Transition from Grey to White and White to Grey in Fe-C-X Eutectic Alloys

1984 ◽  
Vol 34 ◽  
Author(s):  
P. Magnin ◽  
W. Kurz
Keyword(s):  
Growth Rate ◽  
Directional Solidification ◽  
Growth Rates ◽  
Opposite Effect ◽  
Eutectic Temperature ◽  
Alloying Elements ◽  
Qualitative Model ◽  
Eutectic Alloys ◽  
Temperature Growth

ABSTRACTThe effect of small additions of Si, P, Cr, Mn and Ti on transition velocities from grey to white and white to grey of pure Fe-C eutectics has been measured by varying growth rates in directional solidification experiments. Growth undercoolings were measured as a function of growth rate, while white and grey eutectic temperatures were obtained from DTA experiments. As a result of these experiments, alloying elements can be classified into three categories : graphitizing (Si, P), carburizing (Cr) and “opposite effect” (Mn, Ti). Each category is characterized by a given influence on eutectic temperature, growth undercooling, and nucleation of cementite. A qualitative model which permits determination of the influence of alloying elements on these latter three parameters is proposed.

scholarly journals Determination of In Situ Bacterial Growth Rates in Aquifers and Aquifer Sediments

2003 ◽  
Vol 69 (7) ◽  
pp. 3798-3808 ◽  
Author(s):  
Brian J. Mailloux ◽  
Mark E. Fuller
Keyword(s):  
Growth Rate ◽  
Fluorescence Intensity ◽  
Growth Rates ◽  
Direct Determination ◽  
Shallow Aquifer ◽  
Cell Counting ◽  
Field Scale ◽  
Doubling Times

ABSTRACT Laboratory and field-scale studies with stained cells were performed to monitor cell growth in groundwater systems. During cell division, the fluorescence intensity of the protein stain 5-(and 6-)-carboxyfluorescein diacetate succinimidyl ester (CFDA/SE) for each cell is halved, and the intensity can be tracked with a flow cytometer. Two strains of bacteria, Comamonas sp. strain DA001 and Acidovorax sp. strain OY-107, both isolated from a shallow aquifer, were utilized in this study. The change in the average generation or the average fluorescence intensity of the CFDA/SE-stained cells could be used to obtain estimates of doubling times. In microcosm experiments, the CFDA/SE-based doubling times were similar to the values calculated by total cell counting and were independent of cell concentration. Intact and repacked sediment core experiments with the same bacteria indicated that changes in groundwater chemistry were just as important as growth rates in determining planktonic cell concentrations. The growth rates within the sediment cores were similar to those calculated in microcosm experiments, and preferential transport of the daughter cells was not observed. The experiments indicated that the growth rates could be determined in systems with cell losses due to other phenomena, such as attachment to sediment or predation. Application of this growth rate estimation method to data from a field-scale bacterial transport experiment indicated that the doubling time was approximately 15 days, which is the first known direct determination of an in situ growth rate for bacteria in an aquifer.

scholarly journals Determination of the in situ growth rate of Microcystis based on carbon and nitrogen stable isotope fractionation

2017 ◽  
Vol 18 (3) ◽  
pp. 984-993 ◽  
Author(s):  
Shucong Zhen ◽  
Wei Zhu
Keyword(s):  
Growth Rate ◽  
Stable Isotope ◽  
Growth Rates ◽  
Isotope Fractionation ◽  
Taihu Lake ◽  
Nitrogen Stable Isotope ◽  
Average Growth ◽  
Carbon And Nitrogen ◽  
Stable Isotope Fractionation

Abstract Stable isotope fractionation of carbon and nitrogen in algal cells can be affected by photosynthesis, temperature, nutrient and CO2 concentrations, and cell size. As a consequence, carbon and nitrogen stable isotope techniques are not popular for determining algal growth rates. To counter these issues, this study used BG11 medium to cultivate Microcystis in the laboratory. First, the carbon and nitrogen stable isotope values of the culture medium and the algae are determined. Then, based on changes in isotope fractionation before and after cell division, a function μ = 1.32(1 + x)−0.52 relating growth rate and stable isotope fractionation is established. By substituting stable isotope values from Taihu Lake water and Microcystis into this function, the growth rate of the Microcystis in Taihu Lake is calculated to be 0.64 d−1 in May and 0.12 d−1 in September, with an average growth rate of 0.42 d−1. By incorporating most of the above-mentioned factors influencing isotope fractionation, this method can determine the growth rate of algae based directly on the stable isotope fractionation relationship, enabling simple and practical determination of algae growth rates.

