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In this present work, cement slurry flowing in well annuli with narrow or varied radial sizes is investigated, whose purpose is to precisely calculate the equivalent circulating density (ECD) during well cementing in the petroleum industry. The theoretical Metzner-Reed (MR) method and the direct numerical simulation (DNS) are applied to calculate the cementing ECD for different types of cement slurries by considering both the Bingham and Power-Law rheological models. The cementing ECD calculated by the theoretical MR method is verified to be in accordance with the DNS result. Moreover, for the narrow annulus, the cementing ECD is demonstrated to be sensitive to the rheological model. In addition, based on the obtained DNS results, the accuracies of the cementing ECD calculated by three commercial software, including DRILL BENCH (DB), LANDMARK (LM), and PVI, are compared, to determine their corresponding adaptability for different rheological models. According to the detailed comparisons, LM shows the highest accuracy in calculating the cementing ECD for the Power-Law fluid, while PVI is optimal for the Bingham fluid. However, sharp fluctuations of the calculation errors are observed when DB is applied. [ABSTRACT FROM AUTHOR]

As the climate change effects of traditional energy consumption are more pronounced, renewable energy has become increasingly essential in meeting electricity demands and mitigating carbon emissions. Based on the spatial autocorrelation analysis and carbon emission avoided analysis, this study depicts the photovoltaic power geographies, analyzes the spatial-temporal characteristics, and measures the carbon emission reduction potentials of China's photovoltaic power installation by province. Five stages of the photovoltaic power installation including Full operation, Partial operation, Announced construction , Permitted construction , and Under construction are classified. Overall, the provinces with higher installed capacities and emission reduction potentials are mainly distributed in the North and Northwest China, including Inner Mongolia, Qinghai, Ningxia, and Hebei. From the spatial autocorrelation analysis, Inner Mongolia, Shaanxi, and Shanxi belong to the high-high cluster, while most provinces in South China are among the low-low cluster. In terms of cumulative carbon emission reduction, Inner Mongolia, Gansu, Qinghai, Ningxia, Shaanxi, and Xinjiang are main contributors. By comparing the spatial and temporal evolution, geographical characteristics, and low-carbon reduction of photovoltaic power installation in China's provinces and regions, this study provides quantitative supports and feasible suggestions for the achievement of low-carbon targets and sustainable development of China's photovoltaic industry. [ABSTRACT FROM AUTHOR]

In this paper, a dynamic model of an offshore drilling riser is developed based on the Hamilton principle. The developed dynamic model is transformed into a finite element model by introducing an approximate solution which chooses the Hermite cubic interpolation function of bending beam element as the shape function. Thereafter, the standard Newmark integration is applied to numerically simulate the dynamic responses of offshore drilling risers with varied system parameters, including the length of riser, top tension ratio, and buoyant factor. Based on the results of numerical simulation, under the influences of sea wind, sea current, and the periodic excitation of sea wave, the offshore drilling riser experiences a fast lateral deflection phase in the beginning, a reciprocating deflection phase in the following long duration, and then, a periodic oscillation when it reaches the dynamic stable condition, respectively. The riser system working in deeper water with a higher top tension ratio and a lower buoyant factor shows more controllable vibration and less lateral deflection. [ABSTRACT FROM AUTHOR]

Highlights • The dynamic responses of a bit-rock system with both the linear and nonlinear interaction models are verified as similar. Hence, the linear model is suggested to predict the system dynamics due to its higher computing efficiency. • An isola of period-doubling bifurcations is observed during two-parameter continuation, and the isola is formed via two turning points which lie on its left and right endpoints. • As the increase of either excitation amplitude or static force, the ROP of the stable period-one motion can be promoted almost linearly. While, the increase of excitation frequency will lead to a nonlinear decrease of the ROP. Graphical abstract Abstract This paper presents a comprehensive numerical study of a higher order drifting oscillator that has been used to model vibro-impact drilling dynamics in previous publications by our research group [1,2,3,4,5,6,7,8,9]. We focus on the study of the bit-rock interactions, for which both linear and nonlinear models of the drilled medium are considered. Our investigation employed a numerical approach based on direct numerical integration via a newly developed MATLAB-based computational tool, ABESPOL (Chong et al., 2017) [10], and based on path-following methods implemented via a software package for continuation and bifurcation analysis, COCO (Continuation Core) (Dankowicz and Schilder, 2013) [11]. The analysis considered the excitation frequency, amplitude of excitation and the static force as the main control parameters, while the rate of penetration (ROP) was chosen as the main system output so as to assess the performance of the system when linear and nonlinear bit-rock impact models are used. Furthermore, our numerical investigation reveals a rich system dynamics, owing to the presence of codimension-one bifurcations of limit cycles that influence the system behaviour dramatically, as well as multistability phenomenon and chaotic motion. [ABSTRACT FROM AUTHOR]

