Dissertations / Theses on the topic 'Rate constant'
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Saw, Yoo-Sok. "Nonlinear rate control techniques for constant bit rate MPEG video coders." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/1381.
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Digital visual communication has been increasingly adopted as an efficient new medium in a variety of different fields; multi-media computers, digital televisions, telecommunications, etc. Exchange of visual information between remote sites requires that digital video is encoded by compressing the amount of data and transmitting it through specified network connections. The compression and transmission of digital video is an amalgamation of statistical data coding processes, which aims at efficient exchange of visual information without technical barriers due to different standards, services, media, etc. It is associated with a series of different disciplines of digital signal processing, each of which can be applied independently. It includes a few different technical principles; distortionrate theory, prediction techniques and control theory. The MPEG (Moving Picture Experts Group) video compression standard is based on this paradigm, thus, it contains a variety of different coding parameters which may result in different performance depending on their values. It specifies the bit stream syntax and the decoding process as its normative parts. The encoder details remain nonnormative and are configured by a specific design. This means that the MPEG video encoder has a great deal of flexibility in the aspects of performance and implementation. This thesis deals with control techniques for the data rate of compressed video, which determine the encoding efficiency and video quality. The video rate control is achieved by adjusting quantisation step size depending on the occupancy of a transmission buffer memory which stores the compressed video data for a specific period of time. Conventional video rate control techniques have generally been based either on linear predictive or on control theoretic models. However, this thesis takes a different view on digital video and MPEG video coding, and focuses on the non-stationary and nonlinear nature of realistic moving pictures. Furthermore, considering the MPEG encoding structure involved in the different disciplines, A series of improvements for video rate control are proposed, each of which enhances the performance of the MPEG encoder. A nonlinear quantisation control technique is investigated, which controls the buffer occupancy with the quantiser using a series of nonlinear functions. Linear and nonlinear feed-forward networks are also employed to control the quantiser. The linear combiner is used as a linear estimator and a radial basis function network as a nonlinear one. Finally, fuzzy rulebased control is applied to exploit the advantages of the nonlinear control technique which is able to provide linguistic judgement in the control mechanism. All these techniques are employed according to two global approaches (feedforward and feedback) applied to the rate control. The performance evaluation is carried out in terms of controllability over bit rate variation and video quality, by conducting a series of simulations.
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Mandra', S. "Deep Nuclear Resonant Tunneling Thermal Rate Constant Calculations." Doctoral thesis, Università degli Studi di Milano, 2013. http://hdl.handle.net/2434/218725.
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This thesis presents a new method to calculate thermal rate constants for arbitrary one dimensional scattering potentials in the presence of many quasi-bound states. This novel methodology can be proficiently applied to the case of multiple-barrier passages where quasi-bound states are present. After showing that thermal rate constants can be calculated from asymptotic conditions, the Schrödinger equation has been solved as an ordinary differential equation, with the energy as a fixed parameter, by choosing suitable asymptotic boundaries conditions. The method we propose is time-independent and it provides a significant advantage over any available time-dependent method, since time-dependent methods are not adequate for the calculation of rate constants in the presence of long-lived resonance states. The error respect to the exact expression was typically less than 1%, even at extremely low temperatures. Possible multidimensional implementations of the method are under way.
Three main applications of our method have been considered:
i) Separation of Helium isotopes by resonant tunneling in a double layer Polyphenylene system (2D-PP). Due to the presence of resonant states given by the double barrier potential, the 2D-PP filter was able to select between He3 from He4, even at relatively high temperatures.
ii) Extensive studies of the effects of resonant tunneling on the thermal rate constants for double barrier potentials. We numerically observed two important phenomena: the "oscillation" of the thermal rate constant as a function of the distance between the two barriers, and the "Inverse Kinetic Isotope Effect" where the heavier isotope has a larger thermal rate constant with respect to the lighter isotope.
iii) Realization of a quantum protocol for the calculation of the thermal rate constant on a quantum computer. In particular, we take advantage of our time-independent method to devise a quantum algorithm with an exponential speed-up with respect to any equivalent classical algorithm.
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Aieta, C. D. "QUANTUM AND SEMICLASSICAL METHODS FOR RATE CONSTANT CALCULATIONS." Doctoral thesis, Università degli Studi di Milano, 2018. http://hdl.handle.net/2434/546203.
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Chemical reactions are intrinsically dynamical processes. Reaction rate constants, and thus the understanding of chemical kinetics, can be in principle obtained at a very detailed level if one is able to compute the real time quantum dynamics for the reactive system. Unfortunately, the numerical implementation of real time quantum dynamics is very hard to perform, especially for high dimensional systems, because the computational effort scales exponentially with the number of degrees of freedom.
In this Ph.D. thesis, two open problems in reaction rate theory have been addressed. The first one is to extend to high dimensional systems the inclusion of quantum effects in rate constant computations. The second issue deal with the inclusion of real time dynamics into very accurate rate constants calculations.
The thesis is organized as follows. After a general Introduction, the second chapter is an overview of the state of the art in reaction rate theory. Then, in the third chapter, the derivation of Miller's Semiclassical Transition State Theory (SCTST) is recalled. SCTST is the method employed to obtain accurate and quantum-corrected rate constants for high dimensional reactions. In chapter 4, a novel parallel implementation of this theory (that has also been released as an open source code into J. R. Barker's MultiWell suite of codes) is described together with its application to high dimensional systems. In the following chapters, a new quantum rate approach able to include real time dynamics effects is presented. Derivation and applications of the latter are thoroughly described in chapter 6. The thesis ends with some perspectives about possible future developments.
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SUPO, KATHIA CECILIA LOPEZ. "DEVELOPMENT OF A CONSTANT RATE OF FLOW FIELD PERMEAMETER." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=13449@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
presente dissertação descreve o desenvolvimento de um equipamento destinado a determinar a condutividade hidráulica de meios porosos saturados in situ. O permeâmetro consiste em uma sonda que emprega o método da vazão constante. Após sua inserção pelo modo de cravação. Uma bomba de seringa instalada na superfície do terreno é utilizada para aplicar uma vazão constante enquanto que a carga hidráulica induzida no meio é medida através de um transdutor de pressão piezoresistivo instalado no corpo da sonda. O equipamento permite o escoamento das linhas de drenagem e de medição de carga hidráulica a partir da superfície possibilitando a saturação do meio poroso após a cravação da sonda bem como minimiza as incertezas associadas à medição de pressão. Esta última é alcançada através de um transdutor diferencial de pressão com uma faixa de trabalho de 10kPa que possibilita medições de poropressões bem próximas a zona de injeção. Esta característica permite a realização de ensaios num tempo curto e minimiza o problema de compatibilidade de fluidos decorrente do processo de injeção.
This thesis describes a piece of equipment developed to determine the hydraulic conductivity of saturated porous media. The permeameter consists of a pushed in probe and employs the constant flow rate method. A syringe pump installed on the surface is used to develop a constant rate of flow whereas a piezoelectric transducer installed in the probes body measures the induced change in hydraulic head. The great innovation in this device consists on its ability of saturating all of its drainage lines allowing the media to be saturated and minimizing the errors of pressure measurements. Pressure measurement is carried out using a 10kPa differential pressure transducer that enables porepressure to be measured close to the injection zone. This characteristic enables shorter tests to be carried out and minimize problems associated to fluid compability
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Lee, Yew Choong Patrick 1975. "Numerical modeling of constant rate of strain consolidation tests." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29564.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.Includes bibliographical references (leaves 95-96).
