X-ray imaging using single photon processing with semiconductor pixel detectors

More than 10 years experience with semiconductor pixel detectors for vertex detection in high energy physics experiments together with the steady progress in CMOS technology opened the way for the development of single photon processing pixel detectors for various applications including medical X-ray imaging. The state of the art of such pixel devices consists of pixel dimensions as small as 55x55 um2, electronic noise per pixel <100 e- rms, signal-to-noise discrimination levels around 1000 e- with a spread <50 e- and a dynamic range up to 32 bits per pixel. Moreover, the high granularity of hybrid pixel detectors makes it possible to probe inhomogeneities of the attached semiconductor sensor

A Study on Goodwill Accounting Based on the Corporate Competence Theory

在一个多世纪的时间里，商誉问题一直是会计研究领域内极具魅力的主题之一。如今，随着企业的价值创造过程日益依赖于无形资源，随着企业并购市场的日趋扩大，人们对于商誉这个超越了具体产品和服务、提升了企业整体价值的战略性资产日益重视，也更加渴求有关它的高质量会计信息。有关商誉的论述浩如烟海，然而，人们对于商誉的许多问题仍争辩激烈，莫衷一是。本文依据战略管理领域内迅速发展的一种理论——“企业能力论”来对商誉作一系统的研究，希望通过相关学科知识的引入来为商誉研究的发展作出一些贡献。 本文分为八章来进行论述：第一章为引言。第二章进行了系统的文献回顾。第三章介绍了企业能力论，并提出了资源和能力基础的商誉定义，...Since the beginning of last century, goodwill has been an extremely attractive topic in accounting. Nowadays, with the corporate value creation process depending more on intangible resources, and the acquisition and merger market growing dramatically, people pay more attention to goodwill, which overtakes specific product and service and adds to the whole corporate value. Also, people desire for m...学位：管理学硕士院系专业：管理学院会计系_会计学学号：2005130118

On the Advertising Translation from the Perspective of Relevance Theory

摘要 随着中国加入世界贸易组织，国际贸易在中国快速发展起来。国际交流的快速发展和国际竞争的加剧使得企业对于广告的需求也日益增长。不论对于商人还是消费者来说，国际广告都已经成为生活中重要的一部分。一则广告能否在国际市场上获得成功很大程度上取决于它的译本能否引起目的观众的兴趣并促使他们购买产品。因此，广告翻译在国际广告业有着至关重要的地位。 每个广告都蕴含着一个基本意思，这个基本意思正是广告人想要通过这则广告来表达的东西。广告人希望当观众看到这则广告时不费吹灰之力就能理解广告的基本意思。所以，广告的译本也应该以此为目标，帮助目的观众轻松地了解广告人的意图。但由于文化差异，一则广告的原观众和其译...Abstract After China joined the World Trade Organization, international trades have rapidly developed in China. The fast growth of international communications and acute competitions triggers an increasing need for advertising. International advertising has become a very important part not only for merchants but also for consumers. The success of an international advertisement depends largely on ...学位：翻译硕士院系专业：外文学院英语语言文学系_翻译硕士学号：1202009115234

Personal Dosimetry in Pulsed Photon Fields with the Dosepix Detector

First investigations regarding dosimetric properties of the hybrid, pixelated, photon-counting Dosepix detector in a pulsed photon field (RQR8) for the personal dose equivalent $H\mathrm{_p(10)}$ are presented. The influence quantities such as pulse duration and dose rate were varied, and their responses were compared to the legal limits provided in PTB-A 23.2. The variation of pulse duration at a nearly constant dose rate of 3.7$\,$Sv/h shows a flat response around 1.0 from 3.6$\,$s down to 2$\,$ms. A response close to 1.0 is achieved for dose rates from 0.07$\,$mSv/h to 35$\,$Sv/h for both pixel sizes. Above this dose rate, the large pixels (220$\,\mathrm{\mu}$m edge length) are below the lower limit. The small pixels (55$\,\mathrm{\mu}$m edge length) stay within limits up to 704$\,$Sv/h. The count rate linearity is compared to previous results, confirming the saturating count rate for high dose rates.Comment: 6 pages, 3 figures. This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Comparative results on collimation of the SPS beam of protons and Pb ions with bent crystals

New experiments on crystal assisted collimation have been carried out at the CERN SPS with stored beams of 120 GeV/. c protons and Pb ions. Bent silicon crystals of 2 mm long with about 170 μrad bend angle and a small residual torsion were used as primary collimators. In channeling conditions, the beam loss rate induced by inelastic interactions of particles with the crystal nuclei is minimal. The loss reduction was about 6 for protons and about 3 for Pb ions. Lower reduction value for Pb ions can be explained by their considerably larger ionization losses in the crystal. In one of the crystals, the measured fraction of the Pb ion beam halo deflected in channeling conditions was 74%, a value very close to that for protons. The intensity of the off-momentum halo leaking out from the collimation station was measured in the first high dispersion area downstream. The particle population in the shadow of the secondary collimator-absorber was considerably smaller in channeling conditions than for amorphous orientations of the crystal. The corresponding reduction was in the range of 2-5 for both protons and Pb ions.peer-reviewe

