共查询到20条相似文献,搜索用时 15 毫秒
1.
Gamal Ahmed Pual Bühler Olaf Hartmann Johann Marton Ken Suzuki Johann Zmeskal 《Hyperfine Interactions》2012,207(1-3):49-52
Conversion electron M?ssbauer Spectroscopy measurements have been made on ZnO single crystals implanted with 60?keV 57Fe to 4 and 8 at.% peak concentrations, and annealed up to 800°C. The spectra show quite strong changes with annealing, but no evidence of magnetic components, thus precluding the formation of large sized precipitates or secondary phases. Above an annealing temperature of 650°C, the dominant spectral component is a doublet with hyperfine parameters typical of Fe3?+?, which is attributed to Fe3?+? ions in nano-precipitates ~5?nm in size. 相似文献
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Jimmy Castillo Hector Gutierrez Jose Chirinos Jean Carlos Perez 《Optics Communications》2010,283(20):3926-3930
This work presents a new surface plasmon resonance (SPR) instrument based on Kretschmann configuration. This device acquires and processes the reflected SPR image of the sample by using a webcam together with an image processing algorithm that transforms the RGB image in numeric values and correlates the integrated intensity with the refractive index of the solution. Experimental signals were compared with theoretical values and it was found an excellent agreement. In addition, the applicability of the instrument was tested by measuring the refractive index of solutions in a continuous flow mode. Excellent stability and sensitivity of the signal were found in the presence of small changes of the refractive index. 相似文献
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P Lanzer W McKibbin D Bohning B Thorn G Gross G Cranney N Nanda G Pohost 《Magnetic resonance imaging》1990,8(2):107-116
To assess the ability of projective phase sensitive magnetic resonance (MR) angiography to visualize the aortoiliac vascular segment, and to determine the effects of triggering and timing of data acquisition om image quality, we studied 18 healthy volunteers, mean age 33.3 +/- 11 years, by color Doppler imaging and by MR angiography. MR angiography was performed at 1.5 T using a flow-adjustable gradient-echo (FLAG) sequence operated in both ECG-triggered and non-triggered acquisition modes. The images were graded in a blinded fashion by two independent observers. The data were analyzed using Pearson's chi-square analysis. Eighteen triggered time-resolved and 17 non-triggered, time-averaged MR angiograms consisting of 252 and 17 angiographic images, (AI) respectively, were analyzed. In the triggered mode 69 (27.4%) AI and in the non-triggered mode 2 (11.8%) AI were diagnostic. At least one triggered diagnostic AI was obtained in each subject. The image grades were not statistically different between observers (kappa = 0.6686). In the triggered mode diagnostic images were acquired within +/- 90 msec of the peak systolic flow velocity determined by Doppler. The proportion of diagnostic images in the triggered mode was highest (73.3%) within a 30-msec interval before the peak flow. In healthy subjects the aortoiliac segment is reliably visualized by FLAG MR angiography. The optimum results are achieved using the triggered acquisition mode and timing acquisition to the initial 180 msec of the abdominal aortic systolic flow pulse. 相似文献
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基于 FPGA 和 IEEE1588PTPv2 协议设计了 HL-2M 装置时序控制系统,用于在精准时刻为测控系统
提供触发。数据采集系统采用客户端/服务端双模式管理。在 HL-2M 装置初始等离子体放电实验中测试结果表明,
时序控制和采集系统具有纳秒级精度触发,实时性强,数据传输速度快,稳定可靠,方便部署和管理的特点,满
足 HL-2M 等离子体放电实验的应用需求。 相似文献
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We propose to monitor a qubit with a double-dot (DD) resonant-tunneling detector, which can operate at higher temperatures than a single-dot detector. In order to assess the effectiveness of this device, we derive rate equations for the density matrix of the entire system. We show that the signal-to-noise ratio can be greatly improved by a proper choice of the parameters and location of the detector. We demonstrate that quantum interference effects within the DD detector play an important role in the measurement. Surprisingly, these effects produce a systematic measurement error, even when the entire system is in a stationary state. 相似文献
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Preliminary thoughts about the data acquisition system to be developed for the next generation of large area silicon tracker
are presented in this paper. This paper describes the set of data delivered by these tracking systems, and the various stages
of processing and data flow transmission from the front-end chip sitting on the detector to the latest stage in the data processing.
How to best profit from the status of the art technologies is a major goal.
