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排序方式: 共有747条查询结果,搜索用时 15 毫秒
31.
The primary products, 9- and 13-hydroperoxy-octadecadienoic acids, from lipoxygenase catalyzed oxidation of linoleic acid,
were converted into the trimethylsilyl ethers of methyl 9- and 13-hydroxystearates which were completely separated by gas
chromatography on an OV-17 methyl silicone (50% phenyl groups), capillary column. 相似文献
32.
Nolkrantz K Farre C Brederlau A Karlsson RI Brennan C Eriksson PS Weber SG Sandberg M Orwar O 《Analytical chemistry》2001,73(18):4469-4477
We show how an electrolyte-filled capillary (EFC) coupled to a high-voltage power supply can be used as a versatile electroporation tool for the delivery of dyes, drugs, and biomolecules to the cytoplasm of single cells and cells in tissues. A large-voltage pulse applied across the EFC (fused silica, 30 cm long, 375-microm o.d., 30-microm i.d.) gives rise to a small electric field outside the terminus of the EFC, which causes pore formation in cell membranes and induces an electroosmotic flow of electrolyte. When the EFC contains cell-loading agents, then the electroosmotic flow delivers the agents at the site of pore formation. The combination of pore formation and delivery enables loading of materials into the cytoplasm. By patch-clamp and fluorescence microscopy, formation of pores was observed at estimated transmembrane voltages of <85 mV with half-maximum values around 206 mV. The electroporation protocol was demonstrated by introduction of fluorogenic dyes into single NG108-15 cells, cellular processes, and small populations of cells in organotypic hippocampal cultures. Preliminary results are shown in which this protocol was employed for in vivo electroporation of ventral mesencephalon in rat brains. The technique was also used to access organelle-based detection systems inside cells. As a demonstration, 1,4,5-inositoltriphosphate was added to the electrolyte and detected by intracellular organelles in electroporated cells. 相似文献
33.
This paper is concerned with the investigation of a new control technique for the conventional High Voltage Direct Current (HVDC) link. The proposed technique relies upon nonlinear state feedback linearization of the AC/DC power system. 相似文献
34.
The partial oxidation of methane/oxygen mixtures with large exhaust gas dilution (46.3 vol% H2O and 23.1 vol% CO2) has been investigated experimentally and numerically over Rh/CeO2-ZrO2, Rh/ZrO2 and Rh/α-Al2O3 catalysts. Experiments were carried out in a short-contact-time reactor at 5 bar and included exhaust gas analysis, temperature measurements along the reactor, and catalyst characterization. Additional experiments were performed in an optically accessible channel-flow reactor and involved in situ Raman measurements of major gas-phase species concentrations over the catalyst boundary layer and laser-induced fluorescence (LIF) of formaldehyde. A full elliptic two-dimensional numerical code that included elementary hetero-/homogeneous chemical reaction schemes and relevant heat transfer mechanisms in the solid was used in the simulations. The employed heterogeneous reaction mechanism, including only active Rh sites, reproduced the experiments with good accuracy. The ratio of active to geometrical surface area, deduced from hydrogen chemisorption measurements, was the single model parameter needed to account for the effect of different supports. This indicated that water activation occurring on support sites, resulting in inverse OH spillover from the support to the noble metal sites, could be neglected under the present conditions with high water dilution. An evident relationship between noble metal dispersion and catalytic behavior, in terms of methane conversion and synthesis gas yields, could be established. Both measurements and predictions indicated that an increasing Rh dispersion (in the order Rh/α-Al2O3, Rh/ZrO2, and Rh/CeO2-ZrO2) resulted in higher methane conversions, lower surface temperatures, and higher synthesis gas yields. 相似文献
35.
