A weather radar signal simulator that produces an output consisting of a vector of I and Q values representing the radar return permits investigation of the performance of different estimators for the weather signal parameters and their sensitivity when varying radar parameters and precipitation models. Although several empirical statistical models are available to describe precipitation behavior, the creation of a physical model enables adaptation to actual data (e.g. rain rate, wind shears) thereby making it possible to apply and examine different scanning schemes, especially rapid scanning schemes. A physical model allows gradual improvements to realism to study the effects on the radar return for different phenomena. A Weather Radar Signal Simulator has been developed in MATLAB. Several different functionalities have been implemented allowing for stepped frequency, multiple PRFs, pulse compression using a chirp, and variation of both weather and radar input parameters. Post processing capabilities include autocorrelation and FFT (for single PRF only); estimation of weather parameters such as reflectivity factor, Z; average doppler, radial velocity, and velocity spread; pedagogical plots including a Phasor plot of phase change over time and a velocity histogram, instantaneous observed reflectivity and power for each pulse over time.

Concentration polarisation and fouling reduce performance as well as increase costs. In order to mitigate these effects, understanding the cause and effects of these phenomena is crucial. It has been hypothesized, and to a certain extent shown, that amelioration of fouling can be achieved through the use of time varying shear for example use of air-sparging or sharp changes in crossflow velocity. Nevertheless the effect of shear on membrane fouling, in particular its effect on the foulant deposition and the transmission of small molecules in microfiltration, is not well understood. The goal of this project was to achieve an understanding of various foulant be- haviour. The work was divided into two parts. Firstly, the observations of fouling by freshwater algae, Chlorella Sorokiniana, were carried out at Nanyang Technolo- gical University, Singapore. Observations using macroscopic parameters were ex- amined with an optical non-invasive observation technique called Direct Observa- tion Through Membrane (DOTM). The result yielded a novel relationship between operating flux, crossflow velocity and transmission of extracellular polysaccharide. Interestingly shear was shown to have positive as well as negative effects on fouling of microfiltration membrane. The analysis of permeate has clearly shown that a maximisation of shear rate was not ideal. The second part was concerned with observations of the effect of shear patterns on membrane fouling using newly fabricated special membrane filtration cell, Direct Shear Stress Test Cell (DSSTC), designed to fit an Anton Paar rheometer and op- erate at constant flux. Unlike the-constant-shear-filtration cells, one could impose a very wide variety of shear regimes including intermittent sharp changes of direction and sinusoidal oscillations in the DSSTC. The effect of shear patterns on transmis- sion and fouling of a model polysaccharide (Dextran Blue) through microfiltration membranes was carried out at various conditions. Again, the results showed that the maximisation of shear rate was not ideal. The effect of shear patterns and EPS on fouling by yeast suspension was also studied using the DSSTC. The benefit of oscillatory shear is foulant dependent. For example, square wave oscillatory shear led to lower relative fouling for yeast EPS, but it resulted in higher relative fouling for unwashed yeast.

In order to predict the strength of shear wall with cold-formed steel framing members, analytical models were reviewed. Multiple analytical models were studied, as well as twenty-one connection tests were performed. The connection tests consist of 50-ksi cold-formed steel framing track, different fastening configurations, and different sheathing thicknesses (1/8" and 1/2"). No.12 screw resulted in the highest peak load of all fastening configurations, while the rivet connection had the lowest peak load. In addition, failure modes were observed after conducting the connection tests including shear in fastening, screw pullout, and bearing in the sheathing. However, only the rivet and No.10 screw fastening configurations were used in the prediction analysis of the shear wall by the elastic model. Six shear wall tests were conducted on both panels (1/2"and 1/8" thickness). After doing the comparison between the experimental and the elastic model, the percentage difference for the 1/8" and the 1/2" polymer composite panels (3''along the edge and 6''along the chord stud), was very small. It was 6.2% for the 1/8" and 2.96% for the 1/2" panels. This means the analytical model can predict the shear wall peak load. However, the percentage difference was slightly higher being 7.4% for the 1/2" polymer composite panels with 6" along the perimeter with the 12" at the chord stud. After comparing the experimental values to the predicted value of shear walls, it was concluded that this model is the most appropriate analytical method for predicting the shear wall capacity framed with cold-formed steel sheathed with polymer composite panels. Many of these configurations were used in a prototype shelter that was constructed and built at the structural testing laboratory at the University of North Texas.

