Showing papers by "Dong Liu published in 2012"

Enhancing Flow Boiling Heat Transfer in Microchannels for Thermal Management with Monolithically-Integrated Silicon Nanowires

Abstract: Thermal management has become a critical issue for high heat flux electronics and energy systems. Integrated two-phase microchannel liquid-cooling technology has been envisioned as a promising solution, but with great challenges in flow instability. In this work, silicon nanowires were synthesized in situ in parallel silicon microchannel arrays for the first time to suppress the flow instability and to augment flow boiling heat transfer. Significant enhancement in flow boiling heat transfer performance was demonstrated for the nanowire-coated microchannel heat sink, such as an early onset of nucleate boiling, a delayed onset of flow oscillation, suppressed oscillating amplitudes of temperature and pressure drop, and an increased heat transfer coefficient.

Constructed wetlands as biofuel production systems

Abstract: A study advocates the efficient production of cellulosic biofuel using waste nitrogen through wastewater treatment with constructed wetlands in China. The analysis suggests that the net life-cycle energy output of constructed wetlands is higher than many other biofuel production systems.

Studying Protein and Gold Nanoparticle Interaction Using Organothiols as Molecular Probes

Abstract: The protein and gold nanoparticle (AuNP) interfacial interaction has broad implications for biological and biomedical applications of AuNPs. In situ characterization of the morphology and structural evolution of protein on AuNPs is difficult. We have found that the protein coating layer formed by bovine serum albumin (BSA) on AuNP is highly permeable to further organothiol adsorption. Using mercaptobenzimidazole (MBI) as a molecular probe, it is found that BSA interaction with AuNP is an exceedingly lengthy process. Structural modification of BSA coating layer on AuNP continues even after 2 days’ aging of the (AuNP/BSA) mixture. While BSA is in a near full monolayer packing on the AuNPs, it passivates only up to 30% of the AuNP surfaces against MBI adsorption. Aging reduces the kinetics of the MBI adsorption. However, even in the most aged BSA-coated AuNP (3 days), 80% of the MBI adsorption occurs within the first 5 min of the MBI addition to the (AuNP/BSA) mixture. The possibility of MBI displacing the a...

ROP11 GTPase is a negative regulator of multiple ABA responses in Arabidopsis.

Abstract: The phytohormone abscisic acid (ABA) plays crucial roles in plant development and plant responses to environmental stresses. Although ABA receptors and a minimal set of core molecular components have recently been discovered, understanding of the ABA signaling pathway is still far from complete. In this work, we characterized the function of ROP11, a member of the plant-specific ROP small GTPases family, in the ABA signaling process. ROP11 is preferentially expressed in guard cells in all plant organs with stomata. Expression of a constitutively active ROP11 (CA-ROP11) suppresses ABA-mediated responses, whereas reduced expression of ROP11 or expression of its dominant-negative form (DN-ROP11) causes the opposite phenotypes. The affected ABA-mediated responses by ROP11 include seed germination, seedling growth, stomatal closure, induction of ABA-responsive genes, as well as plant response to drought stress. Furthermore, we showed that ROP11 and its closest-related family member, ROP10, act in parallel in mediating these responses. ABA treatment does not affect ROP11 transcription and protein abundance; however, it causes the accumulation of CA-ROP11 in the nucleus. These results demonstrated that ROP11 is a negative regulator of multiple ABA responses in Arabidopsis.

ROP11 GTPase negatively regulates ABA signaling by protecting ABI1 phosphatase activity from inhibition by the ABA receptor RCAR1/PYL9 in Arabidopsis.

Abstract: The phytohormone abscisic acid (ABA) regulates many key processes in plants, such as seed germination, seedling growth, and abiotic stress tolerance. In recent years, a minimal set of core components of a major ABA signaling pathway has been discovered. These components include a RCAR/PYR/PYL family of ABA receptors, a group of PP2C phosphatases, and three SnRK2 kinases. However, how the interactions between the receptors and their targets are regulated by other proteins remains largely unknown. In a companion paper published in this issue, we showed that ROP11, a member of the plant-specific Rho-like small GTPase family, negatively regulates multiple ABA responses in Arabidopsis. The current work demonstrated that the constitutively active ROP11 (CA-ROP11) can modulate the RCAR1/PYL9-mediated ABA signaling pathway based on reconstitution assays in Arabidopsis thaliana protoplasts. Furthermore, using luciferase complementation imaging, yeast two-hybrid assays, co-immunoprecipitation assays in Nicotiana benthamiana and bimolecular fluorescence complementation assays, we demonstrated that CA-ROP11 directly interacts with ABI1, a signaling component downstream of RCAR1/PYL9. Finally, we provided biochemical evidence that CA-ROP11 protects ABI1 phosphatase activity from inhibition by RCAR1/PYL9 and thus negatively regulates ABA signaling in plant cells. A model of how ROP11 acts to negatively regulate ABA signaling is presented.