A complete dynamic model of an offshore drilling tube system with pipe-in-pipe structure is developed in this paper. Specifically, the riser and well are connected at well head to constitute an outer pipe, within which, the drillstring stretching from the drilling platform to downhole is viewed as an inner pipe. The interactions between the inner and outer pipes are described by a series of spring-friction units along the pipe-in-pipe structure. Comparing with the previously published models which mainly focus on the drilling riser, the pipe-in-pipe structure is applied in this new model; moreover, the tube system under the mud line is also considered as an extension of the tube system submerged in the sea. The developed dynamic model is simulated using the finite element (FE) method in Abaqus. Under the same ocean environmental loads, the maximal lateral deflection for the pipe-in-pipe structure is less than that only considering the drilling riser. This finding indicates that, for an actual offshore drilling tube system with the pipe-in-pipe structure, it has stronger capacity of maintaining reliability under heavy ocean environmental loads. Based on the newly developed dynamic model, multi-objective optimization design of the offshore drilling tube system is conducted in Isight. A new flow path of the optimization is designed. Specifically, six-sigma method is adopted to drive genetic algorithm to run the multi-objective optimization, and simultaneously drive Monte Carlo method to analyze the reliability of the obtained optimal solution. Comparing with a series of single-objective optimization designs, the global optimization degree of the obtained multi-objective optimal design is verified as the best. [ABSTRACT FROM AUTHOR]

Carbon footprint (CF) and inequality reductions were two of the most important sustainable development goals. However, there was a lack of understanding of the latest equality of carbon footprint across regions. Based on the multi-regional input-output table and the China Family Panel Studies survey data of 17 provinces, this paper examined the evolution of carbon footprint and inequality in China. The results showed a stark disparity between regions and a declined inequality in the last few years. Specifically, the CF per capita in northern provinces (Liaoning, Shanxi, Heilongjiang, Shandong and Shaanxi) exceeded the average level in 2017. From 2015 to 2017, the carbon inequality showed a downward trend, with a national CF-Gini coefficient decrease from 0.31 to 0.28. Meanwhile, the gap between CF per capita in urban areas and rural areas was declining, with a growth rate at 18% and 32% from 2015 to 2017, respectively. In addition, CF per capita from various consumption categories indicated that household equipment and daily necessities, residential, transportation and communication were the three most important sources, with a downward trend from 2015 to 2017. This study would provide policymakers with deep insights into policies to achieve just transition. [ABSTRACT FROM AUTHOR]

A drillbit-rock vibro-impact system with a linear rock contact law is considered in this paper. This system is a simplified model to study the drillbit oscillation in a percussive drilling system. The main purpose of this work is to explore the optimized vibration condition of the drillbit to improve the drilling efficiency in practical drilling applications. In order to eliminate the influences of drilling progression on the dynamic analysis of drillbit oscillation, the drillbit oscillation is separated from its drift via oscillation reconstruction. The obtained bounded mathematical model is analyzed by numerical integration and numerical continuation. Based on the codimension-one bifurcations detected by TC-HAT during one-parameter continuation, the two-parameter bifurcation curves are traced by two-parameter continuation. These explored two-parameter bifurcation curves constitute the parameter boundaries for the period-one one-impact oscillation of drillbit, which is verified as the optimal oscillation with the highest drilling efficiency. [ABSTRACT FROM AUTHOR]

