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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1081

Étude expérimentale de l'influence de la structure des partenaires dans la fusion de systèmes presque symétriques.

Stodel-Lelay, Christelle 04 December 1998 (has links) (PDF)
Les fonctions d'excitation de fusion-évaporation des systèmes 70Zn+150Nd et 86Kr+130,136Xe sont mesurées pour une énergie d'excitation du noyau composé (216,220,222Th) variant de 7 MeV à 70 MeV (soit 4 à 5 MeV par nucléon d'énergie incidente), auprès de l'UNILAC du laboratoire de recherche GSI, Darmstadt (Allemagne). Après désexciation par évaporation (xn, pxn et αxn), les noyaux résiduels sont séparés du faisceau principal et des autres produits de réaction par le filtre de vitesse SHIP et implantés dans un détecteur à localisation. Les énergies caractéristiques des alphas de décroissance de ces noyaux permettent de les identifier et de déduire leur taux de production. Les fonctions d'excitation expériementales de fusion-évaporation sont comparées avec celles menant aux mêmes noyaux composés obtenus par d'autres combinaisons projectile et cible et avec celles calculées par un code développé au GSI. Ce code permet d'évaluer l'évolution des probabilités de fusion avec l'énergie incidente pour chaque système. La variation des sections efficaces et de la probabilité de fusion est étudiée en fonction des variables macroscopiques et microscopiques des noyaux projectiles et cibles. Dans la synthèse de noyaux super-lourds, ces résultats démontrent quantitativement l'intérêt d'utiliser des partenaires de fusion riches en neutrons d'une part et à couche fermée d'autre part (la section efficace de fusion augmente d'un facteur 9 par paire de neutrons supplémentaires). Par contre, la présence d'une couche fermée dans le noyau composé n'influence pas la section efficace de fusion. Il sera moins difficle de synthétiser des noyaux de Z supérieur à 110 à partir de faisceaux secondaires de projectiles enrichis en neutrons, ce qui permettra aussi d'atteindre les isotopes des noyaux super-lourds proches des vallées de stabilité.
1082

Canadian consumers' functional food choices : labelling and reference-dependent effects

Zou, Ningning 15 June 2011 (has links)
The growing interest among consumers in the link between diet and health makes functional food one of the fastest growing sectors in the global food industry, especially functional dairy products. Understanding consumer choices with respect to functional food is an important and relatively new research area. Given the credence nature of functional food attributes, labelling plays a key role in allowing consumers to make informed choices about foods with enhanced health attributes. In 2007, Canada launched a review of the regulatory system for health claims on functional foods, which included rules concerning the approval, labelling and verification of health claims. In 2010 two new health claims related to oat products and plant sterols were approved by Health Canada. An analysis of how consumers respond to health claim information is therefore timely. This thesis focuses on examining the effects of different types of labelling and verification of health claims on consumers stated preferences for a specific functional food product, Omega-3 milk. The analysis incorporates reference-dependent effects. This study improves the knowledge of Canadian consumer understanding of health claims and the impact of health claims on consumer choice. This research is one of the first studies to simultaneously examine the effects of different types of health claims (e.g. function claims, risk reduction claims and disease prevention claims) and other ways of signalling or implying health benefits (e.g. symbols) on Canadian consumers' functional food choices. This study contributes to the knowledge in this domain by providing a comparative analysis of different types of labelling strategies. The extant knowledge of labelling effects in the formats of risk reduction claims, disease prevention claims and symbols or imagery on functional foods is limited. One of the primary contributions of this study is addressing this gap in the literature. The theoretical framework of this thesis is based on random utility theory. A stated preference choice experiment is designed to examine consumers' response to Omega-3 milk under different labelling scenarios. Using data from an online survey of 740 Canadians conducted in summer 2009, discrete choice models, including Conditional Logit, Random Parameter Logit and Latent Class models, and Willingness-To-Pay (WTP) values are estimated. The results suggest that full labelling (function claims, risk reduction claims and disease prevention claims) is preferred over partial labelling (e.g. the use of a heart symbol to imply a health claim), but primarily for risk reduction claims. There is no significant difference between a function claim, such as "good for your heart" and partial labelling in the form of a red heart symbol. The results also suggest that consumers on average respond positively to verification of health claims by government and the third party agencies, however, the Latent Class models reveal considerable heterogeneity in consumer attitudes toward the source of verification. The influences of key-socio-demographic (e.g. income, education and health status) and attitudinal factors (e.g. attitude, trust and knowledge) provide further insights into consumer responses in the choice experiment to identify different consumer segments. Moreover, the results reveal reference-dependent effects where perceived losses of ingredient or price attributes have a greater influence on consumer choice than perceived gains. In terms of industry and public policy implications, this study suggests that food manufacturers in Canada would benefit from the ability to make more precise health claims. The implications derived from the Latent Class Models could help the Canadian functional food industry to identify target consumer segments with different characteristics for the purpose of developing marketing strategies. Furthermore, the results of this study suggest that Canadian consumers are receptive to both full labelling and partial labelling. It indicates that public policy makers need to pay attention to effectively regulating health claims for functional foods so as to balance the need for credible health claims to facilitate the development of the functional food sector with the imperative of protecting consumers from misleading health claims. Public policy makers should also be aware that the verification of health claims plays an important role in reducing consumers' uncertainty and making health claims more credible.
1083

