scholarly journals Characteristics of Lake Sediment from Southwestern Mongolia and Comparison with Meteorological Data

Geosciences ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 7
Author(s):  
Uyangaa Udaanjargal ◽  
Noriko Hasebe ◽  
Davaadorj Davaasuren ◽  
Keisuke Fukushi ◽  
Yukiya Tanaka ◽  
...  
Keyword(s):  
Grain Size ◽  
Organic Matter ◽  
High Temperature ◽  
Amorphous Silica ◽  
Meteorological Data ◽  
Principal Component ◽  
Short Time Scale ◽  
Mineral Particle ◽  
Grain Sizes ◽  
Silica Concentration

To understand how the climate system works in the continental interior, sediment cores that are approximately 30-cm long were taken from Olgoy, Boontsagaan, and Orog lakes, Mongolia. These cores were analyzed and compared with meteorological data (air temperature, precipitation, and wind) from climate stations in the study area. Comparison of metrological data from four stations shows similar climate fluctuations. When the temperature was high, less precipitation occurred in general. The sedimentary features measured in this study were water content, organic matter, carbonate, amorphous silica contents, whole and mineral grain size, and grain density. Excess 210Pb measurements were used to estimate sedimentary ages. According to principal component analysis (PCA), temperature correlates well to sediment characteristics in Olgoy Lake. Whole and mineral grain sizes are coarser when the temperature is high, while the amorphous-silica concentration is lower. A coarse grain size is interpreted to reflect low lake levels due to evaporation under high temperature with less precipitation. Amorphous silica may be from surrounding plants and reflects less vegetation when the temperature is high. However, in the recent 30 years, after the social system changed and overgrazing became a problem, the amount of amorphous silica has positively correlated with temperature on a short time scale. In the past 30 years, with less vegetation, amorphous silica has mainly come from weathered mineral particles. High temperature caused a thick, weathered mantle for each mineral particle, resulting in high amorphous-silica concentration. In Boontsagaan Lake, whole and mineral grain sizes are coarser when the wind speed is increased. Low precipitation correlates with a decrease in organic matter and an increase in carbonate and amorphous silica. In Orog Lake, it is difficult to establish an age model due to dried-up events. Some fluctuations in sedimentary characteristics may correspond to extreme events, such as earthquakes, and natural hazards, such as dzuds (harsh winters).

scholarly journals Mechanical and Electrical Characteristics of WB2 Synthesized at High Pressure and High Temperature

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1212 ◽  
Author(s):  
Changchun Wang ◽  
Lele Song ◽  
Yupeng Xie
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
Electrical Resistivity ◽  
High Temperature ◽  
Vickers Hardness ◽  
Single Phase ◽  
Hard Material ◽  
Experimental Conditions ◽  
Boundary Density ◽  
Grain Sizes

Single-phase tungsten diboride (WB2) was synthesized at high pressure and high temperature. The different grain sizes ranging from 300 nm to 3 µm were successfully obtained in WB2 by controlling the experimental conditions. The effects of grain size on hardness and resistivity properties were investigated. The Vickers hardness of WB2 was modulated with grain size. The maximum asymptotic Vickers hardness is 25.5 GPa for WB2 with a grain size of 300 nm which is a 10% increase compared to WB2 with a grain size of 3 µm. The optimal electrical resistivity of WB2 was 10−7 Ωm with the biggest grain size of 3 µm, which is ascribed to low grain boundary density. The superior properties of hardness and electrical resistivity demonstrate that WB2 should be a new functional hard material replacing WC which is widely used in industrial production.

scholarly journals Variability of macrofauna distribution along a dissipative log-spiral sandy beach in Rio de Janeiro, Southeastern Brazil

2017 ◽  
Vol 81 (1) ◽  
pp. 111 ◽  
Author(s):  
Carlos A.M. Barboza ◽  
Tatiana Cabrini ◽  
Gustavo Mattos ◽  
Viviane Skinner ◽  
Ricardo Cardoso
Keyword(s):  
Grain Size ◽  
Organic Matter ◽  
Community Structure ◽  
Organic Matter Content ◽  
Principal Component ◽  
Matter Content ◽  
Southeastern Brazil ◽  
Individual Species ◽  
Beach Slope ◽  
Sediment Sorting

