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1
Jones, Joshua L., Brent W. Webb, Bret W. Butler, Matthew B. Dickinson, Daniel Jimenez, James Reardon, and Anthony S. Bova. "Prediction and measurement of thermally induced cambial tissue necrosis in tree stems." International Journal of Wildland Fire 15, no. 1 (2006): 3. http://dx.doi.org/10.1071/wf05017.
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A model for fire-induced heating in tree stems is linked to a recently reported model for tissue necrosis. The combined model produces cambial tissue necrosis predictions in a tree stem as a function of heating rate, heating time, tree species, and stem diameter. Model accuracy is evaluated by comparison with experimental measurements in two hardwood and two softwood species: red maple (Acer rubrum), chestnut oak (Quercus prinus), ponderosa pine (Pinus ponderosa), and Douglas-fir (Pseudotsuga menziesii). Results are promising, and indicate that the model predicts stem mortality/survival correctly in ~75–80% of the test cases. A limited sensitivity analysis of model kill depth predictions suggests that the model is more sensitive to required input data for some species than for others, and that the certainty in predicting vascular cambium necrosis decreases as stem diameter decreases.
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Jones, Joshua L., Brent W. Webb, Dan Jimenez, James Reardon, and Bret Butler. "Development of an advanced one-dimensional stem heating model for application in surface fires." Canadian Journal of Forest Research 34, no. 1 (January 1, 2004): 20–30. http://dx.doi.org/10.1139/x03-187.
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A new one-dimensional heat conduction model for predicting stem heating during fires is presented. The model makes use of moisture- and temperature-dependent thermal properties for layers of bark and wood. The thermal aspects of the processes of bark swelling, desiccation, and devolatilization are treated in an approximate fashion. An energy balance reveals that simulation with a heat flux input boundary condition requires that these phenomena be accounted for. Previous models have used temperaturetime boundary conditions, which prevents them from being used in conjunction with fire behavior models. This model uses a fluxtime profile for its boundary condition, making it possible to eventually couple it to fire behavior models. The model was developed and validated with laboratory experiments on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) samples. It is intended that this model be used in conjunction with fire behavior and cell mortality models to make predictions of stem heating related mortality before prescribed burns.
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Wei, Rui, Guang Yang, Jili Zhang, Xiaohong Wang, and Xin Zhou. "The thermal insulation properties of oak (Quercus mongolica) bark and the applicability of stem heating models." International Journal of Wildland Fire 28, no. 12 (2019): 969. http://dx.doi.org/10.1071/wf18232.
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The survival probability of a tree exposed to surface fire varies widely depending on its bark. To advance the understanding of insulation properties of bark, mean thickness (BT), moisture content (MCb), surface structure (BS) and density (ρb) of bark samples of Mongolian oak (Quercus mongolica) (n=395) for four diameter classes were investigated. In addition, data from 158 heating experiments simulating low-intensity surface fires in the laboratory were used to assess the relative importance of these properties affecting thermal insulation and evaluate the applicability of two stem heating models, an analytical, one-dimensional model and the FireStem2D model. Overall, BT is the best predictor of bark insulation capacity and MCb only contributes significantly to explain the residence time of cambial temperature >60°C (τ>60), whereas ρb and BS have minor effects. Although the two stem heating models overestimate the time required for cambium temperatures to reach 60°C (τ60), FireStem2D performed better than analytical model. Furthermore, FireStem2D provides good predictions of τ>60 and maximal cambial temperature (Tmax). In addition, errors in FireStem2D may be driven mainly by the errors in temperature measurement and the limitation of a two-dimensional model. The study provides a better knowledge of interactions between bark properties and heat transfer, which may improve the predictability of fire-caused stem injury for Mongolian oak and other species with similar bark properties.
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Bova, Anthony S., and Matthew B. Dickinson. "An inverse method to estimate stem surface heat flux in wildland fires." International Journal of Wildland Fire 18, no. 6 (2009): 711. http://dx.doi.org/10.1071/wf07122.
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Models of wildland fire-induced stem heating and tissue necrosis require accurate estimates of inward heat flux at the bark surface. Thermocouple probes or heat flux sensors placed at a stem surface do not mimic the thermal response of tree bark to flames. We show that data from thin thermocouple probes inserted just below the bark can be used, by means of a one-dimensional inverse heat conduction method, to estimate net heat flux (inward minus outward heat flow) and temperature at the bark surface. Further, we estimate outward heat flux from emitted water vapor and bark surface re-radiation. Estimates of surface heat flux and temperature made by the inverse method confirm that surface-mounted heat flux sensors and thermocouple probes overestimate surface heat flux and temperature. As a demonstration of the utility of the method, we characterized uneven stem heating, due to leeward, flame-driven vortices, in a prescribed surface fire. Advantages of using an inverse method include lower cost, ease of multipoint measurements and negligible effects on the target stem. Drawbacks of the simple inverse model described herein include inability to estimate heat flux in very moist bark and uncertainty in estimates when extensive charring occurs.
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Potter, Brian E., and Jeffrey A. Andresen. "A finite-difference model of temperatures and heat flow within a tree stem." Canadian Journal of Forest Research 32, no. 3 (March 1, 2002): 548–55. http://dx.doi.org/10.1139/x01-226.
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The authors present a finite-difference numerical model of heat flow within a horizontal section of a tree stem. Processes included in the model are solar radiative heating, infrared emission and absorption, convective heat exchange between tree surface and the atmosphere, and conduction inside the tree. Input variables include wood density, wood thermal conductivity, wood specific heat, wind speed, air temperature, and insolation. The model produces time series of temperature for grid points inside the tree stem. Based on comparison with observations from two case studies, the model appears capable of reproducing relative timing and amplitude of temperature patterns at the cardinal aspects. Sensitivity tests show that insolation and convection parameters, as well as the physical properties of the tree, can all have a strong influence on model results.
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Barthakur, NN, and NP Arnold. "A Transient Method for Determining Thermal Diffusivity of Tobacco Stems." Beiträge zur Tabakforschung International/Contributions to Tobacco Research 14, no. 5 (October 1, 1989): 321–26. http://dx.doi.org/10.2478/cttr-2013-0609.
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AbstractA microwave generator and a closed-circuit wind tunnel were used to measure the thermal diffusivity of tobacco (Nicotianatabacum L.) stems in vivo by the unsteady-state method. A simple mathematical model for heat flow, based on Fourier's heat-conduction equation and Newton's law of cooling, was used in this study. The microwave method was found to be relatively rapid as both heating and cooling of a cylindrical stem in an air stream could be completed in approximately 30 minutes for thermal-diffusivity determinations. Thermal-diffusivity value of the tobacco stems, containing 94 % moisture and a mean stem temperature of 30°C, was found to be (1.38 ± 0.06) × 10-7 m2 s-1. The coefficient of variation for the measurements did not exceed 1.4 % as determined through the analysis of cooling curves for five different air-flow rates over the stems. This study showed that the microwave technique could be effectively used to determine both accurately and reliably the thermal diffusivity of tobacco stems in vivo.
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Gu, Tianbao, Torsten Berning, and Chungen Yin. "Application of a New Statistical Model for the Description of Solid Fuel Decomposition in the Analysis of Artemisia apiacea Pyrolysis." Energies 14, no. 18 (September 14, 2021): 5789. http://dx.doi.org/10.3390/en14185789.
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Pyrolysis, one of the key thermochemical conversion technologies, is very promising to obtain char, oil and combustible gases from solid fuels. Kinetic modeling is a crucial method for the prediction of the solid conversion rate and analysis of the pyrolysis process. We recently developed a new statistical model for the universal description of solid fuel decomposition, which shows great potential in studying solid fuel pyrolysis. This paper demonstrates three essential applications of this new model in the analysis of Artemisia apiacea pyrolysis, i.e., identification of the conversion rate peak position, determination of the reaction mechanism, and evaluation of the kinetics. The results of the first application show a very good agreement with the experimental data. From the second application, the 3D diffusion-Jander reaction model is considered as the most suitable reaction mechanism for the description of Artemisia stem pyrolysis. The third application evaluates the kinetics of Artemisia stem pyrolysis. The evaluated kinetics vary with the conversion degree and heating rates, in which the activation energies and pre-exponential factors (i.e., lnA vs. Ea) show a linear relationship, regardless of the conversion and heating rates. Moreover, the prediction of the conversion rate using the obtained kinetics shows an excellent fit with the experimental data.
8
Tseng, Ling-Shu, Sheng-Hsien Chen, Mao-Tsun Lin, and Ying-Chu Lin. "Umbilical Cord Blood-Derived Stem Cells Improve Heat Tolerance and Hypothalamic Damage in Heat Stressed Mice." BioMed Research International 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/685683.
