Study on the Pressure-Volume-Temperature Properties of Polypropylene at Various Cooling and Shear Rates

Pengcheng Xie,Huaguang Yang,Tianze Cai,Zheng Li,Yuelin Li,Weimin Yang 한국고분자학회 2018 폴리머 Vol.42 No.2

To understand the pressure-volume-temperature (PVT) properties of polymer in injection process, a dilatometer with high cooling rate (up to 25 oC/s) and shear rate (up to 320 s-1) was developed. The working pressure and temperature of the dilatometer range from 0 to 100 MPa, and from 30 to 300 oC, respectively. With this instrument, a crystalline polymer polypropylene (PP) was employed to study the effects of cooling rate, shear rate, pressure and their coupling effect on its PVT properties. It was demonstrated that the cooling rate showed a significant effect on the PVT properties. With the increase of cooling rate, the transition temperature of PP from melt state to crystallization decreases gradually and the temperature range of crystallization was also extended. Shear increased the transition temperature of PP from melt state to crystallization. Meanwhile, the initial temperature of shear and crystalline segment was shifted to a higher temperature region with increasing shear duration or shear rate. Above the transition temperature, the effect of shear on the PVT properties weakened gradually with increasing the initial temperature. The coupling analysis of cooling and shear processes showed that increase in cooling rate was enhanced the effect of shear on the transition temperature of PP from melt state to crystallization.

Development of reduced-order thermal stratification model for upper plenum of a lead–bismuth fast reactor based on CFD

Yang Tao,Zhao Pengcheng,Zhao Yanan,Yu Tao 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8

After an emergency shutdown of a lead-bismuth fast reactor, thermal stratification occurs in the upper Plenum, which negatively impacts the integrity of the reactor structure and the residual heat removal capacity of natural circulation flow. The research on thermal stratification of reactors has mainly been conducted using an experimental method, a system program, and computational fluid dynamics (CFD). However, the equipment required for the experimental method is expensive, accuracy of the system program is unpredictable, and resources and time required for the CFD approach are extensive. To overcome the defects of thermal stratification analysis, a high-precision full-order thermal stratification model based on CFD technology is prepared in this study. Furthermore, a reduced-order model has been developed by combining proper orthogonal decomposition (POD) with Galerkin projection. A comparative analysis of thermal stratification with the proposed full-order model reveals that the reduced-order thermal stratification model can well simulate the temperature distribution in the upper plenum and rapidly elucidate the thermal stratification interface characteristics during the lead-bismuth fast reactor accident. Overall, this study provides an analytical tool for determining the thermal stratification mechanism and reducing thermal stratification

Long non-coding RNA RP11-6O2.4 indicates poor prognosis and suppresses cell cycle progression through the p38-MAPK signaling pathway in gastric cancer

Yang Feng,Zhiming Fu,Yajun Luo,Wang Tan,Zilin Liu,Pengcheng Ye,Fei Lu,Wanping Xiang,Linghan Tang,Lin Yao,Mengyun Song,Qingmei Huang,Yilun Liu,Jiangwei Xiao 대한독성 유전단백체 학회 2019 Molecular & cellular toxicology Vol.15 No.3

Backgrounds: The role of long non-coding RNAs (lncRNA) in gastric cancer (GC) has been highlighted in studies conducted over the past decade. However, the potential clinical value and the mechanisms of action of RP11-6O2.4 in GC have not been thoroughly elucidated to date. The specific aim of the present study was to assess RP11-6O2.4 and to explore its role in human GC. Methods: Quantitative real-time polymerase chain reaction (qPCR) was performed to analyze the expression levels of RP11-6O2.4 in GC tissues, paired adjacent noncancerous tissues (ANTs) and GC cell lines. In addition, the correlation between RP11-6O2.4 expression and the clinical characteristics and prognosis of patients with GC was statistically analyzed. The effects of RP11- 6O2.4 on the GC cell cycle transformation through the p38-MAPK signaling pathway were explored by flow cytometry, qPCR and Western blot analysis after treatment with SB203580, a p38MAPK specific inhibitor, in vitro. Results: The expression levels of RP11-6O2.4 in GC tissues were significantly lower than the paired ANTs (P<0.05). In addition, RP11-6O2.4 expression was significantly lower in cases with older age, longer maximum tumor diameter, higher ASA grade and deeper invasive depth (P<0.05). RP11-6O2.4 expression was significantly higher in cases with well/middle differentiation than poor/no differentiation; higher in cases without lymph node metastasis than in lymph node metastasis; and higher in cases in stage Ⅰ/Ⅱ than in stage Ⅲ/Ⅳ. An in vitro assay showed that RP11-6O2.4 induced G0/ G1 phase cell cycle arrest, likely by regulating the p38- MAPK signaling pathway. Conclusion: The above mentioned data suggested that RP11-6O2.4 was a tumor-suppressor gene in GC. RP11- 6O2.4 might play an important role in the cell cycle transformation by regulating the p38-MAPK signaling pathway, thereby representing a specific biomarker and a potential molecular target for the treatment of GC.

