Steel frame optimal design using MHBMO algorithm

Various deterministic and stochastic algorithms have been used as optimization tools in different engineering problems over the last decade. In this regard, the Modified Honey Bee Mating Optimization (MHBMO) algorithm may be considered as a typical swarm-based approach for optimizing numerous problems in engineering fields. In this paper, a design procedure based on the MHBMO technique was developed for discrete optimization of frames consisting W-shapes. The objective function in this research is to obtain the minimum weight of frames subjected to both strength and displacement requirements imposed by the American Institute for Steel Construction (AISC) and Load Resistance Factor Design (LRFD). Several frame examples from the literature were examined to verify not only the suitability of the design procedure but also the robustness of the MHBMO algorithm for frame structure design. The optimum results obtained by the MHBMO algorithm performs the best in comparison with other available techniques in the literature for all three steel frames. In conclusion, the results shows that the MHBMO algorithm is a powerful and applicable optimization method for design of frames consisting W-shapes.     

Intelligent timetable evaluation using fuzzy AHP

There is a substantial body of empirical literature that establishes the benefits of customer satisfaction for enterprises. Among different available options to present our service, selecting the best choice in the customers’ eyes is a vital decision.Developing appropriate passenger train schedules is counted as one of the major managerial concerns in transportation environment. Although different algorithms have been developed to create predictive schedules for a fleet of passenger trains using different performance indicators, selecting the best one embraces some ambiguities and uncertainties. That is because a one-dimensional objective function may not be sufficient for responding customer concerns.The main objective of this paper is to propose an approach within the fuzzy AHP framework for tackling the complexity of multidimensional service evaluations, where “sum of weighted waiting times”, “average of unit waiting time” and “maximum ratio of waiting time to journey time” of a schedule are evaluated and the ultimate judgment on goodness of the schedule is made via the aggregation of the performance measures used. The study is based on the knowledge of certain managers and experts in IRC (Iran Railways Corporation) who are aware of available complexities in train scheduling and have been dealing with customers for several years.     

Analysis of an access node multiplexer in a system serving CBR and VBR traffic

This paper considers a multiplexer at the access node of a system serving both CBR and VBR services in a B-ISDN environment. The CBR traffic component represents fixed bit rate services in an ATM network. Such services need to be allocated a fixed number of time slots in each output frame. The VBR traffic here represents connectionless and connection oriented variable bit rate services that are loss sensitive but delay insensitive. A mathematical model is developed for such a system and performance parameters are evaluated. These results are verified by simulation.     

High-speed fiber-optic links for distribution of satellite traffic

Low-loss fiber-optic links are designed for distribution of data and the frequency reference in large-aperture phased-array antennas based on the transmit/receive-level data mixing architecture. In particular, design aspects of a fiber-optic link satisfying the distribution requirements of satellite data traffic are presented. The design is addressed in terms of reactively matched optical transmitter and receiver modules. Analog and digital characterization of a 50-m fiber-optic link realized using these modules indicates the applicability of this architecture as the only viable alternative for distribution of data signals inside a satellite at present. It is demonstrated that the design of a reactive matching modules enhances the link performance. A dynamic range of 88 dB/MHz was measured for analog data over 500-1000-MHz bandwidth     

Novel strategy for diameter-selective separation and functionalization of single-wall carbon nanotubes

The problem of separating single-wall carbon nanotubes (CNTs) by diameter and/or chirality is one of the greatest impediments toward the widespread application of these promising materials in nanoelectronics. In this paper, we describe a novel physical-chemical method for diameter-selective CNT separation that is both simple and effective and that allows up-scaling to large volumes at modest cost. Separation is based on size-selective noncovalent matching of an appropriate anchor molecule to the wall of the CNT, enabling suspension of the CNTs in solvents in which they would otherwise not be soluble. We demonstrate size-selective separation in the 1-2 nm diameter range using easily synthesized oligo-acene adducts as a diameter-selective molecular anchor. CNT field effect transistors fabricated from diameter-selected CNTs show markedly improved electrical properties as compared to nonselected CNTs.     

