High-temperature Phenomena Research Articles

Rutting performance of hydrated lime modified bituminous mixes

Hydrated lime has conventionally been used in bituminous mixes primarily for improving the moisture damage resistance of bituminous mixes. Most of the available literature is about studies conducted on mixes in which lime was added as filler. The present study explores the effect of different proportions of hydrated lime added by two different methods (wet and dry) on the rutting performance of bituminous mixes. The rutting characteristics of unmodified and lime modified binders were evaluated in terms of superpave binder rutting parameter (G∗/sinδ) and non-recoverable creep compliance (Jnr). Mix rutting performance was measured in terms of E∗, E∗/sinφ, flow number and accumulated strain measured in dynamic creep test. Rutting performance of mixes improved significantly by lime modification. Wet method of addition of lime has significantly higher beneficial effect than the dry method. Flow number determined at 60 °C demonstrated the beneficial effect of lime more distinctly compared with the dynamic creep test conducted at 40 °C. It was also observed in this study that the beneficial effect of lime addition in reducing rutting (which is a high temperature phenomenon) was realized more at higher mix temperatures.

Damage of an Ultrasonic-Waveguide Surface during Cavitation Accompanied by Sonoluminescence

The surface of a titanium (VT1-0) waveguide, which exhibits the sonoluminescence effect, is analyzed. The effect of sonoluminescence on the waveguide induces the formation of a series of cavities on its surface. Temperatures at the waveguide surface have been estimated, which makes it possible to assess the processes occurring upon sonoluminescence. If the effect observed is a high-temperature phenomenon, traces of metal melting are expected to be found on the waveguide surface. Analysis of the titanium waveguide shows that the observed surface destruction is due to mechanical impact and the absence of visible melting traces is likely to indicate that high temperatures are not reached.

On the origin of high-temperature phenomena in Pt/Al2O3.

Treatments of Pt/γ-Al2O3 with H2 under harsh conditions have long been known to strongly influence the properties of this important catalytic system, but the true causes of the high-temperature effects still remain unclear. We have performed a more detailed study of this issue, having used H2-TPD as a sensitive probe of metal-support interactions. The experimental results are in accordance with previous studies and demonstrate strong changes in adsorption and catalytic properties of Pt/γ-Al2O3 after high-temperature H2 treatments, as well as the possibility to reverse the changes, completely or in part, through O2 and H2O treatments. Thorough examination has shown that such behaviour is an intrinsic property of Pt/γ-Al2O3 and cannot be attributed to impurities or experimental artifacts. Moreover, there is no abrupt transition to a high-temperature state, but the system undergoes smooth and gradual changes upon increasing the H2-treatment temperature (TTR), with the changes being already apparent at a TTR of ∼ 300 °C. The results suggest that hydrogen can generate oxygen vacancies on the surface of the support in close vicinity to the Pt particles, and the system appears under equilibrium to be kinetically driven by temperature and thermodynamically driven by the PH2/PH2O ratio or local concentration of surface hydroxyls near Pt particles. The generated vacancies change the properties of contacting particles, and the changes are most pronounced for sub-nanometric Pt clusters and single atoms. Implications of the phenomena for the synthesis, study, and use of Pt/γ-Al2O3 and its related nanosystems are discussed.

A Free-Radical Pathway to Hydrogenated Phenanthrene in Molecular Clouds-Low Temperature Growth of Polycyclic Aromatic Hydrocarbons.

The hydrogen-abstraction/acetylene-addition mechanism has been fundamental to unravelling the synthesis of polycyclic aromatic hydrocarbons (PAHs) detected in combustion flames and carbonaceous meteorites like Orgueil and Murchison. However, the fundamental reaction pathways accounting for the synthesis of complex PAHs, such as the tricyclic anthracene and phenanthrene along with their dihydrogenated counterparts, remain elusive to date. By investigating the hitherto unknown chemistry of the 1-naphthyl radical with 1,3-butadiene, we reveal a facile barrierless synthesis of dihydrophenanthrene adaptable to low temperatures. These aryl-type radical additions to conjugated hydrocarbons via resonantly stabilized free-radical intermediates defy conventional wisdom that PAH growth is predominantly a high-temperature phenomenon and thus may represent an overlooked path to PAHs as complex as coronene and corannulene in cold regions of the interstellar medium like in the Taurus Molecular Cloud.

