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Homogenized thermal properties of 3D composites with full uncertainty in the microstructure
Juan Ma,Peter Wriggers,Liangjie Li 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.57 No.2
In this work, random homogenization analysis for the effective thermal properties of a three-dimensional composite material with unidirectional fibers is presented by combining the equivalent inclusion method with Random Factor Method (RFM). The randomness of the micro-structural morphology and constituent material properties as well as the correlation among these random parameters are completely accounted for, and stochastic effective thermal properties as thermal expansion coefficients as well as their correlation are then sought. Results from the RFM and the Monte-Carlo Method (MCM) are compared. The impact of randomness and correlation of the micro-structural parameters on the random homogenized results is revealed by two methods simultaneously, and some important conclusions are obtained.
Juan Ma,Peng Yue,Wenyi Du,Changping Dai,Peter Wriggers 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.83 No.3
In this work, a novel reliability approach for combined high and low cycle fatigue (CCF) estimation is developed by combining active learning strategy with least squares support vector machines (LS-SVM) (named as ALS-SVM) surrogate model to address the multi-resources uncertainties, including working loads, material properties and model itself. Initially, a new active learner function combining LS-SVM approach with Monte Carlo simulation (MCS) is presented to improve computational efficiency with fewer calls to the performance function. To consider the uncertainty of surrogate model at candidate sample points, the learning function employs k-fold cross validation method and introduces the predicted variance to sequentially select sampling. Following that, low cycle fatigue (LCF) loads and high cycle fatigue (HCF) loads are firstly estimated based on the training samples extracted from finite element (FE) simulations, and their simulated responses together with the sample points of model parameters in Coffin-Manson formula are selected as the MC samples to establish ALS-SVM model. In this analysis, the MC samples are substituted to predict the CCF reliability of turbine blades by using the built ALSSVM model. Through the comparison of the two approaches, it is indicated that the reliability model by linear cumulative damage rule provides a non-conservative result compared with that by the proposed one. In addition, the results demonstrate that ALS-SVM is an effective analysis method holding high computational efficiency with small training samples to gain accurate fatigue reliability.
Juan P. Hernandez-Ortiz,Hongbo Ma,Juan J. de Pablo,Michael D. Graham 한국유변학회 2008 Korea-Australia rheology journal Vol.20 No.3
Simulations of solutions of flexible polymer molecules during flow in simple or complex confined geometries are performed. Concentrations from ultradilute up to near the overlap concentration are considered. As concentration increases, the hydrodynamic migration effects observed in dilute solution unidirectional flows (Couette flow, Poiseuille flow) become less prominent, virtually vanishing as the overlap concentration is approached. In a grooved channel geometry, the groove is almost completely depleted of polymer chains at high Weissenberg number in the dilute limit, but at finite concentration this depletion effect is dramatically reduced. Only upon inclusion of hydrodynamic interactions can these phenomena be properly captured.
New Amide N-glycosides of Ansamitocins Identified from Actinosynnema pretiosum
Ma, Juan,Zhao, Pei-Ji,Shen, Yue-Mao 대한약학회 2007 Archives of Pharmacal Research Vol.30 No.6
By using preparative TLC as the critical isolation procedure, two compounds, including one new amide N-glycosides of ansamitocin (2), were isolated from Actinosynnema pretiosum. The compounds were elucidated as N-demethyl-N-${\beta}$-D-glucopyranosyl ansamitocin P-2, named ansamitocinoside P-2 (1), and N-demethyl-N-${\beta}$-D-glucopyranosyl ansamitocin P-1, named ansamitocinoside P-1 (2) on the basis of their spectral data. The $^1$H-NMR and $^{13}$C-NMR assignments were made for 1 and 2 while the $^{13}$C-NMR assignment for 1 was revised. Bioassay results showed that 1 had antineoplastic activity.
New Amide N-glycosides of Ansamitocins Identified from Actinosynnema pretiosum
Juan Ma,Pei-Ji Zhao,Yue-Mao Shen 대한약학회 2007 Archives of Pharmacal Research Vol.30 No.6
By using preparative TLC as the critical isolation procedure, two compounds, including one new amide N-glycosides of ansamitocin (2), were isolated from Actinosynnema pretiosum. The compounds were elucidated as N-demethyl-N-β-D-glucopyranosyl ansamitocin P-2, named ansamitocinoside P-2 (1), and N-demethyl-N-β-D-glucopyranosyl ansamitocin P-1, named ansamitocinoside P-1 (2) on the basis of their spectral data. The 1H-NMR and 13C-NMR assignments were made for 1 and 2 while the 13C-NMR assignment for 1 was revised. Bioassay results showed that 1 had antineoplastic activity.
Run Ma,Juan Ma,Yuting Ma 아시아사회과학학회 2023 Jornal of Asia Social Science Vol.11 No.1
The civil war in Syria became the “crater” and “pustule mouth” of the Jasmine Revolution. Looking back at history, the development trend in Syria is based on the logic of “civil strife-civil war-chaotic war-proxy war”. Anti-government armed activities aimed at overthrowing Bashar regime are one after another, and Syria's political and economic development has been seriously affected. Compared with other countries in the Middle East, Syria's civil war is slightly different. This is not just a civil war and sectarian conflict in a strict sense. In the later period, its civil war evolved into a geopolitical game in which the big countries inside and outside the territory and the triple powers in Syria crisscross each other. In addition, the spillover effect of the Syrian civil war has had a substantial impact on the Middle East. The development sequence of Syrian geopolitical conflict is from civil war to Proxy war, which is essentially the external manifestation of several rounds of military and political games between big countries. The logic of this geopolitical conflict is universal in the Middle East. Syria’s geopolitical strategy is prominent, and multi-dimensional forces inside and outside the region participate in it. Its geopolitical game has experienced a long period, while other Middle Eastern countries may have only experienced part of it. In the Middle East, due to sectarian contradictions and political dominance competition within the country, it will eventually develop into a geopolitical situation in which internal and external forces are superimposed. In short, in the future development process, these “indirect forces” inside and outside the domain will probably still play an invisible role in the geopolitical conflicts in the Middle East, and will continue to influence the development trend of the geopolitical pattern of Middle East countries.
Hernandez-Ortiz, Juan P.,Ma, Hong-Bo,de Pablo, Juan J.,Graham, Michael D. The Korean Society of Rheology 2008 Korea-Australia rheology journal Vol.20 No.3
Simulations of solutions of flexible polymer molecules during flow in simple or complex confined geometries are performed. Concentrations from ultradilute up to near the overlap concentration are considered. As concentration increases, the hydrodynamic migration effects observed in dilute solution unidirectional flows (Couette flow, Poiseuille flow) become less prominent, virtually vanishing as the overlap concentration is approached. In a grooved channel geometry, the groove is almost completely depleted of polymer chains at high Weissenberg number in the dilute limit, but at finite concentration this depletion effect is dramatically reduced. Only upon inclusion of hydrodynamic interactions can these phenomena be properly captured.