The Relationship Between Fundamental Motor Skills and Physical Fitness in Children Aged 7-12 Years

The purpose of this study was to examine the relationship between fundamental motor skills (FMS) and physical fitness (PF) in children aged 7-12 years. The participants were 217 children (50.7% female) from a primary school in Shanghai. The FMS was assessed using Chinese version Test of Gross Motor Development–3 edition (CTGMD-3), which includes 6 locomotor skills and 7 ball skills. PF was measured following China’s national physical health standards for students, which includes BMI, vital capacity, sit and reach, 50m sprint, one-minute rope jumping, one-minute sit-ups and 50m * 8 shuttle run. The weighted score of the 7 tests was calculated to represent the performance of PF. Four participants were assigned into one group and took all tests within a physical education class. Two well-trained graduate assistants performed the tests within one month. Descriptive statistics were computed after checking the normality of the scores of CTGMD-3 and PF. Pearson correlation was used to determine the relationship between FMS and PF. The significance level was set at 0.05. The results showed a significantly positive correlation between the CTGMD-3 score and PF score (r = 0.166, p = 0.014). There was a significantly positive correlation between the score of locomotor skills and PF scores (r = 0.269, p \u3c 0.01). No significant correlation between the score of ball skills and PF score (r = 0.065, p = 0.338) was found. It is concluded that FMS, especially locomotor skills, was associated with PF among children aged 7-12 years. The generalizability of this study was limited since the participants were from one primary school in Shanghai. The small sample size might limit the power of this study. Future research is needed to explore the mechanism underlying the relationship between FMS and PF

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

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

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

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

Influence of pressure, coal structure and permeability on CBM well productivity at various burial depths in South Yanchuan Block, China

With a burial depth of 1000 m as the demarcation, the coal reservoir in South Yanchuan Block, China is divided into deep reservoir and shallow reservoir regions. A combination of coalbed methane well production data, well logging interpretation, coalbed methane numerical simulations and reservoir properties were used to research various production characteristics at different depths. The results indicate that coal thickness and gas content are not key factors that influence methane production. The shallow reservoir is located in a tension zone, while the deep reservoir is located in both a transformation zone and a compression zone. Although the reservoir and closure pressures increase with the burial depth, the pressures fluctuate in the deep reservoir, especially in the transformation zone. This fluctuation influences the opened degree of the fractures in the reservoir. The effective stress is lower in the deep reservoir than in the shallow reservoir, leading to higher permeability in the deep reservoir. This difference in effective stress is the key factor that influences the methane production. The combination of coal thickness and gas content also significantly influenced the methane production. Influenced by the reservoir and closure pressures, the Type III coal in the shallow reservoir is more developed, while the deep reservoir contained more developed Type I and Type II coal. The permeability increases exponentially with increasing thickness of Type I and Type II coal, which determines the high reservoir permeability in the deep reservoir. The development of Type III coal leads to the poor reservoir hydraulic fracturing effect. However, a reservoir with thick Type I and Type II coal can have a positive effect. Influencia de la presión, la estructura del carbón y su permeabilidad sobre la productividad de gas metano de carbón en profundidades de enterramiento del bloque Yanchuan Sur, ChinaResumenCon una profundidad de enterramiento de 1000 metros, el yacimiento de carbón del bloque Yanchuan Sur, en China, se divide en dos: el depósito profundo y el depósito superficial. Este trabajo combina los datos de la información de producción de gas metano asociado carbón, la interpretación de registros de pozo, las simulaciones numéricas de metano asociado a carbón y las propiedades del reservorio para encontrar las características de producción a diferentes profundidades. Los resultados indican que el espesor del carbón y el contenido de gas no son factores que alcancen a influir en la producción de metano. El depósito superficial se encuentra en una zona de tensión, mientras el depósito profundo está ubicado en una región tanto de transformación como de compresión. Aunque el reservorio y la presión de cierre se incrementan con la profundidad de enterramiento, las presiones fluctúan en el depósito profundo, especialmente en la zona de transformación. Esta fluctuación influye en el grado de apertura de las fracturas en el depósito. La tensión efectiva es más baja en el depósito profundo, lo que significa una mayor permeabilidad. La diferencia en la tensión efectiva es el factor clave que incide en la producción de metano. Afectado por las presiones de cierre y del yacimiento, el carbón tipo III en el depósito superficial está más desarrollado, mientras que el depósito profundo contiene carbón tipo I y tipo II más desarrollado. La permeabilidad se incrementa exponencialmente con el incremento del espesor en el carbón tipo I y tipo II, lo que determina la alta porosidad en el depósito profundo. El desarrollo de carbón tipo III lleva a un pobre efecto de la fractura hidráulica en el depósito. Sin embargo, un depósito con carbón tipo I y tipo II espeso podría tener un efecto positivo

