Variations In Production Rates Research Articles

Comparison of One- and Two-Variable Linear Regression Models and Classic Energy Intensity for Energy Performance Tracking of Two Manufacturing Sectors

Manufacturing facilities consumed about 32% of total domestic energy in the United States in 2016. To evaluate the energy savings achieved through the implementation of energy conservation projects and to establish powerful arguments for future projects, accurate energy performance tracking methods are necessary. The classic energy intensity method (i.e., the ratio of annual total energy over annual total production) is the means most widely used to measure savings because it can be understood and calculated easily. This method considers the variation in production rates to some extent; however, it fundamentally assumes facilities' base energy consumption (energy consumption at zero production) to be zero, which rarely holds true. Furthermore, this method does not consider variations in other relevant parameters, such as weather conditions. Therefore, the regression models approach is commonly recommended to track energy performance improvements. However, because it requires more data and statistical expertise, the regression models approach has been adopted by only a few facilities, and many others suspect it is not worth the effort for their specific cases. For this reason, the improved accuracy this approach offers needs to be demonstrated. By analyzing 477 monthly energy (electricity and natural gas) data sets, this study quantitatively compared the accuracy of classic energy intensity, one-variable (production only) linear regression models, and two-variable (i.e., production and weather) linear regression models for two manufacturing sectors (primary metal and transportation equipment manufacturing). Results showed that significant improvements in accuracy were achieved with one-variable regression models when compared with the classic energy intensity method and with two-variable regression models when compared with one-variable regression models. These improvements were demonstrated using the p values of intercept, cooling degree days, and heating degree days. Based on these results, to achieve a good balance between accuracy improvements and resources requirements, one-variable (production only) linear regression models for electricity consumption and two-variable (production and heating degree days) linear regression models for natural gas consumption are recommended for both sectors in the case of limited resources. Facilities can also use the results to decide which approaches fit better in their cases.

Quantitative dissection of variations in root growth rate: a matter of cell proliferation or of cell expansion?

Plant organ growth results from cell production and cell expansion. Deciphering the contribution of each of these processes to growth rate is an important issue in developmental biology. Here, we investigated the cellular processes governing root elongation rate, considering two sources of variation: genotype and disturbance by chemicals (NaCl, polyethylene glycol, H2O2, abscisic acid). Exploiting the adventitious rooting capacity of the Populus genus, and using time-lapse imaging under infrared-light, particle image velocimetry, histological analysis, and kinematics, we quantified the cellular processes involved in root growth variation, and analysed the covariation patterns between growth parameters. The rate of cell production by the root apical meristem and the number of dividing cells were estimated in vivo without destructive measurement. We found that the rate of cell division contributed more to the variation in cell production rate than the number of dividing cells. Regardless of the source of variation, the length of the elongation zone was the best proxy for growth rate, summarizing rates of cell production and cell elongation into a single parameter. Our results demonstrate that cell production rate is the main driver of growth rate, whereas elemental elongation rate is a key driver of short-term growth adjustments.

Evolutionary ecology of nectar.

Floral nectar is an important determinant of plant-pollinator interactions and an integral component of pollination syndromes, suggesting it is under pollinator-mediated selection. However, compared to floral display traits, we know little about the evolutionary ecology of nectar. Combining a literature review with a meta-analysis approach, we summarize the evidence for heritable variation in nectar traits and link this variation to pollinator response and plant fitness. We further review associations between nectar traits and floral signals and discuss them in the context of honest signalling and targets of selection. Although nectar is strongly influenced by environmental factors, heritable variation in nectar production rate has been documented in several populations (mean h2 = 0.31). Almost nothing is known about heritability of other nectar traits, such as sugar and amino acid concentrations. Only a handful of studies have quantified selection on nectar traits, and few find statistically significant selection. Pollinator responses to nectar traits indicate they may drive selection, but studies tying pollinator preferences to plant fitness are lacking. So far, only one study conclusively identified pollinators as selective agents on a nectar trait, and the role of microbes, herbivores, nectar robbers and abiotic factors in nectar evolution is largely hypothetical. Finally, there is a trend for positive correlations among floral cues and nectar traits, indicating honest signalling of rewards. Important progress can be made by studies that quantify current selection on nectar in natural populations, as well as experimental approaches that identify the target traits and selective agents involved. Signal-reward associations suggest that correlational selection may shape evolution of nectar traits, and studies exploring these more complex forms of natural selection are needed. Many questions about nectar evolution remain unanswered, making this a field ripe for future research.

