共查询到20条相似文献,搜索用时 0 毫秒
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Medina A Gayá F del Pozo F 《Journal of the Optical Society of America. A, Optics, image science, and vision》2006,23(4):800-805
A novel three-dimensional (3D) camera is capable of providing high-precision 3D images in real time. The camera uses a diode laser to illuminate the scene, a shuttered solid-state charge-coupled device (CCD) sensor, and a simple phase detection technique based on the sensor shutter. The amplitude of the reflected signal carries the luminance information, while the phase of the signal carries range information. The system output is coded as a video signal. This camera offers significant advantages over existing technology. The precision in range is dependent only on phase shift and laser power and theoretically is far superior to existing time-of-flight laser radar systems. Other advantages are reduced size and simplicity and compact and inexpensive construction. We built a prototype that produced high-resolution images in range the (z) and x-y. 相似文献
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Scharf O Ihle S Ordavo I Arkadiev V Bjeoumikhov A Bjeoumikhova S Buzanich G Gubzhokov R Günther A Hartmann R Kühbacher M Lang M Langhoff N Liebel A Radtke M Reinholz U Riesemeier H Soltau H Strüder L Thünemann AF Wedell R 《Analytical chemistry》2011,83(7):2532-2538
For many applications there is a requirement for nondestructive analytical investigation of the elemental distribution in a sample. With the improvement of X-ray optics and spectroscopic X-ray imagers, full field X-ray fluorescence (FF-XRF) methods are feasible. A new device for high-resolution X-ray imaging, an energy and spatial resolving X-ray camera, is presented. The basic idea behind this so-called "color X-ray camera" (CXC) is to combine an energy dispersive array detector for X-rays, in this case a pnCCD, with polycapillary optics. Imaging is achieved using multiframe recording of the energy and the point of impact of single photons. The camera was tested using a laboratory 30 μm microfocus X-ray tube and synchrotron radiation from BESSY II at the BAMline facility. These experiments demonstrate the suitability of the camera for X-ray fluorescence analytics. The camera simultaneously records 69,696 spectra with an energy resolution of 152 eV for manganese K(α) with a spatial resolution of 50 μm over an imaging area of 12.7 × 12.7 mm(2). It is sensitive to photons in the energy region between 3 and 40 keV, limited by a 50 μm beryllium window, and the sensitive thickness of 450 μm of the chip. Online preview of the sample is possible as the software updates the sums of the counts for certain energy channel ranges during the measurement and displays 2-D false-color maps as well as spectra of selected regions. The complete data cube of 264 × 264 spectra is saved for further qualitative and quantitative processing. 相似文献
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We have been developing cryogenic readout integrate circuits using SONY GaAs JFETs for large format arrays of high impedance type detectors especially for submillimeter/terahertz astronomy. The GaAs JFETs manufactured by SONY CO. Ltd have excellent static properties at less than 1 K. Besides, these JFETs have good performance for electrical switches; they have very low gate capacitance (<50 fF), low on resistance (∼10 kΩ), and high off resistance (>100 TΩ). To realize a cryogenic readout system for submillimeter-wave/terahertz camera, we designed multiplexers with sample-and-holds and shift registers. We report the first test results of each circuit and show prospect of a cryogenic multiplex system for a submillimeter-wave/terahertz digital camera. 相似文献
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A simulation and experimental investigation of a recently proposed, compact, phase-conjugating correlator is undertaken. The effects of noise and other distortions in the input image and in the correlator filter plane are considered. As with other phase-only designs, the phase-conjugating correlator is sensitive to distortion of the input image while being robust in the presence of filter-plane distortions; this robustness is enhanced by the phase-conjugating property of the design. 相似文献
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B.F. Zhang 《低温学》1983,23(2):72
This paper describes a dummy test of a cryogenic heat pipe coupled between the infrared detector and cooler. The cryogenic heat pipe provides efficient thermal conduction for 2 W power over a 87.5 cm length with a maximum temperature difference of 0.91 K at 82 K operating temperature. The test results have useful applications. 相似文献
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A second-generation absolute cryogenic radiometer (ACR II) was developed for use at the Low Background Infrared calibration facility at the National Institute of Standards and Technology. The need for spectral calibrations of very sensitive [D* = 10(14) cm (Hz)1/2W(-1)] infrared detectors necessitated the use of a cryogenic infrared monochromator and a more sensitive radiometer. The improved low-power performance of the ACR II compared with the older absolute cryogenic radiometer (ACR) has also made it useful as the primary standard for the calibration of cryogenic blackbody sources that are used as low-power infrared sources. The responsivity of the new radiometer's receiver is 210 K/mW with a type A (random component) standard uncertainty of at most 7 pW when making power measurements of less than 10 nW. The original ACR has a responsivity of 29 K/mW and has a type A standard uncertainty of approximately 100 pW when making a similar low-noise-power measurement. Other properties of the radiometers are also described and compared. 相似文献