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Heatstroke is characterized by excessive hyperthermia associated with systemic inflammatory responses, which leads to multiple organ failure, in which brain disorders predominate. This definition can be almost fulfilled by a mouse model of heatstroke used in the present study. Unanesthetized mice were exposed to whole body heating (41.2°C for 1 hour) and then returned to room temperature (26°C) for recovery. Immediately after termination of whole body heating, heated mice displayed excessive hyperthermia (body core temperature ~42.5°C). Four hours after termination of heat stress, heated mice displayed (i) systemic inflammation; (ii) ischemic, hypoxic, and oxidative damage to the hypothalamus; (iii) hypothalamo-pituitary-adrenocortical axis impairment (reflected by plasma levels of both adrenocorticotrophic-hormone and corticosterone); (iv) decreased fractional survival; and (v) thermoregulatory deficits (e.g., they became hypothermia when they were exposed to room temperature). These heatstroke reactions can be significantly attenuated by human umbilical cord blood-derived CD34+cells therapy. Our data suggest that human umbilical cord blood-derived stem cells therapy may improve outcomes of heatstroke in mice by reducing systemic inflammation as well as hypothalamo-pituitary-adrenocortical axis impairment.
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Joswiak, David J. "Height Measurement of Interplanetary Dust Particles by Scanning Transmission Electron Microscopy (STEM)." Microscopy Today 8, no. 6 (August 2000): 46–49. http://dx.doi.org/10.1017/s1551929500052883.
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Interplanetary dust particles (IDPs) comprise an important source of extraterrestrial materials available for study of our solar system and originate from either the asteroid belt or from short period comets. IDPs from cometary sources are particularly important as they constitute the only physical samples of comets available; all known meteorites are derived from the asteroids, the Moon or Mars. By measuring the densities of IDPs and using an appropriate atmospheric entry heating model, it is possible to determine whether an individual IDP has been derived from an asteraidal or cometary source region. Calculating the density of an IDP requires knowledge of both its mass and volume, which can be determined by using a combination of secondary and transmission electron microscopy techniques. We have developed methods to measure both of these parameters and thus routinely measure densities for individual IDPS in the size range of 5-15 μm.
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Giusti, Ruggero, and Giovanni Lucchetta. "Modeling the Adhesion Bonding Strength in Injection Overmolding of Polypropylene Parts." Polymers 12, no. 9 (September 10, 2020): 2063. http://dx.doi.org/10.3390/polym12092063.
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In this work, the bonding strength of overmolded polypropylene is investigated and modeled. A T-joint specimen was designed to replicate the bonding between a base and an overmolded stem made of the same polymer: a previously molded plaque was used for the base, and the stem was directly overmolded. The effect of melt temperature, holding pressure, and localized heating was investigated following the design of experiments approach. Both the melt and base temperature positively affect the welding strength. On the contrary, the holding pressure negatively contributed, as the crystallization temperature significantly increases with pressure. Then, the bonding strength of the specimens was predicted using a non-isothermal healing model. Moreover, the quadratic distance of diffusion (based on the self-diffusion model) was calculated and correlated with the bonding strength prediction. The non-isothermal healing model well predicts the bonding strength when the reptation time is calculated within the first 0.09 s of the interface temperature evolution. The prediction error ranges from 1% to 35% for the specimens overmolded at high and low melt and base temperatures, respectively.
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Chung, C. E., V. Ramanathan, G. Carmichael, S. Kulkarni, Y. Tang, B. Adhikary, L. R. Leung, and Y. Qian. "Anthropogenic aerosol radiative forcing in Asia derived from regional models with atmospheric and aerosol data assimilation." Atmospheric Chemistry and Physics 10, no. 13 (July 5, 2010): 6007–24. http://dx.doi.org/10.5194/acp-10-6007-2010.
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Abstract. An estimate of monthly 3-D aerosol solar heating rates and surface solar fluxes in Asia from 2001 to 2004 is described here. This product stems from an Asian aerosol assimilation project, in which a) the PNNL regional model bounded by the NCEP reanalyses was used to provide meteorology, b) MODIS and AERONET data were integrated for aerosol observations, c) the Iowa aerosol/chemistry model STEM-2K1 used the PNNL meteorology and assimilated aerosol observations, and d) 3-D (X-Y-Z) aerosol simulations from the STEM-2K1 were used in the Scripps Monte-Carlo Aerosol Cloud Radiation (MACR) model to produce total and anthropogenic aerosol direct solar forcing for average cloudy skies. The MACR model and STEM-2K1 both used the PNNL model resolution of 0.45°×0.4° in the horizontal and of 23 layers in the troposphere. The 2001–2004 averaged anthropogenic all-sky aerosol forcing is −1.3 Wm−2 (TOA), +7.3 Wm−2 (atmosphere) and −8.6 Wm−2 (surface) averaged in Asia (60–138° E and Equator–45° N). In the absence of AERONET SSA assimilation, absorbing aerosol concentration (especially BC aerosol) is much smaller, giving −2.3 Wm−2 (TOA), +4.5 Wm−2 (atmosphere) and −6.8 Wm−2 (surface), averaged in Asia. In the vertical, monthly forcing is mainly concentrated below 600 hPa with maximum around 800 hPa. Seasonally, low-level forcing is far larger in dry season than in wet season in South Asia, whereas the wet season forcing exceeds the dry season forcing in East Asia. The anthropogenic forcing in the present study is similar to that in Chung et al. (2005) in overall magnitude but the former offers fine-scale features and simulated vertical profiles. The interannual variability of the computed anthropogenic forcing is significant and extremely large over major emission outflow areas. Given the interannual variability, the present study's estimate is within the implicated range of the 1999 INDOEX result.
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Chung, C. E., V. Ramanathan, G. Carmichael, S. Kulkarni, Y. Tang, B. Adhikary, L. R. Leung, and Y. Qian. "Anthropogenic aerosol radiative forcing in Asia derived from regional models with atmospheric and aerosol data assimilation." Atmospheric Chemistry and Physics Discussions 10, no. 1 (January 15, 2010): 821–62. http://dx.doi.org/10.5194/acpd-10-821-2010.
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Abstract. A high-resolution estimate of monthly 3-D aerosol solar heating rates and surface solar fluxes in Asia from 2001 to 2004 is described here. This product stems from an Asian aerosol assimilation project, in which a) the PNNL regional model bounded by the NCEP reanalyses was used to provide meteorology, b) MODIS and AERONET data were integrated for aerosol observations, c) the Iowa aerosol/chemistry model STEM-2K1 used the PNNL meteorology and assimilated aerosol observations, and d) 3-D (X-Y-Z) aerosol simulations from the STEM-2K1 were used in the Scripps Monte-Carlo Aerosol Cloud Radiation (MACR) model to produce total and anthropogenic aerosol direct solar forcing for average cloudy skies. The MACR model and STEM both used the PNNL model resolution of 0.45°×0.4° in the horizontal and of 23 layers in the troposphere. The 2001–2004 averaged anthropogenic all-sky aerosol forcing is -1.3 W m-2 (TOA), +7.3 W m-2 (atmosphere) and -8.6 W m-2 (surface) averaged in Asia (60–138° E and Eq. -45° N). In the absence of AERONET SSA assimilation, absorbing aerosol concentration (especially BC aerosol) is much smaller, giving -2.3 W m-2 (TOA), +4.5 W m-2 (atmosphere) and -6.8 W mm-2 (surface), averaged in Asia. In the vertical, monthly forcing is mainly concentrated below 600 hPa with maxima around 800 hPa. Seasonally, low-level forcing is far larger in dry season than in wet season in South Asia, whereas the wet season forcing exceeds the dry season forcing in East Asia. The anthropogenic forcing in the present study is similar to that in Chung et al. (2005) in overall magnitude but the former offers fine-scale features and simulated vertical profiles. The interannual variability of the computed anthropogenic forcing is significant and extremely large over major emission outflow areas. Given the interannual variability, the present study's estimate is within the implicated range of the 1999 INDOEX result. However, NCAR/CCSM3's anthropogenic aerosol forcing is much smaller than the present study's estimate at the surface, and is outside of what the INDOEX findings can support.
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Shackel, Kenneth A., R. Scott Johnson, Charles K. Medawar, and Claude J. Phene. "Substantial Errors in Estimates of Sap Flow Using the Heat Balance Technique on Woody Stems under Field Conditions." Journal of the American Society for Horticultural Science 117, no. 2 (March 1992): 351–56. http://dx.doi.org/10.21273/jashs.117.2.351.
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The heat balance method was used to estimate transpirational sap flow through 60- to 75-mm-diameter stems (trunks) of 3-year-old peach [Prunus persica (L.) Batsch. cv. O'Henry] trees under field conditions. On rare occasions, heat balance estimates agreed well with independent lysimetric measurements, but on most occasions, heat balance estimates of sap flow were unrealistic in both direction and magnitude. In some cases, the errors in sap flow approached two orders of magnitude and were always the result of a calculation involving division by a very small and sometimes negative temperature differential between the stem surface temperature above and below the gauge heater. The occurrence of negative temperature differentials under positive transpiration conditions may be inconsistent with a fundamental assumption in the heat balance model, namely that temperature differentials are solely a consequence of the dissipation of energy supplied to the gauge heater. In the absence of heating power applied to the gauge, temperature differentials exceeding - 1C were correlated with the rate of change in stem temperature, indicating that ambient conditions themselves can impose a bias in gauge signals and, hence, influence gauge accuracy. Our results suggest that the effect of ambient conditions on gauge signals should be critically evaluated before considering heat balance estimates of sap flow as reliable under any given conditions.