Log-spiral beaches display defined physical gradients alongshore. However, the majority of studies focus on the variability of a single population of macrofauna species. We aimed to investigate the variation in species distribution and in community structure along ten transects on a log-spiral beach. Principal component analysis indicated a clear physical gradient alongshore. Redundancy analysis showed that the sheltered end was related to smaller particle sizes, higher organic matter content and high densities of polychaetes. The exposed end was characterized by coarser sand, lower organic matter content and a high presence of crustaceans. Model selection indicated that the “best fit” to explain the variability in the number of individuals included grain size and beach slope. Variability of the polychaete Scolelepis squamata was best explained by grain size, slope and sediment sorting. The best model for the cirolanid Excirolana armata only included sediment sorting. The physical gradient in sediment texture and the beach slope explained more than one-third of the variability in community structure. The physical variables were also correlated with the distribution of the individual species. We showed that the physical gradient on log-spiral coasts may be an important driver of macrofauna variability, even at mesoscales and in dissipative conditions.

In Situ Observation of Grain Growth and Recrystallization of Steel at High Temperature

2010 ◽  
Vol 638-642 ◽  
pp. 1077-1082 ◽  
Author(s):  
Yasuhiro Yogo ◽  
Kouji Tanaka ◽  
Koukichi Nakanishi
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Grain Growth ◽  
In Situ Observation ◽  
Initial Structure ◽  
Grain Sizes ◽  
Dynamic Observation ◽  
Average Grain Size ◽  
Observation Method

An in-situ observation method for structures at high temperature is developed. The new observation device can reveal grain boundaries at high temperature and enables dynamic observation of these boundaries. Grain growth while maintaining microstructure at high temperature is observed by the new observation device with only one specimen for the entire observation, and grain sizes are quantified. The quantifying process reveals two advantages particular to the use of the new observation device: (1) the ability to quantify grain sizes of specified sizes and (2) the results of average grain size for many grains have significantly less errors because the initial structure is the same for the entire observation and the quantifying process. The new observation device has the function to deform a specimen while observing structures at high temperature, so that enables it to observe dynamic recrystallization of steel. The possibility to observe recrystallization is also shown.

Study on Statistical Characteristics of Nonpoint Pollutants Deposited in Urban Areas

1993 ◽  
Vol 28 (3-5) ◽  
pp. 283-290 ◽  
Author(s):  
Kiyoshi Yamada ◽  
Tatsuya Umehara ◽  
Atsushi Ichiki
Keyword(s):  
Grain Size ◽  
Organic Matter ◽  
Urban Areas ◽  
Physical Property ◽  
Principal Component ◽  
Factor Loading ◽  
Principal Factor ◽  
Statistical Characteristics ◽  
Run Off ◽  
Kyoto City

The objective of this study is to clarify the statistical characteristics of pollutants deposited in urban areas, taking account of stages (road surfaces, street inlets and streams) and land uses where they accumulated, from surveys over a period of 16 years in Kyoto City. The result of correlation analysis showed that there are intimate relationship between grain size and such pollutants as organic matter and nutrients. It showed the dependence of pollutants on grain size. After principal component analysis, the distribution of principal factor loading showed that the first and the second components meant the type of pollution and the physical property of pollutants. The distribution of the principal factor score showed that each land use had different pollutant characteristics. On the other hand, the characteristics of the pollutants that accumulated on a road surface were shown to be affected by storms, and nutrients were more likely to run off in a storm than organic matter. The content rate of pollutants accumulated in a stream was shown to decrease in proportion to the progress of sewer construction, but it was also shown that the rate of some pollutants has not changed in the area of a separate sewer system. As a result, some valuable information for the control of nonpoint pollutants in urban area was obtained.

