Properties of Poly(vinyl chloride)/PB-g-PMMA Composites

Guangfeng Wu,Hailong Zhang,Huixuan Zhang 한국고분자학회 2015 폴리머 Vol.39 No.5

To improve the mechanical properties of poly(vinyl chloride) (PVC), the characters of combining PVC with elastomers were considered. Polybutadiene grafted poly(methyl methacrylate) (PB-g-PMMA, MB) core-shell particles were prepared by emulsion polymerization, and were used as an impact modifier for PVC. The impact resistance, fracture, brittle-ductile transition and the morphology of PVC/MB blends were investigated. It was found that MB particles had a high toughening efficiency for PVC resin, the impact strength was more than 1100 J·m-1 when MB was 8 phr. Two factors influence the impact strength and brittle-ductile transition, one is the modifier content, and the other is core-shell weight ratio. The impact curves are Ω-like shape, the impact strength value is the highest at the middle part and the PVC/ MB blends show ductile break behaviors. The core shell ratio of ductile areas are limited from 80/20 to 90/10 for PVC/MB=100/8, and 70/30 to 93/7 for PVC/MB=100/10.

원형 실린더를 포함한 Lid-driven 캐비티 내의 혼합대류에 관한 수치적 연구

정광봉(Guangfeng Zheng),윤현식(Hyun Sik Yoon),하만영(Man Yeong Ha),박용갑(Yong Gap Park) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5

내부에 원형 실린더가 들어있는 Lid-driven 캐비티 내의 혼합대류에 대한 2차원에서의 수치적 연구를 진행하였다. 본 연구에서 유한체적법에 기초한 가상 경계기법(Immersed Boundary Method)을 이용하여 Gr 수를 10?으로 고정하고 서로 다른 3 가지 Ri 수 10, 0.4 및 0.1 의 범위에서 혼합대류 현상에 대해 연구를 수행하였다. 원형 실린더의 크기와 위치를 변화시키면서 원형 실린더가 캐비티 내의 유동 및 열전달에 미치는 영향을 세부적으로 연구하였다. 연구 결과 캐비티 내의 유동은 원형 실린더의 크기의 변화에 영향이 작았지만 크기가 커질수록 벽면 평균 Nu 값이 더 크고 캐비티 내부 유동과 열전달이 원형 실린더의 위치변화에 강한 영향을 받는 것을 발견하였다. Two-dimensional numerical simulations were carried out for the mixed convection in the lid-driven cavity with the inner circular cylinder at three different Richadson numbers of 0.1, 0.4 and 10 under the fixed Grashof number of 10?. The immersed boundary method based on the finite volume method was adopted in order to model the boundary of the circular cylinder in the cavity. The effects of the location and size of the inner circular cylinder on the flow and heat transfer in the cavity were carefully investigated in the present study. as a result, the mean Nusselt number is found to increase with the radius of the inner circular cylinder increasing, but the flow fields have nearly no change, and the flow and heat transfer are strongly affected from the changing of the location of the inner circular cylinder.

Simulation and Analysis of Mechanical behavior of Groove-shaped Over-Squeezing during Mechanical Ruling

Chaochao Shi,Guangfeng Shi,Guoquan Shi,Haichao Li 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.7

The single crystal diamond chisel-edge tool is used to machine the 79 g/mm echelle diffraction grating, which is used as the research background. DEFORM-3D finite element software is used to simulate the mechanical ruling grating processing, and the influence of the parameters of the ruling tool on the squeezing force of aluminum film material is obtained. By analyzing the flow law of several sampling points in the groove-shaped over-squeezing region, the slip deformation characteristics of the aluminum film during the groove-shaped over-squeezing are clarified. Moreover, the velocity and stress field of aluminum film are analyzed under groove over-squeezing phenomenon. Therefore, it provides a basis for predicting the phenomenon of groove-shaped over-squeezing in the mechanical ruling grating processing.

