High-frequency financial data are not only discretely sampled in time but the time separating successive observations is often random. We review the paper of Aït-Sahalia and Mykland (2003), that measure the effects of discreteness sampling and ignoring the randomness of the sampling for estimating the m.l.e of a continuous-time diffusion model. In that article, three different assumptions and restrict in one made on the sampling intervals, and the corresponding likelihood function, asymptotic normality, and covariance matrix are obtained. It is concluded that the effects due to discretely sampling are smaller than the effect of simply ignoring the sampling randomness. This study focuses on rechecking the results in the paper of A¡Lıt-Sahalia and Mykland (2003) including theory, simulation and application. We derive a different likelihood function expression from A¡Lıt-Sahalia and Mykland (2003)¡¦s result. However, the asymptotic covariance are consistent for both approaching in the O-U process. Furthermore, we conduct an empirical study on the high frequency transaction time data by using non-homogeneous Poisson Processes.

This thesis investigates the high frequency discharging characteristics of the lithium iron phosphate battery. The investigation focuses on effects of the high-frequency current on the dischargeable capacity of the battery. Included are the current profiles of triangle, saw-tooth, and trapezoidal waves, which are produced from commonly used DC-DC converters. Experimental results show that the current with the higher frequency has less dischargeable capacity. On the other hand, the converter current resonating into and out from the battery results the additional losses. The possible reasons that affect the discharged capacities are explained by the equivalent circuit of the battery.

In this study, a dieless drawing prototype machine has been developed for tube or wire drawing forming. This dieless drawing machine used a high-frequency heating apparatus as the heating source and used stainless steel SUS304 tube as specimens. A series of experiments with different relative speed between heating source and drawing grip were conducted. The moving power is transformed by two servo-motor connecting with screws. Infrared thermoscope and cooling device are setting on the high-frequency heating apparatus to control the temperature of specimen. The forming stability between different relative speed ratio, drawing speed and heating temperature has been discussed. The maximum stable reduction of area obtained can reach over 40 percent , and the drawing speed can be reach to 0.8mm/s. FE analysis was also conducted to analyz the formability of the tube. Then the validity of the analytical model was verified by comparing the uniformity and similarity between FE analysis and experiment value. A series of FE simulation results were used to understand the distribution of true stress and temperature in tube dieless drawing process, tryingand to improve the drawing speed and the reduction of area.

As science advances, computer technologies are developing rapidly in the past decades. The previous way of traders¡¦ yelling for orders in the house of exchange has been replaced by the Internet and computers. The trading modes of institutional investors are transforming gradually, particularly the radical changes in the US stock market for the past 5 years. The transaction volume from high frequency trading and algorithmic trading is growing dramatically per year, accounting for at least 70% in the U.S. market. And many researchers find these trading methods based on the computer programs good in increasing liquidity, reducing volatility and facilitating price discovery. By using intraday data of Taiwan stock market in 2008 to conduct empirical research, this study intends to analyze the effect of this trend on the TW stock market. Empirical results found that the greater the market capitalization, liquidity, stock volatility are, the higher the proportion of algorithmic trading will be, but which only exists in foreign institutional investors. On the other hand, the increase of the proportion of algorithmic trading can improve liquidity, meanwhile raise the volatility. The conclusion remains unchanged when applied to control the effect of financial tsunami. That means algorithmic trader¡¦s behaviors are not always positive. This result could be related to the special transaction mechanism or lower competition of algorithmic trading in Taiwan. As to trading strategy, the result found that foreign institutional investors focus on momentum strategies, whereas particular dealers act for the sake of index arbitrage or hedge. In summary, the algorithmic trader¡¦s transaction bears positive (liquidity) and negative (volatility) impact on the market at the same time. For individual investors, algorithmic trading¡¦s momentum strategy could appeal to them, but they may not make a profit from these trades, because this strategy could merely want to pull price higher and sell stock or the opposite. About regulators, algorithmic traders¡¦ behavior should be regulated partly; regulatory authorities might also consider adding the circuit mechanism similar to South Koreas¡¦, especially on the program trading. Keywords: algorithmic trading, high frequency trading, intraday, strategy, liquidity, volatility, market quality

