Neutron monitors detect secondary particles produced by the collision of cosmic rays and atmospheric nuclei. The need exists for a mini-neutron monitor data acquisition system (MNM-DAS) to replace the existing recording system of the calibration neutron monitor developed in 2003 at the North-West University Centre for Space Research. The MNM-DAS must also replace the recording system of a standard NM64 neutron monitor. This research thus includes the development of the MNM-DAS using Design Science Research (DSR) in conjunction with Systems Engineering (SE) to streamline the design phase and maximize research output. A literature study is conducted, where an overview of the calibration monitor system is provided, together with the objectives for the development of the MNM system. An abstract system architecture was drawn up in the conceptual design phase of the project to provide a coherent description of all system functions. The system architecture was derived for the existing system, including additional functions of the required system, by performing a functional analysis. The architecture describes the function and fit of each functional unit and all interfaces that form an integrated system. From the conceptual design and system architecture, a preliminary synthesis was done. Following the preliminary synthesis, electronic circuitry was developed to capture the arrival time of pulses from the proportional neutron monitor counter tubes along with environmental variables, such as temperature, pressure, and location, which all influence the count rate. The MNM-DAS was successfully designed and developed by following this Systems-Engineering approach embedded into a Design Science Research framework. The MNM-DAS was constructed and tested, and is currently being used to provide neutron count data in real-world applications internationally. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2014

Neutron monitors detect secondary particles produced by the collision of cosmic rays and atmospheric nuclei. The need exists for a mini-neutron monitor data acquisition system (MNM-DAS) to replace the existing recording system of the calibration neutron monitor developed in 2003 at the North-West University Centre for Space Research. The MNM-DAS must also replace the recording system of a standard NM64 neutron monitor. This research thus includes the development of the MNM-DAS using Design Science Research (DSR) in conjunction with Systems Engineering (SE) to streamline the design phase and maximize research output. A literature study is conducted, where an overview of the calibration monitor system is provided, together with the objectives for the development of the MNM system. An abstract system architecture was drawn up in the conceptual design phase of the project to provide a coherent description of all system functions. The system architecture was derived for the existing system, including additional functions of the required system, by performing a functional analysis. The architecture describes the function and fit of each functional unit and all interfaces that form an integrated system. From the conceptual design and system architecture, a preliminary synthesis was done. Following the preliminary synthesis, electronic circuitry was developed to capture the arrival time of pulses from the proportional neutron monitor counter tubes along with environmental variables, such as temperature, pressure, and location, which all influence the count rate. The MNM-DAS was successfully designed and developed by following this Systems-Engineering approach embedded into a Design Science Research framework. The MNM-DAS was constructed and tested, and is currently being used to provide neutron count data in real-world applications internationally. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2014

Master of Science / Department of Statistics / Paul I. Nelson / The Calibration-Inverse Prediction Problem was investigated in a mixed model setting. Two methods were used to construct inverse prediction intervals. Method 1 ignores the random block effect in the mixed model and constructs the inverse prediction interval in the standard manner using quantiles from an F distribution. Method 2 uses a bootstrap to estimate quantiles of an approximate pivotal and then follows essentially the same procedure as in method 1. A simulation study was carried out to compare how the intervals created by the two methods performed in terms of coverage rate and mean interval length. Results from our simulation study suggest that when the variance component of the block is large relative to the location variance component, the coverage rate of the intervals produced by the two methods differ significantly. Method 2 appears to yield intervals which have a slightly higher coverage rate and wider interval length then did method 1. Both methods yielded intervals with coverage rates below nominal for approximately 1/3 of the simulation settings.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Historically, different aspects of the configuration of an airborne instrumentation system were specified in a variety of different software applications. Instrumentation setup software handled the definition of measurements and PCM Formats while separate applications handled pre-flight checkout, calibration and post-flight data analysis. This led to the manual entry of the same data multiple times. Industry standards such as TMATS strive to address this problem by creating a data-interchange format for passing setup information from one application to another. However, a better alternative is to input all of the relevant setup information about the sensor and the measurement when it is initially created in the instrumentation vendor’s software. Furthermore, an additional performance enhancement can be achieved by adding the ability to perform sensor calibration and engineering unit conversions to pre-flight data visualization software that is tightly coupled with the instrumentation setup software. All of the setup information can then be transferred to the ground station for post-flight processing and data reduction. Detailed reports can also be generated for each measurement. This paper describes the flow of data through an integrated airborne instrumentation setup application that allows sensors and measurements to be defined, acquired, calibrated and converted from raw counts to engineering units. The process of performing a sensor calibration, configuring engineering unit conversions, and importing calibration and transducer data sheets will also be discussed.

