First application of plutonium in soil erosion research on terraces

The spatial distributions of ^(239+240)Pu and ^(137)Cs in soils from Longji Rice Terraces were investigated to evaluate soil erosion.The activity concentrations of ^(239+240)Pu and ^(137)Cs in the surface soils of the paddy fields were in the range of 0.089–0.734 and1.80–7.88 mBq/g,respectively.The activities of ^(239+240)Pu and ^(137)Cs showed very similar distribution trends,first increasing and then decreasing with increasing elevation.The 240Pu/239Pu atom ratios in the surface soils ranged from 0.162 to 0.232.The activities of ^(239+240)Pu and ^(137)Cs in the soil cores tended to be uniformly distributed within the plowed layer and declined exponentially below this depth.The mean soil erosion rates of Longji Rice Terraces estimated by ^(239+240)Pu and ^(137)Cs tracer methods were 5.44 t/(ha·a)and 5.16 t/(ha·a),respectively,which demonstrated that plutonium can replace ^(137)Cs as an ideal tracer for soil erosion research in the future.Landform features are the main factors affecting the distribution of plutonium and ^(137)Cs as well as soil erosion in the Longji Rice Terraces.

Room temperature non-balanced electric bridge ethanol gas sensor based on a single ZnO microwire

In this paper,ultra-long and large-scaled ZnO microwire arrays are grown by the chemical vapor deposition method,and a single ZnO microwire-based non-balanced electric bridge ethanol gas sensor is fabricated.The experimental results show that the gas sensor has good repeatability,high response rate,short response,and recovery time at room temperature(25℃).The response rate of the gas sensor exposed to 90-ppm ethanol is about 93%,with a response time and recovery time are 0.3 s and 0.7 s respectively.As a contrast,the traditional resistive gas sensor of a single ZnO microwire shows very small gas response rate.Therefore,ethanol gas sensor based on non-balanced electric bridge can obviously enhance gas sensing characteristics,which provides a feasible method of developing the high performance ZnO-based gas sensor.

Associations of decimetric type Ⅲ bursts with coronal mass ejections and Hα flares

We present a statistical study of decimetric type Ⅲ radio bursts, coronal mass ejections （CMEs）, and Hα flares observed in the period from July 2000 to March 2005. In total, we investigated 395 decimetric type Ⅲ radio burst events, 21% of which showed apparent correlation to CMEs that were associated with Hα flares. We noticed that the Hα flares which were strongly associated with CMEs were gradual events, and 82% of them took place before CMEs appeared in the field of view of LASCO C2; that most of the CME-associated radio bursts started in the frequency range around 750 MHz with a frequency drifting rate of several hundred MHz s-1, of which both positive and negative ones were recognized; and that the correlation of type Ⅲ radio bursts to CMEs without associated flares is fairly vague, less than 9%.

Prediction of performance of a non-icebreaking ship in marginal ice zone

The Arctic is rapidly transforming into a navigable ocean because of global warming.The retreat of ice extent and widened marginal ice zone(MIZ)in the Arctic made it possible for non-icebreaking commercial vessels to sail into Arctic waters where ice floes of various concentrations and thicknesses exist.The main objective of this work is to estimate the performance of a non-icebreaking cargo ship that sails in the Arctic marginal ice zone.Different numerical approaches are utilized to calculate ice-induced resistance and compared with those proposed in empirical formulas.The comparison shows that the resistances predicted by the two numerical tools differ obviously and are in general smaller in comparison with the ones calculated from the empirical formulas under lower ice concentrations.The total resistances are further calculated to predict the required propulsion powers for the case study vessel to enable navigation under severe ice conditions.This work highlights the significance of developing new and more sophisticated tools for estimation of ship’s ice performance in MIZ,which is the prerequisite to enable non-icebreaking cargo fleet to utilize the Arctic shipping lane.