Šiame darbe detaliai išanalizuotas klaidos skleidimo atgal algoritmas, atlikti tyrimai. Išsamiai analizuota neuroninių tinklų teorija. Algoritmui taikyti ir analizuoti sistemoje Visual Studio Web Developer 2008 sukurta programa su įvairiais tyrimo metodais, padedančiais ištirti algoritmo daromą klaidą. Taip pat naudotasi Matlab 7.1 sistemos įrankiais neuroniniams tinklams apmokyti. Tyrimo metu analizuotas daugiasluoksnis dirbtinis neuroninis tinklas su vienu paslėptu sluoksniu. Tyrimams naudoti gėlių irisų ir oro taršos duomenys. Atlikti gautų rezultatų palyginimai. / The present work provides an in-depth analysis of the error back-propagation algorithm, as well as information on the investigation carried out. A neural network theory has been analysed in detail. For the application and analysis of the algorithm in the system Visual Studio Web Developer 2008, a program has been developed with various investigation methods, which help to research into the error of the algorithm. For training neural networks, Matlab 7.1 tools have been used. In the course of the investigation, a multilayer artificial neural network with one hidden layer has been analysed. For the purpose of the investigation, data on irises (plants) and air pollution have been used. Comparisons of the results obtained have been made.

Aircraft operators demand an ever increasing availability of their fleets with constant reduction of their operational costs. With the age of many fleets measured in decades, the options to face these challenges are limited. Integrated Vehicle Health Management (IVHM) uses data gathered through sensors in the aircraft to assess the condition of components to detect and isolate faults or even estimate their Remaining Useful Life (RUL). This information can then be used to improve the planning of maintenance operations and even logistics and operational planning, resulting in shorter maintenance stops and lower cost. Retrofitting health monitoring technology onto legacy aircraft has the capability to deliver what operators and maintainers demand, but working on aging platforms presents numerous challenges. This thesis presents a novel methodology to select the combination of diagnostic and prognostic tools for legacy aircraft that best suits the stakeholders’ needs based on economic return and financial risk. The methodology is comprised of different steps in which a series of quantitative analyses are carried out to reach an objective solution. Beginning with the identification of which components could bring higher reduction of maintenance cost and time if monitored, the methodology also provides a method to define the requirements for diagnostic and prognostic tools capable of monitoring these components. It then continues to analyse how combining these tools affects the economic return and financial risk. Each possible combination is analysed to identify which of them should be retrofitted. Whilst computer models of maintenance operations can be used to analyse the effect of retrofitting IVHM technology on a legacy fleet, the number of possible combinations of diagnostic and prognostic tools is too big for this approach to be practicable. Nevertheless, computer models can go beyond the economic analysis performed thus far and simulations are used as part of the methodology to get an insight of other effects or retrofitting the chosen toolset.

The effect of coupled thermo-poroelastic behavior on hydraulic fracture propagation is of much interest in geothermal- and petroleum-related geomechanics problems such as wellbore stability and hydraulic fracturing as pore pressure and temperature variations can significantly induce rock deformation, fracture initiation, and propagation. In this dissertation, a two-dimensional (2D) boundary element method (BEM) was developed to simulate the fully coupled thermo-poroelastic fracture propagation process. The influence of pore pressure and temperature changes on the fracture propagation length and path, as well as on stress and pore pressure distribution near wellbores and fractures, was considered in isotropic and homogeneous rock formations. The BEM used in this work consists of the displacement discontinuity (DD) method and the fictitious stress (FS) method. Also, a combined FS-DD numerical model was implemented for the hydraulically or thermally-induced fractures in the vicinity of a wellbore. The linear elastic fracture mechanics (LEFM) theory was adopted to numerically model within the framework of poroelasticity and thermo-poroelasticity theory. For high accuracy of crack tip modeling, a special displacement discontinuity tip element was developed and extended to capture the pore pressure and temperature influence at the tip. For poroelastic fracture propagation, a steadily propagating crack driven by fluid pressure was modeled to find the effect of pore pressure on crack path under the two limiting poroelastic conditions (undrained and drained). The results indicate that the pore pressure diffusion has no influence on the crack growth under the undrained condition because the crack propagation velocity is too fast for the diffusion effect to take place. On the other hand, its influence on the crack path under the drained condition with its low propagation velocity has significance because it induces a change in principal stress direction, resulting in an alteration of fracture orientation. For the thermal fracturing, when the rock around a wellbore and a main fracture is cooled by injecting cold water in a hot reservoir, the rapid decrease in temperature gives rise to thermal stress, which causes a crack to initiate and propagate into the rock matrix. The single and multiple fracture propagation caused by transient cooling in both thermoelastic and poro-thermoelastic rock were numerically modeled. The results of this study indicate that the thermal stresses induced by cooling may exceed the in-situ stress in the reservoir, creating secondary fractures perpendicular to main fracture. Furthermore, the faster cooling rate produces longer crack extension of the secondary thermal fractures. This implies that the faster cooling induces a higher tensile stress zone around the fracture, which tends to produce larger driving forces to make the secondary fractures penetrate deeper into the geothermal reservoir.

