scholarly journals Recent Advances in Brazing Fillers for Joining of Dissimilar Materials

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1037
Author(s):  
Byungmin Ahn

Brazing fillers for joining applications are essential for manufacturing and designing advanced materials. Several types of brazing fillers have been developed in recent decades to join similar or different engineering materials. Important parts of automotive and aircraft components, including steel, are often joined by brazing. In addition, ceramic components in microwave devices and circuits have been joined with a high level of integration in microelectronic devices. Similarly, in the medical field, metallic implants have been brazed to ceramic dental crowns. These advances have made human life more convenient. However, in brazing, there are certain issues with intermetallic compound (IMC) formation and residual stresses in joints at high temperatures. Nanoparticle-reinforced fillers have been proposed to control IMCs, but there are other dispersion and particle segregation issues at the joints. In this study, various types of brazing fillers, joint fabrication processes, and brazing technologies developed in recent decades are reviewed. Furthermore, new developments in brazing materials and their specific applications are presented. Finally, the emerging areas in brazing, including the recent entropy-modified brazing fillers for various structural and technological fields, are discussed.

1996 ◽  
Vol 451 ◽  
Author(s):  
Guen Nakayama ◽  
Yuichi Fukaya ◽  
Masatsune Akashi

ABSTRACTIn the scheme for geological disposal of high level radioactive nuclear wastes, the burial pit is to be isolated from the sphere of human life by a multiple-barrier system, which consists of an artificial barrier, composed of a canister, an overpack and a bentonite cushioning layer, and a natural barrier, which is essentially the bedrock. As the greatest as well as essentially the sole detriment to its integrity would be corrosion by groundwater. The groundwater comes to it seeping through the bentonite zone, thereby attaining conceivably the pH of transition from general corrosion to passivity, pHd, the behaviors of mild steel in such a groundwater environment have been examined. It has been shown that the pHd is lowered (enlargement of the passivity domain) with rising temperature and carbonate-bicarbonate concentration, while it is raised (enlargement of the general corrosion region) with increasing concentrations of chloride and sulfate ions.


2009 ◽  
Vol 160 (10) ◽  
pp. 311-317 ◽  
Author(s):  
Pierre Mollet ◽  
Dominik Thiel

The present study investigated whether the flushing distance, the territorial use and the stress hormone physiology of the capercaillie (Tetrao urogallus) were influenced in the winter by the presence of a large number of people engaged in sporting activities. In most cases flushing distances were greater, and higher concentrations of stress hormone were found in the blood serum, in areas having a high intensity of sporting activities than in forest stands relatively undisturbed by tourists. During the ski season capercaillie avoided forest patches within their home ranges where there was a high level of recreational activity. The results lead to the conclusion that intensive winter tourism can be a serious threat to the remaining capercaillie populations in middle Europe. It is recommended that the construction of new recreational facilities and new developments should be avoided in the most important habitats for capercaillie. The important habitats which today already lie in the immediate vicinity of areas intensively used by tourists could clearly receive enhanced status, according to each situation, either as tranquility areas for wildlife where entrance is forbidden or with regulations requiring winter tourists to stay on trails.


2021 ◽  
Vol 22 (8) ◽  
pp. 4137
Author(s):  
Jan Frohlich ◽  
George N. Chaldakov ◽  
Manlio Vinciguerra

Studies over the past 30 years have revealed that adipose tissue is the major endocrine and paracrine organ of the human body. Arguably, adiopobiology has taken its reasonable place in studying obesity and related cardiometabolic diseases (CMDs), including Alzheimer’s disease (AD), which is viewed herein as a neurometabolic disorder. The pathogenesis and therapy of these diseases are multiplex at basic, clinical and translational levels. Our present goal is to describe new developments in cardiometabolic and neurometabolic adipobiology. Accordingly, we focus on adipose- and/or skeletal muscle-derived signaling proteins (adipsin, adiponectin, nerve growth factor, brain-derived neuroptrophic factor, neurotrophin-3, irisin, sirtuins, Klotho, neprilysin, follistatin-like protein-1, meteorin-like (metrnl), as well as growth differentiation factor 11) as examples of metabotrophic factors (MTFs) implicated in the pathogenesis and therapy of obesity and related CMDs. We argue that these pathologies are MTF-deficient diseases. In 1993 the “vascular hypothesis of AD” was published and in the present review we propose the “vasculometabolic hypothesis of AD.” We discuss how MTFs could bridge CMDs and neurodegenerative diseases, such as AD. Greater insights on how to manage the MTF network would provide benefits to the quality of human life.