Aggregated Versus Disaggregated Forward Looking Information: Effects on Risk Taking

Parekh, Rishabh 01 January 2012 (has links)
In previous research, aggregation of returns has been found as a way to counteract the risk averse behavior that is the result of investors' myopia. This paper expands the study of aggregation by analyzing its effect on forward looking probabilities. Namely, through the disaggregation of future information, subjects become myopic and trade with varying risk preferences. In an experimental market, subjects trading securities with disaggregated forward looking information are found to 'buy high and sell low', while subjects trading the same securities, but with aggregated information, trade with more consistent risk preferences.
1084

Performance des jets et mesure de la section efficace de production de paires t tbar dans le canal tout hadronique auprès du détecteur ATLAS.

Ghodbane, N. 22 November 2012 (has links) (PDF)
Dans ce mémoire, nous présentons nos travaux de recherche que nous avons menés au sein de la collaboration ATLAS au LHC dans la période 2005-2012. Ces travaux inclus la préparation de deux des sous-détecteurs composant le système de détecteurs internes, l'étude et l'optimisation des algorithmes de reconstruction des jets afin d'en améliorer les performances et enfin l'utilisation des données collectées à partir des collisions proton-proton pour une énergie de collision de 7 TeV dans le centre de masse pour en extraire la mesure de la section efficace de production du quark top dans le mode de désintégration tout-hadronique.
1085

Impact of free-living diazotrophs, Azospirillum lipoferum and Gluconacetobacter azotocaptans, on growth and nitrogen utilization by wheat (Triticum aestivum cv. Lillian)

