In this thesis, the properties of the metamaterials are studied. We analyze and discuss the artificial structure called metamaterials. The the effects on the radiation pattern and antenna gain are discussed when the structure is placed above the antenna. First, the propagation of electromagnetic wave in metamaterials is discussed. The metamaterial composed of metal rod array and split-ring is introduced. Next, the effects on permittivity, permeability and refraction index are studied when the structure parameters are changing. Thirdly, according to the above-mentioned summary, we use the structures to achieve an antenna radome. The radome can reduce 3 dB beam-width by about 31.25 percent at 10.75 GHz. The maximum gain achieves 7.25 dBi. In the fourth part, we also discusse the method of reducing the frequency band where negative refraction index occurs. The metamaterial is used to be a radome at the lower frequency band. The maximum gain is about 7.87 dBi. The 3 dB beam-width reduces by about 37.25 percent by the radome structure. Fifthly, the methods of improving the bandwidth are discussed when the antenna radome over the antenna . The enhancement of the antenna performance can be applied to the point-to-point communication. It also can save the cost of the feed network and the numbers of array antenna.

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Magister Scientiae Dentium - MSc(Dent) / The aim of this study was to determine whether there are changes in the interdental arch widths and arch lengths of the mandibular and maxillary arches during nonextraction and extraction orthodontic treatment. The records of 78 patients treated by one orthodontist were used for this study. Three treatment groups were selected: a nonextraction group (Group NE), a group treated with extraction of maxillary and mandibular first premolars (Group 44), and a group treated with extraction of maxillary first premolars and mandibular second premolars (Group 45). The arch width measurements were measured in the inter-canine, inter-premolar and inter-molar areas. The arch length was measured as the sum of the left and right distances from mesial anatomic contact points of the first permanent molars to the contact point of the central incisors or to the midpoint between the central incisor contacts, if spaced.Statistical analysis included descriptive statistics of the data, analysis of the correlation matrices, Wilcoxon Signed Rank tests and Kruskal-Wallis tests of the changes which occurred during treatment. The intercanine widths in the mandible and maxilla increased during treatment in all three groups, with the extraction groups showing a greater increase than Group NE (p<0.05). In Group NE the mandibular arch length increased (p>0.05), while the maxillary arch length remained essentially unchanged. Both extraction groups showed decreases in arch length in the dentitions (p<0.05), with greater decreases occurring in the maxilla. The difference in arch length change between the two extraction groups was not significant (p<0.05). The inter-canine arch width increased in all three treatment groups, more so in the two extraction groups. From this it is evident that extraction treatment does not necessarily lead to narrowing of the dental arches in the canine region. The inter-second premolar arch width decreased in both extraction groups. Non-extraction treatment resulted in an increase in the inter-premolar and inter-molar arch widths. / South Africa

<p>The aim of this study was to determine whether there are changes in the interdental arch widths and arch lengths of the mandibular and maxillary arches during nonextraction and extraction orthodontic treatment. The records of 78 patients treated by one orthodontist were used for this study. Three treatment groups were selected: a nonextraction group (Group NE), a group treated with extraction of maxillary and mandibular first premolars (Group 44), and a group treated with extraction of maxillary first premolars and mandibular second premolars (Group 45). The arch width measurements were measured in the inter-canine, inter-premolar and inter-molar areas. The arch length was measured as the sum of the left and right distances from mesial anatomic contact points of the first permanent molars to the contact point of the central incisors or to the midpoint between the central incisor contacts, if spaced.</p> <p>Statistical analysis included descriptive statistics of the data, analysis of the correlation matrices, Wilcoxon Signed Rank tests and Kruskal-Wallis tests of the changes which occurred during treatment. The intercanine widths in the mandible and maxilla increased during treatment in all three groups, with the extraction groups showing a greater increase than Group NE (p&lt / 0.05). In Group NE the mandibular arch length increased (p&lt / 0.05), while the maxillary arch length remained essentially unchanged. Both extraction groups showed decreases in arch length in the dentitions (p&lt / 0.05), with greater decreases occurring in the maxilla. The difference in arch length change between the two extraction groups was not significant (p&gt / 0.10). The inter-canine arch width increased in all three treatment groups, more so in the two extraction groups. From this it is evident that extraction treatment does not necessarily lead to narrowing of the dental arches in the canine region. The inter-second premolar arch width decreased in both extraction groups. Non-extraction treatment resulted in an increase in the inter-premolar and inter-molar arch widths.</p>

