Tesi sul tema "Rate effects"

The purpose of this study was to analyze those factors that affect the commitment rate of juveniles and how outside variables such as gender, race, parents, and school attendance affect the commitment rate of crime and delinquency. The variables used for this study came from the Gang Resistance Education and Training (G.R.E.A.T.) data collected by Esbensen and Osgood (1999). The analysis revealed that females are more likely to have a higher commit rate than males, that Whites have a higher commit rate than other races, that those juveniles living with their father have a lower commit rate than those living with others, and those juveniles who do not attend school often are less likely to commit crimes and delinquent actions than those who attend more often.

The strain rate dependent behaviour of fine grained soils is an important aspect of geotechnical engineering. During dynamic or rapid events such as earthquakes and rapid pile testing, a fine grained soil will display significantly different behaviour than may be observed over the long life span of a structure. There is currently little understanding of the factors which influence the behaviour of fine grained soils during dynamic events (extremely high strain rates), making their response difficult to predict. This research investigates the behaviour of fine grained soils subjected to a wide range of constant strain rates in monotonic triaxial compression testing. Each test is conducted under drained conditions to observe the behaviour of soils as they transition from a drained response at lower strain rates, through to an undrained or viscous response at higher strain rate tests. Where the response of soils is drained or partially drained, higher strain rate tests measure a decrease in strength. The point of transition from partially drained to undrained behaviour corresponds to the lowest strain rate dependent strength. Further tests at higher strain rates measure consistently greater strength. The strain rate dependence of three fine grained soils is investigated, enabling a comparison of strain rate effects with soil index properties. The influence of initial state on the strain rate dependence of these Kaolin based model soils is also evaluated. The drained to partially drained response of the soils to strain rate increase is controlled by the coefficient of consolidation. Tests at high strain rates show the undrained or viscous strain rate effect on strength is related to liquidity index. Local strain instrumentation allowed comparison of strain rate effects on small strain stiffness. At higher strain rate the soils display increasingly linear behaviour. At non-linear elastic strains, liquidity index appears to control the magnitude of the strain rate effects on stiffness.

Soil-filled wire and geotextile gabions are commonly used to construct defensive infrastructure in military bases, where the attenuating properties of soil are used to protect personnel and key assets from the effects of blast and fragmentation. The behaviour of soils in these extreme loading regimes is not well understood, and so designers require data at these high pressures and strain rates in order to develop robust soil constitutive models and adapt to new threats. The one-dimensional compression of three sandy soils was compared under quasi-static loading to axial stresses of 800 MPa. Trends in behaviour were identified with respect to the particle size distributions of the soils, and were found to correspond to the relationships observed at lower stresses. Split Hopkinson pressure bar (SHPB) experiments were used to investigate the strain rate dependence of this behaviour. Measurements of radial stress indicated that an increase in the axial stiffness of the soils between strain rates of 10^-3 s^-1 and 10^3 s^-1 was likely due to radial inertial effects. Potential sources of error were identified in the SHPB experiments, leading to the implementation of a dispersion-correction algorithm, which improved the measurement of axial stresses. Analysis of the electromagnetic activity around the specimen isolated the cause of erroneous radial stress measurements. Quasi-static experiments were used to investigate the effect of moisture content on soil stiffness at high pressures, and SHPB experiments at the same moisture contents were used to consider the effect of strain rate on the quasi-static behaviour. Recovery SHPB experiments were designed to enable reliable post-test particle size analyses to be performed, and the range of moisture contents was expanded to investigate the change in soil behaviour on reaching full saturation. Reduced triaxial compression experiments were used to define the yield surface of a sand to a mean stress of 400 MPa. The high-pressure compression and yield strength data was used to calibrate LS-DYNA soil models, and the performance of the models was assessed through modelling of the SHPB experiments.

Thesis (Ph. D.)--West Virginia University, 1998.
Title from document title page. Document formatted into pages; contains vii, 108 p. : ill. Includes abstract. Includes bibliographical references (p. 87-93).

In this study, the effects of CBRT monetary policy decisions on the consumer, automobile, housing and commercial loans of the banks during the period from the early of 2004 to the middle of 2011 are examined. In order to perform this study, it is benefited from weekly weighted average loan interest rate data of the banks, which is the data having the highest frequency that could be obtained from the electronic data distribution system of CBRT. Monetary policy instruments of Central Bank may change in the course of time or monetary policy could be executed by more than one instrument. Therefore, as the political interest rate would be insufficient in the calculation of the effect of monetary policy on loan interest rates of the banks, Government Dept Securities&rsquo
premiums are used instead of the political interest rates in this study to make it reflect the policies of central bank more clearly as a whole. Among the Government Dept Securities that have different maturity structure, benchmark bonds that are adapted to the expected political interest rate changes and that react to the unexpected interest rate changes at the high rate (reaction coefficient 0.983) are used. In order to weight the cointegration relation between interest rates, unrestricted error correction model is established and it is determined by Bound Test that there is a long-term relation between each interest rate and interest rate of benchmark bond. After a cointegration relation is determined among the serials, autoregressive distributed lag model is used to determine the level of transitivity and it is determined that monetary policy decisions affect the banking interest rate at 77% level and by 13 weeks delay on average.

