摘要 :
Irregular access patterns are a major problem for today's optimizing compilers. In this paper, a novel approach will be presented that enables transformations that were designed for regular loop structures to be applied to linked ...
展开
Irregular access patterns are a major problem for today's optimizing compilers. In this paper, a novel approach will be presented that enables transformations that were designed for regular loop structures to be applied to linked list data structures. This is achieved by linearizing access to a linked list, after which further data restructuring can be performed. Two subsequent optimization paths will be considered: annihilation and sublimation, which are driven by the occurring regular and irregular access patterns in the applications. These intermediate codes are amenable to traditional compiler optimizations targeting regular loops. In the case of sublimation, a run-time step is involved which takes the access pattern into account and thus generates a data instance specific optimized code. Both approaches are applied to a sparse matrix multiplication algorithm and an iterative solver: preconditioned conjugate gradient. The resulting transformed code is evaluated using the major compilers for the x86 platform, GCC and the Intel C compiler.
收起
摘要 :
We explored correlation in diet trends for five piscivorous predators that reproduce on the Pribilof Islands as illustrative of the shifting structure of the Bering Sea ecosystem. We evaluated the size and species of prey consumed...
展开
We explored correlation in diet trends for five piscivorous predators that reproduce on the Pribilof Islands as illustrative of the shifting structure of the Bering Sea ecosystem. We evaluated the size and species of prey consumed by adult female and juvenile northern fur seals (Callorhinus ursinus) and adults and chicks of black-legged kittiwakes (Rissa tridactyla), red-legged kittiwakes (Rissa brevirostris), thick-billed murres (Uria lomvia), and common murres (Una aalge) from data collected between July and October 1960-2000. Sample sources included stomachs from seals and seabirds collected on pelagic foraging grounds in the eastern Bering Sea, seal scats from rookeries and seabird regurgitations and whole prey from nest sites on St. Paul and St. George Islands of the Pribilof Island archipelago. Typical prey included small fish and invertebrates (≤ 20 cm for seals and ≤ 12 cm for seabirds) that concentrate along frontal boundaries of the continental shelf/slope and in the epi-pelagic zone. Squids and fishes including walleye pollock (Theragra chalcogramma), capelin (Mallotus villosus), and sand lance (Ammodytes hexapterus) were variably important in the diet of all five predators. Some prey, such as capelin, were principal in predator diets during the 1960s (seals) and into the early 1980s (seabirds), but declined or disappeared from all predator diets thereafter while others, such as walleye pollock, occurred with increasing frequency from the 1970s forward. As the number of individuals consuming walleye pollock increased, the overall volume of pollock in seabird diets declined. This decline was coincident with a decrease in the age and body size of pollock consumed by both seabirds and fur seals. Squid and pollock were negatively correlated in the diets of their primary consumers, northern fur seals (Pearson's coefficient -0.71, p = 0.016) and thick-billed murres (Pearson's coefficient = -0.74, p = 0.015) from the 1970s forward. Inter-island variation in diet was evident to varying degrees for all predators, with a prevalence offish on St. Paul Island and invertebrates on St. George Island. Bayesian time-series analysis of synthesized data described significant temporal cross-correlation in diet among northern fur seals, red- and black-legged kittiwakes, and thick-billed murres. For all correlated predators except common murres, beta-binomial modeling indicated that trends in the occurrence of four of the five primary prey (sand lance, capelin, squid, and pollock) evaluated, were significantly associated with eastern Bering Sea time-series trends in sea surface temperature, ice retreat or a combination of both. Data synthesis highlighted potential competition and a scenario for the effects of an altered prey field on the population stability of predators. The association between correlated diet changes among predators and indices of oceanographic shifts in the 1970s and the 1990s allow scrutiny of hypotheses concerning causal mechanisms in population declines.
收起
摘要 :
Sediment is one of the principal pollutants of surface waters of the United States. Efforts by the USDA to quantify and control sediment erosion have historically focused on fields and upland areas. There is a growing body of evid...
展开
Sediment is one of the principal pollutants of surface waters of the United States. Efforts by the USDA to quantify and control sediment erosion have historically focused on fields and upland areas. There is a growing body of evidence in agricultural areas, however, that the locus of sediment erosion has shifted from fields and uplands to channels. This is a critical issue in the Conservation Effects Assessment Project that evaluates the effectiveness of controls on sediment erosion. Rapid geomorphic assessments indicate that channel contributions are significant sources of sediment in the studied watersheds. The relative importance of channel processes are obtained by comparing "reference" yields for the ecoregion with the respective watershed yields. Annual suspended sediment yields for the Conservation Effects Assessment Project watersheds exceed the median value for stable streams by 243% in Iowa, 290% in New York, 630% in Mississippi, and between 2,120% and 7,410% in Oklahoma. Erosion from streambanks is an important process that must be addressed in management strategies aimed at controlling sediment production and delivery.
收起
摘要 :
Time-resolved optical spectroscopy has been used to measure the shock pressure steadiness, emissivity, and temperature of liquid deuterium shocked to 22-90 GPa. The shock was produced using magnetically accelerated flyer plate imp...
