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

Computation and verification of workpiece shape in electrochemical machining

This investigation was motivated by the need for accurate prediction of electrochemical machined surfaces relative to corresponding tool geometries for given sets of machining parameters. A mathematical model was formulated which simulates the electrochemical erosion achieved by primary current distribution under steady tool feed rate, but with correction for variable efficiency. The equations comprising the mathematical model were programmed for solution by a digital computer, using discrete steps and a quasi-steady approach. The model was not completely analytical; it utilised an empirical values for specific metal removal rates. The efficiency of machining with NaNO₃ electrolyte was estimated from experimental results of other investigators. To assess the validity of the model, drilling test runs were performed with tubular electrodes having two geometries at the leading edge of the tool. Work specimens were made out of EN58J stainless steel, both NaC1 and NaNO₃ electrolytes were used. The correlation between experimentally obtained drilled surfaces and the computer predicted surfaces were satisfactory, justifying the assumptions made during the development of the model and the numerical methods of the solution used. This investigation has provided a method which could be successfully employed to predict the electrochemically machined profiles relative to tool geometries. This undoubtedly helps the production engineer in achieving the desired tolerances of the finished component eliminating the high cost of trial and error techniques.This investigation was motivated by the need for accurate prediction of electrochemical machined surfaces relative to corresponding tool geometries for given sets of machining parameters. A mathematical model was formulated which simulates the electrochemical erosion achieved by primary current distribution under steady tool feed rate, but with correction for variable efficiency. The equations comprising the mathematical model were programmed for solution by a digital computer, using discrete steps and a quasi-steady approach. The model was not completely analytical; it utilised an empirical values for specific metal removal rates. The efficiency of machining with NaNO₃ electrolyte was estimated from experimental results of other investigators. To assess the validity of the model, drilling test runs were performed with tubular electrodes having two geometries at the leading edge of the tool. Work specimens were made out of EN58J stainless steel, both NaC1 and NaNO₃ electrolytes were used. The correlation between experimentally obtained drilled surfaces and the computer predicted surfaces were satisfactory, justifying the assumptions made during the development of the model and the numerical methods of the solution used. This investigation has provided a method which could be successfully employed to predict the electrochemically machined profiles relative to tool geometries. This undoubtedly helps the production engineer in achieving the desired tolerances of the finished component eliminating the high cost of trial and error techniques

The role of morphology of the thumb in anthropomorphic grasping : a review

The unique musculoskeletal structure of the human hand brings in wider dexterous capabilities to grasp and manipulate a repertoire of objects than the non-human primates. It has been widely accepted that the orientation and the position of the thumb plays an important role in this characteristic behavior. There have been numerous attempts to develop anthropomorphic robotic hands with varying levels of success. Nevertheless, manipulation ability in those hands is to be ameliorated even though they can grasp objects successfully. An appropriate model of the thumb is important to manipulate the objects against the fingers and to maintain the stability. Modeling these complex interactions about the mechanical axes of the joints and how to incorporate these joints in robotic thumbs is a challenging task. This article presents a review of the biomechanics of the human thumb and the robotic thumb designs to identify opportunities for future anthropomorphic robotic hands

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

A simple layout optimization formulation for load-carrying tensegrity structures

Traditional tensegrity structures comprise isolated compression members lying inside a continuous network of tension members. In this contribution, a simple numerical layout optimization formulation is presented and used to identify the topologies of minimum volume tensegrity structures designed to carry external applied loads. Binary variables and associated constraints are used to limit (usually to one) the number of compressive elements connecting a node. A computationally efficient two-stage procedure employing mixed integer linear programming (MILP) is used to identify structures capable of carrying both externally applied loads and the self-stresses present when these loads are removed. Although tensegrity structures are often regarded as inherently ‘optimal’, the presence of additional constraints in the optimization formulation means that they can never be more optimal than traditional, non-tensegrity, structures. The proposed procedure is programmed in a MATLAB script (available for download) and a range of examples are used to demonstrate the efficacy of the approach presented

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

Phenotypic characteristics contributing to the enhanced growth of Escherichia coli bloom strains

During bloom events, Escherichia coli cell counts increase to between 10,000 and 100,000 cfu/100 ml of water. The strains responsible for bloom events belong to E. coli phylogenetic groups A and B1, and all have acquired a capsule from Klebsiella. A pan‐genome comparison of phylogroup A E. coli revealed that the ferric citrate uptake system (fecIRABCDE) was overrepresented in phylogroup A bloom strains compared with non‐bloom E. coli. A series of experiments were carried out to investigate if the capsule together with ferric citrate uptake system could confer a growth rate advantage on E. coli. Capsulated strains had a growth rate advantage regardless of the media composition and the presence/absence of the fec operon, and they had a shorter lag phase compared with capsule‐negative strains. The results suggest that the Klebsiella capsule may facilitate nutrient uptake or utilization by a strain. This, together with the protective roles played by the capsule and the shorter lag phase of capsule‐positive strains, may explain why it is only capsule‐positive strains that produce elevated counts in response to nutrient influx

Periodic orbits for classical particles having complex energy

This paper revisits earlier work on complex classical mechanics in which it was argued that when the energy of a classical particle in an analytic potential is real, the particle trajectories are closed and periodic, but that when the energy is complex, the classical trajectories are open. Here it is shown that there is a discrete set of eigencurves in the complex-energy plane for which the particle trajectories are closed and periodic.Comment: 12 pages, 9 figure

PROTECTED AREA MANAGEMENT THROUGH A COMMUNITY CENTERED APPROACH EXPERIENCE OF DUNUVILAPITIY A AND RATHTOTAYAYA VILLAGES IN WASGOMUWA NATIONAL PARK

Wasgomuwa National Park was initially declared as a Strict Nature Reservein 1938, and became a National Park with the commencement of theAccelerated Mahaweli Development Program in 1984. It possesses richdiversity of fauna and flora.The average poverty level of the communities who are living close toWasgomuwa National Park is generally much higher than that of the nationalaverage. Lack of employment opportunities, land tenure insecurity, lowprices for agricultural and farm produce etc. have also contributed for thedepressed rural economy and poverty, which is directly linked with thedependency on park resources, causing rapid depletion of resource base.Therefore activities such as encroachments, cattle grazing, poaching,gemming, illicit tree felling is common. Human-elephant confrontations arealso severe near the southern boundary of the park. Dunuwilapitiya andRathtotayaya villages being located in this area are constantly subjected toelephant attacks.Community Outreach concept which promotes proactive involvement ofbuffer zone communities in protected area management was used to addressthe issues of the communities in Dunuwilapitiya &amp; Rathtotayaya villages. Byusing this community centered participatory approach, village actionplans/micro-plans for the two villages were formulated. Two new communitybased organizations (CBOs) were established as a result of the institutionalanalysis.Provision has been made under the Protected Area Conservation Fund tofinance environment friendly livelihood improvement initiatives and projectsfocused on the reduction of dependency of park resources that are originatingthrough the micro-planning process. Community managed grassland of 70hais presently being developed by the villagers of Dunuwilapitiya while anirrigation canal rehabilitation project was also launched by the same community recently. The Rathtotayaya community is implementing anelectric fencing project as a measure to reduce human-elephant conflict. Acommunity based social monitoring system has also been introduced formonitoring progress of related activities.With the introduction of the participatory development approach and thecommunity empowerment process, improved interaction between the parkmanagement and the community is evident while the dependency on parkresources is in the process of being reduced.