Subsurface Characterization of Flexible Pavements Constructed Over Expansive Soil Subgrades and Selection of Suitable Rehabilitation Alternatives

Expansive soils present significant engineering challenges, with annual costs associated with repairing structures constructed over expansive soils estimated to run into several billion dollars. Volume changes in expansive soil deposits induced by fluctuations in the moisture content can result in severe damage to overlying structures. A flexible pavement section near the Western Border of Idaho has experienced recurrent damage due to volume changes in the underlying expansive soil layer; traditional stabilization methods have provided partial success over the years. The main objective of this research effort was to characterize the problematic soil layer contributing to the recurrent pavement damage and propose suitable rehabilitation alternatives. An extensive laboratory test matrix was carried out to characterize soil samples collected from underneath the problematic pavement section. Laboratory tests showed that the problematic expansive soil deposit was often at depths greater than 6 ft. (183 cm) from the pavement surface. Potential Vertical Rise (PVR) values calculated for ten boreholes strategically placed along the problematic pavement section closely matched with the surface roughness profile observed in the field. Liquidity Index (LI) calculations indicated that the active-zone extended to a depth of least 11 ft. (335 cm) from the pavement surface, and therefore, most of the heaving likely originates from soil layers as deep as 11 ft. (335 cm) from the pavement surface. Clay mineralogy tests indicated the presence of high amounts of Montmorillonite that can lead to significant volume changes. Moreover, high sulfate contents were detected in soil samples obtained from several of the boreholes, indicating a potential for sulfate-induced heaving upon chemical stabilization using calcium-based stabilizers. Based on findings from the laboratory testing, it was concluded that chemical stabilization or shallow treatment alternatives are not likely to be successful in mitigating the recurrent differential heave problems. A mechanical stabilization approach using geocells was proposed as a likely rehabilitation alternative for this pavement section. By dissipating the heave-induced stresses over a wider area, this reinforcement configuration was hypothesized to significantly reduce the differential heave. Finite-element models of the pavement section comprising six alternative geocell-reinforced configurations were prepared using the commercially available package, ABAQUS®. Moisture swelling and suction properties for the expansive soil deposit were established in the laboratory and were used in the numerical model to simulate the swelling behavior. Results from the numerical modeling effort established that placing two layers of geocell within the unbound granular base layer led to the highest reduction (~60%) in the differential heave. Placing a single layer of geocell, on the other hand, reduced the differential heave magnitude by approximately 50%. A single layer of geocell was therefore recommended for implementation to achieve the optimal balance between pavement performance and construction costs

Robust Face Representation and Recognition Under Low Resolution and Difficult Lighting Conditions

This dissertation focuses on different aspects of face image analysis for accurate face recognition under low resolution and poor lighting conditions. A novel resolution enhancement technique is proposed for enhancing a low resolution face image into a high resolution image for better visualization and improved feature extraction, especially in a video surveillance environment. This method performs kernel regression and component feature learning in local neighborhood of the face images. It uses directional Fourier phase feature component to adaptively lean the regression kernel based on local covariance to estimate the high resolution image. For each patch in the neighborhood, four directional variances are estimated to adapt the interpolated pixels. A Modified Local Binary Pattern (MLBP) methodology for feature extraction is proposed to obtain robust face recognition under varying lighting conditions. Original LBP operator compares pixels in a local neighborhood with the center pixel and converts the resultant binary string to 8-bit integer value. So, it is less effective under difficult lighting conditions where variation between pixels is negligible. The proposed MLBP uses a two stage encoding procedure which is more robust in detecting this variation in a local patch. A novel dimensionality reduction technique called Marginality Preserving Embedding (MPE) is also proposed for enhancing the face recognition accuracy. Unlike Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA), which project data in a global sense, MPE seeks for a local structure in the manifold. This is similar to other subspace learning techniques but the difference with other manifold learning is that MPE preserves marginality in local reconstruction. Hence it provides better representation in low dimensional space and achieves lower error rates in face recognition. Two new concepts for robust face recognition are also presented in this dissertation. In the first approach, a neural network is used for training the system where input vectors are created by measuring distance from each input to its class mean. In the second approach, half-face symmetry is used, realizing the fact that the face images may contain various expressions such as open/close eye, open/close mouth etc., and classify the top half and bottom half separately and finally fuse the two results. By performing experiments on several standard face datasets, improved results were observed in all the new proposed methodologies. Research is progressing in developing a unified approach for the extraction of features suitable for accurate face recognition in a long range video sequence in complex environments