Phase-transition-like phenomenon of NH4H2PO4 observed using MAS NMR and static NMR near characteristic temperature

We used Fourier-transform nuclear magnetic resonance (NMR) spectroscopy to investigate the temperature dependences of the chemical shift and resonance frequency observed with magic-angle spinning NMR and static NMR, respectively, to confirm a high-temperature behavior of NH4H2PO4. The hydrogen bonds in both O–H–O between two PO4 groups and N–H–O between NH4 and PO4 were distinguished, and the changes occurring in the chemical shift and resonance frequency near the characteristic temperature TP are related to changes in the atomic positions. The experimental results of thermogravimetric analysis conducted to interpret the high-temperature phenomena without the critical change around TP are consistent with a phase-transition-like phenomenon at TP.

Multi-focused microlens array optimization and light field imaging study based on Monte Carlo method.

Plenoptic cameras are used for capturing flames in studies of high-temperature phenomena. However, simulations of plenoptic camera models can be used prior to the experiment improve experimental efficiency and reduce cost. In this work, microlens arrays, which are based on the established light field camera model, are optimized into a hexagonal structure with three types of microlenses. With this improved plenoptic camera model, light field imaging of static objects and flame are simulated using the calibrated parameters of the Raytrix camera (R29). The optimized models improve the image resolution, imaging screen utilization, and shooting range of depth of field.

Feasibility of Electrochemical Deposition of Nickel/Silicon Carbide Fibers Composites over Nickel Superalloys

Nickel superalloys are typical materials used for the hot parts of engines in aircraft and space vehicles. They are very important in this field as they offer high-temperature mechanical strength together with a good resistance to oxidation and corrosion. Due to high-temperature buckling phenomena, reinforcement of the nickel superalloy might be needed to increase stiffness. For this reason, it was thought to investigate the possibility of producing composite materials that might improve properties of the metal at high temperature. The composite material was produced by using electrochemical deposition method in which a composite with nickel matrix and long silicon carbide fibers was deposited over the nickel superalloy. The substrate was Inconel 718, and monofilament continuous silicon carbide fibers were chosen as reinforcement. Chemical compatibility was studied between Inconel 718 and the reinforcing fibers, with fibers both in an uncoated condition, and coated with carbon or carbon/titanium diboride. Both theoretical calculations and experiments were conducted, which suggested the use of a carbon coating over the fibers and a buffer layer of nickel to avoid unwanted reactions between the substrate and silicon carbide. Deposition was then performed, and this demonstrated the practical feasibility of the process. Yield strength was measured to detect the onset of interface debonding between the substrate and the composite layer.

폭염에 의한 지역별 인명피해 발생에 관한 연구

With the global temperature rises, South Korea frequently experiences heat wave, tropical nights and abnormal high temperature phenomena. Impacts of such heat wave, even if at the same intensity, can vary according to individuals' adaption to heat wave and regional climate characteristics. This study thus aims to examine the impacts on regional heat-wave frequency on heat-related disease deaths, and to propose heat-wave reduction measures for the minimization of heat wave damage. Various domestic and overseas heat-wave criteria and regional heat-wave criteria were examined. Based on the domestic heat wave criteria, guidelines for watch and warning over heat wave, the regional heat wave occurrence frequency was analyzed, and the correlation between the frequency, and heat-wave-affected deaths, and death rates was analyzed. Regional heat wave occurrence days and heat-wave-affected death rates were analyzed, revealing that regions with more occurrences of heat wave had a high heat-wave-affected death rate (about 76%), and that even regions with a low correlation between heat wave and death rate had a death rate of about 24%. In addition, heat wave reduction measures to minimize such heat wave damage were proposed, and a need to prepare differentiated heat wave countermeasures considering the aforementioned regional characteristics was indicated.

