Estimation of rail tilting under the design load is an important factor in the rational design of rail fastening systems. Rail tilting has been estimated using the practical solution based on the torsion theory. However, a recent study has reported that rail tilting estimated by the conventional solution does not agree well with the experimental values. This study aims to establish a practical and high-accuracy solution for rail tilting. First, a FEM model for rail titling is proposed and the validity of the model is examined by comparing the analytical values with the experimental values. As a result, rail tilting estimated by the model was in good agreement with the experimental values. Therefore, the results show that the model is available for predicting the response of a rail and its fastenings. Second, the model was applied to determine the loading condition of the performance test of rail fastening systems. The findings show that it is possible to evaluate the performance of rail fastenings with high accuracy as compared with the conventional evaluation.
This paper presents a method for evaluating the strength of bearings supports in bridges subjected to tsunami-induced forces, to allow an estimation of the effects of a tsunami on bridge functionality. The tsunami-induced forces striking the bearing supports were studied in previous flume tests and numerical analyses conducted by the authors. Through comparison with the actual performance of bridges affected by the tsunami in the 2011 Great East Japan Earthquake, we verified the effectiveness of the method in estimating the tsunami effects on bridges.
With the earthquake records obtained during the last 23 years, analyses of transfer function, cross-spectrum and coherence function have been performed for a rockfill dam named Aratozawa dam (74.4m high and with central clay core). Based on analysis results, the fundamental frequencies and acceleration amplification factors of the dam were investigated. It was found that the fundamental (first natural) frequencies and the acceleration amplification factors of the dam sharply decreased temporarily, after being struck by the Iwate-Miyagi Nairiku Earthquake on June 14, 2008. However, these characteristics recovered almost to their original status about a week after the main shock. By investigating the propagating behavior of seismic motion in the dam-foundation system, it has been pointed out that in the low frequency range up to the fundamental frequency of the dam, the response of the dam crest mainly depends on the seismic motion of the subjacent bedrock. On the other hand, in the higher frequency ranges, the contribution of the seismic motion of both banks may become dominant depending on frequency.
More reasonable seismic design can be achieved by considering input loss effects of soil-foundation interaction. However, in the present seismic design, there is no practical evaluation method available for a static analysis of input losses for foundations widely used in a railway field. In order to achieve optimal structural design, this paper illustrates a practical method for evaluating input loss effects for static analysis. First, sensitivity analysis was conducted for varying conditions of both soil and piles, and input loss effects caused by pile foundations were investigated. Then, a practical method for calculating effective input losses by the seismic deformation method was proposed, along with a brief method for lowering the nonlinear response spectra considering input losses based on the random vibration theory. Furthermore, applicability of these methods was verified by comparing the dynamic analysis results and evaluated results.
New waterway projects such as cutoffs and gravel extractions have been carried out all over the country. The shortcuts have lowered river water surface elevation during flooding, and they have been shown to suppress these flooding events. On the other hand, the riverbed elevations rapidly decreased as bed slope changed artificially and canyons were formed in several rivers. Little is known about how riverbed degradation occurs or how the canyon is formed by change in the bed slope. In this study, we conducted numerical simulations to evaluate the deformations of alluvial bed and peat bed. The results suggest that the bed slope becomes constant on the alluvial bed and the erosion proceeds at the bare peat bed. The results also show that the upstream migration of the peat bed slope forms cyclic steps morphology. Also, we carried out numerical simulation to reproduce bed degradation of the Yubari River caused by cutoffs.
A damage function that indicates the relationship between flood depth and damage is important to quantify natural catastrophe risks. Previous studies estimated the flood damage ratio using theoretical methodologies and in-person interviews. Although it is difficult to obtain actual damage information, it can be reflected in damage functions using insurance loss data. This work aims to develop damage functions for buildings and their contents using insurance loss data from the 2015 Kanto–Tohoku heavy rainfall incident. First, we collected information on the insurance losses and calculated damage ratio by property. Second, we analyzed inundation from the Kinugawa river using the flood model. Finally, we combined the simulation results with the damage ratio and developed flood damage functions as useful risk-assessment tools.
