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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.
281

Design of Microwave Filter Using Band-Gap Structures

Wang, Yu-Tsai 04 August 2004 (has links)
Using compact structure to improve the defect of traditional transmission line filter which size is too big or transmission line is too long. Two special structures are used to implement the filter that is smaller or superior characteristic. One of the two structures is called DGS that etched defect in the ground plane. The etched lattice shape for the transmission line consists of narrow and wide etched areas in backside metallic ground, which give rise to increasing the effective capacitance and inductance of a transmission line, respectively. Thus, by using this character, the low-pass filters are designed and implemented easily. Another structure is coupled of microstrip square open-loop resonators. First, the coupling coefficients of the three basic coupling structures versus distance between adjacent resonators and different offset is established by means of three-dimensional field analysis methods. Then, the band-pass filter will be implemented by the combination of three basic coupling structures. Finally, two low-pass filter which have cutoff frequency 5.4GHz¡B2.26GHz and a four-pole band-pass filter are designed and fabricated. All theoretical and experimental performance is presented.
282

A Study of Antenna Factor of Broadband Antennas for Electromagnetic Compatibility by simulation and measurement

Tien, Kai-Wen 22 July 2005 (has links)
The researches of this thesis are divided into two parts. One is to investigate the applicability of ANSI C63.5 in high frequencies of 1 GHz to 6 GHz. In general, the Standard Site Method (SSM) of C63.5 is usually used to calculate the antenna factors for the calibration of broadband antennas. Through the theoretical calculations, the numerical simulations and measurements, we found that the discrepancies between the calibrated results of horizontal and vertical polarization related to the un-dipole-like pattern in higher frequencies. Furthermore, we analyzed the relations of the antenna factors, the heights of receive antennas and the radiation patterns. We also found that the predicted calibration results can be close to the practical ones by including the effects of radiation patterns. The other research is to study the issue about the ground plane size of a test site. The ground plane size of a qualified test site must be larger than the minimum size defined by C63.7. For this reason, we provide a method which combines the tilted antennas measurement with a trapezoid shape ground. By using this method in the smaller ground size, we can obtain the measured results close to those obtained in the larger ground size. This method can effectively reduce the required ground size and then decrease the installation cost of a test site. Meanwhile, this method can be applied for both of the horizontal and vertical polarizations.
283

Temporal and Spatial Distribution of the Ground-dwelling Invertebrates in Nanjen Forest

Huang, Ho-Chi 27 August 2001 (has links)
This study uses pitfall traps to collect ground-dwelling invertebrates in Nanjen Forest. The ground-dwelling invertebrates in Gufu Area are mainly contributed by Hymenoptera, Collembola, Coleoptera, Araneida. There is no significant difference between the diversity index of pitfalls with various distances to the edge of forest in Gufu Area. The similarity index between each pitfall is relatively low, it suggests that the heterogeneity of various micro-habitats is high. The sex-ratio of different spider species varied from 0.09 - 1.73, and the habitat preference is specific. The number of the spiders is positive-correlated with the number of the Collembola and the Orthoptera.
284

Consolidation and structure of paper coating and fibre systems

Kugge, Christian January 2003 (has links)
<p>Paper coatings or coating colours are high solidssuspensions that are applied to paper to improve chieflyprintability and optical properties. A paper coatingsuspension, including pigments, binders and thickeners, is acomplex system which must be understood if the end-useproperties of paper are to be improved. Some of the importantissues that need to be addressed are the mechanisms ofmigration of latices in a drying film, the influence ofthickener on the overall consolidation and the behaviour ofpaper coatings under compression.U nderstanding theconsolidation of paper coatings is essential as the aggregatestructures formed at this stage largely determine theperformance of the paper coating.Similarly, the forming ofpaper itself from pulp fibres requires a detailed understandingof the consolidation and dewatering process.</p><p>In this thesis several approaches have been used in order tostudy the consolidation of paper coatings before and afterapplication to substrates. The techniques utilised arerheometry, centrifugation with NMR-imaging, scanning electronmicroscopy (SEM) and atomic force microscopy (AFM).Furthermore, investigations of the compressional rheology offibre systems has indicated that stepped pressure filtrationcan be a useful tool in the study of fibre dewatering.</p><p>The primary findings presented in this thesis can besummarised as follows. Studies of the compressive yield stressand rheological properties of ground calcium carbonate (GCC)suspensions indicate that the addition of a commonly usedthickener can cause flocculation, most likely of a depletiontype, which leads to more compact structures during dewatering.When applied to substrates, migration and film formation ofbinder latices in the presence of calcium carbonate pigmentsand CMC thickeners occurs concurrently and collectively. Thisis shown to influence the consolidation of the top layer of thecoating to a great extent. It was found that CMC retards themigration of latices and that ethyl(hydroxyethyl)cellulose(EHEC) adsorbs to latex and creates a composite material uponlocal film formation. The composite retains an internalhoneycomb structure in the film, that is revealed by mapping ofelastic variations using AFM phase imaging.</p><p>For fibre systems, the novel method of stepped pressurefiltration has been applied to study the compressional rheologyof pulp suspensions, and the effect of added surfactantsinvestigated. The technique is shown to be a promising tool forthe study of structure-dewatering relationships in fibresuspensions.</p>
285

Structure and tectonics of the Puerto Rico-Virgin Islands platform and multi-confirguration ground penetrating radar data /

Van Gestel, Jean-Paul. January 2000 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 205-213). Available also in a digital version from Dissertation Abstracts.
286

Temporal processing of figures and grounds

Hecht, Lauren Nicole. Vecera, Shaun P. January 2009 (has links)
Thesis supervisor: Shaun P. Vecera. Includes bibliographic references (p. 111-116).
287

Arthropod and plant communities as indicators of land rehabilitation effectiveness in a semi-arid shrub-steppe /

Gardner, Eric Ty. January 2008 (has links) (PDF)
Thesis (M.S.)--Brigham Young University. Dept. of Plant and Wildlife Sciences, 2008. / Includes bibliographical references (p. 20-22).
288

2-D numerical simulation and design of fully grouted bolts for underground coal mines

Yassien, Asmaa Mohamed. January 1900 (has links)
Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xiii, 167 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 139-143).
289

Geologic feature prediction using roof bolter drilling parameters

Mirabile, Benjamin T. January 2003 (has links)
Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xii, 84 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 83).
290

Design considerations for longwall yield pillar stability

Mohamed, Khaled Morsy. January 1900 (has links)
Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xi, 187 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 181-187).

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