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Computational design of Mg alloys with minimal galvanic corrosion

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Journal of Magnesium and Alloys 2022年第7期10卷 1972-1980页

作者： Krishnamohan Thekkepat Hyung-Seop Han Ji-Won Choi Seung-Cheol Lee Eul Sik Yoon Guangzhe Li Hyun-Kwang Seok Yu-chan Kim Jae-Hun Kim Pil-ryung cha Indo-Korea Science and Technology Center JakkurBangalore 560065India Division of Nano&Information Technology KIST SchoolKorea University of Science and TechnologySeoul 02792Republic of Korea Electronic Materials Research Center Korea Institute of Science and TechnologySeoul 02792Republic of Korea Center for Biomaterials Biomedical Research InstituteKorea Institute of Science and TechnologySeoul 02792Republic of Korea Department of Plastic and Reconstructive Surgery Korea University College of MedicineSeoul 02841Republic of Korea Division of Bio-Medical Science and Technology KIST SchoolKorea University of Science and TechnologySeoul 02792Republic of Korea School of Advanced Materials Engineering Kookmin UniversitySeoul 02707Republic of Korea

Formation of galvanic cells between constituent phases is largely responsible for corrosion in Mg-based *** develop a methodology to calculate the electrochemical potentials of intermetallic compounds and alloys using a simple model based on the Born-Haber *** electrochemical potentials are used to predict and control the formation of galvanic cells and minimize *** demonstrate the applicability of our model by minimizing galvanic corrosion in Mg-3wt%Sr-x Zn alloy by tailoring the Zn *** methodology proposed in this work is applicable for any general alloy system and will facilitate efficient design of corrosion resistant alloys.

关键词： Galvanic corrosion First-principles Cluster expansion Thermodynamics Modeling Magnesium alloys

A theoretical and 1-D numerical investigation on a valve/valveless air-breathing pulse detonation engine

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Chinese Journal of Aeronautics 2021年第1期34卷 68-78页

作者： Hua QIU cha XIONG Jianling LI School of Power and Energy Northwestern Polytechnical UniversityXi'an 710072China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

The important operating characteristics of pulsed Pressure Gain Combustion(PGC)propulsion are the pressure gain of the combustor component and the propulsive performance gain of the engine.A ramjet-type valve/valveless air-breathing pulsed detonation engine with a supersonic internal compression inlet is *** on an ideal thermal cycle,the ideal equivalent pressure ratios(pcb)of the Pulsed Detonation Combustor(PDC)are obtained theoretically which are directly related with the propulsive performance of the *** introducing an orifice loss model into the cycles,the critical pressure drop ratios through the orifice for the PDC achieving pressure gain and the engine achieving thrust gain are *** influencing factors are investigated by the use of a one-dimensional(1-D)numerical simulation *** operating characteristics of the pulse detonation engine are investigated with changes of the valve type,the inlet/outlet area ratio of the PDC,the nozzle area ratio,and flight *** these factors can affect pcbof the PDC,and pcbcan be optimized by changing the geometry of the *** most important influence parameter is the valve *** using an orifice-type aerodynamic valve,simulation results show that the PDC cannot achieve the pressure gain *** a supersonic internal compression inlet is introduced to the engine,whether the Pulse Detonation Engine(PDE)can achieve thrust gain comparable with that of an ideal Brayton cycle engine not only is related to the pressure gain of the combustor,but also needs to optimize the engine structure to reduce the total pressure loss.

关键词： Detonation Pressure gain characteristics Propulsive performance Supersonic internal compression inlet Valve/valveless Thermal cycle

Updates on esophageal and gastric cancers

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World Journal of Gastroenterology 2006年第20期12卷 3237-3242页

作者： Amy Gallo charles cha Resident Department of Surgery Yale University School of Medicine333 Cedar St.FMB 121New HavenCT 06520United States Department of Surgery Yale University of School of Medicine 333 Cedar St.FMB 121New HavenCT 06520United States

Esophageal and gastric cancers are both common and deadly. Patients present most often after disease progression and survival is therefore poor. Due to demographic variability and recent changes in disease incidence, much emphasis has been placed on studying risk factors for both esophageal and gastric cancers. However, with increasing understanding of these diseases, low survival rates persist and continued intensive studies are necessary to optimize treatment plans. This review article discusses updates in the evolving epidemiology, clinical presentation, risk factors, and diagnostic and treatment modalities of esophageal and gastric cancers.

