Mineralogical and textural discrimination of loess derived from a tephra near Rotorua, New Zealand

Soil Research ◽  
1988 ◽  
Vol 26 (2) ◽  
pp. 301 ◽  
Author(s):  
LA Benny ◽  
NM Kennedy ◽  
JH Kirkman ◽  
RB Stewart
Keyword(s):  
Grain Size ◽  
New Zealand ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Field Observations ◽  
Mean Grain Size ◽  
Mean Size ◽  
The Mean ◽  
Grain Size Parameters

Grain size parameters and clay mineralogical analyses were used to characterize and compare Okareka Ash and post-Okareka tephric loess sampled at eight sites on a transect in Rotorua district, North Island, New Zealand. Grain size distribution analyses show consistently lower mean size and better sorting of the tephric loess compared with the Okareka Ash. The mean grain size of the loess is strongly influenced by the mean grain size of the tephra. Trends in the distribution of biotite and halloysite support the grain size distribution analyses. Taken with field observations, the analytical evidence allows differentiation between Okareka Ash and overlying associated tephric loess.

Ordering and Grain Growth Kinetics in CoPt Thin Films

1995 ◽  
Vol 398 ◽  
Author(s):  
R. A. Ristau ◽  
K. Barmak ◽  
D. W. Hess ◽  
K. R. Coffey ◽  
M. A. Parker ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Growth ◽  
Grain Size Distribution ◽  
Volume Fraction ◽  
Domain Size ◽  
Face Centered Cubic ◽  
Temperature Range ◽  
Mean Grain Size ◽  
The Mean

ABSTRACTOrdering and grain growth have been studied in a 10 nm thick CoPt alloy film of equiatomic composition annealed in the temperature range 550–700°C by quantifying ordered domain size, volume fraction ordered, grain size, and grain size distribution. Ordering occurs by nucleation and growth of Ll0 ordered domains, with a mean size of 3 nm at 550°C and 19 nm at 700°C. The volume percent ordered shows a dramatic increase from <y1% to approximately 28% between the two extremes of annealing temperature. The mean grain size of the as-deposited films is 5 nm and the entire film is face-centered cubic. Upon annealing in the temperature range 550–600°C, the mean grain size reaches a stagnation limit of 27 nm and the grain size distribution is log-normal. Grain growth resumes beyond 600°C and the mean grain size reaches as high as 55 nm at 700°C. The increase in the coercivity of the annealed films follows the increase in the ordered fraction more closely than the increase in grain size. The shape of the M-H loop shows evidence of coupling between the magnetically hard (ordered) and soft (disordered) regions.

Effect of Grain Size Distribution on Second Order Stresses in Plastically Deformed Polycrystals

2006 ◽  
Vol 524-525 ◽  
pp. 505-510
Author(s):  
Stephane Berbenni ◽  
Marcel Berveiller
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Yield Stress ◽  
Internal Structure ◽  
Grain Size Distribution ◽  
Second Order ◽  
Local Flow ◽  
Mean Grain Size ◽  
The Mean ◽  
Size Dispersion

The overall behaviour of metals composed of grains with different sizes is simulated as well as the evolution of their internal structure making use a self-consistent modelling for elasticviscoplastic materials. The Representative Volume Element is composed of isotropic spherical grains randomly distributed with a grain size distribution following a log-normal statistical function. Thus the heterogeneity of the RVE comes only from the grain size dependence of the local flow stress. The viscoplastic strain rate of the grains is modelled through a classic isotropic power law involving a reference stress depending on the individual grain size and the local plastic strain. Numerical results applied to IF steels firstly display that the overall yield stress depends not only on the mean grain size but also on the dispersion of the grain diameter distribution. The role of the grain size dispersion becomes significant when the mean grain size is on the order of "m, and, a decrease of the overall yield stress with an increase of the dispersion is observed. Secondly, prediction of the evolution of the internal structure indicates an increase of second order internal stresses with grain size dispersion. When this one is large enough and the mean grain size is on the order of "m, residual stresses due to heterogeneities arising from the grain size distribution are on the same order than the ones related to heterogeneities associated with plastic anisotropy found for polycrystalline IF steels.