Dynamic Rheological Behavior, Processability and Mechanical Properties of PVC/Butyl Acrylate-grafted-Methyl Methacrylate/Styrene Blends

Yu Fan,Hailong Zhang,Guangfeng Wu,Huixuan Zhang 한국고분자학회 2015 폴리머 Vol.39 No.6

Core-shell structured grafted copolymer particles of butyl acrylate (BA) grafted methyl methacrylate (MMA) and styrene (St) monomers (ACR-g-St) were prepared by seed emulsion polymerization. Poly(vinyl chloride) (PVC)/ACR-g-St blends were proposed. The fusion properties, dynamic mechanical behavior, rheological behavior, mechanical properties and morphology of blends were characterized by a torque rheometer, dynamic mechanical analyzer (DMA), rotational rheometer, universal mechanical testing machine and scanning electron microscope (SEM). The results showed that the ACR-g-St particles accelerated the fusion of PVC resins, but the equilibrium torque increased slightly. The storage modulus (G′), loss modulus (G″) and complex viscosity (η<SUP>*</SUP>) of melts exhibited a monotonic changing with frequency and all had minimum values when ACR-g-St content was 16 phr. The tensile and impact strength were highest at 8 phr content of ACR-g-St. ACR-g-St not only can be used as an efficient impact aid but also plays a role of lubricant, which is helpful for PVC processing.

Image Retrieval Based on the Weighted and Regional Integration of CNN Features

Kaiyang Liao,Bing Fan,Yuanlin Zheng,Guangfeng Lin,Congjun Cao 한국인터넷정보학회 2022 KSII Transactions on Internet and Information Syst Vol.16 No.3

The features extracted by convolutional neural networks are more descriptive of images than traditional features, and their convolutional layers are more suitable for retrieving images than are fully connected layers. The convolutional layer features will consume considerable time and memory if used directly to match an image. Therefore, this paper proposes a feature weighting and region integration method for convolutional layer features to form global feature vectors and subsequently use them for image matching. First, the 3D feature of the last convolutional layer is extracted, and the convolutional feature is subsequently weighted again to highlight the edge information and position information of the image. Next, we integrate several regional eigenvectors that are processed by sliding windows into a global eigenvector. Finally, the initial ranking of the retrieval is obtained by measuring the similarity of the query image and the test image using the cosine distance, and the final mean Average Precision (mAP) is obtained by using the extended query method for rearrangement. We conduct experiments using the Oxford5k and Paris6k datasets and their extended datasets, Paris106k and Oxford105k. These experimental results indicate that the global feature extracted by the new method can better describe an image.

Extracorporeal Shock Wave Combined with Teriparatide-Loaded Hydrogel Injection Promotes Segmental Bone Defects Healing in Osteoporosis

Chen Qi,Xia Chen,Shi Binbin,Chen Chuyong,Yang Chen,Mao Guangfeng,Shi Fangfang 한국조직공학과 재생의학회 2021 조직공학과 재생의학 Vol.18 No.6

