This dissertation is a study of the composition dynamics of multicomponent distillation in a plate column. A ten-plate bubble-cap distillation column 21 feet in length with a two-foot inside diameter and a one-foot plate spacing was used. There were 22 two-inch bubble caps per plate. The feed system consisted of benzene, n-heptane, toluene, and xylene. Three experimental tests were analyzed; (1) a steady state test in which there was no forcing of the feed stream composition, (2) a transient test in which the feed stream benzene concentration was increased for a twenty-minute period, and (3) a pulse test in which the feed stream benzene concentration was increased for a five-minute period. The sampling frequency for the steady state and transient tests was one sample per minute from the.liquid of each of the plates and the feed, bottoms, and reflux streams. The sampling frequency for the pulse test was one sample every thirty seconds from the liquid and vapor of each plate and from the three terminal streams. The dynamic periods of the transient and pulse tests were simulated by means of a digital computer program. The program was written to solve by a finite difference method the differential equations describing the composition dynamics of the column. The transient and pulse composition response functions were transformed into the frequency domain by means of numerical methods. Simple lumped parameter transfer functions were then fit to the frequency response plots derived from the experimental data. It was determined that the digital computer program used to simulate the composition variations gave satisfactory results in comparison with the experimental data. The method of determining the initial conditions of the dynamic simulation program by means of a steady state multicomponent distillation computer program proved to be satisfactory. / Ph. D.

The aim of this study is to investigate means of efficiently assessing the effects of distributed structural modification on the dynamic properties of a complex structure. The helicopter structure is normally designed to avoid resonance at the main rotor rotational frequency. However, very often military helicopters have to be modified (such as to carry a different weapon system or an additional fuel tank) to fulfill operational requirements. Any modification to a helicopter structure has the potential of changing its resonance frequencies and mode shapes. The dynamic properties of the modified structure can be determined by experimental testing or numerical simulation, both of which are complex, expensive and time-consuming. Assuming that the original dynamic characteristics are already established and that the modification is a relatively simple attachment such as beam or plate modification, the modified dynamic properties may be determined numerically without solving the equations of motion of the full-modified structure. The frequency response functions (FRFs) of the modified structure can be computed by coupling the original FRFs and a delta dynamic stiffness matrix for the modification introduced. The validity of this approach is investigated by applying it to several cases, 1) 1D structure with structural modification but no change in the number of degree of freedom (DOFs). A simply supported beam with double thickness in the middle section is treated as an example for this case; 2) 1D structure with additional DOFs. A cantilever beam to which a smaller beam is attached is treated as an example for this case, 3) 2D structure with a reduction in DOFs. A four-edge-clamped plate with a cut-out in the centre is treated as an example for this case; and 4) 3D structure with additional DOFs. A box frame with a plate attached to it as structural modification with additional DOFs and combination of different structures. The original FRFs were obtained numerically and experimentally except for the first case. The delta dynamic stiffness matrix was determined numerically by modelling the part of the modified structure including the modifying structure and part of the original structure at the same location. The FRFs of the modified structure were then computed. Good agreement is obtained by comparing the results to the FRFs of the modified structure determined experimentally as well as by numerical modelling of the complete modified structure.

Frequency response analysis (FRA) has emerged as the de-facto industry standard condition-monitoring tool to assess mechanical integrity of transformer windings during its service life. It the prerequisite detection sensitivity and customized portable commercial instruments are also available. Considering its importance and taking cognizance of its hidden potential, international bodies, viz., IEEE, IEC, and CIGRE have published standards/guides on its use and interpretation. In spite of all the progress witnessed over the past two decades, FRA has still not attained the status of a diagnostics tool. Probing the vast literature and research carried out in this points to the fact that lack of a rigorous mathematical basis to explain the underlying complex processes is, perhaps, one of the main reasons for the present predicament of FRA method. How-ever, it must be acknowledged that domain-knowledge is di cult to generalize in this. Having said that, the diagnostic part, which involves, the task of working back-wards starting from the FRA data to interpret a winding damage, locate it, and assess its severity, has so far remained teasingly elusive. As a consequence, FRA continues to remain as a sensitive condition-monitoring tool. Given its inherent potential, this situation seems to be a paradox, and so, calls for investigations. Once a mechanical damage has been detected by FRA, the next task is to locate its position and estimate its severity. An engineer expects FRA to provide these answers, so that corrective action, if needed, can be determined and initiated. In this context, even though FRA has attained global acceptance as a monitoring tool, it has failed as a diagnostic tool. Therefore, e orts that aim to address this issue are desirable. Driven by this motivation, the author's thesis proposes to explore a new school of thought in this direction, viz., to theoretically analyze the problem of localization of an incipient/minor mechanical damage (displacement in particular) and also assess its severity. Such an investigation seems to have not been undertaken previously. So, the goal is to establish a relationship to capture the complex interactions that exist between specific winding damages, winding parameters, and their overall in hence on the natural frequency deviations observable in the FRA data. Hence, exploring this possibility, subject to the constraint that the proposed method shall use inputs that are measurable at the terminals, becomes the primary objective of this research. In this thesis, a generalized analytical framework for handling winding displacements and FRA data has been successfully formulated. The formulation provides a general platform for localization and severity assessment of true radial and axial winding dis-placements occurring in an actual winding. An analytical solution becomes possible mainly due to manipulation of the system matrix, i.e., to consider the harmonic sum of squares of natural frequencies, instead of just the natural frequencies. This manipulation leads to an elegant closed-form expression that connects the displacement location and its severity, to changes in natural frequencies. For its implementation, short circuit natural frequencies and a few other terminal measurements are the only inputs that are necessary. This formulation is initially used in Chapter-3 to demonstrate localization of radial displacement in an isolated, actual, single, air-cored continuous-disk winding. Armed with this success, the supplicant proceeds further to show (in Chapter-4) how a minor manipulation of the formulation renders it suitable for localization of actual axial displacements as well. Extensive experimental verification was done and the results are encouraging. Accuracy of localization of radial/axial displacement is uniformly good for all positions, and so is the estimation of severity. Further details are presented in the thesis.