2013 April 1900 (has links)
Nitrogen (N) is an essential plant nutrient, widely applied as N-fertilizer to improve yields of agriculturally important crops. An alternative to fertilizer use could be the exploitation of plant growth-promoting bacteria, capable of enhancing growth and yield of many plant species. Azospirillum and Gluconacetobacter are root colonizing, free-living, N2-fixing bacteria (diazotrophs) with the potential to transfer fixed N to associated plants. The purpose of this study was to evaluate the agronomic efficiency of two diazotrophs, Azospirillum lipoferum and Gluconacetobacter azotocaptans, inoculated onto wheat. Physiological parameters and yield components were evaluated. The objectives of this study were to: 1) determine the survival of each diazotroph species on wheat seeds over time; 2) determine the survival of A. lipoferum and G. azotocaptans inoculated on wheat seed treated with a fungicide seed treatment, Dividend® XL RTA®; 3) determine if inoculation of wheat with the diazotrophs under controlled conditions causes an increase in dry matter, N2-fixation and N uptake; 4) determine if fertilizer N applied at three levels influences atmospheric N2-fixation by A. lipoferum or G. azotocaptans; 5) determine if inoculation of wheat with A. lipoferum or G. azotocaptans under field conditions causes any increase in dry matter, N2-fixation and N uptake; 6) determine if N-fertilization levels under field conditions influenced N2-fixation by A. lipoferum or G. azotocaptans. In order to meet these objectives lab, growth chamber, and field studies were completed. Laboratory investigations revealed that the decline in recovery of colony forming units (CFU) of G. azotocaptans was not significantly different (P<0.05) for any seed treatment. There was a general decrease in CFU over time regardless of seed treatment. Analysis of the recovered CFU of A. lipoferum over time showed that there was a significant difference (P<0.05) between both the non-sterilized seed and the Dividend® XL RTA® treated seed when compared sterilized seed. Recovery of CFU on sterilized seed declined at a more rapid rate compared to the other two seed treatments. Gluconacetobacter azotocaptans and A. lipoferum were not negatively influenced by the Dividend® XL RTA® seed treatment. Also, both diazotrophs were able to compete with other microorganisms that may have been on the seed coat of unsterilized seeds. Azospirillum lipoferum and G. azotocaptans were able to fix atmospheric N, but, there were no significant (P<0.05) differences between the diazotroph species. Additions of fertilizer N enhanced N2-fixation, in both the growth chamber and field studies. As the amount of fertilizer N increased, so did the %Ndfa and N uptake. In the growth chamber study, inoculated wheat, and fertilized with 12.2 and 24.5 µg N g-1 had the highest %Ndfa of 25.5%, and wheat fertilized with 24 µg N g-1 had the highest N uptake (1.3 g pot-1) at maturity. In the field study, inoculated wheat fertilized with of 80 kg N ha-1 had significantly higher (P<0.05) %Ndfa (10.5%) compared to wheat grown with the other fertilizer levels, which also corresponded to the highest N uptake in wheat plants (47 kg ha-1). The diazotrophs also affected the partitioning of N in the wheat plants differently. Wheat inoculated with A. lipoferum had significantly higher (P<0.05) amounts of N accumulated in heads of plants, and wheat inoculated with G. azotocaptans had significantly higher (P<0.05) amounts of N accumulated in stems of plants. However, this trend was not evident in the field study.
1086

Thermo-hydro-mechanical analysis of soft rock. Application to a large scale heating test and large scale ventilation test

