Substantial Temperature Difference Research Articles

Regional relationships between surface temperature, vegetation, and human settlement in a rapidly urbanizing ecosystem

Regional climate change induced by rapid urbanization is responsible for and may result from changes in coupled human-ecological systems. Specifically, the distribution of urban vegetation may be an important intermediary between patterns of human settlement and regional climate spatial variability. To test this hypothesis we identified the relationships between surface temperature, one component of regional climate, vegetation, and human settlement patterns in the Phoenix, AZ, USA region. Combining satellite-derived surface temperature and vegetation data from an early summer day with US Census and topographic data, we found substantial surface temperature differences within the city that correlate primarily with an index of vegetation cover. Furthermore, both of these patterns vary systematically with the social characteristics of neighborhoods through the region. Overall, every $10,000 increase in neighborhood annual median household income was associated with a 0.28°C decrease in surface temperature on an early summer day in Phoenix. Temperature variation within a neighborhood was negatively related to population density. A multivariate model generated using path analysis supports our hypothesis that social impacts on surface temperature occur primarily through modifications of vegetation cover. Higher income neighborhoods were associated with increased vegetation cover and higher density neighborhoods were associated with decreased vegetation variability. These results suggest that settlement patterns in the central Arizona region influence regional climate through multiple pathways that are heterogeneously distributed throughout the city.

VENTILATION OF SMALL MULTISPAN GREENHOUSE IN RELATION TO THE WINDOW OPENINGS CALCULATED WITH CFD

Ventilation is the most important aspect for the climatization of greenhouses. Heat, moisture, and CO2 are removed through ventilation. The effect of the dimensions of the ventilation windows and the orientation to the wind are investigated for a summer condition for a greenhouse design with a crop. Calculations are done using computational fluid dynamics (CFD). The ventilation rate and the temperature distribution in the greenhouse are compared for the different ventilation openings. The influence of wind direction is determined at 5 m s-1 windspeed together with the situation when no wind is present. The results show a large temperature gradient in the greenhouse. This gradient can be explained from the fact that the heat input is high causing a substantial temperature difference between the greenhouse air and the ambient. Ventilation increased as the window opening increased as expected. Opening only the window on the windward side resulted in almost double the ventilation than opening both the leeward and windward orientated windows. Side ventilation increases the ventilation especially when no wind is present

Coronal Emission Measures and Abundances for Moderately Active K Dwarfs Observed byChandra

We have used Chandra to resolve the nearby 70 Oph (K0 V+K5 V) and 36 Oph (K1 V+K1 V) binary systems for the first time in X-rays. The LETG/HRC-S spectra of all four of these stars are presented and compared with an archival LETG spectrum of another moderately active K dwarf, Epsilon Eri. Coronal densities are estimated from O VII line ratios and emission measure distributions are computed for all five of these stars. We see no substantial differences in coronal density or temperature among these stars, which is not surprising considering that they are all early K dwarfs with similar activity levels. However, we do see significant differences in coronal abundance patterns. Coronal abundance anomalies are generally associated with the first ionization potential (FIP) of the elements. On the Sun, low-FIP elements are enhanced in the corona relative to high-FIP elements, the so-called Different levels of FIP effect are seen for our stellar sample, ranging from 70 Oph A, which shows a prominent solar-like FIP effect, to 70 Oph B, which has no FIP bias at all or possibly even a weak inverse FIP effect. The strong abundance difference exhibited by the two 70 Oph stars is unexpected considering how similar these stars are in all other respects (spectral type, age, rotation period, X-ray flux). It will be difficult for any theoretical explanation for the FIP effect to explain how two stars so similar in all other respects can have coronae with different degrees of FIP bias. Finally, for the stars in our sample exhibiting a FIP effect, a curious difference from the solar version of the phenomenon is that the data seem to be more consistent with the high-FIP elements being depleted in the corona rather than a with a low-FIP enhancement

Thermionic-tunneling multilayer nanostructures for power generation

A method for power generation based on nanoengineered interface design with partially filled gap is presented. The proposed device allows a substantial temperature difference to exist between heat source and heat sink or two electrodes, thereby maximizing heat source utilization. A unified model and detailed analyses are provided for the solid device operating either as a power generator or as a cooler. Our analyses show that efficiency of about 50% of the corresponding Carnot efficiency can be achieved.

