Timing Recovery for Ultra Wideband Systems

This paper examines the problems of symbol timing estimation and timing recovery for ultra wideband impulse radio signals. Two different approaches based onthe maximum likelihood technique are investigated. The first approach is based on derivative matched filter and the second one takes advantage of the early-late technique. Furthermore, two non-coherent timing recovery circuits are proposed and discussed. The first circuit is a digital delay-locked loop (DDLL) and the second circuit is based on early-late technique. Finally, performance analysis of the proposed techniques for IEEE 802.15.3a channel models in terms of the minimum squared error (MSE) is provided

Cationic surfactant modification and its impact on the engineering behaviors of montmorillonite.

This study focuses on the microstructure of organoclays after organic surfactant modifications and the potential use in geoenvironmental engineering applications including waste containment in earthen barrier, rheological control agents for drilling fluid and soil stabilization. Organoclays, or clays modified by organic matters, are often synthesized by exchanging the naturally occurring interlayer inorganic cations (e.g., Na+, Ca2+) of the clay with organic cationic surfactants. In this research, montmorillonites intercalated with two quaternary ammonium surfactants, hexadecyltrimethylammonium (HDTMA+) and bis (hydrogenated tallow alkyl) dimethyl ammonium were used as the representative organo-rich, partitioning clays. The laboratory characterization techniques including XRD, TEM and FT-IR were employed to examine the interactions between montmorillonite minerals, surfactants, and organic sorbates. The results of XRD and TEM showed the successive interlayer expansion of montmorillonite because of intercalation of surfactants and hydrocarbons sorbates. The FT-IR results further confirmed the arrangement of the intercalated surfactant and the organic sorbates due to primary and secondary sorption. To understand the engineering behaviors of organoclays in earthen barriers, the free swelling and hydraulic conductivity tests were conducted to evaluate the permeability of compacted clay and geosynthetic clay liner (GCL) amended with HDTMA-organoclay. The results suggested that the addition of organoclay (less than 10%) in compacted clay slightly increased the permeability of the mixture to water. However, due to the interaction between the organophilic phase in organoclays and non-polar liquids, low amounts of organoclay within the compacted clay admixture significantly decreased its permeability for non-polar liquids such as gasoline. Moreover, it was observed that low weight percentages of HDTMA-bentonite (up to 20% by weight) had little or no impact on the hydraulic conductivity of the Na-bentonite or Ca-bentonite GCL. However, higher dosages of organoclay in GCLs could reduce the permeability to organic fluids such as gasoline. The impact of the amount of organoclay additives, pressure and temperature on the rheological behavior of organoclay/oil-based drilling fluids was investigated. The obtained results from XRD test suggested that the oil molecules entered the PM199 interlayer, resulting in swelling and exfoliation of PM199. It was observed that the viscosity of 5% PM199 suspension slightly decreased by increasing the temperature from 25 to 60 °C, and then the viscosity increased when the temperature raised from 60 to 150 °C. Moreover, it was found that the viscosity of 5% PM199 suspension increased when the pressure increased from 0 to 200 bar due to physical changes on both oil and organoclay particles. The effectiveness of organoclay and Portland cement for the solidification and stabilization (S/S) of contaminated soils was investigated in the laboratory. The results indicated that the addition of cement (5% or 10% by weight) reduced the hydraulic conductivity and increased the compressive strength of the solidification and stabilization soil specimens. Additionally, the leaching test results indicated that the addition of organoclay during solidification and stabilization significantly reduced the leaching of naphthalene and phenanthrene from the stabilized soil specimen. The results suggested that organoclay particles sorbed the organic contaminates and consequently reduced the naphthalene and phenanthrene leachate concentration. Also, it was observed that the naphthalene and phenanthrene leachate concentration decreased by increasing the curing time of S/S products. Overall, this study performed laboratory tests to obtain information regarding the microsturcture of cationic surfactant modifed bentonties and their engineering behaviors (e.g. hydrophobicity, swelling, permeability, stability in oil suspension). The obtained results are expected to yield significant insights into their potential applications as sorbents in hydraulic and sorptive barriers for organic compounds; rheological control additives in oil-based drilling fluid; agents for stabilization and solidification of contaminated soils

Evaluation of asphalt pavements construction practice in West Virginia

Construction practice is a key factor in building high quality pavement. Unfortunately failure and distresses frequently develop shortly after construction. These distresses may be due to the contractors failing to follow the guidelines and specifications. Monitoring pavement construction provides information for evaluating contractors\u27 practices relative to the best practices as documented in various training courses. Accordingly, the West Virginia Department of Highways (WVDOH) decided to review construction practices. The WVDOH hired 4 co-ops during summer 2012 and 2 co-ops during summer 2013 to document asphalt pavement construction projects. The co-ops were assigned to observe and record pavement construction practices. Observations were documented on forms with supporting photographs and video records. West Virginia University was contracted to train and monitor the co-ops and gather and analyze the construction monitoring information. All the observations data were put into and analyzed using a Microsoft Access database. The results for summer 2012 shows that plant operations comply with best management practices in most areas. However, the observations did indicate several opportunities for improvement in the hauling, placement and compaction of the asphalt concrete. Observations from summer 2013 showed plant operations remained good , the performance of hauling, surface preparation, placement and compaction of the asphalt concrete were better than observed in 2012

An Analytically Based Approach for Evaluating the Impact of the Noise on the Microwave Imaging Detection

