Temporal Temperature Distribution Research Articles

大口径望远镜结构热分析

In order to evaluate the temperature effect of telescopes, a precise thermal finite element model consists of telescope optical assembly systems, mount structure and electrical equipment was established. Temporal and spatial temperature distributions of the optical assembly and telescope structure were calculated under various thermal conditions including conductions, air convections, radiation and heat flux loading. Moreover, the thermo-elastic analysis was made to obtain thermal deformations of the telescope structure based on the resulting temperature distributions. The obtained results show that temperature variation has large effect on telescope mount and main optical system, and induced displacement between primary and second mirror has a magnitude of millimeter, so it must be controlled strictly. At last some thermal control ways were given in terms of protection dome, mount, primary mirror and so on.

皮秒激光烧蚀Al膜的理论分析与实验验证

In order to investigate the energy transport process in Al film irradiated by 10 ps lasers, a semi-classical two temperature model (TTM) was applied, and a 1D finite element calculation model was constructed with finite element software. Considering phase change region of material during laser ablation, reasonable expression was added to the TTM. According to the calculation, the surface lattice temperature evolutions along with time for single pulse lasers with different powers were presented. In order to investigate the surface plasma reflectivity and the heat absorption coefficient changing with lattice temperature during laser irradiation, the free-electron gas theory was applied. Moreover, the laser generated thermoelectric field and the electron drift velocity distribution map were depicted. The results verify that the thermoelectric field is the major reason for the electron drift movement, and the location of maximum velocity is changed with time. The spatial and temporal lattice temperature distribution map of Al film irradiated by 0.12 W picosecond laser was depicted. According to the calculation, the phase explosion is the reason for ablation, and it occurs during the process of laser energy deposition. The over-heated zone (OHZ) was defined, and the relationship between ablated depths and time was found. The calculated ablation depths of single pulses coincide with the experiment for 10 ps laser.

Characterization of double diffusive convection steps and heat budget in the deep Arctic Ocean

In this paper, we explore the hydrographic structure and heat budget in the deep Canada Basin by using data measured with McLane‐Moored‐Profilers (MMP), bottom pressure recorders (BPR), and conductivity‐temperature‐depth (CTD) profilers. Upward from the bottom, a homogeneous bottom layer and its overlaying double diffusive convection (DDC) steps are well identified at Mooring A ( ). We find that the deep water is in weak diapycnal mixing because the effective diffusivity of the bottom layer is , while that of the other steps is . The vertical heat flux through the DDC steps is evaluated by using different methods. We find that the heat flux ( ) is much smaller than geothermal heating ( ). This suggests that the stack of DDC steps acts as a thermal barrier in the deep basin. Moreover, the temporal distributions of temperature and salinity differences across the interface are exponential, whereas those of heat flux and effective diffusivity are found to be approximately lognormal. Both are the result of strong intermittency. Between 2003 and 2011, temperature fluctuations close to the sea floor were distributed asymmetrically and skewed toward positive values, which provide a direct observation that geothermal heating was transferred into the ocean. Both BPR and CTD data suggest that geothermal heating and not the warming of the upper ocean is the dominant mechanism responsible for the warming of deep water. As the DDC steps prevent vertical heat transfer, geothermal heating is unlikely to have a significant effect on the middle and upper Arctic Ocean.

Ellipsometric analysis of silicon surfaces textured by ns and sub-ps KrF laser pulses

Efficiency of solar cells can be enhanced by lowering their surface reflectance. A possible method to produce textured surfaces with low reflectance is by irradiating them with multiple low intensity nano-, pico- or femtosecond length laser pulses. In this study, the treatment of single crystal silicon surface by series of sub-ps and ns pulses from KrF excimer lasers was investigated. The change in surface properties was observed by spectroscopic ellipsometry, scanning electron microscopy and Raman spectroscopy. Spatial and temporal temperature distributions due to single laser pulse irradiations were numerically calculated and used for interpretation of experimental results. Ellipsometry and Raman spectroscopy clearly indicated that in the case of the sub-ps laser irradiation the first laser pulse caused the formation of a ~15nm thick amorphous silicon layer. In the case of the irradiation by ns laser pulses, the thickening of the top oxide layer and the appearance of a modified, less crystalline silicon layer, up to ~200nm thickness was observed. A series of ns laser pulses resulted in cycles of surface melting followed by recrystallization, which introduced partial degradation of crystalline structure. As indicated by scanning electron microscopy images and decreasing fitting quality of the ellipsometric spectra, the surface became structured after 5 and 100 laser shots in the case of sub-ps and ns length laser pulses, respectively.

