A novel tool monitoring approach for diamond wire sawing

Mobile diamond wire sawing is a highly flexible, productive and, versatile cutting process. Accordingly, it is used in many areas, such as the dismantling of nuclear power plants or wind turbines. Despite the widespread use of the process, the cutting process requires continuous manual monitoring by the machine operator. This is due to the continuously changing cutting conditions. A common process error is tool breakage. It is often caused by the displacement of the grinding segments (cutting beads). Due to the cutting speed (up to 30 m/s), these failures cannot be detected and prevented by the machine operator. However, a measuring system or process monitoring does not exist yet. Accordingly, a damaged diamond wire can become hooked, which often results in wire breaks. As a result, grinding segments break away from the wire, which can lead to deadly accidents. Therefore, a new approach for monitoring the tool for diamond wire grinding will be investigated. The paper is divided into five sections. First, the requirements for the sensor system are derived. After the selection of a measuring principle and the functional verification in the grinding process, the monitoring approach is presented and features for monitoring the tool with regard to the displacement of grinding segments are described. It was shown that the developed approach is suitable for monitoring the diamond wire tool during the sawing process. The investigation on a prepared diamond wire tool also demonstrated that the feature allows the detection of displacing grinding segments already from 2 mm

Hypertension with hypokalemia: unusual presentation of pheochromocytoma - case report

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenÞrjátíu og sjö ára gömul kona leitaði endurtekið til heimilislæknis á rúmu hálfu ári. Færslur í sjúkraskrá hennar frá þeim tíma einkennast af kvörtunum um höfuðverki, svima og brjóstverki. Þessi einkenni voru í fyrstu talin upprunnin í stoðkerfi og fékk hún meðal annars ávísað bólgueyðandi lyfjum (NSAID). Greiningin obs. pericarditis er nefnd. Blóðþrýstingur reyndist hækkaður á bilinu 140-200/70-110 mmHg þrátt fyrir að lyfjameðferð væri hafin með amlodipine 5 mg daglega (fimm árum áður hafði blóðþrýstingur í þungun mælst 125/75 mmHg). Endurteknar mælingar án lyfja staðfestu kalíumbrest í sermi (s-K+ 3,2 & 3,3 & 3,4 mmól/l) sem brugðist var við með ávísun á kalíum klóríð 750 mg tvisvar á dag. Hjartarafrit og lungnamynd voru eðlileg. Aldósterón var mælt í sermi í tvígang og talið eðlilegt (646 og 650 pmol/l). Þessu næst voru katekólamín í þvagi mæld (tafla I) og í fyrra skiptið án lyfja var um að ræða noradrenalín hækkun sem nam 2,4 sinnum efri vikmörkum en í seinna skiptið (nýhafin meðferð með amlodipine) nam noradrenalín hækkunin 5,3 földum efri vikmörkum. Heilsufarssaga var annars ómarkverð og konan neytti hvorki áfengis né reykti. Ættarsaga var jákvæð með tilliti til hjartasjúkdóma og háþrýstings

Energy-efficient control of dust extraction for the machining of fibre-reinforced plastics

Fibre-reinforced plastics (FRPs) are becoming increasingly important in aerospace and automotive applications. However, dry machining of FRPs generates abrasive and electrically conductive dust particles that can furthermore cause explosive dust-air mixtures in the enclosed workspace of the machine tool. In order to protect the machine operator and the machine tool, powerful extraction systems (engine power > 5 kW) are usually installed and operated with a constant flow rate, resulting in a significant increase of the machine tool’s overall energy requirement. This paper introduces a novel approach for a demand-oriented control of the flow rate to increase the energy efficiency of dust extraction systems. The objective of the developed control mechanisms is to maintain the maximum permissible dust limit with minimum energy demand. A low-cost dust sensor serves as a feedback system for the applied control mechanism. In a further stage, a force measuring platform was added to provide additional signals for an increased performance of the controlled system. To evaluate the presented approach, milling tests were carried out with carbon-fibre-reinforced plastic (CFRP). The experimental results show that the energy requirement can be reduced by up to 70%

Modelling and validation of synthesis of poly lactic acid using an alternative energy source through a continuous reactive extrusion process