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Bukowski, Jennie, and Susan C. van den Heever. "Convective distribution of dust over the Arabian Peninsula: the impact of model resolution." Atmospheric Chemistry and Physics 20, no. 5 (March 12, 2020): 2967–86. http://dx.doi.org/10.5194/acp-20-2967-2020.
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Abstract. Along the coasts of the Arabian Peninsula, convective dust storms are a considerable source of mineral dust to the atmosphere. Reliable predictions of convective dust events are necessary to determine their effects on air quality, visibility, and the radiation budget. In this study, the Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem) is used to simulate a 2016 summertime dust event over the Arabian Peninsula and examine the variability in dust fields and associated vertical transport due to the choice of convective parameterization and convection-permitting versus parameterized convection. Simulations are run at 45 and 15 km grid spacing with multiple cumulus parameterizations, and are compared to a 3 km simulation that permits explicit dry and moist convective processes. Five separate cumulus parameterizations at 15 km grid spacing were tested to quantify the spread across different parameterizations. Finally, the impact these variations have on radiation, specifically aerosol heating rates is also investigated. On average, in these simulations the convection-permitting case produces higher quantities of dust than the parameterized cases in terms of dust uplift potential, vertical dust concentrations, and vertical dust fluxes. Major drivers of this discrepancy between the simulations stem from the convection-permitting case exhibiting higher surface wind speeds during convective activity; lower dust emission wind threshold velocities due to drier soil; and more frequent, stronger vertical velocities which transport dust aloft and increase the atmospheric lifetime of these particles. For aerosol heating rates in the lowest levels, the shortwave effect prevails in the convection-permitting case with a net cooling effect, whereas a longwave net warming effect is present in the parameterized cases. The spread in dust concentrations across cumulus parameterizations at the same grid resolution (15 km) is an order of magnitude lower than the impact of moving from parameterized towards explicit convection. We conclude that tuning dust emissions in coarse-resolution simulations can only improve the results to first-order and cannot fully rectify the discrepancies originating from disparities in the representation of convective dust transport.
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Dickinson, M. B., J. Jolliff, and A. S. Bova. "Vascular cambium necrosis in forest fires: using hyperbolic temperature regimes to estimate parameters of a tissue-response model." Australian Journal of Botany 52, no. 6 (2004): 757. http://dx.doi.org/10.1071/bt03111.
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Hyperbolic temperature exposures (in which the rate of temperature rise increases with time) and an analytical solution to a rate-process model were used to characterise the impairment of respiration in samples containing both phloem (live bark) and vascular-cambium tissue during exposures to temperatures such as those experienced by the vascular cambium in tree stems heated by forest fires. Tissue impairment was characterised for red maple (Acer rubrum), chestnut oak (Quercus prinus), Douglas fir (Pseudotsuga menziesii), and ponderosa pine (Pinus ponderosa) samples. The estimated temperature dependence of the model’s rate parameter (described by the Arrhenius equation) was a function of the temperature regime to which tissues were exposed. Temperatures rising hyperbolically from near ambient (30°C) to 65°C produced rate parameters for the deciduous species that were similar at 60°C to those from the literature, estimated by using fixed temperature exposures. In contrast, samples from all species showed low rates of impairment, conifer samples more so than deciduous, after exposure to regimes in which temperatures rose hyperbolically between 50 and 60°C. A hypersensitive response could explain an early lag in tissue-impairment rates that apparently caused the differences among heating regimes. A simulation based on stem vascular-cambium temperature regimes measured during fires shows how temperature-dependent impairment rates can be used to predict tissue necrosis in fires. To our knowledge, hyperbolic temperature exposures have not been used to characterise plant tissue thermal tolerance and, given certain caveats, could provide more realistic data more efficiently than fixed-temperature exposures.
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Sari, Fahriya Puspita, Dede Heri Yuli Yanto, and Gustan Pari. "Activated Carbon Derived From OPEFB by One Step Steam Activation and Its Application for Dye Adsorption : Kinetics and Isothermal Studies." Reaktor 19, no. 2 (August 11, 2019): 68–76. http://dx.doi.org/10.14710/reaktor.19.2.68-76.
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Activated carbon was prepared from OPEFB by one step steam activation method. The adsorption performance for the removal of acid orange 52 (AO 52), reactive blue 19 (RB 19), basic violet 1 (BV 1) was investigated. Each dye has a different chemical structure such as azoic, anthraquinone, triarylmethane for AO 52, RB 19, and BV 1 respectively. The effects of adsorbent dosage, pH, and contact time on the adsorption process were studied. Experimental data were analyzed by model equations such as Langmuir, Freundlich and Temkin isotherms and it was found that the Langmuir isotherm model best fitted for all three dyes with R2 values is higher than 0.95. Langmuir model assumes a homogeneous nature and monolayer coverage of dye molecules at the outer surface of activated carbon. Adsorption kinetics was determined using pseudo-first-order, pseudo-second-order rate equations, Elovich model and also intraparticle diffusion models. Kinetic studies showed that the pseudo-second-order kinetic model better described the adsorption process with R2 values exceeds 0,99 compared with the other kinetics model. The SEM images showed AC pores was well developed with steam activation while wider porosity is created in the macropore range. FT-IR analysis had shown that the AC functional groups were disappeared because of vaporization the volatile materials when the heating process. Keywords: Activated Carbon, Adsorption Isotherms, Kinetic, OPEFB, Steam Activation
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Räisänen, P., H. W. Barker, and J. N. S. Cole. "The Monte Carlo Independent Column Approximation’s Conditional Random Noise: Impact on Simulated Climate." Journal of Climate 18, no. 22 (November 15, 2005): 4715–30. http://dx.doi.org/10.1175/jcli3556.1.
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Abstract The Monte Carlo Independent Column Approximation (McICA) method for computing domain-average radiative fluxes is unbiased with respect to the full ICA, but its flux estimates contain conditional random noise. Results for five experiments are used to assess the impact of McICA-related noise on simulations of global climate made by the NCAR Community Atmosphere Model (CAM). The experiment with the least noise (an order of magnitude below that of basic McICA) is taken as the reference. Two additional experiments help demonstrate how the impact of noise depends on the time interval between calls to the radiation code. Each experiment is an ensemble of seven 15-month simulations. Experiments with very high noise levels feature significant reductions to cloudiness in the lowermost model layer over tropical oceans as well as changes in highly related quantities. This bias appears immediately, stabilizes after a couple of model days, and appears to stem from nonlinear interactions between clouds and radiative heating. Outside the Tropics, insignificant differences prevail. When McICA sampling is confined to cloudy subcolumns and when, on average, 50% more samples, relative to basic McICA, are drawn for selected spectral intervals, McICA noise is much reduced and the results of the simulation are almost statistically indistinguishable from the reference. This is true both for mean fields and for the nature of fluctuations on scales ranging from 1 day to at least 30 days. While calling the radiation code once every 3 h instead of every hour allows the CAM additional time to incorporate McICA-related noise, the impact of noise is enhanced only slightly. In contrast, changing the radiative time step by itself produces effects that generally exceed the impact of McICA’s noise.
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Fuse, Hiraku, Tatsuya Fujisaki, Shinji Abe, Kenji Yasue, and Satoshi Oyama. "Quantifying temperature-equilibrium time using temperature analysis inside a Farmer ionization chamber." Journal of Radiation Research 61, no. 5 (July 13, 2020): 712–17. http://dx.doi.org/10.1093/jrr/rraa045.
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Abstract In this study, we propose a methodology for temperature determination of the temperature and pressure correction factor, PTP, by analyzing the temperature distribution of the modeled ionization chamber taking into account the thermal effect of a water phantom on neighboring materials in the process. Additionally, we present an appropriate temperature-equilibrium time for conducting measurements. The temporal response in the cavity is acquired at 20-s intervals using a Farmer ionization chamber and an electrometer. The initial temperature of the water phantom is 20–25°C with continuous heating/cooling. The temporal response is measured until temperature equilibrium is confirmed, specifically when a temperature difference of 1–5°C is observed between the ionization chamber and the water phantom. Using an ionization-chamber model, temperature distribution is simulated between 20 and 25°C with various parameters set to receive heating and cooling from surrounding media. The results suggest that the temporal response of the ionization chamber essentially coincides with the temperature change at the tip and middle; moreover, the predicted temperature change for temporal response and the simulated temperature of water are different by ~0.16°C at the tip and ~0.79°C at the bottom. Overall, the temperature-equilibration time for absorbed dosimetry is affected by two factors: the cavity wall and the stem side of the cavity; moreover, 400 s is required to obtain complete temperature equilibrium in the water phantom. This analytical study supports the experimental value obtained in previous research. Therefore, analytical representation of the temperature distribution in the ionization chamber is possible.
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Showkat, Muhammad Mir, Anne Bergljot Falck-Ytter, and Knut Olav Strætkvern. "Phenolic Acids in Jerusalem Artichoke (Helianthus tuberosus L.): Plant Organ Dependent Antioxidant Activity and Optimized Extraction from Leaves." Molecules 24, no. 18 (September 10, 2019): 3296. http://dx.doi.org/10.3390/molecules24183296.
