Preheat Time Research Articles

On the unchanging shape of thermoluminescence peaks in preheated feldspars: Implications for temperature sensing and thermochronometry

Significant advances have been made during the past 10 years in our understanding of the nature of thermoluminescence (TL) signals from feldspars. Modeling insights into the luminescence mechanism have been obtained based on quantum tunneling, and this has led to the development of new analytical equations for quantifying the luminescence signals. In addition, Monte Carlo studies have helped researchers understand the effect of random distributions of charges and of energy distributions on the TL signals. From an experimental point of view, there has been renewed interest in using these signals for particle temperature sensing in the microseconds-to-seconds time scale, and in thermochronometry applications involving a much larger geological time scale (103–105 yr). One of the fundamental issues in these field applications is the difficulty of calibrating the TL signals from feldspars as a function of the preheating temperature and of the preheating time.This paper presents new analytical expressions describing the changes in the TL glow curves in feldspar samples, when they are heated at different temperatures and for different preheat times. The behavior of the TL glow curves is described and some universal characteristics of TL glow curves are pointed out, which can be useful in analyzing regenerative TL signals. Good agreement is found between the analytical equations and experimental data for several geological feldspar samples. The insights obtained from the new equations and the model can help in understanding how feldspar TL signals record recent or geologic thermal signatures in temperature sensing and thermochronometry applications.

Thermoluminescence glow curves in preheated feldspar: A Monte Carlo study

Thermoluminescence (TL) glow curves from feldspars have been the subject of numerous experimental and modeling studies, because of their importance in dosimetry and luminescence dating. Recently there also has been increased interest in using these signals for temperature sensing and for thermochronometry studies. It is now generally accepted that these materials exhibit anomalous fading phenomena due to quantum mechanical tunneling, and that several of their luminescence signals can be described by localized energy transitions taking place in a randomly distributed system of trapped electrons and recombination centers. Our recent modeling work showed that the TL signals of freshly irradiated feldspar samples can also be described from a completely microscopic point of view, by using Monte Carlo methods. This paper extends this recent work, and shows how the Monte Carlo method can also describe TL signals from thermally pretreated feldspars. Specifically, the simulations show that the Monte Carlo method can describe several types of TL experiments for irradiated samples that underwent partial thermal cleaning, and for samples that underwent more complex multistage isothermal procedures. The results from the Monte Carlo simulations are compared quantitatively with experimental data from several types of feldspars, which were preheated at temperatures above 200–300 °C. Common experimental characteristics are pointed out for these preheated feldspars, and the experimental data suggest the possibility of a universal description of the thermal behavior of TL glow curves in feldspars. Specifically, it is found that the shape and width of the experimental TL glow curves do not change significantly for different preheat temperatures, and also do not change when different preheat times are used at a fixed preheat temperature. The relevance of these results for dosimetric and thermochronometry studies is discussed.

An innovative asphalt patch repair pre–heating method using dynamic heating

In hot mix asphalt patch repair, inadequate temperature at the interfaces is one of the influencing factors for inferior compaction and poor interface bonding. To enhance repair performance, a precisely controlled infrared pre-heating method for patch repair has been investigated. Asphalt slabs with 45 mm, 75 mm and 100 mm deep pothole excavations were subjected to dynamic heating with infrared heater operating power from 6.6 kW to 7.7 kW. The heater was kept either stationary or moving slowly across the excavations at 130 mm and 230 mm offsets. The tests included evaluating temperature increase throughout the excavations and inside the slab, recording heat power of infrared heater and heating time to avoid burning the asphalt. Irrespective of excavation depth, heating power and offset, the temperature distribution was found non-uniform in the pothole excavations and into the asphalt slab. The temperatures were higher at the faces of the excavation than inside the slab. Dynamic heating for approximately 10 min yielded better heat distribution while minimising the possibility of asphalt overheating and long pre-heating time. It has been concluded that 45 mm and 100 mm deep pothole excavations can be pre-heated with 6.6 kW and stationary heater or 7.5 kW and moving heater at 230 mm and 130 mm offset respectively. 75 mm deep excavation can be pre-heated with 7.1 kW and stationary heater at 230 mm offset.

