Дисертації з теми "Operating properties"

When studying detection systems, parameters associated with the Receiver Operating Characteristic (ROC) curve are often estimated to assess system performance. In some applied settings it is often not possible to test the detection system with large numbers of stimuli. The resulting small sample statistics many have undesirable properties. The characteristics of these small sample ROC estimators were examined in a Monte Carlo simulation. Three popular ROC parameters were chosen for study. One of the parameters was a single parameter index of system performance, Area under the ROC curve. The other parameters, ROC intercept and slope, were considered as a pair. ROC intercept and slope were varied along with sample size and points on the certainty rating scale to form a four way factorial design. Several types of estimators were examined. For the parameter, Area under the curve, Maximum Likelihood (ML), three types of Least Squares (LS), and Distribution Free (DF) estimators were considered. Except for the DF estimator, the same estimators were considered for the parameters, intercept and slope. These estimators were compared with respect to three characteristics: bias, efficiency, and consistency. For Area under the curve, the ML estimator was the least biased. The DF estimator was the most efficient, and all the estimators except the DF estimator appeared to be consistent. For intercept and slope the LS estimator that minimized vertical error of the points from the ROC curve (line) was the least biased for both estimators. This LS estimator was also the most efficient. This estimator along with the ML estimator also appeared to be the most consistent. The other two estimators had no significant trend toward consistency. These results along with other findings, illustrate that different estimators may be "best" for different sample sizes and for different parameters. Therefore, researchers should carefully consider the characteristics of ROC estimators before using them as indices of system performance.

The influences of operating pressure, temperature and gas velocity on electrostatics in a fluidized bed of glass beads and different grades of polyethylene resin were investigated in a fluidization column of 150 mm inner diameter and 2.0 m height. Eight collision probes at different levels and radial positions measured the electrostatics in the bed. The electrostatics increased as pressure increased, probably due to an increase in bubble rise velocity, frequency and volume fraction. As the pressure increased, particle-particle and particle-wall collisions near the distributor and wall contributed heavily to charge generation. Temperature also played a role. At higher temperatures (up to 90°C), the polarity of net cumulative charge in the bed reversed. As the superficial gas velocity increased, the electrostatics increased. However, at higher gas velocities, the polarity in the freeboard was opposite to that in the bed, indicating that fines entrained from the column carried charges, resulting in a net charge of opposite polarity to that inside the bed. For Geldart group B particles the degree of electrification in the bed slightly increased with decreasing particle size. Charging for group A particles was significantly greater than for group B particles. For binary mixtures of group A and B particles the electrostatics increased as the proportion of small particles increased. As the relative humidity (RH) of fluidizing air increased, the electrostatics decreased. For the RH range (5-30%) explored, the sensitivity of the charging to RH varied significantly depending on the location of the probes. As the proportion of fine glass beads (<30 µm) increased to 2.0 wt% in a fluidized bed of large glass beads (574 µm), the electrostatics in the bed decreased, likely because the fines acted as spacers between larger particles. The electrostatics decreased as the proportion of an antistatic agent (Larostat) increased from 0.0 to 0.5 wt%, because Larostat tends to adsorb moisture and attach to the surface of the glass beads, consequently enhancing their surface conductivity. However, the degree of electrification increased when the wt% of Larostat exceeded 1.0%, likely due to the tendency of Larostat particles to adsorb water and to agglomerate.

Receiver operating characteristic (ROC) curves are widely used in medical decision making. It was recognized in the last decade that only a specific region of the ROC curve is of clinical interest, which can be summarized by the partial area under the ROC curve (partial AUC). Early statistical methods for evaluating partial AUC assume that the data are from a specified underlying distribution. Nonparametric estimators of the partial AUC emerged recently, but there are theoretical issues to be addressed. In this dissertation, we propose two new nonparametric statistics, partially integrated ROC and partially integrated weighted ROC, for estimating partial AUC. We show that our partially integrated ROC statistic is a consistent estimator of the partial AUC, and derive its asymptotic distribution which is distribution free under the null hypothesis. In the partially integrated ROC statistic, when the ROC curve crosses the Uniform distribution function (CDF) and if the partial area evaluated contains the crossing point, or when there are multiple crossing, the partially integrated ROC statistic might not perform well. To address this issue, we propose the partially integrated weighted ROC statistic. This statistic evaluates the partially weighted AUC, where larger weight is given when the ROC curve is above the Uniform CDF and smaller weight is given when the ROC curve is below the Uniform CDF. We show that our partially integrated weighted ROC statistic is a consistent estimator of the partially weighted AUC. We derive its asymptotic distribution which is distribution free under the null hypothesis. We propose to apply our two nonparametric statistics to functional category analysis in microarray experiments. We define the functional category analysis to be the statistical identification of over-represented functional gene categories in a microarray experiment based on differential gene expression. We compare our statistics with existing methods for the functional category analysis both via simulation study and application to a real microarray data, and demonstrate that our two statistics are effective for identifying over-represented functional gene categories. We also emphasize the essential role of the empirical distribution function plots and the ROC curves in the functional category analysis.

The effects of superfical gas velocity, pressure, and temperature on entrainment and electrostatic charge with glass beads and polyethylene as bed particles were investigated in a fluidization column of 0.15 m inner diameter and 2.0 m height. Four collision probes at different levels, a freeboard sampler, and a current detection pipe measured the electrostatics in the bed, freeboard, and column exit. The entrainment and electrostatic charge inside the bed and freeboard region increased as the superficial gas velocity or pressure increased. Temperature had negligible effect on the entrainment over the limited range studied. However, electrostatic charges decreased and the charge polarity reversed as the bed temperature increased from 20 to 75 °C. The calculated electrostatic forces resulting from fine-fine and fine-coarse particle interactions are comparable to the gravitational force on fine particles in the fluidized bed. Entrainment empirical correlations developed in this work showed much better performance after the effect of electrostatic forces was taken into account, with the entrainment flux deceasing as electrostatic forces increase. The Choi et al. (1999) entrainment correlation shows better prediction of the entrainment flux in our system after the effect of the electrostatic force is considered. The electrostatic charges in the bed decreased with increasing air relative humidity. The charge density of fines decreased and entrainment increased as the air relative humidity increased. The relative humdity had no effect on the charge density or entrainment of polyethylene particles, which can also probably be attributed to the hydrophobic nature of polyethylene. The magnitude of electrostatic charges generated inside the fluidized bed increased slightly as the size of the coarse particles decreased. The entrainment decreased as the coarse particle size decreased. The electrostatic charges increased and entrainment decreased as the coarse particle density increased. The magnitude of electrostatic charges generated inside the fluidized bed increased and entrainment decreased as the fine particle density increased. The electrostatic charges and entrainment also increased as the fine concentration increased. The fines concentration had little or no effect on fines charge densities. Bipolar charging was observed in all experiments with fine particles charged positively, whereas large particles were charged negatively.

Expanded bed adsorption (EBA) combines clarification, concentration and purification into a single processing step reducing processing time and increasing productivity. Much work has been conducted on model proteins but little attention has been paid to the emerging issues of tailoring the operational variables of matrix size, operating flowrate and ligand type so as to maximise process outputs. The aims of this study were to investigate the effects of matrix properties and operating parameters on breakthrough behaviour and productivity. Second generation matrices designed to operate at high flowrates were also examined. Operating at low velocities, beds formed from smaller particles had a shallower breakthrough than beds formed from large particles but the latter were more productive. At the higher velocities typically utilised in EBA, the behaviour of beds formed from either small or large particles was comparable in terms of breakthrough with the beds made up of small particles being slightly more productive than those containing large particles. A prototype 2nd generation EBA matrix consisting of a multi-modal ligand that could operate at high conductivity levels typical of fermentation broths was also examined. It was found that the productivity could be increased 5-fold as compared with commercially available matrices, with no loss of yield or purity. Conventional breakthrough curve analysis is not applicable in situations of variable particle size and operating velocity. Results using a novel dimensionless group to facilitate comparison between unlike systems is presented. The thesis presents an analysis of the relative productivity of a range of systems and highlights the gains in terms of productivity to be achieved with the development of 2nd generation EBA multi-modal adsorbents. The thesis concludes with an analysis of the commercial and regulatory aspects of EBA.

Thesis (M.S.)--Massachusetts Institute of Technology, Sloan School of Management, 1994, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science & Engineering, 1994.
Includes bibliographical references (p. 177-180).
by Bryan Gary Eagle.
M.S.

