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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Investigation of broadband over power line channel capacity of shipboard power system cables for ship communications networks

Akinnikawe, Ayorinde 15 May 2009 (has links)
Broadband over Power Line (BPL) technology has garnered significant attention lately due to recent advancements in solid state technologies and channel coding schemes. The successful application of BPL technology for in-home automation and networking has led to suggestions of applying BPL in other systems including ships. The application of BPL technology using the Shipboard Power System (SPS) as a potential communications network for ship automation systems has been proposed, to achieve recent U.S. Navy ship management concepts geared toward reducing ship manning while improving operational efficiency. This thesis presents an analytical model developed to examine the channel response characteristics and estimated throughput capacity of SPS cables. The work used a multiconductor transmission line theory based approach to model the channel response of SPS distribution lines and estimated the channel throughput capacity using a “water-filling” communication technique. This work found that BPL using the SPS holds a strong potential for use as a communications network for ship communication systems.
72

The effects of Broadband spread on growth in GDP

Kindbom, Sebastian January 2012 (has links)
This paper investigates whether there is a correlation between broadband use and econom-ic growth by using an endogenous growth model along with previous studies of broadband use and theories for its spread an equation was developed accordingly. The estimation was done using data from the World Bank and ITU for the years 2002-2008, with minor imbalance in the dataset. Moreover, the estimation was done using two-way fixed effects and heteroskedasticity and autocorrelation robust errors, given tests for heteroskedasticity and autocorrelation in the regressions. The result from the regressions showed that broadband spread has a significant effect on GDP growth, while the signifi-cance of the coefficients for human capital do vary with education stage. In the analysis of the subject it was also shown that there are more underlying matters to be dealt with to give a fair estimation and conclusion, such as the difference between markets and difference in speed of broadband which may could have given slightly different results. Also that the range of time for broadband is relatively short, a longer range could have giv-en a better estimate. Furthermore, the analysis shone light on that there are both weakness-es by spread of broadband as exacerbation of poverty and strengths as possibility to savings in healthcare and increase spread of education via broadband. In addition to this there is possibly reversed causality and the fact that all ICT technology are general purpose tech-nologies has the impact that one should see the results with somewhat scepticism. In conclusion, the positive effect from broadband spread on economic growth is stated-with an addition, that more data and taking account of broadband differences globally would be needed in a future research to fully establish the effect, as well as mentioned limi-tations to result should be taken into account.
73

The Study of Organic Light Emitting Device with a Novel Fluorescent Material 2,2¡¦,7,7¡¦-tetra-(pyren-1-yl)-9,9¡¦-spirobifluorene (TPSBF)

Chao, Chun-ming 24 August 2011 (has links)
Recently, ¡§Pyrene¡¨ is a well-known substitutive group because the rigid structure and hole-injection ability of pyrene units can improve the thermal and electronic properties of blue OLED materials. The aromatic ring of pyrene not only improves the thermal and hole-injection ability of derivatives, but also provides high photoluminescence (PL) efficiency and high carrier mobility. Through these characteristics we can understand that the electron-rich pyrene derivatives can enhance the properties of OLED device. In this study, we developed low-molecular-weight structures with spiro-type molecules based on 9,9-spirobifluorene and fabricated the OLED device with the structure of ITO(170 nm)/PEDOT:PSS(50 nm)/PVK:TPSBF (40%)(90 mm)/BPhen (30 nm)/ LiF(1 nm)/Al(200 nm). It exhibited a maximum luminance at 500 mA/cm2 of 4130 cd/m2 with the Commission Internationale de l'Eclairage (CIE) of (0.16 , 0.16), and the maximum current and power efficiency were 1.9 cd/A and 0.9 lm/W, respectively. We concluded that TPSBF has good emission efficiency according to device performances. The PL maximum of the thick film of TPSBF, prepared by vacuum vapor deposition appears broadband spectrum, that resulted from the aggregation of the pyrene moieties. From Atomatic Force Microscopy (AFM) results, we propose three emission mechanisms. 1. Intramolecular spectrum ¡÷ 450 nm 2. Molecular aggregation spectrum ¡÷ 500 nm 3. Longer conjugation spectrum of intermolecular ¡÷ 550 nm We could fabricate the organic white light emitting device with a single and thicker emitting layer TPSBF and the more broadband emitting spectrum can be obtained. Finally, we fabricated the organic white light emitting device with a structure of ITO(170 nm)/2T-NATA(15 nm)/NPB(65 nm)/TPSBF(50 nm)/Alq3(30 nm)/LiF(0.8 nm)/Al(200 nm). It exhibited a maximum luminance at 1300 mA/cm2 of 57680 cd/m2, the maximum current and power efficiency were 6.51 cd/A and 4.07 lm/W, respectively, and with good CIE coordinate of (0.29 , 0.36).
74

