The Experts below are selected from a list of 4295064 Experts worldwide ranked by ideXlab platform
C Monroe - One of the best experts on this subject based on the ideXlab platform.
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efficient ground state cooling of large trapped ion chains with an electromagnetically induced transparency tripod scheme
Physical Review Letters, 2020Co-Authors: Lei Feng, W L Tan, A Menon, A Chu, Guido Pagano, C MonroeAbstract:We report the electromagnetically-induced-transparency (EIT) cooling of a large trapped $^{171}{\mathrm{Yb}}^{+}$ ion chain to the quantum ground state. Unlike conventional EIT cooling, we engage a four-level tripod structure and achieve fast sub-Doppler cooling over all motional modes. We observe simultaneous ground-state cooling across the complete transverse mode spectrum of up to 40 ions, occupying a bandwidth of over 3 MHz. The cooling time is observed to be less than $300\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$, independent of the number of ions. Such efficient cooling across the entire spectrum is essential for high-fidelity quantum operations using trapped ion crystals for quantum simulators or quantum computers.
Guido Pagano - One of the best experts on this subject based on the ideXlab platform.
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efficient ground state cooling of large trapped ion chains with an electromagnetically induced transparency tripod scheme
Physical Review Letters, 2020Co-Authors: Lei Feng, W L Tan, A Menon, A Chu, Guido Pagano, C MonroeAbstract:We report the electromagnetically-induced-transparency (EIT) cooling of a large trapped $^{171}{\mathrm{Yb}}^{+}$ ion chain to the quantum ground state. Unlike conventional EIT cooling, we engage a four-level tripod structure and achieve fast sub-Doppler cooling over all motional modes. We observe simultaneous ground-state cooling across the complete transverse mode spectrum of up to 40 ions, occupying a bandwidth of over 3 MHz. The cooling time is observed to be less than $300\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$, independent of the number of ions. Such efficient cooling across the entire spectrum is essential for high-fidelity quantum operations using trapped ion crystals for quantum simulators or quantum computers.
Nurhayati Mellon - One of the best experts on this subject based on the ideXlab platform.
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Unraveling the effect of Sub-Cooling temperatures on the kinetic performance of biopolymers for methane hydrate
Journal of Natural Gas Science and Engineering, 2019Co-Authors: Sana Yaqub, Bhajan Lal, Azmi Mohd Shariff, Nurhayati MellonAbstract:Abstract In deep sea plays, where the driving force or Sub-Cooling temperature for hydrate formation is high, the commercially used kinetic hydrate inhibitors (KHIs) lose their kinetic inhibition performance, additionally they are toxic. Though, biodegradable biopolymers are deliberated as an alternative KHIs. However, the inhibition performance of biopolymers solely for methane hydrate formation at high Sub-Cooling temperatures has not been evaluated. In current work the kinetic inhibition performance of five biopolymers (Pectin, Sodium- Carboxymethyl cellulose (Na-CMC), Tapioca starch, Dextran and Xanthan gum) on methane hydrate formation is evaluated using isochoric constant cooling method on sapphire hydrate reactor at 95 bar and Sub-Cooling temperatures of 9 °C and 12 °C. Induction time, hydrate formation rate, amount of methane consumed and percentage relative inhibition power are determined and used as kinetic inhibition indicators. Present data-set reveals that biopolymers efficiently inhibit methane hydrate formation at high Sub-Cooling temperatures. Among all studied biopolymers Pectin and Na-CMC commendably delayed hydrate nucleation for 78 and 61min respectively. Furthermore, Tapioca starch, Pectin and Na-CMC significantly reduced hydrate formation rate, methane consumption and percentage relative inhibition power. For further analysis on molecular level Conductor like Screening Model for Real Solvents (COSMO-RS) software is used. The interaction energy estimation using COSMO-RS showed that attractive interactions between biopolymers and water molecules are leading to prolonged nucleation. Furthermore, the effect of biopolymer concentrations (0.12 wt% - 1.5 wt%) on kinetic inhibition is elaborated by establishing a relationship between induction time, air-liquid interfacial and electrokinetic properties.
