An experimental study of the hadron calorimeter module response to protons and pions with energies of 1–5 GeV

The design of the hadron calorimeter module is discussed. Such modules are expected to be used in the forward calorimeters of the Multi Purpose Detector (MPD) (Dubna, Russia) and Compressed Barionic Matter (CBM) (Darmstadt, Germany) experiments. The module has transverse dimensions of 20 × 20 cm² and is composed of 60 16-mm-thick lead layers interleaved with 4-mm-thick scintillator plates. Light from scintillator plates is captured by wavelength-shifting optical fibers. The module has longitudinal segmentation and consists of 10 sections. Light collected from each section is read out by micropixel photodiodes with a sensitive area of 3 × 3 mm². Test measurements of the energy resolution and linearity of the calorimeter module response in the hadron momentum range of 2–6 GeV/c have been performed. The longitudinal profiles of the hadron shower, obtained in the measurable energy range both for pion and proton beams, are discussed. The measured energy resolution and the linearity of the calorimeter module response at low energies are presented and compared to the data obtained at high energies.     

A method for measuring the energy spectrum of neutrons with energies of 1–15 MeV

The characteristics of the detector prototype for 1–15 MeV neutrons are described. The prototype is a full absorption detector consisting of interlaced plastic scintillators and ⁶Li doped glasses. A neutron incident on the detector deposits all its energy in the plastic scintillator, is moderated to thermal energies, and detected in the lithium glass. The measured time of complete neutron moderation is ～60 μs. Recording two signals in this time interval from the first event of neutron scattering in the plastic scintillator and from the neutron absorption by a lithium atom in the glass, it is possible to effectively suppress background thermal neutrons and γ rays and, therefore, detect low-intensity neutron sources. Owing to the proposed detector design, the direction toward the neutron source can be determined.     

A technique for selecting γ rays with energies above 50 GeV from the background of charged particles in the GAMMA-400 space-based γ-ray telescope

The task of selecting neutral γ rays from the background of charged particle fluxes, which arises in investigation of high-energy (>50 GeV) cosmic rays, is complicated by the presence of the backsplash effect. The backsplash is composed of a great number of low-energy (~1 MeV) particles produced in an electromagnetic shower being developed in the calorimeter of the γ-ray telescope. A technique of charged particle rejection using an anticoincidence system has been developed. A method for discriminating events of charged particle detection from γ-ray detection events accompanied by the backsplash phenomenon is proposed. This method is based on the difference of the signals in time and makes it possible to maintain a high detection efficiency even for high-energy γ rays.     

A new design method for PI–PD control of unstable processes with dead time

PID controllers are still widely practiced in the industrial systems. In the literature, many publications can be found considering PID controller design for unstable processes. However, owing to the structural limitations of PID controllers, generally, good closed loop performance cannot be achieved with a PID for controlling unstable processes and usually a step response with a high overshoot and oscillation is obtained. On the other hand, PI–PD controllers are proved to give very satisfactory closed loop performances for unstable processes. The paper presents a simple design method to tune parameters of a PI–PD controller for the control of the unstable processes with time delay. The proposed method is based on plotting the stability boundary locus, which is a locus dependent on the parameters of the controller and frequency, in the parameter plane. The method uses a new concept named centroid of the convex stability region. Simulation examples and an experimental application are given to illustrate the superiority of the proposed method over some existing ones.     

Discrimination of particles by the scintillation pulse shape in the range of low energies (6–100 keV for electrons) using the linear filters

The use of the linear filters for particle discrimination by the scintillation pulse shape is considered. The particle separation process has been simulated by the Monte Carlo method, taking into account that the slow scintillation component decays according to the hyperbolic law and that its relative contribution is energy dependent. The best figures of merit of particle discrimination attainable with this technique have been obtained assuming that the PMT and electronic noises are zero. It is shown that, by contrast to the zero crossing method, pulse shape discrimination of particles using the linear filters can ensure rejection of the γ-ray background to a level of ∼10⁻⁴ at particle energies of up to 12 keV of the electron equivalent. For energies of <24 keV, it is expedient that the signal acquisition time be increased to a few microseconds.     