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Z. M. Zhang L. M. Hanssen R. U. Datla H. D. Drew 《International Journal of Thermophysics》1996,17(6):1441-1454
A facility for measuring the optical properties of solid materials at cryogenic temperatures is being developed at the National Institute of Standards and Technology. A cryostat that houses four ur bolometric detectors and a six-position sample holder was designed and built. The bolometers operate near 5 K, and the sample temperature can he varied from 6 to 100 K. The beam from a Fourier transform spectrometer is directed to the cryostat by reflective optical components. The measurable wavelengths extend from 1m to 1 mm, with appropriate sources and beamsplitters in the spectrometer as well as windows and detectors in the cryostat. The angle of incidence on the sample ranges from 7.5 to 60. The mechanical electrical, and optical designs are described in this paper. Initial measurement results at wavelengths from 2 to 30m and a sample temperature of 10 K are presented. 相似文献
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Spatiotemporal regularization for digital image correlation: Application to infrared camera frames 下载免费PDF全文
《International journal for numerical methods in engineering》2018,114(12):1331-1349
The spatiotemporal response of a stainless steel plate undergoing cyclic laser shock is recorded with an infrared camera, and digital image correlation is used to analyze both displacement and temperature fields. Two very challenging difficulties are addressed: (i) large gray‐level variations (due to temperature changes) and (ii) convection effects affecting images. To this aim, a spatiotemporal regularization is designed exploiting a numerical model of the test. The thermomechanical space‐time predictions are first processed through Karhunen‐Loève decomposition to extract dominant temporal and spatial modes. The temporal modes are then inserted in a spatiotemporal digital image correlation framework to estimate the experimental spatial modes that account for both gray‐level variations (and hence temperature) and displacement fields. It is shown that with only 3 modes, the full thermomechanical response of the material is captured. The temporal regularization issued from the model also allows the spurious effect of convection to be filtered out. Due to the drastic decrease in the number of degrees of freedom because of data reduction, the number of analyzed frames can be reduced from 50 down to 6 to capture the thermomechanical response, thereby leading to enhanced efficiency. 相似文献
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This paper describes the design and optimization of a cryogenic refrigerator using the LBL computer program GEOTHM. This computer program has been used extensively to design and optimize geothermal power plants and power cycles of other types. GEOTHM can calculate the thermodynamics of a wide variety of cycles including refrigeration cycles. GEOTHM has an optimizer which permits single step multi-parameter optimization of a thermodynamic cycle. A refrigeration cycle may be optimized for minimum cost refrigeration, or maximum thermodynamic performance using up to 55 optimizable parameters. The use of the optimizer in GEOTHM is demonstrated on two liquid nitrogen refrigeration cycles which are optimized for minimum refrigeration cost and minimum input power. 相似文献
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Principle, design and experimental validation of a flywheel-battery hybrid source for heavy-duty electric vehicles 总被引:1,自引:0,他引:1
《Electric Power Applications, IET》2007,1(5):665-674
The design and the integration of an electromechanical storage system into an electric vehicle power train are discussed. The objective of this study is to highlight the interest of sources hybridisation for heavy-duty vehicles with discontinuous mission profiles as garbage collection. This behaviour is characterised by a high peak-to-average battery power ratio. A solution to increase vehicle performances is to maintain the battery power within rated levels for charges and discharges with an auxiliary peak-power source which supplies or recovers the energy during acceleration or braking, respectively. In this case, the battery can be considered as an energy source. The authors have focused on a hybrid source made of a battery and an electromechanical storage system, which behaves as a power source. This principle has been verified with the help of simulations through Matlab/Simulinkreg. To validate the simulation results, an experimental test bench including the hybrid source has been designed. This test bench allows to recreate the dynamic vehicle behaviour on a given mission profile. Experimental results are shown and discussed. 相似文献
