Changes In Production Rate Research Articles

High-resolution forest carbon modelling for climate mitigation planning over the RGGI region, USA

The inclusion of forest carbon in climate change mitigation planning requires the development of models able to project potential future carbon stocks—a step beyond traditional monitoring, reporting and verification frameworks. Here, we updated and expanded a high-resolution forest carbon modelling approach previously developed for the state of Maryland to 11 states in the Regional Greenhouse Gas Initiative (RGGI) domain, which includes Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont. In this study, we employ an updated version of the Ecosystem Demography (ED) model, an improved lidar initialization strategy, and an expanded calibration/validation approach. High resolution (90 m) wall-to-wall maps of present aboveground carbon, aboveground carbon sequestration potential, aboveground carbon sequestration potential gap (CSPG), and time to reach sequestration potential were produced over the RGGI domain where airborne lidar data were available, including 100% of eight states, 62% of Maine, 12% of New Jersey, and 0.65% of New York. For the eight states with complete data, an area of 228 552 km2, the contemporary forest aboveground carbon stock is estimated to be 1134 Tg C, and the forest aboveground CSPG is estimated to be larger at >1770 Tg C. Importantly, these estimates of the potential for added aboveground carbon sequestration in forests are spatially resolved, are further partitioned between continued growth of existing trees and new afforested/reforested areas, and include time estimates for realization. They are also assessed for sensitivity to potential changes in vegetation productivity and disturbance rate in response to climate change. The results from this study are intended as input into regional, state, and local planning efforts that consider future climate mitigation in forests along with other land-use considerations.

Geomagnetic dipole moment variations for the last glacial period inferred from cosmogenic radionuclides in Greenland ice cores via disentangling the climate and production signals

The geomagnetic dipole moment (GDM) modulates the production rates of cosmogenic radionuclides via the shielding of galactic cosmic rays. Therefore, it is possible to use this linkage to reconstruct past changes in the GDM based on cosmogenic radionuclide records from natural archives such as ice cores. Here we present a GDM reconstruction based on 10Be and 36Cl data from two Greenland ice cores from 11.7 ka to 108 ka b2k (before A.D. 2000). We find that the cosmogenic radionuclide records reflect a mixture of climate and production effects that require separation to evaluate the changes in the GDM. To minimize climate-related variations on isotope data, we applied a multi-linear correction method by removing common variability between 10Be and 36Cl and climate parameters (accumulation rates, δ18O and ion data) from radionuclide records. The resulting “climate corrected” radionuclide data are converted to GDM using a theoretical production model. Comparison of “climate corrected” radionuclides based GDM reconstructions with independent paleomagnetic-derived GDM records shows a good agreement. Furthermore, the “climate correction” leads to an improved agreement with GDM reconstructions than simply using radionuclide fluxes, lending support to the validity of our correction method to isolate production rate changes from ice core radionuclide records. With this correction method, we can extend the GDM reconstructions based on the cosmogenic radionuclides in ice cores to a period when there is a strong climate signal in the data.

Dynamic Material Balance Method for Estimating Gas in Place of Abnormally High-Pressure Gas Reservoirs

Abstract Determination of gas in place (GIP) is among the hotspot issues in the field of oil/gas reservoir engineering. The conventional material balance method and other relevant approaches have found widespread application in estimating GIP of a gas reservoir or well-controlled gas reserves, but they are normally not cost-effective. To calculate GIP of abnormally pressured gas reservoirs economically and accurately, this paper deduces an iteration method for GIP estimation from production data, taking into consideration the pore shrinkage of reservoir rock and the volume expansion of irreducible water, and presents a strategy for selecting an initial iteration value of GIP. The approach, termed DMBM-APGR (dynamic material balance method for abnormally pressured gas reservoirs) here, is based on two equations: dynamic material balance equation and static material balance equation for overpressured gas reservoirs. The former delineates the relationship between the quasipressure at bottomhole pressure and the one at average reservoir pressure, and the latter reflects the relationship between average reservoir pressure and cumulative gas production, both of which are rigidly demonstrated in the paper using the basic theory of gas flow through porous media and material balance principle. The method proves effective with several numerical cases under various production schedules and a field case under a variable rate/variable pressure schedule, and the calculation error of GIP does not go beyond 5% provided that the production data are credible. DMBM-APGR goes for gas reservoirs with abnormally high pressure as well as those with normal pressure in virtue of its strict theoretical foundation, which not only considers the compressibilities of rock and bound water, but also reckons with the changes in production rate and variations of gas properties as functions of pressure. The method may serve as a valuable and reliable tool in determining gas reserves.

