A Study of Grain Growth and Microstructure Control in Silicon Nitride by Computer Simulation

1998 ◽  
Vol 538 ◽  
Author(s):  
Y. Okamoto ◽  
N. Hirosaki ◽  
H. Matsubara
Keyword(s):  
Silicon Nitride ◽  
Grain Growth ◽  
Early Stage ◽  
High Growth ◽  
Ceramic Materials ◽  
High Growth Rate ◽  
Seed Particles ◽  
The Difference ◽  
Grain Growth Behavior ◽  
Equiaxed Grains

AbstractA grain growth simulation technique is developed for microstructure design of ceramic materials by extending the Potts model. The simulation model has successfully reproduced the self-reinforced microstructure which is peculiar to silicon nitride, consists of large elongated grains and small equiaxed grains.To control the microstructure of silicon nitride further, a seeding technique is effective and often employed. Grain growth behavior of seed particles in the simulation is studied. It is found that the seed grains grow with a relatively high growth rate during the early stage of grain growth. In contrast in the later stage, the difference between microstructures with and without seed particles decreases. This behavior agrees well with that of actual silicon nitride. These results demonstrate the consistency of the simulation.

Look Before You Leap (A): Considering a Job Offer With an Early-Stage Company

2017 ◽  
pp. 1-9
Author(s):  
Steven Rogers ◽  
Sachin Waikar ◽  
Scott T. Whitaker
Keyword(s):  
Early Stage ◽  
High Growth ◽  
Point Of View ◽  
Entrepreneurial Firm ◽  
Start Up ◽  
Management Responsibility ◽  
Base Salary ◽  
The Difference ◽  
To Come ◽  
Real Person

In the fall of 2007 a senior director of product marketing at Qwest in Denver, Colorado, gets an offer to work for an entrepreneurial high-growth venture. The vision is for greater wealth, accelerated business opportunity, more thrill on the job, and faster path to leadership by pursuing a position with a start-up firm. Kiva Allgood has management responsibility in her current position (e.g., manages a high-budget portfolio), with compensation of $145,000 in salary and incentive bonuses up to 100% of base salary. She realizes that she is not prepared for the negotiation because she has only negotiated job offers within large firms. She needs to know what many of these entrepreneurial finance terms mean and to understand whether she is being offered terms and amounts commensurate with the value she feels she will bring to the entrepreneur. She also needs to understand her opportunity cost and the expected value of her options: staying with the current job, starting her own venture, or taking this offer at the entrepreneurial venture. She had no idea there were also so many additional, non-financial factors to take into consideration. With her future on the line, she needs to work through the numbers fast. The entrepreneur gave her five days to come back with a counter offer, which he considered a generous amount of time. In evaluating these questions, students will take Allgood's point of view. The case is based on a real job offer to a real person named Kiva Allgood. The entrepreneur and his firm are fictitious in order to heighten the issues in this situation.Exposes customary negotiations between a prospective employee and an entrepreneur, taking into account the valuation of the entrepreneurial firm, salary, stock options, ownership percentage, etc.; Examines the difference between considering a position with an entrepreneurial venture and one at a stable corporate organization; Looks at typical compensation criteria for entrepreneurial venture capital-backed firms; Introduces method for assessing an entrepreneur as a prospective future employer.

Development of LPE process for fabrication of coated conductors

2000 ◽  
Vol 659 ◽  
Author(s):  
Teruo Izumi ◽  
Natsuro Hobara ◽  
Toru Izumi ◽  
Katsuya Hasegawa ◽  
Masahiko Kai ◽  
...  
Keyword(s):  
Growth Temperature ◽  
Recent Progress ◽  
High Growth ◽  
High Growth Rate ◽  
Coated Conductors ◽  
The Other ◽  
Lower Growth ◽  
The Difference ◽  
Lower Growth Temperature ◽  
Selection Of

ABSTRACTRecent Progress of development for coated conductors by the LPE technique was reviewed. Double layered LPE films were applied to the growth on metal substrates. In both cases of MgO- and NiO- buffers, the constructions were succeeded to grow on Hastelloy and Ni tapes, respectively. In the case of the MgO-buffer, the problem, which is the melting back of the 1st LPE layer during dipping for the growth of the 2nd LPE layer, was found. The problem was solved by means of the selection of the materials for each LPE layer to introduce the difference in the growth temperature for the 1st and the 2nd layers. The lower growth temperature for the 1st LPE layer than that for 2nd one is effective to avoid the problem. On the other hand, the double layered LPE films on Ni tapes revealed Tc of 85K. Concerning the long tape processing, the high growth rate of 1≈ was confirmed even without rotation using the long tape apparatus.

scholarly journals Heterophyllous Shoots of Japanese Larch Trees: The Seasonal and Yearly Variation in CO2 Assimilation Capacity of the Canopy Top with Changing Environment