In the case of coastal dikes and seawalls, since big waves break before reaching these structures, the frequency in which they are broken directly by strong wave force is low.On the other hand, with continuous impact of middle waves, scour arises in these fronts. Before long, incident waves infiltrate into these bodies, backfilling materials flow out, and caves in these bodies become big. Owing to these phenomena, the frequency of destruction of these dikes and seawalls becomes high. Therefore, the development of methods for predicting scour rates in these fronts and sand outflow rates of backfilling materials is useful. Regarding scour rates in these fronts, there are already some accurate methods that specialists can use under various conditions. However, for sand outflow rates of backfilling materials, there are some prediction methods limited to simple types of dikes and seawalls.
In this research, the authors develop a numerical model that calculates the flow velocity and pressure in the dike or seawall with arbitrary form using “CADMAS-SURF.” The model can predict the time change in the sand outflow rate and the development of the cave. First, for a sand outflow rate simulation, the authors propose empirical equations to modify the pressure calculated by CADMAS-SURF using hydraulic experiment data. Then, they confirm the practical feasibility of the numerical model by applying it to field cases on sand outflow damage in Japan and Thailand.
This study aims to analyze the influence of observed river channel conditions on inundation simulation in terms of discharge within a river channel and inundation area and depth over a floodplain. The target area is the Lower Mekong River Basin, which suffered from severe floods in 2000 and 2011. First, measurement using an acoustic Doppler current profiler is conducted to understand the longitudinal distribution of cross-sectional shapes and roughness change during a flood in a river channel. Based on the observation results, inundation simulation with the Rainfall-Runoff-Inundation model is conducted. The calculation results show that the reproducibility of discharge improves by taking the longitudinal distribution of the width and depth of the river reach into consideration, and that the water depth over the floodplain has a high sensitivity to both cross-sectional shapes and roughness change during the flood.
Recent advances in regional ensemble weather prediction systems (EPS) can considerably improve the prediction of torrential rainfall and resulting severe floods with a longer lead time. To maximize this advantage, we developed an ensemble flood forecasting system, composed of an ensemble Kalman filter and a regional numerical weather prediction on the atmospheric part and the Rainfall-Runoff-Inundation (RRI) model on the hydrological part. Simple downscaling of global EPS was also conducted to compare the superiority of the developed system. We applied the system to the Kinugawa flood event in September 2015 and studied its feasibility for forecasting. Ensemble flood forecasting with a lead time of 9–15 h was successfully conducted in quantitative prediction of a flood discharge peak. Forecasting with a lead time of 21–39 h showed a possibility of flood occurrence though its probability was low. The flood forecasting system was superior to deterministic forecasting based on the Japan Meteorological Agency (JMA) operational Mesoscale Model (MSM) in the predictability of a flow peak. A simple EPS by downscaling global EPS had an advantage with a lead time of 57 h compared to the previous system. This study revealed the potential and limitations of the ensemble flood forecasting system in predicting high flood peaks.
The catch of Manila clams in Japan has drastically decreased recently. It is necessary to promote the growth of benthic microalgae, which is their main feed, for the reproduction of tidal flats where clams grow. In this study, we applied dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and Fe-eluting fertilizer to tidal flats surrounded by a sealing plate to prevent fertilizer outflow.
We found that DIN and DIP in pore waters and chlorophyll a in the surface sediments almost increased in concentration at fertilizing sites. However, periods of nutrient elution from the fertilizer were considered to be less than half a year In addition, the weight of clams collected from the 1600g fertilizing site was significantly greater (t-test, p<0.05) than that from the control area. Consequently, the total weights of clams collected from the control site and fertilizing sites increased to approximately 7.2 and 10.4-12.6 times greater than the initial weights, respectively, four months after the experiment started.
In conclusion, using a combination of fertilizers and sealing plates is effective for increasing the weight of clams inhabiting the tidal flats.
