Nested coloured timed Petri nets for production configuration of product families

Production configuration is as an effective technique to deal with product variety while maintaining production stability and efficiency. It involves a diverse set of process elements (e.g., machines, operations), a high variety of component parts and assemblies and many constraints arising from product and process variety. Production configuration entails the selection and subsequent arrangement of process elements into complete production processes and the final evaluation of configured multiple alternatives. To better understand production configuration and its implementation, we study the underlying logic for configuring production processes using a dynamic modelling and visualisation approach. This is accomplished by developing a new formalism of nested coloured timed Petri nets (PNs). In view of the inherent modelling difficulties, in the formalism three types of nets–process nets, assembly nets and manufacturing nets–together with a nested net system are defined. Using an industrial example of vibration motors, we show how the proposed formalism can be applied to specify production processes at different levels of abstraction to achieve production configuration.     

The designs of a scalable optical packet switching architecture

Abstract

This paper proposes a new switching architecture to be used in all optical packet switching networks. The proposed switch is derived from an original 2 × ?2 two‐stage multi‐buffer switched delay line based optical switching node, known as an M‐Quadro node. By incorporating bypass lines into the M‐Quadro architecture and employing a novel switch control strategy, the optical packet switching node can effectively resolve packet contentions, thus reducing the packet deflection probability substantially. Furthermore, we show that such architecture is scalable for a generic multiple stages optical packet switch with a larger number of input/output ports.     

Multiagent approach to solve project team work allocation problems

In today's fiercely competitive market, embedded software development teams are driven to do more with less: reduce time to market, costs and risk, while improving quality and predictability. There is also an increasing need to deliberately organise the teams that initially involves the division of the project into tasks; the selection of the right people; and the correct allocation of those tasks for the selected people. Team configuration process is typically performed by a project manager based on his/her past experience and the available (though frequently scarce, uncertain and dynamic) information about the cognitive, emotion and social characteristics of the potential team members. To support this decision-making process we propose the Fuzzy Belief-Desire-Intention architecture, a multiagent approach that given an initial team configuration and a set of tasks, simulates the most possible team performance. Its architecture bases are fuzzy set theory and fuzzy logic and it is implemented using Multiagent Systems technology in Java and Jadex. Tests have been carried out in which the architecture has been applied to a set of tasks involving the embedded software development. The result predicted by our architecture with the performance of an engineering team in a real industrial project is made.     

The impact of maintainability on the manufacturing system architecture

The rapid development of big data technologies can improve the maintainability of machines and equipment in manufacturing systems, which could impact the selection of the optimal system architecture. In this paper, two typical architectures for large manufacturing systems ? serial lines in parallel and reconfigurable manufacturing systems ? are considered, and their productivities are compared. A decision locus is calculated that divides the configuration space into two areas; in each area, one of the architectures is the preferred one. It is also investigated how the locus is affected by different parameters, such as system size, buffer capacity and machine or gantry maintainability. The analysis provides valuable managerial insights for designing the architecture of large manufacturing systems.     

Extending the bandwidth of magnetic tunnel junction sensors by abuffer amplifier

A simple buffer amplifier, consisting of a transistor in an emitter-follower configuration, is proposed to extend the bandwidth of magnetic tunnel junction read sensors. To maximize the bandwidth improvement, the buffer should be used on the slider or on the suspension as near to the slider as possible. The channel front-end (sensor, buffer, interconnect, and preamp) bandwidth is still somewhat limited by the RC product of the sensor resistance and shunt capacitance. However, the buffer can reduce the shunt capacitance to subpicofarad levels, allowing for bandwidths near 1 GHz. Merging the buffer with an interconnect and preamp gives a low-frequency signal-to-noise ratio (SNR) reduction at the preamp input of 0.1 dB and an SNR improvement of 5 to 10 dB over a no-buffer configuration for frequencies between 100 MHz and 1 GHz     

Optimizing the configuration of a keyboard assembly cell

This paper describes how the configuration of a three station serial keyboard assembly cell can be optimized using a combination of discrete event simulation modelling and experimental design techniques. The investigation is based on a discrete event simulation model written in ARENATM. Optimum buffer sizes and number of pallets are initially determined by factorial design to identify the most significant factors affecting the throughput of the cell. Response surface methodology is then used to determine the optimal settings. The paper illustrates the methodology of using a combination of discrete event simulation modelling and experimental design techniques to design the optimal configuration of serial assembly cells and similar configurations in the manufacturing environment.     