C. F. Wallgren F. H. Bark R. Eriksson D. S. Simonsson J. Perssont R. I. Karlsson 《Journal of Applied Electrochemistry》1996,26(12):1235-1244
A study of natural convection in an electrochemical system with a Rayleigh number of the order 1010 is presented. Theoretical and experimental results for the unsteady behaviour of the concentration and velocity fields during electrolysis of an aqueous solution of a metal salt are given. The cell geometry is a vertical slot and the reaction kinetics is governed by a Butler-Volmer law. To reduce the effects of stratification, the flush mounted electrodes are located (symmetrically) in the middle parts of the vertical walls. It is demonstrated, both theoretically and experimentally, that a weak stratification develops after a short time, regardless of cell geometry, even in the central part of the cell. This stratification has a strong effect on the velocity field, which rapidly attains boundary layer character. Measured profiles of concentration and vertical velocity at and above the cathode are in good agreement with numerical predictions. For a constant cell voltage, numerical computations show that between the initial transient and the time when stronger stratification reaches the electrode area, the distribution of electric current is approximately steady.List of symbols
a
i
left hand side of equation system
-
b
i
right hand side of equation system
-
c
concentration (mol m–3)
-
c
dimensionless concentration
-
c
i
concentration of species i' (mol m–3)
-
c0
initial cell concentration (300 mol m–3)
-
c
0
dimensionless initial cell concentration
-
cwall
concentration at electrode surface (mol m–3)
- dx
increment solution vector in Newton's method
-
D
i
diffusion coefficient of species i (m2 s–1)
-
D
1
0.38 × 10–9 m2 s–1
-
D
2
0.82 × 10–9 m2 s–1
-
D
effective diffusion coefficient of the electrolyte (0.52 × 10–9 m2 s–1)
-
x
unit vector in the vertical direction
-
y
unit vector in the horizontal direction
-
F
Faraday's constant (96 487 A s mol–1)
-
g
acceleration of gravity (9.81 m s–2)
-
i
dummy referring to positive (i = 1) or negative (i = 2) ion
- f
current density (A m–2)
- f
dimensionless current density
-
i0
exchange current density (0.01 A m–2)
-
J
ij
Jacobian of system matrix
-
L
length of electrode (0.03 m)
- N
i
transport flux density of ion i (mol m–2 s–1)
- n
unit normal vector
-
p
pressure (Nm–2)
-
p
dimensionless pressure
-
R
gas constant molar (8.31 J K–1 mol–1)
-
R
i
residual of equation system
-
Ra
Rayleigh number gL
3
c
0/D (2.54 × 10110)
-
S
c
Schmidt number /D (1730)
-
t
time (s)
-
t
dimensionless time
-
T
temperature (293 K)
-
velocity vector (m s–1)
-
dimensionless velocity vector
-
U
characteristic velocity in the vertical direction
-
V
±
potential of anode and cathode, respectively
-
x
spatial coordinate in vertical direction (m)
-
x
dimensionless spatial coordinate in vertical direction
- x
solution vector for c, and
-
y
spatial coordinate in horizontal direction (m)
-
y
dimensionless spatial coordinate in horizontal direction
-
z
i
charge number of ion i
Greek symbols
symmetry factor of the electrode kinetics, 0.5
-
volume expansion coefficient (1.24 × 10–4 m3 mol–1)
-
s
surface overpotential
-
constant in equation for the electric potential (–5.46)
-
s
diffusion layer thickness
-
scale of diffusion layer thickness
-
constant relating c/y to the Butler-Volmer law (0.00733)
-
kinematic viscosity (0.9 × 10–6 m2 s–1) 相似文献
36.
The effects of precursor and calcination temperature on the nano morphology of ruthenium dioxide on titanium, prepared from thermal decomposition of aqueous salt solutions were investigated. Transmission electron microscopy, X-ray diffraction, gas porosimetry and cyclic voltammetry showed that lower calcination temperature yielded smaller crystallites. The crystallites were between 6 and 22 nm in diameter. When using ruthenium nitrosyl nitrate the firing temperature had a large impact on the grain size, but for chloride there was only a minor effect in the temperature range 350-550 °C. 相似文献
37.
Managing requirements specifications for product lines - An approach and industry case study 总被引:1,自引:0,他引:1
Magnus Eriksson Author Vitae Jürgen Börstler Author Vitae 《Journal of Systems and Software》2009,82(3):435-447
Software product line development has emerged as a leading approach for software reuse. This paper describes an approach to manage natural-language requirements specifications in a software product line context. Variability in such product line specifications is modeled and managed using a feature model. The proposed approach has been introduced in the Swedish defense industry. We present a multiple-case study covering two different product lines with in total eight product instances. These were compared to experiences from previous projects in the organization employing clone-and-own reuse. We conclude that the proposed product line approach performs better than clone-and-own reuse of requirements specifications in this particular industrial context. 相似文献
38.
