Variability of coronal structures and ion components in the solar wind

The variations of solar wind ion fluxes of protons and-particles are studied in a wide timescale: from parts of a second to several months. A persistence time of about 60 hours was obtained for the large-scale variations of-particles. Power density spectra of velocity, density and magnetic field were studied in the frequency range from 10^–5 to 10^–3 Hz. Middle-scale fluctuations of both protons and-particles are close to each other and the spectrum for-particles has a somewhat greater slope than that for protons. Estimates of the variations of the flux power density are given in the frequency range from 10^–3 to 3 Hz.Presented at the VII STP-Symposium in the Hague (Netherlands), 1990.     

Phonons in Ge/Si quantum dot structures: influence of growth temperature

In this paper we present the results of a Raman study of Ge/Si quantum dot (QD) superlattices grown with different thicknesses of a Si interlayer and at different substrate temperatures. The built-in strain and atomic intermixing in the QDs are deduced from an analysis of optical phonon frequencies of the QDs obtained from Raman spectra of the structures.     

Rate determining factors in protein model structures

Previous research has shown a strong correlation of protein folding rates to the native state geometry, yet a complete explanation for this dependence is still lacking. Here we study the rate-geometry relationship with a simple statistical physics model, and focus on two classes of model geometries, representing ideal parallel and antiparallel structures. We find that the logarithm of the rate shows an almost perfect linear correlation with the "absolute contact order", but the slope depends on the particular class considered. We discuss these findings in the light of experimental results.     

The importance of self-consistency in determining interface properties of SIN and DIN structures

We develop a method to solve the Bogoliubov–de Gennes equation for superconductors self-consistently, using the recursion method. The method allows the pairing interaction to be either local or nonlocal corresponding to s-and d-wave superconductivity, respectively. Using this method, we examine the properties of various SIN and DIN interfaces. In particular, we self-consistently calculate the spatially varying density of states and the superconducting order parameter. We see that changing the strength of the insulating barrier at the interface, does not, in the case of an s-wave superconductor, dramatically change the low-energy local density of states in the superconducting region near the interface. This is in stark contrast to what we see in the case of a DIN interface where the local particle density of states is changed dramatically. Hence we deduce that in calculating such properties as the conductance of SIN and DIN structures it is far more important to carry out self-consistent calculations in the d-wave case.     

The influence of surface states on in-plane-gated structures

A model for in-plane-gated structures is proposed, taking into account surface currents and surface charges. The lateral band structures and barrier heights are calculated self-consistently for different bias voltages utilizing this new model. Accumulated negative surface charges lead to a strongly increased depletion length at the positively biased side of the lateral barriers. Most of the applied bias drops in this depleted region and does not affect the barrier height. We have found good agreement between these theoretical results and experimentally determined barrier heights and depletion lengths obtained from temperature-dependent current measurements and optical-beam-induced current measurements.     

The influence of transverse structures on the coupling of solid-state lasers

We demonstrate the influence of transverse structures on the coherent coupling of laser modes. From the Maxwell-Bloch equations in the approximation of a finite mode expansion we derive Adler equations for the relative phases. We use an improved model to describe the gain-induced coupling of two non-orthogonal modes of a solid-state laser. Experimental results for some time-dependent experiments are presented and compared with theoretical predictions of our model.     

Using the photopyrometric method for determining temperature fields

A photopyrometric method is described with special emphasis on its practical application. The accuracy of the method is evaluated, the temperature range in which it can be used is determined and, the conditions of its use in gas studies are considered.     

Large two-dimensional clusters of equal-area bubbles: The influence of the boundary in determining the minimum-energy configuration

Finite monodisperse two-dimensional clusters of bubbles are shown to behave like a crystal rather than a liquid. They attain their lowest-energy configuration when they find an arrangement close to a hexagonal lattice, as predicted by the Wulff construction. The deviation from hexagonal shape of the bubbles in a cluster and the variation in bubble pressure throughout the structure are calculated. It is shown that the effect of reducing the length of the boundary is negligible, explaining why configurations retaining the structure of the lattice will give the lowest energy.     

The role of demagnetization factor in determining the ‘true’ value of the Curie temperature

The Curie temperature, T_C, is the temperature above which a material loses its long-range ferromagnetic order. Considering the equation of state of a ferromagnet in the mean-field approximation it has been shown theoretically that the value of the demagnetization factor N has a significant influence on the perceived location of T_C on the temperature scale. A series of precise measurements of magnetization using two differently shaped single crystals of high-purity gadolinium was carried out to prove this result experimentally and develop a procedure leading to the ‘true’ value of T_C.     

The influence of electric-field penetration upon electron distribution in M-I-M structures

The penetration of the electric field into the electrodes can modify the angular distribution of electrons in the basic metal electrode of the sandwich cathode. Electrons obtain additional energy n the normal direction so that the transmission probability of the dielectric potential barrier ncreases. The change of the leakage current can reach the value of tens per cent.     

