A hybrid clustering approach for multivariate time series – A case study applied to failure analysis in a gas turbine

A clustering problem involving multivariate time series (MTS) requires the selection of similarity metrics. This paper shows the limitations of the PCA similarity factor (SPCA) as a single metric in nonlinear problems where there are differences in magnitude of the same process variables due to expected changes in operation conditions. A novel method for clustering MTS based on a combination between SPCA and the average-based Euclidean distance (AED) within a fuzzy clustering approach is proposed. Case studies involving either simulated or real industrial data collected from a large scale gas turbine are used to illustrate that the hybrid approach enhances the ability to recognize normal and fault operating patterns. This paper also proposes an oversampling procedure to create synthetic multivariate time series that can be useful in commonly occurring situations involving unbalanced data sets.     

Simulation Analysis of a PCB Factory using Factorial Design – A Case Study

This study describes simulation modelling and analysis of a serial production line in a printed circuit board (PCB) factory. Simulation technique is applied to evaluate the performance of the existing manufacturing system, which requires modification to achieve two conflicting objectives, i.e. to maximise the average throughput rate and to minimise the average lead time. Based on a full factorial design, the computer model, which is developed using SIMFACTORY, has been used for finding out the active factors that have a great impact on the current operational problems. Then, a new system design is proposed to enhance the overall performance and is verified using a simulation model. The simulation approach presented here is also applicable to a wide variety of complex operational problems. ID="A1"Correspondance and offprint requests to: Dr F.T.S.Chan, Department of Industrial and Manufacturing Systems Engineering, University of Hong Kong, Pokfulam Road, Hong Kong. E-mail: ftschan@hkucc.hku.hk     

Determination of the significant anthropometry dimensions for user-friendly designs of domestic furniture and appliances – Experience from a study in Malaysia

Future design for the elderly is undoubtedly important for their survival to live independently in this challenging world. Therefore to realize the mentioned design, an anthropometric database for Malaysian elderly population need to be developed. A total of 107 participants took part in the study which involved 61 females and 46 males with ages ranging between 55 and 70 years. An earlier anthropometric database for Malaysian elderly population has been developed. Sixty body dimensions were measured in the study. It is hoped that from this study, the database can be used as a guideline in designing household facilities for the Malaysian elderly and elderly of other countries. The design of the household facilities should be influenced by sound ergonomics dimensions in order to create a safe and healthy environment for the elderly.     

Reduction of sloshing effects in a rectangular tank through an air-trapping mechanism – a numerical study

A 2D rectangular tank subjected to horizontal excitations is used to analyze the effects of sloshing. The tank is fitted with horizontal baffles on two sides to suppress the impact pressure of sloshing by using an air-trapping mechanism. The volume of fluid method is adopted to create sloshing phenomena. Five cases with fixed baffle gaps and various baffle lengths are used to analyze the effects of suppressing the sloshing impact pressure in the tank. The peak pressure values of the cases with baffles are compared with those of the cases without baffles. Results show that the maximum suppression rate achieved is 63.6 % due to air trapping and baffle effects. Baffle ratio (Defined by G/L), a geometrical dimensionless factor, is considered to analyze the effects of baffle length and gap. A baffle ratio of 0.5 results in a 14.2 % reduction in the sloshing impact rate. An increasing amount of air is trapped within the baffle array as BR decreases.     

Integration of the fish bone diagram, brainstorming, and AHP method for problem solving and decision making—a case study

Decision making is one of the management’s elements and using suitable methods in proportion with decisions, plays an effective role in any organizations success. By recognizing the value of group decision making methods in organizations, managers are seeking for recognizing their organizations problems in one process of group problem solving methods, and finding a suitable approach for it. In one case study performed in a soap production line, namely Tage Co., the problem of redoing and as a result increasing the wastes during production is a large-sized problem. By selecting a proper method in a brainstorming meeting, the effective factors in this regard are identified. Furthermore, by using a fish bone (or cause-and-effect) diagram, the cause-and-effect relationships between the problem’s phenomena become apparent. Finally, by using the analytical hierarchy process analysis and determining the priority for the possible solutions, an efficient decision is made and performed. An application of the above-mentioned decision is presented the promising and valuable results.     

