Frictional drag reduction with air lubricant over a super-water-repellent surface

This paper presents a new technique for reducing frictional drag using a super-water-repellent surface and air-injection (called an SWR & A technique). Its effectiveness was examined by carrying out pressure-loss measurements with a tube of rectangular cross section, along with resistance tests on a horizontal flat plate, a 7.2-m-long tanker model, and a 12-m-long high length-to-beam-ratio model ship. These test results showed that the new technique can significantly reduce the models' frictional drag; for example, the frictional resistance on the SWR surface was reduced by 80% at a speed of 4 m/s and 55% at 8 m/s. Received: October 16, 2000 / Accepted: December 4, 2000     

Transformation Plasticity─The Effect on Metallo-Thermo-Mechanical Simulation of Carburized Quenching Process

IntroductionInelashcorhaersiblestrainaccompaniedbyslidingofcrystalsduetothermalandphasetransformationdilatationiswellknowntointensivelythethedistonionofworkpieceunderqUopching,andsomanynumericalsimulatonsll-7]havebeencAnedoutintheframeworkofmotallochermo-mechwhcsl1].Transformationplasticity(TP),anothekindofbeversiblestrain,isalsorecognizedasoneofdominantparwtersthechngthestr6ssanddistorton,andsomenumcricalcalculationaremadebytakingtheeffectintoconsideration.Figurelschematicallyillustraresthe…     

Anaerobic digestion of marine biomass for practical operation

Marine biomass such as seaweed and fishery waste is a potential energy source although it has not yet been practically utilized. This work focuses on renewable energy technologies, particularly anaerobic digestion, for the utilization of various organic wastes as energy resources. Primarily fundamental data for the efficient operation of an anaerobic digestion plant with marine biomass was obtained and a practical operation method was proposed using a simple model based on the carbon mass balance. Batch-processing experiments for seaweed, fishery waste and vegetable waste were carried out and each digestion characteristic was presented. The results indicate that fishery waste is the most efficient even though the accumulation of ammonium ions may inhibit methane production. Seaweeds are not efficient in either the production rate or the yield of methane gas. We investigated the efficient continuous operation for 6 biomass input scenarios with the proposed model. The results show that seaweed can be a useful supplement for the efficient operation.     

Container liner freight index based on data from e-booking platforms

This article proposes a framework for a daily container freight index (DCFI) and investigates a number of principles in the design of this type of indices. Based on a comparative analysis with the existing container freight indices, we explore a method of integrating the framework with the use of data from e-booking platforms and illustrate why the new index can provide more insightful information for shippers. We also apply the framework to have a daily Shanghai container freight index by combining data sources from the platforms linked to the Shanghai port. By implementing the index to a risk analysis problem, we use numerical results to show the DCFI’s potential position in real hedging problems for container liner markets.     

Estimation of the hydrodynamic coefficients of the complex-shaped autonomous underwater vehicle TUNA-SAND

Hydrodynamic coefficients strongly affect the dynamic performance of autonomous underwater vehicles (AUVs). Thus it is important to have the true values of the coefficients in order to simulate the AUV’s dynamic performance accurately. Although these coefficients can be predicted by many methods, most are only applicable for AUVs with streamlined shapes. Computational fluid dynamics (CFD) can be applied to estimate the hydrodynamic coefficients of AUVs with complex shapes. In this study, CFD was applied to estimate the hydrodynamic coefficients of the AUV TUNA-SAND (which stands for terrain-based underwater navigable AUV for seafloor and natural resources development), which has a complex block-like structure. First, the validity of the CFD simulation was verified by comparison with experimental results. Second, the relationships between hydrodynamic loads and motions for all six degrees of freedom were analyzed using the simulated results. Third, the importance of each hydrodynamic coefficient was investigated based on these relationships. There are 16 key damping coefficients that relate to viscosity and 12 key inertial coefficients that relate to the potential flow around TUNA-SAND. Finally, the values of all the key coefficients were obtained and verified by comparing the solutions of the simulated dynamics with the experimental results.     

Numerical Simulation of Coupled Thermo-mechanical Behavior of a Cylinder Billet during Hot-forging Process

IntroductionInhotforging,variationanddistributiol1oftemperatureplayveryimportantroIeinviewofthermalstressesorthermalstrainaswe1lasthemateria1properties.MechanicaldefOrmationcangenerateheatbyfrictionalslidingand/ordissipatiOI1ofplasticwork.Theboundaryconditionfortemperatureismodifiedbythechangeinmaterialshape.Dietemperatureusuallyislowerthanworkpiecetemperatureandthisfactresultsindiechilling.Itsignificantlyaffectsthetemperatureoftheworkpiecea11d,consequently,alterstheflowstress.Whenthedieisr…     

降低自然灾害对铁道车辆的影响

介绍了日本为了降低自然灾害对铁道车辆的影响而进行的各项研究。