| 2681. |
- Liu, F., et al.
(författare)
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Silicon-chip-based frequency quadrupling for optical millimeter-wave signal generation
- 2009
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Ingår i: 2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009. - Washington, D.C. : OSA. - 9781557528773 ; , s. 5377263-
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Konferensbidrag (refereegranskat)abstract
- We propose a prototype of a silicon-chip-based frequency quadrupling system integrating a single-drive silicon Mach-Zehnder modulator and a microring resonator. A proof-of-concept demonstration of 40-GHz millimeter-wave signal generation using 10-GHz driving signal is experimentally provided.
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| 2682. |
- Liu, F., et al.
(författare)
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The detailed chemical composition of the terrestrial planet host Kepler-10
- 2016
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 456:3, s. 2636-2646
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Tidskriftsartikel (refereegranskat)abstract
- Chemical abundance studies of the Sun and solar twins have demonstrated that the solar composition of refractory elements is depleted when compared to volatile elements, which could be due to the formation of terrestrial planets. In order to further examine this scenario, we conducted a line-by-line differential chemical abundance analysis of the terrestrial planet host Kepler-10 and 14 of its stellar twins. Stellar parameters and elemental abundances of Kepler-10 and its stellar twins were obtained with very high precision using a strictly differential analysis of high quality Canada-France-Hawaii Telescope, Hobby-Eberly Telescope and Magellan spectra. When compared to the majority of thick disc twins, Kepler-10 shows a depletion in the refractory elements relative to the volatile elements, which could be due to the formation of terrestrial planets in the Kepler-10 system. The average abundance pattern corresponds to similar to 13 Earth masses, while the two known planets in Kepler-10 system have a combined similar to 20 Earth masses. For two of the eight thick disc twins, however, no depletion patterns are found. Although our results demonstrate that several factors [e.g. planet signature, stellar age, stellar birth location and Galactic chemical evolution (GCE)] could lead to or affect abundance trends with condensation temperature, we find that the trends give further support for the planetary signature hypothesis.
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| 2683. |
- Liu, Goksin, et al.
(författare)
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Conformational multiplicity of bacterial ferric binding protein revealed by small angle x-ray scattering and molecular dynamics calculations
- 2023
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 158:8
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Tidskriftsartikel (refereegranskat)abstract
- This study combines molecular dynamics (MD) simulations with small angle x-ray scattering (SAXS) measurements to investigate the range of conformations that can be adopted by a pH/ionic strength (IS) sensitive protein and to quantify its distinct populations in solution. To explore how the conformational distribution of proteins may be modified in the environmental niches of biological media, we focus on the periplasmic ferric binding protein A (FbpA) from Haemophilus influenzae involved in the mechanism by which bacteria capture iron from higher organisms. We examine iron-binding/release mechanisms of FbpA in varying conditions simulating its biological environment. While we show that these changes fall within the detectable range for SAXS as evidenced by differences observed in the theoretical scattering patterns calculated from the crystal structure models of apo and holo forms, detection of conformational changes due to the point mutation D52A and changes in ionic strength (IS) from SAXS scattering profiles have been challenging. Here, to reach conclusions, statistical analyses with SAXS profiles and results from different techniques were combined in a complementary fashion. The SAXS data complemented by size exclusion chromatography point to multiple and/or alternative conformations at physiological IS, whereas they are well-explained by single crystallographic structures in low IS buffers. By fitting the SAXS data with unique conformations sampled by a series of MD simulations under conditions mimicking the buffers, we quantify the populations of the occupied substates. We also find that the D52A mutant that we predicted by coarse-grained computational modeling to allosterically control the iron binding site in FbpA, responds to the environmental changes in our experiments with conformational selection scenarios that differ from those of the wild type.
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| 2684. |
- Liu, G., et al.
(författare)
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Experimental and numerical studies on melting/solidification of PCM in a horizontal tank filled with graded metal foam
- 2023
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier B.V.. - 0927-0248 .- 1879-3398. ; 250
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Tidskriftsartikel (refereegranskat)abstract
- Although solar energy is a clean and abundant resource, it has an unstable nature. It is demonstrated that latent thermal energy storage (LTES) systems have been an excellent way to utilize solar energy fully and widely. However, LTES has the problem of insufficient thermal conductivity. For this reason, it is inevitable to consider effective methods to intensify the thermal conductivity of LTES system. In the current study, experiment and numerical simulation are used to study the influence of non-uniform metal foams on heat transfer during phase transition. In this study, a horizontal shell-and-tube LTES test system is established. Moreover, the phase change melting rate of radially filled metal foams with different porosity gradients is compared. According to the numerical simulation results of phase interface, velocity field and temperature field, natural convection can accelerate the melting of PCM. However, there is no distinct effect on the solidification process. When the equivalent porosity is 0.94, the optimal combination (melting process is 0.84-0.92-0.99 and solidification process is 0.87-0.94-0.97), compared with the uniform structure, can shorten the total consumption time by 9.7% and 6.2%, respectively.
