An adjustable force field for multiple robot mission and path planning

Mission and path planning for multiple robots in dynamic environments is required when multiple mobile robots or unmanned vehicles are used for geographically distributed tasks. Assigning tasks and paths for robots for cooperatively accomplishing a mission of reaching to number of target points are addressed in this paper. The methodology that is proposed is based on using an adjustable force field which is suitable for dynamic environment. From the force field analysis, the decisions to assign tasks for each robot are then made. The force field is also used to plan a collision free path for each robot. Adjustable weights for the force field model are proposed to satisfy the constraints of the motion. In this research, the constraints are the cooperation of the robots, the precedence between the targets and between robots, and the discrimination between different obstacles. Two simulations for mission and path planning in 2D and 3D dynamic spaces with multiple robots are presented based on the proposed adjustable force filed. The result of the mission and path planning for three robots cooperatively doing eight target points are shown.

Sharpening the focus of force field analysis

The purpose is to explore the inherent complexity of Kurt Lewin's force field theory through applied analysis of organizational case examples and related methods. The methodology applies a range of tools from the consultancy research domain, including force field analysis of complex organizational scenarios, and applies bricolage and corroboration to emerging discoveries from semi-structured interviews, author experience, critical reflection and literature survey. Findings are that linear representation of internal and external forces in organizational applications of field theory does not fully explain the paradox of inverse vectors in the forces of change. The force field is not an impermeable thing; instead, it morphs. Examples of the inverse principle and its effects are detailed and extended in this analysis. The implications of the research are that force field analysis and related change processes promoted in organizational change literature run the risk of missing key complexities. The inclusion of the inverse principle can provide enhanced, holistic understanding of the prevailing forces for change. The augmentation of the early work of Kurt Lewin, and extension of previous analyses of his legacy in the Journal of Change Management and elsewhere, provide, in this article, change analysis insights that align well with current organizational environments.

First-principles based force-field for the interaction of proteins with Au(100)(5 x 1): an extension of GolP-CHARMM

Noncovalent recognition between peptides and inorganic materials is an established phenomenon. Key to exploiting these interactions in a wide range of materials self-assembly applications would be to harness the facet-selective control of peptide binding onto these materials. Fundamental understanding of what drives facet-selectivity in peptide binding is developing, but as yet is not sufficient to enable design of predictable facet-specific sequences. Computational simulation of the aqueous peptide-gold interface, commonly used to understand the mechanisms driving adsorption at an atomic level, has thus far neglected the role that surface reconstruction might play in facet specificity. Here the polarizable GolP-CHARMM suite of force fields is extended to include the reconstructed Au(100) surface. The force field, compatible with the bio-organic force field CHARMM, is parametrized using first-principles data. Our extended force field is tailored to reproduce the heterogeneity of weak chemisorbing N and S species to specific locations in the Au(100)(5 × 1) surface identified from the first-principles calculations. We apply our new model to predict and compare the three-dimensional structure of liquid water at Au(111), Au(100)(1 × 1), and Au(100)(5 × 1) interfaces. Using molecular dynamics simulations, we predict an increased likelihood for water-mediated peptide adsorption at the aqueous-Au(100)(1 × 1) interface compared with the Au(100)(5 × 1) interface. Therefore, our findings suggest that peptide binding can discriminate between the native and reconstructed Au(100) interfaces and that the role of reconstruction on binding at the Au(100) interface should not be neglected. © 2013 American Chemical Society.

Molecular dynamics study of response of liquid N,N-dimethylformamide to externally applied electric field using a polarizable force field

The behavior of Liquid N,N-dimethylformamide subjected to a wide range of externally applied electric fields (from 0.001 V/nm to 1 V/nm) has been investigated through molecular dynamics simulation. To approach the objective the AMOEBA polarizable force field was extended to include the interaction of the external electric field with atomic partial charges and the contribution to the atomic polarization. The simulation results were evaluated with quantum mechanical calculations. The results from the present force field for the liquid at normal conditions were compared with the experimental and molecular dynamics results with non-polarizable and other polarizable force fields. The uniform external electric fields of higher than 0.01 V/nm have a significant effect on the structure of the liquid, which exhibits a variation in numerous properties, including molecular polarization, local cluster structure, rotation, alignment, energetics, and bulk thermodynamic and structural properties.

Haptic guidance for microrobotic intracellular injection

The ability for a bio-operator to utilise a haptic device to manipulate a microrobot for intracellular injection offers immense benefits. One significant benefit is for the bio-operator to receive haptic guidance while performing the injection process. In order to address this, this paper investigates the use of haptic virtual fixtures for cell injection and proposes a novel force field virtual fixture. The guidance force felt by the bio-operator is determined by force field analysis within the virtual fixture. The proposed force field virtual fixture assists the bio-operator when performing intracellular injection by limiting the micropipette tip's motion to a conical volume as well as recommending the desired path for optimal injection. A virtual fixture plane is also introduced to prevent the bio-operator from moving the micropipette tip beyond the deposition target inside the cell. Simulation results demonstrate the operation of the guidance system.

