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characterization of the High-Strength Mg–3Nd–0.5Zn Alloy Prepared by Thermomechanical Processing

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Acta Metallurgica Sinica(English Letters) 2019年第3期32卷 321-331页

作者： Ji■í Kub■sek Drahomír Dvorsk■ Jozef Vesel■ Peter Min■rik M■ria Zemkov■ dalibor vojtěch Department of Metals and Corrosion Engineering Faculty of Chemical Technology University of Chemistry and Technology Prague Department of Physics of Materials Charles University

Magnesium alloys based on Nd and Zn are promising materials for both aviation industry and medical *** mechanical properties of these materials can be achieved by thermomechanical processing such as extrusion or rolling and by aging treatment, which can significantly strengthen the alloy. The question remains especially about the connection of texture strength created in the alloys based on the specific conditions of preparation. This work focuses on the Mg–3 Nd–0.5 Zn magnesium alloy prepared by hot extrusion of the as-cast state at two different temperatures combined with heat pre-treatment. Extrusion ratio of 16 and rate of 0.2 mm/s at 350 and 400 °C were selected for material preparation. The structures of prepared materials were studied by scanning electron microscopy and transmission electron microscopy. The effect of microstructure on mechanical properties was evaluated. Obtained results revealed the strong effect of thermal pre-treatment on final microstructure and mechanical properties of extruded materials. The Hall–Petch relation between grain size and tensile yield strength has been suggested in this paper based on the literature review and presented data. The observed behavior strongly supports the fact that the Hall–Petch of extruded Mg–3Nd–0.5 Zn alloys with different texture intensities cannot be clearly estimated and predicted. In addition, Hall–Petch relations presented in literature can be sufficiently obtained only for fraction of the Mg–3Nd–0.5 Zn alloys.

关键词： Mg–Nd–Zn alloys Extrusion Thermal treatment Microstructure Mechanical properties

The effect of powder size on the mechanical and corrosion properties and the ignition temperature of WE43 alloy prepared by spark plasma sintering

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Journal of Magnesium and Alloys 2021年第4期9卷 1356-1369页

作者： Drahomír Dvorský JiríKubásek Michaela Roudnická Filip Pruša David Necas Peter Minárik Jitka Stráská dalibor vojtech University of chemistry and Technology Faculty of Chemical TechnologyDepartment of Metals and Corrosion EngineeringTechnická516628 Praha 6–DejvicePragueCzech Republic Institute of Physics Czech Academy of ScienceNa Slovance 1999/218221 Praha 8PragueCzech Republic Department of Physics of Materials Charles UniversityKe Karlovu 5Prague 12116Czech Republic

Powder metallurgy is a powerful method for the preparation of materials with superior *** work aimed to investigate the effect of powder size on the microstructure,mechanical,and corrosion properties of advanced WE43(Mg-4Y-3REE-Zr)alloy prepared by spark plasma sintering(SPS).At the same time,the effect of HF pre-treatment of the powder on the properties of final compacted products is *** powder particles yielded microstructure with more interfaces formed by Y_(2)O_(3),or MgF_(2) and YF_(3).These interfaces work as barriers against corrosion,which greatly improves corrosion *** suggested pre-treatment of powder in HF further reduced the corrosion rate of the compacted *** the contrary,fragile interfaces of YF_(3) decreased mechanical properties as the crack primarily propagates through these *** original powder containing the mixture of all powder fractions exerted the best combination of mechanical *** size has also shown to affect ignition *** highest ignition temperature was measured for the finest powder fraction.

关键词： Powder metallurgy Mechanical properties Corrosion Interface SPS

Adipokinetic hormones control amylase activity in the cockroach （Periplaneta americana） gut

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Insect Science 2017年第2期24卷 259-269页

作者： Karolina Bodlakova Pavel Jedlicka dalibor Kodrik Gymnasium Ceska 64 370 21 Ceske Budejovice Institute of Organic chemistry and Biochemistry CAS Flemingovo sq. 2 166 10 Prague Institute of Entomology Biology Centre CAS and Faculty of Science University of South Bohemia Branisovska 31 370 05 Ceske Budejovice Czech Republic

