Distribution of antifouling biocides and organophosphorous compounds were surveyed in aquatic areas from Suruga Bay to the Japan trench, Japan. Tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) compounds in surface water were detected in the range of 5-6 ng/L, 2-3 ng/L and 34-104 ng/L, respectively. Although the concentrations of phenyltin (PTs) compounds were lower in comparison with TBT, Triphenyltin (TPT) compounds were the dominant species among phenyltins. Higher concentrations of Sea Nine 211 and Dichlofluanid were observed among alternative compounds. Among organophosphorous compounds, Triethyl phosphate (TEP), Tributyl phosphate (TBP), Tris (2-chloroethyl) phosphate (TCEP), Tris (2-butoxyethyl) phosphate (TBXP), Triphenyl phosphate (TPP), Tricresyl phosphate (TCP) and Fenitrothion were detected in surface water. In general, the concentrations of antifouling biocides and organophosphorous compounds in water column (water depth; 2000m) were distributed uniformly between upper and bottom layer, while the concentrations of Sea Nine 211, Diuron and TEP were high in the surface water and decrease towards the bottom layer, suggesting the inputs of these compounds from surface water have continued.
In ordinary displacement type ships, frictional drag is the largest component of total ship drag. Generally, it is difficult for common towing tank test to evaluate, within an accuracy of 1%, the difference in frictional drag of a ship for different surface conditions. This difficulty comes from the fact that each measurement is carried out under different tank conditions, i.e., they are due to the disturbance in the towing tank, difference in temperature gradient, fluctuation of towing force, existence of seiche in the tank, etc. The present method is intended to cancel out experimental errors from these causes by using a newly developed parallel towing system. In the present method, a test plate and a reference plate are set parallel to each other and towed simultaneously in the towing tank. In this report, a brief introduction of the present method and discussion of experimental results are presented.
The new anti-biofouling system, which utilizes titanium film to prevent the deposition of marine life on various surfaces of the sea equipment, can keep its superior antifouling effect for extended periods of time eliminating the need for repainting of antifouling paint as well as decreasing marine life fouling which is treated as industrial waste. This system has a catalyzed surface on the titanium film acting as an electrode connected to an external electric power supply. The active oxygen generated on the electrode surface oxidizes and degrades organic matters in seawater electrochemically when they make contact with the catalyzed surface. Since organic matters are nutrients for bacteria, bacterial growth and the subsequent slime formation can be inhibited. Thus, the consequent attachment of seaweedsand the fouling of larger marine organisms can be prevented.
This paper reviews the authors’ ongoing research activities for the development of toxicity tests for marine organisms and the ecological hazard assessment process for anti-fouling agents in the marine environment. Some test protocols based on the response of marine organisms have been standardized by governmental agencies and international organizations. However, in Japan there are still only a few standardized test protocols for domestic marine organisms. The accurate prediction of the No Effect Concentration for anti-fouling agents requires the standardization of (i) a toxicity test method with a toxicant-sensitive organism, (ii) a simple and easy chronic-toxicity test protocol with domestic species, (iii) the toxicity test method for easily decomposable chemicals, and (iv) the cumulative-toxicity test method for a mixture of chemicals.
As environmental problems have become serious in recent years, calls for energy savings in marine vessels have been made. This paper proposes a mathematical model for the dynamic simulation of ship propulsion systems. The model was implemented and solved using the computational environment MATLAB Simulink. In this model, various elements of the system were described as individual blocks linked together to take into account interactions between them. The behaviors and performances of individual components of the system were statically and dynamically analyzed and evaluated. From the simulation results, it was clarified that the disturbance cycle influences the fuel consumption rate of the engine.
In engineering applications, fractures occur mostly from surface or internal three-dimensional cracks due to defects already existing in the material. These generally propagate in all directions and often have irregular shapes, and are not limited only to metallurgical defects but also include those which are due to the fastening of parts, configuration design, as well as those that result from the need to provide lubrication of ships and offshore structures. Since these generate a stress concentration zone, fatigue crack initiation and propagation are strongly affected. However, these are inevitable in design. Therefore, a study on the characteristics of fatigue crack growth that occur when surface cracks initiated from initial defects propagate into stress concentration zones such as those in lubricating oil holes of connecting rods was conducted.