Study on the influence of flow blockage in severe accident scenario of CAP1400 reactor

Gao Pengcheng,Zhang Bin,Li Jishen,Miao Fan,Tang Shaowei,Cao Sheng,Yang Hao,Shan Jianqiang 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.3

Deformed fuel rods can cause a partial blockage of the flow area in a subchannel. Such flow blockage will influence the core coolant flow and further the core heat transfer during the reflooding phase and subsequent severe accidents. Nevertheless, most of the system analysis codes simulate the accident process based on the assumed flow blockage ratio, resulting in inconsistencies between simulated results and actual conditions. This paper aims to study the influence of flow blockage in severe accident scenario of the CAP1400 reactor. First, the flow blockage model of ISAA code is improved based on the FRTMB module. Then, the ISAA-FRTMB coupling system is adopted to model and calculate the QUENCH-LOCA- 0 experiment. The correctness and validity of the flow blockage model are verified by comparing the peak cladding temperature. Finally, the DVI Line-SBLOCA accident is induced to analyze the influence of flow blockage on subsequent CAP1400 reactor core heat transfer and core degradation. From the results of the DVI Line-SBLOCA accident analysis, it can be concluded that the blockage ratio is in the range of 40%e60%, and the position of severe blockage is the same as that of cladding rupture. The blockage reduces the circulation area of the core coolant, which in turn impacts the heat exchange between the core and the coolant, leading to the early failure and collapse of some core assemblies and accelerating the core degradation process.

Resonance Parameter of Variable Mode LLC Converter for Auxiliary Converter

XiaoQiong He,Yang Chen,Chen Chen,ZhiQin Zhao,PengCheng Han 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

A precise modeling and resonant calculation method are proposed for variable mode LLC resonant converter. With normal operation of the converter, the redundancy of components is reduced. By establishing equivalent circuit model considering device characteristics, DC gain function is deduced. The resonant parameters are solved by simulated annealing algorithm. The DC gain obtained by the general algorithm and the proposed algorithm are compared. The stable operation of the converter is realized by using the control strategy of digital voltage controlled oscillator and intermittent modulation strategy. The feasibility of this research is verified by simulation and experiment.

Geometric and Semantic Improvement for Unbiased Scene Graph Generation

Ruhui Zhang,Pengcheng Xu,Kang Kang,You Yang 한국인터넷정보학회 2023 KSII Transactions on Internet and Information Syst Vol.17 No.10

Scene graphs are structured representations that can clearly convey objects and the relationships between them, but are often heavily biased due to the highly skewed, long-tailed relational labeling in the dataset. Indeed, the visual world itself and its descriptions are biased. Therefore, Unbiased Scene Graph Generation (USGG) prefers to train models to eliminate long-tail effects as much as possible, rather than altering the dataset directly. To this end, we propose Geometric and Semantic Improvement (GSI) for USGG to mitigate this issue. First, to fully exploit the feature information in the images, geometric dimension and semantic dimension enhancement modules are designed. The geometric module is designed from the perspective that the position information between neighboring object pairs will affect each other, which can improve the recall rate of the overall relationship in the dataset. The semantic module further processes the embedded word vector, which can enhance the acquisition of semantic information. Then, to improve the recall rate of the tail data, the Class Balanced Seesaw Loss (CBSLoss) is designed for the tail data. The recall rate of the prediction is improved by penalizing the body or tail relations that are judged incorrectly in the dataset. The experimental findings demonstrate that the GSI method performs better than mainstream models in terms of the mean Recall@K (mR@K) metric in three tasks. The long-tailed imbalance in the Visual Genome 150 (VG150) dataset is addressed better using the GSI method than by most of the existing methods.

