Large area position-sensitive channel-plate detector system and ΔE-E ionization chamber for a time-of-flight spectrometer

For the magnetically focussed time-of-flight spectrometer installed at GSI, Darmstadt, a detector system consisting of two channel-plate time-pick up units and an ionization chamber for ΔE-E measurement has been developed.The design of the time-pick up system utilizes secondary electrons, which are produced by heavy ions passing through a thin carbon foil, and are deflected magnetically by 180° onto a channel-plate with position readout, providing a position resolution of 0.6 and 0.4 mm fwhm for the start and stop detector respectively. The intrinsic angular resolution of the spectrometer, determined by the positions at the two detectors, is Δθ < 0.02°. Due to target effects and beam conditions this deteriorates to typically 0.1°. The overall time-resolution is 200 ps fwhm at an efficiency of 95%. The energy- and Z-resolution of the ionization chamber for ⁶⁴Ni-ions of 5–7.9 MeV/amu are ΔE/E = 0.5% and ΔZ/Z = 1.3%, respectively.The general properties, the construction and the time- and position-resolutions achieved in a recent experiment are described.     

Hand–eye calibration and positioning for a robot drilling system

In the aircraft manufacturing, drilling large amount of assembly holes in aircraft board is one of the key bottlenecks of production efficiency. To enhance the efficiency and quality of assembly holes' manufacturing, robot drilling system replacing manual operation becomes more and more urgent. Normally, a robot system needs accurate mathematical models of the manufactured object and the environment when it's working; as a matter of fact, because of the manufacturing error, the homogeneity between aircraft board and its mathematical model is dissatisfied. So a hand–eye vision system is introduced to realize the positioning of the end effector in order to improve the flexibility and robustness of a robot drilling system. The paper discusses the calibration and positioning of a hand–eye vision system for a robotic aircraft board drilling system. Because the drill must be vertical and keep a fixed distance to the aircraft board surface before drilling, the depth information of hand–eye relationship is neglected and by defining an intermediate scene coordinate system the hand–eye relationship between the robot coordinate system and the vision coordinate system is established. Then the position of target point can be described in the robot coordinate system by using the calibrated hand–eye relationship, and thus the navigation information for the robot drilling system can be provided. Experimental results of the calibration and positioning of the hand–eye vision of a robot drilling system is provided, and the main factors that affect the positioning error are analyzed.     

Development of a compact and long range XYθ(z) nano-positioning stage

In this study, we describe the development of a novel, compact, and long range in-plane XYθ(z) nano-positioning stage with piezoelectric actuator and flexure mechanism. The stage is composed of an X-directional motion part and a Y, θ(z)-directional motion part, which are linked serially. The stage consists of a bridge-type amplifying mechanism for the amplification of deformation of the piezoelectric actuator, a double compound guide mechanism for performing only desired motion, and a circular hinge mechanism that permits rotational motion in the Y and θ(z)-stages. To set the design variables of the stage, optimal design is carried out. To verify the results of the optimal design process and the performance of the stage, the FEM simulation and experiment are carried out. The proposed XYθ(z) nano-positioning stage has a translational motion range of 700 μm and a rotational motion range of 0.3°; it has a closed-loop resolution of 5 nm, 5 nm, and 0.025 arcsec in the X-, Y-, and θ(z)-directional motions, respectively. The proposed stage is a novelty in that it has a compact size of 200 × 200 × 30 mm(3), and decoupled kinematic design.     

Multi-variable measurements and optimization of GMAW parameters for API-X42 steel alloy using a hybrid BPNN–PSO approach

This research addresses multi criteria modeling and optimization procedure for Gas Metal Arc Welding (GMAW) process of API-X42 alloy. Experimental data needed for modeling are gathered as per L₃₆ Taguchi matrix. Model inputs include work piece groove angle as well as the five main GMAW process parameters. The proposed back propagation neural network (BPNN) simultaneously predicts weld bead geometry (WBG) and heat affected zone (HAZ). Image processing technique along with Bridge Cam and AWS gauges are used to take accurate measurements of WBGs and HAZs. The adequacy of the developed BPNN is established through comparisons against measured process outputs. Measurements indicate that the BPNN model simulates GMAW process with average errors of 0.33 to 0.82%. Next, the BPNN model is implanted into a particle swarm optimization (PSO) algorithm to simultaneously optimize HAZ and WBG characteristics. The hybrid BPNN–PSO determines process parameters values and groove angle so as a desired WBG is achieved while HAZ is minimized. Verification tests demonstrate that the proposed BPNN–PSO is quite efficient for in multi-criteria modeling and optimization of GMAW.     