Currently, around 80% of large ships use Bunker oil (JIS C heavy oil) as the base fuel in marine diesel engines. With its very high kinematic viscosity, this oil is considered the lowest grdae of fossil fuel. Thus, it needs to be heated to reduce its viscosity. The authors have reported that the blending of liquefied DME improved the combustion performance of Marine Diesel Oil (JIS Aheavy oil). This study aims to clarify the effectiveness of DME — Bunker oil blends. The kinematic viscosity measurement of DME and Bunker oil blended fuel was performed using a capillary tube type viscometer. A pressure cell which contains the viscometer was developed to measure the fuel viscosity while keeping DME ina liquid state. From experiments, it was shown that the cell pressurization resulted in smaller values of kinematic viscosity, and modification was needed to obtain true viscosity values. It was shown that at 323K, the kinematic viscosity of Bunker oil can be reduced drastically from 54~89% with DME blending.
Heat and mass transfer coefficients during ammonia gas absorption into a falling liquid film formed by ammonia water on a horizontal tube were obtained experimentally. The test absorber is comprised of a 200-mm i.d., 600-mm long stainless steel shell; a 17.3-mm o.d., 14.9-mm i.d. stainless steel test tube with a working length of 600-mm mounted along the axis of the shell; and a 12.7-mm o.d. pipe manifold for supplying the absorbent. The results clarified that absorption volume could be increased and heat and mass transfer coefficients could be enhanced by increasing the difference in concentration between the inlet absorbent solution and the ammonia gas. The heat transfer of the falling liquid film was affected by the driving force between the temperature of the liquid film and the temperature difference between the vapor and the inlet absorbent solution. The mass transfer was affected by the driving force between the concentration of the liquid film and the difference in concentration between the vapor and the inlet absorbent solution. A new correlation for heat transfer in a dimensionless form was proposed taking into consideration the driving force resulting from the difference between the temperature in the liquid film and the difference between the vapor and the inlet absorbent solution. Also, a new correlation for mass transfer in the vapor-liquid phase interface in a dimensionless form was proposed taking into consideration the driving force resulting from the difference between the concentration in the liquid film and the difference between the vapor and the inlet absorbent solution.
Autonomous small fish robots are ideal for surveys of fish resources and underwater structural inspections where electric wires hinder the movement of the robot or where radio signals, such as GPS, cannot be received. For practical usage such as taking pictures of fishes in the sea, the fish robot needs to follow the target fish and estimate its self-position to swim autonomously in water. The authors have developed a small fish robot named FPGA Offline Control Underwater Searcher (FOCUS) which has some micro CMOS cameras and an FPGA circuit board for data processing. Red objects can be detected with the CMOS camera. Using visual information from images taken from the bottom facing camera, self-position estimation becomes possible. The self-position estimation has been tested utilizing a real-time digital image correlation method using an FPGA. Development of a VHDL program for the FPGA and the mounting of FPGA on a circuit board have been conducted for target following and self-position estimation. This FPGA board executes both the control of the swimming fish robot and image processing at the same time. Results confirm that the small fish robot can follow the target and can measure simultaneously its self-position.
A marine SCR (Selective Catalytic Reduction) system will be needed as an exhaust gas aftertreatment to reduce NOx emissions from a marine Diesel engine. The SCR system is used in a transient engine load condition which has changing concentrations of NOx and exhaust gas quantities. In transient conditions, the amount of injected reducing agent should be controlled to prevent unreacted-NH3, which is called slipped NH3. However, it is difficult to estimate slipped NH3 using the first-order reaction rate constant of NOx reduction. To estimate slipped NH3 in detail, adsorption-desorption of NH3 to a catalyst and SCR reaction rate should be considered. In this paper, NOx reduction performance and slipped NH3 are evaluated with one-dimensional SCR simulation using the kinetic parameters of catalytic reaction. As a result, it is confirmed that one-dimensional SCR simulation can effectively simulate the actual SCR system, and thus it can evaluate NOx reduction performance and slipped NH3 by considering the amount of reducing agent.