Brief communication: Increased glacier mass loss in the Russian High Arctic (2010–2017)

Glaciers in the Russian High Arctic have been subject to extensive atmospheric warming due to global climate change, yet their contribution to sea level rise has been relatively small over the past decades. Here we show surface elevation change measurements and geodetic mass balances of 93 % of all glacierized areas of Novaya Zemlya, Severnaya Zemlya, and Franz Josef Land using interferometric synthetic aperture radar measurements taken between 2010 and 2017. We calculate an overall mass loss rate of -22±6 Gt a−1, corresponding to a sea level rise contribution of 0.06±0.02 mm a−1. Compared to measurements prior to 2010, mass loss of glaciers on the Russian archipelagos has doubled in recent years.

Experimental Study on Freeze-Thaw Effects on Creep Characteristics of Rubber Concrete

Crumb Rubber Concrete (CRC) can exhibit high freeze-thaw resistance, but its long-term creep behavior under various freeze-thaw conditions remains unclear, which is essential for the safety of pavement engineering in the severe cold zone. In this study, the freeze-thaw effects on the creep behavior of CRC under different stress levels were systematically analyzed by testing the compressive strength, the uniaxial creep under different stress levels, and the dynamic elastic modulus. To simulate real conditions of the road environment in the cold area, the lowest temperature of −20°C, six freeze-thaw cycles of 0, 30, 60, 90, 120, and 150, and seven different stress levels of 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9 of the compressive strength were employed in this study. The test results showed that the mass loss rate was 6%–11.2% and the compressive strength decreased by 6.51%–47% after 30–150 freeze-thaw cycles. When the stress level reached its critical value, the relative dynamic elastic modulus decreased with the number of freeze-thaw cycles. After 150 freeze-thaw cycles, failure did not appear when the stress level was lower than 50%, above which the creep failure was determined by the stress level and the number of the freeze-thaw cycles. Meanwhile, it was found that the cracking and interfacial debonding between the matrix and the crumb rubber particle were the main reasons for the degradation of CRC creep performance. Finally, a Weibull distribution-based empirical creep damage model was established to predict the failure of CRC, which can enhance its application to related engineering.

Effect of Bentonite on the Structure and Performance of Sodium Alginate as Microsphere Carrier of Essential Oil

The effect of bentonite (BT) on the structure and performance of sodium alginate (SA) as microsphere carrier of essential oil is studied. The addition of BT can improve the performance of alginate gel microspheres through the study of the properties of single carrier SA and composite carrier SA/BT. The experimental results show that the viscosity of composite carrier SA/BT solution is higher than that of carrier SA solution, and the increasing rate of viscosity of composite solution with temperature is less than that of SA. The addition of BT can effectively inhibit the swelling of SA microspheres. The hydrogen bonding between SA and BT is shown in FTIR, and the interlayer spacing of BT crystal structure is not changed in XRD analysis. The mass loss rate of SA/BT microspheres is lower than that of SA in TGA analysis. The more dense structure of SA/BT microspheres than that of SA microspheres is confirmed by SEM. The release rate of cinnamon oil in SA/BT gel microspheres is significantly lower than that in SA gel microspheres under different temperature conditions. The addition of BT could better control the volatilization of essential oil encapsulated in SA gel microspheres.

Final Moments. I. Precursor Emission, Envelope Inflation, and Enhanced Mass Loss Preceding the Luminous Type II Supernova 2020tlf