Doctor of Philosophy (PhD)
In recent times significant public attention has been drawn to the topic of combustion. This has been due to the fact that combustion is the underlying mechanism of several key challenges to modern society: climate change, energy security (finite reserves of fossil fuels) and air pollution. The further development of combustion science is undoubtedly necessary to find improved solutions to manage these combustion science related challenges in the near and long term future. Combustion is essentially an exothermic process, this exothermicity or heat release essentially occurs at small scales, by small scales it meant these scales are small relative to the fluid length scales, for example heat release layer thicknesses in flames are typically much less than the fluid integral length scales. As heat release occurs at small scales this means that in turbulent combustion the small scales of the turbulence (which can be of the order of the heat release layer thickness) can possibly interact and influence the heat release and thus chemistry of the flame reaction zone. Premixed combustion is a combustion mode where the fuel and oxidiser are completely premixed prior to the flame reaction zone, this mode of combustion has been shown to be a promising method to maximise combustion efficiency and minimise pollutant formation. The continued and further application of premixed combustion to practical applications is limited by the current understanding of turbulent premixed combustion, these limitations in understanding are linked to the specific flame phenomena that can significantly influence premixed combustion in a combustion device, examples of such phenomena are: flame flashback, flame extinction and fuel consumption rate – all phenomena that are influenced by the interaction of the small scales of turbulence and chemistry. It is the study and investigation of the interaction of turbulence and chemistry at the small scales (termed finite-rate chemistry) in turbulent premixed flames that is the aim of this thesis which is titled “Finite-rate chemistry effects in turbulent premixed combustion”. Two very closely related experimental burner geometries have been developed in this thesis: the Piloted Premixed Jet Burner (PPJB) and the Premixed Jet Burner (PJB). Both feature an axisymmetric geometry and exhibit a parabolic like flow field. The PPJB and PJB feature a small 4mm diameter central jet from which a high velocity lean-premixed methane-air mixture issues. Surrounding the central jet in the PPJB is a 23.5mm diameter pilot of stoichiometric methane-air products, the major difference between the PPJB and the PJB is that the PJB does not feature a stoichiometric pilot. The pilot in the PPJB provides a rich source of combustion intermediates and enthalpy which promotes initial ignition of the central jet mixture. Surrounding both the central jet and pilot is a large diameter hot coflow of combustion products. It is possible to set the temperature of the hot coflow to the adiabatic flame temperature of the central jet mixture to simulate straining and mixing against and with combustion products without introducing complexities such as quenching and dilution from cold air. By parametrically increasing the central jet velocity in the PPJB it is possible to show that there is a transition from a thin conical flame brush to a flame that exhibits extinction and re-ignition effects. The flames that exhibit extinction and re-ignition effects have a luminous region near the jet exit termed the initial ignition region. This is followed by a region of reduced luminosity further downstream termed the extinction region. Further downstream the flame luminosity increases this region is termed the re-ignition region. For the flames that exhibit extinction and re-ignition it is proposed that intense turbulent mixing and high scalar dissipation rates drives the initial extinction process after the influence of the pilot has ceased (x/D>10). Re-ignition is proposed to occur downstream where turbulent mixing and scalar dissipation rates have decreased allowing robust combustion to continue. As the PJB does not feature a pilot, the flame stabilisation structure is quite different to the PPJB. The flame structure in the PJB is essentially a lifted purely premixed flame, which is an experimental configuration that is also quite unique. A suite of laser diagnostic measurements has been parametrically applied to flames in the PPJB and PJB. Laser Doppler Velocimetry (LDV) has been utilised to measure the mean and fluctuating radial and axial components of velocity at a point, with relevant time and length scale information being extracted from these measurements. One of the most interesting results from the LDV measurements is that in the PPJB the pilot delays the generation of high turbulence intensities, for flames that exhibit extinction the rapid increase of turbulence intensity after the pilot corresponds to the start of the extinction region. Using the LDV derived turbulence characteristics and laminar flame properties and plotting these flames on a traditional turbulent regime diagram indicates that all of the flames examined should fall in the so call distributed reaction regime. Planar imaging experiments have been conducted for flames using the PPJB and PJB to investigate the spatial structure of the temperature and selected minor species fields. Results from two different simultaneous 2D Rayleigh and OH PLIF experiments and a simultaneous 2D Rayleigh, OH PLIF and CH2O PLIF experiment are reported. For all of the flames examined in the PPJB and PJB a general trend of decreasing conditional mean temperature gradient with increasing turbulence intensity is observed. This indicates that a trend of so called flame front thickening with increased turbulence levels occurs for the flames examined. It is proposed that the mechanism for this flame front thickening is due to eddies penetrating and embedding in the instantaneous flame front. In the extinction region it is found that the OH concentration is significantly reduced compared to the initial ignition region. In the re-ignition region it is found that the OH level increases again indicating that an increase in the local reaction rate is occurring. In laminar premixed flames CH2O occurs in a thin layer in the reaction zone, it is found for all of the flames examined that the CH2O layer is significantly thicker than the laminar flame. For the high velocity flames beyond x/D=15, CH2O no longer exist in a distinct layer but rather in a near uniform field for the intermediate temperature regions. Examination of the product of CH2O and OH reveals that the heat release in the initial ignition region is high and rapidly decreases in the extinction region, an increase in the heat release further downstream is observed corresponding to the re-ignition region. This finding corresponds well with the initial hypothesis of an extinction region followed by a re-ignition region that was based on the mean chemiluminescence images. Detailed simultaneous measurement of major and minor species has been conducted using the line Raman-Rayleigh-LIF technique with CO LIF and crossed plane-OH PLIF at Sandia National Laboratories. By measuring all major species it is also possible to define a mixture fraction for all three streams of the PPJB. Using these three mixture fractions it was found that the influence of the pilot in the PPJB decays very rapidly for all but the lowest velocity flames. It was also found that for the high velocity flames exhibiting extinction, a significant proportion of the coflow fluid is entrained into the central jet combustion process at both the extinction region and re-ignition regions. The product of CO and OH conditional on temperature is shown to be proportion to the net production rate of CO2 for certain temperature ranges. By examining the product of CO and OH the hypothesis of an initial ignition region followed by an extinction region then a re-ignition region for certain PPJB flames has been further validated complementing the [CH2O][OH] imaging results. Numerical modelling results using the transported composition probability density function (TPDF) method coupled to a conventional Reynolds averaged Naiver Stokes (RANS) solver are shown in this thesis to successfully predict the occurrence of finite-rate chemistry effects for the PM1 PPJB flame series. To calculate the scalar variance and the degree of finite-rate chemistry effects correctly, it is found that a value of the mixing constant ( ) of approximately 8.0 is required. This value of is much larger than the standard excepted range of 1.5-2.3 for that has been established for non-premixed combustion. By examining the results of the RANS turbulence model in a non-reacting variable density jet, it is shown that the primary limitation of the predictive capability of the TPDF-RANS method is the RANS turbulence model when applied to variable density flows.

It has been observed in other wheat growing regions that stands that are thin rarely have problems with low grain protein. The purpose of this study was to determine if this is indeed the case in Arizona. A study was conducted at Maricopa where the durum varieties Duraking, Minos, and Turbo were sown at rates from 30 to 360 lbs seed/acre. Seeding rate had no effect on grain protein or yield in this study. The reported effects of thin stands on grain protein may be related to low yield rather than seeding rate per se.

