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排序方式: 共有49条查询结果,搜索用时 500 毫秒
1.
A digital pixel sensor array with programmable dynamic range 总被引:1,自引:0,他引:1
This paper presents a digital pixel sensor (DPS) array employing a time domain analogue-to-digital conversion (ADC) technique featuring adaptive dynamic range and programmable pixel response. The digital pixel comprises a photodiode, a voltage comparator, and an 8-bit static memory. The conversion characteristics of the ADC are determined by an array-based digital control circuit, which linearizes the pixel response, and sets the conversion range. The ADC response is adapted to different lighting conditions by setting a single clock frequency. Dynamic range compression was also experimentally demonstrated. This clearly shows the potential of the proposed technique in overcoming the limited dynamic range typically imposed by the number of bits in a DPS. A 64 /spl times/ 64 pixel array prototype was manufactured in a 0.35-/spl mu/m, five-metal, single poly, CMOS process. Measurement results indicate a 100 dB dynamic range, a 41-s mean dark time and an average current of 1.6 /spl mu/A per DPS. 相似文献
2.
A feasibility study of X‐ray phase‐contrast mammographic tomography at the Imaging and Medical beamline of the Australian Synchrotron
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Yakov I. Nesterets Timur E. Gureyev Sheridan C. Mayo Andrew W. Stevenson Darren Thompson Jeremy M. C. Brown Marcus J. Kitchen Konstantin M. Pavlov Darren Lockie Francesco Brun Giuliana Tromba 《Journal of synchrotron radiation》2015,22(6):1509-1523
Results are presented of a recent experiment at the Imaging and Medical beamline of the Australian Synchrotron intended to contribute to the implementation of low‐dose high‐sensitivity three‐dimensional mammographic phase‐contrast imaging, initially at synchrotrons and subsequently in hospitals and medical imaging clinics. The effect of such imaging parameters as X‐ray energy, source size, detector resolution, sample‐to‐detector distance, scanning and data processing strategies in the case of propagation‐based phase‐contrast computed tomography (CT) have been tested, quantified, evaluated and optimized using a plastic phantom simulating relevant breast‐tissue characteristics. Analysis of the data collected using a Hamamatsu CMOS Flat Panel Sensor, with a pixel size of 100 µm, revealed the presence of propagation‐based phase contrast and demonstrated significant improvement of the quality of phase‐contrast CT imaging compared with conventional (absorption‐based) CT, at medically acceptable radiation doses. 相似文献
3.
Describes an efficient and effective image similarity calculation method for object-based image comparison at the level of object classes. It uses probabilistic-prediction voting based on the predicted class distribution of each segment of the contour of an object in an image to determine the class of the object. The C4.5 inductive learning algorithm is used to predict the class distribution of object-contour segments. This method is invariant to rotation, scaling and translation of objects. Experimental results show that the method is effective and efficient. It can be used for object-based image retrieval. 相似文献
4.
The provision of a supervisory/service channel on digital transmission systems by direct modulation of the transmitted data bit rate is described. The technique is examined in the context of high bit rate fibre optic system applications and both theoretical as well as practical results are presented. 相似文献
5.
6.
Kitchen J.N. Chu C. Kiaei S. Bakkaloglu B. 《Solid-State Circuits, IEEE Journal of》2009,44(2):404-413
A combined linear and delta-modulated (DeltaM) switch-mode PA supply modulator for polar transmitters in wireless handsets is designed in a 0.25 mum CMOS process. The modulator employs a DeltaM switch-mode DC-DC buck converter to enhance the efficiency of a linear regulator at backed-off supply voltages and powers. The delta-modulator's noise-shaping characteristic, linear regulator's power supply rejection, digital pre-emphasis of the input envelope, and a closed-loop amplitude path from the PA output are simultaneously used to achieve state-of-the-art modulator performance. The presented supply modulator follows the input signal's envelope with 20 dB output dynamic range, maximum efficiency of 75.5% at an output power of 30.8 dBm, and 75 dB SFDR for envelope signals up to 4 MHz occupied RF bandwidth. For a 1625 kb/s 8 PSK RF input signal at 900 MHz, polar modulation of a commercial low-power GSM-900 PA provides 10 dB ACPR improvement. 相似文献
7.
