Nonlinear isolators with high-static-low-dynamic-stiffness have received considerable attention in the recent literature due to their performance benefits compared to linear vibration isolators. A quasi-zero-stiffness (QZS) isolator is a particular case of this type of isolator, which has a zero dynamic stiffness at the static equilibrium position. These types of isolators can be used to achieve very low frequency vibration isolation, but a drawback is that they have purely hardening stiffness behavior. If something occurs to destroy the symmetry of the system, for example, by an additional static load being applied to the isolator during operation, or by the incorrect mass being suspended on the isolator, then the isolator behavior will change dramatically. The question is whether this will be detrimental to the performance of the isolator and this is addressed in this paper. The analysis in this paper shows that although the asymmetry will degrade the performance of the isolator compared to the perfectly tuned case, it will still perform better than the corresponding linear isolator provided that the amplitude of excitation is not too large.

The concept of transporting medical products by drone is gaining a lot of interest amongst the medical and logistics communities. Such innovation has generated several questions, a key one being the potential effects of flight on the stability of medical products. The aims of this study were to quantify the vibration present within drone flight, study its effect on the quality of the medical insulin through live flight trials, and compare the effects of vibration from drone flight with traditional road transport. Three trials took place in which insulin ampoules and mock blood stocks were transported to site and flown using industry standard packaging by a fixed-wing or a multi-copter drone. Triaxial vibration measurements were acquired, both in-flight and during road transit, from which overall levels and frequency spectra were derived. British Pharmacopeia quality tests were undertaken in which the UV spectra of the flown insulin samples were compared to controls of known turbidity. In-flight vibration levels in both the drone types exceeded road induced levels by up to a factor of three, and predominant vibration occurred at significantly higher frequencies. Flown samples gave clear insulin solutions that met the British Pharmacopoeia specification, and no aggregation of insulin was detected.

The timely distribution of medicines to patients is an essential part of the patient care plan, and maximising efficiency in the logistics systems behind these movements is vital to minimise cost. Before drones can be used for moving medical cargo, medical regulatory authorities require assurance that the transported products will not be adversely affected by in-flight conditions unique to each drone. This study set out to (i) quantify the vibration profile by phases of flight, (ii) determine to what extent there were significant differences in the observed vibration between the phases, and (iii) assess the quality of flown monoclonal antibody (mAb) infusions used in the treatment of cancer. Vibrations emanating from the drone and transmitted through standard medical packaging were monitored with the storage specifications for mean kinematic temperature (2–8 °C) being met. Vibration levels were recorded between 1.5 and 3 g, with the dominant octave band being 250 Hz. After 60 flights, the quality attributes of flown infusions regarding size integrity were found to be no different from those of the control infusions. For example, the particle size had a variation of less than 1 nm; one peak for Trastuzumab was 14.6 ± 0.07 nm, and Rituximab was 13.3 ± 0.90 nm. The aggregation (%) and fragmentation (%) remained at 0.18 ± 0.01% and 0.11 ± 0.02% for Trastuzumab, 0.11 ± 0.01% and 2.82 ± 0.15% for Rituximab. The results indicated that in the case of mAbs, the quality assurance specifications were met and that drone vibration did not adversely affect the quality of drone-flown medicines.

The acceleration response of road vehicles to shock inputs from road irregularities such as bumps and hollows is an important consideration in the design of vehicle suspensions and damping characteristics, in particular. In this paper, the influence of the damper on the shock response of a simple vehicle model is considered. An analysis is presented of a single degree-of-freedom model subjected to a transient displacement input. Simple approximate expressions are given for the peak acceleration during an impulse of both short and long durations compared to the natural period, from which the role of the damper is clearly apparent. For impulses of short duration the peak acceleration occurs during the impulse and is shown to be approximately proportional to the damping ratio. Corollary to this, the peak acceleration can be reduced by switching the damper to a lower value during the impulse. The potential benefits of doing so are illustrated through numerical simulation, and a simple formula is given for the maximum possible reduction in peak acceleration. The results are also contrasted with those of a conventional dual-rate automotive damper model. The switchable damper is found to offer sufficient benefit to warrant further investigation.

Background: Drone transport regulations in Europe require a crash-protected container (CPC) to be used for the carriage of dangerous goods. With increasing interest in the use of drones for medical logistics, the motivation behind this research was to investigate whether the existing approved medical carriers could also pass as CPCs. To date, there has been little practical experimentation on or theoretical research into the crash protection performance of medical containers. Methods: Addressing this gap, this paper reports findings from a series of drop test experiments to investigate the crashworthiness of a standard medical carrier bag used by the National Health Service (NHS) in the UK. Th drop tests were performed from heights of up to 122 m using standard medical carriers containing bags of dyed saline to examine the robustness of the carrier and whether it could contain any leakages, a key requirement for transporting dangerous goods. Results: The tests found that the medical carrier failed on some drops, with the zipped lid being identified as the main weakness. Conclusions: A new understanding of the carrier’s terminal velocity, impact acceleration, and failure mechanisms were gained and subsequent strengthening and waterproofing remedial measures recommended. New insights and practical recommendations are provided relating to performing formal drop tests and how to conduct these using a drone.

The Semi-Analytical Finite-Element (SAFE) method represents one of the most established numerical approaches for predicting the propagation of elastic waves in one-dimensional structures of arbitrary cross-sections. Its implementation in the commercial finite-element software COMSOL Multiphysics has been proposed in recent years; however, it is limited to only the free wave propagation for computing dispersion curves. To overcome this limitation, this paper proposes an extension of this approach that combines COMSOL and its Livelink for Matlab tool. This enables the extraction from COMSOL of the assembled mass and stiffness SAFE matrices to solve problems of both free and forced wave propagation in the Matlab environment. The resulting customised software takes advantage of both the potential of commercial FE software and the power of Matlab without worrying about compatibility issues. A model of a simply supported plate strip and that of a more complex geometry are implemented to validate, respectively, the SAFE matrix extraction procedure and the implemented forced response formulation. The results agree well with corresponding analytical and numerical results validating the proposed implementation of the SAFE method.