We present panchromatic observations and modeling of supernova (SN) 2020tlf, the first normal Type II-P/L SN with confirmed precursor emission, as detected by the Young Supernova Experiment transient survey. Pre-SN activity was detected in riz-bands at −130 days and persisted at relatively constant flux until first light. Soon after discovery, “flash” spectroscopy of SN 2020tlf revealed narrow, symmetric emission lines that resulted from the photoionization of circumstellar material (CSM) shed in progenitor mass-loss episodes before explosion. Surprisingly, this novel display of pre-SN emission and associated mass loss occurred in a red supergiant (RSG) progenitor with zero-age main-sequence mass of only 10–12 M ⊙, as inferred from nebular spectra. Modeling of the light curve and multi-epoch spectra with the non-LTE radiative-transfer code CMFGEN and radiation-hydrodynamical code HERACLES suggests a dense CSM limited to r ≈ 1015 cm, and mass-loss rate of 10−2 M ⊙ yr−1. The luminous light-curve plateau and persistent blue excess indicates an extended progenitor, compatible with an RSG model with R ⋆ = 1100 R ⊙. Limits on the shock-powered X-ray and radio luminosity are consistent with model conclusions and suggest a CSM density of ρ < 2 × 10−16 g cm−3 for distances from the progenitor star of r ≈ 5 × 1015 cm, as well as a mass-loss rate of M ̇ < 1.3 × 10 − 5 M ☉ yr − 1 at larger distances. A promising power source for the observed precursor emission is the ejection of stellar material following energy disposition into the stellar envelope as a result of gravity waves emitted during either neon/oxygen burning or a nuclear flash from silicon combustion.

The Physical Parameters of Four WC-type Wolf–Rayet Stars in the Large Magellanic Cloud: Evidence of Evolution*

We present a spectral analysis of four Large Magellanic Cloud (LMC) WC-type Wolf–Rayet (WR) stars (BAT99-8, BAT99-9, BAT99-11, and BAT99-52) to shed light on two evolutionary questions surrounding massive stars. The first is: are WO-type WR stars more oxygen enriched than WC-type stars, indicating further chemical evolution, or are the strong high-excitation oxygen lines in WO-type stars an indication of higher temperatures. This study will act as a baseline for answering the question of where WO-type stars fall in WR evolution. Each star’s spectrum, extending from 1100 to 25000 Å, was modeled using cmfgen to determine the star’s physical properties such as luminosity, mass-loss rate, and chemical abundances. The oxygen abundance is a key evolutionary diagnostic, and with higher resolution data and an improved stellar atmosphere code, we found the oxygen abundance to be up to a factor of 5 lower than that of previous studies. The second evolutionary question revolves around the formation of WR stars: do they evolve by themselves or is a close companion star necessary for their formation? Using our derived physical parameters, we compared our results to the Geneva single-star evolutionary models and the Binary Population and Spectral Synthesis (BPASS) binary evolutionary models. We found that both the Geneva solar-metallicity models and BPASS LMC-metallicity models are in agreement with the four WC-type stars, while the Geneva LMC-metallicity models are not. Therefore, these four WC4 stars could have been formed either via binary or single-star evolution.

Evaluation of Concrete Durability Based on Cloud Model and D-S Evidence Theory

The environment in alpine region is complex and harsh, and the durability of concrete is seriously affected by freeze-thaw and salt invasion. In this paper, the relative dynamic modulus of elasticity, chloride permeability coefficient, mass loss rate and carbonation depth are selected as the evaluation indexes of concrete durability in Northeast China. Based on prior knowledge and expert group decision-making, the durability grade is divided and the evaluation standard is established; The evaluation model of concrete durability based on cloud model and D-S evidence theory is established. According to the engineering experimental data, the membership degree of concrete durability evaluation index in different grades is obtained through the correlation measurement of cloud model. The normalized evidence is formed and fused by D-S evidence theory. The results show that the durability grade of concrete is grade I, which is consistent with the actual project. It shows that using cloud model and evidence theory evaluation model to evaluate the durability of concrete is a new and effective method.

Influence of Waste Tire Particles on Freeze–Thaw Resistance and Impermeability Performance of Waste Tires/Sand-Based Autoclaved Aerated Concrete Composites

Waste tires/sand-based autoclaved aerated concrete (SAAC) composites were prepared by mixing waste tires, which have different particle sizes and content. The physical performance, mechanical properties, freeze–thaw resistance, impermeability performance, phase composition, and microstructure of waste tires/sand-based autoclaved aerated concrete composite materials were examined. The results demonstrated that the 750-μm-sized waste tire particles on the surface of the SAAC composite did not agglomerate. Moreover, these particles did not damage the pore structure of the composites. The SAAC composites, with a relatively high compressive strength and low mass-loss rate, were obtained when the contents of waste tire particles ranged from 1.0 to 2.5 wt.%. For composites prepared with 2.0 wt.% of 750-μm-sized waste tire particles, the optimal compressive and flexural strength values were 3.20 and 0.95 MPa, respectively. The increase in the rate of water absorption on SAAC composites was lowest (i.e., 16.3%) when the soaking time was from 24 to 120 h.