BACKGROUND: Osteoporosis is a systemic bone disease characterized by decreased bone density and deterioration of bone microstructure, leading to an increased probability of fragility fractures. Once segmental bone defect occurs, it is easy to cause delayed union and nonunion. METHODS: The aim of this study is to investigate the efficacy of extracorporeal shock wave (ESW) and teriparatide-loaded hydrogel (T-Gel) combined strategy on the cell activity and differentiation of osteoporosis derived bone marrow mesenchymal stem cells (OP-BMSCs) in vitro and bone regeneration in osteoporotic segmental bone defects in vivo. RESULTS: In vitro, the strategy of combining ESW and T-Gel significantly enhanced OP-BMSCs proliferation, survival, migration, and osteogenic differentiation by up-regulating the alkaline phosphatase activity, mineralization, and expression of runt-related transcription factor-2, type I collagen, osteocalcin, and osteopontin. In the segmental bone defect models of osteoporotic rabbits, Micro-CT evaluation and histological observation demonstrated this ESW-combined with T-Gel injection significantly induced bone healing by enhancing the osteogenic activity of the local microenvironment in osteoporotic defects. CONCLUSION: In conclusion, ESW-combined with T-Gel injection could regulate the poor osteogenic microenvironment in osteoporotic defects and show potential for enhancing fragility fractures healing. BACKGROUND: Osteoporosis is a systemic bone disease characterized by decreased bone density and deterioration of bone microstructure, leading to an increased probability of fragility fractures. Once segmental bone defect occurs, it is easy to cause delayed union and nonunion. METHODS: The aim of this study is to investigate the efficacy of extracorporeal shock wave (ESW) and teriparatide-loaded hydrogel (T-Gel) combined strategy on the cell activity and differentiation of osteoporosis derived bone marrow mesenchymal stem cells (OP-BMSCs) in vitro and bone regeneration in osteoporotic segmental bone defects in vivo. RESULTS: In vitro, the strategy of combining ESW and T-Gel significantly enhanced OP-BMSCs proliferation, survival, migration, and osteogenic differentiation by up-regulating the alkaline phosphatase activity, mineralization, and expression of runt-related transcription factor-2, type I collagen, osteocalcin, and osteopontin. In the segmental bone defect models of osteoporotic rabbits, Micro-CT evaluation and histological observation demonstrated this ESW-combined with T-Gel injection significantly induced bone healing by enhancing the osteogenic activity of the local microenvironment in osteoporotic defects. CONCLUSION: In conclusion, ESW-combined with T-Gel injection could regulate the poor osteogenic microenvironment in osteoporotic defects and show potential for enhancing fragility fractures healing.

Induced Intermediate Mesoderm Combined with Decellularized Kidney Scaffolds for Functional Engineering Kidney

Jianye Zhang,Kailin Li,Feng Kong,Chao Sun,Denglu Zhang,Xin Yu,Xuesheng Wang,Xian Li,Tongyan Liu,Guangfeng Shao,Yong Guan,Shengtian Zhao 한국조직공학과 재생의학회 2019 조직공학과 재생의학 Vol.16 No.6

BACKGROUND: Chronic kidney disease is a severe threat to human health with no ideal treatment strategy. Mature mammalian kidneys have a fixed number of nephrons, and regeneration is difficult once they are damaged. For this reason, developing an efficient approach to achieve kidney regeneration is necessary. The technology of the combination of decellularized kidney scaffolds with stem cells has emerged as a new strategy; however, in previous studies, the differentiation of stem cells in decellularized scaffolds was insufficient for functional kidney regeneration, and many problems remain. METHODS: We used 0.5% sodium dodecyl sulfate (SDS) to produce rat kidney decellularized scaffolds, and induce adipose-derived stem cells (ADSCs) into intermediate mesoderm by adding Wnt agonist CHIR99021 and FGF9 in vitro. The characteristics of decellularized scaffolds and intermediate mesoderm induced from adipose–derived stem cells were identified. The scaffolds were recellularized with ADSCs and intermediate mesoderm cells through the renal artery and ureter. After cocultured for 10 days, cells adhesion and differentiation was evaluated. RESULTS: Intermediate mesoderm cells were successfully induced from ADSCs and identified by immunofluorescence and Western blotting assays (OSR1 ? , PAX2 ?). Immunofluorescence showed that intermediate mesoderm cells differentiated into tubular-like (E-CAD ? , GATA3 ?) and podocyte-like (WT1 ?) cells with higher differentiation efficiency than ADSCs in the decellularized scaffolds. Comparatively, this phenomenon was not observed in induced intermediate mesoderm cells cultured in vitro. CONCLUSION: In this study, we demonstrated that intermediate mesoderm cells could be induced from ADSCs and that they could differentiate well after cocultured with decellularized scaffolds.

