Using computational intelligence for large scale air route networks design

Due to the rapid development of air transportation, Air Route Networks (ARNs) need to be carefully designed to improve both efficiency and safety of air traffic service. The Crossing Waypoints Location Problem (CWLP) plays a crucial role in the design of an ARN. This paper investigates this problem in the context of designing the national ARN of China. Instead of adopting the single-objective formulation established in previous research, we propose to formulate CWLP as a bi-objective optimization problem. An algorithm named Memetic Algorithm with Pull–Push operator (MAPP) is proposed to tackle it. MAPP employs the Pull–Push operator, which is specifically designed for CWLP, for local search and the Comprehensive Learning Particle Swarm Optimizer for global search. Empirical studies using real data of the current national ARN of China showed that MAPP outperformed an existing approach to CWLP as well as three well-known Multi-Objective Evolutionary Algorithms (MOEAs). Moreover, MAPP not only managed to reduce the cost of the current ARN, but also improved the airspace safety. Hence, it has been implemented as a module in the software that is currently used for ARN planning in China. The data used in our experimental studies have been made available online and can be used as a benchmark problem for research on both ARN design and evolutionary multi-objective optimization.     

Optimizing wheel profiles and suspensions for railway vehicles operating on specific lines to reduce wheel wear: a case study

Multibody System Dynamics - The selection of a wheel profile is a topic of great interest as it can affect running performances and wheel wear, which needs to be determined based on the actual...     

Surface green function matching for a three-dimensional nonlocal continuum

With a view toward helping to bridge the gap, from the continuum side, between discrete and continuum models of crystalline, elastic solids, explicit results are presented for nonlocal stress tensors that describe exactly some lattice dynamical models that have been widely used in the literature for cubic lattices. The surface Green function matching (SGFM) method, which has been used successfully for a variety of surface problems, is then extended, within a continuum approach, to a nonlocal continuum that models a three-dimensional discrete lattice. The practical use of the method is demonstrated by performing a fairly complete analytical study of the vibrational surface modes of the SCC semi-infinite medium. Some results are presented for the [100] direction of the (001) surface of the SCC lattice.     

A foundation for a knowledge-base computer integrated manufacturing system

The true potential of a CIM system cannot as yet be fully realised. A further requirement is for a device which can extract manufacturing information from the outset. The main aim of the research described in this paper is to develop a knowledge-base system for extracting such information and to promote a coming together of design and manufacture. The major goal must be to enable industry to manufacture without manual intervention. A prototype knowledge-base system called HOLDEX described in this paper is an implementation that relies on combining the advantages of existing technology such as AI, CAD representation schemes, advanced manufacturing systems, man-machine interface and most importantly the encapsulated knowledge of a manufacturing engineer. The aim of the prototype system is to encourage a workpiece designer towards manufacturing standards and to assist him in the use of a general purpose CAD package. One benefit to be obtained from providing such assistance is to facilitate the ease of extracting manufacturing information. The scope of the extracted information includes the detailed specification of a set of cutting tools, the recognition of a list of required activities prior to a machining operation, the recommendation of the appropriate machine tool and the automated design of fixtures.     

OPQL: Querying scientific workflow provenance at the graph level

Provenance has become increasingly important in scientific workflows to understand, verify, and reproduce the result of scientific data analysis. Most existing systems store provenance data in provenance stores with proprietary provenance data models and conduct query processing over the physical provenance storages using query languages, such as SQL, SPARQL, and XQuery, which are closely coupled to the underlying storage strategies. Querying provenance at such low level leads to poor usability of the system: a user needs to know the underlying schema to formulate queries; if the schema changes, queries need to be reformulated; and queries formulated for one system will not run in another system. In this paper, we present OPQL, a provenance query language that enables the querying of provenance directly at the graph level. An OPQL query takes a provenance graph as input and produces another provenance graph as output. Therefore, OPQL queries are not tightly coupled to the underlying provenance storage strategies. Our main contributions are: (i) we design OPQL, including six types of graph patterns, a provenance graph algebra, and OPQL syntax and semantics, that supports querying provenance at the graph level; (ii) we implement OPQL using a Web service via our OPMProv system; therefore, users can invoke the Web service to execute OPQL queries in a provenance browser, called OPMProVis. The result of OPQL queries is displayed as a provenance graph in OPMProVis. An experimental study is conducted to evaluate the feasibility and performance of OPMProv on OPQL provenance querying.     

