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排序方式: 共有221条查询结果,搜索用时 62 毫秒
1.
Anders Riisager K. Michael Eriksen Peter Wasserscheid Rasmus Fehrmann 《Catalysis Letters》2003,90(3-4):149-153
Supported ionic liquid-phase (SILP) catalysts were made by immobilizing Rh-monophosphine complexes of bis(m-phenylguanidinium)phenylphosphine 1 and NORBOS 2 ligands in 1-n-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF6], on a silica support. The catalysts were active in continuous gas- and liquid-phase hydroformylation of propene and 1-octene, exhibiting TOFs up to 88 h-1 for SILP Rh-2 catalysts, while only low selectivities up to 74% n-aldehyde (n/iso ratio of 2.8) were obtained. This is the first example of continuous fixed-bed liquid-phase hydroformylation using SILP catalysts. 相似文献
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Rasmus E. Christiansen Boyan S. Lazarov Jakob S. Jensen Ole Sigmund 《Structural and Multidisciplinary Optimization》2015,52(4):737-754
Resonance and wave-propagation problems are known to be highly sensitive towards parameter variations. This paper discusses topology optimization formulations for creating designs that perform robustly under spatial variations for acoustic cavity problems. For several structural problems, robust topology optimization methods have already proven their worth. However, it is shown that direct application of such methods is not suitable for the acoustic problem under consideration. A new double filter approach is suggested which makes robust optimization for spatial variations possible. Its effect and limitations are discussed. In addition, a known explicit penalization approach is considered for comparison. For near-uniform spatial variations it is shown that highly robust designs can be obtained using the double filter approach. It is finally demonstrated that taking non-uniform variations into account further improves the robustness of the designs. 相似文献
4.
Simon Stisen Inge Sandholt Anette Nørgaard Rasmus Fensholt Karsten Høgh Jensen 《Remote sensing of environment》2008,112(3):1242-1255
Spatially distributed estimates of evaporative fraction and actual evapotranspiration are pursued using a simple remote sensing technique based on a remotely sensed vegetation index (NDVI) and diurnal changes in land surface temperature. The technique, known as the triangle method, is improved by utilizing the high temporal resolution of the geostationary MSG-SEVIRI sensor. With 15 min acquisition intervals, the MSG-SEVIRI data allow for a precise estimation of the morning rise in land surface temperature which is a strong proxy for total daytime sensible heat fluxes. Combining the diurnal change in surface temperature, dTs with an interpretation of the triangular shaped dTs − NDVI space allows for a direct estimation of evaporative fraction. The mean daytime energy available for evapotranspiration (Rn − G) is estimated using several remote sensors and limited ancillary data. Finally regional estimates of actual evapotranspiration are made by combining evaporative fraction and available energy estimates. The estimated evaporative fraction (EF) and actual evapotranspiration (ET) for the Senegal River basin have been validated against field observations for the rainy season 2005. The validation results showed low biases and RMSE and R2 of 0.13 [−] and 0.63 for EF and RMSE of 41.45 W m− 2 and R2 of 0.66 for ET. 相似文献
5.
Jibo Qin Yibo Dou Jianchi Zhou Victor M. Candelario Henrik Rasmus Andersen Claus Hélix-Nielsen Wenjing Zhang 《Advanced functional materials》2023,33(28):2214839
The conversion of waste plastic into high-value-added chemicals is regarded as a promising approach for relieving global plastic pollution and contributing to the circular economy. Herein, a partial calcination strategy is developed to fabricate a zinc oxide/UiO66-NH2 (ZnO/UiO66-NH2) heterojunction, in which ZnO is encapsulated in porous UiO66-NH2 for the photocatalytic valorization of plastic. This strategy preserves the framework structure of UiO66-NH2, thus enabling the formation of ZnO with ultra-small size distributed inside the skeleton. The synergistic effect of the obtained ZnO/UiO66-NH2 heterojunction facilitates providing an efficient channel for carrier/mass transfer and guarantees structural stability. As a result, ZnO/UiO66-NH2 exhibits high activity for converting polylactic acid (PLA) and polyvinyl chloride (PVC) into acetic acid, coupled with H2 production. This work provides a feasible strategy for rationally designing heterojunction photocatalysts, as well as an insight into understanding the process of photocatalytic valorization of plastic. 相似文献
6.