Constant Rate of Strain Consolidation Testing (CRSC) is an effective testing method to determine cohesive soil properties including stress history, compressibility, hydraulic conductivity and coefficient of consolidation. However, testing at varying strain rates have resulted in inconsistent results with respect to expected soil behavior. This theoretical study develops at numerical model to simulate the important details of a CRSC test using a finite difference approach in a spreadsheet in Microsoft Excel. The model provides a tool which can be used to study the test interpolation errors. The model based on void ratio versus log of effective vertical stress and versus log of hydraulic conductivity relationship of soil and includes the pore pressure compressibility of base measuring system. Parametric studies are preformed on Resedimented Boston Blue Clay normally consolidated behavior to investigate the effects of apparatus compressibility and strain rate. Finally, the predicted base pore pressure from the model simulation are used with the conventional interpretation equations to quantify the errors in soil parameters due to apparatus compressibility. It was found that bottom drainage of the specimen into the measuring system in a pore pressure distribution such that the base excess pore water pressure is not equal to the maximum excess pore water pressure. The magnitude of this difference increases with strain rate and neutral plane location. When using the conventional interpretation, this causes a shift in the compression curve to higher effective vertical stress. The error is small when the pore water pressure ratio is less than 5%. The error in hydraulic conductivity is much more significant and causes an overestimate of the hydraulic conductivity. This research forms the basis for which future experimental validation, normally consolidated to overly consolidated and steady state to transient state analysis. It can form the basis of new theories for the interpretation of constant rate of strain consolidation tests.
by Yew Choong Patrick Lee.
M.Eng.
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Tao, Jianping. "PULSE SHAPED CONSTANT ENVELOPE 8-PSK MODULATION STUDY." International Foundation for Telemetering, 1997. http://hdl.handle.net/10150/609753.
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International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, NevadaThe most bandwidth-efficient communication methods are imperative to cope with the congested frequency bands. Pulse Shaping methods have excellent effects on narrowing bandwidth and increasing band utilization. The position of the baseband filters for the pulse shaping is crucial. Filters after the modulator will have non-constant envelope and before the modulator will have constant envelope. These two types have different effects on narrowing the bandwidth and producing bit errors. The constant envelope 8 PSK is used throughout the simulations and is compared with the non-constant envelope results. This work provides simulation results of spectrum analysis and measure of bit errors produced by pulse shaping in an AWGN channel.
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Hariharakumar, Pradeep. "Constant displacement rate experiments and constitutive modeling of asphalt mixtures." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3066.
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The focus of this dissertation is on constant displacment rate experiments on asphalt concrete and on developing continuum models in a general thermo-mechanical setting which will corroborate with the experimental results. Modeling asphalt concrete and predicting its response is of great importance to the pavement industry. More than 90 percent of the US Highways uses asphalt concrete as a pavement material.
Asphalt concrete exhibits nonlinear response even at small strains and the response of asphalt concrete to different types of loading is quite different. The properties of asphalt concrete are highly influenced by the type and amount of the aggregates and the asphalt used. The internal structure of asphalt concrete keeps on evolving during the loading process. This is due to the influence of different kinds of activities at the microlevel and also due to the interaction with the environment. The properties of asphalt concrete depend on its internal structure. Hence we need to take the evolution of the internal structure in modeling the response of asphalt concrete.
Experiments were carried out at different confinement pressures and displacement rates on cylindrical samples of asphalt concrete. Two different aggregates were used to make the sample -limestone and granite. The samples were tested at a constant displacement rate at a given confinement pressure. The force required to maintain this constant displacement rate is measured and recorded.
The frame-work has been developed using the idea of multiple natural configurations that was introduced recently to study a variety of non-linear dissipative response of materials. By specifying the forms of the stored energy and rate of dissipation function of the material, specific models were developed using this frame work. In this work both a compressible and an incompressible model were developed by choosing appropriate forms of stored energy and rate of dissipation function. Finally the veracity of the models were tested by corroborating with the experimental results.
It is anticipated that the present work will aid in the development of better constitutive equations which in turn will accurately model asphalt concrete in laboratory and in field.
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González, Jorge H. (Jorge Hugo) 1971. "Experimental and theoretical investigation of constant rate of strain consolidation." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8985.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000.Includes bibliographical references (leaves 212-216).
The Constant Rate of Strain (CRS) test provides an efficient and a relatively rapid method to determine properties (stress history, compressibility, hydraulic conductivity, and rate of consolidation) of a cohesive soil and possess many advantages over the incremental oedometer test. Ease of operation and the ability to take frequent readings provides tremendous labor savings and a better definition of the compression curve. However, the test has some disadvantages including, pore pressure measurement errors, initial transient conditions, and strain rate dependent soil behavior. There is also no set standard for the method of analysis to be used for interpretation of the CRS data. This experimental and theoretical study evaluates parameters that affect CRS test results, including strain rate sensitivity, testing device effects, and different methods used to interpret the data. An extensive program was conducted on Resedimented Boston Blue Clay (RBBC) and Resedimented Vicksburg Buckshot Clay (RVBC) to study the behavior during constant rate of strain consolidation. Strain rate sensitivity was measured using the Wissa Constant rate of strain device. Two special CRS tests were performed to evaluate the pore pressure measuring system and to. assess transient conditions. Two analysis methods proposed by Wissa et al. (1971) were scrutinized using a numerical simulation on a model soil. The stiffness of the pore pressure system relative to the soil stiffness is extremely important in tests with high ... Both soils were found to be strain rate sensitive. The softer RVBC had little sensitivity in compression and c, behavior. However, the k, decreased with increasing hydraulic gradient. Stiffer RBBC had a high sensitivity in compression and cv behavior. kv was insensitive to gradient but this observation is believed to be an error caused by the system stiffness. The findings support the use of either the linear or nonlinear theory provided the ... is kept below 0.15. The system stiffness, relative to the soil stiffness, is very important and negatively impacts results as the ... increases. The transient duration is well predicted by Wissa's F3 = 0.4 limit. Based on numerical simulation, it was shown that the established equations to compute k, and c, should be modified to account for large deformations.
by Jorge H. Gonzalez.
S.M.
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McCoy, Tammy Michelle. "Extension of the master sintering curve for constant heating rate modeling." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22532.
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Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2008.Committee Chair: Dr. Joe K. Cochran; Committee Co-Chair: Dr. Thomas H. Sanders; Committee Member: Dr. John Elton; Committee Member: Dr. Meilin Liu; Committee Member: Dr. Robert F. Speyer.
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Bird, Nicholas James. "Use of the terminal rate constant in the assessment of glomerular filtration rate by clearance of injected tracers." Thesis, University of Surrey, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436077.
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Lai, Yeh-Hung. "The constrained blister - a nearly constant strain energy release rate test for adhesives." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/44077.
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This study developed and analyzed a modification of the blister test permitting nearly constant strain energy release rate testing of adhesive bonds. The work consisted of three parts; (1) development of the testing technique to evaluate strain energy release rate and to record the time dependent nature of the fracture process, (2) numerical analysis of the constrained blister test to determine the applicability of an approximate solution for several materials, and (3) development of an. analytical technique to evaluate the strain energy release rate for relatively stiff specimens.
Master of Science
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Yandek, Lindsay E. "MULTIPLE SUBSTRATE KINETICS OF RIBONUCLEASE P: RELATIVE RATE CONSTANT DETERMINATION THROUGH INTERNAL COMPETITION." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1371041699.
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Li, Vincent Yiu Fai. "An artificial intelligence approach to the processing of radar return signals for target detection." Thesis, University of Plymouth, 1999. http://hdl.handle.net/10026.1/2814.
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Most of the operating vessel traffic management systems experience problems, such as track loss and track swap, which may cause confusion to the traffic regulators and lead to potential hazards in the harbour operation. The reason is mainly due to the limited adaptive capabilities of the algorithms used in the detection process. The decision on whether a target is present is usually based on the magnitude of the returning echoes. Such a method has a low efficiency in discriminating between the target and clutter, especially when the signal to noise ratio is low. The performance of radar target detection depends on the features, which can be used to discriminate between clutter and targets. To have a significant improvement in the detection of weak targets, more obvious discriminating features must be identified and extracted. This research investigates conventional Constant False Alarm Rate (CFAR) algorithms and introduces the approach of applying ar1ificial intelligence methods to the target detection problems. Previous research has been unde11aken to improve the detection capability of the radar system in the heavy clutter environment and many new CFAR algorithms, which are based on amplitude information only, have been developed. This research studies these algorithms and proposes that it is feasible to design and develop an advanced target detection system that is capable of discriminating targets from clutters by learning the .different features extracted from radar returns. The approach adopted for this further work into target detection was the use of neural networks. Results presented show that such a network is able to learn particular features of specific radar return signals, e.g. rain clutter, sea clutter, target, and to decide if a target is present in a finite window of data. The work includes a study of the characteristics of radar signals and identification of the features that can be used in the process of effective detection. The use of a general purpose marine radar has allowed the collection of live signals from the Plymouth harbour for analysis, training and validation. The approach of using data from the real environment has enabled the developed detection system to be exposed to real clutter conditions that cannot be obtained when using simulated data. The performance of the neural network detection system is evaluated with further recorded data and the results obtained are compared with the conventional CFAR algorithms. It is shown that the neural system can learn the features of specific radar signals and provide a superior performance in detecting targets from clutters. Areas for further research and development arc presented; these include the use of a sophisticated recording system, high speed processors and the potential for target classification.
