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.     

直接驱动式牵引电动机

直接驱动式牵引电动机是一种直接用于驱动车辆车轴的电动机.车辆采用这种电动机可以省却传统的齿轮传动装置,使得驱动装置结构变得更紧凑、重量更轻以及更省维修,列车运行时铁路沿线噪声更小.介绍直接驱动式牵引电动机的开发思路、结构、主要技术参数,试验结果,试验结论.     

Active Steering Systems Based on Model Reference Adaptive Nonlinear Control

This paper presents a model reference adaptive nonlinear control strategy for active steering of a two wheel steering car which is realized by steer-by-wire technology. The ideal fixed property of a steering system, which is provided by a reference model, is attained by D * control. The proposed method can treat the nonlinear relationships between the slip angles and the lateral forces on tires, and the uncertainties on the friction of the road surface, whose compensations are very important under critical situations. Some results of realtime simulation with a steering equipment show the effectiveness of the proposed method.     

Distribution of void fraction in bubbly flow through a horizontal channel: Bubbly boundary layer flow, 2nd report

A method of enveloping the hull with a sheet of microbubbles is discussed. It forms part of a study on means of reducing the skin friction acting on a ship's hull. In this report, a bubble traveling through a horizontal channel is regarded as a diffusive particle. Based on this assumption, an equation based on flow flux balance is derived for determining the void fraction in approximation. The equation thus derived is used for calculation, and the calculation results are compared with reported experimental data. The equation is further manipulated to make it compatible with a mixing length model that takes into account the presence of bubbles in the liquid stream. Among the factors contained in the equation thus derived, those affected by the presence of bubbles are the change of mixing length and the difference in the ratio of skin friction between cases with and without bubbles. These factors can be calculated using the mean void fraction in the boundary layer determined by the rate of air supply into the flow field. It is suggested that the ratio between boundary layer thickness and bubble diameter could constitute a significant parameter to replace the scale effect in estimating values applicable to actual ships from corresponding data obtained in model experiments.List of symbols a ₁ proportionality constant indicating directionality of turbulence - B law-of-the-wall constant - C _f local skin-friction coefficient in the presence of bubbles - C _f0 local skin-friction coefficient in the absence of bubbles - d _b bubble diameter (m) - g acceleration of gravity (m/s²) - j _g flow flux of gas phase accountable to buoyancy (m/s) - j _t flow flux of gas phase accountable to turbulence (m/s) - k ₄ constant relating reduction of liquid shear stress by bubble presence to decrease of force imparted to bubble by its displacement due to turbulence - l _b mixing length of gas phase (m) - l _m mixing length of liquid phase (m) - l _mb diminution of liquid phase mixing length by bubble presence (m) - Q _G rate of air supply to liquid stream (l/min) - q _/g velocity of bubble rise (m/s) - 2R height of horizontal channel (m) - T _* integral time scale (s) - U _m mean stream velocity in channel (m/s) - U friction velocity in channel (m/s) - V volume of a bubble (m³) - u, ¯ v time-averaged stream velocities inx- andy-directions, respectively (m/s) - u, v turbulent velocity components inx- andy-directions, respectively (m/s) - v root mean square of turbulence component in they-direction (m/s) - root mean square of bubble displacement iny-direction with reference to turbulent liquid phase velocity (m) - y displacement from ceiling (m) - local void fraction - _m mean void fraction in boundary layer - _m constant relating local void fraction to law-of-the-wall constant - _t reduction of turbulent stress (N/m²) - law-of-the-wall constant in turbulent liquid region in absence of bubbles - ₁ law-of-the-wall constant in turbulent liquid region in presence of bubbles - ₂ law-of-the-wall constant in gas phase - _m constant indicating representative turbulence scale (m) - viscosity (Pa × s) - v kinematic viscosity (m²/s) - density (kg/m³) Suffixes G gas - L liquid - 0 absence of bubbles     