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Phenolic acids including chlorogenic acids are major polyphenolic compounds found in Jerusalem artichoke (Helianthus tuberosus L.). The plant itself is an emerging biorefinery crop due to the inulin-rich tubers, a bioethanol feedstock, but the aerial parts represent a rich source of bioactive compounds. We have determined the level of major phenolic acids in extracts of four plant organs: tuber, leaf, flower, and stem. Employing three heating conditions (20 °C, 60 °C, and microwaving), corrected total phenolic content (TPC) was highest in the leaves (4.5–5.7 mg gallic acid equivalents g−1 dry substance), followed by flower (2.1–2.9), tuber (0.9–1.4), and lowest in stem extracts (0.1–0.2). A previously overlooked interference of the Folin–Ciocalteu assay, namely a signal contribution from ascorbic acid, caused overestimation of TPC in various organs ranging from 65% to 94%. Radical scavenging activity of extracts correlated significantly with TPC, both on corrected (R2 = 0.841) and uncorrected (R2 = 0.884) values. Out of the identified phenolic acids determined by quantitative HPLC-UV analysis, chlorogenic and dicaffeoylquinic acids accounted for 72–82% of corrected TPC in leaf and tuber extracts. Optimization of leaf extraction was tested in a 23-factorial Central Composite Face (CCF) design. Temperature was the most important model term, and a solvent strength of less than 50% ethanol promoted the highest TPC yields. Further developments in extraction processing of crop residues may open avenues for improving the utilization of Jerusalem artichoke in valuable products.
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Tum, M., M. Buchhorn, K. P. Günther, and B. C. Haller. "Validation of modelled forest biomass in Germany using BETHY/DLR." Geoscientific Model Development Discussions 4, no. 3 (July 26, 2011): 1685–722. http://dx.doi.org/10.5194/gmdd-4-1685-2011.
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Abstract. We present a new approach to the validation of modelled forest Net Primary Productivity (NPP), using empirical data on the mean annual increment, or MAI, in above-ground forest stock. The dynamic biomass model BETHY/DLR is used to estimate the NPP of forest areas in Germany, driven by remote sensing data from VEGETATION, meteorological data from the European Centre for Medium-Range Weather Forecasts (ECMWF), and additional tree coverage information from the MODIS Vegetation Continuous Field (VCF). The output of BETHY/DLR, Gross Primary Productivity (GPP), is converted to NPP by subtracting the cumulative plant maintenance and growth respiration, and then validated against MAI data derived from German forestry inventories. Validation is conducted for 2000 and 2001 by converting modelled NPP to stem volume at a regional level. Our analysis shows that the presented method fills an important gap in methods for validating modelled NPP against empirically derived data. In addition, we examine theoretical energy potentials calculated from the modelled and validated NPP, assuming sustainable forest management and using species-specific tree heating values. Such estimated forest biomass energy potentials play an important role in the sustainable energy debate.
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Mäki, Antti-Juhana, Jarmo Verho, Joose Kreutzer, Tomi Ryynänen, Dhanesh Rajan, Mari Pekkanen-Mattila, Antti Ahola, et al. "A Portable Microscale Cell Culture System with Indirect Temperature Control." SLAS TECHNOLOGY: Translating Life Sciences Innovation 23, no. 6 (May 3, 2018): 566–79. http://dx.doi.org/10.1177/2472630318768710.
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A physiologically relevant environment is essential for successful long-term cell culturing in vitro. Precise control of temperature, one of the most crucial environmental parameters in cell cultures, increases the fidelity and repeatability of the experiments. Unfortunately, direct temperature measurement can interfere with the cultures or prevent imaging of the cells. Furthermore, the assessment of dynamic temperature variations in the cell culture area is challenging with the methods traditionally used for measuring temperature in cell culture systems. To overcome these challenges, we integrated a microscale cell culture environment together with live-cell imaging and a precise local temperature control that is based on an indirect measurement. The control method uses a remote temperature measurement and a mathematical model for estimating temperature at the desired area. The system maintained the temperature at 37±0.3 °C for more than 4 days. We also showed that the system precisely controls the culture temperature during temperature transients and compensates for the disturbance when changing the cell cultivation medium, and presented the portability of the heating system. Finally, we demonstrated a successful long-term culturing of human induced stem cell–derived beating cardiomyocytes, and analyzed their beating rates at different temperatures.
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Tum, M., M. Buchhorn, K. P. Günther, and B. C. Haller. "Validation of modelled forest biomass in Germany using BETHY/DLR." Geoscientific Model Development 4, no. 4 (November 18, 2011): 1019–34. http://dx.doi.org/10.5194/gmd-4-1019-2011.
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Abstract. We present a new approach to the validation of modelled forest Net Primary Productivity (NPP), using empirical data on the mean annual increment, or MAI, in above-ground forest stock. The soil-vegetation-atmosphere-transfer model BETHY/DLR is used, with a particular focus on a detailed parameterization of photosynthesis, to estimate the NPP of forest areas in Germany, driven by remote sensing data from VEGETATION, meteorological data from the European Centre for Medium-Range Weather Forecasts (ECMWF), and additional tree coverage information from the MODIS Vegetation Continuous Field (VCF). The output of BETHY/DLR, Gross Primary Productivity (GPP), is converted to NPP by subtracting the cumulative plant maintenance and growth respiration, and then validated against MAI data that was calculated from German forestry inventories. Validation is conducted for 2000 and 2001 by converting modelled NPP to stem volume at a regional level. Our analysis shows that the presented method fills an important gap in methods for validating modelled NPP against empirically derived data. In addition, we examine theoretical energy potentials calculated from the modelled and validated NPP, assuming sustainable forest management and using species-specific tree heating values. Such estimated forest biomass energy potentials play an important role in the sustainable energy debate.
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Zhang, H., X. Jing, and J. Li. "Application and evaluation of a new radiation code under McICA scheme in BCC_AGCM2.0.1." Geoscientific Model Development 7, no. 3 (May 6, 2014): 737–54. http://dx.doi.org/10.5194/gmd-7-737-2014.
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Abstract. This research incorporates the correlated k distribution BCC-RAD radiation model into the climate model BCC_AGCM2.0.1 and examines the change in climate simulation by implementation of the new radiation algorithm. It is shown that both clear-sky radiation fluxes and cloud radiative forcings (CRFs) are improved. The modeled atmospheric temperature and specific humidity are also improved due to changes in radiative heating rates, which most likely stem from the revised treatment of gaseous absorption. Subgrid cloud variability, including vertical overlap of fractional clouds and horizontal inhomogeneity in cloud condensate, is addressed by using the Monte Carlo Independent Column Approximation (McICA) method. In McICA, a cloud-type-dependent function for cloud fraction decorrelation length, which gives zonal mean results very close to the observations of CloudSat/CALIPSO, is developed. Compared to utilizing a globally constant decorrelation length, the maximum changes in seasonal CRFs by the new scheme can be as large as 10 and 20 W m−2 for longwave (LW) and shortwave (SW) CRFs, respectively, mostly located in the tropics. The inclusion of an observation-based horizontal inhomogeneity of cloud condensate has also a significant impact on CRFs, with global means of ~ 1.5 W m−2 and ~ 3.7 Wm−2 for LW and SW CRFs at the top of atmosphere (TOA), respectively. Generally, incorporating McICA and horizontal inhomogeneity of cloud condensate in the BCC-RAD model reduces global mean TOA and surface SW and LW flux biases in BCC_AGCM2.0.1. These results demonstrate the feasibility of the new model configuration to be used in BCC_AGCM2.0.1 for climate simulations, and also indicate that more detailed real-world information on cloud structures should be obtained to constrain cloud settings in McICA in the future.
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Lehotová, Veronika, Karla Miháliková, Alžbeta Medveďová, and Ľubomír Valík. "Modelling the inactivation of Staphylococcus aureusat moderate heating temperatures." Czech Journal of Food Sciences 39, No. 1 (February 26, 2021): 42–48. http://dx.doi.org/10.17221/201/2020-cjfs.
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The survival of bacterial contaminants at moderate processing temperatures is of interest to many food producers, especially in terms of the safety and quality of the final products. That is why the heat resistance of Staphylococcus aureus 2064, an isolate from artisanal Slovakian cheese, was studied in the moderate temperature range (57–61 °C) by the capillary method. The fourth decimal reduction time t<sub>4D</sub>- and z-values were estimated in two steps by traditional log-linear Bigelow and non-linear Weibull models. In addition, a one-step fitting procedure using the Weibull model was also applied. All the approaches provided comparable t<sub>4D</sub>-values resulting in the following z-values of 11.8 °C, 12.3 °C and 11.3 °C, respectively. Moreover, the one-step approach takes all the primary data into z-value calculation at once, thus providing a more representative output at the reasonable high coefficient of determination R<sub>2</sub> = 0.961
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Kulkarni, M., T. Borse, and S. Chaphalkar. "Mining anatomical traits: a novel modelling approach for increased water use efficiency under drought conditions in plants." Czech Journal of Genetics and Plant Breeding 44, No. 1 (March 28, 2008): 11–21. http://dx.doi.org/10.17221/1330-cjgpb.