Investigation of broadband over power line channel capacity of shipboard power system cables for ship communications networks

Akinnikawe, Ayorinde 15 May 2009 (has links)
Broadband over Power Line (BPL) technology has garnered significant attention lately due to recent advancements in solid state technologies and channel coding schemes. The successful application of BPL technology for in-home automation and networking has led to suggestions of applying BPL in other systems including ships. The application of BPL technology using the Shipboard Power System (SPS) as a potential communications network for ship automation systems has been proposed, to achieve recent U.S. Navy ship management concepts geared toward reducing ship manning while improving operational efficiency. This thesis presents an analytical model developed to examine the channel response characteristics and estimated throughput capacity of SPS cables. The work used a multiconductor transmission line theory based approach to model the channel response of SPS distribution lines and estimated the channel throughput capacity using a “water-filling” communication technique. This work found that BPL using the SPS holds a strong potential for use as a communications network for ship communication systems.
75

Design of Stripline-Fed Dual Polarization Aperture-Coupled Stacked Microstrip Patch Phased Array Antenna for Wideband Application

Kim, David G. 2010 August 1900 (has links)
Recent days, antennas play an important role in wireless communication system. Microstrip patch antennas are well known to have positive features for cost-effective, low profile and broadband. This type of antenna can be used in wide range of applications such as in wireless communications, radar systems, and satellites. Inhibiting characteristics of single patch antenna with low gain and narrow band leads to the research area to have array configuration. Beam steering antennas are the ideal solution for various systems such as traffic control and collision avoidance radar systems. The goal of this work is to design and implement a dual-linear polarization stacked microstrip patch phased array antenna. Single stacked microstrip patch antenna fed by microstrip line was designed to have approximately 3 GHz bandwidth in X-band with another ground plane to form a stripline-fed. Stripline-fed design protects feed lines from any outside effects. The array configuration was adapted to design in order to accomplish beam scan angle of /- 30 degrees by /- 15 degrees. Binomial power distribution of 3x2 array structure was used in order to reduce grating lobes, and changing length of feed lines was implemented for phase shifting. Bowtie cross shape aperture and dual-offset microstrip feedline was used to feed radiating patches. For the feed network, T-split power divider was implemented and optimized to achieve low loss. The length of microstrip line was adjusted to meet desired phase shift that in wideband application, the length of the line had to be long enough to have similar wavelength response over broad frequency range. The antenna array was designed using standard equations and simulated by electromagnetic analysis software called Zealand's IE3D which is method-of-moments based simulator. The resulting measured impedance bandwidth and gain of both microstrip and stripline-fed single antenna are 43 percent and 5 to 10 dBi with low cross polarizations for all frequencies. The array antenna was measured to have 29 to 60 percent impedance bandwidths depending on the different types of beam scan angles. The gain of the array antenna is 8 to 13 dBi, and the beams are directed as required with /- 3 degrees beam scan angle tolerance. The array antenna had a small offset as compared with simulated results because of the fabrication process such as alignment, distorted feed lines while etching, and etc, but the bandwidths and array patterns were acceptable.
76

