Effective temperature of thermal radiation from non-uniform temperature distributions and nanoparticles

We study thermal radiation properties from non-uniform temperature distributions and nanoparticles, and define effective temperature. Conventionally, the temperature of a body is measured by fitting with the blackbody radiation spectrum, which assumes a uniform temperature throughout the body. We show the energy density of thermal radiation for non-uniform temperature distribution of the body and derive the effective temperature. Furthermore, the energy density of thermal radiation from nanoparticles is derived and the effective temperature of the body is shown to depend on the particle size.     

图像光谱技术实现精确测温

建立了一种以灰体辐射为基础测量温度的新方法,它不仅可以测定辐射体的实时温度,而且可以实现无接触和高精度测量。首先,利用多通道CCD图像光谱仪精确测量辐射体在较宽波段内的辐射光谱,作为该辐射体的指纹光谱,将其定义为一个等效的灰体;其次,通过对所测光谱的拟合确定该辐射体的灰体辐射模型的系数,从而确定待测辐射体的灰体辐射模型;最后,通过光谱技术与灰体辐射模型的结合确定给定辐射体的任意温度。通过对无火焰和有火焰这两类热辐射体的实验检验,表明该测温方法具有实时、准确和无接触等优点。     

Generalized thermal radiation from arbitrary fractional dimension

Properties of the thermal radiation from arbitrary fractional dimension are investigated. Generalized blackbody radiation for arbitrary dimension can be obtained and the energy density is shown as a function of arbitrary dimension as well as temperature. Maximum frequency factor representing the relation between most probable photon energy and thermal energy is shown as a function of arbitrary fractional dimension. It is also shown how to measure the arbitrary fractional dimension of the body with thermal radiation.     

An approach for the performance analysis of an uncooled infrared bolometer imager

As an approach for analyzing an uncooled infrared bolometer imager, a method is introduced which supposes that a thermal system is built into the infrared radiation detection mechanism. In this analysis, the bi-directional radiation energy flows between two thermal elements are considered and a radiation thermal conductance between them is defined. Based on the values of the radiation thermal conductances and conventional material thermal conductance, an equivalent thermal circuit for a bolometer detector element is extracted. Calculations were carried out using software written in visual C++. The analysis shows a Noise Equivalent Temperature Difference (NETD) of 50 mK is obtained as a typical value, assuming that no additional noise other than temperature fluctuation noise exists, and that the NETD becomes better as the system time constant built into the equivalent thermal circuit increases.     

Thermal heat radiation,near-field energy density and near-field radiative heat transfer of coated materials

We investigate the thermal radiation and thermal near-field energy density of a metal-coated semi-infinite body for different substrates. We show that the surface polariton coupling within the metal coating leads to an enhancement of the TM-mode part of the thermal near-field energy density when a polar substrate is used. In this case the result obtained for a free standing metal film is retrieved. In contrast, in the case of a metal substrate there is no enhancement in the TM-mode part, as can also be explained within the framework of surface plasmon coupling within the coating. Finally, we discuss the influence of the enhanced thermal energy density on the near-field radiative heat transfer between a simple semi-infinite and a coated semi-infinite body for different material combinations.     

热辐射谱的多道采集及最小二乘法温度解析

本文报道一种以CCD光学多道分析器采集热辐射谱，用最小二乘法计算拟合普朗克黑体辐射曲线，从而解析获得辐射温度的新方法。使用上述方法对钨带灯辐射谱进行了采集解析，温度计算结果与计量检定值误差小于1％。讨论了该测试方法的优越性。     

Temperature recovery of opaque bodies by thermal radiation spectrum: the use of relative emissivity to select the optimal spectral range

The approach based on relative emissivity was tested and developed using the experimental data. It was assumed that the medium separating an opaque body and measuring device was diathermic or nonradiating (it is characterized by its transmittance); radiation source emissivity and medium transmittance were unknown. Data on comparison of spectral radiances (spectral intensities), obtained within 220–2500 nm for the temperature lamps in the metrological laboratories of Europe, Russia, and USA were used as the initial experimental data. It is shown that the use of relative emissivity allows graphical interpretation for the solution to the initial nonlinear system of equations. In this case, the problem of determining the true temperature of the body by the thermal radiation spectrum in a graphical interpretation is reduced to the choice depending on relative emissivity at the desired temperature. It is shown that to narrow the interval, which includes the true temperature, the criterion was based on a change in convexity of spectral dependence of the relative emissivity in the process of desired temperature selection. The use of relative emissivity in a spectral range, where the Rayleigh—Jeans approximation is satisfied, allows unambiguous determination for the shape of emissivity dependence on the wavelength. The relationship for determination of the peak wavelength within the registered thermal radiation spectrum on the basis of data about the true temperature of the body and its spectral emissivity is presented.     