Engineered Nanocrystallites for Enhanced Performance of Ceramic Coatings by Ion Beam Assisted Deposition

1996 ◽  
Vol 438 ◽  
Author(s):  
F. Namavar ◽  
J. Haupt ◽  
E. Tobin ◽  
H. Karimy ◽  
J. Trogolo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
High Temperature ◽  
Low Temperatures ◽  
Ion Beam ◽  
Film Deposition ◽  
Tin Films ◽  
Grain Sizes ◽  
Ion Beam Assisted Deposition

AbstractTypical high-temperature thin-film deposition techniques are not suitable for certain substrates such as polymers and thermally-sensitive steels. In this work, ion beam assisted deposition (IBAD) was used to deposit ceramic and metallic films at temperatures below 150°C with nanocrystalline (< 100Å diameter) grain size. Nanoindentation studies of these films have shown hardnesses 50 to 100% greater than larger-grained films and, in some cases, fracture toughness approaching that of Si3N4.By combining chromium evaporation with nitrogen beam bombardment, hard, adherent CrN films without any porosity have been produced at low temperatures with a N/Cr arrival ratio of about 1. The grain size is typically smaller than 100Å and hardness is typically higher than 25 GPa. For a N/Cr arrival ratio slightly less than 1, we observed possible grain boundary porosity. However, even with porosity, hardness is typically 20 to 24 GPa for grain sizes smaller than 100Å. For a N/Cr arrival ratio of 1/4 we deposited elemental Cr with a grain size of 300 to 500Å and a hardness greater than that of silicon (12 GPa). Using Ar ions and a N backfill, we produced elemental Cr containing a mixture of coarse (120 to 150Å) and fine (25 to 30Å) grains. For high-temperature deposition of CrN, the grain size increases (200 to 600Å) with a noticeable decrease in hardness. Mechanical properties of CrN are greatly influenced by impurities, as well as by surface conditioning of the substrate.TiN films having gold color and grain sizes from 50 to 1000Å have been produced at low temperatures. Nanoindentation measurements of hardness and fracture toughness indicate that impurity-free TiN (with grains smaller than 100Å) has a hardness higher than 25 GPa and a fracture toughness close to that of Si3N4, but with higher wear resistance. Mechanical properties of our TiN films are greatly influenced by impurities, particularly oxygen, although it does not influence the gold color of TiN.

Polarization Mechanism of Fine-Grained BaTiO3 Ceramics at High Temperature Region

2013 ◽  
Vol 566 ◽  
pp. 12-15
Author(s):  
Takahiro Yamazaki ◽  
Takuya Hoshina ◽  
Hiroaki Takeda ◽  
Takaaki Tsurumi
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Barium Titanate ◽  
Boundary Effect ◽  
High Temperature Region ◽  
Fine Grained ◽  
Grain Sizes ◽  
Polarization Mechanism ◽  
Sintering Method ◽  
Grain Boundary Effect

Pure Barium titanate (BaTiO3) ceramics with grain sizes of 0.6, 1.5, and 18 μm on average were prepared by using a two-step sintering method. The wideband dielectric spectra in the range from kHz to THz were measured at 25 and 150 °C to understand the polarization mechanism of fine-grained BaTiO3ceramics. It was revealed that the dipole and ionic polarizations decreased with decreasing grain size at 25 and 150 °C when the grain size was smaller than 1 μm. These mechanisms were interpreted as a grain boundary effect.

HAYNES ALLOY No. 625SQ

Alloy Digest ◽  
2003 ◽  
Vol 52 (8) ◽  
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Fatigue Resistance ◽  
Heat Treating ◽  
Temperature Performance ◽  
Haynes Alloy

Abstract Haynes 625SQ alloy is a modification of Haynes 625 alloy (see Alloy Digest Ni-354, January 1988) with tighter controls on chemistry and a finer grain size for fatigue resistance up to 680 deg C (1250 deg F). This datasheet provides information on composition, physical properties, microstructure, elasticity, and tensile properties as well as fatigue. It also includes information on high temperature performance as well as heat treating. Filing Code: Ni-612. Producer or source: Haynes International Inc.

