Output Flux Research Articles

3D printed membrane‐integrated spacers for enhanced antifouling in ultrafiltration

AbstractFeed spacers are an important component of membrane‐based filtration systems as they promote turbulence and mass transfer during the filtration process—thereby, reducing the membrane fouling and improving the flux. Whereas spacers are used as a separate component in conjunction with membranes, herein, we demonstrate that membrane‐integrated spacers offer superior fouling resistance and hence an improved output flux during filtration. The integrated spacers were fabricated by 3D printing a composite slurry of UV curable resin and polyvinylidene fluoride on the Polyethersulfone‐based ultrafiltration (UF) membrane. After curing under the UV light, the 3D printed spacers showed excellent flexibility and mechanical integrity along with permanent adhesion to the UF membrane. When tested for filtration using humic acid as foulant, the integrated spacer offered significantly reduced fouling and an increased flux as compared with the commercial spacer. Moreover, it was found that the geometry of the integrated spacers plays an important role in their performance. Among different geometries, the “gyroid” geometry, with an optimal infill density, provided the highest fouling resistance while improving the flux by nearly 150% as compared with the commercial spacer. When tested as stand‐alone spacers, the 3D spacers with identical geometries resulted in an increased fouling and lower flux which confirmed the superior performance of membrane integrated spacers.

Effects of bioelectricity generation processes on methane emission and bacterial community in wetland and carbon fate analysis

Wetlands are an important carbon sink for greenhouse gases (GHGs), and embedding microbial fuel cell (MFC) into constructed wetland (CW) has become a new technology to control methane (CH4) emission. Rhizosphere anode CW–MFC was constructed by selecting rhizome-type wetland plants with strong hypoxia tolerance, which could provide photosynthetic organics as alternative fuel. Compared with non-planted system, CH4 emission flux and power output from the planted CW–MFC increased by approximately 0.48 ± 0.02 mg/(m2·h) and 1.07 W/m3, respectively. The CH4 emission flux of the CW–MFC operated under open-circuit condition was approximately 0.46 ± 0.02 mg/(m2·h) higher than that under closed-circuit condition. The results indicated that plants contributed to the CH4 emission from the CW–MFC, especially under open-circuit mode conditions. The CH4 emission from the CW–MFC was proportional to external resistance, and it increased by 0.67 ± 0.01 mg/(m2·h) when the external resistance was adjusted from 100 to 1000 Ω. High throughput sequencing further showed that there was a competitive relationship between electrogenic bacteria and methanogens. The flora abundance of electrogenic bacteria was high, while methanogens mainly consisted of Methanothrix, Methanobacterium and Methanolinea. The form and content of element C were analysed from solid phase, liquid phase and gas phase. It was found that a large amount of carbon source (TC = 254.70 mg/L) was consumed mostly through microbial migration and conversion, and carbon storage and GHGs emission accounted for 60.38% and 35.80%, respectively. In conclusion, carbon transformation in the CW–MFC can be properly regulated via competition of microorganisms driven by environmental factors, which provides a new direction and idea for the control of CH4 emission from wetlands.Graphical

Research of Anode Structure of High Emission Flux X-ray Source Based on Composite Structure

This study presents the design of an X-ray source anode structure that can boost X-ray emission flux. The construction makes use of the properties of the composite structure to increase thermal conductivity of the anode. To indirectly enhance the X-ray output flux, the number of electron beams at the source is increased. In addition to explaining the composite anode’s design and manufacturing process, this paper concentrates on a study of the material’s thermal conductivity. X-ray flux of several anode are simulated and compared using finite element analysis (FEA) techniques. It was found that the substrate material for the composite anode construction needed to have a high melting point and thermal conductivity. The characteristic enables rapid conduction of the heat produced in focal region of the anode. In addition, the anode’s thermal stability is assured while the high temperature phenomena brought on by energy buildup is prevented. It establishes the framework for making subsequent anodes.

