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排序方式: 共有549条查询结果,搜索用时 0 毫秒
51.
Solution state 1H NMR is employed to study the mode and strength of chloroform adsorption on conjugated acid–base pairs of cation-exchanged Y-zeolites. 1H NMR results indicate that two different surface bonding orientations may exist. An acidic hydrogen site of zeolite favours orientation where the chloroform hydrogen points towards the zeolite cage centre. An exchanged electropositive cation increases the basicity of framework oxygens of zeolite and directs the chloroform to adsorb on framework oxygens with a hydrogen bond. In this adsorption site the chemical shift of the chloroform hydrogen has a linear dependence on the electronegativity of the cation. 相似文献
52.
Tiihonen P Kinnunen J Töyräs J Mervaala E Pääkkönen A 《Computer methods and programs in biomedicine》2008,89(1):83-92
Monitoring level of consciousness or depth of sedation is essential in modern intensive care units and emergency rooms. Current methods are based on spontaneous EEG providing only indirect information on the reactivity of the brain. Measurement of auditory event-related potentials (ERPs) has been shown to have additional potential for evaluation of the level of consciousness. Unfortunately, compact and easy-to-use devices are not commercially available. In this study a portable battery-powered device for clinical auditory ERP measurements was designed, constructed and validated. The device consists of a five-channel data logger and a 16-bit stereo audio stimulator. The signals are digitized with a 22-bit sigma-delta analogue-to-digital converter and stored to a PC Card hard disk. Prior to the in vivo application, the device was validated with extensive technical tests. Importantly, the RMS noise amplitude of the EEG channels was found to be less than 1 mivroV and the delivered auditory stimulus intensity corresponded accurately the settings (mean difference 0.2+/-0.5 dB). In addition to technical tests the device was successfully validated in vivo. To summarize, a novel portable instrument for measurement of auditory event-related potentials in intensive care environment is introduced. 相似文献
53.
L. Juha M. F rní kov V. Hamplov J. Kodymov A. Mü llerov J. Kr sa L. L ska O. palek P. Kub t L. Stibor E. Koudoumas S. Couris 《Fullerenes, Nanotubes and Carbon Nanostructures》2000,8(4):289-318
Experiments designed to clarify the role of molecular oxygen in the photolysis of fullerene are described. The formation of oxygen-fullerene adducts, both in fullerene solutions in various solvents and in micro-crystallites formed by evaporating these solutions, and their photolysis was studied under various experimental conditions. The results confirm that the role of oxygen in the photolysis process in these systems is ambivalent and highly dependent on the conditions under which the irradiation of the fullerenes occurs (wavelength and intensity of the photolyzing radiation, character of the solvent molecules, presence of additional molecules in the solvent-fullerene-oxygen system, etc.). 相似文献
54.
A study on the restoration method of friction, wear and fatigue performance of remanufactured crankshaft 总被引:1,自引:0,他引:1
Yasutoshi Tominaga Jinsoo Kim Youngsik Pyun Ravil Kayumov Junhyong Kim Juha Woo 《Journal of Mechanical Science and Technology》2013,27(10):3047-3051
Crankshaft translates reciprocating linear piston motion into rotation in internal combustion engine. So it receives complex combination of stresses. Therefore, crankshaft remanufacturing process is designed thoroughly with special attention to fatigue and tribological performance. Experimental study is carried out in order to show that UNSM (ultrasonic nanocrystal surface modification) technology which will be used as final surface treatment after 0.2 mm depth surface grinding, could restore original fatigue strength and tribological performance. Furthermore the feasibility steady to replace conventional overlay welding in crankshaft remanufacturing process by UNSM (ultrasonic nanocrystal surface modification) technology is carried out. Effects of UNSM technology are established through rotary bending test, rolling contact fatigue (RCF) test and wear simulation test. The test specimen used SCM435 material of crankshaft and commercial bush. The test result showed fatigue limit improved by 30% and RCF life increased by 40% for UNSM treated specimen. And friction coefficient decreased by 24% and wear amount decreased by 85%. 相似文献
55.
Elias Pentti Juho Rysti Anssi Salmela Alexander Sebedash Juha Tuoriniemi 《Journal of Low Temperature Physics》2011,165(3-4):132-165
We present results of low-temperature experiments on dilute mixtures of 3He in 4He and on pure 3He, obtained by means of two kinds of mechanical oscillators immersed in the liquid sample: vibrating wires and quartz tuning forks. The helium sample was cooled either by adiabatic demagnetization of an immersed copper nuclear stage or by adiabatic melting of 4He in superfluid 3He. The measured effect of the surrounding fluid on the mechanical resonance of the oscillators is compared with existing theories. We also discuss resonances of second sound and the state of supersaturation, both observed by a tuning fork in helium mixtures. 相似文献
56.
