NBG–18 graphite is developed by SGL Carbon for the Pebble Bed Modular Reactor Company (PBMR), and is used as the preferred material for the internal graphite core structures of a high–temperature gas–cooled nuclear reactor (HTR). The NBG–18 graphite is manufactured using pitch coke, and is vibrationally molded. To assess the structural behaviour of graphite many destructive techniques have been performed in the past. Though the destructive techniques are easy and in some cases relative inexpensive to perform, these methods lead to waste material and require cumbersome time consuming sample preparations. To overcome this problem numerous non–destructive testing techniques are available such as sonic resonance, resonant inspection, ultrasonic testing, low and multifrequency Eddy current analysis, acoustic emission and impulse excitation techniques. The Hammer Impulse Excitation technique was used as a method in predicting the fatigue life of NBG–18 graphite by focussing on the application of modal frequency analysis of determined natural frequencies. Moreover, the typical fatigue characteristics of NBG–18 graphite were determined across a comprehensive set of load ranges. In order to be able to correlate modal frequency parameters with fatigue life, suitable uniaxial fatigue test specimen geometry needed to be obtained. The uniaxial fatigue test specimens were manufactured from two NBG–18 graphite sample blocks. The relationship between natural frequencies of uniaxial test specimens, fatigue life, sample positioning and sample orientation was investigated for different principle stress ratios. Load ratios R = –oo and R = +2 tested proved to show the highest r–values for the Pearson correlation coefficients investigated. However, there was no significant trend found between the natural frequency and the fatigue life. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

Impulse buying or unplanned purchases by consumers constitute a major proportion of purchases in certain product categories. Studies in the United States widely reported that impulse consumer buying behaviour accounts for up to 80% of all purchases in certain product categories, and it has been suggested that purchases of new products result more from impulse purchasing than from prior planning. South Africa is a nation of shoppers with increasing numbers defined as impulse buyers who respond to glossy adverts such as „never to be beaten bargains‟ and „buy one get one free‟. Culture has a profound effect on why people buy. Culture affects the specific products people buy as well as the structures of consumption, individual decision-making and communication in a society. Since South Africa has quite a diverse group of different cultures, it has been of great importance to determine whether cultural differences had an influence on impulsive buying behaviour. The primary research objective was to assess the influence of different cultures on consumer impulsive buying behaviour of students. The findings of this research study did not clearly indicate if culture had an effect on students‟ impulsive buying behaviour. / Thesis (M.Com. (Business Management))--North-West University, Vaal Triangle Campus, 2011

Impulse buying or unplanned purchases by consumers constitute a major proportion of purchases in certain product categories. Studies in the United States widely reported that impulse consumer buying behaviour accounts for up to 80% of all purchases in certain product categories, and it has been suggested that purchases of new products result more from impulse purchasing than from prior planning. South Africa is a nation of shoppers with increasing numbers defined as impulse buyers who respond to glossy adverts such as „never to be beaten bargains‟ and „buy one get one free‟. Culture has a profound effect on why people buy. Culture affects the specific products people buy as well as the structures of consumption, individual decision-making and communication in a society. Since South Africa has quite a diverse group of different cultures, it has been of great importance to determine whether cultural differences had an influence on impulsive buying behaviour. The primary research objective was to assess the influence of different cultures on consumer impulsive buying behaviour of students. The findings of this research study did not clearly indicate if culture had an effect on students‟ impulsive buying behaviour. / Thesis (M.Com. (Business Management))--North-West University, Vaal Triangle Campus, 2011

NBG–18 graphite is developed by SGL Carbon for the Pebble Bed Modular Reactor Company (PBMR), and is used as the preferred material for the internal graphite core structures of a high–temperature gas–cooled nuclear reactor (HTR). The NBG–18 graphite is manufactured using pitch coke, and is vibrationally molded. To assess the structural behaviour of graphite many destructive techniques have been performed in the past. Though the destructive techniques are easy and in some cases relative inexpensive to perform, these methods lead to waste material and require cumbersome time consuming sample preparations. To overcome this problem numerous non–destructive testing techniques are available such as sonic resonance, resonant inspection, ultrasonic testing, low and multifrequency Eddy current analysis, acoustic emission and impulse excitation techniques. The Hammer Impulse Excitation technique was used as a method in predicting the fatigue life of NBG–18 graphite by focussing on the application of modal frequency analysis of determined natural frequencies. Moreover, the typical fatigue characteristics of NBG–18 graphite were determined across a comprehensive set of load ranges. In order to be able to correlate modal frequency parameters with fatigue life, suitable uniaxial fatigue test specimen geometry needed to be obtained. The uniaxial fatigue test specimens were manufactured from two NBG–18 graphite sample blocks. The relationship between natural frequencies of uniaxial test specimens, fatigue life, sample positioning and sample orientation was investigated for different principle stress ratios. Load ratios R = –oo and R = +2 tested proved to show the highest r–values for the Pearson correlation coefficients investigated. However, there was no significant trend found between the natural frequency and the fatigue life. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