Wave Flow Simulations Over Arctic Leads

We investigate the flow over Arctic leads using a mesoscale numerical model, typical of both summer and winter, under idealised conditions. We find that Arctic leads may be the source of standing atmospheric internal gravity waves during both seasons. The summertime wave may be compared with the wave generated by a small ridge, though with the phase reversed. The mechanism for exciting the wave is found to be the internal boundary layer developing due to horizontal variations in surface temperature and roughness length. During the more exploratory wintertime simulations, with substantial temperature difference between the lead and the ice surface, we find that secondary circulations and intermittent wave-breaking may occur. The effects of the lead appear far downstream.

Reproductive Biology and Ecology of Shortspine Thornyhead Rockfish, Sebastolobus alascanus, and longspine thornyhead rockfish, S. altivelis, from the northeastern Pacific Ocean

We examined the reproductive biology and estimated life history parameters for female shortspine thornyhead, Sebastolobus alascanus, and longspine thornyhead, S. altivelis, from histological samples prepared from specimens collected from both Alaska and the West Coast of the United States. Both species spawn pelagic gelatinous egg masses, although timing differs between taxa and locations. Shortspines spawn between April and July in Alaska and between December and May along the West Coast. Longspines spawn between January and April along the West Coast. Length at 50% maturity differed between species and areas, with shortspines at 21.48 cm in Alaska and 18.19 cm on the West Coast, and longspines at 17.83 cm on the West Coast. We used the gonadosomatic index to estimate instantaneous rates of natural mortality (M). Values of M differed little between species and areas despite substantial differences in temperature and dissolved oxygen concentrations. Estimates for shortspines from both Alaska and the West Coast ranged between 0.013 and 0.017, while longspines from the West Coast showed an M value of 0.015. Such low estimates of M suggest Sebastolobus are extremely long-lived.

Environmental variation, vegetation distribution, carbon dynamics and water/energy exchange at high latitudes

Abstract. The responses of high latitude ecosystems to global change involve complex interactions among environmental variables, vegetation distribution, carbon dynamics, and water and energy exchange. These responses may have important consequences for the earth system. In this study, we evaluated how vegetation distribution, carbon stocks and turnover, and water and energy exchange are related to environmental variation spanned by the network of the IGBP high latitude transects. While the most notable feature of the high latitude transects is that they generally span temperature gradients from southern to northern latitudes, there are substantial differences in temperature among the transects. Also, along each transect temperature co‐varies with precipitation and photosynthetically active radiation, which are also variable among the transects. Both climate and disturbance interact to influence latitudinal patterns of vegetation and soil carbon storage among the transects, and vegetation distribution appears to interact with climate to determine exchanges of heat and moisture in high latitudes. Despite limitations imposed by the data we assembled, the analyses in this study have taken an important step toward clarifying the complexity of interactions among environmental variables, vegetation distribution, carbon stocks and turnover, and water and energy exchange in high latitude regions. This study reveals the need to conduct coordinated global change studies in high latitudes to further elucidate how interactions among climate, disturbance, and vegetation distribution influence carbon dynamics and water and energy exchange in high latitudes.