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Gardiner, Kelly Ann. "A mechanistic investigation of the reactions of diselenides with biological oxidants." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/20957.
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Reactive oxygen species (ROS) [e.g. hydrogen peroxide (H2O2), hypochlorous acid (HOCl), singlet oxygen (1O2)] can cause oxidative stress, with damage implicated in inflammatory conditions including atherosclerosis. Antioxidants, both enzymatic and non-enzymatic [e.g. glutathione (GSH)], often rely on sulfur or selenium centres for reactivity. Selenium is more nucleophilic than sulfur, so selenocompounds [e.g. selenocysteine (Sec)] typically display higher rate constants than the analogous sulfur species (e.g. Cys). Thus, selenium species may minimise biological damage via removal of oxidants and subsequent rapid reduction of oxidised compounds. Selenols (RSeH, e.g. Sec) are unstable and rapidly auto-oxidise, making therapeutic application problematic. This thesis investigates diselenides (RSeSeR) as shelf-stable alternatives which can be reduced to the reactive selenol in situ. Rate constants were determined for the reactions of low-molecular-mass diselenides [selenocystamine (SeCA), 3,3’-diselenodipropionic acid (DSePA), 2,2’-dipyridyl diselenide (DPDSe), dipyrimidin-2-yl diselenide (DPMSe)], fluorescently-tagged selenocystine (Fmoc-SeCystine; the diselenide of Sec) and the selenium analogue of oxidised GSH [seleno-diglutathione (GSeSeG)] with HOCl, H2O2 and 1O2-generated amino acid/peptide hydroperoxides, with products characterised by LC/MS. Oxidation of diselenides by HOCl (k = 103 – 105 M-1 s-1) was more rapid than with H2O2 (k = 10-4 – 10-2 M-1 s-1). SeCA oxidation was similar between the hydroperoxides (k ~ 10-2 M-1 s-1) but DSePA was oxidised by Trp hydroperoxide (TrpOOH) ca. 50 – 150-fold faster than other diselenides, revealing that the ionisation state of the terminal groups affects the oxidation rate. Product characterisation revealed the major product of oxidation by HOCl, H2O2 and TrpOOH to be the seleninic acid (RSeO2H), postulated to form via an initial transient intermediate and diselenide bond cleavage, as per the pathway of the sulfur species.
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Adams, Amy Lynn. "Laboratory evaluation of the constant rate of strain and constant head techniques for measurement of the hydraulic conductivity of fine grained soils." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66859.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 185-187).
This thesis evaluates the constant rate of strain and constant head techniques for measurement of the hydraulic conductivity of fine grained soils. A laboratory program compares hydraulic conductivity measurements made using both measurement techniques on a total of 12 specimens. Both resedimented and intact materials covering a wide range of plasticity are investigated. Specific material types include Boston Blue Clay, San Francisco Bay Mud, Maine Clay, Ugnu Clay and Kaolinite. Constant rate of strain (CRS) and constant head tests were conducted in a standard Trautwein CRS device modified to allow control of the base pore pressure for constant head testing. A flexible wall permeameter device was used to perform constant head hydraulic conductivity testing on two specimens; this allowed for comparison with the constant head measurements made in the CRS device. A bottom seating error was found in the CRS device. Bottom seating error occurs during set up when the top of the base porous stone is not flush with the bottom of the rigid specimen ring, causing a gap to form between the specimen and the porous stone. A bottom seating error translates into a strain error, which affects both the measured CRS compression and hydraulic conductivity results. Bottom seating error can be avoided using a modified set up procedure. Void ratio errors are sometimes noted between the void ratio measured in the CRS device and that measured upon removal from the CRS device. These errors are likely resultant from specimen swelling following load removal. Based on comparison to the results of an interlaboratory study into the reproducibility of the saturated hydraulic conductivity measured in a flexible wall permeameter, the CRS and constant head techniques were found to measure the same hydraulic conductivity. This conclusion is independent of specimen origin, i.e. resedimented or intact. The CRS and constant head techniques measure the same average hydraulic conductivity even when non uniformities are present, provided the non uniformities are continuous and oriented perpendicular to the axial loading direction.
by Amy Lynn Adams.
S.M.
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Saghaian, Nejad Esfahani Sayed Mahdi. "STATISTICAL MODELS FOR CONSTANT FALSE-ALARM RATE THRESHOLD ESTIMATION IN SOUND SOURCE DETECTION SYSTEMS." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/46.
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Constant False Alarm Rate (CFAR) Processors are important for applications where thousands of detection tests are made per second, such as in radar. This thesis introduces a new method for CFAR threshold estimation that is particularly applicable to sound source detection with distributed microphone systems. The novel CFAR Processor exploits the near symmetry about 0 for the acoustic pixel values created by steered-response coherent power in conjunction with a partial whitening preprocessor to estimate thresholds for positive values, which represent potential targets.
To remove the low frequency components responsible for degrading CFAR performance, fixed and adaptive high-pass filters are applied. A relation is proposed and it tested the minimum high-pass cut-off frequency and the microphone geometry.
Experimental results for linear, perimeter and planar arrays illustrate that for desired false alarm (FA) probabilities ranging from 10-1 and 10-6, a good CFAR performance can be achieved by modeling the coherent power with Chi-square and Weibull distributions and the ratio of desired over experimental FA probabilities can be limited within an order of magnitude.
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Karaca, Ümit Özen Serdar. "Constant False Alarm Rate (cfar) Detection Based Estimators With Applications to Sparse Wireless Channels/." [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/elektrikveelektronikmuh/T000586.pdf.
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Liang, Y., C. Zeng, J. J. Wang, M. W. Liu, Yeh T. C. Jim, and Y. Y. Zha. "Constant Gradient Erosion Apparatus for Appraisal of Piping Behavior in Upward Seepage Flow." AMER SOC TESTING MATERIALS, 2017. http://hdl.handle.net/10150/625214.
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Seepage direction is crucial for understanding the critical state and development of piping erosion. A stress-controlled apparatus was designed to investigate the piping behavior of cohesionless soil under upward flow condition. The components of the new apparatus included a loading chamber, a vertical and confining loading system, an upstream water supply device, a soil-water separating system, and a water collecting system. The loading chamber provides space for a soil specimen setting and loading. The combination of a vertical and a confining loading system was designed to apply complex stresses to a soil specimen. Under the stresses, the specimen was then eroded by the gradually increasing hydraulic head supplied by the water supply system. The eroded particle and spilling water were collected and detected by the soil-water separating system and the water collecting system. A series of experiments were carried out using the new apparatus. Results demonstrated the repeatability experiments and usefulness of the apparatus. The new apparatus allowed us to investigate the piping behavior under different stress states and hydraulic gradients. With this new apparatus and experiments, we found that lower and high critical hydraulic gradients (CHGs) should be included as the criteria of piping development based on the relationship between the hydraulic gradient and the seepage response. In addition, the stress state on the CHG and the particle erosion rate played important roles in the piping development. The outer pressure on the specimen can retard the development of erosion. In contrast, the hydraulic gradient was found to be positively correlated to the erosion rate. Results also indicated that a specimen would collapse once the amount of eroded small particles exceeds the critical value of 46.5 % of the soil.
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Soloshenko, E. N., A. K. Kondakova, V. G. Kolesnikov, N. V. Khmil, Z. M. Shevchenko, and T. P. Yarmak. "The investigation of dielectric constant of blood during sensitization to penicillin G." Thesis, Львів, 2019. http://openarchive.nure.ua/handle/document/10277.
