Given the surmounting disagreement amongst researchers in the area of liquid flow behavior at the microscale for the past thirty years, this work presents a fundamental approach to analyzing the pressure losses experienced by the laminar flow of water (Re = 7 to Re = 130) through both rectangular straight duct microchannels (of widths ranging from 50 to 130 micrometers), and microchannels with sudden expansions and contractions (with area ratios ranging from 0.4 to 1.0) all with a constant depth of 104 micrometers. The simplified Bernoulli equations for uniform, steady, incompressible, internal duct flow were used to compare flow through these microchannels to macroscale theory predictions for pressure drop. One major advantage of the channel design (and subsequent experimental set-up) was that pressure measurements could be taken locally, directly before and after the test section of interest, instead of globally which requires extensive corrections to the pressure measurements before an accurate result can be obtained. Bernoulli's equation adjusted for major head loses (using Darcy friction factors) and minor head losses (using appropriate K values) was found to predict the flow behavior within the calculated theoretical uncertainty (~12%) for all 150+ microchannels tested, except for sizes that pushed the aspect ratio limits of the manufacturing process capabilities (microchannels fabricated via soft lithography using PDMS). The analysis produced conclusive evidence that liquid flow through microchannels at these relative channel sizes and Reynolds numbers follow macroscale predictions without experiencing any of the reported anomalies expressed in other microfluidics research. This work also perfected the delicate technique required to pierce through the PDMS material and into the microchannel inlets, exit and pressure ports without damaging the microchannel. Finally, two verified explanations for why prior researchers have obtained poor agreement between macroscale theory predictions and tests at the microscale were due to the presence of bubbles in the microchannel test section (producing higher than expected pressure drops), and the occurrence of localized separation between the PDMS slabs and thus, the microchannel itself (producing lower than expected pressure drops).

Hydraulic losses in sewer pipes are caused by wall roughness, blockages and in-pipe sedimentation. Hydraulic resistance is a key parameter that is used to account for the hydraulic energy losses and predict the sewer system propensity to flood. Unfortunately, there are no objective methods to measure the hydraulic resistance in live sewers. A common method to estimate the hydraulic resistance of a sewer is to analyse collected CCTV images and then to compare them against a number of suggested hydraulic roughness values published in the Sewer Rehabilitation Manual. This thesis reports on the development of a novel, non-invasive acoustic method and instrumentation to measure the hydraulic roughness in partially filled pipes under various structural and operational conditions objectively. This research presents systematic laboratory and field studies of the hydraulic and surface water wave characteristics, of shallow water flows in a sewer pipes with the presence of local and distributed roughness, in order to relate them to some fundamental properties of the acoustic field measured in the vicinity of the flow surface. The results of this thesis indicate that for the local roughness the energy content of the reflected acoustic signal is an indicator of the pipe head loss and hydraulic roughness. In the case of the distributed roughness, the variation in the temporal and frequency characteristics of the propagated sound wave can be related empirically to the mean flow depth, mean velocity, wave standard deviation and hydraulic roughness.

In the uplink direction of 5G New Radio, signals are sent between Ra-dio Units and Digital Units. The production of these signals is non-deterministic, leading to signals often being produced in bursts. Thesesignal bursts can lead to exceeding the Data Link Layer capacity, whichcauses packet losses. It is possible to control the burstiness by delay-ing signals over time. However, excessive delays should be avoidedsince the processing of signals must be completed within strict time con-straints. In this paper, two machine-learning-based algorithms with theobjective of avoiding packet losses by introducing delays to signals wereproposed. One algorithm was based on the symbol number of the sig-nals, and the other one used a queue-based approach. Only the symbol-based algorithm was thoroughly evaluated. Visualizations of test data,as well as lab tests, showed that the symbol-based algorithm was ableto efficiently delay signals in order to reduce the maximum load on theData Link Layer.

Microgrid (MG) concept has been emerged to enable integration of renewable energy sources and storage devices using power electronic converters. An MG can be grid connected to exchange power with the main grid, isolated that is completely separated from the grid, or islanded that is temporarily separated from the grid. The P and Q-V drooping approach is commonly used to control and achieve power sharing among the generators.\\ This study presents an approach for systematically modeling a class of microgrid (MG) systems. The derived model 1) accommodates grid-connected and islanded operation of the MG simultaneously, and 2) allows modeling of converter-based as well as directly-interfaced resources. The originally nonlinear model is then converted to a linear model whose eigenvalues determine local stability of the MG. \\The model is used to analyze the impacts of adding cross-coupling droop terms (P-V and Q) on an MG's performance. Various performance aspects such as stability, stability robustness, transmission power loss, voltage profile, and power sharing are considered. The conclusions are as follows. (1) Addition of a small portion of cross-coupling will reduce the losses without compromising other aspects in a grid-connected MG. Larger cross-coupling terms will compromise the system stability. (2) Large cross-coupling terms can be added to reduce the power loss and to improve the system stability in an isolated MG. Simulation and experimental results are presented to verify the derivations.

No description available.

No description available.

No description available.

No description available.

No description available.

Effective determination of long-term prestress losses is important in the design of prestressed concrete bridges. Over-predicting prestress losses results in an overly conservative design for service load stresses, and under-predicting prestress losses, can result in cracking at service loads. Creep and shrinkage produce the most significant time-dependent effect on prestress losses, and research has shown that high performance and high strength concretes (HPC and HSC) exhibit less creep and shrinkage than conventional concrete. For this reason, the majority of traditional creep and shrinkage models and methods for estimating prestress losses, over-predict the prestress losses of HPC and HSC girders. Nine HPC girders, with design compressive strengths ranging from 8,000 psi to 10,000 psi, and three 8,000 psi lightweight HPC (HPLWC) girders were instrumented to determine the changes in strain and prestress losses. Several creep and shrinkage models were used to model the instrumented girders. For the HPLWC, each model over-predicted the long-term strains, and the Shams and Kahn model was the best predictor of the measured strains. For the normal weight HPC, the models under-estimated the measured strains at early ages and over-estimated the measured strains at later ages, and the B3 model was the best-predictor of the measured strains. The PCI-BDM model was the most consistent model across all of the instrumented girders. Several methods for estimating prestress losses were also investigated. The methods correlated to high strength concrete, the PCI-BDM and NCHRP 496 methods, predicted the total losses more accurately than the methods provided in the AASHTO Specifications. The newer methods over-predicted the total losses of the HPLWC girders by no more than 8 ksi, and although they under-predicted the total losses of the normal weight HPC girders, they did so by less than 5 ksi. / Ph. D.