External controls on CO2 in Gibraltar cave air and ground air: Implications for interpretation of δ13C in speleothems

The principles of cave ventilation and ground air advection are outlined. CO2 concentrations were monitored every 2–4 h from 2006 to 2012 at twelve locations in two Gibraltar caves, New St. Michael's (240–275 m altitude) and Ragged Staff (0–70 m), providing detailed records of spatial distribution and temporal changes responding to transient meteorological conditions and seasonal cycles. Cave atmospheres are dynamic mixtures of external air and CO2-rich ground air containing soil-respired CO2 augmented by CO2 derived from oxidation of organic matter washed down into the vadose fracture porosity. The dominant feature of the cave air records is seasonal alternation between high and low CO2 states caused by reversals in ventilation and ground air advection into or away from the caves. The high and low pCO2 states are tightly coupled between the two caves in an antiphase relationship, with rapid switching in response to temperature-controlled density differences between external air and isothermal ground air at mean annual surface temperature (18 °C). The diurnal temperature cycle modulates this pattern, producing four ventilation-advection modes. Summer and winter modes occur when diurnal temperatures are respectively entirely above or below the core temperature of the Rock. During transitional modes the core temperature lies within the diurnal range and pCO2 fluctuates rapidly as the flow of low-CO2 external air through cave entrances alters in response. Strong easterly winds reduce CO2 concentrations in ground air entering the caves and progressively lower cave air CO2. The effects of the CO2 regime on δ13C in speleothem are restricted to variations of 2–3‰, suggesting that larger changes of up to 6‰ across major climatic transitions probably reflect changes in production, transport and oxidation rate of organic matter in the vadose zone. Direct observations of these processes would improve future understanding of the climatic significance of δ13C records in speleothems.

The Whip and the Hoe

Abstract Spectacular physical punishments such as whipping were at the core of the master-slave relationship but it was the chronic and acute physical demands of forced labor that did the most destructive and lasting damage to enslaved people. Plantation field work caused more extensive damage to enslaved bodies than non-field work. Field work was more debilitating to enslaved women than to their male counterparts. Work on sugar plantations caused more damage to the enslaved than work on cotton plantations. Changes in crops, productivity rates, and work regimes had a compound and cumulative effect on the health of the enslaved.

Time-resolved non-invasive metabolomic monitoring of a single cancer spheroid by microfluidic NMR

We present a quantitative study of the metabolic activity of a single spheroid culture of human cancer cells. NMR (nuclear magnetic resonance) spectroscopy is an ideal tool for observation of live systems due to its non-invasive nature. However, limited sensitivity has so far hindered its application in microfluidic culture systems. We have used an optimised micro-NMR platform to observe metabolic changes from a single spheroid. NMR spectra were obtained by directly inserting microfluidic devices containing spheroids ranging from 150 upmum to 300 upmum in diameter in 2.5 upmuL of culture medium into a dedicated NMR probe. Metabolite concentrations were found to change linearly with time, with rates approximately proportional to the number of cells in the spheroid. The results demonstrate that quantitative monitoring of a single spheroid with le 2500 cells is possible. A change in spheroid size by 600 cells leads to a clearly detectable change in the l-Lactic acid production rate (p=3.5times 10^{-3}). The consumption of d-Glucose and production of l-Lactic acid were approximately 2.5 times slower in spheroids compared to monolayer culture of the same number of cells. Moreover, while cells in monolayer culture were found to produce l-Alanine and l-Glutamine, spheroids showed slight consumption in both cases.