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The aim of this work was to evaluate the effect of penicillin G on the patients’ blood with antibiotic sensitization in a history in vitro using the parameters of dielectric constant. To study the dielectric constant, venous blood was used in 23 patients with antibiotic sensitization between the ages of 35 and 50 years. Sensitization to penicillin G in these patients was confirmed by the method of leukocyte agglomeration reaction (LAR) and by estimating the erythrocyte sedimentation rate (ESR) loaded with the suspected allergen.
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Chun, Geumju 1965. "Critical strain for dynamic recrystallization during the constant strain rate hot deformation of Nb steels." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81532.
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The presence of peak points in constant strain rate flow curves is generally considered to indicate the onset of dynamic recrystallization (DRX). However, not all materials display clear peaks when tested under these conditions. It has been suggested that DRX is initiated when the strain reaches a critical value epsilonc that is related to the peak strain epsilonp and that this critical strain can be detected from the inflection point in plots of the strain hardening rate theta against stress sigma, regardless of the presence or absence of peaks. This is of importance because many works regarding DRX have been carried out by physical simulation using laboratory torsion tests.However, one of the main problems in laboratory simulation is that the inflection point for DRX is not easily determined, particularly in microalloyed steels. This problem is rendered more difficult in torsion testing because of the strain gradient along the radius of the specimen. As an alternative, compression testing can provide more accurate data regarding the initiation of DRX.
In this work, the DRX behavior of three Nb microalloyed steels was investigated using compression testing. Continuous deformation by axisymmetric compression was employed in the temperature range 850 to 1050°C at strain rates of 0.01, 0.1 and 1/sec. Stress-strain curves were obtained and then the critical strains for initiation were calculated using a method based on the presence of an inflection point at the moment of initiation. The critical strain was observed to increase when the deformation temperature was decreased or when the strain rate was increased. No significant effect of the level of microalloying addition on the DRX behavior was detected within the range studied.
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Cai, Wei. "Discrete element modelling of constant strain rate and creep tests on a graded asphalt mixture." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/29249/.
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This thesis investigates the use of Discrete Element Modelling (DEM) to simulate the elastic and viscoelastic deformation behaviour of an asphalt mixture. A numerical specimen preparation procedure has been developed to produce specimens with an isotropic stress and correct volumetrics. Stone mastic asphalt has been chosen in this project because of its high content of coarse aggregate and binder-rich mortar. A range of uniaxial compression tests have been undertaken in the laboratory under various loading speeds and stresses. The axial stress, axial strain and radial strain were recorded during the tests. The peak stress is found to be as a power-law function of the strain rates for the asphaltic material. Elastic contact properties have been used to investigate the effect of particle number and location, loading speed, normal and shear contact stiffness. The Poisson's ratio was found to increase with the ratio of normal to shear contact stiffness but was independent of the stiffnesses. The Young's modulus was found to be dependent on both normal and shear stiffnesses, in agreement with previous work on idealised asphalt mixtures. The Burger's model was introduced to give time-dependent stiffness for the viscoelastic modelling. The Burger's model was implemented to give moment and torsional resistance as well as in direct tension and compression. To reduce the computational time in the creep simulations, the effect of scaling both viscosities in the Burger's model to simulate a shorter time, have been investigated. The effects of each parameter on the deformation of asphalt mixture were also investigated. The stress-strain response for the laboratory tests and the simulations were recorded. The results show good agreement when the bond strengths in the model are made to be a function of strain rate for both constant strain rate and creep conditions. Both normal and Weibull distributions have been used for the bond strengths between the aggregate particles. The constant strain rate tests results were proved to be independent of the bond strength variability and position of particles, while the creep tests results were dependent on the hand strength variability and position of particles. This is in good agreement with experimental tests: different specimens at the same stress level gave variability in the creep behaviour, at higher stress levels. Bond breakages were recorded during the simulations to investigate the micromechanical deformation behaviour of asphalt mixtures. It was found that a well-defined rupture at higher stress levels coincided with the maximum rate of bond breakage. The modified Burger's model has therefore proven to be a useful tool in modelling the moment and torsional resistance at particle contacts in an asphalt mixtures, in order to correctly predict observed behaviour.
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Wang, Xipeng. "CONSTANT FALSE ALARM RATE PERFORMANCE OF SOUND SOURCE DETECTION WITH TIME DELAY OF ARRIVAL ALGORITHM." UKnowledge, 2017. http://uknowledge.uky.edu/ece_etds/105.
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Time Delay of Arrival (TDOA) based algorithms and Steered Response Power (SRP) based algorithms are two most commonly used methods for sound source detection and localization. SRP is more robust under high reverberation and multi-target conditions, while TDOA is less computationally intensive. This thesis introduces a modified TDOA algorithm, TDOA delay table search (TDOA-DTS), that has more stable performance than the original TDOA, and requires only 4% of the SRP computation load for a 3-dimensional space of a typical room. A 2-step adaptive thresholding procedure based on a Weibull noise peak distributions for the cross-correlations and a binomial distribution for combing potential peaks over all microphone pairs for the final detection. The first threshold limits the potential target peaks in the microphone pair cross-correlations with a user-defined false-alarm (FA) rates. The initial false-positive peak rate can be set to a higher level than desired for the final FA target rate so that high accuracy is not required of the probability distribution model (where model errors do not impact FA rates as they work for threshold set deep into the tail of the curve). The final FA rate can be lowered to the actual desired value using an M out of N (MON) rule on significant correlation peaks from different microphone pairs associated is a point in the space of interest. The algorithm is tested with simulated and real recorded data to verify resulting FA rates are consistent with the user-defined rates down to 10-6.
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Green, Dale. "A probabilistic approach to reaction coordinate and rate constant modeling applied to epoxide ring-opening reactions." Kansas State University, 2012. http://hdl.handle.net/2097/15085.
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Master of ScienceDepartment of Chemical Engineering
Keith Hohn
The study will utilize a probabilistic reaction modeling method for ring-opening reactions of epoxide. In particular, to elucidate the reaction mechanism by the methods presented, focus will be placed on the nucleophillic attack of ethylene oxide by ammonia and its anion. This focus was chosen because of the potential to gain significant advantage in computational intensity required to model the epoxy-amino macromolecular curing reactions and resulting thermochemical and physical properties of the cured resin. The method employed utilizes the combinatorial probability that 1. Two molecules will approach a transition state with sufficient energy to drive reaction 2. Any reaction will occur for a given penetration into the potential energy surface. The concept of a transition state is relaxed to allow a dynamic probability that any reaction will proceed given a position on the intrinsic reaction coordinate (IRC) rather than searching for a specific transition state of theoretical reaction probability. 3. The reaction that occurs yields a desired stable or semi-stable molecular complex This study will focus on identifying possible stable and semi-stable products and corresponding rate constants. The technique developed here is novel in that it provides an unsupervised method to identify all structures corresponding to minima on the potential energy surface. The technique provides a pragmatic and efficient approach to sample a molecular system for different reaction mechanisms and provides a relative energy requirement to achieve these mechanisms with no presupposition of the mechanism, product, or transition state. It is possible from this data to derive rate constants for a reacting system, however, the rate constant derived for the EO/NH2 molecular system yielded significantly understated reaction probabilities and therefore rate constants.
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Phan, Anthony. "Development of a rate of injection bench and constant volume combustion chamber for diesel spray diagnostics." [Ames, Iowa : Iowa State University], 2009.
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Dean, Valarie Nichole. "Time Constant Analysis of Initial 'Jump' in Firing Rate of Human Motor Units During Isometic Contraction." Thesis, The University of Arizona, 2010. http://hdl.handle.net/10150/146201.
Full textAbstract:
Ongoing research studying the underlying mechanism and prevalence of Persistent Inward Currents (PICs) has posed a challenge to the conventional view that the firing rate of a motor unit is proportional to the amount of synaptic input it receives. Near the time of human motor unit recruitment during isometric muscle contraction, a sudden steep rise in firing rate is observed, which is suggested to result from rapid triggering of PICs, an intrinsic property of motor neurons. In evaluating the time constants associated with these steep rises in firing rate across different contractile speeds, it has been found that the time course of the steep rise is dependent on the time course of muscle contraction. This evidence suggests that the mechanism underlying this steep rise in firing rate is not PIC-associated, but rather depends on an alternate, unknown mechanism.