Astragaloside IV reversed the autophagy and oxidative stress induced by the intestinal microbiota of AIS in mice

Nan Xu,Pengcheng Kan,Xiuhua Yao,Ping Yang,Jiwei Wang,Lei Xiang,Yu Zhu 한국미생물학회 2018 The journal of microbiology Vol.56 No.11

Acute ischaemic stroke (AIS) seriously affects patient quality of life. We explored the role of the intestinal microbiota on oxidative stress and autophagy in stroke, and Astragaloside IV (AS-IV) reversed the changes induced by intestinal microbiota. We determined the characteristics of the intestinal microbiota of AIS and transient ischaemic attack (TIA) patients by 16S sequencing and found that the structure and diversity of the intestinal microbiota in patients with AIS and TIA were significantly different from those in healthy subjects. Specifically, the abundance of genus Bifidobacterium, Megamonas, Blautia, Holdemanella, and Clostridium, content of homocysteine and triglyceride was increased significantly, thus it may be as a potential mechanism of AIS and TIA. Furthermore, germ-free mice were infused intracolonically with fecal supernatants of TIA and AIS with/without feed AS-IV for 12 weeks, and we found that the feces of AIS up-regulated the autophagy markers Beclin-1, light chain 3 (LC3)-II and autophagy-related gene (Atg)12, and the expression of reactive oxygen species (ROS) and NADPH oxidase 2/4 (NOX2/4), malondialdehyde (MDA), however, the expression of total antioxidant capacity (T-AOC) and activity of superoxide dismutase (SOD) and glutathione (GSH) was down-regulated in brain tissue, the content of homocysteine and free fatty acids (FFA) in serum of the mice. Meanwhile, AS-IV could reverse the above phenomenon, however, it does not affect the motor function of mice. AS-IV reversed these changes and it may be a potential drug for AIS therapeutics.

Development of a dynamic sensing system for civil revolving structures and its field tests in a large revolving auditorium

Luo, Yaozhi,Yang, Pengcheng,Shen, Yanbin,Yu, Feng,Zhong, Zhouneng,Hong, Jiangbo Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.13 No.6

In civil engineering, revolving structures (RS) are a unique structural form applied in innovative architecture design. Such structures are able to revolve around themselves or along a certain track. However, few studies are dedicated to safety design or health monitoring of RS. In this paper, a wireless dynamic sensing system is developed for RS, and field tests toward a large revolving auditorium are conducted accordingly. At first, a wheel-rail problem is proposed: The internal force redistributes in RS, which is due to wheel-rail irregularity. Then the development of the sensing system for RS is presented. It includes system architecture, network organization, vibrating wire sensor (VWS) nodes and online remote control. To keep the sensor network identifiable during revolving, the addresses of sensor nodes are reassigned dynamically when RS position changes. At last, the system is mounted on a huge outdoor revolving auditorium. Considering the influence of the proposed problem, the RS of the auditorium has been designed conservatively. Two field tests are conducted via the sensing system. In the first test, 2000 people are invited to act as the live load. During the revolving process, data is collected from RS in three different load cases. The other test is the online monitoring for the auditorium during the official performances. In the end, the field-testing result verifies the existence of the wheel-rail problem. The result also indicates the dynamic sensing system is applicable and durable even while RS is rotating.

Enhancement of the Molding Quality of Light Guide Plates by means of Multi-Coating Surface Treatments of the Injection Molding Screw

Ranran Jian,Weimin Yang,Pengcheng Xie 한국고분자학회 2017 폴리머 Vol.41 No.1

The effects of different surface treatments of an injection molding screw have been investigated using light guide plates as a representative precision component. The quality of the fabricated light guide plates was compared for different screw coatings, using the stripping performance, surface microstructure and adhesion strength as criteria. In addition, the results obtained using different combinations of screw coatings were analyzed in order to identify the optimum screw surface treatment method for the large scale production of polycarbonate light guide plates. It was found that light guide plate parts fabricated using a screw with a TiAlN/Cr multi-coating had the best performance, with a defect percentage of only 0.11%, much lower than the value of 19.21% obtained using a screw with a conventional hard chrome coating.

Numerical Simulation on the Enhanced Mixing of Polymer Melt by Single Screw with Torsion Elements in the Homogenizing Section

Ranran Jian,Weimin Yang,Lisheng Cheng,Pengcheng Xie 한국고분자학회 2018 폴리머 Vol.42 No.6

As one of key factors that determine the quality of products, the homogenization of polymer melt is closely dependent on the mixing of polymers. The mixing of polymer melt in the homogenizing section by a single screw with torsion elements was analyzed with the computational fluid dynamics (CFD) simulation. The simulation results reveal that screws with such torsion elements arranged in a decentralized form have smaller segregation scale, distribution index and higher mixing efficiency, compared with the conventional screw. The decentralized arrangement is more effective for mixing than the centralized distribution. The rotational flow induced by the torsion elements can significantly enhance the mass transfer process and improve mixing and plasticizing. Compared with those in conventional screw, the distributions of temperature and viscosity are more uniform at the outlet of torsion screws, which also made the torsion element generally more effective and efficient for mixing and plasticizing.