Initial transient process in a simple helical flux compression generator

An analytical scheme on the initial transient process in a simple helical flux compression generator, which includes the distributions of both the magnetic field in the hollow of an armature and the conducting current density in the stator, is developed by means of a diffusion equation. A relationship between frequency of the conducting current, root of the characteristic function of Bessel equation and decay time in the armature is given. The skin depth in the helical stator is calculated and is compared with the approximate one which is widely used in the calculation of magnetic diffusion. Our analytical results are helpful to understanding the mechanism of the loss of magnetic flux in both the armature and stator and to suggesting an optimal design for improving performance of the helical flux compression generator.

Experimental study on propagation characteristics of rotating detonation wave with kerosene fuel-rich gas

In this study, kerosene fuel-rich gas produced by the combustion in the gas generator was used as the fuel and oxygen-rich air was used as the oxidant to investigate the propagation characteristics of the rotating detonation wave (RDW). The initiation of the kerosene fuel-rich gas and propagation process of the RDW were analyzed. The influences of the oxygen content in the oxidizer, kerosene mass flow rate of the gas generator, and temperature of the kerosene fuel-rich gas on the propagation process of the RDW were studied. The experimental results revealed that the propagation velocity of the RDW could be improved by increasing the three parameters mentioned above with the kerosene mass flow rate as the strongest factor. The minimum oxygen content that could successfully initiate and maintain the stable propagation of the RDW was 32%, achieving the RDW velocity of 1141.9 m/s. The RDW mainly propagated as two-counter rotating waves and a single wave when the equivalent ratios were 0.62–0.79 and 0.85–0.87, respectively. The highest RDW velocity of 1637.2 m/s was obtained when the kerosene mass flow rate, oxygen content, and equivalent ratio were 74.6 g/s, 44%, and 0.87, respectively.

Initial Rifting Process and Dynamics Mechanism of Huaguang Sag: Evidence from a Numerical Modeling Method

Huaguang Sag is located in the deep seawater area of Qiongdongnan Basin, and its tectonic position belongs to the intersection of NE-trending, SN-trending and NW-trending tectonic systems in the continental margin of the Northwest South China Sea. To investigate the initial rifting process and further more the dynamics mechanism of Huaguang Sag, this paper sets up the structure model of basement which mainly makes up with several depression-controlling faults, and simulates the initial rifting process of Huaguang Sag by the FLAC software. The simulation results show that only affected by the S-N trending extensional stress, the rifting center appears in northern boundary basement faults（two NEE-trending and NWW-trending faults） of Huaguang Sag while does not take place at the NNE-trending and NE-trending basement fault zone in the middle sag, and doesn’t match the current pattern that the basement fault plays a main role in controlling the sediment. In the other case, affected by the S-N trending and E-W trending extensional stress at the same time, the areas of the northern boundary faults zone and internal NNE-trending basement faults zone come to be rifting center quickly, the sedimentary is controlled by the main basement faults to different degrees, and is consistent with the tectonic-sedimentary framework of Huaguang Sag which obtained by the data of geophysical interpretation. In combination with the analysis of regional tectonic background, the paper proposes that two remote tectonic effects occurred by the collision of India-Eurasian Plate： One remote effect was the rotational extrusion of Indo China Block, which led to form a series of NE-trending and NNE-trending basement faults, as well as the E-W trending tensile stress field in Huaguang Sag. The other remote effect was that the deep mantle material of South China Block flowed southward, which resulted in the S-N trending extensional rifting of the lithosphere in northern South China Sea, and finally formed a series of EW-trending and NEE-trending basement faults and the S-N trending tensile stress field in Huaguang Sag. Affected by the above tensile stress fields and the basement faults, the initial rifting occurred in E-W and nearly S-N directions along the pre-existed basement faults（the weak structural zones） in Huaguang Sag.

Eventual Leader Election with Weak Assumptions on Initial Knowledge,Communication Reliability,and Synchrony

This paper considers the eventual leader election problem in asynchronous message-passing systems where an arbitrary number t of processes can crash（t〈n,where n is the total number of processes）.It considers weak assumptions both on the initial knowledge of the processes and on the network behavior.More precisely,initially,a process knows only its identity and the fact that the process identities are different and totally ordered（it knows neither n nor t）.Two eventual leader election protocols and a lower bound are presented.The first protocol assumes that a process also knows a lower bound α on the number of processes that do not crash.This protocol requires the following behavioral properties from the underlying network：the graph made up of the correct processes and fair lossy links is strongly connected,and there is a correct process connected to（n〈f）-α other correct processes（where f is the actual number of crashes in the considered run） through eventually timely paths（paths made up of correct processes and eventually timely links）.This protocol is not communication-efficient in the sense that each correct process has to send messages forever.The second protocol is communication-efficient：after some time,only the final common leader has to send messages forever.This protocol does not require the processes to know α,but requires stronger properties from the underlying network：each pair of correct processes has to be connected by fair lossy links（one in each direction）,and there is a correct process whose n〈f-1 output links to the rest of correct processes have to be eventually timely.A matching lower bound result shows that any eventual leader election protocol must have runs with this number of eventually timely links,even if all processes know all the processes identities.In addition to being communication-efficient,the second protocol has another noteworthy efficiency property,namely,be the run finite or infinite,all the local variables and message fields have a finite domain in the run.