Plants ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 1278
Author(s):  
Satoshi Kitaoka ◽  
Qu Laiye ◽  
Yoko Watanabe ◽  
Makoto Watanabe ◽  
Toshihiro Watanabe ◽  
...  
Keyword(s):  
Seasonal Change ◽  
High Growth ◽  
Co2 Assimilation ◽  
High Growth Rate ◽  
Japanese Larch ◽  
Leaf Mass Per Area ◽  
Larix Kaempferi ◽  
Yearly Variation ◽  
The Difference ◽  
Assimilation Capacity

Japanese larch (Larix kaempferi = L. leptolepis) is often characterized by its high growth rate with heterophyllous shoots, but the functional differences of heterophyllous shoots still remain unclear. Recently, abrupt high temperature and drought during spring induced high photosynthetic rate via change in leaf morphology of the deciduous habit. In order to reveal the photosynthetic characteristics of both short and long-shoot needles of sunny canopy of the larch trees using a canopy tower, we calculated the seasonal change of gas exchange characters and leaf mass per area (LMA) and foliar nitrogen content (N) of heterophyllous needles: short and long-shoot needles over 3 years. No marked difference in light-saturated photosynthetic rates (Psat) was observed between short and long shoots after leaf maturation to yellowing, although the difference was obvious in a specific year, which only shows that seasonal change in temperature and soil moisture determines the in situ photosynthetic capacity of needles. The large annual and seasonal variations in Psat in both shoots were found to be mainly determined by climatic variations, while shoot types determined the strategy of their photosynthetic N utilization as well as the stomatal regulation.

Grain Growth Behavior During Microwave Annealing of Silicon Nitride

1996 ◽  
Vol 430 ◽  
Author(s):  
M. Hirota ◽  
M. E. Brito ◽  
K. Hirao ◽  
K. Watari ◽  
M. Toriyama ◽  
...  
Keyword(s):  
Growth Rate ◽  
Silicon Nitride ◽  
Comparative Study ◽  
Grain Growth ◽  
Microwave Radiation ◽  
Microstructural Analysis ◽  
Growth Behavior ◽  
Radiation Frequency ◽  
Microwave Annealing ◽  
Grain Growth Behavior

AbstractA comparative study of grain growth behavior in silicon nitride under conventional and microwave annealing is presented. Microwave annealed specimens showed a faster growth rate as indicated by the quantitative microstructural analysis. The phenomenon was used in combination with seeding techniques to develop a silicon nitride exhibiting a bi-modal microstructure. Microwave annealing was carried out using a microwave radiation frequency of 28 GHz.

scholarly journals Sustainability in the Chemical Industry in Brazil

2016 ◽  
Author(s):  
Lívia Gabriele Azevedo Garcia ◽  
Carolina Cabral Netto ◽  
Simone Georges El Khouri Miraglia
Keyword(s):  
Chemical Industry ◽  
Negative Impact ◽  
Raw Materials ◽  
Early Stage ◽  
High Growth ◽  
Relevant Information ◽  
High Growth Rate ◽  
Environmental Indicators ◽  
Qualitative Assessment ◽  
Sustainability Reports

ABSTRACT Over the past few decades, the Chemical Industry has shown a high growth rate resulting in higher consumption of raw materials, natural resources and also higher waste generation. In this context, a more sustainable attitude was adopted by the industry in order to reduce its negative impact, the results of such efforts are published in Sustainability Reports. However there are only but a few academic papers related to the subject, the objective of this graduation project is to help to fill this gap by presenting, through the analysis of sustainability reports of ten companies previously selected and by their economic, social and environmental indicators, the level of quantitative and qualitative application of sustainability in the processes, policies and culture of the chemical industry. The reports were analyzed by means of Excel Spreadsheets that were elaborated based on GRI guidelines, containing the description of the topic or sustainability indicator and also a field designated to the inclusion of relevant information that was exposed in the report. For the qualitative analysis, the companies were grouped by sector of performance and/or similar processes, enabling the development and analysis of relative indicators. It was also performed a qualitative assessment of the GRI application levels. The analysis of relative indicators allowed us to understand and measure the level of sustainability across industries that, together with the other analysis, allowed the authors to conclude that sustainability in the national chemical industry is at an early stage , where the industry is currently focusing its attention on aspects of energy consumption, water and emissions, further progress in the area requires greater investments in research and development of cleaner processes and that result in less waste. Keywords:Chemical Industry; Sustainability; Sustainability - indicators

scholarly journals Bacterial Load Comparison of the Three Main Lineages of Mycobacterium tuberculosis Complex in West Africa

2021 ◽  
Vol 12 ◽  
Author(s):  
Stephen Osei-Wusu ◽  
Portia Morgan ◽  
Prince Asare ◽  
Godfrey Adams ◽  
Abdul Basit Musah ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
West Africa ◽  
Bacterial Load ◽  
Rna Extraction ◽  
High Growth ◽  
High Growth Rate ◽  
Smear Microscopy ◽  
Culture Positivity ◽  
Significant Difference ◽  
The Difference

