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排序方式: 共有1610条查询结果,搜索用时 15 毫秒
91.
92.
Magnus Bäckström Mohammad Al-Emrani Rober Kliger 《Construction and Building Materials》2009,23(12):3556-3563
The shape of timber changes due to variations in moisture content (MC). Analytical models, which explain how the cladding restrains the timber studs that are prone to twist, are presented. The models are used for parametric studies of various properties, such as longitudinal shrinkage, torsional modulus of elasticity and cross-sectional size of the timber stud and stiffness of the cladding. With respect to twist, the bending stiffness of the cladding is of great importance. Large bending stiffness increases the restraint in the twist-prone studs and results in a straighter wall. Low torsional stiffness in the studs makes it easier for the cladding to restrain twist. 相似文献
93.
Nina Hammer Karina Mathisen Tina Zscherpe De Chen Magnus R?nning 《Topics in Catalysis》2011,54(13-15):922-930
The impact of thermal treatment at various preparation stages of carbon supported Au/TiO2 catalysts prior to oxidation of CO in the presence and absence of hydrogen was studied. An increase in catalytic activity for thermally treated samples due to a more ordered structure of TiO2 was observed. A reversible deactivation of the catalysts occurred in the absence of hydrogen. However, the activity was restored at preferential CO oxidation conditions in presence of hydrogen. 相似文献
94.
Artur Glavic Jörg VoigtJörg Persson Yixi SuJürgen Schubert Joost de GrootWilli Zande Thomas Brückel 《Journal of Alloys and Compounds》2011,509(16):5061-5063
High quality thin films of TbMnO3 were grown by pulsed laser deposition on orthorhombicYAlO3 (1 0 0). The interface and surface roughness of a 55 nm thick film were probed by X-ray reflectometry and atomic force microscopy, yielding a roughness of 1 nm. X-ray diffraction revealed untwinned films and a small mosaic spread of 0.04° and 0.2° for out-of-plane and in-plane reflections, respectively. This high degree of epitaxy was also confirmed by Rutherford backscattering spectrometry. Using polarized neutron diffraction we could identify a magnetic structure with the propagation vector (0 0.27 0), identical to the bulk magnetic structure of TbMnO3. 相似文献
95.
We studied the coupled impurity states in a freestanding semiconductor nanowire (NW), within the effective mass approximation and including the effect of the dielectric mismatch, by using finite element method. Bonding and anti-bonding states are found and their energies converge with increasing distance di between the two impurities. The dependence of the binding energy on the wire radius R and the distance di between the two impurities is investigated, and we compare it with the result of a freestanding NW that contains a single impurity. 相似文献
96.
The shape of timber changes due to variations in moisture content (MC). A poor way of designing and/or erecting a structure may result in excessive deformation. An analytical model, which explains spring in a partition wall, is presented. The model is used for parametric studies of various properties such as longitudinal shrinkage coefficient, modulus of elasticity and cross-sectional size of the timber studs and stiffness of the cladding. With respect to spring, a problem is likely to occur when erecting a wall with single-sided cladding in a drying climate and the structure will benefit from relatively stiff studs and weak cladding. 相似文献
97.
A. Magnus G. Carvalho A.A. CoelhoP.J. von Ranke C.S. Alves 《Journal of Alloys and Compounds》2011,509(8):3452-3456
The determination of the isothermal variation of the entropy (ΔST) is discussed in the present work. We show that ΔST has very different profiles and magnitudes when calculated from M vs. H or M vs. T experimental data. For MnAs compound, ΔST obtained from M vs. T data does not present a colossal peak. This result and the agreement between theoretical and experimental non-colossal magnetocaloric effect indicate that the colossal peak may be miscalculated from M vs. H experimental data. For Gd5Ge2Si2 compound, ΔST obtained from M vs. T data does not present the peak observed in ΔST from M vs. H data. 相似文献
98.
