scholarly journals Dual Entropy Regime in Channel Flow Subjected to Temperature Dependent Convection Mechanism

2021 ◽  
Vol 39 (2) ◽  
pp. 424-432
Author(s):  
Paresh Vyas ◽  
Sahanawaz Khan
Keyword(s):  
Temperature Regime ◽  
Quantitative Difference ◽  
Convection Coefficient ◽  
Temperature Dependent ◽  
Dual Systems ◽  
Thermal Systems ◽  
Entropy Generation Number ◽  
Simple Geometry ◽  
Dual Distribution ◽  
Parameter Values

The central stimuli of this brief note is to underscore the effect of the temperature dependent convection coefficient that give rise to a dual temperature regime facilitating dual entropy distribution. In order to avoid unwarranted complexities, a simple geometry of shear flow in a channel is considered. The energy equation amenable to an analytic solution is simulated to extract the desired numerical findings in as much as for what parameters’ values, the temperature has dual distribution /does not yield temperature distribution at all. In fact, a range of parameter values have been worked out for which dual temperature regime exists or not. The plots of entropy generation number Ns also show the dual regime. The findings reveal a qualitative and quantitative difference in dual systems of temperature and entropy. It further underlines that the thermal systems with the idealized uniform heat transfer coefficient may be far distinct from actual behaviour and even weak temperature dependence of convection coefficient need due attention while designing a system.

Transfer and language mode

1998 ◽  
Vol 1 (3) ◽  
pp. 175-176 ◽  
Author(s):  
FRANÇOIS GROSJEAN
Keyword(s):  
Language Acquisition ◽  
Quantitative Difference ◽  
Language Learner ◽  
The Other ◽  
Bilingual Children ◽  
Main Argument ◽  
Bilingual Learners ◽  
Main Thrust ◽  
Transfer Parameter ◽  
Parameter Values

Natascha Müller's proposal to view transfer as a relief strategy used by bilingual learners to cope with problematic input is very interesting and has far-reaching consequences for theories of bilingual language acquisition. The author makes a strong case for the fact that bilingual children transfer parameter values from the language presenting unambiguous input to the other “puzzling language”. In what follows, I will not question the main thrust of her argument. Rather I will return to the definitions that have been proposed for transfer in the literature and show that they are usually too broad. I will then propose that anyone interested in studying transfer must take into account the language mode the language learner or bilingual subject is in when being studied, and I will end by showing the consequences that this may have if it is not done. Natascha Müller's main argument is not affected by the language mode factor but the quantitative difference she finds between monolingual and bilingual children could be.

scholarly journals Small-Polaron Hopping and Low-Temperature (45–225 K) Photo-Induced Transient Absorption in Magnesium-Doped Lithium Niobate

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 809
Author(s):  
Simon Messerschmidt ◽  
Andreas Krampf ◽  
Laura Vittadello ◽  
Mirco Imlau ◽  
Tobias Nörenberg ◽  
...  
Keyword(s):  
Lithium Niobate ◽  
Temperature Regime ◽  
Transient Absorption ◽  
Small Polaron ◽  
Good Representation ◽  
Temperature Dependent ◽  
Polaron Hopping ◽  
Two Parameters ◽  
Oppositely Charged ◽  
Small Polarons

A strongly temperature-dependent photo-induced transient absorption is measured in 6.5 mol% magnesium-doped lithium niobate at temperatures ranging from 45 K to 225 K. This phenomenon is interpreted as resulting from the generation and subsequent recombination of oppositely charged small polarons. Initial two-photon absorptions generate separated oppositely charged small polarons. The existence of these small polarons is monitored by the presence of their characteristic absorption. The strongly temperature-dependent decay of this absorption occurs as series of thermally assisted hops of small polarons that facilitate their merger and ultimate recombination. Our measurements span the high-temperature regime, where small-polaron jump rates are Arrhenius and strongly dependent on temperature, and the intermediate-temperature regime, where small-polaron jump rates are non-Arrhenius and weakly dependent on temperature. Distinctively, this model provides a good representation of our data with reasonable values of its two parameters: Arrhenius small-polaron hopping’s activation energy and the material’s characteristic phonon frequency.

scholarly journals Thermocells for Hybrid Photovoltaic/Thermal Systems

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1928
Author(s):  
Gilyong Shin ◽  
Jei Gyeong Jeon ◽  
Ju Hyeon Kim ◽  
Ju Hwan Lee ◽  
Hyeong Jun Kim ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Conversion Efficiency ◽  
Large Scale ◽  
Electric Energy ◽  
Practical Implementation ◽  
Temperature Dependent ◽  
Thermal Systems ◽  
Photovoltaic Conversion Efficiency ◽  
Increasing Temperature