Environmental variation, vegetation distribution, carbon dynamics and water/energy exchange at high latitudes

Abstract. The responses of high latitude ecosystems to global change involve complex interactions among environmental variables, vegetation distribution, carbon dynamics, and water and energy exchange. These responses may have important consequences for the earth system. In this study, we evaluated how vegetation distribution, carbon stocks and turnover, and water and energy exchange are related to environmental variation spanned by the network of the IGBP high latitude transects. While the most notable feature of the high latitude transects is that they generally span temperature gradients from southern to northern latitudes, there are substantial differences in temperature among the transects. Also, along each transect temperature co-varies with precipitation and photosynthetically active radiation, which are also variable among the transects. Both climate and disturbance interact to influence latitudinal patterns of vegetation and soil carbon storage among the transects, and vegetation distribution appears to interact with climate to determine exchanges of heat and moisture in high latitudes. Despite limitations imposed by the data we assembled, the analyses in this study have taken an important step toward clarifying the complexity of interactions among environmental variables, vegetation distribution, carbon stocks and turnover, and water and energy exchange in high latitude regions. This study reveals the need to conduct coordinated global change studies in high latitudes to further elucidate how interactions among climate, disturbance, and vegetation distribution influence carbon dynamics and water and energy exchange in high latitudes.

The effects of land use in meteorological modeling: implications for assessment of future air quality scenarios

In recent years, there has been an increased use of prognostic meteorological models to assess current and future air quality related problems. Often, these meteorological models are applied in their forecasting mode with current land use/land cover patterns and data assimilation techniques to generate historical meteorological data for use in air quality models. In this study, we examined the sensitivity of land use/land cover on the predicted meteorological fields, and the implications for examining air quality in a future year. A community-based mesoscale meteorological model (MM5-Version 1) was applied to the northeastern US urban corridor under two scenarios, one with the existing land use/land cover (base case), and the second reflecting a hypothetical change in about 40% of the base case urban grid cells to deciduous forest. A comparison of the two meteorological fields reveals substantial localized differences in surface temperature and zonal wind speeds. These findings suggest reevaluation of the practice of using historical meteorological fields to assess future air quality, especially if one expects large changes in land use patterns.

Influence of coal quality on combustion performance

Three coals have been fired in a tangentially and an opposed fired full scale power plant (about 400 MW e) and in a pilot scale test rig (160 kW t) in order to investigate the influence of coal quality on nitrogen oxide (NO) formation and unburned carbon in relation to furnace design. In-flame and furnace gas temperatures have been measured, and substantial differences in temperature between the coals were observed in the full scale furnaces. Identical trends in NO emission as a function of coal type were obtained for the three furnaces. The emissions correlated well with the high temperature volatile yield obtained from heated wire mesh analysis. Under air staging conditions the pilot scale test rig was able to reproduce quantitatively the amount of NO from the tangentially fired plant, which operates with over fire air. This is probably due to the relatively small influence of the near burner mixing pattern on NO formation under these conditions. Emissions from the opposed fire plant with all combustion air introduced through the burners could only be qualitatively reproduced by the pilot furnace. Under single stage conditions the test rig provided higher NO levels. Carbon in ash levels did not show any correlation between the coals and the furnaces. An engineering, mathematical model has been developed describing radiation heat transfer and coal combustion in full scale furnaces. The model has been validated against measured temperatures and the amount of carbon in fly ash. The model was well able to predict average temperature and carbon in ash levels, but failed to predict the influence of coal quality on both temperature and carbon in ash. This may be due to a lack of knowledge on char reactivity and deactivation as a function of temperature and coal type. A brief parametric study has been performed on important model parameters.

A Comparison of the Atmospheric Circulations Simulated by the CCM3 and CSM1*

Abstract The atmospheric state simulated by the National Center for Atmospheric Research (NCAR) Community Climate Model, version 3 (CCM3), is compared to that simulated by the NCAR Climate System Model, version 1 (CSM1). CCM3 is an atmospheric general circulation model that uses specified sea surface temperatures (SSTs) for a lower boundary condition. Observed monthly mean SSTs for 1979–93 were used in the present study. CSM1 is a coupled general circulation model in which the SSTs are determined as part of the simulation and CCM3 serves as the atmospheric component. It is found that the differences between CCM3 and CSM1 are quite small in most measures of the atmospheric circulation, consistent with the accurate and drift-free simulation of the SSTs in the coupled model. There are substantial temperature differences near the surface in the Arctic and over the ocean around Antarctica, resulting from different sea-ice distributions. The tropical precipitation also has significant differences, although neit...