Identification and Online Updating of Dynamic Models for Demand Response of an Industrial Air Separation Unit

Demand-response operation of air separation units requires frequent changes in production rate(s), and scheduling calculations must explicitly consider process dynamics to ensure feasibility of the solutions. To this end, scale-bridging models (SBMs) approximate the scheduling-relevant dynamics of a process and its controller in a low-order representation. In contrast to previous works that have employed nonlinear SBMs, this paper proposes linear SBMs, developed using time-series analysis, to facilitate online scheduling computations. Using a year-long industrial dataset, we find that compact linear SBMs are suitable approximations over typical scheduling horizons, but that their accuracies are unpredictable over time. We introduce a strategy for online updating of the SBMs, based on Kalman filtering schemes for online parameter estimation. The approach greatly improves the accuracy of SBM predictions and will enable the use of linear SBM-based demand-response scheduling in the future.

Workforce Adjustment to Absorb Changes in Production Rate in Continuous Production Systems.(Dept.M)

This paper presents some mathematical models that deal with the planning of the workforce requirement on continuous production lines to react with changes in production rates in order to meet sudden changes in product's demand. Norms for operation times and workers production rates are normally set by management based on the design capacity of the production line. The models presented in this paper can assist management in evaluating the workforce needed to react to the changes in production required over the normal production volume in order to satisfy any sudden changes in product demand, especially for short term planning. Cost aspects and analysis are also considered to include the profitability impact of workforce scheduling according to any adopted new production plan. It is expected that these models will provide management with powerful tools to alleviate the effect of any disturbances that may occur due to sudden changes in production plans, and thereby maximizing profitability.

Zooplankton functional group responses to environmental drivers off the west coast of Vancouver Island, Canada

Zooplankton diversity and biomass are integral to marine ecosystem functioning. Functional trait-based approaches enable an examination of ecosystem dynamics in which species groups are defined by their functional roles (i.e. functional groups) within the ecosystem, rather their taxonomic identity. Changes in the relative and absolute biomass of zooplankton functional groups may affect the productivity of higher trophic levels via change in secondary production rates and the efficiency of energy transfer. Traits from 55 mesozooplankton species were assembled from the literature and applied to a 35-year time series (1980–2016) for the southern shelf area off the west coast of Vancouver Island, Canada. Eight functional groups were identified by clustering species on the basis of functional trait similarity. A time series of biomass anomalies was calculated for each functional group, after which links between functional group biomass anomalies and several environmental variables were examined. Generalized additive modeling (GAM) identified local sea surface temperature as the most important driver of biomass anomaly patterns for three groups: Doliolids, Omnivore-Herbivores, and the Active Ambush Omnivores. The Southern Oscillation Index (SOI) was also a main driver for three groups: Egg-Brooding Carnivores, Broadcast Carnivores, and Cruise Carnivores-A. The Ocean Niño Index (ONI) was significant for Active Ambush Omnivores and Egg-Brooding Carnivores, whereas the Pacific Decadal Oscillation (PDO) was a driver of Broadcast Carnivores and Cruise Carnivores-A. The Doliolids group also varied with surface salinity, and Cruise Carnivores-B with the North Pacific Gyre Oscillation (NPGO). The relative contribution of several zooplankton functional groups to the overall biomass showed no temporal trends but some groups had increased or decreased abundance contributions. This suggests functional redundancy within groups, as smaller or larger species may dominate based on environmental conditions. Our analysis demonstrates that functional group biomass anomalies vary with environmental variables, where conditions may favor certain functional groups, therefore dictating how the ecosystem is functioning.

Total Cellular ATP Production Changes With Primary Substrate in MCF7 Breast Cancer Cells.