MEMS gyroscopes have become an essential component in consumer, industrial and automotive applications, owing to their small form factor and low production cost. However, their poor stability, also known as drift, has hindered their penetration into high-end tactical and navigation applications, where highly stable bias and scale factor are required over long period of time to avoid significant positioning error. Improving the long-term stability of MEMS gyroscopes has created new challenges in both the physical sensor design and fabrication, as well as the system architecture used for interfacing with the physical sensor. The objective of this research is to develop interface circuits and systems for in-situ control and self-calibration of MEMS resonators and resonant gyroscopes to enhance the stability of bias and scale factor without the need for any mechanical rotary stage, or expensive bulky lab characterization equipment. The self-calibration techniques developed in this work provide 1-2 orders of magnitude improvement in the drift of bias and scale factor of a resonant gyroscope over temperature and time.

Many powders and particulate solids are stored and handled in large quantities across various industries. These solids often encounter handling and storage difficulties that are caused by the material cohesion. The cohesive strength of a bulk material is a function of its past consolidation stress. For example, high material cohesive strength as a result from high storage stresses in a silo can cause ratholing problems during discharge. Therefore, it is essential to consider the stress-history dependence when evaluating such handling behaviour. In recent years the Discrete Element Method (DEM) has been used extensively to study the complex behaviour of granular materials. Whilst extensive DEM studies have been performed on cohesionless solids, much less work exists on modelling of cohesive solids. The commonly used DEM models to model adhesion such as the JKR, DMT and linear cohesion models have been shown to have difficulty in predicting the stress-history dependent behaviour for cohesive solids. DEM modelling of cohesive solid at individual particle level is very challenging. To apply the model at single particle level accurately would require one to determine the model parameters at particle level and consider the enormous complexity of interfacial interaction. Additionally it is computationally prohibitive to model each and every individual particle and cohesion arising from several different phenomena. In this study an adhesive elasto-plastic contact model for the mesoscopic discrete element method (DEM) with three dimensional non-spherical particles is proposed with the aim of achieving quantitative predictions of cohesive powder flowability. Simulations have been performed for uniaxial consolidation followed by unconfined compression to failure using this model. Additionally, the scaling laws necessary to produce scale independent predictions for cohesionless and cohesive solids was also investigated. The influence of DEM input parameters and model implementation have been explored to study the effect of particle (meso-scale) properties on the bulk behaviour in uniaxial test simulation. The DEM model calibration was achieved using the Edinburgh Powder Tester (EPT) – an extended uniaxial tester to measure flowability of bulk solids. The EPT produced highly repeatable flowability measurements and was shown to be a good candidate for DEM model calibration. The implemented contact model has been shown to be capable of predicting the experimental flow function (unconfined compressive strength versus the prior consolidation stress) for a limestone powder which has been selected as a reference solid in the Europe wide PARDEM research network. Contact plasticity in the model is shown to affect the flowability significantly and is thus essential for producing satisfactory computations of the behaviour of a cohesive granular material. The model predicted a linear relationship between a normalized unconfined compressive strength and the product of coordination number and solid fraction. Significantly, it has been found that contribution of adhesive force to the limiting friction has a significant effect on bulk unconfined strength. Failure to include the adhesive contribution in the calculation of the frictional resistance may lead to under-prediction of unconfined strength and incorrect failure mode. The results provide new insights and propose a micromechanical based measure for characterising the strength and flowability of cohesive granular materials. Scaling of DEM input parameters in a 3D simulation of the loading regimes in a uniaxial test indicated that whilst both normal and tangential contact stiffness (loading, unloading, and load dependent) scales linearly with radius of the particle, the adhesive forces scales with the square of the radius of the particles. This is a first step towards a mesoscopic representation of a cohesive powder that is phenomenological based to produce the key bulk characteristics of a granular solid and the results indicate that it has potential to gain considerable computational advantage for large scale DEM simulations. The contact model parameters explored include particle contact normal loading stiffness, tangential stiffness, and contact friction coefficient. The DEM model implementation parameters included numerical time step, strain rate, and boundary condition. Many useful observations have been made with significant implications for the relative importance of the DEM input parameters. Finally the calibration procedure was applied to a spray dried detergent powder and the simulation results are compared to whole spectrum of loading regime in a uniaxial experiment. The experimental and simulation results were found to be in reasonable agreement for the flow function and compression behaviour.

The purpose of this paper is to create an easily understandable version of the Ho-Lee interest rate model. The first part analyzes the model in detail, and the second part calibrates it to demonstrate how it can be applied to real market data.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Emerging technologies in the field of "Test & Measurement" have recently enabled the development of the Rapidly Adaptable Instrumentation Tester (RAIT). Based on software developed with LabVIEW®, the RAIT design enables quick reconfiguration to test and calibrate a wide variety of telemetry systems. The consequences of inadequate testing could be devastating if a telemetry system were to fail during an expensive flight mission. Supporting both open-bench testing as well as automated test sequences, the RAIT has significantly lowered total time required to test and calibrate a system. This has resulted in an overall lower per unit testing cost than has been achievable in the past.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy