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In order to improve the arc quenching ability of the multigap system, it is important to know the principle of arc quenching and how the chamber structure affects the arc development process in the multigap system. In this study, the two-dimensional geometric model of the multigap system is established based on the magnetohydrodynamics theory in COMSOL multiphysics simulation platform. The principle of arc quenching in the multigap system is explained in detail by analysing the physical characteristics of the arc in the multigap system. The simulation result shows that the arc is compressed at large scales in the semi-closed chambers of the multigap system, which results in an instantaneous temperature rise of the arc, thus, forming the self-expanding airflow. The strong self-expanding airflow cuts off the arc channel and blocks the energy supply of the arc. The influence of the chamber structure on arc quenching in the multigap system is manifested in the fact that proper improvement of the width and depth of the chamber subserves arc cooling, the reduction of the deflection angle and the increment of the number of the chambers are conductive to arc extinction.

Drawing a discriminative pattern in quantitative datasets is often represented to return a high utility pattern (HUP). The traditional methods output patterns with a utility above a pre-given threshold. Nevertheless, the current user-centered algorithm requires outputting the results in a timely manner to strengthen the interaction between the mining system and users. Pattern sampling can return results with a probability guarantee in a short time, and it could be a candidate technology to mine such discriminative patterns. In this paper, a novel approach named HUPSampler is proposed to sample one potential HUP, which is extracted with probability significance according to its utility in the database. HUPSampler introduces an interval constraint on the length of HUP and randomly extracts an integer k according to the utility proportion firstly; then, the HUPs could be obtained efficiently from a random tree by using a pattern growth way, and finally, it returns a HUP of length k randomly. The experimental study shows that HUPSampler is efficient in regard to memory usage, runtime, and utility distribution. In addition, case studies show that HUPSampler can be significantly used in analyzing the COVID-19 epidemic by identifying critical locations.

The process of arc suppression with a super-strong arc-extinguishing gas (AEG) includes arc truncation and reburning suppression. In this paper, the plasma mechanics, the mechanics of the super-strong AEG, and the arc-reburning suppression by the AEG are all modeled. Combined with test data, the characteristics of arc truncation, pressure characteristics, and time characteristics of the AEG are analyzed, and the law of medium recovery and reignition suppression of arc fracture under the action of the super-strong AEG are discussed. The test results show that with a super-strong AEG, the arc-extinguishing threshold and time are 40 kA and less than 0.5 ms, respectively.

A dual-jet arc-extinguishing method is proposed in order to improve the performance of jet-extinguishing gaps for extinguishing large currents and reducing the lightning trip-out rate of power lines. Meanwhile, we studied the arc-extinguishing effect of the dual-jet non-equilibrium field gas flow. Based on this, a Double Jet Arc Extinguishing Gap (DJAEG) is developed. First of all, the jet field arc extinction modeling analysis is carried out by coupling the typical MAYR arc model with the jet field. Then, the COMSOL MUTIPHSICS simulation software is used to simulate the arc extinction of the DJAEG in the balanced flow field and the non-balanced flow field. Finally, the DJAEG extinguishment arc test is carried out through the construction of the power frequency continuous flow interruption test. The simulation results show that the velocity of the high-speed jet emitted by the DJAEG can reach 3000 m/s, and the arc can be extinguished within 4 ms. These results also verified that the dual jet non-equilibrium flow field has the characteristics of long jet sustaining time. The test results show that the DJAEG successfully extinguished the arc within 4 ms, and there was no reignition. This means that the dual-jet non-equilibrium field has an obvious arc extinction effect.