The influence of finite cavities on the sound insulation of double-plate structures

Lightweight walls are often designed as frameworks of studs with plates on each side--a double-plate structure. The studs constitute boundaries for the cavities, thereby both affecting the sound transmission directly by short-circuiting the plates, and indirectly by disturbing the sound field between the plates. The paper presents a deterministic prediction model for airborne sound insulation including both effects of the studs. A spatial transform technique is used, taking advantage of the periodicity. The acoustic field inside the cavities is expanded by means of cosine-series. The transmission coefficient (angle-dependent and diffuse) and transmission loss are studied. Numerical examples are presented and comparisons with measurement are performed. The result indicates that a reasonably good agreement between theory and measurement can be achieved.     

日冕反常加热之谜新解

日冕加热之谜是当代天文学、天体物理学中的八大难题之一。自日冕高温发现七十多年以来,人们建立了许多模型试图解决这一难题,但到目前为止,现有的模型几乎都无法给出一个完整的解答。近年来,人们从观测上取得了一系列新的发现,如从光球到日冕的超精细磁通道中的快速上升热流、二型针状体、极紫外龙卷风等。这些发现给我们一个新的启示,即日冕的加热能量很可能是直接通过热物质上升并在日冕区域沉积而实现的。但是,这些上升热流又是如何形成的呢？鉴于太阳大气中普遍存在具有磁场梯度的磁通量管,作者最近提出了磁场梯度抽运机制(magnetic gradient pumping mechanism,MGP),每一磁通量管就像一个抽水机一般,将底层热分布的等离子体中的高能端粒子抽运到高层大气中沉积,并最终形成了高温的日冕大气。这一机制为我们探索日冕加热之谜提供了一个新的思路。     

The influence of annealing temperature on the morphology of graphene islands

We report on temperature-programmed growth of graphene islands on Ru(0001) at annealing temperatures of 700°C,800°C,and 900°C.The sizes of the islands each show a nonlinear increase with the annealing temperature.In 700°C and 800°C annealings,the islands have nearly the same sizes and their ascending edges are embedded in the upper steps of the ruthenium substrate,which is in accordance with the etching growth mode.In 900°C annealing,the islands are much larger and of lower quality,which represents the early stage of Smoluchowski ripening.A longer time annealing at 900°C brings the islands to final equilibrium with an ordered moir’e pattern.Our work provides new details about graphene early growth stages that could facilitate the better control of such a growth to obtain graphene with ideal size and high quality.     

The influence of breaking of exchange bonds on the Curie temperature

The size effect of magnetically ordered nanoparticles on the Curie temperature is discussed. For a system of Fe₃O₄ nanoparticles with different dispersities, it is demonstrated that the smaller the size of the particles, the larger the thickness of their surface layer, which is characterized by considerable distortions of the regular structure.     

The influence of temperature on the optical properties of gold nanoparticles

The optical properties of gold nanoparticles in a transparent matrix are studied at temperatures from 300 to 1000 K within the spectral range from 450 nm to 1.5 μm. It is shown that, in the case of small nanoparticles and short wavelengths in the plasmon resonance band, an increase in temperature leads to a decrease in the absorption efficiency factor. The light absorption efficiency factor of gold nanoparticles with a radius exceeding 40 nm increases with increasing temperature in the entire spectral range studied. The single scattering efficiency factor always decreases with increasing temperature. The effects observed are related to a change in the refractive indices of gold and the matrix with comparable contributions. It is shown that results of calculations agree qualitatively with available experimental data. The results are necessary to optimize the composition of the actuators, including gold nanoparticles, in the transparent matrices.     

The influence of Landau quantization on the propagation of solitary structures in collisional plasmas

In this work, we study damped ion acoustic solitary wave structures in magnetized dense plasmas. The collisional effects of ions with electrons and neutrals are considered. The trapping effects of electrons and Landau quantization are included in the plasma model under consideration. We assume that magnetic field is quantized such that the condition■ is satisfied. We have derived the damped Korteweg–de Vries(dKdV) equation by using small amplitude reductive perturbation technique. The time-dependent analytical and numerical solutions of the dKdV equation are presented. For numerical solutions we apply a two level finite difference scheme with the help of the Runge Kutta method. The effects of variations of different plasma parameters on the propagation characteristics of damped solitary structures in the presence of collisions are discussed.     

Theoretical split-window algorithms for determining the actual surface temperature

Summary Two split-window strategies for obtaining the actual surface temperature (AST) from an infra-red sensor system are investigated by means of simulations of radiometer signals for a wide range of different geophysical situations. The differences between strategies are closely related to the strong or weak presence of atmospheric effects in the split-window coefficient. It has been demonstrated that the strong presence makes it necessary to know the total atmospheric water vapour as well as the effective emissivities in the two thermal channels for applying the strong split-window method, whereas for the weak presence one only needs to know the emissivities. Simplified algorithms have been obtained from these methods when some of the input data are unknown. Likewise, included for all these algorithms is a rigorous evaluation of their accuracies that takes into account the uncertainties in the emissivity and the noise-equivalent temperature. In this way several algorithms are provided for determining the AST, leaving to the choice of the reader the algorithm that best responds to the required accuracy and the available input data.