176 research outputs found
Effects of sediment erosion in guide vanes of Francis turbines
No full textErosive wear of turbine components has been a major operational challenge for the runoff-river hydropower plants across the basins of Himalaya in Asia. The hard mineral particles, which are carried by rivers reach the turbines and erode the surface in contact. In Francis turbines, guide vanes, cover plates, hub at runner inlet and blades at runner outlet are the most affected areas due to the sediment erosion. Several attempts have been made in the past to minimize the losses due to the sediment erosion in the hydraulic turbines. However, the problem has not been solved satisfactorily.
A dry clearance gap between the guide vanes and the cover plates usually exists in the Francis turbines, fromthe design. The deflection of cover plates and the erosion of the components causes the clearance gap to increase by multiple times of its design value. Inherit pressure difference between guide vane surfaces forces a leakage flow from the increased clearance gap. A systematic study of the characteristics of the leakage flow, and its effects on the flow conditions inside the Francis turbine distributor has not been reported yet. Such studies are necessary for the design optimization of the turbine components and to plan the effective maintenance schedules for repairing the eroded turbine parts.
The main objective of this work is to study the effects of sediment erosion in hydro turbines, with the focus on the flow around the guide vanes of a low specific speed Francis turbine. Experimental investigations of the characteristics of leakage flow from the increased clearance gap between eroded guide vanes and cover plates, has been the focus of this study.
A one-guide vane cascade has been developed to represent the flow inside a low specific speed Francis turbine distributor. Cases with five different sizes of clearance gap are investigated for the guide vane shaped with a symmetric profile. Particle Image Velocimetry techniques are applied for the flow measurement. All experiments have been carried out at the Waterpower Laboratory of Norwegian University of Science and Technology. Flow velocity exceeding 35 m/s, at the runner inlet of Francis turbine, is reported for the first time from such experimental studies.
The results show that, that the clearance gap up to 0.5 mm does not have significant effects on the flow parameters and hence can be accepted as the maximum limit. The leakage flow, with clearance gap more than 1 mm, is found to change the velocity components at the runner inlet significantly. The case with the clearance gap of 2 mm is found to have the highest effects on the flow velocities and is considered as the critical size. The total crosswise leakage flow, from the critical clearance gap, is measured to be more than 1% of the main flow. As the consequence of the leakage flow, the relative velocity at the runner inlet is found to increase locally up to three times from its design value. This local increase in relative velocity is identified as the cause to have severe erosion at the runner hub in the sediment-laden projects. The leakage flow also changes the pressure distribution around guide vane, causing the torque on the guide vane shaft to increase up to 28%.
Further investigation of the propagation of the leakage flow into the turbine runner, and its effects on the runner’s performance is necessary. Alternative designs of guide vane geometry, to minimize the differential pressure across is recommended as the future works
Aldose reductase inhibitors and nanodelivery of diabetic therapeutics
No full textCitation: Prior, A.M., Thapa, M., & Hua, D.H. (2012). Aldose reductase inhibitors and
nanodelivery of diabetic therapeutics. Mini-Reviews in Medicinal Chemistry, 12(4), 326-
336.Nanotechnology is a rapidly emerging drug-delivery system that makes possible the controlled release of small molecules, and nanodelivery of therapeutic molecules using nanoparticles or nanogels represents a major improvement for more focused delivery of such therapeutic molecules. The delivery of insulin for the control of diabetes mellitus (DM) and aldose reductase inhibitor (ARI) for diabetic complications may provide better treatment of diabetes. A structural
overview of aldose reductase including computational docking experiments with HAR-1, various ARIs, aldose-keto reductase, and nanodelivery of insulin, ARI’s, and drug molecules are described
The relationship between farm size and productivity: empirical evidence from the Nepalese mid-hills
