Neste trabalho é analisada a medição de viscosidade de líquidos por ultrasom pelo método da reflexão de ondas de cisalhamento. O método baseiase na medição da magnitude e fase do coeficiente de reflexão quando as ondas de cisalhamento incidem na interface entre um sólido e o líquido testado. Foram analisados os conceitos teóricos do método da medição de viscosidade e desenvolvida a metodologia experimental a fim de evitar a influência indesejada de fatores externos, como a temperatura e a instabilidade da eletrônica, sobre a medição. Foram obtidos resultados com dois óleos alimentícios (azeite de oliva e óleo de milho) e quatro óleos automotivos do tipo SAE (40, 90, 140 e 250). Foi mostrado que para uma freqüência de operação baixa o suficiente para garantir comportamento Newtoniano do líquido, os valores de viscosidade têm excelente concordância numérica com os valores obtidos usando o viscosímetro rotacional, no caso dos óleos menos viscosos. Já no caso dos óleos mais viscosos, foram obtidos valores de viscosidade menores que os obtidos com viscosímetro rotacional, e o aumento no módulo elástico sugere um comportamento mais viscoelástico. Foi mostrado que o método de cálculo simplificado usado por alguns autores, que permite calcular a viscosidade a partir somente da magnitude do coeficiente de reflexão, não fornece os valores esperados de viscosidade. / This work deals with the ultrasonic measurement of liquids viscosity by means of the shear reflectance method. The method is based on the measurement of the magnitude and phase of the complex reflection coefficient of shear waves at a solidliquid sample interface. Basic concepts of the viscosity measurement method were analyzed and the experimental methodology was developed to avoid the undesired influence of external factors, such as temperature and electronic instability. Experimental results were obtained with two kinds of eatable oils (olive and corn oils) and four different automotive oils (SAE 40, 90, 140 e 250). For an operating frequency low enough to obtain Newtonian liquid behavior, as for less viscous liquids, it was shown that the viscosity results have good agreement with rotational viscometer measurements. In the case of more viscous liquids, the measured viscosity values were smaller than those obtained by the rotational viscometer, and the elastic modulus is increased, suggesting viscoelastic behavior. It is shown that a simplified model used by other authors, which obtains the viscosity without measuring the phase of the complex reflection coefficient, results in greater errors associated with the values obtained by the rotational viscometer.

Estágio realizado na UNICER e orientado pelo Eng.º Vasco Carvalho / Tese de mestrado integrado. Engenharia Química. Faculdade de Engenharia. Universidade do Porto. 2009

本論文計分七章，茲就各章內容略述如后： 第一章：緒論。本章 先闡述公司權利能力之概念及其所受限制，而後導引出公司權利能力受目 的上限制之「能力外行為理論」及該理論在我國之關聯問題，並敘明本論 文之研究方法。 第二章：能力外行為理論之概念。乃針對公司「能力 外行為理論」之內涵、能力外行為效果、理論基礎、與法人本質之關係以 及能力外行為與違法行為之區辨暨能力外行為與代表權限外行為之區辨等 方面之探討，以釐清「能力外行為理論」之真義。 第三章：公司能力 外行為理論之歷史沿革。能力外行為理論源於英國，後為美、日等國所繼 受，本章乃分別就英、美兩國及日本有關該理論之歷史沿革予以介紹。 第四章：公司能力外行為理論在英、美、日法上之問題點。英國法部分， 以該國於一九七二年為加入歐洲共同體，就能力外行為理論之修正為討論 重點，美國法部分，則以晚近美國公司法對能力外行為理論之態度，以及 學者就有關規定之檢討予以介紹，至於日本法部分，係就能力外行為理論 之適用，在日本判例及學說上之發展情形及有關之檢討，加以論述。 第五章：公司權利能力與政治獻金。公司究有無逾越其章程所定之目的範 圍，公司社會責任之考量已成為其判斷方向之一，本章乃就公司社會責任 之概念略予介紹，並論及以公司社會責任之概念肯定公司所為政治獻金亦 屬其權利能力範圍之問題點所在，歸納出應以法令限制公司政治獻金行為 之結論。 第六章：公司能力外行為理論在我國之適用。就我國公司法 之現有規定，認能力外行為理論為我國所採行，並以外國有關能力外行為 理論相關規定之發展趨勢，檢討我國公司法有關規定之妥適性。 第七 章：結論。本章就全文作一總結，並指出我國現階段公司法對能力外行為 理論應有之態度，公司能力外行為效力之判斷標準，以及今後之修法方向 。 The main configuration of this thesis can be summarized as follows: First, the concept of the capacity of company and the limitation of the capacity are described. Next, the concept of Ultra Vires Doctrine is introduced. Third, the history of the Ultra Vires Doctrine in U.K., U.S.A., andJapan are also presented, respectively. Fourth, the keypoint of the Ultra Vires Doctrine in U.K., U.S.A., and Japan are discussed, respectively, and the viewpoint of the Ultra Vires Doctrine in Germany is also studied. Fifth, the relationship between the company political donatrions andthe Ultra Vires Rule is investigated. Sixth, the executive condition of Ultra Vires Doctrine in Taiwan, R.O.C. is investigated. Finally, the conclusions of the thesis are presented.

