An integrated methodology for the design of Ro-Ro passenger ships

The present paper provides a brief introduction to the holistic approach to ship design, defines the generic ship design optimization problem and demonstrates its solution by use of advanced optimization techniques

Advanced damage stability assessment for surface combatants

One of the major contributors to the survivability of a surface combatant is her reduced vulnerability to weapon effects and as such the ship's damage stability characteristics determine a ship's ability to resist the consequences of possible flooding, namely to not capsize and/or sink. There are serious concerns about the limitations of the current semi-empirical deterministic criteria in which a combatant's damage stability is assessed upon. This paper details a comparison between the current approach and a newly presented probabilistic approach with the aim of determining which will result in a more accurate way of estimating the level of survivability of a particular design. A study is also presented in which the maximum damage length used in the naval ship assessment is increased to merchant ship standards of 0.24L bp

Assessment of survivability of surface combatants after damage in the sea environment

The operating conditions of modern warships, in the natural sea environment, have a significant influence on their survivability in the event that watertight integrity is lost. Up to now, the consideration of sea and weather conditions has been implicitly accounted for in a naval ship’s damaged stability assessment. This paper outlines a probabilistic approach to assessing a naval ship’s damage stability, in which some of the limitations of the currently used damage stability criteria are identified, including the validity of the assumption of moderate sea states at the time of damage. An investigation into the operability of a frigate design found that there is a significant increase in the risk of a ship’s loss when changing the operational area from the North Atlantic to the North Pacific. A remarkable additional finding of the study showed that the assumed distribution for the damage penetration has no significant effect on the ship’s survivability due to the way modern combatants are designed

Parametric design and multi-objective optimisation of containerships

The introduction of new regulations by the International Maritime Organisation, the fluctuation of fuel price levels, along with the continuous endeavour of the shipping industry for economic growth and profits has led the shipbuilding industry to explore new and cost-efficient designs for various types of merchant ships. In this respect, proper use of modern computer-aided design/computer-aided engineering systems (CAD/CAE) extends the design space, while generating competitive designs in short lead time. The present paper deals with the parametric design and optimisation of containerships. The developed methodology, which is based on the CAESES/Friendship-Framework software system, is demonstrated by the conceptual design and multi-objective optimisation of a midsized, 6,500 TEU containership. The methodology includes a complete parametric model of the ship’s external and internal geometry and the development and coding of all models necessary for the determination of the design constraints and the design efficiency indicators, which are used for the evaluation of parametrically generated designs. Such indicators defining the objective functions of a multi-objective optimisation problem are herein the energy efficiency design index, the required freight rate, the ship’s zero ballast container box capacity and the ratio of the above to below deck number of containers. The set-up multi-objective optimisation problem is solved by use of the genetic algorithms

Tuning the spontaneous light emission in phoxonic cavities

The modulation of spontaneous light emission of active centers through elastic waves in Si/SiO_2 multilayer phoxonic structures that support dual photonic-phononic localized modes, in the bulk or at the surface, is studied by means of rigorous full electrodynamic and elastodynamic calculations. Our results show that strong dynamic modulation of the spontaneous emission can be achieved through an enhanced acousto-optic interaction when light and elastic energy are simultaneously localized in the same region

Lipid production by yeasts growing on commercial xylose in submerged cultures with process water being partially replaced by olive mill wastewaters

Six yeast strains belonging to Rhodosporidium toruloides, Lipomyces starkeyi, Rhodotorula glutinis and Cryptococcus curvatus were shake-flask cultured on xylose (initial sugar – S0 =70±10 g/L) under nitrogen-limited conditions. C. curvatus ATCC 20509 and L. starkeyi DSM 70296 were further cultured in media where process waters were partially replaced by the phenol-containing olive-mill wastewaters (OMWs). In flasks with S0≈100 g/L and OMWs added yielding to initial phenolic compounds concentration (PCC0) between 0.0 g/L (blank experiment) and 2.0 g/L, C. curvatus presented maximum total dry cell weight - TDCWmax ≈27 g/L, in all cases. The more the PCC0 increased, the fewer lipids were produced. In OMW-enriched media with PCC0≈1.2 g/L, TDCW=20.9 g/L containing ≈40% w/w of lipids was recorded. In L. starkeyi cultures, when PCC0≈2.0 g/L, TDCW≈25 g/L was synthesized, whereas lipids in TDCW =24-28% w/w, similar to the experiments without OMWs, were recorded. Non-negligible dephenolization and species-dependant decolorization of the wastewater occurred. A batch-bioreactor trial by C. curvatus only with xylose (S0≈110 g/L) was performed, and TDCW=35.1 g/L (lipids in TDCW=41.3% w/w) was produced. Yeast total lipids were composed of oleic and palmitic and to lesser extent linoleic and stearic acids. C. curvatus lipids were mainly composed of non-polar fractions (i.e. triacylglycerols)

Advanced damaged stability assessment for surface combatants

One of the major contributors to survivability of a surface combatant is her vulnerability to weapon effects and as such the damage stability characteristics have a direct influence on vulnerability. There are serious concerns about the limitations of the current semi-empirical deterministic criteria in which a combatant’s damage stability is assessed upon. This paper details a comparison between the current approach and a newly presented probabilistic approach with the aim of determining which will result in a more accurate way of estimating the level of survivability of a particular design. A study is also presented in which the damage length used is increased to merchant standards of 0.24Lbp

Aromatase inhibitors in stimulated IVF cycles

Aromatase inhibitors have been introduced as a new treatment modality that could challenge clomiphene citrate as an ovulation induction regiment in patients with PCOS. Although several randomized trials have been conducted regarding their use as ovulation induction agents, only few trials are available regarding their efficacy in IVF stimulated cycles. Current available evidence support that letrozole may have a promising role in stimulated IVF cycles, either when administered during the follicular phase for ovarian stimulation. Especially for women with poor ovarian response, letrozole appears to have the potential to increase clinical pregnancy rates when combined with gonadotropins, whereas at the same time reduces the total gonadotropin dose required for ovarian stimulation. However, given that in all of the trials letrozole has been administered in GnRH antagonist cycles, it is intriguing to test in the future how it may perform when used in GnRH agonist cycles. Finally administration of letrozole during luteal phase in IVF cycles offers another treatment modality for patients at high risk for OHSS taking into account that it drastically reduces estradiol level