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Rheological Behaviors and Microstructure of Oviductus Ranae Hydrogels
Qing Liang,Shouqin Zhang,Jinsong Zhang 한국식품과학회 2012 Food Science and Biotechnology Vol.21 No.2
The rheological properties of Oviductus Ranae (OR) hydrogels were systematically investigated with shear viscosity, dynamic oscillation, and creep-recovery measurements. The viscosity curves displayed phenomena of shear thinning with increase of shear rate. The flow behaviors of the hydrogels were described using 2representative rheological models. The lesser water was absorbed by OR, the higher viscosity and greater extent of thixotropy it presents. Dynamic viscoelasticity measurements indicated that the samples exhibit viscoelastic properties as physical gels. Creep curves also revealed that the hydrogels behave as viscoelastic solids. Damped oscillations were observed in the initial stage of creep tests (0-1 s). The viscoelastic moduli obtained from dynamic oscillations and those from damped oscillations agreed with each other. The strong dependence of rheological behaviour on network of OR hydrogels had been confirmed by electron microscopy.
Grinding Damage of BK7 using Copper-Resin Bond Coarse-Grained Diamond Wheel
Qingliang Zhao,Junyun Chen,Haitao Huang,Xiaoyan Fang 한국정밀공학회 2011 International Journal of Precision Engineering and Vol. No.
Coarse-grained wheels can realize high efficient grinding of optical glass. However, the serious surface and subsurface damage will be inevitably introduced by the coarse-grained wheels. In this paper, the grinding damage of a copper-resin bond coarse-grained diamond wheel with grain size of 150μm was investigated on optical glass BK7. The wheel was first properly trued with a metal bond diamond wheel, then pre-dressing for the wheel and grinding experiments are carried out on a precision grinder assisted with electrolytic in process dressing (ELID) method. The surface roughness (Ra) of ground surface was measured using an atomic force microscope (AFM) and the surface topography were imaged by a white light interferometer (WLI) and the AFM. The subsurface damage level of ground surface was evaluated by means of both MRF spot method and taper polishing-etching method, in term of the biggest depth of subsurface damage, distribution of micro defects beneath the ground surface, the cluster depth of subsurface damage, relationship between subsurface damage (SSD)and PV surface roughness (SR), propagating distance and pattern of cracks beneath the ground surface. Experimental results indicate that a well conditioned copper-resin bond coarse-grained diamond wheel on a precision grinder can generate good surface quality of Ra less than 50nm and good subsurface integrity with SSD depth less than 3.5μm for optical glass BK7.
Molecular Mechanisms of Tight Binding through Fuzzy Interactions
Shen, Qingliang,Shi, Jie,Zeng, Danyun,Zhao, Baoyu,Li, Pingwei,Hwang, Wonmuk,Cho, Jae-Hyun Elsevier 2018 Biophysical journal Vol.114 No.6
<P><B>Abstract</B></P> <P>Many intrinsically disordered proteins (IDPs) form fuzzy complexes upon binding to their targets. Although many IDPs are weakly bound in fuzzy complexes, some IDPs form high-affinity complexes. One example is the nonstructural protein 1 (NS1) of the 1918 Spanish influenza A virus, which hijacks cellular CRKII through the strong binding affinity (K<SUB>d</SUB> ∼10 nM) of its proline-rich motif (PRM<SUP>NS1</SUP>) to the N-terminal Src-homology 3 domain of CRKII. However, its molecular mechanism remains elusive. Here, we examine the interplay between structural disorder of a bound PRM<SUP>NS1</SUP> and its long-range electrostatic interactions. Using x-ray crystallography and NMR spectroscopy, we found that PRM<SUP>NS1</SUP> retains substantial conformational flexibility in the bound state. Moreover, molecular dynamics simulations showed that structural disorder of the bound PRM<SUP>NS1</SUP> increases the number of electrostatic interactions and decreases the mean distances between the positively charged residues in PRM<SUP>NS1</SUP> and the acidic residues in the N-terminal Src-homology 3 domain. These results are analyzed using a polyelectrostatic model. Our results provide an insight into the molecular recognition mechanism for a high-affinity fuzzy complex.</P>
Bing Guo,Qingliang Zhao,Xinyu Zhao 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.