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Fritsch, LeaAnn Thompson. "Effects of chronic suboptimal energy intake on constant-load exercise in young women." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-09182008-063227/.
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Holm, Daniélle. "Influence of strain rate in CRS tests : A laboratory study of three Swedish clays." Thesis, KTH, Jord- och bergmekanik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192212.
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The Constant Rate of Strain (CRS) test is currently the most widely used method for determination of consolidation parameters in Sweden. These parameters are used to calculate the probable settlements and behavior of soils. With the Swedish standard strain rate, the duration of a single the test is about 24h, but a higher strain rate would allow for more tests to be performed in the same amount of time. For all clays in Sweden, the Swedish standard for the CRS test suggests a fixed rate of strain that is independent of soil properties, while the North American standard proposes a strain rate that generates a pore pressure ratio of 3-15%. Soil properties such as water content, liquid limit, sensitivity and shear strength vary greatly between different regions of Sweden. It would be beneficial if these properties could be used to find the ideal strain rate for the CRS test. Performing the tests at a higher strain rate, and thus performing more tests within a shorter amount of time, would save both time and money. In this report, 24 CRS tests are performed on three different clays with distinctive properties. Each clay is tested with three different strain rates: the Swedish standard rate of 0.680%/h, a higher rate of 3.00%/h and a lower rate of 0.154%/h. The results are evaluated according to both standards, and are compared and analyzed to determine whether there is any indication that the strain rate can be selected based on the soil properties. The results indicate that the selection of the strain rate is dependent on the soil properties. In addition, the majority of the tests can be conducted with higher strain rates than what is required by the Swedish standard and still manage to lie within the 3-15% limit of the pore pressure ratio, which is acceptable for the North American standard. However, the preconsolidation pressure does rise with increased strain rates, which can generate problems and erroneous results when calculating the settlements. A more extensive testing program with CRS tests and full-scale field tests must be carried out before any recommendation of a higher strain rate can be made.
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Stang, Eric Thomas. "Constitutive Modeling of Creep in Leaded and Lead-Free Solder Alloys Using Constant Strain Rate Tensile Testing." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1548338008633472.
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Sherrell, Ian M. "Development of a Flotation Rate Equation from First Principles under Turbulent Flow Conditions." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29943.
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A flotation model has been proposed that is applicable in a turbulent environment. It is the first turbulent model that takes into account hydrodynamics of the flotation cell as well as all relevant surface forces (van der Waals, electrostatic, and hydrophobic) by use of the Extended DLVO theory. The model includes probabilities for attachment, detachment, and froth recovery as well as a collision frequency. A review of the effects fluids have on the flotation process has also been given. This includes collision frequencies, attachment and detachment energies, and how the energies of the turbulent system relate to them. Flotation experiments have been conducted to verify this model. Model predictions were comparable to experimental results with similar trends. Simulations were also run that show trends and values seen in industrial flotation systems. These simulations show the many uses of the model and how it can benefit the industries that use flotation.Ph. D.
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Killian, Marie Coy. "Kinetics of Atmospheric Reactions of Biogenic Volatile Organic Compounds: Measurement of the Rate Constant ofThujone + Cl· at 296 K and Calculation ofthe Equilibrium Constant for the HO2CH2CH2O2· H2O Complex." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3642.
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Biogenic volatile organic compounds (VOCs) react with Cl and OH radicals and the resulting radicals combine with oxygen to form peroxy radicals RO2. Organic peroxy radicals can then react with NO to form NO2, a precursor of tropospheric ozone. The work presented here explored the initial reaction between Cl and thujone, a VOC emitted by Great Basin sagebrush. The rate constant for the reaction of thujone + Cl at 296 K was measured with the method of relative rates with FTIR for detection of reactants. LEDs were used to photolyze Cl2 to generate Cl in the reaction cell. Thujone was also photolyzed by the LEDs and therefore the relative rates model was revised to account for this photolysis. With toluene as the reference compound, the rate constant for thujone + Cl at 296 K is 2.62 ± 1.90 × 10-12 molecules-1 s-1, giving an atmospheric lifetime of 0.5--2.6 minutes for thujone. Cline et al. showed that the rate of the self-reaction of HO2CH2CH2O2 (β-HEP) increases in the presence of water vapor. This enhancement has a strong temperature dependence with a greater enhancement observed at colder temperatures. The observed rate enhancement has been attributed to the formation of a β-HEP--H2O complex. In this work, the equilibrium constant for the formation of the β-HEP--H2O complex was calculated by ab initio calculations. Given the energy available at room temperature, the complex will populate three local minimum geometries and β-HEP will populate two local minimum geometries. The partition function for each of these geometries was calculated and used to calculate the equilibrium constant for complex formation as a function of temperature. Based on these computational results, the observed temperature dependence for the rate enhancement can be attributed to the strong temperature dependence for the rate constant of the reaction of β-HEP--H2O + β-HEP rather than the temperature dependence of complex formation.
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Guzainuer, Maimaitiyiming. "Boundary Summation Equation Preconditioning for Ordinary Differential Equations with Constant Coefficients on Locally Refined Meshes." Thesis, Linköpings universitet, Matematiska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-102573.
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This thesis deals with the numerical solution of ordinary differential equations (ODEs) using finite difference (FD) methods. In particular, boundary summation equation (BSE) preconditioning for FD approximations for ODEs with constant coefficients on locally refined meshes is studied. Firstly, the BSE for FD approximations of ODEs with constant coefficients is derived on a locally refined mesh. Secondly, the obtained linear system of equations are solved by the iterative method GMRES. Then, the arithmetic complexity and convergence rate of the iterative solution of the BSE formulation are discussed. Finally, numerical experiments are performed to compare the new approach with the FD approach. The results show that the BSE formulation has low arithmetic complexity and the convergence rate of the iterative solvers is fast and independent of the number of grid points.
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Jani, Parth K. "Experimental Investigation of Influence of Liquid Physicochemical Properties on Adiabatic Bubble Growth from Submerged Capillary Orifice under Constant Flow Rate Conditions." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1623169715636338.
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Short, Hayden B. "Chemically Accurate Calculations of Rate Constants of Spin Trap-Hydroxyl Radical Addition Reactions." Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/honors/252.
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The DMPO type spin trap 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) and the exceptionally similar spin trap 2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-l-oxide (EMPO) are widely studied in computational and theoretical works. This particular study examines the addition reactions that both these molecules undergo with the carcinogenic hydroxyl radical. This work used a relatively new approximation method, called the correlation consistent composite approach or ccCA, for carrying out quantum mechanical calculations to give the free energies of the products and reactants of the reactions. The free energies are to be used to extrapolate the rate constants of the reactions from the Arrhenius equation. Though both the spin traps studied have been widely examined and assessed in both theoretical and experimental work, accurately calculated rate constants have not been previously obtained using computational methods. The results obtained here will help to assess the efficiency and the accuracy of the ccCA method, as well as lead to the design of better, more novel spin traps.
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Tyagi, P. K. "Linear Instability Of Laterally Strained Constant Pressure Boundary Layer Flows." Thesis, Indian Institute of Science, 2001. https://etd.iisc.ac.in/handle/2005/265.
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The linear instability of laterally diverging/converging flows is an important aspect towards understanding the laminar-transition process in many viscous flows. In this work the linear instability of constant pressure laterally diverging/converging flow has been investigated.
The laminar velocity field for laterally diverging/converging flows, under the source/sink approximation, has been reduced to two-dimensional flows. This reduction is alternative to the Mangier transformation used earlier. For a constant pressure laterally strained flow, the laminar velocity is found to be governed by the Blasius equation for flow over a flat plate.
The non-parallel linear instability of constant pressure laterally strained flows has been examined. The instability equation is found to be same as that for the Blasius flow. This implies that the stability is same as that for the Blasius flow. A lateral divergence/convergence is shown to alter the Reynolds number from that in a two-dimensional flow. The instability of a laterally converging/diverging flow thus can be obtained from the available results for the Blasius flow by scaling the Reynolds numbers. This leads to the result that while a diverging flow is more unstable than the Blasius flow, a converging flow is more stable. Some additional relevant results are also presented.
