Development and demonstration of a pico-Watt calorimeter for optical absorption spectroscopy

An optical calorimeter for sensitive absorption measurements of non-radiative samples at 4 K was designed, built, and demonstrated. It consists of a cryostat cooled by a commercial pulse tube (PTC) refrigerator, a measurement chamber housing the sample and thermometers, and various fiber-coupled light sources. By employing measures to damp mechanical noise from the environment and active temperature stabilization of critical components of the instrument temperature noise as low as 6 nK/√Hz at 50 mHz was achieved under 15 mW of optical excitation. An optical absorption induced temperature increase of the sample as small as 2.5 nK could be resolved using paramagnetic temperature sensors with SQUID (Superconducting Quantum Interference Device) readout. This resulted in an absorption sensitivity of 0.3 ppm and 0.6 ppb for tunable 30 μW optical excitation from 330 nm to 1700 nm and for 15-mW laser excitation, respectively. The instrument was applied to the characterization of stacks of dielectric films for material science studies and laser mirror development

Developing a novel mechanistic model for four-phase oil-water-gas-sand stratified flow in a horizontal pipe.

Presence of sand and solid particles in untreated petroleum sometime is inevitable. Although many techniques have been developed to prevent sand particles from entering the pipeline, such as downhole gravel packs, these downhole sand control devices can cause significant production loss due to the risk of blockage. Transporting sand along with other flowing phases is the best way of managing produced sand. Pipelines should be designed in such a way that flowing phases keep the sand particles moving and formation of the stationary sand bed should be mitigated by understanding flow physics under realistic multiphase conditions. To better understand the behaviour of multiphase flow, this research aimed to develop and verify a mechanistic model for the stratified four-phase (gas-oil-water-sand) flow in a horizontal pipe. This model takes into account some aspects of the existing multi-layer liquid-liquid and liquid-solid models. The entire stratified flow structure comprising of the stationary sand bed, moving sand bed, water, oil and gas layers are modelled by a system of twelve non-linear equations. An iterative numerical method has been developed to solve this system of non-linear equations. This solving method is using pressure balance in the moving phases as a criterion to converge to a solution that is physically possible. This model can also predict the flow structure by differentiating between fully suspended flow, stratified flow with moving and stationary beds, and stratified flow with moving bed only, and then adjusting and solving the governing equations accordingly. In the case of three-phase water-oil-gas flow, the developed code was run for two oil viscosity values of 1 (cP) and 100 (cP), where variation in the height of each layer versus total flow rate was studied. Comparison with three layer solid-liquid model was done by running the code while sand volumetric concentration was increased from 4% to 20% with 2% increments. Results of simulations compare well with the published data. The developed code was then employed to model the four-phase horizontal stratified sand-water-oil-gas flow. A parametric study was performed to evaluate the impact of particle size, solid concentration, solid density, slurry velocity and oil velocity on holdup and pressure gradient. At constant solid concentration, increase in solid size up to a certain threshold resulted in a reduction in stationary sand bed height and an increase in moving sand bed height, due to an increase in particle surface and torque applied on each particle. A further increase in particle size resulted in accumulation of stagnated particles. To further study the effect of particle size, slurry and oil flow rates were increased whilst gas flow rate remained unchanged. This resulted in an increase in both oil and water layer heights. An increase in particle size resulted in an increase in pressure gradient. The effect of solid concentration was studied by gradually increasing the concentration, whilst slurry, oil and gas flow rates remained unchanged. It was demonstrated that an increase in solid concentration results in sand build-up. Oil layer height showed a downward trend while sand concentration increases and pressure gradient showed a linear increasing trend as solid concentration increases. The effect of particle density was studied by increasing the density whilst other parameters - including particle size - remained unchanged. Density increase resulted in an increase in total sand height and a reduction in water layer height. An increase in slurry flow rate showed a linear relationship with water layer height and also resulted in an increase in moving sand bed height, while at the same time stationary sand bed height was reduced. An increase in oil flow rate showed no noticeable impact on sand bed height. In conclusion, this research developed a technique to solve non-linear equations governing four-phase stratified flow, which proved to be reliable and resulted in satisfactory results. The mechanistic model, which is developed in this research along with the solution algorithm, can be used as a starting point to develop numerical models for flow regimes other than stratified. The code was developed in MATLAB software version "R2017b"

