S. Ullah¹, B. Pichler¹, S. Scheiner^1,2, C. Hellmich^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.57, No.3, pp. 279-316, 2010, DOI:10.3970/cmes.2010.057.279

Abstract Point-wise optical measurements of 3D displacement vectors over time are a key input for monitoring shotcrete tunnel shells during construction according to the New Austrian Tunnelling Method (NATM). Aiming at estimation of the stresses prevailing in the highly loaded, hydrating material, we here deal with two different interpolation strategies for reconstructing, from measured displacement vectors, the 3D displacement field histories of the inner surface of the tunnel shell. The first approach considers spatial interpolation of displacement components in a fixed Cartesian base frame, while the second (new) approach refers to displacement components in a moving… More >

G. P. Russo¹, A. Esposito¹, B. Esposito², R. Renis^1,1, F. Parente¹

FDMP-Fluid Dynamics & Materials Processing, Vol.6, No.3, pp. 319-336, 2010, DOI:10.3970/fdmp.2010.006.319

Abstract A low-cost facility, able to simulate icing conditions occurring in flight, has been built via modification of a small blow-down supersonic wind tunnel. As the storage tank (30bar) is emptied through the wind tunnel, expansion of the contained air makes temperature to decrease down to -20 C and a control valve holds such temperature for about 200s. In order to increase the liquid water content (LWC) of the flow allowing ice formation on model surfaces within the test chamber, water is sprayed in the stream within the stagnation chamber by means of a controlled spray… More >

Alamusi¹, Y.L. Liu¹, N. Hu^1,2

CMC-Computers, Materials & Continua, Vol.20, No.2, pp. 101-118, 2010, DOI:10.3970/cmc.2010.020.101

Abstract In this work, we propose a 3 dimensional (3D) numerical model to predict the piezoresistivity behaviors of a nanocomposite material made from an insulating polymer filled by carbon nanotubes (CNTs). This material is very hopeful for its application in highly sensitive strain sensor by measuring its piezoresistivity, i.e., the ratio of resistance change versus applied strain. In this numerical approach, a 3D resistor network model is firstly proposed to predict the electrical conductivity of the nanocomposite with a large amount of randomly dispersed CNTs under the zero strain state. By focusing on the fact that… More >

Oliver K. Johnson¹, Calvin J. Gardner¹, David T. Fullwood¹, Brent L.Adams¹, Nathan Hansen², George Hansen²

CMC-Computers, Materials & Continua, Vol.15, No.2, pp. 87-112, 2010, DOI:10.3970/cmc.2010.015.087

Abstract A novel nickel nanostrand-silicone composite material at an optimized 15 vol% filler concentration demonstrates a dramatic piezoresistive effect with a negative gauge factor (ratio of percent change in resistivity to strain). The composite volume resistivity decreases in excess of three orders of magnitude at a 60% strain. The piezoresistivity does decrease slightly as a function of cycles, but not significantly as a function of time. The material's resistivity is also temperature dependent, once again with a negative dependence.
The evidence indicates that nickel strands are physically separated by matrix material even at high volume fractions, and More >

Frederic L. Pellet¹

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.3, pp. 279-296, 2009, DOI:10.3970/cmes.2009.052.279

Abstract In this study, the contact and interaction between a tunnel lining support and a damage-susceptible viscoplastic medium is investigated. First, back-analysis of the time-dependent behaviour of a drift excavated across a carboniferous rock mass which exhibited large delayed displacements was undertaken. Drift closure was simulated using an elasto-viscoplastic constitutive model that included the strength degradation process. This 3D numerical simulation was performed taking into account both stage construction sequence and rate of excavation advancement. A comparison of the numerical results with the data measured on site allowed for the calibration of the model parameters. Subsequently, More >

J. H. Jackson¹, A. S. Kobayashi², S. N. Atluri³

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.1, pp. 17-30, 2004, DOI:10.3970/cmes.2004.006.017

Abstract The T_ε^*  integral was calculated numerically along an extending, tunneling crack front in an 8 mm thick, aluminum three-point bend (3PB) specimen, using a numerical model driven by experimentally obtained surface displacements. The model provided input to a contour integration for the T_ε^*  integral, via the Equivalent Domain Integral (EDI) method with incremental plasticity. Validity of the analysis was ensured by the agreement of the T_ε^*  integral obtained on the surface (plane stress) and the plane stress values from previous studies. T_ε^*   was observed to decrease from the outer surface of the specimen to More >

David G. Bell, Marc Anthony Fischer

Canadian Journal of Urology, Vol.9, No.1, pp. 1470-1474, 2002

Abstract The establishment and maintenance of effective urinary tract drainage for patients with malignant extrinsic ureteric obstruction is a formidable challenge for the urologist. We have utilized an alternative method of urinary diversion, called Palliative Subcutaneous Tunneled Nephrostomy Tubes (PSTN), for long term urinary tract drainage when intracoropreal stenting has failed or is not tolerated. PSTN provides a simple and effective method of external urinary diversion and preservation of renal function. This technique should be an option in the armamentarium of urologists for management of malignant ureteral obstruction. More >