A new critical depth (zcr) model was developed by adding light saturation effects during photosynthesis to a Sverdrup zcr model in order to design an artificial circulation system as a countermeasure to eutrophication. A Blackman-type equation was selected from various P-I equations for its accuracy and relationship to the original Sverdrup model. Quantitative differences between the zcr values of some new equations were found to be remarkable in specific high light conditions. Furthermore, the zcr calculated by the Sverdrup model overestimated the zcr compared to the modified Sverdrup equation proposed by this research. We discuss methods for the design of a practical air diffuser depth that prevents cyanobacteria bloom from the point of view of design and management of bubble circulation countermeasures.
It is important to capture driftwood or woody debris, in upstream areas to prevent debris flows from blocking downstream bridges. Specific details of the conditions of dams in Japan must be taken into consideration when investigating this issue. There have been recent proposals to use steel stakes as counter-measures to block woody debris at impermeable sabo dams. To design such a countermeasure effectively, it is necessary to clarify the mechanisms of woody debris capture implemented by the countermeasure. We propose a structure consisting of steel stakes for use at impermeable sabo dams. This proposal is based on experiments that take into consideration the rotation of woody debris at sabo dams and the mechanism by which woody debris is captured at the stakes.
The Nippon Chisso Hiryo K.K. company constructed the Pujon River Hydropower Plant in colonial Korea during the 1920s. The plant was very large for its time, even when compared to those built in the Japanese Empire. It later became an important trigger for Korean industrialization in the 1930s. The construction plan was proposed by electrical engineer Kazuo Morita (1872 – 1966). Although Morita conducted several large and similarly important hydropower projects in Japan, the scope of his work has not received a great deal of attention. This study therefore follows Morita’s work to clarify three characteristics that he acquired during that time of fierce electric power development boom in Japan (between World War I and the 1920s). This research determined the kind of experience Morita gained and what development concepts he maintained in the years before planning the giant Pujon River plant. First, he expanded his work assignments through the personal contacts he gained while developing giant hydropower plants for the Anglo-Japanese Hydro-Electric Co. during the late Meiji Period. Second, he was earnestly oriented toward and held a positive attitude about new technology. Third, he developed a technological system centered on electrical engineers and brought construction companies together to achieve the “formation of a construction cooperative” that specialized in hydropower plant construction. These events helped build the framework for Morita’s later construction of the Pujon River Hydropower Plant.
The emergence of autonomous vehicles is expected to shape the urban transportation system in various ways. In this study, a large-scale agent-based disaggregate simulation model, MATSim, is employed to measure the impact of autonomous vehicles on accessibility changes. This study used disaggregate spatial data from the Gunma Prefecture Person Trip Survey as the initial travel demand input for the model. Two new autonomous transport modes, namely shared autonomous vehicle (SAV) and private autonomous vehicle (PAV), are included in the simulation, in addition to the existing human-driven private vehicles. A scenario analysis is conducted using fleet size of SAV, ownership of PAV, operation cost, value of time changes as the key variables in the scenario setting. Based on the final travel demand results, a Hansen-type accessibility analysis is conducted, providing quantitative evidence to measure the potential impact of autonomous vehicles on accessibility changes in Japanese regional cities. Results suggest a considerable market share of AVs in scenarios with positive assumptions, and an overall accessibility increase in the scenario where PAVs were introduced. Particularly, suburban areas seemed to enjoy more accessibility gains, which might result in further urban sprawl in the future.
This article presents an exploratory analysis of personal networks and social interactions in the Greater Tokyo Area. A personal networks survey was conducted in Japan using an unrestricted name generator and a name interpreter. Social network characteristics in the sample were analyzed, focusing on network size, composition and spatial distribution, as well as interaction frequency patterns among network members. In addition, two models were estimated: (i) a multilevel probit model of friendship formation, used to evaluate factors associated with generation of new network ties, and (ii) a multivariate hierarchical ordinal probit model to evaluate how personal and relational characteristics were associated with social interaction contact frequency by probability mode.
Michi-no-Eki provide free parking, toilets, and information on specific areas in Japan and play important roles as sales offices for local products. After the Great East Japan Earthquake in 2011, these stations attracted attention as possible disaster shelters. The purpose of this study is to consider their function as disaster shelters and to grasp the current situation of these stations nationwide. We conducted a questionnaire survey among station operators, obtaining responses from 73.2% of the stations. The results showed that there were not enough facilities and systems to counter disaster. On the other hand, the results suggested that although many stations are privately managed, most station operators have intention to serve as disaster shelters. Michi-no-Eki seem to have high utility during both normal times and disasters. However, for the stations to function as disaster shelters, their equipment and the system must be improved.