Application of dynamic vibration absorbers on double-deck circular railway tunnels to mitigate railway-induced ground-borne vibration

This dissertation is concerned with investigating the efficiency of dynamic vibration absorbers (DVAs) as measures to mitigate ground-borne vibrations induced by railway traffic in double-deck tunnels. The main topics of the dissertation are the coupling of a set of longitudinal distributions of DVAs to the interior floor of a double-deck tunnel dynamic model, the computation of the response of this coupled system due to train traffic and obtaining the optimum design parameters of the DVAs to minimize this response. To address the first concern, a methodology for coupling a set of longitudinal distributions of DVAs to any railway subsystem in the context of a theoretical dynamic model of railway infrastructure is developed. The optimum design parameters of the DVAs are obtained using an optimization process based on a genetic algorithm. The effectiveness of the DVAs is assessed by two response parameters, which are used as objective functions to be minimized in the optimization process: the energy flow radiated upwards by the tunnel and the maximum transient vibration value (MTVV) in the building near the tunnel. The model used to compute the former is a two-and-a-half dimensional (2.5D) semi-analytical model of a train-track-tunnel-soil system that considers a full-space soil model, and the one used to compute the latter is a hybrid experimental-numerical model of a train-track-tunnel-soil-building system. In the hybrid model, a numerical model of the track-tunnel system based on 2.5D coupled finite element-boundary element formulation along with a dynamic rigid multi-body model of the vehicle is used to compute the response in the tunnel wall, and then, the response in the building is computed using experimentally obtained transfer functions between the tunnel wall and the building. The triaxial response in the building is used to compute the MTVV. An alternative option to evaluate the MTVV in a building is to use a fully theoretical model of the train-track-tunnel-soil-building system. In the context of this modeling strategy, a computationally efficient method to calculate the 2.5D Green's functions of a layered soil is also presented. The results show that the DVAs would be an effective mitigation measure for railway-induced vibrations in double-deck tunnels as reductions up to 6.6 dB in total radiated energy flow and up to 3.3 dB in the vibration inside a nearby building are achieved in the simulations presented in this work.En esta tesis se estudia la eficiencia de los absorbedores de vibraciones dinámicos (DVAs) como medidas de mitigación de las vibraciones inducidas por infraestructuras ferroviarias aplicados a túneles ferroviarios de dos niveles. Los principales desarrollos de la tesis son el acoplamiento de un conjunto de distribuciones longitudinales de DVAs a la losa intermedia de un modelo dinámico de túnel de dos niveles, el cálculo de la respuesta de este sistema acoplado debido al paso del tren y la obtención de los parámetros óptimos de los DVAs para minimizar esta respuesta. Para abordar la primer punto, se ha desarrollado una metodología con el fin de acoplar un conjunto de distribuciones longitudinales de DVAs a cualquier subsistema ferroviario en el contexto de modelos teóricos de la dinámica de infraestructura ferroviarias. Los parámetros óptimos de los DVAs han sido obtenidos mediante un proceso de optimización basado en un algoritmo genético. La eficiencia de los DVAs se evalúa mediante dos quantificadores de la respuesta dinámica del sistema, los cuales se utilizan como funciones objetivo a minimizar en el proceso de optimización: el flujo de energía total radiado hacia arriba desde el túnel y el valor máximo de vibración transitoria (MTVV) en el forjada de un edificio cercano al túnel. El modelo utilizado para calcular el primero es un modelo semi-analítico del sistema vehículo-vía-túnel-terreno que considera un modelo de terreno de espacio completo, y el que se utiliza para calcular el segundo es un modelo híbrido experimental-numérico del sistema vehículo-vía-túnel-terreno-edificio. En el modelo híbrido, se utiliza un modelo numérico del sistema vía-túnel basado en la formulación acoplada de elementos finitos-elementos de contorno acoplados, formulada en el dominio del número de onda y la frecuencia, junto con un modelo dinámico multicuerpo del vehículo con el objetivo de calcular la respuesta en la pared del túnel. Luego, la respuesta en el edificio se calcula utilizando funciones de transferencia obtenidas experimentalmente entre la pared del túnel y el edificio. Para calcular el MTVV, se utiliza la respuesta triaxial en el edificio. Una opción alternativa para evaluar el MTVV en un edificio es utilizar un modelo totalmente teórico del sistema vehículo-vía-túnel-terreno-edificio. En el contexto de esta estrategia de modelado, también se presenta un método computacionalmente eficiente para calcular las funciones de Green de un terreno en capas en el dominio 2.5D. Los resultados muestran que los DVAs pueden ser una medida de mitigación efectiva para las vibraciones inducidas por infraestructuras ferroviarias en el marco de un túnel ferroviario de dos niveles, ya que en las simulaciones presentadas en esta tesis se alcanzan reducciones de hasta 6.6 dB en el flujo de energía total radiado y hasta 3.3 dB en la vibración dentro de un edificio cercano.Postprint (published version