This paper introduces a dynamic method for the stiffness identification of an impacted object via analysis of its corresponding impact duration. To accurately detect the impact durations from experimental signals, nonlinear time series methods are applied. Two low-dimensional dynamical systems, including a piecewise-linear impact oscillator and a rock impacting system, are studied experimentally and numerically to demonstrate the proposed method. Meanwhile, the analytical prediction of the impact duration for the period-one one-impact motion is developed. The results of both systems indicate that, for a certain stiffness, the impact duration of the period-one one-impact motion is nearly constant. The higher the stiffness, the lower the impact duration. This monotone correlation provides a mechanism to estimate the stiffness of the impacted object once the impact duration has been accurately detected. The developed method can be used to optimise percussive drilling parameters. [ABSTRACT FROM AUTHOR]

The dynamics of a self-propelled capsule robot for small-bowel endoscopy driven by its internal vibro-impact excitation is studied in this paper. Due to its complex anatomy, the frictional environment in the small bowel is uncertain, so this work aims to maintain the progression of the robot at a desired velocity in the presence of such an uncertainty by using a new optimisation method. The optimisation method consists of the Six Sigma and the Multi-Island Genetic algorithms, and its reliability analysis is carried out with the consideration of parametric and environmental uncertainties by using the Monte Carlo algorithm. In total, five different motions of the capsule, including fast, slow, forward, backward and hovering, are optimised. Extensive numerical studies show that the five desired motions can be fulfilled by various combinations of system and control parameters. Experimental verification is also carried out using a capsule prototype to demonstrate the efficacy of the proposed method. A mismatch between the numerical optimisation and the experimental results for the backward motion of the prototype was observed. However, optimisations for forward and hovering motions show good agreements with experimental observations. Potentially, the proposed approach can be used for optimising various progressive robots in different scales with multiple control objectives and constraints. [Display omitted] • The dynamics of a capsule robot for small-bowel endoscopy is studied. • Robot's velocity is optimised in the presence of frictional uncertainty. • It combines various optimisation algorithms with a reliability analysis. • Numerical and experimental results are compared to validate its efficacy. • It suits for the robots with multiple control objectives and constraints. [ABSTRACT FROM AUTHOR]

Controllable dynamic behavior of an offshore drilling tube system is significant to secure the operation safety for deep water drilling. In the present work, a dynamic model of a drilling riser system is developed based on Hamilton's principle; and the corresponding finite element model is obtained via introducing the Hermite cubic interpolation function of a curved beam element. In order to consider the effect of the vibration of drill string on the dynamics of drilling riser, a new drift element model is proposed to describe the interaction between the riser and the drill string, and thus a coupled finite element model for the drilling tube system with pipe-in-pipe structure is developed according to the virtual work principle. The Newmark integral method is used to solve the mathematical model numerically; moreover, the obtained dynamic response of the pipe-in-pipe system is further verified and modified according to different collision states. The system dynamics are analyzed in both the frequency domain and the time domain, the vibration of the drill string is demonstrated to restrict the lateral deflection of the riser system; hence, for an actual offshore drilling tube system with pipe-in-pipe structure, it has stronger capacity of maintaining stability and reliability to overcome heavy ocean environmental loads. In addition, in order to effectively control the lateral deflection of the drilling riser, the strategy with high top tension and low buoyancy coefficient is suggested. [ABSTRACT FROM AUTHOR]