scholarly journals Paleolimnology of Lake Yamanaka as reflected on particle-size distribution

1970 ◽  
Vol 14 ◽  
pp. 35-42 ◽  
Author(s):  
Danda Pani Adhikari
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Size Distribution ◽  
Central Japan ◽  
Size Frequency Distribution ◽  
Factors Affecting ◽  
Mean Grain Size ◽  
The Mean ◽  
Main Factors ◽  
Lake Size

A 17.63 m long bore-hole core extracted from the deepest part of Lake Yamanaka, one of the Fuji-five Lakes at the northeasternfoot of Mount Fuji, central Japan, composed of sediment with intercalations of scoria fallout deposits. The sediment of the upper11.4 m was investigated for grain-size distribution by using a laser diffraction particle size analyser. The mean grain-size profileshowed various degrees of fluctuations, both short-and long-terms, and the size-frequency distribution revealed unimodal-trimodalmixing of sediments. Changes in lake size and water depth appear to be the main factors affecting the variability in the grain-sizedistribution and properties. The lake level appears low during 7000–5000 cal BP and 2800–1150 cal BP and relatively high during5000–2800 cal BP and 1150 cal BP– present.DOI: http://dx.doi.org/10.3126/bdg.v14i0.5437Bulletin of the Department of Geology Vol.14 2011, pp.35-42 

scholarly journals Microstructural evolution in the fine-grained region of the Siple Dome (Antarctica) ice core

2011 ◽  
Vol 57 (206) ◽  
pp. 1046-1056 ◽  
Author(s):  
R.W. Obbard ◽  
K.E. Sieg ◽  
I. Baker ◽  
D. Meese ◽  
G.A. Catania
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Electron Backscatter Diffraction ◽  
Ice Core ◽  
Axis Orientation ◽  
Fine Grained ◽  
Depth Analysis ◽  
Siple Dome ◽  
Mean Grain Size

AbstractAn in-depth analysis of seven samples from the Siple Dome (Antarctica) ice core, using optical microscopy and electron backscatter diffraction, illustrates rotational recrystallization or polygonization in the fine-grained region of the core between 700 and 800 m. Between 640 and 700 m, the microstructure is characterized by a bimodal grain-size distribution and a broken girdle fabric with evidence of polygonization. From 727 to 770 m, mean grain size decreases and a single-maximum fabric is found, and, by 790 m, mean grain size has again increased and a multiple-maxima fabric manifests itself. We compare grain-size distribution, c- and a-axis orientation, and misorientation between adjacent grains. We found that misorientations between adjacent grains in the 727–770 m region were predominantly low-angle and typically around a common a-axis, suggesting polygonization. This conclusion is supported by radar evidence of a physical disturbance at 757 m, which may be correlated with higher than usual strain in the 700–800 m range. Below 770 m, larger less regular misorientations and textural evidence show that migration recrystallization is the primary recrystallization mechanism.

Aeolian Sand Size on the Surface of the Northern Foothill of Yinshan Mountain

2014 ◽  
Vol 668-669 ◽  
pp. 1499-1508
Author(s):  
Hong Tao Jiang ◽  
Chun Rong Guo ◽  
Chun Xing Hai ◽  
Jun Xiu Liu ◽  
Yun Hu Xie ◽  
...  
Keyword(s):  
Grain Size ◽  
Fine Sand ◽  
Aeolian Sand ◽  
Size Characteristic ◽  
Different Seasons ◽  
Mean Size ◽  
The Mean ◽  
Soil Flux ◽  
The Vertical Distribution ◽  
Grain Size Parameters

Sand samplers were laid out in the grassland in the northern foot of Yinshan Mountain for collecting soil flux samples from 0 to 1.5m height above the surface from Mar, 1, 2008 to Feb,29,2009.Grain size parameters proposed by Folk and Ward, including average, SD, skewness and kurtosis of grain size were used. The vertical distribution of grain size characteristic of sediments trapped by sand samplers in different seasons was analyzed by using electrical mirror technology. The results indicated that size of aeolian sand in desert steppe is mainly sand and silt. The content of coarse silt, very fine sand and medium sand are 20~60%,10~30% and 10~20%,respectively,in the sediment–for all seasons. As height increased, the content of sand decreased while silt increased and the mean size of particle changed from fine sand to very fine sand. The mean diameter of particle ranged from 2.4~4.2and standard deviation ranged from 0.7~1.5Skewness is positive with the value ranges from 0 to 0.2,while Kurtosis mainly concentrated on 0.7 to 1.3.