Author(s):  
Marta Makara-Studzińska ◽  
Kornelia Zaręba ◽  
Natalia Kawa ◽  
Dorota Matuszyk

SARS-CoV-2 coronavirus emerged in the world at the end of 2019. The introduction of a number of restrictions had a significant effect on numerous aspects of human life with particular influence being exerted on pregnant women and their sense of security. The study aimed to assess the level of anxiety and its main determinants in women in the third trimester of pregnancy during the coronavirus pandemic. The study technique included the present purposely designed questionnaire, Labor Anxiety Questionnaire (KLPII), and the State-Trait Anxiety Inventory (STAI). The study was conducted in a group of 315 women in the third trimester of pregnancy. A total of 258 women (81.9%) completed the questionnaire in May 2020, and 57 of them (18.1%) completed it in October 2020. The overall analysis of the Labor Anxiety Questionnaire and the STAI inventory revealed a high level of anxiety, particularly situational anxiety, in pregnant women during the SARS-CoV-2 pandemic. The age and financial status of the women were the factors which contributed to the intensification of tokophobia. Women interviewed in October 2020 were characterized by higher tokophobia levels compared to the respondents included in May 2020. It seems justified to in-crease the vigilance in the diagnostics of possible mental disorders in the perinatal period during pandemic.


2021 ◽  
pp. 114-124
Author(s):  
Татьяна Вячеславовна Кошкина

Показано, что высокий уровень физической подготовленности студентов обеспечит их способность к качественному выполнению будущей трудовой деятельности. Для оценки уровня физической подготовленности студентов в рамках их физического воспитания в вузе возможно использовать нормативы комплекса «Готов к труду и обороне» (ГТО) как универсального оценочного механизма, позволяющего выделять наиболее физически развитых представителей данного поколения. С этой целью определено соответствие уровня физической подготовленности современных студентов не физкультурных специальностей с нормами комплекса ГТО. Выявлены пути совершенствования физической подготовки студентов в условиях современного вуза. Материалом для исследования послужили теоретические и эмпирические данные, полученные на основе использования методов теоретического анализа специальной литературы и передового педагогического опыта, педагогического эксперимента, контрольных испытаний, математико-статистических методов обработки и анализа данных. Результаты исследования подтверждают, что в настоящее время уровень физической подготовленности студентов не всегда соответствует требованиям норм ГТО. Данный факт был доказан экспериментально на базе Марийского государственного университета. Требуется дополнительная работа по физической подготовке студентов. С этой целью сформулированы методические рекомендации по совершенствованию физической подготовки студентов в соответствии с нормами ГТО. Теоретически обоснована и эмпирически доказана целесообразность использования нормативов ГТО в качестве системы оценивания физической подготовленности студентов. Сформулированы методические рекомендации по повышению уровня физической подготовленности студентов в соответствии с нормативами комплекса ГТО. The importance of physical culture and sports in human life, associated with maintaining the health of the nation as a whole and ensuring individual health and working capacity of the individual in particular, is realized in the form of physical education carried out in educational institutions, including universities. A high level of physical fitness of students will ensure their ability to perform high-quality future work activities. In order to assess the level of physical fitness of students within the framework of their physical education at the university, it is possible to use the standards of the GTO complex as a universal evaluation mechanism that allows identifying the most physically developed representatives of this generation. The purpose is to determine the compliance of the level of physical fitness of modern students of non-physical education specialties with the norms of the GTO complex and to identify on this basis ways to improve the physical training of students in the conditions of a modern university. The materials for the study were theoretical and empirical data obtained on the basis of the use of methods of theoretical analysis of special literature and advanced pedagogical experience, pedagogical experiment, control tests, mathematical and statistical methods of data processing and analysis. When studying the advanced pedagogical experience accumulated in our country since the introduction of the revived GTO standards in 2014, reflected in relevant publications, as well as scientific and methodological literature in the field of physical education, it was shown that at present the level of physical fitness of students does not always meet the requirements of GTO standards. This fact was proved experimentally, by conducting control tests on the basis of the Mari State University. This indicated that additional work is required on the physical training of students, and those indicators of physical fitness of students that require the greatest development were also identified. Methodological recommendations were formulated to improve the physical training of students in accordance with the standards of the GTO. The expediency of using the GTO standards as a system for assessing students’ physical fitness was theoretically justified and empirically proved.


