warheads. For the low-velocity penetration below 400 m/s, the effect of frictional resistance of the head as well as the sidewall on the penetration depth can be ignored, but the overload curve when considering the sidewall friction is more realistic. Using a combination of experimental and theoretical methods, the influence of the projectile material on the mass erosion of high-speed kinetic energy projectiles was studied, and the Jones erosion model based on the thermal melting principle was improved. Based on the cavity expansion theory, the calculation method of the shape evolution of the bullet head was established. The comparison with the experimental results shows that the improved model is applicable to different types of soft and hard materials and can accurately calculate the mass erosion amount, erosion depth, and shape evolution of the bullet head.

The Impact of Environmental Information Disclosure on Enterprise Value

The construction of ecological civilization and the development of green finance have gradually become the theme of the times, so it is particularly important for enterprises to gradually realize voluntary scientific environmental information disclosure. This paper examines the "U" curve relationship between the quality of environmental information disclosure and enterprise value, as well as the moderating effects of institutional shareholding ratio and nature of ownership, using heavy pollution enterprises in Shanghai and Shenzhen of A-shares from 2015 to 2019 as a research sample. The results show that the relationship between environmental information disclosure and enterprise value of heavy polluters has a relationship of positive "U"-shaped curve; institutional shareholding has a positive moderating effect on the value effect of environmental information disclosure; the nature of ownership shows significant heterogeneity in the effect of environmental information disclosure on enterprise value, and the "U"-shaped value effect of environmental information disclosure of non-SOEs has a positive effect on the value effect of environmental information disclosure of heavy pollute enterprises. The "U"-shaped value effect of environmental information disclosure is more significant for non-SOEs. In further research, this paper conducts robustness analysis of enterprise value, monetary environmental information disclosure and non-monetary environmental information disclosure and endogeneity test. The findings of the study provide empirical evidence for improving the environmental information disclosure system and strengthening the supervision of SOEs, and also provide useful references for enterprises to comprehensively understand the value effect of environmental information disclosure, establish a management mechanism for enterprise environmental information disclosure and correctly view the importance of institutional investors.

Spatial and temporal distribution characteristics of carbon emissions and their drivers in shrinking cities in China: Empirical evidence based on the NPP/VIIRS nighttime lighting index

Shrinking cities are a category of cities characterized by population loss, and the environmental problems of these cities are often neglected. Using panel data from 2012 to 2019, this paper investigates the spatial and temporal distribution characteristics of carbon emissions in shrinking cities in China and the driving factors. The results find that: (1) From 2012 to 2019, carbon emissions tend to increase in shrinking cities and decrease in non-shrinking cities. Due to earlier industrial development and ecological neglect, shrinking cities in Northeast China have higher carbon emissions than other regions. (2) Population size, industrial structure and public services promote the growth of carbon emissions in shrinking cities. The influence of living environment on carbon emissions in shrinking cities is not significant. There is an environmental Kuznets curve (EKC) relationship between economic level and carbon emission. (3) In shrinking cities, the increase in commuting time and distance due to spatial expansion promotes the growth of carbon emissions. Foreign investment decreases with the loss of population, which reduces carbon emissions. Technological progress gradually declines as investment in science and technology decreases, which makes carbon emissions grow. This paper clarifies the driving factors of carbon emissions in shrinking cities in China, and therefore, the findings of this paper have important reference value for the formulation of carbon reduction policies in shrinking cities in developing countries.

Quantitative assessment of the risk of human activities on landscape fragmentation: A case study of Northeast China Tiger and Leopard National Park