Product–service systems in health care: case study of a drug–device combination

A radio-frequency identification (RFID) system has been considered as one of the most promising systems for information technology (IT) asset management because of its well-developed level of technology, worldwide standards and its lower price than other wireless protocols such as WiFi, WiMAX, and Bluetooth. However, RFID systems for IT asset management in business-to-business (B2B) environments are still limited by several constraints such as readable range, sensor capability, and battery problems inherent in existing RFID technologies. In particular, only few research works deal with asset management in a real office environment. This paper proposes a new way of managing IT assets using surface acoustic wave (SAW)-based RFID technology to solve these problems. To show its effectiveness and feasibility, the proposed approach analyzes RFID tag performance based on an electromagnetic test and measures the readability of SAW-based RFID in an office environment. Experimental results show that one of the most hopeful candidates for managing B2B IT assets is the SAW-based RFID system because of its batteryless passive RFID characteristic, relatively long readable range, its potential and inherent sensor capability, and its expandability compared to other RFID systems. Furthermore, the proposed approach systematically analyzes where to attach RFID tags on IT asset devices considering electromagnetic performance based on ID- and sensor-detecting capabilities, which suggests the most appropriate tag position on the device.     

Sensory platform architecture for IN SITU monitoring the thermal comfort in rural environments – The case study at Federal Rural University of Amazonian,Brazil

This research presents an IN SITU sensory platform developed through the integration of air temperature and relative humidity sensors on an ecosystem in order to obtain some thermal characteristic of the rural environments. This sensory platform contains an expert system to detect the behaviors of environmental variables that result in risk or without risk alert to the thermal comfort for human and animal health. For this, the expert system analyses the environmental thermal conditions of the UFRA University, through temperature and humidity index (THI). The THI values estimated (processed) from data of temperature and relative humidity during the year 2012. Four intervals of THI were used to classify human health performance (THI < 74: comfort, 74 ⩽ THI < 79: hot; 79 ⩽ THI ⩽ 84: too hot, and THI > 84: extremely hot), and two intervals to classify animal production (79 ⩽ THI ⩽ 84: dangerous and THI > 84: emergency). The Amazon is located in the equatorial region and has a warm and humid climate that the prevailing mode reveals an alternation of two seasons throughout the year, hot and humid summer and rainy winter. The results that the most critical period occurs between May and October, although it was observed in every day of every year, the THI values during the hottest hours of the day (15:00 pm) range between 75.9 and 86.3, where humans and animals can suffer some degree of thermal stress, affecting negatively both. Therefore, we consider this platform as a good solution for thermal monitoring, which is based on IN SITU measurement technologies for rural environments.     

Value stream mapping and benefit–cost analysis application for value visibility of a pilot project on RFID investment integrated to a manual production control system—a case study

The importance of responding to customer demand to stay competitive in the global market and to increase market share has been increasing for companies lately. Due to demand fluctuations and difficulties to estimate it, gradually it becomes more difficult to sustain profitability and to fulfill demand. The company’s main problem is how to cut costs while producing small numbers of many types of products. For that reason, cost-conscious companies have focused on monitoring and controlling manufacturing and supplier-related activities by means of manual/electronic control devices in order to enhance the efficiency in the supply chain management and logistics process. This paper presents a case study about deployment of radio frequency identification (RFID) technology-based electronic Kanban system in an automotive industry supplier firm. In this project, by deploying RFID technology in a pilot area within the current manual Kanban system of this company, it has been possible to measure the true value added time in the production process. Value stream mapping is used to exhibit the mandatory requirements of RFID technology deployment in the shop floor. As a part of the study, we generate a current value stream map and a future value stream map, which contain the recommended revisions for the automotive supplier company. To evaluate the return of the investment, performance metrics were established and benefit–cost analysis is made. Obviously, future gains will include better inventory management to reduce the inventory levels within the production system.     

Effects of friction conditions on the formation of dead metal zone in orthogonal cutting – a finite element study

Abstract

A numerical study of the effects of friction conditions on the formation of dead metal zone (DMZ) is presented. The friction conditions are classified as three different cases in the form of coefficient: (1) constant coefficient of friction, (2) “smooth” and “sharp” change of the friction coefficient and (3) time-dependent friction coefficient. These friction cases are numerically investigated using the finite element (FE) code ABAQUS/Explicit. A FE model based on the arbitrary-Lagrangian–Eulerian approach is developed to simulate the cutting process and investigate the influences of the friction conditions. The simulated results, for a wide range of friction conditions, are obtained, analyzed and compared with previously published experimental/numerical data. It has been found that the friction coefficient has a direct effect on the amount and shape of DMZ, the sharp change of coefficient has a larger effect on the DMZ formation than the smooth one and the formation of DMZ is more determined by the value of the friction coefficient than its duration.     