Queuing network analysis approach for estimating the sizes of the time buffers in Theory of Constraints-controlled production systems

The present paper describes an open queuing network modelling approach to estimate the size of the time buffers in production systems controlled by the Theory of Constraints philosophy. Workstations in the production network are modelled as GI/G/m queues and a queuing network analysis multiproduct open queuing network modelling method is used to estimate the average flow time to the time buffer origin and the standard deviation of flow time. Using these two values together with an assumption of normally distributed flow times and a chosen service level, the final time buffer length is determined. The queuing network analysis method has been modified to enable the modelling of production networks with machine failures, batch service and varying transfer batch sizes. The modelling approach has also been incorporated in a computerized tool that uses product specific information such as bill-of-material and routing data, and production network information such as resource data to estimate the sizes and location of the necessary time buffers for each product. Simulation experiments indicate that the procedure is sufficiently accurate to provide an initial quick estimate of the needed time buffer lengths at the design stage of the line.     

Optimal weighed Holoentropy for video compression: an advanced HEVC

ABSTRACT

In recent times, the applications of multimedia are rising in a greedy mode and hence the amount of video transactions is also increasing exponentially. This has shouted great demands on effective models on video encoding and also for reducing the transmission channel congestion. This research work introduces a managing technique termed weighted encoding for High-Efficiency Video Coding (HEVC). HEVC, also termed as MPEG-H Part 2 and H.265 is a video compression standard that is widely utilized AVC (H.264 or MPEG-4 Part 10). When compared to AVC, HEVC grants double the ratio of data compression at a similar level of quality of the video or considerably enhanced video quality at a similar bit rate. This work intends to optimize the weight that adopted in HEVC for encoding. For this, this paper proposes a new Iterative based propagation update in the water wave Optimization Algorithm (IPU-WWO), which is the improved form of Water wave Optimization (WWO). The performance of proposed IPU-WWO is compared over other conventional methods like Artificial Bee Colony (ABC), Firefly (FF), Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) with respect to Peak Signal to Noise Ratio (PSNR). By doing the encoding process, it minimizes the video size with perceptually better quality video or PSNR.     

Quantum-chemical simulation of Al- and Sc-bound hole polarons in BaTiO3 crystal

Quantum-chemical modelling of impurity-bound hole polarons in BaTiO₃ crystal was carried out employing the semi-empirical method of intermediate neglect of differential overlap (INDO) modified for crystals. Two-site hole has been found to be the most common configuration in the BaTiO₃ crystal doped with Al or Sc atoms. The automated geometry optimisation was carried out to obtain the polaron spatial configuration and atomic displacements in the defective region. The ΔSCF calculated absorption energy for the aluminium-bound polaron was found to be equal to 0.27 eV and the corresponding absorption energies for scandium-bound polaron were computed to be 1.92 and 0.62 eV.     

A framework for characterising energy consumption of machining manufacturing systems

Energy consumption in machining manufacturing systems is increasingly of interest due to concern for global climate change and manufacturing sustainability. To utilise energy more effectively, it is paramount to understand and characterise the energy consumption of machining manufacturing systems. To this end, a framework to analyse energy consumption characteristics in machining manufacturing systems from a holistic point of view is proposed in this paper. Taking into account the complexity of energy consumption in machining manufacturing systems, energy flow is described in terms of three layers of machining manufacturing systems including machine tool layer, task layer and auxiliary production layer. Furthermore, the energy consumption of machining manufacturing systems is modelled in the spatial and temporal dimensions, respectively, in order to quantitatively characterise the energy flow. The application of the proposed modelling framework is demonstrated by employing a comprehensive analysis of energy consumption for a real-world machining workshop. The characteristics of energy consumption for machine tool layer, task layer and auxiliary production layer are, respectively, obtained using quantitative models in the spatial and temporal dimensions, which provides a valuable insight into energy consumption to support the exploration of energy-saving potentials for the machining manufacturing systems.     