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| 2685. |
- Liu, G, et al.
(författare)
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Interaction of size-fractionated heparins with lipoprotein lipase and hepatic lipase in the rat.
- 1992
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 285 ( Pt 3), s. 731-6
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Tidskriftsartikel (refereegranskat)abstract
- Heparin and heparin partially depolymerized by enzymic digestion were separated into six size fractions. Hep 1 (tetrasaccharides), with a mean M(r) of 1200, did not release significant amounts of either lipoprotein lipase (LPL) or hepatic lipase (HL) on intravenous injection into rats. Hep 2 (mainly octa- and deca-saccharides), with a mean M(r) of 2400-3000, released both lipases. To evoke the same plasma activity of LPL and HL required about 10 times more by weight, or about 40 times more molecules, of this heparin than of hep 5 (mean M(r) 12,000, similar to conventional heparin). Hep 5 impeded binding and degradation of 125I-labelled bovine LPL by perfused rat livers. In contrast, hep 2 had no detectable effect on these processes. This demonstrates a difference between the sites in the liver that mediate binding, uptake and degradation of LPL, and the extrahepatic sites that bind functional LPL, and the hepatic sites that bind functional HL. After injection of 3.25 mg of hep 5/kg body weight, plasma LPL activity rapidly rose and then remained high for at least 1 h. With hep 2, plasma LPL also rose rapidly, but then decreased to almost basal by 1 h. When a labelled triacylglycerol emulsion was injected 1 h after the heparins, the fractional catabolic rate was enhanced in the rats that had received conventional heparin, as expected from the high plasma LPL activity, but decreased compared with controls in rats that had received hep 2, indicating that available LPL had been depleted through enhanced transport to and uptake in the liver.
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| 2686. |
- Liu, G., et al.
(författare)
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Numerical analysis of inner heating tube position for improving solid-phase transition in a shell-and-tube heat accumulator
- 2023
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Ingår i: Alexandria Engineering Journal. - : Elsevier B.V.. - 1110-0168 .- 2090-2670. ; 65, s. 771-784
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Tidskriftsartikel (refereegranskat)abstract
- Latent heat thermal storage (LHTS) system is vital to reduce environment pollution. In the shell-and-tube heat accumulator, the position of the inner heating tube plays a vital role in the thermal storage. To analyze the effect of the inner tube position on the phase transition, a two-dimensional numerical model is developed. The structure has the minimum full melting time of 3480 s when the inner tube is 12 mm (L = 12 mm) from the center. Compared with L = 0 mm, the full melting time at L = 12 mm can be reduced by 13.4%.
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| 2687. |
- Liu, Hailong, et al.
(författare)
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A simulation study of airborne wear particles from laboratory wheel-rail contacts
- 2016
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Ingår i: Particuology. - : Elsevier. - 1674-2001 .- 2210-4291.
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory measurements of airborne particles from sliding contacts are often performed using a tribometer located in a ventilation chamber. Although knowledge of particle transport behavior inside the chamber is required because it can influence the analysis of measurements, this knowledge is lacking. A numerical model was built based on the same geometry as a pin-on-disc measurement system to explain particle transport behavior inside the chamber and to determine the deviation between real amounts of generated and measured particles at the outlet. The effect of controlled flow conditions on the airflow pattern and particle transport inside the chamber was studied for different experimental conditions. Calculations show that a complex airflow pattern is formed by the spinning disc, and that it differs for each rotational speed. Simulation results reveal that particle transport in the chamber is governed mainly by the airflow pattern. The deposition velocity in the chamber was estimated and the possibility that part of the generated particles would remain in the chamber was studied. This led to an approximate estimation of particle loss rate. A comparison between experimental and simulated results with respect to the particle mass flow rate close to the outlet yields a reference factor of 0.7, which provides an indication of the difference between measured and real values.
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| 2688. |
- Liu, Hailong, et al.
