机翼热气防冰及冰脊形成数值模拟

应用N-S方程求解空气外流场和防冰腔内流场，用Euler法获得过冷水滴撞击特性，将内外流场进行耦合传热稳定后，开始结冰，来实现机翼热气防冰及冰脊形成的数值模拟.计算结果表明，热气防冰开启时，加热区蒙皮最低温度为286 K保证加热区没有结冰，但在加热区后的上下表面由于蒙皮温度降低至273.15 K以下，防冰区的溢流水到此处形成冰脊，这个计算结果表明了热气防冰数值模拟的可行性与合理性.但在将前缘积冰除去的情况下，防冰区外形成冰脊对气动特性影响很大，对带冰脊的机翼绕流流场进行数值模拟，对计算结果进行分析，得出环境温度越低、形成冰脊的位置越靠近防冰区，冰脊的高度越高；结冰时间越长，冰脊后的非定常特性越明显，流动细节的捕捉越困难，对气动特性的影响越大.      

CO2激光热熔法除冰的研究

介绍了CO2激光在高压线除冰中的实验研究情况.由于直接热融法除冰效率较低,提出了激光热融加上冰块自身重力脱落法除冰的实验方案.利用功率为35 W的CO2激光照射冰块与绝缘子的接触面,降低其粘结力以致整体脱落从而达到除冰的目的,测得除去1 kg冰需要90kJ的能量,耗时26 min.     

人工自旋冰中阻挫现象的研究进展

磁学中的阻挫现象近些年来是实验及理论研究的热点.本文就磁学中阻挫研究的新进展进行了介绍.描述了用显微刻蚀制备的人工自旋冰的研究,讨论了其潜在的应用前景以及计算机模拟的结果.     

Relation between the high density phase and the very-high density phase of amorphous solid water

It has been suggested that high-density amorphous (HDA) ice is a structurally arrested form of high-density liquid (HDL) water, while low-density amorphous ice is a structurally arrested form of low-density liquid (LDL) water. Recent experiments and simulations have been interpreted to support the possibility of a second distinct high-density structural state, named very high-density amorphous (VHDA) ice, questioning the LDL-HDL hypothesis. We test this interpretation using extensive computer simulations and find that VHDA is a more stable form of HDA and that, in fact, VHDA should be considered as the amorphous ice of the quenched HDL.     

Causes of phase variations in the air–ice boundary reflection coefficient in the microwave range

We study phase variations in the coefficient of reflection from a flat air–ice boundary at the ice melting point. The measurements were performed by different methods at frequencies 3.3, 6, 13, and 32 GHz. The experimental data were compared with simple theoretical models. It was found that ice wettening in thin layers leads to a phase variation in the reflection coefficient by up to a few ten degrees with satisfactory agreement between the experiment and the theory. However, anomalies of the transmission properties of the samples unexplainable in terms of the model of effective dielectric permittivity of the melting layers were observed in a narrow temperature range before the ice destruction. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 3, pp. 260–266, March 2009.     

Reactive ion scattering from ice in a molecular dynamics perspective

This is a study into the scattering dynamics of the alkaline ions Cs⁺, K⁺, Na⁺, and Li⁺ from an ice surface, and the process of abstracting water molecules by the scattered ions to form ion–water clusters as a result of the ion–dipole attraction. In a classical molecular dynamics computer simulation a semi-empirical ion–water interaction potential and a modified version of the TIP3P ice model are employed.The thickness of the ice structure at the surface greatly affects the abstraction efficiency. From a thin ice overlayer all alkaline ions exhibit similar scattering probabilities, but Cs⁺ abstracts water molecules most efficiently; its lower speed facilitates a mechanism where the Cs⁺ in its outgoing trajectory pulls water molecules out of the ice structure. From a thick ice structure the scattering probabilities decrease dramatically due to an effective energy transfer to the ice structure. A more grazing angle of incidence reduces the energy transfer and enhances the scattering probabilities for the lighter alkaline ions. The deprived formation of ion–water clusters in the simulations confirms that from thick ice the cluster formation probability is reduced by at least three orders of magnitude.     

电热法测定冰的熔化热实验仪的研制

为了解决混合法测量冰的熔化热实验中热量损失的问题,设计了电热法测定冰的熔化热实验仪.真空保温杯和冰水混合物双重隔离实验对象,降低了冰与环境的热交换,通过移液管测量冰熔化成水的体积变化,进而测定冰的熔化热.     

Proton disorder and superionicity in hot dense ammonia ice

We report the experimental discovery of a new phase of ammonia ice, stable at pressures above 57 GPa and temperatures above 700 K. The combination of our experimental results and ab initio molecular dynamics simulations reveal that this new phase is a superionic conductor, characterized by a large proton diffusion coefficient (1.0×10(-4) cm(2)/s at 70 GPa, 850 K). Proton diffusion occurs via a Grotthuss-like mechanism, at a surprisingly lower temperature than in water ice. This may have implications for the onset of superionicity in the molecular ice mixtures present in Jovian planets. Our simulations further suggest that the anisotropic proton hopping along different H bonds in the molecular solid may explain the formation of the recently predicted ionic phase at low temperatures.     