Given that the losses incurred from natural disasters are uncertain and characterized by considerable fluctuation, restoration funds intended for disaster preparation are usually calculated based on the assumption of probable maximum loss (PML). However, preparing for PML via the acquisition of sufficient funding is difficult for railway companies that suffer from financial difficulties. These companies urgently need to implement risk financing (RF) strategies against frequent storm and flood disasters to avoid insolvency. Meanwhile, there is also a great need for an analysis of storm and flood disaster RF with targeting multiple railway businesses for reasons of group insurance or consolidated accounting. To address these issues, this study develop a financial risk model that considers the disaster-related characteristics and financial conditions of multiple railway businesses and establish a ruin probability model for the mathematical analysis of the procurement of funds, including initial reserves, insurance money, and subsidy. These models are designed to help multiple railway businesses prepare for losses estimated on the grounds of data on past damages. Case studies that feature actual data on railway companies across Japan are conducted to demonstrate and verify the effectiveness of the proposed models.
The storm and flood disasters account for 90% of the disasters that have led to the abolishment of railways in Japan. Such disasters are an overwhelming risk factor for many railway businesses in this country. Because the numbers of storm and flooding disasters have increased and intensified globally due to climate change, the importance of storm and flooding disaster risk financing (RF) has increased in many railway businesses. In this context, based on the Cramér-Lundberg model of disaster characteristics and financial conditions, this study proposes convenient approximation techniques to determine ruin probability and additional procurable funds, which are vital in storm and flooding disaster RF. Specifically, we present six theoretical approximation formulas of ruin probability and additional procurable funds, which meet the technical requirements (i.e., conservativeness, approximation accuracies, and domain) for practical work in RF. The technical requirements of these theoretical approximation formulas are evaluated using actual data collected in railway companies across Japan. The convenient usage of these formulas is also evaluated.
Nanoscale Zero Valent Iron (NZVI) is one of the materials that have gained attention in the field of water treatment and environmental remediation in recent years. The main purpose of this study is to develop and evaluate a phosphorus removal system using NZVI particles. The NZVI used for the experiments was synthesized under optimum conditions using the chemical reduction method. This continuous system consisted of Continuous Stirred Flask Reactor (CSFR), settler, polishing unit, and sand column. The continuous experiment showed that 73.84% phosphorus was removed mainly at CSFR. Further, 80.62% total iron was removed and recycled at the settler. Based on the continuous operation results, there was a strong relationship between iron concentration and ORP value (R2 = 0.9969). This result indicated that ORP would be an important monitoring parameter while operating the continuous system. The aerobic condition contributed the highest phosphorus overall removal efficiency (91.37%) due to the enhancement of iron corrosion. Copper bimetal particles also achieved the highest removal efficiency (94.96%) after increasing the active site and decreasing the solution pH. Finally, comparing the aerobic and bimetallic cases, we concluded that the bimetallic case is the best condition for removing phosphorus because it could treat large solution volume than the aerobic one could.
Despite the ecotoxicological value of the freshwater ostracod Heterocypris incongruens, there is little nucleotide sequence information on this species. With the aim to develop transcriptome resources of this species, we performed a de novo transcriptome analysis using a high-throughput sequencing technology and determined the sequences of antioxidant gene, such as catalase (cat), glutathione peroxidase (gpx), glutathione S-transferase C-terminal domain-containing protein (gstcd), and superoxide dismutase [Cu-Zn] (sod). To provide an application example of expression analyses using the obtained genes, we examined the expressions of the obtained genes by quantitative PCR (qPCR) in H. incongruens exposed to urban road dust, as a model of contaminated environmental sample. The expressions of all the target genes remained unchanged in response to road dust during six days of exposure. Our transcriptome data and sets of stress response genes of H. incongruens should be useful references to investigate the mechanism of sediment toxicity and to aid linkage between environmental contamination and biological responses.