Characterization and assessment of liquefaction potential of gravelly soil in a reliable cost-effective manner has always been a great challenge for the geotechnical engineers. The typical laboratory investigation techniques have proven to be ineffective for characterizing gravelly soil due to the cost and difficulty of extracting undisturbed sample from gravelly deposits. The traditional in-situ tests like SPT or CPT are not very suitable for gravelly soil because of interference with large size gravel particles which can artificially increase the penetration resistance. The Becker Penetration Test, well known for gravelly soil characterization, is cost-prohibitive for routine projects and is not available in most of the world. The Chinese dynamic cone penetration test (DPT) with a larger diameter probe compared to the SPT or CPT, can be economically performed with conventional drilling equipment. Besides the penetration testing, in-situ measurement of shear wave velocity (Vs) is another alternative of characterizing gravel liquefaction. Probabilistic liquefaction triggering curves were developed by performing both DPT and shear wave velocity test at the Chengdu Plain of China where massive gravel liquefaction took place during 2008 Wenchuan earthquake. These curves have significant uncertainty as they were developed from a single event database. As a part of this study, both DPT and Vs tests have been performed at various sites around the world where gravelly soil did or did not liquefy in various past earthquakes. These newly collected data have been added to the existing Chinese dataset to form a large database on gravel liquefaction case histories for both DPT and Vs. Based on this larger database, new magnitude dependent probabilistic liquefaction triggering procedures have been developed for both DPT and Vs. The larger database has significantly improved the triggering curves by reducing the spread and constraining the curves at both the higher and lower end. New Magnitude Scaling Factor (MSF) curves have been developed for both DPT and Vs which were found to be consistent with existing MSF curves. Further, an instructive comparison has been drawn between the performance of CPT and newly developed DPT triggering procedure the liquefaction potential of gravelly deposits CentrePort in Wellington. Results showed that both DPT and CPT performed reasonably well in liquefaction assessment of the gravelly fill. However, the CPT-based CRR profiles contain intermittent spikes due to the interaction with gravel particles whereas the DPT resistance appear to be relatively smooth. Similar comparison has been presented between the DPT and BPT in performing liquefaction assessment of gravelly soil at the Borah Peak sites in Idaho. It is found that both DPT and BPT successfully evaluate the liquefaction potential of the loose critical layers but the medium dense to dense layers are identified as non-liquefiable by the DPT whereas the same deposits are identified as liquefiable by the BPT. Lastly, an investigation has been carried out to observe the effect of hydraulic conductivity and in-situ drainage on the liquefaction triggering in gravelly soils based on field data along with a group of numerical analyses. It is found that the hydraulic conductivity of gravelly soil reduces with sand content which eventually may cause liquefaction during earthquake shaking. Low permeability cap layer may also impede the drainage path to generate excess pore pressure to trigger liquefaction in the gravelly strata.

BACKGROUND: Electronic cigarettes (e-cigarettes) are nicotine delivery systems that generate an aerosol that can be inhaled and come in a variety of attractive designs and e- liquid flavorings. E-cigarettes are the second most commonly used tobacco product in the United States and are predominantly used by youth and young adults. The cardiovascular health risk of combustible cigarette use is well-established, but whether e-cigarettes increase the risk of cardiovascular events is less clear. Evaluating the short-term vascular effects of e-cigarette use is an approach to gain insight into the cardiovascular health impact. Limited studies have shown that acute e-cigarette use in combustible cigarette users was associated with increased central hemodynamic values and arterial stiffness. Few studies have assessed the effects of chronic e-cigarette use on arterial stiffness, particularly in young adults. OBJECTIVE: To assess the effects of e-cigarette use on central hemodynamics and arterial stiffness in regular e-cigarette users in comparison to combustible cigarette users and non-users. METHODS: Combustible cigarette users, e-cigarette users, and non-users without known cardiovascular disease (CVD) or CVD risk factors between the ages of 18 and 45 were enrolled in the ongoing Cardiovascular Injury due to Tobacco Products 2.0 (CITU 2.0) study at the Boston University School of Medicine and the University of Louisville School of Medicine starting from 2019. Non-invasive arterial tonometry, using the SphygmoCor system, was performed to measure peripheral artery waveforms to obtain central hemodynamic values and arterial stiffness parameters: augmentation index (AIx), carotid-radial (CR) and carotid-femoral pulse wave velocities (CFPWV). RESULTS: We had available arterial stiffness measures in 209 study participants (mean age 26±7, 48% female) across 3 tobacco product use groups: combustible cigarette users (N=51), e-cigarette users (N=97), and non-users (N=61). Amongst the e-cigarette users, 41 were dual users (use of both e-cigarettes and combustible cigarettes), 25 were exclusive e-cigarette users who were former combustible cigarette users, and 31 were exclusive e-cigarette users who were never combustible cigarette users. The majority (87%) of e-cigarette users used a pod-based product with fruit and mint/wintergreen or menthol as the most popular e-liquid flavors. In unadjusted analyses, central systolic blood pressure, AIx, CRPWV, and CFPWV differed across the three tobacco product use categories. In multivariable regression models adjusting for age, sex, race and study site, e-cigarette users and combustible cigarette users had higher central systolic blood pressure (β=3.9±2.0, p=0.048 and β=4.8±2.4, p=0.04, respectively) whereas combustible cigarette smokers also had higher central AIx, and CRPWV compared to non-users (β=6.9±3.3, p=0.04 and β=0.97±0.31, p=0.002, respectively). In unadjusted analyses across the five groups, we found similar patterns of differences in vascular measures. In multivariable regression models comparing to combustible cigarette users, dual product users had similar measures of vascular function whereas exclusive e-cigarette users who were former smokers had lower CRPWV (β=-0.95±0.36, p=0.009), and exclusive e- cigarette users who were never combustible cigarette users had lower AIx (β=-9.0±4.2, 0.04). CONCLUSIONS: Our findings suggest that in young adults, combustible cigarette use is associated with measures of arterial stiffness. Dual e-cigarette use was largely similar to combustible cigarette use whereas exclusive e-cigarette use had a lesser degree of vascular stiffening. Further studies are needed to evaluate the long-term impact of e- cigarette use on cardiovascular health.