새만금호 내 방수제 공사 및 준설에 의한 수리동역학적 특성 변화 수치 모델링

The study area is located on the western coast, and the inner development construction has been ongoing since 2011. The purposes of current study are to effectively simulate and quantitatively predict a temporal and spatial distributions of water temperature and salinity due to the stages of inner development construction in saemangeum reclaimed area. The transient-state numerical modeling using EFDC model is done, and the numerical simulation results are validated reasonably by repetitive numerical model calibration procedures with respect to field measurements of water temperature and salinity. The spatial distributions of water temperature and salinity show similar trends before and after construction of the dikes. In spring season, the salinity has maximum value of 21 psu, while, in summer season, the salinity shows 7 psu in a whole modeling domain. Thus, it is clearly observed that salt water is replaced by freshwater. However, the salinity and temperature reach their initial conditions at the end of the year. The salinity after construction of the dikes is lower than that before construction of them at Mankyeong area. On the other hands, after construction of the dikes, the salinity after dredging operations is higher than that before dredging. Because drastical increasing of water volume in Saemangeum Lake leads to increasing of stagnation time at bottom layer, and salt water is easily intruded to the two estuaries. Therefore, it may be concluded that hydrodynamic characteristics on Saemangeum are dominated by either Mankyeong and Dongjin discharge or sluice gates in/out-flow amounts, and thus they must be properly considered when rigorous and reasonable predictions of water temperature and salinity according to the stages of inner development construction.

Diagnostic of Laser-Induced Plasma Using Abel Inversion and Radiation Modeling

A method based on matching synthetic and experimental emissivity spectra was applied to spatially resolved measurements of a laser-induced plasma ignited in argon at atmospheric pressure. The experimental emissivity spectra were obtained by Abel inversion of intensity spectra measured from a thin plasma slice perpendicular to the plasma axis. The synthetic spectra were iteratively calculated from an equilibrium model of plasma radiation that included free-free, free-bound, and bound-bound transitions. From both the experimental and synthetic emissivity spectra, spatial and temporal distributions of plasma temperature and number densities of plasma species (atoms, ions, and electrons) were obtained and compared. For the best-fit synthetic spectra, the temperature and number densities were read directly from the model; for experimental spectra, these parameters were obtained by traditional Boltzmann plot and Stark broadening methods. In both cases, the same spectroscopic data were used. Two approaches revealed a close agreement in electron number densities, but differences in plasma excitation temperatures and atom number densities. The trueness of the two methods was tested by the direct Abel transform that reconstructed the original intensity spectra for comparing them to the measured spectra. The comparison yielded a 9 and 13% difference between the reconstructed and experimental spectra for the numerical and traditional methods, respectively. It was thus demonstrated that the spectral fit method is capable of providing more accurate plasma diagnostics than the Boltzmann plot and Stark broadening methods.

Heating during infrared neural stimulation

Infrared neural stimulation (INS) has recently evoked interest as an alternative to electrical stimulation. The mechanism of activation is the heating of water, which induces changes in cell membrane potential but may also trigger heat sensitive receptors. To further elucidate the mechanism, which may be dependent on cell type, a detailed description of the temperature distribution is necessary. A good control of the resulting temperature during INS is also necessary to avoid excessive heating that may damage the cells. Here we present a detailed model for the heating during INS and apply it for INS of in vitro neural networks of rat cerebral cortex neurons. A model of the heating during INS of a cell culture in a non-turbid media was prepared using multiphysics software. Experimental parameters such as initial temperature, beam distribution, pulse length, pulse duration, frequency and laser-cell distance were used. To verify the model, local temperature measurements using open pipette resistance were conducted. Furthermore, cortical neurons in culture were stimulated by a 500 mW pulsed diode laser (wavelength 1,550 nm) launched into a 200 µm multimodal optical fiber positioned 300 µm from the glass surface. The radiant exposure was 5.2 J/cm(2) . The model gave detailed information about the spatial and temporal temperature distribution in the heated volume during INS. Temperature measurements using open pipette resistance verified the model. The peak temperature experienced by the cells was 48°C. Cortical neurons were successfully stimulated using the 1,550 nm laser and single cell activation as well as neural network inhibition were observed. The model shows the spatial and temporal temperature distribution in the heated volume and could serve as a useful tool for future studies of the heating during INS.