Design and application of a borehole–surface microseismic monitoring system

Borehole–surface microseismic monitoring is a new approach for monitoring artificially induced hydraulic fracturing in an oil or gas field. However, ineffective communication links and incompatible data formats between current borehole- and surface-based monitoring systems mean that borehole–surface monitoring cannot be reported in real time. To solve this problem, the borehole–surface microseismic monitoring system reported here allows fracturing points through inversion and the development of fractures to be viewed in real time. Private cloud technology is used to control the instruments, manage the borehole and the surface database, and process the data. This system ensures high performance and availability of the system. The data acquisition modules and the geophones used in the borehole and surface instruments were calibrated in the laboratory to ensure the consistency of the acquired microseismic signals. The monitoring system located 82 microseismic events with a fracture azimuth of N84°E during fracture production in the Daqing Oilfield. Subsequent analysis showed that the locations of the fractures and their strike directions were consistent with the theory of hydraulic fracture propagation and the local crustal stress field. The results demonstrate that the monitoring system effectively and promptly processed data, thus enabling real-time borehole–surface microseismic monitoring.     

Application of a Bonner sphere spectrometer for determination of the energy spectra of neutrons generated by ≈1 MJ plasma focus

The spectra of neutrons outside the plasma focus device PF-1000 with an upper energy limit of ≈1 MJ was measured using a Bonner spheres spectrometer in which the active detector of thermal neutrons was replaced by nine thermoluminescent chips. As an a priori spectrum for the unfolding procedure, the spectrum calculated by means of the Monte Carlo method with a simplified model of the discharge chamber was selected. Differences between unfolded and calculated spectra are discussed with respect to properties of the discharge vessel and the laboratory layout.     

Multi-objective optimization design of a fixture layout considering locator displacement and force–deformation

The fixture determines the workpiece position in a machining process; therefore, an increasing amount of attention has been given to fixture layout design. While machining, the workpiece position is affected by two major sources: (a) the locator displacement and (b) the force–deformation of the workpiece–fixture system. In the beginning of this paper, a geometric model considering the shape of a locator is developed to analyze the location performance, followed by the presentation of a simplified solving method and a location layout performance index. Second, to complete the force–deformation analysis, a finite element method-based force–deformation model is built and accelerated by a new method with a lower computer memory cost. Based on these two models, multiple objects of fixture layout optimization problems are proposed, and a multi-objective genetic algorithm-based optimization method is constructed. Finally, testing examples are approved to examine the validity of the method represented in this paper. These methods can provide a more accurate prediction of the locating performance in more widely used cases, and they have faster calculating speeds with lower computer memory costs.     

Tool fabrication system for micro/nano milling—function analysis and design of a six-axis Wire EDM machine

The dies or molds used for the fabrication of micro products usually are made of ultra-hard materials such as tungsten carbide or silicon carbide and have sophisticated three-dimensional geometries. Such kind of dies or molds can only be fabricated by milling operations instead of grinding processes with ultra-hard milling tools made of PCD or CBN. Electrical discharge machining (EDM) is a good choice for the fabrication of such ultra-hard tools. In this paper, a function analysis and design of a six-axis Wire EDM (WEDM) machine is introduced. Based on the typical micro/nano cutting tool geometry features, a mathematical model between the cutting tool and the electrode wire is built. Then, the mathematical model is analyzed and it turns out that six axes are needed for cutting such complicated tool geometries. According to the WEDM features, first the axes are allocated to the workpiece side and the electrode wire side. The workpiece is assigned three linear motions and one rotary motion around its center line and the wire has two rotary motions. Second, the axis sequences are defined. At last, the best concept of the mechanical structure for the six-axis WEDM machine is selected.     