Research on adsorption characteristics of main coal seams of Bide-Santang basin in Western Guizhou, China

The adsorption isotherms of Bide-Santang Basin's main coal seams is studied based on analyzing two coalbed methane (CBM) wells in Huale exploration region and testing the coal samples. A conclusion has been made that the adsorption capacity of Bide-Santang Basin's main coal seams is high. The Langmuir volume (VL) of dry ash-free basis range from 17.69 m3/t to 21.38 m3/t, and the average is 19.46 m3/t. The methane saturation of the coal reservoir is lower than 100%, ranging from 75.04% to 105.55% commonly, and the average is 84.51%. It indicates that coal reservoir in the research area is undersaturation. The critical desorption pressures are between 1.22MPa and 9.1MPa, and the average is 3.25MPa. The coalbed methane theory recovery rates are between 19.96% and 46.15% with average of 34.51%

Research on the Abnormal Isothermal Adsorption of Shale

The adsorption content of the shale sample and pure clay minerals decreased at a high pressure and clearly declined for pure clay minerals. With the increase in the test pressure, the degree of deviation between the gaseous phase CH₄ density increment rate and the adsorbed phase CH₄ mass increment rate decreased, which resulted in a decrease in the methane adsorption values calculated at a high pressure. As the test pressure increased, the measurement volume of the shale sample and the pure clay minerals decreased. In the adsorption measurement, the diameter of CH₄ is larger than that of He, with the development of the micropores in shale; the actual measurement volume was larger compared to that in the buoyancy measurement. Accompanied by the increase in the test pressure and adsorption, the volume of the adsorbed phase CH₄ should also be considered in the calculation performed in the adsorption measurement. All of these factors have reinforced the calculated degree of reduction of methane adsorption at a high pressure. Besides the adsorption capacities of different pure clay minerals being different, the content and types of pure clay minerals also affected the adsorption capacity of shale at a high pressure

Geochemical characteristics of produced water from coalbed methane wells and its influence on productivity in Laochang Coalfield, China

The water produced from the coalbed methane (CBM) wells contains abundant geochemical information, which is of great significance in evaluating the productivity of these wells. Based on the data of water produced from five CBM wells, geochemical characteristics of the produced water and its influence on the productivity of the wells are analyzed in Laochang Block. The results show that with the increase in the produced water of the five wells, δD and δ18O show a downward trend in general, reflecting that the influence of coal seams and surrounding rock on the produced water is weak, while the water–rock interaction of the Y-3 and Y-5 wells is more stable than that of the Y-1, Y-2, and Y-4 wells. Combining the water production characteristics of the Y-3 and Y-5 wells with better drainage and recovery effects, it is proposed that 0 ≤ σM < 0.3 and 0 ≤ σY < 600 or 0.7 < σM < 0.8 and 1,200 < σY < 1,300, and the fluctuation ranges of Ca2+, Mg2+, HCO3− and SO42− can provide a basis for quantitative characterization and evaluation of CBM well production

Geochemical Characteristics and Productivity Response of Produced Water from Coalbed Methane Wells in the Yuwang Block, Eastern Yunnan, China

Coalbed methane (CBM) well-produced water contains abundant geochemical information that can guide productivity predictions of CBM wells. The geochemical characteristics and productivity responses of water produced from six CBM wells in the Yuwang block, eastern Yunnan, were analyzed using data of conventional ions, hydrogen and oxygen isotopes, and dissolved inorganic carbon (DIC). The results showed that the produced water type of well L-3 is mainly Na-HCO3, while those from the other five wells are Na-Cl-HCO3. The isotope characteristics of produced water are affected greatly by water-rock interaction. Combined with the enrichment mechanisms of isotopes D and 18O, we found that the water samples exhibit an obvious D drift trend relative to the local meteoric water line. The 13C enrichment of DIC in the water samples suggests that DIC is mainly produced by the dissolution of carbonate minerals in coal seams. The concentration of HCO3-, D drift trend, and enrichment of 13CDIC in produced water are positively correlated with CBM production, which can be verified by wells L-4 and L-6