M.Sc., Faculty of Science, University of the Witwatersrand, 2011 / Rayleigh wave dispersion curves are used to invert for the group velocity maps of the southwestern block of the Congo craton. The group velocity maps were then inverted to obtain the three dimensional shear-wave velocity of the lithosphere beneath the region. In the process, the adjacent Kalahari craton and Damara mobile belt were also mapped to help constrain the southernmost edge of the Congo craton. To obtain the surface wave group velocity tomography, event-station dispersion curves of Rayleigh waves were measured using the multiple filter analysis method. Then the dispersion curves were inverted using the conjugate gradient least-square (CGLSQR) inversion method. To check the reliability of the result, a checkerboard test was performed. The 2-dimensional group velocities and 3-dimensonal shear-wave velocities were found to be faster beneath the southwestern block of the Congo craton and the Kalahari craton and slower in the Damara mobile belt. The group velocity map at 20s period shows that basins are 0 to 3% slower than PREM model. For longer period (50s to 120s), the Central and East African Rift system are ~ 5 % faster, cratons are 5 to 8% faster, and the adjacent mobile belts are 0 to 4% faster than the PREM model. The Afar depression is the slowest, up to 6% slower than the continental PREM model at all periods. The shear-wave velocity maps reveal that (1) the Afar area is the slowest (up to 8% slower than the IASP91 model), (2) the cratons are faster (up to 6% faster than IASP91) than the surrounding mobile belts (up to 2% faster than IASP91). The East African Rifts system is also slow (up to 5%). The Damara mobile belt constitutes a clear separation terrain between the Congo craton and the Kalahari craton. This result is consistent with previous studies by Pasyanos and Nyblade (2007), and Priestly et al. (2006, 2008), who also found faster shear-wave velocities beneath the Kalahari, Congo and Tanzania cratons. The relatively slow seismic velocities (-1 to 2% compared to IASP91) in the Proterozoic Damara mobile belt between the southwestern block of the Congo craton and the Kalahari craton are explained by the view that the Proterozoic lithosphere has hotter rock materials than the SW block of the Congo craton and the Kalahari craton. Our model of faster lithosphere beneath the SW block of the Congo and the Kalahari craton is also consistent with the model of strongly depleted (in basaltic components) lithosphere beneath these craton; compared to less depleted lithosphere beneath the DMB.

No description available.

Shelf seas occupy only 7% in area and less than 0.5% in volume of the entire ocean, but they play an important role in the carbon cycle by taking about 20% - 50% of all the CO2 absorbed by the ocean. Diapycnal mixing is a key process in transporting nutrients, carbon, water mass etc. between the surface and the lower mixed layers in a seasonally stratified shelf sea. The identification and quantification of the processes responsible for driving diapycnal mixing in seasonally stratified seas are the subjects worth study. Early researchers have examined the correlation between enhanced bulk shear and the wind. The bulk shear is defined as the average of the shear in two defined layers which are either side of the thermocline. However the contribution from the barotropic tide has generally been neglected. This study examines two stages of the evolution of water column stratification: the spring development stage and the autumn break down stage. Rotary spectral analysis shows that the shear across thermocline corresponds to different drivers when the water stratification is different. At the spring development stage, the shear across the thermocline corresponds to near-inertial oscillations, which are related to wind. Whilst at the autumn break down stage, the shear across thermocline relates to both the near-inertial oscillations and the barotropic tide. Thus, in contraction to earlier research, our research suggests that the barotropic tide is another dominant driver in the generation of shear. However not all observations can be explained by the wind or barotropic tide. The additional consideration of the baroclinic tide helps explain the signal of an odd shear spike observed in the northern North Sea, which occurred during a period of weak shear production by the wind and barotropic tide. A 1D two-layer vertical dynamic numerical model and a 1D turbulence closure numerical model were applied to investigate the impact of wind and barotropic tide on shear, respectively. In addition, the impacts of hydrographic conditions on the driver of shear were considered. Coherence analysis was applied to examine the similarity of constituents (in frequency domain) between the modelled shear production and the observations. The model sensitivity analysis demonstrates that the switch of driver of shear is highly related to the depth ratio, which is the ratio of thermocline depth over water depth.