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Crop yields are reduced by 70–80% due to a water stress situation specifically during the reproductive stage and are not able to fulfil the needs of food requirement in developed and developing countries of the world. Earlier work was mainly focused on the use of morphological or physiological and molecular aspects for improved stress tolerance. Efforts are being made to overcome this problem with the help of today’s sophisticated and advanced technology through genomics, proteomics and metabolomics. The presented model summarizes our work in the last five years to mine anatomical parameters as a novel approach to further improving introgression or exploitation of stress adaptive traits. We have focused on some key anatomical traits playing a substantial role in water stress tolerance. This new conceptual model encompasses increased palisade mesophyll height, higher leaf strength index (LSI), higher number of conducting tissues with increased diameter in leaf, stem and root and controlled transpiration rate due to a lower number of stomata per unit leaf area along with the increased guard cell size. Different plants viz. Lycopersicon esculentum, Capsicum annuum, and Calotropis gigantea were screened by developing polyploids to validate this model approach. Genotypes of Vitis vinifera and Solanum melongena were also screened. Wild relatives like Lycopersicon esculentum var. cerasiforme and Solanum khasianum were evaluated for comparison. These observations were further correlated with various stress adaptation traits like yield under stress, in vitro screening, chlorophyll content, transpiration heating and cooling, molecular markers etc. A new scoring method is proposed which will be helpful to screen a large set of germplasms on a preliminary basis to discriminate genotypes for drought tolerance. There is an urgent need to study the genetics of these stress adaptive traits using high throughput molecular markers to make them more useful for a higher magnitude of genetic gain.
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Weller, Robert A., Sudip Majumder, and Amit Tandon. "Diurnal Restratification Events in the Southeast Pacific Trade Wind Regime." Journal of Physical Oceanography 44, no. 9 (September 1, 2014): 2569–87. http://dx.doi.org/10.1175/jpo-d-14-0026.1.
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Abstract This paper describes the occurrence of diurnal restratification events found in the southeast trade wind regime off northern Chile. This is a region where persistent marine stratus clouds are found and where there is a less than complete understanding of the dynamics that govern the maintenance of the sea surface temperature. A surface mooring deployed in the region provides surface meteorological, air–sea flux, and upper-ocean temperature, salinity, and velocity data. In the presence of steady southeast trade winds and strong evaporation, a warm, salty surface mixed layer is found in the upper ocean. During the year, these trade winds, at times, drop dramatically and surface heating leads to the formation of shallow, warm diurnal mixed layers over one to several days. At the end of such a low wind period, mean sea surface temperature is warmer. Though magnitudes of the individual diurnal warming events are consistent with local forcing, as judged by running a one-dimensional model, the net warming at the end of a low wind event is more difficult to predict. This is found to stem from differences between the observed and predicted near-inertial shear and the depths over which the warmed water is distributed. As a result, the evolution of SST has a dependency on these diurnal restratification events and on near-surface processes that govern the depth over which the heat gained during such events is distributed.
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Li, Qi, and Mei Li. "Modeling of Heat Network Heating Process." Applied Mechanics and Materials 325-326 (June 2013): 1253–57. http://dx.doi.org/10.4028/www.scientific.net/amm.325-326.1253.
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District heating process is a complicated dynamic and thermal nonlinear system. For controlling it the system model should be found firstly. Through the research and analysis of the knowledge about heating system, this paper on the basis of mechanism model, researched the establishment of experimental models. Firstly by measuring the response data, the model parameter identification of the heating process can be made to got the heating determining part model, then random part of the system model can be described by the method of Autoregressive Integrated Moving Average Model. Finally using the MATLAB to simulate and make the model step response curve analysis. Simulation results show the model is effective and verified.
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Xu, Dandan, Ling Zhu, Robert Grand, Volker Springel, Shude Mao, Glenn van de Ven, Shengdong Lu, et al. "A study of stellar orbit fractions: simulated IllustrisTNG galaxies compared to CALIFA observations." Monthly Notices of the Royal Astronomical Society 489, no. 1 (August 19, 2019): 842–54. http://dx.doi.org/10.1093/mnras/stz2164.
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ABSTRACT Motivated by the recently discovered kinematic ‘Hubble sequence’ shown by the stellar orbit-circularity distribution of 260 CALIFA galaxies, we make use of a comparable galaxy sample at z = 0 with a stellar mass range of $M_{*}/\mathrm{M}_{\odot }\in [10^{9.7},\, 10^{11.4}]$ selected from the IllustrisTNG simulation and study their stellar orbit compositions in relation to a number of other fundamental galaxy properties. We find that the TNG100 simulation broadly reproduces the observed fractions of different orbital components and their stellar mass dependences. In particular, the mean mass dependences of the luminosity fractions for the kinematically warm and hot orbits are well reproduced within model uncertainties of the observed galaxies. The simulation also largely reproduces the observed peak and trough features at $M_{*}\approx 1\rm {-}2\times 10^{10}\, \mathrm{M}_{\odot }$ in the mean distributions of the cold- and hot-orbit fractions, respectively, indicating fewer cooler orbits and more hotter orbits in both more- and less-massive galaxies beyond such a mass range. Several marginal disagreements are seen between the simulation and observations: the average cold-orbit (counter-rotating) fractions of the simulated galaxies below (above) $M_{*}\approx 6\times 10^{10}\, \mathrm{M}_{\odot }$ are systematically higher than the observational data by $\lesssim 10{{\ \rm per\ cent}}$ (absolute orbital fraction); the simulation also seems to produce more scatter for the cold-orbit fraction and less so for the non-cold orbits at any given galaxy mass. Possible causes that stem from the adopted heating mechanisms are discussed.
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Saimon, Nur Nazlina, Norzita Ngadi, Mazura Jusoh, and Zaki Yamani Zakaria. "A Two-Step SO3H/ICG Catalyst Synthesis for Biodiesel Production: Optimization of Sulfonation Step via Microwave Irradiation." Bulletin of Chemical Reaction Engineering & Catalysis 16, no. 1 (January 24, 2021): 63–75. http://dx.doi.org/10.9767/bcrec.16.1.9613.63-75.
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Conventional heating, a common method used for heterogeneous solid acid catalyst synthesis unknowingly consumes massive time and energy. In this study, acid catalyst was prepared through sulfonation process of incomplete carbonized glucose (ICG) via microwave-assisted technique to shorten the heating time and energy consumption. Optimization of the sulfonation process of ICG via microwave-assisted was carried out. Four-factor-three-level central composite design (CCD) was used to develop the design of experiments (DOE). Interaction between two factors was evaluated to determine the optimum process conditions. A quadratic model was proposed for prediction of biodiesel yield (Y) from palm fatty acid distillate (PFAD) and its conversion (C). The application of DOE successfully optimized the operating conditions for the two-step SO3H/ICG catalyst synthesis to be used for the esterification process. The optimized conditions of the best performing SO3H/ICG with maximum Y and C were at 7.5 minutes of reaction time, 159.5 mL of H2SO4 used, 671 rpm of stirring rate as well as 413.64 watt of power level. At these optimum conditions the predicted yield percentage and conversion percentage were 94.01% and 91.89%, respectively, which experimentally verified the accuracy of the model. The utilization of sulfonated glucose solid acid catalyst via microwave-assisted in biodiesel production has great potential towards sustainable and green method of synthesizing catalyst for biodiesel. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
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Genovski, Ivan, and Kaloyan Hristov. "Model research of the energy efficiency of a cogeneration backpressure steam turbine installation." E3S Web of Conferences 207 (2020): 02004. http://dx.doi.org/10.1051/e3sconf/202020702004.
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In the contemporary district heating systems (DHS) heat energy for the customers is generated by cogeneration method, which leads to the saving of primary energy resources compared to the separate production method. The most widespread technology for combined production is based on steam turbine installations with adjustable steam extraction and backpressure steam turbine. In these technologies district heating water is heated to the required temperature either in district heaters in case of steam turbine with adjustable steam extractions or in boiler-condenser in case of backpressure steam turbine installations. The temperature of the district heat water at the inlet of the CHP installation depends on the mode of operation of the DHS. The heat load, distributed to consumers, is regulated at the heat source (CHP installation) by temperature and flow rate of the district heating water, mainly following the change in climatic factors. Current study presents the development of a simulation model of existing CHP backpressure steam turbine. The object studied is a backpressure steam turbine type SST-300 CE2L/V36S. Presented are results from the validation of the simulated model with data from the design documentation. The model has been used to study the energy efficiency of a steam turbine installation based on multivariate simulation calculations. The results obtained relate the energy efficiency indicators of CHP backpressure steam turbine with the factors that characterize the mode of operation of the district heating system.
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Nowicki, Lech, Dorota Siuta, and Maciej Markowski. "Pyrolysis of Rapeseed Oil Press Cake and Steam Gasification of Solid Residues." Energies 13, no. 17 (August 31, 2020): 4472. http://dx.doi.org/10.3390/en13174472.