Due to the multi-phase tectonic movements in Chengbei Fault Zone, a superimposed pattern of Paleozoic buried hill and Cenozoic fault-step slope was developed on the North China platform. The fault–unconformity composite transport played a vital role in the oil and gas supply for the underlying buried hill and the distal high slope, resulting in the accumulation forming of multi-layer multi-type oil and gas. On the basis of seismic and well logging data, the characteristics of fault–unconformity composite transport in Chenghai buried hill and southern high slope were determined. And the reservoir-controlling mechanisms of fault–unconformity composite transport were revealed through oil and gas filling simulation experiments under different transport conditions. The results showed that the composite transport of fault and unconformity in buried hill zone was beneficial to the forming of large-scale reservoirs, and the dominant thick reservoirs or even negative tectonics under unconformity with abundant oil source were the main hydrocarbon accumulation area. As to the forming of reservoirs in the high slope, the key was the lithology configurations around the unconformity of “upper sand and lower mud” and “upper gravel and lower mudstone”. With the help of fault, the composite transport enables long-distance migration of oil and gas from the northern source rocks in Shahejie Formation, leading to hydrocarbon accumulation above the unconformity of Guantao Formation and even in the structural trough of southern high slope. These results revealed that fault–unconformity composite transport was helpful to hydrocarbon accumulation on a large scale, and even negative tectonics in buried hill below unconformity or structural troughs in high slope above unconformity are potential to form reservoirs. This provides a useful reference for theoretical research on reservoir forming in fault basins and a beneficial guidance for oil exploration in similar areas to a certain extent.

Hydrocarbon accumulates in multiple layers of the high, middle and low parts of Chengbei fault zone, in vicinity of Qikou Sag and Qinan Subsag, which represents a breakthrough for large-scale hydrocarbon exploration in recent years. Based on the size, abundance, and attitute of hydrocarbon inclusions, as well as their microscopic polarization and fluorescence characteristics, the hydrocarbon occurrence and the charging difference in the high, middle and low faulted terraces were analyzed systematically in this paper. There are two types of occurrence in the intergranular pores and fractures in the reservoirs, namely, the medium to light oil that shows green fluorescent light, and the solid bitumen charged with a certain amount of hydrocarbon that does not show any fluorescent light. This indicates that the zone has experienced at least two stages of hydrocarbon migration and accumulation, and that diversified forms of hydrocarbon exist in the reservoirs of the zone. The characteristics of hydrocarbon inclusions show that two stages of inclusions were found in the tectonic positions of different faulted terrace. The first-stage inclusions were developed in the early secondary enlargement of quartz grains, with a low degree of development abundance; while the second-stage inclusions were developed after the secondary enlargement of quartz grains, with a high degree of development abundance. The second-stage hydrocarbon inclusions of the reservoir samples obtained at tectonic positions of the high, middle and low fault terrace represent the main filling stage of the present-day reservoirs. Their fluorescence characteristics demonstrate the oil charging difference, which is the maturity of the hydrocarbon decreases as the terraces lift up along the slope. Identifying the hydrocarbon occurrence and charging differences from the perspective of inclusions is conducive to recognizing the regularity of hydrocarbon charging and migration and the distribution patterns in fault terrace zones, and lay the foundation for hydrocarbon exploration of slopes in the future.

To study the process by which an explosive high-speed airflow extinguishes an arc and the characteristics of arc dielectric recovery in a semienclosed space, this study investigates the principles and processes of the formation, development, and extinction of an arc under the action of a high-speed airflow. When the impact arc occurs in a semienclosed arc-extinguishing chamber, the high-speed air suppresses arc development. Due to the high-speed airflow, the arc cools at an accelerated rate; the arc energy weakens, breakpoints occur, and the continuity of the arc energy channel is broken, preventing the arc from forming in the arc-extinguishing chamber and extinguishing it. This article employs AUTODYN software to establish a model for high-speed airflow arc extinguishing in a semienclosed space and then reveals a process by which a high-speed airflow extinguishes an arc in such a space. To verify whether a high-speed airflow can extinguish an arc, we conduct experiments in which high-speed airflow extinguishes a large impact arc and a power frequency arc. We recorded the arc extinguishing process with high-speed and ordinary cameras. The time taken to extinguish the arc is approximately 7 ms, and the arc does not regenerate.