Effects of grain size distribution on Cole-Cole plots of polycrystalline spinels

2001 ◽  
Vol 699 ◽  
Author(s):  
M. P. Gutiérrez-Amador ◽  
R. Valenzuela
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Mean Free Path ◽  
Size Distributions ◽  
Frequency Range ◽  
Impedance Response ◽  
Grain Size Distributions ◽  
The Mean ◽  
Different Grain Size

AbstractSpinel ferrites of composition Ni0.5Zn0.5Fe2O4 were prepared by coprecipitation. Different grain size and grain size distributions were obtained by various heat treatments. Their electrical properties were investigated by impedance spectroscopy in the temperature range 25-200°C and in the frequency range of 5Hz-13MHz. A decrease in resistivity was observed as grain size increased, which can be explained by an increase in the mean free path of electrons. Cole-Cole plots showed two well-resolved semicircles for samples with a narrow grain size distribution. As the width of the distribution increased, the semicircles exhibited a deformation and eventually became unresolved. These results are interpreted on the basis of a distribution of time-constant of the impedance response, associated with the grain size distribution.

A new easy-to-use tool for grain size distribution analysis

2020 ◽  
Author(s):  
Yuming Liu ◽  
Xingxing Liu ◽  
Youbin Sun
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Quaternary Geology ◽  
Distribution Analysis ◽  
Lacustrine Deposits ◽  
Mean Grain Size ◽  
Different Types ◽  
Geological Information ◽  
End Members

&lt;p&gt;Grain size distribution (GSD) data have been widely used in Earth sciences, especially Quaternary Geology, due to its convenience and reliability. However, the usages of GSD are still oversimplified. The geological information contained in GSD is very abundant, but only some simplified proxies (e.g. mean grain size) are widely used. The most important reason is that GSD data are hard to interpret and visualize directly.&lt;/p&gt;&lt;p&gt;To overcome this, some researchers have developed the methods to unmix the mixed multi-modal GSD to some components to make the interpretation and visualization easier. These methods can be divided into two routes. One is end-member analysis (EMA) which takes a batch of samples for the calculation of the end-members. Another is called single-specimen unmixing (SSU) (Sun et al., 2002) which treats each sample as an individual. The key difference between the two routes is that whether the end-members of a batch of samples are consistent. EMA believes that the end-members between different samples are consistent, the variations of GSD are only caused by the changing of fractions of the end-members. On the contrary, SSU has no assumption on the end-members, i.e. it admits that the end-members may vary between different samples. Some mature tools (Paterson and Heslop, 2015; Dietze and Dietze, 2019) taking the EMA route have appeared, but there is no available public and easy-to-use tool for SSU.&lt;/p&gt;&lt;p&gt;Here we introduce a free and open-source GUI tool which is called QGrain, it can help researchers to analyze the GSD data easily and bring new insights for the interpretation of GSD. QGrain is based on SSU but applied some algorithms (e.g. data preprocessing and global optimization) to improve its precision and robustness. It supports Lognormal or Weibull as the base distribution and it is easy to add more base distributions. QGrain can handle different types of sediments (e.g. aeolian, fluvial and lacustrine deposits). QGrain can export all detailed data and generate the charts automatically.&lt;/p&gt;

scholarly journals Influence of Grain Size Distribution on Estimation of Mean Grain Size

1988 ◽  
Vol 52 (9) ◽  
pp. 835-842 ◽  
Author(s):  
Yoshimasa Takayama ◽  
Tatsumi Tozawa ◽  
Hajime Kato ◽  
Norio Furushiro ◽  
Shigenori Hori
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Mean Grain Size
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