Modelling method based on idealised fibre bundles

Abstract

In the fibrous structures such as textiles and composites there are fibre assemblies exhibiting statistical bundle like behaviour. This paper presents a modelling method and software FibreSpace, based on a system of structuralised statistical fibre bundles, so called fibre bundle cells. These fibre bundle cells introduced before represent different idealised and typified fibre properties such as fibre shape, state of deformation, gripping as a connection with the vicinity, and the characteristic of force-transmitting and damage. With the help of the weighted parallel connection of the fibre bundle cells the mechanical behaviour and the damage process of real fibrous systems can be modelled as well as some structural properties or the strength data of single fibres can be determined by a fibre bundle cells model identified on the basis of measurements. The applicability of the fibre bundle cells method and modelling program developed is demonstrated by modelling the load and damage process of real textile structures and unidirectional composites during tensile or flexural test.     

MODEL-BASED DEVELOPMENT OF REAL-TIME SOFTWARE SYSTEM FOR ELECTRONIC UNIT PUMP SYSTEM

A real-time operating system (RTOS), also named OS, is designed based on the hardware platform of MC68376, and is implemented in the electronic control system for unit pump in diesel engine. A parallel and time-based task division method is introduced and the multi-task software architecture is built in the software system for electronic unit pump (EUP) system. The V-model software development process is used to control algorithm of each task. The simulation results of the hardware-in-the-loop simulation system (HILSS) and the engine experimental results show that the OS is an efficient real-time kernel, and can meet the real-time demands of EUP system; The built multi-task software system is real-time, determinate and reliable. V-model development is a good development process of control algorithms for EUP system, the control precision of control system can be ensured, and the development cycle and cost are also decreased.     

Quantitative Evaluation of Register Pressure on Software Pipelined Loops

Software Pipelining is a loop scheduling technique that extracts loop parallelism by overlapping the execution of several consecutive iterations. One of the drawbacks of software pipelining is its high register requirements, which increase with the number of functional units and their degree of pipelining. This paper analyzes the register requirements of software pipelined loops. It also evaluates the effects on performance of the addition of spill code. Spill code is needed when the number of registers required by the software pipelined loop is larger than the number of registers of the target machine. This spill code increases memory traffic and can reduce performance. Finally, compilers can apply transformations in order to reduce the number of memory accesses and increase functional unit utilization. The paper also evaluates the negative effect on register requirements that some of these transformations might produce on loops.     

Implementation Issues for Multiuser DS-CDMA Receivers

Multiuser detection for CDMA has been an area ofconsiderable interest in the research community due tothe significant performance gains that can be obtainedthrough the use of sophisticated receivers that exploit the intrinsic structure of themultiple access interference. Recent advances inhigh-speed digital and mixed signal technologies arespawning practical implementations of real-timesuboptimal multiuser receivers. This paper focuses onimplementation issues for advanced DS-CDMA structuresbased on multiuser detection principles, reviewingseveral of the most interesting multiuser detectionschemes from a practical implementation point of view.The computational complexity of these algorithms, a keycriterion in the selection of a joint detection schemefor practical implementation, is evaluated in terms of the time complexity per bit (TCB)decision. Various approaches for multiuser parameterestimation are also reported in this paper, since ingeneral, accurate estimation of the received amplitudes, user delays, and carrier phases is central tomultiuser detection. Subsequently, two low-complexityasynchronous real-time multiuser detectors developed atVirginia Tech are presented along with experimental measurements. Finally, other importantdevelopments leading to practical implementation ofmultiuser receivers are described.     

