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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.
1

Dynamic Probability Control Limits for Risk-Adjusted Bernoulli Cumulative Sum Charts

Zhang, Xiang 12 December 2015 (has links)
The risk-adjusted Bernoulli cumulative sum (CUSUM) chart developed by Steiner et al. (2000) is an increasingly popular tool for monitoring clinical and surgical performance. In practice, however, use of a fixed control limit for the chart leads to quite variable in-control average run length (ARL) performance for patient populations with different risk score distributions. To overcome this problem, the simulation-based dynamic probability control limits (DPCLs) patient-by-patient for the risk-adjusted Bernoulli CUSUM charts is determined in this study. By maintaining the probability of a false alarm at a constant level conditional on no false alarm for previous observations, the risk-adjusted CUSUM charts with DPCLs have consistent in-control performance at the desired level with approximately geometrically distributed run lengths. Simulation results demonstrate that the proposed method does not rely on any information or assumptions about the patients' risk distributions. The use of DPCLs for risk-adjusted Bernoulli CUSUM charts allows each chart to be designed for the corresponding particular sequence of patients for a surgeon or hospital. The effect of estimation error on performance of risk-adjusted Bernoulli CUSUM chart with DPCLs is also examined. Our simulation results show that the in-control performance of risk-adjusted Bernoulli CUSUM chart with DPCLs is affected by the estimation error. The most influential factors are the specified desired in-control average run length, the Phase I sample size and the overall adverse event rate. However, the effect of estimation error is uniformly smaller for the risk-adjusted Bernoulli CUSUM chart with DPCLs than for the corresponding chart with a constant control limit under various realistic scenarios. In addition, there is a substantial reduction in the standard deviation of the in-control run length when DPCLs are used. Therefore, use of DPCLs has yet another advantage when designing a risk-adjusted Bernoulli CUSUM chart. These researches are results of joint work with Dr. William H. Woodall (Department of Statistics, Virginia Tech). Moreover, DPCLs are adapted to design the risk-adjusted CUSUM charts for multiresponses developed by Tang et al. (2015). It is shown that the in-control performance of the charts with DPCLs can be controlled for different patient populations because these limits are determined for each specific sequence of patients. Thus, the risk-adjusted CUSUM chart for multiresponses with DPCLs is more practical and should be applied to effectively monitor surgical performance by hospitals and healthcare practitioners. This research is a result of joint work with Dr. William H. Woodall (Department of Statistics, Virginia Tech) and Mr. Justin Loda (Department of Statistics, Virginia Tech). / Ph. D.
2

A Study of Control Charts with Variable Sample Size

Huang, Guo-Tai 08 July 2004 (has links)
Shewhart X bar control charts with estimated control limits are widely used in practice. When the sample size is not fixed,we propose seven statistics to estimate the standard deviation sigma . These estimators are applied to estimate the control limits of Shewhart X bar control chart. The estimated results through simulated computation are given and discussed. Finally, we investigate the performance of the Shewhart X bar control charts based on the seven estimators of sigma via its simulated average run length (ARL).
3

Fractionation in the Evolution of Syntenic Homology in Coffea Arabica

Yu, Zhe 13 August 2021 (has links)
Gene loss is the obverse of novel gene acquisition by a genome through a variety of evolutionary processes. It serves a number of functional and structural roles, compensating for the energy and material costs of gene complement expansion. A type of gene loss widespread in the lineages of plant genomes is ``fractionation" after whole genome doubling or tripling, where one of a pair or triplet of paralogous genes in parallel syntenic contexts is discarded. Based on previous mathematical work on the distribution of gap sizes caused by fractionation in synteny blocks, we studied fractionation in the evolutionary history of the allotetraploid Coffea arabica (CA) and its two diploid progenitors, C. canephora (CC) and C. eugenioides (CE), annotated genome assemblies being provided by the Arabica Coffee Genome Consortium. By taking advantage of synteny blocks produced by SynMap, we studied the fractionation process after speciation and tetraploidization events, including visualization and modelling the distribution of deletion segments, and mechanisms of deletion events. We also expanded the research to eight other plant species to verify the dominance of DNA excision over pseudigenization during the fractionation and other gene loss.
4

Episode 3.12 – Run Length Limited Coding

Tarnoff, David 01 January 2020 (has links)
By examining Run Length Limited (RLL) coding, we discover a way to compress the ones and zeros of our binary data by using differential coding. We also chat a bit about magnetic storage media.
5

A Performance Analysis of the Minimax Multivariate Quality Control Chart

Rehmert, Ian Jon 18 December 1997 (has links)
A performance analysis of three different Minimax control charts is performed with respect to their Chi-Square control chart counterparts under several different conditions. A unique control chart must be constructed for each process described by a unique combination of quality characteristic mean vector and associated covariance matrix. The three different charts under consideration differ in the number of quality characteristic variables of concern. In each case, without loss of generality the in-control quality characteristic mean vector is assumed to have zero entries and the associated covariance matrix is assumed to have non-negative entries. The performance of the Chi-Square and Minimax charts are compared under different values of the sample size, the probability of a Type I error, and selected shifts in the quality characteristic mean vector. Minimax and Chi-Square charts that are compared share identical in-control average run lengths (ARL) making the out-of-control ARL the appropriate performance measure. A combined Tausworthe pseudorandom number generator is used to generate the out-of-control mean vectors. Issues regarding multivariate uniform pseudorandom number generation are addressed. / Master of Science
6

