共查询到20条相似文献,搜索用时 10 毫秒
1.
Estimating the location of a radiating source from recorded sensor signals requires accurate arrival time estimates. If the sensor signals have a short time duration, generating accurate arrival time estimates is a challenging task. This paper proposes a new cross-correlation averaging algorithm which is integrated with a visual ‘peak picking’ alignment approach to improve the estimation of the arrival times. An important application that results in short time duration signals is seismic activity in mines. This seismic activity is produced by high stress faults in the vicinity of the mining operations. Locating the source of these seismic events is important for mine safety. This paper focuses on this mining application to demonstrate how the cross-correlation averaging algorithm can improve the arrival time delay estimation and thus provide better hypocenter location estimates of seismic events in mines. 相似文献
2.
Individual x rays of 5.9 and 22.4 keV have been detected and energy analyzed in single pixels of a CCD image sensor. The results indicate the CCD operates as an array of tiny Si solid state detectors providing both high spatial resolution and x-ray energy discrimination. These devices will prove useful sensors at the focus of future x-ray telescopes. 相似文献
3.
Acremann Y Chembrolu V Strachan JP Tyliszczak T Stöhr J 《The Review of scientific instruments》2007,78(1):014702
The time structure of synchrotron radiation allows time resolved experiments with sub-100 ps temporal resolution using a pump-probe approach. However, the relaxation time of the samples may require a lower repetition rate of the pump pulse compared to the full repetition rate of the x-ray pulses from the synchrotron. The use of only the x-ray pulse immediately following the pump pulse is not efficient and often requires special operation modes where only a few buckets of the storage ring are filled. We designed a novel software defined photon counting system that allows to implement a variety of pump-probe schemes at the full repetition rate. The high number of photon counters allows to detect the response of the sample at multiple time delays simultaneously, thus improving the efficiency of the experiment. The system has been successfully applied to time resolved scanning transmission x-ray microscopy. However, this technique is applicable more generally. 相似文献
4.
Steinmann R Chushkin Y Caronna C Chavanne J Madsen A 《The Review of scientific instruments》2011,82(2):025109
A low temperature sample environment for x-ray photon correlation spectroscopy measurements in small-angle scattering geometry is presented. The chamber has been designed to allow investigations of dynamical phenomena in supercooled liquids and the typical working temperature range is 110-330 K with a thermal stability ΔT/T down to 10(-4). A variable external magnetic field up to 0.12 T can be applied, which is of interest in studies of, e.g., ferrofluids and liquid crystalline materials. Here, technical details about the sample environment are given together with examples of recent applications. 相似文献
5.
为了精确测量三代微光像增强器的信噪比,采用光子计数法研制了瞬态类针孔弱光照度计来实现微光像增强器阴极面上φ0.2 mm类针孔成像光斑的1.08×10-4 lx照度测量.首先,分析了色温为2 856 K的光源形成的类针孔弱光光斑的光子分布概率及光子数涨落偏差等光子统计特性,计算了平均光子通量.然后,针对类针孔弱光光斑的光子通量特点及成像特性,研究了光子计数法测量弱光照度原理.最后,介绍了瞬态类针孔弱光照度计的组成及测量方法.对三代微光像增强器的信噪比进行了测量实验,结果显示:三代微光像增强器信噪比测量装置的照度测量偏差为0.4%,像增强器信噪比测量不确定度为5.0%,表明基于光子计数法研制的瞬态类针孔弱光照度计有效提高了类针孔光斑极弱照度测量的准确度. 相似文献
6.
New technology, especially in the field of microelectronics and mechatronics, created the need for making, positioning and inspection techniques of long microbore-holes and gaps (defined by length/width to diameter ratio l/d > 10 for d < 200 μm). The technological aspect is, in principle, subdued but the metrological one is still unsolved.In Zosel et al. [Zosel J, Guth U, Thies A, Reents B. Flow measurements in micro holes with electrochemical and optical methods. Electrochim Acta 2003;48:3299–305] the properties (power loss and phase distortion) of focused laser microbeam penetrating extremely long through microbores is described; it was proved that the measurement information is distorted depending on the microbore geometry. The samples were prepared of glass–resin laminate with microbore diameter ranging from 35 to 200 μm.In present research an adjustable 100 μm microbore is used as a master. It is formed of mutually accurately adjusted 20 metal plates 100 μm thick set of coaxially in pile. Precise positioning of each plate enables creating free-shaped microbore.The photon batching device emitting 2.5 million photons per second is used as a generator of incident photon beam. The measured transmission efficiency is understood as a relation between outgoing and incoming light energy. The outgoing energy, for particular microbore, was determined by scanning linearly and angularly the bore with photon beam and integrating the results. Experiments were performed in dark room with background 2/5 photons per second (including dark current of photomultiplier).These changes describe the relationship between the shape of the microbore and the transmission energy and can be considered as a measure of microbore cylindricity deviation. 相似文献
7.