A Study on the Thermal Characteristics of Midsummer in Daegu Metropolitan Area

This study aims to examine the actual status of the urban heat island in Daegu by analyzing the data of 17 automatic weather stations installed in the Daegu area. And the results can be summarized as follows: First, regarding the temperature distribution in Daegu by summer time zones, for the 31 days(August 1st till 31st), 18 days showed daily maximum temperature over <TEX>$30^{\circ}C$</TEX>, and 11 days indicated daily minimum temperature over <TEX>$25^{\circ}C$</TEX>. The day that showed the highest daily maximum temperature was August 5th, which indicated <TEX>$36^{\circ}C$</TEX>. Second, about the spatial distribution of time ratio exceeding <TEX>$30^{\circ}C$</TEX> and <TEX>$25^{\circ}C$</TEX>, the area with the highest time ratio exceeding <TEX>$30^{\circ}C$</TEX> is mostly the downtown(central area), eastern area, and northern area. Meanwhile, regarding the time ratio exceeding <TEX>$25^{\circ}C$</TEX>, the downtown area centering around the central area were high as over 70%, and the outskirts were low as under 65%. Third, considering the temporal distribution of daily maximum temperature and daily minimum temperature, daily maximum temperature was shown around 14:00 to 15:00 while the daily minimum temperature was indicated around 17:00 to 18:00. Daily maximum and minimum temperature were appeared at northeast and downtown, respectively. Fourth, regarding the spatial distribution of tropical days and tropical night days, tropical days showed 77% and tropical night days indicated 42% before and after the 24th and also the 13th each. Tropical days were occurred up to 24 days at northeastern area. And the southwestern area of Daegu showed under 22 days. The downtown showed the 14 days of the tropical night. However, the outskirts indicated relatively few days as under 10 days. Fifth, about the spatial distribution of the average daily temperature range (the difference between the highest temperature and lowest temperature), the central area, the central part of the city, showed the smallest as <TEX>$7.2^{\circ}C$</TEX>, and as it was closer to the northern area, it became larger, so in the eastern and northern area, it was over <TEX>$8.8^{\circ}C$</TEX> or so.

Projected changes in wind speed over the Republic of Korea under A1B climate change scenario

ABSTRACTIn this study, an attempt was made to investigate a future wind‐speed change over the Republic of Korea using a mesoscale weather research and forecasting (WRF) model. We presented dynamically downscaled wind fields and the physical processes that derived the surface wind changes. A double‐nested WRF model within the global‐scale scenario from the fifth generation of the ECHAM general‐circulation model (ECHAM5) was integrated for the present‐day (the late 20th century, 1990–1999) and future (the mid‐21st century, 2045–2054) wind climate. The ensemble mean of the simulated results for the sensitivity of planetary boundary‐layer physics provided a relative advantage in determining synoptic and surface fields. A reasonable and realistic wind climatology, influenced by the asymmetric heating of land and sea, was identified over the East Asian monsoon region. The observed spatial and temporal distributions of temperature and wind speed were also reproduced well by the mesoscale simulations. Projected wind‐speed changes at 80 m above ground level varied from –9.53 to 29.80% depending on the location and season. [Correction added 3 March 2014 after original online publication: in the preceding sentence ‘9.53’ has been corrected to ‘–9.53’.] The strong wind speed in the cold season decreased (–5.45%), whereas the weak wind speed in the warm season increased (4.54%). A possible cause of the weakened and strengthened winds in cold and warm seasons, respectively, is shown to be the effects in the lower‐tropospheric pressure‐gradient force accompanied by pronounced warming.

