Hot Layer Research Articles

A REVIEW ON CRACK RELIEF LAYER IN AIRPORT RUNWAY

This article reviews the behaviour and function of the crack relief layer (CRL) in a pavement. The significance and effectiveness of implementing CRL into pavement layers to prevent reflective cracking are also included. Over the years, crack in pavement has been a major problem that causes obstacle to transportation system which has cost multi-millions of dollars. This is especially true in airport runway business industry where the traffic flow of aircrafts cannot be easily diverted or disturbed as it involve many parties and would jeopardize public safety. The characteristic of the CRL will be thoroughly investigated to achieve it desirable functional capability to act as the crack relieving agent. CRL is a layer made out of hot mixed asphalt that to the strata of the pavement with thickness of 100 to 150mm on top of base layer and under surface course. The significant of this hot mixed asphalt layer is in its capability to reduce reflective cracks development by separating bound and unbound layer and acting as buffer zone between those layers. Thus the layer designed to be semi-unbound layer to efficiently in creating the buffer zone for the crack transfer from the bottom to the top of the pavement. The layer also acts as the reducer by allowing cracks to develop on the layer thus the crack generate on top of the pavement surface would decrease in the process.

Mechanical Properties of Al-Si Galvanic Coating and its Influence on Resistance Weldability of 22MnB5 Steel

Increase of quality and productivity in the same time are the most important in automotive industry. Use of high-strength steel 22MnB5 allows decrease of sheet metal thickness compared to standard steel. Commonly the steel 22MnB5 is welded with laser [1]. Use of this steel for spot resistance welding is not yet fully described. Steel 22MnB5 is coated with Al-Si galvanic coating for increasing high temperature oxidation resistance [2]. During hot stamping and subsequent heat treatment diffusion layer is created between coating and steel. The thickness of this layer is strongly dependent on temperature and time of heat process [3]. The paper deals with mechanical properties (chemical composition, indentation hardness) of this diffusion layer and Al-Si coating. Different thicknesses of diffusion layers were compared and its influence on weldability was described. Thin thicknesses have negligible effect on weldability, yet large thicknesses very negatively influence the weldability.

Asthenosphere and lithosphere structure controls on early onset oceanic crust production in the southern South Atlantic

The southern South Atlantic has often been considered a classic example of continental break-up in the presence of a starting mantle plume. Evidence for a mantle plume includes the Paranà-Etendeka continental flood basalts, which are associated with the Rio Grande Rise and Walvis Ridge, and the wide-spread presence of seaward dipping reflectors and high-velocity lower-crustal bodies along the conjugate margins. Observations from seaward dipping reflector distributions suggested that lithospheric segmentation played a major role in the pattern of volcanism during break-up in this region, and consequent numerical modelling was used to test this. We tested this hypothesis ourselves by measuring the thickness of the earliest oceanic crust generated. This was done through the use of 37 measurements of initial oceanic crustal thickness from wide-angle and multichannel seismic profiles collected along the conjugate margins. These measurements show that at 450kmsouth of the Paranà-Etendeka flood basalts the oceanic crust is thicker than the global average at 11.7km. Farther south the oceanic crust thins, reaching 6.1km at a distance of 2300km along-strike. Overall, the along-strike trend of oceanic crustal thickness is linear with a regression coefficient of 0.7 and little indication of segmentation. From numerical models representing extension of the lithosphere, we find that observed melt volumes are matched with the presence of a hot layer. If we assume this region of hot mantle has a thickness of 100km, its excess temperature relative to the asthenosphere has to decrease from 200 to 50°C, north to south. This decrease in temperature, also seen in published thermobarometry results, suggests that temperature was the primary control of volcanism during the opening of the southern South Atlantic.