This thesis deals with Symbol Error Rate (SER)-simulation of wireless communications and its application into throughput analysis of UltraWideband (UWB) systems. The SERs will be simulated in C++ using the Monte Carlo method and when some are calculated, the rest will be estimated using a novel extrapolation method. These SER values will be very accurate and in this thesis go as low as 1.0e-14. Reaching that low values would otherwise be impossible using the traditional Monte Carlo method, because of very large computation time. However, the novel extrapolation method, can simulate a SER-curve in less than 30 seconds. It is assumed that the noise belongs to the Generalized Gaussian distribution family and among them noise from the Normal distribution (Gaussian noise) gives the best result. It is to be noted that Gaussian noise is the most commonly used in digital communication simulations. Although the program is used for throughput analysis of UWB, the program could easily be adapted to various signals. In this thesis, throughput analysis means a plot with symbol rate vs distance. From any given symbols, the user can, with a desired minimum SER, generate an extrapolated SER-curve and see what symbol rate can be achieved by the system, while obeying power constraints of signals imposed by international laws. The developed program is, by comparing with published theoretical results, tested for QAM and PSK cases, but can easily be extended to UWB systems.

Ultra Wide Band (UWB) is a short-pulse electrical signal which is widely used for short distant wireless communication because its low path loss, good immunity to multipath propagation, and high data rate. The reason of using optical fiber as carrier is fiber can bust up the communication capacitance in long distance range because of high capacitance, low loss propagation. Thereby, the technique of UWB signal on fiber has become more and more important. In this work, a novel method using electro-absorption modulation with short termination for interface of optical fiber and generate UWB signal is proposed and demonstrated. The structure is simple.This method don¡¦t need employing any complicated frequency mixer, or complex systems. This work need to generate optical pulse with high energy, which is feded into the EAM. The signal can generate electrical pulse and build electrical field on EAM in the same time. The optical pulse is modulated by the electrical field on EAM. Using this way, we can generate UWB optical signal.

In this thesis, an estimation method adapted from MUSIC algorithm is presented for estimation of signal arrival time for impulse radio UWB systems. An accurate estimate of signal arrival time is considered essential in time-based wireless and indoor location systems. Since most wireless communications systems used for indoor position location may suffer from dense multipath situation, the accuracy of determining signal arrival time become an important issue for the time-based location systems. The fine resolution of UWB signals provides potentially accurate ranging for indoor location applications. However, the ambiguity caused by the unresolved first arrival path may still yield an error in determining the true signal arrival time. The presented method uses improved MUSIC techniques in time domains to estimate the shortest and the real signal arrival time for UWB radio link. For a two-multipath case, analysis and simulation results of multipath resolvability and the variance of estimation errors of signal arrival time are discussed.

The maximum capacity of an optical fiber transmission system more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1300nm to 1600nm. The fast increasing demand of communication capacity results in the emergence of wavelength division multiplexing (WDM) technology, which results in the need for ultra-wideband optical amplifier. Cr4+:YAG has a strong spontaneous emission that covers 1300nm to 1600nm. Besides, its absorption spectrum is between 900nm to 1200nm, which matches with the pumping source in current erbium doped optical amplifier. Such a fiber is, therefore, eminently suitable for optical amplifier applications. In this article, we will introduce the development of ultra-wideband optical amplifier using the double-clad Cr4+:YAG crystal fiber, which is grown by laser heated pedestal growth(LHPG) technique. Its material properties as well as optical gain will be characterized. By butt-coupling method, a low insertion loss of 4.2 dB was achieved in a SMF-CDF-SMF configuration, and it was measured to demonstrate a gross gain of 2.4 dB at 1 W bi-directional pump power. Moreover, theoretical models and numerical simulations have been developed to predict the experimental results. Numerical simulation indicates that the efficiency of mode overlapping between signal and pump is crucial to gain performance. The mode overlapping efficiency is about 25%~30% for our crystal fiber under current circumstances. In the future, we will make an attempt to reduce the index contrast between core and cladding for better mode overlapping efficiency. At the same time, we also try to grow crystal fiber of smaller core diameter to improve gain performance.