A control system for the “shashlyk” forward calorimeter in the PANDA experiment

The use of soft- and hardware, in particular, the EPICS software environment and the Control System Studio, for building the control system of the “shashlyk” calorimeter in the PANDA experiment is described. The control unit of the Cockcroft–Walton generators, as well as the processing of its data using single-board Raspberry Pi computers, is briefly described.     

A Peltier cells differential calorimeter with kinetic correction for the measurement of cp(H,T) and Δs(H,T) of magnetocaloric materials

In this paper we describe and test a setup for the characterization of the magnetocaloric effect around room temperature. The setup is a differential calorimeter able to measure both the specific heat c(p)(H,T) under constant magnetic field H and the isothermal entropy change induced by changing H, Δs(H,T), in the room temperature range. The setup uses miniaturized Peltier cells to measure the heat flux, with resolution of about 1 μW, and power Peltier cells to regulate the temperature in the range from 243 K (-30 °C) to 343 K (+70 °C). The kinetic effects due to the heat capacity of the measuring cells are taken into account by a simple model of the heat flux diffusion in the calorimetric cell. As measurement examples, we show the characterization of the magnetocaloric effect in magnetic materials with a second order transition [without latent heat and without hysteresis, as in the La(1)(Fe(1-x-y)Co(y)Si(x))(13) alloy with x=0.077 and y=0.079] and with a first order transitions (with latent heat and hysteresis as in Ni(50)Mn(36)Co(1)Sn(13)). As a result we compare the entropy change Δs(H,T) derived from (i) the integration of the specific heat c(p)(H,T) and (ii) the direct isothermal measurements, obtaining an excellent agreement.     

A Spectral–Thermal Bench with a Special Fiber-Optic Probe–Objective for Measuring Diffuse-Reflection Spectra

The results of tests of a new fiber-optic probe–objective for measuring both IR diffuse-reflection spectra and other types of spectra of solids at various temperatures are presented. In comparison with the conventional devices, the new scheme for measuring diffuse-reflection spectra has such advantages as the minimum distortion of spectra by the specular and Fresnel diffuse components of the reflection from surface irregularities and the linearity of the concentration dependences. The use of a fiber-optic probe–objective provides the ability for the simultaneous analysis of the solid phase and outgoing gases with increasing temperature and calibration of the spectral methods using the thermogravimetric-analysis data. An example of monitoring the process of drying catalysts in laboratory studies when analyzing composite and other materials is used to consider the prospects for using the probe–objective.     

A Wavelet–Fractal-Based Approach for Composite Characterisation of Engineering Surfaces

Many types of engineering surfaces have been seen to have fractal characteristics. A good model of the properties can be produced using wavelet-based expansions. For multiscale analysis of surface topography, a difficulty exists in determining quantitatively the feature separation index for comprehensively characterising roughness, waviness, and form errors from a primary surface structure. In this project, we utilise the fractal dimension, which has proved to be an intrinsic parameter capable of measuring surface irregularities, to quantify the feature separation index in the wavelet transform for a composite characterisation of engineering surfaces. The effectiveness of the proposed method is validated in the computational testing of 2D and 3D surfaces. ID="A1"Correspondance and offprint requests to: Dr Y. Gao, Department of Mechanical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong. E-mail: meygao@ust.hk     

A Min–Max multiregulator system with stability analysis for aeroengine propulsion control

Stability analysis is an essential issue in Min–Max multiregulator control strategy for commercial aircraft engines. In this paper, a Min–Max selector scheme along with a stability analysis method is provided for aeroengine propulsion control. It is assumed that the main regulator is a dynamic compensator and the limit regulators are constant gains. The regulators are determined in such a way that the individual control loops are stable. However, due to the switching nature of Min–Max structure, the stability of single loops does not necessarily ensure the overall system stability. In order to analyze the stability of the presented Min–Maxapproach, the architecture of the control system is transformed into the canonical form of Lure’s system and the condition for absolute stability is specified using Multivariable Circle Criterion. The theoretical results can also be applied to investigate the stability of min-only or max-only schemes. Afterwards, using the provided methodology, the global asymptotic stability is proved for the control system of a high bypass two-spool turbofan engine and the performance of the designed Min–Max controller in tracking a desired fan speed and limit protection in fault-free and fault tolerant situations is compared with the well-known Min–Max/SMC approach.     