Strength Behavior of Mortar Using Fly Ash as Partial Replacement of Cement

This paper reports the results of an experimental investigation carried out to study the effects of fly ash on strength development of mortar and the optimum use of fly ash in mortar. Cement was partially replaced with six percentages (10%, 20%, 30%, 40%, 50% and 60%) of class F fly ash by weight. Ordinary Portland cement (OPC) mortar was also prepared as reference mortar. Compressive as well as tensile strengths of the mortar specimens were determined at 3, 7, 14, 28, 60 and 90 days. Test results show that strength increases with the increase of fly ash up to an optimum value, beyond which, strength values start decreasing with further addition of fly ash. Among the six fly ash mortars, the optimum amount of cement replacement in mortar is about 40%, which provides 14% higher compressive strength and 8% higher tensile strength as compared to OPC mortar

Characterization of the Line Configuration in Wired Communication Networks

This thesis presents an algorithm to identify the full configuration of a wired transmission line from its frequency response. It is assumed that the line can have up to two bridged taps. Each bridged tap divides the main line to two segments, and with two bridged taps there will be at most three segments in the main line. Furthermore, each segment of the main line and the bridged taps can have three different gauges. The problem of characterizing the line configuration is concerned with identifying each segment (main line segments and bridged taps) in terms of its length and gauge. The problem is solved in two phases: initialization and optimization. The algorithm can be used as single ended line testing, which means the line can be characterized by performing a simple test from the central office. Simulations demonstrate the accuracy of the proposed method

Advanced Digital Signal Processing Based Redefined Power Quality Indices, and Their Applications to Wind Power

This dissertation proposes a time-frequency distribution (TFD) based new method to redefine the power quality (PQ) indices for the assessment of PQ disturbances typically present in electric power systems. The redefined PQ indices are applied to various types of synthetic and real-world PQ disturbances in order to verify the efficacy and applicability of the proposed method. The case studies show that the proposed method provides actual results with respect to the existing TFD-based transient PQ indices, and provides much more accurate results than the traditional fast Fourier transform (FFT) based PQ indices under stationary and nonstationary PQ disturbances. In addition, utilizing the proposed method, the power components contained in the IEEE Standard 1459-2010 are redefined for single-phase, and three-phase power systems under sinusoidal, nonsinusoidal, balanced and unbalanced conditions. Unlike the traditional FFT-based method, the proposed method is able to extract the time information lost in the FFT, and provides very accurate and instantaneous assessment of the power components according to the IEEE Standard 1459-2010. Also, the proposed method will have the advantage of finding the instantaneous direction of time-varying harmonics power flow which can be positive or negative depending on the harmonics flow to the network or to the load. According to the IEEE Standard 1459-2010, the harmonic active power PH is obtained by subtracting the fundamental active power P1 from the total active power P (PH = P−P1). However, the indirect measurement of the harmonic active power may provide imprecise result since harmonic active power is generally very small part of the total active power. In this dissertation, a direct assessment of the harmonic active power is carried out to obtain accurate result based on the proposed method. In addition, a new perspective for wind power grid codes is proposed in order to verify that a wind generating plant conforms to grid codes requirements under stationary and nonstationary PQ disturbances, and to obtain supervisory data to protect system reliability. The proposed method is also able to extract the dynamic signature of PQ disturbances introduced by variable speed wind energy conversion systems onto the electrical grid. Also, a TFD-based newmethod is proposed for the assessment of grid frequency deviation caused by wind power fluctuations in fixed speed wind energy conversion systems