Spatial and Temporal Distribution of Air Temperature in the Northern Hemisphere

In the present study, the spatial and temporal surface air temperature variability for the Northern Hemisphere has been examined, for the period 1900-1996. Factor Analysis has been applied to 5o Latitude x 10o Longitude grid box data covering the area from almost the equator to 70o N. These data are anomalies of the mean annual air temperature from the respective mean values of the period 1961- 1990. The analysis showed that, mainly 20 regions were determined in the Northern Hemisphere with significantly covariant air temperature time series. The comparison of the trends of the mean annual surface air temperature time series of these regions, revealed such common characteristics as the minimum of the first decade of the 20th century and the recent years warming. The results of this study are also compared to the respective results of a former study in which data for the last half of the century (1948-1996) have been analyzed. The findings extracted indicate the stability of climate distribution in Northern Hemisphere during the 20th century.

Green Compact Temperature Evolution during Current-Activated Tip-Based Sintering (CATS) of Nickel

Current-activated tip-based sintering (CATS) is a novel process where spark plasma sintering conditions are applied through an electrically conducting tip on a locally controlled area on a green powder compact/bed. The localization of electric current in CATS allows for unique temporal and spatial current and temperature distributions within the tip and powder compact. In this paper, special experimental setups were used to monitor the temperature profiles in the tip and at multiple locations on the surface of nickel powder compacts. A variation in the initial green density was found to have a significant effect on the maximum temperature in the tip as well as the temperature distribution across the powder compact. In general, the lowest green density specimens displayed the best conditions for localized densification. The concept of effective current density is introduced and results are discussed in relation to the densification parameter.

Characteristics of interfacial signatures on a wind-driven gravity-capillary wave

[1] Direct numerical simulation of a wind-driven gravity-capillary wave and the underlying turbulent flow is conducted to identify the characteristic signatures of various surface parameters, including temperature, gas flux, velocities, and roughness, and to reveal the impacts of the nonbreaking surface waves on these surface flow and tracer parameters. Three characteristic surface signatures and the corresponding flow processes are identified: the carrier gravity wave, the parasitic capillary wavelets, and the elongated streaks. The elongated streaks are induced by both the coherent streamwise vortices formed within the turbulent shear layer and the Langmuir circulations arising from nonlinear interaction between the carrier gravity wave and the drift current. All three surface signatures can be observed in the distributions of various quantities, although some are more apparent than the others. Image-processing techniques, employing empirical mode decomposition and phase averaging, are developed to decompose the distinct signatures thus to quantify the contributions by the responsible flow processes. It is found that elongated streaks prevail the distribution of surface temperature and gas flux, indicating that Langmuir cells and the coherent eddies contribute to the major interfacial heat and gas transport. These eddies also induced strong cross-stream velocity divergence at the water surface, which exhibits resemblant elongated distribution as that of gas flux (correlation coefficient � 0.6). High correlation between the surface distributions of temperature and gas flux is observed (correlation coefficient � 0.8 to 0.9), suggesting that the spatial and temporal distribution of surface temperature is a good proxy tracer of interfacial gas transfer.

Double-Nested Dynamical Downscaling Experiments over the Tibetan Plateau and Their Projection of Climate Change under Two RCP Scenarios

AbstractA high-resolution regional climate model is used to simulate climate change over the Tibetan Plateau (TP). The model is driven at the grid spacing of 10 km by nesting the outputs of 50-km-resolution simulations. The results show that the models can capture the spatial and temporal distributions of the surface air temperature over the TP. The so-called double-nested method has a higher horizontal resolution and represents more spatial details. For example, the temperature simulations from the double-nested method reflect the observations better compared to the 50-km-resolution models. This is mainly due to the fact that topographical effects of complex terrains are detected better at higher resolution. Although both models can represent the basic patterns of precipitation, the simulated results are not as good as those of temperature. In the future, significant warming seems to develop over the TP under two representative concentration pathway (RCP) scenarios. Greater increases occur in December–February (DJF) compared with June–August (JJA). The increasing temperature trend is more pronounced over the Gangdese Mountains and over the Himalayas than in the central TP. The projection of precipitation shows the main increases in DJF. In JJA, it predicts decreases or slight changes in the southern TP. The comparison between RCP8.5 and RCP4.5 scenarios shows a similar spatial distributions of temperature and precipitation, whereas the respective values of RCP8.5 are enhanced compared with those under RCP4.5.