M. Santoro L. Eriksson J. Askne C. Schmullius 《International journal of remote sensing》2013,34(16):3425-3454
JERS‐1 L‐band SAR backscatter from test sites in Sweden, Finland and Siberia has been investigated to determine the accuracy level achievable in the boreal zone for stand‐wise forest stem volume retrieval using a model‐based approach. The extensive ground‐data and SAR imagery datasets available allowed analysis of the backscatter temporal dynamics. In dense forests the backscatter primarily depended on the frozen/unfrozen state of the canopy, showing a ~4 dB difference. In sparse forests, the backscatter depended primarily on the dielectric properties of the forest floor, showing smaller differences throughout the year. Backscatter modelling as a function of stem volume was carried out by means of a simple L‐band Water Cloud related scattering model. At each test site, the model fitted the measurements used for training irrespective of the weather conditions. Of the three a priori unknown model parameters, the forest transmissivity coefficient was most affected by seasonal conditions and test site specific features (stand structure, forest management, etc.). Several factors determined the coefficient's estimate, namely weather conditions at acquisition, structural heterogeneities of the forest stands within a test site, forest management practice and ground data accuracy. Stem volume retrieval was strongly influenced by these factors. It performed best under unfrozen conditions and results were temporally consistent. Multi‐temporal combination of single‐image estimates eliminated outliers and slightly decreased the estimation error. Retrieved and measured stem volumes were in good agreement up to maximum levels in Sweden and Finland. For the intensively managed test site in Sweden a 25% relative rms error was obtained. Higher errors were achieved in the larger and more heterogeneous forest test sites in Siberia. Hence, L‐band backscatter can be considered a good candidate for stand‐wise stem volume retrieval in boreal forest, although the forest site conditions play a fundamental role for the final accuracy. 相似文献
39.
Ride comfort optimization of a city bus is considered in this article, using stiffness and related damping of the power unit
mounts as design variables. The response of the bus, due to road irregularities, is calculated in the time domain by using
a finite element (FE) model describing the complete vehicle. The body of the bus is condensed, using a substructuring technique,
in order to reduce the simulation times. Operational deflection shapes (ODS) have been used to compare measured and calculated
vibrations and some corrections of the FE model have been done. The response, i.e. acceleration, at three locations in the
bus has been frequency-weighted according to the comfort standard ISO 2631:1997. The resulting root mean square (RMS) values
of these responses are then used in the objective functions in the optimization procedure. The computational results show
that it is possible to increase the ride comfort. However, the improvement of the ride comfort is probably too small to have
a substantial subjective impact on the passenger in the bus. The results show that the objective function, regarding the overall
ride comfort in the bus, has local optima.
Received October 10, 1999 相似文献
40.
Impact of understory vegetation on forest canopy reflectance and remotely sensed LAI estimates 总被引:2,自引:0,他引:2
Helena Margaretha Eriksson Lars Eklundh Tiit Nilson 《Remote sensing of environment》2006,103(4):408-418
Forest leaf area index (LAI), is an important variable in carbon balance models. However, understory vegetation is a recognized problem that limits the accuracy of satellite-estimated forest LAI. A canopy reflectance model was used to investigate the impact of the understory vegetation on LAI estimated from reflectance values estimated from satellite sensor data. Reflectance spectra were produced by the model using detailed field data as input, i.e. forest LAI, tree structural parameters, and the composition, distribution and reflectance of the forest floor. Common deciduous and coniferous forest types in southern Sweden were investigated. A negative linear relationship (r2 = 0.6) was observed between field estimated LAI and the degree of understory vegetation, and the results indicated better agreement when coniferous and deciduous stands were analysed separately. The simulated spectra verified that the impact of the understory on the reflected signal from the top of the canopy is important; the reflectance values varying by up to ± 18% in the red and up to ± 10% in the near infra-red region of the spectra due to the understory. In order to predict the variation in LAI due to the understory vegetation, model inversions were performed where the input spectra were changed between the minimum, average and maximum reflectance values obtained from the forward runs. The resulting variation in LAI was found to be 1.6 units on average. The LAI of the understory could be predicted indirectly from simple stand data on forest characteristics, i.e. from allometric estimates, as an initial step in the process of estimating LAI. It is suggested here that compensation for the effect of the understory would improve the accuracy in the estimates of canopy LAI considerably. 相似文献