Observational connection between local high-temperature phenomena within magnetic clouds and the Sun

Magnetic clouds (MCs) frequently show abnormal high-ionization states of heavy ions. The abnormal high-charge distributions are related to the coronal temperature of their source regions. We examined the plasma and magnetic field data of 74 MCs observed by the Advanced Composition Explorer from February 1998 to December 2008. We determined that 14 of the 74 events showed local high-temperature phenomena. We analyzed the correlation between proton temperature and O7/O6 ratio (or high mean Fe charge state 〈Fe〉) within the local high-temperature regions in the 14 MCs. Results show that proton temperature and O7/O6 ratio (or high mean Fe charge state) had good correlations in nine MCs, but had no evident correlation in the other five MCs. The local high-temperature phenomena within the nine MCs have resulted from the Sun.

Parametric analysis of SLM using comprehensive optical monitoring

Purpose – This paper aims to propose methods for on-line monitoring and process quality assurance of Selective Laser Melting (SLM) technology as a competitive advantage to enhance its implementation into modern manufacturing industry. Design/methodology/approach – Monitoring of thermal emission from the laser impact zone was carried out by an originally developed pyrometer and a charge-coupled device (CCD) camera which were integrated with the optical system of the PHENIX PM-100 machine. Experiments are performed with variation of the basic process parameters such as powder layer thickness (0-120 μm), hatch distance (60-1,000 μm) and fabrication strategy (the so-called “one-zone” and “two-zone”). Findings – The pyrometer signal from the laser impact zone and the 2D temperature mapping from HAZ are rather sensible to variation of high-temperature phenomena during powder consolidation imposed by variation of the operational parameters. Research limitations/implications – Pyrometer measurements are in arbitrary units. This limitation is due to the difficulty to integrate diagnostic tools into the optical system of a commercial SLM machine. Practical implications – Enhancement of SLM process stability and efficiency through comprehensive optical diagnostics and on-line control. Originality/value – High-temperature phenomena in SLM were monitored coaxially with the laser beam for variation of several operational parameters.

高温干旱复合胁迫对构树幼苗抗氧化酶活性和活性氧代谢的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 高温干旱复合胁迫对构树幼苗抗氧化酶活性和活性氧代谢的影响 DOI: 10.5846/stxb201409201862 作者: 作者单位: 南京林业大学,南京林业大学 作者简介: 通讯作者: 中图分类号: 基金项目: 江苏省自然科学基金项目(BK2012819);江苏省高校自然科学研究重大项目(15KJA180003);江苏省生物学优势学科建设项目 Effects of combined elevated temperature and drought stress on anti-oxidative enzyme activities and reactive oxygen species metabolism of Broussonetia papyrifera seedlings Author: Affiliation: Jiangsu Key Laboratory of Forestry and Ecological Engineering,Nanjing Forestry University,Jiangsu Key Laboratory of Forestry and Ecological Engineering,Nanjing Forestry University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:近年来,全球气温不断升高,亚热带部分地区夏季高温和临时性干旱现象日益显著,高温与干旱严重威胁着植物的生存与生长。采用盆栽和人工气候室方式模拟不同的温度和土壤水分梯度,研究了高温与干旱复合胁迫对构树幼苗超氧化物歧化酶(SOD)、过氧化物酶(POD)与过氧化氢酶(CAT)活性、活性氧代谢和丙二醛(MDA)含量的影响。结果表明:(1)高温或干旱单一胁迫下,构树幼苗SOD、POD、CAT活性增加,复合胁迫下,SOD和POD酶活性高于单一胁迫,且随着复合胁迫时间延长而升高。SOD活性受温度和土壤水分双因素影响极其显著,复合胁迫对SOD活性有一定程度的叠加效应;(2)复合胁迫下,活性氧代谢物与MDA含量均显著高于单一胁迫,表明复合胁迫加剧对植物的伤害。通过改变抗氧化酶活性以减轻膜脂过氧化的伤害作用是有限的。 Abstract:In recent years, under the global climate change scenario, the occurrence of seasonal high temperature and temporal drought phenomena has increased in some subtropical regions. Consequently, the survival and growth of plants are restrained under the combined stress of elevated temperature and drought. In the present study, a pot experiment was performed at the Xiashu Forest Station of Nanjing Forestry University in 2013. One-year-old Broussonetia papyrifera seedlings were grown in 27-cm pots with brown loam soil, using a completely randomized design with four replicates. Seedlings were initially grown in the field environment and then transferred to a controlled greenhouse with three elevated-temperature and soil-moisture treatments, and the effects of combined elevated temperature and drought stress on anti-oxidative enzyme activities and reactive oxygen species(ROS) metabolism were measured in B.papyrifera seedling leaves. The results indicated that under either elevated temperature or drought stress, the superoxide dismutase(SOD), peroxidase(POD), and catalase(CAT) activities of seedlings increased with the increase of stress level. Under the combined elevated temperature and drought stress, the activities of SOD and POD were higher than those under single temperature or drought stress, and increased over stress exposure time. Significant variation was observed in SOD activity of the seedlings between combined stress treatments, revealing the synergistic effects of combined stress on SOD activities. Under the combined elevated temperature and drought stress, ROS, including O2- production rates and hydrogen peroxide(H2O2) and malondialdehyde(MDA) contents, were significantly higher than those under the single temperature or drought stress treatment, which suggests the limited role of antioxidant enzyme activities in alleviating the damage of the cell membrane of seedlings due to differences in ROS metabolite accumulation. 参考文献 相似文献 引证文献

