Performance Analysis of Integrating Directional Reception and Realistic Multipath Modelling in Cognitive Communication Systems

M.S. University of Hawaii at Manoa 2016.Includes bibliographical references.The establishment of a cost effective, reliable, and high data rate wireless communication system in rural areas remains to be a significant challenge that requires a fresh and innovative approach. In this thesis, the development of advanced nodes from a physical layer perspective is proposed with a fully directional antenna array and fast digital signal processing without any modifications in the medium access control layer. The proposed physical layer focused solution is based on the use of broadband directional antennas, integrating accurate propagation modeling resources and adaptive cognitive communication capabilities for real-time applications. It is shown that by integrating these diverse resources in the advanced base station or nodes, it is possible to address and solve the long standing problem of adequate communication and high data rate needs in rural areas. Separate hexagonal antenna array is used for user discovery (via scanning) and for data communication with users. Each advanced base station is capable of digital beamforming, beam steering, handover, load management and coordinated multipoint transmission or reception. The directional antennas facilitate base station-to-base station and base station to mobile user connectivity. The predictable time required to estimate the Angle of Arrival (AoA), compute the beamforming weight, and apply the beamforming weights is estimated and inter-frame space where the AoA estimation and beamforming calculation can be applied for IEEE 802.11 is also offered to ensure practical implementation in available standards. Software and hardware simulations confirm that using real devices (FPGAs) it is guaranteed to behave as in the simulation and hence would satisfy the timing constraints. As a part of effective radio network planning and design, Genetic Algorithm (GA) and geospatial assets are used to place base stations in order to optimize the cellular coverage in rural areas such as Maui Island, Hawaii and Kohala region of the Big Island, Hawaii. Main finding and major results show that instead of four isotropic regular base stations (5 dBi), only two directional antenna array based advanced base stations (19 dBi) can be used to cover approximately the same area for both the islands (~91% for Maui and ~83% for Kohala). In perspective to this thesis, capabilities for directional antenna systems and related propagation issues to play a more important role in the system level performance of cognitive communication systems are also investigated as part of the environment awareness engine. The proposed adaptive cognitive communication approach is applied at the base station and the performances of two modern communication systems i.e. Orthogonal Frequency Division Multiple Access (OFDMA) and Multiuser Wireless System are evaluated. Investigation is carried out on trade-offs between accuracy in realistic propagation modeling (number of multipath) and computational time as well as determining the most advantageous beamwidth for directional antennas. This approach is designed to help decide not only if employing the channel parameters, and associated processing delays would help in improving the cognitive communications, but also in determining an acceptable level of modeling details that would achieve acceptable cognitive performance in adaptive and real-time processing. Simulations results show that for realistic SNR/bit values, just the path gain and AoA data for as few as 5 paths could be sufficient in forming a propagation model at the receiver while satisfying certain desired performance criteria. When compared to using all the available propagation modeling data, the use of only 5 paths or less results in 85% reduction in computation time required for generating the channel matrix

Experimental investigation, modelling and optimization in hard turning of high strength low alloy steel (AISI 4340)

The present study addresses the machinability investigation of high strength low alloy grade AISI 4340 steel with coated ceramic tools on surface roughness, tool wear, and economic analysis by considering the hard turning process parameters such as cutting speed, feed and depth of cut. Twenty seven set of trials according to full factorial design of experiments are conducted. Analysis of variance, multiple regression method, Taguchi method, desirability function approach and Gilbert’s technique are employed for parametric influence study, predictive modelling, response optimization, tool life estimation followed by cost analysis. Results indicated that feed and cutting speed are the most significant and crucial factors for hard turning operation in order to achieve minimum surface roughness of machined component as well as flank wear of cutting tool. Abrasions, adhesion followed by plastic deformation are the key wear mechanisms of coated ceramic insert, resulted 47 min of tool life under optimum cutting conditions and ensued lower total machining cost per part ($ 0.29 only) due to higher tool life, and reduced downtime that justifies cost effectiveness of hard turning. Novelty aspects, the current research work demonstrates the substitution of conventional, expensive and slow cylindrical grinding process, and proposes the most expensive CBN tool alternative using coated ceramic tools in hard turning process from techno-economical and ecological point of views in line with the industrial requirements

