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81.
Christof Vockenhuber Marcus ChristlCornelia Hofmann Johannes LachnerArnold Milenko Müller Hans-Arno Synal 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(24):3199-3203
The performance of the compact ETH-TANDY system for accelerator mass spectrometry measurements of 236U is presented. Despite the low ion energies of around 1.2 MeV we can demonstrate a background level that is comparable to larger facilities. The careful ion-optical design of the high-energy spectrometer leads to a high suppression of neighboring isotopes sufficient to measure samples with isotopic ratios of 236U/238U > 10-11 the ion chamber only, as demonstrated by systematic investigations with different slit settings and time-of-flight measurements. Additionally, a high overall efficiency is achieved due to a high transmission through the accelerator. 相似文献
82.
Christof Lanzerstorfer 《Fuel Processing Technology》2011,92(5):1095-1100
Utilization of biomass ash as a soil improvement material is limited by the admissible input of heavy metals. It is well known that heavy metal concentrations are increased in fine ash fractions. In this study, two models are investigated to describe the distribution of various heavy metals in different size fractions of fly ash from a grate-fired biomass incineration plant incinerating wood chips. The second model assuming a dependence of the heavy metal concentration from the reciprocal particle diameter to the power of the variable N correlated well with measured concentrations. This model was then used in the calculation of the required cut size of a classifier for the production of a coarse fraction with heavy metal concentrations below limits from a fly ash sample exceeding the Austrian limits for a soil improvement material. The predicted concentrations of the critical heavy metals Cd and Pb and the total mass of the coarse fraction produced corresponded well with measured values, and although the concentration of Zn was considerably underestimated in the model, the produced coarse fraction was within the limits for utilization. 相似文献
83.
Object
Two approaches of reconstructing undersampled partial k-space data, acquired with multiple coils are compared: homodyne detection combined with SENSE (HM_SENSE) and analytic image reconstruction combined with SENSE (AI_SENSE). The latter overcomes limitations of HM_ SENSE by considering aliased images as analytic thus avoiding the need for phase correction required for HM_SENSE. 相似文献84.
Dana E Gheorghe Lili Cui Christof Karmonik Audrius Brazdeikis Jose M Penaloza Joseph K Young Rebekah A Drezek Malavosklish Bikram 《Nanoscale research letters》2011,6(1):554
We have developed novel gold-silver alloy nanoshells as magnetic resonance imaging (MRI) dual T1 (positive) and T2 (negative) contrast agents as an alternative to typical gadolinium (Gd)-based contrast agents. Specifically, we have doped iron oxide nanoparticles with Gd ions and sequestered the ions within the core by coating the nanoparticles with an alloy of gold and silver. Thus, these nanoparticles are very innovative and have the potential to overcome toxicities related to renal clearance of contrast agents such as nephrogenic systemic fibrosis. The morphology of the attained nanoparticles was characterized by XRD which demonstrated the successful incorporation of Gd(III) ions into the structure of the magnetite, with no major alterations of the spinel structure, as well as the growth of the gold-silver alloy shells. This was supported by TEM, ICP-AES, and SEM/EDS data. The nanoshells showed a saturation magnetization of 38 emu/g because of the presence of Gd ions within the crystalline structure with r1 and r2 values of 0.0119 and 0.9229 mL mg-1 s-1, respectively (Au:Ag alloy = 1:1). T1- and T2-weighted images of the nanoshells showed that these agents can both increase the surrounding water proton signals in the T1-weighted image and reduce the signal in T2-weighted images. The as-synthesized nanoparticles exhibited strong absorption in the range of 600-800 nm, their optical properties being strongly dependent upon the thickness of the gold-silver alloy shell. Thus, these nanoshells have the potential to be utilized for tumor cell ablation because of their absorption as well as an imaging agent. 相似文献
85.
Philipp Pretis ;Jurgen Fabian ;Christof Sumereder ;Michael Muhr ;Helmut Heinle ;Christoph Richter ;Bernhard Brandstatter 《能源与动力工程:英文版》2014,(8):1443-1448
Nowadays, PD (partial discharge) measurements are a crucial part of the preventive maintenance of electrical equipment within high voltage engineering. Especially for electrical machines, both the supplier and the user are interested in the results of PD measurements. However, PDs hardly represent the cause of the failure, more likely they are claimed as the outcome of a failure. This paper deals with the insulation of a 6 kV electrical machine, whereas PD measurements were carried out at a single stator from wound coils. During manufacturing, these coils were equipped with different materials for the OCP (outer corona protection). Using different PD measurement systems and different bandwidths, investigations of the PD behavior of the coils were carried out. Additionally, the surface resistivity of the corona protection was determined. As a result, conclusions for the correlations between the resistance of the OCP as well as the PD behavior are stated. Furthermore, the influence of using different measurement systems, different measuring circuits, and different bandwidths is shown. 相似文献
86.
Christof Huebner Rachel Cardell‐Oliver Stefan Hanelt Tino Wagenknecht Alvaro Monsalve 《Wireless Communications and Mobile Computing》2013,13(17):1499-1510
Wireless sensor networks for environmental monitoring and agricultural applications often face Long‐range requirements at low bit rates together with a large numbers of nodes. This paper presents the design and test of a novel wireless sensor network that combines a large radio range with very low power consumption and cost. Our asymmetric sensor network uses ultra‐low‐cost 40‐MHz transmitters and a sensitive software‐defined radio receiver with multi‐channel capability. Experimental radio range measurements in two different outdoor environments demonstrate a single‐hop range of up to 1.8 km. A theoretical model for radio propagation at 40 MHz in outdoor environments is proposed and validated with the experimental measurements. The reliability and fidelity of network communication over longer periods is evaluated with a deployment for distributed temperature measurements. Our results demonstrate the feasibility of the transmit‐only low‐frequency system design approach for future environmental sensor networks. Although there have been several papers proposing the theoretical benefits of this approach, to the best of our knowledge, this is the first paper to provide experimental validation of such claims. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
87.