Survey evaluation of thermal boundary condition in the inside and outside of double skin facade

Purpose: Double skin facade is a representative advantageous passive technology of building skin in the aspect of energy saving and environment improvement, reduces heat loss with buffer space in winter season and enhances indoor air and comfort of residents by activating natural ventilation in mid-season. However, in summer season, temperature increase in the intermediate space due to solar energy from exterior transparent skin could be a potential problem; also, relatively weak buoyancy of air caused by low density difference between double-skin facade could increase cooling load as air of intermediate space in high temperature hangs. However, proof data is insufficient to objectify such phenomenon. Method: In this study, researchers surveyed air temperature of intermediate space and airflow and diagnosed its cause targeting on applied multistory facade in the building which gives thermal uncomfort to residents. Also, the researchers produced Solar-air heat transfer coefficient meter, measured thermal boundary condition of double-skin facade, and presented the result of measurement as an objectified verification material regarding overheating phenomenon in the intermediate space of double-skin facade in summer season. Result: Inefficient condition was verified that total heat increases and overheating due to insufficient natural ventilation in multistory facade. In addition, logic behind preceding research was objectified and verified regarding high temperature phenomenon in the intermediate space which could increase cooling load in summer season.

High-temperature discrete dislocation plasticity

A framework for solving problems of dislocation-mediated plasticity coupled with point-defect diffusion is presented. The dislocations are modeled as line singularities embedded in a linear elastic medium while the point defects are represented by a concentration field as in continuum diffusion theory. Plastic flow arises due to the collective motion of a large number of dislocations. Both conservative (glide) and nonconservative (diffusion-mediated climb) motions are accounted for. Time scale separation is contingent upon the existence of quasi-equilibrium dislocation configurations. A variational principle is used to derive the coupled governing equations for point-defect diffusion and dislocation climb. Superposition is used to obtain the mechanical fields in terms of the infinite-medium discrete dislocation fields and an image field that enforces the boundary conditions while the point-defect concentration is obtained by solving the stress-dependent diffusion equations on the same finite-element grid. Core-level boundary conditions for the concentration field are avoided by invoking an approximate, yet robust kinetic law. Aspects of the formulation are general but its implementation in a simple plane strain model enables the modeling of high-temperature phenomena such as creep, recovery and relaxation in crystalline materials. With emphasis laid on lattice vacancies, the creep response of planar single crystals in simple tension emerges as a natural outcome in the simulations. A large number of boundary-value problem solutions are obtained which depict transitions from diffusional to power-law creep, in keeping with long-standing phenomenological theories of creep. In addition, some unique experimental aspects of creep in small scale specimens are also reproduced in the simulations.