Serum MicroRNA Levels as a Noninvasive Diagnostic Biomarker for the Early Diagnosis of Hepatitis B Virus-Related Liver Fibrosis

( Suxia Bao ),( Jianming Zheng ),( Ning Li ),( Chong Huang ),( Mingquan Chen ),( Qi Cheng ),( Kangkang Yu ),( Shengshen Chen ),( Mengqi Zhu ),( Guangfeng Shi ) 대한간학회 2017 Gut and Liver Vol.11 No.6

Background/Aims: To investigate the role of selected serum microRNA (miRNA) levels as potential noninvasive biomarkers for differentiating S0-S2 (early fibrosis) from S3-S4 (late fibrosis) in patients with a chronic hepatitis B virus (HBV) infection. Methods: One hundred twenty-three treatment-naive patients with a chronic HBV infection who underwent a liver biopsy were enrolled in this study. The levels of selected miRNAs were measured using a real-time quantitative polymerase chain reaction assay. A logistic regression analysis was performed to assess factors associated with fibrosis progression. Receiver operating characteristic (ROC) curve and discriminant analyses validated these the ability of these predicted variables to discriminate S0-S2 from S3-S4. Results: Serum miR-29, miR-143, miR-223, miR-21, and miR-374 levels were significantly downregulated as fibrosis progressed from S0-S2 to S3-S4 (p<0.05), but not miR-16. The multivariate logistic regression analysis identified a panel of three miRNAs and platelets that were associated with a high diagnostic accuracy in discriminating S0-S2 from S3-S4, with an area under the curve of 0.936. Conclusions: The levels of the studied miRNAs, with the exception of miR-16, varied with fibrosis progression. A panel was identified that was capable of discriminating S0-S2 from S3-S4, indicating that serum miRNA levels could serve as a potential noninvasive biomarker of fibrosis progression. (Gut Liver 2017;11:860-869)

The Risk Factors and Outcomes for Radiological Abnormalities in Early Convalescence of COVID-19 Patients Caused by the SARS-CoV-2 Omicron Variant: A Retrospective, Multicenter Follow-up Study

Wang Hong,Yang Qingyuan,Li Fangfei,Wang Huiying,Yu Jing,Ge Xihong,Gao Guangfeng,Xia Shuang,Xing Zhiheng,Shen Wen 대한의학회 2023 Journal of Korean medical science Vol.38 No.8

Background: The emergence of the severe acute respiratory syndrome coronavirus 2 omicron variant has been triggering the new wave of coronavirus disease 2019 (COVID-19) globally. However, the risk factors and outcomes for radiological abnormalities in the early convalescent stage (1 month after diagnosis) of omicron infected patients are still unknown. Methods: Patients were retrospectively enrolled if they were admitted to the hospital due to COVID-19. The chest computed tomography (CT) images and clinical data obtained at baseline (at the time of the first CT image that showed abnormalities after diagnosis) and 1 month after diagnosis were longitudinally analyzed. Uni-/multi-variable logistic regression tests were performed to explore independent risk factors for radiological abnormalities at baseline and residual pulmonary abnormalities after 1 month. Results: We assessed 316 COVID-19 patients, including 47% with radiological abnormalities at baseline and 23% with residual pulmonary abnormalities at 1-month follow-up. In a multivariate regression analysis, age ≥ 50 years, body mass index ≥ 23.87, days after vaccination ≥ 81 days, lymphocyte count ≤ 1.21 × 10-9/L, interleukin-6 (IL-6) ≥ 10.05 pg/mL and IgG ≤ 14.140 S/CO were independent risk factors for CT abnormalities at baseline. The age ≥ 47 years, presence of interlobular septal thickening and IL-6 ≥ 5.85 pg/mL were the independent risk factors for residual pulmonary abnormalities at 1-month follow-up. For residual abnormalities group, the patients with less consolidations and more parenchymal bands at baseline could progress on CT score after 1 month. There were no significant changes in the number of involved lung lobes and total CT score during the early convalescent stage. Conclusion: The higher IL-6 level was a common independent risk factor for CT abnormalities at baseline and residual pulmonary abnormalities at 1-month follow-up. There were no obvious radiographic changes during the early convalescent stage in patients with residual pulmonary abnormalities.