The photovoltaic conversion efficiency of solar cells is highly temperature dependent and decreases with increasing temperature. Therefore, the thermal management of solar cells is crucial for the efficient utilization of solar energy. We fabricate a hybrid photovoltaic/thermocell (PV/T) module by integrating a thermocell directly into the back of a solar panel and explore the feasibility of the module for its practical implementation. The proposed PV/T hybrid not only performs the cooling of the solar cells but also produces an additional power output by converting the heat stored in the solar cell into useful electric energy through the thermocell. Under illumination with an air mass of 1.5 G, the conversion efficiency of the solar cell can improve from 13.2% to 15% by cooling the solar cell from 61 °C to 34 °C and simultaneously obtaining an additional power of 3.53 μW/cm2 from the thermocell. The advantages of the PV/T module presented in this work, such as the additional power generation from the thermocell as well as the simultaneous cooling of the solar cells and its convenient installation, can lead to the module’s importance in practical and large-scale deployment.

WORM ALGORITHM PATH INTEGRAL MONTE CARLO APPLIED TO THE 3He–4He II SANDWICH SYSTEM

2012 ◽  
Vol 26 (31) ◽  
pp. 1250173 ◽  
Author(s):  
AMER AL-OQALI ◽  
ASAAD R. SAKHEL ◽  
HUMAM B. GHASSIB ◽  
ROGER R. SAKHEL
Keyword(s):  
Monte Carlo ◽  
Path Integral ◽  
Temperature Regime ◽  
Graphite Substrate ◽  
Temperature Dependent ◽  
Path Integral Monte Carlo ◽  
Density Profiles ◽  
Pair Correlations ◽  
Sandwich System ◽  
Matsubara Green's Function

We present a numerical investigation of the thermal and structural properties of the 3 He –4 He sandwich system adsorbed on a graphite substrate using the worm algorithm path integral Monte Carlo (WAPIMC) method [M. Boninsegni, N. Prokof'ev and B. Svistunov, Phys. Rev. E74, 036701 (2006)]. For this purpose, we have modified a previously written WAPIMC code originally adapted for 4 He on graphite, by including the second 3 He -component. To describe the fermions, a temperature-dependent statistical potential has been used. This has proven very effective. The WAPIMC calculations have been conducted in the millikelvin temperature regime. However, because of the heavy computations involved, only 30, 40 and 50 mK have been considered for the time being. The pair correlations, Matsubara Green's function, structure factor, and density profiles have been explored at these temperatures.

Two temperature regimes of triplet transfer in the dissociation of the correlated triplet pair after singlet fission

2019 ◽  
Vol 97 (6) ◽  
pp. 465-473 ◽  
Author(s):  
Tia S. Lee ◽  
YunHui L. Lin ◽  
Hwon Kim ◽  
Barry P. Rand ◽  
Gregory D. Scholes
Keyword(s):  
Low Temperature ◽  
Temperature Dependence ◽  
Temperature Regime ◽  
Transient Absorption Spectroscopy ◽  
Type Model ◽  
Singlet Fission ◽  
Temperature Dependent ◽  
Thermally Activated ◽  
Pair Separation ◽  
Triplet Pair

The ability to undergo spin-allowed exciton multiplication makes singlet fission materials promising for photovoltaic applications. Here, we examine the separation of correlated triplet pairs, 1(T…T), in polycrystalline pentacene films via temperature-dependent transient absorption spectroscopy. Single wavelength analysis reveals a profound delay in 1(T…T) dynamics. Moreover, the dynamics of 1(T…T) exhibit temperature dependence, whereas other features show no discernable temperature dependence. Previous literatures have suggested that correlated triplet separation is mediated by a thermally activated hopping process. Surprisingly, we found that the time constants governing triplet pair separation display two distinct temperature-dependent regimes of triplet transport. The high temperature regime follows a thermally activated hopping mechanism. The experimentally derived reorganization energy and electronic coupling is verified by density matrix renormalization group quantum chemical calculations. In addition, we evaluated the low temperature regime and show that the trend can be modelled by a Miller–Abrahams-type model that incorporates the effects of energetic disorder. We conclude that the correlated triplet pair separation is mediated by thermally activated hopping or a disorder driven Miller–Abrahams-type mechanism at high and low temperature, respectively. We observe that crossover between two regimes occurs ∼226 K. We find the time constant for triplet–triplet energy transfer to be 1.8 ps at ambient temperature and 21 ps at 77 K.