The growth in coal consumption worldwide as well as the high oil prices in the recent past has led to the current increased interest in the application of coal gasification technologies. The Sasoi-Lurgi Fixed Bed Dry Bottom (S-L FBDB) gasification technology is one such technology that has the biggest market share in the world and maintains its competitive edge particularly with regard to gasification of low grade and low rank coal. To ensure sustained competitive advantage through technology development, it is important to understand the fundamentals of the process as well as the behaviour of coals of different rank in the reactor. The main objective of this study was to investigate the fuel bed behaviour as well as coal properties transformational behaviour in a S-L FBDB gasifier that gasifies North Dakota (NO) lignite. It was hypothesised in this study that using the FBDB gasifier sampling methodologies available in the literature, with some modifications to suit the context of this study, can help to explain the fuel bed behaviour as well as the coal properties transformational behaviour during gasification of lignite in the S-L FBDB process. To test the hypothesis and to achieve the objectives of the study, two MK IV S-L FBDB gasifiers (i.e. "Albert" and "Bernice") operating at the Great Plains Synfuels Plant of the Dakota Gasification Company (DGC) in the United States of America (USA) were sampled using the Turn-Out method developed by Bunt (2006) and modified in this study to suit lignite. The samples were characterised for their chemical, physical, petrographic and mineralogical properties which were then interpreted in terms of their transformation in the various reaction zones of the gasifiers. The different reaction zones In the "Bernice" and "Albert" gasifiers were successfully identified using chemical analyses (i.e. proximate and ultimate analyses as well as Fischer tar yields). Identification of reaction zones in the S-L FBDB gasifiers operating on lignite is a first in the history of the process. In comparing Secunda GG41 gasifier operating on bituminous coal with the DGC "Bernice" and "Albert" gasifiers operating on lignite, the reaction zones were found to be very different due to, amongst other things, the different operating philosophy, stability and coal rank. About two thirds of the reactor volume, in the case of DGC "Bernice" and "Albert" gasifiers, was found to be drying and devolatilizing the coal, leaving only about a third of the reactor volume for gasification and combustion. Nonetheless, due to the high reactivity of the lignite, more than 98% of the char/fixed carbon was consumed within a third of the re•maining gasifier volume and this is a significant new finding. The fact that the entire reactor volume was utilized for drying, devolatilization, gasification and combustion with carbon conversion of >98%, makes the S-L FBDB gasifier very suitable for lignite gasification. In line with the Secunda GG41 gasifier, clear overlaps between the reaction zones were observed in the "Bernice" and "Albert" gasifiers. This therefore confirms the gradual transition from one reaction zone to another as reported in the literature. The volatile matter in the ash from both the "Bernice" and "Albert" gasifiers was about 10% (dry basis). This volatile matter is most probably inorganic in nature given the presence, in the samples obtained from the ash bed, of calcite (CaCO3), gypsum (CaSO4.2H2O) and melanterite (FeSO4.7H2O) which are expected to decompose during volatile matter determination at 900 °C. Using only •the volatile matter, as determined by proximate analyses, to determine the pyrolysis zone position in the reactor will in the case of DGC gasifiers therefore be delusive. As expected, most of the H, N and S were released in the pyrolysis zone of both the "Albert" and "Bernice" gasifiers. A significant increase in the reactivity of the chars from both the "Bernice" and "Albert" gasifiers was observed in the gasification zones. It is due to this increased reactivity that the char/carbon in these gasifiers were consumed ,within only a third of the gasifier volume. The increased reactivity is most probably due to the catalytic reactions effected by the organically bound alkali and alkaline earth metals, particularly calcium as the coal was found to be rich in this element. Thermal fragmentation was found to be severe with the NO lignite tested. The feed coal was found to decrease in size from 3% in the feed to 90% of <6.3 mm fine particles in the drying and pyrolysis zones of both the "Albert" and "Bernice" gasifiers. This is also a new significant finding in the history of the SL FBDB gasification process which is traditionally known to operate on coarse coal. Mineral matter in the feed coal to the "Bernice" gasifier was mainly dominated by the organically bound calcium. The crystalline phases in the gasification and combustion zones were dominated by gehlenite and bredigite which may have formed from the transformation, at higher temperatures, of the organically bound Ca and Mg to GaO and MgO and subsequent interaction with the reactive silica and transformation products of the clays. In the "Bernice" gasifier, a significant amount of calcite was found to be forming in the beginning of the gasification zone, towards the end of pyrolysis, and decomposing slightly in the hotter combustion zone. It is suggested that the calcite was formed from the reaction of GaO (formed from the transformation of the organically bound Ca) with the CO2 from the raw gas in the gasifier. As expected, the glass phase was found to be the major part of the ash minerals in the gasification and combustion zones of the "Bernice" gasifier. This phase was composed mainly of the Ca, Mg, Na aluminosilicates with some Fe. This composition is common to the slag formed from the Fort Union lignite. There was therefore a significant amount of melting in the hotter reaction zones (i.e. gasification and combustion zones) of these gasifiers. The organically bound Ca, Mg and Na seemed to have played a significant role in the formation of this glass phase in the gasifiers. Oxygen scavenging by the ash minerals in the combustion and gasification zones of both "Albert" and "Bernice" gasifiers was observed. In the "Bernice" gasifier, it was estimated at about 16% of the oxygen fed as agent to the gasifier. From an economic viewpoint this is significant given the high cost of producing the 99% pure oxygen for gasification. The AFT in the feed coal to both "Albert" and "Bernice" gasifiers was found to be higher as compared to the ash samples from the ash bed. This may have implications on the design and operating philosophy since the gasifiers are normally designed to operate between the initial deformation and flow temperatures of the ASTM ash, which is not the same as the ash formed in the gasifier. This is also another new significant finding. The high concentration of the fluxing elements (i.e. Ca, Mg, Na and Fe) in the dominating glass phase determined in the gasification and combustion zones of these gasifiers was most probably the reason behind this phenomenon. The char particles formed in both "Bernice" and "Albert" gasifiers were, as determined petrographically, mainly dominated by the dense chars which were highly reactive. An induced "coalification" process was observed in both "Bernice" and "Albert" gasifiers with the macerals/char particles being transformed from lignite to bituminous and anthracitic coal particles. In the "Bernice" gasifier, the average temperature of solids in the combustion zone was found to be about 700 °C, peaking at 11 00 °C in the combustion zone. The average temperature is in line with the predicted figures (i.e. 741 °C for the predicted temperature at which the water gas shift reaction was forced into equilibrium). Overall, there was an excellent match in the trends of the chemical, physical, petrographic and mineralogical properties of the samples obtained at different levels of the "Albert" and "Bernice" gasifiers. This may therefore confirm plug flow during the Turn-Out sampling methodology and hence supports the hypothesis of this study. It is hoped that the results obtained in this study will not only benefit Sasol or Sasoi-Lurgi Technology Company with regard. to the understanding of the reactors and improvement in modelling and design, but will also assist DGC in further optimising their lignite gasification process.
Thesis (PhD (MIng (Chemical Engineering))--North-West University, Potchefstroom Campus, 2009

Le développement de solutions de stockage de l'énergie est un défi majeur pour permettre la transition énergétique d'un mix énergétique fortement carboné vers une part plus importante des énergies renouvelables. La nécessité de stocker de l'énergie vient de la dissociation, spatiale et temporelle, entre la source et la demande d'énergie. Stocker de l'énergie répond à deux besoins principaux : disposer d'énergie à l'endroit et au moment où on en a besoin. La consommation de chaleur à basse température (pour le chauffage des logements et des bureaux) représente une part importante de la consommation totale d'énergie (environ 35 % en France en 2010). Le développement de solutions de stockage de chaleur est donc d'une grande importance, d'autant plus avec la montée en puissance des énergies renouvelables. Parmi les technologies de stockage envisageables, le stockage par adsorption semble être le meilleur compromis en termes de densité de stockage et de maintient des performances sur plusieurs cycles de charge-décharge. Cette thèse se focalise donc sur le stockage de chaleur par adsorption, et traite de l'amélioration des performances du stockage et de l'intégration du système au bâtiment. L'approche développée pour répondre à ces questions est numérique. L'influence des propriétés thermophysiques de l'adsorbant et du fluide sur la densité de puissance d'une part, mais aussi sur la densité de stockage et l'autonomie du système, est étudiée. L'analyse des résultats permet de sélectionner les propriétés des matériaux les plus influentes et de mieux comprendre les transferts de chaleur et de masse au sein du réacteur. L'influence des conditions opératoires est aussi mise en avant. Enfin, il est montré que la capacité de stockage est linéairement dépendante du volume de matériau, tandis que la puissance dépend de la surface de section et que l'autonomie dépend de la longueur du lit d'adsorbant. Par ailleurs, le rapport entre l'énergie absorbée (charge) et relâchée (décharge) est d'environ 70 %. Mais pendant la phase de charge, environ 60 % de la chaleur entrant dans le réacteur n'est pas absorbée et est directement relâchée à la sortie. La conversion globale entre l'énergie récupérable et l'énergie fournie n'est donc que de 25 %. Cela montre qu'un système de stockage de chaleur par adsorption ne peut pas être pensé comme un système autonome mais doit être intégré aux autres systèmes de chauffage du bâtiment et aux lois de commande qui les régissent. Utiliser la ressource solaire pour le préchauffage du réacteur est une idée intéressante car elle améliore l’efficacité de la charge et permet une réutilisation de la part récupérée en sortie pour le chauffage direct du bâtiment. La part stockée sous forme sensible peut être récupérée plusieurs heures plus tard. Le système est ainsi transformé en un stockage combiné sensible/adsorption, avec une solution pour du stockage à long terme et pour du stockage à court terme
The development of energy storage solutions is a key challenge to enable the energy transition from fossil resources to renewable energies. The need to store energy actually comes from a dissociation between energy sources and energy demand. Storing energy meets two principal expectations: have energy available where and when it is required. Low temperature heat, for dwellings and offices heating, represents a high share of overall energy consumption (i.e. about 35 %). The development of heat storage solutions is then of great importance for energy management, especially in the context of the growing part of renewable energies. Adsorption heat storage appears to be the best trade off among available storage technologies in terms of heat storage density and performances over several cycles. Then, this PhD thesis focuses on adsorption heat storage and addresses the enhancement of storage performances and system integration. The approach developed to address these issues is numerical. Then, a model of an adsorption heat storage tank is developed, and validated using experimental data. The influence of material thermophysical properties on output power but also on storage density and system autonomy is investigated. This analysis enables a selection of particularly influencing material properties and a better understanding of heat and mass transfers. The influence of operating conditions is also underlined. It shows the importance of inlet humidity on both storage capacity and outlet power and the great influence of discharge flowrate on outlet power. Finally, it is shown heat storage capacity depends on the storage tank volume, while outlet power depends on cross section area and system autonomy on bed length. Besides, the conversion efficiency from absorbed energy (charge) to released energy (discharge) is 70 %. But during the charging process, about 60 % of incoming heat is not absorbed by the material and directly released. The overall conversion efficiency from energy provided to energy released is as low as 25 %. This demonstrates that an adsorption heat storage system cannot be thought of as a self-standing component but must be integrated into the building systems and control strategy. A clever use of heat losses for heating applications (in winter) or inlet fluid preheating (in summer) enhances global performances. Using available solar heat for system preheating is an interesting option since a part is instantly retrieved at the outlet of the storage tank and can be used for direct heating. Another part is stored as sensible heat and can be retrieved a few hours later. At least, it has the advantage of turning the adsorption storage tank into a combined sensible-adsorption storage tank that offers short-term and long-term storage solutions. Then, it may differ avoidable discharges of the sorption potential and increase the overall autonomy (or coverage fraction), in addition to optimizing chances of partial system recharge

Increasing ecological and economic pressures, as well as increased technical requirements, have given rise to the need for research into alternative wear layers for hydrodynamic plain bearings. Previous investigations have tested and researched the bonded coating GL92. It has been possible to demonstrate that the bonded coating (plastic base) is a viable alternative to a conventional white metal alloy. However, this coating was not able to address all the issues experienced by industrial users, for example the behaviour of the system (changes to operating properties) during penetration of particles, or behaviour in a mixed friction area. The literature has not – or not sufficiently – answered the questions relating to damage patterns and damage tolerance. Therefore, regardless of the proven benefits, industrial use of this coating is currently not possible or is connected with significant risks. In the study, tests were carried out in the mixed friction area (start-stop testing, emergency testing without oil, insufficient lubrication tests) as well as in the hydrodynamic area. The comparative tests were performed on different wear layer materials. This paper demonstrates and discusses the results for both a conventional white metal alloy bearing and for the bearing with bonded coating (GL92). Depending on the operating point, the bearing systems exhibit significant differences at the maximum bearing load, lubricating film pressure distribution and maximum bearing temperature. The investigation has proven that GL92 is a technically useful alternative to conventional wear layers.