Studies have shown an association between bacterial load and virulence; however, not much is known about the diversity in this phenotypic characteristic of Mycobacterium tuberculosis complex (MTBC). This study was therefore aimed to determine the differences in bacterial load of the three most prevalent MTBC genotypes (L4, L5, and L6) in West Africa at the time of diagnosis. A total of 170 paired fresh sputum samples were collected; one part in guanidinium thiocyanate (GTC) was used for RNA extraction and tuberculosis molecular bacterial load assay (TB-MBLA), and the other part without GTC was confirmed for TB positivity using GeneXpert MTB/RIF, smear microscopy grading, and culture on Löwenstein–Jensen media slants. The 170 sputum samples comprised 155 new cases, three follow-up cases, and 12 TB negative sputum samples. The time-to-culture positivity (TTP) and degree of culture positivity (DCP) were recorded. All 122 isolates obtained were spoligotyped for lineage (L) classification, but spoligotypes were obtained from 120 isolates. Of the typed isolates, 70.0, 10.8, 10.8, 4.2, 2.5, 0.8, and 0.8% were lineages 4, 5, 6, 2, 3, 1, and Mycobacterium bovis, respectively. Further analysis of the three most prevalent lineages showed significantly shorter TTP and higher DCP by L4 compared to L5 and L6, respectively: TTP 20.8, vs. 26.5, and 28.2 days; p-value = 0.005 and DCP 1.27, vs. 0.81 and 0.29, p < 0.001. The average TB-MBLA measured bacterial load of L4 was 3.82 Log10eCFU/ml which was not significantly different from 3.81 and 3.80 Log10eCFU/ml of L5 and L6, respectively, p = 0.84. Degrees of smear microscopy L4 = 1.20, L5 = 1.20, and L6 = 0.92 and GeneXpert Cq values L4 = 17.08, L5 = 18.37, and L6 = 17.59 showed no significant difference between the lineages, p = 0.72 and p = 0.48, respectively. Retrospective analysis of a larger sample confirmed the difference in TTP, p < 0.001. In conclusion, the observed shorter TTP and high DCP of L4 could signify high growth rate in culture that is independent of total bacterial load at diagnosis.

Grain growth behavior in Fe3Al alloys fabricated by different methods

1994 ◽  
Vol 9 (6) ◽  
pp. 1384-1391 ◽  
Author(s):  
B.H. Rabin ◽  
J.K. Wright ◽  
R.N. Wright ◽  
C.H. Sellers
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Hot Isostatic Pressing ◽  
Hot Extrusion ◽  
Growth Behavior ◽  
Elemental Powder ◽  
Ingot Metallurgy ◽  
Prealloyed Powder ◽  
The Difference ◽  
Grain Growth Behavior

Grain sizes were measured after various heat treatments in three Fe3Al alloys having similar composition that were fabricated using the techniques of ingot metallurgy (cast and wrought), hot extrusion of prealloyed powder, and hot isostatic pressing (HIP) of elemental powders. The ingot metallurgy (I/M) material exhibited normal grain growth behavior at temperatures above 750 °C, in agreement with previous observations. Both powder metallurgy (P/M) materials displayed unusual resistance to grain growth compared to the I/M alloy. In the case of the prealloyed P/M material, the initial (recrystallized) grain size was larger than the initial grain size of the I/M material, although little grain growth was observed for heat-treatment temperatures up to 1100 °C. At higher temperatures grain growth occurred at a rate comparable to that observed to the I/M alloy. The elemental powder P/M material exhibited similar grain growth behavior to the prealloyed P/M material, although the initial (as-HIPed) grain size was considerably smaller. Transmission electron microscopy (TEM) indicated that the grain growth resistance of the P/M materials could be attributed to grain boundary pinning by oxide particles presumed to originate from the powder particle surfaces. The difference in the stable grain size between the prealloyed and elemental powder P/M materials was attributed to the nature of the particle dispersions resulting from processing.

The Effect of Deformation and Reinforcement Particles on the Grain Growth Behavior of MoSi2

1993 ◽  
Vol 322 ◽  
Author(s):  
Ajoy Basu ◽  
Amit Ghosh
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
High Growth ◽  
Growth Behavior ◽  
Dislocation Creep ◽  
Grain Boundary Mobility ◽  
Agglomeration Effects ◽  
Static Annealing ◽  
Grain Growth Kinetics ◽  
Grain Growth Behavior

AbstractThe grain growth behavior of polycrystalline MoSi2 and composites containing SiC particulates has been studied in the temperature range of 1200-1800°C during static annealing as well as under concurrent deformation conditions. Monolithic MoSi2, with ∼ 26 μm grain size appears to be extremely resistant to grain growth up to 1500°C. However, the grain growth rate above this temperature is quite rapid. When particulate reinforcements are used to reduce the grain size of MoSi2 to 4.4 μm, a stable microstructure is maintained up to 1500°C. Accelerated grain growth kinetics are observed at 1800°C under conditions of large plastic strain. This enhanced grain boundary mobility is associated with particle sweeping and particle agglomeration effects. At lower temperatures, where dislocation creep is the more dominant deformation mechanism these effects are absent. In the presence of a Si concentration gradient extremely high growth rates of columnar MoSi2 grains have been observed during reaction synthesis of MoSi2.

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