Solidification Behavior of Technical Metastable Near-Eutectic Iron-Carbon Alloys (Experimental and Numerical Simulation)

1984 ◽  
Vol 34 ◽  
Author(s):  
G. Wolf ◽  
E. Flender ◽  
P. R. Sahm
Keyword(s):  
Numerical Simulation ◽  
Growth Rate ◽  
Cast Iron ◽  
Growth Rates ◽  
Structural Parameters ◽  
Unidirectional Solidification ◽  
Critical Parameters ◽  
Eutectic Alloys ◽  
Solidification Behavior ◽  
Metastable Transition

ABSTRACTBy way of unidirectional solidification, the critical parameters of the transition from a metastable to a stable eutectic in technical cast-iron alloys were investigated. A critical growth rate which was determined for near-eutectic alloys can be attributed to the stable-to-metastable transition. The structural parameters for the metastable eutectic were defined as a function of the growth rates.

Influence of growth parameters on the microstructure of directionally solidified Bi2Sr2CaCu2Oy

1990 ◽  
Vol 5 (9) ◽  
pp. 1834-1849 ◽  
Author(s):  
M. J. Cima ◽  
X. P. Jiang ◽  
H. M. Chow ◽  
J. S. Haggerty ◽  
M. C. Flemings ◽  
...  
Keyword(s):  
Growth Rate ◽  
Directional Solidification ◽  
Growth Rates ◽  
Growth Parameters ◽  
Directionally Solidified ◽  
Primary Solidification Phase ◽  
Float Zone ◽  
The Matrix ◽  
Laser Heated ◽  
Planar Growth

Laser-heated float zone growth was used to study the directional solidification behavior of Bi–Sr–Ca–Cu–O superconductors. The phases that solidify from the melt, their morphology, and their composition are altered by growth rate. Highly textured microstructures are achieved by directional solidification at all growth rates. The superconducting phase is found always to have the composition Bi2.5Sr2CaCu2.2Oy when grown from boules with composition 2:2:1:2 (BiO1.5:SrO:CaO:CuO). Planar growth fronts of Bi2.5Sr2CaCu2.2Oy are observed when the temperature gradient divided by the growth rate (G/R) is larger than 3 ⊠ 1011 K-s/m2 in 2.75 atm oxygen. Thus, the 2212 compound was observed to solidify directly from the melt at the slowest growth rates used in this study. Measurement of the steady-state liquid zone composition indicates that it becomes bismuth-rich as the growth rate decreases. Dendrites of the primary solidification phase, (Sr1−xCax)14Cu24Oy, form in a matrix of Bi2.5Sr2CaCu2.2Oy when G/R is somewhat less than 3 ⊠ 1011 K-s/m2. Observed microstructures are consistent with a peritectic relationship among Bi2.5Sr2CaCu2.2Oy, (Sr1−xCax)14Cu24Oy (x = 0.4), and a liquid rich in bismuth at elevated oxygen pressure. At lower values of G/R, Sr3Ca2Cu5Oy is the primary solidification phase and negligible Bi2.5Sr2CaCu2.2Oy forms in the matrix.