Carapelle A Fleury-Frenette K Collette JP Garnir HP Harlet P 《The Review of scientific instruments》2007,78(12):123109
A handheld x-ray spectrometer has been realized and tested. The purpose of the device is to measure the thickness of coated samples in the range of 1-1500 nm in an industrial environment. Accuracy of approximately 3% has been achieved in this range with a measurement time of 1 min. Automated software has been implemented to allow utilization by a nonspecialist operator. An automated calibration procedure, based on measurements of reference samples, is used. 相似文献
8.
A continuous flow device to characterize the growth of nanometer particles was assembled. In-situ millisecond or second-order time-resolved small angle x-ray scattering and x-ray absorption spectroscopy was performed using this device at the Beijing Synchrotron Radiation Facility. The time resolution was adjusted from 10 ms to 1.0 s by changing the flow rate of the solution. The temperature was variable from 5–95°C. Custom-designed pulse eliminators were employed to eliminate adverse pump fluctuations and improve the quality of measurements. The system was used to characterize zinc sulfide nanoparticles by small angle x-ray scattering and x-ray absorption spectroscopy. 相似文献
9.
在北京同步辐射光源上使用自由空气电离室绝对测量了同步辐射硬X射线光子通量。通过自由空气电离室复现空气比释动能率量值,根据在电离辐射量及其单位中定义的空气比释动能与注量及通量的关系,定量得到了光子通量。由于在测量期间,光子通量随时间变化,而测量需要一定的时间,因此,研究了配套的在线通量监测系统,监测带来的不确定度为0.03%。通过测量空气衰减修正因子及复合损失修正因子,结合在线通量监测,在能量为15keV的同步辐射X射线上用自由空气电离室复现了空气比释动能率。在实际实验条件下复现的空气比释动能率为0.239Gy/s,从而得到同步辐射X射线的光子通量为5.28×10~9 photons/s,相对标准不确定度为0.68%。 相似文献
10.
An on-line Ferrograph was used to monitor the wear rates of oil-lubricated ball-bearings. Periodically, the test bearings were also removed from the test stand and cleaned and weighed on an analytical balance.A comparison of the mass loss data obtained by each of these two methods showed that the Ferrograph readings did provide on-line quantitative wear data for each individual test. However, the rates at which the ball-bearings wore were not consistent from test to test. For the four ball-bearings that were evaluated, plots of the Ferrograph concentration readings versus bearing mass loss gave slopes that varied between 1.1 and 2.5. Nevertheless, the results showed that semiquantitative data on the wear rates of machine components could be obtained with this on-line instrumentation. 相似文献
11.
Madden T Fernandez P Jemian P Narayanan S Sandy AR Sikorski M Sprung M Weizeorick J 《The Review of scientific instruments》2011,82(7):075109
We present a data acquisition system to perform on-the-fly background subtraction and lower-level discrimination compression of streaming x-ray photon correlation spectroscopy data from a fast charge-coupled device (CCD) area detector. The system is built using a commercial frame grabber with an on-board field-programmable gate array. The system is capable of continuously processing at least 60 CCD frames per second each consisting of 1024 × 1024 16-bit pixels with ? 15,000 photon hits per frame at a maximum compression factor of ≈95%. 相似文献
12.
Dunn J London RA Cone KV Rocca JJ Rohringer N 《The Review of scientific instruments》2010,81(10):10E330
An inner-shell photoionized x-ray laser pumped by the Linac Coherent Light Source (LCLS) free electron laser has been proposed recently. The measurement of the on-axis 849 eV Ne?Kα laser and protection of the x-ray spectrometer from damage require attenuation of the 1 keV LCLS beam. An Al/Cu foil combination is well suited, serving as a low energy bandpass filter below the Cu L-edge at 933 eV. A high resolution grating spectrometer is used to measure the transmission of a candidate filter with an intense laser-produced x-ray backlighter developed at the Lawrence Livermore National Laboratory Jupiter Laser Facility Janus. The methodology and discussion of the observed fine structure above the Cu L-edge will be presented. 相似文献
13.
Journal of Mechanical Science and Technology - The reuse of machining process, by which the process for a new mechanical part is determined by referencing to the existing and matured processes, is... 相似文献
14.
Zhang Z Nishimura H Namimoto T Fujioka S Arikawa Y Nishikino M Kawachi T Sagisaka A Hosoda H Orimo S Ogura K Pirozhkov A Yogo A Okano Y Kiriyama H Kondo K Ohshima S Azechi H 《The Review of scientific instruments》2012,83(5):053502
X-ray line spectra ranging from 17 to 77 keV were quantitatively measured with a Laue spectrometer, composed of a cylindrically curved crystal and a detector. Either a visible CCD detector coupled with a CsI phosphor screen or an imaging plate can be chosen, depending on the signal intensities and exposure times. The absolute sensitivity of the spectrometer system was calibrated using pre-characterized laser-produced x-ray sources and radioisotopes. The integrated reflectivity for the crystal is in good agreement with predictions by an open code for x-ray diffraction. The energy transfer efficiency from incident laser beams to hot electrons, as the energy transfer agency for specific x-ray line emissions, is derived as a consequence of this work. 相似文献
15.
