Application of resonant acoustic spectroscopy to asphalt concrete beams for determination of the dynamic modulus

In this paper, a new application of resonant acoustic spectroscopy (RAS) is examined for constructing asphalt concrete mastercurves from seismic testing. The frequency-dependent material properties can be characterized from multiple modes of vibration through the use of RAS. Beam-shaped asphalt specimens are tested at multiple temperatures to determine the resonance frequencies of the specimens. The resonance frequencies are estimated by applying a small load impulse and measuring the resulting acceleration through the specimens. Using RAS, the material properties of the specimens are determined numerically using the measured resonance frequencies. The results presented show that the frequency-dependent dynamic modulus of the asphalt concrete specimens can be characterized using several modes of vibration at each testing temperature

Apps for modal analysis to characterize the complex modulus of asphalt concrete

The time and temperature dependent dynamic modulus of asphalt concrete is a key parameter to modern pavement design and to pavement quality. However, accurate measurements of the complex modulus through conventional cyclic testing are expensive regarding both time and costs. Novel test methods based on modal analysis facilitate economic, accurate and faster determination of linear viscoelastic material properties of asphalt concrete. The modal analysis is performed by using an impact hammer and an accelerometer to measure frequency response functions of asphalt concrete specimens with free boundary conditions. The complex modulus and complex Poisson’s ratio are determined by matching finite element computed frequency response functions to the measurements. This paper presents one software application to perform the modal testing and one application to compute and optimize frequency response functions to determine the complex modulus and complex Poisson’s ratio. The software applications greatly simplifies the methodology to determine material properties through modal analysis of asphalt concrete specimens

Improving the patient's experience of a bone marrow biopsy -- an RCT.

noImproving the patient¿s experience of a bone marrow biopsy ¿ an RCT Aims. To compare nitrous oxide 50%/oxygen 50% (N2O/O2 ¿ entonox) plus local anaesthetic (LA) with placebo (oxygen) plus LA in the management of pain experienced by patients undergoing a bone marrow biopsy. Background. Bone marrow biopsies are a common procedure for many haematological conditions. Despite the use of a LA, pain during the procedure has frequently been reported by patients. Previous research in pain management of other invasive diagnostic procedures (e.g. sigmoidoscopy) has reported N2O/O2 as an effective alternative to LA. Design. Double-blind randomized controlled trial. Methods. Forty-eight patients requiring a bone marrow biopsy were randomized to receive either N2O/O2 or oxygen in addition to their LA. Participants were asked to complete a pain score and comment on their experience of the procedure. Results. Although the overall pain scores were moderate, there was a wide range of scores. N2O/O2 resulted in significantly less pain for men, but not for women. All patients who had had previous biopsies reported significantly more pain, regardless of the gas used. There were no significant adverse effects in either group. Conclusion. N2O/O2 is a safe, effective, easy-to-use analgesic which merits further investigation in potentially painful diagnostic (and other) interventions