Recent tsunami events have inflicted devastating damage to coastal communities. Existing design standards provide a certain level of evaluation of tsunami effects such that critical infrastructure can be designed to resist tsunamis. Tsunami momentum flux, used to design structures is a function of water level height and velocity of tsunami bores. Understanding tsunamis and developing mitigation measures is essential. So far, some mitigation measures have been suggested, and to improve them, further investigations are required. The design of tsunami inundation effects mitigation canals is one of the suggested solutions which has received limited attention. The first objective of this study was to investigate the effects of a rectangular canal on the hydrodynamics of turbulent bores before and after the canal by conducting a series of physical experiments. A dam-break wave was used to simulate the tsunami-like turbulent waves passing over a smooth and horizontal surface, in the presence and/or absence of a canal. Three canal water depths were used to model shallow, moderate, and deep conditions, and three canal widths were also selected to model narrow to wide conditions while the dam break waves were generated from three different impoundment depths in a reservoir located upstream of the canal. The dam-break wave propagation over a horizontal, dry, and smooth bed revealed four regimes describing the variations of bore height with time. The time to reach the maximum bore height and the quasi steady-state regime were correlated with each impoundment depth and an empirical formulation was proposed to estimate the onset of the quasi steady-state flow. The maximum bore heights measured before and after the mitigation canal location were approximately 40 % and 50 % respectively, higher compared with those recorded in the corresponding tests without the presence of a canal. The second objective of this study was to experimentally investigate the effects of canal depth on the time history of bore height and its velocity. The experimental results were used for calibration and validation of a developed numerical model. The rapid release of an upstream impoundment water depth was employed to generate a bore analogous to a tsunami-induced inundation. The time histories of wave heights and velocity were measured upstream and downstream of the canal. The recorded time-series of the water surface levels and velocities were compared with the simulation results and good agreement was found between experimental and numerical water surface profiles using a Root Mean Square Error (RMSE) and the Relative Error. Three turbulence models:, namely the standard k-ε, the Realizable k-ε, and the RNG k-ε were tested, and it was found that all turbulence models perform well but the standard k-ε model provided satisfactory accuracy. The velocity contour plots for shallow, medium, and deep mitigation canals showed the formation and evolution of jets of different characteristics. The energy dissipation and air bubble entrainment of the tsunami bore, as it plunged into a canal, increased as the canal depth increased, and the jet flow of the maximum bore velocity decreased with increased canal depth. It was found that the eye of the vortex in the canal moved steadily in the downstream direction. Generally, the bore fully plunged almost nearly into the middle of the canal and started to divide into two small vortices. The third objective of this study dealt with a sequence of numerical experiments conducted to investigate the impact of mitigation canals on the hydrodynamics of a tsunami-like turbulent bore moving across a flat bed. The effects of mitigation canal depth and its orientation on the reduction of maximum specific momentum and energy of turbulent bores crossing over it were investigated numerically. Variations in the ratio between the downstream and upstream maximum specific momentum and mean flow energy decreased as the canal depth increased, and the time history of the mean flow energy over a canal with a rectangular endwise profile revealed that the canal depth affects the jet stream of the maximum mean flow energy. As the canal depth increased, the period of time needed to dissipate the area of the jet stream with the maximum turbulent kinetic energy, vorticity, and energy dissipation rate decreased. Both the angled and perpendicular to flow direction canals caused the maximum specific momentum and energy of the turbulent bore to decrease downstream of the canal. The specific momentum and energy achieved their highest values for a canal orientation of 45º. The greatest reductions in maximum specific momentum for turbulent bores over canals with different depths and orientations were achieved for 𝜃 = 30°.