No full textThis paper examines the farm size and productivity relationship using data from Nepalese mid hills. The household data used has been drawn from a survey conducted by the author and financed by the Norwegian University of Life Science. The analysis uses models both allowing for and not allowing for village dummies(as cluster controls), the ratio of irrigated land (as proxy for land quality), and other socio-economic variables such as households, belonging to caste groups, and family size (as proxy for access to resources). The result supported the almost âstylized factâ of inverse relationship (IR) between farm size and output per hectare. Total cash input use and labour hours per hectare were found to be higher on small farms. The findings of regression equations allowing for village dummies and other socio-economic variables do not support the explanation that the IR between farm size and productivity is due to variation in regions as well as access to resources. Nevertheless, family size and caste dummies show some effects on farm value added. The paper further investigates returns to scale in Nepalese agriculture, applying the Cobb-Douglas (CD) production function. The result shows constant returns to scale. Labour input seems more influential in farm production, followed by manure, in the sample farms. The overall result shows that the IR between farm size and output per hectare is perhaps due to the result more of other inputs used by small farms rather than diseconomies of scale.inverse relationship, farm size, productivity, returns to scale, Nepal, Q15, O13, Farm Management,
The relationship between farm size and productivity: empirical evidence from the Nepalese mid-hills
No full textThis paper examines the farm size and productivity relationship using data from Nepalese mid hills. The household data used has been drawn from a survey conducted by the author and financed by the Norwegian University of Life Science. The analysis uses models both allowing for and not allowing for village dummies(as cluster controls), the ratio of irrigated land (as proxy for land quality), and other socio-economic variables such as households, belonging to caste groups, and family size (as proxy for access to resources). The result supported the almost ‘stylized fact’ of inverse relationship (IR) between farm size and output per hectare. Total cash input use and labour hours per hectare were found to be higher on small farms. The findings of regression equations allowing for village dummies and other socio-economic variables do not support the explanation that the IR between farm size and productivity is due to variation in regions as well as access to resources. Nevertheless, family size and caste dummies show some effects on farm value added. The paper further investigates returns to scale in Nepalese agriculture, applying the Cobb-Douglas (CD) production function. The result shows constant returns to scale. Labour input seems more influential in farm production, followed by manure, in the sample farms. The overall result shows that the IR between farm size and output per hectare is perhaps due to the result more of other inputs used by small farms rather than diseconomies of scale.inverse relationship; farm size; productivity; returns to scale; Nepal
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No full textThe Ca2+-sensor synaptotagmin-1 that triggers neuronal exocytosis binds to negatively charged membrane lipids (mainly phosphatidylserine (PtdSer) and phosphoinositides (Ptdlns)) but the molecular details of this process are not fully understood. Using quantitative thermodynamic, kinetic and structural methods, we show that synaptotagmin-1 (from Rattus norvegicus and expressed in Escherichia coli) binds to Ptdlns(4,5)P-2 via a polybasic lysine patch in the C2B domain, which may promote the priming or docking of synaptic vesicles. Ca2+ neutralizes the negative charges of the Ca2+-binding sites, resulting in the penetration of synaptotagmin-1 into the membrane, via binding of PtdSer, and an increase in the affinity of the polybasic lysine patch to phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P-2). These Ca2+-induced events decrease the dissociation rate of synaptotagmin-1 membrane binding while the association rate remains unchanged. We conclude that both membrane penetration and the increased residence time of synaptotagmin-1 at the plasma membrane are crucial for triggering exocytotic membrane fusion
MyFutures: Imagining speculative care and support futures in The Netherlands
No full textIn many Western societies, decisions about leaving home and spending your last years in a care home are often taken suddenly. Immediate health issues force family, friends and neighbours who offer informal support to ask for immediate formal support. Such urgent situations do not lead to the best solutions.Design Conceptualization and Communicatio
Malposition of Central Venous Catheter Inserted under Ultrasound Guidance in Intensive Care Unit: A Case Series
No full textMalposition of central venous catheter tip inserted into the subclavian and internal jugular vein is a rare unavoidable complication that can be decreased if inserted under ultrasound guidance. We report case series of three patients, two of subclavian and another of internal jugular inserted central venous catheter, in which the catheter malpositioned into ipsilateral internal jugular and subclavian vein respectively but had no effect on patient management. From this, we want to emphasize that the effect of malposition of central venous catheter tip depends upon the indication for which central venous catheter was inserted; it can be detected bedside by ultrasound and flush test