Problemas de instrumentación y problemas en las presas terrestres (estudio de caso; presa Shah Qasim en Yasouj, Irán)

La instalación y el seguimiento de la instrumentación es uno de los métodos prácticos para controlar la seguridad y estabilidad de las presas de tierra. Los piezómetros existentes en el cuerpo de la presa y los estribos de la presa son uno de los diversos tipos de instrumentos de precisión utilizados en las presas, que indican la altura del nivel del agua en diferentes partes de la presa. Para evaluar el rendimiento de los piezómetros de la presa Shah Qasim en Kohgiluyeh y la provincia de Boyerahmad (en el sureste de Irán), comparamos los cambios del nivel del agua en el piezómetro y los cambios del nivel del agua en el lago de la presa a lo largo del tiempo. En este artículo, la presa mencionada anteriormente se modela utilizando el software SEEP / W, luego, después de imponer condiciones de contorno, los niveles de agua se calculan en varios puntos. Para una comparación más precisa, los cambios en el nivel del agua se trazan en piezómetros transversales y longitudinales a lo largo del tiempo. Los resultados del análisis indican un aumento significativo de la permeabilidad en las proximidades de algunos piezómetros. Los piezómetros BX4, BX14, BX13 y SP6, y la región cercana a ellos, así como los piezómetros SP24 y SP18 y su área circundante, tienen condiciones críticas que deben ser inspeccionadas lo antes posible

Long-term results, functional outcomes and complications after open reduction and internal fixation of neglected and displaced greater tuberosity of humerus fractures

Background: Humerus fractures include 5 to 8 of total fractures. Non-union and delayed union of GT (GT) fractures is uncommon; however they present a challenge to the orthopedic surgeons. Significant controversy surrounds optimal treatment of neglected fractures. The purpose of this article was to perform a comparative study to evaluate the outcomes of open reduction and internal fixation (ORIF) of neglected GT fractures. Methods: We retrospectively evaluated the results of surgical intervention in 12 patients with displaced nonunion of GT fractures who were referred to our center. Before and minimally 25 months after surgery ROM, muscle forces, Constant Shoulder Score (Constant-Murley score) (CSS), Visual Analogue Scale (VAS), Activities of Daily Living (ADL) Score and American Shoulder and Elbow Surgeons (ASES) Score were all recorded. Additionally, the results were compared with undamaged shoulder. Results: Between March 2006 and January 2013, 12 patients underwent surgical intervention and followed for 36.2 months in average. All fractures healed. Anatomic reduction achieved only in 6 cases with no report of avascular necrosis or infection. All ROMs and muscle forces increased significantly (Mean Forward Flexion: 49.16 to 153.3, Mean Internal Rotation: 3 to 9, Mean External Rotation: -5 to 27.5) (P value < 0.0001). All functional scores including CSS, VAS, ADL and ASES score improved significantly (Mean VAS: 6.5 to 1.3, Mean CSS: 29.83 to 86, Mean ADL: 6.6 to 27.1, Mean ASES: 28.6 to 88.9) (P value < 0.0001). Conclusion: ORIF for neglected and displaced GT fractures has satisfactory functional outcomes, despite of nonanatomical reduction of the fracture. © 2016 by the Archives of Bone and Joint Surgery