Effects of long-term nitrogen addition on the δ15N and δ13C of Larix gmelinii and soil in a boreal forest

BackgroundNatural abundance of carbon (C) and nitrogen (N) stable isotope ratios (δ13C and δ15N) has been used to indicate the state and cycle of ecosystem C and N. However, it is still unclear how C and N cycle of boreal forests respond to the N deposition.ResultsWe conducted an 8-year continuous N addition field experiment in a Larix gmelinii forest in Greater Khingan Mountains, Northeast China. Four N treatments (0, 25, 50, 75 kg N ha−1 year−1) were built. The effects of N addition on the δ13C and δ15N of needle, branch, bark, and fine root of Larix gmelinii and soil were studied. The result of the balance between the N input and output flux showed that N addition significantly increased the δ15N in each organ of Larix gmelinii, but did not change the δ15N of soil. We also found that the N absorption by needles of Larix gmelinii could increase the needle photosynthesis rate and δ13C by increasing carboxylation, but N addition had no significant effect on the δ13C of soil and other organs. In addition, both the soil δ15N and δ13C increased with the soil depth.ConclusionsLong-term N addition may lead to more open C and N cycles and further affect plant nutrient acquisition strategies in boreal forest ecosystems.

Ocean Surface Flux Algorithm Effects on Tropical Indo-Pacific Intraseasonal Precipitation.

Surface latent heat fluxes help maintain tropical intraseasonal precipitation. We develop a latent heat flux diagnostic that depicts how latent heat fluxes vary with the near‐surface specific humidity vertical gradient (Δq) and surface wind speed (|V|). Compared to fluxes estimated from |V| and Δq measured at tropical moorings and the Coupled Ocean Atmosphere Response Experiment 3.0 (COARE3.0) algorithm, tropical latent heat fluxes in the National Center for Atmospheric Research CEMS2 and Department of Energy E3SMv1 models are significantly overestimated at |V| and Δq extrema. Madden–Julian oscillation (MJO) sensitivity to surface flux algorithm is tested with offline and inline flux corrections. The offline correction adjusts model output fluxes toward mooring‐estimated fluxes; the inline correction replaces the original bulk flux algorithm with the COARE3.0 algorithm in atmosphere‐only simulations of each model. Both corrections indicate reduced latent heat flux feedback to intraseasonal precipitation, in better agreement with observations, suggesting that model‐simulated fluxes are overly supportive for maintaining MJO convection.

Methane emissions from trees planted on a closed landfill site.

Trees have morphological adaptations that allow methane (CH4) generated below ground to bypass oxidation in aerobic surface soils. This natural phenomenon however has not been measured in a landfill context where planted trees may alter the composition and magnitude of CH4 fluxes from the surface. To address this research gap, we measured tree stem and soil greenhouse gas (GHG) emissions (CH4 and CO2) from a closed UK landfill and comparable natural site, using an off-axis integrated cavity output spectroscopy analyser and flux chambers. Analyses showed average CH4 stem fluxes from the landfill and non-landfill sites were 31.8 ± 24.4 µg m–2 h–1 and –0.3 ± 0.2 µg m–2 h–1, respectively. The landfill site showed seasonal patterns in CH4 and CO2 stem emissions, but no significant patterns were observed in CH4 and CO2 fluxes at different stem heights or between tree species. Tree stem emissions accounted for 39% of the total CH4 surface flux (7% of the CO2); a previously unknown contribution that should be included in future carbon assessments.

Geochemical characteristics of strontium isotopes in a coastal watershed: implications for anthropogenic influenced chemical weathering and export flux.

