The paper presents a method of fabrication and a comparison of the characteristics of obtained cemented carbide samples based on tungsten carbide with 10% metal binder. They were synthesized by spark ...plasma sintering (SPS) at different sintering temperatures: Co (1200 °C), Fe and Ni (1150 °C), Cr (1500 °C), and Ti (1400 °C). During the SPS-consolidation process, investigations of the dilatometric characteristics of samples of starting powders of identical granulometric composition obtained by mixing/grinding resulting in the fractional composition in the particle size range up to 10 μm are presented. The mechanism of phase formation and microstructure of the obtained materials is investigated by XRD, SEM, and EDS. The possibility of synthesizing hard alloys WC – 10%Ti and WC – 10% Cr by the mechanism of reaction SPS synthesis with a reduction in the synthesis time in comparison with traditional sintering methods has been demonstrated. Analyses have shown that during sintering of alloys containing Ti and Cr the volume content of WC decreases to 47% because of dissolution and interaction, while in alloys containing Co, Ni, and Fe, the volume content of WC remains unchanged (85–86%). This led to a dramatic change in hardness, fracture toughness, and strength when replacing Co, Ni, or Fe with Ti or Cr.
•WC-based hard alloys with binder phase high concentration content was SPS obtained.•Alloy's starting powders are obtained via WC mixing/milling with binders in one stage.•SPS-RS data of WC-10%Cr and WC-10%Ti are first presented.
ABSTRACT
The behaviour of the solar wind (SW) proton temperature and velocity and their relationship during Forbush decreases (FDs) associated with various types of solar source – coronal mass ...ejections (CMEs) and coronal holes (CHs) – have been studied. Analysis of cosmic ray variations, SW temperature, velocity, density, plasma beta, and magnetic field (from 1965–2019) is carried out using three databases: the OMNI database, Variations of Cosmic Rays database (IZMIRAN) and Forbush Effects & Interplanetary Disturbances database (IZMIRAN). Comparison of the observed SW temperature (T) and velocity (V) for the undisturbed SW allows us to derive a formula for the expected SW temperature (Texp, the temperature given by a T–V formula, if V is the observed SW speed). The results reveal a power-law T–V dependence with a steeper slope for low speeds (V < 425 km s−1, exponent = 3.29 ± 0.02) and flatter slope for high speeds (V > 425 km s−1, exponent = 2.25 ± 0.02). A study of changes in the T–V dependence over the last five solar cycles finds that this dependence varies with solar activity. The calculated temperature index KT = T/Texp can be used as an indicator of interplanetary and solar sources of FDs. It usually has abnormally large values in interaction regions of different-speed SW streams and abnormally low values inside magnetic clouds (MCs). The results obtained help us to identify the different kinds of interplanetary disturbance: interplanetary CMEs, sheaths, MCs, corotating interaction regions, high-speed streams from CHs, and mixed events.
In magnesium alloys castings, the casting defects such as shrinkage porosity often occur. Such defects can be suppressed by repair welding or surfacing using a special filler rod. Unfortunately, in ...Russia, a low amount of filler rod is consumed. Therefore, domestic enterprises do not manufacture it, limiting themselves to imports or homemade low-quality substitutes. Nevertheless, there is a need for filler rod, and recently it has become unprofitable to replace them with imported materials owing to a significantly increased price. Therefore, there is a need to study the technology of its production to replace imported filler rod with domestic material. Magnesium alloys based on the Mg–Zn–Zr (La, Nd) system SV1, SV122, and ZK51 (ML12) that used as a filler rod for repair welding of ZK51 alloy castings were studied in this work. The samples were obtained by permanent mold casting into aluminum molds followed by hot extrusion into a filler rod with a diameter of 4 mm. It was shown that all the investigated alloys could be obtained in the form of a rod with a diameter of 4 mm. Therefore, the investigated rod samples from the SV122 alloy were used as filler material for repair welding of ZK51 magnesium alloy castings. The weld seam in the T1 condition has an ultimate tensile strength (UTS) about 80% of the UTS of the casting material.
Room temperature lateral p
-i-n
light-emitting diodes (LEDs) with photonic crystals embedded in the i-region were fabricated on structures with Ge(Si) self-assembled islands and their optical ...properties were investigated. The use of preliminary amorphization and solid phase epitaxy of the implanted p
and n
contact regions made it possible to reduce the impurity activation temperature from 800 °С-1100 °С to 600 °С, which corresponds to the growth temperature of Ge(Si) islands. This resulted in a significant reduction of the detrimental effect of the high-temperature annealing used for diode formation on the intensity and spectral position of the luminescence signal from the islands. It was shown that significant enhancement (more than an order of magnitude) of room temperature electroluminescence of Ge(Si) islands in the spectral range of 1.3-1.55
m can be achieved due to their interaction with different modes of the photonic crystals. The measured radiation power of the obtained diodes in the spectral range of 1.3-1.55
m exceeds 50 pW at a pump current of 8 mA, which is an order of magnitude higher than the previously achieved values for micro-LEDs with Ge(Si) nanoislands. The obtained results open up new possibilities for the realization of silicon-based light emitting devices operating at telecommunication wavelengths.
Abstract
The optical reflection method is considered for detection of the forest areas where coniferous or broadleaved trees are dominant. Statistical modelling of correct detection and false alarm ...probabilities for identifying dominant (coniferous or broadleaved) tree species by the two-spectral reflection method has been conducted. It has been shown that monitoring enables us to identify dominant (coniferous or broadleaved) tree species with correct detection probability close to 1 and false alarms probability ~ second decimal places for the temperate climate zone at the wavelengths of 532 and 1540 nm or 532 and 1480 nm. As to the subtropical climate zone, due to a great variety of reflection spectra of vegetation, a selection of the spectral detection bands for reliable identification of dominant coniferous or broadleaved tree species is possible only for specific forestlands where the number of evergreen broadleaved and coniferous tree species is relatively small.