scholarly journals Impact of aquaculture on distribution of dissolved organic matter in coastal Jeju Island, Korea, based on absorption and fluorescence spectroscopy

2021 ◽  
Author(s):  
Jeonghyun Kim ◽  
Yeseul Kim ◽  
Sung Eun Park ◽  
Tae-Hoon Kim ◽  
Bong-Guk Kim ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Fluorescence Spectroscopy ◽  
Dissolved Organic Matter ◽  
Coastal Water ◽  
Coastal Region ◽  
Principal Component ◽  
Distribution Patterns ◽  
Organic Pollution ◽  
Jeju Island

AbstractIn Jeju Island, multiple land-based aquafarms were fully operational along most coastal region. However, the effect of effluent on distribution and behaviours of dissolved organic matter (DOM) in the coastal water are still unknown. To decipher characteristics of organic pollution, we compared physicochemical parameters with spectral optical properties near the coastal aquafarms in Jeju Island. Absorption spectra were measured to calculate the absorption coefficient, spectral slope coefficient, and specific UV absorbance. Fluorescent DOM was analysed using fluorescence spectroscopy coupled with parallel factor analysis. Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were measured using high-temperature catalytic oxidation. The DOC concentration near the discharge outlet was twice higher than that in natural groundwater, and the TDN concentration exponentially increased close to the outlet. These distribution patterns indicate that aquafarms are a significant source of DOM. Herein, principal component analysis was applied to categorise the DOM origins. There were two distinct groups, namely, aquaculture activity for TDN with humic-like and high molecular weights DOM (PC1: 48.1%) and natural biological activity in the coastal water for DOC enrichment and protein-like DOM (PC2: 18.8%). We conclude that the aquafarms significantly discharge organic nitrogen pollutants and provoke in situ production of organic carbon. Furthermore, these findings indicate the potential of optical techniques for the efficient monitoring of anthropogenic organic pollutants from aquafarms worldwide.

scholarly journals The modification effect of temperature on the relationship between air pollutants and daily incidence of influenza in Ningbo, China

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Rui Zhang ◽  
Yujie Meng ◽  
Hejia Song ◽  
Ran Niu ◽  
Yu Wang ◽  
...  
Keyword(s):  
Air Pollution ◽  
High Temperature ◽  
Air Pollutants ◽  
Meteorological Data ◽  
Effect Of Temperature ◽  
Distributed Lag ◽  
Modification Effect ◽  
Incidence Risk ◽  
The Impact ◽  
The Relationship

Abstract Background Although exposure to air pollution has been linked to many health issues, few studies have quantified the modification effect of temperature on the relationship between air pollutants and daily incidence of influenza in Ningbo, China. Methods The data of daily incidence of influenza and the relevant meteorological data and air pollution data in Ningbo from 2014 to 2017 were retrieved. Low, medium and high temperature layers were stratified by the daily mean temperature with 25th and 75th percentiles. The potential modification effect of temperature on the relationship between air pollutants and daily incidence of influenza in Ningbo was investigated through analyzing the effects of air pollutants stratified by temperature stratum using distributed lag non-linear model (DLNM). Stratified analysis by sex and age were also conducted. Results Overall, a 10 μg/m3 increment of O3, PM2.5, PM10 and NO2 could increase the incidence risk of influenza with the cumulative relative risk of 1.028 (95% CI 1.007, 1.050), 1.061 (95% CI 1.004, 1.122), 1.043 (95% CI 1.003, 1.085), and 1.118 (95% CI 1.028, 1.216), respectively. Male and aged 7–17 years were more sensitive to air pollutants. Through the temperature stratification analysis, we found that temperature could modify the impacts of air pollution on daily incidence of influenza with high temperature exacerbating the impact of air pollutants. At high temperature layer, male and the groups aged 0–6 years and 18–64 years were more sensitive to air pollution. Conclusion Temperature modified the relationship between air pollution and daily incidence of influenza and high temperature would exacerbate the effects of air pollutants in Ningbo.

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