Resonance of a flexible plate immersed in a von Kármán vortex street

Journal of Mechanical Science and Technology - This work presents a theoretical and experimental study of a flexible plate immersed in a von Kármán vortex street. The wake is generated in...     

Balancing–sequencing procedure for a mixed model assembly system in case of finite buffer capacity

In the last decades, the necessity to make production more versatile and flexible has forced assembly line production systems to change from fixed assembly lines to mixed model assembly lines, where the output products are variations of the same base product and only differ in specific customizable attributes. Such assembly lines allow reduced setup time, since products can be jointly manufactured in intermixed sequences (Boysen, Flieder, Scholl. Jena Research Papers in Business and Economics, Friedrich-Schiller-Universitat Jena, 1;1–11, 2007a; Boysen, Flieder, Scholl. Jena Research Papers in Business and Economics, Friedrich-Schiller-Universitat Jena, 2;1–33, 2007b). Unfortunately, the installation of customization options typically leads to variations in process times, and when the cycle is exceeded within a certain station, an overload is created, forcing other stations to wait and idle. Normally, process time variation in an un-paced line are absorbed by buffers, but in some industrial application the buffer dimensions are critical not only for the reduction of work in progress but also in reducing other constrains (space, technology, model dimensions, etc.). The problem of balancing mixed model assembly lines (MALBP), in the long term, and that of sequencing mixed model assembly lines (MMS), in the short term (Merengo, Nava, Pozetti. Int J Prod Res 37:2835–2860, 1999), are the two major problems to solve. The object of this paper is to illustrate an innovative balancing–sequencing step-by-step procedure that aims to optimize the assembly line performance and at the same time contain the buffer dimensions in function of different market demand and production mix. The model is validated using a simulation software and an industrial application is presented.     

A multi-echelon reverse logistics network design for product recovery—a case of truck tire remanufacturing

Due to increasing environmental deterioration, government regulations, social responsibilities, resource reduction, and economic factors, many companies are engaged in the product recovery business. Product recovery refers to the set of activities designed to reclaim value from a product at the end of its useful life. Due to the increasing number of vehicles in the country like India, large quantities of used tires are generated every year, and proper disposal of these used tires creates a significant problem in the day-to-day life. An alternative way to recover the value (tire remanufacturing also called retreading) from the used tire is proposed in this work. The implementation of such remanufacturing system usually requires an appropriate reverse logistics network for choosing the physical locations, facilities, and transportation links to convey the used products from customers to the remanufacturing facility and from there to secondary markets. The main objective of this work is to develop a mixed integer nonlinear programming model for maximizing the profit of a multi-echelon reverse logistics network and also to present a real-life case study of truck tire remanufacturing for the secondary market segment. The proposed model is solved using LINGO 8.0 optimization solver which provides the decisions related to the number of facilities to open, their locations, and also the allocation of the corresponding product flows. Finally, it is concluded that the choice of using retreaded tires is a profitable one by the way of cost reduction. Sensitivity analysis of the model is also presented to find the maximum allowable distance between the customers and initial collection points.     

The prediction technology study of fatigue life for key parts of a tracked vehicle’s suspension system

In allusion to fatigue life of a tracked vehicle torsion bar, a virtual prototype model of the tracked vehicle suspension system including a flexible torsion bar was built based on dynamic simulation software ADAMS. Node force and stress results of the torsion bar from last step simulation were acquired; taking into account the material characteristics and influential factors, fatigue life of the flexible body of the torsion bar was predicted. Engineering results can be acquired through the contrast of the result of virtual test and statistical fatigue.     

Augmented ε-constraint method in multiobjective staff scheduling problem: a case study

Staff scheduling is one of the most relevant issues among production planning managers. The problem is to set up an appropriate schedule for various employees to maximize the performance measurement. There are different conflicting criteria with any scheduling problem such as cost minimization, efficiency maximization, etc. The proposed model of this paper develops a new multiobjective decision-making scheduling problem, and the resulted problem is solved using two different techniques of goal programming and augmented epsilon constraint. The implementation of the new proposed model is demonstrated with a real-world case study, and they are analyzed. The preliminary results indicate that the epsilon-constraint method somewhat performs better than goal programming technique.     