Magnesium alloys are used in aircraft because of their light weight. However, for these alloys to be applied in electronic devices, high thermal conductivities are required. Several high-potential ...compositions of Mg–Zn–Y–Zr alloys were selected by phase composition and their freezing ranges calculated using Thermo-Calc software. The alloys were prepared, and their fluidity, hot tearing susceptibility, mechanical properties, and thermal conductivity were obtained and compared. The alloy composed of Mg–4 wt% Zn–3 wt% Y–0.3 wt% Zr was selected for further investigation, because of its high thermal conductivity and satisfactory mechanical properties. The Mg–4 wt% Zn–3 wt% Y–0.3 wt% Zr alloy's fluidity and hot tearing susceptibility were similar to those of the widespread AZ91 commercial casting magnesium alloy. The influence of a heat treatment regime on the microstructure, thermal conductivity, and mechanical properties of the developed alloy was also investigated. It was established that the room temperature thermal conductivity of the Mg–4 wt% Zn–3 wt% Y–0.3 wt% Zr alloy after aging at 300 °C for 5 h was 105 W/mK. Additionally, the following tensile test results were obtained in aged condition: 120 MPa yield strength, 200 MPa ultimate tensile strength, and 4% elongation. The utilization of solid solution heat treatment at 520 °C for 8 h prior to aging can promote up to 9% increase in elongation. The Mg–4 wt% Zn–3 wt% Y–0.3 wt% Zr casting alloy can be used as a high thermal conductivity material with industrial applications.
•Innovative single-step SPS technique to fabricate close type IRS is suggested.•Non-dispersible Cs-containing cores for IRS were produced using cheap zeolite raw.•SPS regimes require low temperature ...and short time compared to conventional methods.•Obtained cores show exceptional characteristics meeting ISO standards.
The work presents a novel method for fabrication of the high-quality ionizing radiation source (IRS), which is promising to replace unsafe commercial products based on 137CsCl prohibited by IAEA. Spark plasma sintering (SPS) technique has been applied to produce dense ceramic and glass-ceramic matrixes from Cs-containing (˜13.5 wt.%) zeolite yielding in non-dispersible cores sealed in the container of radiation-resistant steel (J93503, US standard). One-stage SPS regimes to provide high-quality product have been optimized: sintering temperature <1000 °C, heating and holging duration 13 and 5 min, respectively, pressure 24.5 MPa. XRD, SEM, EDX, BET, XFS and solid-state MAS NMR 133Cs methods prove exceptional physico-chemical and mechanical characteristics of the obtained materials, namely: density 99.8% from theoretical, compressive strength ˜477 MPa, leaching rate 10−4–10−6 g cm−2 day−1. Results of the investigation can be promising for fabrication of the IRS cores on a large scale as done for similar Russian products RSL, IGI-C, M37C, GID-C.
We consider multilayered metal-dielectric metamaterials composed of alternating nanolayers of two types and calculate the components of their effective dielectric permittivity tensors as functions of ...both frequency and wave vector. We demonstrate that such structures can be described as strongly nonlocal uniaxial effective media, and we analyze how the nonlocal permittivity tensor components are related to other manifestations of strong spatial dispersion in such structures, and how the resonance of permittivity depends on the propagation direction.
This study identified helminthic species among wild boars (
) in Primorsky Krai, Russia. In total, 66 fecal samples were taken from wild boars and examined using the floatation-sedimentation method ...to identify helminths eggs and protozoan cysts. Age and sex were estimated for each host animal investigated. The helminthic fauna of the wild boars examined involved six parasite genera, but 4 are helminths and 2 are protozoans: the nematodes
.,
,
. and
; and the protozoan parasites
sp. and
The most prevalent parasite was
spp. (13.6 %) followed by
(7.6 %).
The other parasites found were
sp. (3 %),
(3 %),
sp. (1.5 %) and
(1.5 %).
Not found positive correlation between the host’s age and sex and the parasite prevalence. This was the first detailed study on helminths infections among wild boars in Primorsky Krai.
The Olympic and Paralympic Games in Tokyo in July–September 2021 took place in a challenging social environment that seriously affected the public perception of events. When preparing for the ...Olympics in 2013–2019, the Japanese people actively supported the Games, which was confirmed by the results of numerous sociological studies. In March 2020, the COVID-19 pandemic began, followed by several waves of infection. The competition was postponed for a year. Vaccination in Japan was delayed compared to most G7 countries. Against this background, in the summer of 2021, the most dangerous Delta strain of coronavirus began to spread in the country, bringing the rise in mortality rates, and the overflowing of hospitals in large cities. In such a difficult epidemiological and social situation, surveys recorded a negative attitude towards the Olympics. However, during the competition, the majority opinion once again turned positive, mainly due to the athletic successes of the Japanese team and effective anti-virus control measures. The absence of spectators in the venues, most probably, did not affect the sporting achievements significantly. At least, Japanese Olympic team won a record number of medals. Infection prevention measures proved effective in limiting the transmission of the virus among the athletes and the Japanese service personnel. The economic and symbolic achievements of the Games did not meet expectations, as, during the Olympics, it was not possible to properly address its significance as the end point of the low-growth “lost decades”, evidence of economic recovery after the triple disaster of 2011, and as a tool to increase Japan’s tourist attractiveness. Therefore, during a pandemic, major sports events should be held primarily to train top-class athletes and to increase populace satisfaction with the success of the national team rather than to obtain direct economic benefits or improve the host country’s image.
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