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 / Modern telemetry systems require flexible bit rate telemetry encoders in order to optimize mission formats for varying data rate requirements and/or signal to noise conditions given a fixed transmitter power. Implementing a variable bit rate telemetry encoder requires consideration of several possible architectural topologies that place different system requirements on data acquisition modules within the encoder in order to maintain adequate signal fidelity of sensor information. This paper focuses on the requirements, design considerations and tradeoffs associated with differing architectural topologies for implementing a variable bit rate encoder and the resulting implications on the encoder systems data acquisition units.

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper describes a kind of Microwave Digital Frequency Synthesizer used for S-band telemetry receivers. As well known many modern electronic systems employ a Frequency Synthesizer whose spectral purity is critical. The characteristics of a PLL (Phase-Locked Loop) Frequency Synthesizer, such as frequency resolution, phase noise, spurious suppression and switch time, should be compromised in our design. A heterodyne Frequency Synthesis is often considered as a good approach to solve the problem. But it is complicated in structure and circuit. A variable-reference-driven PLL Frequency Synthesizer was introduced which can give an improved trade-off among frequency resolution, phase noise, spurious suppression. In this paper the phase noise and spurious suppression characteristic of variable-reference-driven PLL Frequency Synthesizer is analyzed theoretically and compared with that of the heterodyne Frequency Synthesizer. For engineering application, a practical Microwave Digital Frequency Synthesizer used for telemetry receiver has been designed, which is characterized by simply structure, low phase noise and low spurious output. The output spectrum of experimental measurements is given.

This paper considers four approaches to ordinal predictors in linear regression to evaluate how these contrast with respect to predictive accuracy. The two most typical treatments, namely, dummy coding and classic linear regression on assigned level scores are compared with two improved methods; penalized smoothed coefficients and a generalized additive model with cubic splines. A simulation study is conducted to assess all on the basis of predictive performance. Our results show that the dummy based methods surpass the numeric at low sample sizes. Although, as sample size increases, differences between the methods diminish. Tendencies of overfitting are identified among the dummy methods. We conclude by stating that the choice of method not only ought to be context driven, but done in the light of all characteristics.

Submitted in fulfillment of the requirements for the Master of Engineering Degree, Department of Electronic Engineering, Durban University of Technology, Durban, South Africa, 2016. / The aim of this research project is to design a three phase four quadrant variable speed drive (VSD) for a permanent magnet brushless direct current motor (PMBLDC) that can be applied to an electric bicycle (e-bike). The design is confined to PMBLDC motors with a maximum power rating of 1.5kW. The speed controller operates in current mode at a maximum voltage and current rating of 50V and 30A, respectively. The VSD has the ability to smoothly control the current delivered to the DC motor and therefore controls its torque. The motor’s current is limited in all four quadrants of operation, and its speed is limited in the forward and reverse directions. The performance of the proposed DC motor VSD system is tested on an electric- bicycle. The PMBLDC motor has three hall sensors embedded into the stator to determine rotor position. A phase switcher module interprets the position signals and produces a switching pattern. This effectively transforms the BLDC motor into a direct current (DC) brushed motor. The unipolar switching scheme used ensures that current flows out of the battery only for motoring operation and into the battery during regenerative braking. The current and torque are directly proportional in a BLDC motor. Torque control is achieved in the BLDC motor using a single channel current controller. The phase switcher current is monitored and used to control the duty cycle of the synchronous converter switches. The proposed e-bike speed control system provides efficient control in all four quadrants of operation and it is a suitable alternative for a low cost transportation mode. / M

Along with the general requirement of continuously increasing efficiency of hydrostatic drivetrains, variable displacement machines are of major concern in research and development. To this effect, the whole machine performance is mainly dependent of the displacement variation system (DVS) performance. A lot of work to this topic focusses on the controller and actuator level. The aim of this paper is to offer a more fundamental view on DVS by giving a focus to the basic hydro-mechanical principles.