Coastal watershed are essential in transporting dissolved loads from terrestrial biogeochemical process of surface environment to the adjacent oceans. The solute chemistry of coastal river water contains significant information about environmental processes under the impact of both natural lithology and anthropogenic pressure. In this study, strontium (Sr) isotopes and water chemistry data of the Jiulongjiang (JLJ) river water were analyzed in detail to trace the contribution of bedrock weathering, and quantify Sr flux to the East China Sea (ECS). The dissolved Sr contents ranged 0.07–0.90 μmol L−1 and greatly fluctuated where tributaries encountered, and 87Sr/86Sr values relatively fluctuated between 0.7140 and 0.7514. Silicate weathering was identified to be the predominant contribution of riverine dissolved loads. Strontium flux to the ocean in dry season was estimated to be 689.2 tons per year, implying an essential influence on oceanic strontium evolution. In accordance with forward model, the silicate weathering rate and CO2 consumption rate were 55.7 tons km−2 per year and 16.9 × 105 mol km−2 per year, respectively, slightly higher than world average. Considering anthropogenic impacts alongside the river, the integrated effect of lower runoff and longer retention time of river water in dry season may aggravate weathering processes. Although CO2 sink by silicate weathering in JLJ seems less than the sink in world’s central reservoirs, it should still be taken into consideration for coastal carbon budget. These findings highlight the use of geochemical characteristics of strontium and its isotopes in identifying weathering process and output flux to the ocean, which provides basic data for sustainable coastal water resource management.

Comparative analysis of recirculating and collimating cesium ovens.

We have performed a study of several cesium oven designs. A comparison between recirculating (or sticking-wall) and collimating (or re-emitting-wall) ovens is made in order to extract the most efficient design in terms of beam brightness. Unfortunately, non-reproducible behaviors have been observed, and the most often observed output flux is similar to the sticking-wall case, which is the lowest theoretical value of the two cases, with a beam brightness close to 1018 at. sr-1 s-1 cm-2. The reason of this universally observed behavior is unclear despite having tested several materials for the collimating tube. Conclusion on possible improved design based on sticking of cesium on several (un)cleaned surfaces is given.

3D-printed hierarchical pillar array electrodes for high-performance semi-artificial photosynthesis.

The rewiring of photosynthetic biomachineries to electrodes is a forward-looking semi-artificial route for sustainable bio-electricity and fuel generation. Currently, it is unclear how the electrode and biomaterial interface can be designed to meet the complex requirements for high biophotoelectrochemical performance. Here we developed an aerosol jet printing method for generating hierarchical electrode structures using indium tin oxide nanoparticles. We printed libraries of micropillar array electrodes varying in height and submicrometre surface features, and studied the energy/electron transfer processes across the bio-electrode interfaces. When wired to the cyanobacterium Synechocystis sp. PCC 6803, micropillar array electrodes with microbranches exhibited favourable biocatalyst loading, light utilization and electron flux output, ultimately almost doubling the photocurrent of state-of-the-art porous structures of the same height. When the micropillars' heights were increased to 600 µm, milestone mediated photocurrent densities of 245 µA cm-2 (the closest thus far to theoretical predictions) and external quantum efficiencies of up to 29% could be reached. This study demonstrates how bio-energy from photosynthesis could be more efficiently harnessed in the future and provide new tools for three-dimensional electrode design.

Luminous output improvement in chip scale packaged Ce3+:YAG-based ceramic phosphors-converted white LEDs via laser assistance for application in automobile headlights

In this study, two kinds of composite ceramic phosphors, Ce3+:YAG/Al2O3 and Ce3+:Y(Gd)AG/Al2O3 were prepared via solid state reaction sintering in flowing pure oxygen at atmospheric pressure. The ceramic phosphors were packaged into chip-scale white light emitting diodes (w-LEDs), and laser assisted w-LED automobile headlight prototypes were assembled. The luminous flux output of the w-LEDs was significantly improved through additional blue diode laser excitation. Notably, the Al2O3 phase is able to impart an improvement in the luminescence saturation exhibited by Ce3+:Y(Gd)AG, which typically reaches saturation prior to Ce3+:YAG.

