MESOSCALE MICROSTRUCTURE EVOLUTION, RELIABILITY AND FAILURE ANALYSIS OF HIGH TEMPERATURE TRANSIENT LIQUID PHASE SINTERING JOINTS

The continuous increase in application temperature of power electronic devices, due to the growing power density, miniaturization, and functionality in military and commercial applications, requires new packaging technologies with high temperature and reliability capabilities. Currently, the traditional maximum allowable temperature of power electronics (125°C) is a limiting factor for high temperature applications, such as space exploration, drilling, avionics, and electronic vehicles. Substitution of Silicon devices with wide bandgap (e.g., SiC) devices has extended the maximum allowable temperatures to 475 ̊C. However, this created the need for robust high temperature packaging materials, especially interconnects and attachments. High temperature solders are often too expensive, too brittle, or environmentally toxic to be used, leading to increased study of low temperature joining techniques, such as solid phase sintering and Transient Liquid Phase Sintering (TLPS), for producing high temperature stable attachments. TLPS is an emerging electronic interconnect technology enabling the formation of high temperature robust joints between metallic surfaces at low temperatures by the consumption of a transient, low temperature, liquid phase to form high temperature stable intermetallic compounds (IMCs). The performance and durability of these materials strongly depend on their microstructure, which is determined by their processing. The complicated process of IMC formation through eutectic solidification and the extensive number of parameters affecting the final microstructure make it impractical to experimentally study the effect of each factor. In this work, phase field modeling of the microstructure of TLPS materials fabricated by different processing methods will be conducted. Phase-field modeling (PFM) is a powerful thermodynamic consistent method in mesoscale modeling that simulates the evolution of intermetallic compounds during the solidification process, providing insight into the final microstructure. Application of this method facilitates the optimization of influential processing factors. Efforts will also be conducted to identify failure modes and mechanisms experimentally under dynamic, power and thermal cycling loads as a function of critical microstructural features, facilitating the optimization of joining parameters to obtain higher durability TLPS interconnections. The objective of this dissertation is to provide an insight into the processing of a reliable high temperature TLPS and facilitate their application in power electronic industries

Protective effect of Sildenafil on contralateral epididymal sperm concentration and motility following unilateral blunt testicular trauma in pre-pubertal male mice

Background and aims: Blunt testicular trauma adversely affects fertility in later periods. The purpose of the present study was to examine the effect of sildenafil on contralateral epididymal sperm count and motility following unilateral blunt testicular trauma in mice. Methods: In this randomized controlled experimental study, 24 pre-pubertal male mice were distributed into four groups of six mice each. In two groups of mice, the abdomen was opened and the right testis was placed on a sterile firm surface and 5 g sterile weight was dropped on to the testis from a height of 10 cm. One of these groups received sildenafil (0.1 mg/kg per day) intraperitoneally for 7 days starting from the day of induction of trauma. A control group and a sildenafil control group were also included. The left epididymal sperm characteristics of all animals were evaluated after 7 weeks. Results: Trauma caused a significant decrease in the sperm concentration and motility as compared to control mice (P<0.05). Sildenafil administration markedly ameliorated all changes in the above-mentioned parameters (P<0.05). Conclusion: Sildenafil administration could attenuate blunt testicular trauma-induced contralateral epididymal sperm impairment

Sex Determination Using Human Sphenoid Sinus in a Northeast Iranian Population: A Discriminant Function Analysis.