黑体热辐射的微机描绘

本文用 QBASIC程序实现了黑体热辐射的微机描绘 .程序具有良好的界面和坚固性 ,通过编程、运行程序 ,一方面可以让学生从交互操作过程中深入理解黑体热辐射规律 ,另一方面还可以让学生在学习物理知识的同时使他们的程序设计能力得到培养 .     

General Tortoise Coordinate Transformation in a Dynamical Kerr-Newman Black Hole

Under the extended dynamical tortoise coordinate transformation, Damour-Ruffini method has been applied to calculate the charged particles’ Hawking radiation from the apparent horizon of a dynamical Kerr-Newman black hole. It is shown that Hawking radiation is still purely thermal black body spectrum. Moreover, the temperature of Hawking radiation is corresponding to the apparent horizon surface gravity and the first law of thermodynamics can also be constructed successfully on the apparent horizon in the dynamical Kerr-Newman black hole.     

The interaction between radiation and the Linen of Turin

In this paper, we study the possible interactions between radiation and the Linen of Turin. The work is in line with the research focused, by scholars and scientists, on the detection mechanism of the Shroud body image formation. We have analysed the interactions between thermal, UV and particle radiation with the linen fabric. The performed analysis shows that any hypothesis of the Shroud body image formation by radiation must be rejected. Only the background was produced by the action of electromagnetic radiation.     

The anomalous thermal radiation of metals produced by ultrashort laser pulses

The spectral-time characteristics of the secondary radiation produced in silver and tungsten by picosecond laser pules of varying duration and fluence (energy density) have been studied theoretically and experimentally. It is established that the secondary radiation is due to heating. In silver, however, it is not usual and does not correspond, for example, to grey body radiation. This radiation — the anomalous thermal radiation — is defined by the following mechanism. When the electron and phonon subsystems in a metal are heated (including also the nonisothermal process), there appears the glow with the continuous spectral distribution and the intensity exceeding the radiation intensity of the grey body whose temperature is equal to the temperature of the ion or electron subsystem of a metal. This anomaly is either due to overheat of the electron subsystem with respect to the ion subsystem or due to recombination of electrons and therm-ions in a microlayer above the metal surface.     

Transient heat transfer in a spherical protective material, submitted to flux and mixed boundary conditions: an investigation on zirconia

An analytic solution is presented for describing combined radiation and conduction heat transfer in a spherical fiber thermal protection exposed to combined radiative and convective heating. The solution includes the equation of radiative transfer within the material, coupled to a transient energy equation that contains both radiative and convective terms. At elevated temperatures radiative transfer becomes important, and if several hot surfaces view each other, the radiation exchange process must be considered carefully. Some thermal protections are partially transparent to thermal radiation. Hence, an exchange process is complicated by radiation penetrating into and coming out of material. The radiation leaving an area depends on the temperature distribution inside that area and that is unknown and is affected by the exchange process to other areas. The analysis has allowed for unlimited spectral detail but assumes that the various material properties do not vary significantly with temperature. Transient temperature distributions are obtained for the boundary conditions of external radiation and convection. The present analysis includes the influence of reflectivity, surface radiative properties and spectral properties on the temperature distributions.     

Using spectral distribution of radiance temperature and relative emissivity for determination of the true temperature of opaque materials

A method for determining the thermodynamic (true) temperature of opaque materials by the registered spectrum of thermal radiation under the conditions when we do not know emissivity of a free-radiating body is presented. A special function, which is a product of relative emissivity of tungsten by the radiation wavelength, was used as the input data. The accuracy of results is analyzed. It is shown that when using relative emissivity, the proposed algorithm can be used both within the range of applicability of the Wien approximation and the Planck formula.     

Stochastic distribution of the fibrils that yielded the Shroud of Turin body image

The fibrils that yielded the Shroud body image show a stochastic distribution on the Linen of Turin. In fact, the probability of a fibril yellowing is a function of the energy, while this is not the case for the optical density value. This means that the above image is a latent image. We suggest thermal radiation or low-temperature chemical processes as possible natural energy sources to explain, by stochastic effects, the Shroud body image formation. Unfortunately, due to the nature of the phenomenon, we are not able to extract the energy source.     

On some properties of the entropy of a system containing a black hole

We show that the entropy of a system constituted by a massive Schwarzschild black hole in stable thermal equilibrium with black body radiation is superadditive in Landsberg's sense. Furthermore, we comment on some consequences arising from the negative character of the heat capacity of that system.     

