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- Bonilla Hernández, Ana Esther
(author)
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Analysis and direct optimization of cutting tool utilization in CAM
- 2015
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Licentiate thesis (other academic/artistic)abstract
- The search for increased productivity and cost reduction in machining can be interpreted as the desire to increase the material removal rate, MRR, and maximize the cutting tool utilization. The CNC process is complex and involves numerous limitations and parameters, ranging from tolerances to machinability. A well-managed preparation process creates the foundations for achieving a reduction in manufacturing errors and machining time. Along the preparation process of the NC-program, two different studies have been conducted and are presented in this thesis. One study examined the CAM programming preparation process from the Lean perspective. The other study includes an evaluation of how the cutting tools are used in terms of MRR and tool utilization.The material removal rate is defined as the product of three variables, namely the cutting speed, the feed and the depth of cut, which all constitute the cutting data. Tool life is the amount of time that a cutting tool can be used and is mainly dependent on the same variables. Two different combinations of cutting data might provide the same MRR, however the tool life will be different. Thereby the difficulty is to select the cutting data to maximize both MRR and cutting tool utilization. A model for the analysis and efficient selection of cutting data for maximal MRR and maximal tool utilization has been developed and is presented. The presented model shortens the time dedicated to the optimized cutting data selection and the needed iterations along the program development.
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- de Roos, André M., et al.
(author)
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Stage-specific predator species help each other to persist while competing for a single prey
- 2008
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In: Proceedings from the National Academy of Science of the United States of America. - Washington, USA : The National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 105:37, s. 13930-13935
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Journal article (peer-reviewed)abstract
- Prey in natural communities are usually shared by many predator species. How predators coexist while competing for the same prey is one of the fundamental questions in ecology. Here we show that competing predator species may not only coexist on a single prey but even help each other to persist, if they specialize on different life history stages of the prey. By changing the prey size distribution a predator species may in fact increase the amount of prey available for its competitor. Surprisingly, a predator may even not be able to persist at all unless its competitor is also present. The competitor thus increases significantly the range of conditions for which a particular predator can persist. This “emergent facilitation” is a long-term, population-level effect that results from asymmetric increases in the rate of prey maturation and reproduction when predation relaxes competition among prey. Emergent facilitation explains observations of correlated increases of predators on small and large conspecific prey as well as concordance in their distribution patterns. Our results suggest that emergent facilitation may promote the occurrence of complex, stable community food webs and that persistence of these communities could critically depend on diversity within predator guilds.
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- Dittmann, Niklas, 1987, et al.
(author)
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Equilibrium finite-frequency noise of an interacting mesoscopic capacitor studied in time-dependent density functional theory
- 2018
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In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 969:1
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Conference paper (peer-reviewed)abstract
- We calculate the frequency-dependent equilibrium noise of a mesoscopic capacitor in time-dependent density functional theory (TDDFT). The capacitor is modeled as a single-level quantum dot with on-site Coulomb interaction and tunnel coupling to a nearby reservoir. The noise spectra are derived from linear-response conductances via the fluctuation-dissipation theorem. Thereby, we analyze the performance of a recently derived exchange-correlation potential with time-nonlocal density dependence in the finite-frequency linear-response regime. We compare our TDDFT noise spectra with real-time perturbation theory and find excellent agreement for noise frequencies below the reservoir temperature.
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- Fernström, Anders
(author)
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Factors affecting body weight development and eating behaviour in patients on continuous ambulatory peritoneal dialysis treatment
- 1998
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Doctoral thesis (other academic/artistic)abstract
- Continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD) have different metabolic effects in dialysis patients, since absorption of intraperitoneal glucose implies an additional energy source in CAPD patients. In spite of this, protein-energy malnutrition is known to occur frequently, both in patients on hemodialysis and in patients on CAPD, and an association with increased morbidity and mortality is well established. It is therefore of great importance to identify factors which have the potential of negatively influencing the nutritional state. In this thesis, it is demonstrated that taste acuity of primary tastes in end-stage renal disease (ESRD) patients is hampered in the form of increased recognition thresholds. The taste thresholds were significantly higher for salt and bitter in preuremic patients, compared to control subjects. In CAPD patients, taste recognition of bitter was impaired and in HD patients, recognition of salty taste was impaired. Patients with ESRD have significantly fewer fungiform taste buds, which might be an important factor contributing to the impaired taste acuity. In addition to the study of the number of taste buds, the presence of peripheral nervous tissue in taste buds with the aid of specific markers (primary antibodies) was also analysed. With these antibodies, no major immunohistochemical differences were disclosed between uremic patients and healthy controls. In a study of energy intake in CAPD patients (five days food recording), it is also established that dietary energy intake from carbohydrates, protein and fat is lower in patients treated with CAPD than in those treated with hemodialysis, although the energy percentage composition of the dietary macronutrients is unaffected. Transperitoneal energy intake compensates for this lower dietary energy intake, and makes total energy intake almost the same in CAPD and HD patients, but with a change in the composition of the diet of CAPD patients towards a significantly higher carbohydrate percentage in energy intake. The level of total energy intake observed places both patient groups in the risk zone for developing malnutrition. CAPD patients have a slower gastric emptying rate, as measured with scintigraphy. This impairment of gastric emptying rate correlates with disturbances in the normal myoelectric rhythm of the stomach (tachygastria), as measured with electrogastrography. A body composition analysis of CAPD patients, as studied with computed tomography of the abdomen and of the right thigh, as well as with dual energy x-ray absorptiometry, reveals an increase in the intraabdominal fat area after commencement of peritoneal dialysis. Thus CAPD induces a distribution of body fat that resembles the pattern observed in the metabolic syndrome. In conclusion, several factors which have the potential of negatively influencing the nutritional state in CAPD patients have been identified. Moreover, a metabolic consequence in the form of an increase in intraabdominal fat is demonstrated in patients treated with CAPD, which may accelerate the development of risk factors for cardiovascular disease.
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| 9. |
- Helldin, Rolf, et al.
(author)
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Opportunities for a democratic pedagogy : a comparative study of South African and Swedish teachers' attitudes to inclusive education
- 2011
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In: Journal of Research in Special Educational Needs. - : Blackwell. - 1471-3802. ; 11:2, s. 107-119
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Journal article (peer-reviewed)abstract
- This paper is based upon the collaboration between two research groups from Stockholm University and the University of South Africa. The main objective is to compare attitudes between South African (SA) and Swedish teachers regarding inclusive education (IE). IE in this paper is examined as a distinct part of the Swedish welfare system. The method used can be characterised as a combined, quantitative and qualitative research design with a purposive sampling. A similar adapted questionnaire was distributed in the two countries. The Swedish teachers in our data are more pro‐inclusion and more hesitating to accommodate learners with barriers in special schools. However, both the Swedish and the SA teachers in the study are hesitating towards the feasibility to implement IE practically. A team approach is concluded to be an adequate pedagogy for supporting IE both in South Africa and Sweden.
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