the prevalent method of irrigation in paddy fields in iran is continuous ponding, which changes to intermittent method at the time of water shortage. soil cracks are the main problem in intermittent irrigation. in this study, effects of adding rice straw on some soil physical characteristics and cracks were studied in paddy soils of the guilan province of iran. the experiment was performed as s...

the silica aerogel was prepared by the acid–base sol–gel polymerization of tetraethylorthosilicate precursor followed by ambient pressure drying. the prepared silica aerogels were characterized by fourier transform infrared )ft-ir(, thermo-gravimetric and differential thermal analysis )tg/dta(, x-ray diffractometer )xrd(, energy dispersive x-ray microanalysis )edx(, brunauer–emmitt–teller (bet)...

The polychaete Nereis virens burrows through muddy sediments by exerting dorsoventral forces against the walls of its tongue-depressor-shaped burrow to extend an oblate hemispheroidal crack. Stress is concentrated at the crack tip, which extends when the stress intensity factor (KI) exceeds the critical stress intensity factor (KIc). Relevant forces were measured in gelatin, an analog for elast...

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A technique to estimate the depth of surface-breaking cracks in concrete is presented. The surface wave transmission coefficient across the crack plane is determined and used to estimate the depth. A self-compensating testing scheme is applied to eliminate experimental difficulties. Here the self-compensating testing scheme is introduced, and the approach used to estimate crack depth from the m...

Miniaturized, wireless instrumentation is now a reality and this paper describes development of such a system to monitor crack response. Comparison of environmental (long-term) and blast-induced (dynamic) crack width changes in residential structures has lead to a new approach to monitoring and controlling construction vibrations. A low power consumption potentiometer displacement transducer an...

We describe a Matlab-based, interactive, selfcontained, graphics-oriented code to process shearwave splitting data from microearthquakes in order to image the fractured subsurface in geothermal reservoirs. The code consists of three main modules: 1) data processing, 2) forward modeling, and 3) inverse modeling. The first module allows for rapid and precise measurement of fast S-wave polarizatio...

the problem of crack identification in continuous beam like structures is considered. the cracks’ locations and their depths are identified by employing experimental modal test results performed on the structure. the cracks are modeled using generic elements to include the coupling effects between shear forces and bending moments at the crack section. in the identification procedure eigen- sens...