Hybrid Petri-nets for modelling and performance evaluation of supply chains

Modelling and analysis of complex and co-ordinated supply chains is a crucial task due to its inherent complexity and uncertainty. Therefore, the current research direction is to devise an efficient modelling technique that maps the dynamics of a real life supply chain and assists industrial practitioners in evaluating and comparing their network with other competing networks. Here an effective modelling technique, the hybrid Petri-net, is proposed to efficiently handle the dynamic behaviour of the supply chain. This modelling methodology embeds two enticing features, i.e. cost and batch sizes, in deterministic and stochastic Petri-net for the modelling and performance evaluation of supply chain networks. The model is subsequently used for risk management to investigate the issues of supply chain vulnerability and risk that has become a major research subject in recent years. In the test bed, a simple productive supply chain and an industrial supply chain are modelled with fundamental inventory replenishment policy. Subsequently, its performance is evaluated along with the identification and assessment of risk factors using analytical and simulation techniques respectively. Thus, this paper presents a complete package for industrial practitioners to model, evaluate performance and manage risky events in a supply chain.     

A Petri Net based approach to determine the disassembly strategy of a product

In order to protect the environment and regain value added to products, a process known as disassembly has come into the limelight. This process is to be applied to reuse abandoned goods and materials. Manufacturers are being forced to establish disassembly plants and to develop their products' designs so as to maintain the government's dictate to dispose off their products in an environmentally responsible manner. This research presents a cost-based heuristic analysis for a circuit board assembly. Various components of the product and their assembly relationships are represented by a Petri Net diagram. Firing the transitions of the disassembly Petri Net is integrated with cost-based indices to develop an effective disassembly strategy. The methodology discussed here simplifies the decisionmaking process involved in disassembly planning. A comprehensive disassembly process planning system is proposed here and is exemplified by a case study of circuit board assembly.     

Schrifttumsberichte

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Schrifttumsberichte

Ohne Zusammenfassung     

Mechanische Holzverwertung,Holzindustrie

Ohne Zusammenfassung     

Polarographic Study of Thio-acetic Acid

The polarographic behaviour of thio-acetic acid (RSH) at dropping mercury electrode (d.m.e.) has been investigated in presence of KNO₃ in the pH range 2–10.5 at 30.0 ± 0.2°C in 50% alcoholic medium at 0.2 M ionic strength. Well defined anodic waves were obtained at all pH values in the concentration range studied. At pH < 2.2 and > 10.5 ill defined anodic waves were obtained. The effect of pH, concentration of RSH, temperature, drop time and alcohol on the wave characteristic and the mechanism of the reaction occurring at the surface of the mercury drop have been studied in detail. A small prewave was also observed at pH 9.1 and 10.5, which has been assigned adsorption characteristics. The reversibility of the reaction mechanism was confirmed by a number of methods. The wave is diffusion controlled and reversible involving one electron transfer process: Mathematical and experimental evidence shows that the anodic wave of RSH at. d.m.e. does not correspond to formation of (RSSR) but to a mercury compound RSHg according to the above equation. The diffusion coefficient and temperature coefficient for (30–45°C) of i_d at pH 4.0 and 9.1 have been found to be 1.698; 1.965 × 10⁻⁶ cm²/sec and 1.08%; 1.20% per degree respectively. The dissociation constant pKa was found to be 4.25 by the plot of E_1/2 vs. pH. The linearity of i_d with RSH concentrations provides a rapid and precise method for the determination of RSH down to 0.2 mM.     

Oxidation behavior of Mo-Si-B-(X) alloys: Macro- and microalloying (X= Cr,Zr, La<Subscript>2</Subscript>O<Subscript>3</Subscript>)

High melting Mo-Si-B based alloys exhibit good mechanical properties and oxidation resistance at very high temperatures. The alloy composition Mo-9Si-8B (at.%) shows excellent oxidation behavior between 900°C–1,300°C as a consequence of protective silica scale formation. Below 900°C, a protective oxide layer does not form as a consequence of simultaneous and competitive Mo- and Si-oxide formation. Macro- and microalloying strategies as well as pre-treatment prior to oxidation in air were examined in order to determine their impact on the oxidation performance. Alloying with Cr is a suitable means for protective Cr-oxide scale formation at intermediate temperatures; adding small amounts of reactive elements was found to have a strong impact on the silica scale forming ability. Furthermore, the oxidation behavior can be controlled and enhanced by selective oxidation in oxygen-deficient atmospheres prior to exposure to air.     

Crosstalk reduction in mixed-signal 3-D integrated circuits with interdevice layer ground planes

We show nearly 8 dB of crosstalk reduction using ground planes between active device layers in three-dimensional (3-D) integrated circuits. Our experimental work utilizes two planes of MOS transistors with tungsten or polysilicon ground planes designed to attenuate crosstalk. Theoretical simulations, using an electromagnetic solver, and the experimental results are consistent with analytical results. The key result verified is that a ground plane, whose footprint shadows the device area, is sufficiently large for effective attenuation. The interdevice layer ground plane provides an effective means to achieve crosstalk reduction in 3-D mixed-signal/RF integration because of simple fabrication and high coupling isolation.     

Energy-optimized cluster head selection based on enhanced remora optimization algorithm in underwater wireless sensor network

With the technological advancements, wireless sensor network (WSN) has played an impeccable role in monitoring the underwater applications. Underwater WSN (UWSN) is supported by WSN but subjected to data dissemination in an acoustic medium. Due to challenging conditions in underwater scenario, the limited battery resources of these sensor nodes stem to a crucial research problem that needs to address the energy-efficient routing in UWSN. In this research work, we intend to propose an energy-optimized cluster head (CH) selection based on enhanced remora optimization algorithm (ECERO) in UWSN. Since CH devours the maximum energy among the nodes, we perform selection of CH based on EROA while considering energy, Euclidean distance from sink, node density, network's average energy, acoustic path loss model and lastly, the adaptive quantity of CHs in the network. Further, to reduce the load on CH node, we introduce the concept of sleep scheduling among the closely located cluster nodes. The proposed work improves the performance of recently proposed EOCSR algorithm by great magnitude which claims to mitigate hot-spot problem, but EOCSR still suffers from the same due to relaying a large magnitude of data.     

Unified BER and optimum threshold analysis of binary modulations in simple and cascaded Rayleigh fading channels with switched combining

Following a unified analytical framework, the bit error rate (BER) of several coherent and non‐coherent binary modulation schemes is derived for a switched diversity system. The two variants of switched combining that have been investigated are switch and stay combining and switch and examine combining. For channel modelling, at first a simple slow flat fading channel is assumed, where the amplitude attenuation obeys the Rayleigh distribution. Later the BER calculations are repeated for cascaded Rayleigh fading channel case. Rayleigh fading is the most popular model for electromagnetic signal propagation in wireless media when both or either of the transmitter/receiver is fixed. On the other hand, when both the transmitter and the receiver are mobile, a cascaded (or double) Rayleigh fading model is better suited. The applicability of these two models, namely simple and cascaded Rayleigh model, has been indicated by several theoretical studies and their suitability is established by various field measurements. In our paper, simple closed‐form BER expressions as a function of switching threshold have been found and optimum switching thresholds have been computed for both these models as well as for both types of diversity combining described earlier. The results presented in this paper can be very useful for communication system designers to analyze link quality of switched diversity assisted systems in various wireless environments. Copyright © 2010 John Wiley & Sons, Ltd.