Novel microwave transmitter and receiver circuits have been developed for implementing UWB (Ultra-Wideband) impulse radar imaging sensor operating in frequency band 0.2 to 4 GHz. with tunable operating frequency band. The fundamental system design parameters such as the required transmitting pulse power and the pulse duration were estimated for a presumed specific application, the pavement assessment. The designed transmitter is the tunable monocycle pulse generator with tuning capability for the output pulse duration from 450- to 1200- ps, and has relatively high transmitting pulse power from 200 to 400 mW. Tuning of the pulse duration was implemented by novel PIN diode switch configuration and decoupling circuit, and boosting of transmitting pulse power was made possible by using a high power pulse driving circuit and SRD coupling circuit. The synchronous sampling receiver system was designed by using the integrated sampling mixer and two reference clock oscillators placed in the transmitter and receiver respectively for timing control. A novel integrated CSH (Coupled-Slotline Hybrid)sampling mixer has been developed along with the design of the strobe pulse generator appropriate for the impulse radar system. The integrated sampling mixer has unprecedented conversion loss of 2.5 dB for the pulse signal, bandwidth 5.5 GHz, and dynamic range 50 dB. The introduced UWB LNA (Low Noise Amplifier) design operating up to 4 GHz should be useful for weak signal detection applications. The design of the UWB microstrip quasi-horn antenna was optimized for short pulse transmission with respect to the input return loss and the pulse stretching effect. For signal detection in the signal processing stage, the background subtraction technique and B-scan data format were used. A novel signal monitoring technique was introduced in the signal processing to compensate the frequency modulation effect of the reference clock. The test results for the complete system with respect to some sample multi-layer structures shows good receiving pulse waveform with low distortion, enough pulse penetration depth for 13” pavement sample structure, and minimum 1-in of range resolution.

The breakthrough technology in dry fiber fabrication has opened the possibility for using fiber bandwidths all the way from 1.3 to 1.6 £gm. However, the fiber amplifier used in commercial product, such as erbium-doped fiber amplifier (EDFA), can not fully cover the whole fiber bandwidths from 1.3 to 1.6 £gm with a single fiber amplifier. Recently, the Cr4+-doped fiber has shown a broadband emission from 1.3 to 1.6 £gm. Therefore, it is interesting to develop a single fiber amplifier which can operate the wide bandwidth of the 1.3 ~ 1.6 £gm emission. In this study, we have successfully fabricated and measured the Cr-doped fibers by using a commercial drawing-tower technique. The Cr-doped YAG preform was firstly fabricated by a rod-in-tube method. By employing a negative pressure control in drawing-tower technique on the YAG preform, the Cr-doped fibers with a better core circularity and uniformity, and good interface between core and cladding were fabricated. The drawing speed was up to 200m/min. The core diameters were 26 and 16 £gm and the non-circularity was smaller than 3%. The spontaneous emission spectrum showed a broadband emission of 1.2 to 1.6 £gm with the output power density about a few nW/nm. The Cr-doped fibers fabricated by drawing tower are beneficial when integrated with the standard single-mode fibers and broadband WDM couplers for lightwave communication systems. Therefore, the Cr-doped fibers may be used as a broadband fiber amplifier to cover the whole 1.3-1.6 £gm range of silica fibers and have a potential for commercial production and application to lightwave communication systems.

Ultra Wide Band (UWB) is a short-pulse electrical signal, which is widely used for short distant wireless communication due to its low path loss, good immunity to multipath propagation, and high data rate. The main target transmission area of UWB is within 10 meters. Using optical fiber as carrier can bust up the communication capacitance in long distance range because of high capacitance, low loss propagation, and TDM and WDM compatible properties of fiber. Thereby, the technique of UWB on fiber has become more and more important. In this work, a novel method using waveguide photodetector (WP) with short termination for interface of optical fiber and wireless is proposed and demonstrated. The structure is simple without employing any complicated frequency mixer, intermediate frequency, or complex systems. This work is divided into two parts: (1) generation of UWB electrical signals and (2) wavelength conversion of UWB through WP. In the former, a WP with short termination is used in the device. The photocurrent excited by short optical pulse is distributive generated through the waveguide, forming two opposite directions of electrical waves. By reflection on the short termination, the reversed phase of one electrical wave is added to another electrical wave through a delay line, forming a monocycle of UWB signal. By appropriate design on the length of waveguide, the band of 2-10GH is demonstrated, fitting the requirement of FCC (Federal Communications Commission). In the second part of this paper is the wavelength conversion of UWB. The active region of WG is multiple quantum wells (M.Q.W.), which is not only served as photo-absorption layer, but also can be used the electroabsorption material. By pumping M.Q.W.s with high optical power, the cross absorption properties can be applied for wavelength conversion. By pumping power of 12dBm, the wavelength-converted UWB signal is successfully demonstrated at range of 1545nm-1570nm. Using this method, the application of UWB on router of fiber optical network is expectable.