船用液控蝶阀节流调速系统的数字仿真(英文)

Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve. It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.     

The two-dimensional study of the interaction between liquid loshing and elastic structures

Sloshing phenomenon in the liquid cargo carriers has caught the attention of researchers as the interaction between the sloshing waves and structure is one of the key point and difficulty in the study of sloshing. In this paper, we captured the free surface with a volume of fluid (VOF) method and then calculated the motions and responses of the structure by adopting the Reynolds-averaged Navier-Stokes (RANS) equations for the whole fluid domain. With the use of user defined functions (UDF) in Fluent, the interaction between fluid and structure was then simulated. As a reasonable simplification, the authors studied the response of a single cantilever in a tank under sloshing loads; Further study should pay more attention to the mechanisms of interaction between sloshing waves and elastic structures.     

Research of scalability of the belt-type sensor networks

For the large-scale application requirements of the belt-type networks, the mathematical modeling as well as quantitative analysis for the scalability of the network based on average path length is completed in this paper, and the theorem for the scale scalability of the belt-type networks is derived. The theorem provides a calculation formula for the upper limit of node scale theory of the belt-type networks and a calculation formula for the upper limit of single node load theory.     

External Costs of Domestic Container Transportation: Short‐Sea Shipping versus Trucking in Taiwan

Abstract

This paper explores the external costs of domestic container transportation in Taiwan by analysing the origin and destination of current container cargoes. After reviewing an extensive literature survey of methods of external cost, a comparison of external costs between trucking and short sea shipping (SSS) by corridor is made by using a model developed in this paper. Based on the findings that external costs of SSS are considerably lower than truck transport and can be a viable alternative to current domestic container cargo transportation, we discuss the significance and managerial implications of SSS from the perspective of green logistics. In so doing, a top‐down approach is employed for developing government policies, which aim to not only reduce the external costs of domestic container transportation but also promote SSS in Taiwan.     

Robust design optimization of suspension system considering steering pull reduction

This paper presents robust design optimization method to reduce steering pull phenomenon. One of the biggest causes of steering pull phenomenon is tolerance of suspension system such as hard point, spring, damper and bush. Therefore, the relationship between suspension systems and steering pull phenomenon has as nonlinear characteristics. But, it can be very difficult to evaluate the analytical design sensitivity. Thus, it is impossible to directly apply a well-developed optimization algorithm based on gradient information. To avoid these difficulty, this study uses sequential approximation optimization process based on a meta-model. The robust design process has 28 random design variables with tolerance. For efficient design process, the sample variances for the design goals are approximated from meta-models. The proposed approach required only 62 evaluations until it converged. Optimal design reduced the drift by 80% and its deviation by 38.7%, respectively. This result proves that the suggested design method of suspension system is effective and useful.     

Objective evaluation of door-closing sound quality based on physiological acoustics

This paper presents a new method to objectively quantify the sound quality of doors closing in premium passenger cars. In previous works, psychoacoustic parameters have been used for objective quantification. However, these parameters do not agree well with subsequent subjective assessments. Therefore, the correlation between the psychoacoustic parameters and the subjective rating of door closing sounds in sampled cars is low, and it is not sufficient to use psychoacoustic parameters as an objective metric to quantify the quality of door-closing sounds. In this paper, a new method is proposed to objectively quantify the sound quality based on physiological acoustics and statistical signal processing. A gammatone filter is used as a pre-processing method in models of the auditory system and kurtosis, which is the fourth-order moment of the temporal signal and is used to extract quantitative information about the quality of door-closing sounds. The new metric obtained from the proposed method is highly correlated to subjective ratings and has been successfully applied to the quantification of door-closing sound quality.     

Experiments and thermal-electrical analysis of buss bar and relay assemblies in junction blocks

A junction block (or electrical distribution box) is electrical equipment that has been densely assembled from components such as buss bars, relays, and fuses to control the electric current flow in vehicles. Joule heat is generated in these parts as a result of electrical bulk resistance and electrical contact resistance. The generation of heat increases due to the complex behavior of modern vehicle electronic systems. Overheated parts can be damaged during operation due to thermal energy. The thermal assessment of a junction block is an important issue in automobile development. We suggest a methodology to simulate the transient temperature distribution of buss bars and electrical relays in a junction block. A finite element formulation of a coupled electro-thermal problem, which includes the effect of Joule heating, is introduced to the simulation. Finite element analysis (FEA) and experiments at the component level of buss bars and relays are conducted to investigate the thermal performance of a junction block. To verify the accuracy of the FEA procedure, the temperature history obtained by FEA is compared with the results obtained from experiments. The thermal-electric analysis of a typical junction block assembly is also discussed.     

Angular position error detection of variable reluctance resolver using simulation-based approach

The variable reluctance type resolver is widely used in an electric motor for hybrid electric vehicles as a rotor position sensor. The purpose of this paper is to present a simulation-based approach capable of determining a more accurate rotor shape of variable reluctance resolver in order to cut the time and cost of its development before testing a physical prototype. For the verification of the simulation-based approach to the position error detection of rotor, experiments for 8XVR resolver were conducted. Based on this approach, an optimal salient-pole rotor shape of 4X-VR resolver is proposed.     

Research of order allocation model based on cloud and hybrid genetic algorithm under ecommerce environment

For massive order allocation problem of the third party logistics (TPL) in ecommerce, this paper proposes a general order allocation model based on cloud architecture and hybrid genetic algorithm (GA), implementing cloud deployable MapReduce (MR) code to parallelize allocation process, using heuristic rule to fix illegal chromosome during encoding process and adopting mixed integer programming (MIP) as fitness function to guarantee rationality of chromosome fitness. The simulation experiment shows that in mass processing of orders, the model performance in a multi-server cluster environment is remarkable superior to that in stand-alone environment. This model can be directly applied to cloud based logistics information platform (LIP) in near future, implementing fast auto-allocation for massive concurrent orders, with great application value.     

Longer-term changes in mode choice decisions in Chennai: a comparison between cross-sectional and dynamic models

The rapid and continuing changes in travel and mobility needs in India over the last decade necessitates the development and use of dynamic models for travel demand forecasting rather than cross-sectional models. In this context, this paper investigates mode choice dynamics among workers in Chennai city, India over a period of five years (1999–2004). Dynamics in mode choice is captured at four levels: exogenous variable change, state-dependence, changes in users’ sensitivity to attributes, and unobserved error terms. The results show that the dynamic models provide a substantial improvement (of over 500 log-likelihood points and ρ² increases from 44% to 68%) over the cross-sectional model. The performance was compared using two illustrative policy scenarios with important methodological and practical implications. The results indicate that cross-sectional models tend to provide inflated estimates of potential improvement measures. Improving the Level of Service (LOS) alone will not produce the anticipated benefits to transit agencies, as it fails to overcome the persistent inertia captured in the state-dependence factors. The results and models have important applications in the context of growing motorization and congestion management in developing countries.