Cancer growth is predicted to require substantial rates of substrate catabolism and ATP turnover to drive unrestricted biosynthesis and cell growth. While substrate limitation can dramatically alter cell behavior, the effects of substrate limitation on total cellular ATP production rate is poorly understood. Here, we show that MCF7 breast cancer cells, given different combinations of the common cell culture substrates glucose, glutamine, and pyruvate, display ATP production rates 1.6-fold higher than when cells are limited to each individual substrate. This increase occurred mainly through faster oxidative ATP production, with little to no increase in glycolytic ATP production. In comparison, non-transformed C2C12 myoblast cells show no change in ATP production rate when substrates are limited. In MCF7 cells, glutamine allows unexpected access to oxidative capacity that pyruvate, also a strictly oxidized substrate, does not. Pyruvate, when added with other exogenous substrates, increases substrate-driven oxidative ATP production, by increasing both ATP supply and demand. Overall, we find that MCF7 cells are highly flexible with respect to maintaining total cellular ATP production under different substrate-limited conditions, over an acute (within minutes) timeframe that is unlikely to result from more protracted (hours or more) transcription-driven changes to metabolic enzyme expression. The near-identical ATP production rates maintained by MCF7 and C2C12 cells given single substrates reveal a potential difficulty in using substrate limitation to selectively starve cancer cells of ATP. In contrast, the higher ATP production rate conferred by mixed substrates in MCF7 cells remains a potentially exploitable difference.

ВИКОРИСТАННЯ МЕТОДУ ПОСЛІДОВНИХ ПОСТУПОК ДЛЯ РОЗВ’ЯЗУВАННЯ ЗАДАЧІ ПІДВИЩЕННЯ СОБІВАРТОСТІ ПРОДУКЦІЇ

The processes of optimization of the production plan according to certain criteria were investigated. One of the problems is the difficulty of coordination and taking into account the impact of criteria on the optimal production plan. In practice, every company often faces tasks that require decisions that are quite complex and significantly affect the result. The choice of the best solutions is usually made by using a single numerical function - the criterion of optimality. The best solution is one that provides the maximum (or minimum) of the selected criterion. For the most part, the quality of decisions is characterized not by one but by many incomparable criteria. Therefore, it is necessary to make decisions based not on one but on many criteria. That is why the investigation and implementation of multicriteria models is an important stage in the development of modern science. The current rate of change in production is very high. To meet new needs and maintain the competitiveness each enterprise, firm, company must be able to make fast and correct decisions. Properly formed production program allows companies to meet the needs of consumers in products that are produced with the best use of resources, and get the maximum profit. Quite often there is a need to use mathematical methods to study this problem. The results obtained by solving a mathematical problem will make it possible to make optimal recommendations for certain actions. The main purpose of the company is usually to make a profit. One of the factors on which profit depends is the cost price. In view of this, an optimization model of the problem of increasing the cost price was proposed. The maximum price of manufactured products and the minimum costs for production was taken as criteria. At the same time it is impossible to ensure the maximum price and minimum production costs. Therefore, the solution was achieved by step-by-step solution of the proposed mathematical model of optimization of the production plan using the idea of the method of successive concessions, which would provide a certain price at low cost. An example shows an algorithm for solving this problem.

Evolution of Production and Transport Characteristics of Steeply-Dipping Ultra-Thick Coalbed Methane Reservoirs

The large spatial variability of in-situ stress and initial reservoir pressure in steeply-dipping ultra-thick coalbed methane (UTCBM) reservoirs exert strong control on the initial distribution of stress-sensitive permeability. This results in significant differences in the propagation of reservoir depressurization, gas production characteristics, distribution of fluid saturation, and evolution of permeability relative to flat-lying and thin counterpart coalbed methane (CBM) reservoirs. We contrast these responses using the Fukang mining area of the Junggar Basin, Xinjiang, China, as a type-example using coupled hydro-mechanical modeling. Production response indicates: (1) Dual peaks in CBM production rate, due to the asynchronous changes in the gas production rate in each the upper and lower sections of the reservoir; (2) higher depressurization and water saturation levels in the lower section of the reservoir relative to the upper at any given distance from the production well that ameliorate with time to be similar to those of standard horizontal reservoirs; (3) the heterogeneity in effective stress is further amplified by the asymmetry of the initial pressure drawdown distribution of the reservoir to exert extreme control on the down-dip evolution of absolute permeability—with implications for production. Field drainage data and simulation results obtained in this study more accurately reflect the drainage characteristics of the steeply-dipping UTCBM reservoirs. For ultra-thick low-rank coal seams, permeability anisotropy plays an important role in determining the utility of horizontal wells and hydraulic fracturing to maximize rates and yields CBM production, and requiring further study.

