Upstream Position Research Articles

Numerical simulation of wake flow around two square cylinders through passive control method

Two-dimensional numerical simulations are performed to study the effect of height of control plates placed at the downstream location in a vertical direction of a channel for flow past two inline square cylinders. The numerical method used is the lattice Boltzmann method (LBM) and Reynolds number is kept constant at Re = 150 (Re = Uinf d/ν) for fixed gap spacing g = 3.5 (g = s/d). The height of the control plate varies from h = 0.1 to 8. First, the validity of code for the present problem and suitable grid points are checked along the selection of uniform inflow velocity. After that verification, the numerical simulations are performed to obtain the results under the effect of height of control plates using the passive control method. Calculated results are, in terms of vorticity contour, drag and lift coefficients, pressure contour, energy spectrum, and force statistics. Under the discussion of vorticity contour visualization, we obtained six types of flow mode and named them according to flow behavior and their characteristics. In pressure contour, it is visualized that the maximum pressure occurred at near the upstream position of the first cylinder as well as the upper and lower edge of the main cylinder as compared to the downstream cylinder and control plate, but at some position inside the domain, pressure contour contained negative values as well in between the gap of two square cylinders and control plate. In force statistics, we computed the values of Cdmean, Cdrms, Clrms, and St. Mean drag coefficients for both upstream cylinder (C1) and downstream cylinder (C2) are increased as the height of the control plate increased from 0.1 to 1.5, but as the height of the control plate reached its maximum value, the value of Cdmean turned toward the decline. The maximum value of Cdmean obtained at h = 2.25 and the minimum value occurred at h = 8. For cylinder C2, negative values for some selected heights such as h = 0.1–1.25 and h = 4–8 are also observed because of thrust. The value of the Strouhal number for both the cylinders C1 and C2 are similar at h = 0.1–4.5, but at h = 5, the values of the Strouhal number differ for both cylinders, but at the largest values of control plate's height, i.e., h = 6–8, the Strouhal number contains zero values for both cylinders C1 and C2. At these zero values of the Strouhal number, in vorticity contour jet type of flow mode is observed at h = 6–8, as a new flow mode, which is not identified before in the passive control method for flow past two or more square cylinders.

Investigation of the causality between participation in global value chains and CO2 emissions between developed and developing countries

The production and consumption activities are cross-border and therefore, it is important to understand the role of Global Value Chains (GVCs) in fulfilling a country’s specific climate commitments. This study examines the causal relationship between selected GVC indices and CO2 emissions. We use the GVC position index, considered robust in comparison to the frequently used GVC participation index, for determining the impact on emissions. The forward and backward participation indices are considered in the analysis. The paper presents an analysis of 62 developing and developed economies from 1995 to –2018 using the Juodis A., Y. Karavias, and V. Sarafidis [2021. “A Homogeneous Approach to Testing for Granger non-Causality in Heterogeneous Panels.” Empirical Economics 60 (1): 93–112] approach, which is an improvement over the traditional approaches to analysing causality. The results show that the overall position in GVCs positively affects CO2 emissions for developing countries but a causal relationship does not exist for the developed countries. The developed countries attain a higher participation index but a lower position index. On the other hand, developing countries with fewer stringent environmental regulations may opt for an upstream position (more export-oriented) and by design specialize in more pollution-intensive industries. Noteworthy, production-based emissions in developed countries are reduced because of an increase in imports of emission-intensive products from developing countries.

Large-Eddy Simulations of Flow over a Backward-Facing Ramp with a Wall-Mounted Cube

Passive flow control devices, such as vortex generators (VGs), can effectively modulate the turbulent boundary layer flow near regions of adverse pressure gradients, but the interactions between the salient flow structures produced by VGs and those of the separated flow are not fully understood. In this study, a spatially evolving turbulent boundary layer interacting with a wall-mounted cube ahead of a backward-facing ramp is investigated using wall-resolved large-eddy simulations for a Reynolds number of 19,600, based on the inlet boundary layer thickness and freestream velocity. Different cube configurations are examined to isolate the effects of cube height and streamwise position. The large counter-rotating flow produced by the larger cubes generated more turbulent kinetic energy, thereby resulting in smaller separated regions over the ramp. Although significantly lower levels of turbulent kinetic energy dissipation than production are observed in the outer flow regions of the horseshoe vortex and in the induced counter-rotating flow, the spatial distribution of dissipation is similar to that of the turbulent kinetic energy. When the upstream position of an isolated single cube, relative to the leading ramp edge, is more than three cube heights, the streamwise decay of the counter-rotating flow results in lower levels of turbulent kinetic energy.

