Effect of Al on the Microstructure and Mechanical Properties of Mg–Sn–Ca–Mn Wrought Alloy

Yun Feng,Yuanyuan Yang,Zongqi Xiao,Xianglong Meng,Guorong Zhou,Jinfeng Leng,Xinying Teng 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.6

Mg–Sn–Ca–Mn–xAl (x = 0,1.5 wt%) alloys with ultra-fine recrystallized grains were prepared by conventional extrusion(400 °C, 0.5 mm/s). Effects of aluminum (Al) on mechanical properties and microstructure of the Mg–1Sn–1Ca–0.5Mn(wt%) alloy were systematically investigated. By the addition of 1.5 wt% Al, the yield strength of the as-extruded alloysignificantly increased from 183 to 237 MPa. The as-cast alloys show a dendritic structure consists of α-Mg, (Mg, Al)2Ca,and CaMgSn phases. The as-extruded Mg–1Sn–1Ca–0.5Mn–1.5Al alloys exhibit a bimodal grain structure composed ofdynamic recrystallized (DRXed) fine grains and coarse unDRXed grains. Compared with Al free alloy, a lot of nano-scaleplanar Al2Caand rectangle shape Al8Mn5precipitated in the as-extruded alloy with 1.5 wt% Al. Meanwhile, the addition ofAl significantly strengthened alloys’ fiber texture with < 10–10 >//ED.

Intragranular and Intergranular Crack Propagation in Nanocrystalline Ni Under Single-Cycle Mode I Loading

Yan Feng,Jie Li,Xinhua Yang 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7

As the first step to study the fatigue crack propagation, the molecular simulations were performed to investigate theopening, propagation and closure behaviors of intragranular and intergranular cracks in nanocrystalline Ni under single-cyclemode I loading. The atomic crack angle was proposed to characterize the crack-tip blunting and sharpening quantitatively. There are obvious different mechanisms between intragranular and intergranular crack propagation. Intragranular crack propagationcould be induced by stacking faults and can change its direction very easily, but the intergranular crack perpendicularto the loading direction would propagate along the grain boundary and encounter strong resistance at the triple junction. New cracks could form in the grain boundaries ahead of the original crack. Different from the traditional understanding forintragranular and intergranular cracks, however, the dislocation density increases even in the unloading process and the cracktip is possibly sharpened temporarily during loading.

마그네슘 풍부 해양미네랄 용액이 hairless 마우스의 아토피성 피부염에 미치는 영향

김동희,이규재,최주봉,이영미,윤양숙,김정례,장병수,양용석 韓國電子顯微鏡學會 2008 Applied microscopy Vol.38 No.3

Atopic dermatitis (AD) is a chronically relapsing inflammatory skin disease that often has asthma and allergic rhinitis. Magnesium salts, the important component of minerals in Dead Sea water, are known to exhibit beneficial effects in inflammatory disease. Favorable effects of magnesium ions and sea water treated to the skin of patients with contact dermatitis have been reported. But histological and immunological investigations are insufficient. This study was performed to examine the inhibitory effect of magnesium-rich sea mineral water on the development of AD-like skin lesions in hairless mice. AD-like skin lesions are induced by the repeated application of 2,4-dinitrochlorobenzene (DNCB). Local application of magnesium-rich sea mineral water on hairless mice skin applied with DNCB inhibited the development of AD-like skin lesions as exemplified by a significant increase in skin hydration (p<0.01), and a decrease in epidermal water loss (p<0.01). Serum IgE level was also significantly decreased (p<0.01). These results suggest that magnesiumrich sea mineral water inhibits the development of DNCB-induced AD-like skin lesions in hairless mice. These observations indicate that magnesium-rich sea mineral water may be alternative and assistant substances for the management of AD. 아토피성 피부염은 주로 천식과 비염 등을 동반하는, 주위에서 흔히 볼 수 있는 만성 염증성 피부질환으로 유전학적, 환경적, 면역학적 요인이 복잡하게 연관되어 발병한다. 해수에 포함된 마그네슘염은 피부에 작용하여 피부장벽을 보호하는 것으로 알려지고 그에 대한 면역학적인 연구와 조직학적 연구는 아직 부족한 실정이다. 이번 연구에서는 피부염을 인위적으로 일으키는 hapten 형성물질인 DNCB를 hairless mice에 도포하여 아토피 피부염 동물 모델로 만든 후, 마그네슘이 다량 함유된 해양 미네랄수를 처리한 후 피부장벽에 미치는 영향을 관찰하였다. DNCB로 피부염을 유발한 hairless mice에 해양미네랄수를 국소적으로 도포하였을 때 유의한 피부수분함량이 증가와 경피수분손실의 감소를 확인하였다 (p<0.01). 피부측정에서 피부거칠기(skin roughness, p<0.05)와 스케일생성 (skin scaliness, p<0.01)은 실험군에서 유의한 개선효과를 나타내었으며 조직학적 검사에서도 피부손상지수의 유의한 감소 (p<0.01)와 비만세포와 (p<0.01) 호산구의 감소(p<0.05) 소견을 보였고 또한 혈청 IgE의 감소를 관찰할 수 있었다(p<0.01). 이상과 같이 마그네슘이 다량 함유된 해양 미네랄수 도포는 피부장벽의 손상을 줄이고 피부수분손실을 효과적으로 줄임으로 아토피성 피부염 증상 유발을 억제할수 있음을 확인하였다. 현재까지 아토피성 피부염의 관리를 위하여 세라마이드나 식물성 오일의 보습제가 주로 활용되고 있는 상황에서 부가적인 피부장벽의 보호를 위하여 탈염 해양 미네랄수의 활용이 가능할 것으로 판단되며 장기적으로 아토피 피부염치료의 대체, 혹은 보조적 물질로 활용될 수 있을 것으로 기대된다.

