Врахування вітчизняних умов при використанні закордонних Z-моделей прогнозування банкрутства

The green cw laser presented in this work is realized by means of a Pr:YLF crystal emitting at 523 nm that is pumped by a blue GaN laser diode in an extremely short resonator. With a 500 mW-diode a laser has been achieved with M2 = 1, a slope of 40 % and an output power of 140mW with an absorbed pump power of 410 mW which results in an electrooptical efficiency of 6.5 %. Despite the reduced overlap with a 1 W-diode the output power rises to 290 mW with an absorbed pump power of 850 mW and the M2 increases only slightly. Based on these results a compact laser package has been accomplished using a monolithic micro optics for the beam shaping of the diode light and joining all components with a low-shrinkage adhesive on a common base plate. In a first test of the alignment strategy a laser with an output power of 92 mW has been achieved by means of the 500 mW pump power

Fixed bobbin friction stir welding of marine grade aluminium.

PROBLEM - The bobbin friction stir welding (BFSW) process has potential benefits for welding thin sheet aluminium alloy. The main benefits of friction stir welding over conventional thermal welding processes are minimisation of energy usage, no need for consumables, potential for good weld quality without porosity, no fumes, minimal adverse environmental effects (green), minimal waste (lean), and reduced threats to personal health and safety. The BFSW process has further advantages over conventional friction stir welding (CFSW) in the reduction of welding forces, faster welding, and less fixturing. It is especially attractive to industries that join thin sheet material, e.g. boat-building. The industrial need for this project arose from the desire to apply the technology at a ship manufacturing company, INCAT located in Hobart, Tasmania, Australia. However there are peculiar difficulties with the specific grade of material used in this industry, namely thin sheet aluminium Al6082-T6. Early efforts with a portable friction stir welding machine identified the process to have low repeatability and reproducibility, i.e. process-instability. There are a large number of process variables and situational factors that affect weld quality, and many of these are covert. This is also the reason for divergent recommendations in the literature for process settings. PURPOSE - The main purpose of this research was to identify covert variables and better understand their potentially adverse effects on weld quality. Therefore, this thesis investigated the hidden variables and their interactions. Developing this knowledge is a necessity for making reliable and repeatable welds for industrial application. APPROACH - An explorative approach that focused on the functional perspective was taken. An extensive empirical testing programme was undertaken to identify the variables and their effects. In the process a force platform and BFSW tools were designed and built. A variety of machine platforms were used, namely portable friction stir welding, manual milling machine and computer numerical control (CNC) milling machine. The trials were grouped into 14 test plans. These are tool shoulder gap, spindle and travel speed, tool features, machines, tool fixation, machinery, welding direction, plate size (width and dimension), support insulation, tool materials, substrate properties and fixation. For the welded plates besides visual inspection of the weld, current, force, and temperature were measured. The Fourier transform was used to analyse the frequency response of machines. Also the welded samples were tested to the maritime standards of Det Norske Veritas (DNV). A number of relationships of causality were identified whereby certain variables affected weld quality. A model was developed to represent the proposed causality using the IDEF0 systems engineering method. FINDINGS - From these trials six main variables have been identified. These are tool features, spindle speed, travel speed, shoulder gap compression, machine variability, tool and substrate fixation. A rigid system is required for a consistent weld results. Under this condition, full