The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Shuto Yamada - One of the best experts on this subject based on the ideXlab platform.
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controlled rate thermal decomposition of synthetic bayerite under vacuum
Solid State Ionics, 2004Co-Authors: Nobuyoshi Koga, Shuto YamadaAbstract:Abstract Influences of the controlled decomposition rate and controlled Residual Pressure on the thermal decomposition process of synthetic bayerite were investigated by applying a method of controlled rate evolved gas detection (CREGD). Comparing with the conventional process under linearly increasing temperature, the thermal decomposition process of the synthetic bayerite at a controlled decomposition rate (∼10 −2 mg min −1 ) under controlled Residual Pressure (∼10 −3 Pa) was characterized by the lowered reaction temperature profile and small changes in the specific surface area of the sample during the course of reaction. Formation of an amorphous alumina as the decomposition product is another important result of the process control by the present CREGD. The amorphous alumina crystallizes to η-Al 2 O 3 at around 1100 K. It is worth noting that the characteristics of the reaction process under controlled rate conditions and the formation of amorphous alumina as the decomposition product are very similar to those of mechanochemically activated bayerite under conventional linear heating.
Nobuyoshi Koga - One of the best experts on this subject based on the ideXlab platform.
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controlled rate thermal decomposition of synthetic bayerite under vacuum
Solid State Ionics, 2004Co-Authors: Nobuyoshi Koga, Shuto YamadaAbstract:Abstract Influences of the controlled decomposition rate and controlled Residual Pressure on the thermal decomposition process of synthetic bayerite were investigated by applying a method of controlled rate evolved gas detection (CREGD). Comparing with the conventional process under linearly increasing temperature, the thermal decomposition process of the synthetic bayerite at a controlled decomposition rate (∼10 −2 mg min −1 ) under controlled Residual Pressure (∼10 −3 Pa) was characterized by the lowered reaction temperature profile and small changes in the specific surface area of the sample during the course of reaction. Formation of an amorphous alumina as the decomposition product is another important result of the process control by the present CREGD. The amorphous alumina crystallizes to η-Al 2 O 3 at around 1100 K. It is worth noting that the characteristics of the reaction process under controlled rate conditions and the formation of amorphous alumina as the decomposition product are very similar to those of mechanochemically activated bayerite under conventional linear heating.
He Jacobs - One of the best experts on this subject based on the ideXlab platform.
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An assessment of sub-standard water Pressure in South African potable distribution systems
Journal of Water Sanitation and Hygiene for Development, 2017Co-Authors: Louis Strijdom, Vanessa Speight, He JacobsAbstract:Sub-standard Residual water Pressures in urban water distribution systems (WDS) are a prevalent phenomenon in developing countries – South Africa being no exception. The phenomenon of sub-standard Pressure is poorly understood, with intermittent supply ultimately resulting when there is no Residual Pressure left in the system. This research addressed the prevalence and extent of sub-standard Pressures by using hydraulic models of potable WDS for 71 South African towns, located in 17 different South African municipalities geographically spread over the country. The hydraulic models included 539,388 modelled nodes, which were analysed to determine the number of nodes with sub-standard Pressure heads during peak hour flow conditions. The results show that the Residual Pressure head was
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Evaluation of minimum Residual Pressure as design criterion for South African water distribution systems
Water SA, 2012Co-Authors: He Jacobs, Jl StrijdomAbstract:The South African civil engineering fraternity has grown to accept 24 m as the design criterion for minimum Residual Pressure in water distribution systems. However, the theoretical peak demand in many systems has increased beyond the point where minimum Residual Pressure exceeds 24 m – at least according to hydraulic models. Additions of customers to existing supply systems have led to increased peak flows with time, often without infrastructure upgrades to internal reticulation. Increased flows imply reduced Pressures. This is not necessarily a concern: peak flow conditions rarely occur in a supply system and also, customer complaints often act as a first sign of ‘low Pressures’. No complaints imply ‘no low Pressures’. The researchers analysed hydraulic models for 14 different towns in 5 municipal areas of South Africa, including 2 large metros, to identify the minimum Residual Pressures currently expected. The results include almost 55 000 model nodes and show that about 20% of the nodes in the distribution systems analysed have Pressures of below 24 m, while Pressures of below 14 m are not uncommon. Whether this relatively common occurrence of low Pressures under modelled peak demand is found in practice is not known at this stage. A new guideline for minimum Residual Pressure based on previous criteria and results from this study is presented, noting that a physical lower limit of about 10 m water Pressure is specified in home appliance specifications.