Similar to global currencies, the Zambian currency (kwacha) has varied considerably against major currencies since the early 1990s. Existing empirical evidence reveals that fluctuations in exchange rates can potentially generate distortions in the economy. However, insufficient empirical evidence on Zambia exists. Thus, this thesis contributes empirically to the literature on exchange rate volatility and its impact on the economy with Zambia as a case study. Consequently, volatility in the kwacha bilateral exchange rates is modelled using three alternative GARCH models in order to characterise the underlying currency volatility. The influence of fundamental factors on conditional volatility of exchange rates is also examined. In addition, principal components analysis (PCA) is used to capture the common underlying pattern in the estimated conditional volatility series through which a new GARCH series (GARCH-PCA) is constructed and used in trade and monetary and foreign exchange intervention rule analysis as an alternative measure of exchange rate risk. PCA has not been previously employed in such analyses. Cointegration analysis is used for trade-exchange rate volatility analysis while SVAR and GMM are employed with variations to the conventional specification of monetary and foreign exchange intervention rules in the literature in determining the relevance of exchange rate volatility in monetary and foreign exchange policies. The results reveal that the kwacha bilateral exchange rates examined are characterised by different conditional dynamics in terms of volatility persistence and response to price shocks. The positive influences of exchange rate regime, money supply and openness on conditional volatility predominate. Exchange rate volatility affects international trade flows and underpins monetary policy and foreign exchange decision-making process. Thus, the results are amenable for trade policy formulation and monetary policy improvements and they justify foreign exchange interventions. GARCH-PCA, an index of exchange rate volatility, reflecting influences from Zambia proves to be a useful alternative measure of exchange rate volatility. Its performance is comparable to the trade-weighted measure in terms of sign, size and statistical significance of the estimated coefficients.

A study was conducted to evaluate the effect of specimen dimensions in slow strain-rate environmental effects testing. Tension tests of free machining brass were conducted in a mercuric nitrate solution at a constant crosshead displacement rate of 10⁻³(inch/sec). Thirty-six smooth round bar specimens with different dimensions were tested. It was shown that percent elongation to failure was inversely proportional to an effective ratio of length to diameter, ((D - 2a)L / D²), where D is the specimen diameter, L is the length of the reduced cross section of the specimen, and a is the environmentally induced crack depth. This effective length to diameter ratio correlates with the applied tearing modulus for a cracked round bar tension specimen as defined by P. C. Paris and co-workers in 1979. The results verify that the tearing modulus may be used as a parameter to evaluate tearing instability in terms of elastic-plastic fracture mechanics. More directly, these results show a possible source of error in evaluating the degree of susceptibility to environmentally induced cracking in a material-environment interaction.
Master of Science

The study of the relationship between the shear strength of the clay and the rate at which it is loaded is relevant to the application of a new rapid load pile testing technique called Statnamic. There are problems associated with interpreting the test results in clay soils due to the non linear variation in shear resistance with rate of shearing. An investigation has been conducted for two clay soils which were used in an associated research project. These were a reconstituted kaolin clay (KSS) used for model pile tests and undisturbed glacial clay taken from a full scale prototype pile testing site near Grimsby. Monotonic and multistage strain controlled triaxial tests were carried out on both clays using a, pneumatic computer, controlled rapid load triaxial system at rates from 0.001 mm/s to 200 mm/s. The shear strength increased and the excess pore pressure decreased as the rate of shearing increased. A power law was proposed relating dynamic and static shear strength. The damping coefficients and hence the rate effects, defined as a function of strain, were similar for both clays Based on the triaxial test results and a back analysis of Statnamic and "static" constant rate of penetration data from the associated model and full scale pile tests in both clays, a non-linear model has been proposed relating the static resistance of a pile to the measured Statnamic load taking into account the rate effects and the inertia of the pile. The non-linear model was used to develop a new multistage interpretation method for the analysis of Statnamic tests in clays.

xii, 132 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
Motivated by conflicting prior evidence for exchange rate effects on foreign direct investment (FDI), the first chapter of this dissertation explores theoretical evidence of the exchange rate effect on FDI in terms of different types of FDI. Based on a simple two-country model, I demonstrate that the profit function of a horizontal FDI investor is a decreasing function of the exchange rate, while the profit function for a vertical FDI investor is an increasing function of the exchange rate. This implies that a depreciation of a host country currency depresses horizontal FDI and promotes vertical FDI. Moreover, comparing the FDI investor's intertemporal profit in a simple two-period time frame, I lay out a theoretical basis for a relation between the effects of the exchange rate and the expectations of the exchange rate effect on different types of FDI. The second chapter of this dissertation examines the empirical evidence for the exchange rate effects on different types of FDI. Using cross-border mergers and acquisitions among 37 countries from 1985 to 2007, I measure horizontal and vertical FDI in 4 different ways, and constructing directional country pairs, I estimate the exchange rate effects on horizontal and vertical FDI by a Poisson and a negative binomial regression with fixed and random effects. The estimation results provide considerable support for the model's predictions of the first chapter. The third chapter of this dissertation extends the first and second chapters with an analysis of the effect of exchange rate expectations on different types of FDI. I examine 4 different measures of exchange rate expectations. Using a methodology similar to that in the second chapter, the estimation results suggest that the expected exchange rate effects on horizontal and vertical FDI are not very significant. However, the expectations of the exchange rate shed more light on the exchange rate effects on different types of FDI under all of the exchange rate expectation measures. This suggests that the exchange rate is a more influential determinant of the allocation of different types of FDI than the expected exchange rate.
Committee in charge: Bruce Blonigen, Chairperson, Economics; Jeremy Piger, Member, Economics; Stephen Haynes, Member, Economics; Neviana Petkova, Outside Member, Finance

An overview of the theoretical literature for the last two decades suggests that there is no clear-cut relationship one can pin down between exchange rate volatility and trade flows. Analytical results are based on specific assumptions and only hold in certain cases. Especially, the impact of exchange rate volatility on export and import activity investigated separately leads also to dissimilar conclusions among countries studied. The general presumption is that an increase in exchange rate volatility will have an adverse effect on trade flows and consequently, the overall heath of the world economy. However, neither theoretical models nor empirical studies provide us with a definitive answer, leaving obtained results highly ambiguous and inconsistent (Baum and Caglayan, 2006). We purposed to empirically investigate trade effects of exchange rate fluctuations in Sweden from the perspective of export and import in this research. The data comprises period from January 1993 to December 2006, where export and import volumes are considered from the point of their determinants, including exchange rate volatility, which has been measured through EGARCH model. The results for the case of Sweden show that short run dynamics of volatility negatively associated with both export and import, whereas considered from the case of previous period volatility it exhibits positive relationship. These results are consistent with the most findings of prior studies, where the relationship remained ambiguous.