Muñoz, Juan Jorge 30 March 2007 (has links)
Esta Tesis está dirigida al análisis teórico y experimental de problemas acoplados Termo-Hidro Mecánico (THM) que se desarrollan en formaciones geológicas profundas destinadas al almacenamiento de residuos radiactivos de alta actividad. En las últimas décadas, han sido estudiadas las formaciones arcillosas para ser utilizadas como barreras geológicas debido a su reducida conductividad hidráulica. La degradación de las rocas arcillosas producida por efectos de temperatura y por efectos de variación en el grado de saturación, es un factor de fundamental importancia, que es actualmente investigado en ensayos in situ a gran escala, como así también en ensayos de laboratorio. En ésta tesis, la roca Opalinus Clay ha sido ampliamente caracterizada mediante ensayos de laboratorios. Desde un punto de vista macro-estructural se ha obtenido la curva de retención de agua, conductividad hidráulica, resistencia y deformación. El análisis micro-estructural está enfocado a la caracterización mineralógica obtenida por difracción de rayos X, la distribución del tamaño de los poros determinada por porosimetría de mercurio (MIP) y microscopía electrónica (SEM). La tesis describe también un ensayo in situ de calentamiento diseñado para analizar la interacción entre la barrera de ingeniería (bloques de bentonita compactada) y la barrera geológica (Opalinus clay). Esta interacción ha sido analizada a través de simulaciones numéricas realizadas con el código de elementos finitos CODE_BRIGHT. Una célula termo-hidráulica fue especialmente diseñada para observar el comportamiento THM de la roca en condición drenada y no drenada, a través de pulsos de calor. Parámetros térmicos e hidráulicos de la roca fueron determinados por retro análisis a través de simulaciones numéricas realizadas con CODE_BRIGHT. Desde el punto de vista mecánico, un modelo constitutivo ha sido formulado en 3D e implementado en CODE_BRIGHT con el objetivo de reproducir el comportamiento mecánico anisótropo y rotura frágil de las rocas arcillosas. El modelo es formulado en un marco viscoplástico y considera la resistencia y deformabilidad de la matriz y de las juntas. El criterio de falla de la matriz y de las juntas es definido por superficies de fluencias hiperbólicas en el espacio de tensiones p-J y &#964;&#8722;&#963;, respectivamente. El comportamiento frágil de las rocas arcillosas es simulado por un reblandecimiento isótropo y cinemático definido en términos de trabajo de deformación plástico. El modelo constitutivo ha sido calibrado mediante ensayos triaxiales de laboratorio realizados en especimenes con diferentes ángulos de buzamiento. El modeloconstitutivo anisótropo ha sido aplicado a la simulación numérica en 3D de un ensayo de calentamiento in-situ. Una simulación numérica en 3D de un ensayo de ventilación in-situ realizado en un micro-túnel sin recubrimiento ha sido realizada para reproducir el brusco cambio de permeabilidad por efectos de secado de la roca. En este caso, un modelo hidráulico que considera la apertura de las juntas por efectos de secado ha sido implementado para reproducir los cambios de permeabilidad en excavaciones subterráneas. / This thesis deals with the theoretical and experimental analysis of the coupled Thermo- Hydro-Mechanical (THM) processes developed in geological formations suitable for the repository of radioactive waste of high activity. In the last decades, the argillaceous formations have been studied to be used as geological barriers, due to its reduced hydraulic conductivity. The degradation of clay shales induced by temperature and saturation effects is an important factor which is currently being investigated in large scale in situ tests as well as in laboratory studies. In this thesis, the Opalinus clay rock has been widely characterized by means of laboratory tests. From a macro-structural point of view, the water retention curve, hydraulic conductivity, strength and deformability parameters have been determined. The micro-structural analysis is focused to the mineralogical characterization obtained by means of X ray diffraction, pore size distribution (PSD) determined by means of mercury intrusion porosimetry (MIP) and scanning electronic microscopy (SEM). The thesis describes also a large scale heating in situ test designed to analyze the interaction between the engineer barrier (compacted bentonite blocks) and by the geological barrier, (Opalinus clay). This interaction has been analyzed by means of numerical simulations performed with the finite element code CODE_BRIGHT. A thermo hydraulic cell was specially designed to observe the coupled THM behaviour of the clay shale rock under drained and undrained conditions by means of heat pulses. Thermal and hydraulic parameters of rock were determined by means of back-analysis performed with the help of CODE_BRIGHT. In order to reproduce the anisotropic and brittle behaviour of the clay shale, a 3D mechanical constitutive model has been formulated and implemented in CODE_BRIGHT. The constitutive model is formulated in a viscoplastic framework and it considers the strength and deformability of both matrix and discontinuities (joints). The failure criterion of the matrix and the joints is defined by means of hyperbolic yield surfaces in the p-J and &#964;-&#963; stress space, respectively. The brittle behaviour of clay shale is simulated by means of isotropic and kinematic softening defined in terms of a workhardening criterion. The anisotropic constitutive model has been calibrated against triaxial laboratory tests performed on specimens with a main family of discontinuities having different dip angles. The constitutive model has been applied to a 3D numerical simulation of an "in-situ" heating test. A 3D numerical simulation of a ventilation test performed in an unlined micro tunnel was also performed in order to reproduce the changes of the rock permeability by drying effects. In this case, a hydraulic model able to consider the changes in joint thickness by drying effects has been developed to reproduce the changes of permeability in underground excavations.
1087

An Experimental Investigation of the Fire Characteristics of the University of Waterloo Burn House Structure