Impact of new maize variety adoption on yield and fertilizer input in China: Implications for sustainable food and agriculture

CONTEXTCrop variety adoption is considered as one of the main strategies for farmers to enhance productivity under stress brought by the climate change, with less environmental impacts. It holds an upstream position in the whole life cycle of agricultural clean production, compared to the field management and agricultural non-point source pollution treatment. OBJECTIVEThis paper aims to (i) assess the impact of new maize variety adoption on maize yield and fertilizer input; (ii) analyze the main determinants of farmers' new maize variety choice in the context of climate change, and (iii) identify the heterogeneity of small-scale and large-scale farmers in maize variety choice and its impacts. METHODSBased on plot-level data collected from three major grain producing provinces in China, we employ a treatment effects model to correct the potential bias resulting from the farmers' self-selection and estimate the direct impacts of farmers' new maize variety adoption and the main determinants of such adoption. RESULTS AND CONCLUSIONSThe empirical results indicate that the adoption of new maize varieties significantly increases maize yield by 9.4% but fertilizer use by 16.6 kg/mu (1 mu = 1/15 ha) as well, and this trade-off between economic impacts and environmental impacts is more pronounced among small-scale farmers. However, in the face of natural disasters, adopting new maize varieties results in a significant reduction in yield losses by 1.4% and a decrease in fertilizer input for natural disaster management by 2.45 kg/mu, as compared to the adoption of old varieties. What's more, our findings suggest that a higher frequency of pest and disease disasters significantly increases the probability of new maize variety adoption by farmers, while a higher frequency of climate disasters significantly decreases the probability. SIGNIFICANCEThe estimated impacts of new maize varieties point out the need of synergistically optimized resistance and nutrient use efficiency for crop breeding, which have important policy implications for sustainable food and agriculture. Also, the significant factor analysis contributes to the proposal of feasible ways to promote the farmers' adoption behavior.

The transcription factor CpMYB62 controls the genetic network that leads to the determination of female flowers in Cucurbita pepo.

In monoecious species, female flowering constitutes the developmental process that determines the onset and production of fruit and is therefore closely related to crop yield. This article presents the identification and phenotypic and molecular characterization of myb62, an ethylmethane sulfonate loss-of-function mutation that completely blocks the female floral transition, converting all female flowers into male flowers. BSA-seq analysis coupled with WGS showed that myb62 corresponds to a C>T transition in the coding region of the gene CpMYB62, generating a premature stop codon and a truncated transcription factor without its N-terminal effector domain. The myb62 phenotype was partially rescued by exogenous ethylene application, indicating that the function of CpMYB62 is mediated by ethylene. Different evidence supports this conclusion: first, the reduced ethylene production of the mutant, and second, the male flower productive phenotype of the double mutant between myb62 and the ethylene-insensitive mutant etr2b, which demonstrated that myb62 is epistatic over etr2b. Furthermore, transcriptomic analysis of WT and myb62 apical shoots confirmed that CpMYB62 regulates master sex-determining genes, upregulating those encoding the ethylene biosynthesis enzymes CpACO2B and CpACS27A and those encoding for transcription factors that promote the development of carpels(CpCRC), but downregulating those involved in the arrest of carpels (CpWIP1), In the gene network controlling sex determination in cucurbits, CpMYB62 occupies the most upstream position, activating ethylene and other sex determining genes involved in female flower determination in Cucurbita pepo.

Recent progress in microRNA detection using integrated electric fields and optical detection methods

Low-cost, highly-sensitivity, and minimally invasive tests for the detection and monitoring of life-threatening diseases and disorders can reduce the worldwide disease burden. Despite a number of interdisciplinary research efforts, there are still challenges remaining to be addressed, so clinically significant amounts of relevant biomarkers in body fluids can be detected with low assay cost, high sensitivity, and speed at point-of-care settings. Although the conventional proteomic technologies have shown promise, their ability to detect all levels of disease progression from early to advanced stages is limited to a limited number of diseases. One potential avenue for early diagnosis is microRNA (miRNA). Due to their upstream positions in regulatory cascades, blood-based miRNAs are sensitive biomarkers that are detectable earlier than those targeted by other methods. Therefore, miRNA is a promising diagnostic biomarker for many diseases, including those lacking optimal diagnostic tools. Electric fields have been utilized to develop various biomedical assays including cell separation, molecules detection and analysis. Recently, there has been a great interest in the utility of electric fields with optical detection methods, including fluorescence and surface plasmons toward biomarker detection. This mini review first summarizes the recent development of miRNA as a biomarker. Second, the utility of electric fields and their integration with fluorescence detection methods will be discussed. Next, recent studies that utilized electric fields and optical detection methods will be discussed. Finally, in conclusion, technology gaps and improvements needed to enable low-cost and sensitive biomarker detection in point-of-care settings will be discussed.

