Compared with Nd:YAG, the traditional high power solid state laser gain medium, Yb:YAG has less quantum defect, no excited state absorption, and longer fluorescence lifetime, which makes it suitable for Q-switched laser. In addition, concentration quenching is absent in Yb:YAG, higher concentration of active ion makes the thickness of gain medium thinner. For ring cavities, the necessity of symmetrical beam path is important, a thinner Yb:YAG crystal can reduce the shift of optical beam path and avoids cavity unstability. Thus, Yb:YAG is suitable for the two-mirror ring cavity. In this study, a compact and efficient Yb:YAG ring laser with 50.3% slope efficiency was demonstrated. And the Yb:YAG ring laser performances influenced by thermal effect was analyzed and compared to that of Nd:YAG ring laser. The polarization of ring lasers with different configurations were also discussed. In manufacturing process, the coating design on gain medium and laser mirrors were introduced. The advantages of passively Q-switched laser are efficient, compact, simple setup and no complicated driving circuits. They make passively Q-switched laser suitable for various applications, such as nonlinear optics, medical treatment, micromachining, material processing, and range finder. Due to spontaneous noise from the gain medium, conventional passively Q-switched laser has large timing jitter. This study is to build up a passively Q-switched Yb:YAG/Cr4+:YAG ring laser with lower timing jitter. At present, a Q-switched ring laser with a peak power of 208 W and a pulse width of 33 ns, was developed. Its slope efficiency is 18.1% with a timing jitter of 11.9%. To our knowledge, this is the first passively Q-switched Yb:YAG/Cr4+:YAG ring laser.

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In the last few years, it has been proved that the movements of financial asset have the property of non-linearity and show some tendency within a given period. Increasing evidence that technical trading rules can detect non-linearity in financial time series has renewed interest in technical analysis. This study evaluates the market timing ability of the moving average trading rules in twelve equity markets in the developed markets and the emerging markets from January 1990 through Match 2002. We use traditional test, bootstrap p-value test, Cumby-Modest¡¦s market timing ability test and simulation stock trade to evaluate market timing ability. The overall results indicate that the moving average trading rules have predictive ability with respect to market indices in the Asia emerging stock markets. These findings may provide investors with important asset allocation information.

The purpose of this thesis is to derive and analyze the theoretical limits for estimatingthe symboltiming delayof Multiple-Input Multiple-Output (MIMO)systems. Two main N X M system models are considered, where N represents the number of transmit antennas and M denotes the number of receive antennas, the 2 X 2 system used by S.-A. Yangand J. Wu and the 4 X 4system used by Y.-C. Wu and E. Serpedin. The second model has been extended to take into account the symbol time-varying fading. The theoretical estimation limits are shown by several bounds: modified Cramer-Rao bound (MCRB), Cramer-Rao bound (CRB) and Barankin bound (BB). BB will be exploited to obtain accurate information regarding the necessary length of data to obtain good estimation. Two scenarios for synchronization are presented: data-aided (DA) and non-data-aided (NDA). Two models for the fading process are considered: block fading and symbol time-varying fading, respectively, the second case being assumed to be Rayleigh distributed. The asymptotic Cramer-Rao bounds for low signal-to-noise ratio (low-SNR) and for high-SNR are derived and the performance of several estimators is presented. The performance variation of bounds and estimators is studied byvarying different parameters, such as the number of antennas, the length of data taken into consideration during the estimation process, the SNR, the oversampling factor, the power and the Doppler frequency shift of the fading.

In this dissertation, the problem of symbol timing synchronization for the following three different communication systems is studied: 1) conventional single-carrier transmissions with single antenna in both transmitter and receiver; 2) single-carrier transmissions with multiple antennas at both transmitter and receiver; and 3) orthogonal frequency division multiplexing (OFDM) based IEEE 802.11a wireless local area networks (WLANs). For conventional single-carrier, single-antenna systems, a general feedforward symbol-timing estimation framework is developed based on the conditional maximum likelihood principle. The proposed algorithm is applied to linear modulations and two commonly used continuous phase modulations: MSK and GMSK. The performance of the proposed estimator is analyzed analytically and via simulations. Moreover, using the newly developed general estimation framework, all the previously proposed digital blind feedforward symbol timing estimators employing second-order statistics are cast into a unified framework. The finite sample mean-square error expression for this class of estimators is established and the best estimators are determined. Simulation results are presented to corroborate the analytical results. Moving on to single-carrier, multiple-antenna systems, we present two algorithms. The first algorithm is based on a heuristic argument and it improves the optimum sample selection algorithm by Naguib et al. so that accurate timing estimates can be obtained even if the oversampling ratio is small. The performance of the proposed algorithm is analyzed both analytically and via simulations. The second algorithm is based on the maximum likelihood principle. The data aided (DA) and non-data aided (NDA) ML symbol timing estimators and their cor- responding CCRB and MCRB in MIMO correlated ??at-fading channels are derived. It is shown that the improved algorithm developed based on the heuristic argument is just a special case of the DA ML estimator. Simulation results under different operating conditions are given to assess and compare the performances of the DA and NDA ML estimators with respect to their corresponding CCRBs and MCRBs. In the last part of this dissertation, the ML timing synchronizer for IEEE 802.11a WLANs on frequency-selective fading channels is developed. The proposed algorithm is compared with four of the most representative timing synchronization algorithms, one specically designed for IEEE 802.11a WLANs and three other algorithms designed for general OFDM frame synchronization.