Author(s):  
Ewa Bonusiak ◽  

Legal sciences, raising food safety as the subject of research, focus mainly on striving to ensure sufficiently effective legal regulations and the system of bodies controlling and supervising the food market that determine the correct health quality of food. One such body is the Veterinary Inspection. And while it focuses in its tasks mainly on the protection of animal health, it directly and indirectly affects the maintenance of food health requirements. Supervision exercised by the said Inspection plays an important role in ensuring a high level of protection of human life and health, and also protects the economic interests of the consumer. These two goals are basic. Additional objectives are protection of the reliability of commercial transactions, ensuring the free movement of food in the European Union, protection of animal health and living conditions and protection of the environment. They are of particular importance for determining acceptable limits of competences that can be entrusted to public administration bodies, including the said Inspection. The article presents the activities of the Veterinary Inspection to protect food safety and selected executive forms that it uses for this purpose. These types of entities are equipped with such forms of activity because they fulfill a protective function in the public administration system. However, this function implies the obligation to protect many different values desired individually, as well as maintain (ensure) objectively desired states of affairs, phenomena and processes.


Biometrics ◽  
2017 ◽  
pp. 559-572 ◽  
Author(s):  
Maulilio J. Kipanyula ◽  
Anna M. Geofrey ◽  
Kadeghe G. Fue ◽  
Malongo R.S. Mlozi ◽  
Siza D. Tumbo ◽  
...  

Rabies has continued to claim human life despite different efforts to controls its transmission cycles between humans and domestic dogs. New developments in ICT have provided an opportunity for increased possibilities for community involvement in rabies surveillance. The main objective of this study was to investigate on approaches and practices to improve the communication of rabies surveillance information at different levels. Specifically, a study was carried to establish the significance of applying human sensor web system. Human sensor web has a potential of strengthening rabies surveillance system and serves as applied research tools for investigating strategic spatially targeted control activities, identifying areas most at risk and early detection of rabies incursions. Web and mobile based rabies surveillance system was developed and piloted as a support tool for the detection, surveillance and control of rabies. Wide application of the developed system will pave way for effective and efficient country-wide sharing of rabies surveillance information.


2007 ◽  
Vol 539-543 ◽  
pp. 4008-4012 ◽  
Author(s):  
Vinzenz Bissig ◽  
Jolanta Janczak-Rusch ◽  
Matteo Galli

Three different approaches for metal to ceramic brazing are compared using the example of Si3N4/TiN-steel joints: the use of an active filler metal (single layer brazing system), the metallisation of the ceramic and brazing with a non active filler (two-layer brazing system), the use of a composite brazing filler system (three layer brazing system). Different aspects are analysed: the development of the joint’s microstructure in the as-brazed state, the thermally induced residual stresses and the resulting bend strength of the joint’s strength. With two layers and three layers brazing system, bend strength of about 400 MPa, about 15% higher then single filler metal, were achieved. The three layer brazing system has two advantages: firstly one step processing secondly lower scattering of joint bend strength compared to two layers brazing system. The key factors in all cases are the selection of the brazing fillers and the braze design. In all cases a careful selection of the brazing fillers and the braze design are the key factors. The first criteria for the selection of the brazing fillers for joints of dissimilar materials can be done by considering only the main filler characteristics like titanium content, processing temperature and yield stress. It’s necessary to simulate the joint behaviour by finite element simulation for verifying the final selection of filler metals. It was clearly seen that the plasticity of the filler metal is the main factor affecting residual stresses for the joint geometry in this current work.


2010 ◽  
Vol 63 ◽  
pp. 114-119
Author(s):  
Ming Yung Chen ◽  
Cheng Gang Chen

Availability of advanced materials has opened up opportunities in meeting several functional requirements through hybridization. Hybrids consisting of ceramics, metals and high performance polymers could benefit many aircraft and space satellite applications. They could meet requirements of low weight, high environmental stability, and high thermal or dimensional stability. In this study, hybrid materials consisting of high performance polymer, porous ceramics (glass microballoons) and other constituents such as Zircornium Tungstate (with negative coefficient of thermal expansion (CTE)) and nanoclay were studied. Specimens were successfully produced with a range of density from 0.4 to 1.1 g/cm3 depending on the degree of fill in the syntactic foams. CTE tailoring was achieved to greatly reduce the residual stress arising from processing and CTE mismatch of dissimilar materials. The evaluations of dimensional stability were examined from thermomechanical analysis. The synergistic effects of resin, ceramic constituents and pores on the hybrid properties will be presented.


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