| 1. |
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| 2. |
- Gao, Jinlong, et al.
(författare)
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Dynamical Relativistic Effects in Quasielastic 1p-Shell Proton Knockout from 16O
- 2000
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Ingår i: Physical Review Letters. - 1079-7114. ; 84:15, s. 3265-3269
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the cross section for quasielastic 1p-shell proton knockout in the 16O(e,e′p) reaction at ω=0.439GeV and Q2=0.8(GeV/c)2 for missing momentum Pmiss≤355MeV/c. We have extracted the response functions RL+TT, RT, RLT, and the left-right asymmetry, ALT, for the 1p1/2 and the 1p3/2 states. The data are well described by relativistic distorted wave impulse approximation calculations. At large Pmiss, the structure observed in ALT indicates the existence of dynamical relativistic effects.
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| 3. |
- Gao, Jinlong, et al.
(författare)
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In-Situ Non-intrusive Diagnostics of Toluene Removal by a Gliding Arc Discharge Using Planar Laser-Induced Fluorescence
- 2017
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Ingår i: Plasma Chemistry and Plasma Processing. - : Springer Science and Business Media LLC. - 0272-4324 .- 1572-8986. ; 37:2, s. 433-450
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Tidskriftsartikel (refereegranskat)abstract
- A non-equilibrium gliding arc discharge anchored on two diverging stainless steel electrodes was extended into open air by a toluene-containing air jet. The removal process of the toluene by the non-equilibrium gliding arc discharge was investigated through in situ and non-intrusive laser-based techniques. Simultaneous planar laser-induced fluorescence (PLIF) of toluene and OH radicals were employed to achieve on-line visualization of the toluene decomposing process by the gliding arc discharge column. Toluene PLIF images with high spatial and temporal resolution showed that the non-equilibrium plasma of the gliding arc discharge is effective in decomposing toluene molecules. Instantaneous toluene removal efficiency was estimated from the toluene PLIF images, showing that the initial toluene concentrations and oxygen concentrations affected the toluene removal efficiency. The toluene removal efficiency decreased with the initial toluene concentration, whereas the efficiency increased with the oxygen concentration. The OH generation in the discharge was found to be enhanced with an increase of the toluene concentration from the OH PLIF results. The relative instantaneous distribution between the OH produced from the discharge channels and the toluene flow was simultaneously visualized. The instantaneous distributions of toluene and OH radicals that were acquired simultaneously by PLIF, were well complementary, suggesting that radicals generated by the gliding arc discharge were responsible for toluene removal in the active volume of the gliding arc discharge. The effective width of the plasma volume for the toluene removal were measured, which gives a new insight into the optimization of industrial design for practical gliding arc reactors.
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| 4. |
- Gao, Jinlong, et al.
(författare)
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Planar laser-induced imaging of CH3 for high resolution single-shot reaction-zone visualization in premixed methane/air flames over broad stoichiometric ratios
- 2022
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 243
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Tidskriftsartikel (refereegranskat)abstract
- We report a novel approach for single-shot planar imaging of CH3 radicals in premixed methane and air flames. A 213 nm beam from the 5th harmonic of an Nd:YAG laser was resonantly absorbed by the CH3 radicals, which were excited to the highly pre-dissociative upper level and dissociated to H2 and CH (X), as the main dissociation channel. The CH radicals were consequently excited by a 388 nm beam from an alexandrite laser, and the fluorescence from the excited CH radicals was collected off-resonant at 431 nm. Using this Photo-Fragmentation Planar Laser-Induced Fluorescence (PF-PLIF) technique, instantaneous flame front structures, represented by CH3 radicals, can be visualized with high spatial resolution over a broad range of stoichiometric ratios. Signal-to-noise ratios up to 50 were observed for premixed methane/air flame with stoichiometric ratio as low as 0.26. The CH radicals naturally presented in flame front are more than 400 times lower in concentration than the CH3 radicals in premixed methane/air flames even at the conditions close to stoichiometric or slightly fuel rich cases where the highest CH concentrations exist, and the CH3/CH concentration ratios increase dramatically moving towards fuel lean conditions. By adopting a structured illumination of the 213 nm pump beam, the naturally presented CH radicals were visualized simultaneously with CH3 at slightly fuel rich laminar flames, where the CH signal intensity was 5 times lower than that from CH3. The results indicate that the CH3 PF-PLIF technique can provide much stronger signal than the CH PLIF and presented a much promising potential for applications in fuel-lean flames. Finally, the CH3 PF-PLIF was performed in premixed turbulent flames to demonstrate the feasibility of this technique for flame front visualization in turbulent premixed flames.
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| 5. |
- Gao, Jinlong, et al.
(författare)
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Visualization of instantaneous structure and dynamics of large-scale turbulent flames stabilized by a gliding arc discharge
- 2019
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 37:4, s. 5629-5636
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Tidskriftsartikel (refereegranskat)abstract
- A burner design with integrated electrodes was used to couple a gliding arc (GA) discharge to a high-power and large-scale turbulent flame for flame stabilization. Simultaneous OH and CH2O planar laser-induced fluorescence (PLIF) and CH PLIF measurements were conducted to visualize instantaneous structures of the GA-assisted flame. Six different regions of the GA-assisted flame were resolved by the multi-species PLIF measurements, including the plasma core, the discharge-induced OH region, the post-flame OH region, the flame front, the preheat CH2O region and the fresh gas mixture. Specifically, the OH profile was observed to be ring-shaped around the gliding arc discharge channel. The formaldehyde (CH2O) was found to be widely distributed in the entire measurement volume even at a low equivalence ratio of 0.4, which suggest that long-lived species from the gliding arc discharge have induced low-temperature oxidations of CH4. The CH layer coincides with the interface of the OH and CH2O regions and indicates that the flame front and the discharge channel are spatially separated by a distance of 3-5 mm. These results reveal that the discharge column acts as a movable pilot flame, providing active radicals and thermal energy to sustain the flame. High-speed video photography was also employed to record the dynamics of the GA-assisted flame. This temporally resolved data was used to study the ignition and propagation behaviors of the flame in response to a temporally modulated burst-mode discharge. The results indicate that turbulent flame can be sustained by matching temporal parameters of the high-voltage bursts to the extinction time of flame.