Research on digital calibration method for optical surface defect dimension

Abstract: A digital calibration method for defect dimension of the optical surface is put forward to get the correspondence between the actual scale of defect on optical surface and the number of pixels of the defect image captured by CCD. Standard scratches, with their width ranging from 0.5μm to 40μm, are fabricated by electron beam exposure and reactive ion beam etching on two kinds of standard calibration board, quartz calibration board with and without chromium film. Calibration experiments are accomplished in five different microscope magnifications. Threshold segmentation, morphological operation and feature extraction are carried out in the images of calibration board to obtain the width of standard scratches in pixels. Interpret the theoretic trend of the calibration function as well as the linear range of it, and fit the calibration function based on the experimental results. According to the analysis and comparing of the calibration results in different microscope magnifications, error source and the factors limiting the resolving accuracy of the calibration system are analyzed. Ultimately, a standardization process including fabrication of the standard scratch, establishment of the standard calibration library for different microscope magnifications and the rapid calibration of actual detect is established. The calibration of the defects on the optical element in the size of 450mm× 450mm is successfully realized.

Application of image entropy evaluation function for the leveling of large aperture components in auto defects detecting

Abstract: In large aperture component’s dark-field scattering defects imaging system, the component’s size is large and part with a wedge. When the component is in the completely level position, the surface defects image can be clearly acquired by a high magnification microscope. Otherwise, fuzzy defects image would be gained because of defocusing which makes digital identification can’t be able to be done. For the problem of leveling large aperture, wedge component, this paper proposes a method that using image information entropy as focusing evaluation function for leveling large aperture components. Firstly, in three different points of component surface acquiring multi-images by the same continuous steps. Then calculating the images’ entropy and fitting a curve to it. Based on minimum image information entropy value criterion, the focal plane can be found and each point’s defocusingamount of the fist acquisition position can be gained. Relay on the relation model of acquisition points, adjust points and defocusingamount that has been built, each adjust point’s adjustment can be got. The component’s level position can be achieved by adjusting the adjust points. In the experiment that using a high magnification (of 16) microscope scans over the whole surface of the component with the size of 430mm×430mm. The image microscope is always in the depth of focus which shows that the leveling precision has achieved 20μm. Until now, this method has been successfully used in large aperture component’s dark-field scattering defects imaging system.

Study on distortion correction for image mosaic of surface defects

Abstract: It is hard to quantitate the micron-scale defects on large aperture (102mm×102mm) optical components by the conventional optical testing methods. This paper proposes a super-smooth surface defects measurement and evaluation system, achieved by using microscopic dark-field scattering imaging device, two-dimensional sub-image scanning mechanism and multi-cycle image mosaic algorithm. The defects detecting system, with a lateral resolution of 0.5μm, applies a large field of view design (largest FOV: 15mm×15mm). In order to test the largest element (430mm×430mm), however, over 1000 sub-pictures are captured. It takes more than 30 minutes to process these sub-pictures by multi-cycle image mosaic algorithm. This paper also presents a distortion correction method to revise the image mosaic mismatch caused by the optical distortion in the defects testing system on the platform of MATLAB. A binary optical grid plate (BOE) is fabricated as standard board to evaluate distortion. The proposed method applies image division multi-steps to build a look-up matrix of distortion parameters. According to the look-up matrix, all pixels on a sub-image are repositioned from the distortion Cartesian coordinates to the ideal Cartesian coordinates. Finally, feasibility of the distortion correction method is demonstrated by comparing the mosaic results of defect images before and after this process. The full field view distortion is reduced from more than 4% to less than 0.1%. After distortion correction, subimages can be directly mosaicked without using multi-cycle image mosaic algorithm, which improves test efficiency significantly. The method mentioned in this paper may also apply to other optical testing systems for image mosaic.

Research on reconstruction of spatial density distribution using optical interferometry and tomography

Abstract: In this article, an interference digital testing method for measuring spatial density distribution of transmissive objects is presented. This method applies a radial shearing interferometer to test the density field from 8 projections in the same plane. By taking advantage of the regularized phase-tracking technique (RPT), the single interferogram will be demodulated to two-dimensional phase distribution of the corresponding projection beam. Then the phase data on one given cross-section of every projection is selected to form 8 curves, which describe one-dimensional phase variation on the given cross-section from each projection. Regarding these curves as computer tomography projection data, the refractive index distribution of the given cross-section can be reconstructed utilizing the algebraic reconstruction technique (ART). Thus, a three-dimensional distribution of refractive index can be obtained by applying the method above to different cross-sections in order. Finally, we are capable of calculating the spatial density distribution with the relation between density and refractive index of the substance tested. In addition, the density field testing for hypersonic flow field is investigated as an example in this article. Considering the fact that the target model in the optical window center of a wind tunnel will inevitably block some testing beams, which will lead to the sharp decline in accuracy of the testing results, a modified algebraic reconstruction technique which improves accuracy by introducing biharmonic spline interpolation is presented. In simulation, an error less than 3% in non-block situation is reached while an error less than 8% in small-area-block situation is also obtained.