Level Crossings in Complex Two-Dimensional Potentials

Two-dimensional PT-symmetric quantum-mechanical systems with the complex cubic potential V_{12}=x^2+y^2+igxy^2 and the complex Henon-Heiles potential V_{HH}=x^2+y^2+ig(xy^2-x^3/3) are investigated. Using numerical and perturbative methods, energy spectra are obtained to high levels. Although both potentials respect the PT symmetry, the complex energy eigenvalues appear when level crossing happens between same parity eigenstates.Comment: 9 pages, 4 figures. Submitted as a conference proceeding of PHHQP

Perceived patient control over personal health information in the presence of context-specific concerns

Information privacy issues have plagued the world of electronic media since its inception. This research focused mainly on factors that increase or decrease perceived patient control over personal health information (CTL) in the presence of context-specific concerns. Control agency theory was used for the paper\u27s theoretical contributions. Personal and proxy control agencies acted as the independent variables, and context-specific concerns for information privacy (CFIP) were used as the moderator between proxy control agency, healthcare provider, and CTL. Demographic data and three control variables— the desire for information control, privacy experience, and trust propensity—were also included in the model to gauge the contribution to CTL from external factors. Only personal control agency and desire for information control were found to impact CT

Finite element analysis for the elastic stability of thin walled open section columns under generalized loading

The current interest in collapse characteristics brought about by crashworthiness requirements ýas shown the need for a better understanding and predictive capability for the thin walled open section structures. In general three possible modes exist in which a loaded thin walled open section column can buckle: 1) they can bend in the plane of one of the principal axes; 2) they can twist about the shear. centre; 3) or they can bend and twist simultaneously. The following study was undertaken to investigate the general failure of thin walled open section structures. A literature survey was conducted and it prevailed that a basic fundamental theoretical study was vital in describing the behaviour of thin walled structural members. The following stages of theoretical study have been completed: 1) Formulation of the stiffness matrix to predict the generalised force-displacement relationships assuming the small displacement theory in the linear elastic range. 2) Formulation of the geometric stiffness matrix to predict the buckling criteria under generalised loading and end constraints in the linear elastic range. 3) Formulation of the compound coordinate transformation matrix to relate local and global displacements or forces. 4) Preparation of the associated finite element computer program to solve general thin walled open sections structural problems

Investigation of the agricultural resources in Sri Lanka

The author has identified the following significant results. Several in-house capabilities were developed. The facilities to prepare color composites of excellent quality were developed, using bulk B/W 70 mm transparencies or 1:1,000,000 positive transparencies. These color composites were studied through optical devices on light tables. A zoom transfer scope was also added, enabling direct transfer of LANDSAT composite data on to base maps

Classical Trajectories for Complex Hamiltonians

It has been found that complex non-Hermitian quantum-mechanical Hamiltonians may have entirely real spectra and generate unitary time evolution if they possess an unbroken \cP\cT symmetry. A well-studied class of such Hamiltonians is $H= p^2+x^2(ix)^\epsilon$ ($\epsilon\geq0$). This paper examines the underlying classical theory. Specifically, it explores the possible trajectories of a classical particle that is governed by this class of Hamiltonians. These trajectories exhibit an extraordinarily rich and elaborate structure that depends sensitively on the value of the parameter $\epsilon$ and on the initial conditions. A system for classifying complex orbits is presented.Comment: 24 pages, 34 figure

Strucral property improvements to aerospace sandwich composites using z-pins

The general aim of this PhD project is to advance the science and technology of zpinned sandwich composites by performing an in-depth investigation into their mechanical properties, strengthening mechanisms and damage modes. The PhD thesis presents a comprehensive and critical review of the published scientific literature into z-pinned sandwich composites. While past studies often report large improvements to the mechanical performance of sandwich composites due to zpinning, the research is incomplete and gaps exist in the characterisation of these materials. The identification of these gaps in the characterisation of z-pinned sandwich composites provides the basis for the original research work performed in this PhD project. The PhD thesis presents a study into the through-thickness compression properties, strengthening mechanisms and damage modes of a sandwich composite structure reinforced with orthogonal z-pins. It was found that less than 4% in z-pin volume content was required to increase greatly the compression modulus (up to 300%), strength (700%) and strain energy absorption capacity (500%). While the compression properties were found to be highly sensitive to the z-pin content, the properties were much less dependent on the end constraint (i.e. built-in column or unsupported column) and diameter of the pins. An investigation into the compressive failure mechanisms of the z-pins within the foam core using acoustic emission monitoring, scanning electron microscopy and x-ray computed microtomography revealed for the first time that the fibrous z-pins failed during both elastic and plastic deformation of the core foam via a complex damage process involving splintering, kinking and fragmentation. It is shown that existing models fail to accurately determine the compression properties due to the complex failure mechanism of the zpins, which are not accounted for in the existing models. The PhD thesis presents a comprehensive experimental study into the impact damage resistance, post-impact mechanical properties of z-pinned sandwich composites and localised loading behaviour, which has not been previously investigated to any great detail. The research showed that there was no improvement to the impact damage resistance of the z-pinned sandwich composite at low impact energies (when damage was confined to the impacted face skin). The post-impact compressive stiffness and failure load for the z-pinned sandwich composite remained the same (within experimental scatter) as the unpinned material. Z-pinning was found to be only marginally effective at increasing the damage resistance when the impact energy was high enough to cause core crushing. This study showed that under a localised impact load, z-pins were not particularly effective at increasing the damage resistance or post-impact mechanical properties of sandwich composites and this is attributed to the small number of pins available to resist a localised (point) impact load. It was discovered that increasing the loading area improved the indentation stiffness and crush strength, and this was due to the increased number of z-pins resisting indentation. The experimental indentation results were further analysed against predictions using an indentation model for z-pinned sandwich composites. As a final novel study, the effect of z-pinning on the mechanical performance of Tshaped bonded sandwich joints was investigated. Experimental testing revealed that the stiffness, ultimate load and absorbed energy capacity of the sandwich composite joint was improved by z-pinning. The failure load and energy absorption were increased by the z-pins suppressing skin-to-core failure by generating bridging traction loads through the foam core. Pin pull-out tests revealed that z-pins generated high mode I bridging traction loads during frictional pull-out from the face skins, and this increased the load capability and stabilised the fracture process of the sandwich joint. The improvements to the mechanical properties of the T-joint are discussed using mechanical models for the bridging laws of z-pins in composite materials. This research revealed for the first time that z-pinning could be used an as alterative to mechanical fastening for the high strength joining of T-section sandwich composite components. The PhD thesis concludes with a summary of the major research findings, a discussion of future research directions into z-pinned sandwich composite panels and joints, and the remaining challenges in the certification of z-pinned sandwich composites for use in aircraft structures