Temperature distribution in polymer samples during DSC-scans

Differential Scanning Calorimetry is frequently used for measurements of thermal properties on all kinds of substances. The temperature lag in the samples depend on the thermal properties and the thermal contact between sample and sample holder. In the paper, we discuss the temperature distribution in samples of comparatively low thermal conductivity, such as polymers. The purpose of this study is to pinpoint the substantial temperature differences that may occur in such bad conducting samples under different conditions. The calculations of the temperature gradients have been carried out by using a finite element software package.

The climate of antarctica in the UGAMP GCM: Sensitivity to topography

Most spectral general circulation models (GCMs) use an envelope topography to set on land surface elevations. The UK Universities Global Atmospheric Modelling Programme General Circulation Model (UGAMP GCM) uses such a formulation for Antarctica, based on the US Navy 10 are minute charts of the region. In the marginal regions of the continent, an envelope topography consistently overestimates the elevation leading to lower-than-observed surface temperatures. Furthermore, errors in excess of 1000 m exist in the US Navy data, and the UGAMP GCM treats the major ice shelves as sea ice, introducing a 12% reduction in the snow-covered area of the continent. Here, we use a new high-resolution, high-accuracy digital elevation model to improve the representation of Antarctica in the UGAMP GCM. The effect of changing the land-sea mask and the topography on the surface temperature, precipitation and wind held is investigated for both summer and winter runs. Changing the land�sea mask had a dramatic effect on temperature, producing a reduction of 13.3°C for the sector west of the Ross Ice Shelf. Using the new mean topography also introduces substantial differences in temperature, wind speed and precipitation for summer and winter.

The climate of antarctica in the UGAMP GCM: Sensitivity to topography

Most spectral general circulation models (GCMs) use an envelope topography to set on land surface elevations. The UK Universities Global Atmospheric Modelling Programme General Circulation Model (UGAMP GCM) uses such a formulation for Antarctica, based on the US Navy 10 are minute charts of the region. In the marginal regions of the continent, an envelope topography consistently overestimates the elevation leading to lower-than-observed surface temperatures. Furthermore, errors in excess of 1000 m exist in the US Navy data, and the UGAMP GCM treats the major ice shelves as sea ice, introducing a 12% reduction in the snow-covered area of the continent. Here, we use a new high-resolution, high-accuracy digital elevation model to improve the representation of Antarctica in the UGAMP GCM. The effect of changing the land–sea mask and the topography on the surface temperature, precipitation and wind held is investigated for both summer and winter runs. Changing the land–sea mask had a dramatic effect on temperature, producing a reduction of 13.3°C for the sector west of the Ross Ice Shelf. Using the new mean topography also introduces substantial differences in temperature, wind speed and precipitation for summer and winter.

Variability in temperature regulation of CO2 fluxes and N mineralization from five Hawaiian soils: implications for a changing climate

AbstractWe examined the possibility that microbial adaptation to temperature could affect rates of CO2, N2O and CH4 release from soils. Laboratory incubations were used to determine the functional relationship between temperature and CO2, N2O and CH4 fluxes for five soils collected across an elevational range in Hawaii. Initial rates of CO2 production and net N mineralization increased exponentially from 15 °C to 55 °C; initial rates of CH4 and N2O release were more complex. No optimum temperature (in which rates decline at higher and lower temperatures) was apparent for any of the gases, but respiration declined with time at higher temperatures, suggesting rapid depletion of readily available substrate. Mean Q10S for respiration varied from 1.4 to 2.0, a typical range for tropical soils. The functional relationship between CO2 production and temperature was consistent among all five soils, despite the substantial differences in mean annual temperature, soils, and land‐use among the sites. Temperature responses of N2O and CH4 fluxes did not follow simple Q10 relationships suggesting that temperature functions developed for CO2 release from heterotrophic respiration cannot be simply extrapolated. Expanding this study to tropical heterotrophic respiration, the flux is more sensitive to changes in Q10 than to changes in temperature on a per unit basis: the partial derivative with respect to temperature is 2.4 Gt C ·° C−1 with respect to Q10, it is 3.5 Gt C · Q10 unit−1. Therefore, what appears to be minor variability might still produce substantial uncertainty in regional estimates of gas exchange.