Temperature-dependent performance of amorphous silicon photovoltaic/thermal systems in the long term operation

2020 ◽  
Vol 275 ◽  
pp. 115156 ◽  
Author(s):  
Xiao Ren ◽  
Jing Li ◽  
Dongsheng Jiao ◽  
Datong Gao ◽  
Gang Pei
Keyword(s):  
Amorphous Silicon ◽  
Temperature Dependent ◽  
Thermal Systems ◽  
Term Operation

Slip system determination in cubic carbides by hardness anisotropy

1972 ◽  
Vol 326 (1566) ◽  
pp. 409-420 ◽  
Keyword(s):  
Slip System ◽  
Temperature Regime ◽  
Niobium Carbide ◽  
High Mobility ◽  
Zirconium Carbide ◽  
Metal Carbides ◽  
Temperature Dependent ◽  
Covalent Bonds ◽  
Temperature Regimes ◽  
Dependent Change

Hardness has been examined as a function of indenter orientation on the (001) surfaces of the cubic transition-metal carbides titanium carbide, vanadium carbide, zirconium carbide and niobium carbide. To emphasize the observed anisotropy a Knoop indenter was used. Experiments have been performed in the temperature range —196 to 610 °C. The anisotropy curves obtained at each temperature have been analysed in terms of operative slip systems. Three different temperature regimes for the anisotropy have been identified. These correspond to the {110} <110> slip system for the low-temperature regime, the {111} <110> slip system for the high-temperature regime and a combination of these two systems for the intermediatetemperature regime. To explain this change in slip system it is proposed that an important temperature dependent change in bonding occurs. A qualitative model is suggested for this change in which an increased density of high mobility electrons increasingly screens the directional covalent bonds as the temperature is raised.

Heatsum–emergence relationship in Douglas-fir seedlings

1978 ◽  
Vol 8 (1) ◽  
pp. 23-29 ◽  
Author(s):  
W. J. Bloomberg
Keyword(s):  
Computer Model ◽  
Temperature Regime ◽  
Soil Depth ◽  
Douglas Fir ◽  
Air Temperatures ◽  
Temperature Regimes ◽  
Emergence Percentage ◽  
Parameter Values ◽  
The Relationship ◽  
High Emergence

Usefulness of classifying Douglas-fir seed lots using heatsum–emergence relationship parameters was examined by (1) comparing nursery emergence with that predicted by the relationship, (2) testing seed lots for conformity to the relationship, and (3) computer simulation of emergence under various temperature regimes. The emergence parameters used were threshold heatsum (degree-hours above 0 °C that must be accumulated before emergence starts), emergence coefficient (percentage emergence per thousand degree-hours above the threshold), slow emergence percentage (percentage emergence at which the emergence rate is reduced), and slow emergence factor (amount by which the emergence coefficient is reduced). Emergence of seed lots at two nurseries was accurately predicted by a computer model based on the heatsum–emergence relationship. Five seed lots sown in growth chambers under two temperature regimes showed good conformity to the relationship. Computation of emergence percentage and days to 50 or 100% emergence was carried out by a computer model using various emergence parameter values chosen from the observed range and simulated temperature regimes comprising daily heatsums at the 0.5-cm soil depth for 40 days after sowing. These heatsums were derived by regression equation from air temperatures at a forest nursery and were increased or decreased to represent warm or cool regimes or combinations of both. Generally, emergence percentage increased and number of days to 50 or 100% emergence decreased as emergence coefficient and slow emergence percentage increased and threshold heatsum decreased. Emergence percentage was affected by temperature regime only at low emergence coefficients. Number of days to 100% emergence was affected by temperature regime only at average or high emergence coefficients.

scholarly journals Temperature dependent analytical model for submicron GaAs-MESFET

2021 ◽  
Vol 10 (3) ◽  
pp. 1271-1282
Author(s):  
Mohamed Djouder ◽  
Arezki Benfdila ◽  
Ahcene Lakhlef
Keyword(s):  
Analytical Model ◽  
Temperature Dependent ◽  
Gaas Mesfet ◽  
Voltage Variation ◽  
Proposed Model ◽  
Current Voltage ◽  
Current Voltage Characteristics ◽  
Simulation Results ◽  
Parameter Values ◽  
Good Agreement

MESFET are used in circuitsof gigahertz frequencies as they are based on gallium arsenide (GaAs) having electron mobility six times higher than that of silicon. An analytical model simulating different device current-voltage characteristics, i.e., output conductance and output transconductance of a 0.3μm gate MESFET with temperature dependence is proposed. The model is validated by comparing the results of the proposed model and those of the numerical simulation. The parameter values are computed using an intrinsic MESFET of two-dimensional geometry. In this work, the distribution of different output loads for varied applied voltages is considered. Simulation results obtainedunder temperature variation effectsfor load distribution and applied driven voltage variation are considered. The RMS and average errors between the different models and GaAs MESFET simulations are calculated to evidence the proposed model accuracy. This was demonstrated by a good agreement between the proposed model and the simulation results, which are found in good agreement. The simulation results obtained under temperature variations were discussed and found to complement those obtained in the literature. This clarifies the relevance of the suggested model analytical.

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