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Vegetation acclimation to changing climate, in particular elevated atmospheric concentrations of carbon dioxide (CO2), has been observed to include modifications to the biochemical and ecophysiological functioning of leaves and the structural components of the canopy. These responses have the potential to significantly modify plant carbon uptake and surface energy partitioning, and have been attributed with large-scale changes in surface hydrology over recent decades. While the aggregated effects of vegetation acclimation can be pronounced, they often result from subtle changes in canopy properties that require the resolution of physical, biochemical and ecophysiological processes through the canopy for accurate estimation. In this paper, the first of two, a multilayer canopy-soil-root system model developed to capture the emergent vegetation responses to environmental change is presented. The model incorporates both C3 and C4 photosynthetic pathways, and resolves the vertical radiation, thermal, and environmental regimes within the canopy. The tight coupling between leaf ecophysiological functioning and energy balance determines vegetation responses to climate states and perturbations, which are modulated by soil moisture states through the depth of the root system. The model is validated for three growing seasons each for soybean (C3) and maize (C4) using eddy-covariance fluxes of CO2, latent, and sensible heat collected at the Bondville (Illinois) Ameriflux tower site. The data set provides an opportunity to examine the role of important environmental drivers and model skill in capturing variability in canopy-atmosphere exchange. Vertical variation in radiative states and scalar fluxes over a mean diurnal cycle are examined to understand the role of canopy structure on the patterns of absorbed radiation and scalar flux magnitudes and the consequent differences in sunlit and shaded source/sink locations through the canopies. An analysis is made of the impact of soil moisture stress on carbon uptake and energy flux partitioning at the canopy-scale and resolved through the canopy, providing insight into the roles of canopy structure and metabolic pathway on the response of each crop to moisture deficits. Model calculations indicate increases in water use efficiency (WUE) with increasing moisture stress, with average maize WUE increases of 45% at the highest levels of plant stress examined here, relative to 20% increases for soybean.

The ability to accurately predict land-atmosphere exchange of mass, energy, and momentum over the coming century requires the consideration of plant biochemical, ecophysiological, and structural acclimation to modifications of the ambient environment. Amongst the most important environmental changes experienced by terrestrial vegetation over the last century has been the increase in ambient carbon dioxide (CO2) concentrations, with a projected doubling in CO2 from preindustrial levels by the middle of this century. This change in atmospheric composition has been demonstrated to significantly alter a variety of leaf and plant properties across a range of species, with the potential to modify land-atmosphere interactions and their associated feedbacks. Free Air Carbon Enrichment (FACE) technology has provided significant insight into the functioning of vegetation in natural conditions under elevated CO2, but remains limited in its ability to quantify the exchange of CO2, water vapor, and energy at the canopy scale. This paper addresses the roles of ecophysiological, biochemical, and structural plant acclimation on canopy-scale exchange of CO2, water vapor, and energy through the application of a multilayer canopy-root-soil model (MLCan) capable of resolving changes induced by elevated CO2 through the canopy and soil systems. Previous validation of MLCan flux estimates were made for soybean and maize in the companion paper using a record of six growing seasons of eddy covariance data from the Bondville Ameriflux site. Observations of leaf-level photosynthesis, stomatal conductance, and surface temperature collected at the SoyFACE experimental facility in central Illinois provide a basis for examining the ability of MLCan to capture vegetation responses to an enriched CO2 environment. Simulations of control (370 [ppm]) and elevated (550 [ppm]) CO2 environments allow for an examination of the vertical variation and canopy-scale responses of vegetation states and fluxes to elevated CO2. The unique metabolic pathways of the C3 soybean and C4 maize produce contrasting modes of response to elevated CO2 for each crop. To examine the relative roles of direct reduction in stomatal aperature, observed structural augmentation of leaf area, and biochemical down-regulation of Rubisco carboxylation capacity in soybean, a set of simulations were conducted in which one or more of these acclimations are synthetically removed. A 10% increase in canopy leaf area is shown to offset the ecophysiologically driven reduction in latent energy flux by 40% on average at midday. Considering all observed acclimations for soybean, average midday LE (H) were decreased (increased) by 10.5 (18) [W m−2]. A lack of direct stimulation of photosynthesis for maize, and no observed structural or biochemical acclimation resulted in decreases (increases) in average midday LE (H) by 40–50 [W m−2]. An examination of canopy-scale responses at a range of CO2 concentrations projected to be seen over the coming century showed a general continuation in the direction of flux responses. Flux responses showed little sensitivity to assumptions of constant versus linear trends in structural and biochemical acclimation magnitudes over the 400–700 [ppm] concentration range examined here.

Understanding the cause of differences among general circulation model projections of carbon dioxide-induced climatic change is a necessary step toward improving the models. An intercomparison of 14 atmospheric general circulation models, for which sea surface temperature perturbations were used as a surrogate climate change, showed that there was a roughly threefold variation in global climate sensitivity. Most of this variation is attributable to differences in the models' depictions of cloud-climate feedback, a result that emphasizes the need for improvements in the treatment of clouds in these models if they are ultimately to be used as climatic predictors.