Akhilesh Gupta - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of vapor condensation of iso-butane over single horizontal plain tube under different vapor pressures
Applied Thermal Engineering, 2015Co-Authors: Sanjeev K. Sajjan, Ravi Kumar, Akhilesh GuptaAbstract:Abstract In this study, condensation heat transfer coefficients of refrigerant R-600a (iso-butane) over a single horizontal smooth tube of diameter 19 mm were measured at different vapor pressures and different wall Sub-Cooling temperatures. Like other refrigerants, condensation heat transfer coefficients of R-600a showed the same trend with wall Sub-Cooling that external condensation HTCs decrease as wall sub cooling temperatures increase. All data were taken under three different pressures of 0.52 MPa, 0.48 MPa, and 0.43 MPa of the refrigerant-vapor with wall Sub-Cooling temperatures of 5–12 °C on a plain tube of 19 mm outside diameter under a heat flux of 8–20 kW/m2. Based upon the Data taken in this study, different graphs were plotted varying different parameters to show their dependency on other parameters. The experimental data were validated by comparing them against the standard model for condensation over plain tube. In this study, Nusselt's model was used as the standard model for validating the experimental results. The values given by Nusselt's equation were in the range of −10% to +12% of the experimental values.
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Experimental investigation during condensation of R-600a vapor over single horizontal integral-fin tubes
International Journal of Heat and Mass Transfer, 2015Co-Authors: Sanjeev K. Sajjan, Ravi Kumar, Akhilesh GuptaAbstract:Abstract In this study, condensation heat transfer coefficients (HTCs) of refrigerant R-600a (iso-butane) over a horizontal smooth tube of outer diameter 19 mm and five integral fin tubes of different fin-densities (945, 1024, 1102, 1181, and 1260 fpm) were determined at vapor temperature of 39 ± 0.5 °C with different wall Sub-Cooling temperatures in a range of 3–12 °C. Like other refrigerants, condensation heat transfer coefficients of R-600a showed the same trend with wall Sub-Cooling where condensation HTCs decrease with the rise in wall sub cooling temperatures. The heat flux was 11–20 kW/m 2 for the plain tube and 28–82 kW/m 2 for integral fin tubes. Based upon the data taken in this study, different graphs were plotted varying different parameters to show their dependency on other parameters. The experimental data were also validated by comparing them against different models.
Bilal Ahmed Qureshi - One of the best experts on this subject based on the ideXlab platform.
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Mechanical Sub-Cooling vapor compression systems: Current status and future directions
International Journal of Refrigeration-revue Internationale Du Froid, 2013Co-Authors: Bilal Ahmed QureshiAbstract:Abstract Using mechanical Sub-Cooling systems to increase COP of vapor compression cycles is a known method in literature to save energy and increase efficiency. Recently, much progress has been made with respect to investigation into its different aspects that can help to put it into practice. Numerical and experimental works are considered for the purpose of highlighting this progress. These can be categorized as: a) simulation of performance characteristics resulting from different refrigerant combinations in dedicated mechanical Sub-Cooling systems, b) variation in performance characteristics for a vapor compression cycle using integrated mechanical Sub-Cooling because of fouling, c) experimental study about consequences of employing a dedicated mechanical subcooling cycle with a simple vapor compression system, and d) experimental investigation about consequences of employing a subcooler in a two-stage refrigeration cycle. Some important results are discussed. Finally, some suggestions are made to provide direction into future research in this area to help put it into practice.
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the effect of refrigerant combinations on performance of a vapor compression refrigeration system with dedicated mechanical sub cooling
International Journal of Refrigeration-revue Internationale Du Froid, 2012Co-Authors: Bilal Ahmed Qureshi, Syed M ZubairAbstract:Abstract Performance characteristics due to use of different refrigerant combinations in vapor compression cycles with dedicated mechanical Sub-Cooling are investigated. For scratch designs, R134a used in both cycles produced the best results in terms of COP, COP gain and relative compressor sizing. In retrofit cases, considering the high sensitivity of COP to the relative size of heat exchangers in the sub-cooler cycle and the low gain in COP obtained due to installation of a dedicated Sub-Cooling cycle when R717 is the main cycle refrigerant, it seems that dedicated mechanical Sub-Cooling may be more suited to cycles using R134a as the main cycle refrigerant rather than R717. With R134a as the main cycle refrigerant, no major difference was noted, by changing the sub-cooler cycle refrigerant, in the degradation of the performance parameters such as COP and cooling capacity, due to equal fouling of the heat exchangers.