The actual shear capacity of existing concrete structures is often unable to meet current standard requirements. This may be attributable to increased load requirements, inadequate shear provisions in the original design or increased demand in shear capacity owing to flexural strengthening. However, available methods of assessment are often conservative, and the actual strength may be sufficient to sustain the specified assessment load. Therefore, it is important that realistic assessment methods are employed. This research comprises an investigation into the shear capacity of prestressed concrete bridges and into the feasibility of a novel strengthening approach, both through comprehensive laboratory experimentation and theoretical analyses. The laboratory testing indicates that the shear capacity of prestressed concrete bridges, post-tensioned transversely to form a deck, can be significantly greater than suggested by the relevant standards. The strengthening method proposed, namely deep embedment of steel or fibre-reinforced polymer (FRP) bars, is found to be feasible and very effective for reinforced concrete (RC) and prestressed concrete (PSC) beams of any size. Analytical models based on the upper-bound theorem of plasticity theory are successfully developed and applied, resulting in much more realistic predictions than those from current standards and codes when assessing shear capacity. For the strengthened beams, in addition to an upper-bound model, a strengthening design method based on a truss analogy is developed, which can be directly implemented into codes of practice. The analytical methods permit the assessment of existing longitudinally and laterally prestressed concrete bridges for shear capacity in a rational manner, and then to determine the capacity of a practical shear strengthening system if the bridge turns out to actually be understrength. Use of the proposed methodology will allow significant savings, as the costs associated with replacing or strengthening the structure can be avoided or minimised, encouraging a sustainable approach.

The coupled effect of using geosynthetic reinforcement and randomly distributed fibers on the stability of slopes was evaluated using finite element modeling and limit equilibrium methods by analyzing a case study in Oslo, Norway. The main objective was to simulate the failure condition of the original slope and quantify the improved stability of a hypothetical reinforced slope constructed with geosynthetic layers and distributed discrete fibers. The stability of the slope was evaluated in both the short-term condition with its' undrained shear strength parameters, and the long-term drained condition. Results indicate that the combination of the techniques was found to have a possible increase of about 40% in the short-term condition and about 60% in the long-term condition of the factor safety associated with the slope. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Turbulence is a familiar phenomenon which gives rise to complicated problems in many branches of engineering. Hinze has set forth the following definition for turbulence: "Turbulent fluid motion is an irregular condition of flow in which the various quantities show a random variation in time pnd space coordinates, so that statistically distinct average values can be discerned." Osborne Reynolds (1894) was the first to introduce the notion of statistical mean values into the study of turbulence. He visualized turbulent flow as the sum of mean and eddying motion. By introducing this sum of mean velocity and fluctuating velocity into the Navier-Stokes equations and with the aid of the continuity equation, he derived equations giving relationships between the various components of the fluctuating velocity. It was soon realized that before any further results could be obtained from a theoretical analysis of Reynold;s equations of motion, a mechanism had to be postulated for the ihteraction of fluctuating v~locity components at different points in the turbulent field. Consequently, three decades after Reynold's: work, phenomenological theories of turbulence, such as the momentum-transfer theory of Prandtl (1926), the vorticity transport theory of Taylor (1932) and the similarity theory of Karman (1930) were introduced. Not only are they based on unrealistic physical models, but they do not furnish any information beyond temporal-mean velocity distribution. A complete theory of turbulence should describe the mechanism of production of turbulence, its convection, diffusion, distribution, and eventual dissipation for any given boundary conditions.

Precast concrete sandwich wall panels (PCSWPs) have been used in the precast industry for decades due to their durability, rapid construction, and thermal efficiency. Shear connectors are used to connect the two wythes of concrete to allow composite action of the system. The use of glass fiber reinforced polymer (GFRP) connectors is a relatively recent breakthrough in PCSWP design. GFRP connectors allow full composite action to occur, while still maintaining the thermal efficiency of the system by not allowing thermal bridging to occur. In order to design concrete sandwich panel systems to act compositely, the engineer must obtain design values from a connector manufacturer, often times making engineers uncomfortable. Shear connectors are typically proprietary and are required to first have design values often times varies by each company. This project aimed to compare existing testing methodologies in order to better inform engineers about design decisions. This project used two methodologies of shear testing on five different types of composite action connectors. Testing was performed using single-shear and double-shear "push-off" tests. In order to gather enough statistical data to compare the testing methodologies, 22 single-shear and 48 double-shear small scale specimens were designed, fabricated, and loaded through failure at the Utah State University SMASH Lab. Testing was performed by applying loads perpendicular to the connectors and measuring the load and amount of deflection that occurred. Using the load-deflection relationships obtained, stiffness values were calculated and recorded for each test. A statistical analysis was performed based on the observed data. This study concluded that the ultimate strength capacity and stiffness of connectors will change depending on the testing methodology used. Single-shear testing will generally provide less ultimate strength and less stiffness when compared to double-shear testing.