• Consumption, international trade, and carbon emissions were examined in Japan. • Carbon emission transfers among sectors/countries were identified from 2000 to 2014. • Japan was found to be an emissions net import country (58% of emissions from China). • Household consumption accounted for ∼60% of consumption-based emissions. • These findings can help Japan customise sectoral carbon reduction priorities. International trade accelerates the separation between consumption and production on a global scale, thus leading to carbon transfer. Consequently, carbon flow embodied in international trade reallocates global carbon emission responsibilities, consisting of domestic demand and imports but excluding exports. To tackle the geographic flow of emissions embodied in products and services, carbon emissions must be quantified according to the global value chains. Using Japan as a case study, this study tracked the evolution of consumption patterns, international trade, and related carbon emissions based on multi-regional input-output tables, and carbon emissions inventories. Carbon emission transfers among sectors and countries were identified from 2000 to 2014. As a result, imports from the industrial sector led to a gap between production- and consumption-based carbon emissions. Japan was found to be an emissions net import country over the study period, with about 58% of the total carbon emissions inflow coming from China. Moreover, household consumption accounted for nearly 60% of consumption-based emissions, with industrial sector products and services being the primary source of carbon inflow, and the service, transport, and industry sectors are responsible for the majority of domestically released emissions. These conclusions provide valuable information for Japan to customize sectoral carbon reduction priorities, an essential component of setting decarbonization goals from the consumer perspective. [ABSTRACT FROM AUTHOR]

• The axial vibration condition of indenter is verified to be independent to the rock rotation. • In order to obtain powerful impacts, the high excitation frequency and amplitude are suggested; however, the high pneumatic pressure should be avoided since it can trigger the chattering of indenter. • The linear force-penetration correlation of rock is better to simulate the deformation of hard rocks under impacts rather than soft rocks with high ductility. This paper focuses on the experimental verification of a dynamical model describing percussive drilling. The design of the experimental apparatus is introduced firstly, and then the dynamic interactions between rock and indenter are studied experimentally by varying three control parameters, including frequency and amplitude of excitation, and pneumatic pressure applied on the indenter. Additionally, the influence of rock stiffness is analyzed by testing different rock-indenter combinations. Meanwhile, the corresponding numerical simulations were conducted showing good agreements with the experimental results. According to the detailed bifurcation analyses, the dynamic responses of indenter mainly display period-one motions which can further develop into period-two motions via period-doubling bifurcation scenarios, or even chaotic motions by period-doubling cascade. The chaotic vibration of indenter can also return to periodic motions via inverse period-doubling bifurcation or fold bifurcation. Although the period-one motion is the main dynamic response in the considered parameter ranges, its impact number per excitation period varies with parameters, which directly affects the maximal impact acceleration of indenter. This results in more energy being dissipated during repeated weak impacts. Therefore, strong impacts are obtained if the indenter is exhibiting the period-one with one-impact motion. For such a purpose, high excitation frequency and amplitude are suggested, however, the high pneumatic pressure should be avoided since it can trigger chattering of the indenter. [ABSTRACT FROM AUTHOR]

Based on data of the manufacturing sector of China and Japan from 2003 to 2016, this paper attempts to measure the progresses in energy-biased technology and energy efficiency by constructing a threshold panel regression model with variables including foreign direct investment (FDI) and energy consumption structure to explain energy efficiency using energy-biased technology as the key explaining variable. The estimation indicates significant differences in the energy efficiency of China's and Japan's manufacturing industries. In general, Japan's total energy efficiency is higher than China's. The industry with more intensive technology has higher energy efficiency which rises much faster. The paper finds that the energy efficiency of China's manufacturing sector shows an upward trend in general, while Japan's fluctuates more, showing two peaks and two troughs. Our empirical results show that there is a threshold value of progress in energy-biased technology; below this, progress in energy-biased technology will have a positive effect on energy efficiency and beyond it, the effect will be negative. Since this effect is not one-way, we define it as a 'double-edged effect'. It is estimated that the level of energy-biased technology progress of most manufacturing industries in China is below the threshold value, indicating that the technology progress in China's manufacturing sector has not been excessively biased towards energy consumption, and the impact on energy efficiency is still positive. The China-Japan comparison shows that the threshold value for Japan's manufacturing sector is significantly lower than that for China's, indicating a marginal effect on the 'double-edged effect': The threshold value will decrease when energy efficiency reaches a certain level. Therefore, it is necessary to offset these negative externalities from technological progress with other factors such as by increasing FDI and improving energy consumption structure. • This paper examines the influence of energy-biased technological progress alone on energy efficiency. • It proves the influence of energy-biased technological progress on energy efficiency to be nonlinear. • It measures the energy-biased technological progress and energy efficiency of some industries of the manufacturing sector of China and Japan. • It proves the rebound effect to be conditional in the manufacturing sector of China and Japan. • It also proves the threshold effect in the influence of energy-biased technological progress on energy efficiency. [ABSTRACT FROM AUTHOR]

