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Microstructural Stability and Creep Performance of a Novel Low-Cost Single Crystal Superalloy
Z. H. Tan,X. G. Wang,Y. L. Du,Y. M. Li,Y. H. Yang,J. L. Liu,J. D. Liu,J. G. Li,Y. Z. Zhou,X. F. Sun 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7
The increasing pursuit of advanced aero-engines with lower ratio between the cost and performance has greatly promotedthe demanding of single crystal superalloys characterized by low cost and outstanding temperature capability. In this study,a novel low-cost single crystal superalloy was designed and the creep tests as well as micro-characterization were carried outon the experimental alloy. The results illustrated that the novel single crystal alloy exhibited an ideal microstructural stabilitywithout precipitating TCP phases, after long-term thermal exposure at the ultimate service temperature of third generationsingle crystal superalloys. Moreover, the experimental alloy with only 3 wt% Re addition demonstrated remarkable creepresistance and maintained a very low minimum creep rate at 1100 °C/137 MPa and 1120 °C/137 MPa, while the accumulationand coalescence of micro-pores had eventually led to the alloy fracture. Apart from that, the compact interfacial dislocationnetworks the 2nd γ′ phase were observed after high-temperature creep rupture, and the typical a < 010 > superdislocationswith relatively poor mobility was found at 1120 °C. At 760 °C/800 MPa, both the minimum creep velocity and entire creepstain was increased evidently, however, the ultimate creep rupture life of the alloy had still reached 200 h. The correspondingdeformation mechanism was identified as the combination of superdislocation pairs shearing and a/3 < 121 > partial dislocationcutting the γ′ phase with a SISF being generated. In general, the novel single crystal alloy characterized by remarkablemechanical properties and cost reduction possesses a great potential for future application in the advanced aircraft engines.
Ž,uvela, Petar,Liu, J. Jay,Macur, Katarzyna,Bą,czek, Tomasz American Chemical Society 2015 ANALYTICAL CHEMISTRY - Vol.87 No.19
<P>In this work, performance of five nature-inspired optimization algorithms, genetic algorithm (GA), particle swarm optimization (PSO), artificial bee colony (ABC), firefly algorithm (FA), and flower pollination algorithm (EPA), was compared in molecular descriptor selection for development of quantitative structure retention relationship (QSRR) models for 83 peptides that originate from eight model proteins. The matrix with 423 descriptors was used as input, and QSRR models based on selected descriptors were built using partial least squares (PLS), whereas root mean square error of prediction (RMSEP) was used as a fitness function for their selection. Three performance criteria, prediction accuracy, computational cost, and the number of selected descriptors, were used to evaluate the developed QSRR models. The results show that all five variable selection methods outperform interval PLS (iPLS), sparse PLS (sPLS), and the full PLS model, whereas GA is superior because of its lowest computational cost and higher accuracy (RMSEP of 5.534%) with a smaller number of variables (nine descriptors). The GA-QSRR model was validated initially through Y-randomization. In addition, it was successfully validated with an external testing set out of 102 peptides originating from Bacillus subtilis proteomes (RMSEP of 22.030%). Its applicability domain was defined, from which it was evident that the developed GA-QSRR exhibited strong robustness. All the sources of the model's error were identified, thus allowing for further application of the developed methodology in proteomics.</P>
Chi, Oak Z.,Chang, Qiang,Wang, Guolin,Liu, Xia,Harvey R. Weiss 경희대학교 동서의학연구소 1999 INTERNATIONAL SYMPOSIUM ON EAST-WEST MEDICINE Vol.1999 No.1
Oak Z.Chi,Qiang Chang, Guolin Wang*, Xia Liu, Harvey R. Weiss□.Deprtments of Anesthesai, Departments of Physiology and Biophysics, University of Medicne and Dentisrty of New Jersey,Robert Wood Johnson Medical School, New Brunswick, New Jersey, USA and*Department of Anesthesia, Medical University, Tianjing, People's Republic of China. A non-NMDA antagonist, GYKI 52466 improves microscopic O² balance in the cortex during focal cerebral ischemia. Proceedings of International Symposium on East-West Medicine, Seoul. 172-182, 1999.