This study examined the biochemical characteristics of a-amylase and hor- monal （adipokinetic hormone： AKH） stimulation of a-amylase activity in the cockroach （Periplaneta americana） midgut. We applied two AKHs in vivo and in vitro, then measured resultant amylase activity and gene expression, as well as the expression of AKH receptor （AKHR）. The results revealed that optimal amylase activity is characterized by the follow- ing： pH： 5.7, temperature： 38.4 ℃, Km （Michaelis-Menten constant）： 2.54 mg starch/mL, and Vmax （maximum reaction velocity）： 0.185 μmol maltose/mL/min. In vivo application of AKHs resulted in significant increase of amylase activity： by two-fold in the gastric caeca and 4-7 fold in the rest of the midgut. In vitro experiments supported results seen in vivo： a 24-h incubation with the hormones resulted in the increase of amylase activity by 1.4 times in the caeca and 4-9 times in the midgut. Further, gene expression analyses reveal that AKt-IR is expressed in both the caeca and the rest of the midgut, although expression levels in the former were 23 times higher than levels in the latter. A similar pattern was found for the amylase （AMY） gene. Hormonal treatment did not affect the expression of either gene. This study is the first to provide evidence indicating direct AKH stimulation of digestive enzyme activity in the insect midgut, supported by specific AKHR gene expression in this organ.

关键词： AKH AKH receptor amylase enzyme gene expression midgut

Astrocytes in the cerebral cortex play a role in the spontaneous motor recovery following experimental striatal hemorrhage

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Neural Regeneration Research 2018年第1期13卷 67-68页

作者： Juliana dalibor Neves Régis Gemerasca Mestriner Carlos Alexandre Netto Graduate Program of Physiology Institute of Basic Health Sciences Universidade Federal do Rio Grande do Sul Department of Biochemistry Institute of Basic Health Science Universidade Federal do Rio Grande do Sul Neurorehabilitation and Neural Repair Research Group Pontifícia Universidade Católica do Rio Grande do Sul

Intracerebral hemorrhage （Ich） is a stroke subtype caused by spontaneous rupture of small vessels and bleeding into the brain paren- chyma, resulting in cell death and sensorimotor deficits. Despite the greater prevalence of the ischemic form of stroke （87%）, Ich has the highest mortality rate of all stroke subtypes. The striatum is the most affected structure in hemorrhagic stroke （35-70%）, followed by cere- bral cortex （15-30%）, brain stem and cerebellum （5-10%）; patients suffering striatal and/or cortical Ich bear persistent sensorimotor disabilities. Although chronic sensorimotor impairment is established, a considerable amount of patients experience some degree of spontaneous recovery during the first six months after stroke （Qureshi et al., 2009）, and the neurobiological basis of this process is not understood.

关键词： Astrocytes in the cerebral cortex play a role in the spontaneous motor recovery following experimental striatal hemorrhage Ich

The effects of selection for early and late reproduction on metabolite pools in Acanthoscelides obtectus Say

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Insect Science 2012年第3期19卷 303-314页

作者： Jelica Lazarevie Nikola Tucic Darka Se.slija Jovanovic Josef Vecera dalibor Kodrik Institute for Biological Research Belgrade Biological faculty University of Belgrade Belgrade Serbia Institute of Entomology Biology Centre Czech Academy of Sciences Ceske Budejovice Faculty of Sciences University of South Bohemia Ceske Budejovice Czech Republic

The present study was aimed at revealing the responses of metabolite pools to selection for alternative reproductive schedules in the seed beetle, Acanthoscelides obtectus Say （Coleoptera： chrysomelidae： Bruchinae）. The levels of metabolites （free sugars, glycogen, lipids, soluble and hydrophobic proteins） that were determined in virgin females and males at three ages from adult eclosion onwards were compared among the base population （B） and two derived lines that were selected for either early （Y） or late （O） reproduction. The results showed differences in the accumulation of metabolites during pre-adult development, as well as in the pattern of their changes during adult ageing, Generally, in comparison to the B population, the short-lived beetles from the Y line showed increased protein content and reduced carbohydrate and lipid content, whereas the opposite was true for the long-lived beetles from the O line. Females from the O line exhibited slower utilization of energy reserves and a slower increase in protein contents than females from the Y line. Females contained higher levels of free sugars, glycogen and hydrophobic proteins and lower levels of lipids and soluble proteins than males, although the sexual dimorphism was not evenly expressed among lines. Age-specific changes in metabolite contents were slower in females than males. Our findings suggest that trade-offs among capital resources are a physiological basis of early/late fitness trade-offs and point to a conservation of resources that can be used for somatic maintenance.

