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81.
In a simple diode system for asymmetric radio frequency sputtering, steel specimens were covered with iron oxide and the corrosion behaviour was studied by electrochemical methods. The specimens, which were covered with a compact layer of Fe2O3, had film resistances of 108–1015 Ω cm, due to the conditions of production and the purity of the target material. Potentiometric measurements on steel electrodes covered with quasi-crystalline α-Fe2O3 showed a distinct passivation of the basic material in neutral and slightly acid media. An outlook is given concerning future fundamental studies on this problem. 相似文献
82.
Particle size analysis of particles < 10 μm – methods and difficulties . A review of possible methods for the determination of particle size distributions in the range < 10 μm is presented. Important factors regarding the specimen dispersion are dealt with, particularly those which must be taken into consideration in the “fines” region, and the limits and difficulties of individual analytical equipment are illustrated with the aid of examples. Finally, analytical results obtained by various methods of measurement are compared and the criteria of assessment such as operational possibility and costing are discussed. 相似文献
83.
In recent years, a rising number of different table waters supersaturated with oxygen have hit the market with claims of both positive health effects and an increase in athletic performance. In addition to research on the correctness of these claims and their possible physiological reasons, the appearance of oxygen supersaturation as a marketing promise also creates a need for appropriate analytical techniques allowing a rapid and reliable determination of oxygen contents in such waters. Here, we present NMR relaxometry as a possible analytical tool for such studies. NMR relaxation in oxygen supersaturated water is not only of interest in the context of monitoring the oxygen content in such drinking water products, but also might offer some interesting possibilities in medical and environmental science MRI applications. As a contact-less measuring method, NMR relaxometry avoids disturbance of the measurement due to outgassing. The method was applied in the concentration range from 10 mg l(-1) to over 100 mg l(-1) dissolved oxygen. In addition to freshly sampled drinking waters, also oxygen losses during storage of the water in open drinking vials was studied. 相似文献
84.
Fall BI Eberlein-König B Behrendt H Niessner R Ring J Weller MG 《Analytical chemistry》2003,75(3):556-562
The described in vitro test system for allergy diagnosis is based on microscope glass slides activated with (3-glycidyloxypropyl)trimethoxysilane. Allergen solutions are immobilized as small droplets (approximately 10 nL) on the activated glass slides with a piezoelectric arrayer. In contrast to other tests for specific IgE, such as Pharmacia CAP FEIA, AlaSTAT, or FAST, only a 25-microL serum sample is needed for the screening of allergen-specific IgE against a multitude of allergens and the test can be performed in less than 1 h. Compared with multiallergen dipstick screening tests (e.g., IgEquick, CMG Immunodot) based on multiallergen-coated nitrocellulose strips, the measurement of the microarray-based system can be performed automatically. The chemiluminescence intensities are detected with a sensitive CCD camera. Allergen extracts and recombinant/purified allergens (24 preparations) have been used on the same modified surface for the screening of allergen-specific IgE. With these disposable microarray slides, it is possible to distinguish between patients with and without elevated levels of allergen-specific IgE. Repeated measurements of serum samples demonstrated a sufficient reproducibility. Detection limits (microg/L) of 0.35 (r Betvl), 0.16 (PLA2), and 1.9 (Der p1) were achieved. 相似文献
85.
IT infrastructure, such as servers and networking equipment, accounts for a large proportion of the IT costs in modern organizations.
Typically, this IT infrastructure is shared among multiple applications and customers. Cost allocation of shared IT infrastructure
is difficult and regularly based on biased cost allocation keys, which often causes free-rider problems. Measuring usage is
technically difficult and incurs high costs. In this paper we propose a method to derive adequate estimators for the resource
consumption of a customer-oriented service. These so-called resource profiles can then provide a basis for cost allocation
keys. The estimators are derived from a series of load tests, as they are typically done before an application is launched
in larger organizations. Such profiles need to be unbiased and precise even in cases of varying workloads and in rather heterogeneous
environments. We describe the results of a set of experiments in an infrastructure provided by the BMW Group, and illustrate
how the estimation can be integrated into existing IT service management processes. In our experiments we use Queuing Networks
to validate the estimated resource profiles under different workloads. 相似文献
86.