Seabed gouging by ice, also known as ice scouring, is a common feature of the Arctic and sub Arctic regions of the planet as well as in Antarctica. It is a phenomenon which occurs when ice moves while in contact with the seabed. Ice gouging is of economical significance due to the probability of disruption of seabed structures such as subsea pipelines. Small scale laboratory tests were conducted at 1g to investigate the scour force produced when a scaled iceberg model scours a test bed in dry and saturated conditions. The tests were conducted for a range of scour depths, scour widths, frontal rake angles and soil conditions to study the performance of a rigid indenter (iceberg keel) scouring a test bed. Furthermore, the tests were also conducted at various speeds to study the rate effect in sand. The effect of the drifting speed on the drag force was found to be important: a sandy seabed scoured by an iceberg with a mean drifting speed of 0.1 m/s can generate scour loads twice as large as the static loads. The methods used currently to predict ice scour loads consider only the static loads under drained conditions and these should be revised. The PIV (Particle Image Velocimetry) technique was utilized to study the sub-gouge deformation and the soil failure mechanism associated with ice gouging. The soil resistance and the sub gouge deformation results obtained in the laboratory were compared with centrifuge investigations (the PRISE and PIRAM programs) in order to examine the viability of extrapolating the results from the model scale to a prototype scale.

The general work presented in this thesis describes the implementation and optimization of CEST MRI techniques on a preclinical 9.4 T MRI scanner for quantifying the chemical exchange rate or the exchange relaxation term both in vitro and in pathological conditions. A novel pulse sequence for measuring chemical exchange rates through a progressive saturation recovery process, called PRO-QUEST (PROgressive saturation for Quantifying Exchange rates using Saturation Times) has been developed. A complete theoretical framework has been set up, and the exchange rates calculated in several aminoacids using PRO-QUEST were compared and found in good agreement with standard methods. A reduction of scan time from 58min to 16min has been obtained using PRO-QUEST for measurement in both healthy and infarcted rat after 24 hours and revealed that imaging specificity to ischemic acidification was substantially increased relative to standard APT-weighted imaging. The second part of this thesis describes the development of CEST contrast agents based on liposome encapsulation. For this work a concise analytical model has been developed for characterizing the liposomal contrast. In addition, combining this analytical model with measurements of the CEST signal enhancement using liposomes as a model membrane system provides a new technique for studying membrane permeability. All theoretical developments are included as part of this second major chapter. The final part of the thesis describes applications of CEST and high-resolution magnetic resonance spectroscopy for studying prion protein misfolding and neurodegeneration in Prion disease. Here alterations in CEST signal are detected before structural changes or any clinical signs of Prion disease, most likely based on changes in exchange rates, which is encouraging for translation of CEST imaging for early detection of neurodegenerative processes. Thus, CEST signal displays different patterns at different stages of the disease indicating the potential of using CEST to separate different groups of Prion-infected mice.

This thesis focuses on the relationship between the exchange rate and its determinants using an endogenous monetary policy rule as represented by the Taylor rule. Compared to the recent literature on out-of-sample exchange rate predictability, I extend the model of Molodtsova and Papell (2009) by including two variables representing wealth effects, as has been suggested in the standard Taylor rule models. Using quarterly data from 1975-2008, I first investigate the econometric properties of the Taylor rule applied to U.K., Australian and Swedish data against the US dollar. Various unit root tests indicate that variables commonly used in such models are likely to be integrated of order one. However, by accounting for structural breaks, I can conclude that all variables are stationary. Parameter estimates suggest wealth effects are strongly related to the nominal exchange rates in these countries, in contrast to the standard monetary variables. Furthermore, I evaluate short-horizon exchange rate predictability with the Taylor rule fundamentals model for the U.S. dollar against the Australian dollar, Swedish Krona and British Pound. Following the recent literature, a robust set of out-of-sample statistics, including the Clark and West statistic, Diebold-Mariano statistics and Theil’s U ratio are used to evaluate the forecast performance. Current results from the Theil’s U ratio and CW statistics shows the Taylor rule incorporating the wealth effect improves the short run exchange rate forecast performance. Finally, we model the exchange rate from 1975 to 2008 as a Smooth Transition Regression (STR) based model in which a series of economically meaningful transition variables drive the movement across exchange rate regimes. The overall findings show strong evidence supporting the nonlinear relationship between the exchange rate and economic variables. Moreover, the STR Taylor rule models of the exchange rate substantially outperform both the random walk model and the linear Taylor rule model in forecasting the exchange rate.

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.
Includes bibliographical references (p. 30-31).
This thesis uses measurements from a deployed wireless ad hoc network to illustrate the effects of link loss rates on routing protocol performance. Measurements of this network show that the radio links between the majority of nodes have substantial loss rates. These loss rates are high enough to decrease forwarding performance, but not high enough to prevent existing ad hoc routing protocols from using the links. Link-level retransmission can mask high loss rates, at the cost of substantial decreases in throughput. Simulations, driven by the observed loss rates, show that the shortest paths chosen by existing routing protocols tend to find routes with much less capacity than is available along the best route.
by Daniel Aguayo.
M.Eng.

This thesis sets out to investigate and resolve a number of technical issues relating to the residual shear strength of clay soils. For this research the principal objectives concerned strain rate effects using the Bromhead Ring Shear and associated other factors their effects on residual shear strength, replication of the stress path and the homogeneity of clay. The principal areas of investigation are concerned with effects of varying rates of strain on residual shear strength, influence of "stress path" in determining residual shear strength and innate variability of residual strength in natural strata. Finally the principal conclusions were that the Ring Shear was excellent for British Landslides but at high strain rates there were problems with pore water movement and extrusion which are artefacts of the design. Stepless application of normal stress reduces these effects as it removes extreme stress changes. Clay strata are non homogeneous hence the requirement for continuous characterization tests.

