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  • 1
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    Electric structure of dipolarizaiton fronts associated with interchange instability in the magnetotail (2013)
    Wiley
    Details
    Publication Date: 2013-09-21
    Description: [1]  The electric structure of dipolarization fronts (DFs) is very important to both DF dynamics and particle acceleration. We performed two-dimensional Hall MHD simulation to study the electric structure of DF produced by interchange instability on the scale of ion inertial length in the flow braking region of near-Earth tail. The results indicate that Hall effect makes the structures of plasma density and magnetic field deformed in the dawn-dusk direction. This deformation is caused by the induced Lorentz force along the tangent plane of DF, which is associated with the outward moving of demagnetized ions driven by the ion-scale Earthward electric field on DF. In addition, the x component of electric field contributed jointly by Hall and electron pressure gradient terms along with Bz can produce a dawnward E  ×  B drift to the whole “mushroom” structure. Inside the DF, the electric field is mainly produced by Hall term, and the contributions from the convectional and electron pressure gradient electric fields are very small. This indicates that the ion frozen-in condition of magnetic field is violated inside the DF. Therefore it is the electric field contributed by Hall term inside the DF that changes the overall MHD “mushroom” pattern. The comparison between the simulation results and the observations of THEMIS satellites demonstrates that the model of Hall MHD simulation can reproduce the plasma and electric field observed at DF.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Experimental investigation on a pulsating heat pipe with hydrogen (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-12-19
    Description: The pulsating heat pipe (PHP) has been increasingly studied in cryogenic application, for its high transfer coefficient and quick response. Compared with Nb 3 Sn and NbTi, MgB 2 whose critical transformation temperature is 39 K, is expected to replace some high-temperature superconducting materials at 25 K. In order to cool MgB 2 , this paper designs a Hydrogen Pulsating Heat Pipe, which allows a study of applied heat, filling ratio, turn number, inclination angle and length of adiabatic section on the thermal performance of the PHP. The thermal performance of the hydrogen PHP is investigated for filling ratios of 35%, 51%, 70% at different heat inputs, and provides information regarding the starting process is received at three filling ratios.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 3
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    A preliminary soil security assessment of agricultural land in middle‐eastern China (2018)
    Wiley
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    Publication Date: 2018
    Description: Abstract Sustainable management of agricultural land requires not only an accurate assessment of the biophysical status of the soil but also estimates of the social and economic aspects of the soil. This paper focuses on soil security mapping of an approximately 80 000 km2 agricultural area in middle‐eastern China. We examined a digital soil assessment framework in mapping soil security and its five dimensions (capability, condition, capital, connectivity and codification) using digital soil maps and environmental variables. The main objective is to improve the understanding of soil protection in agricultural practices. Soil and environmental variables were coded as indicator values based on their functions, and three averaging models were used to integrate the indicators for soil security mapping. Results show that agricultural land in the study area currently has a high potential to achieve the crop production function, while there is still lack of sufficient social connectivity. Most of agricultural land has been properly protected by the public policy. More than half of the agricultural land has high security for cropping, while there is no unsecured soil. In general, most of the agricultural lands have already been well developed for cropping. The low soil security mainly contributes to the lack of proper connection to the soil. The findings suggest that digital soil security assessment is highly recommended for guiding sustainable development of agricultural land, because it could provide the knowledge of factors affecting soil security from complex multifaceted dimensions, and potential solutions to make agriculture soil more secure.
    Print ISSN: 0266-0032
    Electronic ISSN: 1475-2743
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 4
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    Synergistic Effect of Corn Leaf Volatile Odor Substances on Sex Pheromone of Asian Corn Borer, Ostrinia furnacalis (Guenée) (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-10-12
    Description: After proposing a new total synthetic route for pheromone of Ostrinia furnacalis (Guenée) in a high overall yields, short synthetic, and cheap starting materials way, we used the method of electroantennogram (EAG) to detect the synergistic effects of five common corn leaf volatiles, which include benzaldehyde, phenylacetaldehyde, cis-3-hexenol, trans-2-hexenol and corn oil, on sex pheromones of Asian corn borer. The result showed that the five substances can significantly increase the activity of Asian corn borer sex pheromone and have a synergistic effect, but there was no significant difference between each other.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 5
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    Estimates of Ionospheric Transport and Ion Loss at Mars (2017)
    Wiley
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    Publication Date: 2017-10-01
    Description: Ion loss from the topside ionosphere of Mars associated with the solar wind interaction makes an important contribution to the loss of volatiles from this planet. Data from NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission combined with theoretical modeling are now helping us to understand the processes involved in the ion loss process. Given the complexity of the solar wind interaction, motivation exists for considering a simple approach to this problem and for understanding how the loss rates might scale with solar wind conditions and solar extreme ultraviolet irradiance. This paper reviews the processes involved in the ionospheric dynamics. Simple analytical and semi-empirical expressions for ion flow speeds and ion loss are derived. In agreement with more sophisticated models and with purely empirical studies, it is found that the oxygen loss rate from ion transport is about 5% (i.e., global O ion loss rate of Q ion ≈ 4 x 10 24 s -1 ) of the total oxygen loss rate. The ion loss is found to approximately scale as the square root of the solar ionizing photon flux and also as the square root of the solar wind dynamic pressure. Typical ion flow speeds are found to be about 1 km/s in the topside ionosphere near an altitude of 300 km on the dayside. Not surprisingly, the plasma flow speed is found to increase with altitude due to the decreasing ion-neutral collision frequency.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Design of a In-situ Ammonia Nitrogen Analyzer in Seawater (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-06-03