High dissolved organic carbon deposition is buffered by surface soil in a headwater catchment of a subtropical plantation

High atmospheric dry and wet deposition of dissolved organic carbon (DOC) may contribute to net ecosystem carbon balance (NECB), but the input and output fluxes of DOC and their transport processes in a catchment remain unclear. Here, to elucidate the importance of DOC in NECB from the view of Earth’s critical zone, we measured the water fluxes of inputs (precipitation, throughfall, and stemflow) and outputs (soil leachate, surface flow, interflow, streamflow and groundwater) and their DOC concentrations in a subtropical plantation headwater catchment. Our results showed that dry DOC deposition from plant-derived dust and exudates (22,317 kg C km−2 yr−1) was about 4.5 times higher than the wet DOC deposition from precipitation (4966 kg C km−2 yr−1), and accounted for 3.88 and 0.86% of the net ecosystem C productivity (NEP) (5.75×105 kg C km−2 yr−1), respectively. In comparison, DOC fluxes in stream and groundwater were 5912 and 3905 kg C km−2 yr−1, indicating that soil-buffered DOC flux was 17,466 kg C km−2 yr−1 and accounted for 3.04% of NEP. A positive correlation between DOC and pH and total dissolved solids in soil leachate indicated that the biophysical and chemical absorption bridged the interaction between soil minerals and organic carbon. Our results underline the importance of including plant-derived DOC deposition in carbon sink estimations in subtropical plantation headwater catchments.

Sediment Recycling and the Evolution of Analog Orogenic Wedges

AbstractIn convergent systems, the interplay between tectonics, erosion, and sedimentation controls the orogenic evolution. The nature of the interactions between these factors is still elusive due to the complex feedbacks that operate across different temporal and spatial scales. Here, we investigate these feedbacks with analog models of landscape evolution designed to account for both tectonic forcing and surface processes, using a water‐saturated granular material that allows to simulate contemporary brittle deformation and surface processes. The deformation is imposed by the movement of a rigid backstop, and surface processes are triggered by simulated rainfall and runoff. We vary the convergence velocity, rainfall rate, and basal angle of the box, testing how different boundary conditions affect the balance between tectonics and surface processes. We measure the competition between input fluxes (tectonics) and output fluxes (erosion) of material, showing how sedimentation strongly affects the balance between these fluxes. The results suggest that the experimental equilibrium between tectonics and erosion can be achieved, in the analog models, only for low convergence rates (about 10 mm hr−1) and/or for high basal angle (>2°, limited sedimentation). If the foreland is overfilled with sediments and/or if convergence velocity is higher, channels decrease their erosional efficiency, moving the dynamic equilibrium between tectonics and erosion toward the former.

A Novel Parallel Hybrid Excitation Field Modulated Machine With Efficient Utilization of Multiworking Harmonics

In this article, a novel parallel hybrid excitation field modulated machine with efficient utilization of multiworking harmonics is proposed. The key of the proposed machine is to efficiently integrate the parallel hybrid excitation and multiworking harmonics to enhance average output torque and flux regulation capability. First, operation principle and air-gap magnetic field harmonics of the machine are investigated by using field modulated principle, which reveals the contribution of each working harmonic to flux linkage and torque. Then, performances of the machine are analyzed, such as open-circuit back-EMF, flux regulation capability, torque-speed characteristics, etc. Also, the proposed machine is compared to conventional ones for evaluation. Finally, a prototype is manufactured and tested to validate the theoretical and simulated results.

Revisiting Ice Flux and Mass Balance of the Lambert Glacier–Amery Ice Shelf System Using Multi-Remote-Sensing Datasets, East Antarctica