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| 6. |
- Hu, Siyuan, et al.
(författare)
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Numerical and Experimental Study on Laminar Methane/Air Premixed Flames at Varying Pressure
- 2017
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 105, s. 4970-4975
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Tidskriftsartikel (refereegranskat)abstract
- Laminar methane/air premixed Bunsen flames were studied using detailed numerical simulations and laser diagnostics. In the numerical simulations one-dimensional and two-dimensional configurations were considered with detailed transport properties and chemical kinetic mechanism. In the measurements OH PLIF was employed. The flame structures vary with varying equivalence ratio and pressure. For stoichiometric mixture at atmospheric pressure the flame exhibits a single reaction zone structure, while at high-pressures the flame exhibits a two-reaction zone structure: an inner premixed flame and an outer diffusion flame. The predicted two-zone structure is confirmed in the OH PLIF measurements. Using the numerical and the experimental data the methods of flame-cone-angle and flame-area have been used to extract the laminar flame speed for different equivalence ratios and pressures. It is found that although the flame cone angle method is widely used, it yields a lower accuracy than that of the flame surface area method. The inlet velocity of the burner is shown to affect the accuracy of extracted laminar flame speed. It is suggested that the most suitable inlet velocity of methane-air mixture is about 6 times the laminar flame speed.
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| 7. |
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| 8. |
- Jiang, Jun, et al.
(författare)
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Structure dependent quantum confinement effect in hydrogen-terminated nanodiamond clusters
- 2010
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 108:9, s. 094303-
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Tidskriftsartikel (refereegranskat)abstract
- Size-dependent quantum confinement effect on electronic structure of hydrogen-terminated carbon nanodiamond (ND) cluster has been investigated at the hybrid density functional theory level. Large scale all-electron calculations have been carried out for ND clusters of 0.76 nm (29 carbons) to 7.3 nm (20 959 carbons) in diameter. It is demonstrated that the quantum confinement effect in these clusters shows strong structural dependence. An important structural factor, describing the ratio between the number of atoms within the inner core and outer shell of the cluster, is identified which dictates the size-dependent behavior of the electronic states. For ND clusters with diameter smaller than 1.5 nm, the core-shell ratio changes fast with the increase in cluster size, and the evolution of electronic properties does not follow conventional quantum confinement models. For ND clusters exceeding the threshold of 1.5 nm in diameter, the change in the core-shell ratio saturates and quantum confinement effect becomes visible. Electronic states within the inner core and surface show different size dependence, but a general formula is proposed and describes their structure dependent quantum confinement effects. This formula provides useful insights into quantum confinement behavior in ND clusters, and thereby leads to important physical property information. The calculated electron effective masses for core and surface states of ND clusters are in very good agreement with the experiments.
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| 9. |
- Joo, Peter, et al.
(författare)
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Experimental apparatus with full optical access for combustion experiments with laminar flames from a single circular nozzle at elevated pressures.
- 2015
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 86:3
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Tidskriftsartikel (refereegranskat)abstract
- The design and features of a high pressure chamber and burner that is suitable for combustion experiments at elevated pressures are presented. The high pressure combustion apparatus utilizes a high pressure burner that is comprised of a chamber burner module and an easily accessible interchangeable burner module to add to its flexibility. The burner is well suited to study both premixed and non-premixed flames. The optical access to the chamber is provided through four viewports for direct visual observations and optical-based diagnostic techniques. Auxiliary features include numerous access ports and electrical connections and as a result, the combustion apparatus is also suitable to work with plasmas and liquid fuels. Images of methane flames at elevated pressures up to 25 atm and preliminary results of optical-based measurements demonstrate the suitability of the high pressure experimental apparatus for combustion experiments.
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| 10. |
- Kong, Chengdong, et al.
(författare)
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Characteristics of a Gliding Arc Discharge Under the Influence of a Laminar Premixed Flame
- 2019
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Ingår i: IEEE Transactions on Plasma Science. - 0093-3813. ; 47:1, s. 403-409
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Tidskriftsartikel (refereegranskat)abstract
- The effect of combustion on a gliding arc (GA) discharge is investigated using simultaneous measurements of current and voltage waveforms, as well as imaging and spectroscopic analysis of plasma and flame luminescence. Attributed to the existence of flame, the breakdown voltage and current peak are reduced and the bright sparks during breakdown are dampened. The intrinsic reason is largely owing to the thermal effect of flame. Electrical breakdown is mainly determined by the reduced electric field strength (E/N), which is inversely proportional to temperature. Assuming a constant E/N for breakdown, the combustion-induced temperature increment gives rise to a reduction of the breakdown voltage. The gas composition seems to have less impact on the breakdown voltage. However, the addition of CH₄ can induce more radicals (e.g., H atoms) that enhance the intensity of relevant spectral emissions, especially from OH*. Due to the transport of relatively long-lived radicals, the width of the plasma column of the GA discharge is broadened to form a local reaction zone, serving as a flame holder. Interestingly, the plasma channel moves more smoothly as the flame is present. It implies that the flow field is less turbulent owing to combustion.
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