The scale dependence of cloud–radiation interaction associated with the parameterizations for fractional cloudiness and radiation used in a global climate model is studied by examining the averages, for different spatial scales, of detailed structure of cloudiness and radiation simulated from a regional climate model that incorporates these parameterizations. The regional model simulation is conducted over an area about (360 km)2 located on the southern Great Plains for the period 10–17 April 1994 during which both satellite and surface measurements of radiation fluxes and clouds are available from the Intensive Observing Period of the Atmospheric Radiation Measurement program. The area corresponds approximately to one gridpoint size of a global climate model with horizontal resolution T31. The regional model simulates well the overall cloud and radiation temporal features when averaged over the entire region. However, specific biases exist in the spatial patterns such as the high clouds, the TOA upwelling solar radiation under cloudy conditions, and the net longwave surface flux under clear conditions at night. The cloud and radiation parameterizations are found to be sensitive to the spatial scale of the computation. The diagnosed total cloudiness shows a strong horizontal resolution dependence that leads to large changes in the surface and TOA radiation budgets. An additional experiment, in which the diagnosed cloud at each level is held constant while the radiation parameterization is recalculated, still produces a substantial sensitivity to spatial scale in the calculated radiation quantities. This is because the nature of the cloud vertical overlapping assumption changes as the horizontal scale of the computation varies.

Global warming, caused by an increase in the concentrations of greenhouse gases, is the direct result of greenhouse gas-induced radiative forcing. When a doubling of atmospheric carbon dioxide is considered, this forcing differed substantially among 15 atmospheric general circulation models. Although there are several potential causes, the largest contributor was the carbon dioxide radiation parameterizations of the models.

Differential evolution (DE) is studied in detail for optimal reactive power flow (ORPF) problems. The concept, mechanism and parameter setting of DE are discussed. Based on the IEEE 14-, 30- and 57-bus system test cases, DE is compared with some basic or improved evolutionary algorithms that have been applied to ORPF. It is found that DE is generally a good algorithm for ORPF and worthy of more attention. However, it is also found that DE requires relatively large populations to avoid premature convergence. The impact of this shortcoming is made clear in the IEEE 118-bus system test case. The effectiveness of parallel computing technology for speeding up the computation of DE-based ORPF is also analysed.

This study aims to investigate the effect of dietary γ-aminobutyric acid (GABA) on the development of thymus tissue structure and function in chicks under heat stress. One-day-old male Wenchang chicks were randomly divided into control group (CK), heat stress group (HS), and GABA+HS group. The chicks from GABA+HS group were administered 0.2 ml of GABA solution daily by oral gavage (50 mg/kg of body weight). Chicks from HS and GABA+HS groups were subjected to heat stress treatment at 40 ± 0.5°C for 2 h every day. Blood and thymus tissue were collected from the chicks at the end of weeks 1–6. Results showed that the thymus weight and index, thickness of cortex, cortex/medulla ratio, number of lymphocytes, activity of superoxide dismutase, total antioxidant capacity, and glutathione peroxidase, and plasma level of tumor necrosis factor-α in HS group were significantly lower than in CK group (P < 0.05). The Toll-like receptor 2 (TLR2) expression in the late stage of heat stress, malondialdehyde (MDA) content, thymocyte apoptosis rate, number of lymphocytes in the S and G2/M phases, and plasma levels of interleukin-4 and interferon-γ in HS group were significantly higher than in CK group (P < 0.05). In contrast, the integrity of thymus tissue structure of GABA+HS group was improved compared with HS group. The TLR2 expression in the early stage of heat stress and the activity of antioxidant enzymes in GABA+HS group were significantly higher than in HS group (P < 0.05), and the MDA content, thymocyte apoptosis rate, number of lymphocytes in the S and G2/M phases, and plasma level of IL-4 and IFN-γ in GABA+HS group were significantly lower than in HS group (P < 0.05). We concluded that heat stress caused structure damage to thymus tissue of chicks, changed the plasma levels of cytokines, reduced the antioxidant activity, and increased cell apoptosis in chick thymus. GABA alleviated the negative effects on the development of chick thymus, improved the immune function of thymus, and played a protective role by regulating the plasma levels of cytokines and antioxidant activity of thymus tissue.

The generation of welding residual stress easily causes fatigue cracks in the interior of the structure where the welding residual stress is high. It finally causes the fatigue fracture under the combined action of external load and internal stress, resulting in failure of welded structural parts. It has the fatigue crack and fracture failure during the use of the radial engineering steel ring. In view of this phenomenon, this paper proposes a spectrum aging test analysis of steel rings using spectral harmonic vibration stress relief system. Through the statistical analysis of the test data, the results show that after the vibration aging treatment, the transverse and longitudinal welding residual stresses in the steel ring's weld seam have a large downward trend as a whole, and the residual stress reduction rate of each test point is about 25%. This study provides a reference for the application of vibration aging technology to steel ring weldments.

Thermal cycling parameters of pulse arc welding for SAPH440 steel was experimentally determined for different heat inputs. The welding thermal cycle curves of the weld fusion and heat-affected zones were successfully constructed based on the thermocouple measurements through the back drilling hole. The hardness and tensile strength variations under different heat inputs were also analyzed. This provided a database for the determination and optimization of process parameters, improvement of microstructure and properties of weld fusion and heat affected zones, and overall quality of pulse arc welding of steels.

In order to study the effect of Ri/T on welding residual stress in forging presses for Auto parts material, a welding experiment program was developed. The residual stress of thick pipe 10mm joint was measured by the blind hole drilling method. The simulation results within and near the weld joint, the transverse residual stresses are tensile on the inside surface which already close to yield strength with creasing the Ri/T ratio, and compressive on the outer surface; The prediction results from FEM are in a good agreement with the experimental measurement which are important to apply data for manufacturing plant.