Due to rapid global warming, the relationship between the mass loss of the Antarctic ice sheet and rising sea levels are attracting widespread attention. The Lambert–Amery glacial system is the largest drainage system in East Antarctica, and its mass balance has an important influence on the stability of the Antarctic ice sheet. In this paper, the recent ice flux in the Lambert Glacier of the Lambert–Amery system was systematically analyzed based on recently updated remote sensing data. According to Landsat-8 ice velocity data from 2018 to April 2019 and the updated Bedmachine v2 ice thickness dataset in 2021, the contribution of ice flux approximately 140 km downstream from Dome A in the Lambert Glacier area to downstream from the glacier is 8.5 ± 1.9 Gt·a−1, and the ice flux in the middle of the convergence region is 18.9 ± 2.9 Gt·a−1. The ice mass input into the Amery ice shelf through the grounding line of the whole glacier is 19.9 ± 1.3 Gt·a−1. The ice flux output from the mainstream area of the grounding line is 19.3 ± 1.0 Gt·a−1. Using the annual SMB data of the regional atmospheric climate model (RACMO v2.3) as the quality input, the mass balance of the upper, middle, and lower reaches of the Lambert Glacier was analyzed. The results show that recent positive accumulation appears in the middle region of the glacier (about 74–78°S, 67–85°E) and the net accumulation of the whole glacier is 2.4 ± 3.5 Gt·a−1. Although the mass balance of the Lambert Glacier continues to show a positive accumulation, and the positive value in the region is decreasing compared with values obtained in early 2000.

Measurement of color, photometry and electrical parameters of street light LEDs

This paper presents the procedure to evaluate the performance parameters of street light LEDs i.e. color, photometry, and electrical characteristics such as voltage, current, power, and power factor using a standard Sphere Spectroradiometer. The integrating Sphere 1.5 Meter measures total radiant flux (W/nm), from which total Luminous flux and color quantities are obtained at different levels of the supply voltage. There are three street light LEDs tested experimentally with the Spectroradiometer for different voltage levels for flux and power output. The simulated spectrum test reports give values of parameters such as color, photometry, and electrical quantities. At the later stage, the performance of LED is compared with the conventional incandescent lamp. The simulated spectral, as well as experimental results, have shown the superiority of LED street light over an incandescent lamp.

Effects of interfacial properties on conversion efficiency of Bi2Te3-based segmented thermoelectric devices

The conversion efficiency η of a thermoelectric (TE) device can be effectively improved by constructing segmented TE legs, but the specific interfaces between the heterogeneous materials inevitably degrade the performance. Focusing on the Bi2Te3-based two-segmented module, we systematically investigated the influences of the Peltier effect, interfacial electrical resistance Re, and interfacial thermal resistance Rt on the conversion efficiency η. It is found that the Peltier heat can increase the conversion efficiency if the Seebeck coefficient increases along the direction of an electric current. An applicable Re should be kept on the order of magnitudes of 10−5 Ω cm2 for segmented TE devices, since the increased Re significantly decreases η. With a determined Re, η depends on the leg height L rather than the cross-sectional area A. In contrast, η is hardly affected by the variation in the interfacial thermal resistance Rt, while both the input heat flux Qin and output power P decrease with the increasing Rt.

Improving Predictions of Stream CO2 Concentrations and Fluxes Using a Stream Network Model: A Case Study in the East River Watershed, CO, USA

AbstractInland waters are an important component of the global carbon budget. However, our ability to predict carbon fluxes from stream systems remains uncertain, as pCO2 varies within streams at scales of 1–100 m. This makes direct monitoring of large‐scale CO2 fluxes impractical. We incorporate CO2 input and output fluxes into a stream network advection‐reaction model, representing the first process‐based representation of stream CO2 dynamics at watershed scales. This model includes groundwater (GW) CO2 inputs, water column (WC), benthic hyporheic zone (BHZ) respiration, downstream advection, and atmospheric exchange. We evaluate this model against existing statistical methods including upscaling and multiple linear regressions through comparisons to high‐resolution stream pCO2 data collected across the East River Watershed in the Colorado Rocky Mountains (USA). The stream network model accurately captures GW, evasion, and respiration‐driven pCO2 variability and significantly outperforms multiple linear regressions for predicting pCO2. Further, the model provides estimates of CO2 contributions from internal versus external sources suggesting that streams transition from GW‐ to BHZ‐dominated sources between 3rd and 4th Strahler orders, with GW, BHZ, and WC accounting for 49.3%, 50.6%, and 0.1% of CO2 fluxes from the watershed, respectively. Lastly, stream network model atmospheric CO2 fluxes are 4‐12x times smaller than upscaling technique predictions, largely due to relationships between stream pCO2 and gas exchange velocities. Taken together, this stream network model improves our ability to predict stream CO2 dynamics and efflux. Furthermore, future applications to regional and global scales may result in a significant downward revision of global flux estimates.