相似文献
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A. A. Kosterev P. R. Buerki L. Dong M. Reed T. Day F. K. Tittel 《Applied physics. B, Lasers and optics》2010,100(1):173-180
A quartz enhanced photoacoustic spectroscopy sensor designed for fast response was used in combination with a pulsed external
cavity quantum cascade laser to rapidly acquire gas absorption data over the 1196–1281 cm−1 spectral range. The system was used to measure concentrations of water vapor, pentafluoroethane (freon-125), acetone, and
ethanol both individually and in combined mixtures. The precision achieved for freon-125 concentration in a single 1.1 s long
spectral scan is 13 ppbv. 相似文献
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M. Voytchev D. Klein A. Chambaudet G. Georgiev M. Iovtchev 《Radiation measurements》1999,31(1-6):375-378
An application of our developed silicon photodiode detector for radon progeny measurements is presented in this paper. It was determined the deposition velocity for free (3.6 ± 0.7) × 10−3 m s−1 and attached (1.0 ± 0.5) × 10−5 m s−1 fraction of short living radon progeny. 相似文献
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Jong Chul Han Ho Kyung Kim Dong Woon Kim Seungman Yun Hanbean Youn Soohwa Kam Jesse Tanguay Ian A. Cunningham 《Current Applied Physics》2014,14(12):1734-1742
We describe a multi-layer (“sandwich”) configuration detector consisting of two x-ray imaging flat-panel detectors for single-shot (single-kV) dual-energy imaging. An intermediate copper filter is used to increase spectral separation between the two detectors to improve contrast at the expense of image noise. Monte Carlo and cascaded-systems analyses of the signal and noise performance are described that quantify performance characteristics. Image quality of dual-energy images obtained from a prototype sandwich-detector system is evaluated using a figure of merit (FOM), defined as the squared contrast-to-noise ratio normalized by x-ray exposure for a mouse phantom for preclinical imaging. Demonstration dual-energy bone and soft-tissues images of a postmortem mouse are obtained using the prototype system. While the FOM with the single-shot detector is lower than that achieved using a conventional dual-shot (dual-kV) method, the single-shot approach may be preferable when imaging speed or insensitivity to motion artifacts is a primary concern. 相似文献
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Ken-ichiro Matsumoto Kazunori Anzai Hideo Utsumi 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,197(2):161-166
A combination of the constant-time spectral-spatial imaging (CTSSI) modality and projection-reconstruction modality was tested to simplify data acquisition for multi-dimensional CW EPR spectral-spatial imaging. In this method, 3D spectral-spatial image data were obtained by simple repetition of conventional 2D CW imaging process, except that the field gradient amplitude was incremented in constant steps in each repetition. The data collection scheme was no different from the conventional CW imaging system for spectral-spatial data acquisition. No special equipment and/or rewriting of existing software were required. The data acquisition process for multi-dimensional spectral-spatial imaging is consequently simplified. There is also no “missing-angle” issue because the CTSSI modality was employed to reconstruct 2D spectral-spatial images. Extra reconstruction processes to obtain higher spatial dimensions were performed using a conventional projection-reconstruction modality. This data acquisition technique can be applied to any conventional CW EPR (spatial) imaging system for multi-dimensional spectral-spatial imaging. 相似文献
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Michael Quentin Gael Pentang Lars Schimmöller Olga Kott Anja Müller-Lutz Dirk Blondin Christian Arsov Andreas Hiester Robert Rabenalt Hans-Jörg Wittsack 《Magnetic resonance imaging》2014
Purpose
To assess the feasibility of full diffusional kurtosis tensor imaging (DKI) in prostate MRI in clinical routine. Histopathological correlation was achieved by targeted biopsy.Materials and Methods
Thirty-one men were prospectively included in the study. Twenty-one were referred to our hospital with increased prostate specific antigen (PSA) values (> 4 ng/ml) and suspicion of prostate cancer. The other 10 men were volunteers without any history of prostate disease. DKI applying diffusion gradients in 20 different spatial directions with four b-values (0, 300, 600, 1000 s/mm2) was performed additionally to standard functional prostate MRI. Region of interest (ROI)-based measurements were performed in all histopathologically verified lesions of every patient, as well as in the peripheral zone, and the central gland of each volunteer.Results
DKI showed a substantially better fit to the diffusion-weighted signal than the monoexponential apparent diffusion coefficient (ADC). Altogether, 29 lesions were biopsied in 14 different patients with the following results: Gleason score 3 + 3 = 6 (n = 1), 3 + 4 = 7 (n = 7), 4 + 3 = 7 (n = 6), 4 + 4 = 8 (n = 1), and 4 + 5 = 9 (n = 2), and prostatitis (n = 12). Values of axial (Kax) and mean kurtosis (Kmean) were significantly different in the tumor (Kax 1.78 ± 0.39, Kmean 1.84 ± 0.43) compared with the normal peripheral zone (Kax 1.09 ± 0.12, Kmean 1.16 ± 0.13; p < 0.001) or the central gland (Kax 1.40 ± 0.12, Kmean 1.44 ± 0.17; p = 0.01 respectively). There was a minor correlation between axial kurtosis (r = 0.19) and the Gleason score.Conclusion
Full DKI is feasible to utilize in a routine clinical setting. Although there is some overlap some DKI parameters can significantly distinguish prostate cancer from the central gland or the normal peripheral zone. Nevertheless, the additional value of DKI compared with conventional monoexponential ADC calculation remains questionable and requires further research. 相似文献14.