Klinck, Amanda January 2006 (has links)
This thesis reports on the procedure, results and analysis of four full scale fire tests that were performed at the University of Waterloo's Live Fire Research Facility. The purpose of these tests was to investigate the thermal characteristics of one room of the Burn House structure. Comparisons were made of Burn House experimental data to previous residential fire studies undertaken by researchers from the University of Waterloo. This analysis showed similarities in growth rate characteristics, illustrating that fire behaviour in the Burn House is typical of residential structure fire behaviour. The Burn House experimental data was also compared to predictions from a fire model, CFAST. Recommendations were made for future work in relation to further investigation of the fire characteristics of the Burn House.
1088

Observations of Atmospheric Gases Using Fourier Transform Spectrometers

Fu, Dejian January 2007 (has links)
Remote sensing of atmospheric gases improves our understanding of the state and evolution of the Earth’s environment. At the beginning of the thesis, the basic principles for the retrieval of concentrations of atmospheric gases from spectra are presented with a focus on ground-based observations. An overview of the characteristic features of different platforms, viewing geometries, measurement sites, and Fourier Transform Spectrometers (FTSs) used in the measurements are provided. The thesis covers four main projects. The first study of the global distribution of atmospheric phosgene was carried out using a total of 5614 measured profiles from the satellite-borne Atmospheric Chemistry Experiment FTS (ACE-FTS) spanning the period February 2004 through May 2006. The phosgene concentrations display a zonally symmetric pattern with the maximum concentration located approximately over the equator, at about 25 km in altitude, and the concentrations decrease towards the poles. A layer of enhanced concentration of phosgene spans the lower stratosphere at all latitudes, with volume mixing ratios of 20-60 pptv. The reasons for the formation of the phosgene distribution pattern are explained by the insolation, lifetime of phosgene and the Brewer-Dobson circulation. The ACE observations show lower phosgene concentrations in the stratosphere than were obtained from previous observations in the 1980s and 1990s due to a significant decrease in source species. The Portable Atmospheric Research Interferometric Spectrometer for the Infrared (PARIS-IR) is a copy of the ACE-FTS that was designed for ground-based and balloon-borne measurements. The first balloon flight was part of the Middle Atmosphere Nitrogen TRend Assessment (MANTRA) 2004 balloon payload. Some useful engineering information was obtained on the thermal performance of the instrument during the flight. As part of the MANTRA program, a ground-based inter-instrument comparison campaign was conducted with the objective of assessing instrument performance, and evaluating data processing routines and retrieval codes. PARIS-IR provides similar quality results for stratospheric species as does the University of Toronto FTS. An advanced study was carried out for the Carbon Cycle science by Fourier Transform Spectroscopy (CC-FTS) mission, which is a proposed future satellite mission to obtain a better understanding of the sources and sinks of greenhouse gases in the Earth’s atmosphere by monitoring total and partial columns of CO2, CH4, N2O, and CO in the near infrared together with the molecular O2 column. To evaluate the spectral regions, resolution, optical components, and spectroscopic parameters required for the mission, ground-based Fourier transform spectra, recorded at Kiruna, Kitt Peak, and Waterloo, were used. Dry air volume mixing ratios of CO2 and CH4 were retrieved from the ground-based observations. A FTS with a spectral resolution of 0.1 cm-1, operating between 2000 and 15000 cm-1, is suggested as the primary instrument for the mission. Further progress in improving the atmospheric retrievals for CO2, CH4 and O2 requires new laboratory measurements to improve the spectroscopic line parameters. Atmospheric observations were made with three FTSs at the Polar Environment Atmospheric Research Laboratory (PEARL) during spring 2006. The vertical column densities of O3, HCl, HNO3, HF, NO2, ClONO2 and NO from PARIS-IR, the Eureka DA8 FTS, and the ACE-FTS show good agreement. Chorine activation and denitrification in the Arctic atmosphere were observed in the extremely cold stratosphere near Eureka, Nunavut, Canada. The observed ozone depletion during the 2006 campaign was attributed to chemical removal.
1089

