| 61. |
- Bergström, David, et al.
(författare)
-
The reflectance of steels and non-ferrous alloys to Nd:YAG and Nd:YLF laser light
- 2006
-
Ingår i: Peer reviewed conference proceedings. - Orlando, Fla. : Laser institute of America. - 0912035846 ; , s. 140-145
-
Konferensbidrag (refereegranskat)abstract
- The measurement of reflectance is important for the analysis and modelling of laser-material interactions. Unfortunately, most of the reflectance data presently available consider only polished pure metals rather than the commercially available (unpolished, oxidised) alloys which are actually being processed. This paper presents the results of reflectance measurements carried out on asreceived engineering grade metals including: hot and cold rolled mild steel, zinc coated mild steel, stainless steel, aluminium alloys, copper and brass. The measurements were made using an integrating sphere with an Nd:YLF laser at two wavelengths (1053 nm and 527 nm). The results obtained differ considerably from existing data for polished, pure metals and should help to improve the accuracy of laser-material interaction models.
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| 62. |
- Blackburn, Landen D., et al.
(författare)
-
Dynamic machine learning-based optimization algorithm to improve boiler efficiency
- 2022
-
Ingår i: Journal of Process Control. - : Elsevier BV. - 0959-1524. ; 120, s. 129-149
-
Forskningsöversikt (refereegranskat)abstract
- With decreasing computational costs, improvement in algorithms, and the aggregation of large industrial and commercial datasets, machine learning is becoming a ubiquitous tool for process and business innovations. Machine learning is still lacking applications in the field of dynamic optimization for real-time control. This work presents a novel framework for performing constrained dynamic optimization using a recurrent neural network model combined with a metaheuristic optimizer. The framework is designed to augment an existing control system and is purely data-driven, like most industrial Model Predictive Control applications. Several recurrent neural network models are compared as well as several metaheuristic optimizers. Hyperparameters and optimizer parameters are tuned with parameter sweeps, and the resulting values are reported. The best parameters for each optimizer and model combination are demonstrated in closed-loop control of a dynamic simulation, and several recommendations are made for generalizing this framework to other systems. Up to 0.953% improvement is realized over the non-optimized case for a simulated coal-fired boiler. While this is not a large improvement in percentage, the total economic impact is $991,000 per year, and this study builds a foundation for future machine learning with dynamic optimization.
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| 63. |
- Bombarda, F., et al.
(författare)
-
Runaway electron beam control
- 2019
-
Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 61:1
-
Tidskriftsartikel (refereegranskat)
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| 64. |
- Bäckstrand, Jenny, 1979-, et al.
(författare)
-
Towards a framework for enhanced ETO supply chain performance
- 2019
-
Ingår i: Proceedings of the 9th International Conference on Operations and Supply Chain Management, Vietnam, 2019. - 9786027060470
-
Konferensbidrag (refereegranskat)abstract
- ETO supply chains seem to exhibit natural barriers and resistance to continuous improvements. This paper aims to construct a framework to understand the links between Lean thinking, organizational learning and supply chain delivery capabilities in an ETO- context. The paper identifies the research gap between three specific research areas; ETO supply chains, organizational learning, and lean.
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| 65. |
- Clayton, Emma L., et al.
(författare)
-
Early microgliosis precedes neuronal loss and behavioural impairment in mice with a frontotemporal dementia-causing CHMP2B mutation
- 2017
-
Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 26:5, s. 873-887
-
Tidskriftsartikel (refereegranskat)abstract
- Frontotemporal dementia (FTD)-causing mutations in the CHMP2B gene lead to the generation of mutant C-terminally truncated CHMP2B. We report that transgenic mice expressing endogenous levels of mutant CHMP2B developed late-onset brain volume loss associated with frank neuronal loss and FTD-like changes in social behaviour. These data are the first to show neurodegeneration in mice expressing mutant CHMP2B and indicate that our mouse model is able to recapitulate neurodegenerative changes observed in FTD. Neuroinflammation has been increasingly implicated in neurodegeneration, including FTD. Therefore, we investigated neuroinflammation in our CHMP2B mutant mice. We observed very early microglial proliferation that develops into a clear pro-inflammatory phenotype at late stages. Importantly, we also observed a similar inflammatory profile in CHMP2B patient frontal cortex. Aberrant microglial function has also been implicated in FTD caused by GRN, MAPT and C9orf72 mutations. The presence of early microglial changes in our CHMP2B mutant mice indicates neuroinflammation may be a contributing factor to the neurodegeneration observed in FTD.