A shape memory alloy (SMA) is an intermetallic compound able to recover, in a continuous and reversible way, a predetermined shape during a thermal cycle while generating mechanical work. In this thesis, its use in developing an actuator for a machining process is investigated. The actuator is to drive the tool cross feed into an aluminium workpiece in a finishing lathe operation. The actuator structure was designed with an output shaft to transfer the movement and force of the SMA wire outside the device. The actuator was fabricated and the experimental setup was assembled which also included a power supply control circuit, displacement sensor, temperature sensor and current sensor for feedback, and data collection and monitoring within software. PID control was implemented within the software that regulated the power supplied to the SMA, thereby providing the position control. This study covers the mechatronics system design and development of the actuator, the experiments carried out to determine performance and the results. Open loop tests were conducted to determine the maximum stroke, the effect of cooling and response to radial forces. These tests revealed the expected non-linearity of the SMA. The actuator achieved the rated maximum stroke of 3-4 percent. The forced cooling test showed a general improvement of approximately 65 percent with fans. The radial force tests showed the value of the maximum stroke remained unaffected by force. The results from the closed loop tests responses with a tuned PID controller produced a stable system for various displacement setpoints. The actuator had a feed rate of 0.25 mm/s and an accuracy of 0.0153mm, which was within the acceptable accuracy for turning operations. The system was deemed accurate for a conventional lathe machine cross feed.

Thesis (M.S.)--West Virginia University, 2005.
Title from document title page. Document formatted into pages; contains vii, 74 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 62).

This thesis compares the numerical performance of digital control laws implemented in the Z operator, z, and the Euler operator, $ epsilon$ = ${z-1 over T}$ where T is the sampling period, and provides some useful guidelines for estimating the conservative wordlength for relatively low order controllers which are implemented using floating point arithmetic. The relative merits of these two discrete-time operators are studied analytically with regard to coefficient representation and roundoff errors, which are two major sources of numerical error. It is shown in this thesis that the $ epsilon$ operator form has superior performance in the coefficient representation to the z operator form for the sampling rates often used in practice. It is also shown that control laws implemented in the $ epsilon$ operator provide superior performance in the introduction of roundoff errors and in the propagation of these errors through subsequent sampling instants than the z operator, at least for high sampling rates. Extensive numerical simulations are also performed to compare the $ epsilon$ and z forms to obtain useful rules of thumb for estimating the wordlength required by a controller based on the sampling rate and the dynamic characteristics of the controller.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center, 2000.
Includes bibliographical references (leaves 95-102).
Survivorship bias influences statistical inference in Finance. Through a series of Monte Carlo simulations in the style of Brown, Goetzmann, Ibbotson, and Ross {1992), we study the sampling distribution of the mean return, standard deviation, beta, Fama & MacBeth {1973) t-statistic, and Jegadeesh & Titman (1993) momentum strategy return in progressively truncated datasets. Survivor-biased datasets have higher mean returns, lower return standard deviations and lower betas than the full sample. Beta has no explanatory power even when the CAPM is true, a finding virtually unaffected by survivorship bias. Returns to a momentum strategy are positive even when stock idiosyncratic returns are serially and cross-sectionally uncorrelated, but survivorship bias overestimates the returns and underestimates the beta of the strategy.
by Jonathan David Taylor.
Ph.D.

In this thesis we obtain several interesting algebraic properties of the operations used in the block cipher IDEA which are important for cryptographic analyzes. We view each of these operations as a function from $mathbb Z_{2}^n times mathbb Z_{2}^n to mathbb Z_{2}^n$. By fixing one of variables $v(z)=mathbf Z$ in $mathbb Z_{2}^n times mathbb Z_{2}^n$, we define functions $mathbf {f}_z$ and $mathbf {g}_z$ from $mathbb Z_{2}^n$ to $mathbb Z_{2}^n$ for the addition $BIGboxplus$ and the multiplication $BIGodot$ operations, respectively. We first show that the nonlinearity of $mathbf {g}_z$ remains the same under some transformations of $z$. We give an upper bound for the nonlinearity of $mathbf {g}_{2^k}$, where $2leq k <
n-1$. We list all linear relations which make the nonlinearity of $mathbf {f}_z$ and $mathbf {g}_z$ zero and furthermore, we present all linear relations for $mathbf {g}_z$ having a high probability. We use these linear relations to derive many more linear relations for 1-round IDEA. We also devise also a new algorithm to find a set of new linear relations for 1-round IDEA based on known linear relations. Moreover, we extend the largest known linear class of weak keys with cardinality $2^{23}$ to two classes with cardinality $2^{24}$ and $2^{27}$. Finally, we obtain several interesting properties of the set $ { ({mathbf X},{mathbf X} BIGoplus {mathbf A}) in mathbb Z_2^n times mathbb Z_2^n ,|, (mathbf {X}BJoin {mathbf Z})BIGoplus( ({mathbf X} BIGoplus {mathbf A} ) BJoin mathbf {Z} ) = {mathbf B} }$ for varying ${mathbf A}, {mathbf B}$ and ${mathbf Z}$ in $mathbb Z_2^n$, where $BJoin in { BIGodot,BIGboxplus }$. By using some of these properties, we present impossible differentials for 1-round IDEA and Pseudo-Hadamard Transform.

Thesis: S.M. in Engineering Systems, Massachusetts Institute of Technology, School of Engineering, Institute for Data, Systems, and Society, 2016.
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 (pages 221-224).
High-Speed Rail (HSR) has been expanding throughout the world, providing various nations with alternative solutions for the infrastructure design of intercity passenger travel. HSR is a capital-intensive infrastructure, in which multiple subsystems are closely integrated. Also, HSR operation lasts for a long period, and its performance indicators are continuously altered by incremental updates. With this background, design and monitoring of lifecycle properties, or "ilities", is an important factor to achieve long-term successful operation. This thesis aims to analyze and evaluate dynamic behaviors of "ilities" and their interactions in HSR operation. After the literature review and the study of industrial trends about HSR "ilities", safety, availability and profitability are chosen as key "ilities" which should be monitored in HSR operation. The Tokaido Shinkansen in Japan, and Amtrak's service in the US Northeast Corridor (NEC) are chosen as cases to study "ilities" trends. In the Tokaido Shinkansen, three "ilities" form a positive feedback loop to make HSR operation successful. The NEC shows high profitability, but it does not perform as well in terms of safety and availability due to several systemic factors. System Dynamics (SD) is applied to visualize interactions of "ilities" and other variables of interest. Qualitative causal loop diagrams (CLD) reveal several feedback loops affecting "ilities". In particular, the integration of train operation and infrastructure / rolling stock management results in the emergence of major feedback loops which cannot easily be captured by other methodologies. Qualitative SD models are converted into quantitative SD models, and numerical simulations are run to further understand the structure of causal loop diagrams. Estimated parameters in the Tokaido and the NEC suggest the different relationships among "ilities" and other variables. Further, sensitivity analyses are conducted to evaluate how different policies affect "ilities" in future HSR operations.
by Tatsuya Doi.
S.M. in Engineering Systems

A special porous coating is applied on the surface of dental implants to improve it`s biocompatibility. During the maintenance the tensions originate in such coatings, which is added to the residual pressure and significantly reduce the strength of the coatings. It is almost impossible to get the numericalled value of these tensions experimentally, so in this article we solve the problem of mathematical model operation of the tension originating in porous coatings in the process of their forming, and in the course of maintenance. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35293

The thesis discusses the operating costs and the possibilities for their optimization. Specifically, it focuses on one of the greatest possible operating costs and it's heating costs. In the first part of the thesis are defined in general expenses, the price and the production, operating costs, optimization of these costs, life cycle of buildings and technological methods to improve the thermal and technical properties of the object. Finally, the theoretical part describes the terms for calculating the energy performance of the building and the payback period, which evaluates the effectiveness of investments. The practical part is assessed according to specific building energy performance, and especially in terms of its demand for heating. The building is designed for six variants of insulation, which is again judged on their energy performance. Subsequently these measures for better thermal insulating properties of the object assessed according to their cost efficiency and return on investment of individual variants.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 60).
An experimental study is performed to understand the sensitivity of ground deformation to subsurface properties and operations of oil and gas fields. Ground deformation, or more severely subsidence, may pose concerns for human settlements situated above the reservoir. This Masters thesis will study a realistic sample problem on its surface deformation sensitivity, in hopes of providing a sound basis for future characterization of subsurface properties and the forecast of surface deformation due to oil and gas production. Iteratively coupled simulations are performed to test how sensitive the surface deformation is to changing subsurface parameters. To test the validity of such coupled simulator, comparison of the displacement results with those of another commercially available software is also carried out. Results show that the change of surface displacement particularly in the vertical direction tends to be within the range of detection of satellites, of which data will serve as the input of future inversions with the Ensemble Kalman Filter (EnKF).
by Pui-Wa Li.
S.M.

A novel design of a moving-coil transducer coupled with a low-hardness elastomer called “the gel surround” is presented in this thesis. This device is termed a “gel-type audio transducer”. The gel-type audio transducer has been developed to overcome the problems that conventional loudspeakers have suffered - that is, the problem with size of the audio device against the quality of sound at low frequency range. Therefore the research work presented herein aims to develop the “gel-type audio transducer” as a next-generation audio transducer for miniaturized woofers. The gel-type audio transducer consists of the magnetic and coil-drive plate assembly, and these parts are coupled by the gel surround. The transducer is driven by the electromagnetic conversion mechanism (a moving-coil transducer) and its output driving force can be greatly enhanced by applying the novel mechanism of the gel surround especially at low frequency range, resulting in the enhanced acoustic efficiency. The transducer can be attached to a stiff and light panel with both the optimized impedance matching and minimised wave collisions. The performance of the gel-type audio transducer is greatly influenced by the mass of the magnetic assembly and compliance of the “gel surround”. But as the size of the magnet and its weight have to be kept minimal for a miniaturisation of the device, the focus of the research is on the effect of the of the gel surround. As a result, the effect of the gel surround, made of the RTV (room-temperature vulcanising) silicone elastomer, TPE (thermoplastic elastomer), and the silicone foam, on generation of the output driving force, the energy transfer from the transducer to a panel to which the transducer is attached, and sound radiation from the vibrating panel, was investigated. This effect was studied by COMSOL multiphysics (FE analysis) and thereby, the simulated results were verified by experiments such as the laser scanning measurement, DMA (dynamic mechanical analyzer), and the acoustic test. Successful development of prototypes of the gel-type audio transducers, with an enhanced acoustic efficiency at reduced size and weight, was achieved. Implementation of the transducers into consumer applications was also demonstrated with their commercial values.