Hendrik Schröder Linda Hoffmann Joachim Müller Petra Alhorn Markus Fleger Andreas Neyer Christof M. Niemeyer 《Small (Weinheim an der Bergstrasse, Germany)》2009,5(13):1547-1552
A microfluidic polymer chip for the self‐assembly of DNA conjugates through DNA‐directed immobilization is developed. The chip is fabricated from two parts, one of which contains a microfluidic channel produced from poly(dimethylsiloxane) (PDMS) by replica‐casting technique using a mold prepared by photolithographic techniques. The microfluidic part is sealed by covalent bonding with a chemically activated glass slide containing a DNA oligonucleotide microarray. The dimension of the PDMS–glass microfluidic chip is equivalent to standard microscope slides (76 × 26 mm2). The DNA microarray surface inside the microfluidic channels is configured through conventional spotting, and the resulting DNA patches can be conveniently addressed with compounds containing complementary DNA tags. To demonstrate the utility of the addressable surface within the microfluidic channel, DNA‐directed immobilization (DDI) of DNA‐modified gold nanoparticles (AuNPs) and DNA‐conjugates of the enzymes glucose oxidase (GOx) and horseradish peroxidase (HRP) are carried out. DDI of AuNPs is used to demonstrate site selectivity and reversibility of the surface‐modification process. In the case of the DNA–enzyme conjugates, the patterned assembly of the two enzymes allows the establishment and investigation of the coupled reaction of GOx and HRP, with particular emphasis on surface coverage and lateral flow rates. The results demonstrate that this addressable chip is well suited for the generation of fluidically coupled multi‐enzyme microreactors. 相似文献
88.
Gia Quyet Ngo Antony George Robin Tristan Klaus Schock Alessandro Tuniz Emad Najafidehaghani Ziyang Gan Nils C. Geib Tobias Bucher Heiko Knopf Sina Saravi Christof Neumann Tilman Lühder Erik P. Schartner Stephen C. Warren-Smith Heike Ebendorff-Heidepriem Thomas Pertsch Markus A. Schmidt Andrey Turchanin Falk Eilenberger 《Advanced materials (Deerfield Beach, Fla.)》2020,32(47):2003826
Atomically thin transition metal dichalcogenides are highly promising for integrated optoelectronic and photonic systems due to their exciton-driven linear and nonlinear interactions with light. Integrating them into optical fibers yields novel opportunities in optical communication, remote sensing, and all-fiber optoelectronics. However, the scalable and reproducible deposition of high-quality monolayers on optical fibers is a challenge. Here, the chemical vapor deposition of monolayer MoS2 and WS2 crystals on the core of microstructured exposed-core optical fibers and their interaction with the fibers’ guided modes are reported. Two distinct application possibilities of 2D-functionalized waveguides to exemplify their potential are demonstrated. First, the excitonic 2D material photoluminescence is simultaneously excited and collected with the fiber modes, opening a novel route to remote sensing. Then it is shown that third-harmonic generation is modified by the highly localized nonlinear polarization of the monolayers, yielding a new avenue to tailor nonlinear optical processes in fibers. It is anticipated that the results may lead to significant advances in optical-fiber-based technologies. 相似文献
89.
Hannaford Blake Krischer Christof C. Stark Lawrence 《IEEE transactions on bio-medical engineering》1985,(1):86-89
A portable personal computer has been programmed as a flexible and economical text display device capable of delivering single and multiple words or symbols flashed in the center of the screen with a wide range of repetition times and duty cycles (fraction of stimulus on/off time). All aspects of a computer-controlled experiment are controlled by a command file which can be created by workers with basic word processing skills and no knowledge of computer programming. Digital output is provided for recording stimulus timing on a chart recorder or computer for comparison to eye movements or other externally recorded variables. The system is ideal for zero-eye-movement reading experiments in which sentences are flashed a word or group of words at a time in the center of a CRT screen. If the subject is then asked to repeat the sentence aloud, the percentage of words correctly recalled is a measure of "reading comprehension." Results with nine subjects match previous data [1] obtained cinematographically. 相似文献
90.
A method is described for visualization and recording, as well as for numerical simulation of particle motion during the deposition onto single electrically charged filter fibres (electret fibres). For this a microscope and a high-speed cine camera are used to record the trajectories of particles in the process of flowing around, and being deposited on, a fibre (two-dimensionally in a plane perpendicular to the fibre axis). The particle trajectories are then modeled, based on the experimental data and suitable mathematical models for the fluid flow and the electric fields of the fibre charges. As the fibre charge density, in general, is not known, it is used as a fitting parameter in the model calculation. Using the example of split-fibres with a rectangular cross-section and a bipolar electric charge it is shown that, using models known from the literature, very good agreement can be achieved between experiment and simulation. With this electret fibre type, the trajectory simulations, assuming an ideal bipolar charge configuration, gave effective charge densities between roughly 100 and 500 μAs m−2, corresponding to total surface charge densities between 230 and 1150 μAs m−2. 相似文献