Density profile of hot mix asphalt layer during compaction with various types of rollers and lift thickness

The effects of different compactors and lift thickness on hot mix asphalt (HMA) have been persistently discussed among asphalt experts. In many cases, pavements paved with the high-in-place air voids permit water to penetrate the permeable pavement causing an increased tendency for pavement deformation. The thin lifts have had problems achieving high density, which leads to high-in-place air voids. The present paper is aimed at evaluating the effects of different compactors, an 11-ton steel drum compactor and a 15-ton pneumatic tyre roller, on the HMA mat with different ratios of thickness to nominal maximum aggregate size (t/NMAS). In order to achieve this aim, seven field sections with a total 36 locations with distinct HMA mixes, thicknesses and rolling patterns were built. Each of the sections was approximately 40m long and 3.5m wide. The section was constructed with t/NMAS ratio varying from 2.0 at the beginning to 5.0 at the end of the section. The air temperature during construction varied from 26°C to 35°C. More so, for comparison purposes, the simulated HMA mat temperatures using MultiCool 3.0 software and their respective measured temperature were also taken. The results indicate that the optimum number of passes to achieve maximum density is four passes. This could be achieved by merely using the steel roller with vibratory mode. However, the introduction of rubber tyre roller during the intermediate rolling initially reduced the density by one to two percent but started to increase after several passes.

Near-infrared chemical imaging used for in-line analysis of inside adhesive layers in textile laminates

This paper demonstrates for the first time that near-infrared (NIR) chemical imaging can be used for in-line analysis of textile lamination processes. In particular, it was applied for the quantitative determination of the applied coating weight and for monitoring of the spatial distribution of hot melt adhesive layers using chemometric approaches for spectra evaluation. Layers with coating weights between about 25 and 130 g m−2 were used for the lamination of polyester fabrics and nonwovens as well as for polyurethane foam. It was shown that quantitative data with adequate precision can be actually obtained for layers applied to materials with significantly heterogeneous surface structure such as foam or for hidden layers inside fabric laminates. Even the coating weight and the homogeneity of adhesive layers in composites consisting of black textiles only could be quantitatively analyzed. The prediction errors (RMSEP) determined in an external validation of each calibration model were found to range from about 2 g m−2 to 6 g m−2 depending on the specific system under investigation. All calibration models were applied for chemical imaging in order to prove their performance for monitoring the thickness and the homogeneity of adhesive layers in the various textile systems. Moreover, they were used for the detection of irregularities and coating defects. Investigations were carried out with a large hyperspectral camera mounted above a conveyor. Therefore, this method allows large-area monitoring of the properties of laminar materials. Consequently, it is potentially suited for process and quality control during the lamination of fabrics, foams and other materials in field-scale.

The thermal criteria on rubber ignition in flashover fires under longitudinal ventilation surroundings

Flashover tests and theoretical analysis were conducted in a test chamber with two openings under longitudinal ventilation conditions with rubber as the target fuel. The radiant heat flux to the floor, the mass loss rate of fuels, the upper hot smoke layer temperature, the oxygen and smoke composition concentrations were measured to identify the thermal critical criteria of rubber ignition. The up-wind rubber sample was early ignited by the ∅500mm alcohol under 0.1m/s surroundings at the radiant heat flux to the floor 15.17kW/m2 and the average upper hot smoke layer temperature 519°C. The ∅500mm diesel of thick sootiness ignited the rubber earlier at a lower average upper hot smoke layer temperature 409°C and a higher radiant heat flux to the floor 16.2kW/m2. The rubber cannot be ignited by the ∅500mm alcohol or diesel at 0.5m/s smoke discharge velocity. It is concluded that the radiant heat flux to the floor is the predominant point to rubber ignition. The longitudinal smoke discharge can restrain the ignition of rubber in flashover by the dramatic reduction of the radiant heat flux to the floor based on the increased convection heat loss and the decreased smoke sootiness.

Evaluation of the Effect of Thermal Stratification on the Residual Life of the Surge Line of the Pressure Compensator in the No. 5 Unit of the Novovoronezh NPP