展开
Time-resolved optical spectroscopy has been used to measure the shock pressure steadiness, emissivity, and temperature of liquid deuterium shocked to 22-90 GPa. The shock was produced using magnetically accelerated flyer plate impact, and spectra were acquired with a suite of four fiber-optic-coupled spectrometers with streak camera detectors. The shock pressure changes by an average of -1.2% over the 10-30 ns cell transit time, determined from the relative changes in the shock front self-emission with time. The shock front reflectivity was measured from 5140 A and 5320 A laser light reflected from the D_2 shock. The emissivity inferred from the reflectivity measurements was in reasonably good agreement with quantum molecular dynamics simulation predictions. The spectral radiance wavelength dependence was found to agree well (average normalized χ~2=1.6) with a Planckian multiplied by the emissivity. The shock front temperature was determined from the emissivity and the wavelength-dependent shock self-emission. Thirty-seven temperature measurements spanning the 22-90 GPa range were accumulated. The large number of temperature measurements enables a comparison of the scatter in the data with expectations for a Gaussian distribution. This facilitates determination of uncertainties that incorporate both apparatus contributions and otherwise unquantified systematic effects that cause self-emission variations from one experiment to another. Agreement between temperatures determined from the absolute spectral radiance and from the relative shape of the spectrum further substantiates the absence of systematic biases. The weighted mean temperature uncertainties were as low as ±3-4%, enabling the discrimination between competing models for the D_2 equation of state (EOS). The temperature results agree well with models that predict a maximum compression of ～4.4. Softer models that predict approximately sixfold compression are inconsistent with the data to a very high statistical confidence level. Previous analysis [D. Saumon and T. Guillot, Astrophys. J. 609, 1170 (2004)] of Jupiter's internal structure has shown that the core mass is restricted to be less than approximately three times the mass of the Earth, if EOS models consistent with these temperature measurements are employed.
收起
摘要 :
This paper is concerned with the design and the analysis of a semi-active suspension controller. In the recent years different kinds of semi-active control strategies, like two-state Skyhook, LQ-clipped or model-predictive control...
展开
This paper is concerned with the design and the analysis of a semi-active suspension controller. In the recent years different kinds of semi-active control strategies, like two-state Skyhook, LQ-clipped or model-predictive control, have already been developed in the literature. In this paper, a new semi-active suspension control strategy that a priori satisfies the principal limitations of a semi-active suspension actuator (dissipative constraint and force bounds) is introduced using the tools of the linear parameter varying (LPV) theory. This new approach exhibits some interesting advantages (implementation, performance flexibility, robustness, etc.) compared to already existing methods. Both industrial criterion based evaluation and simulations on a nonlinear quarter vehicle model are performed to show the efficiency of the method and to validate the theoretical approach.
收起
摘要 :
A nutritive sausage-type product was developed with beef tripe, beef liver and soybeans as ingredients. A three-component mixture design was used to obtain seven different formulations (minimum of each main ingredient: 16.5%, maxi...
展开
A nutritive sausage-type product was developed with beef tripe, beef liver and soybeans as ingredients. A three-component mixture design was used to obtain seven different formulations (minimum of each main ingredient: 16.5%, maximum: 67.0%). Ingredients were ground, mixed and packed tightly with a polypropylene film to obtain a roll. Pieces were cooked in boiling water for 90 min. The composition of the obtained products varied within the following ranges: proteins 17.32-25.56 g/100 g, lipids 3.22-3.87 g/100 g, crude fiber 1.50-4.50 g/100 g, minerals 1.44-2.72 g/100 g. Total iron levels varied between 1.39 and 2.98 mg/100 g and calcium levels between 15.07 and 34.01 mg/100 g. Surface response analysis was applied to parameters obtained from texture profile analysis (hardness, adhesiveness, cohesiveness and elasticity). Products hardness increased when the soy content increased; on the contrary, formulations enriched in beef tripe were those of higher elasticity and cohesiveness. Color was mainly determined by the incorporation of liver. A nontrained panel was used to evaluate the acceptance of the different formulations. The most accepted one was that with equal proportions of the three main ingredients. Microbiological challenge testing showed that the thermal treatment was enough for assuring the product safeness even in samples with high initial microbial charge.
收起
摘要 :
The Choptank River is an estuary, tributary of the Chesapeake Bay, and an ecosystem in decline due partly to excessive nutrient and sediment loads from agriculture. The Conservation "Effects Assessment Project for the Choptank Riv...
