Cooperative Wideband Spectrum Sensing Based on Joint Sparsity

COOPERATIVE WIDEBAND SPECTRUM SENSING BASED ON JOINT SPARSITY By Ghazaleh Jowkar, Master of Science A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science at Virginia Commonwealth University Virginia Commonwealth University 2017 Major Director: Dr. Ruixin Niu, Associate Professor of Department of Electrical and Computer Engineering In this thesis, the problem of wideband spectrum sensing in cognitive radio (CR) networks using sub-Nyquist sampling and sparse signal processing techniques is investigated. To mitigate multi-path fading, it is assumed that a group of spatially dispersed SUs collaborate for wideband spectrum sensing, to determine whether or not a channel is occupied by a primary user (PU). Due to the underutilization of the spectrum by the PUs, the spectrum matrix has only a small number of non-zero rows. In existing state-of-the-art approaches, the spectrum sensing problem was solved using the low-rank matrix completion technique involving matrix nuclear-norm minimization. Motivated by the fact that the spectrum matrix is not only low-rank, but also sparse, a spectrum sensing approach is proposed based on minimizing a mixed-norm of the spectrum matrix instead of low-rank matrix completion to promote the joint sparsity among the column vectors of the spectrum matrix. Simulation results are obtained, which demonstrate that the proposed mixed-norm minimization approach outperforms the low-rank matrix completion based approach, in terms of the PU detection performance. Further we used mixed-norm minimization model in multi time frame detection. Simulation results shows that increasing the number of time frames will increase the detection performance, however, by increasing the number of time frames after a number of times the performance decrease dramatically

Mechanical and dentin bond strength properties of the nanosilver enriched glass ionomer cement

The aim of this study was to investigate the mechanical properties and dentin microshear bond strength of a conventional glass ionomer cement (GIC) compared to GIC supplemented with silver nanoparticles (SNPs) at 0.1% and 0.2% (w/w). SNPs were incorporated into a conventional GIC at 0.1% and 0.2% (w/w). The unmodified GIC was used as the control group. Compressive strength, flexural strength, and micro-shear bond strength (µSBS) to dentin were evaluated using a universal testing machine. Surface microhardness was determined using a Vickers microhardness tester. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey?s test. GICs containing 0.1% and 0.2% (w/w) SNPs significantly improved compressive strength, surface microhardness, and dentin µSBS compared to the unmodified GIC (p<0.05). A significant increase in the flexural strength was found for the GIC containing 0.2% (w/w) SNPs (p<0.05). However, the GIC containing 0.1% (w/w) SNPs did not affect flexural strength. GIC supplemented with SNP is a promising material for restoration because of its improved mechanical and bond strength properties. Therefore, it may be suggested for use especially in higher stress-bearing site restorations

The Impact Of Fake-Bad And Fake-Good Responding On The Millon Clinical Multiaxial Inventory, Fourth Edition (MCMI-IV)

The MCMI-IV is a personality scale that attempts to measure psychopathology as well as normal personality functioning. The MCMI-IV has a number of validity scales designed to measure over-reporting and under-reporting of psychological symptoms. No research has been done on the MCMI-IV’s ability to discriminate between respondents who are either over-reporting or under-reporting symptoms. Studies on previous versions of the test suggest elevations on the validity scale Y and elevations on personality scales 4, 5, and 7 in clients who are underreporting symptoms. Previous research also suggests elevations on the validity scale X and Z in clients who are over-reporting symptoms and multiple clinical scales above 85 BR. This study analyzed differences in validity scales when participants were instructed to over-report and under-report symptoms when compared to honest respondents. It was hypothesized underreporters would score high on scale Y, while over-reporters would score high on scales X with a low scale Y and Z. The results were consistent with the hypothesis. Additionally, ROC curves were analyzed between the H and FG group to identify specificity and sensitivity at BR 75 and 85 recommended by the test manual. An optimal cutoff score of 73.50 was identified for the best trade-off of specificity and sensitivity

Performance of Geogrid Reinforced Ballast under Dynamic Loading

Railroad ballast consists of open graded crushed stone used as a bed for railroad track to provide stability. It plays a significant role in providing support for the track base and distributing the load to the weaker subgrade below. Ballast also helps with drainage, which is an important factor for any type of transportation structure, including railroads. This issue has become more acute as heavier car loads place more demand on track structure than before. Over time ballast degrades and loses its strength. Fouling of ballast with fines has been a major issue of railway engineering. Fouling could be caused by break down of ballast itself or intrusion of fines from below or from the environment

Mapping the Scientific Outputs in the Field of Library and Information Science among Islamic Countries in the Web of Science Database from 1994 to 2009

