Biodegradable cross-linked poly(L-lactide-co-e-caprolactone) networks for ureteral stent formed by gamma irradiation under vacuum

Xiliang Liu,Song Liu,Youkun Fan,Jin Qi,Xin Wang,Wei Bai,Dongliang Chen,Chengdong Xiong,Lifang Zhang 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.104 No.-

The poly(L-lactide-co-e-caprolactone) (PLCL) ureteral stent creeps and loses shape stability, increasingthe risk of stent tube dislocation. The rubbery biodegradable cross-linked PLCL networks were preparedthrough gamma irradiation under vacuum in the presence of trimethylolpropane triacrylate (TMPTA),pentaerythritol tetraacrylate (PET4A), and pentaerythritol triacrylate (PETA). At a standard sterilizationdose of 25 kGy, the gel content and network density of PLCL networks increased with increasingcrosslinking agent content (1, 3, 5, 7 wt%), and crosslinking efficiency decreased in the order ofPETA > PET4A > TMPTA. The average molecular weight (Mc ) between two crosslinks ranged from 2000to 105 g/mol. To perform the beneficial semi-interpenetrated polymer network and characterized bythe principle, the networks were processed in several doses (25, 50, 75, 100, and 125 kGy). In place ofthe Charlesby-Pinner equation, the irradiation cross-linking followed the Chen-Liu-Tang equation. ThePLCL network with 7 wt% PETA had a gel fraction of 83%, tensile strength of 34.7 MPa, and tensile setvalue as low as 5%. Furthermore, degradation in vitro was slowed down. Thus, PLCL networks with appropriateelasticity and flexibility, inherent biodegradability, and excellent biocompatibility can provide apromising alternative method for soft tissue repair engineering, such as ureteral stents.

Recrystallization and Microstructural Evolution During Hot Extrusion of Mg97Y2Zn1 Alloy

Bin Chen,Xiaoling Li,Chen Lu,Dongliang Lin 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.3

This study revealed that the extrusion temperature has a great influence on microstructure and mechanicalproperties of the Mg97Y2Zn1 alloy. The average grain sizes increased from 3 μm to 8 μm with increasingextrusion temperatures from 623K to 773 K. Both dynamic recrystallization (DRX) and static recrystallization(SRX), which occur during and after deformation, respectively, were observed. The alloy, which extrudedat a relatively high temperature, exhibited lower strength because the strain strengthening was balanced bythe softening that originated from DRX. Three types of morphologies, namely, big recrystallized grains, fine recrystallizedgrains, and non-recrystallized grains, were observed in the extruded microstructures obtained at 623 K. The dislocation density was quite high in the fully recrystallized grain. The extruded microstructures obtainedat 773 K were composed of large grains with more uniform size. Their degree of recrystallization was higherand the dislocation density also declined. All dislocation in the grain were distinguished as <c+a> dislocations. Submicron scale precipitates were distributed along the newly formed recrystallized grain boundaries andhad a remarkable pinning effect on the recrystallized grain growth after extrusion at 773 K. The precipitates canbe divided into two main types: mixed type and single type.

Microstructural Evolution and Mechanical Properties of Mg95.5Y3Zn1.5 Alloy Processed by Extrusion and ECAP

Bin Cheng,Chen Lu,Dongliang Lin,Xiaoqin Zeng 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.2

A Mg95.5Y3Zn1.5 alloy processed via a two-step processing route of extrusion plus ECAP has been investigated. It was found that the ECAP processed Mg95.5Y3Zn1.5 alloy contained ultrafine grains and exhibitedexcellent mechanical properties. After ECAP, the average grain size of Mg95.5Y3Zn1.5 alloy was refined toabout 300 nm. The highest strengths, with yield strength of 444.6 MPa and ultimate tensile strength of472.7 MPa, were obtained after 1 pass at 623 K. The SAED patterns indicated that the microstructure afterECAP consisted of both high angle and low angle grain boundaries. The fraction of high-angle boundariesincreased with increasing numbers of ECAP passes. The Mg95.5Y3Zn1.5 alloy contained a high volume fractionof X-Mg12ZnY phase due to high yttrium and zinc addition. And, it accelerated the growth and coalescenceof cracks during tensile testing, resulting in premature fracture and lower elongation of alloy.