The Redshift Evolution of Rest-UV Spectroscopic Properties in Lyman-break Galaxies at z ∼ 2–4

Abstract We present the first comprehensive evolutionary analysis of the rest-frame UV spectroscopic properties of star-forming galaxies at z ∼ 2–4. We match samples at different redshifts in UV luminosity and stellar mass, and perform systematic measurements of spectral features and stellar population modeling. By creating composite spectra grouped according to Lyα equivalent width (EW) and various galaxy properties, we study the evolutionary trends among Lyα, low- and high-ionization interstellar (LIS and HIS) absorption features, and integrated galaxy properties. We also examine the redshift evolution of Lyα and LIS absorption kinematics, and fine-structure emission EWs. The connections among the strengths of Lyα, LIS lines, and dust extinction are redshift independent, as is the decoupling of the Lyα and HIS line strengths, and the bulk outflow kinematics as traced by the LIS lines. Stronger Lyα emission is observed at higher redshift at fixed UV luminosity, stellar mass, SFR, and age. Much of this variation in the average Lyα strength with redshift, and the variation in Lyα strength at fixed redshift, can be explained in terms of variations in the neutral gas covering fraction and/or dust content in the ISM and CGM. However, based on the connection between Lyα and C iii] emission strengths, we additionally find evidence for variations in the intrinsic production rate of Lyα photons at the highest Lyα EWs. The challenge now is to understand the observed evolution of the neutral gas covering fraction and dust extinction within a coherent model for galaxy formation, and make robust predictions for the escape of ionizing radiation at z > 6.

A Semi-Analytical Method for History Matching and Improving Geological Models of Layered Reservoirs: CGM Analytical Method

History matching is used to constrain flow simulations and reduce uncertainty in forecasts. In this work, we revisited some fundamental engineering tools for predicting waterflooding behavior to better understand the flaws in our simulation and thus find some models which are more accurate with better matching. The Craig-Geffen-Morse (CGM) analytical method was used to predict recovery performance calculations and it was simple enough which can be applied in a spreadsheet. In this study, the analytical approach of history matching was applied to a layered reservoir from a shallow marine deposit which was composed of different facies includes lower shoreface facies (LSF), middle shoreface facies (MSF) and upper shoreface facies (USF). Truncated Gaussian Simulation (TGS) is often used to stochastically distribute the facies in the geological model around a deterministic mean representation. The actual distribution is often hard to determine. Starting with the deterministic element of the facies distributions, corrections were made by matching the CGM method predictions to historical data. These corrections were amalgamated in the model and produced a much better history match. Further, the modifications were used to condition the stochastic simulator to provide a geologically more robust model that also matched history. The results showed that the variation of the total field production rate (FPR) between the deterministic model and history data was reduced by about 19.8% (from 21.52% to 1.73%) after applying history match analytically.

Intraflower variation in nectar secretion: Secretion patterns and pollinator behavior in male- and female-phase flowers.

Plants that secrete abundant nectar attract many pollinator visits, potentially leading to a high frequency of geitonogamous pollination. However, intraflower variation in nectar volume might enhance early departure from the flower or inflorescence, reducing geitonogamy. To examine the adaptive significance of multiple nectar-producing spurs within flowers, we related intraflower variation in nectar characteristics to pollinator foraging behavior and plant reproductive success in protandrous Aquilegia buergeriana var. oxysepala. We investigated if nectar volume and sugar mass relate to spur length and if intraflower variation in nectar characteristics differ between male- and female-phase flowers. Because male function requires more pollinator visits than female function, male-phase flowers are expected to have greater nectar volume and lower intraflower variation in nectar volume than female-phase flowers. We used intraflower variation in spur length as an indicator of variation in nectar characteristics and investigated how spur length variation affects pollinator behavior, pollen removal, and seed production. Male-phase flowers had greater nectar volume and lower intraflower variation in nectar volume than female-phase flowers. Intraflower variation in spur length reduced the duration of bumblebee visits. Short visits reduced seed production, but increased pollen removal. Our results suggest that high intraflower variation in nectar production rate can reduce geitonogamy and potentially increase the genetic diversity of pollen received. Such pattern of nectar secretion within and among flowers may allow flowers to ensure effective pollen transfer or high seed production.