Application of dynamic vibration absorbers on double-deck circular railway tunnels to mitigate railway-induced ground-borne vibration

This dissertation is concerned with investigating the efficiency of dynamic vibration absorbers (DVAs) as measures to mitigate ground-borne vibrations induced by railway traffic in double-deck tunnels. The main topics of the dissertation are the coupling of a set of longitudinal distributions of DVAs to the interior floor of a double-deck tunnel dynamic model, the computation of the response of this coupled system due to train traffic and obtaining the optimum design parameters of the DVAs to minimize this response. To address the first concern, a methodology for coupling a set of longitudinal distributions of DVAs to any railway subsystem in the context of a theoretical dynamic model of railway infrastructure is developed. The optimum design parameters of the DVAs are obtained using an optimization process based on a genetic algorithm. The effectiveness of the DVAs is assessed by two response parameters, which are used as objective functions to be minimized in the optimization process: the energy flow radiated upwards by the tunnel and the maximum transient vibration value (MTVV) in the building near the tunnel. The model used to compute the former is a two-and-a-half dimensional (2.5D) semi-analytical model of a train-track-tunnel-soil system that considers a full-space soil model, and the one used to compute the latter is a hybrid experimental-numerical model of a train-track-tunnel-soil-building system. In the hybrid model, a numerical model of the track-tunnel system based on 2.5D coupled finite element-boundary element formulation along with a dynamic rigid multi-body model of the vehicle is used to compute the response in the tunnel wall, and then, the response in the building is computed using experimentally obtained transfer functions between the tunnel wall and the building. The triaxial response in the building is used to compute the MTVV. An alternative option to evaluate the MTVV in a building is to use a fully theoretical model of the train-track-tunnel-soil-building system. In the context of this modeling strategy, a computationally efficient method to calculate the 2.5D Green's functions of a layered soil is also presented. The results show that the DVAs would be an effective mitigation measure for railway-induced vibrations in double-deck tunnels as reductions up to 6.6 dB in total radiated energy flow and up to 3.3 dB in the vibration inside a nearby building are achieved in the simulations presented in this work.En esta tesis se estudia la eficiencia de los absorbedores de vibraciones dinámicos (DVAs) como medidas de mitigación de las vibraciones inducidas por infraestructuras ferroviarias aplicados a túneles ferroviarios de dos niveles. Los principales desarrollos de la tesis son el acoplamiento de un conjunto de distribuciones longitudinales de DVAs a la losa intermedia de un modelo dinámico de túnel de dos niveles, el cálculo de la respuesta de este sistema acoplado debido al paso del tren y la obtención de los parámetros óptimos de los DVAs para minimizar esta respuesta. Para abordar la primer punto, se ha desarrollado una metodología con el fin de acoplar un conjunto de distribuciones longitudinales de DVAs a cualquier subsistema ferroviario en el contexto de modelos teóricos de la dinámica de infraestructura ferroviarias. Los parámetros óptimos de los DVAs han sido obtenidos mediante un proceso de optimización basado en un algoritmo genético. La eficiencia de los DVAs se evalúa mediante dos quantificadores de la respuesta dinámica del sistema, los cuales se utilizan como funciones objetivo a minimizar en el proceso de optimización: el flujo de energía total radiado hacia arriba desde el túnel y el valor máximo de vibración transitoria (MTVV) en el forjada de un edificio cercano al túnel. El modelo utilizado para calcular el primero es un modelo semi-analítico del sistema vehículo-vía-túnel-terreno que considera un modelo de terreno de espacio completo, y el que se utiliza para calcular el segundo es un modelo híbrido experimental-numérico del sistema vehículo-vía-túnel-terreno-edificio. En el modelo híbrido, se utiliza un modelo numérico del sistema vía-túnel basado en la formulación acoplada de elementos finitos-elementos de contorno acoplados, formulada en el dominio del número de onda y la frecuencia, junto con un modelo dinámico multicuerpo del vehículo con el objetivo de calcular la respuesta en la pared del túnel. Luego, la respuesta en el edificio se calcula utilizando funciones de transferencia obtenidas experimentalmente entre la pared del túnel y el edificio. Para calcular el MTVV, se utiliza la respuesta triaxial en el edificio. Una opción alternativa para evaluar el MTVV en un edificio es utilizar un modelo totalmente teórico del sistema vehículo-vía-túnel-terreno-edificio. En el contexto de esta estrategia de modelado, también se presenta un método computacionalmente eficiente para calcular las funciones de Green de un terreno en capas en el dominio 2.5D. Los resultados muestran que los DVAs pueden ser una medida de mitigación efectiva para las vibraciones inducidas por infraestructuras ferroviarias en el marco de un túnel ferroviario de dos niveles, ya que en las simulaciones presentadas en esta tesis se alcanzan reducciones de hasta 6.6 dB en el flujo de energía total radiado y hasta 3.3 dB en la vibración dentro de un edificio cercano