The conditioned coarse-grained diamond wheels are able to achieve the identical surface roughness, higher form accuracy and largergrinding rate when compared to the traditional fine-grained diamond wheels. However, deeper subsurface damage could be inevitablyintroduced due to the flat tops of the coarse diamond grains. This work presents a micro-structuring method for coarse-graineddiamond wheels by means of nanosecond pulsed laser, which allows the generation of micro grooves arrays on the coarse diamondgrains distributed on the whole grinding wheel cylindrical surface. The influence of laser parameters such as focal point shift, laserpower, scanning speed and scanning passes on micro-structured surface was investigated, and then the laser machining process wasoptimized in fabricating uniform and continuous micro-structures. The grinding experiments indicate that, when compared to the nonmicro-structured grinding wheels, the subsurface cracks depth of ground optical glass was reduced effectually by using the microstructuredcoarse-grained diamond wheels.
Jinhu Wang,Qingliang Zhao,Chunyu Zhang,Bing Guo,Julong Yuan 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.4
In order to improve the grinding wheel wear during the sapphire steep aspheric surface grinding process, a SiC-reinforced resin-bonded hemispherical diamond wheel was used and the arc envelope grinding performance was investigated. Firstly, the mapping relationship between the contours of the grinding wheel and the aspheric surface was established based on the grinding conditions. The wear of the hemispherical diamond wheel was modelled, and the result indicates that the maximum wear occurred at the edge of the hemisphere, decreases along the generatrix and increases near the center. Then, the formtrued diamond wheel was used for grinding the sapphire steep aspheric surface. The concave and convex surface form error obtained at the central part of Φ 50 mm are 2.5 μm and 1.3 μm, respectively. The surface roughness R a is 230–450 nm, which is affected by the material removal rate and the sapphire crystal anisotropy. The SiC-reinforced resin-bonded diamond wheel possesses favorable self-sharpening ability and sufficient diamond grain retention capacity for sapphire grinding. The wear distribution shows that the most severe wear parts of the grinding wheel are at the edge and the center of the grinding zone, which is consistent with the model-predicted results.
Sheng Wang,Qingliang Zhao,Bing Guo 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.5
Free-form optics made of hard and brittle materials possesses the reflection and imaging functions that are difficult to be achieved by traditional optics and are widely used in various high energy space optical systems. However, free-form optics made of hard and brittle materials poses great challenges to ultra-precision machining due to its extreme demands of complex surface shapes with nonrotational asymmetric, submicron profile accuracy, controllable scallop height, nanometer surface roughness and ductile grinding surfaces. The freeform generation technique of the slow tool servo with diamond grinding wheel (STS-DGW) previously proposed by us was used to manufacture free-form optics made of hard and brittle materials. First, a theoretical model of scallop height during grinding of biconical free-form surface was established, and the effects of curvature changes on scallop height were studied. Subsequently, the profile error caused by the centering error of diamond wheel was calculated theoretically, and an accurate adjustment method of the grinding wheel position was proposed. Then, an undeformed chip thickness model for achieving ductile grinding was established, and the simulation calculation of critical grinding parameters was carried out. Ultimately, a typical off-axis biconical free-form optics with submicron profile accuracy, a controllable scallop height, nanometer surface roughness, and ductile grinding surfaces was successfully fabricated on single-crystal silicon using the proposed STS-DGW. Compared with the previous research, the profile accuracy was further improved, a controllable scallop height and ductile grinding surface was achieved.
Mingtao Wu,Bing Guo,Qingliang Zhao,Jun Zhang,Xiaoyan Fang,Ping He 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.6 No.3
Accompanying with the extensive applications of micro-structured surfaces on hard and brittle material in MEMS and NEMS sensors, optical elements, electronic devices and medical products, efficiently fabricating of these surface has gradually become the focus of manufacturing community. Basing on precision grinding with conditioned and laser micro-structured coarse-grained diamond grinding wheel, a novel high efficiency technique for micro-structured surfaces on hard and brittle material, such as silicon carbide, was developed in this paper. Firstly, the maximum undeformed chip thickness for conditioned coarse-grained wheel and the ductile grinding of silicon carbide was theoretically and experimentally studied. Silicon carbide surface formed mainly in ductile regime was successfully achieved. And then, the strategy for micro-structuring the conditioned wheel with designed micro-structure geometry, sharp edge and small inclination angle side-wall was investigated. Finally, the linear and square micro-structured surfaces with high form accuracy and ultra-precision surface roughness were successfully and efficiently fabricated on silicon carbide by the technique developed in this paper.