The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform
Rune Bredesen - One of the best experts on this subject based on the ideXlab platform.
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on the high Pressure Performance of thin supported pd 23 ag membranes evidence of ultrahigh hydrogen flux after air treatment
Journal of Membrane Science, 2011Co-Authors: Thijs Peters, M Stange, Rune BredesenAbstract:Abstract The hydrogen flux, selectivity and stability of ∼1.9–3.8 μm thick supported palladium alloy (Pd–23%Ag) films are reported. Applying a hydrogen feed Pressure of 26 bar, one of the highest hydrogen fluxes reported equal to 2477 mL min−1 cm−2 (STP) or 132 kg H2 m−2 h−1 was measured at 400 °C. This flux corresponds to a permeance of 1.5 × 10−2 mol m−2 s−1 Pa−0.5. The H2/N2 permselectivity at 25 bar transmembrane Pressure difference was 2900. Allowing the value of n to float between 0.5 and 1, in order to obtain the best fit between the fluxes and ( p H 2 r e t n − p H 2 p e r m n ) , gives a value for n equal to 0.631 after air pre-treatment and correction for the support resistance. The analysis of flux data suggests that diffusional transport through the membrane is rate-limiting. By forcing n equal to 0.5, permeability values as a function of the Pressure have been obtained linking it qualitatively to solution and diffusion behaviour. At the limiting value of zero hydrogen partial Pressure, hydrogen permeabilities of 9.1 × 10−9 mol m−1 s−1 Pa−0.5 and 3.2 × 10−8 mol m−1 s−1 Pa−0.5 have been obtained before and after air treatment, respectively. During continuous operation over 85 days, the membrane showed a good stability up to 350 °C while the nitrogen leakage flux increases very slowly at higher temperatures (Pfeed = 10 bar).
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high Pressure Performance of thin pd 23 ag stainless steel composite membranes in water gas shift gas mixtures influence of dilution mass transfer and surface effects on the hydrogen flux
Journal of Membrane Science, 2008Co-Authors: T A Peters, M Stange, Hallgeir Klette, Rune BredesenAbstract:Abstract The hydrogen permeation and stability of tubular palladium alloy (Pd–23%Ag) composite membranes have been investigated at elevated temperatures and Pressures. In our analysis we differentiate between dilution of hydrogen by other gas components, hydrogen depletion along the membrane length, concentration polarization adjacent to the membrane surface, and effects due to surface adsorption, on the hydrogen flux. A maximum H 2 flux of 1223 mL cm −2 min −1 or 8.4 mol m −2 s −1 was obtained at 400 °C and 26 bar hydrogen feed Pressure, corresponding to a permeance of 6.4 × 10 −3 mol m −2 s −1 Pa −0.5 . A good linear relationship was found between hydrogen flux and Pressure as predicted for rate controlling bulk diffusion. In a mixture of 50% H 2 + 50% N 2 a maximum H 2 flux of 230 mL cm −2 min −1 and separation factor of 1400 were achieved at 26 bar. The large reduction in hydrogen flux is mainly caused by the build-up of a hydrogen-depleted concentration polarization layer adjacent to the membrane due to insufficient mass transport in the gas phase. Substituting N 2 with CO 2 results in further reduction of flux, but not as large as for CO where adsorption prevail as the dominating flow controlling factor. In WGS conditions (57.5% H 2 , 18.7% CO 2 , 3.8% CO, 1.2% CH 4 and 18.7% steam), a H 2 permeance of 1.1 × 10 −3 mol m −2 s −1 Pa −0.5 was found at 400 °C and 26 bar feed Pressure. Operating the membrane for 500 h under various conditions (WGS and H 2 + N 2 mixtures) at 26 bars indicated no membrane failure, but a small decrease in flux. A peculiar flux inhibiting effect of long term exposure to high concentration of N 2 was observed. The membrane surface was deformed and expanded after operation, mainly following the topography of the macroporous support.
Nikil Dutt - One of the best experts on this subject based on the ideXlab platform.
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hybrid compiled simulation an efficient technique for instruction set architecture simulation
ACM Transactions in Embedded Computing Systems, 2009Co-Authors: Mehrdad Reshadi, Prabhat Mishra, Nikil DuttAbstract:Instruction-set simulators are critical tools for the exploration and validation of new processor architectures. Due to the increasing complexity of architectures and time-to-market Pressure, Performance is the most important feature of an instruction-set simulator. Interpretive simulators are flexible but slow, whereas compiled simulators deliver speed at the cost of flexibility and compilation overhead. This article presents a hybrid instruction-set-compiled simulation (HISCS) technique for generation of fast instruction-set simulators that combines the benefit of both compiled and interpretive simulation. This article makes two important contributions: (i) it improves the interpretive simulation Performance by applying compiled simulation at the instruction level using a novel template-customization technique to generate optimized decoded instructions during compile time; and (ii) it reduces the compile-time overhead by combining the benefits of both static and dynamic-compiled simulation. Our experimental results using two contemporary processors (ARM7 and SPARC) demonstrate an order-of-magnitude reduction in compilation time as well as a 70p Performance improvement, on average, over the best-known published result in instruction-set simulation.