Дисертація на здобуття наукового ступеня доктора технічних наук за спеціальністю 05.02.08 – технологія машинобудування (13 – механічна інженерія). – Національний технічний університет «Харківський політехнічний інститут», Харків, 2019. У дисертаційній роботі проведено комплекс досліджень, спрямованих на вирішення важливої науково-технічної проблеми в області технології машинобудування: розробка інноваційних та короткотривалих технологій поверхневого зміцнення деталей машин порошковими сумішами керованого складу для забезпечення експлуатаційних властивостей виробів на високому рівні при значному зниженні затрат на їх виготовлення. Наукова новизна отриманих результатів полягає у розробці наукових основ інноваційних та короткотривалих технологій поверхневого зміцнення деталей машин порошковими сумішами керованого складу, що дозволило вирішити актуальну науково-практичну проблему підвищення терміну служби деталей машин та інструменту: – вперше розраховано локальні максимуми поверхневої твердості та глибини дифузійних шарів сплавів і встановлено теоретичні оптимальні умови процесів дифузійного зміцнення, що дозволяє отримати конкретні технологічні параметри проведення хіміко-термічної обробки (ХТО) та забезпечити оптимальні характеристики дифузійних шарів; – вперше створено математичні моделі та номограми існуючих технологій поверхневого зміцнення сталей, що дозволило визначити конкретні умови ХТО (температуру і тривалість), виходячи із заданої глибини дифузійного шару або поверхневої твердості сталей, що суттєво впливає на ефективність реалізації процесів зміцнення; – вперше на основі використання інноваційних технологій і системного аналізу при мінімальних витратах, розроблено загальний методологічний підхід керування технологічними процесами поверхневого зміцнення деталей порошковими сумішами керованого складу при насиченні поверхневих шарів азотом, вуглецем і бором, це дозволило підвищити експлуатаційні властивості виробів при значному скороченні тривалості ХТО; – набули подальшого розвитку розроблені комплексні ХТО, які значно знижують крихкість борованих шарів за рахунок більш плавного зниження твердості від поверхні до серцевини виробів зі сталей, що дозволило підвищити експлуатаційні властивості виробів та термін служби деталей машин та інструменту на відміну від відомих методів ХТО, які підвищують лише поверхневу твердість; – вперше розроблено математичну модель розподілу температури за глибиною дифузійного шару, що дозволило визначити характер залежностей та отримати дані про розподіл температури за глибиною виробу при різних технологічних режимах обробки; – удосконалено технологію борування з паст титанових сплавів за рахунок використання нанодисперсного насичувального середовища, що дозволило скоротити процес борування у 2-3 рази та скоротити технологічний процес виготовлення деталей за рахунок поєднання двох операцій: борування і гартування титанового сплаву; – запропоновано розв’язання крайових задач дифузії методом граничних елементів, що дозволило вперше створити математичну модель розподілу концентрації бору за товщиною зміцненого шару титанового сплаву; − удосконалено технологію інтенсифікації процесів ХТО методами нагрівання струмами високої частоти та за рахунок попередньої лазерної обробки деталей, що дозволило отримати високі експлуатаційні властивості поверхневих шарів при значному скороченні тривалості обробок. Практичне значення роботи полягає у розробці технологій комбінованого зміцнення поверхневих шарів деталей зі сплавів. На основі комплексу проведених теоретичних та експериментальних досліджень, сформульованих принципів, закономірностей і положень отримані наступні практичні результати: 1. Спосіб комбінованої обробки сталевих виробів, що включає попередню лазерну обробку поверхні матеріалу з потужністю лазерного випромінювання -1,0±0,1 кВт, швидкістю пересування лазерного променя - 0,5-1,5 м/хв. з наступним азотуванням. Крім цього, азотування проводять в середовищі меламіну з 3-5% фтористого натрію при температурі 530-560 °C протягом 2-3 годин (патент України №111066). 2. Спосіб дифузійного борування сталевих виробів, що включає попереднє нанесення на поверхню обмазки, в склад якої входить боровмісна речовина, активатор фторид натрію і зв'язуюча речовина розчину клею БФ в ацетоні, і нагрівання струмами високої частоти. При цьому в обмазці як боровмісну речовину використовують поліборид магнію або аморфний бор і додатково введено активатор фторид літію (патент України №116177). 3. Спосіб поверхневого зміцнення сталевих виробів, що включає нанесення на поверхню деталі обмазки, до складу якої' входить боровмісна речовина і активатор, сушіння і нагрівання струмами високої частоти. В обмазці як боровмісну речовину використовують аморфний бор і активатор фторид літію. Нагрівання проводять при температурі 800-1100 °С протягом 1-5 хвилин (патент України №116178). 4. Спосіб отримання твердого покриття на поверхні сталевих виробів, що включає попередню обробку поверхні матеріалу та борування. Проводять попередню лазерну обробку поверхні матеріалу з наступним боруванням в середовищі полібориду магнію, активаторами: фтористий натрій і фтористий літій (патент України №116116). 5. Сплав на основі заліза з ефектом пам'яті форми, що містить: залізо, марганець, кремній, вуглець, хром, нікель, кобальт, мідь, ванадій, ніобій, молібден. При цьому до сплаву додатково введено сірку та фосфор (ваг. %): марганець від 4 до 20; кремній від 1,0 до 4,5; вуглець від 0,1 до 1,0; хром від 10,0 до 25,0; нікель від 1,0 до 10,0; кобальт від 1,0 до 10,0; мідь від 1,0 до 4,0; ванадій від 0,5 до 2,0; ніобій від 0,3 до 1,5; молібден від 0,5 до 2,0; сірка до 0,01; фосфор до 0,045; залізо решта (патент України №116117). 6. Склад для борування сталевих виробів, що містить аморфний бор, тетрафтороборат калію, нітрид бору і доломіт (патент України №117775). 7. Спосіб поверхневого зміцнення титанових сплаві, що включає насичення поверхневих шарів компонентами боровмісного середовища, до складу якого входить боровмісна речовина та активатор, і нагрівання. Насичення поверхневих шарів здійснюють компонентами боровмісного середовища, яке складається з аморфного бору і фториду літію (патент України №117770). 8. Дисперсійно-твердіючий сплав на основі заліза з ефектом пам'яті форми, що містить: залізо, марганець, кремній, вуглець, ванадій, ніобій, вольфрам. Додатково введено алюміній, мідь, нікель, хром, сірку та фосфор (патент України №117757). 9. Розроблені технологічні процеси ХТО були впроваджені для підвищення поверхневої твердості сталевих виробів на ТОВ «АСТИЛ М» (м. Харків), що дозволило підвищити зносостійкість втулки у 1,5 рази після нітроцементації, у 4,3 рази після послідовній нітроцементації та боруванні, у 5 разів після цементації, нітроцементації та боруванні та у 2 рази після боруванні з нагріванням СВЧ у порівняні зі втулкою без поверхневого зміцнення (Акт впровадження від 05.10.2017 р.). 10. Розроблені технологічні процеси комбінованого зміцнення були впроваджені для підвищення поверхневої твердості сталевих виробів на ПАТ «Харківський машинобудівний завод «Світло шахтаря» (м. Харків). Виробничими випробуваннями встановлено, що запропоновані ефективні технологічні процеси комбінованого зміцнення поверхневого шару сталевих виробів дозволили значно прискорити технологічні процеси хіміко-термічної обробки у 2-10 разів, що привело до зменшення витрат на їх проведення за рахунок економії електричної енергії (Акт впровадження від 17.10.2017 р.). 11. Розроблені технологічні процеси були впроваджені на ТОВ «НВЦ ЄТМ» (м. Харків), що дозволило підвищити зносостійкість втулки у 1,5 рази після нітроцементації, у 4,3 рази після послідовній нітроцементації та боруванні (Акт впровадження від 31.10.2017 р.). 12. Прийняті для впровадження в виробництві розроблені номограми, які дозволяють визначити конкретні умови газового азотування (температуру і тривалість) виходячи із заданої глибини азотованого шару або поверхневої твердості виробів зі сталі 38Х2МЮА на ПАТ «Харківський машинобудівний завод «Світло шахтаря» (м. Харків). Встановлено, що запропоновані номограми дозволили значно спростити роботу інженера-технолога, а також номограми дозволили вирішувати зворотну задачу, а саме, оцінити можливу товщину зміцненого шару і поверхневу твердість при одночасному впливі температури і тривалості газового азотування (Акт впровадження від 15.11.2017 р.). 13. Розроблений ефективний технологічний процес нітроцементації у порошковій макродисперсній суміші для підвищення експлуатаційної стійкості зубчастого колеса зі сталі 38Х2МЮА на АТ «Харківський тракторний завод» (м. Харків). Встановлено, що використання макродисперсної суміші прискорило процес хіміко-термічній обробки у 1,5-2 рази при отриманні властивостей поверхневого шару виробу таких, як і після традиційного процесу нітроцементації, що дозволило зменшити витрати на проведення хіміко-термічної обробки у 2 рази (Акт впровадження від 24.01.2018 р.). 14. Розробки, виконані в дисертації, впроваджені в навчальний процес для студентів механіко-технологічного факультету НТУ «ХПІ» спеціальностей 131 «Прикладна механіка» спеціалізації 131-09 «Обладнання та технології ливарного виробництва» та 151 «Автоматизація та комп’ютерно інтегровані технології» спеціалізації 151-07 «Комп’ютеризовані системи управління технологічними процесами» (Акт впровадження від 20.12.2017 р.).
The thesis for the scientific degree of doctor of technical sciences, specialty 05.02.08 – technology of mechanical engineering (13 – mechanical engineering). – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2019. In the thesis a set of studies was aimed at solving an important scientific and technical problem in the field of engineering technology: the development of innovative and short-term technologies of machine parts surface hardening with controlled composition powder mixtures to ensure the performance properties of products at a high level with a significant reduction in the cost of their production. The scientific novelty of the results lies in the development of scientific foundations of innovative and short-term technologies of surface hardening of machine parts by powder mixtures of controlled composition, which allowed to solve the actual scientific and practical problem of increasing the service life of machine parts and tools: - for the first time, local maxima of surface hardness and depth of diffusion layers of alloys were calculated and theoretical optimal conditions of diffusion hardening processes were established, which allows obtaining specific technological parameters of the chemical and heat treatment (CHT) process and providing optimal characteristics of diffusion layers; - for the first time created mathematical models and nomograms of existing technologies of surface hardening of steels, which allowed to determine the specific conditions of the CHT process (temperature and duration), based on a given depth of the diffusion layer or surface hardness of steels, which significantly affects the effectiveness of the implementation of strengthening processes; - for the first time through the use of innovative technologies and systems analysis at minimal cost, developed a general methodological approach for control of technological processes of surface hardening of parts by the powder mixtures of controlled composition at saturation of surface layers with nitrogen, carbon and boron, it is possible to improve the performance properties of products with a significant reduction in the CHT duration; – further development of the developed CHT complex, which significantly reduces the fragility of boriding layers due to a more gradual decrease in hardness from the surface to the core products of steels, thus improving the operational properties of the goods and service life of machine parts and tools in contrast to known methods of the CHT, which only increase surface hardness; - for the first time, a mathematical model of temperature distribution over the depth of the diffusion layer was developed, which made it possible to determine the nature of the dependences and obtain data on the temperature distribution over the depth of the product at different processing modes; – improved boriding technology with pastes of titanium alloys through the use of nanodispersed saturating environment, thereby reducing the boriding process to 2-3 times and to shorten the manufacturing process of components by combining two operations: boriding and hardening a titanium alloy; - solutions of boundary-value problems of diffusion by the boundary element method are proposed, which allowed for the first time to create a mathematical model of the distribution of boron concentration over the thickness of the hardened layer of a titanium alloy; - the technology of intensification of processes by CHT of heating by high-frequency currents and by means of preliminary laser processing of details was improved, which allowed to obtain high performance properties of surface layers with a significant reduction in the duration of treatments. The practical value of the work is to develop a technology of combined hardening of the surface layers of alloys making parts. The following practical results are obtained on the basis of a set of theoretical and experimental studies, formulated principles, regularities and the following practical results are obtained: 1. Method of combined processing of steel products, including advanced laser processing of material surface with the laser radiation power of -1.0±0.1 kW, the speed of movement of the laser beam of 0.5–1.5 m/min with subsequent nitriding. In addition, the nitriding is carried out in an environment of melamine with 3 to 5 % of sodium fluoride at a temperature of 530-560 °C for 2–3 hours (the patent of Ukraine No. 111066). 2. Method diffusion boriding steel products, including pre-application to the surface of the coating, which includes boriding substance, the activator sodium fluoride and a binder solution of glue BF in acetone, and heating by high frequency currents. In the coating as boriding substance use polyboride magnesium or amorphous boron, and optionally an activator is introduced lithium fluoride (the patent of Ukraine No. 116177). 3. Method of surface hardening steel parts comprising coating the surface of the part coating, which' is included boriding substance and activator, drying and heating by high frequency currents. In the coating as boriding substance use amorphous boron activator and lithium fluoride. The heating is carried out at a temperature of 800-1100 °C for 1-5 minutes (the patent of Ukraine No. 116178). 4. A method of producing a solid coating on the surface of steel products, including pre-processing the surface of the material and boriding. Carry out a preliminary laser treatment of the surface of the material with subsequent boriding in the environment polyboride magnesium, activators: sodium fluoride and lithium fluoride (the patent of Ukraine No. 116116). 5. The iron-based alloy with shape memory effect, contains: iron, manganese, silicon, carbon, chromium, nickel, cobalt, copper, vanadium, niobium, molybdenum. In this case, the alloy additionally introduced sulfur and phosphorus (weights. %): the manganese from 4 to 20; silicon 1.0 to 4.5; carbon 0.1 to 1.0; chromium, 10.0 to 25.0; nickel 1.0-10.0; cobalt 1.0-10.0; copper 1.0-4.0; vanadium 0.5 to 2.0; niobium from 0.3 to 1.5; molybdenum from 0.5 to 2.0; sulfur up to 0.01; phosphorus up to 0,045; iron-rest (the patent of Ukraine No. 116117). 6. Сomposition for boriding steel products containing amorphous boron, tetrafluoroborate potassium, boron nitride and dolomite (the patent of Ukraine No. 117775). 7. Method of surface hardening of titanium alloys, including a saturation of the surface layers of components boron environment, which includes boriding substance and the activator, and heating. The saturation of the surface layers is performed by components boron environment that consists of amorphous boron and lithium fluoride (the patent of Ukraine No. 117770). 8. The dispersion hardening iron-based alloy with shape memory effect, contains: iron, manganese, silicon, carbon, vanadium, niobium, tungsten. Included aluminum, copper, nickel, chromium, sulfur and phosphorus (the patent of Ukraine No. 117757). 9. Developed technological processes were introduced to improve the surface hardness of steel products at the limited liability company "ASTIL M" (Kharkіv), improving the durability of the sleeve by 1.5 times after nitrocarburizing, 4.3-fold after successive nitrocarburizing and boriding, 5 times after carburizing, nitrocarburizing and boriding and 2 times after boriding with microwave heating compared to a sleeve without surface hardening (the implementation Act from 05.10.2017). 10. Developed technological processes of the combined consolidation was implemented to improve surface hardness of steel products at Public company «Kharkiv machine-building plant "SVET SHAKHTYORA" (Kharkiv). Production tests have proved that the proposed effective technological processes of the combined hardening of surface layers of steel products will significantly accelerate the technological processes of chemical heat treatment in 2-10 times, led to reduced costs for them by saving electrical energy (the implementation Act from 17.10.2017). 11. Developed technological processes have been introduced at the limited liability company "Scientific-production Centre of the European mechanical engineering technology" (Kharkiv), thus improving the durability of the sleeve by 1.5 times after nitrocarburizing, 4.3-fold after successive nitrocarburizing and boriding (the implementation Act from 31.10.2017). 12. Adopted for implementation in production of developed nomograms that allow to define specific conditions of gas nitriding (temperature and duration) based on the desired depth of nitrided layer or the surface hardness of products of steel 38Cr2MoAl at Public company "Kharkiv machine-building plant «SVET SHAKHTYORA" (Kharkiv). Determined that the proposed nomograms greatly simplified the work of the engineer and these nomograms allowed to solve the inverse problem, to estimate the possible thickness of the hardened layer and surface hardness, at the same time of temperature and duration of gas nitriding (the implementation Act from 15.11.2017). 13. Developed an effective technological process of nitrocarburizing in microdisperse powder mixture to improve the operational stability of the toothed wheel of steel 38Cr2MoAl at private joint stock company "Kharkiv Tractor Plant". The use of microdisperse mixture accelerated the process of chemical-heat treatment by 1,5-2 times while getting the properties of the surface layer of the product such as after the nitrocarburizing, which reduced the costs of conducting chemical-thermal treatment by 2 times (the implementation Act from 24.01.2018). 14. The developments made in the thesis introduced in the educational process for students of mechanical engineering faculty of NTU "KhPI" special 131 "Applied mechanics" specialization 131-09 "Equipment and technology of foundry" and 151 "Automation and computer integrated technologies" specialization 151-07 "Computerized control of technological processes" (the implementation Act from 20.12.2017).