Camera System Design

Risberg, Robert January 2003 (has links)
<p>Devices have become increasingly more interconnected to their surroundings over the last few years. The introduction of Bluetooth is likely to further accelerate this trend. With Bluetooth's bandwidth and expected low price, many devices will likely be fitted with Bluetooth chips and thus enable more devices to exchange data. </p><p>This master thesis aims at connecting a Personal Digital Assistant to an ARM Thumb microcontroller over Bluetooth. To the ARM Thumb shall an image capturing device be interfaced and the captured images shall be sent over Bluetooth to the Personal Digital Assistant which shall display them.</p>
7

Cooperative behavior of motor proteins

Beeg, Janina January 2007 (has links)
The cytoskeletal motor protein kinesin-1 (conventional kinesin) is the fast carrier for intracellular cargo transport along microtubules. So far most studies aimed at investigating the transport properties of individual motor molecules. However, the transport in cells usually involves the collective work of more than one motor. In the present work, we have studied the movement of beads as artificial loads/organelles pulled by several kinesin-1 motors in vitro. For a wide range of motor coverage of the beads and different bead (cargo) sizes the transport parameters walking distance or run length, velocity and force generation are measured. The results indicate that the transport parameters are influenced by the number of motors carrying the bead. While the transport velocity slightly decreases, an increase in the run length was measured and higher forces are determined, when more motors are involved. The effective number of motors pulling a bead is estimated by measuring the change in the hydrodynamic diameter of kinesin-coated beads using dynamic light scattering. The geometrical constraints imposed by the transport system have been taken into account. Thus, results for beads of different size and motor-surface coverage could be compared. In addition, run length-distributions obtained for the smallest bead size were matched to theoretically calculated distributions. The latter yielded an average number of pulling motors, which is in agreement with the effective motor numbers determined experimentally. / Kinesin-1 (konventionelles Kinesin) ist ein Motorprotein des Zytoskeletts, das für den schnellen intrazellulären Lastentransport auf Mikrotubuli verantwortlich ist. Das Hauptinteresse vieler Studien lag bisher auf der Erforschung der Transporteigenschaften von Einzelmotormolekülen. Der Transport in der Zelle erfordert aber gewöhnlich kollektive Arbeit von mehreren Motoren. In dieser Arbeit wurde die Bewegung von Kugeln als Modell für Zellorganellen, die von Kinesin-1 Molekülen gezogen werden, in Anhängigkeit von der Motorendichte auf der Kugeloberfläche und unterschiedlichen Kugeldurchmessern in vitro untersuchten. Die Transportparameter Weglänge, Geschwindigkeit und die erzeugte Kraft wurden gemessen. Die Ergebnisse zeigen, dass die Transportgeschwindigkeit leicht abnimmt, wohingegen die Weglänge und die erzeugten Kräfte mit steigender Molekülkonzentration zunehmen. Die tatsächliche Anzahl der Motoren, die aktiv am Transport der Kugeln beteiligt sind, wurde bestimmt, indem die Änderung des hydrodynamischen Durchmessers der mit Kinesin bedeckten Kugeln mittels dynamischer Lichtstreuung gemessen wurde. Außerdem wurden sterische Effekte des verwendeten Transportsystems in die Berechnung einbezogen. Damit werden Ergebnisse vergleichbar, die für unterschiedliche Kugeldurchmesser und Motorkonzentrationen ermittelt wurden. Zusätzlich wurden die Verteilungen der Weglängen für die kleinste Kugelgröße mit theoretisch ermittelten Verteilungen verglichen. Letzteres ergab durchschnittliche Anzahlen der aktiv am Transport beteiligten Motormoleküle, die mit den experimentell bestimmten Ergebnissen übereinstimmen.
8

Factors affecting the variance, the bias and the MSE of time averages in Markovian event systems

Sethi, Sanjeev 13 June 2007
In simulation, time averages are important for estimating equilibrium parameters. In particular, we would like to have the variance, bias and mean-square error for time averages. First, we will discuss various factors and their effect on the bias, the variance and the mean-square error. We will use the Markovian Event System to model various systems, including M/M/1 queues, M/E_k/1 queues, M/M/c queues, sequential queues, inventory systems and queueing networks. We use a numerical method for the computation of the variance, the bias and the mean-square error of the time average. The effectiveness of the method is tested by experimenting with models of various stochastic systems. The contribution of this thesis is to use numerical and graphical interpretations to study the general characteristics of the measures. The important characteristics included in our study are decomposability and periodicity.
9

Camera System Design

Risberg, Robert January 2003 (has links)
Devices have become increasingly more interconnected to their surroundings over the last few years. The introduction of Bluetooth is likely to further accelerate this trend. With Bluetooth's bandwidth and expected low price, many devices will likely be fitted with Bluetooth chips and thus enable more devices to exchange data. This master thesis aims at connecting a Personal Digital Assistant to an ARM Thumb microcontroller over Bluetooth. To the ARM Thumb shall an image capturing device be interfaced and the captured images shall be sent over Bluetooth to the Personal Digital Assistant which shall display them.
10

Factors affecting the variance, the bias and the MSE of time averages in Markovian event systems

Sethi, Sanjeev 13 June 2007 (has links)
In simulation, time averages are important for estimating equilibrium parameters. In particular, we would like to have the variance, bias and mean-square error for time averages. First, we will discuss various factors and their effect on the bias, the variance and the mean-square error. We will use the Markovian Event System to model various systems, including M/M/1 queues, M/E_k/1 queues, M/M/c queues, sequential queues, inventory systems and queueing networks. We use a numerical method for the computation of the variance, the bias and the mean-square error of the time average. The effectiveness of the method is tested by experimenting with models of various stochastic systems. The contribution of this thesis is to use numerical and graphical interpretations to study the general characteristics of the measures. The important characteristics included in our study are decomposability and periodicity.

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