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instruction set compiled simulation a technique for fast and flexible instruction set simulation
Design Automation Conference, 2003Co-Authors: Mehrdad Reshadi, Prabhat Mishra, Nikil DuttAbstract:Instruction set simulators are critical tools for the exploration and validation of new programmable architectures. Due to increasing complexity of the architectures and time-to-market Pressure, Performance is the most important feature of an instruction-set simulator. Interpretive simulators are flexible but slow, whereas compiled simulators deliver speed at the cost of flexibility. This paper presents a novel technique for generation of fast instruction set simulators that combines the benefit of both compiled and interpretive simulation. We achieve fast instruction accurate simulation through two mechanisms. First, we move the time consuming decoding process from run-time to compile time while maintaining the flexibility of the interpretive simulation. Second, we use a novel instruction abstraction technique to generate aggressively optimized decoded instructions that further improves simulation Performance. Our instruction set compiled simulation (IS-CS) technique delivers upto 40% Performance improvement over the best known published result that has the flexibility of interpretive simulation. We illustrate the applicability of the IS-CS technique using the ARM7 embedded processor.
Mehrdad Reshadi - One of the best experts on this subject based on the ideXlab platform.
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hybrid compiled simulation an efficient technique for instruction set architecture simulation
ACM Transactions in Embedded Computing Systems, 2009Co-Authors: Mehrdad Reshadi, Prabhat Mishra, Nikil DuttAbstract:Instruction-set simulators are critical tools for the exploration and validation of new processor architectures. Due to the increasing complexity of architectures and time-to-market Pressure, Performance is the most important feature of an instruction-set simulator. Interpretive simulators are flexible but slow, whereas compiled simulators deliver speed at the cost of flexibility and compilation overhead. This article presents a hybrid instruction-set-compiled simulation (HISCS) technique for generation of fast instruction-set simulators that combines the benefit of both compiled and interpretive simulation. This article makes two important contributions: (i) it improves the interpretive simulation Performance by applying compiled simulation at the instruction level using a novel template-customization technique to generate optimized decoded instructions during compile time; and (ii) it reduces the compile-time overhead by combining the benefits of both static and dynamic-compiled simulation. Our experimental results using two contemporary processors (ARM7 and SPARC) demonstrate an order-of-magnitude reduction in compilation time as well as a 70p Performance improvement, on average, over the best-known published result in instruction-set simulation.
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instruction set compiled simulation a technique for fast and flexible instruction set simulation
Design Automation Conference, 2003Co-Authors: Mehrdad Reshadi, Prabhat Mishra, Nikil DuttAbstract:Instruction set simulators are critical tools for the exploration and validation of new programmable architectures. Due to increasing complexity of the architectures and time-to-market Pressure, Performance is the most important feature of an instruction-set simulator. Interpretive simulators are flexible but slow, whereas compiled simulators deliver speed at the cost of flexibility. This paper presents a novel technique for generation of fast instruction set simulators that combines the benefit of both compiled and interpretive simulation. We achieve fast instruction accurate simulation through two mechanisms. First, we move the time consuming decoding process from run-time to compile time while maintaining the flexibility of the interpretive simulation. Second, we use a novel instruction abstraction technique to generate aggressively optimized decoded instructions that further improves simulation Performance. Our instruction set compiled simulation (IS-CS) technique delivers upto 40% Performance improvement over the best known published result that has the flexibility of interpretive simulation. We illustrate the applicability of the IS-CS technique using the ARM7 embedded processor.
Yoshinobu Tsujimoto - One of the best experts on this subject based on the ideXlab platform.
