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RISS 인기검색어
- 검색키워드
- 저자 : Zhen-yu Li (검색결과 152 건)
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Li, Zhen-Yu,Akhtar, M. Shaheer,Yang, O-Bong Elsevier 2015 Journal of alloys and compounds Vol.653 No.-
<P><B>Abstract</B></P> <P>High performance electrochemical double-layer (EDL) supercapacitor was fabricated with highly efficient electro-active electrode based on mesoporous carbon nanofibers (MCFs) materials. The prepared MCFs from dextrose as carbon source exhibited the high surface to volume ratio, large pore volume and high mesoporous nature. The cyclic voltammetry, electrochemical impedance and galvanostatic charge–discharge measurements were carried out to investigate the capacitive and electrochemical behavior of fabricated EDL supercapacitor based on MCFs electrode. A reasonably high specific capacitance of 201 F/g at current density of 0.6 A/g was achieved by the fabricated EDL supercapacitor based on MCFs electrode. A relation of capacitive performance, specific surface area, accessible average pore size and current density was manifested to evaluate the impact of capacitance parameters. The fabricated EDL supercapacitor based on MCFs electrode attained the ultra high energy density of 54.7 W h/kg and reasonable power density of 0.842 kW/kg at the current density of 0.6 A/g. The fabricated EDL supercapacitor manifested an excellent stability by keeping about 88% of initial capacity after 1000 cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly efficient electro-active electrode prepared by mesoporous carbon nanofibers. </LI> <LI> High performance electrochemical double layer (EDL) supercapacitor was fabricated. </LI> <LI> EDL supercapacitor with MCFs electrode showed the high specific capacitance of 201 F/g. </LI> <LI> Ultra high energy density of 54.7 W h/kg and power density of 0.842 kW/kg attained. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Xu, Shu-Sheng,Weng, Li-Jun,Liu, Yu-Zhen,Kang, Kyeong-Hee,Kim, Chang-Lae,Kim, Dae-Eun Elsevier Sequoia 2017 Surface & coatings technology Vol.325 No.-
<P><B>Abstract</B></P> <P>Ni-doped WS<SUB>2</SUB> composite coatings with various Ni contents were co-deposited using a radio frequency sputtering system on silicon wafer and AISI 440C stainless steel substrates. The microstructural characteristics of the WS<SUB>2</SUB>-Ni composite coatings and their tribological properties in vacuum were assessed. During introduction of Ni dopant in the WS<SUB>2</SUB>-Ni composite coating the sulfur/tungsten (S/W) ratio in the coating increased due to reduced preferential resputtering of sulfur atoms in the growing coating. The microstructure of the WS<SUB>2</SUB>-Ni composite coating varied from a fine columnar structure for Ni content equal to or less than 7.7at.% to a featureless structure as the Ni content increased further. The Ni dopant inhibited the growth of the coarse columnar WS<SUB>2</SUB> platelets which was accompanied by nanocrystallization and amorphization of the composite coating structure. WS<SUB>2</SUB>-Ni composite coatings with fine columnar structure exhibited relatively low hardness but showed a high tendency to form a lubricating transfer layer. It also demonstrated low brittleness and prolonged wear life in vacuum condition compared to coatings with dense featureless structure. The variation in tribological performance between the composite coatings resulted from the different wear mechanisms associated with their distinct microstructures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Microstructure of WS<SUB>2</SUB> coating was modified by incorporating Ni as a dopant. </LI> <LI> The introduction of Ni increased the S/W ratio of the WS<SUB>2</SUB> composite coating. </LI> <LI> High Ni content in the WS<SUB>2</SUB> coating led to high brittleness and low wear resistance. </LI> <LI> WS<SUB>2</SUB>–5at.% Ni coating showed 5 times longer wear life than pure WS<SUB>2</SUB> film in vacuum. </LI> <LI> Superior tribological properties were attributed to transfer layer and high hardness. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Rotary ultrasonic machining of woven CFRP composite in a cryogenic environment