AES for multiscale localization modeling in granular media

This work presents a multiscale strong discontinuity approach to tackle key challenges in modeling localization behavior in granular media: accommodation of discontinuities in the kinematic fields, and direct linkage to the underlying grain-scale information. Assumed enhanced strain (AES) concepts are borrowed to enhance elements for post-localization analysis, but are reformulated within a recently-proposed hierarchical multiscale computational framework. Unlike classical AES methods, where material properties are usually constants or assumed to evolve with some arbitrary phenomenological laws, this framework provides a bridge to extract evolutions of key material parameters, such as friction and dilatancy, based on grain scale computational or experimental data. More importantly, the phenomenological softening modulus typically used in AES methods is no longer required. Numerical examples of plane strain compression tests are presented to illustrate the applicability of this method and to analyze its numerical performance.     

Comparative studies of normally-off Al0.26Ga0.74N/AlN/GaN/Si high electron mobility transistors with different gate structures

Systematic designs to achieve normally-off operation and improved device performance for Al_0.26Ga_0.74N/AlN/GaN high electron mobility transistors (HEMTs) grown on a Si substrate are investigated in this work. The step-by-step approach includes: (1) devising a thin AlGaN/AlN composite barrier, (2) introducing fluoride ions within the active region by using CF₄ plasma treatment, (3) growing the Al₂O₃ oxide passivation layers within gate-drain/source regions by using a cost-effective ozone water oxidization technique, and (4) integrating a metal-oxide-semiconductor gate (MOS-gate) design with high-k Al₂O₃ gate dielectric. Devices with four different evolutionary gate structures have been compared and studied. Variations of threshold voltage (V_th), Hooge coefficients (α_H), maximum drain-source current density (I_{DS, max}), maximum extrinsic transconductance (g_{m, max}), gate-voltage swing (GVS) linearity, two-terminal gate-drain breakdown/turn-on voltages (BV_GD/V_on), on/off current ratio (I_on/I_off), and high-temperature characteristics up to 450 K are also investigated.     

Going from green to white color electroluminescence through a nanoscale complex of Zinc (II)

In this paper, we report application of four novel Nano Zinc (II) complexes as the emitter dyes in organic light emitting diodes (OLEDs). The Nano Zinc (II) complexes emission, particularly its absorption, fluorescence spectra and quantum yield, tuned by varying sizes which affects environments of the Zinc (II) ion. OLED Devices with Nano Zinc (II) complexes were fabricated, giving rise to devices with peak emission ranging from 498 to 541 nm. Here, we have successfully employed sonoelectrochemical method for fabricating white OLEDs. The white emission ascribed to the exciton emission in Nano Zinc (II) complex emitter and from exciplex formation at the interface of PVK/Nano Zinc (II) complex. The experimental results demonstrate that this approach is ideal for color tuning of single and multilayer conducting semiconducting thin films used in the fabrication of organic electronic devices such as OLEDs.     

Exploring the effects of optically generated dipoles on organic photodetector infrared detection

Sensing from the ultraviolet–visible to the infrared is bringing more attentions recently. Here, we report the effects of optically generated dipoles within PTB7 layer on photocurrent and photoresponse in single wall carbon nanotube-based photodetectors. The observations in this work provide the direct evidence that optically generated dipoles within the PTB7 layer can be aligned by a built-in field, and then consequently affect dissociation of photo-excited electron-hole pairs in single wall carbon nanotubes. Additionally, PL (photoluminescence) of single wall carbon nanotubes can be appreciably quenched by optically generated dipoles in PTB7 layer. This quenched PL provides further information to back up photodetectivity increasing through dipoles alignment in PTB7 layer.     

Role of dual SiOx: H based buffer at the p/i interface on the performance of single junction microcrystalline solar cells

In p-i-n structure a-Si solar cell a buffer layer with proper characteristics plays important role in improving the p/i interface of the cell, reducing mismatch of band gaps and number of recombination centres. However for p-i-n structure microcrystalline ( µc-Si: H) cell which has much less light induced degradation than a-Si:H cell, not much work has been done on development of proper buffer layer and its application to µc-Si:H cell. In this paper we have reported the development of two intrinsic oxide based microcrystalline layer having different characteristics for use as buffer layers at the p/i interface of µc-Si:H cell. Previously SiO_x:H buffer layer has been used at the p/i interface which showed positive effects. To explore the possibility of improving the performance of p-i-n structure µc-Si:H cell further we have thought it interesting to use two buffer layers with different characteristics at the p/i interface. The two buffer layers have been characterized in detail and applied at the p/i interface of the µc-Si:H cell with positive effects on all the PV parameters mainly improves the open circuit voltage (V_oc) and enhances short circuit current (I_sc). The maximum initial efficiency obtained is 8.97% with dual buffer which is 6.7% higher than that obtained by using conventional single buffer layer at the p/i interface. Stabilized efficiency of the cell with dual buffer is found to be ~9.5% higher than that with single buffer after 600 h of light soakings.