A Multi-Objective Mixed-Model Assembly Line Sequencing Problem With Stochastic Operation Time

In today’s competitive market, those producers who can quickly adapt themselves todiverse demands of customers are successful. Therefore, in order to satisfy these demands of market, Mixed-model assembly line (MMAL) has an increasing growth in industry. A mixed-model assembly line (MMAL) is a type of production line in which varieties of products with common base characteristics are assembled on. This paper focuses on this type of production line in a stochastic environment with three objective functions: 1) total utility work cost, 2) total idle cost, and 3) total production rate variation cost that are simultaneously considered. In real life, especially in manual assembly lines, because of some inevitable human mistakes, breakdown of machines, lack of motivation in workers and the things alike, events are notdeterministic, sowe consideroperation time as a stochastic variable independently distributed with normal distributions; for dealing with it, chance constraint optimization is used to model the problem. At first, because of NP-hard nature of the problem, multi-objective harmony search (MOHS) algorithm is proposed to solve it. Then, for evaluating the performance of the proposed algorithm, it is compared with NSGA-II that is a powerful and famous algorithm in this area. At last, numerical examples for comparing these two algorithms with some comparing metrics are presented. The results have shown that MOHS algorithm has a good performance in our proposed model.

Measuring the respiratory gas exchange by grazing cattle using an automated, open-circuit gas quantification system.

Ruminants are a source of enteric CH4, which has been identified as an anthropogenic greenhouse gas that contributes to climate change. With interest in developing technologies to decrease enteric CH4 emissions, systems are currently being developed to measure CH4 emissions by cattle. An issue with grazing cattle is the ability to measure CH4 emissions in open-air environments. A scientific instrument for this task is an automated, open-circuit gas quantification system (GQS; C-Lock, Inc., Rapid City, SD). The GQS is a head chamber that grazing cattle occasionally visit (3 to 8 min/visit; 3 to 6 visits/d), and while the animal consumes a small portion of bait (0.5 to 1.0 kg/visit), the GQS captures the animal's breath cloud by exhausting air through the GQS. The breath cloud is then analyzed for CH4, CO2, and O2 concentrations. Data are hourly uploaded to a server where it is processed using algorithms to determine total daily fluxes. Several factors affect emission estimates generated by the GQS including the animal's visitation rate, length of sampling period, and airflow through the system. The location of the GQS is an important factor in determining the cattle's willingness to visit. Further, cattle need to be trained to use the GQS, which normally requires 4 to 8 wk. Several researchers have shown that 30 or more visits are required to obtain high-quality estimates of gas fluxes. Once cattle are trained to use the GQS, the bait delivery rate has little effect on the animal's willingness to use the system. Airflow through the GQS is an important factor, but as long as airflow is maintained above 26 L/s the breath-cloud capture seems nearly complete. There is great concern regarding circadian variation in the instantaneous production rates of CH4 because the GQS normally only spot-samples 2 to 4 times/d. Preliminary analysis has shown that variation in the instantaneous production rates of CH4 do not vary as greatly with grazing cattle compared with meal-fed cattle. It seems that increasing the visitation length decreases variation in estimated emissions, but there is a diminishing return to increasing visitation length. The GQS is a useful tool for researching the nutrition and emissions of grazing cattle, but great care must be taken to obtain the best quality data possible for use in this high-impact research.