Industrial culture and its implication for a development concept for a “culture of manufacturing”

A great challenge for mankind is to shape the dynamic tension and relationship between the emergence of global structures and regional structures, to encourage productive cooperation. The science of cognitive anthropology provides an interdisciplinary approach to this problem by a combination of cognitive science, cultural anthropology, occupational science and engineering science.Industrialised countries usually have a tradition of handicraft production which forms a basis for the acquisition of the skills of technological development and transfer. Technological development can be considered as a cyclic process in which the diverging elements of the regional industrial culture, and the converging elements of the global industrial society are dynamically related. In the initial stages of design and development, cultural elements tend to dominate, in the later stages socio-industrial forces become more effective, transforming the initial divergent phase into a convergent one. The traditional approach to product development is considered and its deficiencies in relation to the development of complex organizational structures are outlined. The paper concludes that the concept of culture of manufacture can only be developed by an interdisciplinary approach and if academic knowledge and the specific abilities and approach of appliers and users are integrated into the technology shaping process.     

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.     

Active nonlinear partial-state feedback control of contacting force for a pantograph–catenary system

In this paper, a nonlinear partial-state feedback control is designed for a 3-DOF pantograph–catenary system by using backstepping approach, such that the contacting force of the closed-loop system is capable of tracking its reference profile. In the control design, the pantograph–catenary model is transformed into a triangular form, facilitating the utilization of backstepping. Derivatives of virtual controls in backstepping are calculated explicitly. A high-order differentiator is designed to estimate the unknown time derivatives of elasticity coefficient; and an observer is proposed to reconstruct the unmeasurable states. It can be proved theoretically that, with the proposed nonlinear partial-state feedback control, the tracking error of the contacting force is ultimately bounded with tunable ultimate bounds. Theoretical results are demonstrated by numerical simulations.     

M-LFM: a multi-level fusion modeling method for shape−performance integrated digital twin of complex structure

As a virtual representation of a specific physical asset, the digital twin has great potential for realizing the life cycle maintenance management of a dynamic system. Nevertheless, the dynamic stress concentration is generated since the state of the dynamic system changes over time. This generation of dynamic stress concentration has hindered the exploitation of the digital twin to reflect the dynamic behaviors of systems in practical engineering applications. In this context, this paper is interested in achieving real-time performance prediction of dynamic systems by developing a new digital twin framework that includes simulation data, measuring data, multi-level fusion modeling (M-LFM), visualization techniques, and fatigue analysis. To leverage its capacity, the M-LFM method combines the advantages of different surrogate models and integrates simulation and measured data, which can improve the prediction accuracy of dynamic stress concentration. A telescopic boom crane is used as an example to verify the proposed framework for stress prediction and fatigue analysis of the complex dynamic system. The results show that the M-LFM method has better performance in the computational efficiency and calculation accuracy of the stress prediction compared with the polynomial response surface method and the kriging method. In other words, the proposed framework can leverage the advantages of digital twins in a dynamic system: damage monitoring, safety assessment, and other aspects and then promote the development of digital twins in industrial fields.     

Design,development, and calibration of a force-moment measurement system for wheel–rail contact mechanics in roller rigs

A force measurement system, referred to as “dynamometer”, for accurately acquiring the contact forces and moment in a single-wheel roller rig using piezo-electric load cells is designed and developed. Accurate determination of the wheel–rail contact forces and moments is an essential requirement for studying the wheel–rail contact mechanics. The dynamometer is placed in the load-path between the wheel–rail interface and the ground, enabling it to measure the forces and moments at the interface. A series of tests are performed to determine the quasi-static and dynamic characteristics of the dynamometer. Additionally, finite element analysis and multi-body dynamic modeling are used to establish flexural modes and dynamic interface between the components. The simulation and test results indicate that the dynamometer is able to accurately and reliably measure the contact forces and moments at the wheel–rail interface.     

Development of a Setup for the Discrimination of β+ and γ Rays

Abstract

A β⁺–γ discrimination set‐up was developed and applied to the ²²Na radioisotope. The radioisotope emits positrons (β⁺) and these positrons create γ rays by annihilating with electrons. These annihilation γ rays were used here, and the discrimination between these positrons and γ rays was investigated by the coincidence measurement between time signals and the energy signals. The detection system presented here uses a 3 inch (diameter) by 3 inch (length) NaI(Tl) inorganic scintillation detector for γ detection and 3 inch (diameter) by 3 inch (length) plastic scintillation detector for β⁺ detection.     

