System cost/performance analysis (study 2.3). Volume 1: Executive summary

The relationships between performance, safety, cost, and schedule parameters were identified and quantified in support of an overall effort to generate program models and methodology that provide insight into a total space vehicle program. A specific space vehicle system, the attitude control system (ACS), was used, and a modeling methodology was selected that develops a consistent set of quantitative relationships among performance, safety, cost, and schedule, based on the characteristics of the components utilized in candidate mechanisms. These descriptive equations were developed for a three-axis, earth-pointing, mass expulsion ACS. A data base describing typical candidate ACS components was implemented, along with a computer program to perform sample calculations. This approach, implemented on a computer, is capable of determining the effect of a change in functional requirements to the ACS mechanization and the resulting cost and schedule. By a simple extension of this modeling methodology to the other systems in a space vehicle, a complete space vehicle model can be developed. Study results and recommendations are presented

dOpenCL: Towards a Uniform Programming Approach for Distributed Heterogeneous Multi-/Many-Core Systems

Modern computer systems are becoming increasingly heterogeneous by comprising multi-core CPUs, GPUs, and other accelerators. Current programming approaches for such systems usually require the application developer to use a combination of several programming models (e. g., MPI with OpenCL or CUDA) in order to exploit the full compute capability of a system. In this paper, we present dOpenCL (Distributed OpenCL) – a uniform approach to programming distributed heterogeneous systems with accelerators. dOpenCL extends the OpenCL standard, such that arbitrary computing devices installed on any node of a distributed system can be used together within a single application. dOpenCL allows moving data and program code to these devices in a transparent, portable manner. Since dOpenCL is designed as a fully-fledged implementation of the OpenCL API, it allows running existing OpenCL applications in a heterogeneous distributed environment without any modifications. We describe in detail the mechanisms that are required to implement OpenCL for distributed systems, including a device management mechanism for running multiple applications concurrently. Using three application studies, we compare the performance of dOpenCL with MPI+OpenCL and a standard OpenCL implementation

Design and simulation of hydraulic shaking table

Recent industrial progress and computational technology made it possible to construct more complex structures. Vibration of these structures due to seismic strength must be measured and proved to prevent them from damage when they are subjected to earthquake. However, the accuracy of estimating the effect of vibrating structures is limited by the mathematical models, which are normally simplified from the actual complex structures. Due to this problem, a study on the development of shaking table is proposed. The main purpose of this study is to obtain the design specifications for a 1-axis (horizontal) hydraulic shaking table with medium loading, which can function primarily as an earthquake simulator and a dynamic structural testing apparatus. The project employs a three stage electrohydraulic servovalve, actuator system complete with hydraulic system as the power and drive unit. Mathematical model for closed loop control experimentation was presented and used to investigate the influence of various parameters on the overall system. The investigation includes the study on the effect of controller gain setting (for PD and AFC), disturbances and system stability. Time domain analysis using computer simulation was conducted to explain and predict the system’s response. Comparison between PD and PD-AFC controllers was done and it was found that latter PD-AFC fulfills the performance and robustness specifications for this project. Other design outcome that limits the change of disturbances on the system was also identified and taken as the framework for real world. This suggests that the next stage in implementation of the designed system can be made for the purpose of an earthquake simulator, since it works very well especially at low frequency level of shakin

A comparison of some performance evaluation techniques

In this thesis we look at three approaches to modelling interactive computer systems: Simulation, Operational analysis and Performance-Oriented design. The simulation approach, presented first, is applied to a general purpose, multiprogrammed, machine independent, virtual memory computer system. The model is used to study the effects of different performance parameters upon important performance indices. It is also used to compare or validate the results produced by the other two methods. The major drawback of the simulation model (i.e. its relatively high cost) has been overcome by combining regression techniques with simulation, using simple experimental case studies. Next, operational analysis was reviewed in a hierarchical way (starting by analysing a single-resource queue and ending up by analysing a multi-class customer general interactive system), to study the performance model of general interactive systems. The results of the model were compared with the performance indices produced using the simulation results. The performance-oriented design technique was the third method used for building system performance models. Here, several optimization design problems have been reviewed to minimize the response time or maximize the system throughput subject to a cost constraint. Again, the model results were compared with the simulation results using different cost constraints. We suggest finally, that the above methods should be used together to assist the designer in building computer performance models