Elmes RB Kitchen JA Williams DC Gunnlaugsson T 《Dalton transactions (Cambridge, England : 2003)》2012,41(22):6607-6610
The new Ru(II) polypyridyl complex 1 was synthesised using microwave irradiation from the new polypyridyl ligand 2'DipyTAP', and its photophysical properties, and DNA binding abilities were investigated using various spectroscopic techniques; and 1 was shown to act as a 'NIR molecular light switch' for DNA with an emission window between 680 and 860 nm. 相似文献
8.
Breeuwer M. Wadley J.P. de Bliek H.L.T. Buurman J. Desmedt P.A.C. Gieles P. Gerritsen F.A. Dorward N.L. Kitchen N.D. Velani B. Thomas D.G.T. Wink O. Blankensteijn J.D. Eikelboom B.C. Mali W.P.T.M. Viergever M.A. Penney G.P. Gaston R. Hill D.L.G. Maurer C.R. Hawkes D.J. Maes F. Vandermeulen D. Verbeeck R. Suetens P. Schmitz G. Buzug T.M. Lorenz C. Sabczynski J. Weese J. Zylka W. Kuhn M.H. 《IEEE transactions on information technology in biomedicine》1998,2(3):156-168
In recent years, advances in computer technology and a significant increase in the accuracy of medical imaging have made it possible to develop systems that can assist the clinician in diagnosis, planning, and treatment. This paper deals with an area that is generally referred to as computer-assisted surgery, image-directed surgery, or image-guided surgery. We report the research, development, and clinical validation performed since January 1996 in the European Applications in Surgical Interventions (EASI) project, which is funded by the European Commission in their “4th Framework Telematics Applications for Health” program. The goal of this project is the improvement of the effectiveness and quality of image-guided neurosurgery of the brain and image-guided vascular surgery of abdominal aortic aneurysms, while at the same time reducing patient risks and overall cost. We have developed advanced prototype systems for preoperative surgical planning and intraoperative surgical navigation, and we have extensively clinically validated these systems. The prototype systems and the clinical validation results are described in this paper 相似文献
9.
Attempts to use alkylation to introduce a positive charge at the nitrogen atom of the 4‐pyridyl ring in the bis(bidentate) triazole ligand N4‐(4‐pyridyl)‐3,5‐di(2‐pyridyl)‐1,2,4‐triazole ( pydpt ) were made to ascertain what effect a strongly electron‐withdrawing group would have on the magnetic properties of any subsequent iron(II) complexes. Alkylation of pydpt under relatively mild conditions led in some cases to unexpected rearrangement products. Specifically, when benzyl bromide is used as the alkylating agent, and the reaction is carried out in refluxing acetonitrile, the N4 substituent moves to the N1 position. However, when the same reaction is performed in dichloromethane at room temperature, the rearrangement does not occur and the desired product containing an alkylated N4 substituent is obtained. Heating a pure sample of N4‐Bzpydpt?Br to reflux in MeCN resulted in clean conversion to N1Bzpydpt.Br . This is consistent with N4‐Bzpydpt.Br being the kinetic product whereas N1Bzpydpt.Br is the thermodynamic product. When methyl iodide is used as the alkylating agent, the N4 to N1 rearrangement occurs even at room temperature, and at reflux pydpt is doubly alkylated. The observation of the lowest reported temperatures for an N4 to N1 rearrangement is due to this particular rearrangement involving nucleophilic aromatic substitution: a possible mechanism for this transformation is suggested. 相似文献
10.
A proposed modification to the component geometry of a fibre amplifier repeater which allows on on-board cable fault location facility to be incorporated is reported. The measurement technique, based on OTDR, allows cable breaks in the section of optical fibre between two fibre amplifier repeaters to be located.<> 相似文献