Analysis and optimisation of a mixed fluid cascade (MFC) process

A mixed fluid cascade (MFC) process that comprises three refrigeration cycles has great capacity for large-scale LNG production, which consumes a great amount of energy. Therefore, any performance enhancement of the liquefaction process will significantly reduce the energy consumption. The MFC process is simulated and analysed by use of proprietary software, Aspen HYSYS. The effect of feed gas pressure, LNG storage pressure, water-cooler outlet temperature, different pre-cooling regimes, liquefaction, and sub-cooling refrigerant composition on MFC performance are investigated and presented. The characteristics of its excellent numerical calculation ability and the user-friendly interface of MATLAB™ and powerful thermo-physical property package of Aspen HYSYS are combined. A genetic algorithm is then invoked to optimise the MFC process globally. After optimisation, the unit power consumption can be reduced to 4.655 kW h/kmol, or 4.366 kW h/kmol on condition that the compressor adiabatic efficiency is 80%, or 85%, respectively. Additionally, to improve the process further, with regards its thermodynamic efficiency, configuration optimisation is conducted for the MFC process and several configurations are established. By analysing heat transfer and thermodynamic performances, the configuration entailing a pre-cooling cycle with three pressure levels, liquefaction, and a sub-cooling cycle with one pressure level is identified as the most efficient and thus optimal: its unit power consumption is 4.205 kW h/kmol. Additionally, the mechanism responsible for the weak performance of the suggested liquefaction cycle configuration lies in the unbalanced distribution of cold energy in the liquefaction temperature range.     

Self-localizing sensor network architectures

This paper faces the problem of configuration and communication in a distributed radio sensor network, composed of identical sensors randomly placed in a two- or three-dimensional space. The reference is provided by objects with known positions called masters. Two architectures are shown; the first uses one master, the second three masters. The one master architecture makes it possible to identify and locate all the sensors in space and to calculate for each of them the lowest energy transmission path to reach the master. The three-master architecture locates, by triangulation, each sensor when a transmission of information occurs and cannot optimize energy consumption during sensor communication. On the other hand, it is also able to localize moving sensors or to handle dynamically changing sensor topologies. The results show that the three-master architecture is faster, but it implies an energy waste of about 30 times greater than the one-master architecture for a constellation of 50 sensors.     

Calcium carbide synthesis using a solar furnace

Calcium carbide can be synthesized from limestone and petroleum coke in a furnace employing direct heating by solar radiation. The proposed technological process, based on the firing of an initial limestone-coke mixture by exposure to concentrated solar radiation at a power density of about 110 W/cm², is ecologically safe and effective, requiring no significant electric energy consumption.     

Nature‐Inspired Lightweight Cellular Co‐Continuous Composites with Architected Periodic Gyroidal Structures

Shell‐core cellular composites are a unique class of cellular materials, where the base constituent is made of a composite material such that the best distinctive physical and/or mechanical properties of each phase of the composite are employed. In this work, the authors demonstrate the additive manufacturing of a nature inspired cellular three‐dimensional (3D), periodic, co‐continuous, and complex composite materials made of a hard‐shell and soft‐core system. The architecture of these composites is based on the Schoen's single Gyroidal triply periodic minimal surface. Results of mechanical testing show the possibility of having a wide range of mechanical properties by tuning the composition, volume fraction of core, shell thickness, and internal architecture of the cellular composites. Moreover, a change in deformation and failure mechanism is observed when employing a shell‐core composite system, as compared to the pure stiff polymeric standalone cellular material. This shell‐core configuration and Gyroidal topology allowed for accessing toughness values that are not realized by the constituent materials independently, showing the suitability of this cellular composite for mechanical energy absorption applications.