A review of information flow diagrammatic models for product–service systems

Quality of an assembly of any manufactured product is mainly based on the quality of mating components. Due to random variations in sources such as materials, machines, operators, and measurements, mating components manufactured by even the same process may vary in their dimensions. When mating components are assembled linearly, the resulting assembly tolerance will be the sum of the mating components tolerances. All precision assemblies demand for a closer assembly tolerance. A significant amount of research has already been done to minimize assembly variation using selective assembly, when the dimensions of components follow normal distribution. However, in reality, the dimensions of components produced especially in smaller to medium size batches, invariably have some skewness (non-normality), which makes the methods developed and reported in the literature, often not suitable for practice. In this work, batch selective assembly methodology is proposed for components having non-normal distributions to minimize the assembly tolerance variations. The proposed method which employs a genetic algorithm for obtaining the best combination of mating components is able to achieve minimum variations in assembly tolerances and also maximum number of acceptable assemblies. The proposed algorithm is tested with a set of experimental problem datasets and is found outperforming the other existing methods found in the literature, in producing solutions with minimum assembly variation.     

DZ10—100A自动空气开关

该产品通过鉴定,已投入成教七生产。它主·哥用于交流电压至3 30伏,50~60赫芝;直流电压主220伏的低压配电线路中,能自动断开线路的过载和短路等故障,具有体积小,结构紧凑、外形美观、使用安全方便等优点,基本达到国内先进水平。     

A micro-contact and wear model for chemical–mechanical polishing of silicon wafers

A micro-contact and wear model for chemical–mechanical polishing (CMP) of silicon wafers is presented in this paper. The model is developed on the basis of elastic–plastic micro-contact mechanics and abrasive wear theory. The synergetic effects of mechanical and chemical actions are formulated into the model. A close-form equation of material removal rate from the wafer surface is derived relating to the material, geometric, chemical and operating parameters in a CMP process. The model is evaluated by comparing the theoretical removal rates with those experimentally determined. Good agreement is obtained for both chemically active and inactive polishing processes. The model reveals some insights into the micro-contact and wear mechanisms of the CMP process. It suggests that the removal rate is sensitive to the particle concentration in the slurry, more sensitive to the applied load and operating speed and most sensitive to the surface hardness and slurry particle size. The model may be used to study the effects of different materials, geometry, slurry chemistry and operating conditions on CMP processes.     

A Model for the Assessment of Wheel–Rail Contact in the Presence of Solid Contaminants

An analytical model for the assessment of a contact in the presence of a solid contaminant is presented, mainly aimed at studying the damage to railway wheels and rails operating in third-body-contaminated environments. The model, developed under 2D plane strain idealization, includes multiple evenly spaced rigid cylindrical contaminant bodies entrapped between two elastic cylinders. It allows a very fast calculation of the pressure distribution on the surfaces in contact and it can be used for evaluating the stress field in the subsurface region, at both the small scale of the contact between the main body and the contaminant body and the full scale of the contact between the two main bodies. The model was validated by comparison with finite element (FE) analyses, showing its accuracy. Some examples of application showed the model’s ability to predict the limit of the influence of the solid contaminant bodies and the depth where cyclic plasticity phenomena occur in wheel–rail contacts.     