(författare)
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A simulation study of off-gas particles generated from contact between pellets in a laboratory test
- 2015
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Ingår i: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015. - : Chinese Society for Metals. ; , s. 972-976
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Konferensbidrag (refereegranskat)abstract
- A pin-on-disc tribometer situated in a sealed cylindrical chamber was redesigned and used to find out the correlation between pellets properties and generated particles. To understand the results, it is important to understand the dust particle transport behavior inside the chamber. This could be achieved by using a simulation method. With the simulation, it is also possible to determine the operational parameters which in turn could be used to obtain good experimental results. Therefore, a model was built based on the same geometry as the particle measurement system. The flow field was firstly solved with the renormalized group (RNG) k-e turbulence model. Thereafter, a simplified drift-flux method was applied to simulate the particle transport inside the test chamber. Two important characteristics, gravitational separation and diffusion are considered in the modelling. Three groups of particles with different diameters (1nm, 1μm and 10μm) were released at the contact area between the pellets. The simulation results show that the influence of gravitational setting on particle transport is noticeable for 10μm particles, while the influence can be neglected for 1nm and 1μm. On the other hand, the diffusion has a lesser effect on particle dispersion for 1nm, 1μm and 10μm particles. Moreover, the particle loss rate was estimated by the ratio between the amount of released and escaped particles in elapsed time. The results show that the measurable portion of large micro-particles can be increased by increasing the inlet air velocity.
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| 2689. |
- Liu, H. B., et al.
(författare)
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Linearly polarized millimeter and submillimeter continuum emission of Sgr A* constrained by ALMA
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 593
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Tidskriftsartikel (refereegranskat)abstract
- Aims. Our aim is to characterize the polarized continuum emission properties including intensity, polarization position angle, and polarization percentage of Sgr A* at similar to 100 (3.0 mm), similar to 230 (1.3 mm), similar to 345 (0.87 mm), similar to 500 (0.6 mm), and similar to 700 GHz (0.43 mm). Methods. We report continuum emission properties of Sgr A* at the above frequency bands, based on the Atacama Large Millimeter Array (ALMA) observations. We measured flux densities of Sgr A* from ALMA single pointing and mosaic observations. We performed sinusoidal fittings to the observed (XX-YY)/I intensity ratios, to derive the polarization position angles and polarization percentages. Results. We successfully detect polarized continuum emission from all observed frequency bands. We observed lower Stokes I intensity at similar to 700 GHz than that at similar to 500 GHz, which suggests that emission at greater than or similar to 500 GHz is from the optically thin part of a synchrotron emission spectrum. Both the Stokes I intensity and the polarization position angle at our highest observing frequency of similar to 700 GHz, may vary with time. However, as yet we do not detect variation in the polarization percentage at >500 GHz. The polarization percentage at similar to 700 GHz is likely lower than that at similar to 500 GHz. By comparing the similar to 500 GHz and similar to 700 GHz observations with the observations at lower frequency bands, we suggest that the intrinsic polarization position angle of Sgr A* varies with time. This paper also reports the measurable polarization properties from the observed calibration quasars. Conclusions. Future simultaneous multi-frequency polarization observations are required to clarify the time and frequency variation of the polarization position angle and polarization percentage.
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| 2690. |
- Liu, Hailong, et al.
(författare)
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Computational and experimental characterization of 3D-printed PCL structures toward the design of soft biological tissue scaffolds
- 2020
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 188
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Tidskriftsartikel (refereegranskat)abstract
- Degradable porous polymeric structures are attractive candidates for biological tissue scaffolds, and adequate mechanical, transport, chemical and biological properties determine their functionality. Aside from the properties of polymer-based materials, the scaffold's meso-structure controls its elasticity at the organ length-scale. This study investigated the effect of the meso-structure on scaffolds' mechanical and transport properties using finite element analysis (FEA) and computational fluid dynamics (CFD). A number of poly (ε-caprolactone) (PCL) - based scaffolds were 3D printed, analyzed by microcomputed tomography (micro-CT) and mechanically tested. We found that the gradient (G) and gradient and staggered (GS) meso-structure designs led to a higher scaffold permeability, a more homogeneous flow inside the scaffold, and a lower wall shear stress (WSS) in comparison with the basic (B) meso-structure design. The GS design resulted in scaffold stiffness as low as 1.07/0.97 MPa under compression/tension, figures that are comparative with several soft tissues. Image processing of micro-CT data demonstrated that the imposed meso-structures could have been adequately realized through 3D printing, and experimental testing validated FEA analysis. Our results suggest that the properties of 3D-printed PCL-based scaffolds can be tuned via meso-structures toward soft tissue engineering applications. The biological function of designed scaffolds should be further explored in-situ studies.
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