Mixed-model sequencing problem under capacity and machine idle time constraints in JIT production systems

Abstract Sequencing problems in mixed-model production systems assume a negligible set-up time that permits unconstrained product interspersing. This assumption offers better production sequences in terms of just-in-time objectives such as minimizing parts usage rate variation and minimizing Production Rate Variation (PRV). However, set-up times turn out to be critical in many realistic situations. The present paper addresses the sequencing problem in mixed-model production systems, where internal and external set-up times are considerable measures. Internal set-up time limits free mixing of products, resulting in batching of products; while external set-up time causes machine idle time. The authors present a mathematical model for the problem to find sequences that minimize PRV, satisfying capacity and zero machine idle time constraints. LINGO 15.0 solver could solve the model for small-size problems in a reasonable computational time. For large-size problems, a modified bit-wise mutation algorithm that uses a single unary genetic operator has been developed. The authors have applied the algorithm for diverse problem instances at different production capacities. The same problems are also analyzed by relaxing the zero machine idle time constraint. Results demonstrate how the constraints on capacity and machine idle time disturb the leveling of sequences in mixed-model production systems. The model provides decision makers with the opportunity to select smooth sequences based on the available production time and acceptable machine idle time.

Influence of Reservoir Stimulation on Marine Gas Hydrate Conversion Efficiency in Different Accumulation Conditions

In this paper, we used a method of combining reservoir stimulation technique (RST) with depressurization to investigate the conversion efficiency of marine natural gas hydrate (NGH) reservoirs in the Shenhu area, on the northern slope of the South China Sea, which differ in intrinsic permeability and initial NGH saturation conditions. We also analyzed the influence of the variable-stimulation effect on marine NGH conversion efficiency in different accumulation conditions, providing a reference scheme for improving the NGH conversion efficiency in the Shenhu area. In this work, we performed calculations for the variations in CH4 production rate and cumulative volume of CH4 in different initial NGH saturation, intrinsic permeability, and stimulation effect conditions. Variance analysis and range analysis methods were used to analyze the significance of these key factors and their interaction. Furthermore, we investigated the sensitivity of stimulation effect on NGH conversion efficiency. The simulation results showed that the stimulation effect has a significant influence on NGH conversion efficiency, and the influence of interaction between these three factors was not obvious. Possibly most importantly, we clarified that the sparsely fractured networks (N = 3) had a better effect for higher NGH conversion efficiency under higher saturation conditions. For lower permeability cases, the influence between sparsely (N = 3) and densely (N = 5) fractured networks were similar.

Interminimum foF1 Differences and Their Physical Interpretation

AbstractInterminimum changes of June noontime monthly median foF1 were analyzed for European and Japanese ionosonde stations over the period of five (Moscow six) solar cycles. The magnitude of these changes is different at different stations and depends on the solar minima considered. In particular, both European and Japanese stations manifest a pronounced foF1 change between 1996/1997 and 2008/2009 solar minima, the latter being the deepest one. For the first time, the total EUV solar flux with λ ≤ 1,050 Å has been retrieved for the 1946–2015 period using observed June monthly median foF1. The deep solar minimum in 2008/2009 was the lowest one among the last six solar cycles comparing the retrieved EUV. The change from 1996/1997 to 2008/2009 in the retrieved EUV is ~2.0%, and this is much less than the difference of ~10–12% being discussed in the literature. A 10% interminimum change in the total EUV flux results in neutral temperature and gas density, which are larger in 2008 than in 1996, and this contradicts the satellite drag neutral gas density observations. The mechanism of foF1 interminimum changes is based on an interplay between molecular (NO+ and O2+) and O+ ions. The main contribution (>72%) to the interminimum NmF1 change provides [M+] ions via the total ion production rate variation, the rest is provided via O+ ions. The absence (or inversed) difference in foF1 between 1996 and 2008 minima implies that neutral temperature and density are larger in 2008 than in 1996, and this contradicts the satellite drag observations.