pin features (threads and flats) need to be used to balance the adverse effects of individual features. It has been shown that fabricated bobbin tools with sharp edges can cause cuts and digging thus this feature should be avoided. Additionally, the substrate should have continuous interaction with the tool so the shoulder interference needs to be fixed and well-controlled. It is found that the compression generated by the shoulder towards the substrate helps material grabbing for better tool-substrate interaction. It is also shown that tool entry causes ejection of material and hence an enduring mass deficit, which manifests as a characteristic tunnel defect. The new explanation of the formation, origin and location of this defect has been explained. Material transportation mechanisms within the weld have been elucidated. It is also found that the role of the travel speed is not only to control heat generation but also for replacing the deficit material. Additionally, heat supplied to the weld depends not only on thickness, but also the width of the plate. Different types of machine cause an interaction in the material flow through their controller strategies. Jerking motion can occur at a slow travel speed, which also alters the way material is being transported. The Fourier transform (FFT) has been used to identify the characteristics of good and bad BFSW welds. This has the potential to be expanded for real-time process control. IMPLICATIONS - Tool deflection and positioning, material flow and availability are identified as affecting weld quality through stated mechanisms. The impact is even more severe when involving thin-plate aluminium. For the industry to successfully adopt this technology the process typically needs tight control of shoulder gap, tool strength and stiffness, feature fabrication, substrate and tool fixation. Additionally spindle and travel speed need to be adjusted not only based on the type of materials and thickness, but also the width, type of machine and method of tool entry. ORIGINALITY - New data are presented, which lead to new insights into the welding mechanics, production settings, material transportation and weld defects for BFSW on thin sheet material. The conventional idea that the welding tool has a semi-steady interaction with the substrate is not supported. Instead the interaction is highly dynamic, and this materially affects the weld-quality, especially in the difficult-to-weld material under examination. Factors such as shoulder gap, tool and substrate fixation compliance and machine types emerge as variables that need to be given attention in the selection of process parameters. The causal relationships have been represented in a conceptual model using an IDEF0 system approach. This study has made several original contributions to the body of knowledge. First is the identification of previously hidden variables that effect weld formation for the fixed gap BFSW process. The second contribution is a new way of understanding the material transportation mechanics within the weld. This includes the flow around the pin in the plane of the weld, the vertical transportation of material up the pin, the formation of turbulent-like knit lines at the advancing side, and the formation of tunnel defects. Also included here is a new understanding of how material deficit arises at tool entry and exit, and from flash/chips, and how this contributes to the tunnel weld defect. In addition, new understandings of the role of feed rate have been identified. Related to the material transportation, the work has also identified the importance of an interference fit between the substrate and tool. A third contribution is the identification of the dynamic interaction between tool and substrate. This identifies the important role rigidity plays. Associated with this is the identification of frequency characteristics of the motors under load. The fourth contribution is identification of the specific process settings for the difficult-to-weld material of AL6082-T6. The fifth contribution is the development of a novel method of fabricating bobbin friction stir welding tools as embodied in a patent application