Vibrations are very common phenomenon. It influences structures and generates acoustic noise which might be harmful to human beings. The vibration isolator was invented to reduce the effect from vibrations. However, the behavior of rubber material, which many vibration isolators are made of, is hard to predict. Consequently, vibration tests are needed to obtain the dynamic properties of rubber isolator.In this case, a six-year old LORD 2204-5 rubber isolator provided by Atlas Copco was tested. The aim of this paper is to obtain the FRF (Frequency Response Function) diagram which can describe the property of the rubber material. Moreover, the influence of aging of rubber material on the dynamic properties was studied.As the vibration test should simulate the working environment of the isolators that are both a static load from the structure and a dynamic force from the engine, a new excitation method was designed. The camshaft with the shape of an epitrochoid induced the sinusoidal signal of the isolator and the frame transferred the static load from the hydraulic machine. The artificial aging was performed in a hot air oven in 90°C for 42 hours, which according to Arrhenius equation should be equivalent to six years of natural aging. The vibration isolator was tested again after being aged.The obtained data showed that the aging process decreased the stiffness of the material. The results were corresponding with other studies regarding aging of rubber.

<p>Frequency response analysis (FRA) is a method which is used to detect mechanical faults in transformers. The FRA response of a transformer is determined by its geometry and material properties, and it can be considered as the transformer’s fingerprint. If there are any mechanical changes in the transformer, for example if the windings are moved or distorted, its fingerprint will also be changed so, theoretically, mechanical changes in the transformer can be detected with FRA.</p><p>The purpose of this thesis is to partly create a simple model for the ferromagnetic material in the transformer core, and partly to investigate the high frequency part of the FRA response of the transformer winding. To be able to realize these goals, two different models are developed separately from each other. The first one is a time- and frequency domain complex permeability model for the ferromagnetic core material, and the second one is a time- and frequency domain winding model based on lumped circuits, in which the discretization is made finer and finer in three steps. Capacitances and inductances in the circuit are calculated with use of analytical expressions derived from approximated geometrical parameters.</p><p>The developed core material model and winding model are then implemented in MATLAB separately, using state space analysis for the winding model, to simulate the time- and frequency response.</p><p>The simulations are then compared to measurements to verify the correctness of the models. Measurements were performed on a magnetic material and on a winding, and were compared with obtained results from the models. It was found that the model developed for the core material predicts the behavior of the magnetic field for frequencies higher than 100 Hz, and that the model for the winding predicts the FRA response of the winding for frequencies up to 20 MHz.</p>

No description available.

Master of Science / Department of Biological & Agricultural Engineering / Naiqian Zhang / Permittivity is an important property of dielectric materials. By measuring the permittivity of a material, it is possible to obtain information about the material’s physical and chemical properties, which are of great importance to many applications. In this study, a realtime control system for a frequency-response (FR) permittivity sensor was developed. The core of the hardware was a kitCON167 microcontroller (PHYTEC America, LLC), which controlled and communicated with peripheral devices. The system consisted of circuits for waveform generation, signal conditioning, signal processing, data acquisition, data display, data storage, and temperature measurement. A C program was developed in the TASKING Embedded Development Environment (EDE) to control the system. The control system designed in this study embodied improvements over a previously designed version in the following aspects: 1) it used a printed circuit board (PCB); 2) the measurement frequency range was extended from 120 MHz to 400 MHz; 3) the resolution of measured FR data was improved by using programmable gain amplifiers; 4) a data storage module and a real-time temperature measurement module were added to the system; 5) an LCD display and a keypad were added to the system to display the FR data with corresponding frequencies and to allow users to enter commands. Impedance transformation models for the sensor probe, the coaxial cable that connects the control system with the sensor probe, and the signal processing circuit were studied in order to acquire information on the permittivity of measured materials from measured FR data. Coaxial cables of the same length terminated with different loads, including an open circuit, a short circuit, a 50 resistor, and a 50 resistor paralleled by a capacitor, were tested. The results indicated that the models were capable of predicting the impedances of these specific loads using the FR data. Sensor probes with different sizes and coaxial cables with two different lengths terminated with the same sensor probe were also tested. The results were discussed. Additional tests for the gain and phase detector were conducted to compare FR data measured by the gain and phase detector with those observed on an oscilloscope. The results were discussed.