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An in-plane constant-efficiency variable-diffraction-angle grating and an in-plane high-angular-selectivity grating are combined to enable a new compact silicon diffractive sensor. This sensor is fabricated in silicon-on-insulator and uses telecommunications wavelengths. A single sensor element has a micron-scale device size and uses intensity-based (as opposed to spectral-based) detection for increased integrability. In-plane diffraction gratings provide an intrinsic splitting mechanism to enable a two-dimensional sensor array. Detection of the relative values of diffracted and transmitted intensities is independent of attenuation and is thus robust. The sensor prototype measures refractive index changes of 10(-4). Simulations indicate that this sensor configuration may be capable of measuring refractive index changes three or four orders of magnitude smaller. The characteristics of this sensor type make it promising for lab-on-a-chip applications. 相似文献
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The adjoint form of the photon transport equation is applied to a generalized fluorescence detection problem, and its accuracy is empirically tested. This approach can be interpreted as mathematically reversing the temporal flow of fluorescent photons; that is, they are tracked from the detector back to potential sites of origin in the scattering medium. The result is a distribution of potential fluorescing sites that, when properly normalized, gives a probability field of the relative importance of the photon starting position and direction to the resulting signal. This adjoint solution can be combined with the temporally forward-derived distribution of absorbed excitation photons to evaluate the fluorescence excitation detection scheme. This bypasses the normal, temporal derivation wherein the fluorescence transport solution is dependent on the result of the excitation transport solution. 相似文献
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Yamaner FY Olçum S Oğuz HK Bozkurt A Köymen H Atalar A 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2012,59(6):1276-1284
Capacitive micromachined ultrasonic transducers (CMUTs) have great potential to compete with piezoelectric transducers in high-power applications. As the output pressures increase, nonlinearity of CMUT must be reconsidered and optimization is required to reduce harmonic distortions. In this paper, we describe a design approach in which uncollapsed CMUT array elements are sized so as to operate at the maximum radiation impedance and have gap heights such that the generated electrostatic force can sustain a plate displacement with full swing at the given drive amplitude. The proposed design enables high output pressures and low harmonic distortions at the output. An equivalent circuit model of the array is used that accurately simulates the uncollapsed mode of operation. The model facilities the design of CMUT parameters for high-pressure output, without the intensive need for computationally involved FEM tools. The optimized design requires a relatively thick plate compared with a conventional CMUT plate. Thus, we used a silicon wafer as the CMUT plate. The fabrication process involves an anodic bonding process for bonding the silicon plate with the glass substrate. To eliminate the bias voltage, which may cause charging problems, the CMUT array is driven with large continuous wave signals at half of the resonant frequency. The fabricated arrays are tested in an oil tank by applying a 125-V peak 5-cycle burst sinusoidal signal at 1.44 MHz. The applied voltage is increased until the plate is about to touch the bottom electrode to get the maximum peak displacement. The observed pressure is about 1.8 MPa with -28 dBc second harmonic at the surface of the array. 相似文献
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低温真空腔体结构设计及传热分析 总被引:1,自引:0,他引:1
为适应未来航天低温光学系统的需要,研制了1套测量光学元件低温场和低温变形的系统。该系统由真空机组、低温真空腔体、防振系统、测量装置等主要部分组成。其中低温真空腔体是该系统中关键的装置,为光学元件的低温真空实验提供了必要的条件。对低温真空腔体的结构设计、真空度和传热进行了分析探讨,并且对梯形薄壁绝热支撑进行了详细结构热分析和COSMOSWORK软件的传热分析,结果表明可以满足低温真空的实验要求。 相似文献
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Standard material parameters identification strategies for constitutive equations generally use an extensive number of classical tests for collecting the required experimental data. Recently, new specimen geometries for heterogeneous tests were designed to enhance the richness of the strain field and capture supplementary strain states using full‐field measurement techniques. The butterfly specimen is an example of such a geometry, designed through a numerical optimization procedure where an indicator capable of evaluating the heterogeneity and the richness of strain information is used. The aim of this work is to experimentally validate the heterogeneous butterfly mechanical test in the parameter identification framework. Blanks of mild steel DC04 are cut with the butterfly geometry, and specific grips are designed. Tests are performed with Digital Image Correlation technique, and a Finite Element Model Update inverse strategy is used for the parameter identification, as well as the calculation of the indicator. The identification strategy is accomplished with the data obtained from the experimental tests, and the results are compared with quasi‐homogeneous tests. 相似文献