Properties of Fired Bricks Incorporating TFT-LCD Waste Glass Powder with Reservoir Sediments

In view of increasing concerns over nonrenewable resource depletion and waste management, this study aimed to apply the Taguchi optimization technique to determine the process conditions for producing bricks by incorporating thin-film transition liquid crystal display (TFT-LCD) waste glass powder with reservoir sediments. An orthogonal array L16(45) was adopted, which consisted of five controllable four-level factors (i.e., cullet content, drying method, preheat time, sintering temperature, and error). Moreover, the analysis of variance method was used to explore the effects of the experimental factors on the density, water absorption, shrinkage ratio, loss on ignition, porosity, and compressive strength of the fired bricks. The microstructures of the fired specimens were investigated by scanning electron microscopy. Then, large-scale production techniques for fired bricks containing recycled TFT-LCD glass cullet and reservoir sediments were developed in a commercially available tunnel kiln. The test results showed that the structure of the fired specimen was loose at a sintering temperature ranging from 900 to 950 °C. However, the fired specimen showed a significant densification at the sintering temperature of 1050 °C. In addition, the Taguchi method was found to be a feasible approach for optimizing the process condition of bricks using recycled TFT-LCD glass cullet and reservoir sediments and it significantly reduced the number of tests. Further, the characteristics of fired bricks developed in the tunnel kiln were in compliance with Chinese National Standards class Ι building bricks criteria.

A model to compare convective and radiant heating systems for intermittent space heating

In this paper, a dynamic heat transfer model based on thermal-electrical analogy has been built to compare convective and radiative heating systems for intermittent heating. An experiment has been set up to validate the model we built. The RMS Error was within 0.5 °C, confirming the accuracy of the model. The validated model was then applied to compare four typical space heating systems, namely all-air, radiator, in-slab floor heating, and lightweight floor heating systems. The concept of “ineffective heat” has been proposed to explain why the intermittent heating could reduce heating load. Two ideal characters of heating systems have been identified for intermittent heating, i.e. high heating capacity and low thermal mass, both of which are crucial to shorten the preheat time and to reduce the ineffective heat. The results indicate that convective heating systems were more comfortable (more rapidly raise the indoor temperature) and more energy efficient (lower heating load) for intermittent operation than radiative heating systems. The performance gap between radiative and convective heating systems would be enlarged in colder conditions. Among the four heating systems, convective heating system was the most suitable one for intermittent heating, and floor heating was the most unsuitable one. Though belonging to radiative heating systems, the radiator performs differently from floor heating for its potential to enhance heating capacity and relatively low thermal mass. Additionally, outdoor climate and building thermal insulation level also affect the choice of the most suitable heating system and heating mode. The findings of this research might shed some light on the debate of the choice of space heating systems in areas with similar climate conditions with China’s Hot Summer Cold Winter region.

An experimental effort on the impact of hot press forming process parameters on tensile, flexural & impact properties of bamboo fiber composites with the help of Taguchi experimental design

In the existent scenario of alarmingly accrescent demography of the universe, the pretensions of biodegradable green composites made from natural fibers are at their summit point due to their superior properties such as renewable character, low weight, low density, cost effectiveness, comparable specific strength, CO2 sequestration, admissible mechanical, acoustic & thermal insulation properties which also able to rendition themselves as a brawny & trade alternative to the petroleum based composite materials in various industrial & other applications. Inspite of their biodegradability & eco-friendly behaviour, the most influential factors that control the properties of the green composites are processing conditions, methodology, fiber/matrix adhesion & moisture resistivity of natural fibers nevertheless proper control of these factors can make the manifested composites more proficient & lithesome to different kinds of applications. Henceforth one endeavour is taken in this ploy to amplify the mechanical properties of bamboo fiber composites by optimizing the hot press forming process parameters such as temperature, pressure, pre-heat time, heating time & cooling rate with the help of Taguchi L16orthogonal array experimental design. By applying the analysis of the signal-to-noise ratio (S/N ratio) the optimum combination of process parameters has been acquired. Bring to Bear of analysis of variance (ANOVA) ascertained the importance of the levels on process parameters. Put Forth of regression analysis were mathematically modelled the metamorphism of tensile, flexural & impact properties with process parameters. In Fine, the presented models are also corroborated by a set of confirmation test.