Risk assessment of human activities on landscape fragmentation in nature reserves can effectively balance the conflict between wildlife conservation and human development. However, previous studies had been unable to quantitatively assess the risk of human activities on landscape fragmentation. Thus, we constructed a risk assessment methodology to quantitatively assess the risk of different human activities on the Landscape Fragmentation Composite Index (LFCI) in the Northeast China Tiger and Leopard National Park (NCTLNP). First, we fitted the relationship curve between LFCI and different human activity factors based on the Generalized Additive Model (GAM) to determine the impact patterns of each factor on LFCI. Secondly, we identified impact risk areas of each human activity factor on LFCI by the location of threshold points in the curve and analyzed their spatiotemporal variation characteristics from 2015 to 2020. The results show that the relationship between LFCI and Land Use Intensity (LUI) showed an inverted “U” shape, the relationship with Population Density (POPD) showed a “rising-flat-rising” trend, and the relationship with Traffic Accessibility (TA) and Industrial and Mining Activity (IMA) showed a positive correlation after a flat interval. In addition, we found that the LUI and IMA impact risk areas were widely distributed and remained stable for five years. But the POPD impact risk area was mainly distributed around settlements and expanded by 6.6 % from 2015 to 2020. The TA impact risk area was distributed in strips and expanded by 16.38 % from 2015 to 2017 due to the construction of the G331 national road. And the joint impact risk area of these four factors expanded by 1.55 times in five years. Our research can provide a reference for ecological risk assessment under the impact of human activities on other nature reserves in the world.

Can Female Directors Improve Performance Consequences of Executives’ External Pay Gap? Evidence from China

Drawing on the perspectives of the tournament theory and critical mass theory, the paper investigates the moderating mechanism of female directors’ participation in the board on the relationship between executives’ external pay gap (EEPG) and firm performance. An unbalanced panel data consisting of 21082 firm-year observations from 2783 non-financial listed companies in Shanghai and Shenzhen Stock Exchange of China from 2008 to 2018 is selected as the research sample, and multiple regression analysis, robustness test and endogenous test are taken as the statistical methods. Theoretical analysis and empirical data conclude that EEPG has an inverted U-shaped impact on firm performance, and a mass level of female directors, i.e., exceeding 1/3 in proportion or 3 in number, would change the curve relationship into a positive linear one by enhancing the positive effects and constraining the negative effects of larger EEPG. The paper adds new knowledge to the literature on consequences of female directors and antecedents of firm performance, specifically by providing a comprehensive understanding how and why female directors improve EEPG’s performance consequences.

What is the spatiotemporal relationship between urbanization and ecosystem services? A case from 110 cities in the Yangtze River Economic Belt, China

Rapid urbanization has altered landscape patterns and ecological functions, causing a decline in ecosystem service and generating many ecological and environmental issues. Studying the spatiotemporal interaction between urbanization and ecosystem service (ES) can provide effective supports for regional sustainability and policy formulation. This research utilizes the Yangtze River Economic Belt (YREB) as a case to analyze the spatiotemporal interaction between multi-urbanization indicators and multi-ESs over a large-scale region. The results show that the urbanization process in the YREB evolves from a rapidly growing state to a steady state with a slower rise. The urbanization level of the Yangtze River Delta urban agglomeration is relatively higher than the other regions. The distribution pattern of urbanization shows an overall characteristic of lower urbanization in the west and higher in the east. From 2009 to 2016, ecosystem service value (ESV) in the YREB decreased first and then increased, ESV in 2016 showed a reduction of 12.768 billion yuan compared with the 2009 level. ESV increases gradually from highly urbanized areas to those with lower levels of urbanization. Areas with high ESV levels are distributed at the middle reaches of YREB. There is a U-shaped curve relationship between urbanization and ESV, the ESV sharply increased when the urbanization index exceeded 0.6 in 2012. Land urbanization has the greatest impact on ESV among the four subtypes of urbanization indicators. Urbanization and ESV show the synergy relationship mostly in the eastern region, accounting for 18.18% of the total 110 cities. By contrast, they present the trade-off relationship in northern, southern and central regions, occupying 47.27% of the total observations. This study is helpful to provide scientific suggestions regarding the development of new urbanization, the protection of ESV, and the issue of how to achieve synergistic and sustainable development between them.

