A digital method for pulse-shape discrimination between neutrons and γ rays at a high counting rate and a low energy of detected radiation

A digital method for pulse-shape discrimination between neutrons and γ rays was used in measurements at counting rates of up to ～10⁶ counts/s in the energy range of ～2–800 keV. Pulses produced by neutrons and γ rays in a stilbene-based scintillation detector were digitized by a digital oscilloscope and transmitted to a computer for carrying out particle identification. Identification was performed for radiation of radionuclide sources and a pulsed neutron generator operating in a repeated triggering mode. Amplitude spectra of pulses identified as neutrons and γ rays of radiation from the generator were measured. At a detector counting rate of ～8.5 × 10⁵ counts/s, ～90% of all recorded pulses were recognized as neutrons. In the energy range of ～30–800 keV, the γ-ray suppression factor was ～10⁴–10³ at counting rates of ～1.5×10⁵–5 × 10⁵ counts/s, while the efficiency of identifying neutrons was >0.9. The suppression factor for γ rays with an energy of ～10 keV was ～300, and the neutron identification efficiency was ～0.75.     

Improved (10)B-loaded liquid scintillator with pulse-shape discrimination

An improved (10)B-loaded liquid scintillator solution has been developed containing trimethylborate, 1-methylnaphthalene, and 9,10-diphenylanthracene. Cells up to 5 cm in diameter by 15.2 cm long have been prepared and tested with (10)B-loadings up to 7.2% by weight (80% trimethylborate). The solution has excellent light output and pulse-shape discrimination properties and is stable at temperatures as low as -17 degrees C. Neutron efficiency calculations are also presented.     

A method for nondestructive assay of nuclear materials in facilities with a pulse neutron generator and a digital technology for discrimination between neutrons and photons

A method for determining the ²³⁵U concentration in fuel assemblies of a high-power channel-type PBMK reactor is described. The measure of ²³⁵U content of an analyzed sample is the number of neutrons from thermal-neutron fission of ²³⁵U, normalized to the number of γ quanta produced in thermal neutron capture by hydrogen nuclei in the scintillator or by ¹⁰B in the glass of a photomultiplier tube. A pulse neutron generator based on DT reaction is the neutron source, and an organic scintillator with the pulse shape discrimination between neutrons and γ rays with the aid of the digital technology is a detector. The scintillator is also used as a neutron moderator. Simulation of the method shows that the ²³⁵U content of the analyzed sample can be determined for 1 min with an accuracy of 1% or better. The efficiency of the method has been confirmed by experimental investigations on a model of the setup.     

A simple and efficient method for objective discrimination between pseudostratified,metaplastic and dysplastic nasal epithelium

Morphologic features may sometimes be interpreted differently by different pathologists. By introducing objective methods in the histological evaluation the subjectivity of the judgement is reduced and a higher degree of consistency achieved. In the present study three linear parameters of nasal epithelial basal cells: the largest transversal nuclear diameter, the sum of the longitudinal and transversal nucleolar axes and the basal cell width, i.e. the width of the attachment face to the basement membrane, were classified by means of three-class rulers. From this classification weighted indices were made which were then given equal weight and transformed, so that when added up their sum, the joint index (Q) to the largest possible extent was consistent with pseudostratified/stratified cuboidal, stratified squamous and dysplastic epithelium when Q ≤ 1, 1 < Q ≤ 2 and Q > 2 respectively. Tested prospectively we found 91% agreement between the morphometric and histological classification. The method presented is extremely simple and rapid to perform, and appears to have diagnostic potential in distinguishing various types of epithelial alterations of the nasal mucosa. The method may also be useful in approaching similar problems in other epithelia.     

A novel method for digital ultrasonic time-of-flight measurement

Most ultrasonic ranging measurements are based on the determination of the ultrasonic time-of-flight (TOF). This paper develops a novel method for the TOF measurement which combines both the improved self-interference driving technique and the optional optimization signal processing algorithms. By stimulating the transmitter with the amplitude modulation and the phase modulation envelope square waveforms (APESWs), the proposed system can effectively reduce the errors caused by inertia delay and amplitude attenuation. In addition, based on different signal-to-noise ratio test conditions, the resultant received zero-crossing samples, which are deteriorated by noise, can be precisely inspected and calculated with two optimized algorithms named zero-crossing tracking (ZCT) and time-shifted superposition (TSS) method. The architecture of the designed system is divided into two parts. The novel APESW driving module, the received envelope zero-crossings phase detection module, and the ZCT method processing module are designed in a complex programmable logic device. The TSS signal processing module and the optimization algorithm discrimination program module are integrated in a digital signal processor. The TOF measurements calibrated in ultrasonic ranging experiments indicate that the relative errors of the method are limited in ±0.8%. Therefore, a feasible method is provided with the advantages of high noise immunity, accuracy, low cost, and ease of implementation.     