It is well known that surface water waves interact with fluid mud on the sea bed. Wave mud interaction results in high wave energy dissipation and mud mass transport. This kind of wave energy dissipation, which generally is much more significant than wave dissipation due to bottom friction, should be considered in the simulation of wave evolution and transformation in muddy coastal environments. In this research, a two-dimensional horizontal wave propagation and morphodynamic model for muddy coasts was developed. The model can be applied on a general three dimensional bathymetry of a soft muddy coast to calculate wave damping, fluid mud transport and resulting bathymetry change under wave action. In addition to the effect of wave-mud interaction on wave propagation, the dissipation due to wave-mud interaction was also implemented in SWAN (a third generation numerical model for Simulating WAves Nearshore) using a multilayered wave mud interaction model. These two models combined can be used for generation and propagation of waves in muddy coastal areas. The nonlinear constitutive equations of the visco-elastic-plastic model are adopted for the rheological behavior of fluid mud in this research. The results of the numerical model are compared against a series of wave-basin experiments, wave flume experiments and field observations. Comparisons between the simulated results with the both field and laboratory data reveal the capability of the proposed model to predict the wave transformation and mud mass transport. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2009-07-24 11:18:18.622

No description available.

No description available.

This study examined the effect of density on rhizome bud production in quackgrass (Elytrigia repens (L.) Nevski). The treatments consisted of two biotypes (L8 and L9), and nine density levels ranging from 1 to 22 plants m$ sp{-2}$. The results showed that bud production per plant diminished with increasing density in both biotypes. However, biotype L8 was less productive at low densities, but almost equal to L9 at higher densities. A second experiment was undertaken to measure the expansion of clonal colonies and the distribution of shoots within these colonies. For both biotypes the growth rate was highest in late summer and early fall, but colonies of L9 grew more rapidly. Biotype L9 had 59% of its total biomass located within 40 cm of the centre as compared with 81% in L8. Overall, Biotype L9 produced more rhizome buds, responded more strongly to intraspecific interference, and grew more rapidly as a colony.

No abstract available. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2003.

Embryogenic tissue of Pinus patula Scheide et Deppe was initiated from immature green female cones during the months of November 1996 to February 1997 and December 1997 to January 1998. Tissue was maintained on MSG3 medium (BECWAR, NAGMANI and WANN 1990) supplemented with maltose. A comparison of various sugars as a carbohydrate source for maintaining embryogenic tissue showed that maltose was far superior to sucrose and the other sugars tested. Embryogenic tissue was successfully cryopreserved for up to 8 weeks using 0.3 M sorbitol and 5 % DMSO. Recovered tissue initially underwent a lag phase in tissue regrowth, but by the end of 5 weeks post-thaw, tissue proliferation was as vigorous as the unfrozen, untreated control. Fluoresceine diacetate (FDA) staining revealed that the embryonal head survived cryopreservation, but the highly vacuolated suspensor tissue had ruptured and died. Embryogenic tissue from two different families and four genotypes were successfully cryopreserved using this protocol. A comparison of commonly used cryopreservation techniques was conducted. It was found that the slow addition of the cryoprotectants over two days slowed the recovery rate of the tissue and increased the chances of contamination. Embryogenic tissue did not respond well to cryopreservation using a combination of the cryoprotectants PEG, glucose and DMSO (10-8-10%). Only a small proportion of the tissue survived, and initial tissue regrowth took up to 5 weeks. Embryogenic tissue was also set in gel and immersed directly in liquid nitrogen in an effort to cryopreserve tissue using the process of vitrification. However, none of the tissue survived, possibly due to insufficient dehydration prior to immersion in liquid nitrogen. Tissue recovery was highest when the tissue was precooled to -70°C in a container filled with isopropyl alcohol placed in a static freezer prior to immersion in liquid nitrogen. Recovery of tissue was improved by suspending the tissue on polyester grids and removing the liquid medium prior to placing onto MSG3 medium. Recovered tissue was bulked up using suspension cultures, and then paced onto MSG5 (BECWAR, NAGMANI and WANN 1990) or 240 medium (PULLMAN and WEBB 1994) to mature. Mature embryos were isolated from both media and germinated. Somatic plantlets were successfully hardened-off under greenhouse conditions. The successful cryopreservation of a number of genotypes and lines, and the maturation of recovered tissue has been achieved. This technique is now being actively incorporated into P. patula somatic embryo research, enabling the long-term storage of juvenile reference tissue while field trials are carried out and evaluated. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1999.

Hypericum is a most useful and versatile cut flower which within the last ten years has gained significant economic importance, recently having been included in the top fifty cut flowers on the Dutch Auctions. This study has investigated the cultural requirements of the crop, focusing on the following; propagation, insect and disease control, fertilisation, crop manipulation, marketing of the finished product, business theory and the interpretation of business theory. Propagation and multiplication techniques were investigated in order to reduce the reliance of external seedling growers and in so doing reducing the start up costs ofthe project. Insect and disease control were investigated as the import requirements for many countries are stringent. Contamination of the finished product results in the cargo being rejected at the port of entry. Insect and disease infestation reduce the quality and subsequently the return that is generated from the project. Fertilisation plays an important role in producing high quality sterns. Failure to fertilise the crop at the correct stage results in quality degradation, or additional expenditure on labour to groom the plants. Crop manipulation was investigated for the purpose of supplying crop into the market place on a sustained basis, ensuring optimal utilisation of resources whilst building customer loyalty. Product marketing plays an integral role in determining the success of a venture. Markets were evaluated in order to determine which markets would yield the greatest return on investment. Chapter three deals with various business theories that may be applied to the data and observations. Chapter four integrates business theory with the data and observations in an attempt to gain a meaningful picture of the economic potential of this proposed venture. The last chapter deals with a proposed strategy that the company should follow, having evaluated and integrated the business theory, data and observations. / Thesis (MBA)-University of Natal, Durban, 2003.