An Analysis of the Possible Migration Routes of Oedaleus decorus asiaticus Bey-Bienko (Orthoptera: Acrididae) from Mongolia to China

Oedaleus decorus asiaticus (Bey-Bienko) is a destructive pest in grasslands and adjacent farmland in northern China, Mongolia, and other countries in Asia. It has been supposed that this insect pest can migrate a long distance and then induce huge damages, however, the migration mechanism is still unrevealed. The current study uses insect light trap data from Yanqing (Beijing), together with regional meteorological data to determine how air flow contributes to the long-distance migration of O. decorus asiaticus. Our results indicate that sinking airflow is the main factor leading to the insects’ forced landing, and the prevailing northwest wind was associated with O. decorus asiaticus taking off in the northwest and moving southward with the airflow from July to September. Meanwhile, the insects have a strong migratory ability, flying along the airflow for several nights. Thus, when the airflow from the northwest met the northward-moving warm current from the southwest, a large number of insects were dropped due to sinking airflow, resulting in a large outbreak. Our simulations suggest that the source of the grasshoppers involved in these outbreaks during early 2000s in northern China probably is in Mongolia, and all evidence indicates that there are two important immigrant routes for O. decorus asiaticus migration from Mongolia to Beijing. These findings improves our understanding of the factors guiding O. decorus asiaticus migration, providing valuable information to reduce outbreaks in China that have origins from outside the country.

Indian Migrants in Brunei: The Role of Social Networks

Indian immigrants have emerged as a dominant community in Brunei nowadays. Since the colonial period, there has been an influx of Indian migrants to Brunei. This research investigates the social networks that Indians used to get to Brunei. Evidently, there has been little research on these group of people in Brunei. This study employs a sample of 17 low, semi, and unskilled Indian migrants chosen on snow-ball basis. Face-to-face interviews were conducted. According to the findings of this study, social networks played a significant role in making the decision to migrate over to Brunei. We found that chain migration mechanism has been active in the India-Brunei migration domain since long. As a risk diversification approach, migration networks act as a web of interpersonal connections that connect migrants, former migrants, and non-migrants in their origin and destination countries via relationships of kinship, friendship, and common community origin.

Influence of the Visitor Walking on Airflow and the Bioaerosol Particles in Typical Open Tomb Chambers: An Experimental and Case Study

Effective maintenance of ancient buildings is paid more and more attention worldwide. Many ancient buildings with high inheritance value were gradually destroyed, especially for murals in the open tombs. The bioaerosol particles (BPs) are the major source of contamination in murals and visitor walking could increase this hazard. In order to study the impact of visitors walking on the air flow and the distribution of BPs in the typical tomb chambers, the k-ε and Lagrangian discrete phase model were adopted. The walking visitor was described by the dynamic mesh, and the concentration of BPs in the simulation was verified by experimental sampling. The distribution and migration mechanism of contamination in the chamber were dynamically analyzed. The results indicate that the denser vortex generated when a visitor was walking, and the concentration of BPs changed obviously. Therefore, the number of BPs deposited on some precious murals increased and the contamination location shifted in the direction of visitor walking. In addition, the deposition time of BPs was lagging which would cause potential risk. This research can provide scientific basis for reducing murals contamination during visitor visiting and a reference for the maintenance of ancient buildings.

Giant Planets, Tiny Stars: Producing Short-period Planets around White Dwarfs with the Eccentric Kozai–Lidov Mechanism

The recent discoveries of WD J091405.30+191412.25 (WD J0914 hereafter), a white dwarf (WD) likely accreting material from an ice-giant planet, and WD 1856+534 b (WD 1856 b hereafter), a Jupiter-sized planet transiting a WD, are the first direct evidence of giant planets orbiting WDs. However, for both systems, the observations indicate that the planets’ current orbital distances would have put them inside the stellar envelope during the red-giant phase, implying that the planets must have migrated to their current orbits after their host stars became WDs. Furthermore, WD J0914 is a very hot WD with a short cooling time that indicates a fast migration mechanism. Here, we demonstrate that the Eccentric Kozai–Lidov Mechanism, combined with stellar evolution and tidal effects, can naturally produce the observed orbital configurations, assuming that the WDs have distant stellar companions. Indeed, WD 1856 is part of a stellar triple system, being a distant companion to a stellar binary. We provide constraints for the orbital and physical characteristics for the potential stellar companion of WD J0914 and determine the initial orbital parameters of the WD 1856 system.

Study on Oil-water Two-phase Migration Mechanism of Low Permeability Fractured Core based on the Online NMR Testing

Understanding the dynamic migration mechanism of oil-water two-phase is the key to improve the effect of water injection development in low permeability fractured reservoir. Based on artificial fracturing of core and basic physical parameter testing, the online NMR displacement experiments of cores with different fracture widths are conducted to analyze the oil-water dynamic distribution characteristics and migration mechanisms. The experimental results show that when water breaks through at the outlet, oil volume in the small pores is basically unchanged. In the large pores it decreases to a certain extent, while in the fracture it decreases greatly. When the displacement is over, oil volume in the small pores still changes little, while it decreases greatly in the large pores, and it is almost zero in the fracture. With the decrease of fracture width, the recovery ratio when waterflooding front breaks through and the final recovery ratio after displacement increase gradually. The contribution proportion of recovery ratio in the fracture decreases as a whole, while in the large pores it increases gradually, and in the small pores it decreases slightly. The research results lay a foundation for the optimal design of fracture parameters and the adjustment of water injection development technology policy in low permeability fractured reservoir.