Purification and Structure Analysis of Mycolic Acids in Corynebacterium glutamicum

Yang Yang,Feng Shi,Guanjun Tao,Xiaoyuan Wang 한국미생물학회 2012 The journal of microbiology Vol.50 No.2

Corynebacterium glutamicum is widely used for producing amino acids. Mycolic acids, the major components in the cell wall of C. glutamicum might be closely related to the secretion of amino acids. In this study, mycolic acids were extracted from 5 strains of C. glutamicum, including ATCC 13032,ATCC 13869, ATCC 14067, L-isoleucine producing strain IWJ-1, and L-valine producing strain VWJ-1. Structures of these mycolic acids were analyzed using thin layer chromatography and electrospray ionization mass spectrometry. More than twenty molecular species of mycolic acid were observed in all 5 strains. They differ in the length (20–40carbons) and saturation (0–3 double bonds) of their constituent fatty acids. The dominant species of mycolic acid in every strain was different, but their two hydrocarbon chains were similar in length (14–18 carbons), and the meromycolate chain usually contained double bonds. As the growth temperature of cells increased from 30°C to 34°C, the proportion of mycolic acid species containing unsaturated and shorter hydrocarbon chains increased. These results provide new information on mycolic acids in C. glutamicum,and could be useful for modifying the cell wall to increase the production of amino acids.

Prognostic Role of Nucleophosmin in Colorectal Carcinomas

Yang, Yu-Feng,Zhang, Xi-Ying,Yang, Mei,He, Ze-Hua,Peng, Ning-Fu,Xie, Shu-Rui,Xie, Yan-Fang Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.5

Aim: Recent research suggests that nucleophosmin (NPM) may be a prognostic marker in colorectal carcinomas (CRC). We here tested its use to predict the survival of CRC patients. Methods: We investigated NPM expression by immunohistochemistry in histologically normal to malignant colorectal tissues and evaluated its association with clinicopathological variables. Overall and disease-free survival after tumor removal were calculated by the Kaplan-Meier method, and differences in survival curves were analyzed by the log-rank test. The Cox proportional hazards model was used for multivariate analysis of prognostic factors. Results: NPM expression was found significantly upregulated in CRC compared to adjacent colorectal tissue, villous adenoma, tubular adenoma and normal colorectal mucosa (p<0.05 for all). NPM expression was statistically linked to cancer embolus, lymph node metastasis, differentiation grade, and recurrence of CRC. Overall and disease-free survival of NPM-negative CRC patients tended to be better than those for patients with NPM-positive lesions (log-rank statistic, p<0.05 for all). Multivariate analysis indicated NPM expression as an independent prognostic indicator for CRC patients (p<0.05 ). Conclusion: Our results suggest that NPM expression can predict the survival of CRC patients. Prognosis of CRC is determined by not only many known prognostic factors but also by NPM expression.

A Comparison of Developmental Trajectories of Prepulse Inhibition between Male and Female Rats

Yang Yang,Yun'ai Su,Chunmei Guo,Yu Feng,Jitao Li,Tianmei Si 대한정신약물학회 2010 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.8 No.3

Objective: Various studies have demonstrated that childhood and adolescence are critical periods of brain development characterized by both dramatic changes and sexual dimorphism in anatomy, physiology and cognition. Prepulse inhibition (PPI) is an operational model of sensorimotor gating process, but data concerning the interactions of sex and normal ontogeny of PPI is of a particular paucity. Methods: We led a longitudinal study to compare the PPI between male and female Sprague-Dawley rats during postnatal day 23 to 43. Results: We found that the PPI of both male and female rats increased during this period. We also found that the PPI of male and female rats had different developmental trajectories when the prepulse intensity was 20 dB [A] above background, a result similar with a previous study done in humans. Conclusion: The finding confirms the face validity of PPI as a model of information processing across species and supports its utilization for investigation of potential aetiological factors implicated in mental disorders.

