Experimental and numerical studies of stress/strain characteristics in riveted aircraft lap joints

Chao Zeng,Wei Tian,Xiang Yao Liu,Jiu Tian Xue 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.7

The fatigue property of riveted lap joint is greatly related to the riveting-induced residual stress, especially the stress distribution on the faying surface. However, an accurate study of the residual stress characteristics in the riveted sheet could be very difficult. In this paper, both numerical and experimental investigations were carried out on the stress/strain characteristics in riveted aircraft lap joints. A special specimen was designed for the test of strain variations on the faying surface of the sheet by microstrain gages. For the numerical simulation, the rivet squeezing process was analyzed using the explicit dynamic finite element (FE) method, whilst a general static FE analysis was employed for the elastic springback after the squeeze force was removed. A comparison of the strain variations between the experimental results and FE simulations shows a general good agreement, although there may be some difference for points measured near the hole surface. The FE analysis reveals that both compressive and tensile residual stresses could be introduced in the riveted sheet. Massive compressive residual stress can be created in the near-surface layer of the hole. However, the stress level is not always increased with increasing the squeeze force, and so is the improvement of fatigue life observed. Further study is still necessary to account for the fatigue life decreasing effect caused by a high squeeze force.

A Stable Gait Planning Method of Biped Robot Based on Ankle motion Smooth Fitting

Dong En Zeng,Wang Dan Dan,Tong Ji Gang,Chen Chao,Wang Zeng Hui 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.1

In ankle joint trajectory planning of biped robots, the spline interpolation generally leads to acceleration mutations on the key points, which weakens the stability of the biped robot. To solve this problem, a smooth function fitting method on ankle joint trajectory planning is proposed in this paper. In this method, the higher order derivatives of the ankle joint trajectory is smooth, and the acceleration mutation can be avoided. The biped robot gait planning of a whole cycle is accomplished by calculating the joint angle sequences of hip, knee and ankle. The effectiveness of the proposed method is demonstrated by numerical simulations on NAO robot gait planning. Experimental results show that the proposed method can improve the stability of the zero moment point (ZMP) margin effectively when it is applied to the bipedal robot gait planning on the non-horizontal ground.

Comparative Study of Two Common In Vitro Models for the Pancreatic Islet with MIN6

Chao Xinxin,Zhao Furong,Hu Jiawei,Yu Yanrong,Xie Renjian,Zhong Jianing,Huang Miao,Zeng Tai,Yang Hui,Luo Dan,Peng Weijie 한국조직공학과 재생의학회 2023 조직공학과 재생의학 Vol.20 No.1

BACKGROUND: Islet transplantation is currently considered the most promising method for treating insulin-dependent diabetes. The two most-studied artificial islets are alginate-encapsulated b cells or b cell spheroids. As three-dimensional (3D) models, both artificial islets have better insulin secretory functions and transplantation efficiencies than cells in twodimensional (2D) monolayer culture. However, the effects of these two methods have not been compared yet. Therefore, in this study, cells from the mouse islet b cell line Min6 were constructed as scaffold-free spheroids or alginate-encapsulated dispersed cells. METHODS: MIN6 cell spheroids were prepared by using Agarose-base microwell arrays. The insulin secretion level was determined by mouse insulin ELISA kit, and the gene and protein expression status of the MIN6 were performed by Quantitative polymerase chain reaction and immunoblot, respectively. RESULTS: Both 3D cultures effectively promoted the proliferation and glucose-stimulated insulin release (GSIS) of MIN6 cells compared to 2D adherent cells. Furthermore, 1% alginate-encapsulated MIN6 cells demonstrated more significant effects than the spheroids. In general, three pancreatic genes were expressed at higher levels in response to the 3D culture than to the 2D culture, and pancreatic/duodenal homeobox-1 (PDX1) expression was higher in the cells encapsulated in 1% alginate than that in the spheroids. A western blot analysis showed that 1% alginate-encapsulated MIN6 cells activated the phosphoinositide 3-kinase (PI3K)/serine/threonine protein kinase (AKT)/forkhead transcription factor FKHR (FoxO1) pathway more than the spheroids, 0.5% alginate-, or 2% alginate-encapsulated cells did. The 3D MIN6 culture, therefore, showed improved effects compared to the 2D culture, and the 1% alginate-encapsulated MIN6 cells exhibited better effects than the spheroids. The upregulation of PDX1 expression through the activation of the PI3K/AKT/FoxO1 pathway may mediate the improved cell proliferation and GSIS in 1% alginate-encapsulated MIN6 cells. CONCLUSION: This study may contribute to the construction of in vitro culture systems for pancreatic islets to meet clinical requirements.

