Adjoint time domain method for fluorescent imaging in turbid media

Application of adjoint time domain methods to the inverse problem in 3D fluorescence imaging is a novel approach. We demonstrate the feasibility of this approach experimentally on the basis of a time gating technique completely in the time domain by using a small number of time windows. The evolution of the fluorescence energy density function inside a highly scattering cylinder was reconstructed together with optical parameters. Reconstructed energy density was used in localizing two fluorescent tubes. Relatively accurate reconstruction demonstrates the effectiveness and the potential of the proposed technique.     

Procedure to Perform a Validated Incremental Hole Drilling Measurement: Application to Shot Peening Residual Stresses

Abstract: The paper describes a test rig designed to check and assess the accuracy of the incremental hole drilling (IHD) method. An external load produces a controlled linearly through thickness variable uniaxial stress field (reference bending stress), known with good accuracy, that can be applied and removed at each hole increment. After the separation between the bending relaxed strain from the residual stress relaxed strain, it is possible to reproduce the bending stress distribution in order to have complete confidence of the residual stress measurement. The bending verification of the IHD method was already proposed by other investigators before, but residual stress measurements were then performed on independent configurations. The proposed testing procedure gives a ‘real time’ verification of the residual stress measurement. Any experimental malfunctioning due to the operator inexperience, or any error during the stress calculation from the relaxed strain would produce an evident difference between the expected reference bending stress and the IHD bending stress output. Moreover, the reference bending stress helped for understanding that the not perfect hole cylindrical shape causes an underestimate of the predicted stress near the surface. A zero depth offset correction was proposed. This correction was tested on the reference bending stress, and then applied to the residual stress prediction. Three shot peening residual stresses IHD measurements were successfully validated by means of the bending stress; moreover, they were in good agreement with independent X‐ray diffraction measures also proposed in the paper.     

Dual-phase steel rebars for high-ductile r.c. structures, Part 1: Microstructural and mechanical characterization of steel rebars

The considerable influence of steel’s mechanical behaviour on the dissipative capacity of r.c. structures has led to increasing interest in optimizing the mechanical properties of the reinforcing bars used for seismic applications.

The work presented herein is part of a broad-ranging study on the potential utilization of highly innovative types of steel for reinforced concrete earthquake-resistant structures. In particular, we present the main results obtained in experimental trials on a low-C, Mn–Si steel in the form of concrete reinforcing bars subjected to intercritical tempering treatment in a temperature range between 740 and 820 C to obtain various dual-phase ferrite–martensite structures. The samples were characterized via mechanical tests and metallographic analyses in order to correlate the bars’ characteristics with the microstructure of the steel itself.

Experimental characterization of this steel has allowed for the development of a mathematical model to enable the evaluation of the ductility performance of concrete structural elements reinforced with dual-phase steel bars.     

An experimental and numerical approach to investigate the dynamic response of a four‐flue chimney of a thermo‐electrical plant

This paper describes an experimental procedure and a numerical model for the study of the dynamic behaviour of a chimney of a thermo‐electrical plant. The experimental part is based on the measurement of the structure's dynamic response by means of several accelerometers. Different signals from forced time‐periodic excitations, spanning a range of frequencies, have been collected and compared with those from a finite elements model. In particular, the first four modal shapes and their frequencies are computed. Following this validation, the finite element model has also been applied to investigate the response of the chimney subjected to a generic wind periodic excitation (vortex shedding). The numerical results show good agreement with the experimentally collected data. Copyright © 2003 John Wiley & Sons, Ltd.     