<p>The aim of this study was to determine whether there are changes in the interdental arch widths and arch lengths of the mandibular and maxillary arches during nonextraction and extraction orthodontic treatment. The records of 78 patients treated by one orthodontist were used for this study. Three treatment groups were selected: a nonextraction group (Group NE), a group treated with extraction of maxillary and mandibular first premolars (Group 44), and a group treated with extraction of maxillary first premolars and mandibular second premolars (Group 45). The arch width measurements were measured in the inter-canine, inter-premolar and inter-molar areas. The arch length was measured as the sum of the left and right distances from mesial anatomic contact points of the first permanent molars to the contact point of the central incisors or to the midpoint between the central incisor contacts, if spaced.</p> <p>Statistical analysis included descriptive statistics of the data, analysis of the correlation matrices, Wilcoxon Signed Rank tests and Kruskal-Wallis tests of the changes which occurred during treatment. The intercanine widths in the mandible and maxilla increased during treatment in all three groups, with the extraction groups showing a greater increase than Group NE (p&lt / 0.05). In Group NE the mandibular arch length increased (p&lt / 0.05), while the maxillary arch length remained essentially unchanged. Both extraction groups showed decreases in arch length in the dentitions (p&lt / 0.05), with greater decreases occurring in the maxilla. The difference in arch length change between the two extraction groups was not significant (p&gt / 0.10). The inter-canine arch width increased in all three treatment groups, more so in the two extraction groups. From this it is evident that extraction treatment does not necessarily lead to narrowing of the dental arches in the canine region. The inter-second premolar arch width decreased in both extraction groups. Non-extraction treatment resulted in an increase in the inter-premolar and inter-molar arch widths.</p>

It has been demonstrated in past studies that drainage area (Ada) and mean annual precipitation depth (Pmean) are significant independent variables for predicting bankfull channel geometry. Bankfull width (Wbf), a particularly useful measure of bankfull channel geometry, is used in hydrology, fluvial geomorphology and stream ecology applications. Since precipitation depth does not generally have a normal distribution over a basin it is reasonable to question whether or not Pmean is the best measure of precipitation across a basin. That is, perhaps the median precipitation depth (P50) or the mean annual precipitation depth at the basin outlet (Poutlet) is more representative of precipitation in a basin. The objective of the study is to see if Pmean, P50, or Poutlet is a significantly better measure of precipitation in a watershed. Along with Ada, each of these precipitation measures was used to develop relationships for predicting Wbf for basins located across the continental U.S. Using several goodness-of-fit statistics i.e., coefficient of determination(R2), Standard error of estimates(SEE) and Akaike Information Criterion(∆AIC), the relationships were compared to determine which one had the greatest predictive strength. Estimates of Pmean, P50, and Poutlet were derived from a precipitation model developed by PRISM. Results from this study tentatively indicate that all three measures of precipitation depth yield models for predicting Wbf that have comparable goodness-of-fit statistics.

Under weak turbulence theory, we will use the random thin phase screen model and the Kolmogorov power-law spectrum to derive approximate models for the scintillation index, covariance function of irradiance fluctuations, and temporal spectrum of irradiance fluctuations for collimated beams. In addition, we will provide an expression for the quasi-frequency of a collimated beam and investigate the relationship between the quasi-frequency and the maximum width of the normalized temporal spectrum of irradiance for a collimated beam.

This thesis emphasizes the critical importance of crack control in designing and constructing reinforced concrete (RC) structures. Cracks in such structures can significantly reduce strength and durability, pose safety risks, and lead to high repair costs. Existing codes and standards offer varying approaches, resulting in inconsistent results in designing for serviceability limit state (SLS). The evolution of modern reinforced concrete, incorporating additives like superplasticizers and silica fume, requires an update to crack control models based on outdated conceptions. The thesis aims to compare crack width calculations, understand bond stress in contemporary concrete models, and enhance crack control models. The study covers crack development, mathematical aspects of crack design, laboratory testing, and analysis of RC specimens. The findings aim to offer valuable recommendations and improve crack control measures, contributing to a more robust database and aiding the development of effective global model codes and standards for crack control in RC structures.:1. Introduction 2. General knowledge of cracks in RC structures 2.1. Cause of crack formation 2.1.1. Crack during the hardening process 2.1.1.1. Plastic shrinkage cracks 2.1.1.2. Plastic settlement cracks 2.1.2. Crack of hardened concrete 2.1.2.1. Drying shrinkage cracks 2.1.2.2. Thermal cracks 2.1.2.3. Crack due to chemical reaction 2.1.3. Crack due to external loads 2.2. Crack development in an axially loaded member 3. Crack width calculations 3.1. Design formula according to EN:1992 3.1.1. Calculating crack width 3.1.2. Calculating minimum reinforcement 3.1.3. Detailing of reinforcement 3.2. Design formula according to fib Model Code 3.2.1. Crack width calculation per fib Model Code 1990 3.2.2. Crack width calculation per fib Model Code 2010 3.3. Design formula in other codes and standards 3.3.1. Crack width calculation in American standard (ACI) 3.3.2. Crack width calculation in British standard (BS) 3.3.3. Crack width calculation in Vietnamese standard (TCVN) 3.3.4. Summary and example of crack width calculations a. Crack control per EN 1992-1-1 b. Crack control per Model Code 1990 c. Crack control per Model Code 2010 d. Crack control per ACI e. Crack control per BS f. Crack control per TCVN 4. Pull-out experiments 4.1. Experimental basis 4.2. Experiment setup 4.2.1. Test machine 4.2.2. Test cubes 5. Results and Discussion 5.1. Failure modes and bond-slip curves 5.2. The bond-slip functions 6. Conclusion 7. References

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