Optimizing Planting Density to Increase Maize Yield and Water Use Efficiency and Economic Return in the Arid Region of Northwest China

High grain yield and water use efficiency (WUE) are the key goals when producing maize (Zea mays L.) under irrigation in arid areas. Increasing the planting density and optimizing irrigation are important agronomic practices for increasing the maize grain yield and WUE. A two-year field experiment was conducted to investigate the effects of planting density and irrigation on the maize grain yield, WUE, and economic return of spring maize under a mulch drip irrigation system in Xinjiang, Northwest China. The experiment included four irrigation levels and five planting densities. The results showed that the reduction of irrigation decreased the yield and evapotranspiration (ETc) but improved the WUE. Increasing the planting density increased the ETc, but there was a quadratic curve relationship between yield and WUE and planting density. Treatment with 600 mm of water and 12 plants m−2 obtained the highest grain yield (21.0–21.2 t ha−1) and economic return (3036.0 USD ha−1) and a relatively high WUE (2.64–2.70 kg kg−1). Therefore, a reasonable increase in planting density and an appropriate reduction of irrigation combined with drip irrigation under a mulch system can simultaneously achieve high yields and economic return and high WUE in maize production.

Surface plasmon resonance sensor based on D-shaped photonic crystal fiber for low refractive index detection

A D-shaped photonic crystal fiber (PCF) low refractive index (RI) sensor based on surface plasmon resonance (SPR) is proposed, and its properties are investigated by the finite element method. Gold is selected as the plasmonic material and coated on the open-ring structure to excite the plasmonic modes. The simulation results indicate that the sensor can detect the RI in the range of 1.00 to 1.29, which is a fairly wide detection range in the detection field of SPR-based PCF low RI sensors. When the analyte of the RI varies from 1.28 to 1.29, the maximum sensitivity of 10,000 nm / RIU and the corresponding resolution of 1 × 10 − 5 RIU are obtained in the wavelength range of 1.6 to 2.4 μm. When the RI of the analyte changes from 1.00 to 1.29, the relationship curve between the RI and the resonance wavelength fits well, and the adjusted R2 value is 0.99609. Furthermore, the sensor achieves the figure of merit of 56.98 RIU − 1 and an amplitude sensitivity of 82.76 RIU − 1, respectively. Therefore, the designed sensor can be effectively applied to low RI detection, having a certain commercial potential in medical detection, organic chemistry detections, and related applications.

Application of tabular data synthesis using generative adversarial networks on machine learning-based multiaxial fatigue life prediction

Machine learning has gradually developed into a new and effective scheme for fatigue life prediction. The novelty of this work is the proposal and verification of using virtual synthetic multiaxial fatigue data as input of machine learning models. First, the data generated by tabular generative adversarial networks are applied to machine learning models for life prediction. Then based on equivalent stress (strain) amplitude-life relationship curve, a multiaxial fatigue data generation evaluation metric is proposed. Finally, the effect of the generated sample size on the predictions of machine learning models is investigated. The method is demonstrated on 5 multiaxial fatigue data sets. The results indicate the synthetic data help machine learning models arrive at good life prediction ability. Using this method will help expand the application of machine learning-based multiaxial fatigue life prediction.

Experimental and Numerical Study on Dou-Gong Joint of Ancient Wooden Structure in Qing Dynasty

ABSTRACT Three full-scale Dou-Gong specimens at column tops are made according to the Qing Dynasty “code of engineering practice,” based on the prototype of one Dou and two Sheng Jiaomaye Dou-Gong of Jiayuguan tower. The three-dimensional load-displacement curve of Dou-Gong is obtained using three-dimensional static loading tests. Furthermore, the deformation characteristics, three-dimensional compression stiffness, and three-dimensional load transfer law of each layer of the Dou-Gong are analyzed. The test results indicate that the vertical failure characteristics of the Dou-Gong are the splitting of the Flat-Fang, and there is no obvious damage to the horizontal members until toppling. The three-dimensional load-displacement relationship curve of the Dou-Gong can be simplified to a two-fold line model, vertical stiffness of the Dou-Gong is significantly greater than the horizontal stiffness, and the horizontal stiffness in the beam direction is greater than the horizontal stiffness in the Fang direction. Using ABAQUS software, a comparative analysis of the difference in mechanical properties between the Dou-Gong at the column tops and the Dou-Gong between the columns is performed. The research results can provide a theoretical basis for the structural performance safety assessment and preventive protection of the Jiayuguan tower and similar Chinese ancient wooden structures.