Malignant duodenocolic fistula: report of two cases, each with one or more other synchronous gastointestinal cancers

Two patients had duodenocolic fistulas, each following a carcinoma of the colon in the area of the hepatic flexure that had perforated into the duodenum. The first patient was treated by a radical pancreatoduodenectomy with right colectomy; the second by subtotal colectomy with excision of the duodenal wall and suture. Both patients are alive and without evidence of recurrent disease. In addition, the first patient had two other primary carcinomas, in the cecum and in the stomach, and the second patient had another primary in the sigmoid. The definitive procedure had to be adjusted to encompass all lesions. The radical operation in one stage seems to be the preferred procedure and certainly is most satisfactory as a cancer operation. Our patient treated by this procedure has survived more than 11 years. An intestinal fistula related to colonic carcinoma, evan though rare, should not be considered as a separate entity. Treatment of the cancer with an en-bloc resection of the communicating organs should be employed if possible.     

In‐Situ XRD Measurement and Quantitative Analysis of Hydrating Cement: Implications for Sulfate Incorporation in C–S–H

The study of hydration kinetics by in‐situ X‐ray powder diffraction can provide fundamental details on the time evolution of the phase assemblage in hydrating cement pastes. The main limit of the technique is the lack of quantitative information about the amount of C–S–H and unbound water, which cannot be measured directly by conventional quantitative phase analysis procedures based on X‐ray diffraction, due to their X‐ray amorphous nature. Here, a mass balance algorithm, which can be used to determine the amount of both C–S–H and capillary water, is presented and compared with methods based on standards. This method can also provide information about the stoichiometry of C–S–H formed by the reaction of C₃S, hydrated in the presence of gypsum, suggesting the incorporation of 0.3 mol of sulfate per mole of C–S–H precipitated. In addition, the results show a significant increase in the rate of C₃S hydration, when gypsum is added to the system.     

Physical and mechanical behavior of single‐walled carbon nanotube/polypropylene/ethylene–propylene–diene rubber nanocomposites

The effects of the incorporation of single‐walled carbon nanotubes (SWNTs) on the physical and mechanical properties of thermoplastic elastomers based on blends of isotactic polypropylene (iPP) and ethylene–propylene–diene rubber (EPDM) are described. A marked decrease of the half‐time of PP–EPDM crystallization and a sensible increase of the overall crystallization rate were observed in the presence of SWNTs. These results confirmed the expected nucleant effect of nanotubes on the crystallization of polypropylene. This effect was not linearly dependent on the SWNTs' content, showing a saturation of the nucleant effect at high nanotube concentrations. Dynamic mechanical analysis results showed a significant and controversial change of the mechanical behavior of the PP–EPDM/SWNT composites depending on the nanotube content. In particular, the storage modulus increased at the lowest incorporation of SWNTs, whereas a further increase of nanotubes led to a reduction of the storage modulus with respect to the pristine polymer matrix. Raman spectroscopy and scanning electron microscopy were successfully applied to demonstrate that in the composite films, the changes in the crystallization kinetics and mechanical properties could be explained in terms of the changes of the distance between nanotubes in bundles after a different intercalation of the polymer matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2657–2663, 2003     

Modulation of electrical properties in single-walled carbon nanotube/conducting polymer composites

The preparation and electrical characterization of a new class of composite layers formed by dispersing single-walled carbon nanotubes (SWNT) in 1,8-diaminonaphthalene polymer, the poly(1,8-DAN), are described.The material was grown on the surface of Pt plates by electropolymerization of 1,8-diaminonaphthalene (1,8-DAN) monomer in the presence of nanotubes. This synthesis method allows the simultaneous deposition of both the host polymer matrix and the filler nanotubes. A series of composite films were prepared using untreated nanotubes as well as nanotubes treated with KOH, HNO₃ and HNO₃/H₂SO₄ solutions. The structural features of the nanotubes and of the films produced have been investigated using Raman spectroscopy. Insight into the nature of nanotube dispersion and nanotube-polymer association was gained by AFM and STM analysis and by FE-SEM inspection after removing the outermost portion of composite films.The charge transport in composite films is found to be strongly enhanced by the nanotube insertion. Depending on the SWNTs processing, currents up to 30 mA, higher by a factor of about 140 than those of the pure poly(1,8-DAN) films, were measured with an applied voltage of 250 mV.