Etude de l’impact de micro-cavités (voids) dans les attaches de puces des modules électroniques de puissance

Power converters nowadays are required to function under harsh conditions in meeting energy efficiency and reliability requirement. Whereas, industrial specifications tend toward a higher level of power integration in respect to the cost constraint. As a result, the die attach is one of the key elements in power module packaging because of high current densities and high heat flow which are transported through. Void formation in the die attach may lead to performance degradation and premature aging of the component. This study introduces a methodology based on the comparison of numerical simulations and experimental campaigns. The obtained results help to improve our understanding on the electro-thermal behaviour of MOSFETs with solder voids. In this thesis, we depict a finite element model in which electro-thermal coupling of a MOSFET active layer is taken in to account. Simulation results will be correlated to the experimental responses. Later on, a parametric numerical study based on the response surface method (RSM) which minimizes the number of simulations and future tests will be exploited to quantify the impact of void position and size on several selective performance criteria. A future serial experimental study in respect to the same RSM design is expected in prospect, in order to fulfil the complementarity for this approach.Les convertisseurs électroniques de puissance sont voués à fonctionner sous des conditions applicatives de plus en plus sévères tout en respectant les impératifs d’efficacité énergétique et de fiabilité. Or, les besoins industriels tendent vers un plus haut niveau d’intégration fonctionnelle tout en améliorant le rapport qualité-prix. Dès lors, la solution utilisée pour le report des puces semi-conductrices est le siège de densités de courant importantes et d’un flux thermique élevé. La présence de défauts dans cette couche d’interconnexion peut conduire à la dégradation de ses performances et au vieillissement prématuré du composant. L’objectif de nos recherches est d’évaluer la pertinence d’une méthodologie basée sur la confrontation de simulations numériques et de campagnes expérimentales. L’objectif est d’améliorer la compréhension du comportement électrothermique en régime de conduction d’un transistor MOSFET en présence d’un void dans sa brasure. Dans cette manuscrite, nous présenterons la construction d’un modèle intégrant le couplage électrothermique de la partie active qui sera confronté à la réponse de résultats expérimentaux. Puis, une étude numérique basée sur la théorie des plans fractionnaires, qui minimise le nombre de simulations, sera exploitée afin de quantifier l’impact de la taille et de la position du défaut sur la réponse électrothermique du composant et de ses liaisons électriques. Les détails de la mise en place d’une étude expérimentale analogue permettront de mettre en perspective la complémentarité de cette approche

A Murnaghan-Nakayama rule for Grothendieck polynomials of Grassmannian type

We consider the Grothendieck polynomials appearing in the K-theory of Grassmannians, which are analogs of Schur polynomials. This paper aims to establish a version of the Murnaghan-Nakayama rule for Grothendieck polynomials of the Grassmannian type. This rule allows us to express the product of a Grothendieck polynomial with a power sum symmetric polynomial into a linear combination of other Grothendieck polynomials.Comment: 10 pages, 7 figure

Embedding Sustainable Consumption into Higher Education in Vietnam

Changing in the way that human produces and consumes are indispensable to achieve sustainable consumption. All of the countries in developed economies, economies in transition and developing economies should promote sustainable consumption. This will require larger changes in society. Higher education plays a vital role in promoting understanding, awareness of professors, staff members and students of sustainable consumption. Through higher education, these people would be positively change their mind about this issue. National Economics University (NEU) is one of the leading university in economics in Vietnam as a case study. Students graduated from the university will be future experts, leaders and businessmen. After graduation, as academic citizens with acquainted knowledge and skills, they will influence the economic and social changes though their business and private purchasing habits and decisions. Using data from the University, this paper will reveal the current landscape of sustainable consumption at National Economics University through the years. In order to embed this issues into education, the university should incorporate sustainable consumption into the curriculum, create and implement a sustainability plan and adjust teaching method to encourage students asking questions, analyzing, thinking critically and making decisions toward sustainable consumption. Keywords: Embedding sustainable consumption, higher education DOI: 10.7176/EJBM/11-18-12 Publication date:June 30th 201

Applying the Theory of Planned Behavior (TPB) in Investigating Consumption Behavior in Vietnam

This study explored the consumer behavior based on TPB model in Vietnam. The hypotheses are empirically tested using survey data obtained from consumer who purchased green products of household appliances in Hanoi– the capital of Vietnam. During the study, the research team added the “trend” variable which is a characteristic variable in Vietnam. The results of the multiple regression analysis show that attitude, subjective norm, perceived behavioral control, trend have significant and positive effect on household appliances product. The research findings are discussed and implications for government, manufacturing businesses, retail businesses to embrace green consumption behavior Keywords: Consumption Behavior; Vietnam; TPB; Household appliances DOI: 10.7176/EJBM/12-18-16 Publication date:June 30th 202