57.
Heikki Kallio Saska Tuomasjukka Anu Johansson Raija Tahvonen Niina Nieminen Olli Sjvall Juha‐Pekka Kurvinen Hanna Kivini 《European Journal of Lipid Science and Technology》2005,107(2):101-106
Currant oils have special health properties due to their moderate contents of α‐linolenic, γ‐linolenic and stearidonic acids. The distribution of fatty acids (FA) in the triacylglycerols (TAG) may affect the beneficial effects. Seed oils of wild northern red currant (NRC) (Ribes spicatum L.) from Northern Finland and of wild alpine currant (AC) (R. alpinum L.) from the South‐West coast of Finland were investigated. The purified TAG were analysed by tandem mass spectrometry by applying the ammonia negative ion chemical ionisation – collision‐induced dissociation method. Molecular weight fractions rich in C18:3 FA and C18:4 FA were investigated. Of the total oil, the molecular weight species 54:7 (ACN:DB), 54:8 and 54:9 were more abundant in NRC than in AC, being 21.0%, 15.8%, 7.4% and 16.2%, 11.2%, 4.8%, respectively (p <0.05). The species 52:6 was more abundant in AC (3.1%) than in NRC (2.6%) (p <0.05). The preferential order of FA to be in the sn‐2 position in both berries was typically C18:1 > C18:2 > C18:4 > C18:3. No difference was observed between relative locations of C16:0 FA and C18:3 FA in either of the oils. Within the TAG consisting of FA combinations C18:3/C18:3/C18:1 (54:7), C18:1 was more preferentially in the sn‐2 position (p <0.05) in AC (93.2%) than in NRC (74.6%), and in the case of C18:3, the preference was vice versa. Within the molecular weight species 54:9, FA combination C18:4/C18:3/C18:2, linoleic acid preferentially occupied the secondary position (p <0.005) in both berries, and the proportion of the TAG regioisomer pair sn‐C18:3‐C18:4‐C18:2 + sn‐C18:2‐C18:4‐C18:3 was more abundant (30.2%) in NRC than in AC (15.3%). Within the TAG species 52:6, proportions of all the existing combinations, C16:0/C18:3/C18:3, C16:0/C18:4/C18:2 and C16:1/C18:3/C18:2, varied between the two berry species (p <0.005). 相似文献
58.
59.
Nicolai Czink Giovanni Del Galdo Xuefeng Yin Ernst Bonek Juha Ylitalo 《Wireless Personal Communications》2008,46(1):83-98
In this work we introduce a novel metric for characterizing the double-directional propagation environment and use this metric
to assess the performance of a SAGE parameter estimator for MIMO channels. Using the IlmProp, a geometry-based MIMO channel
modeling tool, we construct synthetic channels for three different scenarios showing: (i) well separated clusters containing
dense propagation paths, and single-bounce scattering; (ii) partly overlapping clusters containing widely spread propagation
paths, and single-bounce scattering; (iii) unclustered multipath components (“rich scattering”), and double-bounce-only scattering.
We model the scatterers and the receiver in the environment as fixed, but the transmitter as moving. The Initialization and
Search-Improved SAGE (ISIS) estimation tool is used to extract the propagation paths from the constructed channels. Both true
and estimated paths are fed to the new system-independent metric which genuinely reflects the structure of the channel and
the compactness of the propagation paths. We use this metric to decide on the accuracy of the channel estimator. The results
show a convincing agreement between true and estimated paths. 相似文献
60.
L. Juha B. Ehrenberg S. Couris E. Koudoumas V. Hamplov Z. Pokorn A. Mü llerov M. Pavel 《Fullerenes, Nanotubes and Carbon Nanostructures》2000,8(4):319-336
In this paper we describe the efficient and substantial decomposition of C60 in toluene solution, induced by moderate intensity (I = 20 - 55 MW cm-2) near infrared (γ = 1064 nm) laser radiation. This behavior is surprising since both uncharged fullerene and toluene do not have any absorption bands at this wavelength. The decomposition efficiency and products are investigated with UV-Vis absorption spectrophotometry and high-performance liquid-chromatography (HPLC). Possible mechanisms of the fullerene decomposition are discussed. 相似文献