Orientational defects in ice Ih: an interpretation of electrical conductivity measurements

We present a first-principles study of the structure and energetics of Bjerrum defects in ice Ih and compare the results to experimental electrical conductivity data. While the DFT result for the activation energy is in good agreement with experiment, we find that its two components have quite different values. Aside from providing new insight into the fundamental parameters of the microscopic electrical theory of ice, our results suggest the activity of traps in doped ice in the temperature regime typically assumed to be controlled by the free migration of L defects.     

Polarization Effects Due to Scattering of Microwave Radiation in ihe Summer Cloudy Atmosphere

We present the results of the spectral analysis of polarization of the thermal microwave emission from the summer cloudy atmosphere at 37 and 94 GHz. A significant polarization of the microwave emission from summer clouds is revealed, which is attributed to scattering of the thermal emission from the atmosphere by melted ice crystals in the melting layer. Based on a model of polarized radiation transfer in the mixed clouds containing melted ice crystals and supercooled water drops, we interpret the experimental data with allowance for all orders of scattering. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 4, pp. 314–326, April 2005.     

Dynamics of hydrogen-bonded water networks under high pressure: Neutron scattering and computer simulation

Abstract

Molecular dynamics simulation of proton-ordered high pressure ice modifications II and IX was performed. Dynamics of both isotope varieties, H₂O and D₂O, was simulated. Rectangular simulation box of ice II contained 576 and that of ice IX 768 molecules. The average kinetic energy corresponded to 82 and 201 K for ice II and to 87 and 203 K for ice IX. One-phonon densities of states were calculated via Fourier transformation of velocity autocorrelation functions and compared with those found experimentally from inelastic incoherent neutron scattering. This characteristic was calculated for all the molecules, as well as for the molecules of a particular crystallographic type. Both simulated ice modifications contain molecules of two different structural types. Dynamic characteristics of molecules of different types are slightly different. Splitting of the librational peak at about 60–70meV observed in the ice II experimental spectrum is mainly due to such difference. In the case of ice II simulated spectra reproduce experimental ones quite reasonably in the whole range of energies, while in the case of ice IX agreement with the experiment is worse.     

Thermodynamics of high-pressure ice polymorphs: ice II

Thermodynamic properties of high-pressure solid phase ice II are studied theoretically. The P-V-T equation of state of ice II is derived and its thermodynamic functions are calculated based on the available experimental data. New results are presented concerning the equilibrium solid-solid phase transitions between ice II and ice Ih, ice II and III, and ice II and V.     

The conductivity properties of protons in ice and mechanism of magnetization of liquid water

From a study of electrical conductivity of protons in the hydrogen-bonded chains in ice we confirm that the magnetization of liquid water is caused by proton transfer in closed hydrogen-bonded chains occurring as a first order phase transition, through which the ice becomes liquid water. We first study the conductive properties of proton transfer along molecular chains in ice crystals in our model. Ice is a typical hydrogen-bonded molecular system, in which the interaction of localized fluctuation of hydrogen ions (H⁺) with deformation of a structure of hydroxyl group (OH) results in soliton motion of the protons along the molecular chains via ionic and bonded defects. We explain further the quantum conductive properties of proton transfer and determine its mobility and conductivity under constant electric-field using a new theory of proton transfer, which agree with experimental values. From features of first order phase-transition for ice, and some experimental data of pure and magnetized water we confirm further that there are not only free water molecules, but also many linear and closed hydrogen-bonded chains consisting of many polarized water-molecules in the liquid water. Thus a ring proton-current, which resembles to a “molecular current” or a “small magnet” in solids, can occur in the closed hydrogen-bond chains under action of an externally applied magnetic field. Then the water molecules in the closed chains can be orderly arrayed due to the magnetic interaction among these ring proton currents and the externally applied magnetic field. This is just the magnetized effect of the water. In such a case the optical and electronic properties of the water, including the dielectric constant, magnetoconductivity, refraction index, Raman and Infrared absorption spectra, are changed. We determine experimentally the properties of the magnetized water which agree with the theoretical results of our model. However, the magnetized effect of water is, in general, very small, and vanishes at temperatures above 100 ^○C.     

Hydrogen mean force and anharmonicity in polycrystalline and amorphous ice

The hydrogen mean force from experimental neutron Compton profiles is derived using deep inelastic neutron scattering on amorphous and polycrystalline ice. The formalism of mean force is extended to probe its sensitivity to anharmonicity in the hydrogen-nucleus effective potential. The shape of the mean force for amorphous and polycrystalline ice is primarily determined by the anisotropy of the underlying quasi-harmonic effective potential. The data from amorphous ice show an additional curvature reflecting the more pronounced anharmonicity of the effective potential with respect to that of ice Ih.     