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| 66. |
- Conte, Michael S, et al.
(författare)
-
Global vascular guidelines on the management of chronic limb-threatening ischemia.
- 2019
-
Ingår i: Journal of Vascular Surgery. - : Elsevier BV. - 0741-5214 .- 1097-6809. ; 69:6S, s. 3S-125S.e40
-
Tidskriftsartikel (refereegranskat)abstract
- Chronic limb-threatening ischemia (CLTI) is associated with mortality, amputation, and impaired quality of life. These Global Vascular Guidelines (GVG) are focused on definition, evaluation, and management of CLTI with the goals of improving evidence-based care and highlighting critical research needs. The term CLTI is preferred over critical limb ischemia, as the latter implies threshold values of impaired perfusion rather than a continuum. CLTI is a clinical syndrome defined by the presence of peripheral artery disease (PAD) in combination with rest pain, gangrene, or a lower limb ulceration >2 weeks duration. Venous, traumatic, embolic, and nonatherosclerotic etiologies are excluded. All patients with suspected CLTI should be referred urgently to a vascular specialist. Accurately staging the severity of limb threat is fundamental, and the Society for Vascular Surgery Threatened Limb Classification system, based on grading of Wounds, Ischemia, and foot Infection (WIfI) is endorsed. Objective hemodynamic testing, including toe pressures as the preferred measure, is required to assess CLTI. Evidence-based revascularization (EBR) hinges on three independent axes: Patient risk, Limb severity, and ANatomic complexity (PLAN). Average-risk and high-risk patients are defined by estimated procedural and 2-year all-cause mortality. The GVG proposes a new Global Anatomic Staging System (GLASS), which involves defining a preferred target artery path (TAP) and then estimating limb-based patency (LBP), resulting in three stages of complexity for intervention. The optimal revascularization strategy is also influenced by the availability of autogenous vein for open bypass surgery. Recommendations for EBR are based on best available data, pending level 1 evidence from ongoing trials. Vein bypass may be preferred for average-risk patients with advanced limb threat and high complexity disease, while those with less complex anatomy, intermediate severity limb threat, or high patient risk may be favored for endovascular intervention. All patients with CLTI should be afforded best medical therapy including the use of antithrombotic, lipid-lowering, antihypertensive, and glycemic control agents, as well as counseling on smoking cessation, diet, exercise, and preventive foot care. Following EBR, long-term limb surveillance is advised. The effectiveness of nonrevascularization therapies (eg, spinal stimulation, pneumatic compression, prostanoids, and hyperbaric oxygen) has not been established. Regenerative medicine approaches (eg, cell, gene therapies) for CLTI should be restricted to rigorously conducted randomizsed clinical trials. The GVG promotes standardization of study designs and end points for clinical trials in CLTI. The importance of multidisciplinary teams and centers of excellence for amputation prevention is stressed as a key health system initiative.
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| 67. |
- Conte, Michael S., et al.
(författare)
-
Global Vascular Guidelines on the Management of Chronic Limb-Threatening Ischemia
- 2019
-
Ingår i: European Journal of Vascular and Endovascular Surgery. - : Saunders Elsevier. - 1078-5884 .- 1532-2165. ; 58:1, s. S1-S109
-
Tidskriftsartikel (refereegranskat)abstract
- Chronic limb-threatening ischemia (CLTI) is associated with mortality, amputation, and impaired quality of life. These Global Vascular Guidelines (GVG) are focused on definition, evaluation, and management of CLTI with the goals of improving evidence-based care and highlighting critical research needs. The term CLTI is preferred over critical limb ischemia, as the latter implies threshold values of impaired perfusion rather than a continuum. CLTI is a clinical syndrome defined by the presence of peripheral artery disease (PAD) in combination with rest pain, gangrene, or a lower limb ulceration >2 weeks duration. Venous, traumatic, embolic, and nonatherosclerotic etiologies are excluded. All patients with suspected CLTI should be referred urgently to a vascular specialist. Accurately staging the severity of limb threat is fundamental, and the Society for Vascular Surgery Threatened Limb Classification system, based on grading of Wounds, Ischemia, and foot Infection (WIfI) is endorsed. Objective hemodynamic testing, including toe pressures as the preferred measure, is required to assess CLTI. Evidence-based revascularization (EBR) hinges on three independent axes: Patient risk, Limb severity, and ANatomic complexity (PLAN). Average-risk and high-risk patients are defined by estimated procedural and 2-year all-cause mortality. The GVG proposes a new Global Anatomic Staging System (GLASS), which involves defining a preferred target artery