This article is concerned with investigations of temperature stratifi cation of the fi rst-loop coolant in the surge line of the pressure compensator in the No. 5 unit of the Novovoronezh NPP. The actual stress-strain state and accumulated structural damage in the surge line in different operating regimes was analyzed by means of multiparametric computational and experimental monitoring. The experimental data demonstrate thermal stratifi cation, giving rise to a temperature differential over the cross section ranging from 30°C under normal operating conditions to 150°C, as a result of disruption of the normal operating conditions, and high thermal stresses. The analysis shows that the cyclic strength of the weld connection of the surge line can be exhausted by the end of the 60-yr life of the No. 5 unit. It is concluded that the actual residual stresses must be measured and calculations of the cyclic strength and the residual life of the surge line must be performed. It is suggested that a technology be developed to strengthen the weld-joint metal in order to reduce the formation of operational surface defects. Since 1980, tens of operating defects and even through cracks formed in pipelines because of stratifi cation were discovered in NPP with PWR and VVER [1, 2]. Defects in the form of shallow surface cracks in transitional surfacing were found in the piping of the pressure compensation system of the No. 5 unit of the Novovoronezh NPP during operational monitoring of the weld connections. According to the recommendations of the International Insurance Inspectorate the infl uence of thermal stratifi cation on the damage rate for the surge line of the pressure compensator should be determined. The function of the pressure compensation system is to create and maintain the coolant pressure in the fi rst loop in order to prevent the coolant from boiling in stationary regimes and to limit the deviation in transitional and emergency regimes. The pressure compensator communicates with the coolant in the hot string of the fourth loop of the main circulation pipeline (MSP) via the 426 × 40 mm connecting surge line (Fig. 1). While the reactor is operating, the surge line is heated owing to the closed circulation of the coolant. When the average temperature of the fi rst-loop coolant changes in transitional regimes associated with the disruption of equipment operation and accompanying a change in the load, part of the coolant fl ows from the pressurizer into the loop or from the loop into the pressurizer along the surge line. In addition, a limitation on the deviation of the pressure from the nominal value is attained by compression or expansion of the steam blanket in the pressurizer. Thus, the integrity of the surge line is directly related with the reliability of fi rst-loop operation. In the course of operation the following loading factors act on the pipeline: mass of the structure, internal pressure, temperature change, and temperature stratifi cation in transient regimes. Thermal stratifi cation is associated with the separation of the coolant fl ow over the section of the pipeline into a cold layer at the bottom and hot layer at the top. The temperature gradients in the coolant result in beyond design-basis stresses in

Numerical analysis on the heat and work transfer due to shear in a hot cascade Ranque–Hilsch vortex tube

Cascading of vortex tubes is a possible implementation to extract significantly larger amount of useful work. A hot cascade-type RHVT makes use of the cold gas for cooling purposes while improving the heating capacity of the hot gas. In a vortex tube inflow pressure is the only source of energy which converts into thermal energy. The conversion of pressure energy into thermal energy is associated with the heat and work transfer due to shear along the radial, axial and tangential directions. In this paper, the physics of fluid flow and thermal separation are studied based on the heat and work transfer due to shear along all three directions. The work transfer due to the action of tangential shear is always from the cold to hot fluid layers and is the most dominant factor in the thermal separation process. The contribution increases considerably with hot cascading. However, the process of thermal separation degrades due to the effect of sensible heat transfer.

Fire risk analysis based on one-dimensional model in nuclear power plant

Fire probabilistic safety assessment (fire PSA) is developed to give the insight of nuclear power plant risk induced by fire accident and the main contributors, and fire accident scenario analysis is one of the important parts in the work to get the key factors such as time to target damage and time to detection. The thermal–hydraulic model simulating fire accident should have enough accuracy and high speed to satisfy the request of fire PSA. Many researches indicate that in a large volume the hot fluid will concentrate in the upper part while the cold fluid will be in the lower part because of density difference under fire condition, that is, the gradients of temperature and of some other parameters in vertical direction are much greater than in horizontal direction. Based on such thermal stratification theory a one-dimensional model is developed, and the buoyant jet is used to simulate the process of heated air flowing up. In this paper a fire in a compartment is analyzed based on one-dimensional model and the temperature distribution is obtained, the results are compared with those of commercial software such as FDT, CFAST and FDS, then the time to target damage is evaluated based on results of different models and the fire non-suppression probabilities are evaluated. The results illustrate that one-dimensional model has better accuracy than FDT and CFAST since such a model can simulate the thermal stratification and natural circulation which exist in the volume simultaneously. Moreover when the fire power is low, the thermal stratification is apparent and air temperature in the hot upper layer is much lower than the critical value of target damage, the one-dimensional model has enough accuracy to be used directly in fire PSA. While the thermal stratification will be weakened when the fire power increases because of the effects of radiation heat transfer and the entrainment by the jet, so more detailed model such as FDS is needed for such situations, however the results of one-dimensional model can give the advice for the proper simulation time of FDS to improve the calculation efficiency when the upper part temperature is close to or higher than the critical value.