Numerical Evaluation of a Sensible Heat Balance Method to Determine Rates of Soil Freezing and Thawing

In situ determination of soil freezing and thawing is difficult despite its importance for many environmental processes. A sensible heat balance (SHB) method using a sequence of heat pulse probes has been shown to accurately measure water evaporation in subsurface soil, and it has the potential to measure soil freezing and thawing. Determination of soil freezing and thawing may be more challenging than evaporation, however, because the latent heat of fusion is smaller than the latent heat of vaporization. Furthermore, convective heat flow associated with liquid water flow and occurrence of evaporation or condensation during freezing and thawing may cause inaccurate estimation of freezing and thawing with the SHB method. The objective of this study was to examine the applicability of the SHB concept to soil freezing and thawing. Soil freezing and thawing events were simulated with the simultaneous heat and water (SHAW) model. Ice contents were estimated by applying the SHB concept to numerical data produced by the SHAW model. Close agreement between the SHB‐estimated and the SHAW‐simulated ice contents were observed at depths below 24 mm. The main cause of inaccuracies with the SHB method was poor estimation of heat conduction at the 12‐mm depth, possibly due to simplifications of temporal or vertical distributions of temperature and thermal conductivity. The effects of convective heat flow and concurrent evaporation or condensation and freezing or thawing on the SHB method were small. The results indicate that the SHB method is conceptually suitable for estimating soil freezing and thawing. Independent, accurate estimates of thermal properties must be available to effectively use the SHB method to determine in situ soil freezing and thawing.

Real time optimization for quality control of batch thermal sterilization of prepackaged foods

In this contribution, we present a distributed decision-making architecture for control to optimally command thermal sterilization, despite process uncertainty or unexpected process disturbances. The control structure combines in a synchronous way modeling and simulation environments with efficient system identification and dynamic optimization tools and methods. Process simulation provides a complete dynamic description of the current status of the operation, including the evolution of temperature and pressure in the retort unit as well as temporal and spatial distribution of temperature and quality or safety parameters within the product. Such virtual representation will be regularly confronted with plant measurements to quantify the degree of discrepancy (uncertainty) between real plant and models and react accordingly when such discrepancy becomes unacceptable by re-estimating plant parameters, either during the cycle or from batch to batch. The virtual plant will be also accessed by the regulatory system as well as the dynamic optimization module. In the first instance to estimate unmeasured states related with the product status (e.g. temperature in the product or lethality) under feed-back control. In the second, to continuously recompute optimal cycle profiles so to respond to unexpected disturbances or deviations from the prescribed safety constraints while maximizing quality attributes. Experimental evidence of the complete control system performance will be given on the operation of a pilot plant prototype.

Experimental investigation on the temperature distribution in the cavity pool of ex-vessel cooling system

During the external reactor vessel cooling process, the cavity pool might be stratified due to the buoyancy effect. The purpose of this study is to investigate the temperature distribution and the effect of main factors on the thermal stratification phenomena in the cavity pool. A large rectangular tank of the REPEC test facility, with a dimension of 2m in length, 1.5m in width and 1.5m in height, is used to simulate the cavity pool. And the water level of the tank can be set to any value in the range of 0.9–1.5m. In the experiment, the hot water enters into the tank through the top inlet, while the relative cold water withdraws from the bottom outlet. 24 T type thermocouples are used to measure the temperature profiles in the tank. The experiment investigation mainly focuses on the temporal and spatial temperature distribution, heat loss rate to the ambient, the effect of initial tank temperature and charging flow rate on the thermal stratification phenomena in the tank. The experiment results indicate that thermal stratification occurs spontaneously when the flow rate is low, but the thermal stratification phenomenon weakens with the increase of flow rate. It is demonstrated that the initial water temperature has little effect on the thermal stratification process. The temperature distribution varies in the gravity direction and is almost uniform in the horizontal direction. Consequently, a simplified 1D analytical model is proposed and Pe number is derived from the model to qualitatively characterize the stratification in the tank.