Simulation Analysis of the Characteristics of Layered Cores during Pulse Decay Tests

The permeability of low-permeability cores is generally measured using a pulse decay method. The core of low-permeability rocks, such as shale, often has a layered structure. The applicability of pulse decay testing for layered cores is not clear. In this study, the performance of the pulse decay method on layered cores was comprehensively investigated. Numerical simulations were conducted to investigate the influence of the interlayer permeability ratio, storativity ratio, layer thickness, interlayer location, and number of layers on the pulse decay pressure and pressure derivative curves, as well as the permeability obtained from pulse decay testing. The results revealed that the pressure curves of layered cores exhibit distinct differences from those of homogeneous cores if the upstream permeability is larger than the downstream one. The pressure derivative curve shows more inclined or horizontal straight-line segments than in the homogeneous case. The shapes of the pressure and pressure derivative curves are affected by the upstream and downstream positions of the core, but the tested permeability is not affected. The tested permeability differs from the equivalent model permeability, with an error of up to 22%. If the number of layers is not less than 10, the permeability obtained from the pulse decay test is consistent with that of the equivalent model. These differences are influenced by the interlayer permeability ratio, storativity ratio, layer thickness, interlayer location, and number of layers. To improve the accuracy of permeability analysis in pulse decay testing for layered cores, curve fitting using the characteristics of the pressure derivative curve can be employed.

The Status, Trend, and Global Position of China’s Forestry Industry: An Anatomy Based on the Global Value Chain Paradigm

This study aims to systematically examine the developmental attributes and trends within China’s forestry sector through the lens of a global value chain (GVC) framework. To this end, this research analyzes the Organization for Economic Co-operation and Development Inter-Country Input–Output (OECD-ICIO) database, using a cohesive set of GVC methods, including the forward decomposition of industry value-added, an assessment of industry upstream and downstream positions, the decomposition of export values, and analysis of trade competitiveness indicators. The trajectory of China’s forestry industry hinges upon the interplay between foreign demand and domestic demand. The results reveal a transition in China’s forestry sector development model from export-focused to a domestically driven approach. The proportion of value-added that is devoted to meeting domestic demands within the wood processing and papermaking industries has surged to 76% and 82%, respectively. Among the major economies, China has the highest output upstream index and input downstream index in the forestry industry, playing a vital role in propelling and pulling other industries into the global value chain system. The proportion of domestic added-value in China’s forestry industry exports ranks among the top, reflecting strong self-sufficiency in export production. Although China’s forestry industry possesses a high world market share, its overall international competitiveness is weak, especially with clear signs of weakening comparative advantages in the wood processing industry.

Limitations of Dual-Single Guide RNA CRISPR Strategies for the Treatment of Central Nervous System Genetic Disorders.

Huntington's disease (HD) is a fatal neurodegenerative disorder caused by a toxic gain-of-function CAG expansion in the first exon of the huntingtin (HTT) gene. The monogenic nature of HD makes mutant HTT (mHTT) inactivation a promising therapeutic strategy. Single nucleotide polymorphisms frequently associated with CAG expansion have been explored to selectively inactivate mHTT allele using the CRISPR/Cas9 system. One of such allele-selective approaches consists of excising a region flanking the first exon of mHTT by inducing simultaneous double-strand breaks at upstream and downstream positions of the mHTT exon 1. The removal of the first exon of mHTT deletes the CAG expansion and important transcription regulatory sites, leading to mHTT inactivation. However, the frequency of deletion events is yet to be quantified either in vitro or in vivo. Here, we developed accurate quantitative digital polymerase chain reaction-based assays to assess HTT exon 1 deletion in vitro and in fully humanized HU97/18 mice. Our results demonstrate that dual-single guide RNA (sgRNA) strategies are efficient and that 67% of HTT editing events are leading to exon 1 deletion in HEK293T cells. In contrast, these sgRNA actively cleaved HTT in HU97/18 mice, but most editing events do not lead to exon 1 deletion (10% exon 1 deletion). We also showed that the in vivo editing pattern is not affected by CAG expansion but may potentially be due to the presence of multiple copies of wildtype (wt)/mHTT genes HU97/18 mice as well as the slow kinetics of AAV-mediated CRISPR/Cas9 delivery.