The Importance of Hillslope Scale in Responses of Chemical Erosion Rate to Changes in Tectonics and Climate

AbstractChemical erosion is of wide interest due to its influence on topography, nutrient supply to streams and soils, sediment composition, and Earth's climate. While controls on chemical erosion rate have been studied extensively in steady‐state models, few studies have explored the controls on chemical erosion rate during transient responses to external perturbations. Here we develop a numerical model for the coevolution of soil‐mantled topography, soil thickness, and soil mineralogy, and we use it to simulate responses to step changes in rates of rock uplift, soil production, soil transport, and mineral dissolution. These simulations suggest that tectonic and climatic perturbations can generate responses in soil chemical erosion rate that differ in speed, magnitude, and spatial pattern and that climatic and tectonic perturbations may impart distinct signatures on hillslope mass fluxes, soil chemistry, and sediment composition. The response time of chemical erosion rate is dominantly controlled by hillslope length and is secondarily modulated by rates of rock uplift, soil production, transport, and mineral dissolution. This strong dependence on drainage density implies that a landscape's chemical erosion response should depend on the relative efficiencies of river incision and soil transport and thus may be mediated by climatic and biological factors. The simulations further suggest that the timescale of the hillslope response may be long relative to that of river channel profiles, implying that chemical erosion response times may be limited more by the sluggishness of the hillslopes than by the rate of signal propagation through river channel profiles.

A hybrid intelligent model for reservoir production and associated dynamic risks

This research presents a hybrid model to predict oil production and to provide a dynamic risk profile of the production system. The introduced predictive approach combines a multilayer perceptron (MLP)-artificial neural network (ANN) model with a hybrid connectionist strategy (BN-DBN), which comprises a Bayesian network (BN) model and a dynamic Bayesian network (DBN) model. The proposed hybrid methodology (MLP-BN-DBN) is designed to find the correlations between the input and output data to forecast the desired oil production rate. The MLP model captures the variabilities in the fluid and rock properties, model's uncertainties, and the effects of pressure maintenance on the production process. The BN model uses the 3σ mathematical rule to promptly signal the arrival of any production rate change and captures the pressure maintenance impact using the early warning source indexes. The DBN model provides a dynamic risk profile of the production system using the observed evidence and reservoir production hyperbolic decline concept.The proposed methodology offers the field operators better opportunity to obtain real time estimate of the likelihood of any impending production loss at any time during production operations. The model exhibits a high capability of oil production prediction with the minimum, average, and maximum percentage errors of 0.01%, 6.57%, and 15.28%, respectively. The developed hybrid model serves as a risk monitoring system. The model is cost-effective and eases the computational burden of history matching processes and bridges the gaps in the existing systems for oilfield development dynamic risk forecast and production predictions. Hence, the proposed methodology offers a multipurpose tool for dynamic risk assessment and for proper reservoir production optimization.

Bacterial production prevails over photo- and chemosynthesis in a eutrophic tropical lagoon

