Active Exterior Cloaking

A new method of cloaking is presented. For two-dimensional quasistatics it is proven how a single active exterior cloaking device can be used to shield an object from surrounding fields, yet produce very small scattered fields. The problem is reduced to finding a polynomial which is approximately one within one disk and zero within a second disk, and such a polynomial is constructed. For the two-dimensional Helmholtz equation, it is numerically shown that three active exterior devices placed around the object suffice to produce very good cloaking.Comment: 4 pages, 3 figures, submitted to Physical Review Letter

Paraplegia and squamous cell carcinoma of the bladder in young women: findings from a case-control study.

A death certificate-based case-control study was conducted on 207 women aged 25-44 who died of bladder cancer in England and Wales in the period 1971-89 and 411 controls matched on sex, year of death and age at death. An odds ratio of 12.0 (95% CI 1.5-99.7) was found for women with a history of paraplegia. Four of the six paraplegic women were reported to have had squamous cell carcinoma of the bladder compared with only 19 of the 201 non-paraplegic women. These findings suggest that squamous cell carcinomas of the bladder, especially in paraplegics, may be the result of chronic urinary tract infection

Exterior optical cloaking and illusions by using active sources: a boundary element perspective

Recently, it was demonstrated that active sources can be used to cloak any objects that lie outside the cloaking devices [Phys. Rev. Lett. \textbf{103}, 073901 (2009)]. Here, we propose that active sources can create illusion effects, so that an object outside the cloaking device can be made to look like another object. invisibility is a special case in which the concealed object is transformed to a volume of air. From a boundary element perspective, we show that active sources can create a nearly "silent" domain which can conceal any objects inside and at the same time make the whole system look like an illusion of our choice outside a virtual boundary. The boundary element method gives the fields and field gradients (which can be related to monopoles and dipoles) on continuous curves which define the boundary of the active devices. Both the cloaking and illusion effects are confirmed by numerical simulations

Superantenna made of transformation media

We show how transformation media can make a superantenna that is either completely invisible or focuses incoming light into a needle-sharp beam. Our idea is based on representating three-dimensional space as a foliage of sheets and performing two-dimensional conformal maps on each shee

Building protypes of damaged systems from analysis simulations

Our rapid prototype of damaged systems project seeks to provide a technology for allowing engineers to build demonstration prototypes of damaged products from analysis post-processing data. Most commercial finite element programs do not have a capability to construct deformed geometry at the conclusion of an analysis simulation. It is therefore not presently possible to build prototypes of predicted states of a product as the result of being subjected to simulated adverse environments. Our approach is to reverse engineer a description of a deformed finite element mesh into a stereolithography format for prototyping using a Selective Laser Sintering (SLS) machine. This stereolithography file can be generated from deformed surface node information as well as from a reconstructed surface defined by inspection data. We are developing software to allow users to represent a part or assembly in a deformed condition. The damaged part can then be manufactured using the SLS process for visualization and assessment purposes. The resulting representation can also be used to create simulated X-rays of a damaged or deformed configuration for comparison with experimental test results or field data. This allows engineers to benchmark their analysis methods and provide increased understanding of analysis results through enhanced visualization. The process of reverse engineering `in-use` or damaged products allows for a more refined inspection and comparison of imperfect parts. It addresses the issue of whether or not a part will still work when subjected to certain environments or scenarios. Answers to this question can be found using our model reconstruction technique that represents an `as- built` engineering model configuration. An additional feature of this reverse engineering process is product benchmarking and closer engineer/manufacturer interactions

Partial Transmutation of Singularities in Optical Instruments

Some interesting optical instruments such as the Eaton lens and the Invisible Sphere require singularities of the refractive index for their implementation. We show how to transmute those singularities into harmless topological defects in anisotropic media without the need for anomalous material properties