Assessment of the impact of commonly used beverages on durability of suture materials: An In Vitro study

Aim: The current study was conducted to evaluate the influence of frequently ingested beverages on the stability of suture materials. Materials and Methods: This research comprised of two kinds of chromic catgut, polyglactin 910 (4-0) absorbable suture materials. Every specimen was subjected to tying using a square surgeon's knot. Subsequent to pretensioning, 80 suture samples (40 of every material) were employed in this research. Every specimen was subjected to immersion in artificial saliva to replicate the oral atmosphere. Specimens were sunken in the acidic drink (Coca Cola) and tea for 10 min every day. Tensile strengths of the suture specimens were subjected to test at particular time periods: before immersion and 1, 7, and 14 days after immersion. Tensile strength evaluation of the suture specimens was performed employing the microtensile tester at a cross-head speed of 2.0 mm/60 s. Results: When subjected to exposure to acidic beverages, the tensile strength of chromic catgut suture before immersing was 25.14 ± 0.16, 25.02 ± 0.08 on the first day, 16.34 ± 0.23 on the seventh day, and 9.18 ± 0.28 on the fourteenth day. When the suture substance made contact with tea, the tensile strength before immersing was 24.48 ± 0.02, 24.14 ± 0.16 on the first day, 18.26 ± 0.11 on the seventh day, and 12.39 ± 0.14 on the fourteenth day. When subjected to exposure to acidic beverages, the tensile strength of polyglactin 910 sutures before immersing was 25.21 ± 0.02, 25.08 ± 0.01 on the first day, 18.12 ± 0.06 on the seventh day, and 10.06 ± 0.32 on the fourteenth day. When the suture substance made contact with tea, the tensile strength before immersing was 25.02 ± 0.14, 24.96 ± 0.04 on the first day, 20.48 ± 0.18 on the seventh day, and 14.10 ± 0.08 on the fourteenth day. The differences between the groups were statistically significant. Conclusion: In conclusion, polyglactin 910 exhibited a maintained strength superior than chromic catgut sutures subsequent to 14 days

Assessment of oral health-related quality of life in patients receiving corticobasal dental implants

Background: Among various treatment modalities for tooth replacement, dental implants are considered the best one. This study assessed the effects of smoking, periodontitis, and diabetes on oral health-related quality of life (OHRQoL) in patients receiving corticobasal dental implants. Materials and Methods: One hundred twenty patients of either gender who received corticobasal dental implants were enrolled. All were subjected to Oral Health Impact Profile-20 (OHIP-20) for dental implant patients (OHRQoL questionnaire). The patient satisfaction level was measured on a scale with points ranging from 0 to 5. The value 0 indicates no satisfaction, whereas the value 5 shows highly satisfied. Results: Of 120 patients, males were 70 and females were 50. The overall satisfaction level was 4.92, articulation speech was 4.12, implants were 4.80, and construction was 4.88. The overall satisfaction, articulation speech, implants, and construction values in patients with and without diabetes were 4.90 vs 4.93, 4.56 vs 4.86, 4.76 vs 4.92, and 4.94 vs 4.83, respectively. The overall satisfaction, articulation speech, implants, and construction values in patients with and without smoking were 4.83 vs 4.91, 4.52 vs 4.88, 4.70 vs 4.82, and 4.12 vs 4.84, respectively. The overall satisfaction, articulation speech, implants, and construction values in patients with and without periodontitis were 4.72 vs 4.96, 4.52 vs 4.88, 4.73 vs 4.98, and 4.81 vs 4.95, respectively. The overall satisfaction, articulation speech, implants, and construction values in patients with one to three risk factors and control were 4.85 vs 4.96, 4.82 vs 4.94, 4.88 vs 4.97, and 4.76 vs 4.86, respectively. There was a significant difference in pain, infections and/or swelling, sleeping problems, problems with self-confidence, taste, chewing discomfort and/or difficulties, and influence on food choice before and after in patients treated with corticobasal dental implants (P < 0.05). Conclusion: The satisfaction level is higher after obtaining corticobasal dental implants in patients with diabetes, smoking, and periodontitis as compared to control. Thus, corticobasal dental implants may be considered alternate treatment options for these patients