This thesis presents a spatial sound rendering system for the use in immersive virtual environments. Spatial sound rendering aims at artificially reproducing the acoustics of a space. It has many applications such as music production, movies, electronic gaming and teleconferencing. Conventionally, spatial sound rendering is implemented by digital signal processing algorithms derived from perceptual models or simplified physical models. While being flexible and/or efficient, these models are not able to capture the acoustical impression of a space faithfully. On the other side, convolving the sound sources with properly measured impulse responses produces the highest possible fidelity, but it is not practically useful for many applications because one impulse response corresponds to one source/listener configuration so that the sources or the listeners can not be relocated. In this thesis, techniques for measuring multichannel room impulse responses (MMRIR) are reviewed. Then, methods for analyzing measured MMRIR and rendering virtual acoustical environment based on such analysis are presented and evaluated. The analysis can be performed off-line. During this stage, a set of filters that represent the characteristics of the air and walls inside the acoustic space are obtained. Based on the assumption that the MMRIR acquired at one "good" position in the target space can be used to simulate the late reverb at other positions in the same space, appropriate segments that can be used as reverb tails are extracted from the measured MMRIR. The rendering system first constructs an early reflection model based on the positions of the listener-source pair and the filters derived, then combines with the late reverb segments to form a complete listener-source-room acoustical model that can be used to synthesize high quality multi-channel audio for arbitrary listener-source positions. Another merit of the proposed framework is that it is scalable. At the expense of slightly degraded rendering quality, the computational complexity can be greatly reduced. This makes this framework suitable for a wide range of applications that have different quality and complexity requirements. The proposed framework has been evaluated by formal listening tests. These tests have proven the effectiveness in preserving the spatial quality while positioning the listener-source pair accurately, as well as justified the key assumptions made by the proposed system.

No description available.

In this thesis, we investigate Sturmian comparison theory and oscillation for second order impulsive differential equations with fixed moments of impulse actions. It is shown that impulse actions may greatly alter the oscillation behavior of solutions. In chapter two, besides Sturmian type comparison results, we give Leightonian type comparison theorems and obtain Wirtinger type inequalities for linear, half-linear and non-selfadjoint equations. We present analogous results for forced super linear and super half-linear equations with damping. In chapter three, we derive sufficient conditions for oscillation of nonlinear equations. Integral averaging, function averaging techniques as well as interval criteria for oscillation are discussed. Oscillation criteria for solutions of impulsive Hill&amp / #8217 / s equation with damping and forced linear equations with damping are established.

In this thesis work, a new partial discharge magnitude indicator with LCD display was designed. This system was implemented in high voltage partial discharge detection and measurement systems. AVRISP In-System programmer is used to program the microprocessors used inside the display unit. The time resolution of the system (one pixel of the display unit) is 4 microseconds. The unit is capable of counting the number of impulses of the input voltage that is coming from the high voltage system within user selectable time intervals. The changeable values of the time intervals are 2, 4, 6, 8 and 10 seconds. It is also capable of showing the maximum value of the impulses in a given time interval. This maximum value is a number changing between 0 and 256. By calibration of the system, it was possible to indicate the discharge magnitudes in picocoulombs.

Thesis (M.S.)--State University of New York at Binghamton, Department of Psychology, 2007. / Includes bibliographical references.

Thesis (Ph.D.); Submitted to New Mexico State Univ., Las Cruces, NM (US); 1 May 2003. / Published through the Information Bridge: DOE Scientific and Technical Information. "JLAB-PHY-03-22" "DOE/ER/40150-2731" David McKee. 05/01/2003. Report is also available in paper and microfiche from NTIS.