scholarly journals Characterization of Newly Developed Zinc Composite with the Content of 8 wt.% of Hydroxyapatite Particles Processed by Extrusion

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1716 ◽  
Author(s):  
Jan Pinc ◽  
Jaroslav Čapek ◽  
Vojtěch Hybášek ◽  
Filip Průša ◽  
Klára Hosová ◽  
...  

Zinc and its alloys belong to a group of biodegradable materials, which can be potentially used for the preparation of temporary orthopedic implants. The research of biodegradable zinc materials revealed a lot of limitations; however, the new processing approaches of those materials can enhance their properties, which are insufficient for now. In this study, the zinc composite with 8 wt.% of hydroxyapatite (Zn/HA8) prepared for the first time by extrusion process was characterized from the point of view of the structural, mechanical and corrosion properties. The extrusion process led to good integrity of the interfaces between the zinc and hydroxyapatite particles. Mechanical behavior confirmed the role of hydroxyapatite as a defect in the material structure, which led to a decrease of the Zn/HA8 mechanical properties by approximately 30% (compressive yield strength (CYS) = 154 MPa Zn, 113 MPa Zn/HA8). Despite that, the Zn/HA8 composite showed sufficient mechanical properties for cancellous bone replacement and reached the lower limit for cortical bone. Additionally, the presence of hydroxyapatite caused the preferential precipitation of hydroxyapatite (HA) from the solution and can lead to a significant enhancement of the tissue/implant interface interactions.

2020 ◽  
Vol 62 (4) ◽  
pp. 395-399
Author(s):  
Jiehui Liu ◽  
Hongjun Hu ◽  
Yang Liu ◽  
Dingfei Zhang ◽  
Zhongwen Ou ◽  
...  

Abstract Compound extrusion (CE) is a newly developed plastic deformation technique which combines direct extrusion (DE) with a two-pass equal channel angular extrusion (ECAE). This paper focuses on the strength, ductility and anti-corrosion properties of an NaCl solution at certain concentrations and the wear-resistance of dry sliding AZ61 magnesium alloy prepared by CE and DE. It is found that the strength and elongation of the AZ61 alloy prepared by CE are enhanced because of grain refinement. Furthermore, AZ61 magnesium alloy made by CE displays higher corrosion and wear resistance than that prepared by DE. Experimental results prove that CE is a prospective manufacturing method for improving the mechanical properties, anti-corrosion and anti-wear of AZ61 magnesium alloy.


2012 ◽  
Vol 25 (0) ◽  
pp. 188
Author(s):  
Helena Sgouramani ◽  
Chris Muller ◽  
Leon van Noorden ◽  
Marc Leman ◽  
Argiro Vatakis

We report two experiments aiming to define how experience and stimulus enactment affect multisensory temporal integration for ecologically-valid stimuli. In both experiments, a number of different dance steps were used as audiovisual displays at a range of stimulus onset asynchronies using the method of constant stimuli. Participants were either professional dancers or non-dancers. In Experiment 1, using a simultaneity judgment (SJ) task, we aimed at defining — for the first time — the temporal window of integration (TWI) for dancers and non-dancers and the role of experience in SJ performance. Preliminary results showed that dancers had smaller TWI in comparison to non-dancers for all stimuli tested, with higher complexity (participant rated) dance steps requiring larger auditory leads for both participant groups. In Experiment 2, we adapted a more embodied point of view by examining how enactment of the stimulus modulates the TWIs. Participants were presented with simple audiovisual dance steps that could be synchronous or asynchronous and were asked to synchronize with the audiovisual display by actually performing the step indicated. A motion capture system recorded their performance at a millisecond level of accuracy. Based on the optimal integration hypothesis, we are currently looking at the data in terms of which modality will be dominant, considering that dance is a spatially (visual) and temporally (audio) coordinated action. Any corrective adjustments, accelerations–decelerations, hesitations will be interpreted as indicators of the perception of ambiguity in comparison to their performance at the synchronous condition, thus, for the first time, an implicit SJ response will be measured.