Optimal Bias Current Design for Visible Light Communications Based on LED Electrical-Thermal Effect

In visible light communication (VLC) system, the intensity of light emitting diode (LED) is modulated to transmit data. As a transmitter, the design of LED should consider the performance of lighting and communication simulataneously. However, the output flux of LED is jointly determined by the electrical and thermal characteristics, and is concave-related to the forward bias current. In order to maximize the use of LEDs, in this paper, the mutual restriction of optical, electrical and thermal mechanisms for the LED systems are considered, and a dynamic photoelectrothermal model is established. Then, the optimal bias current is presented according to the electrical-thermal relationship of LED. Modulating LED at this bias current can maximize the communication performance without sacrificing the light flux. Finally, a BER experiment to verify the optimal communication performance is conducted at this bias current.

Biogeochemistry of selenium compounds in the water column of warm monomictic Lake Kinneret

The biogeochemistry of dissolved selenium (Se) was investigated over 3 years (2015–2017) in the subtropical, warm monomictic and meso-eutrophic Lake Kinneret (Sea of Galilee, Israel). We monitored seasonal variation and vertical distribution of dissolved total Se (T.Se), inorganic oxyanions (Se(IV) & Se(VI)), reduced Se fraction (Red.Se), organic (Org.Se) and volatile Se compounds. T.Se varied between ~ 100 and 160 ng L−1 with Red.Se comprising 40–80% of the Se inventory, and Se(VI) dominating over Se(IV) most of the time. The variation in T.Se and species correlated with winter holomixis vs. summer fall stratification periods. The annual cycle includes: (a) increase of T.Se from fall/winter to spring, representing increased allochthonous Se input flux, along with Se recycling via holomixis; (b) decrease of T.Se from spring to the end of the year, representing the diminishing Se inputs and the evolving output fluxes to the lake’s bottom and to the atmosphere. Org.Se variations are directly associated with Chlorophyll-a and primary production attesting for the significant role of phytoplankton activity in the Se cycle. An important Se output flux comprises spring to summer Se uptake by phytoplankton and further volatile compounds production and volatilization accounting for ~ 10% of estimated Se input. The similarity of total dissolved Se concentrations in this work and from mid 1990s attests for long-term stability of the Se inventory. The TVSe concentrations in lacustrine systems being similar to that of estuary systems, the biological role of phytoplankton and eventually the degradation of organic material may produce similar fluxes of volatile Se to the atmosphere.

Design and analysis of semi-closed stator core transverse flux permanent magnet generator

Purpose The purpose of this paper is to modernize the generator system of wind turbine concept that not only improves the efficiency and power density but also reduces the system cost making design simpler and less expensive, especially in large-scale production. Design/methodology/approach This paper presents a new permanent magnet transverse flux generator (PMTFG) for wind energy production. The key feature of its composition is the double armature coil in a semi-closed stator core. The main structural difference of the presented design is the use of double coil in the same space of semi-closed stator core and reduced number of stator pole pairs and rotor magnets from 12/24 to 10/20. 3D simulations are performed using finite element analysis (FEA) to measure induced voltage and magnetic field distribution at no load. The FEA is performed to quantify the change in flux linkage, induced voltage and output power as a function of different speeds and load current. Findings Results show that PMTFG with double coil configuration has improved electromagnetic performance in terms of flux linkage, induced voltage, output power and efficiency. The power density of 10/20 PMTFG with the double coil is 0.0524 KW/Kg, about an 18% increase compared to the conventional design. Research limitations/implications The proposed PMTFG is highly recommended for direct drive applications such as wind power. Originality/value Four models are simulated by FEA with single and double coil configuration, and load analysis is performed on all simulated models. Finally, results are compared with conventional PMTFG.