Image guide couplers with dielectric coupling elements and radiation reduction

Directional couplers in image guide technique for millimeter-wave circuits are discussed, and steps to improve their properties are demonstrated. The simple two-line-9 dB coupler with periodical coupling is compared to a design with an intermediate dielectric coupling element to reduce the frequency dependence. Radiation from the waveguide bends can be reduced significantly by inserting absorber materials at critical points. Experimental results for a-3 dB coupler are also given.     

A simplified model for the simulation and transformation of speech

This paper explores a model that reduces speech production to the specification of four time-varying parameters; F1 and F2, voice fundamental frequency (F₀), and a relative amplitude of the voice. The trajectory of the first two formants, F1 and F2, is treated as a series of coordinate pairs that are mapped from the F1F2 plane into a two-dimensional plane of coefficients. These coefficients are multipliers of two empirically-based orthogonal basis vectors which, when added to a neutral vowel area function, will produce a new area function with the desired locations of F1 and F2. Thus, area functions and voice parameters extracted at appropriate time intervals can be fed into a speech simulation model to recreate the original speech. A transformation of the speech can also be imposed by manipulating the area function and voice characteristics prior to the recreation of speech by simulation. The model has initially been developed for vowel-like speech utterances, but the effect of consonants on the F1F2 trajectory is also briefly addressed.     

Scalable Ray Tracing Using the Distributed FrameBuffer

Image‐ and data‐parallel rendering across multiple nodes on high‐performance computing systems is widely used in visualization to provide higher frame rates, support large data sets, and render data in situ. Specifically for in situ visualization, reducing bottlenecks incurred by the visualization and compositing is of key concern to reduce the overall simulation runtime. Moreover, prior algorithms have been designed to support either image‐ or data‐parallel rendering and impose restrictions on the data distribution, requiring different implementations for each configuration. In this paper, we introduce the Distributed FrameBuffer, an asynchronous image‐processing framework for multi‐node rendering. We demonstrate that our approach achieves performance superior to the state of the art for common use cases, while providing the flexibility to support a wide range of parallel rendering algorithms and data distributions. By building on this framework, we extend the open‐source ray tracing library OSPRay with a data‐distributed API, enabling its use in data‐distributed and in situ visualization applications.     

Deciphering ADFGVX messages from the Eastern Front of World War I

In the last months of World War I (WW I), the German Army and diplomatic services used the ADFGVX hand-cipher system to encrypt radio messages between Germany and its outposts and stations in the Balkans, the Black Sea, and in the Middle East. Hundreds of cryptograms were intercepted from July to December 1918 by British and U.S. military intelligence, who were able to recover most of the keys and decipher most of the cryptograms using manual cryptanalysis methods. Fortunately, the original cryptograms have been preserved by James Rives Childs, the U.S. officer assigned to G.2 A.6, the SIGINT section of American Expeditionary Forces (AEF) in Paris, and they appear in his book, General Solution of the ADFGVX Cipher System, published by Aegean Press Park in 2000.

In this article, the authors present the results of an effort toward the complete cryptanalysis of the messages, and an analysis of their contents. The authors present a new computerized method for the ciphertext-only cryptanalysis of ADFGVX messages which they developed for that purpose. They also provide details on how all the keys were recovered and almost all the messages decrypted, despite the low quality of significant parts of the intercepted material.

The analysis of the messages in their historical context provides a unique insight into key events, such as the withdrawal of the German troops from Romania, and the impact of the Kiel Mutiny on communications. Both events had major political and military consequences for Germany in the Eastern Front. Cryptanalysis allowed the Entente Powers to closely monitor those events as well as others developments, also highlighting inherent weaknesses in German cryptographic and cryptanalytic capabilities. The authors plan to publish online all the decrypted messages.     

Designing end-to-end resource reservations in predictable distributed embedded systems

Contemporary distributed embedded systems in many domains have become highly complex due to ever-increasing demand on advanced computer controlled functionality. The resource reservation techniques can be effective in lowering the software complexity, ensuring predictability and allowing flexibility during the development and execution of these systems. This paper proposes a novel end-to-end resource reservation model for distributed embedded systems. In order to support the development of predictable systems using the proposed model, the paper provides a method to design resource reservations and an end-to-end timing analysis. The reservation design can be subjected to different optimization criteria with respect to runtime footprint, overhead or performance. The paper also presents and evaluates a case study to show the usability of the proposed model, reservation design method and end-to-end timing analysis.     

Multi‐view reconstruction of dynamic real‐world objects and their integration in augmented and virtual reality applications

We present a flexible system for high‐quality three‐dimensional reconstruction of dynamic real‐world objects based on a modular multi‐camera capture setup. The proposed algorithmic pipeline aims at the acquisition and digitization of natural and realistic representations of real people that can be easily integrated into augmented and virtual reality applications. In this context, we discuss the reduction of mesh complexity as one of the key challenges for visualizing reconstructed three‐dimensional content with augmented and virtual reality glasses and demonstrate different fields of application.     

Structures and gas separation properties of asymmetric polysulfone membranes made by dry,wet, and dry/wet phase inversion

Integrally skinned asymmetric gas separation membranes were prepared by (i) dry, (ii) wet, and (iii) dry/wet phase inversion processes. The membranes were cast from a polysulfone/methylene chloride/1,1,2-trichloroethane/2-methyl-2-butanol casting system. Wet and dry/wet phase inversion membranes were quenched in methanol. Membranes made by dry/wet phase inversion using convective evaporation showed optimum gas separation performance. The average O₂/N₂ and He/N₂ selectivities of these membranes were within 85% of those determined for a dense, solution-cast polysulfone film, suggesting that the ultrathin skin layers were essentially defect free. The average apparent skin layer thickness of all samples tested was 270 Å. Scanning electron photomicrographs revealed that optimum membranes made by dry/wet phase inversion consist of an ultrathin skin layer, a tightly packed nodular transition layer, and an open-cell, sponge-like substructure. Dry/wet phase inversion membranes prepared by free-standing evaporation resulted either in high flux and low selectivity membranes or essentially defect-free membranes with fluxes lower than those made by convective evaporation. Dry-phase inversion membranes exhibited extremely low gas fluxes due to thick (17.5 μm) skin layers. On the other hand, wet phase inversion membranes showed O₂/N₂ selectivities < 1, indicating that gas transport was determined by pore flow through skin layer defects.