关键词： Gastric cancer Esophageal cancer Surgery Treatment

Conception and Design of Active Balancer for Planar Mechanisms

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Chinese Journal of Mechanical Engineering 2009年第6期22卷 822-832页

作者： ZHANG Ying YAO Yan-An cha Jianzhong School of Mechanical and Electronic Control Engineering Beijing Jiaotong University Beijing 100044 China

The dynamic balancing is an important issue in mechanism design. For the existing balancing methods, both passive and active ones, there is still room for improvement in adaplability and independency. In view of this, a concept of active balancer is developed as a new solution for the dynamic balancing with more flexibility. The proposed balancer is an independent additional device with a control system inside, which consists of a two-degree-of-freedom （DOF） linkage and a controllable motor, and can be attached to a machine expediently with little change to its original structure and motion. One of the two inputs of the two-DOF linkage shares the same shaft with its output, which is connected to the input shaft of a machine to be balanced and driven by the original actuator. The other input is driven by the control motor. By properly selecting the speed trajectories of the control motor and link parameters of the two-DOF linkage, one or more dynamic effects of the mechanisms can be minimized or eliminated adaptively. The design procedure of the active balancer is put forward and a two-step optimization is developed to find out optimal design parameters of the balancer for various design requirements and constraints. Taking a force-balanced crank-rocker mechanism as the reference mechanism, numerical examples are given to illustrate the design procedure. The balancing effects of the proposed balancer are compared with those of the existing adding dyads （DYAD） method. The results show that the introduction of the control system provides the active balancer with better balancing effect and more flexibility than the DYAD method. A considerable reduction in the dynamic effects （input torque, shaking moment and shaking force） can be achieved for different balancing object by designing the structural and control parameters of the balancer, and the deterioration of dynamic performance caused by alterative working conditions can be compensated effectively by redesigning the

关键词： active balancing shaking moment input torque shaking force optimum balancing two-degree-of-freedom linkage

Variations in dynamic recrystallization behavior and mechanical properties of AZ31 alloy with extrusion temperature

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Journal of Magnesium and Alloys 2023年第7期11卷 2351-2365页

作者： Jae Won cha Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea

This study investigates the effects of extrusion temperature on the dynamic recrystallization(DRX)behavior of a Mg-3Al-1Zn-0.3Mn(AZ31,wt%)alloy during hot extrusion and on the microstructural characteristics and mechanical properties of materials extruded at 350 and 450℃.An increase in the extrusion temperature causes a decrease in the amount of strain energy accumulated in the material during extrusion,because of promoted activation of pyramidalslip and dynamic *** reduced strain energy weakens the DRX behavior during extrusion,which eventually results in a decrease in the area fraction of recrystallized grains of the extruded *** material extruded at 450℃has coarser grains and a stronger basal fiber texture than that extruded at 350℃.As the extrusion temperature increases from 350 to 450℃,the tensile yield strength(TYS)of the extruded material increases from 191.8 to 201.5 MPa,whereas its compressive yield strength(CYS)decreases from 122.5 to 111.0 MPa;consequently,its tension-compression yield stress ratio(CYS/TYS)decreases from 0.64 to *** increase in the TYS is attributed mainly to the stronger texture hardening and strain hardening effects of the extruded material,and the decrease in the CYS is attributed to the reduced twinning stress resulting from grain coarsening and texture *** microstructural and textural evolutions of the materials during extrusion and the deformation and hardening mechanisms of the extruded materials are discussed in detail.

关键词： Mg-Al-Zn alloy Extrusion Dynamic recrystallization Microstructure Yield asymmetry

Posterior propriety in nonparametric mixed efects model

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Applied Mathematics(A Journal of Chinese Universities) 2013年第3期28卷 369-378页

作者： XU An-cha TANG Yin-cai College of Mathematics and Information Science Wenzhou University School of Finance and Statistics East China Normal University

It is well known that spline smoothing estimator relates to the Bayesian estimate under partially informative normal prior. In this paper, we derive the conditions for the pro- priety of the posterior in the nonparametric mixed effects model under this class of partially informative normal prior for fixed effect with inverse gamma priors on the variance compo- nents and hierarchical priors for covariance matrix of random effect, then we explore the Gibbs sampling procedure.

关键词： nonparametric mixed effect model Bayesian spline smoothing Gibbs sampling.

Anti-aging properties of Ribes fasciculatum in Caenorhabditis elegans

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Chinese Journal of Natural Medicines 2016年第5期14卷 335-342页

作者： Hoon Jeon Dong Seok cha Department of Oriental Pharmacy College of Pharmacy Woosuk University

The present study investigated the effects and underlying mechanism of ethylacetate fraction of Ribes fasciculatum （ERF） on the lifespan and stress tolerance using a Caenorhabditis elegans model. The longevity activity of ERF was determined by lifespan assay under normal culture condition. The survival rate of nematodes under various stress conditions was assessed to validate the effects of ERF on the stress tolerance. To determine the antioxidant potential of ERF, the superoxide dismutase （SOD） activities and intracellular reactive oxygen species （ROS） levels were investigated. The ERF-mediated change in SOD-3 expression was examined using GFP-expressing transgenic strain. The effects of ERF on the aging-related factors were investigated by reproduction assay and pharyngeal pumping assay. The intestinal lipofuscin levels of aged nematodes were also measured. The mechanistic studies were performed using selected mutant strains. Our results indicated that ERF showed potent lifespan extension effects on the wild-type nematode under both normal and various stress conditions. The ERF treatment also enhanced the activity and expression of superoxide dismutase （SOD） and attenuated the intracellular ROS levels. Moreover, ERF-fed nematodes showed decreased lipofuscin accumulation, indicating ERF might affect age-associated changes in C. elegans. The results of mechanistic studies indicated that there was no significant lifespan extension in ERF-treated daf-2, age-l, sir-2.1, and daf-16 null mutants, suggesting that they were involved in ERF-mediated lifespan regulation. In conclusion, R. fasciculatum confers increased longevity and stress resistance in C. elegans via SIR-2.1-mediated DAF-16 activation, dependent on the insulin/1GF signaling pathway.

