Low density parity check (LDPC) codes are linear block codes constructed by pseudo-random parity check matrices. These codes are powerful in terms of error performance and, especially, have low decoding complexity. While infinite-length LDPC codes approach the capacity of communication channels, finite-length LDPC codes also perform well, and simultaneously meet the delay requirement of many communication applications such as voice and backbone transmissions. Therefore, finite-length LDPC codes are attractive to employ in low-latency communication systems. This thesis mainly focuses on the bandwidth-efficient communication systems using finite-length LDPC codes. Such bandwidth-efficient systems are realized by mapping a group of LDPC coded bits to a symbol of a high-order signal constellation. Depending on the systems' infrastructure and knowledge of the channel state information (CSI), the signal constellations in different coded modulation systems can be two-dimensional multilevel/multiphase constellations or multi-dimensional space-time constellations. In the first part of the thesis, two basic bandwidth-efficient coded modulation systems, namely LDPC coded modulation and multilevel LDPC coded modulation, are investigated for both additive white Gaussian noise (AWGN) and frequency-flat Rayleigh fading channels. The bounds on the bit error rate (BER) performance are derived for these systems based on the maximum likelihood (ML) criterion. The derivation of these bounds relies on the union bounding and combinatoric techniques. In particular, for the LDPC coded modulation, the ML bound is computed from the Hamming distance spectrum of the LDPC code and the Euclidian distance profile of the two-dimensional constellation. For the multilevel LDPC coded modulation, the bound of each decoding stage is obtained for a generalized multilevel coded modulation, where more than one coded bit is considered for level. For both systems, the bounds are confirmed by the simulation results of ML decoding and/or the performance of the ordered-statistic decoding (OSD) and the sum-product decoding. It is demonstrated that these bounds can be efficiently used to evaluate the error performance and select appropriate parameters (such as the code rate, constellation and mapping) for the two communication systems.<p>The second part of the thesis studies bandwidth-efficient LDPC coded systems that employ multiple transmit and multiple receive antennas, i.e., multiple-input multiple-output (MIMO) systems. Two scenarios of CSI availability considered are: (i) the CSI is unknown at both the transmitter and the receiver; (ii) the CSI is known at both the transmitter and the receiver. For the first scenario, LDPC coded unitary space-time modulation systems are most suitable and the ML performance bound is derived for these non-coherent systems. To derive the bound, the summation of chordal distances is obtained and used instead of the Euclidean distances. For the second case of CSI, adaptive LDPC coded MIMO modulation systems are studied, where three adaptive schemes with antenna beamforming and/or antenna selection are investigated and compared in terms of the bandwidth efficiency. For uncoded discrete-rate adaptive modulation, the computation of the bandwidth efficiency shows that the scheme with antenna selection at the transmitter and antenna combining at the receiver performs the best when the number of antennas is small. For adaptive LDPC coded MIMO modulation systems, an achievable threshold of the bandwidth efficiency is also computed from the ML bound of LDPC coded modulation derived in the first part.

Previous work on Chinese idioms has made significant on both meaning derivation process as well as internal combination patterns. As for teaching idioms at junior high schools, recent textbooks encounter three problems: first, there is no appropriate idiom lists; second, teachers rarely mention their syntactic functions and collocational relations; third, students often use idioms in the wrong way. This study aims to investigate syntactic functions of idioms, by examing the learners¡¦ errors. Chap1 clarifies the definition and the characteristics of idioms. Chap2 prosecutes error analysis. Three types of error are identified: semantic errors, grammar errors and semantic restriction errors which are the most frequent type. With regard to the influence of the familiarity and transparency of idioms, idioms that are low familiar and opaque make learning more difficult. After understanding the learning difficulties, chap4 studies syntactic functions and internal construction of idioms. The main construction type is subject-predicate and the most popular function is predicate. We cannot predict the function of an idiom by its construction, and the argument of an idiom doesn¡¦t affect its function neither. However, the core elements of an idiom is correlate with its function. Chap5 explains learners¡¦ difficulties and designs teaching strategies, such as teaching collocation. Moreover, this paper provides two idiom lists, one for junior high school students, the other for advanced learners.