Splitting for strength: Manipulating polymerization reactor split ratios to control mechanical and rheological properties in bimodal polyethylene resins

This study integrates advanced mathematical modeling and experimental methodologies to investigate the simultaneous impact of modifications in the split ratio and molecular weight (MW) of chains on the rheological and mechanical properties of bimodal polyethylene (BiPE) resins. The outcomes underscored the viability of fine-tuning the molecular weight distribution (MWD) of a BiPE resin by augmenting the MW of high molecular weight (HMW) chains while simultaneously diminishing their proportion in the final alloy formulation. In addition, the experimental results illuminated the prospect of attaining a targeted melt flow index for the final polymers by elevating the MW of HMW chains alongside an increase in the proportion of low molecular weight chains. Significantly, these adjustments resulted in remarkable enhancements in the shear thinning index and strain hardening modulus of the fabricated resins.     

Improving quality of service in WiMAX communication at vehicular speeds: a new call admission control solution

Call admission control (CAC) scheme serves as a useful tool for the WiMAX technology, which ensures that resources are not overcommitted and thereby, all existing connections enjoy guaranteed quality of service (QoS). CAC schemes largely rely on readily available information like currently available resources and bandwidth demand of the new call while making an acceptance or rejection decision once a new request arrives. Since wireless channels are not as reliable as wired communication, CAC scheme in WiMAX communication faces a serious challenge of making a right estimate of the usable channel capacity (i.e., effective throughput capacity) while computing the available resources in various communication scenarios. Existing CAC schemes do not consider the impact of mobility at vehicular speeds when computing the usable link capacity and available resources. The main limitation of such CAC scheme is that when a mobile node moves at a slower speed and makes a connection request to the base station (BS), the BS evaluates the situation based on the currently available information. The BS in such cases, is short‐sighted and often overestimates the available resources as it completely ignores the scenario when the SS reaches its top speed within a very short time after a CAC decision is made, causing a significant drop in usable throughput. In this paper, we address this limitation of existing WiMAX CAC schemes and propose a new CAC scheme that estimates the usable link capacity for WiMAX communication at vehicular speeds and uses this information while making a CAC decision. We also present a CAC scheme that takes the speed distribution model of a mobile node into account during the CAC decision making process. Simulation results confirm that the proposed scheme achieves lower dropping rate and improved QoS compared to existing schemes. Copyright © 2011 John Wiley & Sons, Ltd.     

Indirect optical injection-locking of multiple X-band oscillators

Experimental results of indirect optical injection-locking of two X-band oscillators are presented. An S-band master source is used to lock both oscillators over 18 MHz using the laser diode nonlinearities. System FM noise degradation is 14 dB and the means to improve system performance are suggested.     

On an efficient multilevel inverter assembly: structural savings and design optimisations

This study puts forward an efficient unit cell to be taken in use in multilevel inverter assemblies. The proposed structure is in line with reductions in number of direct current (dc) voltage sources, insulated-gate bipolar transistors (IGBTs), gate driver circuits, installation area, and hence the implementation costs. Such structural savings do not sacrifice the technical performance of the proposed design wherein an increased number of output voltage levels is attained, interestingly. Targeting a techno-economic characteristic, the contemplated structure is included as the key unit of cascaded multilevel inverters. Such extensions require development of applicable design procedures. To this end, two efficient strategies are elaborated to determine the magnitudes of input dc voltage sources. As well, an optimisation process is developed to explore the optimal allocation of different parameters in overall performance of the proposed inverter. These parameters are investigated as the number of IGBTs, dc sources, diodes, and overall blocked voltage on switches. In the lights of these characteristics, a comprehensive analysis is established to compare the proposed design with the conventional and recently developed structures. Detailed simulation and experimental studies are conducted to assess the performance of the proposed design. The obtained results are discussed in depth.