Dark carbon fixation is a combination of processes performed by microorganisms to fix inorganic carbon driven the energy generated by chemical reactions. Our study quantified microbial primary and secondary production rates to evaluate the relative importance of dark carbon fixation in relation to photosynthetic rates and heterotrophic bacterial production and their contribution to the carbon cycle in a tropical eutrophic and human-impacted lagoon (Rodrigo de Freitas Lagoon, Brazil). Samples were collected daily at a fixed point to assess short-term temporal variations and at six different stations to assess spatial variability. Water samples were incubated using 14C-bicarbonate at 100% of light and in the dark to quantify photosynthesis and dark carbon fixation, respectively; and 3H-leucine incubations were performed to measure bacterial production. Environmental parameters (temperature, salinity, dissolved oxygen, dissolved organic carbon and inorganic nutrients) were measured to characterize the hydrology of the studied area, and to evaluate their influence on the microbial production rates. There were no significant changes in production rates over time or within different depths. Bacterial production rates varied significantly over space, and were correlated with nitrogen compounds, temperature, salinity and pH. However, a short rainfall event, although not strong or extreme, promoted rapid changes in the shallow water column, such as a decrease in temperature and nitrogen compounds, inducing responses to microbial production rates, such as higher rates of dark carbon fixation and bacterial production at the bottom and lower rates of photosynthesis. Heterotrophic bacterial production was significantly higher than dark and light carbon fixation, being the most important carbon-cycling process in Rodrigo de Freitas Lagoon, possibly favored by the high allochthonous organic matter and nutrient inputs. This study showed that, on average, dark carbon fixation accounted for 30% at the surface and 43% near the bottom of the total primary production and up to 10% of heterotrophic production in the water column, which may be related to the availability of ammonia and methane. We concluded that, even for this short-term temporal and spatial assessment, dark carbon fixation is relevant, although usually disregarded, and this process should be taken into account when evaluating carbon budgets, metabolic balance and ecosystem functioning in tropical coastal lagoons.

Impacts of prescribed burnings on litter production, nitrogen concentration, δ13C and δ15N in a suburban eucalypt natural forest of subtropical Australia

Prescribed burning is projected to be adopted more frequently with intensifying climate change; thus, a long-term study is necessary to understand the burning impacts on forest productivity and carbon (C) and nitrogen (N) cycling. Litter fall production rate can be used to indicate burning impacts on forest productivity, whereas N concentration, and C and N isotope composition (δ13C and δ15N) can be used to infer burning impacts on C and N cycling in plant-soil system. In this study, the impacts of low-intensity prescribed burning on litter production, N concentration, and C and N isotope compositions were continuously investigated for 6 years at five study sites in a natural eucalypt forest of subtropical Australia. Higher leaf litter production rate, N concentration and δ15N, and lower δ13C could be seen shortly after prescribed burning. The higher leaf litter N concentration and lower δ13C were likely due to the ease of competition for soil N and moisture from understory vegetation in the short term by prescribed burning. Leaf δ15N and N concentration were closely correlated, and seasonal changes in leaf litter production rate, δ13C and δ15N were observed. Burning season and related severity might determine the suppression degree of understory vegetation. Time since fire (TSF) was a significant impact factor influencing the litter fall production rate, N concentration, δ13C and δ15N of leaf litter fall for a decade following prescribed burning. However, monthly rainfall and temperature were less consistent in their impacts. Nitrogen limitation was enhanced by prescribed burning through the removal of litter and understory vegetation in the N poor forest and might be responsible for the long-term burning impacts. Low-intensity prescribed burning might have a long-lasting impact on forest litter productivity in nutrient poor forests in subtropical Australia.

Solar and climate signals revealed by seasonal 10Be data from the NEEM ice core project for the neutron monitor period

10Be in ice cores has been instrumental for reconstructing past changes in solar activity prior to direct observations. For a robust use of these records, it is pivotal to understand the 10Be transport and deposition. However, there are only few high-resolution seasonal 10Be data longer than one full solar cycle (11 years) that could enable a quantification of the influences of atmospheric circulation and deposition processes on the 10Be signal in ice. Here we present a seasonally resolved 10Be data set covering the neutron monitor period (1951–2002) from a firn core connected to the NEEM (North Greenland Eemian Ice Drilling) project. The results suggest that both summer and winter 10Be reflect the production signal induced by solar modulation of galactic cosmic rays. However, superimposed on this solar signal we find additional meteorologically driven influences on 10Be transport and deposition. We found that the tropopause pressure over 30°N represents an important factor influencing NEEM 10Be concentrations on seasonal and annual scales. 10Be deposited in summer also correlates significantly with the tropopause pressure over Greenland suggesting a direct contribution of stratospheric intrusions during summer to the 10Be deposition in Greenland. To correct for these transport/deposition influences, we apply a first-order correction to the 10Be data using a multi-linear regression model. The “climate-corrected” 10Be data shows a comparable skill for reconstructing production rate changes as the 10Be composite record from five different ice cores in Greenland. The results suggest that the correction approach can be a complementary method to the stacking to better isolate the production rate signal from the 10Be data when only limited data are available.