Method of measuring the stress of ferromagnetic materials based on EMAT and magnetic Barkhausen noise characteristic parameters

The magnetostrictive properties of ferromagnetic materials are related to their microstructure which varies between different stress states. This paper proposes a new method of stress detection based on EMAT (electromagnetic ultrasonic transducer) to better identify the early defect and stress state of materials. For experimental verification, an experimental platform consisting of cantilever beam, strain gauge and EMAT detection system was constructed. Compared with the traditional method of magnetostrictive effect detection, the transmitter and the receiver were deployed in 7 different ways to explore the relationship between electromagnetic ultrasonic signal and stress. According to the amplitude of EMAT signal and the intensity of magnetic field as obtained under different stress states, the relationship curves between them were drawn, with ten representative EMAT characteristic parameters selected. In addition, BP (back propagation) neural network was applied to establish the mapping relationship between the electromagnetic ultrasonic characteristic parameters and the stress state of the specimen, and the material stress was predicted with the maximum error of 8.10%. Moreover, BP neural network was adopted to combine EMAT characteristic parameters with Barkhausen characteristic parameters for establishing the mapping relationship between the characteristic parameters and stress state of specimen. The research results show that the accuracy of quantitative prediction was improved for material stress, with the maximum error reaching 6.27%.

The Relationship between Trade Liberalization, Financial Development and Carbon Dioxide Emission—An Empirical Analysis

In recent years, the global economy has become more closely related among countries, and people’s pursuit of economic growth has caused the destruction of the environment. This paper selected panel data from 30 provinces in China from 1997 to 2020 to investigate the dynamic relationship between trade liberalization, financial development and carbon dioxide emissions by constructing a PVAR model. We also consider technology as an important variable for studying the effect on carbon dioxide emissions. We draw the following conclusions. First, financial development promotes carbon dioxide emissions, while trade liberalization has no significant impact on carbon dioxide emissions. Second, China’s trade liberalization promotes financial development, which has limited support for international trade. Third, there is a two-way causal relationship between financial development and carbon dioxide emissions, and there is also a two-way causal relationship between trade liberalization and financial development. Finally, there is a significant inverted “U” curve relationship between trade liberalization and innovation efficiency, environmental regulation and innovation. According to the results, we believe that openness to trade impacts emissions of carbon dioxide, opening a new function path: namely, trade openness and financial development result in high carbon dioxide emissions; consequently, China has relied on this process in the development of their financial system.

Associations between Physical Fitness Index and Body Mass Index in Tibetan Children and Adolescents in Different High-Altitude Areas: Based on a Study in Tibet, China.

Objective: To investigate the relationship between physical fitness index (PFI) and body mass index (BMI) of Tibetan children and adolescents in different high-altitude areas in Tibet, China. Methods: Using the stratified cluster sampling method, 3819 Tibetan children and adolescents from three different high-altitude areas including Nyingchi, Lhasa and Nagqu in the Tibet area of China were given grip strength, standing long jump, sitting forward bend, 50 m running and endurance running tests. One-way analysis of variance was used to compare the physical fitness index in different high-altitude areas. In addition, the method of curve regression analysis was used to analyze the relationship between PFI and BMI. Results: In general, the level of PFI in Nagqu, Tibet, China was lower than that in Nyingchi and Lhasa, and the levels of girls were generally lower than those of boys. The proportions of malnourished, normal, overweight and obese Tibetan boys in high-altitude areas were 11.8%, 79.7%, and 8.5%; those of girls were 3.3%, 82.3%, and 14.4%, respectively. The curve regression analysis showed that the model fitting of male Nyingchi, Lhasa, Nagqu and female Nyingchi, Lhasa, Nagqu were all significant (F values were 29.697, 34.709, 37.500, 9.123, 9.785, 6.939, p < 0.01). The relationship between BMI and PFI generally showed an inverted “U” curve relationship. Conclusion: The negative impact of overweight and obesity on physical fitness of Tibetan boys in high-altitude areas is significantly higher than that of girls, and the negative impact of overweight and obesity on physical fitness of boys in Lhasa and Nyingchi area is more significant than that in the Nagqu area. In the future, attention should be paid to Lhasa and the occurrence of overweight and obesity among Tibetan boys in Nyingchi area in order to prevent the sharp decline of physical fitness and promote the physical and mental development of Tibetan children and adolescents in high-altitude areas.