Application of Line Boundary Technique to 2D Tidal Current Simulation

To deal with the problems concerning the shore boundary, moving boundary and engineering boundary which are encountered frequently in 2D tidal current simulation by the finite difference method, the concept of line boundary is introduced and studied here, and then the line boundary technique in common use is proposed in this paper. Analysis of some calculation cases shows that this technique is practical, effective, and simple in 2D tidal current simulation involving different boundaries.

THE EXACT SOLUTIONS OF ELASTIC－PLASTIC CRACK LINE FIELD FOR MODE Ⅱ PLANE STRESS CRACK

The near crack line field analysis method has been used to investigate into the exact elastic-plastic solutions of a mode Ⅱ crack under plane stress condition in anelastic-perfectly plastic solid. The assumptions of the usual small scale yielding theoryhave been completely. dbandoned and the correct .formulations of matching conditionsat the elastic-plastic boundary have been given. By matching the general solution of the plastic stress field (but not the special solution used to be adopted) will the exactelastic stress field (but not the crack tip K-dominant field) at the elastic-plasticboundary. near the crack line, the plastic .stresses, the length of the plastic zone and theunit normal vector of the elaslic-plastic boundary. which sufficiently precise nearthe crack line region, hare been given.

THE EXACT SOLUTIONS OF ELASTIC－PLASTIC CRACK LINE FIELD FOR MODE Ⅱ PLANE STRESS CRACK

The near crack line field analysis method has been used io investigate into theexact elastic-plastic solutions of a mode II crack under plane stress condilion in anelastic-perfectly plastic solid. The assumptions of the usual small scale yielding theory.hare been completely. dbandoned and the correct formulations of matching conditionsat the elaslic-plastic boundary. have been given. By, matching the general solution ofthe plastic slress field (bul not the special solution used to be adopted) with the exactelastic stress field (but not the crack tip K-dominant field) at the elastic-plasticboundary, near the crack line, the plastic stresses. the length of the plastic =one and theunit normal vector of the elastic-plastic boundary.which are sufficiently precise near the crack line region ,have been given.

A simple method to extract glacier length based on Digital Elevation Model and glacier boundaries for simple basin type glacier

Glacier length is a key morphological element that has many glaciological applications; however, it is often difficult to determine, especially for glaciers that cover larger spatial areas or those that exhibit frequent temporal change. In this paper, we describe a new Arc GIS-based method that can derive glacier flow lines for determining glacier length based on digital elevation model and glacier outlines. This method involves(1) extraction of the highest and lowest points on a glacier,(2) calculation of 10-m contour lines on the glacier from 10 m to 100 m height, and(3) connection of the midpoints of each contour line with the highest and the lowest points in order to create a flow line, which is subsequently smoothed. In order to assess the reliability of this method, we tested the algorithm's results against flow lines calculated using field measurements, analysing data from the Chinese Glacier Inventory, and manual interpretation. These data showed that the new automated method is effective in deriving glacier flow lines when contour lines are relatively large; in particular, when they are between 70 m and 100 m. Nonetheless, a key limitation of the algorithm is the requirement to automatically delete repeated and closed curves in the pre-treatment processes. In addition to calculating glacier flow lines for derivation of glacier length, this method also can be used to effectively determine glacier terminus change.

Prediction of the Mooring Force of a 2-D Floating Oil Storage Tank

A Constrained Interpolation Profile （CIP）-based model is developed to predict the mooring force of a two-dimensional floating oil storage tank under wave conditions, which is validated against to a newly performed experiment. In the experiment, a box-shaped floating oil storage apparatus is used. Computations are performed by an improved CIP-based Cartesian grid model, in which the THINC/SW scheme （THINC： tangent of hyperbola for interface capturing; SW： Slope Weighting）, is used for interface capturing. A multiphase flow solver is adopted to treat the water-air-body interactions. The Immersed Boundary Method （IBM） is implemented to treat the body surface. Main attention is paid to the sum force of mooring line and velocity field around the body. It is found that the sum force of the mooring line increases with increasing wave amplitude. The body suffers from water wave impact and large body motions occur near the free surface. The vortex occurs near the sharp edge, i.e., the sharp bottom comers of the float- ing oil storage tank and the vortex shedding can be captured by the present numerical model. The present model could be further improved by including turbulence model which is currently under development. Comparison between the computational mooring forces and the measured mooring forces is presented with a reasonable agreement. The developed numerical model can predict the mooring line forces very well.

PLANT DENSITY,IRRIGATION AND NITROGEN MANAGEMENT:THREE MAJOR PRACTICES IN CLOSING YIELD GAPS FOR AGRICULTURAL SUSTAINABILITY IN NORTH-WEST CHINA

Agriculture faces the dual challenges of food security and environmental sustainability.Here,we investigate current maize production at the field scale,analyze the yield gaps and impacting factors,and recommend measures for sustainably closing yield gaps.An experiment was conducted on a 3.9-ha maize seed production field in arid north-west China,managed with border and drip irrigation,respectively,in 2015 and 2016.The relative yield reached 70%in both years.However,drip irrigation saved 227 mm irrigation water during a drier growing season compared with traditional border irrigation,accounting for 44%of the maize evapotranspiration(ET).Yield variability under drip irrigation was12.1%,lower than the 18.8%under border irrigation.Boundary line analysis indicates that a relative yield increase of 8%to 10%might be obtained by optimizing the yield-limiting factors.Plant density and soil available water content and available nitrogen were the three major factors involved.In conclusion,closing yield gaps with agricultural sustainability may be realized by optimizing agronomic,irrigation and fertilizer management,using water-saving irrigation methods and using site-specific management.