Einfluss der Versuchsunterstützung auf die Abschätzungsgenauigkeit mittels künstlich neuronaler Netze

Suitable methods and transferability criteria and knowledge of the cyclic material behaviour is essential for a durable design of a component. For this reason, the cyclic material parameters are determined as a function of the product's properties (level of deformation, microstructure, surface finish, residual stresses) and different loading parameters. However, since the determination of the cyclic parameters is associated with considerable experimental effort and costs, a cost‐effective and easy method is sought to determine these parameters. A very promising approach for this is the application of artificial neural networks (ANN) since they have the ability to generate the influences on the fatigue strength from the manufacturing and environmental parameters using sensibly selected input parameters. They offer the possibility to access acquired knowledge and to thus construct a multidimensional map based on a few tests. By combining a few experimental tests with the ANN, the result of the estimation can be improved and the experimental effort can be reduced.     

浅谈国家标准GB／T11918修订的意义

国家标准GB／T11918．1和GB／T11918．2根据IEC60309的修订新版本进行修订，其中增加了IK抗撞击防护等级。国家标准第一次提出IK抗撞击机械防护等级，表明电器设备的防护已经引起各级的重视，说明IK抗撞击防护等级对于电器设备防护的重要性。本文阐述标准修订将进一步提高工业电器的安全性和可靠性；对于发展防护电器产业具有重要意义。     

Examining the misalignment of a linear guideway pair on a feed drive system under different ball screw preload levels with a cost-effective MEMS vibration sensing system

This paper presents an innovative and cost-effective scheme for examining on line the degree of misalignment of a pair of linear guideway rails in a feed drive system. Prototype MEMS-based vibration detection modules were constructed and installed on the ball screw nut and linear guideway block. The ball screw preload was adjusted with four settings by changing ball sizes in this feed drive system. For each preload setting, a linear guideway rail was adjusted using feeler gauges to produce 11 misalignment statuses. The y-axis deviation caused by misalignment along the feed direction (x-axis) was measured with a dial gauge. For each preload and misalignment setting, the vibration signal was ascertained from the installed detection modules while the work table was driven by the controller. By analyzing the vibration signals from the detection module on the linear guideway block, we found that the characteristic frequency in a specific spectrum band could be used as a misalignment index. The characteristic frequencies exhibited a descending trend when the deviation was less than 40 μm and an increasing trend when the deviation was 40–120 μm. These findings demonstrate the feasibility of using cost-effective sensing units to examine the parallelism or distinguish the deviation between the linear guideway rails without disassembling the work table. This could be valuable for machine intelligence applications in the automation industry.     

Design,development and testing twin pulse tube cryocooler

The design and development of Twin Pulse Tube Cryocooler (TPTC) is presented. Both the coolers are driven by a single Linear Moving Magnet Synchronous Motor (LMMSM) with piston heads at both ends of the mover shaft. Magnetostatic analysis for flux line distribution was carried-out during design and development of LMMSM based pressure wave generator. Based on the performance of PWG, design of TPTC was carried out using Sage and Computational Fluid Dynamics (CFD) analysis. Detailed design, fabrication and testing of LMMSM, TPTC and their integration tests are presented in this paper.     

Spatial distribution of thorium fission rate in a fast spallation and fission neutron field: An experimental and Monte Carlo study

The Energy plus Transmutation (EpT) set-up of the Joint Institute for Nuclear Research (JINR), Dubna, Russia is composed of a lead spallation target surrounded by a blanket of natural uranium. The resultant neutron spectrum is a combination of spallation and fission spectra, modified by a reflective external layer of polyethylene and an internal absorbing layer of cadmium. The EpT set-up was irradiated with a beam of 4 GeV deuterons from the Nuclotron Accelerator at JINR. The spatial distribution of thorium fission rate within the assembly was determined experimentally, using a fission track detector technique, and compared with Monte Carlo predictions of the MCNPX code. Contributions of neutrons, protons, deuterons, photons and pions to total fission were taken into account. Close agreement between the experimental and calculated results was found.     

