Evaluation of a substructured soft Real-time Hybrid Test for performing Seismic analysis of complex structural systems

The hybrid test method is a relatively recently developed dynamic testing technique that uses numerical modelling combined with simultaneous physical testing. The concept of substructuring allows the critical or highly nonlinear part of the structure that is difficult to numerically model with accuracy to be physically tested whilst the remainder of the structure, that has a more predictable response, is numerically modelled. In this paper, a substructured soft-real time hybrid test is evaluated as an accurate means of performing seismic tests of complex structures. The structure analysed is a three-storey, two-by-one bay concentrically braced frame (CBF) steel structure subjected to seismic excitation. A ground storey braced frame substructure whose response is critical to the overall response of the structure is tested, whilst the remainder of the structure is numerically modelled. OpenSees is used for numerical modelling and OpenFresco is used for the communication between the test equipment and numerical model. A novel approach using OpenFresco to define the complex numerical substructure of an X-braced frame within a hybrid test is also presented. The results of the hybrid tests are compared to purely numerical models using OpenSees and a simulated test using a combination of OpenSees and OpenFresco. The comparative results indicate that the test method provides an accurate and cost effective procedure for performing
full scale seismic tests of complex structural systems.

Toward A Reliable Quality Control Test For Microneedle Insertion

Microneedles (MNs) are emerging devices that can be used for the delivery of drugs at specific locations1. Their performance is primarily judged by different features and the penetration through tissue is one of the most important aspects to evaluate. For detailed studies of MN performance different kind of in-vitro, exvivo and in-vivo tests should be performed. The main limitation of some of these tests is that biological tissue is too heterogeneous, unstable and difficult to obtain. In addition the use of biological materials sometimes present legal issues. There are many studies dealing with artificial membranes for drug diffusion2, but studies of artificial membranes for Microneedle mechanical characterization are scarce3. In order to overcome these limitations we have developed tests using synthetic polymeric membranes instead of biological tissue. The selected artificial membrane is homogeneous, stable, and readily available. This material is mainly composed of a roughly equal blend of a hydrocarbon wax and a polyolefin and it is commercially available under the brand name Parafilm®. The insertion of different kind of MN arrays prepared from crosslinked polymers were performed using this membrane and correlated with the insertion of the MN arrays in ex-vivo neonatal porcine skin. The insertion depth of the MNs was evaluated using Optical coherence tomography (OCT). The implementation of MN transdermal patches in the market can be improved by make this product user-friendly and easy to use. Therefore, manual insertion is preferred to other kind of procedures. Consequently, the insertion studies were performed in neonatal porcine skin and the artificial membrane using a manual insertion force applied by human volunteers. The insertion studies using manual forces correlated very well with the same studies performed with a Texture Analyzer equipment. These synthetic membranes seem to mimic closely the mechanical properties of the skin for the insertion of MNs using different methods of insertion. In conclusion, this artificial membrane substrate offers a valid alternative to biological tissue for the testing of MN insertion and can be a good candidate for developing a reliable quality control MN insertion test.

Test stimulus characteristics determine the perceived speed of the dynamic motion aftereffect

Using a speed-matching task, we measured the speed tuning of the dynamic motion aftereVect (MAE). The results of our Wrst experiment, in which we co-varied dot speed in the adaptation and test stimuli, revealed a speed tuning function. We sought to tease apart what contribution, if any, the test stimulus makes towards the observed speed tuning. This was examined by independently manipulating dot speed in the adaptation and test stimuli, and measuring the eVect this had on the perceived speed of the dynamic MAE. The results revealed that the speed tuning of the dynamic MAE is determined, not by the speed of the adaptation stimulus, but by the local motion characteristics of the dynamic test stimulus. The role of the test stimulus in determining the perceived speed of the dynamic MAE was conWrmed by showing that, if one uses a test stimulus containing two sources of local speed information, observers report seeing a transparent MAE; this is despite the fact that adaptation is induced using a single-speed stimulus. Thus while the adaptation stimulus necessarily determines perceived direction of the dynamic MAE, its perceived speed is determined by the test stimulus. This dissociation of speed and direction supports the notion that the processing of these two visual attributes may be partially independent.