PLA is one of the most promising bio-compostable and bio-degradable thermoplastic polymers made from renewable sources. PLA is generally produced by ring opening polymerization (ROP) of lactide using the metallic/bimetallic catalyst (Sn, Zn, and Al) or other organic catalysts in a suitable solvent. In this work, reactive extrusion experiments using stannous octoate Sn(Oct)2 and tri-phenyl phosphine (PPh)3 were considered to perform ROP of lactide. Ultrasound energy source was used for activating and/or boosting the polymerization as an alternative energy (AE) source. Ludovic® software, designed for simulation of the extrusion process, had to be modified in order to simulate the reactive extrusion of lactide and for the application of an AE source in an extruder. A mathematical model for the ROP of lactide reaction was developed to estimate the kinetics of the polymerization process. The isothermal curves generated through this model were then used by Ludovic software to simulate the “reactive” extrusion process of ROP of lactide. Results from the experiments and simulations were compared to validate the simulation methodology. It was observed that the application of an AE source boosts the polymerization of lactide monomers. However, it was also observed that the predicted residence time was shorter than the experimental one. There is potentially a case for reducing the residence time distribution (RTD) in Ludovic® due to the ‘liquid’ monomer flow in the extruder. Although this change in parameters resulted in validation of the simulation, it was concluded that further research is needed to validate this assumption

Háþrýstingur með kalíumbresti : óvenjuleg sýnd litfíklaæxlis : sjúkratilfelli

Þrjátíu og sjö ára gömul kona leitaði endurtekið til heimilislæknis á rúmu hálfu ári. Færslur í sjúkraskrá hennar frá þeim tíma einkennast af kvörtunum um höfuðverki, svima og brjóstverki. Þessi einkenni voru í fyrstu talin upprunnin í stoðkerfi og fékk hún meðal annars ávísað bólgueyðandi lyfjum (NSAID). Greiningin obs. pericarditis er nefnd. Blóðþrýstingur reyndist hækkaður á bilinu 140-200/70-110 mmHg þrátt fyrir að lyfjameðferð væri hafin með amlodipine 5 mg daglega (fimm árum áður hafði blóðþrýstingur í þungun mælst 125/75 mmHg). Endurteknar mælingar án lyfja staðfestu kalíumbrest í sermi (s-K+ 3,2 & 3,3 & 3,4 mmól/l) sem brugðist var við með ávísun á kalíum klóríð 750 mg tvisvar á dag. Hjartarafrit og lungnamynd voru eðlileg. Aldósterón var mælt í sermi í tvígang og talið eðlilegt (646 og 650 pmol/l). Þessu næst voru katekólamín í þvagi mæld (tafla I) og í fyrra skiptið án lyfja var um að ræða noradrenalín hækkun sem nam 2,4 sinnum efri vikmörkum en í seinna skiptið (nýhafin meðferð með amlodipine) nam noradrenalín hækkunin 5,3 földum efri vikmörkum. Heilsufarssaga var annars ómarkverð og konan neytti hvorki áfengis né reykti. Ættarsaga var jákvæð með tilliti til hjartasjúkdóma og háþrýstings.Peer reviewe

A Numerical Test Rig for Turbomachinery Flows Based on Large Eddy Simulations With a High-Order Discontinuous Galerkin Scheme - Part 3: Secondary Flow Effects

In this final paper of a three-part series, we apply the numerical test rig based on a high-order Discontinuous Galerkin scheme to the MTU T161 low pressure turbine with diverging end walls at off-design Reynolds number of 90,000, Mach number of 0.6 and inflow angle of 41'. The inflow end wall boundary layers are prescribed in accordance with the experiment. Validation of the setup is shown against recent numerical references and the corresponding experimental data. Additionally, we propose and conduct a purely numerical experiment with upstream bar wake generators at a Strouhal number of 1.25, which is well above what was possible in the experiment. We discuss the flow physics at midspan and in the end wall region and highlight the influence of the wakes from the upstream row on the complex secondary flow system using instantaneous flow visualization, phase averages and modal decomposition techniques