A STUDY ON HOW TO MAKE THE MOST FUNCTION OF BROADBAND NETWORK IN TAIWAN

Huang, Chih-Jung 09 February 2004 (has links)
Abstract Along with the increasingly developed computer technology and the wide application of Internet, the use of Internet has been more and more diverse. The function of narrowband network that was limited in the transmission of texts and basic graphs cannot meet the needs of the transmission of multimedia which is consisted of audio, data, video, etc. Therefore, the broadband network has gradually become the mainstream of the network application. The objectives of this study are to discuss the technologies commonly applied in broadband network and to find out how the function of broadband network could be promoted in Taiwan. This study is an industrial policy research. The comparative analysis was conducted on the secondary data collected from both domestic and foreign sources. As shown by the statistics, the number of broadband subscribers has been increasing rapidly in both domestic and foreign areas. This reflects the rising demand of broadband. The conclusions of the study are as follows: 1. The government policy and the industry support make the number of broadband subscriber increase sharply. 2. ADSL and Cable Modem are the technologies commonly adopted among various countries. 3. The economy factor is the primary consideration in adopting the broadband technologies. 4. The content of network is the key factor to the popularity of broadband network. 5. The popularity of broadband network will promote the electronic commerce. There are five suggestions in this study: 1. To install a full optical-fiber network. 2. To accelerate the network into the Internet Protocol one. 3. To cultivate the software professionals. 4. To rationalize the fee of broadband network. 5. To implement the policy on speeding up the construction of broadband network. Key word: Internet, Broadband network, ADSL, Cable Modem
77

NOVEL DESIGNS OF PATCH ANTENNAS WITH CONICAL RADIATION PATTERNS

Lin, Shun-Yun 25 April 2002 (has links)
Novel designs of three-dimensional patch antennas for beamdwidth enhancement and broadband operation have been proposed in this dissertation. For the beamwidth enhancement, the patch antenna with an inverted V-shaped patch has been proposed, and the antenna¡¦s radiation beamwidths have been broadened. Another beamwidth enhancement design using a three-dimensional square ground structure has also been demonstrated, and the 3-dB beamwidth of the CP radiation can reach more than 110¢X. In addition to the designs of beamwidth enhancement, the broadband patch antennas with a V-shaped patch, a W-shaped ground plane and a short probe-pin have been proposed. These novel structures can have significantly reduced probe-pin length and obtain a good impedance matching over a wide frequency range. Finally, a 1 ¡Ñ 2 broadband patch antenna array, suitable for base-station antenna applications for mobile communications systems, has also been studied
78

CMOS front-end amplifier for broadband DTV tuner

Zhang, Guang 29 August 2005 (has links)
In this work, the design of a CMOS broadband low noise amplifier with inherent high performance single-to-differential conversion is presented. These characteristics are driven by the double quadrature single conversion digital television tuner which requires accurately balanced differential signals to perform its function and to improve image rejection. A three-stage amplifier is designed to satisfy several requirements of front-end circuits at the same time. The resistive shunt-feedback topology is adopted to implement a single-ended broadband low-noise amplifier as the first stage. The second stage is an on-chip single-to-differential converter, which employs a novel method to improve its balancing performance. A fully differential buffer capable of driving heavy loads is used as the third stage to further suppress the phase and magnitude errors of output differential signals. Fabricated in 0.35??m TSMC standard CMOS technology, the designed broadband front-end amplifier manages to limit the phase error to within ??1.5?? and magnitude error ??0.75dB over 50~850 MHz frequency range, with 16dB gain and a noise figure of 4dB.
79

Fabrication and Characteristics of Ultra Broadband Cr-doped Fibers by Drawing Tower

Huang, Yi-chung 02 January 2008 (has links)
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.
80

Advances in optical power budgets and bandwidth capacity of broadband networks /

Mysore, Sudhesh M. January 1999 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 247-259). Also available on the Internet.

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