Modeling and analysis on the internal impact of a Stewart platform utilized for spacecraft docking

In this paper, impacts at the joints of a closed-chain mechanism are modeled and analyzed. It is assumed that a Stewart platform is attached to one end of a spacecraft to be utilized as a docking platform and the spacecraft docks with another spacecraft. When the spacecrafts dock with each other, impact will rise at the docking point and the impact is absorbed by the docking platform. Although the impact at the contact point is very large, most of the impact is absorbed by the docking platform and negligible impact is transmitted to the spacecraft. The docking platform can absorb the shock by inertial effect, not by damping or friction. To show this, modeling of the internal impulses at the joints of a multi-body system is introduced and the internal impulses of the docking platform are analyzed by the modeling method.     

Multimedia Resources: An Information Model and Its Application to an MPEG2 Video Codec

Still today, diagnosing a problem withmultimedia resources, such as video and sound cards, isinsufficiently automated. These resources thereforecannot be accurately managed. One reason for this is the lack of their thorough modeling. In this paper,we fulfill this need, by proposing a generic informationmodel, which we further apply to an MPEG2 video codec.We highlight the main characteristics of this kind of codec, identify parameters thatinfluence these characteristics, and reveal some of thetrade-offs that the application developer can considerin order to design efficient software for MPEG2 codecs. In addition to the benefits of this modelingfor the user and the application developer, we also showhow useful it could be for the providers of distributionservices, such as "live" video transmission. These providers can use our model to achieveresource management on an end-to-end basis.     

一种基于双周期时间序列的短时交通流预测算法

根据城市道路短时交通流特征,在ARIMA(autoregressive integrated moving average model)模型和SARIMA(seasonal autoregressive integrated moving average model)模型的基础上,提出一种既满足城市道路日周期性和周周期性的短时交通流预测模型DSARIMA(double seasonal autoregressive integrated moving average model)模型,并根据城市道路工作日与非工作日交通流特点,提出该模型的预测算法。该算法采用两种方式利用ARIMA模型进行交通流预测,一种方式采用当前时刻前N1段时间进行预测,另一种方式采用当前时刻前N2天同一时段的交通流进行预测,并用改进的贝叶斯模型算法根据两种预测结果与实际值的误差来确定该种方式的权值,最后的预测结果为两种方式预测结果与其权值乘积之和。实验结果表明,该模型在交通流预测上,相比ARIMA模型和SARIMA模型预测具有更好的平稳性与更高的预测精度。     

Behaviour of manganese oxides during magnetising reduction of Baharia iron ore by CO–CO2 gas mixture

Abstract

High manganese containing iron ore samples were isothermally reduced with a CO–CO₂ gas mixture at 600–1000°C. The course of reduction was followed by a weight loss technique. The influence of reducing gas composition and temperature on the reduction kinetics was investigated. The different phases formed during reduction were identified by X-ray phase analysis, while their structures were microscopically examined. The reduced samples were magnetically tested by means of a Davis tube tester. The effect of grain size, drum speed, and cleaning conditions on the efficiency of magnetic separation was studied using a Box-Mag wet low intensity magnetic separator. The separation efficiency was determined by analysing total iron, manganese, and acid insoluble contents in both magnetic and non-magnetic fractions. Best testing results were obtained on separation of the sample reduced with 80CO–20CO₂ (vol.-%) at 800°C. The optimum grain size for magnetic separation is below 0·15 mm while that of the drum speed is 100 rev min^-1 . The cleaning of the magnetic fraction increases the iron content and decreases the manganese and acid insoluble contents.     

ONLINE MODEL AND ACTUATOR FAULT TOLERANT CONTROL FOR AUTONOMOUS MOBILE ROBOT

A novel fault-tolerant adaptive control methodology against the actuator faults is proposed. The actuator effectiveness factors (AEFs) are introduced to denote the healthy of actuator, and the unscented Kalman filter (UKF) is employed for online estimation of both the motion states and the AEFs of mobile robot. A square root version of the UKF is introduced to improve efficiency and numerical stability. Using the information from the UKF, the reconfigurable controller is designed automatically based on an enhancement inverse dynamic control (IDC) methodology. The experiment on a 3-DOF omni-directional mobile robot is performed, and the effectiveness of the proposed method is demonstrated.     

Support for Efficient Programming on the SB-PRAM

The SB-PRAM is a shared-memory parallel computer that has been designed according to the PRAM model from theoretical computer science. The SB-PRAM realizes a concurrent-read, concurrent-write PRAM where each processor can access the global memory in unit time. This article describes the programming environment of the SB-PRAM that enables a programmer to develop efficient and portable programs without dealing with architectural details of the machine. In particular, we discuss compiler and operating system issues and show that the runtime functions of the P4 environment and several parallel data structures can be implemented very efficiently by using special features of the SB-PRAM. In contrast to other parallel machines, the synchronization of processors and the management of concurrent accesses to the global memory only require a few machine instructions independent of the number of processors participating in the operation. This efficient implementation of the runtime system is the basis for good performance of many challenging applications.