Greenhouse gas cycling in experimental boreal reservoirs

Venkiteswaran, Jason James January 2008 (has links)
Hydroelectric reservoirs account for 59% of the installed electricity generating capacity in Canada and 26% in Ontario. Reservoirs also provide irrigation capacity, drinking water, and recreational opportunities. Further, they continue to be built in northern Canada, neighbouring boreal countries, and around the world. Yet given their socio-economic importance, they are understudied with respect to greenhouse gas emissions, nutrient and mercury cycling, and aquatic metabolism. As one of many electricity generating options, hydroelectricity is viewed as well-tested because of its long history and diverse applications in mega-projects, run-of-the-river dams, and small, local applications. It is also considered renewable from a fuel stand-point because an adequate long-term supply of water is assumed. One of several significant criticisms of hydroelectric development is that reservoirs may be a significant source of greenhouse gases to the atmosphere relative to the amount of electricity produced due to flooding the landscape. As a result of the dearth of information on reservoir development and both greenhouse gases and aquatic metabolism, a pair of whole-ecosystem reservoir experiments were conducted staring in 1991. Three upland boreal forest reservoirs with differing amounts of pre-flood stored organic carbon were built in northwestern Ontario and flooded for five years. The rates of net greenhouse gas production in these reservoirs were determined by calculating mass budgets for carbon dioxide and methane. Additionally, rates of biological processes were determined by combining the mass budgets with measurements of the stable isotopes of carbon and oxygen. Assembling mass and isotope-mass budgets required three related projects on gas exchange, methane oxidation, and oxygen isotopes. To estimate the gas exchange coefficient for each of the upland reservoirs, a comparative-methods study was undertaken. Methane oxidation enrichment factors were determined in upland and wetland boreal reservoirs so that the importance of methane oxidation in these ecosystems could be assessed. In order to interpret the diel changes in both oxygen concentrations and their isotopic ratios, a dynamic model was developed. This model, PoRGy, was successfully applied to the upland boreal reservoirs as well as prairie rivers and ponds. Further, PoRGy was used to understand the interplay between the key parameters that control oxygen concentrations, to compare aquatic ecosystems, to make quantitative estimates of ecosystem metabolism, and to assess the vulnerability of aquatic ecosystems under various environmental stressors. Carbon isotope-mass budgets were used to conclude that community respiration rates declined quickly in the upland reservoirs and had declined by half over five years. This suggested that the most labile organic carbon is quickly consumed but decomposition continued for the five-year life of the project. Net primary production rates were similar for three years, with a small peak in the second or third year, before declining by half by the fifth year. Together, these results indicated that aquatic metabolism slowed over five years while the reservoirs remained a source of greenhouse gases to the atmosphere each year. Net methane production was greatest in the third year of flooding then decreasing by about half by the fifth year. Methane ebullition also peaked in the third year and declined by two-thirds by the fifth year. Together, these results indicated that methanogenesis was greatest in the third year of flooding. The flux of methane to the atmosphere grew in importance relative to that of carbon dioxide over the five years of the experiment. Community respiration and primary production could not be estimated directly from the oxygen isotope-mass budgets since the oxygen respiration enrichment factor remains poorly constrained. Instead, three estimates were made, each based on a different assumption. In general, these estimates suggested that rates of community respiration and primary production decreased slightly for three years and most rapidly in the final two years. The oxygen isotope-mass budgets provided a new method for assessing and constraining community metabolism and greenhouse gas fluxes to the atmosphere. One of the major hypotheses of the whole-ecosystem reservoir experiments was that pre-flood organic carbon stores less tree boles were positively related to greenhouse gas fluxes. Within the three upland boreal forest reservoirs, this hypothesis did not hold true. Over five years, community respiration in the three reservoirs was within 5% of each other. When methane is included, to assess total greenhouse gas fluxes to the atmosphere, the reservoirs were within 1% of each other. Organic carbon stores were therefore poor short-term predictors of carbon lability and greenhouse gas fluxes. This research presented two methods for determining biological rates at the whole-ecosystem scale: one using carbon isotopes and one using oxygen isotopes. Temporal evolution of greenhouse gas cycling within the upland reservoirs was different than in the wetland reservoir and should inform how reservoir development is done vis-à-vis the amount of flooded land of each type versus electricity production. Medium-term estimates of greenhouse gas fluxes suggest that upland reservoirs do not have adequate pre-flood organic carbon stores to sustain elevated levels of decomposition the way wetlands do. The strong evidence of continued production of dissolved organic carbon in the upland reservoirs should concern operators of municipal drinking water reservoirs since elevated dissolved organic carbon can make disinfection difficult.
1090