I study how the properties of management earnings forecasts change after a firm merges with or acquires another company. I find management is more likely to issue a forecast in a merger or an acquisition firm-year than in a non-M&A firm-year. Compared to forecasts issued by the firm in non-M&A periods, the first forecast issued after completing an M&A deal is less likely to be bundled with an earnings announcement and the forecast range is wider, although more likely to be optimistic than non-M&A forecasts. I find the increase in forecast range width and optimism persist in forecasts issued up to the end of the fiscal year but are not present in the initial forecast issued in the subsequent year. Finally, I find variation in M&A experience and M&A type influence management earnings forecast properties. Because prior studies of management forecasts often delete observations containing mergers and acquisitions or simply include the firm’s market-to-book, my study informs researchers about how the properties of management forecasts are impacted by the uncertainty from a merger or an acquisition.

The importance of cement integrity in the downhole well cannot be over looked. Cement designed for a particular well may not work for another well. As a result, there is a need to design well cement based on appropriate well conditions in order to achieve good integrity during the life time of the well. This research focused on micro-annulus and crack problems associated with downhole well cements. Waste tires have contributed to environmental problems.

Waste tires can be crushed into small particles and used for construction purposes. This is seen as a promising avenue to get rid of the waste tires. This research focused on the possibility of adding tire rubber particles to well cement to reduce the effect of micro-annuli and cracks in well cement. Tire rubber particles of 4 different sizes were used in this research, which was then divided into two parts. The first part dealt with rheology and compressive strength of concretes. These parameters were used to select cement designs with optimum value for subsequent tests. The other part included permeability and creep tests. Permeability measured the amount of water the concrete materials could yield while the creep test measured strain developed when concrete specimen was subjected to a constant stress for 30 minutes and the amount of strain recovered when the concrete specimen was unloaded for another 30 minutes. Creep compliance was done to measure the rate at which strain was developing, which is a function of time under constant stress.

Concrete containing the largest rubber particle size had good amount of strain recovery after unloading while concrete samples containing the smallest rubber particle size had the lowest amount of strain recovery.

As the major electricity consumer, electrical machines play a key role for global energy savings. Machine manufacturers put considerable efforts into the development of more efficient electrical machines for loss reduction and higher power density achievements. A consolidated knowledge of the occurring losses in electrical machines is a basic requirement for efficiency improvements. This thesis deals with iron losses in electrical machines. The major focus is on the influences of the stator core magnetic material due to the machine manufacturing process, temperature influences, and the impact of inverter operation. The first part of the thesis gives an overview of typical losses in electrical machines, with focus put on iron losses. Typical models for predicting iron losses in magnetic materials are presented in a comprehensive literature study. A broad comparison of magnetic materials and the introduction of a new material selection tool conclude this part. Next to the typically used silicon-iron lamination alloys for electrical machines, this thesis investigates also cobalt-iron and nickel-iron lamination sheets. These materials have superior magnetic properties in terms of saturation magnetization and hysteresis losses compared to silicon-iron alloys. The second and major part of the thesis introduces the developed measurement system of this project and presents experimental iron loss investigations. Influences due to machine manufacturing changes are studied, including punching, stacking and welding effects. Furthermore, the effect of pulse-width modulation schemes on the iron losses and machine performance is examined experimentally and with finite-element method simulations. For nickel-iron lamination sheets, a special focus is put on the temperature dependency, since the magnetic characteristics and iron losses change considerably with increasing temperature. Furthermore, thermal stress-relief processes (annealing) are examined for cobalt-iron and nickel-iron alloys by magnetic measurements and microscopic analysis. A thermal method for local iron loss measurements is presented in the last part of the thesis, together with experimental validation on an outer-rotor permanent magnet synchronous machine.

