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Analysis of Material Flow in Screw Extrusion of Aluminum
Bjørn Haugen,Magnus Ørnskar,Torgeir Welo,Fredrik Widerøe 한국소성가공학회 2010 기타자료 Vol.2010 No.6
Screw extrusion of aluminum is a new process for production of aluminum profiles. The commercial potential could be large. Little experimental and numerical work has been done with respect to this process. The material flow of hot aluminum in a screw extruder has been analyzed using finite element formulations for the non-Newtonian Navier-Stokes equations. Aluminum material properties are modeled using the Zener-Holloman material model. Effects of stick-slip conditions are investigated with respect to pressure build up and mixing quality of the extrusion process. The numerical results are compared with physical experiments using an experimental screw extruder.
The Rotor-Stator Interaction Onboard A Low Specific Speed Francis Turbine.
Einar Agnalt,Bjørn Winther Solemslie,Pal-Tore Selbo Storli,Ole Gunnar Dahlhaug 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.2
Over the last years, several breakdowns in hydropower plants with low specific speed Francis runners have been reported. One of the main excitation forces in such runners is the pressure fluctuations originating from the rotor stator interaction. In this paper, the rotor-stator interaction has been analyzed utilizing pressure sensors onboard the runner. The pressure sensors were flush mounted in the hub of the runner and the signals were transmitted through a slip-ring system. The measurements have been analyzed relative to the runner angular position by utilizing an angular position sensor mounted to the shaft end. Measurements with different guide vane angle have been compared in order to study the potential flow interaction and the viscous wake effects for the pressure inside the runner. The results from the onboard pressure measurements found that the phase of the guide vane passing pressure seen by the onboard pressure sensors was independent of the guide vane opening. Hence, the potential flow interaction was found to be the dominant effect and no evidence from the viscous wake effect was found on the onboard pressure.
Multimedia Educational Material and Remote Laboratory for Sliding Mode Control Measurements
Bela Takarics,Gabor Sziebig,Bjørn Solvang,Peter Korondi 전력전자학회 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.6
The paper presents a multimedia educational program of DC servo drives for distant learning with a special emphasis on sliding mode control. The program contains of three parts: animation, simulation and internet based measurement. The animation program explains the operation of DC motors, gives its time- and frequency-domain equations, transfer functions and the theoretical background necessary for controller design for DC servo motors. The simulation model of the DC servo motor and the controller can be designed by the students based on the animation program. The students can also test their controllers through the internet based measurement, which is the most important part from engineering point of view. After the measurements are executed, the students can download the measured data and compare them to the simulation results.
Nonfatal Occupational Injuries in Norwegian Farmersq
Kristin Svendsen,Oddfrid Aas,Bjørn Hilt 한국산업안전보건공단 산업안전보건연구원 2014 Safety and health at work Vol.5 No.3
Background: Agriculture ranks among the most dangerous trades worldwide. There is, however, still alack of knowledge on nonfatal injuries in agriculture. The aim of this study was to describe the natureand occurrence of nonfatal injuries in farmers in two counties in central Norway. Methods: A questionnaire was sent to 7,004 farmers in Norway. We asked for information about therespondents and the farm, whether the farmer had had work-related injuries on the farm during the past12 months, and details about the incidence and seriousness of the injury. Results: A total of 2,699 respondents gave a response rate of 42%. Of the respondents, 249 (9.2%) reportedone or more work-related injuries. The most usual cause of injury involved an animal, and >75% of thesehappened inside the outbuilding. Among these, 17.5% had a consequence of sick leave or a more seriousresult. When all the accidents were analyzed by stepwise logistic regression, only the variables: worksalone, has >3,500 stipulated working hours at the farm, and the type of production were statisticalsignificant explanatory variables for having an injury. Conclusion: Incorporating safety aspects to a greater extend in the design and construction of outbuildingswould make a substantial contribution to injury prevention in agriculture.