Two-Phase Defect Detection Using Clustering and Classification Methods

Autonomous fault management of network and distributed systems is a challenging research problem and attracts many research activities. Solving this problem heavily depends on expertise knowledge and supporting tools for monitoring and detecting defects automatically. Recent research activities have focused on machine learning techniques that scrutinize system output data for mining abnormal events and detecting defects. This paper proposes a two-phase defect detection for network and distributed systems using log messages clustering and classification. The approach takes advantage of K-means clustering method to obtain abnormal messages and random forest method to detect the relationship of the abnormal messages and the existing defects. Several experiments have evaluated the performance of this approach using the log message data of Hadoop Distributed File System (HDFS) and the bug report data of Bug Tracking System (BTS). Evaluation results have disclosed some remarks with lessons learned

Level of Factors impact on the Buyers’ Intention in Buying Private Health Insurance with the Case of Vietnam Non-Life Insurance Companies

The study aims to determine the influence of factors affecting the intention to purchase private health insurance at non-life insurance companies in Vietnam. The samples were surveyed from 500 people from many areas but mostly in Hanoi. The study identified and clarified 5 independent factors affecting the intention to buy private health insurance at non-life health insurance companies in Vietnam. The analysis results show 5 variables: "Past experience", "Perception of service quality of insurance companies", "Perceived behavioral control", "Attitude towards risks and private health insurance ", and the variable "Subjective norms on private health insurance" affect people's intention to buy private health insurance. Several policies have been proposed to increase customers' intention to buy private health insurance at non-life insurance companies from the analysis. To raise customer's intention to purchase private health insurance, the research team recommends non-life insurance company to improve service quality, especially after-sales service, the quality and expertise of staff, and the government to complete policies and legal framework on private health insurance. Moreover, the research team also recommend to renovate the quality of organizing the private health insurance regime and form the basis of the entire population pathology record. Keywords: private health insurance, intention to purchase, non-life insurance company. DOI: 10.7176/EJBM/12-27-06 Publication date:September 30th 202

Genetic Diversity and Population Structure of Canarium tramdenum Dai and Yakovl. in Northern Vietnam

Canarium tramdenum occurs naturally in subtropical and tropical regions of Indochina and China. The wood is used for making high quality furniture and the fruit and leaves are used in traditional medicine. However, a lack of information on genetic diversity and population structure has handicapped the genetic conservation and domestication of this high-value species. This study evaluated genetic variation within and among four C. tramdenum populations. Sixty individuals were collected from four natural populations in Vietnam in the provinces of Ninhbinh, Bacgiang, Nghean, and Backan. Genetic diversity and genetic structure were determined using 20 ISSR markers. A total of 192 DNA fragments with sizes ranging from 110 bp to 3,000 bp were detected, of which 154 segments (80.2%) were polymorphic and 38 segments (19.8%) were monomorphic. The ISSR data indicated a moderate degree of genetic diversity for the species (h = 0.252). The four populations were separated into three genetic clusters with low levels of genetic distance between them. AMOVA result showed that most (78%) of the genetic variation was within the populations. The moderate to high genetic diversity of C. tramdenum and the low genetic differentiation among populations suggested that all existing natural populations in the particular regions needed to be preserved to protect the genetic diversity of this species

Comparative analysis of root transcriptomes from two contrasting drought-responsive Williams 82 and DT2008 soybean cultivars under normal and dehydration conditions

The economically important DT2008 and the model Williams 82 (W82) soybean cultivars were reported to have differential drought-tolerant degree to dehydration and drought, which was associated with root trait. Here, we used 66K Affymetrix Soybean Array GeneChip to compare the root transcriptomes of DT2008 and W82 seedlings under normal, as well as mild (2h treatment) and severe (10h treatment) dehydration conditions. Out of the 38172 soybean genes annotated with high confidence, 822 (2.15%) and 632 (1.66%) genes showed altered expression by dehydration in W82 and DT2008 roots, respectively, suggesting that a larger machinery is required to be activated in the drought-sensitive W82 cultivar to cope with the stress. We also observed that long-term dehydration period induced expression change of more genes in soybean roots than the short-term one, independently of the genotypes. Furthermore, our data suggest that the higher drought tolerability of DT2008 might be attributed to the higher number of genes induced in DT2008 roots than in W82 roots by early dehydration, and to the expression changes of more genes triggered by short-term dehydration than those by prolonged dehydration in DT2008 roots vs. W82 roots. Differentially expressed genes (DEGs) that could be predicted to have a known function were further analyzed to gain a basic understanding on how soybean plants respond to dehydration for their survival. The higher drought tolerability of DT2008 vs. W82 might be attributed to differential expression in genes encoding osmoprotectant biosynthesis-, detoxification- or cell wall-related proteins, kinases, transcription factors and phosphatase 2C proteins. This research allowed us to identify genetic components that contribute to the improved drought tolerance of DT2008, as well as provide a useful genetic resource for in-depth functional analyses that ultimately leads to development of soybean cultivars with improved tolerance to drought