A generating method for digital gear tooth surfaces

Based on the theories of digital conjugate surface and gear meshing, a generating method for digital gear tooth surfaces (DGTS) is demonstrated in this paper. The research focuses on the conjugate motion between the DGTS, represented by discrete points, and the cutter figuration determined by analytic function in the manufacture process. Conjugate points in the cutter section corresponding to the discrete points on the digital surface and conjugate movements are solved. Automated sequence arrangements of the generating movement parameters have been performed and the discrete generating movements are interpolated in a continuous conjugate motion along the order. Strategies of error analysis and error compensation are also discussed in this paper. Computer-simulated examples of the generating machining of involute DGTS and non-standard shaped DGTS, the parameters of machining motions and real tooth surfaces verify the developed method. The research develops a new idea for the machining of DGTS, which breaks the limitations of conventional approaches based on analytic surfaces. It is of important theoretical and practical value to manufacture digital surfaces. Our method is not only be applicable in generating machining of discrete DGTS and analytic gear tooth surfaces with complex geometric design, but also in contributing to the processing of discrete digital cam and other 3-D digital surfaces .     

A new digital measurement method for accurate curve grinding process

In this paper, an online measurement and error compensation system for curve grinding based on pattern recognition was presented and verified by experiments. The measurement system organization and its principle of operation were introduced in detail. The work piece and grinding wheel image were sampled at certain positions to avoid spark influence. In order to increase system resolution, images were sampled only at local areas of the work piece and grinding wheel. A discrimination technology based on a circular tolerance zone was proposed which can solve the problem of local image edge comparison. For image de-noising, a local threshold algorithm was applied to determine new wavelet coefficients. Furthermore, a two-step edge detection method was used to realize sub-pixel precision. Finally, a series of experiments were carried out to examine the detection precision of the image measurement system and its influencing factors. From experiments, it can be said that the proposed method in this paper is effective, and its detection precision is much better than traditional methods.     

一种数码相机几何畸变的检测方法

针对数码相机普遍存在的几何畸变现象,提出了一种基于数字图像处理的畸变检测方法.在阐述数码相机畸变产生原因和检测原理的基础上,将待测数码相机拍摄目标靶板后的图片输入计算机,利用MatLab工具对图片进行数字图像处理,由像素间距获取实际像大小,由几何光学演算获得理想像大小,从而计算出相对畸变量.实验表明,该方法过程简单,易...     

动态公路车辆自动衡器检定中动态鉴别力的研究

本文通过对JJG 907-2006《动态公路车辆自动衡器计量检定规程》中关于衡器的车辆动态测试项目与静态测试项目进行对比,提出车辆动态测试中应当增加动态鉴别力测试,并挖掘了动态鉴别力的定义以及测试的方法。在进一步完善动态公路车辆自动衡器的动态测试上具有一定的现实意义。     

A method for material decomposition in dual-energy contrast enhancement digital mammography

Background and purpose: Dual-energy mammography is a technique which is being used for accuracy enhancement of the breast cancer diagnosis especially in dense breasts. It is also a valuable and practical way for obtaining detailed information about tumor’s size, disease progression and micro-calcification detection which is the earlier sign of breast cancer. The aim of this study was to investigate the possibility of separating different thicknesses of micro-calcifications, Iodine, and Bismuth contrast agents, simultaneously.Material and methods: A breast phantom was made from acrylic and olive oil containing various density thicknesses of Iodine and Bismuth contrast agents. To simulate micro-calcifications, different thicknesses of the Aluminum sheets were used and placed in the phantom as well. In this work, an X-ray tube with Tungsten anode and a flat panel semiconductor detector were used for imaging processes. To customize the X-ray spectrum, a combination of copper and aluminum were used as filters to optimize the X-ray high energy spectrum in dual energy imaging.Results: According to the results, separating of Iodine images was prepared by using of Iodine’s k-edge property for thicknesses greater than 0.5 mg/cm². Also, Bismuth and Aluminum images with thicknesses greater than 0.53 mg/cm² and 200 μm, respectively, were isolated automatically by material thicknesses estimation method in dual-energy imaging technique.Conclusion: The results demonstrated that Iodine and Bismuth contrast agents together with micro-calcifications can be separated from breast tissue with good accuracy by using proposed dual-energy contrast enhanced mammography technique.     

A method for providing comparative counts of small particles in electron microscopy

A method for estimating the relative concentrations of particles by electron microscopy is described. The method involves the determination of the area of the field of view in the microscope binoculars, relative to a standard area, and is independent of grid type, magnification, operator or microscope. Particle counts using this method are in close agreement with counts made from electron micrographs. The method is simple, rapid and reproducible, and, for low numbers of particles, more accurate than conventional methods.     

Coherent fluctuation nephelometry: A high-sensitivity method for detecting particles in liquids

A new method for detecting micron and submicron particles in liquids by measuring the intensity fluctuations of coherent radiation scattered from these particles is described and compared to available techniques. It is shown that this method allows the record-breaking detection sensitivities of 10³–10⁴ particles/ml to be attained at a simple design of the analyzer.     