Enhancement of CO2 desorption using ultrasound and vacuum in water scrubbing biogas upgrading system

Fuqiang Jin,Haipeng Xu,Dongliang Hua,Lei Chen,Yan Li,Yuxiao Zhao,Bin Zuo 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.1

Ultrasound and vacuum were respectively employed to enhance CO2 desorption in a water scrubbing biogas upgrading system. Results showed that incomplete CO2 desorption could cause a high CO2 content in the water and seriously affect the purity of the product gas. Vacuum had a strong enhancement effect on CO2 desorption. When a vacuum of 0.04MPa was used to enhance CO2 desorption, the amount of the stripping air could be reduced to 1/16- th of that without enhancement, indicating that vacuum could greatly enhance CO2 desorption and significantly decrease the amount of the stripping air, which was expected to reduce a large amount of energy consumption. In contrast, the enhancement effect of ultrasound was not so obvious for CO2 desorption in the desorption column with air stripping, since the solution could be well desorbed by gas stripping, though ultrasound could strongly affect the static CO2 desorption.

Enhanced bone regeneration using poly(trimethylene carbonate)/ vancomycin hydrochloride porous microsphere scaffolds in presence of the silane coupling agent modified hydroxyapatite nanoparticles

Jian He,Xulin Hu,Luyao Xing,Dongliang Chen,Lijun Peng,Gaofeng Liang,Chengdong Xiong,Xiangchun Zhang,Lifang Zhang 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.99 No.-

Tissue-engineered scaffolds acted as active natural extracellular matrices that allowed for cellattachment, migration, proliferation, and differentiation. To enhance the drug loading, degradationcontrol, and mechanical features of tissue-engineered scaffolds used in bone regeneration applications,we synthesized novel poly(trimethylene carbonate) (PTMC)/modified HA nanoparticles (KHA NPs,modified by silane coupling agent)/vancomycin hydrochloride (VH) porous microspheres scaffold. Thefabricated PTMC/KHA/VH scaffold has unique surface corrosion degradation, excellent surface properties,and high cytocompatibility. The novel PTMC/KHA/VH scaffold was characterized by 42% porosity,100 mmpore size, and 208.2 MPa compressive modulus. After the treatment of a rat femur defect for 4, 8, and 12weeks, the surface corrosion biodegraded of the PTMC/KHA/VH scaffold remarkably decreasedinflammation response and promoted bone regeneration, suggesting its use as a bioactive structurein bone tissue engineering.

The impacts of resveratrol on the retinal degeneration in a rat model of retinitis pigmentosa induced by alkylation: an in-vivo study

Weiming Yan,Yan Sun,Yutong Wang,Wangjiao Liang,Yuxin Xia,Weihua Yan,Meizhu Chen,Tao Chen,Dongliang Li 한국통합생물학회 2023 Animal cells and systems Vol.27 No.1

Upregulation of Sirtuin Type 1 (SIRT1), a nicotinamide adeninedinucleotide (NAD+)-dependentdeacetylase, has been proved to protect against ample ocular diseases, while its effect onretinitis pigmentosa (RP) has not been illustrated. The study was aimed to explore the impactsof resveratrol (RSV), a SIRT1 activator, on the photoreceptor degeneration in a rat model of RPinduced by N-methyl-N-nitrosourea (MNU), an alkylation. The rats were induced RP phenotypesvia the intraperitoneal injection of MNU. The electroretinogram was conducted and revealedthat RSV could not prevent the decline of retinal function in the RP rats. The optical coherencetomography (OCT) and the retinal histological examination were performed and showed thatthe reduced thickness of the outer nuclear layer (ONL) was not preserved by RSV intervention. The immunostaining technique was applied. Afther the MNU administration, the number of theapoptotic photoreceptors in the ONL throughout the retinasand the number of microglia cellspresent among the outer part throughout the retinas were not significantly reduced by RSV. Western blotting was also performed. The data showed that the level of SIRT1 protein wasdecreased after MNU administration, while RSV was not able to obviously alleviate thedownregulation. Our data together indicated that RSV was not able to rescue thephotoreceptor degeneration in the MNU-induced RP rats, which might be due to the MNUinducedconsumption of the NAD+.

