391 |
Scheduling in Large Scale MIMO Downlink SystemsBayesteh, Alireza January 2008 (has links)
This dissertation deals with
the problem of scheduling in wireless MIMO (Multiple-Input Multiple-Output) downlink systems. The focus is on the large-scale systems when the number of subscribers is large.
In part one, the problem of user selection in MIMO Broadcast channel is studied. An efficient user selection algorithm is proposed and is shown to achieve the sum-rate capacity of the system asymptotically (in terms of the number of users), while requiring (i)~low-complexity precoding scheme of zero-forcing beam-forming at the base station, (ii)~low amount of feedback from the users to the base station, (iii)~low complexity of search.
Part two studies the problem of MIMO broadcast channel with partial Channel State Information (CSI) at the transmitter. The necessary and sufficient conditions for the amount of CSI at the transmitter (which is provided to via feedback links from the receivers) in order to achieve the sum-rate capacity of the system are derived. The analysis is performed in various singnal to noise ratio regimes.
In part three, the problem of sum-rate maximization in a broadcast channel with large number of users, when each user has a stringent delay constraint, is studied. In this part, a new definition of fairness, called short-term fairness is introduced. A scheduling algorithm is proposed that achieves: (i) Maximum sum-rate throughput and (ii) Maximum short-term fairness of the system, simultaneously, while satisfying the delay constraint for each individual user with probability one.
In part four, the sum-rate capacity of MIMO broadcast channel, when the channels are Rician fading, is derived in various scenarios in terms of the value of the Rician factor and the distribution of the specular components of the channel.
|
392 |
Territoriality and Behaviour On and Around Large Vertical Publicly-Shared DisplaysAzad, Alec 22 May 2012 (has links)
Large displays and information kiosks are becoming increasingly common installations in public venues to provide an efficient self-serve means for patrons to access information and/or services. They have evolved over a relatively short period of time from non-digital, non-interactive static displays to more elaborate media-rich digital interactive systems. While the content and purposes of kiosks have changed, they are still largely based on the traditional single-user-driven design paradigm despite the fact that people often venture to these venues in small social groups, i.e., with family and/or friends. This often limits how groups collaborate and forces transactions to be serialized. This thesis explores design constraints for interaction by multiple social groups in parallel on shared large vertical displays.
To better understand design requirements for these systems, this research is separated into two parts: a preliminary observational field study and a follow-up controlled study. Using an observational field study, fundamental patterns of how people use existing public displays are studied: their orientation, positioning, group identification, and behaviour within and between social groups just-before, during, and just-after usage. These results are then used to motivate a controlled experiment where two individuals or two pairs of individuals complete tasks concurrently on a low-fidelity large vertical display. Results from the studies demonstrate that vertical surface territories are similar to those found in horizontal tabletops in function, but their definitions and social conventions are different. In addition, the nature of use-while-standing systems results in more complex and dynamic physical territories around the display. We show that the anthropological notion of personal space must be slightly refined for application to vertical displays.
|
393 |
Comparison between Optimization and Heuristic Methods for Large-Scale Infrastructure Rehabilitation ProgramsBinhomaid, Omar January 2012 (has links)
Civil infrastructure systems are the foundation of economic growth and prosperity in all nations. In recent years, infrastructure rehabilitation has been a focus of attention in North America and around the world. A large percentage of existing infrastructure assets is deteriorating due to harsh environmental conditions, insufficient capacity, and age. Ideally, an assets management system would include functions such as condition assessment, deterioration modeling, repair modeling, life-cycle cost analysis, and asset prioritization for repair along a planning horizon. While many asset management systems have been introduced in the literature, few or no studies have reported on the performance of either optimization or heuristic tools on large-scale networks of assets.
This research presents an extensive comparison between heuristic and genetic-algorithm optimization methods for handling large-scale rehabilitation programs. Heuristic and optimization fund-allocation approaches have been developed for three case studies obtained from the literature related to buildings, pavements, and bridges with different life cycle cost analysis (LCCA) formulations. Large-scale networks were constructed for comparing the efficiency of heuristic and optimization approaches on large-scale rehabilitation programs. Based on extensive experiments with various case studies on different network sizes, the heuristic technique proved its practicality for handling various network sizes while maintaining the same efficiency and performance levels. The performance of the genetic algorithm optimization approach decreased with network size and model complexity. The optimization technique can provide a high performance level, given enough processing time.