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Tyagi, P. K. "Linear Instability Of Laterally Strained Constant Pressure Boundary Layer Flows." Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/265.
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The linear instability of laterally diverging/converging flows is an important aspect towards understanding the laminar-transition process in many viscous flows. In this work the linear instability of constant pressure laterally diverging/converging flow has been investigated.
The laminar velocity field for laterally diverging/converging flows, under the source/sink approximation, has been reduced to two-dimensional flows. This reduction is alternative to the Mangier transformation used earlier. For a constant pressure laterally strained flow, the laminar velocity is found to be governed by the Blasius equation for flow over a flat plate.
The non-parallel linear instability of constant pressure laterally strained flows has been examined. The instability equation is found to be same as that for the Blasius flow. This implies that the stability is same as that for the Blasius flow. A lateral divergence/convergence is shown to alter the Reynolds number from that in a two-dimensional flow. The instability of a laterally converging/diverging flow thus can be obtained from the available results for the Blasius flow by scaling the Reynolds numbers. This leads to the result that while a diverging flow is more unstable than the Blasius flow, a converging flow is more stable. Some additional relevant results are also presented.
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Stromský, Tomáš. "Studium slinování pokročilých keramických materiálů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230343.
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The influence of various pressure-less heating schedules (CRH - Constant Rate of Heating, TSS - Two Step Sintering, RCS – Rate Controlled Sintering) on the final microstructure of cubic zirconia ceramics was studied in this master´s thesis. There were used nanopowders ZrO2 (stabilized with 8 mol.% Y2O3) with initial particle size 80 nm (TZ-8Y) and 140 nm (TZ-8YSB). Powders were cold isostatically pressed and pressure-less sintered in air by different heating regimes. It was found that for both studied materials the modification of conventional sintering (CRH) using lower sintering temperatures and longer sintering dwell times can result in samples with finer microstructure. For example, the sintering of TZ-8YSB ceramics at a relatively low temperature (1270 °C) but for very long time (60 h) led to ceramics with the same final density (99,25 % of theoretical density) and almost identical grains (1,31 m vs. 1,27 m) in compare with TSS (1440 °C/ 1290 °C/ 15 h). On the other hand, RCS method showed no positive effect on the microstructure of both materials in comparison with CRH method. The obtained results indicate that the microstructure of c-ZrO2 ceramics can be influenced rather in its third sintering stage (by CRH and TSS methods) than in the second sintering stage (by RCS method).
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Beyene, Mussie Abraham. "Modelling the Resilience of Offshore Renewable Energy System Using Non-constant Failure Rates." Thesis, Uppsala universitet, Institutionen för elektroteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-445650.
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Offshore renewable energy systems, such as Wave Energy Converters or an Offshore Wind Turbine, must be designed to withstand extremes of the weather environment. For this, it is crucial both to have a good understanding of the wave and wind climate at the intended offshore site, and of the system reaction and possible failures to different weather scenarios. Based on these considerations, the first objective of this thesis was to model and identify the extreme wind speed and significant wave height at an offshore site, based on measured wave and wind data. The extreme wind speeds and wave heights were characterized as return values after 10, 25, 50, and 100 years, using the Generalized Extreme Value method. Based on a literature review, fragility curves for wave and wind energy systems were identified as function of significant wave height and wind speed. For a wave energy system, a varying failure rate as function of the wave height was obtained from the fragility curves, and used to model the resilience of a wave energy farm as a function of the wave climate. The cases of non-constant and constant failure rates were compared, and it was found that the non-constant failure rate had a high impact on the wave energy farm's resilience. When a non-constant failure rate as a function of wave height was applied to the energy wave farm, the number of Wave Energy Converters available in the farm and the absorbed energy from the farm are nearly zero. The cases for non-constant and an averaged constant failure of the instantaneous non-constant failure rate as a function of wave height were also compared, and it was discovered that investigating the resilience of the wave energy farm using the averaged constant failure rate of the non-constant failure rate results in better resilience. So, based on the findings of this thesis, it is recommended that identifying and characterizing offshore extreme weather climates, having a high repair rate, and having a high threshold limit repair vessel to withstand the harsh offshore weather environment.
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Shope, Ronald L. "Response of Wide Flange Steel Columns Subjected to Constant Axial Load and Lateral Blast Load." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/29521.
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The response of wide flange steel columns subjected to constant axial loads and lateral blast loads was examined. The finite element program ABAQUS was used to model W8x40 sections with different slendernesses and boundary conditions. For the response calculations, a constant axial force was first applied to the column and the equilibrium state was determined. Next, a short duration, lateral blast load was applied and the response time history was calculated. Changes in displacement time histories and plastic hinge formations resulting from varying the axial load were examined. The cases studied include single-span and two-span columns. In addition to ideal boundary conditions, columns with linear elastic, rotational supports were also studied. Non-uniform blast loads were considered. Major axis, minor axis, and biaxial bending were investigated. The effects of strain rate and residual stresses were examined. The results for each column configuration are presented as a set of curves showing the critical blast impulse versus axial load. The critical blast impulse is defined as the impulse that either causes the column to collapse or to exceed the limiting deflection criterion.
A major goal of this effort was to develop simplified design and analysis methods. To accomplish this, two single-degree-of-freedom approaches that include the effects of the axial load were derived. The first uses a bilinear resistance function that is similar to the one used for beam analysis. This approach provides a rough estimate of the critical impulse and is suitable only for preliminary design or quick vulnerability calculations. The second approach uses a nonlinear resistance function that accounts for the gradual yielding that occurs during the dynamic response. This approach can be easily implemented in a simple computer program or spreadsheet and provides close agreement with the results from the finite element method.Ph. D.
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Östman, Andreas. "Detection and Tracking of Human Targets using Ultra-Wideband Radar." Thesis, Uppsala universitet, Signaler och System, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-305427.
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The purpose of this thesis was to assess the plausibility of using two Ultra- Wideband radars for detecting and tracking human targets. The detection has been performed by two different types of methods, constant false-alarm rate methods and a type of CLEAN algorithm. For tracking the targets, multiple hypothesis tracking has been studied. Particle filtering has been used for the state prediction, considering a significant amount of uncertainty in a motion model used in this thesis project. The detection and tracking methods have been implemented in MATLAB. Tracking in the cases of a single target and multiple targets has been investigated in simulation and experiment. The simulation results in these cases were compared with accurate ground truth data obtained using a VICON optical tracking system. The detection methods showed poor performance when using data that had been collected by the two radars and post-processed to enhance target features. For single targets, the detections were accurate enough to continuously track a target moving randomly in a controlled area. In the multiple target cases the tracker was not able to distinguish the multiple moving subjects.
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Diamanti, Aikaterini. "On the determination of the reaction rate constant and selectivity in gas and liquid-phase organic reactions : temperature and solvent effects." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/44727.
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Chemical reactions occur abundantly in nature and the rates at which they proceed are critically influenced by factors such as the temperature and the solvent medium in which they take place. These two factors do not only affect the rate of a given reaction but may also have a significant impact on other metrics, such as the selectivity and the catalytic activity, as well as on the overall performance of a process application. Faced with such a broad scope of considerations, the identification of an optimum reaction environment remains a challenge. This thesis provides an in-depth investigation of gas and liquid-phase reactions in the context of predicting selected reaction metrics under different thermodynamic and media conditions. In particular, the effect of temperature on the rate constant of a gas-phase reaction and the effects of solvent media on the rate constant and selectivity of a liquid-phase reaction are considered. A gas-phase hydrogen abstraction reaction between ethane and the hydroxyl radical is studied in a broad range of temperatures. A thorough computational investigation is performed of the temperature dependence of the reaction rate constant, assessing several ab initio and density functional theory methods with various basis sets. A novel hybrid strategy is proposed for the development of correlative kinetic models that incorporate information from the quantum-mechanical calculations and experiments into classical Arrhenius expressions. The hybrid models derived bring new insight into the value and contribution of the data obtained via quantum-mechanical calculations and via measurements. The benefits of such models in the context of accuracy, statistical significance, applicability and practical importance on the study of reactions with scarce experimental data, are highlighted. A regioselective Williamson reaction between sodium β-naphthoxide and benzyl bromide is selected for the investigation of solvent effects on the reaction rate constant and product selectivity. The solvent medium has a key impact on the selectivity of the reaction for alkylation at two possible sites (an oxygen or a carbon atom) resulting in O- and C-alkylated products. For this reaction, a systematic study is performed combining detailed kinetic experiments and density functional theory calculations to determine the reaction rate constant in a set of solvents. The challenges in conducting reliable experiments using NMR spectroscopy are highlighted, and the performance of the various computational methods is scrutinized. Good agreement is obtained between computational predictions and experimental data for the reaction rate constants as well as for the ranking of solvents in terms of the product selectivity ratios for a number of the theoretical methods considered. These promising results pave the way for future computer-aided molecular design tools for the identification of solvents for improved reaction performance.