path (TAP) and then estimating limb-based patency (LBP), resulting in three stages of complexity for intervention. The optimal revascularization strategy is also influenced by the availability of autogenous vein for open bypass surgery. Recommendations for EBR are based on best available data, pending level 1 evidence from ongoing trials. Vein bypass may be preferred for average-risk patients with advanced limb threat and high complexity disease, while those with less complex anatomy, intermediate severity limb threat, or high patient risk may be favored for endovascular intervention. All patients with CLTI should be afforded best medical therapy including the use of antithrombotic, lipid-lowering, antihypertensive, and glycemic control agents, as well as counseling on smoking cessation, diet, exercise, and preventive foot care. Following EBR, long-term limb surveillance is advised. The effectiveness of nonrevascularization therapies (eg, spinal stimulation, pneumatic compression, prostanoids, and hyperbaric oxygen) has not been established. Regenerative medicine approaches (eg, cell, gene therapies) for CLTI should be restricted to rigorously conducted randomizsed clinical trials. The GVG promotes standardization of study designs and end points for clinical trials in CLTI. The importance of multidisciplinary teams and centers of excellence for amputation prevention is stressed as a key health system initiative.
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| 68. |
- Ducharme, R., et al.
(författare)
-
Effects of different shielding gas compositions on the process of cw CO2 laser welding in the hyperbaric range
- 1996
-
Ingår i: XI International Symposium on Gas Flow and Chemical Lasers and High-Power Laser Conference. - Bellingham, Wash : SPIE - International Society for Optical Engineering. ; , s. 530-533
-
Konferensbidrag (refereegranskat)abstract
- A continuous carbon-dioxide laser of 1.35 kW has been used to study the welding of 5 mm thick stainless steel for pressures ranging from 0.1 to 0.8 MPa in increments of 0.1 MPa. Experimental data, including penetration depths, weld widths, and in some cases weld pool profiles, has been obtained for each value of the pressure using different mixtures of argon and helium shielding gases. In a previous paper it has been reported that keyhole welding could not be carried out for pressures significantly in excess of atmospheric pressure using pure argon and nitrogen shielding gases, but that the process was possible at pressures up to 0.8 MPa using helium. In the present paper the critical pressure for keyhole welding is determined as a function of the mixed shielding gas composition. The laser material interaction is analyzed by solving the heat conduction equation with line and point heat sources representing the keyhole and plume respectively. The line source strength is itself calculated from consideration of the inverse bremsstrahlung and Fresnel absorption processes in the keyhole. It is concluded that successful laser welding in the hyperbaric range crucially hinges on good plume control through the effective delivery of an appropriate shielding gas mixture.
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| 69. |
- Eriksson, Ingemar, et al.
(författare)
-
Guidelines in the choice of parameters for hybrid laser arc welding with fiber lasers
- 2013
-
Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3892. ; 41, s. 119-127
-
Tidskriftsartikel (refereegranskat)abstract
- Laser arc hybrid welding has been a promising technology for three decades and laser welding in combination with gas metal arc welding (GMAW) has shown that it is an extremely promising technique. On the other hand the process is often considered complicated and difficult to set up correctly. An important factor in setting up the hybrid welding process is an understanding of the GMAW process. It is especially important to understand how the wire feed rate and the arc voltage (the two main parameters) affect the process. In this paper the authors show that laser hybrid welding with a 1 μm laser is similar to ordinary GMAW, and several guidelines are therefore inherited by the laser hybrid process.
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| 70. |
- Eriksson, Ingemar, et al.
(författare)
-
High speed video analysis of melt flow inside fiber laser welding keyholes
- 2011
-
Ingår i: Congress proceedings ICALEO. - : Laser institute of America. ; , s. 221-226
-
Konferensbidrag (refereegranskat)abstract
- A high speed video survey of melt flow within fiber laser welding keyholes has revealed a number of interesting observations about the mechanics of weld formation. Using Streak Images and FFT (Fast Fourier Transform) techniques to interpret the video results, quantitative values of fluid flow velocities down the keyhole front have been established. The results have lead to a phenomenological understanding of some of the quality problems which arise at high welding speeds -such as undercut and humping.
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