Integrated computer-aided working-fluid design and thermoeconomic ORC system optimisation

The successful commercialisation of organic Rankine cycle (ORC) systems across a range of power outputs and heat-source temperatures demands step-changes in both improved thermodynamic performance and reduced investment costs. The former can be achieved through high-performance components and optimised system architectures operating with novel working-fluids, whilst the latter requires careful component-technology selection, economies of scale, learning curves and a proper selection of materials and cycle configurations. In this context, thermoeconomic optimisation of the whole power-system should be completed aimed at maximising profitability. This paper couples the computer-aided molecular design (CAMD) of the working-fluid with ORC thermodynamic models, including recuperated and other alternative (e.g., partial evaporation or trilateral) cycles, and a thermoeconomic system assessment. The developed CAMD-ORC framework integrates an advanced molecular-based group-contribution equation of state, SAFT-γ Mie, with a thermodynamic description of the system, and is capable of simultaneously optimising the working-fluid structure, and the thermodynamic system. The advantage of the proposed CAMD-ORC methodology is that it removes subjective and pre-emptive screening criteria that would otherwise exist in conventional working-fluid selection studies. The framework is used to optimise hydrocarbon working-fluids for three different heat sources (150, 250 and 350 °C, each with mcp = 4.2 kW/K). In each case, the optimal combination of working-fluid and ORC system architecture is identified, and system investment costs are evaluated through component sizing models. It is observed that optimal working fluids that minimise the specific investment cost (SIC) are not the same as those that maximise power output. For the three heat sources the optimal working-fluids that minimise the SIC are isobutane, 2-pentene and 2-heptene, with SICs of 4.03, 2.22 and 1.84 £/W respectively

Probabilistic robust control: theory and applications

In this work, the development of a probabilistic approach to robust control is motivated by structural control applications in civil engineering. Often in civil structural applications, a system's performance is specified in terms of its reliability. In addition, the model and input uncertainty for the system may be described most appropriately using probabilistic or "soft" bounds on the model and input sets. The probabilistic robust control methodology contrasts with existing W... /A robust control methodologies that do not use probability information for the model and input uncertainty sets, yielding only the guaranteed (i.e., "worst-case") system performance, and no information about the system's probable performance which would be of interest to civil engineers. The design objective for the probabilistic robust controller is to maximize the reliability of the uncertain structure/controller system for a probabilistically-described uncertain excitation. The robust performance is computed for a set of possible models by weighting the conditional performance probability for a particular model by the probability of that model, then integrating over the set of possible models. This integration is accomplished efficiently using an asymptotic approximation. The probable performance can be optimized numerically over the class of allowable controllers to find the optimal controller. Also, if structural response data becomes available from a controlled structure, its probable performance can easily be updated using Bayes's Theorem to update the probability distribution over the set of possible models. An updated optimal controller can then be produced, if desired, by following the original procedure. Thus, the probabilistic framework integrates system identification and robust control in a natural manner. The probabilistic robust control methodology is applied to two systems in this thesis. The first is a high-fidelity computer model of a benchmark structural control laboratory experiment. For this application, uncertainty in the input model only is considered. The probabilistic control design minimizes the failure probability of the benchmark system while remaining robust with respect to the input model uncertainty. The performance of an optimal low-order controller compares favorably with higher-order controllers for the same benchmark system which are based on other approaches. The second application is to the Caltech Flexible Structure, which is a light-weight aluminum truss structure actuated by three voice coil actuators. A controller is designed to minimize the failure probability for a nominal model of this system. Furthermore, the method for updating the model-based performance calculation given new response data from the system is illustrated