-This study was performed to test whether GYKI 52466, a non-NMDA receptor antagonist, would improve microregional oxygen supply and consumption balance in the focal cerebral ischemic area. Rats were anesthetized with 1.4% isoflurance. For the GYKI Group (n=8), 19 min before middle cerebral artery (MCA) occlusion, a bolus of 5mg/kg of GYKI 52466 iv was administered and was followed by an infusion of 5mg/kg/hr. For the control Group(n=8), the same volume of the vehicle was administered. One hour after MCA occlusion, regional cerebral blood flow (rCBF) was measured using the 14C-iodoantipyrine autoradiographic technique. Microscopic arterial and venous oxygen saturations were determined using microspectrophotometry. In the cortex contralateral to MCA occlusion, the average rCBF and the average O² consumption were lower in the GYKI Group than in the Control Group (rCBF:GYKI 65.5±24.1, Control 97.7 33.4ml/100g/min;O² consumption: GYKI3.9±1.2, Control 6.2±2.5ml O²/100g/min) without a significant difference in the number of veins with SvO²<50%. In the ischemic cortex, the number of veins with SvO²<50% was significantly smaller in the GYKI Group (21 veins out of 63)than in the Control Group(45 out of 59)without a significant difference in the average rCBF(GYKI44.9±17.7, Control 29.7±10.4) or regional O² consumption between these two groups (GYKI 3.3±1.4,Control 27.7±1.2). Our data demonstrated that GYKI 52466 was effective in improving microscopic O² balance in the focal ischemic cortical area of the brain and it decreased O² consumption in the non-ischemic cortex. [Neurological Research 1999;21:299-304]
Liu, Z.,Kang, S.M.,Ume, J.S. Pergamon Press ; Elsevier Science Ltd 2010 COMPUTERS & MATHEMATICS WITH APPLICATIONS - Vol.59 No.11
The aim of this paper is to study the following first-order nonlinear neutral delay differential equation ddt[x(t)+c(t)x(t-τ)]+h(t)f(x(t-σ<SUB>1</SUB>),x(t-σ<SUB>2</SUB>),...,x(t-σ<SUB>k</SUB>))=g(t),t≥t<SUB>0</SUB>, where c,h,g@?C([t<SUB>0</SUB>,+~),R), τ>0,σ<SUB>i</SUB>@?R<SUP>+</SUP> for i@?J<SUB>k</SUB>={1,...,k}, and f@?C(R<SUP>k</SUP>,R). By using the Schauder and Krasnoselskii fixed point theorems, we establish the existence of uncountably many bounded nonoscillatory solutions for the above equation. To dwell upon the importance and advantages of our results, seven nontrivial examples are included.
Stress wave propagation in 1-D and 2-D media using Smooth Particle Hydrodynamics method
Liu, Z.S.,Swaddiwudhipong, S.,Koh, C.G. Techno-Press 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.4
The paper involves the study on the elastic and elasto-plastic stress wave propagation in the 1-D and 2-D solid media. The Smooth Particle Hydrodynamics equations governing the elastic and elasto-plastic large deformation dynamic response of solid structures are presented. The proposed additional stress points are introduced in the formulation to mitigate the tensile instability inherent in the SPH approach. Both incremental rate approach and leap-frog algorithm for time integration are introduced and the new solution algorithm is developed and implemented. Two examples on stress wave propagation in aluminium bar and 2-D elasto-plastic steel plate are included. Results from the proposed SPH approach are compared with available analytical values and finite element solutions. The comparison illustrates that the stress wave propagation problems can be effectively solved by the proposed SPH method. The study shows that the SPH simulation is a reliable and robust tool and can be used with confidence to treat transient dynamics such as linear and non-linear transient stress wave propagation problems.
Liu, L.,Yang, Z.B.,Yang, W.R.,Jiang, S.Z.,Zhang, G.G. Asian Australasian Association of Animal Productio 2009 Animal Bioscience Vol.22 No.4
Alfalfa (Medicago sativa L) is a high-quality forage for ruminants and the main stem is the dominant morphological component contributing to the forage nutritive value in mature alfalfa forage. Shearing force, a fracturing property of plant stem, is an important indictor of forage value. The objectives of this study were to investigate the effects of morphological characteristic on shearing force, the relationship between shearing force and chemical composition, and the relationship between shearing force and in situ digestibility of alfalfa stem. The results showed that linear density (weight per unit length of stem) was more important than chemical composition in affecting shearing force. There was a positive relationship between lignin content and shearing force (r = 0.78). Correlations were not found between shearing force and other chemical components such as neutral detergent fiber (NDF), acid detergent fiber (ADF), cellulose and hemicelluloses. In situ digestibility (of dry matter and NDF) was related to shearing force. A negative correlation was found between shearing force and dry matter (DM) digestibility (r = -0.70), and there was also a negative correlation between shearing force and NDF digestibility (r = -0.87). When shearing force was standardized for stem diameter or stem linear density, the relationship between shearing force and digestibility was consistent regardless of stem diameter and stem linear density. Shearing force was significantly correlated with lignin content and in situ digestibility (of DM and NDF), and was a more direct indicator for estimating forage nutritive value related to animal performance, so it can be used to predict the forage value of alfalfa.