Background The canine cardiac system has been the model against which many Class III cardiac devices are validated. Thus, it is expected that the canine heart has very similar electrical model to that found in humans. In 1999, the absence of Heart Rate Turbulence (HRT) after a single Pre-Ventricular Contraction (PVC) was linked to high-risk patient after acute myocardial infarction. Studies of HRT were performed on high-risk patients with Holter-Monitors as were most subsequent HRT studies. If HRT could potentially be used as a risk factor of heart disease, it is interesting to study whether HRT is present following a PVC in otherwise healthy canines. Methods For multiple months, five non-medicated, healthy canines were chronically monitored from between 1 and 8 sessions each. At each session, the canines were ventricularly paced to induce PVCs. Electrical signals, as seen through both a right-ventricular lead and Electrocardiogram (ECG) signals, were captured and analyzed to determine whether the canines displayed HRT following each induced PVC. As a contrasting data set, for the majority of the canines, data was also collected once the canines were sedated. Results HRT was noted in all non-medicated and healthy canines. Of the two factors of HRT (slope and onset), TS was the most prominent indicator of HRT. In each canine, the slope was far greater than the 2.5 ms per RR interval threshold varying from 9.8 to 68.8 ms per RR interval. The onset was marked as HRT (onset less than 0%) in 22 of the 26 session. Additional data was analyzed for healthy yet medicated canines showed that sedation affected HRT, but that HRT was generally noted. Conclusion The canine model displayed a similar HRT characteristic as humans during normal and parasympathetic inhibited states. The presence of HRT in canines is most reliable when using TS. Further study in this area with naturally occurring PVCs would be of interest.

This thesis focuses on development of spline-based hazard estimation models for cure rate data. Such data can be found in survival studies with long term survivors. Consequently, the population consists of the susceptible and non-susceptible sub-populations with the latter termed as "cured". The modeling of both the cure probability and the hazard function of the susceptible sub-population is of practical interest. Here we propose two smoothing-splines based models falling respectively into the popular classes of two component mixture cure rate models and promotion time cure rate models. Under the framework of two component mixture cure rate model, Wang, Du and Liang (2012) have developed a nonparametric model where the covariate effects on both the cure probability and the hazard component are estimated by smoothing splines. Our first development falls under the same framework but estimates the hazard component based on the accelerated failure time model, instead of the proportional hazards model in Wang, Du and Liang (2012). Our new model has better interpretation in practice. The promotion time cure rate model, motivated from a simplified biological interpretation of cancer metastasis, was first proposed only a few decades ago. Nonetheless, it has quickly become a competitor to the mixture models. Our second development aims to provide a nonparametric alternative to the existing parametric or semiparametric promotion time models.
Ph. D.

The objective of this research is the development of a new constitutive model to describe the behavior of cohesive soils under time dependent loading. In the work presented here, the modified SIMPLE DSS model is expanded to account for the effects of strain rate on clays in simple shear conditions. The response of clay soils is highly dependent on the rate of strain for both effective stress path and stress-strain behavior. The undrained shear strength is strongly influenced by strain rate both in monotonic and cyclic simple shear tests. Nevertheless, the few available experimental results cover a very limited range of loading conditions and rates. The existing literature established that the soil response display a unique relationship between shear strength and log scale of strain rate. To include the effects of strain rate, the modified simple effective stress model starts with two assumptions: (1) a specific shear strength corresponds to a specific strain rate in a unique relation; and (2) the effect of strain rate does not change the failure envelope. The proposed model is developed from the original SIMPLE DSS model, based on an effective stress formulation in a reduced stress space, and utilizing concepts related to the framework of bounding surface plasticity. The proposed model evaluationwas carried out comparing model simulations with results of simple shear tests on Boston Blue Clay and San Francisco Young Bay Mud. The model capability is useful especially in strain rate dependent responses for both monotonic and cyclic behavior, including irregular loading and step-changed condition. It was found that undrained shear strength in simple shear is directly related to strain rate effects and the responses in cyclic test show the more rate dependent behavior than those in monotonic test. The proposed model is able to predict the increase in undrained shear strength for higher strain rate.

This study investigated the effects of a precision teaching package on response rates of children with autism. Prior to both experiments a preference assessment was conducted to identify high preference activities for each participant. Experiment 1 investigated whether response rates would shift as a function of rate-contingent consequences during an academic task. Different activities were associated with different rates of responding. The experimental package of 1 minute timings, rate contingent consequences, and charting was successful in increasing the rates of responding when the most highly preferred activity was associated with high rates of responding. When the contingencies were switched and the most highly preferred activity was contingent on lower rates of responding, the participant's responding did not decrease. Experiment 2 was an attempt to replicate the results of Experiment 1 using a multiple baseline across tasks. The experimental package was not successful in increasing the rate of responding.

Problem: The creation of the European Union gave people the right of free movement between the membership countries. In theory, the creation of a single market should create many additional employment and earning opportunities for the workers in the member states of the EU (Bauer & Zammermann, 1999 cited at Borjas, 2010). Some natives believe that an increase in immigration will post a threat to them. They believe that their wages will go down and jobs will be taken from them. Is this true or is it just a sign of xenophobia? Purpose of the Research: The purpose of this study was to replicate successfully the study: “Examining the Relationship between Immigration and Unemployment Using National Insurance Number Registration Data” by Lucchino, P., Rosazza – Bondibene, C., and Portes, J. from 2012. Then the same research methods were used in Swedish data analysis. Methods: Data on unemployment and immigration was collected from Sweden and the UK and multiple regressions were run using the STATA11 software. Conclusion: The immigration rate had no significant affect on the unemployment rate both in the UK and Sweden. However, adding a one year lagged immigration rate was found to be significant at a 5% significance level in the Swedish analysis, but was insignificant in the UK analysis. The control variables for labor supply proved to be insignificant in the analysis of both countries.