A Sweeping Pulsed Radar–Reflectometer for Measuring the Electron Concentration Profile of Plasma

An instrument for measuring the electron concentration profile in magnetic confinement plasma devices is described. The instrument combines the advantages of rapidly tuned (sweeping) phase reflectometers and multichannel time-of-flight pulsed reflectometers and ensures measurements of the electron concentration profile at electron densities of 4.7 × 10¹²–4.5 × 10¹³ cm^–3 for 16 s.     

A Complementarity Problem–Based Solution Procedure for 2D Steady-State Rolling Contacts with Dry Friction

The problem of steady-state rolling contact between two cylinders with dry friction was formulated into standard linear complementarity problems (LCPs) using the explicit physical definition. For normal contacts, the complementarity variables are the normal pressure and the gap. For the tangential contact, the traction distribution and relative slip are the variables obtained by solving the LCP. The frictional behavior is assumed to be governed by the Coulomb friction law, and LCP formulations of both similar elastic (Carter problem) and dissimilar elastic rolling contacts are presented in this work. Good agreement was found between the current LCP approach and publicly available software for both the rolling contact of similar elastic and dissimilar elastic cylinders. Moreover, the surface roughness was taken into account in this article by the verified approach. The results show the initial slope of the traction-relative creepage curve decreases as the surface roughness increases.     

A Low-Pressure Excimer Light Source for a Spectral Region of 170–310 nm

A low-pressure excimer light source pumped by a longitudinal dc glow discharge operates on the B–X and D–X transitions of Ar, Kr, and Xe chlorides and on the D–A transition of chlorine molecules. The output characteristics of a source with a discharge region 100 mm long and an inner diameter of the discharge tube of 5 mm were optimized on Xe(Kr, Ar)/Cl₂, Ar/Kr/Cl₂, Ar/Xe/Cl₂, and Kr/Xe/Cl₂ mixtures. The light source operated within a spectral range of 170 to 310 nm. The average radiation power and operation efficiency were 1.8–8.2 W and 21%, respectively.     

A flexible artificial neural network–fuzzy simulation algorithm for scheduling a flow shop with multiple processors

One of the most popular approaches for scheduling manufacturing systems is dispatching rules. Different types of dispatching rules exist, but none of them is known to be globally the best. A flexible artificial neural network–fuzzy simulation (FANN–FS) algorithm is presented in this study for solving the multiattribute combinatorial dispatching (MACD) decision problem. Artificial neural networks (ANNs) are one of the commonly used metaheuristics and are a proven tool for solving complex optimization problems. Hence, multilayered neural network metamodels and a fuzzy simulation using the α-cuts method were trained to provide a complex MACD problem. Fuzzy simulation is used to solve complex optimization problems to deal with imprecision and uncertainty. The proposed flexible algorithm is capable of modeling nonlinear, stochastic, and uncertain problems. It uses ANN simulation for crisp input data and fuzzy simulation for imprecise and uncertain input data. The solution quality is illustrated by two case studies from a multilayer ceramic capacitor manufacturing plant. The manufacturing lead times produced by the FANN–FS model turned out to be superior to conventional simulation models. This is the first study that introduces an intelligent and flexible approach for handling imprecision and nonlinearity of scheduling problems in flow shops with multiple processors.     

A sequential electrochemical–electrodischarge process for micropart manufacturing

Among the processes of micropart manufacturing, special attention is paid to applying electrochemical (ECMM) and electrodischarge (EDMM) micromachining. These processes have especially been predicted for 3D-sculptured surface (i.e. tools for microforming processes) manufacturing. In the first part of the paper a review and comparison of ECMM and EDMM are presented with special focus on accuracy and productivity. Additionally the solutions of the integration of the electrochemical and electrodischarge machining are reviewed. The analysis was the background for the concept of combining ECMM and EDMM (EC/EDMM) into a sequential process carried out on the same machine tool. Such a combination gives the possibility of minimizing the disadvantages and emphasizing the advantages of the ECMM and EDMM processes. All of these considerations were carried out based on the literature review. In the second part of the paper, overviews of the special EC/EDMM machine design, CAD/CAM support and examples of applying the EC/EDMM sequence are presented.