Neural network-based fuel consumption estimation for container ships in Korea

ABSTRACT

Due to the outstanding strength of advanced machine-learning techniques, they have become increasingly common in predictive studies in recent years, particularly in predicting ship energy performance. In constructing predictive models, prior studies have mostly employed vessels’ technical parameters to establish machine-learning algorithms. To bridge this research gap and enable wider applications, this paper presents the design of a multilayer perceptron artificial neural network (MLP ANN) as a machine-learning technique to estimate ship fuel consumption. We utilized the real operational data from 100–143 container ships to estimate fuel consumption for five different container ships grouped by size. We compared the performance of two ANN models and two multiple-regression models. Four input parameters (sailing time, speed, cargo weight, and capacity) were included in the first ANN and the first regression model, while the other two models only consider two inputs from physical function. The mean absolute percentage error of the ANN models with four inputs was the smallest and less than those in extended statistical models, demonstrating the MLP’s superiority over the statistical model. The MLP ANN model can thus be applied to confirm the effectiveness of the slow-steaming method for achieving energy efficiency.     

看跌期权在集装箱租赁契约中的应用研究

本文将看跌期权引入到集装箱租赁契约中,针对单个集装箱租赁公司和单个承运人组成的单周期、两阶段集装箱租赁服务链,建立了基于看跌期权的承运人决策模型,推导出承运人的最优租箱量和最优期权执行量及其利润函数。同时,文章通过算例分析得出：在需求低迷情况下,与传统契约模型相比较,看跌期权的引入有利于提高承运人的利润,而且随着期权执行价格和需求信息更新准确性的提高,承运人的利润会逐渐增加。     

A probabilistic stationary speed–density relation based on Newell’s simplified car-following model

Probabilistic models describing macroscopic traffic flow have proven useful both in practice and in theory. In theoretical investigations of wide-scatter in flow–density data, the statistical features of flow density relations have played a central role. In real-time estimation and traffic forecasting applications, probabilistic extensions of macroscopic relations are widely used. However, how to obtain such relations, in a manner that results in physically reasonable behavior has not been addressed. This paper presents the derivation of probabilistic macroscopic traffic flow relations from Newell’s simplified car-following model. The probabilistic nature of the model allows for investigating the impact of driver heterogeneity on macroscopic relations of traffic flow. The physical features of the model are verified analytically and shown to produce behavior which is consistent with well-established traffic flow principles. An empirical investigation is carried out using trajectory data from the New Generation SIMulation (NGSIM) program and the model’s ability to reproduce real-world traffic data is validated.     

Evaluating bus transit performance of Chinese cities: Developing an overall bus comfort model

In order to improve the level of bus service, a field study was undertaken to develop a combined bus comfort model. This paper provides a comprehensive review of the different ways to predict the bus comfort, in addition to the variable experimental techniques used. It was found some environment parameters like noise, vibration, thermal comfort and the acceleration would affect the passengers’ experience. In this model, both the measurement of objective physical parameters and subjective questionnaire survey were conducted to gather the practical environment date, as well as to distribute questionnaires on board city buses during the same trips. By comparing the subjective views of bus passengers to objective physical parameters, a combined bus comfort model was established. This model helps to calculate the concrete value of passengers’ perceived bus comfort. An effective approach integrated the comfort model, measuring instrument and the driver monitor could greatly improve the bus service quality.     

An integrated analysis of workers’ physically active activity and active travel choice behavior

Using Texas add-on sample data from the 2009 National Household Travel Survey, this study examines adult workers’ daily active choice decisions in the context of physical activity and attendant health benefits. The study looked at workers’ two choice behaviors: active activity and active travel. The first choice behavior, active activity, is developed as an ordered-response model based on the number of physically active recreational activities pursued during the workday. The second choice behavior, active travel, is developed as a binary-response model that examines workers’ active travel choices—whether or not the worker used any active mode of travel during the same workday. The study improves the understanding and knowledge of observed factors influencing workers’ physically active activity-travel behavior. The study also provides several observations regarding the role (and constraints) of employment in individuals’ active choices. Using a flexible copula modeling methodology, we explore the true correlation (or dependence) between the two behavior choices that could occur due to the presence of unobserved factors, suggesting a simultaneously low or simultaneously high propensity for being physically active across workers. The study findings suggest that transportation and public health policy makers can mutually benefit from encouraging workers to be physically active (from an activity and/or travel perspective). Overall, the study draws attention to the integrated nature of the public health and transportation fields, thereby providing a distinct view of active/inactive choice behavior. To our knowledge, this is the first study exploring a rich variety of components for workers’ active activity-travel behavior through a robust copula approach.     