QC 20140516

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.
Includes bibliographical references (p. 197-198).
Practical application of Homogeneous Charge Compression Ignition (HCCI) combustion must demonstrate robust responses to variations in environmental conditions. This work examines the impact of ambient conditions and fuel changes on HCCI engine operation, and evaluates cam phasing as a mechanism to compensate for these changes. Experiments were carried out on a modified 2.3 L 14 production engine, and HCCI operation was achieved by the use of residual trapping by negative valve overlap. The first phase of the project examined the impact of changes in intake air temperature and humidity on HCCI operation. Exhaust cam phasing was used to control load, and intake cam phasing was use to produce a change in combustion phasing. Cam timing control was largely able to compensate for changes in combustion due to changes in air temperature and humidity. Higher intake air temperature advanced combustion phasing and resulted in a 1 bar reduction of the net indicated mean effective pressure (NIMEP) at the high load limit for lower engine speeds. Intake air temperature did have more of an impact during lean operation. Higher intake air humidity delayed combustion phasing.
(cont.) During stoichiometric operation, this delay allowed a small extension (a few tenths of a bar in NIMEP) in the high load limit. During lean operation, the delay in combustion timing resulted in a reduction of the high load limit. The second phase of the project examined the impact of market fuel composition variations on HCCI operation. Twelve test fuels were created to vary the composition of 5 fuel properties: Research Octane Number (RON), Reid Vapor Pressure (RVP), olefin content, aromatic content, and ethanol content. The test fuels were blends of different commercial refinery streams and contained hundreds of different hydrocarbons to be representative market gasolines. Fuel type was found to have only a small impact on the HCCI operating range, and cam phasing was largely able to compensate for changes in fuel composition. The main effect of the different fuel composition appeared to be differences in ignition delay.
by Morgan M. Andreae.
Ph.D.

A major focus of contemporary IS research is the emergent nature of organisational use of information technologies: its contextual, evolutionary, often unanticipated character. Most studies have approached this topic from the viewpoint of emergence in IT based practices as a process, led by social actors. However, the investigation of emergence as a property has been neglected. The systems thinking approach is particularly concerned with emergent properties, but has hitherto been poorly developed for the socio-technical analysis of IT use. In redress, this research presents a new framework of interpretive systems thinking for performing such analysis. This framework permits a researcher or organisational analyst to form an understanding of emergent phenomena in IT based operations as constituted by the interaction of various elements or factors in relations of contrariety, contradiction or association. The emergent nature of an organisation's activities may consequently be illuminated in terms of principle tensions or contradictions, that shape its trajectory of transformation, or form a persistent pattern in its functioning. This method of analysis is applied to two case studies of IT based call centre operations. The case analyses demonstrate the utility of this inter-relational, integrative framework. It supports supra-individual analysis of the shaping of significance concerning IT based activities. The emergent dynamics of integration and transformation related to the use of IT capacities in call centre activities are revealed in multi-faceted, contextually specific forms, that transcend simple binary alternatives in the appraisal of IT usage (e.g. IT is rigid or flexible). The framework's main benefit is its ability to highlight contradictions that are easy to miss, or difficult to pinpoint, in IT enabled work practices. This study's third-person, property-focussed account of emergence in IT based operations provides a different but complementary emphasis to the micro agency-centred model of emergence that has dominated recent IS studies.

Surgical myocardial revascularization remains the standard of care for patients with multi-vessel coronary artery disease. A growing body of evidence indicates that systemic inflammation and myocardial oxidative stress are associated with the development of postoperative atrial fibrillation (POAF) and low cardiac output syndrome in patients undergoing cardiac surgery. Statins have been shown to exert rapid anti-inflammatory and antioxidant effects by inhibiting myocardial NOX2 oxidases and by increasing the bioavailability of nitric oxide (NO). However, whether these so-called pleiotropic effects of statins result in improved patient outcomes remains to be established. To provide further insights into the mechanisms of action and impact on clinical outcomes of peri-operative statin treatment in patients undergoing cardiac surgery, I studied the molecular mechanisms underlying the myocardial nitroso-redox balance in samples of the right atrial appendages (RAA) obtained before (PRE) and after cardiopulmonary bypass (CPB) and reperfusion (POST) and setup two double-blind randomised placebo-controlled trials: 1) STARR (Statin Treatment on Atrial Refractoriness and Reperfusion injury), which tested the effect of Atorvastatin (80 mg once daily for up to 6 days before surgery and 5 days after) on the atrial effective refractory period (AERP, over 4 post-operative days) and superoxide production in paired PRE- and POST- RAA samples from 60 patients 2) STICS (Statin Treatment In Cardiac Surgery), which assessed the effects of peri-operative treatment with Rosuvastatin (20mg od) on POAF (assessed by continuous holter ECG monitoring for 5 days postoperatively) and myocardial injury (assessed by serial troponin I measurements) in 1922 patients undergoing elective cardiac surgery. I observed that atrial superoxide production increased significantly after reperfusion due to increased mitochondrial and NOX2 oxidase activity and to uncoupling of NOS activity. NOS activity in RAA samples decreased significantly after reperfusion (by 60%), but this reduction was not prevented by BH4 supplementation (10 μM) or NOX2 inhibition. Instead, I identified increased endothelial NOS S-glutathionylation as the main mechanism responsible for NOS uncoupling after reperfusion. In STARR, atorvastatin prevented increase in RAA superoxide production, maintained the functionally coupled status of NOS and NO bioavailability after reperfusion but had no measurable effect on postoperative AERP. In STICS, treatment with rosuvastatin significantly reduced LDL-C concentration by 48 hours after surgery but had no effect on the incidence of POAF (203 (21%) of the Rosuvastatinallocated patients vs. 197 (20%) of the placebo-allocated patients) or on perioperative myocardial damage (P = 0.80). Pre-defined subgroup analyses (age, sex, prior statin use, baseline troponin concentration, duration of randomized treatment before surgery, type of cardiac surgery, and postoperative use of anti-inflammatory drugs) did not identify any category of patient who benefited from perioperative rosuvastatin treatment. Nor were there beneficial effects on any of the other in-hospital clinical outcomes that were assessed. In conclusion, cardiac surgery on CPB is associated with myocardial nitroso redox imbalance that is reversed by perioperative intensive therapy with statins. However, these effects have no beneficial effects on common in-hospital complications after elective cardiac surgery. Although the benefits of long-term statin therapy in patients requiring myocardial revascularization are well established, the work presented in this thesis does not support routine use of perioperative intensive therapy with statins for the prevention of postoperative complications in patients undergoing elective cardiac surgery.

This work is aimed to design and implement software for simulating operational properties of heat pumps and process data from measurements. Work contains the issue of heat pumps, their principle of functionality, different types of systems and coefficients used for rating of efficiency of heat pumps. Next it contains physical or electrical parameters that needs to be measured by designed system. The result is functional software, which contains mathematical library written in C++ and graphical user interface written in C#.

The X-ray optics of synchrotron radiation beamlines are considered in this paper. The characteristics of synchrotron radiation which make it the premier source of light for studies in many regions of the electromagnetic spectrum are given. A chapter is devoted to the collimating, focusing and monochromating optics of two X-ray diffraction beamlines at the National Synchrotron Light Source. The beamlines are operated by the Naval Research Laboratory (NRL) and the Oak Ridge National Lab (ORNL). The major optical components of these beamlines are reviewed in regards to their function and their flexibility. A detailed analysis is performed on the NRL X-ray collimating mirror. The mirror is treated as an elastically bent beam. Deflection and slope error equations are developed which relate the shape of the bent mirror to its ideal surface. Visible light diffraction patterns collected from the mirror helped to establish operating conditions which provide good collimation. When the observed patterns are wed to the theoretical calculations, estimates of the average figure error are made. Finally, the effect of a highly collimated synchrotron beam on the reproducibility of the integrated intensities from polycrystalline materials is considered. The calculations show that except for the most fine grained materials, representative intensity measurements can only be made when the sample is permitted to move.
M.S.

The process of generalization in mathematics was identified by mathematics education and educational psychology research, out of many mental actions or operations, as a cognitive function fundamentally required in the thinking process. Moreover, the current changes in education in the United States bring forward the dual goal of mathematics teaching and learning: students should have strong and rigorous mathematical content knowledge and students should be involved in practices that define the status of doing mathematical work. This dual role is totally dependent on the process of generalization. This study uses theories and research findings from the field of algebraic thinking, teaching, and learning to understand how the third grade teacher’s edition textbooks of three mathematics curricula portray the process of generalization. I started my study with the development of a theoretical coding system obtained by combining Kaput’s theory about algebra (Kaput, 2008), Krutetskii’s two way of generalization (Krutetskii, 1976), and the five mathematical representations identified by Lesh, Post, and Behr (1987). Then, I used the coding system to identify tasks that have the potential to involve students in the process of generalization. The findings from my study provide evidence that following a well-structured theory, such as Kaput’s theory about algebra, allows us to identify tasks that support algebraic thinking and to create new ones with higher potential to involve children in the process of generalization. Such tasks may support the development of algebraic thinking as a continuous process that should start from early grades of elementary school.