Deviation Calculation and Analysis of Tooth Surfaces of Conjugate-Curve Gear Drive

Dong Liang,Bingkui Chen,Shuai Peng,Chengli Hua,Ruijin Liao 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.5

Conjugate-curve gears are point contact gears and the locus curves of contact points are conjugate curves. For conjugate-curve gear drive, the application of rack cutters may result in geometrical deviation between the theoretical tooth profiles and the generated tooth profiles. To discuss the deviation conditions between two tooth surfaces, generation of theoretical tooth profiles is described and the tooth profiles generated by the rack cutters are derived. General calculation method for the deviation is provided and the analysis of tooth surfaces is also carried out. Numerical examples utilizing the circular-arc curve and parabolic curve are performed, respectively. The obtained results are discussed and the influences of design parameters including the design parameter, helix angle and the radius of pitch circle on the deviation are shown. The summarized contents of this paper are finally present.

Theoretical and Experimental Investigations on Parallel- Axis Gear Transmission with Tubular Meshing Surfaces

Dong Liang,Bingkui Chen,Yane Gao 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

Theoretical and experimental investigations on parallel-axis gears with tubular meshing surfaces are performed in this study. Based on theory of conjugate curves, the parametric design for tubular tooth profiles is provided and solid models are established for motion simulation. Tubular meshing surfaces are evaluated according to geometric and meshing characteristics including undercutting condition, interference with engagement and curvature, calculation of sliding ratios, and successive meshing property. The meshing essence of tubular tooth surfaces is determined. The mechanics properties of tooth surfaces are analyzed using the finite element method. The contact stress, meshing law and deformation analysis of tooth surfaces are presented. The transmission efficiency experiment is based on the developed gear prototype, and a comparison of the prototype with an involute gear drive is provided. Further research on the dynamics analysis and key manufacturing technology will be conducted, and this gear drive is expected to exhibit excellent transmission performance.

Research on Concrete Cracks Recognition based on Dual Convolutional Neural Network

Dong Liang,Xue-Feng Zhou,Song Wang,Chen-Jing Liu 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.7

Cracks are the most common and important diseases of concrete bridges. A dual convolutional neural network (DCN) model which is composed of one convolutional neural network (CNN) model and one fully convolutional network (FCN) model is proposed to recognize the cracks in image. Firstly, the CNN model is used to identify the crack area. The interfering factors such as spot, shadow, water stain, and graffiti in the non-crack area will be excluded by CNN model. Then, the CNN results will be segmented by the FCN model with the structure of merging layer-by-layer to extract crack features such as length and width. The DCN model is trained to recognize the actual concrete bridge cracks in this paper. The recognition results show that the DCN model has a good balance between high accuracy and low noise in the process of crack recognition compared with the current image recognition method. The reliability and accuracy of recognition are both greatly improved. The DCN model is helpful for automatic identification of cracks in concrete bridges.

Mathematical model and meshing analysis of internal meshing gear transmission with curve element

Dong Liang,Weibin Li,Bingkui Chen 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.12

A new internal meshing gear transmission with curve element is put forward in this paper. The mathematical principle of tooth profile generation is described based on conjugate curves theory. For a given spatial curve, the meshing equation and its conjugated spatial curve under the motion law were derived. Considering the equidistant kinematic method, general internal tooth profiles models were established by the conjugate-curve pair. Numerical example of the internal gear pair was developed according to gear parameters and gear solid models were established by MATLAB and UG software. Motion simulation result shows that the gear pair satisfies point contact condition and design requirements. Meshing analysis of tooth profiles using FEA method was carried out. Stress analysis results of tooth profiles with single point contact and two points contact were, respectively, obtained. The conclusions lay the foundation for multi-point contact generation and tooth profile design. Also, further studies on transmission characteristics and manufacturing technology of the new gear drive will be carried out.