Effect of divalent oxides on the structure of glasses for HLW immobilisation

The mixed alkali borosilicate glass system used for high-level waste immobilisation, has been studied with different divalent additive oxides such as CaO, Srf), BaO, MnO, ZnO and PbO added to the BNFL base glass (MW). A number of techniques have been employed in order to study the effect of these oxide additives. lIB MAS NMR was performed to measure the fraction of tetrahedrally coordinated boron atoms N4 and 29Si MAS NMR to measure the Qn speciation. Durability tests were carried out and compared with electrical conduction behaviour. Densities, glass transition temperatures and thermal expansion coefficients are also reported. The change in N4 with concentration has been determined for different additive oxides. The addition of BaO, CaO and srO to the base (MW) BNFL vitrification glass caused N4 to increase with alkaline earth content, and maximum values were attained at compositions depending on the M2+ ion type. In contrast, the addition of divalent oxides such as ZnO and PbO to MW reduced the N4 values, with the rate of decrease being greater for ZnO than PbO. The 29Si NMR studies have shown the presence of significant concentrations of non-bridging oxygens which can influence the aqueous corrosion behaviour of the glass. The durability tests revealed that the alkaline earth oxides BaO, srO and CaO decrease the durability. In contrast, oxides such as ZnO and PbO improve the corrosion resistance. The presence of a surface Mn7Si012 crystallisation phase was identified on corroded MnO containing glasses. The reduction in electrical conductivity with oxide addition shows a similar trend to the corrosion behaviour for chemically resistant glasses. In contrast, the opposite trend is found for less durable glasses. UV visible transmission of MnO doped glass shows a decrease in transmittance at - 380 run. The absorption band centred at - 49Onm, moves towards longer wavelength, caused by generation ofNBOs on the [Si04] tetrahedral unit

The Utilization of Bacillus Subtilis Bacteria to Improve the Mechanical Properties of Concrete

The utilization of concrete as a building material is well-known worldwide and increasing continuously due to its sustainability, low maintenance cost, durability, performance, etc. The ingredients of concrete, its constructional methodology, and exposure conditions have been observed to be moderating and improving daily but the focus of this research is on the laboratory investigation of Bacterial Concrete which is the technology established on the application of the mineral producing microbes like Bacillus subtilis which have the properties of bio-calcification and the ability to precipitate CaCO3 effectively inside concrete structures. This CaCO3 precipitation is able to fill the pores and cracks internally and this subsequently makes the structure to become more compact. Nutrient Broth (NB) media was employed for the growth and spore formation of Bacillus subtilis bacteria in this experimental study and four different bacterial culture densities including 0.107, 0.2, 0.637, and 1.221 were estimated at OD600 and directly added to the concrete matrix using the previously fixed water to culture ratio of 0.5:0.5. Moreover, 100 mm cubical concrete specimens were cast, subjected to compressive and tensile strength tests for different curing ages, and finally compared with Conventional Concrete with OD600=0. A significant increase was observed in the mechanical strengths due to the addition of Bacillus subtilis bacteria in concretes with a culture density of 0.637. Furthermore, cylindrical concrete specimens with 100 mm diameter and 200 mm height were prepared for Ultrasonic Pulse Velocity (UPV) analysis and the results showed specimens prepared with culture density of 0.637 have higher pulse velocity than other microbial groups. A UPV vs. compressive strength relationship curve was, however, later proposed for different strengths of concrete

Estimating the Environmental Cost of Shrimp Farming in Coastal Areas of Chittagong and Coxs bazaar in Bangladesh

During the last three decades, shrimp has remained one of the major export items in Bangladesh. It contributes to the development of this country by enhancing export earnings and promoting employment. However, coastal wetlands and agricultural lands are used for shrimp culture, which reduces agricultural opportunity and peasants income, and destroys the mangroves and coastal eco-system. These are the external environmental costs that are not reflected in farmers price and output decisions. This study has aimed to estimate those external environmental costs through the contingent valuation method. The calculated environmental cost of shrimp farming is USD 13.66 per acre per year. Findings suggest that current shrimp production and shrimp price will no longer be optimal once the external costs are internalized. Thus alternative policy recommendations have been proposed so that shrimp farming becomes a sustainable and equitable means of aquaculture.Comment: 28 page

Does Use of Twitter by Political Leaders Matter in a Health Crisis? The Perspective of COVID-19

While extant literature has reached a consensus on the effectiveness of Twitter in crisis communication, this paper contextualizes the use of Twitter specifically by political leaders during the COVID-19 crisis. We first identify political leaders on Twitter using machine learning techniques and then examine the significant properties of their networks. The findings demonstrate that the network of political leaders on Twitter is relatively dense and well-connected. However, a few nodes are highly prominent and have a large number of connections. Our study detects twenty-three communities of political leaders and observes the evidence of political polarization in the network. We also find two large communities representing the Republican and Democratic parties at the national-level. The remaining communities are reasonably well-balanced in size and center at the state-level. In further analysis, we plan to investigate the patterns of COVID-19 crisis communications through this network and explore the association with COVID-19 outcomes using panel data