Improving the accuracy of single radioactive particle technique for flow velocity measurements

An original method of flow velocity estimation for a radioactive particle technique is presented. It is based on exchanging measured pulses into cumulative signals, and determination of time delay as time difference of occurrences of inflection points of cumulative curves. To determine the inflection points, a suitable algorithm is proposed. The preliminary results show that the proposed method is especially more precise than the classical cross-correlation approach. The preliminary results show that this method can be successfully applied in a laminar flow with any type of fluid, and can without limitation be applied for different types of radioactive detectors.     

Comparison of the radial profiles of particles velocity between invasive and non-invasive measurement techniques

In this work, the radial profiles of the particles velocity in gas-solid fluidized beds were measured using two techniques: (1) an advanced optical fiber probe, an invasive technique, and (2) radioactive particle tracking (RPT), a noninvasive technique. Two gas-solid fluidized bed columns of 0.14 and 0.44 m inside diameters were used to estimate the radial profile of the particles velocity. The particle velocity was measured at different operating conditions and axial heights. It was found that the implementation of the noninvasive radioisotope particle tracking (RPT) technique was able to successfully guide the measurement of the radial profile of the particle velocity using the optical fiber probe technique. The average inversion point of the radial particle velocity, from positive to negative, was identified from the measurements using both techniques for different operating conditions and axial heights.     

Numerical simulation of concrete pumping process and investigation of wear mechanism of the piping wall

A numerical simulation has been conducted to study the solid-fluid multi-phase flow problem in concrete pumping process. The kinematics and trajectory of the discrete particles as well as the particle-particle interaction were predicted by DEM while the motion of the continuous fluid phase was evaluated by a Navier-Stokes solver, and a pressure gradient force model was adopted to calculate the solid-fluid interaction force. A case of pneumatic conveying was utilized to demonstrate the capability of the coupling model. The concrete pumping process was then simulated, where several flow features were observed such as roping, particle segregation and particle concentration. The frequency of the particles impacting on the bended pipe was monitored, a new time average collision intensity model based on impact force has been proposed to investigate the wear mechanism of the elbow. The location of maximum erosive wear damage in the elbow was predicted. Statistical results were in good agreement with that observed in actual pumping process. It is found that the present multi-phase coupling model can predict the wear behavior of the bended pipe accurately, and consequently provide an effective guidance for the design of concrete pumping pipe.     

Investigating the characteristics of scintillation detectors for the NEVOD-EAS experiment

A cluster type NEVOD-EAS setup is being constructed by the National Research Nuclear University MEPhI on the basis of the Unique Scientific Facility “Experimental Complex NEVOD”. The NEVODEAS setup is intended for the detection of extensive air showers (EASs) with energies in the region of the knee in the energy spectrum of primary cosmic rays (10¹⁵–10¹⁷ eV). The key elements of the setup are 192 particle detectors for EAS electron–photon and muon components. These detectors are composed of NE102A organic scintillators and Philips XP3462 photomultiplier tubes enclosed in pyramidal steel cases. The techniques used to investigate the characteristics of scintillator plates, photomultiplier tubes, and NEVOD-EAS detectors, as well as the results of this investigation, are discussed. All measurements have been taken using special testing facilities and the precision URAGAN muon hodoscope, with which it is possible to comprehensively investigate the nonuniformity of light collection in the detector (the dependence of the detector response on the location of the passage of a charged particle through its operating volume).     

Intelligent recognition of gas-oil-water three-phase flow regime and determination of volume fraction using radial basis function

The problem of how to accurately measure the flow rate of oil–gas–water mixtures in a pipeline remains one of the key challenges in the petroleum industry. This paper proposes a new methodology for identifying flow regimes and predicting volume fractions in gas-oil-water multiphase systems using dual energy fan-beam gamma-ray attenuation technique and artificial neural networks. The novelty of this study in comparison with previous works, is using just 4 extracted features (photo peaks of ²⁴¹Am and ¹³⁷Cs in 2 detectors) from the gamma ray spectrums instead of using the whole gamma ray spectrum, which reduces the undesired noises and also improves the speed of recognition in real situations. Radial basis function was used for developing the neural network model in MATLAB software in order to classify the flow patterns (annular, stratified and homogenous) and predict the value of volume fractions. The ideal and static theoretical models for flow regimes have been developed using MCNP-X code. The proposed networks could correctly recognize all the three different flow regimes and also determine volume fractions with mean absolute error of less than 5.68% according to the recognized regime.     

Heavy charged particle detectors based on high-resistivity epitaxial silicon layers

A technique for manufacturing heavy charged particle detectors based on high-resistance epitaxial silicon layers is described. The special feature of this technique is the design of a rectifying structure based on a Pd₂Si−Si heterojunction. The intrinsic resolution obtainedR _int=17 keV for α-particles of²³⁸Pu (E _α=5.49 MeV) demonstrates that it is possible to design heavy charged particle detectors based on epitaxial silicon layers with good spectrometric characteristics.     