Multi-dimensional structure of accreting young stars

This work is the first attempt to describe the multi-dimensional structure of accreting young stars based on fully compressible time implicit multi-dimensional hydrodynamics simulations. One major motivation is to analyse the validity of accretion treatment used in previous 1D stellar evolution studies. We analyse the effect of accretion on the structure of a realistic stellar model of the young Sun. Our work is inspired by the numerical work of Kley \& Lin (1996, ApJ, 461, 933) devoted to the structure of the boundary layer in accretion disks. We analyse the redistribution of accreted material with a range of values of specific entropy relative to the bulk specific entropy of the material in the accreting object's convective envelope. A primary goal is to understand whether and how accreted energy deposited onto a stellar surface is redistributed in the interior. This study focusses on the high accretion rates characteristic of FU Ori systems. We find that the highest entropy cases produce a distinctive behaviour in the mass redistribution, rms velocities, and enthalpy flux in the convective envelope. This change in behaviour is characterised by the formation of a hot layer on the surface of the accreting object, which tends to suppress convection in the envelope. We analyse the long-term effect of such a hot buffer zone on the structure and evolution of the accreting object with 1D stellar evolution calculations. We study the relevance of the assumption of redistribution of accreted energy into the stellar interior used in the literature. One conclusion is that, for a given amount of accreted energy transferred to the accreting object, a treatment assuming accretion energy redistribution throughout the stellar interior could significantly overestimate the effects on the stellar structure, in particular, on the resulting expansion.

He II λ4686 EMISSION FROM THE MASSIVE BINARY SYSTEM IN η CAR: CONSTRAINTS TO THE ORBITAL ELEMENTS AND THE NATURE OF THE PERIODIC MINIMA* † ‡ §

ABSTRACT Eta Carinae (η Car) is an extremely massive binary system in which rapid spectrum variations occur near periastron. Most notably, near periastron the He ii λ4686 line increases rapidly in strength, drops to a minimum value, then increases briefly before fading away. To understand this behavior, we conducted an intense spectroscopic monitoring of the He ii λ4686 emission line across the 2014.6 periastron passage using ground- and space-based telescopes. Comparison with previous data confirmed the overall repeatability of the line equivalent width (EW), radial velocities, and the timing of the minimum, though the strongest peak was systematically larger in 2014 than in 2009 by 26%. The EW variations, combined with other measurements, yield an orbital period of 2022.7 ± 0.3 days. The observed variability of the EW was reproduced by a model in which the line flux primarily arises at the apex of the wind–wind collision and scales inversely with the square of the stellar separation, if we account for the excess emission as the companion star plunges into the hot inner layers of the primary’s atmosphere, and including absorption from the disturbed primary wind between the source and the observer. This model constrains the orbital inclination to 135°–153°, and the longitude of periastron to 234°–252°. It also suggests that periastron passage occurred on T 0 = 2456874.4 ( ± 1.3 ?> days). Our model also reproduced EW variations from a polar view of the primary star as determined from the observed He ii λ 4686 ?> emission scattered off the Homunculus nebula.

Effect of Non-uniform Temperature Gradient on Marangoni Convection in a Relatively Hotter or Cooler Layer of Liquid

The effect of non-uniform temperature gradient on the onset of convection driven by surface tension gradients in a relatively hotter or cooler layer of liquid is studied by means of linear stability analysis. The upper boundary is considered to be free where surface tension gradients arise on account of variation in temperature and the lower boundary is stress free, each subject to constant heat flux. The single-term Galerkin technique is used to obtain the eigenvalue equation. Eigenvalues are obtained and presented. The results are compared with the existing ones and found that even a single-term Galerkin expansion gives quite accurate results. Further, this analysis predicts that the critical eigenvalues for different non-uniform temperature gradients are greater in a relatively hotter layer of liquid than the cooler one under identical conditions otherwise. This qualitative effect is quite significant quantitatively as well.