Thermodynamical Stability of Hagedorn and Radiation Regimes in Closed String Gas Cosmology

In this paper, we investigate thermal equilibrium in string gas cosmology which is dominated by closed string. We consider two interesting regimes, Hagedorn and radiation regimes. We find that for short strings in small radius of Hagedorn regime very large amount of energy requested to have thermal equilibrium but for long strings in such system a few energy is sufficient to have thermal equilibrium. On the other hand in the large radius of Hagedorn regime, which pressure is not negligible, we obtain a relation between the energy and pressure in terms of cosmic time which is satisfied by thermal equilibrium. Then we discuss about radiation regime and find that in all cases there is thermal equilibrium.     

石墨烯增强半导体态二氧化钒近场热辐射

本文基于涨落耗散定理和并矢格林函数求解麦克斯韦方程来研究两个半无限大平板的近场热辐射净热流,提出了两个半无限大块状二氧化钒组成的V/V结构、石墨烯覆盖两个半无限大块状二氧化钒组成的GV/GV结构和石墨烯覆盖VO2薄膜组成的GV0/GV0结构,深入研究了这三种结构中二氧化钒与石墨烯间的近场热辐射,并分析了真空间距、二氧化钒薄膜厚度和石墨烯化学势等物理参量变化对近场热辐射的影响.研究表明:三种结构的近场热辐射均随间距增大而减小;在真空间距为10 nm时,由石墨烯覆盖的GV/GV结构的近场辐射热流比无石墨烯覆盖的V/V结构增强35倍,耦合效果最好的是GV0/GV0结构,该结构的近场辐射热流比GV/GV结构增强8.6倍;在GV0/GV0结构中,当二氧化钒薄膜厚度为30 nm时,石墨烯化学势从0.1 eV增加到0.6 eV辐射热流会减小3.3倍.本文系统研究了二氧化钒与石墨烯间相互耦合的近场热辐射,对相关结构的近场热辐射实验和实际应用具有理论指导意义.     

钟速同步的传递性等价于热力学第零定律

平直或弯曲时空中的平衡热辐射,表现出用坐标量表示的普朗克黑体谱.把热平衡系统的辐射具有普朗克黑体谱作为一条基本的物理规律,以此为基础,论证钟速同步的传递性等价于热力学第零定律.钟速同步的条件比建立同时面的条件要弱.满足这一条件的时空,热力学第零定律在其中成立.第零定律成立的时空,一定可以定义统一的钟速. 关键词：     

Quantum Decoherence of Gaussian Steering and Entanglement in Hawking Radiation and Thermal Bath

We study the effects of Hawking radiation and bath temperature on quantum steering and entanglement for a two-mode Gaussian state exposed in the background of a black hole and immersed in the two independent thermal baths. We find that both the effects can destroy the quantum steering and entanglement. Quantum steering always exists sudden death for any Hawking temperature and any bath temperature, but entanglement does not in zero-temperature thermal bath. Both the Hawking radiation and the asymmetry of thermal baths can induce the asymmetry of quantum steering, but the latter effect is much weaker than the former. An unintuitive result is that the observer who stays in the Hawking radiation or in the thermal bath with higher temperature has more stronger steerability than the other one. We also find that Hawking radiation and thermal noise can change the asymptotic behavior of steering and entanglement versus the squeezing parameter.

     

The Blackbody Radiation Spectrum Follows from Zero-Point Radiation and the Structure of Relativistic Spacetime in Classical Physics

The analysis of this article is entirely within classical physics. Any attempt to describe nature within classical physics requires the presence of Lorentz-invariant classical electromagnetic zero-point radiation so as to account for the Casimir forces between parallel conducting plates at low temperatures. Furthermore, conformal symmetry carries solutions of Maxwell’s equations into solutions. In an inertial frame, conformal symmetry leaves zero-point radiation invariant and does not connect it to non-zero-temperature; time-dilating conformal transformations carry the Lorentz-invariant zero-point radiation spectrum into zero-point radiation and carry the thermal radiation spectrum at non-zero temperature into thermal radiation at a different non-zero temperature. However, in a non-inertial frame, a time-dilating conformal transformation carries classical zero-point radiation into thermal radiation at a finite non-zero-temperature. By taking the no-acceleration limit, one can obtain the Planck radiation spectrum for blackbody radiation in an inertial frame from the thermal radiation spectrum in an accelerating frame. Here this connection between zero-point radiation and thermal radiation is illustrated for a scalar radiation field in a Rindler frame undergoing relativistic uniform proper acceleration through flat spacetime in two spacetime dimensions. The analysis indicates that the Planck radiation spectrum for thermal radiation follows from zero-point radiation and the structure of relativistic spacetime in classical physics.