The influence of the characteristics of polyethylene on thermoelectric properties of their composites with black carbon

The work is devoted to the study of the effect of characteristics (melt flow and density) of various grades of polyethylene on the electrical resistance of polyethylene composites with carbon black at normal and elevated temperatures. Such polyethylene composites are characterized by abnormally high values of the positive temperature coefficient of electrical resistance in the melting temperature range of the polyethylene matrix. This causes the effect of power self-regulation of such heaters (selfregulating polymer heaters). It has been established that the content of carbon black, which provides a stable and clear effect of self-regulation of such heaters, is located in a concentration region approaching the region of the second concentration-structural percolation transition, which for all investigated polyethylene composites was about 12 vol% of carbon black. The growth rate of electrical resistance at these carbon-black contents is influenced by crystallinity of the polyethylene matrix.

Сhanges of the Structure Indicators and the Salinity Field Average Value in the Sea of Azov

Purpose. The work is aimed at continuing the started in the previous papers investigations of structure of the Azov Sea salinity field based on the oceanographic survey data collected since 2000. Interest in studying this parameter is conditioned by its anomalous increase after 2006. Methods and Results. The data of 49 seasonal oceanographic surveys carried out in the Sea of Azov by the Azov-Black Sea Branch of "VNIRO" ("AzNIIRKH") from 2001 to 2016 permitted to calculate the following: the radii in the concentration region of the field spatial correlation function in the meridional and zonal directions for the surface and bottom layers (the characteristic of the field homogeneity); the ratio between these radii; the sea-average values of salinity field for the surface and bottom layers. The time graphical and the paired correlation analyses of the calculated indicators’ series were done. The average values of the meridional and zonal radii of the concentration region of the spatial correlation function (42.5 and 47.1 km) testify presence of two relatively isolated zones in the sea related to the water circulation. These zones are formed under the conditions of the eastern winds dominating in the region. The average values of the above-mentioned radii the near-bottom sea layer were approximately equal, whereas in the surface layer, the average zonal radii exceeded the meridional ones. In spring and summer, the meridional radius in the bottom layer surpassed the zonal one. Long-term variability shows that in the surface layer, the meridional radius values tend to increase, and in the bottom layer, the zonal radius ones – to decrease. These trends demonstrate a change in the nature of water exchange in the sea, namely from predominance of the zonal transport to that of the meridional one. Conclusions. Since 2006, the changes in the structure of the Azov Sea water salinity field (trends towards decrease of the zonal radii and increase of the meridional ones in the concentration region of the field spatial correlation function) resulted from decrease in the river water inflow and increase of water exchange with the Kerch Strait, and were accompanied by growth of average salinity. Water exchange with the Kerch Strait in the bottom layer was the most active in spring and summer. The anticipatory shift of the field structural characteristics by 1 and 2 years relative to its average values makes it possible to forecast them with a two-year advance time.

Сhanges of the Structure Indicators and the Salinity Field Average Value in the Sea of Azov

Purpose. The work is aimed at continuing the started in the previous papers investigations of structure of the Azov Sea salinity field based on the oceanographic survey data collected since 2000. Interest in studying this parameter is conditioned by its anomalous increase after 2006. Methods and Results. The data of 49 seasonal oceanographic surveys carried out in the Sea of Azov by the Azov-Black Sea Branch of "VNIRO" ("AzNIIRKH") from 2001 to 2016 permitted to calculate the following: the radii in the concentration region of the field spatial correlation function in the meridional and zonal directions for the surface and bottom layers (the characteristic of the field homogeneity); the ratio between these radii; the sea-average values of salinity field for the surface and bottom layers. The time graphical and the paired correlation analyses of the calculated indicators’ series were done. The average values of the meridional and zonal radii of the concentration region of the spatial correlation function (42.5 and 47.1 km) testify presence of two relatively isolated zones in the sea related to the water circulation. These zones are formed under the conditions of the eastern winds dominating in the region. The average values of the above-mentioned radii in the near-bottom sea layer were approximately equal, whereas in the surface layer, the average zonal radii exceeded the meridional ones. In spring and summer, the meridional radius in the bottom layer surpassed the zonal one. Long-term variability shows that in the surface layer, the meridional radius values tend to increase, and in the bottom layer, the zonal radius ones – to decrease. These trends demonstrate a change in the nature of water exchange in the sea, namely from predominance of the zonal transport to that of the meridional one. Conclusions. Since 2006, the changes in the structure of the Azov Sea water salinity field (trends towards decrease of the zonal radii and increase of the meridional ones in the concentration region of the field spatial correlation function) resulted from decrease in the river water inflow and increase of water exchange with the Kerch Strait, and were accompanied by growth of average salinity. Water exchange with the Kerch Strait in the bottom layer was the most active in spring and summer. The anticipatory shift of the field structural characteristics by 1 and 2 years relative to its average values makes it possible to forecast them with a two-year advance time.