Reinhard König Cezary Sielużycki Piotr J. Durka 《Journal of Low Temperature Physics》2007,146(5-6):697-718
Low-temperature superconductivity plays an important role in some specific biomedical applications, and, in particular, in
non-invasive imaging methods of human brain activity. Superconducting magnets are indispensable for functional magnetic resonance
imaging (fMRI) which allows functional imaging of the brain with high spatial but poor temporal resolution. Superconducting
quantum interference devices (SQUIDs) are the most sensitive magnetic field detectors. Up to a few hundreds of SQUIDs are
nowdays used in modern whole-head magnetoencephalography (MEG) systems. They allow tracking brain activation with a superior
temporal resolution of milliseconds, which is a quintessential condition for the monitoring of brain dynamics and the understanding
of information processing in the human brain. We introduce the prerequisites of MEG data acquisition and briefly review two
established methods of biomagnetic signal processing: The concept of signal averaging, and the subsequent source identification
as a solution of the biomagnetic inverse problem. Beside these standard techniques, we discuss advanced methods for signal
processing in MEG, which take into account the frequency content of the recorded signal. We briefly refer to the prospects
of Fourier analysis and wavelet transform in MEG data analysis, and suggest matching pursuit as a promising tool for signal
decomposition and reconstruction with high resolution in time-frequency plane. 相似文献
87.
Bidirectional Texture Functions (BTFs) are among the highest quality material representations available today and thus well suited whenever an exact reproduction of the appearance of a material or complete object is required. In recent years, BTFs have started to find application in various industrial settings and there is also a growing interest in the cultural heritage domain. BTFs are usually measured from real‐world samples and easily consist of tens or hundreds of gigabytes. By using data‐driven compression schemes, such as matrix or tensor factorization, a more compact but still faithful representation can be derived. This way, BTFs can be employed for real‐time rendering of photo‐realistic materials on the GPU. However, scenes containing multiple BTFs or even single objects with high‐resolution BTFs easily exceed available GPU memory on today's consumer graphics cards unless quality is drastically reduced by the compression. In this paper, we propose the Bidirectional Sparse Virtual Texture Function, a hierarchical level‐of‐detail approach for the real‐time rendering of large BTFs that requires only a small amount of GPU memory. More importantly, for larger numbers or higher resolutions, the GPU and CPU memory demand grows only marginally and the GPU workload remains constant. For this, we extend the concept of sparse virtual textures by choosing an appropriate prioritization, finding a trade off between factorization components and spatial resolution. Besides GPU memory, the high demand on bandwidth poses a serious limitation for the deployment of conventional BTFs. We show that our proposed representation can be combined with an additional transmission compression and then be employed for streaming the BTF data to the GPU from from local storage media or over the Internet. In combination with the introduced prioritization this allows for the fast visualization of relevant content in the users field of view and a consecutive progressive refinement. 相似文献
88.
In applicative theories the recursion theorem provides a term
which solves recursive equations. However, it is not provable that a solution obtained by
is minimal. In the present paper we introduce an applicative theory in which it is possible to define a least fixed point operator. Still, our theory has a standard recursion theoretic interpretation. 相似文献
89.
It has been shown earlier that hypergravity slows down inner ear otolith growth in developing fish as an adaptation towards increased environmental gravity. Suggesting that otolith growth is regulated by the central nervous system, thus adjusting otolithic weight to produce a test mass, applying functional weightlessness should yield an opposite effect, i.e. larger than normal otoliths. Therefore, larval siblings of cichlid fish (Oreochromis mossambicus) were housed for 7 days in a submersed, two-dimensional clinostat, which provided a residual gravity of approximately 0.007g. After the experiment, otoliths were dissected and their size (area grown during the experiment) was determined. Maintenance in the clinostat resulted in significantly larger utricular otoliths (lapilli, involved in graviperception). There were no statistical significant differences regarding saccular otoliths obtained (sagittae, involved in transmitting linear acceleration and, especially, in the hearing process). These results indicated, that the animals had in fact received functional weightlessness. In line and contrasting results on the otoliths of other teleost species kept at actual microgravity (spaceflight) or within rotating wall vessels are discussed. 相似文献
90.
Tobias Plieninger Andreas Thiel Oliver Bens Reinhard F. Hüttl 《Biomass & bioenergy》2009,33(3):384-392
The paper presents an empirical study on the use of woody biomass for energy supply in Germany and the federal state of Brandenburg. It aims to explain the role forestry enterprises have for bioenergy provision in this area. The ‘Institutions of Sustainability’ framework is used as an analytical tool to investigate the role of private and public actors in these transactions, respectively, in the governance structures they are subject to. Empirical evidence was gathered by in-depth interviews with actors from forestry and bioenergy practice. Triggered by favorable governance structures, i.e. strong support by national and regional policies, rising prices for fossil energy sources, and co-operation of committed individuals and groups, a new bioenergy industry has been successfully established. However, the forestry sector has so far been just a marginal fuel supplier for this industry. The study identifies pitfalls impeding a broad implementation of wood-energy supply in forestry: not cost-covering prices offered by the bioenergy sector, lacking market transparency and security of supply, lacking mobilization of forest wood, and a preference among forest managers to sell products to the wood-processing industry. In terms of the Institutions of Sustainability the properties of transactions (asset specificities, uncertainties, separability), characteristics of actors (values, rationality) and governance structures (long-term contractual obligations elsewhere) are decisive in explaining the current form of transaction. 相似文献