Approach to Assessment of Corrosion Growth in Pipelines

2002 ◽  
Author(s):  
Bill Gu ◽  
Richard Kania ◽  
Sandeep Sharma ◽  
Ming Gao
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Assessment Tool ◽  
Accurate Determination ◽  
Soil Drainage ◽  
Corrosion Condition ◽  
Preliminary Corrosion ◽  
Corrosion Defects ◽  
Growth Assessment

Two key components of corrosion growth assessment in pipelines are accurate determination of corrosion growth rate and application of corrosion growth to future integrity of a pipeline. PII has developed a corrosion growth assessment tool, Run Comparison (RunCom) software that allows accurate determination of corrosion growth. RunCom compares the raw signals of the same defect present in two inspection runs to report the real active corrosion defects and their growth with less error. Since variations in corrosion growth along the pipeline can be significant, a single value of average or maximum corrosion growth rate does not represent the corrosion condition of the pipeline and could result in a conservative or non-conservative conclusion for future integrity. PII introduces a Decision Tree Analysis method to categorize the corroded regions along the pipeline and calculate the mean corrosion growth rates in these specific areas. Relationships between corrosion growth rate and defect geometry are also identified. The influence of soil, drainage, and topography on corrosion rates is examined to determine representative corrosion growth rates along the pipeline. A systematic approach incorporating statistical analysis with mechanistic understanding of corrosion for preliminary corrosion assessment of pipeline systems is discussed.

A Relationship between the Crystalization Rate and the Structure and Strength Characteristics or the Fe-C-Cr, Fe-C-Cr-Ti and Fe-C-Cr-Ce Alloys Subjected to Directional Solidification

1984 ◽  
Vol 34 ◽  
Author(s):  
Edward Fras ◽  
Edward Guzik ◽  
Antoni Karamara
Keyword(s):  
Growth Rate ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Directional Solidification ◽  
Strength Characteristics ◽  
A Value ◽  
Coupled Growth

ABSTRACTThe paper present the results of investigation into the directional solidification of Fe-C-Cr alloys containing about 30% Cr and various contents of carbon. The main types of the structure of these alloys were given and the zone of a coupled growth of the eutectic was determined as well as an effect of the growth rate on the interfacial distance λ and on the tensile strengthof these alloys. It was proved that the additions of titanium and cerium considerably reduce the distance λ and increase the tensile strength, which in the case of an Fe-Cr-C-Ce alloy can reach a value of about 3250 MPa. The alloys solidified in the form of bars and plates which also enabled the determination of an effect of angle between the axis of the carbide fibres and the direction of loading on the ultimate tensile strength. of these alloys.

Radiocarbon dating of Chinese Ancient Tea Trees

Radiocarbon ◽  
2019 ◽  
Vol 61 (6) ◽  
pp. 1741-1748
Author(s):  
Jia Chen ◽  
Hongtao Shen ◽  
Kimikazu Sasa ◽  
Haihui Lan ◽  
Tetsuya Matsunaka ◽  
...  
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Radial Growth ◽  
Accurate Determination ◽  
Annual Rings ◽  
The World ◽  
Automated Sample Preparation ◽  
The University

ABSTRACTThe jungles of Linyun and Longlin Autonomous Prefecture, located in the heart of the southwestern Guangxi Zhuang Autonomous Region of China, are home to the oldest tea trees (Camellia sinensis) in the world. In the absence of regular annual rings, radiocarbon (14C) dating is one of the most powerful tools that can assist in the determination of the ages and growth rates of these plants. In this work, cores were extracted from large ancient tea trees in a central Longlin rain forest; extraction of carbon was performed with an automated sample preparation system. The 14C levels in the tree cores were measured using accelerator mass spectrometry (AMS) at the University of Tsukuba. These measurements indicated that contrary to conventional views, the ages of trees in these forests range up to ~700 years, and the growth rate of this species is notably slow, exhibiting a long-term radial growth rate of 0.039±0.006 cm/yr. It was demonstrated that 14C analyses provide accurate determination of ages and growth rates for subtropical wild tea trees.

scholarly journals Spreadsheet Iteration of Reversionary Leasehold Rental Growth Rate Within The Framework of Explicit DCF Appraisals