SUBSOLIDUS STRUCTURE OF THE MgO – FeO – Al2O3 SYSTEM

Three-component systems constitute the physicochemical basis of most refractory materials and the analysis of their subsolidus structure makes it possible to accurately predict the areas of compositions with optimal properties, as well as give recommendations on the technological parameters of production, sintering, and operation of the materials obtained. As a result of the carried out thermodynamic analysis of the MgO – FeO – Al2O3 system, it was found that the partition of the system into elementary triangles undergoes changes in two temperature ranges: I – up to a temperature of 1141 K and II – above a temperature of 1141 K. By calculation methods, the geometrical-topological characteristics of the subsolidus structure of the system are determined MgO – FeO – Al2O3: areas of elementary triangles, degree of their asymmetry, area of regions in which phases exist, probability of phase existence in the system. It has been established that, over the entire temperature range, there is a fairly extended concentration region of spinel phases: hercynite (FeAl2O4) – noble spinel (MgAl2O4). Moreover, periclase (MgO) coexists simultaneously with both spinels only in the low-temperature region. This indicates that when obtaining periclase-spinel refractories with increased heat resistance, an important technological parameter is a cooling rate below 1141 K. To obtain periclase-spinel refractories with branched microcracking of the structure due to differences in the thermal expansion coefficients of periclase, hercynite and noble spinel, the most rational concentration region of the system under study is which is common for two elementary triangles (MgO – FeAl2O4 – MgAl2O4 and MgO – FeO – MgAl2O4) existing in different temperature ranges. At high firing temperatures, the elementary triangle MgO – FeO – MgAl2O4 has a maximum area and a minimum degree of asymmetry, and upon cooling, MgO – FeAl2O4 – MgAl2O4 is formed, which is quite large in area, but has a high degree of asymmetry. Therefore, the composition of the charge for periclase-spinel refractories should be predicted with a high dosage accuracy and with a significant homogenization time of the components during mixing, since the concentration region common for both of the above elementary triangles is significantly reduced. Thus, the division of the MgO – FeO – Al2O3 system into elementary triangles and the analysis of the geometrical-topological characteristics of the phases of the system made it possible to select in the system under study the range of compositions with optimal properties for obtaining spinel-containing materials.

Extraction efficiency of alcohols from activated carbon and silica gel sampling agents in the low concentration region

Activated carbon and silica gel adsorbents are commonly used as sampling agents in small glass tube products for work environment measurements of organic solvent vapor in air. In the measurements, extraction efficiency of organic solvent components from sampling agents is very important for accuracy of the determination. We have investigated the effect of two representative efficiency determination methods as established by the Industrial Safety and Health Act in Japan: the direct addition and phase equilibrium methods, using both of these adsorbent materials found in typical recent sampling tube products in Japan and four types of alcohol. The results indicate that the phase equilibrium method has a tendency to show slightly higher values compared with the direct addition method for each adsorbent. In addition, compared with silica gel, petroleum-based activated carbon can be a preferable sampling agent of alcohols in the extremely low concentration region, below approximately 10 ppm.

Effects of the Japanese 2016 Kumamoto Earthquake on Nitrate Content in Groundwater Supply

The 2016 Kumamoto earthquake had a significant impact on groundwater levels and quality. In some areas, the groundwater level increased significantly due to the release of groundwater from upstream mountainous regions. Conversely, the groundwater level in other areas greatly decreased due to the creation of new fracture networks by the earthquake. There were also significant changes in certain groundwater quality variables. In this study, we used clustering based SOM (self-organizing maps) analysis to improve the understanding of earthquake effects on groundwater quality. We were especially interested in effects on groundwater used for drinking purposes and in nitrate concentration. For this purpose, we studied groundwater nitrate (NO3− + NO2−–N) concentrations for the period 2012–2017. Nitrate concentration changes were classified into seven typical SOM clusters. The clusters were distributed in three representative geographical regions: a high concentration region (>4 mg/L), a low concentration region (<1.6 mg/L) with minimal anthropogenic loading area, and an intermediate concentration region (2–4 mg/L). Depending on these regions, the nitrate concentration changes just before and after the earthquake had both increasing and decreasing trends between 2015–2017. This points to complex physiographical relationships for release of stored upstream groundwater, promotion of infiltration of shallow soil water/groundwater, and nitrate concentration as affected by earthquakes. We present an analysis of these complex relationships and a discussion of causes of nitrate concentration changes due to earthquakes.

Description of Unsteady Flow Characteristics in a Side Channel Pump with a Convex Blade

To investigate the unsteady flow characteristics in side channel pumps, the vortex structures and their evolutions in the impeller and side channel flow passages have been comprehensively studied. Systematically, three impeller schemes were designed with different ratios of convex blade height h to impeller blade length l (h/l=0.2, 0.5, and 0.8) for detailed analysis. The findings indicated that the convex blade broadens the high-efficiency range and improves the efficiency at the best efficiency point for scheme h/l=0.2. Impeller scheme h/l=0.2 records the highest vortex concentration region, scheme h/l=0.5 displays as scattered spots, while scheme h/l=0.8 exhibits significant flow pattern changes in the impeller. The vortex distribution area and vortex intensity in the lengthways between the impeller and side channel of h/l=0.2 are almost analogous, but the other two impeller schemes have obvious separation and very chaotic. Although the shrinkages of axial vortexes in the impeller did not reflect on hydraulic performance, impeller schemes h/l=0.5 and 0.8 provided an outstanding performance in reducing the pressure fluctuations. The objective of this study is to provide a theoretical basis for optimal design and analysis of strong vortex flows in side channel pumps.