低温生物医学与热物理

本文阐述了低温生物学、低温医学与热物理的关系；着重讨论生物体低温保存的问题，细胞和组织的低温损伤是溶液冻结相变过程所引起的冰晶损伤和高浓度溶液的损伤；这个过程和传热传质密切相关；而低温保存的机理则是溶液的非晶态化（玻璃化）。本文还讨论了低温生物医学当前的研究热点，以及其中的热物理问题。     

Polar nephelometer for light-scattering measurements of ice crystals

We report on a small, lightweight polar nephelometer for the measurement of the light-scattering properties of cloud particles, specifically designed for use on a balloonborne platform in cirrus cloud conditions. The instrument consists of 33 fiber-optic light guides positioned in a two-dimensional plane from 5 degrees to 175 degrees that direct the scattered light to photodiode detectors-amplifier units. The system uses an onboard computer and data acquisition card to collect and store the measured signals. The instrument's calibration is tested by measurement of light scattered into a two-dimensional plane from small water droplets generated by an ultrasonic humidifier. Excellent comparisons between the measured water-droplet scattering properties and expectations generated by Mie calculation are shown. The measured scattering properties of ice crystals generated in a cold chamber also compare reasonably well with the theoretical results based on calculations from a unified theory of light scattering by ice crystals that use the particle size distribution measured in the chamber.     

Artificial square ice and related dipolar nanoarrays

We study a frustrated dipolar array recently manufactured lithographically by Wang in order to realize the square ice model in an artificial structure. We discuss models for thermodynamics and dynamics of this system. We show that an ice regime can be stabilized by small changes in the array geometry; a different magnetic state, kagome ice, can similarly be constructed. At low temperatures, the square ice regime is terminated by a thermodynamic ordering transition, which can be chosen to be ferro- or antiferromagnetic. We show that the arrays do not fully equilibrate experimentally, and identify a likely dynamical bottleneck.     

NEUTRON SCATTERING AND LATTICE DYNAMICAL STUDIES OF THE HIGH-PRESSURE PHASE ICE (II)

Lattice dynamical calculations have been carried out for ice II based on the force field constructed for ice Ih. In order to fully understand ice II inelastic neutron scattering spectra, the decomposed phonon density of states was shown mode by mode. Calculated results have shown that the hydrogen bond force constant between the six-molecule rings is significantly weaker, 75eV/nm², compared with the force constant, 220eV/nm², within the rings. Inelastic neutron scattering spectra of clathrate hydrate H₂O+He are almost the same as ice II. This means that the absorption of He atoms cannot affect the bond strengths of the ice II host lattice. Based on the force field model for ice II, the van der Waals interactions between water molecules and helium atoms are considered. The results obtained are consistent with experimental data. Lattice dynamical calculations have been carried out for ice II using seven rigid pairwise potentials. It was found that MCY makes the stretching and bending interactions in ice II too weak and makes the O-O bond length too long (～5%), thus its lattice densities are obviously lower than other potential lattices or experimental values.     

Ice nucleation of water droplet containing solid particles under weak ultrasonic vibration

Water with small volume (a few microlitres or less) often maintains its liquid state even at temperatures much lower than 0 °C. In this study, we examine the onset of ice nucleation in micro-sized water droplets with immersed solid particles under weak ultrasonic vibrations. The experimental results show that ice nucleation inside the water droplets can be successfully induced at relatively high temperatures. The experimental observations indicate that the nucleation sites are commonly encountered in the region between the particle and the substrate. A numerical study is conducted to gain insight into the possible underlying phenomenon for ice nucleation in such systems. The simulation results show that the collapse of cavitation bubbles in the crevice at the particle surface is structure sensitive with the hemisphere-shape crevice generating pressures as high as 1.63 GPa, which is theoretically suitable for inducing ice nucleation.     

Substrate dependent sublimation kinetics of mesoscopic ice films

We have measured the sublimation kinetics of 2–30 nm thick ice layers deposited in ultra high vacuum at 100 K, on different surfaces; Pt(111) and graphite (0001) surfaces with and without various pre-adsorbed monolayers. The results reveal (i) a much more complex sublimation kinetics than expected for a simple molecular solid, and (ii) a strong influence of the underlying substrate on the kinetics. These features, which are reproduced by computer simulations, are due to (i) a phase transition from amorphous to crystalline ice during sublimation, and (ii) substrate dependent nucleation and growth of the ice layers, respectively. The results are correlated with the hydrophobicity-hydrophilicity of the surfaces, and suggest a new method to characterize the wetting properties of solid surfaces. It can be easily performed with state-of-the-art surface cleanliness control, contrary to conventional wetting methods. Applied to the present results, and those of Smith et al. in the preceding paper [Surf. Sci. 367 (1996) L13], this gives, in order of decreasing wetting of water; clean Pt(111)>cleanRu(001)>Cs covered graphite>clean graphite>octane covered Pt(111)⩾clean Au(111).