Water Absorption of Polyethylene Heat-Shrinkable Tape

In this paper the water absorption properties of polyethylene shrink tape were analyzed for long-distance pipeline. In the water absorption experiments, the normal and high temperature type heat shrinkable tape from six different manufacturers were respectively immersed in water range from 24 h to 28 d. The results show that the water absorption of the normal and high temperature type heat shrinkable tape was steady under the condition of 144 h. Once exceeding 144h, the water absorption increased gradually. Furthermore, the glue layer of heat shrinkable tape had a greater impact on water absorption. And the water absorption of glue layer of heat shrinkable tape decreased with an increase of the hot glue layer thickness,

Microstructure and properties of the hot work tool steel gradient surface layer obtained using laser alloying with tungsten carbide ceramic powder

Microstructure and properties of the hot work tool steel gradient surface layer obtained using laser alloying with tungsten carbide ceramic powder

FUV IRRADIATED DISK ATMOSPHERES: LYα AND THE ORIGIN OF HOT H2 EMISSION

ABSTRACT Protoplanetary disks are strongly irradiated by a stellar FUV spectrum that is dominated by Ly &agr; ?> photons. We investigate the impact of stellar Ly &agr; ?> irradiation on the terrestrial planet region of disks (≲1 AU) using an updated thermal-chemical model of a disk atmosphere irradiated by stellar FUV and X-rays. The radiative transfer of Ly &agr; ?> is implemented in a simple approach that includes scattering by H i and absorption by molecules and dust. Because of their non-radial propagation path, scattered Ly &agr; ?> photons deposit their energy deeper in the disk atmosphere than the radially propagating FUV continuum photons. We find that Ly &agr; ?> has a significant impact on the thermal structure of the atmosphere. Photochemical heating produced by scattered Ly &agr; ?> photons interacting with water vapor and OH leads to a layer of hot (1500–2500 K) molecular gas. The temperature in the layer is high enough to thermally excite the H 2 ?> to vibrational levels from which they can be fluoresced by Ly &agr; ?> to produce UV fluorescent H 2 ?> emission. The resulting atmospheric structure may help explain the origin of UV fluorescent H 2 ?> that is commonly observed from classical T Tauri stars.

Laying of all Asphalt Courses in One Step

Typical asphalt pavements consist of two or three asphalt layers which are installed successively. Construction and road closure times could be reduced, if those layers were built simultaneously. As part of the project “Construction Time Reduction by Optimized Asphalt Pavement” concepts were developed to enhance the compact asphalt pavement method in terms of installing thick asphalt layer packages by a single paver passage. For this purpose, a new base/binder course mix AC 45 B/T S was designed that can be installed in thicknesses of 20–22 cm and serve as a base for a simultaneously built, very thin surface course. Furthermore, paving and compaction equipment as well as roadwork processes were adjusted to the new method. First tests on proving grounds have shown paving results that were technically equivalent to conventional asphalt structures. Computational analyses have shown a lower fatigue sensitivity for the structures built by the new method. Paving test tracks on the German federal road B 68 and German motorway A 96 has proven that laying of all asphalt courses in one step is viable even under real site conditions and that it effects a significant reduction in construction time. Although reclaimed asphalt material was used for the base courses of both projects (up to the amount of 60M.-%), most technical requirements were achieved. Evenness turned out to be the only critical factor. Compaction loads on hot and thick layer packages evoke deformations, especially in the edge zones. The stability of the edges has to be improved by the development of new compaction modules.

Application of Nonlinear Dynamics in Studying Flashover Fire in a Small Open Kitchen

Open kitchen designs are found in small units in tall residential buildings of Asian-Oceania regions for better space utilization. As many combustibles are stored in small residential units, fire originated in the open kitchen can grow and spread fast. Consequently, flashover can occur to give a big fire and result in severe casualties and property damage. Nonlinear dynamics can be applied to predict critical heat release rate to flashover in the unit with an open kitchen and will be illustrated in this paper. Based on a two-zone model, temperature of the hot smoke layer was taken as the system state variable. An evolution equation was developed with selective control parameters. Onsetting of flashover using a nonlinear dynamical system was demonstrated in the example residential units. Effects of the floor dimensions, the radiation feedback coefficient and thermal properties of wall material on the onset of flashover were then examined and analyzed. The developed nonlinear dynamical model for studying the onset of flashover gives a better understanding of the various control parameters.

