Applied Mechanics and Materials Vol. 621

Abstract: In the age of big data, MapReduce is developed as an important tool to process massive datasets in a parallel way on cluster and Hadoop is an open-source implementation of it. However, with the increasing size of clusters, it becomes more and more difficult to identify and diagnose faulty nodes, especially those continuing running but with degraded performance. Then, based on an observation that the behaviors of all nodes in the cluster are relatively similar, we propose a peer-comparison approach that can automatically diagnose performance problems in Hadoop cluster through extracting, analyzing both Hadoop logs and OS-level performance metrics on each node. Compared with previous works, our approach is more scalable and effective and can pinpoint the underlying bug of faulty node in Hadoop clusters.

Abstract: A large number of weakly rigid parts are used in the progress of aircraft assembly, while it’s deviation will affect the quality of the product finally. The assembly variation model of aircraft weakly rigid parts based on influence coefficient method are constructed for controlling assembly accuracy effectively. Based on the linear elastic hypothesis of small deformation, the model carry out the mechanical analysis of aircraft weakly rigid parts in the typical process of positioning, clamping, jointing and spring-back. Influence coefficient matrix of the key features affected by parts manufacturing variation and fixture variation is calculated through the Finite Element method and Monte Carlo simulation, then the assembly variation model is constructed. Finally, based on the above model, an engineering example of assembly variation prediction of aircraft panels was given.

Abstract: This document presents an interactive tool for notch fatigue analysis and life prediction. Modified Neuber’s rule is used to determine notch-root elastic-plastic stress and strain. The effect of mean stress on fatigue crack initiation life is accounted by utilizing a deviatoric formulation of the Smith-Watson-Topper parameter. For variable amplitude loading a rainflow method is used and the corresponding hysteresis loops at the notch-root are determined. Then, the relevant interactive graphs and calculated values are displayed. The propose methodology is intended to be a comprehensive fatigue analysis tool used by any designer engineer in global market environment. A brief flow chart of the intended tool is presented here.

Abstract: Queuing problems present a gap in the availability of knowledge at port container terminals. This study is focused on various types of services for port container terminal queuing system. The purpose of this paper is to introduce a methodology to decrease waiting time without any reduction in productivity. A new approach for servicing at the queue is proposed, and with this idea waiting time will be reduced without any change in productivity or additional cost. To execute this approach in a port container terminal, berthing areas of the port are simulated with ARENA 13.5, and this new approach is implemented in the model. The result of this change are compared with results of a port container terminal as case study. With implementing this method the waiting time is reduced dramatically and productivity increased slowly.

Abstract: The underwater diver visible light communication system integrating information collection, transmission and processing achieves the optical communication device established for the diver’s underwater wireless transmission and underwater sensor network. The front-end signal acquisition module capable of carrying out voice and image acquisition utilizes a MEMS digital microphone and a high performance CMOS camera to change optical signals in to digital ones. The signal source applies wavelet conversion and the channel coding and decoding apply Turbo algorithms, channel modulation and demodulation adopt PPM modulation, so compression, coding and modulation are mounted on TI's high-performance DSP TMS320DM642 platform to ensure the stability and reliability of data transmission. Back-end data acquisition module utilizes a photomultiplier tube and its peripheral circuits for receiving and converting optical signals. Display and storage modules are TFT and SD cards to achieve data reception and sound and light reduction and storage functions.

Abstract: Hadoop is a popular software framework supports distributed processing of large data sets. However, with Hadoop being a relatively new technology, practitioners and administers often lack the expertise to tune it to get better performance. Hadoop parameters configuration is one of the key factors which influence the performance. In this article, we present a novel Hadoop parameters tuning method based on function monitoring. This method monitors the function call information during task run to analyze why the performance of Hadoop changes when tuning parameters, which will be helpful for practitioners and administer to tune parameters to get better performance.

Abstract: As many sensor networks have been deployed in industry monitoring area, the focus on sensor data quality has also increased. Sensor networks provide us with process details which we can utilize to help making decisions on process monitoring.In order to make meaningful decisions, the quality of the data produced by sensors must be validated. As we evaluate the status of a specific sensor, we may also regard the status of the related sensors. If a sensor’s data show some abnormal, but the sensors related to it didn’t, we may have much more confidence to believe that the sensor is malfunction. In our early study, the sensors grouping strategy is manual. In this paper, we proposed a sensor grouping algorithm, which combines both PCA decouple method and the K-means cluster method. Finally, a test has been made with real data from an oilfield.

Abstract: The external effect of decentralized wastewater reuse project will be divided into external factors and the impact of external factors on the reuse of sewage project itself, apply this two integrated impacts of evaluation analysis method Benefit - Cost - Opportunity - Threat (BCOT) to analyze comprehensively the wastewater project external effect and use the Xi`an Greenland Century City project as an example. The study on the BCOT evaluation analysis gives the external effects of researching decentralized wastewater resource a new idea.

Abstract: The structure of the power tunnel is unique as a special place. It is built under the surface of the earth crust,belongs to half-hidden project. In recent years, affected by operating life, geological conditions, design and construction, the number of the tunnels which has structural safety risks apears more and more, so the safety of the tunnel structure always has been a very important issue of construction, operation and maintenance. This paper presents a tunnel structure safety monitoring system based on BOTDA technology.This system has good adaptability to the scene, and can remotely monitor the structural safety of the tunnel in real time, and it also has advantages of distribution, long-distance, high-precision, etc.