A derivation of high-frequency asymptotic values of 3D added mass and damping based on properties of the Cummins' equation

This brief paper provides a novel derivation of the known asymptotic values of three-dimensional (3D) added mass and damping of marine structures in waves. The derivation is based on the properties of the convolution terms in the Cummins's Equation as derived by Ogilvie. The new derivation is simple and no approximations or series expansions are made. The results follow directly from the relative degree and low-frequency asymptotic properties of the rational representation of the convolution terms in the frequency domain. As an application, the extrapolation of damping values at high frequencies for the computation of retardation functions is also discussed.

Economics of maritime disasters : essays on the Titanic and Lusitania

This work seeks to fill some of the gap existing in the economics and behavioural economics literature pertaining to the decision making process of individuals under extreme environmental situations (life and death events). These essays specifically examine the sinking’s of the R.M.S. Titanic, on 14th April of 1912, and the R.M.S. Lusitania, on 7th May 1915, using econometric (multivariate) analysis techniques. The results show that even under extreme life and death conditions, social norms matter and are reflected in the survival probabilities of individuals onboard the Titanic. However, results from the comparative analysis of the Titanic and Lusitania show that social norms take time to organise and be effective. In the presence of such time constraints, the traditional “homo economicus” model of individual behaviour becomes evident as a survival of the fittest competition.

A nonlinear position controller for maritime operations of Rotary-wing UAVs

This paper presents a disturbance attenuation controller for horizontal position stabilization for hover and automatic landings of a Rotary-wing Unmanned Aerial Vehicle (RUAV) operating in rough seas. Based on a helicopter model representing aerodynamics during the landing phase, a nonlinear state feedback H-infinity controller is designed to achieve rapid horizontal position tracking in a gusty environment. The resultant control variables are further treated in consideration of practical constraints (flapping dynamics, servo dynamics and time lag effect) for implementation purpose. The high-fidelity closed-loop simulation using parameters of the Vario helicopter verifies performance of the proposed position controller. It not only increases the disturbance attenuation capability of the RUAV, but also enables rapid position response when gusts occur. Comparative studies show that the H-infinity controller exhibits great performance improvement and can be applied to ship/RUAV landing systems.

State responsibility for maritime terrorism

Maritime terrorism is one of the main maritime security issues in the contemporary world. The threat of maritime terrorism is more apparent than ever in the post-September 11 era. Although maritime terrorism is an old issue, the disastrous events of 11 September 2001 brought this issue again onto the global agenda. This incident brought to the forefront the longstanding concerns that terrorists could severely disrupt the global maritime supply chain by using shipping containers or vessels to attack major business centres, port facilities and offshore installations. A number of international criminal law studies have been conducted to identify international legal challenges in maritime security. Some of these works have critically examined the international legal framework for maritime security and identified the lacunas in the existing system. Some of these writings have also identified that emerging maritime terrorism issues are prompting States to introduce some stringent measures. Although the international legal regime related to maritime terrorism is a well-researched area, very little research work has explored the legal issues related to State responsibility for maritime terrorism. This article argues that, although the United Nations Convention on the Law of the Sea (UNCLOS) provisions related to maritime piracy may not be applicable for some dimensions of maritime violence, different provisions of UNCLOS may relevant in identifying State responsibility for maritime terrorism.

Analysis and prevention of extreme vibration in high speed craft - A research framework

Extreme vibration has been reported for small, high speed craft in the maritime sector, with performance and health threatening effects on boat operators and crew. Musculoskeletal injuries are an enduring problem for high speed craft passengers. Spinal or joint injuries and neurological disorders may occur from repetitive pounding over rough water, continued vibration and single impact events. The risk from whole body vibration (WBV) induced through the small vessels mainly depends on time spent on the craft, which can’t be changed in a military scenario; as well as the number of shocks and jolts, and their magnitude and frequency. In the European Union for example, physical agents directives require all employers to control exposure to a number of physical agents including noise and vibration. The EC Vibration Directive 2002/44/EC then sets out regulations for the control of health and safety risks from the exposure of workers to hand arm vibration (HAV) and WBV in the workplace. Australia has exposure standards relating to WBV, AS 2670.1-2001 – Evaluation of human exposure to whole body vibration. This standard is identical to the ISO 2631-1:1997, Mechanical vibration and shock – Evaluation of human exposure to whole-body vibration. Currently, none of the jurisdictions in Australia have specific regulations for vibration exposures in workplaces. However vibration is mentioned to varying degrees in their general regulations, codes of practice and guidance material. WBV on high speed craft is normally caused by “continuous 'hammering' from short steep seas or wind against tide conditions. Shock on High Speed Craft is usually caused by random impacts. Military organisations need the knowledge to make informed decisions regarding their marine operations, compliance with legislation and potentially harmful health effects, and develop and implement appropriate counter-measures. Marine case studies in the UK such as published MAIB (Marine Accident Investigation Branch) reports show injuries that have occurred in operation, and subsequent MCA (Maritime Coastguard Agency) guidance is provided (MGN 436 (M+F), WHOLE-BODY VIBRATION: Guidance on Mitigating Against the Effects of Shocks and Impacts on Small Vessels. MCA, 2011). This paper proposes a research framework to study the origin, impact and pathways for prevention of WBV in small, high speed craft in a maritime environment.