A more realistic approach for airport ground movement optimisation with stand holding

In addition to having to handle constantly increasing numbers of aircraft, modern airports also have to address a wide range of environmental regulations and requirements. As airports work closer and closer to their maximal possible capacity, the operations problems that need to be solved become more and more complex. This increasing level of complexity leads to a situation where the introduction of advanced decision support systems becomes more and more attractive. Such systems have the potential to improve efficient airside operations and to mitigate against the environmental impact of those operations. This paper addresses the problem of moving aircraft from one location within an airport to another as efficiently as possible in terms of time and fuel spent. The problem is often called the ground movement problem and the movements are usually from gate/stands to a runway or vice-versa. We introduce a new sequential graph based algorithm to address this problem. This approach has several advantages over previous approaches. It increases the realism of the modelling and it draws upon a recent methodology to more accurately estimate taxi times. The algorithm aims to absorb as much waiting time for delay as possible at the stand (with engines off) rather than out on the taxiways (with engines running). The impact of successfully achieving this aim is to reduce the environmental pollution. This approach has been tested using data from a European hub airport and it has demonstrated very promising results. We compare the performance of the algorithm against a lower bound on the taxi time and the limits to the amount of waiting time that can be absorbed at stand.     

SURFACE WAVES IN A HEAT-CONDUCTING ELASTIC BODY: CORRECTION AND EXTENSION OF A PAPER OF CHADWICK AND WINDLE

In 1964 Chadwick and Windle published a detailed investigation of the secular equation governing the propagation of surface waves in a semi-infinite,isotropic, heat-conducting elastic body the surface of which is traction-free and either at constant uniform temperature or thermally insulated. The purpose of the present paper is first to remedy a defect in the work of Chadwick and Windle and then to extend the scope of their analysis by allowing the transmitting body to exchange heat with a constant-temperature environment. The defect arises from the insufficiency of the criteria used to decide whether or not a branch of the algebraic function defined by the rationalized secular equation represents a surface wave. When it is corrected the non-uniqueness of the surface-wave solutions found by Chadwick and Windle is removed and there exists precisely one quasi-elastic surface wave for all frequencies and for all values of the heat-transfer coefficient appearing in the thermal boundary condition, including the extremes considered in the original study.     

High cocoa polyphenol rich chocolate may reduce the burden of the symptoms in chronic fatigue syndrome

Background  

Chocolate is rich in flavonoids that have been shown to be of benefit in disparate conditions including cardiovascular disease and cancer. The effect of polyphenol rich chocolate in subjects with chronic fatigue syndrome (CFS) has not been studied previously.     

A fast current preamplifier for silicon detectors

A circuit of a fast current preamplifier for silicon detectors is designed. The main purpose of the preamplifier is to record signals from silicon detectors, which repeat the detector current shape. The preamplifier noise is 0.43 nV/Hz1/2.     

Analysis of irregular three-dimensional packing problems in additive manufacturing: a new taxonomy and dataset

With most Additive Manufacturing (AM) technology variants, build processes take place inside an internal enclosed build container, referred to as a ‘build volume’. It has been demonstrated that the effectiveness with which this volume is filled with product geometries forms an important determinant of overall process efficiency in AM. For effective operations management, it is important to understand not only the problem faced, but also which methods have proved effective (or ineffective) for problems with these characteristics in the past. This research aims to facilitate this increased understanding. The build volume packing task can be formulated as a three-dimensional irregular packing (3DIP) problem, which is a combinatorial optimisation problem requiring the configuration of a set of arbitrary volumetric items. This paper reviews existing general cutting and packing taxonomies and provides a new specification which is more appropriate for classifying the problems encountered in AM. This comprises a clear-cut problem definition, a set of precise categorisation criteria for objectives and problem instances, and a simple notation. Furthermore, the paper establishes an improved terminology with terms that are familiar to, but not limited to, researchers and practitioners in the field of AM. Finally, this paper describes a new dataset to be used in the evaluation of existing and proposed computational solution methods for 3DIP problems encountered in AM and discusses the importance of this research for further underpinning work.     

On the performance of a hybrid frequency and phase shift keyingmodulation technique

The performance of a hybrid modulation technique derived from binary frequency shift keying is presented. In the hybrid scheme, each frequency is allowed to be phase modulated with any of p discrete, equally spaced phase shifts. The spectral separation between frequencies is chosen to make the carriers orthogonal, thus generating a multidimensional modulation scheme. The performance of complete and expurgated phase codes is examined for the Gaussian and Rayleigh fading channels, and their spectral characteristics are determined