Specifying the saturation temperature for the HyspIRI 4-μm channel

The investigation of high-temperature natural phenomena, such as wildland fires and active lava flows, is a primary science objective for the proposed Hyperspectral Infrared Imager (HyspIRI) mission. Current planning for HyspIRI includes a mid-infrared (MIR) channel centered at 4μm that will allow measurement of radiance emitted from high-temperature targets. In this paper we present the results of a study to specify the saturation temperature for the MIR channel. This study was based on reviews of the literature, together with case studies of airborne and satellite-based data acquired over high-temperature targets. The spatial resolution of MIR radiance measurements is an important consideration in the remote sensing of high-temperature phenomena, due to the presence of materials at different temperatures within the area covered by an image pixel. The HyspIRI MIR channel will provide a spatial resolution of 60m, which is ~40 times finer (in terms of area) than the finest spatial resolution provided by heritage instruments (370m). This fine spatial resolution will increase the probability that high-temperature targets fill an image pixel and, therefore, the HyspIRI MIR channel will require a saturation temperature 2 to 4 times higher than the saturation limits of heritage instruments. Based on our study, we recommend a saturation temperature of 1200K (927°C). This recommendation accounts for the high temperatures expected for natural phenomena, expected performance of the MIR channel, and overlap in sensitivity between the MIR and thermal infrared (7.5–12μm) HyspIRI channels.

VISIR-SAT – A PROSPECTIVE MICRO-SATELLITE BASED MULTI-SPECTRAL THERMAL MISSION FOR LAND APPLICATIONS

Abstract. Current space-borne thermal infrared satellite systems aimed at land surface remote sensing retain some significant deficiencies, in particular in terms of spatial resolution, spectral coverage, number of imaging bands and temperature-emissivity separation. The proposed VISible-to-thermal IR micro-SATellite (VISIR-SAT) mission addresses many of these limitations, providing multi-spectral imaging data with medium-to-high spatial resolution (80m GSD from 800 km altitude) in the thermal infrared (up to 6 TIR bands, between 8 and 11μm) and in the mid infrared (1 or 2 MIR bands, at 4μm). These MIR/TIR bands will be co-registered with simultaneously acquired high spatial resolution (less than 30 m GSP) visible and near infrared multi-spectral imaging data. To enhance the spatial resolution of the MIR/TIR multi-spectral imagery during daytime, data fusion methods will be applied, such as the Multi-sensor Multi-resolution Technique (MMT), already successfully tested over agricultural terrain. This image processing technique will make generation of Land Surface Temperature (LST) EO products with a spatial resolution of 30 x 30 m2 possible. For high temperature phenomena such as vegetation- and peat-fires, the Fire Disturbance Essential Climate Variables (ECV) “Active fire location” and “Fire Radiative Power” will be retrieved with less than 100 m spatial resolution. Together with the effective fire temperature and the spatial extent even for small fire events the innovative system characteristics of VISIR-SAT go beyond existing and planned IR missions. The comprehensive and physically high-accuracy products from VISIR-SAT (e.g. for fire monitoring) may synergistically complement the high temperature observations of Sentinel-3 SLSTR in a unique way. Additionally, VISIR-SAT offers a very agile sensor system, which will be able to conduct intelligent and flexible pointing of the sensor’s line-of-sight with the aim to provide global coverage of cloud free imagery every 5–10 days with only one satellite (using near real time cloud cover information). VISIRSAT may be flown in convoy with Sentinel-3 and/or Sentinel-2.

Some Physical Principles of High Temperature Shape Memory Alloys Design

Nowadays, martensitic transformation and shape memory effect, superelasticity, high damping capacity and other effects associated with this type of structural phase transitions are still in the focus of scientists and engineers, especially once these phenomena are taking place at elevated temperatures. The list of the materials undergoing this kind of transformation is constantly widening. Yet, industrial application of these materials, called high temperature shape memory alloys, is still hindered due to the lack of understanding of the peculiarities of the high temperature martensitic transformation and shape memory effect. Present work summarizes results of scientific studies of these high temperature phenomena oriented onto the development of physical principles suitable for industrial high temperature shape memory alloys design.