This thesis analyzes the timing issue related to informed trades under two different market frameworks. Firstly, the issue under the competitive market framework is analyzed. In financial market, a widely accepted assumption that competitive informed traders elect to trade immediately upon receiving their private information is now questioned. We propose a competitive rational expectations model to demonstrate that under some situations informed traders tend to trade late on their information because of the fear of adverse effect on prices from their informed trades. This phenomenon from delayed informed trades leads to the following: Price volatility will increase and adjacent price changes may exhibit positive serial correlation. Secondly, we turn to the alternative framework, i.e., a market microstructure framework. A large number of market microstructure models had already investigated the timing issue of informed trades. Most of them found that the competition among informed traders will make the informed traders incline to trade early than late on their information and the market therefore becomes more efficient. We develop a market microstructure model with competitive, risk averse informed traders and uninformed market makers. It is found that when the mass of informed traders is larger or the precision of private information is higher, the market becomes less efficient, that is, prices will delay revealing the private information and the market will postpone becoming liquid. Our results stand in contrast to those of other market microstructure models simply because informed traders in our model choose to trade late on their information. In conclusion, the thesis has proved that the timing to trade on their information is an important consideration for informed traders to determine their trading strategy maximizing their expected utility. Since this issue is seldom discussed in the previous literature, I deeply believe that there are many works to be done followed this work.

A circuit design of Fast Fourier Transform for DVB-H system is presented in this thesis. This circuit is based on SDF (single path delay feedback) pipeline architecture with radix-2 computation element. We propose a novel method of timing scheduling that can share one complex multiplier for couple of stage and promote the utilization of complex multiplier to 100%, so we can improve the implementation with radix-2 computation. The number of bits is carefully selected by system simulation to meetthe requirements of DVB-H system. In addition, a memory table permutation deletion method for memory scheduling, which can reduce the size of memory storing twiddle factors tables. The circuit is carried out by CMOS 0.18£gm 1P6M process with core area 2.08 x 2.076 mm2. In the gate level simulation, the output data rate of this circuit is above 50MHz, so the circuit can meet the requirement of DVB-H system.

In standard models of informed trading, they implicitly assume that all informed traders receive their information at the same time and then trade on their private information immediately, whether competitive or imperfect competitive¡]strategic¡^rational expectations model, differing on the speed of information revelation. In reality, the informed traders may quietly and skillfully perform noninformational trading to accumulate their ¡§line¡¨ cheaply. In this paper, we develop the multiperiod competitive rational expectations model with asymmetric information to show, under some conditions, delaying their informed trades is in the interests of informed traders; then we explore the implications of our model for the behavior of stock price, especially we find that, delaying the informed trades may increase price volatility and display the momentum effect, consistent with the empirical results.

We study timing effects of carbon mitigation and solar radiation management (SRM) policies for correlated pollutants, CO₂ and SO₂. We show that national levels of carbon and sulfur emissions quotas and SRM implementation are positively correlated with each other. First-mover advantages exist when deciding both carbon quotas and SRM levels. Moreover, we use an example to illustrate that if international equity is considered, governments would be willing to choose SRM levels before carbon quotas since it yields higher payoffs and less acid rain and droughts damages. This timing was neglected by all previous theoretical economic models on geoengineering.

<p>The development of fuel efficient internal combustion engines (ICE)have resulted in a variety of different solutions. One of those are the variable valve timing and an implemenation of such is the Continuous Variable Cam Phasing (CVCP). This thesis have used a simulation package, psPack, for the simulation of the gas exchange process for an ICE with CVCP. The purpose of the simulations was to investigate what kind of design parameters, e.g. the length of an intake pipe or the duration of combustion, that were significant for the gas exchange process with the alternation of intake pressure, engine speed and valve setting. The parameters that showed a vast impact were those who affected the amount of residual gas and the temperature of the air charge. Furthermore a validation was made between simulation data acquired from psPack and measured data provided in Heywood (1988). The validation showed that for the general behaviour the simulation results from psPack corresponded well to the measured data.</p>