Forecasting hydrogen production potential in islamabad from solar energy using water electrolysis

The focus of this study is the use of Machine Learning methods to forecast Solar Hydrogen production potential for the Islamabad region of Pakistan. For this purpose, we chose a Photovoltaic-Electrolytic (PV-E) system to forecast electricity and, hence, hydrogen production. The weather data used for forecasting and simulation were recorded with precise meteorological instruments stationed in Islamabad, over the course of 13 and a half months. Out of the three tested algorithms, Prophet performs the best with Mean Absolute Percentage Error of 3.7%, forecasting a daily average Hydrogen production of 93.3 × 10³ kg/Km². Although, the forecast in this study is made for the month of August and September, during which the local season moves towards winter, this study demonstrates solar hydrogen production, as a green energy source, has a tremendous potential in this region.     

Easily too difficult: Estimating item difficulty in computer simulated microworlds

Dealing with complexity and dynamics is increasingly becoming part of people's everyday lives. The necessity of dealing with complex systems has instigated the use of computer simulations, so-called microworlds (MWs), to assess and study human behavior in complex situations. Although these MWs enjoy great popularity with both practitioners and researchers, their psychometric qualities have been questioned, and studies that have investigated these qualities have been sparse. In particular, only a few studies have investigated the factors that contribute to item difficulty in MWs. To fill this gap, we analyzed data from 3128 Finnish students with a linear logistic test model. Our results suggest that item difficulty in MWs can be almost perfectly predicted by six basic item characteristics, namely, (a) the use and number of eigendynamics, the numbers of (b) input and (c) output variables, the numbers of (d) input and (e) output variables not related to any other variables, and (f) the total number of relations between all variables. In addition, we provide evidence for the necessity of differentiating between the difficulty of controlling an MW (knowledge application) and understanding its underlying structure (knowledge acquisition). Finally, we discuss further theoretical and practical implications of an increased understanding of MWs for their use as assessment instruments.     

Note To The Mixed-Type Splitting Iterative Method For The Positive Real Linear System

In [5] a new iterative method is given for the linear system of equations Au=b , where A is large, sparse and nonsymmetrical and A^{\rm T}+A is symmetric and positive definite (SPD) or equivalently A is positive real. The new iterative method is based on a mixed-type splitting of the matrix A and is called the mixed-type splitting iterative method. The iterative method contains an auxiliary matrix D_1 that is restricted to be symmetric. In this note, the auxiliary matrix is allowed to be more general and it is shown that by proper choice of D 1 , the new iterative method is still convergent. It is also shown that by special choice of D_{1} , the new iterative method becomes the well-known (point) accelerated overrelaxation (AOR) [1] method. Hence, it is shown that the (point) AOR method applied to the positive real system is convergent under the proper choice of the overrelaxation parameters y and .     

Robust disturbance rejection in modified repetitive control system

This study concerns disturbance rejection for a modified repetitive control system (MRCS) that contains a strictly proper plant with time-varying uncertainties. Since an MRCS is affected by both periodic and aperiodic disturbances, and since the disturbances are often unknown, an equivalent-input-disturbance (EID)-based estimator was added to an MRCS to yield an EID-based MRCS that compensates for all types of disturbances. In this system, the repetitive controller ensures tracking of a periodic reference input, and the incorporation of an EID estimate into the control input enables rejection of unknown periodic and aperiodic disturbances. A robust stability condition for the MRCS was established in the form of a linear matrix inequality, and the condition was used to design the parameters of the controller. This design method handles uncertainties and enables the preferential adjustment of the tracking and control performance of the MRCS. Simulation results demonstrate the validity of the method.     

Pinhole imaging to observe spatial jitters of a triple-pulse X-ray source on the Dragon-Ⅱ LIA

In high-energy flash radiography,scattered photons degrade the acquiring image,which limits the resolving power of interfaces and density of dense object.The application of large anti-scatter grid can reduce the scattered photons remarkably,but this requires a stable source position in order to reduce the loss of signal photons in the grid structure.The pinhole imaging technique is applied to observe spatial jitters of a triple-pulse radiographic source of a linear induction accelerator.Numerical simulations are conducted to analyze the imaging performance with the same or close parameters of the pinhole object and experimental alignment.Experiments are carried out to observe spatial jitters of the source between different measurements.Deviations of the source position between different pulses are measured in each experiment.