关键词： ageing energy resources laboratory evolution proteins seed beetle,trade-off

Microstructure and corrosion resistance of a duplex structured Mg–7.5Li–3Al–1Zn

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Journal of Magnesium and Alloys 2021年第2期9卷 467-477页

作者： Anna Dobkowska Bogusława Adamczyk–Cieslak JiríKubásek dalibor vojtech Dariusz Kuc Eugeniusz Hadasik Jarosław Mizera Faculty of Materials Science and Engineering Warsaw University of Technology141 Wołoska St02-507 WarsawPoland chemistry Department Western University of Ontario1151 Richmond StLondonON N6A 5B7Canada Department of Metals and Corrosion Engineering University of Chemistry and TechnologyTechnicka 516628 Prague 6Czechia Institute of Materials Engineering Silesian University of TechnologyKrasinskiego 8St40-019 KatowicePoland

This study describes the corrosion resistance of extruded,and extruded with post-processing annealing,Mg–7.5 Li–3 Al–1 Zn *** results demonstrate that extrusion at 350°C with an extrusion speed 0.5 s^(-1) does not lead to the full recrystallization of the alloy,and the material still exhibits a dendritic *** post-processing annealing triggers the microstructure transformation,and the relative composition of the alloy *** ratio ofβ(Li)toα(Mg)in the extruded alloy was 29–71%;after annealing amount ofβ(Li)increased,and the ratio ofβ(Li)toα(Mg)in the annealed alloy was 35–65%.Corrosion testing shows that in 3.5 wt%Na Cl the extruded alloys immediately undergo strong *** a result of the subsequent annealing,an improvement of corrosion resistance is *** higher amount ofβ(Li)in the annealed alloy reduces the area ratio of cathodic to anodic sites of corrosion,and this makes the annealed alloy more resistive under the analyzed conditions.

关键词： Magnesium-Lithium corrosion Extrusion Annealing

Joint Rock Coefficient Estimation Based on Hausdorff Dimension

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Advances in Pure Mathematics 2017年第11期7卷 615-640页

作者： dalibor Martisek Institute of Mathematics Faculty of Mechanical Engineering Brno University of Technology Brno Czech Republic

The strength of rock structures strongly depends inter alia on surface irregularities of rock joints. These irregularities are characterized by a coefficient of joint roughness. For its estimation, visual comparison is often used. This is rather a subjective method, therefore, fully computerized image recognition procedures were proposed. However, many of them contain imperfections, some of them even mathematical nonsenses and their application can be very dangerous in technical practice. In this paper, we recommend mathematically correct method of fully automatic estimation of the joint roughness coefficient. This method requires only the Barton profiles as a standard.

关键词： Hausdorff Dimension Self-Similarity Self-Affinity Box Counting Method Power Function Method Barton Profile JRC Index

Selection of IT Sourcing Alternatives in Public Sector Using the Analytic Hierarchy Process

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Computer Technology and Application 2012年第7期3卷 485-498页

作者： dalibor Stanimirovic Mirko Vintar Faculty of Administration University of Ljubljana Ljubljana 1000 Slovenia

Recent research carried out in the public sector shows that outsourcing can indisputably bring many benefits to the organizations which master the art of devising, deploying and maintaining outsourcing relationships. However, for many organizations, these benefits remain elusive, while outsourcing projects are usually accompanied by unexpected and often negative effects. The paper focuses on in-depth analysis of the current situation concerning outsourcing of information technology projects （IT-projects） in Slovenian public sector. Presented research initially analyses substantive, procedural and other relevant aspects of outsourcing and provides a set of applicable decision making criteria. Stemming from the analysis results, this paper eventually presents the development of a multi criteria decision-support model based on Analytic Hierarchy Process （AHP） which could facilitate enhanced evaluation, selection and implementation of IT outsourcing projects in the public sector.

关键词： Public sector management IT (information technology) outsourcing outsourcing criteria AHP (analytic hierarchy process) decision-support model.

EFFECTS OF END-WALL SHAPING ON STEAM TURBINE EFFICIENCY

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Transactions of Nanjing University of Aeronautics and Astronautics 2011年第1期28卷 23-31页

作者： Hoznedl Michal Tajc Ladislav Bednar Lukas Dvorak dalibor 斯柯达动力公司实验研究部西波黑米亚大学动力系统工程系

The end-wall shaping effects of the guide blade in the steam turbine stages are *** research of the end-wall shaping effects on turbine efficiency applies CFD numerical simulations and the measurement of straight blade cascades in the wind *** final stage of research activities includes the experimental verification of the findings in an experimental steam *** the findings are interesting in terms of efficiency,a series of 3-D numerical simulations are *** demonstrate the certain improvement when the shaping is used,especially in the blade tip *** steam turbine is used to measure the shaping effects on both sides（bilateral shaping）as well as only in the blade tip *** process indicates the efficiency improvement on the blade tip ***,this occurs only in partial *** the other hand,there is a drop in efficiency compared with blades with straight end-walls.

关键词： turbines turbine blade efficiency end-wall shaping