Professional imaging systems, particularly motion picture cameras, usually employ larger photosites and lower pixel counts than many amateur cameras. This results in the desirable characteristics of improved dynamic range, signal to noise and sensitivity. However, high performance optics often have frequency response characteristics that exceed the Nyquist limit of the sensor, which, if not properly addressed, results in aliasing artifacts in the captured image. Most contemporary still and video cameras employ various optically birefringent materials as optical low-pass filters (OLPF) in order to minimize aliasing artifacts in the image. Most OLPFs are designed as optical elements with a frequency response that does not change even if the frequency responses of the other elements of the capturing systems are altered. An extended evaluation of currently used birefringent-based OLPFs is provided. In this work, the author proposed and demonstrated the use of a parallel optical window p ositioned between a lens and a sensor as an OLPF. Controlled X- and Y-axes rotations of the optical window during the image exposure results in a manipulation of the system's point-spread function (PSF). Consequently, changing the PSF affects some portions of the frequency components contained in the image formed on the sensor. The system frequency response is evaluated when various window functions are used to shape the lens' PSF, such as rectangle, triangle, Tukey, Gaussian, Blackman-Harris etc. In addition to the ability to change the PSF, this work demonstrated that the PSF can be manipulated dynamically, which allowed us to modify the PSF to counteract any alteration of other optical elements of the capturing system. There are several instances presented in the dissertation in which it is desirable to change the characteristics of an OLPF in a controlled way. / In these instances, an OLPF whose characteristics can be altered dynamically results in an improvement of the image quality. / by Branko Petljanski. / Thesis (Ph.D.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

This thesis presents a comparative analysis of various low-frequency sonar signature representations and their ability to discriminate between proud targets of varying physical parameters. The signature representations used include: synthetic aperture sonar (SAS) beamformed images, acoustic color plot images, and bispectral images. A relative Mean-Square Error (rMSE) performance metric and an effective Signal-to-Noise Ratio (SNReff) performance metric have been developed and implemented to quantify the target differentiation. The analysis is performed on a subset of the synthetic sonar stave data provided by the Naval Surface Warfare Center - Panama City Division (NSWC-PCD). The subset is limited to aluminum and stainless steel, thin-shell, spherical targets in contact with the seafloor (proud). It is determined that the SAS signature representation provides the best, least ambiguous, target differentiation with a minimum mismatch difference of 14.5802 dB. The acoustic color plot and bispectrum representations resulted in a minimum difference of 9.1139 dB and 1.8829 dB, respectively / by Brenton Mallen. / Thesis (M.S.C.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

Neste trabalho são apresentados diversos métodos de localização de vazamentos, desde as técnicas e equipamentos mais elementares, como a inspeção visual e o geofone mecânico, até o uso dos sofisticados armazenadores de ruídos e de modelação computacional. Algumas dessas técnicas são amplamente difundidas e largamente utilizadas pelas empresas de saneamento, outras porém, constituem-se em ótimas promessas para o aperfeiçoamento do controle das perdas físicas nos sistemas de abastecimento. É dada ênfase na utilização do diagrama de resposta em freqüência para localizar e quantificar vazamentos, com especial aplicação às adutoras de água tratada. A técnica de utilização da resposta em freqüência desenvolvida por Lee et al. (2005) é esmiuçada, inclusive acerca do impacto que um vazamento impõe ao diagrama de resposta em freqüência. São abordadas as formas de obtenção do referido diagrama, tanto do ponto de vista do modelo matemático e computacional, quanto dos ensaios de campo necessários. / This work presents some methods for leak location, from de most elementary techniques and equipments, as visual inspection and mechanical geophone, until using sophisticated noise data-logger and computational modeling. Some of these techniques are very well issued and largely used by water companies, but others play excellent promises for the improvement of leak control in systems of water supply. The pattern of the frequency response diagram is used for leak location and quantification, with special application in drinking water pipelines. The frequency response technique developed by Lee et al. (2005) is studied in details, including the impact produced by the leak on the frequency response diagram. The ways to obtain the frequency response diagram, by using mathematical and computational models or necessary field data survey, are also discussed.