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排序方式: 共有67条查询结果,搜索用时 15 毫秒
1.
In this study, graphene was synthesized from graphite. Graphite was oxidized via modified Hummer’s method and sonicated to form graphene oxide (GO). Infrared spectroscopy revealed the successful oxidation of graphite by the emergence of oxygen functionalities. The spectrum of GO showed peaks at 3270, 1629, 1227 and 1096 cm?1, indicating O–H, C=O, C–OH and C–O–C functional groups, respectively. Graphene hydrogels were prepared by the addition of L-ascorbic acid to GO suspensions and subsequent heating at 90°C. Composite hydrogels of graphene and titanium (IV) oxide (TiO2) were synthesized with various TiO2 to GO mass ratios. Composites were applied to photocatalytic hydrogen evolution reaction (HER) and the hydrogen gas produced was analysed by gas chromatography with thermal conductivity detector. Highest HER yield was 66.00% H2. 相似文献
2.
苹-乳发酵管理是优质葡萄酒酿造工艺中极其重要的一环 总被引:3,自引:0,他引:3
郭永亮 《中外葡萄与葡萄酒》2002,(3):49-51
过去,人们似乎有一种误解,认为苹-乳发酵的主要作用只是降解苹果酸,并最终降低葡萄酒的总酸度。事实上,苹果酸-乳酸发酵管理是优质葡萄酒酿造工艺这一大管理系统中必不可少的重要一环。研究表明,苹-乳发酵过程中,通常会产生众多的化合物,其中许多化合物对葡萄酒风味的复杂性有着重要的影响。此外,随着不断满足消费者对葡萄酒风味复杂多样性的这一酿酒趋势的日益明显,人们越来越清楚地认识到葡萄酒中乳酸菌所扮演角色的重要性。正是基于上述认识,对酿酒师来说,现在比以往任何时候都重要的一点是,如何通过苹-乳发酵的科学控制,对… 相似文献
3.
The regulator problem is studied for linear discrete-time systems with non-symmetrical constrained control, i.e. systems described by the state equation x k+1 = Ax k + Bu k, where u k ? Ω, and u k = Fx k. Necessary and sufficient conditions allowing us to obtain the largest non-symmetrical polyhedral domain of positive invariance and contractivity with respect to motions of the system in the closed loop are established. The case of symmetrically constrained control is obtained as a particular case. 相似文献
4.
5.
Abstract A specific hybrid tool, the Vienna Knowledge Engineering Tool, is used, in discussing the advantages and disadvantages of hybrid systems during their development and application. An object-oriented programming approach is introduced to serve as binding agent between the system components and as friendly interface to the user. 相似文献
6.
EINAR SVENDSEN CHRISTIAN MATZLER THOMAS C. GRENFELL 《International journal of remote sensing》2013,34(10):1479-1487
Abstract An algorithm has been developed for estimating total ice concentration from spaceborne high-frequency passive microwave instrumentation. The algorithm is intended for use with the coming Special Sensor Microwave/Imager (SSM/I) data giving a spatial resolution of 12 km. It is based on radiation physics and detailed millimetre wave surface signature measurements and can therefore be applied to other similar data. However, due to large effects on the signals caused by time varying atmospheric conditions and radiation properties of the ice, the algorithm is made self-adjusting. The atmospheric effects are implicitly treated as a smooth function of the ice concentration with tie points over open ocean and 100 per cent ice for each orbit. This means that the main errors are due to patches of heavy clouds and ice floes with atypical radiation properties. An error analysis indicates possible errors of the order of 5 percent for concentrations representative for the Arctic Basin, increasing with decreasing concentration. 相似文献
7.
DR. CHRISTIAN MUELLER-SCHLOER 《Cryptologia》2013,37(3):257-273
Secrecy and authentication are two important features of a secure communication system. Public Key Cryptosystems, based, e.g., on the Rivest-Shamir-Adleman (RSA) algorithm, provide a very elegant solution to the problem of authenticity verification or true electronic signatures. Practical problems, however, mainly the lack of execution speed, prevent a straightforward application. In order to sign a long message it is much faster to first calculate a short digest or checksum and then sign the compressed message. For this checksum calculation the fast, inexpensive and extensively tested Data Encryption Standard (DES) can be used. But care must be taken that this additional processing step does not introduce any weakness into the signature scheme. This paper investigates two DES-based hashing methods. It is shown that neither method seems to introduce any statistical regularities in the generated checksums. The “Cipher/Message to Plain Feedback,” however, is not secure under a modification compensation attack. It is further shown how the second method, the “Cipher to Plain Feedback” proposed by Davies and Price, can be broken by a “meet in the middle attack.” This checksum method, however, can be used safely with a slight modification. 相似文献
8.
AN APPROACH to STUDY and MODEL the HYDRODYNAMIC CLEANING EFFECT 总被引:1,自引:0,他引:1
A sensor has been developed for continuous measurements of the removal of deposit. the sensor, which was based on heat transfer measurements, was also able to measure the wall shear stress. The device was used to study the mechanical effect during cleaning. It was found that the removal rate of deposits, at a surface, could be scaled by the mean wall shear stress. Measurements were performed under both laminar and turbulent flow conditions. the turbulent fluctuations did not influence the removal rate. 相似文献
9.
Enabling the detection of UV signal in multimodal nonlinear microscopy with catalogue lens components
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MARTIN VOGEL AXEL WINGERT RAINER H.A. FINK CHRISTIAN HAGL FERUZ GANIKHANOV CHRISTIAN P. PFEFFER 《Journal of microscopy》2015,260(1):62-72
Using an optical system made from fused silica catalogue optical components, third‐order nonlinear microscopy has been enabled on conventional Ti:sapphire laser‐based multiphoton microscopy setups. The optical system is designed using two lens groups with straightforward adaptation to other microscope stands when one of the lens groups is exchanged. Within the theoretical design, the optical system collects and transmits light with wavelengths between the near ultraviolet and the near infrared from an object field of at least 1 mm in diameter within a resulting numerical aperture of up to 0.56. The numerical aperture can be controlled with a variable aperture stop between the two lens groups of the condenser. We demonstrate this new detection capability in third harmonic generation imaging experiments at the harmonic wavelength of ~300 nm and in multimodal nonlinear optical imaging experiments using third‐order sum frequency generation and coherent anti‐Stokes Raman scattering microscopy so that the wavelengths of the detected signals range from ~300 nm to ~660 nm. 相似文献
10.
Franz Leingruber Christian Chimani Franz Wimmer 《钢铁》2004,39(Z1):404-407
1前言
奥钢联近终形异型坯浇铸技术对于大型和中型型钢以及工字梁,与薄板坯生产扁材产品具有同样的优点. 相似文献