The purpose of our work is to estimate arterial stiffness based on the virtual fields method and using pressure gradients and arterial wall motion. Currently, the gold standard to estimate arterial stiffness relies primarily on the pulse wave velocity, which provides a relation between arterial stiffness and the velocity of the pressure wave propagating through the arterial wall. The pulse wave velocity method has been improved over the years, but still depends on specific assumptions regarding, for example, blood pressure, arterial geometry, and linear material response. The proposed method directly links arterial wall displacements and pressure gradients to arterial stiffness and paves the way to computing arterial stiffness with higher accuracy.

No description available.

No description available.

Overpressure, or abnormally low effective pressures, is hazardous in drilling operations and construction of sea-bottom facilities in deepwater environments. Estimation of the locations of overpressure can improve safety in these operations and significantly reduce overall project costs. Propagation velocities of both seismic P and S wave are sensitive to bulk elastic parameters and density of the sediments, which can be related to porosity, pore fluid content, lithology, and effective pressures. Overpressured areas can be analyzed using 4C seismic reflection data, which includes P-P and P-SV reflections. In this thesis, the effects on compressional (P) and shear (S) wave velocities are investigated to estimate the magnitude and location of excess pore pressure utilizing Eaton’s approach for pressure prediction (Eaton, 1969). Eaton’s (1969) method relates changes in pore pressure to changes in seismic P-wave velocity. The underlying assumption of this method utilizes the ratio of observed P-wave velocity obtained from areas of both normal and abnormal pressure. This velocity ratio evaluated through an empirically determined exponent is then related to the ratio of effective stress under normal and abnormal pressure conditions. Effective stress in a normal pressured condition is greater than the effective stress value in abnormally overpressured conditions. Due to an increased sensitivity of variations in effective pressure to seismic interval velocity, Ebrom et al. (2003) employ a modified Eaton equation to incorporate the S-wave velocity in pore pressure prediction. The data preparation and subsequent observations of seismic P and S wave velocity estimates in this thesis represent a preliminary analysis for pore pressure prediction. Six 2D receiver gathers in the regional dip direction are extracted from six individual ocean-bottom 4C seismic recording nodes for P-P and P-SV velocity analysis. The receiver gathers employed have minimal pre-processing procedures applied. The main processing steps applied were: water bottom mute, 2D rotation of horizontal components to SV and SH orientation, deconvolution, and frequency filtering. Most the processing was performed in Matlab with a volume of scripts designed by research scientists from the University of Texas, Bureau of Economic Geology. In this thesis, fluid pressure prediction is estimated utilizing several 4C multicomponent ocean-bottom nodes in the Atlantis Field in deepwater Gulf of Mexico. Velocity analysis is performed through a ray tracing approach utilizing P-P and P-SV registration. A modified Eaton’s Algorithm is then used for pore pressure prediction using both P and S wave velocity values. I was able to successfully observe both compressional and shear wave velocities to sediment depths of approximately 800 m below the seafloor. Using Hamilton (1972, 1976) and Eberhart-Phillips et al. (1989) regressions as background depth dependent velocity values and well-log derived background effective pressure values from deepwater Gulf of Mexico, I am able to solve for predicted effective pressure for the study area. The results show that the Atlantis subsurface study area experiences a degree of overpressure. / text