Complex Adaptive Systems, Agent-Based Modeling and Information Assurance

Management of information security issues can be viewed as a complex adaptive system in that hackers are constantly developing new means of trying to penetrate security systems and access information assets. Organizational must adapt too these threats by updating security procedures and systems and by training employees in what must be done to counteract new threats. We present agent-based models that illustrate “phishing” problems, and General Deterrence Theory and Protection Motivation Theory and their application to IA problems. These models are written in Netlogo, an open-source agent-based modeling system, and are freely available for education and training in IA

Identification of Haptic Based Guiding Using Hard Reins

This paper presents identifications of human-human interaction in which one person with limited auditory and visual perception of the environment (a follower) is guided by an agent with full perceptual capabilities (a guider) via a hard rein along a given path. We investigate several identifications of the interaction between the guider and the follower such as computational models that map states of the follower to actions of the guider and the computational basis of the guider to modulate the force on the rein in response to the trust level of the follower. Based on experimental identification systems on human demonstrations show that the guider and the follower experience learning for an optimal stable state-dependent novel 3rd and 2nd order auto-regressive predictive and reactive control policies respectively. By modeling the follower's dynamics using a time varying virtual damped inertial system, we found that the coefficient of virtual damping is most appropriate to explain the trust level of the follower at any given time. Moreover, we present the stability of the extracted guiding policy when it was implemented on a planar 1-DoF robotic arm. Our findings provide a theoretical basis to design advanced human-robot interaction algorithms applicable to a variety of situations where a human requires the assistance of a robot to perceive the environment

Newly Discovered Bright z~9-10 Galaxies and Improved Constraints on Their Prevalence Using the Full CANDELS Area

We report the results of an expanded search for z~9-10 candidates over the ~883 arcmin^2 CANDELS+ERS fields. This study adds 147 arcmin^2 to the search area we consider over the CANDELS COSMOS, UDS, and EGS fields, while expanding our selection to include sources with bluer J_{125}-H_{160} colors than our previous J_{125}-H_{160}>0.5 mag selection. In searching for new z~9-10 candidates, we make full use of all available HST, Spitzer/IRAC, and ground-based imaging data. As a result of our expanded search and use of broader color criteria, 3 new candidate z~9-10 galaxies are identified. We also find again the z=8.683 source previously confirmed by Zitrin+2015. This brings our sample of probable z~9-11 galaxy candidates over the CANDELS+ERS fields to 19 sources in total, equivalent to 1 candidate per 47 arcmin^2 (1 per 10 WFC3/IR fields). To be comprehensive, we also discuss 28 mostly lower likelihood z~9-10 candidates, including some sources that seem to be reliably at z>8 using the HST+IRAC data alone, but which the ground-based data show are much more likely at z<4. One case example is a bright z~9.4 candidate COS910-8 which seems instead to be at z~2. Based on this expanded sample, we obtain a more robust LF at z~9 and improved constraints on the volume density of bright z~9 and z~10 galaxies. Our improved z~9-10 results again reinforce previous findings for strong evolution in the UV LF at z>8, with a factor of ~10 evolution seen in the luminosity density from z~10 to z~8.Comment: 22 pages, 12 figures, 6 tables, accepted for publication in the Astrophysical Journa

Significance of the compliance of the joints on the dynamic slip resistance of a bioinspired hoof

Robust mechanisms for slip resistance are an open challenge in legged locomotion. Animals such as goats show impressive ability to resist slippage on cliffs. It is not fully known what attributes in their body determine this ability. Studying the slip resistance dynamics of the goat may offer insight toward the biologically inspired design of robotic hooves. This article tests how the embodiment of the hoof contributes to solving the problem of slip resistance. We ran numerical simulations and experiments using a passive robotic goat hoof for different compliance levels of its three joints. We established that compliant yaw and pitch and stiff roll can increase the energy required to slide the hoof by ≈ 20% compared to the baseline (stiff hoof). Compliant roll and pitch allow the robotic hoof to adapt to the irregularities of the terrain. This produces an antilock braking system-like behavior of the robotic hoof for slip resistance. Therefore, the pastern and coffin joints have a substantial effect on the slip resistance of the robotic hoof, while the fetlock joint has the lowest contribution. These shed insights into how robotic hooves can be used to autonomously improve slip resistance