High-resolution astrochronological record for the Paleocene-Oligocene (66–23 Ma) from the rapidly subsiding Bohai Bay Basin, northeastern China

The Paleogene succession of the Bohai Bay Basin (BBB), a highly productive petroleum basin in northeastern China with predominantly lacustrine fill, is poorly dated at present. Here, we generated an internal astronomical time scale (ATS) for the Paleogene strata of the Bohai Bay Basin (Dongying Depression, Jiyang Subbasin) using multitaper method (MTM) spectral analysis of high-resolution gamma ray logs. This ATS, which extends from 66 to 23Ma, is anchored to the standard geologic time scale by calibration to the Paleogene/Neogene boundary (23.03Ma) at the top of Dongying Formation. Based on this ATS, we recalibrated the ages of biozones, rifting episodes, and paleoclimate stages within the BBB. The recalibrated ages of rifting episodes and related fluctuations in sedimentation rates exhibit a close relationship to secular variation in production rates of Pacific oceanic plateaus and spreading rates of the Southeast Indian Ridge, confirming that the subsidence history of the BBB was significantly influenced by subduction of the Pacific Plate along the eastern margin of Asia and by collision of the Indian and Eurasian plates. Age recalibration also facilitated re-evaluation of the relationship of sedimentation in the Bohai Bay Basin to the Paleogene climate history of East Asia, e.g., confirming a cooling and drying trend throughout the Eocene.

Sediment nitrogen cycling rates and microbial abundance along a submerged vegetation gradient in a eutrophic lake

Decline of submerged vegetation is one of the most serious ecological problems in eutrophic lakes worldwide. Although restoration of submerged vegetation is widely assumed to enhance ecological functions (e.g., nitrogen removal) and aquatic biodiversity, the evidence for this assumption is very limited. Here, we investigated the spatio-temporal patterns of sediment potential nitrification, unamended denitrification and N2O production rates along a vegetation gradient in the Lake Honghu, where submerged vegetation was largely restored by prohibiting net-pen aquaculture. We also used five functional genes as markers to quantify the abundance of sediment nitrifying and denitrifying microorganisms. Results showed that unvegetated sediments supported greater nitrification rates than rhizosphere sediments of perennial or seasonal vegetation. However, the absence of submerged vegetation had no significant effect on denitrification and N2O production rates. Additionally, the abundance of functional microorganisms in sediments was not significantly different among vegetation types. Season had a strong effect on both nitrogen cycling processes and microbial abundances. The highest nitrification rates were observed in September, while the highest denitrification rates occurred in December. The temporal variation of sediment nitrification, denitrification and N2O production rates could be due to changes in water quality and sediment properties rather than submerged vegetation and microbial abundances. Our findings highlight that vegetation restoration in eutrophic lakes improves water quality but does not enhance sediment nitrogen removal rates and microbial abundances. Therefore, for reducing the N level in eutrophic lakes, major efforts should be made to control nutrients export from terrestrial ecosystems.

Synergistic effects of anaerobic co-digestion of whey, manure and fish ensilage

Biogas production potential of the three feedstocks fish ensilage, manure and whey was evaluated using biochemical methane potential (BMP) tests. Since anaerobic digestion of single substrates may be inefficient due to imbalances in the carbon-nitrogen ratio, degree of biodegradability and/or due to lack of nutrients needed by the microbial community, co-digestion of these substrates was also assessed, revealing synergistic effects and a particularly good effect of combining manure with fish ensilage. In this latter case, methane yields were up to 84% higher than the weighted average of the methane yields obtained with the individual substrates. The type of substrate was the dominating cause of variation in methane production rates and yields.

Modulating the External Facets of Functional Nanocrystals Enabled by Two-Dimensional Oxide Crystal Templates.

The nature of the external crystal facets is critical to control the (photo)catalytic properties. Two-dimensional materials can expose only one type of crystal facet among zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) materials. Controllable tuning of the nature of the external crystal facets of 2D materials is highly desirable but very challenging. Here, we show that 2D particles with the desirable crystal facet for high-performance photocatalytic H2 generation can be obtained by using 2D metal oxide materials (i.e., nanosheets of Ca2Nb3O10 and Ti0.87O2) as templates taking consideration of the crystal configuration of 2D oxide and target compounds. We demonstrate that anatase TiO2 crystals grown on different nanosheet templates exhibit variations in photocatalytic hydrogen production rates from aqueous phase methanol solutions (6.7%), which can be attributed to the nature of the main crystal facet exposed. In view of the large number of 2D materials that have already been synthesized, this work offers a key to design and synthesize nanoparticles with the desirable specific external crystal facet for (photo)catalysis application.