Thirumalai Kumaran, S.,Ko, Tae Jo,Li, Changping,Yu, Zhen,Uthayakumar, M. ELSEVIER SCIENCE 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.698 No.-
<P><B>Abstract</B></P> <P>In the present study, rotary ultrasonic machining (RUM) was adopted to perform drilling of carbon fiber reinforced plastics (CFRP) in a cryogenic environment. An L27 orthogonal array was selected to conduct experiments by varying the spindle speed (denoted as N), feed rate (denoted as f), and ultrasonic power (denoted as P). The thrust force (denoted as Fz), exit burr area, and surface roughness (denoted as Ra) were measured to evaluate the machining performance. The influence of process parameters and the regression model were derived for each output quality response. Additionally, multi-objective optimization was performed using desirability analysis, and the predicted levels were used for confirmation. The results indicated that the feed rate (f) contributed more to the thrust force (Fz) by 45.85% and a maximum thrust force was recorded at 0.1 mm/rev. A decrease in spindle speed (N) was associated with an increase in feed rate (f) and ultrasonic power (P), and it resulted in minimum exit burr area. The influence of ultrasonic power (P) was highly significant in reducing burrs with a contribution of 52.45%. Conversely, the surface roughness (Ra) of the drill holes decreased at 3000 rpm, and this was attributed to the brittle fracture of the fibers at a lower temperature. Both N (30.88%) and f (30.83%) had an equal influence on producing a better surface finish in the drill holes. Furthermore, the predicted optimal settings were used to validate the results and were found to be within 95% confidence and prediction interval. Finally, the microscopic images of tool wear, burr formation, and drill hole surface morphology were analyzed and examined.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Prediction of regression model for RUM of CFRP in a cryogenic environment. </LI> <LI> Output responses such as thrust force, burr area and roughness are investigated. </LI> <LI> The adequacy of an ANOVA model is checked for each output response. </LI> <LI> Optimization is performed by desirability analysis and the results are validated. </LI> <LI> Tool wear, burr formation, and drill hole surface morphology are analyzed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Effect of Sub-Structure and Precipitation Behavior on Mechanical Properties of Al–xCu–Li Alloys
Yu‑zhuo Li,Guang‑jun Zeng,Ding‑ding Lu,Zhen‑zhen Liu,San‑xi Deng,Peng‑cheng Ma,Yong‑lai Chen,Rui‑feng Zhang,Jin‑feng Li 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.11
The tensile properties and microstructure of extruded and cold rolled 2A55 Al–Li alloys with different Cu content werestudied. After solution treatment, the strength of extruded sheets is slightly higher than that of cold rolled sheets due to strongdeformation texture and high density of substructure. However, the strength change order is different with the increase of Cucontent with T6-24 h. The extruded sample with higher Cu content have higher strength due to many dense T1precipitates. The δ′/θ′/δ′ composite precipitates and θ′ precipitates suppress the formation of T1precipitates, which cause cold rolled samplewith higher Cu content shows lower strength. Additionally, many fine T1precipitates nucleate at the sub-grain boundariesformed in the extrusion process, which have a significant effect on the mechanical property.