|
394 |
Exploring factors affecting math achievement using large scale assessment results in SaskatchewanLai, Hollis 16 September 2008 (has links)
Current research suggests that a high level of confidence and a low level of anxiety are predictive of higher math achievement. Compared to students from other provinces, previous research has found that Saskatchewan students have a higher level of confidence and a lower level of anxiety for learning math, but still tend to achieve lower math scores compared to students in other provinces. The data suggest that there may be unique factors effecting math learning for students in Saskatchewan. The purpose of the study is to determine the factors that may affect Saskatchewan students math achievement. Exploratory factor analyses and regression methods were employed to investigate possible traits that aid students in achieving higher math scores. Results from a 2007 math assessment administered to grade 5 students in Saskatchewan were used for the current study. The goal of the study was to provide a better understanding of the factors and trends unique to students for mathematic achievements in Saskatchewan.<p> Using results from a province-wide math assessment and an accompanying questionnaire administered to students in grade five across public school in Saskatchewan (n=11,279), the present study found statistical significance in three factors that have been supported by previous studies to influence math achievement differences, specifically in (1) confidence in math, (2) parental involvement in math and (3) extracurricular participation in math. The three aforementioned factors were found to be related to math achievement as predicted by the Assessment for Learning (AFL) program in Saskatchewan, although there were reservations to the findings due to a weak amount of variances accounted for in the regression model (r2 =.084). Furthermore, a multivariate analysis of variance indicated gender and locations of schools to have effects on students math achievement scores. Although a high amount of measurement errors in the questionnaire (and subsequently a low variance accounted for by the regression model) limited the scope and implications of the model, future implications and improvements are discussed
|
395 |
Modeling and validation of crop feeding in a large square balerRemoué, Tyler 01 November 2007 (has links)
This study investigated the crop density in a New Holland BB960 (branch of CNH Global N.V.) large square baler as examined by crop trajectory from the precompression room to the bale chamber. This study also examined both the top and bottom plunger pressures and critical factors affecting the final top and bottom bale densities.<p>The crop trajectories (wad of crop) were measured using a high-speed camera from the side of the baler through viewing windows. The viewing windows were divided into four regions for determining the crop displacement, velocity and acceleration. Crop strain was used to evaluate the potential change in density of the crop before being compressed by the plunger. Generally, the vertical crop strain was found to be higher in the top half of the bale compared to the bottom. <p>Average strain values for side measurements were 12.8% for the top and 2.1% for the bottom. Plunger pressures were measured to compare peak pressures between the top and bottom halves of each compressed wad of crop, and to develop pressure profiles based on the plungers position. Results of comparing the mean peak plunger pressures between the top and bottom locations indicated the mean pressures were significantly higher at the top location with the exception of one particular setting. Resulting pressure profile graphs aided in qualitatively describing the compression process for both top and bottom locations.<p>A stepwise regression model was developed to examine the difference in material quantity in the top half of the bale compared to the bottom, based on bale weights. The model indicated that flake setting, stuffer ratio and number of flakes had the greatest effect on maintaining consistent bale density by comparing top to bottom halves of each bale. The R2 (coefficient of determination) value for the developed model was of 59.9%. The R2 was low although could be accounted for due to the limited number of data points in the developed model.
|
396 |
Ska åkerier leasa eller köpa? : Optimal kapitalstruktur för företag med stora investeringarRickard, Svensson, Nicolina, Svensson January 2012 (has links)
This study deals with the road freight sector's capital structure and how leases, loans and equity affect the ratios. The study is based on a ten-year period between 2000-2010 in Sweden. Investments in finance is a complex and interesting subject to study, there are many factors that can affect how the company best choose their investments when they have many great business investment the decisions plays a greater role. The aim is to find an optimal capital structure from a financial investment point of view. The purpose will be answered by the following research question: Are there significant differences between leases, loans and equity financed fleet of factors, profitability, tax, turnover, age, and cyclicality. The study will also examine how debt is related to profit margin, DuPont and the tax, all through a regression analysis. Then were plausible economic theories for the study. These theories are the financial growth cycle, the pecking order theory, Trade off theory, and DuPont. In order to answer the purpose and problem definition, data was collected from the database retriever business where we got a sample of 121 companies. The study is based on bigger haulers that have a turnover of more than 10 million SEK and mainly engaged in road transport. The study has concluded that equity is the alternative that is best in general. To minimize the risks of the company is leasing better but generates less profit. Debt financing is better if you want a fast growth.