A digital method for separation and reconstruction of pile-up events in germanium detectors

The problem of pulse pile-up is very often encountered in precise measurements of γ-rays using germanium detectors. The standard method of treating the pile-up events is to identify and reject them using an appropriate electronic system. Digital acquisition techniques now allow the recording of waveforms of pile-up events that can be analyzed and the contributing single pulses recovered, rather than simply tolerating the losses associated with pile-up. In this paper, a method for the off-line digital processing of pile-up events from germanium detectors is demonstrated. The method is based on an appropriate fitting of the detector signals, shaped with a suitable digital pulse shaper. It is shown that the method is able to recover the pile-up events with good accuracy even when the constituent signals are in close proximity. The method is very useful for γ-ray spectroscopy in nuclear physics experiments, where the low intensity signals can be lost due to the pile-up in a high-rate environment.     

A new method for integrating analog to digital conversion based on error reduction

This paper presents a method for eliminating errors of electronic components in integrating analog to digital converters. Offset error in integrator, comparator and amplifiers of dual-slope converter is a great limitation for increasing the resolution of this type of analog to digital converter. The paper proposes an idea that effectively eliminates offset error of integrator and reduces errors of other components. To validate the efficiency of the proposed method, simulation and experimental results are represented in this paper. As a result, this method can potentially allow a cost-effective design of high-resolution ADCs with low performance Op-Amps.     

一种数字显微图像白平衡方法

为了补偿各种不同光源对光学显微镜造成的色差,提出了一种基于光学显微镜的数字图像白平衡方法,该方法根据光学显微数字图像系统光照不均匀的特点,将全局校正与逐点补色相结合。对不符合全局校正的像素点按该点实际曝光值进行调整,先由光源感光情况确定各点的校正系数,再对相同条件的数字图像进行逐点校正。实验表明该方法能够精确地实现显微数字图像的白平衡调整。     

数字温度传感器自适应动态补偿方法

针对数字温度传感器具有较大温度滞后性的缺点,将自适应决策与基于数字滤波方法的动态补偿有机结合,提出了一种数字温度传感器自适应动态补偿方法:利用后向差分法设计的数字滤波器,实现了数字温度传感器工作频带扩展,完成了其动态补偿,并在动态补偿后面串联一个数字低通滤波器,以防高频噪声干扰;根据数字温度传感器的输出量、数字低通滤波的输出结果以及决策阈值,自适应地选择是否需要动态补偿,避免了补偿过度.以高精度数字温度传感器DS1624为补偿对象的实验表明,这种白适应动态补偿方法大大改善了数字温度传感器的动态性能,响应时间缩短至补偿前的30%～40%.     

A spectrometric method for determining α emitters based on acid extraction of fuel particles

A method for determining the ²³⁸U, ²³⁴U, ²⁴²Pu, ²⁴¹Pu, ²⁴⁰Pu + ²³⁹Pu, ²³⁸Pu, ²⁴³Am, ²⁴¹Am, ²⁴⁴Cm, and ²⁴²Cm contents of fuel particles is proposed. The lower detection limit for these radionuclides is 0.001 Bq per particle.     

A new method for charged particles identification with a CsI(Tl) crystal

A spectrometer for detecting and identifying light charged particles with low energies (>∼1 MeV) is described. The spectrometer consists of a thin CsI(Tl) crystal, an ФЭУ-176 photomultiplier, and a waveform digitizer. Digital oscillograms of anode pulses are stored and analyzed in off-line processing. In order to reconstruct the energy and specific energy losses, the two-component character of the scintillation fluorescence decay in a CsI(Tl) crystal and the dependence of the fast component on the specific loss value are used. A digital particle identification method is proposed. The results of experimental studies of the CsI(Tl) crystal scintillation properties and efficiency in identifying electrons, protons, and α-particles in an energy range of ∼1–10 MeV are presented. It is shown that the efficiency of the digital method for proton and α-particle identification is 1.5–2 times higher than that of the known analog methods.     

A method for measuring the size distribution of latex particles by scanning force microscopy

A methodology has been developed to accurately determine the size distribution of latex particles using the scanning force microscope (SFM). Unlike other workers, who have generally measured the lateral dimensions of monolayers of latex particles using a global quantification method, we have measured the heights of individual latex particles located at the edges of latex monolayers that were immobilised onto mica substrates. In agreement with other work, we noted that the edges of monolayers of latex particles provided stable and reproducible scanning force imaging.

Whilst SFM imaging noise, image processing artifacts, tip/sample forces and variations in the mica substrate are sources of measurement error that should not be overlooked, our experience has been that the variation over time of the sensitivity of the Z actuator is the greatest potential uncertainty in determining the heights of latex particles. The methodology that we used requires frequent calibration of the Z actuator of the SFM, typically before and after two or three images, in order to ensure that the uncertainties in the Z sensitivity are known and minimised. This methodology was developed for an SFM instrument that was equipped with open loop piezoelectric actuators following a careful study of the behaviour of those actuators.

Using this methodology, we have measured the size distributions of populations of 300–400 latex particles from each of several different latex samples, with the maximum variation in the Z-actuator calibration experienced during the measurement of a sample being less than 2%, often about 1% and occasionally better still. In so doing, we have demonstrated that SFMs equipped with open loop actuators can be used for high confidence quantitative measurements of step heights.