La présente étude porte sur les effets de CO2 sur la pyrolyse de la biomasse et la gazéification de chars dans des conditions de chauffe lente et de chauffe rapide. Dans la première partie de ce travail, nous avons étudié les effets du CO2 sur la réaction de pyrolyse rapide à haute température et évalué ses effets sur la vitesse de pyrolyse, sur le rendement de gaz ainsi que sur les propriétés du char. Nous avons aussi étudié la réaction de gazéification en atmosphère mixte en présence de CO2 et de H2O. Enfin, nous avons imaginé le cas hypothétique d’un gazogène au CO2 pur. Le cas d’une pyro-gazéification sous CO2 pur a été abordé au niveau de la particule de biomasse, expérimentalement et théoriquement par la modélisation numérique avec l’objectif de fournir des temps caractéristiques de pyrolyse et de gazéification, et de comprendre le déroulement de la pyro-gazéification sous CO2. Dans la deuxième partie, nous nous sommes intéressés à la question de la gazéification des chars obtenus par chauffe lente, en présence de CO2 avec deux objectifs principaux : d’une part, de fournir des données de réactivité dans des conditions opératoires de réacteurs de gazéification et d’autre part, de comprendre les mécanismes de réaction de gazéification sous CO2, H2O et leurs mélanges. Nous avons examiné l’influence de la taille des particules sur la vitesse de gazéification sous des atmosphères simples de CO2 et H2O en utilisant une approche basée sur le module de Thiele. Nous avons également étudié les effets de la température et de la taille des particules sur la gazéification du char sous atmosphères mixtes contenant CO2 et H2O à 900°C. Nous avons également abordé la question des atmosphères cycliques en examinant l’effet de la gazéification du char sous CO2 sur sa réactivité à H2O et vice versa. Pour mieux comprendre les mécanismes de gazéification dans des atmosphères simples et mixtes de CO2 et H2O, nous avons suivi l’évolution de la texture, de la structure et de la chimie de surface du char le long de la gazéification sous CO2, H2O et leurs mélanges. Des caractérisations chimiques, texturales et structurales ont été ainsi effectuées sur des particules de char partiellement gazéifiés à 20%, 50% et 70% de conversion sous CO2, H2O et leurs mélanges. Ces caractérisations conduisent à une meilleure compréhension du déroulement de la réaction de gazéification
The present work deals about the effects of CO2 enriched atmospheres on biomass pyrolysis and char gasification reactions in High Heating Rate (HHR) and Low Heating Rate (LHR) conditions, at the biomass particle level. In the first part, we studied the effects of CO2 on the high temperature fast pyrolysis reaction and evaluate its effects on the pyrolysis rate, on the gas yield as well as on the char properties including chemical composition, texture and reactivity at 850°C. We focused also on the effects of CO2 on the HHR-char gasification reaction when injected as a co-reactant with steam. We studied the mixed atmosphere gasification reaction in CO2 and H2O for different atmosphere compositions. Finally, we imagined a hypothetical case of a pure CO2 operating gasifier. The case of a pure CO2 pyrogasification process was tackled experimentally and theoretically by numerical modelling with aim to provide pyrolysis and gasification characteristic reaction times, and to understand the unfolding of the global CO2 pyro-gasification reaction. In the second part, we were interested on the issue of LHR-char gasification in the presence of CO2 with two principal objectives: on one hand, providing reactivity data for practical gasification operations and on the other hand, understanding the gasification reaction mechanisms (in CO2, H2O and their mixtures) at the level of the char basic structural units (BSU). We examined the influence of particle size on the single atmosphere gasification in CO2 and H2O using the Thiele modulus approach. We also studied the effects of temperature and particle size on the char gasification in mixed atmosphere of CO2 and steam at 900°C. We also had a focus on the issue of cyclic atmosphere gasification and studied the effects of a prior CO2 gasification on the char reactivity towards H2O and vice versa. To further understand the char gasification mechanisms in single and mixed atmospheres of CO2 and H2O, we opted to monitor the evolution of the chemical, structural and textural char properties along the gasification in CO2, H2O and their mixtures. Deep char characterization were performed on small LHR-char particles partially gasified at 20%, 50% and 70% of conversion in CO2, H2O and their mixtures. These characterisations are of high interest as they shed light on the unfolding of the gasification reaction in CO2, H2O and their mixtures

The deterioration of freshly harvested horticultural crops can be minimised by precooling prior to storage. This technique of quickly cooling the produce does not only increases the shelf life, but it also reduces the size of the refrigeration system needed for storage facility. Vacuum cooling is an effective method of precooling leafy vegetables, but has a major drawback of requiring substantial initial capital investment. Thus, vacuum coolers are generally limited to large-scale or co-op operations where the initial investment can be spread across a large quantity of produce.
The conventional philosophy behind precooling design is to establish systems to cool produce as quickly as possible; this concept is more so with vacuum coolers. By changing certain design criteria of a vacuum cooler, it may be possible to reduce the capital cost of vacuum coolers by reducing the rate of vacuum. Though the time to cool the produce may be increased, the reduction in the size of the vacuum pump and the refrigeration system, and hence the capital cost of the cooler, may be beneficial to small-scale producers who can not justify the large expenses incurred when purchasing a conventional system.
Experiments were performed on a modified vacuum cooler in which the rate of vacuum could be controlled. The cooling characteristics, including the temperature distribution and mass loss, and the lettuce quality were determined for different rates of vacuum. A relationship between the speed of the vacuum and the peak product refrigeration load was developed and tested with experimental data. The results suggest that slower vacuum coolers can be successfully designed and built for small-scale operations.

This study focuses on the effects of nominal shocks on the real exchange rate. The model used to determine the effects of a monetary expansion on the real exchange rate assumes instantaneously clearing asset markets and sticky goods prices. A monetary expansion causes the nominal exchange rate to initially overshoot its long run equilibrium value followed by a series of appreciations. The real exchange rate depreciates sharply and then appreciates until its initial value is restored.
A simple monetary model, a sticky price monetary model and a random walk model are empirically tested with Canadian/U.S. data over the 1972-1989 time period. Both monetary models were rejected and the random walk model represented the best fit to the data. This evidence supports the hypothesis that the Canadian/U.S. nominal exchange rate follows a random walk process.
An empirical examination of the Canadian real exchange rate over the 1970-1989 period confirms the hypothesis that since the advent of the floating exchange rate period, the Canadian real exchange rate movements have been much larger than most economists predicted.