The Effect of Herb-Partition Moxibustion on Toll-like Receptor 4 in Rabbit Aorta during Atherosclerosis

Zeng-Hui Yue,Xin-Qun He,Xiao-Rong Chang,Jian-Ling Yuan,Bao-Sheng Yu,Mi Liu,Ling Fu,Liang Zhang,Li-Chao Shang 사단법인약침학회 2012 Journal of Acupuncture & Meridian Studies Vol.5 No.2

Objective: To explore the mechanism of Toll-like receptor (TLR4) inhibition in the delay of formation of atherosclerosis by herb-partition moxibustion. Method: Seventy-five rabbits were randomly assigned to one of five groups: blank, atherosclerosis (AS) model, direct moxibustion, herb-partition moxibustion, and drug treatment. With the exception of the blank group, all rabbits were given a high-fat diet in addition to immunologic injury to create the AS model. The experiments were carried out for 16 weeks, at which time the aorta was removed from each rabbit. Immunohistochemical methods were used to detect the gray level of the aortic TLR4 to observe the immunologic competence of its antigens. Fluorescent quantitative polymerase chain reaction was used to detect the expression of TLR4 messenger RNA (mRNA) in the aorta. Results: The gray-scale value of TLR4 and the TLR4 mRNA expression significantly decreased (p < 0.05) in the direct moxibustion, herb-partition moxibustion, and drug treatment groups. Furthermore, the effects of the herb-partition moxibustion and drug treatment were superior to those of the direct moxibustion. Conclusion: Herb-partition moxibustion inhibits aortic TLR4 activity and mRNA expression,showing that herb-partition moxibustion delays the formation of atherosclerosis through the inhibition of TLR4 expression.

Review : Characterization of a Recombinant Thermostable Arylsulfatase from Deep-Sea Bacterium Flammeovirga pacifica

( Chao Gao ),( Min Jin ),( Zhiwei Yi ),( Runying Zeng ) 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.11

A novel sulfatase gene, ary423 (1,536 bp ORF), encoding a protein of 511 amino acids with a calculated molecular mass of 56 kDa, was identified from Flammeovirga pacifica, which was isolated from deep-sea sediments of west Pacific Ocean. Amino acid sequence analysis revealed that Ary423 possessed a conserved C-X-A-X-R motif, which was recognized as the sulfatase signature. Phylogenetic analysis suggested that Ary423 belonged to arylsulfatases. After heterologous expression in Escherichia coli cells, the recombinant Ary423 was purified with a N i+ affinity column, and was shown to be highly active at a broad range of temperatures from 30° to 70°C, with maximum activity at 40°C. Furthermore, recombinant Ary423 retained more than 70% and 40% of its maximum activity after 12 h of incubation at 50°C and 60°C, respectively, exhibiting good thermostability at high temperatures. The optimal pH for Ary423 was determined to be 8.0 and the activity of Ary423 could be slightly enhanced by Mg2+. The recombinant enzyme could hydrolyze sulfate ester bonds in pnitrophenyl sulfate (NPS) and Asparagus crude polysaccharides with a specific activity of 64.8 U/mg and 25.4 U/mg, respectively. These favorable properties could make Ary423 attractive for application in the desulfating process of agar production.

Ag‑doping behavior on (8, 0) single‑walled carbon nanotube with single C‑vacancy or pyridine‑like N3 defect: a DFT study

Chao Yan,Qunfeng Zeng,Jianing Zhu 한국탄소학회 2019 Carbon Letters Vol.29 No.6

Single C-vacancy and pyridine-like N3 defect are usually formed on the single-walled carbon nanotube (SWCNT) and they have unique properties for potential applications. In this paper, we use density functional theory to investigate the discrepancies of such two structures from the geometric and electronic aspects. Our results indicate that the existed single vacancy in the SWCNT can lead to somewhat electron localization because of the lone pair electrons; while the N3 embedded SWCNT ( N3-SWCNT) has stronger chemical reactivity and electron localization than the single vacancy SWCNT (SV-SWCNT) due to the great charge transfer between N3 group and C atom on the tube sidewall. Through the investigation of Ag-doping on the above two nano-structures, we found that the single Ag atom is much more stably adsorbed on the N3- SWCNT sidewall compared with SV-SWCNT, forming higher binding energy and higher electron transfer. Our calculation would shed light on the physicochemical property of SWCNT-based material and thus extend their potential applications in many fields.