In a realistic scenario, it is inevitable to have noise on the images due to the noise from the system's hardware, which results in producing inaccurate images. This paper presents an investigation on the impact of adding noises into the simulation for an Ultra-Wideband (UWB) Microwave Imaging (MWI) procedure based on the Huygens principle (HP). A comparison between uniform and Gaussian noises at different amplitudes is provided, with the aim of investigating the detection process for applications such as bone fracture detection. This is done using analytical simulations. To construct the electric field at the perimeter of the external cylinder, simulations have been run mimicking UWB signals transmitted onto a simulated cylindrical bone-mimicking phantom containing an inclusion with different dielectric properties. This field was simulated using MATLAB and generated a value for the electric field at frequencies between 3 and 5 GHz. To investigate the impact of noise on the detection capability, two types of common noises have been applied to the signal at different amplitudes. The resulting images have visually been compared and the imaging performance has also been analysed using an image quantification metric, signal-to-clutter ratio (SCR). The impact of noise on the detection capability was quantified using this image quantification metric

Combined Beamforming and Space-Time Block Coding with Sparse Array Antennas

We continue our investigation of joint beamforming and transmit diversity with space-time block coding. In particular, the performance of a four-element array antenna is considered, in the context of an indoor wireless communication system. The main contribution is to show that transmit diversity may be practically achieved, even with correlated beams produced by a sparse array antenna

PROCJENA UTJECAJA GEOMETRIJE PUKOTINA NA PROPUSNOST, PRIMJER LABORATORIJSKOGA ISPITIVANJA I NUMERIČKOGA MODELIRANJA

The geometry of fractures includes orientation, spacing, aperture are among the parameters affecting permeability in rocks. Studying the effect of fractures geometry on the permeability in a laboratory scale requires the selection of a suitable sample in terms of physical and mechanical properties. Therefore, in this study, fibrous fiber was selected due to low water absorption and permeability as well as its non-brittle behavior and flexibility. In order to investigate the effect of fracture geometry on the permeability, 1, 2, 3, and 4 fractures with spacing greater than 50 mm, 50 mm, 25 mm, and 15 mm and with orientations of 0, 15, 30, 45, and 60 degrees to the horizon in the sample were created. The fractures did not come into contact with the surface of the sample .The results showed that the permeability raises exponentially with increasing orientation and decreasing the spacing. This situation is mostly seen in fractures with orientations larger than 30 degrees. Also, the permeability measured in the laboratory was compared with the results obtained from the numerical method of distinct elements and UDEC software. The results showed an error of about 10-15%, which is well-matched between the permeability obtained from the laboratory and the numerical method.Geometrija pukotina uglavnom obuhvaća orijentaciju, razmak i promjer, kao varijable koje određuju propusnost stijena. Studije koje se bave izučavanjem geometrije pukotina na laboratorijskim uzorcima imaju preduvjet odabira prikladnih uzoraka za ocjenu fizičkih i mehaničkih svojstava. Stoga je ovdje odabrano vlakno s malom apsorpcijom vode i propusnošću te sa svojstvima nekrtosti, odnosno savitljivosti. Ispitane su 1, 2, 3 i 4 pukotine s razmacima većim od 50 mm, od 50 mm, od 25 i od 15 mm te orijentacijama od 0, 15, 30, 45 i 60 stupnjeva od vodoravne ravnine. Pukotine nisu bile u dodiru s površinom uzorka. Propusnost je rasla eksponencijalno, prateći porast kuta orijentacije i smanjivanje razmaka među pukotinama. To je najbolje opaženo s pukotinama pod kutom većim od 30 stupnjeva. Propusnost dobivena laboratorijski uspoređena je s rezultatima izmjerenim metodom konačnih elemenata i programom UDEC. Dobivena je pogrješka od 10 do 15 % čime je dokazano dobro podudaranje laboratorijskih i numeričkih rezultata

Subject-Based Information Retrieval System in Digital Libraries

Abstract Objective: Information visualization is the study of interactive depictions of abstract and data to strengthen the human cognition. Designing an appropriate information visualization system may be very useful technique for scholars, who intent to get scientific information from digital libraries. The objective of current study was to map and visualize the key-information of dissertations in academic libraries. To achieve the aim, an information retrieval system was designed to present the interactive graphic view of dissertations' subjects in academic. Methods: An information retrieval system was designed by information visualization toolkit that presents the related subjects of dissertations in academic libraries. In addition, the satisfaction-levels of library-users were analyzed by administrating a standard questionnaire (QUIS Questionnaire). Results: The study indicated that the designed IR system helped to provide a user-friendly environment through displaying subjective relations of dissertations, overwhelming variety of colors in displaying information. Fast and easy access to the cover-to-cover information of dissertations and userinteraction facilities are the advantages of designed IR. Analysis of data furthermore indicated that the users' satisfaction from the system was from medium to high grade. Conclusion: Designing the IR-system revealed an excessive influence on users' satisfaction; therefore, proposing such systems for employing in academic libraries is very suitable and its implementation is necessary

A Consensus-Based Generalized Multi-Population Aggregative Game with Application to Charging Coordination of Electric Vehicles

This paper introduces a consensus-based generalized multi-population aggregative game coordination approach with application to electric vehicles charging under transmission line constraints. The algorithm enables agents to seek an equilibrium solution while considering the limited infrastructure capacities that impose coupling constraints among the users. The Nash-seeking algorithm consists of two interrelated iterations. In the upper layer, population coordinators collaborate for a distributed estimation of the coupling aggregate term in the agents' cost function and the associated Lagrange multiplier of the coupling constraint, transmitting the latest updated values to their population's agents. In the lower layer, each agent updates its best response based on the most recent information received and communicates it back to its population coordinator. For the case when the agents' best response mappings are non-expansive, we prove the algorithm's convergence to the generalized Nash equilibrium point of the game. Simulation results demonstrate the algorithm's effectiveness in achieving equilibrium in the presence of a coupling constraint.Comment: 8 pages, 5 figures, journa