2020 ◽  
Vol 8 (1) ◽  
pp. 29-45
Author(s):  
Joseph Obaje Ataguba
Keyword(s):  
Growth Rate ◽  
Scenario Analysis ◽  
Growth Rates ◽  
Income Growth ◽  
Valuation Model ◽  
Analysis Tools ◽  
Tools And Techniques ◽  
Analytical Tools ◽  
Equivalent Yield

Income growth rates are required to justify decisions and strategies for property investments. Although existing studies addressed this phenomenon in freehold investments, a relative question regarding the determination of rental growth rates of leasehold investment properties valued part-way through rent review periods has not been addressed before now. This study examined the spreadsheet-assisted scenario analysis tools and techniques that are required for the determination of rental growth rates of leasehold investment properties valued part-way through rent review periods. A precursor to the scenario analysis was the development of a hybrid leasehold DCF valuation model arising from the equation of the formula for reversionary leasehold equivalent yield valuation to the formula for reversionary leasehold growth explicit DCF valuation model; thereby culminating into the identification of four unknown variables comprising the all risks yield and the implied growth rates of leasehold cash inflows and cash outflows which were subsequently derived using the solver tool of Excel®. From a total of eleven scenarios generated, the 9th successive scenario produced optimal results indicating zero slack between iterated and calculated values for the growth rates of leasehold cash inflows and cash outflows respectively. With recourse to the hybrid leasehold DCF valuation model, the spreadsheet-assisted scenario was found to produce mathematically valid growth rates that justify the valuation of leasehold investment properties part-way through rent review periods. The value of this research is the analytical tools and rigour it avails investors seeking income returns and growth from reversionary leasehold property as an instance of terminable investments.

Selection for biomass production based on respiration parameters in eucalypts: acclimation of growth and respiration to changing growth temperature

1996 ◽  
Vol 26 (9) ◽  
pp. 1569-1576 ◽  
Author(s):  
R.S. Criddle ◽  
T.S. Anekonda ◽  
R.M. Sachs ◽  
R.W. Breidenbach ◽  
L.D. Hansen
Keyword(s):  
Growth Rate ◽  
Biomass Production ◽  
Growth Temperature ◽  
Growth Rates ◽  
Heat Rate ◽  
Metabolic Rates ◽  
Different Temperatures ◽  
Controlled Environments ◽  
Respiration Parameters

This paper examines the relation between respiratory physiology and growth rate and the effects of environment on this relation for the purpose of developing means for accelerating and improving selection of trees for biomass production. The relations among biomass production, respiratory metabolism, and growth temperature in controlled environments were determined for three Eucalyptus genotypes (clones). Eucalyptuscamaldulensis 4016, E. camaldulensis C11, and Eucalyptusgundal (Eucalyptusgunnii × Eucalyptusdalrympleana hybrid) GD1 were selected for this study because of known qualitative differences in their field growth responses to temperature. These clones were grown in controlled environments at three temperatures. Measurements were made of growth rate, metabolic heat rate, and dark CO2 production rate for plants grown at each of the three temperatures. This allowed determination of respiration rates of plants originally adapted for growth in different climates, but acclimated during growth at three different controlled temperatures, and also determination of respiration changes resulting from short-term changes in temperature. Growth rates of the three clones differed in their patterns of response to changes in growth temperature. For example, C11 grew most rapidly at the highest temperature, while GD1 was slowest at high temperature. Metabolic rates and the temperature dependence of metabolic rates of the clones differed and the pattern of differences changed when plants became acclimated to growth at different temperatures. Changes in metabolic properties of the three clones with growth and measurement temperatures are consistent with the growth rate changes. In general, increased growth rate was accompanied by increased respiration rate measured either as heat rate or as rate of CO2 production. Growth rates were inversely related to two measures of metabolic energy use efficiency. Growth rates decreased as values of heat loss per gram dry weight produced and values of heat loss per mole of CO2 produced increased. Recognition of these relations between growth rate and respiration parameters at different temperatures in controlled environement may allow prediction of relative growth rate performance of Eucalyptus clones over a range of growth climates.

Sign in / Sign up

Export Citation Format

Share Document