Market Feedback and Valuation Judgment: Revisited

Freybote, Julia 11 May 2012 (has links)
Appraisers receive feedback from a variety of sources such as other appraisers, clients and the real estate market. Previous studies find client feedback to introduce an upward bias into commercial and residential appraisal judgments. Hansz and Diaz (2001) find that the provision of transaction price (market) feedback for a previously valued property biases commercial appraisers upwardly in subsequent valuations. The authors provide market optimism, client feedback and a reduced conservatism bias as explanations for their findings. However, previous client and market feedback studies were conducted in upward-trending or booming real estate markets. The identified upward bias in valuation judgments may have been the result of positive real estate market conditions. This study investigates the impact of transaction price feedback on residential appraisal judgment in a changed appraisal task environment, characterized by a depressed housing market, market pessimism, conservative lenders and a changed residential appraisal industry. As Hansz and Diaz (2001) find an upward appraisal bias in an upward-trending market, I expect market feedback to introduce a downward bias into residential appraisal judgments in a depressed market. Compared to a “no feedback” control group, residential appraisers receiving the feedback that their previous value estimates were too high, compared to the realized transaction price, are expected to make significantly lower subsequent value judgments for an unrelated property. The “too low” feedback is not expected to have an impact on subsequent value judgments. I test the hypotheses with a controlled experiment using a pre-posttest design. The experimental design has one factor (transaction price feedback) fixed at three different levels (“too low”, “too high”, “no feedback”). A posttest-only validity control group is added to test for a potential testing bias in the pre-posttest design. This study uses residential expert appraisers, defined as active Oregon State certified residential appraisers, from the Portland metropolitan statistical area (MSA) as subjects. Experimental subjects are randomly selected from a list of all certified residential appraisers in the Portland MSA. Experimental subjects are randomly assigned to the control and treatment groups (10 subjects per group; N=40). Subjects in the treatment groups and pre-posttest “no feedback” control group are asked to value a lot of vacant residential land in the geographically unfamiliar Roswell, Georgia. After they provide their value estimates for this first valuation case, subjects in the treatment groups are given a note from a seller’s broker stating the transaction price for the previously valued property. Subjects in the “too high” feedback group receive a transaction price that is 15% below their estimates and subjects in the “too low” feedback group receive a transaction price that is 15% above their value estimates. The control group receives no feedback. All treatment and control groups are then given a second (unrelated) valuation case of vacant residential land in Newnan, Georgia and asked for their value estimate. The experiment is concluded with an exit questionnaire containing demographic and professional questions as well as manipulation checks. The experimental data are analyzed using the parametric independent samples t-test. The assumptions of normality and equal variances are not violated by the dataset. A one-way ANOVA and the non-parametric Mann-Whitney U test are used as robustness checks. All statistical tests conclude that neither the mean of the “too high” feedback group nor the mean of the “too low” feedback group are statistically different at the 5% level from the mean of the “no feedback” control group. Thus, no evidence is found that transaction price feedback biases residential appraisal judgments in a depressed market. The insignificant results are further analyzed to assess whether they are due to a non-reception of the treatment by subjects, low statistical power or a non-existing relationship: The explanation that subjects did not read the treatment note can be excluded. A power analysis reveals low statistical power and very small effect sizes for both treatments. An alternative explanation for the insignificant results is the absence of the hypothesized relationship. The main client group of experimental subjects is appraisal management companies, which due to legislation passed after 2007, work with appraisers on behalf of lenders. As a consequence, residential appraisers do not receive direct client feedback anymore (compared to Hansz and Diaz, 2001) and may not respond subconsciously to the “too high” feedback.

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