Hard Foulers Induced Crevice Corrosion of HSLA Steel in theCoastal Waters of the Gulf of Mannar （Bay of Bengal）, India

In the present study an attempt has been made toinvestigate the relationship between the variations in the foulingassemblage and corrosion behaviour of HSLA steel at three coastallocations in the Gulf of Marmar, India, over a period of 24 months.Oyster fouling was dominant in the Tuticorin open sea, whilebarnacles were the major foulants in the Tuticorin harbour andMandapam. The fouling load in the Tuticorin waters was higherwhen compared to the Mandapam waters. The corrosion ratesdecreased progressively with the immersion time at all three testlocations. In the Tuticorin open sea, the corrosion rates were higherwhen compared to the other two locations throughout the studyperiod. The surface of the coupons was characterized by crevicesbeneath the hard foulers in the Tuticorin harbour and Mandapam,whereas in the Tuticorin open sea, the coupons experiencedcrevices of a tunneling nature. The percentage of the loss of thetensile strength increased with time at all the test locations.     

Modelling port choice in an uncertain environment

Port choice is an important issue to be investigated to ensure the effective integration of container supply chains and the sustainable development of regional economy. The selection of appropriate ports to facilitate shipping activities and international trade is crucial for many stakeholders, including shipping lines, port administrators, cargo shippers and national governments. The task is essentially a process of multiple criterion decision-making (MCDM) under uncertainty, requiring analysts to derive rational decisions from uncertain and incomplete data related to different quantitative and qualitative determinants. This paper aims at proposing a new conceptual port choice method by explaining the role fuzzy logic in evidential reasoning in a complementary way, in which various forms of raw data (either objective or subjective) collected to evaluate port performance can first be converted into and presented as fuzzy grades defined using linguistics terms with degrees of belief (DoBs) and second be combined using evidential reasoning to produce a port choice preference score. The method is applied to analyse the selection of major Northeast Asian (NEA) container ports from a shipping line’s perspective. The outcome, a port choice preference score, is calculated using evidential reasoning to directly synthesize the true estimation of the port with respect to each criterion and therefore, unlike a relative ranking index, keeps the ‘goodness’ of port evaluation, capable of benchmarking a specific port’s performance and monitoring the increase of its competitiveness in a longitude study with respect to an individual criterion or all the criteria as a whole.     

An interpretation of inter-container port relationships from the demand perspective

Container ports serve as important conduits to facilitate the efficient flow of containerized cargo. As part of value-driven chain systems that intersect between hinterlands, efficiency gains that are generated within the container port will have a direct impact on the competitive advantage of its users and affect the economic potential of both the origin and destination hinterlands. As such, the paper proposes the usage of indifference analysis propounded in microeconomic theory as a useful means to examine inter-container port competition and complementarity. The framework presented can also be combined with Porter's ‘Diamond’ model in order for inter-container port demand relationships to be quantified, measured and analysed in an holistic manner. Apart from analysing inter-port relationships from the standpoint of container ports, the framework can also be used to analyse inter-port relationships from the perspective of other key players in the value-driven chain system and modified accordingly to incorporate various indicators that are deemed to be relevant to these parties.     

Ship underwater noise assessment by the acoustic analogy. Part I: nonlinear analysis of a marine propeller in a uniform flow

The aim of this work is to analyze the hydroacoustic behavior of a marine propeller through the acoustic analogy and to test the versatility and effectiveness of this approach in dealing with the many (and relatively unexplored) issues concerning the underwater noise and its numerical prediction. In particular, a propeller in a noncavitating open water condition is examined here by coupling a Reynolds averaged Navier–Stokes hydrodynamic solver to a hydroacoustic code implementing different resolution forms of the Ffowcs Williams–Hawkings (FWH) equation. The numerical results suggest that unlike the analogous aeronautical problem, where the role played by the nonlinear quadrupole sources is known to be relevant just at high transonic or supersonic regime, the pressure field underwater seems to be significantly affected by the flow nonlinearities, while the contribution from the linear terms (the thickness and loading noise components) is dominant only in a spatially very limited region. Then, contrary to popular belief and regardless of the low blade rotational speed, a reliable hydroacoustic analysis of a marine propeller cannot put aside the contribution of the nonlinear noise sources represented by the turbulence and vorticity three-dimensional fields and requires the computation of the FWH quadrupole source terms.     