关键词： Ribesfasciculatum Lifespan Aging Stress tolerance Caenorhabditis elegans

Proline Accumulation,Photosynthetic Abilities and Growth characters of Sugarcane(Saccharum officinarum L.) Plantlets in Response to Iso-Osmotic Salt and Water-Deficit Stress

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Agricultural Sciences in China 2009年第1期8卷 51-58页

作者： Suriyan cha-um chalermpol Kirdmanee National Center for Genetic Engineering and Biotechnology(BIOTEC) National Science and Technology Development Agency(NSTDA)

The aim of this study was to investigate the biochemical, physiological and morphological responses of sugarcane to iso- osmotic salt and water-deficit stress. Disease-free sugarcane plantlets derived from meristem cuttings were photo- autotrophically grown in MS media and subsequently exposed to -0.23 （control）, -0.67 or -1.20 MPa iso-osmotic NaCl （salt stress） or mannitol （water-deficit stress）. Chlorophyll a （Chl a）, chlorophyll b （Chl b）, total carotenoids （Cx＋c）, maximum quantum yield of PSII （Fv/Fm）, photon yield of PSII （ΦPSII）, stomatal conductance （Gs） and transpiration rate （E） in the stressed plantlets were significantly reduced when compared to those of plantlets of the control group （without mannitol or NaCl）, leading to net-photosynthetic rate （Pn） and growth reduction with positive correlation. In addition, physiological changes and growth parameters of plantlets in the salt stress conditions were more sharply reduced than those in waterdeficit stress conditions. On the other hand, the proline content and non-photochemical quenching （NPQ） in the leaves of stressed plantlets increased significantly, especially in response to iso-osmotic salt stress. The chlorophyll pigments in iso-osmotic stressed leaves were significantly degraded （r^2 = 0.93）, related to low water oxidation （r^2 = 0.87）, low net- photosynthetic rate （r^2 = 0.81）, and growth reduction （r^2 = 0.97）. The multivariate biochemical, physiological and growth parameters in the present study should be further used to develop salt, or drought, tolerance indices in sugarcane breeding programs.

关键词： growth performances net-photosynthetic rate pigment degradation proline water oxidation

Suppression of pheromone biosynthesis and mating behavior by RNA interference of pheromone gland-specific fatty acyl reductase in Maruca vitrata

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Insect Science 2022年第4期29卷 1135-1144页

作者： Wook Hyun cha Dae-Weon Lee Department of Biosafety Kyungsung UniversityBusanRepublic of Korea Metabolomics Research Center for Functional Materials Kyungsung UniversityBusanRepublic of Korea

In moths,various enzymes,such as fatty acid synthases,fatty acyl desaturases,and fatty acyl reductases(FARs),are involved in pheromone *** particular,pheromone gland-specific FAR(pgFAR)plays an important role in converting the functional group from carboxylic to alcohol during pheromone biosynthesis.A novel pgFAR of Maruca vitrata,Mvi-pgFAR,was identified through transcriptome sequencing of its pheromone *** investigate the involvement of Mvi-pgFAR in pheromone biosynthesis,Mvi-pgFAR was cloned from the pheromone gland and suppressed by RNA interference(RNAi).Mvi-pgFAR harbored several conserved motifs related to NAD(P)H-binding,N-glycosylation,and adenosine/guanosine triphosphate *** analysis revealed that Mvi-pgFAR with other lepidopteran pgFARs formed an independent ***-pgFAR was specifically expressed only in the pheromone *** real-time polymerase chain reaction showed that the diurnal expression levels of Mvi-pgFAR in the pheromone gland were the highest at 2 h before the *** primarily confirming Mvi-pgFAR suppression by RNAi,(E,E)-10,12-hexadecadienal(E10E12-16:Ald),a major sex pheromone component,was quantified by gas *** Mvi-pgFAR was successfully suppressed,E10E12-16:Ald production was reduced by up to half of that of the control,and the mating rate was subsequently *** results demonstrate that Mvi-pgFAR downregulation can suppress mating behavior by changing the relative sex pheromone component ratio,suggesting that Mvi-pgFAR can be used as a novel control target.

关键词： (EE)-10,12-hexadecadienal gas chromatography Maruca viruta pgFAR RNAi sex pheromone