Intra-country inequality and involvement in GVCs: the case of EU-28

Nowadays, production is configured around Global Value Chains, and countries’ involvement in those has become important objectives for achieving economic upgrading. However, social outcomes are neither equally distributed between countries, nor among social classes within countries. Indeed, GVCs and the potential gains of countries' involvement in them, yield uncertain implications of the effects of globalization on inequality within countries. In this context, the aim of this work is to analyze the link between the performance of countries in GVCs (measured trough participation and position) and the levels of intra-country inequality. In more depth, we focus on Europe (specifically, EU28 countries), as it offers a wide and cohesive scenario of developed countries in which to test the effects of linking into GVCs on internal inequalities. We get a positive effect of participation in GVCs on increasing intra-country inequality, while more upstream positions are linked to decreases in income inequality. Besides, if we differentiate by geographical area, Western and Southern European countries would achieve higher reductions in inequality than Northern countries by moving towards more upstream positions.

Transonic buffet alleviation via virtual control surfaces

In this work, computational fluid dynamics simulations are carried out to assess the ability of control surfaces to alleviate or suppress transonic buffet. Among the available control surfaces, upper trailing edge flaps were considered since they modify the aerofoil pressure distribution and fix the shock at an upstream position. Spoilers were also studied as they produce a similar effect by interfering with the pressure disturbance propagation in the boundary layer and prevent buffet. For both devices, the sensitivities to geometric parameters are studied. The effectiveness of these buffet control methods is first assessed for 2D computations around different wing sections. As spoilers were considered more effective, results on a 3D configuration are provided to discuss the influence of finite-span devices on aerodynamic performance. In addition, a simple model accounting for changes in the flight Mach number together with the spoiler is presented to simulate a simple flight scenario and provide an effective strategy for buffet suppression. In the framework of numerical investigations, the adoption of virtual control surfaces allows for avoiding difficulties associated with the modelling of slotted and deployable devices.

Supply chain pressures and SMEs’ CSR practices: the moderation effect of supply chain position

ABSTRACT Drawing from institutional and resource dependence theories, this paper investigates how supply chain pressures influence the various dimensions of CSR, i.e. environmental practices, human resources practices, community involvement practices, and marketplace practices, in SMEs. Using a structural equation modelling approach and data collected from 273 SMEs, our findings indicate that institutional pressures exerted by supply chain partners differently influence the level of CSR practices in SMEs. Notably, the study demonstrates that coercive pressures have no significant influence on CSR practices, whereas mimetic and normative pressures positively and significantly influence the level of CSR practices. Furthermore, the positive influence of normative pressures on CSR practices is stronger for SMEs situated downstream in their supply chains, whereas SMEs in further upstream positions are sensitive to mimetic pressures for their environmental, workplace and marketplace practices. Overall, this study provides unique insight on the association between supply chain pressures and CSR practices in SMEs.

TRPIV experimental study of coherent structures and their burst events in the boundary layer on JBC

Turbulent drag on the hull surface is one of the main sources of drag during the navigation of a ship, which is significantly influenced by the boundary layer's coherent structures. To investigate the evolution and energy transport of the coherent structures, this study applied time-resolved particle image velocimetry (TRPIV) to realise the fine measurement of the flow field at different upstream and downstream positions on the surface of the Japanese bulk carrier (JBC). Finite-time Lyapunov exponent (FTLE), proper orthogonal decomposition (POD) and quadrant analysis were used to conduct a detailed analysis of the coherent structures and their evolution. The results show that the skin friction drag is notably affected by the coherent structures at the turbulent boundary layer of the JBC hull surface and their burst events. In addition, the turbulent energy that enhances the skin friction drag mainly comes from the outward-inward transport in the turbulent boundary layer, and the intensity of fluctuation velocity contained within the burst events also obviously affects the skin friction drag. The results of this study can provide physical evidence for the optimisation design of similar hull configurations, the optimisation design of unmanned underwater vehicle configuration, and the planning of drag reduction strategy.