Massive stars: flare activity due to infalls of comet-like bodies

AbstractPassages of comet-like bodies through the atmosphere/chromosphere of massive stars at velocities more than 600 km/s will be accompanied, due to aerodynamic effects as crushing and flattening, by impulse generation of hot plasma within a relatively very thin layer near the stellar surface/photosphere as well as “blast” shock wave, i.e., impact-generated photospheric stellar/solar flares. Observational manifestations of such high-temperature phenomena will be eruption of the explosive layer's hot plasma, on materials of the star and “exploding” comet nuclei, into the circumstellar environment and variable anomalies in chemical abundances of metal atoms/ions like Fe, Si etc. Interferometric and spectroscopic observations/monitoring of young massive stars with dense protoplanetary discs are of interest for massive stars physics/evolution, including identification of mechanisms for massive stars variability.

Magnetic reconnection as a possible heating mechanism of the local high temperature protons within magnetic clouds

Magnetic clouds have the outstanding observational features of low proton temperature and plasma beta value, but numerous observations show that some magnetic clouds often have local high temperature phenomena. The local high temperature protons may be heated by magnetic reconnections within magnetic clouds. Here we take the magnetic cloud on 18–20 October 1995 as an example to discuss the possible heating mechanism. There is a famous protuberance in proton temperature between the front boundary and 11: 00 UT on 19 October 1995. Eight magnetic reconnection events were identified within the magnetic cloud, whose duration was less than 31 hours, and most of these reconnection events occurred within the proton temperature enhanced part of the magnetic cloud. Hence, it is possible for the local protons in the magnetic cloud to be heated by magnetic reconnections.

SHPB Test on Dynamical Mechanical Behavior of Concrete with High Temperature

An experimental system is designed by combining the split Hopkinson pressure bar (SHPB) with microwave heating device, based on numerical simulation and stress wave theory, availability of the experiment technique is analyzed. Tests of concrete whose temperature changes from room temperature to 650°C and impact velocity from 5m /s to 12m /s are completed and for the first time high-temperature dynamical damaging phenomena of concrete are obtained. Based on data analysis, the dynamical mechanical behavior of concrete with high temperature is affected by not only the strain rate effect whose influence keeps on decreasing with temperature increasing, but also the high temperature weakening effect. And the strain rate hardening effect is coupled with high temperature weakening effect, but the latter has greater influence.

Exploring high temperature phenomena related to post-detonation using an electric arc

We report a study of materials recovered from a uranium-containing plasma generated by an electric arc. The device used to generate the arc is capable of sustaining temperatures of an eV or higher for up to 100 μs. Samples took the form of a 4 μm-thick U238 film deposited onto 8 pairs of 17 μm-thick Cu electrodes supported on a 25 μm-thick Kapton backing and sandwiched between glass plates. Materials recovered from the glass plates and around the electrode tips after passage of an arc were characterized using scanning and transmission electron microscopy. Recovered materials included a variety of crystalline compounds (e.g., UO2, UC2, UCu5,) as well as mixtures of uranium and amorphous glass. Most of the materials collected on the glass plates took the form of spherules having a wide range of diameters from tens of nanometers to tens of micrometers. The composition and size of the spherules depended on location, indicating different chemical and physical environments. A theoretical analysis we have carried out suggests that the submicron spherules presumably formed by deposition during the arc discharge, while at the same time the glass plates were strongly heated due to absorption of plasma radiation mainly by islands of deposited metals (Cu, U). The surface temperature of the glass plates is expected to have risen to ∼2300 K thus producing a liquefied glass layer, likely diffusions of the deposited metals on the hot glass surface and into this layer were accompanied by chemical reactions that gave rise to the observed materials. These results, together with the compact scale and relatively low cost, suggest that the experimental technique provides a practical approach to investigate the complex physical and chemical processes that occur when actinide-containing material interacts with the environment at high temperature, for example, during fallout formation following a nuclear detonation.