<p>An analog-to-digital converter (ADC) is a link between the analog and digital domains and plays a vital role in modern mixed signal processing systems. There are several architectures, for example flash ADCs, pipeline ADCs, sigma delta ADCs,successive approximation (SAR) ADCs and time interleaved ADCs. Among the various architectures, the pipeline ADC offers a favorable trade-off between speed,power consumption, resolution, and design effort. The commonly used applications of pipeline ADCs include high quality video systems, radio base stations,Ethernet, cable modems and high performance digital communication systems.Unfortunately, static errors like comparators offset errors, capacitors mismatch errors and gain errors degrade the performance of the pipeline ADC. Hence, there is need for accuracy enhancement techniques. The conventional way to overcome these mentioned errors is to calibrate the pipeline ADC after fabrication, the so-called post fabrication calibration techniques. But environmental changes like temperature and device aging necessitates the recalibration after regular intervals of time, resulting in a loss of time and money. A lot of effort can be saved if the digital outputs of the pipeline ADC can be used for the estimation and correctionof these errors, further classified as foreground and background techniques. In this thesis work, an algorithm is proposed that can estimate 10% inter stage gain errors in pipeline ADC without any need for a special calibration signal. The efficiency of the proposed algorithm is investigated on an 8-bit pipeline ADC architecture.The first seven stages are implemented using the 1.5-bit/stage architecture whilethe last stage is a one-bit flash ADC. The ADC and error correction algorithms simulated in Matlab and the signal to noise and distortion ratio (SNDR) is calculated to evaluate its efficiency.</p>

<p>As the rapid development of the wireless communication system and mobile video devices, the integrated chip with low power consuming and high conversion efficiency is widely needed. ADC and DAC are playing an important role in these applications.</p><p>The aim of this thesis is to verify a post-correction method which is used for improving the performance of ADC. First of all, this report introduces the development and present status of ADC, and expatiate its important parameters from two different classes (static performance and dynamic performance). Based on the fundamental principle, the report then focuses on the dynamic integral non-linearity modeling of ADC. Refer to this model, one post-correction method is described and verified.</p><p>Upon the face of post-correction, this method is to modify the output signals which have been converted from analog to digital format by adding a correction term. Improvement made by the post-correction needs to be checked out. Thus the performance analysis mainly relay on the measures of total harmonic distortion and signal to noise and distortion ratio is also included in this thesis.</p>

<p>For marine sciences sometimes there is a need to perform underwater photography. Optical properties of light cause severe quality problems for underwater photography. Light of different energies is absorbed at highly different rates under water causing significant bluishness of the images. If the colour dependent attenuation under water can be properly estimated it should be possible to use computerised image processing to colour correct digital images using Beer’s Law.</p><p>In this thesis we have developed such estimation and correction methods that have become progressively more complicated and more accurate giving successively better correction results. A process of estimation of downwelling attenuation coefficients from multi or hyper spectral data is a basis for automatic colour restoration of underwater taken images. The results indicate that for each diving site the unique and precise coefficients can be obtained.</p><p>All standard digital cameras have built in white balancing and colour enhancement functions designed to make the images as aesthetically pleasing as possible. These functions can in most cameras not be switched off and the algorithms used are proprietary and undocumented. However, these enhancement functions can be estimated. Applying their reverse creates un-enhanced images and we show that our algorithms for underwater colour correction works significantly better when applied to such images.</p><p>Finally, we have developed a method that uses point spectra from the spectrometer together with RGB colour images from a camera to generate pseudo-hyper-spectral images. Each of these can then be colour corrected. Finally, the images can be weighted together in the proportions needed to create new correct RGB images. This method is somewhat computationally demanding but gives very encouraging results.</p><p>The algorithms and applications presented in this thesis show that automatic colour correction of underwater images can increase the credibility of data taken underwater for marine scientific purposes.</p>

<p>In this thesis I study the German housing market and specifically the level of housing investment. First, a theoretical background to housing market dynamics is presented and then I test whether there is a relationship between housing investments and GDP, the size of the population, Tobin’s Q and construction costs. An Error Correction Model is estimated and the result is that the equilibrium level of housing investment is restored after less then two quarters after a change in one of the explainable variables. The estimation indicates that GDP, the size of the population and construction costs affect the level of construction in the short run. However, in the long run the only significant effect is changes in construction cost.</p>