Study of suspension grafting process of polypropylene

ABSTRACTGrafting efficiency is an important indicator of polypropylene grafting reaction. A series of studies have been accomplished, including the conditions of free radical presence on PP backbone during peroxide initiation, the effect of preheat treatment and reaction time on PP suspension grafting results, and the effect of peroxide residue on properties of modified PP. An optimized grafting process was proposed by mixing and preheating polypropylene (PP) and the initiator benzoyl peroxide (BPO) before adding the grafting monomer glycidyl methacrylate (GMA),resulting in an increase in grafting efficiency from 50.0% to 78.2%. With initiator residue removed by alternating temperature treatment, the suspension grafting reaction time could be substantially reduced.

Application of the Taguchi Method for Optimizing the Process Parameters of Producing Lightweight Aggregates by Incorporating Tile Grinding Sludge with Reservoir Sediments.

This study aimed to apply the Taguchi optimization technique to determine the process conditions for producing synthetic lightweight aggregate (LWA) by incorporating tile grinding sludge powder with reservoir sediments. An orthogonal array L16(45) was adopted, which consisted of five controllable four-level factors (i.e., sludge content, preheat temperature, preheat time, sintering temperature, and sintering time). Moreover, the analysis of variance method was used to explore the effects of the experimental factors on the particle density, water absorption, bloating ratio, and loss on ignition of the produced LWA. Overall, the produced aggregates had particle densities ranging from 0.43 to 2.1 g/cm3 and water absorption ranging from 0.6% to 13.4%. These values are comparable to the requirements for ordinary and high-performance LWAs. The results indicated that it is considerably feasible to produce high-performance LWA by incorporating tile grinding sludge with reservoir sediments.

Effects of cold start control strategy on cold start performance of the diesel engine based on a comprehensive preheat diesel engine model

It is really vital for the diesel engine to achieve a fast cold startup under low temperature environment especially in alpine region with the winter temperature in the range of –30 °C to 0 °C. The development of diesel engine cold start-up research is under the limits of the test equipments and the funds. In order to explore the cold start ability of diesel engine, the simulation and experiment were attributed to be combined on the basis of previous research methods in this work with a comprehensive consideration of low temperature, atmospheric pressure, preheating effect et al. The related low-temperature dependent maps (preheat time, running speed, torque and so on) were made by simulations for specific engine and then have been loaded down to the ECU (Electronic Control Unit) and the vehicle experiments were carried outdoor of Heihe site in China. The results indicate that the maps with preheat function simulated by using detailed engine parameters can achieve the requirements of the cold start under the low temperature range (–25.5 °C to –16 °C). Preheat time, start voltage and start duration are employed to investigate the cold start ability for the diesel engine, which provide a better reference for strengthening the cold start capacity research. The longest preheat time is 10 s longer than the shortest warm-up time which can increased the intake temperature directly. The cold start-voltage drops by 15% as the temperature drops by 9.5 °C which tends to decrease with the temperature reduce.

Coupling effects of preheating time and extraction medium pH on red radish anthocyanin yield, glucosinolate degradation and off-odour removal