The achievement of predictable and long lasting adhesive restorations in posterior teeth have always been a major objective of studies in the context of materials and techniques development. The use of bulk fill composites could provide better outcomes, but it is important to assess their physico-mechanical properties, responsible for their clinical behavior. The purpose of the present study was to assess the mechanical and physical properties of bulk fill composites. The composites were divided into 2 groups according to their viscosity. For low viscosity composites, the present study assessed: Surefill SDR flow (SDR), X-tra Base (XB), Filtek Bulk Fill Flowable (FBF), and Filtek Z350XT Flow (Z3F- control); and for high viscosity composites: Tetric Evo Ceram Bulk Fill (TBF), X-tra Fil (XF), Filtek Bulk Fill (FBP), Admira Fusion x-tra (ADM) and Filtek Z350 XT (Z3XT- control). Composites were assessed through shrinkage stress test (using 12 and 24mm3 of composite in a custom device adapted in an Universal Testing Machine); volumetric shrinkage (using 64mm3 of composite placed on a Teflon mold and scanned in a micro computed tomography/CT); Youngs modulus (through a 3-point bending test device adapted in an Universal Testing Machine); microhardness and depth of cure tests (using longitudinal Knoop microhardness). All data was evaluated regarding their homogeneity using Shapiro-Wilk test. For polymerization stress, 3-way Variance Analysis (ANOVA) was used. Considering Volumetric Shrinkage, Youngs Modulus, Microhardness and Depth of Cure, one-way ANOVA was used. All ANOVA tests were followed by Tukeys test and 5% was adopted as significance level. Shrinkage stress test with 12mm3 showed SDR, TBF and XF generating the lowest stress after 300s, followed by other high viscosity composites (ADM, FBF, XB and FBP/Z3XT). The regular low viscosity composite (Z3F) generated the highest stress for all assessed times. Considering the same test, with 24mm3, after 300s, SDR, FBP and ADM generated similar stress, followed by TBF and XF. Low viscosity bulk fill composites generated lower stress than Z3F. Considering Youngs modulus, low viscosity composites (SDR, FBF, XB and Z3F) showed the lowest values, followed by ADM and TBF. The other high viscosity composites (Z3XT, FBP and XF) showed the highest values. For microhardness test, all low viscosity composites showed lower values (FBF being the lowest). For high viscosity composites, Z3XT showed the highest values, followed by XF, FBP/TBF and ADM. Assessing depth of cure, regular composites showed lower values when compared with bulk fill composites. All bulk fill composites showed adequate depth of cure over 4.5mm (microhardness 80% of initial reading). SDR and XB showed the highest depth of cure. All high viscosity bulk fill composites generated lower volumetric shrinkage than regular composites. All low viscosity bulk fill composites showed similar volumetric shrinkage when compared to the regular composites (Z3F and Z3XT). Bulk fill composites show characteristics that allow their use in larger increments (i.e. volumetric shrinkage and polymerization stress similar or lower when compared with regular composites). Nonetheless, the mechanical properties of bulk fill composites were widely variable, being important to individually assess each material previously to its clinical application.
A obtenção de restaurações adesivas previsíveis e duradouras em dentes posteriores sempre foi objetivo de estudos na área de desenvolvimento de materiais e técnicas. O uso de resinas compostas do tipo bulk fill pode possibilitar melhores resultados, porém é importante o estudo de suas propriedades físico-mecânicas, responsáveis por seus comportamentos clínicos. O objetivo do presente estudo foi o de avaliar as propriedades físicas e mecânicas das resinas bulk fill. As resinas foram divididas em 2 grupos de acordo com sua viscosidade. Para resinas de baixa viscosidade, o presente estudo avaliou: Surefill SDR flow (SDR), X-tra Base (XB), Filtek Bulk Fill Flowable (FBF) e Filtek Z350XT Flow (Z3F-controle); e, para alta viscosidade: Tetric Evo Ceram Bulk Fill (TBF), X-tra Fil (XF), Filtek Bulk Fill (FBP), Admira Fusion x-tra (ADM) e Filtek Z350 XT (Z3XT-controle). As resinas foram avaliadas em relação à tensão de polimerização (utilizando 12 e 24mm3 de resina adaptadas em um dispositivo adaptado a uma máquina de testes universal); contração volumétrica (utilizando 64mm3 de resina composta inserida em um molde de Teflon e escaneada em um micro-tomógrafo/CT), modulo de Young (através de um dispositivo de flexão em 3 pontos adaptado a uma máquina de testes universal), microdureza e profundidade de polimerização (utilizando microdureza Knoop). Todos os resultados foram avaliados em relação à homogeneidade utilizando o teste de Shapiro-Wilk. Para avaliação da tensão de polimerização, foi empregada a Análise de Variância (ANOVA) a 3 critérios. Para as analyses de contração volumétrica, Módulo de Young, microdureza e profundidade de polimerizaçao, ANOVA a um critério foi empregada. Todas as Análises de Variância foram seguidas pelo teste de Tukey e 5% foi adotado como nível de significância. A tensão de polimerização com 12mm3 demonstrou que SDR, TBF e XF geraram valores significantemente mais baixos após 300s, seguidas por outras resinas de alta viscosidade (ADM, FBF, XB e FBP/Z3XT). A resina convencional de baixa viscosidade (Z3F) gerou valores de tensão significantemente mais elevados para todos os tempos avaliados. Considerando o mesmo teste, com 24mm3, após 300s, SDR, FBP e ADM geraram valores estatisticamente inferiores, seguidas por TBF e XF. As resinas bulk fill de baixa visocidade geraram menor tensão de polimerização que a Z3F. Considerando o modulo de Young, resinas de baixa viscosidade (SDR, FBF, XB e Z3F) apresentaram valores significantemente inferiores, seguidas por ADM e TBF. As outras resinas de alta viscosidade (Z3XT, FBP e XF) apresentaram valores significantemente mais elevados. Para o teste de microdureza, todas as resinas de baixa viscosidade apresentaram valores inferiores (FBF apresentou o menor). Para as resinas de alta viscosidade, Z3XT apresentou os valores mais elevados, seguida por XF, FBP/TBF e ADM. Para profundidade de polimerização, resinas compostas convencionais apresentaram valores signifixantemente mais baixos quando comparadas com resinas bulk fill. Todas as resinas bulk fill apresentaram profundidade de polimerização adequada até pelo menos 4,5mm (microdureza 80% da leitura inicial/superfície). SDR e XB apresentaram os valores mais altos de profundidade de polimerização. Todas as resinas bulk fill de alta viscosidade geraram menor contração volumétrica que resinas compostas convencionais. Todas as resinas bulk fill de baixa viscosidade apresentaram contração volumétrica similar às resinas convencionais (Z3F e Z3XT). Resinas compostas bulk fill apresentaram características que possibilitam sua indicação para serem empregadas em grandes incrementos (contração volumétrica e tensão de polimerização similar ou inferiores às resinas convencionais, além de maior profundidade de polimerização). No entanto, as propriedades mecânicas variaram grandemente entre as resinas estudadas sendo importante uma avaliação individual de cada material previamente ao seu uso clínico.

The overall aim of the present thesis was to explore and compare professional co-operation in child welfare investigations, explore the psychometric properties, and describe the clinical utility from different perspectives of a translated Swedish version of the standardized assessment instrument the Home Observation for Measurement of the Environment (the HOME Inventory). Social workers in Sweden, Denmark, Britain, Germany, and Texas (USA) co-operated with different professionals around a fictitious child welfare case. Differences were found between and within country-based samples, indicating an unsystematic work procedure in the social work agencies studied. The psychometric properties of the translated Early Childhood version (EC-HOME) and Middle Childhood version (MC-HOME) of the HOME Inventory were explored in terms of inter-observer reliability and by Rasch analysis. The samples were authentic Swedish child welfare cases recruited from a field setting. Inter-observer reliability was satisfactory. Results were ambiguous regarding measurement construction of the two versions studied. Because of the differentiating ability of the EC-HOME and MC-HOME, total scores could provide an indication of inadequate home environments. Experiences of social work practitioners of the clinical utility of the HOME Inventory suggested that they considered the instrument to be comprehensive and have explicit potential benefits, i.e. to be clinically useful. Correspondingly, caregivers’ overall perceptions of the HOME Inventory were positive, determining the content relevant and the format acceptable. However, certain flaws have to be rectified before the HOME Inventory is to be implemented and used successfully. Further, education and the possibility to practice administering the instrument seemed to be essential conditions for future use according to social workers. When social workers and teachers’ apprehensions about support and stimulation provided by caregivers to children in their home environments were compared, preschool teachers’ apprehensions correlated poorly with the social workers’ assessment. These results suggest that the HOME Inventory is promising but cultural adaptation and further studies of psychometric properties are necessary. Different forms of support to practitioners and agencies for successful implementation are required. Awareness of the type of information provided by different sources is important when co-operating in child welfare.

Les composants actifs en électronique de puissance sont principalement à base de Silicium. Or, le silicium a des limites en termes de température d'utilisation, fréquence de commutation et de tenue en tension. Une alternative au Si peut être les semi-conducteurs à grand gap tels que le SiC-4H. Grâce aux travaux de plusieurs équipes de chercheurs dans le monde, les performances s'améliorent d'année en année. Le laboratoire AMPERE conçoit, réalise et caractérise des composants de puissance en SiC-4 H. Cette thèse s'inscrit dans les projets SiCHT2 et VHVD du laboratoire. Le travail réalisé au cours de cette thèse repose sur la conception la fabrication et la caractérisation électrique de composantes haute tension en SiC-4H. Les paramètres de protection pour la diode bipolaire 6500V sont optimisés à l'aide des simulations à base d'éléments finis. Les paramètres du SiC pour les modèles utilisés pour la simulation sont développés par des travaux précédents. Ensuite, le masque est dessiné. La diode est réalisée chez IBS. La première caractérisation est effectuée avant le recuit post-métallisation en directe et inverse sans passivation finale. Après le recuit post-métallisation la résistance de contact est plus faible. La caractérisation de la tenue en tension a été effectuée à AMPERE puis à l'ISL à très haute tension. A l'aide de simulations à base d'éléments finis, les paramètres tels que la résistance de contact et la durée de vie des porteurs ont été affinés à partir des caractérisations électriques obtenues par l'expérience. Les autres travaux portent sur la conception, les optimisations et les fabrications des diodes 10 kV et transistors 6500 V.

In patients undergoing adolescent idiopathic scoliosis (AIS) surgery the yield and differentiation capacities of mesenchymal stem cells (MSCs) from vertebral body (VB) and iliac crest (IC) bone marrow (BM) were investigated comparing the effectiveness of two MSC-harvesting procedures [density gradient centrifugation (Lymphoprep, LMP) and red cell lysis (Ammonium Chloride, AC)]. The burden of surgery of 3 surgical approaches (posterior, posterior-costoplasty, antero-posterior), for AIS correction was also quantified. In 18 patients 10ml of BM were aspirated intraoperatively from IC and VB and MSCs were isolated using AC and LMP harvesting procedures. MSCs were enumerated and phenotypically characterised using colony-forming-unit-fibroblast (CFU-F), flow cytometry and trilineage differentiation assays. For the immuno-inflammatory study 23 patients were recruited. ELISA-assays were performed on serum from 4ml of peripheral blood, at 6 peri-operative time-points (T), measuring 4 cytokines [(Interleukin) IL-6, IL-10, IL-18 and Procalcitonin (PCT)]. Surgical parameters and gender variability were also analysed. Both IC and VB exhibited similar concentrations of MSCs, however AC yielded significantly more MSC/ml by 1.8-fold (IC, p=0.012) and 1.5-fold (VB, p=0.043), compared to LMP. Calcium and glycosaminoglycan (GAG) concentrations were both significantly higher from VB MSCs, compared to IC [Calcium: AC 8.7-fold (p=0.001), LMP 1.2-fold, GAG: AC 3.8-fold (p=0.0005), LMP 1.9-fold (p=0.003)]. Adipogenesis did not show significant differences. VB AC-harvested MSCs presented a significantly smaller colony area by 1.9-fold (p=0.039), compared to IC AC. The post-operative concentrations of IL-6 and IL-10 were always significatintly elevated at T2 and T3 points, in all 3 approaches (p < 0.01) with antero-posterior approach presenting the highest levels followed by posterior-costoplasty and posterior approaches. Although prolonged procedures and gender type affected cytokine concentrations, their levels were not statistically significant. In summary, AC isolated more effectively MSCs, without affecting their function. VBBM MSCs demonstrated higher osteo- and chondro-genic differentiation capacities, representing a valid source of MSCs in spinal surgery. The surgical stress reaction quantified with immune-inflammatory markers, was higher in more aggressive and extensile procedures, suggesting greater vigilance in identifying and preventing complications.