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A deoiled rapeseed press cake (RPC) was pyrolyzed by heating at a slow heating rate to 1000 °C in a fixed bed reactor, and the produced char was then gasified to obtain data for the kinetic modeling of the process. The gasification experiments were performed in a thermogravimetric analyzer (TGA) under steam/argon mixtures at different temperatures (750, 800 and 850 °C) and steam mole fractions (0.17 and 0.45). The three most commonly used gas-solid kinetic models, the random pore model, the volumetric model and the shrinking core model were used to describe the conversion of char during steam gasification. The objective of the kinetic study was to determine the kinetic parameters and to assess the ability of the models to predict the RPC conversion during steam gasification. A TGA-MS analysis was applied to assess the composition of the product gas. The main steam gasification product of the RPC was hydrogen (approximately 60 mol % of the total product). The volumetric model was able to accurately predict the behavior of the RPC char gasification with steam at temperatures of 750–850 °C and steam concentrations less than 0.45 mole fraction. The activation energy and the reaction order with respect to steam were equal to 166 kJ/mol and 0.5, respectively, and were typical values for the gasification of biomass chars with steam
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Zhao, Ning, Xiaoying Fan, Lite Ji, and Ya-mi Chen. "The analysis and research on variable operating condition of exhaust steam and waste heat Cascade utilization system of air cooling heating unit." E3S Web of Conferences 136 (2019): 01002. http://dx.doi.org/10.1051/e3sconf/201913601002.
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The series and parallel exhaust heat cascade utilization system was adopted by the large direct air cooling heating units. On the one hand, this system could reduce the adverse impact on power generation; on the other hand, it could reduce the temperature difference of heat transfer through step by step heating, the irreversible loss could be reduced, and the energy utilization efficiency could be made higher. On the basis of grasping the design performance of exhaust steam utilization system and the variable operating performance of main equipment by analysing the data of typical operating conditions, the optimization analysis model of heat pump group and the whole plant was established by this paper. The performance of heat pump unit under variable operating conditions was analysed and calculated, the influence of different exhaust pressure and backwater temperature on the economy of the whole machine was analysed, and the optimal operation mode of the heat pump was obtained. Finally, the pumping and condensing ratio curves under different conditions of winter heating conditions were determined, which could guide the optimal operation of heat pump units. It also provided technical support and basis for deep peak regulation or flexible transformation of heating units.
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Kang, Wen Jin, and De Qi Peng. "Design of Steam Heated Drying Line-Finned Tubes." Advanced Materials Research 926-930 (May 2014): 1293–96. http://dx.doi.org/10.4028/www.scientific.net/amr.926-930.1293.
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This article describes how to build an efficient steam heating system heat warped tube models. And steam heating fin tube geometry was optimized in this paper. Steam heating for drying is very important to enhance heat pipe heat transfer system..
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Reid, J., P. J. Cargill, C. D. Johnston, and A. W. Hood. "Linking computational models to follow the evolution of heated coronal plasma." Monthly Notices of the Royal Astronomical Society 505, no. 3 (May 4, 2021): 4141–50. http://dx.doi.org/10.1093/mnras/stab1255.
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ABSTRACT A ‘proof of principle’ is presented, whereby the Ohmic and viscous heating determined by a three-dimensional (3D) MHD model of a coronal avalanche are used as the coronal heating input for a series of field-aligned, one-dimensional (1D) hydrodynamic models. Three-dimensional coronal MHD models require large computational resources. For current numerical parameters, it is difficult to model both the magnetic field evolution and the energy transport along field lines for coronal temperatures much hotter than $1\, \mathrm{MK}$, because of severe constraints on the time step from parallel thermal conduction. Using the 3D MHD heating derived from a simulation and evaluated on a single field line, the 1D models give coronal temperatures of $1\, \mathrm{MK}$ and densities $10^{14}\textrm {--}10^{15}\, \mathrm{m}^{-3}$ for a coronal loop length of $80\, \mathrm{Mm}$. While the temperatures and densities vary smoothly along the field lines, the heating function leads to strong asymmetries in the plasma flows. The magnitudes of the velocities in the 1D model are comparable with those seen in 3D reconnection jets in our earlier work. Advantages and drawbacks of this approach for coronal modelling are discussed.
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Yuan, Han, Francesco Restuccia, and Guillermo Rein. "Spontaneous ignition of soils: a multi-step reaction scheme to simulate self-heating ignition of smouldering peat fires." International Journal of Wildland Fire 30, no. 6 (2021): 440. http://dx.doi.org/10.1071/wf19128.
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As organic porous soil, peat is prone to self-heating ignition, a type of spontaneous initiation of fire that can take place at ambient temperatures without an external source. Despite the urgency to tackle peat fires, the understanding of the self-heating ignition of peat is insufficient. In this study, a computational model that integrates the mechanisms of heat transfer, mass transfer and chemistry is incorporated with a three-step reaction scheme that includes drying, biological reaction and oxidative oxidation to simulate the self-heating ignition of smouldering peat. The model is first validated against 13 laboratory-scale experiments from literature. For critical ignition temperature (Tig), the model gives accurate predictions for all experiments with a maximum error of 5°C. The validated model is then upscaled to predict Tig for field-size peat soil layers and compared with the predictions using a one-step scheme. The three-step scheme is shown to give more reliable predictions of Tig than the one-step scheme. According to the simulation results, for a 1.5-m-deep peat layer, self-heating ignition can occur at an average ambient temperature above 40°C. This is the first time that a multi-step scheme is used to simulate the self-heating ignition of peat, aiming to help in the prevention and mitigation of these wildfires.
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Bova, A. S., and M. B. Dickinson. "Linking surface-fire behavior, stem heating, and tissue necrosis." Canadian Journal of Forest Research 35, no. 4 (April 1, 2005): 814–22. http://dx.doi.org/10.1139/x05-004.
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Data from 69 experimental, small-plot fires are used to describe relationships among fire intensity, bark-surface heat flux, and depth of necrosis in stem tissue for red maple (Acer rubrum L.) and chestnut oak (Quercus prinus L.). A tetrazolium staining technique was used to determine the depth of necrosis in tree boles subjected to fires with intensities of 20 to 2000 kW/m. Over a range of bark moistures (28%83%) and bole diameters (320 cm), depth of necrosis appears to be primarily a function of fire intensity, flame residence time at the stem, and the corresponding time-integrated heat flux at the bark surface. Our results, along with known relations between bole diameter and bark thickness, and improved models of fire behavior and heat transfer, may be useful for estimating tree mortality resulting from prescribed fires.
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Diniz, Hélio A. G., Tiago F. Paulino, Juan J. G. Pabon, Antônio A. T. Maia, and Raphael N. Oliveira. "Dynamic Model of a Transcritical CO2 Heat Pump for Residential Water Heating." Sustainability 13, no. 6 (March 21, 2021): 3464. http://dx.doi.org/10.3390/su13063464.
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This paper presents a distributed mathematical model for a carbon dioxide direct expansion solar-assisted heat pump used to heat bath water. The main components are a gas cooler, a needle valve, an evaporator/collector, and a compressor. To develop the heat exchange models, mass, energy, and momentum balances were used. The model was validated for transient as well as steady state conditions using experimental data. A reasonably good agreement was observed between the predicted temperatures and experimental data. The simulations showed that the time step required to demonstrate the behavior of the heat pump in the transient regime is greater than the time step required for the steady state. The results obtained with the mathematical model revealed that a reduction in the water mass flow rate results in an increase in the water outlet temperature. In addition, when the carbon dioxide mass flow rate is reduced, the compressor inlet and outlet temperatures increase as well as the water outlet temperature.
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Tarazona-Romero, Brayan Eduardo, Álvaro Campos-Celador, Yecid Alfonso Muñoz-Maldonado, Camilo Leonardo Sandoval-Rodríguez, and Javier Gonzalo Ascanio-Villabona. "Prototype of lineal solar collector Fresnel." Visión electrónica 14, no. 1 (January 31, 2020): 35–42. http://dx.doi.org/10.14483/22484728.16013.
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The development of a prototype linear solar collector Type Fresnel, has a purpose the use of direct solar heat radiation for water heating and/or steam production, as an alternative to supply conventional water heating systems or steam generators, which consume energy from fossil fuels.
For the development of the system, used the solar radiation of the UTS, located in Bucaramanga, Colombia, is identify the mathematical models to perform the sizing, then materials based on technical specifications and availability in Colombia, in order to perform the assembly and field tests, measuring the ambient and in the collector temperature to determine the efficiency of the model.
It should be noted that, the model presented does not have a control system for flow, temperature, pressure and level, it has no solar tracking of any kind; Its movement was done manually with each reflex. Finally, the model does not have a hydraulic system forced, and has a preheater at the entry of the concentration point.
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Maljkovic, Danica. "Modelling Influential Factors of Consumption in Buildings Connected to District Heating Systems." Energies 12, no. 4 (February 13, 2019): 586. http://dx.doi.org/10.3390/en12040586.
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Assessing the influential factors on measured (or allocated) heat consumption in district heating systems is often limited by the available data. Within a project of modelling consumption in district heating systems in Croatia for the Ministry of Environmental Protection and Environment, an access to a complete billing database of the largest Croatian district heating company was granted. The company supplies approximately 126,400 final consumers (both households and businesses) over 375 km of distribution network. The billing database has 40 vectors in a few million single inputs. In addition to these data, a questionnaire is distributed to the final consumers in several buildings labelled as “model buildings”, gathering behavioural and demographic data of final consumers (such as occupancy, mode of space usage, heat comfort level, age of occupants, etc.). The two sets of data are then merged, and a correlation analysis is performed. Furthermore, a two-step regression analysis is performed based on variables from billing database in the first step, with added behavioural and demographic variables obtained from the questionnaires in the second step. The models from two steps are compared, tested and interpreted. Results of the most influential factors on heat consumption in district heating systems are given and the influence of the behavioural/demographic variables on the prediction accuracy of heating consumption is interpreted.