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Colorectal Cancer Concealment Predicts a Poor Survival: A Retrospective Study
Li, Xiao-Pan,Xie, Zhen-Yu,Fu, Yi-Fei,Yang, Chen,Hao, Li-Peng,Yang, Li-Ming,Zhang, Mei-Yu,Li, Xiao-Li,Feng, Li-Li,Yan, Bei,Sun, Qiao Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.7
Objectives: Understanding the situation of cancer awareness which doctors give to patients might lead to prognostic prediction in cases of of colorectal cancer (CRC). Methods: Subsets of 10,779 CRC patients were used to screen the risk factors from the Cancer Registry in Pudong New Area in cancer awareness, age, TNM stage, and gender. Survival of the patients was calculated by the Kaplan-Meier method and assessed by Cox regression analysis. The views of cancer awareness in doctors and patients were surveyed by telephone or household. Results: After a median observation time of 1,616 days (ranging from 0 to 4,083 days) of 10,779 available patients, 2,596 of the 4,561 patients with cancer awareness survived, whereas 2,258 of the 5,469 patients without cancer awareness and 406 of the 749 patients without information on cancer awareness died of the disease. All-cause and cancer-specific survival were poorer for the patients without cancer awareness than those with (P < 0.001 for each, log-rank test). Cox multivariate regression analysis showed that cancer concealment cases had significantly lower cancer-specific survival (hazard ratio (HR) = 1.299; 95 % confidence interval (CI): 1.200-1.407)and all-cause survival (HR = 1.324; 95 % CI: 1.227-1.428). Furthermore, attitudes of cancer awareness between doctors and patients were significantly different (P < 0.001). Conclusion: Cancer concealment, not only late-stage tumor and age, is associated with a poor survival of CRC patients.
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Li, Zheng,Zhang, Li-Juan,Zhang, Hong-Ru,Tian, Gao-Fei,Tian, Jun,Mao, Xiao-Li,Jia, Zheng-Hu,Meng, Zi-Yu,Zhao, Li-Qing,Yin, Zhi-Nan,Wu, Zhen-Zhou Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.13
Tumors have evolved numerous mechanisms by which they can escape from immune surveillance. One of these is to produce immunosuppressive cytokines. Transforming growth factor-${\beta}$(TGF-${\beta}$) is a pleiotropic cytokine with a crucial function in mediating immune suppression, especially in the tumor microenvironment. TGF-${\beta}$ produced by T cells has been demonstrated as an important factor for suppressing antitumor immune responses, but the role of tumor-derived TGF-${\beta}$ in this process is poorly understood. In this study, we demonstrated that knockdown of tumor-derived TGF-${\beta}$ using shRNA resulted in dramatically reduced tumor size, slowing tumor formation, prolonging survival rate of tumor-bearing mice and inhibiting metastasis. We revealed possible underlying mechanisms as reducing the number of myeloid-derived suppressor cells (MDSC) and $CD4^+Foxp3^+$ Treg cells, and consequently enhanced IFN-${\gamma}$ production by CTLs. Knockdown of tumor-derived TGF-${\beta}$ also significantly reduced the conversion of na$\ddot{i}$ve $CD4^+$ T cells into Treg cells in vitro. Finally, we found that knockdown of TGF-${\beta}$ suppressed cell migration, but did not change the proliferation and apoptosis of tumor cells in vitro. In summary, our study provided evidence that tumor-derived TGF-${\beta}$ is a critical factor for tumor progression and evasion of immune surveillance, and blocking tumor-derived TGF-${\beta}$ may serve as a potential therapeutic approach for cancer.
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Novel Environmentally Friendly Manufacturing Method for Micro-Textured Cutting Tools
Changping Li,Xinyi Qiu,Zhen Yu,Shujian Li,Pengnan Li,Qiulin Niu,Rendi Kurniawan,고태조 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.1
Surface texturing on cutting tools has a great influence on reducing the friction force between tool and chip interfaces. In this study, a grinding method was developed to fabricate micro-groove textures on cutting tools using a special diamond grinding wheel on the tool rake face. A comparative experiment was done using a laser and other grinding method to fabricate micro-grooves. The developed grinding method does not produce harmful gases, it is environmentally friendly, and it fabricates groove textures with high efficiency and quality. Various micro-grooves with depths of 30–90 μm, groove pitches of 0.5–1 mm, and groove angles of 30–60 o were made on the rake faces of non-coated end-mill tools using the developed grinding method. Milling experiments on aluminum alloy (Al6061-T6) and tool steel (SKD11) with non-water-soluble coolant were carried out using the textured tools, and the cutting force and tool wear were investigated. In most cases, the cutting force produced by the micro-grooved tools is significantly reduced. In addition, the wear resistance of the micro-groove cutting tool is better than that of a conventional cutting tool, and there is no chipping.
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