The accuracy issue of a rapid prototyping-direct laser sintering system is studied in this paper. The sources of errors are analyzed for their contribution to the final accuracy of built parts. The error sources are related to the hardware and software of the machine, the materials and the process. Special measures were exploited to improve the accuracy of the direct laser sintering system and process. For the errors caused by hardware like laser scanner, compensation by software was developed to correct the errors resulting from galvano-mirrors and F-θ lens. A compensation function mode was added to the slicing software to compensate the errors caused by material shrinkage and laser beam offset. Based on the analysis and improvement, a desired accuracy of 0.2mm has been achieved for the direct laser sintering system, which was verified by experiments. / Singapore-MIT Alliance (SMA)

This thesis reports the methods to simulate flows withcomplex boundary such as orifice flow. The method is forgeneral purposes so that it has been tested on different flowsincluding orifice flow. Also it contains a chapter about theexperiment of orifice flow. Higher-order precision interpolation schemes are used inumerical simulation to improve prediction at acceptable gridrefinement. Because higher-order schemes cause instability inconvection-diffusion problems or involve a large computationalkernel, they are implemented with deferred correction method. Alower-order scheme such as upwind numerical scheme is used tomake preliminary guess. A deferred (defect) correction term isadded to maintain precision. This avoids the conflict betweenprecision order and implementation difficulty. The authorproposes a shifting between upwind scheme and centraldifference scheme for the preliminary guess. This has beenproven to improve convergence while higher order schemes havewider range of stability. Non-orthogonal grid is a necessity for complex flow. Usuallyone can map coordinate of such a grid to a transformed domainwhere the grid is regular. The cost is that differentialequations get much more complex form. If calculated directly innon-orthogonal grid, the equations keep simple forms. However,it is difficult to make interpolation in a non-orthogonal grid.Three methods can be used: local correction, shape function andcurvilinear interpolation. The local correction method cannotinsure second-order precision. The shape function method uses alarge computational molecule. The curvilinear interpolationthis author proposes imports the advantage of coordinatetransformation method: easy to do interpolation. A coordinatesystem staggered half control volume used in the coordinatetransformation method is used as accessory to deriveinterpolation schemes. The calculation in physical domain withnon-orthogonal grid becomes as easy as that in a Cartesianorthogonal grid. The author applies this method to calculate turbulentorifice flow. The usual under-prediction of eddy length isimproved with the ULTRA-QUICK scheme to reflect the highgradients in orifice flow. In the last chapter, the author quantifies hydraulicabruptness to describe orifice geometry. The abruptness canhelp engineers to interpolate existing data to a new orifice,which saves detailed experiments

For marine sciences sometimes there is a need to perform underwater photography. Optical properties of light cause severe quality problems for underwater photography. Light of different energies is absorbed at highly different rates under water causing significant bluishness of the images. If the colour dependent attenuation under water can be properly estimated it should be possible to use computerised image processing to colour correct digital images using Beer’s Law. In this thesis we have developed such estimation and correction methods that have become progressively more complicated and more accurate giving successively better correction results. A process of estimation of downwelling attenuation coefficients from multi or hyper spectral data is a basis for automatic colour restoration of underwater taken images. The results indicate that for each diving site the unique and precise coefficients can be obtained. All standard digital cameras have built in white balancing and colour enhancement functions designed to make the images as aesthetically pleasing as possible. These functions can in most cameras not be switched off and the algorithms used are proprietary and undocumented. However, these enhancement functions can be estimated. Applying their reverse creates un-enhanced images and we show that our algorithms for underwater colour correction works significantly better when applied to such images. Finally, we have developed a method that uses point spectra from the spectrometer together with RGB colour images from a camera to generate pseudo-hyper-spectral images. Each of these can then be colour corrected. Finally, the images can be weighted together in the proportions needed to create new correct RGB images. This method is somewhat computationally demanding but gives very encouraging results. The algorithms and applications presented in this thesis show that automatic colour correction of underwater images can increase the credibility of data taken underwater for marine scientific purposes.