2011 ◽  
Vol 255-260 ◽  
pp. 3404-3410
Author(s):  
Shuang Xi Li ◽  
An Quan Xu ◽  
Xin Jun Tang ◽  
Quan Hu

It takes on the technical and economic double benefits that fly ash taking the place of cement. However, water/binder of modern concrete is generally low; the research on the concrete performance which is based on large water/binder is no longer suitable for analysis of modern concrete. As to this problem, using different proportions of W/B and FA dosage as influencing factors, specimen is compounded for the compressive strength test. Then, mechanical properties of HPC are studied systematically. Based on this, macro-performance is analyzed from a micro-mechanism point of view through taking the electron micrograph. As the study shows, strength of HPC mixed with fly ash has low characteristics at early period while high ones at later period. At later hydration, fly ash effect plays a significant role, the growth rate of concrete strength increases as the increase of FA dosage. Compressive strength of concrete decreases as the increase of W/B and FA dosage. When the W/B is high, compressive strength is not sensitive to the change of W/B and FA dosage; but when the W/B decreases from 0.30 to 0.25, the concrete strength transition occurs. The influence of W/B on concrete compressive strength is more significant than that of the FA dosage; in the preparation of HPC, fly ash can be added more and cement is added less relatively by decreasing the W/B, displaying the role of micro-aggregate filling and modification, improving the strength and other performance of concrete. The study on micro-mechanism proves well the macro-phenomena above.


Dialogue ◽  
1999 ◽  
Vol 38 (2) ◽  
pp. 297-326
Author(s):  
Stéphane Courtois

AbstractThe general aim of this paper is to question the idea that hermeneutic and critical social sciences have to be conceived as specific embodiments of the scientific enterprise. This idea is rather implicit in Habermas's work, but has its grounds in his thesis about the argumentative unity of all sciences, upheld for the first time in 1973. Such a point of view turns out to be untenable for two reasons. First, the indiscriminating inclusion of the hermeneutic and critical social sciences in scientific enterprise raises problems of consistency with regard to the systematic guidelines of The Theory of Communicative Action. Moreover, the thesis of argumentative unity of the sciences itself is incompatible with Habermas's methodological conception of the role of Verstehen in the social sciences developed in section 1.4 of the book. Finally, the author argues that this conception calls for another understanding of the status and role of the hermeneutic and critical disciplines, which is outlined in some detail.