Summary In this study, the effect of combined preheating time (2, 5, and 10 min) and extraction medium pH (2.5, 3.5, and 4.5) on total monomeric anthocyanin yield, and removal of off-odour in red radish anthocyanins were evaluated. The tentative anthocyanin identification showed twelve pelargonidin anthocyanins, and only nine were identified in samples preheated for 10 min. Sample preheated for 10 min and extracted at pH 4.5 showed lower the anthocyanin yield (98.02 mg/100 g, FW), lighter colour and higher percentage polymeric colour compared with that preheated for 2 min and extracted at pH 2.5. However, prolonged preheating time (10 min) significantly reduced myrosinase enzyme activity by 73%. Additionally, results showed that preheating time and extraction medium pH have negative and significant effect on the total monomeric anthocyanin yield, while they showed positive and negative significant effect on the total glucosinolate degradation. Furthermore, the sensory evaluation results revealed no significant difference in radish odour for samples preheated for 2 and 5 min followed by anthocyanin extraction in pH 2.5 medium. It might therefore be concluded that the combination of moderated preheating treatment time (≤5 min) and lower extraction medium pH could be effective to reduce the off-odour characteristics and maintaining high yield and stable red radish pigment.

IMPACTS OF PLASTICIZER AND PRE-HEATING CONDITIONS ON PROPERTIES OF BOVINE AND FISH GELATIN FILMS FABRICATED BY THERMO-COMPRESSION MOLDING TECHNIQUE

Bovine and fish gelatin films were prepared by thermo-compression molding technique. Effects of glycerol levels (15-35%) and resin pre-heating conditions including pre-heating temperatures (120, 140 and 160 °C) and times (5 and 10 min) on film properties were investigated. Tensile strength (TS), elastic modulus (EM) and yellowness of films decreased but elongation at break (EAB), water-vapor permeability (WVP) and transparency increased with increasing glycerol level. Gelatin films had generally decreased TS, EM, WVP and transparency, whilst increased yellowness as pre-heating temperature and time increased. Therefore, glycerol level and condition used for resin pre-heating directly influenced the film properties.

Effects on Mechanical Properties of Solid State Recycled Aluminium 6061 by Extrusion Material Processing

In this research, mechanical properties of recycled 6061 aluminium alloy, produced by solid state recycling through extrusion, were compared to as-received billets. Aluminum 6061 chips were extruded using a hot extrusion machine. The effects of extrusion parameters on the mechanical properties of the produced recycled 6061 aluminium alloy were investigated. The objective of the study was to analyze the mechanical and structural features of the alloy after plastic consolidation. The extrusion processes were conducted at different preheat temperatures and preheat times, while the ram speed was kept constant. The findings of the study highlighted the potential of combining the extrusion process parameters as an efficient processing route for production of high quality and high-performance type of extruded billets. Tensile test results showed that, material extruded at 550°C exhibited better mechanical properties compared to that extruded at 400°C. The higher temperature resulted in a higher tensile strength being produced, at the expense of a trade-off in ductility. Overall, it was revealed that, the ultimate tensile strength (UTS) and elongation (ETF) of the produced recycled 6061 aluminium through extrusion exhibited mechanical and structural properties comparable to those of the as-received billets.

Effect of Pre-Heat Time on Force During Friction Stir Welding Of Aluminium 1050 Alloy

Friction stir welding (FSW) uses a non consumable, continuously rotating tool to generate frictional heat required for joining different surfaces. Various welding parameters like tool shoulder diameter, tool rotational speed, tool pin length, welding speed, etc., play a major role in deciding the properties of friction stir welded joint. Three levels of input variables namely tool rotational speed and pre-heat time have been considered to carry out FSW process on 3mm thickness work piece of aluminium 1050 alloy. The experimental investigation is followed by statistical analysis to find out theoretical (predicted) values of the force. In this work an attempt has been made to analyze the effect of pre-heat time on force during friction stir welding of aluminium 1050 alloy. The results show that force decreases continuously with increase in pre-heat time