Haptic microrobotic intracellular injection assistance using virtual fixtures

In manual cell injection the operator relies completely on visual information for task feedback and is subject to extended training times as well as poor success rates and repeatability. From this perspective, enhancing human-in-the-loop intracellular injection through haptic interaction offers significant benefits. This paper outlines two haptic virtual fixtures aiming to assist the human operator while performing cell injection. The first haptic virtual fixture is a parabolic force field designed to assist the operator in guiding the micropipette's tip to a desired penetration point on the cell's surface. The second is a planar virtual fixture which attempts to assist the operator from moving the micropipette's tip beyond the deposition target location inside the cell. Preliminary results demonstrate the operation of the haptically assisted microrobotic cell injection system.

Evaluating the stability of disulfide bridges in proteins: a torsional potential energy surface for diethyl disulfide

Disulfide bonds formed by the oxidation of cysteine residues in proteins are the major form of intra- and inter-molecular covalent linkages in the polypeptide chain. To better understand the conformational energetics of this linkage, we have used the MP2(full)/6-31G(d) method to generate a full potential energy surface (PES) for the torsion of the model compound diethyl disulfide (DEDS) around its three critical dihedral angles (χ2, χ3, χ2′). The use of ten degree increments for each of the parameters resulted in a continuous, fine-grained surface. This allowed us to accurately predict the relative stabilities of disulfide bonds in high resolution structures from the Protein Data Bank. The MP2(full) surface showed significant qualitative differences from the PES calculated using the Amber force field. In particular, a different ordering was seen for the relative energies of the local minima. Thus, Amber energies are not reliable for comparison of the relative stabilities of disulfide bonds. Surprisingly, the surface did not show a minimum associated with χ2 − 60°, χ390, χ2′ − 60°. This is due to steric interference between Hα atoms. Despite this, significant populations of disulfides were found to adopt this conformation. In most cases this conformation is associated with an unusual secondary structure motif, the cross-strand disulfide. The relative instability of cross-strand disulfides is of great interest, as they have the potential to act as functional switches in redox processes.

Shifting ground in some Australian photography

This is a report of a practice-as-research project. The chapter outlines McArdle's discoveries of means by which the pre-conscious processes of binocular vision and steropsis can be made visible in an effect which with one-eyed vision renders the scene 3-dimensional.

In the book's introduction editor Mehigan writes "[The] will to creation is only assayable once we estimate the role of the observer in the construction of space. McArdle's contribution, in engaging with the question of the animating presence of the observer focuses not just on what is caught in the lens of the photographer at the moment of depiction, but how the photographer's movement through space is the 'force field' that insinuates itself into the landscape and enters into a reciprocal relationship with it. The schematism of Euclidean geometry, for this reason, cannot account for the truth of the photographer's images; McArdle's metaphors are singularly non-Euclidean in their description of how objects are held together in the imaginative space of mental awareness."

The future of diversity and difference : can the national curriculum for English be hospitable?

This chapter explores the context of constructing the Australian Curriculum: English and how it represents and responds to the diversity of students. It starts with the brief genealogy of neoliberal standards-based reforms as a way of managing differences. In doing so, the chapter situates the national agenda of curriculum reforms in the semiotic order of ‘risk societies’ (Beck, 1992) through which various risks are both manufactured and managed. The semiotic order of managing educational risks through reforms is presented as a discursive force-field that both creates ‘moral panics’ and provides solutions, thereby appealing to the broader public and securing its consent. This discussion prepares the ground for the reading of texts produced in the lead-up to the actual release of the national curriculum for English and statements about diversity in these documents as well as in the curriculum itself. The chapter then goes on to explore what might be possible in the process of the curriculum implementation, by drawing on ideas of hospitality, responsibility and dialogism. In conclusion, this essay argues that no national curriculum can be successfully implemented unless it is sensitive to the textual and cultural practices of other groups and unless it wins their political consent. Equally, no national curriculum can be ethically implemented unless it recognises and responds to difference and unless it creates a possibility of transcending the logic of the Same.

Dossier Chris Marker : the suffering image

Dossier Chris Marker: The Suffering Image is a study of a late-modern chiasmus, impersonal-personal agency, as it comes to expression in the works of French artist and filmmaker, Chris Marker, as the dynamic interplay of political and subjective agency. As chiasmus, the complementary halves of this often-apocalyptic dynamis (a semi-catastrophic, temporal or historical force-field) also – arguably – secretly agree to meet, through the work of art, in the futural. Consistent with the classical figure of concordia discors, these irreducible warring aspects of life experience are, in fact, resolved in an atemporal and ahistorical moment that inhabits the work of art from its inception. This redemptive aspect in art is also the ultimate gesture of the artwork as “mask” or “screen” for forces that reside beyond the frame of the image or work, as its proverbial Other, or within the frame, as other to that Other. A topological “knot,” or ontological “problem,” it is this very conflict that animates all of Marker’s extensive works – filmic and otherwise.