Active collimators in experiments with exotic nuclear beams

The active collimator method for experiments with exotic nuclear beams at energies near the Coulomb barrier of nuclear reactions is described. The technique is based on the use of detectors composed of microchannel plates (MCPs) and thin strips of metal foils (Au, Ag, Al) with a thickness of 200–300 μg/cm² or less, which are oriented along axes X and Y (axis Z is collinear to the beam axis). Exotic nuclei passing through the foils are detected by the MCPs by electron emission from these foils, which provides a means for obtaining spatial information on the particle trajectory and the time mark of an event. The proposed setup is characterized by the smallest (of the available techniques) material budget on the particle path (≤8.0 × 10¹⁷ atoms/cm²) in the zone of detected particles, the high efficiency (ɛ ∼ 90% for every MCP), and the time resolution sufficient for performing additional identification of radioactive nuclei using the time-of-flight method.     

基于维诺图匹配的粒子跟踪测速法

针对密集颗粒流速度场分布的测量问题,提出了基于维诺图匹配的粒子跟踪测速法。首先,通过对图像粒子进行维诺图构建,给出面积相似度筛选匹配粒子的条件;其次,引入Delaunay三角网搜索结构,通过计算维诺多边形的形状相似度来匹配粒子;再次,研究了去除错误匹配粒子矢量的方法和匹配算法中的关键参数;最后,通过模拟二维旋转流场运动以及二维转盘中的颗粒流实验对算法进行了测试。结果表明:维诺图匹配的匹配准确率高于DT-PTV并且在处理密集粒子匹配效果上更好;维诺图匹配算法适用于测量密集颗粒流速度场分布,颗粒匹配准确率高达99%,并由得到的颗粒流速度场分布验证了算法的有效性。     

Three-phase flow meters based on X-rays and artificial neural network to measure the flow compositions

The methodology presented in this study is based on a 149.5 keV X-ray beam and two planar germanium detectors for X-ray transmission and scattering measurements for prediction of volume fractions in a three-phase system. Fluid volume fractions have been modeled using the MCNP6 code for an annular flow regime. A mathematical algorithm based on an artificial neural network was used to correlate the energy spectra from both detectors with the fluids volume fractions. The pulse height distributions obtained by the detectors are used as input data of the network that outputs the volume fractions of gas and water. The mean relative error, using the procedure presented here, for all data, was below 2.5% for both phases investigated. These results show that the methodology based on an X-ray beam has the potential to be used with flow meters.     

Phase discrimination and a high accuracy algorithm for PIV image processing of particle–fluid two-phase flow inside high-speed rotating centrifugal slurry pump

PIV technology is an efficient and powerful measurement method to investigate the characteristics of fluid flow field. But for PIV particle image post-processing, some problems still exit in two-phase particles discrimination and velocity field algorithm, especially for high-speed rotating centrifugal slurry pump. In this study, through summarization and comparison of the various phase discrimination methods, we proposed a two-phase identification method based on statistics of gray-scale level and particle size. The assessment of performance through experimental PIV images shows that a satisfying effect for particle identification. For high speed rotation of the impeller, a combination of adaptive cross-correlation window deformation algorithm and multistage grid subdivision is presented. The algorithm is applied to experimental PIV images of solid–liquid two-phase flow in a centrifugal slurry pump, the results show that the algorithm in the present study has less pseudo vector number and more matching particle pairs than those of fixed window and window translation methods, having the ability to remove pseudo vector efficiently. It confirmed that the algorithm proposed in the present study has good performance and reliability for PIV image processing of particle–fluid two-phase flow inside high-speed rotating centrifugal slurry pump.     

DEVELOPMENT OF AN X-RAY FLUORESCENCE SPECTROMETER FOR ENVIRONMENTAL SCIENCE APPLICATIONS

The performance of a new X-ray spectrometer is presented. The device was designed originally to be employed in environmental sciences, and allows the use of different types of primary radiation sources, such as a radioactive source (²⁴¹Am) or tubes with anodes of different metals (Rh or W). Among the advantages of this spectrometer are the possibility of exchanging detectors to improve efficiency at different X-ray energy ranges [such as Si (Li), Si-PIN, hyperpure Ge, or CdTe detectors], to attach it to a wavelength dispersive system, and its use in vacuum or atmospheric pressure. Furthermore, it is feasible to modify the geometry so a secondary target may be installed for using polarized X-rays as exciting radiation.     

Two-arm semiconductor spectrometer for charged particles for the investigation of absorption by nuclei of stopped negative pions

A two-arm semiconductor spectrometer for the detection of secondary charged particles, such as p, d, t, ³He, ⁴He and of their correlations in the process of stopped pion absorption by nuclei is described. The spectrometer consists of two telescopes of Si-detectors with a sensitive surface of 800 mm², two semiconductor detectors as monitors and the “live” target, a silicon surface barrier detector. The number of semiconductor detectors is 19.A technique for pion stop selection in thin targets is described.The problem of particle identification and of measurements of their energy with the help of a multicrystal semiconductor telescope is discussed. The technique provides an absolute normalization of spectra. The “alive” target helps to obtain more information on the process of pion absorption by Si-nuclei.     