Numerical Study of Colliding Winds in Massive Stars

We run a numerical experiment ejecting stellar winds in a very massive binary system measuring the properties of the resulting colliding wind structure and accreted mass onto the companion under different conditions. Colliding massive binaries interact and create a colliding wind structure with a shape that depends on the momentum ratio, orbital motion, distance between the stars, and other factors. We run simulations of a static LBV-WR binary and in each simulation abruptly varying the mass loss rate of the LBV from the fiducial value. The modified wind front propagates and interacts with the previous colliding wind structure, and modifies its shape. We calculate the emitted X-ray from the interaction and investigate the proprieties of the new shape. We derive the mass accretion rate onto the secondary, and find that it depends on the momentum ratio of the winds. We then add orbital velocity that reduces the mass accretion rate, a similar behaviour as the analytical estimates based on modified Bondi–Hoyle–Lyttleton. Creating a large set of simulations like those presented here can allow constraining parameters for specific colliding wind binaries and derive their stellar parameters and orbital solution.

Study on Combustion Characteristics and Thermodynamic Parameters of Thermal Degradation of Guinea Grass (Megathyrsus maximus) in N2-Pyrolytic and Oxidative Atmospheres

This study provides an extensive investigation on the kinetics, combustion characteristics, and thermodynamic parameters of the thermal degradation of guinea grass (Megathyrsus maximus) in N2-pyrolytic and oxidative atmospheres. A model-fitting technique and three different iso-conversional techniques were used to investigate the kinetics of the thermal process, after which an analysis of the combustion characteristics and thermodynamic parameters was undertaken. Prior to this, experiments on the physico-chemical characterization, thermogravimetric, and spectroscopic analyses were carried out to provide insight into the compositional structure of the guinea grass. The volatile matter, fixed carbon, and total lignin contents by mass were 73.0%, 16.1%, and 21.5%, respectively, while the higher heating value was 15.46 MJ/kg. The cellulose crystallinity index, determined by XRD, was 0.43. The conversion of the GG in air proceeded at a relatively much higher rate as the maximum mass-loss rate peak in a 20 K/min read was −23.1 and −12.3%/min for the oxidative and the pyrolytic, respectively. The kinetics investigation revealed three distinctive stages of decomposition with their corresponding values of activation energy. The average values of activation energy (FWO) at the latter stages of decomposition in the pyrolytic processes (165 kJ/mol) were higher than those in the oxidative processes (125 kJ/mol)—an indication of the distinctive phenomenon at this stage of the reaction. The Coats–Redfern kinetic model revealed that chemical reactions and diffusional models played a predominant role in the thermal decomposition process of the GG. This study showed that the thermodynamic parameters varied with the conversion ratio, and the combustion performance increased with the heating rates. The use of GG as an energy feedstock is recommended based on the findings from this work.

INVESTIGATION THE FIRE HAZARD OF PLYWOODS USING A CONE CALORIMETER

A high-efficiency fire retardant composition was prepared with dicyandiamide, phosphoric acid, boric acid, borax, urea and magnesium sulfate and it was used to process veneers which were then to prepare the plywood. Meanwhile, heat release and smoke release from combustion of plywood were tested by a cone calorimeter, including heat release rate, mass loss rate, CO yield, CO2 yield and oxygen consumption. Results showed that the plywood with this fire retardant treatment had the better flame-retardant performance and smoke suppression effect as well as the stronger char-forming capability compared to plywood without fire retardant treatment. The average heat release rate, total heat release, average effective heat of combustion, total smoke release, CO yield and oxygen consumption of the plywood with fire retardant treatment were decreased by 63.72%, 91.94%, 53.70%, 76.81%, 84.99% and 91.86%, respectively. Moreover, the fire growth index of plywood treated by fire retardant was relatively low (3.454 kW·m-2·s-1) and it took longer time to reach the peak heat release rate, accompanied with slow fire spreading. The fire performance index was relatively high (0.136 s·m2·kW-1) and it took longer time to be ignited, thus leaving a long time for escaping at fire accidents. The fire hazard of plywood with fire retardant treatment was low, and its safety level was high.