The floating cup principle is a general hydrostatic principle for both constant and variable displacement pumps and motors, as well as for hydraulic transformers. In this paper, the focus will be entirely on the control of the displacement of the variable 28 cc Floating Cup pump (FCVP28). The floating cup principle features two opposed swash plates, for which both angular positions need to be controlled in order to cover the entire range from zero to full displacement. The results of both extended numerical analysis as well as simplified linearized models will be compared to test results on a 28 cc FCVP. Special emphasis will be on the dynamic behaviour of the displacement control.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / This paper describes the design and characteristics of a digital voice encoding circuit that uses the continuously variable slope delta (CVSD) modulation/demodulation method. With digital voice encoding, the audio signal can be placed into the pulse code modulation (PCM) data stream. Some methods of digitizing voice can require a large amount of bandwidth. Using the CVSD method, an acceptable quality of audio signal is obtained with a minimum of bandwidth. Presently, there is a CVSD microchip commercially available; however, this paper will describe the design of a circuit based on individual components that apply the CVSD method. With the advances in data acquisition technology, increased bit rates, and introduction of a corresponding MIL-STD, CVSD modulated voice will become more utilized in the flight test programs and a good knowledge of CVSD will become increasingly important. This paper will present CVSD theory, supported by graphical investigations of a working circuit under different conditions. Finally, several subjects for further study into CVSD will be addressed.

An explanation of the emission line behavior in cataclysmic variables has been among the most important and elusive problems in eruptive star research. This work expands accretion disk chromosphere models of line emission to predict line behavior qualitatively. A search for UX UMa-like thick disk cataclysmics in the Palomar Green survey sample gave space densities consistent only with luminous high accretion rate disks: Ṁ ≥ 10⁻⁷·⁰Mₒ/yr. Instead, 20 composites whose combined energy distributions were "flat", Fᵥ α ν⁰, were discovered. These typically were early K dwarfs paired with 30,000K subdwarf O stars. The study also showed that a substantial fraction of subdwarf O and B stars are binary. The detached eclipsing binary BE UMa showed a reflection effect emission line spectrum due to the close 7Rₒ separation between an EUV-emitting subdwarf O star and an M1-5 dwarf. Analysis gave the hot star physical parameters as: 80,000K ≤ T(p)(K) ≤ 100,000, 7.0 ≤ log g(p) ≤ 8.0, and log (He/H) = 1.0 ± 1.0. The BE UMa optical emission line spectrum was modeled using a quantitative photoionization-recombination stellar atmosphere-like code. A rich high excitation continuum fluorescence and recombinational spectrum including HeII λ4686 and CIII λ4650 was formed at lower optical depths corresponding to nₑ ≤ 10¹³·⁵ cm⁻³ and Tₑ = 20,000K. The model suggests that T(p) = 100,000K. Cataclysmic variables too have a central source due to loss of half the accretion energy at the white dwarf surface. This temperature is no higher than the innermost disk regions; hence, mass accretion rates determine the character of the EUV radiation. Observations of 13 cataclysmics representing most types were obtained. From these data, the H, HeI, HeII, CaII, and high excitation metal emission line behavior in cataclysmics were analyzed. Cataclysmic variable accretion rates were shown to follow a sequence; from the low excitation dwarf novae [10⁻⁹·⁵ ≤ Ṁ (Mₒ/yr) ≤ 10⁻⁸·⁵] to the high excitation novae and nova-like systems [10⁻⁸·⁵ < Ṁ(Mₒ/yr) ≤ 10⁻⁶·⁵]. Predicted line profiles were consistent with observations. Thus, the model accounts well for the considered observations.

published_or_final_version / Statistics and Actuarial Science / Master / Master of Philosophy

This thesis presents the modeling of tool data produced during ion implantation for the prediction of wafer sheet resistance. In this work, we will use various statistical techniques to address challenges due to the nature of equipment data: high dimensionality, colinearity, parameter interactions, and non-linearities. The emphasis will be data integrity, variable selection, and model building methods. Different variable selection and modeling techniques will be evaluated using an industrial data set. Ion implant processes are fast and depending on the monitoring frequency of the equipment, late detection of a process shift could lead to the loss of a significant amount of product. The main objective of the research presented in this thesis is to identify any ion implant parameters that can be used to formulate a virtual metrology model. The virtual metrology model would then be used for process monitoring to ensure stable processing conditions and consequent yield guarantees. / text