Modelling the spectral energy distribution of the red giant in RS Ophiuchi: evidence for irradiation

We present an analysis of optical and infrared spectra of the recurrent nova RS Oph obtained during between 2006 and 2009. The best fit to the optical spectrum for 2006 September 28 gives effective temperature Tef = 3900~K for log g = 2.0, while for log g = 0.0 we find Tef = 4700~K, and a comparison with template stellar spectra provides Tef $\sim$ 4500 K. The observed spectral energy distribution (SED), and the intensities of the emission lines, vary on short ($\sim 1$~day) time-scales, due to disc variability. We invoke a simple one-component model for the accretion disc, and a model with a hot boundary layer, with high ($\sim 3.9 \times 10^{-6}$ \Mdot) and low ($\sim 2 \times 10^{-8}$ \Mdot) accretion rates, respectively. Fits to the accretion disc-extracted infrared spectrum (2008 July 15) yield effective temperatures for the red giant of Tef = 3800 +/- 100~K (log g = 2.0) and Tef = 3700 +/- 100~K (log g = 0.0). Furthermore, using a more sophisticated approach, we reproduced the optical and infrared SEDs of the red giant in the RS Oph system with a two-component model atmosphere, in which 90\% of the surface has Tef = 3600 K and 10\% has Tef = 5000~K. Such structure could be due to irradiation of the red giant by the white dwarf.

Microstructure and mechanical properties of hot wire laser clad layers for repairing precipitation hardening martensitic stainless steel

Abstract Precipitation hardening martensitic stainless steel (PH-MSS) is widely used as load-bearing parts because of its excellent overall properties. It is economical and flexible to repair the failure parts instead of changing new ones. However, it is difficult to keep properties of repaired part as good as those of the substrate. With preheating wire by resistance heat, hot wire laser cladding owns both merits of low heat input and high deposition efficiency, thus is regarded as an advantaged repairing technology for damaged parts of high value. Multi-pass layers were cladded on the surface of FV520B by hot wire laser cladding. The microstructure and mechanical properties were compared and analyzed for the substrate and the clad layer. For the as-cladded layer, microstructure was found non-uniform and divided into quenched and tempered regions. Tensile strength was almost equivalent to that of the substrate, while ductility and impact toughness deteriorated much. With using laser scanning layer by layer during laser cladding, microstructure of the clad layers was tempered to fine martensite uniformly. The ductility and toughness of the clad layer were improved to be equivalent to those of the substrate, while the tensile strength was a little lower than that of the substrate. By adding TiC nanoparticles as well as laser scanning, the precipitation strengthening effect was improved and the structure was refined in the clad layer. The strength, ductility and toughness were all improved further. Finally, high quality clad layers were obtained with equivalent or even superior mechanical properties to the substrate, offering a valuable technique to repair PH-MSS.

The Structural Properties Assessment of Thin Hot Mixture Asphalt for Pavement Preservation

Thin Hot Mixture Asphalt Concrete Overlays (THMACO’s) are comprised of a thin layer less than one inch hot mix asphalt concrete layer and a binder material/tack coat. The uses of thin layer are necessary to compromise with the environment issue especially to protect the natural resources and save the energy used during asphalt construction. THMACO’s can be used as preventative maintenance on pavement preservation or as a new surface on a pavementconstruction. This layeris usually regarded as non-structural layer at pavement design. However, this paper presents the structural assessment of this materials and their comparison to the conventional asphalt concrete mixtures. This research was conducted based on indirect tensile strength (ITS), unconfined compressive strength (UCS) and indirect tensile stiffness modulus (ITSM) of thin hot mixture asphalt. The results show that the thin hot mixture asphalt has performed slightly different on the Marshall and structural properties compare to conventional asphalt concrete.