铁水包加废钢再受铁可行性探究

为了降低生产成本，提高生存能力，挖潜增效，永钢通过在2#~5#高炉和1#钢厂实施“铁水包加废钢再受铁”的工业性试验，来间接提高废钢比，并探索废钢预热、加入量、停留时间等对炼钢用铁水的影响。研究结果表明：废钢未预热，铁水包无结底；废钢种类选择了材质较薄的散装电工钢；废钢加入量占铁水包容量的百分比为3%；加废钢的铁水包对铁水停留时间影响不大。综合计算1#钢厂的废钢比由16%提高至18%，效果十分显著，为“铁水加废钢”常态化运行提供了依据。 In order to reduce the production cost and improve survival ability, tapping potential and in-creasing efficiency, Yong Steel indirectly increases the scrap steel rate through the implementation of test ladle with scrap in 2#~5# blast furnace and 1# steel mill, and explores the effect of scrap preheating and residence time on molten iron of steelmaking; the industrial test begins to take effect in Yong Steel. The results show that: without preheating, the hot metal ladle bottom is clean; the bulk electrical steel scrap material is thin and easy to be melted in the high temperature molten iron; each hot metal ladle add some scrap steel, and the amount of steel added to each ladle accounts for 3 percent of the iron ladle; The hot metal ladle packing with scrap steel has little impact on the residence time of the hot metal. The steel scrap ratio of 1# steel mill is increased from 16% to 18%, and the effect is remarkable. Thus it can be seen that it provides a basic research for normalizing operation of “the adding scrap steel into ladle”.

Relationship between the Physical Properties and Perceived Saltiness of Various Surimi Gels Prepared by Different Setting Conditions

Salt intake is an important concern for health reasons and saltiness is affected not only by content of food, but also by the texture. Surimi-based products, such as kamaboko, are elastic gels with approximately 2% NaCl; despite recent concerns among Japanese consumers regarding high-salt foods, little is known about the relationship between saltiness and texture in these products. This study was aimed to clarify the relationship between saltiness and texture using heat-induced surimi gels as a model of surimi-based product. Various types of heat-induced gels with different physical properties were prepared from surimi and washed surimi by two-step heating with different setting (preheating) times at 30°C. Washed surimi was prepared to remove the additives, because the additives were thought to affect the taste of surimi gel. The physical properties of heat-induced gels were characterized by puncture breaking strength and expressible water. The perceived saltiness of the heat-induced surimi gels was evaluated with fixed number of chewing. Next, to improve the demerit of this method, the perceived saltiness of the washed surimi gels was evaluated by free chewing conditions. The perceived saltiness after fixed number of chewing and the maximum saltiness intensity during free chewing was evaluated using sensory tests by comparisons with salt solutions of known concentrations. The physical properties of heat-induced gels differed considerably depending on the salt content and heating conditions. A longer setting time was associated with a higher breaking force and lower expressible water, regardless of salt content. On the other hand, perceived saltiness depended on the NaCl concentration, but not greatly influenced by the physical properties of the gels prepared from both surimi and washed surimi. The perceived saltiness of all gels tested was less than 1/3 of solution with the same NaCl concentration. The maximum saltiness intensity did not correlate with breaking force, breaking strain and expressible water of heat-induced gels. From these results, it was suggested that the difference in physical properties derived by setting did not affect the relative saltiness intensity of gels to NaCl solution during consumption of surimi gels.

Effects of Pre-heating Time on Pre-heating Amplitude-modulation in the Lower Ionosphere

基于电离层连续方程和能量方程，建立预加热模式下低电离层幅度调制加热理论模型，模拟大功率电波幅度调制电离层电导率和电流随时间的变化，分析预加热时间对幅度调制产生的极低频/甚低频（ELF/VLF）强度的影响.结果表明，低电离层中的电流能够被大功率电波有效调制，可以作为ELF/VLF电波的辐射源.预加热幅度调制模式在预加热时间较长时效果更明显.在考虑能耗的情况下，当有效辐射功率为200MW及高频波的调制频率<i>f</i>_ELF/VLF为1kHz时，预加热幅度调制模式辐射ELF/VLF加热0.1s时效果最好，强度可提高约7.95dB.