Compatibility of fuel delivery materials (FDM) with biodiesel fuel in the fuel delivery system (FDS) under real-life common rail diesel engine (CRDE) operation poses a challenge to researchers and engine manufacturers alike. Although standard methods such as ASTM G31 and ASTM D471 for metals and elastomers, respectively, are deemed suitable for evaluating the effects of water content, total acid number (TAN) and oxidation products in biodiesel on FDM degradation, they do not resemble the actual engine operation conditions such as varying fuel pressure/temperature as well as the presence of a wide range of materials in the FDS of a diesel engine. Hence, the current allowable maximum 20 vol% of biodiesel with 80 vol% of diesel (B20) for use in diesel engines to date is debatable. Additionally, biodiesel utilization beyond B20 is essential to combat declining air quality and to reduce the dependence on fuel imports. This thesis aims to elucidate the actual compatibility present between FDM and biodiesel in the FDS under real-life CRDE operation. This was achieved through multi-faceted experimentations which commenced with analyses on the deteriorated palm biodiesel samples collected during and after CRDE operation. Next, the fuel properties which should be emphasized based on the deteriorated fuel were determined. This was then followed by ascertaining the effects of the emphasized fuel properties towards FDM degradation. Ultimately, the actual compatibility of FDM with biodiesel under engine operation through modified immersion investigations was determined. FDM degradation acceleration factors such as oxidized biodiesel, TAN and water content were eliminated since these factors were not affected based on the analysed fuel samples collected after engine operation. No oxidation products such as aldehydes, ketones and carboxylic acids were detected while the TAN and water content were within 0.446% and 0.625% of their initial values, respectively. Instead, the biodiesel’s dissolved oxygen (DO) concentration and conductivity value were not only found to have changed during and after engine operation by -93% and 293%, respectively, but were also found to have influenced biodiesel deterioration under engine operation. These two properties were subsequently discovered to have adversely affected FDM degradation independently. The copper corrosion rate and nitrile rubber (NBR) volume change increased by 9% and 13%, respectively, due to 22% increase in the conductivity value. In contrast, the copper corrosion rate and NBR volume swelling reduced by 91% and 27%, respectively, due to 96% reduction in the DO concentration. Ultimately, copper corrosion and NBR degradation were determined to be lowered by up to 92% and 73%, respectively, under modified immersion as compared to typical immersion condition. These outcomes distinctly show that acceptable to good compatibility is present between FDM and biodiesel under CRDE operation. The good compatibility is strongly supported since only a maximum lifespan reduction of 1.5 years is predicted for metal exposed to biodiesel as compared to diesel for a typical component lifespan of 15 years. For the elastomers, acceptable compatibility is found present between elastomer and biodiesel based on the determined 11% volume change which conforms to the tolerance level of elastomer degradation as stated by the elastomer manufacturers. These are especially true for the evaluated metals and elastomers investigated under the modified laboratory immersion which replicates similar conditions to a real-life CRDE. Overall, this work has contributed to the advancement of knowledge and application of biodiesel use in diesel engines.

Syfte: En fasad måste vara robust för att fylla sin funktion och materialet måste kunna stå emot angrepp utifrån, biologiska, kemiska och fysikaliska faktorer. Trä och tegel är eftertraktade som fasadmaterial för dagens nybyggda bostadshus. Eftersom olika material reagerar olika på angrepp är det viktigt att det finns skillnader i underhållsstrategier beroende på vilket fasadmaterial som används. Underhållsarbetet är en faktor som påverkar beslutet på fasadmaterial. Undersökningen ger ett underlag inför valet mellan materialen genom att utveckla underhållsstrategier för respektive material. Metod: För att uppnå målet med arbetet har tre metoder använts för att samla in empiri Dessa är litteraturstudie, intervjuer och dokumentanalys. I litteraturstudien samlades information från olika källor på internet in. Dessa källor hjälpte till att bygga ett teoretiskt ramverk om fastighetsförvaltning och underhållsstrategier. Dokumenten och intervjuerna gav praktisk kunskap om förhållningssätt till underhåll. Metoderna var lämpliga eftersom de tillsammans gav teoretisk såväl som praktisk kunskap kring material och underhåll. Den insamlade empirin analyserades och jämfördes för att kunna besvara frågeställningarna och uppnå målet. Resultat: Idag finns olika underhållsstrategier på trä- och tegelfasader. Den generella åsikten är att trä kräver fler underhållsåtgärder än tegel. Det har dock visat sig att det även förekommer problem med till exempel frostsprängning i större omfattning än vad som tidigare antagits. Underhållsplaner upprättas ofta efter grundlig undersökning av en byggnads egenskaper och kartläggning av dess underhållsbehov. Dessa planer används inte regelbundet hos förvaltningsföretag men det finns en önskan bland vissa förvaltare att ha en mer strukturell underhållsplanering i framtiden. Kategorisering av skador och tillkommande underhållsåtgärder kan användas vid upprättande av underhållsplaner. Ett sådant system är Monument Damage Diagnosis System, förkortat MDDS. Underhållsplaner kan också utformas som stegvisa processer som kan användas tillsammans med databaser över fasadens egenskaper och nödvändiga underhållsåtgärder. Konsekvenser: Denna rapport kommer att ge aktörer inom byggbranschen kunskap och olika strategier vid fasadunderhåll. Konsekvenserna blir att: Företag inom byggbranschen upprättar underhållsplaner mer i framtiden. Det upprättas strukturerade bedömningar om risker kopplade till material, byggnadsdel och yttre påverkan. För- och nackdelarna med trä- och tegelfasader uppmärksammas i högre grad än idag. Många riskfaktorer för tegel såsom frostsprängning har tidigare inte beaktats tillräckligt. Det rekommenderas att byggföretag tar till sig den forskning som finns av underhåll av trä- respektive tegelfasader. Eftersom trä är billigare än tegel i byggskedet men dyrare vid underhåll behöver dessa företag göra fler undersökningar om båda materials för- och nackdelar ur ekonomisk synpunkt. Byggföretag behöver om förutsättningarna finns även upprätta underhållsplaner eftersom dessa planer leder till att fel upptäcks tidigare och därmed minskar kostnaderna på lång sikt. Begränsningar: Resultatet är enbart tillämpbart på fasader av trä och fasader av tegel.  Vidare kan resultatet bara tillämpas på bostadshus eftersom inga andra byggnadstyper har undersökts. Underhållsstrategin som utvecklats i rapporten kan i grunden användas i alla typer av klimat dock måste alltid lokala klimatförhållanden beaktas när strategin appliceras i praktiken. Att upprätta en underhållsplan kräver även en god ekonomi därför är det inte säkert att rapportens underhållsstrategi alltid kan upprättas i verkligheten om det finns ekonomiska hinder.  Litteraturstudien har studerat underhållsstrategier på global nivå medan dokumentanalysen och intervjuerna har fokuserat på de lokala förhållandena i Sverige.
Purpose: A façade must be robust to be able to fulfil its role and the material must be able to withstand exterior threats. These threats could be biological, chemical, or physical. Wood and brick are popular as façade materials when it comes to the newly constructed residential buildings of today. Since different materials react different on threats it is vital that there are separate maintenance strategies depending on the choice of façade material. The examination gives the choice between the materials a basis by developing maintenance strategies for respective material Method: To achieve the goal of the project, three methods have been used to collect empirical data. These methods are literature study, interviews, and document analysis. In the literature study, information from different sources on the internet were collected. The sources helped building a theoretical about property management and maintenance management. The document and interviews provided practical knowledge about maintenance approaches. The methods were suitable since together they provided both theoretical and practical knowledge about materials and maintenance. The collected data was analysed and compared to answer the questions and achieve the projects goal. Findings: Today there are different maintenance strategies for wood and brick facades. The general opinion is that wooden facades require more maintenance than brick facades. Although brick facades have had more problems with for example frost shattering than what was assumed before. Maintenance plans are often established after thorough investigation of a building’s properties and mapping of its maintenance needs. These plans aren’t used regularly among property managers but there’s a wish among some of them to have more structural maintenance planning in the future. Categorization of damages and additional maintenance activities can be used when establishing maintenance plans. One such system is Monument Damage Diagnosis System, abbreviated MDDS. Maintenance plans could also be formulated as step-by-step processes that could be used together with databases of a façade's properties and necessary maintenance actions. Implications: This study will give actors in the construction industry better knowledge about different strategies for façade maintenance. The consequences will be: That companies in the construction industry establish maintenance plans more in the future. That structural evaluations of risks depending on material, building component and external influence are established That strengths and weaknesses with wooden facades and brick facades are paid attention to more in the future. Many risk factors affecting brick facades has not been sufficiently acknowledged before. It is recommended that construction companies take note of current research on maintenance of wooden and brick facades. Since wood is cheaper to build with but more expensive to maintain than brick companies need to do more studies about these materials strengths and weaknesses. Construction companies also need to establish and follow maintenance plans if the conditions are right since that would lead to damages being discovered earlier and therefore decreases costs in a long term. Limitations: The result is only applicable on wooden and brick facades. Furthermore, the result can only be applied on residential houses since no other type of building has been examined. The maintenance strategy that has been developed in the report is in can be used in all climates, but local climate circumstances must always be considered then the strategy is applied in practice. Establishing a maintenance plan requires a good economy therefore it is not certain that the report’s maintenance strategy will always be possible to establish in reality if there are economical limits. The literature study has examined maintenance strategies on a global scale while the document analysis and the interviews has focused on the local circumstances in Sweden.