Observation of parametric X-rays produced by 400 GeV/c protons in bent crystals

Spectral maxima of parametric X-ray radiation (PXR) produced by 400 GeV/c protons in bent silicon crystals aligned with the beam have been observed in an experiment at the H8 external beam of the CERN SPS. The total yield of PXR photons was about 10-6 per proton. Agreement between calculations and the experimental data shows that the PXR kinematic theory is valid for bent crystals with sufficiently small curvature as used in the experiment. The intensity of PXR emitted from halo protons in a bent crystal used as a primary collimator in a circular accelerator may be considered as a possible tool to control its crystal structure, which is slowly damaged because of irradiation. The intensity distribution of PXR peaks depends on the crystal thickness intersected by the beam, which changes for different orientations of a crystal collimator. This dependence may be used to control crystal collimator alignment by analyzing PXR spectra produced by halo protons.peer-reviewe

Performance and limitations of high granularity single photon processing X-ray imaging detectors

Zsfassung in dt. SpracheDer rasante Fortschritt in der CMOS Technologie und in den Verbindungstechniken zwischen Halbleiterdetektor und Auslesechip erlauben die Entwicklung von photonenzählenden Detektorkonzepten für Anwendungen in der Röntgenbildgebung. Pixelabstände in der Größenordnung von 50 µm stellen eine Ortsauflösung zur Verfügung, die vergleichbar ist mit der von konventionellen CCDs und Flachbilddetektoren. Die Verarbeitung des Signals einzelner Photonen eröffnet die Möglichkeit, Detektoren für spektrale Bildgebung zu konstruieren. Im Rahmen dieser Dissertation wurde sowohl die Wechselwirkung von Röntgenphotonen im Energiebereich von 5-70 keV mit verschiedenen Detektormaterialen untersucht, als auch das Ansprechverhalten des Medipix2 Detektorsystems auf monoenergetische und spektrale Röntgenquellen studiert. Die Simulationen und Messungen zeigen, dass die erreichbare Orts- und Energieaufösung durch Diffusion während der Ladungssammlung im Sensor und die Emission charakteristischer Röntgenstrahlung in Sensormaterialien höherer Ordnungszahl begrenzt sind. Nach Anwendung geeigneter Flatfield-Korrekturen folgt das Bildrauschen der Poisson Statistik. Das Rauschen einer Pixelelektronik des Medipix2 Chips ist ~100 e- rms und die untere Energieschwelle für die Detektierung typischerweise ~1000 e-. Die gemessene Modulations-Transfer-Funktion folgt derjenigen der Pixelapertur mit einer Ortsauflösung von 9.1 lp/mm. Die Detektor-Quanteneffizienz ist limitiert durch die Absorptionseffizienz des Sensormaterials und ist unabhängig von der Bilddosis. Die Ergebnisse zeigen das große Potential, das photonenzählende Detektoren für die Röntgenbildgebung, speziell bei niedriger Dosis, bieten. Der Medipix2 Detektor erlaubt es, ein Energiefenster mit einer minimalen Breite von 1.4 keV FWHM in einem Bereich von 4 bis 100 keV zu setzen. Erste Aufnahmen, die dieses Energiefenster verwenden, demonstrieren, dass selbst bei Verwendung Röntgenquellen mit breitem Energiespektrum mit Hilfe dieser Technik spektrale Information gewonnen werden kann.Progress in CMOS technology and in fine pitch bump bonding has made possible the development of single photon counting detectors for X-ray imaging with pixel pitches on the order of 50 µm giving a spatial resolution which is comparable to conventional CCD and flat panel detectors. This thesis studies the interaction of X-ray photons in the energy range of 5 keV to 70 keV with various sensor materials as well as the response of the Medipix2 readout system to both monochromatic and wide spectrum X-ray sources. Single photon processing offers the potential for spectroscopic imaging. However, this thesis demonstrates using simulations and measurements that the charge diffusion during collection in the sensor and the generation of fluorescence photons in heavier sensor materials impose fundamental limits on the achievable spatial and energy resolution. With the application of appropriate flat-field correction maps, the system operates to the Poisson limit. The Modulation Transfer Function has been measured to be 9.1 lp/mm corresponding to the pixel aperture function. The Detective Quantum Efficiency is only limited by the sensor material used and does not change as a function of dose, highlighting the enormous potential for low dose imaging. The Medipix2 system allows for an energy window of down to 1.4 keV FWHM to be selected and scanned in the range of 4 keV to 100 keV. First images using the energy threshold window demonstrate the potential of the technique to extract a spectral image when only a broad band source of X-rays is available.16

Overview on Measured Properties of VTT's Edgeless Detectors and their use in High Energy Physics

During the past five years VTT has actively developed fabrication processes for the state-of-the-art edgeless strip and pixel detectors with a negligible dead region at the edges. The article summarizes the measured properties of VTT's edgeless detectors and gives references to the relevant journal papers. The measured properties include leakage current, breakdown voltage and capacitance dependences on the detector thickness and polarity. Earlier X-ray tube and radiation source characterization results are revised and new ones are introduced to reveal a pixel response as a function of bias voltage and pixel location in the detector's pixel matrix. Part of the article concentrates on alpha particle characterization of the detectors, especially to the pixel response properties at the edge regions of the detector. The article shows that the edgeless detectors are not losing charge collections efficiency at the edge and the spectroscopic response is comparable to the inner regions of the detector. In addition, the distortion of the electric field at the edge of the detector is almost independent on the applied reverse bias voltage