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Ward, Christopher W. "The role of the apparent rate constant of cross-bridge transition from the strong binding state (ga̳p̳p̳) in skeletal muscle force production /." This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-06062008-151126/.
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Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1996.On t.p. "a̳p̳p̳" is subscript. Vita. Abstract. Includes bibliographical references (leaves 76-80). Also available via the Internet.
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Alanazi, Mohammed Awwad. "Non-invasive Method to Measure Energy Flow Rate in a Pipe." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/103179.
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Current methods for measuring energy flow rate in a pipe use a variety of invasive sensors, including temperature sensors, turbine flow meters, and vortex shedding devices. These systems are costly to buy and install. A new approach that uses non-invasive sensors that are easy to install and less expensive has been developed. A thermal interrogation method using heat flux and temperature measurements is used. A transient thermal model, lumped capacitance method LCM, before and during activation of an external heater provides estimates of the fluid heat transfer coefficient h and fluid temperature. The major components of the system are a thin-foil thermocouple, a heat flux sensor (PHFS), and a heater. To minimize the thermal contact resistance R" between the thermocouple thickness and the pipe surface, two thermocouples, welded and parallel, were tested together in the same set-up. Values of heat transfer coefficient h, thermal contact resistance R", time constant �[BULLET], and the water temperature �[BULLET][BULLET], were determined by using a parameter estimation code which depends on the minimum root mean square RMS error between the analytical and experimental sensor temperature values. The time for processing data to get the parameter estimation values is from three to four minutes. The experiments were done over a range of flow rates (1.5 gallon/minute to 14.5 gallon/minute). A correlation between the heat transfer coefficient h and the flow rate Q was done for both the parallel and the welded thermocouples. Overall, the parallel thermocouple is better than the welded thermocouple. The parallel thermocouple gives small average thermal contact resistance average R"=0.00001 (m2.�[BULLET][BULLET]/W), and consistence values of water temperature and heat transfer coefficient h, with good repeatability and sensitivity. Consequently, a non-invasive energy flow rate meter or (BTU) meter can be used to estimate the flow rate and the fluid temperature in real life.MS
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Ward, Christopher W. "The role of the apparent rate constant of cross-bridge transition from the strong binding state (G app ) in skeletal muscle force production." Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/37983.
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Force regulation at the level of the actin-myosin cross-bridge (XB) can be
described by a 2 state model in which the XB's cycle between a strongly bound (SB), force
generating state and a weakly bound (WB), non-force generating state. This cycle can be
characterized by the apparent rate constants for transition into the SB state (fapp) and
returning to the WB state (gapp), Increases in XB force can be accounted for by an increase
in fapp a decrease in gapp., or both. While effort towards understanding XB force regulation
has focused on the notion that force production is primarily regulated by fapp the purpose
of this investigation was to determine if gapp continues to force regulation at the XB and
to determine whether gapp differs in,muscles with differing contractile characteristics.Ph. D.
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Rycroft, Ashley McLean. "Development of a constant rate step test to assess exertional dyspnea in the primary care setting in patients with chronic obstructive pulmonary disease (COPD)." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112359.
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Rationale. There is a need for the development of a field test to evaluate exertional dyspnea in the primary care setting. This study examined the applicability of a 3-minute constant rate step test in patients with COPD.Methods. This test involved 4 stepping rates (18, 22, 26, 32 steps.min-1) equivalent to approximately 4.5, 5.3, 6.0, and 7.2 MET with the ultimate goal that in its final development, the assessment will be made a single stepping rate based on disease severity. Stable COPD patients (N = 43; 65 +/- 6.5 years; FEV1 = 49 +/- 16% pred.; SpO2 (%) rest: 95 +/- 2) were equipped with a portable Jaeger Oxycon MobileRTM metabolic system and followed an audio signal for stepping up and down a single 20 cm step for 3 minutes. Borg dyspnea scores were obtained at the end each stepping bout. A 10-min rest was given between each stepping bout.
Results. Of the 43 patients, 80% completed stages 1 and 2, 74 and 37% stages 3 and 4 while no patient of MRC class 4 or 5 (N = 8) completed stage 1. Breathing frequency (breaths.min-1) spanned from 26.5 +/- 4.1 to 39.0 +/- 6.4 but VT (L) remained unchanged (1.4 +/- 0.3 vs. 1.5 +/- 0.4) from stage 1 to 4 while Borg scores were 3 +/- 1, 4 +/- 1, 5 +/- 2, 6 +/- 3 respectively and SpO2 (%) were 92 +/- 5, 91 +/- 4, 91 +/- 4 and 90 +/- 4.
Conclusions. Preliminary findings indicate that a 3-minute constant rate step test may present a feasible alternative to laboratory testing to assess exertional dyspnea in moderately severe COPD. In this population, a stepping rate of 26 steps.min-1 could be sustained by the majority of patients while producing a level of dyspnea potentially amenable to therapy.
This study was supported by an unrestricted grant from Boehringer-Ingelheim/Pfizer.
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Bien-Aime, Andre J. "Effect of Cement Chemistry and Properties on Activation Energy." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4439.
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The objective of this work is to examine the effect of cement chemistry and physical properties on activation energy. Research efforts indicated that time dependent concrete properties such as strength, heat evolution, and thermal cracking are predictable through the concept of activation energy. Equivalent age concept, which uses the activation energy is key to such predictions. Furthermore, research has shown that Portland cement concrete properties are affected by particles size distribution, Blaine fineness, mineralogy and chemical composition. In this study, four Portland cements were used to evaluate different methods of activation energy determination based on strength and heat of hydration of paste and mortar mixtures. Moreover, equivalency of activation energy determined through strength and heat of hydration is addressed. The findings indicate that activation energy determined through strength measurements cannot be used for heat of hydration prediction. Additionally, models were proposed that are capable of predicting the activation energy for heat of hydration and strength. The proposed models incorporated the effect of cement chemistry, mineralogy, and particle size distribution in predicting activation energy.
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Ko, Tae Young. "SUBCRITICAL CRACK GROWTH UNDER MODE I, II, AND III LOADING FOR COCONINO SANDSTONE." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/193702.
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In systems subjected to long-term loading, subcritical crack growth is the principal mechanism causing the time-dependent deformation and failure of rocks. Subcritical crack growth is environmentally-assisted crack growth, which can allow cracks to grow over a long period of time at stresses far smaller than their failure strength and at tectonic strain rates. The characteristics of subcritical crack growth can be described by a relationship between the stress intensity factor and the crack velocity. This study presents the results of studies conducted to validate the constant stress-rate test for determining subcritical crack growth parameters in Coconino sandstone, compared with the conventional testing method, the double torsion test. The results of the constant stress-rate test are in good agreement with the results of double torsion test. More importantly, the stress-rate tests can determine the parameter A with a much smaller standard deviation than the double torsion test. Thus the constant stress-rate test seems to be both a valid and preferred test method for determining the subcritical crack growth parameters in rocks. We investigated statistical aspects of the constant stress-rate test. The effects of the number of tests conducted on the subcritical crack growth parameters were examined and minimum specimen numbers were determined. The mean and standard deviation of the subcritical crack growth parameters were obtained by randomly selecting subsets from the original strength data. In addition, the distribution form of the subcritical crack growth parameters and the relation between the parameter n and A were determined. We extended the constant stress-rate test technique to modes II and III subcritical crack growth in rocks. The experimental results of the modes I, II and III tests show that the values of the subcritical crack growth parameters are similar to each other. The subcritical crack growth parameter n value for Coconino sandstone has the range of 34 to 38 and the parameter A has the range of 1.02x10⁻² to 6.52x10⁻² m/s. The effect of confining stress, specimen size, and water saturation on subcritical crack growth under mode II loading has also been investigated. Finally strength parameters for Coconino sandstone were determined experimentally, including tensile strength, uniaxial compressive strength, cohesion, internal friction angle, in-plane / our-of-plane shear strength and the fracture toughness under mode I, II, and III loading.