Design and theoretical analysis of test system for propellants’gas pressure in warhead

针对子母弹中心爆管抛撒环境恶劣及传统测试系统安装布线困难等问题,提出了一种基于MSP430系列16位超低功耗单片机的利用内触发及断线上电方式的子母弹抛撒火药燃气压力存储测试系统。研究了系统低功耗设计中各模块数据采集过程中的工作状态,推导了圆柱状密实接触中心管爆炸开舱战斗部内部燃气压力变化过程的计算公式,进行了相应的实弹测试试验并取得了良好的试验结果。     

A feasibility study using simulation-based optimization and Taguchi experimental design method for material handling—transfer system in the automobile industry

Nowadays, so as to adapt to the global market, where competition is getting tougher, firms producing through the modern production approach need to bring not the only performance of the system designed both during the research and development phase and the production phase but also the performance of the product to be developed as well as the process to be improved to the highest level. The Taguchi method is an experimental design technique seeking to minimize the effect of uncontrollable factors, using orthogonal arrays. It can also be designed as a set of plans showing the way data are collected through experiments. Experiments are carried out using factors defined at different levels and a solution model generated in ARENA 3.0 program using SIMAN, which is a simulation language. Many experimental investigations reveal that the speed and capacity of automated-guided vehicle, the capacities of local depots, and the mean time between shipping from the main depot are the major influential parameters that affect the performance criteria of the storage system. For the evaluation of experiment results and effects of related factors, variance analysis and signal/noise ratio are used and the experiments are carried out in MINITAB15 according to Taguchi L16 scheme. The purpose of this study is to prove that experimental design is an utilizable method not only for product development and process improvement but it can also be used effectively in the design of material handling–transfer systems and performance optimization of automation technologies, which are to be integrated to the firms.     

The prediction technology study of fatigue life for key parts of a tracked vehicle’s suspension system

In allusion to fatigue life of a tracked vehicle torsion bar, a virtual prototype model of the tracked vehicle suspension system including a flexible torsion bar was built based on dynamic simulation software ADAMS. Node force and stress results of the torsion bar from last step simulation were acquired; taking into account the material characteristics and influential factors, fatigue life of the flexible body of the torsion bar was predicted. Engineering results can be acquired through the contrast of the result of virtual test and statistical fatigue.     

Fatigue properties of the pantograph–insulator system of metro trains: Experiments and the design for improvement

Journal of Mechanical Science and Technology - The power of a metro vehicle is supplied by the pantograph on the vehicle roof. During pantograph lifting, the insulator set of the pantograph is...     

General bounds for the optimal value of retailers’ reorder point in a two-level inventory control system with and without information sharing

In this study, an inventory system consisting of a single product, one supplier, and multiple identical retailers is considered. Each retailer replenishes inventory from the supplier according to the well known (R,Q) policy. Transit times are constant and retailers face independent Poisson demand. The supplier utilizing the retailers' information in decision making for replenishment policy with a given order size starts with m initial batches (of size Q) and places an order in a batch of size Q to an outside source when a new order is placed. In this inventory system, excess demand is backordered, delayed orders are satisfied on a first-come first-serve basis, and no partial shipment is allowed. By partitioning the cost function of this system, general upper and lower bounds for the optimal value of R are determined. Based on several numerical examples, it is shown that these bounds (especially the lower bound) allow the optimal reorder point to be found more effectively with a shorter solving time.     

An experimental setup for studying spectra of β particles emitted by mixtures of 235U and 239Pu thermal neutron fission products

An experimental setup on the thermal neutron beam of the IR-8 reactor at the National Research Centre Kurchatov Institute is described. This setup has been designed to precisely measure the ratio of spectra of β particles emitted by mixtures of ²³⁵U and ²³⁹Pu fission products. The experiment is based on simultaneous measurements of β spectra from fissile isotopes ²³⁵U and ²³⁹Pu and the background spectrum in the same neutron beam. Measurements of the β spectra are taken by a high-selectivity β spectrometer in the time interval when the neutron beam is intercepted by a mechanical chopper. The evolution of the measurement technique is considered.