Economic analysis of Japanese air pollution regulation: An optimal retirement problem under the vehicle type regulation in the NOx–particulate matter law

This paper examines the vehicle type regulation that was introduced under the Automobile Nitrogen Oxides–Particulate Matter Law to mitigate air pollution in Japanese metropolitan areas. The vehicle type regulation effectively sets the timing for vehicle retirement by initial registration year and type. However, there was no consideration of cost or efficiency in choosing the timing of retirement. We solve an optimal problem to maximize the social net benefit under the current framework of the vehicle type regulation. The analysis finds that the net benefit can more than double if the optimal retirement timing is chosen. Further, we find that even a simple alteration of the retirement timing can increase the social net benefit by 13%.     

On the water impact and elastic response of a flat plate at small impact angles

It is well known that Wagner's theory for the impact between a flat body and a water surface cannot be applied to very small impact angles because of the effects of the trapped air. We focus our attention on the impact problem with a small impact angle, which has not been studied in detail owing to theoretical and experimental difficulties. In order to investigate the transitional impact behavior from a trapped-air impact to a Wagner-type impact, we carried out precise pressure and strain measurements by dropping a plate and increasing the impact angle, β, from 0° to 4° by increments of 0.5°. Based on the experimental results, the time histories of the measured pressures were identified as belonging to three patterns: the Wagner type, the trapped-air type, and the intermediate type. During the transitional impact process, the Wagner-type pattern was observed near the keel at the beginning of the impact, with the trapped-air pattern toward the edge of the plate. The Wagner-type pressure pattern dominated with increasing impact angle. Although high peak pressures appeared in the transitional impact process, the maximum strains measured in the plate were not so sensitive to the impact angle. It was found that the structural response can be estimated by using the average pressure at impact, which leads to a new design approach for small impact angles.     

Measurement and computation of the acoustic field in a cavitation tunnel

Sound pressure distribution around a monotone sound source was measured inside a marine propeller cavitation tunnel and compared with the calculated result by a two-dimensional boundary element method. The measured sound pressure distribution showed some peaks due to the reflection effect of the tunnel test section boundary. As the frequency increased, the sound pressure distribution became more complicated, showing more peaks. The tunnel reverberant effect should be taken into account when the noise data measured in the tunnel are converted into full-scale values. In the boundary element method calculation, the boundary condition at the acrylic observation window of the tunnel was examined in detail. The calculated sound pressure distribution pattern in the tunnel transverse section agreed well with the measured distribution when a reasonable boundary condition was adopted. The boundary element method is an effective method for theoretically predicting the acoustic field inside the cavitation tunnel if the precise boundary condition is adopted.     

Simplified estimation for the dynamic behavior and reliability analysis of very large floating structures under wave-induced loads

This paper deals with the dynamic response and strength of very large floating structures (VLFS) in regular and irregular waves, considering the propagation of the hydroelastic deflection wave of the structure. First, a simplified estimation method is presented for the dynamic response and strength of the structure in regular waves. Then, the validity of the method is demonstrated by comparing its results with analytical results and experimental results for a mat-type floating structure model. Next, a simplified estimation method for dynamic responses under long crested irregular wave conditions is presented by using the above results and by combining them with irregular sea wave spectra. Finally, the applicability of the method is investigated through numerical examples carried out for a 4,800-m class VLFS under trial design. Characteristics of the hydroelastic waves, short-term responses, and reliability levels are numerically identified. Received for publication on April 14, 1999; accepted on Sept. 10, 1999     

Application of Analytic Hierarchy Process to Stochastic Robustness Synthesis of Integrated Vehicle Controllers

This paper deals with the robust design procedure of integrated vehicle dynamics controller based on Stochastic Robustness Synthesis with use of a rational decision making process of the controller parameters. The basic control structure that integrates four-wheel steering and four-wheel torque control is determined using a nonlinear predictive control theory. The Analytic Hierarchy Process, a basic approach to decision making, is applied to determine the weight coefficients of robustness evaluation function of the controller. The desired vehicle dynamic performance is described as four-layer hierarchy structure and the design priority is determined with respect to several design criteria. The proposed design process produced a control system with excellent stability and performance robustness to vehicle parameter variations.     