Purpose: The aim of this research was to study the documents produced in the field of Library and Information Science (LIS) by Islamic Countries which are members of the Organization of the Islamic Conference, during 1994-2009. Design/ Methodology/Approach: By applying the method of citation analysis, the best authors and publications in the field of LIS were identified and a historiographic map of the scientific outputs of Islamic countries was depicted. Findings: The average annual growth rate of publications in Islamic countries during the years studied is calculated to be 13.78%. Furthermore, the annual growth of publications in each Islamic country is calculated using the exponential regression method; results show that according to R2 which shows the annual growth rate of the countries’ scientific outputs, the growth of Iran, Bangladesh, Turkey, UAE, Pakistan and Egypt is statistically significant during the 16 years studied (p<0.05). During this 16-year period, the highest rates of growth compared with other countries belong to Iran (33%), Bangladesh (28%) and Turkey (17%). The clusters formed on the historiographic map, which are on the basis of “LCS” and “GCS”, are depicted along with the best publications in this field. Conclusion: With respect to the explosive growth of information, the growth of scientific outputs of the Islamic countries in the Web of Science database does not seem to be all it could be. Authorities of these countries are required to make a serious attempt in producing scientific publications and indexing them in valid international databases

Comparison between the effect of adding microhydroxyapatite and chitosan on surface roughness and Microhardness of resin modified and conventional glass ionomer cements

This study aimed to compare the effect of chitosan (CH) and hydroxyapatite (HP) on the surface roughness and microhardness of a conventional glass ionomer cement (CGIC) and a resin modified glass ionomer cement (RMGIC). 60 disk-shaped specimens (2mm x 6

The effect of silver nanoparticles, zinc oxide nanoparticles, and titanium dioxide nanoparticles on the push-out bond strength of fiber posts

This study was undertaken to investigate the effect of intraradicular dentin pretreatment with silver nanoparticles (SNPs), zinc oxide nanoparticles (ZNPs), and titanium oxide nanoparticles (TNPs) on the push-out bond strength (PBS) of fiber posts to root dentin using two types of resin cements. Eighty single-rooted human premolar roots were randomly divided into eight groups after endodontic treatment and post space preparation, according to the type of intraradicular dentin pretreatment with different nanoparticle solutions (n=20). The groups included no pretreatment (control) and pretreatments with SNPs, ZNPs, and TNPs. Each group was divided into 2 subgroups (n=10) according to cementation: Excite DSC/Variolink II and ED Primer II/Panavia F2.0. The PBS values were measured in different areas of the post space. The data were subjected to the three-way analysis of variance and Tukey tests (p=0.05). The SNP-pretreated groups showed significantly higher PBS values than the other groups. No significant differences in PBS were noted among the control, ZNP-pretreated, and TNP-pretreated groups. There was no significant difference in the PBS of the fiber posts with respect to cement type. The PBS was significantly lower in the apical region than in the other two regions. There was no statistically significant difference between the PBSs of the cervical and middle thirds. Intraradicular dentin pretreatment with SNPs, TNPs, and ZNPs did not interfere with the PBS of the fiber posts. The best result was obtained for the SNP-pretreated groups for both types of cement. Also, the lowest PBS was found in the apical third of the root canal spaces

Effect of laser heat treatment on Pull-out bond strength of fiber posts treated with different silanes

This study evaluated the effect of three different silanes and post-silanization treatments on the retentive strength of fiber posts luted with an etch-and-rinse resin cement. One hundred intact maxillary central incisors were randomly divided into 10 groups after endodontic treatment and post space preparation (n=10). The fiber posts were etched using 24% hydrogen peroxide. Posts of the control group did not receive silane. In nine experimental groups, each of the three silanes used, Scotchbond Universal adhesive, Bis-Silane and Porcelain Primer, was subjected to three treatments: air-drying at 25°C, warm air-drying and CO2 laser heat treatment. After cementation of the treated posts using One-Step Plus/Duo-Link cement, the specimens were stored for one weak and then subjected to pull-out bond strength (PBS) testing. The data in Newton (N) were analyzed using two-way ANOVA and Tukey tests (?=0.05). PBS was significantly affected by silane type and post-silanization treatment (p<0.001). The interaction of the two factors was not statistically significant (p=0.15). The effect of Porcelain Primer on PBS was significantly higher than those of universal adhesive (p<0.001) and Bis-Silane (p=0.01), with similar results for the two latter. Warm air-drying and laser treatment significantly increased PBS (p<0.001). The lowest and highest PBS was obtained in the control (no silane) group (190.9±31) and laser-treated/ Porcelain Primer group (377.1±50), respectively. Warm air-drying and CO2 laser heat treatment had a significantly beneficial effect on retentive strength of fiber posts. Porcelain Primer was significantly more effective than universal adhesive and Bis-Silane