CO2 emissions and global value chains indicators:new evidence for 1995–2018

Globalization and the configuration of production processes around Global Value Chains (GVCs) have become key factors for explaining the recent evolution of environmental and economic indicators. Indeed, previous research found evidence on the significant impact of GVCs indicators (participation and position) on CO2 emissions. Additionally, results obtained in previous literature vary depending on the time period and geographical areas considered. In this context, the main aims of this paper are to analyze the role the GVCs in explaining the evolution of CO2 emissions, and to identify possible structural breaks. This study uses the Multiregional Input-Output framework to calculate a position indicator and two different measures of participation in GVCs (interpreted either as trade openness or international competitiveness). The analysis useS Inter-Country Input-Output tables (ICIO) as main database, which includes 66 countries and 45 industries and covers the period 1995–2018. It is first concluded that upstream positions in GVCs are associated to lower global emissions. Additionally, the effect of participation depends on the measure used: trade openness is linked to lower emissions, while a higher competitiveness in international trade leads to higher emissions. Finally, two structural breaks are identified in 2002 and 2008, revealing that position is significant in the two first subperiods, while participation becomes significant from 2002 onwards. Thus, policies to mitigate CO2 emissions might to be different before and after 2008: currently, reductions in emissions can be achieved by increasing value-added embodied in trade while decreasing the volume of transactions.

Analysis of the Position of China Information Industry in the Global Value Chain

Identifying the division of labor position of China information industry in the global value chain is particularly important for optimizing the structure of China's information industry and improving its overall competitiveness. The article calculates the global value chain revenue generated by the participation of the information industry in the global value chain division of labor production in various countries, and then establishes a global value chain height index to analyze the global scale and development of China information industry; Analyze the degree of vertical specialization of the information industry through the decomposition of international trade flows, and finally calculate the global value chain status index of the information industry in different countries. The results indicate that: (1) the value chain height index of China's information manufacturing industry is continuously decreasing, at the level of middle and lower reaches; The telecommunications industry and computer programming industry in China information service industry are in an upstream position in the value chain. (2) There is an imbalance in bilateral trade between China and the United States in information manufacturing and information service industries. Compared to the United States, China information industry has a lower value chain position. The United States mainly engages in research and development, design, and other work, while China is more engaged in less value-added work such as assembly and reprocessing. (3) From the global value chain status index, China information manufacturing industry is at the middle and lower reaches of the world, with Japan firmly ranking first and the United States second. The ranking of other developed countries is basically in the top 20, fluctuating between the middle and upper reaches. The position of China's information service industry in the global value chain is at the mid to upper level. Russia, Japan, and the United States are among the top three countries in the global value chain of the information services industry, while developed countries such as the UK, France, and Germany are in the upper reaches of the information services industry.

Do Turkish firms benefit from GVC participation?

PurposeThe study evaluates the effects of GVC participation on firm productivity and profitability. Hence this study aims to find evidence whether there is a clear difference between the productivity and profitability effects of simple and complex backward and forward participations for Turkish firms.Design/methodology/approachThe authors employ a firm level data from the Türkiye's both first and second top 500 industrial enterprises from 1993 to 2019. In addition, the authors calculate country-sector level both backward and forward GVC participation indices with their simple and complex sub-indices for each year from 1990 to 2015 from the Full Eora data of the Eora Global Supply Chain Database. The authors estimate the model with OLS and fixed effects. To understand the role of the 2008 global crisis, the authors also undertake estimations for the pre-crisis and post-crisis. The authors also divide the data by R&D intensity of sectors.FindingsWhile backward GVC participation lowers both labor productivity and profitability growth, forward GVC participation promotes both. Moreover, simple and complex backward participation have similarly negative effects on productivity and profitability growth, simple and complex forward participation have the completely opposite effects though. The authors then provide substantial evidence for the differing effects of participation on productivity and profitability growth between pre-crisis and post-crisis periods. Interestingly, backward participation has a negative impact for both hi-tech and low-tech firms while forward participation boosts the productivity growth only for low-tech firms, probably due to the relatively more upstream position of low-tech firms.Originality/valueTo the best of the knowledge, no previous study has yet examined the profitability effects of GVC for firms. Second, in addition to overall backward and forward GVC participation rates, the authors also calculate and utilize simple and complex GVC measures in the estimations. Third, to reveal whether the global financial crisis leads to a shift in the productivity and profitability effects of GVCs, the authors separately run the regressions for the pre- and post-crisis periods. Fourth, the authors then investigate the argument that hi-tech sectors/firms could benefit more from joining GVCs compared to firms in low-tech technology sectors.

Imaging temperature and thickness of thin planar liquid water jets in vacuum.