In recent years, there are more and more researches on semi-fragile watermarking scheme which can resist JPEG compression. But, there are few researches focused on the recovery of semi-fragile watermarked image. Therefore, in this paper, we not only present a semi-fragile watermarking scheme which can resist JPEG compression but use the error correction code (Reed-Solomon Code) to recover the area being malicious manipulated. At first, we use the semi-fragile watermarking scheme proposed by Lin and Hsieh to detect the counterfeit under the JPEG compression [9]. Its main effect is to resist JPEG compression and to detect the attacked parts without the need of the original image. And then, we will introduce how we use RS code to recover the attacked parts being detected by the semi-fragile watermarking scheme. We use the scheme ¡§Interleaving¡¨ to spread the local pixels to the global area. Next, we encode to each little image block by RS code. The redundant symbols generated by RS code will be signed to be signature attached with the watermarked image. Finally, the receiver can use semi-fragile watermarking scheme to detect attacked part and use the information of the signature to decode these attacked parts. Additionally, we also discuss how to decrease the load of the signature, thus, it can not significant loading of the watermarked image.

When video transmits over error-prone channels, the fragile property of compressed stream makes it sensitive to bit error. Often even a slight error can make video unable to correctly decode. Therefore, there is a need for a good error control method to solve the problem. This paper presents a novel error detection and concealment strategy along with watermark technique. The proposed watermark-based scheme utilizes two kinds of watermark technique, a fragile watermark is used to detect and localize errors, and a robust watermark is used to reconstruct error areas when errors exist. Experimental results show the proposed watermark-based scheme has good error detection capabilities and complete error recovery information, therefore significant improves video quality after errors happened, especially in the case of higher loss probabilities.

Abstract In the researches of image tracking to restore an object¡¦s position or velocity in the space, it is expectable that increasing numbers of camera can reduce the error. In fact, this phenomenon happens in practical applications. But so far, the physical theory behind this effect has not been fully known. Therefore, based on this motivation, this thesis tends to lay the physical foundation of specific machine vision problem using the statistical probability concept. Extensive error analysis and computer simulation for motion vector of translation movement solved by the least squares technique are conducted by incorporating Gaussian noised into optical flow components. It is expected to provide an effective theoretical model for further developments. Keywords¡GImage tracking, The least squares method, Gauss distribution, Error analysis.

This thesis includes two topics. The first one is the architecture as well as the circuit implementation of an ultra low-power direct digital frequency synthesizer (DDFS) based on the straight line approximation. The second one is the circuit implementation of the low-power DDFS with an error compensation. The proposed approximation technique replaces the conventional ROM-based phase-to-amplitude conversion circuitry and the linear digital-to-analog converter with a nonlinear digital-to-analog converter (DAC) to realize a simple approximation of the sine function. Thus, the overall power dissipation as well as hardware complexity can be significantly reduced. Besides, by adding the error compensation, the spurious-free dynamic range (SFDR) of the synthesized output signal can be raised drastically.

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As the electronic products are gotten smaller and the quantity of output is to be requested, the trend of the needs for speed and accuracy is more precise. Therefore, upgrading the speed and the accuracy of contour error on tracking control has become an important point. This research is focus on the improvement of tracking error and contour error. In tracking error, we propose that the compensation of friction disturbance is by building friction model. And then adaptive robust controller is used to eliminate other disturbance. Finally, velocity feedforward controller is used to improve system dynamic response and to remove the effect of time delay. The combination of such controllers can improve tracking error directly and contour error indirectly. In contour error, we use cross-coupled controller to coordinate the motors and to reform contour error. On the association of such controllers, we propose the design method of cross-coupled controller, to replace the traditional way of try-and-error, and improving contour error again. Finally, the above improving strategies are verified by the simulation and experimental results.

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