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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.
101

The consolidation of forecests with regression models

Venter, Daniel Jacobus Lodewyk January 2014 (has links)
The primary objective of this study was to develop a dashboard for the consolidation of multiple forecasts utilising a range of multiple linear regression models. The term dashboard is used to describe with a single word the characteristics of the forecasts consolidation application that was developed to provide the required functionalities via a graphical user interface structured as a series of interlinked screens. Microsoft Excel© was used as the platform to develop the dashboard named ConFoRM (acronym for Consolidate Forecasts with Regression Models). The major steps of the consolidation process incorporated in ConFoRM are: 1. Input historical data. Select appropriate analysis and holdout samples. 3. Specify regression models to be considered as candidates for the final model to be used for the consolidation of forecasts. 4. Perform regression analysis and holdout analysis for each of the models specified in step 3. 5. Perform post-holdout testing to assess the performance of the model with best holdout validation results on out-of-sample data. 6. Consolidate forecasts. Two data transformations are available: the removal of growth and time-periods effect from the time series; a translation of the time series by subtracting ̅i, the mean of all the forecasts for data record i, from the variable being predicted and its related forecasts for each data record I. The pre-defined regression models available for ordinary least square linear regression models (LRM) are: a. A set of k simple LRM’s, one for each of the k forecasts; b. A multiple LRM that includes all the forecasts: c. A multiple LRM that includes all the forecasts and as many of the first-order interactions between the input forecasts as allowed by the sample size and the maximum number of predictors provided by the dashboard with the interactions included in the model to be those with the highest individual correlation with the variable being predicted; d. A multiple LRM that includes as many of the forecasts and first-order interactions between the input forecasts as allowed by the sample size and the maximum number of predictors provided by the dashboard: with the forecasts and interactions included in the model to be those with the highest individual correlation with the variable being predicted; e. A simple LRM with the predictor variable being the mean of the forecasts: f. A set of simple LRM’s with the predictor variable in each case being the weighted mean of the forecasts with different formulas for the weights Also available is an ad hoc user specified model in terms of the forecasts and the predictor variables generated by the dashboard for the pre-defined models. Provision is made in the regression analysis for both of forward entry and backward removal regression. Weighted least squares (WLS) regression can be performed optionally based on the age of forecasts with smaller weight for older forecasts.
102

Spatial competition and nonlinear responses in marketing

Krider, Robert E. 11 1900 (has links)
Spatial competition, in the context of industry-wide changes in retailing formats and strategies, is addressed in this dissertation from a theoretical modelling perspective. Chapter2 develops a normative individual choice model to explore how "power retailers" affect grocery shopping behaviour, and, consequently, market share. Power retailers are very large retail outlets that compete primarily on price, and are known variously as warehouse clubs, category killers, and superstores. The model shows that consideration of consumer stockpiling can lead to an "increasing returns" nonlinear response of market share to price reductions, and that the effect is not noticeable when competitors have small price differences. The model also differentiates between perishable and nonperishable goods, and shows that this may drive planned multistore shopping. Chapter 3 starts with the observation that competent management in many sectors of retailing, including grocery retailing, requires an ability to respond quickly and effectively to unexpected adversity. This dynamic is included in an oligopolistic spatial interaction model, and the system is shown to evolve to a novel and robust stochastic steady state known as self-organized criticality (SOC). One characteristic of the SOC state is that it allows small exogenous shocks to produce large responses at a rate greater than would be expected if the law of large numbers applied. This work represents the first known investigation of SOC in a marketing setting. / Business, Sauder School of / Graduate
103

An empirical test of a probabilistic model of consumer spatial behaviour

Wiginton, John Cameron January 1966 (has links)
This thesis is concerned with making an empirical test of a probabilistic model of intra-urban retail trade interactions. The model, termed a probabilistic model of consumer spatial behaviour, is related to a series of models in social science known as gravimetric models. The particular model considered used store area and distance in time units as its major variables. It also includes an exponential parameter, the value of which must be estimated from empirical data. The major hypothesis on which the model is tested is based on the behaviour of this parameter. The hypothesis states that values of this parameter vary significantly, depending upon the type of shopping trip being considered. The type of shopping trip is determined by the particular type of shopping goods apparently sought by the consumer. The hypothesis is tested by means of empirical data on consumer purchasing patterns gathered in the Vancouver Metropolitan area through the use of an interview survey conducted randomly by census tracts. The data are analyzed in an especially written, iterative computer programme. Statistical tests usually applied to such data are found to be inadequate to the analysis of the results. A special test which is intended to show the sensitivity of the model to the parameter is presented and applied. An independent test of the representativeness of the data is presented. The data are found to be representative, but the model is found to be insensitive to the behaviour of the parameter. Further, measures of variation in observed behaviour explained by the model are generally low. It is concluded that the model in its present form does not apply to Vancouver. The thesis is unable to conclude whether changes are required in the factors of the model or in the relationship specified, though there is evidence which shows that both may require attention. / Business, Sauder School of / Graduate
104