It is of utmost importance for learners to master language in order to learn effectively at school. Problems in language development can cause learning problems that have negative results for the learner. Language consists mainly of the spoken language (listening and speaking), reading and writing. These three aspects of language form an integrated unit so that a problem with one will influence the others. Learners are initially taught in school to read and write. Learners should later be able to use acquired reading skills to learn, and acquired writing skills must be applied to reproduce that which has been learnt. If learners do not master the foregoing skills, their progress at school will be seriously handicapped. A further aggravating factor within the milieu of the South African education system is the complicated socio-political history of the country that created a large number of disadvantaged schools. A Report by the Ministerial Committee on Education in Disadvantaged Areas (2005:10, 43) emphasises the needs and skills of learners; training, dedication and competencies of teachers; as well as the importance of instructional media in disadvantaged areas. In spite of the implementation of the National Curriculum Statement Grade R-9 (Schools) and Grade 10-12 (Schools), illiteracy is still a serious problem in South Africa. Because the basis of all reading and writing skills are laid in the Foundation Phase, it is necessary for drastic steps to be taken to ensure that learners will be able to read with comprehension in their first years at school. This research is aimed at proving the significant relationship between high frequency words and reading skills (measured by word recognition and reading comprehension) and also improving the reading skills of learners by the acquisition of high frequency words. An effort has also been made to meet the requirements of the core elements for good teaching/instruction. To achieve this objective, the focus of this study is binary. In the first phase the researcher determines if there is a significant relationship between the visual recognition of the high frequency words and reading skills (measured by visual word recognition and reading comprehension) of learners in the Foundation Phase (Grade 2). After completion of Phase 1 it was determined that there is a correlation between the visual recognition of high frequency words and the reading skills (measured by visual word recognition and reading comprehension) of learners in the Foundation Phase (Grade 2). After the successful completion of Phase 1 the focus shifts to the study of Phase 2. In Phase 2 the researcher makes a contribution to the instruction/teaching milieu and meets the requirements of the stated criteria to ensure good instruction/teaching as determined by the Report of the Ministerial Committee on Education in Disadvantaged Areas (2005:10, 43). This contribution is made through the designing of a reading instruction programme that is aimed at the improvement of reading skills (measured by visual word recognition and reading comprehension) of learners in the Foundation Phase. The focus of this Reading Instruction Programme is the acquisition of the first 100 high frequency words as they appear in Aucamp's list (1932: 79 - 80). The gathering/collection of data in both phases is characterised by the use of standardised tests. In Phase 1 use was made of descriptive statistics; Pearson's product moment correlations and Cohen's r-values; t-tests and Cohen's d-values; as well as one sample t-tests to analyse and interpret data. In Phase 2 pre- and post-tests were used. Statistical techniques used during the analysis reporting and interpretation of data in Phase 2 are descriptive statistics; Wilcoxon rank sum tests; one-way covariance analysis; Wilcoxon symmetry-tests, and Cohen's d-values. This study contributes to the education milieu when it proves that the instruction of high frequency words by means of this Reading Instruction Programme leads to the improvement of the reading skills (measured byword recognition and reading comprehension) of learners in Grade 3. The Reading Instruction Programme is based on a balanced reading approach in which the main components of reading integrated with high frequency words are instructed. This instruction is characterised among others by direct, explicit instruction; multi-sensory methods; the use of high quality instructional media; and the automatisation of high frequency words. The Reading Instruction Programme is based on the behaviouristic and cognitive learning theories as well as the transactional reading theory. / Thesis (Ph.D. (Education))--North-West University, Potchefstroom Campus, 2009.

Affine term structure models (ATSMs) are known to have a trade-off in predicting future Treasury yields and fitting the time-varying volatility of interest rates. First, I empirically study the role of macroeconomic variables in simultaneously achieving these two goals under affine models. To this end, I incorporate a liquidity demand theory via a measure of the velocity of money into affine models. I find that this considerably reduces the statistical tension between matching the first and second moments of interest rates. In terms of forecasting yields, the models with the velocity of money outperform among the ATSMs examined, including those with inflation and real activity. My result is robust across maturities, forecasting horizons, risk price specifications, and the number of latent factors. Next, I incorporate latent macro factors and the spread factor between the short-term Treasury yield and the federal funds rate into an affine term structure model by imposing cross-equation restrictions from no-arbitrage using daily data. In doing so, I identify the highfrequency monetary policy rule that describes the central bank's reaction to expected inflation and real activity at daily frequency. I find that my affine model with macro factors and the spread factor shows better forecasting performance.

Electromagnetic wave scattering from a semi-infinite array of dipoles in free space is described by using asymptotic high frequency methods. An electric field integral expression is obtained and solved with asymptotic high frequency methods. An asymptotic field expression is obtained for a finite &times / infinite array of dipoles in free space. The analytical closed form expression for the array guided surface wave launching coefficient is obtained via a combination of an asymptotic high frequency analysis of a related reciprocal problem and Lorentz reciprocity integral formulation for the semi-infinite planar dipole array in which modified Kirchhoff approximation is used. The accuracy and the validity of the asymptotic analytical solutions are compared with the numerical solutions available in the literature before.