基于dSPACE的船用异步电机矢量控制研究

为了能够反复便捷地对船用异步电机矢量控制技术进行研究,需要对整个系统进行仿真。而传统的离线仿真技术已不能满足现在系统多样的需求,而本文研究的d SPACE实时仿真技术可以很好的解决这一问题。本文首先研究船用异步电机矢量控制技术,然后针对该控制方案进行基于Simulink的离线仿真,接着搭建了基于d SPACE半实物仿真平台的船用异步电机矢量控制系统,并借助于该系统展开船用异步电机矢量控制实验,验证基于d SPACE进行船用异步电机矢量控制的可行性、实用性与便捷性。     

Continuous formulations and analytical properties of the link transmission model

The link transmission model (LTM) has great potential for simulating traffic flow in large-scale networks since it is much more efficient and accurate than the Cell Transmission Model (CTM). However, there lack general continuous formulations of LTM, and there has been no systematic study on its analytical properties such as stationary states and stability of network traffic flow. In this study we attempt to fill the gaps. First we apply the Hopf–Lax formula to derive Newell’s simplified kinematic wave model with given boundary cumulative flows and the triangular fundamental diagram. We then apply the Hopf–Lax formula to define link demand and supply functions, as well as link queue and vacancy functions, and present two continuous formulations of LTM, by incorporating boundary demands and supplies as well as invariant macroscopic junction models. With continuous LTM, we define and solve the stationary states in a road network. We also apply LTM to directly derive a Poincaré map to analyze the stability of stationary states in a diverge-merge network. Finally we present an example to show that LTM is not well-defined with non-invariant junction models. We can see that Newell’s model and continuous LTM complement each other and provide an alternative formulation of the network kinematic wave theory. This study paves the way for further extensions, analyses, and applications of LTM in the future.     

生本视角下我国高校教师教学质量评价的三重审视

伴随高等教育大众化进程,我国高校逐步进入以质量取胜的内涵式发展阶段,质量成为高等院校赖以生存与发展的生命线,尤其是高职院校人才培养质量遭受质疑,在新的时代背景下高职教育如何从大变局和新占位视域跳出传统思维定式走向理性。教师教学质量评价作为高校一项常规性工作,不只是一个管理工具和评价手段的应用,而是关乎人才培养质量的管理与生成,集中体现为学生需求满足程度的价值判断过程,其根本目的在于提高人才培养质量。本文基于生本视角,从问题缘起、理论探源及结构要素三个逻辑层面重视高校教师教学质量评价,深刻回答教师教学质量评价"为什么、是什么、怎么样"的元生逻辑问题,以期从学理层面厘清教师教学质量评价的本质内涵和应然之义,科学指导实践。     

Thermodynamic,environmental and economic analysis of absorption air conditioning unit for emissions reduction onboard passenger ships

In this paper, the waste heat of exhaust gases and jacket cooling water in marine diesel engines are analyzed to operate the absorption refrigeration unit (ARU). Thermo-economic and environmental analysis of the absorption refrigeration cycle operated with the two heat sources that use lithium bromide as an absorbent is carried out. The analysis is performed using Engineering Equation Solver (EES) software package where the thermodynamic properties of the steam and the LiBr-water mixtures are provided. The used EES code is verified by published experimental data. As a case study, high speed passenger vessel operating in the Red Sea area has been investigated. The results show that a considerable specific economic benefit could be achieved from ARU jacket cooling water operated over that gained from main engine exhaust gases. Environmentally, applying ARU machine during cruise will reduce the annual fuel consumption for the diesel generators by 156 ton with a reduction percentage of 23%. This will reduce the exhaust gas emissions by 6.3% from the applied main engine emissions. In addition, this will result in reducing NO_x, SO_x, and CO₂ emissions with cost-effectiveness of 4.99 $/kg, 13.18 $/kg, and 0.08 $/kg, respectively.     

“工程力学”课程教学中加强高职学生工程能力和兴趣培养的探索

概述了工程力学性质,对学生现状进行了分析,提出了从引入工程案例、制作力学模型、苦练教师内功等三个方面来加强高职学生工程能力和兴趣的培养。