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Jin, Hui, Hai Xia Guo, Guo Zhong Cao, and Sai Na Wei. "Function Innovation Design Model and its Application in Heating Equipment." Applied Mechanics and Materials 401-403 (September 2013): 371–74. http://dx.doi.org/10.4028/www.scientific.net/amm.401-403.371.
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Function design is an important step in the process of product design. This article mainly focuses on process and realization of product function innovation. Function innovation and forecasting method is presented, and the product function innovation process model is proposed. Finally, the heating equipment is taken as an example to validate the effectiveness of the model.
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Brkic, Dejan. "Natural gas heating in Serbian settlements according to urbanity parameters." Facta universitatis - series: Architecture and Civil Engineering 6, no. 1 (2008): 139–53. http://dx.doi.org/10.2298/fuace0801139b.
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Natural gas can be directly used for heating of flats by gas distribution system. Indirectly, heating power plant can disburse natural gas and deliver hot water or steam for heating of flats. Decision of optimal way for gas heating usage is done based on spatial disposal of building, number and size of buildings in settlement, etc. Optimal solution, between gas distribution and district heating system (local or district heating by natural gas), can be done according to methodology (model approach) shown in this paper. According to variety of Serbian settlements (in density, size and layout of buildings) model which has ability to represent their different characteristics is formed. This model could be simple and useful tool for initial decision about energy supply system.
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Zoder, Marius, Janosch Balke, Mathias Hofmann, and George Tsatsaronis. "Simulation and Exergy Analysis of Energy Conversion Processes Using a Free and Open-Source Framework—Python-Based Object-Oriented Programming for Gas- and Steam Turbine Cycles." Energies 11, no. 10 (September 30, 2018): 2609. http://dx.doi.org/10.3390/en11102609.
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State-of-the-art thermodynamic simulation of energy conversion processes requires proprietary software. This article is an attempt to refute this statement. Based on object-oriented programming a simulation and exergy analysis of a combined cycle gas turbine is carried out in a free and open-source framework. Relevant basics of a thermodynamic analysis with exergy-based methods and necessary fluid property models are explained. Thermodynamic models describe the component groups of a combined heat and power system. The procedure to transform a physical model into a Python-based simulation program is shown. The article contains a solving algorithm for a precise gas turbine model with sophisticated equations of state. As an example, a system analysis of a combined cycle gas turbine with district heating is presented. Herein, the gas turbine model is validated based on literature data. The exergy analysis identifies the thermodynamic inefficiencies. The results are graphically presented in a Grassmann chart. With a sensitivity analysis a thermodynamic optimization of the district heating system is discussed. Using the exergy destruction rate in heating condensers or the overall efficiency as the objective function yields to different results.
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Kulkarni, S., N. Sobhani, J. P. Miller-Schulze, M. M. Shafer, J. J. Schauer, P. A. Solomon, P. E. Saide, et al. "Source sector and region contributions to BC and PM<sub>2.5</sub> in Central Asia." Atmospheric Chemistry and Physics Discussions 14, no. 8 (May 7, 2014): 11343–92. http://dx.doi.org/10.5194/acpd-14-11343-2014.
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Abstract. Particulate matter (PM) mass concentrations, seasonal cycles, source sector and source region contributions in Central Asia (CA) are analyzed for the period April 2008–July 2009 using the Sulfur Transport and dEposition Model (STEM) chemical transport model and modeled meteorology from the Weather Research and Forecasting (WRF) model. Predicted Aerosol Optical Depth (AOD) values (annual mean value ∼0.2) in CA vary seasonally with lowest values in the winter. Surface PM2.5 concentrations (annual mean value ∼10 μg m−3) also exhibit a seasonal cycle, with peak values and largest variability in the spring/summer, and lowest values and variability in the winter (hourly values from 2–90 μg m−3). Surface concentrations of black carbon (BC) (mean value ∼0.1 μg m−3) show peak values in the winter. The simulated values are compared to surface measurements of AOD, and PM2.5, PM10, BC, organic carbon (OC) mass concentrations at two regional sites in the Kyrgyz Republic (Lidar Station Teplokluchenka (LST) and Bishkek). The predicted values of AOD and PM mass concentrations and their seasonal cycles are fairly well captured. The carbonaceous aerosols are underpredicted in winter, and analysis suggests that the winter heating emissions are underestimated in the current inventory. Dust, from sources within and outside CA, is a significant component of the PM mass and drives the seasonal cycles of PM and AOD. On an annual basis, the power and industrial sectors are found to be the most important contributors to the anthropogenic portion of PM2.5. Residential combustion and transportation are shown to be the most important sectors for BC. Biomass burning within and outside the region also contributes to elevated PM and BC concentrations. The analysis of the transport pathways and the variations in particulate matter mass and composition in CA demonstrate that this region is strategically located to characterize regional and intercontinental transport of pollutants. Aerosols at these sites are shown to reflect dust, biomass burning and anthropogenic sources from Europe, South, East and CA, and Russia depending on the time period. Simulations for a reference 2030 emission scenario based on pollution abatement measures already committed to in current legislation show that PM2.5 and BC concentrations in the region increase, with BC growing more than PM2.5 on a relative basis. This suggests that both the health impacts and the climate warming associated with these particles may increase over the next decades unless additional control measures are taken. The importance of observations in CA to help characterize the changes that are rapidly taking place in the region are discussed.
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Kulkarni, S., N. Sobhani, J. P. Miller-Schulze, M. M. Shafer, J. J. Schauer, P. A. Solomon, P. E. Saide, et al. "Source sector and region contributions to BC and PM<sub>2.5</sub> in Central Asia." Atmospheric Chemistry and Physics 15, no. 4 (February 18, 2015): 1683–705. http://dx.doi.org/10.5194/acp-15-1683-2015.
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Abstract. Particulate matter (PM) mass concentrations, seasonal cycles, source sector, and source region contributions in Central Asia (CA) are analyzed for the period April 2008–July 2009 using the Sulfur Transport and dEposition Model (STEM) chemical transport model and modeled meteorology from the Weather Research and Forecasting (WRF) model. Predicted aerosol optical depth (AOD) values (annual mean value ~0.2) in CA vary seasonally, with lowest values in the winter. Surface PM2.5 concentrations (annual mean value ~10 μg m−3) also exhibit a seasonal cycle, with peak values and largest variability in the spring/summer, and lowest values and variability in the winter (hourly values from 2 to 90 μg m−3). Surface concentrations of black carbon (BC) (mean value ~0.1 μg m−3) show peak values in the winter. The simulated values are compared to surface measurements of AOD as well as PM2.5, PM10, BC, and organic carbon (OC) mass concentrations at two regional sites in Kyrgyzstan (Lidar Station Teplokluchenka (LST) and Bishkek). The predicted values of AOD and PM mass concentrations and their seasonal cycles are fairly well captured. The carbonaceous aerosols are underpredicted in winter, and analysis suggests that the winter heating emissions are underestimated in the current inventory. Dust, from sources within and outside CA, is a significant component of the PM mass and drives the seasonal cycles of PM and AOD. On an annual basis, the power and industrial sectors are found to be the most important contributors to the anthropogenic portion of PM2.5. Residential combustion and transportation are shown to be the most important sectors for BC. Biomass burning within and outside the region also contributes to elevated PM and BC concentrations. The analysis of the transport pathways and the variations in particulate matter mass and composition in CA demonstrates that this region is strategically located to characterize regional and intercontinental transport of pollutants. Aerosols at these sites are shown to reflect dust, biomass burning, and anthropogenic sources from Europe; South, East, and Central Asia; and Russia depending on the time period. Simulations for a reference 2030 emission scenario based on pollution abatement measures already committed to in current legislation show that PM2.5 and BC concentrations in the region increase, with BC growing more than PM2.5 on a relative basis. This suggests that both the health impacts and the climate warming associated with these particles may increase over the next decades unless additional control measures are taken. The importance of observations in CA to help characterize the changes that are rapidly taking place in the region are discussed.
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Lebo, Z. J., H. Morrison, and J. H. Seinfeld. "Are simulated aerosol-induced effects on deep convective clouds strongly dependent on saturation adjustment?" Atmospheric Chemistry and Physics Discussions 12, no. 4 (April 19, 2012): 10059–114. http://dx.doi.org/10.5194/acpd-12-10059-2012.