     

Modelling a maintenance management framework based on PAS 55 standard

This article shows the process of modelling a reference maintenance management framework (MMF) that represents the general requirements of the asset management specification PAS 55. The modelled MMF is expressed using the standardized and publicly available Business Process Modelling (BPM) languages UML 2.1 (Unified Modelling Language) and BPMN 1.0 (BPM Notation). The features of these notations allow to easily integrate the modelled processes into the general information system of an organization and to create a flexible structure that can be quickly and even automatically adapted to new necessities. This article presents a brief review about the usage of UML in maintenance projects, general characteristics of PAS 55, modelling concepts and their applications in the project of modelling the MMF. The arguments underlying the methodology and the choice of UML and BPMN are exposed. The general architecture of the suggested MMF is described and modelled through diagrams elucidating the general operation of PAS 55. From this development is appreciated the operation structure of a software tool that can incorporate MIMOSA standards and that can be made suitable for e‐maintenance functions, as an alternative to the commercial systems. Finally, some conclusions about the modelled framework are presented. Copyright © 2010 John Wiley & Sons, Ltd.     

An algorithm analog-to-digital converter using unity-gain buffers

An algorithmic stage for bipolar 1-b analog-to-digital (A/D) conversion using a unity-gain buffer is proposed. Cyclic and pipeline A/D converter architectures using this stage iteratively or in cascade are also described. Error analysis and SPICE simulations show that a conversion accuracy higher than 8-b and a conversion rate up to 10 Mb/s are attainable with presently available 3-μm CMOS technologies. Video frequency operation is also possible with finer linewidths. The component requirement is minimum, and thus it is best suited for an analog interface in application-specific integrated circuits (ASIC). A prototype cyclid A/D converter built using discrete components confirms the principles of operation     

Extension of Thru de-embedding technique for asymmetrical and differential devices

Accurate radiofrequency (RF) characterisation of on-chip or on-board devices often requires de-embedding to account for parallel and serial parasitics associated with bonding pads and interconnects. It is usually performed by well-known techniques such as Open-Short, Pad-Open-Short or Thru. However, these approaches or alternative techniques employing more standards assume a specific lumped-element model of bonding structures. This reduces de-embedding accuracy at higher frequencies. The Thru de-embedding technique is analysed in this paper and it is shown that under certain conditions de-embedding can be performed without modelling of the internal structure of the thru standard. The possibility to obtain the parameters of an error network by using a single test structure reduces significantly the costs of manufacturing standards and saves the measurement time. Further, an extension of the Thru technique is introduced. It is shown that at the expense of one more measurement, it is possible to characterise the system without additional assumptions. The presented method can be applied, for example, for de-embedding of fixtures with different connectors on either side. Additionally, the extension of Thru technique for de-embedding of differential devices is proposed. The paper verifies the extension for asymmetrical structures by simulation performed using Sonnet electromagnetic field solver in the frequency range 1-40-GHz. Finally, the extension for differential devices is verified by measurement in the frequency range 1-20-GHz and comparison of the results with Open-Short de-embedding technique.     

酒品包装生产中动态缓冲管理机制

考虑存在资源约束的流线式酒品包装生产车间,为了减少企业生产成本,提出了一种以控制在制品(WIP)库存为主要参考指标的动态缓冲管理方法。本方法通过实时监控缓冲区的WIP库存,根据在监控窗口中缓冲区出现WIP库存由高于安全下限变化到低于安全下限的频率以及随后是否出现WIP库存耗尽的情况,对库存安全上下限进行动态调节进而实现对缓冲的动态管理。为了验证方法的有效性,安排了3组不同的仿真实验。实验结果表明：与传统的缓冲管理策略相比,基于动态缓冲管理策略的控制方法在WIP库存控制方面存在22%以上的优势,采用该方法可以有效的控制生产系统中的在制品库存。