R Niepraschk - One of the best experts on this subject based on the ideXlab platform.
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New, fully automated, primary standard for generating vacuum Pressures between 10?10 Pa and 3 ? 10?2 Pa with respect to Residual Pressure
Metrologia, 1999Co-Authors: K Jousten, H Menzer, D Wandrey, R NiepraschkAbstract:A new primary standard for the realization of vacuum Pressures between 10-10 Pa and 3 × 10-2 Pa has been completed at the Physikalisch-Technische Bundesanstalt (PTB). It is based on the continuous expansion method, whereby the range is extended to lower Pressures by the use of a flow divider. In this flow divider, the gas flow from the fully automated flowmeter with throughputs ranging from 10-6 Pa l/s up to 3 Pa l/s (at 23 degrees C) is directed via two differently sized orifices into two chambers: the XHV calibration chamber, which is designed for calibration Pressures 10-10 Pa to 10-4 Pa, takes up 1% of the flow, while the UHV calibration chamber, which is designed for Pressures 10-8 Pa to 3 × 10-2 Pa, takes up 99% of the flow. Both calibration chambers are operated with cryopumps during calibration. The relative standard uncertainties of Pressures generated by this new standard range from 7 × 10-3 at 10-10 Pa, when a perfectly stable Residual Pressure is assumed, to 2 × 10-3 at 10-4 Pa.
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new fully automated primary standard for generating vacuum Pressures between 10 10 pa and 3 10 2 pa with respect to Residual Pressure
Metrologia, 1999Co-Authors: K Jousten, H Menzer, D Wandrey, R NiepraschkAbstract:A new primary standard for the realization of vacuum Pressures between 10-10 Pa and 3 × 10-2 Pa has been completed at the Physikalisch-Technische Bundesanstalt (PTB). It is based on the continuous expansion method, whereby the range is extended to lower Pressures by the use of a flow divider. In this flow divider, the gas flow from the fully automated flowmeter with throughputs ranging from 10-6 Pa l/s up to 3 Pa l/s (at 23 degrees C) is directed via two differently sized orifices into two chambers: the XHV calibration chamber, which is designed for calibration Pressures 10-10 Pa to 10-4 Pa, takes up 1% of the flow, while the UHV calibration chamber, which is designed for Pressures 10-8 Pa to 3 × 10-2 Pa, takes up 99% of the flow. Both calibration chambers are operated with cryopumps during calibration. The relative standard uncertainties of Pressures generated by this new standard range from 7 × 10-3 at 10-10 Pa, when a perfectly stable Residual Pressure is assumed, to 2 × 10-3 at 10-4 Pa.
Andreas Eicken - One of the best experts on this subject based on the ideXlab platform.
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a low Residual Pressure gradient yields excellent long term outcome after percutaneous pulmonary valve implantation
Jacc-cardiovascular Interventions, 2019Co-Authors: Stanimir Georgiev, Peter Ewert, Daniel Tanase, John Hess, Alfred Hager, Julie Cleuziou, Christian Meierhofer, Andreas EickenAbstract:Abstract Objectives The aim of this study was to report long-term outcomes after percutaneous pulmonary valve implantation (PPVI). Background Excellent short- and mid-term results after PPVI for right ventricular outflow tract (RVOT) dysfunction have been reported. Data on long-term results after PPVI are scarce. Methods All 226 patients treated with PPVI at a single institution were prospectively enrolled in a database and included in the study. Follow-up information regarding outcomes was collected. Risk-factor analysis for death and reinterventions was performed. Results Follow-up data (up to 11 years) were available in 96% of the patients. At the end of the study period, 219 patients (92.8%) still lived with the initially implanted valve. Seven patients died, 2 of them from procedure-related complications. Seventeen patients (7.2%) needed valve replacement surgically (n = 11) or percutaneously (n = 6) for infectious endocarditis (n = 10) or valve degeneration (n = 7). In the remaining patients, the valves retained excellent function, and right ventricular dimensions and exercise capacity improved. A post-interventional RVOT gradient >15 mm Hg was a risk factor for death (hazard ratio: 7.57; 95% confidence interval: 1.26 to 45.38; p = 0.027) and for valve failure (hazard ratio: 3.76; 95% confidence interval: 1.43 to 9.93; p = 0.007). The best outcome was achieved with RVOT pre-stenting and a post-interventional gradient Conclusions Patients after PPVI have excellent long-term outcomes. Right ventricular volumes, function, and exercise capacity improve significantly. A Residual RVOT gradient