An Integrated Hardware/Software Data Prefetching Scheme for Shared-Memory Multiprocessors1

Both hardware and software prefetching have been shown to be effective in tolerating the large memory latencies inherent in shared-memory multiprocessors; however, both types of prefetching have their shortcomings. While software schemes require less hardware support than hardware schemes, they must generate address calculation instructions and a prefetch instruction for each datum that needs to be prefetched. Hardware schemes, however, must become progressively more complex to be able to compute data access strides and to increase the prefetching lookahead. In this paper, we propose an integrated hardware/software prefetching method that uses simple hardware that can handle most data accesses and software prefetching for the few remaining accesses. A compile time algorithm analyzes the access streams formed by array references and determines sequences of consecutive memory accesses to an access stream that can be prefetched by the hardware mechanism. This analysis is based on the relative memory locations of consecutive accesses to an access stream and the number of intervening data references between consecutive accesses to an access stream. In addition, the prefetching lookahead can be set separately for each access stream. Our approach yields an effective scheme that minimizes both CPU overhead and hardware costs. Execution-driven simulations show our method to be very effective.     

Artificial neural networks – an aid to welding induced ship plate distortion?

Abstract

A preliminary study on the potential application of artificial neural networks in welded structures was expanded to metal inert gas welding of steel plates of grades D and DH 36. The main controllable variables were plate thickness, steel grade, plate cutting process, and heat input. A series of welded plates of each grade was manufactured, covering plate thicknesses of 6 and 8 mm. The topography of each welded plate was evaluated after tacking the plates together and after welding, allowing the actual distortion to be calculated. It was established that a multilayer perceptron network architecture configuration accurately represented the distortion for the 6 mm thickness plate, and for the 8 mm thickness plate after treatment of the data. The data generated were used to develop the PREDICTOR software package, which allows a distortion prediction to be produced, and to carry out a sensitivity analysis. Heat input was found to be the most sensitive factor related to distortion, with carbon content of the plates, yield/tensile strength ratio, carbon equivalent, and steel grade also having significant effects. Some test plates were modelled using finite element method software packages: the initially poor agreement was improved via the addition of significant detail, but the finite element model by its nature will normally predict symmetrical distortion from a symmetric weld, whereas the artificial neural network model developed was capable of predicting the asymmetric distortion observed in reality.     

A programming environment for real-time control of distributed multiple robotic systems

In recent years there has been great interest in robot software control architectures. However, although many interesting solutions have been presented, most of the research problems tackled related to a single robot perception, navigation and action in everyday environments. Instead, most of the practical applications of mobile robotics for service tasks in civilian environments consist of systems composed of multiple robots communicating with each other, with external sensing and actuating devices, and with external supervising workstations. RoboCup offers a great opportunity to deal with this problem. In fact the software architecture of a robot soccer player must allow successful intra-robot integration of the different activities (visual perception, path planning, strategy planning, motion control, etc.) spanning many different types of representation (raw sensor data, images, symbolic plans, etc.) and it must also guarantee successful inter-robot integration by supporting communication and cooperation. This paper focuses on this problem, presenting ETHNOS-IV - a programming environment for the design of a real-time control system composed of different robots, devices and external supervising or control stations - which has been successfully used within the Italian ART robot team in the RoboCup-99 competition. ETHNOS provides support from three main point of views which will be addressed in detail: inter-robot and intra-robot communication, realtime task scheduling, and software engineering and code reuse. Experimental results illustrating the advantages of this approach will also be presented.     

Reconfigurable Testbed for Interference Cancellation in DS-CDMA Systems

Interference cancellation techniques fordirect-sequence code division multiple access (DS-CDMA)systems have the potential to provide significantcapacity gains over conventional matched filterreceivers. The complexity of the signal processingalgorithms for interference cancellation often requiresprocessing speeds that are beyond that of currentdigital signal processor (DSP) technology. In thispaper, we show that this difficulty can be overcome bypartitioning the algorithmic functionality into two coretechnologies (field programmable gate arrays [FPGA] andDSP devices) based on processing speed requirements. We give implementation proofs via a testbedthat allows a dynamic reconfiguration among constituentreceivers being considered. Experimental results on theperformance of the receivers are presented.