To reduce the damage from the power frequency follow current of distribution lines, a multi-fracture compression airflow arc-extinguishing structure is studied. The structure is mainly composed of a compression tube, a metal electrode, and metal connection fittings, and the multi-fracture compression airflow arc-extinguishing body is formed by the combination of packaging and insulation fittings. The body and the air gap are parallel to both ends of the insulator. When lightning strikes, the internal short gap of the main body and the air gap break down, and the lightning arc enters the arc-extinguishing body through the breakdown channel. In the structure, the arc is compressed by force to form internal and external gradients of temperature and to produce jet airflow. The jet airflow acts on the subsequent power frequency follow current arc, which is suppressed and extinguished. In this paper, a model coupling an arc and a compressed jet airflow in a multi-fracture compression airflow arc-extinguishing structure is established theoretically and simulated by simulation software. Finally, a power frequency follow current interruption test is carried out. The simulation results show that a high-speed airflow of 600 m/s is formed around the fracture at approximately 0.99 ms, and the airflow is proportional to the rate of temperature variation. The test results show that the power frequency follow current of 1.289 kA is cut off within approximately 3 ms without a reburning phenomenon. The effect of power frequency follow current interruption is obvious in the structure.

In order to apply the multichamber structure to DC lines, it’s necessary to know the principle of arc quenching and the arc development process in the multichamber structure. Through analyzing the quenching characteristics of DC arc and establishing the 2-D geometric model of multichamber structure based on the magnetohydrodynamics theory in COMSOL Multiphysics simulation platform, this paper reveals and explains the principle of arc quenching in the multichamber structure. The simulation result shows that the strong self-expanding airflow which caused by the instantaneous temperature rise in the chambers can cut off the arc channel and block the energy supply of the arc. Then the Impulse-DC arc quenching test is carried out to verify the arcing performance of the improved multichamber structure. The arc is finally extinguished at 1.5ms, which manifests that the improved device can effectively suppress DC arc development.

To evaluate the influence of long-term highly active antiretroviral therapy (HAART) on bone metabolism in patients with acquired immune deficiency syndrome (AIDS).A total of 82 AIDS patients who received HAART in the First Affiliated Hospital of Zhejiang University Medical School during January 2012 and May 2016 were enrolled in the study. Patients were divided into TDF group (n=41) and AZT group (n=41), and glomerular filtration rate (GFR), serum calcium, serum phosphate and serum ALP levels in 6, 12, 18, 24 and 30-month during the treatment were analyzed in both groups.Both TDF-based and AZT-based therapies significantly improved CD4(+) T-cell levels of the patients, and no significant difference was observed between the groups. Compared with the baseline, GFR [(120.71±62.85) vs(110.08±39.18) mL/min] and serum phosphate [(1.25±0.19) vs(1.22±0.21) mmol/L] levels rose after 6-month treatment in TDF group, but the difference was not statistically significant (P0.05); Serum ALP [99.0(79.5-124.0) U/L vs 80.0(60.5-96.0) U/L] and serum calcium [(2.32±0.12) vs(2.25±0.17) mmol/L] levels rose significantly (P0.05). As treatment continued, the levels of GFR, serum calcium and serum phosphate declined, while the serum ALP number was still increasing. After 30 months of HAART, the level of serum calcium [(2.16±0.15) vs(2.25±0.17) mmol/L], serum phosphate [(1.06±0.17) vs(1.22±0.21) mmol/L], GFR [(98.13±30.43) vs (110.08±39.18) mL/min] declined significantly (P0.05) in TDF group, while serum ALP [110.0(98.5-120.5) U/L vs 80.0(60.5-96.0) U/L, P0.05] increased. In AZT group, serum calcium and serum ALP levels rose and GFR level was declined (P0.05), while serum phosphate level was not significantly changed during the treatment (P0.05). Compared with AZT group, there were greater changes on the levels of GFR, serum calcium, serum phosphate and serum ALP in TDF group.HAART is effective for patients with AIDS, and TDF-based therapy may have significant impact on bone metabolism of the patients, which needs close monitoring and timely intervention or adjustment if necessary.