Experimental Optimization of Using Natural Pozzolan in Chloride Ion Exposed Concrete via Taguchi Method

Concrete durability is one of the most important concerns in the field of construction. The environmentally friendly materials that can provide the durability are of great value in the construction of concrete structures. The use of natural pozzolans is one of the cheapest and most efficient methods in this field, which offers a good performance from environmental and economic point of view and satisfies required engineering parameters. In this study, the effect of using natural pozzolan in the manufacture of concrete exposed to sulfate and chloride ion of Oman sea water was investigated. The Taguchi optimization method was used to reduce the number of samples prepared, reduce the cost of experiments and achieve an optimal mix design. The four parameters, namely water to cement ratio, different percentages of natural pozzolan, super-plasticizer and cement grade with different ratios, were considered as problem variables. The Taguchi optimization method proposed 8 mix designs based on the defined levels for the variables. By constructing 96 samples, two parameters of permeability and water absorption from Oman Sea and drinking water were investigated in the samples. By introducing the results of the experiments into the Taguchi method, the final optimal design was presented by this method, and by constructing 12 additional samples and conducting permeability and water absorption experiments, the behavior of this optimal mix design was verified. The appropriate performance of the Taguchi method was demonstrated by obtaining the optimal mix designs from the Taguchi method, constructing this mix design and comparing the results with the regulation limitations. The results showed that it is acceptable to use natural pozzolan under moderate to severe chloride and sulfate ion attacks, but it is not recommended in the extreme environmental conditions

A method based on 3D stiffness matrices in Cartesian coordinates for computation of 2.5D elastodynamic Green's functions of layered half-spaces

This article elaborates on an extension to the classical stiffness matrix method to obtain the Green's functions for two-and-a-half dimensional (2.5D) elastodynamic problems in homogeneous and horizontally layered half-spaces. Exact expressions for the three-dimensional (3D) stiffness matrix method for isotropic layered media in Cartesian coordinates are used to determine the stiffness matrices for a system of horizontal layers underlain by an elastic half–space. In the absence of interfaces, virtual interfaces are considered at the positions of external loads. The analytic continuation is used to find the displacements at any receiver point placed within a layer. The responses of a horizontally layered half-space subjected to a unit harmonic load obtained using the present method are compared with those calculated using a well-established methodology, achieving good agreementPostprint (author's final draft

Acute Pulmonary Embolism in Post COVID-19 Infection, A Case Report

COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Many centers have noticed a high number of venous thromboembolism (VTE) events among critically ill inpatients with COVID-19 pneumonia. COVID-19 infection is associated with high morbidity and mortality largely due to respiratory failure, with micro vascular pulmonary thrombosis or PE originating from the leg veins playing an additional important pathophysiological role. Having undiagnosed or untreated PE may worsen patient outcomes and use of empiric therapeutic anticoagulation in certain COVID patients who do not have PE/DVT has been advocated. Here, we report a cases of COVID-19, in which massive pulmonary thromboembolism (PTE) occurred a few days after discharge