Increase in phytoplankton production and consumption in response to a typhoon passing through the southern East China Sea

The northwestern Pacific Ocean and East China Sea (ECS) are frequently affected by typhoons during the summer period. To identify changes in production and consumption rates of phytoplankton (<20 and 20~200 µm) affected by Typhoon Maria (9-10 July 2018), 2 sampling periods were compared: a pre-typhoon cruise (4-9 July 2018) and a post-typhoon cruise (13-17 July 2018). Results showed that <20 and 20~200 µm phytoplankton production was 14- and 1.8-fold higher, respectively, in the post-typhoon period compared to the pre-typhoon. Accompanying this post-typhoon shift from pico- and nanophytoplankton to microphytoplankton, the consumption rate of microzooplankton on <20 µm phytoplankton was 11.6 mgC m-3 d-1 in the pre-typhoon period, and increased to 203.3 mgC m-3 d-1 after the typhoon. Furthermore, the ingestion fluxes were 4.9 and 8.0 mgC m-3 d-1 through mesozooplankton grazing on microzooplankton (ciliates and dinoflagellates) pre- and post-typhoon, respectively. Our findings show that organisms from the microbial food web (i.e. ciliates and dinoflagellates) may control the phytoplankton assemblage during the post-typhoon period of increased productivity, and thus represent an important trophic link between the classical and microbial food webs in the southern ECS.

Numerical investigation of entropy production in SWCNT/H2O nanofluid flowing through inwardly corrugated tube in turbulent flow regime

This work numerically investigates the entropy production rate in single-walled carbon nanotubes (SWCNTs)/H2O nanofluid flowing through an inwardly corrugated pipe in turbulent flow regime. The governing equations (continuity, momentum, energy, rate of turbulent production and specific turbulent dissipation) were solved using $$\left( {{\text{SST}}\,k - \omega } \right)$$ model. Parametric study was carried out on the effect of Reynolds number (5000–40,000), nanoparticle concentration (0–0.25%) and dimensionless amplitude (e/d = 0, 0.08, 0.12 and 0.16) on entropy production rate and Bejan number. The results show the field profile of the Bejan number and the thermal and viscous entropy production rate for various amplitudes of the corrugated pipe. The study also observed that an increment in concentration of SWCNT–water nanofluid and dimensionless amplitude of the corrugation reduced the thermal entropy production but enhanced viscous entropy production. For instance, the change in thermal and viscous entropy production rate at Re = 20,000 and vol = 0.25% between corrugation amplitude 0.12 and 0.16 was − 1.27% and 53.15%, respectively.

Effects of anaerobic digestion enhanced by ultrasound pretreatment on the fuel properties of municipal sludge.

In this study, effects of ultrasound pretreatment on combustion characteristics and elemental composition of municipal sludge were examined for energy-based evaluation of sludge pretreatment. Waste activated sludge (WAS) from a municipal wastewater treatment plant was pretreated with ultrasound at varying durations and was subjected to anaerobic digestion in a biochemical methane potential (BMP) assay. Changes in gas production rates, calorific value (CV), elemental compositions, and ash contents of sludge samples were examined to assess the effects of pretreatment and digestion. Sonication at 0.73W/mL enhanced gas production by 28%. Moreover, volatile solids (VS) and chemical oxygen demand (COD) removals increased from 41 to 45% and 33 to 37%, respectively. Following anaerobic digestion, CVs of samples decreased by about 18%. Sonicated samples exhibited a higher decrease. In order to quantify the change in overall energy content, total solids (TS) reduction was also taken into account. Loss was magnified as both CV and the amount of TS that would provide the overall energy were reduced. This loss was 38% for the control group and 41% for the 15min sonicated sludge. Digestion decreased the C content of sludge by about 20% and H content by 50% due to biogas production. Ash content increased relatively as some of the combustible solids were lost due to digestion. Experimental results indicate that if sludge is to be combusted, digestion with or without ultrasound pretreatment may be disadvantageous if the aim is to maximize energy gain from sludge.