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排序方式: 共有401条查询结果,搜索用时 21 毫秒
391.
Ragnar Hellborg Kjell Håkansson 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1985,235(3):407-413
An inexpensive gas-handling system has been designed and built utilizing standard components. The design of the system and the different safety features are described. Results of a test on the purity of the gas are given. 相似文献
392.
Urban Kjellén 《Accident; analysis and prevention》1984,16(4):307-323
In Part II of this paper measures of the significance of deviations with respect to the risk of accidents and criteria for the assessment of methods for the collection of data on deviations are operationalized. Empirical research on relations between deviations and accidents and on methods for data collection are reviewed on the basis of these measures and criteria. It is concluded that the deviation concept provides a valid basis for the design of information systems for the efficient control of accidents in production systems in operation. Considerations for the design of information systems for the collection, storing, processing, and feedback of information on deviations for accident prevention purposes are discussed. 相似文献
393.
The crystallization of melt-spun amorphous Zr1-xCox alloys with 0.20 ≤ x ≤ 0.41 has been studied under both isothermal and non-isothermal conditions by use of DSC-technique. Up to three peaks were observed. The crystallization temperature varies with composition from 631 K for x = 0.20 to 746 K for x = 0.41. Isothermal annealing of x = 0.41 shows that the kinetics of the crystallization can be described by the Johnson-Mehl-Avrami equation with n ≈ 2.85 at lower annealing temperatures (712.5 – 725 K) while in the temperature range 725 K to 740 K n increases with increasing annealing temperature. The phases formed during the crystallization process have been identified by means of X-ray diffraction techniques and electron microscope studies. For compositions around x = 0.33 microcrystalline phases are formed upon crystallization. 相似文献
394.
Hergum T Bjåstad T Kristoffersen K Torp H 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2007,54(2):271-280
Parallel beamforming is frequently used to increase the acquisition rate of medical ultrasound imaging. However, such imaging systems will not be spatially shift invariant due to significant variation across adjacent beams. This paper investigates a few methods of parallel beam-forming that aims at eliminating this flaw and restoring the shift invariance property. The beam-to-beam variations occur because the transmit and receive beams are not aligned. The underlying idea of the main method presented here is to generate additional synthetic transmit beams (STB) through interpolation of the received, unfocused signal at each array element prior to beamforming. Now each of the parallel receive beams can be aligned perfectly with a transmit beam--synthetic or real--thus eliminating the distortion caused by misalignment. The proposed method was compared to the other compensation methods through a simulation study based on the ultrasound simulation software Field II. The results have been verified with in vitro experiments. The simulations were done with parameters similar to a standard cardiac examination with two parallel receive beams and a transmit-line spacing corresponding to the Rayleigh criterion, wavelength times f-number (lambda x f#). From the results presented, it is clear that straightforward parallel beamforming reduces the spatial shift invariance property of an ultrasound imaging system. The proposed method of using synthetic transmit beams seems to restore this important property, enabling higher acquisition rates without loss of image quality. 相似文献
395.
Autofluorescence spectra have been obtained on beef longissimus dorsi muscles (n=151), and the spectra regressed against Warner-Bratzler (WB) peak values. The spectra obtained depended on the method used, and it is suggested that the difference is related to the use of two different types of Xenon lamps (a pulsed versus a continuous light source) and the inherent kinetic differences in the collection of the fluorochromes' emitted light. Poor to good (R=0.45-0.84) correlations between WB peak values and the emission spectra were obtained. This relationship is established using chemical information originating largely from collagens. Minor differences in predictability were observed using either excitation wavelengths 332 or 380?nm. The emission wavelengths containing the most relevant information about WB peak values were between 360 and 500 nm. Wavelengths around 375 nm, excitation 332 nm, were in particular important and were related to a component in the perimysial tissue, most likely being present in collagen I or III. Excitation at 380?nm revealed the wavelength range 460-480?nm as important presumed due to collagens in the perimysium. An experiment, simulating industrial routines, using 45 samples collected at the slaughterhouse two days post mortem, was carried out. However, for those samples no model was observed between the emission spectra and WB peak values. Only when some samples having very low (1.45?μm) sarcomere lengths were removed, could a significant model be obtained. It is concluded that with the prevailing early post mortem routines in slaughterhouses with, among other things, wide variation in chilling rates between muscles and carcasses, the technique of autofluorescence has limited industrial potential as a sole, rapid non-destructive method for measuring tenderness of the longissimus dorsi muscle (LD). 相似文献
396.
Svensson CP Mårtensson T Trägårdh J Larsson C Rask M Hessman D Samuelson L Ohlsson J 《Nanotechnology》2008,19(30):305201
Vertical light emitting diodes (LEDs) based on GaAs/InGaP core/shell nanowires, epitaxially grown on GaP and Si substrates, have been fabricated. The devices can be fabricated over large areas and can be precisely positioned on the substrates, by the use of standard lithography techniques, enabling applications such as on-chip optical communication. LED functionality was established on both kinds of substrate, and the devices were evaluated in terms of temperature-dependent photoluminescence and electroluminescence. 相似文献
397.
Staffan Johansson Per H. Nilsson Robert Ohlsson Cecilia Anderberg Bengt-Gran Rosn 《Tribology International》2008,41(9-10):854
Anticipated emission legislation and reduced fuel consumption are the main driving forces when developing new engines. Optimization of the active surfaces in the piston system is one possible way to meet the above demands. In this study the effects of surface topography and texture direction of the ring/liner contact on oil film thickness and friction were simulated and experimentally tested. “Low wear” results from the experimental wear tests with “glide honed” smooth liner surfaces supported the “low friction” simulation results. In addition a new wear volume sensitive surface roughness parameter, Rktot, based on the Abbot–Firestone bearing area curve was introduced. 相似文献
398.
Tomas Isaksson Geir Tgersen Arve Iversen Kjell Ivar Hildrum 《Journal of the science of food and agriculture》1995,69(1):95-100
Near infrared (NIR) diffuse spectroscopy was used to determine the fat, moisture and protein contents in whole and ground farmed atlantic salmon fillets. A remote fibre-optic probe was used for NIR measurements on 50 whole salmon fillets. The constituent ranges were: 91-205 g kg?1 fat, 599-709g kg?1 moisture and 186-209 g kg?1 protein. Principal component regression resulted in the following prediction errors for ground salmon fillets, expressed as root mean square error of cross validation: 6.6 g kg-1 fat, 3.8 g kg?1 moisture and 2.0 g kg?1 protein. The corresponding prediction errors for non-destructive measurements on whole salmon fillets were 10.8 g kg?1 fat, 8.5 g kg?1 moisture and 3.7 g kg?1 protein. Regression models using the 760-1100 m range gave lower prediction errors than models using the 1100-2500 mm or 760-2500 nm ranges. The results show that fibre-optic probe NIR instruments are suited to determine fat and moisture in whole salmon fillets non-destructively. 相似文献
399.
Loss of safety assessment and the IEC 61508 standard 总被引:2,自引:2,他引:2
The standard IEC 61508 contains a lot of useful information and guidance for safety improvement regarding the use of safety systems. However, some of the basic concepts and methods for loss of safety quantification are somewhat confusing. This paper discusses the failure classification, the various contributions to the safety unavailability, and in particular the common cause failure (CCF) model presented in this standard. Suggestions for clarifications and improvements are provided. In particular, a new CCF model is suggested, denoted the Multiple Beta Factor model. 相似文献
400.