Aquaculture vis-a-vis agriculture

The effect of aquaculture, especially shrimp farming, on agriculture has caused heated debate among aquaculturists, agriculturists, and non-governmental organizations. As data on the negative impact of shrimp farming on adjacent rice fields are not available, a study was undertaken in rice fields skirting three shrimp farms: a semi-intensive farm; an extensive farm; and a semi-intensive farm with a buffer zone. The buffer zone was found to be helpful in preventing salinization of the adjacent agricultural fields and the Electrical Conductivity (EC) values (less than 1) reported were found to be harmless to the rice crop. Thus, aquaculture and agriculture can coexist in coastal areas if there are buffer zones in between

A thermodynamic framework to develop rate-type models for fluids without instantaneous elasticity

In this paper, we apply the thermodynamic framework recently put into place by Rajagopal and co-workers, to develop rate-type models for viscoelastic fluids which do not possess instantaneous elasticity. To illustrate the capabilities of such models we make a specific choice for the specific Helmholtz potential and the rate of dissipation and consider the creep and stress relaxation response associated with the model. Given specific forms for the Helmholtz potential and the rate of dissipation, the rate of dissipation is maximized with the constraint that the difference between the stress power and the rate of change of Helmholtz potential is equal to the rate of dissipation and any other constraint that may be applicable such as incompressibility. We show that the model that is developed exhibits fluid-like characteristics and is incapable of instantaneous elastic response. It also includes Maxwell-like and Kelvin-Voigt-like viscoelastic materials (when certain material moduli take special values).Comment: 18 pages, 5 figure

Hydrodynamic Models for Heavy Ion Collisions

Application of hydrodynamics for modeling of heavy-ion collisions is reviewed. We consider several physical observables that can be calculated in this approach and compare them to the experimental measurements.Comment: 42 pages, 15 figures, An invited review for Nov. 2006 edition of Annual Review of Nuclear and Particle Physic

A model for the degradation of polyimides due to oxidation

Polyimides, due to their superior mechanical behavior at high temperatures, are used in a variety of applications that include aerospace, automobile and electronic packaging industries, as matrices for composites, as adhesives etc. In this paper, we extend our previous model in [S. Karra, K. R. Rajagopal, Modeling the non-linear viscoelastic response of high temperature polyimides, Mechanics of Materials, In press, doi:10.1016/j.mechmat.2010.09.006], to include oxidative degradation of these high temperature polyimides. Appropriate forms for the Helmholtz potential and the rate of dissipation are chosen to describe the degradation. The results for a specific boundary value problem, using our model compares well with the experimental creep data for PMR-15 resin that is aged in air.Comment: 13 pages, 2 figures, submitted to Mechanics of Time-dependent Material

Inhomogeneous phase of a Gluon Plasma at finite temperature and density

By considering the non-perturbative effects associated with the fundamental modular region, a new phase of a Gluon Plasma at finite density is proposed. It corresponds to the transition from glueballs to non-perturbative gluons which condense at a non vanishing momentum. In this respect the proposed phase is analogous to the color superconducting LOFF phase for fermionic systems.Comment: 5 pages, 2 figure

Entanglement of Pure Two-Mode Gaussian States

The entanglement of general pure Gaussian two-mode states is examined in terms of the coefficients of the quadrature components of the wavefunction. The entanglement criterion and the entanglement of formation are directly evaluated as a function of these coefficients, without the need for deriving local unitary transformations. These reproduce the results of other methods for the special case of symmetric pure states which employ a relation between squeezed states and Einstein-Podolsky-Rosen correlations. The modification of the quadrature coefficients and the corresponding entanglement due to application of various optical elements is also derived.Comment: 12 page

Restructuring seafarers’ welfare under the Maritime Labour Convention: an empirical case study of Greece

Maritime transport is the ‘invisible’ backbone that keeps the global economy moving on any given day, as has become obvious during the COVID-19 crisis. However, shipping and seafarers do not turn up in the public mind as a key sector, with key workers. It is important in this context to look into major issues concerning seafarers. This paper examines three of the major issues relating to the welfare of seafarers, including wages, social security benefits, and onboard and ashore welfare facilities and services. It is impossible to research all countries here, so this paper selects Greece – which is one of today’s primary shipping countries as for shipowning, as well as for global supply and demand for seafarers – to conduct an empirical case study. The entry into force of Maritime Labour Convention 2006 (MLC), which probably is the most comprehensive convention governing maritime labour up to date, has had a significant impact on the world maritime industry. While the Convention aims to ensure fair competition and level-playing field for quality owners of ships, it is indisputable that it will increase shipowners’ operation cost in the first place. Despite involving more than 30,000 seafarers, Greece had not ratified MLC 2006 until 2013 when the Convention entered into force. Based on the existing knowledge and scholarship, and primary data collected in several phases of fieldwork, this paper critically examines the three major issues relating to the welfare of Greek seafarers. The main findings reveal that there is still a gap between the theoretical legal framework and the practical implementation in Greece. The paper explains the legal concepts regarding seafarer welfare matters in detail and collects the opinions from the industry. Such dilemmas are also common in other countries. These include possible delays and irregularities of wage payments, expensive and limited online communications and insufficient rest hours. Thus, the findings and suggestions revealed from this paper are of importance for the shipping industry and other states

Active flutter suppression of a cantilever plate at supersonic speeds

Modern high-speed aircrafts are flown using the fly-by- wire system. The d y n a m i c s of automatic flight control system interacts with aircraft's structural dynamics and aerodynamics to give rise to aero servo elastic problems. Such problems can be avoided using an active control system. AS a feasibility study, active flutter suppression of a cantilever plate wing was carried out. In this study it was demonstrated that the flutter Mach number of the cantilever wing can be increased by 12.5%

Robust Ultrasonic Waveguide Based Distributed Temperature Sensing

AbstractThis is a novel technique for distributed temperature measurements, using single robust ultrasonic wire or strip-like waveguides, special embodiments in the form of Helical or Spiral configurations that can cover large area/volume in enclosed regions. Such distributed temperature sensing has low cost applications in the long term monitoring critical enclosures such as containment vessels, flue gas stacks, furnaces, underground storage tanks, buildings for fire, etc. The range of temperatures that can be measured are from very low to elevated temperatures. The transduction is performed using Piezo-electric crystals that are bonded to one end of the waveguide which acts as both transmitter and receivers. The wires will have periodic reflector embodiments (bends, gratings, etc.) that allow reflections of an input ultrasonic wave, in a pulse echo mode, back to the crystal. Using the time of fight (TOF) variations at the multiple predefined reflector locations, the measured temperatures are mapped with multiple thermocouples. Using either the L(0,1) or the T(0,1)modes, or simultaneously, measurements other than temperature may also be included. This paper will describe the demonstration of this technology using a 0.5MHz longitudinal piezo-crystal for transmitting and receiving the L (0, 1) mode through the special form of waveguide at various temperatures zones