|
397 |
Modeling Point Patterns, Measurement Error and Abundance for Exploring Species DistributionsCHAKRABORTY, AVISHEK January 2010 (has links)
<p>This dissertation focuses on solving some common problems associated with ecological field studies. In the core of the statistical methodology, lies spatial modeling that provides greater flexibility and improved predictive performance over existing algorithms. The applications involve prevalence datasets for hundreds of plants over a large area in the Cape Floristic Region (CFR) of South Africa.</p><p>In Chapter 2, we begin with modeling the categorical abundance data with a multi level spatial model using background information such as environmental and soil-type factors. The empirical pattern is formulated as a degraded version of the potential pattern, with the degradation effect accomplished in two stages. First, we adjust for land use transformation and then we adjust for measurement error, hence misclassification error, to yield the observed abundance classifications. With data on a regular grid over CFR, the analysis is done with a conditionally autoregressive prior on spatial random effects. With around ~ 37000 cells to work with, a novel paralleilization algorithm is developed for updating the spatial parameters to efficiently estimate potential and transformed abundance surfaces over the entire region.</p><p>In Chapter 3, we focus on a different but increasingly common type of prevalence data in the so called <italic>presence-only</italic> setting. We detail the limitations associated with a usual presence-absence analysis for this data and advocate modeling the data as a point pattern realization. The underlying intensity surface is modeled with a point-level spatial Gaussian process prior, after taking into account sampling bias and change in land-use pattern. The large size of the region enforces using an computational approximation with a bias-corrected predictive process. We compare our methodology against the the most commonly used maximum entropy method, to highlight the improvement in predictive performance.</p><p>In Chapter 4, we develop a novel hierarchical model for analyzing noisy point pattern datasets, that arise commonly in ecological surveys due to multiple sources of bias, as discussed in previous chapters. The effect of the noise leads to displacements of locations as well as potential loss of points inside a bounded domain. Depending on the assumption on existence of locations outside the boundary, a couple of different models -- <italic>island</italic> and <italic>subregion</italic>, are specified. The methodology assumes informative knowledge of the scale of measurement error, either pre-specified or learned from a training sample. Its performance is tested against different scales of measurement error related to the data collection techniques in CFR.</p><p>In Chapter 5, we suggest an alternative model for prevalence data, different from the one in Chapter 3, to avoid numerical approximation and subsequent computational complexities for a large region. A mixture model, similar to the one in Chapter 4 is used, with potential dependence among the weights and locations of components. The covariates as well as a spatial process are used to model the dependence. A novel birth-death algorithm for the number of components in the mixture is under construction.</p><p>Lastly, in Chapter 6, we proceed to joint modeling of multiple-species datasets. The challenge is to infer about inter-species competition with a large number of populations, possibly running into several hundreds. Our contribution involves applying hierarchical Dirichlet process to cluster the presence localities and subsequently developing measures of range overlap from posterior draws. This kind of simultaneous inference can potentially have implications for questions related to biodiversity and conservation studies. .</p> / Dissertation
|
398 |
Interrelationships Among Large-Scale Atmospheric Circulation Regimes and Surface Temperature Anomalies in the North American ArcticSmolinski, Kelly Katherine 08 July 2004 (has links)
The focus of this study is to examine the mechanisms involved in the interactions among large-scale atmospheric circulation patterns and how they are related to surface air temperature anomalies in the North American Arctic. Historical temperature data sets of Fairbanks, Alaska and Montreal, Quebec have been analyzed with respect to large-scale atmospheric circulation index data sets to investigate surface temperature anomalies in winter during the period 1960 to 2002.
|
399 |
A New Two-Scale Decomposition Approach for Large-Eddy Simulation of Turbulent FlowsKemenov, Konstantin A. 22 June 2006 (has links)
A novel computational approach, Two Level Simulation (TLS), was developed based on the explicit reconstruction of the small-scale velocity by solving the small-scale governing equations on the domain with reduced dimension representing a collection of one-dimensional lines
embedded in the three-dimensional flow domain. A coupled system of equations, that is not based on an eddy-viscosity hypothesis, was derived based on the decomposition of flow variables into the large-scale and the small-scale components without introducing the concept of filtering. Simplified treatment of the small-scale equations was proposed based on modeling of the small-scale advective derivatives and the small-scale dissipative terms in the directions orthogonal to the lines. TLS approach was tested to simulate benchmark cases of turbulent flows, including forced isotropic turbulence, mixing layers and well-developed channel flow, and demonstrated good capabilities to capture turbulent flow features using relatively coarse grids.
|
400 |
The Study on Business Strategy of the Domestic Finance Holding Group in Post Financial Crisis EraChiu, Wen-Chung 30 July 2010 (has links)
This study aimed to explore the business strategies of large financial groups and risk management, analysis of its implementation in practice strategy and decision-making process, and the development of this policy consideration. Understanding of how large financial holding group do its own resources and risk management controls in the financial turmoil of can be maintained after the high-performance business performance and strategy differences before and after the financial crisis
This study using case study research made exploratory study foundings that with framework of the theory, according to the theory of the systematic collection, induction and data analysis. Research framework is divided into six items: 1.Analysis of the financial industry environment: 2.Before the financial crisis management strategy of the case company's direction. 3. after the financial crisis management strategy of the case company's direction. 4. Response strategy in the future. On selection of Fubon Financial and Cathay Financial Holding and Citigroup Bank of Taiwan.The research findings before and after the strategy differences between the financial financial crisis are listed as below:
1. The strategy differences for Cathay Financial Holding
(1)Reorientation recruitment of manpower; (2).More attention to personnel training function; (3).More and more extensive range of professional services; (4). Information technology continue to improve; (5). Risk management control situations contractor for the previous high-risk business
2. The strategy differences for Fubon Financial Holding
(1).To attracts more international and the recognition concept of talents; (2). From quantity to quality education and training aspects of the improvement; (3). Actively seeking to expand overseas business base; (4). Emphasis on providing clients with timely and consistent with the needs of the product; (5). Information processing and improve the marketing and organizational effectiveness; (6). On the action more attention to risk management and implementation.
3. The strategy differences for Citigroup Bank of Taiwan
(1). More attention to human quality of staff; (2). Employees to obtain relevant training and professional certifications pay more attention to; (3). After the branch has continued to expand product reach economies of scale advantages; (4). Development of the past, Taiwan has not been exposed to products and services; (5). Information technology upgrading hardware and software facilities; (6). into Citigroup's risk control mechanisms.
|
Page generated in 0.031 seconds