James Rowland Suckling

Slow waves caused by cuts perpendicular to a single subwavelength slit in metal

Resonant transmission of microwaves through a subwavelength slit in a thick metal plate, into which subwavelength cuts have been made, is explored. Two orientations of the cuts, parallel and perpendicular to the long axis of the slit, are examined. The results show that the slits act as though filled with a medium with anisotropic effective relative permeability which at low mode numbers has the two values ~(1, 9.1), increasing to ~(1, 14.4) for higher mode numbers.

Resonant transmission of microwaves through a finite length subwavelength metallic slit

The resonant transmission of microwaves polarized perpendicular to a single subwavelength slit of finite length is presented in detail. It is shown that the resonant frequency rises monotonically as slit length is reduced. Increasing confinement of the resonant fields within the slit is shown to cause the frequency rise. Angle dependence of the transmission is also presented. The results show clearly Fabry-Perot-like standing waves in the direction of propagation with waveguide mode behaviour in the orthogonal direction.

Resonant transmission of microwaves through a hexagonal array of holes in a thin metal layer

Resonant transmission of microwaves through a hexagonal array of holes in a very thin aluminium layer is studied. The array of holes, with diameter much less than the incident wavelength, leads to a strong transmission peak at a frequency just lower than the diffraction limit of the array. The results are well-modelled using a finite element package. The effect of metal depth on transmission intensity and the maximum efficiency of the hole array is also explored. Further experimental data are presented for the transmission of microwaves as a function of angle of incidence. It is shown that strong transmission occurs at frequencies just lower than the diffraction edges of the array. Incidentally, it is also shown that less than 0.01% of normally incident microwave radiation is transmitted through a continuous metal layer of thickness only 40% of the skin depth.

Integrating Environmental and Social Life Cycle Assessment: Asking the Right Question

Mobile phones offer many potential social benefits throughout their lifetime, but this life is often much shorter than design intent. Reuse of the phone in a developing country allows these social benefits to be fully realized. Unfortunately, under the current state of development of recycling infrastructure, recovery rates of phones after reuse are very low in those markets, which may lead to an environmental burden due to loss of materials to landfill. In order to recover those materials most effectively, recycling in developed countries may be the best option, but at a cost of the ability to reuse the phones. The issues facing integration of social and environmental concerns into a single life cycle assessment and resulting challenges of identifying the disposal option with the most sustainable outcome are explored using mobile phones as a case study. These include obtaining sufficient geographical and temporal detail of the end of life options, the collation and analysis of the large amounts of data generated and the weighting of the disparate environmental and social impact categories. The numerous challenges may mount up to make performing life cycle assessment of mobile phones unwieldy. Instead of trying to encompass every aspect in full, it is proposed that focus is given to answering a question which takes into account the resources available: it is important to ask the question which has the best chance of being answered.

Engaging stakeholders in research to address water-energy-food (WEF) nexus challenges

The water–energy–food (WEF) nexus has become a popular, and potentially powerful, frame through which to analyse interactions and interdependencies between these three systems. Though the case for transdisciplinary research in this space has been made, the extent of stakeholder engagement in research remains limited with stakeholders most commonly incorporated in research as end-users. Yet, stakeholders interact with nexus issues in a variety of ways, consequently there is much that collaboration might offer to develop nexus research and enhance its application. This paper outlines four aspects of nexus research and considers the value and potential challenges for transdisciplinary research in each. We focus on assessing and visualising nexus systems; understanding governance and capacity building; the importance of scale; and the implications of future change. The paper then proceeds to describe a novel mixed-method study that deeply integrates stakeholder knowledge with insights from multiple disciplines. We argue that mixed-method research designs—in this case orientated around a number of cases studies—are best suited to understanding and addressing real-world nexus challenges, with their inevitable complex, non-linear system characteristics. Moreover, integrating multiple forms of knowledge in the manner described in this paper enables research to assess the potential for, and processes of, scaling-up innovations in the nexus space, to contribute insights to policy and decision making.

What Is ‘Value’ and How Can We Capture It from the Product Value Chain?

The mobile phone industry is based upon the rapid development of handsets and the high turnover of devices in order to drive sales. Phones are often used for shorter periods of time than their designed life, and when discarded it is often through channels that result in lost resource. This unsustainable business model places strain on resources and creates adverse environmental and social impacts. Through interrogation of a stock and flow model, a product-service system (PSS) for a small consumer electronic device, a mobile telephone, is proposed. The points at which value may be extracted from the PSS are identified. A quantitative measure of value is proposed in order to allow the evaluation of the most appropriate time to extract it. This value is not solely monetary, but is derived from the combination of indicators which encompass environmental, economic, and technological factors. A worked example is presented, in which it is found that the precious metals within the phone are the main determinants for value extraction. These metals are found in the printed circuit board, leading to a requirement to design phones for ease of extraction of these components in order to access the value within.

Microwaves: thin metal slits and liquid crystals

Using liquid crystals to control the propagation of microwaves is a potentially interesting technology. By incorporating small amounts of liquid crystal in thin slat metal structures through which the microwaves may resonantly pass a whole new range of voltage tuned microwave devices are becoming available. Metallic sub-wavelength slit structures at microwave frequencies have been constructed which show Fabry-Perot type resonances in very thin slits. If the dielectric in such thin slits is an aligned liquid crystal it is found possible to voltage-control the resonant frequencies. Novel selective filters and structures for microwave beam steering have been fabricated leading to a new generation of liquid crystal controlled devices.

Resonant microwave transmission through individual subwavelength slits

It is well established that much more radiation may be transmitted through a set of apertures in a metallic screen than a simple calculation from the transmission through the aperture area alone would predict. There has been substantial debate regarding the exact cause of this enhanced transmission, and confusion over the difference between the behaviors of subwavelength apertures as opposed to subwavelength slits. In this study we have analyzed the transmission response of individual slits, using microwave radiation to ensure that transmission is in no part due to direct passage through the metal screen itself. A set of resonant transmission peaks is caused by the excitation of standing-wave-coupled surface plamsons in the finite length slit. It is also found that the high but finite value of the metals’ conductivity influences the transmission response of such slit channels when they are less than 100 microns in width. Indeed there is a strong decrease in transmitted resonant frequency, remarkably tending to zero as the slit width decreases. In addition we have explored the effect of misalignment of the two metal plates that comprise the slit. This modifies resonant frequencies and transmitted intensities through the changing boundary conditions at the slit ends.