INFILTRATION KINETICS MODEL OF LIQUID METAL INTO A FIBROUS PREFORM IN CENTRIFUGAL ACCELERATING FIELD

The infiltration kinetics of the metal melt into a fibrous preform in centrifugal accelerating field is analyzed on the basis of Darcy's law and the assumption that the fibrous preform is treated as 'bundle of capillaries' The critical rotating speed is analyzed with the established model The influences of the metal melt mass,the rotating speed of the equipment,the casting height, the original outer radius of the metal melt and the fibrous volume fraction in fibrous preform on infilatration are studied The results show that the critical rotating speed is dependent on critical pressure, casting height, metal melt mass and the character of fibrous preform With the increase in the metal melt mass, rotating speed of the equipment and original outer radius of the metal melt, or the decrease in casting height and fibrous volume fraction in fibrous of the metal melt,or the decrease in casting height and fibrous volume fraction in fibrous preform,infiltration of metal melt for fibrous preform becomes easier.

PARTICLE DISTRIBUTION IN CENTRIFUGAL ACCELERATING FIELDS

Based on continuum theory and moving law of particles, a model is presentedto obtain gradient distribution of particles in centrifugal accelerating field, by which theparticle distribution in gradient composite material can be predicted. The simulation shows withincreases in rotating time, four regions gradually appear from the internal periphery to theexternal one, they are free region, transition region, steady region and surface reinforced region,and the latest three regions are defined as a rich region. Finally, the steady region disappears,and the rich region only includes transition region and surface reinforced region. The influences ofcentrifugal acceleration coefficient G, primary volume fraction phi_0, pouring temperature theta_pand density difference between the particle and the metal matrix on particles gradient distributionare studied in detail. The results of the theoretical analysis agree with experiment ones. Both ofanalysis and experiment results indicate that with the increase in G and theta_p the particledistribution becomes more centralized and the consistence of particle in the surface peripherybecomes larger.

Adjusting the accelerating field distribution of a superconducting CH cavity

In a superconducting CH （cross bar H mode） cavity, the method of regulating the length of a drift tube is employed to adjust the distribution of the accelerating field. In this article, we simulate the electromagnetic field of a CH structure to illustrate the reason for adjusting the field distribution by varying drift tube length. Meanwhile, that the presence of the drift tube will cause a sharp rise in the maximum electric field is also shown. This phenomenon is contrary to superconducting cavity design principles in which the cavity geometry needs to be optimized to reduce the maximum electric field to avoid field emission. We propose a variable diameter superconducting CH cavity design to solve this conflict. The simulation of the variable diameter superconducting CH cavity shows that this method is feasible.

Accelerations in the Local Magnetic Field on the Adriatic Tectonic Microplate

The high level of noise is a special feature of the geomagnetic field on the territory of Slovenia. The tension of the Adriatic tectonic microplate, on which Slovenia entirely lies, was recognized as one of its sources. The interior of the Earth is also the source of geomagnetic jerks. They are impulses in the secular variation calculated on the basis of monthly or annual mean values of variation of the geomagnetic field. The paper presents an analysis of accelerations in a local magnetic field calculated on the bases of daily mean values of the magnetic field measured at PIA geomagnetic Observatory (Piran, Slovenia) in 2020. These accelerations indicate geomagnetic impulses at the regional level over days or weeks. Then these results are compared with the registered seismic activity in the West Balkans.

Non-static plane symmetric inflationary Universe in scalar tensor theory

Non-static plane symmetric cosmological solutions are presented in the presence of cosmic strings in the scalar-tensor theory of gravitation formulated by Sen ＆ Dunn. It is shown that string cosmological models representing geometric strings （ρ = λ） and massive strings （ρ ＋λ = 0） do exist in this theory. Further, it is found that the Takabayasi string, i.e. ρ= （1 ＋ζ）λ, does not exist. Some physical and geometrical features of these models are discussed.

Mini-DDL and Its Applications in the Radiation Field Measurement around Accelerators

The variation of the radiation field around accelerator is complex.Only by real-time monitoring can one learn them in detail.The traditional measurement methods have been out of date.The mini-DDL is a specific device designed for such radiation field real-time monitoring.It has huge flash memories and is small in size.It can communicate with the control PC via intranet or RS232 port.So it is suitable to be applied not only in area monitoring but also in temporary monitoring.The radiation field measurements results obtained using the Mini-DDL are introduced in this paper.

Origin and structures of solar eruptions Ⅰ: Magnetic flux rope

Coronal mass ejections(CMEs) and solar flares are the large-scale and most energetic eruptive phenomena in our solar system and able to release a large quantity of plasma and magnetic flux from the solar atmosphere into the solar wind. When these high-speed magnetized plasmas along with the energetic particles arrive at the Earth, they may interact with the magnetosphere and ionosphere, and seriously affect the safety of human high-tech activities in outer space. The travel time of a CME to 1 AU is about 1–3 days, while energetic particles from the eruptions arrive even earlier. An efficient forecast of these phenomena therefore requires a clear detection of CMEs/flares at the stage as early as possible. To estimate the possibility of an eruption leading to a CME/flare, we need to elucidate some fundamental but elusive processes including in particular the origin and structures of CMEs/flares. Understanding these processes can not only improve the prediction of the occurrence of CMEs/flares and their effects on geospace and the heliosphere but also help understand the mass ejections and flares on other solar-type stars. The main purpose of this review is to address the origin and early structures of CMEs/flares, from multi-wavelength observational perspective. First of all, we start with the ongoing debate of whether the pre-eruptive configuration, i.e., a helical magnetic flux rope(MFR), of CMEs/flares exists before the eruption and then emphatically introduce observational manifestations of the MFR. Secondly, we elaborate on the possible formation mechanisms of the MFR through distinct ways. Thirdly, we discuss the initiation of the MFR and associated dynamics during its evolution toward the CME/flare. Finally, we come to some conclusions and put forward some prospects in the future.