Effect of coal rank and process conditions on temperature distribution in a liquefaction reactor

The temperature distribution in a liquefaction reactor in the integrated TSL process is studied. The effects of gas and slurry superficial velocities, process solvent characteristics, reactor length, and catalyst sulfiding agent on the exotherm and temperature difference in the reactor are studied. A substantial temperature difference is observed with subbituminous coal as compared with bituminous coal, at comparable reactor conditions. Some of the factors that are believed to have contributed to the large exotherm and temperature difference in the reactor are slow kinetics and high reaction heat for subbituminous coal conversion and pyrrhotite catalysis.

Intrinsically irreversible acoustic heat engine

Thermodynamic effects will be described associated with structures placed within a gas contained in an acoustically resonant tube. For suitable geometries and frequencies substantial temperature differences, perhaps 50 times the adiabatic temperature changes in the gas, can be produced. The experiments can be understood in a context of certain principles, including the principle of broken thermodynamic symmetry, which describe intrinsically irreversible reciprocating heat engines. [Work supported by LANL and by the D.O.E.]

Properties and microstructure of nickel and nickel-alloy wire produced by working sintered blanks

1. A study was made of the mechanical properties of 3-,2-, and 1-mm-diameter wires (reductions of e = 35, 55, and 75%, respectively) in unalloyed nickel and nickel alloys, produced by powder-metallurgy techniques from carbonyl nickel powder. 2. The mechanical properties (σV,σS,δ, and number of bends n) of such wire in the work-hardened condition are determined by its degree of cold deformation: The maximum values of strength (σV andσS) and the minimum values of ductility characteristics (δ and n) correspond to the highest value ofe, i.e., 75%. 3. The elongation and number of bends of wires of all diameters gradually improve as the annealing temperature is raised from 500 to 700°C, which can be ascribed to both propagation of recrystallization processes and a slight refining of metal brought about by annealing in a hydrogen atmosphere with a dew point of between −35 and −40°C. 4. The mechanical properties of 1-mm-diameter wire (e = 75%) in alloys with fine oxide inclusions vary within a narrow range and, in spite of substantial differences in recrystallization temperature, depend only little on alloy composition, which is due to the severe deformation of the materials and the effect that such deformation has on dispersion-hardened alloys. 5. A Ni + 4% W alloy has a high recrystallization temperature, and, because of this, wire in this alloy retains its high strength and low ductility properties right up to an annealing temperature of 700°C. 6. Unalloyed-nickel and nickel-alloy wires produced by cold-working sintered blanks can be successfully used in either the work-hardened or annealed condition. Heat-treatment parameters must be chosen individually for each specific type of operation.

The transfer of heat from a rotating disk to a liquid in a regime of laminar flow

We present the results from an experimental study of the transfer of heat from a disk for a substantial temperature difference between the liquid and the disk, and for a change in the viscosity of the liquid over a wide range.

Forced Convection Heat Transfer From an Isothermal Sphere to Water

Heat transfer from a spherical heating element by forced convection occurs in many situations of practical importance. While the present investigation stems from interest in spherical fuel elements for liquid-cooled nuclear reactors, similar heat-transfer conditions may prevail in chemical process reactors and in other engineering applications. Previously reported measurements of convective heat-transfer coefficients from spheres to liquids have been limited to low Reynolds numbers and to negligibly small temperature differences. This paper correlates these earlier data with new measurements taken at much higher Reynolds numbers and with substantial temperature difference between the heating surface and the liquid. The significance of the larger temperature difference is twofold: Since the viscosity variation of liquids with temperature is usually strong, there may be an important viscosity change across the boundary layer. Furthermore, natural convection effects may not be ignored in regions of large temperature difference and low or moderate Reynolds number. Both of these effects are discussed in the paper.