Temporal and spatial temperature distribution in the glabrous skin of rats induced by short-pulse CO2 laser

Pain is a natural alarm that aids the body in avoiding potential danger and can also present as an important indicator in clinics. Infrared laser-evoked potentials can be used as an objective index to evaluate nociception. In animal studies, a short-pulse laser is crucial because it completes the stimulation before escape behavior. The objective of the present study was to obtain the temporal and spatial temperature distributions in the skin caused by the irradiation of a short-pulse laser. A fast speed infrared camera was used to measure the surface temperature caused by a CO2 laser of different durations (25 and 35 ms) and power. The measured results were subsequently implemented with a three-layer finite element model to predict the subsurface temperature. We found that stratum corneum was crucial in the modeling of fast temperature response, and escape behaviors correlated with predictions of temperature at subsurface. Results indicated that the onset latency and duration of activated nociceptors must be carefully considered when interpreting physiological responses evoked by infrared irradiation.

Roadbed temperature study based on earth-atmosphere coupled system in permafrost regions of the Qinghai-Tibet Plateau

Abstract In this work, a two-dimensional unsteady model for analyzing the roadbed temperature in permafrost regions of the Qinghai-Tibet Plateau (QTP) is developed and the heat transfer processes of comprehensive earth-atmosphere coupled system are simulated by the numerical method. In the computation, the surrounding air environment of ground surface is brought into the research model and the corresponding unsteady and non-uniform influence factors of earth-atmosphere coupled system are also considered to obtain reasonable simulation results. Meanwhile, the model is validated with monitored data at a depth of 0.5 m in different roadbed positions. Based on the above model, the spatial and temporal temperature distributions of the roadbed surface in Wudaoliang region are determined. Then the influences of the system parameters, such as the ambient temperature, wind speed, roadbed height and route trends, on the local temperature distribution are investigated. The results show that, temperature of surface regions exhibits a periodic sinusoid trend and always higher than the ambient air temperature. For different surface regions, the temperature of asphalt pavement keeps the maximum value and the natural ground surface has an abrupt step change in temperature at beginning of April and end of October. The variation of ambient air temperature has little influence on annual average temperature of permafrost roadbed surface. The deviations between the surfaces' annual average temperature increase and their average values are less than 1%. Annual average temperature of various surfaces decreases as the wind speed and the roadbed height increase. Furthermore, the annual average temperature of leeward slope (also sunny side) along EW direction is the highest one among all three route directions and such temperature decreased systematically from SW45° direction to SN direction. However, the annual temperature of upwind slope (also shady side) is just contrary to the leeward slope.

Numerical simulation of two-stage combustion in SI engine with prechamber

Burning lean mixture in spark ignition (SI) engine leads to decrease in temperature of combustion process and is one of the methods of limiting nitric oxide emission and increasing the engine efficiency. The two-stage combustion system of stratified mixture (engine with prechamber) can be an effective method of lean mixture combustion. The paper presents the results of three-dimensional modeling of fuel mixture preparation and combustion in SI engine with sectional combustion chamber powered by liquefied fuel. Three dimensional modeling was performed in KIVA-3V code. The modeling results were compared with results obtained from the analysis of experimental measurements of two-stage combustion test engine operating at the Institute of Internal Combustion Engines and Control Engineering (Czestochowa University of Technology). The performed simulations of the combustion process provided data concerning the spatial and temporal distributions of turbulent kinetic energy, pressure, temperature and nitric oxides concentration in the combustion chambers of the engine. The engine model with two-stage combustion system properly represents the real processes which occur in the combustion chambers of the test engine. Pressure and temperature courses in function of CA obtained from the experiment and modeling were in good qualitative and quantitative consistence. Comparison of modeled and measured nitric oxide emissions revealed relatively significant discrepancies. In case of λ=1.4, the measured values of NOx concentration were 1.75 times higher than the modeled values. In case of λ=2.0, the modeled and measured values were close to each other and were within the range of measurement error.

Thermal diffusivity measurements of spherical samples using active infrared thermography

This work presents a method for measuring the thermal diffusivity of spherical samples using active infrared thermography. The principal novelty of this method lies in the deduction of an analytical model to obtain the spatial and temporal distribution of temperature in spherical samples. The model is obtained from the classical theory of heat conduction or the 3D heat diffusion equation. In order to analyze the behavior of the model, an active infrared thermography is used in order to monitor the spatial and temporal temperature distribution. Three different materials are used as spherical samples and they are heated by radiation increasing this way its temperature. The recorded data is fitted to the model by adjusting the diffusivity parameter. The results of the diffusivity values obtained using this model are consistent with those obtained from a standard thermal properties analyzer.