If there is currency substitution, the central bank will lose independence in monetary policy even if the flexible exchange rate system is adopted. In this paper, we investigate the existence of currency substitution between Taiwan and the United States in an open economy during the period of the managed floating exchange rate system, and examine the role of the factor influencing monetary policy and domestic money demand function derived from a small-country portfolio balance approach. To take account of currency substitution, we use quarterly data over 1981-2005 period on the demand for money and include data on the real exchange rate in addition to real income, domestic nominal interest rate and foreign nominal interest rate. The methodology is based on an application of the Johansen and Juselius¡]1990¡^cointegration technique. Also use error correction model to discuss short-run dynamic adjustment processes of these variables. Application of the Augmented Dickey-Fuller test and Phillips-Perron test indeed reveal that all variables are integrated of order one. The result from the Johansen¡¦s maximum likelihood mehtod reveal that there is only one cointegrating vector among the variables. This implies that there is long-run equilibrium relationship among the variables. There is clear evidence that demand for money is affected not only by changes in domestic variables such as real income, domestic nominal interest rate but also by fluctuations in foreign nominal interest rate and real exchange rate. And the coefficiect of the real exchange rate is negative and statistically significant. That means currency substitution is significant factor in the domestic money demand equation and currency substitution indeed exists in Taiwan. This paper successfully provides a consistent result, currency substitution indeed exists in Taiwan. Therefore, to have an effective monetary policy, the monetary authorities should take into account the international factors.

It is necessary to subtracting the tidal height from the observed depth to derived real depth while conduct hydrographic survey. The tidal data can be collected by conventional tide gauge or by using real time kinematics (RTK) GPS survey in the near shore region. However, when setting up tidal instruments in the offshore areas, many restricts still remained due to many factors such as topography, weather, and sea state. On contrary, the RTK GPS survey method has the limitation on the radio transmitting range. Therefore, the tidal zone method integrates the tidal station data to calculate the offshore tide data which can solve these problems. Generally, the tidal zone is constructed by using real tidal station data around the narrow channel. But the tide data is not possible to integrate on both side of the Taiwan Strait due to the vertical datum is not identical due to current political separation. To overcome this problem, this study proposed tidal zone method based on the tidal height derived from a tide numerical model. The tidal zone method is consequently applied to improve the accuracy of the offshore hydrographic survey. After processing the tide data derived from the model output and performing harmonic analysis, this study utilized the analysis result to draw a co-tidal chart to demonstrate the tidal characteristics for the purpose of establishing the tidal zone of the Taiwan Strait. This study also accomplished correspondent tidal zones for all the tide stations of Taiwan west coast within 12 miles territorial waters. This study further proposed a virtual station method for offshore hydrographic survey tide correction which applied the analysis result of each numerical model grid point as a virtual tidal station to derive the offshore tide correction values with spatial continuous characteristics. This study selected three experiment areas based on the multi-beam echo sounder survey data acquired offshore Ma-Liuo tide station. The direct tide station correction, tidal zone correction, and virtual station correction methods are applied to the hydrographic survey data to evaluate the performance of the tidal zone and virtual station correction methods. According to the experiment results, the tidal zone and virtual station correction method improve 20 and 16 cm respectively over the direct tide station correction method in the offshore area with the distance 25 km to the Ma-Liuo tide station. It indicates that the feasibility of the tidal zone method and it can improve the hydrographic survey results significant while the tide characteristics are different. Tidal zone can provide the required information to decide a proper reference tide station according to the tidal characteristics for the hydrographic survey data post-processing.

In this thesis I study the German housing market and specifically the level of housing investment. First, a theoretical background to housing market dynamics is presented and then I test whether there is a relationship between housing investments and GDP, the size of the population, Tobin’s Q and construction costs. An Error Correction Model is estimated and the result is that the equilibrium level of housing investment is restored after less then two quarters after a change in one of the explainable variables. The estimation indicates that GDP, the size of the population and construction costs affect the level of construction in the short run. However, in the long run the only significant effect is changes in construction cost.