Young-Sam Ham Dong-Hyong Lee Seok-Jin Kwon Won-Hee You Taek-Yul Oh 《International Journal of Precision Engineering and Manufacturing》2009,10(1):35-39
Oscillatory wheel load fluctuation of considerable amplitude is always observed in railway cars traveling at high speed. This
paper describes a continuous method for measuring the derailment coefficient and the forces between the wheel and rail. The
acceleration measured on the axle box indicates that the frequency of this fluctuation can be as high as 70 Hz. Continuous
measurement of wheel load using conventional methods is not possible due to this high frequency phenomenon. We have developed
a new method for continuous measurement of these forces and the derailment coefficient using two pairs of strain gauge bridges
with output phases shifted by 90°, and summing their outputs with a weighting function. This method works for measuring the
forces between wheel and rail at high frequencies. 相似文献
16.
17.
基于伪随机序列调制的荧光测量系统 总被引:1,自引:0,他引:1
荧光分析法和伪随机序列技术均在多个领域有广泛应用。荧光测量过程中常伴随着复杂的背景噪声和干扰,为测量精度的提高带来了困难。利用伪随机序列的相关特性和频谱扩展效应,提出了一种适用于荧光测量系统的,基于伪随机序列的激发光调制方法。通过建立数学模型,从信号和噪声的频谱角度定量分析了伪随机序列调制系统对噪声和干扰的抑制能力,给出了序列参数与测量系统信噪比之间的关系。最后将该调制方法应用于一个典型的荧光测量系统(荧光型叶绿素仪)中。理论和实验结果都表明,使用伪随机序列调制方式能显著提高荧光检测信噪比,叶绿素仪的线性响应相关系数R2在0.999以上,达到国外同类型高端仪器水平。 相似文献
18.
Saha SK Hui AK Chowdhury S Raychaudhuri S Banik D 《The Review of scientific instruments》2010,81(12):123506
A diagnostic has been developed for the measurement and characterization of the magnetic turbulence occurring in the core region of a tokamak. A specially shielded detector looking in the tangential direction has been employed to measure the thin target bremsstrahlung from the core plasma. The thick target bremsstrahlung from the limiter is also recorded at the same time. Auto- and cross-correlation analyses have been shown to yield, respectively, the stochasticity of the magnetic fluctuations in the core region and the consequent diffusion coefficient of the nonthermal electrons. The measured stochasticity bears a relationship with the diffusion coefficient. Data obtained from internal magnetic probes corroborate the above trend but the hard x-ray measurement data are shown to be more reliable than those obtained from magnetic probes. 相似文献
19.
High-throughput measurement of rice tillers using a conveyor equipped with x-ray computed tomography 总被引:2,自引:0,他引:2
Yang W Xu X Duan L Luo Q Chen S Zeng S Liu Q 《The Review of scientific instruments》2011,82(2):025102
Tillering is one of the most important agronomic traits because the number of shoots per plant determines panicle number, a key component of grain yield. The conventional method of counting tillers is still manual. Under the condition of mass measurement, the accuracy and efficiency could be gradually degraded along with fatigue of experienced staff. Thus, manual measurement, including counting and recording, is not only time consuming but also lack objectivity. To automate this process, we developed a high-throughput facility, dubbed high-throughput system for measuring automatically rice tillers (H-SMART), for measuring rice tillers based on a conventional x-ray computed tomography (CT) system and industrial conveyor. Each pot-grown rice plant was delivered into the CT system for scanning via the conveyor equipment. A filtered back-projection algorithm was used to reconstruct the transverse section image of the rice culms. The number of tillers was then automatically extracted by image segmentation. To evaluate the accuracy of this system, three batches of rice at different growth stages (tillering, heading, or filling) were tested, yielding absolute mean absolute errors of 0.22, 0.36, and 0.36, respectively. Subsequently, the complete machine was used under industry conditions to estimate its efficiency, which was 4320 pots per continuous 24 h workday. Thus, the H-SMART could determine the number of tillers of pot-grown rice plants, providing three advantages over the manual tillering method: absence of human disturbance, automation, and high throughput. This facility expands the application of agricultural photonics in plant phenomics. 相似文献
20.
介绍了一种已获取发明专利的相序测定计数方法,以Atmel89S52单片机为基础,通过编码器的输出脉冲A和其反向脉冲A-产生中断,在中断服务程序中读取脉冲A、A-及与A脉冲相位差为90°的脉冲B的电平并与已在E2PROM中储存的状态字进行比较,由此来确定旋转方向并对脉冲进行加减计数。同时,该文也介绍了相应的硬件电路和软件程序。该方法在实际应用中的测试表明,当编码器频繁改变旋转方向时仍具有很高的测量准确度并能有效地抑制脉冲干扰信号。 相似文献