Study on the assessment of seafarers\u27 fatigue

Global concern about the issue of fatigue at sea is widely evident across the shipping industry. Fatigue-induced human errors have been identified as major contributing factors in most maritime accidents. This paper attempts to explore an approach to evaluate the degree of seafarers’ fatigue and to propose some suggestions on fatigue prevention and management. According to the definition given by the IMO, Fatigue is a state of feeling tired, weary, or sleepy that results from prolonged mental or physical work, extended periods of anxiety, exposure to harsh environments, or loss of sleep. The effects of fatigue are impaired performance and diminished alertness. In this study, the definition and effects of fatigue at sea are first examined, followed by a review of fatigue-induced maritime incidents and the prevalence of fatigue in the maritime industry. The factors affecting navigation officers’ fatigue are categorized into four groups in this study: crew-specific factors, management factors, ship-specific factors and environmental factors. The evaluation index system and weight of evaluating indexes are determined by applying the AHP. Efforts are made to develop an evaluation model for seafarers’ fatigue with the application of multi-level fuzzy comprehensive evaluation. Consequently, recommendations on supervision and prevention of fatigue onboard ships are proposed for maritime organizations, shipping companies and seafarers

Fault diagnosis of refrigerant charge based on PCA and decision tree for variable refrigerant flow systems

Variable refrigerant flow (VRF) systems are easily subjected to performance degradation due to refrigerant leakage, mechanical failure or improper maintenance after years of operation. Ideal VRF systems should equip with fault detection and diagnosis (FDD) program to sustain its normal operation. This paper presents the fault diagnosis method for refrigerant charge faults of variable refrigerant flow (VRF) systems. It is developed based on the principal component analysis (PCA) feature extraction method and the decision tree (DT) classification algorithm. Nine refrigerant charge schemes are implemented on the VRF system in the laboratory, which contain the normal and faulty refrigerant charge conditions. In addition, data of the online operating VRF systems are collected in this work. Firstly, data from both experimental VRF system and online operating systems are pre-processed by outlier cleaning, feature extraction and data normalization, because the original data of the VRF system usually has poor quality and complex structure. Secondly, the fault diagnosis model based on the PCA-DT method is built using the data of the experimental VRF system. In this step, the PCA method is used to obtain a new data sample which includes four comprehensive features, then the new data sample are randomly split into training and testing sets as the input of DT classifier for fault diagnosis. Thirdly, the advantages of the PCA-DT method is validated using the experimental data of different fault severity levels. Results show that the combined use of PCA and DT methods can achieve better fault diagnosis efficiency than the single decision tree method. Further, the robustness of the PCA-DT method in online fault diagnosis is verified using the data from online VRF systems. The online VRF systems have the same or different number of indoor units as the trained (experimental) VRF system. The PCA-DT method also shows desirable goodness on the online fault diagnosis process. In this sense, this work provides a promising fault diagnosis strategy for refrigerant charge faults of VRF system application

Effects of Composition and Calcination Temperature on Photocatalytic Evolution over from Glycerol and Water Mixture

A series of sulfide coupled semiconductors supported on SiO2, (), was prepared by incipient wet impregnation method. The photocatalysts were characterized by XRD, XPS, TPR, and UV/Vis DRS. Characterization results show that the chemical actions between ZnS and CdS resulted in the formation of solid solutions on the surface of the support and the formation of them is affected by the molar ratio of ZnS/CdS and calcination temperature. Performance of photocatalysts was tested in the home made reactor under both UV light and solar-simulated light irradiation by detecting the rate of the photocatalytic H2 evolution from glycerol solution. The hydrogen production rates are related to the catalyst composition, surface structure, photoabsorption property, as well as the amount of solid solution. The maximum rate of hydrogen production, 550 μmol·h−1 under UV light irradiation and 210 μmol·h−1 under solar-simulated light irradiation, was obtained over Cd0.8Zn0.2S/SiO2 solid solution calcined at 723 K

Fault Diagnosis Observer Design for Discrete-Time Delayed Complex Interconnected Networks with Linear Coupling

Fault diagnosis for a class of discrete-time delayed complex interconnected networks with linear coupling in the case of actuator fault is studied. For the case of unavailability of network state, a state observer is first designed. Then a fault diagnosis observer is designed to detect the actuator fault on the basis of online adaptive approximator, which can approximate the unmodeled dynamics of the complex networks. Lastly, by choosing a suitable threshold, the actuator fault can be detected. A numerical simulation is used to show the effectiveness of the proposed method

Correlative Analysis of TOEFL IBT Scores of Listening Skill Versus Scores of Business English Speaking Skill Among Binus University Sophomores

Article found out whether BINUS university sophomore\u27s TOEFL iBT scores of Listening skill are correlated with those of speaking skill. The research project was expected to result in the best teaching technique of delivering conversational tasks at BINUS University by using alternative approaches of integrated, isolated, or mixed skills. The research project applied the descriptive approach of quantitative method, and thus depends on numerical data. The research project examined the set of data under two skills of the same class groups, which were to compare the listening scores with the speaking ones. Then, the degree of correlation of the two skills was tested so as to find its significance. Interpretation and explanation of data was made based on the statistical results by using correlation research analysis. Based on the statistical results, the listening scores significantly correlated with those of the speaking skill, and there is a moderately linear relationship between these paired scores

An Advanced Multicarrier Residential Energy Hub System Based on Mixed Integer Linear Programming

This work proposes a multicarrier energy hub system with the objective of minimizing the economy cost and the CO2 emissions of a residential building without sacrificing the household comfort and increasing the exploitation of renewable energy in daily life. The energy hub combines the electrical grid and natural gas network, a gas boiler, a heat pump, a photovoltaic plant, and a photovoltaic/thermal (PV/T) system. In addition, to increase the overall performance of the system, a battery-based energy storage system is integrated. To evaluate the optimal capacity of each energy hub component, an optimization scheduling process and the optimization problem have been solved with the YALMIP platform in the MATLAB environment. The result showed that this advanced system not only can decrease the economic cost and CO2 emissions but also reduce the impact to electrical grid