Strong bottom–up effects on phytoplankton community caused by a rainfall during spring and summer in Sagami Bay,Japan

To assess the consequences of bottom-up effects on phytoplankton community composition during the rainy season, phytoplankton levels and environmental factors were monitored daily from 12 April to 22 July 2003 in Sagami Bay, Japan. The relevant environmental factors were analyzed using cross-correlation analyses. Based on time-series analysis, low surface salinity conditions lasting 0 or 2 days after heavy rainfalls resulted in significant nutrient loading, such as dissolved inorganic nitrogen (DIN), into the coastal area. Also, Chlorophyll-a (Chl-a) concentration frequently increased 2 and 6 days after rainfall. Based on the high total Chl-a concentration, the time was divided into three periods, from 1 to 11 May (Period A), 26 May to 9 June (Period B) and 30 June to 22 July (Period C). The phytoplankton assemblages during Period A were dominated by two dinoflagellates, Ceratium furca and Ceratium fusus. Prior to these species blooming, the heterotrophic dinoflagellate Noctiluca scintillans was dominant. During Period B, the phytoplankton communities were dominated primarily by the diatoms Rhizosolenia delicatula, Hemiaulus sinensis and Navicula spp. Finally, Cerataulina dentata, Rhizosolenia spp., Lauderia borealis and Neodelphineis pelagica were dominant during Period C. After increases in phytoplankton abundance, available nitrogen (N) and phosphorous (P) were consumed and exhausted, which were considered a potential cause of the shift in the dominant organisms from large diatoms to pico- and nano-plankton in the low Chl-a environment. In particular, silicate (Si) was not a major limiting factor for phytoplankton production, since the Si:DIN and Si:P ratios clearly demonstrated that there were no any potential stoichiometric Si limitations, and almost all silicate concentrations were > 2.0 µM during this study. Our results reveal that nutrient sources supplied by river discharge are a main cue for strong bottom–up effects on algal bloom succession during the early summer season in Sagami Bay.     

A simulation model of train travel on a rail transit line

A simplified simulation model for the operational analysis of a rail rapid transit train is presented. The model simulates the movement of a train along a route, and develops the relationships of time—distance, time—speed and distance—speed. The inputs to the model are the profile of speed limits and the dynamic characteristics of the train. Without the information on the track geometry and tractive effort, the model determines the speed of the train at a location based on the previous and future speed limits relative to the location. It was found that the model can fairly accurately simulate the relationship between travel time and distance. A comparison of the train travel times between the actual and simulated runs is presented. Because of the simplicity of input and calculation method, the model can be a useful tool for the “desk-top” analysis of frequently occurring planning problems of a commuter rail or rail rapid transit line, such as the impacts of changes in speed limits, station locations, station stopping policy, addition/elimination of stations, and types of rail cars.     

Monorail development and application in Japan

The monorail has emerged recently as a serious mode for transit use in Japan. Three monorail lines are operational, and three more are being constructed. Approximately thirty other cities in Japan are considering the introduction of the monorail. This paper reviews the recent development of the monorail in Japan, examines its components, compares its performance with other transit modes, and assesses its potential in the context of the family of urban transit modes. This examination and comparison will be based on the features of the monorail designs recently adopted in Japan.     

A method to estimate trip O‐D patterns using a neural network approach

This paper proposes a method which identifies the trip origin‐destination (O‐D) matrix when many pairs of values for the right hand side column (B) and the bottom row (A) of the matrix are given. The method considers B and A as the cause (input) and effect (output) of a system, respectively, and that the O‐D matrix represents the relationship between the cause and the effect. The relationship which satisfies all pairs of the cause and the effect data exactly may not be identified, but, should a general pattern of the relationship exist, it should emerge when many data sets of B and A are given. Two steps are involved in the method: the first step examines if a consistent O‐D pattern exists; if a pattern is found to exist, the second step identifies the values of the elements of the O‐D matrix. The first step is based on the shape of the possibility distributions of the values of the matrix elements. The second step uses a simple back‐propagation neural network. The method is useful to problems that require identification of the cause‐effect relationship when many sets of data for the cause and effect are available, for example, the station‐to‐station travel pattern on a rapid transit line when the total entering and exiting passengers are known at each station for many different days. The model can also be applied to other transportation problems which involve input and output relation.     

Development of computerized vehicle scheduling system for specialized transportation: delaware case

A computer‐aided vehicle scheduling system is developed for Delaware's state‐wide specialized transportation system for elderly and handicapped persons. This paper presents the model, computer program package, system implementation, evaluation and the lessons learned from the project. The project which spanned two and a half years consists of five phases: (1) examine the manual method of vehicle scheduling (prior to the computerization); (2) develop a scheduling model; (3) develop a computer program package for the operation of the model; (4) install and operate the system; and (5) evaluate the system performance. The scheduling model consolidates passengers by block of time, origin and destination zones and along the direction of vehicle travel, first; second, minimizes the empty vehicle travel; and, lastly, assigns drivers to route considering assignment priority among the types of drivers and passengers. The product of the model is a set of driver log‐sheets which specify the sequence of passenger pick‐ups and drop‐offs. The computer program package includes necessary auxiliary data management functions such as registration of trip reservation, operating statistics and parameter value changes, as well as the execution of the model. It also allows the dispatcher to override the computer generated log‐sheet based on his discretion. The system has been operational for more than one year and it has brought about a number of changes in the operation and the role of the dispatcher. A before‐and‐after comparison of the operation and the lessons learned are also shown.     

Empty freight car dispatching model under freight car pool concept

In the last few years, growing attention has been given to the cost savings potential of the specialized freight car pool concept. Under this concept, a fleet of single-purpose freight cars are pooled at many loading points, and the cars emptied at unloading terminals can be sent back to any loading point in order to reduce empty car miles and time. As part of a continuing effort to improve the car dispatching method for this concept, this paper offers an improvement to the traditional linear programming transportation problem approach, incorporating daily variations of empty car supply and demand characteristics in the model. The proposed method, therefore, allocates cars between supply and demand points with the dispatching date specified, enabling the dispatcher to make daily car disposition decisions. It can incorporate both the travel distance cost and inventory cost of empty cars at terminals in the objective. If the holding of empty vehicles at the terminals for future dispatch is allowed, the problem is structured as a transshipment problem in which the overnight storage is the transshipment point.     

Mode Mixity for Orthotropic Interface Delamination in Laminated Composites

The mode mixity is defined based on nonoscillatory strain energy release rate components of delamination between two different orthotropic materials to evaluate the delamination behavior of laminated composites.The result showes that the relative location of the delamination through the thickness influences the mode mixity in a relatively well-regulated way,and that the reinforcement directions of the adjacent plies along the delamination front have a more complicated impact on the mode mixity.This is caused by the bending/twist coupling and bending/bending coupling in the stress field at the crack tip for delamination between multidirectional plies,which completely modifies the stress and strain fields ahead of the crack tip.These kinds of couplings account for the non-uniform distribution of mode mixity values along the delamination front.Application of appropriate mode mixity values is necessary for accurate prediction of delamination growth.