El hormigón armado compuesto de cemento Portland fue inventado hace algo más de un siglo aproximadamente y se ha convertido en el material más utilizado en la construcción. La durabilidad de este hormigón es una de las consideraciones más importantes a ser tenidas en cuenta en el diseño de nuevas estructuras y en la evaluación estructural de las ya existentes. Cuando un hormigón sujeto a un ambientes o cargas que puede degradarlo, como puede ser su uso en puentes y ambientes marinos o si contiene grandes cantidades de alúmina o áridos reciclados, el conocimiento o predicción de su durabilidad es una aspecto crítico para su comportamiento en servicio. Los ensayos no destructivos se han mostrado como unos de los ensayos preceptivos con una importancia económica y social más relevante desde que se han aplicado para la auscultación de la durabilidad de las estructuras de hormigón pertenecientes a la ingeniería civil, donde estos materiales son ampliamente utilizados. En cualquier caso, el uso de las técnicas no destructivas en estos materiales no está suficientemente implementado, hecho este motivado por las características heterogéneas de su microestructura. De todos los métodos no destructivos aplicables para el hormigón, el uso de pulsos ultrasónicos es de gran interés para la caracterización de la microestructura y las propiedades de materiales heterogéneos. El objetivo del presente trabajo es obtener un procedimiento de evaluación del ciclo de vida del hormigón preparado y puesto en servicio para ambientes marinos. Además, será estudiado y analizado la incorporación de varias metodologías (destructivas y non destructivas) para caracterizar el proceso de degradación de morteros y hormigones expuestos a disolución de sulfato de sodio y a exposición en disolución de nitrato amónico. Con esta finalidad, una integración adecuada de diferentes técnicas será usada para la caracterización de propiedades y el seguimiento del proceso de degradación que afectan al hormigón. Como objetivos adicionales, destaca que fueron estudiadas las relaciones entre los parámetros destructivos y no destructivos, así como la relación entre los distintos parámetros no destructivos entre sí. Muchos de los estudios anteriores que han usado la inspección ultrasónica las cuáles fueron utilizadas para determinar la relación agua/cemento del mortero, de la pasta de cemento y del hormigón, o para monitorizar los cambios estructurales, para diferentes relaciones a/c, en el proceso de curado. En este trabajo de investigación fue analizado el efecto que tiene para diferentes relaciones a/c en los parámetros ultrasónicos durante el proceso de degradación. Para este objetivo, se utilizaron un Cemento Portland tipo II A L 42.5 (LPC), y otro sulforresistente tipo I 42.5R/SR (SRPC) que fueron usados en la fabricación de dos marcos de hormigón, los cuales fueron utilizados como hormigón en servicio (caso real). Para el estudio del efecto de la variación de a/c en los parámetros ultrasónicos durante la degradación se utilizaron muestras de mortero con deferentes relaciones agua cemento 0.525- 0.45- 0.375 and 0.30 a partir de LPC para obtener diferentes niveles de degradación. Para monitorizar el proceso de degradación se utilizó la inspección por pulso/eco (1 y 3.5 MHz) para la obtención del parámetro del área del perfil de atenuaciones (APA) el cual fue estimado por L Vergara et al., 2003 y usado por Fuente et al, 2004. Para seguir el proceso de curado de pasta de cemento y morteros, este parámetro ha demostrado una alta sensibilidad para caracterizar los cambios microestructurales de materiales derivados del cemento a lo largo de su curado. El método de transmisión se ha utilizado para la determinación de las velocidades de ondas longitudinales con la frecuencia de 1MHz y transversales con la frecuencia de 500 kHz. La velocidad ultrasónica también ha demostrado la capacidad para seguir los cambios microestructurales de un modo sencillo porque dicho parámetro está relacionado con la variación de las propiedades mecánicas, y bajo ciertas premisas, con la variación de la porosidad. El análisis con la imagen ultrasónica con 2 MHz fue también usada para la consecución de los mismos objetivos. Como métodos destructivos, los ensayos de resistencia a la compresión y flexión fueron los utilizados para determinar la pérdida de actividad resistente de morteros y hormigones, y la porosidad conectada al agua para analizar los cambios en la matriz porosa por el efecto de la difusión de elementos agresivos que penetran en el material provocando su degradación. La porosimetría de mercurio (MIP) fue usada para observar las variaciones del volumen y tamaño de poro y, por último, la microscopía electrónica de barrido (MEB) que fue utilizada para cuantificar y detectar los cambios en la microestructura por el ataque de elementos agresivos. Los resultados obtenidos muestran que, la degradación producida por exposición a sulfato de sodio, tiene dos etapas, en la primera etapa se forma la etringita que llena los poros pero que no produce microfisuración. En esta etapa se observó una variación en los parámetros obtenidos por ejemplo, incremento de la velocidad de la onda ultrasónica, de las resistencias a compresión y a la flexión o la disminución de la porosidad. Esta variación en los parámetros podría indicar una mejora en las prestaciones mecánicas del material objeto de la investigación, pero en realidad esto no es cierto porque los poros están llenos de etringita, provocando una expansión, que es la causa de la degradación en la segunda etapa. En dicha segunda etapa, se produce una microfisuración generalizada por la expansión de la etringita e incrementando su volumen dentro de los poros. Este hecho produjo un cambio en los parámetros medidos que contrastan con la evolución en la primera etapa, disminución de la velocidad de las ondas ultrasónicas, y de las resistencias mecánicas y consecuentemente un aumento de la porosidad. Por otro lado, la degradación por ataque de nitrato amonio tiene una única etapa debida al proceso de descalificación que comienza desde el principio del proceso de exposición y es lineal durante todo el periodo de exposición. Para ambos casos, la integración de las diversas técnicas se revela como satisfactoria para el seguimiento del proceso de degradación, encontrando buenas correlaciones entre los parámetros no destructivos y los parámetros destructivos de técnicas de análisis físico-químico. / Mahmoud, TI. (2013). Evaluation of the degradation process of cement-based materials exposed to aggressive environment by using ultrasonic techniques and physical characterisation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/27550 / TESIS