STATEMENT OF THE PROBLEM Sex determination, using skeletal remains, is of paramount importance in forensic studies. The skull accounts for the most sexual dimorphism after the pelvis. Recent studies have shown that paranasal sinuses are valuable in sex determination and considering the location of the sphenoid sinus, the risk of traumatic injuries to this structure is low. PURPOSE The present study aimed to evaluate the morphology of the sphenoid sinus and determine the validity of sphenoid sinus volume (SSV) in sex determination using cone beam computed tomography (CBCT) images. MATERIALS AND METHOD In this cross-sectional retrospective study, CBCT images of 469 Iranian patients (186 male and 283 female), aged 24-45 years, were selected. The morphology of the sphenoid sinus was recorded. 3D Slicer software (4.10.0) was used to assess SSVs in coronal and axial planes. For data analysis, t-test, chi-square test, and discriminant function analysis (DFA) were performed using predictive analytics software (ver. 18.0). RESULTS The most common morphology of the sphenoid sinus in both genders was the sellar type (50.5%). SSV was significantly larger in males than in females (p< 0.001). DFA showed that the capability of SSV in sex identification was 86.0% and 92.9% in males and females, respectively. CONCLUSION The findings of this study suggest that SSV is a reliable variable in gender discrimination in a northeast Iranian population. However, since the morphology of the sphenoid sinus and sex were independent of each other, the morphology of the sphenoid sinus is not a suitable indicator for sex determination

Framework for Determining Data Management Responsibilities in Federal Organizations

Massive data volume, on the one hand, and the growing importance of the role of data in organizations, on the other hand, make data management inevitable. One of the important issues in data management is to determine the necessary roles and division of responsibilities and rights arising from it. The pattern of division of responsibilities in an organization depends on its structure, and the structure of an organization is a function of the three elements of complexity, formality, and focus. In coalition organizations, the division of responsibilities and powers between the central unit and its affiliated units is more complex and requires a clear and codified model for joint efforts and cooperation in various issues, including management. In this research, using the responsibility-sharing matrix, a model for cooperation and division of responsibilities related to data management in the main body and affiliated subdivisions of a coalition organization has been obtained and using the Delphi method to reach the consensus of experts and using, how to divide data management responsibilities in the Ministry of Science, Research and Technology of the Islamic Republic of Iran and its affiliated universities is explained

Quantum Random Number Generator Based on LED

Quantum Random Number Generators Produce random numbers based on the intrinsic probability nature of quantum mechanics, making them true random number generators. In this paper, we design and fabricate an embedded QRNG that produces random numbers based on fluctuations of spontaneous emission in a LED. Additionally, a new perspective on the randomness of the recombination process in a LED is introduced that is consistent with experimental results. To achieve a robust and reliable QRNGm we compare some usual post processing methods and select the best one for a real time device. This device could pass NIST tests, the output speed is 1 Mbit per S and the randomness of the output data is invariant in time and different temperatures

Actor-Network methodology in science and technology studies

Actor-Network theory (ANT), in social sense, is an approach to sociological analysis in the field of science and technology studies and focuses on understanding how things get to the situations in which they find themselves. In recent years, this theory has been considered by researchers as a methodological approach to analyze the use of technology in the workplace and describe the various dimensions of socio-technical systems. Despite numerous examples of research based on ANT methodology, no codified framework has been introduced for it and no examples of using this theory in the form of methodology have been found in the country. The present study tries to introduce a framework for data collection and analysis in the context of this theory, while explaining the methodology of this theory in an analytical-descriptive manner. The feasibility and validity of the proposed framework have been assessed in the form of a case study. The results of the research can be effective in the systematic application of ANT methodology, especially in the country

The Semantically Rich Learning Environments: A Systematic Literature Review

Purpose: The research is intended to extract repetitive themes in the field of semantic-rich learning and to express the basic opportunities and challenges therein. Method: The method applied was to review the articles published in the WOS database, during the years 2000 to 2020 by using the paradigm funnel technique; moreover the Nvivo software was used for document analysis and theme extraction. Findings: In the study, it was found that establishing access to appropriate educational content, proper analysis and representation of knowledge, human capabilities enhancement, personalization of learning, and improving the quality of assessment, are the most important positive effects of using STs in learning; Also, in this study, nine themes and seven major challenges in the field of semantic-rich learning were identified. Conclusion: personalization and adaptation, and the development of various ontologies, are the most cited themes; and access to learning content and concerns about the design and development of learning systems are the most important challenges facing semantic-rich learning environments. We believe that in order to overcome the enumerated challenges, the combination of STs with other emerging cognitive and communication technologies, such as IoT, is necessary and could be the subject of future research in this field