Control of a flexible planar truss using proof mass actuators

A flexible structure was modeled and actively controlled by using a single space realizable linear proof mass actuator. The NASA/UVA/UB actuator was attached to a flexible planar truss structure at an optimal location and it was considered as both passive and active device. The placement of the actuator was specified by examining the eigenvalues of the modified model that included the actuator dynamics, and the frequency response functions of the modified system. The electronic stiffness of the actuator was specified, such that the proof mass actuator system was tuned to the fourth structural mode of the truss by using traditional vibration absorber design. The active control law was limited to velocity feedback by integrating of the signals of two accelerometers attached to the structure. The two lower modes of the closed-loop structure were placed further in the LHS of the complex plane. The theoretically predicted passive and active control law was experimentally verified

The Selection Process of Enterprise Resource Planning (ERP) Systems

The significant number of ERP systems installations worldwide during the last decade represents a major paradigm shift in organizational and information systems management. A large number of enterprises are currently extending their base ERP systems or are in the process of acquiring and implementing core ERP modules. Failure to do so successfully can be extremely costly as demonstrated by a number of reported failure cases. The paper aims at providing a framework for the selection process of ERP systems, which can be useful for both identifying critical issues for further research and assisting managers considering ERP projects

Dark energy after GW170817, revisited

We revisit the status of scalar-tensor theories with applications to dark energy in the aftermath of the gravitational wave signal GW170817 and its optical counterpart GRB170817A. At the level of the cosmological background, we identify a class of theories, previously declared unviable in this context, whose anomalous gravitational wave speed is proportional to the scalar equation of motion. As long as the scalar field is assumed not to couple directly to matter, this raises the possibility of compatibility with the gravitational wave data, for any cosmological sources, thanks to the scalar dynamics. This newly "rescued" class of theories includes examples of generalised quintic galileons from Horndeski theories. Despite the promise of this leading order result, we show that the loophole ultimately fails when we include the effect of large scale inhomogeneities.Comment: Updated with corrections to the gravitational wave propagation coming from higher order terms in the presence of large scale inhomogeneities. These close off any remaining loopholes. References adde

Development and field evaluation of an online monitor for near-continuous measurement of iron, manganese, and chromium in coarse airborne particulate matter (PM)

A novel air sampling monitor was developed for near-continuous (i.e., 2-h time resolution) measurement of iron (Fe), manganese (Mn), and chromium (Cr) concentrations in ambient coarse particulate matter (PM) (i.e., PM10–2.5). The developed monitor consists of two modules: (1) the coarse PM collection module, utilizing two virtual impactors (VIs) connected to a modified BioSampler to collect ambient coarse PM into aqueous slurry samples; (2) the metal concentration measurement module, which quantifies the light absorption of colored complexes formed through the reactions between the soluble and solubilized target metals and pertinent analytical reagents in the collected slurries using a micro volume flow cell (MVFC) coupled with UV/VIS spectrophotometry. The developed monitor was deployed in the field for continuous ambient PM collection and measurements from January to April 2016 to evaluate its performance and reliability. Overall, the developed monitor could achieve accurate and reliable measurements of the trace metals Fe, Mn, and Cr over long sampling periods, based on the agreement between the metal concentrations measured via this online monitor and off-line parallel measurements obtained using filter samplers. Based on our results, it can be concluded that the developed monitor is a promising technology for near-continuous measurements of metal concentrations in ambient coarse PM. Moreover, this monitor can be readily configured to measure the speciation (i.e., water-soluble portion as well as specific oxidation states) of these metal species. These unique abilities are essential tools in investigations of sources and atmospheric processes influencing the concentrations of these redox-active metals in coarse PM. Copyright © 2016 American Association for Aerosol Research © 2016 American Association for Aerosol Research

Jet correlation measurement in heavy-ion collisions: from RHIC to LHC

We attempt to deduce simple options of `jet quenching' phenomena in heavy-ion collisions at \snn=5.5 \tev at the LHC from the present knowledge of leading-hadron suppression at RHIC energies. In light of the nuclear modification factor for leading particles we introduce the nuclear modification factor for jets, \RAA^{jet}, and for the longitudinal momenta of particles along the jet axis, \RAA^{p_{\rm L}}.Comment: 9 pages, 7 figures, proceedings, MIT workshop on fluctuations and correlations in relativistic nuclear collision

Evaluation of bone excision on occipital area of simulated human skull

Surgical effects of bone and soft tissue tumours, whether for biopsy or full excision have been researched from as early as the 1970’s [1]. These researches though have as main focus the biological (histological) rather the mechanical aspects of the effects [2]. With technological advances in biomedical and biomechanical modelling, a plethora of researchers have been exploring the possibilities of understanding [3] or even predicting musculoskeletal behaviour under different loading conditions [4]. This research is seeking to bridge these two different facets by looking into the mechanical effects bone tumour surgery might have to the structural rigidity of a simulated human skull

Unusual patterns of Monteggia fracture-dislocation

BACKGROUND: High-energy trauma may result in uncommon open injuries around the elbow joint. The management of these injuries can be difficult. CASE DESCRIPTION: Fourteen patients were treated between 1999 and 2003 and their injuries consisted of Monteggia fracture-dislocations combined with segmental fractures of the ulna or fractures of the forearm bones and/or various more complex trauma such as neural injuries, bone comminution and severe soft tissue injuries around the elbow. Eight of them (57%) were multiply injured with severe additional injuries. All patients underwent surgery within first 4–6 hours. Internal fixation, external fixation or a combination of both methods were used to stabilize fractures while open wounds had secondary closure. RESULTS: Additional operations were required in 6 patients. The functional results according to the Mayo Elbow Performance Index were excellent or good in eleven patients, and fair or poor in the remaining three. The patients with fair and poor results had suffered from severe neural and soft tissue trauma and/or multiple fractures of the upper extremity. CONCLUSION: These injuries should be treated as an emergency. The surgeon should apply any available method that can provide stability to the bone fragments and safe handling of the soft tissues giving priority to internal fixation of the fractures. Severe osseous, soft tissue and neural trauma affect the functional results of the elbow region

Architecture independent parallel selection with applications to parallel priority queues

AbstractWe present a randomized selection algorithm whose performance is analyzed in an architecture independent way on the bulk-synchronous parallel (BSP) model of computation along with an application of this algorithm to dynamic data structures, namely parallel priority queues. We show that our algorithms improve previous results upon both the communication requirements and the amount of parallel slack required to achieve optimal performance. We also establish that optimality to within small multiplicative constant factors can be achieved for a wide range of parallel machines. While these algorithms are fairly simple themselves, descriptions of their performance in terms of the BSP parameters is somewhat involved; the main reward of quantifying these complications is that it allows transportable software to be written for parallel machines that fit the model