Объектом исследования являются 3 образца нанокерамики на основе Al2O3, и 4 образца кварцевых стекол: КИ, КВ, КУ, КС-4В. Цель данной работы – исследование акустических свойств, обусловленных особенностями микро- (нано)структуры двух категорий материалов микро- и оптоэлектроники – нанокерамики на основе Al2O3 и оптических кварцевых стекол. В процессе работы были: исследованы акустические свойства материалов микро- (нанокерамика на основе Al2O3) и оптоэлектроники (кварцевые стекла), исследованы оптические параметры кварцевых стекол и установлена корреляция между акустическими и оптическими параметрами. В результате исследования был создан оригинальный измерительный стенд и разработана методика измерения значений скоростей поперечных ультразвуковых волн, определены упругие характеристики нанокерамики на основе Al2O3 и кварцевых стекол, а также оптические параметры стекол. В данной работе удалось установить корреляцию между акустическими и оптическими параметрами. Используя измерения скоростей ультразвука и оптического поглощения, были определены фундаментальные характеристики образцов. Это способствует пониманию структурно-чувствительных свойств, а значит, в дальнейшем и влиять на них, создавая материалы с нужными параметрами для лучшей работы приборов микро- и оптоэлектроники. / Objects of research are 3 samples of nanoceramiсs based on Al2O3 and 4 samples of quartz glasses: KI, KU, KV, KS-4V. The aim of this work is the study of the acoustic properties due to the peculiarities of micro- (nano)structures of the two categories of micro- and optoelectronics materials: nanoceramics based on Al2O3 and optical quartz glass. The acoustic properties of materials micro- (nanoceramics based on Al2O3) and optoelectronics (quartz glass) were studied, the optical parameters of quartz glass were investigated, and a correlation between acoustic and optical parameters was found. The original test stand and the method of measuring the transverse ultrasonic waves velocities were created, the elastic characteristics of nanoceramics based on Al2O3 and optical quartz glass and the optical parameters of glass were determine. In this paper we determined a correlation between acoustic and optical parameters. Using measurements of the velocity of ultrasound and optical absorption fundamental characteristics of the samples were determined. This contributes to an understanding of structure-sensitive properties that will help create materials with the necessary parameters for the best performance of micro- and optoelectronics.

Subsurface volume loss takes place in many geotechnical situations, and it is inherently accompanied by complex stress and displacement fields that may influence the performance of engineered geosystems. This research is a deformation-centered analysis, it depends on soil compressibility and it is implemented using finite elements. Soil stiffness plays a central role in predicting ground deformation. First, an enhanced Terzaghi’s soil compressibility model is proposed to satisfy asymptotic conditions at low and high stress levels with a small number of physically meaningful parameters. Then, the difference between small and large strain stiffness is explored using published small and large-strain stress-strain data. Typically, emphasis is placed on the laboratory-measured stiffness or compressibility; however, there are pronounced differences between laboratory measurements and field values, in part due to seating effects that prevail in small-thickness oedometer specimens. Many geosystems are subjected to repetitive loads; volumetric strains induced by drained repetitive ko-loads are experimentally investigated to identify shakedown and associated terminal density. The finite element numerical simulation environment is used to explore the effect of localized subsurface mass loss on free-surface deformation and shallow foundations settlement and bearing capacity. A stress relaxation module is developed to reproduce the change in stress associated to dissolution features and soft zone formation. The comprehensive parametric study is summarized in terms of dimensionless ratios that can be readily used for engineering applications. Field settlement data gathered at the Savannah River Site SRS are back-analyzed to compare measured values with predictions based on in situ shear wave velocity and strain-dependent stiffness reduction. The calibrated model is used to estimate additional settlements due to the pre-existing cavities, new cavities, and potential seismic events during the design life of the facility.