­^¤åºK­n Electro-optic probing techniques are advancing rapidly in recent years. These techniques have been proven to be an effective tool in parameter extraction of semiconductor devices such as response time, delay time as well as scattering parameters. Not only the magnitude of the electric field but also the direction of the corresponding E-field direction are measured in several developed electro-optic probing system. By incorporated these techniques, the near-field electric field vectors can be estimated and they are valuable information for the analysis of RF circuit devices, e.g., micro-strip transmission line, patch antenna, etc. When probing the 2-D E-field vectors, one can only measure 1-D E-field direction, then rotate the device under test by 90¢X for another orthogonal tangential E-field direction. However the process not only reduces the probing accuracy but also increases the time interval for achieving measurement and lead to obstacles in use. In the thesis, 2D E-field can be obtained without rotating the DUT by using two kinds of modulation schemes, i.e., compressed/stretched deformation modulation(CSDM) and rotational deformation modulation(RDM). These novel techniques provide a total solution for the above bottleneck and improve the sensitivity for different E-field direction. Besides, a heterodyne method is developed to measure the high frequency near-field 2D E-field distribution. By the heterodyne method, the EO probing system can incorporate the CW laser instead of the pulse laser for reducing the cost and enhancing the merits when applied.

Recently, matrix converter has received considerable interest as a viable alternative to the conventional back-to-back PWM (Pulse Width Modulation) converter in the ac/ac conversion. This direct ac/ac converter provides some attractive characteristics such as: inherent four-quadrant operation; absence of bulky dc-link electrolytic capacitors; clean input power characteristics and increased power density. However, industrial application of the converter is still limited because of some practical issues such as common mode voltage effects, high susceptibility to input power disturbances and low voltage transfer ratio. This dissertation proposes several new matrix converter topologies together with control strategies to provide a solution about the above issues. In this dissertation, a new modulation method which reduces the common mode voltage at the matrix converter is first proposed. The new method utilizes the proper zero vector selection and placement within a sampling period and results in the reduction of the common mode voltage, square rms of ripple components of input current and switching losses. Due to the absence of a dc-link, matrix converter powered ac drivers suffer from input voltage disturbances. This dissertation proposes a new ride-through approach to improve robustness for input voltage disturbances. The conventional matrix converter is modified with the addition of ride-through module and the add-on module provides ride-through capability for matrix converter fed adjustable speed drivers. In order to increase the inherent low voltage transfer ratio of the matrix converter, a new three-phase high-frequency link matrix converter is proposed, where a dual bridge matrix converter is modified by adding a high-frequency transformer into dc-link. The new converter provides flexible voltage transfer ratio and galvanic isolation between input and output ac sources. Finally, the matrix converter concept is extended to dc/ac conversion from ac/ac conversion. The new dc/ac direct converter consists of soft switching full bridge dc/dc converter and three phase voltage source inverter without dc link capacitors. Both converters are synchronized for zero current/voltage switching and result in higher efficiency and lower EMI (Electro Magnetic Interference) throughout the whole load range. Analysis, design example and experimental results are detailed for each proposed topology.

In this dissertation, new high frequency link power conversion systems for the fuel cell power conditioning are proposed to improve the performance and optimize the cost, size, and weight of the power conversion systems. The first study proposes a new soft switching technique for the phase-shift controlled bi-directional dc-dc converter. The described dc-dc converter employs a low profile high frequency transformer and two active full-bridge converters for bidirectional power flow capability. The proposed new soft switching technique guarantees soft switching over wide range from no load to full load without any additional circuit components. The load range for proposed soft switching technique is analyzed by mathematical approach with equivalent circuits and verified by experiments. The second study describes a boost converter cascaded high frequency link direct dc-ac converter suitable for fuel cell power sources. A new multi-loop control for a boost converter to reduce the low frequency input current harmonics drawn from the fuel cell is proposed, and a new PWM technique for the cycloconverter at the secondary to reject the low order harmonics in the output voltages is presented. The performance of the proposed scheme is verified by the various simulations and experiments, and their trade-offs are described in detail using mathematical evaluation approach. The third study proposes a current-fed high frequency link direct dc-ac converter suitable for residential fuel cell power systems. The high frequency full-bridge inverter at the primary generates sinusoidally PWM modulated current pulses with zero current switching (ZCS), and the cycloconverter at the secondary which consists of only two bidirectional switches and output filter capacitors produces sinusoidally modulated 60Hz split single phase output voltage waveforms with near zero current switching. The active harmonic filter connected to the input terminal compensates the low order input current harmonics drawn from the fuel cell without long-term energy storage devices such as batteries and super capacitors.