The effect of sloshing on the sway motions of 2D rectangular cylinders in regular waves

In this paper, we investigated the effect of sloshing on the sway motions of two-dimensional rectangular cylinders in regular waves, bearing in mind possible applications for LNG-FPSO and LNG-FSRU. First, we carried out experiments for two models with different drafts, or the same draft but different filling ratios, in which the models were firmly connected to each other. The sway motion was measured with a noncontact video camera. This is an extension of Rognebakke and Faltinsen’s work for a single model (J Ship Res 47(3):208–221, 2003). It was found that the sway motion became small when the incident wave frequency was close to the lowest natural frequency of each model. The sway motion greatly increased when the wave frequency was higher than this frequency. The measured data were compared with numerical results obtained by a single-dominant multi-modal method; relatively good agreement was noted. However, the numerical results deviated from the experimental results near the lowest natural frequency of the smaller model, which was believed to be due to overturning waves, as observed during the experiment. Since this is out of the valid range for the single-dominant multi-modal method, other, more appropriate, methods such as the multi-dominant modal method must be applied instead.     

近年我国煤炭贸易形势变化对航运市场的影响

为推动我国航运市场发展,分析全球金融危机后的我国煤炭市场情况,以及煤炭贸易形势发生重大变化的主要原因,并展望我国煤炭贸易形势变化对未来航运市场的影响：使全球煤炭平均海运运距增加,成为支撑未来国际煤炭价格的重要因素之一。     

Lubrication characteristics of spiral groove liquid seals for use in the carrier of a vane-type external LPG fuel pump

We analyzed the lubrication characteristics of a design-selected spiral groove liquid seal for the critical component, the carrier, of a rotary vane-type fuel pump developed for external installation on fuel tanks for liquid phase LPG (liquefied petroleum gas) injection (LPLi) vehicles, with the aim of fundamentally improving lubrication performance and so protecting the carrier from early frictional wear damage at its suction face. The main reason for selecting a spiral groove pattern was because the viscosity of liquid LPG is very low, comparable to that of air, and current commercial dry gas seals adopting spiral grooves have been successfully employed in completely noncontacting applications. Utilizing the Galerkin finite element lubrication analysis method, a detailed lubrication characteristic analysis of the seal was performed, and lubrication performance optimization was performed by systematic parameter analyses of the design variables. Compared to the initial reference design, the final optimized spiral groove seal design had a groove depth increased by 66.7% and an equilibrium seal clearance increased by 65.3%. Our model also predicted that under a condition of equilibrium between the closing force of the pumping pressure and the seal opening force, the optimally designed carrier spiral groove liquid seal was capable of maintaining a stable lubricating film with sufficient axial stiffness and thereby demonstrated successful noncontact operation; in addition, leakage through the seal was minimal.     

Finite-element analysis of quasistatic fracture in CV joints under full-turn and full-throttle conditions

Quasistatic fractures at high joint angles constitute a chronic quality problem in CV joints. This type of fracture occurs when a driver unintentionally depresses the brake and accelerator simultaneously under a full-turn retreat condition. In general, the cage in a ball joint can be broken only at these high joint angles. Here we present a flexible quasistatic simulation model developed to simulate fracture in a CV joint. The cause and process of the quasistatic fracture were analyzed using simulations and physical tests. Static fracture simulations and tests at high joint angles showed that, initially, only one of the six cage posts was damaged. In a simulation of one revolution at constant torque, we found that an imbalance in ball loads generated an excessive cage load. Moreover, if this high cage load was applied when the cage protruded outward, the cage post was subjected to severe shear loading. The cage post was damaged in this specific rotational range. Quasistatic fracture simulations and tests at high joint angles showed that all six cage posts were damaged sequentially. Because entire cage posts were damaged, the quasistatic fracture torque was approximately half of the static torque. The plastic strain in each cage post displayed one step-like jump per revolution in the quasistatic simulations. The ball indentation created by a high ball load was interrupted by the cage-window edges as the ball joint rotated. This hindrance by ball indentation triggered the final breakage of the cage, although it was not the major cause of cage fractures.     

Sensorless adaptive speed control of a permanent-magnet dc motor for anti-lock brake systems

An adaptive control algorithm was developed for the sensorless speed control of a permanent-magnet DC motor directly connected to the hydraulic pump of an antilock brake system. Due to the severe cost and reliability constraints of the application, the motor speed was controlled by a very simple on-off switching method, in which the only measurement required is the voltage across the control switch. The motor speed was calculated solely from the back-EMF voltage during the period of the control cycle when the switching controller is in the switch-off mode. The stability of the developed adaptiveswitching control algorithm was proven mathematically and confirmed experimentally in several vehicle tests over a wide range of target speeds and pump-load conditions. The accuracy and the response time of the controller can easily be tuned by adjusting a single tuning parameter. The switching frequency of the controller can also easily be tuned by adjusting the over-and undershoot thresholds independently from the accuracy of the speed-tracking control.