Upper-bound Finite Element Analysis of Stability of Tunnel Face Subjected to Surcharge Loading in Cohesive-frictional Soil

Feng Yang,Jian Zhang,Lianheng Zhao,Junsheng Yang 대한토목학회 2016 KSCE Journal of Civil Engineering Vol.20 No.6

The stability of a plane strain tunnel face in a cohesive-frictional soil (idealized as a homogeneously Mohr-Coulomb material) subjected to ground surface surcharge loading was investigated. Continuous loading is applied to the ground surface, and both smooth and rough interface conditions are modeled. The upper-bound solutions with critical load parameters for a practical range of tunnel depth-to-height values, as well as the soil properties, are obtained by using the Upper-bound Finite Element Method with Rigid Translatory Moving Elements (UBFEM-RTME). For practical use, the results are presented in the form of dimensionless stability charts. Failure mechanisms consisting of two groups of slip lines, which explicitly reflect the relative movement of blocks, are also presented. To verify the solutions, the Upper-bound Finite Element Method with Plastic Deformation Elements (UMFEMPDE) has been developed and the collapsed loads are compared with those from UBFEM-RTME. The solutions obtained with these two upper-bound finite element methods are found to be in good agreement with each other.

Study on the Buckling Behaviour of Cold-Formed Angles in Transmission Towers

Fengli Yang,Junke Han,Jingbo Yang,Zhenbao Li 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.4

Considering the structural characteristics of transmission towers, four sections of cold-formed angles with different slenderness ratios and constrained types were selected for the experimental and numerical study. Experiments and finite element analysis for the ultimate loads of the compression cold-formed angles were carried out. The finite element model well predicts the buckling behaviour of the cold-formed members. For the axial compression members, the load-strain curves as well as the ultimate loads were analyzed, and the experimental ultimate loads were compared with those of calculated by the applicable standards. It shows that the applicable standards aren’t adaptive to the strength design of the compression cold-formed members in transmission towers. Through the analysis of the experimental and FEA results, the fitting curve of the stability coefficients for the cold-formed members in transmission towers was determined. The ultimate loads calculated by the fitting curve are well agreed with the experimental values, especially for the members with relatively low slenderness ratios. Some modification suggestions were proposed for the calculation of the ultimate load for the axial compression cold-formed angle. Experimental analysis on the cold-formed members of the other five constrained types was completed, and the modification formulas of the slenderness ratios for members of different constrained types were obtained.

Two case studies on structural analysis of transmission towers under downburst

FengLi Yang,HongJie Zhang 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.22 No.6

Downbursts are of great harm to transmission lines and many towers can even be destroyed. The downburst wind field model by Chen and Letchford was applied, and the wind loads of two typical transmission towers in inland areas and littoral areas were calculated separately. Spatial finite element models of the transmission towers were established by elastic beam and link elements. The wind loads as well as the dead loads of conductors and insulators were simplified and applied on the suspension points by concentrated form. Structural analysis on two typical transmission towers under normal wind and downburst was completed. The bearing characteristics and the failure modes of the transmission towers under downburst were determined. The failure state of tower members can be judged by the calculated stress ratios. It shows that stress states of the tower members were mainly controlled by 45 degree wind load. For the inland areas with low deign wind velocity, though the structural height is not in the highest wind velocity zone of downburst, the wind load under downburst is much higher than that under normal wind. The main members above the transverse separator of the legs will be firstly destroyed. For the littoral areas with high deign wind velocity, the wind load under downburst is lower than under normal wind. Transmission towers are not controlled by the wind loads from downbursts in design process.

Two case studies on structural analysis of transmission towers under downburst

Yang, FengLi,Zhang, HongJie Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.22 No.6

Downbursts are of great harm to transmission lines and many towers can even be destroyed. The downburst wind field model by Chen and Letchford was applied, and the wind loads of two typical transmission towers in inland areas and littoral areas were calculated separately. Spatial finite element models of the transmission towers were established by elastic beam and link elements. The wind loads as well as the dead loads of conductors and insulators were simplified and applied on the suspension points by concentrated form. Structural analysis on two typical transmission towers under normal wind and downburst was completed. The bearing characteristics and the failure modes of the transmission towers under downburst were determined. The failure state of tower members can be judged by the calculated stress ratios. It shows that stress states of the tower members were mainly controlled by 45 degree wind load. For the inland areas with low deign wind velocity, though the structural height is not in the highest wind velocity zone of downburst, the wind load under downburst is much higher than that under normal wind. The main members above the transverse separator of the legs will be firstly destroyed. For the littoral areas with high deign wind velocity, the wind load under downburst is lower than under normal wind. Transmission towers are not controlled by the wind loads from downbursts in design process.