Thesis (M.S. in Information Technology Management) Naval Postgraduate School, Sept. 2000.
"September 2000." Thesis advisor(s): Darken, Rudolph P.; Brady, Terrance C. Includes bibliographical references (p. 77-78). Also available online.

Thesis (B.Sc)--University of Hong Kong, 2002.
"A dissertation submitted in partial fulfilment of the requirements for the Bachelor of Science (Speech and Hearing Sciences), The University of Hong Kong, 10th May, 2002." Also available in print.

Thesis (Ph. D.) -- University of Maryland, College Park, 2005.
Thesis research directed by: Chemical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

This research investigates the effect that combat exposure has on the divorce rate for military personnel. The thesis uses demographic data from the Defense Manpower Data Center (DMDC) coupled with responses from the post-deployment health assessment (PDHA). The sample contains enlisted personnel from all four services who were married and deployed between 2001 and 2007. The probability of divorce after deployment was predicted using a probit model. Combat exposure is divided into two distinct categories, casualty experience and weapon usage. Casualty experience and weapon usage were used to create interaction terms with occupational specialties (combat arms, medical service, combat service, service support) and gender. Results indicate that in most cases, combat exposure will increase the likelihood of divorce. Additionally, a casualty experience tends to have a greater impact on divorce than does weapon usage. Specifically, weapon usage was found to increase the likelihood of divorce for personnel in the medical service (Navy) and service support (Army). A casualty experience increased the likelihood of divorce for personnel in combat arms (Marines, Army) and service support (Marines). Aside from combat exposure, the results indicate that divorce rates vary across occupational specialties and the likelihood of divorce is substantially higher for women.

Thesis (Ph. D.)--West Virginia University, 2008.
Title from document title page. Document formatted into pages; contains iv, 75 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 37-42).

Thesis (Ph. D.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains x, 103 p. : ill. Includes abstract. Includes bibliographical references (p. 60-65).