基于无线传感器网络自校正定位算法

节点定位是无线传感器网络的重要应用之一,为了抑制实际应用中各种环境因素对无线传感器节点精度的影响,提出了一种基于误差校正的定位算法。通过基于粒子群优化算法的粒子群优化-接收信号强度指示算法(par-ticle swarm optimization-received signal strength indication,简称PSO-RSSI算法)将未知节点收到信标节点一定数量的存在偏差的链路质量指示值进行优化,实现对误差的补偿。将链路质量指示值转化为接收信号强度指示值,从而得到距离。实验结果表明,该算法可提高定位精度,具有普遍应用价值。     

Optimization the design of venturi gas mixer for syngas engine using three-dimensional CFD modeling

A venturi mixer prototype is developed for mixing air and synthesis gas or “syngas” as a fuel. Syngas is recognized as a viable energy source worldwide, particularly for stationary power generation. It has a very low energy density, so a mixer with λ (ratio of actual to stoichiometric air-fuel ratio) in the range of 1.1 to 1.7 is expected. In this study, three-dimensional computational fluid dynamics (CFD) modeling is used to investigate and analyze the influence of the throat diameter, gas chamber thickness and gas exits diameter on mixer characteristics and performance. Attention is focused on the effect of venturi mixer geometry on the air-fuel ratio, pressure loss and mixing quality. Based on the numerical results, an optimized design of venturi gas mixer is made. The optimized design has λ in the range of 1.2 to 1.3, and gives very good mixing quality and acceptable pressure loss. The CFD results are validated with experimental data. The CFD results show good agreement with experimental data.     

Effect of circular cylinder location on three-dimensional natural convection in a cubical enclosure

This paper presents the results of immersed boundary method-based three-dimension numerical simulations of natural convection in a cubical enclosure with an inner circular cylinder at a Prandtl number of 0.7. This simulation spans three decades of Rayleigh number, Ra, from 10³ to 10⁶. The location of the inner circular cylinder is changed vertically along the centerline of the cubical enclosure. This study primarily focuses on the effects of both buoyancy-induced convection and the location of the inner circular cylinder on heat transfer and fluid flow in the cubical enclosure. In the range of Rayleigh numbers considered in this study, the thermal and flow fields eventually reach steady state, regardless of the location of the inner cylinder. When Ra is 10³, the end wall of the cubical enclosure has a negligible effect on the thermal and flow fields in the enclosure. However, in the range of 10⁴ ≤ Ra ≤ 10⁶, the effect of the end wall on heat transfer and fluid flow in the enclosure depends on both the location of the inner cylinder and the Rayleigh number. Detailed analysis results for the distribution of streamlines, isotherms, and Nusselt numbers are presented in this paper.     

Reentrant two-stage multiprocessor flow shop scheduling with due windows

Reentrant flow shop scheduling allows a job to revisit a particular machine several times. The topic has received considerable interest in recent years; with related studies demonstrating that particle swarm algorithm (PSO) is an effective and efficient means of solving scheduling problems. By selecting a wafer testing process with the due window problem as a case study, this study develops a farness particle swarm optimization algorithm (FPSO) to solve reentrant two-stage multiprocessor flow shop scheduling problems in order to minimize earliness and tardiness. Computational results indicate that either small- or large-scale problems are involved in which FPSO outperforms PSO and ant colony optimization with respect to effectiveness and robustness. Importantly, this study demonstrates that FPSO can solve such a complex scheduling problem efficiently.     

Choosing the basic system in the application of the thin layer activation technique to cutting tools

Cemented carbide tools made radioactive by irradiating them with ³He²⁺ ions were used to measure tool wear. The detector used to monitor the radioactivity incorporated a sodium iodide scintillation counter. The use of ³He²⁺ ions for irradiation is preferable to that of protons. Consideration of the characteristics of commercially available radiation detectors showed that the use of a scintillation counter was most appropriate for this application.     

A Radiochemical Installation for Handling Small Amounts of High-Purity Gases

A radiochemical installation capable of performing precision operations involving small amounts of gases, including high-purity radioactive gases, is described. The installation is used to produce, purify, and proportion the gaseous components of working mixtures for proportional counters. The basic parameters of the installation, as a whole, and of its systems are given. The potentialities of the installation are illustrated through a technique for the extraction and purification of ³⁷Ar. This radioisotope is intended for use as a neutrino source for calibrating neutrino detectors.     

混合体锥度对油气混合器性能的影响

根据一种新的油气混合原理,在混合腔体中加入一个锥形体,设计了一种新型油气混合器,并利用FLUENT对三种不同混合体锥度的油气混合器内流场进行了仿真分析。仿真实验结果显示：锥体锥度对油气两相环状流的形成和周向分布均匀性有一定影响;选择合理的锥度有利于提高混合器性能。