Physico Chemical, Antioxidant and Pasting Properties of Pre-heated Purple Sweet Potato Flour

Purple sweet potatoes contain anthocyanins which could function as a natural food colorant, and an antioxidant. One of the problems in handling the fresh roots is their susceptibility during storage, and to extend their uses, fresh purple sweet potato could be processed into flour. However, during flouring process, the properties of the purple sweet potato may undergo some changes such as partial gelatinization of the starch and discolorization. Therefore, the purpose of this study was to investigate the effect of pre-heating treatment during flouring process on degree of gelatinization, the anthocyanin content, the antioxidant activity and the total phenolic content of heat treated purple sweet potato flour. Other objectives were to observed the changes in the starch properties such as rheological properties, granular appearance of the heat treated- purple sweet potato flour. Pre-heating treatment of purple sweet potato flour was prepared by heating grated purple sweet potato in a single rotary drum cooker at 90°C for 15, 30, 45, 60 and 75 min, followed by drying in a cabinet dryer at 60°C for 8 h. The results showed the longer pre-heating time at 90°C had caused increase in the degree of gelatinization, increase in total phenolic and anthocyanin retention. In addition, differences in gelatinization temperature, maximum viscosity, paste stability and retrogradation, and differences in scanning electron microscope (SEM) of granular appearance were also observed. The overall results indicated that pre-heating treatment can be used for modifying the physical, chemical and rheological properties to suit various applications and preserving functional properties of purple sweet potato flour.

An approach to reduce the pre-heating time in a convection oven via CFD simulation

Convective ovens require a pre-heating stage to achieve a homogenous temperature. Energy consumption is high during the pre-heating stage and proportional to pre-heating time. The pre-heating time depends on the set-point temperature. In this work a pilot scale convective oven was represented as a nominal scenario, and provided experimental data for temperature. The strategy consisted of 3-D computational fluid dynamic (CFD) simulations at different temperatures and geometrical variants of the internal baffle plate. The simulations were carried out using the ANSYS CFX package and were contrasted with experimental measurements. Results proved that the baffle plate geometry exerted an important hydrodynamic influence in the reduction of the pre-heating time.

Developing an Optimum Protocol for Thermoluminescence Dosimetry with GR-200 Chips using Taguchi Method.

Thermoluminescence dosimetry (TLD) is a powerful technique with wide applications in personal, environmental and clinical dosimetry. The optimum annealing, storage and reading protocols are very effective in accuracy ofTLD response. The purpose of this study is to obtain an optimum protocol for GR-200; LiF: Mg, Cu, P, by optimizing the effective parameters, to increase the reliability of the TLD response using Taguchi method. Taguchi method has been used in this study for optimization of annealing, storage and reading protocols of the TLDs. A number of 108 GR-200 chips were divided into 27 groups, each containing four chips. The TLDs were exposed to three different doses, and stored, annealed and read out by different procedures as suggested by Taguchi Method. By comparing the signal-to-noise ratios the optimum dosimetry procedure was obtained. According to the results, the optimum values for annealing temperature (°C), Annealing Time (s), Annealing to Exposure time (d), Exposure to Readout time (d), Pre-heat Temperature (°C), Pre-heat Time (s), Heating Rate (°C/s), Maximum Temperature of Readout (°C), readout time (s) and Storage Temperature (°C) are 240, 90, 1, 2, 50, 0, 15, 240, 13 and -20, respectively. Using the optimum protocol, an efficient glow curve with low residual signals can be achieved. Using optimum protocol obtained by Taguchi method, the dosimetry can be effectively performed with great accuracy.

Numerical Simulation of the Effects of Preheating on Electron Beam Additive Manufactured Ti-6Al-4V Build Plate

In an earlier study, a 3-D thermomechanical coupled finite element model was built and experimentally validated to investigate the evolution of the thermal residual stresses and distortions in electron beam additive manufactured Ti-6Al-4V build plates. In this study, an investigation using this robust and accurate model was focused on an efficient preheating method, in which the electron beam quickly scanned across the substrate to preheat the build plate prior to the deposition. Various preheat times, beam powers, scan rates, scanning paths and cooling times (between the end of current preheat scan/deposition layer and the beginning of the next preheat scan/deposition layer) were examined, and the maximum distortion along the centerline of the substrate and the maximum longitudinal residual stress along the normal direction on the middle cross-section of the build plate were quantitatively compared. The results show that increasing preheat times and beam powers could effectively reduce both distortion and residual stress for multiple layers/passes components.