We present spatially resolved measurements of the temperature of a flat liquid water microjet for varying ambient pressures, from vacuum to 100% relative humidity. The entire jet surface is probed in a single shot by a high-resolution infrared camera. Obtained 2D images are substantially influenced by the temperature of the apparatus on the opposite side of the infrared camera; a protocol to correct for the thermal background radiation is presented. In vacuum, we observe cooling rates due to water evaporation on the order of 105 K/s. For our system, this corresponds to a temperature decrease in approximately 15 K between upstream and downstream positions of the flowing leaf. Making reasonable assumptions on the absorption of the thermal background radiation in the flatjet, we can extend our analysis to infer a thickness map. For a reference system, our value for the thickness is in good agreement with the one reported from white light interferometry.

Quantifying nonlocal bedload transport: A regional-based nonlocal model for bedload transport from local to global scales

Recent studies have emphasized the importance of nonlocal models in characterizing bedload transport in natural rivers, particularly in mixed-size gravel beds or steep hillslopes. Nonlocality denotes that a quantity (flux) at a specific location x is dependent on the conditions in the surrounding area, as opposed to solely at the location itself. This concept applies in bedload transport even in planar flumes, where particles are entrained at an upstream position and travel a finite distance, ultimately contributing nonlocally to the sediment flux. However, existing bedload transport models, such as the advection–diffusion equation (ADE) or the fractional derivative equation (FDE) models, are inadequate in characterizing the nonlocal transport behavior of bedload at a regional scale. Large errors may arise from the lack of an accurate description of the nonlocal bedload transport processes at regional scales. This study proposes a regional-based nonlocal bedload transport model, which is conceptualized from the probabilistic Exner-based equations and the peridynamic (PD) differential operator. The PD model encapsulates the nonlocal motion of bedload sediments on the basis of the PD differential operator, by utilizing a pre-defined weight function and influence domain. Comparisons demonstrate that the PD model serves as a generalized tool connecting the local and the global models with different PD functions and influence domains. Its variability on kernel function and influence domain, enable it conveniently describe sub-, super-, and normal diffusion behaviors of bedload transport.

Hydrodynamic performance of a rim-driven thruster improved with gap geometry adjustment

The hubless rim-driven thruster (RDT) has become increasingly interesting for ship propulsion. Gap flow has been proven as the main feature of RDT that cannot be simply neglected. In this study, based on a classical hubless RDT, the effects of the gap geometry are studied by adjusting its axial passage length, and inlet and outlet oblique angles. The hydrodynamic characteristics of the RDT were simulated with OpenFOAM based on the k – ω shear stress transport turbulence model. Due to the pressure increase after the main flow passes through the rotating blades, the flow inside gap is driven upstream, which is opposite to the main flow direction. It is found that the hydrodynamic efficiency is increased as the gap axial passage length is shortened, which is realized by increasing the oblique angle with the fixed inlet and outlet positions. Moving the inlet and outlet to further downstream and upstream positions has negligible effects on the hydrodynamic efficiency and leads to recirculating flow within the gap near its inlet. These findings shed light on the design of the gap geometry to improve the RDT hydrodynamic performance.

Spatial patterns of diffusive greenhouse gas emissions from cascade hydropower reservoirs

Greenhouse gas (GHG) emissions from reservoirs have received increasing attention in recent years. Despite extensive studies in single reservoirs, GHG emission patterns in cascades of multiple reservoirs, which are becoming increasingly common worldwide, remain unknown. This study investigated the spatial patterns of diffusive carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions, as well as their total CO2-equivalent (CO2-eq), for a cascade hydropower system in the heavily dammed upper Mekong River, China. Results demonstrated that GHG emissions in cascade reservoirs were higher than that in the upstream channel since the accumulated sediments fueled microbes for GHG production. In cascade reservoirs, CO2 made the largest contribution (58.6%–84.8%) to total CO2-eq, while the contribution of N2O was marginal. Deep reservoirs emitted less CO2, which was attributed to higher CO2 consumption by phytoplankton. Reservoirs formerly occupying the most upstream position for the longest period of time in the cascade emitted the most CH4, perhaps due to accumulations of river borne sediments. The total CO2-eq generally increased with distance downstream except within deep reservoirs. These findings indicate that, with respect to mitigating GHG emissions, the deepest, most upstream reservoir should be constructed first in the configuration of cascade hydropower reservoirs, and less sediment will enter downstream reservoirs, which have higher CO2-eq emissions.