HCCI combustion characteristics during operation on DME and methane fuels

The Homogeneous Charge Compression Ignition (HCCI) engine has attracted much interest because it can simultaneously achieve high efficiency and low emissions. However, the ignition timing is difficult to control because this engine has no physical ignition mechanism. In addition, combustion proceeds very rapidly because the premixed mixture ignites simultaneously at multiple locations in the cylinder, making it difficult to increase the operating load. In this study, an HCCI engine was operated using blended test fuels comprised of dimethyl ether (DME) and methane, each of which have different ignition characteristics. The effects of mixing ratios and absolute quantities of the two types of fuel on the ignition timing and rapidity of combustion were investigated. Cool flame reaction behavior, which significantly influences the ignition, was also analyzed in detail on the basis of in-cylinder spectroscopic measurements. The experimental results revealed that within the range of the experimental conditions used in this study, the quantity of DME supplied substantially influenced the ignition timing, whereas there was little observed effect from the quantity of methane supplied. Spectroscopic measurements of the behavior of a substance corresponding to HCHO also indicated that the quantity of DME supplied significantly influenced the cool flame behavior. However, the rapidity of combustion could not be controlled even by varying the mixing ratios of DME and methane. It was made clear that changes in the ignition timing substantially influence the rapidity of combustion.     

Empirical analysis of hazard perception and driving behaviors among high school and college students on motorcycles in Phnom Penh,Cambodia

In Cambodia, motorcycle use has spread rapidly in recent years, and serious accidents involving motorcycles have increased. Motorcycle accidents involving young people are particularly common, and there are various issues concerning traffic safety. To understand the situation in Phnom Penh, Cambodia, we conducted a questionnaire survey on driving attitude and behavior of motorcycle users targeted at high school and college students and a video observation survey of motorcycle driving conditions. Based on the survey analysis results, we held a traffic safety workshop (WS) comprising practical skills and classroom learning centered on hazard anticipation. In this study, we conducted a statistical comparative analysis of driving behavior frequency on non-intersection intervals of arterial roads before and after the WS, based on observational results from video cameras mounted on motorcycles. The results showed that the WS effects were associated with a reduction in average travel speeds and changes in driving behavior, such as frequency of lane changing. Different responses to the WS were observed according to attributes, and thus, the relationship between the content of this kind of traffic safety WS and behavioral changes needs to be clarified and a more advanced traffic safety WS program developed.     

基于旅客-车体耦合振动的车辆振动分析

利用实验方法研究了旅客对车体振动特性的影响,建立了旅客-车体耦合振动分析模型,针对旅客人数及旅客分布对车体振动的影响,进行了仿真分析。     

Adaptive Control of 4WS System by Using Neural Network

An adaptive control system of the model following type is proposed for drive motion control of a four wheel steering (4WS) car with using neural network (NN) which has mastered nonlinear friction force between tire and road surface. A model of one rigid body is adopted which represents appropriately two kinds of car motion caused by steering action, namely the lateral displacement and the yawing rotation, and an equation of motion is described in a simplified form to make a system equation for motion control possible. Nonlinear relation between the cornering force of tire and the slip angle is obtained by numerical analysis with the tire model proposed by E. Fiala, taking friction coefficient and car speed as the parameters. The result is used as the teaching signal for NN. Three NN are used in the control system composed of both the feed-forward and the feedback circuits in order to realize adaptive control. Validity and usefulness of the proposed adaptive control system with NN are verified by three kinds of computer simulation.     

A study on the estimation of the seaquake response of a floating structure considering the characteristics of seismic wave propagation in the ground and the water

 Seaquakes, which are characterized by the propagation of vertical earthquake motion at the sea bottom as a compression (longitudinal) wave, are reported to cause damage to ships, and their effect on floating structures is a matter of great concern. To comprehend the basic properties of seaquakes, we first discuss a method to calculate the displacement of the seabed when it is subjected to hydrodynamic pressure. To investigate the interrelationship between the vibration of a floating structure and the deformation of the seabed, a new boundary integral equation is derived which assumes that the seabed is a semiinfinite homogeneous elastic solid in order to analyze the seaquake-induced hydrodynamic pressure acting on the floating structure. By considering the propagation of the seismic wave in the ground and in the water, the incident wave potential in seaquake problems is also deduced and its characteristics are discussed. Finally, the response of a very large floating structure in a seaquake is investigated using a fluid force analysis method, and considering the interrelationship between the vibration of the floating structure and the deformation of the seabed. Received: August 19, 2002 / Accepted: November 11, 2002 Address correspondence to: H. Takamura (hiroaki_takamura@nishimatsu.co.jp) Updated from the Japanese original, which won the 2002 SNAJ prize (J Soc Nav Archit Jpn 2001;189:87–92,93–100 and 190:381–386)