Utility of an image-based canopy reflectance modeling tool for remote estimation of LAI and leaf chlorophyll content at the field scale 总被引:6,自引:0,他引:6
This paper presents a physically-based approach for estimating critical variables describing land surface vegetation canopies, relying on remotely sensed data that can be acquired from operational satellite sensors. The REGularized canopy reFLECtance (REGFLEC) modeling tool couples leaf optics (PROSPECT), canopy reflectance (ACRM), and atmospheric radiative transfer (6SV1) model components, facilitating the direct use of at-sensor radiances in green, red and near-infrared wavelengths for the inverse retrieval of leaf chlorophyll content (Cab) and total one-sided leaf area per unit ground area (LAI). The inversion of the canopy reflectance model is constrained by assuming limited variability of leaf structure, vegetation clumping, and leaf inclination angle within a given crop field and by exploiting the added radiometric information content of pixels belonging to the same field. A look-up-table with a suite of pre-computed spectral reflectance relationships, each a function of canopy characteristics, soil background effects and external conditions, is accessed for fast pixel-wise biophysical parameter retrievals. Using 1 m resolution aircraft and 10 m resolution SPOT-5 imagery, REGFLEC effectuated robust biophysical parameter retrievals for a corn field characterized by a wide range in leaf chlorophyll levels and intermixed green and senescent leaf material. Validation against in-situ observations yielded relative root-mean-square deviations (RMSD) on the order of 10% for the 1 m resolution LAI (RMSD = 0.25) and Cab (RMSD = 4.4 μg cm− 2) estimates, due in part to an efficient correction for background influences. LAI and Cab retrieval accuracies at the SPOT 10 m resolution were characterized by relative RMSDs of 13% (0.3) and 17% (7.1 μg cm− 2), respectively, and the overall intra-field pattern in LAI and Cab was well established at this resolution. The developed method has utility in agricultural fields characterized by widely varying distributions of model variables and holds promise as a valuable operational tool for precision crop management. Work is currently in progress to extend REGFLEC to regional scales. 相似文献
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We present a static program analysis for overlaid data structures such that a node in the structure includes links for multiple data structures and these links are intended to be used at the same time. These overlaid data structures are frequently used in systems code, in order to impose multiple types of indexing structures over the same set of nodes. Our analysis implements two main ideas. The first is to run multiple sub-analyses that track information about non-overlaid data structures, such as lists. The second idea is to control the communication among the sub-analyses using ghost states and ghost instructions. The purpose of this control is to achieve a high level of efficiency by allowing only necessary information to be transferred among sub-analyses and at as few program points as possible. Our analysis has been successfully applied to prove the memory safety of the Linux deadline IO scheduler and AFS server. 相似文献
9.
Antti Lindfors Corresponding author Kai Rasmus Niklas Strömbeck 《International journal of remote sensing》2013,34(2):415-423
A method for measuring continuously the inherent optical properties of water together with the salinity and the temperature values was developed and tested at the Division of Geophysics, University of Helsinki. The flow‐through system operates from a moving boat and has been used to collect parameters for optical modelling, coastal zone and inland water studies and to track the path of the fresh water spreading into sea areas. The system was also used in Lake Vänern, Sweden, to calculate the radiance reflectance, R r, and total back‐scattering efficiency, b b eff, along a transect. An example from the Gulf of Finland is presented, which shows how the spectral behaviour of light changes when moving away from a fresh water source. Data collected from the River Kymijoki estuary showed that the details in a rapidly changing environment were strongly smoothed in a Moderate Resolution Imaging Spectroradiometer (MODIS) data image. The correlation for continuously measured scattering values and MODIS channel 1 data varied between 0.70 and 0.85, n?=?126. Flow‐through measurement datasets can be used to obtain representative sites for vertical profiles or calibration measurements. 相似文献
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