Semiparametric specification of the utility function in a travel mode choice model

We propose a semiparametric approach that can capture the nonlinearity of deterministic components of the utility functions in discrete choice models and demonstrate it by analyzing travel mode choice behaviour for an interregional trip. The proposed smoothing spline-based specification method can be used to make ex ante evaluations regarding the parametric specifications of the deterministic utility functions in discrete choice models.     

Simulation-based joint optimization framework for congestion mitigation in multimodal urban network: a macroscopic approach

Transportation - Travel demand management (TDM) is an important measure that will aid in the realization of efficient and sustainable transportation systems. However, in cities where the most...     

Productive efficiency of public and private solid waste logistics and its implications for waste management policy

This paper measures the productive efficiency of municipal solid waste (MSW) logistics by applying data envelopment analysis (DEA) to cross-sectional data of prefectures in Japan. Either through public operations or by outsourcing to private waste collection operators, prefectural governments possess the fundamental authority over waste processing operations in Japan. Therefore, we estimate a multi-input multi-output production efficiency at the prefectural level via DEA, employing several different model settings. Our data classify the MSW into household solid waste (HSW) and business solid waste (BSW) collected by both private and public operators as separate outputs, while the numbers of trucks and workers used by private and public operators are used as inputs. The results consistently show that geographical characteristics, such as the number of inhabited remote islands, are relatively more dominant factors for determining inefficiency. While the implication that a minimum efficient scale is not achieved in these small islands is in line with the literature suggesting that waste logistics has increasing returns at the municipal level, our results indicate that waste collection efficiency in Japan is well described by CRS technology at the prefectural level. The results also show that prefectures with higher private-sector participation, measured in terms of HSW collection, are more efficient, whereas a higher private–labor ratio negatively affects efficiency. We also provide evidence that prefectures with inefficient MSW logistics have a higher tendency of suffering from the illegal dumping of industrial waste.     

Distribution of drifting seaweeds in eastern East China Sea

In offshore waters with relatively low primary production, drifting seaweeds composed of Sargassum species form an identical ecosystem such as an oasis in desert. Commercially important pelagic fishes such as jack mackerel (Trachurus japonicus) and yellow tail (Seriola quinqueradiata) spawn in East China Sea pass their juvenile period accompanying drifting seaweeds. Therefore drifting seaweeds are very important not only in offshore ecosystem but also fishery resources. However the distribution of drifting seaweeds in East China Sea has scarcely known. Then we conducted two research cruises of R/V Hakuho–Maru in May 2002 and in March 2004. During the cruises, drifting seaweeds were visually observed from the bridge and sampled with a towing net. The observation revealed that the drifting seaweeds were distributed along the front between the Kuroshio Current and coastal waters and mainly composed of one seaweed species, Sargassum horneri (Turner) C. Agardh from spring to early summer. There are no reports on geographical distribution of this species in the coasts south of southern Kyushu Island in Japan. Kuroshio Current flows northeastward there. Buoys with GPS attached to drifting seaweeds released off Zhejiang Province, China, in March 2005 to track their transport. Their positions monitored by ORBCOM satellite showed that they were transported to the area in East China Sea, where the drifting seaweeds were observed during the cruises, in 2 months. These facts suggest that S. horneri detached from Chinese coast in March or months earlier than March could be transported to fringe area of continental shelf and waters influenced by Kuroshio Current from March to May. Therefore the Sargassum forests, especially S. horneri, along the Chinese coast play a very important role in the ecosystem of the East China Sea as a source of drifting seaweeds.     

Study on real-time estimation of the ship motion cross spectra

 Time-varying coefficient vector autoregressive (T-VVAR) modeling with instantaneous responses is applied to spectrum analysis based on the nonstationary motion data of ships. Because of the ship's maneuvers, changes such as course and speed, the ship motions in waves are regarded as a nonstationary random process, although the seaway can be considered as a stationary stochastic process. The T-VVAR model is transformed into a state space model, and the time-varying coefficients can be evaluated by using the Kalman filter algorithm. Using the estimated time-varying coefficients, the instantaneous cross spectra of the ship motions can be calculated at every moment. In order to examine the reliability of the proposed procedure, on-board tests were carried out. Under stationary conditions, at a constant speed and course, the proposed method shows good agreement with stationary vector autoregressive (SVAR) modeling analysis. Moreover, it is confirmed that the proposed method can estimate the instantaneous cross spectra of the ship motions even under nonstationary conditions, showing that this is a powerful tool for on-line analysis of the nonstationary motion data of ships. Received: August 2, 2002 / Accepted: November 28, 2002 Acknowledgments. The authors thank the captain and crew of the training ship Shioji Maru, Tokyo University of Mercantile Marine. Address correspondence to: T. Iseki (iseki@ipc.tosho-u.ac.jp) Updated from the Japanese original, which won the 2002 SNAJ prize (J Soc Nav Archit Jpn 2001;190:161–168)     

Numerical analysis of water circulation and thermohaline structures in the Caspian Sea

The Caspian Sea has a unique ecosystem that consists of endemic species. The deterioration of the unique ecosystem has become increasingly worrisome since a wide variety of pollutants have been released into the water. Water circulation plays a key role in advection and diffusion of these pollutants. In the present study, water circulation and thermohaline structures in the Caspian Sea were analyzed by means of a three dimensional numerical simulation. The effects of meteorological changes, river inflow, and an icing event were taken into account as boundary conditions. Numerical simulation was carried out for 20 years to achieve stable seasonal variations in model variables. As a result, the horizontal distributions of water temperature and salinity could be reproduced; the gradient of water temperature in the north–south direction, the decrease in water temperature along the east coast of the middle Caspian Sea due to coastal upwelling, and low salinity in the northern Caspian Sea. The icing event kept the water temperature in the northern Caspian Sea from decreasing to an unrealistic value. The observed cyclonic gyres were basically formed by the density-driven current due to thermohaline structure.     

Apparent phytoplankton bloom due to island mass effect

A continuous monitoring of temperature and chlorophyll-a (Chl-a) concentration from a surface water monitoring system and a towed free fall instrument (MVP) around a small island in the Kuroshio showed low sea surface temperature (SST) and high surface Chl-a concentration (SCC) distribution in the lee of the island that indicates typical “island mass effect” phenomena. When the observed Chl-a profiles (0 to 250 m) were integrated, the total amounts in the lee side data were slightly smaller than those of the upstream side of the island. The difference was statistically significant at the 95% confidence level. The cross section diagram of Chl-a indicated the diffusion of subsurface Chl-a maximum (SCM) from the upstream to the downstream flanks of the island. The diffusivity of SCM and the change of potential energy require the same level of strong turbulent dissipation rate at the flanks of the island. That is consistent with our previous direct measurement in a similar hydrodynamic condition. Therefore, the observed high SCC is due to turbulent diffusion of SCM, and clearly showed that high SCC does not require any new production. Although a high fluorescence field behind an isolated island in a strong flow is often visible from satellite images, the images do not necessarily indicate an enhanced primary production at that moment.