Lituanistica ◽  
2020 ◽  
Vol 65 (4) ◽  
Author(s):  
Aurelijus Gieda

It has been emphasised on several occasions that Professor Eduard Wolter was a prominent figure and a broad-profile humanitarian in the history of Lithuanian humanities, who for many decades was actively interested in Lithuanian studies, among other things. The revolutionary changes in Russia divided Wolter’s academic career into two unequal parts: nearly forty years of academic work in Tsarist Russia and thirteen years in Kaunas. Bearing in mind the status of academic Lithuanian studies at the beginning of the twentieth century, his was an unprecedented case in Lithuania until 1940. We can claim that before 1940, no other Lithuanian humanitarian had such a long academic career of several decades devoted to Lithuanian studies. However, we still do not have an academic biography of Wolter, and Stasė Bušmienė’s work Eduardas Volteris, published almost 50 years ago, remains the most comprehensive publication in the field. Because of these circumstances, we must search for new problematic aspects, updated interpretations, and new material-based approaches. The article analyses the context of the revolutionary changes in Russia, the role of Augustinas Voldemaras in the history of the Wolters’ emigration, and Prof. Wolter’s recurrent concern about the academic possessions he had left in St. Petersburg when he was already in Lithuania. This article seeks new solutions: the emigration of the Wolter family to Lithuania is viewed as a potentially crucial knot in the professor’s biography. It allows understanding and linking two seemingly very different stages in his biography (Tsarist Russia and independent Lithuania). Lithuanian research interests and the related circle of like-minded people that had evolved in the course of many decades form a consistent deep-rooted epicentre of Prof. Wolter’s biography. The research method chosen imparts inner integrity to the biography of Prof. Wolter and an opportunity to look into the path of this scholar, who was also a member of the Russian Academy of Sciences, in the long term perspective. This text develops and substantiates the thesis that scholars’ emigration from Bolshevik Russia took place under dire circumstances: they had to leave not only their homes but also their libraries behind, their manuscripts and much of the material accumulated over many decades of academic work. Also, from the point of view of a collective biography, the context of the loss of the old University of St. Petersburg after the Bolshevik takeover in Russia is shown. While in Lithuania, Prof. Wolter made great efforts to recover the manuscripts, the library, and the collections he had left behind in St. Petersburg. This moment justifies the emigration of the Wolter family to Lithuania as a relevant key to the whole biography of Prof. Wolter. For the first time in historiography, the article gives a detailed analysis of Augustinas Voldemaras’ 53 letters to Alexandra Wolter (translated and published by Gediminas Rudis). The letters offer an interesting and characteristic description of the actual circumstances of the emigration of the Wolter family to Lithuania. This correspondence reveals a special connection between Voldemaras and the Wolter family. Voldemaras, who had lived in the Wolters’ house in St. Petersburg for over a decade, became a true family member, and their communication in the process of the emigration of the Wolter family was best described as close familial relations. In this way, the article sheds light on the role of Prof. Voldemaras in the relocation of the Wolter family to Lithuania, which did not find reflection either in Wolter’s biography or in general historiography.


2021 ◽  
Vol 11 (4) ◽  
pp. 1820
Author(s):  
Shijie Jiang ◽  
Tiankuo Dong ◽  
Yang Zhan ◽  
Weibing Dai ◽  
Ming Zhan

Due to the stratified nature of the manufacturing process, material extrusion (ME) parts have lower mechanical properties than those fabricated by traditional technology. This is one of the most significant defects hindering the development and application of this rapid prototyping technique. In this paper, vibration was applied to the ME process by using piezoelectric ceramics for the first time to improve the mechanical properties of the built parts. The vibrating ME equipment was established, and the specimens processed in different build directions were individually fabricated without applied vibration and with different applied vibrations. To quantify the effect of applied vibration on their mechanical properties and to summarize the influencing rule, a series of experimental tests were then performed on these specimens. A comparison between the testing results shows that the tensile strength and plasticity of the specimens, especially those processed in the Z direction, can be obviously improved by applied vibration. The orthogonal anisotropy is decreased obviously. The improvement becomes greater with increasing vibration frequency or amplitude. From the microscopic point of view, it can be seen that applied vibration can reduce the part’s defects of porosity and inclusion as well as separation between layers and, thereby, improve the bonding strength.


2018 ◽  
Vol 25 (2) ◽  
pp. 489-516 ◽  
Author(s):  
Manojkumar Vithalrao Dalvi ◽  
Ravi Kant

Purpose The purpose of this paper is to examine the role of supplier development activities (SDAs) in the context of three major performance outcomes (POs), i.e. supplier performance improvement (SPI), buyer’s competitive advantage improvement (BCAI) and buyer-supplier relationship improvement (BSRI). Design/methodology/approach A survey was conducted of 214 manufacturing organizations and the data were analyzed using factor analysis, correlation analysis and multiple hierarchical regression analysis. Findings This paper categorizes the identified 28 SDAs and 33 POs into five and three major categories of SDAs and POs, respectively. The results indicate a significant relationship between each aspect of SDAs and POs, except investment. The effect of each category of SDA is determined through a developed framework. Research limitations/implications This present study analyzes the SDAs and POs from the buyer’s point of view. A paired buyer and supplier data may provide some additional information about the relationship between SDAs and POs. Practical implications The outcome of this study will provide significant information for managers and academicians who are involved in outsourcing. Originality/value For the first time, the relationship and effect of each category of SDAs was analyzed in combination with three major POs, i.e. SPI, BSRI and BCAI.


Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7847
Author(s):  
Viacheslav Bazhenov ◽  
Anastasia Lyskovich ◽  
Anna Li ◽  
Vasily Bautin ◽  
Alexander Komissarov ◽  
...  

Mg alloys have mechanical properties similar to those of human bones, and have been studied extensively because of their potential use in biodegradable medical implants. In this study, the influence of different heat treatment regimens on the microstructure and mechanical and corrosion properties of biodegradable Mg–Zn–Ga alloys was investigated, because Ga is effective in the treatment of disorders associated with accelerated bone loss. Solid–solution heat treatment (SSHT) enhanced the mechanical properties of these alloys, and a low corrosion rate in Hanks’ solution was achieved because of the decrease in the cathodic-phase content after SSHT. Thus, the Mg–4 wt.% Zn–4 wt.% Ga–0.5 wt.% Y alloy after 18 h of SSHT at 350 °C (ultimate tensile strength: 207 MPa; yield strength: 97 MPa; elongation at fracture: 7.5%; corrosion rate: 0.27 mm/year) was recommended for low-loaded orthopedic implants.


Author(s):  
E.A. Cherkasova

This essay examines for the first time the three editions, from 1891, 1895, and 1900, of Solovyov’s collected poetry from the point of view of their internal organization and relationship. The task posed is the identification and description of the most important components of the poetry book, which are present in all three editions and contribute to an understanding of the author's conception as it was realized in the books under consideration. To fulfill this task the comparative and descriptive methods of analysis are used. The evolution of the author’s artistic consciousness is described on the basis of the collected editions of Solovyov's poetry, his epistolary heritage, and the research of contemporary scholars. The different levels of the author's dialogue with the reader, with critics, as well as with poets and writers are highlighted. The author outlines the ways of researching the examined theme. In particular, the chronological order of the development of Solovyov's lyrical books, as well as the definite recurrence of the separate lyrical components in each of the three books, is shown. We see that the content of the author's three prefaces determines their function in the structure of the poetry books. The special role of critical works, included by the author in the third edition, in shaping the structure of the book of poems, as well as their relation with the foreword, is emphasized. The author concludes with genre renewal of art forms to solve new aesthetic tasks. Solovyov's aspiration to realize the life-creative conception within the framework of work on three lifetime editions is affirmed. In conclusion, the author substantiates the idea that the presented editions in their unity are a transitional genre form, which corresponds to the poet’s individual artistic searching and which establishes the literary trends of the turn of XIX–XX centuries.


2018 ◽  
Vol 782 ◽  
pp. 136-141
Author(s):  
Corneliu Munteanu ◽  
Ștefan Lupescu ◽  
Bogdan Istrate ◽  
Vasile Iulian Antoniac ◽  
Marcelin Benchea ◽  
...  

Biodegradable materials are a further development of new medical applications, such as orthopedic implants and vascular stents, or the tissue scaffold. The variety of alloying elements introduced into magnesium alloys lead to superior corrosion resistance and mechanical properties similar to the biological bone. From a mechanical point of view, increasing the percentage of calcium leads to decreased strength and elongation resistance, and Yttrium addition greatly improves tensile strength and favors a slower degradation process. Three different Mg-0.5Ca-xY alloys were obtained, varying the concentration of the Y-element. The Mg-0.5Ca-xY system was tested from the point of view of micro-scratch and micro-indentation with three determinations each, obtaining results for Young's mode, micro-hardness, COF and stiffness. These alloys possess mechanical properties for use as orthopaedic applications. As future studies, mechanical properties can be improved by performing heat treatments.


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