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effect of internal flow in symmetric and asymmetric micro regenerative pump impellers on their Pressure Performance
International Journal of Fluid Machinery and Systems, 2009Co-Authors: Hironori Horiguchi, Yoshinobu Tsujimoto, Shinji Matsumoto, Masaaki Sakagami, Shigeo TanakaAbstract:The effect of symmetric and asymmetric micro regenerative pump impellers on their Pressure Performance was studied. The shut off head of the pump with the symmetric impeller was about 2.5 times as that with the asymmetric impeller. The computation of the internal flow was performed to clarify the cause of the increase of the head. It was found that the contribution of the angular momentum supply was larger than that of shear stress for the head development in both cases. The larger head and momentum supply in the case of the symmetric impeller were caused by larger recirculated flow rate and larger angular momentum difference between the inlet and outlet to the impeller. The larger recirculated flow rate was caused by smaller Pressure gradient in the direction of recirculated flow. The decrease of the circumferential velocity in the casing was attributed to the smaller local flow rate in the casing.
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effect of internal flow in symmetric and asymmetric micro regenerative pump impellers on their Pressure Performance
Transactions of the Japan Society of Mechanical Engineers. B, 2008Co-Authors: Hironori Horiguchi, Yoshinobu Tsujimoto, Shinji Matsumoto, Masaaki Sakagami, Shigeo TanakaAbstract:The effect of internal flow in symmetric and asymmetric micro regenerative pump impellers on their Pressure Performance was studied. It was found that the shut off head of the pump with the symmetric impeller was about 2.5 times as that with the asymmetric impeller. The computation of the internal flow was performed to clarify the cause of the increase of the head. It was found that the contribution of the angular momentum supply was larger than that of shear stress for the head development for both cases. The larger head and momentum supply with the symmetric impeller were caused by larger recirculated flow rate and larger angular momentum difference between the inlet and outlet to the impeller. The larger recirculated flow rate was caused by smaller Pressure gradient in the direction of recirculated flow. The decrease of the circumferential velocity in the casing was attributed to the smaller local flow rate in the casing.
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alternate blade stall and rotating stall in a vaned diffuser
Jsme International Journal Series B-fluids and Thermal Engineering, 2002Co-Authors: Takeshi Sano, Yuki Nakamura, Yoshiki Yoshida, Yoshinobu TsujimotoAbstract:Flow instability in a vaned diffuser with an even number of blades was examined experimentally and analytically. In the experiments, an alternate blade stall, an asymmetric stall, and two types of rotating stalls (backward/forward rotating stall) were observed depending on the impeller/diffuser clearance. For narrow clearance with strong impeller/diffuser interaction, the alternate blade stall and backward rotating stall mainly occurred. With increasing the clearance, the forward rotating stall also occurred, and the onset of rotating stall shifted toward the higher flow rate corresponding to the Pressure Performance in the vaned diffuser. Simple 2D stability analysis showed that the impeller/diffuser clearance affects the speed and direction of the stall propagation, and the slope of the diffuser Pressure Performance vs. flow rate curve affects fundamentally the onset of the flow instability within the diffuser.
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numerical study of rotating stall in a pump vaned diffuser
Journal of Fluids Engineering-transactions of The Asme, 2002Co-Authors: Takeshi Sano, Yuki Nakamura, Yoshiki Yoshida, Yoshinobu Tsujimoto, Tatsuhito MatsushimaAbstract:We treat the flow instabilities in a vaned diffuser by using CFD. A commercial code with the standard κ-e turbulence model was used for the present work. The flow instabilities in the vaned diffuser: i.e., rotating stall, alternate blade stall, and asymmetric stall, could be simulated by the present calculations. These instabilities were observed in a range with negative slope of the Pressure Performance curve of the diffuser. The rotating stall onset flow rate is larger for the case with larger clearance between the impeller and diffuser vanes
Harald Kallevik - One of the best experts on this subject based on the ideXlab platform.
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our current understanding of water in crude oil emulsions recent characterization techniques and high Pressure Performance
Advances in Colloid and Interface Science, 2003Co-Authors: Johan Sjoblom, Narve Aske, Inge Harald Auflem, Oystein Brandal, Trond Erik Havre, O Saether, Arild Westvik, Einar Eng Johnsen, Harald KallevikAbstract:Abstract Stable water-in-oil emulsions may form during the production of crude oil, as co-produced water is mixed with the oil from reservoir to separation facilities. Such emulsions introduce technical challenges, as they must be resolved to provide the specified product quality. Asphaltenes and resins indigenous to the oil are acknowledged as the most important components in respect to stabilization of the interface against coalescence. Fine solids may also contribute to the stabilization, as may the presence of naphthenic acids. Combined, this creates a complex picture of several contributing mechanisms, and it is established that the Pressure conditions will influence the behavior of active components and the properties of the interface. In order to successfully mitigate the problems of stable emulsions, a thorough knowledge of component properties, behavior, interactions and effect on water/oil interfacial properties must be developed for Pressures ranging from ambient to high. This review seeks to bring to light recent findings related to these topics.