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Abstract. Three configurations of a bulk microphysics scheme in conjunction with a detailed bin scheme are implemented in the Weather Research and Forecasting (WRF) model to specifically address the role of the saturation adjustment assumption (i.e., condensing/evaporating the surplus/deficit water vapor relative to saturation in one time step) on aerosol-induced invigoration of deep convective clouds. The bulk model configurations are designed to treat cloud droplet condensation/evaporation using either saturation adjustment, as employed in most bulk models, or an explicit representation of supersaturation over a time step, as used in bin models. Results demonstrate that the use of saturation adjustment artificially enhances condensation and latent heating at low levels and limits the potential for an increase in aerosol concentration to increase buoyancy at mid to upper levels. This leads to a small weakening of the time- and domain-averaged convective mass flux (~ -3%) in polluted compared to clean conditions. In contrast, the bin model and bulk scheme with explicit prediction of supersaturation simulate an increase in latent heating aloft and the convective updraft mass flux is weakly invigorated (~5%). The bin model also produces a large increase in domain-mean cumulative surface precipitation in polluted conditions (~18%), while all of the bulk model configurations simulate little change in precipitation. Finally, it is shown that the cold pool weakens substantially with increased aerosol loading when saturation adjustment is applied, which acts to reduce the low-level convergence and weaken the convective dynamics. With an explicit treatment of supersaturation in the bulk and bin models there is little change in cold pool strength, so that the convective response to polluted conditions is influenced more by changes in latent heating aloft. It is concluded that the use of saturation adjustment can explain differences in the response of cold pool evolution and convective dynamics with aerosol loading simulated by the bulk and bin models, but cannot explain large differences in the response of surface precipitation between these models.
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Lebo, Z. J., H. Morrison, and J. H. Seinfeld. "Are simulated aerosol-induced effects on deep convective clouds strongly dependent on saturation adjustment?" Atmospheric Chemistry and Physics 12, no. 20 (October 30, 2012): 9941–64. http://dx.doi.org/10.5194/acp-12-9941-2012.
Full textAbstract:
Abstract. Three configurations of a bulk microphysics scheme in conjunction with a detailed bin scheme are implemented in the Weather Research and Forecasting (WRF) model to specifically address the role of the saturation adjustment assumption (i.e., condensing/evaporating the surplus/deficit water vapor relative to saturation in one time step) on aerosol-induced invigoration of deep convective clouds. The bulk model configurations are designed to treat cloud droplet condensation/evaporation using either saturation adjustment, as employed in most bulk models, or an explicit representation of supersaturation over a time step, as used in bin models. Results demonstrate that the use of saturation adjustment artificially enhances condensation and latent heating at low levels and limits the potential for an increase in aerosol concentration to increase buoyancy at mid to upper levels. This leads to a small weakening of the time- and domain-averaged convective mass flux (~-3%) in polluted compared to clean conditions. In contrast, the bin model and bulk scheme with explicit prediction of supersaturation simulate an increase in latent heating aloft and the convective updraft mass flux is weakly invigorated (~5%). The bin model also produces a large increase in domain-mean cumulative surface precipitation in polluted conditions (~18%), while all of the bulk model configurations simulate little change in precipitation. Finally, it is shown that the cold pool weakens substantially with increased aerosol loading when saturation adjustment is applied, which acts to reduce the low-level convergence and weaken the convective dynamics. With an explicit treatment of supersaturation in the bulk and bin models there is little change in cold pool strength, so that the convective response to polluted conditions is influenced more by changes in latent heating aloft. It is concluded that the use of saturation adjustment can explain differences in the response of cold pool evolution and convective dynamics with aerosol loading simulated by the bulk and bin models, but cannot explain large differences in the response of surface precipitation between these models.
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Egorov, Mikle, Alexander Ivanov, Ivan Kovalenko, Irina Krectunova, Nadezhda Litvinova, and Elena Popova. "Steam reheater with helical tube bundle for wet steam turbine." E3S Web of Conferences 178 (2020): 01069. http://dx.doi.org/10.1051/e3sconf/202017801069.
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Since steam heat exchangers, used at steam cycle of Russian nuclear power stations, were designed while the knowledge about the separation and the heat exchange processes was limited, deviations between its empirical and theoretical characteristics occur. This limitation also determined application of heating pipes with simple straight shape rather than curved. This study explores a steam heat exchanger with helical heating pipes. It was shown that the model may work stably within the range of parameters, simulating work conditions of the moisture separator and steam reheater at Leningrad nuclear power plant. The experiment included processing of pure water steam as well as mixture of steam and nitrogen. It was obtained a relationship between empirical the heat transfer coefficient and the steam mass flow rate. It was noted that presence of incondensable gas does not affect significantly the heat transfer from the coils, processing high pressure steam.
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Wang, Yan Ping. "Application of Model Predictive Control Based on BPNN to Heating Boiler." Advanced Materials Research 383-390 (November 2011): 2242–48. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.2242.
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This paper presents the algorithm of model predictive control (MPC) based on BP neural network to the burden system of the heating boiler. Because the burden system of the heating boiler is complex, the proposed approach uses steady, effective way to control the boiler. There is a closed-loop, repeating online optimization, model-based control algorithm which deals with the feedback information and the quantity of the fuel entering the boiler by the way of multi-step future predicting and compensating based on BP neural network. By simulation, it is demonstrated that the burden system of the heating boiler using MPC as control method is better in performance than the traditional PID. Besides, it is compliant to the model of the controlled object, especially to those which parameters of the model are variable.
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Кривоносова, Дина Владимировна, and Евгений Сергеевич Ермолаев. "MATHEMATICAL MODEL AND EXPERIMENTAL ESTIMATION OF THERMAL PROCESSES IN HEATING MODULE AS A PART OF STEAM ABLATION DEVICE FOR VARICOSE VEINS TREATMENT." СИСТЕМНЫЙ АНАЛИЗ И УПРАВЛЕНИЕ В БИОМЕДИЦИНСКИХ СИСТЕМАХ, no. 1 (April 19, 2021): 117–25. http://dx.doi.org/10.36622/vstu.2021.20.1.016.
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На сегодняшний день в России для лечения варикозного расширения вен часто проводятся малоинвазивные операции методами радиочастотной или лазерной облитерации, при этом метод паровой облитерации при лечении варикозной болезни не применяется совсем. Однако метод паровой облитерации обладает существенными преимуществами: малый объём и биоинертность рабочей среды - водяного пара, его невысокая температура - 120 °С, исключающая вероятность образования нагара и перфорации венозной стенки. Целью данной работы является разработка математической модели для расчёта тепловых характеристик блока нагревания, входящего в устройство для лечения варикозной болезни методом паровой облитерации. Модель описывает теплообменные процессы в гидравлической трубке блока нагревания и может быть полезна при расчёте размеров нагревательного элемента, обеспечивающих нагрев и парообразование определённой порции воды. С целью верификации математической модели результаты моделирования были сопоставлены с экспериментальными данными. Была проведена серия экспериментов, в ходе которых были получены значения энергии, содержащейся в одной инжекции пара, и объём воды в одной инжекции, а также оценена фактическая тепловая мощность нагревателя. Сравнение результатов имитационного моделирования и значения фактической тепловой мощности пара, полученной экспериментальным путем, показала работоспособность математической модели. Разработанная математическая модель позволяет подбирать геометрические параметры нагревательного элемента в зависимости от требуемой тепловой мощности, которая должна быть обеспечена блоком нагревания, а также варьировать параметры нагревательного элемента для разной степени нагрева тканей Today in Russia minimally invasive varicose veins treatment is often performed using radiofrequency or laser ablation, while the method of steam ablation is not used at all. However, the steam ablation method has significant advantages: a small volume and biological inertness of the working substance - sterile water vapor, its low temperature - 120 °C, excluding the carbon deposits and perforation of the vein wall. The purpose of this work is to develop a mathematical model for calculating the thermal characteristics of the heating module as a part of the device for varicose veins treatment using steam ablation. The model describes heat exchange processes in the hydraulic circuit of the heating module and can be applied to calculate the dimensions of the heating module which provides heating and vaporization of a certain portion of water. In order to verify the mathematical model, the simulation results were compared with experimental data. A series of experiments were carried out in which the energy contained in one steam injection and the volume of water in one injection were estimated, as well as the actual thermal power of the heating module. Comparison of the results of simulation and the value of the actual thermal power of steam obtained experimentally showed the efficiency of the mathematical model. The proposed mathematical model allows to select the geometric parameters of the heating element depending on the required thermal power, which must be provided by the heating module, and also to vary the parameters of the heating element for different degrees of tissue heating
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Wu, Zhi Qiang, Shu Zhong Wang, Jun Zhao, Lin Chen, and Hai Yu Meng. "Investigation on Pyrolysis Characteristic and Kinetic Analysis of Lignocellulosic Biomass Model Compound." Advanced Materials Research 953-954 (June 2014): 224–29. http://dx.doi.org/10.4028/www.scientific.net/amr.953-954.224.
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Lignocellulosic biomass gasification is considered as one of the effective methods for transforming scattered biomass into heat, power and various chemicals. As a fundamental step for biomass gasification, pyrolysis has remarkable influence on products distribution and char reactivity during the further step. Further research on the pyrolysis process of lignocellulosic biomass is beneficial to optimize and promote the process of gasification. In this paper, pyrolysis characteristic of a kind of lignocellulosic biomass model compound (cellulose) was explored through thermogravimetric analyzer. The temperature was from 25 °C to 950 °C under various heating rates (10, 20, 40 °C·min-1) with nitrogen atmosphere. A three step selecting method for mechanism function was used to check out the optimum model from fifteen kinds of most frequently used mechanisms. The results indicated that under various heating rates, the optimum mechanism model for the cellulose in this paper was different. The values of activation energy and frequency factor for cellulose pyrolysis calculated by the three step method in this paper under 10, 20, 40 °C·min-1 were 245.95, 212.09 and 144.27 kJ·mol-1, 8.47E+17, 5.35E+18 and 1.20E+11 s-1, respectively.