• Location quotient, supply and consumption linkages are selected to measure localisation economies. • Localisation economies and IPRs protection can explain entrepreneurship well. • The effects of IPRs protection at both prefecture and provincial levels are significant in all models. • Multi-level and random parameters models are more suitable than the simple NB model for the process of modelling entrepreneurship with hierarchically structured data. Entrepreneurship is an important determinant of innovation and growth with an uneven spatial distribution. In addition, the mechanism of entrepreneurship is affected by administrative hierarchies. However, the driving forces behind the spatial differences are not clear. Therefore, this study aims to examine the key determinants of entrepreneurship by clarifying the roles of localisation economies and intellectual property rights (IPRs) protection from 2008 to 2017 using a Bayesian analysis of multi-level spatial correlation. The empirical results indicate that localisation economies and IPRs protection have a major influence on entrepreneurship. In particular, although it is insignificant, the role of localisation economies at prefecture level is important, because the impact of supplier linkages at provincial level is negative. The effects of IPRs protection at both prefecture and provincial levels are significant in all the models, and its effect increases with the improvement in model performance. Moreover, these determinants vary across different spatial scales. [ABSTRACT FROM AUTHOR]

Bisphenol A (BPA) is a common endocrine disruptor and a high-fat diet (HFD) also affects fertility. However, little is known about the long-term consequences of simultaneous exposure to BPA and a HFD on reproductive health. Herein, we assessed the effects of maternal exposure to BPA in combination with a HFD on reproductive function in subsequent generations of female mice and evaluated its effects on the hypothalamic-pituitary-gonadal axis. We found that the combination of maternal exposure to BPA and a HFD led to increased urine BPA levels, precocious puberty, altered estrous cyclicity, decreased follicle numbers, and altered hypothalamic Kiss1 methylation status in F1 and F2 mice. Therefore, we demonstrated that maternal exposure to BPA in combination with a HFD exerts a trans-generational effect on female reproduction. • BPA exerts toxic effects on reproduction and other physiological functions. • Combined maternal BPA and HFD exposure increases urine BPA levels. • Maternal exposure to BPA and a HFD induced dystocia and prolonged pregnancy. • Mice exposed to BPA alone showed high infertility rates. • HFD exacerbates the reproductive dysfunction caused by chronic BPA exposure. [ABSTRACT FROM AUTHOR]

Controlling coal dust pollution is confronted with numerous challenges in the demanding environment of deep mining. Chemical additives, imidazolium ionic liquids (ILs), have been considered an effective strategy to boost the hydrophilicity of coal and reduce dust emissions. This work conducted experiments with molecular dynamics (MD) simulation to study the wetting characteristics of ILs ([Emim][Cl], [Bmim][Cl], and [Hmim][Cl]) with different chain-length on coal. The static wettability tests results indicated that the wettability of ILs was improved as the chain-length increased, and the wettability on bituminous coal followed the rule of water<[Emim][Cl]<[Bmim][Cl]<[Hmim][Cl]. The dynamic dust suppression experiments in the roadway showed that the dust suppression efficiency of 2% [Hmim][Cl] reached 77.5%, 2.45 times that of water. The ESP and frontier orbital energy show that the chain-length increase can enhance the ILs activity. The MD results indicated that short-chain ionic liquid ([Emim][Cl]) tends to accumulate on the surface of coal molecules, whereas long-chain ionic liquid ([Hmim][Cl]) possesses the capability to permeate coal molecules and serves as a tunneling role between coal and water, thereby enhancing the hydrophilicity of bituminous coal. The research results could be used to determine and design ILs with excellent wetting performance for improving the coal dust suppression effect. • The large-scale tunnel dynamic spray dust reduction experiment with ILs for the first time. • As The chain length of ILs increases, the hydrophobicity of bituminous coal gradually decreases. • The wetting mechanism of ILs under the influence of chain length was analysed. [ABSTRACT FROM AUTHOR]