Potencial de emissão de biogás de célula já finalizada do aterro sanitário municipal de Cascavel - PR

Diante da necessidade de aumentar a matriz energética e a mitigação de impactos ambientais, este artigo analisa o potencial energético de parte do aterro sanitário do município de Cascavel – PR. Inicialmente realizado o georreferenciamento dos drenos para então realizar medições de vazão de biogás proveniente do material depositado em célula já fechada. A célula em estudo recebeu RSU por 8 anos e no decorrer de 2 e 3 anos após sua finalização foi medido a emissão e temperatura de biogás que escoou através dos drenos do aterro sanitário; foram obtidos respectivamente, 378,3 m3h-1 após 2 anos e 315,8 m3h-1 após 3 anos de sua finalização. Calculou-se o potencial energético apresentado pelos dois anos de medição sendo respectivos 1.7  MWh-1  e 1.5 MWh-1. As emissões de biogás foram maiores onde a temperatura de saída do gás é maior

Kompakte, grün emittierende Laser auf Basis von Pr:YLF

Solid-state lasers have become an established tool in the sectors of production and metrology. The processing conditions common in these sectors determine requirements upon the energetic, spatial, temporal and spectral characteristics of the laser in question. While material processing requires high power output at short pulse durations, applications such as those in medicine, metrology and entertainment need continuous power below one watt at an adapted wavelength in the visual spectrum. These requirements strongly limit the choice of active laser media and designs, and have only been examined in the last few years. Lasers based on Pr:YLF, can emit in the visible spectral ranges of cyan via green, orange and red. When InGaN diodes emitting blue are used as a pump source, lasers can be built with a high efficiency and a compact set up. These lasers exhibit, thus, a high potential for applications in diverse fields of medicine, metrology and entertainment, where a mobile use or the integration in a treatment, measurement or entertainment devise is required. Currently, laser-based digital projectors for mobile use provide a clear example for the use of beam sources of moderate output power in the visible spectral range in large lot sizes. The use of laser-based projectors would increase the efficiency in a much smaller space, but has, however, failed to date because the lack of a compact and efficient laser source with an adequate output power in the green spectral range. The demands upon a high degree of integration of the source creates a challenge which had not been examined for the sources based on Pr:YLF. In this work, a systematic comparison has been made of the potential of highly compact free-space and waveguide lasers on the basis of this active medium. For this purpose laser-beam sources are examined with an emission in the green spectrum, which aim for a high degree of compactness and efficiency. The concrete requirements result from the application as a beam source for digital projectors; the use of the sources examined, however, is not limited to this application. As a pump source, an InGaN laser diode emitting blue is used, whose emission wavelength suits an absorption line of Pr:YLF. Configurations of free-space lasers as well as waveguide lasers were investigated analytically, numerically and experimentally. A very compact demonstrator model of a free-space laser fulfills all the requirements placed on the beam source regarding output power, beam quality, efficiency and volume. For the first time, a compact Pr:YLF laser with a power density of 200 mW / cm^3 has been demonstrated to be feasible. In addition, the design and the construction strategy allow automation and enable a cost-effective mass production. Moreover this study compares under which conditions regarding dimension and losses waveguide laser have advantages over the design presented here of a free-space laser. For this, waveguide structures are generated by means of fs-laser irradiation and, through experimental investigations of a waveguide laser, its losses are determined. Furthermore, this paper examines the potential, for the first time, that microscopically manufactured waveguides made out of Pr:YLF exhibit

Kompakte, grün emittierende Laser auf Basis von Pr:YLF

Solid-state lasers have become an established tool in the sectors of production and metrology. The processing conditions common in these sectors determine requirements upon the energetic, spatial, temporal and spectral characteristics of the laser in question. While material processing requires high power output at short pulse durations, applications such as those in medicine, metrology and entertainment need continuous power below one watt at an adapted wavelength in the visual spectrum. These requirements strongly limit the choice of active laser media and designs, and have only been examined in the last few years. Lasers based on Pr:YLF, can emit in the visible spectral ranges of cyan via green, orange and red. When InGaN diodes emitting blue are used as a pump source, lasers can be built with a high efficiency and a compact set up. These lasers exhibit, thus, a high potential for applications in diverse fields of medicine, metrology and entertainment, where a mobile use or the integration in a treatment, measurement or entertainment devise is required. Currently, laser-based digital projectors for mobile use provide a clear example for the use of beam sources of moderate output power in the visible spectral range in large lot sizes. The use of laser-based projectors would increase the efficiency in a much smaller space, but has, however, failed to date because the lack of a compact and efficient laser source with an adequate output power in the green spectral range. The demands upon a high degree of integration of the source creates a challenge which had not been examined for the sources based on Pr:YLF. In this work, a systematic comparison has been made of the potential of highly compact free-space and waveguide lasers on the basis of this active medium. For this purpose laser-beam sources are examined with an emission in the green spectrum, which aim for a high degree of compactness and efficiency. The concrete requirements result from the application as a beam source for digital projectors; the use of the sources examined, however, is not limited to this application. As a pump source, an InGaN laser diode emitting blue is used, whose emission wavelength suits an absorption line of Pr:YLF. Configurations of free-space lasers as well as waveguide lasers were investigated analytically, numerically and experimentally. A very compact demonstrator model of a free-space laser fulfills all the requirements placed on the beam source regarding output power, beam quality, efficiency and volume. For the first time, a compact Pr:YLF laser with a power density of 200 mW / cm^3 has been demonstrated to be feasible. In addition, the design and the construction strategy allow automation and enable a cost-effective mass production. Moreover this study compares under which conditions regarding dimension and losses waveguide laser have advantages over the design presented here of a free-space laser. For this, waveguide structures are generated by means of fs-laser irradiation and, through experimental investigations of a waveguide laser, its losses are determined. Furthermore, this paper examines the potential, for the first time, that microscopically manufactured waveguides made out of Pr:YLF exhibit