Electrochemical etching of AlGaN for the realization of thin-film devices

Heterogeneously integrated AlGaN epitaxial layers will be essential for future optical and electrical devices like thin-film flip-chip ultraviolet (UV) light-emitting diodes, UV vertical-cavity surface-emitting lasers, and high-electron mobility transistors on efficient heat sinks. Such AlGaN-membranes will also enable flexible and micromechanical devices. However, to develop a method to separate the AlGaN-device membranes from the substrate has proven to be challenging, in particular, for high-quality device materials, which require the use of a lattice-matched AlGaN sacrificial layer. We demonstrate an electrochemical etching method by which it is possible to achieve complete lateral etching of an AlGaN sacrificial layer with up to 50% Al-content. The influence of etching voltage and the Al-content of the sacrificial layer on the etching process is investigated. The etched N-polar surface shows the same macroscopic topography as that of the as-grown epitaxial structure, and the root-mean square roughness is 3.5 nm for 1 \ub5m x 1 \ub5m scan areas. Separated device layers have a well-defined thickness and smooth etched surfaces. Transferred multi-quantum-well structures were fabricated and investigated by time-resolved photoluminescence measurements. The quantum wells showed no sign of degradation caused by the thin-film process

Large Eddy Simulation of a Low-Pressure Turbine Cascade with Turbulent End Wall Boundary Layers

We present results of implicit large eddy simulation (LES) and different Reynolds-averaged Navier-Stokes (RANS) models of the MTU 161 low pressure turbine at an exit Reynolds number of 90000 and exit Mach number of 0.6. The LES results are based on a high-order discontinuous Galerkin method and the RANS is computed using a classical finite-volume approach. The paper discusses the steps taken to create realistic inflow boundary conditions in terms of end wall boundary layer thickness and freestream turbulence intensity. This is achieved by tailoring the input distribution of total pressure and temperature, Reynolds stresses and turbulence length scale to a Fourier series based synthetic turbulence generator. With this procedure, excellent agreement with the experiment can be achieved in terms of blade loading at midspan and wake total pressure losses at midspan and over the channel height. Based on the validated setup, we focus on the discussion of secondary flow structures emerging due to the interaction of the incoming boundary layer and the turbine blade and compare the LES to two commonly used RANS models. Since we are able to create consistent setups for both LES and RANS, all discrepancies can be directly attributed to physical modelling problems. We show that both a linear eddy viscosity model and a differential Reynolds stress model coupled with a state-of-the-art correlation-based transition model fail, in this case, to predict the separation induced transition process around midspan. Moreover, their prediction of secondary flow losses leaves room for improvement as shown by a detailed discussion of turbulence kinetic energy and anisotropy fields

A Numerical Test Rig for Turbomachinery Flows Based on Large Eddy Simulations With a High-Order Discontinuous Galerkin Scheme - Part II: Shock Capturing and Transonic Flows

In the second paper of this three-part series, we focus on the simulation of transonic test cases for turbomachinery applications using a high-order discontinuous Galerkin spectral element method (DGSEM). High-fidelity simulations of transonic compressors and turbines are particularly challenging, as they typically occur at high Reynolds numbers and require additional treatment to reliably capture the shock waves characterizing such flows. A recently developed finite-volume subcell shock capturing scheme tailored for the DGSEM is applied and evaluated with regard to the shock sensor. To this end, we conduct implicit large eddy simulations of a high-pressure turbine cascade from the public literature and a transonic compressor cascade measured at the German Aerospace Center, both at a high Reynolds number above 10E6. Based on the results, we examine modal-energy and flow-feature based shock indicator functions, compare the simulation data to experimental and numerical studies, and present an analysis of the unsteady features of the flows

Early detection of anastomotic leakage after pancreatoduodenectomy with microdialysis catheters: an observational Study

Background Microdialysis catheters can detect focal inflammation and ischemia, and thereby have a potential for early detection of anastomotic leakages after pancreatoduodenectomy. The aim was to investigate whether microdialysis catheters placed near the pancreaticojejunostomy can detect leakage earlier than the current standard of care. Methods Thirty-five patients with a median age 69 years were included. Two microdialysis catheters were placed at the end of surgery; one at the pancreaticojejunostomy, and one at the hepaticojejunostomy. Concentrations of glucose, lactate, pyruvate, and glycerol were analyzed hourly in the microdialysate during the first 24 h, and every 2–4 h thereafter. Results Seven patients with postoperative pancreatic fistulae (POPF) had significantly higher glycerol levels (P 400 μmol/L during the first 12 postoperative hours detected patients with POPF with a sensitivity of 100% and a specificity of 93% (P < 0.001). After 24 h, lactate and lactate-to-pyruvate ratio were significantly higher (P < 0.05) and glucose was significantly lower (P < 0.05) in patients with POPF. Conclusion High levels of glycerol in microdialysate was an early detector of POPF. The subsequent inflammation was detected as increase in lactate and lactate-to-pyruvate ratio and a decrease in glucose (NCT03627559).publishedVersio