Jeanett Klubien,Jacob Rosenberg,Bjørn Ole Skjoldbye,Torben Lorentzen,Christian Pállson Nolsøe,Hans-Christian Lykkegaard Pommergaard 대한초음파의학회 2023 ULTRASONOGRAPHY Vol.42 No.3
Purpose: Ablation is a valuable treatment alternative to surgery for colorectal liver metastases. This study reports the long-term clinical outcomes in patients treated with ablation for colorectal liver metastases with or without extrahepatic metastases. Methods: Patients with colorectal liver metastases treated with ultrasound-guided ablation at Herlev Hospital, Denmark were included in this retrospective study. Results: This study included 284 patients with 582 metastases. Complete ablation was obtained in 258 patients (91%) evaluated within 6 weeks. During follow-up, 94 patients (33%) developed local recurrence. The median survival for all patients was 31 months, with 1-, 3-, and 5-year survival rates of 82%, 45%, and 21%, respectively. The median survival for patients with extrahepatic metastases (n=49, 17%) was 24 months compared with 33 months for patients without (P=0.142). Propensity score-adjusted Cox regression showed that extrahepatic metastases were associated with increased mortality, with a hazard ratio (HR) of 1.45 (95% confidence interval [CI], 1.02 to 2.05; P=0.039). In multivariate Cox regression analysis for all patients, increased mortality risk was found for a diameter ≥2.6 cm (HR, 1.59; 95% CI, 1.23 to 2.05), >1 metastasis (HR, 1.66; 95% CI, 1.28 to 2.16), and extrahepatic metastases (HR, 1.45; 95% CI, 1.04 to 2.03). Male sex (HR, 0.75; 95% CI, 0.58 to 0.98) and receiving chemotherapy (HR, 0.69; 95% CI, 0.52 to 0.92) were associated with decreased mortality. Conclusion: Ablation for colorectal liver metastases offers acceptable survival rates, including for patients with extrahepatic metastases. In addition, chemotherapy was associated with improved survival for both patients with and without extrahepatic metastases.
( Rune Giske ),( Tommy Haugen ),( Bjørn Tore Johansen ) 한국스포츠정책과학원(구 한국스포츠개발원) 2016 International Journal of Applied Sports Sciences Vol.28 No.1
It has been suggested that highly motivated and passionate referees are more inclined to pursue higher league levels and, thereby, invest more hours in performance preparations and more general soccer activity. However, limited knowledge is available about practice and mental preparation among elite soccer referees. Our study aim was to investigate referees’ practice and involvement in unmediated soccer activity. We further sought to examine possible preparation differences between elite and sub-elite referees. Comparing elite with sub-elite referees practice may reveal underlying performance principles that may form a basis for trainings methods facilitating referee performance. The following hypotheses were tested: a) elite referees will report higher frequency of physical and mental training compared with sub-elite referees and b) elite referees will report higher involvement in unmediated relevant soccer activity compared with sub-elite referees. Among the 98 top-class referees in Norway, 83 (84.7% response rate, 73 men and ten women, aged 20.46 years) completed a survey about their training volume and content, mental training and involvement in unmediated soccer activity. Reported training volume and content are consistent with referees’ physical demands. Elite referees report significantly greater use of mental training compared with sub-elite referees, while there were no group differences on physical training volume and content or unmediated soccer activity. The results confirm only one of the hypotheses and support the assumption that mental training requires more motivation than physical training even though the latter has quantifiable results that are more regularly measured.
Hydrodynamic Damping of a Fluttering Hydrofoil in High-speed Flows
Carl W. Bergan,Bjørn W. Solemslie,Petter Østby,Ole G. Dahlhaug 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.2
A hydrofoil resembling a high head Francis runner blade was submerged in a rectangular channel and attached to the walls in a fixed-beam configuration. The hydrofoil was excited by piezoelectric Macrofiber composite actuators (MFCs), and the vibration was measured at the trailing edge with Laser Doppler Vibrometry (LDV) and semiconductor strain gauges. The hydrofoil was exposed to water velocities ranging from 0 to 25 m/s. Lock-in occurred at approx. 11m/s. The damping increased linearly with the water velocity, with a slope of 0.02 %/(m/s) below lock-in, and 0.13 %/(m/s) above lock-in. The natural frequency of the foil increased slightly with increasing water velocity below lock-in, due to the added stiffness of the passing water. Additionally, the natural frequency increased significantly when passing through lock-in, due to the vortex shedding phase shift.