Housing demand : an empirical intertemporal model

Schwann, Gregory Michael January 1987 (has links)
I develop an empirical model of housing demand which is based as closely as possible on a theoretical intertemporal model of consumer demand. In the empirical model, intertemporal behavior by households is incorporated in two ways. First, a household's expected length of occupancy in a dwelling is a parameter in the model; thus, households are able to choose when to move. Second, a household's decision to move and its choice of dwelling are based on the same intertemporal utility function. The parameters of the utility function are estimated using a switching regresion model in which the decision to move and the choice of housing quantity are jointly determined. The model has four other features: (1) a characteristics approach to housing demand is taken, (2) the transaction costs of changing dwellings are incorporated in the model, (3) sample data on household mortgages are employed in computing the user cost of owned dwellings, and (4) demographic variables are incorporated systematically into the household utility function. Rosen's two step proceedure is used to estimate the model. Cragg's technique for estimating regressions in the presence of heteroscedasticity of unknown form is used to estimate the hedonic regressions in step one of the proceedure. In the second step, the switching regression model, is estimated by maximum likelihood. A micro data set of 2,513 Canadian households is used in the estimations. The stage one hedonic regressions indicate that urban housing markets are not in long run equilibrium, that the errors of the hedonic regressions are heteroscedastic, and that simple functional forms for hedonic regressions may perform as well as more complex forms. The stage two estimates establish that a tight link between the theoretical and empirical models of housing demand produces a better model. My results show that conventional static models of housing demand are misspecified. They indicate that households have vastly different planned lengths of dwelling occupancy. They also indicate that housing demand is determined to a great extent by demographic factors. / Arts, Faculty of / Vancouver School of Economics / Graduate
105

Sensitivity and uncertainty analysis of subsurface drainage design

Wu, Guangxi January 1988 (has links)
Literature on subsurface drainage theories, determination of drainage parameters, and analysis approaches of uncertainty was reviewed. Sensitivity analysis was carried out on drain spacing equations for steady state and nonsteady state, in homogeneous soils and in layered soils. It was found that drain spacing is very sensitive to the hydraulic conductivity, the drainage coefficient, and the design midspan water table height. Spacing is not sensitive to the depth of the impermeable layer and the drain radius. In transient state, spacing is extremely sensitive to the midspan water table heights if the water table fall is relatively small. In that case steady state theory will yield more reliable results and its use is recommended. Drain spacing is usually more sensitive to the hydraulic conductivity of the soil below the drains than to that of the soil above the drains. Therefore, it is desirable to take samples from deeper soil when measuring hydraulic conductivity. A new spacing formula was developed for two-layered soils and a special case of three-layered soils with drains at the interface of the top two layers. This equation was compared with the Kirkham equation. The new formula yields spacings close to the Kirkham equation if the hydraulic conductivity of the soil above the drains is relatively small; otherwise, it tends to give more accurate results. First and second order analysis methods were employed to analyze parameter uncertainty in subsurface drainage design. It was found that conventional design methods based on a deterministic framework may result in inadequate spacing due to the uncertainty involved. Uncertainty may be incorporated into practical design by using the simple equations and graphs presented in this research; the procedure was illustrated through an example. Conclusions were drawn from the present study and recommendations were made for future research. / Applied Science, Faculty of / Graduate
106

On the inertial stability of coastal flows

Helbig, James Alfred January 1978 (has links)
This thesis investigates two separate but related problems. In Part I a study is made of the propagation of continental shelf waves and barotropic Rossby waves in a steady, laterally sheared current of the form V + Є W, where W is a centred random function and Є << 1. If the correlation length of W is small compared with the characteristic horizontal length scale of the system; for example, the shelf width or a channel width, the waves are unstable. Their growth rate is largely determined by the magnitude of the correlation length, while the phase speed is given by the sum of weighted averages of the mean current V and the lateral gradient of potential vorticity. Application of the theory to the Brooks and Mooers (1977a) model of the Florida Straits yields wave parameters that are in accord with those measured by Duing (1975). In Part II, an attempt is made to understand the dynamics governing observed low-frequency currents in the Strait of Georgia (GS). A simple two-layer model indicates that the mean currents in GS are probably baroclinically stable. A barotropic stability model implies that a shear instability might be of some importance. However, the analysis of current meter data shows that the velocity components of the fluctuations are either nearly in phase or close to 180° out of phase; this means that the motions are not due to the type of waves considered here. Analysis of the relationship between the winds and currents in both the frequency and time domains implies that the wind may play an indirect role in forcing GS motions. It is conjectured that the wind and tide interact with the Fraser River outflow to modulate the estuarine circulation in the system and force low-frequency currents. Direct nonlinear interaction between tidal constituents produces a coherent fortnightly variation in the currents, but cannot account for the observations. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
107

Hydrodynamic modeling of shallow basins

Marchand, Philippe, 1972- January 1997 (has links)
No description available.
108

Is source memory continuous or discrete? : an Roc analysis.

Wong, Mungchen 01 January 2003 (has links) (PDF)
No description available.
109

A fundamental flotation model and flotation column scale-up /

Dobby, G. S. (Glenn Stephen), 1952- January 1984 (has links)
No description available.
110

Finite amplitude waves in a model boundary layer

Balagondar, Puttappa Mallappa. January 1981 (has links)
No description available.

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