TECNOLOGIAS EMPREGADAS NO TRATAMENTO DE EFLUENTES DE LATICÍNIOS DO VALE DO RIO BRAÇO DO NORTE - SC

Associada à atividade produtiva de laticínios está o grande montante de efluentes gerados no processo de beneficiamento do leite. Pela complexidade de composição, variação nas taxas de produção e variação na própria composição do efluente gerado nesta atividade, a escolha de um sistema eficaz na remoção dos contaminantes ali presentes pode ser bastante complexa. Desta forma, com o presente estudo buscou-se apresentar as técnicas utilizadas em escala global para essa finalidade, e paralelamente traçar um perfil das tecnologias aplicadas pelas empresas de laticínios na região do Vale do rio Braço do Norte, sul de Santa Catarina, bem como demais aspectos relacionados à gestão ambiental dessas empresas. Após levantamento de dados, por meio de pesquisa de campo via questionário e avaliação documental, observou-se que as empresas dessa região aplicam predominantemente sistemas anaeróbios para remoção de matéria orgânica biodegradável, atingindo níveis de remoção dentro da legislação. Contudo, demais parâmetros analisados, como óleos e graxas, pH e sólidos sedimentáveis apresentaram alguns valores fora do preconizado pelos órgãos ambientais. A gestão ambiental das empresas é realizada predominantemente por pessoal terceirizado, deixando evidente a falta de pessoal interno, tecnicamente capacitado para atuar nas empresas.

Water production activity of nine long-period comets from SOHO/SWAN observations of hydrogen Lyman-alpha: 2013–2016

Nine recently discovered long-period comets were observed by the Solar Wind Anisotropies (SWAN) Lyman-alpha all-sky camera on board the Solar and Heliosphere Observatory (SOHO) satellite during the period of 2013 to 2016. These were C/2012 K1 (PanSTARRS), C/2013 US10 (Catalina), C/2013 V5 (Oukaimeden), C/2013 R1 (Lovejoy), C/2014 E2 (Jacques), C/2014 Q2 (Lovejoy), C/2015 G2 (MASTER), C/2014 Q1 (PanSTARRS) and C/2013 XI (PanSTARRS). Of these 9 comets 6 were long-period comets and 3 were possibly dynamically new. Water production rates were calculated from each of the 885 images using our standard time-resolved model that accounts for the whole water photodissociation chain, exothermic velocities and collisional escape of H atoms. For most of these comets there were enough observations over a broad enough range of heliocentric distances to calculate power-law fits to the variation of production rate with heliocentric distances for pre- and post-perihelion portions of the orbits. Comet C/2014 Q1 (PanSTARRS), with a perihelion distance of only ∼0.3 AU, showed the most unusual variation of water production rate with heliocentric distance and the resulting active area variation, indicating that when the comet was within 0.7 AU its activity was dominated by the continuous release of icy grains and chunks, greatly increasing the active sublimation area by more than a factor of 10 beyond what it had at larger heliocentric distances. A possible interpretation suggests that a large fraction of the comet's mass was lost during the apparition.