Die lateinamerikanischen Währungskrisen lenkten erst kürzlich wieder das Augenmerk auf die Gefahren wechselkursbasierter Stabilisierungen (WKBS). Dies sind Inflationsstabilisierungsprogramme, die den nominalen Wechselkurs als vorrangiges geldpolitisches Instrument einsetzen. Die vorliegende Dissertation dokumentiert die Wirkung der Stabilisierungen und präsentiert Erklärungsmodelle für deren stilisierte Fakten. Das erste Kapitel untersucht in Burns-Mitchell-Diagrammen typische reale und monetäre Effekte von 13 Stabilisierungsepisoden. Der anfängliche Anstieg des Konsums und des BIPs, die reale Aufwertung und die Verschlechterung der Leistungsbilanz sind dabei die auffälligsten stilisierten Fakten. Auf die Expansion folgt eine wirtschaftliche Abschwächung, d. h. niedrigeres oder Nullwachstum, falls die Stabilisierung noch andauert, und negative Wachstumsraten, falls das Programm bereits aufgegeben wurde. Die Kapitalimporte folgen einem ähnlichen Zyklus: Dem Anstieg zu Beginn der Stabilisierung folgt drei bis sechs Jahre später eine drastische Umkehr, die häufig mit dem Zusammenbruch des Programms einhergeht. Die Kurzlebigkeit von WKBS ist ein weiterer stilisierter Fakt: 70 % der betrachteten Stabilisierungen scheiterten innerhalb von 10 Jahren. Die anfängliche reale Aufwertung während WKBS wird meist als Anstieg des relativen Preises nicht-handelbarer Güter modelliert; empirische Ergebnisse hingegen unterstreichen die Bedeutung der internationalen Preisunterschiede handelbarer Güter. Kapitel 2 untersucht diese Ursachen durch die Anwendung von Engels Methode der Varianzzerlegung auf den realen Wechselkurs zwischen Brasilien und den USA. Die Ergebnisse bestätigen dabei sowohl die Modelle als auch den empirischen Befund: Bei Betrachtung der gesamten Stichprobe (von Januar 1981 bis Mai 2001) bestimmen Veränderungen der Preise handelbarer Güter und des nominalen Wechselkurses nahezu die gesamten Bewegungen des realen Wechselkurses. Während Perioden fester Wechselkurse hingegen sind die Preise nicht-handelbarer Güter von ähnlicher Bedeutung. Aufgrund dieses Ergebnisses wird in den in Kapitel 3 und 4 präsentierten Modellen der reale Wechselkurs in Abhängigkeit des relativen Preises nicht-handelbarer Güter dargestellt. Diese Modelle bilden kleine, offene Volkswirtschaften ab, die von nutzenmaximierenden repräsentativen Agenten mit perfekter Voraussicht bevölkert sind. Monetäre Größen sind aufgrund von cash-in-advance- Beschränkungen von Bedeutung. Weitere wichtige Modellelemente sind die Existenz von Marktimperfektionen (Preisstarrheiten und unvollständige Kapitalmobilität) sowie die mangelnde Glaubwürdigkeit der Stabilisierung. In Kapitel 3 ist diese durch die Antizipation einer Währungskrise à la Krugman (1979) begründet. Die reale Aufwertung kann dann mit vorausblickender Preissetzung der monopolistischen Produzenten nicht-handelbarer Güter erklärt werden: Aufgrund von Preisstarrheiten erhöhen diese ihre Preise in Erwartung der Währungsabwertung. Da die Preise handelbarer Güter durch das Gesetz des einheitlichen Preises bestimmt werden, folgt daraus ein Anstieg des relativen Preises nicht-handelbarer Güter und eine reale Aufwertung. Zudem wird aufgrund intertemporaler Konsumsubstitution der anfängliche Konsumboom reproduziert. Ökonometrische Evidenz bestätigt den Preissetzungsmechanismus: KQ-Schätzungen mit monatlichen mexikanischen Daten zeigen für Perioden fester Wechselkurse einen signifikanten positiven Zusammenhang zwischen dem relativen Preis nicht-handelbarer Güter und dem mexikanisch-US-amerikanischen Zinsdifferential als Approximation der Abwertungserwartung. Während das Ende der Stabilisierung in obigen Modell durch eine fundamentale Inkonsistenz von Wechselkursziel und Staatsausgaben bedingt ist, zeigt Kapitel 4, daß der Zusammenbruch auch aus sich-selbst-erfüllenden Erwartungen resultieren kann. Ein wesentliches Element ist dabei die Begrenzung der internationalen Kapitalmobilität. Diese erlaubt es, sowohl den anfänglichen Konsumboom als auch das Ende der Stabilisierung mit Erwartungen bezüglich der Dauer des Pegs und der nachfolgenden Geldpolitik zu erklären. Zusammenfassend zeigt die Dissertation die Gefahren wechselkursbasierter Stabilisierungen auf: Im Gegensatz zur herkömmlichen Meinung sind sogar relativ erfolgreiche und langlebige WKBS mittelfristig mit einer Kontraktion verbunden; nur wenige Programme erzielen eine nachhaltige Reduktion der Inflation. Die hier präsentierten Modelle zeigen, daß die mangelnde Glaubwürdigkeit der Programme - selbst wenn diese nicht durch Fundamentaldaten gerechtfertigt ist - zu Allokationsverzerrungen führt und den Erfolg der Stabilisierungsmaßnahmen gefährdet.
Exchange rate crises in Latin America recently put a spotlight on the perils of Exchange Rate-Based Stabilizations (ERBS), which use the nominal exchange rate as the main policy target for stabilizing inflation. This dissertation documents the effects of ERBS in high inflation economies and develops models to explain these stylized facts. The first chapter assesses the empirical regularities associated with ERBS. Based on a sample of 13 stabilization episodes, typical real and monetary dynamics are investigated in Burns-Mitchell diagrams. Stylized facts of ERBS are the initial increases in consumption and GDP, the real appreciation and the current account deterioration. Moreover, consumption and output are found to follow a boom-slowdown cycle, where slowdown means reduced or zero growth if the ERBS is still in effect, and negative growth rates for failed ERBS. Capital inflows follow a similar boom-bust cycle: Their increase at the stabilization''s inception is followed by a sharp reversal three to six years later, very often coinciding with the program''s collapse. This transitoriness of ERBS constitutes an additional stylized fact: 70 % of the programs under consideration failed within 10 years after their implementation. The origin of the initial real exchange rate appreciation during ERBS has been subject to controversy: Most models assume an increase in the relative price of non-traded goods. Empirical findings, in contrast, emphasize the contribution of traded goods'' cross-country prices. Chapter 2 sheds light on this issue by applying Engel''s (1995) method of variance decomposition on Brazilian-US real exchange rate fluctuations. The results confirm both the models and the empirical findings: When considering the full sample (from January 1981 to May 2001), changes in traded goods'' prices and the nominal exchange rate account for almost all of the observed real exchange rate movements. During periods of pegged exchange rates, however, non-traded goods'' prices are equally important for real exchange rate fluctuations. Thus, changes in relative non-tradables'' prices are incorporated as a determinant of real exchange rate fluctuations during ERBS in the theoretical frameworks presented in chapters 3 and 4. These explain the stylized facts in models of small, open economies populated by a utility-maximizing representative agent endowed with perfect foresight. Money matters due to cash-in-advance constraints. Further important features are the existence of market imperfections - price stickiness or imperfect capital mobility - and the stabilization''s deficient credibility. In chapter 3, the latter is due to the anticipation of a Krugman (1979)-style currency crisis. The initial real appreciation during ERBS can then be explained with forward-looking price setting by monopolistic non-tradable goods'' producers: These are subject to staggered price setting and incorporate the peg''s anticipated termination - i.e. higher future devaluation rates - by increasing their current prices. As tradables'' prices are determined by the law of one price, this implies higher relative non-tradables'' prices and thus a real exchange rate appreciation. Furthermore, due to intertemporal consumption substitution, the observed initial consumption boom is reproduced. Econometric evidence confirms the proposed price setting mechanism: Using the Mexican-US interest rate differential as an indicator for devaluation rate expectations, OLS regressions with monthly Mexican data find a significant positive relation between relative non-tradables'' prices and the interest rate spread during periods of pegged exchange rates. In the previous model, the stabilization effort collapses due to a fundamental inconsistency between the exchange rate target and government finance. Chapter 4 shows that the collapse can also result from self-fulfilling expectations. This is achieved by introducing partial international capital mobility. Given this constraint, both the initial consumption boom and the stabilization''s collapse can be shown to result from expectations about the duration of the peg and post-stabilization monetary policy. In conclusion, the dissertation points to the perils of ERBS in high inflation countries: Contrary to what is commonly believed, even relatively successful and long-lived exchange rate pegs are associated with a late slowdown; only very few ERBS are successful at stabilizing inflation rates in the medium and long run. The models show that stabilizations'' deficient credibility - regardless if justified by fundamentals or not - engenders real dynamics which distort economic activity and jeopardize the stabilization effort: The miracle of ERBS turns into a mirage.

An investigation of the factors affecting the biological effectiveness of neutron beams suitable for Boron Neutron Capture Therapy (BNCT) has been carried out. The primary experimental work described in this thesis concerns the degree of interaction, if any, between biological damage caused by low LET radiation and that caused by high LET radiation. The second area investigated concerns the biological impact of delivering a BNCT irradiation at differing dose rates. In mixed photon alpha particle irradiations, no synergistic effect was observed above the response from the separate components. Maximum alpha particle doses delivered were 2.54 Gy. In mixed X-ray and alpha particle exposures, no synergy effect was seen with 2.54 Gy of alpha particles delivered to the cells. At the 3.18Gy alpha particle dose level significantly lower cell survival was observed than would be predicted from survival in single fields. Dose rate experiments were carried out in the Massachusetts Institute of Technology (MIT) Fission Converter neutron Beam (FCB). Cells loaded with boric acid were exposed at dose rates differing by a factor of approximately 15. A dose rate effect was observed at both of the irradiation depths used, although this was only clearly significant at 50 mm treatment depth.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 29-30).
by Amanda Olender.
S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.
Includes bibliographical references (p. 60-62).
by Jean Chrstine Krause.
M.S.