    Description: A in-situ ammonia nitrogen analyzer in seawater was designed based on wet chemical reaction principle, combined the fluorospectrophotometry method with flow injection analysis. The analyzer was controlled by peristaltic pump and tree-way valve, which has the advantages of high sensitivity, low-reagent consumption and can measure the concentration of ammonia nitrogen in seawater in-situ. The detection range was 10∼500μg/L, while the detection limit was 1.80μg/L and the relative standard deviation (RSD) was less than 2%. The on-site comparison tests between the ammonia nitrogen analyzer and the national standard methods were finished, and the results indicated that the analyzer was entirely feasible and could reflect the content and changes of the ammonia nitrogen in the seawater.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 7
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    Investigating the origin of the Chinese name for alfalfa (2017)
    Institute of Physics (IOP)
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    Publication Date: 2017-03-08
    Description: It is assured that alfalfa ( Medicago sativa L.) was introduced in Han dynasty. There are cognitive differences on whether Zhang Qian introduced alfalfa. Based on the previous studies, research inductive method was used. The relationship between Zhang Qian and alfalfa introduction was analyzed from the motivation, experience and influence of Zhang Qian to the Western Regions and the image generation of Zhang Qian brought back alfalfa’s seeds. Till to now, there are four opinions about Zhang Qian introducing Alfalfa seeds, including : (1) Zhang Qian introduced alfalfa seeds;(2) Zhang Qian did not introduce alfalfa seeds;(3) the information of Zhang Qian transferring alfalfa;(4)for commemoration Zhang Qian to the Western Regions. Although there are not direct historical materials to support Zhang Qian brought alfalfa seed to Han dynasty, it believes and confirms that the introducing of alfalfa is inextricably interwoven with Zhang Qian’s western travel. Zhangqian brought rel...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 8
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    CFD analysis on a turbulence generator of medium consistency pump (2013)
    Institute of Physics (IOP)
    Details
    Publication Date: 2013-12-22
    Description: Medium concentration paper suspension is a water-air-fibre three phase suspension. It has complicated physical features. When concentration exceeds 7%, it stops flowing and acts like a solid. A generator suspension is installed before the impeller to disturb the flocs and networks to make it start to flow. In this paper, CFD method is adopted to study the effects of the turbulence generator. As there is not a mature model to describe the characteristic of pulp suspension, Newtonian fluid is used to get the general property of the turbulence generator. In the CFD simulation, apparent viscosity of the pulp suspension is used to characterize the mixture. Firstly, numerical method is applied to get the turbulence generator properties in different rotational speed and different viscosity. From another point of view, air contained in the suspension is separate initially by means of centrifugal force. As it is difficult to describe a practical model of pulp suspension, it is simplified...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 9
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    Survey of magnetic reconnection signatures in the Martian magnetotail with MAVEN (2017)
    Wiley
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    Publication Date: 2017-03-30
    Description: We conduct an extended survey of reconnection signatures observed in the Martian magnetotail by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. Although it is well established that magnetic reconnection plays a fundamental role in the dynamics of intrinsic magnetospheres, the role of reconnection in the dynamics of induced magnetospheres remains poorly understood. Based on comprehensive plasma and field measurements by MAVEN in the Martian magnetotail, we first identified 776 current sheet crossings and then selected 34 crossings with Hall magnetic field signatures, which are indicative of the ion diffusion region of tail reconnection. For the majority of the identified Hall field events, we observe ion flow enhancements in the directions consistent with the reconnection outflow directions expected from the Hall magnetic field polarity. The reconnection signatures are preferentially observed in the − E hemisphere of the near-Mars magnetotail at ∼1–2 Mars radii downstream from Mars. We have found no strong correlation of the likelihood of observing reconnection signatures with local crustal field strengths or with upstream drivers. The duty cycle of tail reconnection is estimated to be ∼1–10% or even higher. The MAVEN observations suggest that magnetic reconnection can play an important role in the dynamics of the Martian magnetotail.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
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    Transmission line icing prediction based on DWT feature extraction (2016)
    Institute of Physics (IOP)
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    Publication Date: 2016-09-27
    Description: Transmission line icing prediction is the premise of ensuring the safe operation of the network as well as the very important basis for the prevention of freezing disasters. In order to improve the prediction accuracy of icing, a transmission line icing prediction model based on discrete wavelet transform (DWT) feature extraction was built. In this method, a group of high and low frequency signals were obtained by DWT decomposition, and were fitted and predicted by using partial least squares regression model (PLS) and wavelet least square support vector model (w-LSSVM). Finally, the final result of the icing prediction was obtained by adding the predicted values of the high and low frequency signals. The results showed that the method is effective and feasible in the prediction of transmission line icing.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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