In this work we studied the feasibility of detecting the depth of interaction (DOI) with two layers of crystal arrays of LYSO and BGO scintillators coupled to a position-sensitive photomultiplier tube (PS-PMT) R8900-C12. A front-end electronics was designed, with which we got different pulse shapes for different crystals to obtain depth information. With the double integration method, we got the DOI histogram of a divided integration ratio of two crystals as the standard to determine the layer-of-interaction. The DOI accuracy, measured by scanning a 22Na slit source along the side of the module, was 98% for the LYSO layer and 95% for the BGO layer. The energy resolution at 511keV was 13.1% for LYSO and 17.1% for BGO. We obtained good crystal separation in 2D position histograms of both layers. These results could be useful in the manufacture of PET scanners with high spatial resolutions. 相似文献
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《Infrared physics》1985,25(4):633-640
Measurement of the e.m.f. generated by the electron emission from laser-produced solid target plasmas shows the evolution of the laser pulse. Using this phenomenon, a “plasma detector” is constructed. The feasibility of the plasma detector is demonstrated for a long TEA CO2 laser pulse (100 mJ, 60ns). Good time resolution is obtained by using an anode coated with ceramics. The linearity of response with the incident laser intensity for the 109–1010 W/cm2 range is confirmed. The relation of the output voltage to the incident laser intensity is analyzed according to the isothermal rarefaction model. This theoretical analysis and experimental results suggest that there exists an optimum separation between the anode and the cathode. 相似文献
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Summary An infra-red detector produced by the Elettronica SPA Company for the European Space Agency to be used in the Earth surface
mapping from aircraft has been tested in our laboratory. We present the characteristics of the detector working in the spectral
range (1÷2.5) μm. The acquisition system and the electronics are discussed and a detailed study of all the noise sources is
presented; the measured NEP is 3.2·10−14W Hz−1/2 at a temperature of 108 K.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
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In this work, we characterized an X-ray position sensitive gaseous detector based in a triple stack of gas electron multipliers. The readout circuit is divided in 256 strips for each dimension and using a resistive chain interconnecting the strips, we are able to reconstruct the radiation interaction points by resistive charge division. The detector achieved gains above 104, energy resolution of 15.28% (full width at half maximum) for 5.9 keV X-rays, and position resolution of 1.2 mm, while operating in Ar/CO2(90/10) at atmospheric pressure. 相似文献
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Polycrystalline solid state solutions of BaySr1 − yCl2 have been produced; these adopt the cubic fluorite phase for y ≤ 0.30. The cubic structure minimizes optical scattering from grain boundaries, and so for y ≤ 0.30 the materials are transparent, a key advantage for ceramic scintillators and phosphors. The substitution of Sr2+ ions with Ba2+ ions has the advantage that it substantially increases the x-ray absorption coefficient with respect to pure SrCl2. Additional doping with rare earth ions such as Sm2+ and Eu2+ gives bright x-ray phosphor materials. The Sm or Eu-doped materials show a broad 4f55 d1 → 4f6 emission peaked at 685 nm or a broad 4f65 d1 → 4f7 emission peaked at 406 nm respectively. These materials have been tested as x-ray phosphors and the spatial resolution was determined to be at least 6 LP/mm, whilst the x-ray radioluminescence intensity is around 40% that of the commercial x-ray phosphor Gd2O2S:Tb. A stratified phoswich structure, comprising Eu and Sm-doped layers of BaySr1 − yCl2 was produced in which the relative intensities of the two emissions varies with x-ray beam energy; this can be used for energy discrimination in imaging by way of emission spectra as opposed to the more commonly used pulse shape discrimination. A dual energy imaging technique based on these bi-layered structures and utilizing a semi-professional grade digital SLR camera is described and composition-sensitive imaging has been demonstrated. 相似文献