Anaerobic digestion/co-digestion kinetic potentials of different agro-industrial wastes: A comparative batch study for C/N optimisation

Anaerobic digestion (AD) of different agro-industrial wastes and their co-digestion potential has been exhaustively studied in this research. It explores variation of feedstock characteristics such as biodegradability and methane potential during AD and anaerobic co-digestion (ACoD) of chicken litter (CL) with yoghurt whey (YW), organic fraction of municipal solid waste (OFMSW), hay grass (HG) and wheat straw (WS) under mesophilic conditions. Comparative performance was made at different loading concentrations (2%, 3% and 4% VS) with 1:2g/g VS of substrate to inoculum and carrying C/N ratio. Among different kinetic models, the AD of single substrates showed better fit to the modified Gompertz model (R2: 0.93–0.997) indicating variation in lag phase and methane production rate depend on the substrate characteristics. During ACoD, the methane yield improved by 9–85% through the addition of two, three or four substrates due to the synergistic effect asa result of increased biodegradability and optimum conditions (such asC/N ratio). A surface (optimisation) model indicated that maximum methane production can be achieved by blending chicken litter (30–35%) and a (65–70%) mixture of yoghurt whey, hay and wheat straw with aC/N ratio of (26–27.5).

Non-linear modelling of a heaving point absorber: The surge effect

This paper presents a numerical model that simulates the behaviour of an offshore point absorber wave energy converter (WEC). The model receives 1st order irregular waves as input and delivers instantaneous displacements, velocities and power as output. The model outputs are strongly non-linear due to the nature of some parts of the device, such as the power take off system (PTO), the mooring wires and the drag forces exerted on the wet bodies.Two different devices are modelled, a two-body device consisting in a floating buoy attached to a linear generator placed at the sea bed and a three-body device, which also includes a submerged sphere located halfway from the float and the generator. For each device, the model takes into account either the heave mode only or the heave and surge modes combined.The devices have been tuned to the Mediterranean wave climate, taking particular attention to the floater dimensions and to the geometrical design of the PTO, which has been redesigned to adapt to the newly introduced surge conditions.For the two-body device, although the dynamic behaviour changes when the surge is included, no relevant differences are observed regarding the power production. When studying the three-body device, results show two clear trends. For high waves, the surge leads to a decrease in the production, whereas for smaller waves it affects positively the power absorption. Overall, the negative contribution is more relevant but also less frequent, leading to no substantial change in the power production.Including the surge mode in the model does not give significant variations in production rates and therefore, may be neglected only for energy production assessment. However, it should always be taken into account at the design stage.

Physiographic factors underlie rates of biomass production during succession in Great Lakes forest landscapes

Biomass production in living trees is the basis of numerous forest ecosystem functions and services. However, rates of and controls on biomass production vary widely across temperate forests, particularly over successional timescales of decades and centuries. Biomass production in temperate forests is most often interpreted within the context of biotic or top-down controls, such as species composition or disturbance. However, there is need to investigate how bottom-up physiographic factors, such as landform attributes, drainage, and soil properties mediate biomass production. In order to investigate patterns, controls, and potentials for biomass production across spatial levels ranging from individual ecosystems, to landscapes, to entire regions, we synthesized long-term forest inventory datasets from the United States Great Lakes region, placed them in the context of a hierarchical ecological unit classification, and tested the influence of physiographic factors on biomass production rates and temporal trajectories across ecological levels. Key findings include: 1) At nearly all ecological levels, physiographic controls (e.g., soil texture, drainage class, water table depth) on soil moisture status are significant predictors of variation in biomass production rates, with mesic sites accumulating biomass more rapidly than xeric sites, which, in turn accumulate biomass more rapidly than hydric sites. 2) Aboveground live biomass can apparently continue to accumulate through 2–3 centuries of succession, exceeding 300–400Mgha−1 on mesic sites throughout the region. 3) Stand age distributions indicate that hydric sites are harvested least often, while the high production rates of mesic sites suggest they are most appropriate for frequent harvesting. 4) Median, 1st-quartile, and 3rd-quartile growth rates of individual ecosystems, landscapes, and ecoregional subsections and sections reveal ecological units in which forests may vary in their potential for increases or decreases in biomass production, e.g., due to management interventions, climate change, or disturbances. Specifically, some units have tightly constrained distributions, suggesting little capacity for change in production rates relative to observed medians, while other units have wide variation in biomass production rates, indicating the potential for relatively large increases or decreases in production. Altogether, the results of this analysis show that physiography exerts widespread, bottom-up controls on biomass production across the region of study, and can be used in spatially explicit frameworks to understand ecosystem functioning and inform scientific forest management.