Sea trial of prototype Vertical Weight Stabilizer (VWS) anti-rolling system for small ships

Anti-rolling is an important technique for safety and efficient ship operation. In the era of sailing ships, rolling motions were not so severe compared to those of modern ships running by prime mover without sails, because the sail itself had a damping effect on rolling motion. After propeller driven ships exceeded sailing ships in number and performance, namely, from the end of the nineteenth century, many types of anti-rolling–related techniques were invented and developed, of both passive and active types. Recently (2009, 2010), as sea trials, we carried out proto-type experiments on an anti-rolling system and confirmed its effectiveness. The new concept utilizes the so-called Corioli’s effect, which appears in the rotational coordinate system. Usually, this effect is considered as virtual, but the real effect appears when a mass moves in the radial direction in a rotating coordinate system. In the case of ship rolling, the vertical motion of a mass generates Corioli’s force to finally generate anti-rolling moment. This is the reason the system was named Vertical Weight Stabilizer (VWS). This new system was invented in 1998 by Hirayama, and confirmed by the model experiments in a towing tank. Numerical simulations were carried out by the Sea and Air Control System laboratory of Yokohama National University, but the actual system could not be realized, because we could not find an appropriate actuator. The key technology for the success of the current sea experiment is the powerful, high-speed, compact actuator for the vertical movement of the weight. In this paper, we introduce this new concept by adopting a simple experiment, the control system with new actuator used in an actual sea experiment, and report on the successful results.     

Model and full scale CFD analysis of propeller boss cap fins (PBCF)

Computational fluid dynamics (CFD) analyses of propeller boss cap fins (PBCF) were carried out for two different propellers at model and full scale Reynolds numbers with two different inflow conditions. Computations corresponding to the reverse propeller open test (POT) experiment were confirmed to be in a good agreement with the measurement. The results of computations at different conditions have shown that increased Reynolds number and presence of hull wake both positively influence the effects of PBCF. Due to the combined effect of the Reynolds number and the wake, the gain in the propeller efficiency at the full scale condition was found to be significantly larger than that at the model test condition. The detailed investigation of the results suggested that the fin drag becomes smaller and the reduction of the boss drag becomes larger at the full scale condition. However, the predicted gain is still smaller than the values reported in the sea trial and logbook analysis. The remaining gap may be attributed to the difference in the estimated and actual wake distribution or to other factors such as interactions with hull and rudder, surface roughness, unsteadiness and hub vortex cavitation.     

First year ice interactions on Molikpaq: Measurements and experiments

The Molikpaq is a steel mobile arctic structure which has been used for exploration of hydrocarbon reserves on the Canadian Beaufort shelf. In early 1986, the Molikpaq experienced numerous interactions with various ice features at Amanuligak I-65. An extensive ice loads investigation program was conducted as a joint industrial project. Ishikawajima-Harima Heary Industries (IHI) has proposed a method to estimate the global ice load on an arctic structure by utilizing results from ice tank experiments. Experiments were conducted in the IHI ice model tank using a model of the Molikpaq. A comparison between the measured ice loads and the estimated ice loads was made and it was found to be in fair agreement, in spite of some uncertainties involved in both the measured and the estimated ice loads. In this paper, instrumentation which the Molikpaq employed in the investigation program is briefly introduced. Failure modes of ice features observed in the program are also mentioned. The basic idea behind the dual parameters testing and estimating method (DuPTEM) is described. The model experiments and the results are then outlined. The comparison between the measured and estimated ice loads is shown. Finally, uncertainties in both the estimated and the measured ice loads are discussed.