A Topologically-informed Hyperstreamline Seeding Method for Alignment Tensor Fields

A topologically-informed method is presented for seeding of hyperstreamlines for visualization of alignment tensor fields. The method is inspired by and applied to visualization of nematic liquid crystal (LC) reorientation dynamics simulations. The method distributes hyperstreamlines along domain boundaries and edges of a nearest-neighbor graph whose vertices are degenerate regions of the alignment tensor field, which correspond to orientational defects in a nematic LC domain. This is accomplished without iteration while conforming to a user-specified spacing between hyperstreamlines and avoids possible failure modes associated with hyperstreamline integration in the vicinity of degeneracies of alignment (orientational defects). It is shown that the presented seeding method enables automated hyperstreamline-based visualization of a broad range of alignment tensor fields which enhances the ability of researchers to interpret these fields and provides an alternative to using glyph-based techniques.Comment: 8 pages, 9 figure

Field-driven dynamics of nematic microcapillaries

Polymer-dispersed liquid crystal (PDLC) composites have long been a focus of study for their unique electro-optical properties which have resulted in various applications such as switchable (transparent/translucent) windows. These composites are manufactured using desirable "bottom-up" techniques, such as phase separation of a liquid crystal/polymer mixture, which enable production of PDLC films at very large scales. LC domains within PDLCs are typically spheroidal, as opposed to rectangular for an LCD panel, and thus exhibit substantially different behaviour in the presence of an external field. The fundamental difference between spheroidal and rectangular nematic domains is that the former results in the presence of nanoscale orientational defects in LC order while the latter does not. Progress in the development and optimization of PDLC electro-optical properties has progressed at a relatively slow pace due to this increased complexity. In this work, continuum simulations are performed in order to capture the complex formation and electric field-driven switching dynamics of approximations of PDLC domains. Using a simplified elliptic cylinder (microcapillary) geometry as an approximation of spheroidal PDLC domains, the effects of geometry (aspect ratio), surface anchoring, and external field strength are studied through the use of the Landau--de Gennes model of the nematic LC phase.Comment: 22 pages, 9 figures, Physical Review

Security proof of differential phase shift quantum key distribution in the noiseless case

Differential phase shift quantum key distribution systems have a high potential for achieving high speed key generation. However, its unconditional security proof is still missing, even though it has been proposed for many years. Here, we prove its security against collective attacks with a weak coherent light source in the noiseless case (i.e. no bit error). The only assumptions are that quantum theory is correct, the devices are perfect and trusted and the key size is infinite. Our proof works on threshold detectors. We compute the lower bound of the secret key generation rate using the information-theoretical security proof method. Our final result shows that the lower bound of the secret key generation rate per pulse is linearly proportional to the channel transmission probability if Bob's detection counts obey the binomial distribution.Comment: Published version, 13 pages, 4 figures, minor changes, references added, acknowledgement adde

Measurement-device-independent quantum key distribution with uncharacterized qubit sources

Measurement-device-independent quantum key distribution (MDIQKD) is proposed to be secure against any possible detection attacks. The security of the original proposal relies on the assumption that the legitimate users can fully characterize the encoding systems including sources. Here, we propose a MDIQKD protocol where we allow uncharacterized encoding systems as long as qubit sources are used. A security proof of the MDIQKD protocol is presented that does not need the knowledge of the encoding states. Simulation results show that the scheme is practical

Mismatched-basis statistics enable quantum key distribution with uncharacterized qubit sources

In the postprocessing of quantum key distribution, the raw key bits from the mismatched-basis measurements, where two parties use different bases, are normally discarded. Here, we propose a postprocessing method that exploits measurement statistics from mismatched-basis cases, and prove that incorporating these statistics enables uncharacterized qubit sources to be used in the measurement-device-independent quantum key distribution protocol and the Bennett-Brassard 1984 protocol, a case which is otherwise impossible.Comment: Part of this article contains a significant improvement over arXiv:1309.381

Indication of insensitivity of planetary weathering behavior and habitable zone to surface land fraction

It is likely that unambiguous habitable zone terrestrial planets of unknown water content will soon be discovered. Water content helps determine surface land fraction, which influences planetary weathering behavior. This is important because the silicate weathering feedback determines the width of the habitable zone in space and time. Here a low-order model of weathering and climate, useful for gaining qualitative understanding, is developed to examine climate evolution for planets of various land-ocean fractions. It is pointed out that, if seafloor weathering does not depend directly on surface temperature, there can be no weathering-climate feedback on a waterworld. This would dramatically narrow the habitable zone of a waterworld. Results from our model indicate that weathering behavior does not depend strongly on land fraction for partially ocean-covered planets. This is powerful because it suggests that previous habitable zone theory is robust to changes in land fraction, as long as there is some land. Finally, a mechanism is proposed for a waterworld to prevent complete water loss during a moist greenhouse through rapid weathering of exposed continents. This process is named a "waterworld self-arrest," and it implies that waterworlds can go through a moist greenhouse stage and end up as planets like Earth with partial ocean coverage. This work stresses the importance of surface and geologic effects, in addition to the usual incident stellar flux, for habitability.Comment: 15 pages, 6 figures, accepted at Ap

MultiFarm: A benchmark for multilingual ontology matching

In this paper we present the MultiFarm dataset, which has been designed as a benchmark for multilingual ontology matching. The MultiFarm dataset is composed of a set of ontologies translated in different languages and the corresponding alignments between these ontologies. It is based on the OntoFarm dataset, which has been used successfully for several years in the Ontology Alignment Evaluation Initiative (OAEI). By translating the ontologies of the OntoFarm dataset into eight different languages – Chinese, Czech, Dutch, French, German, Portuguese, Russian, and Spanish – we created a comprehensive set of realistic test cases. Based on these test cases, it is possible to evaluate and compare the performance of matching approaches with a special focus on multilingualism

Formation and Field-switching Dynamics of Nematic Droplets

Liquid crystals (LCs) refer to a class of materials which have anisotropic properties. They are used in many technological applications ranging from displays to biological sensors. One example of a category of technologically relevant LC applications is optical functional materials, which include polymer-dispersed liquid crystal (PDLC) films. In these films, non-deformable micron-scale LC droplets are dispersed in a solid polymer matrix. Application of an electric field through the thickness of a PDLC film results in "switching" between a transparent "on" state (field-on) and a translucent "off" state (field-off). Thus the main application of these films are as switchable windows. Key to this mechanism is the ability for external fields to reorient the direction LC molecules within the droplets. In this work, the LC phase formation and external electric field-switching dynamics of orientationally-ordered LC droplets are studied using the continuum Landau--de Gennes model. The model is able to capture phase transition and reorientation dynamics on device-relevant length and time scales when combined with numerical methods such as the finite element method. Formation dynamics correspond to transitioning from a high-temperature disordered liquid phase to an orientationally-ordered phase referred to as a nematic LC. Field-switching dynamics correspond to the imposition and release of an external (electric) field. Particular emphasis is placed on non-spherical droplets, which may form naturally or intentionally under controlled conditions in the manufacturing of PDLC films. The interactions between shape, LC/polymer interfacial effects, electric field strength, and other parameters are first investigated for capillary geometries using a simplified model, which is then followed by fully three-dimensional droplet simulations. Finally, simulation results predicting a symmetry-breaking phase transformation process for spherical droplet domain are presented. This observation is found to be predicted when using physically-realistic material parameters approximating the LC compound pentyl-cyanobiphenyl (5CB), but not for simulations with a typical simplification of nematic elasticity known as the single elastic constant approximation