展开
The Choptank River is an estuary, tributary of the Chesapeake Bay, and an ecosystem in decline due partly to excessive nutrient and sediment loads from agriculture. The Conservation "Effects Assessment Project for the Choptank River watershed was established to evaluate the effectiveness of conservation practices on water quality within this watershed. Several measurement frameworks are being used to assess conservation practices. Nutrients (nitrogen and phosphorus) and herbicides (atrazine and metolachlor) are monitored within 15 small, agricultural subwatersheds and periodically in the lower portions of the river estuary. Initial results indicate that land use within these subwatersheds is a major determinant of nutrient concentration in streams. In addition, the ~(18)O isotope signature of nitrate was used to provide a landscape assessment of denitrification processes in the presence of the variable land use. Herbicide concentrations were not correlated to land use, suggesting that herbicide delivery to the streams is influenced by other factors and/or processes. Remote sensing technologies have been used to scale point measurements of best management practice effectiveness from field to subwatershed and watershed scales. Optical satellite (SPOT-5) data and ground-level measurements have been shown to be effective for monitoring nutrient uptake by winter cover crops in fields with a wide range of management practices. Synthetic Aperture Radar (RADARSAT-1) data have been shown to detect and to characterize accurately the hydrology (hydroperiod) of forested wetlands at landscape and watershed scales. These multiple approaches are providing actual data for assessment of conservation practices and to help producers, natural resource managers, and policy makers maintain agricultural production while protecting this unique estuary.
收起
摘要 :
The aim of this study was to improve the removal of heavy metals from sewage sludge ash by a thermochemical process. The resulting detoxified ash was intended for use as a raw material rich in phosphorus (P) for inorganic fertilis...
展开
The aim of this study was to improve the removal of heavy metals from sewage sludge ash by a thermochemical process. The resulting detoxified ash was intended for use as a raw material rich in phosphorus (P) for inorganic fertiliser production. The thermochemical treatment was performed in a rotary kiln where the evaporation of relevant heavy metals was enhanced by additives. The four variables investigated for process optimisation were treatment temperature, type of additive (KCl, MgCl_2) and its amount, as well as type of reactor (directly or indirectly heated rotary kiln). The removal rates of Cd, Cr, Cu, Ni, Pb, Zn and of Ca, P and Cl were investigated.
The best overall removal efficiency for Cd, Cu, Pb and Zn could be found for the indirectly heated system. The type of additive was critical, since MgCl_2 favours Zn- over Cu-removal, while KCl acts conversely. The use of MgCl_2 caused less particle abrasion from the pellets in the kiln than KCl. In the case of the additive KCl, liquid KCl - temporarily formed in the pellets - acted as a barrier to heavy metal evaporation as long as treatment temperatures were not sufficiently high to enhance its reaction or evaporation.
收起
摘要 :
This article explores individual and community action taken in response to perceived environmental risks by investigating the determinants of environmental action across a range of action types. A conceptual framework is first pre...
展开
This article explores individual and community action taken in response to perceived environmental risks by investigating the determinants of environmental action across a range of action types. A conceptual framework is first presented, which provides a foundation for investigating the role of local compositional (i.e., individual characteristics), contextual (i.e., neighborhood environment), and collective (i.e., social networks) factors in environmental action. To test the utility of the conceptual framework, a quantitative survey was administered to a random sample of households (n = 512) in Hamilton, Canada. The results suggest that the predictors of environmental action vary by action type (i.e., personal change, individual civic action, and cooperative civic action), and that factors related to perceived environmental exposure and social capital generally play a stronger, more consistent role in civic environmental action than so-ciodemographic or neighborhood factors. The results underscore the role of social connection in responses to perceived environmental risks.
收起
摘要 :
A boundary-type meshless method named dual reciprocity hybrid boundary node method (DRHBNM) is presented. It can be applied to solve elasticity problems with body force, centrifugal load, or other similar problems. In this method,...
展开
A boundary-type meshless method named dual reciprocity hybrid boundary node method (DRHBNM) is presented. It can be applied to solve elasticity problems with body force, centrifugal load, or other similar problems. In this method, the solution comprises two parts, i.e., the general solution and the particular solution. The general solution is solved by the hybrid boundary node method (HBNM), and the particular one is obtained by the dual reciprocity method (DRM). This method extends the Kelvin fundamental solution for static elastic problems without body force to non-homogeneous problems with body or inertial forces. A modified variational formulation is applied to form the discrete equations of HBNM. The moving least squares (MLS) are employed to approximate the boundary variables, while the domain variables are interpolated by the classical fundamental solution. The particular solution for the body force is obtained by DRM, and the integration in the domain is interpolated by the radial basis function. The proposed method retains the characteristics of the meshless method. At the same time, it employs the fundamental solution as in the boundary element method (BEM). Therefore, this method has the advantages of both meshless method and BEM. It does not require a 'boundary element mesh', either for the purpose of interpolation of the solution variables, or for the integration of the 'energy'. The points in the domain are used only to interpolate particular solutions by the radial basis function and it is not necessary for the integration and approximation of the solution variables. Finally, the boundary solution variables are interpolated by the independent smooth segment boundary. As special treatments for corners are not required, it can obtain accurate boundary tractions for non-smooth boundaries.
Numerical examples of 2-D elasticity problems with body force are used to demonstrate the versatility of the method and its fast convergence. The computational results for unknown variables are accurate. Also, the variable parameters have little influence on the results and can be changed in wide ranges. It is shown that the present method is effective and can be widely applied to practical problems.
收起