Comments on “enhancement of an efficient liveness-enforcing supervisor for flexible manufacture systems”

Region theory can synthesize maximally permissive supervisors by solving a set of inequalities based on the marking/transition-separation instances (MTSIs). It is infeasible to solve these inequalities for either a sizable net or a small net with a sizable initial marking. Huang et al. [1] propose novel crucial MTSIs to reduce the number of MTSIs. Experimental results show that the proposed control policy is the most efficient algorithm among the closely related approaches. One example shows that it not only reaches all live states but also employs fewer control arcs than that by Li et al. Huang et al. offer no hints on why it employs fewer control arcs. This paper develops theory to explain the physics behind.     

Design of a neuro-fuzzy–regression expert system to estimate cost in a flexible jobshop automated manufacturing system

We propose a cost estimation model based on a fuzzy rule backpropagation network, configuring the rules to estimate the cost under uncertainty. A multiple linear regression analysis is applied to analyze the rules and identify the effective rules for cost estimation. Then, using a dynamic programming approach, we determine the optimal path of the manufacturing network. Finally, an application of this model is illustrated through a numerical example showing the effectiveness of the proposed model for solving the cost estimation problem under uncertainty.     

Dynamics and stability – A proposal for related terms in Metrology from a mathematical point of view

We describe measurement quantities and measurement processes verbally by using everyday terms, often sanctioned by international standards and guides. However, we apply some of these terms inconsistently as compared to definitions in base sciences like Logic and Mathematics, Signal and System Theory, Stochastics and Statistics, Estimation and Optimisation Theory. This is especially true for a group of terms in Metrology, namely for the terms kinetic, static, time dependent, time invariant, stable, stationary, drifting etc., which all populate the general environment of the main term dynamics. The paper explores systematic relations between these and similar terms and discusses the aptitude of their implementation in everyday practice. Cardinal point is the term dynamic, which will be investigated thoroughly. So, derived terms can be defined, incorporated and judged accordingly. For the field of Metrology some new and, maybe, surprising results arise, worth being considered in the near future.     

Perspective study of abrasive water jet machining of composites — a review

Journal of Mechanical Science and Technology - Even though composite materials are prominent amongst the advanced engineering materials, but machining of composites using conventional machining...     

A study on the modeling and analysis of a helicopter’s occupant seat belt for crashworthiness

Abstrac  In this paper, a method of modeling a seat belt on a crew seat during a dynamic seat testing was studied. The body segments of the occupant were modeled with joints that consisted of various stiffness, damping, and friction. Three types of seat belt restraint systems were investigated and an analysis on the injury assessment of the helicopter’s crew under a drop impact was conducted. The effectiveness of the seat belt system for crashworthiness and safety was likewise evaluated. From the impact analysis results, it was determined that the head, neck, and spine of the crew body can be easily damaged in the vertical direction more than the longitudinal direction. Based on the verified model, the human body’s behavior was studied using three point restraint systems. The displacement and injury level of the 12-point restraint system was the smallest. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Young-Shin Lee received a B.S. degree in Mechanical Engi-neering from Younsei University, Korea in 1972. He received master and Ph.D. degree in Mechanical Engineering from Yonsei University, Korea in 1974 and 1980 respectively. He is currently professor and Dean of Industry Graduate School and Director of BK21 Mechatronics Group at Chungnam National University, Korea. Prof. Lee’s research interests are in area of impact mechanics, optimal design, biomechanical analysis and shell structure analysis. Jung-Hyun Lee received a B.S. degree in Mechanical Design Engineering from Chungnam Na-tional University, Korea in 2007. He received master degree in Mechanical Design Engineering from Chungnam National Uni-versity, Korea in 2009. He is currently researcher of Korea Aerospace Research Institute, Korea. Kyu-Hyun Han received a B.S. degree in Mechanical Design Engineering from Hanbat National University, Korea in 2002. He received master degree in Mechanical Design Engineering from Chungnam National University, Korea in 2004. He is currently researcher of Simuline Inc, Korea.