Temperature-Dependent Translation-Rotation Diffusivity Divergence in Hot Brownian Motion Directly Observed by Single-Particle T-Jump Tracking
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A nanoscale heat source suspended in fluids constitutes a highly localized yet mobile system that is far from equilibrium. Remarkably, its translational and rotational dynamics can still be theoretically described by Brownian-type equations of diffusion, a "hot Brownian motion" framework (HBM), while the original formulation of diffusive dynamics premises a system that is at or near thermal equilibrium. The HBM theory predicts a steeper temperature dependence for the nanoscale heat source's rotational dynamics over its translational movements─a breakdown of the equipartition principle. Here, we present the first experiment that consistently assessed the HBM prediction by evaluating the diffusivities resulting from both types of motion on an equal footing. We simultaneously tracked the dynamics of all six translational and rotational degrees of freedom for single gold nanoparticles after laser-induced temperature jumps up to ∼30 K above ambient. Without the need for adjustment parameters, the experimental data were recapitulated by the HBM theory across a panel of particle sizes and heating-laser intensities. Our results thus corroborated the translation-rotation diffusivity divergence predicted by the theory, solidifying its underlying microscopic picture which is expected to have important implications in such applications as photothermal imaging, molecular thermobiology and biophysics, nonequilibrium physics and active matters, as well as chemical dynamics, to name a few.Keywords:
Divergence (linguistics)
Tracking (education)
Particle (ecology)
An experiment of measuring thermal diffusivity of material by laser pyoelectric effect is reported. The phase of pyoelectric signal is detected by photothermal pyoelectric technique, then the thermal diffusivity of material is determined by nonlinear fitting. The detection system is designed. Single-arrange composite Al 2O 3/Al is measured, and thermal diffusivity at arbitrary direction was measured by this method.
Laser flash analysis
SIGNAL (programming language)
Thermal conductivity measurement
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収縮座標拡散方程式は脱溶媒に基づく体積収縮を自動的に考慮する点有用であるが, その濃度依存diffusivityは初期溶媒濃度が高く広い濃度範囲にわたる脱着過程では必ず極大値をもつ. このような場合を含む脱着過程につき, 積分型収縮座標拡散方程式に基づき, (diffusivity積分値)/(脱着速度×脱着達成率)を算出する方法を示した. このとき, 濃度分布の0次と1次モーメントの関係式, および (平均濃度/中心濃度) の比を脱着速度マスター曲線より算出する経験式を用いた. (diffusivity積分値) と (脱着速度×脱着達成率) は共にpenetration periodで一定値をとる. この両者の比は, 中心濃度と点綴すると単調に減少しregular regimeの最終段階で0.65の一定値に収束する. この比をpenetration period終点, およびregular regimeで算出する式を示し, また, (平均濃度/中心濃度) との関係を示す図を得た. 表面濃度一定で初期濃度を種々変え得られた脱着実験データより (diffusivity積分値)/(脱着速度×脱着達成率) を算出し, これらをまとめて (diffusivity積分値) vs. 中心濃度の関係に点綴し, これを中心濃度で図微分することにより, 濃度依存diffusivityおよび相互拡散係数が濃度の関数として算出される. 指数関数型, べき乗型のモデル式のほか, diffusivity濃度依存性に極大値を示す系として食品水溶液 (sucrose-H2O) および高分子溶液 (PVA-H2O, polystyrene-ethylbenzene, polyimide-parachlorophenol) につき濃度依存拡散係数の実験式を用い収縮座標拡散方程式に基づく数値解を求め, 上記解析を行うとともに濃度依存拡散係数算出法を検証した.
Mass diffusivity
Penetration (warfare)
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The thermal diffusivity of γ-alumina is determined by the photoacoustic method. The method is calibrated by determining the thermal diffusivity of copper and aluminum. The effect of the chemisorbed hydroxyl groups on thermal diffusivity is studied by degassing the sample at different temperatures.
Laser flash analysis
Photoacoustic effect
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Solid thermal diffusivity is very important to study unsteady heat conduction under low temperature.In order to study solid thermal diffusivity under low temperature,sample thermal diffusivity under different temperature is computed in term of thermal diffusivity theory model in the paper.Besides,function relation between laser frequency and phase lag is gained by numerical simulation.The two groups of data are approximately equal by contrasting the numerical result and experimental result.The research indicates that solid thermal diffusivity could be measured availably by laser photothermal.Numerical simulation of solid thermal diffusivity under low temperature shows that solid thermal diffusivity changes remarkably when the scope of temperature is from 20 K to 80 K,however,the change is less from 80 K to 300 K.
Laser flash analysis
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Photoacoustic effect
Laser flash analysis
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Concrete can be regarded as a composite material composed of cement paste or mortar as a matrix and gravel as an aggregate. Thermal diffusivity is a measure of material's ability to undergo a temperature change. In this study, the thermal diffusivity of concrete was measured and the results were examined from the viewpoint of a composite material.When both of the fine and the coarse aggregates are of the same rock type, the diffusivity of the concrete shows a tendency to increase with increasing the aggregate content. When they are different, however, such tendency no longer exists. Hence the rock type is one of the most important factors which determine the diffusivity of concrete.Since the exact value of diffusivity of aggregate is generally unknown, a model coarse aggregate was made of the mortar of known diffusivity and was used to make concrete samples. The measurement of the diffusivity on these samples showed that the diffusivity of concrete can be expressed in terms of the diffusivities and the volume fractions of the constituent materials. This result can be used to estimate an unknown diffusivity of aggregate, mortar or concrete when two of these three quantities are known.
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The concept of apparent thermal diffusivity in soil is discussed and defined as consisting of an intrinsic and a pseudo part. A method that uses a numerical model of heat conduction and measured soil temperatures to estimate apparent thermal diffusivity is introduced. The method requires measurement of temperatures at three depths to make an estimate for diffusivity between the lowest and uppermost depths. This method is applied to a five-day data set obtained in Sweden. Time-dependent apparent diffusivities are estimated for periods of five days, one day, and three hours. An empirical method is used to determine the intrinsic diffusivity. Values close to those calculated for the empirical relationships have been obtained for the one- and five-day periods, whereas values of the three-hour period show wider variation. The results indicate that the outlined method is feasible and satisfactory for estimating the intrinsic thermal diffusivity in soils near the surface on a daily basis. It also is argued that the root-mean-square error (RMSE) of a simulation using the estimated diffusivity, together with the diffusivity, is a better indicator for non-conductive processes than diffusivity alone.
Root mean square
Empirical modelling
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ABSTRACT A transient method was used to measure thermal diffusivity of a Millhopper fine sand. Tests were conducted for three bulk densities and seven volumetric water contents. Deviation of individual measurements was within 5% of the mean. Sensitivity analysis was used to analyze the effect of experimental errors on measured thermal diffusivity. The effect of diffusion of water vapor on the measured thermal diffusivity was found to be insignificant using the described procedure.
Transient (computer programming)
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Sample (material)
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In this work the diffusivity of mercury in a commercial additived activated carbon was experimentally determined using an Argelian condensate. The diffusivity was estimated using the homogeneous solid diffusion model (HSDM) for short and long times (effective diffusivity). To the employed solid/liquid ratios, the values the diffusivity at short times were smaller than the corresponding values at long times and were in range obtained to diffusivity of organic solutes in activated carbon. The effective diffusivity was found to better represent the process than the diffusivity determined at short times, indicating that diffusivity depends on solute concentration in solid.
Mercury
Mass diffusivity
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