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Alves, Tiago Vinicius. "Estudo teórico da reação do radical metila com nitrogênio atômico (4S): aspectos estruturais, energéticos, espectroscópicos e cinéticos." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/46/46132/tde-19052008-134755/.
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A busca de uma melhor compreensão dos ciclos químicos que ocorrem na atmosfera de Titan, um dos satélites naturais de Saturno, tem posto em relevância a importância de reações químicas envolvendo nitrogênio atômico e hidrocarbonetos, principalmente o radical metila. Além desta ênfase astroquìmica, essa reação tem também um papel importante no estudo da decomposição de metano em plasma pós-descarga de nitrogênio e no entendimento de processos de combustão. Neste trabalho, dando continuidade a estudos teóricos envolvendo reações de espécies atômicas com hidrocarbonetos realizados por este grupo e utilizando o estado da arte em termos de cálculos de estrutura eletrônica, realizou-se uma ampla investigação da superfície tripleto de energia potencial 3[H3, C, N] com ênfase nos aspectos estruturais, energéticos e espectroscópicos dos pontos estacionários e na cinética global da reação. Nesta superfície de energia potencial, foram caracterizados 7 pontos estacionários, sendo 3 estados de transição e 4 mínimos. No melhor nível de cálculo, CCSD(T)/CBS, o mínimo global corresponde à formação do radical metilnitreno, 71,01 kcal/mol mais estável do que o canal de entrada N(4S) + CH3 (2A2\"). Entretanto, via caminhos distintos, a reação prossegue formando H2CN + H como o principal produto, resultado esse que não confirma uma suposição anterior de que HCN seria o produto principal. No aspecto cinético, verificou-se que a etapa determinante da reação é regida pelo canal de entrada bimolecular, sem barreira, e que o valor para a constante de velocidade global, na melhor descrição deste trabalho, de 1,93 x 10-10 cm3 molécula?1 s-1, é bem superior à de estudo teórico anterior. Além da boa concordância com dados experimentais, nossos resultados também mostram um aumento da constante de velocidade com a temperatura, o que não foi previsto nesse estudo anterior.The search for a better understanding of chemical cycles in Titan´s atmosphere, one of Saturn´s largest natural satellite, has emphasized the importance of chemical reactions between atomic nitrogen and hydrocarbons, especially methyl radical. Besides this astrochemical relevance, this reaction also plays a key role in the study of methane decomposition in after-glow nitrogen plasma, and in combustion processes. In this work, as another step towards theoretical studies of reactions involving atomic species with hydrocarbons carried out by this group, and using state-of-the-art electronic structure calculations, a wide investigation of the triplet potential energy surface 3[H3, C, N] was made with emphasis on structural, energetic, and spectroscopic aspects of the stationary points, and on the global kinetic description of the reaction. In this potential energy surface, 7 stationary points were characterized: 3 transition states and 4 minima. In our best description, CCSD(T)/CBS, the global minimum corresponds to the formation of the methylnitrene radical, 71.01 kcal/mol more stable than the entrance channel N(4S) + CH3 (2A2\"). However, by different paths, the reaction proceeds leading to the formation of H2CN + H as the major product, a result that does not confirm a previous supposition that HCN would be the major product. Kinetically, we have shown that the rate determining step is the barrierless bimolecular collision of CH3 and N(4S), and that the global rate constant, in the best estimate of this work, 1.93 x 10-10 cm3 molecule-1 s-1, is well superior to that of a previous theoretical study. Besides the good agreement with the experimental data, our results also show an increase of the rate constant with the temperature, a result not predicted by that previous study.
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Vasquez, Emilie. "Techniques statistiques de détection de cibles dans des images infrarouges inhomogènes en milieu maritime." Thesis, Aix-Marseille 3, 2011. http://www.theses.fr/2011AIX30001.
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Des techniques statistiques de détection d'objet ponctuel dans le ciel ou résolu dans la mer dans des images infrarouges de veille panoramique sont développées. Ces techniques sont adaptées aux inhomogénéités présentes dans ce type d'image. Elles ne sont fondées que sur l'analyse de l'information spatiale et ont pour objectif de maîtriser le taux de fausse alarme sur chaque image. Pour les zones de ciel, une technique conjointe de segmentation et détection adaptée aux variations spatiales de la luminosité moyenne est mise en œuvre et l'amélioration des performances auxquelles elle conduit est analysée. Pour les zones de mer, un détecteur de bord à taux de fausse alarme constant en présence d'inhomogénéités et de corrélations spatiales des niveaux de gris est développé et caractérisé. Dans chaque cas, la prise en compte des inhomogénéités dans les algorithmes statistiques s'avère essentielle pour maîtriser le taux de fausse alarme et améliorer les performances de détectionStatistical detection techniques of point target in the sky or resolved target in the sea in infrared surveillance system images are developed. These techniques are adapted to inhomogeneities present in this kind of images. They are based on the spatial information analysis and allow the control of the false alarm rate in each image.For sky areas, a joint segmentation detection technique adapted to spatial variations of the mean luminosity is developed and its performance improvement is analyzed. For sea areas, an edge detector with constant false alarm rate when inhomogeneities and grey level spatial correlations are present is developed and characterized. In each case, taking into account the inhomogeneities in these statistical algorithms is essential to control the false alarm rate and to improve the detection performance
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Pöppel, Nina Franziska [Verfasser]. "Influence of ketamine or xylazine constant rate infusion on quality of anaesthesia, cardiopulmonary function and recovery in isoflurane anaesthetised horses - a clinical trial / Nina Franziska Pöppel." Hannover : Bibliothek der Tierärztlichen Hochschule Hannover, 2014. http://d-nb.info/1049571312/34.
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Henophy, Sara Catherine 1983. "Test-re-test reproducibility of constant rate step and shuttle walking tests for the assessment of exertional dyspnea in patients with chronic obstructive pulmonary disease (COPD)." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116085.
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Purpose: Exercise testing modalities to assess the effects of a given intervention should prove to be reliable and reproducible. This study reports on test-retest reproducibility of the 3-min shuttle walking and step testing exercise protocols to assess exertional dyspnea and exercise physiology in COPD patients.Methods: Stable COPD patients (N=43; 65 +/- 6.5 years; FEV1 = 49 +/- 16% pred.) equipped with a portable Jaeger Oxycon MobileRTM metabolic system repeated the walking or stepping tests on two occasions separated by 7 to 14 days. At each visit, participants performed, in a randomized order, four externally paced 3-min bouts of shuttle walking at speeds of 1.5, 2.5, 4.0 and 6.0 km·h-1 or of stepping at a constant rate of 18, 22, 26 and 32 steps·min-1, respectively. Each exercise bout was separated by a 10-min rest period. Ventilation, heart rate, gas exchange parameters and Borg dyspnea score were obtained for each bout during the last 30-seconds of exercise.
Results: The majority of patients completed stepping or walking at the slowest cadence but only 33% completed walking at 6.0 km·h -1 and 40% completed stepping at 32 steps·min-1. Test-retest Pearson correlation coefficients for ventilation, heart rate, gas exchange parameters and dyspnea scores over the four exercise bouts, all exceeded 0.80 with the highest coefficient found for ventilation (r≥.95). Intra-class correlation coefficients were similar to Pearson. Bland & Altman representation showed that a similar proportion of dyspnea data points (92 vs. 96%) lied within 2 SD of the mean difference between test-retest values for dyspnea Borg scores during walking and stepping.
Conclusion: Results show very good reproducibility for both 3-min shuttle walking and stepping exercise protocols in patients with COPD.
This study was supported by an unrestricted grant from Boehringer-Ingelheim/Pfizer.