Psychological, social and welfare interventions for psychological health and well-being of torture survivors
No full textThis is the protocol for a review and there is no abstract. The objectives are as follows: Primary objective 1. To assess beneficial and adverse effects of psychological, social and welfare interventions versus no treatment for the reduction of psychological distress in torture survivors. Secondary objectives 2. To describe the quality and generalisability of the studies evaluating the effects of these treatment approaches on torture survivors, and specifically: • to provide an objective assessment of risk of bias in these studies; • to describe the specific populations evaluated in studies of torture survivors (including demographics, torture experiences and psychological status); • to describe the variety of interventions that have been evaluated in these populations; and • to describe the outcomes evaluated in these intervention studies
Cómo acabar con la pobreza que es lo que funciona cuando los métodos tradicionales fracasan
No full textThere are about eight hundred million people living with a dollar a day worldwide. The author focuses on the fact that the same people who suffer from poverty can generate novel and simple opportunities to generate change. Combating poverty implies, speaking and listening to those involved and understanding their context. The methodology is narrated through the story of Krishna Bahadur Thapa of Nepal who emerges from poverty using Polak methodologies.En el mundo hay cerca de ochocientos millones de personas que viven con un dólar al día. El autor se centra en que las mismas personas que sufren de pobreza pueden generar oportunidades novedosas y simples para generar cambios. Combatir la pobreza implica, hablar y escuchar a los involucrados y entender su contexto. La metodología es narrada mediante la historia de Krishna Bahadur Thapa de Nepal que sale de la pobreza utilizando las metodologías de Polak.
 
Remote prediction of soil types: A working methodology to predict Unified Soil Classification System (USCS) classes based on total geological history
No full textThe Dutch Ministry of Defence is interested in developing a tool or workflow that can be used to remotely predict Unified Soil Classification System (USCS) classes of any area to aid mobility-related decisions. Therefore, this study was initiated by Cohere Consultants in collaboration with NEO, a Dutch remote sensing company and Utrecht University to create such tool or workflow. This MSc thesis provides a study in how the total geological history (TGH) approach as proposed by \cite{TGHA} can be used for predicting soil USCS classes. This is done by implementing the core concept of the TGH into a decision tree model that makes use of many modules, sub-modules and supporting modules to characterise the tectonic, geologic and geomorphological setting of a soil unit. The modules are divided depending if the unit dealt with is a soil, rock or part of a mountain, whereby the soil module incorporates 7 sub-modules that characterize alluvial, lacustrine, coastal, marsh, aeolian, evaporitic and glacial/periglacial environments. The rock and mountain modules, on the other hand, attempt to determine the presence and characteristics of residual soils using a weathering grade system and a table with the weathering products of 23 common rock types. The performance of the decision tree model was tested using two pilot studies in Konna, Mali and Zamora, Spain and one validation study in 's Hertogenbosch. For each study, a map with the predicted USCS soil classes was generated for the study area. The pilot studies explored the possibility of combining the predicted USCS soil maps with topographic wetness index (TWI) and slope angle maps to make a qualitative prediction on the trafficability of the area. The pilot studies showed that the TGH-based decision tree model has potential for being expanded into a tool for aiding military mobility predictions. Next, the validation study compared the predicted USCS map for 's Hertogenbosch to 5 ground truth data points collected by the Dutch Ministry of Defence. The validation study concluded that the decision tree was in general able to distinguish between coarse grained soils and fine grained soils, however struggled with correctly predicting if a soil has high or low plasticity. Finally, the Mali pilot study was able to compare USCS soil predictions made using the decision tree model to those made by a classification of hyperspectral data (made by \cite{flipsen_2022}). Based on the comparison, there seems to be promise for future works to integrate the two methods to benefit from the detail achievable by the hyperspectral method and the qualitative soil descriptions using the TGH-based decision tree. Future recommendations include fine-tuning the decision tree model so that is is able to incorporate more detailed geologic or soil maps (currently has been trained with maps of about 1:500,000), incorporating remote sensing data to create soil units, quantifying uncertainty and possibly automatising the workflow.Applied Earth SciencesGeo-Engineerin
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