Probabilistic Load Flow for Power Systems with Wind Power Considering the Multi-time Scale Dispatching Strategy

Chao Qin,Yixin Yu,Yuan Zeng 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.4

This paper proposes a novel probabilistic load flow model for power systems integrated with large-scale wind power, which considers the multi-time scale dispatching features. The ramp limitations of the units and the steady-state security constraints of the network have been comprehensively considered for the entire duration of the study period; thus, the coupling of the system operation states at different time sections has been taken into account. For each time section, the automatic generation control (AGC) strategy is considered, and all variations associated with the wind power and loads are compensated by all AGC units. Cumulants and the Gram–Charlier expansion are used to solve the proposed model. The effectiveness of the proposed method is validated using the modified IEEE RTS 24-bus system and the modified IEEE 118-bus system.

Ag-doping behavior on (8, 0) single-walled carbon nanotube with single C-vacancy or pyridine-like N3 defect: a DFT study

Yan Chao,Zeng Qunfeng,Zhu Jianing 한국탄소학회 2019 Carbon Letters Vol.29 No.6

Single C-vacancy and pyridine-like N3 defect are usually formed on the single-walled carbon nanotube (SWCNT) and they have unique properties for potential applications. In this paper, we use density functional theory to investigate the discrepancies of such two structures from the geometric and electronic aspects. Our results indicate that the existed single vacancy in the SWCNT can lead to somewhat electron localization because of the lone pair electrons; while the N3 embedded SWCNT (N3-SWCNT) has stronger chemical reactivity and electron localization than the single vacancy SWCNT (SV-SWCNT) due to the great charge transfer between N3 group and C atom on the tube sidewall. Through the investigation of Ag-doping on the above two nano-structures, we found that the single Ag atom is much more stably adsorbed on the N3-SWCNT sidewall compared with SV-SWCNT, forming higher binding energy and higher electron transfer. Our calculation would shed light on the physicochemical property of SWCNT-based material and thus extend their potential applications in many fields.

High-performance broadband heterojunction photodetectors based on multilayered PtSe₂ directly grown on a Si substrate

Xie, Chao,Zeng, Longhui,Zhang, Zhixiang,Tsang, Yuen-Hong,Luo, Linbao,Lee, Jung-Ho The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.32

<P>Two-dimensional group-10 transition metal dichalcogenides have recently attracted increasing research interest because of their unique electronic and optoelectronic properties. Herein, we present vertical hybrid heterojunctions of multilayered PtSe2 and Si, which take advantage of large-scale homogeneous PtSe2 films grown directly on Si substrates. These heterojunctions show obvious rectifying behavior and a pronounced photovoltaic effect, enabling them to function as self-driven photodetectors operating at zero bias. The photodetectors can operate in both photovoltage and photocurrent modes, with responsivity values as high as 5.26 × 10<SUP>6</SUP> V W<SUP>−1</SUP> and 520 mA W<SUP>−1</SUP> at 808 nm, respectively. The <I>I</I>light/<I>I</I>dark ratio, specific detectivity, and response speed are 1.5 × 10<SUP>5</SUP>, 3.26 × 10<SUP>13</SUP> Jones, and 55.3/170.5 μs, respectively. Furthermore, the heterojunctions are highly sensitive in a broad spectral region ranging from deep ultraviolet to near-infrared (NIR) (200-1550 nm). Because of the strong NIR light absorption of PtSe2, the heterojunctions exhibit photocurrent responsivities of 33.25 and 0.57 mA W<SUP>−1</SUP> at telecommunication wavelengths of 1310 and 1550 nm, respectively. Considering the excellent performance of the PtSe2/Si heterojunctions, they are highly suitable for application in high-performance broadband photodetectors. The generality of the above results also signifies that the proposed <I>in situ</I> synthesis method has great potential for future large-scale optoelectronic device integration.</P>

Coordinated Control Strategy for Power Systems with Wind Farms Integration Based on Phase-plane Trajectory

Yuan Zeng,Yang Yang,Chao Qin,Jiangtao Chang,Jian Zhang,Jingzhe Tu 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.1

The dynamic characteristics of power systems become more and more complex because of the integration of large-scale wind power, which needs appropriate control strategy to guarantee stable operation. With wide area measurement system(WAMS) creating conditions for realizing realtime transient stability analysis, a new coordinated control strategy for power system transient stability control based on phase-plane trajectory was proposed. When the outputs of the wind farms change, the proposed control method is capable of selecting optimal generators to balance the deviation of wind power and prevent transient instability. With small disturbance on the base operating point, the coordinated sensitivity of each synchronous generator is obtained. Then the priority matrix can be formed by sorting the coordinated sensitivity in ascending order. Based on the real-time output change of wind farm, coordinated generators can be selected to accomplish the coordinated control with wind farms. The results in New England 10-genrator 39-bus system validate the effectiveness and superiority of the proposed coordinated control strategy.