Jennifer M. Ullbrand José M. Córdoba Javier Tamayo-Ariztondo María R. Elizalde Mats Nygren Jon M. Molina-Aldareguia Magnus Odén 《Composites Science and Technology》2010
Several types of carbon nanofibres (CNF) were coated with a uniform and dense copper layer by electroless copper deposition. The coated fibres were then sintered by two different methods, spark plasma sintering (SPS) and hot pressing (HP). The Cu coating thickness was varied so that different volume fraction of fibres was achieved in the produced composites. In some cases, the CNF were pre-coated with Cr for the improvement the Cu adhesion on CNF. The results show that the dispersion of the CNF into the Cu matrix is independent of the sintering method used. On the contrary, the dispersion is directly related to the efficiency of the Cu coating, which is tightly connected to the CNF type. Overall, strong variations of the thermal conductivity (TC) of the composites were observed (20–200 W/mK) as a function of CNF type, CNF volume fraction and Cr content, while the coefficient of thermal expansion (CTE) in all cases was found to be considerably lower than Cu (9.9–11.3 ppm/K). The results show a good potential for SPS to be used to process this type of materials, since the SPS samples show better properties than HP samples even though they have a higher porosity, in applications where moderate TC and low CTE are required. 相似文献
99.
L. Ekman A.-K. Nyman H. Landin U. Magnusson K. Persson Waller 《Journal of dairy science》2018,101(1):556-571
Udder cleft dermatitis (UCD) is an inflammatory skin condition affecting the anterior parts of the udder of dairy cows. The lesions may present as mild or severe skin lesions and have been associated with mastitis and digital dermatitis. The full etiology and pathogenesis are not understood and no large-scale studies have investigated prevalence and risk factors. Therefore, the main objectives of the study were to investigate the prevalence of mild and severe UCD in Swedish dairy herds and to identify risk factors associated with such lesions. We also wanted to investigate risk factors for all cases of UCD and to determine whether UCD increases the risk for mastitis and culling. A random sample of 100 freestall dairy herds were included in the study, and each herd was visited once. Cows were registered as having no, mild, or severe UCD. Additional cow and herd data were obtained via observations, interviews, and the Swedish Official Milk Recording Scheme. The data were analyzed using logistic regression models to identify risk factors for mild and severe UCD. In total, data from 3,479 cows in 99 herds were analyzed. The prevalence of mild and severe UCD was 19 and 9%, respectively. Lesions were found in 98 of 99 herds but the within-herd prevalence of mild (0–43%) and severe (0–33%) UCD varied notably between herds. Breed (Swedish Red compared with Swedish Holstein), certain udder conformation traits, and higher parity were risk factors associated with increased risk of UCD. In addition, cows with hock lesions and cows in herds with high incidence of culling due to hoof and leg diseases had a higher risk for mild UCD. More days in milk and high milk yield were cow-related risk factors associated with severe UCD. Three housing-related factors (shorter cubicles, mattress as cubicle base, and cubicles installed before 2001 compared with 2001–2005), a high incidence of veterinary-treated clinical mastitis and culling due to udder diseases, and a low incidence of culling of first-parity cows in early lactation were herd-related risk factors associated with increased risk for severe UCD. In addition, cows in herds with a high proportion of heifers older than 17 mo that were not inseminated were associated with lower risk of all UCD. Finally, UCD was not associated with the outcomes milk somatic cell count, veterinary-treated clinical mastitis, or culling in the multivariable analyses. The etiology of UCD is most likely multifactorial, involving udder conformation traits and other cow-related risk factors as well as herd-related risk factors. The high prevalence of severe UCD lesions in Swedish dairy cows emphasizes the need for preventive measures and efficient treatments. 相似文献
100.
Hemmendorff M Andersson MT Kronander T Knutsson H 《IEEE transactions on medical imaging》2002,21(12):1536-1543
We present a method for accurate image registration and motion compensation in multidimensional signals, such as two-dimensional (2-D) X-ray images and three-dimensional (3-D) computed tomography/magnetic resonance imaging volumes. The method is based on phase from quadrature filters, which makes it robust to noise and temporal intensity variations. The method is equally applicable to signals of two, three or higher number of dimensions. We use parametric models, e.g., affine models, finite elements or local affine models with global regularization. Experimental results show high accuracy for 2-D and 3-D motion compensation. 相似文献